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, 2009
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
26 @c readline appendices use @vindex, @findex and @ftable,
27 @c annotate.texi and gdbmi use @findex.
31 @c !!set GDB manual's edition---not the same as GDB version!
32 @c This is updated by GNU Press.
35 @c !!set GDB edit command default editor
38 @c THIS MANUAL REQUIRES TEXINFO 4.0 OR LATER.
40 @c This is a dir.info fragment to support semi-automated addition of
41 @c manuals to an info tree.
42 @dircategory Software development
44 * Gdb: (gdb). The GNU debugger.
48 Copyright @copyright{} 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995, 1996,
49 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009
50 Free Software Foundation, Inc.
52 Permission is granted to copy, distribute and/or modify this document
53 under the terms of the GNU Free Documentation License, Version 1.1 or
54 any later version published by the Free Software Foundation; with the
55 Invariant Sections being ``Free Software'' and ``Free Software Needs
56 Free Documentation'', with the Front-Cover Texts being ``A GNU Manual,''
57 and with the Back-Cover Texts as in (a) below.
59 (a) The FSF's Back-Cover Text is: ``You are free to copy and modify
60 this GNU Manual. Buying copies from GNU Press supports the FSF in
61 developing GNU and promoting software freedom.''
65 This file documents the @sc{gnu} debugger @value{GDBN}.
67 This is the @value{EDITION} Edition, of @cite{Debugging with
68 @value{GDBN}: the @sc{gnu} Source-Level Debugger} for @value{GDBN}
69 @ifset VERSION_PACKAGE
70 @value{VERSION_PACKAGE}
72 Version @value{GDBVN}.
78 @title Debugging with @value{GDBN}
79 @subtitle The @sc{gnu} Source-Level Debugger
81 @subtitle @value{EDITION} Edition, for @value{GDBN} version @value{GDBVN}
82 @ifset VERSION_PACKAGE
84 @subtitle @value{VERSION_PACKAGE}
86 @author Richard Stallman, Roland Pesch, Stan Shebs, et al.
90 \hfill (Send bugs and comments on @value{GDBN} to @value{BUGURL}.)\par
91 \hfill {\it Debugging with @value{GDBN}}\par
92 \hfill \TeX{}info \texinfoversion\par
96 @vskip 0pt plus 1filll
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 @*
104 This edition of the GDB manual is dedicated to the memory of Fred
105 Fish. Fred was a long-standing contributor to GDB and to Free
106 software in general. We will miss him.
111 @node Top, Summary, (dir), (dir)
113 @top Debugging with @value{GDBN}
115 This file describes @value{GDBN}, the @sc{gnu} symbolic debugger.
117 This is the @value{EDITION} Edition, for @value{GDBN}
118 @ifset VERSION_PACKAGE
119 @value{VERSION_PACKAGE}
121 Version @value{GDBVN}.
123 Copyright (C) 1988-2009 Free Software Foundation, Inc.
125 This edition of the GDB manual is dedicated to the memory of Fred
126 Fish. Fred was a long-standing contributor to GDB and to Free
127 software in general. We will miss him.
130 * Summary:: Summary of @value{GDBN}
131 * Sample Session:: A sample @value{GDBN} session
133 * Invocation:: Getting in and out of @value{GDBN}
134 * Commands:: @value{GDBN} commands
135 * Running:: Running programs under @value{GDBN}
136 * Stopping:: Stopping and continuing
137 * Reverse Execution:: Running programs backward
138 * Process Record and Replay:: Recording inferior's execution and replaying it
139 * Stack:: Examining the stack
140 * Source:: Examining source files
141 * Data:: Examining data
142 * Optimized Code:: Debugging optimized code
143 * Macros:: Preprocessor Macros
144 * Tracepoints:: Debugging remote targets non-intrusively
145 * Overlays:: Debugging programs that use overlays
147 * Languages:: Using @value{GDBN} with different languages
149 * Symbols:: Examining the symbol table
150 * Altering:: Altering execution
151 * GDB Files:: @value{GDBN} files
152 * Targets:: Specifying a debugging target
153 * Remote Debugging:: Debugging remote programs
154 * Configurations:: Configuration-specific information
155 * Controlling GDB:: Controlling @value{GDBN}
156 * Extending GDB:: Extending @value{GDBN}
157 * Interpreters:: Command Interpreters
158 * TUI:: @value{GDBN} Text User Interface
159 * Emacs:: Using @value{GDBN} under @sc{gnu} Emacs
160 * GDB/MI:: @value{GDBN}'s Machine Interface.
161 * Annotations:: @value{GDBN}'s annotation interface.
162 * JIT Interface:: Using the JIT debugging interface.
164 * GDB Bugs:: Reporting bugs in @value{GDBN}
166 * Command Line Editing:: Command Line Editing
167 * Using History Interactively:: Using History Interactively
168 * Formatting Documentation:: How to format and print @value{GDBN} documentation
169 * Installing GDB:: Installing GDB
170 * Maintenance Commands:: Maintenance Commands
171 * Remote Protocol:: GDB Remote Serial Protocol
172 * Agent Expressions:: The GDB Agent Expression Mechanism
173 * Target Descriptions:: How targets can describe themselves to
175 * Operating System Information:: Getting additional information from
177 * Copying:: GNU General Public License says
178 how you can copy and share GDB
179 * GNU Free Documentation License:: The license for this documentation
188 @unnumbered Summary of @value{GDBN}
190 The purpose of a debugger such as @value{GDBN} is to allow you to see what is
191 going on ``inside'' another program while it executes---or what another
192 program was doing at the moment it crashed.
194 @value{GDBN} can do four main kinds of things (plus other things in support of
195 these) to help you catch bugs in the act:
199 Start your program, specifying anything that might affect its behavior.
202 Make your program stop on specified conditions.
205 Examine what has happened, when your program has stopped.
208 Change things in your program, so you can experiment with correcting the
209 effects of one bug and go on to learn about another.
212 You can use @value{GDBN} to debug programs written in C and C@t{++}.
213 For more information, see @ref{Supported Languages,,Supported Languages}.
214 For more information, see @ref{C,,C and C++}.
217 Support for Modula-2 is partial. For information on Modula-2, see
218 @ref{Modula-2,,Modula-2}.
221 Debugging Pascal programs which use sets, subranges, file variables, or
222 nested functions does not currently work. @value{GDBN} does not support
223 entering expressions, printing values, or similar features using Pascal
227 @value{GDBN} can be used to debug programs written in Fortran, although
228 it may be necessary to refer to some variables with a trailing
231 @value{GDBN} can be used to debug programs written in Objective-C,
232 using either the Apple/NeXT or the GNU Objective-C runtime.
235 * Free Software:: Freely redistributable software
236 * Contributors:: Contributors to GDB
240 @unnumberedsec Free Software
242 @value{GDBN} is @dfn{free software}, protected by the @sc{gnu}
243 General Public License
244 (GPL). The GPL gives you the freedom to copy or adapt a licensed
245 program---but every person getting a copy also gets with it the
246 freedom to modify that copy (which means that they must get access to
247 the source code), and the freedom to distribute further copies.
248 Typical software companies use copyrights to limit your freedoms; the
249 Free Software Foundation uses the GPL to preserve these freedoms.
251 Fundamentally, the General Public License is a license which says that
252 you have these freedoms and that you cannot take these freedoms away
255 @unnumberedsec Free Software Needs Free Documentation
257 The biggest deficiency in the free software community today is not in
258 the software---it is the lack of good free documentation that we can
259 include with the free software. Many of our most important
260 programs do not come with free reference manuals and free introductory
261 texts. Documentation is an essential part of any software package;
262 when an important free software package does not come with a free
263 manual and a free tutorial, that is a major gap. We have many such
266 Consider Perl, for instance. The tutorial manuals that people
267 normally use are non-free. How did this come about? Because the
268 authors of those manuals published them with restrictive terms---no
269 copying, no modification, source files not available---which exclude
270 them from the free software world.
272 That wasn't the first time this sort of thing happened, and it was far
273 from the last. Many times we have heard a GNU user eagerly describe a
274 manual that he is writing, his intended contribution to the community,
275 only to learn that he had ruined everything by signing a publication
276 contract to make it non-free.
278 Free documentation, like free software, is a matter of freedom, not
279 price. The problem with the non-free manual is not that publishers
280 charge a price for printed copies---that in itself is fine. (The Free
281 Software Foundation sells printed copies of manuals, too.) The
282 problem is the restrictions on the use of the manual. Free manuals
283 are available in source code form, and give you permission to copy and
284 modify. Non-free manuals do not allow this.
286 The criteria of freedom for a free manual are roughly the same as for
287 free software. Redistribution (including the normal kinds of
288 commercial redistribution) must be permitted, so that the manual can
289 accompany every copy of the program, both on-line and on paper.
291 Permission for modification of the technical content is crucial too.
292 When people modify the software, adding or changing features, if they
293 are conscientious they will change the manual too---so they can
294 provide accurate and clear documentation for the modified program. A
295 manual that leaves you no choice but to write a new manual to document
296 a changed version of the program is not really available to our
299 Some kinds of limits on the way modification is handled are
300 acceptable. For example, requirements to preserve the original
301 author's copyright notice, the distribution terms, or the list of
302 authors, are ok. It is also no problem to require modified versions
303 to include notice that they were modified. Even entire sections that
304 may not be deleted or changed are acceptable, as long as they deal
305 with nontechnical topics (like this one). These kinds of restrictions
306 are acceptable because they don't obstruct the community's normal use
309 However, it must be possible to modify all the @emph{technical}
310 content of the manual, and then distribute the result in all the usual
311 media, through all the usual channels. Otherwise, the restrictions
312 obstruct the use of the manual, it is not free, and we need another
313 manual to replace it.
315 Please spread the word about this issue. Our community continues to
316 lose manuals to proprietary publishing. If we spread the word that
317 free software needs free reference manuals and free tutorials, perhaps
318 the next person who wants to contribute by writing documentation will
319 realize, before it is too late, that only free manuals contribute to
320 the free software community.
322 If you are writing documentation, please insist on publishing it under
323 the GNU Free Documentation License or another free documentation
324 license. Remember that this decision requires your approval---you
325 don't have to let the publisher decide. Some commercial publishers
326 will use a free license if you insist, but they will not propose the
327 option; it is up to you to raise the issue and say firmly that this is
328 what you want. If the publisher you are dealing with refuses, please
329 try other publishers. If you're not sure whether a proposed license
330 is free, write to @email{licensing@@gnu.org}.
332 You can encourage commercial publishers to sell more free, copylefted
333 manuals and tutorials by buying them, and particularly by buying
334 copies from the publishers that paid for their writing or for major
335 improvements. Meanwhile, try to avoid buying non-free documentation
336 at all. Check the distribution terms of a manual before you buy it,
337 and insist that whoever seeks your business must respect your freedom.
338 Check the history of the book, and try to reward the publishers that
339 have paid or pay the authors to work on it.
341 The Free Software Foundation maintains a list of free documentation
342 published by other publishers, at
343 @url{http://www.fsf.org/doc/other-free-books.html}.
346 @unnumberedsec Contributors to @value{GDBN}
348 Richard Stallman was the original author of @value{GDBN}, and of many
349 other @sc{gnu} programs. Many others have contributed to its
350 development. This section attempts to credit major contributors. One
351 of the virtues of free software is that everyone is free to contribute
352 to it; with regret, we cannot actually acknowledge everyone here. The
353 file @file{ChangeLog} in the @value{GDBN} distribution approximates a
354 blow-by-blow account.
356 Changes much prior to version 2.0 are lost in the mists of time.
359 @emph{Plea:} Additions to this section are particularly welcome. If you
360 or your friends (or enemies, to be evenhanded) have been unfairly
361 omitted from this list, we would like to add your names!
364 So that they may not regard their many labors as thankless, we
365 particularly thank those who shepherded @value{GDBN} through major
367 Andrew Cagney (releases 6.3, 6.2, 6.1, 6.0, 5.3, 5.2, 5.1 and 5.0);
368 Jim Blandy (release 4.18);
369 Jason Molenda (release 4.17);
370 Stan Shebs (release 4.14);
371 Fred Fish (releases 4.16, 4.15, 4.13, 4.12, 4.11, 4.10, and 4.9);
372 Stu Grossman and John Gilmore (releases 4.8, 4.7, 4.6, 4.5, and 4.4);
373 John Gilmore (releases 4.3, 4.2, 4.1, 4.0, and 3.9);
374 Jim Kingdon (releases 3.5, 3.4, and 3.3);
375 and Randy Smith (releases 3.2, 3.1, and 3.0).
377 Richard Stallman, assisted at various times by Peter TerMaat, Chris
378 Hanson, and Richard Mlynarik, handled releases through 2.8.
380 Michael Tiemann is the author of most of the @sc{gnu} C@t{++} support
381 in @value{GDBN}, with significant additional contributions from Per
382 Bothner and Daniel Berlin. James Clark wrote the @sc{gnu} C@t{++}
383 demangler. Early work on C@t{++} was by Peter TerMaat (who also did
384 much general update work leading to release 3.0).
386 @value{GDBN} uses the BFD subroutine library to examine multiple
387 object-file formats; BFD was a joint project of David V.
388 Henkel-Wallace, Rich Pixley, Steve Chamberlain, and John Gilmore.
390 David Johnson wrote the original COFF support; Pace Willison did
391 the original support for encapsulated COFF.
393 Brent Benson of Harris Computer Systems contributed DWARF 2 support.
395 Adam de Boor and Bradley Davis contributed the ISI Optimum V support.
396 Per Bothner, Noboyuki Hikichi, and Alessandro Forin contributed MIPS
398 Jean-Daniel Fekete contributed Sun 386i support.
399 Chris Hanson improved the HP9000 support.
400 Noboyuki Hikichi and Tomoyuki Hasei contributed Sony/News OS 3 support.
401 David Johnson contributed Encore Umax support.
402 Jyrki Kuoppala contributed Altos 3068 support.
403 Jeff Law contributed HP PA and SOM support.
404 Keith Packard contributed NS32K support.
405 Doug Rabson contributed Acorn Risc Machine support.
406 Bob Rusk contributed Harris Nighthawk CX-UX support.
407 Chris Smith contributed Convex support (and Fortran debugging).
408 Jonathan Stone contributed Pyramid support.
409 Michael Tiemann contributed SPARC support.
410 Tim Tucker contributed support for the Gould NP1 and Gould Powernode.
411 Pace Willison contributed Intel 386 support.
412 Jay Vosburgh contributed Symmetry support.
413 Marko Mlinar contributed OpenRISC 1000 support.
415 Andreas Schwab contributed M68K @sc{gnu}/Linux support.
417 Rich Schaefer and Peter Schauer helped with support of SunOS shared
420 Jay Fenlason and Roland McGrath ensured that @value{GDBN} and GAS agree
421 about several machine instruction sets.
423 Patrick Duval, Ted Goldstein, Vikram Koka and Glenn Engel helped develop
424 remote debugging. Intel Corporation, Wind River Systems, AMD, and ARM
425 contributed remote debugging modules for the i960, VxWorks, A29K UDI,
426 and RDI targets, respectively.
428 Brian Fox is the author of the readline libraries providing
429 command-line editing and command history.
431 Andrew Beers of SUNY Buffalo wrote the language-switching code, the
432 Modula-2 support, and contributed the Languages chapter of this manual.
434 Fred Fish wrote most of the support for Unix System Vr4.
435 He also enhanced the command-completion support to cover C@t{++} overloaded
438 Hitachi America (now Renesas America), Ltd. sponsored the support for
439 H8/300, H8/500, and Super-H processors.
441 NEC sponsored the support for the v850, Vr4xxx, and Vr5xxx processors.
443 Mitsubishi (now Renesas) sponsored the support for D10V, D30V, and M32R/D
446 Toshiba sponsored the support for the TX39 Mips processor.
448 Matsushita sponsored the support for the MN10200 and MN10300 processors.
450 Fujitsu sponsored the support for SPARClite and FR30 processors.
452 Kung Hsu, Jeff Law, and Rick Sladkey added support for hardware
455 Michael Snyder added support for tracepoints.
457 Stu Grossman wrote gdbserver.
459 Jim Kingdon, Peter Schauer, Ian Taylor, and Stu Grossman made
460 nearly innumerable bug fixes and cleanups throughout @value{GDBN}.
462 The following people at the Hewlett-Packard Company contributed
463 support for the PA-RISC 2.0 architecture, HP-UX 10.20, 10.30, and 11.0
464 (narrow mode), HP's implementation of kernel threads, HP's aC@t{++}
465 compiler, and the Text User Interface (nee Terminal User Interface):
466 Ben Krepp, Richard Title, John Bishop, Susan Macchia, Kathy Mann,
467 Satish Pai, India Paul, Steve Rehrauer, and Elena Zannoni. Kim Haase
468 provided HP-specific information in this manual.
470 DJ Delorie ported @value{GDBN} to MS-DOS, for the DJGPP project.
471 Robert Hoehne made significant contributions to the DJGPP port.
473 Cygnus Solutions has sponsored @value{GDBN} maintenance and much of its
474 development since 1991. Cygnus engineers who have worked on @value{GDBN}
475 fulltime include Mark Alexander, Jim Blandy, Per Bothner, Kevin
476 Buettner, Edith Epstein, Chris Faylor, Fred Fish, Martin Hunt, Jim
477 Ingham, John Gilmore, Stu Grossman, Kung Hsu, Jim Kingdon, John Metzler,
478 Fernando Nasser, Geoffrey Noer, Dawn Perchik, Rich Pixley, Zdenek
479 Radouch, Keith Seitz, Stan Shebs, David Taylor, and Elena Zannoni. In
480 addition, Dave Brolley, Ian Carmichael, Steve Chamberlain, Nick Clifton,
481 JT Conklin, Stan Cox, DJ Delorie, Ulrich Drepper, Frank Eigler, Doug
482 Evans, Sean Fagan, David Henkel-Wallace, Richard Henderson, Jeff
483 Holcomb, Jeff Law, Jim Lemke, Tom Lord, Bob Manson, Michael Meissner,
484 Jason Merrill, Catherine Moore, Drew Moseley, Ken Raeburn, Gavin
485 Romig-Koch, Rob Savoye, Jamie Smith, Mike Stump, Ian Taylor, Angela
486 Thomas, Michael Tiemann, Tom Tromey, Ron Unrau, Jim Wilson, and David
487 Zuhn have made contributions both large and small.
489 Andrew Cagney, Fernando Nasser, and Elena Zannoni, while working for
490 Cygnus Solutions, implemented the original @sc{gdb/mi} interface.
492 Jim Blandy added support for preprocessor macros, while working for Red
495 Andrew Cagney designed @value{GDBN}'s architecture vector. Many
496 people including Andrew Cagney, Stephane Carrez, Randolph Chung, Nick
497 Duffek, Richard Henderson, Mark Kettenis, Grace Sainsbury, Kei
498 Sakamoto, Yoshinori Sato, Michael Snyder, Andreas Schwab, Jason
499 Thorpe, Corinna Vinschen, Ulrich Weigand, and Elena Zannoni, helped
500 with the migration of old architectures to this new framework.
502 Andrew Cagney completely re-designed and re-implemented @value{GDBN}'s
503 unwinder framework, this consisting of a fresh new design featuring
504 frame IDs, independent frame sniffers, and the sentinel frame. Mark
505 Kettenis implemented the @sc{dwarf 2} unwinder, Jeff Johnston the
506 libunwind unwinder, and Andrew Cagney the dummy, sentinel, tramp, and
507 trad unwinders. The architecture-specific changes, each involving a
508 complete rewrite of the architecture's frame code, were carried out by
509 Jim Blandy, Joel Brobecker, Kevin Buettner, Andrew Cagney, Stephane
510 Carrez, Randolph Chung, Orjan Friberg, Richard Henderson, Daniel
511 Jacobowitz, Jeff Johnston, Mark Kettenis, Theodore A. Roth, Kei
512 Sakamoto, Yoshinori Sato, Michael Snyder, Corinna Vinschen, and Ulrich
515 Christian Zankel, Ross Morley, Bob Wilson, and Maxim Grigoriev from
516 Tensilica, Inc.@: contributed support for Xtensa processors. Others
517 who have worked on the Xtensa port of @value{GDBN} in the past include
518 Steve Tjiang, John Newlin, and Scott Foehner.
520 Michael Eager and staff of Xilinx, Inc., contributed support for the
521 Xilinx MicroBlaze architecture.
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 system-wide @dfn{init file} (if @option{--with-system-gdbinit} was
1222 used when building @value{GDBN}; @pxref{System-wide configuration,
1223 ,System-wide configuration and settings}) and executes all the commands in
1227 Reads the init file (if any) in your home directory@footnote{On
1228 DOS/Windows systems, the home directory is the one pointed to by the
1229 @code{HOME} environment variable.} and executes all the commands in
1233 Processes command line options and operands.
1236 Reads and executes the commands from init file (if any) in the current
1237 working directory. This is only done if the current directory is
1238 different from your home directory. Thus, you can have more than one
1239 init file, one generic in your home directory, and another, specific
1240 to the program you are debugging, in the directory where you invoke
1244 Reads command files specified by the @samp{-x} option. @xref{Command
1245 Files}, for more details about @value{GDBN} command files.
1248 Reads the command history recorded in the @dfn{history file}.
1249 @xref{Command History}, for more details about the command history and the
1250 files where @value{GDBN} records it.
1253 Init files use the same syntax as @dfn{command files} (@pxref{Command
1254 Files}) and are processed by @value{GDBN} in the same way. The init
1255 file in your home directory can set options (such as @samp{set
1256 complaints}) that affect subsequent processing of command line options
1257 and operands. Init files are not executed if you use the @samp{-nx}
1258 option (@pxref{Mode Options, ,Choosing Modes}).
1260 To display the list of init files loaded by gdb at startup, you
1261 can use @kbd{gdb --help}.
1263 @cindex init file name
1264 @cindex @file{.gdbinit}
1265 @cindex @file{gdb.ini}
1266 The @value{GDBN} init files are normally called @file{.gdbinit}.
1267 The DJGPP port of @value{GDBN} uses the name @file{gdb.ini}, due to
1268 the limitations of file names imposed by DOS filesystems. The Windows
1269 ports of @value{GDBN} use the standard name, but if they find a
1270 @file{gdb.ini} file, they warn you about that and suggest to rename
1271 the file to the standard name.
1275 @section Quitting @value{GDBN}
1276 @cindex exiting @value{GDBN}
1277 @cindex leaving @value{GDBN}
1280 @kindex quit @r{[}@var{expression}@r{]}
1281 @kindex q @r{(@code{quit})}
1282 @item quit @r{[}@var{expression}@r{]}
1284 To exit @value{GDBN}, use the @code{quit} command (abbreviated
1285 @code{q}), or type an end-of-file character (usually @kbd{Ctrl-d}). If you
1286 do not supply @var{expression}, @value{GDBN} will terminate normally;
1287 otherwise it will terminate using the result of @var{expression} as the
1292 An interrupt (often @kbd{Ctrl-c}) does not exit from @value{GDBN}, but rather
1293 terminates the action of any @value{GDBN} command that is in progress and
1294 returns to @value{GDBN} command level. It is safe to type the interrupt
1295 character at any time because @value{GDBN} does not allow it to take effect
1296 until a time when it is safe.
1298 If you have been using @value{GDBN} to control an attached process or
1299 device, you can release it with the @code{detach} command
1300 (@pxref{Attach, ,Debugging an Already-running Process}).
1302 @node Shell Commands
1303 @section Shell Commands
1305 If you need to execute occasional shell commands during your
1306 debugging session, there is no need to leave or suspend @value{GDBN}; you can
1307 just use the @code{shell} command.
1311 @cindex shell escape
1312 @item shell @var{command string}
1313 Invoke a standard shell to execute @var{command string}.
1314 If it exists, the environment variable @code{SHELL} determines which
1315 shell to run. Otherwise @value{GDBN} uses the default shell
1316 (@file{/bin/sh} on Unix systems, @file{COMMAND.COM} on MS-DOS, etc.).
1319 The utility @code{make} is often needed in development environments.
1320 You do not have to use the @code{shell} command for this purpose in
1325 @cindex calling make
1326 @item make @var{make-args}
1327 Execute the @code{make} program with the specified
1328 arguments. This is equivalent to @samp{shell make @var{make-args}}.
1331 @node Logging Output
1332 @section Logging Output
1333 @cindex logging @value{GDBN} output
1334 @cindex save @value{GDBN} output to a file
1336 You may want to save the output of @value{GDBN} commands to a file.
1337 There are several commands to control @value{GDBN}'s logging.
1341 @item set logging on
1343 @item set logging off
1345 @cindex logging file name
1346 @item set logging file @var{file}
1347 Change the name of the current logfile. The default logfile is @file{gdb.txt}.
1348 @item set logging overwrite [on|off]
1349 By default, @value{GDBN} will append to the logfile. Set @code{overwrite} if
1350 you want @code{set logging on} to overwrite the logfile instead.
1351 @item set logging redirect [on|off]
1352 By default, @value{GDBN} output will go to both the terminal and the logfile.
1353 Set @code{redirect} if you want output to go only to the log file.
1354 @kindex show logging
1356 Show the current values of the logging settings.
1360 @chapter @value{GDBN} Commands
1362 You can abbreviate a @value{GDBN} command to the first few letters of the command
1363 name, if that abbreviation is unambiguous; and you can repeat certain
1364 @value{GDBN} commands by typing just @key{RET}. You can also use the @key{TAB}
1365 key to get @value{GDBN} to fill out the rest of a word in a command (or to
1366 show you the alternatives available, if there is more than one possibility).
1369 * Command Syntax:: How to give commands to @value{GDBN}
1370 * Completion:: Command completion
1371 * Help:: How to ask @value{GDBN} for help
1374 @node Command Syntax
1375 @section Command Syntax
1377 A @value{GDBN} command is a single line of input. There is no limit on
1378 how long it can be. It starts with a command name, which is followed by
1379 arguments whose meaning depends on the command name. For example, the
1380 command @code{step} accepts an argument which is the number of times to
1381 step, as in @samp{step 5}. You can also use the @code{step} command
1382 with no arguments. Some commands do not allow any arguments.
1384 @cindex abbreviation
1385 @value{GDBN} command names may always be truncated if that abbreviation is
1386 unambiguous. Other possible command abbreviations are listed in the
1387 documentation for individual commands. In some cases, even ambiguous
1388 abbreviations are allowed; for example, @code{s} is specially defined as
1389 equivalent to @code{step} even though there are other commands whose
1390 names start with @code{s}. You can test abbreviations by using them as
1391 arguments to the @code{help} command.
1393 @cindex repeating commands
1394 @kindex RET @r{(repeat last command)}
1395 A blank line as input to @value{GDBN} (typing just @key{RET}) means to
1396 repeat the previous command. Certain commands (for example, @code{run})
1397 will not repeat this way; these are commands whose unintentional
1398 repetition might cause trouble and which you are unlikely to want to
1399 repeat. User-defined commands can disable this feature; see
1400 @ref{Define, dont-repeat}.
1402 The @code{list} and @code{x} commands, when you repeat them with
1403 @key{RET}, construct new arguments rather than repeating
1404 exactly as typed. This permits easy scanning of source or memory.
1406 @value{GDBN} can also use @key{RET} in another way: to partition lengthy
1407 output, in a way similar to the common utility @code{more}
1408 (@pxref{Screen Size,,Screen Size}). Since it is easy to press one
1409 @key{RET} too many in this situation, @value{GDBN} disables command
1410 repetition after any command that generates this sort of display.
1412 @kindex # @r{(a comment)}
1414 Any text from a @kbd{#} to the end of the line is a comment; it does
1415 nothing. This is useful mainly in command files (@pxref{Command
1416 Files,,Command Files}).
1418 @cindex repeating command sequences
1419 @kindex Ctrl-o @r{(operate-and-get-next)}
1420 The @kbd{Ctrl-o} binding is useful for repeating a complex sequence of
1421 commands. This command accepts the current line, like @key{RET}, and
1422 then fetches the next line relative to the current line from the history
1426 @section Command Completion
1429 @cindex word completion
1430 @value{GDBN} can fill in the rest of a word in a command for you, if there is
1431 only one possibility; it can also show you what the valid possibilities
1432 are for the next word in a command, at any time. This works for @value{GDBN}
1433 commands, @value{GDBN} subcommands, and the names of symbols in your program.
1435 Press the @key{TAB} key whenever you want @value{GDBN} to fill out the rest
1436 of a word. If there is only one possibility, @value{GDBN} fills in the
1437 word, and waits for you to finish the command (or press @key{RET} to
1438 enter it). For example, if you type
1440 @c FIXME "@key" does not distinguish its argument sufficiently to permit
1441 @c complete accuracy in these examples; space introduced for clarity.
1442 @c If texinfo enhancements make it unnecessary, it would be nice to
1443 @c replace " @key" by "@key" in the following...
1445 (@value{GDBP}) info bre @key{TAB}
1449 @value{GDBN} fills in the rest of the word @samp{breakpoints}, since that is
1450 the only @code{info} subcommand beginning with @samp{bre}:
1453 (@value{GDBP}) info breakpoints
1457 You can either press @key{RET} at this point, to run the @code{info
1458 breakpoints} command, or backspace and enter something else, if
1459 @samp{breakpoints} does not look like the command you expected. (If you
1460 were sure you wanted @code{info breakpoints} in the first place, you
1461 might as well just type @key{RET} immediately after @samp{info bre},
1462 to exploit command abbreviations rather than command completion).
1464 If there is more than one possibility for the next word when you press
1465 @key{TAB}, @value{GDBN} sounds a bell. You can either supply more
1466 characters and try again, or just press @key{TAB} a second time;
1467 @value{GDBN} displays all the possible completions for that word. For
1468 example, you might want to set a breakpoint on a subroutine whose name
1469 begins with @samp{make_}, but when you type @kbd{b make_@key{TAB}} @value{GDBN}
1470 just sounds the bell. Typing @key{TAB} again displays all the
1471 function names in your program that begin with those characters, for
1475 (@value{GDBP}) b make_ @key{TAB}
1476 @exdent @value{GDBN} sounds bell; press @key{TAB} again, to see:
1477 make_a_section_from_file make_environ
1478 make_abs_section make_function_type
1479 make_blockvector make_pointer_type
1480 make_cleanup make_reference_type
1481 make_command make_symbol_completion_list
1482 (@value{GDBP}) b make_
1486 After displaying the available possibilities, @value{GDBN} copies your
1487 partial input (@samp{b make_} in the example) so you can finish the
1490 If you just want to see the list of alternatives in the first place, you
1491 can press @kbd{M-?} rather than pressing @key{TAB} twice. @kbd{M-?}
1492 means @kbd{@key{META} ?}. You can type this either by holding down a
1493 key designated as the @key{META} shift on your keyboard (if there is
1494 one) while typing @kbd{?}, or as @key{ESC} followed by @kbd{?}.
1496 @cindex quotes in commands
1497 @cindex completion of quoted strings
1498 Sometimes the string you need, while logically a ``word'', may contain
1499 parentheses or other characters that @value{GDBN} normally excludes from
1500 its notion of a word. To permit word completion to work in this
1501 situation, you may enclose words in @code{'} (single quote marks) in
1502 @value{GDBN} commands.
1504 The most likely situation where you might need this is in typing the
1505 name of a C@t{++} function. This is because C@t{++} allows function
1506 overloading (multiple definitions of the same function, distinguished
1507 by argument type). For example, when you want to set a breakpoint you
1508 may need to distinguish whether you mean the version of @code{name}
1509 that takes an @code{int} parameter, @code{name(int)}, or the version
1510 that takes a @code{float} parameter, @code{name(float)}. To use the
1511 word-completion facilities in this situation, type a single quote
1512 @code{'} at the beginning of the function name. This alerts
1513 @value{GDBN} that it may need to consider more information than usual
1514 when you press @key{TAB} or @kbd{M-?} to request word completion:
1517 (@value{GDBP}) b 'bubble( @kbd{M-?}
1518 bubble(double,double) bubble(int,int)
1519 (@value{GDBP}) b 'bubble(
1522 In some cases, @value{GDBN} can tell that completing a name requires using
1523 quotes. When this happens, @value{GDBN} inserts the quote for you (while
1524 completing as much as it can) if you do not type the quote in the first
1528 (@value{GDBP}) b bub @key{TAB}
1529 @exdent @value{GDBN} alters your input line to the following, and rings a bell:
1530 (@value{GDBP}) b 'bubble(
1534 In general, @value{GDBN} can tell that a quote is needed (and inserts it) if
1535 you have not yet started typing the argument list when you ask for
1536 completion on an overloaded symbol.
1538 For more information about overloaded functions, see @ref{C Plus Plus
1539 Expressions, ,C@t{++} Expressions}. You can use the command @code{set
1540 overload-resolution off} to disable overload resolution;
1541 see @ref{Debugging C Plus Plus, ,@value{GDBN} Features for C@t{++}}.
1543 @cindex completion of structure field names
1544 @cindex structure field name completion
1545 @cindex completion of union field names
1546 @cindex union field name completion
1547 When completing in an expression which looks up a field in a
1548 structure, @value{GDBN} also tries@footnote{The completer can be
1549 confused by certain kinds of invalid expressions. Also, it only
1550 examines the static type of the expression, not the dynamic type.} to
1551 limit completions to the field names available in the type of the
1555 (@value{GDBP}) p gdb_stdout.@kbd{M-?}
1556 magic to_delete to_fputs to_put to_rewind
1557 to_data to_flush to_isatty to_read to_write
1561 This is because the @code{gdb_stdout} is a variable of the type
1562 @code{struct ui_file} that is defined in @value{GDBN} sources as
1569 ui_file_flush_ftype *to_flush;
1570 ui_file_write_ftype *to_write;
1571 ui_file_fputs_ftype *to_fputs;
1572 ui_file_read_ftype *to_read;
1573 ui_file_delete_ftype *to_delete;
1574 ui_file_isatty_ftype *to_isatty;
1575 ui_file_rewind_ftype *to_rewind;
1576 ui_file_put_ftype *to_put;
1583 @section Getting Help
1584 @cindex online documentation
1587 You can always ask @value{GDBN} itself for information on its commands,
1588 using the command @code{help}.
1591 @kindex h @r{(@code{help})}
1594 You can use @code{help} (abbreviated @code{h}) with no arguments to
1595 display a short list of named classes of commands:
1599 List of classes of commands:
1601 aliases -- Aliases of other commands
1602 breakpoints -- Making program stop at certain points
1603 data -- Examining data
1604 files -- Specifying and examining files
1605 internals -- Maintenance commands
1606 obscure -- Obscure features
1607 running -- Running the program
1608 stack -- Examining the stack
1609 status -- Status inquiries
1610 support -- Support facilities
1611 tracepoints -- Tracing of program execution without
1612 stopping the program
1613 user-defined -- User-defined commands
1615 Type "help" followed by a class name for a list of
1616 commands in that class.
1617 Type "help" followed by command name for full
1619 Command name abbreviations are allowed if unambiguous.
1622 @c the above line break eliminates huge line overfull...
1624 @item help @var{class}
1625 Using one of the general help classes as an argument, you can get a
1626 list of the individual commands in that class. For example, here is the
1627 help display for the class @code{status}:
1630 (@value{GDBP}) help status
1635 @c Line break in "show" line falsifies real output, but needed
1636 @c to fit in smallbook page size.
1637 info -- Generic command for showing things
1638 about the program being debugged
1639 show -- Generic command for showing things
1642 Type "help" followed by command name for full
1644 Command name abbreviations are allowed if unambiguous.
1648 @item help @var{command}
1649 With a command name as @code{help} argument, @value{GDBN} displays a
1650 short paragraph on how to use that command.
1653 @item apropos @var{args}
1654 The @code{apropos} command searches through all of the @value{GDBN}
1655 commands, and their documentation, for the regular expression specified in
1656 @var{args}. It prints out all matches found. For example:
1667 set symbol-reloading -- Set dynamic symbol table reloading
1668 multiple times in one run
1669 show symbol-reloading -- Show dynamic symbol table reloading
1670 multiple times in one run
1675 @item complete @var{args}
1676 The @code{complete @var{args}} command lists all the possible completions
1677 for the beginning of a command. Use @var{args} to specify the beginning of the
1678 command you want completed. For example:
1684 @noindent results in:
1695 @noindent This is intended for use by @sc{gnu} Emacs.
1698 In addition to @code{help}, you can use the @value{GDBN} commands @code{info}
1699 and @code{show} to inquire about the state of your program, or the state
1700 of @value{GDBN} itself. Each command supports many topics of inquiry; this
1701 manual introduces each of them in the appropriate context. The listings
1702 under @code{info} and under @code{show} in the Index point to
1703 all the sub-commands. @xref{Index}.
1708 @kindex i @r{(@code{info})}
1710 This command (abbreviated @code{i}) is for describing the state of your
1711 program. For example, you can show the arguments passed to a function
1712 with @code{info args}, list the registers currently in use with @code{info
1713 registers}, or list the breakpoints you have set with @code{info breakpoints}.
1714 You can get a complete list of the @code{info} sub-commands with
1715 @w{@code{help info}}.
1719 You can assign the result of an expression to an environment variable with
1720 @code{set}. For example, you can set the @value{GDBN} prompt to a $-sign with
1721 @code{set prompt $}.
1725 In contrast to @code{info}, @code{show} is for describing the state of
1726 @value{GDBN} itself.
1727 You can change most of the things you can @code{show}, by using the
1728 related command @code{set}; for example, you can control what number
1729 system is used for displays with @code{set radix}, or simply inquire
1730 which is currently in use with @code{show radix}.
1733 To display all the settable parameters and their current
1734 values, you can use @code{show} with no arguments; you may also use
1735 @code{info set}. Both commands produce the same display.
1736 @c FIXME: "info set" violates the rule that "info" is for state of
1737 @c FIXME...program. Ck w/ GNU: "info set" to be called something else,
1738 @c FIXME...or change desc of rule---eg "state of prog and debugging session"?
1742 Here are three miscellaneous @code{show} subcommands, all of which are
1743 exceptional in lacking corresponding @code{set} commands:
1746 @kindex show version
1747 @cindex @value{GDBN} version number
1749 Show what version of @value{GDBN} is running. You should include this
1750 information in @value{GDBN} bug-reports. If multiple versions of
1751 @value{GDBN} are in use at your site, you may need to determine which
1752 version of @value{GDBN} you are running; as @value{GDBN} evolves, new
1753 commands are introduced, and old ones may wither away. Also, many
1754 system vendors ship variant versions of @value{GDBN}, and there are
1755 variant versions of @value{GDBN} in @sc{gnu}/Linux distributions as well.
1756 The version number is the same as the one announced when you start
1759 @kindex show copying
1760 @kindex info copying
1761 @cindex display @value{GDBN} copyright
1764 Display information about permission for copying @value{GDBN}.
1766 @kindex show warranty
1767 @kindex info warranty
1769 @itemx info warranty
1770 Display the @sc{gnu} ``NO WARRANTY'' statement, or a warranty,
1771 if your version of @value{GDBN} comes with one.
1776 @chapter Running Programs Under @value{GDBN}
1778 When you run a program under @value{GDBN}, you must first generate
1779 debugging information when you compile it.
1781 You may start @value{GDBN} with its arguments, if any, in an environment
1782 of your choice. If you are doing native debugging, you may redirect
1783 your program's input and output, debug an already running process, or
1784 kill a child process.
1787 * Compilation:: Compiling for debugging
1788 * Starting:: Starting your program
1789 * Arguments:: Your program's arguments
1790 * Environment:: Your program's environment
1792 * Working Directory:: Your program's working directory
1793 * Input/Output:: Your program's input and output
1794 * Attach:: Debugging an already-running process
1795 * Kill Process:: Killing the child process
1797 * Inferiors and Programs:: Debugging multiple inferiors and programs
1798 * Threads:: Debugging programs with multiple threads
1799 * Forks:: Debugging forks
1800 * Checkpoint/Restart:: Setting a @emph{bookmark} to return to later
1804 @section Compiling for Debugging
1806 In order to debug a program effectively, you need to generate
1807 debugging information when you compile it. This debugging information
1808 is stored in the object file; it describes the data type of each
1809 variable or function and the correspondence between source line numbers
1810 and addresses in the executable code.
1812 To request debugging information, specify the @samp{-g} option when you run
1815 Programs that are to be shipped to your customers are compiled with
1816 optimizations, using the @samp{-O} compiler option. However, some
1817 compilers are unable to handle the @samp{-g} and @samp{-O} options
1818 together. Using those compilers, you cannot generate optimized
1819 executables containing debugging information.
1821 @value{NGCC}, the @sc{gnu} C/C@t{++} compiler, supports @samp{-g} with or
1822 without @samp{-O}, making it possible to debug optimized code. We
1823 recommend that you @emph{always} use @samp{-g} whenever you compile a
1824 program. You may think your program is correct, but there is no sense
1825 in pushing your luck. For more information, see @ref{Optimized Code}.
1827 Older versions of the @sc{gnu} C compiler permitted a variant option
1828 @w{@samp{-gg}} for debugging information. @value{GDBN} no longer supports this
1829 format; if your @sc{gnu} C compiler has this option, do not use it.
1831 @value{GDBN} knows about preprocessor macros and can show you their
1832 expansion (@pxref{Macros}). Most compilers do not include information
1833 about preprocessor macros in the debugging information if you specify
1834 the @option{-g} flag alone, because this information is rather large.
1835 Version 3.1 and later of @value{NGCC}, the @sc{gnu} C compiler,
1836 provides macro information if you specify the options
1837 @option{-gdwarf-2} and @option{-g3}; the former option requests
1838 debugging information in the Dwarf 2 format, and the latter requests
1839 ``extra information''. In the future, we hope to find more compact
1840 ways to represent macro information, so that it can be included with
1845 @section Starting your Program
1851 @kindex r @r{(@code{run})}
1854 Use the @code{run} command to start your program under @value{GDBN}.
1855 You must first specify the program name (except on VxWorks) with an
1856 argument to @value{GDBN} (@pxref{Invocation, ,Getting In and Out of
1857 @value{GDBN}}), or by using the @code{file} or @code{exec-file} command
1858 (@pxref{Files, ,Commands to Specify Files}).
1862 If you are running your program in an execution environment that
1863 supports processes, @code{run} creates an inferior process and makes
1864 that process run your program. In some environments without processes,
1865 @code{run} jumps to the start of your program. Other targets,
1866 like @samp{remote}, are always running. If you get an error
1867 message like this one:
1870 The "remote" target does not support "run".
1871 Try "help target" or "continue".
1875 then use @code{continue} to run your program. You may need @code{load}
1876 first (@pxref{load}).
1878 The execution of a program is affected by certain information it
1879 receives from its superior. @value{GDBN} provides ways to specify this
1880 information, which you must do @emph{before} starting your program. (You
1881 can change it after starting your program, but such changes only affect
1882 your program the next time you start it.) This information may be
1883 divided into four categories:
1886 @item The @emph{arguments.}
1887 Specify the arguments to give your program as the arguments of the
1888 @code{run} command. If a shell is available on your target, the shell
1889 is used to pass the arguments, so that you may use normal conventions
1890 (such as wildcard expansion or variable substitution) in describing
1892 In Unix systems, you can control which shell is used with the
1893 @code{SHELL} environment variable.
1894 @xref{Arguments, ,Your Program's Arguments}.
1896 @item The @emph{environment.}
1897 Your program normally inherits its environment from @value{GDBN}, but you can
1898 use the @value{GDBN} commands @code{set environment} and @code{unset
1899 environment} to change parts of the environment that affect
1900 your program. @xref{Environment, ,Your Program's Environment}.
1902 @item The @emph{working directory.}
1903 Your program inherits its working directory from @value{GDBN}. You can set
1904 the @value{GDBN} working directory with the @code{cd} command in @value{GDBN}.
1905 @xref{Working Directory, ,Your Program's Working Directory}.
1907 @item The @emph{standard input and output.}
1908 Your program normally uses the same device for standard input and
1909 standard output as @value{GDBN} is using. You can redirect input and output
1910 in the @code{run} command line, or you can use the @code{tty} command to
1911 set a different device for your program.
1912 @xref{Input/Output, ,Your Program's Input and Output}.
1915 @emph{Warning:} While input and output redirection work, you cannot use
1916 pipes to pass the output of the program you are debugging to another
1917 program; if you attempt this, @value{GDBN} is likely to wind up debugging the
1921 When you issue the @code{run} command, your program begins to execute
1922 immediately. @xref{Stopping, ,Stopping and Continuing}, for discussion
1923 of how to arrange for your program to stop. Once your program has
1924 stopped, you may call functions in your program, using the @code{print}
1925 or @code{call} commands. @xref{Data, ,Examining Data}.
1927 If the modification time of your symbol file has changed since the last
1928 time @value{GDBN} read its symbols, @value{GDBN} discards its symbol
1929 table, and reads it again. When it does this, @value{GDBN} tries to retain
1930 your current breakpoints.
1935 @cindex run to main procedure
1936 The name of the main procedure can vary from language to language.
1937 With C or C@t{++}, the main procedure name is always @code{main}, but
1938 other languages such as Ada do not require a specific name for their
1939 main procedure. The debugger provides a convenient way to start the
1940 execution of the program and to stop at the beginning of the main
1941 procedure, depending on the language used.
1943 The @samp{start} command does the equivalent of setting a temporary
1944 breakpoint at the beginning of the main procedure and then invoking
1945 the @samp{run} command.
1947 @cindex elaboration phase
1948 Some programs contain an @dfn{elaboration} phase where some startup code is
1949 executed before the main procedure is called. This depends on the
1950 languages used to write your program. In C@t{++}, for instance,
1951 constructors for static and global objects are executed before
1952 @code{main} is called. It is therefore possible that the debugger stops
1953 before reaching the main procedure. However, the temporary breakpoint
1954 will remain to halt execution.
1956 Specify the arguments to give to your program as arguments to the
1957 @samp{start} command. These arguments will be given verbatim to the
1958 underlying @samp{run} command. Note that the same arguments will be
1959 reused if no argument is provided during subsequent calls to
1960 @samp{start} or @samp{run}.
1962 It is sometimes necessary to debug the program during elaboration. In
1963 these cases, using the @code{start} command would stop the execution of
1964 your program too late, as the program would have already completed the
1965 elaboration phase. Under these circumstances, insert breakpoints in your
1966 elaboration code before running your program.
1968 @kindex set exec-wrapper
1969 @item set exec-wrapper @var{wrapper}
1970 @itemx show exec-wrapper
1971 @itemx unset exec-wrapper
1972 When @samp{exec-wrapper} is set, the specified wrapper is used to
1973 launch programs for debugging. @value{GDBN} starts your program
1974 with a shell command of the form @kbd{exec @var{wrapper}
1975 @var{program}}. Quoting is added to @var{program} and its
1976 arguments, but not to @var{wrapper}, so you should add quotes if
1977 appropriate for your shell. The wrapper runs until it executes
1978 your program, and then @value{GDBN} takes control.
1980 You can use any program that eventually calls @code{execve} with
1981 its arguments as a wrapper. Several standard Unix utilities do
1982 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
1983 with @code{exec "$@@"} will also work.
1985 For example, you can use @code{env} to pass an environment variable to
1986 the debugged program, without setting the variable in your shell's
1990 (@value{GDBP}) set exec-wrapper env 'LD_PRELOAD=libtest.so'
1994 This command is available when debugging locally on most targets, excluding
1995 @sc{djgpp}, Cygwin, MS Windows, and QNX Neutrino.
1997 @kindex set disable-randomization
1998 @item set disable-randomization
1999 @itemx set disable-randomization on
2000 This option (enabled by default in @value{GDBN}) will turn off the native
2001 randomization of the virtual address space of the started program. This option
2002 is useful for multiple debugging sessions to make the execution better
2003 reproducible and memory addresses reusable across debugging sessions.
2005 This feature is implemented only on @sc{gnu}/Linux. You can get the same
2009 (@value{GDBP}) set exec-wrapper setarch `uname -m` -R
2012 @item set disable-randomization off
2013 Leave the behavior of the started executable unchanged. Some bugs rear their
2014 ugly heads only when the program is loaded at certain addresses. If your bug
2015 disappears when you run the program under @value{GDBN}, that might be because
2016 @value{GDBN} by default disables the address randomization on platforms, such
2017 as @sc{gnu}/Linux, which do that for stand-alone programs. Use @kbd{set
2018 disable-randomization off} to try to reproduce such elusive bugs.
2020 The virtual address space randomization is implemented only on @sc{gnu}/Linux.
2021 It protects the programs against some kinds of security attacks. In these
2022 cases the attacker needs to know the exact location of a concrete executable
2023 code. Randomizing its location makes it impossible to inject jumps misusing
2024 a code at its expected addresses.
2026 Prelinking shared libraries provides a startup performance advantage but it
2027 makes addresses in these libraries predictable for privileged processes by
2028 having just unprivileged access at the target system. Reading the shared
2029 library binary gives enough information for assembling the malicious code
2030 misusing it. Still even a prelinked shared library can get loaded at a new
2031 random address just requiring the regular relocation process during the
2032 startup. Shared libraries not already prelinked are always loaded at
2033 a randomly chosen address.
2035 Position independent executables (PIE) contain position independent code
2036 similar to the shared libraries and therefore such executables get loaded at
2037 a randomly chosen address upon startup. PIE executables always load even
2038 already prelinked shared libraries at a random address. You can build such
2039 executable using @command{gcc -fPIE -pie}.
2041 Heap (malloc storage), stack and custom mmap areas are always placed randomly
2042 (as long as the randomization is enabled).
2044 @item show disable-randomization
2045 Show the current setting of the explicit disable of the native randomization of
2046 the virtual address space of the started program.
2051 @section Your Program's Arguments
2053 @cindex arguments (to your program)
2054 The arguments to your program can be specified by the arguments of the
2056 They are passed to a shell, which expands wildcard characters and
2057 performs redirection of I/O, and thence to your program. Your
2058 @code{SHELL} environment variable (if it exists) specifies what shell
2059 @value{GDBN} uses. If you do not define @code{SHELL}, @value{GDBN} uses
2060 the default shell (@file{/bin/sh} on Unix).
2062 On non-Unix systems, the program is usually invoked directly by
2063 @value{GDBN}, which emulates I/O redirection via the appropriate system
2064 calls, and the wildcard characters are expanded by the startup code of
2065 the program, not by the shell.
2067 @code{run} with no arguments uses the same arguments used by the previous
2068 @code{run}, or those set by the @code{set args} command.
2073 Specify the arguments to be used the next time your program is run. If
2074 @code{set args} has no arguments, @code{run} executes your program
2075 with no arguments. Once you have run your program with arguments,
2076 using @code{set args} before the next @code{run} is the only way to run
2077 it again without arguments.
2081 Show the arguments to give your program when it is started.
2085 @section Your Program's Environment
2087 @cindex environment (of your program)
2088 The @dfn{environment} consists of a set of environment variables and
2089 their values. Environment variables conventionally record such things as
2090 your user name, your home directory, your terminal type, and your search
2091 path for programs to run. Usually you set up environment variables with
2092 the shell and they are inherited by all the other programs you run. When
2093 debugging, it can be useful to try running your program with a modified
2094 environment without having to start @value{GDBN} over again.
2098 @item path @var{directory}
2099 Add @var{directory} to the front of the @code{PATH} environment variable
2100 (the search path for executables) that will be passed to your program.
2101 The value of @code{PATH} used by @value{GDBN} does not change.
2102 You may specify several directory names, separated by whitespace or by a
2103 system-dependent separator character (@samp{:} on Unix, @samp{;} on
2104 MS-DOS and MS-Windows). If @var{directory} is already in the path, it
2105 is moved to the front, so it is searched sooner.
2107 You can use the string @samp{$cwd} to refer to whatever is the current
2108 working directory at the time @value{GDBN} searches the path. If you
2109 use @samp{.} instead, it refers to the directory where you executed the
2110 @code{path} command. @value{GDBN} replaces @samp{.} in the
2111 @var{directory} argument (with the current path) before adding
2112 @var{directory} to the search path.
2113 @c 'path' is explicitly nonrepeatable, but RMS points out it is silly to
2114 @c document that, since repeating it would be a no-op.
2118 Display the list of search paths for executables (the @code{PATH}
2119 environment variable).
2121 @kindex show environment
2122 @item show environment @r{[}@var{varname}@r{]}
2123 Print the value of environment variable @var{varname} to be given to
2124 your program when it starts. If you do not supply @var{varname},
2125 print the names and values of all environment variables to be given to
2126 your program. You can abbreviate @code{environment} as @code{env}.
2128 @kindex set environment
2129 @item set environment @var{varname} @r{[}=@var{value}@r{]}
2130 Set environment variable @var{varname} to @var{value}. The value
2131 changes for your program only, not for @value{GDBN} itself. @var{value} may
2132 be any string; the values of environment variables are just strings, and
2133 any interpretation is supplied by your program itself. The @var{value}
2134 parameter is optional; if it is eliminated, the variable is set to a
2136 @c "any string" here does not include leading, trailing
2137 @c blanks. Gnu asks: does anyone care?
2139 For example, this command:
2146 tells the debugged program, when subsequently run, that its user is named
2147 @samp{foo}. (The spaces around @samp{=} are used for clarity here; they
2148 are not actually required.)
2150 @kindex unset environment
2151 @item unset environment @var{varname}
2152 Remove variable @var{varname} from the environment to be passed to your
2153 program. This is different from @samp{set env @var{varname} =};
2154 @code{unset environment} removes the variable from the environment,
2155 rather than assigning it an empty value.
2158 @emph{Warning:} On Unix systems, @value{GDBN} runs your program using
2160 by your @code{SHELL} environment variable if it exists (or
2161 @code{/bin/sh} if not). If your @code{SHELL} variable names a shell
2162 that runs an initialization file---such as @file{.cshrc} for C-shell, or
2163 @file{.bashrc} for BASH---any variables you set in that file affect
2164 your program. You may wish to move setting of environment variables to
2165 files that are only run when you sign on, such as @file{.login} or
2168 @node Working Directory
2169 @section Your Program's Working Directory
2171 @cindex working directory (of your program)
2172 Each time you start your program with @code{run}, it inherits its
2173 working directory from the current working directory of @value{GDBN}.
2174 The @value{GDBN} working directory is initially whatever it inherited
2175 from its parent process (typically the shell), but you can specify a new
2176 working directory in @value{GDBN} with the @code{cd} command.
2178 The @value{GDBN} working directory also serves as a default for the commands
2179 that specify files for @value{GDBN} to operate on. @xref{Files, ,Commands to
2184 @cindex change working directory
2185 @item cd @var{directory}
2186 Set the @value{GDBN} working directory to @var{directory}.
2190 Print the @value{GDBN} working directory.
2193 It is generally impossible to find the current working directory of
2194 the process being debugged (since a program can change its directory
2195 during its run). If you work on a system where @value{GDBN} is
2196 configured with the @file{/proc} support, you can use the @code{info
2197 proc} command (@pxref{SVR4 Process Information}) to find out the
2198 current working directory of the debuggee.
2201 @section Your Program's Input and Output
2206 By default, the program you run under @value{GDBN} does input and output to
2207 the same terminal that @value{GDBN} uses. @value{GDBN} switches the terminal
2208 to its own terminal modes to interact with you, but it records the terminal
2209 modes your program was using and switches back to them when you continue
2210 running your program.
2213 @kindex info terminal
2215 Displays information recorded by @value{GDBN} about the terminal modes your
2219 You can redirect your program's input and/or output using shell
2220 redirection with the @code{run} command. For example,
2227 starts your program, diverting its output to the file @file{outfile}.
2230 @cindex controlling terminal
2231 Another way to specify where your program should do input and output is
2232 with the @code{tty} command. This command accepts a file name as
2233 argument, and causes this file to be the default for future @code{run}
2234 commands. It also resets the controlling terminal for the child
2235 process, for future @code{run} commands. For example,
2242 directs that processes started with subsequent @code{run} commands
2243 default to do input and output on the terminal @file{/dev/ttyb} and have
2244 that as their controlling terminal.
2246 An explicit redirection in @code{run} overrides the @code{tty} command's
2247 effect on the input/output device, but not its effect on the controlling
2250 When you use the @code{tty} command or redirect input in the @code{run}
2251 command, only the input @emph{for your program} is affected. The input
2252 for @value{GDBN} still comes from your terminal. @code{tty} is an alias
2253 for @code{set inferior-tty}.
2255 @cindex inferior tty
2256 @cindex set inferior controlling terminal
2257 You can use the @code{show inferior-tty} command to tell @value{GDBN} to
2258 display the name of the terminal that will be used for future runs of your
2262 @item set inferior-tty /dev/ttyb
2263 @kindex set inferior-tty
2264 Set the tty for the program being debugged to /dev/ttyb.
2266 @item show inferior-tty
2267 @kindex show inferior-tty
2268 Show the current tty for the program being debugged.
2272 @section Debugging an Already-running Process
2277 @item attach @var{process-id}
2278 This command attaches to a running process---one that was started
2279 outside @value{GDBN}. (@code{info files} shows your active
2280 targets.) The command takes as argument a process ID. The usual way to
2281 find out the @var{process-id} of a Unix process is with the @code{ps} utility,
2282 or with the @samp{jobs -l} shell command.
2284 @code{attach} does not repeat if you press @key{RET} a second time after
2285 executing the command.
2288 To use @code{attach}, your program must be running in an environment
2289 which supports processes; for example, @code{attach} does not work for
2290 programs on bare-board targets that lack an operating system. You must
2291 also have permission to send the process a signal.
2293 When you use @code{attach}, the debugger finds the program running in
2294 the process first by looking in the current working directory, then (if
2295 the program is not found) by using the source file search path
2296 (@pxref{Source Path, ,Specifying Source Directories}). You can also use
2297 the @code{file} command to load the program. @xref{Files, ,Commands to
2300 The first thing @value{GDBN} does after arranging to debug the specified
2301 process is to stop it. You can examine and modify an attached process
2302 with all the @value{GDBN} commands that are ordinarily available when
2303 you start processes with @code{run}. You can insert breakpoints; you
2304 can step and continue; you can modify storage. If you would rather the
2305 process continue running, you may use the @code{continue} command after
2306 attaching @value{GDBN} to the process.
2311 When you have finished debugging the attached process, you can use the
2312 @code{detach} command to release it from @value{GDBN} control. Detaching
2313 the process continues its execution. After the @code{detach} command,
2314 that process and @value{GDBN} become completely independent once more, and you
2315 are ready to @code{attach} another process or start one with @code{run}.
2316 @code{detach} does not repeat if you press @key{RET} again after
2317 executing the command.
2320 If you exit @value{GDBN} while you have an attached process, you detach
2321 that process. If you use the @code{run} command, you kill that process.
2322 By default, @value{GDBN} asks for confirmation if you try to do either of these
2323 things; you can control whether or not you need to confirm by using the
2324 @code{set confirm} command (@pxref{Messages/Warnings, ,Optional Warnings and
2328 @section Killing the Child Process
2333 Kill the child process in which your program is running under @value{GDBN}.
2336 This command is useful if you wish to debug a core dump instead of a
2337 running process. @value{GDBN} ignores any core dump file while your program
2340 On some operating systems, a program cannot be executed outside @value{GDBN}
2341 while you have breakpoints set on it inside @value{GDBN}. You can use the
2342 @code{kill} command in this situation to permit running your program
2343 outside the debugger.
2345 The @code{kill} command is also useful if you wish to recompile and
2346 relink your program, since on many systems it is impossible to modify an
2347 executable file while it is running in a process. In this case, when you
2348 next type @code{run}, @value{GDBN} notices that the file has changed, and
2349 reads the symbol table again (while trying to preserve your current
2350 breakpoint settings).
2352 @node Inferiors and Programs
2353 @section Debugging Multiple Inferiors and Programs
2355 @value{GDBN} lets you run and debug multiple programs in a single
2356 session. In addition, @value{GDBN} on some systems may let you run
2357 several programs simultaneously (otherwise you have to exit from one
2358 before starting another). In the most general case, you can have
2359 multiple threads of execution in each of multiple processes, launched
2360 from multiple executables.
2363 @value{GDBN} represents the state of each program execution with an
2364 object called an @dfn{inferior}. An inferior typically corresponds to
2365 a process, but is more general and applies also to targets that do not
2366 have processes. Inferiors may be created before a process runs, and
2367 may be retained after a process exits. Inferiors have unique
2368 identifiers that are different from process ids. Usually each
2369 inferior will also have its own distinct address space, although some
2370 embedded targets may have several inferiors running in different parts
2371 of a single address space. Each inferior may in turn have multiple
2372 threads running in it.
2374 To find out what inferiors exist at any moment, use @w{@code{info
2378 @kindex info inferiors
2379 @item info inferiors
2380 Print a list of all inferiors currently being managed by @value{GDBN}.
2382 @value{GDBN} displays for each inferior (in this order):
2386 the inferior number assigned by @value{GDBN}
2389 the target system's inferior identifier
2392 the name of the executable the inferior is running.
2397 An asterisk @samp{*} preceding the @value{GDBN} inferior number
2398 indicates the current inferior.
2402 @c end table here to get a little more width for example
2405 (@value{GDBP}) info inferiors
2406 Num Description Executable
2407 2 process 2307 hello
2408 * 1 process 3401 goodbye
2411 To switch focus between inferiors, use the @code{inferior} command:
2414 @kindex inferior @var{infno}
2415 @item inferior @var{infno}
2416 Make inferior number @var{infno} the current inferior. The argument
2417 @var{infno} is the inferior number assigned by @value{GDBN}, as shown
2418 in the first field of the @samp{info inferiors} display.
2422 You can get multiple executables into a debugging session via the
2423 @code{add-inferior} and @w{@code{clone-inferior}} commands. On some
2424 systems @value{GDBN} can add inferiors to the debug session
2425 automatically by following calls to @code{fork} and @code{exec}. To
2426 remove inferiors from the debugging session use the
2427 @w{@code{remove-inferior}} command.
2430 @kindex add-inferior
2431 @item add-inferior [ -copies @var{n} ] [ -exec @var{executable} ]
2432 Adds @var{n} inferiors to be run using @var{executable} as the
2433 executable. @var{n} defaults to 1. If no executable is specified,
2434 the inferiors begins empty, with no program. You can still assign or
2435 change the program assigned to the inferior at any time by using the
2436 @code{file} command with the executable name as its argument.
2438 @kindex clone-inferior
2439 @item clone-inferior [ -copies @var{n} ] [ @var{infno} ]
2440 Adds @var{n} inferiors ready to execute the same program as inferior
2441 @var{infno}. @var{n} defaults to 1. @var{infno} defaults to the
2442 number of the current inferior. This is a convenient command when you
2443 want to run another instance of the inferior you are debugging.
2446 (@value{GDBP}) info inferiors
2447 Num Description Executable
2448 * 1 process 29964 helloworld
2449 (@value{GDBP}) clone-inferior
2452 (@value{GDBP}) info inferiors
2453 Num Description Executable
2455 * 1 process 29964 helloworld
2458 You can now simply switch focus to inferior 2 and run it.
2460 @kindex remove-inferior
2461 @item remove-inferior @var{infno}
2462 Removes the inferior @var{infno}. It is not possible to remove an
2463 inferior that is running with this command. For those, use the
2464 @code{kill} or @code{detach} command first.
2468 To quit debugging one of the running inferiors that is not the current
2469 inferior, you can either detach from it by using the @w{@code{detach
2470 inferior}} command (allowing it to run independently), or kill it
2471 using the @w{@code{kill inferior}} command:
2474 @kindex detach inferior @var{infno}
2475 @item detach inferior @var{infno}
2476 Detach from the inferior identified by @value{GDBN} inferior number
2477 @var{infno}, and remove it from the inferior list.
2479 @kindex kill inferior @var{infno}
2480 @item kill inferior @var{infno}
2481 Kill the inferior identified by @value{GDBN} inferior number
2482 @var{infno}, and remove it from the inferior list.
2485 After the successful completion of a command such as @code{detach},
2486 @code{detach inferior}, @code{kill} or @code{kill inferior}, or after
2487 a normal process exit, the inferior is still valid and listed with
2488 @code{info inferiors}, ready to be restarted.
2491 To be notified when inferiors are started or exit under @value{GDBN}'s
2492 control use @w{@code{set print inferior-events}}:
2495 @kindex set print inferior-events
2496 @cindex print messages on inferior start and exit
2497 @item set print inferior-events
2498 @itemx set print inferior-events on
2499 @itemx set print inferior-events off
2500 The @code{set print inferior-events} command allows you to enable or
2501 disable printing of messages when @value{GDBN} notices that new
2502 inferiors have started or that inferiors have exited or have been
2503 detached. By default, these messages will not be printed.
2505 @kindex show print inferior-events
2506 @item show print inferior-events
2507 Show whether messages will be printed when @value{GDBN} detects that
2508 inferiors have started, exited or have been detached.
2511 Many commands will work the same with multiple programs as with a
2512 single program: e.g., @code{print myglobal} will simply display the
2513 value of @code{myglobal} in the current inferior.
2516 Occasionaly, when debugging @value{GDBN} itself, it may be useful to
2517 get more info about the relationship of inferiors, programs, address
2518 spaces in a debug session. You can do that with the @w{@code{maint
2519 info program-spaces}} command.
2522 @kindex maint info program-spaces
2523 @item maint info program-spaces
2524 Print a list of all program spaces currently being managed by
2527 @value{GDBN} displays for each program space (in this order):
2531 the program space number assigned by @value{GDBN}
2534 the name of the executable loaded into the program space, with e.g.,
2535 the @code{file} command.
2540 An asterisk @samp{*} preceding the @value{GDBN} program space number
2541 indicates the current program space.
2543 In addition, below each program space line, @value{GDBN} prints extra
2544 information that isn't suitable to display in tabular form. For
2545 example, the list of inferiors bound to the program space.
2548 (@value{GDBP}) maint info program-spaces
2551 Bound inferiors: ID 1 (process 21561)
2555 Here we can see that no inferior is running the program @code{hello},
2556 while @code{process 21561} is running the program @code{goodbye}. On
2557 some targets, it is possible that multiple inferiors are bound to the
2558 same program space. The most common example is that of debugging both
2559 the parent and child processes of a @code{vfork} call. For example,
2562 (@value{GDBP}) maint info program-spaces
2565 Bound inferiors: ID 2 (process 18050), ID 1 (process 18045)
2568 Here, both inferior 2 and inferior 1 are running in the same program
2569 space as a result of inferior 1 having executed a @code{vfork} call.
2573 @section Debugging Programs with Multiple Threads
2575 @cindex threads of execution
2576 @cindex multiple threads
2577 @cindex switching threads
2578 In some operating systems, such as HP-UX and Solaris, a single program
2579 may have more than one @dfn{thread} of execution. The precise semantics
2580 of threads differ from one operating system to another, but in general
2581 the threads of a single program are akin to multiple processes---except
2582 that they share one address space (that is, they can all examine and
2583 modify the same variables). On the other hand, each thread has its own
2584 registers and execution stack, and perhaps private memory.
2586 @value{GDBN} provides these facilities for debugging multi-thread
2590 @item automatic notification of new threads
2591 @item @samp{thread @var{threadno}}, a command to switch among threads
2592 @item @samp{info threads}, a command to inquire about existing threads
2593 @item @samp{thread apply [@var{threadno}] [@var{all}] @var{args}},
2594 a command to apply a command to a list of threads
2595 @item thread-specific breakpoints
2596 @item @samp{set print thread-events}, which controls printing of
2597 messages on thread start and exit.
2598 @item @samp{set libthread-db-search-path @var{path}}, which lets
2599 the user specify which @code{libthread_db} to use if the default choice
2600 isn't compatible with the program.
2604 @emph{Warning:} These facilities are not yet available on every
2605 @value{GDBN} configuration where the operating system supports threads.
2606 If your @value{GDBN} does not support threads, these commands have no
2607 effect. For example, a system without thread support shows no output
2608 from @samp{info threads}, and always rejects the @code{thread} command,
2612 (@value{GDBP}) info threads
2613 (@value{GDBP}) thread 1
2614 Thread ID 1 not known. Use the "info threads" command to
2615 see the IDs of currently known threads.
2617 @c FIXME to implementors: how hard would it be to say "sorry, this GDB
2618 @c doesn't support threads"?
2621 @cindex focus of debugging
2622 @cindex current thread
2623 The @value{GDBN} thread debugging facility allows you to observe all
2624 threads while your program runs---but whenever @value{GDBN} takes
2625 control, one thread in particular is always the focus of debugging.
2626 This thread is called the @dfn{current thread}. Debugging commands show
2627 program information from the perspective of the current thread.
2629 @cindex @code{New} @var{systag} message
2630 @cindex thread identifier (system)
2631 @c FIXME-implementors!! It would be more helpful if the [New...] message
2632 @c included GDB's numeric thread handle, so you could just go to that
2633 @c thread without first checking `info threads'.
2634 Whenever @value{GDBN} detects a new thread in your program, it displays
2635 the target system's identification for the thread with a message in the
2636 form @samp{[New @var{systag}]}. @var{systag} is a thread identifier
2637 whose form varies depending on the particular system. For example, on
2638 @sc{gnu}/Linux, you might see
2641 [New Thread 46912507313328 (LWP 25582)]
2645 when @value{GDBN} notices a new thread. In contrast, on an SGI system,
2646 the @var{systag} is simply something like @samp{process 368}, with no
2649 @c FIXME!! (1) Does the [New...] message appear even for the very first
2650 @c thread of a program, or does it only appear for the
2651 @c second---i.e.@: when it becomes obvious we have a multithread
2653 @c (2) *Is* there necessarily a first thread always? Or do some
2654 @c multithread systems permit starting a program with multiple
2655 @c threads ab initio?
2657 @cindex thread number
2658 @cindex thread identifier (GDB)
2659 For debugging purposes, @value{GDBN} associates its own thread
2660 number---always a single integer---with each thread in your program.
2663 @kindex info threads
2665 Display a summary of all threads currently in your
2666 program. @value{GDBN} displays for each thread (in this order):
2670 the thread number assigned by @value{GDBN}
2673 the target system's thread identifier (@var{systag})
2676 the current stack frame summary for that thread
2680 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2681 indicates the current thread.
2685 @c end table here to get a little more width for example
2688 (@value{GDBP}) info threads
2689 3 process 35 thread 27 0x34e5 in sigpause ()
2690 2 process 35 thread 23 0x34e5 in sigpause ()
2691 * 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
2697 @cindex debugging multithreaded programs (on HP-UX)
2698 @cindex thread identifier (GDB), on HP-UX
2699 For debugging purposes, @value{GDBN} associates its own thread
2700 number---a small integer assigned in thread-creation order---with each
2701 thread in your program.
2703 @cindex @code{New} @var{systag} message, on HP-UX
2704 @cindex thread identifier (system), on HP-UX
2705 @c FIXME-implementors!! It would be more helpful if the [New...] message
2706 @c included GDB's numeric thread handle, so you could just go to that
2707 @c thread without first checking `info threads'.
2708 Whenever @value{GDBN} detects a new thread in your program, it displays
2709 both @value{GDBN}'s thread number and the target system's identification for the thread with a message in the
2710 form @samp{[New @var{systag}]}. @var{systag} is a thread identifier
2711 whose form varies depending on the particular system. For example, on
2715 [New thread 2 (system thread 26594)]
2719 when @value{GDBN} notices a new thread.
2722 @kindex info threads (HP-UX)
2724 Display a summary of all threads currently in your
2725 program. @value{GDBN} displays for each thread (in this order):
2728 @item the thread number assigned by @value{GDBN}
2730 @item the target system's thread identifier (@var{systag})
2732 @item the current stack frame summary for that thread
2736 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2737 indicates the current thread.
2741 @c end table here to get a little more width for example
2744 (@value{GDBP}) info threads
2745 * 3 system thread 26607 worker (wptr=0x7b09c318 "@@") \@*
2747 2 system thread 26606 0x7b0030d8 in __ksleep () \@*
2748 from /usr/lib/libc.2
2749 1 system thread 27905 0x7b003498 in _brk () \@*
2750 from /usr/lib/libc.2
2753 On Solaris, you can display more information about user threads with a
2754 Solaris-specific command:
2757 @item maint info sol-threads
2758 @kindex maint info sol-threads
2759 @cindex thread info (Solaris)
2760 Display info on Solaris user threads.
2764 @kindex thread @var{threadno}
2765 @item thread @var{threadno}
2766 Make thread number @var{threadno} the current thread. The command
2767 argument @var{threadno} is the internal @value{GDBN} thread number, as
2768 shown in the first field of the @samp{info threads} display.
2769 @value{GDBN} responds by displaying the system identifier of the thread
2770 you selected, and its current stack frame summary:
2773 @c FIXME!! This example made up; find a @value{GDBN} w/threads and get real one
2774 (@value{GDBP}) thread 2
2775 [Switching to process 35 thread 23]
2776 0x34e5 in sigpause ()
2780 As with the @samp{[New @dots{}]} message, the form of the text after
2781 @samp{Switching to} depends on your system's conventions for identifying
2784 @kindex thread apply
2785 @cindex apply command to several threads
2786 @item thread apply [@var{threadno}] [@var{all}] @var{command}
2787 The @code{thread apply} command allows you to apply the named
2788 @var{command} to one or more threads. Specify the numbers of the
2789 threads that you want affected with the command argument
2790 @var{threadno}. It can be a single thread number, one of the numbers
2791 shown in the first field of the @samp{info threads} display; or it
2792 could be a range of thread numbers, as in @code{2-4}. To apply a
2793 command to all threads, type @kbd{thread apply all @var{command}}.
2795 @kindex set print thread-events
2796 @cindex print messages on thread start and exit
2797 @item set print thread-events
2798 @itemx set print thread-events on
2799 @itemx set print thread-events off
2800 The @code{set print thread-events} command allows you to enable or
2801 disable printing of messages when @value{GDBN} notices that new threads have
2802 started or that threads have exited. By default, these messages will
2803 be printed if detection of these events is supported by the target.
2804 Note that these messages cannot be disabled on all targets.
2806 @kindex show print thread-events
2807 @item show print thread-events
2808 Show whether messages will be printed when @value{GDBN} detects that threads
2809 have started and exited.
2812 @xref{Thread Stops,,Stopping and Starting Multi-thread Programs}, for
2813 more information about how @value{GDBN} behaves when you stop and start
2814 programs with multiple threads.
2816 @xref{Set Watchpoints,,Setting Watchpoints}, for information about
2817 watchpoints in programs with multiple threads.
2820 @kindex set libthread-db-search-path
2821 @cindex search path for @code{libthread_db}
2822 @item set libthread-db-search-path @r{[}@var{path}@r{]}
2823 If this variable is set, @var{path} is a colon-separated list of
2824 directories @value{GDBN} will use to search for @code{libthread_db}.
2825 If you omit @var{path}, @samp{libthread-db-search-path} will be reset to
2828 On @sc{gnu}/Linux and Solaris systems, @value{GDBN} uses a ``helper''
2829 @code{libthread_db} library to obtain information about threads in the
2830 inferior process. @value{GDBN} will use @samp{libthread-db-search-path}
2831 to find @code{libthread_db}. If that fails, @value{GDBN} will continue
2832 with default system shared library directories, and finally the directory
2833 from which @code{libpthread} was loaded in the inferior process.
2835 For any @code{libthread_db} library @value{GDBN} finds in above directories,
2836 @value{GDBN} attempts to initialize it with the current inferior process.
2837 If this initialization fails (which could happen because of a version
2838 mismatch between @code{libthread_db} and @code{libpthread}), @value{GDBN}
2839 will unload @code{libthread_db}, and continue with the next directory.
2840 If none of @code{libthread_db} libraries initialize successfully,
2841 @value{GDBN} will issue a warning and thread debugging will be disabled.
2843 Setting @code{libthread-db-search-path} is currently implemented
2844 only on some platforms.
2846 @kindex show libthread-db-search-path
2847 @item show libthread-db-search-path
2848 Display current libthread_db search path.
2852 @section Debugging Forks
2854 @cindex fork, debugging programs which call
2855 @cindex multiple processes
2856 @cindex processes, multiple
2857 On most systems, @value{GDBN} has no special support for debugging
2858 programs which create additional processes using the @code{fork}
2859 function. When a program forks, @value{GDBN} will continue to debug the
2860 parent process and the child process will run unimpeded. If you have
2861 set a breakpoint in any code which the child then executes, the child
2862 will get a @code{SIGTRAP} signal which (unless it catches the signal)
2863 will cause it to terminate.
2865 However, if you want to debug the child process there is a workaround
2866 which isn't too painful. Put a call to @code{sleep} in the code which
2867 the child process executes after the fork. It may be useful to sleep
2868 only if a certain environment variable is set, or a certain file exists,
2869 so that the delay need not occur when you don't want to run @value{GDBN}
2870 on the child. While the child is sleeping, use the @code{ps} program to
2871 get its process ID. Then tell @value{GDBN} (a new invocation of
2872 @value{GDBN} if you are also debugging the parent process) to attach to
2873 the child process (@pxref{Attach}). From that point on you can debug
2874 the child process just like any other process which you attached to.
2876 On some systems, @value{GDBN} provides support for debugging programs that
2877 create additional processes using the @code{fork} or @code{vfork} functions.
2878 Currently, the only platforms with this feature are HP-UX (11.x and later
2879 only?) and @sc{gnu}/Linux (kernel version 2.5.60 and later).
2881 By default, when a program forks, @value{GDBN} will continue to debug
2882 the parent process and the child process will run unimpeded.
2884 If you want to follow the child process instead of the parent process,
2885 use the command @w{@code{set follow-fork-mode}}.
2888 @kindex set follow-fork-mode
2889 @item set follow-fork-mode @var{mode}
2890 Set the debugger response to a program call of @code{fork} or
2891 @code{vfork}. A call to @code{fork} or @code{vfork} creates a new
2892 process. The @var{mode} argument can be:
2896 The original process is debugged after a fork. The child process runs
2897 unimpeded. This is the default.
2900 The new process is debugged after a fork. The parent process runs
2905 @kindex show follow-fork-mode
2906 @item show follow-fork-mode
2907 Display the current debugger response to a @code{fork} or @code{vfork} call.
2910 @cindex debugging multiple processes
2911 On Linux, if you want to debug both the parent and child processes, use the
2912 command @w{@code{set detach-on-fork}}.
2915 @kindex set detach-on-fork
2916 @item set detach-on-fork @var{mode}
2917 Tells gdb whether to detach one of the processes after a fork, or
2918 retain debugger control over them both.
2922 The child process (or parent process, depending on the value of
2923 @code{follow-fork-mode}) will be detached and allowed to run
2924 independently. This is the default.
2927 Both processes will be held under the control of @value{GDBN}.
2928 One process (child or parent, depending on the value of
2929 @code{follow-fork-mode}) is debugged as usual, while the other
2934 @kindex show detach-on-fork
2935 @item show detach-on-fork
2936 Show whether detach-on-fork mode is on/off.
2939 If you choose to set @samp{detach-on-fork} mode off, then @value{GDBN}
2940 will retain control of all forked processes (including nested forks).
2941 You can list the forked processes under the control of @value{GDBN} by
2942 using the @w{@code{info inferiors}} command, and switch from one fork
2943 to another by using the @code{inferior} command (@pxref{Inferiors and
2944 Programs, ,Debugging Multiple Inferiors and Programs}).
2946 To quit debugging one of the forked processes, you can either detach
2947 from it by using the @w{@code{detach inferior}} command (allowing it
2948 to run independently), or kill it using the @w{@code{kill inferior}}
2949 command. @xref{Inferiors and Programs, ,Debugging Multiple Inferiors
2952 If you ask to debug a child process and a @code{vfork} is followed by an
2953 @code{exec}, @value{GDBN} executes the new target up to the first
2954 breakpoint in the new target. If you have a breakpoint set on
2955 @code{main} in your original program, the breakpoint will also be set on
2956 the child process's @code{main}.
2958 On some systems, when a child process is spawned by @code{vfork}, you
2959 cannot debug the child or parent until an @code{exec} call completes.
2961 If you issue a @code{run} command to @value{GDBN} after an @code{exec}
2962 call executes, the new target restarts. To restart the parent
2963 process, use the @code{file} command with the parent executable name
2964 as its argument. By default, after an @code{exec} call executes,
2965 @value{GDBN} discards the symbols of the previous executable image.
2966 You can change this behaviour with the @w{@code{set follow-exec-mode}}
2970 @kindex set follow-exec-mode
2971 @item set follow-exec-mode @var{mode}
2973 Set debugger response to a program call of @code{exec}. An
2974 @code{exec} call replaces the program image of a process.
2976 @code{follow-exec-mode} can be:
2980 @value{GDBN} creates a new inferior and rebinds the process to this
2981 new inferior. The program the process was running before the
2982 @code{exec} call can be restarted afterwards by restarting the
2988 (@value{GDBP}) info inferiors
2990 Id Description Executable
2993 process 12020 is executing new program: prog2
2994 Program exited normally.
2995 (@value{GDBP}) info inferiors
2996 Id Description Executable
3002 @value{GDBN} keeps the process bound to the same inferior. The new
3003 executable image replaces the previous executable loaded in the
3004 inferior. Restarting the inferior after the @code{exec} call, with
3005 e.g., the @code{run} command, restarts the executable the process was
3006 running after the @code{exec} call. This is the default mode.
3011 (@value{GDBP}) info inferiors
3012 Id Description Executable
3015 process 12020 is executing new program: prog2
3016 Program exited normally.
3017 (@value{GDBP}) info inferiors
3018 Id Description Executable
3025 You can use the @code{catch} command to make @value{GDBN} stop whenever
3026 a @code{fork}, @code{vfork}, or @code{exec} call is made. @xref{Set
3027 Catchpoints, ,Setting Catchpoints}.
3029 @node Checkpoint/Restart
3030 @section Setting a @emph{Bookmark} to Return to Later
3035 @cindex snapshot of a process
3036 @cindex rewind program state
3038 On certain operating systems@footnote{Currently, only
3039 @sc{gnu}/Linux.}, @value{GDBN} is able to save a @dfn{snapshot} of a
3040 program's state, called a @dfn{checkpoint}, and come back to it
3043 Returning to a checkpoint effectively undoes everything that has
3044 happened in the program since the @code{checkpoint} was saved. This
3045 includes changes in memory, registers, and even (within some limits)
3046 system state. Effectively, it is like going back in time to the
3047 moment when the checkpoint was saved.
3049 Thus, if you're stepping thru a program and you think you're
3050 getting close to the point where things go wrong, you can save
3051 a checkpoint. Then, if you accidentally go too far and miss
3052 the critical statement, instead of having to restart your program
3053 from the beginning, you can just go back to the checkpoint and
3054 start again from there.
3056 This can be especially useful if it takes a lot of time or
3057 steps to reach the point where you think the bug occurs.
3059 To use the @code{checkpoint}/@code{restart} method of debugging:
3064 Save a snapshot of the debugged program's current execution state.
3065 The @code{checkpoint} command takes no arguments, but each checkpoint
3066 is assigned a small integer id, similar to a breakpoint id.
3068 @kindex info checkpoints
3069 @item info checkpoints
3070 List the checkpoints that have been saved in the current debugging
3071 session. For each checkpoint, the following information will be
3078 @item Source line, or label
3081 @kindex restart @var{checkpoint-id}
3082 @item restart @var{checkpoint-id}
3083 Restore the program state that was saved as checkpoint number
3084 @var{checkpoint-id}. All program variables, registers, stack frames
3085 etc.@: will be returned to the values that they had when the checkpoint
3086 was saved. In essence, gdb will ``wind back the clock'' to the point
3087 in time when the checkpoint was saved.
3089 Note that breakpoints, @value{GDBN} variables, command history etc.
3090 are not affected by restoring a checkpoint. In general, a checkpoint
3091 only restores things that reside in the program being debugged, not in
3094 @kindex delete checkpoint @var{checkpoint-id}
3095 @item delete checkpoint @var{checkpoint-id}
3096 Delete the previously-saved checkpoint identified by @var{checkpoint-id}.
3100 Returning to a previously saved checkpoint will restore the user state
3101 of the program being debugged, plus a significant subset of the system
3102 (OS) state, including file pointers. It won't ``un-write'' data from
3103 a file, but it will rewind the file pointer to the previous location,
3104 so that the previously written data can be overwritten. For files
3105 opened in read mode, the pointer will also be restored so that the
3106 previously read data can be read again.
3108 Of course, characters that have been sent to a printer (or other
3109 external device) cannot be ``snatched back'', and characters received
3110 from eg.@: a serial device can be removed from internal program buffers,
3111 but they cannot be ``pushed back'' into the serial pipeline, ready to
3112 be received again. Similarly, the actual contents of files that have
3113 been changed cannot be restored (at this time).
3115 However, within those constraints, you actually can ``rewind'' your
3116 program to a previously saved point in time, and begin debugging it
3117 again --- and you can change the course of events so as to debug a
3118 different execution path this time.
3120 @cindex checkpoints and process id
3121 Finally, there is one bit of internal program state that will be
3122 different when you return to a checkpoint --- the program's process
3123 id. Each checkpoint will have a unique process id (or @var{pid}),
3124 and each will be different from the program's original @var{pid}.
3125 If your program has saved a local copy of its process id, this could
3126 potentially pose a problem.
3128 @subsection A Non-obvious Benefit of Using Checkpoints
3130 On some systems such as @sc{gnu}/Linux, address space randomization
3131 is performed on new processes for security reasons. This makes it
3132 difficult or impossible to set a breakpoint, or watchpoint, on an
3133 absolute address if you have to restart the program, since the
3134 absolute location of a symbol will change from one execution to the
3137 A checkpoint, however, is an @emph{identical} copy of a process.
3138 Therefore if you create a checkpoint at (eg.@:) the start of main,
3139 and simply return to that checkpoint instead of restarting the
3140 process, you can avoid the effects of address randomization and
3141 your symbols will all stay in the same place.
3144 @chapter Stopping and Continuing
3146 The principal purposes of using a debugger are so that you can stop your
3147 program before it terminates; or so that, if your program runs into
3148 trouble, you can investigate and find out why.
3150 Inside @value{GDBN}, your program may stop for any of several reasons,
3151 such as a signal, a breakpoint, or reaching a new line after a
3152 @value{GDBN} command such as @code{step}. You may then examine and
3153 change variables, set new breakpoints or remove old ones, and then
3154 continue execution. Usually, the messages shown by @value{GDBN} provide
3155 ample explanation of the status of your program---but you can also
3156 explicitly request this information at any time.
3159 @kindex info program
3161 Display information about the status of your program: whether it is
3162 running or not, what process it is, and why it stopped.
3166 * Breakpoints:: Breakpoints, watchpoints, and catchpoints
3167 * Continuing and Stepping:: Resuming execution
3169 * Thread Stops:: Stopping and starting multi-thread programs
3173 @section Breakpoints, Watchpoints, and Catchpoints
3176 A @dfn{breakpoint} makes your program stop whenever a certain point in
3177 the program is reached. For each breakpoint, you can add conditions to
3178 control in finer detail whether your program stops. You can set
3179 breakpoints with the @code{break} command and its variants (@pxref{Set
3180 Breaks, ,Setting Breakpoints}), to specify the place where your program
3181 should stop by line number, function name or exact address in the
3184 On some systems, you can set breakpoints in shared libraries before
3185 the executable is run. There is a minor limitation on HP-UX systems:
3186 you must wait until the executable is run in order to set breakpoints
3187 in shared library routines that are not called directly by the program
3188 (for example, routines that are arguments in a @code{pthread_create}
3192 @cindex data breakpoints
3193 @cindex memory tracing
3194 @cindex breakpoint on memory address
3195 @cindex breakpoint on variable modification
3196 A @dfn{watchpoint} is a special breakpoint that stops your program
3197 when the value of an expression changes. The expression may be a value
3198 of a variable, or it could involve values of one or more variables
3199 combined by operators, such as @samp{a + b}. This is sometimes called
3200 @dfn{data breakpoints}. You must use a different command to set
3201 watchpoints (@pxref{Set Watchpoints, ,Setting Watchpoints}), but aside
3202 from that, you can manage a watchpoint like any other breakpoint: you
3203 enable, disable, and delete both breakpoints and watchpoints using the
3206 You can arrange to have values from your program displayed automatically
3207 whenever @value{GDBN} stops at a breakpoint. @xref{Auto Display,,
3211 @cindex breakpoint on events
3212 A @dfn{catchpoint} is another special breakpoint that stops your program
3213 when a certain kind of event occurs, such as the throwing of a C@t{++}
3214 exception or the loading of a library. As with watchpoints, you use a
3215 different command to set a catchpoint (@pxref{Set Catchpoints, ,Setting
3216 Catchpoints}), but aside from that, you can manage a catchpoint like any
3217 other breakpoint. (To stop when your program receives a signal, use the
3218 @code{handle} command; see @ref{Signals, ,Signals}.)
3220 @cindex breakpoint numbers
3221 @cindex numbers for breakpoints
3222 @value{GDBN} assigns a number to each breakpoint, watchpoint, or
3223 catchpoint when you create it; these numbers are successive integers
3224 starting with one. In many of the commands for controlling various
3225 features of breakpoints you use the breakpoint number to say which
3226 breakpoint you want to change. Each breakpoint may be @dfn{enabled} or
3227 @dfn{disabled}; if disabled, it has no effect on your program until you
3230 @cindex breakpoint ranges
3231 @cindex ranges of breakpoints
3232 Some @value{GDBN} commands accept a range of breakpoints on which to
3233 operate. A breakpoint range is either a single breakpoint number, like
3234 @samp{5}, or two such numbers, in increasing order, separated by a
3235 hyphen, like @samp{5-7}. When a breakpoint range is given to a command,
3236 all breakpoints in that range are operated on.
3239 * Set Breaks:: Setting breakpoints
3240 * Set Watchpoints:: Setting watchpoints
3241 * Set Catchpoints:: Setting catchpoints
3242 * Delete Breaks:: Deleting breakpoints
3243 * Disabling:: Disabling breakpoints
3244 * Conditions:: Break conditions
3245 * Break Commands:: Breakpoint command lists
3246 * Error in Breakpoints:: ``Cannot insert breakpoints''
3247 * Breakpoint-related Warnings:: ``Breakpoint address adjusted...''
3251 @subsection Setting Breakpoints
3253 @c FIXME LMB what does GDB do if no code on line of breakpt?
3254 @c consider in particular declaration with/without initialization.
3256 @c FIXME 2 is there stuff on this already? break at fun start, already init?
3259 @kindex b @r{(@code{break})}
3260 @vindex $bpnum@r{, convenience variable}
3261 @cindex latest breakpoint
3262 Breakpoints are set with the @code{break} command (abbreviated
3263 @code{b}). The debugger convenience variable @samp{$bpnum} records the
3264 number of the breakpoint you've set most recently; see @ref{Convenience
3265 Vars,, Convenience Variables}, for a discussion of what you can do with
3266 convenience variables.
3269 @item break @var{location}
3270 Set a breakpoint at the given @var{location}, which can specify a
3271 function name, a line number, or an address of an instruction.
3272 (@xref{Specify Location}, for a list of all the possible ways to
3273 specify a @var{location}.) The breakpoint will stop your program just
3274 before it executes any of the code in the specified @var{location}.
3276 When using source languages that permit overloading of symbols, such as
3277 C@t{++}, a function name may refer to more than one possible place to break.
3278 @xref{Ambiguous Expressions,,Ambiguous Expressions}, for a discussion of
3281 It is also possible to insert a breakpoint that will stop the program
3282 only if a specific thread (@pxref{Thread-Specific Breakpoints})
3283 or a specific task (@pxref{Ada Tasks}) hits that breakpoint.
3286 When called without any arguments, @code{break} sets a breakpoint at
3287 the next instruction to be executed in the selected stack frame
3288 (@pxref{Stack, ,Examining the Stack}). In any selected frame but the
3289 innermost, this makes your program stop as soon as control
3290 returns to that frame. This is similar to the effect of a
3291 @code{finish} command in the frame inside the selected frame---except
3292 that @code{finish} does not leave an active breakpoint. If you use
3293 @code{break} without an argument in the innermost frame, @value{GDBN} stops
3294 the next time it reaches the current location; this may be useful
3297 @value{GDBN} normally ignores breakpoints when it resumes execution, until at
3298 least one instruction has been executed. If it did not do this, you
3299 would be unable to proceed past a breakpoint without first disabling the
3300 breakpoint. This rule applies whether or not the breakpoint already
3301 existed when your program stopped.
3303 @item break @dots{} if @var{cond}
3304 Set a breakpoint with condition @var{cond}; evaluate the expression
3305 @var{cond} each time the breakpoint is reached, and stop only if the
3306 value is nonzero---that is, if @var{cond} evaluates as true.
3307 @samp{@dots{}} stands for one of the possible arguments described
3308 above (or no argument) specifying where to break. @xref{Conditions,
3309 ,Break Conditions}, for more information on breakpoint conditions.
3312 @item tbreak @var{args}
3313 Set a breakpoint enabled only for one stop. @var{args} are the
3314 same as for the @code{break} command, and the breakpoint is set in the same
3315 way, but the breakpoint is automatically deleted after the first time your
3316 program stops there. @xref{Disabling, ,Disabling Breakpoints}.
3319 @cindex hardware breakpoints
3320 @item hbreak @var{args}
3321 Set a hardware-assisted breakpoint. @var{args} are the same as for the
3322 @code{break} command and the breakpoint is set in the same way, but the
3323 breakpoint requires hardware support and some target hardware may not
3324 have this support. The main purpose of this is EPROM/ROM code
3325 debugging, so you can set a breakpoint at an instruction without
3326 changing the instruction. This can be used with the new trap-generation
3327 provided by SPARClite DSU and most x86-based targets. These targets
3328 will generate traps when a program accesses some data or instruction
3329 address that is assigned to the debug registers. However the hardware
3330 breakpoint registers can take a limited number of breakpoints. For
3331 example, on the DSU, only two data breakpoints can be set at a time, and
3332 @value{GDBN} will reject this command if more than two are used. Delete
3333 or disable unused hardware breakpoints before setting new ones
3334 (@pxref{Disabling, ,Disabling Breakpoints}).
3335 @xref{Conditions, ,Break Conditions}.
3336 For remote targets, you can restrict the number of hardware
3337 breakpoints @value{GDBN} will use, see @ref{set remote
3338 hardware-breakpoint-limit}.
3341 @item thbreak @var{args}
3342 Set a hardware-assisted breakpoint enabled only for one stop. @var{args}
3343 are the same as for the @code{hbreak} command and the breakpoint is set in
3344 the same way. However, like the @code{tbreak} command,
3345 the breakpoint is automatically deleted after the
3346 first time your program stops there. Also, like the @code{hbreak}
3347 command, the breakpoint requires hardware support and some target hardware
3348 may not have this support. @xref{Disabling, ,Disabling Breakpoints}.
3349 See also @ref{Conditions, ,Break Conditions}.
3352 @cindex regular expression
3353 @cindex breakpoints in functions matching a regexp
3354 @cindex set breakpoints in many functions
3355 @item rbreak @var{regex}
3356 Set breakpoints on all functions matching the regular expression
3357 @var{regex}. This command sets an unconditional breakpoint on all
3358 matches, printing a list of all breakpoints it set. Once these
3359 breakpoints are set, they are treated just like the breakpoints set with
3360 the @code{break} command. You can delete them, disable them, or make
3361 them conditional the same way as any other breakpoint.
3363 The syntax of the regular expression is the standard one used with tools
3364 like @file{grep}. Note that this is different from the syntax used by
3365 shells, so for instance @code{foo*} matches all functions that include
3366 an @code{fo} followed by zero or more @code{o}s. There is an implicit
3367 @code{.*} leading and trailing the regular expression you supply, so to
3368 match only functions that begin with @code{foo}, use @code{^foo}.
3370 @cindex non-member C@t{++} functions, set breakpoint in
3371 When debugging C@t{++} programs, @code{rbreak} is useful for setting
3372 breakpoints on overloaded functions that are not members of any special
3375 @cindex set breakpoints on all functions
3376 The @code{rbreak} command can be used to set breakpoints in
3377 @strong{all} the functions in a program, like this:
3380 (@value{GDBP}) rbreak .
3383 @kindex info breakpoints
3384 @cindex @code{$_} and @code{info breakpoints}
3385 @item info breakpoints @r{[}@var{n}@r{]}
3386 @itemx info break @r{[}@var{n}@r{]}
3387 @itemx info watchpoints @r{[}@var{n}@r{]}
3388 Print a table of all breakpoints, watchpoints, and catchpoints set and
3389 not deleted. Optional argument @var{n} means print information only
3390 about the specified breakpoint (or watchpoint or catchpoint). For
3391 each breakpoint, following columns are printed:
3394 @item Breakpoint Numbers
3396 Breakpoint, watchpoint, or catchpoint.
3398 Whether the breakpoint is marked to be disabled or deleted when hit.
3399 @item Enabled or Disabled
3400 Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints
3401 that are not enabled.
3403 Where the breakpoint is in your program, as a memory address. For a
3404 pending breakpoint whose address is not yet known, this field will
3405 contain @samp{<PENDING>}. Such breakpoint won't fire until a shared
3406 library that has the symbol or line referred by breakpoint is loaded.
3407 See below for details. A breakpoint with several locations will
3408 have @samp{<MULTIPLE>} in this field---see below for details.
3410 Where the breakpoint is in the source for your program, as a file and
3411 line number. For a pending breakpoint, the original string passed to
3412 the breakpoint command will be listed as it cannot be resolved until
3413 the appropriate shared library is loaded in the future.
3417 If a breakpoint is conditional, @code{info break} shows the condition on
3418 the line following the affected breakpoint; breakpoint commands, if any,
3419 are listed after that. A pending breakpoint is allowed to have a condition
3420 specified for it. The condition is not parsed for validity until a shared
3421 library is loaded that allows the pending breakpoint to resolve to a
3425 @code{info break} with a breakpoint
3426 number @var{n} as argument lists only that breakpoint. The
3427 convenience variable @code{$_} and the default examining-address for
3428 the @code{x} command are set to the address of the last breakpoint
3429 listed (@pxref{Memory, ,Examining Memory}).
3432 @code{info break} displays a count of the number of times the breakpoint
3433 has been hit. This is especially useful in conjunction with the
3434 @code{ignore} command. You can ignore a large number of breakpoint
3435 hits, look at the breakpoint info to see how many times the breakpoint
3436 was hit, and then run again, ignoring one less than that number. This
3437 will get you quickly to the last hit of that breakpoint.
3440 @value{GDBN} allows you to set any number of breakpoints at the same place in
3441 your program. There is nothing silly or meaningless about this. When
3442 the breakpoints are conditional, this is even useful
3443 (@pxref{Conditions, ,Break Conditions}).
3445 @cindex multiple locations, breakpoints
3446 @cindex breakpoints, multiple locations
3447 It is possible that a breakpoint corresponds to several locations
3448 in your program. Examples of this situation are:
3452 For a C@t{++} constructor, the @value{NGCC} compiler generates several
3453 instances of the function body, used in different cases.
3456 For a C@t{++} template function, a given line in the function can
3457 correspond to any number of instantiations.
3460 For an inlined function, a given source line can correspond to
3461 several places where that function is inlined.
3464 In all those cases, @value{GDBN} will insert a breakpoint at all
3465 the relevant locations@footnote{
3466 As of this writing, multiple-location breakpoints work only if there's
3467 line number information for all the locations. This means that they
3468 will generally not work in system libraries, unless you have debug
3469 info with line numbers for them.}.
3471 A breakpoint with multiple locations is displayed in the breakpoint
3472 table using several rows---one header row, followed by one row for
3473 each breakpoint location. The header row has @samp{<MULTIPLE>} in the
3474 address column. The rows for individual locations contain the actual
3475 addresses for locations, and show the functions to which those
3476 locations belong. The number column for a location is of the form
3477 @var{breakpoint-number}.@var{location-number}.
3482 Num Type Disp Enb Address What
3483 1 breakpoint keep y <MULTIPLE>
3485 breakpoint already hit 1 time
3486 1.1 y 0x080486a2 in void foo<int>() at t.cc:8
3487 1.2 y 0x080486ca in void foo<double>() at t.cc:8
3490 Each location can be individually enabled or disabled by passing
3491 @var{breakpoint-number}.@var{location-number} as argument to the
3492 @code{enable} and @code{disable} commands. Note that you cannot
3493 delete the individual locations from the list, you can only delete the
3494 entire list of locations that belong to their parent breakpoint (with
3495 the @kbd{delete @var{num}} command, where @var{num} is the number of
3496 the parent breakpoint, 1 in the above example). Disabling or enabling
3497 the parent breakpoint (@pxref{Disabling}) affects all of the locations
3498 that belong to that breakpoint.
3500 @cindex pending breakpoints
3501 It's quite common to have a breakpoint inside a shared library.
3502 Shared libraries can be loaded and unloaded explicitly,
3503 and possibly repeatedly, as the program is executed. To support
3504 this use case, @value{GDBN} updates breakpoint locations whenever
3505 any shared library is loaded or unloaded. Typically, you would
3506 set a breakpoint in a shared library at the beginning of your
3507 debugging session, when the library is not loaded, and when the
3508 symbols from the library are not available. When you try to set
3509 breakpoint, @value{GDBN} will ask you if you want to set
3510 a so called @dfn{pending breakpoint}---breakpoint whose address
3511 is not yet resolved.
3513 After the program is run, whenever a new shared library is loaded,
3514 @value{GDBN} reevaluates all the breakpoints. When a newly loaded
3515 shared library contains the symbol or line referred to by some
3516 pending breakpoint, that breakpoint is resolved and becomes an
3517 ordinary breakpoint. When a library is unloaded, all breakpoints
3518 that refer to its symbols or source lines become pending again.
3520 This logic works for breakpoints with multiple locations, too. For
3521 example, if you have a breakpoint in a C@t{++} template function, and
3522 a newly loaded shared library has an instantiation of that template,
3523 a new location is added to the list of locations for the breakpoint.
3525 Except for having unresolved address, pending breakpoints do not
3526 differ from regular breakpoints. You can set conditions or commands,
3527 enable and disable them and perform other breakpoint operations.
3529 @value{GDBN} provides some additional commands for controlling what
3530 happens when the @samp{break} command cannot resolve breakpoint
3531 address specification to an address:
3533 @kindex set breakpoint pending
3534 @kindex show breakpoint pending
3536 @item set breakpoint pending auto
3537 This is the default behavior. When @value{GDBN} cannot find the breakpoint
3538 location, it queries you whether a pending breakpoint should be created.
3540 @item set breakpoint pending on
3541 This indicates that an unrecognized breakpoint location should automatically
3542 result in a pending breakpoint being created.
3544 @item set breakpoint pending off
3545 This indicates that pending breakpoints are not to be created. Any
3546 unrecognized breakpoint location results in an error. This setting does
3547 not affect any pending breakpoints previously created.
3549 @item show breakpoint pending
3550 Show the current behavior setting for creating pending breakpoints.
3553 The settings above only affect the @code{break} command and its
3554 variants. Once breakpoint is set, it will be automatically updated
3555 as shared libraries are loaded and unloaded.
3557 @cindex automatic hardware breakpoints
3558 For some targets, @value{GDBN} can automatically decide if hardware or
3559 software breakpoints should be used, depending on whether the
3560 breakpoint address is read-only or read-write. This applies to
3561 breakpoints set with the @code{break} command as well as to internal
3562 breakpoints set by commands like @code{next} and @code{finish}. For
3563 breakpoints set with @code{hbreak}, @value{GDBN} will always use hardware
3566 You can control this automatic behaviour with the following commands::
3568 @kindex set breakpoint auto-hw
3569 @kindex show breakpoint auto-hw
3571 @item set breakpoint auto-hw on
3572 This is the default behavior. When @value{GDBN} sets a breakpoint, it
3573 will try to use the target memory map to decide if software or hardware
3574 breakpoint must be used.
3576 @item set breakpoint auto-hw off
3577 This indicates @value{GDBN} should not automatically select breakpoint
3578 type. If the target provides a memory map, @value{GDBN} will warn when
3579 trying to set software breakpoint at a read-only address.
3582 @value{GDBN} normally implements breakpoints by replacing the program code
3583 at the breakpoint address with a special instruction, which, when
3584 executed, given control to the debugger. By default, the program
3585 code is so modified only when the program is resumed. As soon as
3586 the program stops, @value{GDBN} restores the original instructions. This
3587 behaviour guards against leaving breakpoints inserted in the
3588 target should gdb abrubptly disconnect. However, with slow remote
3589 targets, inserting and removing breakpoint can reduce the performance.
3590 This behavior can be controlled with the following commands::
3592 @kindex set breakpoint always-inserted
3593 @kindex show breakpoint always-inserted
3595 @item set breakpoint always-inserted off
3596 All breakpoints, including newly added by the user, are inserted in
3597 the target only when the target is resumed. All breakpoints are
3598 removed from the target when it stops.
3600 @item set breakpoint always-inserted on
3601 Causes all breakpoints to be inserted in the target at all times. If
3602 the user adds a new breakpoint, or changes an existing breakpoint, the
3603 breakpoints in the target are updated immediately. A breakpoint is
3604 removed from the target only when breakpoint itself is removed.
3606 @cindex non-stop mode, and @code{breakpoint always-inserted}
3607 @item set breakpoint always-inserted auto
3608 This is the default mode. If @value{GDBN} is controlling the inferior
3609 in non-stop mode (@pxref{Non-Stop Mode}), gdb behaves as if
3610 @code{breakpoint always-inserted} mode is on. If @value{GDBN} is
3611 controlling the inferior in all-stop mode, @value{GDBN} behaves as if
3612 @code{breakpoint always-inserted} mode is off.
3615 @cindex negative breakpoint numbers
3616 @cindex internal @value{GDBN} breakpoints
3617 @value{GDBN} itself sometimes sets breakpoints in your program for
3618 special purposes, such as proper handling of @code{longjmp} (in C
3619 programs). These internal breakpoints are assigned negative numbers,
3620 starting with @code{-1}; @samp{info breakpoints} does not display them.
3621 You can see these breakpoints with the @value{GDBN} maintenance command
3622 @samp{maint info breakpoints} (@pxref{maint info breakpoints}).
3625 @node Set Watchpoints
3626 @subsection Setting Watchpoints
3628 @cindex setting watchpoints
3629 You can use a watchpoint to stop execution whenever the value of an
3630 expression changes, without having to predict a particular place where
3631 this may happen. (This is sometimes called a @dfn{data breakpoint}.)
3632 The expression may be as simple as the value of a single variable, or
3633 as complex as many variables combined by operators. Examples include:
3637 A reference to the value of a single variable.
3640 An address cast to an appropriate data type. For example,
3641 @samp{*(int *)0x12345678} will watch a 4-byte region at the specified
3642 address (assuming an @code{int} occupies 4 bytes).
3645 An arbitrarily complex expression, such as @samp{a*b + c/d}. The
3646 expression can use any operators valid in the program's native
3647 language (@pxref{Languages}).
3650 You can set a watchpoint on an expression even if the expression can
3651 not be evaluated yet. For instance, you can set a watchpoint on
3652 @samp{*global_ptr} before @samp{global_ptr} is initialized.
3653 @value{GDBN} will stop when your program sets @samp{global_ptr} and
3654 the expression produces a valid value. If the expression becomes
3655 valid in some other way than changing a variable (e.g.@: if the memory
3656 pointed to by @samp{*global_ptr} becomes readable as the result of a
3657 @code{malloc} call), @value{GDBN} may not stop until the next time
3658 the expression changes.
3660 @cindex software watchpoints
3661 @cindex hardware watchpoints
3662 Depending on your system, watchpoints may be implemented in software or
3663 hardware. @value{GDBN} does software watchpointing by single-stepping your
3664 program and testing the variable's value each time, which is hundreds of
3665 times slower than normal execution. (But this may still be worth it, to
3666 catch errors where you have no clue what part of your program is the
3669 On some systems, such as HP-UX, PowerPC, @sc{gnu}/Linux and most other
3670 x86-based targets, @value{GDBN} includes support for hardware
3671 watchpoints, which do not slow down the running of your program.
3675 @item watch @var{expr} @r{[}thread @var{threadnum}@r{]}
3676 Set a watchpoint for an expression. @value{GDBN} will break when the
3677 expression @var{expr} is written into by the program and its value
3678 changes. The simplest (and the most popular) use of this command is
3679 to watch the value of a single variable:
3682 (@value{GDBP}) watch foo
3685 If the command includes a @code{@r{[}thread @var{threadnum}@r{]}}
3686 clause, @value{GDBN} breaks only when the thread identified by
3687 @var{threadnum} changes the value of @var{expr}. If any other threads
3688 change the value of @var{expr}, @value{GDBN} will not break. Note
3689 that watchpoints restricted to a single thread in this way only work
3690 with Hardware Watchpoints.
3693 @item rwatch @var{expr} @r{[}thread @var{threadnum}@r{]}
3694 Set a watchpoint that will break when the value of @var{expr} is read
3698 @item awatch @var{expr} @r{[}thread @var{threadnum}@r{]}
3699 Set a watchpoint that will break when @var{expr} is either read from
3700 or written into by the program.
3702 @kindex info watchpoints @r{[}@var{n}@r{]}
3703 @item info watchpoints
3704 This command prints a list of watchpoints, breakpoints, and catchpoints;
3705 it is the same as @code{info break} (@pxref{Set Breaks}).
3708 @value{GDBN} sets a @dfn{hardware watchpoint} if possible. Hardware
3709 watchpoints execute very quickly, and the debugger reports a change in
3710 value at the exact instruction where the change occurs. If @value{GDBN}
3711 cannot set a hardware watchpoint, it sets a software watchpoint, which
3712 executes more slowly and reports the change in value at the next
3713 @emph{statement}, not the instruction, after the change occurs.
3715 @cindex use only software watchpoints
3716 You can force @value{GDBN} to use only software watchpoints with the
3717 @kbd{set can-use-hw-watchpoints 0} command. With this variable set to
3718 zero, @value{GDBN} will never try to use hardware watchpoints, even if
3719 the underlying system supports them. (Note that hardware-assisted
3720 watchpoints that were set @emph{before} setting
3721 @code{can-use-hw-watchpoints} to zero will still use the hardware
3722 mechanism of watching expression values.)
3725 @item set can-use-hw-watchpoints
3726 @kindex set can-use-hw-watchpoints
3727 Set whether or not to use hardware watchpoints.
3729 @item show can-use-hw-watchpoints
3730 @kindex show can-use-hw-watchpoints
3731 Show the current mode of using hardware watchpoints.
3734 For remote targets, you can restrict the number of hardware
3735 watchpoints @value{GDBN} will use, see @ref{set remote
3736 hardware-breakpoint-limit}.
3738 When you issue the @code{watch} command, @value{GDBN} reports
3741 Hardware watchpoint @var{num}: @var{expr}
3745 if it was able to set a hardware watchpoint.
3747 Currently, the @code{awatch} and @code{rwatch} commands can only set
3748 hardware watchpoints, because accesses to data that don't change the
3749 value of the watched expression cannot be detected without examining
3750 every instruction as it is being executed, and @value{GDBN} does not do
3751 that currently. If @value{GDBN} finds that it is unable to set a
3752 hardware breakpoint with the @code{awatch} or @code{rwatch} command, it
3753 will print a message like this:
3756 Expression cannot be implemented with read/access watchpoint.
3759 Sometimes, @value{GDBN} cannot set a hardware watchpoint because the
3760 data type of the watched expression is wider than what a hardware
3761 watchpoint on the target machine can handle. For example, some systems
3762 can only watch regions that are up to 4 bytes wide; on such systems you
3763 cannot set hardware watchpoints for an expression that yields a
3764 double-precision floating-point number (which is typically 8 bytes
3765 wide). As a work-around, it might be possible to break the large region
3766 into a series of smaller ones and watch them with separate watchpoints.
3768 If you set too many hardware watchpoints, @value{GDBN} might be unable
3769 to insert all of them when you resume the execution of your program.
3770 Since the precise number of active watchpoints is unknown until such
3771 time as the program is about to be resumed, @value{GDBN} might not be
3772 able to warn you about this when you set the watchpoints, and the
3773 warning will be printed only when the program is resumed:
3776 Hardware watchpoint @var{num}: Could not insert watchpoint
3780 If this happens, delete or disable some of the watchpoints.
3782 Watching complex expressions that reference many variables can also
3783 exhaust the resources available for hardware-assisted watchpoints.
3784 That's because @value{GDBN} needs to watch every variable in the
3785 expression with separately allocated resources.
3787 If you call a function interactively using @code{print} or @code{call},
3788 any watchpoints you have set will be inactive until @value{GDBN} reaches another
3789 kind of breakpoint or the call completes.
3791 @value{GDBN} automatically deletes watchpoints that watch local
3792 (automatic) variables, or expressions that involve such variables, when
3793 they go out of scope, that is, when the execution leaves the block in
3794 which these variables were defined. In particular, when the program
3795 being debugged terminates, @emph{all} local variables go out of scope,
3796 and so only watchpoints that watch global variables remain set. If you
3797 rerun the program, you will need to set all such watchpoints again. One
3798 way of doing that would be to set a code breakpoint at the entry to the
3799 @code{main} function and when it breaks, set all the watchpoints.
3801 @cindex watchpoints and threads
3802 @cindex threads and watchpoints
3803 In multi-threaded programs, watchpoints will detect changes to the
3804 watched expression from every thread.
3807 @emph{Warning:} In multi-threaded programs, software watchpoints
3808 have only limited usefulness. If @value{GDBN} creates a software
3809 watchpoint, it can only watch the value of an expression @emph{in a
3810 single thread}. If you are confident that the expression can only
3811 change due to the current thread's activity (and if you are also
3812 confident that no other thread can become current), then you can use
3813 software watchpoints as usual. However, @value{GDBN} may not notice
3814 when a non-current thread's activity changes the expression. (Hardware
3815 watchpoints, in contrast, watch an expression in all threads.)
3818 @xref{set remote hardware-watchpoint-limit}.
3820 @node Set Catchpoints
3821 @subsection Setting Catchpoints
3822 @cindex catchpoints, setting
3823 @cindex exception handlers
3824 @cindex event handling
3826 You can use @dfn{catchpoints} to cause the debugger to stop for certain
3827 kinds of program events, such as C@t{++} exceptions or the loading of a
3828 shared library. Use the @code{catch} command to set a catchpoint.
3832 @item catch @var{event}
3833 Stop when @var{event} occurs. @var{event} can be any of the following:
3836 @cindex stop on C@t{++} exceptions
3837 The throwing of a C@t{++} exception.
3840 The catching of a C@t{++} exception.
3843 @cindex Ada exception catching
3844 @cindex catch Ada exceptions
3845 An Ada exception being raised. If an exception name is specified
3846 at the end of the command (eg @code{catch exception Program_Error}),
3847 the debugger will stop only when this specific exception is raised.
3848 Otherwise, the debugger stops execution when any Ada exception is raised.
3850 When inserting an exception catchpoint on a user-defined exception whose
3851 name is identical to one of the exceptions defined by the language, the
3852 fully qualified name must be used as the exception name. Otherwise,
3853 @value{GDBN} will assume that it should stop on the pre-defined exception
3854 rather than the user-defined one. For instance, assuming an exception
3855 called @code{Constraint_Error} is defined in package @code{Pck}, then
3856 the command to use to catch such exceptions is @kbd{catch exception
3857 Pck.Constraint_Error}.
3859 @item exception unhandled
3860 An exception that was raised but is not handled by the program.
3863 A failed Ada assertion.
3866 @cindex break on fork/exec
3867 A call to @code{exec}. This is currently only available for HP-UX
3871 @itemx syscall @r{[}@var{name} @r{|} @var{number}@r{]} @r{...}
3872 @cindex break on a system call.
3873 A call to or return from a system call, a.k.a.@: @dfn{syscall}. A
3874 syscall is a mechanism for application programs to request a service
3875 from the operating system (OS) or one of the OS system services.
3876 @value{GDBN} can catch some or all of the syscalls issued by the
3877 debuggee, and show the related information for each syscall. If no
3878 argument is specified, calls to and returns from all system calls
3881 @var{name} can be any system call name that is valid for the
3882 underlying OS. Just what syscalls are valid depends on the OS. On
3883 GNU and Unix systems, you can find the full list of valid syscall
3884 names on @file{/usr/include/asm/unistd.h}.
3886 @c For MS-Windows, the syscall names and the corresponding numbers
3887 @c can be found, e.g., on this URL:
3888 @c http://www.metasploit.com/users/opcode/syscalls.html
3889 @c but we don't support Windows syscalls yet.
3891 Normally, @value{GDBN} knows in advance which syscalls are valid for
3892 each OS, so you can use the @value{GDBN} command-line completion
3893 facilities (@pxref{Completion,, command completion}) to list the
3896 You may also specify the system call numerically. A syscall's
3897 number is the value passed to the OS's syscall dispatcher to
3898 identify the requested service. When you specify the syscall by its
3899 name, @value{GDBN} uses its database of syscalls to convert the name
3900 into the corresponding numeric code, but using the number directly
3901 may be useful if @value{GDBN}'s database does not have the complete
3902 list of syscalls on your system (e.g., because @value{GDBN} lags
3903 behind the OS upgrades).
3905 The example below illustrates how this command works if you don't provide
3909 (@value{GDBP}) catch syscall
3910 Catchpoint 1 (syscall)
3912 Starting program: /tmp/catch-syscall
3914 Catchpoint 1 (call to syscall 'close'), \
3915 0xffffe424 in __kernel_vsyscall ()
3919 Catchpoint 1 (returned from syscall 'close'), \
3920 0xffffe424 in __kernel_vsyscall ()
3924 Here is an example of catching a system call by name:
3927 (@value{GDBP}) catch syscall chroot
3928 Catchpoint 1 (syscall 'chroot' [61])
3930 Starting program: /tmp/catch-syscall
3932 Catchpoint 1 (call to syscall 'chroot'), \
3933 0xffffe424 in __kernel_vsyscall ()
3937 Catchpoint 1 (returned from syscall 'chroot'), \
3938 0xffffe424 in __kernel_vsyscall ()
3942 An example of specifying a system call numerically. In the case
3943 below, the syscall number has a corresponding entry in the XML
3944 file, so @value{GDBN} finds its name and prints it:
3947 (@value{GDBP}) catch syscall 252
3948 Catchpoint 1 (syscall(s) 'exit_group')
3950 Starting program: /tmp/catch-syscall
3952 Catchpoint 1 (call to syscall 'exit_group'), \
3953 0xffffe424 in __kernel_vsyscall ()
3957 Program exited normally.
3961 However, there can be situations when there is no corresponding name
3962 in XML file for that syscall number. In this case, @value{GDBN} prints
3963 a warning message saying that it was not able to find the syscall name,
3964 but the catchpoint will be set anyway. See the example below:
3967 (@value{GDBP}) catch syscall 764
3968 warning: The number '764' does not represent a known syscall.
3969 Catchpoint 2 (syscall 764)
3973 If you configure @value{GDBN} using the @samp{--without-expat} option,
3974 it will not be able to display syscall names. Also, if your
3975 architecture does not have an XML file describing its system calls,
3976 you will not be able to see the syscall names. It is important to
3977 notice that these two features are used for accessing the syscall
3978 name database. In either case, you will see a warning like this:
3981 (@value{GDBP}) catch syscall
3982 warning: Could not open "syscalls/i386-linux.xml"
3983 warning: Could not load the syscall XML file 'syscalls/i386-linux.xml'.
3984 GDB will not be able to display syscall names.
3985 Catchpoint 1 (syscall)
3989 Of course, the file name will change depending on your architecture and system.
3991 Still using the example above, you can also try to catch a syscall by its
3992 number. In this case, you would see something like:
3995 (@value{GDBP}) catch syscall 252
3996 Catchpoint 1 (syscall(s) 252)
3999 Again, in this case @value{GDBN} would not be able to display syscall's names.
4002 A call to @code{fork}. This is currently only available for HP-UX
4006 A call to @code{vfork}. This is currently only available for HP-UX
4011 @item tcatch @var{event}
4012 Set a catchpoint that is enabled only for one stop. The catchpoint is
4013 automatically deleted after the first time the event is caught.
4017 Use the @code{info break} command to list the current catchpoints.
4019 There are currently some limitations to C@t{++} exception handling
4020 (@code{catch throw} and @code{catch catch}) in @value{GDBN}:
4024 If you call a function interactively, @value{GDBN} normally returns
4025 control to you when the function has finished executing. If the call
4026 raises an exception, however, the call may bypass the mechanism that
4027 returns control to you and cause your program either to abort or to
4028 simply continue running until it hits a breakpoint, catches a signal
4029 that @value{GDBN} is listening for, or exits. This is the case even if
4030 you set a catchpoint for the exception; catchpoints on exceptions are
4031 disabled within interactive calls.
4034 You cannot raise an exception interactively.
4037 You cannot install an exception handler interactively.
4040 @cindex raise exceptions
4041 Sometimes @code{catch} is not the best way to debug exception handling:
4042 if you need to know exactly where an exception is raised, it is better to
4043 stop @emph{before} the exception handler is called, since that way you
4044 can see the stack before any unwinding takes place. If you set a
4045 breakpoint in an exception handler instead, it may not be easy to find
4046 out where the exception was raised.
4048 To stop just before an exception handler is called, you need some
4049 knowledge of the implementation. In the case of @sc{gnu} C@t{++}, exceptions are
4050 raised by calling a library function named @code{__raise_exception}
4051 which has the following ANSI C interface:
4054 /* @var{addr} is where the exception identifier is stored.
4055 @var{id} is the exception identifier. */
4056 void __raise_exception (void **addr, void *id);
4060 To make the debugger catch all exceptions before any stack
4061 unwinding takes place, set a breakpoint on @code{__raise_exception}
4062 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Exceptions}).
4064 With a conditional breakpoint (@pxref{Conditions, ,Break Conditions})
4065 that depends on the value of @var{id}, you can stop your program when
4066 a specific exception is raised. You can use multiple conditional
4067 breakpoints to stop your program when any of a number of exceptions are
4072 @subsection Deleting Breakpoints
4074 @cindex clearing breakpoints, watchpoints, catchpoints
4075 @cindex deleting breakpoints, watchpoints, catchpoints
4076 It is often necessary to eliminate a breakpoint, watchpoint, or
4077 catchpoint once it has done its job and you no longer want your program
4078 to stop there. This is called @dfn{deleting} the breakpoint. A
4079 breakpoint that has been deleted no longer exists; it is forgotten.
4081 With the @code{clear} command you can delete breakpoints according to
4082 where they are in your program. With the @code{delete} command you can
4083 delete individual breakpoints, watchpoints, or catchpoints by specifying
4084 their breakpoint numbers.
4086 It is not necessary to delete a breakpoint to proceed past it. @value{GDBN}
4087 automatically ignores breakpoints on the first instruction to be executed
4088 when you continue execution without changing the execution address.
4093 Delete any breakpoints at the next instruction to be executed in the
4094 selected stack frame (@pxref{Selection, ,Selecting a Frame}). When
4095 the innermost frame is selected, this is a good way to delete a
4096 breakpoint where your program just stopped.
4098 @item clear @var{location}
4099 Delete any breakpoints set at the specified @var{location}.
4100 @xref{Specify Location}, for the various forms of @var{location}; the
4101 most useful ones are listed below:
4104 @item clear @var{function}
4105 @itemx clear @var{filename}:@var{function}
4106 Delete any breakpoints set at entry to the named @var{function}.
4108 @item clear @var{linenum}
4109 @itemx clear @var{filename}:@var{linenum}
4110 Delete any breakpoints set at or within the code of the specified
4111 @var{linenum} of the specified @var{filename}.
4114 @cindex delete breakpoints
4116 @kindex d @r{(@code{delete})}
4117 @item delete @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4118 Delete the breakpoints, watchpoints, or catchpoints of the breakpoint
4119 ranges specified as arguments. If no argument is specified, delete all
4120 breakpoints (@value{GDBN} asks confirmation, unless you have @code{set
4121 confirm off}). You can abbreviate this command as @code{d}.
4125 @subsection Disabling Breakpoints
4127 @cindex enable/disable a breakpoint
4128 Rather than deleting a breakpoint, watchpoint, or catchpoint, you might
4129 prefer to @dfn{disable} it. This makes the breakpoint inoperative as if
4130 it had been deleted, but remembers the information on the breakpoint so
4131 that you can @dfn{enable} it again later.
4133 You disable and enable breakpoints, watchpoints, and catchpoints with
4134 the @code{enable} and @code{disable} commands, optionally specifying one
4135 or more breakpoint numbers as arguments. Use @code{info break} or
4136 @code{info watch} to print a list of breakpoints, watchpoints, and
4137 catchpoints if you do not know which numbers to use.
4139 Disabling and enabling a breakpoint that has multiple locations
4140 affects all of its locations.
4142 A breakpoint, watchpoint, or catchpoint can have any of four different
4143 states of enablement:
4147 Enabled. The breakpoint stops your program. A breakpoint set
4148 with the @code{break} command starts out in this state.
4150 Disabled. The breakpoint has no effect on your program.
4152 Enabled once. The breakpoint stops your program, but then becomes
4155 Enabled for deletion. The breakpoint stops your program, but
4156 immediately after it does so it is deleted permanently. A breakpoint
4157 set with the @code{tbreak} command starts out in this state.
4160 You can use the following commands to enable or disable breakpoints,
4161 watchpoints, and catchpoints:
4165 @kindex dis @r{(@code{disable})}
4166 @item disable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4167 Disable the specified breakpoints---or all breakpoints, if none are
4168 listed. A disabled breakpoint has no effect but is not forgotten. All
4169 options such as ignore-counts, conditions and commands are remembered in
4170 case the breakpoint is enabled again later. You may abbreviate
4171 @code{disable} as @code{dis}.
4174 @item enable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4175 Enable the specified breakpoints (or all defined breakpoints). They
4176 become effective once again in stopping your program.
4178 @item enable @r{[}breakpoints@r{]} once @var{range}@dots{}
4179 Enable the specified breakpoints temporarily. @value{GDBN} disables any
4180 of these breakpoints immediately after stopping your program.
4182 @item enable @r{[}breakpoints@r{]} delete @var{range}@dots{}
4183 Enable the specified breakpoints to work once, then die. @value{GDBN}
4184 deletes any of these breakpoints as soon as your program stops there.
4185 Breakpoints set by the @code{tbreak} command start out in this state.
4188 @c FIXME: I think the following ``Except for [...] @code{tbreak}'' is
4189 @c confusing: tbreak is also initially enabled.
4190 Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks,
4191 ,Setting Breakpoints}), breakpoints that you set are initially enabled;
4192 subsequently, they become disabled or enabled only when you use one of
4193 the commands above. (The command @code{until} can set and delete a
4194 breakpoint of its own, but it does not change the state of your other
4195 breakpoints; see @ref{Continuing and Stepping, ,Continuing and
4199 @subsection Break Conditions
4200 @cindex conditional breakpoints
4201 @cindex breakpoint conditions
4203 @c FIXME what is scope of break condition expr? Context where wanted?
4204 @c in particular for a watchpoint?
4205 The simplest sort of breakpoint breaks every time your program reaches a
4206 specified place. You can also specify a @dfn{condition} for a
4207 breakpoint. A condition is just a Boolean expression in your
4208 programming language (@pxref{Expressions, ,Expressions}). A breakpoint with
4209 a condition evaluates the expression each time your program reaches it,
4210 and your program stops only if the condition is @emph{true}.
4212 This is the converse of using assertions for program validation; in that
4213 situation, you want to stop when the assertion is violated---that is,
4214 when the condition is false. In C, if you want to test an assertion expressed
4215 by the condition @var{assert}, you should set the condition
4216 @samp{! @var{assert}} on the appropriate breakpoint.
4218 Conditions are also accepted for watchpoints; you may not need them,
4219 since a watchpoint is inspecting the value of an expression anyhow---but
4220 it might be simpler, say, to just set a watchpoint on a variable name,
4221 and specify a condition that tests whether the new value is an interesting
4224 Break conditions can have side effects, and may even call functions in
4225 your program. This can be useful, for example, to activate functions
4226 that log program progress, or to use your own print functions to
4227 format special data structures. The effects are completely predictable
4228 unless there is another enabled breakpoint at the same address. (In
4229 that case, @value{GDBN} might see the other breakpoint first and stop your
4230 program without checking the condition of this one.) Note that
4231 breakpoint commands are usually more convenient and flexible than break
4233 purpose of performing side effects when a breakpoint is reached
4234 (@pxref{Break Commands, ,Breakpoint Command Lists}).
4236 Break conditions can be specified when a breakpoint is set, by using
4237 @samp{if} in the arguments to the @code{break} command. @xref{Set
4238 Breaks, ,Setting Breakpoints}. They can also be changed at any time
4239 with the @code{condition} command.
4241 You can also use the @code{if} keyword with the @code{watch} command.
4242 The @code{catch} command does not recognize the @code{if} keyword;
4243 @code{condition} is the only way to impose a further condition on a
4248 @item condition @var{bnum} @var{expression}
4249 Specify @var{expression} as the break condition for breakpoint,
4250 watchpoint, or catchpoint number @var{bnum}. After you set a condition,
4251 breakpoint @var{bnum} stops your program only if the value of
4252 @var{expression} is true (nonzero, in C). When you use
4253 @code{condition}, @value{GDBN} checks @var{expression} immediately for
4254 syntactic correctness, and to determine whether symbols in it have
4255 referents in the context of your breakpoint. If @var{expression} uses
4256 symbols not referenced in the context of the breakpoint, @value{GDBN}
4257 prints an error message:
4260 No symbol "foo" in current context.
4265 not actually evaluate @var{expression} at the time the @code{condition}
4266 command (or a command that sets a breakpoint with a condition, like
4267 @code{break if @dots{}}) is given, however. @xref{Expressions, ,Expressions}.
4269 @item condition @var{bnum}
4270 Remove the condition from breakpoint number @var{bnum}. It becomes
4271 an ordinary unconditional breakpoint.
4274 @cindex ignore count (of breakpoint)
4275 A special case of a breakpoint condition is to stop only when the
4276 breakpoint has been reached a certain number of times. This is so
4277 useful that there is a special way to do it, using the @dfn{ignore
4278 count} of the breakpoint. Every breakpoint has an ignore count, which
4279 is an integer. Most of the time, the ignore count is zero, and
4280 therefore has no effect. But if your program reaches a breakpoint whose
4281 ignore count is positive, then instead of stopping, it just decrements
4282 the ignore count by one and continues. As a result, if the ignore count
4283 value is @var{n}, the breakpoint does not stop the next @var{n} times
4284 your program reaches it.
4288 @item ignore @var{bnum} @var{count}
4289 Set the ignore count of breakpoint number @var{bnum} to @var{count}.
4290 The next @var{count} times the breakpoint is reached, your program's
4291 execution does not stop; other than to decrement the ignore count, @value{GDBN}
4294 To make the breakpoint stop the next time it is reached, specify
4297 When you use @code{continue} to resume execution of your program from a
4298 breakpoint, you can specify an ignore count directly as an argument to
4299 @code{continue}, rather than using @code{ignore}. @xref{Continuing and
4300 Stepping,,Continuing and Stepping}.
4302 If a breakpoint has a positive ignore count and a condition, the
4303 condition is not checked. Once the ignore count reaches zero,
4304 @value{GDBN} resumes checking the condition.
4306 You could achieve the effect of the ignore count with a condition such
4307 as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that
4308 is decremented each time. @xref{Convenience Vars, ,Convenience
4312 Ignore counts apply to breakpoints, watchpoints, and catchpoints.
4315 @node Break Commands
4316 @subsection Breakpoint Command Lists
4318 @cindex breakpoint commands
4319 You can give any breakpoint (or watchpoint or catchpoint) a series of
4320 commands to execute when your program stops due to that breakpoint. For
4321 example, you might want to print the values of certain expressions, or
4322 enable other breakpoints.
4326 @kindex end@r{ (breakpoint commands)}
4327 @item commands @r{[}@var{bnum}@r{]}
4328 @itemx @dots{} @var{command-list} @dots{}
4330 Specify a list of commands for breakpoint number @var{bnum}. The commands
4331 themselves appear on the following lines. Type a line containing just
4332 @code{end} to terminate the commands.
4334 To remove all commands from a breakpoint, type @code{commands} and
4335 follow it immediately with @code{end}; that is, give no commands.
4337 With no @var{bnum} argument, @code{commands} refers to the last
4338 breakpoint, watchpoint, or catchpoint set (not to the breakpoint most
4339 recently encountered).
4342 Pressing @key{RET} as a means of repeating the last @value{GDBN} command is
4343 disabled within a @var{command-list}.
4345 You can use breakpoint commands to start your program up again. Simply
4346 use the @code{continue} command, or @code{step}, or any other command
4347 that resumes execution.
4349 Any other commands in the command list, after a command that resumes
4350 execution, are ignored. This is because any time you resume execution
4351 (even with a simple @code{next} or @code{step}), you may encounter
4352 another breakpoint---which could have its own command list, leading to
4353 ambiguities about which list to execute.
4356 If the first command you specify in a command list is @code{silent}, the
4357 usual message about stopping at a breakpoint is not printed. This may
4358 be desirable for breakpoints that are to print a specific message and
4359 then continue. If none of the remaining commands print anything, you
4360 see no sign that the breakpoint was reached. @code{silent} is
4361 meaningful only at the beginning of a breakpoint command list.
4363 The commands @code{echo}, @code{output}, and @code{printf} allow you to
4364 print precisely controlled output, and are often useful in silent
4365 breakpoints. @xref{Output, ,Commands for Controlled Output}.
4367 For example, here is how you could use breakpoint commands to print the
4368 value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
4374 printf "x is %d\n",x
4379 One application for breakpoint commands is to compensate for one bug so
4380 you can test for another. Put a breakpoint just after the erroneous line
4381 of code, give it a condition to detect the case in which something
4382 erroneous has been done, and give it commands to assign correct values
4383 to any variables that need them. End with the @code{continue} command
4384 so that your program does not stop, and start with the @code{silent}
4385 command so that no output is produced. Here is an example:
4396 @c @ifclear BARETARGET
4397 @node Error in Breakpoints
4398 @subsection ``Cannot insert breakpoints''
4400 If you request too many active hardware-assisted breakpoints and
4401 watchpoints, you will see this error message:
4403 @c FIXME: the precise wording of this message may change; the relevant
4404 @c source change is not committed yet (Sep 3, 1999).
4406 Stopped; cannot insert breakpoints.
4407 You may have requested too many hardware breakpoints and watchpoints.
4411 This message is printed when you attempt to resume the program, since
4412 only then @value{GDBN} knows exactly how many hardware breakpoints and
4413 watchpoints it needs to insert.
4415 When this message is printed, you need to disable or remove some of the
4416 hardware-assisted breakpoints and watchpoints, and then continue.
4418 @node Breakpoint-related Warnings
4419 @subsection ``Breakpoint address adjusted...''
4420 @cindex breakpoint address adjusted
4422 Some processor architectures place constraints on the addresses at
4423 which breakpoints may be placed. For architectures thus constrained,
4424 @value{GDBN} will attempt to adjust the breakpoint's address to comply
4425 with the constraints dictated by the architecture.
4427 One example of such an architecture is the Fujitsu FR-V. The FR-V is
4428 a VLIW architecture in which a number of RISC-like instructions may be
4429 bundled together for parallel execution. The FR-V architecture
4430 constrains the location of a breakpoint instruction within such a
4431 bundle to the instruction with the lowest address. @value{GDBN}
4432 honors this constraint by adjusting a breakpoint's address to the
4433 first in the bundle.
4435 It is not uncommon for optimized code to have bundles which contain
4436 instructions from different source statements, thus it may happen that
4437 a breakpoint's address will be adjusted from one source statement to
4438 another. Since this adjustment may significantly alter @value{GDBN}'s
4439 breakpoint related behavior from what the user expects, a warning is
4440 printed when the breakpoint is first set and also when the breakpoint
4443 A warning like the one below is printed when setting a breakpoint
4444 that's been subject to address adjustment:
4447 warning: Breakpoint address adjusted from 0x00010414 to 0x00010410.
4450 Such warnings are printed both for user settable and @value{GDBN}'s
4451 internal breakpoints. If you see one of these warnings, you should
4452 verify that a breakpoint set at the adjusted address will have the
4453 desired affect. If not, the breakpoint in question may be removed and
4454 other breakpoints may be set which will have the desired behavior.
4455 E.g., it may be sufficient to place the breakpoint at a later
4456 instruction. A conditional breakpoint may also be useful in some
4457 cases to prevent the breakpoint from triggering too often.
4459 @value{GDBN} will also issue a warning when stopping at one of these
4460 adjusted breakpoints:
4463 warning: Breakpoint 1 address previously adjusted from 0x00010414
4467 When this warning is encountered, it may be too late to take remedial
4468 action except in cases where the breakpoint is hit earlier or more
4469 frequently than expected.
4471 @node Continuing and Stepping
4472 @section Continuing and Stepping
4476 @cindex resuming execution
4477 @dfn{Continuing} means resuming program execution until your program
4478 completes normally. In contrast, @dfn{stepping} means executing just
4479 one more ``step'' of your program, where ``step'' may mean either one
4480 line of source code, or one machine instruction (depending on what
4481 particular command you use). Either when continuing or when stepping,
4482 your program may stop even sooner, due to a breakpoint or a signal. (If
4483 it stops due to a signal, you may want to use @code{handle}, or use
4484 @samp{signal 0} to resume execution. @xref{Signals, ,Signals}.)
4488 @kindex c @r{(@code{continue})}
4489 @kindex fg @r{(resume foreground execution)}
4490 @item continue @r{[}@var{ignore-count}@r{]}
4491 @itemx c @r{[}@var{ignore-count}@r{]}
4492 @itemx fg @r{[}@var{ignore-count}@r{]}
4493 Resume program execution, at the address where your program last stopped;
4494 any breakpoints set at that address are bypassed. The optional argument
4495 @var{ignore-count} allows you to specify a further number of times to
4496 ignore a breakpoint at this location; its effect is like that of
4497 @code{ignore} (@pxref{Conditions, ,Break Conditions}).
4499 The argument @var{ignore-count} is meaningful only when your program
4500 stopped due to a breakpoint. At other times, the argument to
4501 @code{continue} is ignored.
4503 The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the
4504 debugged program is deemed to be the foreground program) are provided
4505 purely for convenience, and have exactly the same behavior as
4509 To resume execution at a different place, you can use @code{return}
4510 (@pxref{Returning, ,Returning from a Function}) to go back to the
4511 calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
4512 Different Address}) to go to an arbitrary location in your program.
4514 A typical technique for using stepping is to set a breakpoint
4515 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Catchpoints}) at the
4516 beginning of the function or the section of your program where a problem
4517 is believed to lie, run your program until it stops at that breakpoint,
4518 and then step through the suspect area, examining the variables that are
4519 interesting, until you see the problem happen.
4523 @kindex s @r{(@code{step})}
4525 Continue running your program until control reaches a different source
4526 line, then stop it and return control to @value{GDBN}. This command is
4527 abbreviated @code{s}.
4530 @c "without debugging information" is imprecise; actually "without line
4531 @c numbers in the debugging information". (gcc -g1 has debugging info but
4532 @c not line numbers). But it seems complex to try to make that
4533 @c distinction here.
4534 @emph{Warning:} If you use the @code{step} command while control is
4535 within a function that was compiled without debugging information,
4536 execution proceeds until control reaches a function that does have
4537 debugging information. Likewise, it will not step into a function which
4538 is compiled without debugging information. To step through functions
4539 without debugging information, use the @code{stepi} command, described
4543 The @code{step} command only stops at the first instruction of a source
4544 line. This prevents the multiple stops that could otherwise occur in
4545 @code{switch} statements, @code{for} loops, etc. @code{step} continues
4546 to stop if a function that has debugging information is called within
4547 the line. In other words, @code{step} @emph{steps inside} any functions
4548 called within the line.
4550 Also, the @code{step} command only enters a function if there is line
4551 number information for the function. Otherwise it acts like the
4552 @code{next} command. This avoids problems when using @code{cc -gl}
4553 on MIPS machines. Previously, @code{step} entered subroutines if there
4554 was any debugging information about the routine.
4556 @item step @var{count}
4557 Continue running as in @code{step}, but do so @var{count} times. If a
4558 breakpoint is reached, or a signal not related to stepping occurs before
4559 @var{count} steps, stepping stops right away.
4562 @kindex n @r{(@code{next})}
4563 @item next @r{[}@var{count}@r{]}
4564 Continue to the next source line in the current (innermost) stack frame.
4565 This is similar to @code{step}, but function calls that appear within
4566 the line of code are executed without stopping. Execution stops when
4567 control reaches a different line of code at the original stack level
4568 that was executing when you gave the @code{next} command. This command
4569 is abbreviated @code{n}.
4571 An argument @var{count} is a repeat count, as for @code{step}.
4574 @c FIX ME!! Do we delete this, or is there a way it fits in with
4575 @c the following paragraph? --- Vctoria
4577 @c @code{next} within a function that lacks debugging information acts like
4578 @c @code{step}, but any function calls appearing within the code of the
4579 @c function are executed without stopping.
4581 The @code{next} command only stops at the first instruction of a
4582 source line. This prevents multiple stops that could otherwise occur in
4583 @code{switch} statements, @code{for} loops, etc.
4585 @kindex set step-mode
4587 @cindex functions without line info, and stepping
4588 @cindex stepping into functions with no line info
4589 @itemx set step-mode on
4590 The @code{set step-mode on} command causes the @code{step} command to
4591 stop at the first instruction of a function which contains no debug line
4592 information rather than stepping over it.
4594 This is useful in cases where you may be interested in inspecting the
4595 machine instructions of a function which has no symbolic info and do not
4596 want @value{GDBN} to automatically skip over this function.
4598 @item set step-mode off
4599 Causes the @code{step} command to step over any functions which contains no
4600 debug information. This is the default.
4602 @item show step-mode
4603 Show whether @value{GDBN} will stop in or step over functions without
4604 source line debug information.
4607 @kindex fin @r{(@code{finish})}
4609 Continue running until just after function in the selected stack frame
4610 returns. Print the returned value (if any). This command can be
4611 abbreviated as @code{fin}.
4613 Contrast this with the @code{return} command (@pxref{Returning,
4614 ,Returning from a Function}).
4617 @kindex u @r{(@code{until})}
4618 @cindex run until specified location
4621 Continue running until a source line past the current line, in the
4622 current stack frame, is reached. This command is used to avoid single
4623 stepping through a loop more than once. It is like the @code{next}
4624 command, except that when @code{until} encounters a jump, it
4625 automatically continues execution until the program counter is greater
4626 than the address of the jump.
4628 This means that when you reach the end of a loop after single stepping
4629 though it, @code{until} makes your program continue execution until it
4630 exits the loop. In contrast, a @code{next} command at the end of a loop
4631 simply steps back to the beginning of the loop, which forces you to step
4632 through the next iteration.
4634 @code{until} always stops your program if it attempts to exit the current
4637 @code{until} may produce somewhat counterintuitive results if the order
4638 of machine code does not match the order of the source lines. For
4639 example, in the following excerpt from a debugging session, the @code{f}
4640 (@code{frame}) command shows that execution is stopped at line
4641 @code{206}; yet when we use @code{until}, we get to line @code{195}:
4645 #0 main (argc=4, argv=0xf7fffae8) at m4.c:206
4647 (@value{GDBP}) until
4648 195 for ( ; argc > 0; NEXTARG) @{
4651 This happened because, for execution efficiency, the compiler had
4652 generated code for the loop closure test at the end, rather than the
4653 start, of the loop---even though the test in a C @code{for}-loop is
4654 written before the body of the loop. The @code{until} command appeared
4655 to step back to the beginning of the loop when it advanced to this
4656 expression; however, it has not really gone to an earlier
4657 statement---not in terms of the actual machine code.
4659 @code{until} with no argument works by means of single
4660 instruction stepping, and hence is slower than @code{until} with an
4663 @item until @var{location}
4664 @itemx u @var{location}
4665 Continue running your program until either the specified location is
4666 reached, or the current stack frame returns. @var{location} is any of
4667 the forms described in @ref{Specify Location}.
4668 This form of the command uses temporary breakpoints, and
4669 hence is quicker than @code{until} without an argument. The specified
4670 location is actually reached only if it is in the current frame. This
4671 implies that @code{until} can be used to skip over recursive function
4672 invocations. For instance in the code below, if the current location is
4673 line @code{96}, issuing @code{until 99} will execute the program up to
4674 line @code{99} in the same invocation of factorial, i.e., after the inner
4675 invocations have returned.
4678 94 int factorial (int value)
4680 96 if (value > 1) @{
4681 97 value *= factorial (value - 1);
4688 @kindex advance @var{location}
4689 @itemx advance @var{location}
4690 Continue running the program up to the given @var{location}. An argument is
4691 required, which should be of one of the forms described in
4692 @ref{Specify Location}.
4693 Execution will also stop upon exit from the current stack
4694 frame. This command is similar to @code{until}, but @code{advance} will
4695 not skip over recursive function calls, and the target location doesn't
4696 have to be in the same frame as the current one.
4700 @kindex si @r{(@code{stepi})}
4702 @itemx stepi @var{arg}
4704 Execute one machine instruction, then stop and return to the debugger.
4706 It is often useful to do @samp{display/i $pc} when stepping by machine
4707 instructions. This makes @value{GDBN} automatically display the next
4708 instruction to be executed, each time your program stops. @xref{Auto
4709 Display,, Automatic Display}.
4711 An argument is a repeat count, as in @code{step}.
4715 @kindex ni @r{(@code{nexti})}
4717 @itemx nexti @var{arg}
4719 Execute one machine instruction, but if it is a function call,
4720 proceed until the function returns.
4722 An argument is a repeat count, as in @code{next}.
4729 A signal is an asynchronous event that can happen in a program. The
4730 operating system defines the possible kinds of signals, and gives each
4731 kind a name and a number. For example, in Unix @code{SIGINT} is the
4732 signal a program gets when you type an interrupt character (often @kbd{Ctrl-c});
4733 @code{SIGSEGV} is the signal a program gets from referencing a place in
4734 memory far away from all the areas in use; @code{SIGALRM} occurs when
4735 the alarm clock timer goes off (which happens only if your program has
4736 requested an alarm).
4738 @cindex fatal signals
4739 Some signals, including @code{SIGALRM}, are a normal part of the
4740 functioning of your program. Others, such as @code{SIGSEGV}, indicate
4741 errors; these signals are @dfn{fatal} (they kill your program immediately) if the
4742 program has not specified in advance some other way to handle the signal.
4743 @code{SIGINT} does not indicate an error in your program, but it is normally
4744 fatal so it can carry out the purpose of the interrupt: to kill the program.
4746 @value{GDBN} has the ability to detect any occurrence of a signal in your
4747 program. You can tell @value{GDBN} in advance what to do for each kind of
4750 @cindex handling signals
4751 Normally, @value{GDBN} is set up to let the non-erroneous signals like
4752 @code{SIGALRM} be silently passed to your program
4753 (so as not to interfere with their role in the program's functioning)
4754 but to stop your program immediately whenever an error signal happens.
4755 You can change these settings with the @code{handle} command.
4758 @kindex info signals
4762 Print a table of all the kinds of signals and how @value{GDBN} has been told to
4763 handle each one. You can use this to see the signal numbers of all
4764 the defined types of signals.
4766 @item info signals @var{sig}
4767 Similar, but print information only about the specified signal number.
4769 @code{info handle} is an alias for @code{info signals}.
4772 @item handle @var{signal} @r{[}@var{keywords}@dots{}@r{]}
4773 Change the way @value{GDBN} handles signal @var{signal}. @var{signal}
4774 can be the number of a signal or its name (with or without the
4775 @samp{SIG} at the beginning); a list of signal numbers of the form
4776 @samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the
4777 known signals. Optional arguments @var{keywords}, described below,
4778 say what change to make.
4782 The keywords allowed by the @code{handle} command can be abbreviated.
4783 Their full names are:
4787 @value{GDBN} should not stop your program when this signal happens. It may
4788 still print a message telling you that the signal has come in.
4791 @value{GDBN} should stop your program when this signal happens. This implies
4792 the @code{print} keyword as well.
4795 @value{GDBN} should print a message when this signal happens.
4798 @value{GDBN} should not mention the occurrence of the signal at all. This
4799 implies the @code{nostop} keyword as well.
4803 @value{GDBN} should allow your program to see this signal; your program
4804 can handle the signal, or else it may terminate if the signal is fatal
4805 and not handled. @code{pass} and @code{noignore} are synonyms.
4809 @value{GDBN} should not allow your program to see this signal.
4810 @code{nopass} and @code{ignore} are synonyms.
4814 When a signal stops your program, the signal is not visible to the
4816 continue. Your program sees the signal then, if @code{pass} is in
4817 effect for the signal in question @emph{at that time}. In other words,
4818 after @value{GDBN} reports a signal, you can use the @code{handle}
4819 command with @code{pass} or @code{nopass} to control whether your
4820 program sees that signal when you continue.
4822 The default is set to @code{nostop}, @code{noprint}, @code{pass} for
4823 non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and
4824 @code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the
4827 You can also use the @code{signal} command to prevent your program from
4828 seeing a signal, or cause it to see a signal it normally would not see,
4829 or to give it any signal at any time. For example, if your program stopped
4830 due to some sort of memory reference error, you might store correct
4831 values into the erroneous variables and continue, hoping to see more
4832 execution; but your program would probably terminate immediately as
4833 a result of the fatal signal once it saw the signal. To prevent this,
4834 you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
4837 @cindex extra signal information
4838 @anchor{extra signal information}
4840 On some targets, @value{GDBN} can inspect extra signal information
4841 associated with the intercepted signal, before it is actually
4842 delivered to the program being debugged. This information is exported
4843 by the convenience variable @code{$_siginfo}, and consists of data
4844 that is passed by the kernel to the signal handler at the time of the
4845 receipt of a signal. The data type of the information itself is
4846 target dependent. You can see the data type using the @code{ptype
4847 $_siginfo} command. On Unix systems, it typically corresponds to the
4848 standard @code{siginfo_t} type, as defined in the @file{signal.h}
4851 Here's an example, on a @sc{gnu}/Linux system, printing the stray
4852 referenced address that raised a segmentation fault.
4856 (@value{GDBP}) continue
4857 Program received signal SIGSEGV, Segmentation fault.
4858 0x0000000000400766 in main ()
4860 (@value{GDBP}) ptype $_siginfo
4867 struct @{...@} _kill;
4868 struct @{...@} _timer;
4870 struct @{...@} _sigchld;
4871 struct @{...@} _sigfault;
4872 struct @{...@} _sigpoll;
4875 (@value{GDBP}) ptype $_siginfo._sifields._sigfault
4879 (@value{GDBP}) p $_siginfo._sifields._sigfault.si_addr
4880 $1 = (void *) 0x7ffff7ff7000
4884 Depending on target support, @code{$_siginfo} may also be writable.
4887 @section Stopping and Starting Multi-thread Programs
4889 @cindex stopped threads
4890 @cindex threads, stopped
4892 @cindex continuing threads
4893 @cindex threads, continuing
4895 @value{GDBN} supports debugging programs with multiple threads
4896 (@pxref{Threads,, Debugging Programs with Multiple Threads}). There
4897 are two modes of controlling execution of your program within the
4898 debugger. In the default mode, referred to as @dfn{all-stop mode},
4899 when any thread in your program stops (for example, at a breakpoint
4900 or while being stepped), all other threads in the program are also stopped by
4901 @value{GDBN}. On some targets, @value{GDBN} also supports
4902 @dfn{non-stop mode}, in which other threads can continue to run freely while
4903 you examine the stopped thread in the debugger.
4906 * All-Stop Mode:: All threads stop when GDB takes control
4907 * Non-Stop Mode:: Other threads continue to execute
4908 * Background Execution:: Running your program asynchronously
4909 * Thread-Specific Breakpoints:: Controlling breakpoints
4910 * Interrupted System Calls:: GDB may interfere with system calls
4914 @subsection All-Stop Mode
4916 @cindex all-stop mode
4918 In all-stop mode, whenever your program stops under @value{GDBN} for any reason,
4919 @emph{all} threads of execution stop, not just the current thread. This
4920 allows you to examine the overall state of the program, including
4921 switching between threads, without worrying that things may change
4924 Conversely, whenever you restart the program, @emph{all} threads start
4925 executing. @emph{This is true even when single-stepping} with commands
4926 like @code{step} or @code{next}.
4928 In particular, @value{GDBN} cannot single-step all threads in lockstep.
4929 Since thread scheduling is up to your debugging target's operating
4930 system (not controlled by @value{GDBN}), other threads may
4931 execute more than one statement while the current thread completes a
4932 single step. Moreover, in general other threads stop in the middle of a
4933 statement, rather than at a clean statement boundary, when the program
4936 You might even find your program stopped in another thread after
4937 continuing or even single-stepping. This happens whenever some other
4938 thread runs into a breakpoint, a signal, or an exception before the
4939 first thread completes whatever you requested.
4941 @cindex automatic thread selection
4942 @cindex switching threads automatically
4943 @cindex threads, automatic switching
4944 Whenever @value{GDBN} stops your program, due to a breakpoint or a
4945 signal, it automatically selects the thread where that breakpoint or
4946 signal happened. @value{GDBN} alerts you to the context switch with a
4947 message such as @samp{[Switching to Thread @var{n}]} to identify the
4950 On some OSes, you can modify @value{GDBN}'s default behavior by
4951 locking the OS scheduler to allow only a single thread to run.
4954 @item set scheduler-locking @var{mode}
4955 @cindex scheduler locking mode
4956 @cindex lock scheduler
4957 Set the scheduler locking mode. If it is @code{off}, then there is no
4958 locking and any thread may run at any time. If @code{on}, then only the
4959 current thread may run when the inferior is resumed. The @code{step}
4960 mode optimizes for single-stepping; it prevents other threads
4961 from preempting the current thread while you are stepping, so that
4962 the focus of debugging does not change unexpectedly.
4963 Other threads only rarely (or never) get a chance to run
4964 when you step. They are more likely to run when you @samp{next} over a
4965 function call, and they are completely free to run when you use commands
4966 like @samp{continue}, @samp{until}, or @samp{finish}. However, unless another
4967 thread hits a breakpoint during its timeslice, @value{GDBN} does not change
4968 the current thread away from the thread that you are debugging.
4970 @item show scheduler-locking
4971 Display the current scheduler locking mode.
4974 @cindex resume threads of multiple processes simultaneously
4975 By default, when you issue one of the execution commands such as
4976 @code{continue}, @code{next} or @code{step}, @value{GDBN} allows only
4977 threads of the current inferior to run. For example, if @value{GDBN}
4978 is attached to two inferiors, each with two threads, the
4979 @code{continue} command resumes only the two threads of the current
4980 inferior. This is useful, for example, when you debug a program that
4981 forks and you want to hold the parent stopped (so that, for instance,
4982 it doesn't run to exit), while you debug the child. In other
4983 situations, you may not be interested in inspecting the current state
4984 of any of the processes @value{GDBN} is attached to, and you may want
4985 to resume them all until some breakpoint is hit. In the latter case,
4986 you can instruct @value{GDBN} to allow all threads of all the
4987 inferiors to run with the @w{@code{set schedule-multiple}} command.
4990 @kindex set schedule-multiple
4991 @item set schedule-multiple
4992 Set the mode for allowing threads of multiple processes to be resumed
4993 when an execution command is issued. When @code{on}, all threads of
4994 all processes are allowed to run. When @code{off}, only the threads
4995 of the current process are resumed. The default is @code{off}. The
4996 @code{scheduler-locking} mode takes precedence when set to @code{on},
4997 or while you are stepping and set to @code{step}.
4999 @item show schedule-multiple
5000 Display the current mode for resuming the execution of threads of
5005 @subsection Non-Stop Mode
5007 @cindex non-stop mode
5009 @c This section is really only a place-holder, and needs to be expanded
5010 @c with more details.
5012 For some multi-threaded targets, @value{GDBN} supports an optional
5013 mode of operation in which you can examine stopped program threads in
5014 the debugger while other threads continue to execute freely. This
5015 minimizes intrusion when debugging live systems, such as programs
5016 where some threads have real-time constraints or must continue to
5017 respond to external events. This is referred to as @dfn{non-stop} mode.
5019 In non-stop mode, when a thread stops to report a debugging event,
5020 @emph{only} that thread is stopped; @value{GDBN} does not stop other
5021 threads as well, in contrast to the all-stop mode behavior. Additionally,
5022 execution commands such as @code{continue} and @code{step} apply by default
5023 only to the current thread in non-stop mode, rather than all threads as
5024 in all-stop mode. This allows you to control threads explicitly in
5025 ways that are not possible in all-stop mode --- for example, stepping
5026 one thread while allowing others to run freely, stepping
5027 one thread while holding all others stopped, or stepping several threads
5028 independently and simultaneously.
5030 To enter non-stop mode, use this sequence of commands before you run
5031 or attach to your program:
5034 # Enable the async interface.
5037 # If using the CLI, pagination breaks non-stop.
5040 # Finally, turn it on!
5044 You can use these commands to manipulate the non-stop mode setting:
5047 @kindex set non-stop
5048 @item set non-stop on
5049 Enable selection of non-stop mode.
5050 @item set non-stop off
5051 Disable selection of non-stop mode.
5052 @kindex show non-stop
5054 Show the current non-stop enablement setting.
5057 Note these commands only reflect whether non-stop mode is enabled,
5058 not whether the currently-executing program is being run in non-stop mode.
5059 In particular, the @code{set non-stop} preference is only consulted when
5060 @value{GDBN} starts or connects to the target program, and it is generally
5061 not possible to switch modes once debugging has started. Furthermore,
5062 since not all targets support non-stop mode, even when you have enabled
5063 non-stop mode, @value{GDBN} may still fall back to all-stop operation by
5066 In non-stop mode, all execution commands apply only to the current thread
5067 by default. That is, @code{continue} only continues one thread.
5068 To continue all threads, issue @code{continue -a} or @code{c -a}.
5070 You can use @value{GDBN}'s background execution commands
5071 (@pxref{Background Execution}) to run some threads in the background
5072 while you continue to examine or step others from @value{GDBN}.
5073 The MI execution commands (@pxref{GDB/MI Program Execution}) are
5074 always executed asynchronously in non-stop mode.
5076 Suspending execution is done with the @code{interrupt} command when
5077 running in the background, or @kbd{Ctrl-c} during foreground execution.
5078 In all-stop mode, this stops the whole process;
5079 but in non-stop mode the interrupt applies only to the current thread.
5080 To stop the whole program, use @code{interrupt -a}.
5082 Other execution commands do not currently support the @code{-a} option.
5084 In non-stop mode, when a thread stops, @value{GDBN} doesn't automatically make
5085 that thread current, as it does in all-stop mode. This is because the
5086 thread stop notifications are asynchronous with respect to @value{GDBN}'s
5087 command interpreter, and it would be confusing if @value{GDBN} unexpectedly
5088 changed to a different thread just as you entered a command to operate on the
5089 previously current thread.
5091 @node Background Execution
5092 @subsection Background Execution
5094 @cindex foreground execution
5095 @cindex background execution
5096 @cindex asynchronous execution
5097 @cindex execution, foreground, background and asynchronous
5099 @value{GDBN}'s execution commands have two variants: the normal
5100 foreground (synchronous) behavior, and a background
5101 (asynchronous) behavior. In foreground execution, @value{GDBN} waits for
5102 the program to report that some thread has stopped before prompting for
5103 another command. In background execution, @value{GDBN} immediately gives
5104 a command prompt so that you can issue other commands while your program runs.
5106 You need to explicitly enable asynchronous mode before you can use
5107 background execution commands. You can use these commands to
5108 manipulate the asynchronous mode setting:
5111 @kindex set target-async
5112 @item set target-async on
5113 Enable asynchronous mode.
5114 @item set target-async off
5115 Disable asynchronous mode.
5116 @kindex show target-async
5117 @item show target-async
5118 Show the current target-async setting.
5121 If the target doesn't support async mode, @value{GDBN} issues an error
5122 message if you attempt to use the background execution commands.
5124 To specify background execution, add a @code{&} to the command. For example,
5125 the background form of the @code{continue} command is @code{continue&}, or
5126 just @code{c&}. The execution commands that accept background execution
5132 @xref{Starting, , Starting your Program}.
5136 @xref{Attach, , Debugging an Already-running Process}.
5140 @xref{Continuing and Stepping, step}.
5144 @xref{Continuing and Stepping, stepi}.
5148 @xref{Continuing and Stepping, next}.
5152 @xref{Continuing and Stepping, nexti}.
5156 @xref{Continuing and Stepping, continue}.
5160 @xref{Continuing and Stepping, finish}.
5164 @xref{Continuing and Stepping, until}.
5168 Background execution is especially useful in conjunction with non-stop
5169 mode for debugging programs with multiple threads; see @ref{Non-Stop Mode}.
5170 However, you can also use these commands in the normal all-stop mode with
5171 the restriction that you cannot issue another execution command until the
5172 previous one finishes. Examples of commands that are valid in all-stop
5173 mode while the program is running include @code{help} and @code{info break}.
5175 You can interrupt your program while it is running in the background by
5176 using the @code{interrupt} command.
5183 Suspend execution of the running program. In all-stop mode,
5184 @code{interrupt} stops the whole process, but in non-stop mode, it stops
5185 only the current thread. To stop the whole program in non-stop mode,
5186 use @code{interrupt -a}.
5189 @node Thread-Specific Breakpoints
5190 @subsection Thread-Specific Breakpoints
5192 When your program has multiple threads (@pxref{Threads,, Debugging
5193 Programs with Multiple Threads}), you can choose whether to set
5194 breakpoints on all threads, or on a particular thread.
5197 @cindex breakpoints and threads
5198 @cindex thread breakpoints
5199 @kindex break @dots{} thread @var{threadno}
5200 @item break @var{linespec} thread @var{threadno}
5201 @itemx break @var{linespec} thread @var{threadno} if @dots{}
5202 @var{linespec} specifies source lines; there are several ways of
5203 writing them (@pxref{Specify Location}), but the effect is always to
5204 specify some source line.
5206 Use the qualifier @samp{thread @var{threadno}} with a breakpoint command
5207 to specify that you only want @value{GDBN} to stop the program when a
5208 particular thread reaches this breakpoint. @var{threadno} is one of the
5209 numeric thread identifiers assigned by @value{GDBN}, shown in the first
5210 column of the @samp{info threads} display.
5212 If you do not specify @samp{thread @var{threadno}} when you set a
5213 breakpoint, the breakpoint applies to @emph{all} threads of your
5216 You can use the @code{thread} qualifier on conditional breakpoints as
5217 well; in this case, place @samp{thread @var{threadno}} before the
5218 breakpoint condition, like this:
5221 (@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
5226 @node Interrupted System Calls
5227 @subsection Interrupted System Calls
5229 @cindex thread breakpoints and system calls
5230 @cindex system calls and thread breakpoints
5231 @cindex premature return from system calls
5232 There is an unfortunate side effect when using @value{GDBN} to debug
5233 multi-threaded programs. If one thread stops for a
5234 breakpoint, or for some other reason, and another thread is blocked in a
5235 system call, then the system call may return prematurely. This is a
5236 consequence of the interaction between multiple threads and the signals
5237 that @value{GDBN} uses to implement breakpoints and other events that
5240 To handle this problem, your program should check the return value of
5241 each system call and react appropriately. This is good programming
5244 For example, do not write code like this:
5250 The call to @code{sleep} will return early if a different thread stops
5251 at a breakpoint or for some other reason.
5253 Instead, write this:
5258 unslept = sleep (unslept);
5261 A system call is allowed to return early, so the system is still
5262 conforming to its specification. But @value{GDBN} does cause your
5263 multi-threaded program to behave differently than it would without
5266 Also, @value{GDBN} uses internal breakpoints in the thread library to
5267 monitor certain events such as thread creation and thread destruction.
5268 When such an event happens, a system call in another thread may return
5269 prematurely, even though your program does not appear to stop.
5272 @node Reverse Execution
5273 @chapter Running programs backward
5274 @cindex reverse execution
5275 @cindex running programs backward
5277 When you are debugging a program, it is not unusual to realize that
5278 you have gone too far, and some event of interest has already happened.
5279 If the target environment supports it, @value{GDBN} can allow you to
5280 ``rewind'' the program by running it backward.
5282 A target environment that supports reverse execution should be able
5283 to ``undo'' the changes in machine state that have taken place as the
5284 program was executing normally. Variables, registers etc.@: should
5285 revert to their previous values. Obviously this requires a great
5286 deal of sophistication on the part of the target environment; not
5287 all target environments can support reverse execution.
5289 When a program is executed in reverse, the instructions that
5290 have most recently been executed are ``un-executed'', in reverse
5291 order. The program counter runs backward, following the previous
5292 thread of execution in reverse. As each instruction is ``un-executed'',
5293 the values of memory and/or registers that were changed by that
5294 instruction are reverted to their previous states. After executing
5295 a piece of source code in reverse, all side effects of that code
5296 should be ``undone'', and all variables should be returned to their
5297 prior values@footnote{
5298 Note that some side effects are easier to undo than others. For instance,
5299 memory and registers are relatively easy, but device I/O is hard. Some
5300 targets may be able undo things like device I/O, and some may not.
5302 The contract between @value{GDBN} and the reverse executing target
5303 requires only that the target do something reasonable when
5304 @value{GDBN} tells it to execute backwards, and then report the
5305 results back to @value{GDBN}. Whatever the target reports back to
5306 @value{GDBN}, @value{GDBN} will report back to the user. @value{GDBN}
5307 assumes that the memory and registers that the target reports are in a
5308 consistant state, but @value{GDBN} accepts whatever it is given.
5311 If you are debugging in a target environment that supports
5312 reverse execution, @value{GDBN} provides the following commands.
5315 @kindex reverse-continue
5316 @kindex rc @r{(@code{reverse-continue})}
5317 @item reverse-continue @r{[}@var{ignore-count}@r{]}
5318 @itemx rc @r{[}@var{ignore-count}@r{]}
5319 Beginning at the point where your program last stopped, start executing
5320 in reverse. Reverse execution will stop for breakpoints and synchronous
5321 exceptions (signals), just like normal execution. Behavior of
5322 asynchronous signals depends on the target environment.
5324 @kindex reverse-step
5325 @kindex rs @r{(@code{step})}
5326 @item reverse-step @r{[}@var{count}@r{]}
5327 Run the program backward until control reaches the start of a
5328 different source line; then stop it, and return control to @value{GDBN}.
5330 Like the @code{step} command, @code{reverse-step} will only stop
5331 at the beginning of a source line. It ``un-executes'' the previously
5332 executed source line. If the previous source line included calls to
5333 debuggable functions, @code{reverse-step} will step (backward) into
5334 the called function, stopping at the beginning of the @emph{last}
5335 statement in the called function (typically a return statement).
5337 Also, as with the @code{step} command, if non-debuggable functions are
5338 called, @code{reverse-step} will run thru them backward without stopping.
5340 @kindex reverse-stepi
5341 @kindex rsi @r{(@code{reverse-stepi})}
5342 @item reverse-stepi @r{[}@var{count}@r{]}
5343 Reverse-execute one machine instruction. Note that the instruction
5344 to be reverse-executed is @emph{not} the one pointed to by the program
5345 counter, but the instruction executed prior to that one. For instance,
5346 if the last instruction was a jump, @code{reverse-stepi} will take you
5347 back from the destination of the jump to the jump instruction itself.
5349 @kindex reverse-next
5350 @kindex rn @r{(@code{reverse-next})}
5351 @item reverse-next @r{[}@var{count}@r{]}
5352 Run backward to the beginning of the previous line executed in
5353 the current (innermost) stack frame. If the line contains function
5354 calls, they will be ``un-executed'' without stopping. Starting from
5355 the first line of a function, @code{reverse-next} will take you back
5356 to the caller of that function, @emph{before} the function was called,
5357 just as the normal @code{next} command would take you from the last
5358 line of a function back to its return to its caller
5359 @footnote{Unles the code is too heavily optimized.}.
5361 @kindex reverse-nexti
5362 @kindex rni @r{(@code{reverse-nexti})}
5363 @item reverse-nexti @r{[}@var{count}@r{]}
5364 Like @code{nexti}, @code{reverse-nexti} executes a single instruction
5365 in reverse, except that called functions are ``un-executed'' atomically.
5366 That is, if the previously executed instruction was a return from
5367 another instruction, @code{reverse-nexti} will continue to execute
5368 in reverse until the call to that function (from the current stack
5371 @kindex reverse-finish
5372 @item reverse-finish
5373 Just as the @code{finish} command takes you to the point where the
5374 current function returns, @code{reverse-finish} takes you to the point
5375 where it was called. Instead of ending up at the end of the current
5376 function invocation, you end up at the beginning.
5378 @kindex set exec-direction
5379 @item set exec-direction
5380 Set the direction of target execution.
5381 @itemx set exec-direction reverse
5382 @cindex execute forward or backward in time
5383 @value{GDBN} will perform all execution commands in reverse, until the
5384 exec-direction mode is changed to ``forward''. Affected commands include
5385 @code{step, stepi, next, nexti, continue, and finish}. The @code{return}
5386 command cannot be used in reverse mode.
5387 @item set exec-direction forward
5388 @value{GDBN} will perform all execution commands in the normal fashion.
5389 This is the default.
5393 @node Process Record and Replay
5394 @chapter Recording Inferior's Execution and Replaying It
5395 @cindex process record and replay
5396 @cindex recording inferior's execution and replaying it
5398 On some platforms, @value{GDBN} provides a special @dfn{process record
5399 and replay} target that can record a log of the process execution, and
5400 replay it later with both forward and reverse execution commands.
5403 When this target is in use, if the execution log includes the record
5404 for the next instruction, @value{GDBN} will debug in @dfn{replay
5405 mode}. In the replay mode, the inferior does not really execute code
5406 instructions. Instead, all the events that normally happen during
5407 code execution are taken from the execution log. While code is not
5408 really executed in replay mode, the values of registers (including the
5409 program counter register) and the memory of the inferior are still
5410 changed as they normally would. Their contents are taken from the
5414 If the record for the next instruction is not in the execution log,
5415 @value{GDBN} will debug in @dfn{record mode}. In this mode, the
5416 inferior executes normally, and @value{GDBN} records the execution log
5419 The process record and replay target supports reverse execution
5420 (@pxref{Reverse Execution}), even if the platform on which the
5421 inferior runs does not. However, the reverse execution is limited in
5422 this case by the range of the instructions recorded in the execution
5423 log. In other words, reverse execution on platforms that don't
5424 support it directly can only be done in the replay mode.
5426 When debugging in the reverse direction, @value{GDBN} will work in
5427 replay mode as long as the execution log includes the record for the
5428 previous instruction; otherwise, it will work in record mode, if the
5429 platform supports reverse execution, or stop if not.
5431 For architecture environments that support process record and replay,
5432 @value{GDBN} provides the following commands:
5435 @kindex target record
5439 This command starts the process record and replay target. The process
5440 record and replay target can only debug a process that is already
5441 running. Therefore, you need first to start the process with the
5442 @kbd{run} or @kbd{start} commands, and then start the recording with
5443 the @kbd{target record} command.
5445 Both @code{record} and @code{rec} are aliases of @code{target record}.
5447 @cindex displaced stepping, and process record and replay
5448 Displaced stepping (@pxref{Maintenance Commands,, displaced stepping})
5449 will be automatically disabled when process record and replay target
5450 is started. That's because the process record and replay target
5451 doesn't support displaced stepping.
5453 @cindex non-stop mode, and process record and replay
5454 @cindex asynchronous execution, and process record and replay
5455 If the inferior is in the non-stop mode (@pxref{Non-Stop Mode}) or in
5456 the asynchronous execution mode (@pxref{Background Execution}), the
5457 process record and replay target cannot be started because it doesn't
5458 support these two modes.
5463 Stop the process record and replay target. When process record and
5464 replay target stops, the entire execution log will be deleted and the
5465 inferior will either be terminated, or will remain in its final state.
5467 When you stop the process record and replay target in record mode (at
5468 the end of the execution log), the inferior will be stopped at the
5469 next instruction that would have been recorded. In other words, if
5470 you record for a while and then stop recording, the inferior process
5471 will be left in the same state as if the recording never happened.
5473 On the other hand, if the process record and replay target is stopped
5474 while in replay mode (that is, not at the end of the execution log,
5475 but at some earlier point), the inferior process will become ``live''
5476 at that earlier state, and it will then be possible to continue the
5477 usual ``live'' debugging of the process from that state.
5479 When the inferior process exits, or @value{GDBN} detaches from it,
5480 process record and replay target will automatically stop itself.
5482 @kindex set record insn-number-max
5483 @item set record insn-number-max @var{limit}
5484 Set the limit of instructions to be recorded. Default value is 200000.
5486 If @var{limit} is a positive number, then @value{GDBN} will start
5487 deleting instructions from the log once the number of the record
5488 instructions becomes greater than @var{limit}. For every new recorded
5489 instruction, @value{GDBN} will delete the earliest recorded
5490 instruction to keep the number of recorded instructions at the limit.
5491 (Since deleting recorded instructions loses information, @value{GDBN}
5492 lets you control what happens when the limit is reached, by means of
5493 the @code{stop-at-limit} option, described below.)
5495 If @var{limit} is zero, @value{GDBN} will never delete recorded
5496 instructions from the execution log. The number of recorded
5497 instructions is unlimited in this case.
5499 @kindex show record insn-number-max
5500 @item show record insn-number-max
5501 Show the limit of instructions to be recorded.
5503 @kindex set record stop-at-limit
5504 @item set record stop-at-limit
5505 Control the behavior when the number of recorded instructions reaches
5506 the limit. If ON (the default), @value{GDBN} will stop when the limit
5507 is reached for the first time and ask you whether you want to stop the
5508 inferior or continue running it and recording the execution log. If
5509 you decide to continue recording, each new recorded instruction will
5510 cause the oldest one to be deleted.
5512 If this option is OFF, @value{GDBN} will automatically delete the
5513 oldest record to make room for each new one, without asking.
5515 @kindex show record stop-at-limit
5516 @item show record stop-at-limit
5517 Show the current setting of @code{stop-at-limit}.
5519 @kindex info record insn-number
5520 @item info record insn-number
5521 Show the current number of recorded instructions.
5523 @kindex record delete
5526 When record target runs in replay mode (``in the past''), delete the
5527 subsequent execution log and begin to record a new execution log starting
5528 from the current address. This means you will abandon the previously
5529 recorded ``future'' and begin recording a new ``future''.
5534 @chapter Examining the Stack
5536 When your program has stopped, the first thing you need to know is where it
5537 stopped and how it got there.
5540 Each time your program performs a function call, information about the call
5542 That information includes the location of the call in your program,
5543 the arguments of the call,
5544 and the local variables of the function being called.
5545 The information is saved in a block of data called a @dfn{stack frame}.
5546 The stack frames are allocated in a region of memory called the @dfn{call
5549 When your program stops, the @value{GDBN} commands for examining the
5550 stack allow you to see all of this information.
5552 @cindex selected frame
5553 One of the stack frames is @dfn{selected} by @value{GDBN} and many
5554 @value{GDBN} commands refer implicitly to the selected frame. In
5555 particular, whenever you ask @value{GDBN} for the value of a variable in
5556 your program, the value is found in the selected frame. There are
5557 special @value{GDBN} commands to select whichever frame you are
5558 interested in. @xref{Selection, ,Selecting a Frame}.
5560 When your program stops, @value{GDBN} automatically selects the
5561 currently executing frame and describes it briefly, similar to the
5562 @code{frame} command (@pxref{Frame Info, ,Information about a Frame}).
5565 * Frames:: Stack frames
5566 * Backtrace:: Backtraces
5567 * Selection:: Selecting a frame
5568 * Frame Info:: Information on a frame
5573 @section Stack Frames
5575 @cindex frame, definition
5577 The call stack is divided up into contiguous pieces called @dfn{stack
5578 frames}, or @dfn{frames} for short; each frame is the data associated
5579 with one call to one function. The frame contains the arguments given
5580 to the function, the function's local variables, and the address at
5581 which the function is executing.
5583 @cindex initial frame
5584 @cindex outermost frame
5585 @cindex innermost frame
5586 When your program is started, the stack has only one frame, that of the
5587 function @code{main}. This is called the @dfn{initial} frame or the
5588 @dfn{outermost} frame. Each time a function is called, a new frame is
5589 made. Each time a function returns, the frame for that function invocation
5590 is eliminated. If a function is recursive, there can be many frames for
5591 the same function. The frame for the function in which execution is
5592 actually occurring is called the @dfn{innermost} frame. This is the most
5593 recently created of all the stack frames that still exist.
5595 @cindex frame pointer
5596 Inside your program, stack frames are identified by their addresses. A
5597 stack frame consists of many bytes, each of which has its own address; each
5598 kind of computer has a convention for choosing one byte whose
5599 address serves as the address of the frame. Usually this address is kept
5600 in a register called the @dfn{frame pointer register}
5601 (@pxref{Registers, $fp}) while execution is going on in that frame.
5603 @cindex frame number
5604 @value{GDBN} assigns numbers to all existing stack frames, starting with
5605 zero for the innermost frame, one for the frame that called it,
5606 and so on upward. These numbers do not really exist in your program;
5607 they are assigned by @value{GDBN} to give you a way of designating stack
5608 frames in @value{GDBN} commands.
5610 @c The -fomit-frame-pointer below perennially causes hbox overflow
5611 @c underflow problems.
5612 @cindex frameless execution
5613 Some compilers provide a way to compile functions so that they operate
5614 without stack frames. (For example, the @value{NGCC} option
5616 @samp{-fomit-frame-pointer}
5618 generates functions without a frame.)
5619 This is occasionally done with heavily used library functions to save
5620 the frame setup time. @value{GDBN} has limited facilities for dealing
5621 with these function invocations. If the innermost function invocation
5622 has no stack frame, @value{GDBN} nevertheless regards it as though
5623 it had a separate frame, which is numbered zero as usual, allowing
5624 correct tracing of the function call chain. However, @value{GDBN} has
5625 no provision for frameless functions elsewhere in the stack.
5628 @kindex frame@r{, command}
5629 @cindex current stack frame
5630 @item frame @var{args}
5631 The @code{frame} command allows you to move from one stack frame to another,
5632 and to print the stack frame you select. @var{args} may be either the
5633 address of the frame or the stack frame number. Without an argument,
5634 @code{frame} prints the current stack frame.
5636 @kindex select-frame
5637 @cindex selecting frame silently
5639 The @code{select-frame} command allows you to move from one stack frame
5640 to another without printing the frame. This is the silent version of
5648 @cindex call stack traces
5649 A backtrace is a summary of how your program got where it is. It shows one
5650 line per frame, for many frames, starting with the currently executing
5651 frame (frame zero), followed by its caller (frame one), and on up the
5656 @kindex bt @r{(@code{backtrace})}
5659 Print a backtrace of the entire stack: one line per frame for all
5660 frames in the stack.
5662 You can stop the backtrace at any time by typing the system interrupt
5663 character, normally @kbd{Ctrl-c}.
5665 @item backtrace @var{n}
5667 Similar, but print only the innermost @var{n} frames.
5669 @item backtrace -@var{n}
5671 Similar, but print only the outermost @var{n} frames.
5673 @item backtrace full
5675 @itemx bt full @var{n}
5676 @itemx bt full -@var{n}
5677 Print the values of the local variables also. @var{n} specifies the
5678 number of frames to print, as described above.
5683 The names @code{where} and @code{info stack} (abbreviated @code{info s})
5684 are additional aliases for @code{backtrace}.
5686 @cindex multiple threads, backtrace
5687 In a multi-threaded program, @value{GDBN} by default shows the
5688 backtrace only for the current thread. To display the backtrace for
5689 several or all of the threads, use the command @code{thread apply}
5690 (@pxref{Threads, thread apply}). For example, if you type @kbd{thread
5691 apply all backtrace}, @value{GDBN} will display the backtrace for all
5692 the threads; this is handy when you debug a core dump of a
5693 multi-threaded program.
5695 Each line in the backtrace shows the frame number and the function name.
5696 The program counter value is also shown---unless you use @code{set
5697 print address off}. The backtrace also shows the source file name and
5698 line number, as well as the arguments to the function. The program
5699 counter value is omitted if it is at the beginning of the code for that
5702 Here is an example of a backtrace. It was made with the command
5703 @samp{bt 3}, so it shows the innermost three frames.
5707 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
5709 #1 0x6e38 in expand_macro (sym=0x2b600, data=...) at macro.c:242
5710 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
5712 (More stack frames follow...)
5717 The display for frame zero does not begin with a program counter
5718 value, indicating that your program has stopped at the beginning of the
5719 code for line @code{993} of @code{builtin.c}.
5722 The value of parameter @code{data} in frame 1 has been replaced by
5723 @code{@dots{}}. By default, @value{GDBN} prints the value of a parameter
5724 only if it is a scalar (integer, pointer, enumeration, etc). See command
5725 @kbd{set print frame-arguments} in @ref{Print Settings} for more details
5726 on how to configure the way function parameter values are printed.
5728 @cindex value optimized out, in backtrace
5729 @cindex function call arguments, optimized out
5730 If your program was compiled with optimizations, some compilers will
5731 optimize away arguments passed to functions if those arguments are
5732 never used after the call. Such optimizations generate code that
5733 passes arguments through registers, but doesn't store those arguments
5734 in the stack frame. @value{GDBN} has no way of displaying such
5735 arguments in stack frames other than the innermost one. Here's what
5736 such a backtrace might look like:
5740 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
5742 #1 0x6e38 in expand_macro (sym=<value optimized out>) at macro.c:242
5743 #2 0x6840 in expand_token (obs=0x0, t=<value optimized out>, td=0xf7fffb08)
5745 (More stack frames follow...)
5750 The values of arguments that were not saved in their stack frames are
5751 shown as @samp{<value optimized out>}.
5753 If you need to display the values of such optimized-out arguments,
5754 either deduce that from other variables whose values depend on the one
5755 you are interested in, or recompile without optimizations.
5757 @cindex backtrace beyond @code{main} function
5758 @cindex program entry point
5759 @cindex startup code, and backtrace
5760 Most programs have a standard user entry point---a place where system
5761 libraries and startup code transition into user code. For C this is
5762 @code{main}@footnote{
5763 Note that embedded programs (the so-called ``free-standing''
5764 environment) are not required to have a @code{main} function as the
5765 entry point. They could even have multiple entry points.}.
5766 When @value{GDBN} finds the entry function in a backtrace
5767 it will terminate the backtrace, to avoid tracing into highly
5768 system-specific (and generally uninteresting) code.
5770 If you need to examine the startup code, or limit the number of levels
5771 in a backtrace, you can change this behavior:
5774 @item set backtrace past-main
5775 @itemx set backtrace past-main on
5776 @kindex set backtrace
5777 Backtraces will continue past the user entry point.
5779 @item set backtrace past-main off
5780 Backtraces will stop when they encounter the user entry point. This is the
5783 @item show backtrace past-main
5784 @kindex show backtrace
5785 Display the current user entry point backtrace policy.
5787 @item set backtrace past-entry
5788 @itemx set backtrace past-entry on
5789 Backtraces will continue past the internal entry point of an application.
5790 This entry point is encoded by the linker when the application is built,
5791 and is likely before the user entry point @code{main} (or equivalent) is called.
5793 @item set backtrace past-entry off
5794 Backtraces will stop when they encounter the internal entry point of an
5795 application. This is the default.
5797 @item show backtrace past-entry
5798 Display the current internal entry point backtrace policy.
5800 @item set backtrace limit @var{n}
5801 @itemx set backtrace limit 0
5802 @cindex backtrace limit
5803 Limit the backtrace to @var{n} levels. A value of zero means
5806 @item show backtrace limit
5807 Display the current limit on backtrace levels.
5811 @section Selecting a Frame
5813 Most commands for examining the stack and other data in your program work on
5814 whichever stack frame is selected at the moment. Here are the commands for
5815 selecting a stack frame; all of them finish by printing a brief description
5816 of the stack frame just selected.
5819 @kindex frame@r{, selecting}
5820 @kindex f @r{(@code{frame})}
5823 Select frame number @var{n}. Recall that frame zero is the innermost
5824 (currently executing) frame, frame one is the frame that called the
5825 innermost one, and so on. The highest-numbered frame is the one for
5828 @item frame @var{addr}
5830 Select the frame at address @var{addr}. This is useful mainly if the
5831 chaining of stack frames has been damaged by a bug, making it
5832 impossible for @value{GDBN} to assign numbers properly to all frames. In
5833 addition, this can be useful when your program has multiple stacks and
5834 switches between them.
5836 On the SPARC architecture, @code{frame} needs two addresses to
5837 select an arbitrary frame: a frame pointer and a stack pointer.
5839 On the MIPS and Alpha architecture, it needs two addresses: a stack
5840 pointer and a program counter.
5842 On the 29k architecture, it needs three addresses: a register stack
5843 pointer, a program counter, and a memory stack pointer.
5847 Move @var{n} frames up the stack. For positive numbers @var{n}, this
5848 advances toward the outermost frame, to higher frame numbers, to frames
5849 that have existed longer. @var{n} defaults to one.
5852 @kindex do @r{(@code{down})}
5854 Move @var{n} frames down the stack. For positive numbers @var{n}, this
5855 advances toward the innermost frame, to lower frame numbers, to frames
5856 that were created more recently. @var{n} defaults to one. You may
5857 abbreviate @code{down} as @code{do}.
5860 All of these commands end by printing two lines of output describing the
5861 frame. The first line shows the frame number, the function name, the
5862 arguments, and the source file and line number of execution in that
5863 frame. The second line shows the text of that source line.
5871 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
5873 10 read_input_file (argv[i]);
5877 After such a printout, the @code{list} command with no arguments
5878 prints ten lines centered on the point of execution in the frame.
5879 You can also edit the program at the point of execution with your favorite
5880 editing program by typing @code{edit}.
5881 @xref{List, ,Printing Source Lines},
5885 @kindex down-silently
5887 @item up-silently @var{n}
5888 @itemx down-silently @var{n}
5889 These two commands are variants of @code{up} and @code{down},
5890 respectively; they differ in that they do their work silently, without
5891 causing display of the new frame. They are intended primarily for use
5892 in @value{GDBN} command scripts, where the output might be unnecessary and
5897 @section Information About a Frame
5899 There are several other commands to print information about the selected
5905 When used without any argument, this command does not change which
5906 frame is selected, but prints a brief description of the currently
5907 selected stack frame. It can be abbreviated @code{f}. With an
5908 argument, this command is used to select a stack frame.
5909 @xref{Selection, ,Selecting a Frame}.
5912 @kindex info f @r{(@code{info frame})}
5915 This command prints a verbose description of the selected stack frame,
5920 the address of the frame
5922 the address of the next frame down (called by this frame)
5924 the address of the next frame up (caller of this frame)
5926 the language in which the source code corresponding to this frame is written
5928 the address of the frame's arguments
5930 the address of the frame's local variables
5932 the program counter saved in it (the address of execution in the caller frame)
5934 which registers were saved in the frame
5937 @noindent The verbose description is useful when
5938 something has gone wrong that has made the stack format fail to fit
5939 the usual conventions.
5941 @item info frame @var{addr}
5942 @itemx info f @var{addr}
5943 Print a verbose description of the frame at address @var{addr}, without
5944 selecting that frame. The selected frame remains unchanged by this
5945 command. This requires the same kind of address (more than one for some
5946 architectures) that you specify in the @code{frame} command.
5947 @xref{Selection, ,Selecting a Frame}.
5951 Print the arguments of the selected frame, each on a separate line.
5955 Print the local variables of the selected frame, each on a separate
5956 line. These are all variables (declared either static or automatic)
5957 accessible at the point of execution of the selected frame.
5960 @cindex catch exceptions, list active handlers
5961 @cindex exception handlers, how to list
5963 Print a list of all the exception handlers that are active in the
5964 current stack frame at the current point of execution. To see other
5965 exception handlers, visit the associated frame (using the @code{up},
5966 @code{down}, or @code{frame} commands); then type @code{info catch}.
5967 @xref{Set Catchpoints, , Setting Catchpoints}.
5973 @chapter Examining Source Files
5975 @value{GDBN} can print parts of your program's source, since the debugging
5976 information recorded in the program tells @value{GDBN} what source files were
5977 used to build it. When your program stops, @value{GDBN} spontaneously prints
5978 the line where it stopped. Likewise, when you select a stack frame
5979 (@pxref{Selection, ,Selecting a Frame}), @value{GDBN} prints the line where
5980 execution in that frame has stopped. You can print other portions of
5981 source files by explicit command.
5983 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
5984 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
5985 @value{GDBN} under @sc{gnu} Emacs}.
5988 * List:: Printing source lines
5989 * Specify Location:: How to specify code locations
5990 * Edit:: Editing source files
5991 * Search:: Searching source files
5992 * Source Path:: Specifying source directories
5993 * Machine Code:: Source and machine code
5997 @section Printing Source Lines
6000 @kindex l @r{(@code{list})}
6001 To print lines from a source file, use the @code{list} command
6002 (abbreviated @code{l}). By default, ten lines are printed.
6003 There are several ways to specify what part of the file you want to
6004 print; see @ref{Specify Location}, for the full list.
6006 Here are the forms of the @code{list} command most commonly used:
6009 @item list @var{linenum}
6010 Print lines centered around line number @var{linenum} in the
6011 current source file.
6013 @item list @var{function}
6014 Print lines centered around the beginning of function
6018 Print more lines. If the last lines printed were printed with a
6019 @code{list} command, this prints lines following the last lines
6020 printed; however, if the last line printed was a solitary line printed
6021 as part of displaying a stack frame (@pxref{Stack, ,Examining the
6022 Stack}), this prints lines centered around that line.
6025 Print lines just before the lines last printed.
6028 @cindex @code{list}, how many lines to display
6029 By default, @value{GDBN} prints ten source lines with any of these forms of
6030 the @code{list} command. You can change this using @code{set listsize}:
6033 @kindex set listsize
6034 @item set listsize @var{count}
6035 Make the @code{list} command display @var{count} source lines (unless
6036 the @code{list} argument explicitly specifies some other number).
6038 @kindex show listsize
6040 Display the number of lines that @code{list} prints.
6043 Repeating a @code{list} command with @key{RET} discards the argument,
6044 so it is equivalent to typing just @code{list}. This is more useful
6045 than listing the same lines again. An exception is made for an
6046 argument of @samp{-}; that argument is preserved in repetition so that
6047 each repetition moves up in the source file.
6049 In general, the @code{list} command expects you to supply zero, one or two
6050 @dfn{linespecs}. Linespecs specify source lines; there are several ways
6051 of writing them (@pxref{Specify Location}), but the effect is always
6052 to specify some source line.
6054 Here is a complete description of the possible arguments for @code{list}:
6057 @item list @var{linespec}
6058 Print lines centered around the line specified by @var{linespec}.
6060 @item list @var{first},@var{last}
6061 Print lines from @var{first} to @var{last}. Both arguments are
6062 linespecs. When a @code{list} command has two linespecs, and the
6063 source file of the second linespec is omitted, this refers to
6064 the same source file as the first linespec.
6066 @item list ,@var{last}
6067 Print lines ending with @var{last}.
6069 @item list @var{first},
6070 Print lines starting with @var{first}.
6073 Print lines just after the lines last printed.
6076 Print lines just before the lines last printed.
6079 As described in the preceding table.
6082 @node Specify Location
6083 @section Specifying a Location
6084 @cindex specifying location
6087 Several @value{GDBN} commands accept arguments that specify a location
6088 of your program's code. Since @value{GDBN} is a source-level
6089 debugger, a location usually specifies some line in the source code;
6090 for that reason, locations are also known as @dfn{linespecs}.
6092 Here are all the different ways of specifying a code location that
6093 @value{GDBN} understands:
6097 Specifies the line number @var{linenum} of the current source file.
6100 @itemx +@var{offset}
6101 Specifies the line @var{offset} lines before or after the @dfn{current
6102 line}. For the @code{list} command, the current line is the last one
6103 printed; for the breakpoint commands, this is the line at which
6104 execution stopped in the currently selected @dfn{stack frame}
6105 (@pxref{Frames, ,Frames}, for a description of stack frames.) When
6106 used as the second of the two linespecs in a @code{list} command,
6107 this specifies the line @var{offset} lines up or down from the first
6110 @item @var{filename}:@var{linenum}
6111 Specifies the line @var{linenum} in the source file @var{filename}.
6113 @item @var{function}
6114 Specifies the line that begins the body of the function @var{function}.
6115 For example, in C, this is the line with the open brace.
6117 @item @var{filename}:@var{function}
6118 Specifies the line that begins the body of the function @var{function}
6119 in the file @var{filename}. You only need the file name with a
6120 function name to avoid ambiguity when there are identically named
6121 functions in different source files.
6123 @item *@var{address}
6124 Specifies the program address @var{address}. For line-oriented
6125 commands, such as @code{list} and @code{edit}, this specifies a source
6126 line that contains @var{address}. For @code{break} and other
6127 breakpoint oriented commands, this can be used to set breakpoints in
6128 parts of your program which do not have debugging information or
6131 Here @var{address} may be any expression valid in the current working
6132 language (@pxref{Languages, working language}) that specifies a code
6133 address. In addition, as a convenience, @value{GDBN} extends the
6134 semantics of expressions used in locations to cover the situations
6135 that frequently happen during debugging. Here are the various forms
6139 @item @var{expression}
6140 Any expression valid in the current working language.
6142 @item @var{funcaddr}
6143 An address of a function or procedure derived from its name. In C,
6144 C@t{++}, Java, Objective-C, Fortran, minimal, and assembly, this is
6145 simply the function's name @var{function} (and actually a special case
6146 of a valid expression). In Pascal and Modula-2, this is
6147 @code{&@var{function}}. In Ada, this is @code{@var{function}'Address}
6148 (although the Pascal form also works).
6150 This form specifies the address of the function's first instruction,
6151 before the stack frame and arguments have been set up.
6153 @item '@var{filename}'::@var{funcaddr}
6154 Like @var{funcaddr} above, but also specifies the name of the source
6155 file explicitly. This is useful if the name of the function does not
6156 specify the function unambiguously, e.g., if there are several
6157 functions with identical names in different source files.
6164 @section Editing Source Files
6165 @cindex editing source files
6168 @kindex e @r{(@code{edit})}
6169 To edit the lines in a source file, use the @code{edit} command.
6170 The editing program of your choice
6171 is invoked with the current line set to
6172 the active line in the program.
6173 Alternatively, there are several ways to specify what part of the file you
6174 want to print if you want to see other parts of the program:
6177 @item edit @var{location}
6178 Edit the source file specified by @code{location}. Editing starts at
6179 that @var{location}, e.g., at the specified source line of the
6180 specified file. @xref{Specify Location}, for all the possible forms
6181 of the @var{location} argument; here are the forms of the @code{edit}
6182 command most commonly used:
6185 @item edit @var{number}
6186 Edit the current source file with @var{number} as the active line number.
6188 @item edit @var{function}
6189 Edit the file containing @var{function} at the beginning of its definition.
6194 @subsection Choosing your Editor
6195 You can customize @value{GDBN} to use any editor you want
6197 The only restriction is that your editor (say @code{ex}), recognizes the
6198 following command-line syntax:
6200 ex +@var{number} file
6202 The optional numeric value +@var{number} specifies the number of the line in
6203 the file where to start editing.}.
6204 By default, it is @file{@value{EDITOR}}, but you can change this
6205 by setting the environment variable @code{EDITOR} before using
6206 @value{GDBN}. For example, to configure @value{GDBN} to use the
6207 @code{vi} editor, you could use these commands with the @code{sh} shell:
6213 or in the @code{csh} shell,
6215 setenv EDITOR /usr/bin/vi
6220 @section Searching Source Files
6221 @cindex searching source files
6223 There are two commands for searching through the current source file for a
6228 @kindex forward-search
6229 @item forward-search @var{regexp}
6230 @itemx search @var{regexp}
6231 The command @samp{forward-search @var{regexp}} checks each line,
6232 starting with the one following the last line listed, for a match for
6233 @var{regexp}. It lists the line that is found. You can use the
6234 synonym @samp{search @var{regexp}} or abbreviate the command name as
6237 @kindex reverse-search
6238 @item reverse-search @var{regexp}
6239 The command @samp{reverse-search @var{regexp}} checks each line, starting
6240 with the one before the last line listed and going backward, for a match
6241 for @var{regexp}. It lists the line that is found. You can abbreviate
6242 this command as @code{rev}.
6246 @section Specifying Source Directories
6249 @cindex directories for source files
6250 Executable programs sometimes do not record the directories of the source
6251 files from which they were compiled, just the names. Even when they do,
6252 the directories could be moved between the compilation and your debugging
6253 session. @value{GDBN} has a list of directories to search for source files;
6254 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
6255 it tries all the directories in the list, in the order they are present
6256 in the list, until it finds a file with the desired name.
6258 For example, suppose an executable references the file
6259 @file{/usr/src/foo-1.0/lib/foo.c}, and our source path is
6260 @file{/mnt/cross}. The file is first looked up literally; if this
6261 fails, @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c} is tried; if this
6262 fails, @file{/mnt/cross/foo.c} is opened; if this fails, an error
6263 message is printed. @value{GDBN} does not look up the parts of the
6264 source file name, such as @file{/mnt/cross/src/foo-1.0/lib/foo.c}.
6265 Likewise, the subdirectories of the source path are not searched: if
6266 the source path is @file{/mnt/cross}, and the binary refers to
6267 @file{foo.c}, @value{GDBN} would not find it under
6268 @file{/mnt/cross/usr/src/foo-1.0/lib}.
6270 Plain file names, relative file names with leading directories, file
6271 names containing dots, etc.@: are all treated as described above; for
6272 instance, if the source path is @file{/mnt/cross}, and the source file
6273 is recorded as @file{../lib/foo.c}, @value{GDBN} would first try
6274 @file{../lib/foo.c}, then @file{/mnt/cross/../lib/foo.c}, and after
6275 that---@file{/mnt/cross/foo.c}.
6277 Note that the executable search path is @emph{not} used to locate the
6280 Whenever you reset or rearrange the source path, @value{GDBN} clears out
6281 any information it has cached about where source files are found and where
6282 each line is in the file.
6286 When you start @value{GDBN}, its source path includes only @samp{cdir}
6287 and @samp{cwd}, in that order.
6288 To add other directories, use the @code{directory} command.
6290 The search path is used to find both program source files and @value{GDBN}
6291 script files (read using the @samp{-command} option and @samp{source} command).
6293 In addition to the source path, @value{GDBN} provides a set of commands
6294 that manage a list of source path substitution rules. A @dfn{substitution
6295 rule} specifies how to rewrite source directories stored in the program's
6296 debug information in case the sources were moved to a different
6297 directory between compilation and debugging. A rule is made of
6298 two strings, the first specifying what needs to be rewritten in
6299 the path, and the second specifying how it should be rewritten.
6300 In @ref{set substitute-path}, we name these two parts @var{from} and
6301 @var{to} respectively. @value{GDBN} does a simple string replacement
6302 of @var{from} with @var{to} at the start of the directory part of the
6303 source file name, and uses that result instead of the original file
6304 name to look up the sources.
6306 Using the previous example, suppose the @file{foo-1.0} tree has been
6307 moved from @file{/usr/src} to @file{/mnt/cross}, then you can tell
6308 @value{GDBN} to replace @file{/usr/src} in all source path names with
6309 @file{/mnt/cross}. The first lookup will then be
6310 @file{/mnt/cross/foo-1.0/lib/foo.c} in place of the original location
6311 of @file{/usr/src/foo-1.0/lib/foo.c}. To define a source path
6312 substitution rule, use the @code{set substitute-path} command
6313 (@pxref{set substitute-path}).
6315 To avoid unexpected substitution results, a rule is applied only if the
6316 @var{from} part of the directory name ends at a directory separator.
6317 For instance, a rule substituting @file{/usr/source} into
6318 @file{/mnt/cross} will be applied to @file{/usr/source/foo-1.0} but
6319 not to @file{/usr/sourceware/foo-2.0}. And because the substitution
6320 is applied only at the beginning of the directory name, this rule will
6321 not be applied to @file{/root/usr/source/baz.c} either.
6323 In many cases, you can achieve the same result using the @code{directory}
6324 command. However, @code{set substitute-path} can be more efficient in
6325 the case where the sources are organized in a complex tree with multiple
6326 subdirectories. With the @code{directory} command, you need to add each
6327 subdirectory of your project. If you moved the entire tree while
6328 preserving its internal organization, then @code{set substitute-path}
6329 allows you to direct the debugger to all the sources with one single
6332 @code{set substitute-path} is also more than just a shortcut command.
6333 The source path is only used if the file at the original location no
6334 longer exists. On the other hand, @code{set substitute-path} modifies
6335 the debugger behavior to look at the rewritten location instead. So, if
6336 for any reason a source file that is not relevant to your executable is
6337 located at the original location, a substitution rule is the only
6338 method available to point @value{GDBN} at the new location.
6340 @cindex @samp{--with-relocated-sources}
6341 @cindex default source path substitution
6342 You can configure a default source path substitution rule by
6343 configuring @value{GDBN} with the
6344 @samp{--with-relocated-sources=@var{dir}} option. The @var{dir}
6345 should be the name of a directory under @value{GDBN}'s configured
6346 prefix (set with @samp{--prefix} or @samp{--exec-prefix}), and
6347 directory names in debug information under @var{dir} will be adjusted
6348 automatically if the installed @value{GDBN} is moved to a new
6349 location. This is useful if @value{GDBN}, libraries or executables
6350 with debug information and corresponding source code are being moved
6354 @item directory @var{dirname} @dots{}
6355 @item dir @var{dirname} @dots{}
6356 Add directory @var{dirname} to the front of the source path. Several
6357 directory names may be given to this command, separated by @samp{:}
6358 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
6359 part of absolute file names) or
6360 whitespace. You may specify a directory that is already in the source
6361 path; this moves it forward, so @value{GDBN} searches it sooner.
6365 @vindex $cdir@r{, convenience variable}
6366 @vindex $cwd@r{, convenience variable}
6367 @cindex compilation directory
6368 @cindex current directory
6369 @cindex working directory
6370 @cindex directory, current
6371 @cindex directory, compilation
6372 You can use the string @samp{$cdir} to refer to the compilation
6373 directory (if one is recorded), and @samp{$cwd} to refer to the current
6374 working directory. @samp{$cwd} is not the same as @samp{.}---the former
6375 tracks the current working directory as it changes during your @value{GDBN}
6376 session, while the latter is immediately expanded to the current
6377 directory at the time you add an entry to the source path.
6380 Reset the source path to its default value (@samp{$cdir:$cwd} on Unix systems). This requires confirmation.
6382 @c RET-repeat for @code{directory} is explicitly disabled, but since
6383 @c repeating it would be a no-op we do not say that. (thanks to RMS)
6385 @item show directories
6386 @kindex show directories
6387 Print the source path: show which directories it contains.
6389 @anchor{set substitute-path}
6390 @item set substitute-path @var{from} @var{to}
6391 @kindex set substitute-path
6392 Define a source path substitution rule, and add it at the end of the
6393 current list of existing substitution rules. If a rule with the same
6394 @var{from} was already defined, then the old rule is also deleted.
6396 For example, if the file @file{/foo/bar/baz.c} was moved to
6397 @file{/mnt/cross/baz.c}, then the command
6400 (@value{GDBP}) set substitute-path /usr/src /mnt/cross
6404 will tell @value{GDBN} to replace @samp{/usr/src} with
6405 @samp{/mnt/cross}, which will allow @value{GDBN} to find the file
6406 @file{baz.c} even though it was moved.
6408 In the case when more than one substitution rule have been defined,
6409 the rules are evaluated one by one in the order where they have been
6410 defined. The first one matching, if any, is selected to perform
6413 For instance, if we had entered the following commands:
6416 (@value{GDBP}) set substitute-path /usr/src/include /mnt/include
6417 (@value{GDBP}) set substitute-path /usr/src /mnt/src
6421 @value{GDBN} would then rewrite @file{/usr/src/include/defs.h} into
6422 @file{/mnt/include/defs.h} by using the first rule. However, it would
6423 use the second rule to rewrite @file{/usr/src/lib/foo.c} into
6424 @file{/mnt/src/lib/foo.c}.
6427 @item unset substitute-path [path]
6428 @kindex unset substitute-path
6429 If a path is specified, search the current list of substitution rules
6430 for a rule that would rewrite that path. Delete that rule if found.
6431 A warning is emitted by the debugger if no rule could be found.
6433 If no path is specified, then all substitution rules are deleted.
6435 @item show substitute-path [path]
6436 @kindex show substitute-path
6437 If a path is specified, then print the source path substitution rule
6438 which would rewrite that path, if any.
6440 If no path is specified, then print all existing source path substitution
6445 If your source path is cluttered with directories that are no longer of
6446 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
6447 versions of source. You can correct the situation as follows:
6451 Use @code{directory} with no argument to reset the source path to its default value.
6454 Use @code{directory} with suitable arguments to reinstall the
6455 directories you want in the source path. You can add all the
6456 directories in one command.
6460 @section Source and Machine Code
6461 @cindex source line and its code address
6463 You can use the command @code{info line} to map source lines to program
6464 addresses (and vice versa), and the command @code{disassemble} to display
6465 a range of addresses as machine instructions. You can use the command
6466 @code{set disassemble-next-line} to set whether to disassemble next
6467 source line when execution stops. When run under @sc{gnu} Emacs
6468 mode, the @code{info line} command causes the arrow to point to the
6469 line specified. Also, @code{info line} prints addresses in symbolic form as
6474 @item info line @var{linespec}
6475 Print the starting and ending addresses of the compiled code for
6476 source line @var{linespec}. You can specify source lines in any of
6477 the ways documented in @ref{Specify Location}.
6480 For example, we can use @code{info line} to discover the location of
6481 the object code for the first line of function
6482 @code{m4_changequote}:
6484 @c FIXME: I think this example should also show the addresses in
6485 @c symbolic form, as they usually would be displayed.
6487 (@value{GDBP}) info line m4_changequote
6488 Line 895 of "builtin.c" starts at pc 0x634c and ends at 0x6350.
6492 @cindex code address and its source line
6493 We can also inquire (using @code{*@var{addr}} as the form for
6494 @var{linespec}) what source line covers a particular address:
6496 (@value{GDBP}) info line *0x63ff
6497 Line 926 of "builtin.c" starts at pc 0x63e4 and ends at 0x6404.
6500 @cindex @code{$_} and @code{info line}
6501 @cindex @code{x} command, default address
6502 @kindex x@r{(examine), and} info line
6503 After @code{info line}, the default address for the @code{x} command
6504 is changed to the starting address of the line, so that @samp{x/i} is
6505 sufficient to begin examining the machine code (@pxref{Memory,
6506 ,Examining Memory}). Also, this address is saved as the value of the
6507 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
6512 @cindex assembly instructions
6513 @cindex instructions, assembly
6514 @cindex machine instructions
6515 @cindex listing machine instructions
6517 @itemx disassemble /m
6518 @itemx disassemble /r
6519 This specialized command dumps a range of memory as machine
6520 instructions. It can also print mixed source+disassembly by specifying
6521 the @code{/m} modifier and print the raw instructions in hex as well as
6522 in symbolic form by specifying the @code{/r}.
6523 The default memory range is the function surrounding the
6524 program counter of the selected frame. A single argument to this
6525 command is a program counter value; @value{GDBN} dumps the function
6526 surrounding this value. Two arguments specify a range of addresses
6527 (first inclusive, second exclusive) to dump.
6529 If the range of memory being disassembled contains current program counter,
6530 the instruction at that location is shown with a @code{=>} marker.
6533 The following example shows the disassembly of a range of addresses of
6534 HP PA-RISC 2.0 code:
6537 (@value{GDBP}) disas 0x32c4 0x32e4
6538 Dump of assembler code from 0x32c4 to 0x32e4:
6539 0x32c4 <main+204>: addil 0,dp
6540 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
6541 0x32cc <main+212>: ldil 0x3000,r31
6542 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
6543 0x32d4 <main+220>: ldo 0(r31),rp
6544 0x32d8 <main+224>: addil -0x800,dp
6545 0x32dc <main+228>: ldo 0x588(r1),r26
6546 0x32e0 <main+232>: ldil 0x3000,r31
6547 End of assembler dump.
6550 Here is an example showing mixed source+assembly for Intel x86, when the
6551 program is stopped just after function prologue:
6554 (@value{GDBP}) disas /m main
6555 Dump of assembler code for function main:
6557 0x08048330 <main+0>: push %ebp
6558 0x08048331 <main+1>: mov %esp,%ebp
6559 0x08048333 <main+3>: sub $0x8,%esp
6560 0x08048336 <main+6>: and $0xfffffff0,%esp
6561 0x08048339 <main+9>: sub $0x10,%esp
6563 6 printf ("Hello.\n");
6564 => 0x0804833c <main+12>: movl $0x8048440,(%esp)
6565 0x08048343 <main+19>: call 0x8048284 <puts@@plt>
6569 0x08048348 <main+24>: mov $0x0,%eax
6570 0x0804834d <main+29>: leave
6571 0x0804834e <main+30>: ret
6573 End of assembler dump.
6576 Some architectures have more than one commonly-used set of instruction
6577 mnemonics or other syntax.
6579 For programs that were dynamically linked and use shared libraries,
6580 instructions that call functions or branch to locations in the shared
6581 libraries might show a seemingly bogus location---it's actually a
6582 location of the relocation table. On some architectures, @value{GDBN}
6583 might be able to resolve these to actual function names.
6586 @kindex set disassembly-flavor
6587 @cindex Intel disassembly flavor
6588 @cindex AT&T disassembly flavor
6589 @item set disassembly-flavor @var{instruction-set}
6590 Select the instruction set to use when disassembling the
6591 program via the @code{disassemble} or @code{x/i} commands.
6593 Currently this command is only defined for the Intel x86 family. You
6594 can set @var{instruction-set} to either @code{intel} or @code{att}.
6595 The default is @code{att}, the AT&T flavor used by default by Unix
6596 assemblers for x86-based targets.
6598 @kindex show disassembly-flavor
6599 @item show disassembly-flavor
6600 Show the current setting of the disassembly flavor.
6604 @kindex set disassemble-next-line
6605 @kindex show disassemble-next-line
6606 @item set disassemble-next-line
6607 @itemx show disassemble-next-line
6608 Control whether or not @value{GDBN} will disassemble the next source
6609 line or instruction when execution stops. If ON, @value{GDBN} will
6610 display disassembly of the next source line when execution of the
6611 program being debugged stops. This is @emph{in addition} to
6612 displaying the source line itself, which @value{GDBN} always does if
6613 possible. If the next source line cannot be displayed for some reason
6614 (e.g., if @value{GDBN} cannot find the source file, or there's no line
6615 info in the debug info), @value{GDBN} will display disassembly of the
6616 next @emph{instruction} instead of showing the next source line. If
6617 AUTO, @value{GDBN} will display disassembly of next instruction only
6618 if the source line cannot be displayed. This setting causes
6619 @value{GDBN} to display some feedback when you step through a function
6620 with no line info or whose source file is unavailable. The default is
6621 OFF, which means never display the disassembly of the next line or
6627 @chapter Examining Data
6629 @cindex printing data
6630 @cindex examining data
6633 @c "inspect" is not quite a synonym if you are using Epoch, which we do not
6634 @c document because it is nonstandard... Under Epoch it displays in a
6635 @c different window or something like that.
6636 The usual way to examine data in your program is with the @code{print}
6637 command (abbreviated @code{p}), or its synonym @code{inspect}. It
6638 evaluates and prints the value of an expression of the language your
6639 program is written in (@pxref{Languages, ,Using @value{GDBN} with
6640 Different Languages}).
6643 @item print @var{expr}
6644 @itemx print /@var{f} @var{expr}
6645 @var{expr} is an expression (in the source language). By default the
6646 value of @var{expr} is printed in a format appropriate to its data type;
6647 you can choose a different format by specifying @samp{/@var{f}}, where
6648 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
6652 @itemx print /@var{f}
6653 @cindex reprint the last value
6654 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
6655 @dfn{value history}; @pxref{Value History, ,Value History}). This allows you to
6656 conveniently inspect the same value in an alternative format.
6659 A more low-level way of examining data is with the @code{x} command.
6660 It examines data in memory at a specified address and prints it in a
6661 specified format. @xref{Memory, ,Examining Memory}.
6663 If you are interested in information about types, or about how the
6664 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
6665 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
6669 * Expressions:: Expressions
6670 * Ambiguous Expressions:: Ambiguous Expressions
6671 * Variables:: Program variables
6672 * Arrays:: Artificial arrays
6673 * Output Formats:: Output formats
6674 * Memory:: Examining memory
6675 * Auto Display:: Automatic display
6676 * Print Settings:: Print settings
6677 * Value History:: Value history
6678 * Convenience Vars:: Convenience variables
6679 * Registers:: Registers
6680 * Floating Point Hardware:: Floating point hardware
6681 * Vector Unit:: Vector Unit
6682 * OS Information:: Auxiliary data provided by operating system
6683 * Memory Region Attributes:: Memory region attributes
6684 * Dump/Restore Files:: Copy between memory and a file
6685 * Core File Generation:: Cause a program dump its core
6686 * Character Sets:: Debugging programs that use a different
6687 character set than GDB does
6688 * Caching Remote Data:: Data caching for remote targets
6689 * Searching Memory:: Searching memory for a sequence of bytes
6693 @section Expressions
6696 @code{print} and many other @value{GDBN} commands accept an expression and
6697 compute its value. Any kind of constant, variable or operator defined
6698 by the programming language you are using is valid in an expression in
6699 @value{GDBN}. This includes conditional expressions, function calls,
6700 casts, and string constants. It also includes preprocessor macros, if
6701 you compiled your program to include this information; see
6704 @cindex arrays in expressions
6705 @value{GDBN} supports array constants in expressions input by
6706 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
6707 you can use the command @code{print @{1, 2, 3@}} to create an array
6708 of three integers. If you pass an array to a function or assign it
6709 to a program variable, @value{GDBN} copies the array to memory that
6710 is @code{malloc}ed in the target program.
6712 Because C is so widespread, most of the expressions shown in examples in
6713 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
6714 Languages}, for information on how to use expressions in other
6717 In this section, we discuss operators that you can use in @value{GDBN}
6718 expressions regardless of your programming language.
6720 @cindex casts, in expressions
6721 Casts are supported in all languages, not just in C, because it is so
6722 useful to cast a number into a pointer in order to examine a structure
6723 at that address in memory.
6724 @c FIXME: casts supported---Mod2 true?
6726 @value{GDBN} supports these operators, in addition to those common
6727 to programming languages:
6731 @samp{@@} is a binary operator for treating parts of memory as arrays.
6732 @xref{Arrays, ,Artificial Arrays}, for more information.
6735 @samp{::} allows you to specify a variable in terms of the file or
6736 function where it is defined. @xref{Variables, ,Program Variables}.
6738 @cindex @{@var{type}@}
6739 @cindex type casting memory
6740 @cindex memory, viewing as typed object
6741 @cindex casts, to view memory
6742 @item @{@var{type}@} @var{addr}
6743 Refers to an object of type @var{type} stored at address @var{addr} in
6744 memory. @var{addr} may be any expression whose value is an integer or
6745 pointer (but parentheses are required around binary operators, just as in
6746 a cast). This construct is allowed regardless of what kind of data is
6747 normally supposed to reside at @var{addr}.
6750 @node Ambiguous Expressions
6751 @section Ambiguous Expressions
6752 @cindex ambiguous expressions
6754 Expressions can sometimes contain some ambiguous elements. For instance,
6755 some programming languages (notably Ada, C@t{++} and Objective-C) permit
6756 a single function name to be defined several times, for application in
6757 different contexts. This is called @dfn{overloading}. Another example
6758 involving Ada is generics. A @dfn{generic package} is similar to C@t{++}
6759 templates and is typically instantiated several times, resulting in
6760 the same function name being defined in different contexts.
6762 In some cases and depending on the language, it is possible to adjust
6763 the expression to remove the ambiguity. For instance in C@t{++}, you
6764 can specify the signature of the function you want to break on, as in
6765 @kbd{break @var{function}(@var{types})}. In Ada, using the fully
6766 qualified name of your function often makes the expression unambiguous
6769 When an ambiguity that needs to be resolved is detected, the debugger
6770 has the capability to display a menu of numbered choices for each
6771 possibility, and then waits for the selection with the prompt @samp{>}.
6772 The first option is always @samp{[0] cancel}, and typing @kbd{0 @key{RET}}
6773 aborts the current command. If the command in which the expression was
6774 used allows more than one choice to be selected, the next option in the
6775 menu is @samp{[1] all}, and typing @kbd{1 @key{RET}} selects all possible
6778 For example, the following session excerpt shows an attempt to set a
6779 breakpoint at the overloaded symbol @code{String::after}.
6780 We choose three particular definitions of that function name:
6782 @c FIXME! This is likely to change to show arg type lists, at least
6785 (@value{GDBP}) b String::after
6788 [2] file:String.cc; line number:867
6789 [3] file:String.cc; line number:860
6790 [4] file:String.cc; line number:875
6791 [5] file:String.cc; line number:853
6792 [6] file:String.cc; line number:846
6793 [7] file:String.cc; line number:735
6795 Breakpoint 1 at 0xb26c: file String.cc, line 867.
6796 Breakpoint 2 at 0xb344: file String.cc, line 875.
6797 Breakpoint 3 at 0xafcc: file String.cc, line 846.
6798 Multiple breakpoints were set.
6799 Use the "delete" command to delete unwanted
6806 @kindex set multiple-symbols
6807 @item set multiple-symbols @var{mode}
6808 @cindex multiple-symbols menu
6810 This option allows you to adjust the debugger behavior when an expression
6813 By default, @var{mode} is set to @code{all}. If the command with which
6814 the expression is used allows more than one choice, then @value{GDBN}
6815 automatically selects all possible choices. For instance, inserting
6816 a breakpoint on a function using an ambiguous name results in a breakpoint
6817 inserted on each possible match. However, if a unique choice must be made,
6818 then @value{GDBN} uses the menu to help you disambiguate the expression.
6819 For instance, printing the address of an overloaded function will result
6820 in the use of the menu.
6822 When @var{mode} is set to @code{ask}, the debugger always uses the menu
6823 when an ambiguity is detected.
6825 Finally, when @var{mode} is set to @code{cancel}, the debugger reports
6826 an error due to the ambiguity and the command is aborted.
6828 @kindex show multiple-symbols
6829 @item show multiple-symbols
6830 Show the current value of the @code{multiple-symbols} setting.
6834 @section Program Variables
6836 The most common kind of expression to use is the name of a variable
6839 Variables in expressions are understood in the selected stack frame
6840 (@pxref{Selection, ,Selecting a Frame}); they must be either:
6844 global (or file-static)
6851 visible according to the scope rules of the
6852 programming language from the point of execution in that frame
6855 @noindent This means that in the function
6870 you can examine and use the variable @code{a} whenever your program is
6871 executing within the function @code{foo}, but you can only use or
6872 examine the variable @code{b} while your program is executing inside
6873 the block where @code{b} is declared.
6875 @cindex variable name conflict
6876 There is an exception: you can refer to a variable or function whose
6877 scope is a single source file even if the current execution point is not
6878 in this file. But it is possible to have more than one such variable or
6879 function with the same name (in different source files). If that
6880 happens, referring to that name has unpredictable effects. If you wish,
6881 you can specify a static variable in a particular function or file,
6882 using the colon-colon (@code{::}) notation:
6884 @cindex colon-colon, context for variables/functions
6886 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
6887 @cindex @code{::}, context for variables/functions
6890 @var{file}::@var{variable}
6891 @var{function}::@var{variable}
6895 Here @var{file} or @var{function} is the name of the context for the
6896 static @var{variable}. In the case of file names, you can use quotes to
6897 make sure @value{GDBN} parses the file name as a single word---for example,
6898 to print a global value of @code{x} defined in @file{f2.c}:
6901 (@value{GDBP}) p 'f2.c'::x
6904 @cindex C@t{++} scope resolution
6905 This use of @samp{::} is very rarely in conflict with the very similar
6906 use of the same notation in C@t{++}. @value{GDBN} also supports use of the C@t{++}
6907 scope resolution operator in @value{GDBN} expressions.
6908 @c FIXME: Um, so what happens in one of those rare cases where it's in
6911 @cindex wrong values
6912 @cindex variable values, wrong
6913 @cindex function entry/exit, wrong values of variables
6914 @cindex optimized code, wrong values of variables
6916 @emph{Warning:} Occasionally, a local variable may appear to have the
6917 wrong value at certain points in a function---just after entry to a new
6918 scope, and just before exit.
6920 You may see this problem when you are stepping by machine instructions.
6921 This is because, on most machines, it takes more than one instruction to
6922 set up a stack frame (including local variable definitions); if you are
6923 stepping by machine instructions, variables may appear to have the wrong
6924 values until the stack frame is completely built. On exit, it usually
6925 also takes more than one machine instruction to destroy a stack frame;
6926 after you begin stepping through that group of instructions, local
6927 variable definitions may be gone.
6929 This may also happen when the compiler does significant optimizations.
6930 To be sure of always seeing accurate values, turn off all optimization
6933 @cindex ``No symbol "foo" in current context''
6934 Another possible effect of compiler optimizations is to optimize
6935 unused variables out of existence, or assign variables to registers (as
6936 opposed to memory addresses). Depending on the support for such cases
6937 offered by the debug info format used by the compiler, @value{GDBN}
6938 might not be able to display values for such local variables. If that
6939 happens, @value{GDBN} will print a message like this:
6942 No symbol "foo" in current context.
6945 To solve such problems, either recompile without optimizations, or use a
6946 different debug info format, if the compiler supports several such
6947 formats. For example, @value{NGCC}, the @sc{gnu} C/C@t{++} compiler,
6948 usually supports the @option{-gstabs+} option. @option{-gstabs+}
6949 produces debug info in a format that is superior to formats such as
6950 COFF. You may be able to use DWARF 2 (@option{-gdwarf-2}), which is also
6951 an effective form for debug info. @xref{Debugging Options,,Options
6952 for Debugging Your Program or GCC, gcc.info, Using the @sc{gnu}
6953 Compiler Collection (GCC)}.
6954 @xref{C, ,C and C@t{++}}, for more information about debug info formats
6955 that are best suited to C@t{++} programs.
6957 If you ask to print an object whose contents are unknown to
6958 @value{GDBN}, e.g., because its data type is not completely specified
6959 by the debug information, @value{GDBN} will say @samp{<incomplete
6960 type>}. @xref{Symbols, incomplete type}, for more about this.
6962 Strings are identified as arrays of @code{char} values without specified
6963 signedness. Arrays of either @code{signed char} or @code{unsigned char} get
6964 printed as arrays of 1 byte sized integers. @code{-fsigned-char} or
6965 @code{-funsigned-char} @value{NGCC} options have no effect as @value{GDBN}
6966 defines literal string type @code{"char"} as @code{char} without a sign.
6971 signed char var1[] = "A";
6974 You get during debugging
6979 $2 = @{65 'A', 0 '\0'@}
6983 @section Artificial Arrays
6985 @cindex artificial array
6987 @kindex @@@r{, referencing memory as an array}
6988 It is often useful to print out several successive objects of the
6989 same type in memory; a section of an array, or an array of
6990 dynamically determined size for which only a pointer exists in the
6993 You can do this by referring to a contiguous span of memory as an
6994 @dfn{artificial array}, using the binary operator @samp{@@}. The left
6995 operand of @samp{@@} should be the first element of the desired array
6996 and be an individual object. The right operand should be the desired length
6997 of the array. The result is an array value whose elements are all of
6998 the type of the left argument. The first element is actually the left
6999 argument; the second element comes from bytes of memory immediately
7000 following those that hold the first element, and so on. Here is an
7001 example. If a program says
7004 int *array = (int *) malloc (len * sizeof (int));
7008 you can print the contents of @code{array} with
7014 The left operand of @samp{@@} must reside in memory. Array values made
7015 with @samp{@@} in this way behave just like other arrays in terms of
7016 subscripting, and are coerced to pointers when used in expressions.
7017 Artificial arrays most often appear in expressions via the value history
7018 (@pxref{Value History, ,Value History}), after printing one out.
7020 Another way to create an artificial array is to use a cast.
7021 This re-interprets a value as if it were an array.
7022 The value need not be in memory:
7024 (@value{GDBP}) p/x (short[2])0x12345678
7025 $1 = @{0x1234, 0x5678@}
7028 As a convenience, if you leave the array length out (as in
7029 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
7030 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
7032 (@value{GDBP}) p/x (short[])0x12345678
7033 $2 = @{0x1234, 0x5678@}
7036 Sometimes the artificial array mechanism is not quite enough; in
7037 moderately complex data structures, the elements of interest may not
7038 actually be adjacent---for example, if you are interested in the values
7039 of pointers in an array. One useful work-around in this situation is
7040 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
7041 Variables}) as a counter in an expression that prints the first
7042 interesting value, and then repeat that expression via @key{RET}. For
7043 instance, suppose you have an array @code{dtab} of pointers to
7044 structures, and you are interested in the values of a field @code{fv}
7045 in each structure. Here is an example of what you might type:
7055 @node Output Formats
7056 @section Output Formats
7058 @cindex formatted output
7059 @cindex output formats
7060 By default, @value{GDBN} prints a value according to its data type. Sometimes
7061 this is not what you want. For example, you might want to print a number
7062 in hex, or a pointer in decimal. Or you might want to view data in memory
7063 at a certain address as a character string or as an instruction. To do
7064 these things, specify an @dfn{output format} when you print a value.
7066 The simplest use of output formats is to say how to print a value
7067 already computed. This is done by starting the arguments of the
7068 @code{print} command with a slash and a format letter. The format
7069 letters supported are:
7073 Regard the bits of the value as an integer, and print the integer in
7077 Print as integer in signed decimal.
7080 Print as integer in unsigned decimal.
7083 Print as integer in octal.
7086 Print as integer in binary. The letter @samp{t} stands for ``two''.
7087 @footnote{@samp{b} cannot be used because these format letters are also
7088 used with the @code{x} command, where @samp{b} stands for ``byte'';
7089 see @ref{Memory,,Examining Memory}.}
7092 @cindex unknown address, locating
7093 @cindex locate address
7094 Print as an address, both absolute in hexadecimal and as an offset from
7095 the nearest preceding symbol. You can use this format used to discover
7096 where (in what function) an unknown address is located:
7099 (@value{GDBP}) p/a 0x54320
7100 $3 = 0x54320 <_initialize_vx+396>
7104 The command @code{info symbol 0x54320} yields similar results.
7105 @xref{Symbols, info symbol}.
7108 Regard as an integer and print it as a character constant. This
7109 prints both the numerical value and its character representation. The
7110 character representation is replaced with the octal escape @samp{\nnn}
7111 for characters outside the 7-bit @sc{ascii} range.
7113 Without this format, @value{GDBN} displays @code{char},
7114 @w{@code{unsigned char}}, and @w{@code{signed char}} data as character
7115 constants. Single-byte members of vectors are displayed as integer
7119 Regard the bits of the value as a floating point number and print
7120 using typical floating point syntax.
7123 @cindex printing strings
7124 @cindex printing byte arrays
7125 Regard as a string, if possible. With this format, pointers to single-byte
7126 data are displayed as null-terminated strings and arrays of single-byte data
7127 are displayed as fixed-length strings. Other values are displayed in their
7130 Without this format, @value{GDBN} displays pointers to and arrays of
7131 @code{char}, @w{@code{unsigned char}}, and @w{@code{signed char}} as
7132 strings. Single-byte members of a vector are displayed as an integer
7136 @cindex raw printing
7137 Print using the @samp{raw} formatting. By default, @value{GDBN} will
7138 use a type-specific pretty-printer. The @samp{r} format bypasses any
7139 pretty-printer which might exist for the value's type.
7142 For example, to print the program counter in hex (@pxref{Registers}), type
7149 Note that no space is required before the slash; this is because command
7150 names in @value{GDBN} cannot contain a slash.
7152 To reprint the last value in the value history with a different format,
7153 you can use the @code{print} command with just a format and no
7154 expression. For example, @samp{p/x} reprints the last value in hex.
7157 @section Examining Memory
7159 You can use the command @code{x} (for ``examine'') to examine memory in
7160 any of several formats, independently of your program's data types.
7162 @cindex examining memory
7164 @kindex x @r{(examine memory)}
7165 @item x/@var{nfu} @var{addr}
7168 Use the @code{x} command to examine memory.
7171 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
7172 much memory to display and how to format it; @var{addr} is an
7173 expression giving the address where you want to start displaying memory.
7174 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
7175 Several commands set convenient defaults for @var{addr}.
7178 @item @var{n}, the repeat count
7179 The repeat count is a decimal integer; the default is 1. It specifies
7180 how much memory (counting by units @var{u}) to display.
7181 @c This really is **decimal**; unaffected by 'set radix' as of GDB
7184 @item @var{f}, the display format
7185 The display format is one of the formats used by @code{print}
7186 (@samp{x}, @samp{d}, @samp{u}, @samp{o}, @samp{t}, @samp{a}, @samp{c},
7187 @samp{f}, @samp{s}), and in addition @samp{i} (for machine instructions).
7188 The default is @samp{x} (hexadecimal) initially. The default changes
7189 each time you use either @code{x} or @code{print}.
7191 @item @var{u}, the unit size
7192 The unit size is any of
7198 Halfwords (two bytes).
7200 Words (four bytes). This is the initial default.
7202 Giant words (eight bytes).
7205 Each time you specify a unit size with @code{x}, that size becomes the
7206 default unit the next time you use @code{x}. (For the @samp{s} and
7207 @samp{i} formats, the unit size is ignored and is normally not written.)
7209 @item @var{addr}, starting display address
7210 @var{addr} is the address where you want @value{GDBN} to begin displaying
7211 memory. The expression need not have a pointer value (though it may);
7212 it is always interpreted as an integer address of a byte of memory.
7213 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
7214 @var{addr} is usually just after the last address examined---but several
7215 other commands also set the default address: @code{info breakpoints} (to
7216 the address of the last breakpoint listed), @code{info line} (to the
7217 starting address of a line), and @code{print} (if you use it to display
7218 a value from memory).
7221 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
7222 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
7223 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
7224 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
7225 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
7227 Since the letters indicating unit sizes are all distinct from the
7228 letters specifying output formats, you do not have to remember whether
7229 unit size or format comes first; either order works. The output
7230 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
7231 (However, the count @var{n} must come first; @samp{wx4} does not work.)
7233 Even though the unit size @var{u} is ignored for the formats @samp{s}
7234 and @samp{i}, you might still want to use a count @var{n}; for example,
7235 @samp{3i} specifies that you want to see three machine instructions,
7236 including any operands. For convenience, especially when used with
7237 the @code{display} command, the @samp{i} format also prints branch delay
7238 slot instructions, if any, beyond the count specified, which immediately
7239 follow the last instruction that is within the count. The command
7240 @code{disassemble} gives an alternative way of inspecting machine
7241 instructions; see @ref{Machine Code,,Source and Machine Code}.
7243 All the defaults for the arguments to @code{x} are designed to make it
7244 easy to continue scanning memory with minimal specifications each time
7245 you use @code{x}. For example, after you have inspected three machine
7246 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
7247 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
7248 the repeat count @var{n} is used again; the other arguments default as
7249 for successive uses of @code{x}.
7251 When examining machine instructions, the instruction at current program
7252 counter is shown with a @code{=>} marker. For example:
7255 (@value{GDBP}) x/5i $pc-6
7256 0x804837f <main+11>: mov %esp,%ebp
7257 0x8048381 <main+13>: push %ecx
7258 0x8048382 <main+14>: sub $0x4,%esp
7259 => 0x8048385 <main+17>: movl $0x8048460,(%esp)
7260 0x804838c <main+24>: call 0x80482d4 <puts@@plt>
7263 @cindex @code{$_}, @code{$__}, and value history
7264 The addresses and contents printed by the @code{x} command are not saved
7265 in the value history because there is often too much of them and they
7266 would get in the way. Instead, @value{GDBN} makes these values available for
7267 subsequent use in expressions as values of the convenience variables
7268 @code{$_} and @code{$__}. After an @code{x} command, the last address
7269 examined is available for use in expressions in the convenience variable
7270 @code{$_}. The contents of that address, as examined, are available in
7271 the convenience variable @code{$__}.
7273 If the @code{x} command has a repeat count, the address and contents saved
7274 are from the last memory unit printed; this is not the same as the last
7275 address printed if several units were printed on the last line of output.
7277 @cindex remote memory comparison
7278 @cindex verify remote memory image
7279 When you are debugging a program running on a remote target machine
7280 (@pxref{Remote Debugging}), you may wish to verify the program's image in the
7281 remote machine's memory against the executable file you downloaded to
7282 the target. The @code{compare-sections} command is provided for such
7286 @kindex compare-sections
7287 @item compare-sections @r{[}@var{section-name}@r{]}
7288 Compare the data of a loadable section @var{section-name} in the
7289 executable file of the program being debugged with the same section in
7290 the remote machine's memory, and report any mismatches. With no
7291 arguments, compares all loadable sections. This command's
7292 availability depends on the target's support for the @code{"qCRC"}
7297 @section Automatic Display
7298 @cindex automatic display
7299 @cindex display of expressions
7301 If you find that you want to print the value of an expression frequently
7302 (to see how it changes), you might want to add it to the @dfn{automatic
7303 display list} so that @value{GDBN} prints its value each time your program stops.
7304 Each expression added to the list is given a number to identify it;
7305 to remove an expression from the list, you specify that number.
7306 The automatic display looks like this:
7310 3: bar[5] = (struct hack *) 0x3804
7314 This display shows item numbers, expressions and their current values. As with
7315 displays you request manually using @code{x} or @code{print}, you can
7316 specify the output format you prefer; in fact, @code{display} decides
7317 whether to use @code{print} or @code{x} depending your format
7318 specification---it uses @code{x} if you specify either the @samp{i}
7319 or @samp{s} format, or a unit size; otherwise it uses @code{print}.
7323 @item display @var{expr}
7324 Add the expression @var{expr} to the list of expressions to display
7325 each time your program stops. @xref{Expressions, ,Expressions}.
7327 @code{display} does not repeat if you press @key{RET} again after using it.
7329 @item display/@var{fmt} @var{expr}
7330 For @var{fmt} specifying only a display format and not a size or
7331 count, add the expression @var{expr} to the auto-display list but
7332 arrange to display it each time in the specified format @var{fmt}.
7333 @xref{Output Formats,,Output Formats}.
7335 @item display/@var{fmt} @var{addr}
7336 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
7337 number of units, add the expression @var{addr} as a memory address to
7338 be examined each time your program stops. Examining means in effect
7339 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining Memory}.
7342 For example, @samp{display/i $pc} can be helpful, to see the machine
7343 instruction about to be executed each time execution stops (@samp{$pc}
7344 is a common name for the program counter; @pxref{Registers, ,Registers}).
7347 @kindex delete display
7349 @item undisplay @var{dnums}@dots{}
7350 @itemx delete display @var{dnums}@dots{}
7351 Remove item numbers @var{dnums} from the list of expressions to display.
7353 @code{undisplay} does not repeat if you press @key{RET} after using it.
7354 (Otherwise you would just get the error @samp{No display number @dots{}}.)
7356 @kindex disable display
7357 @item disable display @var{dnums}@dots{}
7358 Disable the display of item numbers @var{dnums}. A disabled display
7359 item is not printed automatically, but is not forgotten. It may be
7360 enabled again later.
7362 @kindex enable display
7363 @item enable display @var{dnums}@dots{}
7364 Enable display of item numbers @var{dnums}. It becomes effective once
7365 again in auto display of its expression, until you specify otherwise.
7368 Display the current values of the expressions on the list, just as is
7369 done when your program stops.
7371 @kindex info display
7373 Print the list of expressions previously set up to display
7374 automatically, each one with its item number, but without showing the
7375 values. This includes disabled expressions, which are marked as such.
7376 It also includes expressions which would not be displayed right now
7377 because they refer to automatic variables not currently available.
7380 @cindex display disabled out of scope
7381 If a display expression refers to local variables, then it does not make
7382 sense outside the lexical context for which it was set up. Such an
7383 expression is disabled when execution enters a context where one of its
7384 variables is not defined. For example, if you give the command
7385 @code{display last_char} while inside a function with an argument
7386 @code{last_char}, @value{GDBN} displays this argument while your program
7387 continues to stop inside that function. When it stops elsewhere---where
7388 there is no variable @code{last_char}---the display is disabled
7389 automatically. The next time your program stops where @code{last_char}
7390 is meaningful, you can enable the display expression once again.
7392 @node Print Settings
7393 @section Print Settings
7395 @cindex format options
7396 @cindex print settings
7397 @value{GDBN} provides the following ways to control how arrays, structures,
7398 and symbols are printed.
7401 These settings are useful for debugging programs in any language:
7405 @item set print address
7406 @itemx set print address on
7407 @cindex print/don't print memory addresses
7408 @value{GDBN} prints memory addresses showing the location of stack
7409 traces, structure values, pointer values, breakpoints, and so forth,
7410 even when it also displays the contents of those addresses. The default
7411 is @code{on}. For example, this is what a stack frame display looks like with
7412 @code{set print address on}:
7417 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
7419 530 if (lquote != def_lquote)
7423 @item set print address off
7424 Do not print addresses when displaying their contents. For example,
7425 this is the same stack frame displayed with @code{set print address off}:
7429 (@value{GDBP}) set print addr off
7431 #0 set_quotes (lq="<<", rq=">>") at input.c:530
7432 530 if (lquote != def_lquote)
7436 You can use @samp{set print address off} to eliminate all machine
7437 dependent displays from the @value{GDBN} interface. For example, with
7438 @code{print address off}, you should get the same text for backtraces on
7439 all machines---whether or not they involve pointer arguments.
7442 @item show print address
7443 Show whether or not addresses are to be printed.
7446 When @value{GDBN} prints a symbolic address, it normally prints the
7447 closest earlier symbol plus an offset. If that symbol does not uniquely
7448 identify the address (for example, it is a name whose scope is a single
7449 source file), you may need to clarify. One way to do this is with
7450 @code{info line}, for example @samp{info line *0x4537}. Alternately,
7451 you can set @value{GDBN} to print the source file and line number when
7452 it prints a symbolic address:
7455 @item set print symbol-filename on
7456 @cindex source file and line of a symbol
7457 @cindex symbol, source file and line
7458 Tell @value{GDBN} to print the source file name and line number of a
7459 symbol in the symbolic form of an address.
7461 @item set print symbol-filename off
7462 Do not print source file name and line number of a symbol. This is the
7465 @item show print symbol-filename
7466 Show whether or not @value{GDBN} will print the source file name and
7467 line number of a symbol in the symbolic form of an address.
7470 Another situation where it is helpful to show symbol filenames and line
7471 numbers is when disassembling code; @value{GDBN} shows you the line
7472 number and source file that corresponds to each instruction.
7474 Also, you may wish to see the symbolic form only if the address being
7475 printed is reasonably close to the closest earlier symbol:
7478 @item set print max-symbolic-offset @var{max-offset}
7479 @cindex maximum value for offset of closest symbol
7480 Tell @value{GDBN} to only display the symbolic form of an address if the
7481 offset between the closest earlier symbol and the address is less than
7482 @var{max-offset}. The default is 0, which tells @value{GDBN}
7483 to always print the symbolic form of an address if any symbol precedes it.
7485 @item show print max-symbolic-offset
7486 Ask how large the maximum offset is that @value{GDBN} prints in a
7490 @cindex wild pointer, interpreting
7491 @cindex pointer, finding referent
7492 If you have a pointer and you are not sure where it points, try
7493 @samp{set print symbol-filename on}. Then you can determine the name
7494 and source file location of the variable where it points, using
7495 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
7496 For example, here @value{GDBN} shows that a variable @code{ptt} points
7497 at another variable @code{t}, defined in @file{hi2.c}:
7500 (@value{GDBP}) set print symbol-filename on
7501 (@value{GDBP}) p/a ptt
7502 $4 = 0xe008 <t in hi2.c>
7506 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
7507 does not show the symbol name and filename of the referent, even with
7508 the appropriate @code{set print} options turned on.
7511 Other settings control how different kinds of objects are printed:
7514 @item set print array
7515 @itemx set print array on
7516 @cindex pretty print arrays
7517 Pretty print arrays. This format is more convenient to read,
7518 but uses more space. The default is off.
7520 @item set print array off
7521 Return to compressed format for arrays.
7523 @item show print array
7524 Show whether compressed or pretty format is selected for displaying
7527 @cindex print array indexes
7528 @item set print array-indexes
7529 @itemx set print array-indexes on
7530 Print the index of each element when displaying arrays. May be more
7531 convenient to locate a given element in the array or quickly find the
7532 index of a given element in that printed array. The default is off.
7534 @item set print array-indexes off
7535 Stop printing element indexes when displaying arrays.
7537 @item show print array-indexes
7538 Show whether the index of each element is printed when displaying
7541 @item set print elements @var{number-of-elements}
7542 @cindex number of array elements to print
7543 @cindex limit on number of printed array elements
7544 Set a limit on how many elements of an array @value{GDBN} will print.
7545 If @value{GDBN} is printing a large array, it stops printing after it has
7546 printed the number of elements set by the @code{set print elements} command.
7547 This limit also applies to the display of strings.
7548 When @value{GDBN} starts, this limit is set to 200.
7549 Setting @var{number-of-elements} to zero means that the printing is unlimited.
7551 @item show print elements
7552 Display the number of elements of a large array that @value{GDBN} will print.
7553 If the number is 0, then the printing is unlimited.
7555 @item set print frame-arguments @var{value}
7556 @kindex set print frame-arguments
7557 @cindex printing frame argument values
7558 @cindex print all frame argument values
7559 @cindex print frame argument values for scalars only
7560 @cindex do not print frame argument values
7561 This command allows to control how the values of arguments are printed
7562 when the debugger prints a frame (@pxref{Frames}). The possible
7567 The values of all arguments are printed.
7570 Print the value of an argument only if it is a scalar. The value of more
7571 complex arguments such as arrays, structures, unions, etc, is replaced
7572 by @code{@dots{}}. This is the default. Here is an example where
7573 only scalar arguments are shown:
7576 #1 0x08048361 in call_me (i=3, s=@dots{}, ss=0xbf8d508c, u=@dots{}, e=green)
7581 None of the argument values are printed. Instead, the value of each argument
7582 is replaced by @code{@dots{}}. In this case, the example above now becomes:
7585 #1 0x08048361 in call_me (i=@dots{}, s=@dots{}, ss=@dots{}, u=@dots{}, e=@dots{})
7590 By default, only scalar arguments are printed. This command can be used
7591 to configure the debugger to print the value of all arguments, regardless
7592 of their type. However, it is often advantageous to not print the value
7593 of more complex parameters. For instance, it reduces the amount of
7594 information printed in each frame, making the backtrace more readable.
7595 Also, it improves performance when displaying Ada frames, because
7596 the computation of large arguments can sometimes be CPU-intensive,
7597 especially in large applications. Setting @code{print frame-arguments}
7598 to @code{scalars} (the default) or @code{none} avoids this computation,
7599 thus speeding up the display of each Ada frame.
7601 @item show print frame-arguments
7602 Show how the value of arguments should be displayed when printing a frame.
7604 @item set print repeats
7605 @cindex repeated array elements
7606 Set the threshold for suppressing display of repeated array
7607 elements. When the number of consecutive identical elements of an
7608 array exceeds the threshold, @value{GDBN} prints the string
7609 @code{"<repeats @var{n} times>"}, where @var{n} is the number of
7610 identical repetitions, instead of displaying the identical elements
7611 themselves. Setting the threshold to zero will cause all elements to
7612 be individually printed. The default threshold is 10.
7614 @item show print repeats
7615 Display the current threshold for printing repeated identical
7618 @item set print null-stop
7619 @cindex @sc{null} elements in arrays
7620 Cause @value{GDBN} to stop printing the characters of an array when the first
7621 @sc{null} is encountered. This is useful when large arrays actually
7622 contain only short strings.
7625 @item show print null-stop
7626 Show whether @value{GDBN} stops printing an array on the first
7627 @sc{null} character.
7629 @item set print pretty on
7630 @cindex print structures in indented form
7631 @cindex indentation in structure display
7632 Cause @value{GDBN} to print structures in an indented format with one member
7633 per line, like this:
7648 @item set print pretty off
7649 Cause @value{GDBN} to print structures in a compact format, like this:
7653 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
7654 meat = 0x54 "Pork"@}
7659 This is the default format.
7661 @item show print pretty
7662 Show which format @value{GDBN} is using to print structures.
7664 @item set print sevenbit-strings on
7665 @cindex eight-bit characters in strings
7666 @cindex octal escapes in strings
7667 Print using only seven-bit characters; if this option is set,
7668 @value{GDBN} displays any eight-bit characters (in strings or
7669 character values) using the notation @code{\}@var{nnn}. This setting is
7670 best if you are working in English (@sc{ascii}) and you use the
7671 high-order bit of characters as a marker or ``meta'' bit.
7673 @item set print sevenbit-strings off
7674 Print full eight-bit characters. This allows the use of more
7675 international character sets, and is the default.
7677 @item show print sevenbit-strings
7678 Show whether or not @value{GDBN} is printing only seven-bit characters.
7680 @item set print union on
7681 @cindex unions in structures, printing
7682 Tell @value{GDBN} to print unions which are contained in structures
7683 and other unions. This is the default setting.
7685 @item set print union off
7686 Tell @value{GDBN} not to print unions which are contained in
7687 structures and other unions. @value{GDBN} will print @code{"@{...@}"}
7690 @item show print union
7691 Ask @value{GDBN} whether or not it will print unions which are contained in
7692 structures and other unions.
7694 For example, given the declarations
7697 typedef enum @{Tree, Bug@} Species;
7698 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
7699 typedef enum @{Caterpillar, Cocoon, Butterfly@}
7710 struct thing foo = @{Tree, @{Acorn@}@};
7714 with @code{set print union on} in effect @samp{p foo} would print
7717 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
7721 and with @code{set print union off} in effect it would print
7724 $1 = @{it = Tree, form = @{...@}@}
7728 @code{set print union} affects programs written in C-like languages
7734 These settings are of interest when debugging C@t{++} programs:
7737 @cindex demangling C@t{++} names
7738 @item set print demangle
7739 @itemx set print demangle on
7740 Print C@t{++} names in their source form rather than in the encoded
7741 (``mangled'') form passed to the assembler and linker for type-safe
7742 linkage. The default is on.
7744 @item show print demangle
7745 Show whether C@t{++} names are printed in mangled or demangled form.
7747 @item set print asm-demangle
7748 @itemx set print asm-demangle on
7749 Print C@t{++} names in their source form rather than their mangled form, even
7750 in assembler code printouts such as instruction disassemblies.
7753 @item show print asm-demangle
7754 Show whether C@t{++} names in assembly listings are printed in mangled
7757 @cindex C@t{++} symbol decoding style
7758 @cindex symbol decoding style, C@t{++}
7759 @kindex set demangle-style
7760 @item set demangle-style @var{style}
7761 Choose among several encoding schemes used by different compilers to
7762 represent C@t{++} names. The choices for @var{style} are currently:
7766 Allow @value{GDBN} to choose a decoding style by inspecting your program.
7769 Decode based on the @sc{gnu} C@t{++} compiler (@code{g++}) encoding algorithm.
7770 This is the default.
7773 Decode based on the HP ANSI C@t{++} (@code{aCC}) encoding algorithm.
7776 Decode based on the Lucid C@t{++} compiler (@code{lcc}) encoding algorithm.
7779 Decode using the algorithm in the @cite{C@t{++} Annotated Reference Manual}.
7780 @strong{Warning:} this setting alone is not sufficient to allow
7781 debugging @code{cfront}-generated executables. @value{GDBN} would
7782 require further enhancement to permit that.
7785 If you omit @var{style}, you will see a list of possible formats.
7787 @item show demangle-style
7788 Display the encoding style currently in use for decoding C@t{++} symbols.
7790 @item set print object
7791 @itemx set print object on
7792 @cindex derived type of an object, printing
7793 @cindex display derived types
7794 When displaying a pointer to an object, identify the @emph{actual}
7795 (derived) type of the object rather than the @emph{declared} type, using
7796 the virtual function table.
7798 @item set print object off
7799 Display only the declared type of objects, without reference to the
7800 virtual function table. This is the default setting.
7802 @item show print object
7803 Show whether actual, or declared, object types are displayed.
7805 @item set print static-members
7806 @itemx set print static-members on
7807 @cindex static members of C@t{++} objects
7808 Print static members when displaying a C@t{++} object. The default is on.
7810 @item set print static-members off
7811 Do not print static members when displaying a C@t{++} object.
7813 @item show print static-members
7814 Show whether C@t{++} static members are printed or not.
7816 @item set print pascal_static-members
7817 @itemx set print pascal_static-members on
7818 @cindex static members of Pascal objects
7819 @cindex Pascal objects, static members display
7820 Print static members when displaying a Pascal object. The default is on.
7822 @item set print pascal_static-members off
7823 Do not print static members when displaying a Pascal object.
7825 @item show print pascal_static-members
7826 Show whether Pascal static members are printed or not.
7828 @c These don't work with HP ANSI C++ yet.
7829 @item set print vtbl
7830 @itemx set print vtbl on
7831 @cindex pretty print C@t{++} virtual function tables
7832 @cindex virtual functions (C@t{++}) display
7833 @cindex VTBL display
7834 Pretty print C@t{++} virtual function tables. The default is off.
7835 (The @code{vtbl} commands do not work on programs compiled with the HP
7836 ANSI C@t{++} compiler (@code{aCC}).)
7838 @item set print vtbl off
7839 Do not pretty print C@t{++} virtual function tables.
7841 @item show print vtbl
7842 Show whether C@t{++} virtual function tables are pretty printed, or not.
7846 @section Value History
7848 @cindex value history
7849 @cindex history of values printed by @value{GDBN}
7850 Values printed by the @code{print} command are saved in the @value{GDBN}
7851 @dfn{value history}. This allows you to refer to them in other expressions.
7852 Values are kept until the symbol table is re-read or discarded
7853 (for example with the @code{file} or @code{symbol-file} commands).
7854 When the symbol table changes, the value history is discarded,
7855 since the values may contain pointers back to the types defined in the
7860 @cindex history number
7861 The values printed are given @dfn{history numbers} by which you can
7862 refer to them. These are successive integers starting with one.
7863 @code{print} shows you the history number assigned to a value by
7864 printing @samp{$@var{num} = } before the value; here @var{num} is the
7867 To refer to any previous value, use @samp{$} followed by the value's
7868 history number. The way @code{print} labels its output is designed to
7869 remind you of this. Just @code{$} refers to the most recent value in
7870 the history, and @code{$$} refers to the value before that.
7871 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
7872 is the value just prior to @code{$$}, @code{$$1} is equivalent to
7873 @code{$$}, and @code{$$0} is equivalent to @code{$}.
7875 For example, suppose you have just printed a pointer to a structure and
7876 want to see the contents of the structure. It suffices to type
7882 If you have a chain of structures where the component @code{next} points
7883 to the next one, you can print the contents of the next one with this:
7890 You can print successive links in the chain by repeating this
7891 command---which you can do by just typing @key{RET}.
7893 Note that the history records values, not expressions. If the value of
7894 @code{x} is 4 and you type these commands:
7902 then the value recorded in the value history by the @code{print} command
7903 remains 4 even though the value of @code{x} has changed.
7908 Print the last ten values in the value history, with their item numbers.
7909 This is like @samp{p@ $$9} repeated ten times, except that @code{show
7910 values} does not change the history.
7912 @item show values @var{n}
7913 Print ten history values centered on history item number @var{n}.
7916 Print ten history values just after the values last printed. If no more
7917 values are available, @code{show values +} produces no display.
7920 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
7921 same effect as @samp{show values +}.
7923 @node Convenience Vars
7924 @section Convenience Variables
7926 @cindex convenience variables
7927 @cindex user-defined variables
7928 @value{GDBN} provides @dfn{convenience variables} that you can use within
7929 @value{GDBN} to hold on to a value and refer to it later. These variables
7930 exist entirely within @value{GDBN}; they are not part of your program, and
7931 setting a convenience variable has no direct effect on further execution
7932 of your program. That is why you can use them freely.
7934 Convenience variables are prefixed with @samp{$}. Any name preceded by
7935 @samp{$} can be used for a convenience variable, unless it is one of
7936 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
7937 (Value history references, in contrast, are @emph{numbers} preceded
7938 by @samp{$}. @xref{Value History, ,Value History}.)
7940 You can save a value in a convenience variable with an assignment
7941 expression, just as you would set a variable in your program.
7945 set $foo = *object_ptr
7949 would save in @code{$foo} the value contained in the object pointed to by
7952 Using a convenience variable for the first time creates it, but its
7953 value is @code{void} until you assign a new value. You can alter the
7954 value with another assignment at any time.
7956 Convenience variables have no fixed types. You can assign a convenience
7957 variable any type of value, including structures and arrays, even if
7958 that variable already has a value of a different type. The convenience
7959 variable, when used as an expression, has the type of its current value.
7962 @kindex show convenience
7963 @cindex show all user variables
7964 @item show convenience
7965 Print a list of convenience variables used so far, and their values.
7966 Abbreviated @code{show conv}.
7968 @kindex init-if-undefined
7969 @cindex convenience variables, initializing
7970 @item init-if-undefined $@var{variable} = @var{expression}
7971 Set a convenience variable if it has not already been set. This is useful
7972 for user-defined commands that keep some state. It is similar, in concept,
7973 to using local static variables with initializers in C (except that
7974 convenience variables are global). It can also be used to allow users to
7975 override default values used in a command script.
7977 If the variable is already defined then the expression is not evaluated so
7978 any side-effects do not occur.
7981 One of the ways to use a convenience variable is as a counter to be
7982 incremented or a pointer to be advanced. For example, to print
7983 a field from successive elements of an array of structures:
7987 print bar[$i++]->contents
7991 Repeat that command by typing @key{RET}.
7993 Some convenience variables are created automatically by @value{GDBN} and given
7994 values likely to be useful.
7997 @vindex $_@r{, convenience variable}
7999 The variable @code{$_} is automatically set by the @code{x} command to
8000 the last address examined (@pxref{Memory, ,Examining Memory}). Other
8001 commands which provide a default address for @code{x} to examine also
8002 set @code{$_} to that address; these commands include @code{info line}
8003 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
8004 except when set by the @code{x} command, in which case it is a pointer
8005 to the type of @code{$__}.
8007 @vindex $__@r{, convenience variable}
8009 The variable @code{$__} is automatically set by the @code{x} command
8010 to the value found in the last address examined. Its type is chosen
8011 to match the format in which the data was printed.
8014 @vindex $_exitcode@r{, convenience variable}
8015 The variable @code{$_exitcode} is automatically set to the exit code when
8016 the program being debugged terminates.
8019 @vindex $_siginfo@r{, convenience variable}
8020 The variable @code{$_siginfo} contains extra signal information
8021 (@pxref{extra signal information}). Note that @code{$_siginfo}
8022 could be empty, if the application has not yet received any signals.
8023 For example, it will be empty before you execute the @code{run} command.
8026 On HP-UX systems, if you refer to a function or variable name that
8027 begins with a dollar sign, @value{GDBN} searches for a user or system
8028 name first, before it searches for a convenience variable.
8030 @cindex convenience functions
8031 @value{GDBN} also supplies some @dfn{convenience functions}. These
8032 have a syntax similar to convenience variables. A convenience
8033 function can be used in an expression just like an ordinary function;
8034 however, a convenience function is implemented internally to
8039 @kindex help function
8040 @cindex show all convenience functions
8041 Print a list of all convenience functions.
8048 You can refer to machine register contents, in expressions, as variables
8049 with names starting with @samp{$}. The names of registers are different
8050 for each machine; use @code{info registers} to see the names used on
8054 @kindex info registers
8055 @item info registers
8056 Print the names and values of all registers except floating-point
8057 and vector registers (in the selected stack frame).
8059 @kindex info all-registers
8060 @cindex floating point registers
8061 @item info all-registers
8062 Print the names and values of all registers, including floating-point
8063 and vector registers (in the selected stack frame).
8065 @item info registers @var{regname} @dots{}
8066 Print the @dfn{relativized} value of each specified register @var{regname}.
8067 As discussed in detail below, register values are normally relative to
8068 the selected stack frame. @var{regname} may be any register name valid on
8069 the machine you are using, with or without the initial @samp{$}.
8072 @cindex stack pointer register
8073 @cindex program counter register
8074 @cindex process status register
8075 @cindex frame pointer register
8076 @cindex standard registers
8077 @value{GDBN} has four ``standard'' register names that are available (in
8078 expressions) on most machines---whenever they do not conflict with an
8079 architecture's canonical mnemonics for registers. The register names
8080 @code{$pc} and @code{$sp} are used for the program counter register and
8081 the stack pointer. @code{$fp} is used for a register that contains a
8082 pointer to the current stack frame, and @code{$ps} is used for a
8083 register that contains the processor status. For example,
8084 you could print the program counter in hex with
8091 or print the instruction to be executed next with
8098 or add four to the stack pointer@footnote{This is a way of removing
8099 one word from the stack, on machines where stacks grow downward in
8100 memory (most machines, nowadays). This assumes that the innermost
8101 stack frame is selected; setting @code{$sp} is not allowed when other
8102 stack frames are selected. To pop entire frames off the stack,
8103 regardless of machine architecture, use @code{return};
8104 see @ref{Returning, ,Returning from a Function}.} with
8110 Whenever possible, these four standard register names are available on
8111 your machine even though the machine has different canonical mnemonics,
8112 so long as there is no conflict. The @code{info registers} command
8113 shows the canonical names. For example, on the SPARC, @code{info
8114 registers} displays the processor status register as @code{$psr} but you
8115 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
8116 is an alias for the @sc{eflags} register.
8118 @value{GDBN} always considers the contents of an ordinary register as an
8119 integer when the register is examined in this way. Some machines have
8120 special registers which can hold nothing but floating point; these
8121 registers are considered to have floating point values. There is no way
8122 to refer to the contents of an ordinary register as floating point value
8123 (although you can @emph{print} it as a floating point value with
8124 @samp{print/f $@var{regname}}).
8126 Some registers have distinct ``raw'' and ``virtual'' data formats. This
8127 means that the data format in which the register contents are saved by
8128 the operating system is not the same one that your program normally
8129 sees. For example, the registers of the 68881 floating point
8130 coprocessor are always saved in ``extended'' (raw) format, but all C
8131 programs expect to work with ``double'' (virtual) format. In such
8132 cases, @value{GDBN} normally works with the virtual format only (the format
8133 that makes sense for your program), but the @code{info registers} command
8134 prints the data in both formats.
8136 @cindex SSE registers (x86)
8137 @cindex MMX registers (x86)
8138 Some machines have special registers whose contents can be interpreted
8139 in several different ways. For example, modern x86-based machines
8140 have SSE and MMX registers that can hold several values packed
8141 together in several different formats. @value{GDBN} refers to such
8142 registers in @code{struct} notation:
8145 (@value{GDBP}) print $xmm1
8147 v4_float = @{0, 3.43859137e-038, 1.54142831e-044, 1.821688e-044@},
8148 v2_double = @{9.92129282474342e-303, 2.7585945287983262e-313@},
8149 v16_int8 = "\000\000\000\000\3706;\001\v\000\000\000\r\000\000",
8150 v8_int16 = @{0, 0, 14072, 315, 11, 0, 13, 0@},
8151 v4_int32 = @{0, 20657912, 11, 13@},
8152 v2_int64 = @{88725056443645952, 55834574859@},
8153 uint128 = 0x0000000d0000000b013b36f800000000
8158 To set values of such registers, you need to tell @value{GDBN} which
8159 view of the register you wish to change, as if you were assigning
8160 value to a @code{struct} member:
8163 (@value{GDBP}) set $xmm1.uint128 = 0x000000000000000000000000FFFFFFFF
8166 Normally, register values are relative to the selected stack frame
8167 (@pxref{Selection, ,Selecting a Frame}). This means that you get the
8168 value that the register would contain if all stack frames farther in
8169 were exited and their saved registers restored. In order to see the
8170 true contents of hardware registers, you must select the innermost
8171 frame (with @samp{frame 0}).
8173 However, @value{GDBN} must deduce where registers are saved, from the machine
8174 code generated by your compiler. If some registers are not saved, or if
8175 @value{GDBN} is unable to locate the saved registers, the selected stack
8176 frame makes no difference.
8178 @node Floating Point Hardware
8179 @section Floating Point Hardware
8180 @cindex floating point
8182 Depending on the configuration, @value{GDBN} may be able to give
8183 you more information about the status of the floating point hardware.
8188 Display hardware-dependent information about the floating
8189 point unit. The exact contents and layout vary depending on the
8190 floating point chip. Currently, @samp{info float} is supported on
8191 the ARM and x86 machines.
8195 @section Vector Unit
8198 Depending on the configuration, @value{GDBN} may be able to give you
8199 more information about the status of the vector unit.
8204 Display information about the vector unit. The exact contents and
8205 layout vary depending on the hardware.
8208 @node OS Information
8209 @section Operating System Auxiliary Information
8210 @cindex OS information
8212 @value{GDBN} provides interfaces to useful OS facilities that can help
8213 you debug your program.
8215 @cindex @code{ptrace} system call
8216 @cindex @code{struct user} contents
8217 When @value{GDBN} runs on a @dfn{Posix system} (such as GNU or Unix
8218 machines), it interfaces with the inferior via the @code{ptrace}
8219 system call. The operating system creates a special sata structure,
8220 called @code{struct user}, for this interface. You can use the
8221 command @code{info udot} to display the contents of this data
8227 Display the contents of the @code{struct user} maintained by the OS
8228 kernel for the program being debugged. @value{GDBN} displays the
8229 contents of @code{struct user} as a list of hex numbers, similar to
8230 the @code{examine} command.
8233 @cindex auxiliary vector
8234 @cindex vector, auxiliary
8235 Some operating systems supply an @dfn{auxiliary vector} to programs at
8236 startup. This is akin to the arguments and environment that you
8237 specify for a program, but contains a system-dependent variety of
8238 binary values that tell system libraries important details about the
8239 hardware, operating system, and process. Each value's purpose is
8240 identified by an integer tag; the meanings are well-known but system-specific.
8241 Depending on the configuration and operating system facilities,
8242 @value{GDBN} may be able to show you this information. For remote
8243 targets, this functionality may further depend on the remote stub's
8244 support of the @samp{qXfer:auxv:read} packet, see
8245 @ref{qXfer auxiliary vector read}.
8250 Display the auxiliary vector of the inferior, which can be either a
8251 live process or a core dump file. @value{GDBN} prints each tag value
8252 numerically, and also shows names and text descriptions for recognized
8253 tags. Some values in the vector are numbers, some bit masks, and some
8254 pointers to strings or other data. @value{GDBN} displays each value in the
8255 most appropriate form for a recognized tag, and in hexadecimal for
8256 an unrecognized tag.
8259 On some targets, @value{GDBN} can access operating-system-specific information
8260 and display it to user, without interpretation. For remote targets,
8261 this functionality depends on the remote stub's support of the
8262 @samp{qXfer:osdata:read} packet, see @ref{qXfer osdata read}.
8265 @kindex info os processes
8266 @item info os processes
8267 Display the list of processes on the target. For each process,
8268 @value{GDBN} prints the process identifier, the name of the user, and
8269 the command corresponding to the process.
8272 @node Memory Region Attributes
8273 @section Memory Region Attributes
8274 @cindex memory region attributes
8276 @dfn{Memory region attributes} allow you to describe special handling
8277 required by regions of your target's memory. @value{GDBN} uses
8278 attributes to determine whether to allow certain types of memory
8279 accesses; whether to use specific width accesses; and whether to cache
8280 target memory. By default the description of memory regions is
8281 fetched from the target (if the current target supports this), but the
8282 user can override the fetched regions.
8284 Defined memory regions can be individually enabled and disabled. When a
8285 memory region is disabled, @value{GDBN} uses the default attributes when
8286 accessing memory in that region. Similarly, if no memory regions have
8287 been defined, @value{GDBN} uses the default attributes when accessing
8290 When a memory region is defined, it is given a number to identify it;
8291 to enable, disable, or remove a memory region, you specify that number.
8295 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
8296 Define a memory region bounded by @var{lower} and @var{upper} with
8297 attributes @var{attributes}@dots{}, and add it to the list of regions
8298 monitored by @value{GDBN}. Note that @var{upper} == 0 is a special
8299 case: it is treated as the target's maximum memory address.
8300 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
8303 Discard any user changes to the memory regions and use target-supplied
8304 regions, if available, or no regions if the target does not support.
8307 @item delete mem @var{nums}@dots{}
8308 Remove memory regions @var{nums}@dots{} from the list of regions
8309 monitored by @value{GDBN}.
8312 @item disable mem @var{nums}@dots{}
8313 Disable monitoring of memory regions @var{nums}@dots{}.
8314 A disabled memory region is not forgotten.
8315 It may be enabled again later.
8318 @item enable mem @var{nums}@dots{}
8319 Enable monitoring of memory regions @var{nums}@dots{}.
8323 Print a table of all defined memory regions, with the following columns
8327 @item Memory Region Number
8328 @item Enabled or Disabled.
8329 Enabled memory regions are marked with @samp{y}.
8330 Disabled memory regions are marked with @samp{n}.
8333 The address defining the inclusive lower bound of the memory region.
8336 The address defining the exclusive upper bound of the memory region.
8339 The list of attributes set for this memory region.
8344 @subsection Attributes
8346 @subsubsection Memory Access Mode
8347 The access mode attributes set whether @value{GDBN} may make read or
8348 write accesses to a memory region.
8350 While these attributes prevent @value{GDBN} from performing invalid
8351 memory accesses, they do nothing to prevent the target system, I/O DMA,
8352 etc.@: from accessing memory.
8356 Memory is read only.
8358 Memory is write only.
8360 Memory is read/write. This is the default.
8363 @subsubsection Memory Access Size
8364 The access size attribute tells @value{GDBN} to use specific sized
8365 accesses in the memory region. Often memory mapped device registers
8366 require specific sized accesses. If no access size attribute is
8367 specified, @value{GDBN} may use accesses of any size.
8371 Use 8 bit memory accesses.
8373 Use 16 bit memory accesses.
8375 Use 32 bit memory accesses.
8377 Use 64 bit memory accesses.
8380 @c @subsubsection Hardware/Software Breakpoints
8381 @c The hardware/software breakpoint attributes set whether @value{GDBN}
8382 @c will use hardware or software breakpoints for the internal breakpoints
8383 @c used by the step, next, finish, until, etc. commands.
8387 @c Always use hardware breakpoints
8388 @c @item swbreak (default)
8391 @subsubsection Data Cache
8392 The data cache attributes set whether @value{GDBN} will cache target
8393 memory. While this generally improves performance by reducing debug
8394 protocol overhead, it can lead to incorrect results because @value{GDBN}
8395 does not know about volatile variables or memory mapped device
8400 Enable @value{GDBN} to cache target memory.
8402 Disable @value{GDBN} from caching target memory. This is the default.
8405 @subsection Memory Access Checking
8406 @value{GDBN} can be instructed to refuse accesses to memory that is
8407 not explicitly described. This can be useful if accessing such
8408 regions has undesired effects for a specific target, or to provide
8409 better error checking. The following commands control this behaviour.
8412 @kindex set mem inaccessible-by-default
8413 @item set mem inaccessible-by-default [on|off]
8414 If @code{on} is specified, make @value{GDBN} treat memory not
8415 explicitly described by the memory ranges as non-existent and refuse accesses
8416 to such memory. The checks are only performed if there's at least one
8417 memory range defined. If @code{off} is specified, make @value{GDBN}
8418 treat the memory not explicitly described by the memory ranges as RAM.
8419 The default value is @code{on}.
8420 @kindex show mem inaccessible-by-default
8421 @item show mem inaccessible-by-default
8422 Show the current handling of accesses to unknown memory.
8426 @c @subsubsection Memory Write Verification
8427 @c The memory write verification attributes set whether @value{GDBN}
8428 @c will re-reads data after each write to verify the write was successful.
8432 @c @item noverify (default)
8435 @node Dump/Restore Files
8436 @section Copy Between Memory and a File
8437 @cindex dump/restore files
8438 @cindex append data to a file
8439 @cindex dump data to a file
8440 @cindex restore data from a file
8442 You can use the commands @code{dump}, @code{append}, and
8443 @code{restore} to copy data between target memory and a file. The
8444 @code{dump} and @code{append} commands write data to a file, and the
8445 @code{restore} command reads data from a file back into the inferior's
8446 memory. Files may be in binary, Motorola S-record, Intel hex, or
8447 Tektronix Hex format; however, @value{GDBN} can only append to binary
8453 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
8454 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
8455 Dump the contents of memory from @var{start_addr} to @var{end_addr},
8456 or the value of @var{expr}, to @var{filename} in the given format.
8458 The @var{format} parameter may be any one of:
8465 Motorola S-record format.
8467 Tektronix Hex format.
8470 @value{GDBN} uses the same definitions of these formats as the
8471 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
8472 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
8476 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
8477 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
8478 Append the contents of memory from @var{start_addr} to @var{end_addr},
8479 or the value of @var{expr}, to the file @var{filename}, in raw binary form.
8480 (@value{GDBN} can only append data to files in raw binary form.)
8483 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
8484 Restore the contents of file @var{filename} into memory. The
8485 @code{restore} command can automatically recognize any known @sc{bfd}
8486 file format, except for raw binary. To restore a raw binary file you
8487 must specify the optional keyword @code{binary} after the filename.
8489 If @var{bias} is non-zero, its value will be added to the addresses
8490 contained in the file. Binary files always start at address zero, so
8491 they will be restored at address @var{bias}. Other bfd files have
8492 a built-in location; they will be restored at offset @var{bias}
8495 If @var{start} and/or @var{end} are non-zero, then only data between
8496 file offset @var{start} and file offset @var{end} will be restored.
8497 These offsets are relative to the addresses in the file, before
8498 the @var{bias} argument is applied.
8502 @node Core File Generation
8503 @section How to Produce a Core File from Your Program
8504 @cindex dump core from inferior
8506 A @dfn{core file} or @dfn{core dump} is a file that records the memory
8507 image of a running process and its process status (register values
8508 etc.). Its primary use is post-mortem debugging of a program that
8509 crashed while it ran outside a debugger. A program that crashes
8510 automatically produces a core file, unless this feature is disabled by
8511 the user. @xref{Files}, for information on invoking @value{GDBN} in
8512 the post-mortem debugging mode.
8514 Occasionally, you may wish to produce a core file of the program you
8515 are debugging in order to preserve a snapshot of its state.
8516 @value{GDBN} has a special command for that.
8520 @kindex generate-core-file
8521 @item generate-core-file [@var{file}]
8522 @itemx gcore [@var{file}]
8523 Produce a core dump of the inferior process. The optional argument
8524 @var{file} specifies the file name where to put the core dump. If not
8525 specified, the file name defaults to @file{core.@var{pid}}, where
8526 @var{pid} is the inferior process ID.
8528 Note that this command is implemented only for some systems (as of
8529 this writing, @sc{gnu}/Linux, FreeBSD, Solaris, Unixware, and S390).
8532 @node Character Sets
8533 @section Character Sets
8534 @cindex character sets
8536 @cindex translating between character sets
8537 @cindex host character set
8538 @cindex target character set
8540 If the program you are debugging uses a different character set to
8541 represent characters and strings than the one @value{GDBN} uses itself,
8542 @value{GDBN} can automatically translate between the character sets for
8543 you. The character set @value{GDBN} uses we call the @dfn{host
8544 character set}; the one the inferior program uses we call the
8545 @dfn{target character set}.
8547 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
8548 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
8549 remote protocol (@pxref{Remote Debugging}) to debug a program
8550 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
8551 then the host character set is Latin-1, and the target character set is
8552 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
8553 target-charset EBCDIC-US}, then @value{GDBN} translates between
8554 @sc{ebcdic} and Latin 1 as you print character or string values, or use
8555 character and string literals in expressions.
8557 @value{GDBN} has no way to automatically recognize which character set
8558 the inferior program uses; you must tell it, using the @code{set
8559 target-charset} command, described below.
8561 Here are the commands for controlling @value{GDBN}'s character set
8565 @item set target-charset @var{charset}
8566 @kindex set target-charset
8567 Set the current target character set to @var{charset}. To display the
8568 list of supported target character sets, type
8569 @kbd{@w{set target-charset @key{TAB}@key{TAB}}}.
8571 @item set host-charset @var{charset}
8572 @kindex set host-charset
8573 Set the current host character set to @var{charset}.
8575 By default, @value{GDBN} uses a host character set appropriate to the
8576 system it is running on; you can override that default using the
8577 @code{set host-charset} command. On some systems, @value{GDBN} cannot
8578 automatically determine the appropriate host character set. In this
8579 case, @value{GDBN} uses @samp{UTF-8}.
8581 @value{GDBN} can only use certain character sets as its host character
8582 set. If you type @kbd{@w{set target-charset @key{TAB}@key{TAB}}},
8583 @value{GDBN} will list the host character sets it supports.
8585 @item set charset @var{charset}
8587 Set the current host and target character sets to @var{charset}. As
8588 above, if you type @kbd{@w{set charset @key{TAB}@key{TAB}}},
8589 @value{GDBN} will list the names of the character sets that can be used
8590 for both host and target.
8593 @kindex show charset
8594 Show the names of the current host and target character sets.
8596 @item show host-charset
8597 @kindex show host-charset
8598 Show the name of the current host character set.
8600 @item show target-charset
8601 @kindex show target-charset
8602 Show the name of the current target character set.
8604 @item set target-wide-charset @var{charset}
8605 @kindex set target-wide-charset
8606 Set the current target's wide character set to @var{charset}. This is
8607 the character set used by the target's @code{wchar_t} type. To
8608 display the list of supported wide character sets, type
8609 @kbd{@w{set target-wide-charset @key{TAB}@key{TAB}}}.
8611 @item show target-wide-charset
8612 @kindex show target-wide-charset
8613 Show the name of the current target's wide character set.
8616 Here is an example of @value{GDBN}'s character set support in action.
8617 Assume that the following source code has been placed in the file
8618 @file{charset-test.c}:
8624 = @{72, 101, 108, 108, 111, 44, 32, 119,
8625 111, 114, 108, 100, 33, 10, 0@};
8626 char ibm1047_hello[]
8627 = @{200, 133, 147, 147, 150, 107, 64, 166,
8628 150, 153, 147, 132, 90, 37, 0@};
8632 printf ("Hello, world!\n");
8636 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
8637 containing the string @samp{Hello, world!} followed by a newline,
8638 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
8640 We compile the program, and invoke the debugger on it:
8643 $ gcc -g charset-test.c -o charset-test
8644 $ gdb -nw charset-test
8645 GNU gdb 2001-12-19-cvs
8646 Copyright 2001 Free Software Foundation, Inc.
8651 We can use the @code{show charset} command to see what character sets
8652 @value{GDBN} is currently using to interpret and display characters and
8656 (@value{GDBP}) show charset
8657 The current host and target character set is `ISO-8859-1'.
8661 For the sake of printing this manual, let's use @sc{ascii} as our
8662 initial character set:
8664 (@value{GDBP}) set charset ASCII
8665 (@value{GDBP}) show charset
8666 The current host and target character set is `ASCII'.
8670 Let's assume that @sc{ascii} is indeed the correct character set for our
8671 host system --- in other words, let's assume that if @value{GDBN} prints
8672 characters using the @sc{ascii} character set, our terminal will display
8673 them properly. Since our current target character set is also
8674 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
8677 (@value{GDBP}) print ascii_hello
8678 $1 = 0x401698 "Hello, world!\n"
8679 (@value{GDBP}) print ascii_hello[0]
8684 @value{GDBN} uses the target character set for character and string
8685 literals you use in expressions:
8688 (@value{GDBP}) print '+'
8693 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
8696 @value{GDBN} relies on the user to tell it which character set the
8697 target program uses. If we print @code{ibm1047_hello} while our target
8698 character set is still @sc{ascii}, we get jibberish:
8701 (@value{GDBP}) print ibm1047_hello
8702 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
8703 (@value{GDBP}) print ibm1047_hello[0]
8708 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
8709 @value{GDBN} tells us the character sets it supports:
8712 (@value{GDBP}) set target-charset
8713 ASCII EBCDIC-US IBM1047 ISO-8859-1
8714 (@value{GDBP}) set target-charset
8717 We can select @sc{ibm1047} as our target character set, and examine the
8718 program's strings again. Now the @sc{ascii} string is wrong, but
8719 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
8720 target character set, @sc{ibm1047}, to the host character set,
8721 @sc{ascii}, and they display correctly:
8724 (@value{GDBP}) set target-charset IBM1047
8725 (@value{GDBP}) show charset
8726 The current host character set is `ASCII'.
8727 The current target character set is `IBM1047'.
8728 (@value{GDBP}) print ascii_hello
8729 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
8730 (@value{GDBP}) print ascii_hello[0]
8732 (@value{GDBP}) print ibm1047_hello
8733 $8 = 0x4016a8 "Hello, world!\n"
8734 (@value{GDBP}) print ibm1047_hello[0]
8739 As above, @value{GDBN} uses the target character set for character and
8740 string literals you use in expressions:
8743 (@value{GDBP}) print '+'
8748 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
8751 @node Caching Remote Data
8752 @section Caching Data of Remote Targets
8753 @cindex caching data of remote targets
8755 @value{GDBN} caches data exchanged between the debugger and a
8756 remote target (@pxref{Remote Debugging}). Such caching generally improves
8757 performance, because it reduces the overhead of the remote protocol by
8758 bundling memory reads and writes into large chunks. Unfortunately, simply
8759 caching everything would lead to incorrect results, since @value{GDBN}
8760 does not necessarily know anything about volatile values, memory-mapped I/O
8761 addresses, etc. Furthermore, in non-stop mode (@pxref{Non-Stop Mode})
8762 memory can be changed @emph{while} a gdb command is executing.
8763 Therefore, by default, @value{GDBN} only caches data
8764 known to be on the stack@footnote{In non-stop mode, it is moderately
8765 rare for a running thread to modify the stack of a stopped thread
8766 in a way that would interfere with a backtrace, and caching of
8767 stack reads provides a significant speed up of remote backtraces.}.
8768 Other regions of memory can be explicitly marked as
8769 cacheable; see @pxref{Memory Region Attributes}.
8772 @kindex set remotecache
8773 @item set remotecache on
8774 @itemx set remotecache off
8775 This option no longer does anything; it exists for compatibility
8778 @kindex show remotecache
8779 @item show remotecache
8780 Show the current state of the obsolete remotecache flag.
8782 @kindex set stack-cache
8783 @item set stack-cache on
8784 @itemx set stack-cache off
8785 Enable or disable caching of stack accesses. When @code{ON}, use
8786 caching. By default, this option is @code{ON}.
8788 @kindex show stack-cache
8789 @item show stack-cache
8790 Show the current state of data caching for memory accesses.
8793 @item info dcache @r{[}line@r{]}
8794 Print the information about the data cache performance. The
8795 information displayed includes the dcache width and depth, and for
8796 each cache line, its number, address, and how many times it was
8797 referenced. This command is useful for debugging the data cache
8800 If a line number is specified, the contents of that line will be
8804 @node Searching Memory
8805 @section Search Memory
8806 @cindex searching memory
8808 Memory can be searched for a particular sequence of bytes with the
8809 @code{find} command.
8813 @item find @r{[}/@var{sn}@r{]} @var{start_addr}, +@var{len}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
8814 @itemx find @r{[}/@var{sn}@r{]} @var{start_addr}, @var{end_addr}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
8815 Search memory for the sequence of bytes specified by @var{val1}, @var{val2},
8816 etc. The search begins at address @var{start_addr} and continues for either
8817 @var{len} bytes or through to @var{end_addr} inclusive.
8820 @var{s} and @var{n} are optional parameters.
8821 They may be specified in either order, apart or together.
8824 @item @var{s}, search query size
8825 The size of each search query value.
8831 halfwords (two bytes)
8835 giant words (eight bytes)
8838 All values are interpreted in the current language.
8839 This means, for example, that if the current source language is C/C@t{++}
8840 then searching for the string ``hello'' includes the trailing '\0'.
8842 If the value size is not specified, it is taken from the
8843 value's type in the current language.
8844 This is useful when one wants to specify the search
8845 pattern as a mixture of types.
8846 Note that this means, for example, that in the case of C-like languages
8847 a search for an untyped 0x42 will search for @samp{(int) 0x42}
8848 which is typically four bytes.
8850 @item @var{n}, maximum number of finds
8851 The maximum number of matches to print. The default is to print all finds.
8854 You can use strings as search values. Quote them with double-quotes
8856 The string value is copied into the search pattern byte by byte,
8857 regardless of the endianness of the target and the size specification.
8859 The address of each match found is printed as well as a count of the
8860 number of matches found.
8862 The address of the last value found is stored in convenience variable
8864 A count of the number of matches is stored in @samp{$numfound}.
8866 For example, if stopped at the @code{printf} in this function:
8872 static char hello[] = "hello-hello";
8873 static struct @{ char c; short s; int i; @}
8874 __attribute__ ((packed)) mixed
8875 = @{ 'c', 0x1234, 0x87654321 @};
8876 printf ("%s\n", hello);
8881 you get during debugging:
8884 (gdb) find &hello[0], +sizeof(hello), "hello"
8885 0x804956d <hello.1620+6>
8887 (gdb) find &hello[0], +sizeof(hello), 'h', 'e', 'l', 'l', 'o'
8888 0x8049567 <hello.1620>
8889 0x804956d <hello.1620+6>
8891 (gdb) find /b1 &hello[0], +sizeof(hello), 'h', 0x65, 'l'
8892 0x8049567 <hello.1620>
8894 (gdb) find &mixed, +sizeof(mixed), (char) 'c', (short) 0x1234, (int) 0x87654321
8895 0x8049560 <mixed.1625>
8897 (gdb) print $numfound
8900 $2 = (void *) 0x8049560
8903 @node Optimized Code
8904 @chapter Debugging Optimized Code
8905 @cindex optimized code, debugging
8906 @cindex debugging optimized code
8908 Almost all compilers support optimization. With optimization
8909 disabled, the compiler generates assembly code that corresponds
8910 directly to your source code, in a simplistic way. As the compiler
8911 applies more powerful optimizations, the generated assembly code
8912 diverges from your original source code. With help from debugging
8913 information generated by the compiler, @value{GDBN} can map from
8914 the running program back to constructs from your original source.
8916 @value{GDBN} is more accurate with optimization disabled. If you
8917 can recompile without optimization, it is easier to follow the
8918 progress of your program during debugging. But, there are many cases
8919 where you may need to debug an optimized version.
8921 When you debug a program compiled with @samp{-g -O}, remember that the
8922 optimizer has rearranged your code; the debugger shows you what is
8923 really there. Do not be too surprised when the execution path does not
8924 exactly match your source file! An extreme example: if you define a
8925 variable, but never use it, @value{GDBN} never sees that
8926 variable---because the compiler optimizes it out of existence.
8928 Some things do not work as well with @samp{-g -O} as with just
8929 @samp{-g}, particularly on machines with instruction scheduling. If in
8930 doubt, recompile with @samp{-g} alone, and if this fixes the problem,
8931 please report it to us as a bug (including a test case!).
8932 @xref{Variables}, for more information about debugging optimized code.
8935 * Inline Functions:: How @value{GDBN} presents inlining
8938 @node Inline Functions
8939 @section Inline Functions
8940 @cindex inline functions, debugging
8942 @dfn{Inlining} is an optimization that inserts a copy of the function
8943 body directly at each call site, instead of jumping to a shared
8944 routine. @value{GDBN} displays inlined functions just like
8945 non-inlined functions. They appear in backtraces. You can view their
8946 arguments and local variables, step into them with @code{step}, skip
8947 them with @code{next}, and escape from them with @code{finish}.
8948 You can check whether a function was inlined by using the
8949 @code{info frame} command.
8951 For @value{GDBN} to support inlined functions, the compiler must
8952 record information about inlining in the debug information ---
8953 @value{NGCC} using the @sc{dwarf 2} format does this, and several
8954 other compilers do also. @value{GDBN} only supports inlined functions
8955 when using @sc{dwarf 2}. Versions of @value{NGCC} before 4.1
8956 do not emit two required attributes (@samp{DW_AT_call_file} and
8957 @samp{DW_AT_call_line}); @value{GDBN} does not display inlined
8958 function calls with earlier versions of @value{NGCC}. It instead
8959 displays the arguments and local variables of inlined functions as
8960 local variables in the caller.
8962 The body of an inlined function is directly included at its call site;
8963 unlike a non-inlined function, there are no instructions devoted to
8964 the call. @value{GDBN} still pretends that the call site and the
8965 start of the inlined function are different instructions. Stepping to
8966 the call site shows the call site, and then stepping again shows
8967 the first line of the inlined function, even though no additional
8968 instructions are executed.
8970 This makes source-level debugging much clearer; you can see both the
8971 context of the call and then the effect of the call. Only stepping by
8972 a single instruction using @code{stepi} or @code{nexti} does not do
8973 this; single instruction steps always show the inlined body.
8975 There are some ways that @value{GDBN} does not pretend that inlined
8976 function calls are the same as normal calls:
8980 You cannot set breakpoints on inlined functions. @value{GDBN}
8981 either reports that there is no symbol with that name, or else sets the
8982 breakpoint only on non-inlined copies of the function. This limitation
8983 will be removed in a future version of @value{GDBN}; until then,
8984 set a breakpoint by line number on the first line of the inlined
8988 Setting breakpoints at the call site of an inlined function may not
8989 work, because the call site does not contain any code. @value{GDBN}
8990 may incorrectly move the breakpoint to the next line of the enclosing
8991 function, after the call. This limitation will be removed in a future
8992 version of @value{GDBN}; until then, set a breakpoint on an earlier line
8993 or inside the inlined function instead.
8996 @value{GDBN} cannot locate the return value of inlined calls after
8997 using the @code{finish} command. This is a limitation of compiler-generated
8998 debugging information; after @code{finish}, you can step to the next line
8999 and print a variable where your program stored the return value.
9005 @chapter C Preprocessor Macros
9007 Some languages, such as C and C@t{++}, provide a way to define and invoke
9008 ``preprocessor macros'' which expand into strings of tokens.
9009 @value{GDBN} can evaluate expressions containing macro invocations, show
9010 the result of macro expansion, and show a macro's definition, including
9011 where it was defined.
9013 You may need to compile your program specially to provide @value{GDBN}
9014 with information about preprocessor macros. Most compilers do not
9015 include macros in their debugging information, even when you compile
9016 with the @option{-g} flag. @xref{Compilation}.
9018 A program may define a macro at one point, remove that definition later,
9019 and then provide a different definition after that. Thus, at different
9020 points in the program, a macro may have different definitions, or have
9021 no definition at all. If there is a current stack frame, @value{GDBN}
9022 uses the macros in scope at that frame's source code line. Otherwise,
9023 @value{GDBN} uses the macros in scope at the current listing location;
9026 Whenever @value{GDBN} evaluates an expression, it always expands any
9027 macro invocations present in the expression. @value{GDBN} also provides
9028 the following commands for working with macros explicitly.
9032 @kindex macro expand
9033 @cindex macro expansion, showing the results of preprocessor
9034 @cindex preprocessor macro expansion, showing the results of
9035 @cindex expanding preprocessor macros
9036 @item macro expand @var{expression}
9037 @itemx macro exp @var{expression}
9038 Show the results of expanding all preprocessor macro invocations in
9039 @var{expression}. Since @value{GDBN} simply expands macros, but does
9040 not parse the result, @var{expression} need not be a valid expression;
9041 it can be any string of tokens.
9044 @item macro expand-once @var{expression}
9045 @itemx macro exp1 @var{expression}
9046 @cindex expand macro once
9047 @i{(This command is not yet implemented.)} Show the results of
9048 expanding those preprocessor macro invocations that appear explicitly in
9049 @var{expression}. Macro invocations appearing in that expansion are
9050 left unchanged. This command allows you to see the effect of a
9051 particular macro more clearly, without being confused by further
9052 expansions. Since @value{GDBN} simply expands macros, but does not
9053 parse the result, @var{expression} need not be a valid expression; it
9054 can be any string of tokens.
9057 @cindex macro definition, showing
9058 @cindex definition, showing a macro's
9059 @item info macro @var{macro}
9060 Show the definition of the macro named @var{macro}, and describe the
9061 source location or compiler command-line where that definition was established.
9063 @kindex macro define
9064 @cindex user-defined macros
9065 @cindex defining macros interactively
9066 @cindex macros, user-defined
9067 @item macro define @var{macro} @var{replacement-list}
9068 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
9069 Introduce a definition for a preprocessor macro named @var{macro},
9070 invocations of which are replaced by the tokens given in
9071 @var{replacement-list}. The first form of this command defines an
9072 ``object-like'' macro, which takes no arguments; the second form
9073 defines a ``function-like'' macro, which takes the arguments given in
9076 A definition introduced by this command is in scope in every
9077 expression evaluated in @value{GDBN}, until it is removed with the
9078 @code{macro undef} command, described below. The definition overrides
9079 all definitions for @var{macro} present in the program being debugged,
9080 as well as any previous user-supplied definition.
9083 @item macro undef @var{macro}
9084 Remove any user-supplied definition for the macro named @var{macro}.
9085 This command only affects definitions provided with the @code{macro
9086 define} command, described above; it cannot remove definitions present
9087 in the program being debugged.
9091 List all the macros defined using the @code{macro define} command.
9094 @cindex macros, example of debugging with
9095 Here is a transcript showing the above commands in action. First, we
9096 show our source files:
9104 #define ADD(x) (M + x)
9109 printf ("Hello, world!\n");
9111 printf ("We're so creative.\n");
9113 printf ("Goodbye, world!\n");
9120 Now, we compile the program using the @sc{gnu} C compiler, @value{NGCC}.
9121 We pass the @option{-gdwarf-2} and @option{-g3} flags to ensure the
9122 compiler includes information about preprocessor macros in the debugging
9126 $ gcc -gdwarf-2 -g3 sample.c -o sample
9130 Now, we start @value{GDBN} on our sample program:
9134 GNU gdb 2002-05-06-cvs
9135 Copyright 2002 Free Software Foundation, Inc.
9136 GDB is free software, @dots{}
9140 We can expand macros and examine their definitions, even when the
9141 program is not running. @value{GDBN} uses the current listing position
9142 to decide which macro definitions are in scope:
9145 (@value{GDBP}) list main
9148 5 #define ADD(x) (M + x)
9153 10 printf ("Hello, world!\n");
9155 12 printf ("We're so creative.\n");
9156 (@value{GDBP}) info macro ADD
9157 Defined at /home/jimb/gdb/macros/play/sample.c:5
9158 #define ADD(x) (M + x)
9159 (@value{GDBP}) info macro Q
9160 Defined at /home/jimb/gdb/macros/play/sample.h:1
9161 included at /home/jimb/gdb/macros/play/sample.c:2
9163 (@value{GDBP}) macro expand ADD(1)
9164 expands to: (42 + 1)
9165 (@value{GDBP}) macro expand-once ADD(1)
9166 expands to: once (M + 1)
9170 In the example above, note that @code{macro expand-once} expands only
9171 the macro invocation explicit in the original text --- the invocation of
9172 @code{ADD} --- but does not expand the invocation of the macro @code{M},
9173 which was introduced by @code{ADD}.
9175 Once the program is running, @value{GDBN} uses the macro definitions in
9176 force at the source line of the current stack frame:
9179 (@value{GDBP}) break main
9180 Breakpoint 1 at 0x8048370: file sample.c, line 10.
9182 Starting program: /home/jimb/gdb/macros/play/sample
9184 Breakpoint 1, main () at sample.c:10
9185 10 printf ("Hello, world!\n");
9189 At line 10, the definition of the macro @code{N} at line 9 is in force:
9192 (@value{GDBP}) info macro N
9193 Defined at /home/jimb/gdb/macros/play/sample.c:9
9195 (@value{GDBP}) macro expand N Q M
9197 (@value{GDBP}) print N Q M
9202 As we step over directives that remove @code{N}'s definition, and then
9203 give it a new definition, @value{GDBN} finds the definition (or lack
9204 thereof) in force at each point:
9209 12 printf ("We're so creative.\n");
9210 (@value{GDBP}) info macro N
9211 The symbol `N' has no definition as a C/C++ preprocessor macro
9212 at /home/jimb/gdb/macros/play/sample.c:12
9215 14 printf ("Goodbye, world!\n");
9216 (@value{GDBP}) info macro N
9217 Defined at /home/jimb/gdb/macros/play/sample.c:13
9219 (@value{GDBP}) macro expand N Q M
9220 expands to: 1729 < 42
9221 (@value{GDBP}) print N Q M
9226 In addition to source files, macros can be defined on the compilation command
9227 line using the @option{-D@var{name}=@var{value}} syntax. For macros defined in
9228 such a way, @value{GDBN} displays the location of their definition as line zero
9229 of the source file submitted to the compiler.
9232 (@value{GDBP}) info macro __STDC__
9233 Defined at /home/jimb/gdb/macros/play/sample.c:0
9240 @chapter Tracepoints
9241 @c This chapter is based on the documentation written by Michael
9242 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
9245 In some applications, it is not feasible for the debugger to interrupt
9246 the program's execution long enough for the developer to learn
9247 anything helpful about its behavior. If the program's correctness
9248 depends on its real-time behavior, delays introduced by a debugger
9249 might cause the program to change its behavior drastically, or perhaps
9250 fail, even when the code itself is correct. It is useful to be able
9251 to observe the program's behavior without interrupting it.
9253 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
9254 specify locations in the program, called @dfn{tracepoints}, and
9255 arbitrary expressions to evaluate when those tracepoints are reached.
9256 Later, using the @code{tfind} command, you can examine the values
9257 those expressions had when the program hit the tracepoints. The
9258 expressions may also denote objects in memory---structures or arrays,
9259 for example---whose values @value{GDBN} should record; while visiting
9260 a particular tracepoint, you may inspect those objects as if they were
9261 in memory at that moment. However, because @value{GDBN} records these
9262 values without interacting with you, it can do so quickly and
9263 unobtrusively, hopefully not disturbing the program's behavior.
9265 The tracepoint facility is currently available only for remote
9266 targets. @xref{Targets}. In addition, your remote target must know
9267 how to collect trace data. This functionality is implemented in the
9268 remote stub; however, none of the stubs distributed with @value{GDBN}
9269 support tracepoints as of this writing. The format of the remote
9270 packets used to implement tracepoints are described in @ref{Tracepoint
9273 This chapter describes the tracepoint commands and features.
9277 * Analyze Collected Data::
9278 * Tracepoint Variables::
9281 @node Set Tracepoints
9282 @section Commands to Set Tracepoints
9284 Before running such a @dfn{trace experiment}, an arbitrary number of
9285 tracepoints can be set. A tracepoint is actually a special type of
9286 breakpoint (@pxref{Set Breaks}), so you can manipulate it using
9287 standard breakpoint commands. For instance, as with breakpoints,
9288 tracepoint numbers are successive integers starting from one, and many
9289 of the commands associated with tracepoints take the tracepoint number
9290 as their argument, to identify which tracepoint to work on.
9292 For each tracepoint, you can specify, in advance, some arbitrary set
9293 of data that you want the target to collect in the trace buffer when
9294 it hits that tracepoint. The collected data can include registers,
9295 local variables, or global data. Later, you can use @value{GDBN}
9296 commands to examine the values these data had at the time the
9299 Tracepoints do not support every breakpoint feature. Conditional
9300 expressions and ignore counts on tracepoints have no effect, and
9301 tracepoints cannot run @value{GDBN} commands when they are
9302 hit. Tracepoints may not be thread-specific either.
9304 This section describes commands to set tracepoints and associated
9305 conditions and actions.
9308 * Create and Delete Tracepoints::
9309 * Enable and Disable Tracepoints::
9310 * Tracepoint Passcounts::
9311 * Tracepoint Conditions::
9312 * Tracepoint Actions::
9313 * Listing Tracepoints::
9314 * Starting and Stopping Trace Experiments::
9317 @node Create and Delete Tracepoints
9318 @subsection Create and Delete Tracepoints
9321 @cindex set tracepoint
9323 @item trace @var{location}
9324 The @code{trace} command is very similar to the @code{break} command.
9325 Its argument @var{location} can be a source line, a function name, or
9326 an address in the target program. @xref{Specify Location}. The
9327 @code{trace} command defines a tracepoint, which is a point in the
9328 target program where the debugger will briefly stop, collect some
9329 data, and then allow the program to continue. Setting a tracepoint or
9330 changing its actions doesn't take effect until the next @code{tstart}
9331 command, and once a trace experiment is running, further changes will
9332 not have any effect until the next trace experiment starts.
9334 Here are some examples of using the @code{trace} command:
9337 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
9339 (@value{GDBP}) @b{trace +2} // 2 lines forward
9341 (@value{GDBP}) @b{trace my_function} // first source line of function
9343 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
9345 (@value{GDBP}) @b{trace *0x2117c4} // an address
9349 You can abbreviate @code{trace} as @code{tr}.
9351 @item trace @var{location} if @var{cond}
9352 Set a tracepoint with condition @var{cond}; evaluate the expression
9353 @var{cond} each time the tracepoint is reached, and collect data only
9354 if the value is nonzero---that is, if @var{cond} evaluates as true.
9355 @xref{Tracepoint Conditions, ,Tracepoint Conditions}, for more
9356 information on tracepoint conditions.
9359 @cindex last tracepoint number
9360 @cindex recent tracepoint number
9361 @cindex tracepoint number
9362 The convenience variable @code{$tpnum} records the tracepoint number
9363 of the most recently set tracepoint.
9365 @kindex delete tracepoint
9366 @cindex tracepoint deletion
9367 @item delete tracepoint @r{[}@var{num}@r{]}
9368 Permanently delete one or more tracepoints. With no argument, the
9369 default is to delete all tracepoints. Note that the regular
9370 @code{delete} command can remove tracepoints also.
9375 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
9377 (@value{GDBP}) @b{delete trace} // remove all tracepoints
9381 You can abbreviate this command as @code{del tr}.
9384 @node Enable and Disable Tracepoints
9385 @subsection Enable and Disable Tracepoints
9387 These commands are deprecated; they are equivalent to plain @code{disable} and @code{enable}.
9390 @kindex disable tracepoint
9391 @item disable tracepoint @r{[}@var{num}@r{]}
9392 Disable tracepoint @var{num}, or all tracepoints if no argument
9393 @var{num} is given. A disabled tracepoint will have no effect during
9394 the next trace experiment, but it is not forgotten. You can re-enable
9395 a disabled tracepoint using the @code{enable tracepoint} command.
9397 @kindex enable tracepoint
9398 @item enable tracepoint @r{[}@var{num}@r{]}
9399 Enable tracepoint @var{num}, or all tracepoints. The enabled
9400 tracepoints will become effective the next time a trace experiment is
9404 @node Tracepoint Passcounts
9405 @subsection Tracepoint Passcounts
9409 @cindex tracepoint pass count
9410 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
9411 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
9412 automatically stop a trace experiment. If a tracepoint's passcount is
9413 @var{n}, then the trace experiment will be automatically stopped on
9414 the @var{n}'th time that tracepoint is hit. If the tracepoint number
9415 @var{num} is not specified, the @code{passcount} command sets the
9416 passcount of the most recently defined tracepoint. If no passcount is
9417 given, the trace experiment will run until stopped explicitly by the
9423 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
9424 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
9426 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
9427 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
9428 (@value{GDBP}) @b{trace foo}
9429 (@value{GDBP}) @b{pass 3}
9430 (@value{GDBP}) @b{trace bar}
9431 (@value{GDBP}) @b{pass 2}
9432 (@value{GDBP}) @b{trace baz}
9433 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
9434 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
9435 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
9436 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
9440 @node Tracepoint Conditions
9441 @subsection Tracepoint Conditions
9442 @cindex conditional tracepoints
9443 @cindex tracepoint conditions
9445 The simplest sort of tracepoint collects data every time your program
9446 reaches a specified place. You can also specify a @dfn{condition} for
9447 a tracepoint. A condition is just a Boolean expression in your
9448 programming language (@pxref{Expressions, ,Expressions}). A
9449 tracepoint with a condition evaluates the expression each time your
9450 program reaches it, and data collection happens only if the condition
9453 Tracepoint conditions can be specified when a tracepoint is set, by
9454 using @samp{if} in the arguments to the @code{trace} command.
9455 @xref{Create and Delete Tracepoints, ,Setting Tracepoints}. They can
9456 also be set or changed at any time with the @code{condition} command,
9457 just as with breakpoints.
9459 Unlike breakpoint conditions, @value{GDBN} does not actually evaluate
9460 the conditional expression itself. Instead, @value{GDBN} encodes the
9461 expression into an agent expression (@pxref{Agent Expressions}
9462 suitable for execution on the target, independently of @value{GDBN}.
9463 Global variables become raw memory locations, locals become stack
9464 accesses, and so forth.
9466 For instance, suppose you have a function that is usually called
9467 frequently, but should not be called after an error has occurred. You
9468 could use the following tracepoint command to collect data about calls
9469 of that function that happen while the error code is propagating
9470 through the program; an unconditional tracepoint could end up
9471 collecting thousands of useless trace frames that you would have to
9475 (@value{GDBP}) @kbd{trace normal_operation if errcode > 0}
9478 @node Tracepoint Actions
9479 @subsection Tracepoint Action Lists
9483 @cindex tracepoint actions
9484 @item actions @r{[}@var{num}@r{]}
9485 This command will prompt for a list of actions to be taken when the
9486 tracepoint is hit. If the tracepoint number @var{num} is not
9487 specified, this command sets the actions for the one that was most
9488 recently defined (so that you can define a tracepoint and then say
9489 @code{actions} without bothering about its number). You specify the
9490 actions themselves on the following lines, one action at a time, and
9491 terminate the actions list with a line containing just @code{end}. So
9492 far, the only defined actions are @code{collect} and
9493 @code{while-stepping}.
9495 @cindex remove actions from a tracepoint
9496 To remove all actions from a tracepoint, type @samp{actions @var{num}}
9497 and follow it immediately with @samp{end}.
9500 (@value{GDBP}) @b{collect @var{data}} // collect some data
9502 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
9504 (@value{GDBP}) @b{end} // signals the end of actions.
9507 In the following example, the action list begins with @code{collect}
9508 commands indicating the things to be collected when the tracepoint is
9509 hit. Then, in order to single-step and collect additional data
9510 following the tracepoint, a @code{while-stepping} command is used,
9511 followed by the list of things to be collected while stepping. The
9512 @code{while-stepping} command is terminated by its own separate
9513 @code{end} command. Lastly, the action list is terminated by an
9517 (@value{GDBP}) @b{trace foo}
9518 (@value{GDBP}) @b{actions}
9519 Enter actions for tracepoint 1, one per line:
9528 @kindex collect @r{(tracepoints)}
9529 @item collect @var{expr1}, @var{expr2}, @dots{}
9530 Collect values of the given expressions when the tracepoint is hit.
9531 This command accepts a comma-separated list of any valid expressions.
9532 In addition to global, static, or local variables, the following
9533 special arguments are supported:
9537 collect all registers
9540 collect all function arguments
9543 collect all local variables.
9546 You can give several consecutive @code{collect} commands, each one
9547 with a single argument, or one @code{collect} command with several
9548 arguments separated by commas: the effect is the same.
9550 The command @code{info scope} (@pxref{Symbols, info scope}) is
9551 particularly useful for figuring out what data to collect.
9553 @kindex while-stepping @r{(tracepoints)}
9554 @item while-stepping @var{n}
9555 Perform @var{n} single-step traces after the tracepoint, collecting
9556 new data at each step. The @code{while-stepping} command is
9557 followed by the list of what to collect while stepping (followed by
9558 its own @code{end} command):
9562 > collect $regs, myglobal
9568 You may abbreviate @code{while-stepping} as @code{ws} or
9572 @node Listing Tracepoints
9573 @subsection Listing Tracepoints
9576 @kindex info tracepoints
9578 @cindex information about tracepoints
9579 @item info tracepoints @r{[}@var{num}@r{]}
9580 Display information about the tracepoint @var{num}. If you don't
9581 specify a tracepoint number, displays information about all the
9582 tracepoints defined so far. The format is similar to that used for
9583 @code{info breakpoints}; in fact, @code{info tracepoints} is the same
9584 command, simply restricting itself to tracepoints.
9586 A tracepoint's listing may include additional information specific to
9591 its passcount as given by the @code{passcount @var{n}} command
9593 its step count as given by the @code{while-stepping @var{n}} command
9595 its action list as given by the @code{actions} command. The actions
9596 are prefixed with an @samp{A} so as to distinguish them from commands.
9600 (@value{GDBP}) @b{info trace}
9601 Num Type Disp Enb Address What
9602 1 tracepoint keep y 0x0804ab57 in foo() at main.cxx:7
9606 A collect globfoo, $regs
9614 This command can be abbreviated @code{info tp}.
9617 @node Starting and Stopping Trace Experiments
9618 @subsection Starting and Stopping Trace Experiments
9622 @cindex start a new trace experiment
9623 @cindex collected data discarded
9625 This command takes no arguments. It starts the trace experiment, and
9626 begins collecting data. This has the side effect of discarding all
9627 the data collected in the trace buffer during the previous trace
9631 @cindex stop a running trace experiment
9633 This command takes no arguments. It ends the trace experiment, and
9634 stops collecting data.
9636 @strong{Note}: a trace experiment and data collection may stop
9637 automatically if any tracepoint's passcount is reached
9638 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
9641 @cindex status of trace data collection
9642 @cindex trace experiment, status of
9644 This command displays the status of the current trace data
9648 Here is an example of the commands we described so far:
9651 (@value{GDBP}) @b{trace gdb_c_test}
9652 (@value{GDBP}) @b{actions}
9653 Enter actions for tracepoint #1, one per line.
9654 > collect $regs,$locals,$args
9659 (@value{GDBP}) @b{tstart}
9660 [time passes @dots{}]
9661 (@value{GDBP}) @b{tstop}
9665 @node Analyze Collected Data
9666 @section Using the Collected Data
9668 After the tracepoint experiment ends, you use @value{GDBN} commands
9669 for examining the trace data. The basic idea is that each tracepoint
9670 collects a trace @dfn{snapshot} every time it is hit and another
9671 snapshot every time it single-steps. All these snapshots are
9672 consecutively numbered from zero and go into a buffer, and you can
9673 examine them later. The way you examine them is to @dfn{focus} on a
9674 specific trace snapshot. When the remote stub is focused on a trace
9675 snapshot, it will respond to all @value{GDBN} requests for memory and
9676 registers by reading from the buffer which belongs to that snapshot,
9677 rather than from @emph{real} memory or registers of the program being
9678 debugged. This means that @strong{all} @value{GDBN} commands
9679 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
9680 behave as if we were currently debugging the program state as it was
9681 when the tracepoint occurred. Any requests for data that are not in
9682 the buffer will fail.
9685 * tfind:: How to select a trace snapshot
9686 * tdump:: How to display all data for a snapshot
9687 * save-tracepoints:: How to save tracepoints for a future run
9691 @subsection @code{tfind @var{n}}
9694 @cindex select trace snapshot
9695 @cindex find trace snapshot
9696 The basic command for selecting a trace snapshot from the buffer is
9697 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
9698 counting from zero. If no argument @var{n} is given, the next
9699 snapshot is selected.
9701 Here are the various forms of using the @code{tfind} command.
9705 Find the first snapshot in the buffer. This is a synonym for
9706 @code{tfind 0} (since 0 is the number of the first snapshot).
9709 Stop debugging trace snapshots, resume @emph{live} debugging.
9712 Same as @samp{tfind none}.
9715 No argument means find the next trace snapshot.
9718 Find the previous trace snapshot before the current one. This permits
9719 retracing earlier steps.
9721 @item tfind tracepoint @var{num}
9722 Find the next snapshot associated with tracepoint @var{num}. Search
9723 proceeds forward from the last examined trace snapshot. If no
9724 argument @var{num} is given, it means find the next snapshot collected
9725 for the same tracepoint as the current snapshot.
9727 @item tfind pc @var{addr}
9728 Find the next snapshot associated with the value @var{addr} of the
9729 program counter. Search proceeds forward from the last examined trace
9730 snapshot. If no argument @var{addr} is given, it means find the next
9731 snapshot with the same value of PC as the current snapshot.
9733 @item tfind outside @var{addr1}, @var{addr2}
9734 Find the next snapshot whose PC is outside the given range of
9737 @item tfind range @var{addr1}, @var{addr2}
9738 Find the next snapshot whose PC is between @var{addr1} and
9739 @var{addr2}. @c FIXME: Is the range inclusive or exclusive?
9741 @item tfind line @r{[}@var{file}:@r{]}@var{n}
9742 Find the next snapshot associated with the source line @var{n}. If
9743 the optional argument @var{file} is given, refer to line @var{n} in
9744 that source file. Search proceeds forward from the last examined
9745 trace snapshot. If no argument @var{n} is given, it means find the
9746 next line other than the one currently being examined; thus saying
9747 @code{tfind line} repeatedly can appear to have the same effect as
9748 stepping from line to line in a @emph{live} debugging session.
9751 The default arguments for the @code{tfind} commands are specifically
9752 designed to make it easy to scan through the trace buffer. For
9753 instance, @code{tfind} with no argument selects the next trace
9754 snapshot, and @code{tfind -} with no argument selects the previous
9755 trace snapshot. So, by giving one @code{tfind} command, and then
9756 simply hitting @key{RET} repeatedly you can examine all the trace
9757 snapshots in order. Or, by saying @code{tfind -} and then hitting
9758 @key{RET} repeatedly you can examine the snapshots in reverse order.
9759 The @code{tfind line} command with no argument selects the snapshot
9760 for the next source line executed. The @code{tfind pc} command with
9761 no argument selects the next snapshot with the same program counter
9762 (PC) as the current frame. The @code{tfind tracepoint} command with
9763 no argument selects the next trace snapshot collected by the same
9764 tracepoint as the current one.
9766 In addition to letting you scan through the trace buffer manually,
9767 these commands make it easy to construct @value{GDBN} scripts that
9768 scan through the trace buffer and print out whatever collected data
9769 you are interested in. Thus, if we want to examine the PC, FP, and SP
9770 registers from each trace frame in the buffer, we can say this:
9773 (@value{GDBP}) @b{tfind start}
9774 (@value{GDBP}) @b{while ($trace_frame != -1)}
9775 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
9776 $trace_frame, $pc, $sp, $fp
9780 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
9781 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
9782 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
9783 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
9784 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
9785 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
9786 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
9787 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
9788 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
9789 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
9790 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
9793 Or, if we want to examine the variable @code{X} at each source line in
9797 (@value{GDBP}) @b{tfind start}
9798 (@value{GDBP}) @b{while ($trace_frame != -1)}
9799 > printf "Frame %d, X == %d\n", $trace_frame, X
9809 @subsection @code{tdump}
9811 @cindex dump all data collected at tracepoint
9812 @cindex tracepoint data, display
9814 This command takes no arguments. It prints all the data collected at
9815 the current trace snapshot.
9818 (@value{GDBP}) @b{trace 444}
9819 (@value{GDBP}) @b{actions}
9820 Enter actions for tracepoint #2, one per line:
9821 > collect $regs, $locals, $args, gdb_long_test
9824 (@value{GDBP}) @b{tstart}
9826 (@value{GDBP}) @b{tfind line 444}
9827 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
9829 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
9831 (@value{GDBP}) @b{tdump}
9832 Data collected at tracepoint 2, trace frame 1:
9833 d0 0xc4aa0085 -995491707
9837 d4 0x71aea3d 119204413
9842 a1 0x3000668 50333288
9845 a4 0x3000698 50333336
9847 fp 0x30bf3c 0x30bf3c
9848 sp 0x30bf34 0x30bf34
9850 pc 0x20b2c8 0x20b2c8
9854 p = 0x20e5b4 "gdb-test"
9861 gdb_long_test = 17 '\021'
9866 @node save-tracepoints
9867 @subsection @code{save-tracepoints @var{filename}}
9868 @kindex save-tracepoints
9869 @cindex save tracepoints for future sessions
9871 This command saves all current tracepoint definitions together with
9872 their actions and passcounts, into a file @file{@var{filename}}
9873 suitable for use in a later debugging session. To read the saved
9874 tracepoint definitions, use the @code{source} command (@pxref{Command
9877 @node Tracepoint Variables
9878 @section Convenience Variables for Tracepoints
9879 @cindex tracepoint variables
9880 @cindex convenience variables for tracepoints
9883 @vindex $trace_frame
9884 @item (int) $trace_frame
9885 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
9886 snapshot is selected.
9889 @item (int) $tracepoint
9890 The tracepoint for the current trace snapshot.
9893 @item (int) $trace_line
9894 The line number for the current trace snapshot.
9897 @item (char []) $trace_file
9898 The source file for the current trace snapshot.
9901 @item (char []) $trace_func
9902 The name of the function containing @code{$tracepoint}.
9905 Note: @code{$trace_file} is not suitable for use in @code{printf},
9906 use @code{output} instead.
9908 Here's a simple example of using these convenience variables for
9909 stepping through all the trace snapshots and printing some of their
9913 (@value{GDBP}) @b{tfind start}
9915 (@value{GDBP}) @b{while $trace_frame != -1}
9916 > output $trace_file
9917 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
9923 @chapter Debugging Programs That Use Overlays
9926 If your program is too large to fit completely in your target system's
9927 memory, you can sometimes use @dfn{overlays} to work around this
9928 problem. @value{GDBN} provides some support for debugging programs that
9932 * How Overlays Work:: A general explanation of overlays.
9933 * Overlay Commands:: Managing overlays in @value{GDBN}.
9934 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
9935 mapped by asking the inferior.
9936 * Overlay Sample Program:: A sample program using overlays.
9939 @node How Overlays Work
9940 @section How Overlays Work
9941 @cindex mapped overlays
9942 @cindex unmapped overlays
9943 @cindex load address, overlay's
9944 @cindex mapped address
9945 @cindex overlay area
9947 Suppose you have a computer whose instruction address space is only 64
9948 kilobytes long, but which has much more memory which can be accessed by
9949 other means: special instructions, segment registers, or memory
9950 management hardware, for example. Suppose further that you want to
9951 adapt a program which is larger than 64 kilobytes to run on this system.
9953 One solution is to identify modules of your program which are relatively
9954 independent, and need not call each other directly; call these modules
9955 @dfn{overlays}. Separate the overlays from the main program, and place
9956 their machine code in the larger memory. Place your main program in
9957 instruction memory, but leave at least enough space there to hold the
9958 largest overlay as well.
9960 Now, to call a function located in an overlay, you must first copy that
9961 overlay's machine code from the large memory into the space set aside
9962 for it in the instruction memory, and then jump to its entry point
9965 @c NB: In the below the mapped area's size is greater or equal to the
9966 @c size of all overlays. This is intentional to remind the developer
9967 @c that overlays don't necessarily need to be the same size.
9971 Data Instruction Larger
9972 Address Space Address Space Address Space
9973 +-----------+ +-----------+ +-----------+
9975 +-----------+ +-----------+ +-----------+<-- overlay 1
9976 | program | | main | .----| overlay 1 | load address
9977 | variables | | program | | +-----------+
9978 | and heap | | | | | |
9979 +-----------+ | | | +-----------+<-- overlay 2
9980 | | +-----------+ | | | load address
9981 +-----------+ | | | .-| overlay 2 |
9983 mapped --->+-----------+ | | +-----------+
9985 | overlay | <-' | | |
9986 | area | <---' +-----------+<-- overlay 3
9987 | | <---. | | load address
9988 +-----------+ `--| overlay 3 |
9995 @anchor{A code overlay}A code overlay
9999 The diagram (@pxref{A code overlay}) shows a system with separate data
10000 and instruction address spaces. To map an overlay, the program copies
10001 its code from the larger address space to the instruction address space.
10002 Since the overlays shown here all use the same mapped address, only one
10003 may be mapped at a time. For a system with a single address space for
10004 data and instructions, the diagram would be similar, except that the
10005 program variables and heap would share an address space with the main
10006 program and the overlay area.
10008 An overlay loaded into instruction memory and ready for use is called a
10009 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
10010 instruction memory. An overlay not present (or only partially present)
10011 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
10012 is its address in the larger memory. The mapped address is also called
10013 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
10014 called the @dfn{load memory address}, or @dfn{LMA}.
10016 Unfortunately, overlays are not a completely transparent way to adapt a
10017 program to limited instruction memory. They introduce a new set of
10018 global constraints you must keep in mind as you design your program:
10023 Before calling or returning to a function in an overlay, your program
10024 must make sure that overlay is actually mapped. Otherwise, the call or
10025 return will transfer control to the right address, but in the wrong
10026 overlay, and your program will probably crash.
10029 If the process of mapping an overlay is expensive on your system, you
10030 will need to choose your overlays carefully to minimize their effect on
10031 your program's performance.
10034 The executable file you load onto your system must contain each
10035 overlay's instructions, appearing at the overlay's load address, not its
10036 mapped address. However, each overlay's instructions must be relocated
10037 and its symbols defined as if the overlay were at its mapped address.
10038 You can use GNU linker scripts to specify different load and relocation
10039 addresses for pieces of your program; see @ref{Overlay Description,,,
10040 ld.info, Using ld: the GNU linker}.
10043 The procedure for loading executable files onto your system must be able
10044 to load their contents into the larger address space as well as the
10045 instruction and data spaces.
10049 The overlay system described above is rather simple, and could be
10050 improved in many ways:
10055 If your system has suitable bank switch registers or memory management
10056 hardware, you could use those facilities to make an overlay's load area
10057 contents simply appear at their mapped address in instruction space.
10058 This would probably be faster than copying the overlay to its mapped
10059 area in the usual way.
10062 If your overlays are small enough, you could set aside more than one
10063 overlay area, and have more than one overlay mapped at a time.
10066 You can use overlays to manage data, as well as instructions. In
10067 general, data overlays are even less transparent to your design than
10068 code overlays: whereas code overlays only require care when you call or
10069 return to functions, data overlays require care every time you access
10070 the data. Also, if you change the contents of a data overlay, you
10071 must copy its contents back out to its load address before you can copy a
10072 different data overlay into the same mapped area.
10077 @node Overlay Commands
10078 @section Overlay Commands
10080 To use @value{GDBN}'s overlay support, each overlay in your program must
10081 correspond to a separate section of the executable file. The section's
10082 virtual memory address and load memory address must be the overlay's
10083 mapped and load addresses. Identifying overlays with sections allows
10084 @value{GDBN} to determine the appropriate address of a function or
10085 variable, depending on whether the overlay is mapped or not.
10087 @value{GDBN}'s overlay commands all start with the word @code{overlay};
10088 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
10093 Disable @value{GDBN}'s overlay support. When overlay support is
10094 disabled, @value{GDBN} assumes that all functions and variables are
10095 always present at their mapped addresses. By default, @value{GDBN}'s
10096 overlay support is disabled.
10098 @item overlay manual
10099 @cindex manual overlay debugging
10100 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
10101 relies on you to tell it which overlays are mapped, and which are not,
10102 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
10103 commands described below.
10105 @item overlay map-overlay @var{overlay}
10106 @itemx overlay map @var{overlay}
10107 @cindex map an overlay
10108 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
10109 be the name of the object file section containing the overlay. When an
10110 overlay is mapped, @value{GDBN} assumes it can find the overlay's
10111 functions and variables at their mapped addresses. @value{GDBN} assumes
10112 that any other overlays whose mapped ranges overlap that of
10113 @var{overlay} are now unmapped.
10115 @item overlay unmap-overlay @var{overlay}
10116 @itemx overlay unmap @var{overlay}
10117 @cindex unmap an overlay
10118 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
10119 must be the name of the object file section containing the overlay.
10120 When an overlay is unmapped, @value{GDBN} assumes it can find the
10121 overlay's functions and variables at their load addresses.
10124 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
10125 consults a data structure the overlay manager maintains in the inferior
10126 to see which overlays are mapped. For details, see @ref{Automatic
10127 Overlay Debugging}.
10129 @item overlay load-target
10130 @itemx overlay load
10131 @cindex reloading the overlay table
10132 Re-read the overlay table from the inferior. Normally, @value{GDBN}
10133 re-reads the table @value{GDBN} automatically each time the inferior
10134 stops, so this command should only be necessary if you have changed the
10135 overlay mapping yourself using @value{GDBN}. This command is only
10136 useful when using automatic overlay debugging.
10138 @item overlay list-overlays
10139 @itemx overlay list
10140 @cindex listing mapped overlays
10141 Display a list of the overlays currently mapped, along with their mapped
10142 addresses, load addresses, and sizes.
10146 Normally, when @value{GDBN} prints a code address, it includes the name
10147 of the function the address falls in:
10150 (@value{GDBP}) print main
10151 $3 = @{int ()@} 0x11a0 <main>
10154 When overlay debugging is enabled, @value{GDBN} recognizes code in
10155 unmapped overlays, and prints the names of unmapped functions with
10156 asterisks around them. For example, if @code{foo} is a function in an
10157 unmapped overlay, @value{GDBN} prints it this way:
10160 (@value{GDBP}) overlay list
10161 No sections are mapped.
10162 (@value{GDBP}) print foo
10163 $5 = @{int (int)@} 0x100000 <*foo*>
10166 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
10170 (@value{GDBP}) overlay list
10171 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
10172 mapped at 0x1016 - 0x104a
10173 (@value{GDBP}) print foo
10174 $6 = @{int (int)@} 0x1016 <foo>
10177 When overlay debugging is enabled, @value{GDBN} can find the correct
10178 address for functions and variables in an overlay, whether or not the
10179 overlay is mapped. This allows most @value{GDBN} commands, like
10180 @code{break} and @code{disassemble}, to work normally, even on unmapped
10181 code. However, @value{GDBN}'s breakpoint support has some limitations:
10185 @cindex breakpoints in overlays
10186 @cindex overlays, setting breakpoints in
10187 You can set breakpoints in functions in unmapped overlays, as long as
10188 @value{GDBN} can write to the overlay at its load address.
10190 @value{GDBN} can not set hardware or simulator-based breakpoints in
10191 unmapped overlays. However, if you set a breakpoint at the end of your
10192 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
10193 you are using manual overlay management), @value{GDBN} will re-set its
10194 breakpoints properly.
10198 @node Automatic Overlay Debugging
10199 @section Automatic Overlay Debugging
10200 @cindex automatic overlay debugging
10202 @value{GDBN} can automatically track which overlays are mapped and which
10203 are not, given some simple co-operation from the overlay manager in the
10204 inferior. If you enable automatic overlay debugging with the
10205 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
10206 looks in the inferior's memory for certain variables describing the
10207 current state of the overlays.
10209 Here are the variables your overlay manager must define to support
10210 @value{GDBN}'s automatic overlay debugging:
10214 @item @code{_ovly_table}:
10215 This variable must be an array of the following structures:
10220 /* The overlay's mapped address. */
10223 /* The size of the overlay, in bytes. */
10224 unsigned long size;
10226 /* The overlay's load address. */
10229 /* Non-zero if the overlay is currently mapped;
10231 unsigned long mapped;
10235 @item @code{_novlys}:
10236 This variable must be a four-byte signed integer, holding the total
10237 number of elements in @code{_ovly_table}.
10241 To decide whether a particular overlay is mapped or not, @value{GDBN}
10242 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
10243 @code{lma} members equal the VMA and LMA of the overlay's section in the
10244 executable file. When @value{GDBN} finds a matching entry, it consults
10245 the entry's @code{mapped} member to determine whether the overlay is
10248 In addition, your overlay manager may define a function called
10249 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
10250 will silently set a breakpoint there. If the overlay manager then
10251 calls this function whenever it has changed the overlay table, this
10252 will enable @value{GDBN} to accurately keep track of which overlays
10253 are in program memory, and update any breakpoints that may be set
10254 in overlays. This will allow breakpoints to work even if the
10255 overlays are kept in ROM or other non-writable memory while they
10256 are not being executed.
10258 @node Overlay Sample Program
10259 @section Overlay Sample Program
10260 @cindex overlay example program
10262 When linking a program which uses overlays, you must place the overlays
10263 at their load addresses, while relocating them to run at their mapped
10264 addresses. To do this, you must write a linker script (@pxref{Overlay
10265 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
10266 since linker scripts are specific to a particular host system, target
10267 architecture, and target memory layout, this manual cannot provide
10268 portable sample code demonstrating @value{GDBN}'s overlay support.
10270 However, the @value{GDBN} source distribution does contain an overlaid
10271 program, with linker scripts for a few systems, as part of its test
10272 suite. The program consists of the following files from
10273 @file{gdb/testsuite/gdb.base}:
10277 The main program file.
10279 A simple overlay manager, used by @file{overlays.c}.
10284 Overlay modules, loaded and used by @file{overlays.c}.
10287 Linker scripts for linking the test program on the @code{d10v-elf}
10288 and @code{m32r-elf} targets.
10291 You can build the test program using the @code{d10v-elf} GCC
10292 cross-compiler like this:
10295 $ d10v-elf-gcc -g -c overlays.c
10296 $ d10v-elf-gcc -g -c ovlymgr.c
10297 $ d10v-elf-gcc -g -c foo.c
10298 $ d10v-elf-gcc -g -c bar.c
10299 $ d10v-elf-gcc -g -c baz.c
10300 $ d10v-elf-gcc -g -c grbx.c
10301 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
10302 baz.o grbx.o -Wl,-Td10v.ld -o overlays
10305 The build process is identical for any other architecture, except that
10306 you must substitute the appropriate compiler and linker script for the
10307 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
10311 @chapter Using @value{GDBN} with Different Languages
10314 Although programming languages generally have common aspects, they are
10315 rarely expressed in the same manner. For instance, in ANSI C,
10316 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
10317 Modula-2, it is accomplished by @code{p^}. Values can also be
10318 represented (and displayed) differently. Hex numbers in C appear as
10319 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
10321 @cindex working language
10322 Language-specific information is built into @value{GDBN} for some languages,
10323 allowing you to express operations like the above in your program's
10324 native language, and allowing @value{GDBN} to output values in a manner
10325 consistent with the syntax of your program's native language. The
10326 language you use to build expressions is called the @dfn{working
10330 * Setting:: Switching between source languages
10331 * Show:: Displaying the language
10332 * Checks:: Type and range checks
10333 * Supported Languages:: Supported languages
10334 * Unsupported Languages:: Unsupported languages
10338 @section Switching Between Source Languages
10340 There are two ways to control the working language---either have @value{GDBN}
10341 set it automatically, or select it manually yourself. You can use the
10342 @code{set language} command for either purpose. On startup, @value{GDBN}
10343 defaults to setting the language automatically. The working language is
10344 used to determine how expressions you type are interpreted, how values
10347 In addition to the working language, every source file that
10348 @value{GDBN} knows about has its own working language. For some object
10349 file formats, the compiler might indicate which language a particular
10350 source file is in. However, most of the time @value{GDBN} infers the
10351 language from the name of the file. The language of a source file
10352 controls whether C@t{++} names are demangled---this way @code{backtrace} can
10353 show each frame appropriately for its own language. There is no way to
10354 set the language of a source file from within @value{GDBN}, but you can
10355 set the language associated with a filename extension. @xref{Show, ,
10356 Displaying the Language}.
10358 This is most commonly a problem when you use a program, such
10359 as @code{cfront} or @code{f2c}, that generates C but is written in
10360 another language. In that case, make the
10361 program use @code{#line} directives in its C output; that way
10362 @value{GDBN} will know the correct language of the source code of the original
10363 program, and will display that source code, not the generated C code.
10366 * Filenames:: Filename extensions and languages.
10367 * Manually:: Setting the working language manually
10368 * Automatically:: Having @value{GDBN} infer the source language
10372 @subsection List of Filename Extensions and Languages
10374 If a source file name ends in one of the following extensions, then
10375 @value{GDBN} infers that its language is the one indicated.
10393 C@t{++} source file
10396 Objective-C source file
10400 Fortran source file
10403 Modula-2 source file
10407 Assembler source file. This actually behaves almost like C, but
10408 @value{GDBN} does not skip over function prologues when stepping.
10411 In addition, you may set the language associated with a filename
10412 extension. @xref{Show, , Displaying the Language}.
10415 @subsection Setting the Working Language
10417 If you allow @value{GDBN} to set the language automatically,
10418 expressions are interpreted the same way in your debugging session and
10421 @kindex set language
10422 If you wish, you may set the language manually. To do this, issue the
10423 command @samp{set language @var{lang}}, where @var{lang} is the name of
10424 a language, such as
10425 @code{c} or @code{modula-2}.
10426 For a list of the supported languages, type @samp{set language}.
10428 Setting the language manually prevents @value{GDBN} from updating the working
10429 language automatically. This can lead to confusion if you try
10430 to debug a program when the working language is not the same as the
10431 source language, when an expression is acceptable to both
10432 languages---but means different things. For instance, if the current
10433 source file were written in C, and @value{GDBN} was parsing Modula-2, a
10441 might not have the effect you intended. In C, this means to add
10442 @code{b} and @code{c} and place the result in @code{a}. The result
10443 printed would be the value of @code{a}. In Modula-2, this means to compare
10444 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
10446 @node Automatically
10447 @subsection Having @value{GDBN} Infer the Source Language
10449 To have @value{GDBN} set the working language automatically, use
10450 @samp{set language local} or @samp{set language auto}. @value{GDBN}
10451 then infers the working language. That is, when your program stops in a
10452 frame (usually by encountering a breakpoint), @value{GDBN} sets the
10453 working language to the language recorded for the function in that
10454 frame. If the language for a frame is unknown (that is, if the function
10455 or block corresponding to the frame was defined in a source file that
10456 does not have a recognized extension), the current working language is
10457 not changed, and @value{GDBN} issues a warning.
10459 This may not seem necessary for most programs, which are written
10460 entirely in one source language. However, program modules and libraries
10461 written in one source language can be used by a main program written in
10462 a different source language. Using @samp{set language auto} in this
10463 case frees you from having to set the working language manually.
10466 @section Displaying the Language
10468 The following commands help you find out which language is the
10469 working language, and also what language source files were written in.
10472 @item show language
10473 @kindex show language
10474 Display the current working language. This is the
10475 language you can use with commands such as @code{print} to
10476 build and compute expressions that may involve variables in your program.
10479 @kindex info frame@r{, show the source language}
10480 Display the source language for this frame. This language becomes the
10481 working language if you use an identifier from this frame.
10482 @xref{Frame Info, ,Information about a Frame}, to identify the other
10483 information listed here.
10486 @kindex info source@r{, show the source language}
10487 Display the source language of this source file.
10488 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
10489 information listed here.
10492 In unusual circumstances, you may have source files with extensions
10493 not in the standard list. You can then set the extension associated
10494 with a language explicitly:
10497 @item set extension-language @var{ext} @var{language}
10498 @kindex set extension-language
10499 Tell @value{GDBN} that source files with extension @var{ext} are to be
10500 assumed as written in the source language @var{language}.
10502 @item info extensions
10503 @kindex info extensions
10504 List all the filename extensions and the associated languages.
10508 @section Type and Range Checking
10511 @emph{Warning:} In this release, the @value{GDBN} commands for type and range
10512 checking are included, but they do not yet have any effect. This
10513 section documents the intended facilities.
10515 @c FIXME remove warning when type/range code added
10517 Some languages are designed to guard you against making seemingly common
10518 errors through a series of compile- and run-time checks. These include
10519 checking the type of arguments to functions and operators, and making
10520 sure mathematical overflows are caught at run time. Checks such as
10521 these help to ensure a program's correctness once it has been compiled
10522 by eliminating type mismatches, and providing active checks for range
10523 errors when your program is running.
10525 @value{GDBN} can check for conditions like the above if you wish.
10526 Although @value{GDBN} does not check the statements in your program,
10527 it can check expressions entered directly into @value{GDBN} for
10528 evaluation via the @code{print} command, for example. As with the
10529 working language, @value{GDBN} can also decide whether or not to check
10530 automatically based on your program's source language.
10531 @xref{Supported Languages, ,Supported Languages}, for the default
10532 settings of supported languages.
10535 * Type Checking:: An overview of type checking
10536 * Range Checking:: An overview of range checking
10539 @cindex type checking
10540 @cindex checks, type
10541 @node Type Checking
10542 @subsection An Overview of Type Checking
10544 Some languages, such as Modula-2, are strongly typed, meaning that the
10545 arguments to operators and functions have to be of the correct type,
10546 otherwise an error occurs. These checks prevent type mismatch
10547 errors from ever causing any run-time problems. For example,
10555 The second example fails because the @code{CARDINAL} 1 is not
10556 type-compatible with the @code{REAL} 2.3.
10558 For the expressions you use in @value{GDBN} commands, you can tell the
10559 @value{GDBN} type checker to skip checking;
10560 to treat any mismatches as errors and abandon the expression;
10561 or to only issue warnings when type mismatches occur,
10562 but evaluate the expression anyway. When you choose the last of
10563 these, @value{GDBN} evaluates expressions like the second example above, but
10564 also issues a warning.
10566 Even if you turn type checking off, there may be other reasons
10567 related to type that prevent @value{GDBN} from evaluating an expression.
10568 For instance, @value{GDBN} does not know how to add an @code{int} and
10569 a @code{struct foo}. These particular type errors have nothing to do
10570 with the language in use, and usually arise from expressions, such as
10571 the one described above, which make little sense to evaluate anyway.
10573 Each language defines to what degree it is strict about type. For
10574 instance, both Modula-2 and C require the arguments to arithmetical
10575 operators to be numbers. In C, enumerated types and pointers can be
10576 represented as numbers, so that they are valid arguments to mathematical
10577 operators. @xref{Supported Languages, ,Supported Languages}, for further
10578 details on specific languages.
10580 @value{GDBN} provides some additional commands for controlling the type checker:
10582 @kindex set check type
10583 @kindex show check type
10585 @item set check type auto
10586 Set type checking on or off based on the current working language.
10587 @xref{Supported Languages, ,Supported Languages}, for the default settings for
10590 @item set check type on
10591 @itemx set check type off
10592 Set type checking on or off, overriding the default setting for the
10593 current working language. Issue a warning if the setting does not
10594 match the language default. If any type mismatches occur in
10595 evaluating an expression while type checking is on, @value{GDBN} prints a
10596 message and aborts evaluation of the expression.
10598 @item set check type warn
10599 Cause the type checker to issue warnings, but to always attempt to
10600 evaluate the expression. Evaluating the expression may still
10601 be impossible for other reasons. For example, @value{GDBN} cannot add
10602 numbers and structures.
10605 Show the current setting of the type checker, and whether or not @value{GDBN}
10606 is setting it automatically.
10609 @cindex range checking
10610 @cindex checks, range
10611 @node Range Checking
10612 @subsection An Overview of Range Checking
10614 In some languages (such as Modula-2), it is an error to exceed the
10615 bounds of a type; this is enforced with run-time checks. Such range
10616 checking is meant to ensure program correctness by making sure
10617 computations do not overflow, or indices on an array element access do
10618 not exceed the bounds of the array.
10620 For expressions you use in @value{GDBN} commands, you can tell
10621 @value{GDBN} to treat range errors in one of three ways: ignore them,
10622 always treat them as errors and abandon the expression, or issue
10623 warnings but evaluate the expression anyway.
10625 A range error can result from numerical overflow, from exceeding an
10626 array index bound, or when you type a constant that is not a member
10627 of any type. Some languages, however, do not treat overflows as an
10628 error. In many implementations of C, mathematical overflow causes the
10629 result to ``wrap around'' to lower values---for example, if @var{m} is
10630 the largest integer value, and @var{s} is the smallest, then
10633 @var{m} + 1 @result{} @var{s}
10636 This, too, is specific to individual languages, and in some cases
10637 specific to individual compilers or machines. @xref{Supported Languages, ,
10638 Supported Languages}, for further details on specific languages.
10640 @value{GDBN} provides some additional commands for controlling the range checker:
10642 @kindex set check range
10643 @kindex show check range
10645 @item set check range auto
10646 Set range checking on or off based on the current working language.
10647 @xref{Supported Languages, ,Supported Languages}, for the default settings for
10650 @item set check range on
10651 @itemx set check range off
10652 Set range checking on or off, overriding the default setting for the
10653 current working language. A warning is issued if the setting does not
10654 match the language default. If a range error occurs and range checking is on,
10655 then a message is printed and evaluation of the expression is aborted.
10657 @item set check range warn
10658 Output messages when the @value{GDBN} range checker detects a range error,
10659 but attempt to evaluate the expression anyway. Evaluating the
10660 expression may still be impossible for other reasons, such as accessing
10661 memory that the process does not own (a typical example from many Unix
10665 Show the current setting of the range checker, and whether or not it is
10666 being set automatically by @value{GDBN}.
10669 @node Supported Languages
10670 @section Supported Languages
10672 @value{GDBN} supports C, C@t{++}, Objective-C, Fortran, Java, Pascal,
10673 assembly, Modula-2, and Ada.
10674 @c This is false ...
10675 Some @value{GDBN} features may be used in expressions regardless of the
10676 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
10677 and the @samp{@{type@}addr} construct (@pxref{Expressions,
10678 ,Expressions}) can be used with the constructs of any supported
10681 The following sections detail to what degree each source language is
10682 supported by @value{GDBN}. These sections are not meant to be language
10683 tutorials or references, but serve only as a reference guide to what the
10684 @value{GDBN} expression parser accepts, and what input and output
10685 formats should look like for different languages. There are many good
10686 books written on each of these languages; please look to these for a
10687 language reference or tutorial.
10690 * C:: C and C@t{++}
10691 * Objective-C:: Objective-C
10692 * Fortran:: Fortran
10694 * Modula-2:: Modula-2
10699 @subsection C and C@t{++}
10701 @cindex C and C@t{++}
10702 @cindex expressions in C or C@t{++}
10704 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
10705 to both languages. Whenever this is the case, we discuss those languages
10709 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
10710 @cindex @sc{gnu} C@t{++}
10711 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
10712 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
10713 effectively, you must compile your C@t{++} programs with a supported
10714 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
10715 compiler (@code{aCC}).
10717 For best results when using @sc{gnu} C@t{++}, use the DWARF 2 debugging
10718 format; if it doesn't work on your system, try the stabs+ debugging
10719 format. You can select those formats explicitly with the @code{g++}
10720 command-line options @option{-gdwarf-2} and @option{-gstabs+}.
10721 @xref{Debugging Options,,Options for Debugging Your Program or GCC,
10722 gcc.info, Using the @sc{gnu} Compiler Collection (GCC)}.
10725 * C Operators:: C and C@t{++} operators
10726 * C Constants:: C and C@t{++} constants
10727 * C Plus Plus Expressions:: C@t{++} expressions
10728 * C Defaults:: Default settings for C and C@t{++}
10729 * C Checks:: C and C@t{++} type and range checks
10730 * Debugging C:: @value{GDBN} and C
10731 * Debugging C Plus Plus:: @value{GDBN} features for C@t{++}
10732 * Decimal Floating Point:: Numbers in Decimal Floating Point format
10736 @subsubsection C and C@t{++} Operators
10738 @cindex C and C@t{++} operators
10740 Operators must be defined on values of specific types. For instance,
10741 @code{+} is defined on numbers, but not on structures. Operators are
10742 often defined on groups of types.
10744 For the purposes of C and C@t{++}, the following definitions hold:
10749 @emph{Integral types} include @code{int} with any of its storage-class
10750 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
10753 @emph{Floating-point types} include @code{float}, @code{double}, and
10754 @code{long double} (if supported by the target platform).
10757 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
10760 @emph{Scalar types} include all of the above.
10765 The following operators are supported. They are listed here
10766 in order of increasing precedence:
10770 The comma or sequencing operator. Expressions in a comma-separated list
10771 are evaluated from left to right, with the result of the entire
10772 expression being the last expression evaluated.
10775 Assignment. The value of an assignment expression is the value
10776 assigned. Defined on scalar types.
10779 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
10780 and translated to @w{@code{@var{a} = @var{a op b}}}.
10781 @w{@code{@var{op}=}} and @code{=} have the same precedence.
10782 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
10783 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
10786 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
10787 of as: if @var{a} then @var{b} else @var{c}. @var{a} should be of an
10791 Logical @sc{or}. Defined on integral types.
10794 Logical @sc{and}. Defined on integral types.
10797 Bitwise @sc{or}. Defined on integral types.
10800 Bitwise exclusive-@sc{or}. Defined on integral types.
10803 Bitwise @sc{and}. Defined on integral types.
10806 Equality and inequality. Defined on scalar types. The value of these
10807 expressions is 0 for false and non-zero for true.
10809 @item <@r{, }>@r{, }<=@r{, }>=
10810 Less than, greater than, less than or equal, greater than or equal.
10811 Defined on scalar types. The value of these expressions is 0 for false
10812 and non-zero for true.
10815 left shift, and right shift. Defined on integral types.
10818 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
10821 Addition and subtraction. Defined on integral types, floating-point types and
10824 @item *@r{, }/@r{, }%
10825 Multiplication, division, and modulus. Multiplication and division are
10826 defined on integral and floating-point types. Modulus is defined on
10830 Increment and decrement. When appearing before a variable, the
10831 operation is performed before the variable is used in an expression;
10832 when appearing after it, the variable's value is used before the
10833 operation takes place.
10836 Pointer dereferencing. Defined on pointer types. Same precedence as
10840 Address operator. Defined on variables. Same precedence as @code{++}.
10842 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
10843 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
10844 to examine the address
10845 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
10849 Negative. Defined on integral and floating-point types. Same
10850 precedence as @code{++}.
10853 Logical negation. Defined on integral types. Same precedence as
10857 Bitwise complement operator. Defined on integral types. Same precedence as
10862 Structure member, and pointer-to-structure member. For convenience,
10863 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
10864 pointer based on the stored type information.
10865 Defined on @code{struct} and @code{union} data.
10868 Dereferences of pointers to members.
10871 Array indexing. @code{@var{a}[@var{i}]} is defined as
10872 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
10875 Function parameter list. Same precedence as @code{->}.
10878 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
10879 and @code{class} types.
10882 Doubled colons also represent the @value{GDBN} scope operator
10883 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
10887 If an operator is redefined in the user code, @value{GDBN} usually
10888 attempts to invoke the redefined version instead of using the operator's
10889 predefined meaning.
10892 @subsubsection C and C@t{++} Constants
10894 @cindex C and C@t{++} constants
10896 @value{GDBN} allows you to express the constants of C and C@t{++} in the
10901 Integer constants are a sequence of digits. Octal constants are
10902 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
10903 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
10904 @samp{l}, specifying that the constant should be treated as a
10908 Floating point constants are a sequence of digits, followed by a decimal
10909 point, followed by a sequence of digits, and optionally followed by an
10910 exponent. An exponent is of the form:
10911 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
10912 sequence of digits. The @samp{+} is optional for positive exponents.
10913 A floating-point constant may also end with a letter @samp{f} or
10914 @samp{F}, specifying that the constant should be treated as being of
10915 the @code{float} (as opposed to the default @code{double}) type; or with
10916 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
10920 Enumerated constants consist of enumerated identifiers, or their
10921 integral equivalents.
10924 Character constants are a single character surrounded by single quotes
10925 (@code{'}), or a number---the ordinal value of the corresponding character
10926 (usually its @sc{ascii} value). Within quotes, the single character may
10927 be represented by a letter or by @dfn{escape sequences}, which are of
10928 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
10929 of the character's ordinal value; or of the form @samp{\@var{x}}, where
10930 @samp{@var{x}} is a predefined special character---for example,
10931 @samp{\n} for newline.
10934 String constants are a sequence of character constants surrounded by
10935 double quotes (@code{"}). Any valid character constant (as described
10936 above) may appear. Double quotes within the string must be preceded by
10937 a backslash, so for instance @samp{"a\"b'c"} is a string of five
10941 Pointer constants are an integral value. You can also write pointers
10942 to constants using the C operator @samp{&}.
10945 Array constants are comma-separated lists surrounded by braces @samp{@{}
10946 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
10947 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
10948 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
10951 @node C Plus Plus Expressions
10952 @subsubsection C@t{++} Expressions
10954 @cindex expressions in C@t{++}
10955 @value{GDBN} expression handling can interpret most C@t{++} expressions.
10957 @cindex debugging C@t{++} programs
10958 @cindex C@t{++} compilers
10959 @cindex debug formats and C@t{++}
10960 @cindex @value{NGCC} and C@t{++}
10962 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use the
10963 proper compiler and the proper debug format. Currently, @value{GDBN}
10964 works best when debugging C@t{++} code that is compiled with
10965 @value{NGCC} 2.95.3 or with @value{NGCC} 3.1 or newer, using the options
10966 @option{-gdwarf-2} or @option{-gstabs+}. DWARF 2 is preferred over
10967 stabs+. Most configurations of @value{NGCC} emit either DWARF 2 or
10968 stabs+ as their default debug format, so you usually don't need to
10969 specify a debug format explicitly. Other compilers and/or debug formats
10970 are likely to work badly or not at all when using @value{GDBN} to debug
10976 @cindex member functions
10978 Member function calls are allowed; you can use expressions like
10981 count = aml->GetOriginal(x, y)
10984 @vindex this@r{, inside C@t{++} member functions}
10985 @cindex namespace in C@t{++}
10987 While a member function is active (in the selected stack frame), your
10988 expressions have the same namespace available as the member function;
10989 that is, @value{GDBN} allows implicit references to the class instance
10990 pointer @code{this} following the same rules as C@t{++}.
10992 @cindex call overloaded functions
10993 @cindex overloaded functions, calling
10994 @cindex type conversions in C@t{++}
10996 You can call overloaded functions; @value{GDBN} resolves the function
10997 call to the right definition, with some restrictions. @value{GDBN} does not
10998 perform overload resolution involving user-defined type conversions,
10999 calls to constructors, or instantiations of templates that do not exist
11000 in the program. It also cannot handle ellipsis argument lists or
11003 It does perform integral conversions and promotions, floating-point
11004 promotions, arithmetic conversions, pointer conversions, conversions of
11005 class objects to base classes, and standard conversions such as those of
11006 functions or arrays to pointers; it requires an exact match on the
11007 number of function arguments.
11009 Overload resolution is always performed, unless you have specified
11010 @code{set overload-resolution off}. @xref{Debugging C Plus Plus,
11011 ,@value{GDBN} Features for C@t{++}}.
11013 You must specify @code{set overload-resolution off} in order to use an
11014 explicit function signature to call an overloaded function, as in
11016 p 'foo(char,int)'('x', 13)
11019 The @value{GDBN} command-completion facility can simplify this;
11020 see @ref{Completion, ,Command Completion}.
11022 @cindex reference declarations
11024 @value{GDBN} understands variables declared as C@t{++} references; you can use
11025 them in expressions just as you do in C@t{++} source---they are automatically
11028 In the parameter list shown when @value{GDBN} displays a frame, the values of
11029 reference variables are not displayed (unlike other variables); this
11030 avoids clutter, since references are often used for large structures.
11031 The @emph{address} of a reference variable is always shown, unless
11032 you have specified @samp{set print address off}.
11035 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
11036 expressions can use it just as expressions in your program do. Since
11037 one scope may be defined in another, you can use @code{::} repeatedly if
11038 necessary, for example in an expression like
11039 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
11040 resolving name scope by reference to source files, in both C and C@t{++}
11041 debugging (@pxref{Variables, ,Program Variables}).
11044 In addition, when used with HP's C@t{++} compiler, @value{GDBN} supports
11045 calling virtual functions correctly, printing out virtual bases of
11046 objects, calling functions in a base subobject, casting objects, and
11047 invoking user-defined operators.
11050 @subsubsection C and C@t{++} Defaults
11052 @cindex C and C@t{++} defaults
11054 If you allow @value{GDBN} to set type and range checking automatically, they
11055 both default to @code{off} whenever the working language changes to
11056 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
11057 selects the working language.
11059 If you allow @value{GDBN} to set the language automatically, it
11060 recognizes source files whose names end with @file{.c}, @file{.C}, or
11061 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
11062 these files, it sets the working language to C or C@t{++}.
11063 @xref{Automatically, ,Having @value{GDBN} Infer the Source Language},
11064 for further details.
11066 @c Type checking is (a) primarily motivated by Modula-2, and (b)
11067 @c unimplemented. If (b) changes, it might make sense to let this node
11068 @c appear even if Mod-2 does not, but meanwhile ignore it. roland 16jul93.
11071 @subsubsection C and C@t{++} Type and Range Checks
11073 @cindex C and C@t{++} checks
11075 By default, when @value{GDBN} parses C or C@t{++} expressions, type checking
11076 is not used. However, if you turn type checking on, @value{GDBN}
11077 considers two variables type equivalent if:
11081 The two variables are structured and have the same structure, union, or
11085 The two variables have the same type name, or types that have been
11086 declared equivalent through @code{typedef}.
11089 @c leaving this out because neither J Gilmore nor R Pesch understand it.
11092 The two @code{struct}, @code{union}, or @code{enum} variables are
11093 declared in the same declaration. (Note: this may not be true for all C
11098 Range checking, if turned on, is done on mathematical operations. Array
11099 indices are not checked, since they are often used to index a pointer
11100 that is not itself an array.
11103 @subsubsection @value{GDBN} and C
11105 The @code{set print union} and @code{show print union} commands apply to
11106 the @code{union} type. When set to @samp{on}, any @code{union} that is
11107 inside a @code{struct} or @code{class} is also printed. Otherwise, it
11108 appears as @samp{@{...@}}.
11110 The @code{@@} operator aids in the debugging of dynamic arrays, formed
11111 with pointers and a memory allocation function. @xref{Expressions,
11114 @node Debugging C Plus Plus
11115 @subsubsection @value{GDBN} Features for C@t{++}
11117 @cindex commands for C@t{++}
11119 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
11120 designed specifically for use with C@t{++}. Here is a summary:
11123 @cindex break in overloaded functions
11124 @item @r{breakpoint menus}
11125 When you want a breakpoint in a function whose name is overloaded,
11126 @value{GDBN} has the capability to display a menu of possible breakpoint
11127 locations to help you specify which function definition you want.
11128 @xref{Ambiguous Expressions,,Ambiguous Expressions}.
11130 @cindex overloading in C@t{++}
11131 @item rbreak @var{regex}
11132 Setting breakpoints using regular expressions is helpful for setting
11133 breakpoints on overloaded functions that are not members of any special
11135 @xref{Set Breaks, ,Setting Breakpoints}.
11137 @cindex C@t{++} exception handling
11140 Debug C@t{++} exception handling using these commands. @xref{Set
11141 Catchpoints, , Setting Catchpoints}.
11143 @cindex inheritance
11144 @item ptype @var{typename}
11145 Print inheritance relationships as well as other information for type
11147 @xref{Symbols, ,Examining the Symbol Table}.
11149 @cindex C@t{++} symbol display
11150 @item set print demangle
11151 @itemx show print demangle
11152 @itemx set print asm-demangle
11153 @itemx show print asm-demangle
11154 Control whether C@t{++} symbols display in their source form, both when
11155 displaying code as C@t{++} source and when displaying disassemblies.
11156 @xref{Print Settings, ,Print Settings}.
11158 @item set print object
11159 @itemx show print object
11160 Choose whether to print derived (actual) or declared types of objects.
11161 @xref{Print Settings, ,Print Settings}.
11163 @item set print vtbl
11164 @itemx show print vtbl
11165 Control the format for printing virtual function tables.
11166 @xref{Print Settings, ,Print Settings}.
11167 (The @code{vtbl} commands do not work on programs compiled with the HP
11168 ANSI C@t{++} compiler (@code{aCC}).)
11170 @kindex set overload-resolution
11171 @cindex overloaded functions, overload resolution
11172 @item set overload-resolution on
11173 Enable overload resolution for C@t{++} expression evaluation. The default
11174 is on. For overloaded functions, @value{GDBN} evaluates the arguments
11175 and searches for a function whose signature matches the argument types,
11176 using the standard C@t{++} conversion rules (see @ref{C Plus Plus
11177 Expressions, ,C@t{++} Expressions}, for details).
11178 If it cannot find a match, it emits a message.
11180 @item set overload-resolution off
11181 Disable overload resolution for C@t{++} expression evaluation. For
11182 overloaded functions that are not class member functions, @value{GDBN}
11183 chooses the first function of the specified name that it finds in the
11184 symbol table, whether or not its arguments are of the correct type. For
11185 overloaded functions that are class member functions, @value{GDBN}
11186 searches for a function whose signature @emph{exactly} matches the
11189 @kindex show overload-resolution
11190 @item show overload-resolution
11191 Show the current setting of overload resolution.
11193 @item @r{Overloaded symbol names}
11194 You can specify a particular definition of an overloaded symbol, using
11195 the same notation that is used to declare such symbols in C@t{++}: type
11196 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
11197 also use the @value{GDBN} command-line word completion facilities to list the
11198 available choices, or to finish the type list for you.
11199 @xref{Completion,, Command Completion}, for details on how to do this.
11202 @node Decimal Floating Point
11203 @subsubsection Decimal Floating Point format
11204 @cindex decimal floating point format
11206 @value{GDBN} can examine, set and perform computations with numbers in
11207 decimal floating point format, which in the C language correspond to the
11208 @code{_Decimal32}, @code{_Decimal64} and @code{_Decimal128} types as
11209 specified by the extension to support decimal floating-point arithmetic.
11211 There are two encodings in use, depending on the architecture: BID (Binary
11212 Integer Decimal) for x86 and x86-64, and DPD (Densely Packed Decimal) for
11213 PowerPC. @value{GDBN} will use the appropriate encoding for the configured
11216 Because of a limitation in @file{libdecnumber}, the library used by @value{GDBN}
11217 to manipulate decimal floating point numbers, it is not possible to convert
11218 (using a cast, for example) integers wider than 32-bit to decimal float.
11220 In addition, in order to imitate @value{GDBN}'s behaviour with binary floating
11221 point computations, error checking in decimal float operations ignores
11222 underflow, overflow and divide by zero exceptions.
11224 In the PowerPC architecture, @value{GDBN} provides a set of pseudo-registers
11225 to inspect @code{_Decimal128} values stored in floating point registers.
11226 See @ref{PowerPC,,PowerPC} for more details.
11229 @subsection Objective-C
11231 @cindex Objective-C
11232 This section provides information about some commands and command
11233 options that are useful for debugging Objective-C code. See also
11234 @ref{Symbols, info classes}, and @ref{Symbols, info selectors}, for a
11235 few more commands specific to Objective-C support.
11238 * Method Names in Commands::
11239 * The Print Command with Objective-C::
11242 @node Method Names in Commands
11243 @subsubsection Method Names in Commands
11245 The following commands have been extended to accept Objective-C method
11246 names as line specifications:
11248 @kindex clear@r{, and Objective-C}
11249 @kindex break@r{, and Objective-C}
11250 @kindex info line@r{, and Objective-C}
11251 @kindex jump@r{, and Objective-C}
11252 @kindex list@r{, and Objective-C}
11256 @item @code{info line}
11261 A fully qualified Objective-C method name is specified as
11264 -[@var{Class} @var{methodName}]
11267 where the minus sign is used to indicate an instance method and a
11268 plus sign (not shown) is used to indicate a class method. The class
11269 name @var{Class} and method name @var{methodName} are enclosed in
11270 brackets, similar to the way messages are specified in Objective-C
11271 source code. For example, to set a breakpoint at the @code{create}
11272 instance method of class @code{Fruit} in the program currently being
11276 break -[Fruit create]
11279 To list ten program lines around the @code{initialize} class method,
11283 list +[NSText initialize]
11286 In the current version of @value{GDBN}, the plus or minus sign is
11287 required. In future versions of @value{GDBN}, the plus or minus
11288 sign will be optional, but you can use it to narrow the search. It
11289 is also possible to specify just a method name:
11295 You must specify the complete method name, including any colons. If
11296 your program's source files contain more than one @code{create} method,
11297 you'll be presented with a numbered list of classes that implement that
11298 method. Indicate your choice by number, or type @samp{0} to exit if
11301 As another example, to clear a breakpoint established at the
11302 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
11305 clear -[NSWindow makeKeyAndOrderFront:]
11308 @node The Print Command with Objective-C
11309 @subsubsection The Print Command With Objective-C
11310 @cindex Objective-C, print objects
11311 @kindex print-object
11312 @kindex po @r{(@code{print-object})}
11314 The print command has also been extended to accept methods. For example:
11317 print -[@var{object} hash]
11320 @cindex print an Objective-C object description
11321 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
11323 will tell @value{GDBN} to send the @code{hash} message to @var{object}
11324 and print the result. Also, an additional command has been added,
11325 @code{print-object} or @code{po} for short, which is meant to print
11326 the description of an object. However, this command may only work
11327 with certain Objective-C libraries that have a particular hook
11328 function, @code{_NSPrintForDebugger}, defined.
11331 @subsection Fortran
11332 @cindex Fortran-specific support in @value{GDBN}
11334 @value{GDBN} can be used to debug programs written in Fortran, but it
11335 currently supports only the features of Fortran 77 language.
11337 @cindex trailing underscore, in Fortran symbols
11338 Some Fortran compilers (@sc{gnu} Fortran 77 and Fortran 95 compilers
11339 among them) append an underscore to the names of variables and
11340 functions. When you debug programs compiled by those compilers, you
11341 will need to refer to variables and functions with a trailing
11345 * Fortran Operators:: Fortran operators and expressions
11346 * Fortran Defaults:: Default settings for Fortran
11347 * Special Fortran Commands:: Special @value{GDBN} commands for Fortran
11350 @node Fortran Operators
11351 @subsubsection Fortran Operators and Expressions
11353 @cindex Fortran operators and expressions
11355 Operators must be defined on values of specific types. For instance,
11356 @code{+} is defined on numbers, but not on characters or other non-
11357 arithmetic types. Operators are often defined on groups of types.
11361 The exponentiation operator. It raises the first operand to the power
11365 The range operator. Normally used in the form of array(low:high) to
11366 represent a section of array.
11369 The access component operator. Normally used to access elements in derived
11370 types. Also suitable for unions. As unions aren't part of regular Fortran,
11371 this can only happen when accessing a register that uses a gdbarch-defined
11375 @node Fortran Defaults
11376 @subsubsection Fortran Defaults
11378 @cindex Fortran Defaults
11380 Fortran symbols are usually case-insensitive, so @value{GDBN} by
11381 default uses case-insensitive matches for Fortran symbols. You can
11382 change that with the @samp{set case-insensitive} command, see
11383 @ref{Symbols}, for the details.
11385 @node Special Fortran Commands
11386 @subsubsection Special Fortran Commands
11388 @cindex Special Fortran commands
11390 @value{GDBN} has some commands to support Fortran-specific features,
11391 such as displaying common blocks.
11394 @cindex @code{COMMON} blocks, Fortran
11395 @kindex info common
11396 @item info common @r{[}@var{common-name}@r{]}
11397 This command prints the values contained in the Fortran @code{COMMON}
11398 block whose name is @var{common-name}. With no argument, the names of
11399 all @code{COMMON} blocks visible at the current program location are
11406 @cindex Pascal support in @value{GDBN}, limitations
11407 Debugging Pascal programs which use sets, subranges, file variables, or
11408 nested functions does not currently work. @value{GDBN} does not support
11409 entering expressions, printing values, or similar features using Pascal
11412 The Pascal-specific command @code{set print pascal_static-members}
11413 controls whether static members of Pascal objects are displayed.
11414 @xref{Print Settings, pascal_static-members}.
11417 @subsection Modula-2
11419 @cindex Modula-2, @value{GDBN} support
11421 The extensions made to @value{GDBN} to support Modula-2 only support
11422 output from the @sc{gnu} Modula-2 compiler (which is currently being
11423 developed). Other Modula-2 compilers are not currently supported, and
11424 attempting to debug executables produced by them is most likely
11425 to give an error as @value{GDBN} reads in the executable's symbol
11428 @cindex expressions in Modula-2
11430 * M2 Operators:: Built-in operators
11431 * Built-In Func/Proc:: Built-in functions and procedures
11432 * M2 Constants:: Modula-2 constants
11433 * M2 Types:: Modula-2 types
11434 * M2 Defaults:: Default settings for Modula-2
11435 * Deviations:: Deviations from standard Modula-2
11436 * M2 Checks:: Modula-2 type and range checks
11437 * M2 Scope:: The scope operators @code{::} and @code{.}
11438 * GDB/M2:: @value{GDBN} and Modula-2
11442 @subsubsection Operators
11443 @cindex Modula-2 operators
11445 Operators must be defined on values of specific types. For instance,
11446 @code{+} is defined on numbers, but not on structures. Operators are
11447 often defined on groups of types. For the purposes of Modula-2, the
11448 following definitions hold:
11453 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
11457 @emph{Character types} consist of @code{CHAR} and its subranges.
11460 @emph{Floating-point types} consist of @code{REAL}.
11463 @emph{Pointer types} consist of anything declared as @code{POINTER TO
11467 @emph{Scalar types} consist of all of the above.
11470 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
11473 @emph{Boolean types} consist of @code{BOOLEAN}.
11477 The following operators are supported, and appear in order of
11478 increasing precedence:
11482 Function argument or array index separator.
11485 Assignment. The value of @var{var} @code{:=} @var{value} is
11489 Less than, greater than on integral, floating-point, or enumerated
11493 Less than or equal to, greater than or equal to
11494 on integral, floating-point and enumerated types, or set inclusion on
11495 set types. Same precedence as @code{<}.
11497 @item =@r{, }<>@r{, }#
11498 Equality and two ways of expressing inequality, valid on scalar types.
11499 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
11500 available for inequality, since @code{#} conflicts with the script
11504 Set membership. Defined on set types and the types of their members.
11505 Same precedence as @code{<}.
11508 Boolean disjunction. Defined on boolean types.
11511 Boolean conjunction. Defined on boolean types.
11514 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
11517 Addition and subtraction on integral and floating-point types, or union
11518 and difference on set types.
11521 Multiplication on integral and floating-point types, or set intersection
11525 Division on floating-point types, or symmetric set difference on set
11526 types. Same precedence as @code{*}.
11529 Integer division and remainder. Defined on integral types. Same
11530 precedence as @code{*}.
11533 Negative. Defined on @code{INTEGER} and @code{REAL} data.
11536 Pointer dereferencing. Defined on pointer types.
11539 Boolean negation. Defined on boolean types. Same precedence as
11543 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
11544 precedence as @code{^}.
11547 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
11550 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
11554 @value{GDBN} and Modula-2 scope operators.
11558 @emph{Warning:} Set expressions and their operations are not yet supported, so @value{GDBN}
11559 treats the use of the operator @code{IN}, or the use of operators
11560 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
11561 @code{<=}, and @code{>=} on sets as an error.
11565 @node Built-In Func/Proc
11566 @subsubsection Built-in Functions and Procedures
11567 @cindex Modula-2 built-ins
11569 Modula-2 also makes available several built-in procedures and functions.
11570 In describing these, the following metavariables are used:
11575 represents an @code{ARRAY} variable.
11578 represents a @code{CHAR} constant or variable.
11581 represents a variable or constant of integral type.
11584 represents an identifier that belongs to a set. Generally used in the
11585 same function with the metavariable @var{s}. The type of @var{s} should
11586 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
11589 represents a variable or constant of integral or floating-point type.
11592 represents a variable or constant of floating-point type.
11598 represents a variable.
11601 represents a variable or constant of one of many types. See the
11602 explanation of the function for details.
11605 All Modula-2 built-in procedures also return a result, described below.
11609 Returns the absolute value of @var{n}.
11612 If @var{c} is a lower case letter, it returns its upper case
11613 equivalent, otherwise it returns its argument.
11616 Returns the character whose ordinal value is @var{i}.
11619 Decrements the value in the variable @var{v} by one. Returns the new value.
11621 @item DEC(@var{v},@var{i})
11622 Decrements the value in the variable @var{v} by @var{i}. Returns the
11625 @item EXCL(@var{m},@var{s})
11626 Removes the element @var{m} from the set @var{s}. Returns the new
11629 @item FLOAT(@var{i})
11630 Returns the floating point equivalent of the integer @var{i}.
11632 @item HIGH(@var{a})
11633 Returns the index of the last member of @var{a}.
11636 Increments the value in the variable @var{v} by one. Returns the new value.
11638 @item INC(@var{v},@var{i})
11639 Increments the value in the variable @var{v} by @var{i}. Returns the
11642 @item INCL(@var{m},@var{s})
11643 Adds the element @var{m} to the set @var{s} if it is not already
11644 there. Returns the new set.
11647 Returns the maximum value of the type @var{t}.
11650 Returns the minimum value of the type @var{t}.
11653 Returns boolean TRUE if @var{i} is an odd number.
11656 Returns the ordinal value of its argument. For example, the ordinal
11657 value of a character is its @sc{ascii} value (on machines supporting the
11658 @sc{ascii} character set). @var{x} must be of an ordered type, which include
11659 integral, character and enumerated types.
11661 @item SIZE(@var{x})
11662 Returns the size of its argument. @var{x} can be a variable or a type.
11664 @item TRUNC(@var{r})
11665 Returns the integral part of @var{r}.
11667 @item TSIZE(@var{x})
11668 Returns the size of its argument. @var{x} can be a variable or a type.
11670 @item VAL(@var{t},@var{i})
11671 Returns the member of the type @var{t} whose ordinal value is @var{i}.
11675 @emph{Warning:} Sets and their operations are not yet supported, so
11676 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
11680 @cindex Modula-2 constants
11682 @subsubsection Constants
11684 @value{GDBN} allows you to express the constants of Modula-2 in the following
11690 Integer constants are simply a sequence of digits. When used in an
11691 expression, a constant is interpreted to be type-compatible with the
11692 rest of the expression. Hexadecimal integers are specified by a
11693 trailing @samp{H}, and octal integers by a trailing @samp{B}.
11696 Floating point constants appear as a sequence of digits, followed by a
11697 decimal point and another sequence of digits. An optional exponent can
11698 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
11699 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
11700 digits of the floating point constant must be valid decimal (base 10)
11704 Character constants consist of a single character enclosed by a pair of
11705 like quotes, either single (@code{'}) or double (@code{"}). They may
11706 also be expressed by their ordinal value (their @sc{ascii} value, usually)
11707 followed by a @samp{C}.
11710 String constants consist of a sequence of characters enclosed by a
11711 pair of like quotes, either single (@code{'}) or double (@code{"}).
11712 Escape sequences in the style of C are also allowed. @xref{C
11713 Constants, ,C and C@t{++} Constants}, for a brief explanation of escape
11717 Enumerated constants consist of an enumerated identifier.
11720 Boolean constants consist of the identifiers @code{TRUE} and
11724 Pointer constants consist of integral values only.
11727 Set constants are not yet supported.
11731 @subsubsection Modula-2 Types
11732 @cindex Modula-2 types
11734 Currently @value{GDBN} can print the following data types in Modula-2
11735 syntax: array types, record types, set types, pointer types, procedure
11736 types, enumerated types, subrange types and base types. You can also
11737 print the contents of variables declared using these type.
11738 This section gives a number of simple source code examples together with
11739 sample @value{GDBN} sessions.
11741 The first example contains the following section of code:
11750 and you can request @value{GDBN} to interrogate the type and value of
11751 @code{r} and @code{s}.
11754 (@value{GDBP}) print s
11756 (@value{GDBP}) ptype s
11758 (@value{GDBP}) print r
11760 (@value{GDBP}) ptype r
11765 Likewise if your source code declares @code{s} as:
11769 s: SET ['A'..'Z'] ;
11773 then you may query the type of @code{s} by:
11776 (@value{GDBP}) ptype s
11777 type = SET ['A'..'Z']
11781 Note that at present you cannot interactively manipulate set
11782 expressions using the debugger.
11784 The following example shows how you might declare an array in Modula-2
11785 and how you can interact with @value{GDBN} to print its type and contents:
11789 s: ARRAY [-10..10] OF CHAR ;
11793 (@value{GDBP}) ptype s
11794 ARRAY [-10..10] OF CHAR
11797 Note that the array handling is not yet complete and although the type
11798 is printed correctly, expression handling still assumes that all
11799 arrays have a lower bound of zero and not @code{-10} as in the example
11802 Here are some more type related Modula-2 examples:
11806 colour = (blue, red, yellow, green) ;
11807 t = [blue..yellow] ;
11815 The @value{GDBN} interaction shows how you can query the data type
11816 and value of a variable.
11819 (@value{GDBP}) print s
11821 (@value{GDBP}) ptype t
11822 type = [blue..yellow]
11826 In this example a Modula-2 array is declared and its contents
11827 displayed. Observe that the contents are written in the same way as
11828 their @code{C} counterparts.
11832 s: ARRAY [1..5] OF CARDINAL ;
11838 (@value{GDBP}) print s
11839 $1 = @{1, 0, 0, 0, 0@}
11840 (@value{GDBP}) ptype s
11841 type = ARRAY [1..5] OF CARDINAL
11844 The Modula-2 language interface to @value{GDBN} also understands
11845 pointer types as shown in this example:
11849 s: POINTER TO ARRAY [1..5] OF CARDINAL ;
11856 and you can request that @value{GDBN} describes the type of @code{s}.
11859 (@value{GDBP}) ptype s
11860 type = POINTER TO ARRAY [1..5] OF CARDINAL
11863 @value{GDBN} handles compound types as we can see in this example.
11864 Here we combine array types, record types, pointer types and subrange
11875 myarray = ARRAY myrange OF CARDINAL ;
11876 myrange = [-2..2] ;
11878 s: POINTER TO ARRAY myrange OF foo ;
11882 and you can ask @value{GDBN} to describe the type of @code{s} as shown
11886 (@value{GDBP}) ptype s
11887 type = POINTER TO ARRAY [-2..2] OF foo = RECORD
11890 f3 : ARRAY [-2..2] OF CARDINAL;
11895 @subsubsection Modula-2 Defaults
11896 @cindex Modula-2 defaults
11898 If type and range checking are set automatically by @value{GDBN}, they
11899 both default to @code{on} whenever the working language changes to
11900 Modula-2. This happens regardless of whether you or @value{GDBN}
11901 selected the working language.
11903 If you allow @value{GDBN} to set the language automatically, then entering
11904 code compiled from a file whose name ends with @file{.mod} sets the
11905 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN}
11906 Infer the Source Language}, for further details.
11909 @subsubsection Deviations from Standard Modula-2
11910 @cindex Modula-2, deviations from
11912 A few changes have been made to make Modula-2 programs easier to debug.
11913 This is done primarily via loosening its type strictness:
11917 Unlike in standard Modula-2, pointer constants can be formed by
11918 integers. This allows you to modify pointer variables during
11919 debugging. (In standard Modula-2, the actual address contained in a
11920 pointer variable is hidden from you; it can only be modified
11921 through direct assignment to another pointer variable or expression that
11922 returned a pointer.)
11925 C escape sequences can be used in strings and characters to represent
11926 non-printable characters. @value{GDBN} prints out strings with these
11927 escape sequences embedded. Single non-printable characters are
11928 printed using the @samp{CHR(@var{nnn})} format.
11931 The assignment operator (@code{:=}) returns the value of its right-hand
11935 All built-in procedures both modify @emph{and} return their argument.
11939 @subsubsection Modula-2 Type and Range Checks
11940 @cindex Modula-2 checks
11943 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
11946 @c FIXME remove warning when type/range checks added
11948 @value{GDBN} considers two Modula-2 variables type equivalent if:
11952 They are of types that have been declared equivalent via a @code{TYPE
11953 @var{t1} = @var{t2}} statement
11956 They have been declared on the same line. (Note: This is true of the
11957 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
11960 As long as type checking is enabled, any attempt to combine variables
11961 whose types are not equivalent is an error.
11963 Range checking is done on all mathematical operations, assignment, array
11964 index bounds, and all built-in functions and procedures.
11967 @subsubsection The Scope Operators @code{::} and @code{.}
11969 @cindex @code{.}, Modula-2 scope operator
11970 @cindex colon, doubled as scope operator
11972 @vindex colon-colon@r{, in Modula-2}
11973 @c Info cannot handle :: but TeX can.
11976 @vindex ::@r{, in Modula-2}
11979 There are a few subtle differences between the Modula-2 scope operator
11980 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
11985 @var{module} . @var{id}
11986 @var{scope} :: @var{id}
11990 where @var{scope} is the name of a module or a procedure,
11991 @var{module} the name of a module, and @var{id} is any declared
11992 identifier within your program, except another module.
11994 Using the @code{::} operator makes @value{GDBN} search the scope
11995 specified by @var{scope} for the identifier @var{id}. If it is not
11996 found in the specified scope, then @value{GDBN} searches all scopes
11997 enclosing the one specified by @var{scope}.
11999 Using the @code{.} operator makes @value{GDBN} search the current scope for
12000 the identifier specified by @var{id} that was imported from the
12001 definition module specified by @var{module}. With this operator, it is
12002 an error if the identifier @var{id} was not imported from definition
12003 module @var{module}, or if @var{id} is not an identifier in
12007 @subsubsection @value{GDBN} and Modula-2
12009 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
12010 Five subcommands of @code{set print} and @code{show print} apply
12011 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
12012 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
12013 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
12014 analogue in Modula-2.
12016 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
12017 with any language, is not useful with Modula-2. Its
12018 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
12019 created in Modula-2 as they can in C or C@t{++}. However, because an
12020 address can be specified by an integral constant, the construct
12021 @samp{@{@var{type}@}@var{adrexp}} is still useful.
12023 @cindex @code{#} in Modula-2
12024 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
12025 interpreted as the beginning of a comment. Use @code{<>} instead.
12031 The extensions made to @value{GDBN} for Ada only support
12032 output from the @sc{gnu} Ada (GNAT) compiler.
12033 Other Ada compilers are not currently supported, and
12034 attempting to debug executables produced by them is most likely
12038 @cindex expressions in Ada
12040 * Ada Mode Intro:: General remarks on the Ada syntax
12041 and semantics supported by Ada mode
12043 * Omissions from Ada:: Restrictions on the Ada expression syntax.
12044 * Additions to Ada:: Extensions of the Ada expression syntax.
12045 * Stopping Before Main Program:: Debugging the program during elaboration.
12046 * Ada Tasks:: Listing and setting breakpoints in tasks.
12047 * Ada Tasks and Core Files:: Tasking Support when Debugging Core Files
12048 * Ada Glitches:: Known peculiarities of Ada mode.
12051 @node Ada Mode Intro
12052 @subsubsection Introduction
12053 @cindex Ada mode, general
12055 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
12056 syntax, with some extensions.
12057 The philosophy behind the design of this subset is
12061 That @value{GDBN} should provide basic literals and access to operations for
12062 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
12063 leaving more sophisticated computations to subprograms written into the
12064 program (which therefore may be called from @value{GDBN}).
12067 That type safety and strict adherence to Ada language restrictions
12068 are not particularly important to the @value{GDBN} user.
12071 That brevity is important to the @value{GDBN} user.
12074 Thus, for brevity, the debugger acts as if all names declared in
12075 user-written packages are directly visible, even if they are not visible
12076 according to Ada rules, thus making it unnecessary to fully qualify most
12077 names with their packages, regardless of context. Where this causes
12078 ambiguity, @value{GDBN} asks the user's intent.
12080 The debugger will start in Ada mode if it detects an Ada main program.
12081 As for other languages, it will enter Ada mode when stopped in a program that
12082 was translated from an Ada source file.
12084 While in Ada mode, you may use `@t{--}' for comments. This is useful
12085 mostly for documenting command files. The standard @value{GDBN} comment
12086 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
12087 middle (to allow based literals).
12089 The debugger supports limited overloading. Given a subprogram call in which
12090 the function symbol has multiple definitions, it will use the number of
12091 actual parameters and some information about their types to attempt to narrow
12092 the set of definitions. It also makes very limited use of context, preferring
12093 procedures to functions in the context of the @code{call} command, and
12094 functions to procedures elsewhere.
12096 @node Omissions from Ada
12097 @subsubsection Omissions from Ada
12098 @cindex Ada, omissions from
12100 Here are the notable omissions from the subset:
12104 Only a subset of the attributes are supported:
12108 @t{'First}, @t{'Last}, and @t{'Length}
12109 on array objects (not on types and subtypes).
12112 @t{'Min} and @t{'Max}.
12115 @t{'Pos} and @t{'Val}.
12121 @t{'Range} on array objects (not subtypes), but only as the right
12122 operand of the membership (@code{in}) operator.
12125 @t{'Access}, @t{'Unchecked_Access}, and
12126 @t{'Unrestricted_Access} (a GNAT extension).
12134 @code{Characters.Latin_1} are not available and
12135 concatenation is not implemented. Thus, escape characters in strings are
12136 not currently available.
12139 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
12140 equality of representations. They will generally work correctly
12141 for strings and arrays whose elements have integer or enumeration types.
12142 They may not work correctly for arrays whose element
12143 types have user-defined equality, for arrays of real values
12144 (in particular, IEEE-conformant floating point, because of negative
12145 zeroes and NaNs), and for arrays whose elements contain unused bits with
12146 indeterminate values.
12149 The other component-by-component array operations (@code{and}, @code{or},
12150 @code{xor}, @code{not}, and relational tests other than equality)
12151 are not implemented.
12154 @cindex array aggregates (Ada)
12155 @cindex record aggregates (Ada)
12156 @cindex aggregates (Ada)
12157 There is limited support for array and record aggregates. They are
12158 permitted only on the right sides of assignments, as in these examples:
12161 (@value{GDBP}) set An_Array := (1, 2, 3, 4, 5, 6)
12162 (@value{GDBP}) set An_Array := (1, others => 0)
12163 (@value{GDBP}) set An_Array := (0|4 => 1, 1..3 => 2, 5 => 6)
12164 (@value{GDBP}) set A_2D_Array := ((1, 2, 3), (4, 5, 6), (7, 8, 9))
12165 (@value{GDBP}) set A_Record := (1, "Peter", True);
12166 (@value{GDBP}) set A_Record := (Name => "Peter", Id => 1, Alive => True)
12170 discriminant's value by assigning an aggregate has an
12171 undefined effect if that discriminant is used within the record.
12172 However, you can first modify discriminants by directly assigning to
12173 them (which normally would not be allowed in Ada), and then performing an
12174 aggregate assignment. For example, given a variable @code{A_Rec}
12175 declared to have a type such as:
12178 type Rec (Len : Small_Integer := 0) is record
12180 Vals : IntArray (1 .. Len);
12184 you can assign a value with a different size of @code{Vals} with two
12188 (@value{GDBP}) set A_Rec.Len := 4
12189 (@value{GDBP}) set A_Rec := (Id => 42, Vals => (1, 2, 3, 4))
12192 As this example also illustrates, @value{GDBN} is very loose about the usual
12193 rules concerning aggregates. You may leave out some of the
12194 components of an array or record aggregate (such as the @code{Len}
12195 component in the assignment to @code{A_Rec} above); they will retain their
12196 original values upon assignment. You may freely use dynamic values as
12197 indices in component associations. You may even use overlapping or
12198 redundant component associations, although which component values are
12199 assigned in such cases is not defined.
12202 Calls to dispatching subprograms are not implemented.
12205 The overloading algorithm is much more limited (i.e., less selective)
12206 than that of real Ada. It makes only limited use of the context in
12207 which a subexpression appears to resolve its meaning, and it is much
12208 looser in its rules for allowing type matches. As a result, some
12209 function calls will be ambiguous, and the user will be asked to choose
12210 the proper resolution.
12213 The @code{new} operator is not implemented.
12216 Entry calls are not implemented.
12219 Aside from printing, arithmetic operations on the native VAX floating-point
12220 formats are not supported.
12223 It is not possible to slice a packed array.
12226 The names @code{True} and @code{False}, when not part of a qualified name,
12227 are interpreted as if implicitly prefixed by @code{Standard}, regardless of
12229 Should your program
12230 redefine these names in a package or procedure (at best a dubious practice),
12231 you will have to use fully qualified names to access their new definitions.
12234 @node Additions to Ada
12235 @subsubsection Additions to Ada
12236 @cindex Ada, deviations from
12238 As it does for other languages, @value{GDBN} makes certain generic
12239 extensions to Ada (@pxref{Expressions}):
12243 If the expression @var{E} is a variable residing in memory (typically
12244 a local variable or array element) and @var{N} is a positive integer,
12245 then @code{@var{E}@@@var{N}} displays the values of @var{E} and the
12246 @var{N}-1 adjacent variables following it in memory as an array. In
12247 Ada, this operator is generally not necessary, since its prime use is
12248 in displaying parts of an array, and slicing will usually do this in
12249 Ada. However, there are occasional uses when debugging programs in
12250 which certain debugging information has been optimized away.
12253 @code{@var{B}::@var{var}} means ``the variable named @var{var} that
12254 appears in function or file @var{B}.'' When @var{B} is a file name,
12255 you must typically surround it in single quotes.
12258 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
12259 @var{type} that appears at address @var{addr}.''
12262 A name starting with @samp{$} is a convenience variable
12263 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
12266 In addition, @value{GDBN} provides a few other shortcuts and outright
12267 additions specific to Ada:
12271 The assignment statement is allowed as an expression, returning
12272 its right-hand operand as its value. Thus, you may enter
12275 (@value{GDBP}) set x := y + 3
12276 (@value{GDBP}) print A(tmp := y + 1)
12280 The semicolon is allowed as an ``operator,'' returning as its value
12281 the value of its right-hand operand.
12282 This allows, for example,
12283 complex conditional breaks:
12286 (@value{GDBP}) break f
12287 (@value{GDBP}) condition 1 (report(i); k += 1; A(k) > 100)
12291 Rather than use catenation and symbolic character names to introduce special
12292 characters into strings, one may instead use a special bracket notation,
12293 which is also used to print strings. A sequence of characters of the form
12294 @samp{["@var{XX}"]} within a string or character literal denotes the
12295 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
12296 sequence of characters @samp{["""]} also denotes a single quotation mark
12297 in strings. For example,
12299 "One line.["0a"]Next line.["0a"]"
12302 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF})
12306 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
12307 @t{'Max} is optional (and is ignored in any case). For example, it is valid
12311 (@value{GDBP}) print 'max(x, y)
12315 When printing arrays, @value{GDBN} uses positional notation when the
12316 array has a lower bound of 1, and uses a modified named notation otherwise.
12317 For example, a one-dimensional array of three integers with a lower bound
12318 of 3 might print as
12325 That is, in contrast to valid Ada, only the first component has a @code{=>}
12329 You may abbreviate attributes in expressions with any unique,
12330 multi-character subsequence of
12331 their names (an exact match gets preference).
12332 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
12333 in place of @t{a'length}.
12336 @cindex quoting Ada internal identifiers
12337 Since Ada is case-insensitive, the debugger normally maps identifiers you type
12338 to lower case. The GNAT compiler uses upper-case characters for
12339 some of its internal identifiers, which are normally of no interest to users.
12340 For the rare occasions when you actually have to look at them,
12341 enclose them in angle brackets to avoid the lower-case mapping.
12344 (@value{GDBP}) print <JMPBUF_SAVE>[0]
12348 Printing an object of class-wide type or dereferencing an
12349 access-to-class-wide value will display all the components of the object's
12350 specific type (as indicated by its run-time tag). Likewise, component
12351 selection on such a value will operate on the specific type of the
12356 @node Stopping Before Main Program
12357 @subsubsection Stopping at the Very Beginning
12359 @cindex breakpointing Ada elaboration code
12360 It is sometimes necessary to debug the program during elaboration, and
12361 before reaching the main procedure.
12362 As defined in the Ada Reference
12363 Manual, the elaboration code is invoked from a procedure called
12364 @code{adainit}. To run your program up to the beginning of
12365 elaboration, simply use the following two commands:
12366 @code{tbreak adainit} and @code{run}.
12369 @subsubsection Extensions for Ada Tasks
12370 @cindex Ada, tasking
12372 Support for Ada tasks is analogous to that for threads (@pxref{Threads}).
12373 @value{GDBN} provides the following task-related commands:
12378 This command shows a list of current Ada tasks, as in the following example:
12385 (@value{GDBP}) info tasks
12386 ID TID P-ID Pri State Name
12387 1 8088000 0 15 Child Activation Wait main_task
12388 2 80a4000 1 15 Accept Statement b
12389 3 809a800 1 15 Child Activation Wait a
12390 * 4 80ae800 3 15 Runnable c
12395 In this listing, the asterisk before the last task indicates it to be the
12396 task currently being inspected.
12400 Represents @value{GDBN}'s internal task number.
12406 The parent's task ID (@value{GDBN}'s internal task number).
12409 The base priority of the task.
12412 Current state of the task.
12416 The task has been created but has not been activated. It cannot be
12420 The task is not blocked for any reason known to Ada. (It may be waiting
12421 for a mutex, though.) It is conceptually "executing" in normal mode.
12424 The task is terminated, in the sense of ARM 9.3 (5). Any dependents
12425 that were waiting on terminate alternatives have been awakened and have
12426 terminated themselves.
12428 @item Child Activation Wait
12429 The task is waiting for created tasks to complete activation.
12431 @item Accept Statement
12432 The task is waiting on an accept or selective wait statement.
12434 @item Waiting on entry call
12435 The task is waiting on an entry call.
12437 @item Async Select Wait
12438 The task is waiting to start the abortable part of an asynchronous
12442 The task is waiting on a select statement with only a delay
12445 @item Child Termination Wait
12446 The task is sleeping having completed a master within itself, and is
12447 waiting for the tasks dependent on that master to become terminated or
12448 waiting on a terminate Phase.
12450 @item Wait Child in Term Alt
12451 The task is sleeping waiting for tasks on terminate alternatives to
12452 finish terminating.
12454 @item Accepting RV with @var{taskno}
12455 The task is accepting a rendez-vous with the task @var{taskno}.
12459 Name of the task in the program.
12463 @kindex info task @var{taskno}
12464 @item info task @var{taskno}
12465 This command shows detailled informations on the specified task, as in
12466 the following example:
12471 (@value{GDBP}) info tasks
12472 ID TID P-ID Pri State Name
12473 1 8077880 0 15 Child Activation Wait main_task
12474 * 2 807c468 1 15 Runnable task_1
12475 (@value{GDBP}) info task 2
12476 Ada Task: 0x807c468
12479 Parent: 1 (main_task)
12485 @kindex task@r{ (Ada)}
12486 @cindex current Ada task ID
12487 This command prints the ID of the current task.
12493 (@value{GDBP}) info tasks
12494 ID TID P-ID Pri State Name
12495 1 8077870 0 15 Child Activation Wait main_task
12496 * 2 807c458 1 15 Runnable t
12497 (@value{GDBP}) task
12498 [Current task is 2]
12501 @item task @var{taskno}
12502 @cindex Ada task switching
12503 This command is like the @code{thread @var{threadno}}
12504 command (@pxref{Threads}). It switches the context of debugging
12505 from the current task to the given task.
12511 (@value{GDBP}) info tasks
12512 ID TID P-ID Pri State Name
12513 1 8077870 0 15 Child Activation Wait main_task
12514 * 2 807c458 1 15 Runnable t
12515 (@value{GDBP}) task 1
12516 [Switching to task 1]
12517 #0 0x8067726 in pthread_cond_wait ()
12519 #0 0x8067726 in pthread_cond_wait ()
12520 #1 0x8056714 in system.os_interface.pthread_cond_wait ()
12521 #2 0x805cb63 in system.task_primitives.operations.sleep ()
12522 #3 0x806153e in system.tasking.stages.activate_tasks ()
12523 #4 0x804aacc in un () at un.adb:5
12526 @item break @var{linespec} task @var{taskno}
12527 @itemx break @var{linespec} task @var{taskno} if @dots{}
12528 @cindex breakpoints and tasks, in Ada
12529 @cindex task breakpoints, in Ada
12530 @kindex break @dots{} task @var{taskno}@r{ (Ada)}
12531 These commands are like the @code{break @dots{} thread @dots{}}
12532 command (@pxref{Thread Stops}).
12533 @var{linespec} specifies source lines, as described
12534 in @ref{Specify Location}.
12536 Use the qualifier @samp{task @var{taskno}} with a breakpoint command
12537 to specify that you only want @value{GDBN} to stop the program when a
12538 particular Ada task reaches this breakpoint. @var{taskno} is one of the
12539 numeric task identifiers assigned by @value{GDBN}, shown in the first
12540 column of the @samp{info tasks} display.
12542 If you do not specify @samp{task @var{taskno}} when you set a
12543 breakpoint, the breakpoint applies to @emph{all} tasks of your
12546 You can use the @code{task} qualifier on conditional breakpoints as
12547 well; in this case, place @samp{task @var{taskno}} before the
12548 breakpoint condition (before the @code{if}).
12556 (@value{GDBP}) info tasks
12557 ID TID P-ID Pri State Name
12558 1 140022020 0 15 Child Activation Wait main_task
12559 2 140045060 1 15 Accept/Select Wait t2
12560 3 140044840 1 15 Runnable t1
12561 * 4 140056040 1 15 Runnable t3
12562 (@value{GDBP}) b 15 task 2
12563 Breakpoint 5 at 0x120044cb0: file test_task_debug.adb, line 15.
12564 (@value{GDBP}) cont
12569 Breakpoint 5, test_task_debug () at test_task_debug.adb:15
12571 (@value{GDBP}) info tasks
12572 ID TID P-ID Pri State Name
12573 1 140022020 0 15 Child Activation Wait main_task
12574 * 2 140045060 1 15 Runnable t2
12575 3 140044840 1 15 Runnable t1
12576 4 140056040 1 15 Delay Sleep t3
12580 @node Ada Tasks and Core Files
12581 @subsubsection Tasking Support when Debugging Core Files
12582 @cindex Ada tasking and core file debugging
12584 When inspecting a core file, as opposed to debugging a live program,
12585 tasking support may be limited or even unavailable, depending on
12586 the platform being used.
12587 For instance, on x86-linux, the list of tasks is available, but task
12588 switching is not supported. On Tru64, however, task switching will work
12591 On certain platforms, including Tru64, the debugger needs to perform some
12592 memory writes in order to provide Ada tasking support. When inspecting
12593 a core file, this means that the core file must be opened with read-write
12594 privileges, using the command @samp{"set write on"} (@pxref{Patching}).
12595 Under these circumstances, you should make a backup copy of the core
12596 file before inspecting it with @value{GDBN}.
12599 @subsubsection Known Peculiarities of Ada Mode
12600 @cindex Ada, problems
12602 Besides the omissions listed previously (@pxref{Omissions from Ada}),
12603 we know of several problems with and limitations of Ada mode in
12605 some of which will be fixed with planned future releases of the debugger
12606 and the GNU Ada compiler.
12610 Currently, the debugger
12611 has insufficient information to determine whether certain pointers represent
12612 pointers to objects or the objects themselves.
12613 Thus, the user may have to tack an extra @code{.all} after an expression
12614 to get it printed properly.
12617 Static constants that the compiler chooses not to materialize as objects in
12618 storage are invisible to the debugger.
12621 Named parameter associations in function argument lists are ignored (the
12622 argument lists are treated as positional).
12625 Many useful library packages are currently invisible to the debugger.
12628 Fixed-point arithmetic, conversions, input, and output is carried out using
12629 floating-point arithmetic, and may give results that only approximate those on
12633 The GNAT compiler never generates the prefix @code{Standard} for any of
12634 the standard symbols defined by the Ada language. @value{GDBN} knows about
12635 this: it will strip the prefix from names when you use it, and will never
12636 look for a name you have so qualified among local symbols, nor match against
12637 symbols in other packages or subprograms. If you have
12638 defined entities anywhere in your program other than parameters and
12639 local variables whose simple names match names in @code{Standard},
12640 GNAT's lack of qualification here can cause confusion. When this happens,
12641 you can usually resolve the confusion
12642 by qualifying the problematic names with package
12643 @code{Standard} explicitly.
12646 @node Unsupported Languages
12647 @section Unsupported Languages
12649 @cindex unsupported languages
12650 @cindex minimal language
12651 In addition to the other fully-supported programming languages,
12652 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
12653 It does not represent a real programming language, but provides a set
12654 of capabilities close to what the C or assembly languages provide.
12655 This should allow most simple operations to be performed while debugging
12656 an application that uses a language currently not supported by @value{GDBN}.
12658 If the language is set to @code{auto}, @value{GDBN} will automatically
12659 select this language if the current frame corresponds to an unsupported
12663 @chapter Examining the Symbol Table
12665 The commands described in this chapter allow you to inquire about the
12666 symbols (names of variables, functions and types) defined in your
12667 program. This information is inherent in the text of your program and
12668 does not change as your program executes. @value{GDBN} finds it in your
12669 program's symbol table, in the file indicated when you started @value{GDBN}
12670 (@pxref{File Options, ,Choosing Files}), or by one of the
12671 file-management commands (@pxref{Files, ,Commands to Specify Files}).
12673 @cindex symbol names
12674 @cindex names of symbols
12675 @cindex quoting names
12676 Occasionally, you may need to refer to symbols that contain unusual
12677 characters, which @value{GDBN} ordinarily treats as word delimiters. The
12678 most frequent case is in referring to static variables in other
12679 source files (@pxref{Variables,,Program Variables}). File names
12680 are recorded in object files as debugging symbols, but @value{GDBN} would
12681 ordinarily parse a typical file name, like @file{foo.c}, as the three words
12682 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
12683 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
12690 looks up the value of @code{x} in the scope of the file @file{foo.c}.
12693 @cindex case-insensitive symbol names
12694 @cindex case sensitivity in symbol names
12695 @kindex set case-sensitive
12696 @item set case-sensitive on
12697 @itemx set case-sensitive off
12698 @itemx set case-sensitive auto
12699 Normally, when @value{GDBN} looks up symbols, it matches their names
12700 with case sensitivity determined by the current source language.
12701 Occasionally, you may wish to control that. The command @code{set
12702 case-sensitive} lets you do that by specifying @code{on} for
12703 case-sensitive matches or @code{off} for case-insensitive ones. If
12704 you specify @code{auto}, case sensitivity is reset to the default
12705 suitable for the source language. The default is case-sensitive
12706 matches for all languages except for Fortran, for which the default is
12707 case-insensitive matches.
12709 @kindex show case-sensitive
12710 @item show case-sensitive
12711 This command shows the current setting of case sensitivity for symbols
12714 @kindex info address
12715 @cindex address of a symbol
12716 @item info address @var{symbol}
12717 Describe where the data for @var{symbol} is stored. For a register
12718 variable, this says which register it is kept in. For a non-register
12719 local variable, this prints the stack-frame offset at which the variable
12722 Note the contrast with @samp{print &@var{symbol}}, which does not work
12723 at all for a register variable, and for a stack local variable prints
12724 the exact address of the current instantiation of the variable.
12726 @kindex info symbol
12727 @cindex symbol from address
12728 @cindex closest symbol and offset for an address
12729 @item info symbol @var{addr}
12730 Print the name of a symbol which is stored at the address @var{addr}.
12731 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
12732 nearest symbol and an offset from it:
12735 (@value{GDBP}) info symbol 0x54320
12736 _initialize_vx + 396 in section .text
12740 This is the opposite of the @code{info address} command. You can use
12741 it to find out the name of a variable or a function given its address.
12743 For dynamically linked executables, the name of executable or shared
12744 library containing the symbol is also printed:
12747 (@value{GDBP}) info symbol 0x400225
12748 _start + 5 in section .text of /tmp/a.out
12749 (@value{GDBP}) info symbol 0x2aaaac2811cf
12750 __read_nocancel + 6 in section .text of /usr/lib64/libc.so.6
12754 @item whatis [@var{arg}]
12755 Print the data type of @var{arg}, which can be either an expression or
12756 a data type. With no argument, print the data type of @code{$}, the
12757 last value in the value history. If @var{arg} is an expression, it is
12758 not actually evaluated, and any side-effecting operations (such as
12759 assignments or function calls) inside it do not take place. If
12760 @var{arg} is a type name, it may be the name of a type or typedef, or
12761 for C code it may have the form @samp{class @var{class-name}},
12762 @samp{struct @var{struct-tag}}, @samp{union @var{union-tag}} or
12763 @samp{enum @var{enum-tag}}.
12764 @xref{Expressions, ,Expressions}.
12767 @item ptype [@var{arg}]
12768 @code{ptype} accepts the same arguments as @code{whatis}, but prints a
12769 detailed description of the type, instead of just the name of the type.
12770 @xref{Expressions, ,Expressions}.
12772 For example, for this variable declaration:
12775 struct complex @{double real; double imag;@} v;
12779 the two commands give this output:
12783 (@value{GDBP}) whatis v
12784 type = struct complex
12785 (@value{GDBP}) ptype v
12786 type = struct complex @{
12794 As with @code{whatis}, using @code{ptype} without an argument refers to
12795 the type of @code{$}, the last value in the value history.
12797 @cindex incomplete type
12798 Sometimes, programs use opaque data types or incomplete specifications
12799 of complex data structure. If the debug information included in the
12800 program does not allow @value{GDBN} to display a full declaration of
12801 the data type, it will say @samp{<incomplete type>}. For example,
12802 given these declarations:
12806 struct foo *fooptr;
12810 but no definition for @code{struct foo} itself, @value{GDBN} will say:
12813 (@value{GDBP}) ptype foo
12814 $1 = <incomplete type>
12818 ``Incomplete type'' is C terminology for data types that are not
12819 completely specified.
12822 @item info types @var{regexp}
12824 Print a brief description of all types whose names match the regular
12825 expression @var{regexp} (or all types in your program, if you supply
12826 no argument). Each complete typename is matched as though it were a
12827 complete line; thus, @samp{i type value} gives information on all
12828 types in your program whose names include the string @code{value}, but
12829 @samp{i type ^value$} gives information only on types whose complete
12830 name is @code{value}.
12832 This command differs from @code{ptype} in two ways: first, like
12833 @code{whatis}, it does not print a detailed description; second, it
12834 lists all source files where a type is defined.
12837 @cindex local variables
12838 @item info scope @var{location}
12839 List all the variables local to a particular scope. This command
12840 accepts a @var{location} argument---a function name, a source line, or
12841 an address preceded by a @samp{*}, and prints all the variables local
12842 to the scope defined by that location. (@xref{Specify Location}, for
12843 details about supported forms of @var{location}.) For example:
12846 (@value{GDBP}) @b{info scope command_line_handler}
12847 Scope for command_line_handler:
12848 Symbol rl is an argument at stack/frame offset 8, length 4.
12849 Symbol linebuffer is in static storage at address 0x150a18, length 4.
12850 Symbol linelength is in static storage at address 0x150a1c, length 4.
12851 Symbol p is a local variable in register $esi, length 4.
12852 Symbol p1 is a local variable in register $ebx, length 4.
12853 Symbol nline is a local variable in register $edx, length 4.
12854 Symbol repeat is a local variable at frame offset -8, length 4.
12858 This command is especially useful for determining what data to collect
12859 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
12862 @kindex info source
12864 Show information about the current source file---that is, the source file for
12865 the function containing the current point of execution:
12868 the name of the source file, and the directory containing it,
12870 the directory it was compiled in,
12872 its length, in lines,
12874 which programming language it is written in,
12876 whether the executable includes debugging information for that file, and
12877 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
12879 whether the debugging information includes information about
12880 preprocessor macros.
12884 @kindex info sources
12886 Print the names of all source files in your program for which there is
12887 debugging information, organized into two lists: files whose symbols
12888 have already been read, and files whose symbols will be read when needed.
12890 @kindex info functions
12891 @item info functions
12892 Print the names and data types of all defined functions.
12894 @item info functions @var{regexp}
12895 Print the names and data types of all defined functions
12896 whose names contain a match for regular expression @var{regexp}.
12897 Thus, @samp{info fun step} finds all functions whose names
12898 include @code{step}; @samp{info fun ^step} finds those whose names
12899 start with @code{step}. If a function name contains characters
12900 that conflict with the regular expression language (e.g.@:
12901 @samp{operator*()}), they may be quoted with a backslash.
12903 @kindex info variables
12904 @item info variables
12905 Print the names and data types of all variables that are declared
12906 outside of functions (i.e.@: excluding local variables).
12908 @item info variables @var{regexp}
12909 Print the names and data types of all variables (except for local
12910 variables) whose names contain a match for regular expression
12913 @kindex info classes
12914 @cindex Objective-C, classes and selectors
12916 @itemx info classes @var{regexp}
12917 Display all Objective-C classes in your program, or
12918 (with the @var{regexp} argument) all those matching a particular regular
12921 @kindex info selectors
12922 @item info selectors
12923 @itemx info selectors @var{regexp}
12924 Display all Objective-C selectors in your program, or
12925 (with the @var{regexp} argument) all those matching a particular regular
12929 This was never implemented.
12930 @kindex info methods
12932 @itemx info methods @var{regexp}
12933 The @code{info methods} command permits the user to examine all defined
12934 methods within C@t{++} program, or (with the @var{regexp} argument) a
12935 specific set of methods found in the various C@t{++} classes. Many
12936 C@t{++} classes provide a large number of methods. Thus, the output
12937 from the @code{ptype} command can be overwhelming and hard to use. The
12938 @code{info-methods} command filters the methods, printing only those
12939 which match the regular-expression @var{regexp}.
12942 @cindex reloading symbols
12943 Some systems allow individual object files that make up your program to
12944 be replaced without stopping and restarting your program. For example,
12945 in VxWorks you can simply recompile a defective object file and keep on
12946 running. If you are running on one of these systems, you can allow
12947 @value{GDBN} to reload the symbols for automatically relinked modules:
12950 @kindex set symbol-reloading
12951 @item set symbol-reloading on
12952 Replace symbol definitions for the corresponding source file when an
12953 object file with a particular name is seen again.
12955 @item set symbol-reloading off
12956 Do not replace symbol definitions when encountering object files of the
12957 same name more than once. This is the default state; if you are not
12958 running on a system that permits automatic relinking of modules, you
12959 should leave @code{symbol-reloading} off, since otherwise @value{GDBN}
12960 may discard symbols when linking large programs, that may contain
12961 several modules (from different directories or libraries) with the same
12964 @kindex show symbol-reloading
12965 @item show symbol-reloading
12966 Show the current @code{on} or @code{off} setting.
12969 @cindex opaque data types
12970 @kindex set opaque-type-resolution
12971 @item set opaque-type-resolution on
12972 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
12973 declared as a pointer to a @code{struct}, @code{class}, or
12974 @code{union}---for example, @code{struct MyType *}---that is used in one
12975 source file although the full declaration of @code{struct MyType} is in
12976 another source file. The default is on.
12978 A change in the setting of this subcommand will not take effect until
12979 the next time symbols for a file are loaded.
12981 @item set opaque-type-resolution off
12982 Tell @value{GDBN} not to resolve opaque types. In this case, the type
12983 is printed as follows:
12985 @{<no data fields>@}
12988 @kindex show opaque-type-resolution
12989 @item show opaque-type-resolution
12990 Show whether opaque types are resolved or not.
12992 @kindex maint print symbols
12993 @cindex symbol dump
12994 @kindex maint print psymbols
12995 @cindex partial symbol dump
12996 @item maint print symbols @var{filename}
12997 @itemx maint print psymbols @var{filename}
12998 @itemx maint print msymbols @var{filename}
12999 Write a dump of debugging symbol data into the file @var{filename}.
13000 These commands are used to debug the @value{GDBN} symbol-reading code. Only
13001 symbols with debugging data are included. If you use @samp{maint print
13002 symbols}, @value{GDBN} includes all the symbols for which it has already
13003 collected full details: that is, @var{filename} reflects symbols for
13004 only those files whose symbols @value{GDBN} has read. You can use the
13005 command @code{info sources} to find out which files these are. If you
13006 use @samp{maint print psymbols} instead, the dump shows information about
13007 symbols that @value{GDBN} only knows partially---that is, symbols defined in
13008 files that @value{GDBN} has skimmed, but not yet read completely. Finally,
13009 @samp{maint print msymbols} dumps just the minimal symbol information
13010 required for each object file from which @value{GDBN} has read some symbols.
13011 @xref{Files, ,Commands to Specify Files}, for a discussion of how
13012 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
13014 @kindex maint info symtabs
13015 @kindex maint info psymtabs
13016 @cindex listing @value{GDBN}'s internal symbol tables
13017 @cindex symbol tables, listing @value{GDBN}'s internal
13018 @cindex full symbol tables, listing @value{GDBN}'s internal
13019 @cindex partial symbol tables, listing @value{GDBN}'s internal
13020 @item maint info symtabs @r{[} @var{regexp} @r{]}
13021 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
13023 List the @code{struct symtab} or @code{struct partial_symtab}
13024 structures whose names match @var{regexp}. If @var{regexp} is not
13025 given, list them all. The output includes expressions which you can
13026 copy into a @value{GDBN} debugging this one to examine a particular
13027 structure in more detail. For example:
13030 (@value{GDBP}) maint info psymtabs dwarf2read
13031 @{ objfile /home/gnu/build/gdb/gdb
13032 ((struct objfile *) 0x82e69d0)
13033 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
13034 ((struct partial_symtab *) 0x8474b10)
13037 text addresses 0x814d3c8 -- 0x8158074
13038 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
13039 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
13040 dependencies (none)
13043 (@value{GDBP}) maint info symtabs
13047 We see that there is one partial symbol table whose filename contains
13048 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
13049 and we see that @value{GDBN} has not read in any symtabs yet at all.
13050 If we set a breakpoint on a function, that will cause @value{GDBN} to
13051 read the symtab for the compilation unit containing that function:
13054 (@value{GDBP}) break dwarf2_psymtab_to_symtab
13055 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
13057 (@value{GDBP}) maint info symtabs
13058 @{ objfile /home/gnu/build/gdb/gdb
13059 ((struct objfile *) 0x82e69d0)
13060 @{ symtab /home/gnu/src/gdb/dwarf2read.c
13061 ((struct symtab *) 0x86c1f38)
13064 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
13065 linetable ((struct linetable *) 0x8370fa0)
13066 debugformat DWARF 2
13075 @chapter Altering Execution
13077 Once you think you have found an error in your program, you might want to
13078 find out for certain whether correcting the apparent error would lead to
13079 correct results in the rest of the run. You can find the answer by
13080 experiment, using the @value{GDBN} features for altering execution of the
13083 For example, you can store new values into variables or memory
13084 locations, give your program a signal, restart it at a different
13085 address, or even return prematurely from a function.
13088 * Assignment:: Assignment to variables
13089 * Jumping:: Continuing at a different address
13090 * Signaling:: Giving your program a signal
13091 * Returning:: Returning from a function
13092 * Calling:: Calling your program's functions
13093 * Patching:: Patching your program
13097 @section Assignment to Variables
13100 @cindex setting variables
13101 To alter the value of a variable, evaluate an assignment expression.
13102 @xref{Expressions, ,Expressions}. For example,
13109 stores the value 4 into the variable @code{x}, and then prints the
13110 value of the assignment expression (which is 4).
13111 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
13112 information on operators in supported languages.
13114 @kindex set variable
13115 @cindex variables, setting
13116 If you are not interested in seeing the value of the assignment, use the
13117 @code{set} command instead of the @code{print} command. @code{set} is
13118 really the same as @code{print} except that the expression's value is
13119 not printed and is not put in the value history (@pxref{Value History,
13120 ,Value History}). The expression is evaluated only for its effects.
13122 If the beginning of the argument string of the @code{set} command
13123 appears identical to a @code{set} subcommand, use the @code{set
13124 variable} command instead of just @code{set}. This command is identical
13125 to @code{set} except for its lack of subcommands. For example, if your
13126 program has a variable @code{width}, you get an error if you try to set
13127 a new value with just @samp{set width=13}, because @value{GDBN} has the
13128 command @code{set width}:
13131 (@value{GDBP}) whatis width
13133 (@value{GDBP}) p width
13135 (@value{GDBP}) set width=47
13136 Invalid syntax in expression.
13140 The invalid expression, of course, is @samp{=47}. In
13141 order to actually set the program's variable @code{width}, use
13144 (@value{GDBP}) set var width=47
13147 Because the @code{set} command has many subcommands that can conflict
13148 with the names of program variables, it is a good idea to use the
13149 @code{set variable} command instead of just @code{set}. For example, if
13150 your program has a variable @code{g}, you run into problems if you try
13151 to set a new value with just @samp{set g=4}, because @value{GDBN} has
13152 the command @code{set gnutarget}, abbreviated @code{set g}:
13156 (@value{GDBP}) whatis g
13160 (@value{GDBP}) set g=4
13164 The program being debugged has been started already.
13165 Start it from the beginning? (y or n) y
13166 Starting program: /home/smith/cc_progs/a.out
13167 "/home/smith/cc_progs/a.out": can't open to read symbols:
13168 Invalid bfd target.
13169 (@value{GDBP}) show g
13170 The current BFD target is "=4".
13175 The program variable @code{g} did not change, and you silently set the
13176 @code{gnutarget} to an invalid value. In order to set the variable
13180 (@value{GDBP}) set var g=4
13183 @value{GDBN} allows more implicit conversions in assignments than C; you can
13184 freely store an integer value into a pointer variable or vice versa,
13185 and you can convert any structure to any other structure that is the
13186 same length or shorter.
13187 @comment FIXME: how do structs align/pad in these conversions?
13188 @comment /doc@cygnus.com 18dec1990
13190 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
13191 construct to generate a value of specified type at a specified address
13192 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
13193 to memory location @code{0x83040} as an integer (which implies a certain size
13194 and representation in memory), and
13197 set @{int@}0x83040 = 4
13201 stores the value 4 into that memory location.
13204 @section Continuing at a Different Address
13206 Ordinarily, when you continue your program, you do so at the place where
13207 it stopped, with the @code{continue} command. You can instead continue at
13208 an address of your own choosing, with the following commands:
13212 @item jump @var{linespec}
13213 @itemx jump @var{location}
13214 Resume execution at line @var{linespec} or at address given by
13215 @var{location}. Execution stops again immediately if there is a
13216 breakpoint there. @xref{Specify Location}, for a description of the
13217 different forms of @var{linespec} and @var{location}. It is common
13218 practice to use the @code{tbreak} command in conjunction with
13219 @code{jump}. @xref{Set Breaks, ,Setting Breakpoints}.
13221 The @code{jump} command does not change the current stack frame, or
13222 the stack pointer, or the contents of any memory location or any
13223 register other than the program counter. If line @var{linespec} is in
13224 a different function from the one currently executing, the results may
13225 be bizarre if the two functions expect different patterns of arguments or
13226 of local variables. For this reason, the @code{jump} command requests
13227 confirmation if the specified line is not in the function currently
13228 executing. However, even bizarre results are predictable if you are
13229 well acquainted with the machine-language code of your program.
13232 @c Doesn't work on HP-UX; have to set $pcoqh and $pcoqt.
13233 On many systems, you can get much the same effect as the @code{jump}
13234 command by storing a new value into the register @code{$pc}. The
13235 difference is that this does not start your program running; it only
13236 changes the address of where it @emph{will} run when you continue. For
13244 makes the next @code{continue} command or stepping command execute at
13245 address @code{0x485}, rather than at the address where your program stopped.
13246 @xref{Continuing and Stepping, ,Continuing and Stepping}.
13248 The most common occasion to use the @code{jump} command is to back
13249 up---perhaps with more breakpoints set---over a portion of a program
13250 that has already executed, in order to examine its execution in more
13255 @section Giving your Program a Signal
13256 @cindex deliver a signal to a program
13260 @item signal @var{signal}
13261 Resume execution where your program stopped, but immediately give it the
13262 signal @var{signal}. @var{signal} can be the name or the number of a
13263 signal. For example, on many systems @code{signal 2} and @code{signal
13264 SIGINT} are both ways of sending an interrupt signal.
13266 Alternatively, if @var{signal} is zero, continue execution without
13267 giving a signal. This is useful when your program stopped on account of
13268 a signal and would ordinary see the signal when resumed with the
13269 @code{continue} command; @samp{signal 0} causes it to resume without a
13272 @code{signal} does not repeat when you press @key{RET} a second time
13273 after executing the command.
13277 Invoking the @code{signal} command is not the same as invoking the
13278 @code{kill} utility from the shell. Sending a signal with @code{kill}
13279 causes @value{GDBN} to decide what to do with the signal depending on
13280 the signal handling tables (@pxref{Signals}). The @code{signal} command
13281 passes the signal directly to your program.
13285 @section Returning from a Function
13288 @cindex returning from a function
13291 @itemx return @var{expression}
13292 You can cancel execution of a function call with the @code{return}
13293 command. If you give an
13294 @var{expression} argument, its value is used as the function's return
13298 When you use @code{return}, @value{GDBN} discards the selected stack frame
13299 (and all frames within it). You can think of this as making the
13300 discarded frame return prematurely. If you wish to specify a value to
13301 be returned, give that value as the argument to @code{return}.
13303 This pops the selected stack frame (@pxref{Selection, ,Selecting a
13304 Frame}), and any other frames inside of it, leaving its caller as the
13305 innermost remaining frame. That frame becomes selected. The
13306 specified value is stored in the registers used for returning values
13309 The @code{return} command does not resume execution; it leaves the
13310 program stopped in the state that would exist if the function had just
13311 returned. In contrast, the @code{finish} command (@pxref{Continuing
13312 and Stepping, ,Continuing and Stepping}) resumes execution until the
13313 selected stack frame returns naturally.
13315 @value{GDBN} needs to know how the @var{expression} argument should be set for
13316 the inferior. The concrete registers assignment depends on the OS ABI and the
13317 type being returned by the selected stack frame. For example it is common for
13318 OS ABI to return floating point values in FPU registers while integer values in
13319 CPU registers. Still some ABIs return even floating point values in CPU
13320 registers. Larger integer widths (such as @code{long long int}) also have
13321 specific placement rules. @value{GDBN} already knows the OS ABI from its
13322 current target so it needs to find out also the type being returned to make the
13323 assignment into the right register(s).
13325 Normally, the selected stack frame has debug info. @value{GDBN} will always
13326 use the debug info instead of the implicit type of @var{expression} when the
13327 debug info is available. For example, if you type @kbd{return -1}, and the
13328 function in the current stack frame is declared to return a @code{long long
13329 int}, @value{GDBN} transparently converts the implicit @code{int} value of -1
13330 into a @code{long long int}:
13333 Breakpoint 1, func () at gdb.base/return-nodebug.c:29
13335 (@value{GDBP}) return -1
13336 Make func return now? (y or n) y
13337 #0 0x004004f6 in main () at gdb.base/return-nodebug.c:43
13338 43 printf ("result=%lld\n", func ());
13342 However, if the selected stack frame does not have a debug info, e.g., if the
13343 function was compiled without debug info, @value{GDBN} has to find out the type
13344 to return from user. Specifying a different type by mistake may set the value
13345 in different inferior registers than the caller code expects. For example,
13346 typing @kbd{return -1} with its implicit type @code{int} would set only a part
13347 of a @code{long long int} result for a debug info less function (on 32-bit
13348 architectures). Therefore the user is required to specify the return type by
13349 an appropriate cast explicitly:
13352 Breakpoint 2, 0x0040050b in func ()
13353 (@value{GDBP}) return -1
13354 Return value type not available for selected stack frame.
13355 Please use an explicit cast of the value to return.
13356 (@value{GDBP}) return (long long int) -1
13357 Make selected stack frame return now? (y or n) y
13358 #0 0x00400526 in main ()
13363 @section Calling Program Functions
13366 @cindex calling functions
13367 @cindex inferior functions, calling
13368 @item print @var{expr}
13369 Evaluate the expression @var{expr} and display the resulting value.
13370 @var{expr} may include calls to functions in the program being
13374 @item call @var{expr}
13375 Evaluate the expression @var{expr} without displaying @code{void}
13378 You can use this variant of the @code{print} command if you want to
13379 execute a function from your program that does not return anything
13380 (a.k.a.@: @dfn{a void function}), but without cluttering the output
13381 with @code{void} returned values that @value{GDBN} will otherwise
13382 print. If the result is not void, it is printed and saved in the
13386 It is possible for the function you call via the @code{print} or
13387 @code{call} command to generate a signal (e.g., if there's a bug in
13388 the function, or if you passed it incorrect arguments). What happens
13389 in that case is controlled by the @code{set unwindonsignal} command.
13391 Similarly, with a C@t{++} program it is possible for the function you
13392 call via the @code{print} or @code{call} command to generate an
13393 exception that is not handled due to the constraints of the dummy
13394 frame. In this case, any exception that is raised in the frame, but has
13395 an out-of-frame exception handler will not be found. GDB builds a
13396 dummy-frame for the inferior function call, and the unwinder cannot
13397 seek for exception handlers outside of this dummy-frame. What happens
13398 in that case is controlled by the
13399 @code{set unwind-on-terminating-exception} command.
13402 @item set unwindonsignal
13403 @kindex set unwindonsignal
13404 @cindex unwind stack in called functions
13405 @cindex call dummy stack unwinding
13406 Set unwinding of the stack if a signal is received while in a function
13407 that @value{GDBN} called in the program being debugged. If set to on,
13408 @value{GDBN} unwinds the stack it created for the call and restores
13409 the context to what it was before the call. If set to off (the
13410 default), @value{GDBN} stops in the frame where the signal was
13413 @item show unwindonsignal
13414 @kindex show unwindonsignal
13415 Show the current setting of stack unwinding in the functions called by
13418 @item set unwind-on-terminating-exception
13419 @kindex set unwind-on-terminating-exception
13420 @cindex unwind stack in called functions with unhandled exceptions
13421 @cindex call dummy stack unwinding on unhandled exception.
13422 Set unwinding of the stack if a C@t{++} exception is raised, but left
13423 unhandled while in a function that @value{GDBN} called in the program being
13424 debugged. If set to on (the default), @value{GDBN} unwinds the stack
13425 it created for the call and restores the context to what it was before
13426 the call. If set to off, @value{GDBN} the exception is delivered to
13427 the default C@t{++} exception handler and the inferior terminated.
13429 @item show unwind-on-terminating-exception
13430 @kindex show unwind-on-terminating-exception
13431 Show the current setting of stack unwinding in the functions called by
13436 @cindex weak alias functions
13437 Sometimes, a function you wish to call is actually a @dfn{weak alias}
13438 for another function. In such case, @value{GDBN} might not pick up
13439 the type information, including the types of the function arguments,
13440 which causes @value{GDBN} to call the inferior function incorrectly.
13441 As a result, the called function will function erroneously and may
13442 even crash. A solution to that is to use the name of the aliased
13446 @section Patching Programs
13448 @cindex patching binaries
13449 @cindex writing into executables
13450 @cindex writing into corefiles
13452 By default, @value{GDBN} opens the file containing your program's
13453 executable code (or the corefile) read-only. This prevents accidental
13454 alterations to machine code; but it also prevents you from intentionally
13455 patching your program's binary.
13457 If you'd like to be able to patch the binary, you can specify that
13458 explicitly with the @code{set write} command. For example, you might
13459 want to turn on internal debugging flags, or even to make emergency
13465 @itemx set write off
13466 If you specify @samp{set write on}, @value{GDBN} opens executable and
13467 core files for both reading and writing; if you specify @kbd{set write
13468 off} (the default), @value{GDBN} opens them read-only.
13470 If you have already loaded a file, you must load it again (using the
13471 @code{exec-file} or @code{core-file} command) after changing @code{set
13472 write}, for your new setting to take effect.
13476 Display whether executable files and core files are opened for writing
13477 as well as reading.
13481 @chapter @value{GDBN} Files
13483 @value{GDBN} needs to know the file name of the program to be debugged,
13484 both in order to read its symbol table and in order to start your
13485 program. To debug a core dump of a previous run, you must also tell
13486 @value{GDBN} the name of the core dump file.
13489 * Files:: Commands to specify files
13490 * Separate Debug Files:: Debugging information in separate files
13491 * Symbol Errors:: Errors reading symbol files
13492 * Data Files:: GDB data files
13496 @section Commands to Specify Files
13498 @cindex symbol table
13499 @cindex core dump file
13501 You may want to specify executable and core dump file names. The usual
13502 way to do this is at start-up time, using the arguments to
13503 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
13504 Out of @value{GDBN}}).
13506 Occasionally it is necessary to change to a different file during a
13507 @value{GDBN} session. Or you may run @value{GDBN} and forget to
13508 specify a file you want to use. Or you are debugging a remote target
13509 via @code{gdbserver} (@pxref{Server, file, Using the @code{gdbserver}
13510 Program}). In these situations the @value{GDBN} commands to specify
13511 new files are useful.
13514 @cindex executable file
13516 @item file @var{filename}
13517 Use @var{filename} as the program to be debugged. It is read for its
13518 symbols and for the contents of pure memory. It is also the program
13519 executed when you use the @code{run} command. If you do not specify a
13520 directory and the file is not found in the @value{GDBN} working directory,
13521 @value{GDBN} uses the environment variable @code{PATH} as a list of
13522 directories to search, just as the shell does when looking for a program
13523 to run. You can change the value of this variable, for both @value{GDBN}
13524 and your program, using the @code{path} command.
13526 @cindex unlinked object files
13527 @cindex patching object files
13528 You can load unlinked object @file{.o} files into @value{GDBN} using
13529 the @code{file} command. You will not be able to ``run'' an object
13530 file, but you can disassemble functions and inspect variables. Also,
13531 if the underlying BFD functionality supports it, you could use
13532 @kbd{gdb -write} to patch object files using this technique. Note
13533 that @value{GDBN} can neither interpret nor modify relocations in this
13534 case, so branches and some initialized variables will appear to go to
13535 the wrong place. But this feature is still handy from time to time.
13538 @code{file} with no argument makes @value{GDBN} discard any information it
13539 has on both executable file and the symbol table.
13542 @item exec-file @r{[} @var{filename} @r{]}
13543 Specify that the program to be run (but not the symbol table) is found
13544 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
13545 if necessary to locate your program. Omitting @var{filename} means to
13546 discard information on the executable file.
13548 @kindex symbol-file
13549 @item symbol-file @r{[} @var{filename} @r{]}
13550 Read symbol table information from file @var{filename}. @code{PATH} is
13551 searched when necessary. Use the @code{file} command to get both symbol
13552 table and program to run from the same file.
13554 @code{symbol-file} with no argument clears out @value{GDBN} information on your
13555 program's symbol table.
13557 The @code{symbol-file} command causes @value{GDBN} to forget the contents of
13558 some breakpoints and auto-display expressions. This is because they may
13559 contain pointers to the internal data recording symbols and data types,
13560 which are part of the old symbol table data being discarded inside
13563 @code{symbol-file} does not repeat if you press @key{RET} again after
13566 When @value{GDBN} is configured for a particular environment, it
13567 understands debugging information in whatever format is the standard
13568 generated for that environment; you may use either a @sc{gnu} compiler, or
13569 other compilers that adhere to the local conventions.
13570 Best results are usually obtained from @sc{gnu} compilers; for example,
13571 using @code{@value{NGCC}} you can generate debugging information for
13574 For most kinds of object files, with the exception of old SVR3 systems
13575 using COFF, the @code{symbol-file} command does not normally read the
13576 symbol table in full right away. Instead, it scans the symbol table
13577 quickly to find which source files and which symbols are present. The
13578 details are read later, one source file at a time, as they are needed.
13580 The purpose of this two-stage reading strategy is to make @value{GDBN}
13581 start up faster. For the most part, it is invisible except for
13582 occasional pauses while the symbol table details for a particular source
13583 file are being read. (The @code{set verbose} command can turn these
13584 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
13585 Warnings and Messages}.)
13587 We have not implemented the two-stage strategy for COFF yet. When the
13588 symbol table is stored in COFF format, @code{symbol-file} reads the
13589 symbol table data in full right away. Note that ``stabs-in-COFF''
13590 still does the two-stage strategy, since the debug info is actually
13594 @cindex reading symbols immediately
13595 @cindex symbols, reading immediately
13596 @item symbol-file @var{filename} @r{[} -readnow @r{]}
13597 @itemx file @var{filename} @r{[} -readnow @r{]}
13598 You can override the @value{GDBN} two-stage strategy for reading symbol
13599 tables by using the @samp{-readnow} option with any of the commands that
13600 load symbol table information, if you want to be sure @value{GDBN} has the
13601 entire symbol table available.
13603 @c FIXME: for now no mention of directories, since this seems to be in
13604 @c flux. 13mar1992 status is that in theory GDB would look either in
13605 @c current dir or in same dir as myprog; but issues like competing
13606 @c GDB's, or clutter in system dirs, mean that in practice right now
13607 @c only current dir is used. FFish says maybe a special GDB hierarchy
13608 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
13612 @item core-file @r{[}@var{filename}@r{]}
13614 Specify the whereabouts of a core dump file to be used as the ``contents
13615 of memory''. Traditionally, core files contain only some parts of the
13616 address space of the process that generated them; @value{GDBN} can access the
13617 executable file itself for other parts.
13619 @code{core-file} with no argument specifies that no core file is
13622 Note that the core file is ignored when your program is actually running
13623 under @value{GDBN}. So, if you have been running your program and you
13624 wish to debug a core file instead, you must kill the subprocess in which
13625 the program is running. To do this, use the @code{kill} command
13626 (@pxref{Kill Process, ,Killing the Child Process}).
13628 @kindex add-symbol-file
13629 @cindex dynamic linking
13630 @item add-symbol-file @var{filename} @var{address}
13631 @itemx add-symbol-file @var{filename} @var{address} @r{[} -readnow @r{]}
13632 @itemx add-symbol-file @var{filename} @r{-s}@var{section} @var{address} @dots{}
13633 The @code{add-symbol-file} command reads additional symbol table
13634 information from the file @var{filename}. You would use this command
13635 when @var{filename} has been dynamically loaded (by some other means)
13636 into the program that is running. @var{address} should be the memory
13637 address at which the file has been loaded; @value{GDBN} cannot figure
13638 this out for itself. You can additionally specify an arbitrary number
13639 of @samp{@r{-s}@var{section} @var{address}} pairs, to give an explicit
13640 section name and base address for that section. You can specify any
13641 @var{address} as an expression.
13643 The symbol table of the file @var{filename} is added to the symbol table
13644 originally read with the @code{symbol-file} command. You can use the
13645 @code{add-symbol-file} command any number of times; the new symbol data
13646 thus read keeps adding to the old. To discard all old symbol data
13647 instead, use the @code{symbol-file} command without any arguments.
13649 @cindex relocatable object files, reading symbols from
13650 @cindex object files, relocatable, reading symbols from
13651 @cindex reading symbols from relocatable object files
13652 @cindex symbols, reading from relocatable object files
13653 @cindex @file{.o} files, reading symbols from
13654 Although @var{filename} is typically a shared library file, an
13655 executable file, or some other object file which has been fully
13656 relocated for loading into a process, you can also load symbolic
13657 information from relocatable @file{.o} files, as long as:
13661 the file's symbolic information refers only to linker symbols defined in
13662 that file, not to symbols defined by other object files,
13664 every section the file's symbolic information refers to has actually
13665 been loaded into the inferior, as it appears in the file, and
13667 you can determine the address at which every section was loaded, and
13668 provide these to the @code{add-symbol-file} command.
13672 Some embedded operating systems, like Sun Chorus and VxWorks, can load
13673 relocatable files into an already running program; such systems
13674 typically make the requirements above easy to meet. However, it's
13675 important to recognize that many native systems use complex link
13676 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
13677 assembly, for example) that make the requirements difficult to meet. In
13678 general, one cannot assume that using @code{add-symbol-file} to read a
13679 relocatable object file's symbolic information will have the same effect
13680 as linking the relocatable object file into the program in the normal
13683 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
13685 @kindex add-symbol-file-from-memory
13686 @cindex @code{syscall DSO}
13687 @cindex load symbols from memory
13688 @item add-symbol-file-from-memory @var{address}
13689 Load symbols from the given @var{address} in a dynamically loaded
13690 object file whose image is mapped directly into the inferior's memory.
13691 For example, the Linux kernel maps a @code{syscall DSO} into each
13692 process's address space; this DSO provides kernel-specific code for
13693 some system calls. The argument can be any expression whose
13694 evaluation yields the address of the file's shared object file header.
13695 For this command to work, you must have used @code{symbol-file} or
13696 @code{exec-file} commands in advance.
13698 @kindex add-shared-symbol-files
13700 @item add-shared-symbol-files @var{library-file}
13701 @itemx assf @var{library-file}
13702 The @code{add-shared-symbol-files} command can currently be used only
13703 in the Cygwin build of @value{GDBN} on MS-Windows OS, where it is an
13704 alias for the @code{dll-symbols} command (@pxref{Cygwin Native}).
13705 @value{GDBN} automatically looks for shared libraries, however if
13706 @value{GDBN} does not find yours, you can invoke
13707 @code{add-shared-symbol-files}. It takes one argument: the shared
13708 library's file name. @code{assf} is a shorthand alias for
13709 @code{add-shared-symbol-files}.
13712 @item section @var{section} @var{addr}
13713 The @code{section} command changes the base address of the named
13714 @var{section} of the exec file to @var{addr}. This can be used if the
13715 exec file does not contain section addresses, (such as in the
13716 @code{a.out} format), or when the addresses specified in the file
13717 itself are wrong. Each section must be changed separately. The
13718 @code{info files} command, described below, lists all the sections and
13722 @kindex info target
13725 @code{info files} and @code{info target} are synonymous; both print the
13726 current target (@pxref{Targets, ,Specifying a Debugging Target}),
13727 including the names of the executable and core dump files currently in
13728 use by @value{GDBN}, and the files from which symbols were loaded. The
13729 command @code{help target} lists all possible targets rather than
13732 @kindex maint info sections
13733 @item maint info sections
13734 Another command that can give you extra information about program sections
13735 is @code{maint info sections}. In addition to the section information
13736 displayed by @code{info files}, this command displays the flags and file
13737 offset of each section in the executable and core dump files. In addition,
13738 @code{maint info sections} provides the following command options (which
13739 may be arbitrarily combined):
13743 Display sections for all loaded object files, including shared libraries.
13744 @item @var{sections}
13745 Display info only for named @var{sections}.
13746 @item @var{section-flags}
13747 Display info only for sections for which @var{section-flags} are true.
13748 The section flags that @value{GDBN} currently knows about are:
13751 Section will have space allocated in the process when loaded.
13752 Set for all sections except those containing debug information.
13754 Section will be loaded from the file into the child process memory.
13755 Set for pre-initialized code and data, clear for @code{.bss} sections.
13757 Section needs to be relocated before loading.
13759 Section cannot be modified by the child process.
13761 Section contains executable code only.
13763 Section contains data only (no executable code).
13765 Section will reside in ROM.
13767 Section contains data for constructor/destructor lists.
13769 Section is not empty.
13771 An instruction to the linker to not output the section.
13772 @item COFF_SHARED_LIBRARY
13773 A notification to the linker that the section contains
13774 COFF shared library information.
13776 Section contains common symbols.
13779 @kindex set trust-readonly-sections
13780 @cindex read-only sections
13781 @item set trust-readonly-sections on
13782 Tell @value{GDBN} that readonly sections in your object file
13783 really are read-only (i.e.@: that their contents will not change).
13784 In that case, @value{GDBN} can fetch values from these sections
13785 out of the object file, rather than from the target program.
13786 For some targets (notably embedded ones), this can be a significant
13787 enhancement to debugging performance.
13789 The default is off.
13791 @item set trust-readonly-sections off
13792 Tell @value{GDBN} not to trust readonly sections. This means that
13793 the contents of the section might change while the program is running,
13794 and must therefore be fetched from the target when needed.
13796 @item show trust-readonly-sections
13797 Show the current setting of trusting readonly sections.
13800 All file-specifying commands allow both absolute and relative file names
13801 as arguments. @value{GDBN} always converts the file name to an absolute file
13802 name and remembers it that way.
13804 @cindex shared libraries
13805 @anchor{Shared Libraries}
13806 @value{GDBN} supports @sc{gnu}/Linux, MS-Windows, HP-UX, SunOS, SVr4, Irix,
13807 and IBM RS/6000 AIX shared libraries.
13809 On MS-Windows @value{GDBN} must be linked with the Expat library to support
13810 shared libraries. @xref{Expat}.
13812 @value{GDBN} automatically loads symbol definitions from shared libraries
13813 when you use the @code{run} command, or when you examine a core file.
13814 (Before you issue the @code{run} command, @value{GDBN} does not understand
13815 references to a function in a shared library, however---unless you are
13816 debugging a core file).
13818 On HP-UX, if the program loads a library explicitly, @value{GDBN}
13819 automatically loads the symbols at the time of the @code{shl_load} call.
13821 @c FIXME: some @value{GDBN} release may permit some refs to undef
13822 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
13823 @c FIXME...lib; check this from time to time when updating manual
13825 There are times, however, when you may wish to not automatically load
13826 symbol definitions from shared libraries, such as when they are
13827 particularly large or there are many of them.
13829 To control the automatic loading of shared library symbols, use the
13833 @kindex set auto-solib-add
13834 @item set auto-solib-add @var{mode}
13835 If @var{mode} is @code{on}, symbols from all shared object libraries
13836 will be loaded automatically when the inferior begins execution, you
13837 attach to an independently started inferior, or when the dynamic linker
13838 informs @value{GDBN} that a new library has been loaded. If @var{mode}
13839 is @code{off}, symbols must be loaded manually, using the
13840 @code{sharedlibrary} command. The default value is @code{on}.
13842 @cindex memory used for symbol tables
13843 If your program uses lots of shared libraries with debug info that
13844 takes large amounts of memory, you can decrease the @value{GDBN}
13845 memory footprint by preventing it from automatically loading the
13846 symbols from shared libraries. To that end, type @kbd{set
13847 auto-solib-add off} before running the inferior, then load each
13848 library whose debug symbols you do need with @kbd{sharedlibrary
13849 @var{regexp}}, where @var{regexp} is a regular expression that matches
13850 the libraries whose symbols you want to be loaded.
13852 @kindex show auto-solib-add
13853 @item show auto-solib-add
13854 Display the current autoloading mode.
13857 @cindex load shared library
13858 To explicitly load shared library symbols, use the @code{sharedlibrary}
13862 @kindex info sharedlibrary
13864 @item info share @var{regex}
13865 @itemx info sharedlibrary @var{regex}
13866 Print the names of the shared libraries which are currently loaded
13867 that match @var{regex}. If @var{regex} is omitted then print
13868 all shared libraries that are loaded.
13870 @kindex sharedlibrary
13872 @item sharedlibrary @var{regex}
13873 @itemx share @var{regex}
13874 Load shared object library symbols for files matching a
13875 Unix regular expression.
13876 As with files loaded automatically, it only loads shared libraries
13877 required by your program for a core file or after typing @code{run}. If
13878 @var{regex} is omitted all shared libraries required by your program are
13881 @item nosharedlibrary
13882 @kindex nosharedlibrary
13883 @cindex unload symbols from shared libraries
13884 Unload all shared object library symbols. This discards all symbols
13885 that have been loaded from all shared libraries. Symbols from shared
13886 libraries that were loaded by explicit user requests are not
13890 Sometimes you may wish that @value{GDBN} stops and gives you control
13891 when any of shared library events happen. Use the @code{set
13892 stop-on-solib-events} command for this:
13895 @item set stop-on-solib-events
13896 @kindex set stop-on-solib-events
13897 This command controls whether @value{GDBN} should give you control
13898 when the dynamic linker notifies it about some shared library event.
13899 The most common event of interest is loading or unloading of a new
13902 @item show stop-on-solib-events
13903 @kindex show stop-on-solib-events
13904 Show whether @value{GDBN} stops and gives you control when shared
13905 library events happen.
13908 Shared libraries are also supported in many cross or remote debugging
13909 configurations. @value{GDBN} needs to have access to the target's libraries;
13910 this can be accomplished either by providing copies of the libraries
13911 on the host system, or by asking @value{GDBN} to automatically retrieve the
13912 libraries from the target. If copies of the target libraries are
13913 provided, they need to be the same as the target libraries, although the
13914 copies on the target can be stripped as long as the copies on the host are
13917 @cindex where to look for shared libraries
13918 For remote debugging, you need to tell @value{GDBN} where the target
13919 libraries are, so that it can load the correct copies---otherwise, it
13920 may try to load the host's libraries. @value{GDBN} has two variables
13921 to specify the search directories for target libraries.
13924 @cindex prefix for shared library file names
13925 @cindex system root, alternate
13926 @kindex set solib-absolute-prefix
13927 @kindex set sysroot
13928 @item set sysroot @var{path}
13929 Use @var{path} as the system root for the program being debugged. Any
13930 absolute shared library paths will be prefixed with @var{path}; many
13931 runtime loaders store the absolute paths to the shared library in the
13932 target program's memory. If you use @code{set sysroot} to find shared
13933 libraries, they need to be laid out in the same way that they are on
13934 the target, with e.g.@: a @file{/lib} and @file{/usr/lib} hierarchy
13937 If @var{path} starts with the sequence @file{remote:}, @value{GDBN} will
13938 retrieve the target libraries from the remote system. This is only
13939 supported when using a remote target that supports the @code{remote get}
13940 command (@pxref{File Transfer,,Sending files to a remote system}).
13941 The part of @var{path} following the initial @file{remote:}
13942 (if present) is used as system root prefix on the remote file system.
13943 @footnote{If you want to specify a local system root using a directory
13944 that happens to be named @file{remote:}, you need to use some equivalent
13945 variant of the name like @file{./remote:}.}
13947 The @code{set solib-absolute-prefix} command is an alias for @code{set
13950 @cindex default system root
13951 @cindex @samp{--with-sysroot}
13952 You can set the default system root by using the configure-time
13953 @samp{--with-sysroot} option. If the system root is inside
13954 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
13955 @samp{--exec-prefix}), then the default system root will be updated
13956 automatically if the installed @value{GDBN} is moved to a new
13959 @kindex show sysroot
13961 Display the current shared library prefix.
13963 @kindex set solib-search-path
13964 @item set solib-search-path @var{path}
13965 If this variable is set, @var{path} is a colon-separated list of
13966 directories to search for shared libraries. @samp{solib-search-path}
13967 is used after @samp{sysroot} fails to locate the library, or if the
13968 path to the library is relative instead of absolute. If you want to
13969 use @samp{solib-search-path} instead of @samp{sysroot}, be sure to set
13970 @samp{sysroot} to a nonexistent directory to prevent @value{GDBN} from
13971 finding your host's libraries. @samp{sysroot} is preferred; setting
13972 it to a nonexistent directory may interfere with automatic loading
13973 of shared library symbols.
13975 @kindex show solib-search-path
13976 @item show solib-search-path
13977 Display the current shared library search path.
13981 @node Separate Debug Files
13982 @section Debugging Information in Separate Files
13983 @cindex separate debugging information files
13984 @cindex debugging information in separate files
13985 @cindex @file{.debug} subdirectories
13986 @cindex debugging information directory, global
13987 @cindex global debugging information directory
13988 @cindex build ID, and separate debugging files
13989 @cindex @file{.build-id} directory
13991 @value{GDBN} allows you to put a program's debugging information in a
13992 file separate from the executable itself, in a way that allows
13993 @value{GDBN} to find and load the debugging information automatically.
13994 Since debugging information can be very large---sometimes larger
13995 than the executable code itself---some systems distribute debugging
13996 information for their executables in separate files, which users can
13997 install only when they need to debug a problem.
13999 @value{GDBN} supports two ways of specifying the separate debug info
14004 The executable contains a @dfn{debug link} that specifies the name of
14005 the separate debug info file. The separate debug file's name is
14006 usually @file{@var{executable}.debug}, where @var{executable} is the
14007 name of the corresponding executable file without leading directories
14008 (e.g., @file{ls.debug} for @file{/usr/bin/ls}). In addition, the
14009 debug link specifies a 32-bit @dfn{Cyclic Redundancy Check} (CRC)
14010 checksum for the debug file, which @value{GDBN} uses to validate that
14011 the executable and the debug file came from the same build.
14014 The executable contains a @dfn{build ID}, a unique bit string that is
14015 also present in the corresponding debug info file. (This is supported
14016 only on some operating systems, notably those which use the ELF format
14017 for binary files and the @sc{gnu} Binutils.) For more details about
14018 this feature, see the description of the @option{--build-id}
14019 command-line option in @ref{Options, , Command Line Options, ld.info,
14020 The GNU Linker}. The debug info file's name is not specified
14021 explicitly by the build ID, but can be computed from the build ID, see
14025 Depending on the way the debug info file is specified, @value{GDBN}
14026 uses two different methods of looking for the debug file:
14030 For the ``debug link'' method, @value{GDBN} looks up the named file in
14031 the directory of the executable file, then in a subdirectory of that
14032 directory named @file{.debug}, and finally under the global debug
14033 directory, in a subdirectory whose name is identical to the leading
14034 directories of the executable's absolute file name.
14037 For the ``build ID'' method, @value{GDBN} looks in the
14038 @file{.build-id} subdirectory of the global debug directory for a file
14039 named @file{@var{nn}/@var{nnnnnnnn}.debug}, where @var{nn} are the
14040 first 2 hex characters of the build ID bit string, and @var{nnnnnnnn}
14041 are the rest of the bit string. (Real build ID strings are 32 or more
14042 hex characters, not 10.)
14045 So, for example, suppose you ask @value{GDBN} to debug
14046 @file{/usr/bin/ls}, which has a debug link that specifies the
14047 file @file{ls.debug}, and a build ID whose value in hex is
14048 @code{abcdef1234}. If the global debug directory is
14049 @file{/usr/lib/debug}, then @value{GDBN} will look for the following
14050 debug information files, in the indicated order:
14054 @file{/usr/lib/debug/.build-id/ab/cdef1234.debug}
14056 @file{/usr/bin/ls.debug}
14058 @file{/usr/bin/.debug/ls.debug}
14060 @file{/usr/lib/debug/usr/bin/ls.debug}.
14063 You can set the global debugging info directory's name, and view the
14064 name @value{GDBN} is currently using.
14068 @kindex set debug-file-directory
14069 @item set debug-file-directory @var{directory}
14070 Set the directory which @value{GDBN} searches for separate debugging
14071 information files to @var{directory}.
14073 @kindex show debug-file-directory
14074 @item show debug-file-directory
14075 Show the directory @value{GDBN} searches for separate debugging
14080 @cindex @code{.gnu_debuglink} sections
14081 @cindex debug link sections
14082 A debug link is a special section of the executable file named
14083 @code{.gnu_debuglink}. The section must contain:
14087 A filename, with any leading directory components removed, followed by
14090 zero to three bytes of padding, as needed to reach the next four-byte
14091 boundary within the section, and
14093 a four-byte CRC checksum, stored in the same endianness used for the
14094 executable file itself. The checksum is computed on the debugging
14095 information file's full contents by the function given below, passing
14096 zero as the @var{crc} argument.
14099 Any executable file format can carry a debug link, as long as it can
14100 contain a section named @code{.gnu_debuglink} with the contents
14103 @cindex @code{.note.gnu.build-id} sections
14104 @cindex build ID sections
14105 The build ID is a special section in the executable file (and in other
14106 ELF binary files that @value{GDBN} may consider). This section is
14107 often named @code{.note.gnu.build-id}, but that name is not mandatory.
14108 It contains unique identification for the built files---the ID remains
14109 the same across multiple builds of the same build tree. The default
14110 algorithm SHA1 produces 160 bits (40 hexadecimal characters) of the
14111 content for the build ID string. The same section with an identical
14112 value is present in the original built binary with symbols, in its
14113 stripped variant, and in the separate debugging information file.
14115 The debugging information file itself should be an ordinary
14116 executable, containing a full set of linker symbols, sections, and
14117 debugging information. The sections of the debugging information file
14118 should have the same names, addresses, and sizes as the original file,
14119 but they need not contain any data---much like a @code{.bss} section
14120 in an ordinary executable.
14122 The @sc{gnu} binary utilities (Binutils) package includes the
14123 @samp{objcopy} utility that can produce
14124 the separated executable / debugging information file pairs using the
14125 following commands:
14128 @kbd{objcopy --only-keep-debug foo foo.debug}
14133 These commands remove the debugging
14134 information from the executable file @file{foo} and place it in the file
14135 @file{foo.debug}. You can use the first, second or both methods to link the
14140 The debug link method needs the following additional command to also leave
14141 behind a debug link in @file{foo}:
14144 @kbd{objcopy --add-gnu-debuglink=foo.debug foo}
14147 Ulrich Drepper's @file{elfutils} package, starting with version 0.53, contains
14148 a version of the @code{strip} command such that the command @kbd{strip foo -f
14149 foo.debug} has the same functionality as the two @code{objcopy} commands and
14150 the @code{ln -s} command above, together.
14153 Build ID gets embedded into the main executable using @code{ld --build-id} or
14154 the @value{NGCC} counterpart @code{gcc -Wl,--build-id}. Build ID support plus
14155 compatibility fixes for debug files separation are present in @sc{gnu} binary
14156 utilities (Binutils) package since version 2.18.
14161 @cindex CRC algorithm definition
14162 The CRC used in @code{.gnu_debuglink} is the CRC-32 defined in
14163 IEEE 802.3 using the polynomial:
14165 @c TexInfo requires naked braces for multi-digit exponents for Tex
14166 @c output, but this causes HTML output to barf. HTML has to be set using
14167 @c raw commands. So we end up having to specify this equation in 2
14172 <em>x</em><sup>32</sup> + <em>x</em><sup>26</sup> + <em>x</em><sup>23</sup> + <em>x</em><sup>22</sup> + <em>x</em><sup>16</sup> + <em>x</em><sup>12</sup> + <em>x</em><sup>11</sup>
14173 + <em>x</em><sup>10</sup> + <em>x</em><sup>8</sup> + <em>x</em><sup>7</sup> + <em>x</em><sup>5</sup> + <em>x</em><sup>4</sup> + <em>x</em><sup>2</sup> + <em>x</em> + 1
14179 @math{x^{32} + x^{26} + x^{23} + x^{22} + x^{16} + x^{12} + x^{11}}
14180 @math{+ x^{10} + x^8 + x^7 + x^5 + x^4 + x^2 + x + 1}
14184 The function is computed byte at a time, taking the least
14185 significant bit of each byte first. The initial pattern
14186 @code{0xffffffff} is used, to ensure leading zeros affect the CRC and
14187 the final result is inverted to ensure trailing zeros also affect the
14190 @emph{Note:} This is the same CRC polynomial as used in handling the
14191 @dfn{Remote Serial Protocol} @code{qCRC} packet (@pxref{Remote Protocol,
14192 , @value{GDBN} Remote Serial Protocol}). However in the
14193 case of the Remote Serial Protocol, the CRC is computed @emph{most}
14194 significant bit first, and the result is not inverted, so trailing
14195 zeros have no effect on the CRC value.
14197 To complete the description, we show below the code of the function
14198 which produces the CRC used in @code{.gnu_debuglink}. Inverting the
14199 initially supplied @code{crc} argument means that an initial call to
14200 this function passing in zero will start computing the CRC using
14203 @kindex gnu_debuglink_crc32
14206 gnu_debuglink_crc32 (unsigned long crc,
14207 unsigned char *buf, size_t len)
14209 static const unsigned long crc32_table[256] =
14211 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
14212 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
14213 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
14214 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
14215 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
14216 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
14217 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
14218 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
14219 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
14220 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
14221 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
14222 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
14223 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
14224 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
14225 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
14226 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
14227 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
14228 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
14229 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
14230 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
14231 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
14232 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
14233 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
14234 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
14235 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
14236 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
14237 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
14238 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
14239 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
14240 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
14241 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
14242 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
14243 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
14244 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
14245 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
14246 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
14247 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
14248 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
14249 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
14250 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
14251 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
14252 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
14253 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
14254 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
14255 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
14256 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
14257 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
14258 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
14259 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
14260 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
14261 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
14264 unsigned char *end;
14266 crc = ~crc & 0xffffffff;
14267 for (end = buf + len; buf < end; ++buf)
14268 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
14269 return ~crc & 0xffffffff;
14274 This computation does not apply to the ``build ID'' method.
14277 @node Symbol Errors
14278 @section Errors Reading Symbol Files
14280 While reading a symbol file, @value{GDBN} occasionally encounters problems,
14281 such as symbol types it does not recognize, or known bugs in compiler
14282 output. By default, @value{GDBN} does not notify you of such problems, since
14283 they are relatively common and primarily of interest to people
14284 debugging compilers. If you are interested in seeing information
14285 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
14286 only one message about each such type of problem, no matter how many
14287 times the problem occurs; or you can ask @value{GDBN} to print more messages,
14288 to see how many times the problems occur, with the @code{set
14289 complaints} command (@pxref{Messages/Warnings, ,Optional Warnings and
14292 The messages currently printed, and their meanings, include:
14295 @item inner block not inside outer block in @var{symbol}
14297 The symbol information shows where symbol scopes begin and end
14298 (such as at the start of a function or a block of statements). This
14299 error indicates that an inner scope block is not fully contained
14300 in its outer scope blocks.
14302 @value{GDBN} circumvents the problem by treating the inner block as if it had
14303 the same scope as the outer block. In the error message, @var{symbol}
14304 may be shown as ``@code{(don't know)}'' if the outer block is not a
14307 @item block at @var{address} out of order
14309 The symbol information for symbol scope blocks should occur in
14310 order of increasing addresses. This error indicates that it does not
14313 @value{GDBN} does not circumvent this problem, and has trouble
14314 locating symbols in the source file whose symbols it is reading. (You
14315 can often determine what source file is affected by specifying
14316 @code{set verbose on}. @xref{Messages/Warnings, ,Optional Warnings and
14319 @item bad block start address patched
14321 The symbol information for a symbol scope block has a start address
14322 smaller than the address of the preceding source line. This is known
14323 to occur in the SunOS 4.1.1 (and earlier) C compiler.
14325 @value{GDBN} circumvents the problem by treating the symbol scope block as
14326 starting on the previous source line.
14328 @item bad string table offset in symbol @var{n}
14331 Symbol number @var{n} contains a pointer into the string table which is
14332 larger than the size of the string table.
14334 @value{GDBN} circumvents the problem by considering the symbol to have the
14335 name @code{foo}, which may cause other problems if many symbols end up
14338 @item unknown symbol type @code{0x@var{nn}}
14340 The symbol information contains new data types that @value{GDBN} does
14341 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
14342 uncomprehended information, in hexadecimal.
14344 @value{GDBN} circumvents the error by ignoring this symbol information.
14345 This usually allows you to debug your program, though certain symbols
14346 are not accessible. If you encounter such a problem and feel like
14347 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
14348 on @code{complain}, then go up to the function @code{read_dbx_symtab}
14349 and examine @code{*bufp} to see the symbol.
14351 @item stub type has NULL name
14353 @value{GDBN} could not find the full definition for a struct or class.
14355 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
14356 The symbol information for a C@t{++} member function is missing some
14357 information that recent versions of the compiler should have output for
14360 @item info mismatch between compiler and debugger
14362 @value{GDBN} could not parse a type specification output by the compiler.
14367 @section GDB Data Files
14369 @cindex prefix for data files
14370 @value{GDBN} will sometimes read an auxiliary data file. These files
14371 are kept in a directory known as the @dfn{data directory}.
14373 You can set the data directory's name, and view the name @value{GDBN}
14374 is currently using.
14377 @kindex set data-directory
14378 @item set data-directory @var{directory}
14379 Set the directory which @value{GDBN} searches for auxiliary data files
14380 to @var{directory}.
14382 @kindex show data-directory
14383 @item show data-directory
14384 Show the directory @value{GDBN} searches for auxiliary data files.
14387 @cindex default data directory
14388 @cindex @samp{--with-gdb-datadir}
14389 You can set the default data directory by using the configure-time
14390 @samp{--with-gdb-datadir} option. If the data directory is inside
14391 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
14392 @samp{--exec-prefix}), then the default data directory will be updated
14393 automatically if the installed @value{GDBN} is moved to a new
14397 @chapter Specifying a Debugging Target
14399 @cindex debugging target
14400 A @dfn{target} is the execution environment occupied by your program.
14402 Often, @value{GDBN} runs in the same host environment as your program;
14403 in that case, the debugging target is specified as a side effect when
14404 you use the @code{file} or @code{core} commands. When you need more
14405 flexibility---for example, running @value{GDBN} on a physically separate
14406 host, or controlling a standalone system over a serial port or a
14407 realtime system over a TCP/IP connection---you can use the @code{target}
14408 command to specify one of the target types configured for @value{GDBN}
14409 (@pxref{Target Commands, ,Commands for Managing Targets}).
14411 @cindex target architecture
14412 It is possible to build @value{GDBN} for several different @dfn{target
14413 architectures}. When @value{GDBN} is built like that, you can choose
14414 one of the available architectures with the @kbd{set architecture}
14418 @kindex set architecture
14419 @kindex show architecture
14420 @item set architecture @var{arch}
14421 This command sets the current target architecture to @var{arch}. The
14422 value of @var{arch} can be @code{"auto"}, in addition to one of the
14423 supported architectures.
14425 @item show architecture
14426 Show the current target architecture.
14428 @item set processor
14430 @kindex set processor
14431 @kindex show processor
14432 These are alias commands for, respectively, @code{set architecture}
14433 and @code{show architecture}.
14437 * Active Targets:: Active targets
14438 * Target Commands:: Commands for managing targets
14439 * Byte Order:: Choosing target byte order
14442 @node Active Targets
14443 @section Active Targets
14445 @cindex stacking targets
14446 @cindex active targets
14447 @cindex multiple targets
14449 There are three classes of targets: processes, core files, and
14450 executable files. @value{GDBN} can work concurrently on up to three
14451 active targets, one in each class. This allows you to (for example)
14452 start a process and inspect its activity without abandoning your work on
14455 For example, if you execute @samp{gdb a.out}, then the executable file
14456 @code{a.out} is the only active target. If you designate a core file as
14457 well---presumably from a prior run that crashed and coredumped---then
14458 @value{GDBN} has two active targets and uses them in tandem, looking
14459 first in the corefile target, then in the executable file, to satisfy
14460 requests for memory addresses. (Typically, these two classes of target
14461 are complementary, since core files contain only a program's
14462 read-write memory---variables and so on---plus machine status, while
14463 executable files contain only the program text and initialized data.)
14465 When you type @code{run}, your executable file becomes an active process
14466 target as well. When a process target is active, all @value{GDBN}
14467 commands requesting memory addresses refer to that target; addresses in
14468 an active core file or executable file target are obscured while the
14469 process target is active.
14471 Use the @code{core-file} and @code{exec-file} commands to select a new
14472 core file or executable target (@pxref{Files, ,Commands to Specify
14473 Files}). To specify as a target a process that is already running, use
14474 the @code{attach} command (@pxref{Attach, ,Debugging an Already-running
14477 @node Target Commands
14478 @section Commands for Managing Targets
14481 @item target @var{type} @var{parameters}
14482 Connects the @value{GDBN} host environment to a target machine or
14483 process. A target is typically a protocol for talking to debugging
14484 facilities. You use the argument @var{type} to specify the type or
14485 protocol of the target machine.
14487 Further @var{parameters} are interpreted by the target protocol, but
14488 typically include things like device names or host names to connect
14489 with, process numbers, and baud rates.
14491 The @code{target} command does not repeat if you press @key{RET} again
14492 after executing the command.
14494 @kindex help target
14496 Displays the names of all targets available. To display targets
14497 currently selected, use either @code{info target} or @code{info files}
14498 (@pxref{Files, ,Commands to Specify Files}).
14500 @item help target @var{name}
14501 Describe a particular target, including any parameters necessary to
14504 @kindex set gnutarget
14505 @item set gnutarget @var{args}
14506 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
14507 knows whether it is reading an @dfn{executable},
14508 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
14509 with the @code{set gnutarget} command. Unlike most @code{target} commands,
14510 with @code{gnutarget} the @code{target} refers to a program, not a machine.
14513 @emph{Warning:} To specify a file format with @code{set gnutarget},
14514 you must know the actual BFD name.
14518 @xref{Files, , Commands to Specify Files}.
14520 @kindex show gnutarget
14521 @item show gnutarget
14522 Use the @code{show gnutarget} command to display what file format
14523 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
14524 @value{GDBN} will determine the file format for each file automatically,
14525 and @code{show gnutarget} displays @samp{The current BDF target is "auto"}.
14528 @cindex common targets
14529 Here are some common targets (available, or not, depending on the GDB
14534 @item target exec @var{program}
14535 @cindex executable file target
14536 An executable file. @samp{target exec @var{program}} is the same as
14537 @samp{exec-file @var{program}}.
14539 @item target core @var{filename}
14540 @cindex core dump file target
14541 A core dump file. @samp{target core @var{filename}} is the same as
14542 @samp{core-file @var{filename}}.
14544 @item target remote @var{medium}
14545 @cindex remote target
14546 A remote system connected to @value{GDBN} via a serial line or network
14547 connection. This command tells @value{GDBN} to use its own remote
14548 protocol over @var{medium} for debugging. @xref{Remote Debugging}.
14550 For example, if you have a board connected to @file{/dev/ttya} on the
14551 machine running @value{GDBN}, you could say:
14554 target remote /dev/ttya
14557 @code{target remote} supports the @code{load} command. This is only
14558 useful if you have some other way of getting the stub to the target
14559 system, and you can put it somewhere in memory where it won't get
14560 clobbered by the download.
14563 @cindex built-in simulator target
14564 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
14572 works; however, you cannot assume that a specific memory map, device
14573 drivers, or even basic I/O is available, although some simulators do
14574 provide these. For info about any processor-specific simulator details,
14575 see the appropriate section in @ref{Embedded Processors, ,Embedded
14580 Some configurations may include these targets as well:
14584 @item target nrom @var{dev}
14585 @cindex NetROM ROM emulator target
14586 NetROM ROM emulator. This target only supports downloading.
14590 Different targets are available on different configurations of @value{GDBN};
14591 your configuration may have more or fewer targets.
14593 Many remote targets require you to download the executable's code once
14594 you've successfully established a connection. You may wish to control
14595 various aspects of this process.
14600 @kindex set hash@r{, for remote monitors}
14601 @cindex hash mark while downloading
14602 This command controls whether a hash mark @samp{#} is displayed while
14603 downloading a file to the remote monitor. If on, a hash mark is
14604 displayed after each S-record is successfully downloaded to the
14608 @kindex show hash@r{, for remote monitors}
14609 Show the current status of displaying the hash mark.
14611 @item set debug monitor
14612 @kindex set debug monitor
14613 @cindex display remote monitor communications
14614 Enable or disable display of communications messages between
14615 @value{GDBN} and the remote monitor.
14617 @item show debug monitor
14618 @kindex show debug monitor
14619 Show the current status of displaying communications between
14620 @value{GDBN} and the remote monitor.
14625 @kindex load @var{filename}
14626 @item load @var{filename}
14628 Depending on what remote debugging facilities are configured into
14629 @value{GDBN}, the @code{load} command may be available. Where it exists, it
14630 is meant to make @var{filename} (an executable) available for debugging
14631 on the remote system---by downloading, or dynamic linking, for example.
14632 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
14633 the @code{add-symbol-file} command.
14635 If your @value{GDBN} does not have a @code{load} command, attempting to
14636 execute it gets the error message ``@code{You can't do that when your
14637 target is @dots{}}''
14639 The file is loaded at whatever address is specified in the executable.
14640 For some object file formats, you can specify the load address when you
14641 link the program; for other formats, like a.out, the object file format
14642 specifies a fixed address.
14643 @c FIXME! This would be a good place for an xref to the GNU linker doc.
14645 Depending on the remote side capabilities, @value{GDBN} may be able to
14646 load programs into flash memory.
14648 @code{load} does not repeat if you press @key{RET} again after using it.
14652 @section Choosing Target Byte Order
14654 @cindex choosing target byte order
14655 @cindex target byte order
14657 Some types of processors, such as the MIPS, PowerPC, and Renesas SH,
14658 offer the ability to run either big-endian or little-endian byte
14659 orders. Usually the executable or symbol will include a bit to
14660 designate the endian-ness, and you will not need to worry about
14661 which to use. However, you may still find it useful to adjust
14662 @value{GDBN}'s idea of processor endian-ness manually.
14666 @item set endian big
14667 Instruct @value{GDBN} to assume the target is big-endian.
14669 @item set endian little
14670 Instruct @value{GDBN} to assume the target is little-endian.
14672 @item set endian auto
14673 Instruct @value{GDBN} to use the byte order associated with the
14677 Display @value{GDBN}'s current idea of the target byte order.
14681 Note that these commands merely adjust interpretation of symbolic
14682 data on the host, and that they have absolutely no effect on the
14686 @node Remote Debugging
14687 @chapter Debugging Remote Programs
14688 @cindex remote debugging
14690 If you are trying to debug a program running on a machine that cannot run
14691 @value{GDBN} in the usual way, it is often useful to use remote debugging.
14692 For example, you might use remote debugging on an operating system kernel,
14693 or on a small system which does not have a general purpose operating system
14694 powerful enough to run a full-featured debugger.
14696 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
14697 to make this work with particular debugging targets. In addition,
14698 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
14699 but not specific to any particular target system) which you can use if you
14700 write the remote stubs---the code that runs on the remote system to
14701 communicate with @value{GDBN}.
14703 Other remote targets may be available in your
14704 configuration of @value{GDBN}; use @code{help target} to list them.
14707 * Connecting:: Connecting to a remote target
14708 * File Transfer:: Sending files to a remote system
14709 * Server:: Using the gdbserver program
14710 * Remote Configuration:: Remote configuration
14711 * Remote Stub:: Implementing a remote stub
14715 @section Connecting to a Remote Target
14717 On the @value{GDBN} host machine, you will need an unstripped copy of
14718 your program, since @value{GDBN} needs symbol and debugging information.
14719 Start up @value{GDBN} as usual, using the name of the local copy of your
14720 program as the first argument.
14722 @cindex @code{target remote}
14723 @value{GDBN} can communicate with the target over a serial line, or
14724 over an @acronym{IP} network using @acronym{TCP} or @acronym{UDP}. In
14725 each case, @value{GDBN} uses the same protocol for debugging your
14726 program; only the medium carrying the debugging packets varies. The
14727 @code{target remote} command establishes a connection to the target.
14728 Its arguments indicate which medium to use:
14732 @item target remote @var{serial-device}
14733 @cindex serial line, @code{target remote}
14734 Use @var{serial-device} to communicate with the target. For example,
14735 to use a serial line connected to the device named @file{/dev/ttyb}:
14738 target remote /dev/ttyb
14741 If you're using a serial line, you may want to give @value{GDBN} the
14742 @w{@samp{--baud}} option, or use the @code{set remotebaud} command
14743 (@pxref{Remote Configuration, set remotebaud}) before the
14744 @code{target} command.
14746 @item target remote @code{@var{host}:@var{port}}
14747 @itemx target remote @code{tcp:@var{host}:@var{port}}
14748 @cindex @acronym{TCP} port, @code{target remote}
14749 Debug using a @acronym{TCP} connection to @var{port} on @var{host}.
14750 The @var{host} may be either a host name or a numeric @acronym{IP}
14751 address; @var{port} must be a decimal number. The @var{host} could be
14752 the target machine itself, if it is directly connected to the net, or
14753 it might be a terminal server which in turn has a serial line to the
14756 For example, to connect to port 2828 on a terminal server named
14760 target remote manyfarms:2828
14763 If your remote target is actually running on the same machine as your
14764 debugger session (e.g.@: a simulator for your target running on the
14765 same host), you can omit the hostname. For example, to connect to
14766 port 1234 on your local machine:
14769 target remote :1234
14773 Note that the colon is still required here.
14775 @item target remote @code{udp:@var{host}:@var{port}}
14776 @cindex @acronym{UDP} port, @code{target remote}
14777 Debug using @acronym{UDP} packets to @var{port} on @var{host}. For example, to
14778 connect to @acronym{UDP} port 2828 on a terminal server named @code{manyfarms}:
14781 target remote udp:manyfarms:2828
14784 When using a @acronym{UDP} connection for remote debugging, you should
14785 keep in mind that the `U' stands for ``Unreliable''. @acronym{UDP}
14786 can silently drop packets on busy or unreliable networks, which will
14787 cause havoc with your debugging session.
14789 @item target remote | @var{command}
14790 @cindex pipe, @code{target remote} to
14791 Run @var{command} in the background and communicate with it using a
14792 pipe. The @var{command} is a shell command, to be parsed and expanded
14793 by the system's command shell, @code{/bin/sh}; it should expect remote
14794 protocol packets on its standard input, and send replies on its
14795 standard output. You could use this to run a stand-alone simulator
14796 that speaks the remote debugging protocol, to make net connections
14797 using programs like @code{ssh}, or for other similar tricks.
14799 If @var{command} closes its standard output (perhaps by exiting),
14800 @value{GDBN} will try to send it a @code{SIGTERM} signal. (If the
14801 program has already exited, this will have no effect.)
14805 Once the connection has been established, you can use all the usual
14806 commands to examine and change data. The remote program is already
14807 running; you can use @kbd{step} and @kbd{continue}, and you do not
14808 need to use @kbd{run}.
14810 @cindex interrupting remote programs
14811 @cindex remote programs, interrupting
14812 Whenever @value{GDBN} is waiting for the remote program, if you type the
14813 interrupt character (often @kbd{Ctrl-c}), @value{GDBN} attempts to stop the
14814 program. This may or may not succeed, depending in part on the hardware
14815 and the serial drivers the remote system uses. If you type the
14816 interrupt character once again, @value{GDBN} displays this prompt:
14819 Interrupted while waiting for the program.
14820 Give up (and stop debugging it)? (y or n)
14823 If you type @kbd{y}, @value{GDBN} abandons the remote debugging session.
14824 (If you decide you want to try again later, you can use @samp{target
14825 remote} again to connect once more.) If you type @kbd{n}, @value{GDBN}
14826 goes back to waiting.
14829 @kindex detach (remote)
14831 When you have finished debugging the remote program, you can use the
14832 @code{detach} command to release it from @value{GDBN} control.
14833 Detaching from the target normally resumes its execution, but the results
14834 will depend on your particular remote stub. After the @code{detach}
14835 command, @value{GDBN} is free to connect to another target.
14839 The @code{disconnect} command behaves like @code{detach}, except that
14840 the target is generally not resumed. It will wait for @value{GDBN}
14841 (this instance or another one) to connect and continue debugging. After
14842 the @code{disconnect} command, @value{GDBN} is again free to connect to
14845 @cindex send command to remote monitor
14846 @cindex extend @value{GDBN} for remote targets
14847 @cindex add new commands for external monitor
14849 @item monitor @var{cmd}
14850 This command allows you to send arbitrary commands directly to the
14851 remote monitor. Since @value{GDBN} doesn't care about the commands it
14852 sends like this, this command is the way to extend @value{GDBN}---you
14853 can add new commands that only the external monitor will understand
14857 @node File Transfer
14858 @section Sending files to a remote system
14859 @cindex remote target, file transfer
14860 @cindex file transfer
14861 @cindex sending files to remote systems
14863 Some remote targets offer the ability to transfer files over the same
14864 connection used to communicate with @value{GDBN}. This is convenient
14865 for targets accessible through other means, e.g.@: @sc{gnu}/Linux systems
14866 running @code{gdbserver} over a network interface. For other targets,
14867 e.g.@: embedded devices with only a single serial port, this may be
14868 the only way to upload or download files.
14870 Not all remote targets support these commands.
14874 @item remote put @var{hostfile} @var{targetfile}
14875 Copy file @var{hostfile} from the host system (the machine running
14876 @value{GDBN}) to @var{targetfile} on the target system.
14879 @item remote get @var{targetfile} @var{hostfile}
14880 Copy file @var{targetfile} from the target system to @var{hostfile}
14881 on the host system.
14883 @kindex remote delete
14884 @item remote delete @var{targetfile}
14885 Delete @var{targetfile} from the target system.
14890 @section Using the @code{gdbserver} Program
14893 @cindex remote connection without stubs
14894 @code{gdbserver} is a control program for Unix-like systems, which
14895 allows you to connect your program with a remote @value{GDBN} via
14896 @code{target remote}---but without linking in the usual debugging stub.
14898 @code{gdbserver} is not a complete replacement for the debugging stubs,
14899 because it requires essentially the same operating-system facilities
14900 that @value{GDBN} itself does. In fact, a system that can run
14901 @code{gdbserver} to connect to a remote @value{GDBN} could also run
14902 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
14903 because it is a much smaller program than @value{GDBN} itself. It is
14904 also easier to port than all of @value{GDBN}, so you may be able to get
14905 started more quickly on a new system by using @code{gdbserver}.
14906 Finally, if you develop code for real-time systems, you may find that
14907 the tradeoffs involved in real-time operation make it more convenient to
14908 do as much development work as possible on another system, for example
14909 by cross-compiling. You can use @code{gdbserver} to make a similar
14910 choice for debugging.
14912 @value{GDBN} and @code{gdbserver} communicate via either a serial line
14913 or a TCP connection, using the standard @value{GDBN} remote serial
14917 @emph{Warning:} @code{gdbserver} does not have any built-in security.
14918 Do not run @code{gdbserver} connected to any public network; a
14919 @value{GDBN} connection to @code{gdbserver} provides access to the
14920 target system with the same privileges as the user running
14924 @subsection Running @code{gdbserver}
14925 @cindex arguments, to @code{gdbserver}
14927 Run @code{gdbserver} on the target system. You need a copy of the
14928 program you want to debug, including any libraries it requires.
14929 @code{gdbserver} does not need your program's symbol table, so you can
14930 strip the program if necessary to save space. @value{GDBN} on the host
14931 system does all the symbol handling.
14933 To use the server, you must tell it how to communicate with @value{GDBN};
14934 the name of your program; and the arguments for your program. The usual
14938 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
14941 @var{comm} is either a device name (to use a serial line) or a TCP
14942 hostname and portnumber. For example, to debug Emacs with the argument
14943 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
14947 target> gdbserver /dev/com1 emacs foo.txt
14950 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
14953 To use a TCP connection instead of a serial line:
14956 target> gdbserver host:2345 emacs foo.txt
14959 The only difference from the previous example is the first argument,
14960 specifying that you are communicating with the host @value{GDBN} via
14961 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
14962 expect a TCP connection from machine @samp{host} to local TCP port 2345.
14963 (Currently, the @samp{host} part is ignored.) You can choose any number
14964 you want for the port number as long as it does not conflict with any
14965 TCP ports already in use on the target system (for example, @code{23} is
14966 reserved for @code{telnet}).@footnote{If you choose a port number that
14967 conflicts with another service, @code{gdbserver} prints an error message
14968 and exits.} You must use the same port number with the host @value{GDBN}
14969 @code{target remote} command.
14971 @subsubsection Attaching to a Running Program
14973 On some targets, @code{gdbserver} can also attach to running programs.
14974 This is accomplished via the @code{--attach} argument. The syntax is:
14977 target> gdbserver --attach @var{comm} @var{pid}
14980 @var{pid} is the process ID of a currently running process. It isn't necessary
14981 to point @code{gdbserver} at a binary for the running process.
14984 @cindex attach to a program by name
14985 You can debug processes by name instead of process ID if your target has the
14986 @code{pidof} utility:
14989 target> gdbserver --attach @var{comm} `pidof @var{program}`
14992 In case more than one copy of @var{program} is running, or @var{program}
14993 has multiple threads, most versions of @code{pidof} support the
14994 @code{-s} option to only return the first process ID.
14996 @subsubsection Multi-Process Mode for @code{gdbserver}
14997 @cindex gdbserver, multiple processes
14998 @cindex multiple processes with gdbserver
15000 When you connect to @code{gdbserver} using @code{target remote},
15001 @code{gdbserver} debugs the specified program only once. When the
15002 program exits, or you detach from it, @value{GDBN} closes the connection
15003 and @code{gdbserver} exits.
15005 If you connect using @kbd{target extended-remote}, @code{gdbserver}
15006 enters multi-process mode. When the debugged program exits, or you
15007 detach from it, @value{GDBN} stays connected to @code{gdbserver} even
15008 though no program is running. The @code{run} and @code{attach}
15009 commands instruct @code{gdbserver} to run or attach to a new program.
15010 The @code{run} command uses @code{set remote exec-file} (@pxref{set
15011 remote exec-file}) to select the program to run. Command line
15012 arguments are supported, except for wildcard expansion and I/O
15013 redirection (@pxref{Arguments}).
15015 To start @code{gdbserver} without supplying an initial command to run
15016 or process ID to attach, use the @option{--multi} command line option.
15017 Then you can connect using @kbd{target extended-remote} and start
15018 the program you want to debug.
15020 @code{gdbserver} does not automatically exit in multi-process mode.
15021 You can terminate it by using @code{monitor exit}
15022 (@pxref{Monitor Commands for gdbserver}).
15024 @subsubsection Other Command-Line Arguments for @code{gdbserver}
15026 The @option{--debug} option tells @code{gdbserver} to display extra
15027 status information about the debugging process. The
15028 @option{--remote-debug} option tells @code{gdbserver} to display
15029 remote protocol debug output. These options are intended for
15030 @code{gdbserver} development and for bug reports to the developers.
15032 The @option{--wrapper} option specifies a wrapper to launch programs
15033 for debugging. The option should be followed by the name of the
15034 wrapper, then any command-line arguments to pass to the wrapper, then
15035 @kbd{--} indicating the end of the wrapper arguments.
15037 @code{gdbserver} runs the specified wrapper program with a combined
15038 command line including the wrapper arguments, then the name of the
15039 program to debug, then any arguments to the program. The wrapper
15040 runs until it executes your program, and then @value{GDBN} gains control.
15042 You can use any program that eventually calls @code{execve} with
15043 its arguments as a wrapper. Several standard Unix utilities do
15044 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
15045 with @code{exec "$@@"} will also work.
15047 For example, you can use @code{env} to pass an environment variable to
15048 the debugged program, without setting the variable in @code{gdbserver}'s
15052 $ gdbserver --wrapper env LD_PRELOAD=libtest.so -- :2222 ./testprog
15055 @subsection Connecting to @code{gdbserver}
15057 Run @value{GDBN} on the host system.
15059 First make sure you have the necessary symbol files. Load symbols for
15060 your application using the @code{file} command before you connect. Use
15061 @code{set sysroot} to locate target libraries (unless your @value{GDBN}
15062 was compiled with the correct sysroot using @code{--with-sysroot}).
15064 The symbol file and target libraries must exactly match the executable
15065 and libraries on the target, with one exception: the files on the host
15066 system should not be stripped, even if the files on the target system
15067 are. Mismatched or missing files will lead to confusing results
15068 during debugging. On @sc{gnu}/Linux targets, mismatched or missing
15069 files may also prevent @code{gdbserver} from debugging multi-threaded
15072 Connect to your target (@pxref{Connecting,,Connecting to a Remote Target}).
15073 For TCP connections, you must start up @code{gdbserver} prior to using
15074 the @code{target remote} command. Otherwise you may get an error whose
15075 text depends on the host system, but which usually looks something like
15076 @samp{Connection refused}. Don't use the @code{load}
15077 command in @value{GDBN} when using @code{gdbserver}, since the program is
15078 already on the target.
15080 @subsection Monitor Commands for @code{gdbserver}
15081 @cindex monitor commands, for @code{gdbserver}
15082 @anchor{Monitor Commands for gdbserver}
15084 During a @value{GDBN} session using @code{gdbserver}, you can use the
15085 @code{monitor} command to send special requests to @code{gdbserver}.
15086 Here are the available commands.
15090 List the available monitor commands.
15092 @item monitor set debug 0
15093 @itemx monitor set debug 1
15094 Disable or enable general debugging messages.
15096 @item monitor set remote-debug 0
15097 @itemx monitor set remote-debug 1
15098 Disable or enable specific debugging messages associated with the remote
15099 protocol (@pxref{Remote Protocol}).
15101 @item monitor set libthread-db-search-path [PATH]
15102 @cindex gdbserver, search path for @code{libthread_db}
15103 When this command is issued, @var{path} is a colon-separated list of
15104 directories to search for @code{libthread_db} (@pxref{Threads,,set
15105 libthread-db-search-path}). If you omit @var{path},
15106 @samp{libthread-db-search-path} will be reset to an empty list.
15109 Tell gdbserver to exit immediately. This command should be followed by
15110 @code{disconnect} to close the debugging session. @code{gdbserver} will
15111 detach from any attached processes and kill any processes it created.
15112 Use @code{monitor exit} to terminate @code{gdbserver} at the end
15113 of a multi-process mode debug session.
15117 @node Remote Configuration
15118 @section Remote Configuration
15121 @kindex show remote
15122 This section documents the configuration options available when
15123 debugging remote programs. For the options related to the File I/O
15124 extensions of the remote protocol, see @ref{system,
15125 system-call-allowed}.
15128 @item set remoteaddresssize @var{bits}
15129 @cindex address size for remote targets
15130 @cindex bits in remote address
15131 Set the maximum size of address in a memory packet to the specified
15132 number of bits. @value{GDBN} will mask off the address bits above
15133 that number, when it passes addresses to the remote target. The
15134 default value is the number of bits in the target's address.
15136 @item show remoteaddresssize
15137 Show the current value of remote address size in bits.
15139 @item set remotebaud @var{n}
15140 @cindex baud rate for remote targets
15141 Set the baud rate for the remote serial I/O to @var{n} baud. The
15142 value is used to set the speed of the serial port used for debugging
15145 @item show remotebaud
15146 Show the current speed of the remote connection.
15148 @item set remotebreak
15149 @cindex interrupt remote programs
15150 @cindex BREAK signal instead of Ctrl-C
15151 @anchor{set remotebreak}
15152 If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote
15153 when you type @kbd{Ctrl-c} to interrupt the program running
15154 on the remote. If set to off, @value{GDBN} sends the @samp{Ctrl-C}
15155 character instead. The default is off, since most remote systems
15156 expect to see @samp{Ctrl-C} as the interrupt signal.
15158 @item show remotebreak
15159 Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to
15160 interrupt the remote program.
15162 @item set remoteflow on
15163 @itemx set remoteflow off
15164 @kindex set remoteflow
15165 Enable or disable hardware flow control (@code{RTS}/@code{CTS})
15166 on the serial port used to communicate to the remote target.
15168 @item show remoteflow
15169 @kindex show remoteflow
15170 Show the current setting of hardware flow control.
15172 @item set remotelogbase @var{base}
15173 Set the base (a.k.a.@: radix) of logging serial protocol
15174 communications to @var{base}. Supported values of @var{base} are:
15175 @code{ascii}, @code{octal}, and @code{hex}. The default is
15178 @item show remotelogbase
15179 Show the current setting of the radix for logging remote serial
15182 @item set remotelogfile @var{file}
15183 @cindex record serial communications on file
15184 Record remote serial communications on the named @var{file}. The
15185 default is not to record at all.
15187 @item show remotelogfile.
15188 Show the current setting of the file name on which to record the
15189 serial communications.
15191 @item set remotetimeout @var{num}
15192 @cindex timeout for serial communications
15193 @cindex remote timeout
15194 Set the timeout limit to wait for the remote target to respond to
15195 @var{num} seconds. The default is 2 seconds.
15197 @item show remotetimeout
15198 Show the current number of seconds to wait for the remote target
15201 @cindex limit hardware breakpoints and watchpoints
15202 @cindex remote target, limit break- and watchpoints
15203 @anchor{set remote hardware-watchpoint-limit}
15204 @anchor{set remote hardware-breakpoint-limit}
15205 @item set remote hardware-watchpoint-limit @var{limit}
15206 @itemx set remote hardware-breakpoint-limit @var{limit}
15207 Restrict @value{GDBN} to using @var{limit} remote hardware breakpoint or
15208 watchpoints. A limit of -1, the default, is treated as unlimited.
15210 @item set remote exec-file @var{filename}
15211 @itemx show remote exec-file
15212 @anchor{set remote exec-file}
15213 @cindex executable file, for remote target
15214 Select the file used for @code{run} with @code{target
15215 extended-remote}. This should be set to a filename valid on the
15216 target system. If it is not set, the target will use a default
15217 filename (e.g.@: the last program run).
15221 @item set tcp auto-retry on
15222 @cindex auto-retry, for remote TCP target
15223 Enable auto-retry for remote TCP connections. This is useful if the remote
15224 debugging agent is launched in parallel with @value{GDBN}; there is a race
15225 condition because the agent may not become ready to accept the connection
15226 before @value{GDBN} attempts to connect. When auto-retry is
15227 enabled, if the initial attempt to connect fails, @value{GDBN} reattempts
15228 to establish the connection using the timeout specified by
15229 @code{set tcp connect-timeout}.
15231 @item set tcp auto-retry off
15232 Do not auto-retry failed TCP connections.
15234 @item show tcp auto-retry
15235 Show the current auto-retry setting.
15237 @item set tcp connect-timeout @var{seconds}
15238 @cindex connection timeout, for remote TCP target
15239 @cindex timeout, for remote target connection
15240 Set the timeout for establishing a TCP connection to the remote target to
15241 @var{seconds}. The timeout affects both polling to retry failed connections
15242 (enabled by @code{set tcp auto-retry on}) and waiting for connections
15243 that are merely slow to complete, and represents an approximate cumulative
15246 @item show tcp connect-timeout
15247 Show the current connection timeout setting.
15250 @cindex remote packets, enabling and disabling
15251 The @value{GDBN} remote protocol autodetects the packets supported by
15252 your debugging stub. If you need to override the autodetection, you
15253 can use these commands to enable or disable individual packets. Each
15254 packet can be set to @samp{on} (the remote target supports this
15255 packet), @samp{off} (the remote target does not support this packet),
15256 or @samp{auto} (detect remote target support for this packet). They
15257 all default to @samp{auto}. For more information about each packet,
15258 see @ref{Remote Protocol}.
15260 During normal use, you should not have to use any of these commands.
15261 If you do, that may be a bug in your remote debugging stub, or a bug
15262 in @value{GDBN}. You may want to report the problem to the
15263 @value{GDBN} developers.
15265 For each packet @var{name}, the command to enable or disable the
15266 packet is @code{set remote @var{name}-packet}. The available settings
15269 @multitable @columnfractions 0.28 0.32 0.25
15272 @tab Related Features
15274 @item @code{fetch-register}
15276 @tab @code{info registers}
15278 @item @code{set-register}
15282 @item @code{binary-download}
15284 @tab @code{load}, @code{set}
15286 @item @code{read-aux-vector}
15287 @tab @code{qXfer:auxv:read}
15288 @tab @code{info auxv}
15290 @item @code{symbol-lookup}
15291 @tab @code{qSymbol}
15292 @tab Detecting multiple threads
15294 @item @code{attach}
15295 @tab @code{vAttach}
15298 @item @code{verbose-resume}
15300 @tab Stepping or resuming multiple threads
15306 @item @code{software-breakpoint}
15310 @item @code{hardware-breakpoint}
15314 @item @code{write-watchpoint}
15318 @item @code{read-watchpoint}
15322 @item @code{access-watchpoint}
15326 @item @code{target-features}
15327 @tab @code{qXfer:features:read}
15328 @tab @code{set architecture}
15330 @item @code{library-info}
15331 @tab @code{qXfer:libraries:read}
15332 @tab @code{info sharedlibrary}
15334 @item @code{memory-map}
15335 @tab @code{qXfer:memory-map:read}
15336 @tab @code{info mem}
15338 @item @code{read-spu-object}
15339 @tab @code{qXfer:spu:read}
15340 @tab @code{info spu}
15342 @item @code{write-spu-object}
15343 @tab @code{qXfer:spu:write}
15344 @tab @code{info spu}
15346 @item @code{read-siginfo-object}
15347 @tab @code{qXfer:siginfo:read}
15348 @tab @code{print $_siginfo}
15350 @item @code{write-siginfo-object}
15351 @tab @code{qXfer:siginfo:write}
15352 @tab @code{set $_siginfo}
15354 @item @code{get-thread-local-@*storage-address}
15355 @tab @code{qGetTLSAddr}
15356 @tab Displaying @code{__thread} variables
15358 @item @code{search-memory}
15359 @tab @code{qSearch:memory}
15362 @item @code{supported-packets}
15363 @tab @code{qSupported}
15364 @tab Remote communications parameters
15366 @item @code{pass-signals}
15367 @tab @code{QPassSignals}
15368 @tab @code{handle @var{signal}}
15370 @item @code{hostio-close-packet}
15371 @tab @code{vFile:close}
15372 @tab @code{remote get}, @code{remote put}
15374 @item @code{hostio-open-packet}
15375 @tab @code{vFile:open}
15376 @tab @code{remote get}, @code{remote put}
15378 @item @code{hostio-pread-packet}
15379 @tab @code{vFile:pread}
15380 @tab @code{remote get}, @code{remote put}
15382 @item @code{hostio-pwrite-packet}
15383 @tab @code{vFile:pwrite}
15384 @tab @code{remote get}, @code{remote put}
15386 @item @code{hostio-unlink-packet}
15387 @tab @code{vFile:unlink}
15388 @tab @code{remote delete}
15390 @item @code{noack-packet}
15391 @tab @code{QStartNoAckMode}
15392 @tab Packet acknowledgment
15394 @item @code{osdata}
15395 @tab @code{qXfer:osdata:read}
15396 @tab @code{info os}
15398 @item @code{query-attached}
15399 @tab @code{qAttached}
15400 @tab Querying remote process attach state.
15404 @section Implementing a Remote Stub
15406 @cindex debugging stub, example
15407 @cindex remote stub, example
15408 @cindex stub example, remote debugging
15409 The stub files provided with @value{GDBN} implement the target side of the
15410 communication protocol, and the @value{GDBN} side is implemented in the
15411 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
15412 these subroutines to communicate, and ignore the details. (If you're
15413 implementing your own stub file, you can still ignore the details: start
15414 with one of the existing stub files. @file{sparc-stub.c} is the best
15415 organized, and therefore the easiest to read.)
15417 @cindex remote serial debugging, overview
15418 To debug a program running on another machine (the debugging
15419 @dfn{target} machine), you must first arrange for all the usual
15420 prerequisites for the program to run by itself. For example, for a C
15425 A startup routine to set up the C runtime environment; these usually
15426 have a name like @file{crt0}. The startup routine may be supplied by
15427 your hardware supplier, or you may have to write your own.
15430 A C subroutine library to support your program's
15431 subroutine calls, notably managing input and output.
15434 A way of getting your program to the other machine---for example, a
15435 download program. These are often supplied by the hardware
15436 manufacturer, but you may have to write your own from hardware
15440 The next step is to arrange for your program to use a serial port to
15441 communicate with the machine where @value{GDBN} is running (the @dfn{host}
15442 machine). In general terms, the scheme looks like this:
15446 @value{GDBN} already understands how to use this protocol; when everything
15447 else is set up, you can simply use the @samp{target remote} command
15448 (@pxref{Targets,,Specifying a Debugging Target}).
15450 @item On the target,
15451 you must link with your program a few special-purpose subroutines that
15452 implement the @value{GDBN} remote serial protocol. The file containing these
15453 subroutines is called a @dfn{debugging stub}.
15455 On certain remote targets, you can use an auxiliary program
15456 @code{gdbserver} instead of linking a stub into your program.
15457 @xref{Server,,Using the @code{gdbserver} Program}, for details.
15460 The debugging stub is specific to the architecture of the remote
15461 machine; for example, use @file{sparc-stub.c} to debug programs on
15464 @cindex remote serial stub list
15465 These working remote stubs are distributed with @value{GDBN}:
15470 @cindex @file{i386-stub.c}
15473 For Intel 386 and compatible architectures.
15476 @cindex @file{m68k-stub.c}
15477 @cindex Motorola 680x0
15479 For Motorola 680x0 architectures.
15482 @cindex @file{sh-stub.c}
15485 For Renesas SH architectures.
15488 @cindex @file{sparc-stub.c}
15490 For @sc{sparc} architectures.
15492 @item sparcl-stub.c
15493 @cindex @file{sparcl-stub.c}
15496 For Fujitsu @sc{sparclite} architectures.
15500 The @file{README} file in the @value{GDBN} distribution may list other
15501 recently added stubs.
15504 * Stub Contents:: What the stub can do for you
15505 * Bootstrapping:: What you must do for the stub
15506 * Debug Session:: Putting it all together
15509 @node Stub Contents
15510 @subsection What the Stub Can Do for You
15512 @cindex remote serial stub
15513 The debugging stub for your architecture supplies these three
15517 @item set_debug_traps
15518 @findex set_debug_traps
15519 @cindex remote serial stub, initialization
15520 This routine arranges for @code{handle_exception} to run when your
15521 program stops. You must call this subroutine explicitly near the
15522 beginning of your program.
15524 @item handle_exception
15525 @findex handle_exception
15526 @cindex remote serial stub, main routine
15527 This is the central workhorse, but your program never calls it
15528 explicitly---the setup code arranges for @code{handle_exception} to
15529 run when a trap is triggered.
15531 @code{handle_exception} takes control when your program stops during
15532 execution (for example, on a breakpoint), and mediates communications
15533 with @value{GDBN} on the host machine. This is where the communications
15534 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
15535 representative on the target machine. It begins by sending summary
15536 information on the state of your program, then continues to execute,
15537 retrieving and transmitting any information @value{GDBN} needs, until you
15538 execute a @value{GDBN} command that makes your program resume; at that point,
15539 @code{handle_exception} returns control to your own code on the target
15543 @cindex @code{breakpoint} subroutine, remote
15544 Use this auxiliary subroutine to make your program contain a
15545 breakpoint. Depending on the particular situation, this may be the only
15546 way for @value{GDBN} to get control. For instance, if your target
15547 machine has some sort of interrupt button, you won't need to call this;
15548 pressing the interrupt button transfers control to
15549 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
15550 simply receiving characters on the serial port may also trigger a trap;
15551 again, in that situation, you don't need to call @code{breakpoint} from
15552 your own program---simply running @samp{target remote} from the host
15553 @value{GDBN} session gets control.
15555 Call @code{breakpoint} if none of these is true, or if you simply want
15556 to make certain your program stops at a predetermined point for the
15557 start of your debugging session.
15560 @node Bootstrapping
15561 @subsection What You Must Do for the Stub
15563 @cindex remote stub, support routines
15564 The debugging stubs that come with @value{GDBN} are set up for a particular
15565 chip architecture, but they have no information about the rest of your
15566 debugging target machine.
15568 First of all you need to tell the stub how to communicate with the
15572 @item int getDebugChar()
15573 @findex getDebugChar
15574 Write this subroutine to read a single character from the serial port.
15575 It may be identical to @code{getchar} for your target system; a
15576 different name is used to allow you to distinguish the two if you wish.
15578 @item void putDebugChar(int)
15579 @findex putDebugChar
15580 Write this subroutine to write a single character to the serial port.
15581 It may be identical to @code{putchar} for your target system; a
15582 different name is used to allow you to distinguish the two if you wish.
15585 @cindex control C, and remote debugging
15586 @cindex interrupting remote targets
15587 If you want @value{GDBN} to be able to stop your program while it is
15588 running, you need to use an interrupt-driven serial driver, and arrange
15589 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
15590 character). That is the character which @value{GDBN} uses to tell the
15591 remote system to stop.
15593 Getting the debugging target to return the proper status to @value{GDBN}
15594 probably requires changes to the standard stub; one quick and dirty way
15595 is to just execute a breakpoint instruction (the ``dirty'' part is that
15596 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
15598 Other routines you need to supply are:
15601 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
15602 @findex exceptionHandler
15603 Write this function to install @var{exception_address} in the exception
15604 handling tables. You need to do this because the stub does not have any
15605 way of knowing what the exception handling tables on your target system
15606 are like (for example, the processor's table might be in @sc{rom},
15607 containing entries which point to a table in @sc{ram}).
15608 @var{exception_number} is the exception number which should be changed;
15609 its meaning is architecture-dependent (for example, different numbers
15610 might represent divide by zero, misaligned access, etc). When this
15611 exception occurs, control should be transferred directly to
15612 @var{exception_address}, and the processor state (stack, registers,
15613 and so on) should be just as it is when a processor exception occurs. So if
15614 you want to use a jump instruction to reach @var{exception_address}, it
15615 should be a simple jump, not a jump to subroutine.
15617 For the 386, @var{exception_address} should be installed as an interrupt
15618 gate so that interrupts are masked while the handler runs. The gate
15619 should be at privilege level 0 (the most privileged level). The
15620 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
15621 help from @code{exceptionHandler}.
15623 @item void flush_i_cache()
15624 @findex flush_i_cache
15625 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
15626 instruction cache, if any, on your target machine. If there is no
15627 instruction cache, this subroutine may be a no-op.
15629 On target machines that have instruction caches, @value{GDBN} requires this
15630 function to make certain that the state of your program is stable.
15634 You must also make sure this library routine is available:
15637 @item void *memset(void *, int, int)
15639 This is the standard library function @code{memset} that sets an area of
15640 memory to a known value. If you have one of the free versions of
15641 @code{libc.a}, @code{memset} can be found there; otherwise, you must
15642 either obtain it from your hardware manufacturer, or write your own.
15645 If you do not use the GNU C compiler, you may need other standard
15646 library subroutines as well; this varies from one stub to another,
15647 but in general the stubs are likely to use any of the common library
15648 subroutines which @code{@value{NGCC}} generates as inline code.
15651 @node Debug Session
15652 @subsection Putting it All Together
15654 @cindex remote serial debugging summary
15655 In summary, when your program is ready to debug, you must follow these
15660 Make sure you have defined the supporting low-level routines
15661 (@pxref{Bootstrapping,,What You Must Do for the Stub}):
15663 @code{getDebugChar}, @code{putDebugChar},
15664 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
15668 Insert these lines near the top of your program:
15676 For the 680x0 stub only, you need to provide a variable called
15677 @code{exceptionHook}. Normally you just use:
15680 void (*exceptionHook)() = 0;
15684 but if before calling @code{set_debug_traps}, you set it to point to a
15685 function in your program, that function is called when
15686 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
15687 error). The function indicated by @code{exceptionHook} is called with
15688 one parameter: an @code{int} which is the exception number.
15691 Compile and link together: your program, the @value{GDBN} debugging stub for
15692 your target architecture, and the supporting subroutines.
15695 Make sure you have a serial connection between your target machine and
15696 the @value{GDBN} host, and identify the serial port on the host.
15699 @c The "remote" target now provides a `load' command, so we should
15700 @c document that. FIXME.
15701 Download your program to your target machine (or get it there by
15702 whatever means the manufacturer provides), and start it.
15705 Start @value{GDBN} on the host, and connect to the target
15706 (@pxref{Connecting,,Connecting to a Remote Target}).
15710 @node Configurations
15711 @chapter Configuration-Specific Information
15713 While nearly all @value{GDBN} commands are available for all native and
15714 cross versions of the debugger, there are some exceptions. This chapter
15715 describes things that are only available in certain configurations.
15717 There are three major categories of configurations: native
15718 configurations, where the host and target are the same, embedded
15719 operating system configurations, which are usually the same for several
15720 different processor architectures, and bare embedded processors, which
15721 are quite different from each other.
15726 * Embedded Processors::
15733 This section describes details specific to particular native
15738 * BSD libkvm Interface:: Debugging BSD kernel memory images
15739 * SVR4 Process Information:: SVR4 process information
15740 * DJGPP Native:: Features specific to the DJGPP port
15741 * Cygwin Native:: Features specific to the Cygwin port
15742 * Hurd Native:: Features specific to @sc{gnu} Hurd
15743 * Neutrino:: Features specific to QNX Neutrino
15744 * Darwin:: Features specific to Darwin
15750 On HP-UX systems, if you refer to a function or variable name that
15751 begins with a dollar sign, @value{GDBN} searches for a user or system
15752 name first, before it searches for a convenience variable.
15755 @node BSD libkvm Interface
15756 @subsection BSD libkvm Interface
15759 @cindex kernel memory image
15760 @cindex kernel crash dump
15762 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
15763 interface that provides a uniform interface for accessing kernel virtual
15764 memory images, including live systems and crash dumps. @value{GDBN}
15765 uses this interface to allow you to debug live kernels and kernel crash
15766 dumps on many native BSD configurations. This is implemented as a
15767 special @code{kvm} debugging target. For debugging a live system, load
15768 the currently running kernel into @value{GDBN} and connect to the
15772 (@value{GDBP}) @b{target kvm}
15775 For debugging crash dumps, provide the file name of the crash dump as an
15779 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
15782 Once connected to the @code{kvm} target, the following commands are
15788 Set current context from the @dfn{Process Control Block} (PCB) address.
15791 Set current context from proc address. This command isn't available on
15792 modern FreeBSD systems.
15795 @node SVR4 Process Information
15796 @subsection SVR4 Process Information
15798 @cindex examine process image
15799 @cindex process info via @file{/proc}
15801 Many versions of SVR4 and compatible systems provide a facility called
15802 @samp{/proc} that can be used to examine the image of a running
15803 process using file-system subroutines. If @value{GDBN} is configured
15804 for an operating system with this facility, the command @code{info
15805 proc} is available to report information about the process running
15806 your program, or about any process running on your system. @code{info
15807 proc} works only on SVR4 systems that include the @code{procfs} code.
15808 This includes, as of this writing, @sc{gnu}/Linux, OSF/1 (Digital
15809 Unix), Solaris, Irix, and Unixware, but not HP-UX, for example.
15815 @itemx info proc @var{process-id}
15816 Summarize available information about any running process. If a
15817 process ID is specified by @var{process-id}, display information about
15818 that process; otherwise display information about the program being
15819 debugged. The summary includes the debugged process ID, the command
15820 line used to invoke it, its current working directory, and its
15821 executable file's absolute file name.
15823 On some systems, @var{process-id} can be of the form
15824 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
15825 within a process. If the optional @var{pid} part is missing, it means
15826 a thread from the process being debugged (the leading @samp{/} still
15827 needs to be present, or else @value{GDBN} will interpret the number as
15828 a process ID rather than a thread ID).
15830 @item info proc mappings
15831 @cindex memory address space mappings
15832 Report the memory address space ranges accessible in the program, with
15833 information on whether the process has read, write, or execute access
15834 rights to each range. On @sc{gnu}/Linux systems, each memory range
15835 includes the object file which is mapped to that range, instead of the
15836 memory access rights to that range.
15838 @item info proc stat
15839 @itemx info proc status
15840 @cindex process detailed status information
15841 These subcommands are specific to @sc{gnu}/Linux systems. They show
15842 the process-related information, including the user ID and group ID;
15843 how many threads are there in the process; its virtual memory usage;
15844 the signals that are pending, blocked, and ignored; its TTY; its
15845 consumption of system and user time; its stack size; its @samp{nice}
15846 value; etc. For more information, see the @samp{proc} man page
15847 (type @kbd{man 5 proc} from your shell prompt).
15849 @item info proc all
15850 Show all the information about the process described under all of the
15851 above @code{info proc} subcommands.
15854 @comment These sub-options of 'info proc' were not included when
15855 @comment procfs.c was re-written. Keep their descriptions around
15856 @comment against the day when someone finds the time to put them back in.
15857 @kindex info proc times
15858 @item info proc times
15859 Starting time, user CPU time, and system CPU time for your program and
15862 @kindex info proc id
15864 Report on the process IDs related to your program: its own process ID,
15865 the ID of its parent, the process group ID, and the session ID.
15868 @item set procfs-trace
15869 @kindex set procfs-trace
15870 @cindex @code{procfs} API calls
15871 This command enables and disables tracing of @code{procfs} API calls.
15873 @item show procfs-trace
15874 @kindex show procfs-trace
15875 Show the current state of @code{procfs} API call tracing.
15877 @item set procfs-file @var{file}
15878 @kindex set procfs-file
15879 Tell @value{GDBN} to write @code{procfs} API trace to the named
15880 @var{file}. @value{GDBN} appends the trace info to the previous
15881 contents of the file. The default is to display the trace on the
15884 @item show procfs-file
15885 @kindex show procfs-file
15886 Show the file to which @code{procfs} API trace is written.
15888 @item proc-trace-entry
15889 @itemx proc-trace-exit
15890 @itemx proc-untrace-entry
15891 @itemx proc-untrace-exit
15892 @kindex proc-trace-entry
15893 @kindex proc-trace-exit
15894 @kindex proc-untrace-entry
15895 @kindex proc-untrace-exit
15896 These commands enable and disable tracing of entries into and exits
15897 from the @code{syscall} interface.
15900 @kindex info pidlist
15901 @cindex process list, QNX Neutrino
15902 For QNX Neutrino only, this command displays the list of all the
15903 processes and all the threads within each process.
15906 @kindex info meminfo
15907 @cindex mapinfo list, QNX Neutrino
15908 For QNX Neutrino only, this command displays the list of all mapinfos.
15912 @subsection Features for Debugging @sc{djgpp} Programs
15913 @cindex @sc{djgpp} debugging
15914 @cindex native @sc{djgpp} debugging
15915 @cindex MS-DOS-specific commands
15918 @sc{djgpp} is a port of the @sc{gnu} development tools to MS-DOS and
15919 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
15920 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
15921 top of real-mode DOS systems and their emulations.
15923 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
15924 defines a few commands specific to the @sc{djgpp} port. This
15925 subsection describes those commands.
15930 This is a prefix of @sc{djgpp}-specific commands which print
15931 information about the target system and important OS structures.
15934 @cindex MS-DOS system info
15935 @cindex free memory information (MS-DOS)
15936 @item info dos sysinfo
15937 This command displays assorted information about the underlying
15938 platform: the CPU type and features, the OS version and flavor, the
15939 DPMI version, and the available conventional and DPMI memory.
15944 @cindex segment descriptor tables
15945 @cindex descriptor tables display
15947 @itemx info dos ldt
15948 @itemx info dos idt
15949 These 3 commands display entries from, respectively, Global, Local,
15950 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
15951 tables are data structures which store a descriptor for each segment
15952 that is currently in use. The segment's selector is an index into a
15953 descriptor table; the table entry for that index holds the
15954 descriptor's base address and limit, and its attributes and access
15957 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
15958 segment (used for both data and the stack), and a DOS segment (which
15959 allows access to DOS/BIOS data structures and absolute addresses in
15960 conventional memory). However, the DPMI host will usually define
15961 additional segments in order to support the DPMI environment.
15963 @cindex garbled pointers
15964 These commands allow to display entries from the descriptor tables.
15965 Without an argument, all entries from the specified table are
15966 displayed. An argument, which should be an integer expression, means
15967 display a single entry whose index is given by the argument. For
15968 example, here's a convenient way to display information about the
15969 debugged program's data segment:
15972 @exdent @code{(@value{GDBP}) info dos ldt $ds}
15973 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
15977 This comes in handy when you want to see whether a pointer is outside
15978 the data segment's limit (i.e.@: @dfn{garbled}).
15980 @cindex page tables display (MS-DOS)
15982 @itemx info dos pte
15983 These two commands display entries from, respectively, the Page
15984 Directory and the Page Tables. Page Directories and Page Tables are
15985 data structures which control how virtual memory addresses are mapped
15986 into physical addresses. A Page Table includes an entry for every
15987 page of memory that is mapped into the program's address space; there
15988 may be several Page Tables, each one holding up to 4096 entries. A
15989 Page Directory has up to 4096 entries, one each for every Page Table
15990 that is currently in use.
15992 Without an argument, @kbd{info dos pde} displays the entire Page
15993 Directory, and @kbd{info dos pte} displays all the entries in all of
15994 the Page Tables. An argument, an integer expression, given to the
15995 @kbd{info dos pde} command means display only that entry from the Page
15996 Directory table. An argument given to the @kbd{info dos pte} command
15997 means display entries from a single Page Table, the one pointed to by
15998 the specified entry in the Page Directory.
16000 @cindex direct memory access (DMA) on MS-DOS
16001 These commands are useful when your program uses @dfn{DMA} (Direct
16002 Memory Access), which needs physical addresses to program the DMA
16005 These commands are supported only with some DPMI servers.
16007 @cindex physical address from linear address
16008 @item info dos address-pte @var{addr}
16009 This command displays the Page Table entry for a specified linear
16010 address. The argument @var{addr} is a linear address which should
16011 already have the appropriate segment's base address added to it,
16012 because this command accepts addresses which may belong to @emph{any}
16013 segment. For example, here's how to display the Page Table entry for
16014 the page where a variable @code{i} is stored:
16017 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
16018 @exdent @code{Page Table entry for address 0x11a00d30:}
16019 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
16023 This says that @code{i} is stored at offset @code{0xd30} from the page
16024 whose physical base address is @code{0x02698000}, and shows all the
16025 attributes of that page.
16027 Note that you must cast the addresses of variables to a @code{char *},
16028 since otherwise the value of @code{__djgpp_base_address}, the base
16029 address of all variables and functions in a @sc{djgpp} program, will
16030 be added using the rules of C pointer arithmetics: if @code{i} is
16031 declared an @code{int}, @value{GDBN} will add 4 times the value of
16032 @code{__djgpp_base_address} to the address of @code{i}.
16034 Here's another example, it displays the Page Table entry for the
16038 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
16039 @exdent @code{Page Table entry for address 0x29110:}
16040 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
16044 (The @code{+ 3} offset is because the transfer buffer's address is the
16045 3rd member of the @code{_go32_info_block} structure.) The output
16046 clearly shows that this DPMI server maps the addresses in conventional
16047 memory 1:1, i.e.@: the physical (@code{0x00029000} + @code{0x110}) and
16048 linear (@code{0x29110}) addresses are identical.
16050 This command is supported only with some DPMI servers.
16053 @cindex DOS serial data link, remote debugging
16054 In addition to native debugging, the DJGPP port supports remote
16055 debugging via a serial data link. The following commands are specific
16056 to remote serial debugging in the DJGPP port of @value{GDBN}.
16059 @kindex set com1base
16060 @kindex set com1irq
16061 @kindex set com2base
16062 @kindex set com2irq
16063 @kindex set com3base
16064 @kindex set com3irq
16065 @kindex set com4base
16066 @kindex set com4irq
16067 @item set com1base @var{addr}
16068 This command sets the base I/O port address of the @file{COM1} serial
16071 @item set com1irq @var{irq}
16072 This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use
16073 for the @file{COM1} serial port.
16075 There are similar commands @samp{set com2base}, @samp{set com3irq},
16076 etc.@: for setting the port address and the @code{IRQ} lines for the
16079 @kindex show com1base
16080 @kindex show com1irq
16081 @kindex show com2base
16082 @kindex show com2irq
16083 @kindex show com3base
16084 @kindex show com3irq
16085 @kindex show com4base
16086 @kindex show com4irq
16087 The related commands @samp{show com1base}, @samp{show com1irq} etc.@:
16088 display the current settings of the base address and the @code{IRQ}
16089 lines used by the COM ports.
16092 @kindex info serial
16093 @cindex DOS serial port status
16094 This command prints the status of the 4 DOS serial ports. For each
16095 port, it prints whether it's active or not, its I/O base address and
16096 IRQ number, whether it uses a 16550-style FIFO, its baudrate, and the
16097 counts of various errors encountered so far.
16101 @node Cygwin Native
16102 @subsection Features for Debugging MS Windows PE Executables
16103 @cindex MS Windows debugging
16104 @cindex native Cygwin debugging
16105 @cindex Cygwin-specific commands
16107 @value{GDBN} supports native debugging of MS Windows programs, including
16108 DLLs with and without symbolic debugging information.
16110 @cindex Ctrl-BREAK, MS-Windows
16111 @cindex interrupt debuggee on MS-Windows
16112 MS-Windows programs that call @code{SetConsoleMode} to switch off the
16113 special meaning of the @samp{Ctrl-C} keystroke cannot be interrupted
16114 by typing @kbd{C-c}. For this reason, @value{GDBN} on MS-Windows
16115 supports @kbd{C-@key{BREAK}} as an alternative interrupt key
16116 sequence, which can be used to interrupt the debuggee even if it
16119 There are various additional Cygwin-specific commands, described in
16120 this section. Working with DLLs that have no debugging symbols is
16121 described in @ref{Non-debug DLL Symbols}.
16126 This is a prefix of MS Windows-specific commands which print
16127 information about the target system and important OS structures.
16129 @item info w32 selector
16130 This command displays information returned by
16131 the Win32 API @code{GetThreadSelectorEntry} function.
16132 It takes an optional argument that is evaluated to
16133 a long value to give the information about this given selector.
16134 Without argument, this command displays information
16135 about the six segment registers.
16139 This is a Cygwin-specific alias of @code{info shared}.
16141 @kindex dll-symbols
16143 This command loads symbols from a dll similarly to
16144 add-sym command but without the need to specify a base address.
16146 @kindex set cygwin-exceptions
16147 @cindex debugging the Cygwin DLL
16148 @cindex Cygwin DLL, debugging
16149 @item set cygwin-exceptions @var{mode}
16150 If @var{mode} is @code{on}, @value{GDBN} will break on exceptions that
16151 happen inside the Cygwin DLL. If @var{mode} is @code{off},
16152 @value{GDBN} will delay recognition of exceptions, and may ignore some
16153 exceptions which seem to be caused by internal Cygwin DLL
16154 ``bookkeeping''. This option is meant primarily for debugging the
16155 Cygwin DLL itself; the default value is @code{off} to avoid annoying
16156 @value{GDBN} users with false @code{SIGSEGV} signals.
16158 @kindex show cygwin-exceptions
16159 @item show cygwin-exceptions
16160 Displays whether @value{GDBN} will break on exceptions that happen
16161 inside the Cygwin DLL itself.
16163 @kindex set new-console
16164 @item set new-console @var{mode}
16165 If @var{mode} is @code{on} the debuggee will
16166 be started in a new console on next start.
16167 If @var{mode} is @code{off}i, the debuggee will
16168 be started in the same console as the debugger.
16170 @kindex show new-console
16171 @item show new-console
16172 Displays whether a new console is used
16173 when the debuggee is started.
16175 @kindex set new-group
16176 @item set new-group @var{mode}
16177 This boolean value controls whether the debuggee should
16178 start a new group or stay in the same group as the debugger.
16179 This affects the way the Windows OS handles
16182 @kindex show new-group
16183 @item show new-group
16184 Displays current value of new-group boolean.
16186 @kindex set debugevents
16187 @item set debugevents
16188 This boolean value adds debug output concerning kernel events related
16189 to the debuggee seen by the debugger. This includes events that
16190 signal thread and process creation and exit, DLL loading and
16191 unloading, console interrupts, and debugging messages produced by the
16192 Windows @code{OutputDebugString} API call.
16194 @kindex set debugexec
16195 @item set debugexec
16196 This boolean value adds debug output concerning execute events
16197 (such as resume thread) seen by the debugger.
16199 @kindex set debugexceptions
16200 @item set debugexceptions
16201 This boolean value adds debug output concerning exceptions in the
16202 debuggee seen by the debugger.
16204 @kindex set debugmemory
16205 @item set debugmemory
16206 This boolean value adds debug output concerning debuggee memory reads
16207 and writes by the debugger.
16211 This boolean values specifies whether the debuggee is called
16212 via a shell or directly (default value is on).
16216 Displays if the debuggee will be started with a shell.
16221 * Non-debug DLL Symbols:: Support for DLLs without debugging symbols
16224 @node Non-debug DLL Symbols
16225 @subsubsection Support for DLLs without Debugging Symbols
16226 @cindex DLLs with no debugging symbols
16227 @cindex Minimal symbols and DLLs
16229 Very often on windows, some of the DLLs that your program relies on do
16230 not include symbolic debugging information (for example,
16231 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
16232 symbols in a DLL, it relies on the minimal amount of symbolic
16233 information contained in the DLL's export table. This section
16234 describes working with such symbols, known internally to @value{GDBN} as
16235 ``minimal symbols''.
16237 Note that before the debugged program has started execution, no DLLs
16238 will have been loaded. The easiest way around this problem is simply to
16239 start the program --- either by setting a breakpoint or letting the
16240 program run once to completion. It is also possible to force
16241 @value{GDBN} to load a particular DLL before starting the executable ---
16242 see the shared library information in @ref{Files}, or the
16243 @code{dll-symbols} command in @ref{Cygwin Native}. Currently,
16244 explicitly loading symbols from a DLL with no debugging information will
16245 cause the symbol names to be duplicated in @value{GDBN}'s lookup table,
16246 which may adversely affect symbol lookup performance.
16248 @subsubsection DLL Name Prefixes
16250 In keeping with the naming conventions used by the Microsoft debugging
16251 tools, DLL export symbols are made available with a prefix based on the
16252 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
16253 also entered into the symbol table, so @code{CreateFileA} is often
16254 sufficient. In some cases there will be name clashes within a program
16255 (particularly if the executable itself includes full debugging symbols)
16256 necessitating the use of the fully qualified name when referring to the
16257 contents of the DLL. Use single-quotes around the name to avoid the
16258 exclamation mark (``!'') being interpreted as a language operator.
16260 Note that the internal name of the DLL may be all upper-case, even
16261 though the file name of the DLL is lower-case, or vice-versa. Since
16262 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
16263 some confusion. If in doubt, try the @code{info functions} and
16264 @code{info variables} commands or even @code{maint print msymbols}
16265 (@pxref{Symbols}). Here's an example:
16268 (@value{GDBP}) info function CreateFileA
16269 All functions matching regular expression "CreateFileA":
16271 Non-debugging symbols:
16272 0x77e885f4 CreateFileA
16273 0x77e885f4 KERNEL32!CreateFileA
16277 (@value{GDBP}) info function !
16278 All functions matching regular expression "!":
16280 Non-debugging symbols:
16281 0x6100114c cygwin1!__assert
16282 0x61004034 cygwin1!_dll_crt0@@0
16283 0x61004240 cygwin1!dll_crt0(per_process *)
16287 @subsubsection Working with Minimal Symbols
16289 Symbols extracted from a DLL's export table do not contain very much
16290 type information. All that @value{GDBN} can do is guess whether a symbol
16291 refers to a function or variable depending on the linker section that
16292 contains the symbol. Also note that the actual contents of the memory
16293 contained in a DLL are not available unless the program is running. This
16294 means that you cannot examine the contents of a variable or disassemble
16295 a function within a DLL without a running program.
16297 Variables are generally treated as pointers and dereferenced
16298 automatically. For this reason, it is often necessary to prefix a
16299 variable name with the address-of operator (``&'') and provide explicit
16300 type information in the command. Here's an example of the type of
16304 (@value{GDBP}) print 'cygwin1!__argv'
16309 (@value{GDBP}) x 'cygwin1!__argv'
16310 0x10021610: "\230y\""
16313 And two possible solutions:
16316 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
16317 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
16321 (@value{GDBP}) x/2x &'cygwin1!__argv'
16322 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
16323 (@value{GDBP}) x/x 0x10021608
16324 0x10021608: 0x0022fd98
16325 (@value{GDBP}) x/s 0x0022fd98
16326 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
16329 Setting a break point within a DLL is possible even before the program
16330 starts execution. However, under these circumstances, @value{GDBN} can't
16331 examine the initial instructions of the function in order to skip the
16332 function's frame set-up code. You can work around this by using ``*&''
16333 to set the breakpoint at a raw memory address:
16336 (@value{GDBP}) break *&'python22!PyOS_Readline'
16337 Breakpoint 1 at 0x1e04eff0
16340 The author of these extensions is not entirely convinced that setting a
16341 break point within a shared DLL like @file{kernel32.dll} is completely
16345 @subsection Commands Specific to @sc{gnu} Hurd Systems
16346 @cindex @sc{gnu} Hurd debugging
16348 This subsection describes @value{GDBN} commands specific to the
16349 @sc{gnu} Hurd native debugging.
16354 @kindex set signals@r{, Hurd command}
16355 @kindex set sigs@r{, Hurd command}
16356 This command toggles the state of inferior signal interception by
16357 @value{GDBN}. Mach exceptions, such as breakpoint traps, are not
16358 affected by this command. @code{sigs} is a shorthand alias for
16363 @kindex show signals@r{, Hurd command}
16364 @kindex show sigs@r{, Hurd command}
16365 Show the current state of intercepting inferior's signals.
16367 @item set signal-thread
16368 @itemx set sigthread
16369 @kindex set signal-thread
16370 @kindex set sigthread
16371 This command tells @value{GDBN} which thread is the @code{libc} signal
16372 thread. That thread is run when a signal is delivered to a running
16373 process. @code{set sigthread} is the shorthand alias of @code{set
16376 @item show signal-thread
16377 @itemx show sigthread
16378 @kindex show signal-thread
16379 @kindex show sigthread
16380 These two commands show which thread will run when the inferior is
16381 delivered a signal.
16384 @kindex set stopped@r{, Hurd command}
16385 This commands tells @value{GDBN} that the inferior process is stopped,
16386 as with the @code{SIGSTOP} signal. The stopped process can be
16387 continued by delivering a signal to it.
16390 @kindex show stopped@r{, Hurd command}
16391 This command shows whether @value{GDBN} thinks the debuggee is
16394 @item set exceptions
16395 @kindex set exceptions@r{, Hurd command}
16396 Use this command to turn off trapping of exceptions in the inferior.
16397 When exception trapping is off, neither breakpoints nor
16398 single-stepping will work. To restore the default, set exception
16401 @item show exceptions
16402 @kindex show exceptions@r{, Hurd command}
16403 Show the current state of trapping exceptions in the inferior.
16405 @item set task pause
16406 @kindex set task@r{, Hurd commands}
16407 @cindex task attributes (@sc{gnu} Hurd)
16408 @cindex pause current task (@sc{gnu} Hurd)
16409 This command toggles task suspension when @value{GDBN} has control.
16410 Setting it to on takes effect immediately, and the task is suspended
16411 whenever @value{GDBN} gets control. Setting it to off will take
16412 effect the next time the inferior is continued. If this option is set
16413 to off, you can use @code{set thread default pause on} or @code{set
16414 thread pause on} (see below) to pause individual threads.
16416 @item show task pause
16417 @kindex show task@r{, Hurd commands}
16418 Show the current state of task suspension.
16420 @item set task detach-suspend-count
16421 @cindex task suspend count
16422 @cindex detach from task, @sc{gnu} Hurd
16423 This command sets the suspend count the task will be left with when
16424 @value{GDBN} detaches from it.
16426 @item show task detach-suspend-count
16427 Show the suspend count the task will be left with when detaching.
16429 @item set task exception-port
16430 @itemx set task excp
16431 @cindex task exception port, @sc{gnu} Hurd
16432 This command sets the task exception port to which @value{GDBN} will
16433 forward exceptions. The argument should be the value of the @dfn{send
16434 rights} of the task. @code{set task excp} is a shorthand alias.
16436 @item set noninvasive
16437 @cindex noninvasive task options
16438 This command switches @value{GDBN} to a mode that is the least
16439 invasive as far as interfering with the inferior is concerned. This
16440 is the same as using @code{set task pause}, @code{set exceptions}, and
16441 @code{set signals} to values opposite to the defaults.
16443 @item info send-rights
16444 @itemx info receive-rights
16445 @itemx info port-rights
16446 @itemx info port-sets
16447 @itemx info dead-names
16450 @cindex send rights, @sc{gnu} Hurd
16451 @cindex receive rights, @sc{gnu} Hurd
16452 @cindex port rights, @sc{gnu} Hurd
16453 @cindex port sets, @sc{gnu} Hurd
16454 @cindex dead names, @sc{gnu} Hurd
16455 These commands display information about, respectively, send rights,
16456 receive rights, port rights, port sets, and dead names of a task.
16457 There are also shorthand aliases: @code{info ports} for @code{info
16458 port-rights} and @code{info psets} for @code{info port-sets}.
16460 @item set thread pause
16461 @kindex set thread@r{, Hurd command}
16462 @cindex thread properties, @sc{gnu} Hurd
16463 @cindex pause current thread (@sc{gnu} Hurd)
16464 This command toggles current thread suspension when @value{GDBN} has
16465 control. Setting it to on takes effect immediately, and the current
16466 thread is suspended whenever @value{GDBN} gets control. Setting it to
16467 off will take effect the next time the inferior is continued.
16468 Normally, this command has no effect, since when @value{GDBN} has
16469 control, the whole task is suspended. However, if you used @code{set
16470 task pause off} (see above), this command comes in handy to suspend
16471 only the current thread.
16473 @item show thread pause
16474 @kindex show thread@r{, Hurd command}
16475 This command shows the state of current thread suspension.
16477 @item set thread run
16478 This command sets whether the current thread is allowed to run.
16480 @item show thread run
16481 Show whether the current thread is allowed to run.
16483 @item set thread detach-suspend-count
16484 @cindex thread suspend count, @sc{gnu} Hurd
16485 @cindex detach from thread, @sc{gnu} Hurd
16486 This command sets the suspend count @value{GDBN} will leave on a
16487 thread when detaching. This number is relative to the suspend count
16488 found by @value{GDBN} when it notices the thread; use @code{set thread
16489 takeover-suspend-count} to force it to an absolute value.
16491 @item show thread detach-suspend-count
16492 Show the suspend count @value{GDBN} will leave on the thread when
16495 @item set thread exception-port
16496 @itemx set thread excp
16497 Set the thread exception port to which to forward exceptions. This
16498 overrides the port set by @code{set task exception-port} (see above).
16499 @code{set thread excp} is the shorthand alias.
16501 @item set thread takeover-suspend-count
16502 Normally, @value{GDBN}'s thread suspend counts are relative to the
16503 value @value{GDBN} finds when it notices each thread. This command
16504 changes the suspend counts to be absolute instead.
16506 @item set thread default
16507 @itemx show thread default
16508 @cindex thread default settings, @sc{gnu} Hurd
16509 Each of the above @code{set thread} commands has a @code{set thread
16510 default} counterpart (e.g., @code{set thread default pause}, @code{set
16511 thread default exception-port}, etc.). The @code{thread default}
16512 variety of commands sets the default thread properties for all
16513 threads; you can then change the properties of individual threads with
16514 the non-default commands.
16519 @subsection QNX Neutrino
16520 @cindex QNX Neutrino
16522 @value{GDBN} provides the following commands specific to the QNX
16526 @item set debug nto-debug
16527 @kindex set debug nto-debug
16528 When set to on, enables debugging messages specific to the QNX
16531 @item show debug nto-debug
16532 @kindex show debug nto-debug
16533 Show the current state of QNX Neutrino messages.
16540 @value{GDBN} provides the following commands specific to the Darwin target:
16543 @item set debug darwin @var{num}
16544 @kindex set debug darwin
16545 When set to a non zero value, enables debugging messages specific to
16546 the Darwin support. Higher values produce more verbose output.
16548 @item show debug darwin
16549 @kindex show debug darwin
16550 Show the current state of Darwin messages.
16552 @item set debug mach-o @var{num}
16553 @kindex set debug mach-o
16554 When set to a non zero value, enables debugging messages while
16555 @value{GDBN} is reading Darwin object files. (@dfn{Mach-O} is the
16556 file format used on Darwin for object and executable files.) Higher
16557 values produce more verbose output. This is a command to diagnose
16558 problems internal to @value{GDBN} and should not be needed in normal
16561 @item show debug mach-o
16562 @kindex show debug mach-o
16563 Show the current state of Mach-O file messages.
16565 @item set mach-exceptions on
16566 @itemx set mach-exceptions off
16567 @kindex set mach-exceptions
16568 On Darwin, faults are first reported as a Mach exception and are then
16569 mapped to a Posix signal. Use this command to turn on trapping of
16570 Mach exceptions in the inferior. This might be sometimes useful to
16571 better understand the cause of a fault. The default is off.
16573 @item show mach-exceptions
16574 @kindex show mach-exceptions
16575 Show the current state of exceptions trapping.
16580 @section Embedded Operating Systems
16582 This section describes configurations involving the debugging of
16583 embedded operating systems that are available for several different
16587 * VxWorks:: Using @value{GDBN} with VxWorks
16590 @value{GDBN} includes the ability to debug programs running on
16591 various real-time operating systems.
16594 @subsection Using @value{GDBN} with VxWorks
16600 @kindex target vxworks
16601 @item target vxworks @var{machinename}
16602 A VxWorks system, attached via TCP/IP. The argument @var{machinename}
16603 is the target system's machine name or IP address.
16607 On VxWorks, @code{load} links @var{filename} dynamically on the
16608 current target system as well as adding its symbols in @value{GDBN}.
16610 @value{GDBN} enables developers to spawn and debug tasks running on networked
16611 VxWorks targets from a Unix host. Already-running tasks spawned from
16612 the VxWorks shell can also be debugged. @value{GDBN} uses code that runs on
16613 both the Unix host and on the VxWorks target. The program
16614 @code{@value{GDBP}} is installed and executed on the Unix host. (It may be
16615 installed with the name @code{vxgdb}, to distinguish it from a
16616 @value{GDBN} for debugging programs on the host itself.)
16619 @item VxWorks-timeout @var{args}
16620 @kindex vxworks-timeout
16621 All VxWorks-based targets now support the option @code{vxworks-timeout}.
16622 This option is set by the user, and @var{args} represents the number of
16623 seconds @value{GDBN} waits for responses to rpc's. You might use this if
16624 your VxWorks target is a slow software simulator or is on the far side
16625 of a thin network line.
16628 The following information on connecting to VxWorks was current when
16629 this manual was produced; newer releases of VxWorks may use revised
16632 @findex INCLUDE_RDB
16633 To use @value{GDBN} with VxWorks, you must rebuild your VxWorks kernel
16634 to include the remote debugging interface routines in the VxWorks
16635 library @file{rdb.a}. To do this, define @code{INCLUDE_RDB} in the
16636 VxWorks configuration file @file{configAll.h} and rebuild your VxWorks
16637 kernel. The resulting kernel contains @file{rdb.a}, and spawns the
16638 source debugging task @code{tRdbTask} when VxWorks is booted. For more
16639 information on configuring and remaking VxWorks, see the manufacturer's
16641 @c VxWorks, see the @cite{VxWorks Programmer's Guide}.
16643 Once you have included @file{rdb.a} in your VxWorks system image and set
16644 your Unix execution search path to find @value{GDBN}, you are ready to
16645 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}} (or
16646 @code{vxgdb}, depending on your installation).
16648 @value{GDBN} comes up showing the prompt:
16655 * VxWorks Connection:: Connecting to VxWorks
16656 * VxWorks Download:: VxWorks download
16657 * VxWorks Attach:: Running tasks
16660 @node VxWorks Connection
16661 @subsubsection Connecting to VxWorks
16663 The @value{GDBN} command @code{target} lets you connect to a VxWorks target on the
16664 network. To connect to a target whose host name is ``@code{tt}'', type:
16667 (vxgdb) target vxworks tt
16671 @value{GDBN} displays messages like these:
16674 Attaching remote machine across net...
16679 @value{GDBN} then attempts to read the symbol tables of any object modules
16680 loaded into the VxWorks target since it was last booted. @value{GDBN} locates
16681 these files by searching the directories listed in the command search
16682 path (@pxref{Environment, ,Your Program's Environment}); if it fails
16683 to find an object file, it displays a message such as:
16686 prog.o: No such file or directory.
16689 When this happens, add the appropriate directory to the search path with
16690 the @value{GDBN} command @code{path}, and execute the @code{target}
16693 @node VxWorks Download
16694 @subsubsection VxWorks Download
16696 @cindex download to VxWorks
16697 If you have connected to the VxWorks target and you want to debug an
16698 object that has not yet been loaded, you can use the @value{GDBN}
16699 @code{load} command to download a file from Unix to VxWorks
16700 incrementally. The object file given as an argument to the @code{load}
16701 command is actually opened twice: first by the VxWorks target in order
16702 to download the code, then by @value{GDBN} in order to read the symbol
16703 table. This can lead to problems if the current working directories on
16704 the two systems differ. If both systems have NFS mounted the same
16705 filesystems, you can avoid these problems by using absolute paths.
16706 Otherwise, it is simplest to set the working directory on both systems
16707 to the directory in which the object file resides, and then to reference
16708 the file by its name, without any path. For instance, a program
16709 @file{prog.o} may reside in @file{@var{vxpath}/vw/demo/rdb} in VxWorks
16710 and in @file{@var{hostpath}/vw/demo/rdb} on the host. To load this
16711 program, type this on VxWorks:
16714 -> cd "@var{vxpath}/vw/demo/rdb"
16718 Then, in @value{GDBN}, type:
16721 (vxgdb) cd @var{hostpath}/vw/demo/rdb
16722 (vxgdb) load prog.o
16725 @value{GDBN} displays a response similar to this:
16728 Reading symbol data from wherever/vw/demo/rdb/prog.o... done.
16731 You can also use the @code{load} command to reload an object module
16732 after editing and recompiling the corresponding source file. Note that
16733 this makes @value{GDBN} delete all currently-defined breakpoints,
16734 auto-displays, and convenience variables, and to clear the value
16735 history. (This is necessary in order to preserve the integrity of
16736 debugger's data structures that reference the target system's symbol
16739 @node VxWorks Attach
16740 @subsubsection Running Tasks
16742 @cindex running VxWorks tasks
16743 You can also attach to an existing task using the @code{attach} command as
16747 (vxgdb) attach @var{task}
16751 where @var{task} is the VxWorks hexadecimal task ID. The task can be running
16752 or suspended when you attach to it. Running tasks are suspended at
16753 the time of attachment.
16755 @node Embedded Processors
16756 @section Embedded Processors
16758 This section goes into details specific to particular embedded
16761 @cindex send command to simulator
16762 Whenever a specific embedded processor has a simulator, @value{GDBN}
16763 allows to send an arbitrary command to the simulator.
16766 @item sim @var{command}
16767 @kindex sim@r{, a command}
16768 Send an arbitrary @var{command} string to the simulator. Consult the
16769 documentation for the specific simulator in use for information about
16770 acceptable commands.
16776 * M32R/D:: Renesas M32R/D
16777 * M68K:: Motorola M68K
16778 * MicroBlaze:: Xilinx MicroBlaze
16779 * MIPS Embedded:: MIPS Embedded
16780 * OpenRISC 1000:: OpenRisc 1000
16781 * PA:: HP PA Embedded
16782 * PowerPC Embedded:: PowerPC Embedded
16783 * Sparclet:: Tsqware Sparclet
16784 * Sparclite:: Fujitsu Sparclite
16785 * Z8000:: Zilog Z8000
16788 * Super-H:: Renesas Super-H
16797 @item target rdi @var{dev}
16798 ARM Angel monitor, via RDI library interface to ADP protocol. You may
16799 use this target to communicate with both boards running the Angel
16800 monitor, or with the EmbeddedICE JTAG debug device.
16803 @item target rdp @var{dev}
16808 @value{GDBN} provides the following ARM-specific commands:
16811 @item set arm disassembler
16813 This commands selects from a list of disassembly styles. The
16814 @code{"std"} style is the standard style.
16816 @item show arm disassembler
16818 Show the current disassembly style.
16820 @item set arm apcs32
16821 @cindex ARM 32-bit mode
16822 This command toggles ARM operation mode between 32-bit and 26-bit.
16824 @item show arm apcs32
16825 Display the current usage of the ARM 32-bit mode.
16827 @item set arm fpu @var{fputype}
16828 This command sets the ARM floating-point unit (FPU) type. The
16829 argument @var{fputype} can be one of these:
16833 Determine the FPU type by querying the OS ABI.
16835 Software FPU, with mixed-endian doubles on little-endian ARM
16838 GCC-compiled FPA co-processor.
16840 Software FPU with pure-endian doubles.
16846 Show the current type of the FPU.
16849 This command forces @value{GDBN} to use the specified ABI.
16852 Show the currently used ABI.
16854 @item set arm fallback-mode (arm|thumb|auto)
16855 @value{GDBN} uses the symbol table, when available, to determine
16856 whether instructions are ARM or Thumb. This command controls
16857 @value{GDBN}'s default behavior when the symbol table is not
16858 available. The default is @samp{auto}, which causes @value{GDBN} to
16859 use the current execution mode (from the @code{T} bit in the @code{CPSR}
16862 @item show arm fallback-mode
16863 Show the current fallback instruction mode.
16865 @item set arm force-mode (arm|thumb|auto)
16866 This command overrides use of the symbol table to determine whether
16867 instructions are ARM or Thumb. The default is @samp{auto}, which
16868 causes @value{GDBN} to use the symbol table and then the setting
16869 of @samp{set arm fallback-mode}.
16871 @item show arm force-mode
16872 Show the current forced instruction mode.
16874 @item set debug arm
16875 Toggle whether to display ARM-specific debugging messages from the ARM
16876 target support subsystem.
16878 @item show debug arm
16879 Show whether ARM-specific debugging messages are enabled.
16882 The following commands are available when an ARM target is debugged
16883 using the RDI interface:
16886 @item rdilogfile @r{[}@var{file}@r{]}
16888 @cindex ADP (Angel Debugger Protocol) logging
16889 Set the filename for the ADP (Angel Debugger Protocol) packet log.
16890 With an argument, sets the log file to the specified @var{file}. With
16891 no argument, show the current log file name. The default log file is
16894 @item rdilogenable @r{[}@var{arg}@r{]}
16895 @kindex rdilogenable
16896 Control logging of ADP packets. With an argument of 1 or @code{"yes"}
16897 enables logging, with an argument 0 or @code{"no"} disables it. With
16898 no arguments displays the current setting. When logging is enabled,
16899 ADP packets exchanged between @value{GDBN} and the RDI target device
16900 are logged to a file.
16902 @item set rdiromatzero
16903 @kindex set rdiromatzero
16904 @cindex ROM at zero address, RDI
16905 Tell @value{GDBN} whether the target has ROM at address 0. If on,
16906 vector catching is disabled, so that zero address can be used. If off
16907 (the default), vector catching is enabled. For this command to take
16908 effect, it needs to be invoked prior to the @code{target rdi} command.
16910 @item show rdiromatzero
16911 @kindex show rdiromatzero
16912 Show the current setting of ROM at zero address.
16914 @item set rdiheartbeat
16915 @kindex set rdiheartbeat
16916 @cindex RDI heartbeat
16917 Enable or disable RDI heartbeat packets. It is not recommended to
16918 turn on this option, since it confuses ARM and EPI JTAG interface, as
16919 well as the Angel monitor.
16921 @item show rdiheartbeat
16922 @kindex show rdiheartbeat
16923 Show the setting of RDI heartbeat packets.
16928 @subsection Renesas M32R/D and M32R/SDI
16931 @kindex target m32r
16932 @item target m32r @var{dev}
16933 Renesas M32R/D ROM monitor.
16935 @kindex target m32rsdi
16936 @item target m32rsdi @var{dev}
16937 Renesas M32R SDI server, connected via parallel port to the board.
16940 The following @value{GDBN} commands are specific to the M32R monitor:
16943 @item set download-path @var{path}
16944 @kindex set download-path
16945 @cindex find downloadable @sc{srec} files (M32R)
16946 Set the default path for finding downloadable @sc{srec} files.
16948 @item show download-path
16949 @kindex show download-path
16950 Show the default path for downloadable @sc{srec} files.
16952 @item set board-address @var{addr}
16953 @kindex set board-address
16954 @cindex M32-EVA target board address
16955 Set the IP address for the M32R-EVA target board.
16957 @item show board-address
16958 @kindex show board-address
16959 Show the current IP address of the target board.
16961 @item set server-address @var{addr}
16962 @kindex set server-address
16963 @cindex download server address (M32R)
16964 Set the IP address for the download server, which is the @value{GDBN}'s
16967 @item show server-address
16968 @kindex show server-address
16969 Display the IP address of the download server.
16971 @item upload @r{[}@var{file}@r{]}
16972 @kindex upload@r{, M32R}
16973 Upload the specified @sc{srec} @var{file} via the monitor's Ethernet
16974 upload capability. If no @var{file} argument is given, the current
16975 executable file is uploaded.
16977 @item tload @r{[}@var{file}@r{]}
16978 @kindex tload@r{, M32R}
16979 Test the @code{upload} command.
16982 The following commands are available for M32R/SDI:
16987 @cindex reset SDI connection, M32R
16988 This command resets the SDI connection.
16992 This command shows the SDI connection status.
16995 @kindex debug_chaos
16996 @cindex M32R/Chaos debugging
16997 Instructs the remote that M32R/Chaos debugging is to be used.
16999 @item use_debug_dma
17000 @kindex use_debug_dma
17001 Instructs the remote to use the DEBUG_DMA method of accessing memory.
17004 @kindex use_mon_code
17005 Instructs the remote to use the MON_CODE method of accessing memory.
17008 @kindex use_ib_break
17009 Instructs the remote to set breakpoints by IB break.
17011 @item use_dbt_break
17012 @kindex use_dbt_break
17013 Instructs the remote to set breakpoints by DBT.
17019 The Motorola m68k configuration includes ColdFire support, and a
17020 target command for the following ROM monitor.
17024 @kindex target dbug
17025 @item target dbug @var{dev}
17026 dBUG ROM monitor for Motorola ColdFire.
17031 @subsection MicroBlaze
17032 @cindex Xilinx MicroBlaze
17033 @cindex XMD, Xilinx Microprocessor Debugger
17035 The MicroBlaze is a soft-core processor supported on various Xilinx
17036 FPGAs, such as Spartan or Virtex series. Boards with these processors
17037 usually have JTAG ports which connect to a host system running the Xilinx
17038 Embedded Development Kit (EDK) or Software Development Kit (SDK).
17039 This host system is used to download the configuration bitstream to
17040 the target FPGA. The Xilinx Microprocessor Debugger (XMD) program
17041 communicates with the target board using the JTAG interface and
17042 presents a @code{gdbserver} interface to the board. By default
17043 @code{xmd} uses port @code{1234}. (While it is possible to change
17044 this default port, it requires the use of undocumented @code{xmd}
17045 commands. Contact Xilinx support if you need to do this.)
17047 Use these GDB commands to connect to the MicroBlaze target processor.
17050 @item target remote :1234
17051 Use this command to connect to the target if you are running @value{GDBN}
17052 on the same system as @code{xmd}.
17054 @item target remote @var{xmd-host}:1234
17055 Use this command to connect to the target if it is connected to @code{xmd}
17056 running on a different system named @var{xmd-host}.
17059 Use this command to download a program to the MicroBlaze target.
17061 @item set debug microblaze @var{n}
17062 Enable MicroBlaze-specific debugging messages if non-zero.
17064 @item show debug microblaze @var{n}
17065 Show MicroBlaze-specific debugging level.
17068 @node MIPS Embedded
17069 @subsection MIPS Embedded
17071 @cindex MIPS boards
17072 @value{GDBN} can use the MIPS remote debugging protocol to talk to a
17073 MIPS board attached to a serial line. This is available when
17074 you configure @value{GDBN} with @samp{--target=mips-idt-ecoff}.
17077 Use these @value{GDBN} commands to specify the connection to your target board:
17080 @item target mips @var{port}
17081 @kindex target mips @var{port}
17082 To run a program on the board, start up @code{@value{GDBP}} with the
17083 name of your program as the argument. To connect to the board, use the
17084 command @samp{target mips @var{port}}, where @var{port} is the name of
17085 the serial port connected to the board. If the program has not already
17086 been downloaded to the board, you may use the @code{load} command to
17087 download it. You can then use all the usual @value{GDBN} commands.
17089 For example, this sequence connects to the target board through a serial
17090 port, and loads and runs a program called @var{prog} through the
17094 host$ @value{GDBP} @var{prog}
17095 @value{GDBN} is free software and @dots{}
17096 (@value{GDBP}) target mips /dev/ttyb
17097 (@value{GDBP}) load @var{prog}
17101 @item target mips @var{hostname}:@var{portnumber}
17102 On some @value{GDBN} host configurations, you can specify a TCP
17103 connection (for instance, to a serial line managed by a terminal
17104 concentrator) instead of a serial port, using the syntax
17105 @samp{@var{hostname}:@var{portnumber}}.
17107 @item target pmon @var{port}
17108 @kindex target pmon @var{port}
17111 @item target ddb @var{port}
17112 @kindex target ddb @var{port}
17113 NEC's DDB variant of PMON for Vr4300.
17115 @item target lsi @var{port}
17116 @kindex target lsi @var{port}
17117 LSI variant of PMON.
17119 @kindex target r3900
17120 @item target r3900 @var{dev}
17121 Densan DVE-R3900 ROM monitor for Toshiba R3900 Mips.
17123 @kindex target array
17124 @item target array @var{dev}
17125 Array Tech LSI33K RAID controller board.
17131 @value{GDBN} also supports these special commands for MIPS targets:
17134 @item set mipsfpu double
17135 @itemx set mipsfpu single
17136 @itemx set mipsfpu none
17137 @itemx set mipsfpu auto
17138 @itemx show mipsfpu
17139 @kindex set mipsfpu
17140 @kindex show mipsfpu
17141 @cindex MIPS remote floating point
17142 @cindex floating point, MIPS remote
17143 If your target board does not support the MIPS floating point
17144 coprocessor, you should use the command @samp{set mipsfpu none} (if you
17145 need this, you may wish to put the command in your @value{GDBN} init
17146 file). This tells @value{GDBN} how to find the return value of
17147 functions which return floating point values. It also allows
17148 @value{GDBN} to avoid saving the floating point registers when calling
17149 functions on the board. If you are using a floating point coprocessor
17150 with only single precision floating point support, as on the @sc{r4650}
17151 processor, use the command @samp{set mipsfpu single}. The default
17152 double precision floating point coprocessor may be selected using
17153 @samp{set mipsfpu double}.
17155 In previous versions the only choices were double precision or no
17156 floating point, so @samp{set mipsfpu on} will select double precision
17157 and @samp{set mipsfpu off} will select no floating point.
17159 As usual, you can inquire about the @code{mipsfpu} variable with
17160 @samp{show mipsfpu}.
17162 @item set timeout @var{seconds}
17163 @itemx set retransmit-timeout @var{seconds}
17164 @itemx show timeout
17165 @itemx show retransmit-timeout
17166 @cindex @code{timeout}, MIPS protocol
17167 @cindex @code{retransmit-timeout}, MIPS protocol
17168 @kindex set timeout
17169 @kindex show timeout
17170 @kindex set retransmit-timeout
17171 @kindex show retransmit-timeout
17172 You can control the timeout used while waiting for a packet, in the MIPS
17173 remote protocol, with the @code{set timeout @var{seconds}} command. The
17174 default is 5 seconds. Similarly, you can control the timeout used while
17175 waiting for an acknowledgment of a packet with the @code{set
17176 retransmit-timeout @var{seconds}} command. The default is 3 seconds.
17177 You can inspect both values with @code{show timeout} and @code{show
17178 retransmit-timeout}. (These commands are @emph{only} available when
17179 @value{GDBN} is configured for @samp{--target=mips-idt-ecoff}.)
17181 The timeout set by @code{set timeout} does not apply when @value{GDBN}
17182 is waiting for your program to stop. In that case, @value{GDBN} waits
17183 forever because it has no way of knowing how long the program is going
17184 to run before stopping.
17186 @item set syn-garbage-limit @var{num}
17187 @kindex set syn-garbage-limit@r{, MIPS remote}
17188 @cindex synchronize with remote MIPS target
17189 Limit the maximum number of characters @value{GDBN} should ignore when
17190 it tries to synchronize with the remote target. The default is 10
17191 characters. Setting the limit to -1 means there's no limit.
17193 @item show syn-garbage-limit
17194 @kindex show syn-garbage-limit@r{, MIPS remote}
17195 Show the current limit on the number of characters to ignore when
17196 trying to synchronize with the remote system.
17198 @item set monitor-prompt @var{prompt}
17199 @kindex set monitor-prompt@r{, MIPS remote}
17200 @cindex remote monitor prompt
17201 Tell @value{GDBN} to expect the specified @var{prompt} string from the
17202 remote monitor. The default depends on the target:
17212 @item show monitor-prompt
17213 @kindex show monitor-prompt@r{, MIPS remote}
17214 Show the current strings @value{GDBN} expects as the prompt from the
17217 @item set monitor-warnings
17218 @kindex set monitor-warnings@r{, MIPS remote}
17219 Enable or disable monitor warnings about hardware breakpoints. This
17220 has effect only for the @code{lsi} target. When on, @value{GDBN} will
17221 display warning messages whose codes are returned by the @code{lsi}
17222 PMON monitor for breakpoint commands.
17224 @item show monitor-warnings
17225 @kindex show monitor-warnings@r{, MIPS remote}
17226 Show the current setting of printing monitor warnings.
17228 @item pmon @var{command}
17229 @kindex pmon@r{, MIPS remote}
17230 @cindex send PMON command
17231 This command allows sending an arbitrary @var{command} string to the
17232 monitor. The monitor must be in debug mode for this to work.
17235 @node OpenRISC 1000
17236 @subsection OpenRISC 1000
17237 @cindex OpenRISC 1000
17239 @cindex or1k boards
17240 See OR1k Architecture document (@uref{www.opencores.org}) for more information
17241 about platform and commands.
17245 @kindex target jtag
17246 @item target jtag jtag://@var{host}:@var{port}
17248 Connects to remote JTAG server.
17249 JTAG remote server can be either an or1ksim or JTAG server,
17250 connected via parallel port to the board.
17252 Example: @code{target jtag jtag://localhost:9999}
17255 @item or1ksim @var{command}
17256 If connected to @code{or1ksim} OpenRISC 1000 Architectural
17257 Simulator, proprietary commands can be executed.
17259 @kindex info or1k spr
17260 @item info or1k spr
17261 Displays spr groups.
17263 @item info or1k spr @var{group}
17264 @itemx info or1k spr @var{groupno}
17265 Displays register names in selected group.
17267 @item info or1k spr @var{group} @var{register}
17268 @itemx info or1k spr @var{register}
17269 @itemx info or1k spr @var{groupno} @var{registerno}
17270 @itemx info or1k spr @var{registerno}
17271 Shows information about specified spr register.
17274 @item spr @var{group} @var{register} @var{value}
17275 @itemx spr @var{register @var{value}}
17276 @itemx spr @var{groupno} @var{registerno @var{value}}
17277 @itemx spr @var{registerno @var{value}}
17278 Writes @var{value} to specified spr register.
17281 Some implementations of OpenRISC 1000 Architecture also have hardware trace.
17282 It is very similar to @value{GDBN} trace, except it does not interfere with normal
17283 program execution and is thus much faster. Hardware breakpoints/watchpoint
17284 triggers can be set using:
17287 Load effective address/data
17289 Store effective address/data
17291 Access effective address ($SEA or $LEA) or data ($SDATA/$LDATA)
17296 When triggered, it can capture low level data, like: @code{PC}, @code{LSEA},
17297 @code{LDATA}, @code{SDATA}, @code{READSPR}, @code{WRITESPR}, @code{INSTR}.
17299 @code{htrace} commands:
17300 @cindex OpenRISC 1000 htrace
17303 @item hwatch @var{conditional}
17304 Set hardware watchpoint on combination of Load/Store Effective Address(es)
17305 or Data. For example:
17307 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
17309 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
17313 Display information about current HW trace configuration.
17315 @item htrace trigger @var{conditional}
17316 Set starting criteria for HW trace.
17318 @item htrace qualifier @var{conditional}
17319 Set acquisition qualifier for HW trace.
17321 @item htrace stop @var{conditional}
17322 Set HW trace stopping criteria.
17324 @item htrace record [@var{data}]*
17325 Selects the data to be recorded, when qualifier is met and HW trace was
17328 @item htrace enable
17329 @itemx htrace disable
17330 Enables/disables the HW trace.
17332 @item htrace rewind [@var{filename}]
17333 Clears currently recorded trace data.
17335 If filename is specified, new trace file is made and any newly collected data
17336 will be written there.
17338 @item htrace print [@var{start} [@var{len}]]
17339 Prints trace buffer, using current record configuration.
17341 @item htrace mode continuous
17342 Set continuous trace mode.
17344 @item htrace mode suspend
17345 Set suspend trace mode.
17349 @node PowerPC Embedded
17350 @subsection PowerPC Embedded
17352 @value{GDBN} provides the following PowerPC-specific commands:
17355 @kindex set powerpc
17356 @item set powerpc soft-float
17357 @itemx show powerpc soft-float
17358 Force @value{GDBN} to use (or not use) a software floating point calling
17359 convention. By default, @value{GDBN} selects the calling convention based
17360 on the selected architecture and the provided executable file.
17362 @item set powerpc vector-abi
17363 @itemx show powerpc vector-abi
17364 Force @value{GDBN} to use the specified calling convention for vector
17365 arguments and return values. The valid options are @samp{auto};
17366 @samp{generic}, to avoid vector registers even if they are present;
17367 @samp{altivec}, to use AltiVec registers; and @samp{spe} to use SPE
17368 registers. By default, @value{GDBN} selects the calling convention
17369 based on the selected architecture and the provided executable file.
17371 @kindex target dink32
17372 @item target dink32 @var{dev}
17373 DINK32 ROM monitor.
17375 @kindex target ppcbug
17376 @item target ppcbug @var{dev}
17377 @kindex target ppcbug1
17378 @item target ppcbug1 @var{dev}
17379 PPCBUG ROM monitor for PowerPC.
17382 @item target sds @var{dev}
17383 SDS monitor, running on a PowerPC board (such as Motorola's ADS).
17386 @cindex SDS protocol
17387 The following commands specific to the SDS protocol are supported
17391 @item set sdstimeout @var{nsec}
17392 @kindex set sdstimeout
17393 Set the timeout for SDS protocol reads to be @var{nsec} seconds. The
17394 default is 2 seconds.
17396 @item show sdstimeout
17397 @kindex show sdstimeout
17398 Show the current value of the SDS timeout.
17400 @item sds @var{command}
17401 @kindex sds@r{, a command}
17402 Send the specified @var{command} string to the SDS monitor.
17407 @subsection HP PA Embedded
17411 @kindex target op50n
17412 @item target op50n @var{dev}
17413 OP50N monitor, running on an OKI HPPA board.
17415 @kindex target w89k
17416 @item target w89k @var{dev}
17417 W89K monitor, running on a Winbond HPPA board.
17422 @subsection Tsqware Sparclet
17426 @value{GDBN} enables developers to debug tasks running on
17427 Sparclet targets from a Unix host.
17428 @value{GDBN} uses code that runs on
17429 both the Unix host and on the Sparclet target. The program
17430 @code{@value{GDBP}} is installed and executed on the Unix host.
17433 @item remotetimeout @var{args}
17434 @kindex remotetimeout
17435 @value{GDBN} supports the option @code{remotetimeout}.
17436 This option is set by the user, and @var{args} represents the number of
17437 seconds @value{GDBN} waits for responses.
17440 @cindex compiling, on Sparclet
17441 When compiling for debugging, include the options @samp{-g} to get debug
17442 information and @samp{-Ttext} to relocate the program to where you wish to
17443 load it on the target. You may also want to add the options @samp{-n} or
17444 @samp{-N} in order to reduce the size of the sections. Example:
17447 sparclet-aout-gcc prog.c -Ttext 0x12010000 -g -o prog -N
17450 You can use @code{objdump} to verify that the addresses are what you intended:
17453 sparclet-aout-objdump --headers --syms prog
17456 @cindex running, on Sparclet
17458 your Unix execution search path to find @value{GDBN}, you are ready to
17459 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}}
17460 (or @code{sparclet-aout-gdb}, depending on your installation).
17462 @value{GDBN} comes up showing the prompt:
17469 * Sparclet File:: Setting the file to debug
17470 * Sparclet Connection:: Connecting to Sparclet
17471 * Sparclet Download:: Sparclet download
17472 * Sparclet Execution:: Running and debugging
17475 @node Sparclet File
17476 @subsubsection Setting File to Debug
17478 The @value{GDBN} command @code{file} lets you choose with program to debug.
17481 (gdbslet) file prog
17485 @value{GDBN} then attempts to read the symbol table of @file{prog}.
17486 @value{GDBN} locates
17487 the file by searching the directories listed in the command search
17489 If the file was compiled with debug information (option @samp{-g}), source
17490 files will be searched as well.
17491 @value{GDBN} locates
17492 the source files by searching the directories listed in the directory search
17493 path (@pxref{Environment, ,Your Program's Environment}).
17495 to find a file, it displays a message such as:
17498 prog: No such file or directory.
17501 When this happens, add the appropriate directories to the search paths with
17502 the @value{GDBN} commands @code{path} and @code{dir}, and execute the
17503 @code{target} command again.
17505 @node Sparclet Connection
17506 @subsubsection Connecting to Sparclet
17508 The @value{GDBN} command @code{target} lets you connect to a Sparclet target.
17509 To connect to a target on serial port ``@code{ttya}'', type:
17512 (gdbslet) target sparclet /dev/ttya
17513 Remote target sparclet connected to /dev/ttya
17514 main () at ../prog.c:3
17518 @value{GDBN} displays messages like these:
17524 @node Sparclet Download
17525 @subsubsection Sparclet Download
17527 @cindex download to Sparclet
17528 Once connected to the Sparclet target,
17529 you can use the @value{GDBN}
17530 @code{load} command to download the file from the host to the target.
17531 The file name and load offset should be given as arguments to the @code{load}
17533 Since the file format is aout, the program must be loaded to the starting
17534 address. You can use @code{objdump} to find out what this value is. The load
17535 offset is an offset which is added to the VMA (virtual memory address)
17536 of each of the file's sections.
17537 For instance, if the program
17538 @file{prog} was linked to text address 0x1201000, with data at 0x12010160
17539 and bss at 0x12010170, in @value{GDBN}, type:
17542 (gdbslet) load prog 0x12010000
17543 Loading section .text, size 0xdb0 vma 0x12010000
17546 If the code is loaded at a different address then what the program was linked
17547 to, you may need to use the @code{section} and @code{add-symbol-file} commands
17548 to tell @value{GDBN} where to map the symbol table.
17550 @node Sparclet Execution
17551 @subsubsection Running and Debugging
17553 @cindex running and debugging Sparclet programs
17554 You can now begin debugging the task using @value{GDBN}'s execution control
17555 commands, @code{b}, @code{step}, @code{run}, etc. See the @value{GDBN}
17556 manual for the list of commands.
17560 Breakpoint 1 at 0x12010000: file prog.c, line 3.
17562 Starting program: prog
17563 Breakpoint 1, main (argc=1, argv=0xeffff21c) at prog.c:3
17564 3 char *symarg = 0;
17566 4 char *execarg = "hello!";
17571 @subsection Fujitsu Sparclite
17575 @kindex target sparclite
17576 @item target sparclite @var{dev}
17577 Fujitsu sparclite boards, used only for the purpose of loading.
17578 You must use an additional command to debug the program.
17579 For example: target remote @var{dev} using @value{GDBN} standard
17585 @subsection Zilog Z8000
17588 @cindex simulator, Z8000
17589 @cindex Zilog Z8000 simulator
17591 When configured for debugging Zilog Z8000 targets, @value{GDBN} includes
17594 For the Z8000 family, @samp{target sim} simulates either the Z8002 (the
17595 unsegmented variant of the Z8000 architecture) or the Z8001 (the
17596 segmented variant). The simulator recognizes which architecture is
17597 appropriate by inspecting the object code.
17600 @item target sim @var{args}
17602 @kindex target sim@r{, with Z8000}
17603 Debug programs on a simulated CPU. If the simulator supports setup
17604 options, specify them via @var{args}.
17608 After specifying this target, you can debug programs for the simulated
17609 CPU in the same style as programs for your host computer; use the
17610 @code{file} command to load a new program image, the @code{run} command
17611 to run your program, and so on.
17613 As well as making available all the usual machine registers
17614 (@pxref{Registers, ,Registers}), the Z8000 simulator provides three
17615 additional items of information as specially named registers:
17620 Counts clock-ticks in the simulator.
17623 Counts instructions run in the simulator.
17626 Execution time in 60ths of a second.
17630 You can refer to these values in @value{GDBN} expressions with the usual
17631 conventions; for example, @w{@samp{b fputc if $cycles>5000}} sets a
17632 conditional breakpoint that suspends only after at least 5000
17633 simulated clock ticks.
17636 @subsection Atmel AVR
17639 When configured for debugging the Atmel AVR, @value{GDBN} supports the
17640 following AVR-specific commands:
17643 @item info io_registers
17644 @kindex info io_registers@r{, AVR}
17645 @cindex I/O registers (Atmel AVR)
17646 This command displays information about the AVR I/O registers. For
17647 each register, @value{GDBN} prints its number and value.
17654 When configured for debugging CRIS, @value{GDBN} provides the
17655 following CRIS-specific commands:
17658 @item set cris-version @var{ver}
17659 @cindex CRIS version
17660 Set the current CRIS version to @var{ver}, either @samp{10} or @samp{32}.
17661 The CRIS version affects register names and sizes. This command is useful in
17662 case autodetection of the CRIS version fails.
17664 @item show cris-version
17665 Show the current CRIS version.
17667 @item set cris-dwarf2-cfi
17668 @cindex DWARF-2 CFI and CRIS
17669 Set the usage of DWARF-2 CFI for CRIS debugging. The default is @samp{on}.
17670 Change to @samp{off} when using @code{gcc-cris} whose version is below
17673 @item show cris-dwarf2-cfi
17674 Show the current state of using DWARF-2 CFI.
17676 @item set cris-mode @var{mode}
17678 Set the current CRIS mode to @var{mode}. It should only be changed when
17679 debugging in guru mode, in which case it should be set to
17680 @samp{guru} (the default is @samp{normal}).
17682 @item show cris-mode
17683 Show the current CRIS mode.
17687 @subsection Renesas Super-H
17690 For the Renesas Super-H processor, @value{GDBN} provides these
17695 @kindex regs@r{, Super-H}
17696 Show the values of all Super-H registers.
17698 @item set sh calling-convention @var{convention}
17699 @kindex set sh calling-convention
17700 Set the calling-convention used when calling functions from @value{GDBN}.
17701 Allowed values are @samp{gcc}, which is the default setting, and @samp{renesas}.
17702 With the @samp{gcc} setting, functions are called using the @value{NGCC} calling
17703 convention. If the DWARF-2 information of the called function specifies
17704 that the function follows the Renesas calling convention, the function
17705 is called using the Renesas calling convention. If the calling convention
17706 is set to @samp{renesas}, the Renesas calling convention is always used,
17707 regardless of the DWARF-2 information. This can be used to override the
17708 default of @samp{gcc} if debug information is missing, or the compiler
17709 does not emit the DWARF-2 calling convention entry for a function.
17711 @item show sh calling-convention
17712 @kindex show sh calling-convention
17713 Show the current calling convention setting.
17718 @node Architectures
17719 @section Architectures
17721 This section describes characteristics of architectures that affect
17722 all uses of @value{GDBN} with the architecture, both native and cross.
17729 * HPPA:: HP PA architecture
17730 * SPU:: Cell Broadband Engine SPU architecture
17735 @subsection x86 Architecture-specific Issues
17738 @item set struct-convention @var{mode}
17739 @kindex set struct-convention
17740 @cindex struct return convention
17741 @cindex struct/union returned in registers
17742 Set the convention used by the inferior to return @code{struct}s and
17743 @code{union}s from functions to @var{mode}. Possible values of
17744 @var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the
17745 default). @code{"default"} or @code{"pcc"} means that @code{struct}s
17746 are returned on the stack, while @code{"reg"} means that a
17747 @code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will
17748 be returned in a register.
17750 @item show struct-convention
17751 @kindex show struct-convention
17752 Show the current setting of the convention to return @code{struct}s
17761 @kindex set rstack_high_address
17762 @cindex AMD 29K register stack
17763 @cindex register stack, AMD29K
17764 @item set rstack_high_address @var{address}
17765 On AMD 29000 family processors, registers are saved in a separate
17766 @dfn{register stack}. There is no way for @value{GDBN} to determine the
17767 extent of this stack. Normally, @value{GDBN} just assumes that the
17768 stack is ``large enough''. This may result in @value{GDBN} referencing
17769 memory locations that do not exist. If necessary, you can get around
17770 this problem by specifying the ending address of the register stack with
17771 the @code{set rstack_high_address} command. The argument should be an
17772 address, which you probably want to precede with @samp{0x} to specify in
17775 @kindex show rstack_high_address
17776 @item show rstack_high_address
17777 Display the current limit of the register stack, on AMD 29000 family
17785 See the following section.
17790 @cindex stack on Alpha
17791 @cindex stack on MIPS
17792 @cindex Alpha stack
17794 Alpha- and MIPS-based computers use an unusual stack frame, which
17795 sometimes requires @value{GDBN} to search backward in the object code to
17796 find the beginning of a function.
17798 @cindex response time, MIPS debugging
17799 To improve response time (especially for embedded applications, where
17800 @value{GDBN} may be restricted to a slow serial line for this search)
17801 you may want to limit the size of this search, using one of these
17805 @cindex @code{heuristic-fence-post} (Alpha, MIPS)
17806 @item set heuristic-fence-post @var{limit}
17807 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
17808 search for the beginning of a function. A value of @var{0} (the
17809 default) means there is no limit. However, except for @var{0}, the
17810 larger the limit the more bytes @code{heuristic-fence-post} must search
17811 and therefore the longer it takes to run. You should only need to use
17812 this command when debugging a stripped executable.
17814 @item show heuristic-fence-post
17815 Display the current limit.
17819 These commands are available @emph{only} when @value{GDBN} is configured
17820 for debugging programs on Alpha or MIPS processors.
17822 Several MIPS-specific commands are available when debugging MIPS
17826 @item set mips abi @var{arg}
17827 @kindex set mips abi
17828 @cindex set ABI for MIPS
17829 Tell @value{GDBN} which MIPS ABI is used by the inferior. Possible
17830 values of @var{arg} are:
17834 The default ABI associated with the current binary (this is the
17845 @item show mips abi
17846 @kindex show mips abi
17847 Show the MIPS ABI used by @value{GDBN} to debug the inferior.
17850 @itemx show mipsfpu
17851 @xref{MIPS Embedded, set mipsfpu}.
17853 @item set mips mask-address @var{arg}
17854 @kindex set mips mask-address
17855 @cindex MIPS addresses, masking
17856 This command determines whether the most-significant 32 bits of 64-bit
17857 MIPS addresses are masked off. The argument @var{arg} can be
17858 @samp{on}, @samp{off}, or @samp{auto}. The latter is the default
17859 setting, which lets @value{GDBN} determine the correct value.
17861 @item show mips mask-address
17862 @kindex show mips mask-address
17863 Show whether the upper 32 bits of MIPS addresses are masked off or
17866 @item set remote-mips64-transfers-32bit-regs
17867 @kindex set remote-mips64-transfers-32bit-regs
17868 This command controls compatibility with 64-bit MIPS targets that
17869 transfer data in 32-bit quantities. If you have an old MIPS 64 target
17870 that transfers 32 bits for some registers, like @sc{sr} and @sc{fsr},
17871 and 64 bits for other registers, set this option to @samp{on}.
17873 @item show remote-mips64-transfers-32bit-regs
17874 @kindex show remote-mips64-transfers-32bit-regs
17875 Show the current setting of compatibility with older MIPS 64 targets.
17877 @item set debug mips
17878 @kindex set debug mips
17879 This command turns on and off debugging messages for the MIPS-specific
17880 target code in @value{GDBN}.
17882 @item show debug mips
17883 @kindex show debug mips
17884 Show the current setting of MIPS debugging messages.
17890 @cindex HPPA support
17892 When @value{GDBN} is debugging the HP PA architecture, it provides the
17893 following special commands:
17896 @item set debug hppa
17897 @kindex set debug hppa
17898 This command determines whether HPPA architecture-specific debugging
17899 messages are to be displayed.
17901 @item show debug hppa
17902 Show whether HPPA debugging messages are displayed.
17904 @item maint print unwind @var{address}
17905 @kindex maint print unwind@r{, HPPA}
17906 This command displays the contents of the unwind table entry at the
17907 given @var{address}.
17913 @subsection Cell Broadband Engine SPU architecture
17914 @cindex Cell Broadband Engine
17917 When @value{GDBN} is debugging the Cell Broadband Engine SPU architecture,
17918 it provides the following special commands:
17921 @item info spu event
17923 Display SPU event facility status. Shows current event mask
17924 and pending event status.
17926 @item info spu signal
17927 Display SPU signal notification facility status. Shows pending
17928 signal-control word and signal notification mode of both signal
17929 notification channels.
17931 @item info spu mailbox
17932 Display SPU mailbox facility status. Shows all pending entries,
17933 in order of processing, in each of the SPU Write Outbound,
17934 SPU Write Outbound Interrupt, and SPU Read Inbound mailboxes.
17937 Display MFC DMA status. Shows all pending commands in the MFC
17938 DMA queue. For each entry, opcode, tag, class IDs, effective
17939 and local store addresses and transfer size are shown.
17941 @item info spu proxydma
17942 Display MFC Proxy-DMA status. Shows all pending commands in the MFC
17943 Proxy-DMA queue. For each entry, opcode, tag, class IDs, effective
17944 and local store addresses and transfer size are shown.
17948 When @value{GDBN} is debugging a combined PowerPC/SPU application
17949 on the Cell Broadband Engine, it provides in addition the following
17953 @item set spu stop-on-load @var{arg}
17955 Set whether to stop for new SPE threads. When set to @code{on}, @value{GDBN}
17956 will give control to the user when a new SPE thread enters its @code{main}
17957 function. The default is @code{off}.
17959 @item show spu stop-on-load
17961 Show whether to stop for new SPE threads.
17963 @item set spu auto-flush-cache @var{arg}
17964 Set whether to automatically flush the software-managed cache. When set to
17965 @code{on}, @value{GDBN} will automatically cause the SPE software-managed
17966 cache to be flushed whenever SPE execution stops. This provides a consistent
17967 view of PowerPC memory that is accessed via the cache. If an application
17968 does not use the software-managed cache, this option has no effect.
17970 @item show spu auto-flush-cache
17971 Show whether to automatically flush the software-managed cache.
17976 @subsection PowerPC
17977 @cindex PowerPC architecture
17979 When @value{GDBN} is debugging the PowerPC architecture, it provides a set of
17980 pseudo-registers to enable inspection of 128-bit wide Decimal Floating Point
17981 numbers stored in the floating point registers. These values must be stored
17982 in two consecutive registers, always starting at an even register like
17983 @code{f0} or @code{f2}.
17985 The pseudo-registers go from @code{$dl0} through @code{$dl15}, and are formed
17986 by joining the even/odd register pairs @code{f0} and @code{f1} for @code{$dl0},
17987 @code{f2} and @code{f3} for @code{$dl1} and so on.
17989 For POWER7 processors, @value{GDBN} provides a set of pseudo-registers, the 64-bit
17990 wide Extended Floating Point Registers (@samp{f32} through @samp{f63}).
17993 @node Controlling GDB
17994 @chapter Controlling @value{GDBN}
17996 You can alter the way @value{GDBN} interacts with you by using the
17997 @code{set} command. For commands controlling how @value{GDBN} displays
17998 data, see @ref{Print Settings, ,Print Settings}. Other settings are
18003 * Editing:: Command editing
18004 * Command History:: Command history
18005 * Screen Size:: Screen size
18006 * Numbers:: Numbers
18007 * ABI:: Configuring the current ABI
18008 * Messages/Warnings:: Optional warnings and messages
18009 * Debugging Output:: Optional messages about internal happenings
18010 * Other Misc Settings:: Other Miscellaneous Settings
18018 @value{GDBN} indicates its readiness to read a command by printing a string
18019 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
18020 can change the prompt string with the @code{set prompt} command. For
18021 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
18022 the prompt in one of the @value{GDBN} sessions so that you can always tell
18023 which one you are talking to.
18025 @emph{Note:} @code{set prompt} does not add a space for you after the
18026 prompt you set. This allows you to set a prompt which ends in a space
18027 or a prompt that does not.
18031 @item set prompt @var{newprompt}
18032 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
18034 @kindex show prompt
18036 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
18040 @section Command Editing
18042 @cindex command line editing
18044 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
18045 @sc{gnu} library provides consistent behavior for programs which provide a
18046 command line interface to the user. Advantages are @sc{gnu} Emacs-style
18047 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
18048 substitution, and a storage and recall of command history across
18049 debugging sessions.
18051 You may control the behavior of command line editing in @value{GDBN} with the
18052 command @code{set}.
18055 @kindex set editing
18058 @itemx set editing on
18059 Enable command line editing (enabled by default).
18061 @item set editing off
18062 Disable command line editing.
18064 @kindex show editing
18066 Show whether command line editing is enabled.
18069 @xref{Command Line Editing}, for more details about the Readline
18070 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
18071 encouraged to read that chapter.
18073 @node Command History
18074 @section Command History
18075 @cindex command history
18077 @value{GDBN} can keep track of the commands you type during your
18078 debugging sessions, so that you can be certain of precisely what
18079 happened. Use these commands to manage the @value{GDBN} command
18082 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
18083 package, to provide the history facility. @xref{Using History
18084 Interactively}, for the detailed description of the History library.
18086 To issue a command to @value{GDBN} without affecting certain aspects of
18087 the state which is seen by users, prefix it with @samp{server }
18088 (@pxref{Server Prefix}). This
18089 means that this command will not affect the command history, nor will it
18090 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
18091 pressed on a line by itself.
18093 @cindex @code{server}, command prefix
18094 The server prefix does not affect the recording of values into the value
18095 history; to print a value without recording it into the value history,
18096 use the @code{output} command instead of the @code{print} command.
18098 Here is the description of @value{GDBN} commands related to command
18102 @cindex history substitution
18103 @cindex history file
18104 @kindex set history filename
18105 @cindex @env{GDBHISTFILE}, environment variable
18106 @item set history filename @var{fname}
18107 Set the name of the @value{GDBN} command history file to @var{fname}.
18108 This is the file where @value{GDBN} reads an initial command history
18109 list, and where it writes the command history from this session when it
18110 exits. You can access this list through history expansion or through
18111 the history command editing characters listed below. This file defaults
18112 to the value of the environment variable @code{GDBHISTFILE}, or to
18113 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
18116 @cindex save command history
18117 @kindex set history save
18118 @item set history save
18119 @itemx set history save on
18120 Record command history in a file, whose name may be specified with the
18121 @code{set history filename} command. By default, this option is disabled.
18123 @item set history save off
18124 Stop recording command history in a file.
18126 @cindex history size
18127 @kindex set history size
18128 @cindex @env{HISTSIZE}, environment variable
18129 @item set history size @var{size}
18130 Set the number of commands which @value{GDBN} keeps in its history list.
18131 This defaults to the value of the environment variable
18132 @code{HISTSIZE}, or to 256 if this variable is not set.
18135 History expansion assigns special meaning to the character @kbd{!}.
18136 @xref{Event Designators}, for more details.
18138 @cindex history expansion, turn on/off
18139 Since @kbd{!} is also the logical not operator in C, history expansion
18140 is off by default. If you decide to enable history expansion with the
18141 @code{set history expansion on} command, you may sometimes need to
18142 follow @kbd{!} (when it is used as logical not, in an expression) with
18143 a space or a tab to prevent it from being expanded. The readline
18144 history facilities do not attempt substitution on the strings
18145 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
18147 The commands to control history expansion are:
18150 @item set history expansion on
18151 @itemx set history expansion
18152 @kindex set history expansion
18153 Enable history expansion. History expansion is off by default.
18155 @item set history expansion off
18156 Disable history expansion.
18159 @kindex show history
18161 @itemx show history filename
18162 @itemx show history save
18163 @itemx show history size
18164 @itemx show history expansion
18165 These commands display the state of the @value{GDBN} history parameters.
18166 @code{show history} by itself displays all four states.
18171 @kindex show commands
18172 @cindex show last commands
18173 @cindex display command history
18174 @item show commands
18175 Display the last ten commands in the command history.
18177 @item show commands @var{n}
18178 Print ten commands centered on command number @var{n}.
18180 @item show commands +
18181 Print ten commands just after the commands last printed.
18185 @section Screen Size
18186 @cindex size of screen
18187 @cindex pauses in output
18189 Certain commands to @value{GDBN} may produce large amounts of
18190 information output to the screen. To help you read all of it,
18191 @value{GDBN} pauses and asks you for input at the end of each page of
18192 output. Type @key{RET} when you want to continue the output, or @kbd{q}
18193 to discard the remaining output. Also, the screen width setting
18194 determines when to wrap lines of output. Depending on what is being
18195 printed, @value{GDBN} tries to break the line at a readable place,
18196 rather than simply letting it overflow onto the following line.
18198 Normally @value{GDBN} knows the size of the screen from the terminal
18199 driver software. For example, on Unix @value{GDBN} uses the termcap data base
18200 together with the value of the @code{TERM} environment variable and the
18201 @code{stty rows} and @code{stty cols} settings. If this is not correct,
18202 you can override it with the @code{set height} and @code{set
18209 @kindex show height
18210 @item set height @var{lpp}
18212 @itemx set width @var{cpl}
18214 These @code{set} commands specify a screen height of @var{lpp} lines and
18215 a screen width of @var{cpl} characters. The associated @code{show}
18216 commands display the current settings.
18218 If you specify a height of zero lines, @value{GDBN} does not pause during
18219 output no matter how long the output is. This is useful if output is to a
18220 file or to an editor buffer.
18222 Likewise, you can specify @samp{set width 0} to prevent @value{GDBN}
18223 from wrapping its output.
18225 @item set pagination on
18226 @itemx set pagination off
18227 @kindex set pagination
18228 Turn the output pagination on or off; the default is on. Turning
18229 pagination off is the alternative to @code{set height 0}.
18231 @item show pagination
18232 @kindex show pagination
18233 Show the current pagination mode.
18238 @cindex number representation
18239 @cindex entering numbers
18241 You can always enter numbers in octal, decimal, or hexadecimal in
18242 @value{GDBN} by the usual conventions: octal numbers begin with
18243 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
18244 begin with @samp{0x}. Numbers that neither begin with @samp{0} or
18245 @samp{0x}, nor end with a @samp{.} are, by default, entered in base
18246 10; likewise, the default display for numbers---when no particular
18247 format is specified---is base 10. You can change the default base for
18248 both input and output with the commands described below.
18251 @kindex set input-radix
18252 @item set input-radix @var{base}
18253 Set the default base for numeric input. Supported choices
18254 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
18255 specified either unambiguously or using the current input radix; for
18259 set input-radix 012
18260 set input-radix 10.
18261 set input-radix 0xa
18265 sets the input base to decimal. On the other hand, @samp{set input-radix 10}
18266 leaves the input radix unchanged, no matter what it was, since
18267 @samp{10}, being without any leading or trailing signs of its base, is
18268 interpreted in the current radix. Thus, if the current radix is 16,
18269 @samp{10} is interpreted in hex, i.e.@: as 16 decimal, which doesn't
18272 @kindex set output-radix
18273 @item set output-radix @var{base}
18274 Set the default base for numeric display. Supported choices
18275 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
18276 specified either unambiguously or using the current input radix.
18278 @kindex show input-radix
18279 @item show input-radix
18280 Display the current default base for numeric input.
18282 @kindex show output-radix
18283 @item show output-radix
18284 Display the current default base for numeric display.
18286 @item set radix @r{[}@var{base}@r{]}
18290 These commands set and show the default base for both input and output
18291 of numbers. @code{set radix} sets the radix of input and output to
18292 the same base; without an argument, it resets the radix back to its
18293 default value of 10.
18298 @section Configuring the Current ABI
18300 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
18301 application automatically. However, sometimes you need to override its
18302 conclusions. Use these commands to manage @value{GDBN}'s view of the
18309 One @value{GDBN} configuration can debug binaries for multiple operating
18310 system targets, either via remote debugging or native emulation.
18311 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
18312 but you can override its conclusion using the @code{set osabi} command.
18313 One example where this is useful is in debugging of binaries which use
18314 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
18315 not have the same identifying marks that the standard C library for your
18320 Show the OS ABI currently in use.
18323 With no argument, show the list of registered available OS ABI's.
18325 @item set osabi @var{abi}
18326 Set the current OS ABI to @var{abi}.
18329 @cindex float promotion
18331 Generally, the way that an argument of type @code{float} is passed to a
18332 function depends on whether the function is prototyped. For a prototyped
18333 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
18334 according to the architecture's convention for @code{float}. For unprototyped
18335 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
18336 @code{double} and then passed.
18338 Unfortunately, some forms of debug information do not reliably indicate whether
18339 a function is prototyped. If @value{GDBN} calls a function that is not marked
18340 as prototyped, it consults @kbd{set coerce-float-to-double}.
18343 @kindex set coerce-float-to-double
18344 @item set coerce-float-to-double
18345 @itemx set coerce-float-to-double on
18346 Arguments of type @code{float} will be promoted to @code{double} when passed
18347 to an unprototyped function. This is the default setting.
18349 @item set coerce-float-to-double off
18350 Arguments of type @code{float} will be passed directly to unprototyped
18353 @kindex show coerce-float-to-double
18354 @item show coerce-float-to-double
18355 Show the current setting of promoting @code{float} to @code{double}.
18359 @kindex show cp-abi
18360 @value{GDBN} needs to know the ABI used for your program's C@t{++}
18361 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
18362 used to build your application. @value{GDBN} only fully supports
18363 programs with a single C@t{++} ABI; if your program contains code using
18364 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
18365 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
18366 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
18367 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
18368 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
18369 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
18374 Show the C@t{++} ABI currently in use.
18377 With no argument, show the list of supported C@t{++} ABI's.
18379 @item set cp-abi @var{abi}
18380 @itemx set cp-abi auto
18381 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
18384 @node Messages/Warnings
18385 @section Optional Warnings and Messages
18387 @cindex verbose operation
18388 @cindex optional warnings
18389 By default, @value{GDBN} is silent about its inner workings. If you are
18390 running on a slow machine, you may want to use the @code{set verbose}
18391 command. This makes @value{GDBN} tell you when it does a lengthy
18392 internal operation, so you will not think it has crashed.
18394 Currently, the messages controlled by @code{set verbose} are those
18395 which announce that the symbol table for a source file is being read;
18396 see @code{symbol-file} in @ref{Files, ,Commands to Specify Files}.
18399 @kindex set verbose
18400 @item set verbose on
18401 Enables @value{GDBN} output of certain informational messages.
18403 @item set verbose off
18404 Disables @value{GDBN} output of certain informational messages.
18406 @kindex show verbose
18408 Displays whether @code{set verbose} is on or off.
18411 By default, if @value{GDBN} encounters bugs in the symbol table of an
18412 object file, it is silent; but if you are debugging a compiler, you may
18413 find this information useful (@pxref{Symbol Errors, ,Errors Reading
18418 @kindex set complaints
18419 @item set complaints @var{limit}
18420 Permits @value{GDBN} to output @var{limit} complaints about each type of
18421 unusual symbols before becoming silent about the problem. Set
18422 @var{limit} to zero to suppress all complaints; set it to a large number
18423 to prevent complaints from being suppressed.
18425 @kindex show complaints
18426 @item show complaints
18427 Displays how many symbol complaints @value{GDBN} is permitted to produce.
18431 @anchor{confirmation requests}
18432 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
18433 lot of stupid questions to confirm certain commands. For example, if
18434 you try to run a program which is already running:
18438 The program being debugged has been started already.
18439 Start it from the beginning? (y or n)
18442 If you are willing to unflinchingly face the consequences of your own
18443 commands, you can disable this ``feature'':
18447 @kindex set confirm
18449 @cindex confirmation
18450 @cindex stupid questions
18451 @item set confirm off
18452 Disables confirmation requests.
18454 @item set confirm on
18455 Enables confirmation requests (the default).
18457 @kindex show confirm
18459 Displays state of confirmation requests.
18463 @cindex command tracing
18464 If you need to debug user-defined commands or sourced files you may find it
18465 useful to enable @dfn{command tracing}. In this mode each command will be
18466 printed as it is executed, prefixed with one or more @samp{+} symbols, the
18467 quantity denoting the call depth of each command.
18470 @kindex set trace-commands
18471 @cindex command scripts, debugging
18472 @item set trace-commands on
18473 Enable command tracing.
18474 @item set trace-commands off
18475 Disable command tracing.
18476 @item show trace-commands
18477 Display the current state of command tracing.
18480 @node Debugging Output
18481 @section Optional Messages about Internal Happenings
18482 @cindex optional debugging messages
18484 @value{GDBN} has commands that enable optional debugging messages from
18485 various @value{GDBN} subsystems; normally these commands are of
18486 interest to @value{GDBN} maintainers, or when reporting a bug. This
18487 section documents those commands.
18490 @kindex set exec-done-display
18491 @item set exec-done-display
18492 Turns on or off the notification of asynchronous commands'
18493 completion. When on, @value{GDBN} will print a message when an
18494 asynchronous command finishes its execution. The default is off.
18495 @kindex show exec-done-display
18496 @item show exec-done-display
18497 Displays the current setting of asynchronous command completion
18500 @cindex gdbarch debugging info
18501 @cindex architecture debugging info
18502 @item set debug arch
18503 Turns on or off display of gdbarch debugging info. The default is off
18505 @item show debug arch
18506 Displays the current state of displaying gdbarch debugging info.
18507 @item set debug aix-thread
18508 @cindex AIX threads
18509 Display debugging messages about inner workings of the AIX thread
18511 @item show debug aix-thread
18512 Show the current state of AIX thread debugging info display.
18513 @item set debug dwarf2-die
18514 @cindex DWARF2 DIEs
18515 Dump DWARF2 DIEs after they are read in.
18516 The value is the number of nesting levels to print.
18517 A value of zero turns off the display.
18518 @item show debug dwarf2-die
18519 Show the current state of DWARF2 DIE debugging.
18520 @item set debug displaced
18521 @cindex displaced stepping debugging info
18522 Turns on or off display of @value{GDBN} debugging info for the
18523 displaced stepping support. The default is off.
18524 @item show debug displaced
18525 Displays the current state of displaying @value{GDBN} debugging info
18526 related to displaced stepping.
18527 @item set debug event
18528 @cindex event debugging info
18529 Turns on or off display of @value{GDBN} event debugging info. The
18531 @item show debug event
18532 Displays the current state of displaying @value{GDBN} event debugging
18534 @item set debug expression
18535 @cindex expression debugging info
18536 Turns on or off display of debugging info about @value{GDBN}
18537 expression parsing. The default is off.
18538 @item show debug expression
18539 Displays the current state of displaying debugging info about
18540 @value{GDBN} expression parsing.
18541 @item set debug frame
18542 @cindex frame debugging info
18543 Turns on or off display of @value{GDBN} frame debugging info. The
18545 @item show debug frame
18546 Displays the current state of displaying @value{GDBN} frame debugging
18548 @item set debug gnu-nat
18549 @cindex @sc{gnu}/Hurd debug messages
18550 Turns on or off debugging messages from the @sc{gnu}/Hurd debug support.
18551 @item show debug gnu-nat
18552 Show the current state of @sc{gnu}/Hurd debugging messages.
18553 @item set debug infrun
18554 @cindex inferior debugging info
18555 Turns on or off display of @value{GDBN} debugging info for running the inferior.
18556 The default is off. @file{infrun.c} contains GDB's runtime state machine used
18557 for implementing operations such as single-stepping the inferior.
18558 @item show debug infrun
18559 Displays the current state of @value{GDBN} inferior debugging.
18560 @item set debug lin-lwp
18561 @cindex @sc{gnu}/Linux LWP debug messages
18562 @cindex Linux lightweight processes
18563 Turns on or off debugging messages from the Linux LWP debug support.
18564 @item show debug lin-lwp
18565 Show the current state of Linux LWP debugging messages.
18566 @item set debug lin-lwp-async
18567 @cindex @sc{gnu}/Linux LWP async debug messages
18568 @cindex Linux lightweight processes
18569 Turns on or off debugging messages from the Linux LWP async debug support.
18570 @item show debug lin-lwp-async
18571 Show the current state of Linux LWP async debugging messages.
18572 @item set debug observer
18573 @cindex observer debugging info
18574 Turns on or off display of @value{GDBN} observer debugging. This
18575 includes info such as the notification of observable events.
18576 @item show debug observer
18577 Displays the current state of observer debugging.
18578 @item set debug overload
18579 @cindex C@t{++} overload debugging info
18580 Turns on or off display of @value{GDBN} C@t{++} overload debugging
18581 info. This includes info such as ranking of functions, etc. The default
18583 @item show debug overload
18584 Displays the current state of displaying @value{GDBN} C@t{++} overload
18586 @cindex packets, reporting on stdout
18587 @cindex serial connections, debugging
18588 @cindex debug remote protocol
18589 @cindex remote protocol debugging
18590 @cindex display remote packets
18591 @item set debug remote
18592 Turns on or off display of reports on all packets sent back and forth across
18593 the serial line to the remote machine. The info is printed on the
18594 @value{GDBN} standard output stream. The default is off.
18595 @item show debug remote
18596 Displays the state of display of remote packets.
18597 @item set debug serial
18598 Turns on or off display of @value{GDBN} serial debugging info. The
18600 @item show debug serial
18601 Displays the current state of displaying @value{GDBN} serial debugging
18603 @item set debug solib-frv
18604 @cindex FR-V shared-library debugging
18605 Turns on or off debugging messages for FR-V shared-library code.
18606 @item show debug solib-frv
18607 Display the current state of FR-V shared-library code debugging
18609 @item set debug target
18610 @cindex target debugging info
18611 Turns on or off display of @value{GDBN} target debugging info. This info
18612 includes what is going on at the target level of GDB, as it happens. The
18613 default is 0. Set it to 1 to track events, and to 2 to also track the
18614 value of large memory transfers. Changes to this flag do not take effect
18615 until the next time you connect to a target or use the @code{run} command.
18616 @item show debug target
18617 Displays the current state of displaying @value{GDBN} target debugging
18619 @item set debug timestamp
18620 @cindex timestampping debugging info
18621 Turns on or off display of timestamps with @value{GDBN} debugging info.
18622 When enabled, seconds and microseconds are displayed before each debugging
18624 @item show debug timestamp
18625 Displays the current state of displaying timestamps with @value{GDBN}
18627 @item set debugvarobj
18628 @cindex variable object debugging info
18629 Turns on or off display of @value{GDBN} variable object debugging
18630 info. The default is off.
18631 @item show debugvarobj
18632 Displays the current state of displaying @value{GDBN} variable object
18634 @item set debug xml
18635 @cindex XML parser debugging
18636 Turns on or off debugging messages for built-in XML parsers.
18637 @item show debug xml
18638 Displays the current state of XML debugging messages.
18641 @node Other Misc Settings
18642 @section Other Miscellaneous Settings
18643 @cindex miscellaneous settings
18646 @kindex set interactive-mode
18647 @item set interactive-mode
18648 If @code{on}, forces @value{GDBN} to operate interactively.
18649 If @code{off}, forces @value{GDBN} to operate non-interactively,
18650 If @code{auto} (the default), @value{GDBN} guesses which mode to use,
18651 based on whether the debugger was started in a terminal or not.
18653 In the vast majority of cases, the debugger should be able to guess
18654 correctly which mode should be used. But this setting can be useful
18655 in certain specific cases, such as running a MinGW @value{GDBN}
18656 inside a cygwin window.
18658 @kindex show interactive-mode
18659 @item show interactive-mode
18660 Displays whether the debugger is operating in interactive mode or not.
18663 @node Extending GDB
18664 @chapter Extending @value{GDBN}
18665 @cindex extending GDB
18667 @value{GDBN} provides two mechanisms for extension. The first is based
18668 on composition of @value{GDBN} commands, and the second is based on the
18669 Python scripting language.
18672 * Sequences:: Canned Sequences of Commands
18673 * Python:: Scripting @value{GDBN} using Python
18677 @section Canned Sequences of Commands
18679 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
18680 Command Lists}), @value{GDBN} provides two ways to store sequences of
18681 commands for execution as a unit: user-defined commands and command
18685 * Define:: How to define your own commands
18686 * Hooks:: Hooks for user-defined commands
18687 * Command Files:: How to write scripts of commands to be stored in a file
18688 * Output:: Commands for controlled output
18692 @subsection User-defined Commands
18694 @cindex user-defined command
18695 @cindex arguments, to user-defined commands
18696 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
18697 which you assign a new name as a command. This is done with the
18698 @code{define} command. User commands may accept up to 10 arguments
18699 separated by whitespace. Arguments are accessed within the user command
18700 via @code{$arg0@dots{}$arg9}. A trivial example:
18704 print $arg0 + $arg1 + $arg2
18709 To execute the command use:
18716 This defines the command @code{adder}, which prints the sum of
18717 its three arguments. Note the arguments are text substitutions, so they may
18718 reference variables, use complex expressions, or even perform inferior
18721 @cindex argument count in user-defined commands
18722 @cindex how many arguments (user-defined commands)
18723 In addition, @code{$argc} may be used to find out how many arguments have
18724 been passed. This expands to a number in the range 0@dots{}10.
18729 print $arg0 + $arg1
18732 print $arg0 + $arg1 + $arg2
18740 @item define @var{commandname}
18741 Define a command named @var{commandname}. If there is already a command
18742 by that name, you are asked to confirm that you want to redefine it.
18743 @var{commandname} may be a bare command name consisting of letters,
18744 numbers, dashes, and underscores. It may also start with any predefined
18745 prefix command. For example, @samp{define target my-target} creates
18746 a user-defined @samp{target my-target} command.
18748 The definition of the command is made up of other @value{GDBN} command lines,
18749 which are given following the @code{define} command. The end of these
18750 commands is marked by a line containing @code{end}.
18753 @kindex end@r{ (user-defined commands)}
18754 @item document @var{commandname}
18755 Document the user-defined command @var{commandname}, so that it can be
18756 accessed by @code{help}. The command @var{commandname} must already be
18757 defined. This command reads lines of documentation just as @code{define}
18758 reads the lines of the command definition, ending with @code{end}.
18759 After the @code{document} command is finished, @code{help} on command
18760 @var{commandname} displays the documentation you have written.
18762 You may use the @code{document} command again to change the
18763 documentation of a command. Redefining the command with @code{define}
18764 does not change the documentation.
18766 @kindex dont-repeat
18767 @cindex don't repeat command
18769 Used inside a user-defined command, this tells @value{GDBN} that this
18770 command should not be repeated when the user hits @key{RET}
18771 (@pxref{Command Syntax, repeat last command}).
18773 @kindex help user-defined
18774 @item help user-defined
18775 List all user-defined commands, with the first line of the documentation
18780 @itemx show user @var{commandname}
18781 Display the @value{GDBN} commands used to define @var{commandname} (but
18782 not its documentation). If no @var{commandname} is given, display the
18783 definitions for all user-defined commands.
18785 @cindex infinite recursion in user-defined commands
18786 @kindex show max-user-call-depth
18787 @kindex set max-user-call-depth
18788 @item show max-user-call-depth
18789 @itemx set max-user-call-depth
18790 The value of @code{max-user-call-depth} controls how many recursion
18791 levels are allowed in user-defined commands before @value{GDBN} suspects an
18792 infinite recursion and aborts the command.
18795 In addition to the above commands, user-defined commands frequently
18796 use control flow commands, described in @ref{Command Files}.
18798 When user-defined commands are executed, the
18799 commands of the definition are not printed. An error in any command
18800 stops execution of the user-defined command.
18802 If used interactively, commands that would ask for confirmation proceed
18803 without asking when used inside a user-defined command. Many @value{GDBN}
18804 commands that normally print messages to say what they are doing omit the
18805 messages when used in a user-defined command.
18808 @subsection User-defined Command Hooks
18809 @cindex command hooks
18810 @cindex hooks, for commands
18811 @cindex hooks, pre-command
18814 You may define @dfn{hooks}, which are a special kind of user-defined
18815 command. Whenever you run the command @samp{foo}, if the user-defined
18816 command @samp{hook-foo} exists, it is executed (with no arguments)
18817 before that command.
18819 @cindex hooks, post-command
18821 A hook may also be defined which is run after the command you executed.
18822 Whenever you run the command @samp{foo}, if the user-defined command
18823 @samp{hookpost-foo} exists, it is executed (with no arguments) after
18824 that command. Post-execution hooks may exist simultaneously with
18825 pre-execution hooks, for the same command.
18827 It is valid for a hook to call the command which it hooks. If this
18828 occurs, the hook is not re-executed, thereby avoiding infinite recursion.
18830 @c It would be nice if hookpost could be passed a parameter indicating
18831 @c if the command it hooks executed properly or not. FIXME!
18833 @kindex stop@r{, a pseudo-command}
18834 In addition, a pseudo-command, @samp{stop} exists. Defining
18835 (@samp{hook-stop}) makes the associated commands execute every time
18836 execution stops in your program: before breakpoint commands are run,
18837 displays are printed, or the stack frame is printed.
18839 For example, to ignore @code{SIGALRM} signals while
18840 single-stepping, but treat them normally during normal execution,
18845 handle SIGALRM nopass
18849 handle SIGALRM pass
18852 define hook-continue
18853 handle SIGALRM pass
18857 As a further example, to hook at the beginning and end of the @code{echo}
18858 command, and to add extra text to the beginning and end of the message,
18866 define hookpost-echo
18870 (@value{GDBP}) echo Hello World
18871 <<<---Hello World--->>>
18876 You can define a hook for any single-word command in @value{GDBN}, but
18877 not for command aliases; you should define a hook for the basic command
18878 name, e.g.@: @code{backtrace} rather than @code{bt}.
18879 @c FIXME! So how does Joe User discover whether a command is an alias
18881 You can hook a multi-word command by adding @code{hook-} or
18882 @code{hookpost-} to the last word of the command, e.g.@:
18883 @samp{define target hook-remote} to add a hook to @samp{target remote}.
18885 If an error occurs during the execution of your hook, execution of
18886 @value{GDBN} commands stops and @value{GDBN} issues a prompt
18887 (before the command that you actually typed had a chance to run).
18889 If you try to define a hook which does not match any known command, you
18890 get a warning from the @code{define} command.
18892 @node Command Files
18893 @subsection Command Files
18895 @cindex command files
18896 @cindex scripting commands
18897 A command file for @value{GDBN} is a text file made of lines that are
18898 @value{GDBN} commands. Comments (lines starting with @kbd{#}) may
18899 also be included. An empty line in a command file does nothing; it
18900 does not mean to repeat the last command, as it would from the
18903 You can request the execution of a command file with the @code{source}
18908 @cindex execute commands from a file
18909 @item source [@code{-v}] @var{filename}
18910 Execute the command file @var{filename}.
18913 The lines in a command file are generally executed sequentially,
18914 unless the order of execution is changed by one of the
18915 @emph{flow-control commands} described below. The commands are not
18916 printed as they are executed. An error in any command terminates
18917 execution of the command file and control is returned to the console.
18919 @value{GDBN} searches for @var{filename} in the current directory and then
18920 on the search path (specified with the @samp{directory} command).
18922 If @code{-v}, for verbose mode, is given then @value{GDBN} displays
18923 each command as it is executed. The option must be given before
18924 @var{filename}, and is interpreted as part of the filename anywhere else.
18926 Commands that would ask for confirmation if used interactively proceed
18927 without asking when used in a command file. Many @value{GDBN} commands that
18928 normally print messages to say what they are doing omit the messages
18929 when called from command files.
18931 @value{GDBN} also accepts command input from standard input. In this
18932 mode, normal output goes to standard output and error output goes to
18933 standard error. Errors in a command file supplied on standard input do
18934 not terminate execution of the command file---execution continues with
18938 gdb < cmds > log 2>&1
18941 (The syntax above will vary depending on the shell used.) This example
18942 will execute commands from the file @file{cmds}. All output and errors
18943 would be directed to @file{log}.
18945 Since commands stored on command files tend to be more general than
18946 commands typed interactively, they frequently need to deal with
18947 complicated situations, such as different or unexpected values of
18948 variables and symbols, changes in how the program being debugged is
18949 built, etc. @value{GDBN} provides a set of flow-control commands to
18950 deal with these complexities. Using these commands, you can write
18951 complex scripts that loop over data structures, execute commands
18952 conditionally, etc.
18959 This command allows to include in your script conditionally executed
18960 commands. The @code{if} command takes a single argument, which is an
18961 expression to evaluate. It is followed by a series of commands that
18962 are executed only if the expression is true (its value is nonzero).
18963 There can then optionally be an @code{else} line, followed by a series
18964 of commands that are only executed if the expression was false. The
18965 end of the list is marked by a line containing @code{end}.
18969 This command allows to write loops. Its syntax is similar to
18970 @code{if}: the command takes a single argument, which is an expression
18971 to evaluate, and must be followed by the commands to execute, one per
18972 line, terminated by an @code{end}. These commands are called the
18973 @dfn{body} of the loop. The commands in the body of @code{while} are
18974 executed repeatedly as long as the expression evaluates to true.
18978 This command exits the @code{while} loop in whose body it is included.
18979 Execution of the script continues after that @code{while}s @code{end}
18982 @kindex loop_continue
18983 @item loop_continue
18984 This command skips the execution of the rest of the body of commands
18985 in the @code{while} loop in whose body it is included. Execution
18986 branches to the beginning of the @code{while} loop, where it evaluates
18987 the controlling expression.
18989 @kindex end@r{ (if/else/while commands)}
18991 Terminate the block of commands that are the body of @code{if},
18992 @code{else}, or @code{while} flow-control commands.
18997 @subsection Commands for Controlled Output
18999 During the execution of a command file or a user-defined command, normal
19000 @value{GDBN} output is suppressed; the only output that appears is what is
19001 explicitly printed by the commands in the definition. This section
19002 describes three commands useful for generating exactly the output you
19007 @item echo @var{text}
19008 @c I do not consider backslash-space a standard C escape sequence
19009 @c because it is not in ANSI.
19010 Print @var{text}. Nonprinting characters can be included in
19011 @var{text} using C escape sequences, such as @samp{\n} to print a
19012 newline. @strong{No newline is printed unless you specify one.}
19013 In addition to the standard C escape sequences, a backslash followed
19014 by a space stands for a space. This is useful for displaying a
19015 string with spaces at the beginning or the end, since leading and
19016 trailing spaces are otherwise trimmed from all arguments.
19017 To print @samp{@w{ }and foo =@w{ }}, use the command
19018 @samp{echo \@w{ }and foo = \@w{ }}.
19020 A backslash at the end of @var{text} can be used, as in C, to continue
19021 the command onto subsequent lines. For example,
19024 echo This is some text\n\
19025 which is continued\n\
19026 onto several lines.\n
19029 produces the same output as
19032 echo This is some text\n
19033 echo which is continued\n
19034 echo onto several lines.\n
19038 @item output @var{expression}
19039 Print the value of @var{expression} and nothing but that value: no
19040 newlines, no @samp{$@var{nn} = }. The value is not entered in the
19041 value history either. @xref{Expressions, ,Expressions}, for more information
19044 @item output/@var{fmt} @var{expression}
19045 Print the value of @var{expression} in format @var{fmt}. You can use
19046 the same formats as for @code{print}. @xref{Output Formats,,Output
19047 Formats}, for more information.
19050 @item printf @var{template}, @var{expressions}@dots{}
19051 Print the values of one or more @var{expressions} under the control of
19052 the string @var{template}. To print several values, make
19053 @var{expressions} be a comma-separated list of individual expressions,
19054 which may be either numbers or pointers. Their values are printed as
19055 specified by @var{template}, exactly as a C program would do by
19056 executing the code below:
19059 printf (@var{template}, @var{expressions}@dots{});
19062 As in @code{C} @code{printf}, ordinary characters in @var{template}
19063 are printed verbatim, while @dfn{conversion specification} introduced
19064 by the @samp{%} character cause subsequent @var{expressions} to be
19065 evaluated, their values converted and formatted according to type and
19066 style information encoded in the conversion specifications, and then
19069 For example, you can print two values in hex like this:
19072 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
19075 @code{printf} supports all the standard @code{C} conversion
19076 specifications, including the flags and modifiers between the @samp{%}
19077 character and the conversion letter, with the following exceptions:
19081 The argument-ordering modifiers, such as @samp{2$}, are not supported.
19084 The modifier @samp{*} is not supported for specifying precision or
19088 The @samp{'} flag (for separation of digits into groups according to
19089 @code{LC_NUMERIC'}) is not supported.
19092 The type modifiers @samp{hh}, @samp{j}, @samp{t}, and @samp{z} are not
19096 The conversion letter @samp{n} (as in @samp{%n}) is not supported.
19099 The conversion letters @samp{a} and @samp{A} are not supported.
19103 Note that the @samp{ll} type modifier is supported only if the
19104 underlying @code{C} implementation used to build @value{GDBN} supports
19105 the @code{long long int} type, and the @samp{L} type modifier is
19106 supported only if @code{long double} type is available.
19108 As in @code{C}, @code{printf} supports simple backslash-escape
19109 sequences, such as @code{\n}, @samp{\t}, @samp{\\}, @samp{\"},
19110 @samp{\a}, and @samp{\f}, that consist of backslash followed by a
19111 single character. Octal and hexadecimal escape sequences are not
19114 Additionally, @code{printf} supports conversion specifications for DFP
19115 (@dfn{Decimal Floating Point}) types using the following length modifiers
19116 together with a floating point specifier.
19121 @samp{H} for printing @code{Decimal32} types.
19124 @samp{D} for printing @code{Decimal64} types.
19127 @samp{DD} for printing @code{Decimal128} types.
19130 If the underlying @code{C} implementation used to build @value{GDBN} has
19131 support for the three length modifiers for DFP types, other modifiers
19132 such as width and precision will also be available for @value{GDBN} to use.
19134 In case there is no such @code{C} support, no additional modifiers will be
19135 available and the value will be printed in the standard way.
19137 Here's an example of printing DFP types using the above conversion letters:
19139 printf "D32: %Hf - D64: %Df - D128: %DDf\n",1.2345df,1.2E10dd,1.2E1dl
19145 @section Scripting @value{GDBN} using Python
19146 @cindex python scripting
19147 @cindex scripting with python
19149 You can script @value{GDBN} using the @uref{http://www.python.org/,
19150 Python programming language}. This feature is available only if
19151 @value{GDBN} was configured using @option{--with-python}.
19154 * Python Commands:: Accessing Python from @value{GDBN}.
19155 * Python API:: Accessing @value{GDBN} from Python.
19158 @node Python Commands
19159 @subsection Python Commands
19160 @cindex python commands
19161 @cindex commands to access python
19163 @value{GDBN} provides one command for accessing the Python interpreter,
19164 and one related setting:
19168 @item python @r{[}@var{code}@r{]}
19169 The @code{python} command can be used to evaluate Python code.
19171 If given an argument, the @code{python} command will evaluate the
19172 argument as a Python command. For example:
19175 (@value{GDBP}) python print 23
19179 If you do not provide an argument to @code{python}, it will act as a
19180 multi-line command, like @code{define}. In this case, the Python
19181 script is made up of subsequent command lines, given after the
19182 @code{python} command. This command list is terminated using a line
19183 containing @code{end}. For example:
19186 (@value{GDBP}) python
19188 End with a line saying just "end".
19194 @kindex maint set python print-stack
19195 @item maint set python print-stack
19196 By default, @value{GDBN} will print a stack trace when an error occurs
19197 in a Python script. This can be controlled using @code{maint set
19198 python print-stack}: if @code{on}, the default, then Python stack
19199 printing is enabled; if @code{off}, then Python stack printing is
19204 @subsection Python API
19206 @cindex programming in python
19208 @cindex python stdout
19209 @cindex python pagination
19210 At startup, @value{GDBN} overrides Python's @code{sys.stdout} and
19211 @code{sys.stderr} to print using @value{GDBN}'s output-paging streams.
19212 A Python program which outputs to one of these streams may have its
19213 output interrupted by the user (@pxref{Screen Size}). In this
19214 situation, a Python @code{KeyboardInterrupt} exception is thrown.
19217 * Basic Python:: Basic Python Functions.
19218 * Exception Handling::
19219 * Auto-loading:: Automatically loading Python code.
19220 * Values From Inferior::
19221 * Types In Python:: Python representation of types.
19222 * Pretty Printing:: Pretty-printing values.
19223 * Selecting Pretty-Printers:: How GDB chooses a pretty-printer.
19224 * Commands In Python:: Implementing new commands in Python.
19225 * Functions In Python:: Writing new convenience functions.
19226 * Objfiles In Python:: Object files.
19227 * Frames In Python:: Acessing inferior stack frames from Python.
19231 @subsubsection Basic Python
19233 @cindex python functions
19234 @cindex python module
19236 @value{GDBN} introduces a new Python module, named @code{gdb}. All
19237 methods and classes added by @value{GDBN} are placed in this module.
19238 @value{GDBN} automatically @code{import}s the @code{gdb} module for
19239 use in all scripts evaluated by the @code{python} command.
19241 @findex gdb.execute
19242 @defun execute command [from_tty]
19243 Evaluate @var{command}, a string, as a @value{GDBN} CLI command.
19244 If a GDB exception happens while @var{command} runs, it is
19245 translated as described in @ref{Exception Handling,,Exception Handling}.
19246 If no exceptions occur, this function returns @code{None}.
19248 @var{from_tty} specifies whether @value{GDBN} ought to consider this
19249 command as having originated from the user invoking it interactively.
19250 It must be a boolean value. If omitted, it defaults to @code{False}.
19253 @findex gdb.parameter
19254 @defun parameter parameter
19255 Return the value of a @value{GDBN} parameter. @var{parameter} is a
19256 string naming the parameter to look up; @var{parameter} may contain
19257 spaces if the parameter has a multi-part name. For example,
19258 @samp{print object} is a valid parameter name.
19260 If the named parameter does not exist, this function throws a
19261 @code{RuntimeError}. Otherwise, the parameter's value is converted to
19262 a Python value of the appropriate type, and returned.
19265 @findex gdb.history
19266 @defun history number
19267 Return a value from @value{GDBN}'s value history (@pxref{Value
19268 History}). @var{number} indicates which history element to return.
19269 If @var{number} is negative, then @value{GDBN} will take its absolute value
19270 and count backward from the last element (i.e., the most recent element) to
19271 find the value to return. If @var{number} is zero, then @value{GDBN} will
19272 return the most recent element. If the element specified by @var{number}
19273 doesn't exist in the value history, a @code{RuntimeError} exception will be
19276 If no exception is raised, the return value is always an instance of
19277 @code{gdb.Value} (@pxref{Values From Inferior}).
19281 @defun write string
19282 Print a string to @value{GDBN}'s paginated standard output stream.
19283 Writing to @code{sys.stdout} or @code{sys.stderr} will automatically
19284 call this function.
19289 Flush @value{GDBN}'s paginated standard output stream. Flushing
19290 @code{sys.stdout} or @code{sys.stderr} will automatically call this
19294 @node Exception Handling
19295 @subsubsection Exception Handling
19296 @cindex python exceptions
19297 @cindex exceptions, python
19299 When executing the @code{python} command, Python exceptions
19300 uncaught within the Python code are translated to calls to
19301 @value{GDBN} error-reporting mechanism. If the command that called
19302 @code{python} does not handle the error, @value{GDBN} will
19303 terminate it and print an error message containing the Python
19304 exception name, the associated value, and the Python call stack
19305 backtrace at the point where the exception was raised. Example:
19308 (@value{GDBP}) python print foo
19309 Traceback (most recent call last):
19310 File "<string>", line 1, in <module>
19311 NameError: name 'foo' is not defined
19314 @value{GDBN} errors that happen in @value{GDBN} commands invoked by Python
19315 code are converted to Python @code{RuntimeError} exceptions. User
19316 interrupt (via @kbd{C-c} or by typing @kbd{q} at a pagination
19317 prompt) is translated to a Python @code{KeyboardInterrupt}
19318 exception. If you catch these exceptions in your Python code, your
19319 exception handler will see @code{RuntimeError} or
19320 @code{KeyboardInterrupt} as the exception type, the @value{GDBN} error
19321 message as its value, and the Python call stack backtrace at the
19322 Python statement closest to where the @value{GDBN} error occured as the
19326 @subsubsection Auto-loading
19327 @cindex auto-loading, Python
19329 When a new object file is read (for example, due to the @code{file}
19330 command, or because the inferior has loaded a shared library),
19331 @value{GDBN} will look for a file named @file{@var{objfile}-gdb.py},
19332 where @var{objfile} is the object file's real name, formed by ensuring
19333 that the file name is absolute, following all symlinks, and resolving
19334 @code{.} and @code{..} components. If this file exists and is
19335 readable, @value{GDBN} will evaluate it as a Python script.
19337 If this file does not exist, and if the parameter
19338 @code{debug-file-directory} is set (@pxref{Separate Debug Files}),
19339 then @value{GDBN} will use the file named
19340 @file{@var{debug-file-directory}/@var{real-name}}, where
19341 @var{real-name} is the object file's real name, as described above.
19343 Finally, if this file does not exist, then @value{GDBN} will look for
19344 a file named @file{@var{data-directory}/python/auto-load/@var{real-name}}, where
19345 @var{data-directory} is @value{GDBN}'s data directory (available via
19346 @code{show data-directory}, @pxref{Data Files}), and @var{real-name}
19347 is the object file's real name, as described above.
19349 When reading an auto-loaded file, @value{GDBN} sets the ``current
19350 objfile''. This is available via the @code{gdb.current_objfile}
19351 function (@pxref{Objfiles In Python}). This can be useful for
19352 registering objfile-specific pretty-printers.
19354 The auto-loading feature is useful for supplying application-specific
19355 debugging commands and scripts. You can enable or disable this
19356 feature, and view its current state.
19359 @kindex maint set python auto-load
19360 @item maint set python auto-load [yes|no]
19361 Enable or disable the Python auto-loading feature.
19363 @kindex show python auto-load
19364 @item show python auto-load
19365 Show whether Python auto-loading is enabled or disabled.
19368 @value{GDBN} does not track which files it has already auto-loaded.
19369 So, your @samp{-gdb.py} file should take care to ensure that it may be
19370 evaluated multiple times without error.
19372 @node Values From Inferior
19373 @subsubsection Values From Inferior
19374 @cindex values from inferior, with Python
19375 @cindex python, working with values from inferior
19377 @cindex @code{gdb.Value}
19378 @value{GDBN} provides values it obtains from the inferior program in
19379 an object of type @code{gdb.Value}. @value{GDBN} uses this object
19380 for its internal bookkeeping of the inferior's values, and for
19381 fetching values when necessary.
19383 Inferior values that are simple scalars can be used directly in
19384 Python expressions that are valid for the value's data type. Here's
19385 an example for an integer or floating-point value @code{some_val}:
19392 As result of this, @code{bar} will also be a @code{gdb.Value} object
19393 whose values are of the same type as those of @code{some_val}.
19395 Inferior values that are structures or instances of some class can
19396 be accessed using the Python @dfn{dictionary syntax}. For example, if
19397 @code{some_val} is a @code{gdb.Value} instance holding a structure, you
19398 can access its @code{foo} element with:
19401 bar = some_val['foo']
19404 Again, @code{bar} will also be a @code{gdb.Value} object.
19406 The following attributes are provided:
19409 @defivar Value address
19410 If this object is addressable, this read-only attribute holds a
19411 @code{gdb.Value} object representing the address. Otherwise,
19412 this attribute holds @code{None}.
19415 @cindex optimized out value in Python
19416 @defivar Value is_optimized_out
19417 This read-only boolean attribute is true if the compiler optimized out
19418 this value, thus it is not available for fetching from the inferior.
19421 @defivar Value type
19422 The type of this @code{gdb.Value}. The value of this attribute is a
19423 @code{gdb.Type} object.
19427 The following methods are provided:
19430 @defmethod Value dereference
19431 For pointer data types, this method returns a new @code{gdb.Value} object
19432 whose contents is the object pointed to by the pointer. For example, if
19433 @code{foo} is a C pointer to an @code{int}, declared in your C program as
19440 then you can use the corresponding @code{gdb.Value} to access what
19441 @code{foo} points to like this:
19444 bar = foo.dereference ()
19447 The result @code{bar} will be a @code{gdb.Value} object holding the
19448 value pointed to by @code{foo}.
19451 @defmethod Value string @r{[}encoding@r{]} @r{[}errors@r{]} @r{[}length@r{]}
19452 If this @code{gdb.Value} represents a string, then this method
19453 converts the contents to a Python string. Otherwise, this method will
19454 throw an exception.
19456 Strings are recognized in a language-specific way; whether a given
19457 @code{gdb.Value} represents a string is determined by the current
19460 For C-like languages, a value is a string if it is a pointer to or an
19461 array of characters or ints. The string is assumed to be terminated
19462 by a zero of the appropriate width. However if the optional length
19463 argument is given, the string will be converted to that given length,
19464 ignoring any embedded zeros that the string may contain.
19466 If the optional @var{encoding} argument is given, it must be a string
19467 naming the encoding of the string in the @code{gdb.Value}, such as
19468 @code{"ascii"}, @code{"iso-8859-6"} or @code{"utf-8"}. It accepts
19469 the same encodings as the corresponding argument to Python's
19470 @code{string.decode} method, and the Python codec machinery will be used
19471 to convert the string. If @var{encoding} is not given, or if
19472 @var{encoding} is the empty string, then either the @code{target-charset}
19473 (@pxref{Character Sets}) will be used, or a language-specific encoding
19474 will be used, if the current language is able to supply one.
19476 The optional @var{errors} argument is the same as the corresponding
19477 argument to Python's @code{string.decode} method.
19479 If the optional @var{length} argument is given, the string will be
19480 fetched and converted to the given length.
19484 @node Types In Python
19485 @subsubsection Types In Python
19486 @cindex types in Python
19487 @cindex Python, working with types
19490 @value{GDBN} represents types from the inferior using the class
19493 The following type-related functions are available in the @code{gdb}
19496 @findex gdb.lookup_type
19497 @defun lookup_type name [block]
19498 This function looks up a type by name. @var{name} is the name of the
19499 type to look up. It must be a string.
19501 Ordinarily, this function will return an instance of @code{gdb.Type}.
19502 If the named type cannot be found, it will throw an exception.
19505 An instance of @code{Type} has the following attributes:
19509 The type code for this type. The type code will be one of the
19510 @code{TYPE_CODE_} constants defined below.
19513 @defivar Type sizeof
19514 The size of this type, in target @code{char} units. Usually, a
19515 target's @code{char} type will be an 8-bit byte. However, on some
19516 unusual platforms, this type may have a different size.
19520 The tag name for this type. The tag name is the name after
19521 @code{struct}, @code{union}, or @code{enum} in C and C@t{++}; not all
19522 languages have this concept. If this type has no tag name, then
19523 @code{None} is returned.
19527 The following methods are provided:
19530 @defmethod Type fields
19531 For structure and union types, this method returns the fields. Range
19532 types have two fields, the minimum and maximum values. Enum types
19533 have one field per enum constant. Function and method types have one
19534 field per parameter. The base types of C@t{++} classes are also
19535 represented as fields. If the type has no fields, or does not fit
19536 into one of these categories, an empty sequence will be returned.
19538 Each field is an object, with some pre-defined attributes:
19541 This attribute is not available for @code{static} fields (as in
19542 C@t{++} or Java). For non-@code{static} fields, the value is the bit
19543 position of the field.
19546 The name of the field, or @code{None} for anonymous fields.
19549 This is @code{True} if the field is artificial, usually meaning that
19550 it was provided by the compiler and not the user. This attribute is
19551 always provided, and is @code{False} if the field is not artificial.
19554 If the field is packed, or is a bitfield, then this will have a
19555 non-zero value, which is the size of the field in bits. Otherwise,
19556 this will be zero; in this case the field's size is given by its type.
19559 The type of the field. This is usually an instance of @code{Type},
19560 but it can be @code{None} in some situations.
19564 @defmethod Type const
19565 Return a new @code{gdb.Type} object which represents a
19566 @code{const}-qualified variant of this type.
19569 @defmethod Type volatile
19570 Return a new @code{gdb.Type} object which represents a
19571 @code{volatile}-qualified variant of this type.
19574 @defmethod Type unqualified
19575 Return a new @code{gdb.Type} object which represents an unqualified
19576 variant of this type. That is, the result is neither @code{const} nor
19580 @defmethod Type reference
19581 Return a new @code{gdb.Type} object which represents a reference to this
19585 @defmethod Type strip_typedefs
19586 Return a new @code{gdb.Type} that represents the real type,
19587 after removing all layers of typedefs.
19590 @defmethod Type target
19591 Return a new @code{gdb.Type} object which represents the target type
19594 For a pointer type, the target type is the type of the pointed-to
19595 object. For an array type (meaning C-like arrays), the target type is
19596 the type of the elements of the array. For a function or method type,
19597 the target type is the type of the return value. For a complex type,
19598 the target type is the type of the elements. For a typedef, the
19599 target type is the aliased type.
19601 If the type does not have a target, this method will throw an
19605 @defmethod Type template_argument n
19606 If this @code{gdb.Type} is an instantiation of a template, this will
19607 return a new @code{gdb.Type} which represents the type of the
19608 @var{n}th template argument.
19610 If this @code{gdb.Type} is not a template type, this will throw an
19611 exception. Ordinarily, only C@t{++} code will have template types.
19613 @var{name} is searched for globally.
19618 Each type has a code, which indicates what category this type falls
19619 into. The available type categories are represented by constants
19620 defined in the @code{gdb} module:
19623 @findex TYPE_CODE_PTR
19624 @findex gdb.TYPE_CODE_PTR
19625 @item TYPE_CODE_PTR
19626 The type is a pointer.
19628 @findex TYPE_CODE_ARRAY
19629 @findex gdb.TYPE_CODE_ARRAY
19630 @item TYPE_CODE_ARRAY
19631 The type is an array.
19633 @findex TYPE_CODE_STRUCT
19634 @findex gdb.TYPE_CODE_STRUCT
19635 @item TYPE_CODE_STRUCT
19636 The type is a structure.
19638 @findex TYPE_CODE_UNION
19639 @findex gdb.TYPE_CODE_UNION
19640 @item TYPE_CODE_UNION
19641 The type is a union.
19643 @findex TYPE_CODE_ENUM
19644 @findex gdb.TYPE_CODE_ENUM
19645 @item TYPE_CODE_ENUM
19646 The type is an enum.
19648 @findex TYPE_CODE_FLAGS
19649 @findex gdb.TYPE_CODE_FLAGS
19650 @item TYPE_CODE_FLAGS
19651 A bit flags type, used for things such as status registers.
19653 @findex TYPE_CODE_FUNC
19654 @findex gdb.TYPE_CODE_FUNC
19655 @item TYPE_CODE_FUNC
19656 The type is a function.
19658 @findex TYPE_CODE_INT
19659 @findex gdb.TYPE_CODE_INT
19660 @item TYPE_CODE_INT
19661 The type is an integer type.
19663 @findex TYPE_CODE_FLT
19664 @findex gdb.TYPE_CODE_FLT
19665 @item TYPE_CODE_FLT
19666 A floating point type.
19668 @findex TYPE_CODE_VOID
19669 @findex gdb.TYPE_CODE_VOID
19670 @item TYPE_CODE_VOID
19671 The special type @code{void}.
19673 @findex TYPE_CODE_SET
19674 @findex gdb.TYPE_CODE_SET
19675 @item TYPE_CODE_SET
19678 @findex TYPE_CODE_RANGE
19679 @findex gdb.TYPE_CODE_RANGE
19680 @item TYPE_CODE_RANGE
19681 A range type, that is, an integer type with bounds.
19683 @findex TYPE_CODE_STRING
19684 @findex gdb.TYPE_CODE_STRING
19685 @item TYPE_CODE_STRING
19686 A string type. Note that this is only used for certain languages with
19687 language-defined string types; C strings are not represented this way.
19689 @findex TYPE_CODE_BITSTRING
19690 @findex gdb.TYPE_CODE_BITSTRING
19691 @item TYPE_CODE_BITSTRING
19694 @findex TYPE_CODE_ERROR
19695 @findex gdb.TYPE_CODE_ERROR
19696 @item TYPE_CODE_ERROR
19697 An unknown or erroneous type.
19699 @findex TYPE_CODE_METHOD
19700 @findex gdb.TYPE_CODE_METHOD
19701 @item TYPE_CODE_METHOD
19702 A method type, as found in C@t{++} or Java.
19704 @findex TYPE_CODE_METHODPTR
19705 @findex gdb.TYPE_CODE_METHODPTR
19706 @item TYPE_CODE_METHODPTR
19707 A pointer-to-member-function.
19709 @findex TYPE_CODE_MEMBERPTR
19710 @findex gdb.TYPE_CODE_MEMBERPTR
19711 @item TYPE_CODE_MEMBERPTR
19712 A pointer-to-member.
19714 @findex TYPE_CODE_REF
19715 @findex gdb.TYPE_CODE_REF
19716 @item TYPE_CODE_REF
19719 @findex TYPE_CODE_CHAR
19720 @findex gdb.TYPE_CODE_CHAR
19721 @item TYPE_CODE_CHAR
19724 @findex TYPE_CODE_BOOL
19725 @findex gdb.TYPE_CODE_BOOL
19726 @item TYPE_CODE_BOOL
19729 @findex TYPE_CODE_COMPLEX
19730 @findex gdb.TYPE_CODE_COMPLEX
19731 @item TYPE_CODE_COMPLEX
19732 A complex float type.
19734 @findex TYPE_CODE_TYPEDEF
19735 @findex gdb.TYPE_CODE_TYPEDEF
19736 @item TYPE_CODE_TYPEDEF
19737 A typedef to some other type.
19739 @findex TYPE_CODE_NAMESPACE
19740 @findex gdb.TYPE_CODE_NAMESPACE
19741 @item TYPE_CODE_NAMESPACE
19742 A C@t{++} namespace.
19744 @findex TYPE_CODE_DECFLOAT
19745 @findex gdb.TYPE_CODE_DECFLOAT
19746 @item TYPE_CODE_DECFLOAT
19747 A decimal floating point type.
19749 @findex TYPE_CODE_INTERNAL_FUNCTION
19750 @findex gdb.TYPE_CODE_INTERNAL_FUNCTION
19751 @item TYPE_CODE_INTERNAL_FUNCTION
19752 A function internal to @value{GDBN}. This is the type used to represent
19753 convenience functions.
19756 @node Pretty Printing
19757 @subsubsection Pretty Printing
19759 @value{GDBN} provides a mechanism to allow pretty-printing of values
19760 using Python code. The pretty-printer API allows application-specific
19761 code to greatly simplify the display of complex objects. This
19762 mechanism works for both MI and the CLI.
19764 For example, here is how a C@t{++} @code{std::string} looks without a
19768 (@value{GDBP}) print s
19770 static npos = 4294967295,
19772 <std::allocator<char>> = @{
19773 <__gnu_cxx::new_allocator<char>> = @{<No data fields>@}, <No data fields>@},
19774 members of std::basic_string<char, std::char_traits<char>, std::allocator<char> >::_Alloc_hider:
19775 _M_p = 0x804a014 "abcd"
19780 After a pretty-printer for @code{std::string} has been installed, only
19781 the contents are printed:
19784 (@value{GDBP}) print s
19788 A pretty-printer is just an object that holds a value and implements a
19789 specific interface, defined here.
19791 @defop Operation {pretty printer} children (self)
19792 @value{GDBN} will call this method on a pretty-printer to compute the
19793 children of the pretty-printer's value.
19795 This method must return an object conforming to the Python iterator
19796 protocol. Each item returned by the iterator must be a tuple holding
19797 two elements. The first element is the ``name'' of the child; the
19798 second element is the child's value. The value can be any Python
19799 object which is convertible to a @value{GDBN} value.
19801 This method is optional. If it does not exist, @value{GDBN} will act
19802 as though the value has no children.
19805 @defop Operation {pretty printer} display_hint (self)
19806 The CLI may call this method and use its result to change the
19807 formatting of a value. The result will also be supplied to an MI
19808 consumer as a @samp{displayhint} attribute of the variable being
19811 This method is optional. If it does exist, this method must return a
19814 Some display hints are predefined by @value{GDBN}:
19818 Indicate that the object being printed is ``array-like''. The CLI
19819 uses this to respect parameters such as @code{set print elements} and
19820 @code{set print array}.
19823 Indicate that the object being printed is ``map-like'', and that the
19824 children of this value can be assumed to alternate between keys and
19828 Indicate that the object being printed is ``string-like''. If the
19829 printer's @code{to_string} method returns a Python string of some
19830 kind, then @value{GDBN} will call its internal language-specific
19831 string-printing function to format the string. For the CLI this means
19832 adding quotation marks, possibly escaping some characters, respecting
19833 @code{set print elements}, and the like.
19837 @defop Operation {pretty printer} to_string (self)
19838 @value{GDBN} will call this method to display the string
19839 representation of the value passed to the object's constructor.
19841 When printing from the CLI, if the @code{to_string} method exists,
19842 then @value{GDBN} will prepend its result to the values returned by
19843 @code{children}. Exactly how this formatting is done is dependent on
19844 the display hint, and may change as more hints are added. Also,
19845 depending on the print settings (@pxref{Print Settings}), the CLI may
19846 print just the result of @code{to_string} in a stack trace, omitting
19847 the result of @code{children}.
19849 If this method returns a string, it is printed verbatim.
19851 Otherwise, if this method returns an instance of @code{gdb.Value},
19852 then @value{GDBN} prints this value. This may result in a call to
19853 another pretty-printer.
19855 If instead the method returns a Python value which is convertible to a
19856 @code{gdb.Value}, then @value{GDBN} performs the conversion and prints
19857 the resulting value. Again, this may result in a call to another
19858 pretty-printer. Python scalars (integers, floats, and booleans) and
19859 strings are convertible to @code{gdb.Value}; other types are not.
19861 If the result is not one of these types, an exception is raised.
19864 @node Selecting Pretty-Printers
19865 @subsubsection Selecting Pretty-Printers
19867 The Python list @code{gdb.pretty_printers} contains an array of
19868 functions that have been registered via addition as a pretty-printer.
19869 Each @code{gdb.Objfile} also contains a @code{pretty_printers}
19872 A function on one of these lists is passed a single @code{gdb.Value}
19873 argument and should return a pretty-printer object conforming to the
19874 interface definition above (@pxref{Pretty Printing}). If a function
19875 cannot create a pretty-printer for the value, it should return
19878 @value{GDBN} first checks the @code{pretty_printers} attribute of each
19879 @code{gdb.Objfile} and iteratively calls each function in the list for
19880 that @code{gdb.Objfile} until it receives a pretty-printer object.
19881 After these lists have been exhausted, it tries the global
19882 @code{gdb.pretty-printers} list, again calling each function until an
19883 object is returned.
19885 The order in which the objfiles are searched is not specified. For a
19886 given list, functions are always invoked from the head of the list,
19887 and iterated over sequentially until the end of the list, or a printer
19888 object is returned.
19890 Here is an example showing how a @code{std::string} printer might be
19894 class StdStringPrinter:
19895 "Print a std::string"
19897 def __init__ (self, val):
19900 def to_string (self):
19901 return self.val['_M_dataplus']['_M_p']
19903 def display_hint (self):
19907 And here is an example showing how a lookup function for the printer
19908 example above might be written.
19911 def str_lookup_function (val):
19913 lookup_tag = val.type.tag
19914 regex = re.compile ("^std::basic_string<char,.*>$")
19915 if lookup_tag == None:
19917 if regex.match (lookup_tag):
19918 return StdStringPrinter (val)
19923 The example lookup function extracts the value's type, and attempts to
19924 match it to a type that it can pretty-print. If it is a type the
19925 printer can pretty-print, it will return a printer object. If not, it
19926 returns @code{None}.
19928 We recommend that you put your core pretty-printers into a Python
19929 package. If your pretty-printers are for use with a library, we
19930 further recommend embedding a version number into the package name.
19931 This practice will enable @value{GDBN} to load multiple versions of
19932 your pretty-printers at the same time, because they will have
19935 You should write auto-loaded code (@pxref{Auto-loading}) such that it
19936 can be evaluated multiple times without changing its meaning. An
19937 ideal auto-load file will consist solely of @code{import}s of your
19938 printer modules, followed by a call to a register pretty-printers with
19939 the current objfile.
19941 Taken as a whole, this approach will scale nicely to multiple
19942 inferiors, each potentially using a different library version.
19943 Embedding a version number in the Python package name will ensure that
19944 @value{GDBN} is able to load both sets of printers simultaneously.
19945 Then, because the search for pretty-printers is done by objfile, and
19946 because your auto-loaded code took care to register your library's
19947 printers with a specific objfile, @value{GDBN} will find the correct
19948 printers for the specific version of the library used by each
19951 To continue the @code{std::string} example (@pxref{Pretty Printing}),
19952 this code might appear in @code{gdb.libstdcxx.v6}:
19955 def register_printers (objfile):
19956 objfile.pretty_printers.add (str_lookup_function)
19960 And then the corresponding contents of the auto-load file would be:
19963 import gdb.libstdcxx.v6
19964 gdb.libstdcxx.v6.register_printers (gdb.current_objfile ())
19967 @node Commands In Python
19968 @subsubsection Commands In Python
19970 @cindex commands in python
19971 @cindex python commands
19972 You can implement new @value{GDBN} CLI commands in Python. A CLI
19973 command is implemented using an instance of the @code{gdb.Command}
19974 class, most commonly using a subclass.
19976 @defmethod Command __init__ name @var{command_class} @r{[}@var{completer_class}@r{]} @r{[}@var{prefix}@r{]}
19977 The object initializer for @code{Command} registers the new command
19978 with @value{GDBN}. This initializer is normally invoked from the
19979 subclass' own @code{__init__} method.
19981 @var{name} is the name of the command. If @var{name} consists of
19982 multiple words, then the initial words are looked for as prefix
19983 commands. In this case, if one of the prefix commands does not exist,
19984 an exception is raised.
19986 There is no support for multi-line commands.
19988 @var{command_class} should be one of the @samp{COMMAND_} constants
19989 defined below. This argument tells @value{GDBN} how to categorize the
19990 new command in the help system.
19992 @var{completer_class} is an optional argument. If given, it should be
19993 one of the @samp{COMPLETE_} constants defined below. This argument
19994 tells @value{GDBN} how to perform completion for this command. If not
19995 given, @value{GDBN} will attempt to complete using the object's
19996 @code{complete} method (see below); if no such method is found, an
19997 error will occur when completion is attempted.
19999 @var{prefix} is an optional argument. If @code{True}, then the new
20000 command is a prefix command; sub-commands of this command may be
20003 The help text for the new command is taken from the Python
20004 documentation string for the command's class, if there is one. If no
20005 documentation string is provided, the default value ``This command is
20006 not documented.'' is used.
20009 @cindex don't repeat Python command
20010 @defmethod Command dont_repeat
20011 By default, a @value{GDBN} command is repeated when the user enters a
20012 blank line at the command prompt. A command can suppress this
20013 behavior by invoking the @code{dont_repeat} method. This is similar
20014 to the user command @code{dont-repeat}, see @ref{Define, dont-repeat}.
20017 @defmethod Command invoke argument from_tty
20018 This method is called by @value{GDBN} when this command is invoked.
20020 @var{argument} is a string. It is the argument to the command, after
20021 leading and trailing whitespace has been stripped.
20023 @var{from_tty} is a boolean argument. When true, this means that the
20024 command was entered by the user at the terminal; when false it means
20025 that the command came from elsewhere.
20027 If this method throws an exception, it is turned into a @value{GDBN}
20028 @code{error} call. Otherwise, the return value is ignored.
20031 @cindex completion of Python commands
20032 @defmethod Command complete text word
20033 This method is called by @value{GDBN} when the user attempts
20034 completion on this command. All forms of completion are handled by
20035 this method, that is, the @key{TAB} and @key{M-?} key bindings
20036 (@pxref{Completion}), and the @code{complete} command (@pxref{Help,
20039 The arguments @var{text} and @var{word} are both strings. @var{text}
20040 holds the complete command line up to the cursor's location.
20041 @var{word} holds the last word of the command line; this is computed
20042 using a word-breaking heuristic.
20044 The @code{complete} method can return several values:
20047 If the return value is a sequence, the contents of the sequence are
20048 used as the completions. It is up to @code{complete} to ensure that the
20049 contents actually do complete the word. A zero-length sequence is
20050 allowed, it means that there were no completions available. Only
20051 string elements of the sequence are used; other elements in the
20052 sequence are ignored.
20055 If the return value is one of the @samp{COMPLETE_} constants defined
20056 below, then the corresponding @value{GDBN}-internal completion
20057 function is invoked, and its result is used.
20060 All other results are treated as though there were no available
20065 When a new command is registered, it must be declared as a member of
20066 some general class of commands. This is used to classify top-level
20067 commands in the on-line help system; note that prefix commands are not
20068 listed under their own category but rather that of their top-level
20069 command. The available classifications are represented by constants
20070 defined in the @code{gdb} module:
20073 @findex COMMAND_NONE
20074 @findex gdb.COMMAND_NONE
20076 The command does not belong to any particular class. A command in
20077 this category will not be displayed in any of the help categories.
20079 @findex COMMAND_RUNNING
20080 @findex gdb.COMMAND_RUNNING
20081 @item COMMAND_RUNNING
20082 The command is related to running the inferior. For example,
20083 @code{start}, @code{step}, and @code{continue} are in this category.
20084 Type @kbd{help running} at the @value{GDBN} prompt to see a list of
20085 commands in this category.
20087 @findex COMMAND_DATA
20088 @findex gdb.COMMAND_DATA
20090 The command is related to data or variables. For example,
20091 @code{call}, @code{find}, and @code{print} are in this category. Type
20092 @kbd{help data} at the @value{GDBN} prompt to see a list of commands
20095 @findex COMMAND_STACK
20096 @findex gdb.COMMAND_STACK
20097 @item COMMAND_STACK
20098 The command has to do with manipulation of the stack. For example,
20099 @code{backtrace}, @code{frame}, and @code{return} are in this
20100 category. Type @kbd{help stack} at the @value{GDBN} prompt to see a
20101 list of commands in this category.
20103 @findex COMMAND_FILES
20104 @findex gdb.COMMAND_FILES
20105 @item COMMAND_FILES
20106 This class is used for file-related commands. For example,
20107 @code{file}, @code{list} and @code{section} are in this category.
20108 Type @kbd{help files} at the @value{GDBN} prompt to see a list of
20109 commands in this category.
20111 @findex COMMAND_SUPPORT
20112 @findex gdb.COMMAND_SUPPORT
20113 @item COMMAND_SUPPORT
20114 This should be used for ``support facilities'', generally meaning
20115 things that are useful to the user when interacting with @value{GDBN},
20116 but not related to the state of the inferior. For example,
20117 @code{help}, @code{make}, and @code{shell} are in this category. Type
20118 @kbd{help support} at the @value{GDBN} prompt to see a list of
20119 commands in this category.
20121 @findex COMMAND_STATUS
20122 @findex gdb.COMMAND_STATUS
20123 @item COMMAND_STATUS
20124 The command is an @samp{info}-related command, that is, related to the
20125 state of @value{GDBN} itself. For example, @code{info}, @code{macro},
20126 and @code{show} are in this category. Type @kbd{help status} at the
20127 @value{GDBN} prompt to see a list of commands in this category.
20129 @findex COMMAND_BREAKPOINTS
20130 @findex gdb.COMMAND_BREAKPOINTS
20131 @item COMMAND_BREAKPOINTS
20132 The command has to do with breakpoints. For example, @code{break},
20133 @code{clear}, and @code{delete} are in this category. Type @kbd{help
20134 breakpoints} at the @value{GDBN} prompt to see a list of commands in
20137 @findex COMMAND_TRACEPOINTS
20138 @findex gdb.COMMAND_TRACEPOINTS
20139 @item COMMAND_TRACEPOINTS
20140 The command has to do with tracepoints. For example, @code{trace},
20141 @code{actions}, and @code{tfind} are in this category. Type
20142 @kbd{help tracepoints} at the @value{GDBN} prompt to see a list of
20143 commands in this category.
20145 @findex COMMAND_OBSCURE
20146 @findex gdb.COMMAND_OBSCURE
20147 @item COMMAND_OBSCURE
20148 The command is only used in unusual circumstances, or is not of
20149 general interest to users. For example, @code{checkpoint},
20150 @code{fork}, and @code{stop} are in this category. Type @kbd{help
20151 obscure} at the @value{GDBN} prompt to see a list of commands in this
20154 @findex COMMAND_MAINTENANCE
20155 @findex gdb.COMMAND_MAINTENANCE
20156 @item COMMAND_MAINTENANCE
20157 The command is only useful to @value{GDBN} maintainers. The
20158 @code{maintenance} and @code{flushregs} commands are in this category.
20159 Type @kbd{help internals} at the @value{GDBN} prompt to see a list of
20160 commands in this category.
20163 A new command can use a predefined completion function, either by
20164 specifying it via an argument at initialization, or by returning it
20165 from the @code{complete} method. These predefined completion
20166 constants are all defined in the @code{gdb} module:
20169 @findex COMPLETE_NONE
20170 @findex gdb.COMPLETE_NONE
20171 @item COMPLETE_NONE
20172 This constant means that no completion should be done.
20174 @findex COMPLETE_FILENAME
20175 @findex gdb.COMPLETE_FILENAME
20176 @item COMPLETE_FILENAME
20177 This constant means that filename completion should be performed.
20179 @findex COMPLETE_LOCATION
20180 @findex gdb.COMPLETE_LOCATION
20181 @item COMPLETE_LOCATION
20182 This constant means that location completion should be done.
20183 @xref{Specify Location}.
20185 @findex COMPLETE_COMMAND
20186 @findex gdb.COMPLETE_COMMAND
20187 @item COMPLETE_COMMAND
20188 This constant means that completion should examine @value{GDBN}
20191 @findex COMPLETE_SYMBOL
20192 @findex gdb.COMPLETE_SYMBOL
20193 @item COMPLETE_SYMBOL
20194 This constant means that completion should be done using symbol names
20198 The following code snippet shows how a trivial CLI command can be
20199 implemented in Python:
20202 class HelloWorld (gdb.Command):
20203 """Greet the whole world."""
20205 def __init__ (self):
20206 super (HelloWorld, self).__init__ ("hello-world", gdb.COMMAND_OBSCURE)
20208 def invoke (self, arg, from_tty):
20209 print "Hello, World!"
20214 The last line instantiates the class, and is necessary to trigger the
20215 registration of the command with @value{GDBN}. Depending on how the
20216 Python code is read into @value{GDBN}, you may need to import the
20217 @code{gdb} module explicitly.
20219 @node Functions In Python
20220 @subsubsection Writing new convenience functions
20222 @cindex writing convenience functions
20223 @cindex convenience functions in python
20224 @cindex python convenience functions
20225 @tindex gdb.Function
20227 You can implement new convenience functions (@pxref{Convenience Vars})
20228 in Python. A convenience function is an instance of a subclass of the
20229 class @code{gdb.Function}.
20231 @defmethod Function __init__ name
20232 The initializer for @code{Function} registers the new function with
20233 @value{GDBN}. The argument @var{name} is the name of the function,
20234 a string. The function will be visible to the user as a convenience
20235 variable of type @code{internal function}, whose name is the same as
20236 the given @var{name}.
20238 The documentation for the new function is taken from the documentation
20239 string for the new class.
20242 @defmethod Function invoke @var{*args}
20243 When a convenience function is evaluated, its arguments are converted
20244 to instances of @code{gdb.Value}, and then the function's
20245 @code{invoke} method is called. Note that @value{GDBN} does not
20246 predetermine the arity of convenience functions. Instead, all
20247 available arguments are passed to @code{invoke}, following the
20248 standard Python calling convention. In particular, a convenience
20249 function can have default values for parameters without ill effect.
20251 The return value of this method is used as its value in the enclosing
20252 expression. If an ordinary Python value is returned, it is converted
20253 to a @code{gdb.Value} following the usual rules.
20256 The following code snippet shows how a trivial convenience function can
20257 be implemented in Python:
20260 class Greet (gdb.Function):
20261 """Return string to greet someone.
20262 Takes a name as argument."""
20264 def __init__ (self):
20265 super (Greet, self).__init__ ("greet")
20267 def invoke (self, name):
20268 return "Hello, %s!" % name.string ()
20273 The last line instantiates the class, and is necessary to trigger the
20274 registration of the function with @value{GDBN}. Depending on how the
20275 Python code is read into @value{GDBN}, you may need to import the
20276 @code{gdb} module explicitly.
20278 @node Objfiles In Python
20279 @subsubsection Objfiles In Python
20281 @cindex objfiles in python
20282 @tindex gdb.Objfile
20284 @value{GDBN} loads symbols for an inferior from various
20285 symbol-containing files (@pxref{Files}). These include the primary
20286 executable file, any shared libraries used by the inferior, and any
20287 separate debug info files (@pxref{Separate Debug Files}).
20288 @value{GDBN} calls these symbol-containing files @dfn{objfiles}.
20290 The following objfile-related functions are available in the
20293 @findex gdb.current_objfile
20294 @defun current_objfile
20295 When auto-loading a Python script (@pxref{Auto-loading}), @value{GDBN}
20296 sets the ``current objfile'' to the corresponding objfile. This
20297 function returns the current objfile. If there is no current objfile,
20298 this function returns @code{None}.
20301 @findex gdb.objfiles
20303 Return a sequence of all the objfiles current known to @value{GDBN}.
20304 @xref{Objfiles In Python}.
20307 Each objfile is represented by an instance of the @code{gdb.Objfile}
20310 @defivar Objfile filename
20311 The file name of the objfile as a string.
20314 @defivar Objfile pretty_printers
20315 The @code{pretty_printers} attribute is a list of functions. It is
20316 used to look up pretty-printers. A @code{Value} is passed to each
20317 function in order; if the function returns @code{None}, then the
20318 search continues. Otherwise, the return value should be an object
20319 which is used to format the value. @xref{Pretty Printing}, for more
20323 @node Frames In Python
20324 @subsubsection Acessing inferior stack frames from Python.
20326 @cindex frames in python
20327 When the debugged program stops, @value{GDBN} is able to analyze its call
20328 stack (@pxref{Frames,,Stack frames}). The @code{gdb.Frame} class
20329 represents a frame in the stack. A @code{gdb.Frame} object is only valid
20330 while its corresponding frame exists in the inferior's stack. If you try
20331 to use an invalid frame object, @value{GDBN} will throw a @code{RuntimeError}
20334 Two @code{gdb.Frame} objects can be compared for equality with the @code{==}
20338 (@value{GDBP}) python print gdb.newest_frame() == gdb.selected_frame ()
20342 The following frame-related functions are available in the @code{gdb} module:
20344 @findex gdb.selected_frame
20345 @defun selected_frame
20346 Return the selected frame object. (@pxref{Selection,,Selecting a Frame}).
20349 @defun frame_stop_reason_string reason
20350 Return a string explaining the reason why @value{GDBN} stopped unwinding
20351 frames, as expressed by the given @var{reason} code (an integer, see the
20352 @code{unwind_stop_reason} method further down in this section).
20355 A @code{gdb.Frame} object has the following methods:
20358 @defmethod Frame is_valid
20359 Returns true if the @code{gdb.Frame} object is valid, false if not.
20360 A frame object can become invalid if the frame it refers to doesn't
20361 exist anymore in the inferior. All @code{gdb.Frame} methods will throw
20362 an exception if it is invalid at the time the method is called.
20365 @defmethod Frame name
20366 Returns the function name of the frame, or @code{None} if it can't be
20370 @defmethod Frame type
20371 Returns the type of the frame. The value can be one of
20372 @code{gdb.NORMAL_FRAME}, @code{gdb.DUMMY_FRAME}, @code{gdb.SIGTRAMP_FRAME}
20373 or @code{gdb.SENTINEL_FRAME}.
20376 @defmethod Frame unwind_stop_reason
20377 Return an integer representing the reason why it's not possible to find
20378 more frames toward the outermost frame. Use
20379 @code{gdb.frame_stop_reason_string} to convert the value returned by this
20380 function to a string.
20383 @defmethod Frame pc
20384 Returns the frame's resume address.
20387 @defmethod Frame older
20388 Return the frame that called this frame.
20391 @defmethod Frame newer
20392 Return the frame called by this frame.
20395 @defmethod Frame read_var variable
20396 Return the value of the given variable in this frame. @var{variable} must
20402 @chapter Command Interpreters
20403 @cindex command interpreters
20405 @value{GDBN} supports multiple command interpreters, and some command
20406 infrastructure to allow users or user interface writers to switch
20407 between interpreters or run commands in other interpreters.
20409 @value{GDBN} currently supports two command interpreters, the console
20410 interpreter (sometimes called the command-line interpreter or @sc{cli})
20411 and the machine interface interpreter (or @sc{gdb/mi}). This manual
20412 describes both of these interfaces in great detail.
20414 By default, @value{GDBN} will start with the console interpreter.
20415 However, the user may choose to start @value{GDBN} with another
20416 interpreter by specifying the @option{-i} or @option{--interpreter}
20417 startup options. Defined interpreters include:
20421 @cindex console interpreter
20422 The traditional console or command-line interpreter. This is the most often
20423 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
20424 @value{GDBN} will use this interpreter.
20427 @cindex mi interpreter
20428 The newest @sc{gdb/mi} interface (currently @code{mi2}). Used primarily
20429 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
20430 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
20434 @cindex mi2 interpreter
20435 The current @sc{gdb/mi} interface.
20438 @cindex mi1 interpreter
20439 The @sc{gdb/mi} interface included in @value{GDBN} 5.1, 5.2, and 5.3.
20443 @cindex invoke another interpreter
20444 The interpreter being used by @value{GDBN} may not be dynamically
20445 switched at runtime. Although possible, this could lead to a very
20446 precarious situation. Consider an IDE using @sc{gdb/mi}. If a user
20447 enters the command "interpreter-set console" in a console view,
20448 @value{GDBN} would switch to using the console interpreter, rendering
20449 the IDE inoperable!
20451 @kindex interpreter-exec
20452 Although you may only choose a single interpreter at startup, you may execute
20453 commands in any interpreter from the current interpreter using the appropriate
20454 command. If you are running the console interpreter, simply use the
20455 @code{interpreter-exec} command:
20458 interpreter-exec mi "-data-list-register-names"
20461 @sc{gdb/mi} has a similar command, although it is only available in versions of
20462 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
20465 @chapter @value{GDBN} Text User Interface
20467 @cindex Text User Interface
20470 * TUI Overview:: TUI overview
20471 * TUI Keys:: TUI key bindings
20472 * TUI Single Key Mode:: TUI single key mode
20473 * TUI Commands:: TUI-specific commands
20474 * TUI Configuration:: TUI configuration variables
20477 The @value{GDBN} Text User Interface (TUI) is a terminal
20478 interface which uses the @code{curses} library to show the source
20479 file, the assembly output, the program registers and @value{GDBN}
20480 commands in separate text windows. The TUI mode is supported only
20481 on platforms where a suitable version of the @code{curses} library
20484 @pindex @value{GDBTUI}
20485 The TUI mode is enabled by default when you invoke @value{GDBN} as
20486 either @samp{@value{GDBTUI}} or @samp{@value{GDBP} -tui}.
20487 You can also switch in and out of TUI mode while @value{GDBN} runs by
20488 using various TUI commands and key bindings, such as @kbd{C-x C-a}.
20489 @xref{TUI Keys, ,TUI Key Bindings}.
20492 @section TUI Overview
20494 In TUI mode, @value{GDBN} can display several text windows:
20498 This window is the @value{GDBN} command window with the @value{GDBN}
20499 prompt and the @value{GDBN} output. The @value{GDBN} input is still
20500 managed using readline.
20503 The source window shows the source file of the program. The current
20504 line and active breakpoints are displayed in this window.
20507 The assembly window shows the disassembly output of the program.
20510 This window shows the processor registers. Registers are highlighted
20511 when their values change.
20514 The source and assembly windows show the current program position
20515 by highlighting the current line and marking it with a @samp{>} marker.
20516 Breakpoints are indicated with two markers. The first marker
20517 indicates the breakpoint type:
20521 Breakpoint which was hit at least once.
20524 Breakpoint which was never hit.
20527 Hardware breakpoint which was hit at least once.
20530 Hardware breakpoint which was never hit.
20533 The second marker indicates whether the breakpoint is enabled or not:
20537 Breakpoint is enabled.
20540 Breakpoint is disabled.
20543 The source, assembly and register windows are updated when the current
20544 thread changes, when the frame changes, or when the program counter
20547 These windows are not all visible at the same time. The command
20548 window is always visible. The others can be arranged in several
20559 source and assembly,
20562 source and registers, or
20565 assembly and registers.
20568 A status line above the command window shows the following information:
20572 Indicates the current @value{GDBN} target.
20573 (@pxref{Targets, ,Specifying a Debugging Target}).
20576 Gives the current process or thread number.
20577 When no process is being debugged, this field is set to @code{No process}.
20580 Gives the current function name for the selected frame.
20581 The name is demangled if demangling is turned on (@pxref{Print Settings}).
20582 When there is no symbol corresponding to the current program counter,
20583 the string @code{??} is displayed.
20586 Indicates the current line number for the selected frame.
20587 When the current line number is not known, the string @code{??} is displayed.
20590 Indicates the current program counter address.
20594 @section TUI Key Bindings
20595 @cindex TUI key bindings
20597 The TUI installs several key bindings in the readline keymaps
20598 (@pxref{Command Line Editing}). The following key bindings
20599 are installed for both TUI mode and the @value{GDBN} standard mode.
20608 Enter or leave the TUI mode. When leaving the TUI mode,
20609 the curses window management stops and @value{GDBN} operates using
20610 its standard mode, writing on the terminal directly. When reentering
20611 the TUI mode, control is given back to the curses windows.
20612 The screen is then refreshed.
20616 Use a TUI layout with only one window. The layout will
20617 either be @samp{source} or @samp{assembly}. When the TUI mode
20618 is not active, it will switch to the TUI mode.
20620 Think of this key binding as the Emacs @kbd{C-x 1} binding.
20624 Use a TUI layout with at least two windows. When the current
20625 layout already has two windows, the next layout with two windows is used.
20626 When a new layout is chosen, one window will always be common to the
20627 previous layout and the new one.
20629 Think of it as the Emacs @kbd{C-x 2} binding.
20633 Change the active window. The TUI associates several key bindings
20634 (like scrolling and arrow keys) with the active window. This command
20635 gives the focus to the next TUI window.
20637 Think of it as the Emacs @kbd{C-x o} binding.
20641 Switch in and out of the TUI SingleKey mode that binds single
20642 keys to @value{GDBN} commands (@pxref{TUI Single Key Mode}).
20645 The following key bindings only work in the TUI mode:
20650 Scroll the active window one page up.
20654 Scroll the active window one page down.
20658 Scroll the active window one line up.
20662 Scroll the active window one line down.
20666 Scroll the active window one column left.
20670 Scroll the active window one column right.
20674 Refresh the screen.
20677 Because the arrow keys scroll the active window in the TUI mode, they
20678 are not available for their normal use by readline unless the command
20679 window has the focus. When another window is active, you must use
20680 other readline key bindings such as @kbd{C-p}, @kbd{C-n}, @kbd{C-b}
20681 and @kbd{C-f} to control the command window.
20683 @node TUI Single Key Mode
20684 @section TUI Single Key Mode
20685 @cindex TUI single key mode
20687 The TUI also provides a @dfn{SingleKey} mode, which binds several
20688 frequently used @value{GDBN} commands to single keys. Type @kbd{C-x s} to
20689 switch into this mode, where the following key bindings are used:
20692 @kindex c @r{(SingleKey TUI key)}
20696 @kindex d @r{(SingleKey TUI key)}
20700 @kindex f @r{(SingleKey TUI key)}
20704 @kindex n @r{(SingleKey TUI key)}
20708 @kindex q @r{(SingleKey TUI key)}
20710 exit the SingleKey mode.
20712 @kindex r @r{(SingleKey TUI key)}
20716 @kindex s @r{(SingleKey TUI key)}
20720 @kindex u @r{(SingleKey TUI key)}
20724 @kindex v @r{(SingleKey TUI key)}
20728 @kindex w @r{(SingleKey TUI key)}
20733 Other keys temporarily switch to the @value{GDBN} command prompt.
20734 The key that was pressed is inserted in the editing buffer so that
20735 it is possible to type most @value{GDBN} commands without interaction
20736 with the TUI SingleKey mode. Once the command is entered the TUI
20737 SingleKey mode is restored. The only way to permanently leave
20738 this mode is by typing @kbd{q} or @kbd{C-x s}.
20742 @section TUI-specific Commands
20743 @cindex TUI commands
20745 The TUI has specific commands to control the text windows.
20746 These commands are always available, even when @value{GDBN} is not in
20747 the TUI mode. When @value{GDBN} is in the standard mode, most
20748 of these commands will automatically switch to the TUI mode.
20753 List and give the size of all displayed windows.
20757 Display the next layout.
20760 Display the previous layout.
20763 Display the source window only.
20766 Display the assembly window only.
20769 Display the source and assembly window.
20772 Display the register window together with the source or assembly window.
20776 Make the next window active for scrolling.
20779 Make the previous window active for scrolling.
20782 Make the source window active for scrolling.
20785 Make the assembly window active for scrolling.
20788 Make the register window active for scrolling.
20791 Make the command window active for scrolling.
20795 Refresh the screen. This is similar to typing @kbd{C-L}.
20797 @item tui reg float
20799 Show the floating point registers in the register window.
20801 @item tui reg general
20802 Show the general registers in the register window.
20805 Show the next register group. The list of register groups as well as
20806 their order is target specific. The predefined register groups are the
20807 following: @code{general}, @code{float}, @code{system}, @code{vector},
20808 @code{all}, @code{save}, @code{restore}.
20810 @item tui reg system
20811 Show the system registers in the register window.
20815 Update the source window and the current execution point.
20817 @item winheight @var{name} +@var{count}
20818 @itemx winheight @var{name} -@var{count}
20820 Change the height of the window @var{name} by @var{count}
20821 lines. Positive counts increase the height, while negative counts
20824 @item tabset @var{nchars}
20826 Set the width of tab stops to be @var{nchars} characters.
20829 @node TUI Configuration
20830 @section TUI Configuration Variables
20831 @cindex TUI configuration variables
20833 Several configuration variables control the appearance of TUI windows.
20836 @item set tui border-kind @var{kind}
20837 @kindex set tui border-kind
20838 Select the border appearance for the source, assembly and register windows.
20839 The possible values are the following:
20842 Use a space character to draw the border.
20845 Use @sc{ascii} characters @samp{+}, @samp{-} and @samp{|} to draw the border.
20848 Use the Alternate Character Set to draw the border. The border is
20849 drawn using character line graphics if the terminal supports them.
20852 @item set tui border-mode @var{mode}
20853 @kindex set tui border-mode
20854 @itemx set tui active-border-mode @var{mode}
20855 @kindex set tui active-border-mode
20856 Select the display attributes for the borders of the inactive windows
20857 or the active window. The @var{mode} can be one of the following:
20860 Use normal attributes to display the border.
20866 Use reverse video mode.
20869 Use half bright mode.
20871 @item half-standout
20872 Use half bright and standout mode.
20875 Use extra bright or bold mode.
20877 @item bold-standout
20878 Use extra bright or bold and standout mode.
20883 @chapter Using @value{GDBN} under @sc{gnu} Emacs
20886 @cindex @sc{gnu} Emacs
20887 A special interface allows you to use @sc{gnu} Emacs to view (and
20888 edit) the source files for the program you are debugging with
20891 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
20892 executable file you want to debug as an argument. This command starts
20893 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
20894 created Emacs buffer.
20895 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
20897 Running @value{GDBN} under Emacs can be just like running @value{GDBN} normally except for two
20902 All ``terminal'' input and output goes through an Emacs buffer, called
20905 This applies both to @value{GDBN} commands and their output, and to the input
20906 and output done by the program you are debugging.
20908 This is useful because it means that you can copy the text of previous
20909 commands and input them again; you can even use parts of the output
20912 All the facilities of Emacs' Shell mode are available for interacting
20913 with your program. In particular, you can send signals the usual
20914 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
20918 @value{GDBN} displays source code through Emacs.
20920 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
20921 source file for that frame and puts an arrow (@samp{=>}) at the
20922 left margin of the current line. Emacs uses a separate buffer for
20923 source display, and splits the screen to show both your @value{GDBN} session
20926 Explicit @value{GDBN} @code{list} or search commands still produce output as
20927 usual, but you probably have no reason to use them from Emacs.
20930 We call this @dfn{text command mode}. Emacs 22.1, and later, also uses
20931 a graphical mode, enabled by default, which provides further buffers
20932 that can control the execution and describe the state of your program.
20933 @xref{GDB Graphical Interface,,, Emacs, The @sc{gnu} Emacs Manual}.
20935 If you specify an absolute file name when prompted for the @kbd{M-x
20936 gdb} argument, then Emacs sets your current working directory to where
20937 your program resides. If you only specify the file name, then Emacs
20938 sets your current working directory to to the directory associated
20939 with the previous buffer. In this case, @value{GDBN} may find your
20940 program by searching your environment's @code{PATH} variable, but on
20941 some operating systems it might not find the source. So, although the
20942 @value{GDBN} input and output session proceeds normally, the auxiliary
20943 buffer does not display the current source and line of execution.
20945 The initial working directory of @value{GDBN} is printed on the top
20946 line of the GUD buffer and this serves as a default for the commands
20947 that specify files for @value{GDBN} to operate on. @xref{Files,
20948 ,Commands to Specify Files}.
20950 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
20951 need to call @value{GDBN} by a different name (for example, if you
20952 keep several configurations around, with different names) you can
20953 customize the Emacs variable @code{gud-gdb-command-name} to run the
20956 In the GUD buffer, you can use these special Emacs commands in
20957 addition to the standard Shell mode commands:
20961 Describe the features of Emacs' GUD Mode.
20964 Execute to another source line, like the @value{GDBN} @code{step} command; also
20965 update the display window to show the current file and location.
20968 Execute to next source line in this function, skipping all function
20969 calls, like the @value{GDBN} @code{next} command. Then update the display window
20970 to show the current file and location.
20973 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
20974 display window accordingly.
20977 Execute until exit from the selected stack frame, like the @value{GDBN}
20978 @code{finish} command.
20981 Continue execution of your program, like the @value{GDBN} @code{continue}
20985 Go up the number of frames indicated by the numeric argument
20986 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
20987 like the @value{GDBN} @code{up} command.
20990 Go down the number of frames indicated by the numeric argument, like the
20991 @value{GDBN} @code{down} command.
20994 In any source file, the Emacs command @kbd{C-x @key{SPC}} (@code{gud-break})
20995 tells @value{GDBN} to set a breakpoint on the source line point is on.
20997 In text command mode, if you type @kbd{M-x speedbar}, Emacs displays a
20998 separate frame which shows a backtrace when the GUD buffer is current.
20999 Move point to any frame in the stack and type @key{RET} to make it
21000 become the current frame and display the associated source in the
21001 source buffer. Alternatively, click @kbd{Mouse-2} to make the
21002 selected frame become the current one. In graphical mode, the
21003 speedbar displays watch expressions.
21005 If you accidentally delete the source-display buffer, an easy way to get
21006 it back is to type the command @code{f} in the @value{GDBN} buffer, to
21007 request a frame display; when you run under Emacs, this recreates
21008 the source buffer if necessary to show you the context of the current
21011 The source files displayed in Emacs are in ordinary Emacs buffers
21012 which are visiting the source files in the usual way. You can edit
21013 the files with these buffers if you wish; but keep in mind that @value{GDBN}
21014 communicates with Emacs in terms of line numbers. If you add or
21015 delete lines from the text, the line numbers that @value{GDBN} knows cease
21016 to correspond properly with the code.
21018 A more detailed description of Emacs' interaction with @value{GDBN} is
21019 given in the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu}
21022 @c The following dropped because Epoch is nonstandard. Reactivate
21023 @c if/when v19 does something similar. ---doc@cygnus.com 19dec1990
21025 @kindex Emacs Epoch environment
21029 Version 18 of @sc{gnu} Emacs has a built-in window system
21030 called the @code{epoch}
21031 environment. Users of this environment can use a new command,
21032 @code{inspect} which performs identically to @code{print} except that
21033 each value is printed in its own window.
21038 @chapter The @sc{gdb/mi} Interface
21040 @unnumberedsec Function and Purpose
21042 @cindex @sc{gdb/mi}, its purpose
21043 @sc{gdb/mi} is a line based machine oriented text interface to
21044 @value{GDBN} and is activated by specifying using the
21045 @option{--interpreter} command line option (@pxref{Mode Options}). It
21046 is specifically intended to support the development of systems which
21047 use the debugger as just one small component of a larger system.
21049 This chapter is a specification of the @sc{gdb/mi} interface. It is written
21050 in the form of a reference manual.
21052 Note that @sc{gdb/mi} is still under construction, so some of the
21053 features described below are incomplete and subject to change
21054 (@pxref{GDB/MI Development and Front Ends, , @sc{gdb/mi} Development and Front Ends}).
21056 @unnumberedsec Notation and Terminology
21058 @cindex notational conventions, for @sc{gdb/mi}
21059 This chapter uses the following notation:
21063 @code{|} separates two alternatives.
21066 @code{[ @var{something} ]} indicates that @var{something} is optional:
21067 it may or may not be given.
21070 @code{( @var{group} )*} means that @var{group} inside the parentheses
21071 may repeat zero or more times.
21074 @code{( @var{group} )+} means that @var{group} inside the parentheses
21075 may repeat one or more times.
21078 @code{"@var{string}"} means a literal @var{string}.
21082 @heading Dependencies
21086 * GDB/MI General Design::
21087 * GDB/MI Command Syntax::
21088 * GDB/MI Compatibility with CLI::
21089 * GDB/MI Development and Front Ends::
21090 * GDB/MI Output Records::
21091 * GDB/MI Simple Examples::
21092 * GDB/MI Command Description Format::
21093 * GDB/MI Breakpoint Commands::
21094 * GDB/MI Program Context::
21095 * GDB/MI Thread Commands::
21096 * GDB/MI Program Execution::
21097 * GDB/MI Stack Manipulation::
21098 * GDB/MI Variable Objects::
21099 * GDB/MI Data Manipulation::
21100 * GDB/MI Tracepoint Commands::
21101 * GDB/MI Symbol Query::
21102 * GDB/MI File Commands::
21104 * GDB/MI Kod Commands::
21105 * GDB/MI Memory Overlay Commands::
21106 * GDB/MI Signal Handling Commands::
21108 * GDB/MI Target Manipulation::
21109 * GDB/MI File Transfer Commands::
21110 * GDB/MI Miscellaneous Commands::
21113 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
21114 @node GDB/MI General Design
21115 @section @sc{gdb/mi} General Design
21116 @cindex GDB/MI General Design
21118 Interaction of a @sc{GDB/MI} frontend with @value{GDBN} involves three
21119 parts---commands sent to @value{GDBN}, responses to those commands
21120 and notifications. Each command results in exactly one response,
21121 indicating either successful completion of the command, or an error.
21122 For the commands that do not resume the target, the response contains the
21123 requested information. For the commands that resume the target, the
21124 response only indicates whether the target was successfully resumed.
21125 Notifications is the mechanism for reporting changes in the state of the
21126 target, or in @value{GDBN} state, that cannot conveniently be associated with
21127 a command and reported as part of that command response.
21129 The important examples of notifications are:
21133 Exec notifications. These are used to report changes in
21134 target state---when a target is resumed, or stopped. It would not
21135 be feasible to include this information in response of resuming
21136 commands, because one resume commands can result in multiple events in
21137 different threads. Also, quite some time may pass before any event
21138 happens in the target, while a frontend needs to know whether the resuming
21139 command itself was successfully executed.
21142 Console output, and status notifications. Console output
21143 notifications are used to report output of CLI commands, as well as
21144 diagnostics for other commands. Status notifications are used to
21145 report the progress of a long-running operation. Naturally, including
21146 this information in command response would mean no output is produced
21147 until the command is finished, which is undesirable.
21150 General notifications. Commands may have various side effects on
21151 the @value{GDBN} or target state beyond their official purpose. For example,
21152 a command may change the selected thread. Although such changes can
21153 be included in command response, using notification allows for more
21154 orthogonal frontend design.
21158 There's no guarantee that whenever an MI command reports an error,
21159 @value{GDBN} or the target are in any specific state, and especially,
21160 the state is not reverted to the state before the MI command was
21161 processed. Therefore, whenever an MI command results in an error,
21162 we recommend that the frontend refreshes all the information shown in
21163 the user interface.
21167 * Context management::
21168 * Asynchronous and non-stop modes::
21172 @node Context management
21173 @subsection Context management
21175 In most cases when @value{GDBN} accesses the target, this access is
21176 done in context of a specific thread and frame (@pxref{Frames}).
21177 Often, even when accessing global data, the target requires that a thread
21178 be specified. The CLI interface maintains the selected thread and frame,
21179 and supplies them to target on each command. This is convenient,
21180 because a command line user would not want to specify that information
21181 explicitly on each command, and because user interacts with
21182 @value{GDBN} via a single terminal, so no confusion is possible as
21183 to what thread and frame are the current ones.
21185 In the case of MI, the concept of selected thread and frame is less
21186 useful. First, a frontend can easily remember this information
21187 itself. Second, a graphical frontend can have more than one window,
21188 each one used for debugging a different thread, and the frontend might
21189 want to access additional threads for internal purposes. This
21190 increases the risk that by relying on implicitly selected thread, the
21191 frontend may be operating on a wrong one. Therefore, each MI command
21192 should explicitly specify which thread and frame to operate on. To
21193 make it possible, each MI command accepts the @samp{--thread} and
21194 @samp{--frame} options, the value to each is @value{GDBN} identifier
21195 for thread and frame to operate on.
21197 Usually, each top-level window in a frontend allows the user to select
21198 a thread and a frame, and remembers the user selection for further
21199 operations. However, in some cases @value{GDBN} may suggest that the
21200 current thread be changed. For example, when stopping on a breakpoint
21201 it is reasonable to switch to the thread where breakpoint is hit. For
21202 another example, if the user issues the CLI @samp{thread} command via
21203 the frontend, it is desirable to change the frontend's selected thread to the
21204 one specified by user. @value{GDBN} communicates the suggestion to
21205 change current thread using the @samp{=thread-selected} notification.
21206 No such notification is available for the selected frame at the moment.
21208 Note that historically, MI shares the selected thread with CLI, so
21209 frontends used the @code{-thread-select} to execute commands in the
21210 right context. However, getting this to work right is cumbersome. The
21211 simplest way is for frontend to emit @code{-thread-select} command
21212 before every command. This doubles the number of commands that need
21213 to be sent. The alternative approach is to suppress @code{-thread-select}
21214 if the selected thread in @value{GDBN} is supposed to be identical to the
21215 thread the frontend wants to operate on. However, getting this
21216 optimization right can be tricky. In particular, if the frontend
21217 sends several commands to @value{GDBN}, and one of the commands changes the
21218 selected thread, then the behaviour of subsequent commands will
21219 change. So, a frontend should either wait for response from such
21220 problematic commands, or explicitly add @code{-thread-select} for
21221 all subsequent commands. No frontend is known to do this exactly
21222 right, so it is suggested to just always pass the @samp{--thread} and
21223 @samp{--frame} options.
21225 @node Asynchronous and non-stop modes
21226 @subsection Asynchronous command execution and non-stop mode
21228 On some targets, @value{GDBN} is capable of processing MI commands
21229 even while the target is running. This is called @dfn{asynchronous
21230 command execution} (@pxref{Background Execution}). The frontend may
21231 specify a preferrence for asynchronous execution using the
21232 @code{-gdb-set target-async 1} command, which should be emitted before
21233 either running the executable or attaching to the target. After the
21234 frontend has started the executable or attached to the target, it can
21235 find if asynchronous execution is enabled using the
21236 @code{-list-target-features} command.
21238 Even if @value{GDBN} can accept a command while target is running,
21239 many commands that access the target do not work when the target is
21240 running. Therefore, asynchronous command execution is most useful
21241 when combined with non-stop mode (@pxref{Non-Stop Mode}). Then,
21242 it is possible to examine the state of one thread, while other threads
21245 When a given thread is running, MI commands that try to access the
21246 target in the context of that thread may not work, or may work only on
21247 some targets. In particular, commands that try to operate on thread's
21248 stack will not work, on any target. Commands that read memory, or
21249 modify breakpoints, may work or not work, depending on the target. Note
21250 that even commands that operate on global state, such as @code{print},
21251 @code{set}, and breakpoint commands, still access the target in the
21252 context of a specific thread, so frontend should try to find a
21253 stopped thread and perform the operation on that thread (using the
21254 @samp{--thread} option).
21256 Which commands will work in the context of a running thread is
21257 highly target dependent. However, the two commands
21258 @code{-exec-interrupt}, to stop a thread, and @code{-thread-info},
21259 to find the state of a thread, will always work.
21261 @node Thread groups
21262 @subsection Thread groups
21263 @value{GDBN} may be used to debug several processes at the same time.
21264 On some platfroms, @value{GDBN} may support debugging of several
21265 hardware systems, each one having several cores with several different
21266 processes running on each core. This section describes the MI
21267 mechanism to support such debugging scenarios.
21269 The key observation is that regardless of the structure of the
21270 target, MI can have a global list of threads, because most commands that
21271 accept the @samp{--thread} option do not need to know what process that
21272 thread belongs to. Therefore, it is not necessary to introduce
21273 neither additional @samp{--process} option, nor an notion of the
21274 current process in the MI interface. The only strictly new feature
21275 that is required is the ability to find how the threads are grouped
21278 To allow the user to discover such grouping, and to support arbitrary
21279 hierarchy of machines/cores/processes, MI introduces the concept of a
21280 @dfn{thread group}. Thread group is a collection of threads and other
21281 thread groups. A thread group always has a string identifier, a type,
21282 and may have additional attributes specific to the type. A new
21283 command, @code{-list-thread-groups}, returns the list of top-level
21284 thread groups, which correspond to processes that @value{GDBN} is
21285 debugging at the moment. By passing an identifier of a thread group
21286 to the @code{-list-thread-groups} command, it is possible to obtain
21287 the members of specific thread group.
21289 To allow the user to easily discover processes, and other objects, he
21290 wishes to debug, a concept of @dfn{available thread group} is
21291 introduced. Available thread group is an thread group that
21292 @value{GDBN} is not debugging, but that can be attached to, using the
21293 @code{-target-attach} command. The list of available top-level thread
21294 groups can be obtained using @samp{-list-thread-groups --available}.
21295 In general, the content of a thread group may be only retrieved only
21296 after attaching to that thread group.
21298 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
21299 @node GDB/MI Command Syntax
21300 @section @sc{gdb/mi} Command Syntax
21303 * GDB/MI Input Syntax::
21304 * GDB/MI Output Syntax::
21307 @node GDB/MI Input Syntax
21308 @subsection @sc{gdb/mi} Input Syntax
21310 @cindex input syntax for @sc{gdb/mi}
21311 @cindex @sc{gdb/mi}, input syntax
21313 @item @var{command} @expansion{}
21314 @code{@var{cli-command} | @var{mi-command}}
21316 @item @var{cli-command} @expansion{}
21317 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
21318 @var{cli-command} is any existing @value{GDBN} CLI command.
21320 @item @var{mi-command} @expansion{}
21321 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
21322 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
21324 @item @var{token} @expansion{}
21325 "any sequence of digits"
21327 @item @var{option} @expansion{}
21328 @code{"-" @var{parameter} [ " " @var{parameter} ]}
21330 @item @var{parameter} @expansion{}
21331 @code{@var{non-blank-sequence} | @var{c-string}}
21333 @item @var{operation} @expansion{}
21334 @emph{any of the operations described in this chapter}
21336 @item @var{non-blank-sequence} @expansion{}
21337 @emph{anything, provided it doesn't contain special characters such as
21338 "-", @var{nl}, """ and of course " "}
21340 @item @var{c-string} @expansion{}
21341 @code{""" @var{seven-bit-iso-c-string-content} """}
21343 @item @var{nl} @expansion{}
21352 The CLI commands are still handled by the @sc{mi} interpreter; their
21353 output is described below.
21356 The @code{@var{token}}, when present, is passed back when the command
21360 Some @sc{mi} commands accept optional arguments as part of the parameter
21361 list. Each option is identified by a leading @samp{-} (dash) and may be
21362 followed by an optional argument parameter. Options occur first in the
21363 parameter list and can be delimited from normal parameters using
21364 @samp{--} (this is useful when some parameters begin with a dash).
21371 We want easy access to the existing CLI syntax (for debugging).
21374 We want it to be easy to spot a @sc{mi} operation.
21377 @node GDB/MI Output Syntax
21378 @subsection @sc{gdb/mi} Output Syntax
21380 @cindex output syntax of @sc{gdb/mi}
21381 @cindex @sc{gdb/mi}, output syntax
21382 The output from @sc{gdb/mi} consists of zero or more out-of-band records
21383 followed, optionally, by a single result record. This result record
21384 is for the most recent command. The sequence of output records is
21385 terminated by @samp{(gdb)}.
21387 If an input command was prefixed with a @code{@var{token}} then the
21388 corresponding output for that command will also be prefixed by that same
21392 @item @var{output} @expansion{}
21393 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(gdb)" @var{nl}}
21395 @item @var{result-record} @expansion{}
21396 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
21398 @item @var{out-of-band-record} @expansion{}
21399 @code{@var{async-record} | @var{stream-record}}
21401 @item @var{async-record} @expansion{}
21402 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
21404 @item @var{exec-async-output} @expansion{}
21405 @code{[ @var{token} ] "*" @var{async-output}}
21407 @item @var{status-async-output} @expansion{}
21408 @code{[ @var{token} ] "+" @var{async-output}}
21410 @item @var{notify-async-output} @expansion{}
21411 @code{[ @var{token} ] "=" @var{async-output}}
21413 @item @var{async-output} @expansion{}
21414 @code{@var{async-class} ( "," @var{result} )* @var{nl}}
21416 @item @var{result-class} @expansion{}
21417 @code{"done" | "running" | "connected" | "error" | "exit"}
21419 @item @var{async-class} @expansion{}
21420 @code{"stopped" | @var{others}} (where @var{others} will be added
21421 depending on the needs---this is still in development).
21423 @item @var{result} @expansion{}
21424 @code{ @var{variable} "=" @var{value}}
21426 @item @var{variable} @expansion{}
21427 @code{ @var{string} }
21429 @item @var{value} @expansion{}
21430 @code{ @var{const} | @var{tuple} | @var{list} }
21432 @item @var{const} @expansion{}
21433 @code{@var{c-string}}
21435 @item @var{tuple} @expansion{}
21436 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
21438 @item @var{list} @expansion{}
21439 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
21440 @var{result} ( "," @var{result} )* "]" }
21442 @item @var{stream-record} @expansion{}
21443 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
21445 @item @var{console-stream-output} @expansion{}
21446 @code{"~" @var{c-string}}
21448 @item @var{target-stream-output} @expansion{}
21449 @code{"@@" @var{c-string}}
21451 @item @var{log-stream-output} @expansion{}
21452 @code{"&" @var{c-string}}
21454 @item @var{nl} @expansion{}
21457 @item @var{token} @expansion{}
21458 @emph{any sequence of digits}.
21466 All output sequences end in a single line containing a period.
21469 The @code{@var{token}} is from the corresponding request. Note that
21470 for all async output, while the token is allowed by the grammar and
21471 may be output by future versions of @value{GDBN} for select async
21472 output messages, it is generally omitted. Frontends should treat
21473 all async output as reporting general changes in the state of the
21474 target and there should be no need to associate async output to any
21478 @cindex status output in @sc{gdb/mi}
21479 @var{status-async-output} contains on-going status information about the
21480 progress of a slow operation. It can be discarded. All status output is
21481 prefixed by @samp{+}.
21484 @cindex async output in @sc{gdb/mi}
21485 @var{exec-async-output} contains asynchronous state change on the target
21486 (stopped, started, disappeared). All async output is prefixed by
21490 @cindex notify output in @sc{gdb/mi}
21491 @var{notify-async-output} contains supplementary information that the
21492 client should handle (e.g., a new breakpoint information). All notify
21493 output is prefixed by @samp{=}.
21496 @cindex console output in @sc{gdb/mi}
21497 @var{console-stream-output} is output that should be displayed as is in the
21498 console. It is the textual response to a CLI command. All the console
21499 output is prefixed by @samp{~}.
21502 @cindex target output in @sc{gdb/mi}
21503 @var{target-stream-output} is the output produced by the target program.
21504 All the target output is prefixed by @samp{@@}.
21507 @cindex log output in @sc{gdb/mi}
21508 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
21509 instance messages that should be displayed as part of an error log. All
21510 the log output is prefixed by @samp{&}.
21513 @cindex list output in @sc{gdb/mi}
21514 New @sc{gdb/mi} commands should only output @var{lists} containing
21520 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
21521 details about the various output records.
21523 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
21524 @node GDB/MI Compatibility with CLI
21525 @section @sc{gdb/mi} Compatibility with CLI
21527 @cindex compatibility, @sc{gdb/mi} and CLI
21528 @cindex @sc{gdb/mi}, compatibility with CLI
21530 For the developers convenience CLI commands can be entered directly,
21531 but there may be some unexpected behaviour. For example, commands
21532 that query the user will behave as if the user replied yes, breakpoint
21533 command lists are not executed and some CLI commands, such as
21534 @code{if}, @code{when} and @code{define}, prompt for further input with
21535 @samp{>}, which is not valid MI output.
21537 This feature may be removed at some stage in the future and it is
21538 recommended that front ends use the @code{-interpreter-exec} command
21539 (@pxref{-interpreter-exec}).
21541 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
21542 @node GDB/MI Development and Front Ends
21543 @section @sc{gdb/mi} Development and Front Ends
21544 @cindex @sc{gdb/mi} development
21546 The application which takes the MI output and presents the state of the
21547 program being debugged to the user is called a @dfn{front end}.
21549 Although @sc{gdb/mi} is still incomplete, it is currently being used
21550 by a variety of front ends to @value{GDBN}. This makes it difficult
21551 to introduce new functionality without breaking existing usage. This
21552 section tries to minimize the problems by describing how the protocol
21555 Some changes in MI need not break a carefully designed front end, and
21556 for these the MI version will remain unchanged. The following is a
21557 list of changes that may occur within one level, so front ends should
21558 parse MI output in a way that can handle them:
21562 New MI commands may be added.
21565 New fields may be added to the output of any MI command.
21568 The range of values for fields with specified values, e.g.,
21569 @code{in_scope} (@pxref{-var-update}) may be extended.
21571 @c The format of field's content e.g type prefix, may change so parse it
21572 @c at your own risk. Yes, in general?
21574 @c The order of fields may change? Shouldn't really matter but it might
21575 @c resolve inconsistencies.
21578 If the changes are likely to break front ends, the MI version level
21579 will be increased by one. This will allow the front end to parse the
21580 output according to the MI version. Apart from mi0, new versions of
21581 @value{GDBN} will not support old versions of MI and it will be the
21582 responsibility of the front end to work with the new one.
21584 @c Starting with mi3, add a new command -mi-version that prints the MI
21587 The best way to avoid unexpected changes in MI that might break your front
21588 end is to make your project known to @value{GDBN} developers and
21589 follow development on @email{gdb@@sourceware.org} and
21590 @email{gdb-patches@@sourceware.org}.
21591 @cindex mailing lists
21593 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
21594 @node GDB/MI Output Records
21595 @section @sc{gdb/mi} Output Records
21598 * GDB/MI Result Records::
21599 * GDB/MI Stream Records::
21600 * GDB/MI Async Records::
21601 * GDB/MI Frame Information::
21604 @node GDB/MI Result Records
21605 @subsection @sc{gdb/mi} Result Records
21607 @cindex result records in @sc{gdb/mi}
21608 @cindex @sc{gdb/mi}, result records
21609 In addition to a number of out-of-band notifications, the response to a
21610 @sc{gdb/mi} command includes one of the following result indications:
21614 @item "^done" [ "," @var{results} ]
21615 The synchronous operation was successful, @code{@var{results}} are the return
21620 @c Is this one correct? Should it be an out-of-band notification?
21621 The asynchronous operation was successfully started. The target is
21626 @value{GDBN} has connected to a remote target.
21628 @item "^error" "," @var{c-string}
21630 The operation failed. The @code{@var{c-string}} contains the corresponding
21635 @value{GDBN} has terminated.
21639 @node GDB/MI Stream Records
21640 @subsection @sc{gdb/mi} Stream Records
21642 @cindex @sc{gdb/mi}, stream records
21643 @cindex stream records in @sc{gdb/mi}
21644 @value{GDBN} internally maintains a number of output streams: the console, the
21645 target, and the log. The output intended for each of these streams is
21646 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
21648 Each stream record begins with a unique @dfn{prefix character} which
21649 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
21650 Syntax}). In addition to the prefix, each stream record contains a
21651 @code{@var{string-output}}. This is either raw text (with an implicit new
21652 line) or a quoted C string (which does not contain an implicit newline).
21655 @item "~" @var{string-output}
21656 The console output stream contains text that should be displayed in the
21657 CLI console window. It contains the textual responses to CLI commands.
21659 @item "@@" @var{string-output}
21660 The target output stream contains any textual output from the running
21661 target. This is only present when GDB's event loop is truly
21662 asynchronous, which is currently only the case for remote targets.
21664 @item "&" @var{string-output}
21665 The log stream contains debugging messages being produced by @value{GDBN}'s
21669 @node GDB/MI Async Records
21670 @subsection @sc{gdb/mi} Async Records
21672 @cindex async records in @sc{gdb/mi}
21673 @cindex @sc{gdb/mi}, async records
21674 @dfn{Async} records are used to notify the @sc{gdb/mi} client of
21675 additional changes that have occurred. Those changes can either be a
21676 consequence of @sc{gdb/mi} commands (e.g., a breakpoint modified) or a result of
21677 target activity (e.g., target stopped).
21679 The following is the list of possible async records:
21683 @item *running,thread-id="@var{thread}"
21684 The target is now running. The @var{thread} field tells which
21685 specific thread is now running, and can be @samp{all} if all threads
21686 are running. The frontend should assume that no interaction with a
21687 running thread is possible after this notification is produced.
21688 The frontend should not assume that this notification is output
21689 only once for any command. @value{GDBN} may emit this notification
21690 several times, either for different threads, because it cannot resume
21691 all threads together, or even for a single thread, if the thread must
21692 be stepped though some code before letting it run freely.
21694 @item *stopped,reason="@var{reason}",thread-id="@var{id}",stopped-threads="@var{stopped}"
21695 The target has stopped. The @var{reason} field can have one of the
21699 @item breakpoint-hit
21700 A breakpoint was reached.
21701 @item watchpoint-trigger
21702 A watchpoint was triggered.
21703 @item read-watchpoint-trigger
21704 A read watchpoint was triggered.
21705 @item access-watchpoint-trigger
21706 An access watchpoint was triggered.
21707 @item function-finished
21708 An -exec-finish or similar CLI command was accomplished.
21709 @item location-reached
21710 An -exec-until or similar CLI command was accomplished.
21711 @item watchpoint-scope
21712 A watchpoint has gone out of scope.
21713 @item end-stepping-range
21714 An -exec-next, -exec-next-instruction, -exec-step, -exec-step-instruction or
21715 similar CLI command was accomplished.
21716 @item exited-signalled
21717 The inferior exited because of a signal.
21719 The inferior exited.
21720 @item exited-normally
21721 The inferior exited normally.
21722 @item signal-received
21723 A signal was received by the inferior.
21726 The @var{id} field identifies the thread that directly caused the stop
21727 -- for example by hitting a breakpoint. Depending on whether all-stop
21728 mode is in effect (@pxref{All-Stop Mode}), @value{GDBN} may either
21729 stop all threads, or only the thread that directly triggered the stop.
21730 If all threads are stopped, the @var{stopped} field will have the
21731 value of @code{"all"}. Otherwise, the value of the @var{stopped}
21732 field will be a list of thread identifiers. Presently, this list will
21733 always include a single thread, but frontend should be prepared to see
21734 several threads in the list.
21736 @item =thread-group-created,id="@var{id}"
21737 @itemx =thread-group-exited,id="@var{id}"
21738 A thread thread group either was attached to, or has exited/detached
21739 from. The @var{id} field contains the @value{GDBN} identifier of the
21742 @item =thread-created,id="@var{id}",group-id="@var{gid}"
21743 @itemx =thread-exited,id="@var{id}",group-id="@var{gid}"
21744 A thread either was created, or has exited. The @var{id} field
21745 contains the @value{GDBN} identifier of the thread. The @var{gid}
21746 field identifies the thread group this thread belongs to.
21748 @item =thread-selected,id="@var{id}"
21749 Informs that the selected thread was changed as result of the last
21750 command. This notification is not emitted as result of @code{-thread-select}
21751 command but is emitted whenever an MI command that is not documented
21752 to change the selected thread actually changes it. In particular,
21753 invoking, directly or indirectly (via user-defined command), the CLI
21754 @code{thread} command, will generate this notification.
21756 We suggest that in response to this notification, front ends
21757 highlight the selected thread and cause subsequent commands to apply to
21760 @item =library-loaded,...
21761 Reports that a new library file was loaded by the program. This
21762 notification has 4 fields---@var{id}, @var{target-name},
21763 @var{host-name}, and @var{symbols-loaded}. The @var{id} field is an
21764 opaque identifier of the library. For remote debugging case,
21765 @var{target-name} and @var{host-name} fields give the name of the
21766 library file on the target, and on the host respectively. For native
21767 debugging, both those fields have the same value. The
21768 @var{symbols-loaded} field reports if the debug symbols for this
21769 library are loaded.
21771 @item =library-unloaded,...
21772 Reports that a library was unloaded by the program. This notification
21773 has 3 fields---@var{id}, @var{target-name} and @var{host-name} with
21774 the same meaning as for the @code{=library-loaded} notification
21778 @node GDB/MI Frame Information
21779 @subsection @sc{gdb/mi} Frame Information
21781 Response from many MI commands includes an information about stack
21782 frame. This information is a tuple that may have the following
21787 The level of the stack frame. The innermost frame has the level of
21788 zero. This field is always present.
21791 The name of the function corresponding to the frame. This field may
21792 be absent if @value{GDBN} is unable to determine the function name.
21795 The code address for the frame. This field is always present.
21798 The name of the source files that correspond to the frame's code
21799 address. This field may be absent.
21802 The source line corresponding to the frames' code address. This field
21806 The name of the binary file (either executable or shared library) the
21807 corresponds to the frame's code address. This field may be absent.
21812 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
21813 @node GDB/MI Simple Examples
21814 @section Simple Examples of @sc{gdb/mi} Interaction
21815 @cindex @sc{gdb/mi}, simple examples
21817 This subsection presents several simple examples of interaction using
21818 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
21819 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
21820 the output received from @sc{gdb/mi}.
21822 Note the line breaks shown in the examples are here only for
21823 readability, they don't appear in the real output.
21825 @subheading Setting a Breakpoint
21827 Setting a breakpoint generates synchronous output which contains detailed
21828 information of the breakpoint.
21831 -> -break-insert main
21832 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
21833 enabled="y",addr="0x08048564",func="main",file="myprog.c",
21834 fullname="/home/nickrob/myprog.c",line="68",times="0"@}
21838 @subheading Program Execution
21840 Program execution generates asynchronous records and MI gives the
21841 reason that execution stopped.
21847 <- *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
21848 frame=@{addr="0x08048564",func="main",
21849 args=[@{name="argc",value="1"@},@{name="argv",value="0xbfc4d4d4"@}],
21850 file="myprog.c",fullname="/home/nickrob/myprog.c",line="68"@}
21855 <- *stopped,reason="exited-normally"
21859 @subheading Quitting @value{GDBN}
21861 Quitting @value{GDBN} just prints the result class @samp{^exit}.
21869 @subheading A Bad Command
21871 Here's what happens if you pass a non-existent command:
21875 <- ^error,msg="Undefined MI command: rubbish"
21880 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
21881 @node GDB/MI Command Description Format
21882 @section @sc{gdb/mi} Command Description Format
21884 The remaining sections describe blocks of commands. Each block of
21885 commands is laid out in a fashion similar to this section.
21887 @subheading Motivation
21889 The motivation for this collection of commands.
21891 @subheading Introduction
21893 A brief introduction to this collection of commands as a whole.
21895 @subheading Commands
21897 For each command in the block, the following is described:
21899 @subsubheading Synopsis
21902 -command @var{args}@dots{}
21905 @subsubheading Result
21907 @subsubheading @value{GDBN} Command
21909 The corresponding @value{GDBN} CLI command(s), if any.
21911 @subsubheading Example
21913 Example(s) formatted for readability. Some of the described commands have
21914 not been implemented yet and these are labeled N.A.@: (not available).
21917 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
21918 @node GDB/MI Breakpoint Commands
21919 @section @sc{gdb/mi} Breakpoint Commands
21921 @cindex breakpoint commands for @sc{gdb/mi}
21922 @cindex @sc{gdb/mi}, breakpoint commands
21923 This section documents @sc{gdb/mi} commands for manipulating
21926 @subheading The @code{-break-after} Command
21927 @findex -break-after
21929 @subsubheading Synopsis
21932 -break-after @var{number} @var{count}
21935 The breakpoint number @var{number} is not in effect until it has been
21936 hit @var{count} times. To see how this is reflected in the output of
21937 the @samp{-break-list} command, see the description of the
21938 @samp{-break-list} command below.
21940 @subsubheading @value{GDBN} Command
21942 The corresponding @value{GDBN} command is @samp{ignore}.
21944 @subsubheading Example
21949 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
21950 enabled="y",addr="0x000100d0",func="main",file="hello.c",
21951 fullname="/home/foo/hello.c",line="5",times="0"@}
21958 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
21959 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
21960 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
21961 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
21962 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
21963 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
21964 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
21965 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
21966 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
21967 line="5",times="0",ignore="3"@}]@}
21972 @subheading The @code{-break-catch} Command
21973 @findex -break-catch
21976 @subheading The @code{-break-commands} Command
21977 @findex -break-commands
21979 @subsubheading Synopsis
21982 -break-commands @var{number} [ @var{command1} ... @var{commandN} ]
21985 Specifies the CLI commands that should be executed when breakpoint
21986 @var{number} is hit. The parameters @var{command1} to @var{commandN}
21987 are the commands. If no command is specified, any previously-set
21988 commands are cleared. @xref{Break Commands}. Typical use of this
21989 functionality is tracing a program, that is, printing of values of
21990 some variables whenever breakpoint is hit and then continuing.
21992 @subsubheading @value{GDBN} Command
21994 The corresponding @value{GDBN} command is @samp{commands}.
21996 @subsubheading Example
22001 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
22002 enabled="y",addr="0x000100d0",func="main",file="hello.c",
22003 fullname="/home/foo/hello.c",line="5",times="0"@}
22005 -break-commands 1 "print v" "continue"
22010 @subheading The @code{-break-condition} Command
22011 @findex -break-condition
22013 @subsubheading Synopsis
22016 -break-condition @var{number} @var{expr}
22019 Breakpoint @var{number} will stop the program only if the condition in
22020 @var{expr} is true. The condition becomes part of the
22021 @samp{-break-list} output (see the description of the @samp{-break-list}
22024 @subsubheading @value{GDBN} Command
22026 The corresponding @value{GDBN} command is @samp{condition}.
22028 @subsubheading Example
22032 -break-condition 1 1
22036 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
22037 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
22038 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
22039 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
22040 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
22041 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
22042 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
22043 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
22044 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
22045 line="5",cond="1",times="0",ignore="3"@}]@}
22049 @subheading The @code{-break-delete} Command
22050 @findex -break-delete
22052 @subsubheading Synopsis
22055 -break-delete ( @var{breakpoint} )+
22058 Delete the breakpoint(s) whose number(s) are specified in the argument
22059 list. This is obviously reflected in the breakpoint list.
22061 @subsubheading @value{GDBN} Command
22063 The corresponding @value{GDBN} command is @samp{delete}.
22065 @subsubheading Example
22073 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
22074 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
22075 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
22076 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
22077 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
22078 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
22079 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
22084 @subheading The @code{-break-disable} Command
22085 @findex -break-disable
22087 @subsubheading Synopsis
22090 -break-disable ( @var{breakpoint} )+
22093 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
22094 break list is now set to @samp{n} for the named @var{breakpoint}(s).
22096 @subsubheading @value{GDBN} Command
22098 The corresponding @value{GDBN} command is @samp{disable}.
22100 @subsubheading Example
22108 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
22109 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
22110 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
22111 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
22112 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
22113 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
22114 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
22115 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
22116 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
22117 line="5",times="0"@}]@}
22121 @subheading The @code{-break-enable} Command
22122 @findex -break-enable
22124 @subsubheading Synopsis
22127 -break-enable ( @var{breakpoint} )+
22130 Enable (previously disabled) @var{breakpoint}(s).
22132 @subsubheading @value{GDBN} Command
22134 The corresponding @value{GDBN} command is @samp{enable}.
22136 @subsubheading Example
22144 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
22145 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
22146 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
22147 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
22148 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
22149 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
22150 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
22151 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
22152 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
22153 line="5",times="0"@}]@}
22157 @subheading The @code{-break-info} Command
22158 @findex -break-info
22160 @subsubheading Synopsis
22163 -break-info @var{breakpoint}
22167 Get information about a single breakpoint.
22169 @subsubheading @value{GDBN} Command
22171 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
22173 @subsubheading Example
22176 @subheading The @code{-break-insert} Command
22177 @findex -break-insert
22179 @subsubheading Synopsis
22182 -break-insert [ -t ] [ -h ] [ -f ] [ -d ]
22183 [ -c @var{condition} ] [ -i @var{ignore-count} ]
22184 [ -p @var{thread} ] [ @var{location} ]
22188 If specified, @var{location}, can be one of:
22195 @item filename:linenum
22196 @item filename:function
22200 The possible optional parameters of this command are:
22204 Insert a temporary breakpoint.
22206 Insert a hardware breakpoint.
22207 @item -c @var{condition}
22208 Make the breakpoint conditional on @var{condition}.
22209 @item -i @var{ignore-count}
22210 Initialize the @var{ignore-count}.
22212 If @var{location} cannot be parsed (for example if it
22213 refers to unknown files or functions), create a pending
22214 breakpoint. Without this flag, @value{GDBN} will report
22215 an error, and won't create a breakpoint, if @var{location}
22218 Create a disabled breakpoint.
22221 @subsubheading Result
22223 The result is in the form:
22226 ^done,bkpt=@{number="@var{number}",type="@var{type}",disp="del"|"keep",
22227 enabled="y"|"n",addr="@var{hex}",func="@var{funcname}",file="@var{filename}",
22228 fullname="@var{full_filename}",line="@var{lineno}",[thread="@var{threadno},]
22229 times="@var{times}"@}
22233 where @var{number} is the @value{GDBN} number for this breakpoint,
22234 @var{funcname} is the name of the function where the breakpoint was
22235 inserted, @var{filename} is the name of the source file which contains
22236 this function, @var{lineno} is the source line number within that file
22237 and @var{times} the number of times that the breakpoint has been hit
22238 (always 0 for -break-insert but may be greater for -break-info or -break-list
22239 which use the same output).
22241 Note: this format is open to change.
22242 @c An out-of-band breakpoint instead of part of the result?
22244 @subsubheading @value{GDBN} Command
22246 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
22247 @samp{hbreak}, @samp{thbreak}, and @samp{rbreak}.
22249 @subsubheading Example
22254 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",
22255 fullname="/home/foo/recursive2.c,line="4",times="0"@}
22257 -break-insert -t foo
22258 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",
22259 fullname="/home/foo/recursive2.c,line="11",times="0"@}
22262 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
22263 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
22264 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
22265 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
22266 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
22267 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
22268 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
22269 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
22270 addr="0x0001072c", func="main",file="recursive2.c",
22271 fullname="/home/foo/recursive2.c,"line="4",times="0"@},
22272 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
22273 addr="0x00010774",func="foo",file="recursive2.c",
22274 fullname="/home/foo/recursive2.c",line="11",times="0"@}]@}
22276 -break-insert -r foo.*
22277 ~int foo(int, int);
22278 ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c,
22279 "fullname="/home/foo/recursive2.c",line="11",times="0"@}
22283 @subheading The @code{-break-list} Command
22284 @findex -break-list
22286 @subsubheading Synopsis
22292 Displays the list of inserted breakpoints, showing the following fields:
22296 number of the breakpoint
22298 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
22300 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
22303 is the breakpoint enabled or no: @samp{y} or @samp{n}
22305 memory location at which the breakpoint is set
22307 logical location of the breakpoint, expressed by function name, file
22310 number of times the breakpoint has been hit
22313 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
22314 @code{body} field is an empty list.
22316 @subsubheading @value{GDBN} Command
22318 The corresponding @value{GDBN} command is @samp{info break}.
22320 @subsubheading Example
22325 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
22326 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
22327 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
22328 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
22329 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
22330 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
22331 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
22332 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
22333 addr="0x000100d0",func="main",file="hello.c",line="5",times="0"@},
22334 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
22335 addr="0x00010114",func="foo",file="hello.c",fullname="/home/foo/hello.c",
22336 line="13",times="0"@}]@}
22340 Here's an example of the result when there are no breakpoints:
22345 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
22346 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
22347 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
22348 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
22349 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
22350 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
22351 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
22356 @subheading The @code{-break-watch} Command
22357 @findex -break-watch
22359 @subsubheading Synopsis
22362 -break-watch [ -a | -r ]
22365 Create a watchpoint. With the @samp{-a} option it will create an
22366 @dfn{access} watchpoint, i.e., a watchpoint that triggers either on a
22367 read from or on a write to the memory location. With the @samp{-r}
22368 option, the watchpoint created is a @dfn{read} watchpoint, i.e., it will
22369 trigger only when the memory location is accessed for reading. Without
22370 either of the options, the watchpoint created is a regular watchpoint,
22371 i.e., it will trigger when the memory location is accessed for writing.
22372 @xref{Set Watchpoints, , Setting Watchpoints}.
22374 Note that @samp{-break-list} will report a single list of watchpoints and
22375 breakpoints inserted.
22377 @subsubheading @value{GDBN} Command
22379 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
22382 @subsubheading Example
22384 Setting a watchpoint on a variable in the @code{main} function:
22389 ^done,wpt=@{number="2",exp="x"@}
22394 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
22395 value=@{old="-268439212",new="55"@},
22396 frame=@{func="main",args=[],file="recursive2.c",
22397 fullname="/home/foo/bar/recursive2.c",line="5"@}
22401 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
22402 the program execution twice: first for the variable changing value, then
22403 for the watchpoint going out of scope.
22408 ^done,wpt=@{number="5",exp="C"@}
22413 *stopped,reason="watchpoint-trigger",
22414 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
22415 frame=@{func="callee4",args=[],
22416 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
22417 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
22422 *stopped,reason="watchpoint-scope",wpnum="5",
22423 frame=@{func="callee3",args=[@{name="strarg",
22424 value="0x11940 \"A string argument.\""@}],
22425 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
22426 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
22430 Listing breakpoints and watchpoints, at different points in the program
22431 execution. Note that once the watchpoint goes out of scope, it is
22437 ^done,wpt=@{number="2",exp="C"@}
22440 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
22441 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
22442 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
22443 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
22444 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
22445 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
22446 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
22447 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
22448 addr="0x00010734",func="callee4",
22449 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
22450 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c"line="8",times="1"@},
22451 bkpt=@{number="2",type="watchpoint",disp="keep",
22452 enabled="y",addr="",what="C",times="0"@}]@}
22457 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
22458 value=@{old="-276895068",new="3"@},
22459 frame=@{func="callee4",args=[],
22460 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
22461 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
22464 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
22465 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
22466 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
22467 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
22468 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
22469 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
22470 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
22471 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
22472 addr="0x00010734",func="callee4",
22473 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
22474 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",times="1"@},
22475 bkpt=@{number="2",type="watchpoint",disp="keep",
22476 enabled="y",addr="",what="C",times="-5"@}]@}
22480 ^done,reason="watchpoint-scope",wpnum="2",
22481 frame=@{func="callee3",args=[@{name="strarg",
22482 value="0x11940 \"A string argument.\""@}],
22483 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
22484 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
22487 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
22488 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
22489 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
22490 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
22491 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
22492 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
22493 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
22494 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
22495 addr="0x00010734",func="callee4",
22496 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
22497 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
22502 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
22503 @node GDB/MI Program Context
22504 @section @sc{gdb/mi} Program Context
22506 @subheading The @code{-exec-arguments} Command
22507 @findex -exec-arguments
22510 @subsubheading Synopsis
22513 -exec-arguments @var{args}
22516 Set the inferior program arguments, to be used in the next
22519 @subsubheading @value{GDBN} Command
22521 The corresponding @value{GDBN} command is @samp{set args}.
22523 @subsubheading Example
22527 -exec-arguments -v word
22534 @subheading The @code{-exec-show-arguments} Command
22535 @findex -exec-show-arguments
22537 @subsubheading Synopsis
22540 -exec-show-arguments
22543 Print the arguments of the program.
22545 @subsubheading @value{GDBN} Command
22547 The corresponding @value{GDBN} command is @samp{show args}.
22549 @subsubheading Example
22554 @subheading The @code{-environment-cd} Command
22555 @findex -environment-cd
22557 @subsubheading Synopsis
22560 -environment-cd @var{pathdir}
22563 Set @value{GDBN}'s working directory.
22565 @subsubheading @value{GDBN} Command
22567 The corresponding @value{GDBN} command is @samp{cd}.
22569 @subsubheading Example
22573 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
22579 @subheading The @code{-environment-directory} Command
22580 @findex -environment-directory
22582 @subsubheading Synopsis
22585 -environment-directory [ -r ] [ @var{pathdir} ]+
22588 Add directories @var{pathdir} to beginning of search path for source files.
22589 If the @samp{-r} option is used, the search path is reset to the default
22590 search path. If directories @var{pathdir} are supplied in addition to the
22591 @samp{-r} option, the search path is first reset and then addition
22593 Multiple directories may be specified, separated by blanks. Specifying
22594 multiple directories in a single command
22595 results in the directories added to the beginning of the
22596 search path in the same order they were presented in the command.
22597 If blanks are needed as
22598 part of a directory name, double-quotes should be used around
22599 the name. In the command output, the path will show up separated
22600 by the system directory-separator character. The directory-separator
22601 character must not be used
22602 in any directory name.
22603 If no directories are specified, the current search path is displayed.
22605 @subsubheading @value{GDBN} Command
22607 The corresponding @value{GDBN} command is @samp{dir}.
22609 @subsubheading Example
22613 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
22614 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
22616 -environment-directory ""
22617 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
22619 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
22620 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
22622 -environment-directory -r
22623 ^done,source-path="$cdir:$cwd"
22628 @subheading The @code{-environment-path} Command
22629 @findex -environment-path
22631 @subsubheading Synopsis
22634 -environment-path [ -r ] [ @var{pathdir} ]+
22637 Add directories @var{pathdir} to beginning of search path for object files.
22638 If the @samp{-r} option is used, the search path is reset to the original
22639 search path that existed at gdb start-up. If directories @var{pathdir} are
22640 supplied in addition to the
22641 @samp{-r} option, the search path is first reset and then addition
22643 Multiple directories may be specified, separated by blanks. Specifying
22644 multiple directories in a single command
22645 results in the directories added to the beginning of the
22646 search path in the same order they were presented in the command.
22647 If blanks are needed as
22648 part of a directory name, double-quotes should be used around
22649 the name. In the command output, the path will show up separated
22650 by the system directory-separator character. The directory-separator
22651 character must not be used
22652 in any directory name.
22653 If no directories are specified, the current path is displayed.
22656 @subsubheading @value{GDBN} Command
22658 The corresponding @value{GDBN} command is @samp{path}.
22660 @subsubheading Example
22665 ^done,path="/usr/bin"
22667 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
22668 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
22670 -environment-path -r /usr/local/bin
22671 ^done,path="/usr/local/bin:/usr/bin"
22676 @subheading The @code{-environment-pwd} Command
22677 @findex -environment-pwd
22679 @subsubheading Synopsis
22685 Show the current working directory.
22687 @subsubheading @value{GDBN} Command
22689 The corresponding @value{GDBN} command is @samp{pwd}.
22691 @subsubheading Example
22696 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
22700 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
22701 @node GDB/MI Thread Commands
22702 @section @sc{gdb/mi} Thread Commands
22705 @subheading The @code{-thread-info} Command
22706 @findex -thread-info
22708 @subsubheading Synopsis
22711 -thread-info [ @var{thread-id} ]
22714 Reports information about either a specific thread, if
22715 the @var{thread-id} parameter is present, or about all
22716 threads. When printing information about all threads,
22717 also reports the current thread.
22719 @subsubheading @value{GDBN} Command
22721 The @samp{info thread} command prints the same information
22724 @subsubheading Example
22729 @{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
22730 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},state="running"@},
22731 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
22732 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
22733 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},state="running"@}],
22734 current-thread-id="1"
22738 The @samp{state} field may have the following values:
22742 The thread is stopped. Frame information is available for stopped
22746 The thread is running. There's no frame information for running
22751 @subheading The @code{-thread-list-ids} Command
22752 @findex -thread-list-ids
22754 @subsubheading Synopsis
22760 Produces a list of the currently known @value{GDBN} thread ids. At the
22761 end of the list it also prints the total number of such threads.
22763 This command is retained for historical reasons, the
22764 @code{-thread-info} command should be used instead.
22766 @subsubheading @value{GDBN} Command
22768 Part of @samp{info threads} supplies the same information.
22770 @subsubheading Example
22775 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
22776 current-thread-id="1",number-of-threads="3"
22781 @subheading The @code{-thread-select} Command
22782 @findex -thread-select
22784 @subsubheading Synopsis
22787 -thread-select @var{threadnum}
22790 Make @var{threadnum} the current thread. It prints the number of the new
22791 current thread, and the topmost frame for that thread.
22793 This command is deprecated in favor of explicitly using the
22794 @samp{--thread} option to each command.
22796 @subsubheading @value{GDBN} Command
22798 The corresponding @value{GDBN} command is @samp{thread}.
22800 @subsubheading Example
22807 *stopped,reason="end-stepping-range",thread-id="2",line="187",
22808 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
22812 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
22813 number-of-threads="3"
22816 ^done,new-thread-id="3",
22817 frame=@{level="0",func="vprintf",
22818 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
22819 @{name="arg",value="0x2"@}],file="vprintf.c",line="31"@}
22823 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
22824 @node GDB/MI Program Execution
22825 @section @sc{gdb/mi} Program Execution
22827 These are the asynchronous commands which generate the out-of-band
22828 record @samp{*stopped}. Currently @value{GDBN} only really executes
22829 asynchronously with remote targets and this interaction is mimicked in
22832 @subheading The @code{-exec-continue} Command
22833 @findex -exec-continue
22835 @subsubheading Synopsis
22838 -exec-continue [--all|--thread-group N]
22841 Resumes the execution of the inferior program until a breakpoint is
22842 encountered, or until the inferior exits. In all-stop mode
22843 (@pxref{All-Stop Mode}), may resume only one thread, or all threads,
22844 depending on the value of the @samp{scheduler-locking} variable. In
22845 non-stop mode (@pxref{Non-Stop Mode}), if the @samp{--all} is not
22846 specified, only the thread specified with the @samp{--thread} option
22847 (or current thread, if no @samp{--thread} is provided) is resumed. If
22848 @samp{--all} is specified, all threads will be resumed. The
22849 @samp{--all} option is ignored in all-stop mode. If the
22850 @samp{--thread-group} options is specified, then all threads in that
22851 thread group are resumed.
22853 @subsubheading @value{GDBN} Command
22855 The corresponding @value{GDBN} corresponding is @samp{continue}.
22857 @subsubheading Example
22864 *stopped,reason="breakpoint-hit",disp="keep",bkptno="2",frame=@{
22865 func="foo",args=[],file="hello.c",fullname="/home/foo/bar/hello.c",
22871 @subheading The @code{-exec-finish} Command
22872 @findex -exec-finish
22874 @subsubheading Synopsis
22880 Resumes the execution of the inferior program until the current
22881 function is exited. Displays the results returned by the function.
22883 @subsubheading @value{GDBN} Command
22885 The corresponding @value{GDBN} command is @samp{finish}.
22887 @subsubheading Example
22889 Function returning @code{void}.
22896 *stopped,reason="function-finished",frame=@{func="main",args=[],
22897 file="hello.c",fullname="/home/foo/bar/hello.c",line="7"@}
22901 Function returning other than @code{void}. The name of the internal
22902 @value{GDBN} variable storing the result is printed, together with the
22909 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
22910 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
22911 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
22912 gdb-result-var="$1",return-value="0"
22917 @subheading The @code{-exec-interrupt} Command
22918 @findex -exec-interrupt
22920 @subsubheading Synopsis
22923 -exec-interrupt [--all|--thread-group N]
22926 Interrupts the background execution of the target. Note how the token
22927 associated with the stop message is the one for the execution command
22928 that has been interrupted. The token for the interrupt itself only
22929 appears in the @samp{^done} output. If the user is trying to
22930 interrupt a non-running program, an error message will be printed.
22932 Note that when asynchronous execution is enabled, this command is
22933 asynchronous just like other execution commands. That is, first the
22934 @samp{^done} response will be printed, and the target stop will be
22935 reported after that using the @samp{*stopped} notification.
22937 In non-stop mode, only the context thread is interrupted by default.
22938 All threads will be interrupted if the @samp{--all} option is
22939 specified. If the @samp{--thread-group} option is specified, all
22940 threads in that group will be interrupted.
22942 @subsubheading @value{GDBN} Command
22944 The corresponding @value{GDBN} command is @samp{interrupt}.
22946 @subsubheading Example
22957 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
22958 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",
22959 fullname="/home/foo/bar/try.c",line="13"@}
22964 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
22968 @subheading The @code{-exec-jump} Command
22971 @subsubheading Synopsis
22974 -exec-jump @var{location}
22977 Resumes execution of the inferior program at the location specified by
22978 parameter. @xref{Specify Location}, for a description of the
22979 different forms of @var{location}.
22981 @subsubheading @value{GDBN} Command
22983 The corresponding @value{GDBN} command is @samp{jump}.
22985 @subsubheading Example
22988 -exec-jump foo.c:10
22989 *running,thread-id="all"
22994 @subheading The @code{-exec-next} Command
22997 @subsubheading Synopsis
23003 Resumes execution of the inferior program, stopping when the beginning
23004 of the next source line is reached.
23006 @subsubheading @value{GDBN} Command
23008 The corresponding @value{GDBN} command is @samp{next}.
23010 @subsubheading Example
23016 *stopped,reason="end-stepping-range",line="8",file="hello.c"
23021 @subheading The @code{-exec-next-instruction} Command
23022 @findex -exec-next-instruction
23024 @subsubheading Synopsis
23027 -exec-next-instruction
23030 Executes one machine instruction. If the instruction is a function
23031 call, continues until the function returns. If the program stops at an
23032 instruction in the middle of a source line, the address will be
23035 @subsubheading @value{GDBN} Command
23037 The corresponding @value{GDBN} command is @samp{nexti}.
23039 @subsubheading Example
23043 -exec-next-instruction
23047 *stopped,reason="end-stepping-range",
23048 addr="0x000100d4",line="5",file="hello.c"
23053 @subheading The @code{-exec-return} Command
23054 @findex -exec-return
23056 @subsubheading Synopsis
23062 Makes current function return immediately. Doesn't execute the inferior.
23063 Displays the new current frame.
23065 @subsubheading @value{GDBN} Command
23067 The corresponding @value{GDBN} command is @samp{return}.
23069 @subsubheading Example
23073 200-break-insert callee4
23074 200^done,bkpt=@{number="1",addr="0x00010734",
23075 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
23080 000*stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
23081 frame=@{func="callee4",args=[],
23082 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
23083 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
23089 111^done,frame=@{level="0",func="callee3",
23090 args=[@{name="strarg",
23091 value="0x11940 \"A string argument.\""@}],
23092 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
23093 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
23098 @subheading The @code{-exec-run} Command
23101 @subsubheading Synopsis
23107 Starts execution of the inferior from the beginning. The inferior
23108 executes until either a breakpoint is encountered or the program
23109 exits. In the latter case the output will include an exit code, if
23110 the program has exited exceptionally.
23112 @subsubheading @value{GDBN} Command
23114 The corresponding @value{GDBN} command is @samp{run}.
23116 @subsubheading Examples
23121 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
23126 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
23127 frame=@{func="main",args=[],file="recursive2.c",
23128 fullname="/home/foo/bar/recursive2.c",line="4"@}
23133 Program exited normally:
23141 *stopped,reason="exited-normally"
23146 Program exited exceptionally:
23154 *stopped,reason="exited",exit-code="01"
23158 Another way the program can terminate is if it receives a signal such as
23159 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
23163 *stopped,reason="exited-signalled",signal-name="SIGINT",
23164 signal-meaning="Interrupt"
23168 @c @subheading -exec-signal
23171 @subheading The @code{-exec-step} Command
23174 @subsubheading Synopsis
23180 Resumes execution of the inferior program, stopping when the beginning
23181 of the next source line is reached, if the next source line is not a
23182 function call. If it is, stop at the first instruction of the called
23185 @subsubheading @value{GDBN} Command
23187 The corresponding @value{GDBN} command is @samp{step}.
23189 @subsubheading Example
23191 Stepping into a function:
23197 *stopped,reason="end-stepping-range",
23198 frame=@{func="foo",args=[@{name="a",value="10"@},
23199 @{name="b",value="0"@}],file="recursive2.c",
23200 fullname="/home/foo/bar/recursive2.c",line="11"@}
23210 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
23215 @subheading The @code{-exec-step-instruction} Command
23216 @findex -exec-step-instruction
23218 @subsubheading Synopsis
23221 -exec-step-instruction
23224 Resumes the inferior which executes one machine instruction. The
23225 output, once @value{GDBN} has stopped, will vary depending on whether
23226 we have stopped in the middle of a source line or not. In the former
23227 case, the address at which the program stopped will be printed as
23230 @subsubheading @value{GDBN} Command
23232 The corresponding @value{GDBN} command is @samp{stepi}.
23234 @subsubheading Example
23238 -exec-step-instruction
23242 *stopped,reason="end-stepping-range",
23243 frame=@{func="foo",args=[],file="try.c",
23244 fullname="/home/foo/bar/try.c",line="10"@}
23246 -exec-step-instruction
23250 *stopped,reason="end-stepping-range",
23251 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",
23252 fullname="/home/foo/bar/try.c",line="10"@}
23257 @subheading The @code{-exec-until} Command
23258 @findex -exec-until
23260 @subsubheading Synopsis
23263 -exec-until [ @var{location} ]
23266 Executes the inferior until the @var{location} specified in the
23267 argument is reached. If there is no argument, the inferior executes
23268 until a source line greater than the current one is reached. The
23269 reason for stopping in this case will be @samp{location-reached}.
23271 @subsubheading @value{GDBN} Command
23273 The corresponding @value{GDBN} command is @samp{until}.
23275 @subsubheading Example
23279 -exec-until recursive2.c:6
23283 *stopped,reason="location-reached",frame=@{func="main",args=[],
23284 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="6"@}
23289 @subheading -file-clear
23290 Is this going away????
23293 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
23294 @node GDB/MI Stack Manipulation
23295 @section @sc{gdb/mi} Stack Manipulation Commands
23298 @subheading The @code{-stack-info-frame} Command
23299 @findex -stack-info-frame
23301 @subsubheading Synopsis
23307 Get info on the selected frame.
23309 @subsubheading @value{GDBN} Command
23311 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
23312 (without arguments).
23314 @subsubheading Example
23319 ^done,frame=@{level="1",addr="0x0001076c",func="callee3",
23320 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
23321 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@}
23325 @subheading The @code{-stack-info-depth} Command
23326 @findex -stack-info-depth
23328 @subsubheading Synopsis
23331 -stack-info-depth [ @var{max-depth} ]
23334 Return the depth of the stack. If the integer argument @var{max-depth}
23335 is specified, do not count beyond @var{max-depth} frames.
23337 @subsubheading @value{GDBN} Command
23339 There's no equivalent @value{GDBN} command.
23341 @subsubheading Example
23343 For a stack with frame levels 0 through 11:
23350 -stack-info-depth 4
23353 -stack-info-depth 12
23356 -stack-info-depth 11
23359 -stack-info-depth 13
23364 @subheading The @code{-stack-list-arguments} Command
23365 @findex -stack-list-arguments
23367 @subsubheading Synopsis
23370 -stack-list-arguments @var{show-values}
23371 [ @var{low-frame} @var{high-frame} ]
23374 Display a list of the arguments for the frames between @var{low-frame}
23375 and @var{high-frame} (inclusive). If @var{low-frame} and
23376 @var{high-frame} are not provided, list the arguments for the whole
23377 call stack. If the two arguments are equal, show the single frame
23378 at the corresponding level. It is an error if @var{low-frame} is
23379 larger than the actual number of frames. On the other hand,
23380 @var{high-frame} may be larger than the actual number of frames, in
23381 which case only existing frames will be returned.
23383 The @var{show-values} argument must have a value of 0 or 1. A value of
23384 0 means that only the names of the arguments are listed, a value of 1
23385 means that both names and values of the arguments are printed.
23387 Use of this command to obtain arguments in a single frame is
23388 deprecated in favor of the @samp{-stack-list-variables} command.
23390 @subsubheading @value{GDBN} Command
23392 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
23393 @samp{gdb_get_args} command which partially overlaps with the
23394 functionality of @samp{-stack-list-arguments}.
23396 @subsubheading Example
23403 frame=@{level="0",addr="0x00010734",func="callee4",
23404 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
23405 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@},
23406 frame=@{level="1",addr="0x0001076c",func="callee3",
23407 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
23408 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@},
23409 frame=@{level="2",addr="0x0001078c",func="callee2",
23410 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
23411 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="22"@},
23412 frame=@{level="3",addr="0x000107b4",func="callee1",
23413 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
23414 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="27"@},
23415 frame=@{level="4",addr="0x000107e0",func="main",
23416 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
23417 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="32"@}]
23419 -stack-list-arguments 0
23422 frame=@{level="0",args=[]@},
23423 frame=@{level="1",args=[name="strarg"]@},
23424 frame=@{level="2",args=[name="intarg",name="strarg"]@},
23425 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
23426 frame=@{level="4",args=[]@}]
23428 -stack-list-arguments 1
23431 frame=@{level="0",args=[]@},
23433 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
23434 frame=@{level="2",args=[
23435 @{name="intarg",value="2"@},
23436 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
23437 @{frame=@{level="3",args=[
23438 @{name="intarg",value="2"@},
23439 @{name="strarg",value="0x11940 \"A string argument.\""@},
23440 @{name="fltarg",value="3.5"@}]@},
23441 frame=@{level="4",args=[]@}]
23443 -stack-list-arguments 0 2 2
23444 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
23446 -stack-list-arguments 1 2 2
23447 ^done,stack-args=[frame=@{level="2",
23448 args=[@{name="intarg",value="2"@},
23449 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
23453 @c @subheading -stack-list-exception-handlers
23456 @subheading The @code{-stack-list-frames} Command
23457 @findex -stack-list-frames
23459 @subsubheading Synopsis
23462 -stack-list-frames [ @var{low-frame} @var{high-frame} ]
23465 List the frames currently on the stack. For each frame it displays the
23470 The frame number, 0 being the topmost frame, i.e., the innermost function.
23472 The @code{$pc} value for that frame.
23476 File name of the source file where the function lives.
23478 Line number corresponding to the @code{$pc}.
23481 If invoked without arguments, this command prints a backtrace for the
23482 whole stack. If given two integer arguments, it shows the frames whose
23483 levels are between the two arguments (inclusive). If the two arguments
23484 are equal, it shows the single frame at the corresponding level. It is
23485 an error if @var{low-frame} is larger than the actual number of
23486 frames. On the other hand, @var{high-frame} may be larger than the
23487 actual number of frames, in which case only existing frames will be returned.
23489 @subsubheading @value{GDBN} Command
23491 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
23493 @subsubheading Example
23495 Full stack backtrace:
23501 [frame=@{level="0",addr="0x0001076c",func="foo",
23502 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="11"@},
23503 frame=@{level="1",addr="0x000107a4",func="foo",
23504 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
23505 frame=@{level="2",addr="0x000107a4",func="foo",
23506 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
23507 frame=@{level="3",addr="0x000107a4",func="foo",
23508 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
23509 frame=@{level="4",addr="0x000107a4",func="foo",
23510 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
23511 frame=@{level="5",addr="0x000107a4",func="foo",
23512 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
23513 frame=@{level="6",addr="0x000107a4",func="foo",
23514 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
23515 frame=@{level="7",addr="0x000107a4",func="foo",
23516 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
23517 frame=@{level="8",addr="0x000107a4",func="foo",
23518 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
23519 frame=@{level="9",addr="0x000107a4",func="foo",
23520 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
23521 frame=@{level="10",addr="0x000107a4",func="foo",
23522 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
23523 frame=@{level="11",addr="0x00010738",func="main",
23524 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="4"@}]
23528 Show frames between @var{low_frame} and @var{high_frame}:
23532 -stack-list-frames 3 5
23534 [frame=@{level="3",addr="0x000107a4",func="foo",
23535 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
23536 frame=@{level="4",addr="0x000107a4",func="foo",
23537 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
23538 frame=@{level="5",addr="0x000107a4",func="foo",
23539 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
23543 Show a single frame:
23547 -stack-list-frames 3 3
23549 [frame=@{level="3",addr="0x000107a4",func="foo",
23550 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
23555 @subheading The @code{-stack-list-locals} Command
23556 @findex -stack-list-locals
23558 @subsubheading Synopsis
23561 -stack-list-locals @var{print-values}
23564 Display the local variable names for the selected frame. If
23565 @var{print-values} is 0 or @code{--no-values}, print only the names of
23566 the variables; if it is 1 or @code{--all-values}, print also their
23567 values; and if it is 2 or @code{--simple-values}, print the name,
23568 type and value for simple data types and the name and type for arrays,
23569 structures and unions. In this last case, a frontend can immediately
23570 display the value of simple data types and create variable objects for
23571 other data types when the user wishes to explore their values in
23574 This command is deprecated in favor of the
23575 @samp{-stack-list-variables} command.
23577 @subsubheading @value{GDBN} Command
23579 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
23581 @subsubheading Example
23585 -stack-list-locals 0
23586 ^done,locals=[name="A",name="B",name="C"]
23588 -stack-list-locals --all-values
23589 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
23590 @{name="C",value="@{1, 2, 3@}"@}]
23591 -stack-list-locals --simple-values
23592 ^done,locals=[@{name="A",type="int",value="1"@},
23593 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
23597 @subheading The @code{-stack-list-variables} Command
23598 @findex -stack-list-variables
23600 @subsubheading Synopsis
23603 -stack-list-variables @var{print-values}
23606 Display the names of local variables and function arguments for the selected frame. If
23607 @var{print-values} is 0 or @code{--no-values}, print only the names of
23608 the variables; if it is 1 or @code{--all-values}, print also their
23609 values; and if it is 2 or @code{--simple-values}, print the name,
23610 type and value for simple data types and the name and type for arrays,
23611 structures and unions.
23613 @subsubheading Example
23617 -stack-list-variables --thread 1 --frame 0 --all-values
23618 ^done,variables=[@{name="x",value="11"@},@{name="s",value="@{a = 1, b = 2@}"@}]
23623 @subheading The @code{-stack-select-frame} Command
23624 @findex -stack-select-frame
23626 @subsubheading Synopsis
23629 -stack-select-frame @var{framenum}
23632 Change the selected frame. Select a different frame @var{framenum} on
23635 This command in deprecated in favor of passing the @samp{--frame}
23636 option to every command.
23638 @subsubheading @value{GDBN} Command
23640 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
23641 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
23643 @subsubheading Example
23647 -stack-select-frame 2
23652 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
23653 @node GDB/MI Variable Objects
23654 @section @sc{gdb/mi} Variable Objects
23658 @subheading Motivation for Variable Objects in @sc{gdb/mi}
23660 For the implementation of a variable debugger window (locals, watched
23661 expressions, etc.), we are proposing the adaptation of the existing code
23662 used by @code{Insight}.
23664 The two main reasons for that are:
23668 It has been proven in practice (it is already on its second generation).
23671 It will shorten development time (needless to say how important it is
23675 The original interface was designed to be used by Tcl code, so it was
23676 slightly changed so it could be used through @sc{gdb/mi}. This section
23677 describes the @sc{gdb/mi} operations that will be available and gives some
23678 hints about their use.
23680 @emph{Note}: In addition to the set of operations described here, we
23681 expect the @sc{gui} implementation of a variable window to require, at
23682 least, the following operations:
23685 @item @code{-gdb-show} @code{output-radix}
23686 @item @code{-stack-list-arguments}
23687 @item @code{-stack-list-locals}
23688 @item @code{-stack-select-frame}
23693 @subheading Introduction to Variable Objects
23695 @cindex variable objects in @sc{gdb/mi}
23697 Variable objects are "object-oriented" MI interface for examining and
23698 changing values of expressions. Unlike some other MI interfaces that
23699 work with expressions, variable objects are specifically designed for
23700 simple and efficient presentation in the frontend. A variable object
23701 is identified by string name. When a variable object is created, the
23702 frontend specifies the expression for that variable object. The
23703 expression can be a simple variable, or it can be an arbitrary complex
23704 expression, and can even involve CPU registers. After creating a
23705 variable object, the frontend can invoke other variable object
23706 operations---for example to obtain or change the value of a variable
23707 object, or to change display format.
23709 Variable objects have hierarchical tree structure. Any variable object
23710 that corresponds to a composite type, such as structure in C, has
23711 a number of child variable objects, for example corresponding to each
23712 element of a structure. A child variable object can itself have
23713 children, recursively. Recursion ends when we reach
23714 leaf variable objects, which always have built-in types. Child variable
23715 objects are created only by explicit request, so if a frontend
23716 is not interested in the children of a particular variable object, no
23717 child will be created.
23719 For a leaf variable object it is possible to obtain its value as a
23720 string, or set the value from a string. String value can be also
23721 obtained for a non-leaf variable object, but it's generally a string
23722 that only indicates the type of the object, and does not list its
23723 contents. Assignment to a non-leaf variable object is not allowed.
23725 A frontend does not need to read the values of all variable objects each time
23726 the program stops. Instead, MI provides an update command that lists all
23727 variable objects whose values has changed since the last update
23728 operation. This considerably reduces the amount of data that must
23729 be transferred to the frontend. As noted above, children variable
23730 objects are created on demand, and only leaf variable objects have a
23731 real value. As result, gdb will read target memory only for leaf
23732 variables that frontend has created.
23734 The automatic update is not always desirable. For example, a frontend
23735 might want to keep a value of some expression for future reference,
23736 and never update it. For another example, fetching memory is
23737 relatively slow for embedded targets, so a frontend might want
23738 to disable automatic update for the variables that are either not
23739 visible on the screen, or ``closed''. This is possible using so
23740 called ``frozen variable objects''. Such variable objects are never
23741 implicitly updated.
23743 Variable objects can be either @dfn{fixed} or @dfn{floating}. For the
23744 fixed variable object, the expression is parsed when the variable
23745 object is created, including associating identifiers to specific
23746 variables. The meaning of expression never changes. For a floating
23747 variable object the values of variables whose names appear in the
23748 expressions are re-evaluated every time in the context of the current
23749 frame. Consider this example:
23754 struct work_state state;
23761 If a fixed variable object for the @code{state} variable is created in
23762 this function, and we enter the recursive call, the the variable
23763 object will report the value of @code{state} in the top-level
23764 @code{do_work} invocation. On the other hand, a floating variable
23765 object will report the value of @code{state} in the current frame.
23767 If an expression specified when creating a fixed variable object
23768 refers to a local variable, the variable object becomes bound to the
23769 thread and frame in which the variable object is created. When such
23770 variable object is updated, @value{GDBN} makes sure that the
23771 thread/frame combination the variable object is bound to still exists,
23772 and re-evaluates the variable object in context of that thread/frame.
23774 The following is the complete set of @sc{gdb/mi} operations defined to
23775 access this functionality:
23777 @multitable @columnfractions .4 .6
23778 @item @strong{Operation}
23779 @tab @strong{Description}
23781 @item @code{-enable-pretty-printing}
23782 @tab enable Python-based pretty-printing
23783 @item @code{-var-create}
23784 @tab create a variable object
23785 @item @code{-var-delete}
23786 @tab delete the variable object and/or its children
23787 @item @code{-var-set-format}
23788 @tab set the display format of this variable
23789 @item @code{-var-show-format}
23790 @tab show the display format of this variable
23791 @item @code{-var-info-num-children}
23792 @tab tells how many children this object has
23793 @item @code{-var-list-children}
23794 @tab return a list of the object's children
23795 @item @code{-var-info-type}
23796 @tab show the type of this variable object
23797 @item @code{-var-info-expression}
23798 @tab print parent-relative expression that this variable object represents
23799 @item @code{-var-info-path-expression}
23800 @tab print full expression that this variable object represents
23801 @item @code{-var-show-attributes}
23802 @tab is this variable editable? does it exist here?
23803 @item @code{-var-evaluate-expression}
23804 @tab get the value of this variable
23805 @item @code{-var-assign}
23806 @tab set the value of this variable
23807 @item @code{-var-update}
23808 @tab update the variable and its children
23809 @item @code{-var-set-frozen}
23810 @tab set frozeness attribute
23811 @item @code{-var-set-update-range}
23812 @tab set range of children to display on update
23815 In the next subsection we describe each operation in detail and suggest
23816 how it can be used.
23818 @subheading Description And Use of Operations on Variable Objects
23820 @subheading The @code{-enable-pretty-printing} Command
23821 @findex -enable-pretty-printing
23824 -enable-pretty-printing
23827 @value{GDBN} allows Python-based visualizers to affect the output of the
23828 MI variable object commands. However, because there was no way to
23829 implement this in a fully backward-compatible way, a front end must
23830 request that this functionality be enabled.
23832 Once enabled, this feature cannot be disabled.
23834 Note that if Python support has not been compiled into @value{GDBN},
23835 this command will still succeed (and do nothing).
23837 This feature is currently (as of @value{GDBN} 7.0) experimental, and
23838 may work differently in future versions of @value{GDBN}.
23840 @subheading The @code{-var-create} Command
23841 @findex -var-create
23843 @subsubheading Synopsis
23846 -var-create @{@var{name} | "-"@}
23847 @{@var{frame-addr} | "*" | "@@"@} @var{expression}
23850 This operation creates a variable object, which allows the monitoring of
23851 a variable, the result of an expression, a memory cell or a CPU
23854 The @var{name} parameter is the string by which the object can be
23855 referenced. It must be unique. If @samp{-} is specified, the varobj
23856 system will generate a string ``varNNNNNN'' automatically. It will be
23857 unique provided that one does not specify @var{name} of that format.
23858 The command fails if a duplicate name is found.
23860 The frame under which the expression should be evaluated can be
23861 specified by @var{frame-addr}. A @samp{*} indicates that the current
23862 frame should be used. A @samp{@@} indicates that a floating variable
23863 object must be created.
23865 @var{expression} is any expression valid on the current language set (must not
23866 begin with a @samp{*}), or one of the following:
23870 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
23873 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
23876 @samp{$@var{regname}} --- a CPU register name
23879 @cindex dynamic varobj
23880 A varobj's contents may be provided by a Python-based pretty-printer. In this
23881 case the varobj is known as a @dfn{dynamic varobj}. Dynamic varobjs
23882 have slightly different semantics in some cases. If the
23883 @code{-enable-pretty-printing} command is not sent, then @value{GDBN}
23884 will never create a dynamic varobj. This ensures backward
23885 compatibility for existing clients.
23887 @subsubheading Result
23889 This operation returns attributes of the newly-created varobj. These
23894 The name of the varobj.
23897 The number of children of the varobj. This number is not necessarily
23898 reliable for a dynamic varobj. Instead, you must examine the
23899 @samp{has_more} attribute.
23902 The varobj's scalar value. For a varobj whose type is some sort of
23903 aggregate (e.g., a @code{struct}), or for a dynamic varobj, this value
23904 will not be interesting.
23907 The varobj's type. This is a string representation of the type, as
23908 would be printed by the @value{GDBN} CLI.
23911 If a variable object is bound to a specific thread, then this is the
23912 thread's identifier.
23915 For a dynamic varobj, this indicates whether there appear to be any
23916 children available. For a non-dynamic varobj, this will be 0.
23919 This attribute will be present and have the value @samp{1} if the
23920 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
23921 then this attribute will not be present.
23924 A dynamic varobj can supply a display hint to the front end. The
23925 value comes directly from the Python pretty-printer object's
23926 @code{display_hint} method. @xref{Pretty Printing}.
23929 Typical output will look like this:
23932 name="@var{name}",numchild="@var{N}",type="@var{type}",thread-id="@var{M}",
23933 has_more="@var{has_more}"
23937 @subheading The @code{-var-delete} Command
23938 @findex -var-delete
23940 @subsubheading Synopsis
23943 -var-delete [ -c ] @var{name}
23946 Deletes a previously created variable object and all of its children.
23947 With the @samp{-c} option, just deletes the children.
23949 Returns an error if the object @var{name} is not found.
23952 @subheading The @code{-var-set-format} Command
23953 @findex -var-set-format
23955 @subsubheading Synopsis
23958 -var-set-format @var{name} @var{format-spec}
23961 Sets the output format for the value of the object @var{name} to be
23964 @anchor{-var-set-format}
23965 The syntax for the @var{format-spec} is as follows:
23968 @var{format-spec} @expansion{}
23969 @{binary | decimal | hexadecimal | octal | natural@}
23972 The natural format is the default format choosen automatically
23973 based on the variable type (like decimal for an @code{int}, hex
23974 for pointers, etc.).
23976 For a variable with children, the format is set only on the
23977 variable itself, and the children are not affected.
23979 @subheading The @code{-var-show-format} Command
23980 @findex -var-show-format
23982 @subsubheading Synopsis
23985 -var-show-format @var{name}
23988 Returns the format used to display the value of the object @var{name}.
23991 @var{format} @expansion{}
23996 @subheading The @code{-var-info-num-children} Command
23997 @findex -var-info-num-children
23999 @subsubheading Synopsis
24002 -var-info-num-children @var{name}
24005 Returns the number of children of a variable object @var{name}:
24011 Note that this number is not completely reliable for a dynamic varobj.
24012 It will return the current number of children, but more children may
24016 @subheading The @code{-var-list-children} Command
24017 @findex -var-list-children
24019 @subsubheading Synopsis
24022 -var-list-children [@var{print-values}] @var{name} [@var{from} @var{to}]
24024 @anchor{-var-list-children}
24026 Return a list of the children of the specified variable object and
24027 create variable objects for them, if they do not already exist. With
24028 a single argument or if @var{print-values} has a value for of 0 or
24029 @code{--no-values}, print only the names of the variables; if
24030 @var{print-values} is 1 or @code{--all-values}, also print their
24031 values; and if it is 2 or @code{--simple-values} print the name and
24032 value for simple data types and just the name for arrays, structures
24035 @var{from} and @var{to}, if specified, indicate the range of children
24036 to report. If @var{from} or @var{to} is less than zero, the range is
24037 reset and all children will be reported. Otherwise, children starting
24038 at @var{from} (zero-based) and up to and excluding @var{to} will be
24041 If a child range is requested, it will only affect the current call to
24042 @code{-var-list-children}, but not future calls to @code{-var-update}.
24043 For this, you must instead use @code{-var-set-update-range}. The
24044 intent of this approach is to enable a front end to implement any
24045 update approach it likes; for example, scrolling a view may cause the
24046 front end to request more children with @code{-var-list-children}, and
24047 then the front end could call @code{-var-set-update-range} with a
24048 different range to ensure that future updates are restricted to just
24051 For each child the following results are returned:
24056 Name of the variable object created for this child.
24059 The expression to be shown to the user by the front end to designate this child.
24060 For example this may be the name of a structure member.
24062 For a dynamic varobj, this value cannot be used to form an
24063 expression. There is no way to do this at all with a dynamic varobj.
24065 For C/C@t{++} structures there are several pseudo children returned to
24066 designate access qualifiers. For these pseudo children @var{exp} is
24067 @samp{public}, @samp{private}, or @samp{protected}. In this case the
24068 type and value are not present.
24070 A dynamic varobj will not report the access qualifying
24071 pseudo-children, regardless of the language. This information is not
24072 available at all with a dynamic varobj.
24075 Number of children this child has. For a dynamic varobj, this will be
24079 The type of the child.
24082 If values were requested, this is the value.
24085 If this variable object is associated with a thread, this is the thread id.
24086 Otherwise this result is not present.
24089 If the variable object is frozen, this variable will be present with a value of 1.
24092 The result may have its own attributes:
24096 A dynamic varobj can supply a display hint to the front end. The
24097 value comes directly from the Python pretty-printer object's
24098 @code{display_hint} method. @xref{Pretty Printing}.
24101 This is an integer attribute which is nonzero if there are children
24102 remaining after the end of the selected range.
24105 @subsubheading Example
24109 -var-list-children n
24110 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
24111 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
24113 -var-list-children --all-values n
24114 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
24115 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
24119 @subheading The @code{-var-info-type} Command
24120 @findex -var-info-type
24122 @subsubheading Synopsis
24125 -var-info-type @var{name}
24128 Returns the type of the specified variable @var{name}. The type is
24129 returned as a string in the same format as it is output by the
24133 type=@var{typename}
24137 @subheading The @code{-var-info-expression} Command
24138 @findex -var-info-expression
24140 @subsubheading Synopsis
24143 -var-info-expression @var{name}
24146 Returns a string that is suitable for presenting this
24147 variable object in user interface. The string is generally
24148 not valid expression in the current language, and cannot be evaluated.
24150 For example, if @code{a} is an array, and variable object
24151 @code{A} was created for @code{a}, then we'll get this output:
24154 (gdb) -var-info-expression A.1
24155 ^done,lang="C",exp="1"
24159 Here, the values of @code{lang} can be @code{@{"C" | "C++" | "Java"@}}.
24161 Note that the output of the @code{-var-list-children} command also
24162 includes those expressions, so the @code{-var-info-expression} command
24165 @subheading The @code{-var-info-path-expression} Command
24166 @findex -var-info-path-expression
24168 @subsubheading Synopsis
24171 -var-info-path-expression @var{name}
24174 Returns an expression that can be evaluated in the current
24175 context and will yield the same value that a variable object has.
24176 Compare this with the @code{-var-info-expression} command, which
24177 result can be used only for UI presentation. Typical use of
24178 the @code{-var-info-path-expression} command is creating a
24179 watchpoint from a variable object.
24181 This command is currently not valid for children of a dynamic varobj,
24182 and will give an error when invoked on one.
24184 For example, suppose @code{C} is a C@t{++} class, derived from class
24185 @code{Base}, and that the @code{Base} class has a member called
24186 @code{m_size}. Assume a variable @code{c} is has the type of
24187 @code{C} and a variable object @code{C} was created for variable
24188 @code{c}. Then, we'll get this output:
24190 (gdb) -var-info-path-expression C.Base.public.m_size
24191 ^done,path_expr=((Base)c).m_size)
24194 @subheading The @code{-var-show-attributes} Command
24195 @findex -var-show-attributes
24197 @subsubheading Synopsis
24200 -var-show-attributes @var{name}
24203 List attributes of the specified variable object @var{name}:
24206 status=@var{attr} [ ( ,@var{attr} )* ]
24210 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
24212 @subheading The @code{-var-evaluate-expression} Command
24213 @findex -var-evaluate-expression
24215 @subsubheading Synopsis
24218 -var-evaluate-expression [-f @var{format-spec}] @var{name}
24221 Evaluates the expression that is represented by the specified variable
24222 object and returns its value as a string. The format of the string
24223 can be specified with the @samp{-f} option. The possible values of
24224 this option are the same as for @code{-var-set-format}
24225 (@pxref{-var-set-format}). If the @samp{-f} option is not specified,
24226 the current display format will be used. The current display format
24227 can be changed using the @code{-var-set-format} command.
24233 Note that one must invoke @code{-var-list-children} for a variable
24234 before the value of a child variable can be evaluated.
24236 @subheading The @code{-var-assign} Command
24237 @findex -var-assign
24239 @subsubheading Synopsis
24242 -var-assign @var{name} @var{expression}
24245 Assigns the value of @var{expression} to the variable object specified
24246 by @var{name}. The object must be @samp{editable}. If the variable's
24247 value is altered by the assign, the variable will show up in any
24248 subsequent @code{-var-update} list.
24250 @subsubheading Example
24258 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
24262 @subheading The @code{-var-update} Command
24263 @findex -var-update
24265 @subsubheading Synopsis
24268 -var-update [@var{print-values}] @{@var{name} | "*"@}
24271 Reevaluate the expressions corresponding to the variable object
24272 @var{name} and all its direct and indirect children, and return the
24273 list of variable objects whose values have changed; @var{name} must
24274 be a root variable object. Here, ``changed'' means that the result of
24275 @code{-var-evaluate-expression} before and after the
24276 @code{-var-update} is different. If @samp{*} is used as the variable
24277 object names, all existing variable objects are updated, except
24278 for frozen ones (@pxref{-var-set-frozen}). The option
24279 @var{print-values} determines whether both names and values, or just
24280 names are printed. The possible values of this option are the same
24281 as for @code{-var-list-children} (@pxref{-var-list-children}). It is
24282 recommended to use the @samp{--all-values} option, to reduce the
24283 number of MI commands needed on each program stop.
24285 With the @samp{*} parameter, if a variable object is bound to a
24286 currently running thread, it will not be updated, without any
24289 If @code{-var-set-update-range} was previously used on a varobj, then
24290 only the selected range of children will be reported.
24292 @code{-var-update} reports all the changed varobjs in a tuple named
24295 Each item in the change list is itself a tuple holding:
24299 The name of the varobj.
24302 If values were requested for this update, then this field will be
24303 present and will hold the value of the varobj.
24306 @anchor{-var-update}
24307 This field is a string which may take one of three values:
24311 The variable object's current value is valid.
24314 The variable object does not currently hold a valid value but it may
24315 hold one in the future if its associated expression comes back into
24319 The variable object no longer holds a valid value.
24320 This can occur when the executable file being debugged has changed,
24321 either through recompilation or by using the @value{GDBN} @code{file}
24322 command. The front end should normally choose to delete these variable
24326 In the future new values may be added to this list so the front should
24327 be prepared for this possibility. @xref{GDB/MI Development and Front Ends, ,@sc{GDB/MI} Development and Front Ends}.
24330 This is only present if the varobj is still valid. If the type
24331 changed, then this will be the string @samp{true}; otherwise it will
24335 If the varobj's type changed, then this field will be present and will
24338 @item new_num_children
24339 For a dynamic varobj, if the number of children changed, or if the
24340 type changed, this will be the new number of children.
24342 The @samp{numchild} field in other varobj responses is generally not
24343 valid for a dynamic varobj -- it will show the number of children that
24344 @value{GDBN} knows about, but because dynamic varobjs lazily
24345 instantiate their children, this will not reflect the number of
24346 children which may be available.
24348 The @samp{new_num_children} attribute only reports changes to the
24349 number of children known by @value{GDBN}. This is the only way to
24350 detect whether an update has removed children (which necessarily can
24351 only happen at the end of the update range).
24354 The display hint, if any.
24357 This is an integer value, which will be 1 if there are more children
24358 available outside the varobj's update range.
24361 This attribute will be present and have the value @samp{1} if the
24362 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
24363 then this attribute will not be present.
24366 If new children were added to a dynamic varobj within the selected
24367 update range (as set by @code{-var-set-update-range}), then they will
24368 be listed in this attribute.
24371 @subsubheading Example
24378 -var-update --all-values var1
24379 ^done,changelist=[@{name="var1",value="3",in_scope="true",
24380 type_changed="false"@}]
24384 @subheading The @code{-var-set-frozen} Command
24385 @findex -var-set-frozen
24386 @anchor{-var-set-frozen}
24388 @subsubheading Synopsis
24391 -var-set-frozen @var{name} @var{flag}
24394 Set the frozenness flag on the variable object @var{name}. The
24395 @var{flag} parameter should be either @samp{1} to make the variable
24396 frozen or @samp{0} to make it unfrozen. If a variable object is
24397 frozen, then neither itself, nor any of its children, are
24398 implicitly updated by @code{-var-update} of
24399 a parent variable or by @code{-var-update *}. Only
24400 @code{-var-update} of the variable itself will update its value and
24401 values of its children. After a variable object is unfrozen, it is
24402 implicitly updated by all subsequent @code{-var-update} operations.
24403 Unfreezing a variable does not update it, only subsequent
24404 @code{-var-update} does.
24406 @subsubheading Example
24410 -var-set-frozen V 1
24415 @subheading The @code{-var-set-update-range} command
24416 @findex -var-set-update-range
24417 @anchor{-var-set-update-range}
24419 @subsubheading Synopsis
24422 -var-set-update-range @var{name} @var{from} @var{to}
24425 Set the range of children to be returned by future invocations of
24426 @code{-var-update}.
24428 @var{from} and @var{to} indicate the range of children to report. If
24429 @var{from} or @var{to} is less than zero, the range is reset and all
24430 children will be reported. Otherwise, children starting at @var{from}
24431 (zero-based) and up to and excluding @var{to} will be reported.
24433 @subsubheading Example
24437 -var-set-update-range V 1 2
24441 @subheading The @code{-var-set-visualizer} command
24442 @findex -var-set-visualizer
24443 @anchor{-var-set-visualizer}
24445 @subsubheading Synopsis
24448 -var-set-visualizer @var{name} @var{visualizer}
24451 Set a visualizer for the variable object @var{name}.
24453 @var{visualizer} is the visualizer to use. The special value
24454 @samp{None} means to disable any visualizer in use.
24456 If not @samp{None}, @var{visualizer} must be a Python expression.
24457 This expression must evaluate to a callable object which accepts a
24458 single argument. @value{GDBN} will call this object with the value of
24459 the varobj @var{name} as an argument (this is done so that the same
24460 Python pretty-printing code can be used for both the CLI and MI).
24461 When called, this object must return an object which conforms to the
24462 pretty-printing interface (@pxref{Pretty Printing}).
24464 The pre-defined function @code{gdb.default_visualizer} may be used to
24465 select a visualizer by following the built-in process
24466 (@pxref{Selecting Pretty-Printers}). This is done automatically when
24467 a varobj is created, and so ordinarily is not needed.
24469 This feature is only available if Python support is enabled. The MI
24470 command @code{-list-features} (@pxref{GDB/MI Miscellaneous Commands})
24471 can be used to check this.
24473 @subsubheading Example
24475 Resetting the visualizer:
24479 -var-set-visualizer V None
24483 Reselecting the default (type-based) visualizer:
24487 -var-set-visualizer V gdb.default_visualizer
24491 Suppose @code{SomeClass} is a visualizer class. A lambda expression
24492 can be used to instantiate this class for a varobj:
24496 -var-set-visualizer V "lambda val: SomeClass()"
24500 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
24501 @node GDB/MI Data Manipulation
24502 @section @sc{gdb/mi} Data Manipulation
24504 @cindex data manipulation, in @sc{gdb/mi}
24505 @cindex @sc{gdb/mi}, data manipulation
24506 This section describes the @sc{gdb/mi} commands that manipulate data:
24507 examine memory and registers, evaluate expressions, etc.
24509 @c REMOVED FROM THE INTERFACE.
24510 @c @subheading -data-assign
24511 @c Change the value of a program variable. Plenty of side effects.
24512 @c @subsubheading GDB Command
24514 @c @subsubheading Example
24517 @subheading The @code{-data-disassemble} Command
24518 @findex -data-disassemble
24520 @subsubheading Synopsis
24524 [ -s @var{start-addr} -e @var{end-addr} ]
24525 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
24533 @item @var{start-addr}
24534 is the beginning address (or @code{$pc})
24535 @item @var{end-addr}
24537 @item @var{filename}
24538 is the name of the file to disassemble
24539 @item @var{linenum}
24540 is the line number to disassemble around
24542 is the number of disassembly lines to be produced. If it is -1,
24543 the whole function will be disassembled, in case no @var{end-addr} is
24544 specified. If @var{end-addr} is specified as a non-zero value, and
24545 @var{lines} is lower than the number of disassembly lines between
24546 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
24547 displayed; if @var{lines} is higher than the number of lines between
24548 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
24551 is either 0 (meaning only disassembly) or 1 (meaning mixed source and
24555 @subsubheading Result
24557 The output for each instruction is composed of four fields:
24566 Note that whatever included in the instruction field, is not manipulated
24567 directly by @sc{gdb/mi}, i.e., it is not possible to adjust its format.
24569 @subsubheading @value{GDBN} Command
24571 There's no direct mapping from this command to the CLI.
24573 @subsubheading Example
24575 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
24579 -data-disassemble -s $pc -e "$pc + 20" -- 0
24582 @{address="0x000107c0",func-name="main",offset="4",
24583 inst="mov 2, %o0"@},
24584 @{address="0x000107c4",func-name="main",offset="8",
24585 inst="sethi %hi(0x11800), %o2"@},
24586 @{address="0x000107c8",func-name="main",offset="12",
24587 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
24588 @{address="0x000107cc",func-name="main",offset="16",
24589 inst="sethi %hi(0x11800), %o2"@},
24590 @{address="0x000107d0",func-name="main",offset="20",
24591 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
24595 Disassemble the whole @code{main} function. Line 32 is part of
24599 -data-disassemble -f basics.c -l 32 -- 0
24601 @{address="0x000107bc",func-name="main",offset="0",
24602 inst="save %sp, -112, %sp"@},
24603 @{address="0x000107c0",func-name="main",offset="4",
24604 inst="mov 2, %o0"@},
24605 @{address="0x000107c4",func-name="main",offset="8",
24606 inst="sethi %hi(0x11800), %o2"@},
24608 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
24609 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
24613 Disassemble 3 instructions from the start of @code{main}:
24617 -data-disassemble -f basics.c -l 32 -n 3 -- 0
24619 @{address="0x000107bc",func-name="main",offset="0",
24620 inst="save %sp, -112, %sp"@},
24621 @{address="0x000107c0",func-name="main",offset="4",
24622 inst="mov 2, %o0"@},
24623 @{address="0x000107c4",func-name="main",offset="8",
24624 inst="sethi %hi(0x11800), %o2"@}]
24628 Disassemble 3 instructions from the start of @code{main} in mixed mode:
24632 -data-disassemble -f basics.c -l 32 -n 3 -- 1
24634 src_and_asm_line=@{line="31",
24635 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
24636 testsuite/gdb.mi/basics.c",line_asm_insn=[
24637 @{address="0x000107bc",func-name="main",offset="0",
24638 inst="save %sp, -112, %sp"@}]@},
24639 src_and_asm_line=@{line="32",
24640 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
24641 testsuite/gdb.mi/basics.c",line_asm_insn=[
24642 @{address="0x000107c0",func-name="main",offset="4",
24643 inst="mov 2, %o0"@},
24644 @{address="0x000107c4",func-name="main",offset="8",
24645 inst="sethi %hi(0x11800), %o2"@}]@}]
24650 @subheading The @code{-data-evaluate-expression} Command
24651 @findex -data-evaluate-expression
24653 @subsubheading Synopsis
24656 -data-evaluate-expression @var{expr}
24659 Evaluate @var{expr} as an expression. The expression could contain an
24660 inferior function call. The function call will execute synchronously.
24661 If the expression contains spaces, it must be enclosed in double quotes.
24663 @subsubheading @value{GDBN} Command
24665 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
24666 @samp{call}. In @code{gdbtk} only, there's a corresponding
24667 @samp{gdb_eval} command.
24669 @subsubheading Example
24671 In the following example, the numbers that precede the commands are the
24672 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
24673 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
24677 211-data-evaluate-expression A
24680 311-data-evaluate-expression &A
24681 311^done,value="0xefffeb7c"
24683 411-data-evaluate-expression A+3
24686 511-data-evaluate-expression "A + 3"
24692 @subheading The @code{-data-list-changed-registers} Command
24693 @findex -data-list-changed-registers
24695 @subsubheading Synopsis
24698 -data-list-changed-registers
24701 Display a list of the registers that have changed.
24703 @subsubheading @value{GDBN} Command
24705 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
24706 has the corresponding command @samp{gdb_changed_register_list}.
24708 @subsubheading Example
24710 On a PPC MBX board:
24718 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",frame=@{
24719 func="main",args=[],file="try.c",fullname="/home/foo/bar/try.c",
24722 -data-list-changed-registers
24723 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
24724 "10","11","13","14","15","16","17","18","19","20","21","22","23",
24725 "24","25","26","27","28","30","31","64","65","66","67","69"]
24730 @subheading The @code{-data-list-register-names} Command
24731 @findex -data-list-register-names
24733 @subsubheading Synopsis
24736 -data-list-register-names [ ( @var{regno} )+ ]
24739 Show a list of register names for the current target. If no arguments
24740 are given, it shows a list of the names of all the registers. If
24741 integer numbers are given as arguments, it will print a list of the
24742 names of the registers corresponding to the arguments. To ensure
24743 consistency between a register name and its number, the output list may
24744 include empty register names.
24746 @subsubheading @value{GDBN} Command
24748 @value{GDBN} does not have a command which corresponds to
24749 @samp{-data-list-register-names}. In @code{gdbtk} there is a
24750 corresponding command @samp{gdb_regnames}.
24752 @subsubheading Example
24754 For the PPC MBX board:
24757 -data-list-register-names
24758 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
24759 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
24760 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
24761 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
24762 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
24763 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
24764 "", "pc","ps","cr","lr","ctr","xer"]
24766 -data-list-register-names 1 2 3
24767 ^done,register-names=["r1","r2","r3"]
24771 @subheading The @code{-data-list-register-values} Command
24772 @findex -data-list-register-values
24774 @subsubheading Synopsis
24777 -data-list-register-values @var{fmt} [ ( @var{regno} )*]
24780 Display the registers' contents. @var{fmt} is the format according to
24781 which the registers' contents are to be returned, followed by an optional
24782 list of numbers specifying the registers to display. A missing list of
24783 numbers indicates that the contents of all the registers must be returned.
24785 Allowed formats for @var{fmt} are:
24802 @subsubheading @value{GDBN} Command
24804 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
24805 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
24807 @subsubheading Example
24809 For a PPC MBX board (note: line breaks are for readability only, they
24810 don't appear in the actual output):
24814 -data-list-register-values r 64 65
24815 ^done,register-values=[@{number="64",value="0xfe00a300"@},
24816 @{number="65",value="0x00029002"@}]
24818 -data-list-register-values x
24819 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
24820 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
24821 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
24822 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
24823 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
24824 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
24825 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
24826 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
24827 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
24828 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
24829 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
24830 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
24831 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
24832 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
24833 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
24834 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
24835 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
24836 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
24837 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
24838 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
24839 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
24840 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
24841 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
24842 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
24843 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
24844 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
24845 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
24846 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
24847 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
24848 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
24849 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
24850 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
24851 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
24852 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
24853 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
24854 @{number="69",value="0x20002b03"@}]
24859 @subheading The @code{-data-read-memory} Command
24860 @findex -data-read-memory
24862 @subsubheading Synopsis
24865 -data-read-memory [ -o @var{byte-offset} ]
24866 @var{address} @var{word-format} @var{word-size}
24867 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
24874 @item @var{address}
24875 An expression specifying the address of the first memory word to be
24876 read. Complex expressions containing embedded white space should be
24877 quoted using the C convention.
24879 @item @var{word-format}
24880 The format to be used to print the memory words. The notation is the
24881 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
24884 @item @var{word-size}
24885 The size of each memory word in bytes.
24887 @item @var{nr-rows}
24888 The number of rows in the output table.
24890 @item @var{nr-cols}
24891 The number of columns in the output table.
24894 If present, indicates that each row should include an @sc{ascii} dump. The
24895 value of @var{aschar} is used as a padding character when a byte is not a
24896 member of the printable @sc{ascii} character set (printable @sc{ascii}
24897 characters are those whose code is between 32 and 126, inclusively).
24899 @item @var{byte-offset}
24900 An offset to add to the @var{address} before fetching memory.
24903 This command displays memory contents as a table of @var{nr-rows} by
24904 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
24905 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
24906 (returned as @samp{total-bytes}). Should less than the requested number
24907 of bytes be returned by the target, the missing words are identified
24908 using @samp{N/A}. The number of bytes read from the target is returned
24909 in @samp{nr-bytes} and the starting address used to read memory in
24912 The address of the next/previous row or page is available in
24913 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
24916 @subsubheading @value{GDBN} Command
24918 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
24919 @samp{gdb_get_mem} memory read command.
24921 @subsubheading Example
24923 Read six bytes of memory starting at @code{bytes+6} but then offset by
24924 @code{-6} bytes. Format as three rows of two columns. One byte per
24925 word. Display each word in hex.
24929 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
24930 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
24931 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
24932 prev-page="0x0000138a",memory=[
24933 @{addr="0x00001390",data=["0x00","0x01"]@},
24934 @{addr="0x00001392",data=["0x02","0x03"]@},
24935 @{addr="0x00001394",data=["0x04","0x05"]@}]
24939 Read two bytes of memory starting at address @code{shorts + 64} and
24940 display as a single word formatted in decimal.
24944 5-data-read-memory shorts+64 d 2 1 1
24945 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
24946 next-row="0x00001512",prev-row="0x0000150e",
24947 next-page="0x00001512",prev-page="0x0000150e",memory=[
24948 @{addr="0x00001510",data=["128"]@}]
24952 Read thirty two bytes of memory starting at @code{bytes+16} and format
24953 as eight rows of four columns. Include a string encoding with @samp{x}
24954 used as the non-printable character.
24958 4-data-read-memory bytes+16 x 1 8 4 x
24959 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
24960 next-row="0x000013c0",prev-row="0x0000139c",
24961 next-page="0x000013c0",prev-page="0x00001380",memory=[
24962 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
24963 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
24964 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
24965 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
24966 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
24967 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
24968 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
24969 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
24973 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
24974 @node GDB/MI Tracepoint Commands
24975 @section @sc{gdb/mi} Tracepoint Commands
24977 The tracepoint commands are not yet implemented.
24979 @c @subheading -trace-actions
24981 @c @subheading -trace-delete
24983 @c @subheading -trace-disable
24985 @c @subheading -trace-dump
24987 @c @subheading -trace-enable
24989 @c @subheading -trace-exists
24991 @c @subheading -trace-find
24993 @c @subheading -trace-frame-number
24995 @c @subheading -trace-info
24997 @c @subheading -trace-insert
24999 @c @subheading -trace-list
25001 @c @subheading -trace-pass-count
25003 @c @subheading -trace-save
25005 @c @subheading -trace-start
25007 @c @subheading -trace-stop
25010 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25011 @node GDB/MI Symbol Query
25012 @section @sc{gdb/mi} Symbol Query Commands
25016 @subheading The @code{-symbol-info-address} Command
25017 @findex -symbol-info-address
25019 @subsubheading Synopsis
25022 -symbol-info-address @var{symbol}
25025 Describe where @var{symbol} is stored.
25027 @subsubheading @value{GDBN} Command
25029 The corresponding @value{GDBN} command is @samp{info address}.
25031 @subsubheading Example
25035 @subheading The @code{-symbol-info-file} Command
25036 @findex -symbol-info-file
25038 @subsubheading Synopsis
25044 Show the file for the symbol.
25046 @subsubheading @value{GDBN} Command
25048 There's no equivalent @value{GDBN} command. @code{gdbtk} has
25049 @samp{gdb_find_file}.
25051 @subsubheading Example
25055 @subheading The @code{-symbol-info-function} Command
25056 @findex -symbol-info-function
25058 @subsubheading Synopsis
25061 -symbol-info-function
25064 Show which function the symbol lives in.
25066 @subsubheading @value{GDBN} Command
25068 @samp{gdb_get_function} in @code{gdbtk}.
25070 @subsubheading Example
25074 @subheading The @code{-symbol-info-line} Command
25075 @findex -symbol-info-line
25077 @subsubheading Synopsis
25083 Show the core addresses of the code for a source line.
25085 @subsubheading @value{GDBN} Command
25087 The corresponding @value{GDBN} command is @samp{info line}.
25088 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
25090 @subsubheading Example
25094 @subheading The @code{-symbol-info-symbol} Command
25095 @findex -symbol-info-symbol
25097 @subsubheading Synopsis
25100 -symbol-info-symbol @var{addr}
25103 Describe what symbol is at location @var{addr}.
25105 @subsubheading @value{GDBN} Command
25107 The corresponding @value{GDBN} command is @samp{info symbol}.
25109 @subsubheading Example
25113 @subheading The @code{-symbol-list-functions} Command
25114 @findex -symbol-list-functions
25116 @subsubheading Synopsis
25119 -symbol-list-functions
25122 List the functions in the executable.
25124 @subsubheading @value{GDBN} Command
25126 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
25127 @samp{gdb_search} in @code{gdbtk}.
25129 @subsubheading Example
25134 @subheading The @code{-symbol-list-lines} Command
25135 @findex -symbol-list-lines
25137 @subsubheading Synopsis
25140 -symbol-list-lines @var{filename}
25143 Print the list of lines that contain code and their associated program
25144 addresses for the given source filename. The entries are sorted in
25145 ascending PC order.
25147 @subsubheading @value{GDBN} Command
25149 There is no corresponding @value{GDBN} command.
25151 @subsubheading Example
25154 -symbol-list-lines basics.c
25155 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
25161 @subheading The @code{-symbol-list-types} Command
25162 @findex -symbol-list-types
25164 @subsubheading Synopsis
25170 List all the type names.
25172 @subsubheading @value{GDBN} Command
25174 The corresponding commands are @samp{info types} in @value{GDBN},
25175 @samp{gdb_search} in @code{gdbtk}.
25177 @subsubheading Example
25181 @subheading The @code{-symbol-list-variables} Command
25182 @findex -symbol-list-variables
25184 @subsubheading Synopsis
25187 -symbol-list-variables
25190 List all the global and static variable names.
25192 @subsubheading @value{GDBN} Command
25194 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
25196 @subsubheading Example
25200 @subheading The @code{-symbol-locate} Command
25201 @findex -symbol-locate
25203 @subsubheading Synopsis
25209 @subsubheading @value{GDBN} Command
25211 @samp{gdb_loc} in @code{gdbtk}.
25213 @subsubheading Example
25217 @subheading The @code{-symbol-type} Command
25218 @findex -symbol-type
25220 @subsubheading Synopsis
25223 -symbol-type @var{variable}
25226 Show type of @var{variable}.
25228 @subsubheading @value{GDBN} Command
25230 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
25231 @samp{gdb_obj_variable}.
25233 @subsubheading Example
25238 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25239 @node GDB/MI File Commands
25240 @section @sc{gdb/mi} File Commands
25242 This section describes the GDB/MI commands to specify executable file names
25243 and to read in and obtain symbol table information.
25245 @subheading The @code{-file-exec-and-symbols} Command
25246 @findex -file-exec-and-symbols
25248 @subsubheading Synopsis
25251 -file-exec-and-symbols @var{file}
25254 Specify the executable file to be debugged. This file is the one from
25255 which the symbol table is also read. If no file is specified, the
25256 command clears the executable and symbol information. If breakpoints
25257 are set when using this command with no arguments, @value{GDBN} will produce
25258 error messages. Otherwise, no output is produced, except a completion
25261 @subsubheading @value{GDBN} Command
25263 The corresponding @value{GDBN} command is @samp{file}.
25265 @subsubheading Example
25269 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
25275 @subheading The @code{-file-exec-file} Command
25276 @findex -file-exec-file
25278 @subsubheading Synopsis
25281 -file-exec-file @var{file}
25284 Specify the executable file to be debugged. Unlike
25285 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
25286 from this file. If used without argument, @value{GDBN} clears the information
25287 about the executable file. No output is produced, except a completion
25290 @subsubheading @value{GDBN} Command
25292 The corresponding @value{GDBN} command is @samp{exec-file}.
25294 @subsubheading Example
25298 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
25305 @subheading The @code{-file-list-exec-sections} Command
25306 @findex -file-list-exec-sections
25308 @subsubheading Synopsis
25311 -file-list-exec-sections
25314 List the sections of the current executable file.
25316 @subsubheading @value{GDBN} Command
25318 The @value{GDBN} command @samp{info file} shows, among the rest, the same
25319 information as this command. @code{gdbtk} has a corresponding command
25320 @samp{gdb_load_info}.
25322 @subsubheading Example
25327 @subheading The @code{-file-list-exec-source-file} Command
25328 @findex -file-list-exec-source-file
25330 @subsubheading Synopsis
25333 -file-list-exec-source-file
25336 List the line number, the current source file, and the absolute path
25337 to the current source file for the current executable. The macro
25338 information field has a value of @samp{1} or @samp{0} depending on
25339 whether or not the file includes preprocessor macro information.
25341 @subsubheading @value{GDBN} Command
25343 The @value{GDBN} equivalent is @samp{info source}
25345 @subsubheading Example
25349 123-file-list-exec-source-file
25350 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c,macro-info="1"
25355 @subheading The @code{-file-list-exec-source-files} Command
25356 @findex -file-list-exec-source-files
25358 @subsubheading Synopsis
25361 -file-list-exec-source-files
25364 List the source files for the current executable.
25366 It will always output the filename, but only when @value{GDBN} can find
25367 the absolute file name of a source file, will it output the fullname.
25369 @subsubheading @value{GDBN} Command
25371 The @value{GDBN} equivalent is @samp{info sources}.
25372 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
25374 @subsubheading Example
25377 -file-list-exec-source-files
25379 @{file=foo.c,fullname=/home/foo.c@},
25380 @{file=/home/bar.c,fullname=/home/bar.c@},
25381 @{file=gdb_could_not_find_fullpath.c@}]
25386 @subheading The @code{-file-list-shared-libraries} Command
25387 @findex -file-list-shared-libraries
25389 @subsubheading Synopsis
25392 -file-list-shared-libraries
25395 List the shared libraries in the program.
25397 @subsubheading @value{GDBN} Command
25399 The corresponding @value{GDBN} command is @samp{info shared}.
25401 @subsubheading Example
25405 @subheading The @code{-file-list-symbol-files} Command
25406 @findex -file-list-symbol-files
25408 @subsubheading Synopsis
25411 -file-list-symbol-files
25416 @subsubheading @value{GDBN} Command
25418 The corresponding @value{GDBN} command is @samp{info file} (part of it).
25420 @subsubheading Example
25425 @subheading The @code{-file-symbol-file} Command
25426 @findex -file-symbol-file
25428 @subsubheading Synopsis
25431 -file-symbol-file @var{file}
25434 Read symbol table info from the specified @var{file} argument. When
25435 used without arguments, clears @value{GDBN}'s symbol table info. No output is
25436 produced, except for a completion notification.
25438 @subsubheading @value{GDBN} Command
25440 The corresponding @value{GDBN} command is @samp{symbol-file}.
25442 @subsubheading Example
25446 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
25452 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25453 @node GDB/MI Memory Overlay Commands
25454 @section @sc{gdb/mi} Memory Overlay Commands
25456 The memory overlay commands are not implemented.
25458 @c @subheading -overlay-auto
25460 @c @subheading -overlay-list-mapping-state
25462 @c @subheading -overlay-list-overlays
25464 @c @subheading -overlay-map
25466 @c @subheading -overlay-off
25468 @c @subheading -overlay-on
25470 @c @subheading -overlay-unmap
25472 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25473 @node GDB/MI Signal Handling Commands
25474 @section @sc{gdb/mi} Signal Handling Commands
25476 Signal handling commands are not implemented.
25478 @c @subheading -signal-handle
25480 @c @subheading -signal-list-handle-actions
25482 @c @subheading -signal-list-signal-types
25486 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25487 @node GDB/MI Target Manipulation
25488 @section @sc{gdb/mi} Target Manipulation Commands
25491 @subheading The @code{-target-attach} Command
25492 @findex -target-attach
25494 @subsubheading Synopsis
25497 -target-attach @var{pid} | @var{gid} | @var{file}
25500 Attach to a process @var{pid} or a file @var{file} outside of
25501 @value{GDBN}, or a thread group @var{gid}. If attaching to a thread
25502 group, the id previously returned by
25503 @samp{-list-thread-groups --available} must be used.
25505 @subsubheading @value{GDBN} Command
25507 The corresponding @value{GDBN} command is @samp{attach}.
25509 @subsubheading Example
25513 =thread-created,id="1"
25514 *stopped,thread-id="1",frame=@{addr="0xb7f7e410",func="bar",args=[]@}
25520 @subheading The @code{-target-compare-sections} Command
25521 @findex -target-compare-sections
25523 @subsubheading Synopsis
25526 -target-compare-sections [ @var{section} ]
25529 Compare data of section @var{section} on target to the exec file.
25530 Without the argument, all sections are compared.
25532 @subsubheading @value{GDBN} Command
25534 The @value{GDBN} equivalent is @samp{compare-sections}.
25536 @subsubheading Example
25541 @subheading The @code{-target-detach} Command
25542 @findex -target-detach
25544 @subsubheading Synopsis
25547 -target-detach [ @var{pid} | @var{gid} ]
25550 Detach from the remote target which normally resumes its execution.
25551 If either @var{pid} or @var{gid} is specified, detaches from either
25552 the specified process, or specified thread group. There's no output.
25554 @subsubheading @value{GDBN} Command
25556 The corresponding @value{GDBN} command is @samp{detach}.
25558 @subsubheading Example
25568 @subheading The @code{-target-disconnect} Command
25569 @findex -target-disconnect
25571 @subsubheading Synopsis
25577 Disconnect from the remote target. There's no output and the target is
25578 generally not resumed.
25580 @subsubheading @value{GDBN} Command
25582 The corresponding @value{GDBN} command is @samp{disconnect}.
25584 @subsubheading Example
25594 @subheading The @code{-target-download} Command
25595 @findex -target-download
25597 @subsubheading Synopsis
25603 Loads the executable onto the remote target.
25604 It prints out an update message every half second, which includes the fields:
25608 The name of the section.
25610 The size of what has been sent so far for that section.
25612 The size of the section.
25614 The total size of what was sent so far (the current and the previous sections).
25616 The size of the overall executable to download.
25620 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
25621 @sc{gdb/mi} Output Syntax}).
25623 In addition, it prints the name and size of the sections, as they are
25624 downloaded. These messages include the following fields:
25628 The name of the section.
25630 The size of the section.
25632 The size of the overall executable to download.
25636 At the end, a summary is printed.
25638 @subsubheading @value{GDBN} Command
25640 The corresponding @value{GDBN} command is @samp{load}.
25642 @subsubheading Example
25644 Note: each status message appears on a single line. Here the messages
25645 have been broken down so that they can fit onto a page.
25650 +download,@{section=".text",section-size="6668",total-size="9880"@}
25651 +download,@{section=".text",section-sent="512",section-size="6668",
25652 total-sent="512",total-size="9880"@}
25653 +download,@{section=".text",section-sent="1024",section-size="6668",
25654 total-sent="1024",total-size="9880"@}
25655 +download,@{section=".text",section-sent="1536",section-size="6668",
25656 total-sent="1536",total-size="9880"@}
25657 +download,@{section=".text",section-sent="2048",section-size="6668",
25658 total-sent="2048",total-size="9880"@}
25659 +download,@{section=".text",section-sent="2560",section-size="6668",
25660 total-sent="2560",total-size="9880"@}
25661 +download,@{section=".text",section-sent="3072",section-size="6668",
25662 total-sent="3072",total-size="9880"@}
25663 +download,@{section=".text",section-sent="3584",section-size="6668",
25664 total-sent="3584",total-size="9880"@}
25665 +download,@{section=".text",section-sent="4096",section-size="6668",
25666 total-sent="4096",total-size="9880"@}
25667 +download,@{section=".text",section-sent="4608",section-size="6668",
25668 total-sent="4608",total-size="9880"@}
25669 +download,@{section=".text",section-sent="5120",section-size="6668",
25670 total-sent="5120",total-size="9880"@}
25671 +download,@{section=".text",section-sent="5632",section-size="6668",
25672 total-sent="5632",total-size="9880"@}
25673 +download,@{section=".text",section-sent="6144",section-size="6668",
25674 total-sent="6144",total-size="9880"@}
25675 +download,@{section=".text",section-sent="6656",section-size="6668",
25676 total-sent="6656",total-size="9880"@}
25677 +download,@{section=".init",section-size="28",total-size="9880"@}
25678 +download,@{section=".fini",section-size="28",total-size="9880"@}
25679 +download,@{section=".data",section-size="3156",total-size="9880"@}
25680 +download,@{section=".data",section-sent="512",section-size="3156",
25681 total-sent="7236",total-size="9880"@}
25682 +download,@{section=".data",section-sent="1024",section-size="3156",
25683 total-sent="7748",total-size="9880"@}
25684 +download,@{section=".data",section-sent="1536",section-size="3156",
25685 total-sent="8260",total-size="9880"@}
25686 +download,@{section=".data",section-sent="2048",section-size="3156",
25687 total-sent="8772",total-size="9880"@}
25688 +download,@{section=".data",section-sent="2560",section-size="3156",
25689 total-sent="9284",total-size="9880"@}
25690 +download,@{section=".data",section-sent="3072",section-size="3156",
25691 total-sent="9796",total-size="9880"@}
25692 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
25699 @subheading The @code{-target-exec-status} Command
25700 @findex -target-exec-status
25702 @subsubheading Synopsis
25705 -target-exec-status
25708 Provide information on the state of the target (whether it is running or
25709 not, for instance).
25711 @subsubheading @value{GDBN} Command
25713 There's no equivalent @value{GDBN} command.
25715 @subsubheading Example
25719 @subheading The @code{-target-list-available-targets} Command
25720 @findex -target-list-available-targets
25722 @subsubheading Synopsis
25725 -target-list-available-targets
25728 List the possible targets to connect to.
25730 @subsubheading @value{GDBN} Command
25732 The corresponding @value{GDBN} command is @samp{help target}.
25734 @subsubheading Example
25738 @subheading The @code{-target-list-current-targets} Command
25739 @findex -target-list-current-targets
25741 @subsubheading Synopsis
25744 -target-list-current-targets
25747 Describe the current target.
25749 @subsubheading @value{GDBN} Command
25751 The corresponding information is printed by @samp{info file} (among
25754 @subsubheading Example
25758 @subheading The @code{-target-list-parameters} Command
25759 @findex -target-list-parameters
25761 @subsubheading Synopsis
25764 -target-list-parameters
25770 @subsubheading @value{GDBN} Command
25774 @subsubheading Example
25778 @subheading The @code{-target-select} Command
25779 @findex -target-select
25781 @subsubheading Synopsis
25784 -target-select @var{type} @var{parameters @dots{}}
25787 Connect @value{GDBN} to the remote target. This command takes two args:
25791 The type of target, for instance @samp{remote}, etc.
25792 @item @var{parameters}
25793 Device names, host names and the like. @xref{Target Commands, ,
25794 Commands for Managing Targets}, for more details.
25797 The output is a connection notification, followed by the address at
25798 which the target program is, in the following form:
25801 ^connected,addr="@var{address}",func="@var{function name}",
25802 args=[@var{arg list}]
25805 @subsubheading @value{GDBN} Command
25807 The corresponding @value{GDBN} command is @samp{target}.
25809 @subsubheading Example
25813 -target-select remote /dev/ttya
25814 ^connected,addr="0xfe00a300",func="??",args=[]
25818 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25819 @node GDB/MI File Transfer Commands
25820 @section @sc{gdb/mi} File Transfer Commands
25823 @subheading The @code{-target-file-put} Command
25824 @findex -target-file-put
25826 @subsubheading Synopsis
25829 -target-file-put @var{hostfile} @var{targetfile}
25832 Copy file @var{hostfile} from the host system (the machine running
25833 @value{GDBN}) to @var{targetfile} on the target system.
25835 @subsubheading @value{GDBN} Command
25837 The corresponding @value{GDBN} command is @samp{remote put}.
25839 @subsubheading Example
25843 -target-file-put localfile remotefile
25849 @subheading The @code{-target-file-get} Command
25850 @findex -target-file-get
25852 @subsubheading Synopsis
25855 -target-file-get @var{targetfile} @var{hostfile}
25858 Copy file @var{targetfile} from the target system to @var{hostfile}
25859 on the host system.
25861 @subsubheading @value{GDBN} Command
25863 The corresponding @value{GDBN} command is @samp{remote get}.
25865 @subsubheading Example
25869 -target-file-get remotefile localfile
25875 @subheading The @code{-target-file-delete} Command
25876 @findex -target-file-delete
25878 @subsubheading Synopsis
25881 -target-file-delete @var{targetfile}
25884 Delete @var{targetfile} from the target system.
25886 @subsubheading @value{GDBN} Command
25888 The corresponding @value{GDBN} command is @samp{remote delete}.
25890 @subsubheading Example
25894 -target-file-delete remotefile
25900 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25901 @node GDB/MI Miscellaneous Commands
25902 @section Miscellaneous @sc{gdb/mi} Commands
25904 @c @subheading -gdb-complete
25906 @subheading The @code{-gdb-exit} Command
25909 @subsubheading Synopsis
25915 Exit @value{GDBN} immediately.
25917 @subsubheading @value{GDBN} Command
25919 Approximately corresponds to @samp{quit}.
25921 @subsubheading Example
25931 @subheading The @code{-exec-abort} Command
25932 @findex -exec-abort
25934 @subsubheading Synopsis
25940 Kill the inferior running program.
25942 @subsubheading @value{GDBN} Command
25944 The corresponding @value{GDBN} command is @samp{kill}.
25946 @subsubheading Example
25951 @subheading The @code{-gdb-set} Command
25954 @subsubheading Synopsis
25960 Set an internal @value{GDBN} variable.
25961 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
25963 @subsubheading @value{GDBN} Command
25965 The corresponding @value{GDBN} command is @samp{set}.
25967 @subsubheading Example
25977 @subheading The @code{-gdb-show} Command
25980 @subsubheading Synopsis
25986 Show the current value of a @value{GDBN} variable.
25988 @subsubheading @value{GDBN} Command
25990 The corresponding @value{GDBN} command is @samp{show}.
25992 @subsubheading Example
26001 @c @subheading -gdb-source
26004 @subheading The @code{-gdb-version} Command
26005 @findex -gdb-version
26007 @subsubheading Synopsis
26013 Show version information for @value{GDBN}. Used mostly in testing.
26015 @subsubheading @value{GDBN} Command
26017 The @value{GDBN} equivalent is @samp{show version}. @value{GDBN} by
26018 default shows this information when you start an interactive session.
26020 @subsubheading Example
26022 @c This example modifies the actual output from GDB to avoid overfull
26028 ~Copyright 2000 Free Software Foundation, Inc.
26029 ~GDB is free software, covered by the GNU General Public License, and
26030 ~you are welcome to change it and/or distribute copies of it under
26031 ~ certain conditions.
26032 ~Type "show copying" to see the conditions.
26033 ~There is absolutely no warranty for GDB. Type "show warranty" for
26035 ~This GDB was configured as
26036 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
26041 @subheading The @code{-list-features} Command
26042 @findex -list-features
26044 Returns a list of particular features of the MI protocol that
26045 this version of gdb implements. A feature can be a command,
26046 or a new field in an output of some command, or even an
26047 important bugfix. While a frontend can sometimes detect presence
26048 of a feature at runtime, it is easier to perform detection at debugger
26051 The command returns a list of strings, with each string naming an
26052 available feature. Each returned string is just a name, it does not
26053 have any internal structure. The list of possible feature names
26059 (gdb) -list-features
26060 ^done,result=["feature1","feature2"]
26063 The current list of features is:
26066 @item frozen-varobjs
26067 Indicates presence of the @code{-var-set-frozen} command, as well
26068 as possible presense of the @code{frozen} field in the output
26069 of @code{-varobj-create}.
26070 @item pending-breakpoints
26071 Indicates presence of the @option{-f} option to the @code{-break-insert} command.
26073 Indicates presence of Python scripting support, Python-based
26074 pretty-printing commands, and possible presence of the
26075 @samp{display_hint} field in the output of @code{-var-list-children}
26077 Indicates presence of the @code{-thread-info} command.
26081 @subheading The @code{-list-target-features} Command
26082 @findex -list-target-features
26084 Returns a list of particular features that are supported by the
26085 target. Those features affect the permitted MI commands, but
26086 unlike the features reported by the @code{-list-features} command, the
26087 features depend on which target GDB is using at the moment. Whenever
26088 a target can change, due to commands such as @code{-target-select},
26089 @code{-target-attach} or @code{-exec-run}, the list of target features
26090 may change, and the frontend should obtain it again.
26094 (gdb) -list-features
26095 ^done,result=["async"]
26098 The current list of features is:
26102 Indicates that the target is capable of asynchronous command
26103 execution, which means that @value{GDBN} will accept further commands
26104 while the target is running.
26108 @subheading The @code{-list-thread-groups} Command
26109 @findex -list-thread-groups
26111 @subheading Synopsis
26114 -list-thread-groups [ --available ] [ @var{group} ]
26117 When used without the @var{group} parameter, lists top-level thread
26118 groups that are being debugged. When used with the @var{group}
26119 parameter, the children of the specified group are listed. The
26120 children can be either threads, or other groups. At present,
26121 @value{GDBN} will not report both threads and groups as children at
26122 the same time, but it may change in future.
26124 With the @samp{--available} option, instead of reporting groups that
26125 are been debugged, GDB will report all thread groups available on the
26126 target. Using the @samp{--available} option together with @var{group}
26129 @subheading Example
26133 -list-thread-groups
26134 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2"@}]
26135 -list-thread-groups 17
26136 ^done,threads=[@{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
26137 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},state="running"@},
26138 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
26139 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
26140 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},state="running"@}]]
26143 @subheading The @code{-interpreter-exec} Command
26144 @findex -interpreter-exec
26146 @subheading Synopsis
26149 -interpreter-exec @var{interpreter} @var{command}
26151 @anchor{-interpreter-exec}
26153 Execute the specified @var{command} in the given @var{interpreter}.
26155 @subheading @value{GDBN} Command
26157 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
26159 @subheading Example
26163 -interpreter-exec console "break main"
26164 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
26165 &"During symbol reading, bad structure-type format.\n"
26166 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
26171 @subheading The @code{-inferior-tty-set} Command
26172 @findex -inferior-tty-set
26174 @subheading Synopsis
26177 -inferior-tty-set /dev/pts/1
26180 Set terminal for future runs of the program being debugged.
26182 @subheading @value{GDBN} Command
26184 The corresponding @value{GDBN} command is @samp{set inferior-tty} /dev/pts/1.
26186 @subheading Example
26190 -inferior-tty-set /dev/pts/1
26195 @subheading The @code{-inferior-tty-show} Command
26196 @findex -inferior-tty-show
26198 @subheading Synopsis
26204 Show terminal for future runs of program being debugged.
26206 @subheading @value{GDBN} Command
26208 The corresponding @value{GDBN} command is @samp{show inferior-tty}.
26210 @subheading Example
26214 -inferior-tty-set /dev/pts/1
26218 ^done,inferior_tty_terminal="/dev/pts/1"
26222 @subheading The @code{-enable-timings} Command
26223 @findex -enable-timings
26225 @subheading Synopsis
26228 -enable-timings [yes | no]
26231 Toggle the printing of the wallclock, user and system times for an MI
26232 command as a field in its output. This command is to help frontend
26233 developers optimize the performance of their code. No argument is
26234 equivalent to @samp{yes}.
26236 @subheading @value{GDBN} Command
26240 @subheading Example
26248 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26249 addr="0x080484ed",func="main",file="myprog.c",
26250 fullname="/home/nickrob/myprog.c",line="73",times="0"@},
26251 time=@{wallclock="0.05185",user="0.00800",system="0.00000"@}
26259 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
26260 frame=@{addr="0x080484ed",func="main",args=[@{name="argc",value="1"@},
26261 @{name="argv",value="0xbfb60364"@}],file="myprog.c",
26262 fullname="/home/nickrob/myprog.c",line="73"@}
26267 @chapter @value{GDBN} Annotations
26269 This chapter describes annotations in @value{GDBN}. Annotations were
26270 designed to interface @value{GDBN} to graphical user interfaces or other
26271 similar programs which want to interact with @value{GDBN} at a
26272 relatively high level.
26274 The annotation mechanism has largely been superseded by @sc{gdb/mi}
26278 This is Edition @value{EDITION}, @value{DATE}.
26282 * Annotations Overview:: What annotations are; the general syntax.
26283 * Server Prefix:: Issuing a command without affecting user state.
26284 * Prompting:: Annotations marking @value{GDBN}'s need for input.
26285 * Errors:: Annotations for error messages.
26286 * Invalidation:: Some annotations describe things now invalid.
26287 * Annotations for Running::
26288 Whether the program is running, how it stopped, etc.
26289 * Source Annotations:: Annotations describing source code.
26292 @node Annotations Overview
26293 @section What is an Annotation?
26294 @cindex annotations
26296 Annotations start with a newline character, two @samp{control-z}
26297 characters, and the name of the annotation. If there is no additional
26298 information associated with this annotation, the name of the annotation
26299 is followed immediately by a newline. If there is additional
26300 information, the name of the annotation is followed by a space, the
26301 additional information, and a newline. The additional information
26302 cannot contain newline characters.
26304 Any output not beginning with a newline and two @samp{control-z}
26305 characters denotes literal output from @value{GDBN}. Currently there is
26306 no need for @value{GDBN} to output a newline followed by two
26307 @samp{control-z} characters, but if there was such a need, the
26308 annotations could be extended with an @samp{escape} annotation which
26309 means those three characters as output.
26311 The annotation @var{level}, which is specified using the
26312 @option{--annotate} command line option (@pxref{Mode Options}), controls
26313 how much information @value{GDBN} prints together with its prompt,
26314 values of expressions, source lines, and other types of output. Level 0
26315 is for no annotations, level 1 is for use when @value{GDBN} is run as a
26316 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
26317 for programs that control @value{GDBN}, and level 2 annotations have
26318 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
26319 Interface, annotate, GDB's Obsolete Annotations}).
26322 @kindex set annotate
26323 @item set annotate @var{level}
26324 The @value{GDBN} command @code{set annotate} sets the level of
26325 annotations to the specified @var{level}.
26327 @item show annotate
26328 @kindex show annotate
26329 Show the current annotation level.
26332 This chapter describes level 3 annotations.
26334 A simple example of starting up @value{GDBN} with annotations is:
26337 $ @kbd{gdb --annotate=3}
26339 Copyright 2003 Free Software Foundation, Inc.
26340 GDB is free software, covered by the GNU General Public License,
26341 and you are welcome to change it and/or distribute copies of it
26342 under certain conditions.
26343 Type "show copying" to see the conditions.
26344 There is absolutely no warranty for GDB. Type "show warranty"
26346 This GDB was configured as "i386-pc-linux-gnu"
26357 Here @samp{quit} is input to @value{GDBN}; the rest is output from
26358 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
26359 denotes a @samp{control-z} character) are annotations; the rest is
26360 output from @value{GDBN}.
26362 @node Server Prefix
26363 @section The Server Prefix
26364 @cindex server prefix
26366 If you prefix a command with @samp{server } then it will not affect
26367 the command history, nor will it affect @value{GDBN}'s notion of which
26368 command to repeat if @key{RET} is pressed on a line by itself. This
26369 means that commands can be run behind a user's back by a front-end in
26370 a transparent manner.
26372 The @code{server } prefix does not affect the recording of values into
26373 the value history; to print a value without recording it into the
26374 value history, use the @code{output} command instead of the
26375 @code{print} command.
26377 Using this prefix also disables confirmation requests
26378 (@pxref{confirmation requests}).
26381 @section Annotation for @value{GDBN} Input
26383 @cindex annotations for prompts
26384 When @value{GDBN} prompts for input, it annotates this fact so it is possible
26385 to know when to send output, when the output from a given command is
26388 Different kinds of input each have a different @dfn{input type}. Each
26389 input type has three annotations: a @code{pre-} annotation, which
26390 denotes the beginning of any prompt which is being output, a plain
26391 annotation, which denotes the end of the prompt, and then a @code{post-}
26392 annotation which denotes the end of any echo which may (or may not) be
26393 associated with the input. For example, the @code{prompt} input type
26394 features the following annotations:
26402 The input types are
26405 @findex pre-prompt annotation
26406 @findex prompt annotation
26407 @findex post-prompt annotation
26409 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
26411 @findex pre-commands annotation
26412 @findex commands annotation
26413 @findex post-commands annotation
26415 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
26416 command. The annotations are repeated for each command which is input.
26418 @findex pre-overload-choice annotation
26419 @findex overload-choice annotation
26420 @findex post-overload-choice annotation
26421 @item overload-choice
26422 When @value{GDBN} wants the user to select between various overloaded functions.
26424 @findex pre-query annotation
26425 @findex query annotation
26426 @findex post-query annotation
26428 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
26430 @findex pre-prompt-for-continue annotation
26431 @findex prompt-for-continue annotation
26432 @findex post-prompt-for-continue annotation
26433 @item prompt-for-continue
26434 When @value{GDBN} is asking the user to press return to continue. Note: Don't
26435 expect this to work well; instead use @code{set height 0} to disable
26436 prompting. This is because the counting of lines is buggy in the
26437 presence of annotations.
26442 @cindex annotations for errors, warnings and interrupts
26444 @findex quit annotation
26449 This annotation occurs right before @value{GDBN} responds to an interrupt.
26451 @findex error annotation
26456 This annotation occurs right before @value{GDBN} responds to an error.
26458 Quit and error annotations indicate that any annotations which @value{GDBN} was
26459 in the middle of may end abruptly. For example, if a
26460 @code{value-history-begin} annotation is followed by a @code{error}, one
26461 cannot expect to receive the matching @code{value-history-end}. One
26462 cannot expect not to receive it either, however; an error annotation
26463 does not necessarily mean that @value{GDBN} is immediately returning all the way
26466 @findex error-begin annotation
26467 A quit or error annotation may be preceded by
26473 Any output between that and the quit or error annotation is the error
26476 Warning messages are not yet annotated.
26477 @c If we want to change that, need to fix warning(), type_error(),
26478 @c range_error(), and possibly other places.
26481 @section Invalidation Notices
26483 @cindex annotations for invalidation messages
26484 The following annotations say that certain pieces of state may have
26488 @findex frames-invalid annotation
26489 @item ^Z^Zframes-invalid
26491 The frames (for example, output from the @code{backtrace} command) may
26494 @findex breakpoints-invalid annotation
26495 @item ^Z^Zbreakpoints-invalid
26497 The breakpoints may have changed. For example, the user just added or
26498 deleted a breakpoint.
26501 @node Annotations for Running
26502 @section Running the Program
26503 @cindex annotations for running programs
26505 @findex starting annotation
26506 @findex stopping annotation
26507 When the program starts executing due to a @value{GDBN} command such as
26508 @code{step} or @code{continue},
26514 is output. When the program stops,
26520 is output. Before the @code{stopped} annotation, a variety of
26521 annotations describe how the program stopped.
26524 @findex exited annotation
26525 @item ^Z^Zexited @var{exit-status}
26526 The program exited, and @var{exit-status} is the exit status (zero for
26527 successful exit, otherwise nonzero).
26529 @findex signalled annotation
26530 @findex signal-name annotation
26531 @findex signal-name-end annotation
26532 @findex signal-string annotation
26533 @findex signal-string-end annotation
26534 @item ^Z^Zsignalled
26535 The program exited with a signal. After the @code{^Z^Zsignalled}, the
26536 annotation continues:
26542 ^Z^Zsignal-name-end
26546 ^Z^Zsignal-string-end
26551 where @var{name} is the name of the signal, such as @code{SIGILL} or
26552 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
26553 as @code{Illegal Instruction} or @code{Segmentation fault}.
26554 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
26555 user's benefit and have no particular format.
26557 @findex signal annotation
26559 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
26560 just saying that the program received the signal, not that it was
26561 terminated with it.
26563 @findex breakpoint annotation
26564 @item ^Z^Zbreakpoint @var{number}
26565 The program hit breakpoint number @var{number}.
26567 @findex watchpoint annotation
26568 @item ^Z^Zwatchpoint @var{number}
26569 The program hit watchpoint number @var{number}.
26572 @node Source Annotations
26573 @section Displaying Source
26574 @cindex annotations for source display
26576 @findex source annotation
26577 The following annotation is used instead of displaying source code:
26580 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
26583 where @var{filename} is an absolute file name indicating which source
26584 file, @var{line} is the line number within that file (where 1 is the
26585 first line in the file), @var{character} is the character position
26586 within the file (where 0 is the first character in the file) (for most
26587 debug formats this will necessarily point to the beginning of a line),
26588 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
26589 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
26590 @var{addr} is the address in the target program associated with the
26591 source which is being displayed. @var{addr} is in the form @samp{0x}
26592 followed by one or more lowercase hex digits (note that this does not
26593 depend on the language).
26595 @node JIT Interface
26596 @chapter JIT Compilation Interface
26597 @cindex just-in-time compilation
26598 @cindex JIT compilation interface
26600 This chapter documents @value{GDBN}'s @dfn{just-in-time} (JIT) compilation
26601 interface. A JIT compiler is a program or library that generates native
26602 executable code at runtime and executes it, usually in order to achieve good
26603 performance while maintaining platform independence.
26605 Programs that use JIT compilation are normally difficult to debug because
26606 portions of their code are generated at runtime, instead of being loaded from
26607 object files, which is where @value{GDBN} normally finds the program's symbols
26608 and debug information. In order to debug programs that use JIT compilation,
26609 @value{GDBN} has an interface that allows the program to register in-memory
26610 symbol files with @value{GDBN} at runtime.
26612 If you are using @value{GDBN} to debug a program that uses this interface, then
26613 it should work transparently so long as you have not stripped the binary. If
26614 you are developing a JIT compiler, then the interface is documented in the rest
26615 of this chapter. At this time, the only known client of this interface is the
26618 Broadly speaking, the JIT interface mirrors the dynamic loader interface. The
26619 JIT compiler communicates with @value{GDBN} by writing data into a global
26620 variable and calling a fuction at a well-known symbol. When @value{GDBN}
26621 attaches, it reads a linked list of symbol files from the global variable to
26622 find existing code, and puts a breakpoint in the function so that it can find
26623 out about additional code.
26626 * Declarations:: Relevant C struct declarations
26627 * Registering Code:: Steps to register code
26628 * Unregistering Code:: Steps to unregister code
26632 @section JIT Declarations
26634 These are the relevant struct declarations that a C program should include to
26635 implement the interface:
26645 struct jit_code_entry
26647 struct jit_code_entry *next_entry;
26648 struct jit_code_entry *prev_entry;
26649 const char *symfile_addr;
26650 uint64_t symfile_size;
26653 struct jit_descriptor
26656 /* This type should be jit_actions_t, but we use uint32_t
26657 to be explicit about the bitwidth. */
26658 uint32_t action_flag;
26659 struct jit_code_entry *relevant_entry;
26660 struct jit_code_entry *first_entry;
26663 /* GDB puts a breakpoint in this function. */
26664 void __attribute__((noinline)) __jit_debug_register_code() @{ @};
26666 /* Make sure to specify the version statically, because the
26667 debugger may check the version before we can set it. */
26668 struct jit_descriptor __jit_debug_descriptor = @{ 1, 0, 0, 0 @};
26671 If the JIT is multi-threaded, then it is important that the JIT synchronize any
26672 modifications to this global data properly, which can easily be done by putting
26673 a global mutex around modifications to these structures.
26675 @node Registering Code
26676 @section Registering Code
26678 To register code with @value{GDBN}, the JIT should follow this protocol:
26682 Generate an object file in memory with symbols and other desired debug
26683 information. The file must include the virtual addresses of the sections.
26686 Create a code entry for the file, which gives the start and size of the symbol
26690 Add it to the linked list in the JIT descriptor.
26693 Point the relevant_entry field of the descriptor at the entry.
26696 Set @code{action_flag} to @code{JIT_REGISTER} and call
26697 @code{__jit_debug_register_code}.
26700 When @value{GDBN} is attached and the breakpoint fires, @value{GDBN} uses the
26701 @code{relevant_entry} pointer so it doesn't have to walk the list looking for
26702 new code. However, the linked list must still be maintained in order to allow
26703 @value{GDBN} to attach to a running process and still find the symbol files.
26705 @node Unregistering Code
26706 @section Unregistering Code
26708 If code is freed, then the JIT should use the following protocol:
26712 Remove the code entry corresponding to the code from the linked list.
26715 Point the @code{relevant_entry} field of the descriptor at the code entry.
26718 Set @code{action_flag} to @code{JIT_UNREGISTER} and call
26719 @code{__jit_debug_register_code}.
26722 If the JIT frees or recompiles code without unregistering it, then @value{GDBN}
26723 and the JIT will leak the memory used for the associated symbol files.
26726 @chapter Reporting Bugs in @value{GDBN}
26727 @cindex bugs in @value{GDBN}
26728 @cindex reporting bugs in @value{GDBN}
26730 Your bug reports play an essential role in making @value{GDBN} reliable.
26732 Reporting a bug may help you by bringing a solution to your problem, or it
26733 may not. But in any case the principal function of a bug report is to help
26734 the entire community by making the next version of @value{GDBN} work better. Bug
26735 reports are your contribution to the maintenance of @value{GDBN}.
26737 In order for a bug report to serve its purpose, you must include the
26738 information that enables us to fix the bug.
26741 * Bug Criteria:: Have you found a bug?
26742 * Bug Reporting:: How to report bugs
26746 @section Have You Found a Bug?
26747 @cindex bug criteria
26749 If you are not sure whether you have found a bug, here are some guidelines:
26752 @cindex fatal signal
26753 @cindex debugger crash
26754 @cindex crash of debugger
26756 If the debugger gets a fatal signal, for any input whatever, that is a
26757 @value{GDBN} bug. Reliable debuggers never crash.
26759 @cindex error on valid input
26761 If @value{GDBN} produces an error message for valid input, that is a
26762 bug. (Note that if you're cross debugging, the problem may also be
26763 somewhere in the connection to the target.)
26765 @cindex invalid input
26767 If @value{GDBN} does not produce an error message for invalid input,
26768 that is a bug. However, you should note that your idea of
26769 ``invalid input'' might be our idea of ``an extension'' or ``support
26770 for traditional practice''.
26773 If you are an experienced user of debugging tools, your suggestions
26774 for improvement of @value{GDBN} are welcome in any case.
26777 @node Bug Reporting
26778 @section How to Report Bugs
26779 @cindex bug reports
26780 @cindex @value{GDBN} bugs, reporting
26782 A number of companies and individuals offer support for @sc{gnu} products.
26783 If you obtained @value{GDBN} from a support organization, we recommend you
26784 contact that organization first.
26786 You can find contact information for many support companies and
26787 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
26789 @c should add a web page ref...
26792 @ifset BUGURL_DEFAULT
26793 In any event, we also recommend that you submit bug reports for
26794 @value{GDBN}. The preferred method is to submit them directly using
26795 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
26796 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
26799 @strong{Do not send bug reports to @samp{info-gdb}, or to
26800 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
26801 not want to receive bug reports. Those that do have arranged to receive
26804 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
26805 serves as a repeater. The mailing list and the newsgroup carry exactly
26806 the same messages. Often people think of posting bug reports to the
26807 newsgroup instead of mailing them. This appears to work, but it has one
26808 problem which can be crucial: a newsgroup posting often lacks a mail
26809 path back to the sender. Thus, if we need to ask for more information,
26810 we may be unable to reach you. For this reason, it is better to send
26811 bug reports to the mailing list.
26813 @ifclear BUGURL_DEFAULT
26814 In any event, we also recommend that you submit bug reports for
26815 @value{GDBN} to @value{BUGURL}.
26819 The fundamental principle of reporting bugs usefully is this:
26820 @strong{report all the facts}. If you are not sure whether to state a
26821 fact or leave it out, state it!
26823 Often people omit facts because they think they know what causes the
26824 problem and assume that some details do not matter. Thus, you might
26825 assume that the name of the variable you use in an example does not matter.
26826 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
26827 stray memory reference which happens to fetch from the location where that
26828 name is stored in memory; perhaps, if the name were different, the contents
26829 of that location would fool the debugger into doing the right thing despite
26830 the bug. Play it safe and give a specific, complete example. That is the
26831 easiest thing for you to do, and the most helpful.
26833 Keep in mind that the purpose of a bug report is to enable us to fix the
26834 bug. It may be that the bug has been reported previously, but neither
26835 you nor we can know that unless your bug report is complete and
26838 Sometimes people give a few sketchy facts and ask, ``Does this ring a
26839 bell?'' Those bug reports are useless, and we urge everyone to
26840 @emph{refuse to respond to them} except to chide the sender to report
26843 To enable us to fix the bug, you should include all these things:
26847 The version of @value{GDBN}. @value{GDBN} announces it if you start
26848 with no arguments; you can also print it at any time using @code{show
26851 Without this, we will not know whether there is any point in looking for
26852 the bug in the current version of @value{GDBN}.
26855 The type of machine you are using, and the operating system name and
26859 What compiler (and its version) was used to compile @value{GDBN}---e.g.@:
26860 ``@value{GCC}--2.8.1''.
26863 What compiler (and its version) was used to compile the program you are
26864 debugging---e.g.@: ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
26865 C Compiler''. For @value{NGCC}, you can say @kbd{@value{GCC} --version}
26866 to get this information; for other compilers, see the documentation for
26870 The command arguments you gave the compiler to compile your example and
26871 observe the bug. For example, did you use @samp{-O}? To guarantee
26872 you will not omit something important, list them all. A copy of the
26873 Makefile (or the output from make) is sufficient.
26875 If we were to try to guess the arguments, we would probably guess wrong
26876 and then we might not encounter the bug.
26879 A complete input script, and all necessary source files, that will
26883 A description of what behavior you observe that you believe is
26884 incorrect. For example, ``It gets a fatal signal.''
26886 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
26887 will certainly notice it. But if the bug is incorrect output, we might
26888 not notice unless it is glaringly wrong. You might as well not give us
26889 a chance to make a mistake.
26891 Even if the problem you experience is a fatal signal, you should still
26892 say so explicitly. Suppose something strange is going on, such as, your
26893 copy of @value{GDBN} is out of synch, or you have encountered a bug in
26894 the C library on your system. (This has happened!) Your copy might
26895 crash and ours would not. If you told us to expect a crash, then when
26896 ours fails to crash, we would know that the bug was not happening for
26897 us. If you had not told us to expect a crash, then we would not be able
26898 to draw any conclusion from our observations.
26901 @cindex recording a session script
26902 To collect all this information, you can use a session recording program
26903 such as @command{script}, which is available on many Unix systems.
26904 Just run your @value{GDBN} session inside @command{script} and then
26905 include the @file{typescript} file with your bug report.
26907 Another way to record a @value{GDBN} session is to run @value{GDBN}
26908 inside Emacs and then save the entire buffer to a file.
26911 If you wish to suggest changes to the @value{GDBN} source, send us context
26912 diffs. If you even discuss something in the @value{GDBN} source, refer to
26913 it by context, not by line number.
26915 The line numbers in our development sources will not match those in your
26916 sources. Your line numbers would convey no useful information to us.
26920 Here are some things that are not necessary:
26924 A description of the envelope of the bug.
26926 Often people who encounter a bug spend a lot of time investigating
26927 which changes to the input file will make the bug go away and which
26928 changes will not affect it.
26930 This is often time consuming and not very useful, because the way we
26931 will find the bug is by running a single example under the debugger
26932 with breakpoints, not by pure deduction from a series of examples.
26933 We recommend that you save your time for something else.
26935 Of course, if you can find a simpler example to report @emph{instead}
26936 of the original one, that is a convenience for us. Errors in the
26937 output will be easier to spot, running under the debugger will take
26938 less time, and so on.
26940 However, simplification is not vital; if you do not want to do this,
26941 report the bug anyway and send us the entire test case you used.
26944 A patch for the bug.
26946 A patch for the bug does help us if it is a good one. But do not omit
26947 the necessary information, such as the test case, on the assumption that
26948 a patch is all we need. We might see problems with your patch and decide
26949 to fix the problem another way, or we might not understand it at all.
26951 Sometimes with a program as complicated as @value{GDBN} it is very hard to
26952 construct an example that will make the program follow a certain path
26953 through the code. If you do not send us the example, we will not be able
26954 to construct one, so we will not be able to verify that the bug is fixed.
26956 And if we cannot understand what bug you are trying to fix, or why your
26957 patch should be an improvement, we will not install it. A test case will
26958 help us to understand.
26961 A guess about what the bug is or what it depends on.
26963 Such guesses are usually wrong. Even we cannot guess right about such
26964 things without first using the debugger to find the facts.
26967 @c The readline documentation is distributed with the readline code
26968 @c and consists of the two following files:
26970 @c inc-hist.texinfo
26971 @c Use -I with makeinfo to point to the appropriate directory,
26972 @c environment var TEXINPUTS with TeX.
26973 @include rluser.texi
26974 @include inc-hist.texinfo
26977 @node Formatting Documentation
26978 @appendix Formatting Documentation
26980 @cindex @value{GDBN} reference card
26981 @cindex reference card
26982 The @value{GDBN} 4 release includes an already-formatted reference card, ready
26983 for printing with PostScript or Ghostscript, in the @file{gdb}
26984 subdirectory of the main source directory@footnote{In
26985 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
26986 release.}. If you can use PostScript or Ghostscript with your printer,
26987 you can print the reference card immediately with @file{refcard.ps}.
26989 The release also includes the source for the reference card. You
26990 can format it, using @TeX{}, by typing:
26996 The @value{GDBN} reference card is designed to print in @dfn{landscape}
26997 mode on US ``letter'' size paper;
26998 that is, on a sheet 11 inches wide by 8.5 inches
26999 high. You will need to specify this form of printing as an option to
27000 your @sc{dvi} output program.
27002 @cindex documentation
27004 All the documentation for @value{GDBN} comes as part of the machine-readable
27005 distribution. The documentation is written in Texinfo format, which is
27006 a documentation system that uses a single source file to produce both
27007 on-line information and a printed manual. You can use one of the Info
27008 formatting commands to create the on-line version of the documentation
27009 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
27011 @value{GDBN} includes an already formatted copy of the on-line Info
27012 version of this manual in the @file{gdb} subdirectory. The main Info
27013 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
27014 subordinate files matching @samp{gdb.info*} in the same directory. If
27015 necessary, you can print out these files, or read them with any editor;
27016 but they are easier to read using the @code{info} subsystem in @sc{gnu}
27017 Emacs or the standalone @code{info} program, available as part of the
27018 @sc{gnu} Texinfo distribution.
27020 If you want to format these Info files yourself, you need one of the
27021 Info formatting programs, such as @code{texinfo-format-buffer} or
27024 If you have @code{makeinfo} installed, and are in the top level
27025 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
27026 version @value{GDBVN}), you can make the Info file by typing:
27033 If you want to typeset and print copies of this manual, you need @TeX{},
27034 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
27035 Texinfo definitions file.
27037 @TeX{} is a typesetting program; it does not print files directly, but
27038 produces output files called @sc{dvi} files. To print a typeset
27039 document, you need a program to print @sc{dvi} files. If your system
27040 has @TeX{} installed, chances are it has such a program. The precise
27041 command to use depends on your system; @kbd{lpr -d} is common; another
27042 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
27043 require a file name without any extension or a @samp{.dvi} extension.
27045 @TeX{} also requires a macro definitions file called
27046 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
27047 written in Texinfo format. On its own, @TeX{} cannot either read or
27048 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
27049 and is located in the @file{gdb-@var{version-number}/texinfo}
27052 If you have @TeX{} and a @sc{dvi} printer program installed, you can
27053 typeset and print this manual. First switch to the @file{gdb}
27054 subdirectory of the main source directory (for example, to
27055 @file{gdb-@value{GDBVN}/gdb}) and type:
27061 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
27063 @node Installing GDB
27064 @appendix Installing @value{GDBN}
27065 @cindex installation
27068 * Requirements:: Requirements for building @value{GDBN}
27069 * Running Configure:: Invoking the @value{GDBN} @file{configure} script
27070 * Separate Objdir:: Compiling @value{GDBN} in another directory
27071 * Config Names:: Specifying names for hosts and targets
27072 * Configure Options:: Summary of options for configure
27073 * System-wide configuration:: Having a system-wide init file
27077 @section Requirements for Building @value{GDBN}
27078 @cindex building @value{GDBN}, requirements for
27080 Building @value{GDBN} requires various tools and packages to be available.
27081 Other packages will be used only if they are found.
27083 @heading Tools/Packages Necessary for Building @value{GDBN}
27085 @item ISO C90 compiler
27086 @value{GDBN} is written in ISO C90. It should be buildable with any
27087 working C90 compiler, e.g.@: GCC.
27091 @heading Tools/Packages Optional for Building @value{GDBN}
27095 @value{GDBN} can use the Expat XML parsing library. This library may be
27096 included with your operating system distribution; if it is not, you
27097 can get the latest version from @url{http://expat.sourceforge.net}.
27098 The @file{configure} script will search for this library in several
27099 standard locations; if it is installed in an unusual path, you can
27100 use the @option{--with-libexpat-prefix} option to specify its location.
27106 Remote protocol memory maps (@pxref{Memory Map Format})
27108 Target descriptions (@pxref{Target Descriptions})
27110 Remote shared library lists (@pxref{Library List Format})
27112 MS-Windows shared libraries (@pxref{Shared Libraries})
27116 @cindex compressed debug sections
27117 @value{GDBN} will use the @samp{zlib} library, if available, to read
27118 compressed debug sections. Some linkers, such as GNU gold, are capable
27119 of producing binaries with compressed debug sections. If @value{GDBN}
27120 is compiled with @samp{zlib}, it will be able to read the debug
27121 information in such binaries.
27123 The @samp{zlib} library is likely included with your operating system
27124 distribution; if it is not, you can get the latest version from
27125 @url{http://zlib.net}.
27128 @value{GDBN}'s features related to character sets (@pxref{Character
27129 Sets}) require a functioning @code{iconv} implementation. If you are
27130 on a GNU system, then this is provided by the GNU C Library. Some
27131 other systems also provide a working @code{iconv}.
27133 On systems with @code{iconv}, you can install GNU Libiconv. If you
27134 have previously installed Libiconv, you can use the
27135 @option{--with-libiconv-prefix} option to configure.
27137 @value{GDBN}'s top-level @file{configure} and @file{Makefile} will
27138 arrange to build Libiconv if a directory named @file{libiconv} appears
27139 in the top-most source directory. If Libiconv is built this way, and
27140 if the operating system does not provide a suitable @code{iconv}
27141 implementation, then the just-built library will automatically be used
27142 by @value{GDBN}. One easy way to set this up is to download GNU
27143 Libiconv, unpack it, and then rename the directory holding the
27144 Libiconv source code to @samp{libiconv}.
27147 @node Running Configure
27148 @section Invoking the @value{GDBN} @file{configure} Script
27149 @cindex configuring @value{GDBN}
27150 @value{GDBN} comes with a @file{configure} script that automates the process
27151 of preparing @value{GDBN} for installation; you can then use @code{make} to
27152 build the @code{gdb} program.
27154 @c irrelevant in info file; it's as current as the code it lives with.
27155 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
27156 look at the @file{README} file in the sources; we may have improved the
27157 installation procedures since publishing this manual.}
27160 The @value{GDBN} distribution includes all the source code you need for
27161 @value{GDBN} in a single directory, whose name is usually composed by
27162 appending the version number to @samp{gdb}.
27164 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
27165 @file{gdb-@value{GDBVN}} directory. That directory contains:
27168 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
27169 script for configuring @value{GDBN} and all its supporting libraries
27171 @item gdb-@value{GDBVN}/gdb
27172 the source specific to @value{GDBN} itself
27174 @item gdb-@value{GDBVN}/bfd
27175 source for the Binary File Descriptor library
27177 @item gdb-@value{GDBVN}/include
27178 @sc{gnu} include files
27180 @item gdb-@value{GDBVN}/libiberty
27181 source for the @samp{-liberty} free software library
27183 @item gdb-@value{GDBVN}/opcodes
27184 source for the library of opcode tables and disassemblers
27186 @item gdb-@value{GDBVN}/readline
27187 source for the @sc{gnu} command-line interface
27189 @item gdb-@value{GDBVN}/glob
27190 source for the @sc{gnu} filename pattern-matching subroutine
27192 @item gdb-@value{GDBVN}/mmalloc
27193 source for the @sc{gnu} memory-mapped malloc package
27196 The simplest way to configure and build @value{GDBN} is to run @file{configure}
27197 from the @file{gdb-@var{version-number}} source directory, which in
27198 this example is the @file{gdb-@value{GDBVN}} directory.
27200 First switch to the @file{gdb-@var{version-number}} source directory
27201 if you are not already in it; then run @file{configure}. Pass the
27202 identifier for the platform on which @value{GDBN} will run as an
27208 cd gdb-@value{GDBVN}
27209 ./configure @var{host}
27214 where @var{host} is an identifier such as @samp{sun4} or
27215 @samp{decstation}, that identifies the platform where @value{GDBN} will run.
27216 (You can often leave off @var{host}; @file{configure} tries to guess the
27217 correct value by examining your system.)
27219 Running @samp{configure @var{host}} and then running @code{make} builds the
27220 @file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty}
27221 libraries, then @code{gdb} itself. The configured source files, and the
27222 binaries, are left in the corresponding source directories.
27225 @file{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
27226 system does not recognize this automatically when you run a different
27227 shell, you may need to run @code{sh} on it explicitly:
27230 sh configure @var{host}
27233 If you run @file{configure} from a directory that contains source
27234 directories for multiple libraries or programs, such as the
27235 @file{gdb-@value{GDBVN}} source directory for version @value{GDBVN},
27237 creates configuration files for every directory level underneath (unless
27238 you tell it not to, with the @samp{--norecursion} option).
27240 You should run the @file{configure} script from the top directory in the
27241 source tree, the @file{gdb-@var{version-number}} directory. If you run
27242 @file{configure} from one of the subdirectories, you will configure only
27243 that subdirectory. That is usually not what you want. In particular,
27244 if you run the first @file{configure} from the @file{gdb} subdirectory
27245 of the @file{gdb-@var{version-number}} directory, you will omit the
27246 configuration of @file{bfd}, @file{readline}, and other sibling
27247 directories of the @file{gdb} subdirectory. This leads to build errors
27248 about missing include files such as @file{bfd/bfd.h}.
27250 You can install @code{@value{GDBP}} anywhere; it has no hardwired paths.
27251 However, you should make sure that the shell on your path (named by
27252 the @samp{SHELL} environment variable) is publicly readable. Remember
27253 that @value{GDBN} uses the shell to start your program---some systems refuse to
27254 let @value{GDBN} debug child processes whose programs are not readable.
27256 @node Separate Objdir
27257 @section Compiling @value{GDBN} in Another Directory
27259 If you want to run @value{GDBN} versions for several host or target machines,
27260 you need a different @code{gdb} compiled for each combination of
27261 host and target. @file{configure} is designed to make this easy by
27262 allowing you to generate each configuration in a separate subdirectory,
27263 rather than in the source directory. If your @code{make} program
27264 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
27265 @code{make} in each of these directories builds the @code{gdb}
27266 program specified there.
27268 To build @code{gdb} in a separate directory, run @file{configure}
27269 with the @samp{--srcdir} option to specify where to find the source.
27270 (You also need to specify a path to find @file{configure}
27271 itself from your working directory. If the path to @file{configure}
27272 would be the same as the argument to @samp{--srcdir}, you can leave out
27273 the @samp{--srcdir} option; it is assumed.)
27275 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
27276 separate directory for a Sun 4 like this:
27280 cd gdb-@value{GDBVN}
27283 ../gdb-@value{GDBVN}/configure sun4
27288 When @file{configure} builds a configuration using a remote source
27289 directory, it creates a tree for the binaries with the same structure
27290 (and using the same names) as the tree under the source directory. In
27291 the example, you'd find the Sun 4 library @file{libiberty.a} in the
27292 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
27293 @file{gdb-sun4/gdb}.
27295 Make sure that your path to the @file{configure} script has just one
27296 instance of @file{gdb} in it. If your path to @file{configure} looks
27297 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
27298 one subdirectory of @value{GDBN}, not the whole package. This leads to
27299 build errors about missing include files such as @file{bfd/bfd.h}.
27301 One popular reason to build several @value{GDBN} configurations in separate
27302 directories is to configure @value{GDBN} for cross-compiling (where
27303 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
27304 programs that run on another machine---the @dfn{target}).
27305 You specify a cross-debugging target by
27306 giving the @samp{--target=@var{target}} option to @file{configure}.
27308 When you run @code{make} to build a program or library, you must run
27309 it in a configured directory---whatever directory you were in when you
27310 called @file{configure} (or one of its subdirectories).
27312 The @code{Makefile} that @file{configure} generates in each source
27313 directory also runs recursively. If you type @code{make} in a source
27314 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
27315 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
27316 will build all the required libraries, and then build GDB.
27318 When you have multiple hosts or targets configured in separate
27319 directories, you can run @code{make} on them in parallel (for example,
27320 if they are NFS-mounted on each of the hosts); they will not interfere
27324 @section Specifying Names for Hosts and Targets
27326 The specifications used for hosts and targets in the @file{configure}
27327 script are based on a three-part naming scheme, but some short predefined
27328 aliases are also supported. The full naming scheme encodes three pieces
27329 of information in the following pattern:
27332 @var{architecture}-@var{vendor}-@var{os}
27335 For example, you can use the alias @code{sun4} as a @var{host} argument,
27336 or as the value for @var{target} in a @code{--target=@var{target}}
27337 option. The equivalent full name is @samp{sparc-sun-sunos4}.
27339 The @file{configure} script accompanying @value{GDBN} does not provide
27340 any query facility to list all supported host and target names or
27341 aliases. @file{configure} calls the Bourne shell script
27342 @code{config.sub} to map abbreviations to full names; you can read the
27343 script, if you wish, or you can use it to test your guesses on
27344 abbreviations---for example:
27347 % sh config.sub i386-linux
27349 % sh config.sub alpha-linux
27350 alpha-unknown-linux-gnu
27351 % sh config.sub hp9k700
27353 % sh config.sub sun4
27354 sparc-sun-sunos4.1.1
27355 % sh config.sub sun3
27356 m68k-sun-sunos4.1.1
27357 % sh config.sub i986v
27358 Invalid configuration `i986v': machine `i986v' not recognized
27362 @code{config.sub} is also distributed in the @value{GDBN} source
27363 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
27365 @node Configure Options
27366 @section @file{configure} Options
27368 Here is a summary of the @file{configure} options and arguments that
27369 are most often useful for building @value{GDBN}. @file{configure} also has
27370 several other options not listed here. @inforef{What Configure
27371 Does,,configure.info}, for a full explanation of @file{configure}.
27374 configure @r{[}--help@r{]}
27375 @r{[}--prefix=@var{dir}@r{]}
27376 @r{[}--exec-prefix=@var{dir}@r{]}
27377 @r{[}--srcdir=@var{dirname}@r{]}
27378 @r{[}--norecursion@r{]} @r{[}--rm@r{]}
27379 @r{[}--target=@var{target}@r{]}
27384 You may introduce options with a single @samp{-} rather than
27385 @samp{--} if you prefer; but you may abbreviate option names if you use
27390 Display a quick summary of how to invoke @file{configure}.
27392 @item --prefix=@var{dir}
27393 Configure the source to install programs and files under directory
27396 @item --exec-prefix=@var{dir}
27397 Configure the source to install programs under directory
27400 @c avoid splitting the warning from the explanation:
27402 @item --srcdir=@var{dirname}
27403 @strong{Warning: using this option requires @sc{gnu} @code{make}, or another
27404 @code{make} that implements the @code{VPATH} feature.}@*
27405 Use this option to make configurations in directories separate from the
27406 @value{GDBN} source directories. Among other things, you can use this to
27407 build (or maintain) several configurations simultaneously, in separate
27408 directories. @file{configure} writes configuration-specific files in
27409 the current directory, but arranges for them to use the source in the
27410 directory @var{dirname}. @file{configure} creates directories under
27411 the working directory in parallel to the source directories below
27414 @item --norecursion
27415 Configure only the directory level where @file{configure} is executed; do not
27416 propagate configuration to subdirectories.
27418 @item --target=@var{target}
27419 Configure @value{GDBN} for cross-debugging programs running on the specified
27420 @var{target}. Without this option, @value{GDBN} is configured to debug
27421 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
27423 There is no convenient way to generate a list of all available targets.
27425 @item @var{host} @dots{}
27426 Configure @value{GDBN} to run on the specified @var{host}.
27428 There is no convenient way to generate a list of all available hosts.
27431 There are many other options available as well, but they are generally
27432 needed for special purposes only.
27434 @node System-wide configuration
27435 @section System-wide configuration and settings
27436 @cindex system-wide init file
27438 @value{GDBN} can be configured to have a system-wide init file;
27439 this file will be read and executed at startup (@pxref{Startup, , What
27440 @value{GDBN} does during startup}).
27442 Here is the corresponding configure option:
27445 @item --with-system-gdbinit=@var{file}
27446 Specify that the default location of the system-wide init file is
27450 If @value{GDBN} has been configured with the option @option{--prefix=$prefix},
27451 it may be subject to relocation. Two possible cases:
27455 If the default location of this init file contains @file{$prefix},
27456 it will be subject to relocation. Suppose that the configure options
27457 are @option{--prefix=$prefix --with-system-gdbinit=$prefix/etc/gdbinit};
27458 if @value{GDBN} is moved from @file{$prefix} to @file{$install}, the system
27459 init file is looked for as @file{$install/etc/gdbinit} instead of
27460 @file{$prefix/etc/gdbinit}.
27463 By contrast, if the default location does not contain the prefix,
27464 it will not be relocated. E.g.@: if @value{GDBN} has been configured with
27465 @option{--prefix=/usr/local --with-system-gdbinit=/usr/share/gdb/gdbinit},
27466 then @value{GDBN} will always look for @file{/usr/share/gdb/gdbinit},
27467 wherever @value{GDBN} is installed.
27470 @node Maintenance Commands
27471 @appendix Maintenance Commands
27472 @cindex maintenance commands
27473 @cindex internal commands
27475 In addition to commands intended for @value{GDBN} users, @value{GDBN}
27476 includes a number of commands intended for @value{GDBN} developers,
27477 that are not documented elsewhere in this manual. These commands are
27478 provided here for reference. (For commands that turn on debugging
27479 messages, see @ref{Debugging Output}.)
27482 @kindex maint agent
27483 @kindex maint agent-eval
27484 @item maint agent @var{expression}
27485 @itemx maint agent-eval @var{expression}
27486 Translate the given @var{expression} into remote agent bytecodes.
27487 This command is useful for debugging the Agent Expression mechanism
27488 (@pxref{Agent Expressions}). The @samp{agent} version produces an
27489 expression useful for data collection, such as by tracepoints, while
27490 @samp{maint agent-eval} produces an expression that evaluates directly
27491 to a result. For instance, a collection expression for @code{globa +
27492 globb} will include bytecodes to record four bytes of memory at each
27493 of the addresses of @code{globa} and @code{globb}, while discarding
27494 the result of the addition, while an evaluation expression will do the
27495 addition and return the sum.
27497 @kindex maint info breakpoints
27498 @item @anchor{maint info breakpoints}maint info breakpoints
27499 Using the same format as @samp{info breakpoints}, display both the
27500 breakpoints you've set explicitly, and those @value{GDBN} is using for
27501 internal purposes. Internal breakpoints are shown with negative
27502 breakpoint numbers. The type column identifies what kind of breakpoint
27507 Normal, explicitly set breakpoint.
27510 Normal, explicitly set watchpoint.
27513 Internal breakpoint, used to handle correctly stepping through
27514 @code{longjmp} calls.
27516 @item longjmp resume
27517 Internal breakpoint at the target of a @code{longjmp}.
27520 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
27523 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
27526 Shared library events.
27530 @kindex set displaced-stepping
27531 @kindex show displaced-stepping
27532 @cindex displaced stepping support
27533 @cindex out-of-line single-stepping
27534 @item set displaced-stepping
27535 @itemx show displaced-stepping
27536 Control whether or not @value{GDBN} will do @dfn{displaced stepping}
27537 if the target supports it. Displaced stepping is a way to single-step
27538 over breakpoints without removing them from the inferior, by executing
27539 an out-of-line copy of the instruction that was originally at the
27540 breakpoint location. It is also known as out-of-line single-stepping.
27543 @item set displaced-stepping on
27544 If the target architecture supports it, @value{GDBN} will use
27545 displaced stepping to step over breakpoints.
27547 @item set displaced-stepping off
27548 @value{GDBN} will not use displaced stepping to step over breakpoints,
27549 even if such is supported by the target architecture.
27551 @cindex non-stop mode, and @samp{set displaced-stepping}
27552 @item set displaced-stepping auto
27553 This is the default mode. @value{GDBN} will use displaced stepping
27554 only if non-stop mode is active (@pxref{Non-Stop Mode}) and the target
27555 architecture supports displaced stepping.
27558 @kindex maint check-symtabs
27559 @item maint check-symtabs
27560 Check the consistency of psymtabs and symtabs.
27562 @kindex maint cplus first_component
27563 @item maint cplus first_component @var{name}
27564 Print the first C@t{++} class/namespace component of @var{name}.
27566 @kindex maint cplus namespace
27567 @item maint cplus namespace
27568 Print the list of possible C@t{++} namespaces.
27570 @kindex maint demangle
27571 @item maint demangle @var{name}
27572 Demangle a C@t{++} or Objective-C mangled @var{name}.
27574 @kindex maint deprecate
27575 @kindex maint undeprecate
27576 @cindex deprecated commands
27577 @item maint deprecate @var{command} @r{[}@var{replacement}@r{]}
27578 @itemx maint undeprecate @var{command}
27579 Deprecate or undeprecate the named @var{command}. Deprecated commands
27580 cause @value{GDBN} to issue a warning when you use them. The optional
27581 argument @var{replacement} says which newer command should be used in
27582 favor of the deprecated one; if it is given, @value{GDBN} will mention
27583 the replacement as part of the warning.
27585 @kindex maint dump-me
27586 @item maint dump-me
27587 @cindex @code{SIGQUIT} signal, dump core of @value{GDBN}
27588 Cause a fatal signal in the debugger and force it to dump its core.
27589 This is supported only on systems which support aborting a program
27590 with the @code{SIGQUIT} signal.
27592 @kindex maint internal-error
27593 @kindex maint internal-warning
27594 @item maint internal-error @r{[}@var{message-text}@r{]}
27595 @itemx maint internal-warning @r{[}@var{message-text}@r{]}
27596 Cause @value{GDBN} to call the internal function @code{internal_error}
27597 or @code{internal_warning} and hence behave as though an internal error
27598 or internal warning has been detected. In addition to reporting the
27599 internal problem, these functions give the user the opportunity to
27600 either quit @value{GDBN} or create a core file of the current
27601 @value{GDBN} session.
27603 These commands take an optional parameter @var{message-text} that is
27604 used as the text of the error or warning message.
27606 Here's an example of using @code{internal-error}:
27609 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
27610 @dots{}/maint.c:121: internal-error: testing, 1, 2
27611 A problem internal to GDB has been detected. Further
27612 debugging may prove unreliable.
27613 Quit this debugging session? (y or n) @kbd{n}
27614 Create a core file? (y or n) @kbd{n}
27618 @cindex @value{GDBN} internal error
27619 @cindex internal errors, control of @value{GDBN} behavior
27621 @kindex maint set internal-error
27622 @kindex maint show internal-error
27623 @kindex maint set internal-warning
27624 @kindex maint show internal-warning
27625 @item maint set internal-error @var{action} [ask|yes|no]
27626 @itemx maint show internal-error @var{action}
27627 @itemx maint set internal-warning @var{action} [ask|yes|no]
27628 @itemx maint show internal-warning @var{action}
27629 When @value{GDBN} reports an internal problem (error or warning) it
27630 gives the user the opportunity to both quit @value{GDBN} and create a
27631 core file of the current @value{GDBN} session. These commands let you
27632 override the default behaviour for each particular @var{action},
27633 described in the table below.
27637 You can specify that @value{GDBN} should always (yes) or never (no)
27638 quit. The default is to ask the user what to do.
27641 You can specify that @value{GDBN} should always (yes) or never (no)
27642 create a core file. The default is to ask the user what to do.
27645 @kindex maint packet
27646 @item maint packet @var{text}
27647 If @value{GDBN} is talking to an inferior via the serial protocol,
27648 then this command sends the string @var{text} to the inferior, and
27649 displays the response packet. @value{GDBN} supplies the initial
27650 @samp{$} character, the terminating @samp{#} character, and the
27653 @kindex maint print architecture
27654 @item maint print architecture @r{[}@var{file}@r{]}
27655 Print the entire architecture configuration. The optional argument
27656 @var{file} names the file where the output goes.
27658 @kindex maint print c-tdesc
27659 @item maint print c-tdesc
27660 Print the current target description (@pxref{Target Descriptions}) as
27661 a C source file. The created source file can be used in @value{GDBN}
27662 when an XML parser is not available to parse the description.
27664 @kindex maint print dummy-frames
27665 @item maint print dummy-frames
27666 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
27669 (@value{GDBP}) @kbd{b add}
27671 (@value{GDBP}) @kbd{print add(2,3)}
27672 Breakpoint 2, add (a=2, b=3) at @dots{}
27674 The program being debugged stopped while in a function called from GDB.
27676 (@value{GDBP}) @kbd{maint print dummy-frames}
27677 0x1a57c80: pc=0x01014068 fp=0x0200bddc sp=0x0200bdd6
27678 top=0x0200bdd4 id=@{stack=0x200bddc,code=0x101405c@}
27679 call_lo=0x01014000 call_hi=0x01014001
27683 Takes an optional file parameter.
27685 @kindex maint print registers
27686 @kindex maint print raw-registers
27687 @kindex maint print cooked-registers
27688 @kindex maint print register-groups
27689 @item maint print registers @r{[}@var{file}@r{]}
27690 @itemx maint print raw-registers @r{[}@var{file}@r{]}
27691 @itemx maint print cooked-registers @r{[}@var{file}@r{]}
27692 @itemx maint print register-groups @r{[}@var{file}@r{]}
27693 Print @value{GDBN}'s internal register data structures.
27695 The command @code{maint print raw-registers} includes the contents of
27696 the raw register cache; the command @code{maint print cooked-registers}
27697 includes the (cooked) value of all registers; and the command
27698 @code{maint print register-groups} includes the groups that each
27699 register is a member of. @xref{Registers,, Registers, gdbint,
27700 @value{GDBN} Internals}.
27702 These commands take an optional parameter, a file name to which to
27703 write the information.
27705 @kindex maint print reggroups
27706 @item maint print reggroups @r{[}@var{file}@r{]}
27707 Print @value{GDBN}'s internal register group data structures. The
27708 optional argument @var{file} tells to what file to write the
27711 The register groups info looks like this:
27714 (@value{GDBP}) @kbd{maint print reggroups}
27727 This command forces @value{GDBN} to flush its internal register cache.
27729 @kindex maint print objfiles
27730 @cindex info for known object files
27731 @item maint print objfiles
27732 Print a dump of all known object files. For each object file, this
27733 command prints its name, address in memory, and all of its psymtabs
27736 @kindex maint print statistics
27737 @cindex bcache statistics
27738 @item maint print statistics
27739 This command prints, for each object file in the program, various data
27740 about that object file followed by the byte cache (@dfn{bcache})
27741 statistics for the object file. The objfile data includes the number
27742 of minimal, partial, full, and stabs symbols, the number of types
27743 defined by the objfile, the number of as yet unexpanded psym tables,
27744 the number of line tables and string tables, and the amount of memory
27745 used by the various tables. The bcache statistics include the counts,
27746 sizes, and counts of duplicates of all and unique objects, max,
27747 average, and median entry size, total memory used and its overhead and
27748 savings, and various measures of the hash table size and chain
27751 @kindex maint print target-stack
27752 @cindex target stack description
27753 @item maint print target-stack
27754 A @dfn{target} is an interface between the debugger and a particular
27755 kind of file or process. Targets can be stacked in @dfn{strata},
27756 so that more than one target can potentially respond to a request.
27757 In particular, memory accesses will walk down the stack of targets
27758 until they find a target that is interested in handling that particular
27761 This command prints a short description of each layer that was pushed on
27762 the @dfn{target stack}, starting from the top layer down to the bottom one.
27764 @kindex maint print type
27765 @cindex type chain of a data type
27766 @item maint print type @var{expr}
27767 Print the type chain for a type specified by @var{expr}. The argument
27768 can be either a type name or a symbol. If it is a symbol, the type of
27769 that symbol is described. The type chain produced by this command is
27770 a recursive definition of the data type as stored in @value{GDBN}'s
27771 data structures, including its flags and contained types.
27773 @kindex maint set dwarf2 max-cache-age
27774 @kindex maint show dwarf2 max-cache-age
27775 @item maint set dwarf2 max-cache-age
27776 @itemx maint show dwarf2 max-cache-age
27777 Control the DWARF 2 compilation unit cache.
27779 @cindex DWARF 2 compilation units cache
27780 In object files with inter-compilation-unit references, such as those
27781 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF 2
27782 reader needs to frequently refer to previously read compilation units.
27783 This setting controls how long a compilation unit will remain in the
27784 cache if it is not referenced. A higher limit means that cached
27785 compilation units will be stored in memory longer, and more total
27786 memory will be used. Setting it to zero disables caching, which will
27787 slow down @value{GDBN} startup, but reduce memory consumption.
27789 @kindex maint set profile
27790 @kindex maint show profile
27791 @cindex profiling GDB
27792 @item maint set profile
27793 @itemx maint show profile
27794 Control profiling of @value{GDBN}.
27796 Profiling will be disabled until you use the @samp{maint set profile}
27797 command to enable it. When you enable profiling, the system will begin
27798 collecting timing and execution count data; when you disable profiling or
27799 exit @value{GDBN}, the results will be written to a log file. Remember that
27800 if you use profiling, @value{GDBN} will overwrite the profiling log file
27801 (often called @file{gmon.out}). If you have a record of important profiling
27802 data in a @file{gmon.out} file, be sure to move it to a safe location.
27804 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
27805 compiled with the @samp{-pg} compiler option.
27807 @kindex maint set show-debug-regs
27808 @kindex maint show show-debug-regs
27809 @cindex hardware debug registers
27810 @item maint set show-debug-regs
27811 @itemx maint show show-debug-regs
27812 Control whether to show variables that mirror the hardware debug
27813 registers. Use @code{ON} to enable, @code{OFF} to disable. If
27814 enabled, the debug registers values are shown when @value{GDBN} inserts or
27815 removes a hardware breakpoint or watchpoint, and when the inferior
27816 triggers a hardware-assisted breakpoint or watchpoint.
27818 @kindex maint space
27819 @cindex memory used by commands
27821 Control whether to display memory usage for each command. If set to a
27822 nonzero value, @value{GDBN} will display how much memory each command
27823 took, following the command's own output. This can also be requested
27824 by invoking @value{GDBN} with the @option{--statistics} command-line
27825 switch (@pxref{Mode Options}).
27828 @cindex time of command execution
27830 Control whether to display the execution time for each command. If
27831 set to a nonzero value, @value{GDBN} will display how much time it
27832 took to execute each command, following the command's own output.
27833 The time is not printed for the commands that run the target, since
27834 there's no mechanism currently to compute how much time was spend
27835 by @value{GDBN} and how much time was spend by the program been debugged.
27836 it's not possibly currently
27837 This can also be requested by invoking @value{GDBN} with the
27838 @option{--statistics} command-line switch (@pxref{Mode Options}).
27840 @kindex maint translate-address
27841 @item maint translate-address @r{[}@var{section}@r{]} @var{addr}
27842 Find the symbol stored at the location specified by the address
27843 @var{addr} and an optional section name @var{section}. If found,
27844 @value{GDBN} prints the name of the closest symbol and an offset from
27845 the symbol's location to the specified address. This is similar to
27846 the @code{info address} command (@pxref{Symbols}), except that this
27847 command also allows to find symbols in other sections.
27849 If section was not specified, the section in which the symbol was found
27850 is also printed. For dynamically linked executables, the name of
27851 executable or shared library containing the symbol is printed as well.
27855 The following command is useful for non-interactive invocations of
27856 @value{GDBN}, such as in the test suite.
27859 @item set watchdog @var{nsec}
27860 @kindex set watchdog
27861 @cindex watchdog timer
27862 @cindex timeout for commands
27863 Set the maximum number of seconds @value{GDBN} will wait for the
27864 target operation to finish. If this time expires, @value{GDBN}
27865 reports and error and the command is aborted.
27867 @item show watchdog
27868 Show the current setting of the target wait timeout.
27871 @node Remote Protocol
27872 @appendix @value{GDBN} Remote Serial Protocol
27877 * Stop Reply Packets::
27878 * General Query Packets::
27879 * Register Packet Format::
27880 * Tracepoint Packets::
27881 * Host I/O Packets::
27883 * Notification Packets::
27884 * Remote Non-Stop::
27885 * Packet Acknowledgment::
27887 * File-I/O Remote Protocol Extension::
27888 * Library List Format::
27889 * Memory Map Format::
27895 There may be occasions when you need to know something about the
27896 protocol---for example, if there is only one serial port to your target
27897 machine, you might want your program to do something special if it
27898 recognizes a packet meant for @value{GDBN}.
27900 In the examples below, @samp{->} and @samp{<-} are used to indicate
27901 transmitted and received data, respectively.
27903 @cindex protocol, @value{GDBN} remote serial
27904 @cindex serial protocol, @value{GDBN} remote
27905 @cindex remote serial protocol
27906 All @value{GDBN} commands and responses (other than acknowledgments
27907 and notifications, see @ref{Notification Packets}) are sent as a
27908 @var{packet}. A @var{packet} is introduced with the character
27909 @samp{$}, the actual @var{packet-data}, and the terminating character
27910 @samp{#} followed by a two-digit @var{checksum}:
27913 @code{$}@var{packet-data}@code{#}@var{checksum}
27917 @cindex checksum, for @value{GDBN} remote
27919 The two-digit @var{checksum} is computed as the modulo 256 sum of all
27920 characters between the leading @samp{$} and the trailing @samp{#} (an
27921 eight bit unsigned checksum).
27923 Implementors should note that prior to @value{GDBN} 5.0 the protocol
27924 specification also included an optional two-digit @var{sequence-id}:
27927 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
27930 @cindex sequence-id, for @value{GDBN} remote
27932 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
27933 has never output @var{sequence-id}s. Stubs that handle packets added
27934 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
27936 When either the host or the target machine receives a packet, the first
27937 response expected is an acknowledgment: either @samp{+} (to indicate
27938 the package was received correctly) or @samp{-} (to request
27942 -> @code{$}@var{packet-data}@code{#}@var{checksum}
27947 The @samp{+}/@samp{-} acknowledgments can be disabled
27948 once a connection is established.
27949 @xref{Packet Acknowledgment}, for details.
27951 The host (@value{GDBN}) sends @var{command}s, and the target (the
27952 debugging stub incorporated in your program) sends a @var{response}. In
27953 the case of step and continue @var{command}s, the response is only sent
27954 when the operation has completed, and the target has again stopped all
27955 threads in all attached processes. This is the default all-stop mode
27956 behavior, but the remote protocol also supports @value{GDBN}'s non-stop
27957 execution mode; see @ref{Remote Non-Stop}, for details.
27959 @var{packet-data} consists of a sequence of characters with the
27960 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
27963 @cindex remote protocol, field separator
27964 Fields within the packet should be separated using @samp{,} @samp{;} or
27965 @samp{:}. Except where otherwise noted all numbers are represented in
27966 @sc{hex} with leading zeros suppressed.
27968 Implementors should note that prior to @value{GDBN} 5.0, the character
27969 @samp{:} could not appear as the third character in a packet (as it
27970 would potentially conflict with the @var{sequence-id}).
27972 @cindex remote protocol, binary data
27973 @anchor{Binary Data}
27974 Binary data in most packets is encoded either as two hexadecimal
27975 digits per byte of binary data. This allowed the traditional remote
27976 protocol to work over connections which were only seven-bit clean.
27977 Some packets designed more recently assume an eight-bit clean
27978 connection, and use a more efficient encoding to send and receive
27981 The binary data representation uses @code{7d} (@sc{ascii} @samp{@}})
27982 as an escape character. Any escaped byte is transmitted as the escape
27983 character followed by the original character XORed with @code{0x20}.
27984 For example, the byte @code{0x7d} would be transmitted as the two
27985 bytes @code{0x7d 0x5d}. The bytes @code{0x23} (@sc{ascii} @samp{#}),
27986 @code{0x24} (@sc{ascii} @samp{$}), and @code{0x7d} (@sc{ascii}
27987 @samp{@}}) must always be escaped. Responses sent by the stub
27988 must also escape @code{0x2a} (@sc{ascii} @samp{*}), so that it
27989 is not interpreted as the start of a run-length encoded sequence
27992 Response @var{data} can be run-length encoded to save space.
27993 Run-length encoding replaces runs of identical characters with one
27994 instance of the repeated character, followed by a @samp{*} and a
27995 repeat count. The repeat count is itself sent encoded, to avoid
27996 binary characters in @var{data}: a value of @var{n} is sent as
27997 @code{@var{n}+29}. For a repeat count greater or equal to 3, this
27998 produces a printable @sc{ascii} character, e.g.@: a space (@sc{ascii}
27999 code 32) for a repeat count of 3. (This is because run-length
28000 encoding starts to win for counts 3 or more.) Thus, for example,
28001 @samp{0* } is a run-length encoding of ``0000'': the space character
28002 after @samp{*} means repeat the leading @code{0} @w{@code{32 - 29 =
28005 The printable characters @samp{#} and @samp{$} or with a numeric value
28006 greater than 126 must not be used. Runs of six repeats (@samp{#}) or
28007 seven repeats (@samp{$}) can be expanded using a repeat count of only
28008 five (@samp{"}). For example, @samp{00000000} can be encoded as
28011 The error response returned for some packets includes a two character
28012 error number. That number is not well defined.
28014 @cindex empty response, for unsupported packets
28015 For any @var{command} not supported by the stub, an empty response
28016 (@samp{$#00}) should be returned. That way it is possible to extend the
28017 protocol. A newer @value{GDBN} can tell if a packet is supported based
28020 A stub is required to support the @samp{g}, @samp{G}, @samp{m}, @samp{M},
28021 @samp{c}, and @samp{s} @var{command}s. All other @var{command}s are
28027 The following table provides a complete list of all currently defined
28028 @var{command}s and their corresponding response @var{data}.
28029 @xref{File-I/O Remote Protocol Extension}, for details about the File
28030 I/O extension of the remote protocol.
28032 Each packet's description has a template showing the packet's overall
28033 syntax, followed by an explanation of the packet's meaning. We
28034 include spaces in some of the templates for clarity; these are not
28035 part of the packet's syntax. No @value{GDBN} packet uses spaces to
28036 separate its components. For example, a template like @samp{foo
28037 @var{bar} @var{baz}} describes a packet beginning with the three ASCII
28038 bytes @samp{foo}, followed by a @var{bar}, followed directly by a
28039 @var{baz}. @value{GDBN} does not transmit a space character between the
28040 @samp{foo} and the @var{bar}, or between the @var{bar} and the
28043 @cindex @var{thread-id}, in remote protocol
28044 @anchor{thread-id syntax}
28045 Several packets and replies include a @var{thread-id} field to identify
28046 a thread. Normally these are positive numbers with a target-specific
28047 interpretation, formatted as big-endian hex strings. A @var{thread-id}
28048 can also be a literal @samp{-1} to indicate all threads, or @samp{0} to
28051 In addition, the remote protocol supports a multiprocess feature in
28052 which the @var{thread-id} syntax is extended to optionally include both
28053 process and thread ID fields, as @samp{p@var{pid}.@var{tid}}.
28054 The @var{pid} (process) and @var{tid} (thread) components each have the
28055 format described above: a positive number with target-specific
28056 interpretation formatted as a big-endian hex string, literal @samp{-1}
28057 to indicate all processes or threads (respectively), or @samp{0} to
28058 indicate an arbitrary process or thread. Specifying just a process, as
28059 @samp{p@var{pid}}, is equivalent to @samp{p@var{pid}.-1}. It is an
28060 error to specify all processes but a specific thread, such as
28061 @samp{p-1.@var{tid}}. Note that the @samp{p} prefix is @emph{not} used
28062 for those packets and replies explicitly documented to include a process
28063 ID, rather than a @var{thread-id}.
28065 The multiprocess @var{thread-id} syntax extensions are only used if both
28066 @value{GDBN} and the stub report support for the @samp{multiprocess}
28067 feature using @samp{qSupported}. @xref{multiprocess extensions}, for
28070 Note that all packet forms beginning with an upper- or lower-case
28071 letter, other than those described here, are reserved for future use.
28073 Here are the packet descriptions.
28078 @cindex @samp{!} packet
28079 @anchor{extended mode}
28080 Enable extended mode. In extended mode, the remote server is made
28081 persistent. The @samp{R} packet is used to restart the program being
28087 The remote target both supports and has enabled extended mode.
28091 @cindex @samp{?} packet
28092 Indicate the reason the target halted. The reply is the same as for
28093 step and continue. This packet has a special interpretation when the
28094 target is in non-stop mode; see @ref{Remote Non-Stop}.
28097 @xref{Stop Reply Packets}, for the reply specifications.
28099 @item A @var{arglen},@var{argnum},@var{arg},@dots{}
28100 @cindex @samp{A} packet
28101 Initialized @code{argv[]} array passed into program. @var{arglen}
28102 specifies the number of bytes in the hex encoded byte stream
28103 @var{arg}. See @code{gdbserver} for more details.
28108 The arguments were set.
28114 @cindex @samp{b} packet
28115 (Don't use this packet; its behavior is not well-defined.)
28116 Change the serial line speed to @var{baud}.
28118 JTC: @emph{When does the transport layer state change? When it's
28119 received, or after the ACK is transmitted. In either case, there are
28120 problems if the command or the acknowledgment packet is dropped.}
28122 Stan: @emph{If people really wanted to add something like this, and get
28123 it working for the first time, they ought to modify ser-unix.c to send
28124 some kind of out-of-band message to a specially-setup stub and have the
28125 switch happen "in between" packets, so that from remote protocol's point
28126 of view, nothing actually happened.}
28128 @item B @var{addr},@var{mode}
28129 @cindex @samp{B} packet
28130 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
28131 breakpoint at @var{addr}.
28133 Don't use this packet. Use the @samp{Z} and @samp{z} packets instead
28134 (@pxref{insert breakpoint or watchpoint packet}).
28136 @cindex @samp{bc} packet
28139 Backward continue. Execute the target system in reverse. No parameter.
28140 @xref{Reverse Execution}, for more information.
28143 @xref{Stop Reply Packets}, for the reply specifications.
28145 @cindex @samp{bs} packet
28148 Backward single step. Execute one instruction in reverse. No parameter.
28149 @xref{Reverse Execution}, for more information.
28152 @xref{Stop Reply Packets}, for the reply specifications.
28154 @item c @r{[}@var{addr}@r{]}
28155 @cindex @samp{c} packet
28156 Continue. @var{addr} is address to resume. If @var{addr} is omitted,
28157 resume at current address.
28160 @xref{Stop Reply Packets}, for the reply specifications.
28162 @item C @var{sig}@r{[};@var{addr}@r{]}
28163 @cindex @samp{C} packet
28164 Continue with signal @var{sig} (hex signal number). If
28165 @samp{;@var{addr}} is omitted, resume at same address.
28168 @xref{Stop Reply Packets}, for the reply specifications.
28171 @cindex @samp{d} packet
28174 Don't use this packet; instead, define a general set packet
28175 (@pxref{General Query Packets}).
28179 @cindex @samp{D} packet
28180 The first form of the packet is used to detach @value{GDBN} from the
28181 remote system. It is sent to the remote target
28182 before @value{GDBN} disconnects via the @code{detach} command.
28184 The second form, including a process ID, is used when multiprocess
28185 protocol extensions are enabled (@pxref{multiprocess extensions}), to
28186 detach only a specific process. The @var{pid} is specified as a
28187 big-endian hex string.
28197 @item F @var{RC},@var{EE},@var{CF};@var{XX}
28198 @cindex @samp{F} packet
28199 A reply from @value{GDBN} to an @samp{F} packet sent by the target.
28200 This is part of the File-I/O protocol extension. @xref{File-I/O
28201 Remote Protocol Extension}, for the specification.
28204 @anchor{read registers packet}
28205 @cindex @samp{g} packet
28206 Read general registers.
28210 @item @var{XX@dots{}}
28211 Each byte of register data is described by two hex digits. The bytes
28212 with the register are transmitted in target byte order. The size of
28213 each register and their position within the @samp{g} packet are
28214 determined by the @value{GDBN} internal gdbarch functions
28215 @code{DEPRECATED_REGISTER_RAW_SIZE} and @code{gdbarch_register_name}. The
28216 specification of several standard @samp{g} packets is specified below.
28221 @item G @var{XX@dots{}}
28222 @cindex @samp{G} packet
28223 Write general registers. @xref{read registers packet}, for a
28224 description of the @var{XX@dots{}} data.
28234 @item H @var{c} @var{thread-id}
28235 @cindex @samp{H} packet
28236 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
28237 @samp{G}, et.al.). @var{c} depends on the operation to be performed: it
28238 should be @samp{c} for step and continue operations, @samp{g} for other
28239 operations. The thread designator @var{thread-id} has the format and
28240 interpretation described in @ref{thread-id syntax}.
28251 @c 'H': How restrictive (or permissive) is the thread model. If a
28252 @c thread is selected and stopped, are other threads allowed
28253 @c to continue to execute? As I mentioned above, I think the
28254 @c semantics of each command when a thread is selected must be
28255 @c described. For example:
28257 @c 'g': If the stub supports threads and a specific thread is
28258 @c selected, returns the register block from that thread;
28259 @c otherwise returns current registers.
28261 @c 'G' If the stub supports threads and a specific thread is
28262 @c selected, sets the registers of the register block of
28263 @c that thread; otherwise sets current registers.
28265 @item i @r{[}@var{addr}@r{[},@var{nnn}@r{]]}
28266 @anchor{cycle step packet}
28267 @cindex @samp{i} packet
28268 Step the remote target by a single clock cycle. If @samp{,@var{nnn}} is
28269 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
28270 step starting at that address.
28273 @cindex @samp{I} packet
28274 Signal, then cycle step. @xref{step with signal packet}. @xref{cycle
28278 @cindex @samp{k} packet
28281 FIXME: @emph{There is no description of how to operate when a specific
28282 thread context has been selected (i.e.@: does 'k' kill only that
28285 @item m @var{addr},@var{length}
28286 @cindex @samp{m} packet
28287 Read @var{length} bytes of memory starting at address @var{addr}.
28288 Note that @var{addr} may not be aligned to any particular boundary.
28290 The stub need not use any particular size or alignment when gathering
28291 data from memory for the response; even if @var{addr} is word-aligned
28292 and @var{length} is a multiple of the word size, the stub is free to
28293 use byte accesses, or not. For this reason, this packet may not be
28294 suitable for accessing memory-mapped I/O devices.
28295 @cindex alignment of remote memory accesses
28296 @cindex size of remote memory accesses
28297 @cindex memory, alignment and size of remote accesses
28301 @item @var{XX@dots{}}
28302 Memory contents; each byte is transmitted as a two-digit hexadecimal
28303 number. The reply may contain fewer bytes than requested if the
28304 server was able to read only part of the region of memory.
28309 @item M @var{addr},@var{length}:@var{XX@dots{}}
28310 @cindex @samp{M} packet
28311 Write @var{length} bytes of memory starting at address @var{addr}.
28312 @var{XX@dots{}} is the data; each byte is transmitted as a two-digit
28313 hexadecimal number.
28320 for an error (this includes the case where only part of the data was
28325 @cindex @samp{p} packet
28326 Read the value of register @var{n}; @var{n} is in hex.
28327 @xref{read registers packet}, for a description of how the returned
28328 register value is encoded.
28332 @item @var{XX@dots{}}
28333 the register's value
28337 Indicating an unrecognized @var{query}.
28340 @item P @var{n@dots{}}=@var{r@dots{}}
28341 @anchor{write register packet}
28342 @cindex @samp{P} packet
28343 Write register @var{n@dots{}} with value @var{r@dots{}}. The register
28344 number @var{n} is in hexadecimal, and @var{r@dots{}} contains two hex
28345 digits for each byte in the register (target byte order).
28355 @item q @var{name} @var{params}@dots{}
28356 @itemx Q @var{name} @var{params}@dots{}
28357 @cindex @samp{q} packet
28358 @cindex @samp{Q} packet
28359 General query (@samp{q}) and set (@samp{Q}). These packets are
28360 described fully in @ref{General Query Packets}.
28363 @cindex @samp{r} packet
28364 Reset the entire system.
28366 Don't use this packet; use the @samp{R} packet instead.
28369 @cindex @samp{R} packet
28370 Restart the program being debugged. @var{XX}, while needed, is ignored.
28371 This packet is only available in extended mode (@pxref{extended mode}).
28373 The @samp{R} packet has no reply.
28375 @item s @r{[}@var{addr}@r{]}
28376 @cindex @samp{s} packet
28377 Single step. @var{addr} is the address at which to resume. If
28378 @var{addr} is omitted, resume at same address.
28381 @xref{Stop Reply Packets}, for the reply specifications.
28383 @item S @var{sig}@r{[};@var{addr}@r{]}
28384 @anchor{step with signal packet}
28385 @cindex @samp{S} packet
28386 Step with signal. This is analogous to the @samp{C} packet, but
28387 requests a single-step, rather than a normal resumption of execution.
28390 @xref{Stop Reply Packets}, for the reply specifications.
28392 @item t @var{addr}:@var{PP},@var{MM}
28393 @cindex @samp{t} packet
28394 Search backwards starting at address @var{addr} for a match with pattern
28395 @var{PP} and mask @var{MM}. @var{PP} and @var{MM} are 4 bytes.
28396 @var{addr} must be at least 3 digits.
28398 @item T @var{thread-id}
28399 @cindex @samp{T} packet
28400 Find out if the thread @var{thread-id} is alive. @xref{thread-id syntax}.
28405 thread is still alive
28411 Packets starting with @samp{v} are identified by a multi-letter name,
28412 up to the first @samp{;} or @samp{?} (or the end of the packet).
28414 @item vAttach;@var{pid}
28415 @cindex @samp{vAttach} packet
28416 Attach to a new process with the specified process ID @var{pid}.
28417 The process ID is a
28418 hexadecimal integer identifying the process. In all-stop mode, all
28419 threads in the attached process are stopped; in non-stop mode, it may be
28420 attached without being stopped if that is supported by the target.
28422 @c In non-stop mode, on a successful vAttach, the stub should set the
28423 @c current thread to a thread of the newly-attached process. After
28424 @c attaching, GDB queries for the attached process's thread ID with qC.
28425 @c Also note that, from a user perspective, whether or not the
28426 @c target is stopped on attach in non-stop mode depends on whether you
28427 @c use the foreground or background version of the attach command, not
28428 @c on what vAttach does; GDB does the right thing with respect to either
28429 @c stopping or restarting threads.
28431 This packet is only available in extended mode (@pxref{extended mode}).
28437 @item @r{Any stop packet}
28438 for success in all-stop mode (@pxref{Stop Reply Packets})
28440 for success in non-stop mode (@pxref{Remote Non-Stop})
28443 @item vCont@r{[};@var{action}@r{[}:@var{thread-id}@r{]]}@dots{}
28444 @cindex @samp{vCont} packet
28445 Resume the inferior, specifying different actions for each thread.
28446 If an action is specified with no @var{thread-id}, then it is applied to any
28447 threads that don't have a specific action specified; if no default action is
28448 specified then other threads should remain stopped in all-stop mode and
28449 in their current state in non-stop mode.
28450 Specifying multiple
28451 default actions is an error; specifying no actions is also an error.
28452 Thread IDs are specified using the syntax described in @ref{thread-id syntax}.
28454 Currently supported actions are:
28460 Continue with signal @var{sig}. The signal @var{sig} should be two hex digits.
28464 Step with signal @var{sig}. The signal @var{sig} should be two hex digits.
28469 The optional argument @var{addr} normally associated with the
28470 @samp{c}, @samp{C}, @samp{s}, and @samp{S} packets is
28471 not supported in @samp{vCont}.
28473 The @samp{t} action is only relevant in non-stop mode
28474 (@pxref{Remote Non-Stop}) and may be ignored by the stub otherwise.
28475 A stop reply should be generated for any affected thread not already stopped.
28476 When a thread is stopped by means of a @samp{t} action,
28477 the corresponding stop reply should indicate that the thread has stopped with
28478 signal @samp{0}, regardless of whether the target uses some other signal
28479 as an implementation detail.
28482 @xref{Stop Reply Packets}, for the reply specifications.
28485 @cindex @samp{vCont?} packet
28486 Request a list of actions supported by the @samp{vCont} packet.
28490 @item vCont@r{[};@var{action}@dots{}@r{]}
28491 The @samp{vCont} packet is supported. Each @var{action} is a supported
28492 command in the @samp{vCont} packet.
28494 The @samp{vCont} packet is not supported.
28497 @item vFile:@var{operation}:@var{parameter}@dots{}
28498 @cindex @samp{vFile} packet
28499 Perform a file operation on the target system. For details,
28500 see @ref{Host I/O Packets}.
28502 @item vFlashErase:@var{addr},@var{length}
28503 @cindex @samp{vFlashErase} packet
28504 Direct the stub to erase @var{length} bytes of flash starting at
28505 @var{addr}. The region may enclose any number of flash blocks, but
28506 its start and end must fall on block boundaries, as indicated by the
28507 flash block size appearing in the memory map (@pxref{Memory Map
28508 Format}). @value{GDBN} groups flash memory programming operations
28509 together, and sends a @samp{vFlashDone} request after each group; the
28510 stub is allowed to delay erase operation until the @samp{vFlashDone}
28511 packet is received.
28513 The stub must support @samp{vCont} if it reports support for
28514 multiprocess extensions (@pxref{multiprocess extensions}). Note that in
28515 this case @samp{vCont} actions can be specified to apply to all threads
28516 in a process by using the @samp{p@var{pid}.-1} form of the
28527 @item vFlashWrite:@var{addr}:@var{XX@dots{}}
28528 @cindex @samp{vFlashWrite} packet
28529 Direct the stub to write data to flash address @var{addr}. The data
28530 is passed in binary form using the same encoding as for the @samp{X}
28531 packet (@pxref{Binary Data}). The memory ranges specified by
28532 @samp{vFlashWrite} packets preceding a @samp{vFlashDone} packet must
28533 not overlap, and must appear in order of increasing addresses
28534 (although @samp{vFlashErase} packets for higher addresses may already
28535 have been received; the ordering is guaranteed only between
28536 @samp{vFlashWrite} packets). If a packet writes to an address that was
28537 neither erased by a preceding @samp{vFlashErase} packet nor by some other
28538 target-specific method, the results are unpredictable.
28546 for vFlashWrite addressing non-flash memory
28552 @cindex @samp{vFlashDone} packet
28553 Indicate to the stub that flash programming operation is finished.
28554 The stub is permitted to delay or batch the effects of a group of
28555 @samp{vFlashErase} and @samp{vFlashWrite} packets until a
28556 @samp{vFlashDone} packet is received. The contents of the affected
28557 regions of flash memory are unpredictable until the @samp{vFlashDone}
28558 request is completed.
28560 @item vKill;@var{pid}
28561 @cindex @samp{vKill} packet
28562 Kill the process with the specified process ID. @var{pid} is a
28563 hexadecimal integer identifying the process. This packet is used in
28564 preference to @samp{k} when multiprocess protocol extensions are
28565 supported; see @ref{multiprocess extensions}.
28575 @item vRun;@var{filename}@r{[};@var{argument}@r{]}@dots{}
28576 @cindex @samp{vRun} packet
28577 Run the program @var{filename}, passing it each @var{argument} on its
28578 command line. The file and arguments are hex-encoded strings. If
28579 @var{filename} is an empty string, the stub may use a default program
28580 (e.g.@: the last program run). The program is created in the stopped
28583 @c FIXME: What about non-stop mode?
28585 This packet is only available in extended mode (@pxref{extended mode}).
28591 @item @r{Any stop packet}
28592 for success (@pxref{Stop Reply Packets})
28596 @anchor{vStopped packet}
28597 @cindex @samp{vStopped} packet
28599 In non-stop mode (@pxref{Remote Non-Stop}), acknowledge a previous stop
28600 reply and prompt for the stub to report another one.
28604 @item @r{Any stop packet}
28605 if there is another unreported stop event (@pxref{Stop Reply Packets})
28607 if there are no unreported stop events
28610 @item X @var{addr},@var{length}:@var{XX@dots{}}
28612 @cindex @samp{X} packet
28613 Write data to memory, where the data is transmitted in binary.
28614 @var{addr} is address, @var{length} is number of bytes,
28615 @samp{@var{XX}@dots{}} is binary data (@pxref{Binary Data}).
28625 @item z @var{type},@var{addr},@var{length}
28626 @itemx Z @var{type},@var{addr},@var{length}
28627 @anchor{insert breakpoint or watchpoint packet}
28628 @cindex @samp{z} packet
28629 @cindex @samp{Z} packets
28630 Insert (@samp{Z}) or remove (@samp{z}) a @var{type} breakpoint or
28631 watchpoint starting at address @var{address} and covering the next
28632 @var{length} bytes.
28634 Each breakpoint and watchpoint packet @var{type} is documented
28637 @emph{Implementation notes: A remote target shall return an empty string
28638 for an unrecognized breakpoint or watchpoint packet @var{type}. A
28639 remote target shall support either both or neither of a given
28640 @samp{Z@var{type}@dots{}} and @samp{z@var{type}@dots{}} packet pair. To
28641 avoid potential problems with duplicate packets, the operations should
28642 be implemented in an idempotent way.}
28644 @item z0,@var{addr},@var{length}
28645 @itemx Z0,@var{addr},@var{length}
28646 @cindex @samp{z0} packet
28647 @cindex @samp{Z0} packet
28648 Insert (@samp{Z0}) or remove (@samp{z0}) a memory breakpoint at address
28649 @var{addr} of size @var{length}.
28651 A memory breakpoint is implemented by replacing the instruction at
28652 @var{addr} with a software breakpoint or trap instruction. The
28653 @var{length} is used by targets that indicates the size of the
28654 breakpoint (in bytes) that should be inserted (e.g., the @sc{arm} and
28655 @sc{mips} can insert either a 2 or 4 byte breakpoint).
28657 @emph{Implementation note: It is possible for a target to copy or move
28658 code that contains memory breakpoints (e.g., when implementing
28659 overlays). The behavior of this packet, in the presence of such a
28660 target, is not defined.}
28672 @item z1,@var{addr},@var{length}
28673 @itemx Z1,@var{addr},@var{length}
28674 @cindex @samp{z1} packet
28675 @cindex @samp{Z1} packet
28676 Insert (@samp{Z1}) or remove (@samp{z1}) a hardware breakpoint at
28677 address @var{addr} of size @var{length}.
28679 A hardware breakpoint is implemented using a mechanism that is not
28680 dependant on being able to modify the target's memory.
28682 @emph{Implementation note: A hardware breakpoint is not affected by code
28695 @item z2,@var{addr},@var{length}
28696 @itemx Z2,@var{addr},@var{length}
28697 @cindex @samp{z2} packet
28698 @cindex @samp{Z2} packet
28699 Insert (@samp{Z2}) or remove (@samp{z2}) a write watchpoint.
28711 @item z3,@var{addr},@var{length}
28712 @itemx Z3,@var{addr},@var{length}
28713 @cindex @samp{z3} packet
28714 @cindex @samp{Z3} packet
28715 Insert (@samp{Z3}) or remove (@samp{z3}) a read watchpoint.
28727 @item z4,@var{addr},@var{length}
28728 @itemx Z4,@var{addr},@var{length}
28729 @cindex @samp{z4} packet
28730 @cindex @samp{Z4} packet
28731 Insert (@samp{Z4}) or remove (@samp{z4}) an access watchpoint.
28745 @node Stop Reply Packets
28746 @section Stop Reply Packets
28747 @cindex stop reply packets
28749 The @samp{C}, @samp{c}, @samp{S}, @samp{s}, @samp{vCont},
28750 @samp{vAttach}, @samp{vRun}, @samp{vStopped}, and @samp{?} packets can
28751 receive any of the below as a reply. Except for @samp{?}
28752 and @samp{vStopped}, that reply is only returned
28753 when the target halts. In the below the exact meaning of @dfn{signal
28754 number} is defined by the header @file{include/gdb/signals.h} in the
28755 @value{GDBN} source code.
28757 As in the description of request packets, we include spaces in the
28758 reply templates for clarity; these are not part of the reply packet's
28759 syntax. No @value{GDBN} stop reply packet uses spaces to separate its
28765 The program received signal number @var{AA} (a two-digit hexadecimal
28766 number). This is equivalent to a @samp{T} response with no
28767 @var{n}:@var{r} pairs.
28769 @item T @var{AA} @var{n1}:@var{r1};@var{n2}:@var{r2};@dots{}
28770 @cindex @samp{T} packet reply
28771 The program received signal number @var{AA} (a two-digit hexadecimal
28772 number). This is equivalent to an @samp{S} response, except that the
28773 @samp{@var{n}:@var{r}} pairs can carry values of important registers
28774 and other information directly in the stop reply packet, reducing
28775 round-trip latency. Single-step and breakpoint traps are reported
28776 this way. Each @samp{@var{n}:@var{r}} pair is interpreted as follows:
28780 If @var{n} is a hexadecimal number, it is a register number, and the
28781 corresponding @var{r} gives that register's value. @var{r} is a
28782 series of bytes in target byte order, with each byte given by a
28783 two-digit hex number.
28786 If @var{n} is @samp{thread}, then @var{r} is the @var{thread-id} of
28787 the stopped thread, as specified in @ref{thread-id syntax}.
28790 If @var{n} is a recognized @dfn{stop reason}, it describes a more
28791 specific event that stopped the target. The currently defined stop
28792 reasons are listed below. @var{aa} should be @samp{05}, the trap
28793 signal. At most one stop reason should be present.
28796 Otherwise, @value{GDBN} should ignore this @samp{@var{n}:@var{r}} pair
28797 and go on to the next; this allows us to extend the protocol in the
28801 The currently defined stop reasons are:
28807 The packet indicates a watchpoint hit, and @var{r} is the data address, in
28810 @cindex shared library events, remote reply
28812 The packet indicates that the loaded libraries have changed.
28813 @value{GDBN} should use @samp{qXfer:libraries:read} to fetch a new
28814 list of loaded libraries. @var{r} is ignored.
28816 @cindex replay log events, remote reply
28818 The packet indicates that the target cannot continue replaying
28819 logged execution events, because it has reached the end (or the
28820 beginning when executing backward) of the log. The value of @var{r}
28821 will be either @samp{begin} or @samp{end}. @xref{Reverse Execution},
28822 for more information.
28828 @itemx W @var{AA} ; process:@var{pid}
28829 The process exited, and @var{AA} is the exit status. This is only
28830 applicable to certain targets.
28832 The second form of the response, including the process ID of the exited
28833 process, can be used only when @value{GDBN} has reported support for
28834 multiprocess protocol extensions; see @ref{multiprocess extensions}.
28835 The @var{pid} is formatted as a big-endian hex string.
28838 @itemx X @var{AA} ; process:@var{pid}
28839 The process terminated with signal @var{AA}.
28841 The second form of the response, including the process ID of the
28842 terminated process, can be used only when @value{GDBN} has reported
28843 support for multiprocess protocol extensions; see @ref{multiprocess
28844 extensions}. The @var{pid} is formatted as a big-endian hex string.
28846 @item O @var{XX}@dots{}
28847 @samp{@var{XX}@dots{}} is hex encoding of @sc{ascii} data, to be
28848 written as the program's console output. This can happen at any time
28849 while the program is running and the debugger should continue to wait
28850 for @samp{W}, @samp{T}, etc. This reply is not permitted in non-stop mode.
28852 @item F @var{call-id},@var{parameter}@dots{}
28853 @var{call-id} is the identifier which says which host system call should
28854 be called. This is just the name of the function. Translation into the
28855 correct system call is only applicable as it's defined in @value{GDBN}.
28856 @xref{File-I/O Remote Protocol Extension}, for a list of implemented
28859 @samp{@var{parameter}@dots{}} is a list of parameters as defined for
28860 this very system call.
28862 The target replies with this packet when it expects @value{GDBN} to
28863 call a host system call on behalf of the target. @value{GDBN} replies
28864 with an appropriate @samp{F} packet and keeps up waiting for the next
28865 reply packet from the target. The latest @samp{C}, @samp{c}, @samp{S}
28866 or @samp{s} action is expected to be continued. @xref{File-I/O Remote
28867 Protocol Extension}, for more details.
28871 @node General Query Packets
28872 @section General Query Packets
28873 @cindex remote query requests
28875 Packets starting with @samp{q} are @dfn{general query packets};
28876 packets starting with @samp{Q} are @dfn{general set packets}. General
28877 query and set packets are a semi-unified form for retrieving and
28878 sending information to and from the stub.
28880 The initial letter of a query or set packet is followed by a name
28881 indicating what sort of thing the packet applies to. For example,
28882 @value{GDBN} may use a @samp{qSymbol} packet to exchange symbol
28883 definitions with the stub. These packet names follow some
28888 The name must not contain commas, colons or semicolons.
28890 Most @value{GDBN} query and set packets have a leading upper case
28893 The names of custom vendor packets should use a company prefix, in
28894 lower case, followed by a period. For example, packets designed at
28895 the Acme Corporation might begin with @samp{qacme.foo} (for querying
28896 foos) or @samp{Qacme.bar} (for setting bars).
28899 The name of a query or set packet should be separated from any
28900 parameters by a @samp{:}; the parameters themselves should be
28901 separated by @samp{,} or @samp{;}. Stubs must be careful to match the
28902 full packet name, and check for a separator or the end of the packet,
28903 in case two packet names share a common prefix. New packets should not begin
28904 with @samp{qC}, @samp{qP}, or @samp{qL}@footnote{The @samp{qP} and @samp{qL}
28905 packets predate these conventions, and have arguments without any terminator
28906 for the packet name; we suspect they are in widespread use in places that
28907 are difficult to upgrade. The @samp{qC} packet has no arguments, but some
28908 existing stubs (e.g.@: RedBoot) are known to not check for the end of the
28911 Like the descriptions of the other packets, each description here
28912 has a template showing the packet's overall syntax, followed by an
28913 explanation of the packet's meaning. We include spaces in some of the
28914 templates for clarity; these are not part of the packet's syntax. No
28915 @value{GDBN} packet uses spaces to separate its components.
28917 Here are the currently defined query and set packets:
28922 @cindex current thread, remote request
28923 @cindex @samp{qC} packet
28924 Return the current thread ID.
28928 @item QC @var{thread-id}
28929 Where @var{thread-id} is a thread ID as documented in
28930 @ref{thread-id syntax}.
28931 @item @r{(anything else)}
28932 Any other reply implies the old thread ID.
28935 @item qCRC:@var{addr},@var{length}
28936 @cindex CRC of memory block, remote request
28937 @cindex @samp{qCRC} packet
28938 Compute the CRC checksum of a block of memory using CRC-32 defined in
28939 IEEE 802.3. The CRC is computed byte at a time, taking the most
28940 significant bit of each byte first. The initial pattern code
28941 @code{0xffffffff} is used to ensure leading zeros affect the CRC.
28943 @emph{Note:} This is the same CRC used in validating separate debug
28944 files (@pxref{Separate Debug Files, , Debugging Information in Separate
28945 Files}). However the algorithm is slightly different. When validating
28946 separate debug files, the CRC is computed taking the @emph{least}
28947 significant bit of each byte first, and the final result is inverted to
28948 detect trailing zeros.
28953 An error (such as memory fault)
28954 @item C @var{crc32}
28955 The specified memory region's checksum is @var{crc32}.
28959 @itemx qsThreadInfo
28960 @cindex list active threads, remote request
28961 @cindex @samp{qfThreadInfo} packet
28962 @cindex @samp{qsThreadInfo} packet
28963 Obtain a list of all active thread IDs from the target (OS). Since there
28964 may be too many active threads to fit into one reply packet, this query
28965 works iteratively: it may require more than one query/reply sequence to
28966 obtain the entire list of threads. The first query of the sequence will
28967 be the @samp{qfThreadInfo} query; subsequent queries in the
28968 sequence will be the @samp{qsThreadInfo} query.
28970 NOTE: This packet replaces the @samp{qL} query (see below).
28974 @item m @var{thread-id}
28976 @item m @var{thread-id},@var{thread-id}@dots{}
28977 a comma-separated list of thread IDs
28979 (lower case letter @samp{L}) denotes end of list.
28982 In response to each query, the target will reply with a list of one or
28983 more thread IDs, separated by commas.
28984 @value{GDBN} will respond to each reply with a request for more thread
28985 ids (using the @samp{qs} form of the query), until the target responds
28986 with @samp{l} (lower-case el, for @dfn{last}).
28987 Refer to @ref{thread-id syntax}, for the format of the @var{thread-id}
28990 @item qGetTLSAddr:@var{thread-id},@var{offset},@var{lm}
28991 @cindex get thread-local storage address, remote request
28992 @cindex @samp{qGetTLSAddr} packet
28993 Fetch the address associated with thread local storage specified
28994 by @var{thread-id}, @var{offset}, and @var{lm}.
28996 @var{thread-id} is the thread ID associated with the
28997 thread for which to fetch the TLS address. @xref{thread-id syntax}.
28999 @var{offset} is the (big endian, hex encoded) offset associated with the
29000 thread local variable. (This offset is obtained from the debug
29001 information associated with the variable.)
29003 @var{lm} is the (big endian, hex encoded) OS/ABI-specific encoding of the
29004 the load module associated with the thread local storage. For example,
29005 a @sc{gnu}/Linux system will pass the link map address of the shared
29006 object associated with the thread local storage under consideration.
29007 Other operating environments may choose to represent the load module
29008 differently, so the precise meaning of this parameter will vary.
29012 @item @var{XX}@dots{}
29013 Hex encoded (big endian) bytes representing the address of the thread
29014 local storage requested.
29017 An error occurred. @var{nn} are hex digits.
29020 An empty reply indicates that @samp{qGetTLSAddr} is not supported by the stub.
29023 @item qL @var{startflag} @var{threadcount} @var{nextthread}
29024 Obtain thread information from RTOS. Where: @var{startflag} (one hex
29025 digit) is one to indicate the first query and zero to indicate a
29026 subsequent query; @var{threadcount} (two hex digits) is the maximum
29027 number of threads the response packet can contain; and @var{nextthread}
29028 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
29029 returned in the response as @var{argthread}.
29031 Don't use this packet; use the @samp{qfThreadInfo} query instead (see above).
29035 @item qM @var{count} @var{done} @var{argthread} @var{thread}@dots{}
29036 Where: @var{count} (two hex digits) is the number of threads being
29037 returned; @var{done} (one hex digit) is zero to indicate more threads
29038 and one indicates no further threads; @var{argthreadid} (eight hex
29039 digits) is @var{nextthread} from the request packet; @var{thread}@dots{}
29040 is a sequence of thread IDs from the target. @var{threadid} (eight hex
29041 digits). See @code{remote.c:parse_threadlist_response()}.
29045 @cindex section offsets, remote request
29046 @cindex @samp{qOffsets} packet
29047 Get section offsets that the target used when relocating the downloaded
29052 @item Text=@var{xxx};Data=@var{yyy}@r{[};Bss=@var{zzz}@r{]}
29053 Relocate the @code{Text} section by @var{xxx} from its original address.
29054 Relocate the @code{Data} section by @var{yyy} from its original address.
29055 If the object file format provides segment information (e.g.@: @sc{elf}
29056 @samp{PT_LOAD} program headers), @value{GDBN} will relocate entire
29057 segments by the supplied offsets.
29059 @emph{Note: while a @code{Bss} offset may be included in the response,
29060 @value{GDBN} ignores this and instead applies the @code{Data} offset
29061 to the @code{Bss} section.}
29063 @item TextSeg=@var{xxx}@r{[};DataSeg=@var{yyy}@r{]}
29064 Relocate the first segment of the object file, which conventionally
29065 contains program code, to a starting address of @var{xxx}. If
29066 @samp{DataSeg} is specified, relocate the second segment, which
29067 conventionally contains modifiable data, to a starting address of
29068 @var{yyy}. @value{GDBN} will report an error if the object file
29069 does not contain segment information, or does not contain at least
29070 as many segments as mentioned in the reply. Extra segments are
29071 kept at fixed offsets relative to the last relocated segment.
29074 @item qP @var{mode} @var{thread-id}
29075 @cindex thread information, remote request
29076 @cindex @samp{qP} packet
29077 Returns information on @var{thread-id}. Where: @var{mode} is a hex
29078 encoded 32 bit mode; @var{thread-id} is a thread ID
29079 (@pxref{thread-id syntax}).
29081 Don't use this packet; use the @samp{qThreadExtraInfo} query instead
29084 Reply: see @code{remote.c:remote_unpack_thread_info_response()}.
29088 @cindex non-stop mode, remote request
29089 @cindex @samp{QNonStop} packet
29091 Enter non-stop (@samp{QNonStop:1}) or all-stop (@samp{QNonStop:0}) mode.
29092 @xref{Remote Non-Stop}, for more information.
29097 The request succeeded.
29100 An error occurred. @var{nn} are hex digits.
29103 An empty reply indicates that @samp{QNonStop} is not supported by
29107 This packet is not probed by default; the remote stub must request it,
29108 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
29109 Use of this packet is controlled by the @code{set non-stop} command;
29110 @pxref{Non-Stop Mode}.
29112 @item QPassSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
29113 @cindex pass signals to inferior, remote request
29114 @cindex @samp{QPassSignals} packet
29115 @anchor{QPassSignals}
29116 Each listed @var{signal} should be passed directly to the inferior process.
29117 Signals are numbered identically to continue packets and stop replies
29118 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
29119 strictly greater than the previous item. These signals do not need to stop
29120 the inferior, or be reported to @value{GDBN}. All other signals should be
29121 reported to @value{GDBN}. Multiple @samp{QPassSignals} packets do not
29122 combine; any earlier @samp{QPassSignals} list is completely replaced by the
29123 new list. This packet improves performance when using @samp{handle
29124 @var{signal} nostop noprint pass}.
29129 The request succeeded.
29132 An error occurred. @var{nn} are hex digits.
29135 An empty reply indicates that @samp{QPassSignals} is not supported by
29139 Use of this packet is controlled by the @code{set remote pass-signals}
29140 command (@pxref{Remote Configuration, set remote pass-signals}).
29141 This packet is not probed by default; the remote stub must request it,
29142 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
29144 @item qRcmd,@var{command}
29145 @cindex execute remote command, remote request
29146 @cindex @samp{qRcmd} packet
29147 @var{command} (hex encoded) is passed to the local interpreter for
29148 execution. Invalid commands should be reported using the output
29149 string. Before the final result packet, the target may also respond
29150 with a number of intermediate @samp{O@var{output}} console output
29151 packets. @emph{Implementors should note that providing access to a
29152 stubs's interpreter may have security implications}.
29157 A command response with no output.
29159 A command response with the hex encoded output string @var{OUTPUT}.
29161 Indicate a badly formed request.
29163 An empty reply indicates that @samp{qRcmd} is not recognized.
29166 (Note that the @code{qRcmd} packet's name is separated from the
29167 command by a @samp{,}, not a @samp{:}, contrary to the naming
29168 conventions above. Please don't use this packet as a model for new
29171 @item qSearch:memory:@var{address};@var{length};@var{search-pattern}
29172 @cindex searching memory, in remote debugging
29173 @cindex @samp{qSearch:memory} packet
29174 @anchor{qSearch memory}
29175 Search @var{length} bytes at @var{address} for @var{search-pattern}.
29176 @var{address} and @var{length} are encoded in hex.
29177 @var{search-pattern} is a sequence of bytes, hex encoded.
29182 The pattern was not found.
29184 The pattern was found at @var{address}.
29186 A badly formed request or an error was encountered while searching memory.
29188 An empty reply indicates that @samp{qSearch:memory} is not recognized.
29191 @item QStartNoAckMode
29192 @cindex @samp{QStartNoAckMode} packet
29193 @anchor{QStartNoAckMode}
29194 Request that the remote stub disable the normal @samp{+}/@samp{-}
29195 protocol acknowledgments (@pxref{Packet Acknowledgment}).
29200 The stub has switched to no-acknowledgment mode.
29201 @value{GDBN} acknowledges this reponse,
29202 but neither the stub nor @value{GDBN} shall send or expect further
29203 @samp{+}/@samp{-} acknowledgments in the current connection.
29205 An empty reply indicates that the stub does not support no-acknowledgment mode.
29208 @item qSupported @r{[}:@var{gdbfeature} @r{[};@var{gdbfeature}@r{]}@dots{} @r{]}
29209 @cindex supported packets, remote query
29210 @cindex features of the remote protocol
29211 @cindex @samp{qSupported} packet
29212 @anchor{qSupported}
29213 Tell the remote stub about features supported by @value{GDBN}, and
29214 query the stub for features it supports. This packet allows
29215 @value{GDBN} and the remote stub to take advantage of each others'
29216 features. @samp{qSupported} also consolidates multiple feature probes
29217 at startup, to improve @value{GDBN} performance---a single larger
29218 packet performs better than multiple smaller probe packets on
29219 high-latency links. Some features may enable behavior which must not
29220 be on by default, e.g.@: because it would confuse older clients or
29221 stubs. Other features may describe packets which could be
29222 automatically probed for, but are not. These features must be
29223 reported before @value{GDBN} will use them. This ``default
29224 unsupported'' behavior is not appropriate for all packets, but it
29225 helps to keep the initial connection time under control with new
29226 versions of @value{GDBN} which support increasing numbers of packets.
29230 @item @var{stubfeature} @r{[};@var{stubfeature}@r{]}@dots{}
29231 The stub supports or does not support each returned @var{stubfeature},
29232 depending on the form of each @var{stubfeature} (see below for the
29235 An empty reply indicates that @samp{qSupported} is not recognized,
29236 or that no features needed to be reported to @value{GDBN}.
29239 The allowed forms for each feature (either a @var{gdbfeature} in the
29240 @samp{qSupported} packet, or a @var{stubfeature} in the response)
29244 @item @var{name}=@var{value}
29245 The remote protocol feature @var{name} is supported, and associated
29246 with the specified @var{value}. The format of @var{value} depends
29247 on the feature, but it must not include a semicolon.
29249 The remote protocol feature @var{name} is supported, and does not
29250 need an associated value.
29252 The remote protocol feature @var{name} is not supported.
29254 The remote protocol feature @var{name} may be supported, and
29255 @value{GDBN} should auto-detect support in some other way when it is
29256 needed. This form will not be used for @var{gdbfeature} notifications,
29257 but may be used for @var{stubfeature} responses.
29260 Whenever the stub receives a @samp{qSupported} request, the
29261 supplied set of @value{GDBN} features should override any previous
29262 request. This allows @value{GDBN} to put the stub in a known
29263 state, even if the stub had previously been communicating with
29264 a different version of @value{GDBN}.
29266 The following values of @var{gdbfeature} (for the packet sent by @value{GDBN})
29271 This feature indicates whether @value{GDBN} supports multiprocess
29272 extensions to the remote protocol. @value{GDBN} does not use such
29273 extensions unless the stub also reports that it supports them by
29274 including @samp{multiprocess+} in its @samp{qSupported} reply.
29275 @xref{multiprocess extensions}, for details.
29278 Stubs should ignore any unknown values for
29279 @var{gdbfeature}. Any @value{GDBN} which sends a @samp{qSupported}
29280 packet supports receiving packets of unlimited length (earlier
29281 versions of @value{GDBN} may reject overly long responses). Additional values
29282 for @var{gdbfeature} may be defined in the future to let the stub take
29283 advantage of new features in @value{GDBN}, e.g.@: incompatible
29284 improvements in the remote protocol---the @samp{multiprocess} feature is
29285 an example of such a feature. The stub's reply should be independent
29286 of the @var{gdbfeature} entries sent by @value{GDBN}; first @value{GDBN}
29287 describes all the features it supports, and then the stub replies with
29288 all the features it supports.
29290 Similarly, @value{GDBN} will silently ignore unrecognized stub feature
29291 responses, as long as each response uses one of the standard forms.
29293 Some features are flags. A stub which supports a flag feature
29294 should respond with a @samp{+} form response. Other features
29295 require values, and the stub should respond with an @samp{=}
29298 Each feature has a default value, which @value{GDBN} will use if
29299 @samp{qSupported} is not available or if the feature is not mentioned
29300 in the @samp{qSupported} response. The default values are fixed; a
29301 stub is free to omit any feature responses that match the defaults.
29303 Not all features can be probed, but for those which can, the probing
29304 mechanism is useful: in some cases, a stub's internal
29305 architecture may not allow the protocol layer to know some information
29306 about the underlying target in advance. This is especially common in
29307 stubs which may be configured for multiple targets.
29309 These are the currently defined stub features and their properties:
29311 @multitable @columnfractions 0.35 0.2 0.12 0.2
29312 @c NOTE: The first row should be @headitem, but we do not yet require
29313 @c a new enough version of Texinfo (4.7) to use @headitem.
29315 @tab Value Required
29319 @item @samp{PacketSize}
29324 @item @samp{qXfer:auxv:read}
29329 @item @samp{qXfer:features:read}
29334 @item @samp{qXfer:libraries:read}
29339 @item @samp{qXfer:memory-map:read}
29344 @item @samp{qXfer:spu:read}
29349 @item @samp{qXfer:spu:write}
29354 @item @samp{qXfer:siginfo:read}
29359 @item @samp{qXfer:siginfo:write}
29364 @item @samp{QNonStop}
29369 @item @samp{QPassSignals}
29374 @item @samp{QStartNoAckMode}
29379 @item @samp{multiprocess}
29384 @item @samp{ConditionalTracepoints}
29389 @item @samp{ReverseContinue}
29394 @item @samp{ReverseStep}
29401 These are the currently defined stub features, in more detail:
29404 @cindex packet size, remote protocol
29405 @item PacketSize=@var{bytes}
29406 The remote stub can accept packets up to at least @var{bytes} in
29407 length. @value{GDBN} will send packets up to this size for bulk
29408 transfers, and will never send larger packets. This is a limit on the
29409 data characters in the packet, including the frame and checksum.
29410 There is no trailing NUL byte in a remote protocol packet; if the stub
29411 stores packets in a NUL-terminated format, it should allow an extra
29412 byte in its buffer for the NUL. If this stub feature is not supported,
29413 @value{GDBN} guesses based on the size of the @samp{g} packet response.
29415 @item qXfer:auxv:read
29416 The remote stub understands the @samp{qXfer:auxv:read} packet
29417 (@pxref{qXfer auxiliary vector read}).
29419 @item qXfer:features:read
29420 The remote stub understands the @samp{qXfer:features:read} packet
29421 (@pxref{qXfer target description read}).
29423 @item qXfer:libraries:read
29424 The remote stub understands the @samp{qXfer:libraries:read} packet
29425 (@pxref{qXfer library list read}).
29427 @item qXfer:memory-map:read
29428 The remote stub understands the @samp{qXfer:memory-map:read} packet
29429 (@pxref{qXfer memory map read}).
29431 @item qXfer:spu:read
29432 The remote stub understands the @samp{qXfer:spu:read} packet
29433 (@pxref{qXfer spu read}).
29435 @item qXfer:spu:write
29436 The remote stub understands the @samp{qXfer:spu:write} packet
29437 (@pxref{qXfer spu write}).
29439 @item qXfer:siginfo:read
29440 The remote stub understands the @samp{qXfer:siginfo:read} packet
29441 (@pxref{qXfer siginfo read}).
29443 @item qXfer:siginfo:write
29444 The remote stub understands the @samp{qXfer:siginfo:write} packet
29445 (@pxref{qXfer siginfo write}).
29448 The remote stub understands the @samp{QNonStop} packet
29449 (@pxref{QNonStop}).
29452 The remote stub understands the @samp{QPassSignals} packet
29453 (@pxref{QPassSignals}).
29455 @item QStartNoAckMode
29456 The remote stub understands the @samp{QStartNoAckMode} packet and
29457 prefers to operate in no-acknowledgment mode. @xref{Packet Acknowledgment}.
29460 @anchor{multiprocess extensions}
29461 @cindex multiprocess extensions, in remote protocol
29462 The remote stub understands the multiprocess extensions to the remote
29463 protocol syntax. The multiprocess extensions affect the syntax of
29464 thread IDs in both packets and replies (@pxref{thread-id syntax}), and
29465 add process IDs to the @samp{D} packet and @samp{W} and @samp{X}
29466 replies. Note that reporting this feature indicates support for the
29467 syntactic extensions only, not that the stub necessarily supports
29468 debugging of more than one process at a time. The stub must not use
29469 multiprocess extensions in packet replies unless @value{GDBN} has also
29470 indicated it supports them in its @samp{qSupported} request.
29472 @item qXfer:osdata:read
29473 The remote stub understands the @samp{qXfer:osdata:read} packet
29474 ((@pxref{qXfer osdata read}).
29476 @item ConditionalTracepoints
29477 The remote stub accepts and implements conditional expressions defined
29478 for tracepoints (@pxref{Tracepoint Conditions}).
29480 @item ReverseContinue
29481 The remote stub accepts and implements the reverse continue packet
29485 The remote stub accepts and implements the reverse step packet
29491 @cindex symbol lookup, remote request
29492 @cindex @samp{qSymbol} packet
29493 Notify the target that @value{GDBN} is prepared to serve symbol lookup
29494 requests. Accept requests from the target for the values of symbols.
29499 The target does not need to look up any (more) symbols.
29500 @item qSymbol:@var{sym_name}
29501 The target requests the value of symbol @var{sym_name} (hex encoded).
29502 @value{GDBN} may provide the value by using the
29503 @samp{qSymbol:@var{sym_value}:@var{sym_name}} message, described
29507 @item qSymbol:@var{sym_value}:@var{sym_name}
29508 Set the value of @var{sym_name} to @var{sym_value}.
29510 @var{sym_name} (hex encoded) is the name of a symbol whose value the
29511 target has previously requested.
29513 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
29514 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
29520 The target does not need to look up any (more) symbols.
29521 @item qSymbol:@var{sym_name}
29522 The target requests the value of a new symbol @var{sym_name} (hex
29523 encoded). @value{GDBN} will continue to supply the values of symbols
29524 (if available), until the target ceases to request them.
29529 @xref{Tracepoint Packets}.
29531 @item qThreadExtraInfo,@var{thread-id}
29532 @cindex thread attributes info, remote request
29533 @cindex @samp{qThreadExtraInfo} packet
29534 Obtain a printable string description of a thread's attributes from
29535 the target OS. @var{thread-id} is a thread ID;
29536 see @ref{thread-id syntax}. This
29537 string may contain anything that the target OS thinks is interesting
29538 for @value{GDBN} to tell the user about the thread. The string is
29539 displayed in @value{GDBN}'s @code{info threads} display. Some
29540 examples of possible thread extra info strings are @samp{Runnable}, or
29541 @samp{Blocked on Mutex}.
29545 @item @var{XX}@dots{}
29546 Where @samp{@var{XX}@dots{}} is a hex encoding of @sc{ascii} data,
29547 comprising the printable string containing the extra information about
29548 the thread's attributes.
29551 (Note that the @code{qThreadExtraInfo} packet's name is separated from
29552 the command by a @samp{,}, not a @samp{:}, contrary to the naming
29553 conventions above. Please don't use this packet as a model for new
29561 @xref{Tracepoint Packets}.
29563 @item qXfer:@var{object}:read:@var{annex}:@var{offset},@var{length}
29564 @cindex read special object, remote request
29565 @cindex @samp{qXfer} packet
29566 @anchor{qXfer read}
29567 Read uninterpreted bytes from the target's special data area
29568 identified by the keyword @var{object}. Request @var{length} bytes
29569 starting at @var{offset} bytes into the data. The content and
29570 encoding of @var{annex} is specific to @var{object}; it can supply
29571 additional details about what data to access.
29573 Here are the specific requests of this form defined so far. All
29574 @samp{qXfer:@var{object}:read:@dots{}} requests use the same reply
29575 formats, listed below.
29578 @item qXfer:auxv:read::@var{offset},@var{length}
29579 @anchor{qXfer auxiliary vector read}
29580 Access the target's @dfn{auxiliary vector}. @xref{OS Information,
29581 auxiliary vector}. Note @var{annex} must be empty.
29583 This packet is not probed by default; the remote stub must request it,
29584 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
29586 @item qXfer:features:read:@var{annex}:@var{offset},@var{length}
29587 @anchor{qXfer target description read}
29588 Access the @dfn{target description}. @xref{Target Descriptions}. The
29589 annex specifies which XML document to access. The main description is
29590 always loaded from the @samp{target.xml} annex.
29592 This packet is not probed by default; the remote stub must request it,
29593 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
29595 @item qXfer:libraries:read:@var{annex}:@var{offset},@var{length}
29596 @anchor{qXfer library list read}
29597 Access the target's list of loaded libraries. @xref{Library List Format}.
29598 The annex part of the generic @samp{qXfer} packet must be empty
29599 (@pxref{qXfer read}).
29601 Targets which maintain a list of libraries in the program's memory do
29602 not need to implement this packet; it is designed for platforms where
29603 the operating system manages the list of loaded libraries.
29605 This packet is not probed by default; the remote stub must request it,
29606 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
29608 @item qXfer:memory-map:read::@var{offset},@var{length}
29609 @anchor{qXfer memory map read}
29610 Access the target's @dfn{memory-map}. @xref{Memory Map Format}. The
29611 annex part of the generic @samp{qXfer} packet must be empty
29612 (@pxref{qXfer read}).
29614 This packet is not probed by default; the remote stub must request it,
29615 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
29617 @item qXfer:siginfo:read::@var{offset},@var{length}
29618 @anchor{qXfer siginfo read}
29619 Read contents of the extra signal information on the target
29620 system. The annex part of the generic @samp{qXfer} packet must be
29621 empty (@pxref{qXfer read}).
29623 This packet is not probed by default; the remote stub must request it,
29624 by supplying an appropriate @samp{qSupported} response
29625 (@pxref{qSupported}).
29627 @item qXfer:spu:read:@var{annex}:@var{offset},@var{length}
29628 @anchor{qXfer spu read}
29629 Read contents of an @code{spufs} file on the target system. The
29630 annex specifies which file to read; it must be of the form
29631 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
29632 in the target process, and @var{name} identifes the @code{spufs} file
29633 in that context to be accessed.
29635 This packet is not probed by default; the remote stub must request it,
29636 by supplying an appropriate @samp{qSupported} response
29637 (@pxref{qSupported}).
29639 @item qXfer:osdata:read::@var{offset},@var{length}
29640 @anchor{qXfer osdata read}
29641 Access the target's @dfn{operating system information}.
29642 @xref{Operating System Information}.
29649 Data @var{data} (@pxref{Binary Data}) has been read from the
29650 target. There may be more data at a higher address (although
29651 it is permitted to return @samp{m} even for the last valid
29652 block of data, as long as at least one byte of data was read).
29653 @var{data} may have fewer bytes than the @var{length} in the
29657 Data @var{data} (@pxref{Binary Data}) has been read from the target.
29658 There is no more data to be read. @var{data} may have fewer bytes
29659 than the @var{length} in the request.
29662 The @var{offset} in the request is at the end of the data.
29663 There is no more data to be read.
29666 The request was malformed, or @var{annex} was invalid.
29669 The offset was invalid, or there was an error encountered reading the data.
29670 @var{nn} is a hex-encoded @code{errno} value.
29673 An empty reply indicates the @var{object} string was not recognized by
29674 the stub, or that the object does not support reading.
29677 @item qXfer:@var{object}:write:@var{annex}:@var{offset}:@var{data}@dots{}
29678 @cindex write data into object, remote request
29679 @anchor{qXfer write}
29680 Write uninterpreted bytes into the target's special data area
29681 identified by the keyword @var{object}, starting at @var{offset} bytes
29682 into the data. @var{data}@dots{} is the binary-encoded data
29683 (@pxref{Binary Data}) to be written. The content and encoding of @var{annex}
29684 is specific to @var{object}; it can supply additional details about what data
29687 Here are the specific requests of this form defined so far. All
29688 @samp{qXfer:@var{object}:write:@dots{}} requests use the same reply
29689 formats, listed below.
29692 @item qXfer:siginfo:write::@var{offset}:@var{data}@dots{}
29693 @anchor{qXfer siginfo write}
29694 Write @var{data} to the extra signal information on the target system.
29695 The annex part of the generic @samp{qXfer} packet must be
29696 empty (@pxref{qXfer write}).
29698 This packet is not probed by default; the remote stub must request it,
29699 by supplying an appropriate @samp{qSupported} response
29700 (@pxref{qSupported}).
29702 @item qXfer:spu:write:@var{annex}:@var{offset}:@var{data}@dots{}
29703 @anchor{qXfer spu write}
29704 Write @var{data} to an @code{spufs} file on the target system. The
29705 annex specifies which file to write; it must be of the form
29706 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
29707 in the target process, and @var{name} identifes the @code{spufs} file
29708 in that context to be accessed.
29710 This packet is not probed by default; the remote stub must request it,
29711 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
29717 @var{nn} (hex encoded) is the number of bytes written.
29718 This may be fewer bytes than supplied in the request.
29721 The request was malformed, or @var{annex} was invalid.
29724 The offset was invalid, or there was an error encountered writing the data.
29725 @var{nn} is a hex-encoded @code{errno} value.
29728 An empty reply indicates the @var{object} string was not
29729 recognized by the stub, or that the object does not support writing.
29732 @item qXfer:@var{object}:@var{operation}:@dots{}
29733 Requests of this form may be added in the future. When a stub does
29734 not recognize the @var{object} keyword, or its support for
29735 @var{object} does not recognize the @var{operation} keyword, the stub
29736 must respond with an empty packet.
29738 @item qAttached:@var{pid}
29739 @cindex query attached, remote request
29740 @cindex @samp{qAttached} packet
29741 Return an indication of whether the remote server attached to an
29742 existing process or created a new process. When the multiprocess
29743 protocol extensions are supported (@pxref{multiprocess extensions}),
29744 @var{pid} is an integer in hexadecimal format identifying the target
29745 process. Otherwise, @value{GDBN} will omit the @var{pid} field and
29746 the query packet will be simplified as @samp{qAttached}.
29748 This query is used, for example, to know whether the remote process
29749 should be detached or killed when a @value{GDBN} session is ended with
29750 the @code{quit} command.
29755 The remote server attached to an existing process.
29757 The remote server created a new process.
29759 A badly formed request or an error was encountered.
29764 @node Register Packet Format
29765 @section Register Packet Format
29767 The following @code{g}/@code{G} packets have previously been defined.
29768 In the below, some thirty-two bit registers are transferred as
29769 sixty-four bits. Those registers should be zero/sign extended (which?)
29770 to fill the space allocated. Register bytes are transferred in target
29771 byte order. The two nibbles within a register byte are transferred
29772 most-significant - least-significant.
29778 All registers are transferred as thirty-two bit quantities in the order:
29779 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
29780 registers; fsr; fir; fp.
29784 All registers are transferred as sixty-four bit quantities (including
29785 thirty-two bit registers such as @code{sr}). The ordering is the same
29790 @node Tracepoint Packets
29791 @section Tracepoint Packets
29792 @cindex tracepoint packets
29793 @cindex packets, tracepoint
29795 Here we describe the packets @value{GDBN} uses to implement
29796 tracepoints (@pxref{Tracepoints}).
29800 @item QTDP:@var{n}:@var{addr}:@var{ena}:@var{step}:@var{pass}[:X@var{len},@var{bytes}]@r{[}-@r{]}
29801 Create a new tracepoint, number @var{n}, at @var{addr}. If @var{ena}
29802 is @samp{E}, then the tracepoint is enabled; if it is @samp{D}, then
29803 the tracepoint is disabled. @var{step} is the tracepoint's step
29804 count, and @var{pass} is its pass count. If an @samp{X} is present,
29805 it introduces a tracepoint condition, which consists of a hexadecimal
29806 length, followed by a comma and hex-encoded bytes, in a manner similar
29807 to action encodings as described below. If the trailing @samp{-} is
29808 present, further @samp{QTDP} packets will follow to specify this
29809 tracepoint's actions.
29814 The packet was understood and carried out.
29816 The packet was not recognized.
29819 @item QTDP:-@var{n}:@var{addr}:@r{[}S@r{]}@var{action}@dots{}@r{[}-@r{]}
29820 Define actions to be taken when a tracepoint is hit. @var{n} and
29821 @var{addr} must be the same as in the initial @samp{QTDP} packet for
29822 this tracepoint. This packet may only be sent immediately after
29823 another @samp{QTDP} packet that ended with a @samp{-}. If the
29824 trailing @samp{-} is present, further @samp{QTDP} packets will follow,
29825 specifying more actions for this tracepoint.
29827 In the series of action packets for a given tracepoint, at most one
29828 can have an @samp{S} before its first @var{action}. If such a packet
29829 is sent, it and the following packets define ``while-stepping''
29830 actions. Any prior packets define ordinary actions --- that is, those
29831 taken when the tracepoint is first hit. If no action packet has an
29832 @samp{S}, then all the packets in the series specify ordinary
29833 tracepoint actions.
29835 The @samp{@var{action}@dots{}} portion of the packet is a series of
29836 actions, concatenated without separators. Each action has one of the
29842 Collect the registers whose bits are set in @var{mask}. @var{mask} is
29843 a hexadecimal number whose @var{i}'th bit is set if register number
29844 @var{i} should be collected. (The least significant bit is numbered
29845 zero.) Note that @var{mask} may be any number of digits long; it may
29846 not fit in a 32-bit word.
29848 @item M @var{basereg},@var{offset},@var{len}
29849 Collect @var{len} bytes of memory starting at the address in register
29850 number @var{basereg}, plus @var{offset}. If @var{basereg} is
29851 @samp{-1}, then the range has a fixed address: @var{offset} is the
29852 address of the lowest byte to collect. The @var{basereg},
29853 @var{offset}, and @var{len} parameters are all unsigned hexadecimal
29854 values (the @samp{-1} value for @var{basereg} is a special case).
29856 @item X @var{len},@var{expr}
29857 Evaluate @var{expr}, whose length is @var{len}, and collect memory as
29858 it directs. @var{expr} is an agent expression, as described in
29859 @ref{Agent Expressions}. Each byte of the expression is encoded as a
29860 two-digit hex number in the packet; @var{len} is the number of bytes
29861 in the expression (and thus one-half the number of hex digits in the
29866 Any number of actions may be packed together in a single @samp{QTDP}
29867 packet, as long as the packet does not exceed the maximum packet
29868 length (400 bytes, for many stubs). There may be only one @samp{R}
29869 action per tracepoint, and it must precede any @samp{M} or @samp{X}
29870 actions. Any registers referred to by @samp{M} and @samp{X} actions
29871 must be collected by a preceding @samp{R} action. (The
29872 ``while-stepping'' actions are treated as if they were attached to a
29873 separate tracepoint, as far as these restrictions are concerned.)
29878 The packet was understood and carried out.
29880 The packet was not recognized.
29883 @item QTFrame:@var{n}
29884 Select the @var{n}'th tracepoint frame from the buffer, and use the
29885 register and memory contents recorded there to answer subsequent
29886 request packets from @value{GDBN}.
29888 A successful reply from the stub indicates that the stub has found the
29889 requested frame. The response is a series of parts, concatenated
29890 without separators, describing the frame we selected. Each part has
29891 one of the following forms:
29895 The selected frame is number @var{n} in the trace frame buffer;
29896 @var{f} is a hexadecimal number. If @var{f} is @samp{-1}, then there
29897 was no frame matching the criteria in the request packet.
29900 The selected trace frame records a hit of tracepoint number @var{t};
29901 @var{t} is a hexadecimal number.
29905 @item QTFrame:pc:@var{addr}
29906 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
29907 currently selected frame whose PC is @var{addr};
29908 @var{addr} is a hexadecimal number.
29910 @item QTFrame:tdp:@var{t}
29911 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
29912 currently selected frame that is a hit of tracepoint @var{t}; @var{t}
29913 is a hexadecimal number.
29915 @item QTFrame:range:@var{start}:@var{end}
29916 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
29917 currently selected frame whose PC is between @var{start} (inclusive)
29918 and @var{end} (exclusive); @var{start} and @var{end} are hexadecimal
29921 @item QTFrame:outside:@var{start}:@var{end}
29922 Like @samp{QTFrame:range:@var{start}:@var{end}}, but select the first
29923 frame @emph{outside} the given range of addresses.
29926 Begin the tracepoint experiment. Begin collecting data from tracepoint
29927 hits in the trace frame buffer.
29930 End the tracepoint experiment. Stop collecting trace frames.
29933 Clear the table of tracepoints, and empty the trace frame buffer.
29935 @item QTro:@var{start1},@var{end1}:@var{start2},@var{end2}:@dots{}
29936 Establish the given ranges of memory as ``transparent''. The stub
29937 will answer requests for these ranges from memory's current contents,
29938 if they were not collected as part of the tracepoint hit.
29940 @value{GDBN} uses this to mark read-only regions of memory, like those
29941 containing program code. Since these areas never change, they should
29942 still have the same contents they did when the tracepoint was hit, so
29943 there's no reason for the stub to refuse to provide their contents.
29946 Ask the stub if there is a trace experiment running right now.
29951 There is no trace experiment running.
29953 There is a trace experiment running.
29959 @node Host I/O Packets
29960 @section Host I/O Packets
29961 @cindex Host I/O, remote protocol
29962 @cindex file transfer, remote protocol
29964 The @dfn{Host I/O} packets allow @value{GDBN} to perform I/O
29965 operations on the far side of a remote link. For example, Host I/O is
29966 used to upload and download files to a remote target with its own
29967 filesystem. Host I/O uses the same constant values and data structure
29968 layout as the target-initiated File-I/O protocol. However, the
29969 Host I/O packets are structured differently. The target-initiated
29970 protocol relies on target memory to store parameters and buffers.
29971 Host I/O requests are initiated by @value{GDBN}, and the
29972 target's memory is not involved. @xref{File-I/O Remote Protocol
29973 Extension}, for more details on the target-initiated protocol.
29975 The Host I/O request packets all encode a single operation along with
29976 its arguments. They have this format:
29980 @item vFile:@var{operation}: @var{parameter}@dots{}
29981 @var{operation} is the name of the particular request; the target
29982 should compare the entire packet name up to the second colon when checking
29983 for a supported operation. The format of @var{parameter} depends on
29984 the operation. Numbers are always passed in hexadecimal. Negative
29985 numbers have an explicit minus sign (i.e.@: two's complement is not
29986 used). Strings (e.g.@: filenames) are encoded as a series of
29987 hexadecimal bytes. The last argument to a system call may be a
29988 buffer of escaped binary data (@pxref{Binary Data}).
29992 The valid responses to Host I/O packets are:
29996 @item F @var{result} [, @var{errno}] [; @var{attachment}]
29997 @var{result} is the integer value returned by this operation, usually
29998 non-negative for success and -1 for errors. If an error has occured,
29999 @var{errno} will be included in the result. @var{errno} will have a
30000 value defined by the File-I/O protocol (@pxref{Errno Values}). For
30001 operations which return data, @var{attachment} supplies the data as a
30002 binary buffer. Binary buffers in response packets are escaped in the
30003 normal way (@pxref{Binary Data}). See the individual packet
30004 documentation for the interpretation of @var{result} and
30008 An empty response indicates that this operation is not recognized.
30012 These are the supported Host I/O operations:
30015 @item vFile:open: @var{pathname}, @var{flags}, @var{mode}
30016 Open a file at @var{pathname} and return a file descriptor for it, or
30017 return -1 if an error occurs. @var{pathname} is a string,
30018 @var{flags} is an integer indicating a mask of open flags
30019 (@pxref{Open Flags}), and @var{mode} is an integer indicating a mask
30020 of mode bits to use if the file is created (@pxref{mode_t Values}).
30021 @xref{open}, for details of the open flags and mode values.
30023 @item vFile:close: @var{fd}
30024 Close the open file corresponding to @var{fd} and return 0, or
30025 -1 if an error occurs.
30027 @item vFile:pread: @var{fd}, @var{count}, @var{offset}
30028 Read data from the open file corresponding to @var{fd}. Up to
30029 @var{count} bytes will be read from the file, starting at @var{offset}
30030 relative to the start of the file. The target may read fewer bytes;
30031 common reasons include packet size limits and an end-of-file
30032 condition. The number of bytes read is returned. Zero should only be
30033 returned for a successful read at the end of the file, or if
30034 @var{count} was zero.
30036 The data read should be returned as a binary attachment on success.
30037 If zero bytes were read, the response should include an empty binary
30038 attachment (i.e.@: a trailing semicolon). The return value is the
30039 number of target bytes read; the binary attachment may be longer if
30040 some characters were escaped.
30042 @item vFile:pwrite: @var{fd}, @var{offset}, @var{data}
30043 Write @var{data} (a binary buffer) to the open file corresponding
30044 to @var{fd}. Start the write at @var{offset} from the start of the
30045 file. Unlike many @code{write} system calls, there is no
30046 separate @var{count} argument; the length of @var{data} in the
30047 packet is used. @samp{vFile:write} returns the number of bytes written,
30048 which may be shorter than the length of @var{data}, or -1 if an
30051 @item vFile:unlink: @var{pathname}
30052 Delete the file at @var{pathname} on the target. Return 0,
30053 or -1 if an error occurs. @var{pathname} is a string.
30058 @section Interrupts
30059 @cindex interrupts (remote protocol)
30061 When a program on the remote target is running, @value{GDBN} may
30062 attempt to interrupt it by sending a @samp{Ctrl-C} or a @code{BREAK},
30063 control of which is specified via @value{GDBN}'s @samp{remotebreak}
30064 setting (@pxref{set remotebreak}).
30066 The precise meaning of @code{BREAK} is defined by the transport
30067 mechanism and may, in fact, be undefined. @value{GDBN} does not
30068 currently define a @code{BREAK} mechanism for any of the network
30069 interfaces except for TCP, in which case @value{GDBN} sends the
30070 @code{telnet} BREAK sequence.
30072 @samp{Ctrl-C}, on the other hand, is defined and implemented for all
30073 transport mechanisms. It is represented by sending the single byte
30074 @code{0x03} without any of the usual packet overhead described in
30075 the Overview section (@pxref{Overview}). When a @code{0x03} byte is
30076 transmitted as part of a packet, it is considered to be packet data
30077 and does @emph{not} represent an interrupt. E.g., an @samp{X} packet
30078 (@pxref{X packet}), used for binary downloads, may include an unescaped
30079 @code{0x03} as part of its packet.
30081 Stubs are not required to recognize these interrupt mechanisms and the
30082 precise meaning associated with receipt of the interrupt is
30083 implementation defined. If the target supports debugging of multiple
30084 threads and/or processes, it should attempt to interrupt all
30085 currently-executing threads and processes.
30086 If the stub is successful at interrupting the
30087 running program, it should send one of the stop
30088 reply packets (@pxref{Stop Reply Packets}) to @value{GDBN} as a result
30089 of successfully stopping the program in all-stop mode, and a stop reply
30090 for each stopped thread in non-stop mode.
30091 Interrupts received while the
30092 program is stopped are discarded.
30094 @node Notification Packets
30095 @section Notification Packets
30096 @cindex notification packets
30097 @cindex packets, notification
30099 The @value{GDBN} remote serial protocol includes @dfn{notifications},
30100 packets that require no acknowledgment. Both the GDB and the stub
30101 may send notifications (although the only notifications defined at
30102 present are sent by the stub). Notifications carry information
30103 without incurring the round-trip latency of an acknowledgment, and so
30104 are useful for low-impact communications where occasional packet loss
30107 A notification packet has the form @samp{% @var{data} #
30108 @var{checksum}}, where @var{data} is the content of the notification,
30109 and @var{checksum} is a checksum of @var{data}, computed and formatted
30110 as for ordinary @value{GDBN} packets. A notification's @var{data}
30111 never contains @samp{$}, @samp{%} or @samp{#} characters. Upon
30112 receiving a notification, the recipient sends no @samp{+} or @samp{-}
30113 to acknowledge the notification's receipt or to report its corruption.
30115 Every notification's @var{data} begins with a name, which contains no
30116 colon characters, followed by a colon character.
30118 Recipients should silently ignore corrupted notifications and
30119 notifications they do not understand. Recipients should restart
30120 timeout periods on receipt of a well-formed notification, whether or
30121 not they understand it.
30123 Senders should only send the notifications described here when this
30124 protocol description specifies that they are permitted. In the
30125 future, we may extend the protocol to permit existing notifications in
30126 new contexts; this rule helps older senders avoid confusing newer
30129 (Older versions of @value{GDBN} ignore bytes received until they see
30130 the @samp{$} byte that begins an ordinary packet, so new stubs may
30131 transmit notifications without fear of confusing older clients. There
30132 are no notifications defined for @value{GDBN} to send at the moment, but we
30133 assume that most older stubs would ignore them, as well.)
30135 The following notification packets from the stub to @value{GDBN} are
30139 @item Stop: @var{reply}
30140 Report an asynchronous stop event in non-stop mode.
30141 The @var{reply} has the form of a stop reply, as
30142 described in @ref{Stop Reply Packets}. Refer to @ref{Remote Non-Stop},
30143 for information on how these notifications are acknowledged by
30147 @node Remote Non-Stop
30148 @section Remote Protocol Support for Non-Stop Mode
30150 @value{GDBN}'s remote protocol supports non-stop debugging of
30151 multi-threaded programs, as described in @ref{Non-Stop Mode}. If the stub
30152 supports non-stop mode, it should report that to @value{GDBN} by including
30153 @samp{QNonStop+} in its @samp{qSupported} response (@pxref{qSupported}).
30155 @value{GDBN} typically sends a @samp{QNonStop} packet only when
30156 establishing a new connection with the stub. Entering non-stop mode
30157 does not alter the state of any currently-running threads, but targets
30158 must stop all threads in any already-attached processes when entering
30159 all-stop mode. @value{GDBN} uses the @samp{?} packet as necessary to
30160 probe the target state after a mode change.
30162 In non-stop mode, when an attached process encounters an event that
30163 would otherwise be reported with a stop reply, it uses the
30164 asynchronous notification mechanism (@pxref{Notification Packets}) to
30165 inform @value{GDBN}. In contrast to all-stop mode, where all threads
30166 in all processes are stopped when a stop reply is sent, in non-stop
30167 mode only the thread reporting the stop event is stopped. That is,
30168 when reporting a @samp{S} or @samp{T} response to indicate completion
30169 of a step operation, hitting a breakpoint, or a fault, only the
30170 affected thread is stopped; any other still-running threads continue
30171 to run. When reporting a @samp{W} or @samp{X} response, all running
30172 threads belonging to other attached processes continue to run.
30174 Only one stop reply notification at a time may be pending; if
30175 additional stop events occur before @value{GDBN} has acknowledged the
30176 previous notification, they must be queued by the stub for later
30177 synchronous transmission in response to @samp{vStopped} packets from
30178 @value{GDBN}. Because the notification mechanism is unreliable,
30179 the stub is permitted to resend a stop reply notification
30180 if it believes @value{GDBN} may not have received it. @value{GDBN}
30181 ignores additional stop reply notifications received before it has
30182 finished processing a previous notification and the stub has completed
30183 sending any queued stop events.
30185 Otherwise, @value{GDBN} must be prepared to receive a stop reply
30186 notification at any time. Specifically, they may appear when
30187 @value{GDBN} is not otherwise reading input from the stub, or when
30188 @value{GDBN} is expecting to read a normal synchronous response or a
30189 @samp{+}/@samp{-} acknowledgment to a packet it has sent.
30190 Notification packets are distinct from any other communication from
30191 the stub so there is no ambiguity.
30193 After receiving a stop reply notification, @value{GDBN} shall
30194 acknowledge it by sending a @samp{vStopped} packet (@pxref{vStopped packet})
30195 as a regular, synchronous request to the stub. Such acknowledgment
30196 is not required to happen immediately, as @value{GDBN} is permitted to
30197 send other, unrelated packets to the stub first, which the stub should
30200 Upon receiving a @samp{vStopped} packet, if the stub has other queued
30201 stop events to report to @value{GDBN}, it shall respond by sending a
30202 normal stop reply response. @value{GDBN} shall then send another
30203 @samp{vStopped} packet to solicit further responses; again, it is
30204 permitted to send other, unrelated packets as well which the stub
30205 should process normally.
30207 If the stub receives a @samp{vStopped} packet and there are no
30208 additional stop events to report, the stub shall return an @samp{OK}
30209 response. At this point, if further stop events occur, the stub shall
30210 send a new stop reply notification, @value{GDBN} shall accept the
30211 notification, and the process shall be repeated.
30213 In non-stop mode, the target shall respond to the @samp{?} packet as
30214 follows. First, any incomplete stop reply notification/@samp{vStopped}
30215 sequence in progress is abandoned. The target must begin a new
30216 sequence reporting stop events for all stopped threads, whether or not
30217 it has previously reported those events to @value{GDBN}. The first
30218 stop reply is sent as a synchronous reply to the @samp{?} packet, and
30219 subsequent stop replies are sent as responses to @samp{vStopped} packets
30220 using the mechanism described above. The target must not send
30221 asynchronous stop reply notifications until the sequence is complete.
30222 If all threads are running when the target receives the @samp{?} packet,
30223 or if the target is not attached to any process, it shall respond
30226 @node Packet Acknowledgment
30227 @section Packet Acknowledgment
30229 @cindex acknowledgment, for @value{GDBN} remote
30230 @cindex packet acknowledgment, for @value{GDBN} remote
30231 By default, when either the host or the target machine receives a packet,
30232 the first response expected is an acknowledgment: either @samp{+} (to indicate
30233 the package was received correctly) or @samp{-} (to request retransmission).
30234 This mechanism allows the @value{GDBN} remote protocol to operate over
30235 unreliable transport mechanisms, such as a serial line.
30237 In cases where the transport mechanism is itself reliable (such as a pipe or
30238 TCP connection), the @samp{+}/@samp{-} acknowledgments are redundant.
30239 It may be desirable to disable them in that case to reduce communication
30240 overhead, or for other reasons. This can be accomplished by means of the
30241 @samp{QStartNoAckMode} packet; @pxref{QStartNoAckMode}.
30243 When in no-acknowledgment mode, neither the stub nor @value{GDBN} shall send or
30244 expect @samp{+}/@samp{-} protocol acknowledgments. The packet
30245 and response format still includes the normal checksum, as described in
30246 @ref{Overview}, but the checksum may be ignored by the receiver.
30248 If the stub supports @samp{QStartNoAckMode} and prefers to operate in
30249 no-acknowledgment mode, it should report that to @value{GDBN}
30250 by including @samp{QStartNoAckMode+} in its response to @samp{qSupported};
30251 @pxref{qSupported}.
30252 If @value{GDBN} also supports @samp{QStartNoAckMode} and it has not been
30253 disabled via the @code{set remote noack-packet off} command
30254 (@pxref{Remote Configuration}),
30255 @value{GDBN} may then send a @samp{QStartNoAckMode} packet to the stub.
30256 Only then may the stub actually turn off packet acknowledgments.
30257 @value{GDBN} sends a final @samp{+} acknowledgment of the stub's @samp{OK}
30258 response, which can be safely ignored by the stub.
30260 Note that @code{set remote noack-packet} command only affects negotiation
30261 between @value{GDBN} and the stub when subsequent connections are made;
30262 it does not affect the protocol acknowledgment state for any current
30264 Since @samp{+}/@samp{-} acknowledgments are enabled by default when a
30265 new connection is established,
30266 there is also no protocol request to re-enable the acknowledgments
30267 for the current connection, once disabled.
30272 Example sequence of a target being re-started. Notice how the restart
30273 does not get any direct output:
30278 @emph{target restarts}
30281 <- @code{T001:1234123412341234}
30285 Example sequence of a target being stepped by a single instruction:
30288 -> @code{G1445@dots{}}
30293 <- @code{T001:1234123412341234}
30297 <- @code{1455@dots{}}
30301 @node File-I/O Remote Protocol Extension
30302 @section File-I/O Remote Protocol Extension
30303 @cindex File-I/O remote protocol extension
30306 * File-I/O Overview::
30307 * Protocol Basics::
30308 * The F Request Packet::
30309 * The F Reply Packet::
30310 * The Ctrl-C Message::
30312 * List of Supported Calls::
30313 * Protocol-specific Representation of Datatypes::
30315 * File-I/O Examples::
30318 @node File-I/O Overview
30319 @subsection File-I/O Overview
30320 @cindex file-i/o overview
30322 The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the
30323 target to use the host's file system and console I/O to perform various
30324 system calls. System calls on the target system are translated into a
30325 remote protocol packet to the host system, which then performs the needed
30326 actions and returns a response packet to the target system.
30327 This simulates file system operations even on targets that lack file systems.
30329 The protocol is defined to be independent of both the host and target systems.
30330 It uses its own internal representation of datatypes and values. Both
30331 @value{GDBN} and the target's @value{GDBN} stub are responsible for
30332 translating the system-dependent value representations into the internal
30333 protocol representations when data is transmitted.
30335 The communication is synchronous. A system call is possible only when
30336 @value{GDBN} is waiting for a response from the @samp{C}, @samp{c}, @samp{S}
30337 or @samp{s} packets. While @value{GDBN} handles the request for a system call,
30338 the target is stopped to allow deterministic access to the target's
30339 memory. Therefore File-I/O is not interruptible by target signals. On
30340 the other hand, it is possible to interrupt File-I/O by a user interrupt
30341 (@samp{Ctrl-C}) within @value{GDBN}.
30343 The target's request to perform a host system call does not finish
30344 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
30345 after finishing the system call, the target returns to continuing the
30346 previous activity (continue, step). No additional continue or step
30347 request from @value{GDBN} is required.
30350 (@value{GDBP}) continue
30351 <- target requests 'system call X'
30352 target is stopped, @value{GDBN} executes system call
30353 -> @value{GDBN} returns result
30354 ... target continues, @value{GDBN} returns to wait for the target
30355 <- target hits breakpoint and sends a Txx packet
30358 The protocol only supports I/O on the console and to regular files on
30359 the host file system. Character or block special devices, pipes,
30360 named pipes, sockets or any other communication method on the host
30361 system are not supported by this protocol.
30363 File I/O is not supported in non-stop mode.
30365 @node Protocol Basics
30366 @subsection Protocol Basics
30367 @cindex protocol basics, file-i/o
30369 The File-I/O protocol uses the @code{F} packet as the request as well
30370 as reply packet. Since a File-I/O system call can only occur when
30371 @value{GDBN} is waiting for a response from the continuing or stepping target,
30372 the File-I/O request is a reply that @value{GDBN} has to expect as a result
30373 of a previous @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
30374 This @code{F} packet contains all information needed to allow @value{GDBN}
30375 to call the appropriate host system call:
30379 A unique identifier for the requested system call.
30382 All parameters to the system call. Pointers are given as addresses
30383 in the target memory address space. Pointers to strings are given as
30384 pointer/length pair. Numerical values are given as they are.
30385 Numerical control flags are given in a protocol-specific representation.
30389 At this point, @value{GDBN} has to perform the following actions.
30393 If the parameters include pointer values to data needed as input to a
30394 system call, @value{GDBN} requests this data from the target with a
30395 standard @code{m} packet request. This additional communication has to be
30396 expected by the target implementation and is handled as any other @code{m}
30400 @value{GDBN} translates all value from protocol representation to host
30401 representation as needed. Datatypes are coerced into the host types.
30404 @value{GDBN} calls the system call.
30407 It then coerces datatypes back to protocol representation.
30410 If the system call is expected to return data in buffer space specified
30411 by pointer parameters to the call, the data is transmitted to the
30412 target using a @code{M} or @code{X} packet. This packet has to be expected
30413 by the target implementation and is handled as any other @code{M} or @code{X}
30418 Eventually @value{GDBN} replies with another @code{F} packet which contains all
30419 necessary information for the target to continue. This at least contains
30426 @code{errno}, if has been changed by the system call.
30433 After having done the needed type and value coercion, the target continues
30434 the latest continue or step action.
30436 @node The F Request Packet
30437 @subsection The @code{F} Request Packet
30438 @cindex file-i/o request packet
30439 @cindex @code{F} request packet
30441 The @code{F} request packet has the following format:
30444 @item F@var{call-id},@var{parameter@dots{}}
30446 @var{call-id} is the identifier to indicate the host system call to be called.
30447 This is just the name of the function.
30449 @var{parameter@dots{}} are the parameters to the system call.
30450 Parameters are hexadecimal integer values, either the actual values in case
30451 of scalar datatypes, pointers to target buffer space in case of compound
30452 datatypes and unspecified memory areas, or pointer/length pairs in case
30453 of string parameters. These are appended to the @var{call-id} as a
30454 comma-delimited list. All values are transmitted in ASCII
30455 string representation, pointer/length pairs separated by a slash.
30461 @node The F Reply Packet
30462 @subsection The @code{F} Reply Packet
30463 @cindex file-i/o reply packet
30464 @cindex @code{F} reply packet
30466 The @code{F} reply packet has the following format:
30470 @item F@var{retcode},@var{errno},@var{Ctrl-C flag};@var{call-specific attachment}
30472 @var{retcode} is the return code of the system call as hexadecimal value.
30474 @var{errno} is the @code{errno} set by the call, in protocol-specific
30476 This parameter can be omitted if the call was successful.
30478 @var{Ctrl-C flag} is only sent if the user requested a break. In this
30479 case, @var{errno} must be sent as well, even if the call was successful.
30480 The @var{Ctrl-C flag} itself consists of the character @samp{C}:
30487 or, if the call was interrupted before the host call has been performed:
30494 assuming 4 is the protocol-specific representation of @code{EINTR}.
30499 @node The Ctrl-C Message
30500 @subsection The @samp{Ctrl-C} Message
30501 @cindex ctrl-c message, in file-i/o protocol
30503 If the @samp{Ctrl-C} flag is set in the @value{GDBN}
30504 reply packet (@pxref{The F Reply Packet}),
30505 the target should behave as if it had
30506 gotten a break message. The meaning for the target is ``system call
30507 interrupted by @code{SIGINT}''. Consequentially, the target should actually stop
30508 (as with a break message) and return to @value{GDBN} with a @code{T02}
30511 It's important for the target to know in which
30512 state the system call was interrupted. There are two possible cases:
30516 The system call hasn't been performed on the host yet.
30519 The system call on the host has been finished.
30523 These two states can be distinguished by the target by the value of the
30524 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
30525 call hasn't been performed. This is equivalent to the @code{EINTR} handling
30526 on POSIX systems. In any other case, the target may presume that the
30527 system call has been finished --- successfully or not --- and should behave
30528 as if the break message arrived right after the system call.
30530 @value{GDBN} must behave reliably. If the system call has not been called
30531 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
30532 @code{errno} in the packet. If the system call on the host has been finished
30533 before the user requests a break, the full action must be finished by
30534 @value{GDBN}. This requires sending @code{M} or @code{X} packets as necessary.
30535 The @code{F} packet may only be sent when either nothing has happened
30536 or the full action has been completed.
30539 @subsection Console I/O
30540 @cindex console i/o as part of file-i/o
30542 By default and if not explicitly closed by the target system, the file
30543 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
30544 on the @value{GDBN} console is handled as any other file output operation
30545 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
30546 by @value{GDBN} so that after the target read request from file descriptor
30547 0 all following typing is buffered until either one of the following
30552 The user types @kbd{Ctrl-c}. The behaviour is as explained above, and the
30554 system call is treated as finished.
30557 The user presses @key{RET}. This is treated as end of input with a trailing
30561 The user types @kbd{Ctrl-d}. This is treated as end of input. No trailing
30562 character (neither newline nor @samp{Ctrl-D}) is appended to the input.
30566 If the user has typed more characters than fit in the buffer given to
30567 the @code{read} call, the trailing characters are buffered in @value{GDBN} until
30568 either another @code{read(0, @dots{})} is requested by the target, or debugging
30569 is stopped at the user's request.
30572 @node List of Supported Calls
30573 @subsection List of Supported Calls
30574 @cindex list of supported file-i/o calls
30591 @unnumberedsubsubsec open
30592 @cindex open, file-i/o system call
30597 int open(const char *pathname, int flags);
30598 int open(const char *pathname, int flags, mode_t mode);
30602 @samp{Fopen,@var{pathptr}/@var{len},@var{flags},@var{mode}}
30605 @var{flags} is the bitwise @code{OR} of the following values:
30609 If the file does not exist it will be created. The host
30610 rules apply as far as file ownership and time stamps
30614 When used with @code{O_CREAT}, if the file already exists it is
30615 an error and open() fails.
30618 If the file already exists and the open mode allows
30619 writing (@code{O_RDWR} or @code{O_WRONLY} is given) it will be
30620 truncated to zero length.
30623 The file is opened in append mode.
30626 The file is opened for reading only.
30629 The file is opened for writing only.
30632 The file is opened for reading and writing.
30636 Other bits are silently ignored.
30640 @var{mode} is the bitwise @code{OR} of the following values:
30644 User has read permission.
30647 User has write permission.
30650 Group has read permission.
30653 Group has write permission.
30656 Others have read permission.
30659 Others have write permission.
30663 Other bits are silently ignored.
30666 @item Return value:
30667 @code{open} returns the new file descriptor or -1 if an error
30674 @var{pathname} already exists and @code{O_CREAT} and @code{O_EXCL} were used.
30677 @var{pathname} refers to a directory.
30680 The requested access is not allowed.
30683 @var{pathname} was too long.
30686 A directory component in @var{pathname} does not exist.
30689 @var{pathname} refers to a device, pipe, named pipe or socket.
30692 @var{pathname} refers to a file on a read-only filesystem and
30693 write access was requested.
30696 @var{pathname} is an invalid pointer value.
30699 No space on device to create the file.
30702 The process already has the maximum number of files open.
30705 The limit on the total number of files open on the system
30709 The call was interrupted by the user.
30715 @unnumberedsubsubsec close
30716 @cindex close, file-i/o system call
30725 @samp{Fclose,@var{fd}}
30727 @item Return value:
30728 @code{close} returns zero on success, or -1 if an error occurred.
30734 @var{fd} isn't a valid open file descriptor.
30737 The call was interrupted by the user.
30743 @unnumberedsubsubsec read
30744 @cindex read, file-i/o system call
30749 int read(int fd, void *buf, unsigned int count);
30753 @samp{Fread,@var{fd},@var{bufptr},@var{count}}
30755 @item Return value:
30756 On success, the number of bytes read is returned.
30757 Zero indicates end of file. If count is zero, read
30758 returns zero as well. On error, -1 is returned.
30764 @var{fd} is not a valid file descriptor or is not open for
30768 @var{bufptr} is an invalid pointer value.
30771 The call was interrupted by the user.
30777 @unnumberedsubsubsec write
30778 @cindex write, file-i/o system call
30783 int write(int fd, const void *buf, unsigned int count);
30787 @samp{Fwrite,@var{fd},@var{bufptr},@var{count}}
30789 @item Return value:
30790 On success, the number of bytes written are returned.
30791 Zero indicates nothing was written. On error, -1
30798 @var{fd} is not a valid file descriptor or is not open for
30802 @var{bufptr} is an invalid pointer value.
30805 An attempt was made to write a file that exceeds the
30806 host-specific maximum file size allowed.
30809 No space on device to write the data.
30812 The call was interrupted by the user.
30818 @unnumberedsubsubsec lseek
30819 @cindex lseek, file-i/o system call
30824 long lseek (int fd, long offset, int flag);
30828 @samp{Flseek,@var{fd},@var{offset},@var{flag}}
30830 @var{flag} is one of:
30834 The offset is set to @var{offset} bytes.
30837 The offset is set to its current location plus @var{offset}
30841 The offset is set to the size of the file plus @var{offset}
30845 @item Return value:
30846 On success, the resulting unsigned offset in bytes from
30847 the beginning of the file is returned. Otherwise, a
30848 value of -1 is returned.
30854 @var{fd} is not a valid open file descriptor.
30857 @var{fd} is associated with the @value{GDBN} console.
30860 @var{flag} is not a proper value.
30863 The call was interrupted by the user.
30869 @unnumberedsubsubsec rename
30870 @cindex rename, file-i/o system call
30875 int rename(const char *oldpath, const char *newpath);
30879 @samp{Frename,@var{oldpathptr}/@var{len},@var{newpathptr}/@var{len}}
30881 @item Return value:
30882 On success, zero is returned. On error, -1 is returned.
30888 @var{newpath} is an existing directory, but @var{oldpath} is not a
30892 @var{newpath} is a non-empty directory.
30895 @var{oldpath} or @var{newpath} is a directory that is in use by some
30899 An attempt was made to make a directory a subdirectory
30903 A component used as a directory in @var{oldpath} or new
30904 path is not a directory. Or @var{oldpath} is a directory
30905 and @var{newpath} exists but is not a directory.
30908 @var{oldpathptr} or @var{newpathptr} are invalid pointer values.
30911 No access to the file or the path of the file.
30915 @var{oldpath} or @var{newpath} was too long.
30918 A directory component in @var{oldpath} or @var{newpath} does not exist.
30921 The file is on a read-only filesystem.
30924 The device containing the file has no room for the new
30928 The call was interrupted by the user.
30934 @unnumberedsubsubsec unlink
30935 @cindex unlink, file-i/o system call
30940 int unlink(const char *pathname);
30944 @samp{Funlink,@var{pathnameptr}/@var{len}}
30946 @item Return value:
30947 On success, zero is returned. On error, -1 is returned.
30953 No access to the file or the path of the file.
30956 The system does not allow unlinking of directories.
30959 The file @var{pathname} cannot be unlinked because it's
30960 being used by another process.
30963 @var{pathnameptr} is an invalid pointer value.
30966 @var{pathname} was too long.
30969 A directory component in @var{pathname} does not exist.
30972 A component of the path is not a directory.
30975 The file is on a read-only filesystem.
30978 The call was interrupted by the user.
30984 @unnumberedsubsubsec stat/fstat
30985 @cindex fstat, file-i/o system call
30986 @cindex stat, file-i/o system call
30991 int stat(const char *pathname, struct stat *buf);
30992 int fstat(int fd, struct stat *buf);
30996 @samp{Fstat,@var{pathnameptr}/@var{len},@var{bufptr}}@*
30997 @samp{Ffstat,@var{fd},@var{bufptr}}
30999 @item Return value:
31000 On success, zero is returned. On error, -1 is returned.
31006 @var{fd} is not a valid open file.
31009 A directory component in @var{pathname} does not exist or the
31010 path is an empty string.
31013 A component of the path is not a directory.
31016 @var{pathnameptr} is an invalid pointer value.
31019 No access to the file or the path of the file.
31022 @var{pathname} was too long.
31025 The call was interrupted by the user.
31031 @unnumberedsubsubsec gettimeofday
31032 @cindex gettimeofday, file-i/o system call
31037 int gettimeofday(struct timeval *tv, void *tz);
31041 @samp{Fgettimeofday,@var{tvptr},@var{tzptr}}
31043 @item Return value:
31044 On success, 0 is returned, -1 otherwise.
31050 @var{tz} is a non-NULL pointer.
31053 @var{tvptr} and/or @var{tzptr} is an invalid pointer value.
31059 @unnumberedsubsubsec isatty
31060 @cindex isatty, file-i/o system call
31065 int isatty(int fd);
31069 @samp{Fisatty,@var{fd}}
31071 @item Return value:
31072 Returns 1 if @var{fd} refers to the @value{GDBN} console, 0 otherwise.
31078 The call was interrupted by the user.
31083 Note that the @code{isatty} call is treated as a special case: it returns
31084 1 to the target if the file descriptor is attached
31085 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
31086 would require implementing @code{ioctl} and would be more complex than
31091 @unnumberedsubsubsec system
31092 @cindex system, file-i/o system call
31097 int system(const char *command);
31101 @samp{Fsystem,@var{commandptr}/@var{len}}
31103 @item Return value:
31104 If @var{len} is zero, the return value indicates whether a shell is
31105 available. A zero return value indicates a shell is not available.
31106 For non-zero @var{len}, the value returned is -1 on error and the
31107 return status of the command otherwise. Only the exit status of the
31108 command is returned, which is extracted from the host's @code{system}
31109 return value by calling @code{WEXITSTATUS(retval)}. In case
31110 @file{/bin/sh} could not be executed, 127 is returned.
31116 The call was interrupted by the user.
31121 @value{GDBN} takes over the full task of calling the necessary host calls
31122 to perform the @code{system} call. The return value of @code{system} on
31123 the host is simplified before it's returned
31124 to the target. Any termination signal information from the child process
31125 is discarded, and the return value consists
31126 entirely of the exit status of the called command.
31128 Due to security concerns, the @code{system} call is by default refused
31129 by @value{GDBN}. The user has to allow this call explicitly with the
31130 @code{set remote system-call-allowed 1} command.
31133 @item set remote system-call-allowed
31134 @kindex set remote system-call-allowed
31135 Control whether to allow the @code{system} calls in the File I/O
31136 protocol for the remote target. The default is zero (disabled).
31138 @item show remote system-call-allowed
31139 @kindex show remote system-call-allowed
31140 Show whether the @code{system} calls are allowed in the File I/O
31144 @node Protocol-specific Representation of Datatypes
31145 @subsection Protocol-specific Representation of Datatypes
31146 @cindex protocol-specific representation of datatypes, in file-i/o protocol
31149 * Integral Datatypes::
31151 * Memory Transfer::
31156 @node Integral Datatypes
31157 @unnumberedsubsubsec Integral Datatypes
31158 @cindex integral datatypes, in file-i/o protocol
31160 The integral datatypes used in the system calls are @code{int},
31161 @code{unsigned int}, @code{long}, @code{unsigned long},
31162 @code{mode_t}, and @code{time_t}.
31164 @code{int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
31165 implemented as 32 bit values in this protocol.
31167 @code{long} and @code{unsigned long} are implemented as 64 bit types.
31169 @xref{Limits}, for corresponding MIN and MAX values (similar to those
31170 in @file{limits.h}) to allow range checking on host and target.
31172 @code{time_t} datatypes are defined as seconds since the Epoch.
31174 All integral datatypes transferred as part of a memory read or write of a
31175 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
31178 @node Pointer Values
31179 @unnumberedsubsubsec Pointer Values
31180 @cindex pointer values, in file-i/o protocol
31182 Pointers to target data are transmitted as they are. An exception
31183 is made for pointers to buffers for which the length isn't
31184 transmitted as part of the function call, namely strings. Strings
31185 are transmitted as a pointer/length pair, both as hex values, e.g.@:
31192 which is a pointer to data of length 18 bytes at position 0x1aaf.
31193 The length is defined as the full string length in bytes, including
31194 the trailing null byte. For example, the string @code{"hello world"}
31195 at address 0x123456 is transmitted as
31201 @node Memory Transfer
31202 @unnumberedsubsubsec Memory Transfer
31203 @cindex memory transfer, in file-i/o protocol
31205 Structured data which is transferred using a memory read or write (for
31206 example, a @code{struct stat}) is expected to be in a protocol-specific format
31207 with all scalar multibyte datatypes being big endian. Translation to
31208 this representation needs to be done both by the target before the @code{F}
31209 packet is sent, and by @value{GDBN} before
31210 it transfers memory to the target. Transferred pointers to structured
31211 data should point to the already-coerced data at any time.
31215 @unnumberedsubsubsec struct stat
31216 @cindex struct stat, in file-i/o protocol
31218 The buffer of type @code{struct stat} used by the target and @value{GDBN}
31219 is defined as follows:
31223 unsigned int st_dev; /* device */
31224 unsigned int st_ino; /* inode */
31225 mode_t st_mode; /* protection */
31226 unsigned int st_nlink; /* number of hard links */
31227 unsigned int st_uid; /* user ID of owner */
31228 unsigned int st_gid; /* group ID of owner */
31229 unsigned int st_rdev; /* device type (if inode device) */
31230 unsigned long st_size; /* total size, in bytes */
31231 unsigned long st_blksize; /* blocksize for filesystem I/O */
31232 unsigned long st_blocks; /* number of blocks allocated */
31233 time_t st_atime; /* time of last access */
31234 time_t st_mtime; /* time of last modification */
31235 time_t st_ctime; /* time of last change */
31239 The integral datatypes conform to the definitions given in the
31240 appropriate section (see @ref{Integral Datatypes}, for details) so this
31241 structure is of size 64 bytes.
31243 The values of several fields have a restricted meaning and/or
31249 A value of 0 represents a file, 1 the console.
31252 No valid meaning for the target. Transmitted unchanged.
31255 Valid mode bits are described in @ref{Constants}. Any other
31256 bits have currently no meaning for the target.
31261 No valid meaning for the target. Transmitted unchanged.
31266 These values have a host and file system dependent
31267 accuracy. Especially on Windows hosts, the file system may not
31268 support exact timing values.
31271 The target gets a @code{struct stat} of the above representation and is
31272 responsible for coercing it to the target representation before
31275 Note that due to size differences between the host, target, and protocol
31276 representations of @code{struct stat} members, these members could eventually
31277 get truncated on the target.
31279 @node struct timeval
31280 @unnumberedsubsubsec struct timeval
31281 @cindex struct timeval, in file-i/o protocol
31283 The buffer of type @code{struct timeval} used by the File-I/O protocol
31284 is defined as follows:
31288 time_t tv_sec; /* second */
31289 long tv_usec; /* microsecond */
31293 The integral datatypes conform to the definitions given in the
31294 appropriate section (see @ref{Integral Datatypes}, for details) so this
31295 structure is of size 8 bytes.
31298 @subsection Constants
31299 @cindex constants, in file-i/o protocol
31301 The following values are used for the constants inside of the
31302 protocol. @value{GDBN} and target are responsible for translating these
31303 values before and after the call as needed.
31314 @unnumberedsubsubsec Open Flags
31315 @cindex open flags, in file-i/o protocol
31317 All values are given in hexadecimal representation.
31329 @node mode_t Values
31330 @unnumberedsubsubsec mode_t Values
31331 @cindex mode_t values, in file-i/o protocol
31333 All values are given in octal representation.
31350 @unnumberedsubsubsec Errno Values
31351 @cindex errno values, in file-i/o protocol
31353 All values are given in decimal representation.
31378 @code{EUNKNOWN} is used as a fallback error value if a host system returns
31379 any error value not in the list of supported error numbers.
31382 @unnumberedsubsubsec Lseek Flags
31383 @cindex lseek flags, in file-i/o protocol
31392 @unnumberedsubsubsec Limits
31393 @cindex limits, in file-i/o protocol
31395 All values are given in decimal representation.
31398 INT_MIN -2147483648
31400 UINT_MAX 4294967295
31401 LONG_MIN -9223372036854775808
31402 LONG_MAX 9223372036854775807
31403 ULONG_MAX 18446744073709551615
31406 @node File-I/O Examples
31407 @subsection File-I/O Examples
31408 @cindex file-i/o examples
31410 Example sequence of a write call, file descriptor 3, buffer is at target
31411 address 0x1234, 6 bytes should be written:
31414 <- @code{Fwrite,3,1234,6}
31415 @emph{request memory read from target}
31418 @emph{return "6 bytes written"}
31422 Example sequence of a read call, file descriptor 3, buffer is at target
31423 address 0x1234, 6 bytes should be read:
31426 <- @code{Fread,3,1234,6}
31427 @emph{request memory write to target}
31428 -> @code{X1234,6:XXXXXX}
31429 @emph{return "6 bytes read"}
31433 Example sequence of a read call, call fails on the host due to invalid
31434 file descriptor (@code{EBADF}):
31437 <- @code{Fread,3,1234,6}
31441 Example sequence of a read call, user presses @kbd{Ctrl-c} before syscall on
31445 <- @code{Fread,3,1234,6}
31450 Example sequence of a read call, user presses @kbd{Ctrl-c} after syscall on
31454 <- @code{Fread,3,1234,6}
31455 -> @code{X1234,6:XXXXXX}
31459 @node Library List Format
31460 @section Library List Format
31461 @cindex library list format, remote protocol
31463 On some platforms, a dynamic loader (e.g.@: @file{ld.so}) runs in the
31464 same process as your application to manage libraries. In this case,
31465 @value{GDBN} can use the loader's symbol table and normal memory
31466 operations to maintain a list of shared libraries. On other
31467 platforms, the operating system manages loaded libraries.
31468 @value{GDBN} can not retrieve the list of currently loaded libraries
31469 through memory operations, so it uses the @samp{qXfer:libraries:read}
31470 packet (@pxref{qXfer library list read}) instead. The remote stub
31471 queries the target's operating system and reports which libraries
31474 The @samp{qXfer:libraries:read} packet returns an XML document which
31475 lists loaded libraries and their offsets. Each library has an
31476 associated name and one or more segment or section base addresses,
31477 which report where the library was loaded in memory.
31479 For the common case of libraries that are fully linked binaries, the
31480 library should have a list of segments. If the target supports
31481 dynamic linking of a relocatable object file, its library XML element
31482 should instead include a list of allocated sections. The segment or
31483 section bases are start addresses, not relocation offsets; they do not
31484 depend on the library's link-time base addresses.
31486 @value{GDBN} must be linked with the Expat library to support XML
31487 library lists. @xref{Expat}.
31489 A simple memory map, with one loaded library relocated by a single
31490 offset, looks like this:
31494 <library name="/lib/libc.so.6">
31495 <segment address="0x10000000"/>
31500 Another simple memory map, with one loaded library with three
31501 allocated sections (.text, .data, .bss), looks like this:
31505 <library name="sharedlib.o">
31506 <section address="0x10000000"/>
31507 <section address="0x20000000"/>
31508 <section address="0x30000000"/>
31513 The format of a library list is described by this DTD:
31516 <!-- library-list: Root element with versioning -->
31517 <!ELEMENT library-list (library)*>
31518 <!ATTLIST library-list version CDATA #FIXED "1.0">
31519 <!ELEMENT library (segment*, section*)>
31520 <!ATTLIST library name CDATA #REQUIRED>
31521 <!ELEMENT segment EMPTY>
31522 <!ATTLIST segment address CDATA #REQUIRED>
31523 <!ELEMENT section EMPTY>
31524 <!ATTLIST section address CDATA #REQUIRED>
31527 In addition, segments and section descriptors cannot be mixed within a
31528 single library element, and you must supply at least one segment or
31529 section for each library.
31531 @node Memory Map Format
31532 @section Memory Map Format
31533 @cindex memory map format
31535 To be able to write into flash memory, @value{GDBN} needs to obtain a
31536 memory map from the target. This section describes the format of the
31539 The memory map is obtained using the @samp{qXfer:memory-map:read}
31540 (@pxref{qXfer memory map read}) packet and is an XML document that
31541 lists memory regions.
31543 @value{GDBN} must be linked with the Expat library to support XML
31544 memory maps. @xref{Expat}.
31546 The top-level structure of the document is shown below:
31549 <?xml version="1.0"?>
31550 <!DOCTYPE memory-map
31551 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
31552 "http://sourceware.org/gdb/gdb-memory-map.dtd">
31558 Each region can be either:
31563 A region of RAM starting at @var{addr} and extending for @var{length}
31567 <memory type="ram" start="@var{addr}" length="@var{length}"/>
31572 A region of read-only memory:
31575 <memory type="rom" start="@var{addr}" length="@var{length}"/>
31580 A region of flash memory, with erasure blocks @var{blocksize}
31584 <memory type="flash" start="@var{addr}" length="@var{length}">
31585 <property name="blocksize">@var{blocksize}</property>
31591 Regions must not overlap. @value{GDBN} assumes that areas of memory not covered
31592 by the memory map are RAM, and uses the ordinary @samp{M} and @samp{X}
31593 packets to write to addresses in such ranges.
31595 The formal DTD for memory map format is given below:
31598 <!-- ................................................... -->
31599 <!-- Memory Map XML DTD ................................ -->
31600 <!-- File: memory-map.dtd .............................. -->
31601 <!-- .................................... .............. -->
31602 <!-- memory-map.dtd -->
31603 <!-- memory-map: Root element with versioning -->
31604 <!ELEMENT memory-map (memory | property)>
31605 <!ATTLIST memory-map version CDATA #FIXED "1.0.0">
31606 <!ELEMENT memory (property)>
31607 <!-- memory: Specifies a memory region,
31608 and its type, or device. -->
31609 <!ATTLIST memory type CDATA #REQUIRED
31610 start CDATA #REQUIRED
31611 length CDATA #REQUIRED
31612 device CDATA #IMPLIED>
31613 <!-- property: Generic attribute tag -->
31614 <!ELEMENT property (#PCDATA | property)*>
31615 <!ATTLIST property name CDATA #REQUIRED>
31618 @include agentexpr.texi
31620 @node Target Descriptions
31621 @appendix Target Descriptions
31622 @cindex target descriptions
31624 @strong{Warning:} target descriptions are still under active development,
31625 and the contents and format may change between @value{GDBN} releases.
31626 The format is expected to stabilize in the future.
31628 One of the challenges of using @value{GDBN} to debug embedded systems
31629 is that there are so many minor variants of each processor
31630 architecture in use. It is common practice for vendors to start with
31631 a standard processor core --- ARM, PowerPC, or MIPS, for example ---
31632 and then make changes to adapt it to a particular market niche. Some
31633 architectures have hundreds of variants, available from dozens of
31634 vendors. This leads to a number of problems:
31638 With so many different customized processors, it is difficult for
31639 the @value{GDBN} maintainers to keep up with the changes.
31641 Since individual variants may have short lifetimes or limited
31642 audiences, it may not be worthwhile to carry information about every
31643 variant in the @value{GDBN} source tree.
31645 When @value{GDBN} does support the architecture of the embedded system
31646 at hand, the task of finding the correct architecture name to give the
31647 @command{set architecture} command can be error-prone.
31650 To address these problems, the @value{GDBN} remote protocol allows a
31651 target system to not only identify itself to @value{GDBN}, but to
31652 actually describe its own features. This lets @value{GDBN} support
31653 processor variants it has never seen before --- to the extent that the
31654 descriptions are accurate, and that @value{GDBN} understands them.
31656 @value{GDBN} must be linked with the Expat library to support XML
31657 target descriptions. @xref{Expat}.
31660 * Retrieving Descriptions:: How descriptions are fetched from a target.
31661 * Target Description Format:: The contents of a target description.
31662 * Predefined Target Types:: Standard types available for target
31664 * Standard Target Features:: Features @value{GDBN} knows about.
31667 @node Retrieving Descriptions
31668 @section Retrieving Descriptions
31670 Target descriptions can be read from the target automatically, or
31671 specified by the user manually. The default behavior is to read the
31672 description from the target. @value{GDBN} retrieves it via the remote
31673 protocol using @samp{qXfer} requests (@pxref{General Query Packets,
31674 qXfer}). The @var{annex} in the @samp{qXfer} packet will be
31675 @samp{target.xml}. The contents of the @samp{target.xml} annex are an
31676 XML document, of the form described in @ref{Target Description
31679 Alternatively, you can specify a file to read for the target description.
31680 If a file is set, the target will not be queried. The commands to
31681 specify a file are:
31684 @cindex set tdesc filename
31685 @item set tdesc filename @var{path}
31686 Read the target description from @var{path}.
31688 @cindex unset tdesc filename
31689 @item unset tdesc filename
31690 Do not read the XML target description from a file. @value{GDBN}
31691 will use the description supplied by the current target.
31693 @cindex show tdesc filename
31694 @item show tdesc filename
31695 Show the filename to read for a target description, if any.
31699 @node Target Description Format
31700 @section Target Description Format
31701 @cindex target descriptions, XML format
31703 A target description annex is an @uref{http://www.w3.org/XML/, XML}
31704 document which complies with the Document Type Definition provided in
31705 the @value{GDBN} sources in @file{gdb/features/gdb-target.dtd}. This
31706 means you can use generally available tools like @command{xmllint} to
31707 check that your feature descriptions are well-formed and valid.
31708 However, to help people unfamiliar with XML write descriptions for
31709 their targets, we also describe the grammar here.
31711 Target descriptions can identify the architecture of the remote target
31712 and (for some architectures) provide information about custom register
31713 sets. They can also identify the OS ABI of the remote target.
31714 @value{GDBN} can use this information to autoconfigure for your
31715 target, or to warn you if you connect to an unsupported target.
31717 Here is a simple target description:
31720 <target version="1.0">
31721 <architecture>i386:x86-64</architecture>
31726 This minimal description only says that the target uses
31727 the x86-64 architecture.
31729 A target description has the following overall form, with [ ] marking
31730 optional elements and @dots{} marking repeatable elements. The elements
31731 are explained further below.
31734 <?xml version="1.0"?>
31735 <!DOCTYPE target SYSTEM "gdb-target.dtd">
31736 <target version="1.0">
31737 @r{[}@var{architecture}@r{]}
31738 @r{[}@var{osabi}@r{]}
31739 @r{[}@var{compatible}@r{]}
31740 @r{[}@var{feature}@dots{}@r{]}
31745 The description is generally insensitive to whitespace and line
31746 breaks, under the usual common-sense rules. The XML version
31747 declaration and document type declaration can generally be omitted
31748 (@value{GDBN} does not require them), but specifying them may be
31749 useful for XML validation tools. The @samp{version} attribute for
31750 @samp{<target>} may also be omitted, but we recommend
31751 including it; if future versions of @value{GDBN} use an incompatible
31752 revision of @file{gdb-target.dtd}, they will detect and report
31753 the version mismatch.
31755 @subsection Inclusion
31756 @cindex target descriptions, inclusion
31759 @cindex <xi:include>
31762 It can sometimes be valuable to split a target description up into
31763 several different annexes, either for organizational purposes, or to
31764 share files between different possible target descriptions. You can
31765 divide a description into multiple files by replacing any element of
31766 the target description with an inclusion directive of the form:
31769 <xi:include href="@var{document}"/>
31773 When @value{GDBN} encounters an element of this form, it will retrieve
31774 the named XML @var{document}, and replace the inclusion directive with
31775 the contents of that document. If the current description was read
31776 using @samp{qXfer}, then so will be the included document;
31777 @var{document} will be interpreted as the name of an annex. If the
31778 current description was read from a file, @value{GDBN} will look for
31779 @var{document} as a file in the same directory where it found the
31780 original description.
31782 @subsection Architecture
31783 @cindex <architecture>
31785 An @samp{<architecture>} element has this form:
31788 <architecture>@var{arch}</architecture>
31791 @var{arch} is one of the architectures from the set accepted by
31792 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
31795 @cindex @code{<osabi>}
31797 This optional field was introduced in @value{GDBN} version 7.0.
31798 Previous versions of @value{GDBN} ignore it.
31800 An @samp{<osabi>} element has this form:
31803 <osabi>@var{abi-name}</osabi>
31806 @var{abi-name} is an OS ABI name from the same selection accepted by
31807 @w{@code{set osabi}} (@pxref{ABI, ,Configuring the Current ABI}).
31809 @subsection Compatible Architecture
31810 @cindex @code{<compatible>}
31812 This optional field was introduced in @value{GDBN} version 7.0.
31813 Previous versions of @value{GDBN} ignore it.
31815 A @samp{<compatible>} element has this form:
31818 <compatible>@var{arch}</compatible>
31821 @var{arch} is one of the architectures from the set accepted by
31822 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
31824 A @samp{<compatible>} element is used to specify that the target
31825 is able to run binaries in some other than the main target architecture
31826 given by the @samp{<architecture>} element. For example, on the
31827 Cell Broadband Engine, the main architecture is @code{powerpc:common}
31828 or @code{powerpc:common64}, but the system is able to run binaries
31829 in the @code{spu} architecture as well. The way to describe this
31830 capability with @samp{<compatible>} is as follows:
31833 <architecture>powerpc:common</architecture>
31834 <compatible>spu</compatible>
31837 @subsection Features
31840 Each @samp{<feature>} describes some logical portion of the target
31841 system. Features are currently used to describe available CPU
31842 registers and the types of their contents. A @samp{<feature>} element
31846 <feature name="@var{name}">
31847 @r{[}@var{type}@dots{}@r{]}
31853 Each feature's name should be unique within the description. The name
31854 of a feature does not matter unless @value{GDBN} has some special
31855 knowledge of the contents of that feature; if it does, the feature
31856 should have its standard name. @xref{Standard Target Features}.
31860 Any register's value is a collection of bits which @value{GDBN} must
31861 interpret. The default interpretation is a two's complement integer,
31862 but other types can be requested by name in the register description.
31863 Some predefined types are provided by @value{GDBN} (@pxref{Predefined
31864 Target Types}), and the description can define additional composite types.
31866 Each type element must have an @samp{id} attribute, which gives
31867 a unique (within the containing @samp{<feature>}) name to the type.
31868 Types must be defined before they are used.
31871 Some targets offer vector registers, which can be treated as arrays
31872 of scalar elements. These types are written as @samp{<vector>} elements,
31873 specifying the array element type, @var{type}, and the number of elements,
31877 <vector id="@var{id}" type="@var{type}" count="@var{count}"/>
31881 If a register's value is usefully viewed in multiple ways, define it
31882 with a union type containing the useful representations. The
31883 @samp{<union>} element contains one or more @samp{<field>} elements,
31884 each of which has a @var{name} and a @var{type}:
31887 <union id="@var{id}">
31888 <field name="@var{name}" type="@var{type}"/>
31893 @subsection Registers
31896 Each register is represented as an element with this form:
31899 <reg name="@var{name}"
31900 bitsize="@var{size}"
31901 @r{[}regnum="@var{num}"@r{]}
31902 @r{[}save-restore="@var{save-restore}"@r{]}
31903 @r{[}type="@var{type}"@r{]}
31904 @r{[}group="@var{group}"@r{]}/>
31908 The components are as follows:
31913 The register's name; it must be unique within the target description.
31916 The register's size, in bits.
31919 The register's number. If omitted, a register's number is one greater
31920 than that of the previous register (either in the current feature or in
31921 a preceeding feature); the first register in the target description
31922 defaults to zero. This register number is used to read or write
31923 the register; e.g.@: it is used in the remote @code{p} and @code{P}
31924 packets, and registers appear in the @code{g} and @code{G} packets
31925 in order of increasing register number.
31928 Whether the register should be preserved across inferior function
31929 calls; this must be either @code{yes} or @code{no}. The default is
31930 @code{yes}, which is appropriate for most registers except for
31931 some system control registers; this is not related to the target's
31935 The type of the register. @var{type} may be a predefined type, a type
31936 defined in the current feature, or one of the special types @code{int}
31937 and @code{float}. @code{int} is an integer type of the correct size
31938 for @var{bitsize}, and @code{float} is a floating point type (in the
31939 architecture's normal floating point format) of the correct size for
31940 @var{bitsize}. The default is @code{int}.
31943 The register group to which this register belongs. @var{group} must
31944 be either @code{general}, @code{float}, or @code{vector}. If no
31945 @var{group} is specified, @value{GDBN} will not display the register
31946 in @code{info registers}.
31950 @node Predefined Target Types
31951 @section Predefined Target Types
31952 @cindex target descriptions, predefined types
31954 Type definitions in the self-description can build up composite types
31955 from basic building blocks, but can not define fundamental types. Instead,
31956 standard identifiers are provided by @value{GDBN} for the fundamental
31957 types. The currently supported types are:
31966 Signed integer types holding the specified number of bits.
31973 Unsigned integer types holding the specified number of bits.
31977 Pointers to unspecified code and data. The program counter and
31978 any dedicated return address register may be marked as code
31979 pointers; printing a code pointer converts it into a symbolic
31980 address. The stack pointer and any dedicated address registers
31981 may be marked as data pointers.
31984 Single precision IEEE floating point.
31987 Double precision IEEE floating point.
31990 The 12-byte extended precision format used by ARM FPA registers.
31994 @node Standard Target Features
31995 @section Standard Target Features
31996 @cindex target descriptions, standard features
31998 A target description must contain either no registers or all the
31999 target's registers. If the description contains no registers, then
32000 @value{GDBN} will assume a default register layout, selected based on
32001 the architecture. If the description contains any registers, the
32002 default layout will not be used; the standard registers must be
32003 described in the target description, in such a way that @value{GDBN}
32004 can recognize them.
32006 This is accomplished by giving specific names to feature elements
32007 which contain standard registers. @value{GDBN} will look for features
32008 with those names and verify that they contain the expected registers;
32009 if any known feature is missing required registers, or if any required
32010 feature is missing, @value{GDBN} will reject the target
32011 description. You can add additional registers to any of the
32012 standard features --- @value{GDBN} will display them just as if
32013 they were added to an unrecognized feature.
32015 This section lists the known features and their expected contents.
32016 Sample XML documents for these features are included in the
32017 @value{GDBN} source tree, in the directory @file{gdb/features}.
32019 Names recognized by @value{GDBN} should include the name of the
32020 company or organization which selected the name, and the overall
32021 architecture to which the feature applies; so e.g.@: the feature
32022 containing ARM core registers is named @samp{org.gnu.gdb.arm.core}.
32024 The names of registers are not case sensitive for the purpose
32025 of recognizing standard features, but @value{GDBN} will only display
32026 registers using the capitalization used in the description.
32032 * PowerPC Features::
32037 @subsection ARM Features
32038 @cindex target descriptions, ARM features
32040 The @samp{org.gnu.gdb.arm.core} feature is required for ARM targets.
32041 It should contain registers @samp{r0} through @samp{r13}, @samp{sp},
32042 @samp{lr}, @samp{pc}, and @samp{cpsr}.
32044 The @samp{org.gnu.gdb.arm.fpa} feature is optional. If present, it
32045 should contain registers @samp{f0} through @samp{f7} and @samp{fps}.
32047 The @samp{org.gnu.gdb.xscale.iwmmxt} feature is optional. If present,
32048 it should contain at least registers @samp{wR0} through @samp{wR15} and
32049 @samp{wCGR0} through @samp{wCGR3}. The @samp{wCID}, @samp{wCon},
32050 @samp{wCSSF}, and @samp{wCASF} registers are optional.
32052 The @samp{org.gnu.gdb.arm.vfp} feature is optional. If present, it
32053 should contain at least registers @samp{d0} through @samp{d15}. If
32054 they are present, @samp{d16} through @samp{d31} should also be included.
32055 @value{GDBN} will synthesize the single-precision registers from
32056 halves of the double-precision registers.
32058 The @samp{org.gnu.gdb.arm.neon} feature is optional. It does not
32059 need to contain registers; it instructs @value{GDBN} to display the
32060 VFP double-precision registers as vectors and to synthesize the
32061 quad-precision registers from pairs of double-precision registers.
32062 If this feature is present, @samp{org.gnu.gdb.arm.vfp} must also
32063 be present and include 32 double-precision registers.
32065 @node MIPS Features
32066 @subsection MIPS Features
32067 @cindex target descriptions, MIPS features
32069 The @samp{org.gnu.gdb.mips.cpu} feature is required for MIPS targets.
32070 It should contain registers @samp{r0} through @samp{r31}, @samp{lo},
32071 @samp{hi}, and @samp{pc}. They may be 32-bit or 64-bit depending
32074 The @samp{org.gnu.gdb.mips.cp0} feature is also required. It should
32075 contain at least the @samp{status}, @samp{badvaddr}, and @samp{cause}
32076 registers. They may be 32-bit or 64-bit depending on the target.
32078 The @samp{org.gnu.gdb.mips.fpu} feature is currently required, though
32079 it may be optional in a future version of @value{GDBN}. It should
32080 contain registers @samp{f0} through @samp{f31}, @samp{fcsr}, and
32081 @samp{fir}. They may be 32-bit or 64-bit depending on the target.
32083 The @samp{org.gnu.gdb.mips.linux} feature is optional. It should
32084 contain a single register, @samp{restart}, which is used by the
32085 Linux kernel to control restartable syscalls.
32087 @node M68K Features
32088 @subsection M68K Features
32089 @cindex target descriptions, M68K features
32092 @item @samp{org.gnu.gdb.m68k.core}
32093 @itemx @samp{org.gnu.gdb.coldfire.core}
32094 @itemx @samp{org.gnu.gdb.fido.core}
32095 One of those features must be always present.
32096 The feature that is present determines which flavor of m68k is
32097 used. The feature that is present should contain registers
32098 @samp{d0} through @samp{d7}, @samp{a0} through @samp{a5}, @samp{fp},
32099 @samp{sp}, @samp{ps} and @samp{pc}.
32101 @item @samp{org.gnu.gdb.coldfire.fp}
32102 This feature is optional. If present, it should contain registers
32103 @samp{fp0} through @samp{fp7}, @samp{fpcontrol}, @samp{fpstatus} and
32107 @node PowerPC Features
32108 @subsection PowerPC Features
32109 @cindex target descriptions, PowerPC features
32111 The @samp{org.gnu.gdb.power.core} feature is required for PowerPC
32112 targets. It should contain registers @samp{r0} through @samp{r31},
32113 @samp{pc}, @samp{msr}, @samp{cr}, @samp{lr}, @samp{ctr}, and
32114 @samp{xer}. They may be 32-bit or 64-bit depending on the target.
32116 The @samp{org.gnu.gdb.power.fpu} feature is optional. It should
32117 contain registers @samp{f0} through @samp{f31} and @samp{fpscr}.
32119 The @samp{org.gnu.gdb.power.altivec} feature is optional. It should
32120 contain registers @samp{vr0} through @samp{vr31}, @samp{vscr},
32123 The @samp{org.gnu.gdb.power.vsx} feature is optional. It should
32124 contain registers @samp{vs0h} through @samp{vs31h}. @value{GDBN}
32125 will combine these registers with the floating point registers
32126 (@samp{f0} through @samp{f31}) and the altivec registers (@samp{vr0}
32127 through @samp{vr31}) to present the 128-bit wide registers @samp{vs0}
32128 through @samp{vs63}, the set of vector registers for POWER7.
32130 The @samp{org.gnu.gdb.power.spe} feature is optional. It should
32131 contain registers @samp{ev0h} through @samp{ev31h}, @samp{acc}, and
32132 @samp{spefscr}. SPE targets should provide 32-bit registers in
32133 @samp{org.gnu.gdb.power.core} and provide the upper halves in
32134 @samp{ev0h} through @samp{ev31h}. @value{GDBN} will combine
32135 these to present registers @samp{ev0} through @samp{ev31} to the
32138 @node Operating System Information
32139 @appendix Operating System Information
32140 @cindex operating system information
32146 Users of @value{GDBN} often wish to obtain information about the state of
32147 the operating system running on the target---for example the list of
32148 processes, or the list of open files. This section describes the
32149 mechanism that makes it possible. This mechanism is similar to the
32150 target features mechanism (@pxref{Target Descriptions}), but focuses
32151 on a different aspect of target.
32153 Operating system information is retrived from the target via the
32154 remote protocol, using @samp{qXfer} requests (@pxref{qXfer osdata
32155 read}). The object name in the request should be @samp{osdata}, and
32156 the @var{annex} identifies the data to be fetched.
32159 @appendixsection Process list
32160 @cindex operating system information, process list
32162 When requesting the process list, the @var{annex} field in the
32163 @samp{qXfer} request should be @samp{processes}. The returned data is
32164 an XML document. The formal syntax of this document is defined in
32165 @file{gdb/features/osdata.dtd}.
32167 An example document is:
32170 <?xml version="1.0"?>
32171 <!DOCTYPE target SYSTEM "osdata.dtd">
32172 <osdata type="processes">
32174 <column name="pid">1</column>
32175 <column name="user">root</column>
32176 <column name="command">/sbin/init</column>
32181 Each item should include a column whose name is @samp{pid}. The value
32182 of that column should identify the process on the target. The
32183 @samp{user} and @samp{command} columns are optional, and will be
32184 displayed by @value{GDBN}. Target may provide additional columns,
32185 which @value{GDBN} currently ignores.
32199 % I think something like @colophon should be in texinfo. In the
32201 \long\def\colophon{\hbox to0pt{}\vfill
32202 \centerline{The body of this manual is set in}
32203 \centerline{\fontname\tenrm,}
32204 \centerline{with headings in {\bf\fontname\tenbf}}
32205 \centerline{and examples in {\tt\fontname\tentt}.}
32206 \centerline{{\it\fontname\tenit\/},}
32207 \centerline{{\bf\fontname\tenbf}, and}
32208 \centerline{{\sl\fontname\tensl\/}}
32209 \centerline{are used for emphasis.}\vfill}
32211 % Blame: doc@cygnus.com, 1991.