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
25 @c readline appendices use @vindex, @findex and @ftable,
26 @c annotate.texi and gdbmi use @findex.
30 @c !!set GDB manual's edition---not the same as GDB version!
31 @c This is updated by GNU Press.
34 @c !!set GDB edit command default editor
37 @c THIS MANUAL REQUIRES TEXINFO 4.0 OR LATER.
39 @c This is a dir.info fragment to support semi-automated addition of
40 @c manuals to an info tree.
41 @dircategory Software development
43 * Gdb: (gdb). The GNU debugger.
47 Copyright @copyright{} 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995, 1996,
48 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009
49 Free Software Foundation, Inc.
51 Permission is granted to copy, distribute and/or modify this document
52 under the terms of the GNU Free Documentation License, Version 1.1 or
53 any later version published by the Free Software Foundation; with the
54 Invariant Sections being ``Free Software'' and ``Free Software Needs
55 Free Documentation'', with the Front-Cover Texts being ``A GNU Manual,''
56 and with the Back-Cover Texts as in (a) below.
58 (a) The FSF's Back-Cover Text is: ``You are free to copy and modify
59 this GNU Manual. Buying copies from GNU Press supports the FSF in
60 developing GNU and promoting software freedom.''
64 This file documents the @sc{gnu} debugger @value{GDBN}.
66 This is the @value{EDITION} Edition, of @cite{Debugging with
67 @value{GDBN}: the @sc{gnu} Source-Level Debugger} for @value{GDBN}
68 @ifset VERSION_PACKAGE
69 @value{VERSION_PACKAGE}
71 Version @value{GDBVN}.
77 @title Debugging with @value{GDBN}
78 @subtitle The @sc{gnu} Source-Level Debugger
80 @subtitle @value{EDITION} Edition, for @value{GDBN} version @value{GDBVN}
81 @ifset VERSION_PACKAGE
83 @subtitle @value{VERSION_PACKAGE}
85 @author Richard Stallman, Roland Pesch, Stan Shebs, et al.
89 \hfill (Send bugs and comments on @value{GDBN} to @value{BUGURL}.)\par
90 \hfill {\it Debugging with @value{GDBN}}\par
91 \hfill \TeX{}info \texinfoversion\par
95 @vskip 0pt plus 1filll
96 Published by the Free Software Foundation @*
97 51 Franklin Street, Fifth Floor,
98 Boston, MA 02110-1301, USA@*
103 This edition of the GDB manual is dedicated to the memory of Fred
104 Fish. Fred was a long-standing contributor to GDB and to Free
105 software in general. We will miss him.
110 @node Top, Summary, (dir), (dir)
112 @top Debugging with @value{GDBN}
114 This file describes @value{GDBN}, the @sc{gnu} symbolic debugger.
116 This is the @value{EDITION} Edition, for @value{GDBN}
117 @ifset VERSION_PACKAGE
118 @value{VERSION_PACKAGE}
120 Version @value{GDBVN}.
122 Copyright (C) 1988-2009 Free Software Foundation, Inc.
124 This edition of the GDB manual is dedicated to the memory of Fred
125 Fish. Fred was a long-standing contributor to GDB and to Free
126 software in general. We will miss him.
129 * Summary:: Summary of @value{GDBN}
130 * Sample Session:: A sample @value{GDBN} session
132 * Invocation:: Getting in and out of @value{GDBN}
133 * Commands:: @value{GDBN} commands
134 * Running:: Running programs under @value{GDBN}
135 * Stopping:: Stopping and continuing
136 * Reverse Execution:: Running programs backward
137 * Stack:: Examining the stack
138 * Source:: Examining source files
139 * Data:: Examining data
140 * Macros:: Preprocessor Macros
141 * Tracepoints:: Debugging remote targets non-intrusively
142 * Overlays:: Debugging programs that use overlays
144 * Languages:: Using @value{GDBN} with different languages
146 * Symbols:: Examining the symbol table
147 * Altering:: Altering execution
148 * GDB Files:: @value{GDBN} files
149 * Targets:: Specifying a debugging target
150 * Remote Debugging:: Debugging remote programs
151 * Configurations:: Configuration-specific information
152 * Controlling GDB:: Controlling @value{GDBN}
153 * Extending GDB:: Extending @value{GDBN}
154 * Interpreters:: Command Interpreters
155 * TUI:: @value{GDBN} Text User Interface
156 * Emacs:: Using @value{GDBN} under @sc{gnu} Emacs
157 * GDB/MI:: @value{GDBN}'s Machine Interface.
158 * Annotations:: @value{GDBN}'s annotation interface.
160 * GDB Bugs:: Reporting bugs in @value{GDBN}
162 * Command Line Editing:: Command Line Editing
163 * Using History Interactively:: Using History Interactively
164 * Formatting Documentation:: How to format and print @value{GDBN} documentation
165 * Installing GDB:: Installing GDB
166 * Maintenance Commands:: Maintenance Commands
167 * Remote Protocol:: GDB Remote Serial Protocol
168 * Agent Expressions:: The GDB Agent Expression Mechanism
169 * Target Descriptions:: How targets can describe themselves to
171 * Operating System Information:: Getting additional information from
173 * Copying:: GNU General Public License says
174 how you can copy and share GDB
175 * GNU Free Documentation License:: The license for this documentation
184 @unnumbered Summary of @value{GDBN}
186 The purpose of a debugger such as @value{GDBN} is to allow you to see what is
187 going on ``inside'' another program while it executes---or what another
188 program was doing at the moment it crashed.
190 @value{GDBN} can do four main kinds of things (plus other things in support of
191 these) to help you catch bugs in the act:
195 Start your program, specifying anything that might affect its behavior.
198 Make your program stop on specified conditions.
201 Examine what has happened, when your program has stopped.
204 Change things in your program, so you can experiment with correcting the
205 effects of one bug and go on to learn about another.
208 You can use @value{GDBN} to debug programs written in C and C@t{++}.
209 For more information, see @ref{Supported Languages,,Supported Languages}.
210 For more information, see @ref{C,,C and C++}.
213 Support for Modula-2 is partial. For information on Modula-2, see
214 @ref{Modula-2,,Modula-2}.
217 Debugging Pascal programs which use sets, subranges, file variables, or
218 nested functions does not currently work. @value{GDBN} does not support
219 entering expressions, printing values, or similar features using Pascal
223 @value{GDBN} can be used to debug programs written in Fortran, although
224 it may be necessary to refer to some variables with a trailing
227 @value{GDBN} can be used to debug programs written in Objective-C,
228 using either the Apple/NeXT or the GNU Objective-C runtime.
231 * Free Software:: Freely redistributable software
232 * Contributors:: Contributors to GDB
236 @unnumberedsec Free Software
238 @value{GDBN} is @dfn{free software}, protected by the @sc{gnu}
239 General Public License
240 (GPL). The GPL gives you the freedom to copy or adapt a licensed
241 program---but every person getting a copy also gets with it the
242 freedom to modify that copy (which means that they must get access to
243 the source code), and the freedom to distribute further copies.
244 Typical software companies use copyrights to limit your freedoms; the
245 Free Software Foundation uses the GPL to preserve these freedoms.
247 Fundamentally, the General Public License is a license which says that
248 you have these freedoms and that you cannot take these freedoms away
251 @unnumberedsec Free Software Needs Free Documentation
253 The biggest deficiency in the free software community today is not in
254 the software---it is the lack of good free documentation that we can
255 include with the free software. Many of our most important
256 programs do not come with free reference manuals and free introductory
257 texts. Documentation is an essential part of any software package;
258 when an important free software package does not come with a free
259 manual and a free tutorial, that is a major gap. We have many such
262 Consider Perl, for instance. The tutorial manuals that people
263 normally use are non-free. How did this come about? Because the
264 authors of those manuals published them with restrictive terms---no
265 copying, no modification, source files not available---which exclude
266 them from the free software world.
268 That wasn't the first time this sort of thing happened, and it was far
269 from the last. Many times we have heard a GNU user eagerly describe a
270 manual that he is writing, his intended contribution to the community,
271 only to learn that he had ruined everything by signing a publication
272 contract to make it non-free.
274 Free documentation, like free software, is a matter of freedom, not
275 price. The problem with the non-free manual is not that publishers
276 charge a price for printed copies---that in itself is fine. (The Free
277 Software Foundation sells printed copies of manuals, too.) The
278 problem is the restrictions on the use of the manual. Free manuals
279 are available in source code form, and give you permission to copy and
280 modify. Non-free manuals do not allow this.
282 The criteria of freedom for a free manual are roughly the same as for
283 free software. Redistribution (including the normal kinds of
284 commercial redistribution) must be permitted, so that the manual can
285 accompany every copy of the program, both on-line and on paper.
287 Permission for modification of the technical content is crucial too.
288 When people modify the software, adding or changing features, if they
289 are conscientious they will change the manual too---so they can
290 provide accurate and clear documentation for the modified program. A
291 manual that leaves you no choice but to write a new manual to document
292 a changed version of the program is not really available to our
295 Some kinds of limits on the way modification is handled are
296 acceptable. For example, requirements to preserve the original
297 author's copyright notice, the distribution terms, or the list of
298 authors, are ok. It is also no problem to require modified versions
299 to include notice that they were modified. Even entire sections that
300 may not be deleted or changed are acceptable, as long as they deal
301 with nontechnical topics (like this one). These kinds of restrictions
302 are acceptable because they don't obstruct the community's normal use
305 However, it must be possible to modify all the @emph{technical}
306 content of the manual, and then distribute the result in all the usual
307 media, through all the usual channels. Otherwise, the restrictions
308 obstruct the use of the manual, it is not free, and we need another
309 manual to replace it.
311 Please spread the word about this issue. Our community continues to
312 lose manuals to proprietary publishing. If we spread the word that
313 free software needs free reference manuals and free tutorials, perhaps
314 the next person who wants to contribute by writing documentation will
315 realize, before it is too late, that only free manuals contribute to
316 the free software community.
318 If you are writing documentation, please insist on publishing it under
319 the GNU Free Documentation License or another free documentation
320 license. Remember that this decision requires your approval---you
321 don't have to let the publisher decide. Some commercial publishers
322 will use a free license if you insist, but they will not propose the
323 option; it is up to you to raise the issue and say firmly that this is
324 what you want. If the publisher you are dealing with refuses, please
325 try other publishers. If you're not sure whether a proposed license
326 is free, write to @email{licensing@@gnu.org}.
328 You can encourage commercial publishers to sell more free, copylefted
329 manuals and tutorials by buying them, and particularly by buying
330 copies from the publishers that paid for their writing or for major
331 improvements. Meanwhile, try to avoid buying non-free documentation
332 at all. Check the distribution terms of a manual before you buy it,
333 and insist that whoever seeks your business must respect your freedom.
334 Check the history of the book, and try to reward the publishers that
335 have paid or pay the authors to work on it.
337 The Free Software Foundation maintains a list of free documentation
338 published by other publishers, at
339 @url{http://www.fsf.org/doc/other-free-books.html}.
342 @unnumberedsec Contributors to @value{GDBN}
344 Richard Stallman was the original author of @value{GDBN}, and of many
345 other @sc{gnu} programs. Many others have contributed to its
346 development. This section attempts to credit major contributors. One
347 of the virtues of free software is that everyone is free to contribute
348 to it; with regret, we cannot actually acknowledge everyone here. The
349 file @file{ChangeLog} in the @value{GDBN} distribution approximates a
350 blow-by-blow account.
352 Changes much prior to version 2.0 are lost in the mists of time.
355 @emph{Plea:} Additions to this section are particularly welcome. If you
356 or your friends (or enemies, to be evenhanded) have been unfairly
357 omitted from this list, we would like to add your names!
360 So that they may not regard their many labors as thankless, we
361 particularly thank those who shepherded @value{GDBN} through major
363 Andrew Cagney (releases 6.3, 6.2, 6.1, 6.0, 5.3, 5.2, 5.1 and 5.0);
364 Jim Blandy (release 4.18);
365 Jason Molenda (release 4.17);
366 Stan Shebs (release 4.14);
367 Fred Fish (releases 4.16, 4.15, 4.13, 4.12, 4.11, 4.10, and 4.9);
368 Stu Grossman and John Gilmore (releases 4.8, 4.7, 4.6, 4.5, and 4.4);
369 John Gilmore (releases 4.3, 4.2, 4.1, 4.0, and 3.9);
370 Jim Kingdon (releases 3.5, 3.4, and 3.3);
371 and Randy Smith (releases 3.2, 3.1, and 3.0).
373 Richard Stallman, assisted at various times by Peter TerMaat, Chris
374 Hanson, and Richard Mlynarik, handled releases through 2.8.
376 Michael Tiemann is the author of most of the @sc{gnu} C@t{++} support
377 in @value{GDBN}, with significant additional contributions from Per
378 Bothner and Daniel Berlin. James Clark wrote the @sc{gnu} C@t{++}
379 demangler. Early work on C@t{++} was by Peter TerMaat (who also did
380 much general update work leading to release 3.0).
382 @value{GDBN} uses the BFD subroutine library to examine multiple
383 object-file formats; BFD was a joint project of David V.
384 Henkel-Wallace, Rich Pixley, Steve Chamberlain, and John Gilmore.
386 David Johnson wrote the original COFF support; Pace Willison did
387 the original support for encapsulated COFF.
389 Brent Benson of Harris Computer Systems contributed DWARF 2 support.
391 Adam de Boor and Bradley Davis contributed the ISI Optimum V support.
392 Per Bothner, Noboyuki Hikichi, and Alessandro Forin contributed MIPS
394 Jean-Daniel Fekete contributed Sun 386i support.
395 Chris Hanson improved the HP9000 support.
396 Noboyuki Hikichi and Tomoyuki Hasei contributed Sony/News OS 3 support.
397 David Johnson contributed Encore Umax support.
398 Jyrki Kuoppala contributed Altos 3068 support.
399 Jeff Law contributed HP PA and SOM support.
400 Keith Packard contributed NS32K support.
401 Doug Rabson contributed Acorn Risc Machine support.
402 Bob Rusk contributed Harris Nighthawk CX-UX support.
403 Chris Smith contributed Convex support (and Fortran debugging).
404 Jonathan Stone contributed Pyramid support.
405 Michael Tiemann contributed SPARC support.
406 Tim Tucker contributed support for the Gould NP1 and Gould Powernode.
407 Pace Willison contributed Intel 386 support.
408 Jay Vosburgh contributed Symmetry support.
409 Marko Mlinar contributed OpenRISC 1000 support.
411 Andreas Schwab contributed M68K @sc{gnu}/Linux support.
413 Rich Schaefer and Peter Schauer helped with support of SunOS shared
416 Jay Fenlason and Roland McGrath ensured that @value{GDBN} and GAS agree
417 about several machine instruction sets.
419 Patrick Duval, Ted Goldstein, Vikram Koka and Glenn Engel helped develop
420 remote debugging. Intel Corporation, Wind River Systems, AMD, and ARM
421 contributed remote debugging modules for the i960, VxWorks, A29K UDI,
422 and RDI targets, respectively.
424 Brian Fox is the author of the readline libraries providing
425 command-line editing and command history.
427 Andrew Beers of SUNY Buffalo wrote the language-switching code, the
428 Modula-2 support, and contributed the Languages chapter of this manual.
430 Fred Fish wrote most of the support for Unix System Vr4.
431 He also enhanced the command-completion support to cover C@t{++} overloaded
434 Hitachi America (now Renesas America), Ltd. sponsored the support for
435 H8/300, H8/500, and Super-H processors.
437 NEC sponsored the support for the v850, Vr4xxx, and Vr5xxx processors.
439 Mitsubishi (now Renesas) sponsored the support for D10V, D30V, and M32R/D
442 Toshiba sponsored the support for the TX39 Mips processor.
444 Matsushita sponsored the support for the MN10200 and MN10300 processors.
446 Fujitsu sponsored the support for SPARClite and FR30 processors.
448 Kung Hsu, Jeff Law, and Rick Sladkey added support for hardware
451 Michael Snyder added support for tracepoints.
453 Stu Grossman wrote gdbserver.
455 Jim Kingdon, Peter Schauer, Ian Taylor, and Stu Grossman made
456 nearly innumerable bug fixes and cleanups throughout @value{GDBN}.
458 The following people at the Hewlett-Packard Company contributed
459 support for the PA-RISC 2.0 architecture, HP-UX 10.20, 10.30, and 11.0
460 (narrow mode), HP's implementation of kernel threads, HP's aC@t{++}
461 compiler, and the Text User Interface (nee Terminal User Interface):
462 Ben Krepp, Richard Title, John Bishop, Susan Macchia, Kathy Mann,
463 Satish Pai, India Paul, Steve Rehrauer, and Elena Zannoni. Kim Haase
464 provided HP-specific information in this manual.
466 DJ Delorie ported @value{GDBN} to MS-DOS, for the DJGPP project.
467 Robert Hoehne made significant contributions to the DJGPP port.
469 Cygnus Solutions has sponsored @value{GDBN} maintenance and much of its
470 development since 1991. Cygnus engineers who have worked on @value{GDBN}
471 fulltime include Mark Alexander, Jim Blandy, Per Bothner, Kevin
472 Buettner, Edith Epstein, Chris Faylor, Fred Fish, Martin Hunt, Jim
473 Ingham, John Gilmore, Stu Grossman, Kung Hsu, Jim Kingdon, John Metzler,
474 Fernando Nasser, Geoffrey Noer, Dawn Perchik, Rich Pixley, Zdenek
475 Radouch, Keith Seitz, Stan Shebs, David Taylor, and Elena Zannoni. In
476 addition, Dave Brolley, Ian Carmichael, Steve Chamberlain, Nick Clifton,
477 JT Conklin, Stan Cox, DJ Delorie, Ulrich Drepper, Frank Eigler, Doug
478 Evans, Sean Fagan, David Henkel-Wallace, Richard Henderson, Jeff
479 Holcomb, Jeff Law, Jim Lemke, Tom Lord, Bob Manson, Michael Meissner,
480 Jason Merrill, Catherine Moore, Drew Moseley, Ken Raeburn, Gavin
481 Romig-Koch, Rob Savoye, Jamie Smith, Mike Stump, Ian Taylor, Angela
482 Thomas, Michael Tiemann, Tom Tromey, Ron Unrau, Jim Wilson, and David
483 Zuhn have made contributions both large and small.
485 Andrew Cagney, Fernando Nasser, and Elena Zannoni, while working for
486 Cygnus Solutions, implemented the original @sc{gdb/mi} interface.
488 Jim Blandy added support for preprocessor macros, while working for Red
491 Andrew Cagney designed @value{GDBN}'s architecture vector. Many
492 people including Andrew Cagney, Stephane Carrez, Randolph Chung, Nick
493 Duffek, Richard Henderson, Mark Kettenis, Grace Sainsbury, Kei
494 Sakamoto, Yoshinori Sato, Michael Snyder, Andreas Schwab, Jason
495 Thorpe, Corinna Vinschen, Ulrich Weigand, and Elena Zannoni, helped
496 with the migration of old architectures to this new framework.
498 Andrew Cagney completely re-designed and re-implemented @value{GDBN}'s
499 unwinder framework, this consisting of a fresh new design featuring
500 frame IDs, independent frame sniffers, and the sentinel frame. Mark
501 Kettenis implemented the @sc{dwarf 2} unwinder, Jeff Johnston the
502 libunwind unwinder, and Andrew Cagney the dummy, sentinel, tramp, and
503 trad unwinders. The architecture-specific changes, each involving a
504 complete rewrite of the architecture's frame code, were carried out by
505 Jim Blandy, Joel Brobecker, Kevin Buettner, Andrew Cagney, Stephane
506 Carrez, Randolph Chung, Orjan Friberg, Richard Henderson, Daniel
507 Jacobowitz, Jeff Johnston, Mark Kettenis, Theodore A. Roth, Kei
508 Sakamoto, Yoshinori Sato, Michael Snyder, Corinna Vinschen, and Ulrich
511 Christian Zankel, Ross Morley, Bob Wilson, and Maxim Grigoriev from
512 Tensilica, Inc.@: contributed support for Xtensa processors. Others
513 who have worked on the Xtensa port of @value{GDBN} in the past include
514 Steve Tjiang, John Newlin, and Scott Foehner.
517 @chapter A Sample @value{GDBN} Session
519 You can use this manual at your leisure to read all about @value{GDBN}.
520 However, a handful of commands are enough to get started using the
521 debugger. This chapter illustrates those commands.
524 In this sample session, we emphasize user input like this: @b{input},
525 to make it easier to pick out from the surrounding output.
528 @c FIXME: this example may not be appropriate for some configs, where
529 @c FIXME...primary interest is in remote use.
531 One of the preliminary versions of @sc{gnu} @code{m4} (a generic macro
532 processor) exhibits the following bug: sometimes, when we change its
533 quote strings from the default, the commands used to capture one macro
534 definition within another stop working. In the following short @code{m4}
535 session, we define a macro @code{foo} which expands to @code{0000}; we
536 then use the @code{m4} built-in @code{defn} to define @code{bar} as the
537 same thing. However, when we change the open quote string to
538 @code{<QUOTE>} and the close quote string to @code{<UNQUOTE>}, the same
539 procedure fails to define a new synonym @code{baz}:
548 @b{define(bar,defn(`foo'))}
552 @b{changequote(<QUOTE>,<UNQUOTE>)}
554 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
557 m4: End of input: 0: fatal error: EOF in string
561 Let us use @value{GDBN} to try to see what is going on.
564 $ @b{@value{GDBP} m4}
565 @c FIXME: this falsifies the exact text played out, to permit smallbook
566 @c FIXME... format to come out better.
567 @value{GDBN} is free software and you are welcome to distribute copies
568 of it under certain conditions; type "show copying" to see
570 There is absolutely no warranty for @value{GDBN}; type "show warranty"
573 @value{GDBN} @value{GDBVN}, Copyright 1999 Free Software Foundation, Inc...
578 @value{GDBN} reads only enough symbol data to know where to find the
579 rest when needed; as a result, the first prompt comes up very quickly.
580 We now tell @value{GDBN} to use a narrower display width than usual, so
581 that examples fit in this manual.
584 (@value{GDBP}) @b{set width 70}
588 We need to see how the @code{m4} built-in @code{changequote} works.
589 Having looked at the source, we know the relevant subroutine is
590 @code{m4_changequote}, so we set a breakpoint there with the @value{GDBN}
591 @code{break} command.
594 (@value{GDBP}) @b{break m4_changequote}
595 Breakpoint 1 at 0x62f4: file builtin.c, line 879.
599 Using the @code{run} command, we start @code{m4} running under @value{GDBN}
600 control; as long as control does not reach the @code{m4_changequote}
601 subroutine, the program runs as usual:
604 (@value{GDBP}) @b{run}
605 Starting program: /work/Editorial/gdb/gnu/m4/m4
613 To trigger the breakpoint, we call @code{changequote}. @value{GDBN}
614 suspends execution of @code{m4}, displaying information about the
615 context where it stops.
618 @b{changequote(<QUOTE>,<UNQUOTE>)}
620 Breakpoint 1, m4_changequote (argc=3, argv=0x33c70)
622 879 if (bad_argc(TOKEN_DATA_TEXT(argv[0]),argc,1,3))
626 Now we use the command @code{n} (@code{next}) to advance execution to
627 the next line of the current function.
631 882 set_quotes((argc >= 2) ? TOKEN_DATA_TEXT(argv[1])\
636 @code{set_quotes} looks like a promising subroutine. We can go into it
637 by using the command @code{s} (@code{step}) instead of @code{next}.
638 @code{step} goes to the next line to be executed in @emph{any}
639 subroutine, so it steps into @code{set_quotes}.
643 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
645 530 if (lquote != def_lquote)
649 The display that shows the subroutine where @code{m4} is now
650 suspended (and its arguments) is called a stack frame display. It
651 shows a summary of the stack. We can use the @code{backtrace}
652 command (which can also be spelled @code{bt}), to see where we are
653 in the stack as a whole: the @code{backtrace} command displays a
654 stack frame for each active subroutine.
657 (@value{GDBP}) @b{bt}
658 #0 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
660 #1 0x6344 in m4_changequote (argc=3, argv=0x33c70)
662 #2 0x8174 in expand_macro (sym=0x33320) at macro.c:242
663 #3 0x7a88 in expand_token (obs=0x0, t=209696, td=0xf7fffa30)
665 #4 0x79dc in expand_input () at macro.c:40
666 #5 0x2930 in main (argc=0, argv=0xf7fffb20) at m4.c:195
670 We step through a few more lines to see what happens. The first two
671 times, we can use @samp{s}; the next two times we use @code{n} to avoid
672 falling into the @code{xstrdup} subroutine.
676 0x3b5c 532 if (rquote != def_rquote)
678 0x3b80 535 lquote = (lq == nil || *lq == '\0') ? \
679 def_lquote : xstrdup(lq);
681 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
684 538 len_lquote = strlen(rquote);
688 The last line displayed looks a little odd; we can examine the variables
689 @code{lquote} and @code{rquote} to see if they are in fact the new left
690 and right quotes we specified. We use the command @code{p}
691 (@code{print}) to see their values.
694 (@value{GDBP}) @b{p lquote}
695 $1 = 0x35d40 "<QUOTE>"
696 (@value{GDBP}) @b{p rquote}
697 $2 = 0x35d50 "<UNQUOTE>"
701 @code{lquote} and @code{rquote} are indeed the new left and right quotes.
702 To look at some context, we can display ten lines of source
703 surrounding the current line with the @code{l} (@code{list}) command.
709 535 lquote = (lq == nil || *lq == '\0') ? def_lquote\
711 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
714 538 len_lquote = strlen(rquote);
715 539 len_rquote = strlen(lquote);
722 Let us step past the two lines that set @code{len_lquote} and
723 @code{len_rquote}, and then examine the values of those variables.
727 539 len_rquote = strlen(lquote);
730 (@value{GDBP}) @b{p len_lquote}
732 (@value{GDBP}) @b{p len_rquote}
737 That certainly looks wrong, assuming @code{len_lquote} and
738 @code{len_rquote} are meant to be the lengths of @code{lquote} and
739 @code{rquote} respectively. We can set them to better values using
740 the @code{p} command, since it can print the value of
741 any expression---and that expression can include subroutine calls and
745 (@value{GDBP}) @b{p len_lquote=strlen(lquote)}
747 (@value{GDBP}) @b{p len_rquote=strlen(rquote)}
752 Is that enough to fix the problem of using the new quotes with the
753 @code{m4} built-in @code{defn}? We can allow @code{m4} to continue
754 executing with the @code{c} (@code{continue}) command, and then try the
755 example that caused trouble initially:
761 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
768 Success! The new quotes now work just as well as the default ones. The
769 problem seems to have been just the two typos defining the wrong
770 lengths. We allow @code{m4} exit by giving it an EOF as input:
774 Program exited normally.
778 The message @samp{Program exited normally.} is from @value{GDBN}; it
779 indicates @code{m4} has finished executing. We can end our @value{GDBN}
780 session with the @value{GDBN} @code{quit} command.
783 (@value{GDBP}) @b{quit}
787 @chapter Getting In and Out of @value{GDBN}
789 This chapter discusses how to start @value{GDBN}, and how to get out of it.
793 type @samp{@value{GDBP}} to start @value{GDBN}.
795 type @kbd{quit} or @kbd{Ctrl-d} to exit.
799 * Invoking GDB:: How to start @value{GDBN}
800 * Quitting GDB:: How to quit @value{GDBN}
801 * Shell Commands:: How to use shell commands inside @value{GDBN}
802 * Logging Output:: How to log @value{GDBN}'s output to a file
806 @section Invoking @value{GDBN}
808 Invoke @value{GDBN} by running the program @code{@value{GDBP}}. Once started,
809 @value{GDBN} reads commands from the terminal until you tell it to exit.
811 You can also run @code{@value{GDBP}} with a variety of arguments and options,
812 to specify more of your debugging environment at the outset.
814 The command-line options described here are designed
815 to cover a variety of situations; in some environments, some of these
816 options may effectively be unavailable.
818 The most usual way to start @value{GDBN} is with one argument,
819 specifying an executable program:
822 @value{GDBP} @var{program}
826 You can also start with both an executable program and a core file
830 @value{GDBP} @var{program} @var{core}
833 You can, instead, specify a process ID as a second argument, if you want
834 to debug a running process:
837 @value{GDBP} @var{program} 1234
841 would attach @value{GDBN} to process @code{1234} (unless you also have a file
842 named @file{1234}; @value{GDBN} does check for a core file first).
844 Taking advantage of the second command-line argument requires a fairly
845 complete operating system; when you use @value{GDBN} as a remote
846 debugger attached to a bare board, there may not be any notion of
847 ``process'', and there is often no way to get a core dump. @value{GDBN}
848 will warn you if it is unable to attach or to read core dumps.
850 You can optionally have @code{@value{GDBP}} pass any arguments after the
851 executable file to the inferior using @code{--args}. This option stops
854 @value{GDBP} --args gcc -O2 -c foo.c
856 This will cause @code{@value{GDBP}} to debug @code{gcc}, and to set
857 @code{gcc}'s command-line arguments (@pxref{Arguments}) to @samp{-O2 -c foo.c}.
859 You can run @code{@value{GDBP}} without printing the front material, which describes
860 @value{GDBN}'s non-warranty, by specifying @code{-silent}:
867 You can further control how @value{GDBN} starts up by using command-line
868 options. @value{GDBN} itself can remind you of the options available.
878 to display all available options and briefly describe their use
879 (@samp{@value{GDBP} -h} is a shorter equivalent).
881 All options and command line arguments you give are processed
882 in sequential order. The order makes a difference when the
883 @samp{-x} option is used.
887 * File Options:: Choosing files
888 * Mode Options:: Choosing modes
889 * Startup:: What @value{GDBN} does during startup
893 @subsection Choosing Files
895 When @value{GDBN} starts, it reads any arguments other than options as
896 specifying an executable file and core file (or process ID). This is
897 the same as if the arguments were specified by the @samp{-se} and
898 @samp{-c} (or @samp{-p}) options respectively. (@value{GDBN} reads the
899 first argument that does not have an associated option flag as
900 equivalent to the @samp{-se} option followed by that argument; and the
901 second argument that does not have an associated option flag, if any, as
902 equivalent to the @samp{-c}/@samp{-p} option followed by that argument.)
903 If the second argument begins with a decimal digit, @value{GDBN} will
904 first attempt to attach to it as a process, and if that fails, attempt
905 to open it as a corefile. If you have a corefile whose name begins with
906 a digit, you can prevent @value{GDBN} from treating it as a pid by
907 prefixing it with @file{./}, e.g.@: @file{./12345}.
909 If @value{GDBN} has not been configured to included core file support,
910 such as for most embedded targets, then it will complain about a second
911 argument and ignore it.
913 Many options have both long and short forms; both are shown in the
914 following list. @value{GDBN} also recognizes the long forms if you truncate
915 them, so long as enough of the option is present to be unambiguous.
916 (If you prefer, you can flag option arguments with @samp{--} rather
917 than @samp{-}, though we illustrate the more usual convention.)
919 @c NOTE: the @cindex entries here use double dashes ON PURPOSE. This
920 @c way, both those who look for -foo and --foo in the index, will find
924 @item -symbols @var{file}
926 @cindex @code{--symbols}
928 Read symbol table from file @var{file}.
930 @item -exec @var{file}
932 @cindex @code{--exec}
934 Use file @var{file} as the executable file to execute when appropriate,
935 and for examining pure data in conjunction with a core dump.
939 Read symbol table from file @var{file} and use it as the executable
942 @item -core @var{file}
944 @cindex @code{--core}
946 Use file @var{file} as a core dump to examine.
948 @item -pid @var{number}
949 @itemx -p @var{number}
952 Connect to process ID @var{number}, as with the @code{attach} command.
954 @item -command @var{file}
956 @cindex @code{--command}
958 Execute @value{GDBN} commands from file @var{file}. @xref{Command
959 Files,, Command files}.
961 @item -eval-command @var{command}
962 @itemx -ex @var{command}
963 @cindex @code{--eval-command}
965 Execute a single @value{GDBN} command.
967 This option may be used multiple times to call multiple commands. It may
968 also be interleaved with @samp{-command} as required.
971 @value{GDBP} -ex 'target sim' -ex 'load' \
972 -x setbreakpoints -ex 'run' a.out
975 @item -directory @var{directory}
976 @itemx -d @var{directory}
977 @cindex @code{--directory}
979 Add @var{directory} to the path to search for source and script files.
983 @cindex @code{--readnow}
985 Read each symbol file's entire symbol table immediately, rather than
986 the default, which is to read it incrementally as it is needed.
987 This makes startup slower, but makes future operations faster.
992 @subsection Choosing Modes
994 You can run @value{GDBN} in various alternative modes---for example, in
995 batch mode or quiet mode.
1002 Do not execute commands found in any initialization files. Normally,
1003 @value{GDBN} executes the commands in these files after all the command
1004 options and arguments have been processed. @xref{Command Files,,Command
1010 @cindex @code{--quiet}
1011 @cindex @code{--silent}
1013 ``Quiet''. Do not print the introductory and copyright messages. These
1014 messages are also suppressed in batch mode.
1017 @cindex @code{--batch}
1018 Run in batch mode. Exit with status @code{0} after processing all the
1019 command files specified with @samp{-x} (and all commands from
1020 initialization files, if not inhibited with @samp{-n}). Exit with
1021 nonzero status if an error occurs in executing the @value{GDBN} commands
1022 in the command files.
1024 Batch mode may be useful for running @value{GDBN} as a filter, for
1025 example to download and run a program on another computer; in order to
1026 make this more useful, the message
1029 Program exited normally.
1033 (which is ordinarily issued whenever a program running under
1034 @value{GDBN} control terminates) is not issued when running in batch
1038 @cindex @code{--batch-silent}
1039 Run in batch mode exactly like @samp{-batch}, but totally silently. All
1040 @value{GDBN} output to @code{stdout} is prevented (@code{stderr} is
1041 unaffected). This is much quieter than @samp{-silent} and would be useless
1042 for an interactive session.
1044 This is particularly useful when using targets that give @samp{Loading section}
1045 messages, for example.
1047 Note that targets that give their output via @value{GDBN}, as opposed to
1048 writing directly to @code{stdout}, will also be made silent.
1050 @item -return-child-result
1051 @cindex @code{--return-child-result}
1052 The return code from @value{GDBN} will be the return code from the child
1053 process (the process being debugged), with the following exceptions:
1057 @value{GDBN} exits abnormally. E.g., due to an incorrect argument or an
1058 internal error. In this case the exit code is the same as it would have been
1059 without @samp{-return-child-result}.
1061 The user quits with an explicit value. E.g., @samp{quit 1}.
1063 The child process never runs, or is not allowed to terminate, in which case
1064 the exit code will be -1.
1067 This option is useful in conjunction with @samp{-batch} or @samp{-batch-silent},
1068 when @value{GDBN} is being used as a remote program loader or simulator
1073 @cindex @code{--nowindows}
1075 ``No windows''. If @value{GDBN} comes with a graphical user interface
1076 (GUI) built in, then this option tells @value{GDBN} to only use the command-line
1077 interface. If no GUI is available, this option has no effect.
1081 @cindex @code{--windows}
1083 If @value{GDBN} includes a GUI, then this option requires it to be
1086 @item -cd @var{directory}
1088 Run @value{GDBN} using @var{directory} as its working directory,
1089 instead of the current directory.
1093 @cindex @code{--fullname}
1095 @sc{gnu} Emacs sets this option when it runs @value{GDBN} as a
1096 subprocess. It tells @value{GDBN} to output the full file name and line
1097 number in a standard, recognizable fashion each time a stack frame is
1098 displayed (which includes each time your program stops). This
1099 recognizable format looks like two @samp{\032} characters, followed by
1100 the file name, line number and character position separated by colons,
1101 and a newline. The Emacs-to-@value{GDBN} interface program uses the two
1102 @samp{\032} characters as a signal to display the source code for the
1106 @cindex @code{--epoch}
1107 The Epoch Emacs-@value{GDBN} interface sets this option when it runs
1108 @value{GDBN} as a subprocess. It tells @value{GDBN} to modify its print
1109 routines so as to allow Epoch to display values of expressions in a
1112 @item -annotate @var{level}
1113 @cindex @code{--annotate}
1114 This option sets the @dfn{annotation level} inside @value{GDBN}. Its
1115 effect is identical to using @samp{set annotate @var{level}}
1116 (@pxref{Annotations}). The annotation @var{level} controls how much
1117 information @value{GDBN} prints together with its prompt, values of
1118 expressions, source lines, and other types of output. Level 0 is the
1119 normal, level 1 is for use when @value{GDBN} is run as a subprocess of
1120 @sc{gnu} Emacs, level 3 is the maximum annotation suitable for programs
1121 that control @value{GDBN}, and level 2 has been deprecated.
1123 The annotation mechanism has largely been superseded by @sc{gdb/mi}
1127 @cindex @code{--args}
1128 Change interpretation of command line so that arguments following the
1129 executable file are passed as command line arguments to the inferior.
1130 This option stops option processing.
1132 @item -baud @var{bps}
1134 @cindex @code{--baud}
1136 Set the line speed (baud rate or bits per second) of any serial
1137 interface used by @value{GDBN} for remote debugging.
1139 @item -l @var{timeout}
1141 Set the timeout (in seconds) of any communication used by @value{GDBN}
1142 for remote debugging.
1144 @item -tty @var{device}
1145 @itemx -t @var{device}
1146 @cindex @code{--tty}
1148 Run using @var{device} for your program's standard input and output.
1149 @c FIXME: kingdon thinks there is more to -tty. Investigate.
1151 @c resolve the situation of these eventually
1153 @cindex @code{--tui}
1154 Activate the @dfn{Text User Interface} when starting. The Text User
1155 Interface manages several text windows on the terminal, showing
1156 source, assembly, registers and @value{GDBN} command outputs
1157 (@pxref{TUI, ,@value{GDBN} Text User Interface}). Alternatively, the
1158 Text User Interface can be enabled by invoking the program
1159 @samp{@value{GDBTUI}}. Do not use this option if you run @value{GDBN} from
1160 Emacs (@pxref{Emacs, ,Using @value{GDBN} under @sc{gnu} Emacs}).
1163 @c @cindex @code{--xdb}
1164 @c Run in XDB compatibility mode, allowing the use of certain XDB commands.
1165 @c For information, see the file @file{xdb_trans.html}, which is usually
1166 @c installed in the directory @code{/opt/langtools/wdb/doc} on HP-UX
1169 @item -interpreter @var{interp}
1170 @cindex @code{--interpreter}
1171 Use the interpreter @var{interp} for interface with the controlling
1172 program or device. This option is meant to be set by programs which
1173 communicate with @value{GDBN} using it as a back end.
1174 @xref{Interpreters, , Command Interpreters}.
1176 @samp{--interpreter=mi} (or @samp{--interpreter=mi2}) causes
1177 @value{GDBN} to use the @dfn{@sc{gdb/mi} interface} (@pxref{GDB/MI, ,
1178 The @sc{gdb/mi} Interface}) included since @value{GDBN} version 6.0. The
1179 previous @sc{gdb/mi} interface, included in @value{GDBN} version 5.3 and
1180 selected with @samp{--interpreter=mi1}, is deprecated. Earlier
1181 @sc{gdb/mi} interfaces are no longer supported.
1184 @cindex @code{--write}
1185 Open the executable and core files for both reading and writing. This
1186 is equivalent to the @samp{set write on} command inside @value{GDBN}
1190 @cindex @code{--statistics}
1191 This option causes @value{GDBN} to print statistics about time and
1192 memory usage after it completes each command and returns to the prompt.
1195 @cindex @code{--version}
1196 This option causes @value{GDBN} to print its version number and
1197 no-warranty blurb, and exit.
1202 @subsection What @value{GDBN} Does During Startup
1203 @cindex @value{GDBN} startup
1205 Here's the description of what @value{GDBN} does during session startup:
1209 Sets up the command interpreter as specified by the command line
1210 (@pxref{Mode Options, interpreter}).
1214 Reads the system-wide @dfn{init file} (if @option{--with-system-gdbinit} was
1215 used when building @value{GDBN}; @pxref{System-wide configuration,
1216 ,System-wide configuration and settings}) and executes all the commands in
1220 Reads the init file (if any) in your home directory@footnote{On
1221 DOS/Windows systems, the home directory is the one pointed to by the
1222 @code{HOME} environment variable.} and executes all the commands in
1226 Processes command line options and operands.
1229 Reads and executes the commands from init file (if any) in the current
1230 working directory. This is only done if the current directory is
1231 different from your home directory. Thus, you can have more than one
1232 init file, one generic in your home directory, and another, specific
1233 to the program you are debugging, in the directory where you invoke
1237 Reads command files specified by the @samp{-x} option. @xref{Command
1238 Files}, for more details about @value{GDBN} command files.
1241 Reads the command history recorded in the @dfn{history file}.
1242 @xref{Command History}, for more details about the command history and the
1243 files where @value{GDBN} records it.
1246 Init files use the same syntax as @dfn{command files} (@pxref{Command
1247 Files}) and are processed by @value{GDBN} in the same way. The init
1248 file in your home directory can set options (such as @samp{set
1249 complaints}) that affect subsequent processing of command line options
1250 and operands. Init files are not executed if you use the @samp{-nx}
1251 option (@pxref{Mode Options, ,Choosing Modes}).
1253 To display the list of init files loaded by gdb at startup, you
1254 can use @kbd{gdb --help}.
1256 @cindex init file name
1257 @cindex @file{.gdbinit}
1258 @cindex @file{gdb.ini}
1259 The @value{GDBN} init files are normally called @file{.gdbinit}.
1260 The DJGPP port of @value{GDBN} uses the name @file{gdb.ini}, due to
1261 the limitations of file names imposed by DOS filesystems. The Windows
1262 ports of @value{GDBN} use the standard name, but if they find a
1263 @file{gdb.ini} file, they warn you about that and suggest to rename
1264 the file to the standard name.
1268 @section Quitting @value{GDBN}
1269 @cindex exiting @value{GDBN}
1270 @cindex leaving @value{GDBN}
1273 @kindex quit @r{[}@var{expression}@r{]}
1274 @kindex q @r{(@code{quit})}
1275 @item quit @r{[}@var{expression}@r{]}
1277 To exit @value{GDBN}, use the @code{quit} command (abbreviated
1278 @code{q}), or type an end-of-file character (usually @kbd{Ctrl-d}). If you
1279 do not supply @var{expression}, @value{GDBN} will terminate normally;
1280 otherwise it will terminate using the result of @var{expression} as the
1285 An interrupt (often @kbd{Ctrl-c}) does not exit from @value{GDBN}, but rather
1286 terminates the action of any @value{GDBN} command that is in progress and
1287 returns to @value{GDBN} command level. It is safe to type the interrupt
1288 character at any time because @value{GDBN} does not allow it to take effect
1289 until a time when it is safe.
1291 If you have been using @value{GDBN} to control an attached process or
1292 device, you can release it with the @code{detach} command
1293 (@pxref{Attach, ,Debugging an Already-running Process}).
1295 @node Shell Commands
1296 @section Shell Commands
1298 If you need to execute occasional shell commands during your
1299 debugging session, there is no need to leave or suspend @value{GDBN}; you can
1300 just use the @code{shell} command.
1304 @cindex shell escape
1305 @item shell @var{command string}
1306 Invoke a standard shell to execute @var{command string}.
1307 If it exists, the environment variable @code{SHELL} determines which
1308 shell to run. Otherwise @value{GDBN} uses the default shell
1309 (@file{/bin/sh} on Unix systems, @file{COMMAND.COM} on MS-DOS, etc.).
1312 The utility @code{make} is often needed in development environments.
1313 You do not have to use the @code{shell} command for this purpose in
1318 @cindex calling make
1319 @item make @var{make-args}
1320 Execute the @code{make} program with the specified
1321 arguments. This is equivalent to @samp{shell make @var{make-args}}.
1324 @node Logging Output
1325 @section Logging Output
1326 @cindex logging @value{GDBN} output
1327 @cindex save @value{GDBN} output to a file
1329 You may want to save the output of @value{GDBN} commands to a file.
1330 There are several commands to control @value{GDBN}'s logging.
1334 @item set logging on
1336 @item set logging off
1338 @cindex logging file name
1339 @item set logging file @var{file}
1340 Change the name of the current logfile. The default logfile is @file{gdb.txt}.
1341 @item set logging overwrite [on|off]
1342 By default, @value{GDBN} will append to the logfile. Set @code{overwrite} if
1343 you want @code{set logging on} to overwrite the logfile instead.
1344 @item set logging redirect [on|off]
1345 By default, @value{GDBN} output will go to both the terminal and the logfile.
1346 Set @code{redirect} if you want output to go only to the log file.
1347 @kindex show logging
1349 Show the current values of the logging settings.
1353 @chapter @value{GDBN} Commands
1355 You can abbreviate a @value{GDBN} command to the first few letters of the command
1356 name, if that abbreviation is unambiguous; and you can repeat certain
1357 @value{GDBN} commands by typing just @key{RET}. You can also use the @key{TAB}
1358 key to get @value{GDBN} to fill out the rest of a word in a command (or to
1359 show you the alternatives available, if there is more than one possibility).
1362 * Command Syntax:: How to give commands to @value{GDBN}
1363 * Completion:: Command completion
1364 * Help:: How to ask @value{GDBN} for help
1367 @node Command Syntax
1368 @section Command Syntax
1370 A @value{GDBN} command is a single line of input. There is no limit on
1371 how long it can be. It starts with a command name, which is followed by
1372 arguments whose meaning depends on the command name. For example, the
1373 command @code{step} accepts an argument which is the number of times to
1374 step, as in @samp{step 5}. You can also use the @code{step} command
1375 with no arguments. Some commands do not allow any arguments.
1377 @cindex abbreviation
1378 @value{GDBN} command names may always be truncated if that abbreviation is
1379 unambiguous. Other possible command abbreviations are listed in the
1380 documentation for individual commands. In some cases, even ambiguous
1381 abbreviations are allowed; for example, @code{s} is specially defined as
1382 equivalent to @code{step} even though there are other commands whose
1383 names start with @code{s}. You can test abbreviations by using them as
1384 arguments to the @code{help} command.
1386 @cindex repeating commands
1387 @kindex RET @r{(repeat last command)}
1388 A blank line as input to @value{GDBN} (typing just @key{RET}) means to
1389 repeat the previous command. Certain commands (for example, @code{run})
1390 will not repeat this way; these are commands whose unintentional
1391 repetition might cause trouble and which you are unlikely to want to
1392 repeat. User-defined commands can disable this feature; see
1393 @ref{Define, dont-repeat}.
1395 The @code{list} and @code{x} commands, when you repeat them with
1396 @key{RET}, construct new arguments rather than repeating
1397 exactly as typed. This permits easy scanning of source or memory.
1399 @value{GDBN} can also use @key{RET} in another way: to partition lengthy
1400 output, in a way similar to the common utility @code{more}
1401 (@pxref{Screen Size,,Screen Size}). Since it is easy to press one
1402 @key{RET} too many in this situation, @value{GDBN} disables command
1403 repetition after any command that generates this sort of display.
1405 @kindex # @r{(a comment)}
1407 Any text from a @kbd{#} to the end of the line is a comment; it does
1408 nothing. This is useful mainly in command files (@pxref{Command
1409 Files,,Command Files}).
1411 @cindex repeating command sequences
1412 @kindex Ctrl-o @r{(operate-and-get-next)}
1413 The @kbd{Ctrl-o} binding is useful for repeating a complex sequence of
1414 commands. This command accepts the current line, like @key{RET}, and
1415 then fetches the next line relative to the current line from the history
1419 @section Command Completion
1422 @cindex word completion
1423 @value{GDBN} can fill in the rest of a word in a command for you, if there is
1424 only one possibility; it can also show you what the valid possibilities
1425 are for the next word in a command, at any time. This works for @value{GDBN}
1426 commands, @value{GDBN} subcommands, and the names of symbols in your program.
1428 Press the @key{TAB} key whenever you want @value{GDBN} to fill out the rest
1429 of a word. If there is only one possibility, @value{GDBN} fills in the
1430 word, and waits for you to finish the command (or press @key{RET} to
1431 enter it). For example, if you type
1433 @c FIXME "@key" does not distinguish its argument sufficiently to permit
1434 @c complete accuracy in these examples; space introduced for clarity.
1435 @c If texinfo enhancements make it unnecessary, it would be nice to
1436 @c replace " @key" by "@key" in the following...
1438 (@value{GDBP}) info bre @key{TAB}
1442 @value{GDBN} fills in the rest of the word @samp{breakpoints}, since that is
1443 the only @code{info} subcommand beginning with @samp{bre}:
1446 (@value{GDBP}) info breakpoints
1450 You can either press @key{RET} at this point, to run the @code{info
1451 breakpoints} command, or backspace and enter something else, if
1452 @samp{breakpoints} does not look like the command you expected. (If you
1453 were sure you wanted @code{info breakpoints} in the first place, you
1454 might as well just type @key{RET} immediately after @samp{info bre},
1455 to exploit command abbreviations rather than command completion).
1457 If there is more than one possibility for the next word when you press
1458 @key{TAB}, @value{GDBN} sounds a bell. You can either supply more
1459 characters and try again, or just press @key{TAB} a second time;
1460 @value{GDBN} displays all the possible completions for that word. For
1461 example, you might want to set a breakpoint on a subroutine whose name
1462 begins with @samp{make_}, but when you type @kbd{b make_@key{TAB}} @value{GDBN}
1463 just sounds the bell. Typing @key{TAB} again displays all the
1464 function names in your program that begin with those characters, for
1468 (@value{GDBP}) b make_ @key{TAB}
1469 @exdent @value{GDBN} sounds bell; press @key{TAB} again, to see:
1470 make_a_section_from_file make_environ
1471 make_abs_section make_function_type
1472 make_blockvector make_pointer_type
1473 make_cleanup make_reference_type
1474 make_command make_symbol_completion_list
1475 (@value{GDBP}) b make_
1479 After displaying the available possibilities, @value{GDBN} copies your
1480 partial input (@samp{b make_} in the example) so you can finish the
1483 If you just want to see the list of alternatives in the first place, you
1484 can press @kbd{M-?} rather than pressing @key{TAB} twice. @kbd{M-?}
1485 means @kbd{@key{META} ?}. You can type this either by holding down a
1486 key designated as the @key{META} shift on your keyboard (if there is
1487 one) while typing @kbd{?}, or as @key{ESC} followed by @kbd{?}.
1489 @cindex quotes in commands
1490 @cindex completion of quoted strings
1491 Sometimes the string you need, while logically a ``word'', may contain
1492 parentheses or other characters that @value{GDBN} normally excludes from
1493 its notion of a word. To permit word completion to work in this
1494 situation, you may enclose words in @code{'} (single quote marks) in
1495 @value{GDBN} commands.
1497 The most likely situation where you might need this is in typing the
1498 name of a C@t{++} function. This is because C@t{++} allows function
1499 overloading (multiple definitions of the same function, distinguished
1500 by argument type). For example, when you want to set a breakpoint you
1501 may need to distinguish whether you mean the version of @code{name}
1502 that takes an @code{int} parameter, @code{name(int)}, or the version
1503 that takes a @code{float} parameter, @code{name(float)}. To use the
1504 word-completion facilities in this situation, type a single quote
1505 @code{'} at the beginning of the function name. This alerts
1506 @value{GDBN} that it may need to consider more information than usual
1507 when you press @key{TAB} or @kbd{M-?} to request word completion:
1510 (@value{GDBP}) b 'bubble( @kbd{M-?}
1511 bubble(double,double) bubble(int,int)
1512 (@value{GDBP}) b 'bubble(
1515 In some cases, @value{GDBN} can tell that completing a name requires using
1516 quotes. When this happens, @value{GDBN} inserts the quote for you (while
1517 completing as much as it can) if you do not type the quote in the first
1521 (@value{GDBP}) b bub @key{TAB}
1522 @exdent @value{GDBN} alters your input line to the following, and rings a bell:
1523 (@value{GDBP}) b 'bubble(
1527 In general, @value{GDBN} can tell that a quote is needed (and inserts it) if
1528 you have not yet started typing the argument list when you ask for
1529 completion on an overloaded symbol.
1531 For more information about overloaded functions, see @ref{C Plus Plus
1532 Expressions, ,C@t{++} Expressions}. You can use the command @code{set
1533 overload-resolution off} to disable overload resolution;
1534 see @ref{Debugging C Plus Plus, ,@value{GDBN} Features for C@t{++}}.
1536 @cindex completion of structure field names
1537 @cindex structure field name completion
1538 @cindex completion of union field names
1539 @cindex union field name completion
1540 When completing in an expression which looks up a field in a
1541 structure, @value{GDBN} also tries@footnote{The completer can be
1542 confused by certain kinds of invalid expressions. Also, it only
1543 examines the static type of the expression, not the dynamic type.} to
1544 limit completions to the field names available in the type of the
1548 (@value{GDBP}) p gdb_stdout.@kbd{M-?}
1549 magic to_delete to_fputs to_put to_rewind
1550 to_data to_flush to_isatty to_read to_write
1554 This is because the @code{gdb_stdout} is a variable of the type
1555 @code{struct ui_file} that is defined in @value{GDBN} sources as
1562 ui_file_flush_ftype *to_flush;
1563 ui_file_write_ftype *to_write;
1564 ui_file_fputs_ftype *to_fputs;
1565 ui_file_read_ftype *to_read;
1566 ui_file_delete_ftype *to_delete;
1567 ui_file_isatty_ftype *to_isatty;
1568 ui_file_rewind_ftype *to_rewind;
1569 ui_file_put_ftype *to_put;
1576 @section Getting Help
1577 @cindex online documentation
1580 You can always ask @value{GDBN} itself for information on its commands,
1581 using the command @code{help}.
1584 @kindex h @r{(@code{help})}
1587 You can use @code{help} (abbreviated @code{h}) with no arguments to
1588 display a short list of named classes of commands:
1592 List of classes of commands:
1594 aliases -- Aliases of other commands
1595 breakpoints -- Making program stop at certain points
1596 data -- Examining data
1597 files -- Specifying and examining files
1598 internals -- Maintenance commands
1599 obscure -- Obscure features
1600 running -- Running the program
1601 stack -- Examining the stack
1602 status -- Status inquiries
1603 support -- Support facilities
1604 tracepoints -- Tracing of program execution without
1605 stopping the program
1606 user-defined -- User-defined commands
1608 Type "help" followed by a class name for a list of
1609 commands in that class.
1610 Type "help" followed by command name for full
1612 Command name abbreviations are allowed if unambiguous.
1615 @c the above line break eliminates huge line overfull...
1617 @item help @var{class}
1618 Using one of the general help classes as an argument, you can get a
1619 list of the individual commands in that class. For example, here is the
1620 help display for the class @code{status}:
1623 (@value{GDBP}) help status
1628 @c Line break in "show" line falsifies real output, but needed
1629 @c to fit in smallbook page size.
1630 info -- Generic command for showing things
1631 about the program being debugged
1632 show -- Generic command for showing things
1635 Type "help" followed by command name for full
1637 Command name abbreviations are allowed if unambiguous.
1641 @item help @var{command}
1642 With a command name as @code{help} argument, @value{GDBN} displays a
1643 short paragraph on how to use that command.
1646 @item apropos @var{args}
1647 The @code{apropos} command searches through all of the @value{GDBN}
1648 commands, and their documentation, for the regular expression specified in
1649 @var{args}. It prints out all matches found. For example:
1660 set symbol-reloading -- Set dynamic symbol table reloading
1661 multiple times in one run
1662 show symbol-reloading -- Show dynamic symbol table reloading
1663 multiple times in one run
1668 @item complete @var{args}
1669 The @code{complete @var{args}} command lists all the possible completions
1670 for the beginning of a command. Use @var{args} to specify the beginning of the
1671 command you want completed. For example:
1677 @noindent results in:
1688 @noindent This is intended for use by @sc{gnu} Emacs.
1691 In addition to @code{help}, you can use the @value{GDBN} commands @code{info}
1692 and @code{show} to inquire about the state of your program, or the state
1693 of @value{GDBN} itself. Each command supports many topics of inquiry; this
1694 manual introduces each of them in the appropriate context. The listings
1695 under @code{info} and under @code{show} in the Index point to
1696 all the sub-commands. @xref{Index}.
1701 @kindex i @r{(@code{info})}
1703 This command (abbreviated @code{i}) is for describing the state of your
1704 program. For example, you can show the arguments passed to a function
1705 with @code{info args}, list the registers currently in use with @code{info
1706 registers}, or list the breakpoints you have set with @code{info breakpoints}.
1707 You can get a complete list of the @code{info} sub-commands with
1708 @w{@code{help info}}.
1712 You can assign the result of an expression to an environment variable with
1713 @code{set}. For example, you can set the @value{GDBN} prompt to a $-sign with
1714 @code{set prompt $}.
1718 In contrast to @code{info}, @code{show} is for describing the state of
1719 @value{GDBN} itself.
1720 You can change most of the things you can @code{show}, by using the
1721 related command @code{set}; for example, you can control what number
1722 system is used for displays with @code{set radix}, or simply inquire
1723 which is currently in use with @code{show radix}.
1726 To display all the settable parameters and their current
1727 values, you can use @code{show} with no arguments; you may also use
1728 @code{info set}. Both commands produce the same display.
1729 @c FIXME: "info set" violates the rule that "info" is for state of
1730 @c FIXME...program. Ck w/ GNU: "info set" to be called something else,
1731 @c FIXME...or change desc of rule---eg "state of prog and debugging session"?
1735 Here are three miscellaneous @code{show} subcommands, all of which are
1736 exceptional in lacking corresponding @code{set} commands:
1739 @kindex show version
1740 @cindex @value{GDBN} version number
1742 Show what version of @value{GDBN} is running. You should include this
1743 information in @value{GDBN} bug-reports. If multiple versions of
1744 @value{GDBN} are in use at your site, you may need to determine which
1745 version of @value{GDBN} you are running; as @value{GDBN} evolves, new
1746 commands are introduced, and old ones may wither away. Also, many
1747 system vendors ship variant versions of @value{GDBN}, and there are
1748 variant versions of @value{GDBN} in @sc{gnu}/Linux distributions as well.
1749 The version number is the same as the one announced when you start
1752 @kindex show copying
1753 @kindex info copying
1754 @cindex display @value{GDBN} copyright
1757 Display information about permission for copying @value{GDBN}.
1759 @kindex show warranty
1760 @kindex info warranty
1762 @itemx info warranty
1763 Display the @sc{gnu} ``NO WARRANTY'' statement, or a warranty,
1764 if your version of @value{GDBN} comes with one.
1769 @chapter Running Programs Under @value{GDBN}
1771 When you run a program under @value{GDBN}, you must first generate
1772 debugging information when you compile it.
1774 You may start @value{GDBN} with its arguments, if any, in an environment
1775 of your choice. If you are doing native debugging, you may redirect
1776 your program's input and output, debug an already running process, or
1777 kill a child process.
1780 * Compilation:: Compiling for debugging
1781 * Starting:: Starting your program
1782 * Arguments:: Your program's arguments
1783 * Environment:: Your program's environment
1785 * Working Directory:: Your program's working directory
1786 * Input/Output:: Your program's input and output
1787 * Attach:: Debugging an already-running process
1788 * Kill Process:: Killing the child process
1790 * Inferiors:: Debugging multiple inferiors
1791 * Threads:: Debugging programs with multiple threads
1792 * Processes:: Debugging programs with multiple processes
1793 * Checkpoint/Restart:: Setting a @emph{bookmark} to return to later
1797 @section Compiling for Debugging
1799 In order to debug a program effectively, you need to generate
1800 debugging information when you compile it. This debugging information
1801 is stored in the object file; it describes the data type of each
1802 variable or function and the correspondence between source line numbers
1803 and addresses in the executable code.
1805 To request debugging information, specify the @samp{-g} option when you run
1808 Programs that are to be shipped to your customers are compiled with
1809 optimizations, using the @samp{-O} compiler option. However, many
1810 compilers are unable to handle the @samp{-g} and @samp{-O} options
1811 together. Using those compilers, you cannot generate optimized
1812 executables containing debugging information.
1814 @value{NGCC}, the @sc{gnu} C/C@t{++} compiler, supports @samp{-g} with or
1815 without @samp{-O}, making it possible to debug optimized code. We
1816 recommend that you @emph{always} use @samp{-g} whenever you compile a
1817 program. You may think your program is correct, but there is no sense
1818 in pushing your luck.
1820 @cindex optimized code, debugging
1821 @cindex debugging optimized code
1822 When you debug a program compiled with @samp{-g -O}, remember that the
1823 optimizer is rearranging your code; the debugger shows you what is
1824 really there. Do not be too surprised when the execution path does not
1825 exactly match your source file! An extreme example: if you define a
1826 variable, but never use it, @value{GDBN} never sees that
1827 variable---because the compiler optimizes it out of existence.
1829 Some things do not work as well with @samp{-g -O} as with just
1830 @samp{-g}, particularly on machines with instruction scheduling. If in
1831 doubt, recompile with @samp{-g} alone, and if this fixes the problem,
1832 please report it to us as a bug (including a test case!).
1833 @xref{Variables}, for more information about debugging optimized code.
1835 Older versions of the @sc{gnu} C compiler permitted a variant option
1836 @w{@samp{-gg}} for debugging information. @value{GDBN} no longer supports this
1837 format; if your @sc{gnu} C compiler has this option, do not use it.
1839 @value{GDBN} knows about preprocessor macros and can show you their
1840 expansion (@pxref{Macros}). Most compilers do not include information
1841 about preprocessor macros in the debugging information if you specify
1842 the @option{-g} flag alone, because this information is rather large.
1843 Version 3.1 and later of @value{NGCC}, the @sc{gnu} C compiler,
1844 provides macro information if you specify the options
1845 @option{-gdwarf-2} and @option{-g3}; the former option requests
1846 debugging information in the Dwarf 2 format, and the latter requests
1847 ``extra information''. In the future, we hope to find more compact
1848 ways to represent macro information, so that it can be included with
1853 @section Starting your Program
1859 @kindex r @r{(@code{run})}
1862 Use the @code{run} command to start your program under @value{GDBN}.
1863 You must first specify the program name (except on VxWorks) with an
1864 argument to @value{GDBN} (@pxref{Invocation, ,Getting In and Out of
1865 @value{GDBN}}), or by using the @code{file} or @code{exec-file} command
1866 (@pxref{Files, ,Commands to Specify Files}).
1870 If you are running your program in an execution environment that
1871 supports processes, @code{run} creates an inferior process and makes
1872 that process run your program. In some environments without processes,
1873 @code{run} jumps to the start of your program. Other targets,
1874 like @samp{remote}, are always running. If you get an error
1875 message like this one:
1878 The "remote" target does not support "run".
1879 Try "help target" or "continue".
1883 then use @code{continue} to run your program. You may need @code{load}
1884 first (@pxref{load}).
1886 The execution of a program is affected by certain information it
1887 receives from its superior. @value{GDBN} provides ways to specify this
1888 information, which you must do @emph{before} starting your program. (You
1889 can change it after starting your program, but such changes only affect
1890 your program the next time you start it.) This information may be
1891 divided into four categories:
1894 @item The @emph{arguments.}
1895 Specify the arguments to give your program as the arguments of the
1896 @code{run} command. If a shell is available on your target, the shell
1897 is used to pass the arguments, so that you may use normal conventions
1898 (such as wildcard expansion or variable substitution) in describing
1900 In Unix systems, you can control which shell is used with the
1901 @code{SHELL} environment variable.
1902 @xref{Arguments, ,Your Program's Arguments}.
1904 @item The @emph{environment.}
1905 Your program normally inherits its environment from @value{GDBN}, but you can
1906 use the @value{GDBN} commands @code{set environment} and @code{unset
1907 environment} to change parts of the environment that affect
1908 your program. @xref{Environment, ,Your Program's Environment}.
1910 @item The @emph{working directory.}
1911 Your program inherits its working directory from @value{GDBN}. You can set
1912 the @value{GDBN} working directory with the @code{cd} command in @value{GDBN}.
1913 @xref{Working Directory, ,Your Program's Working Directory}.
1915 @item The @emph{standard input and output.}
1916 Your program normally uses the same device for standard input and
1917 standard output as @value{GDBN} is using. You can redirect input and output
1918 in the @code{run} command line, or you can use the @code{tty} command to
1919 set a different device for your program.
1920 @xref{Input/Output, ,Your Program's Input and Output}.
1923 @emph{Warning:} While input and output redirection work, you cannot use
1924 pipes to pass the output of the program you are debugging to another
1925 program; if you attempt this, @value{GDBN} is likely to wind up debugging the
1929 When you issue the @code{run} command, your program begins to execute
1930 immediately. @xref{Stopping, ,Stopping and Continuing}, for discussion
1931 of how to arrange for your program to stop. Once your program has
1932 stopped, you may call functions in your program, using the @code{print}
1933 or @code{call} commands. @xref{Data, ,Examining Data}.
1935 If the modification time of your symbol file has changed since the last
1936 time @value{GDBN} read its symbols, @value{GDBN} discards its symbol
1937 table, and reads it again. When it does this, @value{GDBN} tries to retain
1938 your current breakpoints.
1943 @cindex run to main procedure
1944 The name of the main procedure can vary from language to language.
1945 With C or C@t{++}, the main procedure name is always @code{main}, but
1946 other languages such as Ada do not require a specific name for their
1947 main procedure. The debugger provides a convenient way to start the
1948 execution of the program and to stop at the beginning of the main
1949 procedure, depending on the language used.
1951 The @samp{start} command does the equivalent of setting a temporary
1952 breakpoint at the beginning of the main procedure and then invoking
1953 the @samp{run} command.
1955 @cindex elaboration phase
1956 Some programs contain an @dfn{elaboration} phase where some startup code is
1957 executed before the main procedure is called. This depends on the
1958 languages used to write your program. In C@t{++}, for instance,
1959 constructors for static and global objects are executed before
1960 @code{main} is called. It is therefore possible that the debugger stops
1961 before reaching the main procedure. However, the temporary breakpoint
1962 will remain to halt execution.
1964 Specify the arguments to give to your program as arguments to the
1965 @samp{start} command. These arguments will be given verbatim to the
1966 underlying @samp{run} command. Note that the same arguments will be
1967 reused if no argument is provided during subsequent calls to
1968 @samp{start} or @samp{run}.
1970 It is sometimes necessary to debug the program during elaboration. In
1971 these cases, using the @code{start} command would stop the execution of
1972 your program too late, as the program would have already completed the
1973 elaboration phase. Under these circumstances, insert breakpoints in your
1974 elaboration code before running your program.
1976 @kindex set exec-wrapper
1977 @item set exec-wrapper @var{wrapper}
1978 @itemx show exec-wrapper
1979 @itemx unset exec-wrapper
1980 When @samp{exec-wrapper} is set, the specified wrapper is used to
1981 launch programs for debugging. @value{GDBN} starts your program
1982 with a shell command of the form @kbd{exec @var{wrapper}
1983 @var{program}}. Quoting is added to @var{program} and its
1984 arguments, but not to @var{wrapper}, so you should add quotes if
1985 appropriate for your shell. The wrapper runs until it executes
1986 your program, and then @value{GDBN} takes control.
1988 You can use any program that eventually calls @code{execve} with
1989 its arguments as a wrapper. Several standard Unix utilities do
1990 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
1991 with @code{exec "$@@"} will also work.
1993 For example, you can use @code{env} to pass an environment variable to
1994 the debugged program, without setting the variable in your shell's
1998 (@value{GDBP}) set exec-wrapper env 'LD_PRELOAD=libtest.so'
2002 This command is available when debugging locally on most targets, excluding
2003 @sc{djgpp}, Cygwin, MS Windows, and QNX Neutrino.
2005 @kindex set disable-randomization
2006 @item set disable-randomization
2007 @itemx set disable-randomization on
2008 This option (enabled by default in @value{GDBN}) will turn off the native
2009 randomization of the virtual address space of the started program. This option
2010 is useful for multiple debugging sessions to make the execution better
2011 reproducible and memory addresses reusable across debugging sessions.
2013 This feature is implemented only on @sc{gnu}/Linux. You can get the same
2017 (@value{GDBP}) set exec-wrapper setarch `uname -m` -R
2020 @item set disable-randomization off
2021 Leave the behavior of the started executable unchanged. Some bugs rear their
2022 ugly heads only when the program is loaded at certain addresses. If your bug
2023 disappears when you run the program under @value{GDBN}, that might be because
2024 @value{GDBN} by default disables the address randomization on platforms, such
2025 as @sc{gnu}/Linux, which do that for stand-alone programs. Use @kbd{set
2026 disable-randomization off} to try to reproduce such elusive bugs.
2028 The virtual address space randomization is implemented only on @sc{gnu}/Linux.
2029 It protects the programs against some kinds of security attacks. In these
2030 cases the attacker needs to know the exact location of a concrete executable
2031 code. Randomizing its location makes it impossible to inject jumps misusing
2032 a code at its expected addresses.
2034 Prelinking shared libraries provides a startup performance advantage but it
2035 makes addresses in these libraries predictable for privileged processes by
2036 having just unprivileged access at the target system. Reading the shared
2037 library binary gives enough information for assembling the malicious code
2038 misusing it. Still even a prelinked shared library can get loaded at a new
2039 random address just requiring the regular relocation process during the
2040 startup. Shared libraries not already prelinked are always loaded at
2041 a randomly chosen address.
2043 Position independent executables (PIE) contain position independent code
2044 similar to the shared libraries and therefore such executables get loaded at
2045 a randomly chosen address upon startup. PIE executables always load even
2046 already prelinked shared libraries at a random address. You can build such
2047 executable using @command{gcc -fPIE -pie}.
2049 Heap (malloc storage), stack and custom mmap areas are always placed randomly
2050 (as long as the randomization is enabled).
2052 @item show disable-randomization
2053 Show the current setting of the explicit disable of the native randomization of
2054 the virtual address space of the started program.
2059 @section Your Program's Arguments
2061 @cindex arguments (to your program)
2062 The arguments to your program can be specified by the arguments of the
2064 They are passed to a shell, which expands wildcard characters and
2065 performs redirection of I/O, and thence to your program. Your
2066 @code{SHELL} environment variable (if it exists) specifies what shell
2067 @value{GDBN} uses. If you do not define @code{SHELL}, @value{GDBN} uses
2068 the default shell (@file{/bin/sh} on Unix).
2070 On non-Unix systems, the program is usually invoked directly by
2071 @value{GDBN}, which emulates I/O redirection via the appropriate system
2072 calls, and the wildcard characters are expanded by the startup code of
2073 the program, not by the shell.
2075 @code{run} with no arguments uses the same arguments used by the previous
2076 @code{run}, or those set by the @code{set args} command.
2081 Specify the arguments to be used the next time your program is run. If
2082 @code{set args} has no arguments, @code{run} executes your program
2083 with no arguments. Once you have run your program with arguments,
2084 using @code{set args} before the next @code{run} is the only way to run
2085 it again without arguments.
2089 Show the arguments to give your program when it is started.
2093 @section Your Program's Environment
2095 @cindex environment (of your program)
2096 The @dfn{environment} consists of a set of environment variables and
2097 their values. Environment variables conventionally record such things as
2098 your user name, your home directory, your terminal type, and your search
2099 path for programs to run. Usually you set up environment variables with
2100 the shell and they are inherited by all the other programs you run. When
2101 debugging, it can be useful to try running your program with a modified
2102 environment without having to start @value{GDBN} over again.
2106 @item path @var{directory}
2107 Add @var{directory} to the front of the @code{PATH} environment variable
2108 (the search path for executables) that will be passed to your program.
2109 The value of @code{PATH} used by @value{GDBN} does not change.
2110 You may specify several directory names, separated by whitespace or by a
2111 system-dependent separator character (@samp{:} on Unix, @samp{;} on
2112 MS-DOS and MS-Windows). If @var{directory} is already in the path, it
2113 is moved to the front, so it is searched sooner.
2115 You can use the string @samp{$cwd} to refer to whatever is the current
2116 working directory at the time @value{GDBN} searches the path. If you
2117 use @samp{.} instead, it refers to the directory where you executed the
2118 @code{path} command. @value{GDBN} replaces @samp{.} in the
2119 @var{directory} argument (with the current path) before adding
2120 @var{directory} to the search path.
2121 @c 'path' is explicitly nonrepeatable, but RMS points out it is silly to
2122 @c document that, since repeating it would be a no-op.
2126 Display the list of search paths for executables (the @code{PATH}
2127 environment variable).
2129 @kindex show environment
2130 @item show environment @r{[}@var{varname}@r{]}
2131 Print the value of environment variable @var{varname} to be given to
2132 your program when it starts. If you do not supply @var{varname},
2133 print the names and values of all environment variables to be given to
2134 your program. You can abbreviate @code{environment} as @code{env}.
2136 @kindex set environment
2137 @item set environment @var{varname} @r{[}=@var{value}@r{]}
2138 Set environment variable @var{varname} to @var{value}. The value
2139 changes for your program only, not for @value{GDBN} itself. @var{value} may
2140 be any string; the values of environment variables are just strings, and
2141 any interpretation is supplied by your program itself. The @var{value}
2142 parameter is optional; if it is eliminated, the variable is set to a
2144 @c "any string" here does not include leading, trailing
2145 @c blanks. Gnu asks: does anyone care?
2147 For example, this command:
2154 tells the debugged program, when subsequently run, that its user is named
2155 @samp{foo}. (The spaces around @samp{=} are used for clarity here; they
2156 are not actually required.)
2158 @kindex unset environment
2159 @item unset environment @var{varname}
2160 Remove variable @var{varname} from the environment to be passed to your
2161 program. This is different from @samp{set env @var{varname} =};
2162 @code{unset environment} removes the variable from the environment,
2163 rather than assigning it an empty value.
2166 @emph{Warning:} On Unix systems, @value{GDBN} runs your program using
2168 by your @code{SHELL} environment variable if it exists (or
2169 @code{/bin/sh} if not). If your @code{SHELL} variable names a shell
2170 that runs an initialization file---such as @file{.cshrc} for C-shell, or
2171 @file{.bashrc} for BASH---any variables you set in that file affect
2172 your program. You may wish to move setting of environment variables to
2173 files that are only run when you sign on, such as @file{.login} or
2176 @node Working Directory
2177 @section Your Program's Working Directory
2179 @cindex working directory (of your program)
2180 Each time you start your program with @code{run}, it inherits its
2181 working directory from the current working directory of @value{GDBN}.
2182 The @value{GDBN} working directory is initially whatever it inherited
2183 from its parent process (typically the shell), but you can specify a new
2184 working directory in @value{GDBN} with the @code{cd} command.
2186 The @value{GDBN} working directory also serves as a default for the commands
2187 that specify files for @value{GDBN} to operate on. @xref{Files, ,Commands to
2192 @cindex change working directory
2193 @item cd @var{directory}
2194 Set the @value{GDBN} working directory to @var{directory}.
2198 Print the @value{GDBN} working directory.
2201 It is generally impossible to find the current working directory of
2202 the process being debugged (since a program can change its directory
2203 during its run). If you work on a system where @value{GDBN} is
2204 configured with the @file{/proc} support, you can use the @code{info
2205 proc} command (@pxref{SVR4 Process Information}) to find out the
2206 current working directory of the debuggee.
2209 @section Your Program's Input and Output
2214 By default, the program you run under @value{GDBN} does input and output to
2215 the same terminal that @value{GDBN} uses. @value{GDBN} switches the terminal
2216 to its own terminal modes to interact with you, but it records the terminal
2217 modes your program was using and switches back to them when you continue
2218 running your program.
2221 @kindex info terminal
2223 Displays information recorded by @value{GDBN} about the terminal modes your
2227 You can redirect your program's input and/or output using shell
2228 redirection with the @code{run} command. For example,
2235 starts your program, diverting its output to the file @file{outfile}.
2238 @cindex controlling terminal
2239 Another way to specify where your program should do input and output is
2240 with the @code{tty} command. This command accepts a file name as
2241 argument, and causes this file to be the default for future @code{run}
2242 commands. It also resets the controlling terminal for the child
2243 process, for future @code{run} commands. For example,
2250 directs that processes started with subsequent @code{run} commands
2251 default to do input and output on the terminal @file{/dev/ttyb} and have
2252 that as their controlling terminal.
2254 An explicit redirection in @code{run} overrides the @code{tty} command's
2255 effect on the input/output device, but not its effect on the controlling
2258 When you use the @code{tty} command or redirect input in the @code{run}
2259 command, only the input @emph{for your program} is affected. The input
2260 for @value{GDBN} still comes from your terminal. @code{tty} is an alias
2261 for @code{set inferior-tty}.
2263 @cindex inferior tty
2264 @cindex set inferior controlling terminal
2265 You can use the @code{show inferior-tty} command to tell @value{GDBN} to
2266 display the name of the terminal that will be used for future runs of your
2270 @item set inferior-tty /dev/ttyb
2271 @kindex set inferior-tty
2272 Set the tty for the program being debugged to /dev/ttyb.
2274 @item show inferior-tty
2275 @kindex show inferior-tty
2276 Show the current tty for the program being debugged.
2280 @section Debugging an Already-running Process
2285 @item attach @var{process-id}
2286 This command attaches to a running process---one that was started
2287 outside @value{GDBN}. (@code{info files} shows your active
2288 targets.) The command takes as argument a process ID. The usual way to
2289 find out the @var{process-id} of a Unix process is with the @code{ps} utility,
2290 or with the @samp{jobs -l} shell command.
2292 @code{attach} does not repeat if you press @key{RET} a second time after
2293 executing the command.
2296 To use @code{attach}, your program must be running in an environment
2297 which supports processes; for example, @code{attach} does not work for
2298 programs on bare-board targets that lack an operating system. You must
2299 also have permission to send the process a signal.
2301 When you use @code{attach}, the debugger finds the program running in
2302 the process first by looking in the current working directory, then (if
2303 the program is not found) by using the source file search path
2304 (@pxref{Source Path, ,Specifying Source Directories}). You can also use
2305 the @code{file} command to load the program. @xref{Files, ,Commands to
2308 The first thing @value{GDBN} does after arranging to debug the specified
2309 process is to stop it. You can examine and modify an attached process
2310 with all the @value{GDBN} commands that are ordinarily available when
2311 you start processes with @code{run}. You can insert breakpoints; you
2312 can step and continue; you can modify storage. If you would rather the
2313 process continue running, you may use the @code{continue} command after
2314 attaching @value{GDBN} to the process.
2319 When you have finished debugging the attached process, you can use the
2320 @code{detach} command to release it from @value{GDBN} control. Detaching
2321 the process continues its execution. After the @code{detach} command,
2322 that process and @value{GDBN} become completely independent once more, and you
2323 are ready to @code{attach} another process or start one with @code{run}.
2324 @code{detach} does not repeat if you press @key{RET} again after
2325 executing the command.
2328 If you exit @value{GDBN} while you have an attached process, you detach
2329 that process. If you use the @code{run} command, you kill that process.
2330 By default, @value{GDBN} asks for confirmation if you try to do either of these
2331 things; you can control whether or not you need to confirm by using the
2332 @code{set confirm} command (@pxref{Messages/Warnings, ,Optional Warnings and
2336 @section Killing the Child Process
2341 Kill the child process in which your program is running under @value{GDBN}.
2344 This command is useful if you wish to debug a core dump instead of a
2345 running process. @value{GDBN} ignores any core dump file while your program
2348 On some operating systems, a program cannot be executed outside @value{GDBN}
2349 while you have breakpoints set on it inside @value{GDBN}. You can use the
2350 @code{kill} command in this situation to permit running your program
2351 outside the debugger.
2353 The @code{kill} command is also useful if you wish to recompile and
2354 relink your program, since on many systems it is impossible to modify an
2355 executable file while it is running in a process. In this case, when you
2356 next type @code{run}, @value{GDBN} notices that the file has changed, and
2357 reads the symbol table again (while trying to preserve your current
2358 breakpoint settings).
2361 @section Debugging Multiple Inferiors
2363 Some @value{GDBN} targets are able to run multiple processes created
2364 from a single executable. This can happen, for instance, with an
2365 embedded system reporting back several processes via the remote
2369 @value{GDBN} represents the state of each program execution with an
2370 object called an @dfn{inferior}. An inferior typically corresponds to
2371 a process, but is more general and applies also to targets that do not
2372 have processes. Inferiors may be created before a process runs, and
2373 may (in future) be retained after a process exits. Each run of an
2374 executable creates a new inferior, as does each attachment to an
2375 existing process. Inferiors have unique identifiers that are
2376 different from process ids, and may optionally be named as well.
2377 Usually each inferior will also have its own distinct address space,
2378 although some embedded targets may have several inferiors running in
2379 different parts of a single space.
2381 Each inferior may in turn have multiple threads running in it.
2383 To find out what inferiors exist at any moment, use @code{info inferiors}:
2386 @kindex info inferiors
2387 @item info inferiors
2388 Print a list of all inferiors currently being managed by @value{GDBN}.
2390 @kindex set print inferior-events
2391 @cindex print messages on inferior start and exit
2392 @item set print inferior-events
2393 @itemx set print inferior-events on
2394 @itemx set print inferior-events off
2395 The @code{set print inferior-events} command allows you to enable or
2396 disable printing of messages when @value{GDBN} notices that new
2397 inferiors have started or that inferiors have exited or have been
2398 detached. By default, these messages will not be printed.
2400 @kindex show print inferior-events
2401 @item show print inferior-events
2402 Show whether messages will be printed when @value{GDBN} detects that
2403 inferiors have started, exited or have been detached.
2407 @section Debugging Programs with Multiple Threads
2409 @cindex threads of execution
2410 @cindex multiple threads
2411 @cindex switching threads
2412 In some operating systems, such as HP-UX and Solaris, a single program
2413 may have more than one @dfn{thread} of execution. The precise semantics
2414 of threads differ from one operating system to another, but in general
2415 the threads of a single program are akin to multiple processes---except
2416 that they share one address space (that is, they can all examine and
2417 modify the same variables). On the other hand, each thread has its own
2418 registers and execution stack, and perhaps private memory.
2420 @value{GDBN} provides these facilities for debugging multi-thread
2424 @item automatic notification of new threads
2425 @item @samp{thread @var{threadno}}, a command to switch among threads
2426 @item @samp{info threads}, a command to inquire about existing threads
2427 @item @samp{thread apply [@var{threadno}] [@var{all}] @var{args}},
2428 a command to apply a command to a list of threads
2429 @item thread-specific breakpoints
2430 @item @samp{set print thread-events}, which controls printing of
2431 messages on thread start and exit.
2435 @emph{Warning:} These facilities are not yet available on every
2436 @value{GDBN} configuration where the operating system supports threads.
2437 If your @value{GDBN} does not support threads, these commands have no
2438 effect. For example, a system without thread support shows no output
2439 from @samp{info threads}, and always rejects the @code{thread} command,
2443 (@value{GDBP}) info threads
2444 (@value{GDBP}) thread 1
2445 Thread ID 1 not known. Use the "info threads" command to
2446 see the IDs of currently known threads.
2448 @c FIXME to implementors: how hard would it be to say "sorry, this GDB
2449 @c doesn't support threads"?
2452 @cindex focus of debugging
2453 @cindex current thread
2454 The @value{GDBN} thread debugging facility allows you to observe all
2455 threads while your program runs---but whenever @value{GDBN} takes
2456 control, one thread in particular is always the focus of debugging.
2457 This thread is called the @dfn{current thread}. Debugging commands show
2458 program information from the perspective of the current thread.
2460 @cindex @code{New} @var{systag} message
2461 @cindex thread identifier (system)
2462 @c FIXME-implementors!! It would be more helpful if the [New...] message
2463 @c included GDB's numeric thread handle, so you could just go to that
2464 @c thread without first checking `info threads'.
2465 Whenever @value{GDBN} detects a new thread in your program, it displays
2466 the target system's identification for the thread with a message in the
2467 form @samp{[New @var{systag}]}. @var{systag} is a thread identifier
2468 whose form varies depending on the particular system. For example, on
2469 @sc{gnu}/Linux, you might see
2472 [New Thread 46912507313328 (LWP 25582)]
2476 when @value{GDBN} notices a new thread. In contrast, on an SGI system,
2477 the @var{systag} is simply something like @samp{process 368}, with no
2480 @c FIXME!! (1) Does the [New...] message appear even for the very first
2481 @c thread of a program, or does it only appear for the
2482 @c second---i.e.@: when it becomes obvious we have a multithread
2484 @c (2) *Is* there necessarily a first thread always? Or do some
2485 @c multithread systems permit starting a program with multiple
2486 @c threads ab initio?
2488 @cindex thread number
2489 @cindex thread identifier (GDB)
2490 For debugging purposes, @value{GDBN} associates its own thread
2491 number---always a single integer---with each thread in your program.
2494 @kindex info threads
2496 Display a summary of all threads currently in your
2497 program. @value{GDBN} displays for each thread (in this order):
2501 the thread number assigned by @value{GDBN}
2504 the target system's thread identifier (@var{systag})
2507 the current stack frame summary for that thread
2511 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2512 indicates the current thread.
2516 @c end table here to get a little more width for example
2519 (@value{GDBP}) info threads
2520 3 process 35 thread 27 0x34e5 in sigpause ()
2521 2 process 35 thread 23 0x34e5 in sigpause ()
2522 * 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
2528 @cindex debugging multithreaded programs (on HP-UX)
2529 @cindex thread identifier (GDB), on HP-UX
2530 For debugging purposes, @value{GDBN} associates its own thread
2531 number---a small integer assigned in thread-creation order---with each
2532 thread in your program.
2534 @cindex @code{New} @var{systag} message, on HP-UX
2535 @cindex thread identifier (system), on HP-UX
2536 @c FIXME-implementors!! It would be more helpful if the [New...] message
2537 @c included GDB's numeric thread handle, so you could just go to that
2538 @c thread without first checking `info threads'.
2539 Whenever @value{GDBN} detects a new thread in your program, it displays
2540 both @value{GDBN}'s thread number and the target system's identification for the thread with a message in the
2541 form @samp{[New @var{systag}]}. @var{systag} is a thread identifier
2542 whose form varies depending on the particular system. For example, on
2546 [New thread 2 (system thread 26594)]
2550 when @value{GDBN} notices a new thread.
2553 @kindex info threads (HP-UX)
2555 Display a summary of all threads currently in your
2556 program. @value{GDBN} displays for each thread (in this order):
2559 @item the thread number assigned by @value{GDBN}
2561 @item the target system's thread identifier (@var{systag})
2563 @item the current stack frame summary for that thread
2567 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2568 indicates the current thread.
2572 @c end table here to get a little more width for example
2575 (@value{GDBP}) info threads
2576 * 3 system thread 26607 worker (wptr=0x7b09c318 "@@") \@*
2578 2 system thread 26606 0x7b0030d8 in __ksleep () \@*
2579 from /usr/lib/libc.2
2580 1 system thread 27905 0x7b003498 in _brk () \@*
2581 from /usr/lib/libc.2
2584 On Solaris, you can display more information about user threads with a
2585 Solaris-specific command:
2588 @item maint info sol-threads
2589 @kindex maint info sol-threads
2590 @cindex thread info (Solaris)
2591 Display info on Solaris user threads.
2595 @kindex thread @var{threadno}
2596 @item thread @var{threadno}
2597 Make thread number @var{threadno} the current thread. The command
2598 argument @var{threadno} is the internal @value{GDBN} thread number, as
2599 shown in the first field of the @samp{info threads} display.
2600 @value{GDBN} responds by displaying the system identifier of the thread
2601 you selected, and its current stack frame summary:
2604 @c FIXME!! This example made up; find a @value{GDBN} w/threads and get real one
2605 (@value{GDBP}) thread 2
2606 [Switching to process 35 thread 23]
2607 0x34e5 in sigpause ()
2611 As with the @samp{[New @dots{}]} message, the form of the text after
2612 @samp{Switching to} depends on your system's conventions for identifying
2615 @kindex thread apply
2616 @cindex apply command to several threads
2617 @item thread apply [@var{threadno}] [@var{all}] @var{command}
2618 The @code{thread apply} command allows you to apply the named
2619 @var{command} to one or more threads. Specify the numbers of the
2620 threads that you want affected with the command argument
2621 @var{threadno}. It can be a single thread number, one of the numbers
2622 shown in the first field of the @samp{info threads} display; or it
2623 could be a range of thread numbers, as in @code{2-4}. To apply a
2624 command to all threads, type @kbd{thread apply all @var{command}}.
2626 @kindex set print thread-events
2627 @cindex print messages on thread start and exit
2628 @item set print thread-events
2629 @itemx set print thread-events on
2630 @itemx set print thread-events off
2631 The @code{set print thread-events} command allows you to enable or
2632 disable printing of messages when @value{GDBN} notices that new threads have
2633 started or that threads have exited. By default, these messages will
2634 be printed if detection of these events is supported by the target.
2635 Note that these messages cannot be disabled on all targets.
2637 @kindex show print thread-events
2638 @item show print thread-events
2639 Show whether messages will be printed when @value{GDBN} detects that threads
2640 have started and exited.
2643 @xref{Thread Stops,,Stopping and Starting Multi-thread Programs}, for
2644 more information about how @value{GDBN} behaves when you stop and start
2645 programs with multiple threads.
2647 @xref{Set Watchpoints,,Setting Watchpoints}, for information about
2648 watchpoints in programs with multiple threads.
2651 @section Debugging Programs with Multiple Processes
2653 @cindex fork, debugging programs which call
2654 @cindex multiple processes
2655 @cindex processes, multiple
2656 On most systems, @value{GDBN} has no special support for debugging
2657 programs which create additional processes using the @code{fork}
2658 function. When a program forks, @value{GDBN} will continue to debug the
2659 parent process and the child process will run unimpeded. If you have
2660 set a breakpoint in any code which the child then executes, the child
2661 will get a @code{SIGTRAP} signal which (unless it catches the signal)
2662 will cause it to terminate.
2664 However, if you want to debug the child process there is a workaround
2665 which isn't too painful. Put a call to @code{sleep} in the code which
2666 the child process executes after the fork. It may be useful to sleep
2667 only if a certain environment variable is set, or a certain file exists,
2668 so that the delay need not occur when you don't want to run @value{GDBN}
2669 on the child. While the child is sleeping, use the @code{ps} program to
2670 get its process ID. Then tell @value{GDBN} (a new invocation of
2671 @value{GDBN} if you are also debugging the parent process) to attach to
2672 the child process (@pxref{Attach}). From that point on you can debug
2673 the child process just like any other process which you attached to.
2675 On some systems, @value{GDBN} provides support for debugging programs that
2676 create additional processes using the @code{fork} or @code{vfork} functions.
2677 Currently, the only platforms with this feature are HP-UX (11.x and later
2678 only?) and @sc{gnu}/Linux (kernel version 2.5.60 and later).
2680 By default, when a program forks, @value{GDBN} will continue to debug
2681 the parent process and the child process will run unimpeded.
2683 If you want to follow the child process instead of the parent process,
2684 use the command @w{@code{set follow-fork-mode}}.
2687 @kindex set follow-fork-mode
2688 @item set follow-fork-mode @var{mode}
2689 Set the debugger response to a program call of @code{fork} or
2690 @code{vfork}. A call to @code{fork} or @code{vfork} creates a new
2691 process. The @var{mode} argument can be:
2695 The original process is debugged after a fork. The child process runs
2696 unimpeded. This is the default.
2699 The new process is debugged after a fork. The parent process runs
2704 @kindex show follow-fork-mode
2705 @item show follow-fork-mode
2706 Display the current debugger response to a @code{fork} or @code{vfork} call.
2709 @cindex debugging multiple processes
2710 On Linux, if you want to debug both the parent and child processes, use the
2711 command @w{@code{set detach-on-fork}}.
2714 @kindex set detach-on-fork
2715 @item set detach-on-fork @var{mode}
2716 Tells gdb whether to detach one of the processes after a fork, or
2717 retain debugger control over them both.
2721 The child process (or parent process, depending on the value of
2722 @code{follow-fork-mode}) will be detached and allowed to run
2723 independently. This is the default.
2726 Both processes will be held under the control of @value{GDBN}.
2727 One process (child or parent, depending on the value of
2728 @code{follow-fork-mode}) is debugged as usual, while the other
2733 @kindex show detach-on-fork
2734 @item show detach-on-fork
2735 Show whether detach-on-fork mode is on/off.
2738 If you choose to set @samp{detach-on-fork} mode off, then
2739 @value{GDBN} will retain control of all forked processes (including
2740 nested forks). You can list the forked processes under the control of
2741 @value{GDBN} by using the @w{@code{info forks}} command, and switch
2742 from one fork to another by using the @w{@code{fork}} command.
2747 Print a list of all forked processes under the control of @value{GDBN}.
2748 The listing will include a fork id, a process id, and the current
2749 position (program counter) of the process.
2751 @kindex fork @var{fork-id}
2752 @item fork @var{fork-id}
2753 Make fork number @var{fork-id} the current process. The argument
2754 @var{fork-id} is the internal fork number assigned by @value{GDBN},
2755 as shown in the first field of the @samp{info forks} display.
2757 @kindex process @var{process-id}
2758 @item process @var{process-id}
2759 Make process number @var{process-id} the current process. The
2760 argument @var{process-id} must be one that is listed in the output of
2765 To quit debugging one of the forked processes, you can either detach
2766 from it by using the @w{@code{detach fork}} command (allowing it to
2767 run independently), or delete (and kill) it using the
2768 @w{@code{delete fork}} command.
2771 @kindex detach fork @var{fork-id}
2772 @item detach fork @var{fork-id}
2773 Detach from the process identified by @value{GDBN} fork number
2774 @var{fork-id}, and remove it from the fork list. The process will be
2775 allowed to run independently.
2777 @kindex delete fork @var{fork-id}
2778 @item delete fork @var{fork-id}
2779 Kill the process identified by @value{GDBN} fork number @var{fork-id},
2780 and remove it from the fork list.
2784 If you ask to debug a child process and a @code{vfork} is followed by an
2785 @code{exec}, @value{GDBN} executes the new target up to the first
2786 breakpoint in the new target. If you have a breakpoint set on
2787 @code{main} in your original program, the breakpoint will also be set on
2788 the child process's @code{main}.
2790 When a child process is spawned by @code{vfork}, you cannot debug the
2791 child or parent until an @code{exec} call completes.
2793 If you issue a @code{run} command to @value{GDBN} after an @code{exec}
2794 call executes, the new target restarts. To restart the parent process,
2795 use the @code{file} command with the parent executable name as its
2798 You can use the @code{catch} command to make @value{GDBN} stop whenever
2799 a @code{fork}, @code{vfork}, or @code{exec} call is made. @xref{Set
2800 Catchpoints, ,Setting Catchpoints}.
2802 @node Checkpoint/Restart
2803 @section Setting a @emph{Bookmark} to Return to Later
2808 @cindex snapshot of a process
2809 @cindex rewind program state
2811 On certain operating systems@footnote{Currently, only
2812 @sc{gnu}/Linux.}, @value{GDBN} is able to save a @dfn{snapshot} of a
2813 program's state, called a @dfn{checkpoint}, and come back to it
2816 Returning to a checkpoint effectively undoes everything that has
2817 happened in the program since the @code{checkpoint} was saved. This
2818 includes changes in memory, registers, and even (within some limits)
2819 system state. Effectively, it is like going back in time to the
2820 moment when the checkpoint was saved.
2822 Thus, if you're stepping thru a program and you think you're
2823 getting close to the point where things go wrong, you can save
2824 a checkpoint. Then, if you accidentally go too far and miss
2825 the critical statement, instead of having to restart your program
2826 from the beginning, you can just go back to the checkpoint and
2827 start again from there.
2829 This can be especially useful if it takes a lot of time or
2830 steps to reach the point where you think the bug occurs.
2832 To use the @code{checkpoint}/@code{restart} method of debugging:
2837 Save a snapshot of the debugged program's current execution state.
2838 The @code{checkpoint} command takes no arguments, but each checkpoint
2839 is assigned a small integer id, similar to a breakpoint id.
2841 @kindex info checkpoints
2842 @item info checkpoints
2843 List the checkpoints that have been saved in the current debugging
2844 session. For each checkpoint, the following information will be
2851 @item Source line, or label
2854 @kindex restart @var{checkpoint-id}
2855 @item restart @var{checkpoint-id}
2856 Restore the program state that was saved as checkpoint number
2857 @var{checkpoint-id}. All program variables, registers, stack frames
2858 etc.@: will be returned to the values that they had when the checkpoint
2859 was saved. In essence, gdb will ``wind back the clock'' to the point
2860 in time when the checkpoint was saved.
2862 Note that breakpoints, @value{GDBN} variables, command history etc.
2863 are not affected by restoring a checkpoint. In general, a checkpoint
2864 only restores things that reside in the program being debugged, not in
2867 @kindex delete checkpoint @var{checkpoint-id}
2868 @item delete checkpoint @var{checkpoint-id}
2869 Delete the previously-saved checkpoint identified by @var{checkpoint-id}.
2873 Returning to a previously saved checkpoint will restore the user state
2874 of the program being debugged, plus a significant subset of the system
2875 (OS) state, including file pointers. It won't ``un-write'' data from
2876 a file, but it will rewind the file pointer to the previous location,
2877 so that the previously written data can be overwritten. For files
2878 opened in read mode, the pointer will also be restored so that the
2879 previously read data can be read again.
2881 Of course, characters that have been sent to a printer (or other
2882 external device) cannot be ``snatched back'', and characters received
2883 from eg.@: a serial device can be removed from internal program buffers,
2884 but they cannot be ``pushed back'' into the serial pipeline, ready to
2885 be received again. Similarly, the actual contents of files that have
2886 been changed cannot be restored (at this time).
2888 However, within those constraints, you actually can ``rewind'' your
2889 program to a previously saved point in time, and begin debugging it
2890 again --- and you can change the course of events so as to debug a
2891 different execution path this time.
2893 @cindex checkpoints and process id
2894 Finally, there is one bit of internal program state that will be
2895 different when you return to a checkpoint --- the program's process
2896 id. Each checkpoint will have a unique process id (or @var{pid}),
2897 and each will be different from the program's original @var{pid}.
2898 If your program has saved a local copy of its process id, this could
2899 potentially pose a problem.
2901 @subsection A Non-obvious Benefit of Using Checkpoints
2903 On some systems such as @sc{gnu}/Linux, address space randomization
2904 is performed on new processes for security reasons. This makes it
2905 difficult or impossible to set a breakpoint, or watchpoint, on an
2906 absolute address if you have to restart the program, since the
2907 absolute location of a symbol will change from one execution to the
2910 A checkpoint, however, is an @emph{identical} copy of a process.
2911 Therefore if you create a checkpoint at (eg.@:) the start of main,
2912 and simply return to that checkpoint instead of restarting the
2913 process, you can avoid the effects of address randomization and
2914 your symbols will all stay in the same place.
2917 @chapter Stopping and Continuing
2919 The principal purposes of using a debugger are so that you can stop your
2920 program before it terminates; or so that, if your program runs into
2921 trouble, you can investigate and find out why.
2923 Inside @value{GDBN}, your program may stop for any of several reasons,
2924 such as a signal, a breakpoint, or reaching a new line after a
2925 @value{GDBN} command such as @code{step}. You may then examine and
2926 change variables, set new breakpoints or remove old ones, and then
2927 continue execution. Usually, the messages shown by @value{GDBN} provide
2928 ample explanation of the status of your program---but you can also
2929 explicitly request this information at any time.
2932 @kindex info program
2934 Display information about the status of your program: whether it is
2935 running or not, what process it is, and why it stopped.
2939 * Breakpoints:: Breakpoints, watchpoints, and catchpoints
2940 * Continuing and Stepping:: Resuming execution
2942 * Thread Stops:: Stopping and starting multi-thread programs
2946 @section Breakpoints, Watchpoints, and Catchpoints
2949 A @dfn{breakpoint} makes your program stop whenever a certain point in
2950 the program is reached. For each breakpoint, you can add conditions to
2951 control in finer detail whether your program stops. You can set
2952 breakpoints with the @code{break} command and its variants (@pxref{Set
2953 Breaks, ,Setting Breakpoints}), to specify the place where your program
2954 should stop by line number, function name or exact address in the
2957 On some systems, you can set breakpoints in shared libraries before
2958 the executable is run. There is a minor limitation on HP-UX systems:
2959 you must wait until the executable is run in order to set breakpoints
2960 in shared library routines that are not called directly by the program
2961 (for example, routines that are arguments in a @code{pthread_create}
2965 @cindex data breakpoints
2966 @cindex memory tracing
2967 @cindex breakpoint on memory address
2968 @cindex breakpoint on variable modification
2969 A @dfn{watchpoint} is a special breakpoint that stops your program
2970 when the value of an expression changes. The expression may be a value
2971 of a variable, or it could involve values of one or more variables
2972 combined by operators, such as @samp{a + b}. This is sometimes called
2973 @dfn{data breakpoints}. You must use a different command to set
2974 watchpoints (@pxref{Set Watchpoints, ,Setting Watchpoints}), but aside
2975 from that, you can manage a watchpoint like any other breakpoint: you
2976 enable, disable, and delete both breakpoints and watchpoints using the
2979 You can arrange to have values from your program displayed automatically
2980 whenever @value{GDBN} stops at a breakpoint. @xref{Auto Display,,
2984 @cindex breakpoint on events
2985 A @dfn{catchpoint} is another special breakpoint that stops your program
2986 when a certain kind of event occurs, such as the throwing of a C@t{++}
2987 exception or the loading of a library. As with watchpoints, you use a
2988 different command to set a catchpoint (@pxref{Set Catchpoints, ,Setting
2989 Catchpoints}), but aside from that, you can manage a catchpoint like any
2990 other breakpoint. (To stop when your program receives a signal, use the
2991 @code{handle} command; see @ref{Signals, ,Signals}.)
2993 @cindex breakpoint numbers
2994 @cindex numbers for breakpoints
2995 @value{GDBN} assigns a number to each breakpoint, watchpoint, or
2996 catchpoint when you create it; these numbers are successive integers
2997 starting with one. In many of the commands for controlling various
2998 features of breakpoints you use the breakpoint number to say which
2999 breakpoint you want to change. Each breakpoint may be @dfn{enabled} or
3000 @dfn{disabled}; if disabled, it has no effect on your program until you
3003 @cindex breakpoint ranges
3004 @cindex ranges of breakpoints
3005 Some @value{GDBN} commands accept a range of breakpoints on which to
3006 operate. A breakpoint range is either a single breakpoint number, like
3007 @samp{5}, or two such numbers, in increasing order, separated by a
3008 hyphen, like @samp{5-7}. When a breakpoint range is given to a command,
3009 all breakpoints in that range are operated on.
3012 * Set Breaks:: Setting breakpoints
3013 * Set Watchpoints:: Setting watchpoints
3014 * Set Catchpoints:: Setting catchpoints
3015 * Delete Breaks:: Deleting breakpoints
3016 * Disabling:: Disabling breakpoints
3017 * Conditions:: Break conditions
3018 * Break Commands:: Breakpoint command lists
3019 * Error in Breakpoints:: ``Cannot insert breakpoints''
3020 * Breakpoint-related Warnings:: ``Breakpoint address adjusted...''
3024 @subsection Setting Breakpoints
3026 @c FIXME LMB what does GDB do if no code on line of breakpt?
3027 @c consider in particular declaration with/without initialization.
3029 @c FIXME 2 is there stuff on this already? break at fun start, already init?
3032 @kindex b @r{(@code{break})}
3033 @vindex $bpnum@r{, convenience variable}
3034 @cindex latest breakpoint
3035 Breakpoints are set with the @code{break} command (abbreviated
3036 @code{b}). The debugger convenience variable @samp{$bpnum} records the
3037 number of the breakpoint you've set most recently; see @ref{Convenience
3038 Vars,, Convenience Variables}, for a discussion of what you can do with
3039 convenience variables.
3042 @item break @var{location}
3043 Set a breakpoint at the given @var{location}, which can specify a
3044 function name, a line number, or an address of an instruction.
3045 (@xref{Specify Location}, for a list of all the possible ways to
3046 specify a @var{location}.) The breakpoint will stop your program just
3047 before it executes any of the code in the specified @var{location}.
3049 When using source languages that permit overloading of symbols, such as
3050 C@t{++}, a function name may refer to more than one possible place to break.
3051 @xref{Ambiguous Expressions,,Ambiguous Expressions}, for a discussion of
3054 It is also possible to insert a breakpoint that will stop the program
3055 only if a specific thread (@pxref{Thread-Specific Breakpoints})
3056 or a specific task (@pxref{Ada Tasks}) hits that breakpoint.
3059 When called without any arguments, @code{break} sets a breakpoint at
3060 the next instruction to be executed in the selected stack frame
3061 (@pxref{Stack, ,Examining the Stack}). In any selected frame but the
3062 innermost, this makes your program stop as soon as control
3063 returns to that frame. This is similar to the effect of a
3064 @code{finish} command in the frame inside the selected frame---except
3065 that @code{finish} does not leave an active breakpoint. If you use
3066 @code{break} without an argument in the innermost frame, @value{GDBN} stops
3067 the next time it reaches the current location; this may be useful
3070 @value{GDBN} normally ignores breakpoints when it resumes execution, until at
3071 least one instruction has been executed. If it did not do this, you
3072 would be unable to proceed past a breakpoint without first disabling the
3073 breakpoint. This rule applies whether or not the breakpoint already
3074 existed when your program stopped.
3076 @item break @dots{} if @var{cond}
3077 Set a breakpoint with condition @var{cond}; evaluate the expression
3078 @var{cond} each time the breakpoint is reached, and stop only if the
3079 value is nonzero---that is, if @var{cond} evaluates as true.
3080 @samp{@dots{}} stands for one of the possible arguments described
3081 above (or no argument) specifying where to break. @xref{Conditions,
3082 ,Break Conditions}, for more information on breakpoint conditions.
3085 @item tbreak @var{args}
3086 Set a breakpoint enabled only for one stop. @var{args} are the
3087 same as for the @code{break} command, and the breakpoint is set in the same
3088 way, but the breakpoint is automatically deleted after the first time your
3089 program stops there. @xref{Disabling, ,Disabling Breakpoints}.
3092 @cindex hardware breakpoints
3093 @item hbreak @var{args}
3094 Set a hardware-assisted breakpoint. @var{args} are the same as for the
3095 @code{break} command and the breakpoint is set in the same way, but the
3096 breakpoint requires hardware support and some target hardware may not
3097 have this support. The main purpose of this is EPROM/ROM code
3098 debugging, so you can set a breakpoint at an instruction without
3099 changing the instruction. This can be used with the new trap-generation
3100 provided by SPARClite DSU and most x86-based targets. These targets
3101 will generate traps when a program accesses some data or instruction
3102 address that is assigned to the debug registers. However the hardware
3103 breakpoint registers can take a limited number of breakpoints. For
3104 example, on the DSU, only two data breakpoints can be set at a time, and
3105 @value{GDBN} will reject this command if more than two are used. Delete
3106 or disable unused hardware breakpoints before setting new ones
3107 (@pxref{Disabling, ,Disabling Breakpoints}).
3108 @xref{Conditions, ,Break Conditions}.
3109 For remote targets, you can restrict the number of hardware
3110 breakpoints @value{GDBN} will use, see @ref{set remote
3111 hardware-breakpoint-limit}.
3114 @item thbreak @var{args}
3115 Set a hardware-assisted breakpoint enabled only for one stop. @var{args}
3116 are the same as for the @code{hbreak} command and the breakpoint is set in
3117 the same way. However, like the @code{tbreak} command,
3118 the breakpoint is automatically deleted after the
3119 first time your program stops there. Also, like the @code{hbreak}
3120 command, the breakpoint requires hardware support and some target hardware
3121 may not have this support. @xref{Disabling, ,Disabling Breakpoints}.
3122 See also @ref{Conditions, ,Break Conditions}.
3125 @cindex regular expression
3126 @cindex breakpoints in functions matching a regexp
3127 @cindex set breakpoints in many functions
3128 @item rbreak @var{regex}
3129 Set breakpoints on all functions matching the regular expression
3130 @var{regex}. This command sets an unconditional breakpoint on all
3131 matches, printing a list of all breakpoints it set. Once these
3132 breakpoints are set, they are treated just like the breakpoints set with
3133 the @code{break} command. You can delete them, disable them, or make
3134 them conditional the same way as any other breakpoint.
3136 The syntax of the regular expression is the standard one used with tools
3137 like @file{grep}. Note that this is different from the syntax used by
3138 shells, so for instance @code{foo*} matches all functions that include
3139 an @code{fo} followed by zero or more @code{o}s. There is an implicit
3140 @code{.*} leading and trailing the regular expression you supply, so to
3141 match only functions that begin with @code{foo}, use @code{^foo}.
3143 @cindex non-member C@t{++} functions, set breakpoint in
3144 When debugging C@t{++} programs, @code{rbreak} is useful for setting
3145 breakpoints on overloaded functions that are not members of any special
3148 @cindex set breakpoints on all functions
3149 The @code{rbreak} command can be used to set breakpoints in
3150 @strong{all} the functions in a program, like this:
3153 (@value{GDBP}) rbreak .
3156 @kindex info breakpoints
3157 @cindex @code{$_} and @code{info breakpoints}
3158 @item info breakpoints @r{[}@var{n}@r{]}
3159 @itemx info break @r{[}@var{n}@r{]}
3160 @itemx info watchpoints @r{[}@var{n}@r{]}
3161 Print a table of all breakpoints, watchpoints, and catchpoints set and
3162 not deleted. Optional argument @var{n} means print information only
3163 about the specified breakpoint (or watchpoint or catchpoint). For
3164 each breakpoint, following columns are printed:
3167 @item Breakpoint Numbers
3169 Breakpoint, watchpoint, or catchpoint.
3171 Whether the breakpoint is marked to be disabled or deleted when hit.
3172 @item Enabled or Disabled
3173 Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints
3174 that are not enabled.
3176 Where the breakpoint is in your program, as a memory address. For a
3177 pending breakpoint whose address is not yet known, this field will
3178 contain @samp{<PENDING>}. Such breakpoint won't fire until a shared
3179 library that has the symbol or line referred by breakpoint is loaded.
3180 See below for details. A breakpoint with several locations will
3181 have @samp{<MULTIPLE>} in this field---see below for details.
3183 Where the breakpoint is in the source for your program, as a file and
3184 line number. For a pending breakpoint, the original string passed to
3185 the breakpoint command will be listed as it cannot be resolved until
3186 the appropriate shared library is loaded in the future.
3190 If a breakpoint is conditional, @code{info break} shows the condition on
3191 the line following the affected breakpoint; breakpoint commands, if any,
3192 are listed after that. A pending breakpoint is allowed to have a condition
3193 specified for it. The condition is not parsed for validity until a shared
3194 library is loaded that allows the pending breakpoint to resolve to a
3198 @code{info break} with a breakpoint
3199 number @var{n} as argument lists only that breakpoint. The
3200 convenience variable @code{$_} and the default examining-address for
3201 the @code{x} command are set to the address of the last breakpoint
3202 listed (@pxref{Memory, ,Examining Memory}).
3205 @code{info break} displays a count of the number of times the breakpoint
3206 has been hit. This is especially useful in conjunction with the
3207 @code{ignore} command. You can ignore a large number of breakpoint
3208 hits, look at the breakpoint info to see how many times the breakpoint
3209 was hit, and then run again, ignoring one less than that number. This
3210 will get you quickly to the last hit of that breakpoint.
3213 @value{GDBN} allows you to set any number of breakpoints at the same place in
3214 your program. There is nothing silly or meaningless about this. When
3215 the breakpoints are conditional, this is even useful
3216 (@pxref{Conditions, ,Break Conditions}).
3218 @cindex multiple locations, breakpoints
3219 @cindex breakpoints, multiple locations
3220 It is possible that a breakpoint corresponds to several locations
3221 in your program. Examples of this situation are:
3225 For a C@t{++} constructor, the @value{NGCC} compiler generates several
3226 instances of the function body, used in different cases.
3229 For a C@t{++} template function, a given line in the function can
3230 correspond to any number of instantiations.
3233 For an inlined function, a given source line can correspond to
3234 several places where that function is inlined.
3237 In all those cases, @value{GDBN} will insert a breakpoint at all
3238 the relevant locations@footnote{
3239 As of this writing, multiple-location breakpoints work only if there's
3240 line number information for all the locations. This means that they
3241 will generally not work in system libraries, unless you have debug
3242 info with line numbers for them.}.
3244 A breakpoint with multiple locations is displayed in the breakpoint
3245 table using several rows---one header row, followed by one row for
3246 each breakpoint location. The header row has @samp{<MULTIPLE>} in the
3247 address column. The rows for individual locations contain the actual
3248 addresses for locations, and show the functions to which those
3249 locations belong. The number column for a location is of the form
3250 @var{breakpoint-number}.@var{location-number}.
3255 Num Type Disp Enb Address What
3256 1 breakpoint keep y <MULTIPLE>
3258 breakpoint already hit 1 time
3259 1.1 y 0x080486a2 in void foo<int>() at t.cc:8
3260 1.2 y 0x080486ca in void foo<double>() at t.cc:8
3263 Each location can be individually enabled or disabled by passing
3264 @var{breakpoint-number}.@var{location-number} as argument to the
3265 @code{enable} and @code{disable} commands. Note that you cannot
3266 delete the individual locations from the list, you can only delete the
3267 entire list of locations that belong to their parent breakpoint (with
3268 the @kbd{delete @var{num}} command, where @var{num} is the number of
3269 the parent breakpoint, 1 in the above example). Disabling or enabling
3270 the parent breakpoint (@pxref{Disabling}) affects all of the locations
3271 that belong to that breakpoint.
3273 @cindex pending breakpoints
3274 It's quite common to have a breakpoint inside a shared library.
3275 Shared libraries can be loaded and unloaded explicitly,
3276 and possibly repeatedly, as the program is executed. To support
3277 this use case, @value{GDBN} updates breakpoint locations whenever
3278 any shared library is loaded or unloaded. Typically, you would
3279 set a breakpoint in a shared library at the beginning of your
3280 debugging session, when the library is not loaded, and when the
3281 symbols from the library are not available. When you try to set
3282 breakpoint, @value{GDBN} will ask you if you want to set
3283 a so called @dfn{pending breakpoint}---breakpoint whose address
3284 is not yet resolved.
3286 After the program is run, whenever a new shared library is loaded,
3287 @value{GDBN} reevaluates all the breakpoints. When a newly loaded
3288 shared library contains the symbol or line referred to by some
3289 pending breakpoint, that breakpoint is resolved and becomes an
3290 ordinary breakpoint. When a library is unloaded, all breakpoints
3291 that refer to its symbols or source lines become pending again.
3293 This logic works for breakpoints with multiple locations, too. For
3294 example, if you have a breakpoint in a C@t{++} template function, and
3295 a newly loaded shared library has an instantiation of that template,
3296 a new location is added to the list of locations for the breakpoint.
3298 Except for having unresolved address, pending breakpoints do not
3299 differ from regular breakpoints. You can set conditions or commands,
3300 enable and disable them and perform other breakpoint operations.
3302 @value{GDBN} provides some additional commands for controlling what
3303 happens when the @samp{break} command cannot resolve breakpoint
3304 address specification to an address:
3306 @kindex set breakpoint pending
3307 @kindex show breakpoint pending
3309 @item set breakpoint pending auto
3310 This is the default behavior. When @value{GDBN} cannot find the breakpoint
3311 location, it queries you whether a pending breakpoint should be created.
3313 @item set breakpoint pending on
3314 This indicates that an unrecognized breakpoint location should automatically
3315 result in a pending breakpoint being created.
3317 @item set breakpoint pending off
3318 This indicates that pending breakpoints are not to be created. Any
3319 unrecognized breakpoint location results in an error. This setting does
3320 not affect any pending breakpoints previously created.
3322 @item show breakpoint pending
3323 Show the current behavior setting for creating pending breakpoints.
3326 The settings above only affect the @code{break} command and its
3327 variants. Once breakpoint is set, it will be automatically updated
3328 as shared libraries are loaded and unloaded.
3330 @cindex automatic hardware breakpoints
3331 For some targets, @value{GDBN} can automatically decide if hardware or
3332 software breakpoints should be used, depending on whether the
3333 breakpoint address is read-only or read-write. This applies to
3334 breakpoints set with the @code{break} command as well as to internal
3335 breakpoints set by commands like @code{next} and @code{finish}. For
3336 breakpoints set with @code{hbreak}, @value{GDBN} will always use hardware
3339 You can control this automatic behaviour with the following commands::
3341 @kindex set breakpoint auto-hw
3342 @kindex show breakpoint auto-hw
3344 @item set breakpoint auto-hw on
3345 This is the default behavior. When @value{GDBN} sets a breakpoint, it
3346 will try to use the target memory map to decide if software or hardware
3347 breakpoint must be used.
3349 @item set breakpoint auto-hw off
3350 This indicates @value{GDBN} should not automatically select breakpoint
3351 type. If the target provides a memory map, @value{GDBN} will warn when
3352 trying to set software breakpoint at a read-only address.
3355 @value{GDBN} normally implements breakpoints by replacing the program code
3356 at the breakpoint address with a special instruction, which, when
3357 executed, given control to the debugger. By default, the program
3358 code is so modified only when the program is resumed. As soon as
3359 the program stops, @value{GDBN} restores the original instructions. This
3360 behaviour guards against leaving breakpoints inserted in the
3361 target should gdb abrubptly disconnect. However, with slow remote
3362 targets, inserting and removing breakpoint can reduce the performance.
3363 This behavior can be controlled with the following commands::
3365 @kindex set breakpoint always-inserted
3366 @kindex show breakpoint always-inserted
3368 @item set breakpoint always-inserted off
3369 All breakpoints, including newly added by the user, are inserted in
3370 the target only when the target is resumed. All breakpoints are
3371 removed from the target when it stops.
3373 @item set breakpoint always-inserted on
3374 Causes all breakpoints to be inserted in the target at all times. If
3375 the user adds a new breakpoint, or changes an existing breakpoint, the
3376 breakpoints in the target are updated immediately. A breakpoint is
3377 removed from the target only when breakpoint itself is removed.
3379 @cindex non-stop mode, and @code{breakpoint always-inserted}
3380 @item set breakpoint always-inserted auto
3381 This is the default mode. If @value{GDBN} is controlling the inferior
3382 in non-stop mode (@pxref{Non-Stop Mode}), gdb behaves as if
3383 @code{breakpoint always-inserted} mode is on. If @value{GDBN} is
3384 controlling the inferior in all-stop mode, @value{GDBN} behaves as if
3385 @code{breakpoint always-inserted} mode is off.
3388 @cindex negative breakpoint numbers
3389 @cindex internal @value{GDBN} breakpoints
3390 @value{GDBN} itself sometimes sets breakpoints in your program for
3391 special purposes, such as proper handling of @code{longjmp} (in C
3392 programs). These internal breakpoints are assigned negative numbers,
3393 starting with @code{-1}; @samp{info breakpoints} does not display them.
3394 You can see these breakpoints with the @value{GDBN} maintenance command
3395 @samp{maint info breakpoints} (@pxref{maint info breakpoints}).
3398 @node Set Watchpoints
3399 @subsection Setting Watchpoints
3401 @cindex setting watchpoints
3402 You can use a watchpoint to stop execution whenever the value of an
3403 expression changes, without having to predict a particular place where
3404 this may happen. (This is sometimes called a @dfn{data breakpoint}.)
3405 The expression may be as simple as the value of a single variable, or
3406 as complex as many variables combined by operators. Examples include:
3410 A reference to the value of a single variable.
3413 An address cast to an appropriate data type. For example,
3414 @samp{*(int *)0x12345678} will watch a 4-byte region at the specified
3415 address (assuming an @code{int} occupies 4 bytes).
3418 An arbitrarily complex expression, such as @samp{a*b + c/d}. The
3419 expression can use any operators valid in the program's native
3420 language (@pxref{Languages}).
3423 You can set a watchpoint on an expression even if the expression can
3424 not be evaluated yet. For instance, you can set a watchpoint on
3425 @samp{*global_ptr} before @samp{global_ptr} is initialized.
3426 @value{GDBN} will stop when your program sets @samp{global_ptr} and
3427 the expression produces a valid value. If the expression becomes
3428 valid in some other way than changing a variable (e.g.@: if the memory
3429 pointed to by @samp{*global_ptr} becomes readable as the result of a
3430 @code{malloc} call), @value{GDBN} may not stop until the next time
3431 the expression changes.
3433 @cindex software watchpoints
3434 @cindex hardware watchpoints
3435 Depending on your system, watchpoints may be implemented in software or
3436 hardware. @value{GDBN} does software watchpointing by single-stepping your
3437 program and testing the variable's value each time, which is hundreds of
3438 times slower than normal execution. (But this may still be worth it, to
3439 catch errors where you have no clue what part of your program is the
3442 On some systems, such as HP-UX, PowerPC, @sc{gnu}/Linux and most other
3443 x86-based targets, @value{GDBN} includes support for hardware
3444 watchpoints, which do not slow down the running of your program.
3448 @item watch @var{expr} @r{[}thread @var{threadnum}@r{]}
3449 Set a watchpoint for an expression. @value{GDBN} will break when the
3450 expression @var{expr} is written into by the program and its value
3451 changes. The simplest (and the most popular) use of this command is
3452 to watch the value of a single variable:
3455 (@value{GDBP}) watch foo
3458 If the command includes a @code{@r{[}thread @var{threadnum}@r{]}}
3459 clause, @value{GDBN} breaks only when the thread identified by
3460 @var{threadnum} changes the value of @var{expr}. If any other threads
3461 change the value of @var{expr}, @value{GDBN} will not break. Note
3462 that watchpoints restricted to a single thread in this way only work
3463 with Hardware Watchpoints.
3466 @item rwatch @var{expr} @r{[}thread @var{threadnum}@r{]}
3467 Set a watchpoint that will break when the value of @var{expr} is read
3471 @item awatch @var{expr} @r{[}thread @var{threadnum}@r{]}
3472 Set a watchpoint that will break when @var{expr} is either read from
3473 or written into by the program.
3475 @kindex info watchpoints @r{[}@var{n}@r{]}
3476 @item info watchpoints
3477 This command prints a list of watchpoints, breakpoints, and catchpoints;
3478 it is the same as @code{info break} (@pxref{Set Breaks}).
3481 @value{GDBN} sets a @dfn{hardware watchpoint} if possible. Hardware
3482 watchpoints execute very quickly, and the debugger reports a change in
3483 value at the exact instruction where the change occurs. If @value{GDBN}
3484 cannot set a hardware watchpoint, it sets a software watchpoint, which
3485 executes more slowly and reports the change in value at the next
3486 @emph{statement}, not the instruction, after the change occurs.
3488 @cindex use only software watchpoints
3489 You can force @value{GDBN} to use only software watchpoints with the
3490 @kbd{set can-use-hw-watchpoints 0} command. With this variable set to
3491 zero, @value{GDBN} will never try to use hardware watchpoints, even if
3492 the underlying system supports them. (Note that hardware-assisted
3493 watchpoints that were set @emph{before} setting
3494 @code{can-use-hw-watchpoints} to zero will still use the hardware
3495 mechanism of watching expression values.)
3498 @item set can-use-hw-watchpoints
3499 @kindex set can-use-hw-watchpoints
3500 Set whether or not to use hardware watchpoints.
3502 @item show can-use-hw-watchpoints
3503 @kindex show can-use-hw-watchpoints
3504 Show the current mode of using hardware watchpoints.
3507 For remote targets, you can restrict the number of hardware
3508 watchpoints @value{GDBN} will use, see @ref{set remote
3509 hardware-breakpoint-limit}.
3511 When you issue the @code{watch} command, @value{GDBN} reports
3514 Hardware watchpoint @var{num}: @var{expr}
3518 if it was able to set a hardware watchpoint.
3520 Currently, the @code{awatch} and @code{rwatch} commands can only set
3521 hardware watchpoints, because accesses to data that don't change the
3522 value of the watched expression cannot be detected without examining
3523 every instruction as it is being executed, and @value{GDBN} does not do
3524 that currently. If @value{GDBN} finds that it is unable to set a
3525 hardware breakpoint with the @code{awatch} or @code{rwatch} command, it
3526 will print a message like this:
3529 Expression cannot be implemented with read/access watchpoint.
3532 Sometimes, @value{GDBN} cannot set a hardware watchpoint because the
3533 data type of the watched expression is wider than what a hardware
3534 watchpoint on the target machine can handle. For example, some systems
3535 can only watch regions that are up to 4 bytes wide; on such systems you
3536 cannot set hardware watchpoints for an expression that yields a
3537 double-precision floating-point number (which is typically 8 bytes
3538 wide). As a work-around, it might be possible to break the large region
3539 into a series of smaller ones and watch them with separate watchpoints.
3541 If you set too many hardware watchpoints, @value{GDBN} might be unable
3542 to insert all of them when you resume the execution of your program.
3543 Since the precise number of active watchpoints is unknown until such
3544 time as the program is about to be resumed, @value{GDBN} might not be
3545 able to warn you about this when you set the watchpoints, and the
3546 warning will be printed only when the program is resumed:
3549 Hardware watchpoint @var{num}: Could not insert watchpoint
3553 If this happens, delete or disable some of the watchpoints.
3555 Watching complex expressions that reference many variables can also
3556 exhaust the resources available for hardware-assisted watchpoints.
3557 That's because @value{GDBN} needs to watch every variable in the
3558 expression with separately allocated resources.
3560 If you call a function interactively using @code{print} or @code{call},
3561 any watchpoints you have set will be inactive until @value{GDBN} reaches another
3562 kind of breakpoint or the call completes.
3564 @value{GDBN} automatically deletes watchpoints that watch local
3565 (automatic) variables, or expressions that involve such variables, when
3566 they go out of scope, that is, when the execution leaves the block in
3567 which these variables were defined. In particular, when the program
3568 being debugged terminates, @emph{all} local variables go out of scope,
3569 and so only watchpoints that watch global variables remain set. If you
3570 rerun the program, you will need to set all such watchpoints again. One
3571 way of doing that would be to set a code breakpoint at the entry to the
3572 @code{main} function and when it breaks, set all the watchpoints.
3574 @cindex watchpoints and threads
3575 @cindex threads and watchpoints
3576 In multi-threaded programs, watchpoints will detect changes to the
3577 watched expression from every thread.
3580 @emph{Warning:} In multi-threaded programs, software watchpoints
3581 have only limited usefulness. If @value{GDBN} creates a software
3582 watchpoint, it can only watch the value of an expression @emph{in a
3583 single thread}. If you are confident that the expression can only
3584 change due to the current thread's activity (and if you are also
3585 confident that no other thread can become current), then you can use
3586 software watchpoints as usual. However, @value{GDBN} may not notice
3587 when a non-current thread's activity changes the expression. (Hardware
3588 watchpoints, in contrast, watch an expression in all threads.)
3591 @xref{set remote hardware-watchpoint-limit}.
3593 @node Set Catchpoints
3594 @subsection Setting Catchpoints
3595 @cindex catchpoints, setting
3596 @cindex exception handlers
3597 @cindex event handling
3599 You can use @dfn{catchpoints} to cause the debugger to stop for certain
3600 kinds of program events, such as C@t{++} exceptions or the loading of a
3601 shared library. Use the @code{catch} command to set a catchpoint.
3605 @item catch @var{event}
3606 Stop when @var{event} occurs. @var{event} can be any of the following:
3609 @cindex stop on C@t{++} exceptions
3610 The throwing of a C@t{++} exception.
3613 The catching of a C@t{++} exception.
3616 @cindex Ada exception catching
3617 @cindex catch Ada exceptions
3618 An Ada exception being raised. If an exception name is specified
3619 at the end of the command (eg @code{catch exception Program_Error}),
3620 the debugger will stop only when this specific exception is raised.
3621 Otherwise, the debugger stops execution when any Ada exception is raised.
3623 When inserting an exception catchpoint on a user-defined exception whose
3624 name is identical to one of the exceptions defined by the language, the
3625 fully qualified name must be used as the exception name. Otherwise,
3626 @value{GDBN} will assume that it should stop on the pre-defined exception
3627 rather than the user-defined one. For instance, assuming an exception
3628 called @code{Constraint_Error} is defined in package @code{Pck}, then
3629 the command to use to catch such exceptions is @kbd{catch exception
3630 Pck.Constraint_Error}.
3632 @item exception unhandled
3633 An exception that was raised but is not handled by the program.
3636 A failed Ada assertion.
3639 @cindex break on fork/exec
3640 A call to @code{exec}. This is currently only available for HP-UX
3644 A call to @code{fork}. This is currently only available for HP-UX
3648 A call to @code{vfork}. This is currently only available for HP-UX
3653 @item tcatch @var{event}
3654 Set a catchpoint that is enabled only for one stop. The catchpoint is
3655 automatically deleted after the first time the event is caught.
3659 Use the @code{info break} command to list the current catchpoints.
3661 There are currently some limitations to C@t{++} exception handling
3662 (@code{catch throw} and @code{catch catch}) in @value{GDBN}:
3666 If you call a function interactively, @value{GDBN} normally returns
3667 control to you when the function has finished executing. If the call
3668 raises an exception, however, the call may bypass the mechanism that
3669 returns control to you and cause your program either to abort or to
3670 simply continue running until it hits a breakpoint, catches a signal
3671 that @value{GDBN} is listening for, or exits. This is the case even if
3672 you set a catchpoint for the exception; catchpoints on exceptions are
3673 disabled within interactive calls.
3676 You cannot raise an exception interactively.
3679 You cannot install an exception handler interactively.
3682 @cindex raise exceptions
3683 Sometimes @code{catch} is not the best way to debug exception handling:
3684 if you need to know exactly where an exception is raised, it is better to
3685 stop @emph{before} the exception handler is called, since that way you
3686 can see the stack before any unwinding takes place. If you set a
3687 breakpoint in an exception handler instead, it may not be easy to find
3688 out where the exception was raised.
3690 To stop just before an exception handler is called, you need some
3691 knowledge of the implementation. In the case of @sc{gnu} C@t{++}, exceptions are
3692 raised by calling a library function named @code{__raise_exception}
3693 which has the following ANSI C interface:
3696 /* @var{addr} is where the exception identifier is stored.
3697 @var{id} is the exception identifier. */
3698 void __raise_exception (void **addr, void *id);
3702 To make the debugger catch all exceptions before any stack
3703 unwinding takes place, set a breakpoint on @code{__raise_exception}
3704 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Exceptions}).
3706 With a conditional breakpoint (@pxref{Conditions, ,Break Conditions})
3707 that depends on the value of @var{id}, you can stop your program when
3708 a specific exception is raised. You can use multiple conditional
3709 breakpoints to stop your program when any of a number of exceptions are
3714 @subsection Deleting Breakpoints
3716 @cindex clearing breakpoints, watchpoints, catchpoints
3717 @cindex deleting breakpoints, watchpoints, catchpoints
3718 It is often necessary to eliminate a breakpoint, watchpoint, or
3719 catchpoint once it has done its job and you no longer want your program
3720 to stop there. This is called @dfn{deleting} the breakpoint. A
3721 breakpoint that has been deleted no longer exists; it is forgotten.
3723 With the @code{clear} command you can delete breakpoints according to
3724 where they are in your program. With the @code{delete} command you can
3725 delete individual breakpoints, watchpoints, or catchpoints by specifying
3726 their breakpoint numbers.
3728 It is not necessary to delete a breakpoint to proceed past it. @value{GDBN}
3729 automatically ignores breakpoints on the first instruction to be executed
3730 when you continue execution without changing the execution address.
3735 Delete any breakpoints at the next instruction to be executed in the
3736 selected stack frame (@pxref{Selection, ,Selecting a Frame}). When
3737 the innermost frame is selected, this is a good way to delete a
3738 breakpoint where your program just stopped.
3740 @item clear @var{location}
3741 Delete any breakpoints set at the specified @var{location}.
3742 @xref{Specify Location}, for the various forms of @var{location}; the
3743 most useful ones are listed below:
3746 @item clear @var{function}
3747 @itemx clear @var{filename}:@var{function}
3748 Delete any breakpoints set at entry to the named @var{function}.
3750 @item clear @var{linenum}
3751 @itemx clear @var{filename}:@var{linenum}
3752 Delete any breakpoints set at or within the code of the specified
3753 @var{linenum} of the specified @var{filename}.
3756 @cindex delete breakpoints
3758 @kindex d @r{(@code{delete})}
3759 @item delete @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
3760 Delete the breakpoints, watchpoints, or catchpoints of the breakpoint
3761 ranges specified as arguments. If no argument is specified, delete all
3762 breakpoints (@value{GDBN} asks confirmation, unless you have @code{set
3763 confirm off}). You can abbreviate this command as @code{d}.
3767 @subsection Disabling Breakpoints
3769 @cindex enable/disable a breakpoint
3770 Rather than deleting a breakpoint, watchpoint, or catchpoint, you might
3771 prefer to @dfn{disable} it. This makes the breakpoint inoperative as if
3772 it had been deleted, but remembers the information on the breakpoint so
3773 that you can @dfn{enable} it again later.
3775 You disable and enable breakpoints, watchpoints, and catchpoints with
3776 the @code{enable} and @code{disable} commands, optionally specifying one
3777 or more breakpoint numbers as arguments. Use @code{info break} or
3778 @code{info watch} to print a list of breakpoints, watchpoints, and
3779 catchpoints if you do not know which numbers to use.
3781 Disabling and enabling a breakpoint that has multiple locations
3782 affects all of its locations.
3784 A breakpoint, watchpoint, or catchpoint can have any of four different
3785 states of enablement:
3789 Enabled. The breakpoint stops your program. A breakpoint set
3790 with the @code{break} command starts out in this state.
3792 Disabled. The breakpoint has no effect on your program.
3794 Enabled once. The breakpoint stops your program, but then becomes
3797 Enabled for deletion. The breakpoint stops your program, but
3798 immediately after it does so it is deleted permanently. A breakpoint
3799 set with the @code{tbreak} command starts out in this state.
3802 You can use the following commands to enable or disable breakpoints,
3803 watchpoints, and catchpoints:
3807 @kindex dis @r{(@code{disable})}
3808 @item disable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
3809 Disable the specified breakpoints---or all breakpoints, if none are
3810 listed. A disabled breakpoint has no effect but is not forgotten. All
3811 options such as ignore-counts, conditions and commands are remembered in
3812 case the breakpoint is enabled again later. You may abbreviate
3813 @code{disable} as @code{dis}.
3816 @item enable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
3817 Enable the specified breakpoints (or all defined breakpoints). They
3818 become effective once again in stopping your program.
3820 @item enable @r{[}breakpoints@r{]} once @var{range}@dots{}
3821 Enable the specified breakpoints temporarily. @value{GDBN} disables any
3822 of these breakpoints immediately after stopping your program.
3824 @item enable @r{[}breakpoints@r{]} delete @var{range}@dots{}
3825 Enable the specified breakpoints to work once, then die. @value{GDBN}
3826 deletes any of these breakpoints as soon as your program stops there.
3827 Breakpoints set by the @code{tbreak} command start out in this state.
3830 @c FIXME: I think the following ``Except for [...] @code{tbreak}'' is
3831 @c confusing: tbreak is also initially enabled.
3832 Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks,
3833 ,Setting Breakpoints}), breakpoints that you set are initially enabled;
3834 subsequently, they become disabled or enabled only when you use one of
3835 the commands above. (The command @code{until} can set and delete a
3836 breakpoint of its own, but it does not change the state of your other
3837 breakpoints; see @ref{Continuing and Stepping, ,Continuing and
3841 @subsection Break Conditions
3842 @cindex conditional breakpoints
3843 @cindex breakpoint conditions
3845 @c FIXME what is scope of break condition expr? Context where wanted?
3846 @c in particular for a watchpoint?
3847 The simplest sort of breakpoint breaks every time your program reaches a
3848 specified place. You can also specify a @dfn{condition} for a
3849 breakpoint. A condition is just a Boolean expression in your
3850 programming language (@pxref{Expressions, ,Expressions}). A breakpoint with
3851 a condition evaluates the expression each time your program reaches it,
3852 and your program stops only if the condition is @emph{true}.
3854 This is the converse of using assertions for program validation; in that
3855 situation, you want to stop when the assertion is violated---that is,
3856 when the condition is false. In C, if you want to test an assertion expressed
3857 by the condition @var{assert}, you should set the condition
3858 @samp{! @var{assert}} on the appropriate breakpoint.
3860 Conditions are also accepted for watchpoints; you may not need them,
3861 since a watchpoint is inspecting the value of an expression anyhow---but
3862 it might be simpler, say, to just set a watchpoint on a variable name,
3863 and specify a condition that tests whether the new value is an interesting
3866 Break conditions can have side effects, and may even call functions in
3867 your program. This can be useful, for example, to activate functions
3868 that log program progress, or to use your own print functions to
3869 format special data structures. The effects are completely predictable
3870 unless there is another enabled breakpoint at the same address. (In
3871 that case, @value{GDBN} might see the other breakpoint first and stop your
3872 program without checking the condition of this one.) Note that
3873 breakpoint commands are usually more convenient and flexible than break
3875 purpose of performing side effects when a breakpoint is reached
3876 (@pxref{Break Commands, ,Breakpoint Command Lists}).
3878 Break conditions can be specified when a breakpoint is set, by using
3879 @samp{if} in the arguments to the @code{break} command. @xref{Set
3880 Breaks, ,Setting Breakpoints}. They can also be changed at any time
3881 with the @code{condition} command.
3883 You can also use the @code{if} keyword with the @code{watch} command.
3884 The @code{catch} command does not recognize the @code{if} keyword;
3885 @code{condition} is the only way to impose a further condition on a
3890 @item condition @var{bnum} @var{expression}
3891 Specify @var{expression} as the break condition for breakpoint,
3892 watchpoint, or catchpoint number @var{bnum}. After you set a condition,
3893 breakpoint @var{bnum} stops your program only if the value of
3894 @var{expression} is true (nonzero, in C). When you use
3895 @code{condition}, @value{GDBN} checks @var{expression} immediately for
3896 syntactic correctness, and to determine whether symbols in it have
3897 referents in the context of your breakpoint. If @var{expression} uses
3898 symbols not referenced in the context of the breakpoint, @value{GDBN}
3899 prints an error message:
3902 No symbol "foo" in current context.
3907 not actually evaluate @var{expression} at the time the @code{condition}
3908 command (or a command that sets a breakpoint with a condition, like
3909 @code{break if @dots{}}) is given, however. @xref{Expressions, ,Expressions}.
3911 @item condition @var{bnum}
3912 Remove the condition from breakpoint number @var{bnum}. It becomes
3913 an ordinary unconditional breakpoint.
3916 @cindex ignore count (of breakpoint)
3917 A special case of a breakpoint condition is to stop only when the
3918 breakpoint has been reached a certain number of times. This is so
3919 useful that there is a special way to do it, using the @dfn{ignore
3920 count} of the breakpoint. Every breakpoint has an ignore count, which
3921 is an integer. Most of the time, the ignore count is zero, and
3922 therefore has no effect. But if your program reaches a breakpoint whose
3923 ignore count is positive, then instead of stopping, it just decrements
3924 the ignore count by one and continues. As a result, if the ignore count
3925 value is @var{n}, the breakpoint does not stop the next @var{n} times
3926 your program reaches it.
3930 @item ignore @var{bnum} @var{count}
3931 Set the ignore count of breakpoint number @var{bnum} to @var{count}.
3932 The next @var{count} times the breakpoint is reached, your program's
3933 execution does not stop; other than to decrement the ignore count, @value{GDBN}
3936 To make the breakpoint stop the next time it is reached, specify
3939 When you use @code{continue} to resume execution of your program from a
3940 breakpoint, you can specify an ignore count directly as an argument to
3941 @code{continue}, rather than using @code{ignore}. @xref{Continuing and
3942 Stepping,,Continuing and Stepping}.
3944 If a breakpoint has a positive ignore count and a condition, the
3945 condition is not checked. Once the ignore count reaches zero,
3946 @value{GDBN} resumes checking the condition.
3948 You could achieve the effect of the ignore count with a condition such
3949 as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that
3950 is decremented each time. @xref{Convenience Vars, ,Convenience
3954 Ignore counts apply to breakpoints, watchpoints, and catchpoints.
3957 @node Break Commands
3958 @subsection Breakpoint Command Lists
3960 @cindex breakpoint commands
3961 You can give any breakpoint (or watchpoint or catchpoint) a series of
3962 commands to execute when your program stops due to that breakpoint. For
3963 example, you might want to print the values of certain expressions, or
3964 enable other breakpoints.
3968 @kindex end@r{ (breakpoint commands)}
3969 @item commands @r{[}@var{bnum}@r{]}
3970 @itemx @dots{} @var{command-list} @dots{}
3972 Specify a list of commands for breakpoint number @var{bnum}. The commands
3973 themselves appear on the following lines. Type a line containing just
3974 @code{end} to terminate the commands.
3976 To remove all commands from a breakpoint, type @code{commands} and
3977 follow it immediately with @code{end}; that is, give no commands.
3979 With no @var{bnum} argument, @code{commands} refers to the last
3980 breakpoint, watchpoint, or catchpoint set (not to the breakpoint most
3981 recently encountered).
3984 Pressing @key{RET} as a means of repeating the last @value{GDBN} command is
3985 disabled within a @var{command-list}.
3987 You can use breakpoint commands to start your program up again. Simply
3988 use the @code{continue} command, or @code{step}, or any other command
3989 that resumes execution.
3991 Any other commands in the command list, after a command that resumes
3992 execution, are ignored. This is because any time you resume execution
3993 (even with a simple @code{next} or @code{step}), you may encounter
3994 another breakpoint---which could have its own command list, leading to
3995 ambiguities about which list to execute.
3998 If the first command you specify in a command list is @code{silent}, the
3999 usual message about stopping at a breakpoint is not printed. This may
4000 be desirable for breakpoints that are to print a specific message and
4001 then continue. If none of the remaining commands print anything, you
4002 see no sign that the breakpoint was reached. @code{silent} is
4003 meaningful only at the beginning of a breakpoint command list.
4005 The commands @code{echo}, @code{output}, and @code{printf} allow you to
4006 print precisely controlled output, and are often useful in silent
4007 breakpoints. @xref{Output, ,Commands for Controlled Output}.
4009 For example, here is how you could use breakpoint commands to print the
4010 value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
4016 printf "x is %d\n",x
4021 One application for breakpoint commands is to compensate for one bug so
4022 you can test for another. Put a breakpoint just after the erroneous line
4023 of code, give it a condition to detect the case in which something
4024 erroneous has been done, and give it commands to assign correct values
4025 to any variables that need them. End with the @code{continue} command
4026 so that your program does not stop, and start with the @code{silent}
4027 command so that no output is produced. Here is an example:
4038 @c @ifclear BARETARGET
4039 @node Error in Breakpoints
4040 @subsection ``Cannot insert breakpoints''
4042 If you request too many active hardware-assisted breakpoints and
4043 watchpoints, you will see this error message:
4045 @c FIXME: the precise wording of this message may change; the relevant
4046 @c source change is not committed yet (Sep 3, 1999).
4048 Stopped; cannot insert breakpoints.
4049 You may have requested too many hardware breakpoints and watchpoints.
4053 This message is printed when you attempt to resume the program, since
4054 only then @value{GDBN} knows exactly how many hardware breakpoints and
4055 watchpoints it needs to insert.
4057 When this message is printed, you need to disable or remove some of the
4058 hardware-assisted breakpoints and watchpoints, and then continue.
4060 @node Breakpoint-related Warnings
4061 @subsection ``Breakpoint address adjusted...''
4062 @cindex breakpoint address adjusted
4064 Some processor architectures place constraints on the addresses at
4065 which breakpoints may be placed. For architectures thus constrained,
4066 @value{GDBN} will attempt to adjust the breakpoint's address to comply
4067 with the constraints dictated by the architecture.
4069 One example of such an architecture is the Fujitsu FR-V. The FR-V is
4070 a VLIW architecture in which a number of RISC-like instructions may be
4071 bundled together for parallel execution. The FR-V architecture
4072 constrains the location of a breakpoint instruction within such a
4073 bundle to the instruction with the lowest address. @value{GDBN}
4074 honors this constraint by adjusting a breakpoint's address to the
4075 first in the bundle.
4077 It is not uncommon for optimized code to have bundles which contain
4078 instructions from different source statements, thus it may happen that
4079 a breakpoint's address will be adjusted from one source statement to
4080 another. Since this adjustment may significantly alter @value{GDBN}'s
4081 breakpoint related behavior from what the user expects, a warning is
4082 printed when the breakpoint is first set and also when the breakpoint
4085 A warning like the one below is printed when setting a breakpoint
4086 that's been subject to address adjustment:
4089 warning: Breakpoint address adjusted from 0x00010414 to 0x00010410.
4092 Such warnings are printed both for user settable and @value{GDBN}'s
4093 internal breakpoints. If you see one of these warnings, you should
4094 verify that a breakpoint set at the adjusted address will have the
4095 desired affect. If not, the breakpoint in question may be removed and
4096 other breakpoints may be set which will have the desired behavior.
4097 E.g., it may be sufficient to place the breakpoint at a later
4098 instruction. A conditional breakpoint may also be useful in some
4099 cases to prevent the breakpoint from triggering too often.
4101 @value{GDBN} will also issue a warning when stopping at one of these
4102 adjusted breakpoints:
4105 warning: Breakpoint 1 address previously adjusted from 0x00010414
4109 When this warning is encountered, it may be too late to take remedial
4110 action except in cases where the breakpoint is hit earlier or more
4111 frequently than expected.
4113 @node Continuing and Stepping
4114 @section Continuing and Stepping
4118 @cindex resuming execution
4119 @dfn{Continuing} means resuming program execution until your program
4120 completes normally. In contrast, @dfn{stepping} means executing just
4121 one more ``step'' of your program, where ``step'' may mean either one
4122 line of source code, or one machine instruction (depending on what
4123 particular command you use). Either when continuing or when stepping,
4124 your program may stop even sooner, due to a breakpoint or a signal. (If
4125 it stops due to a signal, you may want to use @code{handle}, or use
4126 @samp{signal 0} to resume execution. @xref{Signals, ,Signals}.)
4130 @kindex c @r{(@code{continue})}
4131 @kindex fg @r{(resume foreground execution)}
4132 @item continue @r{[}@var{ignore-count}@r{]}
4133 @itemx c @r{[}@var{ignore-count}@r{]}
4134 @itemx fg @r{[}@var{ignore-count}@r{]}
4135 Resume program execution, at the address where your program last stopped;
4136 any breakpoints set at that address are bypassed. The optional argument
4137 @var{ignore-count} allows you to specify a further number of times to
4138 ignore a breakpoint at this location; its effect is like that of
4139 @code{ignore} (@pxref{Conditions, ,Break Conditions}).
4141 The argument @var{ignore-count} is meaningful only when your program
4142 stopped due to a breakpoint. At other times, the argument to
4143 @code{continue} is ignored.
4145 The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the
4146 debugged program is deemed to be the foreground program) are provided
4147 purely for convenience, and have exactly the same behavior as
4151 To resume execution at a different place, you can use @code{return}
4152 (@pxref{Returning, ,Returning from a Function}) to go back to the
4153 calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
4154 Different Address}) to go to an arbitrary location in your program.
4156 A typical technique for using stepping is to set a breakpoint
4157 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Catchpoints}) at the
4158 beginning of the function or the section of your program where a problem
4159 is believed to lie, run your program until it stops at that breakpoint,
4160 and then step through the suspect area, examining the variables that are
4161 interesting, until you see the problem happen.
4165 @kindex s @r{(@code{step})}
4167 Continue running your program until control reaches a different source
4168 line, then stop it and return control to @value{GDBN}. This command is
4169 abbreviated @code{s}.
4172 @c "without debugging information" is imprecise; actually "without line
4173 @c numbers in the debugging information". (gcc -g1 has debugging info but
4174 @c not line numbers). But it seems complex to try to make that
4175 @c distinction here.
4176 @emph{Warning:} If you use the @code{step} command while control is
4177 within a function that was compiled without debugging information,
4178 execution proceeds until control reaches a function that does have
4179 debugging information. Likewise, it will not step into a function which
4180 is compiled without debugging information. To step through functions
4181 without debugging information, use the @code{stepi} command, described
4185 The @code{step} command only stops at the first instruction of a source
4186 line. This prevents the multiple stops that could otherwise occur in
4187 @code{switch} statements, @code{for} loops, etc. @code{step} continues
4188 to stop if a function that has debugging information is called within
4189 the line. In other words, @code{step} @emph{steps inside} any functions
4190 called within the line.
4192 Also, the @code{step} command only enters a function if there is line
4193 number information for the function. Otherwise it acts like the
4194 @code{next} command. This avoids problems when using @code{cc -gl}
4195 on MIPS machines. Previously, @code{step} entered subroutines if there
4196 was any debugging information about the routine.
4198 @item step @var{count}
4199 Continue running as in @code{step}, but do so @var{count} times. If a
4200 breakpoint is reached, or a signal not related to stepping occurs before
4201 @var{count} steps, stepping stops right away.
4204 @kindex n @r{(@code{next})}
4205 @item next @r{[}@var{count}@r{]}
4206 Continue to the next source line in the current (innermost) stack frame.
4207 This is similar to @code{step}, but function calls that appear within
4208 the line of code are executed without stopping. Execution stops when
4209 control reaches a different line of code at the original stack level
4210 that was executing when you gave the @code{next} command. This command
4211 is abbreviated @code{n}.
4213 An argument @var{count} is a repeat count, as for @code{step}.
4216 @c FIX ME!! Do we delete this, or is there a way it fits in with
4217 @c the following paragraph? --- Vctoria
4219 @c @code{next} within a function that lacks debugging information acts like
4220 @c @code{step}, but any function calls appearing within the code of the
4221 @c function are executed without stopping.
4223 The @code{next} command only stops at the first instruction of a
4224 source line. This prevents multiple stops that could otherwise occur in
4225 @code{switch} statements, @code{for} loops, etc.
4227 @kindex set step-mode
4229 @cindex functions without line info, and stepping
4230 @cindex stepping into functions with no line info
4231 @itemx set step-mode on
4232 The @code{set step-mode on} command causes the @code{step} command to
4233 stop at the first instruction of a function which contains no debug line
4234 information rather than stepping over it.
4236 This is useful in cases where you may be interested in inspecting the
4237 machine instructions of a function which has no symbolic info and do not
4238 want @value{GDBN} to automatically skip over this function.
4240 @item set step-mode off
4241 Causes the @code{step} command to step over any functions which contains no
4242 debug information. This is the default.
4244 @item show step-mode
4245 Show whether @value{GDBN} will stop in or step over functions without
4246 source line debug information.
4249 @kindex fin @r{(@code{finish})}
4251 Continue running until just after function in the selected stack frame
4252 returns. Print the returned value (if any). This command can be
4253 abbreviated as @code{fin}.
4255 Contrast this with the @code{return} command (@pxref{Returning,
4256 ,Returning from a Function}).
4259 @kindex u @r{(@code{until})}
4260 @cindex run until specified location
4263 Continue running until a source line past the current line, in the
4264 current stack frame, is reached. This command is used to avoid single
4265 stepping through a loop more than once. It is like the @code{next}
4266 command, except that when @code{until} encounters a jump, it
4267 automatically continues execution until the program counter is greater
4268 than the address of the jump.
4270 This means that when you reach the end of a loop after single stepping
4271 though it, @code{until} makes your program continue execution until it
4272 exits the loop. In contrast, a @code{next} command at the end of a loop
4273 simply steps back to the beginning of the loop, which forces you to step
4274 through the next iteration.
4276 @code{until} always stops your program if it attempts to exit the current
4279 @code{until} may produce somewhat counterintuitive results if the order
4280 of machine code does not match the order of the source lines. For
4281 example, in the following excerpt from a debugging session, the @code{f}
4282 (@code{frame}) command shows that execution is stopped at line
4283 @code{206}; yet when we use @code{until}, we get to line @code{195}:
4287 #0 main (argc=4, argv=0xf7fffae8) at m4.c:206
4289 (@value{GDBP}) until
4290 195 for ( ; argc > 0; NEXTARG) @{
4293 This happened because, for execution efficiency, the compiler had
4294 generated code for the loop closure test at the end, rather than the
4295 start, of the loop---even though the test in a C @code{for}-loop is
4296 written before the body of the loop. The @code{until} command appeared
4297 to step back to the beginning of the loop when it advanced to this
4298 expression; however, it has not really gone to an earlier
4299 statement---not in terms of the actual machine code.
4301 @code{until} with no argument works by means of single
4302 instruction stepping, and hence is slower than @code{until} with an
4305 @item until @var{location}
4306 @itemx u @var{location}
4307 Continue running your program until either the specified location is
4308 reached, or the current stack frame returns. @var{location} is any of
4309 the forms described in @ref{Specify Location}.
4310 This form of the command uses temporary breakpoints, and
4311 hence is quicker than @code{until} without an argument. The specified
4312 location is actually reached only if it is in the current frame. This
4313 implies that @code{until} can be used to skip over recursive function
4314 invocations. For instance in the code below, if the current location is
4315 line @code{96}, issuing @code{until 99} will execute the program up to
4316 line @code{99} in the same invocation of factorial, i.e., after the inner
4317 invocations have returned.
4320 94 int factorial (int value)
4322 96 if (value > 1) @{
4323 97 value *= factorial (value - 1);
4330 @kindex advance @var{location}
4331 @itemx advance @var{location}
4332 Continue running the program up to the given @var{location}. An argument is
4333 required, which should be of one of the forms described in
4334 @ref{Specify Location}.
4335 Execution will also stop upon exit from the current stack
4336 frame. This command is similar to @code{until}, but @code{advance} will
4337 not skip over recursive function calls, and the target location doesn't
4338 have to be in the same frame as the current one.
4342 @kindex si @r{(@code{stepi})}
4344 @itemx stepi @var{arg}
4346 Execute one machine instruction, then stop and return to the debugger.
4348 It is often useful to do @samp{display/i $pc} when stepping by machine
4349 instructions. This makes @value{GDBN} automatically display the next
4350 instruction to be executed, each time your program stops. @xref{Auto
4351 Display,, Automatic Display}.
4353 An argument is a repeat count, as in @code{step}.
4357 @kindex ni @r{(@code{nexti})}
4359 @itemx nexti @var{arg}
4361 Execute one machine instruction, but if it is a function call,
4362 proceed until the function returns.
4364 An argument is a repeat count, as in @code{next}.
4371 A signal is an asynchronous event that can happen in a program. The
4372 operating system defines the possible kinds of signals, and gives each
4373 kind a name and a number. For example, in Unix @code{SIGINT} is the
4374 signal a program gets when you type an interrupt character (often @kbd{Ctrl-c});
4375 @code{SIGSEGV} is the signal a program gets from referencing a place in
4376 memory far away from all the areas in use; @code{SIGALRM} occurs when
4377 the alarm clock timer goes off (which happens only if your program has
4378 requested an alarm).
4380 @cindex fatal signals
4381 Some signals, including @code{SIGALRM}, are a normal part of the
4382 functioning of your program. Others, such as @code{SIGSEGV}, indicate
4383 errors; these signals are @dfn{fatal} (they kill your program immediately) if the
4384 program has not specified in advance some other way to handle the signal.
4385 @code{SIGINT} does not indicate an error in your program, but it is normally
4386 fatal so it can carry out the purpose of the interrupt: to kill the program.
4388 @value{GDBN} has the ability to detect any occurrence of a signal in your
4389 program. You can tell @value{GDBN} in advance what to do for each kind of
4392 @cindex handling signals
4393 Normally, @value{GDBN} is set up to let the non-erroneous signals like
4394 @code{SIGALRM} be silently passed to your program
4395 (so as not to interfere with their role in the program's functioning)
4396 but to stop your program immediately whenever an error signal happens.
4397 You can change these settings with the @code{handle} command.
4400 @kindex info signals
4404 Print a table of all the kinds of signals and how @value{GDBN} has been told to
4405 handle each one. You can use this to see the signal numbers of all
4406 the defined types of signals.
4408 @item info signals @var{sig}
4409 Similar, but print information only about the specified signal number.
4411 @code{info handle} is an alias for @code{info signals}.
4414 @item handle @var{signal} @r{[}@var{keywords}@dots{}@r{]}
4415 Change the way @value{GDBN} handles signal @var{signal}. @var{signal}
4416 can be the number of a signal or its name (with or without the
4417 @samp{SIG} at the beginning); a list of signal numbers of the form
4418 @samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the
4419 known signals. Optional arguments @var{keywords}, described below,
4420 say what change to make.
4424 The keywords allowed by the @code{handle} command can be abbreviated.
4425 Their full names are:
4429 @value{GDBN} should not stop your program when this signal happens. It may
4430 still print a message telling you that the signal has come in.
4433 @value{GDBN} should stop your program when this signal happens. This implies
4434 the @code{print} keyword as well.
4437 @value{GDBN} should print a message when this signal happens.
4440 @value{GDBN} should not mention the occurrence of the signal at all. This
4441 implies the @code{nostop} keyword as well.
4445 @value{GDBN} should allow your program to see this signal; your program
4446 can handle the signal, or else it may terminate if the signal is fatal
4447 and not handled. @code{pass} and @code{noignore} are synonyms.
4451 @value{GDBN} should not allow your program to see this signal.
4452 @code{nopass} and @code{ignore} are synonyms.
4456 When a signal stops your program, the signal is not visible to the
4458 continue. Your program sees the signal then, if @code{pass} is in
4459 effect for the signal in question @emph{at that time}. In other words,
4460 after @value{GDBN} reports a signal, you can use the @code{handle}
4461 command with @code{pass} or @code{nopass} to control whether your
4462 program sees that signal when you continue.
4464 The default is set to @code{nostop}, @code{noprint}, @code{pass} for
4465 non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and
4466 @code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the
4469 You can also use the @code{signal} command to prevent your program from
4470 seeing a signal, or cause it to see a signal it normally would not see,
4471 or to give it any signal at any time. For example, if your program stopped
4472 due to some sort of memory reference error, you might store correct
4473 values into the erroneous variables and continue, hoping to see more
4474 execution; but your program would probably terminate immediately as
4475 a result of the fatal signal once it saw the signal. To prevent this,
4476 you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
4479 @cindex extra signal information
4480 @anchor{extra signal information}
4482 On some targets, @value{GDBN} can inspect extra signal information
4483 associated with the intercepted signal, before it is actually
4484 delivered to the program being debugged. This information is exported
4485 by the convenience variable @code{$_siginfo}, and consists of data
4486 that is passed by the kernel to the signal handler at the time of the
4487 receipt of a signal. The data type of the information itself is
4488 target dependent. You can see the data type using the @code{ptype
4489 $_siginfo} command. On Unix systems, it typically corresponds to the
4490 standard @code{siginfo_t} type, as defined in the @file{signal.h}
4493 Here's an example, on a @sc{gnu}/Linux system, printing the stray
4494 referenced address that raised a segmentation fault.
4498 (@value{GDBP}) continue
4499 Program received signal SIGSEGV, Segmentation fault.
4500 0x0000000000400766 in main ()
4502 (@value{GDBP}) ptype $_siginfo
4509 struct @{...@} _kill;
4510 struct @{...@} _timer;
4512 struct @{...@} _sigchld;
4513 struct @{...@} _sigfault;
4514 struct @{...@} _sigpoll;
4517 (@value{GDBP}) ptype $_siginfo._sifields._sigfault
4521 (@value{GDBP}) p $_siginfo._sifields._sigfault.si_addr
4522 $1 = (void *) 0x7ffff7ff7000
4526 Depending on target support, @code{$_siginfo} may also be writable.
4529 @section Stopping and Starting Multi-thread Programs
4531 @cindex stopped threads
4532 @cindex threads, stopped
4534 @cindex continuing threads
4535 @cindex threads, continuing
4537 @value{GDBN} supports debugging programs with multiple threads
4538 (@pxref{Threads,, Debugging Programs with Multiple Threads}). There
4539 are two modes of controlling execution of your program within the
4540 debugger. In the default mode, referred to as @dfn{all-stop mode},
4541 when any thread in your program stops (for example, at a breakpoint
4542 or while being stepped), all other threads in the program are also stopped by
4543 @value{GDBN}. On some targets, @value{GDBN} also supports
4544 @dfn{non-stop mode}, in which other threads can continue to run freely while
4545 you examine the stopped thread in the debugger.
4548 * All-Stop Mode:: All threads stop when GDB takes control
4549 * Non-Stop Mode:: Other threads continue to execute
4550 * Background Execution:: Running your program asynchronously
4551 * Thread-Specific Breakpoints:: Controlling breakpoints
4552 * Interrupted System Calls:: GDB may interfere with system calls
4556 @subsection All-Stop Mode
4558 @cindex all-stop mode
4560 In all-stop mode, whenever your program stops under @value{GDBN} for any reason,
4561 @emph{all} threads of execution stop, not just the current thread. This
4562 allows you to examine the overall state of the program, including
4563 switching between threads, without worrying that things may change
4566 Conversely, whenever you restart the program, @emph{all} threads start
4567 executing. @emph{This is true even when single-stepping} with commands
4568 like @code{step} or @code{next}.
4570 In particular, @value{GDBN} cannot single-step all threads in lockstep.
4571 Since thread scheduling is up to your debugging target's operating
4572 system (not controlled by @value{GDBN}), other threads may
4573 execute more than one statement while the current thread completes a
4574 single step. Moreover, in general other threads stop in the middle of a
4575 statement, rather than at a clean statement boundary, when the program
4578 You might even find your program stopped in another thread after
4579 continuing or even single-stepping. This happens whenever some other
4580 thread runs into a breakpoint, a signal, or an exception before the
4581 first thread completes whatever you requested.
4583 @cindex automatic thread selection
4584 @cindex switching threads automatically
4585 @cindex threads, automatic switching
4586 Whenever @value{GDBN} stops your program, due to a breakpoint or a
4587 signal, it automatically selects the thread where that breakpoint or
4588 signal happened. @value{GDBN} alerts you to the context switch with a
4589 message such as @samp{[Switching to Thread @var{n}]} to identify the
4592 On some OSes, you can modify @value{GDBN}'s default behavior by
4593 locking the OS scheduler to allow only a single thread to run.
4596 @item set scheduler-locking @var{mode}
4597 @cindex scheduler locking mode
4598 @cindex lock scheduler
4599 Set the scheduler locking mode. If it is @code{off}, then there is no
4600 locking and any thread may run at any time. If @code{on}, then only the
4601 current thread may run when the inferior is resumed. The @code{step}
4602 mode optimizes for single-stepping; it prevents other threads
4603 from preempting the current thread while you are stepping, so that
4604 the focus of debugging does not change unexpectedly.
4605 Other threads only rarely (or never) get a chance to run
4606 when you step. They are more likely to run when you @samp{next} over a
4607 function call, and they are completely free to run when you use commands
4608 like @samp{continue}, @samp{until}, or @samp{finish}. However, unless another
4609 thread hits a breakpoint during its timeslice, @value{GDBN} does not change
4610 the current thread away from the thread that you are debugging.
4612 @item show scheduler-locking
4613 Display the current scheduler locking mode.
4617 @subsection Non-Stop Mode
4619 @cindex non-stop mode
4621 @c This section is really only a place-holder, and needs to be expanded
4622 @c with more details.
4624 For some multi-threaded targets, @value{GDBN} supports an optional
4625 mode of operation in which you can examine stopped program threads in
4626 the debugger while other threads continue to execute freely. This
4627 minimizes intrusion when debugging live systems, such as programs
4628 where some threads have real-time constraints or must continue to
4629 respond to external events. This is referred to as @dfn{non-stop} mode.
4631 In non-stop mode, when a thread stops to report a debugging event,
4632 @emph{only} that thread is stopped; @value{GDBN} does not stop other
4633 threads as well, in contrast to the all-stop mode behavior. Additionally,
4634 execution commands such as @code{continue} and @code{step} apply by default
4635 only to the current thread in non-stop mode, rather than all threads as
4636 in all-stop mode. This allows you to control threads explicitly in
4637 ways that are not possible in all-stop mode --- for example, stepping
4638 one thread while allowing others to run freely, stepping
4639 one thread while holding all others stopped, or stepping several threads
4640 independently and simultaneously.
4642 To enter non-stop mode, use this sequence of commands before you run
4643 or attach to your program:
4646 # Enable the async interface.
4649 # If using the CLI, pagination breaks non-stop.
4652 # Finally, turn it on!
4656 You can use these commands to manipulate the non-stop mode setting:
4659 @kindex set non-stop
4660 @item set non-stop on
4661 Enable selection of non-stop mode.
4662 @item set non-stop off
4663 Disable selection of non-stop mode.
4664 @kindex show non-stop
4666 Show the current non-stop enablement setting.
4669 Note these commands only reflect whether non-stop mode is enabled,
4670 not whether the currently-executing program is being run in non-stop mode.
4671 In particular, the @code{set non-stop} preference is only consulted when
4672 @value{GDBN} starts or connects to the target program, and it is generally
4673 not possible to switch modes once debugging has started. Furthermore,
4674 since not all targets support non-stop mode, even when you have enabled
4675 non-stop mode, @value{GDBN} may still fall back to all-stop operation by
4678 In non-stop mode, all execution commands apply only to the current thread
4679 by default. That is, @code{continue} only continues one thread.
4680 To continue all threads, issue @code{continue -a} or @code{c -a}.
4682 You can use @value{GDBN}'s background execution commands
4683 (@pxref{Background Execution}) to run some threads in the background
4684 while you continue to examine or step others from @value{GDBN}.
4685 The MI execution commands (@pxref{GDB/MI Program Execution}) are
4686 always executed asynchronously in non-stop mode.
4688 Suspending execution is done with the @code{interrupt} command when
4689 running in the background, or @kbd{Ctrl-c} during foreground execution.
4690 In all-stop mode, this stops the whole process;
4691 but in non-stop mode the interrupt applies only to the current thread.
4692 To stop the whole program, use @code{interrupt -a}.
4694 Other execution commands do not currently support the @code{-a} option.
4696 In non-stop mode, when a thread stops, @value{GDBN} doesn't automatically make
4697 that thread current, as it does in all-stop mode. This is because the
4698 thread stop notifications are asynchronous with respect to @value{GDBN}'s
4699 command interpreter, and it would be confusing if @value{GDBN} unexpectedly
4700 changed to a different thread just as you entered a command to operate on the
4701 previously current thread.
4703 @node Background Execution
4704 @subsection Background Execution
4706 @cindex foreground execution
4707 @cindex background execution
4708 @cindex asynchronous execution
4709 @cindex execution, foreground, background and asynchronous
4711 @value{GDBN}'s execution commands have two variants: the normal
4712 foreground (synchronous) behavior, and a background
4713 (asynchronous) behavior. In foreground execution, @value{GDBN} waits for
4714 the program to report that some thread has stopped before prompting for
4715 another command. In background execution, @value{GDBN} immediately gives
4716 a command prompt so that you can issue other commands while your program runs.
4718 You need to explicitly enable asynchronous mode before you can use
4719 background execution commands. You can use these commands to
4720 manipulate the asynchronous mode setting:
4723 @kindex set target-async
4724 @item set target-async on
4725 Enable asynchronous mode.
4726 @item set target-async off
4727 Disable asynchronous mode.
4728 @kindex show target-async
4729 @item show target-async
4730 Show the current target-async setting.
4733 If the target doesn't support async mode, @value{GDBN} issues an error
4734 message if you attempt to use the background execution commands.
4736 To specify background execution, add a @code{&} to the command. For example,
4737 the background form of the @code{continue} command is @code{continue&}, or
4738 just @code{c&}. The execution commands that accept background execution
4744 @xref{Starting, , Starting your Program}.
4748 @xref{Attach, , Debugging an Already-running Process}.
4752 @xref{Continuing and Stepping, step}.
4756 @xref{Continuing and Stepping, stepi}.
4760 @xref{Continuing and Stepping, next}.
4764 @xref{Continuing and Stepping, nexti}.
4768 @xref{Continuing and Stepping, continue}.
4772 @xref{Continuing and Stepping, finish}.
4776 @xref{Continuing and Stepping, until}.
4780 Background execution is especially useful in conjunction with non-stop
4781 mode for debugging programs with multiple threads; see @ref{Non-Stop Mode}.
4782 However, you can also use these commands in the normal all-stop mode with
4783 the restriction that you cannot issue another execution command until the
4784 previous one finishes. Examples of commands that are valid in all-stop
4785 mode while the program is running include @code{help} and @code{info break}.
4787 You can interrupt your program while it is running in the background by
4788 using the @code{interrupt} command.
4795 Suspend execution of the running program. In all-stop mode,
4796 @code{interrupt} stops the whole process, but in non-stop mode, it stops
4797 only the current thread. To stop the whole program in non-stop mode,
4798 use @code{interrupt -a}.
4801 @node Thread-Specific Breakpoints
4802 @subsection Thread-Specific Breakpoints
4804 When your program has multiple threads (@pxref{Threads,, Debugging
4805 Programs with Multiple Threads}), you can choose whether to set
4806 breakpoints on all threads, or on a particular thread.
4809 @cindex breakpoints and threads
4810 @cindex thread breakpoints
4811 @kindex break @dots{} thread @var{threadno}
4812 @item break @var{linespec} thread @var{threadno}
4813 @itemx break @var{linespec} thread @var{threadno} if @dots{}
4814 @var{linespec} specifies source lines; there are several ways of
4815 writing them (@pxref{Specify Location}), but the effect is always to
4816 specify some source line.
4818 Use the qualifier @samp{thread @var{threadno}} with a breakpoint command
4819 to specify that you only want @value{GDBN} to stop the program when a
4820 particular thread reaches this breakpoint. @var{threadno} is one of the
4821 numeric thread identifiers assigned by @value{GDBN}, shown in the first
4822 column of the @samp{info threads} display.
4824 If you do not specify @samp{thread @var{threadno}} when you set a
4825 breakpoint, the breakpoint applies to @emph{all} threads of your
4828 You can use the @code{thread} qualifier on conditional breakpoints as
4829 well; in this case, place @samp{thread @var{threadno}} before the
4830 breakpoint condition, like this:
4833 (@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
4838 @node Interrupted System Calls
4839 @subsection Interrupted System Calls
4841 @cindex thread breakpoints and system calls
4842 @cindex system calls and thread breakpoints
4843 @cindex premature return from system calls
4844 There is an unfortunate side effect when using @value{GDBN} to debug
4845 multi-threaded programs. If one thread stops for a
4846 breakpoint, or for some other reason, and another thread is blocked in a
4847 system call, then the system call may return prematurely. This is a
4848 consequence of the interaction between multiple threads and the signals
4849 that @value{GDBN} uses to implement breakpoints and other events that
4852 To handle this problem, your program should check the return value of
4853 each system call and react appropriately. This is good programming
4856 For example, do not write code like this:
4862 The call to @code{sleep} will return early if a different thread stops
4863 at a breakpoint or for some other reason.
4865 Instead, write this:
4870 unslept = sleep (unslept);
4873 A system call is allowed to return early, so the system is still
4874 conforming to its specification. But @value{GDBN} does cause your
4875 multi-threaded program to behave differently than it would without
4878 Also, @value{GDBN} uses internal breakpoints in the thread library to
4879 monitor certain events such as thread creation and thread destruction.
4880 When such an event happens, a system call in another thread may return
4881 prematurely, even though your program does not appear to stop.
4884 @node Reverse Execution
4885 @chapter Running programs backward
4886 @cindex reverse execution
4887 @cindex running programs backward
4889 When you are debugging a program, it is not unusual to realize that
4890 you have gone too far, and some event of interest has already happened.
4891 If the target environment supports it, @value{GDBN} can allow you to
4892 ``rewind'' the program by running it backward.
4894 A target environment that supports reverse execution should be able
4895 to ``undo'' the changes in machine state that have taken place as the
4896 program was executing normally. Variables, registers etc.@: should
4897 revert to their previous values. Obviously this requires a great
4898 deal of sophistication on the part of the target environment; not
4899 all target environments can support reverse execution.
4901 When a program is executed in reverse, the instructions that
4902 have most recently been executed are ``un-executed'', in reverse
4903 order. The program counter runs backward, following the previous
4904 thread of execution in reverse. As each instruction is ``un-executed'',
4905 the values of memory and/or registers that were changed by that
4906 instruction are reverted to their previous states. After executing
4907 a piece of source code in reverse, all side effects of that code
4908 should be ``undone'', and all variables should be returned to their
4909 prior values@footnote{
4910 Note that some side effects are easier to undo than others. For instance,
4911 memory and registers are relatively easy, but device I/O is hard. Some
4912 targets may be able undo things like device I/O, and some may not.
4914 The contract between @value{GDBN} and the reverse executing target
4915 requires only that the target do something reasonable when
4916 @value{GDBN} tells it to execute backwards, and then report the
4917 results back to @value{GDBN}. Whatever the target reports back to
4918 @value{GDBN}, @value{GDBN} will report back to the user. @value{GDBN}
4919 assumes that the memory and registers that the target reports are in a
4920 consistant state, but @value{GDBN} accepts whatever it is given.
4923 If you are debugging in a target environment that supports
4924 reverse execution, @value{GDBN} provides the following commands.
4927 @kindex reverse-continue
4928 @kindex rc @r{(@code{reverse-continue})}
4929 @item reverse-continue @r{[}@var{ignore-count}@r{]}
4930 @itemx rc @r{[}@var{ignore-count}@r{]}
4931 Beginning at the point where your program last stopped, start executing
4932 in reverse. Reverse execution will stop for breakpoints and synchronous
4933 exceptions (signals), just like normal execution. Behavior of
4934 asynchronous signals depends on the target environment.
4936 @kindex reverse-step
4937 @kindex rs @r{(@code{step})}
4938 @item reverse-step @r{[}@var{count}@r{]}
4939 Run the program backward until control reaches the start of a
4940 different source line; then stop it, and return control to @value{GDBN}.
4942 Like the @code{step} command, @code{reverse-step} will only stop
4943 at the beginning of a source line. It ``un-executes'' the previously
4944 executed source line. If the previous source line included calls to
4945 debuggable functions, @code{reverse-step} will step (backward) into
4946 the called function, stopping at the beginning of the @emph{last}
4947 statement in the called function (typically a return statement).
4949 Also, as with the @code{step} command, if non-debuggable functions are
4950 called, @code{reverse-step} will run thru them backward without stopping.
4952 @kindex reverse-stepi
4953 @kindex rsi @r{(@code{reverse-stepi})}
4954 @item reverse-stepi @r{[}@var{count}@r{]}
4955 Reverse-execute one machine instruction. Note that the instruction
4956 to be reverse-executed is @emph{not} the one pointed to by the program
4957 counter, but the instruction executed prior to that one. For instance,
4958 if the last instruction was a jump, @code{reverse-stepi} will take you
4959 back from the destination of the jump to the jump instruction itself.
4961 @kindex reverse-next
4962 @kindex rn @r{(@code{reverse-next})}
4963 @item reverse-next @r{[}@var{count}@r{]}
4964 Run backward to the beginning of the previous line executed in
4965 the current (innermost) stack frame. If the line contains function
4966 calls, they will be ``un-executed'' without stopping. Starting from
4967 the first line of a function, @code{reverse-next} will take you back
4968 to the caller of that function, @emph{before} the function was called,
4969 just as the normal @code{next} command would take you from the last
4970 line of a function back to its return to its caller
4971 @footnote{Unles the code is too heavily optimized.}.
4973 @kindex reverse-nexti
4974 @kindex rni @r{(@code{reverse-nexti})}
4975 @item reverse-nexti @r{[}@var{count}@r{]}
4976 Like @code{nexti}, @code{reverse-nexti} executes a single instruction
4977 in reverse, except that called functions are ``un-executed'' atomically.
4978 That is, if the previously executed instruction was a return from
4979 another instruction, @code{reverse-nexti} will continue to execute
4980 in reverse until the call to that function (from the current stack
4983 @kindex reverse-finish
4984 @item reverse-finish
4985 Just as the @code{finish} command takes you to the point where the
4986 current function returns, @code{reverse-finish} takes you to the point
4987 where it was called. Instead of ending up at the end of the current
4988 function invocation, you end up at the beginning.
4990 @kindex set exec-direction
4991 @item set exec-direction
4992 Set the direction of target execution.
4993 @itemx set exec-direction reverse
4994 @cindex execute forward or backward in time
4995 @value{GDBN} will perform all execution commands in reverse, until the
4996 exec-direction mode is changed to ``forward''. Affected commands include
4997 @code{step, stepi, next, nexti, continue, and finish}. The @code{return}
4998 command cannot be used in reverse mode.
4999 @item set exec-direction forward
5000 @value{GDBN} will perform all execution commands in the normal fashion.
5001 This is the default.
5006 @chapter Examining the Stack
5008 When your program has stopped, the first thing you need to know is where it
5009 stopped and how it got there.
5012 Each time your program performs a function call, information about the call
5014 That information includes the location of the call in your program,
5015 the arguments of the call,
5016 and the local variables of the function being called.
5017 The information is saved in a block of data called a @dfn{stack frame}.
5018 The stack frames are allocated in a region of memory called the @dfn{call
5021 When your program stops, the @value{GDBN} commands for examining the
5022 stack allow you to see all of this information.
5024 @cindex selected frame
5025 One of the stack frames is @dfn{selected} by @value{GDBN} and many
5026 @value{GDBN} commands refer implicitly to the selected frame. In
5027 particular, whenever you ask @value{GDBN} for the value of a variable in
5028 your program, the value is found in the selected frame. There are
5029 special @value{GDBN} commands to select whichever frame you are
5030 interested in. @xref{Selection, ,Selecting a Frame}.
5032 When your program stops, @value{GDBN} automatically selects the
5033 currently executing frame and describes it briefly, similar to the
5034 @code{frame} command (@pxref{Frame Info, ,Information about a Frame}).
5037 * Frames:: Stack frames
5038 * Backtrace:: Backtraces
5039 * Selection:: Selecting a frame
5040 * Frame Info:: Information on a frame
5045 @section Stack Frames
5047 @cindex frame, definition
5049 The call stack is divided up into contiguous pieces called @dfn{stack
5050 frames}, or @dfn{frames} for short; each frame is the data associated
5051 with one call to one function. The frame contains the arguments given
5052 to the function, the function's local variables, and the address at
5053 which the function is executing.
5055 @cindex initial frame
5056 @cindex outermost frame
5057 @cindex innermost frame
5058 When your program is started, the stack has only one frame, that of the
5059 function @code{main}. This is called the @dfn{initial} frame or the
5060 @dfn{outermost} frame. Each time a function is called, a new frame is
5061 made. Each time a function returns, the frame for that function invocation
5062 is eliminated. If a function is recursive, there can be many frames for
5063 the same function. The frame for the function in which execution is
5064 actually occurring is called the @dfn{innermost} frame. This is the most
5065 recently created of all the stack frames that still exist.
5067 @cindex frame pointer
5068 Inside your program, stack frames are identified by their addresses. A
5069 stack frame consists of many bytes, each of which has its own address; each
5070 kind of computer has a convention for choosing one byte whose
5071 address serves as the address of the frame. Usually this address is kept
5072 in a register called the @dfn{frame pointer register}
5073 (@pxref{Registers, $fp}) while execution is going on in that frame.
5075 @cindex frame number
5076 @value{GDBN} assigns numbers to all existing stack frames, starting with
5077 zero for the innermost frame, one for the frame that called it,
5078 and so on upward. These numbers do not really exist in your program;
5079 they are assigned by @value{GDBN} to give you a way of designating stack
5080 frames in @value{GDBN} commands.
5082 @c The -fomit-frame-pointer below perennially causes hbox overflow
5083 @c underflow problems.
5084 @cindex frameless execution
5085 Some compilers provide a way to compile functions so that they operate
5086 without stack frames. (For example, the @value{NGCC} option
5088 @samp{-fomit-frame-pointer}
5090 generates functions without a frame.)
5091 This is occasionally done with heavily used library functions to save
5092 the frame setup time. @value{GDBN} has limited facilities for dealing
5093 with these function invocations. If the innermost function invocation
5094 has no stack frame, @value{GDBN} nevertheless regards it as though
5095 it had a separate frame, which is numbered zero as usual, allowing
5096 correct tracing of the function call chain. However, @value{GDBN} has
5097 no provision for frameless functions elsewhere in the stack.
5100 @kindex frame@r{, command}
5101 @cindex current stack frame
5102 @item frame @var{args}
5103 The @code{frame} command allows you to move from one stack frame to another,
5104 and to print the stack frame you select. @var{args} may be either the
5105 address of the frame or the stack frame number. Without an argument,
5106 @code{frame} prints the current stack frame.
5108 @kindex select-frame
5109 @cindex selecting frame silently
5111 The @code{select-frame} command allows you to move from one stack frame
5112 to another without printing the frame. This is the silent version of
5120 @cindex call stack traces
5121 A backtrace is a summary of how your program got where it is. It shows one
5122 line per frame, for many frames, starting with the currently executing
5123 frame (frame zero), followed by its caller (frame one), and on up the
5128 @kindex bt @r{(@code{backtrace})}
5131 Print a backtrace of the entire stack: one line per frame for all
5132 frames in the stack.
5134 You can stop the backtrace at any time by typing the system interrupt
5135 character, normally @kbd{Ctrl-c}.
5137 @item backtrace @var{n}
5139 Similar, but print only the innermost @var{n} frames.
5141 @item backtrace -@var{n}
5143 Similar, but print only the outermost @var{n} frames.
5145 @item backtrace full
5147 @itemx bt full @var{n}
5148 @itemx bt full -@var{n}
5149 Print the values of the local variables also. @var{n} specifies the
5150 number of frames to print, as described above.
5155 The names @code{where} and @code{info stack} (abbreviated @code{info s})
5156 are additional aliases for @code{backtrace}.
5158 @cindex multiple threads, backtrace
5159 In a multi-threaded program, @value{GDBN} by default shows the
5160 backtrace only for the current thread. To display the backtrace for
5161 several or all of the threads, use the command @code{thread apply}
5162 (@pxref{Threads, thread apply}). For example, if you type @kbd{thread
5163 apply all backtrace}, @value{GDBN} will display the backtrace for all
5164 the threads; this is handy when you debug a core dump of a
5165 multi-threaded program.
5167 Each line in the backtrace shows the frame number and the function name.
5168 The program counter value is also shown---unless you use @code{set
5169 print address off}. The backtrace also shows the source file name and
5170 line number, as well as the arguments to the function. The program
5171 counter value is omitted if it is at the beginning of the code for that
5174 Here is an example of a backtrace. It was made with the command
5175 @samp{bt 3}, so it shows the innermost three frames.
5179 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
5181 #1 0x6e38 in expand_macro (sym=0x2b600, data=...) at macro.c:242
5182 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
5184 (More stack frames follow...)
5189 The display for frame zero does not begin with a program counter
5190 value, indicating that your program has stopped at the beginning of the
5191 code for line @code{993} of @code{builtin.c}.
5194 The value of parameter @code{data} in frame 1 has been replaced by
5195 @code{@dots{}}. By default, @value{GDBN} prints the value of a parameter
5196 only if it is a scalar (integer, pointer, enumeration, etc). See command
5197 @kbd{set print frame-arguments} in @ref{Print Settings} for more details
5198 on how to configure the way function parameter values are printed.
5200 @cindex value optimized out, in backtrace
5201 @cindex function call arguments, optimized out
5202 If your program was compiled with optimizations, some compilers will
5203 optimize away arguments passed to functions if those arguments are
5204 never used after the call. Such optimizations generate code that
5205 passes arguments through registers, but doesn't store those arguments
5206 in the stack frame. @value{GDBN} has no way of displaying such
5207 arguments in stack frames other than the innermost one. Here's what
5208 such a backtrace might look like:
5212 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
5214 #1 0x6e38 in expand_macro (sym=<value optimized out>) at macro.c:242
5215 #2 0x6840 in expand_token (obs=0x0, t=<value optimized out>, td=0xf7fffb08)
5217 (More stack frames follow...)
5222 The values of arguments that were not saved in their stack frames are
5223 shown as @samp{<value optimized out>}.
5225 If you need to display the values of such optimized-out arguments,
5226 either deduce that from other variables whose values depend on the one
5227 you are interested in, or recompile without optimizations.
5229 @cindex backtrace beyond @code{main} function
5230 @cindex program entry point
5231 @cindex startup code, and backtrace
5232 Most programs have a standard user entry point---a place where system
5233 libraries and startup code transition into user code. For C this is
5234 @code{main}@footnote{
5235 Note that embedded programs (the so-called ``free-standing''
5236 environment) are not required to have a @code{main} function as the
5237 entry point. They could even have multiple entry points.}.
5238 When @value{GDBN} finds the entry function in a backtrace
5239 it will terminate the backtrace, to avoid tracing into highly
5240 system-specific (and generally uninteresting) code.
5242 If you need to examine the startup code, or limit the number of levels
5243 in a backtrace, you can change this behavior:
5246 @item set backtrace past-main
5247 @itemx set backtrace past-main on
5248 @kindex set backtrace
5249 Backtraces will continue past the user entry point.
5251 @item set backtrace past-main off
5252 Backtraces will stop when they encounter the user entry point. This is the
5255 @item show backtrace past-main
5256 @kindex show backtrace
5257 Display the current user entry point backtrace policy.
5259 @item set backtrace past-entry
5260 @itemx set backtrace past-entry on
5261 Backtraces will continue past the internal entry point of an application.
5262 This entry point is encoded by the linker when the application is built,
5263 and is likely before the user entry point @code{main} (or equivalent) is called.
5265 @item set backtrace past-entry off
5266 Backtraces will stop when they encounter the internal entry point of an
5267 application. This is the default.
5269 @item show backtrace past-entry
5270 Display the current internal entry point backtrace policy.
5272 @item set backtrace limit @var{n}
5273 @itemx set backtrace limit 0
5274 @cindex backtrace limit
5275 Limit the backtrace to @var{n} levels. A value of zero means
5278 @item show backtrace limit
5279 Display the current limit on backtrace levels.
5283 @section Selecting a Frame
5285 Most commands for examining the stack and other data in your program work on
5286 whichever stack frame is selected at the moment. Here are the commands for
5287 selecting a stack frame; all of them finish by printing a brief description
5288 of the stack frame just selected.
5291 @kindex frame@r{, selecting}
5292 @kindex f @r{(@code{frame})}
5295 Select frame number @var{n}. Recall that frame zero is the innermost
5296 (currently executing) frame, frame one is the frame that called the
5297 innermost one, and so on. The highest-numbered frame is the one for
5300 @item frame @var{addr}
5302 Select the frame at address @var{addr}. This is useful mainly if the
5303 chaining of stack frames has been damaged by a bug, making it
5304 impossible for @value{GDBN} to assign numbers properly to all frames. In
5305 addition, this can be useful when your program has multiple stacks and
5306 switches between them.
5308 On the SPARC architecture, @code{frame} needs two addresses to
5309 select an arbitrary frame: a frame pointer and a stack pointer.
5311 On the MIPS and Alpha architecture, it needs two addresses: a stack
5312 pointer and a program counter.
5314 On the 29k architecture, it needs three addresses: a register stack
5315 pointer, a program counter, and a memory stack pointer.
5319 Move @var{n} frames up the stack. For positive numbers @var{n}, this
5320 advances toward the outermost frame, to higher frame numbers, to frames
5321 that have existed longer. @var{n} defaults to one.
5324 @kindex do @r{(@code{down})}
5326 Move @var{n} frames down the stack. For positive numbers @var{n}, this
5327 advances toward the innermost frame, to lower frame numbers, to frames
5328 that were created more recently. @var{n} defaults to one. You may
5329 abbreviate @code{down} as @code{do}.
5332 All of these commands end by printing two lines of output describing the
5333 frame. The first line shows the frame number, the function name, the
5334 arguments, and the source file and line number of execution in that
5335 frame. The second line shows the text of that source line.
5343 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
5345 10 read_input_file (argv[i]);
5349 After such a printout, the @code{list} command with no arguments
5350 prints ten lines centered on the point of execution in the frame.
5351 You can also edit the program at the point of execution with your favorite
5352 editing program by typing @code{edit}.
5353 @xref{List, ,Printing Source Lines},
5357 @kindex down-silently
5359 @item up-silently @var{n}
5360 @itemx down-silently @var{n}
5361 These two commands are variants of @code{up} and @code{down},
5362 respectively; they differ in that they do their work silently, without
5363 causing display of the new frame. They are intended primarily for use
5364 in @value{GDBN} command scripts, where the output might be unnecessary and
5369 @section Information About a Frame
5371 There are several other commands to print information about the selected
5377 When used without any argument, this command does not change which
5378 frame is selected, but prints a brief description of the currently
5379 selected stack frame. It can be abbreviated @code{f}. With an
5380 argument, this command is used to select a stack frame.
5381 @xref{Selection, ,Selecting a Frame}.
5384 @kindex info f @r{(@code{info frame})}
5387 This command prints a verbose description of the selected stack frame,
5392 the address of the frame
5394 the address of the next frame down (called by this frame)
5396 the address of the next frame up (caller of this frame)
5398 the language in which the source code corresponding to this frame is written
5400 the address of the frame's arguments
5402 the address of the frame's local variables
5404 the program counter saved in it (the address of execution in the caller frame)
5406 which registers were saved in the frame
5409 @noindent The verbose description is useful when
5410 something has gone wrong that has made the stack format fail to fit
5411 the usual conventions.
5413 @item info frame @var{addr}
5414 @itemx info f @var{addr}
5415 Print a verbose description of the frame at address @var{addr}, without
5416 selecting that frame. The selected frame remains unchanged by this
5417 command. This requires the same kind of address (more than one for some
5418 architectures) that you specify in the @code{frame} command.
5419 @xref{Selection, ,Selecting a Frame}.
5423 Print the arguments of the selected frame, each on a separate line.
5427 Print the local variables of the selected frame, each on a separate
5428 line. These are all variables (declared either static or automatic)
5429 accessible at the point of execution of the selected frame.
5432 @cindex catch exceptions, list active handlers
5433 @cindex exception handlers, how to list
5435 Print a list of all the exception handlers that are active in the
5436 current stack frame at the current point of execution. To see other
5437 exception handlers, visit the associated frame (using the @code{up},
5438 @code{down}, or @code{frame} commands); then type @code{info catch}.
5439 @xref{Set Catchpoints, , Setting Catchpoints}.
5445 @chapter Examining Source Files
5447 @value{GDBN} can print parts of your program's source, since the debugging
5448 information recorded in the program tells @value{GDBN} what source files were
5449 used to build it. When your program stops, @value{GDBN} spontaneously prints
5450 the line where it stopped. Likewise, when you select a stack frame
5451 (@pxref{Selection, ,Selecting a Frame}), @value{GDBN} prints the line where
5452 execution in that frame has stopped. You can print other portions of
5453 source files by explicit command.
5455 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
5456 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
5457 @value{GDBN} under @sc{gnu} Emacs}.
5460 * List:: Printing source lines
5461 * Specify Location:: How to specify code locations
5462 * Edit:: Editing source files
5463 * Search:: Searching source files
5464 * Source Path:: Specifying source directories
5465 * Machine Code:: Source and machine code
5469 @section Printing Source Lines
5472 @kindex l @r{(@code{list})}
5473 To print lines from a source file, use the @code{list} command
5474 (abbreviated @code{l}). By default, ten lines are printed.
5475 There are several ways to specify what part of the file you want to
5476 print; see @ref{Specify Location}, for the full list.
5478 Here are the forms of the @code{list} command most commonly used:
5481 @item list @var{linenum}
5482 Print lines centered around line number @var{linenum} in the
5483 current source file.
5485 @item list @var{function}
5486 Print lines centered around the beginning of function
5490 Print more lines. If the last lines printed were printed with a
5491 @code{list} command, this prints lines following the last lines
5492 printed; however, if the last line printed was a solitary line printed
5493 as part of displaying a stack frame (@pxref{Stack, ,Examining the
5494 Stack}), this prints lines centered around that line.
5497 Print lines just before the lines last printed.
5500 @cindex @code{list}, how many lines to display
5501 By default, @value{GDBN} prints ten source lines with any of these forms of
5502 the @code{list} command. You can change this using @code{set listsize}:
5505 @kindex set listsize
5506 @item set listsize @var{count}
5507 Make the @code{list} command display @var{count} source lines (unless
5508 the @code{list} argument explicitly specifies some other number).
5510 @kindex show listsize
5512 Display the number of lines that @code{list} prints.
5515 Repeating a @code{list} command with @key{RET} discards the argument,
5516 so it is equivalent to typing just @code{list}. This is more useful
5517 than listing the same lines again. An exception is made for an
5518 argument of @samp{-}; that argument is preserved in repetition so that
5519 each repetition moves up in the source file.
5521 In general, the @code{list} command expects you to supply zero, one or two
5522 @dfn{linespecs}. Linespecs specify source lines; there are several ways
5523 of writing them (@pxref{Specify Location}), but the effect is always
5524 to specify some source line.
5526 Here is a complete description of the possible arguments for @code{list}:
5529 @item list @var{linespec}
5530 Print lines centered around the line specified by @var{linespec}.
5532 @item list @var{first},@var{last}
5533 Print lines from @var{first} to @var{last}. Both arguments are
5534 linespecs. When a @code{list} command has two linespecs, and the
5535 source file of the second linespec is omitted, this refers to
5536 the same source file as the first linespec.
5538 @item list ,@var{last}
5539 Print lines ending with @var{last}.
5541 @item list @var{first},
5542 Print lines starting with @var{first}.
5545 Print lines just after the lines last printed.
5548 Print lines just before the lines last printed.
5551 As described in the preceding table.
5554 @node Specify Location
5555 @section Specifying a Location
5556 @cindex specifying location
5559 Several @value{GDBN} commands accept arguments that specify a location
5560 of your program's code. Since @value{GDBN} is a source-level
5561 debugger, a location usually specifies some line in the source code;
5562 for that reason, locations are also known as @dfn{linespecs}.
5564 Here are all the different ways of specifying a code location that
5565 @value{GDBN} understands:
5569 Specifies the line number @var{linenum} of the current source file.
5572 @itemx +@var{offset}
5573 Specifies the line @var{offset} lines before or after the @dfn{current
5574 line}. For the @code{list} command, the current line is the last one
5575 printed; for the breakpoint commands, this is the line at which
5576 execution stopped in the currently selected @dfn{stack frame}
5577 (@pxref{Frames, ,Frames}, for a description of stack frames.) When
5578 used as the second of the two linespecs in a @code{list} command,
5579 this specifies the line @var{offset} lines up or down from the first
5582 @item @var{filename}:@var{linenum}
5583 Specifies the line @var{linenum} in the source file @var{filename}.
5585 @item @var{function}
5586 Specifies the line that begins the body of the function @var{function}.
5587 For example, in C, this is the line with the open brace.
5589 @item @var{filename}:@var{function}
5590 Specifies the line that begins the body of the function @var{function}
5591 in the file @var{filename}. You only need the file name with a
5592 function name to avoid ambiguity when there are identically named
5593 functions in different source files.
5595 @item *@var{address}
5596 Specifies the program address @var{address}. For line-oriented
5597 commands, such as @code{list} and @code{edit}, this specifies a source
5598 line that contains @var{address}. For @code{break} and other
5599 breakpoint oriented commands, this can be used to set breakpoints in
5600 parts of your program which do not have debugging information or
5603 Here @var{address} may be any expression valid in the current working
5604 language (@pxref{Languages, working language}) that specifies a code
5605 address. In addition, as a convenience, @value{GDBN} extends the
5606 semantics of expressions used in locations to cover the situations
5607 that frequently happen during debugging. Here are the various forms
5611 @item @var{expression}
5612 Any expression valid in the current working language.
5614 @item @var{funcaddr}
5615 An address of a function or procedure derived from its name. In C,
5616 C@t{++}, Java, Objective-C, Fortran, minimal, and assembly, this is
5617 simply the function's name @var{function} (and actually a special case
5618 of a valid expression). In Pascal and Modula-2, this is
5619 @code{&@var{function}}. In Ada, this is @code{@var{function}'Address}
5620 (although the Pascal form also works).
5622 This form specifies the address of the function's first instruction,
5623 before the stack frame and arguments have been set up.
5625 @item '@var{filename}'::@var{funcaddr}
5626 Like @var{funcaddr} above, but also specifies the name of the source
5627 file explicitly. This is useful if the name of the function does not
5628 specify the function unambiguously, e.g., if there are several
5629 functions with identical names in different source files.
5636 @section Editing Source Files
5637 @cindex editing source files
5640 @kindex e @r{(@code{edit})}
5641 To edit the lines in a source file, use the @code{edit} command.
5642 The editing program of your choice
5643 is invoked with the current line set to
5644 the active line in the program.
5645 Alternatively, there are several ways to specify what part of the file you
5646 want to print if you want to see other parts of the program:
5649 @item edit @var{location}
5650 Edit the source file specified by @code{location}. Editing starts at
5651 that @var{location}, e.g., at the specified source line of the
5652 specified file. @xref{Specify Location}, for all the possible forms
5653 of the @var{location} argument; here are the forms of the @code{edit}
5654 command most commonly used:
5657 @item edit @var{number}
5658 Edit the current source file with @var{number} as the active line number.
5660 @item edit @var{function}
5661 Edit the file containing @var{function} at the beginning of its definition.
5666 @subsection Choosing your Editor
5667 You can customize @value{GDBN} to use any editor you want
5669 The only restriction is that your editor (say @code{ex}), recognizes the
5670 following command-line syntax:
5672 ex +@var{number} file
5674 The optional numeric value +@var{number} specifies the number of the line in
5675 the file where to start editing.}.
5676 By default, it is @file{@value{EDITOR}}, but you can change this
5677 by setting the environment variable @code{EDITOR} before using
5678 @value{GDBN}. For example, to configure @value{GDBN} to use the
5679 @code{vi} editor, you could use these commands with the @code{sh} shell:
5685 or in the @code{csh} shell,
5687 setenv EDITOR /usr/bin/vi
5692 @section Searching Source Files
5693 @cindex searching source files
5695 There are two commands for searching through the current source file for a
5700 @kindex forward-search
5701 @item forward-search @var{regexp}
5702 @itemx search @var{regexp}
5703 The command @samp{forward-search @var{regexp}} checks each line,
5704 starting with the one following the last line listed, for a match for
5705 @var{regexp}. It lists the line that is found. You can use the
5706 synonym @samp{search @var{regexp}} or abbreviate the command name as
5709 @kindex reverse-search
5710 @item reverse-search @var{regexp}
5711 The command @samp{reverse-search @var{regexp}} checks each line, starting
5712 with the one before the last line listed and going backward, for a match
5713 for @var{regexp}. It lists the line that is found. You can abbreviate
5714 this command as @code{rev}.
5718 @section Specifying Source Directories
5721 @cindex directories for source files
5722 Executable programs sometimes do not record the directories of the source
5723 files from which they were compiled, just the names. Even when they do,
5724 the directories could be moved between the compilation and your debugging
5725 session. @value{GDBN} has a list of directories to search for source files;
5726 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
5727 it tries all the directories in the list, in the order they are present
5728 in the list, until it finds a file with the desired name.
5730 For example, suppose an executable references the file
5731 @file{/usr/src/foo-1.0/lib/foo.c}, and our source path is
5732 @file{/mnt/cross}. The file is first looked up literally; if this
5733 fails, @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c} is tried; if this
5734 fails, @file{/mnt/cross/foo.c} is opened; if this fails, an error
5735 message is printed. @value{GDBN} does not look up the parts of the
5736 source file name, such as @file{/mnt/cross/src/foo-1.0/lib/foo.c}.
5737 Likewise, the subdirectories of the source path are not searched: if
5738 the source path is @file{/mnt/cross}, and the binary refers to
5739 @file{foo.c}, @value{GDBN} would not find it under
5740 @file{/mnt/cross/usr/src/foo-1.0/lib}.
5742 Plain file names, relative file names with leading directories, file
5743 names containing dots, etc.@: are all treated as described above; for
5744 instance, if the source path is @file{/mnt/cross}, and the source file
5745 is recorded as @file{../lib/foo.c}, @value{GDBN} would first try
5746 @file{../lib/foo.c}, then @file{/mnt/cross/../lib/foo.c}, and after
5747 that---@file{/mnt/cross/foo.c}.
5749 Note that the executable search path is @emph{not} used to locate the
5752 Whenever you reset or rearrange the source path, @value{GDBN} clears out
5753 any information it has cached about where source files are found and where
5754 each line is in the file.
5758 When you start @value{GDBN}, its source path includes only @samp{cdir}
5759 and @samp{cwd}, in that order.
5760 To add other directories, use the @code{directory} command.
5762 The search path is used to find both program source files and @value{GDBN}
5763 script files (read using the @samp{-command} option and @samp{source} command).
5765 In addition to the source path, @value{GDBN} provides a set of commands
5766 that manage a list of source path substitution rules. A @dfn{substitution
5767 rule} specifies how to rewrite source directories stored in the program's
5768 debug information in case the sources were moved to a different
5769 directory between compilation and debugging. A rule is made of
5770 two strings, the first specifying what needs to be rewritten in
5771 the path, and the second specifying how it should be rewritten.
5772 In @ref{set substitute-path}, we name these two parts @var{from} and
5773 @var{to} respectively. @value{GDBN} does a simple string replacement
5774 of @var{from} with @var{to} at the start of the directory part of the
5775 source file name, and uses that result instead of the original file
5776 name to look up the sources.
5778 Using the previous example, suppose the @file{foo-1.0} tree has been
5779 moved from @file{/usr/src} to @file{/mnt/cross}, then you can tell
5780 @value{GDBN} to replace @file{/usr/src} in all source path names with
5781 @file{/mnt/cross}. The first lookup will then be
5782 @file{/mnt/cross/foo-1.0/lib/foo.c} in place of the original location
5783 of @file{/usr/src/foo-1.0/lib/foo.c}. To define a source path
5784 substitution rule, use the @code{set substitute-path} command
5785 (@pxref{set substitute-path}).
5787 To avoid unexpected substitution results, a rule is applied only if the
5788 @var{from} part of the directory name ends at a directory separator.
5789 For instance, a rule substituting @file{/usr/source} into
5790 @file{/mnt/cross} will be applied to @file{/usr/source/foo-1.0} but
5791 not to @file{/usr/sourceware/foo-2.0}. And because the substitution
5792 is applied only at the beginning of the directory name, this rule will
5793 not be applied to @file{/root/usr/source/baz.c} either.
5795 In many cases, you can achieve the same result using the @code{directory}
5796 command. However, @code{set substitute-path} can be more efficient in
5797 the case where the sources are organized in a complex tree with multiple
5798 subdirectories. With the @code{directory} command, you need to add each
5799 subdirectory of your project. If you moved the entire tree while
5800 preserving its internal organization, then @code{set substitute-path}
5801 allows you to direct the debugger to all the sources with one single
5804 @code{set substitute-path} is also more than just a shortcut command.
5805 The source path is only used if the file at the original location no
5806 longer exists. On the other hand, @code{set substitute-path} modifies
5807 the debugger behavior to look at the rewritten location instead. So, if
5808 for any reason a source file that is not relevant to your executable is
5809 located at the original location, a substitution rule is the only
5810 method available to point @value{GDBN} at the new location.
5813 @item directory @var{dirname} @dots{}
5814 @item dir @var{dirname} @dots{}
5815 Add directory @var{dirname} to the front of the source path. Several
5816 directory names may be given to this command, separated by @samp{:}
5817 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
5818 part of absolute file names) or
5819 whitespace. You may specify a directory that is already in the source
5820 path; this moves it forward, so @value{GDBN} searches it sooner.
5824 @vindex $cdir@r{, convenience variable}
5825 @vindex $cwd@r{, convenience variable}
5826 @cindex compilation directory
5827 @cindex current directory
5828 @cindex working directory
5829 @cindex directory, current
5830 @cindex directory, compilation
5831 You can use the string @samp{$cdir} to refer to the compilation
5832 directory (if one is recorded), and @samp{$cwd} to refer to the current
5833 working directory. @samp{$cwd} is not the same as @samp{.}---the former
5834 tracks the current working directory as it changes during your @value{GDBN}
5835 session, while the latter is immediately expanded to the current
5836 directory at the time you add an entry to the source path.
5839 Reset the source path to its default value (@samp{$cdir:$cwd} on Unix systems). This requires confirmation.
5841 @c RET-repeat for @code{directory} is explicitly disabled, but since
5842 @c repeating it would be a no-op we do not say that. (thanks to RMS)
5844 @item show directories
5845 @kindex show directories
5846 Print the source path: show which directories it contains.
5848 @anchor{set substitute-path}
5849 @item set substitute-path @var{from} @var{to}
5850 @kindex set substitute-path
5851 Define a source path substitution rule, and add it at the end of the
5852 current list of existing substitution rules. If a rule with the same
5853 @var{from} was already defined, then the old rule is also deleted.
5855 For example, if the file @file{/foo/bar/baz.c} was moved to
5856 @file{/mnt/cross/baz.c}, then the command
5859 (@value{GDBP}) set substitute-path /usr/src /mnt/cross
5863 will tell @value{GDBN} to replace @samp{/usr/src} with
5864 @samp{/mnt/cross}, which will allow @value{GDBN} to find the file
5865 @file{baz.c} even though it was moved.
5867 In the case when more than one substitution rule have been defined,
5868 the rules are evaluated one by one in the order where they have been
5869 defined. The first one matching, if any, is selected to perform
5872 For instance, if we had entered the following commands:
5875 (@value{GDBP}) set substitute-path /usr/src/include /mnt/include
5876 (@value{GDBP}) set substitute-path /usr/src /mnt/src
5880 @value{GDBN} would then rewrite @file{/usr/src/include/defs.h} into
5881 @file{/mnt/include/defs.h} by using the first rule. However, it would
5882 use the second rule to rewrite @file{/usr/src/lib/foo.c} into
5883 @file{/mnt/src/lib/foo.c}.
5886 @item unset substitute-path [path]
5887 @kindex unset substitute-path
5888 If a path is specified, search the current list of substitution rules
5889 for a rule that would rewrite that path. Delete that rule if found.
5890 A warning is emitted by the debugger if no rule could be found.
5892 If no path is specified, then all substitution rules are deleted.
5894 @item show substitute-path [path]
5895 @kindex show substitute-path
5896 If a path is specified, then print the source path substitution rule
5897 which would rewrite that path, if any.
5899 If no path is specified, then print all existing source path substitution
5904 If your source path is cluttered with directories that are no longer of
5905 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
5906 versions of source. You can correct the situation as follows:
5910 Use @code{directory} with no argument to reset the source path to its default value.
5913 Use @code{directory} with suitable arguments to reinstall the
5914 directories you want in the source path. You can add all the
5915 directories in one command.
5919 @section Source and Machine Code
5920 @cindex source line and its code address
5922 You can use the command @code{info line} to map source lines to program
5923 addresses (and vice versa), and the command @code{disassemble} to display
5924 a range of addresses as machine instructions. You can use the command
5925 @code{set disassemble-next-line} to set whether to disassemble next
5926 source line when execution stops. When run under @sc{gnu} Emacs
5927 mode, the @code{info line} command causes the arrow to point to the
5928 line specified. Also, @code{info line} prints addresses in symbolic form as
5933 @item info line @var{linespec}
5934 Print the starting and ending addresses of the compiled code for
5935 source line @var{linespec}. You can specify source lines in any of
5936 the ways documented in @ref{Specify Location}.
5939 For example, we can use @code{info line} to discover the location of
5940 the object code for the first line of function
5941 @code{m4_changequote}:
5943 @c FIXME: I think this example should also show the addresses in
5944 @c symbolic form, as they usually would be displayed.
5946 (@value{GDBP}) info line m4_changequote
5947 Line 895 of "builtin.c" starts at pc 0x634c and ends at 0x6350.
5951 @cindex code address and its source line
5952 We can also inquire (using @code{*@var{addr}} as the form for
5953 @var{linespec}) what source line covers a particular address:
5955 (@value{GDBP}) info line *0x63ff
5956 Line 926 of "builtin.c" starts at pc 0x63e4 and ends at 0x6404.
5959 @cindex @code{$_} and @code{info line}
5960 @cindex @code{x} command, default address
5961 @kindex x@r{(examine), and} info line
5962 After @code{info line}, the default address for the @code{x} command
5963 is changed to the starting address of the line, so that @samp{x/i} is
5964 sufficient to begin examining the machine code (@pxref{Memory,
5965 ,Examining Memory}). Also, this address is saved as the value of the
5966 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
5971 @cindex assembly instructions
5972 @cindex instructions, assembly
5973 @cindex machine instructions
5974 @cindex listing machine instructions
5976 @itemx disassemble /m
5977 This specialized command dumps a range of memory as machine
5978 instructions. It can also print mixed source+disassembly by specifying
5979 the @code{/m} modifier.
5980 The default memory range is the function surrounding the
5981 program counter of the selected frame. A single argument to this
5982 command is a program counter value; @value{GDBN} dumps the function
5983 surrounding this value. Two arguments specify a range of addresses
5984 (first inclusive, second exclusive) to dump.
5987 The following example shows the disassembly of a range of addresses of
5988 HP PA-RISC 2.0 code:
5991 (@value{GDBP}) disas 0x32c4 0x32e4
5992 Dump of assembler code from 0x32c4 to 0x32e4:
5993 0x32c4 <main+204>: addil 0,dp
5994 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
5995 0x32cc <main+212>: ldil 0x3000,r31
5996 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
5997 0x32d4 <main+220>: ldo 0(r31),rp
5998 0x32d8 <main+224>: addil -0x800,dp
5999 0x32dc <main+228>: ldo 0x588(r1),r26
6000 0x32e0 <main+232>: ldil 0x3000,r31
6001 End of assembler dump.
6004 Here is an example showing mixed source+assembly for Intel x86:
6007 (@value{GDBP}) disas /m main
6008 Dump of assembler code for function main:
6010 0x08048330 <main+0>: push %ebp
6011 0x08048331 <main+1>: mov %esp,%ebp
6012 0x08048333 <main+3>: sub $0x8,%esp
6013 0x08048336 <main+6>: and $0xfffffff0,%esp
6014 0x08048339 <main+9>: sub $0x10,%esp
6016 6 printf ("Hello.\n");
6017 0x0804833c <main+12>: movl $0x8048440,(%esp)
6018 0x08048343 <main+19>: call 0x8048284 <puts@@plt>
6022 0x08048348 <main+24>: mov $0x0,%eax
6023 0x0804834d <main+29>: leave
6024 0x0804834e <main+30>: ret
6026 End of assembler dump.
6029 Some architectures have more than one commonly-used set of instruction
6030 mnemonics or other syntax.
6032 For programs that were dynamically linked and use shared libraries,
6033 instructions that call functions or branch to locations in the shared
6034 libraries might show a seemingly bogus location---it's actually a
6035 location of the relocation table. On some architectures, @value{GDBN}
6036 might be able to resolve these to actual function names.
6039 @kindex set disassembly-flavor
6040 @cindex Intel disassembly flavor
6041 @cindex AT&T disassembly flavor
6042 @item set disassembly-flavor @var{instruction-set}
6043 Select the instruction set to use when disassembling the
6044 program via the @code{disassemble} or @code{x/i} commands.
6046 Currently this command is only defined for the Intel x86 family. You
6047 can set @var{instruction-set} to either @code{intel} or @code{att}.
6048 The default is @code{att}, the AT&T flavor used by default by Unix
6049 assemblers for x86-based targets.
6051 @kindex show disassembly-flavor
6052 @item show disassembly-flavor
6053 Show the current setting of the disassembly flavor.
6057 @kindex set disassemble-next-line
6058 @kindex show disassemble-next-line
6059 @item set disassemble-next-line
6060 @itemx show disassemble-next-line
6061 Control whether or not @value{GDBN} will disassemble next source line
6062 when execution stops. If ON, GDB will display disassembly of the next
6063 source line when execution of the program being debugged stops.
6064 If AUTO (which is the default), or there's no line info to determine
6065 the source line of the next instruction, display disassembly of next
6066 instruction instead.
6071 @chapter Examining Data
6073 @cindex printing data
6074 @cindex examining data
6077 @c "inspect" is not quite a synonym if you are using Epoch, which we do not
6078 @c document because it is nonstandard... Under Epoch it displays in a
6079 @c different window or something like that.
6080 The usual way to examine data in your program is with the @code{print}
6081 command (abbreviated @code{p}), or its synonym @code{inspect}. It
6082 evaluates and prints the value of an expression of the language your
6083 program is written in (@pxref{Languages, ,Using @value{GDBN} with
6084 Different Languages}).
6087 @item print @var{expr}
6088 @itemx print /@var{f} @var{expr}
6089 @var{expr} is an expression (in the source language). By default the
6090 value of @var{expr} is printed in a format appropriate to its data type;
6091 you can choose a different format by specifying @samp{/@var{f}}, where
6092 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
6096 @itemx print /@var{f}
6097 @cindex reprint the last value
6098 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
6099 @dfn{value history}; @pxref{Value History, ,Value History}). This allows you to
6100 conveniently inspect the same value in an alternative format.
6103 A more low-level way of examining data is with the @code{x} command.
6104 It examines data in memory at a specified address and prints it in a
6105 specified format. @xref{Memory, ,Examining Memory}.
6107 If you are interested in information about types, or about how the
6108 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
6109 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
6113 * Expressions:: Expressions
6114 * Ambiguous Expressions:: Ambiguous Expressions
6115 * Variables:: Program variables
6116 * Arrays:: Artificial arrays
6117 * Output Formats:: Output formats
6118 * Memory:: Examining memory
6119 * Auto Display:: Automatic display
6120 * Print Settings:: Print settings
6121 * Value History:: Value history
6122 * Convenience Vars:: Convenience variables
6123 * Registers:: Registers
6124 * Floating Point Hardware:: Floating point hardware
6125 * Vector Unit:: Vector Unit
6126 * OS Information:: Auxiliary data provided by operating system
6127 * Memory Region Attributes:: Memory region attributes
6128 * Dump/Restore Files:: Copy between memory and a file
6129 * Core File Generation:: Cause a program dump its core
6130 * Character Sets:: Debugging programs that use a different
6131 character set than GDB does
6132 * Caching Remote Data:: Data caching for remote targets
6133 * Searching Memory:: Searching memory for a sequence of bytes
6137 @section Expressions
6140 @code{print} and many other @value{GDBN} commands accept an expression and
6141 compute its value. Any kind of constant, variable or operator defined
6142 by the programming language you are using is valid in an expression in
6143 @value{GDBN}. This includes conditional expressions, function calls,
6144 casts, and string constants. It also includes preprocessor macros, if
6145 you compiled your program to include this information; see
6148 @cindex arrays in expressions
6149 @value{GDBN} supports array constants in expressions input by
6150 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
6151 you can use the command @code{print @{1, 2, 3@}} to create an array
6152 of three integers. If you pass an array to a function or assign it
6153 to a program variable, @value{GDBN} copies the array to memory that
6154 is @code{malloc}ed in the target program.
6156 Because C is so widespread, most of the expressions shown in examples in
6157 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
6158 Languages}, for information on how to use expressions in other
6161 In this section, we discuss operators that you can use in @value{GDBN}
6162 expressions regardless of your programming language.
6164 @cindex casts, in expressions
6165 Casts are supported in all languages, not just in C, because it is so
6166 useful to cast a number into a pointer in order to examine a structure
6167 at that address in memory.
6168 @c FIXME: casts supported---Mod2 true?
6170 @value{GDBN} supports these operators, in addition to those common
6171 to programming languages:
6175 @samp{@@} is a binary operator for treating parts of memory as arrays.
6176 @xref{Arrays, ,Artificial Arrays}, for more information.
6179 @samp{::} allows you to specify a variable in terms of the file or
6180 function where it is defined. @xref{Variables, ,Program Variables}.
6182 @cindex @{@var{type}@}
6183 @cindex type casting memory
6184 @cindex memory, viewing as typed object
6185 @cindex casts, to view memory
6186 @item @{@var{type}@} @var{addr}
6187 Refers to an object of type @var{type} stored at address @var{addr} in
6188 memory. @var{addr} may be any expression whose value is an integer or
6189 pointer (but parentheses are required around binary operators, just as in
6190 a cast). This construct is allowed regardless of what kind of data is
6191 normally supposed to reside at @var{addr}.
6194 @node Ambiguous Expressions
6195 @section Ambiguous Expressions
6196 @cindex ambiguous expressions
6198 Expressions can sometimes contain some ambiguous elements. For instance,
6199 some programming languages (notably Ada, C@t{++} and Objective-C) permit
6200 a single function name to be defined several times, for application in
6201 different contexts. This is called @dfn{overloading}. Another example
6202 involving Ada is generics. A @dfn{generic package} is similar to C@t{++}
6203 templates and is typically instantiated several times, resulting in
6204 the same function name being defined in different contexts.
6206 In some cases and depending on the language, it is possible to adjust
6207 the expression to remove the ambiguity. For instance in C@t{++}, you
6208 can specify the signature of the function you want to break on, as in
6209 @kbd{break @var{function}(@var{types})}. In Ada, using the fully
6210 qualified name of your function often makes the expression unambiguous
6213 When an ambiguity that needs to be resolved is detected, the debugger
6214 has the capability to display a menu of numbered choices for each
6215 possibility, and then waits for the selection with the prompt @samp{>}.
6216 The first option is always @samp{[0] cancel}, and typing @kbd{0 @key{RET}}
6217 aborts the current command. If the command in which the expression was
6218 used allows more than one choice to be selected, the next option in the
6219 menu is @samp{[1] all}, and typing @kbd{1 @key{RET}} selects all possible
6222 For example, the following session excerpt shows an attempt to set a
6223 breakpoint at the overloaded symbol @code{String::after}.
6224 We choose three particular definitions of that function name:
6226 @c FIXME! This is likely to change to show arg type lists, at least
6229 (@value{GDBP}) b String::after
6232 [2] file:String.cc; line number:867
6233 [3] file:String.cc; line number:860
6234 [4] file:String.cc; line number:875
6235 [5] file:String.cc; line number:853
6236 [6] file:String.cc; line number:846
6237 [7] file:String.cc; line number:735
6239 Breakpoint 1 at 0xb26c: file String.cc, line 867.
6240 Breakpoint 2 at 0xb344: file String.cc, line 875.
6241 Breakpoint 3 at 0xafcc: file String.cc, line 846.
6242 Multiple breakpoints were set.
6243 Use the "delete" command to delete unwanted
6250 @kindex set multiple-symbols
6251 @item set multiple-symbols @var{mode}
6252 @cindex multiple-symbols menu
6254 This option allows you to adjust the debugger behavior when an expression
6257 By default, @var{mode} is set to @code{all}. If the command with which
6258 the expression is used allows more than one choice, then @value{GDBN}
6259 automatically selects all possible choices. For instance, inserting
6260 a breakpoint on a function using an ambiguous name results in a breakpoint
6261 inserted on each possible match. However, if a unique choice must be made,
6262 then @value{GDBN} uses the menu to help you disambiguate the expression.
6263 For instance, printing the address of an overloaded function will result
6264 in the use of the menu.
6266 When @var{mode} is set to @code{ask}, the debugger always uses the menu
6267 when an ambiguity is detected.
6269 Finally, when @var{mode} is set to @code{cancel}, the debugger reports
6270 an error due to the ambiguity and the command is aborted.
6272 @kindex show multiple-symbols
6273 @item show multiple-symbols
6274 Show the current value of the @code{multiple-symbols} setting.
6278 @section Program Variables
6280 The most common kind of expression to use is the name of a variable
6283 Variables in expressions are understood in the selected stack frame
6284 (@pxref{Selection, ,Selecting a Frame}); they must be either:
6288 global (or file-static)
6295 visible according to the scope rules of the
6296 programming language from the point of execution in that frame
6299 @noindent This means that in the function
6314 you can examine and use the variable @code{a} whenever your program is
6315 executing within the function @code{foo}, but you can only use or
6316 examine the variable @code{b} while your program is executing inside
6317 the block where @code{b} is declared.
6319 @cindex variable name conflict
6320 There is an exception: you can refer to a variable or function whose
6321 scope is a single source file even if the current execution point is not
6322 in this file. But it is possible to have more than one such variable or
6323 function with the same name (in different source files). If that
6324 happens, referring to that name has unpredictable effects. If you wish,
6325 you can specify a static variable in a particular function or file,
6326 using the colon-colon (@code{::}) notation:
6328 @cindex colon-colon, context for variables/functions
6330 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
6331 @cindex @code{::}, context for variables/functions
6334 @var{file}::@var{variable}
6335 @var{function}::@var{variable}
6339 Here @var{file} or @var{function} is the name of the context for the
6340 static @var{variable}. In the case of file names, you can use quotes to
6341 make sure @value{GDBN} parses the file name as a single word---for example,
6342 to print a global value of @code{x} defined in @file{f2.c}:
6345 (@value{GDBP}) p 'f2.c'::x
6348 @cindex C@t{++} scope resolution
6349 This use of @samp{::} is very rarely in conflict with the very similar
6350 use of the same notation in C@t{++}. @value{GDBN} also supports use of the C@t{++}
6351 scope resolution operator in @value{GDBN} expressions.
6352 @c FIXME: Um, so what happens in one of those rare cases where it's in
6355 @cindex wrong values
6356 @cindex variable values, wrong
6357 @cindex function entry/exit, wrong values of variables
6358 @cindex optimized code, wrong values of variables
6360 @emph{Warning:} Occasionally, a local variable may appear to have the
6361 wrong value at certain points in a function---just after entry to a new
6362 scope, and just before exit.
6364 You may see this problem when you are stepping by machine instructions.
6365 This is because, on most machines, it takes more than one instruction to
6366 set up a stack frame (including local variable definitions); if you are
6367 stepping by machine instructions, variables may appear to have the wrong
6368 values until the stack frame is completely built. On exit, it usually
6369 also takes more than one machine instruction to destroy a stack frame;
6370 after you begin stepping through that group of instructions, local
6371 variable definitions may be gone.
6373 This may also happen when the compiler does significant optimizations.
6374 To be sure of always seeing accurate values, turn off all optimization
6377 @cindex ``No symbol "foo" in current context''
6378 Another possible effect of compiler optimizations is to optimize
6379 unused variables out of existence, or assign variables to registers (as
6380 opposed to memory addresses). Depending on the support for such cases
6381 offered by the debug info format used by the compiler, @value{GDBN}
6382 might not be able to display values for such local variables. If that
6383 happens, @value{GDBN} will print a message like this:
6386 No symbol "foo" in current context.
6389 To solve such problems, either recompile without optimizations, or use a
6390 different debug info format, if the compiler supports several such
6391 formats. For example, @value{NGCC}, the @sc{gnu} C/C@t{++} compiler,
6392 usually supports the @option{-gstabs+} option. @option{-gstabs+}
6393 produces debug info in a format that is superior to formats such as
6394 COFF. You may be able to use DWARF 2 (@option{-gdwarf-2}), which is also
6395 an effective form for debug info. @xref{Debugging Options,,Options
6396 for Debugging Your Program or GCC, gcc.info, Using the @sc{gnu}
6397 Compiler Collection (GCC)}.
6398 @xref{C, ,C and C@t{++}}, for more information about debug info formats
6399 that are best suited to C@t{++} programs.
6401 If you ask to print an object whose contents are unknown to
6402 @value{GDBN}, e.g., because its data type is not completely specified
6403 by the debug information, @value{GDBN} will say @samp{<incomplete
6404 type>}. @xref{Symbols, incomplete type}, for more about this.
6406 Strings are identified as arrays of @code{char} values without specified
6407 signedness. Arrays of either @code{signed char} or @code{unsigned char} get
6408 printed as arrays of 1 byte sized integers. @code{-fsigned-char} or
6409 @code{-funsigned-char} @value{NGCC} options have no effect as @value{GDBN}
6410 defines literal string type @code{"char"} as @code{char} without a sign.
6415 signed char var1[] = "A";
6418 You get during debugging
6423 $2 = @{65 'A', 0 '\0'@}
6427 @section Artificial Arrays
6429 @cindex artificial array
6431 @kindex @@@r{, referencing memory as an array}
6432 It is often useful to print out several successive objects of the
6433 same type in memory; a section of an array, or an array of
6434 dynamically determined size for which only a pointer exists in the
6437 You can do this by referring to a contiguous span of memory as an
6438 @dfn{artificial array}, using the binary operator @samp{@@}. The left
6439 operand of @samp{@@} should be the first element of the desired array
6440 and be an individual object. The right operand should be the desired length
6441 of the array. The result is an array value whose elements are all of
6442 the type of the left argument. The first element is actually the left
6443 argument; the second element comes from bytes of memory immediately
6444 following those that hold the first element, and so on. Here is an
6445 example. If a program says
6448 int *array = (int *) malloc (len * sizeof (int));
6452 you can print the contents of @code{array} with
6458 The left operand of @samp{@@} must reside in memory. Array values made
6459 with @samp{@@} in this way behave just like other arrays in terms of
6460 subscripting, and are coerced to pointers when used in expressions.
6461 Artificial arrays most often appear in expressions via the value history
6462 (@pxref{Value History, ,Value History}), after printing one out.
6464 Another way to create an artificial array is to use a cast.
6465 This re-interprets a value as if it were an array.
6466 The value need not be in memory:
6468 (@value{GDBP}) p/x (short[2])0x12345678
6469 $1 = @{0x1234, 0x5678@}
6472 As a convenience, if you leave the array length out (as in
6473 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
6474 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
6476 (@value{GDBP}) p/x (short[])0x12345678
6477 $2 = @{0x1234, 0x5678@}
6480 Sometimes the artificial array mechanism is not quite enough; in
6481 moderately complex data structures, the elements of interest may not
6482 actually be adjacent---for example, if you are interested in the values
6483 of pointers in an array. One useful work-around in this situation is
6484 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
6485 Variables}) as a counter in an expression that prints the first
6486 interesting value, and then repeat that expression via @key{RET}. For
6487 instance, suppose you have an array @code{dtab} of pointers to
6488 structures, and you are interested in the values of a field @code{fv}
6489 in each structure. Here is an example of what you might type:
6499 @node Output Formats
6500 @section Output Formats
6502 @cindex formatted output
6503 @cindex output formats
6504 By default, @value{GDBN} prints a value according to its data type. Sometimes
6505 this is not what you want. For example, you might want to print a number
6506 in hex, or a pointer in decimal. Or you might want to view data in memory
6507 at a certain address as a character string or as an instruction. To do
6508 these things, specify an @dfn{output format} when you print a value.
6510 The simplest use of output formats is to say how to print a value
6511 already computed. This is done by starting the arguments of the
6512 @code{print} command with a slash and a format letter. The format
6513 letters supported are:
6517 Regard the bits of the value as an integer, and print the integer in
6521 Print as integer in signed decimal.
6524 Print as integer in unsigned decimal.
6527 Print as integer in octal.
6530 Print as integer in binary. The letter @samp{t} stands for ``two''.
6531 @footnote{@samp{b} cannot be used because these format letters are also
6532 used with the @code{x} command, where @samp{b} stands for ``byte'';
6533 see @ref{Memory,,Examining Memory}.}
6536 @cindex unknown address, locating
6537 @cindex locate address
6538 Print as an address, both absolute in hexadecimal and as an offset from
6539 the nearest preceding symbol. You can use this format used to discover
6540 where (in what function) an unknown address is located:
6543 (@value{GDBP}) p/a 0x54320
6544 $3 = 0x54320 <_initialize_vx+396>
6548 The command @code{info symbol 0x54320} yields similar results.
6549 @xref{Symbols, info symbol}.
6552 Regard as an integer and print it as a character constant. This
6553 prints both the numerical value and its character representation. The
6554 character representation is replaced with the octal escape @samp{\nnn}
6555 for characters outside the 7-bit @sc{ascii} range.
6557 Without this format, @value{GDBN} displays @code{char},
6558 @w{@code{unsigned char}}, and @w{@code{signed char}} data as character
6559 constants. Single-byte members of vectors are displayed as integer
6563 Regard the bits of the value as a floating point number and print
6564 using typical floating point syntax.
6567 @cindex printing strings
6568 @cindex printing byte arrays
6569 Regard as a string, if possible. With this format, pointers to single-byte
6570 data are displayed as null-terminated strings and arrays of single-byte data
6571 are displayed as fixed-length strings. Other values are displayed in their
6574 Without this format, @value{GDBN} displays pointers to and arrays of
6575 @code{char}, @w{@code{unsigned char}}, and @w{@code{signed char}} as
6576 strings. Single-byte members of a vector are displayed as an integer
6580 For example, to print the program counter in hex (@pxref{Registers}), type
6587 Note that no space is required before the slash; this is because command
6588 names in @value{GDBN} cannot contain a slash.
6590 To reprint the last value in the value history with a different format,
6591 you can use the @code{print} command with just a format and no
6592 expression. For example, @samp{p/x} reprints the last value in hex.
6595 @section Examining Memory
6597 You can use the command @code{x} (for ``examine'') to examine memory in
6598 any of several formats, independently of your program's data types.
6600 @cindex examining memory
6602 @kindex x @r{(examine memory)}
6603 @item x/@var{nfu} @var{addr}
6606 Use the @code{x} command to examine memory.
6609 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
6610 much memory to display and how to format it; @var{addr} is an
6611 expression giving the address where you want to start displaying memory.
6612 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
6613 Several commands set convenient defaults for @var{addr}.
6616 @item @var{n}, the repeat count
6617 The repeat count is a decimal integer; the default is 1. It specifies
6618 how much memory (counting by units @var{u}) to display.
6619 @c This really is **decimal**; unaffected by 'set radix' as of GDB
6622 @item @var{f}, the display format
6623 The display format is one of the formats used by @code{print}
6624 (@samp{x}, @samp{d}, @samp{u}, @samp{o}, @samp{t}, @samp{a}, @samp{c},
6625 @samp{f}, @samp{s}), and in addition @samp{i} (for machine instructions).
6626 The default is @samp{x} (hexadecimal) initially. The default changes
6627 each time you use either @code{x} or @code{print}.
6629 @item @var{u}, the unit size
6630 The unit size is any of
6636 Halfwords (two bytes).
6638 Words (four bytes). This is the initial default.
6640 Giant words (eight bytes).
6643 Each time you specify a unit size with @code{x}, that size becomes the
6644 default unit the next time you use @code{x}. (For the @samp{s} and
6645 @samp{i} formats, the unit size is ignored and is normally not written.)
6647 @item @var{addr}, starting display address
6648 @var{addr} is the address where you want @value{GDBN} to begin displaying
6649 memory. The expression need not have a pointer value (though it may);
6650 it is always interpreted as an integer address of a byte of memory.
6651 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
6652 @var{addr} is usually just after the last address examined---but several
6653 other commands also set the default address: @code{info breakpoints} (to
6654 the address of the last breakpoint listed), @code{info line} (to the
6655 starting address of a line), and @code{print} (if you use it to display
6656 a value from memory).
6659 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
6660 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
6661 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
6662 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
6663 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
6665 Since the letters indicating unit sizes are all distinct from the
6666 letters specifying output formats, you do not have to remember whether
6667 unit size or format comes first; either order works. The output
6668 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
6669 (However, the count @var{n} must come first; @samp{wx4} does not work.)
6671 Even though the unit size @var{u} is ignored for the formats @samp{s}
6672 and @samp{i}, you might still want to use a count @var{n}; for example,
6673 @samp{3i} specifies that you want to see three machine instructions,
6674 including any operands. For convenience, especially when used with
6675 the @code{display} command, the @samp{i} format also prints branch delay
6676 slot instructions, if any, beyond the count specified, which immediately
6677 follow the last instruction that is within the count. The command
6678 @code{disassemble} gives an alternative way of inspecting machine
6679 instructions; see @ref{Machine Code,,Source and Machine Code}.
6681 All the defaults for the arguments to @code{x} are designed to make it
6682 easy to continue scanning memory with minimal specifications each time
6683 you use @code{x}. For example, after you have inspected three machine
6684 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
6685 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
6686 the repeat count @var{n} is used again; the other arguments default as
6687 for successive uses of @code{x}.
6689 @cindex @code{$_}, @code{$__}, and value history
6690 The addresses and contents printed by the @code{x} command are not saved
6691 in the value history because there is often too much of them and they
6692 would get in the way. Instead, @value{GDBN} makes these values available for
6693 subsequent use in expressions as values of the convenience variables
6694 @code{$_} and @code{$__}. After an @code{x} command, the last address
6695 examined is available for use in expressions in the convenience variable
6696 @code{$_}. The contents of that address, as examined, are available in
6697 the convenience variable @code{$__}.
6699 If the @code{x} command has a repeat count, the address and contents saved
6700 are from the last memory unit printed; this is not the same as the last
6701 address printed if several units were printed on the last line of output.
6703 @cindex remote memory comparison
6704 @cindex verify remote memory image
6705 When you are debugging a program running on a remote target machine
6706 (@pxref{Remote Debugging}), you may wish to verify the program's image in the
6707 remote machine's memory against the executable file you downloaded to
6708 the target. The @code{compare-sections} command is provided for such
6712 @kindex compare-sections
6713 @item compare-sections @r{[}@var{section-name}@r{]}
6714 Compare the data of a loadable section @var{section-name} in the
6715 executable file of the program being debugged with the same section in
6716 the remote machine's memory, and report any mismatches. With no
6717 arguments, compares all loadable sections. This command's
6718 availability depends on the target's support for the @code{"qCRC"}
6723 @section Automatic Display
6724 @cindex automatic display
6725 @cindex display of expressions
6727 If you find that you want to print the value of an expression frequently
6728 (to see how it changes), you might want to add it to the @dfn{automatic
6729 display list} so that @value{GDBN} prints its value each time your program stops.
6730 Each expression added to the list is given a number to identify it;
6731 to remove an expression from the list, you specify that number.
6732 The automatic display looks like this:
6736 3: bar[5] = (struct hack *) 0x3804
6740 This display shows item numbers, expressions and their current values. As with
6741 displays you request manually using @code{x} or @code{print}, you can
6742 specify the output format you prefer; in fact, @code{display} decides
6743 whether to use @code{print} or @code{x} depending your format
6744 specification---it uses @code{x} if you specify either the @samp{i}
6745 or @samp{s} format, or a unit size; otherwise it uses @code{print}.
6749 @item display @var{expr}
6750 Add the expression @var{expr} to the list of expressions to display
6751 each time your program stops. @xref{Expressions, ,Expressions}.
6753 @code{display} does not repeat if you press @key{RET} again after using it.
6755 @item display/@var{fmt} @var{expr}
6756 For @var{fmt} specifying only a display format and not a size or
6757 count, add the expression @var{expr} to the auto-display list but
6758 arrange to display it each time in the specified format @var{fmt}.
6759 @xref{Output Formats,,Output Formats}.
6761 @item display/@var{fmt} @var{addr}
6762 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
6763 number of units, add the expression @var{addr} as a memory address to
6764 be examined each time your program stops. Examining means in effect
6765 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining Memory}.
6768 For example, @samp{display/i $pc} can be helpful, to see the machine
6769 instruction about to be executed each time execution stops (@samp{$pc}
6770 is a common name for the program counter; @pxref{Registers, ,Registers}).
6773 @kindex delete display
6775 @item undisplay @var{dnums}@dots{}
6776 @itemx delete display @var{dnums}@dots{}
6777 Remove item numbers @var{dnums} from the list of expressions to display.
6779 @code{undisplay} does not repeat if you press @key{RET} after using it.
6780 (Otherwise you would just get the error @samp{No display number @dots{}}.)
6782 @kindex disable display
6783 @item disable display @var{dnums}@dots{}
6784 Disable the display of item numbers @var{dnums}. A disabled display
6785 item is not printed automatically, but is not forgotten. It may be
6786 enabled again later.
6788 @kindex enable display
6789 @item enable display @var{dnums}@dots{}
6790 Enable display of item numbers @var{dnums}. It becomes effective once
6791 again in auto display of its expression, until you specify otherwise.
6794 Display the current values of the expressions on the list, just as is
6795 done when your program stops.
6797 @kindex info display
6799 Print the list of expressions previously set up to display
6800 automatically, each one with its item number, but without showing the
6801 values. This includes disabled expressions, which are marked as such.
6802 It also includes expressions which would not be displayed right now
6803 because they refer to automatic variables not currently available.
6806 @cindex display disabled out of scope
6807 If a display expression refers to local variables, then it does not make
6808 sense outside the lexical context for which it was set up. Such an
6809 expression is disabled when execution enters a context where one of its
6810 variables is not defined. For example, if you give the command
6811 @code{display last_char} while inside a function with an argument
6812 @code{last_char}, @value{GDBN} displays this argument while your program
6813 continues to stop inside that function. When it stops elsewhere---where
6814 there is no variable @code{last_char}---the display is disabled
6815 automatically. The next time your program stops where @code{last_char}
6816 is meaningful, you can enable the display expression once again.
6818 @node Print Settings
6819 @section Print Settings
6821 @cindex format options
6822 @cindex print settings
6823 @value{GDBN} provides the following ways to control how arrays, structures,
6824 and symbols are printed.
6827 These settings are useful for debugging programs in any language:
6831 @item set print address
6832 @itemx set print address on
6833 @cindex print/don't print memory addresses
6834 @value{GDBN} prints memory addresses showing the location of stack
6835 traces, structure values, pointer values, breakpoints, and so forth,
6836 even when it also displays the contents of those addresses. The default
6837 is @code{on}. For example, this is what a stack frame display looks like with
6838 @code{set print address on}:
6843 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
6845 530 if (lquote != def_lquote)
6849 @item set print address off
6850 Do not print addresses when displaying their contents. For example,
6851 this is the same stack frame displayed with @code{set print address off}:
6855 (@value{GDBP}) set print addr off
6857 #0 set_quotes (lq="<<", rq=">>") at input.c:530
6858 530 if (lquote != def_lquote)
6862 You can use @samp{set print address off} to eliminate all machine
6863 dependent displays from the @value{GDBN} interface. For example, with
6864 @code{print address off}, you should get the same text for backtraces on
6865 all machines---whether or not they involve pointer arguments.
6868 @item show print address
6869 Show whether or not addresses are to be printed.
6872 When @value{GDBN} prints a symbolic address, it normally prints the
6873 closest earlier symbol plus an offset. If that symbol does not uniquely
6874 identify the address (for example, it is a name whose scope is a single
6875 source file), you may need to clarify. One way to do this is with
6876 @code{info line}, for example @samp{info line *0x4537}. Alternately,
6877 you can set @value{GDBN} to print the source file and line number when
6878 it prints a symbolic address:
6881 @item set print symbol-filename on
6882 @cindex source file and line of a symbol
6883 @cindex symbol, source file and line
6884 Tell @value{GDBN} to print the source file name and line number of a
6885 symbol in the symbolic form of an address.
6887 @item set print symbol-filename off
6888 Do not print source file name and line number of a symbol. This is the
6891 @item show print symbol-filename
6892 Show whether or not @value{GDBN} will print the source file name and
6893 line number of a symbol in the symbolic form of an address.
6896 Another situation where it is helpful to show symbol filenames and line
6897 numbers is when disassembling code; @value{GDBN} shows you the line
6898 number and source file that corresponds to each instruction.
6900 Also, you may wish to see the symbolic form only if the address being
6901 printed is reasonably close to the closest earlier symbol:
6904 @item set print max-symbolic-offset @var{max-offset}
6905 @cindex maximum value for offset of closest symbol
6906 Tell @value{GDBN} to only display the symbolic form of an address if the
6907 offset between the closest earlier symbol and the address is less than
6908 @var{max-offset}. The default is 0, which tells @value{GDBN}
6909 to always print the symbolic form of an address if any symbol precedes it.
6911 @item show print max-symbolic-offset
6912 Ask how large the maximum offset is that @value{GDBN} prints in a
6916 @cindex wild pointer, interpreting
6917 @cindex pointer, finding referent
6918 If you have a pointer and you are not sure where it points, try
6919 @samp{set print symbol-filename on}. Then you can determine the name
6920 and source file location of the variable where it points, using
6921 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
6922 For example, here @value{GDBN} shows that a variable @code{ptt} points
6923 at another variable @code{t}, defined in @file{hi2.c}:
6926 (@value{GDBP}) set print symbol-filename on
6927 (@value{GDBP}) p/a ptt
6928 $4 = 0xe008 <t in hi2.c>
6932 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
6933 does not show the symbol name and filename of the referent, even with
6934 the appropriate @code{set print} options turned on.
6937 Other settings control how different kinds of objects are printed:
6940 @item set print array
6941 @itemx set print array on
6942 @cindex pretty print arrays
6943 Pretty print arrays. This format is more convenient to read,
6944 but uses more space. The default is off.
6946 @item set print array off
6947 Return to compressed format for arrays.
6949 @item show print array
6950 Show whether compressed or pretty format is selected for displaying
6953 @cindex print array indexes
6954 @item set print array-indexes
6955 @itemx set print array-indexes on
6956 Print the index of each element when displaying arrays. May be more
6957 convenient to locate a given element in the array or quickly find the
6958 index of a given element in that printed array. The default is off.
6960 @item set print array-indexes off
6961 Stop printing element indexes when displaying arrays.
6963 @item show print array-indexes
6964 Show whether the index of each element is printed when displaying
6967 @item set print elements @var{number-of-elements}
6968 @cindex number of array elements to print
6969 @cindex limit on number of printed array elements
6970 Set a limit on how many elements of an array @value{GDBN} will print.
6971 If @value{GDBN} is printing a large array, it stops printing after it has
6972 printed the number of elements set by the @code{set print elements} command.
6973 This limit also applies to the display of strings.
6974 When @value{GDBN} starts, this limit is set to 200.
6975 Setting @var{number-of-elements} to zero means that the printing is unlimited.
6977 @item show print elements
6978 Display the number of elements of a large array that @value{GDBN} will print.
6979 If the number is 0, then the printing is unlimited.
6981 @item set print frame-arguments @var{value}
6982 @kindex set print frame-arguments
6983 @cindex printing frame argument values
6984 @cindex print all frame argument values
6985 @cindex print frame argument values for scalars only
6986 @cindex do not print frame argument values
6987 This command allows to control how the values of arguments are printed
6988 when the debugger prints a frame (@pxref{Frames}). The possible
6993 The values of all arguments are printed.
6996 Print the value of an argument only if it is a scalar. The value of more
6997 complex arguments such as arrays, structures, unions, etc, is replaced
6998 by @code{@dots{}}. This is the default. Here is an example where
6999 only scalar arguments are shown:
7002 #1 0x08048361 in call_me (i=3, s=@dots{}, ss=0xbf8d508c, u=@dots{}, e=green)
7007 None of the argument values are printed. Instead, the value of each argument
7008 is replaced by @code{@dots{}}. In this case, the example above now becomes:
7011 #1 0x08048361 in call_me (i=@dots{}, s=@dots{}, ss=@dots{}, u=@dots{}, e=@dots{})
7016 By default, only scalar arguments are printed. This command can be used
7017 to configure the debugger to print the value of all arguments, regardless
7018 of their type. However, it is often advantageous to not print the value
7019 of more complex parameters. For instance, it reduces the amount of
7020 information printed in each frame, making the backtrace more readable.
7021 Also, it improves performance when displaying Ada frames, because
7022 the computation of large arguments can sometimes be CPU-intensive,
7023 especially in large applications. Setting @code{print frame-arguments}
7024 to @code{scalars} (the default) or @code{none} avoids this computation,
7025 thus speeding up the display of each Ada frame.
7027 @item show print frame-arguments
7028 Show how the value of arguments should be displayed when printing a frame.
7030 @item set print repeats
7031 @cindex repeated array elements
7032 Set the threshold for suppressing display of repeated array
7033 elements. When the number of consecutive identical elements of an
7034 array exceeds the threshold, @value{GDBN} prints the string
7035 @code{"<repeats @var{n} times>"}, where @var{n} is the number of
7036 identical repetitions, instead of displaying the identical elements
7037 themselves. Setting the threshold to zero will cause all elements to
7038 be individually printed. The default threshold is 10.
7040 @item show print repeats
7041 Display the current threshold for printing repeated identical
7044 @item set print null-stop
7045 @cindex @sc{null} elements in arrays
7046 Cause @value{GDBN} to stop printing the characters of an array when the first
7047 @sc{null} is encountered. This is useful when large arrays actually
7048 contain only short strings.
7051 @item show print null-stop
7052 Show whether @value{GDBN} stops printing an array on the first
7053 @sc{null} character.
7055 @item set print pretty on
7056 @cindex print structures in indented form
7057 @cindex indentation in structure display
7058 Cause @value{GDBN} to print structures in an indented format with one member
7059 per line, like this:
7074 @item set print pretty off
7075 Cause @value{GDBN} to print structures in a compact format, like this:
7079 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
7080 meat = 0x54 "Pork"@}
7085 This is the default format.
7087 @item show print pretty
7088 Show which format @value{GDBN} is using to print structures.
7090 @item set print sevenbit-strings on
7091 @cindex eight-bit characters in strings
7092 @cindex octal escapes in strings
7093 Print using only seven-bit characters; if this option is set,
7094 @value{GDBN} displays any eight-bit characters (in strings or
7095 character values) using the notation @code{\}@var{nnn}. This setting is
7096 best if you are working in English (@sc{ascii}) and you use the
7097 high-order bit of characters as a marker or ``meta'' bit.
7099 @item set print sevenbit-strings off
7100 Print full eight-bit characters. This allows the use of more
7101 international character sets, and is the default.
7103 @item show print sevenbit-strings
7104 Show whether or not @value{GDBN} is printing only seven-bit characters.
7106 @item set print union on
7107 @cindex unions in structures, printing
7108 Tell @value{GDBN} to print unions which are contained in structures
7109 and other unions. This is the default setting.
7111 @item set print union off
7112 Tell @value{GDBN} not to print unions which are contained in
7113 structures and other unions. @value{GDBN} will print @code{"@{...@}"}
7116 @item show print union
7117 Ask @value{GDBN} whether or not it will print unions which are contained in
7118 structures and other unions.
7120 For example, given the declarations
7123 typedef enum @{Tree, Bug@} Species;
7124 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
7125 typedef enum @{Caterpillar, Cocoon, Butterfly@}
7136 struct thing foo = @{Tree, @{Acorn@}@};
7140 with @code{set print union on} in effect @samp{p foo} would print
7143 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
7147 and with @code{set print union off} in effect it would print
7150 $1 = @{it = Tree, form = @{...@}@}
7154 @code{set print union} affects programs written in C-like languages
7160 These settings are of interest when debugging C@t{++} programs:
7163 @cindex demangling C@t{++} names
7164 @item set print demangle
7165 @itemx set print demangle on
7166 Print C@t{++} names in their source form rather than in the encoded
7167 (``mangled'') form passed to the assembler and linker for type-safe
7168 linkage. The default is on.
7170 @item show print demangle
7171 Show whether C@t{++} names are printed in mangled or demangled form.
7173 @item set print asm-demangle
7174 @itemx set print asm-demangle on
7175 Print C@t{++} names in their source form rather than their mangled form, even
7176 in assembler code printouts such as instruction disassemblies.
7179 @item show print asm-demangle
7180 Show whether C@t{++} names in assembly listings are printed in mangled
7183 @cindex C@t{++} symbol decoding style
7184 @cindex symbol decoding style, C@t{++}
7185 @kindex set demangle-style
7186 @item set demangle-style @var{style}
7187 Choose among several encoding schemes used by different compilers to
7188 represent C@t{++} names. The choices for @var{style} are currently:
7192 Allow @value{GDBN} to choose a decoding style by inspecting your program.
7195 Decode based on the @sc{gnu} C@t{++} compiler (@code{g++}) encoding algorithm.
7196 This is the default.
7199 Decode based on the HP ANSI C@t{++} (@code{aCC}) encoding algorithm.
7202 Decode based on the Lucid C@t{++} compiler (@code{lcc}) encoding algorithm.
7205 Decode using the algorithm in the @cite{C@t{++} Annotated Reference Manual}.
7206 @strong{Warning:} this setting alone is not sufficient to allow
7207 debugging @code{cfront}-generated executables. @value{GDBN} would
7208 require further enhancement to permit that.
7211 If you omit @var{style}, you will see a list of possible formats.
7213 @item show demangle-style
7214 Display the encoding style currently in use for decoding C@t{++} symbols.
7216 @item set print object
7217 @itemx set print object on
7218 @cindex derived type of an object, printing
7219 @cindex display derived types
7220 When displaying a pointer to an object, identify the @emph{actual}
7221 (derived) type of the object rather than the @emph{declared} type, using
7222 the virtual function table.
7224 @item set print object off
7225 Display only the declared type of objects, without reference to the
7226 virtual function table. This is the default setting.
7228 @item show print object
7229 Show whether actual, or declared, object types are displayed.
7231 @item set print static-members
7232 @itemx set print static-members on
7233 @cindex static members of C@t{++} objects
7234 Print static members when displaying a C@t{++} object. The default is on.
7236 @item set print static-members off
7237 Do not print static members when displaying a C@t{++} object.
7239 @item show print static-members
7240 Show whether C@t{++} static members are printed or not.
7242 @item set print pascal_static-members
7243 @itemx set print pascal_static-members on
7244 @cindex static members of Pascal objects
7245 @cindex Pascal objects, static members display
7246 Print static members when displaying a Pascal object. The default is on.
7248 @item set print pascal_static-members off
7249 Do not print static members when displaying a Pascal object.
7251 @item show print pascal_static-members
7252 Show whether Pascal static members are printed or not.
7254 @c These don't work with HP ANSI C++ yet.
7255 @item set print vtbl
7256 @itemx set print vtbl on
7257 @cindex pretty print C@t{++} virtual function tables
7258 @cindex virtual functions (C@t{++}) display
7259 @cindex VTBL display
7260 Pretty print C@t{++} virtual function tables. The default is off.
7261 (The @code{vtbl} commands do not work on programs compiled with the HP
7262 ANSI C@t{++} compiler (@code{aCC}).)
7264 @item set print vtbl off
7265 Do not pretty print C@t{++} virtual function tables.
7267 @item show print vtbl
7268 Show whether C@t{++} virtual function tables are pretty printed, or not.
7272 @section Value History
7274 @cindex value history
7275 @cindex history of values printed by @value{GDBN}
7276 Values printed by the @code{print} command are saved in the @value{GDBN}
7277 @dfn{value history}. This allows you to refer to them in other expressions.
7278 Values are kept until the symbol table is re-read or discarded
7279 (for example with the @code{file} or @code{symbol-file} commands).
7280 When the symbol table changes, the value history is discarded,
7281 since the values may contain pointers back to the types defined in the
7286 @cindex history number
7287 The values printed are given @dfn{history numbers} by which you can
7288 refer to them. These are successive integers starting with one.
7289 @code{print} shows you the history number assigned to a value by
7290 printing @samp{$@var{num} = } before the value; here @var{num} is the
7293 To refer to any previous value, use @samp{$} followed by the value's
7294 history number. The way @code{print} labels its output is designed to
7295 remind you of this. Just @code{$} refers to the most recent value in
7296 the history, and @code{$$} refers to the value before that.
7297 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
7298 is the value just prior to @code{$$}, @code{$$1} is equivalent to
7299 @code{$$}, and @code{$$0} is equivalent to @code{$}.
7301 For example, suppose you have just printed a pointer to a structure and
7302 want to see the contents of the structure. It suffices to type
7308 If you have a chain of structures where the component @code{next} points
7309 to the next one, you can print the contents of the next one with this:
7316 You can print successive links in the chain by repeating this
7317 command---which you can do by just typing @key{RET}.
7319 Note that the history records values, not expressions. If the value of
7320 @code{x} is 4 and you type these commands:
7328 then the value recorded in the value history by the @code{print} command
7329 remains 4 even though the value of @code{x} has changed.
7334 Print the last ten values in the value history, with their item numbers.
7335 This is like @samp{p@ $$9} repeated ten times, except that @code{show
7336 values} does not change the history.
7338 @item show values @var{n}
7339 Print ten history values centered on history item number @var{n}.
7342 Print ten history values just after the values last printed. If no more
7343 values are available, @code{show values +} produces no display.
7346 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
7347 same effect as @samp{show values +}.
7349 @node Convenience Vars
7350 @section Convenience Variables
7352 @cindex convenience variables
7353 @cindex user-defined variables
7354 @value{GDBN} provides @dfn{convenience variables} that you can use within
7355 @value{GDBN} to hold on to a value and refer to it later. These variables
7356 exist entirely within @value{GDBN}; they are not part of your program, and
7357 setting a convenience variable has no direct effect on further execution
7358 of your program. That is why you can use them freely.
7360 Convenience variables are prefixed with @samp{$}. Any name preceded by
7361 @samp{$} can be used for a convenience variable, unless it is one of
7362 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
7363 (Value history references, in contrast, are @emph{numbers} preceded
7364 by @samp{$}. @xref{Value History, ,Value History}.)
7366 You can save a value in a convenience variable with an assignment
7367 expression, just as you would set a variable in your program.
7371 set $foo = *object_ptr
7375 would save in @code{$foo} the value contained in the object pointed to by
7378 Using a convenience variable for the first time creates it, but its
7379 value is @code{void} until you assign a new value. You can alter the
7380 value with another assignment at any time.
7382 Convenience variables have no fixed types. You can assign a convenience
7383 variable any type of value, including structures and arrays, even if
7384 that variable already has a value of a different type. The convenience
7385 variable, when used as an expression, has the type of its current value.
7388 @kindex show convenience
7389 @cindex show all user variables
7390 @item show convenience
7391 Print a list of convenience variables used so far, and their values.
7392 Abbreviated @code{show conv}.
7394 @kindex init-if-undefined
7395 @cindex convenience variables, initializing
7396 @item init-if-undefined $@var{variable} = @var{expression}
7397 Set a convenience variable if it has not already been set. This is useful
7398 for user-defined commands that keep some state. It is similar, in concept,
7399 to using local static variables with initializers in C (except that
7400 convenience variables are global). It can also be used to allow users to
7401 override default values used in a command script.
7403 If the variable is already defined then the expression is not evaluated so
7404 any side-effects do not occur.
7407 One of the ways to use a convenience variable is as a counter to be
7408 incremented or a pointer to be advanced. For example, to print
7409 a field from successive elements of an array of structures:
7413 print bar[$i++]->contents
7417 Repeat that command by typing @key{RET}.
7419 Some convenience variables are created automatically by @value{GDBN} and given
7420 values likely to be useful.
7423 @vindex $_@r{, convenience variable}
7425 The variable @code{$_} is automatically set by the @code{x} command to
7426 the last address examined (@pxref{Memory, ,Examining Memory}). Other
7427 commands which provide a default address for @code{x} to examine also
7428 set @code{$_} to that address; these commands include @code{info line}
7429 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
7430 except when set by the @code{x} command, in which case it is a pointer
7431 to the type of @code{$__}.
7433 @vindex $__@r{, convenience variable}
7435 The variable @code{$__} is automatically set by the @code{x} command
7436 to the value found in the last address examined. Its type is chosen
7437 to match the format in which the data was printed.
7440 @vindex $_exitcode@r{, convenience variable}
7441 The variable @code{$_exitcode} is automatically set to the exit code when
7442 the program being debugged terminates.
7445 @vindex $_siginfo@r{, convenience variable}
7446 The variable @code{$_siginfo} is bound to extra signal information
7447 inspection (@pxref{extra signal information}).
7450 On HP-UX systems, if you refer to a function or variable name that
7451 begins with a dollar sign, @value{GDBN} searches for a user or system
7452 name first, before it searches for a convenience variable.
7454 @cindex convenience functions
7455 @value{GDBN} also supplies some @dfn{convenience functions}. These
7456 have a syntax similar to convenience variables. A convenience
7457 function can be used in an expression just like an ordinary function;
7458 however, a convenience function is implemented internally to
7463 @kindex help function
7464 @cindex show all convenience functions
7465 Print a list of all convenience functions.
7472 You can refer to machine register contents, in expressions, as variables
7473 with names starting with @samp{$}. The names of registers are different
7474 for each machine; use @code{info registers} to see the names used on
7478 @kindex info registers
7479 @item info registers
7480 Print the names and values of all registers except floating-point
7481 and vector registers (in the selected stack frame).
7483 @kindex info all-registers
7484 @cindex floating point registers
7485 @item info all-registers
7486 Print the names and values of all registers, including floating-point
7487 and vector registers (in the selected stack frame).
7489 @item info registers @var{regname} @dots{}
7490 Print the @dfn{relativized} value of each specified register @var{regname}.
7491 As discussed in detail below, register values are normally relative to
7492 the selected stack frame. @var{regname} may be any register name valid on
7493 the machine you are using, with or without the initial @samp{$}.
7496 @cindex stack pointer register
7497 @cindex program counter register
7498 @cindex process status register
7499 @cindex frame pointer register
7500 @cindex standard registers
7501 @value{GDBN} has four ``standard'' register names that are available (in
7502 expressions) on most machines---whenever they do not conflict with an
7503 architecture's canonical mnemonics for registers. The register names
7504 @code{$pc} and @code{$sp} are used for the program counter register and
7505 the stack pointer. @code{$fp} is used for a register that contains a
7506 pointer to the current stack frame, and @code{$ps} is used for a
7507 register that contains the processor status. For example,
7508 you could print the program counter in hex with
7515 or print the instruction to be executed next with
7522 or add four to the stack pointer@footnote{This is a way of removing
7523 one word from the stack, on machines where stacks grow downward in
7524 memory (most machines, nowadays). This assumes that the innermost
7525 stack frame is selected; setting @code{$sp} is not allowed when other
7526 stack frames are selected. To pop entire frames off the stack,
7527 regardless of machine architecture, use @code{return};
7528 see @ref{Returning, ,Returning from a Function}.} with
7534 Whenever possible, these four standard register names are available on
7535 your machine even though the machine has different canonical mnemonics,
7536 so long as there is no conflict. The @code{info registers} command
7537 shows the canonical names. For example, on the SPARC, @code{info
7538 registers} displays the processor status register as @code{$psr} but you
7539 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
7540 is an alias for the @sc{eflags} register.
7542 @value{GDBN} always considers the contents of an ordinary register as an
7543 integer when the register is examined in this way. Some machines have
7544 special registers which can hold nothing but floating point; these
7545 registers are considered to have floating point values. There is no way
7546 to refer to the contents of an ordinary register as floating point value
7547 (although you can @emph{print} it as a floating point value with
7548 @samp{print/f $@var{regname}}).
7550 Some registers have distinct ``raw'' and ``virtual'' data formats. This
7551 means that the data format in which the register contents are saved by
7552 the operating system is not the same one that your program normally
7553 sees. For example, the registers of the 68881 floating point
7554 coprocessor are always saved in ``extended'' (raw) format, but all C
7555 programs expect to work with ``double'' (virtual) format. In such
7556 cases, @value{GDBN} normally works with the virtual format only (the format
7557 that makes sense for your program), but the @code{info registers} command
7558 prints the data in both formats.
7560 @cindex SSE registers (x86)
7561 @cindex MMX registers (x86)
7562 Some machines have special registers whose contents can be interpreted
7563 in several different ways. For example, modern x86-based machines
7564 have SSE and MMX registers that can hold several values packed
7565 together in several different formats. @value{GDBN} refers to such
7566 registers in @code{struct} notation:
7569 (@value{GDBP}) print $xmm1
7571 v4_float = @{0, 3.43859137e-038, 1.54142831e-044, 1.821688e-044@},
7572 v2_double = @{9.92129282474342e-303, 2.7585945287983262e-313@},
7573 v16_int8 = "\000\000\000\000\3706;\001\v\000\000\000\r\000\000",
7574 v8_int16 = @{0, 0, 14072, 315, 11, 0, 13, 0@},
7575 v4_int32 = @{0, 20657912, 11, 13@},
7576 v2_int64 = @{88725056443645952, 55834574859@},
7577 uint128 = 0x0000000d0000000b013b36f800000000
7582 To set values of such registers, you need to tell @value{GDBN} which
7583 view of the register you wish to change, as if you were assigning
7584 value to a @code{struct} member:
7587 (@value{GDBP}) set $xmm1.uint128 = 0x000000000000000000000000FFFFFFFF
7590 Normally, register values are relative to the selected stack frame
7591 (@pxref{Selection, ,Selecting a Frame}). This means that you get the
7592 value that the register would contain if all stack frames farther in
7593 were exited and their saved registers restored. In order to see the
7594 true contents of hardware registers, you must select the innermost
7595 frame (with @samp{frame 0}).
7597 However, @value{GDBN} must deduce where registers are saved, from the machine
7598 code generated by your compiler. If some registers are not saved, or if
7599 @value{GDBN} is unable to locate the saved registers, the selected stack
7600 frame makes no difference.
7602 @node Floating Point Hardware
7603 @section Floating Point Hardware
7604 @cindex floating point
7606 Depending on the configuration, @value{GDBN} may be able to give
7607 you more information about the status of the floating point hardware.
7612 Display hardware-dependent information about the floating
7613 point unit. The exact contents and layout vary depending on the
7614 floating point chip. Currently, @samp{info float} is supported on
7615 the ARM and x86 machines.
7619 @section Vector Unit
7622 Depending on the configuration, @value{GDBN} may be able to give you
7623 more information about the status of the vector unit.
7628 Display information about the vector unit. The exact contents and
7629 layout vary depending on the hardware.
7632 @node OS Information
7633 @section Operating System Auxiliary Information
7634 @cindex OS information
7636 @value{GDBN} provides interfaces to useful OS facilities that can help
7637 you debug your program.
7639 @cindex @code{ptrace} system call
7640 @cindex @code{struct user} contents
7641 When @value{GDBN} runs on a @dfn{Posix system} (such as GNU or Unix
7642 machines), it interfaces with the inferior via the @code{ptrace}
7643 system call. The operating system creates a special sata structure,
7644 called @code{struct user}, for this interface. You can use the
7645 command @code{info udot} to display the contents of this data
7651 Display the contents of the @code{struct user} maintained by the OS
7652 kernel for the program being debugged. @value{GDBN} displays the
7653 contents of @code{struct user} as a list of hex numbers, similar to
7654 the @code{examine} command.
7657 @cindex auxiliary vector
7658 @cindex vector, auxiliary
7659 Some operating systems supply an @dfn{auxiliary vector} to programs at
7660 startup. This is akin to the arguments and environment that you
7661 specify for a program, but contains a system-dependent variety of
7662 binary values that tell system libraries important details about the
7663 hardware, operating system, and process. Each value's purpose is
7664 identified by an integer tag; the meanings are well-known but system-specific.
7665 Depending on the configuration and operating system facilities,
7666 @value{GDBN} may be able to show you this information. For remote
7667 targets, this functionality may further depend on the remote stub's
7668 support of the @samp{qXfer:auxv:read} packet, see
7669 @ref{qXfer auxiliary vector read}.
7674 Display the auxiliary vector of the inferior, which can be either a
7675 live process or a core dump file. @value{GDBN} prints each tag value
7676 numerically, and also shows names and text descriptions for recognized
7677 tags. Some values in the vector are numbers, some bit masks, and some
7678 pointers to strings or other data. @value{GDBN} displays each value in the
7679 most appropriate form for a recognized tag, and in hexadecimal for
7680 an unrecognized tag.
7683 On some targets, @value{GDBN} can access operating-system-specific information
7684 and display it to user, without interpretation. For remote targets,
7685 this functionality depends on the remote stub's support of the
7686 @samp{qXfer:osdata:read} packet, see @ref{qXfer osdata read}.
7689 @kindex info os processes
7690 @item info os processes
7691 Display the list of processes on the target. For each process,
7692 @value{GDBN} prints the process identifier, the name of the user, and
7693 the command corresponding to the process.
7696 @node Memory Region Attributes
7697 @section Memory Region Attributes
7698 @cindex memory region attributes
7700 @dfn{Memory region attributes} allow you to describe special handling
7701 required by regions of your target's memory. @value{GDBN} uses
7702 attributes to determine whether to allow certain types of memory
7703 accesses; whether to use specific width accesses; and whether to cache
7704 target memory. By default the description of memory regions is
7705 fetched from the target (if the current target supports this), but the
7706 user can override the fetched regions.
7708 Defined memory regions can be individually enabled and disabled. When a
7709 memory region is disabled, @value{GDBN} uses the default attributes when
7710 accessing memory in that region. Similarly, if no memory regions have
7711 been defined, @value{GDBN} uses the default attributes when accessing
7714 When a memory region is defined, it is given a number to identify it;
7715 to enable, disable, or remove a memory region, you specify that number.
7719 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
7720 Define a memory region bounded by @var{lower} and @var{upper} with
7721 attributes @var{attributes}@dots{}, and add it to the list of regions
7722 monitored by @value{GDBN}. Note that @var{upper} == 0 is a special
7723 case: it is treated as the target's maximum memory address.
7724 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
7727 Discard any user changes to the memory regions and use target-supplied
7728 regions, if available, or no regions if the target does not support.
7731 @item delete mem @var{nums}@dots{}
7732 Remove memory regions @var{nums}@dots{} from the list of regions
7733 monitored by @value{GDBN}.
7736 @item disable mem @var{nums}@dots{}
7737 Disable monitoring of memory regions @var{nums}@dots{}.
7738 A disabled memory region is not forgotten.
7739 It may be enabled again later.
7742 @item enable mem @var{nums}@dots{}
7743 Enable monitoring of memory regions @var{nums}@dots{}.
7747 Print a table of all defined memory regions, with the following columns
7751 @item Memory Region Number
7752 @item Enabled or Disabled.
7753 Enabled memory regions are marked with @samp{y}.
7754 Disabled memory regions are marked with @samp{n}.
7757 The address defining the inclusive lower bound of the memory region.
7760 The address defining the exclusive upper bound of the memory region.
7763 The list of attributes set for this memory region.
7768 @subsection Attributes
7770 @subsubsection Memory Access Mode
7771 The access mode attributes set whether @value{GDBN} may make read or
7772 write accesses to a memory region.
7774 While these attributes prevent @value{GDBN} from performing invalid
7775 memory accesses, they do nothing to prevent the target system, I/O DMA,
7776 etc.@: from accessing memory.
7780 Memory is read only.
7782 Memory is write only.
7784 Memory is read/write. This is the default.
7787 @subsubsection Memory Access Size
7788 The access size attribute tells @value{GDBN} to use specific sized
7789 accesses in the memory region. Often memory mapped device registers
7790 require specific sized accesses. If no access size attribute is
7791 specified, @value{GDBN} may use accesses of any size.
7795 Use 8 bit memory accesses.
7797 Use 16 bit memory accesses.
7799 Use 32 bit memory accesses.
7801 Use 64 bit memory accesses.
7804 @c @subsubsection Hardware/Software Breakpoints
7805 @c The hardware/software breakpoint attributes set whether @value{GDBN}
7806 @c will use hardware or software breakpoints for the internal breakpoints
7807 @c used by the step, next, finish, until, etc. commands.
7811 @c Always use hardware breakpoints
7812 @c @item swbreak (default)
7815 @subsubsection Data Cache
7816 The data cache attributes set whether @value{GDBN} will cache target
7817 memory. While this generally improves performance by reducing debug
7818 protocol overhead, it can lead to incorrect results because @value{GDBN}
7819 does not know about volatile variables or memory mapped device
7824 Enable @value{GDBN} to cache target memory.
7826 Disable @value{GDBN} from caching target memory. This is the default.
7829 @subsection Memory Access Checking
7830 @value{GDBN} can be instructed to refuse accesses to memory that is
7831 not explicitly described. This can be useful if accessing such
7832 regions has undesired effects for a specific target, or to provide
7833 better error checking. The following commands control this behaviour.
7836 @kindex set mem inaccessible-by-default
7837 @item set mem inaccessible-by-default [on|off]
7838 If @code{on} is specified, make @value{GDBN} treat memory not
7839 explicitly described by the memory ranges as non-existent and refuse accesses
7840 to such memory. The checks are only performed if there's at least one
7841 memory range defined. If @code{off} is specified, make @value{GDBN}
7842 treat the memory not explicitly described by the memory ranges as RAM.
7843 The default value is @code{on}.
7844 @kindex show mem inaccessible-by-default
7845 @item show mem inaccessible-by-default
7846 Show the current handling of accesses to unknown memory.
7850 @c @subsubsection Memory Write Verification
7851 @c The memory write verification attributes set whether @value{GDBN}
7852 @c will re-reads data after each write to verify the write was successful.
7856 @c @item noverify (default)
7859 @node Dump/Restore Files
7860 @section Copy Between Memory and a File
7861 @cindex dump/restore files
7862 @cindex append data to a file
7863 @cindex dump data to a file
7864 @cindex restore data from a file
7866 You can use the commands @code{dump}, @code{append}, and
7867 @code{restore} to copy data between target memory and a file. The
7868 @code{dump} and @code{append} commands write data to a file, and the
7869 @code{restore} command reads data from a file back into the inferior's
7870 memory. Files may be in binary, Motorola S-record, Intel hex, or
7871 Tektronix Hex format; however, @value{GDBN} can only append to binary
7877 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
7878 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
7879 Dump the contents of memory from @var{start_addr} to @var{end_addr},
7880 or the value of @var{expr}, to @var{filename} in the given format.
7882 The @var{format} parameter may be any one of:
7889 Motorola S-record format.
7891 Tektronix Hex format.
7894 @value{GDBN} uses the same definitions of these formats as the
7895 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
7896 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
7900 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
7901 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
7902 Append the contents of memory from @var{start_addr} to @var{end_addr},
7903 or the value of @var{expr}, to the file @var{filename}, in raw binary form.
7904 (@value{GDBN} can only append data to files in raw binary form.)
7907 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
7908 Restore the contents of file @var{filename} into memory. The
7909 @code{restore} command can automatically recognize any known @sc{bfd}
7910 file format, except for raw binary. To restore a raw binary file you
7911 must specify the optional keyword @code{binary} after the filename.
7913 If @var{bias} is non-zero, its value will be added to the addresses
7914 contained in the file. Binary files always start at address zero, so
7915 they will be restored at address @var{bias}. Other bfd files have
7916 a built-in location; they will be restored at offset @var{bias}
7919 If @var{start} and/or @var{end} are non-zero, then only data between
7920 file offset @var{start} and file offset @var{end} will be restored.
7921 These offsets are relative to the addresses in the file, before
7922 the @var{bias} argument is applied.
7926 @node Core File Generation
7927 @section How to Produce a Core File from Your Program
7928 @cindex dump core from inferior
7930 A @dfn{core file} or @dfn{core dump} is a file that records the memory
7931 image of a running process and its process status (register values
7932 etc.). Its primary use is post-mortem debugging of a program that
7933 crashed while it ran outside a debugger. A program that crashes
7934 automatically produces a core file, unless this feature is disabled by
7935 the user. @xref{Files}, for information on invoking @value{GDBN} in
7936 the post-mortem debugging mode.
7938 Occasionally, you may wish to produce a core file of the program you
7939 are debugging in order to preserve a snapshot of its state.
7940 @value{GDBN} has a special command for that.
7944 @kindex generate-core-file
7945 @item generate-core-file [@var{file}]
7946 @itemx gcore [@var{file}]
7947 Produce a core dump of the inferior process. The optional argument
7948 @var{file} specifies the file name where to put the core dump. If not
7949 specified, the file name defaults to @file{core.@var{pid}}, where
7950 @var{pid} is the inferior process ID.
7952 Note that this command is implemented only for some systems (as of
7953 this writing, @sc{gnu}/Linux, FreeBSD, Solaris, Unixware, and S390).
7956 @node Character Sets
7957 @section Character Sets
7958 @cindex character sets
7960 @cindex translating between character sets
7961 @cindex host character set
7962 @cindex target character set
7964 If the program you are debugging uses a different character set to
7965 represent characters and strings than the one @value{GDBN} uses itself,
7966 @value{GDBN} can automatically translate between the character sets for
7967 you. The character set @value{GDBN} uses we call the @dfn{host
7968 character set}; the one the inferior program uses we call the
7969 @dfn{target character set}.
7971 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
7972 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
7973 remote protocol (@pxref{Remote Debugging}) to debug a program
7974 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
7975 then the host character set is Latin-1, and the target character set is
7976 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
7977 target-charset EBCDIC-US}, then @value{GDBN} translates between
7978 @sc{ebcdic} and Latin 1 as you print character or string values, or use
7979 character and string literals in expressions.
7981 @value{GDBN} has no way to automatically recognize which character set
7982 the inferior program uses; you must tell it, using the @code{set
7983 target-charset} command, described below.
7985 Here are the commands for controlling @value{GDBN}'s character set
7989 @item set target-charset @var{charset}
7990 @kindex set target-charset
7991 Set the current target character set to @var{charset}. To display the
7992 list of supported target character sets, type
7993 @kbd{@w{set target-charset @key{TAB}@key{TAB}}}.
7995 @item set host-charset @var{charset}
7996 @kindex set host-charset
7997 Set the current host character set to @var{charset}.
7999 By default, @value{GDBN} uses a host character set appropriate to the
8000 system it is running on; you can override that default using the
8001 @code{set host-charset} command. On some systems, @value{GDBN} cannot
8002 automatically determine the appropriate host character set. In this
8003 case, @value{GDBN} uses @samp{UTF-8}.
8005 @value{GDBN} can only use certain character sets as its host character
8006 set. If you type @kbd{@w{set target-charset @key{TAB}@key{TAB}}},
8007 @value{GDBN} will list the host character sets it supports.
8009 @item set charset @var{charset}
8011 Set the current host and target character sets to @var{charset}. As
8012 above, if you type @kbd{@w{set charset @key{TAB}@key{TAB}}},
8013 @value{GDBN} will list the names of the character sets that can be used
8014 for both host and target.
8017 @kindex show charset
8018 Show the names of the current host and target character sets.
8020 @item show host-charset
8021 @kindex show host-charset
8022 Show the name of the current host character set.
8024 @item show target-charset
8025 @kindex show target-charset
8026 Show the name of the current target character set.
8028 @item set target-wide-charset @var{charset}
8029 @kindex set target-wide-charset
8030 Set the current target's wide character set to @var{charset}. This is
8031 the character set used by the target's @code{wchar_t} type. To
8032 display the list of supported wide character sets, type
8033 @kbd{@w{set target-wide-charset @key{TAB}@key{TAB}}}.
8035 @item show target-wide-charset
8036 @kindex show target-wide-charset
8037 Show the name of the current target's wide character set.
8040 Here is an example of @value{GDBN}'s character set support in action.
8041 Assume that the following source code has been placed in the file
8042 @file{charset-test.c}:
8048 = @{72, 101, 108, 108, 111, 44, 32, 119,
8049 111, 114, 108, 100, 33, 10, 0@};
8050 char ibm1047_hello[]
8051 = @{200, 133, 147, 147, 150, 107, 64, 166,
8052 150, 153, 147, 132, 90, 37, 0@};
8056 printf ("Hello, world!\n");
8060 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
8061 containing the string @samp{Hello, world!} followed by a newline,
8062 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
8064 We compile the program, and invoke the debugger on it:
8067 $ gcc -g charset-test.c -o charset-test
8068 $ gdb -nw charset-test
8069 GNU gdb 2001-12-19-cvs
8070 Copyright 2001 Free Software Foundation, Inc.
8075 We can use the @code{show charset} command to see what character sets
8076 @value{GDBN} is currently using to interpret and display characters and
8080 (@value{GDBP}) show charset
8081 The current host and target character set is `ISO-8859-1'.
8085 For the sake of printing this manual, let's use @sc{ascii} as our
8086 initial character set:
8088 (@value{GDBP}) set charset ASCII
8089 (@value{GDBP}) show charset
8090 The current host and target character set is `ASCII'.
8094 Let's assume that @sc{ascii} is indeed the correct character set for our
8095 host system --- in other words, let's assume that if @value{GDBN} prints
8096 characters using the @sc{ascii} character set, our terminal will display
8097 them properly. Since our current target character set is also
8098 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
8101 (@value{GDBP}) print ascii_hello
8102 $1 = 0x401698 "Hello, world!\n"
8103 (@value{GDBP}) print ascii_hello[0]
8108 @value{GDBN} uses the target character set for character and string
8109 literals you use in expressions:
8112 (@value{GDBP}) print '+'
8117 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
8120 @value{GDBN} relies on the user to tell it which character set the
8121 target program uses. If we print @code{ibm1047_hello} while our target
8122 character set is still @sc{ascii}, we get jibberish:
8125 (@value{GDBP}) print ibm1047_hello
8126 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
8127 (@value{GDBP}) print ibm1047_hello[0]
8132 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
8133 @value{GDBN} tells us the character sets it supports:
8136 (@value{GDBP}) set target-charset
8137 ASCII EBCDIC-US IBM1047 ISO-8859-1
8138 (@value{GDBP}) set target-charset
8141 We can select @sc{ibm1047} as our target character set, and examine the
8142 program's strings again. Now the @sc{ascii} string is wrong, but
8143 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
8144 target character set, @sc{ibm1047}, to the host character set,
8145 @sc{ascii}, and they display correctly:
8148 (@value{GDBP}) set target-charset IBM1047
8149 (@value{GDBP}) show charset
8150 The current host character set is `ASCII'.
8151 The current target character set is `IBM1047'.
8152 (@value{GDBP}) print ascii_hello
8153 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
8154 (@value{GDBP}) print ascii_hello[0]
8156 (@value{GDBP}) print ibm1047_hello
8157 $8 = 0x4016a8 "Hello, world!\n"
8158 (@value{GDBP}) print ibm1047_hello[0]
8163 As above, @value{GDBN} uses the target character set for character and
8164 string literals you use in expressions:
8167 (@value{GDBP}) print '+'
8172 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
8175 @node Caching Remote Data
8176 @section Caching Data of Remote Targets
8177 @cindex caching data of remote targets
8179 @value{GDBN} can cache data exchanged between the debugger and a
8180 remote target (@pxref{Remote Debugging}). Such caching generally improves
8181 performance, because it reduces the overhead of the remote protocol by
8182 bundling memory reads and writes into large chunks. Unfortunately,
8183 @value{GDBN} does not currently know anything about volatile
8184 registers, and thus data caching will produce incorrect results when
8185 volatile registers are in use.
8188 @kindex set remotecache
8189 @item set remotecache on
8190 @itemx set remotecache off
8191 Set caching state for remote targets. When @code{ON}, use data
8192 caching. By default, this option is @code{OFF}.
8194 @kindex show remotecache
8195 @item show remotecache
8196 Show the current state of data caching for remote targets.
8200 Print the information about the data cache performance. The
8201 information displayed includes: the dcache width and depth; and for
8202 each cache line, how many times it was referenced, and its data and
8203 state (invalid, dirty, valid). This command is useful for debugging
8204 the data cache operation.
8207 @node Searching Memory
8208 @section Search Memory
8209 @cindex searching memory
8211 Memory can be searched for a particular sequence of bytes with the
8212 @code{find} command.
8216 @item find @r{[}/@var{sn}@r{]} @var{start_addr}, +@var{len}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
8217 @itemx find @r{[}/@var{sn}@r{]} @var{start_addr}, @var{end_addr}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
8218 Search memory for the sequence of bytes specified by @var{val1}, @var{val2},
8219 etc. The search begins at address @var{start_addr} and continues for either
8220 @var{len} bytes or through to @var{end_addr} inclusive.
8223 @var{s} and @var{n} are optional parameters.
8224 They may be specified in either order, apart or together.
8227 @item @var{s}, search query size
8228 The size of each search query value.
8234 halfwords (two bytes)
8238 giant words (eight bytes)
8241 All values are interpreted in the current language.
8242 This means, for example, that if the current source language is C/C@t{++}
8243 then searching for the string ``hello'' includes the trailing '\0'.
8245 If the value size is not specified, it is taken from the
8246 value's type in the current language.
8247 This is useful when one wants to specify the search
8248 pattern as a mixture of types.
8249 Note that this means, for example, that in the case of C-like languages
8250 a search for an untyped 0x42 will search for @samp{(int) 0x42}
8251 which is typically four bytes.
8253 @item @var{n}, maximum number of finds
8254 The maximum number of matches to print. The default is to print all finds.
8257 You can use strings as search values. Quote them with double-quotes
8259 The string value is copied into the search pattern byte by byte,
8260 regardless of the endianness of the target and the size specification.
8262 The address of each match found is printed as well as a count of the
8263 number of matches found.
8265 The address of the last value found is stored in convenience variable
8267 A count of the number of matches is stored in @samp{$numfound}.
8269 For example, if stopped at the @code{printf} in this function:
8275 static char hello[] = "hello-hello";
8276 static struct @{ char c; short s; int i; @}
8277 __attribute__ ((packed)) mixed
8278 = @{ 'c', 0x1234, 0x87654321 @};
8279 printf ("%s\n", hello);
8284 you get during debugging:
8287 (gdb) find &hello[0], +sizeof(hello), "hello"
8288 0x804956d <hello.1620+6>
8290 (gdb) find &hello[0], +sizeof(hello), 'h', 'e', 'l', 'l', 'o'
8291 0x8049567 <hello.1620>
8292 0x804956d <hello.1620+6>
8294 (gdb) find /b1 &hello[0], +sizeof(hello), 'h', 0x65, 'l'
8295 0x8049567 <hello.1620>
8297 (gdb) find &mixed, +sizeof(mixed), (char) 'c', (short) 0x1234, (int) 0x87654321
8298 0x8049560 <mixed.1625>
8300 (gdb) print $numfound
8303 $2 = (void *) 0x8049560
8307 @chapter C Preprocessor Macros
8309 Some languages, such as C and C@t{++}, provide a way to define and invoke
8310 ``preprocessor macros'' which expand into strings of tokens.
8311 @value{GDBN} can evaluate expressions containing macro invocations, show
8312 the result of macro expansion, and show a macro's definition, including
8313 where it was defined.
8315 You may need to compile your program specially to provide @value{GDBN}
8316 with information about preprocessor macros. Most compilers do not
8317 include macros in their debugging information, even when you compile
8318 with the @option{-g} flag. @xref{Compilation}.
8320 A program may define a macro at one point, remove that definition later,
8321 and then provide a different definition after that. Thus, at different
8322 points in the program, a macro may have different definitions, or have
8323 no definition at all. If there is a current stack frame, @value{GDBN}
8324 uses the macros in scope at that frame's source code line. Otherwise,
8325 @value{GDBN} uses the macros in scope at the current listing location;
8328 Whenever @value{GDBN} evaluates an expression, it always expands any
8329 macro invocations present in the expression. @value{GDBN} also provides
8330 the following commands for working with macros explicitly.
8334 @kindex macro expand
8335 @cindex macro expansion, showing the results of preprocessor
8336 @cindex preprocessor macro expansion, showing the results of
8337 @cindex expanding preprocessor macros
8338 @item macro expand @var{expression}
8339 @itemx macro exp @var{expression}
8340 Show the results of expanding all preprocessor macro invocations in
8341 @var{expression}. Since @value{GDBN} simply expands macros, but does
8342 not parse the result, @var{expression} need not be a valid expression;
8343 it can be any string of tokens.
8346 @item macro expand-once @var{expression}
8347 @itemx macro exp1 @var{expression}
8348 @cindex expand macro once
8349 @i{(This command is not yet implemented.)} Show the results of
8350 expanding those preprocessor macro invocations that appear explicitly in
8351 @var{expression}. Macro invocations appearing in that expansion are
8352 left unchanged. This command allows you to see the effect of a
8353 particular macro more clearly, without being confused by further
8354 expansions. Since @value{GDBN} simply expands macros, but does not
8355 parse the result, @var{expression} need not be a valid expression; it
8356 can be any string of tokens.
8359 @cindex macro definition, showing
8360 @cindex definition, showing a macro's
8361 @item info macro @var{macro}
8362 Show the definition of the macro named @var{macro}, and describe the
8363 source location where that definition was established.
8365 @kindex macro define
8366 @cindex user-defined macros
8367 @cindex defining macros interactively
8368 @cindex macros, user-defined
8369 @item macro define @var{macro} @var{replacement-list}
8370 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
8371 Introduce a definition for a preprocessor macro named @var{macro},
8372 invocations of which are replaced by the tokens given in
8373 @var{replacement-list}. The first form of this command defines an
8374 ``object-like'' macro, which takes no arguments; the second form
8375 defines a ``function-like'' macro, which takes the arguments given in
8378 A definition introduced by this command is in scope in every
8379 expression evaluated in @value{GDBN}, until it is removed with the
8380 @code{macro undef} command, described below. The definition overrides
8381 all definitions for @var{macro} present in the program being debugged,
8382 as well as any previous user-supplied definition.
8385 @item macro undef @var{macro}
8386 Remove any user-supplied definition for the macro named @var{macro}.
8387 This command only affects definitions provided with the @code{macro
8388 define} command, described above; it cannot remove definitions present
8389 in the program being debugged.
8393 List all the macros defined using the @code{macro define} command.
8396 @cindex macros, example of debugging with
8397 Here is a transcript showing the above commands in action. First, we
8398 show our source files:
8406 #define ADD(x) (M + x)
8411 printf ("Hello, world!\n");
8413 printf ("We're so creative.\n");
8415 printf ("Goodbye, world!\n");
8422 Now, we compile the program using the @sc{gnu} C compiler, @value{NGCC}.
8423 We pass the @option{-gdwarf-2} and @option{-g3} flags to ensure the
8424 compiler includes information about preprocessor macros in the debugging
8428 $ gcc -gdwarf-2 -g3 sample.c -o sample
8432 Now, we start @value{GDBN} on our sample program:
8436 GNU gdb 2002-05-06-cvs
8437 Copyright 2002 Free Software Foundation, Inc.
8438 GDB is free software, @dots{}
8442 We can expand macros and examine their definitions, even when the
8443 program is not running. @value{GDBN} uses the current listing position
8444 to decide which macro definitions are in scope:
8447 (@value{GDBP}) list main
8450 5 #define ADD(x) (M + x)
8455 10 printf ("Hello, world!\n");
8457 12 printf ("We're so creative.\n");
8458 (@value{GDBP}) info macro ADD
8459 Defined at /home/jimb/gdb/macros/play/sample.c:5
8460 #define ADD(x) (M + x)
8461 (@value{GDBP}) info macro Q
8462 Defined at /home/jimb/gdb/macros/play/sample.h:1
8463 included at /home/jimb/gdb/macros/play/sample.c:2
8465 (@value{GDBP}) macro expand ADD(1)
8466 expands to: (42 + 1)
8467 (@value{GDBP}) macro expand-once ADD(1)
8468 expands to: once (M + 1)
8472 In the example above, note that @code{macro expand-once} expands only
8473 the macro invocation explicit in the original text --- the invocation of
8474 @code{ADD} --- but does not expand the invocation of the macro @code{M},
8475 which was introduced by @code{ADD}.
8477 Once the program is running, @value{GDBN} uses the macro definitions in
8478 force at the source line of the current stack frame:
8481 (@value{GDBP}) break main
8482 Breakpoint 1 at 0x8048370: file sample.c, line 10.
8484 Starting program: /home/jimb/gdb/macros/play/sample
8486 Breakpoint 1, main () at sample.c:10
8487 10 printf ("Hello, world!\n");
8491 At line 10, the definition of the macro @code{N} at line 9 is in force:
8494 (@value{GDBP}) info macro N
8495 Defined at /home/jimb/gdb/macros/play/sample.c:9
8497 (@value{GDBP}) macro expand N Q M
8499 (@value{GDBP}) print N Q M
8504 As we step over directives that remove @code{N}'s definition, and then
8505 give it a new definition, @value{GDBN} finds the definition (or lack
8506 thereof) in force at each point:
8511 12 printf ("We're so creative.\n");
8512 (@value{GDBP}) info macro N
8513 The symbol `N' has no definition as a C/C++ preprocessor macro
8514 at /home/jimb/gdb/macros/play/sample.c:12
8517 14 printf ("Goodbye, world!\n");
8518 (@value{GDBP}) info macro N
8519 Defined at /home/jimb/gdb/macros/play/sample.c:13
8521 (@value{GDBP}) macro expand N Q M
8522 expands to: 1729 < 42
8523 (@value{GDBP}) print N Q M
8530 @chapter Tracepoints
8531 @c This chapter is based on the documentation written by Michael
8532 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
8535 In some applications, it is not feasible for the debugger to interrupt
8536 the program's execution long enough for the developer to learn
8537 anything helpful about its behavior. If the program's correctness
8538 depends on its real-time behavior, delays introduced by a debugger
8539 might cause the program to change its behavior drastically, or perhaps
8540 fail, even when the code itself is correct. It is useful to be able
8541 to observe the program's behavior without interrupting it.
8543 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
8544 specify locations in the program, called @dfn{tracepoints}, and
8545 arbitrary expressions to evaluate when those tracepoints are reached.
8546 Later, using the @code{tfind} command, you can examine the values
8547 those expressions had when the program hit the tracepoints. The
8548 expressions may also denote objects in memory---structures or arrays,
8549 for example---whose values @value{GDBN} should record; while visiting
8550 a particular tracepoint, you may inspect those objects as if they were
8551 in memory at that moment. However, because @value{GDBN} records these
8552 values without interacting with you, it can do so quickly and
8553 unobtrusively, hopefully not disturbing the program's behavior.
8555 The tracepoint facility is currently available only for remote
8556 targets. @xref{Targets}. In addition, your remote target must know
8557 how to collect trace data. This functionality is implemented in the
8558 remote stub; however, none of the stubs distributed with @value{GDBN}
8559 support tracepoints as of this writing. The format of the remote
8560 packets used to implement tracepoints are described in @ref{Tracepoint
8563 This chapter describes the tracepoint commands and features.
8567 * Analyze Collected Data::
8568 * Tracepoint Variables::
8571 @node Set Tracepoints
8572 @section Commands to Set Tracepoints
8574 Before running such a @dfn{trace experiment}, an arbitrary number of
8575 tracepoints can be set. A tracepoint is actually a special type of
8576 breakpoint (@pxref{Set Breaks}), so you can manipulate it using
8577 standard breakpoint commands. For instance, as with breakpoints,
8578 tracepoint numbers are successive integers starting from one, and many
8579 of the commands associated with tracepoints take the tracepoint number
8580 as their argument, to identify which tracepoint to work on.
8582 For each tracepoint, you can specify, in advance, some arbitrary set
8583 of data that you want the target to collect in the trace buffer when
8584 it hits that tracepoint. The collected data can include registers,
8585 local variables, or global data. Later, you can use @value{GDBN}
8586 commands to examine the values these data had at the time the
8589 Tracepoints do not support every breakpoint feature. Conditional
8590 expressions and ignore counts on tracepoints have no effect, and
8591 tracepoints cannot run @value{GDBN} commands when they are
8592 hit. Tracepoints may not be thread-specific either.
8594 This section describes commands to set tracepoints and associated
8595 conditions and actions.
8598 * Create and Delete Tracepoints::
8599 * Enable and Disable Tracepoints::
8600 * Tracepoint Passcounts::
8601 * Tracepoint Actions::
8602 * Listing Tracepoints::
8603 * Starting and Stopping Trace Experiments::
8606 @node Create and Delete Tracepoints
8607 @subsection Create and Delete Tracepoints
8610 @cindex set tracepoint
8612 @item trace @var{location}
8613 The @code{trace} command is very similar to the @code{break} command.
8614 Its argument @var{location} can be a source line, a function name, or
8615 an address in the target program. @xref{Specify Location}. The
8616 @code{trace} command defines a tracepoint, which is a point in the
8617 target program where the debugger will briefly stop, collect some
8618 data, and then allow the program to continue. Setting a tracepoint or
8619 changing its actions doesn't take effect until the next @code{tstart}
8620 command, and once a trace experiment is running, further changes will
8621 not have any effect until the next trace experiment starts.
8623 Here are some examples of using the @code{trace} command:
8626 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
8628 (@value{GDBP}) @b{trace +2} // 2 lines forward
8630 (@value{GDBP}) @b{trace my_function} // first source line of function
8632 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
8634 (@value{GDBP}) @b{trace *0x2117c4} // an address
8638 You can abbreviate @code{trace} as @code{tr}.
8641 @cindex last tracepoint number
8642 @cindex recent tracepoint number
8643 @cindex tracepoint number
8644 The convenience variable @code{$tpnum} records the tracepoint number
8645 of the most recently set tracepoint.
8647 @kindex delete tracepoint
8648 @cindex tracepoint deletion
8649 @item delete tracepoint @r{[}@var{num}@r{]}
8650 Permanently delete one or more tracepoints. With no argument, the
8651 default is to delete all tracepoints. Note that the regular
8652 @code{delete} command can remove tracepoints also.
8657 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
8659 (@value{GDBP}) @b{delete trace} // remove all tracepoints
8663 You can abbreviate this command as @code{del tr}.
8666 @node Enable and Disable Tracepoints
8667 @subsection Enable and Disable Tracepoints
8669 These commands are deprecated; they are equivalent to plain @code{disable} and @code{enable}.
8672 @kindex disable tracepoint
8673 @item disable tracepoint @r{[}@var{num}@r{]}
8674 Disable tracepoint @var{num}, or all tracepoints if no argument
8675 @var{num} is given. A disabled tracepoint will have no effect during
8676 the next trace experiment, but it is not forgotten. You can re-enable
8677 a disabled tracepoint using the @code{enable tracepoint} command.
8679 @kindex enable tracepoint
8680 @item enable tracepoint @r{[}@var{num}@r{]}
8681 Enable tracepoint @var{num}, or all tracepoints. The enabled
8682 tracepoints will become effective the next time a trace experiment is
8686 @node Tracepoint Passcounts
8687 @subsection Tracepoint Passcounts
8691 @cindex tracepoint pass count
8692 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
8693 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
8694 automatically stop a trace experiment. If a tracepoint's passcount is
8695 @var{n}, then the trace experiment will be automatically stopped on
8696 the @var{n}'th time that tracepoint is hit. If the tracepoint number
8697 @var{num} is not specified, the @code{passcount} command sets the
8698 passcount of the most recently defined tracepoint. If no passcount is
8699 given, the trace experiment will run until stopped explicitly by the
8705 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
8706 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
8708 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
8709 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
8710 (@value{GDBP}) @b{trace foo}
8711 (@value{GDBP}) @b{pass 3}
8712 (@value{GDBP}) @b{trace bar}
8713 (@value{GDBP}) @b{pass 2}
8714 (@value{GDBP}) @b{trace baz}
8715 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
8716 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
8717 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
8718 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
8722 @node Tracepoint Actions
8723 @subsection Tracepoint Action Lists
8727 @cindex tracepoint actions
8728 @item actions @r{[}@var{num}@r{]}
8729 This command will prompt for a list of actions to be taken when the
8730 tracepoint is hit. If the tracepoint number @var{num} is not
8731 specified, this command sets the actions for the one that was most
8732 recently defined (so that you can define a tracepoint and then say
8733 @code{actions} without bothering about its number). You specify the
8734 actions themselves on the following lines, one action at a time, and
8735 terminate the actions list with a line containing just @code{end}. So
8736 far, the only defined actions are @code{collect} and
8737 @code{while-stepping}.
8739 @cindex remove actions from a tracepoint
8740 To remove all actions from a tracepoint, type @samp{actions @var{num}}
8741 and follow it immediately with @samp{end}.
8744 (@value{GDBP}) @b{collect @var{data}} // collect some data
8746 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
8748 (@value{GDBP}) @b{end} // signals the end of actions.
8751 In the following example, the action list begins with @code{collect}
8752 commands indicating the things to be collected when the tracepoint is
8753 hit. Then, in order to single-step and collect additional data
8754 following the tracepoint, a @code{while-stepping} command is used,
8755 followed by the list of things to be collected while stepping. The
8756 @code{while-stepping} command is terminated by its own separate
8757 @code{end} command. Lastly, the action list is terminated by an
8761 (@value{GDBP}) @b{trace foo}
8762 (@value{GDBP}) @b{actions}
8763 Enter actions for tracepoint 1, one per line:
8772 @kindex collect @r{(tracepoints)}
8773 @item collect @var{expr1}, @var{expr2}, @dots{}
8774 Collect values of the given expressions when the tracepoint is hit.
8775 This command accepts a comma-separated list of any valid expressions.
8776 In addition to global, static, or local variables, the following
8777 special arguments are supported:
8781 collect all registers
8784 collect all function arguments
8787 collect all local variables.
8790 You can give several consecutive @code{collect} commands, each one
8791 with a single argument, or one @code{collect} command with several
8792 arguments separated by commas: the effect is the same.
8794 The command @code{info scope} (@pxref{Symbols, info scope}) is
8795 particularly useful for figuring out what data to collect.
8797 @kindex while-stepping @r{(tracepoints)}
8798 @item while-stepping @var{n}
8799 Perform @var{n} single-step traces after the tracepoint, collecting
8800 new data at each step. The @code{while-stepping} command is
8801 followed by the list of what to collect while stepping (followed by
8802 its own @code{end} command):
8806 > collect $regs, myglobal
8812 You may abbreviate @code{while-stepping} as @code{ws} or
8816 @node Listing Tracepoints
8817 @subsection Listing Tracepoints
8820 @kindex info tracepoints
8822 @cindex information about tracepoints
8823 @item info tracepoints @r{[}@var{num}@r{]}
8824 Display information about the tracepoint @var{num}. If you don't
8825 specify a tracepoint number, displays information about all the
8826 tracepoints defined so far. The format is similar to that used for
8827 @code{info breakpoints}; in fact, @code{info tracepoints} is the same
8828 command, simply restricting itself to tracepoints.
8830 A tracepoint's listing may include additional information specific to
8835 its passcount as given by the @code{passcount @var{n}} command
8837 its step count as given by the @code{while-stepping @var{n}} command
8839 its action list as given by the @code{actions} command. The actions
8840 are prefixed with an @samp{A} so as to distinguish them from commands.
8844 (@value{GDBP}) @b{info trace}
8845 Num Type Disp Enb Address What
8846 1 tracepoint keep y 0x0804ab57 in foo() at main.cxx:7
8850 A collect globfoo, $regs
8858 This command can be abbreviated @code{info tp}.
8861 @node Starting and Stopping Trace Experiments
8862 @subsection Starting and Stopping Trace Experiments
8866 @cindex start a new trace experiment
8867 @cindex collected data discarded
8869 This command takes no arguments. It starts the trace experiment, and
8870 begins collecting data. This has the side effect of discarding all
8871 the data collected in the trace buffer during the previous trace
8875 @cindex stop a running trace experiment
8877 This command takes no arguments. It ends the trace experiment, and
8878 stops collecting data.
8880 @strong{Note}: a trace experiment and data collection may stop
8881 automatically if any tracepoint's passcount is reached
8882 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
8885 @cindex status of trace data collection
8886 @cindex trace experiment, status of
8888 This command displays the status of the current trace data
8892 Here is an example of the commands we described so far:
8895 (@value{GDBP}) @b{trace gdb_c_test}
8896 (@value{GDBP}) @b{actions}
8897 Enter actions for tracepoint #1, one per line.
8898 > collect $regs,$locals,$args
8903 (@value{GDBP}) @b{tstart}
8904 [time passes @dots{}]
8905 (@value{GDBP}) @b{tstop}
8909 @node Analyze Collected Data
8910 @section Using the Collected Data
8912 After the tracepoint experiment ends, you use @value{GDBN} commands
8913 for examining the trace data. The basic idea is that each tracepoint
8914 collects a trace @dfn{snapshot} every time it is hit and another
8915 snapshot every time it single-steps. All these snapshots are
8916 consecutively numbered from zero and go into a buffer, and you can
8917 examine them later. The way you examine them is to @dfn{focus} on a
8918 specific trace snapshot. When the remote stub is focused on a trace
8919 snapshot, it will respond to all @value{GDBN} requests for memory and
8920 registers by reading from the buffer which belongs to that snapshot,
8921 rather than from @emph{real} memory or registers of the program being
8922 debugged. This means that @strong{all} @value{GDBN} commands
8923 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
8924 behave as if we were currently debugging the program state as it was
8925 when the tracepoint occurred. Any requests for data that are not in
8926 the buffer will fail.
8929 * tfind:: How to select a trace snapshot
8930 * tdump:: How to display all data for a snapshot
8931 * save-tracepoints:: How to save tracepoints for a future run
8935 @subsection @code{tfind @var{n}}
8938 @cindex select trace snapshot
8939 @cindex find trace snapshot
8940 The basic command for selecting a trace snapshot from the buffer is
8941 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
8942 counting from zero. If no argument @var{n} is given, the next
8943 snapshot is selected.
8945 Here are the various forms of using the @code{tfind} command.
8949 Find the first snapshot in the buffer. This is a synonym for
8950 @code{tfind 0} (since 0 is the number of the first snapshot).
8953 Stop debugging trace snapshots, resume @emph{live} debugging.
8956 Same as @samp{tfind none}.
8959 No argument means find the next trace snapshot.
8962 Find the previous trace snapshot before the current one. This permits
8963 retracing earlier steps.
8965 @item tfind tracepoint @var{num}
8966 Find the next snapshot associated with tracepoint @var{num}. Search
8967 proceeds forward from the last examined trace snapshot. If no
8968 argument @var{num} is given, it means find the next snapshot collected
8969 for the same tracepoint as the current snapshot.
8971 @item tfind pc @var{addr}
8972 Find the next snapshot associated with the value @var{addr} of the
8973 program counter. Search proceeds forward from the last examined trace
8974 snapshot. If no argument @var{addr} is given, it means find the next
8975 snapshot with the same value of PC as the current snapshot.
8977 @item tfind outside @var{addr1}, @var{addr2}
8978 Find the next snapshot whose PC is outside the given range of
8981 @item tfind range @var{addr1}, @var{addr2}
8982 Find the next snapshot whose PC is between @var{addr1} and
8983 @var{addr2}. @c FIXME: Is the range inclusive or exclusive?
8985 @item tfind line @r{[}@var{file}:@r{]}@var{n}
8986 Find the next snapshot associated with the source line @var{n}. If
8987 the optional argument @var{file} is given, refer to line @var{n} in
8988 that source file. Search proceeds forward from the last examined
8989 trace snapshot. If no argument @var{n} is given, it means find the
8990 next line other than the one currently being examined; thus saying
8991 @code{tfind line} repeatedly can appear to have the same effect as
8992 stepping from line to line in a @emph{live} debugging session.
8995 The default arguments for the @code{tfind} commands are specifically
8996 designed to make it easy to scan through the trace buffer. For
8997 instance, @code{tfind} with no argument selects the next trace
8998 snapshot, and @code{tfind -} with no argument selects the previous
8999 trace snapshot. So, by giving one @code{tfind} command, and then
9000 simply hitting @key{RET} repeatedly you can examine all the trace
9001 snapshots in order. Or, by saying @code{tfind -} and then hitting
9002 @key{RET} repeatedly you can examine the snapshots in reverse order.
9003 The @code{tfind line} command with no argument selects the snapshot
9004 for the next source line executed. The @code{tfind pc} command with
9005 no argument selects the next snapshot with the same program counter
9006 (PC) as the current frame. The @code{tfind tracepoint} command with
9007 no argument selects the next trace snapshot collected by the same
9008 tracepoint as the current one.
9010 In addition to letting you scan through the trace buffer manually,
9011 these commands make it easy to construct @value{GDBN} scripts that
9012 scan through the trace buffer and print out whatever collected data
9013 you are interested in. Thus, if we want to examine the PC, FP, and SP
9014 registers from each trace frame in the buffer, we can say this:
9017 (@value{GDBP}) @b{tfind start}
9018 (@value{GDBP}) @b{while ($trace_frame != -1)}
9019 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
9020 $trace_frame, $pc, $sp, $fp
9024 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
9025 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
9026 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
9027 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
9028 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
9029 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
9030 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
9031 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
9032 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
9033 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
9034 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
9037 Or, if we want to examine the variable @code{X} at each source line in
9041 (@value{GDBP}) @b{tfind start}
9042 (@value{GDBP}) @b{while ($trace_frame != -1)}
9043 > printf "Frame %d, X == %d\n", $trace_frame, X
9053 @subsection @code{tdump}
9055 @cindex dump all data collected at tracepoint
9056 @cindex tracepoint data, display
9058 This command takes no arguments. It prints all the data collected at
9059 the current trace snapshot.
9062 (@value{GDBP}) @b{trace 444}
9063 (@value{GDBP}) @b{actions}
9064 Enter actions for tracepoint #2, one per line:
9065 > collect $regs, $locals, $args, gdb_long_test
9068 (@value{GDBP}) @b{tstart}
9070 (@value{GDBP}) @b{tfind line 444}
9071 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
9073 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
9075 (@value{GDBP}) @b{tdump}
9076 Data collected at tracepoint 2, trace frame 1:
9077 d0 0xc4aa0085 -995491707
9081 d4 0x71aea3d 119204413
9086 a1 0x3000668 50333288
9089 a4 0x3000698 50333336
9091 fp 0x30bf3c 0x30bf3c
9092 sp 0x30bf34 0x30bf34
9094 pc 0x20b2c8 0x20b2c8
9098 p = 0x20e5b4 "gdb-test"
9105 gdb_long_test = 17 '\021'
9110 @node save-tracepoints
9111 @subsection @code{save-tracepoints @var{filename}}
9112 @kindex save-tracepoints
9113 @cindex save tracepoints for future sessions
9115 This command saves all current tracepoint definitions together with
9116 their actions and passcounts, into a file @file{@var{filename}}
9117 suitable for use in a later debugging session. To read the saved
9118 tracepoint definitions, use the @code{source} command (@pxref{Command
9121 @node Tracepoint Variables
9122 @section Convenience Variables for Tracepoints
9123 @cindex tracepoint variables
9124 @cindex convenience variables for tracepoints
9127 @vindex $trace_frame
9128 @item (int) $trace_frame
9129 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
9130 snapshot is selected.
9133 @item (int) $tracepoint
9134 The tracepoint for the current trace snapshot.
9137 @item (int) $trace_line
9138 The line number for the current trace snapshot.
9141 @item (char []) $trace_file
9142 The source file for the current trace snapshot.
9145 @item (char []) $trace_func
9146 The name of the function containing @code{$tracepoint}.
9149 Note: @code{$trace_file} is not suitable for use in @code{printf},
9150 use @code{output} instead.
9152 Here's a simple example of using these convenience variables for
9153 stepping through all the trace snapshots and printing some of their
9157 (@value{GDBP}) @b{tfind start}
9159 (@value{GDBP}) @b{while $trace_frame != -1}
9160 > output $trace_file
9161 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
9167 @chapter Debugging Programs That Use Overlays
9170 If your program is too large to fit completely in your target system's
9171 memory, you can sometimes use @dfn{overlays} to work around this
9172 problem. @value{GDBN} provides some support for debugging programs that
9176 * How Overlays Work:: A general explanation of overlays.
9177 * Overlay Commands:: Managing overlays in @value{GDBN}.
9178 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
9179 mapped by asking the inferior.
9180 * Overlay Sample Program:: A sample program using overlays.
9183 @node How Overlays Work
9184 @section How Overlays Work
9185 @cindex mapped overlays
9186 @cindex unmapped overlays
9187 @cindex load address, overlay's
9188 @cindex mapped address
9189 @cindex overlay area
9191 Suppose you have a computer whose instruction address space is only 64
9192 kilobytes long, but which has much more memory which can be accessed by
9193 other means: special instructions, segment registers, or memory
9194 management hardware, for example. Suppose further that you want to
9195 adapt a program which is larger than 64 kilobytes to run on this system.
9197 One solution is to identify modules of your program which are relatively
9198 independent, and need not call each other directly; call these modules
9199 @dfn{overlays}. Separate the overlays from the main program, and place
9200 their machine code in the larger memory. Place your main program in
9201 instruction memory, but leave at least enough space there to hold the
9202 largest overlay as well.
9204 Now, to call a function located in an overlay, you must first copy that
9205 overlay's machine code from the large memory into the space set aside
9206 for it in the instruction memory, and then jump to its entry point
9209 @c NB: In the below the mapped area's size is greater or equal to the
9210 @c size of all overlays. This is intentional to remind the developer
9211 @c that overlays don't necessarily need to be the same size.
9215 Data Instruction Larger
9216 Address Space Address Space Address Space
9217 +-----------+ +-----------+ +-----------+
9219 +-----------+ +-----------+ +-----------+<-- overlay 1
9220 | program | | main | .----| overlay 1 | load address
9221 | variables | | program | | +-----------+
9222 | and heap | | | | | |
9223 +-----------+ | | | +-----------+<-- overlay 2
9224 | | +-----------+ | | | load address
9225 +-----------+ | | | .-| overlay 2 |
9227 mapped --->+-----------+ | | +-----------+
9229 | overlay | <-' | | |
9230 | area | <---' +-----------+<-- overlay 3
9231 | | <---. | | load address
9232 +-----------+ `--| overlay 3 |
9239 @anchor{A code overlay}A code overlay
9243 The diagram (@pxref{A code overlay}) shows a system with separate data
9244 and instruction address spaces. To map an overlay, the program copies
9245 its code from the larger address space to the instruction address space.
9246 Since the overlays shown here all use the same mapped address, only one
9247 may be mapped at a time. For a system with a single address space for
9248 data and instructions, the diagram would be similar, except that the
9249 program variables and heap would share an address space with the main
9250 program and the overlay area.
9252 An overlay loaded into instruction memory and ready for use is called a
9253 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
9254 instruction memory. An overlay not present (or only partially present)
9255 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
9256 is its address in the larger memory. The mapped address is also called
9257 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
9258 called the @dfn{load memory address}, or @dfn{LMA}.
9260 Unfortunately, overlays are not a completely transparent way to adapt a
9261 program to limited instruction memory. They introduce a new set of
9262 global constraints you must keep in mind as you design your program:
9267 Before calling or returning to a function in an overlay, your program
9268 must make sure that overlay is actually mapped. Otherwise, the call or
9269 return will transfer control to the right address, but in the wrong
9270 overlay, and your program will probably crash.
9273 If the process of mapping an overlay is expensive on your system, you
9274 will need to choose your overlays carefully to minimize their effect on
9275 your program's performance.
9278 The executable file you load onto your system must contain each
9279 overlay's instructions, appearing at the overlay's load address, not its
9280 mapped address. However, each overlay's instructions must be relocated
9281 and its symbols defined as if the overlay were at its mapped address.
9282 You can use GNU linker scripts to specify different load and relocation
9283 addresses for pieces of your program; see @ref{Overlay Description,,,
9284 ld.info, Using ld: the GNU linker}.
9287 The procedure for loading executable files onto your system must be able
9288 to load their contents into the larger address space as well as the
9289 instruction and data spaces.
9293 The overlay system described above is rather simple, and could be
9294 improved in many ways:
9299 If your system has suitable bank switch registers or memory management
9300 hardware, you could use those facilities to make an overlay's load area
9301 contents simply appear at their mapped address in instruction space.
9302 This would probably be faster than copying the overlay to its mapped
9303 area in the usual way.
9306 If your overlays are small enough, you could set aside more than one
9307 overlay area, and have more than one overlay mapped at a time.
9310 You can use overlays to manage data, as well as instructions. In
9311 general, data overlays are even less transparent to your design than
9312 code overlays: whereas code overlays only require care when you call or
9313 return to functions, data overlays require care every time you access
9314 the data. Also, if you change the contents of a data overlay, you
9315 must copy its contents back out to its load address before you can copy a
9316 different data overlay into the same mapped area.
9321 @node Overlay Commands
9322 @section Overlay Commands
9324 To use @value{GDBN}'s overlay support, each overlay in your program must
9325 correspond to a separate section of the executable file. The section's
9326 virtual memory address and load memory address must be the overlay's
9327 mapped and load addresses. Identifying overlays with sections allows
9328 @value{GDBN} to determine the appropriate address of a function or
9329 variable, depending on whether the overlay is mapped or not.
9331 @value{GDBN}'s overlay commands all start with the word @code{overlay};
9332 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
9337 Disable @value{GDBN}'s overlay support. When overlay support is
9338 disabled, @value{GDBN} assumes that all functions and variables are
9339 always present at their mapped addresses. By default, @value{GDBN}'s
9340 overlay support is disabled.
9342 @item overlay manual
9343 @cindex manual overlay debugging
9344 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
9345 relies on you to tell it which overlays are mapped, and which are not,
9346 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
9347 commands described below.
9349 @item overlay map-overlay @var{overlay}
9350 @itemx overlay map @var{overlay}
9351 @cindex map an overlay
9352 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
9353 be the name of the object file section containing the overlay. When an
9354 overlay is mapped, @value{GDBN} assumes it can find the overlay's
9355 functions and variables at their mapped addresses. @value{GDBN} assumes
9356 that any other overlays whose mapped ranges overlap that of
9357 @var{overlay} are now unmapped.
9359 @item overlay unmap-overlay @var{overlay}
9360 @itemx overlay unmap @var{overlay}
9361 @cindex unmap an overlay
9362 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
9363 must be the name of the object file section containing the overlay.
9364 When an overlay is unmapped, @value{GDBN} assumes it can find the
9365 overlay's functions and variables at their load addresses.
9368 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
9369 consults a data structure the overlay manager maintains in the inferior
9370 to see which overlays are mapped. For details, see @ref{Automatic
9373 @item overlay load-target
9375 @cindex reloading the overlay table
9376 Re-read the overlay table from the inferior. Normally, @value{GDBN}
9377 re-reads the table @value{GDBN} automatically each time the inferior
9378 stops, so this command should only be necessary if you have changed the
9379 overlay mapping yourself using @value{GDBN}. This command is only
9380 useful when using automatic overlay debugging.
9382 @item overlay list-overlays
9384 @cindex listing mapped overlays
9385 Display a list of the overlays currently mapped, along with their mapped
9386 addresses, load addresses, and sizes.
9390 Normally, when @value{GDBN} prints a code address, it includes the name
9391 of the function the address falls in:
9394 (@value{GDBP}) print main
9395 $3 = @{int ()@} 0x11a0 <main>
9398 When overlay debugging is enabled, @value{GDBN} recognizes code in
9399 unmapped overlays, and prints the names of unmapped functions with
9400 asterisks around them. For example, if @code{foo} is a function in an
9401 unmapped overlay, @value{GDBN} prints it this way:
9404 (@value{GDBP}) overlay list
9405 No sections are mapped.
9406 (@value{GDBP}) print foo
9407 $5 = @{int (int)@} 0x100000 <*foo*>
9410 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
9414 (@value{GDBP}) overlay list
9415 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
9416 mapped at 0x1016 - 0x104a
9417 (@value{GDBP}) print foo
9418 $6 = @{int (int)@} 0x1016 <foo>
9421 When overlay debugging is enabled, @value{GDBN} can find the correct
9422 address for functions and variables in an overlay, whether or not the
9423 overlay is mapped. This allows most @value{GDBN} commands, like
9424 @code{break} and @code{disassemble}, to work normally, even on unmapped
9425 code. However, @value{GDBN}'s breakpoint support has some limitations:
9429 @cindex breakpoints in overlays
9430 @cindex overlays, setting breakpoints in
9431 You can set breakpoints in functions in unmapped overlays, as long as
9432 @value{GDBN} can write to the overlay at its load address.
9434 @value{GDBN} can not set hardware or simulator-based breakpoints in
9435 unmapped overlays. However, if you set a breakpoint at the end of your
9436 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
9437 you are using manual overlay management), @value{GDBN} will re-set its
9438 breakpoints properly.
9442 @node Automatic Overlay Debugging
9443 @section Automatic Overlay Debugging
9444 @cindex automatic overlay debugging
9446 @value{GDBN} can automatically track which overlays are mapped and which
9447 are not, given some simple co-operation from the overlay manager in the
9448 inferior. If you enable automatic overlay debugging with the
9449 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
9450 looks in the inferior's memory for certain variables describing the
9451 current state of the overlays.
9453 Here are the variables your overlay manager must define to support
9454 @value{GDBN}'s automatic overlay debugging:
9458 @item @code{_ovly_table}:
9459 This variable must be an array of the following structures:
9464 /* The overlay's mapped address. */
9467 /* The size of the overlay, in bytes. */
9470 /* The overlay's load address. */
9473 /* Non-zero if the overlay is currently mapped;
9475 unsigned long mapped;
9479 @item @code{_novlys}:
9480 This variable must be a four-byte signed integer, holding the total
9481 number of elements in @code{_ovly_table}.
9485 To decide whether a particular overlay is mapped or not, @value{GDBN}
9486 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
9487 @code{lma} members equal the VMA and LMA of the overlay's section in the
9488 executable file. When @value{GDBN} finds a matching entry, it consults
9489 the entry's @code{mapped} member to determine whether the overlay is
9492 In addition, your overlay manager may define a function called
9493 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
9494 will silently set a breakpoint there. If the overlay manager then
9495 calls this function whenever it has changed the overlay table, this
9496 will enable @value{GDBN} to accurately keep track of which overlays
9497 are in program memory, and update any breakpoints that may be set
9498 in overlays. This will allow breakpoints to work even if the
9499 overlays are kept in ROM or other non-writable memory while they
9500 are not being executed.
9502 @node Overlay Sample Program
9503 @section Overlay Sample Program
9504 @cindex overlay example program
9506 When linking a program which uses overlays, you must place the overlays
9507 at their load addresses, while relocating them to run at their mapped
9508 addresses. To do this, you must write a linker script (@pxref{Overlay
9509 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
9510 since linker scripts are specific to a particular host system, target
9511 architecture, and target memory layout, this manual cannot provide
9512 portable sample code demonstrating @value{GDBN}'s overlay support.
9514 However, the @value{GDBN} source distribution does contain an overlaid
9515 program, with linker scripts for a few systems, as part of its test
9516 suite. The program consists of the following files from
9517 @file{gdb/testsuite/gdb.base}:
9521 The main program file.
9523 A simple overlay manager, used by @file{overlays.c}.
9528 Overlay modules, loaded and used by @file{overlays.c}.
9531 Linker scripts for linking the test program on the @code{d10v-elf}
9532 and @code{m32r-elf} targets.
9535 You can build the test program using the @code{d10v-elf} GCC
9536 cross-compiler like this:
9539 $ d10v-elf-gcc -g -c overlays.c
9540 $ d10v-elf-gcc -g -c ovlymgr.c
9541 $ d10v-elf-gcc -g -c foo.c
9542 $ d10v-elf-gcc -g -c bar.c
9543 $ d10v-elf-gcc -g -c baz.c
9544 $ d10v-elf-gcc -g -c grbx.c
9545 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
9546 baz.o grbx.o -Wl,-Td10v.ld -o overlays
9549 The build process is identical for any other architecture, except that
9550 you must substitute the appropriate compiler and linker script for the
9551 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
9555 @chapter Using @value{GDBN} with Different Languages
9558 Although programming languages generally have common aspects, they are
9559 rarely expressed in the same manner. For instance, in ANSI C,
9560 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
9561 Modula-2, it is accomplished by @code{p^}. Values can also be
9562 represented (and displayed) differently. Hex numbers in C appear as
9563 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
9565 @cindex working language
9566 Language-specific information is built into @value{GDBN} for some languages,
9567 allowing you to express operations like the above in your program's
9568 native language, and allowing @value{GDBN} to output values in a manner
9569 consistent with the syntax of your program's native language. The
9570 language you use to build expressions is called the @dfn{working
9574 * Setting:: Switching between source languages
9575 * Show:: Displaying the language
9576 * Checks:: Type and range checks
9577 * Supported Languages:: Supported languages
9578 * Unsupported Languages:: Unsupported languages
9582 @section Switching Between Source Languages
9584 There are two ways to control the working language---either have @value{GDBN}
9585 set it automatically, or select it manually yourself. You can use the
9586 @code{set language} command for either purpose. On startup, @value{GDBN}
9587 defaults to setting the language automatically. The working language is
9588 used to determine how expressions you type are interpreted, how values
9591 In addition to the working language, every source file that
9592 @value{GDBN} knows about has its own working language. For some object
9593 file formats, the compiler might indicate which language a particular
9594 source file is in. However, most of the time @value{GDBN} infers the
9595 language from the name of the file. The language of a source file
9596 controls whether C@t{++} names are demangled---this way @code{backtrace} can
9597 show each frame appropriately for its own language. There is no way to
9598 set the language of a source file from within @value{GDBN}, but you can
9599 set the language associated with a filename extension. @xref{Show, ,
9600 Displaying the Language}.
9602 This is most commonly a problem when you use a program, such
9603 as @code{cfront} or @code{f2c}, that generates C but is written in
9604 another language. In that case, make the
9605 program use @code{#line} directives in its C output; that way
9606 @value{GDBN} will know the correct language of the source code of the original
9607 program, and will display that source code, not the generated C code.
9610 * Filenames:: Filename extensions and languages.
9611 * Manually:: Setting the working language manually
9612 * Automatically:: Having @value{GDBN} infer the source language
9616 @subsection List of Filename Extensions and Languages
9618 If a source file name ends in one of the following extensions, then
9619 @value{GDBN} infers that its language is the one indicated.
9640 Objective-C source file
9647 Modula-2 source file
9651 Assembler source file. This actually behaves almost like C, but
9652 @value{GDBN} does not skip over function prologues when stepping.
9655 In addition, you may set the language associated with a filename
9656 extension. @xref{Show, , Displaying the Language}.
9659 @subsection Setting the Working Language
9661 If you allow @value{GDBN} to set the language automatically,
9662 expressions are interpreted the same way in your debugging session and
9665 @kindex set language
9666 If you wish, you may set the language manually. To do this, issue the
9667 command @samp{set language @var{lang}}, where @var{lang} is the name of
9669 @code{c} or @code{modula-2}.
9670 For a list of the supported languages, type @samp{set language}.
9672 Setting the language manually prevents @value{GDBN} from updating the working
9673 language automatically. This can lead to confusion if you try
9674 to debug a program when the working language is not the same as the
9675 source language, when an expression is acceptable to both
9676 languages---but means different things. For instance, if the current
9677 source file were written in C, and @value{GDBN} was parsing Modula-2, a
9685 might not have the effect you intended. In C, this means to add
9686 @code{b} and @code{c} and place the result in @code{a}. The result
9687 printed would be the value of @code{a}. In Modula-2, this means to compare
9688 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
9691 @subsection Having @value{GDBN} Infer the Source Language
9693 To have @value{GDBN} set the working language automatically, use
9694 @samp{set language local} or @samp{set language auto}. @value{GDBN}
9695 then infers the working language. That is, when your program stops in a
9696 frame (usually by encountering a breakpoint), @value{GDBN} sets the
9697 working language to the language recorded for the function in that
9698 frame. If the language for a frame is unknown (that is, if the function
9699 or block corresponding to the frame was defined in a source file that
9700 does not have a recognized extension), the current working language is
9701 not changed, and @value{GDBN} issues a warning.
9703 This may not seem necessary for most programs, which are written
9704 entirely in one source language. However, program modules and libraries
9705 written in one source language can be used by a main program written in
9706 a different source language. Using @samp{set language auto} in this
9707 case frees you from having to set the working language manually.
9710 @section Displaying the Language
9712 The following commands help you find out which language is the
9713 working language, and also what language source files were written in.
9717 @kindex show language
9718 Display the current working language. This is the
9719 language you can use with commands such as @code{print} to
9720 build and compute expressions that may involve variables in your program.
9723 @kindex info frame@r{, show the source language}
9724 Display the source language for this frame. This language becomes the
9725 working language if you use an identifier from this frame.
9726 @xref{Frame Info, ,Information about a Frame}, to identify the other
9727 information listed here.
9730 @kindex info source@r{, show the source language}
9731 Display the source language of this source file.
9732 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
9733 information listed here.
9736 In unusual circumstances, you may have source files with extensions
9737 not in the standard list. You can then set the extension associated
9738 with a language explicitly:
9741 @item set extension-language @var{ext} @var{language}
9742 @kindex set extension-language
9743 Tell @value{GDBN} that source files with extension @var{ext} are to be
9744 assumed as written in the source language @var{language}.
9746 @item info extensions
9747 @kindex info extensions
9748 List all the filename extensions and the associated languages.
9752 @section Type and Range Checking
9755 @emph{Warning:} In this release, the @value{GDBN} commands for type and range
9756 checking are included, but they do not yet have any effect. This
9757 section documents the intended facilities.
9759 @c FIXME remove warning when type/range code added
9761 Some languages are designed to guard you against making seemingly common
9762 errors through a series of compile- and run-time checks. These include
9763 checking the type of arguments to functions and operators, and making
9764 sure mathematical overflows are caught at run time. Checks such as
9765 these help to ensure a program's correctness once it has been compiled
9766 by eliminating type mismatches, and providing active checks for range
9767 errors when your program is running.
9769 @value{GDBN} can check for conditions like the above if you wish.
9770 Although @value{GDBN} does not check the statements in your program,
9771 it can check expressions entered directly into @value{GDBN} for
9772 evaluation via the @code{print} command, for example. As with the
9773 working language, @value{GDBN} can also decide whether or not to check
9774 automatically based on your program's source language.
9775 @xref{Supported Languages, ,Supported Languages}, for the default
9776 settings of supported languages.
9779 * Type Checking:: An overview of type checking
9780 * Range Checking:: An overview of range checking
9783 @cindex type checking
9784 @cindex checks, type
9786 @subsection An Overview of Type Checking
9788 Some languages, such as Modula-2, are strongly typed, meaning that the
9789 arguments to operators and functions have to be of the correct type,
9790 otherwise an error occurs. These checks prevent type mismatch
9791 errors from ever causing any run-time problems. For example,
9799 The second example fails because the @code{CARDINAL} 1 is not
9800 type-compatible with the @code{REAL} 2.3.
9802 For the expressions you use in @value{GDBN} commands, you can tell the
9803 @value{GDBN} type checker to skip checking;
9804 to treat any mismatches as errors and abandon the expression;
9805 or to only issue warnings when type mismatches occur,
9806 but evaluate the expression anyway. When you choose the last of
9807 these, @value{GDBN} evaluates expressions like the second example above, but
9808 also issues a warning.
9810 Even if you turn type checking off, there may be other reasons
9811 related to type that prevent @value{GDBN} from evaluating an expression.
9812 For instance, @value{GDBN} does not know how to add an @code{int} and
9813 a @code{struct foo}. These particular type errors have nothing to do
9814 with the language in use, and usually arise from expressions, such as
9815 the one described above, which make little sense to evaluate anyway.
9817 Each language defines to what degree it is strict about type. For
9818 instance, both Modula-2 and C require the arguments to arithmetical
9819 operators to be numbers. In C, enumerated types and pointers can be
9820 represented as numbers, so that they are valid arguments to mathematical
9821 operators. @xref{Supported Languages, ,Supported Languages}, for further
9822 details on specific languages.
9824 @value{GDBN} provides some additional commands for controlling the type checker:
9826 @kindex set check type
9827 @kindex show check type
9829 @item set check type auto
9830 Set type checking on or off based on the current working language.
9831 @xref{Supported Languages, ,Supported Languages}, for the default settings for
9834 @item set check type on
9835 @itemx set check type off
9836 Set type checking on or off, overriding the default setting for the
9837 current working language. Issue a warning if the setting does not
9838 match the language default. If any type mismatches occur in
9839 evaluating an expression while type checking is on, @value{GDBN} prints a
9840 message and aborts evaluation of the expression.
9842 @item set check type warn
9843 Cause the type checker to issue warnings, but to always attempt to
9844 evaluate the expression. Evaluating the expression may still
9845 be impossible for other reasons. For example, @value{GDBN} cannot add
9846 numbers and structures.
9849 Show the current setting of the type checker, and whether or not @value{GDBN}
9850 is setting it automatically.
9853 @cindex range checking
9854 @cindex checks, range
9855 @node Range Checking
9856 @subsection An Overview of Range Checking
9858 In some languages (such as Modula-2), it is an error to exceed the
9859 bounds of a type; this is enforced with run-time checks. Such range
9860 checking is meant to ensure program correctness by making sure
9861 computations do not overflow, or indices on an array element access do
9862 not exceed the bounds of the array.
9864 For expressions you use in @value{GDBN} commands, you can tell
9865 @value{GDBN} to treat range errors in one of three ways: ignore them,
9866 always treat them as errors and abandon the expression, or issue
9867 warnings but evaluate the expression anyway.
9869 A range error can result from numerical overflow, from exceeding an
9870 array index bound, or when you type a constant that is not a member
9871 of any type. Some languages, however, do not treat overflows as an
9872 error. In many implementations of C, mathematical overflow causes the
9873 result to ``wrap around'' to lower values---for example, if @var{m} is
9874 the largest integer value, and @var{s} is the smallest, then
9877 @var{m} + 1 @result{} @var{s}
9880 This, too, is specific to individual languages, and in some cases
9881 specific to individual compilers or machines. @xref{Supported Languages, ,
9882 Supported Languages}, for further details on specific languages.
9884 @value{GDBN} provides some additional commands for controlling the range checker:
9886 @kindex set check range
9887 @kindex show check range
9889 @item set check range auto
9890 Set range checking on or off based on the current working language.
9891 @xref{Supported Languages, ,Supported Languages}, for the default settings for
9894 @item set check range on
9895 @itemx set check range off
9896 Set range checking on or off, overriding the default setting for the
9897 current working language. A warning is issued if the setting does not
9898 match the language default. If a range error occurs and range checking is on,
9899 then a message is printed and evaluation of the expression is aborted.
9901 @item set check range warn
9902 Output messages when the @value{GDBN} range checker detects a range error,
9903 but attempt to evaluate the expression anyway. Evaluating the
9904 expression may still be impossible for other reasons, such as accessing
9905 memory that the process does not own (a typical example from many Unix
9909 Show the current setting of the range checker, and whether or not it is
9910 being set automatically by @value{GDBN}.
9913 @node Supported Languages
9914 @section Supported Languages
9916 @value{GDBN} supports C, C@t{++}, Objective-C, Fortran, Java, Pascal,
9917 assembly, Modula-2, and Ada.
9918 @c This is false ...
9919 Some @value{GDBN} features may be used in expressions regardless of the
9920 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
9921 and the @samp{@{type@}addr} construct (@pxref{Expressions,
9922 ,Expressions}) can be used with the constructs of any supported
9925 The following sections detail to what degree each source language is
9926 supported by @value{GDBN}. These sections are not meant to be language
9927 tutorials or references, but serve only as a reference guide to what the
9928 @value{GDBN} expression parser accepts, and what input and output
9929 formats should look like for different languages. There are many good
9930 books written on each of these languages; please look to these for a
9931 language reference or tutorial.
9935 * Objective-C:: Objective-C
9938 * Modula-2:: Modula-2
9943 @subsection C and C@t{++}
9945 @cindex C and C@t{++}
9946 @cindex expressions in C or C@t{++}
9948 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
9949 to both languages. Whenever this is the case, we discuss those languages
9953 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
9954 @cindex @sc{gnu} C@t{++}
9955 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
9956 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
9957 effectively, you must compile your C@t{++} programs with a supported
9958 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
9959 compiler (@code{aCC}).
9961 For best results when using @sc{gnu} C@t{++}, use the DWARF 2 debugging
9962 format; if it doesn't work on your system, try the stabs+ debugging
9963 format. You can select those formats explicitly with the @code{g++}
9964 command-line options @option{-gdwarf-2} and @option{-gstabs+}.
9965 @xref{Debugging Options,,Options for Debugging Your Program or GCC,
9966 gcc.info, Using the @sc{gnu} Compiler Collection (GCC)}.
9969 * C Operators:: C and C@t{++} operators
9970 * C Constants:: C and C@t{++} constants
9971 * C Plus Plus Expressions:: C@t{++} expressions
9972 * C Defaults:: Default settings for C and C@t{++}
9973 * C Checks:: C and C@t{++} type and range checks
9974 * Debugging C:: @value{GDBN} and C
9975 * Debugging C Plus Plus:: @value{GDBN} features for C@t{++}
9976 * Decimal Floating Point:: Numbers in Decimal Floating Point format
9980 @subsubsection C and C@t{++} Operators
9982 @cindex C and C@t{++} operators
9984 Operators must be defined on values of specific types. For instance,
9985 @code{+} is defined on numbers, but not on structures. Operators are
9986 often defined on groups of types.
9988 For the purposes of C and C@t{++}, the following definitions hold:
9993 @emph{Integral types} include @code{int} with any of its storage-class
9994 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
9997 @emph{Floating-point types} include @code{float}, @code{double}, and
9998 @code{long double} (if supported by the target platform).
10001 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
10004 @emph{Scalar types} include all of the above.
10009 The following operators are supported. They are listed here
10010 in order of increasing precedence:
10014 The comma or sequencing operator. Expressions in a comma-separated list
10015 are evaluated from left to right, with the result of the entire
10016 expression being the last expression evaluated.
10019 Assignment. The value of an assignment expression is the value
10020 assigned. Defined on scalar types.
10023 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
10024 and translated to @w{@code{@var{a} = @var{a op b}}}.
10025 @w{@code{@var{op}=}} and @code{=} have the same precedence.
10026 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
10027 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
10030 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
10031 of as: if @var{a} then @var{b} else @var{c}. @var{a} should be of an
10035 Logical @sc{or}. Defined on integral types.
10038 Logical @sc{and}. Defined on integral types.
10041 Bitwise @sc{or}. Defined on integral types.
10044 Bitwise exclusive-@sc{or}. Defined on integral types.
10047 Bitwise @sc{and}. Defined on integral types.
10050 Equality and inequality. Defined on scalar types. The value of these
10051 expressions is 0 for false and non-zero for true.
10053 @item <@r{, }>@r{, }<=@r{, }>=
10054 Less than, greater than, less than or equal, greater than or equal.
10055 Defined on scalar types. The value of these expressions is 0 for false
10056 and non-zero for true.
10059 left shift, and right shift. Defined on integral types.
10062 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
10065 Addition and subtraction. Defined on integral types, floating-point types and
10068 @item *@r{, }/@r{, }%
10069 Multiplication, division, and modulus. Multiplication and division are
10070 defined on integral and floating-point types. Modulus is defined on
10074 Increment and decrement. When appearing before a variable, the
10075 operation is performed before the variable is used in an expression;
10076 when appearing after it, the variable's value is used before the
10077 operation takes place.
10080 Pointer dereferencing. Defined on pointer types. Same precedence as
10084 Address operator. Defined on variables. Same precedence as @code{++}.
10086 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
10087 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
10088 to examine the address
10089 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
10093 Negative. Defined on integral and floating-point types. Same
10094 precedence as @code{++}.
10097 Logical negation. Defined on integral types. Same precedence as
10101 Bitwise complement operator. Defined on integral types. Same precedence as
10106 Structure member, and pointer-to-structure member. For convenience,
10107 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
10108 pointer based on the stored type information.
10109 Defined on @code{struct} and @code{union} data.
10112 Dereferences of pointers to members.
10115 Array indexing. @code{@var{a}[@var{i}]} is defined as
10116 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
10119 Function parameter list. Same precedence as @code{->}.
10122 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
10123 and @code{class} types.
10126 Doubled colons also represent the @value{GDBN} scope operator
10127 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
10131 If an operator is redefined in the user code, @value{GDBN} usually
10132 attempts to invoke the redefined version instead of using the operator's
10133 predefined meaning.
10136 @subsubsection C and C@t{++} Constants
10138 @cindex C and C@t{++} constants
10140 @value{GDBN} allows you to express the constants of C and C@t{++} in the
10145 Integer constants are a sequence of digits. Octal constants are
10146 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
10147 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
10148 @samp{l}, specifying that the constant should be treated as a
10152 Floating point constants are a sequence of digits, followed by a decimal
10153 point, followed by a sequence of digits, and optionally followed by an
10154 exponent. An exponent is of the form:
10155 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
10156 sequence of digits. The @samp{+} is optional for positive exponents.
10157 A floating-point constant may also end with a letter @samp{f} or
10158 @samp{F}, specifying that the constant should be treated as being of
10159 the @code{float} (as opposed to the default @code{double}) type; or with
10160 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
10164 Enumerated constants consist of enumerated identifiers, or their
10165 integral equivalents.
10168 Character constants are a single character surrounded by single quotes
10169 (@code{'}), or a number---the ordinal value of the corresponding character
10170 (usually its @sc{ascii} value). Within quotes, the single character may
10171 be represented by a letter or by @dfn{escape sequences}, which are of
10172 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
10173 of the character's ordinal value; or of the form @samp{\@var{x}}, where
10174 @samp{@var{x}} is a predefined special character---for example,
10175 @samp{\n} for newline.
10178 String constants are a sequence of character constants surrounded by
10179 double quotes (@code{"}). Any valid character constant (as described
10180 above) may appear. Double quotes within the string must be preceded by
10181 a backslash, so for instance @samp{"a\"b'c"} is a string of five
10185 Pointer constants are an integral value. You can also write pointers
10186 to constants using the C operator @samp{&}.
10189 Array constants are comma-separated lists surrounded by braces @samp{@{}
10190 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
10191 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
10192 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
10195 @node C Plus Plus Expressions
10196 @subsubsection C@t{++} Expressions
10198 @cindex expressions in C@t{++}
10199 @value{GDBN} expression handling can interpret most C@t{++} expressions.
10201 @cindex debugging C@t{++} programs
10202 @cindex C@t{++} compilers
10203 @cindex debug formats and C@t{++}
10204 @cindex @value{NGCC} and C@t{++}
10206 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use the
10207 proper compiler and the proper debug format. Currently, @value{GDBN}
10208 works best when debugging C@t{++} code that is compiled with
10209 @value{NGCC} 2.95.3 or with @value{NGCC} 3.1 or newer, using the options
10210 @option{-gdwarf-2} or @option{-gstabs+}. DWARF 2 is preferred over
10211 stabs+. Most configurations of @value{NGCC} emit either DWARF 2 or
10212 stabs+ as their default debug format, so you usually don't need to
10213 specify a debug format explicitly. Other compilers and/or debug formats
10214 are likely to work badly or not at all when using @value{GDBN} to debug
10220 @cindex member functions
10222 Member function calls are allowed; you can use expressions like
10225 count = aml->GetOriginal(x, y)
10228 @vindex this@r{, inside C@t{++} member functions}
10229 @cindex namespace in C@t{++}
10231 While a member function is active (in the selected stack frame), your
10232 expressions have the same namespace available as the member function;
10233 that is, @value{GDBN} allows implicit references to the class instance
10234 pointer @code{this} following the same rules as C@t{++}.
10236 @cindex call overloaded functions
10237 @cindex overloaded functions, calling
10238 @cindex type conversions in C@t{++}
10240 You can call overloaded functions; @value{GDBN} resolves the function
10241 call to the right definition, with some restrictions. @value{GDBN} does not
10242 perform overload resolution involving user-defined type conversions,
10243 calls to constructors, or instantiations of templates that do not exist
10244 in the program. It also cannot handle ellipsis argument lists or
10247 It does perform integral conversions and promotions, floating-point
10248 promotions, arithmetic conversions, pointer conversions, conversions of
10249 class objects to base classes, and standard conversions such as those of
10250 functions or arrays to pointers; it requires an exact match on the
10251 number of function arguments.
10253 Overload resolution is always performed, unless you have specified
10254 @code{set overload-resolution off}. @xref{Debugging C Plus Plus,
10255 ,@value{GDBN} Features for C@t{++}}.
10257 You must specify @code{set overload-resolution off} in order to use an
10258 explicit function signature to call an overloaded function, as in
10260 p 'foo(char,int)'('x', 13)
10263 The @value{GDBN} command-completion facility can simplify this;
10264 see @ref{Completion, ,Command Completion}.
10266 @cindex reference declarations
10268 @value{GDBN} understands variables declared as C@t{++} references; you can use
10269 them in expressions just as you do in C@t{++} source---they are automatically
10272 In the parameter list shown when @value{GDBN} displays a frame, the values of
10273 reference variables are not displayed (unlike other variables); this
10274 avoids clutter, since references are often used for large structures.
10275 The @emph{address} of a reference variable is always shown, unless
10276 you have specified @samp{set print address off}.
10279 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
10280 expressions can use it just as expressions in your program do. Since
10281 one scope may be defined in another, you can use @code{::} repeatedly if
10282 necessary, for example in an expression like
10283 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
10284 resolving name scope by reference to source files, in both C and C@t{++}
10285 debugging (@pxref{Variables, ,Program Variables}).
10288 In addition, when used with HP's C@t{++} compiler, @value{GDBN} supports
10289 calling virtual functions correctly, printing out virtual bases of
10290 objects, calling functions in a base subobject, casting objects, and
10291 invoking user-defined operators.
10294 @subsubsection C and C@t{++} Defaults
10296 @cindex C and C@t{++} defaults
10298 If you allow @value{GDBN} to set type and range checking automatically, they
10299 both default to @code{off} whenever the working language changes to
10300 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
10301 selects the working language.
10303 If you allow @value{GDBN} to set the language automatically, it
10304 recognizes source files whose names end with @file{.c}, @file{.C}, or
10305 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
10306 these files, it sets the working language to C or C@t{++}.
10307 @xref{Automatically, ,Having @value{GDBN} Infer the Source Language},
10308 for further details.
10310 @c Type checking is (a) primarily motivated by Modula-2, and (b)
10311 @c unimplemented. If (b) changes, it might make sense to let this node
10312 @c appear even if Mod-2 does not, but meanwhile ignore it. roland 16jul93.
10315 @subsubsection C and C@t{++} Type and Range Checks
10317 @cindex C and C@t{++} checks
10319 By default, when @value{GDBN} parses C or C@t{++} expressions, type checking
10320 is not used. However, if you turn type checking on, @value{GDBN}
10321 considers two variables type equivalent if:
10325 The two variables are structured and have the same structure, union, or
10329 The two variables have the same type name, or types that have been
10330 declared equivalent through @code{typedef}.
10333 @c leaving this out because neither J Gilmore nor R Pesch understand it.
10336 The two @code{struct}, @code{union}, or @code{enum} variables are
10337 declared in the same declaration. (Note: this may not be true for all C
10342 Range checking, if turned on, is done on mathematical operations. Array
10343 indices are not checked, since they are often used to index a pointer
10344 that is not itself an array.
10347 @subsubsection @value{GDBN} and C
10349 The @code{set print union} and @code{show print union} commands apply to
10350 the @code{union} type. When set to @samp{on}, any @code{union} that is
10351 inside a @code{struct} or @code{class} is also printed. Otherwise, it
10352 appears as @samp{@{...@}}.
10354 The @code{@@} operator aids in the debugging of dynamic arrays, formed
10355 with pointers and a memory allocation function. @xref{Expressions,
10358 @node Debugging C Plus Plus
10359 @subsubsection @value{GDBN} Features for C@t{++}
10361 @cindex commands for C@t{++}
10363 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
10364 designed specifically for use with C@t{++}. Here is a summary:
10367 @cindex break in overloaded functions
10368 @item @r{breakpoint menus}
10369 When you want a breakpoint in a function whose name is overloaded,
10370 @value{GDBN} has the capability to display a menu of possible breakpoint
10371 locations to help you specify which function definition you want.
10372 @xref{Ambiguous Expressions,,Ambiguous Expressions}.
10374 @cindex overloading in C@t{++}
10375 @item rbreak @var{regex}
10376 Setting breakpoints using regular expressions is helpful for setting
10377 breakpoints on overloaded functions that are not members of any special
10379 @xref{Set Breaks, ,Setting Breakpoints}.
10381 @cindex C@t{++} exception handling
10384 Debug C@t{++} exception handling using these commands. @xref{Set
10385 Catchpoints, , Setting Catchpoints}.
10387 @cindex inheritance
10388 @item ptype @var{typename}
10389 Print inheritance relationships as well as other information for type
10391 @xref{Symbols, ,Examining the Symbol Table}.
10393 @cindex C@t{++} symbol display
10394 @item set print demangle
10395 @itemx show print demangle
10396 @itemx set print asm-demangle
10397 @itemx show print asm-demangle
10398 Control whether C@t{++} symbols display in their source form, both when
10399 displaying code as C@t{++} source and when displaying disassemblies.
10400 @xref{Print Settings, ,Print Settings}.
10402 @item set print object
10403 @itemx show print object
10404 Choose whether to print derived (actual) or declared types of objects.
10405 @xref{Print Settings, ,Print Settings}.
10407 @item set print vtbl
10408 @itemx show print vtbl
10409 Control the format for printing virtual function tables.
10410 @xref{Print Settings, ,Print Settings}.
10411 (The @code{vtbl} commands do not work on programs compiled with the HP
10412 ANSI C@t{++} compiler (@code{aCC}).)
10414 @kindex set overload-resolution
10415 @cindex overloaded functions, overload resolution
10416 @item set overload-resolution on
10417 Enable overload resolution for C@t{++} expression evaluation. The default
10418 is on. For overloaded functions, @value{GDBN} evaluates the arguments
10419 and searches for a function whose signature matches the argument types,
10420 using the standard C@t{++} conversion rules (see @ref{C Plus Plus
10421 Expressions, ,C@t{++} Expressions}, for details).
10422 If it cannot find a match, it emits a message.
10424 @item set overload-resolution off
10425 Disable overload resolution for C@t{++} expression evaluation. For
10426 overloaded functions that are not class member functions, @value{GDBN}
10427 chooses the first function of the specified name that it finds in the
10428 symbol table, whether or not its arguments are of the correct type. For
10429 overloaded functions that are class member functions, @value{GDBN}
10430 searches for a function whose signature @emph{exactly} matches the
10433 @kindex show overload-resolution
10434 @item show overload-resolution
10435 Show the current setting of overload resolution.
10437 @item @r{Overloaded symbol names}
10438 You can specify a particular definition of an overloaded symbol, using
10439 the same notation that is used to declare such symbols in C@t{++}: type
10440 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
10441 also use the @value{GDBN} command-line word completion facilities to list the
10442 available choices, or to finish the type list for you.
10443 @xref{Completion,, Command Completion}, for details on how to do this.
10446 @node Decimal Floating Point
10447 @subsubsection Decimal Floating Point format
10448 @cindex decimal floating point format
10450 @value{GDBN} can examine, set and perform computations with numbers in
10451 decimal floating point format, which in the C language correspond to the
10452 @code{_Decimal32}, @code{_Decimal64} and @code{_Decimal128} types as
10453 specified by the extension to support decimal floating-point arithmetic.
10455 There are two encodings in use, depending on the architecture: BID (Binary
10456 Integer Decimal) for x86 and x86-64, and DPD (Densely Packed Decimal) for
10457 PowerPC. @value{GDBN} will use the appropriate encoding for the configured
10460 Because of a limitation in @file{libdecnumber}, the library used by @value{GDBN}
10461 to manipulate decimal floating point numbers, it is not possible to convert
10462 (using a cast, for example) integers wider than 32-bit to decimal float.
10464 In addition, in order to imitate @value{GDBN}'s behaviour with binary floating
10465 point computations, error checking in decimal float operations ignores
10466 underflow, overflow and divide by zero exceptions.
10468 In the PowerPC architecture, @value{GDBN} provides a set of pseudo-registers
10469 to inspect @code{_Decimal128} values stored in floating point registers. See
10470 @ref{PowerPC,,PowerPC} for more details.
10473 @subsection Objective-C
10475 @cindex Objective-C
10476 This section provides information about some commands and command
10477 options that are useful for debugging Objective-C code. See also
10478 @ref{Symbols, info classes}, and @ref{Symbols, info selectors}, for a
10479 few more commands specific to Objective-C support.
10482 * Method Names in Commands::
10483 * The Print Command with Objective-C::
10486 @node Method Names in Commands
10487 @subsubsection Method Names in Commands
10489 The following commands have been extended to accept Objective-C method
10490 names as line specifications:
10492 @kindex clear@r{, and Objective-C}
10493 @kindex break@r{, and Objective-C}
10494 @kindex info line@r{, and Objective-C}
10495 @kindex jump@r{, and Objective-C}
10496 @kindex list@r{, and Objective-C}
10500 @item @code{info line}
10505 A fully qualified Objective-C method name is specified as
10508 -[@var{Class} @var{methodName}]
10511 where the minus sign is used to indicate an instance method and a
10512 plus sign (not shown) is used to indicate a class method. The class
10513 name @var{Class} and method name @var{methodName} are enclosed in
10514 brackets, similar to the way messages are specified in Objective-C
10515 source code. For example, to set a breakpoint at the @code{create}
10516 instance method of class @code{Fruit} in the program currently being
10520 break -[Fruit create]
10523 To list ten program lines around the @code{initialize} class method,
10527 list +[NSText initialize]
10530 In the current version of @value{GDBN}, the plus or minus sign is
10531 required. In future versions of @value{GDBN}, the plus or minus
10532 sign will be optional, but you can use it to narrow the search. It
10533 is also possible to specify just a method name:
10539 You must specify the complete method name, including any colons. If
10540 your program's source files contain more than one @code{create} method,
10541 you'll be presented with a numbered list of classes that implement that
10542 method. Indicate your choice by number, or type @samp{0} to exit if
10545 As another example, to clear a breakpoint established at the
10546 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
10549 clear -[NSWindow makeKeyAndOrderFront:]
10552 @node The Print Command with Objective-C
10553 @subsubsection The Print Command With Objective-C
10554 @cindex Objective-C, print objects
10555 @kindex print-object
10556 @kindex po @r{(@code{print-object})}
10558 The print command has also been extended to accept methods. For example:
10561 print -[@var{object} hash]
10564 @cindex print an Objective-C object description
10565 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
10567 will tell @value{GDBN} to send the @code{hash} message to @var{object}
10568 and print the result. Also, an additional command has been added,
10569 @code{print-object} or @code{po} for short, which is meant to print
10570 the description of an object. However, this command may only work
10571 with certain Objective-C libraries that have a particular hook
10572 function, @code{_NSPrintForDebugger}, defined.
10575 @subsection Fortran
10576 @cindex Fortran-specific support in @value{GDBN}
10578 @value{GDBN} can be used to debug programs written in Fortran, but it
10579 currently supports only the features of Fortran 77 language.
10581 @cindex trailing underscore, in Fortran symbols
10582 Some Fortran compilers (@sc{gnu} Fortran 77 and Fortran 95 compilers
10583 among them) append an underscore to the names of variables and
10584 functions. When you debug programs compiled by those compilers, you
10585 will need to refer to variables and functions with a trailing
10589 * Fortran Operators:: Fortran operators and expressions
10590 * Fortran Defaults:: Default settings for Fortran
10591 * Special Fortran Commands:: Special @value{GDBN} commands for Fortran
10594 @node Fortran Operators
10595 @subsubsection Fortran Operators and Expressions
10597 @cindex Fortran operators and expressions
10599 Operators must be defined on values of specific types. For instance,
10600 @code{+} is defined on numbers, but not on characters or other non-
10601 arithmetic types. Operators are often defined on groups of types.
10605 The exponentiation operator. It raises the first operand to the power
10609 The range operator. Normally used in the form of array(low:high) to
10610 represent a section of array.
10613 The access component operator. Normally used to access elements in derived
10614 types. Also suitable for unions. As unions aren't part of regular Fortran,
10615 this can only happen when accessing a register that uses a gdbarch-defined
10619 @node Fortran Defaults
10620 @subsubsection Fortran Defaults
10622 @cindex Fortran Defaults
10624 Fortran symbols are usually case-insensitive, so @value{GDBN} by
10625 default uses case-insensitive matches for Fortran symbols. You can
10626 change that with the @samp{set case-insensitive} command, see
10627 @ref{Symbols}, for the details.
10629 @node Special Fortran Commands
10630 @subsubsection Special Fortran Commands
10632 @cindex Special Fortran commands
10634 @value{GDBN} has some commands to support Fortran-specific features,
10635 such as displaying common blocks.
10638 @cindex @code{COMMON} blocks, Fortran
10639 @kindex info common
10640 @item info common @r{[}@var{common-name}@r{]}
10641 This command prints the values contained in the Fortran @code{COMMON}
10642 block whose name is @var{common-name}. With no argument, the names of
10643 all @code{COMMON} blocks visible at the current program location are
10650 @cindex Pascal support in @value{GDBN}, limitations
10651 Debugging Pascal programs which use sets, subranges, file variables, or
10652 nested functions does not currently work. @value{GDBN} does not support
10653 entering expressions, printing values, or similar features using Pascal
10656 The Pascal-specific command @code{set print pascal_static-members}
10657 controls whether static members of Pascal objects are displayed.
10658 @xref{Print Settings, pascal_static-members}.
10661 @subsection Modula-2
10663 @cindex Modula-2, @value{GDBN} support
10665 The extensions made to @value{GDBN} to support Modula-2 only support
10666 output from the @sc{gnu} Modula-2 compiler (which is currently being
10667 developed). Other Modula-2 compilers are not currently supported, and
10668 attempting to debug executables produced by them is most likely
10669 to give an error as @value{GDBN} reads in the executable's symbol
10672 @cindex expressions in Modula-2
10674 * M2 Operators:: Built-in operators
10675 * Built-In Func/Proc:: Built-in functions and procedures
10676 * M2 Constants:: Modula-2 constants
10677 * M2 Types:: Modula-2 types
10678 * M2 Defaults:: Default settings for Modula-2
10679 * Deviations:: Deviations from standard Modula-2
10680 * M2 Checks:: Modula-2 type and range checks
10681 * M2 Scope:: The scope operators @code{::} and @code{.}
10682 * GDB/M2:: @value{GDBN} and Modula-2
10686 @subsubsection Operators
10687 @cindex Modula-2 operators
10689 Operators must be defined on values of specific types. For instance,
10690 @code{+} is defined on numbers, but not on structures. Operators are
10691 often defined on groups of types. For the purposes of Modula-2, the
10692 following definitions hold:
10697 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
10701 @emph{Character types} consist of @code{CHAR} and its subranges.
10704 @emph{Floating-point types} consist of @code{REAL}.
10707 @emph{Pointer types} consist of anything declared as @code{POINTER TO
10711 @emph{Scalar types} consist of all of the above.
10714 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
10717 @emph{Boolean types} consist of @code{BOOLEAN}.
10721 The following operators are supported, and appear in order of
10722 increasing precedence:
10726 Function argument or array index separator.
10729 Assignment. The value of @var{var} @code{:=} @var{value} is
10733 Less than, greater than on integral, floating-point, or enumerated
10737 Less than or equal to, greater than or equal to
10738 on integral, floating-point and enumerated types, or set inclusion on
10739 set types. Same precedence as @code{<}.
10741 @item =@r{, }<>@r{, }#
10742 Equality and two ways of expressing inequality, valid on scalar types.
10743 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
10744 available for inequality, since @code{#} conflicts with the script
10748 Set membership. Defined on set types and the types of their members.
10749 Same precedence as @code{<}.
10752 Boolean disjunction. Defined on boolean types.
10755 Boolean conjunction. Defined on boolean types.
10758 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
10761 Addition and subtraction on integral and floating-point types, or union
10762 and difference on set types.
10765 Multiplication on integral and floating-point types, or set intersection
10769 Division on floating-point types, or symmetric set difference on set
10770 types. Same precedence as @code{*}.
10773 Integer division and remainder. Defined on integral types. Same
10774 precedence as @code{*}.
10777 Negative. Defined on @code{INTEGER} and @code{REAL} data.
10780 Pointer dereferencing. Defined on pointer types.
10783 Boolean negation. Defined on boolean types. Same precedence as
10787 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
10788 precedence as @code{^}.
10791 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
10794 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
10798 @value{GDBN} and Modula-2 scope operators.
10802 @emph{Warning:} Set expressions and their operations are not yet supported, so @value{GDBN}
10803 treats the use of the operator @code{IN}, or the use of operators
10804 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
10805 @code{<=}, and @code{>=} on sets as an error.
10809 @node Built-In Func/Proc
10810 @subsubsection Built-in Functions and Procedures
10811 @cindex Modula-2 built-ins
10813 Modula-2 also makes available several built-in procedures and functions.
10814 In describing these, the following metavariables are used:
10819 represents an @code{ARRAY} variable.
10822 represents a @code{CHAR} constant or variable.
10825 represents a variable or constant of integral type.
10828 represents an identifier that belongs to a set. Generally used in the
10829 same function with the metavariable @var{s}. The type of @var{s} should
10830 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
10833 represents a variable or constant of integral or floating-point type.
10836 represents a variable or constant of floating-point type.
10842 represents a variable.
10845 represents a variable or constant of one of many types. See the
10846 explanation of the function for details.
10849 All Modula-2 built-in procedures also return a result, described below.
10853 Returns the absolute value of @var{n}.
10856 If @var{c} is a lower case letter, it returns its upper case
10857 equivalent, otherwise it returns its argument.
10860 Returns the character whose ordinal value is @var{i}.
10863 Decrements the value in the variable @var{v} by one. Returns the new value.
10865 @item DEC(@var{v},@var{i})
10866 Decrements the value in the variable @var{v} by @var{i}. Returns the
10869 @item EXCL(@var{m},@var{s})
10870 Removes the element @var{m} from the set @var{s}. Returns the new
10873 @item FLOAT(@var{i})
10874 Returns the floating point equivalent of the integer @var{i}.
10876 @item HIGH(@var{a})
10877 Returns the index of the last member of @var{a}.
10880 Increments the value in the variable @var{v} by one. Returns the new value.
10882 @item INC(@var{v},@var{i})
10883 Increments the value in the variable @var{v} by @var{i}. Returns the
10886 @item INCL(@var{m},@var{s})
10887 Adds the element @var{m} to the set @var{s} if it is not already
10888 there. Returns the new set.
10891 Returns the maximum value of the type @var{t}.
10894 Returns the minimum value of the type @var{t}.
10897 Returns boolean TRUE if @var{i} is an odd number.
10900 Returns the ordinal value of its argument. For example, the ordinal
10901 value of a character is its @sc{ascii} value (on machines supporting the
10902 @sc{ascii} character set). @var{x} must be of an ordered type, which include
10903 integral, character and enumerated types.
10905 @item SIZE(@var{x})
10906 Returns the size of its argument. @var{x} can be a variable or a type.
10908 @item TRUNC(@var{r})
10909 Returns the integral part of @var{r}.
10911 @item TSIZE(@var{x})
10912 Returns the size of its argument. @var{x} can be a variable or a type.
10914 @item VAL(@var{t},@var{i})
10915 Returns the member of the type @var{t} whose ordinal value is @var{i}.
10919 @emph{Warning:} Sets and their operations are not yet supported, so
10920 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
10924 @cindex Modula-2 constants
10926 @subsubsection Constants
10928 @value{GDBN} allows you to express the constants of Modula-2 in the following
10934 Integer constants are simply a sequence of digits. When used in an
10935 expression, a constant is interpreted to be type-compatible with the
10936 rest of the expression. Hexadecimal integers are specified by a
10937 trailing @samp{H}, and octal integers by a trailing @samp{B}.
10940 Floating point constants appear as a sequence of digits, followed by a
10941 decimal point and another sequence of digits. An optional exponent can
10942 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
10943 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
10944 digits of the floating point constant must be valid decimal (base 10)
10948 Character constants consist of a single character enclosed by a pair of
10949 like quotes, either single (@code{'}) or double (@code{"}). They may
10950 also be expressed by their ordinal value (their @sc{ascii} value, usually)
10951 followed by a @samp{C}.
10954 String constants consist of a sequence of characters enclosed by a
10955 pair of like quotes, either single (@code{'}) or double (@code{"}).
10956 Escape sequences in the style of C are also allowed. @xref{C
10957 Constants, ,C and C@t{++} Constants}, for a brief explanation of escape
10961 Enumerated constants consist of an enumerated identifier.
10964 Boolean constants consist of the identifiers @code{TRUE} and
10968 Pointer constants consist of integral values only.
10971 Set constants are not yet supported.
10975 @subsubsection Modula-2 Types
10976 @cindex Modula-2 types
10978 Currently @value{GDBN} can print the following data types in Modula-2
10979 syntax: array types, record types, set types, pointer types, procedure
10980 types, enumerated types, subrange types and base types. You can also
10981 print the contents of variables declared using these type.
10982 This section gives a number of simple source code examples together with
10983 sample @value{GDBN} sessions.
10985 The first example contains the following section of code:
10994 and you can request @value{GDBN} to interrogate the type and value of
10995 @code{r} and @code{s}.
10998 (@value{GDBP}) print s
11000 (@value{GDBP}) ptype s
11002 (@value{GDBP}) print r
11004 (@value{GDBP}) ptype r
11009 Likewise if your source code declares @code{s} as:
11013 s: SET ['A'..'Z'] ;
11017 then you may query the type of @code{s} by:
11020 (@value{GDBP}) ptype s
11021 type = SET ['A'..'Z']
11025 Note that at present you cannot interactively manipulate set
11026 expressions using the debugger.
11028 The following example shows how you might declare an array in Modula-2
11029 and how you can interact with @value{GDBN} to print its type and contents:
11033 s: ARRAY [-10..10] OF CHAR ;
11037 (@value{GDBP}) ptype s
11038 ARRAY [-10..10] OF CHAR
11041 Note that the array handling is not yet complete and although the type
11042 is printed correctly, expression handling still assumes that all
11043 arrays have a lower bound of zero and not @code{-10} as in the example
11046 Here are some more type related Modula-2 examples:
11050 colour = (blue, red, yellow, green) ;
11051 t = [blue..yellow] ;
11059 The @value{GDBN} interaction shows how you can query the data type
11060 and value of a variable.
11063 (@value{GDBP}) print s
11065 (@value{GDBP}) ptype t
11066 type = [blue..yellow]
11070 In this example a Modula-2 array is declared and its contents
11071 displayed. Observe that the contents are written in the same way as
11072 their @code{C} counterparts.
11076 s: ARRAY [1..5] OF CARDINAL ;
11082 (@value{GDBP}) print s
11083 $1 = @{1, 0, 0, 0, 0@}
11084 (@value{GDBP}) ptype s
11085 type = ARRAY [1..5] OF CARDINAL
11088 The Modula-2 language interface to @value{GDBN} also understands
11089 pointer types as shown in this example:
11093 s: POINTER TO ARRAY [1..5] OF CARDINAL ;
11100 and you can request that @value{GDBN} describes the type of @code{s}.
11103 (@value{GDBP}) ptype s
11104 type = POINTER TO ARRAY [1..5] OF CARDINAL
11107 @value{GDBN} handles compound types as we can see in this example.
11108 Here we combine array types, record types, pointer types and subrange
11119 myarray = ARRAY myrange OF CARDINAL ;
11120 myrange = [-2..2] ;
11122 s: POINTER TO ARRAY myrange OF foo ;
11126 and you can ask @value{GDBN} to describe the type of @code{s} as shown
11130 (@value{GDBP}) ptype s
11131 type = POINTER TO ARRAY [-2..2] OF foo = RECORD
11134 f3 : ARRAY [-2..2] OF CARDINAL;
11139 @subsubsection Modula-2 Defaults
11140 @cindex Modula-2 defaults
11142 If type and range checking are set automatically by @value{GDBN}, they
11143 both default to @code{on} whenever the working language changes to
11144 Modula-2. This happens regardless of whether you or @value{GDBN}
11145 selected the working language.
11147 If you allow @value{GDBN} to set the language automatically, then entering
11148 code compiled from a file whose name ends with @file{.mod} sets the
11149 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN}
11150 Infer the Source Language}, for further details.
11153 @subsubsection Deviations from Standard Modula-2
11154 @cindex Modula-2, deviations from
11156 A few changes have been made to make Modula-2 programs easier to debug.
11157 This is done primarily via loosening its type strictness:
11161 Unlike in standard Modula-2, pointer constants can be formed by
11162 integers. This allows you to modify pointer variables during
11163 debugging. (In standard Modula-2, the actual address contained in a
11164 pointer variable is hidden from you; it can only be modified
11165 through direct assignment to another pointer variable or expression that
11166 returned a pointer.)
11169 C escape sequences can be used in strings and characters to represent
11170 non-printable characters. @value{GDBN} prints out strings with these
11171 escape sequences embedded. Single non-printable characters are
11172 printed using the @samp{CHR(@var{nnn})} format.
11175 The assignment operator (@code{:=}) returns the value of its right-hand
11179 All built-in procedures both modify @emph{and} return their argument.
11183 @subsubsection Modula-2 Type and Range Checks
11184 @cindex Modula-2 checks
11187 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
11190 @c FIXME remove warning when type/range checks added
11192 @value{GDBN} considers two Modula-2 variables type equivalent if:
11196 They are of types that have been declared equivalent via a @code{TYPE
11197 @var{t1} = @var{t2}} statement
11200 They have been declared on the same line. (Note: This is true of the
11201 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
11204 As long as type checking is enabled, any attempt to combine variables
11205 whose types are not equivalent is an error.
11207 Range checking is done on all mathematical operations, assignment, array
11208 index bounds, and all built-in functions and procedures.
11211 @subsubsection The Scope Operators @code{::} and @code{.}
11213 @cindex @code{.}, Modula-2 scope operator
11214 @cindex colon, doubled as scope operator
11216 @vindex colon-colon@r{, in Modula-2}
11217 @c Info cannot handle :: but TeX can.
11220 @vindex ::@r{, in Modula-2}
11223 There are a few subtle differences between the Modula-2 scope operator
11224 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
11229 @var{module} . @var{id}
11230 @var{scope} :: @var{id}
11234 where @var{scope} is the name of a module or a procedure,
11235 @var{module} the name of a module, and @var{id} is any declared
11236 identifier within your program, except another module.
11238 Using the @code{::} operator makes @value{GDBN} search the scope
11239 specified by @var{scope} for the identifier @var{id}. If it is not
11240 found in the specified scope, then @value{GDBN} searches all scopes
11241 enclosing the one specified by @var{scope}.
11243 Using the @code{.} operator makes @value{GDBN} search the current scope for
11244 the identifier specified by @var{id} that was imported from the
11245 definition module specified by @var{module}. With this operator, it is
11246 an error if the identifier @var{id} was not imported from definition
11247 module @var{module}, or if @var{id} is not an identifier in
11251 @subsubsection @value{GDBN} and Modula-2
11253 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
11254 Five subcommands of @code{set print} and @code{show print} apply
11255 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
11256 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
11257 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
11258 analogue in Modula-2.
11260 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
11261 with any language, is not useful with Modula-2. Its
11262 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
11263 created in Modula-2 as they can in C or C@t{++}. However, because an
11264 address can be specified by an integral constant, the construct
11265 @samp{@{@var{type}@}@var{adrexp}} is still useful.
11267 @cindex @code{#} in Modula-2
11268 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
11269 interpreted as the beginning of a comment. Use @code{<>} instead.
11275 The extensions made to @value{GDBN} for Ada only support
11276 output from the @sc{gnu} Ada (GNAT) compiler.
11277 Other Ada compilers are not currently supported, and
11278 attempting to debug executables produced by them is most likely
11282 @cindex expressions in Ada
11284 * Ada Mode Intro:: General remarks on the Ada syntax
11285 and semantics supported by Ada mode
11287 * Omissions from Ada:: Restrictions on the Ada expression syntax.
11288 * Additions to Ada:: Extensions of the Ada expression syntax.
11289 * Stopping Before Main Program:: Debugging the program during elaboration.
11290 * Ada Tasks:: Listing and setting breakpoints in tasks.
11291 * Ada Tasks and Core Files:: Tasking Support when Debugging Core Files
11292 * Ada Glitches:: Known peculiarities of Ada mode.
11295 @node Ada Mode Intro
11296 @subsubsection Introduction
11297 @cindex Ada mode, general
11299 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
11300 syntax, with some extensions.
11301 The philosophy behind the design of this subset is
11305 That @value{GDBN} should provide basic literals and access to operations for
11306 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
11307 leaving more sophisticated computations to subprograms written into the
11308 program (which therefore may be called from @value{GDBN}).
11311 That type safety and strict adherence to Ada language restrictions
11312 are not particularly important to the @value{GDBN} user.
11315 That brevity is important to the @value{GDBN} user.
11318 Thus, for brevity, the debugger acts as if all names declared in
11319 user-written packages are directly visible, even if they are not visible
11320 according to Ada rules, thus making it unnecessary to fully qualify most
11321 names with their packages, regardless of context. Where this causes
11322 ambiguity, @value{GDBN} asks the user's intent.
11324 The debugger will start in Ada mode if it detects an Ada main program.
11325 As for other languages, it will enter Ada mode when stopped in a program that
11326 was translated from an Ada source file.
11328 While in Ada mode, you may use `@t{--}' for comments. This is useful
11329 mostly for documenting command files. The standard @value{GDBN} comment
11330 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
11331 middle (to allow based literals).
11333 The debugger supports limited overloading. Given a subprogram call in which
11334 the function symbol has multiple definitions, it will use the number of
11335 actual parameters and some information about their types to attempt to narrow
11336 the set of definitions. It also makes very limited use of context, preferring
11337 procedures to functions in the context of the @code{call} command, and
11338 functions to procedures elsewhere.
11340 @node Omissions from Ada
11341 @subsubsection Omissions from Ada
11342 @cindex Ada, omissions from
11344 Here are the notable omissions from the subset:
11348 Only a subset of the attributes are supported:
11352 @t{'First}, @t{'Last}, and @t{'Length}
11353 on array objects (not on types and subtypes).
11356 @t{'Min} and @t{'Max}.
11359 @t{'Pos} and @t{'Val}.
11365 @t{'Range} on array objects (not subtypes), but only as the right
11366 operand of the membership (@code{in}) operator.
11369 @t{'Access}, @t{'Unchecked_Access}, and
11370 @t{'Unrestricted_Access} (a GNAT extension).
11378 @code{Characters.Latin_1} are not available and
11379 concatenation is not implemented. Thus, escape characters in strings are
11380 not currently available.
11383 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
11384 equality of representations. They will generally work correctly
11385 for strings and arrays whose elements have integer or enumeration types.
11386 They may not work correctly for arrays whose element
11387 types have user-defined equality, for arrays of real values
11388 (in particular, IEEE-conformant floating point, because of negative
11389 zeroes and NaNs), and for arrays whose elements contain unused bits with
11390 indeterminate values.
11393 The other component-by-component array operations (@code{and}, @code{or},
11394 @code{xor}, @code{not}, and relational tests other than equality)
11395 are not implemented.
11398 @cindex array aggregates (Ada)
11399 @cindex record aggregates (Ada)
11400 @cindex aggregates (Ada)
11401 There is limited support for array and record aggregates. They are
11402 permitted only on the right sides of assignments, as in these examples:
11405 (@value{GDBP}) set An_Array := (1, 2, 3, 4, 5, 6)
11406 (@value{GDBP}) set An_Array := (1, others => 0)
11407 (@value{GDBP}) set An_Array := (0|4 => 1, 1..3 => 2, 5 => 6)
11408 (@value{GDBP}) set A_2D_Array := ((1, 2, 3), (4, 5, 6), (7, 8, 9))
11409 (@value{GDBP}) set A_Record := (1, "Peter", True);
11410 (@value{GDBP}) set A_Record := (Name => "Peter", Id => 1, Alive => True)
11414 discriminant's value by assigning an aggregate has an
11415 undefined effect if that discriminant is used within the record.
11416 However, you can first modify discriminants by directly assigning to
11417 them (which normally would not be allowed in Ada), and then performing an
11418 aggregate assignment. For example, given a variable @code{A_Rec}
11419 declared to have a type such as:
11422 type Rec (Len : Small_Integer := 0) is record
11424 Vals : IntArray (1 .. Len);
11428 you can assign a value with a different size of @code{Vals} with two
11432 (@value{GDBP}) set A_Rec.Len := 4
11433 (@value{GDBP}) set A_Rec := (Id => 42, Vals => (1, 2, 3, 4))
11436 As this example also illustrates, @value{GDBN} is very loose about the usual
11437 rules concerning aggregates. You may leave out some of the
11438 components of an array or record aggregate (such as the @code{Len}
11439 component in the assignment to @code{A_Rec} above); they will retain their
11440 original values upon assignment. You may freely use dynamic values as
11441 indices in component associations. You may even use overlapping or
11442 redundant component associations, although which component values are
11443 assigned in such cases is not defined.
11446 Calls to dispatching subprograms are not implemented.
11449 The overloading algorithm is much more limited (i.e., less selective)
11450 than that of real Ada. It makes only limited use of the context in
11451 which a subexpression appears to resolve its meaning, and it is much
11452 looser in its rules for allowing type matches. As a result, some
11453 function calls will be ambiguous, and the user will be asked to choose
11454 the proper resolution.
11457 The @code{new} operator is not implemented.
11460 Entry calls are not implemented.
11463 Aside from printing, arithmetic operations on the native VAX floating-point
11464 formats are not supported.
11467 It is not possible to slice a packed array.
11470 The names @code{True} and @code{False}, when not part of a qualified name,
11471 are interpreted as if implicitly prefixed by @code{Standard}, regardless of
11473 Should your program
11474 redefine these names in a package or procedure (at best a dubious practice),
11475 you will have to use fully qualified names to access their new definitions.
11478 @node Additions to Ada
11479 @subsubsection Additions to Ada
11480 @cindex Ada, deviations from
11482 As it does for other languages, @value{GDBN} makes certain generic
11483 extensions to Ada (@pxref{Expressions}):
11487 If the expression @var{E} is a variable residing in memory (typically
11488 a local variable or array element) and @var{N} is a positive integer,
11489 then @code{@var{E}@@@var{N}} displays the values of @var{E} and the
11490 @var{N}-1 adjacent variables following it in memory as an array. In
11491 Ada, this operator is generally not necessary, since its prime use is
11492 in displaying parts of an array, and slicing will usually do this in
11493 Ada. However, there are occasional uses when debugging programs in
11494 which certain debugging information has been optimized away.
11497 @code{@var{B}::@var{var}} means ``the variable named @var{var} that
11498 appears in function or file @var{B}.'' When @var{B} is a file name,
11499 you must typically surround it in single quotes.
11502 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
11503 @var{type} that appears at address @var{addr}.''
11506 A name starting with @samp{$} is a convenience variable
11507 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
11510 In addition, @value{GDBN} provides a few other shortcuts and outright
11511 additions specific to Ada:
11515 The assignment statement is allowed as an expression, returning
11516 its right-hand operand as its value. Thus, you may enter
11519 (@value{GDBP}) set x := y + 3
11520 (@value{GDBP}) print A(tmp := y + 1)
11524 The semicolon is allowed as an ``operator,'' returning as its value
11525 the value of its right-hand operand.
11526 This allows, for example,
11527 complex conditional breaks:
11530 (@value{GDBP}) break f
11531 (@value{GDBP}) condition 1 (report(i); k += 1; A(k) > 100)
11535 Rather than use catenation and symbolic character names to introduce special
11536 characters into strings, one may instead use a special bracket notation,
11537 which is also used to print strings. A sequence of characters of the form
11538 @samp{["@var{XX}"]} within a string or character literal denotes the
11539 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
11540 sequence of characters @samp{["""]} also denotes a single quotation mark
11541 in strings. For example,
11543 "One line.["0a"]Next line.["0a"]"
11546 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF})
11550 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
11551 @t{'Max} is optional (and is ignored in any case). For example, it is valid
11555 (@value{GDBP}) print 'max(x, y)
11559 When printing arrays, @value{GDBN} uses positional notation when the
11560 array has a lower bound of 1, and uses a modified named notation otherwise.
11561 For example, a one-dimensional array of three integers with a lower bound
11562 of 3 might print as
11569 That is, in contrast to valid Ada, only the first component has a @code{=>}
11573 You may abbreviate attributes in expressions with any unique,
11574 multi-character subsequence of
11575 their names (an exact match gets preference).
11576 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
11577 in place of @t{a'length}.
11580 @cindex quoting Ada internal identifiers
11581 Since Ada is case-insensitive, the debugger normally maps identifiers you type
11582 to lower case. The GNAT compiler uses upper-case characters for
11583 some of its internal identifiers, which are normally of no interest to users.
11584 For the rare occasions when you actually have to look at them,
11585 enclose them in angle brackets to avoid the lower-case mapping.
11588 (@value{GDBP}) print <JMPBUF_SAVE>[0]
11592 Printing an object of class-wide type or dereferencing an
11593 access-to-class-wide value will display all the components of the object's
11594 specific type (as indicated by its run-time tag). Likewise, component
11595 selection on such a value will operate on the specific type of the
11600 @node Stopping Before Main Program
11601 @subsubsection Stopping at the Very Beginning
11603 @cindex breakpointing Ada elaboration code
11604 It is sometimes necessary to debug the program during elaboration, and
11605 before reaching the main procedure.
11606 As defined in the Ada Reference
11607 Manual, the elaboration code is invoked from a procedure called
11608 @code{adainit}. To run your program up to the beginning of
11609 elaboration, simply use the following two commands:
11610 @code{tbreak adainit} and @code{run}.
11613 @subsubsection Extensions for Ada Tasks
11614 @cindex Ada, tasking
11616 Support for Ada tasks is analogous to that for threads (@pxref{Threads}).
11617 @value{GDBN} provides the following task-related commands:
11622 This command shows a list of current Ada tasks, as in the following example:
11629 (@value{GDBP}) info tasks
11630 ID TID P-ID Pri State Name
11631 1 8088000 0 15 Child Activation Wait main_task
11632 2 80a4000 1 15 Accept Statement b
11633 3 809a800 1 15 Child Activation Wait a
11634 * 4 80ae800 3 15 Runnable c
11639 In this listing, the asterisk before the last task indicates it to be the
11640 task currently being inspected.
11644 Represents @value{GDBN}'s internal task number.
11650 The parent's task ID (@value{GDBN}'s internal task number).
11653 The base priority of the task.
11656 Current state of the task.
11660 The task has been created but has not been activated. It cannot be
11664 The task is not blocked for any reason known to Ada. (It may be waiting
11665 for a mutex, though.) It is conceptually "executing" in normal mode.
11668 The task is terminated, in the sense of ARM 9.3 (5). Any dependents
11669 that were waiting on terminate alternatives have been awakened and have
11670 terminated themselves.
11672 @item Child Activation Wait
11673 The task is waiting for created tasks to complete activation.
11675 @item Accept Statement
11676 The task is waiting on an accept or selective wait statement.
11678 @item Waiting on entry call
11679 The task is waiting on an entry call.
11681 @item Async Select Wait
11682 The task is waiting to start the abortable part of an asynchronous
11686 The task is waiting on a select statement with only a delay
11689 @item Child Termination Wait
11690 The task is sleeping having completed a master within itself, and is
11691 waiting for the tasks dependent on that master to become terminated or
11692 waiting on a terminate Phase.
11694 @item Wait Child in Term Alt
11695 The task is sleeping waiting for tasks on terminate alternatives to
11696 finish terminating.
11698 @item Accepting RV with @var{taskno}
11699 The task is accepting a rendez-vous with the task @var{taskno}.
11703 Name of the task in the program.
11707 @kindex info task @var{taskno}
11708 @item info task @var{taskno}
11709 This command shows detailled informations on the specified task, as in
11710 the following example:
11715 (@value{GDBP}) info tasks
11716 ID TID P-ID Pri State Name
11717 1 8077880 0 15 Child Activation Wait main_task
11718 * 2 807c468 1 15 Runnable task_1
11719 (@value{GDBP}) info task 2
11720 Ada Task: 0x807c468
11723 Parent: 1 (main_task)
11729 @kindex task@r{ (Ada)}
11730 @cindex current Ada task ID
11731 This command prints the ID of the current task.
11737 (@value{GDBP}) info tasks
11738 ID TID P-ID Pri State Name
11739 1 8077870 0 15 Child Activation Wait main_task
11740 * 2 807c458 1 15 Runnable t
11741 (@value{GDBP}) task
11742 [Current task is 2]
11745 @item task @var{taskno}
11746 @cindex Ada task switching
11747 This command is like the @code{thread @var{threadno}}
11748 command (@pxref{Threads}). It switches the context of debugging
11749 from the current task to the given task.
11755 (@value{GDBP}) info tasks
11756 ID TID P-ID Pri State Name
11757 1 8077870 0 15 Child Activation Wait main_task
11758 * 2 807c458 1 15 Runnable t
11759 (@value{GDBP}) task 1
11760 [Switching to task 1]
11761 #0 0x8067726 in pthread_cond_wait ()
11763 #0 0x8067726 in pthread_cond_wait ()
11764 #1 0x8056714 in system.os_interface.pthread_cond_wait ()
11765 #2 0x805cb63 in system.task_primitives.operations.sleep ()
11766 #3 0x806153e in system.tasking.stages.activate_tasks ()
11767 #4 0x804aacc in un () at un.adb:5
11770 @item break @var{linespec} task @var{taskno}
11771 @itemx break @var{linespec} task @var{taskno} if @dots{}
11772 @cindex breakpoints and tasks, in Ada
11773 @cindex task breakpoints, in Ada
11774 @kindex break @dots{} task @var{taskno}@r{ (Ada)}
11775 These commands are like the @code{break @dots{} thread @dots{}}
11776 command (@pxref{Thread Stops}).
11777 @var{linespec} specifies source lines, as described
11778 in @ref{Specify Location}.
11780 Use the qualifier @samp{task @var{taskno}} with a breakpoint command
11781 to specify that you only want @value{GDBN} to stop the program when a
11782 particular Ada task reaches this breakpoint. @var{taskno} is one of the
11783 numeric task identifiers assigned by @value{GDBN}, shown in the first
11784 column of the @samp{info tasks} display.
11786 If you do not specify @samp{task @var{taskno}} when you set a
11787 breakpoint, the breakpoint applies to @emph{all} tasks of your
11790 You can use the @code{task} qualifier on conditional breakpoints as
11791 well; in this case, place @samp{task @var{taskno}} before the
11792 breakpoint condition (before the @code{if}).
11800 (@value{GDBP}) info tasks
11801 ID TID P-ID Pri State Name
11802 1 140022020 0 15 Child Activation Wait main_task
11803 2 140045060 1 15 Accept/Select Wait t2
11804 3 140044840 1 15 Runnable t1
11805 * 4 140056040 1 15 Runnable t3
11806 (@value{GDBP}) b 15 task 2
11807 Breakpoint 5 at 0x120044cb0: file test_task_debug.adb, line 15.
11808 (@value{GDBP}) cont
11813 Breakpoint 5, test_task_debug () at test_task_debug.adb:15
11815 (@value{GDBP}) info tasks
11816 ID TID P-ID Pri State Name
11817 1 140022020 0 15 Child Activation Wait main_task
11818 * 2 140045060 1 15 Runnable t2
11819 3 140044840 1 15 Runnable t1
11820 4 140056040 1 15 Delay Sleep t3
11824 @node Ada Tasks and Core Files
11825 @subsubsection Tasking Support when Debugging Core Files
11826 @cindex Ada tasking and core file debugging
11828 When inspecting a core file, as opposed to debugging a live program,
11829 tasking support may be limited or even unavailable, depending on
11830 the platform being used.
11831 For instance, on x86-linux, the list of tasks is available, but task
11832 switching is not supported. On Tru64, however, task switching will work
11835 On certain platforms, including Tru64, the debugger needs to perform some
11836 memory writes in order to provide Ada tasking support. When inspecting
11837 a core file, this means that the core file must be opened with read-write
11838 privileges, using the command @samp{"set write on"} (@pxref{Patching}).
11839 Under these circumstances, you should make a backup copy of the core
11840 file before inspecting it with @value{GDBN}.
11843 @subsubsection Known Peculiarities of Ada Mode
11844 @cindex Ada, problems
11846 Besides the omissions listed previously (@pxref{Omissions from Ada}),
11847 we know of several problems with and limitations of Ada mode in
11849 some of which will be fixed with planned future releases of the debugger
11850 and the GNU Ada compiler.
11854 Currently, the debugger
11855 has insufficient information to determine whether certain pointers represent
11856 pointers to objects or the objects themselves.
11857 Thus, the user may have to tack an extra @code{.all} after an expression
11858 to get it printed properly.
11861 Static constants that the compiler chooses not to materialize as objects in
11862 storage are invisible to the debugger.
11865 Named parameter associations in function argument lists are ignored (the
11866 argument lists are treated as positional).
11869 Many useful library packages are currently invisible to the debugger.
11872 Fixed-point arithmetic, conversions, input, and output is carried out using
11873 floating-point arithmetic, and may give results that only approximate those on
11877 The GNAT compiler never generates the prefix @code{Standard} for any of
11878 the standard symbols defined by the Ada language. @value{GDBN} knows about
11879 this: it will strip the prefix from names when you use it, and will never
11880 look for a name you have so qualified among local symbols, nor match against
11881 symbols in other packages or subprograms. If you have
11882 defined entities anywhere in your program other than parameters and
11883 local variables whose simple names match names in @code{Standard},
11884 GNAT's lack of qualification here can cause confusion. When this happens,
11885 you can usually resolve the confusion
11886 by qualifying the problematic names with package
11887 @code{Standard} explicitly.
11890 @node Unsupported Languages
11891 @section Unsupported Languages
11893 @cindex unsupported languages
11894 @cindex minimal language
11895 In addition to the other fully-supported programming languages,
11896 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
11897 It does not represent a real programming language, but provides a set
11898 of capabilities close to what the C or assembly languages provide.
11899 This should allow most simple operations to be performed while debugging
11900 an application that uses a language currently not supported by @value{GDBN}.
11902 If the language is set to @code{auto}, @value{GDBN} will automatically
11903 select this language if the current frame corresponds to an unsupported
11907 @chapter Examining the Symbol Table
11909 The commands described in this chapter allow you to inquire about the
11910 symbols (names of variables, functions and types) defined in your
11911 program. This information is inherent in the text of your program and
11912 does not change as your program executes. @value{GDBN} finds it in your
11913 program's symbol table, in the file indicated when you started @value{GDBN}
11914 (@pxref{File Options, ,Choosing Files}), or by one of the
11915 file-management commands (@pxref{Files, ,Commands to Specify Files}).
11917 @cindex symbol names
11918 @cindex names of symbols
11919 @cindex quoting names
11920 Occasionally, you may need to refer to symbols that contain unusual
11921 characters, which @value{GDBN} ordinarily treats as word delimiters. The
11922 most frequent case is in referring to static variables in other
11923 source files (@pxref{Variables,,Program Variables}). File names
11924 are recorded in object files as debugging symbols, but @value{GDBN} would
11925 ordinarily parse a typical file name, like @file{foo.c}, as the three words
11926 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
11927 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
11934 looks up the value of @code{x} in the scope of the file @file{foo.c}.
11937 @cindex case-insensitive symbol names
11938 @cindex case sensitivity in symbol names
11939 @kindex set case-sensitive
11940 @item set case-sensitive on
11941 @itemx set case-sensitive off
11942 @itemx set case-sensitive auto
11943 Normally, when @value{GDBN} looks up symbols, it matches their names
11944 with case sensitivity determined by the current source language.
11945 Occasionally, you may wish to control that. The command @code{set
11946 case-sensitive} lets you do that by specifying @code{on} for
11947 case-sensitive matches or @code{off} for case-insensitive ones. If
11948 you specify @code{auto}, case sensitivity is reset to the default
11949 suitable for the source language. The default is case-sensitive
11950 matches for all languages except for Fortran, for which the default is
11951 case-insensitive matches.
11953 @kindex show case-sensitive
11954 @item show case-sensitive
11955 This command shows the current setting of case sensitivity for symbols
11958 @kindex info address
11959 @cindex address of a symbol
11960 @item info address @var{symbol}
11961 Describe where the data for @var{symbol} is stored. For a register
11962 variable, this says which register it is kept in. For a non-register
11963 local variable, this prints the stack-frame offset at which the variable
11966 Note the contrast with @samp{print &@var{symbol}}, which does not work
11967 at all for a register variable, and for a stack local variable prints
11968 the exact address of the current instantiation of the variable.
11970 @kindex info symbol
11971 @cindex symbol from address
11972 @cindex closest symbol and offset for an address
11973 @item info symbol @var{addr}
11974 Print the name of a symbol which is stored at the address @var{addr}.
11975 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
11976 nearest symbol and an offset from it:
11979 (@value{GDBP}) info symbol 0x54320
11980 _initialize_vx + 396 in section .text
11984 This is the opposite of the @code{info address} command. You can use
11985 it to find out the name of a variable or a function given its address.
11987 For dynamically linked executables, the name of executable or shared
11988 library containing the symbol is also printed:
11991 (@value{GDBP}) info symbol 0x400225
11992 _start + 5 in section .text of /tmp/a.out
11993 (@value{GDBP}) info symbol 0x2aaaac2811cf
11994 __read_nocancel + 6 in section .text of /usr/lib64/libc.so.6
11998 @item whatis [@var{arg}]
11999 Print the data type of @var{arg}, which can be either an expression or
12000 a data type. With no argument, print the data type of @code{$}, the
12001 last value in the value history. If @var{arg} is an expression, it is
12002 not actually evaluated, and any side-effecting operations (such as
12003 assignments or function calls) inside it do not take place. If
12004 @var{arg} is a type name, it may be the name of a type or typedef, or
12005 for C code it may have the form @samp{class @var{class-name}},
12006 @samp{struct @var{struct-tag}}, @samp{union @var{union-tag}} or
12007 @samp{enum @var{enum-tag}}.
12008 @xref{Expressions, ,Expressions}.
12011 @item ptype [@var{arg}]
12012 @code{ptype} accepts the same arguments as @code{whatis}, but prints a
12013 detailed description of the type, instead of just the name of the type.
12014 @xref{Expressions, ,Expressions}.
12016 For example, for this variable declaration:
12019 struct complex @{double real; double imag;@} v;
12023 the two commands give this output:
12027 (@value{GDBP}) whatis v
12028 type = struct complex
12029 (@value{GDBP}) ptype v
12030 type = struct complex @{
12038 As with @code{whatis}, using @code{ptype} without an argument refers to
12039 the type of @code{$}, the last value in the value history.
12041 @cindex incomplete type
12042 Sometimes, programs use opaque data types or incomplete specifications
12043 of complex data structure. If the debug information included in the
12044 program does not allow @value{GDBN} to display a full declaration of
12045 the data type, it will say @samp{<incomplete type>}. For example,
12046 given these declarations:
12050 struct foo *fooptr;
12054 but no definition for @code{struct foo} itself, @value{GDBN} will say:
12057 (@value{GDBP}) ptype foo
12058 $1 = <incomplete type>
12062 ``Incomplete type'' is C terminology for data types that are not
12063 completely specified.
12066 @item info types @var{regexp}
12068 Print a brief description of all types whose names match the regular
12069 expression @var{regexp} (or all types in your program, if you supply
12070 no argument). Each complete typename is matched as though it were a
12071 complete line; thus, @samp{i type value} gives information on all
12072 types in your program whose names include the string @code{value}, but
12073 @samp{i type ^value$} gives information only on types whose complete
12074 name is @code{value}.
12076 This command differs from @code{ptype} in two ways: first, like
12077 @code{whatis}, it does not print a detailed description; second, it
12078 lists all source files where a type is defined.
12081 @cindex local variables
12082 @item info scope @var{location}
12083 List all the variables local to a particular scope. This command
12084 accepts a @var{location} argument---a function name, a source line, or
12085 an address preceded by a @samp{*}, and prints all the variables local
12086 to the scope defined by that location. (@xref{Specify Location}, for
12087 details about supported forms of @var{location}.) For example:
12090 (@value{GDBP}) @b{info scope command_line_handler}
12091 Scope for command_line_handler:
12092 Symbol rl is an argument at stack/frame offset 8, length 4.
12093 Symbol linebuffer is in static storage at address 0x150a18, length 4.
12094 Symbol linelength is in static storage at address 0x150a1c, length 4.
12095 Symbol p is a local variable in register $esi, length 4.
12096 Symbol p1 is a local variable in register $ebx, length 4.
12097 Symbol nline is a local variable in register $edx, length 4.
12098 Symbol repeat is a local variable at frame offset -8, length 4.
12102 This command is especially useful for determining what data to collect
12103 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
12106 @kindex info source
12108 Show information about the current source file---that is, the source file for
12109 the function containing the current point of execution:
12112 the name of the source file, and the directory containing it,
12114 the directory it was compiled in,
12116 its length, in lines,
12118 which programming language it is written in,
12120 whether the executable includes debugging information for that file, and
12121 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
12123 whether the debugging information includes information about
12124 preprocessor macros.
12128 @kindex info sources
12130 Print the names of all source files in your program for which there is
12131 debugging information, organized into two lists: files whose symbols
12132 have already been read, and files whose symbols will be read when needed.
12134 @kindex info functions
12135 @item info functions
12136 Print the names and data types of all defined functions.
12138 @item info functions @var{regexp}
12139 Print the names and data types of all defined functions
12140 whose names contain a match for regular expression @var{regexp}.
12141 Thus, @samp{info fun step} finds all functions whose names
12142 include @code{step}; @samp{info fun ^step} finds those whose names
12143 start with @code{step}. If a function name contains characters
12144 that conflict with the regular expression language (e.g.@:
12145 @samp{operator*()}), they may be quoted with a backslash.
12147 @kindex info variables
12148 @item info variables
12149 Print the names and data types of all variables that are declared
12150 outside of functions (i.e.@: excluding local variables).
12152 @item info variables @var{regexp}
12153 Print the names and data types of all variables (except for local
12154 variables) whose names contain a match for regular expression
12157 @kindex info classes
12158 @cindex Objective-C, classes and selectors
12160 @itemx info classes @var{regexp}
12161 Display all Objective-C classes in your program, or
12162 (with the @var{regexp} argument) all those matching a particular regular
12165 @kindex info selectors
12166 @item info selectors
12167 @itemx info selectors @var{regexp}
12168 Display all Objective-C selectors in your program, or
12169 (with the @var{regexp} argument) all those matching a particular regular
12173 This was never implemented.
12174 @kindex info methods
12176 @itemx info methods @var{regexp}
12177 The @code{info methods} command permits the user to examine all defined
12178 methods within C@t{++} program, or (with the @var{regexp} argument) a
12179 specific set of methods found in the various C@t{++} classes. Many
12180 C@t{++} classes provide a large number of methods. Thus, the output
12181 from the @code{ptype} command can be overwhelming and hard to use. The
12182 @code{info-methods} command filters the methods, printing only those
12183 which match the regular-expression @var{regexp}.
12186 @cindex reloading symbols
12187 Some systems allow individual object files that make up your program to
12188 be replaced without stopping and restarting your program. For example,
12189 in VxWorks you can simply recompile a defective object file and keep on
12190 running. If you are running on one of these systems, you can allow
12191 @value{GDBN} to reload the symbols for automatically relinked modules:
12194 @kindex set symbol-reloading
12195 @item set symbol-reloading on
12196 Replace symbol definitions for the corresponding source file when an
12197 object file with a particular name is seen again.
12199 @item set symbol-reloading off
12200 Do not replace symbol definitions when encountering object files of the
12201 same name more than once. This is the default state; if you are not
12202 running on a system that permits automatic relinking of modules, you
12203 should leave @code{symbol-reloading} off, since otherwise @value{GDBN}
12204 may discard symbols when linking large programs, that may contain
12205 several modules (from different directories or libraries) with the same
12208 @kindex show symbol-reloading
12209 @item show symbol-reloading
12210 Show the current @code{on} or @code{off} setting.
12213 @cindex opaque data types
12214 @kindex set opaque-type-resolution
12215 @item set opaque-type-resolution on
12216 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
12217 declared as a pointer to a @code{struct}, @code{class}, or
12218 @code{union}---for example, @code{struct MyType *}---that is used in one
12219 source file although the full declaration of @code{struct MyType} is in
12220 another source file. The default is on.
12222 A change in the setting of this subcommand will not take effect until
12223 the next time symbols for a file are loaded.
12225 @item set opaque-type-resolution off
12226 Tell @value{GDBN} not to resolve opaque types. In this case, the type
12227 is printed as follows:
12229 @{<no data fields>@}
12232 @kindex show opaque-type-resolution
12233 @item show opaque-type-resolution
12234 Show whether opaque types are resolved or not.
12236 @kindex set print symbol-loading
12237 @cindex print messages when symbols are loaded
12238 @item set print symbol-loading
12239 @itemx set print symbol-loading on
12240 @itemx set print symbol-loading off
12241 The @code{set print symbol-loading} command allows you to enable or
12242 disable printing of messages when @value{GDBN} loads symbols.
12243 By default, these messages will be printed, and normally this is what
12244 you want. Disabling these messages is useful when debugging applications
12245 with lots of shared libraries where the quantity of output can be more
12246 annoying than useful.
12248 @kindex show print symbol-loading
12249 @item show print symbol-loading
12250 Show whether messages will be printed when @value{GDBN} loads symbols.
12252 @kindex maint print symbols
12253 @cindex symbol dump
12254 @kindex maint print psymbols
12255 @cindex partial symbol dump
12256 @item maint print symbols @var{filename}
12257 @itemx maint print psymbols @var{filename}
12258 @itemx maint print msymbols @var{filename}
12259 Write a dump of debugging symbol data into the file @var{filename}.
12260 These commands are used to debug the @value{GDBN} symbol-reading code. Only
12261 symbols with debugging data are included. If you use @samp{maint print
12262 symbols}, @value{GDBN} includes all the symbols for which it has already
12263 collected full details: that is, @var{filename} reflects symbols for
12264 only those files whose symbols @value{GDBN} has read. You can use the
12265 command @code{info sources} to find out which files these are. If you
12266 use @samp{maint print psymbols} instead, the dump shows information about
12267 symbols that @value{GDBN} only knows partially---that is, symbols defined in
12268 files that @value{GDBN} has skimmed, but not yet read completely. Finally,
12269 @samp{maint print msymbols} dumps just the minimal symbol information
12270 required for each object file from which @value{GDBN} has read some symbols.
12271 @xref{Files, ,Commands to Specify Files}, for a discussion of how
12272 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
12274 @kindex maint info symtabs
12275 @kindex maint info psymtabs
12276 @cindex listing @value{GDBN}'s internal symbol tables
12277 @cindex symbol tables, listing @value{GDBN}'s internal
12278 @cindex full symbol tables, listing @value{GDBN}'s internal
12279 @cindex partial symbol tables, listing @value{GDBN}'s internal
12280 @item maint info symtabs @r{[} @var{regexp} @r{]}
12281 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
12283 List the @code{struct symtab} or @code{struct partial_symtab}
12284 structures whose names match @var{regexp}. If @var{regexp} is not
12285 given, list them all. The output includes expressions which you can
12286 copy into a @value{GDBN} debugging this one to examine a particular
12287 structure in more detail. For example:
12290 (@value{GDBP}) maint info psymtabs dwarf2read
12291 @{ objfile /home/gnu/build/gdb/gdb
12292 ((struct objfile *) 0x82e69d0)
12293 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
12294 ((struct partial_symtab *) 0x8474b10)
12297 text addresses 0x814d3c8 -- 0x8158074
12298 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
12299 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
12300 dependencies (none)
12303 (@value{GDBP}) maint info symtabs
12307 We see that there is one partial symbol table whose filename contains
12308 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
12309 and we see that @value{GDBN} has not read in any symtabs yet at all.
12310 If we set a breakpoint on a function, that will cause @value{GDBN} to
12311 read the symtab for the compilation unit containing that function:
12314 (@value{GDBP}) break dwarf2_psymtab_to_symtab
12315 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
12317 (@value{GDBP}) maint info symtabs
12318 @{ objfile /home/gnu/build/gdb/gdb
12319 ((struct objfile *) 0x82e69d0)
12320 @{ symtab /home/gnu/src/gdb/dwarf2read.c
12321 ((struct symtab *) 0x86c1f38)
12324 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
12325 linetable ((struct linetable *) 0x8370fa0)
12326 debugformat DWARF 2
12335 @chapter Altering Execution
12337 Once you think you have found an error in your program, you might want to
12338 find out for certain whether correcting the apparent error would lead to
12339 correct results in the rest of the run. You can find the answer by
12340 experiment, using the @value{GDBN} features for altering execution of the
12343 For example, you can store new values into variables or memory
12344 locations, give your program a signal, restart it at a different
12345 address, or even return prematurely from a function.
12348 * Assignment:: Assignment to variables
12349 * Jumping:: Continuing at a different address
12350 * Signaling:: Giving your program a signal
12351 * Returning:: Returning from a function
12352 * Calling:: Calling your program's functions
12353 * Patching:: Patching your program
12357 @section Assignment to Variables
12360 @cindex setting variables
12361 To alter the value of a variable, evaluate an assignment expression.
12362 @xref{Expressions, ,Expressions}. For example,
12369 stores the value 4 into the variable @code{x}, and then prints the
12370 value of the assignment expression (which is 4).
12371 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
12372 information on operators in supported languages.
12374 @kindex set variable
12375 @cindex variables, setting
12376 If you are not interested in seeing the value of the assignment, use the
12377 @code{set} command instead of the @code{print} command. @code{set} is
12378 really the same as @code{print} except that the expression's value is
12379 not printed and is not put in the value history (@pxref{Value History,
12380 ,Value History}). The expression is evaluated only for its effects.
12382 If the beginning of the argument string of the @code{set} command
12383 appears identical to a @code{set} subcommand, use the @code{set
12384 variable} command instead of just @code{set}. This command is identical
12385 to @code{set} except for its lack of subcommands. For example, if your
12386 program has a variable @code{width}, you get an error if you try to set
12387 a new value with just @samp{set width=13}, because @value{GDBN} has the
12388 command @code{set width}:
12391 (@value{GDBP}) whatis width
12393 (@value{GDBP}) p width
12395 (@value{GDBP}) set width=47
12396 Invalid syntax in expression.
12400 The invalid expression, of course, is @samp{=47}. In
12401 order to actually set the program's variable @code{width}, use
12404 (@value{GDBP}) set var width=47
12407 Because the @code{set} command has many subcommands that can conflict
12408 with the names of program variables, it is a good idea to use the
12409 @code{set variable} command instead of just @code{set}. For example, if
12410 your program has a variable @code{g}, you run into problems if you try
12411 to set a new value with just @samp{set g=4}, because @value{GDBN} has
12412 the command @code{set gnutarget}, abbreviated @code{set g}:
12416 (@value{GDBP}) whatis g
12420 (@value{GDBP}) set g=4
12424 The program being debugged has been started already.
12425 Start it from the beginning? (y or n) y
12426 Starting program: /home/smith/cc_progs/a.out
12427 "/home/smith/cc_progs/a.out": can't open to read symbols:
12428 Invalid bfd target.
12429 (@value{GDBP}) show g
12430 The current BFD target is "=4".
12435 The program variable @code{g} did not change, and you silently set the
12436 @code{gnutarget} to an invalid value. In order to set the variable
12440 (@value{GDBP}) set var g=4
12443 @value{GDBN} allows more implicit conversions in assignments than C; you can
12444 freely store an integer value into a pointer variable or vice versa,
12445 and you can convert any structure to any other structure that is the
12446 same length or shorter.
12447 @comment FIXME: how do structs align/pad in these conversions?
12448 @comment /doc@cygnus.com 18dec1990
12450 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
12451 construct to generate a value of specified type at a specified address
12452 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
12453 to memory location @code{0x83040} as an integer (which implies a certain size
12454 and representation in memory), and
12457 set @{int@}0x83040 = 4
12461 stores the value 4 into that memory location.
12464 @section Continuing at a Different Address
12466 Ordinarily, when you continue your program, you do so at the place where
12467 it stopped, with the @code{continue} command. You can instead continue at
12468 an address of your own choosing, with the following commands:
12472 @item jump @var{linespec}
12473 @itemx jump @var{location}
12474 Resume execution at line @var{linespec} or at address given by
12475 @var{location}. Execution stops again immediately if there is a
12476 breakpoint there. @xref{Specify Location}, for a description of the
12477 different forms of @var{linespec} and @var{location}. It is common
12478 practice to use the @code{tbreak} command in conjunction with
12479 @code{jump}. @xref{Set Breaks, ,Setting Breakpoints}.
12481 The @code{jump} command does not change the current stack frame, or
12482 the stack pointer, or the contents of any memory location or any
12483 register other than the program counter. If line @var{linespec} is in
12484 a different function from the one currently executing, the results may
12485 be bizarre if the two functions expect different patterns of arguments or
12486 of local variables. For this reason, the @code{jump} command requests
12487 confirmation if the specified line is not in the function currently
12488 executing. However, even bizarre results are predictable if you are
12489 well acquainted with the machine-language code of your program.
12492 @c Doesn't work on HP-UX; have to set $pcoqh and $pcoqt.
12493 On many systems, you can get much the same effect as the @code{jump}
12494 command by storing a new value into the register @code{$pc}. The
12495 difference is that this does not start your program running; it only
12496 changes the address of where it @emph{will} run when you continue. For
12504 makes the next @code{continue} command or stepping command execute at
12505 address @code{0x485}, rather than at the address where your program stopped.
12506 @xref{Continuing and Stepping, ,Continuing and Stepping}.
12508 The most common occasion to use the @code{jump} command is to back
12509 up---perhaps with more breakpoints set---over a portion of a program
12510 that has already executed, in order to examine its execution in more
12515 @section Giving your Program a Signal
12516 @cindex deliver a signal to a program
12520 @item signal @var{signal}
12521 Resume execution where your program stopped, but immediately give it the
12522 signal @var{signal}. @var{signal} can be the name or the number of a
12523 signal. For example, on many systems @code{signal 2} and @code{signal
12524 SIGINT} are both ways of sending an interrupt signal.
12526 Alternatively, if @var{signal} is zero, continue execution without
12527 giving a signal. This is useful when your program stopped on account of
12528 a signal and would ordinary see the signal when resumed with the
12529 @code{continue} command; @samp{signal 0} causes it to resume without a
12532 @code{signal} does not repeat when you press @key{RET} a second time
12533 after executing the command.
12537 Invoking the @code{signal} command is not the same as invoking the
12538 @code{kill} utility from the shell. Sending a signal with @code{kill}
12539 causes @value{GDBN} to decide what to do with the signal depending on
12540 the signal handling tables (@pxref{Signals}). The @code{signal} command
12541 passes the signal directly to your program.
12545 @section Returning from a Function
12548 @cindex returning from a function
12551 @itemx return @var{expression}
12552 You can cancel execution of a function call with the @code{return}
12553 command. If you give an
12554 @var{expression} argument, its value is used as the function's return
12558 When you use @code{return}, @value{GDBN} discards the selected stack frame
12559 (and all frames within it). You can think of this as making the
12560 discarded frame return prematurely. If you wish to specify a value to
12561 be returned, give that value as the argument to @code{return}.
12563 This pops the selected stack frame (@pxref{Selection, ,Selecting a
12564 Frame}), and any other frames inside of it, leaving its caller as the
12565 innermost remaining frame. That frame becomes selected. The
12566 specified value is stored in the registers used for returning values
12569 The @code{return} command does not resume execution; it leaves the
12570 program stopped in the state that would exist if the function had just
12571 returned. In contrast, the @code{finish} command (@pxref{Continuing
12572 and Stepping, ,Continuing and Stepping}) resumes execution until the
12573 selected stack frame returns naturally.
12575 @value{GDBN} needs to know how the @var{expression} argument should be set for
12576 the inferior. The concrete registers assignment depends on the OS ABI and the
12577 type being returned by the selected stack frame. For example it is common for
12578 OS ABI to return floating point values in FPU registers while integer values in
12579 CPU registers. Still some ABIs return even floating point values in CPU
12580 registers. Larger integer widths (such as @code{long long int}) also have
12581 specific placement rules. @value{GDBN} already knows the OS ABI from its
12582 current target so it needs to find out also the type being returned to make the
12583 assignment into the right register(s).
12585 Normally, the selected stack frame has debug info. @value{GDBN} will always
12586 use the debug info instead of the implicit type of @var{expression} when the
12587 debug info is available. For example, if you type @kbd{return -1}, and the
12588 function in the current stack frame is declared to return a @code{long long
12589 int}, @value{GDBN} transparently converts the implicit @code{int} value of -1
12590 into a @code{long long int}:
12593 Breakpoint 1, func () at gdb.base/return-nodebug.c:29
12595 (@value{GDBP}) return -1
12596 Make func return now? (y or n) y
12597 #0 0x004004f6 in main () at gdb.base/return-nodebug.c:43
12598 43 printf ("result=%lld\n", func ());
12602 However, if the selected stack frame does not have a debug info, e.g., if the
12603 function was compiled without debug info, @value{GDBN} has to find out the type
12604 to return from user. Specifying a different type by mistake may set the value
12605 in different inferior registers than the caller code expects. For example,
12606 typing @kbd{return -1} with its implicit type @code{int} would set only a part
12607 of a @code{long long int} result for a debug info less function (on 32-bit
12608 architectures). Therefore the user is required to specify the return type by
12609 an appropriate cast explicitly:
12612 Breakpoint 2, 0x0040050b in func ()
12613 (@value{GDBP}) return -1
12614 Return value type not available for selected stack frame.
12615 Please use an explicit cast of the value to return.
12616 (@value{GDBP}) return (long long int) -1
12617 Make selected stack frame return now? (y or n) y
12618 #0 0x00400526 in main ()
12623 @section Calling Program Functions
12626 @cindex calling functions
12627 @cindex inferior functions, calling
12628 @item print @var{expr}
12629 Evaluate the expression @var{expr} and display the resulting value.
12630 @var{expr} may include calls to functions in the program being
12634 @item call @var{expr}
12635 Evaluate the expression @var{expr} without displaying @code{void}
12638 You can use this variant of the @code{print} command if you want to
12639 execute a function from your program that does not return anything
12640 (a.k.a.@: @dfn{a void function}), but without cluttering the output
12641 with @code{void} returned values that @value{GDBN} will otherwise
12642 print. If the result is not void, it is printed and saved in the
12646 It is possible for the function you call via the @code{print} or
12647 @code{call} command to generate a signal (e.g., if there's a bug in
12648 the function, or if you passed it incorrect arguments). What happens
12649 in that case is controlled by the @code{set unwindonsignal} command.
12652 @item set unwindonsignal
12653 @kindex set unwindonsignal
12654 @cindex unwind stack in called functions
12655 @cindex call dummy stack unwinding
12656 Set unwinding of the stack if a signal is received while in a function
12657 that @value{GDBN} called in the program being debugged. If set to on,
12658 @value{GDBN} unwinds the stack it created for the call and restores
12659 the context to what it was before the call. If set to off (the
12660 default), @value{GDBN} stops in the frame where the signal was
12663 @item show unwindonsignal
12664 @kindex show unwindonsignal
12665 Show the current setting of stack unwinding in the functions called by
12669 @cindex weak alias functions
12670 Sometimes, a function you wish to call is actually a @dfn{weak alias}
12671 for another function. In such case, @value{GDBN} might not pick up
12672 the type information, including the types of the function arguments,
12673 which causes @value{GDBN} to call the inferior function incorrectly.
12674 As a result, the called function will function erroneously and may
12675 even crash. A solution to that is to use the name of the aliased
12679 @section Patching Programs
12681 @cindex patching binaries
12682 @cindex writing into executables
12683 @cindex writing into corefiles
12685 By default, @value{GDBN} opens the file containing your program's
12686 executable code (or the corefile) read-only. This prevents accidental
12687 alterations to machine code; but it also prevents you from intentionally
12688 patching your program's binary.
12690 If you'd like to be able to patch the binary, you can specify that
12691 explicitly with the @code{set write} command. For example, you might
12692 want to turn on internal debugging flags, or even to make emergency
12698 @itemx set write off
12699 If you specify @samp{set write on}, @value{GDBN} opens executable and
12700 core files for both reading and writing; if you specify @kbd{set write
12701 off} (the default), @value{GDBN} opens them read-only.
12703 If you have already loaded a file, you must load it again (using the
12704 @code{exec-file} or @code{core-file} command) after changing @code{set
12705 write}, for your new setting to take effect.
12709 Display whether executable files and core files are opened for writing
12710 as well as reading.
12714 @chapter @value{GDBN} Files
12716 @value{GDBN} needs to know the file name of the program to be debugged,
12717 both in order to read its symbol table and in order to start your
12718 program. To debug a core dump of a previous run, you must also tell
12719 @value{GDBN} the name of the core dump file.
12722 * Files:: Commands to specify files
12723 * Separate Debug Files:: Debugging information in separate files
12724 * Symbol Errors:: Errors reading symbol files
12728 @section Commands to Specify Files
12730 @cindex symbol table
12731 @cindex core dump file
12733 You may want to specify executable and core dump file names. The usual
12734 way to do this is at start-up time, using the arguments to
12735 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
12736 Out of @value{GDBN}}).
12738 Occasionally it is necessary to change to a different file during a
12739 @value{GDBN} session. Or you may run @value{GDBN} and forget to
12740 specify a file you want to use. Or you are debugging a remote target
12741 via @code{gdbserver} (@pxref{Server, file, Using the @code{gdbserver}
12742 Program}). In these situations the @value{GDBN} commands to specify
12743 new files are useful.
12746 @cindex executable file
12748 @item file @var{filename}
12749 Use @var{filename} as the program to be debugged. It is read for its
12750 symbols and for the contents of pure memory. It is also the program
12751 executed when you use the @code{run} command. If you do not specify a
12752 directory and the file is not found in the @value{GDBN} working directory,
12753 @value{GDBN} uses the environment variable @code{PATH} as a list of
12754 directories to search, just as the shell does when looking for a program
12755 to run. You can change the value of this variable, for both @value{GDBN}
12756 and your program, using the @code{path} command.
12758 @cindex unlinked object files
12759 @cindex patching object files
12760 You can load unlinked object @file{.o} files into @value{GDBN} using
12761 the @code{file} command. You will not be able to ``run'' an object
12762 file, but you can disassemble functions and inspect variables. Also,
12763 if the underlying BFD functionality supports it, you could use
12764 @kbd{gdb -write} to patch object files using this technique. Note
12765 that @value{GDBN} can neither interpret nor modify relocations in this
12766 case, so branches and some initialized variables will appear to go to
12767 the wrong place. But this feature is still handy from time to time.
12770 @code{file} with no argument makes @value{GDBN} discard any information it
12771 has on both executable file and the symbol table.
12774 @item exec-file @r{[} @var{filename} @r{]}
12775 Specify that the program to be run (but not the symbol table) is found
12776 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
12777 if necessary to locate your program. Omitting @var{filename} means to
12778 discard information on the executable file.
12780 @kindex symbol-file
12781 @item symbol-file @r{[} @var{filename} @r{]}
12782 Read symbol table information from file @var{filename}. @code{PATH} is
12783 searched when necessary. Use the @code{file} command to get both symbol
12784 table and program to run from the same file.
12786 @code{symbol-file} with no argument clears out @value{GDBN} information on your
12787 program's symbol table.
12789 The @code{symbol-file} command causes @value{GDBN} to forget the contents of
12790 some breakpoints and auto-display expressions. This is because they may
12791 contain pointers to the internal data recording symbols and data types,
12792 which are part of the old symbol table data being discarded inside
12795 @code{symbol-file} does not repeat if you press @key{RET} again after
12798 When @value{GDBN} is configured for a particular environment, it
12799 understands debugging information in whatever format is the standard
12800 generated for that environment; you may use either a @sc{gnu} compiler, or
12801 other compilers that adhere to the local conventions.
12802 Best results are usually obtained from @sc{gnu} compilers; for example,
12803 using @code{@value{NGCC}} you can generate debugging information for
12806 For most kinds of object files, with the exception of old SVR3 systems
12807 using COFF, the @code{symbol-file} command does not normally read the
12808 symbol table in full right away. Instead, it scans the symbol table
12809 quickly to find which source files and which symbols are present. The
12810 details are read later, one source file at a time, as they are needed.
12812 The purpose of this two-stage reading strategy is to make @value{GDBN}
12813 start up faster. For the most part, it is invisible except for
12814 occasional pauses while the symbol table details for a particular source
12815 file are being read. (The @code{set verbose} command can turn these
12816 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
12817 Warnings and Messages}.)
12819 We have not implemented the two-stage strategy for COFF yet. When the
12820 symbol table is stored in COFF format, @code{symbol-file} reads the
12821 symbol table data in full right away. Note that ``stabs-in-COFF''
12822 still does the two-stage strategy, since the debug info is actually
12826 @cindex reading symbols immediately
12827 @cindex symbols, reading immediately
12828 @item symbol-file @var{filename} @r{[} -readnow @r{]}
12829 @itemx file @var{filename} @r{[} -readnow @r{]}
12830 You can override the @value{GDBN} two-stage strategy for reading symbol
12831 tables by using the @samp{-readnow} option with any of the commands that
12832 load symbol table information, if you want to be sure @value{GDBN} has the
12833 entire symbol table available.
12835 @c FIXME: for now no mention of directories, since this seems to be in
12836 @c flux. 13mar1992 status is that in theory GDB would look either in
12837 @c current dir or in same dir as myprog; but issues like competing
12838 @c GDB's, or clutter in system dirs, mean that in practice right now
12839 @c only current dir is used. FFish says maybe a special GDB hierarchy
12840 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
12844 @item core-file @r{[}@var{filename}@r{]}
12846 Specify the whereabouts of a core dump file to be used as the ``contents
12847 of memory''. Traditionally, core files contain only some parts of the
12848 address space of the process that generated them; @value{GDBN} can access the
12849 executable file itself for other parts.
12851 @code{core-file} with no argument specifies that no core file is
12854 Note that the core file is ignored when your program is actually running
12855 under @value{GDBN}. So, if you have been running your program and you
12856 wish to debug a core file instead, you must kill the subprocess in which
12857 the program is running. To do this, use the @code{kill} command
12858 (@pxref{Kill Process, ,Killing the Child Process}).
12860 @kindex add-symbol-file
12861 @cindex dynamic linking
12862 @item add-symbol-file @var{filename} @var{address}
12863 @itemx add-symbol-file @var{filename} @var{address} @r{[} -readnow @r{]}
12864 @itemx add-symbol-file @var{filename} @r{-s}@var{section} @var{address} @dots{}
12865 The @code{add-symbol-file} command reads additional symbol table
12866 information from the file @var{filename}. You would use this command
12867 when @var{filename} has been dynamically loaded (by some other means)
12868 into the program that is running. @var{address} should be the memory
12869 address at which the file has been loaded; @value{GDBN} cannot figure
12870 this out for itself. You can additionally specify an arbitrary number
12871 of @samp{@r{-s}@var{section} @var{address}} pairs, to give an explicit
12872 section name and base address for that section. You can specify any
12873 @var{address} as an expression.
12875 The symbol table of the file @var{filename} is added to the symbol table
12876 originally read with the @code{symbol-file} command. You can use the
12877 @code{add-symbol-file} command any number of times; the new symbol data
12878 thus read keeps adding to the old. To discard all old symbol data
12879 instead, use the @code{symbol-file} command without any arguments.
12881 @cindex relocatable object files, reading symbols from
12882 @cindex object files, relocatable, reading symbols from
12883 @cindex reading symbols from relocatable object files
12884 @cindex symbols, reading from relocatable object files
12885 @cindex @file{.o} files, reading symbols from
12886 Although @var{filename} is typically a shared library file, an
12887 executable file, or some other object file which has been fully
12888 relocated for loading into a process, you can also load symbolic
12889 information from relocatable @file{.o} files, as long as:
12893 the file's symbolic information refers only to linker symbols defined in
12894 that file, not to symbols defined by other object files,
12896 every section the file's symbolic information refers to has actually
12897 been loaded into the inferior, as it appears in the file, and
12899 you can determine the address at which every section was loaded, and
12900 provide these to the @code{add-symbol-file} command.
12904 Some embedded operating systems, like Sun Chorus and VxWorks, can load
12905 relocatable files into an already running program; such systems
12906 typically make the requirements above easy to meet. However, it's
12907 important to recognize that many native systems use complex link
12908 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
12909 assembly, for example) that make the requirements difficult to meet. In
12910 general, one cannot assume that using @code{add-symbol-file} to read a
12911 relocatable object file's symbolic information will have the same effect
12912 as linking the relocatable object file into the program in the normal
12915 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
12917 @kindex add-symbol-file-from-memory
12918 @cindex @code{syscall DSO}
12919 @cindex load symbols from memory
12920 @item add-symbol-file-from-memory @var{address}
12921 Load symbols from the given @var{address} in a dynamically loaded
12922 object file whose image is mapped directly into the inferior's memory.
12923 For example, the Linux kernel maps a @code{syscall DSO} into each
12924 process's address space; this DSO provides kernel-specific code for
12925 some system calls. The argument can be any expression whose
12926 evaluation yields the address of the file's shared object file header.
12927 For this command to work, you must have used @code{symbol-file} or
12928 @code{exec-file} commands in advance.
12930 @kindex add-shared-symbol-files
12932 @item add-shared-symbol-files @var{library-file}
12933 @itemx assf @var{library-file}
12934 The @code{add-shared-symbol-files} command can currently be used only
12935 in the Cygwin build of @value{GDBN} on MS-Windows OS, where it is an
12936 alias for the @code{dll-symbols} command (@pxref{Cygwin Native}).
12937 @value{GDBN} automatically looks for shared libraries, however if
12938 @value{GDBN} does not find yours, you can invoke
12939 @code{add-shared-symbol-files}. It takes one argument: the shared
12940 library's file name. @code{assf} is a shorthand alias for
12941 @code{add-shared-symbol-files}.
12944 @item section @var{section} @var{addr}
12945 The @code{section} command changes the base address of the named
12946 @var{section} of the exec file to @var{addr}. This can be used if the
12947 exec file does not contain section addresses, (such as in the
12948 @code{a.out} format), or when the addresses specified in the file
12949 itself are wrong. Each section must be changed separately. The
12950 @code{info files} command, described below, lists all the sections and
12954 @kindex info target
12957 @code{info files} and @code{info target} are synonymous; both print the
12958 current target (@pxref{Targets, ,Specifying a Debugging Target}),
12959 including the names of the executable and core dump files currently in
12960 use by @value{GDBN}, and the files from which symbols were loaded. The
12961 command @code{help target} lists all possible targets rather than
12964 @kindex maint info sections
12965 @item maint info sections
12966 Another command that can give you extra information about program sections
12967 is @code{maint info sections}. In addition to the section information
12968 displayed by @code{info files}, this command displays the flags and file
12969 offset of each section in the executable and core dump files. In addition,
12970 @code{maint info sections} provides the following command options (which
12971 may be arbitrarily combined):
12975 Display sections for all loaded object files, including shared libraries.
12976 @item @var{sections}
12977 Display info only for named @var{sections}.
12978 @item @var{section-flags}
12979 Display info only for sections for which @var{section-flags} are true.
12980 The section flags that @value{GDBN} currently knows about are:
12983 Section will have space allocated in the process when loaded.
12984 Set for all sections except those containing debug information.
12986 Section will be loaded from the file into the child process memory.
12987 Set for pre-initialized code and data, clear for @code{.bss} sections.
12989 Section needs to be relocated before loading.
12991 Section cannot be modified by the child process.
12993 Section contains executable code only.
12995 Section contains data only (no executable code).
12997 Section will reside in ROM.
12999 Section contains data for constructor/destructor lists.
13001 Section is not empty.
13003 An instruction to the linker to not output the section.
13004 @item COFF_SHARED_LIBRARY
13005 A notification to the linker that the section contains
13006 COFF shared library information.
13008 Section contains common symbols.
13011 @kindex set trust-readonly-sections
13012 @cindex read-only sections
13013 @item set trust-readonly-sections on
13014 Tell @value{GDBN} that readonly sections in your object file
13015 really are read-only (i.e.@: that their contents will not change).
13016 In that case, @value{GDBN} can fetch values from these sections
13017 out of the object file, rather than from the target program.
13018 For some targets (notably embedded ones), this can be a significant
13019 enhancement to debugging performance.
13021 The default is off.
13023 @item set trust-readonly-sections off
13024 Tell @value{GDBN} not to trust readonly sections. This means that
13025 the contents of the section might change while the program is running,
13026 and must therefore be fetched from the target when needed.
13028 @item show trust-readonly-sections
13029 Show the current setting of trusting readonly sections.
13032 All file-specifying commands allow both absolute and relative file names
13033 as arguments. @value{GDBN} always converts the file name to an absolute file
13034 name and remembers it that way.
13036 @cindex shared libraries
13037 @anchor{Shared Libraries}
13038 @value{GDBN} supports @sc{gnu}/Linux, MS-Windows, HP-UX, SunOS, SVr4, Irix,
13039 and IBM RS/6000 AIX shared libraries.
13041 On MS-Windows @value{GDBN} must be linked with the Expat library to support
13042 shared libraries. @xref{Expat}.
13044 @value{GDBN} automatically loads symbol definitions from shared libraries
13045 when you use the @code{run} command, or when you examine a core file.
13046 (Before you issue the @code{run} command, @value{GDBN} does not understand
13047 references to a function in a shared library, however---unless you are
13048 debugging a core file).
13050 On HP-UX, if the program loads a library explicitly, @value{GDBN}
13051 automatically loads the symbols at the time of the @code{shl_load} call.
13053 @c FIXME: some @value{GDBN} release may permit some refs to undef
13054 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
13055 @c FIXME...lib; check this from time to time when updating manual
13057 There are times, however, when you may wish to not automatically load
13058 symbol definitions from shared libraries, such as when they are
13059 particularly large or there are many of them.
13061 To control the automatic loading of shared library symbols, use the
13065 @kindex set auto-solib-add
13066 @item set auto-solib-add @var{mode}
13067 If @var{mode} is @code{on}, symbols from all shared object libraries
13068 will be loaded automatically when the inferior begins execution, you
13069 attach to an independently started inferior, or when the dynamic linker
13070 informs @value{GDBN} that a new library has been loaded. If @var{mode}
13071 is @code{off}, symbols must be loaded manually, using the
13072 @code{sharedlibrary} command. The default value is @code{on}.
13074 @cindex memory used for symbol tables
13075 If your program uses lots of shared libraries with debug info that
13076 takes large amounts of memory, you can decrease the @value{GDBN}
13077 memory footprint by preventing it from automatically loading the
13078 symbols from shared libraries. To that end, type @kbd{set
13079 auto-solib-add off} before running the inferior, then load each
13080 library whose debug symbols you do need with @kbd{sharedlibrary
13081 @var{regexp}}, where @var{regexp} is a regular expression that matches
13082 the libraries whose symbols you want to be loaded.
13084 @kindex show auto-solib-add
13085 @item show auto-solib-add
13086 Display the current autoloading mode.
13089 @cindex load shared library
13090 To explicitly load shared library symbols, use the @code{sharedlibrary}
13094 @kindex info sharedlibrary
13097 @itemx info sharedlibrary
13098 Print the names of the shared libraries which are currently loaded.
13100 @kindex sharedlibrary
13102 @item sharedlibrary @var{regex}
13103 @itemx share @var{regex}
13104 Load shared object library symbols for files matching a
13105 Unix regular expression.
13106 As with files loaded automatically, it only loads shared libraries
13107 required by your program for a core file or after typing @code{run}. If
13108 @var{regex} is omitted all shared libraries required by your program are
13111 @item nosharedlibrary
13112 @kindex nosharedlibrary
13113 @cindex unload symbols from shared libraries
13114 Unload all shared object library symbols. This discards all symbols
13115 that have been loaded from all shared libraries. Symbols from shared
13116 libraries that were loaded by explicit user requests are not
13120 Sometimes you may wish that @value{GDBN} stops and gives you control
13121 when any of shared library events happen. Use the @code{set
13122 stop-on-solib-events} command for this:
13125 @item set stop-on-solib-events
13126 @kindex set stop-on-solib-events
13127 This command controls whether @value{GDBN} should give you control
13128 when the dynamic linker notifies it about some shared library event.
13129 The most common event of interest is loading or unloading of a new
13132 @item show stop-on-solib-events
13133 @kindex show stop-on-solib-events
13134 Show whether @value{GDBN} stops and gives you control when shared
13135 library events happen.
13138 Shared libraries are also supported in many cross or remote debugging
13139 configurations. @value{GDBN} needs to have access to the target's libraries;
13140 this can be accomplished either by providing copies of the libraries
13141 on the host system, or by asking @value{GDBN} to automatically retrieve the
13142 libraries from the target. If copies of the target libraries are
13143 provided, they need to be the same as the target libraries, although the
13144 copies on the target can be stripped as long as the copies on the host are
13147 @cindex where to look for shared libraries
13148 For remote debugging, you need to tell @value{GDBN} where the target
13149 libraries are, so that it can load the correct copies---otherwise, it
13150 may try to load the host's libraries. @value{GDBN} has two variables
13151 to specify the search directories for target libraries.
13154 @cindex prefix for shared library file names
13155 @cindex system root, alternate
13156 @kindex set solib-absolute-prefix
13157 @kindex set sysroot
13158 @item set sysroot @var{path}
13159 Use @var{path} as the system root for the program being debugged. Any
13160 absolute shared library paths will be prefixed with @var{path}; many
13161 runtime loaders store the absolute paths to the shared library in the
13162 target program's memory. If you use @code{set sysroot} to find shared
13163 libraries, they need to be laid out in the same way that they are on
13164 the target, with e.g.@: a @file{/lib} and @file{/usr/lib} hierarchy
13167 If @var{path} starts with the sequence @file{remote:}, @value{GDBN} will
13168 retrieve the target libraries from the remote system. This is only
13169 supported when using a remote target that supports the @code{remote get}
13170 command (@pxref{File Transfer,,Sending files to a remote system}).
13171 The part of @var{path} following the initial @file{remote:}
13172 (if present) is used as system root prefix on the remote file system.
13173 @footnote{If you want to specify a local system root using a directory
13174 that happens to be named @file{remote:}, you need to use some equivalent
13175 variant of the name like @file{./remote:}.}
13177 The @code{set solib-absolute-prefix} command is an alias for @code{set
13180 @cindex default system root
13181 @cindex @samp{--with-sysroot}
13182 You can set the default system root by using the configure-time
13183 @samp{--with-sysroot} option. If the system root is inside
13184 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
13185 @samp{--exec-prefix}), then the default system root will be updated
13186 automatically if the installed @value{GDBN} is moved to a new
13189 @kindex show sysroot
13191 Display the current shared library prefix.
13193 @kindex set solib-search-path
13194 @item set solib-search-path @var{path}
13195 If this variable is set, @var{path} is a colon-separated list of
13196 directories to search for shared libraries. @samp{solib-search-path}
13197 is used after @samp{sysroot} fails to locate the library, or if the
13198 path to the library is relative instead of absolute. If you want to
13199 use @samp{solib-search-path} instead of @samp{sysroot}, be sure to set
13200 @samp{sysroot} to a nonexistent directory to prevent @value{GDBN} from
13201 finding your host's libraries. @samp{sysroot} is preferred; setting
13202 it to a nonexistent directory may interfere with automatic loading
13203 of shared library symbols.
13205 @kindex show solib-search-path
13206 @item show solib-search-path
13207 Display the current shared library search path.
13211 @node Separate Debug Files
13212 @section Debugging Information in Separate Files
13213 @cindex separate debugging information files
13214 @cindex debugging information in separate files
13215 @cindex @file{.debug} subdirectories
13216 @cindex debugging information directory, global
13217 @cindex global debugging information directory
13218 @cindex build ID, and separate debugging files
13219 @cindex @file{.build-id} directory
13221 @value{GDBN} allows you to put a program's debugging information in a
13222 file separate from the executable itself, in a way that allows
13223 @value{GDBN} to find and load the debugging information automatically.
13224 Since debugging information can be very large---sometimes larger
13225 than the executable code itself---some systems distribute debugging
13226 information for their executables in separate files, which users can
13227 install only when they need to debug a problem.
13229 @value{GDBN} supports two ways of specifying the separate debug info
13234 The executable contains a @dfn{debug link} that specifies the name of
13235 the separate debug info file. The separate debug file's name is
13236 usually @file{@var{executable}.debug}, where @var{executable} is the
13237 name of the corresponding executable file without leading directories
13238 (e.g., @file{ls.debug} for @file{/usr/bin/ls}). In addition, the
13239 debug link specifies a CRC32 checksum for the debug file, which
13240 @value{GDBN} uses to validate that the executable and the debug file
13241 came from the same build.
13244 The executable contains a @dfn{build ID}, a unique bit string that is
13245 also present in the corresponding debug info file. (This is supported
13246 only on some operating systems, notably those which use the ELF format
13247 for binary files and the @sc{gnu} Binutils.) For more details about
13248 this feature, see the description of the @option{--build-id}
13249 command-line option in @ref{Options, , Command Line Options, ld.info,
13250 The GNU Linker}. The debug info file's name is not specified
13251 explicitly by the build ID, but can be computed from the build ID, see
13255 Depending on the way the debug info file is specified, @value{GDBN}
13256 uses two different methods of looking for the debug file:
13260 For the ``debug link'' method, @value{GDBN} looks up the named file in
13261 the directory of the executable file, then in a subdirectory of that
13262 directory named @file{.debug}, and finally under the global debug
13263 directory, in a subdirectory whose name is identical to the leading
13264 directories of the executable's absolute file name.
13267 For the ``build ID'' method, @value{GDBN} looks in the
13268 @file{.build-id} subdirectory of the global debug directory for a file
13269 named @file{@var{nn}/@var{nnnnnnnn}.debug}, where @var{nn} are the
13270 first 2 hex characters of the build ID bit string, and @var{nnnnnnnn}
13271 are the rest of the bit string. (Real build ID strings are 32 or more
13272 hex characters, not 10.)
13275 So, for example, suppose you ask @value{GDBN} to debug
13276 @file{/usr/bin/ls}, which has a debug link that specifies the
13277 file @file{ls.debug}, and a build ID whose value in hex is
13278 @code{abcdef1234}. If the global debug directory is
13279 @file{/usr/lib/debug}, then @value{GDBN} will look for the following
13280 debug information files, in the indicated order:
13284 @file{/usr/lib/debug/.build-id/ab/cdef1234.debug}
13286 @file{/usr/bin/ls.debug}
13288 @file{/usr/bin/.debug/ls.debug}
13290 @file{/usr/lib/debug/usr/bin/ls.debug}.
13293 You can set the global debugging info directory's name, and view the
13294 name @value{GDBN} is currently using.
13298 @kindex set debug-file-directory
13299 @item set debug-file-directory @var{directory}
13300 Set the directory which @value{GDBN} searches for separate debugging
13301 information files to @var{directory}.
13303 @kindex show debug-file-directory
13304 @item show debug-file-directory
13305 Show the directory @value{GDBN} searches for separate debugging
13310 @cindex @code{.gnu_debuglink} sections
13311 @cindex debug link sections
13312 A debug link is a special section of the executable file named
13313 @code{.gnu_debuglink}. The section must contain:
13317 A filename, with any leading directory components removed, followed by
13320 zero to three bytes of padding, as needed to reach the next four-byte
13321 boundary within the section, and
13323 a four-byte CRC checksum, stored in the same endianness used for the
13324 executable file itself. The checksum is computed on the debugging
13325 information file's full contents by the function given below, passing
13326 zero as the @var{crc} argument.
13329 Any executable file format can carry a debug link, as long as it can
13330 contain a section named @code{.gnu_debuglink} with the contents
13333 @cindex @code{.note.gnu.build-id} sections
13334 @cindex build ID sections
13335 The build ID is a special section in the executable file (and in other
13336 ELF binary files that @value{GDBN} may consider). This section is
13337 often named @code{.note.gnu.build-id}, but that name is not mandatory.
13338 It contains unique identification for the built files---the ID remains
13339 the same across multiple builds of the same build tree. The default
13340 algorithm SHA1 produces 160 bits (40 hexadecimal characters) of the
13341 content for the build ID string. The same section with an identical
13342 value is present in the original built binary with symbols, in its
13343 stripped variant, and in the separate debugging information file.
13345 The debugging information file itself should be an ordinary
13346 executable, containing a full set of linker symbols, sections, and
13347 debugging information. The sections of the debugging information file
13348 should have the same names, addresses, and sizes as the original file,
13349 but they need not contain any data---much like a @code{.bss} section
13350 in an ordinary executable.
13352 The @sc{gnu} binary utilities (Binutils) package includes the
13353 @samp{objcopy} utility that can produce
13354 the separated executable / debugging information file pairs using the
13355 following commands:
13358 @kbd{objcopy --only-keep-debug foo foo.debug}
13363 These commands remove the debugging
13364 information from the executable file @file{foo} and place it in the file
13365 @file{foo.debug}. You can use the first, second or both methods to link the
13370 The debug link method needs the following additional command to also leave
13371 behind a debug link in @file{foo}:
13374 @kbd{objcopy --add-gnu-debuglink=foo.debug foo}
13377 Ulrich Drepper's @file{elfutils} package, starting with version 0.53, contains
13378 a version of the @code{strip} command such that the command @kbd{strip foo -f
13379 foo.debug} has the same functionality as the two @code{objcopy} commands and
13380 the @code{ln -s} command above, together.
13383 Build ID gets embedded into the main executable using @code{ld --build-id} or
13384 the @value{NGCC} counterpart @code{gcc -Wl,--build-id}. Build ID support plus
13385 compatibility fixes for debug files separation are present in @sc{gnu} binary
13386 utilities (Binutils) package since version 2.18.
13391 Since there are many different ways to compute CRC's for the debug
13392 link (different polynomials, reversals, byte ordering, etc.), the
13393 simplest way to describe the CRC used in @code{.gnu_debuglink}
13394 sections is to give the complete code for a function that computes it:
13396 @kindex gnu_debuglink_crc32
13399 gnu_debuglink_crc32 (unsigned long crc,
13400 unsigned char *buf, size_t len)
13402 static const unsigned long crc32_table[256] =
13404 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
13405 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
13406 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
13407 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
13408 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
13409 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
13410 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
13411 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
13412 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
13413 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
13414 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
13415 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
13416 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
13417 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
13418 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
13419 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
13420 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
13421 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
13422 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
13423 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
13424 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
13425 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
13426 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
13427 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
13428 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
13429 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
13430 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
13431 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
13432 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
13433 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
13434 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
13435 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
13436 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
13437 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
13438 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
13439 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
13440 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
13441 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
13442 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
13443 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
13444 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
13445 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
13446 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
13447 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
13448 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
13449 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
13450 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
13451 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
13452 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
13453 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
13454 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
13457 unsigned char *end;
13459 crc = ~crc & 0xffffffff;
13460 for (end = buf + len; buf < end; ++buf)
13461 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
13462 return ~crc & 0xffffffff;
13467 This computation does not apply to the ``build ID'' method.
13470 @node Symbol Errors
13471 @section Errors Reading Symbol Files
13473 While reading a symbol file, @value{GDBN} occasionally encounters problems,
13474 such as symbol types it does not recognize, or known bugs in compiler
13475 output. By default, @value{GDBN} does not notify you of such problems, since
13476 they are relatively common and primarily of interest to people
13477 debugging compilers. If you are interested in seeing information
13478 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
13479 only one message about each such type of problem, no matter how many
13480 times the problem occurs; or you can ask @value{GDBN} to print more messages,
13481 to see how many times the problems occur, with the @code{set
13482 complaints} command (@pxref{Messages/Warnings, ,Optional Warnings and
13485 The messages currently printed, and their meanings, include:
13488 @item inner block not inside outer block in @var{symbol}
13490 The symbol information shows where symbol scopes begin and end
13491 (such as at the start of a function or a block of statements). This
13492 error indicates that an inner scope block is not fully contained
13493 in its outer scope blocks.
13495 @value{GDBN} circumvents the problem by treating the inner block as if it had
13496 the same scope as the outer block. In the error message, @var{symbol}
13497 may be shown as ``@code{(don't know)}'' if the outer block is not a
13500 @item block at @var{address} out of order
13502 The symbol information for symbol scope blocks should occur in
13503 order of increasing addresses. This error indicates that it does not
13506 @value{GDBN} does not circumvent this problem, and has trouble
13507 locating symbols in the source file whose symbols it is reading. (You
13508 can often determine what source file is affected by specifying
13509 @code{set verbose on}. @xref{Messages/Warnings, ,Optional Warnings and
13512 @item bad block start address patched
13514 The symbol information for a symbol scope block has a start address
13515 smaller than the address of the preceding source line. This is known
13516 to occur in the SunOS 4.1.1 (and earlier) C compiler.
13518 @value{GDBN} circumvents the problem by treating the symbol scope block as
13519 starting on the previous source line.
13521 @item bad string table offset in symbol @var{n}
13524 Symbol number @var{n} contains a pointer into the string table which is
13525 larger than the size of the string table.
13527 @value{GDBN} circumvents the problem by considering the symbol to have the
13528 name @code{foo}, which may cause other problems if many symbols end up
13531 @item unknown symbol type @code{0x@var{nn}}
13533 The symbol information contains new data types that @value{GDBN} does
13534 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
13535 uncomprehended information, in hexadecimal.
13537 @value{GDBN} circumvents the error by ignoring this symbol information.
13538 This usually allows you to debug your program, though certain symbols
13539 are not accessible. If you encounter such a problem and feel like
13540 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
13541 on @code{complain}, then go up to the function @code{read_dbx_symtab}
13542 and examine @code{*bufp} to see the symbol.
13544 @item stub type has NULL name
13546 @value{GDBN} could not find the full definition for a struct or class.
13548 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
13549 The symbol information for a C@t{++} member function is missing some
13550 information that recent versions of the compiler should have output for
13553 @item info mismatch between compiler and debugger
13555 @value{GDBN} could not parse a type specification output by the compiler.
13560 @chapter Specifying a Debugging Target
13562 @cindex debugging target
13563 A @dfn{target} is the execution environment occupied by your program.
13565 Often, @value{GDBN} runs in the same host environment as your program;
13566 in that case, the debugging target is specified as a side effect when
13567 you use the @code{file} or @code{core} commands. When you need more
13568 flexibility---for example, running @value{GDBN} on a physically separate
13569 host, or controlling a standalone system over a serial port or a
13570 realtime system over a TCP/IP connection---you can use the @code{target}
13571 command to specify one of the target types configured for @value{GDBN}
13572 (@pxref{Target Commands, ,Commands for Managing Targets}).
13574 @cindex target architecture
13575 It is possible to build @value{GDBN} for several different @dfn{target
13576 architectures}. When @value{GDBN} is built like that, you can choose
13577 one of the available architectures with the @kbd{set architecture}
13581 @kindex set architecture
13582 @kindex show architecture
13583 @item set architecture @var{arch}
13584 This command sets the current target architecture to @var{arch}. The
13585 value of @var{arch} can be @code{"auto"}, in addition to one of the
13586 supported architectures.
13588 @item show architecture
13589 Show the current target architecture.
13591 @item set processor
13593 @kindex set processor
13594 @kindex show processor
13595 These are alias commands for, respectively, @code{set architecture}
13596 and @code{show architecture}.
13600 * Active Targets:: Active targets
13601 * Target Commands:: Commands for managing targets
13602 * Byte Order:: Choosing target byte order
13605 @node Active Targets
13606 @section Active Targets
13608 @cindex stacking targets
13609 @cindex active targets
13610 @cindex multiple targets
13612 There are three classes of targets: processes, core files, and
13613 executable files. @value{GDBN} can work concurrently on up to three
13614 active targets, one in each class. This allows you to (for example)
13615 start a process and inspect its activity without abandoning your work on
13618 For example, if you execute @samp{gdb a.out}, then the executable file
13619 @code{a.out} is the only active target. If you designate a core file as
13620 well---presumably from a prior run that crashed and coredumped---then
13621 @value{GDBN} has two active targets and uses them in tandem, looking
13622 first in the corefile target, then in the executable file, to satisfy
13623 requests for memory addresses. (Typically, these two classes of target
13624 are complementary, since core files contain only a program's
13625 read-write memory---variables and so on---plus machine status, while
13626 executable files contain only the program text and initialized data.)
13628 When you type @code{run}, your executable file becomes an active process
13629 target as well. When a process target is active, all @value{GDBN}
13630 commands requesting memory addresses refer to that target; addresses in
13631 an active core file or executable file target are obscured while the
13632 process target is active.
13634 Use the @code{core-file} and @code{exec-file} commands to select a new
13635 core file or executable target (@pxref{Files, ,Commands to Specify
13636 Files}). To specify as a target a process that is already running, use
13637 the @code{attach} command (@pxref{Attach, ,Debugging an Already-running
13640 @node Target Commands
13641 @section Commands for Managing Targets
13644 @item target @var{type} @var{parameters}
13645 Connects the @value{GDBN} host environment to a target machine or
13646 process. A target is typically a protocol for talking to debugging
13647 facilities. You use the argument @var{type} to specify the type or
13648 protocol of the target machine.
13650 Further @var{parameters} are interpreted by the target protocol, but
13651 typically include things like device names or host names to connect
13652 with, process numbers, and baud rates.
13654 The @code{target} command does not repeat if you press @key{RET} again
13655 after executing the command.
13657 @kindex help target
13659 Displays the names of all targets available. To display targets
13660 currently selected, use either @code{info target} or @code{info files}
13661 (@pxref{Files, ,Commands to Specify Files}).
13663 @item help target @var{name}
13664 Describe a particular target, including any parameters necessary to
13667 @kindex set gnutarget
13668 @item set gnutarget @var{args}
13669 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
13670 knows whether it is reading an @dfn{executable},
13671 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
13672 with the @code{set gnutarget} command. Unlike most @code{target} commands,
13673 with @code{gnutarget} the @code{target} refers to a program, not a machine.
13676 @emph{Warning:} To specify a file format with @code{set gnutarget},
13677 you must know the actual BFD name.
13681 @xref{Files, , Commands to Specify Files}.
13683 @kindex show gnutarget
13684 @item show gnutarget
13685 Use the @code{show gnutarget} command to display what file format
13686 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
13687 @value{GDBN} will determine the file format for each file automatically,
13688 and @code{show gnutarget} displays @samp{The current BDF target is "auto"}.
13691 @cindex common targets
13692 Here are some common targets (available, or not, depending on the GDB
13697 @item target exec @var{program}
13698 @cindex executable file target
13699 An executable file. @samp{target exec @var{program}} is the same as
13700 @samp{exec-file @var{program}}.
13702 @item target core @var{filename}
13703 @cindex core dump file target
13704 A core dump file. @samp{target core @var{filename}} is the same as
13705 @samp{core-file @var{filename}}.
13707 @item target remote @var{medium}
13708 @cindex remote target
13709 A remote system connected to @value{GDBN} via a serial line or network
13710 connection. This command tells @value{GDBN} to use its own remote
13711 protocol over @var{medium} for debugging. @xref{Remote Debugging}.
13713 For example, if you have a board connected to @file{/dev/ttya} on the
13714 machine running @value{GDBN}, you could say:
13717 target remote /dev/ttya
13720 @code{target remote} supports the @code{load} command. This is only
13721 useful if you have some other way of getting the stub to the target
13722 system, and you can put it somewhere in memory where it won't get
13723 clobbered by the download.
13726 @cindex built-in simulator target
13727 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
13735 works; however, you cannot assume that a specific memory map, device
13736 drivers, or even basic I/O is available, although some simulators do
13737 provide these. For info about any processor-specific simulator details,
13738 see the appropriate section in @ref{Embedded Processors, ,Embedded
13743 Some configurations may include these targets as well:
13747 @item target nrom @var{dev}
13748 @cindex NetROM ROM emulator target
13749 NetROM ROM emulator. This target only supports downloading.
13753 Different targets are available on different configurations of @value{GDBN};
13754 your configuration may have more or fewer targets.
13756 Many remote targets require you to download the executable's code once
13757 you've successfully established a connection. You may wish to control
13758 various aspects of this process.
13763 @kindex set hash@r{, for remote monitors}
13764 @cindex hash mark while downloading
13765 This command controls whether a hash mark @samp{#} is displayed while
13766 downloading a file to the remote monitor. If on, a hash mark is
13767 displayed after each S-record is successfully downloaded to the
13771 @kindex show hash@r{, for remote monitors}
13772 Show the current status of displaying the hash mark.
13774 @item set debug monitor
13775 @kindex set debug monitor
13776 @cindex display remote monitor communications
13777 Enable or disable display of communications messages between
13778 @value{GDBN} and the remote monitor.
13780 @item show debug monitor
13781 @kindex show debug monitor
13782 Show the current status of displaying communications between
13783 @value{GDBN} and the remote monitor.
13788 @kindex load @var{filename}
13789 @item load @var{filename}
13791 Depending on what remote debugging facilities are configured into
13792 @value{GDBN}, the @code{load} command may be available. Where it exists, it
13793 is meant to make @var{filename} (an executable) available for debugging
13794 on the remote system---by downloading, or dynamic linking, for example.
13795 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
13796 the @code{add-symbol-file} command.
13798 If your @value{GDBN} does not have a @code{load} command, attempting to
13799 execute it gets the error message ``@code{You can't do that when your
13800 target is @dots{}}''
13802 The file is loaded at whatever address is specified in the executable.
13803 For some object file formats, you can specify the load address when you
13804 link the program; for other formats, like a.out, the object file format
13805 specifies a fixed address.
13806 @c FIXME! This would be a good place for an xref to the GNU linker doc.
13808 Depending on the remote side capabilities, @value{GDBN} may be able to
13809 load programs into flash memory.
13811 @code{load} does not repeat if you press @key{RET} again after using it.
13815 @section Choosing Target Byte Order
13817 @cindex choosing target byte order
13818 @cindex target byte order
13820 Some types of processors, such as the MIPS, PowerPC, and Renesas SH,
13821 offer the ability to run either big-endian or little-endian byte
13822 orders. Usually the executable or symbol will include a bit to
13823 designate the endian-ness, and you will not need to worry about
13824 which to use. However, you may still find it useful to adjust
13825 @value{GDBN}'s idea of processor endian-ness manually.
13829 @item set endian big
13830 Instruct @value{GDBN} to assume the target is big-endian.
13832 @item set endian little
13833 Instruct @value{GDBN} to assume the target is little-endian.
13835 @item set endian auto
13836 Instruct @value{GDBN} to use the byte order associated with the
13840 Display @value{GDBN}'s current idea of the target byte order.
13844 Note that these commands merely adjust interpretation of symbolic
13845 data on the host, and that they have absolutely no effect on the
13849 @node Remote Debugging
13850 @chapter Debugging Remote Programs
13851 @cindex remote debugging
13853 If you are trying to debug a program running on a machine that cannot run
13854 @value{GDBN} in the usual way, it is often useful to use remote debugging.
13855 For example, you might use remote debugging on an operating system kernel,
13856 or on a small system which does not have a general purpose operating system
13857 powerful enough to run a full-featured debugger.
13859 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
13860 to make this work with particular debugging targets. In addition,
13861 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
13862 but not specific to any particular target system) which you can use if you
13863 write the remote stubs---the code that runs on the remote system to
13864 communicate with @value{GDBN}.
13866 Other remote targets may be available in your
13867 configuration of @value{GDBN}; use @code{help target} to list them.
13870 * Connecting:: Connecting to a remote target
13871 * File Transfer:: Sending files to a remote system
13872 * Server:: Using the gdbserver program
13873 * Remote Configuration:: Remote configuration
13874 * Remote Stub:: Implementing a remote stub
13878 @section Connecting to a Remote Target
13880 On the @value{GDBN} host machine, you will need an unstripped copy of
13881 your program, since @value{GDBN} needs symbol and debugging information.
13882 Start up @value{GDBN} as usual, using the name of the local copy of your
13883 program as the first argument.
13885 @cindex @code{target remote}
13886 @value{GDBN} can communicate with the target over a serial line, or
13887 over an @acronym{IP} network using @acronym{TCP} or @acronym{UDP}. In
13888 each case, @value{GDBN} uses the same protocol for debugging your
13889 program; only the medium carrying the debugging packets varies. The
13890 @code{target remote} command establishes a connection to the target.
13891 Its arguments indicate which medium to use:
13895 @item target remote @var{serial-device}
13896 @cindex serial line, @code{target remote}
13897 Use @var{serial-device} to communicate with the target. For example,
13898 to use a serial line connected to the device named @file{/dev/ttyb}:
13901 target remote /dev/ttyb
13904 If you're using a serial line, you may want to give @value{GDBN} the
13905 @w{@samp{--baud}} option, or use the @code{set remotebaud} command
13906 (@pxref{Remote Configuration, set remotebaud}) before the
13907 @code{target} command.
13909 @item target remote @code{@var{host}:@var{port}}
13910 @itemx target remote @code{tcp:@var{host}:@var{port}}
13911 @cindex @acronym{TCP} port, @code{target remote}
13912 Debug using a @acronym{TCP} connection to @var{port} on @var{host}.
13913 The @var{host} may be either a host name or a numeric @acronym{IP}
13914 address; @var{port} must be a decimal number. The @var{host} could be
13915 the target machine itself, if it is directly connected to the net, or
13916 it might be a terminal server which in turn has a serial line to the
13919 For example, to connect to port 2828 on a terminal server named
13923 target remote manyfarms:2828
13926 If your remote target is actually running on the same machine as your
13927 debugger session (e.g.@: a simulator for your target running on the
13928 same host), you can omit the hostname. For example, to connect to
13929 port 1234 on your local machine:
13932 target remote :1234
13936 Note that the colon is still required here.
13938 @item target remote @code{udp:@var{host}:@var{port}}
13939 @cindex @acronym{UDP} port, @code{target remote}
13940 Debug using @acronym{UDP} packets to @var{port} on @var{host}. For example, to
13941 connect to @acronym{UDP} port 2828 on a terminal server named @code{manyfarms}:
13944 target remote udp:manyfarms:2828
13947 When using a @acronym{UDP} connection for remote debugging, you should
13948 keep in mind that the `U' stands for ``Unreliable''. @acronym{UDP}
13949 can silently drop packets on busy or unreliable networks, which will
13950 cause havoc with your debugging session.
13952 @item target remote | @var{command}
13953 @cindex pipe, @code{target remote} to
13954 Run @var{command} in the background and communicate with it using a
13955 pipe. The @var{command} is a shell command, to be parsed and expanded
13956 by the system's command shell, @code{/bin/sh}; it should expect remote
13957 protocol packets on its standard input, and send replies on its
13958 standard output. You could use this to run a stand-alone simulator
13959 that speaks the remote debugging protocol, to make net connections
13960 using programs like @code{ssh}, or for other similar tricks.
13962 If @var{command} closes its standard output (perhaps by exiting),
13963 @value{GDBN} will try to send it a @code{SIGTERM} signal. (If the
13964 program has already exited, this will have no effect.)
13968 Once the connection has been established, you can use all the usual
13969 commands to examine and change data. The remote program is already
13970 running; you can use @kbd{step} and @kbd{continue}, and you do not
13971 need to use @kbd{run}.
13973 @cindex interrupting remote programs
13974 @cindex remote programs, interrupting
13975 Whenever @value{GDBN} is waiting for the remote program, if you type the
13976 interrupt character (often @kbd{Ctrl-c}), @value{GDBN} attempts to stop the
13977 program. This may or may not succeed, depending in part on the hardware
13978 and the serial drivers the remote system uses. If you type the
13979 interrupt character once again, @value{GDBN} displays this prompt:
13982 Interrupted while waiting for the program.
13983 Give up (and stop debugging it)? (y or n)
13986 If you type @kbd{y}, @value{GDBN} abandons the remote debugging session.
13987 (If you decide you want to try again later, you can use @samp{target
13988 remote} again to connect once more.) If you type @kbd{n}, @value{GDBN}
13989 goes back to waiting.
13992 @kindex detach (remote)
13994 When you have finished debugging the remote program, you can use the
13995 @code{detach} command to release it from @value{GDBN} control.
13996 Detaching from the target normally resumes its execution, but the results
13997 will depend on your particular remote stub. After the @code{detach}
13998 command, @value{GDBN} is free to connect to another target.
14002 The @code{disconnect} command behaves like @code{detach}, except that
14003 the target is generally not resumed. It will wait for @value{GDBN}
14004 (this instance or another one) to connect and continue debugging. After
14005 the @code{disconnect} command, @value{GDBN} is again free to connect to
14008 @cindex send command to remote monitor
14009 @cindex extend @value{GDBN} for remote targets
14010 @cindex add new commands for external monitor
14012 @item monitor @var{cmd}
14013 This command allows you to send arbitrary commands directly to the
14014 remote monitor. Since @value{GDBN} doesn't care about the commands it
14015 sends like this, this command is the way to extend @value{GDBN}---you
14016 can add new commands that only the external monitor will understand
14020 @node File Transfer
14021 @section Sending files to a remote system
14022 @cindex remote target, file transfer
14023 @cindex file transfer
14024 @cindex sending files to remote systems
14026 Some remote targets offer the ability to transfer files over the same
14027 connection used to communicate with @value{GDBN}. This is convenient
14028 for targets accessible through other means, e.g.@: @sc{gnu}/Linux systems
14029 running @code{gdbserver} over a network interface. For other targets,
14030 e.g.@: embedded devices with only a single serial port, this may be
14031 the only way to upload or download files.
14033 Not all remote targets support these commands.
14037 @item remote put @var{hostfile} @var{targetfile}
14038 Copy file @var{hostfile} from the host system (the machine running
14039 @value{GDBN}) to @var{targetfile} on the target system.
14042 @item remote get @var{targetfile} @var{hostfile}
14043 Copy file @var{targetfile} from the target system to @var{hostfile}
14044 on the host system.
14046 @kindex remote delete
14047 @item remote delete @var{targetfile}
14048 Delete @var{targetfile} from the target system.
14053 @section Using the @code{gdbserver} Program
14056 @cindex remote connection without stubs
14057 @code{gdbserver} is a control program for Unix-like systems, which
14058 allows you to connect your program with a remote @value{GDBN} via
14059 @code{target remote}---but without linking in the usual debugging stub.
14061 @code{gdbserver} is not a complete replacement for the debugging stubs,
14062 because it requires essentially the same operating-system facilities
14063 that @value{GDBN} itself does. In fact, a system that can run
14064 @code{gdbserver} to connect to a remote @value{GDBN} could also run
14065 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
14066 because it is a much smaller program than @value{GDBN} itself. It is
14067 also easier to port than all of @value{GDBN}, so you may be able to get
14068 started more quickly on a new system by using @code{gdbserver}.
14069 Finally, if you develop code for real-time systems, you may find that
14070 the tradeoffs involved in real-time operation make it more convenient to
14071 do as much development work as possible on another system, for example
14072 by cross-compiling. You can use @code{gdbserver} to make a similar
14073 choice for debugging.
14075 @value{GDBN} and @code{gdbserver} communicate via either a serial line
14076 or a TCP connection, using the standard @value{GDBN} remote serial
14080 @emph{Warning:} @code{gdbserver} does not have any built-in security.
14081 Do not run @code{gdbserver} connected to any public network; a
14082 @value{GDBN} connection to @code{gdbserver} provides access to the
14083 target system with the same privileges as the user running
14087 @subsection Running @code{gdbserver}
14088 @cindex arguments, to @code{gdbserver}
14090 Run @code{gdbserver} on the target system. You need a copy of the
14091 program you want to debug, including any libraries it requires.
14092 @code{gdbserver} does not need your program's symbol table, so you can
14093 strip the program if necessary to save space. @value{GDBN} on the host
14094 system does all the symbol handling.
14096 To use the server, you must tell it how to communicate with @value{GDBN};
14097 the name of your program; and the arguments for your program. The usual
14101 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
14104 @var{comm} is either a device name (to use a serial line) or a TCP
14105 hostname and portnumber. For example, to debug Emacs with the argument
14106 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
14110 target> gdbserver /dev/com1 emacs foo.txt
14113 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
14116 To use a TCP connection instead of a serial line:
14119 target> gdbserver host:2345 emacs foo.txt
14122 The only difference from the previous example is the first argument,
14123 specifying that you are communicating with the host @value{GDBN} via
14124 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
14125 expect a TCP connection from machine @samp{host} to local TCP port 2345.
14126 (Currently, the @samp{host} part is ignored.) You can choose any number
14127 you want for the port number as long as it does not conflict with any
14128 TCP ports already in use on the target system (for example, @code{23} is
14129 reserved for @code{telnet}).@footnote{If you choose a port number that
14130 conflicts with another service, @code{gdbserver} prints an error message
14131 and exits.} You must use the same port number with the host @value{GDBN}
14132 @code{target remote} command.
14134 @subsubsection Attaching to a Running Program
14136 On some targets, @code{gdbserver} can also attach to running programs.
14137 This is accomplished via the @code{--attach} argument. The syntax is:
14140 target> gdbserver --attach @var{comm} @var{pid}
14143 @var{pid} is the process ID of a currently running process. It isn't necessary
14144 to point @code{gdbserver} at a binary for the running process.
14147 @cindex attach to a program by name
14148 You can debug processes by name instead of process ID if your target has the
14149 @code{pidof} utility:
14152 target> gdbserver --attach @var{comm} `pidof @var{program}`
14155 In case more than one copy of @var{program} is running, or @var{program}
14156 has multiple threads, most versions of @code{pidof} support the
14157 @code{-s} option to only return the first process ID.
14159 @subsubsection Multi-Process Mode for @code{gdbserver}
14160 @cindex gdbserver, multiple processes
14161 @cindex multiple processes with gdbserver
14163 When you connect to @code{gdbserver} using @code{target remote},
14164 @code{gdbserver} debugs the specified program only once. When the
14165 program exits, or you detach from it, @value{GDBN} closes the connection
14166 and @code{gdbserver} exits.
14168 If you connect using @kbd{target extended-remote}, @code{gdbserver}
14169 enters multi-process mode. When the debugged program exits, or you
14170 detach from it, @value{GDBN} stays connected to @code{gdbserver} even
14171 though no program is running. The @code{run} and @code{attach}
14172 commands instruct @code{gdbserver} to run or attach to a new program.
14173 The @code{run} command uses @code{set remote exec-file} (@pxref{set
14174 remote exec-file}) to select the program to run. Command line
14175 arguments are supported, except for wildcard expansion and I/O
14176 redirection (@pxref{Arguments}).
14178 To start @code{gdbserver} without supplying an initial command to run
14179 or process ID to attach, use the @option{--multi} command line option.
14180 Then you can connect using @kbd{target extended-remote} and start
14181 the program you want to debug.
14183 @code{gdbserver} does not automatically exit in multi-process mode.
14184 You can terminate it by using @code{monitor exit}
14185 (@pxref{Monitor Commands for gdbserver}).
14187 @subsubsection Other Command-Line Arguments for @code{gdbserver}
14189 The @option{--debug} option tells @code{gdbserver} to display extra
14190 status information about the debugging process. The
14191 @option{--remote-debug} option tells @code{gdbserver} to display
14192 remote protocol debug output. These options are intended for
14193 @code{gdbserver} development and for bug reports to the developers.
14195 The @option{--wrapper} option specifies a wrapper to launch programs
14196 for debugging. The option should be followed by the name of the
14197 wrapper, then any command-line arguments to pass to the wrapper, then
14198 @kbd{--} indicating the end of the wrapper arguments.
14200 @code{gdbserver} runs the specified wrapper program with a combined
14201 command line including the wrapper arguments, then the name of the
14202 program to debug, then any arguments to the program. The wrapper
14203 runs until it executes your program, and then @value{GDBN} gains control.
14205 You can use any program that eventually calls @code{execve} with
14206 its arguments as a wrapper. Several standard Unix utilities do
14207 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
14208 with @code{exec "$@@"} will also work.
14210 For example, you can use @code{env} to pass an environment variable to
14211 the debugged program, without setting the variable in @code{gdbserver}'s
14215 $ gdbserver --wrapper env LD_PRELOAD=libtest.so -- :2222 ./testprog
14218 @subsection Connecting to @code{gdbserver}
14220 Run @value{GDBN} on the host system.
14222 First make sure you have the necessary symbol files. Load symbols for
14223 your application using the @code{file} command before you connect. Use
14224 @code{set sysroot} to locate target libraries (unless your @value{GDBN}
14225 was compiled with the correct sysroot using @code{--with-sysroot}).
14227 The symbol file and target libraries must exactly match the executable
14228 and libraries on the target, with one exception: the files on the host
14229 system should not be stripped, even if the files on the target system
14230 are. Mismatched or missing files will lead to confusing results
14231 during debugging. On @sc{gnu}/Linux targets, mismatched or missing
14232 files may also prevent @code{gdbserver} from debugging multi-threaded
14235 Connect to your target (@pxref{Connecting,,Connecting to a Remote Target}).
14236 For TCP connections, you must start up @code{gdbserver} prior to using
14237 the @code{target remote} command. Otherwise you may get an error whose
14238 text depends on the host system, but which usually looks something like
14239 @samp{Connection refused}. Don't use the @code{load}
14240 command in @value{GDBN} when using @code{gdbserver}, since the program is
14241 already on the target.
14243 @subsection Monitor Commands for @code{gdbserver}
14244 @cindex monitor commands, for @code{gdbserver}
14245 @anchor{Monitor Commands for gdbserver}
14247 During a @value{GDBN} session using @code{gdbserver}, you can use the
14248 @code{monitor} command to send special requests to @code{gdbserver}.
14249 Here are the available commands.
14253 List the available monitor commands.
14255 @item monitor set debug 0
14256 @itemx monitor set debug 1
14257 Disable or enable general debugging messages.
14259 @item monitor set remote-debug 0
14260 @itemx monitor set remote-debug 1
14261 Disable or enable specific debugging messages associated with the remote
14262 protocol (@pxref{Remote Protocol}).
14265 Tell gdbserver to exit immediately. This command should be followed by
14266 @code{disconnect} to close the debugging session. @code{gdbserver} will
14267 detach from any attached processes and kill any processes it created.
14268 Use @code{monitor exit} to terminate @code{gdbserver} at the end
14269 of a multi-process mode debug session.
14273 @node Remote Configuration
14274 @section Remote Configuration
14277 @kindex show remote
14278 This section documents the configuration options available when
14279 debugging remote programs. For the options related to the File I/O
14280 extensions of the remote protocol, see @ref{system,
14281 system-call-allowed}.
14284 @item set remoteaddresssize @var{bits}
14285 @cindex address size for remote targets
14286 @cindex bits in remote address
14287 Set the maximum size of address in a memory packet to the specified
14288 number of bits. @value{GDBN} will mask off the address bits above
14289 that number, when it passes addresses to the remote target. The
14290 default value is the number of bits in the target's address.
14292 @item show remoteaddresssize
14293 Show the current value of remote address size in bits.
14295 @item set remotebaud @var{n}
14296 @cindex baud rate for remote targets
14297 Set the baud rate for the remote serial I/O to @var{n} baud. The
14298 value is used to set the speed of the serial port used for debugging
14301 @item show remotebaud
14302 Show the current speed of the remote connection.
14304 @item set remotebreak
14305 @cindex interrupt remote programs
14306 @cindex BREAK signal instead of Ctrl-C
14307 @anchor{set remotebreak}
14308 If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote
14309 when you type @kbd{Ctrl-c} to interrupt the program running
14310 on the remote. If set to off, @value{GDBN} sends the @samp{Ctrl-C}
14311 character instead. The default is off, since most remote systems
14312 expect to see @samp{Ctrl-C} as the interrupt signal.
14314 @item show remotebreak
14315 Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to
14316 interrupt the remote program.
14318 @item set remoteflow on
14319 @itemx set remoteflow off
14320 @kindex set remoteflow
14321 Enable or disable hardware flow control (@code{RTS}/@code{CTS})
14322 on the serial port used to communicate to the remote target.
14324 @item show remoteflow
14325 @kindex show remoteflow
14326 Show the current setting of hardware flow control.
14328 @item set remotelogbase @var{base}
14329 Set the base (a.k.a.@: radix) of logging serial protocol
14330 communications to @var{base}. Supported values of @var{base} are:
14331 @code{ascii}, @code{octal}, and @code{hex}. The default is
14334 @item show remotelogbase
14335 Show the current setting of the radix for logging remote serial
14338 @item set remotelogfile @var{file}
14339 @cindex record serial communications on file
14340 Record remote serial communications on the named @var{file}. The
14341 default is not to record at all.
14343 @item show remotelogfile.
14344 Show the current setting of the file name on which to record the
14345 serial communications.
14347 @item set remotetimeout @var{num}
14348 @cindex timeout for serial communications
14349 @cindex remote timeout
14350 Set the timeout limit to wait for the remote target to respond to
14351 @var{num} seconds. The default is 2 seconds.
14353 @item show remotetimeout
14354 Show the current number of seconds to wait for the remote target
14357 @cindex limit hardware breakpoints and watchpoints
14358 @cindex remote target, limit break- and watchpoints
14359 @anchor{set remote hardware-watchpoint-limit}
14360 @anchor{set remote hardware-breakpoint-limit}
14361 @item set remote hardware-watchpoint-limit @var{limit}
14362 @itemx set remote hardware-breakpoint-limit @var{limit}
14363 Restrict @value{GDBN} to using @var{limit} remote hardware breakpoint or
14364 watchpoints. A limit of -1, the default, is treated as unlimited.
14366 @item set remote exec-file @var{filename}
14367 @itemx show remote exec-file
14368 @anchor{set remote exec-file}
14369 @cindex executable file, for remote target
14370 Select the file used for @code{run} with @code{target
14371 extended-remote}. This should be set to a filename valid on the
14372 target system. If it is not set, the target will use a default
14373 filename (e.g.@: the last program run).
14377 @item set tcp auto-retry on
14378 @cindex auto-retry, for remote TCP target
14379 Enable auto-retry for remote TCP connections. This is useful if the remote
14380 debugging agent is launched in parallel with @value{GDBN}; there is a race
14381 condition because the agent may not become ready to accept the connection
14382 before @value{GDBN} attempts to connect. When auto-retry is
14383 enabled, if the initial attempt to connect fails, @value{GDBN} reattempts
14384 to establish the connection using the timeout specified by
14385 @code{set tcp connect-timeout}.
14387 @item set tcp auto-retry off
14388 Do not auto-retry failed TCP connections.
14390 @item show tcp auto-retry
14391 Show the current auto-retry setting.
14393 @item set tcp connect-timeout @var{seconds}
14394 @cindex connection timeout, for remote TCP target
14395 @cindex timeout, for remote target connection
14396 Set the timeout for establishing a TCP connection to the remote target to
14397 @var{seconds}. The timeout affects both polling to retry failed connections
14398 (enabled by @code{set tcp auto-retry on}) and waiting for connections
14399 that are merely slow to complete, and represents an approximate cumulative
14402 @item show tcp connect-timeout
14403 Show the current connection timeout setting.
14406 @cindex remote packets, enabling and disabling
14407 The @value{GDBN} remote protocol autodetects the packets supported by
14408 your debugging stub. If you need to override the autodetection, you
14409 can use these commands to enable or disable individual packets. Each
14410 packet can be set to @samp{on} (the remote target supports this
14411 packet), @samp{off} (the remote target does not support this packet),
14412 or @samp{auto} (detect remote target support for this packet). They
14413 all default to @samp{auto}. For more information about each packet,
14414 see @ref{Remote Protocol}.
14416 During normal use, you should not have to use any of these commands.
14417 If you do, that may be a bug in your remote debugging stub, or a bug
14418 in @value{GDBN}. You may want to report the problem to the
14419 @value{GDBN} developers.
14421 For each packet @var{name}, the command to enable or disable the
14422 packet is @code{set remote @var{name}-packet}. The available settings
14425 @multitable @columnfractions 0.28 0.32 0.25
14428 @tab Related Features
14430 @item @code{fetch-register}
14432 @tab @code{info registers}
14434 @item @code{set-register}
14438 @item @code{binary-download}
14440 @tab @code{load}, @code{set}
14442 @item @code{read-aux-vector}
14443 @tab @code{qXfer:auxv:read}
14444 @tab @code{info auxv}
14446 @item @code{symbol-lookup}
14447 @tab @code{qSymbol}
14448 @tab Detecting multiple threads
14450 @item @code{attach}
14451 @tab @code{vAttach}
14454 @item @code{verbose-resume}
14456 @tab Stepping or resuming multiple threads
14462 @item @code{software-breakpoint}
14466 @item @code{hardware-breakpoint}
14470 @item @code{write-watchpoint}
14474 @item @code{read-watchpoint}
14478 @item @code{access-watchpoint}
14482 @item @code{target-features}
14483 @tab @code{qXfer:features:read}
14484 @tab @code{set architecture}
14486 @item @code{library-info}
14487 @tab @code{qXfer:libraries:read}
14488 @tab @code{info sharedlibrary}
14490 @item @code{memory-map}
14491 @tab @code{qXfer:memory-map:read}
14492 @tab @code{info mem}
14494 @item @code{read-spu-object}
14495 @tab @code{qXfer:spu:read}
14496 @tab @code{info spu}
14498 @item @code{write-spu-object}
14499 @tab @code{qXfer:spu:write}
14500 @tab @code{info spu}
14502 @item @code{read-siginfo-object}
14503 @tab @code{qXfer:siginfo:read}
14504 @tab @code{print $_siginfo}
14506 @item @code{write-siginfo-object}
14507 @tab @code{qXfer:siginfo:write}
14508 @tab @code{set $_siginfo}
14510 @item @code{get-thread-local-@*storage-address}
14511 @tab @code{qGetTLSAddr}
14512 @tab Displaying @code{__thread} variables
14514 @item @code{search-memory}
14515 @tab @code{qSearch:memory}
14518 @item @code{supported-packets}
14519 @tab @code{qSupported}
14520 @tab Remote communications parameters
14522 @item @code{pass-signals}
14523 @tab @code{QPassSignals}
14524 @tab @code{handle @var{signal}}
14526 @item @code{hostio-close-packet}
14527 @tab @code{vFile:close}
14528 @tab @code{remote get}, @code{remote put}
14530 @item @code{hostio-open-packet}
14531 @tab @code{vFile:open}
14532 @tab @code{remote get}, @code{remote put}
14534 @item @code{hostio-pread-packet}
14535 @tab @code{vFile:pread}
14536 @tab @code{remote get}, @code{remote put}
14538 @item @code{hostio-pwrite-packet}
14539 @tab @code{vFile:pwrite}
14540 @tab @code{remote get}, @code{remote put}
14542 @item @code{hostio-unlink-packet}
14543 @tab @code{vFile:unlink}
14544 @tab @code{remote delete}
14546 @item @code{noack-packet}
14547 @tab @code{QStartNoAckMode}
14548 @tab Packet acknowledgment
14550 @item @code{osdata}
14551 @tab @code{qXfer:osdata:read}
14552 @tab @code{info os}
14554 @item @code{query-attached}
14555 @tab @code{qAttached}
14556 @tab Querying remote process attach state.
14560 @section Implementing a Remote Stub
14562 @cindex debugging stub, example
14563 @cindex remote stub, example
14564 @cindex stub example, remote debugging
14565 The stub files provided with @value{GDBN} implement the target side of the
14566 communication protocol, and the @value{GDBN} side is implemented in the
14567 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
14568 these subroutines to communicate, and ignore the details. (If you're
14569 implementing your own stub file, you can still ignore the details: start
14570 with one of the existing stub files. @file{sparc-stub.c} is the best
14571 organized, and therefore the easiest to read.)
14573 @cindex remote serial debugging, overview
14574 To debug a program running on another machine (the debugging
14575 @dfn{target} machine), you must first arrange for all the usual
14576 prerequisites for the program to run by itself. For example, for a C
14581 A startup routine to set up the C runtime environment; these usually
14582 have a name like @file{crt0}. The startup routine may be supplied by
14583 your hardware supplier, or you may have to write your own.
14586 A C subroutine library to support your program's
14587 subroutine calls, notably managing input and output.
14590 A way of getting your program to the other machine---for example, a
14591 download program. These are often supplied by the hardware
14592 manufacturer, but you may have to write your own from hardware
14596 The next step is to arrange for your program to use a serial port to
14597 communicate with the machine where @value{GDBN} is running (the @dfn{host}
14598 machine). In general terms, the scheme looks like this:
14602 @value{GDBN} already understands how to use this protocol; when everything
14603 else is set up, you can simply use the @samp{target remote} command
14604 (@pxref{Targets,,Specifying a Debugging Target}).
14606 @item On the target,
14607 you must link with your program a few special-purpose subroutines that
14608 implement the @value{GDBN} remote serial protocol. The file containing these
14609 subroutines is called a @dfn{debugging stub}.
14611 On certain remote targets, you can use an auxiliary program
14612 @code{gdbserver} instead of linking a stub into your program.
14613 @xref{Server,,Using the @code{gdbserver} Program}, for details.
14616 The debugging stub is specific to the architecture of the remote
14617 machine; for example, use @file{sparc-stub.c} to debug programs on
14620 @cindex remote serial stub list
14621 These working remote stubs are distributed with @value{GDBN}:
14626 @cindex @file{i386-stub.c}
14629 For Intel 386 and compatible architectures.
14632 @cindex @file{m68k-stub.c}
14633 @cindex Motorola 680x0
14635 For Motorola 680x0 architectures.
14638 @cindex @file{sh-stub.c}
14641 For Renesas SH architectures.
14644 @cindex @file{sparc-stub.c}
14646 For @sc{sparc} architectures.
14648 @item sparcl-stub.c
14649 @cindex @file{sparcl-stub.c}
14652 For Fujitsu @sc{sparclite} architectures.
14656 The @file{README} file in the @value{GDBN} distribution may list other
14657 recently added stubs.
14660 * Stub Contents:: What the stub can do for you
14661 * Bootstrapping:: What you must do for the stub
14662 * Debug Session:: Putting it all together
14665 @node Stub Contents
14666 @subsection What the Stub Can Do for You
14668 @cindex remote serial stub
14669 The debugging stub for your architecture supplies these three
14673 @item set_debug_traps
14674 @findex set_debug_traps
14675 @cindex remote serial stub, initialization
14676 This routine arranges for @code{handle_exception} to run when your
14677 program stops. You must call this subroutine explicitly near the
14678 beginning of your program.
14680 @item handle_exception
14681 @findex handle_exception
14682 @cindex remote serial stub, main routine
14683 This is the central workhorse, but your program never calls it
14684 explicitly---the setup code arranges for @code{handle_exception} to
14685 run when a trap is triggered.
14687 @code{handle_exception} takes control when your program stops during
14688 execution (for example, on a breakpoint), and mediates communications
14689 with @value{GDBN} on the host machine. This is where the communications
14690 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
14691 representative on the target machine. It begins by sending summary
14692 information on the state of your program, then continues to execute,
14693 retrieving and transmitting any information @value{GDBN} needs, until you
14694 execute a @value{GDBN} command that makes your program resume; at that point,
14695 @code{handle_exception} returns control to your own code on the target
14699 @cindex @code{breakpoint} subroutine, remote
14700 Use this auxiliary subroutine to make your program contain a
14701 breakpoint. Depending on the particular situation, this may be the only
14702 way for @value{GDBN} to get control. For instance, if your target
14703 machine has some sort of interrupt button, you won't need to call this;
14704 pressing the interrupt button transfers control to
14705 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
14706 simply receiving characters on the serial port may also trigger a trap;
14707 again, in that situation, you don't need to call @code{breakpoint} from
14708 your own program---simply running @samp{target remote} from the host
14709 @value{GDBN} session gets control.
14711 Call @code{breakpoint} if none of these is true, or if you simply want
14712 to make certain your program stops at a predetermined point for the
14713 start of your debugging session.
14716 @node Bootstrapping
14717 @subsection What You Must Do for the Stub
14719 @cindex remote stub, support routines
14720 The debugging stubs that come with @value{GDBN} are set up for a particular
14721 chip architecture, but they have no information about the rest of your
14722 debugging target machine.
14724 First of all you need to tell the stub how to communicate with the
14728 @item int getDebugChar()
14729 @findex getDebugChar
14730 Write this subroutine to read a single character from the serial port.
14731 It may be identical to @code{getchar} for your target system; a
14732 different name is used to allow you to distinguish the two if you wish.
14734 @item void putDebugChar(int)
14735 @findex putDebugChar
14736 Write this subroutine to write a single character to the serial port.
14737 It may be identical to @code{putchar} for your target system; a
14738 different name is used to allow you to distinguish the two if you wish.
14741 @cindex control C, and remote debugging
14742 @cindex interrupting remote targets
14743 If you want @value{GDBN} to be able to stop your program while it is
14744 running, you need to use an interrupt-driven serial driver, and arrange
14745 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
14746 character). That is the character which @value{GDBN} uses to tell the
14747 remote system to stop.
14749 Getting the debugging target to return the proper status to @value{GDBN}
14750 probably requires changes to the standard stub; one quick and dirty way
14751 is to just execute a breakpoint instruction (the ``dirty'' part is that
14752 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
14754 Other routines you need to supply are:
14757 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
14758 @findex exceptionHandler
14759 Write this function to install @var{exception_address} in the exception
14760 handling tables. You need to do this because the stub does not have any
14761 way of knowing what the exception handling tables on your target system
14762 are like (for example, the processor's table might be in @sc{rom},
14763 containing entries which point to a table in @sc{ram}).
14764 @var{exception_number} is the exception number which should be changed;
14765 its meaning is architecture-dependent (for example, different numbers
14766 might represent divide by zero, misaligned access, etc). When this
14767 exception occurs, control should be transferred directly to
14768 @var{exception_address}, and the processor state (stack, registers,
14769 and so on) should be just as it is when a processor exception occurs. So if
14770 you want to use a jump instruction to reach @var{exception_address}, it
14771 should be a simple jump, not a jump to subroutine.
14773 For the 386, @var{exception_address} should be installed as an interrupt
14774 gate so that interrupts are masked while the handler runs. The gate
14775 should be at privilege level 0 (the most privileged level). The
14776 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
14777 help from @code{exceptionHandler}.
14779 @item void flush_i_cache()
14780 @findex flush_i_cache
14781 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
14782 instruction cache, if any, on your target machine. If there is no
14783 instruction cache, this subroutine may be a no-op.
14785 On target machines that have instruction caches, @value{GDBN} requires this
14786 function to make certain that the state of your program is stable.
14790 You must also make sure this library routine is available:
14793 @item void *memset(void *, int, int)
14795 This is the standard library function @code{memset} that sets an area of
14796 memory to a known value. If you have one of the free versions of
14797 @code{libc.a}, @code{memset} can be found there; otherwise, you must
14798 either obtain it from your hardware manufacturer, or write your own.
14801 If you do not use the GNU C compiler, you may need other standard
14802 library subroutines as well; this varies from one stub to another,
14803 but in general the stubs are likely to use any of the common library
14804 subroutines which @code{@value{NGCC}} generates as inline code.
14807 @node Debug Session
14808 @subsection Putting it All Together
14810 @cindex remote serial debugging summary
14811 In summary, when your program is ready to debug, you must follow these
14816 Make sure you have defined the supporting low-level routines
14817 (@pxref{Bootstrapping,,What You Must Do for the Stub}):
14819 @code{getDebugChar}, @code{putDebugChar},
14820 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
14824 Insert these lines near the top of your program:
14832 For the 680x0 stub only, you need to provide a variable called
14833 @code{exceptionHook}. Normally you just use:
14836 void (*exceptionHook)() = 0;
14840 but if before calling @code{set_debug_traps}, you set it to point to a
14841 function in your program, that function is called when
14842 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
14843 error). The function indicated by @code{exceptionHook} is called with
14844 one parameter: an @code{int} which is the exception number.
14847 Compile and link together: your program, the @value{GDBN} debugging stub for
14848 your target architecture, and the supporting subroutines.
14851 Make sure you have a serial connection between your target machine and
14852 the @value{GDBN} host, and identify the serial port on the host.
14855 @c The "remote" target now provides a `load' command, so we should
14856 @c document that. FIXME.
14857 Download your program to your target machine (or get it there by
14858 whatever means the manufacturer provides), and start it.
14861 Start @value{GDBN} on the host, and connect to the target
14862 (@pxref{Connecting,,Connecting to a Remote Target}).
14866 @node Configurations
14867 @chapter Configuration-Specific Information
14869 While nearly all @value{GDBN} commands are available for all native and
14870 cross versions of the debugger, there are some exceptions. This chapter
14871 describes things that are only available in certain configurations.
14873 There are three major categories of configurations: native
14874 configurations, where the host and target are the same, embedded
14875 operating system configurations, which are usually the same for several
14876 different processor architectures, and bare embedded processors, which
14877 are quite different from each other.
14882 * Embedded Processors::
14889 This section describes details specific to particular native
14894 * BSD libkvm Interface:: Debugging BSD kernel memory images
14895 * SVR4 Process Information:: SVR4 process information
14896 * DJGPP Native:: Features specific to the DJGPP port
14897 * Cygwin Native:: Features specific to the Cygwin port
14898 * Hurd Native:: Features specific to @sc{gnu} Hurd
14899 * Neutrino:: Features specific to QNX Neutrino
14900 * Darwin:: Features specific to Darwin
14906 On HP-UX systems, if you refer to a function or variable name that
14907 begins with a dollar sign, @value{GDBN} searches for a user or system
14908 name first, before it searches for a convenience variable.
14911 @node BSD libkvm Interface
14912 @subsection BSD libkvm Interface
14915 @cindex kernel memory image
14916 @cindex kernel crash dump
14918 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
14919 interface that provides a uniform interface for accessing kernel virtual
14920 memory images, including live systems and crash dumps. @value{GDBN}
14921 uses this interface to allow you to debug live kernels and kernel crash
14922 dumps on many native BSD configurations. This is implemented as a
14923 special @code{kvm} debugging target. For debugging a live system, load
14924 the currently running kernel into @value{GDBN} and connect to the
14928 (@value{GDBP}) @b{target kvm}
14931 For debugging crash dumps, provide the file name of the crash dump as an
14935 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
14938 Once connected to the @code{kvm} target, the following commands are
14944 Set current context from the @dfn{Process Control Block} (PCB) address.
14947 Set current context from proc address. This command isn't available on
14948 modern FreeBSD systems.
14951 @node SVR4 Process Information
14952 @subsection SVR4 Process Information
14954 @cindex examine process image
14955 @cindex process info via @file{/proc}
14957 Many versions of SVR4 and compatible systems provide a facility called
14958 @samp{/proc} that can be used to examine the image of a running
14959 process using file-system subroutines. If @value{GDBN} is configured
14960 for an operating system with this facility, the command @code{info
14961 proc} is available to report information about the process running
14962 your program, or about any process running on your system. @code{info
14963 proc} works only on SVR4 systems that include the @code{procfs} code.
14964 This includes, as of this writing, @sc{gnu}/Linux, OSF/1 (Digital
14965 Unix), Solaris, Irix, and Unixware, but not HP-UX, for example.
14971 @itemx info proc @var{process-id}
14972 Summarize available information about any running process. If a
14973 process ID is specified by @var{process-id}, display information about
14974 that process; otherwise display information about the program being
14975 debugged. The summary includes the debugged process ID, the command
14976 line used to invoke it, its current working directory, and its
14977 executable file's absolute file name.
14979 On some systems, @var{process-id} can be of the form
14980 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
14981 within a process. If the optional @var{pid} part is missing, it means
14982 a thread from the process being debugged (the leading @samp{/} still
14983 needs to be present, or else @value{GDBN} will interpret the number as
14984 a process ID rather than a thread ID).
14986 @item info proc mappings
14987 @cindex memory address space mappings
14988 Report the memory address space ranges accessible in the program, with
14989 information on whether the process has read, write, or execute access
14990 rights to each range. On @sc{gnu}/Linux systems, each memory range
14991 includes the object file which is mapped to that range, instead of the
14992 memory access rights to that range.
14994 @item info proc stat
14995 @itemx info proc status
14996 @cindex process detailed status information
14997 These subcommands are specific to @sc{gnu}/Linux systems. They show
14998 the process-related information, including the user ID and group ID;
14999 how many threads are there in the process; its virtual memory usage;
15000 the signals that are pending, blocked, and ignored; its TTY; its
15001 consumption of system and user time; its stack size; its @samp{nice}
15002 value; etc. For more information, see the @samp{proc} man page
15003 (type @kbd{man 5 proc} from your shell prompt).
15005 @item info proc all
15006 Show all the information about the process described under all of the
15007 above @code{info proc} subcommands.
15010 @comment These sub-options of 'info proc' were not included when
15011 @comment procfs.c was re-written. Keep their descriptions around
15012 @comment against the day when someone finds the time to put them back in.
15013 @kindex info proc times
15014 @item info proc times
15015 Starting time, user CPU time, and system CPU time for your program and
15018 @kindex info proc id
15020 Report on the process IDs related to your program: its own process ID,
15021 the ID of its parent, the process group ID, and the session ID.
15024 @item set procfs-trace
15025 @kindex set procfs-trace
15026 @cindex @code{procfs} API calls
15027 This command enables and disables tracing of @code{procfs} API calls.
15029 @item show procfs-trace
15030 @kindex show procfs-trace
15031 Show the current state of @code{procfs} API call tracing.
15033 @item set procfs-file @var{file}
15034 @kindex set procfs-file
15035 Tell @value{GDBN} to write @code{procfs} API trace to the named
15036 @var{file}. @value{GDBN} appends the trace info to the previous
15037 contents of the file. The default is to display the trace on the
15040 @item show procfs-file
15041 @kindex show procfs-file
15042 Show the file to which @code{procfs} API trace is written.
15044 @item proc-trace-entry
15045 @itemx proc-trace-exit
15046 @itemx proc-untrace-entry
15047 @itemx proc-untrace-exit
15048 @kindex proc-trace-entry
15049 @kindex proc-trace-exit
15050 @kindex proc-untrace-entry
15051 @kindex proc-untrace-exit
15052 These commands enable and disable tracing of entries into and exits
15053 from the @code{syscall} interface.
15056 @kindex info pidlist
15057 @cindex process list, QNX Neutrino
15058 For QNX Neutrino only, this command displays the list of all the
15059 processes and all the threads within each process.
15062 @kindex info meminfo
15063 @cindex mapinfo list, QNX Neutrino
15064 For QNX Neutrino only, this command displays the list of all mapinfos.
15068 @subsection Features for Debugging @sc{djgpp} Programs
15069 @cindex @sc{djgpp} debugging
15070 @cindex native @sc{djgpp} debugging
15071 @cindex MS-DOS-specific commands
15074 @sc{djgpp} is a port of the @sc{gnu} development tools to MS-DOS and
15075 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
15076 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
15077 top of real-mode DOS systems and their emulations.
15079 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
15080 defines a few commands specific to the @sc{djgpp} port. This
15081 subsection describes those commands.
15086 This is a prefix of @sc{djgpp}-specific commands which print
15087 information about the target system and important OS structures.
15090 @cindex MS-DOS system info
15091 @cindex free memory information (MS-DOS)
15092 @item info dos sysinfo
15093 This command displays assorted information about the underlying
15094 platform: the CPU type and features, the OS version and flavor, the
15095 DPMI version, and the available conventional and DPMI memory.
15100 @cindex segment descriptor tables
15101 @cindex descriptor tables display
15103 @itemx info dos ldt
15104 @itemx info dos idt
15105 These 3 commands display entries from, respectively, Global, Local,
15106 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
15107 tables are data structures which store a descriptor for each segment
15108 that is currently in use. The segment's selector is an index into a
15109 descriptor table; the table entry for that index holds the
15110 descriptor's base address and limit, and its attributes and access
15113 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
15114 segment (used for both data and the stack), and a DOS segment (which
15115 allows access to DOS/BIOS data structures and absolute addresses in
15116 conventional memory). However, the DPMI host will usually define
15117 additional segments in order to support the DPMI environment.
15119 @cindex garbled pointers
15120 These commands allow to display entries from the descriptor tables.
15121 Without an argument, all entries from the specified table are
15122 displayed. An argument, which should be an integer expression, means
15123 display a single entry whose index is given by the argument. For
15124 example, here's a convenient way to display information about the
15125 debugged program's data segment:
15128 @exdent @code{(@value{GDBP}) info dos ldt $ds}
15129 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
15133 This comes in handy when you want to see whether a pointer is outside
15134 the data segment's limit (i.e.@: @dfn{garbled}).
15136 @cindex page tables display (MS-DOS)
15138 @itemx info dos pte
15139 These two commands display entries from, respectively, the Page
15140 Directory and the Page Tables. Page Directories and Page Tables are
15141 data structures which control how virtual memory addresses are mapped
15142 into physical addresses. A Page Table includes an entry for every
15143 page of memory that is mapped into the program's address space; there
15144 may be several Page Tables, each one holding up to 4096 entries. A
15145 Page Directory has up to 4096 entries, one each for every Page Table
15146 that is currently in use.
15148 Without an argument, @kbd{info dos pde} displays the entire Page
15149 Directory, and @kbd{info dos pte} displays all the entries in all of
15150 the Page Tables. An argument, an integer expression, given to the
15151 @kbd{info dos pde} command means display only that entry from the Page
15152 Directory table. An argument given to the @kbd{info dos pte} command
15153 means display entries from a single Page Table, the one pointed to by
15154 the specified entry in the Page Directory.
15156 @cindex direct memory access (DMA) on MS-DOS
15157 These commands are useful when your program uses @dfn{DMA} (Direct
15158 Memory Access), which needs physical addresses to program the DMA
15161 These commands are supported only with some DPMI servers.
15163 @cindex physical address from linear address
15164 @item info dos address-pte @var{addr}
15165 This command displays the Page Table entry for a specified linear
15166 address. The argument @var{addr} is a linear address which should
15167 already have the appropriate segment's base address added to it,
15168 because this command accepts addresses which may belong to @emph{any}
15169 segment. For example, here's how to display the Page Table entry for
15170 the page where a variable @code{i} is stored:
15173 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
15174 @exdent @code{Page Table entry for address 0x11a00d30:}
15175 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
15179 This says that @code{i} is stored at offset @code{0xd30} from the page
15180 whose physical base address is @code{0x02698000}, and shows all the
15181 attributes of that page.
15183 Note that you must cast the addresses of variables to a @code{char *},
15184 since otherwise the value of @code{__djgpp_base_address}, the base
15185 address of all variables and functions in a @sc{djgpp} program, will
15186 be added using the rules of C pointer arithmetics: if @code{i} is
15187 declared an @code{int}, @value{GDBN} will add 4 times the value of
15188 @code{__djgpp_base_address} to the address of @code{i}.
15190 Here's another example, it displays the Page Table entry for the
15194 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
15195 @exdent @code{Page Table entry for address 0x29110:}
15196 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
15200 (The @code{+ 3} offset is because the transfer buffer's address is the
15201 3rd member of the @code{_go32_info_block} structure.) The output
15202 clearly shows that this DPMI server maps the addresses in conventional
15203 memory 1:1, i.e.@: the physical (@code{0x00029000} + @code{0x110}) and
15204 linear (@code{0x29110}) addresses are identical.
15206 This command is supported only with some DPMI servers.
15209 @cindex DOS serial data link, remote debugging
15210 In addition to native debugging, the DJGPP port supports remote
15211 debugging via a serial data link. The following commands are specific
15212 to remote serial debugging in the DJGPP port of @value{GDBN}.
15215 @kindex set com1base
15216 @kindex set com1irq
15217 @kindex set com2base
15218 @kindex set com2irq
15219 @kindex set com3base
15220 @kindex set com3irq
15221 @kindex set com4base
15222 @kindex set com4irq
15223 @item set com1base @var{addr}
15224 This command sets the base I/O port address of the @file{COM1} serial
15227 @item set com1irq @var{irq}
15228 This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use
15229 for the @file{COM1} serial port.
15231 There are similar commands @samp{set com2base}, @samp{set com3irq},
15232 etc.@: for setting the port address and the @code{IRQ} lines for the
15235 @kindex show com1base
15236 @kindex show com1irq
15237 @kindex show com2base
15238 @kindex show com2irq
15239 @kindex show com3base
15240 @kindex show com3irq
15241 @kindex show com4base
15242 @kindex show com4irq
15243 The related commands @samp{show com1base}, @samp{show com1irq} etc.@:
15244 display the current settings of the base address and the @code{IRQ}
15245 lines used by the COM ports.
15248 @kindex info serial
15249 @cindex DOS serial port status
15250 This command prints the status of the 4 DOS serial ports. For each
15251 port, it prints whether it's active or not, its I/O base address and
15252 IRQ number, whether it uses a 16550-style FIFO, its baudrate, and the
15253 counts of various errors encountered so far.
15257 @node Cygwin Native
15258 @subsection Features for Debugging MS Windows PE Executables
15259 @cindex MS Windows debugging
15260 @cindex native Cygwin debugging
15261 @cindex Cygwin-specific commands
15263 @value{GDBN} supports native debugging of MS Windows programs, including
15264 DLLs with and without symbolic debugging information. There are various
15265 additional Cygwin-specific commands, described in this section.
15266 Working with DLLs that have no debugging symbols is described in
15267 @ref{Non-debug DLL Symbols}.
15272 This is a prefix of MS Windows-specific commands which print
15273 information about the target system and important OS structures.
15275 @item info w32 selector
15276 This command displays information returned by
15277 the Win32 API @code{GetThreadSelectorEntry} function.
15278 It takes an optional argument that is evaluated to
15279 a long value to give the information about this given selector.
15280 Without argument, this command displays information
15281 about the six segment registers.
15285 This is a Cygwin-specific alias of @code{info shared}.
15287 @kindex dll-symbols
15289 This command loads symbols from a dll similarly to
15290 add-sym command but without the need to specify a base address.
15292 @kindex set cygwin-exceptions
15293 @cindex debugging the Cygwin DLL
15294 @cindex Cygwin DLL, debugging
15295 @item set cygwin-exceptions @var{mode}
15296 If @var{mode} is @code{on}, @value{GDBN} will break on exceptions that
15297 happen inside the Cygwin DLL. If @var{mode} is @code{off},
15298 @value{GDBN} will delay recognition of exceptions, and may ignore some
15299 exceptions which seem to be caused by internal Cygwin DLL
15300 ``bookkeeping''. This option is meant primarily for debugging the
15301 Cygwin DLL itself; the default value is @code{off} to avoid annoying
15302 @value{GDBN} users with false @code{SIGSEGV} signals.
15304 @kindex show cygwin-exceptions
15305 @item show cygwin-exceptions
15306 Displays whether @value{GDBN} will break on exceptions that happen
15307 inside the Cygwin DLL itself.
15309 @kindex set new-console
15310 @item set new-console @var{mode}
15311 If @var{mode} is @code{on} the debuggee will
15312 be started in a new console on next start.
15313 If @var{mode} is @code{off}i, the debuggee will
15314 be started in the same console as the debugger.
15316 @kindex show new-console
15317 @item show new-console
15318 Displays whether a new console is used
15319 when the debuggee is started.
15321 @kindex set new-group
15322 @item set new-group @var{mode}
15323 This boolean value controls whether the debuggee should
15324 start a new group or stay in the same group as the debugger.
15325 This affects the way the Windows OS handles
15328 @kindex show new-group
15329 @item show new-group
15330 Displays current value of new-group boolean.
15332 @kindex set debugevents
15333 @item set debugevents
15334 This boolean value adds debug output concerning kernel events related
15335 to the debuggee seen by the debugger. This includes events that
15336 signal thread and process creation and exit, DLL loading and
15337 unloading, console interrupts, and debugging messages produced by the
15338 Windows @code{OutputDebugString} API call.
15340 @kindex set debugexec
15341 @item set debugexec
15342 This boolean value adds debug output concerning execute events
15343 (such as resume thread) seen by the debugger.
15345 @kindex set debugexceptions
15346 @item set debugexceptions
15347 This boolean value adds debug output concerning exceptions in the
15348 debuggee seen by the debugger.
15350 @kindex set debugmemory
15351 @item set debugmemory
15352 This boolean value adds debug output concerning debuggee memory reads
15353 and writes by the debugger.
15357 This boolean values specifies whether the debuggee is called
15358 via a shell or directly (default value is on).
15362 Displays if the debuggee will be started with a shell.
15367 * Non-debug DLL Symbols:: Support for DLLs without debugging symbols
15370 @node Non-debug DLL Symbols
15371 @subsubsection Support for DLLs without Debugging Symbols
15372 @cindex DLLs with no debugging symbols
15373 @cindex Minimal symbols and DLLs
15375 Very often on windows, some of the DLLs that your program relies on do
15376 not include symbolic debugging information (for example,
15377 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
15378 symbols in a DLL, it relies on the minimal amount of symbolic
15379 information contained in the DLL's export table. This section
15380 describes working with such symbols, known internally to @value{GDBN} as
15381 ``minimal symbols''.
15383 Note that before the debugged program has started execution, no DLLs
15384 will have been loaded. The easiest way around this problem is simply to
15385 start the program --- either by setting a breakpoint or letting the
15386 program run once to completion. It is also possible to force
15387 @value{GDBN} to load a particular DLL before starting the executable ---
15388 see the shared library information in @ref{Files}, or the
15389 @code{dll-symbols} command in @ref{Cygwin Native}. Currently,
15390 explicitly loading symbols from a DLL with no debugging information will
15391 cause the symbol names to be duplicated in @value{GDBN}'s lookup table,
15392 which may adversely affect symbol lookup performance.
15394 @subsubsection DLL Name Prefixes
15396 In keeping with the naming conventions used by the Microsoft debugging
15397 tools, DLL export symbols are made available with a prefix based on the
15398 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
15399 also entered into the symbol table, so @code{CreateFileA} is often
15400 sufficient. In some cases there will be name clashes within a program
15401 (particularly if the executable itself includes full debugging symbols)
15402 necessitating the use of the fully qualified name when referring to the
15403 contents of the DLL. Use single-quotes around the name to avoid the
15404 exclamation mark (``!'') being interpreted as a language operator.
15406 Note that the internal name of the DLL may be all upper-case, even
15407 though the file name of the DLL is lower-case, or vice-versa. Since
15408 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
15409 some confusion. If in doubt, try the @code{info functions} and
15410 @code{info variables} commands or even @code{maint print msymbols}
15411 (@pxref{Symbols}). Here's an example:
15414 (@value{GDBP}) info function CreateFileA
15415 All functions matching regular expression "CreateFileA":
15417 Non-debugging symbols:
15418 0x77e885f4 CreateFileA
15419 0x77e885f4 KERNEL32!CreateFileA
15423 (@value{GDBP}) info function !
15424 All functions matching regular expression "!":
15426 Non-debugging symbols:
15427 0x6100114c cygwin1!__assert
15428 0x61004034 cygwin1!_dll_crt0@@0
15429 0x61004240 cygwin1!dll_crt0(per_process *)
15433 @subsubsection Working with Minimal Symbols
15435 Symbols extracted from a DLL's export table do not contain very much
15436 type information. All that @value{GDBN} can do is guess whether a symbol
15437 refers to a function or variable depending on the linker section that
15438 contains the symbol. Also note that the actual contents of the memory
15439 contained in a DLL are not available unless the program is running. This
15440 means that you cannot examine the contents of a variable or disassemble
15441 a function within a DLL without a running program.
15443 Variables are generally treated as pointers and dereferenced
15444 automatically. For this reason, it is often necessary to prefix a
15445 variable name with the address-of operator (``&'') and provide explicit
15446 type information in the command. Here's an example of the type of
15450 (@value{GDBP}) print 'cygwin1!__argv'
15455 (@value{GDBP}) x 'cygwin1!__argv'
15456 0x10021610: "\230y\""
15459 And two possible solutions:
15462 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
15463 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
15467 (@value{GDBP}) x/2x &'cygwin1!__argv'
15468 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
15469 (@value{GDBP}) x/x 0x10021608
15470 0x10021608: 0x0022fd98
15471 (@value{GDBP}) x/s 0x0022fd98
15472 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
15475 Setting a break point within a DLL is possible even before the program
15476 starts execution. However, under these circumstances, @value{GDBN} can't
15477 examine the initial instructions of the function in order to skip the
15478 function's frame set-up code. You can work around this by using ``*&''
15479 to set the breakpoint at a raw memory address:
15482 (@value{GDBP}) break *&'python22!PyOS_Readline'
15483 Breakpoint 1 at 0x1e04eff0
15486 The author of these extensions is not entirely convinced that setting a
15487 break point within a shared DLL like @file{kernel32.dll} is completely
15491 @subsection Commands Specific to @sc{gnu} Hurd Systems
15492 @cindex @sc{gnu} Hurd debugging
15494 This subsection describes @value{GDBN} commands specific to the
15495 @sc{gnu} Hurd native debugging.
15500 @kindex set signals@r{, Hurd command}
15501 @kindex set sigs@r{, Hurd command}
15502 This command toggles the state of inferior signal interception by
15503 @value{GDBN}. Mach exceptions, such as breakpoint traps, are not
15504 affected by this command. @code{sigs} is a shorthand alias for
15509 @kindex show signals@r{, Hurd command}
15510 @kindex show sigs@r{, Hurd command}
15511 Show the current state of intercepting inferior's signals.
15513 @item set signal-thread
15514 @itemx set sigthread
15515 @kindex set signal-thread
15516 @kindex set sigthread
15517 This command tells @value{GDBN} which thread is the @code{libc} signal
15518 thread. That thread is run when a signal is delivered to a running
15519 process. @code{set sigthread} is the shorthand alias of @code{set
15522 @item show signal-thread
15523 @itemx show sigthread
15524 @kindex show signal-thread
15525 @kindex show sigthread
15526 These two commands show which thread will run when the inferior is
15527 delivered a signal.
15530 @kindex set stopped@r{, Hurd command}
15531 This commands tells @value{GDBN} that the inferior process is stopped,
15532 as with the @code{SIGSTOP} signal. The stopped process can be
15533 continued by delivering a signal to it.
15536 @kindex show stopped@r{, Hurd command}
15537 This command shows whether @value{GDBN} thinks the debuggee is
15540 @item set exceptions
15541 @kindex set exceptions@r{, Hurd command}
15542 Use this command to turn off trapping of exceptions in the inferior.
15543 When exception trapping is off, neither breakpoints nor
15544 single-stepping will work. To restore the default, set exception
15547 @item show exceptions
15548 @kindex show exceptions@r{, Hurd command}
15549 Show the current state of trapping exceptions in the inferior.
15551 @item set task pause
15552 @kindex set task@r{, Hurd commands}
15553 @cindex task attributes (@sc{gnu} Hurd)
15554 @cindex pause current task (@sc{gnu} Hurd)
15555 This command toggles task suspension when @value{GDBN} has control.
15556 Setting it to on takes effect immediately, and the task is suspended
15557 whenever @value{GDBN} gets control. Setting it to off will take
15558 effect the next time the inferior is continued. If this option is set
15559 to off, you can use @code{set thread default pause on} or @code{set
15560 thread pause on} (see below) to pause individual threads.
15562 @item show task pause
15563 @kindex show task@r{, Hurd commands}
15564 Show the current state of task suspension.
15566 @item set task detach-suspend-count
15567 @cindex task suspend count
15568 @cindex detach from task, @sc{gnu} Hurd
15569 This command sets the suspend count the task will be left with when
15570 @value{GDBN} detaches from it.
15572 @item show task detach-suspend-count
15573 Show the suspend count the task will be left with when detaching.
15575 @item set task exception-port
15576 @itemx set task excp
15577 @cindex task exception port, @sc{gnu} Hurd
15578 This command sets the task exception port to which @value{GDBN} will
15579 forward exceptions. The argument should be the value of the @dfn{send
15580 rights} of the task. @code{set task excp} is a shorthand alias.
15582 @item set noninvasive
15583 @cindex noninvasive task options
15584 This command switches @value{GDBN} to a mode that is the least
15585 invasive as far as interfering with the inferior is concerned. This
15586 is the same as using @code{set task pause}, @code{set exceptions}, and
15587 @code{set signals} to values opposite to the defaults.
15589 @item info send-rights
15590 @itemx info receive-rights
15591 @itemx info port-rights
15592 @itemx info port-sets
15593 @itemx info dead-names
15596 @cindex send rights, @sc{gnu} Hurd
15597 @cindex receive rights, @sc{gnu} Hurd
15598 @cindex port rights, @sc{gnu} Hurd
15599 @cindex port sets, @sc{gnu} Hurd
15600 @cindex dead names, @sc{gnu} Hurd
15601 These commands display information about, respectively, send rights,
15602 receive rights, port rights, port sets, and dead names of a task.
15603 There are also shorthand aliases: @code{info ports} for @code{info
15604 port-rights} and @code{info psets} for @code{info port-sets}.
15606 @item set thread pause
15607 @kindex set thread@r{, Hurd command}
15608 @cindex thread properties, @sc{gnu} Hurd
15609 @cindex pause current thread (@sc{gnu} Hurd)
15610 This command toggles current thread suspension when @value{GDBN} has
15611 control. Setting it to on takes effect immediately, and the current
15612 thread is suspended whenever @value{GDBN} gets control. Setting it to
15613 off will take effect the next time the inferior is continued.
15614 Normally, this command has no effect, since when @value{GDBN} has
15615 control, the whole task is suspended. However, if you used @code{set
15616 task pause off} (see above), this command comes in handy to suspend
15617 only the current thread.
15619 @item show thread pause
15620 @kindex show thread@r{, Hurd command}
15621 This command shows the state of current thread suspension.
15623 @item set thread run
15624 This command sets whether the current thread is allowed to run.
15626 @item show thread run
15627 Show whether the current thread is allowed to run.
15629 @item set thread detach-suspend-count
15630 @cindex thread suspend count, @sc{gnu} Hurd
15631 @cindex detach from thread, @sc{gnu} Hurd
15632 This command sets the suspend count @value{GDBN} will leave on a
15633 thread when detaching. This number is relative to the suspend count
15634 found by @value{GDBN} when it notices the thread; use @code{set thread
15635 takeover-suspend-count} to force it to an absolute value.
15637 @item show thread detach-suspend-count
15638 Show the suspend count @value{GDBN} will leave on the thread when
15641 @item set thread exception-port
15642 @itemx set thread excp
15643 Set the thread exception port to which to forward exceptions. This
15644 overrides the port set by @code{set task exception-port} (see above).
15645 @code{set thread excp} is the shorthand alias.
15647 @item set thread takeover-suspend-count
15648 Normally, @value{GDBN}'s thread suspend counts are relative to the
15649 value @value{GDBN} finds when it notices each thread. This command
15650 changes the suspend counts to be absolute instead.
15652 @item set thread default
15653 @itemx show thread default
15654 @cindex thread default settings, @sc{gnu} Hurd
15655 Each of the above @code{set thread} commands has a @code{set thread
15656 default} counterpart (e.g., @code{set thread default pause}, @code{set
15657 thread default exception-port}, etc.). The @code{thread default}
15658 variety of commands sets the default thread properties for all
15659 threads; you can then change the properties of individual threads with
15660 the non-default commands.
15665 @subsection QNX Neutrino
15666 @cindex QNX Neutrino
15668 @value{GDBN} provides the following commands specific to the QNX
15672 @item set debug nto-debug
15673 @kindex set debug nto-debug
15674 When set to on, enables debugging messages specific to the QNX
15677 @item show debug nto-debug
15678 @kindex show debug nto-debug
15679 Show the current state of QNX Neutrino messages.
15686 @value{GDBN} provides the following commands specific to the Darwin target:
15689 @item set debug darwin @var{num}
15690 @kindex set debug darwin
15691 When set to a non zero value, enables debugging messages specific to
15692 the Darwin support. Higher values produce more verbose output.
15694 @item show debug darwin
15695 @kindex show debug darwin
15696 Show the current state of Darwin messages.
15698 @item set debug mach-o @var{num}
15699 @kindex set debug mach-o
15700 When set to a non zero value, enables debugging messages while
15701 @value{GDBN} is reading Darwin object files. (@dfn{Mach-O} is the
15702 file format used on Darwin for object and executable files.) Higher
15703 values produce more verbose output. This is a command to diagnose
15704 problems internal to @value{GDBN} and should not be needed in normal
15707 @item show debug mach-o
15708 @kindex show debug mach-o
15709 Show the current state of Mach-O file messages.
15711 @item set mach-exceptions on
15712 @itemx set mach-exceptions off
15713 @kindex set mach-exceptions
15714 On Darwin, faults are first reported as a Mach exception and are then
15715 mapped to a Posix signal. Use this command to turn on trapping of
15716 Mach exceptions in the inferior. This might be sometimes useful to
15717 better understand the cause of a fault. The default is off.
15719 @item show mach-exceptions
15720 @kindex show mach-exceptions
15721 Show the current state of exceptions trapping.
15726 @section Embedded Operating Systems
15728 This section describes configurations involving the debugging of
15729 embedded operating systems that are available for several different
15733 * VxWorks:: Using @value{GDBN} with VxWorks
15736 @value{GDBN} includes the ability to debug programs running on
15737 various real-time operating systems.
15740 @subsection Using @value{GDBN} with VxWorks
15746 @kindex target vxworks
15747 @item target vxworks @var{machinename}
15748 A VxWorks system, attached via TCP/IP. The argument @var{machinename}
15749 is the target system's machine name or IP address.
15753 On VxWorks, @code{load} links @var{filename} dynamically on the
15754 current target system as well as adding its symbols in @value{GDBN}.
15756 @value{GDBN} enables developers to spawn and debug tasks running on networked
15757 VxWorks targets from a Unix host. Already-running tasks spawned from
15758 the VxWorks shell can also be debugged. @value{GDBN} uses code that runs on
15759 both the Unix host and on the VxWorks target. The program
15760 @code{@value{GDBP}} is installed and executed on the Unix host. (It may be
15761 installed with the name @code{vxgdb}, to distinguish it from a
15762 @value{GDBN} for debugging programs on the host itself.)
15765 @item VxWorks-timeout @var{args}
15766 @kindex vxworks-timeout
15767 All VxWorks-based targets now support the option @code{vxworks-timeout}.
15768 This option is set by the user, and @var{args} represents the number of
15769 seconds @value{GDBN} waits for responses to rpc's. You might use this if
15770 your VxWorks target is a slow software simulator or is on the far side
15771 of a thin network line.
15774 The following information on connecting to VxWorks was current when
15775 this manual was produced; newer releases of VxWorks may use revised
15778 @findex INCLUDE_RDB
15779 To use @value{GDBN} with VxWorks, you must rebuild your VxWorks kernel
15780 to include the remote debugging interface routines in the VxWorks
15781 library @file{rdb.a}. To do this, define @code{INCLUDE_RDB} in the
15782 VxWorks configuration file @file{configAll.h} and rebuild your VxWorks
15783 kernel. The resulting kernel contains @file{rdb.a}, and spawns the
15784 source debugging task @code{tRdbTask} when VxWorks is booted. For more
15785 information on configuring and remaking VxWorks, see the manufacturer's
15787 @c VxWorks, see the @cite{VxWorks Programmer's Guide}.
15789 Once you have included @file{rdb.a} in your VxWorks system image and set
15790 your Unix execution search path to find @value{GDBN}, you are ready to
15791 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}} (or
15792 @code{vxgdb}, depending on your installation).
15794 @value{GDBN} comes up showing the prompt:
15801 * VxWorks Connection:: Connecting to VxWorks
15802 * VxWorks Download:: VxWorks download
15803 * VxWorks Attach:: Running tasks
15806 @node VxWorks Connection
15807 @subsubsection Connecting to VxWorks
15809 The @value{GDBN} command @code{target} lets you connect to a VxWorks target on the
15810 network. To connect to a target whose host name is ``@code{tt}'', type:
15813 (vxgdb) target vxworks tt
15817 @value{GDBN} displays messages like these:
15820 Attaching remote machine across net...
15825 @value{GDBN} then attempts to read the symbol tables of any object modules
15826 loaded into the VxWorks target since it was last booted. @value{GDBN} locates
15827 these files by searching the directories listed in the command search
15828 path (@pxref{Environment, ,Your Program's Environment}); if it fails
15829 to find an object file, it displays a message such as:
15832 prog.o: No such file or directory.
15835 When this happens, add the appropriate directory to the search path with
15836 the @value{GDBN} command @code{path}, and execute the @code{target}
15839 @node VxWorks Download
15840 @subsubsection VxWorks Download
15842 @cindex download to VxWorks
15843 If you have connected to the VxWorks target and you want to debug an
15844 object that has not yet been loaded, you can use the @value{GDBN}
15845 @code{load} command to download a file from Unix to VxWorks
15846 incrementally. The object file given as an argument to the @code{load}
15847 command is actually opened twice: first by the VxWorks target in order
15848 to download the code, then by @value{GDBN} in order to read the symbol
15849 table. This can lead to problems if the current working directories on
15850 the two systems differ. If both systems have NFS mounted the same
15851 filesystems, you can avoid these problems by using absolute paths.
15852 Otherwise, it is simplest to set the working directory on both systems
15853 to the directory in which the object file resides, and then to reference
15854 the file by its name, without any path. For instance, a program
15855 @file{prog.o} may reside in @file{@var{vxpath}/vw/demo/rdb} in VxWorks
15856 and in @file{@var{hostpath}/vw/demo/rdb} on the host. To load this
15857 program, type this on VxWorks:
15860 -> cd "@var{vxpath}/vw/demo/rdb"
15864 Then, in @value{GDBN}, type:
15867 (vxgdb) cd @var{hostpath}/vw/demo/rdb
15868 (vxgdb) load prog.o
15871 @value{GDBN} displays a response similar to this:
15874 Reading symbol data from wherever/vw/demo/rdb/prog.o... done.
15877 You can also use the @code{load} command to reload an object module
15878 after editing and recompiling the corresponding source file. Note that
15879 this makes @value{GDBN} delete all currently-defined breakpoints,
15880 auto-displays, and convenience variables, and to clear the value
15881 history. (This is necessary in order to preserve the integrity of
15882 debugger's data structures that reference the target system's symbol
15885 @node VxWorks Attach
15886 @subsubsection Running Tasks
15888 @cindex running VxWorks tasks
15889 You can also attach to an existing task using the @code{attach} command as
15893 (vxgdb) attach @var{task}
15897 where @var{task} is the VxWorks hexadecimal task ID. The task can be running
15898 or suspended when you attach to it. Running tasks are suspended at
15899 the time of attachment.
15901 @node Embedded Processors
15902 @section Embedded Processors
15904 This section goes into details specific to particular embedded
15907 @cindex send command to simulator
15908 Whenever a specific embedded processor has a simulator, @value{GDBN}
15909 allows to send an arbitrary command to the simulator.
15912 @item sim @var{command}
15913 @kindex sim@r{, a command}
15914 Send an arbitrary @var{command} string to the simulator. Consult the
15915 documentation for the specific simulator in use for information about
15916 acceptable commands.
15922 * M32R/D:: Renesas M32R/D
15923 * M68K:: Motorola M68K
15924 * MIPS Embedded:: MIPS Embedded
15925 * OpenRISC 1000:: OpenRisc 1000
15926 * PA:: HP PA Embedded
15927 * PowerPC Embedded:: PowerPC Embedded
15928 * Sparclet:: Tsqware Sparclet
15929 * Sparclite:: Fujitsu Sparclite
15930 * Z8000:: Zilog Z8000
15933 * Super-H:: Renesas Super-H
15942 @item target rdi @var{dev}
15943 ARM Angel monitor, via RDI library interface to ADP protocol. You may
15944 use this target to communicate with both boards running the Angel
15945 monitor, or with the EmbeddedICE JTAG debug device.
15948 @item target rdp @var{dev}
15953 @value{GDBN} provides the following ARM-specific commands:
15956 @item set arm disassembler
15958 This commands selects from a list of disassembly styles. The
15959 @code{"std"} style is the standard style.
15961 @item show arm disassembler
15963 Show the current disassembly style.
15965 @item set arm apcs32
15966 @cindex ARM 32-bit mode
15967 This command toggles ARM operation mode between 32-bit and 26-bit.
15969 @item show arm apcs32
15970 Display the current usage of the ARM 32-bit mode.
15972 @item set arm fpu @var{fputype}
15973 This command sets the ARM floating-point unit (FPU) type. The
15974 argument @var{fputype} can be one of these:
15978 Determine the FPU type by querying the OS ABI.
15980 Software FPU, with mixed-endian doubles on little-endian ARM
15983 GCC-compiled FPA co-processor.
15985 Software FPU with pure-endian doubles.
15991 Show the current type of the FPU.
15994 This command forces @value{GDBN} to use the specified ABI.
15997 Show the currently used ABI.
15999 @item set arm fallback-mode (arm|thumb|auto)
16000 @value{GDBN} uses the symbol table, when available, to determine
16001 whether instructions are ARM or Thumb. This command controls
16002 @value{GDBN}'s default behavior when the symbol table is not
16003 available. The default is @samp{auto}, which causes @value{GDBN} to
16004 use the current execution mode (from the @code{T} bit in the @code{CPSR}
16007 @item show arm fallback-mode
16008 Show the current fallback instruction mode.
16010 @item set arm force-mode (arm|thumb|auto)
16011 This command overrides use of the symbol table to determine whether
16012 instructions are ARM or Thumb. The default is @samp{auto}, which
16013 causes @value{GDBN} to use the symbol table and then the setting
16014 of @samp{set arm fallback-mode}.
16016 @item show arm force-mode
16017 Show the current forced instruction mode.
16019 @item set debug arm
16020 Toggle whether to display ARM-specific debugging messages from the ARM
16021 target support subsystem.
16023 @item show debug arm
16024 Show whether ARM-specific debugging messages are enabled.
16027 The following commands are available when an ARM target is debugged
16028 using the RDI interface:
16031 @item rdilogfile @r{[}@var{file}@r{]}
16033 @cindex ADP (Angel Debugger Protocol) logging
16034 Set the filename for the ADP (Angel Debugger Protocol) packet log.
16035 With an argument, sets the log file to the specified @var{file}. With
16036 no argument, show the current log file name. The default log file is
16039 @item rdilogenable @r{[}@var{arg}@r{]}
16040 @kindex rdilogenable
16041 Control logging of ADP packets. With an argument of 1 or @code{"yes"}
16042 enables logging, with an argument 0 or @code{"no"} disables it. With
16043 no arguments displays the current setting. When logging is enabled,
16044 ADP packets exchanged between @value{GDBN} and the RDI target device
16045 are logged to a file.
16047 @item set rdiromatzero
16048 @kindex set rdiromatzero
16049 @cindex ROM at zero address, RDI
16050 Tell @value{GDBN} whether the target has ROM at address 0. If on,
16051 vector catching is disabled, so that zero address can be used. If off
16052 (the default), vector catching is enabled. For this command to take
16053 effect, it needs to be invoked prior to the @code{target rdi} command.
16055 @item show rdiromatzero
16056 @kindex show rdiromatzero
16057 Show the current setting of ROM at zero address.
16059 @item set rdiheartbeat
16060 @kindex set rdiheartbeat
16061 @cindex RDI heartbeat
16062 Enable or disable RDI heartbeat packets. It is not recommended to
16063 turn on this option, since it confuses ARM and EPI JTAG interface, as
16064 well as the Angel monitor.
16066 @item show rdiheartbeat
16067 @kindex show rdiheartbeat
16068 Show the setting of RDI heartbeat packets.
16073 @subsection Renesas M32R/D and M32R/SDI
16076 @kindex target m32r
16077 @item target m32r @var{dev}
16078 Renesas M32R/D ROM monitor.
16080 @kindex target m32rsdi
16081 @item target m32rsdi @var{dev}
16082 Renesas M32R SDI server, connected via parallel port to the board.
16085 The following @value{GDBN} commands are specific to the M32R monitor:
16088 @item set download-path @var{path}
16089 @kindex set download-path
16090 @cindex find downloadable @sc{srec} files (M32R)
16091 Set the default path for finding downloadable @sc{srec} files.
16093 @item show download-path
16094 @kindex show download-path
16095 Show the default path for downloadable @sc{srec} files.
16097 @item set board-address @var{addr}
16098 @kindex set board-address
16099 @cindex M32-EVA target board address
16100 Set the IP address for the M32R-EVA target board.
16102 @item show board-address
16103 @kindex show board-address
16104 Show the current IP address of the target board.
16106 @item set server-address @var{addr}
16107 @kindex set server-address
16108 @cindex download server address (M32R)
16109 Set the IP address for the download server, which is the @value{GDBN}'s
16112 @item show server-address
16113 @kindex show server-address
16114 Display the IP address of the download server.
16116 @item upload @r{[}@var{file}@r{]}
16117 @kindex upload@r{, M32R}
16118 Upload the specified @sc{srec} @var{file} via the monitor's Ethernet
16119 upload capability. If no @var{file} argument is given, the current
16120 executable file is uploaded.
16122 @item tload @r{[}@var{file}@r{]}
16123 @kindex tload@r{, M32R}
16124 Test the @code{upload} command.
16127 The following commands are available for M32R/SDI:
16132 @cindex reset SDI connection, M32R
16133 This command resets the SDI connection.
16137 This command shows the SDI connection status.
16140 @kindex debug_chaos
16141 @cindex M32R/Chaos debugging
16142 Instructs the remote that M32R/Chaos debugging is to be used.
16144 @item use_debug_dma
16145 @kindex use_debug_dma
16146 Instructs the remote to use the DEBUG_DMA method of accessing memory.
16149 @kindex use_mon_code
16150 Instructs the remote to use the MON_CODE method of accessing memory.
16153 @kindex use_ib_break
16154 Instructs the remote to set breakpoints by IB break.
16156 @item use_dbt_break
16157 @kindex use_dbt_break
16158 Instructs the remote to set breakpoints by DBT.
16164 The Motorola m68k configuration includes ColdFire support, and a
16165 target command for the following ROM monitor.
16169 @kindex target dbug
16170 @item target dbug @var{dev}
16171 dBUG ROM monitor for Motorola ColdFire.
16175 @node MIPS Embedded
16176 @subsection MIPS Embedded
16178 @cindex MIPS boards
16179 @value{GDBN} can use the MIPS remote debugging protocol to talk to a
16180 MIPS board attached to a serial line. This is available when
16181 you configure @value{GDBN} with @samp{--target=mips-idt-ecoff}.
16184 Use these @value{GDBN} commands to specify the connection to your target board:
16187 @item target mips @var{port}
16188 @kindex target mips @var{port}
16189 To run a program on the board, start up @code{@value{GDBP}} with the
16190 name of your program as the argument. To connect to the board, use the
16191 command @samp{target mips @var{port}}, where @var{port} is the name of
16192 the serial port connected to the board. If the program has not already
16193 been downloaded to the board, you may use the @code{load} command to
16194 download it. You can then use all the usual @value{GDBN} commands.
16196 For example, this sequence connects to the target board through a serial
16197 port, and loads and runs a program called @var{prog} through the
16201 host$ @value{GDBP} @var{prog}
16202 @value{GDBN} is free software and @dots{}
16203 (@value{GDBP}) target mips /dev/ttyb
16204 (@value{GDBP}) load @var{prog}
16208 @item target mips @var{hostname}:@var{portnumber}
16209 On some @value{GDBN} host configurations, you can specify a TCP
16210 connection (for instance, to a serial line managed by a terminal
16211 concentrator) instead of a serial port, using the syntax
16212 @samp{@var{hostname}:@var{portnumber}}.
16214 @item target pmon @var{port}
16215 @kindex target pmon @var{port}
16218 @item target ddb @var{port}
16219 @kindex target ddb @var{port}
16220 NEC's DDB variant of PMON for Vr4300.
16222 @item target lsi @var{port}
16223 @kindex target lsi @var{port}
16224 LSI variant of PMON.
16226 @kindex target r3900
16227 @item target r3900 @var{dev}
16228 Densan DVE-R3900 ROM monitor for Toshiba R3900 Mips.
16230 @kindex target array
16231 @item target array @var{dev}
16232 Array Tech LSI33K RAID controller board.
16238 @value{GDBN} also supports these special commands for MIPS targets:
16241 @item set mipsfpu double
16242 @itemx set mipsfpu single
16243 @itemx set mipsfpu none
16244 @itemx set mipsfpu auto
16245 @itemx show mipsfpu
16246 @kindex set mipsfpu
16247 @kindex show mipsfpu
16248 @cindex MIPS remote floating point
16249 @cindex floating point, MIPS remote
16250 If your target board does not support the MIPS floating point
16251 coprocessor, you should use the command @samp{set mipsfpu none} (if you
16252 need this, you may wish to put the command in your @value{GDBN} init
16253 file). This tells @value{GDBN} how to find the return value of
16254 functions which return floating point values. It also allows
16255 @value{GDBN} to avoid saving the floating point registers when calling
16256 functions on the board. If you are using a floating point coprocessor
16257 with only single precision floating point support, as on the @sc{r4650}
16258 processor, use the command @samp{set mipsfpu single}. The default
16259 double precision floating point coprocessor may be selected using
16260 @samp{set mipsfpu double}.
16262 In previous versions the only choices were double precision or no
16263 floating point, so @samp{set mipsfpu on} will select double precision
16264 and @samp{set mipsfpu off} will select no floating point.
16266 As usual, you can inquire about the @code{mipsfpu} variable with
16267 @samp{show mipsfpu}.
16269 @item set timeout @var{seconds}
16270 @itemx set retransmit-timeout @var{seconds}
16271 @itemx show timeout
16272 @itemx show retransmit-timeout
16273 @cindex @code{timeout}, MIPS protocol
16274 @cindex @code{retransmit-timeout}, MIPS protocol
16275 @kindex set timeout
16276 @kindex show timeout
16277 @kindex set retransmit-timeout
16278 @kindex show retransmit-timeout
16279 You can control the timeout used while waiting for a packet, in the MIPS
16280 remote protocol, with the @code{set timeout @var{seconds}} command. The
16281 default is 5 seconds. Similarly, you can control the timeout used while
16282 waiting for an acknowledgment of a packet with the @code{set
16283 retransmit-timeout @var{seconds}} command. The default is 3 seconds.
16284 You can inspect both values with @code{show timeout} and @code{show
16285 retransmit-timeout}. (These commands are @emph{only} available when
16286 @value{GDBN} is configured for @samp{--target=mips-idt-ecoff}.)
16288 The timeout set by @code{set timeout} does not apply when @value{GDBN}
16289 is waiting for your program to stop. In that case, @value{GDBN} waits
16290 forever because it has no way of knowing how long the program is going
16291 to run before stopping.
16293 @item set syn-garbage-limit @var{num}
16294 @kindex set syn-garbage-limit@r{, MIPS remote}
16295 @cindex synchronize with remote MIPS target
16296 Limit the maximum number of characters @value{GDBN} should ignore when
16297 it tries to synchronize with the remote target. The default is 10
16298 characters. Setting the limit to -1 means there's no limit.
16300 @item show syn-garbage-limit
16301 @kindex show syn-garbage-limit@r{, MIPS remote}
16302 Show the current limit on the number of characters to ignore when
16303 trying to synchronize with the remote system.
16305 @item set monitor-prompt @var{prompt}
16306 @kindex set monitor-prompt@r{, MIPS remote}
16307 @cindex remote monitor prompt
16308 Tell @value{GDBN} to expect the specified @var{prompt} string from the
16309 remote monitor. The default depends on the target:
16319 @item show monitor-prompt
16320 @kindex show monitor-prompt@r{, MIPS remote}
16321 Show the current strings @value{GDBN} expects as the prompt from the
16324 @item set monitor-warnings
16325 @kindex set monitor-warnings@r{, MIPS remote}
16326 Enable or disable monitor warnings about hardware breakpoints. This
16327 has effect only for the @code{lsi} target. When on, @value{GDBN} will
16328 display warning messages whose codes are returned by the @code{lsi}
16329 PMON monitor for breakpoint commands.
16331 @item show monitor-warnings
16332 @kindex show monitor-warnings@r{, MIPS remote}
16333 Show the current setting of printing monitor warnings.
16335 @item pmon @var{command}
16336 @kindex pmon@r{, MIPS remote}
16337 @cindex send PMON command
16338 This command allows sending an arbitrary @var{command} string to the
16339 monitor. The monitor must be in debug mode for this to work.
16342 @node OpenRISC 1000
16343 @subsection OpenRISC 1000
16344 @cindex OpenRISC 1000
16346 @cindex or1k boards
16347 See OR1k Architecture document (@uref{www.opencores.org}) for more information
16348 about platform and commands.
16352 @kindex target jtag
16353 @item target jtag jtag://@var{host}:@var{port}
16355 Connects to remote JTAG server.
16356 JTAG remote server can be either an or1ksim or JTAG server,
16357 connected via parallel port to the board.
16359 Example: @code{target jtag jtag://localhost:9999}
16362 @item or1ksim @var{command}
16363 If connected to @code{or1ksim} OpenRISC 1000 Architectural
16364 Simulator, proprietary commands can be executed.
16366 @kindex info or1k spr
16367 @item info or1k spr
16368 Displays spr groups.
16370 @item info or1k spr @var{group}
16371 @itemx info or1k spr @var{groupno}
16372 Displays register names in selected group.
16374 @item info or1k spr @var{group} @var{register}
16375 @itemx info or1k spr @var{register}
16376 @itemx info or1k spr @var{groupno} @var{registerno}
16377 @itemx info or1k spr @var{registerno}
16378 Shows information about specified spr register.
16381 @item spr @var{group} @var{register} @var{value}
16382 @itemx spr @var{register @var{value}}
16383 @itemx spr @var{groupno} @var{registerno @var{value}}
16384 @itemx spr @var{registerno @var{value}}
16385 Writes @var{value} to specified spr register.
16388 Some implementations of OpenRISC 1000 Architecture also have hardware trace.
16389 It is very similar to @value{GDBN} trace, except it does not interfere with normal
16390 program execution and is thus much faster. Hardware breakpoints/watchpoint
16391 triggers can be set using:
16394 Load effective address/data
16396 Store effective address/data
16398 Access effective address ($SEA or $LEA) or data ($SDATA/$LDATA)
16403 When triggered, it can capture low level data, like: @code{PC}, @code{LSEA},
16404 @code{LDATA}, @code{SDATA}, @code{READSPR}, @code{WRITESPR}, @code{INSTR}.
16406 @code{htrace} commands:
16407 @cindex OpenRISC 1000 htrace
16410 @item hwatch @var{conditional}
16411 Set hardware watchpoint on combination of Load/Store Effective Address(es)
16412 or Data. For example:
16414 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
16416 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
16420 Display information about current HW trace configuration.
16422 @item htrace trigger @var{conditional}
16423 Set starting criteria for HW trace.
16425 @item htrace qualifier @var{conditional}
16426 Set acquisition qualifier for HW trace.
16428 @item htrace stop @var{conditional}
16429 Set HW trace stopping criteria.
16431 @item htrace record [@var{data}]*
16432 Selects the data to be recorded, when qualifier is met and HW trace was
16435 @item htrace enable
16436 @itemx htrace disable
16437 Enables/disables the HW trace.
16439 @item htrace rewind [@var{filename}]
16440 Clears currently recorded trace data.
16442 If filename is specified, new trace file is made and any newly collected data
16443 will be written there.
16445 @item htrace print [@var{start} [@var{len}]]
16446 Prints trace buffer, using current record configuration.
16448 @item htrace mode continuous
16449 Set continuous trace mode.
16451 @item htrace mode suspend
16452 Set suspend trace mode.
16456 @node PowerPC Embedded
16457 @subsection PowerPC Embedded
16459 @value{GDBN} provides the following PowerPC-specific commands:
16462 @kindex set powerpc
16463 @item set powerpc soft-float
16464 @itemx show powerpc soft-float
16465 Force @value{GDBN} to use (or not use) a software floating point calling
16466 convention. By default, @value{GDBN} selects the calling convention based
16467 on the selected architecture and the provided executable file.
16469 @item set powerpc vector-abi
16470 @itemx show powerpc vector-abi
16471 Force @value{GDBN} to use the specified calling convention for vector
16472 arguments and return values. The valid options are @samp{auto};
16473 @samp{generic}, to avoid vector registers even if they are present;
16474 @samp{altivec}, to use AltiVec registers; and @samp{spe} to use SPE
16475 registers. By default, @value{GDBN} selects the calling convention
16476 based on the selected architecture and the provided executable file.
16478 @kindex target dink32
16479 @item target dink32 @var{dev}
16480 DINK32 ROM monitor.
16482 @kindex target ppcbug
16483 @item target ppcbug @var{dev}
16484 @kindex target ppcbug1
16485 @item target ppcbug1 @var{dev}
16486 PPCBUG ROM monitor for PowerPC.
16489 @item target sds @var{dev}
16490 SDS monitor, running on a PowerPC board (such as Motorola's ADS).
16493 @cindex SDS protocol
16494 The following commands specific to the SDS protocol are supported
16498 @item set sdstimeout @var{nsec}
16499 @kindex set sdstimeout
16500 Set the timeout for SDS protocol reads to be @var{nsec} seconds. The
16501 default is 2 seconds.
16503 @item show sdstimeout
16504 @kindex show sdstimeout
16505 Show the current value of the SDS timeout.
16507 @item sds @var{command}
16508 @kindex sds@r{, a command}
16509 Send the specified @var{command} string to the SDS monitor.
16514 @subsection HP PA Embedded
16518 @kindex target op50n
16519 @item target op50n @var{dev}
16520 OP50N monitor, running on an OKI HPPA board.
16522 @kindex target w89k
16523 @item target w89k @var{dev}
16524 W89K monitor, running on a Winbond HPPA board.
16529 @subsection Tsqware Sparclet
16533 @value{GDBN} enables developers to debug tasks running on
16534 Sparclet targets from a Unix host.
16535 @value{GDBN} uses code that runs on
16536 both the Unix host and on the Sparclet target. The program
16537 @code{@value{GDBP}} is installed and executed on the Unix host.
16540 @item remotetimeout @var{args}
16541 @kindex remotetimeout
16542 @value{GDBN} supports the option @code{remotetimeout}.
16543 This option is set by the user, and @var{args} represents the number of
16544 seconds @value{GDBN} waits for responses.
16547 @cindex compiling, on Sparclet
16548 When compiling for debugging, include the options @samp{-g} to get debug
16549 information and @samp{-Ttext} to relocate the program to where you wish to
16550 load it on the target. You may also want to add the options @samp{-n} or
16551 @samp{-N} in order to reduce the size of the sections. Example:
16554 sparclet-aout-gcc prog.c -Ttext 0x12010000 -g -o prog -N
16557 You can use @code{objdump} to verify that the addresses are what you intended:
16560 sparclet-aout-objdump --headers --syms prog
16563 @cindex running, on Sparclet
16565 your Unix execution search path to find @value{GDBN}, you are ready to
16566 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}}
16567 (or @code{sparclet-aout-gdb}, depending on your installation).
16569 @value{GDBN} comes up showing the prompt:
16576 * Sparclet File:: Setting the file to debug
16577 * Sparclet Connection:: Connecting to Sparclet
16578 * Sparclet Download:: Sparclet download
16579 * Sparclet Execution:: Running and debugging
16582 @node Sparclet File
16583 @subsubsection Setting File to Debug
16585 The @value{GDBN} command @code{file} lets you choose with program to debug.
16588 (gdbslet) file prog
16592 @value{GDBN} then attempts to read the symbol table of @file{prog}.
16593 @value{GDBN} locates
16594 the file by searching the directories listed in the command search
16596 If the file was compiled with debug information (option @samp{-g}), source
16597 files will be searched as well.
16598 @value{GDBN} locates
16599 the source files by searching the directories listed in the directory search
16600 path (@pxref{Environment, ,Your Program's Environment}).
16602 to find a file, it displays a message such as:
16605 prog: No such file or directory.
16608 When this happens, add the appropriate directories to the search paths with
16609 the @value{GDBN} commands @code{path} and @code{dir}, and execute the
16610 @code{target} command again.
16612 @node Sparclet Connection
16613 @subsubsection Connecting to Sparclet
16615 The @value{GDBN} command @code{target} lets you connect to a Sparclet target.
16616 To connect to a target on serial port ``@code{ttya}'', type:
16619 (gdbslet) target sparclet /dev/ttya
16620 Remote target sparclet connected to /dev/ttya
16621 main () at ../prog.c:3
16625 @value{GDBN} displays messages like these:
16631 @node Sparclet Download
16632 @subsubsection Sparclet Download
16634 @cindex download to Sparclet
16635 Once connected to the Sparclet target,
16636 you can use the @value{GDBN}
16637 @code{load} command to download the file from the host to the target.
16638 The file name and load offset should be given as arguments to the @code{load}
16640 Since the file format is aout, the program must be loaded to the starting
16641 address. You can use @code{objdump} to find out what this value is. The load
16642 offset is an offset which is added to the VMA (virtual memory address)
16643 of each of the file's sections.
16644 For instance, if the program
16645 @file{prog} was linked to text address 0x1201000, with data at 0x12010160
16646 and bss at 0x12010170, in @value{GDBN}, type:
16649 (gdbslet) load prog 0x12010000
16650 Loading section .text, size 0xdb0 vma 0x12010000
16653 If the code is loaded at a different address then what the program was linked
16654 to, you may need to use the @code{section} and @code{add-symbol-file} commands
16655 to tell @value{GDBN} where to map the symbol table.
16657 @node Sparclet Execution
16658 @subsubsection Running and Debugging
16660 @cindex running and debugging Sparclet programs
16661 You can now begin debugging the task using @value{GDBN}'s execution control
16662 commands, @code{b}, @code{step}, @code{run}, etc. See the @value{GDBN}
16663 manual for the list of commands.
16667 Breakpoint 1 at 0x12010000: file prog.c, line 3.
16669 Starting program: prog
16670 Breakpoint 1, main (argc=1, argv=0xeffff21c) at prog.c:3
16671 3 char *symarg = 0;
16673 4 char *execarg = "hello!";
16678 @subsection Fujitsu Sparclite
16682 @kindex target sparclite
16683 @item target sparclite @var{dev}
16684 Fujitsu sparclite boards, used only for the purpose of loading.
16685 You must use an additional command to debug the program.
16686 For example: target remote @var{dev} using @value{GDBN} standard
16692 @subsection Zilog Z8000
16695 @cindex simulator, Z8000
16696 @cindex Zilog Z8000 simulator
16698 When configured for debugging Zilog Z8000 targets, @value{GDBN} includes
16701 For the Z8000 family, @samp{target sim} simulates either the Z8002 (the
16702 unsegmented variant of the Z8000 architecture) or the Z8001 (the
16703 segmented variant). The simulator recognizes which architecture is
16704 appropriate by inspecting the object code.
16707 @item target sim @var{args}
16709 @kindex target sim@r{, with Z8000}
16710 Debug programs on a simulated CPU. If the simulator supports setup
16711 options, specify them via @var{args}.
16715 After specifying this target, you can debug programs for the simulated
16716 CPU in the same style as programs for your host computer; use the
16717 @code{file} command to load a new program image, the @code{run} command
16718 to run your program, and so on.
16720 As well as making available all the usual machine registers
16721 (@pxref{Registers, ,Registers}), the Z8000 simulator provides three
16722 additional items of information as specially named registers:
16727 Counts clock-ticks in the simulator.
16730 Counts instructions run in the simulator.
16733 Execution time in 60ths of a second.
16737 You can refer to these values in @value{GDBN} expressions with the usual
16738 conventions; for example, @w{@samp{b fputc if $cycles>5000}} sets a
16739 conditional breakpoint that suspends only after at least 5000
16740 simulated clock ticks.
16743 @subsection Atmel AVR
16746 When configured for debugging the Atmel AVR, @value{GDBN} supports the
16747 following AVR-specific commands:
16750 @item info io_registers
16751 @kindex info io_registers@r{, AVR}
16752 @cindex I/O registers (Atmel AVR)
16753 This command displays information about the AVR I/O registers. For
16754 each register, @value{GDBN} prints its number and value.
16761 When configured for debugging CRIS, @value{GDBN} provides the
16762 following CRIS-specific commands:
16765 @item set cris-version @var{ver}
16766 @cindex CRIS version
16767 Set the current CRIS version to @var{ver}, either @samp{10} or @samp{32}.
16768 The CRIS version affects register names and sizes. This command is useful in
16769 case autodetection of the CRIS version fails.
16771 @item show cris-version
16772 Show the current CRIS version.
16774 @item set cris-dwarf2-cfi
16775 @cindex DWARF-2 CFI and CRIS
16776 Set the usage of DWARF-2 CFI for CRIS debugging. The default is @samp{on}.
16777 Change to @samp{off} when using @code{gcc-cris} whose version is below
16780 @item show cris-dwarf2-cfi
16781 Show the current state of using DWARF-2 CFI.
16783 @item set cris-mode @var{mode}
16785 Set the current CRIS mode to @var{mode}. It should only be changed when
16786 debugging in guru mode, in which case it should be set to
16787 @samp{guru} (the default is @samp{normal}).
16789 @item show cris-mode
16790 Show the current CRIS mode.
16794 @subsection Renesas Super-H
16797 For the Renesas Super-H processor, @value{GDBN} provides these
16802 @kindex regs@r{, Super-H}
16803 Show the values of all Super-H registers.
16805 @item set sh calling-convention @var{convention}
16806 @kindex set sh calling-convention
16807 Set the calling-convention used when calling functions from @value{GDBN}.
16808 Allowed values are @samp{gcc}, which is the default setting, and @samp{renesas}.
16809 With the @samp{gcc} setting, functions are called using the @value{NGCC} calling
16810 convention. If the DWARF-2 information of the called function specifies
16811 that the function follows the Renesas calling convention, the function
16812 is called using the Renesas calling convention. If the calling convention
16813 is set to @samp{renesas}, the Renesas calling convention is always used,
16814 regardless of the DWARF-2 information. This can be used to override the
16815 default of @samp{gcc} if debug information is missing, or the compiler
16816 does not emit the DWARF-2 calling convention entry for a function.
16818 @item show sh calling-convention
16819 @kindex show sh calling-convention
16820 Show the current calling convention setting.
16825 @node Architectures
16826 @section Architectures
16828 This section describes characteristics of architectures that affect
16829 all uses of @value{GDBN} with the architecture, both native and cross.
16836 * HPPA:: HP PA architecture
16837 * SPU:: Cell Broadband Engine SPU architecture
16842 @subsection x86 Architecture-specific Issues
16845 @item set struct-convention @var{mode}
16846 @kindex set struct-convention
16847 @cindex struct return convention
16848 @cindex struct/union returned in registers
16849 Set the convention used by the inferior to return @code{struct}s and
16850 @code{union}s from functions to @var{mode}. Possible values of
16851 @var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the
16852 default). @code{"default"} or @code{"pcc"} means that @code{struct}s
16853 are returned on the stack, while @code{"reg"} means that a
16854 @code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will
16855 be returned in a register.
16857 @item show struct-convention
16858 @kindex show struct-convention
16859 Show the current setting of the convention to return @code{struct}s
16868 @kindex set rstack_high_address
16869 @cindex AMD 29K register stack
16870 @cindex register stack, AMD29K
16871 @item set rstack_high_address @var{address}
16872 On AMD 29000 family processors, registers are saved in a separate
16873 @dfn{register stack}. There is no way for @value{GDBN} to determine the
16874 extent of this stack. Normally, @value{GDBN} just assumes that the
16875 stack is ``large enough''. This may result in @value{GDBN} referencing
16876 memory locations that do not exist. If necessary, you can get around
16877 this problem by specifying the ending address of the register stack with
16878 the @code{set rstack_high_address} command. The argument should be an
16879 address, which you probably want to precede with @samp{0x} to specify in
16882 @kindex show rstack_high_address
16883 @item show rstack_high_address
16884 Display the current limit of the register stack, on AMD 29000 family
16892 See the following section.
16897 @cindex stack on Alpha
16898 @cindex stack on MIPS
16899 @cindex Alpha stack
16901 Alpha- and MIPS-based computers use an unusual stack frame, which
16902 sometimes requires @value{GDBN} to search backward in the object code to
16903 find the beginning of a function.
16905 @cindex response time, MIPS debugging
16906 To improve response time (especially for embedded applications, where
16907 @value{GDBN} may be restricted to a slow serial line for this search)
16908 you may want to limit the size of this search, using one of these
16912 @cindex @code{heuristic-fence-post} (Alpha, MIPS)
16913 @item set heuristic-fence-post @var{limit}
16914 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
16915 search for the beginning of a function. A value of @var{0} (the
16916 default) means there is no limit. However, except for @var{0}, the
16917 larger the limit the more bytes @code{heuristic-fence-post} must search
16918 and therefore the longer it takes to run. You should only need to use
16919 this command when debugging a stripped executable.
16921 @item show heuristic-fence-post
16922 Display the current limit.
16926 These commands are available @emph{only} when @value{GDBN} is configured
16927 for debugging programs on Alpha or MIPS processors.
16929 Several MIPS-specific commands are available when debugging MIPS
16933 @item set mips abi @var{arg}
16934 @kindex set mips abi
16935 @cindex set ABI for MIPS
16936 Tell @value{GDBN} which MIPS ABI is used by the inferior. Possible
16937 values of @var{arg} are:
16941 The default ABI associated with the current binary (this is the
16952 @item show mips abi
16953 @kindex show mips abi
16954 Show the MIPS ABI used by @value{GDBN} to debug the inferior.
16957 @itemx show mipsfpu
16958 @xref{MIPS Embedded, set mipsfpu}.
16960 @item set mips mask-address @var{arg}
16961 @kindex set mips mask-address
16962 @cindex MIPS addresses, masking
16963 This command determines whether the most-significant 32 bits of 64-bit
16964 MIPS addresses are masked off. The argument @var{arg} can be
16965 @samp{on}, @samp{off}, or @samp{auto}. The latter is the default
16966 setting, which lets @value{GDBN} determine the correct value.
16968 @item show mips mask-address
16969 @kindex show mips mask-address
16970 Show whether the upper 32 bits of MIPS addresses are masked off or
16973 @item set remote-mips64-transfers-32bit-regs
16974 @kindex set remote-mips64-transfers-32bit-regs
16975 This command controls compatibility with 64-bit MIPS targets that
16976 transfer data in 32-bit quantities. If you have an old MIPS 64 target
16977 that transfers 32 bits for some registers, like @sc{sr} and @sc{fsr},
16978 and 64 bits for other registers, set this option to @samp{on}.
16980 @item show remote-mips64-transfers-32bit-regs
16981 @kindex show remote-mips64-transfers-32bit-regs
16982 Show the current setting of compatibility with older MIPS 64 targets.
16984 @item set debug mips
16985 @kindex set debug mips
16986 This command turns on and off debugging messages for the MIPS-specific
16987 target code in @value{GDBN}.
16989 @item show debug mips
16990 @kindex show debug mips
16991 Show the current setting of MIPS debugging messages.
16997 @cindex HPPA support
16999 When @value{GDBN} is debugging the HP PA architecture, it provides the
17000 following special commands:
17003 @item set debug hppa
17004 @kindex set debug hppa
17005 This command determines whether HPPA architecture-specific debugging
17006 messages are to be displayed.
17008 @item show debug hppa
17009 Show whether HPPA debugging messages are displayed.
17011 @item maint print unwind @var{address}
17012 @kindex maint print unwind@r{, HPPA}
17013 This command displays the contents of the unwind table entry at the
17014 given @var{address}.
17020 @subsection Cell Broadband Engine SPU architecture
17021 @cindex Cell Broadband Engine
17024 When @value{GDBN} is debugging the Cell Broadband Engine SPU architecture,
17025 it provides the following special commands:
17028 @item info spu event
17030 Display SPU event facility status. Shows current event mask
17031 and pending event status.
17033 @item info spu signal
17034 Display SPU signal notification facility status. Shows pending
17035 signal-control word and signal notification mode of both signal
17036 notification channels.
17038 @item info spu mailbox
17039 Display SPU mailbox facility status. Shows all pending entries,
17040 in order of processing, in each of the SPU Write Outbound,
17041 SPU Write Outbound Interrupt, and SPU Read Inbound mailboxes.
17044 Display MFC DMA status. Shows all pending commands in the MFC
17045 DMA queue. For each entry, opcode, tag, class IDs, effective
17046 and local store addresses and transfer size are shown.
17048 @item info spu proxydma
17049 Display MFC Proxy-DMA status. Shows all pending commands in the MFC
17050 Proxy-DMA queue. For each entry, opcode, tag, class IDs, effective
17051 and local store addresses and transfer size are shown.
17056 @subsection PowerPC
17057 @cindex PowerPC architecture
17059 When @value{GDBN} is debugging the PowerPC architecture, it provides a set of
17060 pseudo-registers to enable inspection of 128-bit wide Decimal Floating Point
17061 numbers stored in the floating point registers. These values must be stored
17062 in two consecutive registers, always starting at an even register like
17063 @code{f0} or @code{f2}.
17065 The pseudo-registers go from @code{$dl0} through @code{$dl15}, and are formed
17066 by joining the even/odd register pairs @code{f0} and @code{f1} for @code{$dl0},
17067 @code{f2} and @code{f3} for @code{$dl1} and so on.
17069 For POWER7 processors, @value{GDBN} provides a set of pseudo-registers, the 64-bit
17070 wide Extended Floating Point Registers (@samp{f32} through @samp{f63}).
17073 @node Controlling GDB
17074 @chapter Controlling @value{GDBN}
17076 You can alter the way @value{GDBN} interacts with you by using the
17077 @code{set} command. For commands controlling how @value{GDBN} displays
17078 data, see @ref{Print Settings, ,Print Settings}. Other settings are
17083 * Editing:: Command editing
17084 * Command History:: Command history
17085 * Screen Size:: Screen size
17086 * Numbers:: Numbers
17087 * ABI:: Configuring the current ABI
17088 * Messages/Warnings:: Optional warnings and messages
17089 * Debugging Output:: Optional messages about internal happenings
17097 @value{GDBN} indicates its readiness to read a command by printing a string
17098 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
17099 can change the prompt string with the @code{set prompt} command. For
17100 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
17101 the prompt in one of the @value{GDBN} sessions so that you can always tell
17102 which one you are talking to.
17104 @emph{Note:} @code{set prompt} does not add a space for you after the
17105 prompt you set. This allows you to set a prompt which ends in a space
17106 or a prompt that does not.
17110 @item set prompt @var{newprompt}
17111 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
17113 @kindex show prompt
17115 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
17119 @section Command Editing
17121 @cindex command line editing
17123 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
17124 @sc{gnu} library provides consistent behavior for programs which provide a
17125 command line interface to the user. Advantages are @sc{gnu} Emacs-style
17126 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
17127 substitution, and a storage and recall of command history across
17128 debugging sessions.
17130 You may control the behavior of command line editing in @value{GDBN} with the
17131 command @code{set}.
17134 @kindex set editing
17137 @itemx set editing on
17138 Enable command line editing (enabled by default).
17140 @item set editing off
17141 Disable command line editing.
17143 @kindex show editing
17145 Show whether command line editing is enabled.
17148 @xref{Command Line Editing}, for more details about the Readline
17149 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
17150 encouraged to read that chapter.
17152 @node Command History
17153 @section Command History
17154 @cindex command history
17156 @value{GDBN} can keep track of the commands you type during your
17157 debugging sessions, so that you can be certain of precisely what
17158 happened. Use these commands to manage the @value{GDBN} command
17161 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
17162 package, to provide the history facility. @xref{Using History
17163 Interactively}, for the detailed description of the History library.
17165 To issue a command to @value{GDBN} without affecting certain aspects of
17166 the state which is seen by users, prefix it with @samp{server }
17167 (@pxref{Server Prefix}). This
17168 means that this command will not affect the command history, nor will it
17169 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
17170 pressed on a line by itself.
17172 @cindex @code{server}, command prefix
17173 The server prefix does not affect the recording of values into the value
17174 history; to print a value without recording it into the value history,
17175 use the @code{output} command instead of the @code{print} command.
17177 Here is the description of @value{GDBN} commands related to command
17181 @cindex history substitution
17182 @cindex history file
17183 @kindex set history filename
17184 @cindex @env{GDBHISTFILE}, environment variable
17185 @item set history filename @var{fname}
17186 Set the name of the @value{GDBN} command history file to @var{fname}.
17187 This is the file where @value{GDBN} reads an initial command history
17188 list, and where it writes the command history from this session when it
17189 exits. You can access this list through history expansion or through
17190 the history command editing characters listed below. This file defaults
17191 to the value of the environment variable @code{GDBHISTFILE}, or to
17192 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
17195 @cindex save command history
17196 @kindex set history save
17197 @item set history save
17198 @itemx set history save on
17199 Record command history in a file, whose name may be specified with the
17200 @code{set history filename} command. By default, this option is disabled.
17202 @item set history save off
17203 Stop recording command history in a file.
17205 @cindex history size
17206 @kindex set history size
17207 @cindex @env{HISTSIZE}, environment variable
17208 @item set history size @var{size}
17209 Set the number of commands which @value{GDBN} keeps in its history list.
17210 This defaults to the value of the environment variable
17211 @code{HISTSIZE}, or to 256 if this variable is not set.
17214 History expansion assigns special meaning to the character @kbd{!}.
17215 @xref{Event Designators}, for more details.
17217 @cindex history expansion, turn on/off
17218 Since @kbd{!} is also the logical not operator in C, history expansion
17219 is off by default. If you decide to enable history expansion with the
17220 @code{set history expansion on} command, you may sometimes need to
17221 follow @kbd{!} (when it is used as logical not, in an expression) with
17222 a space or a tab to prevent it from being expanded. The readline
17223 history facilities do not attempt substitution on the strings
17224 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
17226 The commands to control history expansion are:
17229 @item set history expansion on
17230 @itemx set history expansion
17231 @kindex set history expansion
17232 Enable history expansion. History expansion is off by default.
17234 @item set history expansion off
17235 Disable history expansion.
17238 @kindex show history
17240 @itemx show history filename
17241 @itemx show history save
17242 @itemx show history size
17243 @itemx show history expansion
17244 These commands display the state of the @value{GDBN} history parameters.
17245 @code{show history} by itself displays all four states.
17250 @kindex show commands
17251 @cindex show last commands
17252 @cindex display command history
17253 @item show commands
17254 Display the last ten commands in the command history.
17256 @item show commands @var{n}
17257 Print ten commands centered on command number @var{n}.
17259 @item show commands +
17260 Print ten commands just after the commands last printed.
17264 @section Screen Size
17265 @cindex size of screen
17266 @cindex pauses in output
17268 Certain commands to @value{GDBN} may produce large amounts of
17269 information output to the screen. To help you read all of it,
17270 @value{GDBN} pauses and asks you for input at the end of each page of
17271 output. Type @key{RET} when you want to continue the output, or @kbd{q}
17272 to discard the remaining output. Also, the screen width setting
17273 determines when to wrap lines of output. Depending on what is being
17274 printed, @value{GDBN} tries to break the line at a readable place,
17275 rather than simply letting it overflow onto the following line.
17277 Normally @value{GDBN} knows the size of the screen from the terminal
17278 driver software. For example, on Unix @value{GDBN} uses the termcap data base
17279 together with the value of the @code{TERM} environment variable and the
17280 @code{stty rows} and @code{stty cols} settings. If this is not correct,
17281 you can override it with the @code{set height} and @code{set
17288 @kindex show height
17289 @item set height @var{lpp}
17291 @itemx set width @var{cpl}
17293 These @code{set} commands specify a screen height of @var{lpp} lines and
17294 a screen width of @var{cpl} characters. The associated @code{show}
17295 commands display the current settings.
17297 If you specify a height of zero lines, @value{GDBN} does not pause during
17298 output no matter how long the output is. This is useful if output is to a
17299 file or to an editor buffer.
17301 Likewise, you can specify @samp{set width 0} to prevent @value{GDBN}
17302 from wrapping its output.
17304 @item set pagination on
17305 @itemx set pagination off
17306 @kindex set pagination
17307 Turn the output pagination on or off; the default is on. Turning
17308 pagination off is the alternative to @code{set height 0}.
17310 @item show pagination
17311 @kindex show pagination
17312 Show the current pagination mode.
17317 @cindex number representation
17318 @cindex entering numbers
17320 You can always enter numbers in octal, decimal, or hexadecimal in
17321 @value{GDBN} by the usual conventions: octal numbers begin with
17322 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
17323 begin with @samp{0x}. Numbers that neither begin with @samp{0} or
17324 @samp{0x}, nor end with a @samp{.} are, by default, entered in base
17325 10; likewise, the default display for numbers---when no particular
17326 format is specified---is base 10. You can change the default base for
17327 both input and output with the commands described below.
17330 @kindex set input-radix
17331 @item set input-radix @var{base}
17332 Set the default base for numeric input. Supported choices
17333 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
17334 specified either unambiguously or using the current input radix; for
17338 set input-radix 012
17339 set input-radix 10.
17340 set input-radix 0xa
17344 sets the input base to decimal. On the other hand, @samp{set input-radix 10}
17345 leaves the input radix unchanged, no matter what it was, since
17346 @samp{10}, being without any leading or trailing signs of its base, is
17347 interpreted in the current radix. Thus, if the current radix is 16,
17348 @samp{10} is interpreted in hex, i.e.@: as 16 decimal, which doesn't
17351 @kindex set output-radix
17352 @item set output-radix @var{base}
17353 Set the default base for numeric display. Supported choices
17354 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
17355 specified either unambiguously or using the current input radix.
17357 @kindex show input-radix
17358 @item show input-radix
17359 Display the current default base for numeric input.
17361 @kindex show output-radix
17362 @item show output-radix
17363 Display the current default base for numeric display.
17365 @item set radix @r{[}@var{base}@r{]}
17369 These commands set and show the default base for both input and output
17370 of numbers. @code{set radix} sets the radix of input and output to
17371 the same base; without an argument, it resets the radix back to its
17372 default value of 10.
17377 @section Configuring the Current ABI
17379 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
17380 application automatically. However, sometimes you need to override its
17381 conclusions. Use these commands to manage @value{GDBN}'s view of the
17388 One @value{GDBN} configuration can debug binaries for multiple operating
17389 system targets, either via remote debugging or native emulation.
17390 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
17391 but you can override its conclusion using the @code{set osabi} command.
17392 One example where this is useful is in debugging of binaries which use
17393 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
17394 not have the same identifying marks that the standard C library for your
17399 Show the OS ABI currently in use.
17402 With no argument, show the list of registered available OS ABI's.
17404 @item set osabi @var{abi}
17405 Set the current OS ABI to @var{abi}.
17408 @cindex float promotion
17410 Generally, the way that an argument of type @code{float} is passed to a
17411 function depends on whether the function is prototyped. For a prototyped
17412 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
17413 according to the architecture's convention for @code{float}. For unprototyped
17414 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
17415 @code{double} and then passed.
17417 Unfortunately, some forms of debug information do not reliably indicate whether
17418 a function is prototyped. If @value{GDBN} calls a function that is not marked
17419 as prototyped, it consults @kbd{set coerce-float-to-double}.
17422 @kindex set coerce-float-to-double
17423 @item set coerce-float-to-double
17424 @itemx set coerce-float-to-double on
17425 Arguments of type @code{float} will be promoted to @code{double} when passed
17426 to an unprototyped function. This is the default setting.
17428 @item set coerce-float-to-double off
17429 Arguments of type @code{float} will be passed directly to unprototyped
17432 @kindex show coerce-float-to-double
17433 @item show coerce-float-to-double
17434 Show the current setting of promoting @code{float} to @code{double}.
17438 @kindex show cp-abi
17439 @value{GDBN} needs to know the ABI used for your program's C@t{++}
17440 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
17441 used to build your application. @value{GDBN} only fully supports
17442 programs with a single C@t{++} ABI; if your program contains code using
17443 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
17444 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
17445 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
17446 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
17447 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
17448 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
17453 Show the C@t{++} ABI currently in use.
17456 With no argument, show the list of supported C@t{++} ABI's.
17458 @item set cp-abi @var{abi}
17459 @itemx set cp-abi auto
17460 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
17463 @node Messages/Warnings
17464 @section Optional Warnings and Messages
17466 @cindex verbose operation
17467 @cindex optional warnings
17468 By default, @value{GDBN} is silent about its inner workings. If you are
17469 running on a slow machine, you may want to use the @code{set verbose}
17470 command. This makes @value{GDBN} tell you when it does a lengthy
17471 internal operation, so you will not think it has crashed.
17473 Currently, the messages controlled by @code{set verbose} are those
17474 which announce that the symbol table for a source file is being read;
17475 see @code{symbol-file} in @ref{Files, ,Commands to Specify Files}.
17478 @kindex set verbose
17479 @item set verbose on
17480 Enables @value{GDBN} output of certain informational messages.
17482 @item set verbose off
17483 Disables @value{GDBN} output of certain informational messages.
17485 @kindex show verbose
17487 Displays whether @code{set verbose} is on or off.
17490 By default, if @value{GDBN} encounters bugs in the symbol table of an
17491 object file, it is silent; but if you are debugging a compiler, you may
17492 find this information useful (@pxref{Symbol Errors, ,Errors Reading
17497 @kindex set complaints
17498 @item set complaints @var{limit}
17499 Permits @value{GDBN} to output @var{limit} complaints about each type of
17500 unusual symbols before becoming silent about the problem. Set
17501 @var{limit} to zero to suppress all complaints; set it to a large number
17502 to prevent complaints from being suppressed.
17504 @kindex show complaints
17505 @item show complaints
17506 Displays how many symbol complaints @value{GDBN} is permitted to produce.
17510 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
17511 lot of stupid questions to confirm certain commands. For example, if
17512 you try to run a program which is already running:
17516 The program being debugged has been started already.
17517 Start it from the beginning? (y or n)
17520 If you are willing to unflinchingly face the consequences of your own
17521 commands, you can disable this ``feature'':
17525 @kindex set confirm
17527 @cindex confirmation
17528 @cindex stupid questions
17529 @item set confirm off
17530 Disables confirmation requests.
17532 @item set confirm on
17533 Enables confirmation requests (the default).
17535 @kindex show confirm
17537 Displays state of confirmation requests.
17541 @cindex command tracing
17542 If you need to debug user-defined commands or sourced files you may find it
17543 useful to enable @dfn{command tracing}. In this mode each command will be
17544 printed as it is executed, prefixed with one or more @samp{+} symbols, the
17545 quantity denoting the call depth of each command.
17548 @kindex set trace-commands
17549 @cindex command scripts, debugging
17550 @item set trace-commands on
17551 Enable command tracing.
17552 @item set trace-commands off
17553 Disable command tracing.
17554 @item show trace-commands
17555 Display the current state of command tracing.
17558 @node Debugging Output
17559 @section Optional Messages about Internal Happenings
17560 @cindex optional debugging messages
17562 @value{GDBN} has commands that enable optional debugging messages from
17563 various @value{GDBN} subsystems; normally these commands are of
17564 interest to @value{GDBN} maintainers, or when reporting a bug. This
17565 section documents those commands.
17568 @kindex set exec-done-display
17569 @item set exec-done-display
17570 Turns on or off the notification of asynchronous commands'
17571 completion. When on, @value{GDBN} will print a message when an
17572 asynchronous command finishes its execution. The default is off.
17573 @kindex show exec-done-display
17574 @item show exec-done-display
17575 Displays the current setting of asynchronous command completion
17578 @cindex gdbarch debugging info
17579 @cindex architecture debugging info
17580 @item set debug arch
17581 Turns on or off display of gdbarch debugging info. The default is off
17583 @item show debug arch
17584 Displays the current state of displaying gdbarch debugging info.
17585 @item set debug aix-thread
17586 @cindex AIX threads
17587 Display debugging messages about inner workings of the AIX thread
17589 @item show debug aix-thread
17590 Show the current state of AIX thread debugging info display.
17591 @item set debug dwarf2-die
17592 @cindex DWARF2 DIEs
17593 Dump DWARF2 DIEs after they are read in.
17594 The value is the number of nesting levels to print.
17595 A value of zero turns off the display.
17596 @item show debug dwarf2-die
17597 Show the current state of DWARF2 DIE debugging.
17598 @item set debug displaced
17599 @cindex displaced stepping debugging info
17600 Turns on or off display of @value{GDBN} debugging info for the
17601 displaced stepping support. The default is off.
17602 @item show debug displaced
17603 Displays the current state of displaying @value{GDBN} debugging info
17604 related to displaced stepping.
17605 @item set debug event
17606 @cindex event debugging info
17607 Turns on or off display of @value{GDBN} event debugging info. The
17609 @item show debug event
17610 Displays the current state of displaying @value{GDBN} event debugging
17612 @item set debug expression
17613 @cindex expression debugging info
17614 Turns on or off display of debugging info about @value{GDBN}
17615 expression parsing. The default is off.
17616 @item show debug expression
17617 Displays the current state of displaying debugging info about
17618 @value{GDBN} expression parsing.
17619 @item set debug frame
17620 @cindex frame debugging info
17621 Turns on or off display of @value{GDBN} frame debugging info. The
17623 @item show debug frame
17624 Displays the current state of displaying @value{GDBN} frame debugging
17626 @item set debug infrun
17627 @cindex inferior debugging info
17628 Turns on or off display of @value{GDBN} debugging info for running the inferior.
17629 The default is off. @file{infrun.c} contains GDB's runtime state machine used
17630 for implementing operations such as single-stepping the inferior.
17631 @item show debug infrun
17632 Displays the current state of @value{GDBN} inferior debugging.
17633 @item set debug lin-lwp
17634 @cindex @sc{gnu}/Linux LWP debug messages
17635 @cindex Linux lightweight processes
17636 Turns on or off debugging messages from the Linux LWP debug support.
17637 @item show debug lin-lwp
17638 Show the current state of Linux LWP debugging messages.
17639 @item set debug lin-lwp-async
17640 @cindex @sc{gnu}/Linux LWP async debug messages
17641 @cindex Linux lightweight processes
17642 Turns on or off debugging messages from the Linux LWP async debug support.
17643 @item show debug lin-lwp-async
17644 Show the current state of Linux LWP async debugging messages.
17645 @item set debug observer
17646 @cindex observer debugging info
17647 Turns on or off display of @value{GDBN} observer debugging. This
17648 includes info such as the notification of observable events.
17649 @item show debug observer
17650 Displays the current state of observer debugging.
17651 @item set debug overload
17652 @cindex C@t{++} overload debugging info
17653 Turns on or off display of @value{GDBN} C@t{++} overload debugging
17654 info. This includes info such as ranking of functions, etc. The default
17656 @item show debug overload
17657 Displays the current state of displaying @value{GDBN} C@t{++} overload
17659 @cindex packets, reporting on stdout
17660 @cindex serial connections, debugging
17661 @cindex debug remote protocol
17662 @cindex remote protocol debugging
17663 @cindex display remote packets
17664 @item set debug remote
17665 Turns on or off display of reports on all packets sent back and forth across
17666 the serial line to the remote machine. The info is printed on the
17667 @value{GDBN} standard output stream. The default is off.
17668 @item show debug remote
17669 Displays the state of display of remote packets.
17670 @item set debug serial
17671 Turns on or off display of @value{GDBN} serial debugging info. The
17673 @item show debug serial
17674 Displays the current state of displaying @value{GDBN} serial debugging
17676 @item set debug solib-frv
17677 @cindex FR-V shared-library debugging
17678 Turns on or off debugging messages for FR-V shared-library code.
17679 @item show debug solib-frv
17680 Display the current state of FR-V shared-library code debugging
17682 @item set debug target
17683 @cindex target debugging info
17684 Turns on or off display of @value{GDBN} target debugging info. This info
17685 includes what is going on at the target level of GDB, as it happens. The
17686 default is 0. Set it to 1 to track events, and to 2 to also track the
17687 value of large memory transfers. Changes to this flag do not take effect
17688 until the next time you connect to a target or use the @code{run} command.
17689 @item show debug target
17690 Displays the current state of displaying @value{GDBN} target debugging
17692 @item set debug timestamp
17693 @cindex timestampping debugging info
17694 Turns on or off display of timestamps with @value{GDBN} debugging info.
17695 When enabled, seconds and microseconds are displayed before each debugging
17697 @item show debug timestamp
17698 Displays the current state of displaying timestamps with @value{GDBN}
17700 @item set debugvarobj
17701 @cindex variable object debugging info
17702 Turns on or off display of @value{GDBN} variable object debugging
17703 info. The default is off.
17704 @item show debugvarobj
17705 Displays the current state of displaying @value{GDBN} variable object
17707 @item set debug xml
17708 @cindex XML parser debugging
17709 Turns on or off debugging messages for built-in XML parsers.
17710 @item show debug xml
17711 Displays the current state of XML debugging messages.
17714 @node Extending GDB
17715 @chapter Extending @value{GDBN}
17716 @cindex extending GDB
17718 @value{GDBN} provides two mechanisms for extension. The first is based
17719 on composition of @value{GDBN} commands, and the second is based on the
17720 Python scripting language.
17723 * Sequences:: Canned Sequences of Commands
17724 * Python:: Scripting @value{GDBN} using Python
17728 @section Canned Sequences of Commands
17730 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
17731 Command Lists}), @value{GDBN} provides two ways to store sequences of
17732 commands for execution as a unit: user-defined commands and command
17736 * Define:: How to define your own commands
17737 * Hooks:: Hooks for user-defined commands
17738 * Command Files:: How to write scripts of commands to be stored in a file
17739 * Output:: Commands for controlled output
17743 @subsection User-defined Commands
17745 @cindex user-defined command
17746 @cindex arguments, to user-defined commands
17747 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
17748 which you assign a new name as a command. This is done with the
17749 @code{define} command. User commands may accept up to 10 arguments
17750 separated by whitespace. Arguments are accessed within the user command
17751 via @code{$arg0@dots{}$arg9}. A trivial example:
17755 print $arg0 + $arg1 + $arg2
17760 To execute the command use:
17767 This defines the command @code{adder}, which prints the sum of
17768 its three arguments. Note the arguments are text substitutions, so they may
17769 reference variables, use complex expressions, or even perform inferior
17772 @cindex argument count in user-defined commands
17773 @cindex how many arguments (user-defined commands)
17774 In addition, @code{$argc} may be used to find out how many arguments have
17775 been passed. This expands to a number in the range 0@dots{}10.
17780 print $arg0 + $arg1
17783 print $arg0 + $arg1 + $arg2
17791 @item define @var{commandname}
17792 Define a command named @var{commandname}. If there is already a command
17793 by that name, you are asked to confirm that you want to redefine it.
17794 @var{commandname} may be a bare command name consisting of letters,
17795 numbers, dashes, and underscores. It may also start with any predefined
17796 prefix command. For example, @samp{define target my-target} creates
17797 a user-defined @samp{target my-target} command.
17799 The definition of the command is made up of other @value{GDBN} command lines,
17800 which are given following the @code{define} command. The end of these
17801 commands is marked by a line containing @code{end}.
17804 @kindex end@r{ (user-defined commands)}
17805 @item document @var{commandname}
17806 Document the user-defined command @var{commandname}, so that it can be
17807 accessed by @code{help}. The command @var{commandname} must already be
17808 defined. This command reads lines of documentation just as @code{define}
17809 reads the lines of the command definition, ending with @code{end}.
17810 After the @code{document} command is finished, @code{help} on command
17811 @var{commandname} displays the documentation you have written.
17813 You may use the @code{document} command again to change the
17814 documentation of a command. Redefining the command with @code{define}
17815 does not change the documentation.
17817 @kindex dont-repeat
17818 @cindex don't repeat command
17820 Used inside a user-defined command, this tells @value{GDBN} that this
17821 command should not be repeated when the user hits @key{RET}
17822 (@pxref{Command Syntax, repeat last command}).
17824 @kindex help user-defined
17825 @item help user-defined
17826 List all user-defined commands, with the first line of the documentation
17831 @itemx show user @var{commandname}
17832 Display the @value{GDBN} commands used to define @var{commandname} (but
17833 not its documentation). If no @var{commandname} is given, display the
17834 definitions for all user-defined commands.
17836 @cindex infinite recursion in user-defined commands
17837 @kindex show max-user-call-depth
17838 @kindex set max-user-call-depth
17839 @item show max-user-call-depth
17840 @itemx set max-user-call-depth
17841 The value of @code{max-user-call-depth} controls how many recursion
17842 levels are allowed in user-defined commands before @value{GDBN} suspects an
17843 infinite recursion and aborts the command.
17846 In addition to the above commands, user-defined commands frequently
17847 use control flow commands, described in @ref{Command Files}.
17849 When user-defined commands are executed, the
17850 commands of the definition are not printed. An error in any command
17851 stops execution of the user-defined command.
17853 If used interactively, commands that would ask for confirmation proceed
17854 without asking when used inside a user-defined command. Many @value{GDBN}
17855 commands that normally print messages to say what they are doing omit the
17856 messages when used in a user-defined command.
17859 @subsection User-defined Command Hooks
17860 @cindex command hooks
17861 @cindex hooks, for commands
17862 @cindex hooks, pre-command
17865 You may define @dfn{hooks}, which are a special kind of user-defined
17866 command. Whenever you run the command @samp{foo}, if the user-defined
17867 command @samp{hook-foo} exists, it is executed (with no arguments)
17868 before that command.
17870 @cindex hooks, post-command
17872 A hook may also be defined which is run after the command you executed.
17873 Whenever you run the command @samp{foo}, if the user-defined command
17874 @samp{hookpost-foo} exists, it is executed (with no arguments) after
17875 that command. Post-execution hooks may exist simultaneously with
17876 pre-execution hooks, for the same command.
17878 It is valid for a hook to call the command which it hooks. If this
17879 occurs, the hook is not re-executed, thereby avoiding infinite recursion.
17881 @c It would be nice if hookpost could be passed a parameter indicating
17882 @c if the command it hooks executed properly or not. FIXME!
17884 @kindex stop@r{, a pseudo-command}
17885 In addition, a pseudo-command, @samp{stop} exists. Defining
17886 (@samp{hook-stop}) makes the associated commands execute every time
17887 execution stops in your program: before breakpoint commands are run,
17888 displays are printed, or the stack frame is printed.
17890 For example, to ignore @code{SIGALRM} signals while
17891 single-stepping, but treat them normally during normal execution,
17896 handle SIGALRM nopass
17900 handle SIGALRM pass
17903 define hook-continue
17904 handle SIGALRM pass
17908 As a further example, to hook at the beginning and end of the @code{echo}
17909 command, and to add extra text to the beginning and end of the message,
17917 define hookpost-echo
17921 (@value{GDBP}) echo Hello World
17922 <<<---Hello World--->>>
17927 You can define a hook for any single-word command in @value{GDBN}, but
17928 not for command aliases; you should define a hook for the basic command
17929 name, e.g.@: @code{backtrace} rather than @code{bt}.
17930 @c FIXME! So how does Joe User discover whether a command is an alias
17932 You can hook a multi-word command by adding @code{hook-} or
17933 @code{hookpost-} to the last word of the command, e.g.@:
17934 @samp{define target hook-remote} to add a hook to @samp{target remote}.
17936 If an error occurs during the execution of your hook, execution of
17937 @value{GDBN} commands stops and @value{GDBN} issues a prompt
17938 (before the command that you actually typed had a chance to run).
17940 If you try to define a hook which does not match any known command, you
17941 get a warning from the @code{define} command.
17943 @node Command Files
17944 @subsection Command Files
17946 @cindex command files
17947 @cindex scripting commands
17948 A command file for @value{GDBN} is a text file made of lines that are
17949 @value{GDBN} commands. Comments (lines starting with @kbd{#}) may
17950 also be included. An empty line in a command file does nothing; it
17951 does not mean to repeat the last command, as it would from the
17954 You can request the execution of a command file with the @code{source}
17959 @cindex execute commands from a file
17960 @item source [@code{-v}] @var{filename}
17961 Execute the command file @var{filename}.
17964 The lines in a command file are generally executed sequentially,
17965 unless the order of execution is changed by one of the
17966 @emph{flow-control commands} described below. The commands are not
17967 printed as they are executed. An error in any command terminates
17968 execution of the command file and control is returned to the console.
17970 @value{GDBN} searches for @var{filename} in the current directory and then
17971 on the search path (specified with the @samp{directory} command).
17973 If @code{-v}, for verbose mode, is given then @value{GDBN} displays
17974 each command as it is executed. The option must be given before
17975 @var{filename}, and is interpreted as part of the filename anywhere else.
17977 Commands that would ask for confirmation if used interactively proceed
17978 without asking when used in a command file. Many @value{GDBN} commands that
17979 normally print messages to say what they are doing omit the messages
17980 when called from command files.
17982 @value{GDBN} also accepts command input from standard input. In this
17983 mode, normal output goes to standard output and error output goes to
17984 standard error. Errors in a command file supplied on standard input do
17985 not terminate execution of the command file---execution continues with
17989 gdb < cmds > log 2>&1
17992 (The syntax above will vary depending on the shell used.) This example
17993 will execute commands from the file @file{cmds}. All output and errors
17994 would be directed to @file{log}.
17996 Since commands stored on command files tend to be more general than
17997 commands typed interactively, they frequently need to deal with
17998 complicated situations, such as different or unexpected values of
17999 variables and symbols, changes in how the program being debugged is
18000 built, etc. @value{GDBN} provides a set of flow-control commands to
18001 deal with these complexities. Using these commands, you can write
18002 complex scripts that loop over data structures, execute commands
18003 conditionally, etc.
18010 This command allows to include in your script conditionally executed
18011 commands. The @code{if} command takes a single argument, which is an
18012 expression to evaluate. It is followed by a series of commands that
18013 are executed only if the expression is true (its value is nonzero).
18014 There can then optionally be an @code{else} line, followed by a series
18015 of commands that are only executed if the expression was false. The
18016 end of the list is marked by a line containing @code{end}.
18020 This command allows to write loops. Its syntax is similar to
18021 @code{if}: the command takes a single argument, which is an expression
18022 to evaluate, and must be followed by the commands to execute, one per
18023 line, terminated by an @code{end}. These commands are called the
18024 @dfn{body} of the loop. The commands in the body of @code{while} are
18025 executed repeatedly as long as the expression evaluates to true.
18029 This command exits the @code{while} loop in whose body it is included.
18030 Execution of the script continues after that @code{while}s @code{end}
18033 @kindex loop_continue
18034 @item loop_continue
18035 This command skips the execution of the rest of the body of commands
18036 in the @code{while} loop in whose body it is included. Execution
18037 branches to the beginning of the @code{while} loop, where it evaluates
18038 the controlling expression.
18040 @kindex end@r{ (if/else/while commands)}
18042 Terminate the block of commands that are the body of @code{if},
18043 @code{else}, or @code{while} flow-control commands.
18048 @subsection Commands for Controlled Output
18050 During the execution of a command file or a user-defined command, normal
18051 @value{GDBN} output is suppressed; the only output that appears is what is
18052 explicitly printed by the commands in the definition. This section
18053 describes three commands useful for generating exactly the output you
18058 @item echo @var{text}
18059 @c I do not consider backslash-space a standard C escape sequence
18060 @c because it is not in ANSI.
18061 Print @var{text}. Nonprinting characters can be included in
18062 @var{text} using C escape sequences, such as @samp{\n} to print a
18063 newline. @strong{No newline is printed unless you specify one.}
18064 In addition to the standard C escape sequences, a backslash followed
18065 by a space stands for a space. This is useful for displaying a
18066 string with spaces at the beginning or the end, since leading and
18067 trailing spaces are otherwise trimmed from all arguments.
18068 To print @samp{@w{ }and foo =@w{ }}, use the command
18069 @samp{echo \@w{ }and foo = \@w{ }}.
18071 A backslash at the end of @var{text} can be used, as in C, to continue
18072 the command onto subsequent lines. For example,
18075 echo This is some text\n\
18076 which is continued\n\
18077 onto several lines.\n
18080 produces the same output as
18083 echo This is some text\n
18084 echo which is continued\n
18085 echo onto several lines.\n
18089 @item output @var{expression}
18090 Print the value of @var{expression} and nothing but that value: no
18091 newlines, no @samp{$@var{nn} = }. The value is not entered in the
18092 value history either. @xref{Expressions, ,Expressions}, for more information
18095 @item output/@var{fmt} @var{expression}
18096 Print the value of @var{expression} in format @var{fmt}. You can use
18097 the same formats as for @code{print}. @xref{Output Formats,,Output
18098 Formats}, for more information.
18101 @item printf @var{template}, @var{expressions}@dots{}
18102 Print the values of one or more @var{expressions} under the control of
18103 the string @var{template}. To print several values, make
18104 @var{expressions} be a comma-separated list of individual expressions,
18105 which may be either numbers or pointers. Their values are printed as
18106 specified by @var{template}, exactly as a C program would do by
18107 executing the code below:
18110 printf (@var{template}, @var{expressions}@dots{});
18113 As in @code{C} @code{printf}, ordinary characters in @var{template}
18114 are printed verbatim, while @dfn{conversion specification} introduced
18115 by the @samp{%} character cause subsequent @var{expressions} to be
18116 evaluated, their values converted and formatted according to type and
18117 style information encoded in the conversion specifications, and then
18120 For example, you can print two values in hex like this:
18123 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
18126 @code{printf} supports all the standard @code{C} conversion
18127 specifications, including the flags and modifiers between the @samp{%}
18128 character and the conversion letter, with the following exceptions:
18132 The argument-ordering modifiers, such as @samp{2$}, are not supported.
18135 The modifier @samp{*} is not supported for specifying precision or
18139 The @samp{'} flag (for separation of digits into groups according to
18140 @code{LC_NUMERIC'}) is not supported.
18143 The type modifiers @samp{hh}, @samp{j}, @samp{t}, and @samp{z} are not
18147 The conversion letter @samp{n} (as in @samp{%n}) is not supported.
18150 The conversion letters @samp{a} and @samp{A} are not supported.
18154 Note that the @samp{ll} type modifier is supported only if the
18155 underlying @code{C} implementation used to build @value{GDBN} supports
18156 the @code{long long int} type, and the @samp{L} type modifier is
18157 supported only if @code{long double} type is available.
18159 As in @code{C}, @code{printf} supports simple backslash-escape
18160 sequences, such as @code{\n}, @samp{\t}, @samp{\\}, @samp{\"},
18161 @samp{\a}, and @samp{\f}, that consist of backslash followed by a
18162 single character. Octal and hexadecimal escape sequences are not
18165 Additionally, @code{printf} supports conversion specifications for DFP
18166 (@dfn{Decimal Floating Point}) types using the following length modifiers
18167 together with a floating point specifier.
18172 @samp{H} for printing @code{Decimal32} types.
18175 @samp{D} for printing @code{Decimal64} types.
18178 @samp{DD} for printing @code{Decimal128} types.
18181 If the underlying @code{C} implementation used to build @value{GDBN} has
18182 support for the three length modifiers for DFP types, other modifiers
18183 such as width and precision will also be available for @value{GDBN} to use.
18185 In case there is no such @code{C} support, no additional modifiers will be
18186 available and the value will be printed in the standard way.
18188 Here's an example of printing DFP types using the above conversion letters:
18190 printf "D32: %Hf - D64: %Df - D128: %DDf\n",1.2345df,1.2E10dd,1.2E1dl
18196 @section Scripting @value{GDBN} using Python
18197 @cindex python scripting
18198 @cindex scripting with python
18200 You can script @value{GDBN} using the @uref{http://www.python.org/,
18201 Python programming language}. This feature is available only if
18202 @value{GDBN} was configured using @option{--with-python}.
18205 * Python Commands:: Accessing Python from @value{GDBN}.
18206 * Python API:: Accessing @value{GDBN} from Python.
18209 @node Python Commands
18210 @subsection Python Commands
18211 @cindex python commands
18212 @cindex commands to access python
18214 @value{GDBN} provides one command for accessing the Python interpreter,
18215 and one related setting:
18219 @item python @r{[}@var{code}@r{]}
18220 The @code{python} command can be used to evaluate Python code.
18222 If given an argument, the @code{python} command will evaluate the
18223 argument as a Python command. For example:
18226 (@value{GDBP}) python print 23
18230 If you do not provide an argument to @code{python}, it will act as a
18231 multi-line command, like @code{define}. In this case, the Python
18232 script is made up of subsequent command lines, given after the
18233 @code{python} command. This command list is terminated using a line
18234 containing @code{end}. For example:
18237 (@value{GDBP}) python
18239 End with a line saying just "end".
18245 @kindex maint set python print-stack
18246 @item maint set python print-stack
18247 By default, @value{GDBN} will print a stack trace when an error occurs
18248 in a Python script. This can be controlled using @code{maint set
18249 python print-stack}: if @code{on}, the default, then Python stack
18250 printing is enabled; if @code{off}, then Python stack printing is
18255 @subsection Python API
18257 @cindex programming in python
18259 @cindex python stdout
18260 @cindex python pagination
18261 At startup, @value{GDBN} overrides Python's @code{sys.stdout} and
18262 @code{sys.stderr} to print using @value{GDBN}'s output-paging streams.
18263 A Python program which outputs to one of these streams may have its
18264 output interrupted by the user (@pxref{Screen Size}). In this
18265 situation, a Python @code{KeyboardInterrupt} exception is thrown.
18268 * Basic Python:: Basic Python Functions.
18269 * Exception Handling::
18270 * Values From Inferior::
18271 * Commands In Python:: Implementing new commands in Python.
18272 * Functions In Python:: Writing new convenience functions.
18273 * Frames In Python:: Acessing inferior stack frames from Python.
18277 @subsubsection Basic Python
18279 @cindex python functions
18280 @cindex python module
18282 @value{GDBN} introduces a new Python module, named @code{gdb}. All
18283 methods and classes added by @value{GDBN} are placed in this module.
18284 @value{GDBN} automatically @code{import}s the @code{gdb} module for
18285 use in all scripts evaluated by the @code{python} command.
18287 @findex gdb.execute
18288 @defun execute command [from_tty]
18289 Evaluate @var{command}, a string, as a @value{GDBN} CLI command.
18290 If a GDB exception happens while @var{command} runs, it is
18291 translated as described in @ref{Exception Handling,,Exception Handling}.
18292 If no exceptions occur, this function returns @code{None}.
18294 @var{from_tty} specifies whether @value{GDBN} ought to consider this
18295 command as having originated from the user invoking it interactively.
18296 It must be a boolean value. If omitted, it defaults to @code{False}.
18299 @findex gdb.get_parameter
18300 @defun get_parameter parameter
18301 Return the value of a @value{GDBN} parameter. @var{parameter} is a
18302 string naming the parameter to look up; @var{parameter} may contain
18303 spaces if the parameter has a multi-part name. For example,
18304 @samp{print object} is a valid parameter name.
18306 If the named parameter does not exist, this function throws a
18307 @code{RuntimeError}. Otherwise, the parameter's value is converted to
18308 a Python value of the appropriate type, and returned.
18311 @findex gdb.history
18312 @defun history number
18313 Return a value from @value{GDBN}'s value history (@pxref{Value
18314 History}). @var{number} indicates which history element to return.
18315 If @var{number} is negative, then @value{GDBN} will take its absolute value
18316 and count backward from the last element (i.e., the most recent element) to
18317 find the value to return. If @var{number} is zero, then @value{GDBN} will
18318 return the most recent element. If the element specified by @var{number}
18319 doesn't exist in the value history, a @code{RuntimeError} exception will be
18322 If no exception is raised, the return value is always an instance of
18323 @code{gdb.Value} (@pxref{Values From Inferior}).
18327 @defun write string
18328 Print a string to @value{GDBN}'s paginated standard output stream.
18329 Writing to @code{sys.stdout} or @code{sys.stderr} will automatically
18330 call this function.
18335 Flush @value{GDBN}'s paginated standard output stream. Flushing
18336 @code{sys.stdout} or @code{sys.stderr} will automatically call this
18340 @node Exception Handling
18341 @subsubsection Exception Handling
18342 @cindex python exceptions
18343 @cindex exceptions, python
18345 When executing the @code{python} command, Python exceptions
18346 uncaught within the Python code are translated to calls to
18347 @value{GDBN} error-reporting mechanism. If the command that called
18348 @code{python} does not handle the error, @value{GDBN} will
18349 terminate it and print an error message containing the Python
18350 exception name, the associated value, and the Python call stack
18351 backtrace at the point where the exception was raised. Example:
18354 (@value{GDBP}) python print foo
18355 Traceback (most recent call last):
18356 File "<string>", line 1, in <module>
18357 NameError: name 'foo' is not defined
18360 @value{GDBN} errors that happen in @value{GDBN} commands invoked by Python
18361 code are converted to Python @code{RuntimeError} exceptions. User
18362 interrupt (via @kbd{C-c} or by typing @kbd{q} at a pagination
18363 prompt) is translated to a Python @code{KeyboardInterrupt}
18364 exception. If you catch these exceptions in your Python code, your
18365 exception handler will see @code{RuntimeError} or
18366 @code{KeyboardInterrupt} as the exception type, the @value{GDBN} error
18367 message as its value, and the Python call stack backtrace at the
18368 Python statement closest to where the @value{GDBN} error occured as the
18371 @node Values From Inferior
18372 @subsubsection Values From Inferior
18373 @cindex values from inferior, with Python
18374 @cindex python, working with values from inferior
18376 @cindex @code{gdb.Value}
18377 @value{GDBN} provides values it obtains from the inferior program in
18378 an object of type @code{gdb.Value}. @value{GDBN} uses this object
18379 for its internal bookkeeping of the inferior's values, and for
18380 fetching values when necessary.
18382 Inferior values that are simple scalars can be used directly in
18383 Python expressions that are valid for the value's data type. Here's
18384 an example for an integer or floating-point value @code{some_val}:
18391 As result of this, @code{bar} will also be a @code{gdb.Value} object
18392 whose values are of the same type as those of @code{some_val}.
18394 Inferior values that are structures or instances of some class can
18395 be accessed using the Python @dfn{dictionary syntax}. For example, if
18396 @code{some_val} is a @code{gdb.Value} instance holding a structure, you
18397 can access its @code{foo} element with:
18400 bar = some_val['foo']
18403 Again, @code{bar} will also be a @code{gdb.Value} object.
18405 The following attributes are provided:
18408 @defmethod Value address
18409 If this object is addressable, this read-only attribute holds a
18410 @code{gdb.Value} object representing the address. Otherwise,
18411 this attribute holds @code{None}.
18414 @cindex optimized out value in Python
18415 @defmethod Value is_optimized_out
18416 This read-only boolean attribute is true if the compiler optimized out
18417 this value, thus it is not available for fetching from the inferior.
18421 The following methods are provided:
18424 @defmethod Value dereference
18425 For pointer data types, this method returns a new @code{gdb.Value} object
18426 whose contents is the object pointed to by the pointer. For example, if
18427 @code{foo} is a C pointer to an @code{int}, declared in your C program as
18434 then you can use the corresponding @code{gdb.Value} to access what
18435 @code{foo} points to like this:
18438 bar = foo.dereference ()
18441 The result @code{bar} will be a @code{gdb.Value} object holding the
18442 value pointed to by @code{foo}.
18445 @defmethod Value string @r{[}encoding@r{]} @r{[}errors@r{]}
18446 If this @code{gdb.Value} represents a string, then this method
18447 converts the contents to a Python string. Otherwise, this method will
18448 throw an exception.
18450 Strings are recognized in a language-specific way; whether a given
18451 @code{gdb.Value} represents a string is determined by the current
18454 For C-like languages, a value is a string if it is a pointer to or an
18455 array of characters or ints. The string is assumed to be terminated
18456 by a zero of the appropriate width.
18458 If the optional @var{encoding} argument is given, it must be a string
18459 naming the encoding of the string in the @code{gdb.Value}, such as
18460 @code{"ascii"}, @code{"iso-8859-6"} or @code{"utf-8"}. It accepts
18461 the same encodings as the corresponding argument to Python's
18462 @code{string.decode} method, and the Python codec machinery will be used
18463 to convert the string. If @var{encoding} is not given, or if
18464 @var{encoding} is the empty string, then either the @code{target-charset}
18465 (@pxref{Character Sets}) will be used, or a language-specific encoding
18466 will be used, if the current language is able to supply one.
18468 The optional @var{errors} argument is the same as the corresponding
18469 argument to Python's @code{string.decode} method.
18473 @node Commands In Python
18474 @subsubsection Commands In Python
18476 @cindex commands in python
18477 @cindex python commands
18478 You can implement new @value{GDBN} CLI commands in Python. A CLI
18479 command is implemented using an instance of the @code{gdb.Command}
18480 class, most commonly using a subclass.
18482 @defmethod Command __init__ name @var{command_class} @r{[}@var{completer_class}@r{]} @r{[}@var{prefix}@r{]}
18483 The object initializer for @code{Command} registers the new command
18484 with @value{GDBN}. This initializer is normally invoked from the
18485 subclass' own @code{__init__} method.
18487 @var{name} is the name of the command. If @var{name} consists of
18488 multiple words, then the initial words are looked for as prefix
18489 commands. In this case, if one of the prefix commands does not exist,
18490 an exception is raised.
18492 There is no support for multi-line commands.
18494 @var{command_class} should be one of the @samp{COMMAND_} constants
18495 defined below. This argument tells @value{GDBN} how to categorize the
18496 new command in the help system.
18498 @var{completer_class} is an optional argument. If given, it should be
18499 one of the @samp{COMPLETE_} constants defined below. This argument
18500 tells @value{GDBN} how to perform completion for this command. If not
18501 given, @value{GDBN} will attempt to complete using the object's
18502 @code{complete} method (see below); if no such method is found, an
18503 error will occur when completion is attempted.
18505 @var{prefix} is an optional argument. If @code{True}, then the new
18506 command is a prefix command; sub-commands of this command may be
18509 The help text for the new command is taken from the Python
18510 documentation string for the command's class, if there is one. If no
18511 documentation string is provided, the default value ``This command is
18512 not documented.'' is used.
18515 @cindex don't repeat Python command
18516 @defmethod Command dont_repeat
18517 By default, a @value{GDBN} command is repeated when the user enters a
18518 blank line at the command prompt. A command can suppress this
18519 behavior by invoking the @code{dont_repeat} method. This is similar
18520 to the user command @code{dont-repeat}, see @ref{Define, dont-repeat}.
18523 @defmethod Command invoke argument from_tty
18524 This method is called by @value{GDBN} when this command is invoked.
18526 @var{argument} is a string. It is the argument to the command, after
18527 leading and trailing whitespace has been stripped.
18529 @var{from_tty} is a boolean argument. When true, this means that the
18530 command was entered by the user at the terminal; when false it means
18531 that the command came from elsewhere.
18533 If this method throws an exception, it is turned into a @value{GDBN}
18534 @code{error} call. Otherwise, the return value is ignored.
18537 @cindex completion of Python commands
18538 @defmethod Command complete text word
18539 This method is called by @value{GDBN} when the user attempts
18540 completion on this command. All forms of completion are handled by
18541 this method, that is, the @key{TAB} and @key{M-?} key bindings
18542 (@pxref{Completion}), and the @code{complete} command (@pxref{Help,
18545 The arguments @var{text} and @var{word} are both strings. @var{text}
18546 holds the complete command line up to the cursor's location.
18547 @var{word} holds the last word of the command line; this is computed
18548 using a word-breaking heuristic.
18550 The @code{complete} method can return several values:
18553 If the return value is a sequence, the contents of the sequence are
18554 used as the completions. It is up to @code{complete} to ensure that the
18555 contents actually do complete the word. A zero-length sequence is
18556 allowed, it means that there were no completions available. Only
18557 string elements of the sequence are used; other elements in the
18558 sequence are ignored.
18561 If the return value is one of the @samp{COMPLETE_} constants defined
18562 below, then the corresponding @value{GDBN}-internal completion
18563 function is invoked, and its result is used.
18566 All other results are treated as though there were no available
18571 When a new command is registered, it must be declared as a member of
18572 some general class of commands. This is used to classify top-level
18573 commands in the on-line help system; note that prefix commands are not
18574 listed under their own category but rather that of their top-level
18575 command. The available classifications are represented by constants
18576 defined in the @code{gdb} module:
18579 @findex COMMAND_NONE
18580 @findex gdb.COMMAND_NONE
18582 The command does not belong to any particular class. A command in
18583 this category will not be displayed in any of the help categories.
18585 @findex COMMAND_RUNNING
18586 @findex gdb.COMMAND_RUNNING
18587 @item COMMAND_RUNNING
18588 The command is related to running the inferior. For example,
18589 @code{start}, @code{step}, and @code{continue} are in this category.
18590 Type @kbd{help running} at the @value{GDBN} prompt to see a list of
18591 commands in this category.
18593 @findex COMMAND_DATA
18594 @findex gdb.COMMAND_DATA
18596 The command is related to data or variables. For example,
18597 @code{call}, @code{find}, and @code{print} are in this category. Type
18598 @kbd{help data} at the @value{GDBN} prompt to see a list of commands
18601 @findex COMMAND_STACK
18602 @findex gdb.COMMAND_STACK
18603 @item COMMAND_STACK
18604 The command has to do with manipulation of the stack. For example,
18605 @code{backtrace}, @code{frame}, and @code{return} are in this
18606 category. Type @kbd{help stack} at the @value{GDBN} prompt to see a
18607 list of commands in this category.
18609 @findex COMMAND_FILES
18610 @findex gdb.COMMAND_FILES
18611 @item COMMAND_FILES
18612 This class is used for file-related commands. For example,
18613 @code{file}, @code{list} and @code{section} are in this category.
18614 Type @kbd{help files} at the @value{GDBN} prompt to see a list of
18615 commands in this category.
18617 @findex COMMAND_SUPPORT
18618 @findex gdb.COMMAND_SUPPORT
18619 @item COMMAND_SUPPORT
18620 This should be used for ``support facilities'', generally meaning
18621 things that are useful to the user when interacting with @value{GDBN},
18622 but not related to the state of the inferior. For example,
18623 @code{help}, @code{make}, and @code{shell} are in this category. Type
18624 @kbd{help support} at the @value{GDBN} prompt to see a list of
18625 commands in this category.
18627 @findex COMMAND_STATUS
18628 @findex gdb.COMMAND_STATUS
18629 @item COMMAND_STATUS
18630 The command is an @samp{info}-related command, that is, related to the
18631 state of @value{GDBN} itself. For example, @code{info}, @code{macro},
18632 and @code{show} are in this category. Type @kbd{help status} at the
18633 @value{GDBN} prompt to see a list of commands in this category.
18635 @findex COMMAND_BREAKPOINTS
18636 @findex gdb.COMMAND_BREAKPOINTS
18637 @item COMMAND_BREAKPOINTS
18638 The command has to do with breakpoints. For example, @code{break},
18639 @code{clear}, and @code{delete} are in this category. Type @kbd{help
18640 breakpoints} at the @value{GDBN} prompt to see a list of commands in
18643 @findex COMMAND_TRACEPOINTS
18644 @findex gdb.COMMAND_TRACEPOINTS
18645 @item COMMAND_TRACEPOINTS
18646 The command has to do with tracepoints. For example, @code{trace},
18647 @code{actions}, and @code{tfind} are in this category. Type
18648 @kbd{help tracepoints} at the @value{GDBN} prompt to see a list of
18649 commands in this category.
18651 @findex COMMAND_OBSCURE
18652 @findex gdb.COMMAND_OBSCURE
18653 @item COMMAND_OBSCURE
18654 The command is only used in unusual circumstances, or is not of
18655 general interest to users. For example, @code{checkpoint},
18656 @code{fork}, and @code{stop} are in this category. Type @kbd{help
18657 obscure} at the @value{GDBN} prompt to see a list of commands in this
18660 @findex COMMAND_MAINTENANCE
18661 @findex gdb.COMMAND_MAINTENANCE
18662 @item COMMAND_MAINTENANCE
18663 The command is only useful to @value{GDBN} maintainers. The
18664 @code{maintenance} and @code{flushregs} commands are in this category.
18665 Type @kbd{help internals} at the @value{GDBN} prompt to see a list of
18666 commands in this category.
18669 A new command can use a predefined completion function, either by
18670 specifying it via an argument at initialization, or by returning it
18671 from the @code{complete} method. These predefined completion
18672 constants are all defined in the @code{gdb} module:
18675 @findex COMPLETE_NONE
18676 @findex gdb.COMPLETE_NONE
18677 @item COMPLETE_NONE
18678 This constant means that no completion should be done.
18680 @findex COMPLETE_FILENAME
18681 @findex gdb.COMPLETE_FILENAME
18682 @item COMPLETE_FILENAME
18683 This constant means that filename completion should be performed.
18685 @findex COMPLETE_LOCATION
18686 @findex gdb.COMPLETE_LOCATION
18687 @item COMPLETE_LOCATION
18688 This constant means that location completion should be done.
18689 @xref{Specify Location}.
18691 @findex COMPLETE_COMMAND
18692 @findex gdb.COMPLETE_COMMAND
18693 @item COMPLETE_COMMAND
18694 This constant means that completion should examine @value{GDBN}
18697 @findex COMPLETE_SYMBOL
18698 @findex gdb.COMPLETE_SYMBOL
18699 @item COMPLETE_SYMBOL
18700 This constant means that completion should be done using symbol names
18704 The following code snippet shows how a trivial CLI command can be
18705 implemented in Python:
18708 class HelloWorld (gdb.Command):
18709 """Greet the whole world."""
18711 def __init__ (self):
18712 super (HelloWorld, self).__init__ ("hello-world", gdb.COMMAND_OBSCURE)
18714 def invoke (self, arg, from_tty):
18715 print "Hello, World!"
18720 The last line instantiates the class, and is necessary to trigger the
18721 registration of the command with @value{GDBN}. Depending on how the
18722 Python code is read into @value{GDBN}, you may need to import the
18723 @code{gdb} module explicitly.
18725 @node Functions In Python
18726 @subsubsection Writing new convenience functions
18728 @cindex writing convenience functions
18729 @cindex convenience functions in python
18730 @cindex python convenience functions
18731 @tindex gdb.Function
18733 You can implement new convenience functions (@pxref{Convenience Vars})
18734 in Python. A convenience function is an instance of a subclass of the
18735 class @code{gdb.Function}.
18737 @defmethod Function __init__ name
18738 The initializer for @code{Function} registers the new function with
18739 @value{GDBN}. The argument @var{name} is the name of the function,
18740 a string. The function will be visible to the user as a convenience
18741 variable of type @code{internal function}, whose name is the same as
18742 the given @var{name}.
18744 The documentation for the new function is taken from the documentation
18745 string for the new class.
18748 @defmethod Function invoke @var{*args}
18749 When a convenience function is evaluated, its arguments are converted
18750 to instances of @code{gdb.Value}, and then the function's
18751 @code{invoke} method is called. Note that @value{GDBN} does not
18752 predetermine the arity of convenience functions. Instead, all
18753 available arguments are passed to @code{invoke}, following the
18754 standard Python calling convention. In particular, a convenience
18755 function can have default values for parameters without ill effect.
18757 The return value of this method is used as its value in the enclosing
18758 expression. If an ordinary Python value is returned, it is converted
18759 to a @code{gdb.Value} following the usual rules.
18762 The following code snippet shows how a trivial convenience function can
18763 be implemented in Python:
18766 class Greet (gdb.Function):
18767 """Return string to greet someone.
18768 Takes a name as argument."""
18770 def __init__ (self):
18771 super (Greet, self).__init__ ("greet")
18773 def invoke (self, name):
18774 return "Hello, %s!" % name.string ()
18779 The last line instantiates the class, and is necessary to trigger the
18780 registration of the function with @value{GDBN}. Depending on how the
18781 Python code is read into @value{GDBN}, you may need to import the
18782 @code{gdb} module explicitly.
18784 @node Frames In Python
18785 @subsubsection Acessing inferior stack frames from Python.
18787 @cindex frames in python
18788 When the debugged program stops, @value{GDBN} is able to analyze its call
18789 stack (@pxref{Frames,,Stack frames}). The @code{gdb.Frame} class
18790 represents a frame in the stack. A @code{gdb.Frame} object is only valid
18791 while its corresponding frame exists in the inferior's stack. If you try
18792 to use an invalid frame object, @value{GDBN} will throw a @code{RuntimeError}
18795 Two @code{gdb.Frame} objects can be compared for equality with the @code{==}
18799 (@value{GDBP}) python print gdb.newest_frame() == gdb.selected_frame ()
18803 The following frame-related functions are available in the @code{gdb} module:
18805 @findex gdb.selected_frame
18806 @defun selected_frame
18807 Return the selected frame object. (@pxref{Selection,,Selecting a Frame}).
18810 @defun frame_stop_reason_string reason
18811 Return a string explaining the reason why @value{GDBN} stopped unwinding
18812 frames, as expressed by the given @var{reason} code (an integer, see the
18813 @code{unwind_stop_reason} method further down in this section).
18816 A @code{gdb.Frame} object has the following methods:
18819 @defmethod Frame is_valid
18820 Returns true if the @code{gdb.Frame} object is valid, false if not.
18821 A frame object can become invalid if the frame it refers to doesn't
18822 exist anymore in the inferior. All @code{gdb.Frame} methods will throw
18823 an exception if it is invalid at the time the method is called.
18826 @defmethod Frame name
18827 Returns the function name of the frame, or @code{None} if it can't be
18831 @defmethod Frame type
18832 Returns the type of the frame. The value can be one of
18833 @code{gdb.NORMAL_FRAME}, @code{gdb.DUMMY_FRAME}, @code{gdb.SIGTRAMP_FRAME}
18834 or @code{gdb.SENTINEL_FRAME}.
18837 @defmethod Frame unwind_stop_reason
18838 Return an integer representing the reason why it's not possible to find
18839 more frames toward the outermost frame. Use
18840 @code{gdb.frame_stop_reason_string} to convert the value returned by this
18841 function to a string.
18844 @defmethod Frame pc
18845 Returns the frame's resume address.
18848 @defmethod Frame older
18849 Return the frame that called this frame.
18852 @defmethod Frame newer
18853 Return the frame called by this frame.
18856 @defmethod Frame read_var variable
18857 Return the value of the given variable in this frame. @var{variable} must
18863 @chapter Command Interpreters
18864 @cindex command interpreters
18866 @value{GDBN} supports multiple command interpreters, and some command
18867 infrastructure to allow users or user interface writers to switch
18868 between interpreters or run commands in other interpreters.
18870 @value{GDBN} currently supports two command interpreters, the console
18871 interpreter (sometimes called the command-line interpreter or @sc{cli})
18872 and the machine interface interpreter (or @sc{gdb/mi}). This manual
18873 describes both of these interfaces in great detail.
18875 By default, @value{GDBN} will start with the console interpreter.
18876 However, the user may choose to start @value{GDBN} with another
18877 interpreter by specifying the @option{-i} or @option{--interpreter}
18878 startup options. Defined interpreters include:
18882 @cindex console interpreter
18883 The traditional console or command-line interpreter. This is the most often
18884 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
18885 @value{GDBN} will use this interpreter.
18888 @cindex mi interpreter
18889 The newest @sc{gdb/mi} interface (currently @code{mi2}). Used primarily
18890 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
18891 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
18895 @cindex mi2 interpreter
18896 The current @sc{gdb/mi} interface.
18899 @cindex mi1 interpreter
18900 The @sc{gdb/mi} interface included in @value{GDBN} 5.1, 5.2, and 5.3.
18904 @cindex invoke another interpreter
18905 The interpreter being used by @value{GDBN} may not be dynamically
18906 switched at runtime. Although possible, this could lead to a very
18907 precarious situation. Consider an IDE using @sc{gdb/mi}. If a user
18908 enters the command "interpreter-set console" in a console view,
18909 @value{GDBN} would switch to using the console interpreter, rendering
18910 the IDE inoperable!
18912 @kindex interpreter-exec
18913 Although you may only choose a single interpreter at startup, you may execute
18914 commands in any interpreter from the current interpreter using the appropriate
18915 command. If you are running the console interpreter, simply use the
18916 @code{interpreter-exec} command:
18919 interpreter-exec mi "-data-list-register-names"
18922 @sc{gdb/mi} has a similar command, although it is only available in versions of
18923 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
18926 @chapter @value{GDBN} Text User Interface
18928 @cindex Text User Interface
18931 * TUI Overview:: TUI overview
18932 * TUI Keys:: TUI key bindings
18933 * TUI Single Key Mode:: TUI single key mode
18934 * TUI Commands:: TUI-specific commands
18935 * TUI Configuration:: TUI configuration variables
18938 The @value{GDBN} Text User Interface (TUI) is a terminal
18939 interface which uses the @code{curses} library to show the source
18940 file, the assembly output, the program registers and @value{GDBN}
18941 commands in separate text windows. The TUI mode is supported only
18942 on platforms where a suitable version of the @code{curses} library
18945 @pindex @value{GDBTUI}
18946 The TUI mode is enabled by default when you invoke @value{GDBN} as
18947 either @samp{@value{GDBTUI}} or @samp{@value{GDBP} -tui}.
18948 You can also switch in and out of TUI mode while @value{GDBN} runs by
18949 using various TUI commands and key bindings, such as @kbd{C-x C-a}.
18950 @xref{TUI Keys, ,TUI Key Bindings}.
18953 @section TUI Overview
18955 In TUI mode, @value{GDBN} can display several text windows:
18959 This window is the @value{GDBN} command window with the @value{GDBN}
18960 prompt and the @value{GDBN} output. The @value{GDBN} input is still
18961 managed using readline.
18964 The source window shows the source file of the program. The current
18965 line and active breakpoints are displayed in this window.
18968 The assembly window shows the disassembly output of the program.
18971 This window shows the processor registers. Registers are highlighted
18972 when their values change.
18975 The source and assembly windows show the current program position
18976 by highlighting the current line and marking it with a @samp{>} marker.
18977 Breakpoints are indicated with two markers. The first marker
18978 indicates the breakpoint type:
18982 Breakpoint which was hit at least once.
18985 Breakpoint which was never hit.
18988 Hardware breakpoint which was hit at least once.
18991 Hardware breakpoint which was never hit.
18994 The second marker indicates whether the breakpoint is enabled or not:
18998 Breakpoint is enabled.
19001 Breakpoint is disabled.
19004 The source, assembly and register windows are updated when the current
19005 thread changes, when the frame changes, or when the program counter
19008 These windows are not all visible at the same time. The command
19009 window is always visible. The others can be arranged in several
19020 source and assembly,
19023 source and registers, or
19026 assembly and registers.
19029 A status line above the command window shows the following information:
19033 Indicates the current @value{GDBN} target.
19034 (@pxref{Targets, ,Specifying a Debugging Target}).
19037 Gives the current process or thread number.
19038 When no process is being debugged, this field is set to @code{No process}.
19041 Gives the current function name for the selected frame.
19042 The name is demangled if demangling is turned on (@pxref{Print Settings}).
19043 When there is no symbol corresponding to the current program counter,
19044 the string @code{??} is displayed.
19047 Indicates the current line number for the selected frame.
19048 When the current line number is not known, the string @code{??} is displayed.
19051 Indicates the current program counter address.
19055 @section TUI Key Bindings
19056 @cindex TUI key bindings
19058 The TUI installs several key bindings in the readline keymaps
19059 (@pxref{Command Line Editing}). The following key bindings
19060 are installed for both TUI mode and the @value{GDBN} standard mode.
19069 Enter or leave the TUI mode. When leaving the TUI mode,
19070 the curses window management stops and @value{GDBN} operates using
19071 its standard mode, writing on the terminal directly. When reentering
19072 the TUI mode, control is given back to the curses windows.
19073 The screen is then refreshed.
19077 Use a TUI layout with only one window. The layout will
19078 either be @samp{source} or @samp{assembly}. When the TUI mode
19079 is not active, it will switch to the TUI mode.
19081 Think of this key binding as the Emacs @kbd{C-x 1} binding.
19085 Use a TUI layout with at least two windows. When the current
19086 layout already has two windows, the next layout with two windows is used.
19087 When a new layout is chosen, one window will always be common to the
19088 previous layout and the new one.
19090 Think of it as the Emacs @kbd{C-x 2} binding.
19094 Change the active window. The TUI associates several key bindings
19095 (like scrolling and arrow keys) with the active window. This command
19096 gives the focus to the next TUI window.
19098 Think of it as the Emacs @kbd{C-x o} binding.
19102 Switch in and out of the TUI SingleKey mode that binds single
19103 keys to @value{GDBN} commands (@pxref{TUI Single Key Mode}).
19106 The following key bindings only work in the TUI mode:
19111 Scroll the active window one page up.
19115 Scroll the active window one page down.
19119 Scroll the active window one line up.
19123 Scroll the active window one line down.
19127 Scroll the active window one column left.
19131 Scroll the active window one column right.
19135 Refresh the screen.
19138 Because the arrow keys scroll the active window in the TUI mode, they
19139 are not available for their normal use by readline unless the command
19140 window has the focus. When another window is active, you must use
19141 other readline key bindings such as @kbd{C-p}, @kbd{C-n}, @kbd{C-b}
19142 and @kbd{C-f} to control the command window.
19144 @node TUI Single Key Mode
19145 @section TUI Single Key Mode
19146 @cindex TUI single key mode
19148 The TUI also provides a @dfn{SingleKey} mode, which binds several
19149 frequently used @value{GDBN} commands to single keys. Type @kbd{C-x s} to
19150 switch into this mode, where the following key bindings are used:
19153 @kindex c @r{(SingleKey TUI key)}
19157 @kindex d @r{(SingleKey TUI key)}
19161 @kindex f @r{(SingleKey TUI key)}
19165 @kindex n @r{(SingleKey TUI key)}
19169 @kindex q @r{(SingleKey TUI key)}
19171 exit the SingleKey mode.
19173 @kindex r @r{(SingleKey TUI key)}
19177 @kindex s @r{(SingleKey TUI key)}
19181 @kindex u @r{(SingleKey TUI key)}
19185 @kindex v @r{(SingleKey TUI key)}
19189 @kindex w @r{(SingleKey TUI key)}
19194 Other keys temporarily switch to the @value{GDBN} command prompt.
19195 The key that was pressed is inserted in the editing buffer so that
19196 it is possible to type most @value{GDBN} commands without interaction
19197 with the TUI SingleKey mode. Once the command is entered the TUI
19198 SingleKey mode is restored. The only way to permanently leave
19199 this mode is by typing @kbd{q} or @kbd{C-x s}.
19203 @section TUI-specific Commands
19204 @cindex TUI commands
19206 The TUI has specific commands to control the text windows.
19207 These commands are always available, even when @value{GDBN} is not in
19208 the TUI mode. When @value{GDBN} is in the standard mode, most
19209 of these commands will automatically switch to the TUI mode.
19214 List and give the size of all displayed windows.
19218 Display the next layout.
19221 Display the previous layout.
19224 Display the source window only.
19227 Display the assembly window only.
19230 Display the source and assembly window.
19233 Display the register window together with the source or assembly window.
19237 Make the next window active for scrolling.
19240 Make the previous window active for scrolling.
19243 Make the source window active for scrolling.
19246 Make the assembly window active for scrolling.
19249 Make the register window active for scrolling.
19252 Make the command window active for scrolling.
19256 Refresh the screen. This is similar to typing @kbd{C-L}.
19258 @item tui reg float
19260 Show the floating point registers in the register window.
19262 @item tui reg general
19263 Show the general registers in the register window.
19266 Show the next register group. The list of register groups as well as
19267 their order is target specific. The predefined register groups are the
19268 following: @code{general}, @code{float}, @code{system}, @code{vector},
19269 @code{all}, @code{save}, @code{restore}.
19271 @item tui reg system
19272 Show the system registers in the register window.
19276 Update the source window and the current execution point.
19278 @item winheight @var{name} +@var{count}
19279 @itemx winheight @var{name} -@var{count}
19281 Change the height of the window @var{name} by @var{count}
19282 lines. Positive counts increase the height, while negative counts
19285 @item tabset @var{nchars}
19287 Set the width of tab stops to be @var{nchars} characters.
19290 @node TUI Configuration
19291 @section TUI Configuration Variables
19292 @cindex TUI configuration variables
19294 Several configuration variables control the appearance of TUI windows.
19297 @item set tui border-kind @var{kind}
19298 @kindex set tui border-kind
19299 Select the border appearance for the source, assembly and register windows.
19300 The possible values are the following:
19303 Use a space character to draw the border.
19306 Use @sc{ascii} characters @samp{+}, @samp{-} and @samp{|} to draw the border.
19309 Use the Alternate Character Set to draw the border. The border is
19310 drawn using character line graphics if the terminal supports them.
19313 @item set tui border-mode @var{mode}
19314 @kindex set tui border-mode
19315 @itemx set tui active-border-mode @var{mode}
19316 @kindex set tui active-border-mode
19317 Select the display attributes for the borders of the inactive windows
19318 or the active window. The @var{mode} can be one of the following:
19321 Use normal attributes to display the border.
19327 Use reverse video mode.
19330 Use half bright mode.
19332 @item half-standout
19333 Use half bright and standout mode.
19336 Use extra bright or bold mode.
19338 @item bold-standout
19339 Use extra bright or bold and standout mode.
19344 @chapter Using @value{GDBN} under @sc{gnu} Emacs
19347 @cindex @sc{gnu} Emacs
19348 A special interface allows you to use @sc{gnu} Emacs to view (and
19349 edit) the source files for the program you are debugging with
19352 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
19353 executable file you want to debug as an argument. This command starts
19354 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
19355 created Emacs buffer.
19356 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
19358 Running @value{GDBN} under Emacs can be just like running @value{GDBN} normally except for two
19363 All ``terminal'' input and output goes through an Emacs buffer, called
19366 This applies both to @value{GDBN} commands and their output, and to the input
19367 and output done by the program you are debugging.
19369 This is useful because it means that you can copy the text of previous
19370 commands and input them again; you can even use parts of the output
19373 All the facilities of Emacs' Shell mode are available for interacting
19374 with your program. In particular, you can send signals the usual
19375 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
19379 @value{GDBN} displays source code through Emacs.
19381 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
19382 source file for that frame and puts an arrow (@samp{=>}) at the
19383 left margin of the current line. Emacs uses a separate buffer for
19384 source display, and splits the screen to show both your @value{GDBN} session
19387 Explicit @value{GDBN} @code{list} or search commands still produce output as
19388 usual, but you probably have no reason to use them from Emacs.
19391 We call this @dfn{text command mode}. Emacs 22.1, and later, also uses
19392 a graphical mode, enabled by default, which provides further buffers
19393 that can control the execution and describe the state of your program.
19394 @xref{GDB Graphical Interface,,, Emacs, The @sc{gnu} Emacs Manual}.
19396 If you specify an absolute file name when prompted for the @kbd{M-x
19397 gdb} argument, then Emacs sets your current working directory to where
19398 your program resides. If you only specify the file name, then Emacs
19399 sets your current working directory to to the directory associated
19400 with the previous buffer. In this case, @value{GDBN} may find your
19401 program by searching your environment's @code{PATH} variable, but on
19402 some operating systems it might not find the source. So, although the
19403 @value{GDBN} input and output session proceeds normally, the auxiliary
19404 buffer does not display the current source and line of execution.
19406 The initial working directory of @value{GDBN} is printed on the top
19407 line of the GUD buffer and this serves as a default for the commands
19408 that specify files for @value{GDBN} to operate on. @xref{Files,
19409 ,Commands to Specify Files}.
19411 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
19412 need to call @value{GDBN} by a different name (for example, if you
19413 keep several configurations around, with different names) you can
19414 customize the Emacs variable @code{gud-gdb-command-name} to run the
19417 In the GUD buffer, you can use these special Emacs commands in
19418 addition to the standard Shell mode commands:
19422 Describe the features of Emacs' GUD Mode.
19425 Execute to another source line, like the @value{GDBN} @code{step} command; also
19426 update the display window to show the current file and location.
19429 Execute to next source line in this function, skipping all function
19430 calls, like the @value{GDBN} @code{next} command. Then update the display window
19431 to show the current file and location.
19434 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
19435 display window accordingly.
19438 Execute until exit from the selected stack frame, like the @value{GDBN}
19439 @code{finish} command.
19442 Continue execution of your program, like the @value{GDBN} @code{continue}
19446 Go up the number of frames indicated by the numeric argument
19447 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
19448 like the @value{GDBN} @code{up} command.
19451 Go down the number of frames indicated by the numeric argument, like the
19452 @value{GDBN} @code{down} command.
19455 In any source file, the Emacs command @kbd{C-x @key{SPC}} (@code{gud-break})
19456 tells @value{GDBN} to set a breakpoint on the source line point is on.
19458 In text command mode, if you type @kbd{M-x speedbar}, Emacs displays a
19459 separate frame which shows a backtrace when the GUD buffer is current.
19460 Move point to any frame in the stack and type @key{RET} to make it
19461 become the current frame and display the associated source in the
19462 source buffer. Alternatively, click @kbd{Mouse-2} to make the
19463 selected frame become the current one. In graphical mode, the
19464 speedbar displays watch expressions.
19466 If you accidentally delete the source-display buffer, an easy way to get
19467 it back is to type the command @code{f} in the @value{GDBN} buffer, to
19468 request a frame display; when you run under Emacs, this recreates
19469 the source buffer if necessary to show you the context of the current
19472 The source files displayed in Emacs are in ordinary Emacs buffers
19473 which are visiting the source files in the usual way. You can edit
19474 the files with these buffers if you wish; but keep in mind that @value{GDBN}
19475 communicates with Emacs in terms of line numbers. If you add or
19476 delete lines from the text, the line numbers that @value{GDBN} knows cease
19477 to correspond properly with the code.
19479 A more detailed description of Emacs' interaction with @value{GDBN} is
19480 given in the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu}
19483 @c The following dropped because Epoch is nonstandard. Reactivate
19484 @c if/when v19 does something similar. ---doc@cygnus.com 19dec1990
19486 @kindex Emacs Epoch environment
19490 Version 18 of @sc{gnu} Emacs has a built-in window system
19491 called the @code{epoch}
19492 environment. Users of this environment can use a new command,
19493 @code{inspect} which performs identically to @code{print} except that
19494 each value is printed in its own window.
19499 @chapter The @sc{gdb/mi} Interface
19501 @unnumberedsec Function and Purpose
19503 @cindex @sc{gdb/mi}, its purpose
19504 @sc{gdb/mi} is a line based machine oriented text interface to
19505 @value{GDBN} and is activated by specifying using the
19506 @option{--interpreter} command line option (@pxref{Mode Options}). It
19507 is specifically intended to support the development of systems which
19508 use the debugger as just one small component of a larger system.
19510 This chapter is a specification of the @sc{gdb/mi} interface. It is written
19511 in the form of a reference manual.
19513 Note that @sc{gdb/mi} is still under construction, so some of the
19514 features described below are incomplete and subject to change
19515 (@pxref{GDB/MI Development and Front Ends, , @sc{gdb/mi} Development and Front Ends}).
19517 @unnumberedsec Notation and Terminology
19519 @cindex notational conventions, for @sc{gdb/mi}
19520 This chapter uses the following notation:
19524 @code{|} separates two alternatives.
19527 @code{[ @var{something} ]} indicates that @var{something} is optional:
19528 it may or may not be given.
19531 @code{( @var{group} )*} means that @var{group} inside the parentheses
19532 may repeat zero or more times.
19535 @code{( @var{group} )+} means that @var{group} inside the parentheses
19536 may repeat one or more times.
19539 @code{"@var{string}"} means a literal @var{string}.
19543 @heading Dependencies
19547 * GDB/MI General Design::
19548 * GDB/MI Command Syntax::
19549 * GDB/MI Compatibility with CLI::
19550 * GDB/MI Development and Front Ends::
19551 * GDB/MI Output Records::
19552 * GDB/MI Simple Examples::
19553 * GDB/MI Command Description Format::
19554 * GDB/MI Breakpoint Commands::
19555 * GDB/MI Program Context::
19556 * GDB/MI Thread Commands::
19557 * GDB/MI Program Execution::
19558 * GDB/MI Stack Manipulation::
19559 * GDB/MI Variable Objects::
19560 * GDB/MI Data Manipulation::
19561 * GDB/MI Tracepoint Commands::
19562 * GDB/MI Symbol Query::
19563 * GDB/MI File Commands::
19565 * GDB/MI Kod Commands::
19566 * GDB/MI Memory Overlay Commands::
19567 * GDB/MI Signal Handling Commands::
19569 * GDB/MI Target Manipulation::
19570 * GDB/MI File Transfer Commands::
19571 * GDB/MI Miscellaneous Commands::
19574 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19575 @node GDB/MI General Design
19576 @section @sc{gdb/mi} General Design
19577 @cindex GDB/MI General Design
19579 Interaction of a @sc{GDB/MI} frontend with @value{GDBN} involves three
19580 parts---commands sent to @value{GDBN}, responses to those commands
19581 and notifications. Each command results in exactly one response,
19582 indicating either successful completion of the command, or an error.
19583 For the commands that do not resume the target, the response contains the
19584 requested information. For the commands that resume the target, the
19585 response only indicates whether the target was successfully resumed.
19586 Notifications is the mechanism for reporting changes in the state of the
19587 target, or in @value{GDBN} state, that cannot conveniently be associated with
19588 a command and reported as part of that command response.
19590 The important examples of notifications are:
19594 Exec notifications. These are used to report changes in
19595 target state---when a target is resumed, or stopped. It would not
19596 be feasible to include this information in response of resuming
19597 commands, because one resume commands can result in multiple events in
19598 different threads. Also, quite some time may pass before any event
19599 happens in the target, while a frontend needs to know whether the resuming
19600 command itself was successfully executed.
19603 Console output, and status notifications. Console output
19604 notifications are used to report output of CLI commands, as well as
19605 diagnostics for other commands. Status notifications are used to
19606 report the progress of a long-running operation. Naturally, including
19607 this information in command response would mean no output is produced
19608 until the command is finished, which is undesirable.
19611 General notifications. Commands may have various side effects on
19612 the @value{GDBN} or target state beyond their official purpose. For example,
19613 a command may change the selected thread. Although such changes can
19614 be included in command response, using notification allows for more
19615 orthogonal frontend design.
19619 There's no guarantee that whenever an MI command reports an error,
19620 @value{GDBN} or the target are in any specific state, and especially,
19621 the state is not reverted to the state before the MI command was
19622 processed. Therefore, whenever an MI command results in an error,
19623 we recommend that the frontend refreshes all the information shown in
19624 the user interface.
19626 @subsection Context management
19628 In most cases when @value{GDBN} accesses the target, this access is
19629 done in context of a specific thread and frame (@pxref{Frames}).
19630 Often, even when accessing global data, the target requires that a thread
19631 be specified. The CLI interface maintains the selected thread and frame,
19632 and supplies them to target on each command. This is convenient,
19633 because a command line user would not want to specify that information
19634 explicitly on each command, and because user interacts with
19635 @value{GDBN} via a single terminal, so no confusion is possible as
19636 to what thread and frame are the current ones.
19638 In the case of MI, the concept of selected thread and frame is less
19639 useful. First, a frontend can easily remember this information
19640 itself. Second, a graphical frontend can have more than one window,
19641 each one used for debugging a different thread, and the frontend might
19642 want to access additional threads for internal purposes. This
19643 increases the risk that by relying on implicitly selected thread, the
19644 frontend may be operating on a wrong one. Therefore, each MI command
19645 should explicitly specify which thread and frame to operate on. To
19646 make it possible, each MI command accepts the @samp{--thread} and
19647 @samp{--frame} options, the value to each is @value{GDBN} identifier
19648 for thread and frame to operate on.
19650 Usually, each top-level window in a frontend allows the user to select
19651 a thread and a frame, and remembers the user selection for further
19652 operations. However, in some cases @value{GDBN} may suggest that the
19653 current thread be changed. For example, when stopping on a breakpoint
19654 it is reasonable to switch to the thread where breakpoint is hit. For
19655 another example, if the user issues the CLI @samp{thread} command via
19656 the frontend, it is desirable to change the frontend's selected thread to the
19657 one specified by user. @value{GDBN} communicates the suggestion to
19658 change current thread using the @samp{=thread-selected} notification.
19659 No such notification is available for the selected frame at the moment.
19661 Note that historically, MI shares the selected thread with CLI, so
19662 frontends used the @code{-thread-select} to execute commands in the
19663 right context. However, getting this to work right is cumbersome. The
19664 simplest way is for frontend to emit @code{-thread-select} command
19665 before every command. This doubles the number of commands that need
19666 to be sent. The alternative approach is to suppress @code{-thread-select}
19667 if the selected thread in @value{GDBN} is supposed to be identical to the
19668 thread the frontend wants to operate on. However, getting this
19669 optimization right can be tricky. In particular, if the frontend
19670 sends several commands to @value{GDBN}, and one of the commands changes the
19671 selected thread, then the behaviour of subsequent commands will
19672 change. So, a frontend should either wait for response from such
19673 problematic commands, or explicitly add @code{-thread-select} for
19674 all subsequent commands. No frontend is known to do this exactly
19675 right, so it is suggested to just always pass the @samp{--thread} and
19676 @samp{--frame} options.
19678 @subsection Asynchronous command execution and non-stop mode
19680 On some targets, @value{GDBN} is capable of processing MI commands
19681 even while the target is running. This is called @dfn{asynchronous
19682 command execution} (@pxref{Background Execution}). The frontend may
19683 specify a preferrence for asynchronous execution using the
19684 @code{-gdb-set target-async 1} command, which should be emitted before
19685 either running the executable or attaching to the target. After the
19686 frontend has started the executable or attached to the target, it can
19687 find if asynchronous execution is enabled using the
19688 @code{-list-target-features} command.
19690 Even if @value{GDBN} can accept a command while target is running,
19691 many commands that access the target do not work when the target is
19692 running. Therefore, asynchronous command execution is most useful
19693 when combined with non-stop mode (@pxref{Non-Stop Mode}). Then,
19694 it is possible to examine the state of one thread, while other threads
19697 When a given thread is running, MI commands that try to access the
19698 target in the context of that thread may not work, or may work only on
19699 some targets. In particular, commands that try to operate on thread's
19700 stack will not work, on any target. Commands that read memory, or
19701 modify breakpoints, may work or not work, depending on the target. Note
19702 that even commands that operate on global state, such as @code{print},
19703 @code{set}, and breakpoint commands, still access the target in the
19704 context of a specific thread, so frontend should try to find a
19705 stopped thread and perform the operation on that thread (using the
19706 @samp{--thread} option).
19708 Which commands will work in the context of a running thread is
19709 highly target dependent. However, the two commands
19710 @code{-exec-interrupt}, to stop a thread, and @code{-thread-info},
19711 to find the state of a thread, will always work.
19713 @subsection Thread groups
19714 @value{GDBN} may be used to debug several processes at the same time.
19715 On some platfroms, @value{GDBN} may support debugging of several
19716 hardware systems, each one having several cores with several different
19717 processes running on each core. This section describes the MI
19718 mechanism to support such debugging scenarios.
19720 The key observation is that regardless of the structure of the
19721 target, MI can have a global list of threads, because most commands that
19722 accept the @samp{--thread} option do not need to know what process that
19723 thread belongs to. Therefore, it is not necessary to introduce
19724 neither additional @samp{--process} option, nor an notion of the
19725 current process in the MI interface. The only strictly new feature
19726 that is required is the ability to find how the threads are grouped
19729 To allow the user to discover such grouping, and to support arbitrary
19730 hierarchy of machines/cores/processes, MI introduces the concept of a
19731 @dfn{thread group}. Thread group is a collection of threads and other
19732 thread groups. A thread group always has a string identifier, a type,
19733 and may have additional attributes specific to the type. A new
19734 command, @code{-list-thread-groups}, returns the list of top-level
19735 thread groups, which correspond to processes that @value{GDBN} is
19736 debugging at the moment. By passing an identifier of a thread group
19737 to the @code{-list-thread-groups} command, it is possible to obtain
19738 the members of specific thread group.
19740 To allow the user to easily discover processes, and other objects, he
19741 wishes to debug, a concept of @dfn{available thread group} is
19742 introduced. Available thread group is an thread group that
19743 @value{GDBN} is not debugging, but that can be attached to, using the
19744 @code{-target-attach} command. The list of available top-level thread
19745 groups can be obtained using @samp{-list-thread-groups --available}.
19746 In general, the content of a thread group may be only retrieved only
19747 after attaching to that thread group.
19749 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19750 @node GDB/MI Command Syntax
19751 @section @sc{gdb/mi} Command Syntax
19754 * GDB/MI Input Syntax::
19755 * GDB/MI Output Syntax::
19758 @node GDB/MI Input Syntax
19759 @subsection @sc{gdb/mi} Input Syntax
19761 @cindex input syntax for @sc{gdb/mi}
19762 @cindex @sc{gdb/mi}, input syntax
19764 @item @var{command} @expansion{}
19765 @code{@var{cli-command} | @var{mi-command}}
19767 @item @var{cli-command} @expansion{}
19768 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
19769 @var{cli-command} is any existing @value{GDBN} CLI command.
19771 @item @var{mi-command} @expansion{}
19772 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
19773 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
19775 @item @var{token} @expansion{}
19776 "any sequence of digits"
19778 @item @var{option} @expansion{}
19779 @code{"-" @var{parameter} [ " " @var{parameter} ]}
19781 @item @var{parameter} @expansion{}
19782 @code{@var{non-blank-sequence} | @var{c-string}}
19784 @item @var{operation} @expansion{}
19785 @emph{any of the operations described in this chapter}
19787 @item @var{non-blank-sequence} @expansion{}
19788 @emph{anything, provided it doesn't contain special characters such as
19789 "-", @var{nl}, """ and of course " "}
19791 @item @var{c-string} @expansion{}
19792 @code{""" @var{seven-bit-iso-c-string-content} """}
19794 @item @var{nl} @expansion{}
19803 The CLI commands are still handled by the @sc{mi} interpreter; their
19804 output is described below.
19807 The @code{@var{token}}, when present, is passed back when the command
19811 Some @sc{mi} commands accept optional arguments as part of the parameter
19812 list. Each option is identified by a leading @samp{-} (dash) and may be
19813 followed by an optional argument parameter. Options occur first in the
19814 parameter list and can be delimited from normal parameters using
19815 @samp{--} (this is useful when some parameters begin with a dash).
19822 We want easy access to the existing CLI syntax (for debugging).
19825 We want it to be easy to spot a @sc{mi} operation.
19828 @node GDB/MI Output Syntax
19829 @subsection @sc{gdb/mi} Output Syntax
19831 @cindex output syntax of @sc{gdb/mi}
19832 @cindex @sc{gdb/mi}, output syntax
19833 The output from @sc{gdb/mi} consists of zero or more out-of-band records
19834 followed, optionally, by a single result record. This result record
19835 is for the most recent command. The sequence of output records is
19836 terminated by @samp{(gdb)}.
19838 If an input command was prefixed with a @code{@var{token}} then the
19839 corresponding output for that command will also be prefixed by that same
19843 @item @var{output} @expansion{}
19844 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(gdb)" @var{nl}}
19846 @item @var{result-record} @expansion{}
19847 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
19849 @item @var{out-of-band-record} @expansion{}
19850 @code{@var{async-record} | @var{stream-record}}
19852 @item @var{async-record} @expansion{}
19853 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
19855 @item @var{exec-async-output} @expansion{}
19856 @code{[ @var{token} ] "*" @var{async-output}}
19858 @item @var{status-async-output} @expansion{}
19859 @code{[ @var{token} ] "+" @var{async-output}}
19861 @item @var{notify-async-output} @expansion{}
19862 @code{[ @var{token} ] "=" @var{async-output}}
19864 @item @var{async-output} @expansion{}
19865 @code{@var{async-class} ( "," @var{result} )* @var{nl}}
19867 @item @var{result-class} @expansion{}
19868 @code{"done" | "running" | "connected" | "error" | "exit"}
19870 @item @var{async-class} @expansion{}
19871 @code{"stopped" | @var{others}} (where @var{others} will be added
19872 depending on the needs---this is still in development).
19874 @item @var{result} @expansion{}
19875 @code{ @var{variable} "=" @var{value}}
19877 @item @var{variable} @expansion{}
19878 @code{ @var{string} }
19880 @item @var{value} @expansion{}
19881 @code{ @var{const} | @var{tuple} | @var{list} }
19883 @item @var{const} @expansion{}
19884 @code{@var{c-string}}
19886 @item @var{tuple} @expansion{}
19887 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
19889 @item @var{list} @expansion{}
19890 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
19891 @var{result} ( "," @var{result} )* "]" }
19893 @item @var{stream-record} @expansion{}
19894 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
19896 @item @var{console-stream-output} @expansion{}
19897 @code{"~" @var{c-string}}
19899 @item @var{target-stream-output} @expansion{}
19900 @code{"@@" @var{c-string}}
19902 @item @var{log-stream-output} @expansion{}
19903 @code{"&" @var{c-string}}
19905 @item @var{nl} @expansion{}
19908 @item @var{token} @expansion{}
19909 @emph{any sequence of digits}.
19917 All output sequences end in a single line containing a period.
19920 The @code{@var{token}} is from the corresponding request. Note that
19921 for all async output, while the token is allowed by the grammar and
19922 may be output by future versions of @value{GDBN} for select async
19923 output messages, it is generally omitted. Frontends should treat
19924 all async output as reporting general changes in the state of the
19925 target and there should be no need to associate async output to any
19929 @cindex status output in @sc{gdb/mi}
19930 @var{status-async-output} contains on-going status information about the
19931 progress of a slow operation. It can be discarded. All status output is
19932 prefixed by @samp{+}.
19935 @cindex async output in @sc{gdb/mi}
19936 @var{exec-async-output} contains asynchronous state change on the target
19937 (stopped, started, disappeared). All async output is prefixed by
19941 @cindex notify output in @sc{gdb/mi}
19942 @var{notify-async-output} contains supplementary information that the
19943 client should handle (e.g., a new breakpoint information). All notify
19944 output is prefixed by @samp{=}.
19947 @cindex console output in @sc{gdb/mi}
19948 @var{console-stream-output} is output that should be displayed as is in the
19949 console. It is the textual response to a CLI command. All the console
19950 output is prefixed by @samp{~}.
19953 @cindex target output in @sc{gdb/mi}
19954 @var{target-stream-output} is the output produced by the target program.
19955 All the target output is prefixed by @samp{@@}.
19958 @cindex log output in @sc{gdb/mi}
19959 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
19960 instance messages that should be displayed as part of an error log. All
19961 the log output is prefixed by @samp{&}.
19964 @cindex list output in @sc{gdb/mi}
19965 New @sc{gdb/mi} commands should only output @var{lists} containing
19971 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
19972 details about the various output records.
19974 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19975 @node GDB/MI Compatibility with CLI
19976 @section @sc{gdb/mi} Compatibility with CLI
19978 @cindex compatibility, @sc{gdb/mi} and CLI
19979 @cindex @sc{gdb/mi}, compatibility with CLI
19981 For the developers convenience CLI commands can be entered directly,
19982 but there may be some unexpected behaviour. For example, commands
19983 that query the user will behave as if the user replied yes, breakpoint
19984 command lists are not executed and some CLI commands, such as
19985 @code{if}, @code{when} and @code{define}, prompt for further input with
19986 @samp{>}, which is not valid MI output.
19988 This feature may be removed at some stage in the future and it is
19989 recommended that front ends use the @code{-interpreter-exec} command
19990 (@pxref{-interpreter-exec}).
19992 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19993 @node GDB/MI Development and Front Ends
19994 @section @sc{gdb/mi} Development and Front Ends
19995 @cindex @sc{gdb/mi} development
19997 The application which takes the MI output and presents the state of the
19998 program being debugged to the user is called a @dfn{front end}.
20000 Although @sc{gdb/mi} is still incomplete, it is currently being used
20001 by a variety of front ends to @value{GDBN}. This makes it difficult
20002 to introduce new functionality without breaking existing usage. This
20003 section tries to minimize the problems by describing how the protocol
20006 Some changes in MI need not break a carefully designed front end, and
20007 for these the MI version will remain unchanged. The following is a
20008 list of changes that may occur within one level, so front ends should
20009 parse MI output in a way that can handle them:
20013 New MI commands may be added.
20016 New fields may be added to the output of any MI command.
20019 The range of values for fields with specified values, e.g.,
20020 @code{in_scope} (@pxref{-var-update}) may be extended.
20022 @c The format of field's content e.g type prefix, may change so parse it
20023 @c at your own risk. Yes, in general?
20025 @c The order of fields may change? Shouldn't really matter but it might
20026 @c resolve inconsistencies.
20029 If the changes are likely to break front ends, the MI version level
20030 will be increased by one. This will allow the front end to parse the
20031 output according to the MI version. Apart from mi0, new versions of
20032 @value{GDBN} will not support old versions of MI and it will be the
20033 responsibility of the front end to work with the new one.
20035 @c Starting with mi3, add a new command -mi-version that prints the MI
20038 The best way to avoid unexpected changes in MI that might break your front
20039 end is to make your project known to @value{GDBN} developers and
20040 follow development on @email{gdb@@sourceware.org} and
20041 @email{gdb-patches@@sourceware.org}.
20042 @cindex mailing lists
20044 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20045 @node GDB/MI Output Records
20046 @section @sc{gdb/mi} Output Records
20049 * GDB/MI Result Records::
20050 * GDB/MI Stream Records::
20051 * GDB/MI Async Records::
20052 * GDB/MI Frame Information::
20055 @node GDB/MI Result Records
20056 @subsection @sc{gdb/mi} Result Records
20058 @cindex result records in @sc{gdb/mi}
20059 @cindex @sc{gdb/mi}, result records
20060 In addition to a number of out-of-band notifications, the response to a
20061 @sc{gdb/mi} command includes one of the following result indications:
20065 @item "^done" [ "," @var{results} ]
20066 The synchronous operation was successful, @code{@var{results}} are the return
20071 @c Is this one correct? Should it be an out-of-band notification?
20072 The asynchronous operation was successfully started. The target is
20077 @value{GDBN} has connected to a remote target.
20079 @item "^error" "," @var{c-string}
20081 The operation failed. The @code{@var{c-string}} contains the corresponding
20086 @value{GDBN} has terminated.
20090 @node GDB/MI Stream Records
20091 @subsection @sc{gdb/mi} Stream Records
20093 @cindex @sc{gdb/mi}, stream records
20094 @cindex stream records in @sc{gdb/mi}
20095 @value{GDBN} internally maintains a number of output streams: the console, the
20096 target, and the log. The output intended for each of these streams is
20097 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
20099 Each stream record begins with a unique @dfn{prefix character} which
20100 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
20101 Syntax}). In addition to the prefix, each stream record contains a
20102 @code{@var{string-output}}. This is either raw text (with an implicit new
20103 line) or a quoted C string (which does not contain an implicit newline).
20106 @item "~" @var{string-output}
20107 The console output stream contains text that should be displayed in the
20108 CLI console window. It contains the textual responses to CLI commands.
20110 @item "@@" @var{string-output}
20111 The target output stream contains any textual output from the running
20112 target. This is only present when GDB's event loop is truly
20113 asynchronous, which is currently only the case for remote targets.
20115 @item "&" @var{string-output}
20116 The log stream contains debugging messages being produced by @value{GDBN}'s
20120 @node GDB/MI Async Records
20121 @subsection @sc{gdb/mi} Async Records
20123 @cindex async records in @sc{gdb/mi}
20124 @cindex @sc{gdb/mi}, async records
20125 @dfn{Async} records are used to notify the @sc{gdb/mi} client of
20126 additional changes that have occurred. Those changes can either be a
20127 consequence of @sc{gdb/mi} commands (e.g., a breakpoint modified) or a result of
20128 target activity (e.g., target stopped).
20130 The following is the list of possible async records:
20134 @item *running,thread-id="@var{thread}"
20135 The target is now running. The @var{thread} field tells which
20136 specific thread is now running, and can be @samp{all} if all threads
20137 are running. The frontend should assume that no interaction with a
20138 running thread is possible after this notification is produced.
20139 The frontend should not assume that this notification is output
20140 only once for any command. @value{GDBN} may emit this notification
20141 several times, either for different threads, because it cannot resume
20142 all threads together, or even for a single thread, if the thread must
20143 be stepped though some code before letting it run freely.
20145 @item *stopped,reason="@var{reason}",thread-id="@var{id}",stopped-threads="@var{stopped}"
20146 The target has stopped. The @var{reason} field can have one of the
20150 @item breakpoint-hit
20151 A breakpoint was reached.
20152 @item watchpoint-trigger
20153 A watchpoint was triggered.
20154 @item read-watchpoint-trigger
20155 A read watchpoint was triggered.
20156 @item access-watchpoint-trigger
20157 An access watchpoint was triggered.
20158 @item function-finished
20159 An -exec-finish or similar CLI command was accomplished.
20160 @item location-reached
20161 An -exec-until or similar CLI command was accomplished.
20162 @item watchpoint-scope
20163 A watchpoint has gone out of scope.
20164 @item end-stepping-range
20165 An -exec-next, -exec-next-instruction, -exec-step, -exec-step-instruction or
20166 similar CLI command was accomplished.
20167 @item exited-signalled
20168 The inferior exited because of a signal.
20170 The inferior exited.
20171 @item exited-normally
20172 The inferior exited normally.
20173 @item signal-received
20174 A signal was received by the inferior.
20177 The @var{id} field identifies the thread that directly caused the stop
20178 -- for example by hitting a breakpoint. Depending on whether all-stop
20179 mode is in effect (@pxref{All-Stop Mode}), @value{GDBN} may either
20180 stop all threads, or only the thread that directly triggered the stop.
20181 If all threads are stopped, the @var{stopped} field will have the
20182 value of @code{"all"}. Otherwise, the value of the @var{stopped}
20183 field will be a list of thread identifiers. Presently, this list will
20184 always include a single thread, but frontend should be prepared to see
20185 several threads in the list.
20187 @item =thread-group-created,id="@var{id}"
20188 @itemx =thread-group-exited,id="@var{id}"
20189 A thread thread group either was attached to, or has exited/detached
20190 from. The @var{id} field contains the @value{GDBN} identifier of the
20193 @item =thread-created,id="@var{id}",group-id="@var{gid}"
20194 @itemx =thread-exited,id="@var{id}",group-id="@var{gid}"
20195 A thread either was created, or has exited. The @var{id} field
20196 contains the @value{GDBN} identifier of the thread. The @var{gid}
20197 field identifies the thread group this thread belongs to.
20199 @item =thread-selected,id="@var{id}"
20200 Informs that the selected thread was changed as result of the last
20201 command. This notification is not emitted as result of @code{-thread-select}
20202 command but is emitted whenever an MI command that is not documented
20203 to change the selected thread actually changes it. In particular,
20204 invoking, directly or indirectly (via user-defined command), the CLI
20205 @code{thread} command, will generate this notification.
20207 We suggest that in response to this notification, front ends
20208 highlight the selected thread and cause subsequent commands to apply to
20211 @item =library-loaded,...
20212 Reports that a new library file was loaded by the program. This
20213 notification has 4 fields---@var{id}, @var{target-name},
20214 @var{host-name}, and @var{symbols-loaded}. The @var{id} field is an
20215 opaque identifier of the library. For remote debugging case,
20216 @var{target-name} and @var{host-name} fields give the name of the
20217 library file on the target, and on the host respectively. For native
20218 debugging, both those fields have the same value. The
20219 @var{symbols-loaded} field reports if the debug symbols for this
20220 library are loaded.
20222 @item =library-unloaded,...
20223 Reports that a library was unloaded by the program. This notification
20224 has 3 fields---@var{id}, @var{target-name} and @var{host-name} with
20225 the same meaning as for the @code{=library-loaded} notification
20229 @node GDB/MI Frame Information
20230 @subsection @sc{gdb/mi} Frame Information
20232 Response from many MI commands includes an information about stack
20233 frame. This information is a tuple that may have the following
20238 The level of the stack frame. The innermost frame has the level of
20239 zero. This field is always present.
20242 The name of the function corresponding to the frame. This field may
20243 be absent if @value{GDBN} is unable to determine the function name.
20246 The code address for the frame. This field is always present.
20249 The name of the source files that correspond to the frame's code
20250 address. This field may be absent.
20253 The source line corresponding to the frames' code address. This field
20257 The name of the binary file (either executable or shared library) the
20258 corresponds to the frame's code address. This field may be absent.
20263 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20264 @node GDB/MI Simple Examples
20265 @section Simple Examples of @sc{gdb/mi} Interaction
20266 @cindex @sc{gdb/mi}, simple examples
20268 This subsection presents several simple examples of interaction using
20269 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
20270 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
20271 the output received from @sc{gdb/mi}.
20273 Note the line breaks shown in the examples are here only for
20274 readability, they don't appear in the real output.
20276 @subheading Setting a Breakpoint
20278 Setting a breakpoint generates synchronous output which contains detailed
20279 information of the breakpoint.
20282 -> -break-insert main
20283 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
20284 enabled="y",addr="0x08048564",func="main",file="myprog.c",
20285 fullname="/home/nickrob/myprog.c",line="68",times="0"@}
20289 @subheading Program Execution
20291 Program execution generates asynchronous records and MI gives the
20292 reason that execution stopped.
20298 <- *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
20299 frame=@{addr="0x08048564",func="main",
20300 args=[@{name="argc",value="1"@},@{name="argv",value="0xbfc4d4d4"@}],
20301 file="myprog.c",fullname="/home/nickrob/myprog.c",line="68"@}
20306 <- *stopped,reason="exited-normally"
20310 @subheading Quitting @value{GDBN}
20312 Quitting @value{GDBN} just prints the result class @samp{^exit}.
20320 @subheading A Bad Command
20322 Here's what happens if you pass a non-existent command:
20326 <- ^error,msg="Undefined MI command: rubbish"
20331 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20332 @node GDB/MI Command Description Format
20333 @section @sc{gdb/mi} Command Description Format
20335 The remaining sections describe blocks of commands. Each block of
20336 commands is laid out in a fashion similar to this section.
20338 @subheading Motivation
20340 The motivation for this collection of commands.
20342 @subheading Introduction
20344 A brief introduction to this collection of commands as a whole.
20346 @subheading Commands
20348 For each command in the block, the following is described:
20350 @subsubheading Synopsis
20353 -command @var{args}@dots{}
20356 @subsubheading Result
20358 @subsubheading @value{GDBN} Command
20360 The corresponding @value{GDBN} CLI command(s), if any.
20362 @subsubheading Example
20364 Example(s) formatted for readability. Some of the described commands have
20365 not been implemented yet and these are labeled N.A.@: (not available).
20368 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20369 @node GDB/MI Breakpoint Commands
20370 @section @sc{gdb/mi} Breakpoint Commands
20372 @cindex breakpoint commands for @sc{gdb/mi}
20373 @cindex @sc{gdb/mi}, breakpoint commands
20374 This section documents @sc{gdb/mi} commands for manipulating
20377 @subheading The @code{-break-after} Command
20378 @findex -break-after
20380 @subsubheading Synopsis
20383 -break-after @var{number} @var{count}
20386 The breakpoint number @var{number} is not in effect until it has been
20387 hit @var{count} times. To see how this is reflected in the output of
20388 the @samp{-break-list} command, see the description of the
20389 @samp{-break-list} command below.
20391 @subsubheading @value{GDBN} Command
20393 The corresponding @value{GDBN} command is @samp{ignore}.
20395 @subsubheading Example
20400 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
20401 enabled="y",addr="0x000100d0",func="main",file="hello.c",
20402 fullname="/home/foo/hello.c",line="5",times="0"@}
20409 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
20410 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
20411 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
20412 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
20413 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
20414 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
20415 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
20416 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
20417 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
20418 line="5",times="0",ignore="3"@}]@}
20423 @subheading The @code{-break-catch} Command
20424 @findex -break-catch
20426 @subheading The @code{-break-commands} Command
20427 @findex -break-commands
20431 @subheading The @code{-break-condition} Command
20432 @findex -break-condition
20434 @subsubheading Synopsis
20437 -break-condition @var{number} @var{expr}
20440 Breakpoint @var{number} will stop the program only if the condition in
20441 @var{expr} is true. The condition becomes part of the
20442 @samp{-break-list} output (see the description of the @samp{-break-list}
20445 @subsubheading @value{GDBN} Command
20447 The corresponding @value{GDBN} command is @samp{condition}.
20449 @subsubheading Example
20453 -break-condition 1 1
20457 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
20458 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
20459 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
20460 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
20461 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
20462 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
20463 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
20464 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
20465 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
20466 line="5",cond="1",times="0",ignore="3"@}]@}
20470 @subheading The @code{-break-delete} Command
20471 @findex -break-delete
20473 @subsubheading Synopsis
20476 -break-delete ( @var{breakpoint} )+
20479 Delete the breakpoint(s) whose number(s) are specified in the argument
20480 list. This is obviously reflected in the breakpoint list.
20482 @subsubheading @value{GDBN} Command
20484 The corresponding @value{GDBN} command is @samp{delete}.
20486 @subsubheading Example
20494 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
20495 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
20496 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
20497 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
20498 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
20499 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
20500 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
20505 @subheading The @code{-break-disable} Command
20506 @findex -break-disable
20508 @subsubheading Synopsis
20511 -break-disable ( @var{breakpoint} )+
20514 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
20515 break list is now set to @samp{n} for the named @var{breakpoint}(s).
20517 @subsubheading @value{GDBN} Command
20519 The corresponding @value{GDBN} command is @samp{disable}.
20521 @subsubheading Example
20529 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
20530 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
20531 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
20532 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
20533 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
20534 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
20535 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
20536 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
20537 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
20538 line="5",times="0"@}]@}
20542 @subheading The @code{-break-enable} Command
20543 @findex -break-enable
20545 @subsubheading Synopsis
20548 -break-enable ( @var{breakpoint} )+
20551 Enable (previously disabled) @var{breakpoint}(s).
20553 @subsubheading @value{GDBN} Command
20555 The corresponding @value{GDBN} command is @samp{enable}.
20557 @subsubheading Example
20565 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
20566 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
20567 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
20568 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
20569 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
20570 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
20571 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
20572 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
20573 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
20574 line="5",times="0"@}]@}
20578 @subheading The @code{-break-info} Command
20579 @findex -break-info
20581 @subsubheading Synopsis
20584 -break-info @var{breakpoint}
20588 Get information about a single breakpoint.
20590 @subsubheading @value{GDBN} Command
20592 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
20594 @subsubheading Example
20597 @subheading The @code{-break-insert} Command
20598 @findex -break-insert
20600 @subsubheading Synopsis
20603 -break-insert [ -t ] [ -h ] [ -f ] [ -d ]
20604 [ -c @var{condition} ] [ -i @var{ignore-count} ]
20605 [ -p @var{thread} ] [ @var{location} ]
20609 If specified, @var{location}, can be one of:
20616 @item filename:linenum
20617 @item filename:function
20621 The possible optional parameters of this command are:
20625 Insert a temporary breakpoint.
20627 Insert a hardware breakpoint.
20628 @item -c @var{condition}
20629 Make the breakpoint conditional on @var{condition}.
20630 @item -i @var{ignore-count}
20631 Initialize the @var{ignore-count}.
20633 If @var{location} cannot be parsed (for example if it
20634 refers to unknown files or functions), create a pending
20635 breakpoint. Without this flag, @value{GDBN} will report
20636 an error, and won't create a breakpoint, if @var{location}
20639 Create a disabled breakpoint.
20642 @subsubheading Result
20644 The result is in the form:
20647 ^done,bkpt=@{number="@var{number}",type="@var{type}",disp="del"|"keep",
20648 enabled="y"|"n",addr="@var{hex}",func="@var{funcname}",file="@var{filename}",
20649 fullname="@var{full_filename}",line="@var{lineno}",[thread="@var{threadno},]
20650 times="@var{times}"@}
20654 where @var{number} is the @value{GDBN} number for this breakpoint,
20655 @var{funcname} is the name of the function where the breakpoint was
20656 inserted, @var{filename} is the name of the source file which contains
20657 this function, @var{lineno} is the source line number within that file
20658 and @var{times} the number of times that the breakpoint has been hit
20659 (always 0 for -break-insert but may be greater for -break-info or -break-list
20660 which use the same output).
20662 Note: this format is open to change.
20663 @c An out-of-band breakpoint instead of part of the result?
20665 @subsubheading @value{GDBN} Command
20667 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
20668 @samp{hbreak}, @samp{thbreak}, and @samp{rbreak}.
20670 @subsubheading Example
20675 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",
20676 fullname="/home/foo/recursive2.c,line="4",times="0"@}
20678 -break-insert -t foo
20679 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",
20680 fullname="/home/foo/recursive2.c,line="11",times="0"@}
20683 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
20684 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
20685 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
20686 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
20687 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
20688 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
20689 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
20690 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
20691 addr="0x0001072c", func="main",file="recursive2.c",
20692 fullname="/home/foo/recursive2.c,"line="4",times="0"@},
20693 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
20694 addr="0x00010774",func="foo",file="recursive2.c",
20695 fullname="/home/foo/recursive2.c",line="11",times="0"@}]@}
20697 -break-insert -r foo.*
20698 ~int foo(int, int);
20699 ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c,
20700 "fullname="/home/foo/recursive2.c",line="11",times="0"@}
20704 @subheading The @code{-break-list} Command
20705 @findex -break-list
20707 @subsubheading Synopsis
20713 Displays the list of inserted breakpoints, showing the following fields:
20717 number of the breakpoint
20719 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
20721 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
20724 is the breakpoint enabled or no: @samp{y} or @samp{n}
20726 memory location at which the breakpoint is set
20728 logical location of the breakpoint, expressed by function name, file
20731 number of times the breakpoint has been hit
20734 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
20735 @code{body} field is an empty list.
20737 @subsubheading @value{GDBN} Command
20739 The corresponding @value{GDBN} command is @samp{info break}.
20741 @subsubheading Example
20746 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
20747 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
20748 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
20749 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
20750 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
20751 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
20752 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
20753 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
20754 addr="0x000100d0",func="main",file="hello.c",line="5",times="0"@},
20755 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
20756 addr="0x00010114",func="foo",file="hello.c",fullname="/home/foo/hello.c",
20757 line="13",times="0"@}]@}
20761 Here's an example of the result when there are no breakpoints:
20766 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
20767 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
20768 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
20769 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
20770 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
20771 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
20772 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
20777 @subheading The @code{-break-watch} Command
20778 @findex -break-watch
20780 @subsubheading Synopsis
20783 -break-watch [ -a | -r ]
20786 Create a watchpoint. With the @samp{-a} option it will create an
20787 @dfn{access} watchpoint, i.e., a watchpoint that triggers either on a
20788 read from or on a write to the memory location. With the @samp{-r}
20789 option, the watchpoint created is a @dfn{read} watchpoint, i.e., it will
20790 trigger only when the memory location is accessed for reading. Without
20791 either of the options, the watchpoint created is a regular watchpoint,
20792 i.e., it will trigger when the memory location is accessed for writing.
20793 @xref{Set Watchpoints, , Setting Watchpoints}.
20795 Note that @samp{-break-list} will report a single list of watchpoints and
20796 breakpoints inserted.
20798 @subsubheading @value{GDBN} Command
20800 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
20803 @subsubheading Example
20805 Setting a watchpoint on a variable in the @code{main} function:
20810 ^done,wpt=@{number="2",exp="x"@}
20815 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
20816 value=@{old="-268439212",new="55"@},
20817 frame=@{func="main",args=[],file="recursive2.c",
20818 fullname="/home/foo/bar/recursive2.c",line="5"@}
20822 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
20823 the program execution twice: first for the variable changing value, then
20824 for the watchpoint going out of scope.
20829 ^done,wpt=@{number="5",exp="C"@}
20834 *stopped,reason="watchpoint-trigger",
20835 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
20836 frame=@{func="callee4",args=[],
20837 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
20838 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
20843 *stopped,reason="watchpoint-scope",wpnum="5",
20844 frame=@{func="callee3",args=[@{name="strarg",
20845 value="0x11940 \"A string argument.\""@}],
20846 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
20847 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
20851 Listing breakpoints and watchpoints, at different points in the program
20852 execution. Note that once the watchpoint goes out of scope, it is
20858 ^done,wpt=@{number="2",exp="C"@}
20861 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
20862 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
20863 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
20864 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
20865 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
20866 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
20867 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
20868 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
20869 addr="0x00010734",func="callee4",
20870 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
20871 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c"line="8",times="1"@},
20872 bkpt=@{number="2",type="watchpoint",disp="keep",
20873 enabled="y",addr="",what="C",times="0"@}]@}
20878 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
20879 value=@{old="-276895068",new="3"@},
20880 frame=@{func="callee4",args=[],
20881 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
20882 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
20885 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
20886 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
20887 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
20888 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
20889 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
20890 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
20891 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
20892 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
20893 addr="0x00010734",func="callee4",
20894 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
20895 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",times="1"@},
20896 bkpt=@{number="2",type="watchpoint",disp="keep",
20897 enabled="y",addr="",what="C",times="-5"@}]@}
20901 ^done,reason="watchpoint-scope",wpnum="2",
20902 frame=@{func="callee3",args=[@{name="strarg",
20903 value="0x11940 \"A string argument.\""@}],
20904 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
20905 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
20908 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
20909 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
20910 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
20911 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
20912 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
20913 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
20914 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
20915 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
20916 addr="0x00010734",func="callee4",
20917 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
20918 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
20923 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20924 @node GDB/MI Program Context
20925 @section @sc{gdb/mi} Program Context
20927 @subheading The @code{-exec-arguments} Command
20928 @findex -exec-arguments
20931 @subsubheading Synopsis
20934 -exec-arguments @var{args}
20937 Set the inferior program arguments, to be used in the next
20940 @subsubheading @value{GDBN} Command
20942 The corresponding @value{GDBN} command is @samp{set args}.
20944 @subsubheading Example
20948 -exec-arguments -v word
20954 @subheading The @code{-exec-show-arguments} Command
20955 @findex -exec-show-arguments
20957 @subsubheading Synopsis
20960 -exec-show-arguments
20963 Print the arguments of the program.
20965 @subsubheading @value{GDBN} Command
20967 The corresponding @value{GDBN} command is @samp{show args}.
20969 @subsubheading Example
20973 @subheading The @code{-environment-cd} Command
20974 @findex -environment-cd
20976 @subsubheading Synopsis
20979 -environment-cd @var{pathdir}
20982 Set @value{GDBN}'s working directory.
20984 @subsubheading @value{GDBN} Command
20986 The corresponding @value{GDBN} command is @samp{cd}.
20988 @subsubheading Example
20992 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
20998 @subheading The @code{-environment-directory} Command
20999 @findex -environment-directory
21001 @subsubheading Synopsis
21004 -environment-directory [ -r ] [ @var{pathdir} ]+
21007 Add directories @var{pathdir} to beginning of search path for source files.
21008 If the @samp{-r} option is used, the search path is reset to the default
21009 search path. If directories @var{pathdir} are supplied in addition to the
21010 @samp{-r} option, the search path is first reset and then addition
21012 Multiple directories may be specified, separated by blanks. Specifying
21013 multiple directories in a single command
21014 results in the directories added to the beginning of the
21015 search path in the same order they were presented in the command.
21016 If blanks are needed as
21017 part of a directory name, double-quotes should be used around
21018 the name. In the command output, the path will show up separated
21019 by the system directory-separator character. The directory-separator
21020 character must not be used
21021 in any directory name.
21022 If no directories are specified, the current search path is displayed.
21024 @subsubheading @value{GDBN} Command
21026 The corresponding @value{GDBN} command is @samp{dir}.
21028 @subsubheading Example
21032 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
21033 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
21035 -environment-directory ""
21036 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
21038 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
21039 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
21041 -environment-directory -r
21042 ^done,source-path="$cdir:$cwd"
21047 @subheading The @code{-environment-path} Command
21048 @findex -environment-path
21050 @subsubheading Synopsis
21053 -environment-path [ -r ] [ @var{pathdir} ]+
21056 Add directories @var{pathdir} to beginning of search path for object files.
21057 If the @samp{-r} option is used, the search path is reset to the original
21058 search path that existed at gdb start-up. If directories @var{pathdir} are
21059 supplied in addition to the
21060 @samp{-r} option, the search path is first reset and then addition
21062 Multiple directories may be specified, separated by blanks. Specifying
21063 multiple directories in a single command
21064 results in the directories added to the beginning of the
21065 search path in the same order they were presented in the command.
21066 If blanks are needed as
21067 part of a directory name, double-quotes should be used around
21068 the name. In the command output, the path will show up separated
21069 by the system directory-separator character. The directory-separator
21070 character must not be used
21071 in any directory name.
21072 If no directories are specified, the current path is displayed.
21075 @subsubheading @value{GDBN} Command
21077 The corresponding @value{GDBN} command is @samp{path}.
21079 @subsubheading Example
21084 ^done,path="/usr/bin"
21086 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
21087 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
21089 -environment-path -r /usr/local/bin
21090 ^done,path="/usr/local/bin:/usr/bin"
21095 @subheading The @code{-environment-pwd} Command
21096 @findex -environment-pwd
21098 @subsubheading Synopsis
21104 Show the current working directory.
21106 @subsubheading @value{GDBN} Command
21108 The corresponding @value{GDBN} command is @samp{pwd}.
21110 @subsubheading Example
21115 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
21119 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
21120 @node GDB/MI Thread Commands
21121 @section @sc{gdb/mi} Thread Commands
21124 @subheading The @code{-thread-info} Command
21125 @findex -thread-info
21127 @subsubheading Synopsis
21130 -thread-info [ @var{thread-id} ]
21133 Reports information about either a specific thread, if
21134 the @var{thread-id} parameter is present, or about all
21135 threads. When printing information about all threads,
21136 also reports the current thread.
21138 @subsubheading @value{GDBN} Command
21140 The @samp{info thread} command prints the same information
21143 @subsubheading Example
21148 @{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
21149 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},state="running"@},
21150 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
21151 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
21152 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},state="running"@}],
21153 current-thread-id="1"
21157 The @samp{state} field may have the following values:
21161 The thread is stopped. Frame information is available for stopped
21165 The thread is running. There's no frame information for running
21170 @subheading The @code{-thread-list-ids} Command
21171 @findex -thread-list-ids
21173 @subsubheading Synopsis
21179 Produces a list of the currently known @value{GDBN} thread ids. At the
21180 end of the list it also prints the total number of such threads.
21182 This command is retained for historical reasons, the
21183 @code{-thread-info} command should be used instead.
21185 @subsubheading @value{GDBN} Command
21187 Part of @samp{info threads} supplies the same information.
21189 @subsubheading Example
21194 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
21195 current-thread-id="1",number-of-threads="3"
21200 @subheading The @code{-thread-select} Command
21201 @findex -thread-select
21203 @subsubheading Synopsis
21206 -thread-select @var{threadnum}
21209 Make @var{threadnum} the current thread. It prints the number of the new
21210 current thread, and the topmost frame for that thread.
21212 This command is deprecated in favor of explicitly using the
21213 @samp{--thread} option to each command.
21215 @subsubheading @value{GDBN} Command
21217 The corresponding @value{GDBN} command is @samp{thread}.
21219 @subsubheading Example
21226 *stopped,reason="end-stepping-range",thread-id="2",line="187",
21227 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
21231 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
21232 number-of-threads="3"
21235 ^done,new-thread-id="3",
21236 frame=@{level="0",func="vprintf",
21237 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
21238 @{name="arg",value="0x2"@}],file="vprintf.c",line="31"@}
21242 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
21243 @node GDB/MI Program Execution
21244 @section @sc{gdb/mi} Program Execution
21246 These are the asynchronous commands which generate the out-of-band
21247 record @samp{*stopped}. Currently @value{GDBN} only really executes
21248 asynchronously with remote targets and this interaction is mimicked in
21251 @subheading The @code{-exec-continue} Command
21252 @findex -exec-continue
21254 @subsubheading Synopsis
21257 -exec-continue [--all|--thread-group N]
21260 Resumes the execution of the inferior program until a breakpoint is
21261 encountered, or until the inferior exits. In all-stop mode
21262 (@pxref{All-Stop Mode}), may resume only one thread, or all threads,
21263 depending on the value of the @samp{scheduler-locking} variable. In
21264 non-stop mode (@pxref{Non-Stop Mode}), if the @samp{--all} is not
21265 specified, only the thread specified with the @samp{--thread} option
21266 (or current thread, if no @samp{--thread} is provided) is resumed. If
21267 @samp{--all} is specified, all threads will be resumed. The
21268 @samp{--all} option is ignored in all-stop mode. If the
21269 @samp{--thread-group} options is specified, then all threads in that
21270 thread group are resumed.
21272 @subsubheading @value{GDBN} Command
21274 The corresponding @value{GDBN} corresponding is @samp{continue}.
21276 @subsubheading Example
21283 *stopped,reason="breakpoint-hit",disp="keep",bkptno="2",frame=@{
21284 func="foo",args=[],file="hello.c",fullname="/home/foo/bar/hello.c",
21290 @subheading The @code{-exec-finish} Command
21291 @findex -exec-finish
21293 @subsubheading Synopsis
21299 Resumes the execution of the inferior program until the current
21300 function is exited. Displays the results returned by the function.
21302 @subsubheading @value{GDBN} Command
21304 The corresponding @value{GDBN} command is @samp{finish}.
21306 @subsubheading Example
21308 Function returning @code{void}.
21315 *stopped,reason="function-finished",frame=@{func="main",args=[],
21316 file="hello.c",fullname="/home/foo/bar/hello.c",line="7"@}
21320 Function returning other than @code{void}. The name of the internal
21321 @value{GDBN} variable storing the result is printed, together with the
21328 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
21329 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
21330 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
21331 gdb-result-var="$1",return-value="0"
21336 @subheading The @code{-exec-interrupt} Command
21337 @findex -exec-interrupt
21339 @subsubheading Synopsis
21342 -exec-interrupt [--all|--thread-group N]
21345 Interrupts the background execution of the target. Note how the token
21346 associated with the stop message is the one for the execution command
21347 that has been interrupted. The token for the interrupt itself only
21348 appears in the @samp{^done} output. If the user is trying to
21349 interrupt a non-running program, an error message will be printed.
21351 Note that when asynchronous execution is enabled, this command is
21352 asynchronous just like other execution commands. That is, first the
21353 @samp{^done} response will be printed, and the target stop will be
21354 reported after that using the @samp{*stopped} notification.
21356 In non-stop mode, only the context thread is interrupted by default.
21357 All threads will be interrupted if the @samp{--all} option is
21358 specified. If the @samp{--thread-group} option is specified, all
21359 threads in that group will be interrupted.
21361 @subsubheading @value{GDBN} Command
21363 The corresponding @value{GDBN} command is @samp{interrupt}.
21365 @subsubheading Example
21376 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
21377 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",
21378 fullname="/home/foo/bar/try.c",line="13"@}
21383 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
21388 @subheading The @code{-exec-next} Command
21391 @subsubheading Synopsis
21397 Resumes execution of the inferior program, stopping when the beginning
21398 of the next source line is reached.
21400 @subsubheading @value{GDBN} Command
21402 The corresponding @value{GDBN} command is @samp{next}.
21404 @subsubheading Example
21410 *stopped,reason="end-stepping-range",line="8",file="hello.c"
21415 @subheading The @code{-exec-next-instruction} Command
21416 @findex -exec-next-instruction
21418 @subsubheading Synopsis
21421 -exec-next-instruction
21424 Executes one machine instruction. If the instruction is a function
21425 call, continues until the function returns. If the program stops at an
21426 instruction in the middle of a source line, the address will be
21429 @subsubheading @value{GDBN} Command
21431 The corresponding @value{GDBN} command is @samp{nexti}.
21433 @subsubheading Example
21437 -exec-next-instruction
21441 *stopped,reason="end-stepping-range",
21442 addr="0x000100d4",line="5",file="hello.c"
21447 @subheading The @code{-exec-return} Command
21448 @findex -exec-return
21450 @subsubheading Synopsis
21456 Makes current function return immediately. Doesn't execute the inferior.
21457 Displays the new current frame.
21459 @subsubheading @value{GDBN} Command
21461 The corresponding @value{GDBN} command is @samp{return}.
21463 @subsubheading Example
21467 200-break-insert callee4
21468 200^done,bkpt=@{number="1",addr="0x00010734",
21469 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
21474 000*stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
21475 frame=@{func="callee4",args=[],
21476 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
21477 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
21483 111^done,frame=@{level="0",func="callee3",
21484 args=[@{name="strarg",
21485 value="0x11940 \"A string argument.\""@}],
21486 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
21487 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
21492 @subheading The @code{-exec-run} Command
21495 @subsubheading Synopsis
21501 Starts execution of the inferior from the beginning. The inferior
21502 executes until either a breakpoint is encountered or the program
21503 exits. In the latter case the output will include an exit code, if
21504 the program has exited exceptionally.
21506 @subsubheading @value{GDBN} Command
21508 The corresponding @value{GDBN} command is @samp{run}.
21510 @subsubheading Examples
21515 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
21520 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
21521 frame=@{func="main",args=[],file="recursive2.c",
21522 fullname="/home/foo/bar/recursive2.c",line="4"@}
21527 Program exited normally:
21535 *stopped,reason="exited-normally"
21540 Program exited exceptionally:
21548 *stopped,reason="exited",exit-code="01"
21552 Another way the program can terminate is if it receives a signal such as
21553 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
21557 *stopped,reason="exited-signalled",signal-name="SIGINT",
21558 signal-meaning="Interrupt"
21562 @c @subheading -exec-signal
21565 @subheading The @code{-exec-step} Command
21568 @subsubheading Synopsis
21574 Resumes execution of the inferior program, stopping when the beginning
21575 of the next source line is reached, if the next source line is not a
21576 function call. If it is, stop at the first instruction of the called
21579 @subsubheading @value{GDBN} Command
21581 The corresponding @value{GDBN} command is @samp{step}.
21583 @subsubheading Example
21585 Stepping into a function:
21591 *stopped,reason="end-stepping-range",
21592 frame=@{func="foo",args=[@{name="a",value="10"@},
21593 @{name="b",value="0"@}],file="recursive2.c",
21594 fullname="/home/foo/bar/recursive2.c",line="11"@}
21604 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
21609 @subheading The @code{-exec-step-instruction} Command
21610 @findex -exec-step-instruction
21612 @subsubheading Synopsis
21615 -exec-step-instruction
21618 Resumes the inferior which executes one machine instruction. The
21619 output, once @value{GDBN} has stopped, will vary depending on whether
21620 we have stopped in the middle of a source line or not. In the former
21621 case, the address at which the program stopped will be printed as
21624 @subsubheading @value{GDBN} Command
21626 The corresponding @value{GDBN} command is @samp{stepi}.
21628 @subsubheading Example
21632 -exec-step-instruction
21636 *stopped,reason="end-stepping-range",
21637 frame=@{func="foo",args=[],file="try.c",
21638 fullname="/home/foo/bar/try.c",line="10"@}
21640 -exec-step-instruction
21644 *stopped,reason="end-stepping-range",
21645 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",
21646 fullname="/home/foo/bar/try.c",line="10"@}
21651 @subheading The @code{-exec-until} Command
21652 @findex -exec-until
21654 @subsubheading Synopsis
21657 -exec-until [ @var{location} ]
21660 Executes the inferior until the @var{location} specified in the
21661 argument is reached. If there is no argument, the inferior executes
21662 until a source line greater than the current one is reached. The
21663 reason for stopping in this case will be @samp{location-reached}.
21665 @subsubheading @value{GDBN} Command
21667 The corresponding @value{GDBN} command is @samp{until}.
21669 @subsubheading Example
21673 -exec-until recursive2.c:6
21677 *stopped,reason="location-reached",frame=@{func="main",args=[],
21678 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="6"@}
21683 @subheading -file-clear
21684 Is this going away????
21687 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
21688 @node GDB/MI Stack Manipulation
21689 @section @sc{gdb/mi} Stack Manipulation Commands
21692 @subheading The @code{-stack-info-frame} Command
21693 @findex -stack-info-frame
21695 @subsubheading Synopsis
21701 Get info on the selected frame.
21703 @subsubheading @value{GDBN} Command
21705 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
21706 (without arguments).
21708 @subsubheading Example
21713 ^done,frame=@{level="1",addr="0x0001076c",func="callee3",
21714 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
21715 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@}
21719 @subheading The @code{-stack-info-depth} Command
21720 @findex -stack-info-depth
21722 @subsubheading Synopsis
21725 -stack-info-depth [ @var{max-depth} ]
21728 Return the depth of the stack. If the integer argument @var{max-depth}
21729 is specified, do not count beyond @var{max-depth} frames.
21731 @subsubheading @value{GDBN} Command
21733 There's no equivalent @value{GDBN} command.
21735 @subsubheading Example
21737 For a stack with frame levels 0 through 11:
21744 -stack-info-depth 4
21747 -stack-info-depth 12
21750 -stack-info-depth 11
21753 -stack-info-depth 13
21758 @subheading The @code{-stack-list-arguments} Command
21759 @findex -stack-list-arguments
21761 @subsubheading Synopsis
21764 -stack-list-arguments @var{show-values}
21765 [ @var{low-frame} @var{high-frame} ]
21768 Display a list of the arguments for the frames between @var{low-frame}
21769 and @var{high-frame} (inclusive). If @var{low-frame} and
21770 @var{high-frame} are not provided, list the arguments for the whole
21771 call stack. If the two arguments are equal, show the single frame
21772 at the corresponding level. It is an error if @var{low-frame} is
21773 larger than the actual number of frames. On the other hand,
21774 @var{high-frame} may be larger than the actual number of frames, in
21775 which case only existing frames will be returned.
21777 The @var{show-values} argument must have a value of 0 or 1. A value of
21778 0 means that only the names of the arguments are listed, a value of 1
21779 means that both names and values of the arguments are printed.
21781 @subsubheading @value{GDBN} Command
21783 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
21784 @samp{gdb_get_args} command which partially overlaps with the
21785 functionality of @samp{-stack-list-arguments}.
21787 @subsubheading Example
21794 frame=@{level="0",addr="0x00010734",func="callee4",
21795 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
21796 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@},
21797 frame=@{level="1",addr="0x0001076c",func="callee3",
21798 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
21799 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@},
21800 frame=@{level="2",addr="0x0001078c",func="callee2",
21801 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
21802 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="22"@},
21803 frame=@{level="3",addr="0x000107b4",func="callee1",
21804 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
21805 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="27"@},
21806 frame=@{level="4",addr="0x000107e0",func="main",
21807 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
21808 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="32"@}]
21810 -stack-list-arguments 0
21813 frame=@{level="0",args=[]@},
21814 frame=@{level="1",args=[name="strarg"]@},
21815 frame=@{level="2",args=[name="intarg",name="strarg"]@},
21816 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
21817 frame=@{level="4",args=[]@}]
21819 -stack-list-arguments 1
21822 frame=@{level="0",args=[]@},
21824 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
21825 frame=@{level="2",args=[
21826 @{name="intarg",value="2"@},
21827 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
21828 @{frame=@{level="3",args=[
21829 @{name="intarg",value="2"@},
21830 @{name="strarg",value="0x11940 \"A string argument.\""@},
21831 @{name="fltarg",value="3.5"@}]@},
21832 frame=@{level="4",args=[]@}]
21834 -stack-list-arguments 0 2 2
21835 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
21837 -stack-list-arguments 1 2 2
21838 ^done,stack-args=[frame=@{level="2",
21839 args=[@{name="intarg",value="2"@},
21840 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
21844 @c @subheading -stack-list-exception-handlers
21847 @subheading The @code{-stack-list-frames} Command
21848 @findex -stack-list-frames
21850 @subsubheading Synopsis
21853 -stack-list-frames [ @var{low-frame} @var{high-frame} ]
21856 List the frames currently on the stack. For each frame it displays the
21861 The frame number, 0 being the topmost frame, i.e., the innermost function.
21863 The @code{$pc} value for that frame.
21867 File name of the source file where the function lives.
21869 Line number corresponding to the @code{$pc}.
21872 If invoked without arguments, this command prints a backtrace for the
21873 whole stack. If given two integer arguments, it shows the frames whose
21874 levels are between the two arguments (inclusive). If the two arguments
21875 are equal, it shows the single frame at the corresponding level. It is
21876 an error if @var{low-frame} is larger than the actual number of
21877 frames. On the other hand, @var{high-frame} may be larger than the
21878 actual number of frames, in which case only existing frames will be returned.
21880 @subsubheading @value{GDBN} Command
21882 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
21884 @subsubheading Example
21886 Full stack backtrace:
21892 [frame=@{level="0",addr="0x0001076c",func="foo",
21893 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="11"@},
21894 frame=@{level="1",addr="0x000107a4",func="foo",
21895 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
21896 frame=@{level="2",addr="0x000107a4",func="foo",
21897 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
21898 frame=@{level="3",addr="0x000107a4",func="foo",
21899 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
21900 frame=@{level="4",addr="0x000107a4",func="foo",
21901 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
21902 frame=@{level="5",addr="0x000107a4",func="foo",
21903 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
21904 frame=@{level="6",addr="0x000107a4",func="foo",
21905 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
21906 frame=@{level="7",addr="0x000107a4",func="foo",
21907 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
21908 frame=@{level="8",addr="0x000107a4",func="foo",
21909 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
21910 frame=@{level="9",addr="0x000107a4",func="foo",
21911 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
21912 frame=@{level="10",addr="0x000107a4",func="foo",
21913 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
21914 frame=@{level="11",addr="0x00010738",func="main",
21915 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="4"@}]
21919 Show frames between @var{low_frame} and @var{high_frame}:
21923 -stack-list-frames 3 5
21925 [frame=@{level="3",addr="0x000107a4",func="foo",
21926 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
21927 frame=@{level="4",addr="0x000107a4",func="foo",
21928 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
21929 frame=@{level="5",addr="0x000107a4",func="foo",
21930 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
21934 Show a single frame:
21938 -stack-list-frames 3 3
21940 [frame=@{level="3",addr="0x000107a4",func="foo",
21941 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
21946 @subheading The @code{-stack-list-locals} Command
21947 @findex -stack-list-locals
21949 @subsubheading Synopsis
21952 -stack-list-locals @var{print-values}
21955 Display the local variable names for the selected frame. If
21956 @var{print-values} is 0 or @code{--no-values}, print only the names of
21957 the variables; if it is 1 or @code{--all-values}, print also their
21958 values; and if it is 2 or @code{--simple-values}, print the name,
21959 type and value for simple data types and the name and type for arrays,
21960 structures and unions. In this last case, a frontend can immediately
21961 display the value of simple data types and create variable objects for
21962 other data types when the user wishes to explore their values in
21965 @subsubheading @value{GDBN} Command
21967 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
21969 @subsubheading Example
21973 -stack-list-locals 0
21974 ^done,locals=[name="A",name="B",name="C"]
21976 -stack-list-locals --all-values
21977 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
21978 @{name="C",value="@{1, 2, 3@}"@}]
21979 -stack-list-locals --simple-values
21980 ^done,locals=[@{name="A",type="int",value="1"@},
21981 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
21986 @subheading The @code{-stack-select-frame} Command
21987 @findex -stack-select-frame
21989 @subsubheading Synopsis
21992 -stack-select-frame @var{framenum}
21995 Change the selected frame. Select a different frame @var{framenum} on
21998 This command in deprecated in favor of passing the @samp{--frame}
21999 option to every command.
22001 @subsubheading @value{GDBN} Command
22003 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
22004 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
22006 @subsubheading Example
22010 -stack-select-frame 2
22015 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
22016 @node GDB/MI Variable Objects
22017 @section @sc{gdb/mi} Variable Objects
22021 @subheading Motivation for Variable Objects in @sc{gdb/mi}
22023 For the implementation of a variable debugger window (locals, watched
22024 expressions, etc.), we are proposing the adaptation of the existing code
22025 used by @code{Insight}.
22027 The two main reasons for that are:
22031 It has been proven in practice (it is already on its second generation).
22034 It will shorten development time (needless to say how important it is
22038 The original interface was designed to be used by Tcl code, so it was
22039 slightly changed so it could be used through @sc{gdb/mi}. This section
22040 describes the @sc{gdb/mi} operations that will be available and gives some
22041 hints about their use.
22043 @emph{Note}: In addition to the set of operations described here, we
22044 expect the @sc{gui} implementation of a variable window to require, at
22045 least, the following operations:
22048 @item @code{-gdb-show} @code{output-radix}
22049 @item @code{-stack-list-arguments}
22050 @item @code{-stack-list-locals}
22051 @item @code{-stack-select-frame}
22056 @subheading Introduction to Variable Objects
22058 @cindex variable objects in @sc{gdb/mi}
22060 Variable objects are "object-oriented" MI interface for examining and
22061 changing values of expressions. Unlike some other MI interfaces that
22062 work with expressions, variable objects are specifically designed for
22063 simple and efficient presentation in the frontend. A variable object
22064 is identified by string name. When a variable object is created, the
22065 frontend specifies the expression for that variable object. The
22066 expression can be a simple variable, or it can be an arbitrary complex
22067 expression, and can even involve CPU registers. After creating a
22068 variable object, the frontend can invoke other variable object
22069 operations---for example to obtain or change the value of a variable
22070 object, or to change display format.
22072 Variable objects have hierarchical tree structure. Any variable object
22073 that corresponds to a composite type, such as structure in C, has
22074 a number of child variable objects, for example corresponding to each
22075 element of a structure. A child variable object can itself have
22076 children, recursively. Recursion ends when we reach
22077 leaf variable objects, which always have built-in types. Child variable
22078 objects are created only by explicit request, so if a frontend
22079 is not interested in the children of a particular variable object, no
22080 child will be created.
22082 For a leaf variable object it is possible to obtain its value as a
22083 string, or set the value from a string. String value can be also
22084 obtained for a non-leaf variable object, but it's generally a string
22085 that only indicates the type of the object, and does not list its
22086 contents. Assignment to a non-leaf variable object is not allowed.
22088 A frontend does not need to read the values of all variable objects each time
22089 the program stops. Instead, MI provides an update command that lists all
22090 variable objects whose values has changed since the last update
22091 operation. This considerably reduces the amount of data that must
22092 be transferred to the frontend. As noted above, children variable
22093 objects are created on demand, and only leaf variable objects have a
22094 real value. As result, gdb will read target memory only for leaf
22095 variables that frontend has created.
22097 The automatic update is not always desirable. For example, a frontend
22098 might want to keep a value of some expression for future reference,
22099 and never update it. For another example, fetching memory is
22100 relatively slow for embedded targets, so a frontend might want
22101 to disable automatic update for the variables that are either not
22102 visible on the screen, or ``closed''. This is possible using so
22103 called ``frozen variable objects''. Such variable objects are never
22104 implicitly updated.
22106 Variable objects can be either @dfn{fixed} or @dfn{floating}. For the
22107 fixed variable object, the expression is parsed when the variable
22108 object is created, including associating identifiers to specific
22109 variables. The meaning of expression never changes. For a floating
22110 variable object the values of variables whose names appear in the
22111 expressions are re-evaluated every time in the context of the current
22112 frame. Consider this example:
22117 struct work_state state;
22124 If a fixed variable object for the @code{state} variable is created in
22125 this function, and we enter the recursive call, the the variable
22126 object will report the value of @code{state} in the top-level
22127 @code{do_work} invocation. On the other hand, a floating variable
22128 object will report the value of @code{state} in the current frame.
22130 If an expression specified when creating a fixed variable object
22131 refers to a local variable, the variable object becomes bound to the
22132 thread and frame in which the variable object is created. When such
22133 variable object is updated, @value{GDBN} makes sure that the
22134 thread/frame combination the variable object is bound to still exists,
22135 and re-evaluates the variable object in context of that thread/frame.
22137 The following is the complete set of @sc{gdb/mi} operations defined to
22138 access this functionality:
22140 @multitable @columnfractions .4 .6
22141 @item @strong{Operation}
22142 @tab @strong{Description}
22144 @item @code{-var-create}
22145 @tab create a variable object
22146 @item @code{-var-delete}
22147 @tab delete the variable object and/or its children
22148 @item @code{-var-set-format}
22149 @tab set the display format of this variable
22150 @item @code{-var-show-format}
22151 @tab show the display format of this variable
22152 @item @code{-var-info-num-children}
22153 @tab tells how many children this object has
22154 @item @code{-var-list-children}
22155 @tab return a list of the object's children
22156 @item @code{-var-info-type}
22157 @tab show the type of this variable object
22158 @item @code{-var-info-expression}
22159 @tab print parent-relative expression that this variable object represents
22160 @item @code{-var-info-path-expression}
22161 @tab print full expression that this variable object represents
22162 @item @code{-var-show-attributes}
22163 @tab is this variable editable? does it exist here?
22164 @item @code{-var-evaluate-expression}
22165 @tab get the value of this variable
22166 @item @code{-var-assign}
22167 @tab set the value of this variable
22168 @item @code{-var-update}
22169 @tab update the variable and its children
22170 @item @code{-var-set-frozen}
22171 @tab set frozeness attribute
22174 In the next subsection we describe each operation in detail and suggest
22175 how it can be used.
22177 @subheading Description And Use of Operations on Variable Objects
22179 @subheading The @code{-var-create} Command
22180 @findex -var-create
22182 @subsubheading Synopsis
22185 -var-create @{@var{name} | "-"@}
22186 @{@var{frame-addr} | "*" | "@@"@} @var{expression}
22189 This operation creates a variable object, which allows the monitoring of
22190 a variable, the result of an expression, a memory cell or a CPU
22193 The @var{name} parameter is the string by which the object can be
22194 referenced. It must be unique. If @samp{-} is specified, the varobj
22195 system will generate a string ``varNNNNNN'' automatically. It will be
22196 unique provided that one does not specify @var{name} of that format.
22197 The command fails if a duplicate name is found.
22199 The frame under which the expression should be evaluated can be
22200 specified by @var{frame-addr}. A @samp{*} indicates that the current
22201 frame should be used. A @samp{@@} indicates that a floating variable
22202 object must be created.
22204 @var{expression} is any expression valid on the current language set (must not
22205 begin with a @samp{*}), or one of the following:
22209 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
22212 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
22215 @samp{$@var{regname}} --- a CPU register name
22218 @subsubheading Result
22220 This operation returns the name, number of children and the type of the
22221 object created. Type is returned as a string as the ones generated by
22222 the @value{GDBN} CLI. If a fixed variable object is bound to a
22223 specific thread, the thread is is also printed:
22226 name="@var{name}",numchild="@var{N}",type="@var{type}",thread-id="@var{M}"
22230 @subheading The @code{-var-delete} Command
22231 @findex -var-delete
22233 @subsubheading Synopsis
22236 -var-delete [ -c ] @var{name}
22239 Deletes a previously created variable object and all of its children.
22240 With the @samp{-c} option, just deletes the children.
22242 Returns an error if the object @var{name} is not found.
22245 @subheading The @code{-var-set-format} Command
22246 @findex -var-set-format
22248 @subsubheading Synopsis
22251 -var-set-format @var{name} @var{format-spec}
22254 Sets the output format for the value of the object @var{name} to be
22257 @anchor{-var-set-format}
22258 The syntax for the @var{format-spec} is as follows:
22261 @var{format-spec} @expansion{}
22262 @{binary | decimal | hexadecimal | octal | natural@}
22265 The natural format is the default format choosen automatically
22266 based on the variable type (like decimal for an @code{int}, hex
22267 for pointers, etc.).
22269 For a variable with children, the format is set only on the
22270 variable itself, and the children are not affected.
22272 @subheading The @code{-var-show-format} Command
22273 @findex -var-show-format
22275 @subsubheading Synopsis
22278 -var-show-format @var{name}
22281 Returns the format used to display the value of the object @var{name}.
22284 @var{format} @expansion{}
22289 @subheading The @code{-var-info-num-children} Command
22290 @findex -var-info-num-children
22292 @subsubheading Synopsis
22295 -var-info-num-children @var{name}
22298 Returns the number of children of a variable object @var{name}:
22305 @subheading The @code{-var-list-children} Command
22306 @findex -var-list-children
22308 @subsubheading Synopsis
22311 -var-list-children [@var{print-values}] @var{name}
22313 @anchor{-var-list-children}
22315 Return a list of the children of the specified variable object and
22316 create variable objects for them, if they do not already exist. With
22317 a single argument or if @var{print-values} has a value for of 0 or
22318 @code{--no-values}, print only the names of the variables; if
22319 @var{print-values} is 1 or @code{--all-values}, also print their
22320 values; and if it is 2 or @code{--simple-values} print the name and
22321 value for simple data types and just the name for arrays, structures
22324 @subsubheading Example
22328 -var-list-children n
22329 ^done,numchild=@var{n},children=[@{name=@var{name},
22330 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
22332 -var-list-children --all-values n
22333 ^done,numchild=@var{n},children=[@{name=@var{name},
22334 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
22338 @subheading The @code{-var-info-type} Command
22339 @findex -var-info-type
22341 @subsubheading Synopsis
22344 -var-info-type @var{name}
22347 Returns the type of the specified variable @var{name}. The type is
22348 returned as a string in the same format as it is output by the
22352 type=@var{typename}
22356 @subheading The @code{-var-info-expression} Command
22357 @findex -var-info-expression
22359 @subsubheading Synopsis
22362 -var-info-expression @var{name}
22365 Returns a string that is suitable for presenting this
22366 variable object in user interface. The string is generally
22367 not valid expression in the current language, and cannot be evaluated.
22369 For example, if @code{a} is an array, and variable object
22370 @code{A} was created for @code{a}, then we'll get this output:
22373 (gdb) -var-info-expression A.1
22374 ^done,lang="C",exp="1"
22378 Here, the values of @code{lang} can be @code{@{"C" | "C++" | "Java"@}}.
22380 Note that the output of the @code{-var-list-children} command also
22381 includes those expressions, so the @code{-var-info-expression} command
22384 @subheading The @code{-var-info-path-expression} Command
22385 @findex -var-info-path-expression
22387 @subsubheading Synopsis
22390 -var-info-path-expression @var{name}
22393 Returns an expression that can be evaluated in the current
22394 context and will yield the same value that a variable object has.
22395 Compare this with the @code{-var-info-expression} command, which
22396 result can be used only for UI presentation. Typical use of
22397 the @code{-var-info-path-expression} command is creating a
22398 watchpoint from a variable object.
22400 For example, suppose @code{C} is a C@t{++} class, derived from class
22401 @code{Base}, and that the @code{Base} class has a member called
22402 @code{m_size}. Assume a variable @code{c} is has the type of
22403 @code{C} and a variable object @code{C} was created for variable
22404 @code{c}. Then, we'll get this output:
22406 (gdb) -var-info-path-expression C.Base.public.m_size
22407 ^done,path_expr=((Base)c).m_size)
22410 @subheading The @code{-var-show-attributes} Command
22411 @findex -var-show-attributes
22413 @subsubheading Synopsis
22416 -var-show-attributes @var{name}
22419 List attributes of the specified variable object @var{name}:
22422 status=@var{attr} [ ( ,@var{attr} )* ]
22426 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
22428 @subheading The @code{-var-evaluate-expression} Command
22429 @findex -var-evaluate-expression
22431 @subsubheading Synopsis
22434 -var-evaluate-expression [-f @var{format-spec}] @var{name}
22437 Evaluates the expression that is represented by the specified variable
22438 object and returns its value as a string. The format of the string
22439 can be specified with the @samp{-f} option. The possible values of
22440 this option are the same as for @code{-var-set-format}
22441 (@pxref{-var-set-format}). If the @samp{-f} option is not specified,
22442 the current display format will be used. The current display format
22443 can be changed using the @code{-var-set-format} command.
22449 Note that one must invoke @code{-var-list-children} for a variable
22450 before the value of a child variable can be evaluated.
22452 @subheading The @code{-var-assign} Command
22453 @findex -var-assign
22455 @subsubheading Synopsis
22458 -var-assign @var{name} @var{expression}
22461 Assigns the value of @var{expression} to the variable object specified
22462 by @var{name}. The object must be @samp{editable}. If the variable's
22463 value is altered by the assign, the variable will show up in any
22464 subsequent @code{-var-update} list.
22466 @subsubheading Example
22474 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
22478 @subheading The @code{-var-update} Command
22479 @findex -var-update
22481 @subsubheading Synopsis
22484 -var-update [@var{print-values}] @{@var{name} | "*"@}
22487 Reevaluate the expressions corresponding to the variable object
22488 @var{name} and all its direct and indirect children, and return the
22489 list of variable objects whose values have changed; @var{name} must
22490 be a root variable object. Here, ``changed'' means that the result of
22491 @code{-var-evaluate-expression} before and after the
22492 @code{-var-update} is different. If @samp{*} is used as the variable
22493 object names, all existing variable objects are updated, except
22494 for frozen ones (@pxref{-var-set-frozen}). The option
22495 @var{print-values} determines whether both names and values, or just
22496 names are printed. The possible values of this option are the same
22497 as for @code{-var-list-children} (@pxref{-var-list-children}). It is
22498 recommended to use the @samp{--all-values} option, to reduce the
22499 number of MI commands needed on each program stop.
22501 With the @samp{*} parameter, if a variable object is bound to a
22502 currently running thread, it will not be updated, without any
22505 @subsubheading Example
22512 -var-update --all-values var1
22513 ^done,changelist=[@{name="var1",value="3",in_scope="true",
22514 type_changed="false"@}]
22518 @anchor{-var-update}
22519 The field in_scope may take three values:
22523 The variable object's current value is valid.
22526 The variable object does not currently hold a valid value but it may
22527 hold one in the future if its associated expression comes back into
22531 The variable object no longer holds a valid value.
22532 This can occur when the executable file being debugged has changed,
22533 either through recompilation or by using the @value{GDBN} @code{file}
22534 command. The front end should normally choose to delete these variable
22538 In the future new values may be added to this list so the front should
22539 be prepared for this possibility. @xref{GDB/MI Development and Front Ends, ,@sc{GDB/MI} Development and Front Ends}.
22541 @subheading The @code{-var-set-frozen} Command
22542 @findex -var-set-frozen
22543 @anchor{-var-set-frozen}
22545 @subsubheading Synopsis
22548 -var-set-frozen @var{name} @var{flag}
22551 Set the frozenness flag on the variable object @var{name}. The
22552 @var{flag} parameter should be either @samp{1} to make the variable
22553 frozen or @samp{0} to make it unfrozen. If a variable object is
22554 frozen, then neither itself, nor any of its children, are
22555 implicitly updated by @code{-var-update} of
22556 a parent variable or by @code{-var-update *}. Only
22557 @code{-var-update} of the variable itself will update its value and
22558 values of its children. After a variable object is unfrozen, it is
22559 implicitly updated by all subsequent @code{-var-update} operations.
22560 Unfreezing a variable does not update it, only subsequent
22561 @code{-var-update} does.
22563 @subsubheading Example
22567 -var-set-frozen V 1
22573 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
22574 @node GDB/MI Data Manipulation
22575 @section @sc{gdb/mi} Data Manipulation
22577 @cindex data manipulation, in @sc{gdb/mi}
22578 @cindex @sc{gdb/mi}, data manipulation
22579 This section describes the @sc{gdb/mi} commands that manipulate data:
22580 examine memory and registers, evaluate expressions, etc.
22582 @c REMOVED FROM THE INTERFACE.
22583 @c @subheading -data-assign
22584 @c Change the value of a program variable. Plenty of side effects.
22585 @c @subsubheading GDB Command
22587 @c @subsubheading Example
22590 @subheading The @code{-data-disassemble} Command
22591 @findex -data-disassemble
22593 @subsubheading Synopsis
22597 [ -s @var{start-addr} -e @var{end-addr} ]
22598 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
22606 @item @var{start-addr}
22607 is the beginning address (or @code{$pc})
22608 @item @var{end-addr}
22610 @item @var{filename}
22611 is the name of the file to disassemble
22612 @item @var{linenum}
22613 is the line number to disassemble around
22615 is the number of disassembly lines to be produced. If it is -1,
22616 the whole function will be disassembled, in case no @var{end-addr} is
22617 specified. If @var{end-addr} is specified as a non-zero value, and
22618 @var{lines} is lower than the number of disassembly lines between
22619 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
22620 displayed; if @var{lines} is higher than the number of lines between
22621 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
22624 is either 0 (meaning only disassembly) or 1 (meaning mixed source and
22628 @subsubheading Result
22630 The output for each instruction is composed of four fields:
22639 Note that whatever included in the instruction field, is not manipulated
22640 directly by @sc{gdb/mi}, i.e., it is not possible to adjust its format.
22642 @subsubheading @value{GDBN} Command
22644 There's no direct mapping from this command to the CLI.
22646 @subsubheading Example
22648 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
22652 -data-disassemble -s $pc -e "$pc + 20" -- 0
22655 @{address="0x000107c0",func-name="main",offset="4",
22656 inst="mov 2, %o0"@},
22657 @{address="0x000107c4",func-name="main",offset="8",
22658 inst="sethi %hi(0x11800), %o2"@},
22659 @{address="0x000107c8",func-name="main",offset="12",
22660 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
22661 @{address="0x000107cc",func-name="main",offset="16",
22662 inst="sethi %hi(0x11800), %o2"@},
22663 @{address="0x000107d0",func-name="main",offset="20",
22664 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
22668 Disassemble the whole @code{main} function. Line 32 is part of
22672 -data-disassemble -f basics.c -l 32 -- 0
22674 @{address="0x000107bc",func-name="main",offset="0",
22675 inst="save %sp, -112, %sp"@},
22676 @{address="0x000107c0",func-name="main",offset="4",
22677 inst="mov 2, %o0"@},
22678 @{address="0x000107c4",func-name="main",offset="8",
22679 inst="sethi %hi(0x11800), %o2"@},
22681 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
22682 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
22686 Disassemble 3 instructions from the start of @code{main}:
22690 -data-disassemble -f basics.c -l 32 -n 3 -- 0
22692 @{address="0x000107bc",func-name="main",offset="0",
22693 inst="save %sp, -112, %sp"@},
22694 @{address="0x000107c0",func-name="main",offset="4",
22695 inst="mov 2, %o0"@},
22696 @{address="0x000107c4",func-name="main",offset="8",
22697 inst="sethi %hi(0x11800), %o2"@}]
22701 Disassemble 3 instructions from the start of @code{main} in mixed mode:
22705 -data-disassemble -f basics.c -l 32 -n 3 -- 1
22707 src_and_asm_line=@{line="31",
22708 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
22709 testsuite/gdb.mi/basics.c",line_asm_insn=[
22710 @{address="0x000107bc",func-name="main",offset="0",
22711 inst="save %sp, -112, %sp"@}]@},
22712 src_and_asm_line=@{line="32",
22713 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
22714 testsuite/gdb.mi/basics.c",line_asm_insn=[
22715 @{address="0x000107c0",func-name="main",offset="4",
22716 inst="mov 2, %o0"@},
22717 @{address="0x000107c4",func-name="main",offset="8",
22718 inst="sethi %hi(0x11800), %o2"@}]@}]
22723 @subheading The @code{-data-evaluate-expression} Command
22724 @findex -data-evaluate-expression
22726 @subsubheading Synopsis
22729 -data-evaluate-expression @var{expr}
22732 Evaluate @var{expr} as an expression. The expression could contain an
22733 inferior function call. The function call will execute synchronously.
22734 If the expression contains spaces, it must be enclosed in double quotes.
22736 @subsubheading @value{GDBN} Command
22738 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
22739 @samp{call}. In @code{gdbtk} only, there's a corresponding
22740 @samp{gdb_eval} command.
22742 @subsubheading Example
22744 In the following example, the numbers that precede the commands are the
22745 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
22746 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
22750 211-data-evaluate-expression A
22753 311-data-evaluate-expression &A
22754 311^done,value="0xefffeb7c"
22756 411-data-evaluate-expression A+3
22759 511-data-evaluate-expression "A + 3"
22765 @subheading The @code{-data-list-changed-registers} Command
22766 @findex -data-list-changed-registers
22768 @subsubheading Synopsis
22771 -data-list-changed-registers
22774 Display a list of the registers that have changed.
22776 @subsubheading @value{GDBN} Command
22778 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
22779 has the corresponding command @samp{gdb_changed_register_list}.
22781 @subsubheading Example
22783 On a PPC MBX board:
22791 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",frame=@{
22792 func="main",args=[],file="try.c",fullname="/home/foo/bar/try.c",
22795 -data-list-changed-registers
22796 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
22797 "10","11","13","14","15","16","17","18","19","20","21","22","23",
22798 "24","25","26","27","28","30","31","64","65","66","67","69"]
22803 @subheading The @code{-data-list-register-names} Command
22804 @findex -data-list-register-names
22806 @subsubheading Synopsis
22809 -data-list-register-names [ ( @var{regno} )+ ]
22812 Show a list of register names for the current target. If no arguments
22813 are given, it shows a list of the names of all the registers. If
22814 integer numbers are given as arguments, it will print a list of the
22815 names of the registers corresponding to the arguments. To ensure
22816 consistency between a register name and its number, the output list may
22817 include empty register names.
22819 @subsubheading @value{GDBN} Command
22821 @value{GDBN} does not have a command which corresponds to
22822 @samp{-data-list-register-names}. In @code{gdbtk} there is a
22823 corresponding command @samp{gdb_regnames}.
22825 @subsubheading Example
22827 For the PPC MBX board:
22830 -data-list-register-names
22831 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
22832 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
22833 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
22834 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
22835 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
22836 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
22837 "", "pc","ps","cr","lr","ctr","xer"]
22839 -data-list-register-names 1 2 3
22840 ^done,register-names=["r1","r2","r3"]
22844 @subheading The @code{-data-list-register-values} Command
22845 @findex -data-list-register-values
22847 @subsubheading Synopsis
22850 -data-list-register-values @var{fmt} [ ( @var{regno} )*]
22853 Display the registers' contents. @var{fmt} is the format according to
22854 which the registers' contents are to be returned, followed by an optional
22855 list of numbers specifying the registers to display. A missing list of
22856 numbers indicates that the contents of all the registers must be returned.
22858 Allowed formats for @var{fmt} are:
22875 @subsubheading @value{GDBN} Command
22877 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
22878 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
22880 @subsubheading Example
22882 For a PPC MBX board (note: line breaks are for readability only, they
22883 don't appear in the actual output):
22887 -data-list-register-values r 64 65
22888 ^done,register-values=[@{number="64",value="0xfe00a300"@},
22889 @{number="65",value="0x00029002"@}]
22891 -data-list-register-values x
22892 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
22893 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
22894 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
22895 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
22896 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
22897 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
22898 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
22899 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
22900 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
22901 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
22902 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
22903 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
22904 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
22905 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
22906 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
22907 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
22908 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
22909 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
22910 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
22911 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
22912 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
22913 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
22914 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
22915 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
22916 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
22917 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
22918 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
22919 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
22920 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
22921 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
22922 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
22923 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
22924 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
22925 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
22926 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
22927 @{number="69",value="0x20002b03"@}]
22932 @subheading The @code{-data-read-memory} Command
22933 @findex -data-read-memory
22935 @subsubheading Synopsis
22938 -data-read-memory [ -o @var{byte-offset} ]
22939 @var{address} @var{word-format} @var{word-size}
22940 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
22947 @item @var{address}
22948 An expression specifying the address of the first memory word to be
22949 read. Complex expressions containing embedded white space should be
22950 quoted using the C convention.
22952 @item @var{word-format}
22953 The format to be used to print the memory words. The notation is the
22954 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
22957 @item @var{word-size}
22958 The size of each memory word in bytes.
22960 @item @var{nr-rows}
22961 The number of rows in the output table.
22963 @item @var{nr-cols}
22964 The number of columns in the output table.
22967 If present, indicates that each row should include an @sc{ascii} dump. The
22968 value of @var{aschar} is used as a padding character when a byte is not a
22969 member of the printable @sc{ascii} character set (printable @sc{ascii}
22970 characters are those whose code is between 32 and 126, inclusively).
22972 @item @var{byte-offset}
22973 An offset to add to the @var{address} before fetching memory.
22976 This command displays memory contents as a table of @var{nr-rows} by
22977 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
22978 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
22979 (returned as @samp{total-bytes}). Should less than the requested number
22980 of bytes be returned by the target, the missing words are identified
22981 using @samp{N/A}. The number of bytes read from the target is returned
22982 in @samp{nr-bytes} and the starting address used to read memory in
22985 The address of the next/previous row or page is available in
22986 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
22989 @subsubheading @value{GDBN} Command
22991 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
22992 @samp{gdb_get_mem} memory read command.
22994 @subsubheading Example
22996 Read six bytes of memory starting at @code{bytes+6} but then offset by
22997 @code{-6} bytes. Format as three rows of two columns. One byte per
22998 word. Display each word in hex.
23002 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
23003 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
23004 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
23005 prev-page="0x0000138a",memory=[
23006 @{addr="0x00001390",data=["0x00","0x01"]@},
23007 @{addr="0x00001392",data=["0x02","0x03"]@},
23008 @{addr="0x00001394",data=["0x04","0x05"]@}]
23012 Read two bytes of memory starting at address @code{shorts + 64} and
23013 display as a single word formatted in decimal.
23017 5-data-read-memory shorts+64 d 2 1 1
23018 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
23019 next-row="0x00001512",prev-row="0x0000150e",
23020 next-page="0x00001512",prev-page="0x0000150e",memory=[
23021 @{addr="0x00001510",data=["128"]@}]
23025 Read thirty two bytes of memory starting at @code{bytes+16} and format
23026 as eight rows of four columns. Include a string encoding with @samp{x}
23027 used as the non-printable character.
23031 4-data-read-memory bytes+16 x 1 8 4 x
23032 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
23033 next-row="0x000013c0",prev-row="0x0000139c",
23034 next-page="0x000013c0",prev-page="0x00001380",memory=[
23035 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
23036 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
23037 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
23038 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
23039 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
23040 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
23041 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
23042 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
23046 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
23047 @node GDB/MI Tracepoint Commands
23048 @section @sc{gdb/mi} Tracepoint Commands
23050 The tracepoint commands are not yet implemented.
23052 @c @subheading -trace-actions
23054 @c @subheading -trace-delete
23056 @c @subheading -trace-disable
23058 @c @subheading -trace-dump
23060 @c @subheading -trace-enable
23062 @c @subheading -trace-exists
23064 @c @subheading -trace-find
23066 @c @subheading -trace-frame-number
23068 @c @subheading -trace-info
23070 @c @subheading -trace-insert
23072 @c @subheading -trace-list
23074 @c @subheading -trace-pass-count
23076 @c @subheading -trace-save
23078 @c @subheading -trace-start
23080 @c @subheading -trace-stop
23083 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
23084 @node GDB/MI Symbol Query
23085 @section @sc{gdb/mi} Symbol Query Commands
23088 @subheading The @code{-symbol-info-address} Command
23089 @findex -symbol-info-address
23091 @subsubheading Synopsis
23094 -symbol-info-address @var{symbol}
23097 Describe where @var{symbol} is stored.
23099 @subsubheading @value{GDBN} Command
23101 The corresponding @value{GDBN} command is @samp{info address}.
23103 @subsubheading Example
23107 @subheading The @code{-symbol-info-file} Command
23108 @findex -symbol-info-file
23110 @subsubheading Synopsis
23116 Show the file for the symbol.
23118 @subsubheading @value{GDBN} Command
23120 There's no equivalent @value{GDBN} command. @code{gdbtk} has
23121 @samp{gdb_find_file}.
23123 @subsubheading Example
23127 @subheading The @code{-symbol-info-function} Command
23128 @findex -symbol-info-function
23130 @subsubheading Synopsis
23133 -symbol-info-function
23136 Show which function the symbol lives in.
23138 @subsubheading @value{GDBN} Command
23140 @samp{gdb_get_function} in @code{gdbtk}.
23142 @subsubheading Example
23146 @subheading The @code{-symbol-info-line} Command
23147 @findex -symbol-info-line
23149 @subsubheading Synopsis
23155 Show the core addresses of the code for a source line.
23157 @subsubheading @value{GDBN} Command
23159 The corresponding @value{GDBN} command is @samp{info line}.
23160 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
23162 @subsubheading Example
23166 @subheading The @code{-symbol-info-symbol} Command
23167 @findex -symbol-info-symbol
23169 @subsubheading Synopsis
23172 -symbol-info-symbol @var{addr}
23175 Describe what symbol is at location @var{addr}.
23177 @subsubheading @value{GDBN} Command
23179 The corresponding @value{GDBN} command is @samp{info symbol}.
23181 @subsubheading Example
23185 @subheading The @code{-symbol-list-functions} Command
23186 @findex -symbol-list-functions
23188 @subsubheading Synopsis
23191 -symbol-list-functions
23194 List the functions in the executable.
23196 @subsubheading @value{GDBN} Command
23198 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
23199 @samp{gdb_search} in @code{gdbtk}.
23201 @subsubheading Example
23205 @subheading The @code{-symbol-list-lines} Command
23206 @findex -symbol-list-lines
23208 @subsubheading Synopsis
23211 -symbol-list-lines @var{filename}
23214 Print the list of lines that contain code and their associated program
23215 addresses for the given source filename. The entries are sorted in
23216 ascending PC order.
23218 @subsubheading @value{GDBN} Command
23220 There is no corresponding @value{GDBN} command.
23222 @subsubheading Example
23225 -symbol-list-lines basics.c
23226 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
23231 @subheading The @code{-symbol-list-types} Command
23232 @findex -symbol-list-types
23234 @subsubheading Synopsis
23240 List all the type names.
23242 @subsubheading @value{GDBN} Command
23244 The corresponding commands are @samp{info types} in @value{GDBN},
23245 @samp{gdb_search} in @code{gdbtk}.
23247 @subsubheading Example
23251 @subheading The @code{-symbol-list-variables} Command
23252 @findex -symbol-list-variables
23254 @subsubheading Synopsis
23257 -symbol-list-variables
23260 List all the global and static variable names.
23262 @subsubheading @value{GDBN} Command
23264 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
23266 @subsubheading Example
23270 @subheading The @code{-symbol-locate} Command
23271 @findex -symbol-locate
23273 @subsubheading Synopsis
23279 @subsubheading @value{GDBN} Command
23281 @samp{gdb_loc} in @code{gdbtk}.
23283 @subsubheading Example
23287 @subheading The @code{-symbol-type} Command
23288 @findex -symbol-type
23290 @subsubheading Synopsis
23293 -symbol-type @var{variable}
23296 Show type of @var{variable}.
23298 @subsubheading @value{GDBN} Command
23300 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
23301 @samp{gdb_obj_variable}.
23303 @subsubheading Example
23307 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
23308 @node GDB/MI File Commands
23309 @section @sc{gdb/mi} File Commands
23311 This section describes the GDB/MI commands to specify executable file names
23312 and to read in and obtain symbol table information.
23314 @subheading The @code{-file-exec-and-symbols} Command
23315 @findex -file-exec-and-symbols
23317 @subsubheading Synopsis
23320 -file-exec-and-symbols @var{file}
23323 Specify the executable file to be debugged. This file is the one from
23324 which the symbol table is also read. If no file is specified, the
23325 command clears the executable and symbol information. If breakpoints
23326 are set when using this command with no arguments, @value{GDBN} will produce
23327 error messages. Otherwise, no output is produced, except a completion
23330 @subsubheading @value{GDBN} Command
23332 The corresponding @value{GDBN} command is @samp{file}.
23334 @subsubheading Example
23338 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
23344 @subheading The @code{-file-exec-file} Command
23345 @findex -file-exec-file
23347 @subsubheading Synopsis
23350 -file-exec-file @var{file}
23353 Specify the executable file to be debugged. Unlike
23354 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
23355 from this file. If used without argument, @value{GDBN} clears the information
23356 about the executable file. No output is produced, except a completion
23359 @subsubheading @value{GDBN} Command
23361 The corresponding @value{GDBN} command is @samp{exec-file}.
23363 @subsubheading Example
23367 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
23373 @subheading The @code{-file-list-exec-sections} Command
23374 @findex -file-list-exec-sections
23376 @subsubheading Synopsis
23379 -file-list-exec-sections
23382 List the sections of the current executable file.
23384 @subsubheading @value{GDBN} Command
23386 The @value{GDBN} command @samp{info file} shows, among the rest, the same
23387 information as this command. @code{gdbtk} has a corresponding command
23388 @samp{gdb_load_info}.
23390 @subsubheading Example
23394 @subheading The @code{-file-list-exec-source-file} Command
23395 @findex -file-list-exec-source-file
23397 @subsubheading Synopsis
23400 -file-list-exec-source-file
23403 List the line number, the current source file, and the absolute path
23404 to the current source file for the current executable. The macro
23405 information field has a value of @samp{1} or @samp{0} depending on
23406 whether or not the file includes preprocessor macro information.
23408 @subsubheading @value{GDBN} Command
23410 The @value{GDBN} equivalent is @samp{info source}
23412 @subsubheading Example
23416 123-file-list-exec-source-file
23417 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c,macro-info="1"
23422 @subheading The @code{-file-list-exec-source-files} Command
23423 @findex -file-list-exec-source-files
23425 @subsubheading Synopsis
23428 -file-list-exec-source-files
23431 List the source files for the current executable.
23433 It will always output the filename, but only when @value{GDBN} can find
23434 the absolute file name of a source file, will it output the fullname.
23436 @subsubheading @value{GDBN} Command
23438 The @value{GDBN} equivalent is @samp{info sources}.
23439 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
23441 @subsubheading Example
23444 -file-list-exec-source-files
23446 @{file=foo.c,fullname=/home/foo.c@},
23447 @{file=/home/bar.c,fullname=/home/bar.c@},
23448 @{file=gdb_could_not_find_fullpath.c@}]
23452 @subheading The @code{-file-list-shared-libraries} Command
23453 @findex -file-list-shared-libraries
23455 @subsubheading Synopsis
23458 -file-list-shared-libraries
23461 List the shared libraries in the program.
23463 @subsubheading @value{GDBN} Command
23465 The corresponding @value{GDBN} command is @samp{info shared}.
23467 @subsubheading Example
23471 @subheading The @code{-file-list-symbol-files} Command
23472 @findex -file-list-symbol-files
23474 @subsubheading Synopsis
23477 -file-list-symbol-files
23482 @subsubheading @value{GDBN} Command
23484 The corresponding @value{GDBN} command is @samp{info file} (part of it).
23486 @subsubheading Example
23490 @subheading The @code{-file-symbol-file} Command
23491 @findex -file-symbol-file
23493 @subsubheading Synopsis
23496 -file-symbol-file @var{file}
23499 Read symbol table info from the specified @var{file} argument. When
23500 used without arguments, clears @value{GDBN}'s symbol table info. No output is
23501 produced, except for a completion notification.
23503 @subsubheading @value{GDBN} Command
23505 The corresponding @value{GDBN} command is @samp{symbol-file}.
23507 @subsubheading Example
23511 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
23517 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
23518 @node GDB/MI Memory Overlay Commands
23519 @section @sc{gdb/mi} Memory Overlay Commands
23521 The memory overlay commands are not implemented.
23523 @c @subheading -overlay-auto
23525 @c @subheading -overlay-list-mapping-state
23527 @c @subheading -overlay-list-overlays
23529 @c @subheading -overlay-map
23531 @c @subheading -overlay-off
23533 @c @subheading -overlay-on
23535 @c @subheading -overlay-unmap
23537 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
23538 @node GDB/MI Signal Handling Commands
23539 @section @sc{gdb/mi} Signal Handling Commands
23541 Signal handling commands are not implemented.
23543 @c @subheading -signal-handle
23545 @c @subheading -signal-list-handle-actions
23547 @c @subheading -signal-list-signal-types
23551 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
23552 @node GDB/MI Target Manipulation
23553 @section @sc{gdb/mi} Target Manipulation Commands
23556 @subheading The @code{-target-attach} Command
23557 @findex -target-attach
23559 @subsubheading Synopsis
23562 -target-attach @var{pid} | @var{gid} | @var{file}
23565 Attach to a process @var{pid} or a file @var{file} outside of
23566 @value{GDBN}, or a thread group @var{gid}. If attaching to a thread
23567 group, the id previously returned by
23568 @samp{-list-thread-groups --available} must be used.
23570 @subsubheading @value{GDBN} Command
23572 The corresponding @value{GDBN} command is @samp{attach}.
23574 @subsubheading Example
23578 =thread-created,id="1"
23579 *stopped,thread-id="1",frame=@{addr="0xb7f7e410",func="bar",args=[]@}
23584 @subheading The @code{-target-compare-sections} Command
23585 @findex -target-compare-sections
23587 @subsubheading Synopsis
23590 -target-compare-sections [ @var{section} ]
23593 Compare data of section @var{section} on target to the exec file.
23594 Without the argument, all sections are compared.
23596 @subsubheading @value{GDBN} Command
23598 The @value{GDBN} equivalent is @samp{compare-sections}.
23600 @subsubheading Example
23604 @subheading The @code{-target-detach} Command
23605 @findex -target-detach
23607 @subsubheading Synopsis
23610 -target-detach [ @var{pid} | @var{gid} ]
23613 Detach from the remote target which normally resumes its execution.
23614 If either @var{pid} or @var{gid} is specified, detaches from either
23615 the specified process, or specified thread group. There's no output.
23617 @subsubheading @value{GDBN} Command
23619 The corresponding @value{GDBN} command is @samp{detach}.
23621 @subsubheading Example
23631 @subheading The @code{-target-disconnect} Command
23632 @findex -target-disconnect
23634 @subsubheading Synopsis
23640 Disconnect from the remote target. There's no output and the target is
23641 generally not resumed.
23643 @subsubheading @value{GDBN} Command
23645 The corresponding @value{GDBN} command is @samp{disconnect}.
23647 @subsubheading Example
23657 @subheading The @code{-target-download} Command
23658 @findex -target-download
23660 @subsubheading Synopsis
23666 Loads the executable onto the remote target.
23667 It prints out an update message every half second, which includes the fields:
23671 The name of the section.
23673 The size of what has been sent so far for that section.
23675 The size of the section.
23677 The total size of what was sent so far (the current and the previous sections).
23679 The size of the overall executable to download.
23683 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
23684 @sc{gdb/mi} Output Syntax}).
23686 In addition, it prints the name and size of the sections, as they are
23687 downloaded. These messages include the following fields:
23691 The name of the section.
23693 The size of the section.
23695 The size of the overall executable to download.
23699 At the end, a summary is printed.
23701 @subsubheading @value{GDBN} Command
23703 The corresponding @value{GDBN} command is @samp{load}.
23705 @subsubheading Example
23707 Note: each status message appears on a single line. Here the messages
23708 have been broken down so that they can fit onto a page.
23713 +download,@{section=".text",section-size="6668",total-size="9880"@}
23714 +download,@{section=".text",section-sent="512",section-size="6668",
23715 total-sent="512",total-size="9880"@}
23716 +download,@{section=".text",section-sent="1024",section-size="6668",
23717 total-sent="1024",total-size="9880"@}
23718 +download,@{section=".text",section-sent="1536",section-size="6668",
23719 total-sent="1536",total-size="9880"@}
23720 +download,@{section=".text",section-sent="2048",section-size="6668",
23721 total-sent="2048",total-size="9880"@}
23722 +download,@{section=".text",section-sent="2560",section-size="6668",
23723 total-sent="2560",total-size="9880"@}
23724 +download,@{section=".text",section-sent="3072",section-size="6668",
23725 total-sent="3072",total-size="9880"@}
23726 +download,@{section=".text",section-sent="3584",section-size="6668",
23727 total-sent="3584",total-size="9880"@}
23728 +download,@{section=".text",section-sent="4096",section-size="6668",
23729 total-sent="4096",total-size="9880"@}
23730 +download,@{section=".text",section-sent="4608",section-size="6668",
23731 total-sent="4608",total-size="9880"@}
23732 +download,@{section=".text",section-sent="5120",section-size="6668",
23733 total-sent="5120",total-size="9880"@}
23734 +download,@{section=".text",section-sent="5632",section-size="6668",
23735 total-sent="5632",total-size="9880"@}
23736 +download,@{section=".text",section-sent="6144",section-size="6668",
23737 total-sent="6144",total-size="9880"@}
23738 +download,@{section=".text",section-sent="6656",section-size="6668",
23739 total-sent="6656",total-size="9880"@}
23740 +download,@{section=".init",section-size="28",total-size="9880"@}
23741 +download,@{section=".fini",section-size="28",total-size="9880"@}
23742 +download,@{section=".data",section-size="3156",total-size="9880"@}
23743 +download,@{section=".data",section-sent="512",section-size="3156",
23744 total-sent="7236",total-size="9880"@}
23745 +download,@{section=".data",section-sent="1024",section-size="3156",
23746 total-sent="7748",total-size="9880"@}
23747 +download,@{section=".data",section-sent="1536",section-size="3156",
23748 total-sent="8260",total-size="9880"@}
23749 +download,@{section=".data",section-sent="2048",section-size="3156",
23750 total-sent="8772",total-size="9880"@}
23751 +download,@{section=".data",section-sent="2560",section-size="3156",
23752 total-sent="9284",total-size="9880"@}
23753 +download,@{section=".data",section-sent="3072",section-size="3156",
23754 total-sent="9796",total-size="9880"@}
23755 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
23761 @subheading The @code{-target-exec-status} Command
23762 @findex -target-exec-status
23764 @subsubheading Synopsis
23767 -target-exec-status
23770 Provide information on the state of the target (whether it is running or
23771 not, for instance).
23773 @subsubheading @value{GDBN} Command
23775 There's no equivalent @value{GDBN} command.
23777 @subsubheading Example
23781 @subheading The @code{-target-list-available-targets} Command
23782 @findex -target-list-available-targets
23784 @subsubheading Synopsis
23787 -target-list-available-targets
23790 List the possible targets to connect to.
23792 @subsubheading @value{GDBN} Command
23794 The corresponding @value{GDBN} command is @samp{help target}.
23796 @subsubheading Example
23800 @subheading The @code{-target-list-current-targets} Command
23801 @findex -target-list-current-targets
23803 @subsubheading Synopsis
23806 -target-list-current-targets
23809 Describe the current target.
23811 @subsubheading @value{GDBN} Command
23813 The corresponding information is printed by @samp{info file} (among
23816 @subsubheading Example
23820 @subheading The @code{-target-list-parameters} Command
23821 @findex -target-list-parameters
23823 @subsubheading Synopsis
23826 -target-list-parameters
23831 @subsubheading @value{GDBN} Command
23835 @subsubheading Example
23839 @subheading The @code{-target-select} Command
23840 @findex -target-select
23842 @subsubheading Synopsis
23845 -target-select @var{type} @var{parameters @dots{}}
23848 Connect @value{GDBN} to the remote target. This command takes two args:
23852 The type of target, for instance @samp{remote}, etc.
23853 @item @var{parameters}
23854 Device names, host names and the like. @xref{Target Commands, ,
23855 Commands for Managing Targets}, for more details.
23858 The output is a connection notification, followed by the address at
23859 which the target program is, in the following form:
23862 ^connected,addr="@var{address}",func="@var{function name}",
23863 args=[@var{arg list}]
23866 @subsubheading @value{GDBN} Command
23868 The corresponding @value{GDBN} command is @samp{target}.
23870 @subsubheading Example
23874 -target-select remote /dev/ttya
23875 ^connected,addr="0xfe00a300",func="??",args=[]
23879 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
23880 @node GDB/MI File Transfer Commands
23881 @section @sc{gdb/mi} File Transfer Commands
23884 @subheading The @code{-target-file-put} Command
23885 @findex -target-file-put
23887 @subsubheading Synopsis
23890 -target-file-put @var{hostfile} @var{targetfile}
23893 Copy file @var{hostfile} from the host system (the machine running
23894 @value{GDBN}) to @var{targetfile} on the target system.
23896 @subsubheading @value{GDBN} Command
23898 The corresponding @value{GDBN} command is @samp{remote put}.
23900 @subsubheading Example
23904 -target-file-put localfile remotefile
23910 @subheading The @code{-target-file-get} Command
23911 @findex -target-file-get
23913 @subsubheading Synopsis
23916 -target-file-get @var{targetfile} @var{hostfile}
23919 Copy file @var{targetfile} from the target system to @var{hostfile}
23920 on the host system.
23922 @subsubheading @value{GDBN} Command
23924 The corresponding @value{GDBN} command is @samp{remote get}.
23926 @subsubheading Example
23930 -target-file-get remotefile localfile
23936 @subheading The @code{-target-file-delete} Command
23937 @findex -target-file-delete
23939 @subsubheading Synopsis
23942 -target-file-delete @var{targetfile}
23945 Delete @var{targetfile} from the target system.
23947 @subsubheading @value{GDBN} Command
23949 The corresponding @value{GDBN} command is @samp{remote delete}.
23951 @subsubheading Example
23955 -target-file-delete remotefile
23961 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
23962 @node GDB/MI Miscellaneous Commands
23963 @section Miscellaneous @sc{gdb/mi} Commands
23965 @c @subheading -gdb-complete
23967 @subheading The @code{-gdb-exit} Command
23970 @subsubheading Synopsis
23976 Exit @value{GDBN} immediately.
23978 @subsubheading @value{GDBN} Command
23980 Approximately corresponds to @samp{quit}.
23982 @subsubheading Example
23991 @subheading The @code{-exec-abort} Command
23992 @findex -exec-abort
23994 @subsubheading Synopsis
24000 Kill the inferior running program.
24002 @subsubheading @value{GDBN} Command
24004 The corresponding @value{GDBN} command is @samp{kill}.
24006 @subsubheading Example
24010 @subheading The @code{-gdb-set} Command
24013 @subsubheading Synopsis
24019 Set an internal @value{GDBN} variable.
24020 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
24022 @subsubheading @value{GDBN} Command
24024 The corresponding @value{GDBN} command is @samp{set}.
24026 @subsubheading Example
24036 @subheading The @code{-gdb-show} Command
24039 @subsubheading Synopsis
24045 Show the current value of a @value{GDBN} variable.
24047 @subsubheading @value{GDBN} Command
24049 The corresponding @value{GDBN} command is @samp{show}.
24051 @subsubheading Example
24060 @c @subheading -gdb-source
24063 @subheading The @code{-gdb-version} Command
24064 @findex -gdb-version
24066 @subsubheading Synopsis
24072 Show version information for @value{GDBN}. Used mostly in testing.
24074 @subsubheading @value{GDBN} Command
24076 The @value{GDBN} equivalent is @samp{show version}. @value{GDBN} by
24077 default shows this information when you start an interactive session.
24079 @subsubheading Example
24081 @c This example modifies the actual output from GDB to avoid overfull
24087 ~Copyright 2000 Free Software Foundation, Inc.
24088 ~GDB is free software, covered by the GNU General Public License, and
24089 ~you are welcome to change it and/or distribute copies of it under
24090 ~ certain conditions.
24091 ~Type "show copying" to see the conditions.
24092 ~There is absolutely no warranty for GDB. Type "show warranty" for
24094 ~This GDB was configured as
24095 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
24100 @subheading The @code{-list-features} Command
24101 @findex -list-features
24103 Returns a list of particular features of the MI protocol that
24104 this version of gdb implements. A feature can be a command,
24105 or a new field in an output of some command, or even an
24106 important bugfix. While a frontend can sometimes detect presence
24107 of a feature at runtime, it is easier to perform detection at debugger
24110 The command returns a list of strings, with each string naming an
24111 available feature. Each returned string is just a name, it does not
24112 have any internal structure. The list of possible feature names
24118 (gdb) -list-features
24119 ^done,result=["feature1","feature2"]
24122 The current list of features is:
24125 @item frozen-varobjs
24126 Indicates presence of the @code{-var-set-frozen} command, as well
24127 as possible presense of the @code{frozen} field in the output
24128 of @code{-varobj-create}.
24129 @item pending-breakpoints
24130 Indicates presence of the @option{-f} option to the @code{-break-insert} command.
24132 Indicates presence of the @code{-thread-info} command.
24136 @subheading The @code{-list-target-features} Command
24137 @findex -list-target-features
24139 Returns a list of particular features that are supported by the
24140 target. Those features affect the permitted MI commands, but
24141 unlike the features reported by the @code{-list-features} command, the
24142 features depend on which target GDB is using at the moment. Whenever
24143 a target can change, due to commands such as @code{-target-select},
24144 @code{-target-attach} or @code{-exec-run}, the list of target features
24145 may change, and the frontend should obtain it again.
24149 (gdb) -list-features
24150 ^done,result=["async"]
24153 The current list of features is:
24157 Indicates that the target is capable of asynchronous command
24158 execution, which means that @value{GDBN} will accept further commands
24159 while the target is running.
24163 @subheading The @code{-list-thread-groups} Command
24164 @findex -list-thread-groups
24166 @subheading Synopsis
24169 -list-thread-groups [ --available ] [ @var{group} ]
24172 When used without the @var{group} parameter, lists top-level thread
24173 groups that are being debugged. When used with the @var{group}
24174 parameter, the children of the specified group are listed. The
24175 children can be either threads, or other groups. At present,
24176 @value{GDBN} will not report both threads and groups as children at
24177 the same time, but it may change in future.
24179 With the @samp{--available} option, instead of reporting groups that
24180 are been debugged, GDB will report all thread groups available on the
24181 target. Using the @samp{--available} option together with @var{group}
24184 @subheading Example
24188 -list-thread-groups
24189 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2"@}]
24190 -list-thread-groups 17
24191 ^done,threads=[@{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
24192 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},state="running"@},
24193 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
24194 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
24195 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},state="running"@}]]
24198 @subheading The @code{-interpreter-exec} Command
24199 @findex -interpreter-exec
24201 @subheading Synopsis
24204 -interpreter-exec @var{interpreter} @var{command}
24206 @anchor{-interpreter-exec}
24208 Execute the specified @var{command} in the given @var{interpreter}.
24210 @subheading @value{GDBN} Command
24212 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
24214 @subheading Example
24218 -interpreter-exec console "break main"
24219 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
24220 &"During symbol reading, bad structure-type format.\n"
24221 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
24226 @subheading The @code{-inferior-tty-set} Command
24227 @findex -inferior-tty-set
24229 @subheading Synopsis
24232 -inferior-tty-set /dev/pts/1
24235 Set terminal for future runs of the program being debugged.
24237 @subheading @value{GDBN} Command
24239 The corresponding @value{GDBN} command is @samp{set inferior-tty} /dev/pts/1.
24241 @subheading Example
24245 -inferior-tty-set /dev/pts/1
24250 @subheading The @code{-inferior-tty-show} Command
24251 @findex -inferior-tty-show
24253 @subheading Synopsis
24259 Show terminal for future runs of program being debugged.
24261 @subheading @value{GDBN} Command
24263 The corresponding @value{GDBN} command is @samp{show inferior-tty}.
24265 @subheading Example
24269 -inferior-tty-set /dev/pts/1
24273 ^done,inferior_tty_terminal="/dev/pts/1"
24277 @subheading The @code{-enable-timings} Command
24278 @findex -enable-timings
24280 @subheading Synopsis
24283 -enable-timings [yes | no]
24286 Toggle the printing of the wallclock, user and system times for an MI
24287 command as a field in its output. This command is to help frontend
24288 developers optimize the performance of their code. No argument is
24289 equivalent to @samp{yes}.
24291 @subheading @value{GDBN} Command
24295 @subheading Example
24303 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
24304 addr="0x080484ed",func="main",file="myprog.c",
24305 fullname="/home/nickrob/myprog.c",line="73",times="0"@},
24306 time=@{wallclock="0.05185",user="0.00800",system="0.00000"@}
24314 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
24315 frame=@{addr="0x080484ed",func="main",args=[@{name="argc",value="1"@},
24316 @{name="argv",value="0xbfb60364"@}],file="myprog.c",
24317 fullname="/home/nickrob/myprog.c",line="73"@}
24322 @chapter @value{GDBN} Annotations
24324 This chapter describes annotations in @value{GDBN}. Annotations were
24325 designed to interface @value{GDBN} to graphical user interfaces or other
24326 similar programs which want to interact with @value{GDBN} at a
24327 relatively high level.
24329 The annotation mechanism has largely been superseded by @sc{gdb/mi}
24333 This is Edition @value{EDITION}, @value{DATE}.
24337 * Annotations Overview:: What annotations are; the general syntax.
24338 * Server Prefix:: Issuing a command without affecting user state.
24339 * Prompting:: Annotations marking @value{GDBN}'s need for input.
24340 * Errors:: Annotations for error messages.
24341 * Invalidation:: Some annotations describe things now invalid.
24342 * Annotations for Running::
24343 Whether the program is running, how it stopped, etc.
24344 * Source Annotations:: Annotations describing source code.
24347 @node Annotations Overview
24348 @section What is an Annotation?
24349 @cindex annotations
24351 Annotations start with a newline character, two @samp{control-z}
24352 characters, and the name of the annotation. If there is no additional
24353 information associated with this annotation, the name of the annotation
24354 is followed immediately by a newline. If there is additional
24355 information, the name of the annotation is followed by a space, the
24356 additional information, and a newline. The additional information
24357 cannot contain newline characters.
24359 Any output not beginning with a newline and two @samp{control-z}
24360 characters denotes literal output from @value{GDBN}. Currently there is
24361 no need for @value{GDBN} to output a newline followed by two
24362 @samp{control-z} characters, but if there was such a need, the
24363 annotations could be extended with an @samp{escape} annotation which
24364 means those three characters as output.
24366 The annotation @var{level}, which is specified using the
24367 @option{--annotate} command line option (@pxref{Mode Options}), controls
24368 how much information @value{GDBN} prints together with its prompt,
24369 values of expressions, source lines, and other types of output. Level 0
24370 is for no annotations, level 1 is for use when @value{GDBN} is run as a
24371 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
24372 for programs that control @value{GDBN}, and level 2 annotations have
24373 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
24374 Interface, annotate, GDB's Obsolete Annotations}).
24377 @kindex set annotate
24378 @item set annotate @var{level}
24379 The @value{GDBN} command @code{set annotate} sets the level of
24380 annotations to the specified @var{level}.
24382 @item show annotate
24383 @kindex show annotate
24384 Show the current annotation level.
24387 This chapter describes level 3 annotations.
24389 A simple example of starting up @value{GDBN} with annotations is:
24392 $ @kbd{gdb --annotate=3}
24394 Copyright 2003 Free Software Foundation, Inc.
24395 GDB is free software, covered by the GNU General Public License,
24396 and you are welcome to change it and/or distribute copies of it
24397 under certain conditions.
24398 Type "show copying" to see the conditions.
24399 There is absolutely no warranty for GDB. Type "show warranty"
24401 This GDB was configured as "i386-pc-linux-gnu"
24412 Here @samp{quit} is input to @value{GDBN}; the rest is output from
24413 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
24414 denotes a @samp{control-z} character) are annotations; the rest is
24415 output from @value{GDBN}.
24417 @node Server Prefix
24418 @section The Server Prefix
24419 @cindex server prefix
24421 If you prefix a command with @samp{server } then it will not affect
24422 the command history, nor will it affect @value{GDBN}'s notion of which
24423 command to repeat if @key{RET} is pressed on a line by itself. This
24424 means that commands can be run behind a user's back by a front-end in
24425 a transparent manner.
24427 The server prefix does not affect the recording of values into the value
24428 history; to print a value without recording it into the value history,
24429 use the @code{output} command instead of the @code{print} command.
24432 @section Annotation for @value{GDBN} Input
24434 @cindex annotations for prompts
24435 When @value{GDBN} prompts for input, it annotates this fact so it is possible
24436 to know when to send output, when the output from a given command is
24439 Different kinds of input each have a different @dfn{input type}. Each
24440 input type has three annotations: a @code{pre-} annotation, which
24441 denotes the beginning of any prompt which is being output, a plain
24442 annotation, which denotes the end of the prompt, and then a @code{post-}
24443 annotation which denotes the end of any echo which may (or may not) be
24444 associated with the input. For example, the @code{prompt} input type
24445 features the following annotations:
24453 The input types are
24456 @findex pre-prompt annotation
24457 @findex prompt annotation
24458 @findex post-prompt annotation
24460 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
24462 @findex pre-commands annotation
24463 @findex commands annotation
24464 @findex post-commands annotation
24466 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
24467 command. The annotations are repeated for each command which is input.
24469 @findex pre-overload-choice annotation
24470 @findex overload-choice annotation
24471 @findex post-overload-choice annotation
24472 @item overload-choice
24473 When @value{GDBN} wants the user to select between various overloaded functions.
24475 @findex pre-query annotation
24476 @findex query annotation
24477 @findex post-query annotation
24479 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
24481 @findex pre-prompt-for-continue annotation
24482 @findex prompt-for-continue annotation
24483 @findex post-prompt-for-continue annotation
24484 @item prompt-for-continue
24485 When @value{GDBN} is asking the user to press return to continue. Note: Don't
24486 expect this to work well; instead use @code{set height 0} to disable
24487 prompting. This is because the counting of lines is buggy in the
24488 presence of annotations.
24493 @cindex annotations for errors, warnings and interrupts
24495 @findex quit annotation
24500 This annotation occurs right before @value{GDBN} responds to an interrupt.
24502 @findex error annotation
24507 This annotation occurs right before @value{GDBN} responds to an error.
24509 Quit and error annotations indicate that any annotations which @value{GDBN} was
24510 in the middle of may end abruptly. For example, if a
24511 @code{value-history-begin} annotation is followed by a @code{error}, one
24512 cannot expect to receive the matching @code{value-history-end}. One
24513 cannot expect not to receive it either, however; an error annotation
24514 does not necessarily mean that @value{GDBN} is immediately returning all the way
24517 @findex error-begin annotation
24518 A quit or error annotation may be preceded by
24524 Any output between that and the quit or error annotation is the error
24527 Warning messages are not yet annotated.
24528 @c If we want to change that, need to fix warning(), type_error(),
24529 @c range_error(), and possibly other places.
24532 @section Invalidation Notices
24534 @cindex annotations for invalidation messages
24535 The following annotations say that certain pieces of state may have
24539 @findex frames-invalid annotation
24540 @item ^Z^Zframes-invalid
24542 The frames (for example, output from the @code{backtrace} command) may
24545 @findex breakpoints-invalid annotation
24546 @item ^Z^Zbreakpoints-invalid
24548 The breakpoints may have changed. For example, the user just added or
24549 deleted a breakpoint.
24552 @node Annotations for Running
24553 @section Running the Program
24554 @cindex annotations for running programs
24556 @findex starting annotation
24557 @findex stopping annotation
24558 When the program starts executing due to a @value{GDBN} command such as
24559 @code{step} or @code{continue},
24565 is output. When the program stops,
24571 is output. Before the @code{stopped} annotation, a variety of
24572 annotations describe how the program stopped.
24575 @findex exited annotation
24576 @item ^Z^Zexited @var{exit-status}
24577 The program exited, and @var{exit-status} is the exit status (zero for
24578 successful exit, otherwise nonzero).
24580 @findex signalled annotation
24581 @findex signal-name annotation
24582 @findex signal-name-end annotation
24583 @findex signal-string annotation
24584 @findex signal-string-end annotation
24585 @item ^Z^Zsignalled
24586 The program exited with a signal. After the @code{^Z^Zsignalled}, the
24587 annotation continues:
24593 ^Z^Zsignal-name-end
24597 ^Z^Zsignal-string-end
24602 where @var{name} is the name of the signal, such as @code{SIGILL} or
24603 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
24604 as @code{Illegal Instruction} or @code{Segmentation fault}.
24605 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
24606 user's benefit and have no particular format.
24608 @findex signal annotation
24610 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
24611 just saying that the program received the signal, not that it was
24612 terminated with it.
24614 @findex breakpoint annotation
24615 @item ^Z^Zbreakpoint @var{number}
24616 The program hit breakpoint number @var{number}.
24618 @findex watchpoint annotation
24619 @item ^Z^Zwatchpoint @var{number}
24620 The program hit watchpoint number @var{number}.
24623 @node Source Annotations
24624 @section Displaying Source
24625 @cindex annotations for source display
24627 @findex source annotation
24628 The following annotation is used instead of displaying source code:
24631 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
24634 where @var{filename} is an absolute file name indicating which source
24635 file, @var{line} is the line number within that file (where 1 is the
24636 first line in the file), @var{character} is the character position
24637 within the file (where 0 is the first character in the file) (for most
24638 debug formats this will necessarily point to the beginning of a line),
24639 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
24640 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
24641 @var{addr} is the address in the target program associated with the
24642 source which is being displayed. @var{addr} is in the form @samp{0x}
24643 followed by one or more lowercase hex digits (note that this does not
24644 depend on the language).
24647 @chapter Reporting Bugs in @value{GDBN}
24648 @cindex bugs in @value{GDBN}
24649 @cindex reporting bugs in @value{GDBN}
24651 Your bug reports play an essential role in making @value{GDBN} reliable.
24653 Reporting a bug may help you by bringing a solution to your problem, or it
24654 may not. But in any case the principal function of a bug report is to help
24655 the entire community by making the next version of @value{GDBN} work better. Bug
24656 reports are your contribution to the maintenance of @value{GDBN}.
24658 In order for a bug report to serve its purpose, you must include the
24659 information that enables us to fix the bug.
24662 * Bug Criteria:: Have you found a bug?
24663 * Bug Reporting:: How to report bugs
24667 @section Have You Found a Bug?
24668 @cindex bug criteria
24670 If you are not sure whether you have found a bug, here are some guidelines:
24673 @cindex fatal signal
24674 @cindex debugger crash
24675 @cindex crash of debugger
24677 If the debugger gets a fatal signal, for any input whatever, that is a
24678 @value{GDBN} bug. Reliable debuggers never crash.
24680 @cindex error on valid input
24682 If @value{GDBN} produces an error message for valid input, that is a
24683 bug. (Note that if you're cross debugging, the problem may also be
24684 somewhere in the connection to the target.)
24686 @cindex invalid input
24688 If @value{GDBN} does not produce an error message for invalid input,
24689 that is a bug. However, you should note that your idea of
24690 ``invalid input'' might be our idea of ``an extension'' or ``support
24691 for traditional practice''.
24694 If you are an experienced user of debugging tools, your suggestions
24695 for improvement of @value{GDBN} are welcome in any case.
24698 @node Bug Reporting
24699 @section How to Report Bugs
24700 @cindex bug reports
24701 @cindex @value{GDBN} bugs, reporting
24703 A number of companies and individuals offer support for @sc{gnu} products.
24704 If you obtained @value{GDBN} from a support organization, we recommend you
24705 contact that organization first.
24707 You can find contact information for many support companies and
24708 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
24710 @c should add a web page ref...
24713 @ifset BUGURL_DEFAULT
24714 In any event, we also recommend that you submit bug reports for
24715 @value{GDBN}. The preferred method is to submit them directly using
24716 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
24717 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
24720 @strong{Do not send bug reports to @samp{info-gdb}, or to
24721 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
24722 not want to receive bug reports. Those that do have arranged to receive
24725 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
24726 serves as a repeater. The mailing list and the newsgroup carry exactly
24727 the same messages. Often people think of posting bug reports to the
24728 newsgroup instead of mailing them. This appears to work, but it has one
24729 problem which can be crucial: a newsgroup posting often lacks a mail
24730 path back to the sender. Thus, if we need to ask for more information,
24731 we may be unable to reach you. For this reason, it is better to send
24732 bug reports to the mailing list.
24734 @ifclear BUGURL_DEFAULT
24735 In any event, we also recommend that you submit bug reports for
24736 @value{GDBN} to @value{BUGURL}.
24740 The fundamental principle of reporting bugs usefully is this:
24741 @strong{report all the facts}. If you are not sure whether to state a
24742 fact or leave it out, state it!
24744 Often people omit facts because they think they know what causes the
24745 problem and assume that some details do not matter. Thus, you might
24746 assume that the name of the variable you use in an example does not matter.
24747 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
24748 stray memory reference which happens to fetch from the location where that
24749 name is stored in memory; perhaps, if the name were different, the contents
24750 of that location would fool the debugger into doing the right thing despite
24751 the bug. Play it safe and give a specific, complete example. That is the
24752 easiest thing for you to do, and the most helpful.
24754 Keep in mind that the purpose of a bug report is to enable us to fix the
24755 bug. It may be that the bug has been reported previously, but neither
24756 you nor we can know that unless your bug report is complete and
24759 Sometimes people give a few sketchy facts and ask, ``Does this ring a
24760 bell?'' Those bug reports are useless, and we urge everyone to
24761 @emph{refuse to respond to them} except to chide the sender to report
24764 To enable us to fix the bug, you should include all these things:
24768 The version of @value{GDBN}. @value{GDBN} announces it if you start
24769 with no arguments; you can also print it at any time using @code{show
24772 Without this, we will not know whether there is any point in looking for
24773 the bug in the current version of @value{GDBN}.
24776 The type of machine you are using, and the operating system name and
24780 What compiler (and its version) was used to compile @value{GDBN}---e.g.@:
24781 ``@value{GCC}--2.8.1''.
24784 What compiler (and its version) was used to compile the program you are
24785 debugging---e.g.@: ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
24786 C Compiler''. For @value{NGCC}, you can say @kbd{@value{GCC} --version}
24787 to get this information; for other compilers, see the documentation for
24791 The command arguments you gave the compiler to compile your example and
24792 observe the bug. For example, did you use @samp{-O}? To guarantee
24793 you will not omit something important, list them all. A copy of the
24794 Makefile (or the output from make) is sufficient.
24796 If we were to try to guess the arguments, we would probably guess wrong
24797 and then we might not encounter the bug.
24800 A complete input script, and all necessary source files, that will
24804 A description of what behavior you observe that you believe is
24805 incorrect. For example, ``It gets a fatal signal.''
24807 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
24808 will certainly notice it. But if the bug is incorrect output, we might
24809 not notice unless it is glaringly wrong. You might as well not give us
24810 a chance to make a mistake.
24812 Even if the problem you experience is a fatal signal, you should still
24813 say so explicitly. Suppose something strange is going on, such as, your
24814 copy of @value{GDBN} is out of synch, or you have encountered a bug in
24815 the C library on your system. (This has happened!) Your copy might
24816 crash and ours would not. If you told us to expect a crash, then when
24817 ours fails to crash, we would know that the bug was not happening for
24818 us. If you had not told us to expect a crash, then we would not be able
24819 to draw any conclusion from our observations.
24822 @cindex recording a session script
24823 To collect all this information, you can use a session recording program
24824 such as @command{script}, which is available on many Unix systems.
24825 Just run your @value{GDBN} session inside @command{script} and then
24826 include the @file{typescript} file with your bug report.
24828 Another way to record a @value{GDBN} session is to run @value{GDBN}
24829 inside Emacs and then save the entire buffer to a file.
24832 If you wish to suggest changes to the @value{GDBN} source, send us context
24833 diffs. If you even discuss something in the @value{GDBN} source, refer to
24834 it by context, not by line number.
24836 The line numbers in our development sources will not match those in your
24837 sources. Your line numbers would convey no useful information to us.
24841 Here are some things that are not necessary:
24845 A description of the envelope of the bug.
24847 Often people who encounter a bug spend a lot of time investigating
24848 which changes to the input file will make the bug go away and which
24849 changes will not affect it.
24851 This is often time consuming and not very useful, because the way we
24852 will find the bug is by running a single example under the debugger
24853 with breakpoints, not by pure deduction from a series of examples.
24854 We recommend that you save your time for something else.
24856 Of course, if you can find a simpler example to report @emph{instead}
24857 of the original one, that is a convenience for us. Errors in the
24858 output will be easier to spot, running under the debugger will take
24859 less time, and so on.
24861 However, simplification is not vital; if you do not want to do this,
24862 report the bug anyway and send us the entire test case you used.
24865 A patch for the bug.
24867 A patch for the bug does help us if it is a good one. But do not omit
24868 the necessary information, such as the test case, on the assumption that
24869 a patch is all we need. We might see problems with your patch and decide
24870 to fix the problem another way, or we might not understand it at all.
24872 Sometimes with a program as complicated as @value{GDBN} it is very hard to
24873 construct an example that will make the program follow a certain path
24874 through the code. If you do not send us the example, we will not be able
24875 to construct one, so we will not be able to verify that the bug is fixed.
24877 And if we cannot understand what bug you are trying to fix, or why your
24878 patch should be an improvement, we will not install it. A test case will
24879 help us to understand.
24882 A guess about what the bug is or what it depends on.
24884 Such guesses are usually wrong. Even we cannot guess right about such
24885 things without first using the debugger to find the facts.
24888 @c The readline documentation is distributed with the readline code
24889 @c and consists of the two following files:
24891 @c inc-hist.texinfo
24892 @c Use -I with makeinfo to point to the appropriate directory,
24893 @c environment var TEXINPUTS with TeX.
24894 @include rluser.texi
24895 @include inc-hist.texinfo
24898 @node Formatting Documentation
24899 @appendix Formatting Documentation
24901 @cindex @value{GDBN} reference card
24902 @cindex reference card
24903 The @value{GDBN} 4 release includes an already-formatted reference card, ready
24904 for printing with PostScript or Ghostscript, in the @file{gdb}
24905 subdirectory of the main source directory@footnote{In
24906 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
24907 release.}. If you can use PostScript or Ghostscript with your printer,
24908 you can print the reference card immediately with @file{refcard.ps}.
24910 The release also includes the source for the reference card. You
24911 can format it, using @TeX{}, by typing:
24917 The @value{GDBN} reference card is designed to print in @dfn{landscape}
24918 mode on US ``letter'' size paper;
24919 that is, on a sheet 11 inches wide by 8.5 inches
24920 high. You will need to specify this form of printing as an option to
24921 your @sc{dvi} output program.
24923 @cindex documentation
24925 All the documentation for @value{GDBN} comes as part of the machine-readable
24926 distribution. The documentation is written in Texinfo format, which is
24927 a documentation system that uses a single source file to produce both
24928 on-line information and a printed manual. You can use one of the Info
24929 formatting commands to create the on-line version of the documentation
24930 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
24932 @value{GDBN} includes an already formatted copy of the on-line Info
24933 version of this manual in the @file{gdb} subdirectory. The main Info
24934 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
24935 subordinate files matching @samp{gdb.info*} in the same directory. If
24936 necessary, you can print out these files, or read them with any editor;
24937 but they are easier to read using the @code{info} subsystem in @sc{gnu}
24938 Emacs or the standalone @code{info} program, available as part of the
24939 @sc{gnu} Texinfo distribution.
24941 If you want to format these Info files yourself, you need one of the
24942 Info formatting programs, such as @code{texinfo-format-buffer} or
24945 If you have @code{makeinfo} installed, and are in the top level
24946 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
24947 version @value{GDBVN}), you can make the Info file by typing:
24954 If you want to typeset and print copies of this manual, you need @TeX{},
24955 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
24956 Texinfo definitions file.
24958 @TeX{} is a typesetting program; it does not print files directly, but
24959 produces output files called @sc{dvi} files. To print a typeset
24960 document, you need a program to print @sc{dvi} files. If your system
24961 has @TeX{} installed, chances are it has such a program. The precise
24962 command to use depends on your system; @kbd{lpr -d} is common; another
24963 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
24964 require a file name without any extension or a @samp{.dvi} extension.
24966 @TeX{} also requires a macro definitions file called
24967 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
24968 written in Texinfo format. On its own, @TeX{} cannot either read or
24969 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
24970 and is located in the @file{gdb-@var{version-number}/texinfo}
24973 If you have @TeX{} and a @sc{dvi} printer program installed, you can
24974 typeset and print this manual. First switch to the @file{gdb}
24975 subdirectory of the main source directory (for example, to
24976 @file{gdb-@value{GDBVN}/gdb}) and type:
24982 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
24984 @node Installing GDB
24985 @appendix Installing @value{GDBN}
24986 @cindex installation
24989 * Requirements:: Requirements for building @value{GDBN}
24990 * Running Configure:: Invoking the @value{GDBN} @file{configure} script
24991 * Separate Objdir:: Compiling @value{GDBN} in another directory
24992 * Config Names:: Specifying names for hosts and targets
24993 * Configure Options:: Summary of options for configure
24994 * System-wide configuration:: Having a system-wide init file
24998 @section Requirements for Building @value{GDBN}
24999 @cindex building @value{GDBN}, requirements for
25001 Building @value{GDBN} requires various tools and packages to be available.
25002 Other packages will be used only if they are found.
25004 @heading Tools/Packages Necessary for Building @value{GDBN}
25006 @item ISO C90 compiler
25007 @value{GDBN} is written in ISO C90. It should be buildable with any
25008 working C90 compiler, e.g.@: GCC.
25012 @heading Tools/Packages Optional for Building @value{GDBN}
25016 @value{GDBN} can use the Expat XML parsing library. This library may be
25017 included with your operating system distribution; if it is not, you
25018 can get the latest version from @url{http://expat.sourceforge.net}.
25019 The @file{configure} script will search for this library in several
25020 standard locations; if it is installed in an unusual path, you can
25021 use the @option{--with-libexpat-prefix} option to specify its location.
25027 Remote protocol memory maps (@pxref{Memory Map Format})
25029 Target descriptions (@pxref{Target Descriptions})
25031 Remote shared library lists (@pxref{Library List Format})
25033 MS-Windows shared libraries (@pxref{Shared Libraries})
25037 @cindex compressed debug sections
25038 @value{GDBN} will use the @samp{zlib} library, if available, to read
25039 compressed debug sections. Some linkers, such as GNU gold, are capable
25040 of producing binaries with compressed debug sections. If @value{GDBN}
25041 is compiled with @samp{zlib}, it will be able to read the debug
25042 information in such binaries.
25044 The @samp{zlib} library is likely included with your operating system
25045 distribution; if it is not, you can get the latest version from
25046 @url{http://zlib.net}.
25049 @value{GDBN}'s features related to character sets (@pxref{Character
25050 Sets}) require a functioning @code{iconv} implementation. If you are
25051 on a GNU system, then this is provided by the GNU C Library. Some
25052 other systems also provide a working @code{iconv}.
25054 On systems with @code{iconv}, you can install GNU Libiconv. If you
25055 have previously installed Libiconv, you can use the
25056 @option{--with-libiconv-prefix} option to configure.
25058 @value{GDBN}'s top-level @file{configure} and @file{Makefile} will
25059 arrange to build Libiconv if a directory named @file{libiconv} appears
25060 in the top-most source directory. If Libiconv is built this way, and
25061 if the operating system does not provide a suitable @code{iconv}
25062 implementation, then the just-built library will automatically be used
25063 by @value{GDBN}. One easy way to set this up is to download GNU
25064 Libiconv, unpack it, and then rename the directory holding the
25065 Libiconv source code to @samp{libiconv}.
25068 @node Running Configure
25069 @section Invoking the @value{GDBN} @file{configure} Script
25070 @cindex configuring @value{GDBN}
25071 @value{GDBN} comes with a @file{configure} script that automates the process
25072 of preparing @value{GDBN} for installation; you can then use @code{make} to
25073 build the @code{gdb} program.
25075 @c irrelevant in info file; it's as current as the code it lives with.
25076 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
25077 look at the @file{README} file in the sources; we may have improved the
25078 installation procedures since publishing this manual.}
25081 The @value{GDBN} distribution includes all the source code you need for
25082 @value{GDBN} in a single directory, whose name is usually composed by
25083 appending the version number to @samp{gdb}.
25085 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
25086 @file{gdb-@value{GDBVN}} directory. That directory contains:
25089 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
25090 script for configuring @value{GDBN} and all its supporting libraries
25092 @item gdb-@value{GDBVN}/gdb
25093 the source specific to @value{GDBN} itself
25095 @item gdb-@value{GDBVN}/bfd
25096 source for the Binary File Descriptor library
25098 @item gdb-@value{GDBVN}/include
25099 @sc{gnu} include files
25101 @item gdb-@value{GDBVN}/libiberty
25102 source for the @samp{-liberty} free software library
25104 @item gdb-@value{GDBVN}/opcodes
25105 source for the library of opcode tables and disassemblers
25107 @item gdb-@value{GDBVN}/readline
25108 source for the @sc{gnu} command-line interface
25110 @item gdb-@value{GDBVN}/glob
25111 source for the @sc{gnu} filename pattern-matching subroutine
25113 @item gdb-@value{GDBVN}/mmalloc
25114 source for the @sc{gnu} memory-mapped malloc package
25117 The simplest way to configure and build @value{GDBN} is to run @file{configure}
25118 from the @file{gdb-@var{version-number}} source directory, which in
25119 this example is the @file{gdb-@value{GDBVN}} directory.
25121 First switch to the @file{gdb-@var{version-number}} source directory
25122 if you are not already in it; then run @file{configure}. Pass the
25123 identifier for the platform on which @value{GDBN} will run as an
25129 cd gdb-@value{GDBVN}
25130 ./configure @var{host}
25135 where @var{host} is an identifier such as @samp{sun4} or
25136 @samp{decstation}, that identifies the platform where @value{GDBN} will run.
25137 (You can often leave off @var{host}; @file{configure} tries to guess the
25138 correct value by examining your system.)
25140 Running @samp{configure @var{host}} and then running @code{make} builds the
25141 @file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty}
25142 libraries, then @code{gdb} itself. The configured source files, and the
25143 binaries, are left in the corresponding source directories.
25146 @file{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
25147 system does not recognize this automatically when you run a different
25148 shell, you may need to run @code{sh} on it explicitly:
25151 sh configure @var{host}
25154 If you run @file{configure} from a directory that contains source
25155 directories for multiple libraries or programs, such as the
25156 @file{gdb-@value{GDBVN}} source directory for version @value{GDBVN},
25158 creates configuration files for every directory level underneath (unless
25159 you tell it not to, with the @samp{--norecursion} option).
25161 You should run the @file{configure} script from the top directory in the
25162 source tree, the @file{gdb-@var{version-number}} directory. If you run
25163 @file{configure} from one of the subdirectories, you will configure only
25164 that subdirectory. That is usually not what you want. In particular,
25165 if you run the first @file{configure} from the @file{gdb} subdirectory
25166 of the @file{gdb-@var{version-number}} directory, you will omit the
25167 configuration of @file{bfd}, @file{readline}, and other sibling
25168 directories of the @file{gdb} subdirectory. This leads to build errors
25169 about missing include files such as @file{bfd/bfd.h}.
25171 You can install @code{@value{GDBP}} anywhere; it has no hardwired paths.
25172 However, you should make sure that the shell on your path (named by
25173 the @samp{SHELL} environment variable) is publicly readable. Remember
25174 that @value{GDBN} uses the shell to start your program---some systems refuse to
25175 let @value{GDBN} debug child processes whose programs are not readable.
25177 @node Separate Objdir
25178 @section Compiling @value{GDBN} in Another Directory
25180 If you want to run @value{GDBN} versions for several host or target machines,
25181 you need a different @code{gdb} compiled for each combination of
25182 host and target. @file{configure} is designed to make this easy by
25183 allowing you to generate each configuration in a separate subdirectory,
25184 rather than in the source directory. If your @code{make} program
25185 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
25186 @code{make} in each of these directories builds the @code{gdb}
25187 program specified there.
25189 To build @code{gdb} in a separate directory, run @file{configure}
25190 with the @samp{--srcdir} option to specify where to find the source.
25191 (You also need to specify a path to find @file{configure}
25192 itself from your working directory. If the path to @file{configure}
25193 would be the same as the argument to @samp{--srcdir}, you can leave out
25194 the @samp{--srcdir} option; it is assumed.)
25196 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
25197 separate directory for a Sun 4 like this:
25201 cd gdb-@value{GDBVN}
25204 ../gdb-@value{GDBVN}/configure sun4
25209 When @file{configure} builds a configuration using a remote source
25210 directory, it creates a tree for the binaries with the same structure
25211 (and using the same names) as the tree under the source directory. In
25212 the example, you'd find the Sun 4 library @file{libiberty.a} in the
25213 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
25214 @file{gdb-sun4/gdb}.
25216 Make sure that your path to the @file{configure} script has just one
25217 instance of @file{gdb} in it. If your path to @file{configure} looks
25218 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
25219 one subdirectory of @value{GDBN}, not the whole package. This leads to
25220 build errors about missing include files such as @file{bfd/bfd.h}.
25222 One popular reason to build several @value{GDBN} configurations in separate
25223 directories is to configure @value{GDBN} for cross-compiling (where
25224 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
25225 programs that run on another machine---the @dfn{target}).
25226 You specify a cross-debugging target by
25227 giving the @samp{--target=@var{target}} option to @file{configure}.
25229 When you run @code{make} to build a program or library, you must run
25230 it in a configured directory---whatever directory you were in when you
25231 called @file{configure} (or one of its subdirectories).
25233 The @code{Makefile} that @file{configure} generates in each source
25234 directory also runs recursively. If you type @code{make} in a source
25235 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
25236 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
25237 will build all the required libraries, and then build GDB.
25239 When you have multiple hosts or targets configured in separate
25240 directories, you can run @code{make} on them in parallel (for example,
25241 if they are NFS-mounted on each of the hosts); they will not interfere
25245 @section Specifying Names for Hosts and Targets
25247 The specifications used for hosts and targets in the @file{configure}
25248 script are based on a three-part naming scheme, but some short predefined
25249 aliases are also supported. The full naming scheme encodes three pieces
25250 of information in the following pattern:
25253 @var{architecture}-@var{vendor}-@var{os}
25256 For example, you can use the alias @code{sun4} as a @var{host} argument,
25257 or as the value for @var{target} in a @code{--target=@var{target}}
25258 option. The equivalent full name is @samp{sparc-sun-sunos4}.
25260 The @file{configure} script accompanying @value{GDBN} does not provide
25261 any query facility to list all supported host and target names or
25262 aliases. @file{configure} calls the Bourne shell script
25263 @code{config.sub} to map abbreviations to full names; you can read the
25264 script, if you wish, or you can use it to test your guesses on
25265 abbreviations---for example:
25268 % sh config.sub i386-linux
25270 % sh config.sub alpha-linux
25271 alpha-unknown-linux-gnu
25272 % sh config.sub hp9k700
25274 % sh config.sub sun4
25275 sparc-sun-sunos4.1.1
25276 % sh config.sub sun3
25277 m68k-sun-sunos4.1.1
25278 % sh config.sub i986v
25279 Invalid configuration `i986v': machine `i986v' not recognized
25283 @code{config.sub} is also distributed in the @value{GDBN} source
25284 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
25286 @node Configure Options
25287 @section @file{configure} Options
25289 Here is a summary of the @file{configure} options and arguments that
25290 are most often useful for building @value{GDBN}. @file{configure} also has
25291 several other options not listed here. @inforef{What Configure
25292 Does,,configure.info}, for a full explanation of @file{configure}.
25295 configure @r{[}--help@r{]}
25296 @r{[}--prefix=@var{dir}@r{]}
25297 @r{[}--exec-prefix=@var{dir}@r{]}
25298 @r{[}--srcdir=@var{dirname}@r{]}
25299 @r{[}--norecursion@r{]} @r{[}--rm@r{]}
25300 @r{[}--target=@var{target}@r{]}
25305 You may introduce options with a single @samp{-} rather than
25306 @samp{--} if you prefer; but you may abbreviate option names if you use
25311 Display a quick summary of how to invoke @file{configure}.
25313 @item --prefix=@var{dir}
25314 Configure the source to install programs and files under directory
25317 @item --exec-prefix=@var{dir}
25318 Configure the source to install programs under directory
25321 @c avoid splitting the warning from the explanation:
25323 @item --srcdir=@var{dirname}
25324 @strong{Warning: using this option requires @sc{gnu} @code{make}, or another
25325 @code{make} that implements the @code{VPATH} feature.}@*
25326 Use this option to make configurations in directories separate from the
25327 @value{GDBN} source directories. Among other things, you can use this to
25328 build (or maintain) several configurations simultaneously, in separate
25329 directories. @file{configure} writes configuration-specific files in
25330 the current directory, but arranges for them to use the source in the
25331 directory @var{dirname}. @file{configure} creates directories under
25332 the working directory in parallel to the source directories below
25335 @item --norecursion
25336 Configure only the directory level where @file{configure} is executed; do not
25337 propagate configuration to subdirectories.
25339 @item --target=@var{target}
25340 Configure @value{GDBN} for cross-debugging programs running on the specified
25341 @var{target}. Without this option, @value{GDBN} is configured to debug
25342 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
25344 There is no convenient way to generate a list of all available targets.
25346 @item @var{host} @dots{}
25347 Configure @value{GDBN} to run on the specified @var{host}.
25349 There is no convenient way to generate a list of all available hosts.
25352 There are many other options available as well, but they are generally
25353 needed for special purposes only.
25355 @node System-wide configuration
25356 @section System-wide configuration and settings
25357 @cindex system-wide init file
25359 @value{GDBN} can be configured to have a system-wide init file;
25360 this file will be read and executed at startup (@pxref{Startup, , What
25361 @value{GDBN} does during startup}).
25363 Here is the corresponding configure option:
25366 @item --with-system-gdbinit=@var{file}
25367 Specify that the default location of the system-wide init file is
25371 If @value{GDBN} has been configured with the option @option{--prefix=$prefix},
25372 it may be subject to relocation. Two possible cases:
25376 If the default location of this init file contains @file{$prefix},
25377 it will be subject to relocation. Suppose that the configure options
25378 are @option{--prefix=$prefix --with-system-gdbinit=$prefix/etc/gdbinit};
25379 if @value{GDBN} is moved from @file{$prefix} to @file{$install}, the system
25380 init file is looked for as @file{$install/etc/gdbinit} instead of
25381 @file{$prefix/etc/gdbinit}.
25384 By contrast, if the default location does not contain the prefix,
25385 it will not be relocated. E.g.@: if @value{GDBN} has been configured with
25386 @option{--prefix=/usr/local --with-system-gdbinit=/usr/share/gdb/gdbinit},
25387 then @value{GDBN} will always look for @file{/usr/share/gdb/gdbinit},
25388 wherever @value{GDBN} is installed.
25391 @node Maintenance Commands
25392 @appendix Maintenance Commands
25393 @cindex maintenance commands
25394 @cindex internal commands
25396 In addition to commands intended for @value{GDBN} users, @value{GDBN}
25397 includes a number of commands intended for @value{GDBN} developers,
25398 that are not documented elsewhere in this manual. These commands are
25399 provided here for reference. (For commands that turn on debugging
25400 messages, see @ref{Debugging Output}.)
25403 @kindex maint agent
25404 @item maint agent @var{expression}
25405 Translate the given @var{expression} into remote agent bytecodes.
25406 This command is useful for debugging the Agent Expression mechanism
25407 (@pxref{Agent Expressions}).
25409 @kindex maint info breakpoints
25410 @item @anchor{maint info breakpoints}maint info breakpoints
25411 Using the same format as @samp{info breakpoints}, display both the
25412 breakpoints you've set explicitly, and those @value{GDBN} is using for
25413 internal purposes. Internal breakpoints are shown with negative
25414 breakpoint numbers. The type column identifies what kind of breakpoint
25419 Normal, explicitly set breakpoint.
25422 Normal, explicitly set watchpoint.
25425 Internal breakpoint, used to handle correctly stepping through
25426 @code{longjmp} calls.
25428 @item longjmp resume
25429 Internal breakpoint at the target of a @code{longjmp}.
25432 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
25435 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
25438 Shared library events.
25442 @kindex set displaced-stepping
25443 @kindex show displaced-stepping
25444 @cindex displaced stepping support
25445 @cindex out-of-line single-stepping
25446 @item set displaced-stepping
25447 @itemx show displaced-stepping
25448 Control whether or not @value{GDBN} will do @dfn{displaced stepping}
25449 if the target supports it. Displaced stepping is a way to single-step
25450 over breakpoints without removing them from the inferior, by executing
25451 an out-of-line copy of the instruction that was originally at the
25452 breakpoint location. It is also known as out-of-line single-stepping.
25455 @item set displaced-stepping on
25456 If the target architecture supports it, @value{GDBN} will use
25457 displaced stepping to step over breakpoints.
25459 @item set displaced-stepping off
25460 @value{GDBN} will not use displaced stepping to step over breakpoints,
25461 even if such is supported by the target architecture.
25463 @cindex non-stop mode, and @samp{set displaced-stepping}
25464 @item set displaced-stepping auto
25465 This is the default mode. @value{GDBN} will use displaced stepping
25466 only if non-stop mode is active (@pxref{Non-Stop Mode}) and the target
25467 architecture supports displaced stepping.
25470 @kindex maint check-symtabs
25471 @item maint check-symtabs
25472 Check the consistency of psymtabs and symtabs.
25474 @kindex maint cplus first_component
25475 @item maint cplus first_component @var{name}
25476 Print the first C@t{++} class/namespace component of @var{name}.
25478 @kindex maint cplus namespace
25479 @item maint cplus namespace
25480 Print the list of possible C@t{++} namespaces.
25482 @kindex maint demangle
25483 @item maint demangle @var{name}
25484 Demangle a C@t{++} or Objective-C mangled @var{name}.
25486 @kindex maint deprecate
25487 @kindex maint undeprecate
25488 @cindex deprecated commands
25489 @item maint deprecate @var{command} @r{[}@var{replacement}@r{]}
25490 @itemx maint undeprecate @var{command}
25491 Deprecate or undeprecate the named @var{command}. Deprecated commands
25492 cause @value{GDBN} to issue a warning when you use them. The optional
25493 argument @var{replacement} says which newer command should be used in
25494 favor of the deprecated one; if it is given, @value{GDBN} will mention
25495 the replacement as part of the warning.
25497 @kindex maint dump-me
25498 @item maint dump-me
25499 @cindex @code{SIGQUIT} signal, dump core of @value{GDBN}
25500 Cause a fatal signal in the debugger and force it to dump its core.
25501 This is supported only on systems which support aborting a program
25502 with the @code{SIGQUIT} signal.
25504 @kindex maint internal-error
25505 @kindex maint internal-warning
25506 @item maint internal-error @r{[}@var{message-text}@r{]}
25507 @itemx maint internal-warning @r{[}@var{message-text}@r{]}
25508 Cause @value{GDBN} to call the internal function @code{internal_error}
25509 or @code{internal_warning} and hence behave as though an internal error
25510 or internal warning has been detected. In addition to reporting the
25511 internal problem, these functions give the user the opportunity to
25512 either quit @value{GDBN} or create a core file of the current
25513 @value{GDBN} session.
25515 These commands take an optional parameter @var{message-text} that is
25516 used as the text of the error or warning message.
25518 Here's an example of using @code{internal-error}:
25521 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
25522 @dots{}/maint.c:121: internal-error: testing, 1, 2
25523 A problem internal to GDB has been detected. Further
25524 debugging may prove unreliable.
25525 Quit this debugging session? (y or n) @kbd{n}
25526 Create a core file? (y or n) @kbd{n}
25530 @cindex @value{GDBN} internal error
25531 @cindex internal errors, control of @value{GDBN} behavior
25533 @kindex maint set internal-error
25534 @kindex maint show internal-error
25535 @kindex maint set internal-warning
25536 @kindex maint show internal-warning
25537 @item maint set internal-error @var{action} [ask|yes|no]
25538 @itemx maint show internal-error @var{action}
25539 @itemx maint set internal-warning @var{action} [ask|yes|no]
25540 @itemx maint show internal-warning @var{action}
25541 When @value{GDBN} reports an internal problem (error or warning) it
25542 gives the user the opportunity to both quit @value{GDBN} and create a
25543 core file of the current @value{GDBN} session. These commands let you
25544 override the default behaviour for each particular @var{action},
25545 described in the table below.
25549 You can specify that @value{GDBN} should always (yes) or never (no)
25550 quit. The default is to ask the user what to do.
25553 You can specify that @value{GDBN} should always (yes) or never (no)
25554 create a core file. The default is to ask the user what to do.
25557 @kindex maint packet
25558 @item maint packet @var{text}
25559 If @value{GDBN} is talking to an inferior via the serial protocol,
25560 then this command sends the string @var{text} to the inferior, and
25561 displays the response packet. @value{GDBN} supplies the initial
25562 @samp{$} character, the terminating @samp{#} character, and the
25565 @kindex maint print architecture
25566 @item maint print architecture @r{[}@var{file}@r{]}
25567 Print the entire architecture configuration. The optional argument
25568 @var{file} names the file where the output goes.
25570 @kindex maint print c-tdesc
25571 @item maint print c-tdesc
25572 Print the current target description (@pxref{Target Descriptions}) as
25573 a C source file. The created source file can be used in @value{GDBN}
25574 when an XML parser is not available to parse the description.
25576 @kindex maint print dummy-frames
25577 @item maint print dummy-frames
25578 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
25581 (@value{GDBP}) @kbd{b add}
25583 (@value{GDBP}) @kbd{print add(2,3)}
25584 Breakpoint 2, add (a=2, b=3) at @dots{}
25586 The program being debugged stopped while in a function called from GDB.
25588 (@value{GDBP}) @kbd{maint print dummy-frames}
25589 0x1a57c80: pc=0x01014068 fp=0x0200bddc sp=0x0200bdd6
25590 top=0x0200bdd4 id=@{stack=0x200bddc,code=0x101405c@}
25591 call_lo=0x01014000 call_hi=0x01014001
25595 Takes an optional file parameter.
25597 @kindex maint print registers
25598 @kindex maint print raw-registers
25599 @kindex maint print cooked-registers
25600 @kindex maint print register-groups
25601 @item maint print registers @r{[}@var{file}@r{]}
25602 @itemx maint print raw-registers @r{[}@var{file}@r{]}
25603 @itemx maint print cooked-registers @r{[}@var{file}@r{]}
25604 @itemx maint print register-groups @r{[}@var{file}@r{]}
25605 Print @value{GDBN}'s internal register data structures.
25607 The command @code{maint print raw-registers} includes the contents of
25608 the raw register cache; the command @code{maint print cooked-registers}
25609 includes the (cooked) value of all registers; and the command
25610 @code{maint print register-groups} includes the groups that each
25611 register is a member of. @xref{Registers,, Registers, gdbint,
25612 @value{GDBN} Internals}.
25614 These commands take an optional parameter, a file name to which to
25615 write the information.
25617 @kindex maint print reggroups
25618 @item maint print reggroups @r{[}@var{file}@r{]}
25619 Print @value{GDBN}'s internal register group data structures. The
25620 optional argument @var{file} tells to what file to write the
25623 The register groups info looks like this:
25626 (@value{GDBP}) @kbd{maint print reggroups}
25639 This command forces @value{GDBN} to flush its internal register cache.
25641 @kindex maint print objfiles
25642 @cindex info for known object files
25643 @item maint print objfiles
25644 Print a dump of all known object files. For each object file, this
25645 command prints its name, address in memory, and all of its psymtabs
25648 @kindex maint print statistics
25649 @cindex bcache statistics
25650 @item maint print statistics
25651 This command prints, for each object file in the program, various data
25652 about that object file followed by the byte cache (@dfn{bcache})
25653 statistics for the object file. The objfile data includes the number
25654 of minimal, partial, full, and stabs symbols, the number of types
25655 defined by the objfile, the number of as yet unexpanded psym tables,
25656 the number of line tables and string tables, and the amount of memory
25657 used by the various tables. The bcache statistics include the counts,
25658 sizes, and counts of duplicates of all and unique objects, max,
25659 average, and median entry size, total memory used and its overhead and
25660 savings, and various measures of the hash table size and chain
25663 @kindex maint print target-stack
25664 @cindex target stack description
25665 @item maint print target-stack
25666 A @dfn{target} is an interface between the debugger and a particular
25667 kind of file or process. Targets can be stacked in @dfn{strata},
25668 so that more than one target can potentially respond to a request.
25669 In particular, memory accesses will walk down the stack of targets
25670 until they find a target that is interested in handling that particular
25673 This command prints a short description of each layer that was pushed on
25674 the @dfn{target stack}, starting from the top layer down to the bottom one.
25676 @kindex maint print type
25677 @cindex type chain of a data type
25678 @item maint print type @var{expr}
25679 Print the type chain for a type specified by @var{expr}. The argument
25680 can be either a type name or a symbol. If it is a symbol, the type of
25681 that symbol is described. The type chain produced by this command is
25682 a recursive definition of the data type as stored in @value{GDBN}'s
25683 data structures, including its flags and contained types.
25685 @kindex maint set dwarf2 max-cache-age
25686 @kindex maint show dwarf2 max-cache-age
25687 @item maint set dwarf2 max-cache-age
25688 @itemx maint show dwarf2 max-cache-age
25689 Control the DWARF 2 compilation unit cache.
25691 @cindex DWARF 2 compilation units cache
25692 In object files with inter-compilation-unit references, such as those
25693 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF 2
25694 reader needs to frequently refer to previously read compilation units.
25695 This setting controls how long a compilation unit will remain in the
25696 cache if it is not referenced. A higher limit means that cached
25697 compilation units will be stored in memory longer, and more total
25698 memory will be used. Setting it to zero disables caching, which will
25699 slow down @value{GDBN} startup, but reduce memory consumption.
25701 @kindex maint set profile
25702 @kindex maint show profile
25703 @cindex profiling GDB
25704 @item maint set profile
25705 @itemx maint show profile
25706 Control profiling of @value{GDBN}.
25708 Profiling will be disabled until you use the @samp{maint set profile}
25709 command to enable it. When you enable profiling, the system will begin
25710 collecting timing and execution count data; when you disable profiling or
25711 exit @value{GDBN}, the results will be written to a log file. Remember that
25712 if you use profiling, @value{GDBN} will overwrite the profiling log file
25713 (often called @file{gmon.out}). If you have a record of important profiling
25714 data in a @file{gmon.out} file, be sure to move it to a safe location.
25716 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
25717 compiled with the @samp{-pg} compiler option.
25719 @kindex maint show-debug-regs
25720 @cindex x86 hardware debug registers
25721 @item maint show-debug-regs
25722 Control whether to show variables that mirror the x86 hardware debug
25723 registers. Use @code{ON} to enable, @code{OFF} to disable. If
25724 enabled, the debug registers values are shown when @value{GDBN} inserts or
25725 removes a hardware breakpoint or watchpoint, and when the inferior
25726 triggers a hardware-assisted breakpoint or watchpoint.
25728 @kindex maint space
25729 @cindex memory used by commands
25731 Control whether to display memory usage for each command. If set to a
25732 nonzero value, @value{GDBN} will display how much memory each command
25733 took, following the command's own output. This can also be requested
25734 by invoking @value{GDBN} with the @option{--statistics} command-line
25735 switch (@pxref{Mode Options}).
25738 @cindex time of command execution
25740 Control whether to display the execution time for each command. If
25741 set to a nonzero value, @value{GDBN} will display how much time it
25742 took to execute each command, following the command's own output.
25743 The time is not printed for the commands that run the target, since
25744 there's no mechanism currently to compute how much time was spend
25745 by @value{GDBN} and how much time was spend by the program been debugged.
25746 it's not possibly currently
25747 This can also be requested by invoking @value{GDBN} with the
25748 @option{--statistics} command-line switch (@pxref{Mode Options}).
25750 @kindex maint translate-address
25751 @item maint translate-address @r{[}@var{section}@r{]} @var{addr}
25752 Find the symbol stored at the location specified by the address
25753 @var{addr} and an optional section name @var{section}. If found,
25754 @value{GDBN} prints the name of the closest symbol and an offset from
25755 the symbol's location to the specified address. This is similar to
25756 the @code{info address} command (@pxref{Symbols}), except that this
25757 command also allows to find symbols in other sections.
25759 If section was not specified, the section in which the symbol was found
25760 is also printed. For dynamically linked executables, the name of
25761 executable or shared library containing the symbol is printed as well.
25765 The following command is useful for non-interactive invocations of
25766 @value{GDBN}, such as in the test suite.
25769 @item set watchdog @var{nsec}
25770 @kindex set watchdog
25771 @cindex watchdog timer
25772 @cindex timeout for commands
25773 Set the maximum number of seconds @value{GDBN} will wait for the
25774 target operation to finish. If this time expires, @value{GDBN}
25775 reports and error and the command is aborted.
25777 @item show watchdog
25778 Show the current setting of the target wait timeout.
25781 @node Remote Protocol
25782 @appendix @value{GDBN} Remote Serial Protocol
25787 * Stop Reply Packets::
25788 * General Query Packets::
25789 * Register Packet Format::
25790 * Tracepoint Packets::
25791 * Host I/O Packets::
25793 * Notification Packets::
25794 * Remote Non-Stop::
25795 * Packet Acknowledgment::
25797 * File-I/O Remote Protocol Extension::
25798 * Library List Format::
25799 * Memory Map Format::
25805 There may be occasions when you need to know something about the
25806 protocol---for example, if there is only one serial port to your target
25807 machine, you might want your program to do something special if it
25808 recognizes a packet meant for @value{GDBN}.
25810 In the examples below, @samp{->} and @samp{<-} are used to indicate
25811 transmitted and received data, respectively.
25813 @cindex protocol, @value{GDBN} remote serial
25814 @cindex serial protocol, @value{GDBN} remote
25815 @cindex remote serial protocol
25816 All @value{GDBN} commands and responses (other than acknowledgments
25817 and notifications, see @ref{Notification Packets}) are sent as a
25818 @var{packet}. A @var{packet} is introduced with the character
25819 @samp{$}, the actual @var{packet-data}, and the terminating character
25820 @samp{#} followed by a two-digit @var{checksum}:
25823 @code{$}@var{packet-data}@code{#}@var{checksum}
25827 @cindex checksum, for @value{GDBN} remote
25829 The two-digit @var{checksum} is computed as the modulo 256 sum of all
25830 characters between the leading @samp{$} and the trailing @samp{#} (an
25831 eight bit unsigned checksum).
25833 Implementors should note that prior to @value{GDBN} 5.0 the protocol
25834 specification also included an optional two-digit @var{sequence-id}:
25837 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
25840 @cindex sequence-id, for @value{GDBN} remote
25842 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
25843 has never output @var{sequence-id}s. Stubs that handle packets added
25844 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
25846 When either the host or the target machine receives a packet, the first
25847 response expected is an acknowledgment: either @samp{+} (to indicate
25848 the package was received correctly) or @samp{-} (to request
25852 -> @code{$}@var{packet-data}@code{#}@var{checksum}
25857 The @samp{+}/@samp{-} acknowledgments can be disabled
25858 once a connection is established.
25859 @xref{Packet Acknowledgment}, for details.
25861 The host (@value{GDBN}) sends @var{command}s, and the target (the
25862 debugging stub incorporated in your program) sends a @var{response}. In
25863 the case of step and continue @var{command}s, the response is only sent
25864 when the operation has completed, and the target has again stopped all
25865 threads in all attached processes. This is the default all-stop mode
25866 behavior, but the remote protocol also supports @value{GDBN}'s non-stop
25867 execution mode; see @ref{Remote Non-Stop}, for details.
25869 @var{packet-data} consists of a sequence of characters with the
25870 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
25873 @cindex remote protocol, field separator
25874 Fields within the packet should be separated using @samp{,} @samp{;} or
25875 @samp{:}. Except where otherwise noted all numbers are represented in
25876 @sc{hex} with leading zeros suppressed.
25878 Implementors should note that prior to @value{GDBN} 5.0, the character
25879 @samp{:} could not appear as the third character in a packet (as it
25880 would potentially conflict with the @var{sequence-id}).
25882 @cindex remote protocol, binary data
25883 @anchor{Binary Data}
25884 Binary data in most packets is encoded either as two hexadecimal
25885 digits per byte of binary data. This allowed the traditional remote
25886 protocol to work over connections which were only seven-bit clean.
25887 Some packets designed more recently assume an eight-bit clean
25888 connection, and use a more efficient encoding to send and receive
25891 The binary data representation uses @code{7d} (@sc{ascii} @samp{@}})
25892 as an escape character. Any escaped byte is transmitted as the escape
25893 character followed by the original character XORed with @code{0x20}.
25894 For example, the byte @code{0x7d} would be transmitted as the two
25895 bytes @code{0x7d 0x5d}. The bytes @code{0x23} (@sc{ascii} @samp{#}),
25896 @code{0x24} (@sc{ascii} @samp{$}), and @code{0x7d} (@sc{ascii}
25897 @samp{@}}) must always be escaped. Responses sent by the stub
25898 must also escape @code{0x2a} (@sc{ascii} @samp{*}), so that it
25899 is not interpreted as the start of a run-length encoded sequence
25902 Response @var{data} can be run-length encoded to save space.
25903 Run-length encoding replaces runs of identical characters with one
25904 instance of the repeated character, followed by a @samp{*} and a
25905 repeat count. The repeat count is itself sent encoded, to avoid
25906 binary characters in @var{data}: a value of @var{n} is sent as
25907 @code{@var{n}+29}. For a repeat count greater or equal to 3, this
25908 produces a printable @sc{ascii} character, e.g.@: a space (@sc{ascii}
25909 code 32) for a repeat count of 3. (This is because run-length
25910 encoding starts to win for counts 3 or more.) Thus, for example,
25911 @samp{0* } is a run-length encoding of ``0000'': the space character
25912 after @samp{*} means repeat the leading @code{0} @w{@code{32 - 29 =
25915 The printable characters @samp{#} and @samp{$} or with a numeric value
25916 greater than 126 must not be used. Runs of six repeats (@samp{#}) or
25917 seven repeats (@samp{$}) can be expanded using a repeat count of only
25918 five (@samp{"}). For example, @samp{00000000} can be encoded as
25921 The error response returned for some packets includes a two character
25922 error number. That number is not well defined.
25924 @cindex empty response, for unsupported packets
25925 For any @var{command} not supported by the stub, an empty response
25926 (@samp{$#00}) should be returned. That way it is possible to extend the
25927 protocol. A newer @value{GDBN} can tell if a packet is supported based
25930 A stub is required to support the @samp{g}, @samp{G}, @samp{m}, @samp{M},
25931 @samp{c}, and @samp{s} @var{command}s. All other @var{command}s are
25937 The following table provides a complete list of all currently defined
25938 @var{command}s and their corresponding response @var{data}.
25939 @xref{File-I/O Remote Protocol Extension}, for details about the File
25940 I/O extension of the remote protocol.
25942 Each packet's description has a template showing the packet's overall
25943 syntax, followed by an explanation of the packet's meaning. We
25944 include spaces in some of the templates for clarity; these are not
25945 part of the packet's syntax. No @value{GDBN} packet uses spaces to
25946 separate its components. For example, a template like @samp{foo
25947 @var{bar} @var{baz}} describes a packet beginning with the three ASCII
25948 bytes @samp{foo}, followed by a @var{bar}, followed directly by a
25949 @var{baz}. @value{GDBN} does not transmit a space character between the
25950 @samp{foo} and the @var{bar}, or between the @var{bar} and the
25953 @cindex @var{thread-id}, in remote protocol
25954 @anchor{thread-id syntax}
25955 Several packets and replies include a @var{thread-id} field to identify
25956 a thread. Normally these are positive numbers with a target-specific
25957 interpretation, formatted as big-endian hex strings. A @var{thread-id}
25958 can also be a literal @samp{-1} to indicate all threads, or @samp{0} to
25961 In addition, the remote protocol supports a multiprocess feature in
25962 which the @var{thread-id} syntax is extended to optionally include both
25963 process and thread ID fields, as @samp{p@var{pid}.@var{tid}}.
25964 The @var{pid} (process) and @var{tid} (thread) components each have the
25965 format described above: a positive number with target-specific
25966 interpretation formatted as a big-endian hex string, literal @samp{-1}
25967 to indicate all processes or threads (respectively), or @samp{0} to
25968 indicate an arbitrary process or thread. Specifying just a process, as
25969 @samp{p@var{pid}}, is equivalent to @samp{p@var{pid}.-1}. It is an
25970 error to specify all processes but a specific thread, such as
25971 @samp{p-1.@var{tid}}. Note that the @samp{p} prefix is @emph{not} used
25972 for those packets and replies explicitly documented to include a process
25973 ID, rather than a @var{thread-id}.
25975 The multiprocess @var{thread-id} syntax extensions are only used if both
25976 @value{GDBN} and the stub report support for the @samp{multiprocess}
25977 feature using @samp{qSupported}. @xref{multiprocess extensions}, for
25980 Note that all packet forms beginning with an upper- or lower-case
25981 letter, other than those described here, are reserved for future use.
25983 Here are the packet descriptions.
25988 @cindex @samp{!} packet
25989 @anchor{extended mode}
25990 Enable extended mode. In extended mode, the remote server is made
25991 persistent. The @samp{R} packet is used to restart the program being
25997 The remote target both supports and has enabled extended mode.
26001 @cindex @samp{?} packet
26002 Indicate the reason the target halted. The reply is the same as for
26003 step and continue. This packet has a special interpretation when the
26004 target is in non-stop mode; see @ref{Remote Non-Stop}.
26007 @xref{Stop Reply Packets}, for the reply specifications.
26009 @item A @var{arglen},@var{argnum},@var{arg},@dots{}
26010 @cindex @samp{A} packet
26011 Initialized @code{argv[]} array passed into program. @var{arglen}
26012 specifies the number of bytes in the hex encoded byte stream
26013 @var{arg}. See @code{gdbserver} for more details.
26018 The arguments were set.
26024 @cindex @samp{b} packet
26025 (Don't use this packet; its behavior is not well-defined.)
26026 Change the serial line speed to @var{baud}.
26028 JTC: @emph{When does the transport layer state change? When it's
26029 received, or after the ACK is transmitted. In either case, there are
26030 problems if the command or the acknowledgment packet is dropped.}
26032 Stan: @emph{If people really wanted to add something like this, and get
26033 it working for the first time, they ought to modify ser-unix.c to send
26034 some kind of out-of-band message to a specially-setup stub and have the
26035 switch happen "in between" packets, so that from remote protocol's point
26036 of view, nothing actually happened.}
26038 @item B @var{addr},@var{mode}
26039 @cindex @samp{B} packet
26040 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
26041 breakpoint at @var{addr}.
26043 Don't use this packet. Use the @samp{Z} and @samp{z} packets instead
26044 (@pxref{insert breakpoint or watchpoint packet}).
26047 @cindex @samp{bc} packet
26048 Backward continue. Execute the target system in reverse. No parameter.
26049 @xref{Reverse Execution}, for more information.
26052 @xref{Stop Reply Packets}, for the reply specifications.
26055 @cindex @samp{bs} packet
26056 Backward single step. Execute one instruction in reverse. No parameter.
26057 @xref{Reverse Execution}, for more information.
26060 @xref{Stop Reply Packets}, for the reply specifications.
26062 @item c @r{[}@var{addr}@r{]}
26063 @cindex @samp{c} packet
26064 Continue. @var{addr} is address to resume. If @var{addr} is omitted,
26065 resume at current address.
26068 @xref{Stop Reply Packets}, for the reply specifications.
26070 @item C @var{sig}@r{[};@var{addr}@r{]}
26071 @cindex @samp{C} packet
26072 Continue with signal @var{sig} (hex signal number). If
26073 @samp{;@var{addr}} is omitted, resume at same address.
26076 @xref{Stop Reply Packets}, for the reply specifications.
26079 @cindex @samp{d} packet
26082 Don't use this packet; instead, define a general set packet
26083 (@pxref{General Query Packets}).
26087 @cindex @samp{D} packet
26088 The first form of the packet is used to detach @value{GDBN} from the
26089 remote system. It is sent to the remote target
26090 before @value{GDBN} disconnects via the @code{detach} command.
26092 The second form, including a process ID, is used when multiprocess
26093 protocol extensions are enabled (@pxref{multiprocess extensions}), to
26094 detach only a specific process. The @var{pid} is specified as a
26095 big-endian hex string.
26105 @item F @var{RC},@var{EE},@var{CF};@var{XX}
26106 @cindex @samp{F} packet
26107 A reply from @value{GDBN} to an @samp{F} packet sent by the target.
26108 This is part of the File-I/O protocol extension. @xref{File-I/O
26109 Remote Protocol Extension}, for the specification.
26112 @anchor{read registers packet}
26113 @cindex @samp{g} packet
26114 Read general registers.
26118 @item @var{XX@dots{}}
26119 Each byte of register data is described by two hex digits. The bytes
26120 with the register are transmitted in target byte order. The size of
26121 each register and their position within the @samp{g} packet are
26122 determined by the @value{GDBN} internal gdbarch functions
26123 @code{DEPRECATED_REGISTER_RAW_SIZE} and @code{gdbarch_register_name}. The
26124 specification of several standard @samp{g} packets is specified below.
26129 @item G @var{XX@dots{}}
26130 @cindex @samp{G} packet
26131 Write general registers. @xref{read registers packet}, for a
26132 description of the @var{XX@dots{}} data.
26142 @item H @var{c} @var{thread-id}
26143 @cindex @samp{H} packet
26144 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
26145 @samp{G}, et.al.). @var{c} depends on the operation to be performed: it
26146 should be @samp{c} for step and continue operations, @samp{g} for other
26147 operations. The thread designator @var{thread-id} has the format and
26148 interpretation described in @ref{thread-id syntax}.
26159 @c 'H': How restrictive (or permissive) is the thread model. If a
26160 @c thread is selected and stopped, are other threads allowed
26161 @c to continue to execute? As I mentioned above, I think the
26162 @c semantics of each command when a thread is selected must be
26163 @c described. For example:
26165 @c 'g': If the stub supports threads and a specific thread is
26166 @c selected, returns the register block from that thread;
26167 @c otherwise returns current registers.
26169 @c 'G' If the stub supports threads and a specific thread is
26170 @c selected, sets the registers of the register block of
26171 @c that thread; otherwise sets current registers.
26173 @item i @r{[}@var{addr}@r{[},@var{nnn}@r{]]}
26174 @anchor{cycle step packet}
26175 @cindex @samp{i} packet
26176 Step the remote target by a single clock cycle. If @samp{,@var{nnn}} is
26177 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
26178 step starting at that address.
26181 @cindex @samp{I} packet
26182 Signal, then cycle step. @xref{step with signal packet}. @xref{cycle
26186 @cindex @samp{k} packet
26189 FIXME: @emph{There is no description of how to operate when a specific
26190 thread context has been selected (i.e.@: does 'k' kill only that
26193 @item m @var{addr},@var{length}
26194 @cindex @samp{m} packet
26195 Read @var{length} bytes of memory starting at address @var{addr}.
26196 Note that @var{addr} may not be aligned to any particular boundary.
26198 The stub need not use any particular size or alignment when gathering
26199 data from memory for the response; even if @var{addr} is word-aligned
26200 and @var{length} is a multiple of the word size, the stub is free to
26201 use byte accesses, or not. For this reason, this packet may not be
26202 suitable for accessing memory-mapped I/O devices.
26203 @cindex alignment of remote memory accesses
26204 @cindex size of remote memory accesses
26205 @cindex memory, alignment and size of remote accesses
26209 @item @var{XX@dots{}}
26210 Memory contents; each byte is transmitted as a two-digit hexadecimal
26211 number. The reply may contain fewer bytes than requested if the
26212 server was able to read only part of the region of memory.
26217 @item M @var{addr},@var{length}:@var{XX@dots{}}
26218 @cindex @samp{M} packet
26219 Write @var{length} bytes of memory starting at address @var{addr}.
26220 @var{XX@dots{}} is the data; each byte is transmitted as a two-digit
26221 hexadecimal number.
26228 for an error (this includes the case where only part of the data was
26233 @cindex @samp{p} packet
26234 Read the value of register @var{n}; @var{n} is in hex.
26235 @xref{read registers packet}, for a description of how the returned
26236 register value is encoded.
26240 @item @var{XX@dots{}}
26241 the register's value
26245 Indicating an unrecognized @var{query}.
26248 @item P @var{n@dots{}}=@var{r@dots{}}
26249 @anchor{write register packet}
26250 @cindex @samp{P} packet
26251 Write register @var{n@dots{}} with value @var{r@dots{}}. The register
26252 number @var{n} is in hexadecimal, and @var{r@dots{}} contains two hex
26253 digits for each byte in the register (target byte order).
26263 @item q @var{name} @var{params}@dots{}
26264 @itemx Q @var{name} @var{params}@dots{}
26265 @cindex @samp{q} packet
26266 @cindex @samp{Q} packet
26267 General query (@samp{q}) and set (@samp{Q}). These packets are
26268 described fully in @ref{General Query Packets}.
26271 @cindex @samp{r} packet
26272 Reset the entire system.
26274 Don't use this packet; use the @samp{R} packet instead.
26277 @cindex @samp{R} packet
26278 Restart the program being debugged. @var{XX}, while needed, is ignored.
26279 This packet is only available in extended mode (@pxref{extended mode}).
26281 The @samp{R} packet has no reply.
26283 @item s @r{[}@var{addr}@r{]}
26284 @cindex @samp{s} packet
26285 Single step. @var{addr} is the address at which to resume. If
26286 @var{addr} is omitted, resume at same address.
26289 @xref{Stop Reply Packets}, for the reply specifications.
26291 @item S @var{sig}@r{[};@var{addr}@r{]}
26292 @anchor{step with signal packet}
26293 @cindex @samp{S} packet
26294 Step with signal. This is analogous to the @samp{C} packet, but
26295 requests a single-step, rather than a normal resumption of execution.
26298 @xref{Stop Reply Packets}, for the reply specifications.
26300 @item t @var{addr}:@var{PP},@var{MM}
26301 @cindex @samp{t} packet
26302 Search backwards starting at address @var{addr} for a match with pattern
26303 @var{PP} and mask @var{MM}. @var{PP} and @var{MM} are 4 bytes.
26304 @var{addr} must be at least 3 digits.
26306 @item T @var{thread-id}
26307 @cindex @samp{T} packet
26308 Find out if the thread @var{thread-id} is alive. @xref{thread-id syntax}.
26313 thread is still alive
26319 Packets starting with @samp{v} are identified by a multi-letter name,
26320 up to the first @samp{;} or @samp{?} (or the end of the packet).
26322 @item vAttach;@var{pid}
26323 @cindex @samp{vAttach} packet
26324 Attach to a new process with the specified process ID @var{pid}.
26325 The process ID is a
26326 hexadecimal integer identifying the process. In all-stop mode, all
26327 threads in the attached process are stopped; in non-stop mode, it may be
26328 attached without being stopped if that is supported by the target.
26330 @c In non-stop mode, on a successful vAttach, the stub should set the
26331 @c current thread to a thread of the newly-attached process. After
26332 @c attaching, GDB queries for the attached process's thread ID with qC.
26333 @c Also note that, from a user perspective, whether or not the
26334 @c target is stopped on attach in non-stop mode depends on whether you
26335 @c use the foreground or background version of the attach command, not
26336 @c on what vAttach does; GDB does the right thing with respect to either
26337 @c stopping or restarting threads.
26339 This packet is only available in extended mode (@pxref{extended mode}).
26345 @item @r{Any stop packet}
26346 for success in all-stop mode (@pxref{Stop Reply Packets})
26348 for success in non-stop mode (@pxref{Remote Non-Stop})
26351 @item vCont@r{[};@var{action}@r{[}:@var{thread-id}@r{]]}@dots{}
26352 @cindex @samp{vCont} packet
26353 Resume the inferior, specifying different actions for each thread.
26354 If an action is specified with no @var{thread-id}, then it is applied to any
26355 threads that don't have a specific action specified; if no default action is
26356 specified then other threads should remain stopped in all-stop mode and
26357 in their current state in non-stop mode.
26358 Specifying multiple
26359 default actions is an error; specifying no actions is also an error.
26360 Thread IDs are specified using the syntax described in @ref{thread-id syntax}.
26362 Currently supported actions are:
26368 Continue with signal @var{sig}. The signal @var{sig} should be two hex digits.
26372 Step with signal @var{sig}. The signal @var{sig} should be two hex digits.
26376 Stop with signal @var{sig}. The signal @var{sig} should be two hex digits.
26379 The optional argument @var{addr} normally associated with the
26380 @samp{c}, @samp{C}, @samp{s}, and @samp{S} packets is
26381 not supported in @samp{vCont}.
26383 The @samp{t} and @samp{T} actions are only relevant in non-stop mode
26384 (@pxref{Remote Non-Stop}) and may be ignored by the stub otherwise.
26385 A stop reply should be generated for any affected thread not already stopped.
26386 When a thread is stopped by means of a @samp{t} action,
26387 the corresponding stop reply should indicate that the thread has stopped with
26388 signal @samp{0}, regardless of whether the target uses some other signal
26389 as an implementation detail.
26392 @xref{Stop Reply Packets}, for the reply specifications.
26395 @cindex @samp{vCont?} packet
26396 Request a list of actions supported by the @samp{vCont} packet.
26400 @item vCont@r{[};@var{action}@dots{}@r{]}
26401 The @samp{vCont} packet is supported. Each @var{action} is a supported
26402 command in the @samp{vCont} packet.
26404 The @samp{vCont} packet is not supported.
26407 @item vFile:@var{operation}:@var{parameter}@dots{}
26408 @cindex @samp{vFile} packet
26409 Perform a file operation on the target system. For details,
26410 see @ref{Host I/O Packets}.
26412 @item vFlashErase:@var{addr},@var{length}
26413 @cindex @samp{vFlashErase} packet
26414 Direct the stub to erase @var{length} bytes of flash starting at
26415 @var{addr}. The region may enclose any number of flash blocks, but
26416 its start and end must fall on block boundaries, as indicated by the
26417 flash block size appearing in the memory map (@pxref{Memory Map
26418 Format}). @value{GDBN} groups flash memory programming operations
26419 together, and sends a @samp{vFlashDone} request after each group; the
26420 stub is allowed to delay erase operation until the @samp{vFlashDone}
26421 packet is received.
26423 The stub must support @samp{vCont} if it reports support for
26424 multiprocess extensions (@pxref{multiprocess extensions}). Note that in
26425 this case @samp{vCont} actions can be specified to apply to all threads
26426 in a process by using the @samp{p@var{pid}.-1} form of the
26437 @item vFlashWrite:@var{addr}:@var{XX@dots{}}
26438 @cindex @samp{vFlashWrite} packet
26439 Direct the stub to write data to flash address @var{addr}. The data
26440 is passed in binary form using the same encoding as for the @samp{X}
26441 packet (@pxref{Binary Data}). The memory ranges specified by
26442 @samp{vFlashWrite} packets preceding a @samp{vFlashDone} packet must
26443 not overlap, and must appear in order of increasing addresses
26444 (although @samp{vFlashErase} packets for higher addresses may already
26445 have been received; the ordering is guaranteed only between
26446 @samp{vFlashWrite} packets). If a packet writes to an address that was
26447 neither erased by a preceding @samp{vFlashErase} packet nor by some other
26448 target-specific method, the results are unpredictable.
26456 for vFlashWrite addressing non-flash memory
26462 @cindex @samp{vFlashDone} packet
26463 Indicate to the stub that flash programming operation is finished.
26464 The stub is permitted to delay or batch the effects of a group of
26465 @samp{vFlashErase} and @samp{vFlashWrite} packets until a
26466 @samp{vFlashDone} packet is received. The contents of the affected
26467 regions of flash memory are unpredictable until the @samp{vFlashDone}
26468 request is completed.
26470 @item vKill;@var{pid}
26471 @cindex @samp{vKill} packet
26472 Kill the process with the specified process ID. @var{pid} is a
26473 hexadecimal integer identifying the process. This packet is used in
26474 preference to @samp{k} when multiprocess protocol extensions are
26475 supported; see @ref{multiprocess extensions}.
26485 @item vRun;@var{filename}@r{[};@var{argument}@r{]}@dots{}
26486 @cindex @samp{vRun} packet
26487 Run the program @var{filename}, passing it each @var{argument} on its
26488 command line. The file and arguments are hex-encoded strings. If
26489 @var{filename} is an empty string, the stub may use a default program
26490 (e.g.@: the last program run). The program is created in the stopped
26493 @c FIXME: What about non-stop mode?
26495 This packet is only available in extended mode (@pxref{extended mode}).
26501 @item @r{Any stop packet}
26502 for success (@pxref{Stop Reply Packets})
26506 @anchor{vStopped packet}
26507 @cindex @samp{vStopped} packet
26509 In non-stop mode (@pxref{Remote Non-Stop}), acknowledge a previous stop
26510 reply and prompt for the stub to report another one.
26514 @item @r{Any stop packet}
26515 if there is another unreported stop event (@pxref{Stop Reply Packets})
26517 if there are no unreported stop events
26520 @item X @var{addr},@var{length}:@var{XX@dots{}}
26522 @cindex @samp{X} packet
26523 Write data to memory, where the data is transmitted in binary.
26524 @var{addr} is address, @var{length} is number of bytes,
26525 @samp{@var{XX}@dots{}} is binary data (@pxref{Binary Data}).
26535 @item z @var{type},@var{addr},@var{length}
26536 @itemx Z @var{type},@var{addr},@var{length}
26537 @anchor{insert breakpoint or watchpoint packet}
26538 @cindex @samp{z} packet
26539 @cindex @samp{Z} packets
26540 Insert (@samp{Z}) or remove (@samp{z}) a @var{type} breakpoint or
26541 watchpoint starting at address @var{address} and covering the next
26542 @var{length} bytes.
26544 Each breakpoint and watchpoint packet @var{type} is documented
26547 @emph{Implementation notes: A remote target shall return an empty string
26548 for an unrecognized breakpoint or watchpoint packet @var{type}. A
26549 remote target shall support either both or neither of a given
26550 @samp{Z@var{type}@dots{}} and @samp{z@var{type}@dots{}} packet pair. To
26551 avoid potential problems with duplicate packets, the operations should
26552 be implemented in an idempotent way.}
26554 @item z0,@var{addr},@var{length}
26555 @itemx Z0,@var{addr},@var{length}
26556 @cindex @samp{z0} packet
26557 @cindex @samp{Z0} packet
26558 Insert (@samp{Z0}) or remove (@samp{z0}) a memory breakpoint at address
26559 @var{addr} of size @var{length}.
26561 A memory breakpoint is implemented by replacing the instruction at
26562 @var{addr} with a software breakpoint or trap instruction. The
26563 @var{length} is used by targets that indicates the size of the
26564 breakpoint (in bytes) that should be inserted (e.g., the @sc{arm} and
26565 @sc{mips} can insert either a 2 or 4 byte breakpoint).
26567 @emph{Implementation note: It is possible for a target to copy or move
26568 code that contains memory breakpoints (e.g., when implementing
26569 overlays). The behavior of this packet, in the presence of such a
26570 target, is not defined.}
26582 @item z1,@var{addr},@var{length}
26583 @itemx Z1,@var{addr},@var{length}
26584 @cindex @samp{z1} packet
26585 @cindex @samp{Z1} packet
26586 Insert (@samp{Z1}) or remove (@samp{z1}) a hardware breakpoint at
26587 address @var{addr} of size @var{length}.
26589 A hardware breakpoint is implemented using a mechanism that is not
26590 dependant on being able to modify the target's memory.
26592 @emph{Implementation note: A hardware breakpoint is not affected by code
26605 @item z2,@var{addr},@var{length}
26606 @itemx Z2,@var{addr},@var{length}
26607 @cindex @samp{z2} packet
26608 @cindex @samp{Z2} packet
26609 Insert (@samp{Z2}) or remove (@samp{z2}) a write watchpoint.
26621 @item z3,@var{addr},@var{length}
26622 @itemx Z3,@var{addr},@var{length}
26623 @cindex @samp{z3} packet
26624 @cindex @samp{Z3} packet
26625 Insert (@samp{Z3}) or remove (@samp{z3}) a read watchpoint.
26637 @item z4,@var{addr},@var{length}
26638 @itemx Z4,@var{addr},@var{length}
26639 @cindex @samp{z4} packet
26640 @cindex @samp{Z4} packet
26641 Insert (@samp{Z4}) or remove (@samp{z4}) an access watchpoint.
26655 @node Stop Reply Packets
26656 @section Stop Reply Packets
26657 @cindex stop reply packets
26659 The @samp{C}, @samp{c}, @samp{S}, @samp{s}, @samp{vCont},
26660 @samp{vAttach}, @samp{vRun}, @samp{vStopped}, and @samp{?} packets can
26661 receive any of the below as a reply. Except for @samp{?}
26662 and @samp{vStopped}, that reply is only returned
26663 when the target halts. In the below the exact meaning of @dfn{signal
26664 number} is defined by the header @file{include/gdb/signals.h} in the
26665 @value{GDBN} source code.
26667 As in the description of request packets, we include spaces in the
26668 reply templates for clarity; these are not part of the reply packet's
26669 syntax. No @value{GDBN} stop reply packet uses spaces to separate its
26675 The program received signal number @var{AA} (a two-digit hexadecimal
26676 number). This is equivalent to a @samp{T} response with no
26677 @var{n}:@var{r} pairs.
26679 @item T @var{AA} @var{n1}:@var{r1};@var{n2}:@var{r2};@dots{}
26680 @cindex @samp{T} packet reply
26681 The program received signal number @var{AA} (a two-digit hexadecimal
26682 number). This is equivalent to an @samp{S} response, except that the
26683 @samp{@var{n}:@var{r}} pairs can carry values of important registers
26684 and other information directly in the stop reply packet, reducing
26685 round-trip latency. Single-step and breakpoint traps are reported
26686 this way. Each @samp{@var{n}:@var{r}} pair is interpreted as follows:
26690 If @var{n} is a hexadecimal number, it is a register number, and the
26691 corresponding @var{r} gives that register's value. @var{r} is a
26692 series of bytes in target byte order, with each byte given by a
26693 two-digit hex number.
26696 If @var{n} is @samp{thread}, then @var{r} is the @var{thread-id} of
26697 the stopped thread, as specified in @ref{thread-id syntax}.
26700 If @var{n} is a recognized @dfn{stop reason}, it describes a more
26701 specific event that stopped the target. The currently defined stop
26702 reasons are listed below. @var{aa} should be @samp{05}, the trap
26703 signal. At most one stop reason should be present.
26706 Otherwise, @value{GDBN} should ignore this @samp{@var{n}:@var{r}} pair
26707 and go on to the next; this allows us to extend the protocol in the
26711 The currently defined stop reasons are:
26717 The packet indicates a watchpoint hit, and @var{r} is the data address, in
26720 @cindex shared library events, remote reply
26722 The packet indicates that the loaded libraries have changed.
26723 @value{GDBN} should use @samp{qXfer:libraries:read} to fetch a new
26724 list of loaded libraries. @var{r} is ignored.
26726 @cindex replay log events, remote reply
26728 The packet indicates that the target cannot continue replaying
26729 logged execution events, because it has reached the end (or the
26730 beginning when executing backward) of the log. The value of @var{r}
26731 will be either @samp{begin} or @samp{end}. @xref{Reverse Execution},
26732 for more information.
26738 @itemx W @var{AA} ; process:@var{pid}
26739 The process exited, and @var{AA} is the exit status. This is only
26740 applicable to certain targets.
26742 The second form of the response, including the process ID of the exited
26743 process, can be used only when @value{GDBN} has reported support for
26744 multiprocess protocol extensions; see @ref{multiprocess extensions}.
26745 The @var{pid} is formatted as a big-endian hex string.
26748 @itemx X @var{AA} ; process:@var{pid}
26749 The process terminated with signal @var{AA}.
26751 The second form of the response, including the process ID of the
26752 terminated process, can be used only when @value{GDBN} has reported
26753 support for multiprocess protocol extensions; see @ref{multiprocess
26754 extensions}. The @var{pid} is formatted as a big-endian hex string.
26756 @item O @var{XX}@dots{}
26757 @samp{@var{XX}@dots{}} is hex encoding of @sc{ascii} data, to be
26758 written as the program's console output. This can happen at any time
26759 while the program is running and the debugger should continue to wait
26760 for @samp{W}, @samp{T}, etc. This reply is not permitted in non-stop mode.
26762 @item F @var{call-id},@var{parameter}@dots{}
26763 @var{call-id} is the identifier which says which host system call should
26764 be called. This is just the name of the function. Translation into the
26765 correct system call is only applicable as it's defined in @value{GDBN}.
26766 @xref{File-I/O Remote Protocol Extension}, for a list of implemented
26769 @samp{@var{parameter}@dots{}} is a list of parameters as defined for
26770 this very system call.
26772 The target replies with this packet when it expects @value{GDBN} to
26773 call a host system call on behalf of the target. @value{GDBN} replies
26774 with an appropriate @samp{F} packet and keeps up waiting for the next
26775 reply packet from the target. The latest @samp{C}, @samp{c}, @samp{S}
26776 or @samp{s} action is expected to be continued. @xref{File-I/O Remote
26777 Protocol Extension}, for more details.
26781 @node General Query Packets
26782 @section General Query Packets
26783 @cindex remote query requests
26785 Packets starting with @samp{q} are @dfn{general query packets};
26786 packets starting with @samp{Q} are @dfn{general set packets}. General
26787 query and set packets are a semi-unified form for retrieving and
26788 sending information to and from the stub.
26790 The initial letter of a query or set packet is followed by a name
26791 indicating what sort of thing the packet applies to. For example,
26792 @value{GDBN} may use a @samp{qSymbol} packet to exchange symbol
26793 definitions with the stub. These packet names follow some
26798 The name must not contain commas, colons or semicolons.
26800 Most @value{GDBN} query and set packets have a leading upper case
26803 The names of custom vendor packets should use a company prefix, in
26804 lower case, followed by a period. For example, packets designed at
26805 the Acme Corporation might begin with @samp{qacme.foo} (for querying
26806 foos) or @samp{Qacme.bar} (for setting bars).
26809 The name of a query or set packet should be separated from any
26810 parameters by a @samp{:}; the parameters themselves should be
26811 separated by @samp{,} or @samp{;}. Stubs must be careful to match the
26812 full packet name, and check for a separator or the end of the packet,
26813 in case two packet names share a common prefix. New packets should not begin
26814 with @samp{qC}, @samp{qP}, or @samp{qL}@footnote{The @samp{qP} and @samp{qL}
26815 packets predate these conventions, and have arguments without any terminator
26816 for the packet name; we suspect they are in widespread use in places that
26817 are difficult to upgrade. The @samp{qC} packet has no arguments, but some
26818 existing stubs (e.g.@: RedBoot) are known to not check for the end of the
26821 Like the descriptions of the other packets, each description here
26822 has a template showing the packet's overall syntax, followed by an
26823 explanation of the packet's meaning. We include spaces in some of the
26824 templates for clarity; these are not part of the packet's syntax. No
26825 @value{GDBN} packet uses spaces to separate its components.
26827 Here are the currently defined query and set packets:
26832 @cindex current thread, remote request
26833 @cindex @samp{qC} packet
26834 Return the current thread ID.
26838 @item QC @var{thread-id}
26839 Where @var{thread-id} is a thread ID as documented in
26840 @ref{thread-id syntax}.
26841 @item @r{(anything else)}
26842 Any other reply implies the old thread ID.
26845 @item qCRC:@var{addr},@var{length}
26846 @cindex CRC of memory block, remote request
26847 @cindex @samp{qCRC} packet
26848 Compute the CRC checksum of a block of memory.
26852 An error (such as memory fault)
26853 @item C @var{crc32}
26854 The specified memory region's checksum is @var{crc32}.
26858 @itemx qsThreadInfo
26859 @cindex list active threads, remote request
26860 @cindex @samp{qfThreadInfo} packet
26861 @cindex @samp{qsThreadInfo} packet
26862 Obtain a list of all active thread IDs from the target (OS). Since there
26863 may be too many active threads to fit into one reply packet, this query
26864 works iteratively: it may require more than one query/reply sequence to
26865 obtain the entire list of threads. The first query of the sequence will
26866 be the @samp{qfThreadInfo} query; subsequent queries in the
26867 sequence will be the @samp{qsThreadInfo} query.
26869 NOTE: This packet replaces the @samp{qL} query (see below).
26873 @item m @var{thread-id}
26875 @item m @var{thread-id},@var{thread-id}@dots{}
26876 a comma-separated list of thread IDs
26878 (lower case letter @samp{L}) denotes end of list.
26881 In response to each query, the target will reply with a list of one or
26882 more thread IDs, separated by commas.
26883 @value{GDBN} will respond to each reply with a request for more thread
26884 ids (using the @samp{qs} form of the query), until the target responds
26885 with @samp{l} (lower-case el, for @dfn{last}).
26886 Refer to @ref{thread-id syntax}, for the format of the @var{thread-id}
26889 @item qGetTLSAddr:@var{thread-id},@var{offset},@var{lm}
26890 @cindex get thread-local storage address, remote request
26891 @cindex @samp{qGetTLSAddr} packet
26892 Fetch the address associated with thread local storage specified
26893 by @var{thread-id}, @var{offset}, and @var{lm}.
26895 @var{thread-id} is the thread ID associated with the
26896 thread for which to fetch the TLS address. @xref{thread-id syntax}.
26898 @var{offset} is the (big endian, hex encoded) offset associated with the
26899 thread local variable. (This offset is obtained from the debug
26900 information associated with the variable.)
26902 @var{lm} is the (big endian, hex encoded) OS/ABI-specific encoding of the
26903 the load module associated with the thread local storage. For example,
26904 a @sc{gnu}/Linux system will pass the link map address of the shared
26905 object associated with the thread local storage under consideration.
26906 Other operating environments may choose to represent the load module
26907 differently, so the precise meaning of this parameter will vary.
26911 @item @var{XX}@dots{}
26912 Hex encoded (big endian) bytes representing the address of the thread
26913 local storage requested.
26916 An error occurred. @var{nn} are hex digits.
26919 An empty reply indicates that @samp{qGetTLSAddr} is not supported by the stub.
26922 @item qL @var{startflag} @var{threadcount} @var{nextthread}
26923 Obtain thread information from RTOS. Where: @var{startflag} (one hex
26924 digit) is one to indicate the first query and zero to indicate a
26925 subsequent query; @var{threadcount} (two hex digits) is the maximum
26926 number of threads the response packet can contain; and @var{nextthread}
26927 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
26928 returned in the response as @var{argthread}.
26930 Don't use this packet; use the @samp{qfThreadInfo} query instead (see above).
26934 @item qM @var{count} @var{done} @var{argthread} @var{thread}@dots{}
26935 Where: @var{count} (two hex digits) is the number of threads being
26936 returned; @var{done} (one hex digit) is zero to indicate more threads
26937 and one indicates no further threads; @var{argthreadid} (eight hex
26938 digits) is @var{nextthread} from the request packet; @var{thread}@dots{}
26939 is a sequence of thread IDs from the target. @var{threadid} (eight hex
26940 digits). See @code{remote.c:parse_threadlist_response()}.
26944 @cindex section offsets, remote request
26945 @cindex @samp{qOffsets} packet
26946 Get section offsets that the target used when relocating the downloaded
26951 @item Text=@var{xxx};Data=@var{yyy}@r{[};Bss=@var{zzz}@r{]}
26952 Relocate the @code{Text} section by @var{xxx} from its original address.
26953 Relocate the @code{Data} section by @var{yyy} from its original address.
26954 If the object file format provides segment information (e.g.@: @sc{elf}
26955 @samp{PT_LOAD} program headers), @value{GDBN} will relocate entire
26956 segments by the supplied offsets.
26958 @emph{Note: while a @code{Bss} offset may be included in the response,
26959 @value{GDBN} ignores this and instead applies the @code{Data} offset
26960 to the @code{Bss} section.}
26962 @item TextSeg=@var{xxx}@r{[};DataSeg=@var{yyy}@r{]}
26963 Relocate the first segment of the object file, which conventionally
26964 contains program code, to a starting address of @var{xxx}. If
26965 @samp{DataSeg} is specified, relocate the second segment, which
26966 conventionally contains modifiable data, to a starting address of
26967 @var{yyy}. @value{GDBN} will report an error if the object file
26968 does not contain segment information, or does not contain at least
26969 as many segments as mentioned in the reply. Extra segments are
26970 kept at fixed offsets relative to the last relocated segment.
26973 @item qP @var{mode} @var{thread-id}
26974 @cindex thread information, remote request
26975 @cindex @samp{qP} packet
26976 Returns information on @var{thread-id}. Where: @var{mode} is a hex
26977 encoded 32 bit mode; @var{thread-id} is a thread ID
26978 (@pxref{thread-id syntax}).
26980 Don't use this packet; use the @samp{qThreadExtraInfo} query instead
26983 Reply: see @code{remote.c:remote_unpack_thread_info_response()}.
26987 @cindex non-stop mode, remote request
26988 @cindex @samp{QNonStop} packet
26990 Enter non-stop (@samp{QNonStop:1}) or all-stop (@samp{QNonStop:0}) mode.
26991 @xref{Remote Non-Stop}, for more information.
26996 The request succeeded.
26999 An error occurred. @var{nn} are hex digits.
27002 An empty reply indicates that @samp{QNonStop} is not supported by
27006 This packet is not probed by default; the remote stub must request it,
27007 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
27008 Use of this packet is controlled by the @code{set non-stop} command;
27009 @pxref{Non-Stop Mode}.
27011 @item QPassSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
27012 @cindex pass signals to inferior, remote request
27013 @cindex @samp{QPassSignals} packet
27014 @anchor{QPassSignals}
27015 Each listed @var{signal} should be passed directly to the inferior process.
27016 Signals are numbered identically to continue packets and stop replies
27017 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
27018 strictly greater than the previous item. These signals do not need to stop
27019 the inferior, or be reported to @value{GDBN}. All other signals should be
27020 reported to @value{GDBN}. Multiple @samp{QPassSignals} packets do not
27021 combine; any earlier @samp{QPassSignals} list is completely replaced by the
27022 new list. This packet improves performance when using @samp{handle
27023 @var{signal} nostop noprint pass}.
27028 The request succeeded.
27031 An error occurred. @var{nn} are hex digits.
27034 An empty reply indicates that @samp{QPassSignals} is not supported by
27038 Use of this packet is controlled by the @code{set remote pass-signals}
27039 command (@pxref{Remote Configuration, set remote pass-signals}).
27040 This packet is not probed by default; the remote stub must request it,
27041 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
27043 @item qRcmd,@var{command}
27044 @cindex execute remote command, remote request
27045 @cindex @samp{qRcmd} packet
27046 @var{command} (hex encoded) is passed to the local interpreter for
27047 execution. Invalid commands should be reported using the output
27048 string. Before the final result packet, the target may also respond
27049 with a number of intermediate @samp{O@var{output}} console output
27050 packets. @emph{Implementors should note that providing access to a
27051 stubs's interpreter may have security implications}.
27056 A command response with no output.
27058 A command response with the hex encoded output string @var{OUTPUT}.
27060 Indicate a badly formed request.
27062 An empty reply indicates that @samp{qRcmd} is not recognized.
27065 (Note that the @code{qRcmd} packet's name is separated from the
27066 command by a @samp{,}, not a @samp{:}, contrary to the naming
27067 conventions above. Please don't use this packet as a model for new
27070 @item qSearch:memory:@var{address};@var{length};@var{search-pattern}
27071 @cindex searching memory, in remote debugging
27072 @cindex @samp{qSearch:memory} packet
27073 @anchor{qSearch memory}
27074 Search @var{length} bytes at @var{address} for @var{search-pattern}.
27075 @var{address} and @var{length} are encoded in hex.
27076 @var{search-pattern} is a sequence of bytes, hex encoded.
27081 The pattern was not found.
27083 The pattern was found at @var{address}.
27085 A badly formed request or an error was encountered while searching memory.
27087 An empty reply indicates that @samp{qSearch:memory} is not recognized.
27090 @item QStartNoAckMode
27091 @cindex @samp{QStartNoAckMode} packet
27092 @anchor{QStartNoAckMode}
27093 Request that the remote stub disable the normal @samp{+}/@samp{-}
27094 protocol acknowledgments (@pxref{Packet Acknowledgment}).
27099 The stub has switched to no-acknowledgment mode.
27100 @value{GDBN} acknowledges this reponse,
27101 but neither the stub nor @value{GDBN} shall send or expect further
27102 @samp{+}/@samp{-} acknowledgments in the current connection.
27104 An empty reply indicates that the stub does not support no-acknowledgment mode.
27107 @item qSupported @r{[}:@var{gdbfeature} @r{[};@var{gdbfeature}@r{]}@dots{} @r{]}
27108 @cindex supported packets, remote query
27109 @cindex features of the remote protocol
27110 @cindex @samp{qSupported} packet
27111 @anchor{qSupported}
27112 Tell the remote stub about features supported by @value{GDBN}, and
27113 query the stub for features it supports. This packet allows
27114 @value{GDBN} and the remote stub to take advantage of each others'
27115 features. @samp{qSupported} also consolidates multiple feature probes
27116 at startup, to improve @value{GDBN} performance---a single larger
27117 packet performs better than multiple smaller probe packets on
27118 high-latency links. Some features may enable behavior which must not
27119 be on by default, e.g.@: because it would confuse older clients or
27120 stubs. Other features may describe packets which could be
27121 automatically probed for, but are not. These features must be
27122 reported before @value{GDBN} will use them. This ``default
27123 unsupported'' behavior is not appropriate for all packets, but it
27124 helps to keep the initial connection time under control with new
27125 versions of @value{GDBN} which support increasing numbers of packets.
27129 @item @var{stubfeature} @r{[};@var{stubfeature}@r{]}@dots{}
27130 The stub supports or does not support each returned @var{stubfeature},
27131 depending on the form of each @var{stubfeature} (see below for the
27134 An empty reply indicates that @samp{qSupported} is not recognized,
27135 or that no features needed to be reported to @value{GDBN}.
27138 The allowed forms for each feature (either a @var{gdbfeature} in the
27139 @samp{qSupported} packet, or a @var{stubfeature} in the response)
27143 @item @var{name}=@var{value}
27144 The remote protocol feature @var{name} is supported, and associated
27145 with the specified @var{value}. The format of @var{value} depends
27146 on the feature, but it must not include a semicolon.
27148 The remote protocol feature @var{name} is supported, and does not
27149 need an associated value.
27151 The remote protocol feature @var{name} is not supported.
27153 The remote protocol feature @var{name} may be supported, and
27154 @value{GDBN} should auto-detect support in some other way when it is
27155 needed. This form will not be used for @var{gdbfeature} notifications,
27156 but may be used for @var{stubfeature} responses.
27159 Whenever the stub receives a @samp{qSupported} request, the
27160 supplied set of @value{GDBN} features should override any previous
27161 request. This allows @value{GDBN} to put the stub in a known
27162 state, even if the stub had previously been communicating with
27163 a different version of @value{GDBN}.
27165 The following values of @var{gdbfeature} (for the packet sent by @value{GDBN})
27170 This feature indicates whether @value{GDBN} supports multiprocess
27171 extensions to the remote protocol. @value{GDBN} does not use such
27172 extensions unless the stub also reports that it supports them by
27173 including @samp{multiprocess+} in its @samp{qSupported} reply.
27174 @xref{multiprocess extensions}, for details.
27177 Stubs should ignore any unknown values for
27178 @var{gdbfeature}. Any @value{GDBN} which sends a @samp{qSupported}
27179 packet supports receiving packets of unlimited length (earlier
27180 versions of @value{GDBN} may reject overly long responses). Additional values
27181 for @var{gdbfeature} may be defined in the future to let the stub take
27182 advantage of new features in @value{GDBN}, e.g.@: incompatible
27183 improvements in the remote protocol---the @samp{multiprocess} feature is
27184 an example of such a feature. The stub's reply should be independent
27185 of the @var{gdbfeature} entries sent by @value{GDBN}; first @value{GDBN}
27186 describes all the features it supports, and then the stub replies with
27187 all the features it supports.
27189 Similarly, @value{GDBN} will silently ignore unrecognized stub feature
27190 responses, as long as each response uses one of the standard forms.
27192 Some features are flags. A stub which supports a flag feature
27193 should respond with a @samp{+} form response. Other features
27194 require values, and the stub should respond with an @samp{=}
27197 Each feature has a default value, which @value{GDBN} will use if
27198 @samp{qSupported} is not available or if the feature is not mentioned
27199 in the @samp{qSupported} response. The default values are fixed; a
27200 stub is free to omit any feature responses that match the defaults.
27202 Not all features can be probed, but for those which can, the probing
27203 mechanism is useful: in some cases, a stub's internal
27204 architecture may not allow the protocol layer to know some information
27205 about the underlying target in advance. This is especially common in
27206 stubs which may be configured for multiple targets.
27208 These are the currently defined stub features and their properties:
27210 @multitable @columnfractions 0.35 0.2 0.12 0.2
27211 @c NOTE: The first row should be @headitem, but we do not yet require
27212 @c a new enough version of Texinfo (4.7) to use @headitem.
27214 @tab Value Required
27218 @item @samp{PacketSize}
27223 @item @samp{qXfer:auxv:read}
27228 @item @samp{qXfer:features:read}
27233 @item @samp{qXfer:libraries:read}
27238 @item @samp{qXfer:memory-map:read}
27243 @item @samp{qXfer:spu:read}
27248 @item @samp{qXfer:spu:write}
27253 @item @samp{qXfer:siginfo:read}
27258 @item @samp{qXfer:siginfo:write}
27263 @item @samp{QNonStop}
27268 @item @samp{QPassSignals}
27273 @item @samp{QStartNoAckMode}
27278 @item @samp{multiprocess}
27285 These are the currently defined stub features, in more detail:
27288 @cindex packet size, remote protocol
27289 @item PacketSize=@var{bytes}
27290 The remote stub can accept packets up to at least @var{bytes} in
27291 length. @value{GDBN} will send packets up to this size for bulk
27292 transfers, and will never send larger packets. This is a limit on the
27293 data characters in the packet, including the frame and checksum.
27294 There is no trailing NUL byte in a remote protocol packet; if the stub
27295 stores packets in a NUL-terminated format, it should allow an extra
27296 byte in its buffer for the NUL. If this stub feature is not supported,
27297 @value{GDBN} guesses based on the size of the @samp{g} packet response.
27299 @item qXfer:auxv:read
27300 The remote stub understands the @samp{qXfer:auxv:read} packet
27301 (@pxref{qXfer auxiliary vector read}).
27303 @item qXfer:features:read
27304 The remote stub understands the @samp{qXfer:features:read} packet
27305 (@pxref{qXfer target description read}).
27307 @item qXfer:libraries:read
27308 The remote stub understands the @samp{qXfer:libraries:read} packet
27309 (@pxref{qXfer library list read}).
27311 @item qXfer:memory-map:read
27312 The remote stub understands the @samp{qXfer:memory-map:read} packet
27313 (@pxref{qXfer memory map read}).
27315 @item qXfer:spu:read
27316 The remote stub understands the @samp{qXfer:spu:read} packet
27317 (@pxref{qXfer spu read}).
27319 @item qXfer:spu:write
27320 The remote stub understands the @samp{qXfer:spu:write} packet
27321 (@pxref{qXfer spu write}).
27323 @item qXfer:siginfo:read
27324 The remote stub understands the @samp{qXfer:siginfo:read} packet
27325 (@pxref{qXfer siginfo read}).
27327 @item qXfer:siginfo:write
27328 The remote stub understands the @samp{qXfer:siginfo:write} packet
27329 (@pxref{qXfer siginfo write}).
27332 The remote stub understands the @samp{QNonStop} packet
27333 (@pxref{QNonStop}).
27336 The remote stub understands the @samp{QPassSignals} packet
27337 (@pxref{QPassSignals}).
27339 @item QStartNoAckMode
27340 The remote stub understands the @samp{QStartNoAckMode} packet and
27341 prefers to operate in no-acknowledgment mode. @xref{Packet Acknowledgment}.
27344 @anchor{multiprocess extensions}
27345 @cindex multiprocess extensions, in remote protocol
27346 The remote stub understands the multiprocess extensions to the remote
27347 protocol syntax. The multiprocess extensions affect the syntax of
27348 thread IDs in both packets and replies (@pxref{thread-id syntax}), and
27349 add process IDs to the @samp{D} packet and @samp{W} and @samp{X}
27350 replies. Note that reporting this feature indicates support for the
27351 syntactic extensions only, not that the stub necessarily supports
27352 debugging of more than one process at a time. The stub must not use
27353 multiprocess extensions in packet replies unless @value{GDBN} has also
27354 indicated it supports them in its @samp{qSupported} request.
27356 @item qXfer:osdata:read
27357 The remote stub understands the @samp{qXfer:osdata:read} packet
27358 ((@pxref{qXfer osdata read}).
27363 @cindex symbol lookup, remote request
27364 @cindex @samp{qSymbol} packet
27365 Notify the target that @value{GDBN} is prepared to serve symbol lookup
27366 requests. Accept requests from the target for the values of symbols.
27371 The target does not need to look up any (more) symbols.
27372 @item qSymbol:@var{sym_name}
27373 The target requests the value of symbol @var{sym_name} (hex encoded).
27374 @value{GDBN} may provide the value by using the
27375 @samp{qSymbol:@var{sym_value}:@var{sym_name}} message, described
27379 @item qSymbol:@var{sym_value}:@var{sym_name}
27380 Set the value of @var{sym_name} to @var{sym_value}.
27382 @var{sym_name} (hex encoded) is the name of a symbol whose value the
27383 target has previously requested.
27385 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
27386 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
27392 The target does not need to look up any (more) symbols.
27393 @item qSymbol:@var{sym_name}
27394 The target requests the value of a new symbol @var{sym_name} (hex
27395 encoded). @value{GDBN} will continue to supply the values of symbols
27396 (if available), until the target ceases to request them.
27401 @xref{Tracepoint Packets}.
27403 @item qThreadExtraInfo,@var{thread-id}
27404 @cindex thread attributes info, remote request
27405 @cindex @samp{qThreadExtraInfo} packet
27406 Obtain a printable string description of a thread's attributes from
27407 the target OS. @var{thread-id} is a thread ID;
27408 see @ref{thread-id syntax}. This
27409 string may contain anything that the target OS thinks is interesting
27410 for @value{GDBN} to tell the user about the thread. The string is
27411 displayed in @value{GDBN}'s @code{info threads} display. Some
27412 examples of possible thread extra info strings are @samp{Runnable}, or
27413 @samp{Blocked on Mutex}.
27417 @item @var{XX}@dots{}
27418 Where @samp{@var{XX}@dots{}} is a hex encoding of @sc{ascii} data,
27419 comprising the printable string containing the extra information about
27420 the thread's attributes.
27423 (Note that the @code{qThreadExtraInfo} packet's name is separated from
27424 the command by a @samp{,}, not a @samp{:}, contrary to the naming
27425 conventions above. Please don't use this packet as a model for new
27433 @xref{Tracepoint Packets}.
27435 @item qXfer:@var{object}:read:@var{annex}:@var{offset},@var{length}
27436 @cindex read special object, remote request
27437 @cindex @samp{qXfer} packet
27438 @anchor{qXfer read}
27439 Read uninterpreted bytes from the target's special data area
27440 identified by the keyword @var{object}. Request @var{length} bytes
27441 starting at @var{offset} bytes into the data. The content and
27442 encoding of @var{annex} is specific to @var{object}; it can supply
27443 additional details about what data to access.
27445 Here are the specific requests of this form defined so far. All
27446 @samp{qXfer:@var{object}:read:@dots{}} requests use the same reply
27447 formats, listed below.
27450 @item qXfer:auxv:read::@var{offset},@var{length}
27451 @anchor{qXfer auxiliary vector read}
27452 Access the target's @dfn{auxiliary vector}. @xref{OS Information,
27453 auxiliary vector}. Note @var{annex} must be empty.
27455 This packet is not probed by default; the remote stub must request it,
27456 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
27458 @item qXfer:features:read:@var{annex}:@var{offset},@var{length}
27459 @anchor{qXfer target description read}
27460 Access the @dfn{target description}. @xref{Target Descriptions}. The
27461 annex specifies which XML document to access. The main description is
27462 always loaded from the @samp{target.xml} annex.
27464 This packet is not probed by default; the remote stub must request it,
27465 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
27467 @item qXfer:libraries:read:@var{annex}:@var{offset},@var{length}
27468 @anchor{qXfer library list read}
27469 Access the target's list of loaded libraries. @xref{Library List Format}.
27470 The annex part of the generic @samp{qXfer} packet must be empty
27471 (@pxref{qXfer read}).
27473 Targets which maintain a list of libraries in the program's memory do
27474 not need to implement this packet; it is designed for platforms where
27475 the operating system manages the list of loaded libraries.
27477 This packet is not probed by default; the remote stub must request it,
27478 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
27480 @item qXfer:memory-map:read::@var{offset},@var{length}
27481 @anchor{qXfer memory map read}
27482 Access the target's @dfn{memory-map}. @xref{Memory Map Format}. The
27483 annex part of the generic @samp{qXfer} packet must be empty
27484 (@pxref{qXfer read}).
27486 This packet is not probed by default; the remote stub must request it,
27487 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
27489 @item qXfer:siginfo:read::@var{offset},@var{length}
27490 @anchor{qXfer siginfo read}
27491 Read contents of the extra signal information on the target
27492 system. The annex part of the generic @samp{qXfer} packet must be
27493 empty (@pxref{qXfer read}).
27495 This packet is not probed by default; the remote stub must request it,
27496 by supplying an appropriate @samp{qSupported} response
27497 (@pxref{qSupported}).
27499 @item qXfer:spu:read:@var{annex}:@var{offset},@var{length}
27500 @anchor{qXfer spu read}
27501 Read contents of an @code{spufs} file on the target system. The
27502 annex specifies which file to read; it must be of the form
27503 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
27504 in the target process, and @var{name} identifes the @code{spufs} file
27505 in that context to be accessed.
27507 This packet is not probed by default; the remote stub must request it,
27508 by supplying an appropriate @samp{qSupported} response
27509 (@pxref{qSupported}).
27511 @item qXfer:osdata:read::@var{offset},@var{length}
27512 @anchor{qXfer osdata read}
27513 Access the target's @dfn{operating system information}.
27514 @xref{Operating System Information}.
27521 Data @var{data} (@pxref{Binary Data}) has been read from the
27522 target. There may be more data at a higher address (although
27523 it is permitted to return @samp{m} even for the last valid
27524 block of data, as long as at least one byte of data was read).
27525 @var{data} may have fewer bytes than the @var{length} in the
27529 Data @var{data} (@pxref{Binary Data}) has been read from the target.
27530 There is no more data to be read. @var{data} may have fewer bytes
27531 than the @var{length} in the request.
27534 The @var{offset} in the request is at the end of the data.
27535 There is no more data to be read.
27538 The request was malformed, or @var{annex} was invalid.
27541 The offset was invalid, or there was an error encountered reading the data.
27542 @var{nn} is a hex-encoded @code{errno} value.
27545 An empty reply indicates the @var{object} string was not recognized by
27546 the stub, or that the object does not support reading.
27549 @item qXfer:@var{object}:write:@var{annex}:@var{offset}:@var{data}@dots{}
27550 @cindex write data into object, remote request
27551 @anchor{qXfer write}
27552 Write uninterpreted bytes into the target's special data area
27553 identified by the keyword @var{object}, starting at @var{offset} bytes
27554 into the data. @var{data}@dots{} is the binary-encoded data
27555 (@pxref{Binary Data}) to be written. The content and encoding of @var{annex}
27556 is specific to @var{object}; it can supply additional details about what data
27559 Here are the specific requests of this form defined so far. All
27560 @samp{qXfer:@var{object}:write:@dots{}} requests use the same reply
27561 formats, listed below.
27564 @item qXfer:siginfo:write::@var{offset}:@var{data}@dots{}
27565 @anchor{qXfer siginfo write}
27566 Write @var{data} to the extra signal information on the target system.
27567 The annex part of the generic @samp{qXfer} packet must be
27568 empty (@pxref{qXfer write}).
27570 This packet is not probed by default; the remote stub must request it,
27571 by supplying an appropriate @samp{qSupported} response
27572 (@pxref{qSupported}).
27574 @item qXfer:spu:write:@var{annex}:@var{offset}:@var{data}@dots{}
27575 @anchor{qXfer spu write}
27576 Write @var{data} to an @code{spufs} file on the target system. The
27577 annex specifies which file to write; it must be of the form
27578 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
27579 in the target process, and @var{name} identifes the @code{spufs} file
27580 in that context to be accessed.
27582 This packet is not probed by default; the remote stub must request it,
27583 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
27589 @var{nn} (hex encoded) is the number of bytes written.
27590 This may be fewer bytes than supplied in the request.
27593 The request was malformed, or @var{annex} was invalid.
27596 The offset was invalid, or there was an error encountered writing the data.
27597 @var{nn} is a hex-encoded @code{errno} value.
27600 An empty reply indicates the @var{object} string was not
27601 recognized by the stub, or that the object does not support writing.
27604 @item qXfer:@var{object}:@var{operation}:@dots{}
27605 Requests of this form may be added in the future. When a stub does
27606 not recognize the @var{object} keyword, or its support for
27607 @var{object} does not recognize the @var{operation} keyword, the stub
27608 must respond with an empty packet.
27610 @item qAttached:@var{pid}
27611 @cindex query attached, remote request
27612 @cindex @samp{qAttached} packet
27613 Return an indication of whether the remote server attached to an
27614 existing process or created a new process. When the multiprocess
27615 protocol extensions are supported (@pxref{multiprocess extensions}),
27616 @var{pid} is an integer in hexadecimal format identifying the target
27617 process. Otherwise, @value{GDBN} will omit the @var{pid} field and
27618 the query packet will be simplified as @samp{qAttached}.
27620 This query is used, for example, to know whether the remote process
27621 should be detached or killed when a @value{GDBN} session is ended with
27622 the @code{quit} command.
27627 The remote server attached to an existing process.
27629 The remote server created a new process.
27631 A badly formed request or an error was encountered.
27636 @node Register Packet Format
27637 @section Register Packet Format
27639 The following @code{g}/@code{G} packets have previously been defined.
27640 In the below, some thirty-two bit registers are transferred as
27641 sixty-four bits. Those registers should be zero/sign extended (which?)
27642 to fill the space allocated. Register bytes are transferred in target
27643 byte order. The two nibbles within a register byte are transferred
27644 most-significant - least-significant.
27650 All registers are transferred as thirty-two bit quantities in the order:
27651 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
27652 registers; fsr; fir; fp.
27656 All registers are transferred as sixty-four bit quantities (including
27657 thirty-two bit registers such as @code{sr}). The ordering is the same
27662 @node Tracepoint Packets
27663 @section Tracepoint Packets
27664 @cindex tracepoint packets
27665 @cindex packets, tracepoint
27667 Here we describe the packets @value{GDBN} uses to implement
27668 tracepoints (@pxref{Tracepoints}).
27672 @item QTDP:@var{n}:@var{addr}:@var{ena}:@var{step}:@var{pass}@r{[}-@r{]}
27673 Create a new tracepoint, number @var{n}, at @var{addr}. If @var{ena}
27674 is @samp{E}, then the tracepoint is enabled; if it is @samp{D}, then
27675 the tracepoint is disabled. @var{step} is the tracepoint's step
27676 count, and @var{pass} is its pass count. If the trailing @samp{-} is
27677 present, further @samp{QTDP} packets will follow to specify this
27678 tracepoint's actions.
27683 The packet was understood and carried out.
27685 The packet was not recognized.
27688 @item QTDP:-@var{n}:@var{addr}:@r{[}S@r{]}@var{action}@dots{}@r{[}-@r{]}
27689 Define actions to be taken when a tracepoint is hit. @var{n} and
27690 @var{addr} must be the same as in the initial @samp{QTDP} packet for
27691 this tracepoint. This packet may only be sent immediately after
27692 another @samp{QTDP} packet that ended with a @samp{-}. If the
27693 trailing @samp{-} is present, further @samp{QTDP} packets will follow,
27694 specifying more actions for this tracepoint.
27696 In the series of action packets for a given tracepoint, at most one
27697 can have an @samp{S} before its first @var{action}. If such a packet
27698 is sent, it and the following packets define ``while-stepping''
27699 actions. Any prior packets define ordinary actions --- that is, those
27700 taken when the tracepoint is first hit. If no action packet has an
27701 @samp{S}, then all the packets in the series specify ordinary
27702 tracepoint actions.
27704 The @samp{@var{action}@dots{}} portion of the packet is a series of
27705 actions, concatenated without separators. Each action has one of the
27711 Collect the registers whose bits are set in @var{mask}. @var{mask} is
27712 a hexadecimal number whose @var{i}'th bit is set if register number
27713 @var{i} should be collected. (The least significant bit is numbered
27714 zero.) Note that @var{mask} may be any number of digits long; it may
27715 not fit in a 32-bit word.
27717 @item M @var{basereg},@var{offset},@var{len}
27718 Collect @var{len} bytes of memory starting at the address in register
27719 number @var{basereg}, plus @var{offset}. If @var{basereg} is
27720 @samp{-1}, then the range has a fixed address: @var{offset} is the
27721 address of the lowest byte to collect. The @var{basereg},
27722 @var{offset}, and @var{len} parameters are all unsigned hexadecimal
27723 values (the @samp{-1} value for @var{basereg} is a special case).
27725 @item X @var{len},@var{expr}
27726 Evaluate @var{expr}, whose length is @var{len}, and collect memory as
27727 it directs. @var{expr} is an agent expression, as described in
27728 @ref{Agent Expressions}. Each byte of the expression is encoded as a
27729 two-digit hex number in the packet; @var{len} is the number of bytes
27730 in the expression (and thus one-half the number of hex digits in the
27735 Any number of actions may be packed together in a single @samp{QTDP}
27736 packet, as long as the packet does not exceed the maximum packet
27737 length (400 bytes, for many stubs). There may be only one @samp{R}
27738 action per tracepoint, and it must precede any @samp{M} or @samp{X}
27739 actions. Any registers referred to by @samp{M} and @samp{X} actions
27740 must be collected by a preceding @samp{R} action. (The
27741 ``while-stepping'' actions are treated as if they were attached to a
27742 separate tracepoint, as far as these restrictions are concerned.)
27747 The packet was understood and carried out.
27749 The packet was not recognized.
27752 @item QTFrame:@var{n}
27753 Select the @var{n}'th tracepoint frame from the buffer, and use the
27754 register and memory contents recorded there to answer subsequent
27755 request packets from @value{GDBN}.
27757 A successful reply from the stub indicates that the stub has found the
27758 requested frame. The response is a series of parts, concatenated
27759 without separators, describing the frame we selected. Each part has
27760 one of the following forms:
27764 The selected frame is number @var{n} in the trace frame buffer;
27765 @var{f} is a hexadecimal number. If @var{f} is @samp{-1}, then there
27766 was no frame matching the criteria in the request packet.
27769 The selected trace frame records a hit of tracepoint number @var{t};
27770 @var{t} is a hexadecimal number.
27774 @item QTFrame:pc:@var{addr}
27775 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
27776 currently selected frame whose PC is @var{addr};
27777 @var{addr} is a hexadecimal number.
27779 @item QTFrame:tdp:@var{t}
27780 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
27781 currently selected frame that is a hit of tracepoint @var{t}; @var{t}
27782 is a hexadecimal number.
27784 @item QTFrame:range:@var{start}:@var{end}
27785 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
27786 currently selected frame whose PC is between @var{start} (inclusive)
27787 and @var{end} (exclusive); @var{start} and @var{end} are hexadecimal
27790 @item QTFrame:outside:@var{start}:@var{end}
27791 Like @samp{QTFrame:range:@var{start}:@var{end}}, but select the first
27792 frame @emph{outside} the given range of addresses.
27795 Begin the tracepoint experiment. Begin collecting data from tracepoint
27796 hits in the trace frame buffer.
27799 End the tracepoint experiment. Stop collecting trace frames.
27802 Clear the table of tracepoints, and empty the trace frame buffer.
27804 @item QTro:@var{start1},@var{end1}:@var{start2},@var{end2}:@dots{}
27805 Establish the given ranges of memory as ``transparent''. The stub
27806 will answer requests for these ranges from memory's current contents,
27807 if they were not collected as part of the tracepoint hit.
27809 @value{GDBN} uses this to mark read-only regions of memory, like those
27810 containing program code. Since these areas never change, they should
27811 still have the same contents they did when the tracepoint was hit, so
27812 there's no reason for the stub to refuse to provide their contents.
27815 Ask the stub if there is a trace experiment running right now.
27820 There is no trace experiment running.
27822 There is a trace experiment running.
27828 @node Host I/O Packets
27829 @section Host I/O Packets
27830 @cindex Host I/O, remote protocol
27831 @cindex file transfer, remote protocol
27833 The @dfn{Host I/O} packets allow @value{GDBN} to perform I/O
27834 operations on the far side of a remote link. For example, Host I/O is
27835 used to upload and download files to a remote target with its own
27836 filesystem. Host I/O uses the same constant values and data structure
27837 layout as the target-initiated File-I/O protocol. However, the
27838 Host I/O packets are structured differently. The target-initiated
27839 protocol relies on target memory to store parameters and buffers.
27840 Host I/O requests are initiated by @value{GDBN}, and the
27841 target's memory is not involved. @xref{File-I/O Remote Protocol
27842 Extension}, for more details on the target-initiated protocol.
27844 The Host I/O request packets all encode a single operation along with
27845 its arguments. They have this format:
27849 @item vFile:@var{operation}: @var{parameter}@dots{}
27850 @var{operation} is the name of the particular request; the target
27851 should compare the entire packet name up to the second colon when checking
27852 for a supported operation. The format of @var{parameter} depends on
27853 the operation. Numbers are always passed in hexadecimal. Negative
27854 numbers have an explicit minus sign (i.e.@: two's complement is not
27855 used). Strings (e.g.@: filenames) are encoded as a series of
27856 hexadecimal bytes. The last argument to a system call may be a
27857 buffer of escaped binary data (@pxref{Binary Data}).
27861 The valid responses to Host I/O packets are:
27865 @item F @var{result} [, @var{errno}] [; @var{attachment}]
27866 @var{result} is the integer value returned by this operation, usually
27867 non-negative for success and -1 for errors. If an error has occured,
27868 @var{errno} will be included in the result. @var{errno} will have a
27869 value defined by the File-I/O protocol (@pxref{Errno Values}). For
27870 operations which return data, @var{attachment} supplies the data as a
27871 binary buffer. Binary buffers in response packets are escaped in the
27872 normal way (@pxref{Binary Data}). See the individual packet
27873 documentation for the interpretation of @var{result} and
27877 An empty response indicates that this operation is not recognized.
27881 These are the supported Host I/O operations:
27884 @item vFile:open: @var{pathname}, @var{flags}, @var{mode}
27885 Open a file at @var{pathname} and return a file descriptor for it, or
27886 return -1 if an error occurs. @var{pathname} is a string,
27887 @var{flags} is an integer indicating a mask of open flags
27888 (@pxref{Open Flags}), and @var{mode} is an integer indicating a mask
27889 of mode bits to use if the file is created (@pxref{mode_t Values}).
27890 @xref{open}, for details of the open flags and mode values.
27892 @item vFile:close: @var{fd}
27893 Close the open file corresponding to @var{fd} and return 0, or
27894 -1 if an error occurs.
27896 @item vFile:pread: @var{fd}, @var{count}, @var{offset}
27897 Read data from the open file corresponding to @var{fd}. Up to
27898 @var{count} bytes will be read from the file, starting at @var{offset}
27899 relative to the start of the file. The target may read fewer bytes;
27900 common reasons include packet size limits and an end-of-file
27901 condition. The number of bytes read is returned. Zero should only be
27902 returned for a successful read at the end of the file, or if
27903 @var{count} was zero.
27905 The data read should be returned as a binary attachment on success.
27906 If zero bytes were read, the response should include an empty binary
27907 attachment (i.e.@: a trailing semicolon). The return value is the
27908 number of target bytes read; the binary attachment may be longer if
27909 some characters were escaped.
27911 @item vFile:pwrite: @var{fd}, @var{offset}, @var{data}
27912 Write @var{data} (a binary buffer) to the open file corresponding
27913 to @var{fd}. Start the write at @var{offset} from the start of the
27914 file. Unlike many @code{write} system calls, there is no
27915 separate @var{count} argument; the length of @var{data} in the
27916 packet is used. @samp{vFile:write} returns the number of bytes written,
27917 which may be shorter than the length of @var{data}, or -1 if an
27920 @item vFile:unlink: @var{pathname}
27921 Delete the file at @var{pathname} on the target. Return 0,
27922 or -1 if an error occurs. @var{pathname} is a string.
27927 @section Interrupts
27928 @cindex interrupts (remote protocol)
27930 When a program on the remote target is running, @value{GDBN} may
27931 attempt to interrupt it by sending a @samp{Ctrl-C} or a @code{BREAK},
27932 control of which is specified via @value{GDBN}'s @samp{remotebreak}
27933 setting (@pxref{set remotebreak}).
27935 The precise meaning of @code{BREAK} is defined by the transport
27936 mechanism and may, in fact, be undefined. @value{GDBN} does not
27937 currently define a @code{BREAK} mechanism for any of the network
27938 interfaces except for TCP, in which case @value{GDBN} sends the
27939 @code{telnet} BREAK sequence.
27941 @samp{Ctrl-C}, on the other hand, is defined and implemented for all
27942 transport mechanisms. It is represented by sending the single byte
27943 @code{0x03} without any of the usual packet overhead described in
27944 the Overview section (@pxref{Overview}). When a @code{0x03} byte is
27945 transmitted as part of a packet, it is considered to be packet data
27946 and does @emph{not} represent an interrupt. E.g., an @samp{X} packet
27947 (@pxref{X packet}), used for binary downloads, may include an unescaped
27948 @code{0x03} as part of its packet.
27950 Stubs are not required to recognize these interrupt mechanisms and the
27951 precise meaning associated with receipt of the interrupt is
27952 implementation defined. If the target supports debugging of multiple
27953 threads and/or processes, it should attempt to interrupt all
27954 currently-executing threads and processes.
27955 If the stub is successful at interrupting the
27956 running program, it should send one of the stop
27957 reply packets (@pxref{Stop Reply Packets}) to @value{GDBN} as a result
27958 of successfully stopping the program in all-stop mode, and a stop reply
27959 for each stopped thread in non-stop mode.
27960 Interrupts received while the
27961 program is stopped are discarded.
27963 @node Notification Packets
27964 @section Notification Packets
27965 @cindex notification packets
27966 @cindex packets, notification
27968 The @value{GDBN} remote serial protocol includes @dfn{notifications},
27969 packets that require no acknowledgment. Both the GDB and the stub
27970 may send notifications (although the only notifications defined at
27971 present are sent by the stub). Notifications carry information
27972 without incurring the round-trip latency of an acknowledgment, and so
27973 are useful for low-impact communications where occasional packet loss
27976 A notification packet has the form @samp{% @var{data} #
27977 @var{checksum}}, where @var{data} is the content of the notification,
27978 and @var{checksum} is a checksum of @var{data}, computed and formatted
27979 as for ordinary @value{GDBN} packets. A notification's @var{data}
27980 never contains @samp{$}, @samp{%} or @samp{#} characters. Upon
27981 receiving a notification, the recipient sends no @samp{+} or @samp{-}
27982 to acknowledge the notification's receipt or to report its corruption.
27984 Every notification's @var{data} begins with a name, which contains no
27985 colon characters, followed by a colon character.
27987 Recipients should silently ignore corrupted notifications and
27988 notifications they do not understand. Recipients should restart
27989 timeout periods on receipt of a well-formed notification, whether or
27990 not they understand it.
27992 Senders should only send the notifications described here when this
27993 protocol description specifies that they are permitted. In the
27994 future, we may extend the protocol to permit existing notifications in
27995 new contexts; this rule helps older senders avoid confusing newer
27998 (Older versions of @value{GDBN} ignore bytes received until they see
27999 the @samp{$} byte that begins an ordinary packet, so new stubs may
28000 transmit notifications without fear of confusing older clients. There
28001 are no notifications defined for @value{GDBN} to send at the moment, but we
28002 assume that most older stubs would ignore them, as well.)
28004 The following notification packets from the stub to @value{GDBN} are
28008 @item Stop: @var{reply}
28009 Report an asynchronous stop event in non-stop mode.
28010 The @var{reply} has the form of a stop reply, as
28011 described in @ref{Stop Reply Packets}. Refer to @ref{Remote Non-Stop},
28012 for information on how these notifications are acknowledged by
28016 @node Remote Non-Stop
28017 @section Remote Protocol Support for Non-Stop Mode
28019 @value{GDBN}'s remote protocol supports non-stop debugging of
28020 multi-threaded programs, as described in @ref{Non-Stop Mode}. If the stub
28021 supports non-stop mode, it should report that to @value{GDBN} by including
28022 @samp{QNonStop+} in its @samp{qSupported} response (@pxref{qSupported}).
28024 @value{GDBN} typically sends a @samp{QNonStop} packet only when
28025 establishing a new connection with the stub. Entering non-stop mode
28026 does not alter the state of any currently-running threads, but targets
28027 must stop all threads in any already-attached processes when entering
28028 all-stop mode. @value{GDBN} uses the @samp{?} packet as necessary to
28029 probe the target state after a mode change.
28031 In non-stop mode, when an attached process encounters an event that
28032 would otherwise be reported with a stop reply, it uses the
28033 asynchronous notification mechanism (@pxref{Notification Packets}) to
28034 inform @value{GDBN}. In contrast to all-stop mode, where all threads
28035 in all processes are stopped when a stop reply is sent, in non-stop
28036 mode only the thread reporting the stop event is stopped. That is,
28037 when reporting a @samp{S} or @samp{T} response to indicate completion
28038 of a step operation, hitting a breakpoint, or a fault, only the
28039 affected thread is stopped; any other still-running threads continue
28040 to run. When reporting a @samp{W} or @samp{X} response, all running
28041 threads belonging to other attached processes continue to run.
28043 Only one stop reply notification at a time may be pending; if
28044 additional stop events occur before @value{GDBN} has acknowledged the
28045 previous notification, they must be queued by the stub for later
28046 synchronous transmission in response to @samp{vStopped} packets from
28047 @value{GDBN}. Because the notification mechanism is unreliable,
28048 the stub is permitted to resend a stop reply notification
28049 if it believes @value{GDBN} may not have received it. @value{GDBN}
28050 ignores additional stop reply notifications received before it has
28051 finished processing a previous notification and the stub has completed
28052 sending any queued stop events.
28054 Otherwise, @value{GDBN} must be prepared to receive a stop reply
28055 notification at any time. Specifically, they may appear when
28056 @value{GDBN} is not otherwise reading input from the stub, or when
28057 @value{GDBN} is expecting to read a normal synchronous response or a
28058 @samp{+}/@samp{-} acknowledgment to a packet it has sent.
28059 Notification packets are distinct from any other communication from
28060 the stub so there is no ambiguity.
28062 After receiving a stop reply notification, @value{GDBN} shall
28063 acknowledge it by sending a @samp{vStopped} packet (@pxref{vStopped packet})
28064 as a regular, synchronous request to the stub. Such acknowledgment
28065 is not required to happen immediately, as @value{GDBN} is permitted to
28066 send other, unrelated packets to the stub first, which the stub should
28069 Upon receiving a @samp{vStopped} packet, if the stub has other queued
28070 stop events to report to @value{GDBN}, it shall respond by sending a
28071 normal stop reply response. @value{GDBN} shall then send another
28072 @samp{vStopped} packet to solicit further responses; again, it is
28073 permitted to send other, unrelated packets as well which the stub
28074 should process normally.
28076 If the stub receives a @samp{vStopped} packet and there are no
28077 additional stop events to report, the stub shall return an @samp{OK}
28078 response. At this point, if further stop events occur, the stub shall
28079 send a new stop reply notification, @value{GDBN} shall accept the
28080 notification, and the process shall be repeated.
28082 In non-stop mode, the target shall respond to the @samp{?} packet as
28083 follows. First, any incomplete stop reply notification/@samp{vStopped}
28084 sequence in progress is abandoned. The target must begin a new
28085 sequence reporting stop events for all stopped threads, whether or not
28086 it has previously reported those events to @value{GDBN}. The first
28087 stop reply is sent as a synchronous reply to the @samp{?} packet, and
28088 subsequent stop replies are sent as responses to @samp{vStopped} packets
28089 using the mechanism described above. The target must not send
28090 asynchronous stop reply notifications until the sequence is complete.
28091 If all threads are running when the target receives the @samp{?} packet,
28092 or if the target is not attached to any process, it shall respond
28095 @node Packet Acknowledgment
28096 @section Packet Acknowledgment
28098 @cindex acknowledgment, for @value{GDBN} remote
28099 @cindex packet acknowledgment, for @value{GDBN} remote
28100 By default, when either the host or the target machine receives a packet,
28101 the first response expected is an acknowledgment: either @samp{+} (to indicate
28102 the package was received correctly) or @samp{-} (to request retransmission).
28103 This mechanism allows the @value{GDBN} remote protocol to operate over
28104 unreliable transport mechanisms, such as a serial line.
28106 In cases where the transport mechanism is itself reliable (such as a pipe or
28107 TCP connection), the @samp{+}/@samp{-} acknowledgments are redundant.
28108 It may be desirable to disable them in that case to reduce communication
28109 overhead, or for other reasons. This can be accomplished by means of the
28110 @samp{QStartNoAckMode} packet; @pxref{QStartNoAckMode}.
28112 When in no-acknowledgment mode, neither the stub nor @value{GDBN} shall send or
28113 expect @samp{+}/@samp{-} protocol acknowledgments. The packet
28114 and response format still includes the normal checksum, as described in
28115 @ref{Overview}, but the checksum may be ignored by the receiver.
28117 If the stub supports @samp{QStartNoAckMode} and prefers to operate in
28118 no-acknowledgment mode, it should report that to @value{GDBN}
28119 by including @samp{QStartNoAckMode+} in its response to @samp{qSupported};
28120 @pxref{qSupported}.
28121 If @value{GDBN} also supports @samp{QStartNoAckMode} and it has not been
28122 disabled via the @code{set remote noack-packet off} command
28123 (@pxref{Remote Configuration}),
28124 @value{GDBN} may then send a @samp{QStartNoAckMode} packet to the stub.
28125 Only then may the stub actually turn off packet acknowledgments.
28126 @value{GDBN} sends a final @samp{+} acknowledgment of the stub's @samp{OK}
28127 response, which can be safely ignored by the stub.
28129 Note that @code{set remote noack-packet} command only affects negotiation
28130 between @value{GDBN} and the stub when subsequent connections are made;
28131 it does not affect the protocol acknowledgment state for any current
28133 Since @samp{+}/@samp{-} acknowledgments are enabled by default when a
28134 new connection is established,
28135 there is also no protocol request to re-enable the acknowledgments
28136 for the current connection, once disabled.
28141 Example sequence of a target being re-started. Notice how the restart
28142 does not get any direct output:
28147 @emph{target restarts}
28150 <- @code{T001:1234123412341234}
28154 Example sequence of a target being stepped by a single instruction:
28157 -> @code{G1445@dots{}}
28162 <- @code{T001:1234123412341234}
28166 <- @code{1455@dots{}}
28170 @node File-I/O Remote Protocol Extension
28171 @section File-I/O Remote Protocol Extension
28172 @cindex File-I/O remote protocol extension
28175 * File-I/O Overview::
28176 * Protocol Basics::
28177 * The F Request Packet::
28178 * The F Reply Packet::
28179 * The Ctrl-C Message::
28181 * List of Supported Calls::
28182 * Protocol-specific Representation of Datatypes::
28184 * File-I/O Examples::
28187 @node File-I/O Overview
28188 @subsection File-I/O Overview
28189 @cindex file-i/o overview
28191 The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the
28192 target to use the host's file system and console I/O to perform various
28193 system calls. System calls on the target system are translated into a
28194 remote protocol packet to the host system, which then performs the needed
28195 actions and returns a response packet to the target system.
28196 This simulates file system operations even on targets that lack file systems.
28198 The protocol is defined to be independent of both the host and target systems.
28199 It uses its own internal representation of datatypes and values. Both
28200 @value{GDBN} and the target's @value{GDBN} stub are responsible for
28201 translating the system-dependent value representations into the internal
28202 protocol representations when data is transmitted.
28204 The communication is synchronous. A system call is possible only when
28205 @value{GDBN} is waiting for a response from the @samp{C}, @samp{c}, @samp{S}
28206 or @samp{s} packets. While @value{GDBN} handles the request for a system call,
28207 the target is stopped to allow deterministic access to the target's
28208 memory. Therefore File-I/O is not interruptible by target signals. On
28209 the other hand, it is possible to interrupt File-I/O by a user interrupt
28210 (@samp{Ctrl-C}) within @value{GDBN}.
28212 The target's request to perform a host system call does not finish
28213 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
28214 after finishing the system call, the target returns to continuing the
28215 previous activity (continue, step). No additional continue or step
28216 request from @value{GDBN} is required.
28219 (@value{GDBP}) continue
28220 <- target requests 'system call X'
28221 target is stopped, @value{GDBN} executes system call
28222 -> @value{GDBN} returns result
28223 ... target continues, @value{GDBN} returns to wait for the target
28224 <- target hits breakpoint and sends a Txx packet
28227 The protocol only supports I/O on the console and to regular files on
28228 the host file system. Character or block special devices, pipes,
28229 named pipes, sockets or any other communication method on the host
28230 system are not supported by this protocol.
28232 File I/O is not supported in non-stop mode.
28234 @node Protocol Basics
28235 @subsection Protocol Basics
28236 @cindex protocol basics, file-i/o
28238 The File-I/O protocol uses the @code{F} packet as the request as well
28239 as reply packet. Since a File-I/O system call can only occur when
28240 @value{GDBN} is waiting for a response from the continuing or stepping target,
28241 the File-I/O request is a reply that @value{GDBN} has to expect as a result
28242 of a previous @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
28243 This @code{F} packet contains all information needed to allow @value{GDBN}
28244 to call the appropriate host system call:
28248 A unique identifier for the requested system call.
28251 All parameters to the system call. Pointers are given as addresses
28252 in the target memory address space. Pointers to strings are given as
28253 pointer/length pair. Numerical values are given as they are.
28254 Numerical control flags are given in a protocol-specific representation.
28258 At this point, @value{GDBN} has to perform the following actions.
28262 If the parameters include pointer values to data needed as input to a
28263 system call, @value{GDBN} requests this data from the target with a
28264 standard @code{m} packet request. This additional communication has to be
28265 expected by the target implementation and is handled as any other @code{m}
28269 @value{GDBN} translates all value from protocol representation to host
28270 representation as needed. Datatypes are coerced into the host types.
28273 @value{GDBN} calls the system call.
28276 It then coerces datatypes back to protocol representation.
28279 If the system call is expected to return data in buffer space specified
28280 by pointer parameters to the call, the data is transmitted to the
28281 target using a @code{M} or @code{X} packet. This packet has to be expected
28282 by the target implementation and is handled as any other @code{M} or @code{X}
28287 Eventually @value{GDBN} replies with another @code{F} packet which contains all
28288 necessary information for the target to continue. This at least contains
28295 @code{errno}, if has been changed by the system call.
28302 After having done the needed type and value coercion, the target continues
28303 the latest continue or step action.
28305 @node The F Request Packet
28306 @subsection The @code{F} Request Packet
28307 @cindex file-i/o request packet
28308 @cindex @code{F} request packet
28310 The @code{F} request packet has the following format:
28313 @item F@var{call-id},@var{parameter@dots{}}
28315 @var{call-id} is the identifier to indicate the host system call to be called.
28316 This is just the name of the function.
28318 @var{parameter@dots{}} are the parameters to the system call.
28319 Parameters are hexadecimal integer values, either the actual values in case
28320 of scalar datatypes, pointers to target buffer space in case of compound
28321 datatypes and unspecified memory areas, or pointer/length pairs in case
28322 of string parameters. These are appended to the @var{call-id} as a
28323 comma-delimited list. All values are transmitted in ASCII
28324 string representation, pointer/length pairs separated by a slash.
28330 @node The F Reply Packet
28331 @subsection The @code{F} Reply Packet
28332 @cindex file-i/o reply packet
28333 @cindex @code{F} reply packet
28335 The @code{F} reply packet has the following format:
28339 @item F@var{retcode},@var{errno},@var{Ctrl-C flag};@var{call-specific attachment}
28341 @var{retcode} is the return code of the system call as hexadecimal value.
28343 @var{errno} is the @code{errno} set by the call, in protocol-specific
28345 This parameter can be omitted if the call was successful.
28347 @var{Ctrl-C flag} is only sent if the user requested a break. In this
28348 case, @var{errno} must be sent as well, even if the call was successful.
28349 The @var{Ctrl-C flag} itself consists of the character @samp{C}:
28356 or, if the call was interrupted before the host call has been performed:
28363 assuming 4 is the protocol-specific representation of @code{EINTR}.
28368 @node The Ctrl-C Message
28369 @subsection The @samp{Ctrl-C} Message
28370 @cindex ctrl-c message, in file-i/o protocol
28372 If the @samp{Ctrl-C} flag is set in the @value{GDBN}
28373 reply packet (@pxref{The F Reply Packet}),
28374 the target should behave as if it had
28375 gotten a break message. The meaning for the target is ``system call
28376 interrupted by @code{SIGINT}''. Consequentially, the target should actually stop
28377 (as with a break message) and return to @value{GDBN} with a @code{T02}
28380 It's important for the target to know in which
28381 state the system call was interrupted. There are two possible cases:
28385 The system call hasn't been performed on the host yet.
28388 The system call on the host has been finished.
28392 These two states can be distinguished by the target by the value of the
28393 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
28394 call hasn't been performed. This is equivalent to the @code{EINTR} handling
28395 on POSIX systems. In any other case, the target may presume that the
28396 system call has been finished --- successfully or not --- and should behave
28397 as if the break message arrived right after the system call.
28399 @value{GDBN} must behave reliably. If the system call has not been called
28400 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
28401 @code{errno} in the packet. If the system call on the host has been finished
28402 before the user requests a break, the full action must be finished by
28403 @value{GDBN}. This requires sending @code{M} or @code{X} packets as necessary.
28404 The @code{F} packet may only be sent when either nothing has happened
28405 or the full action has been completed.
28408 @subsection Console I/O
28409 @cindex console i/o as part of file-i/o
28411 By default and if not explicitly closed by the target system, the file
28412 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
28413 on the @value{GDBN} console is handled as any other file output operation
28414 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
28415 by @value{GDBN} so that after the target read request from file descriptor
28416 0 all following typing is buffered until either one of the following
28421 The user types @kbd{Ctrl-c}. The behaviour is as explained above, and the
28423 system call is treated as finished.
28426 The user presses @key{RET}. This is treated as end of input with a trailing
28430 The user types @kbd{Ctrl-d}. This is treated as end of input. No trailing
28431 character (neither newline nor @samp{Ctrl-D}) is appended to the input.
28435 If the user has typed more characters than fit in the buffer given to
28436 the @code{read} call, the trailing characters are buffered in @value{GDBN} until
28437 either another @code{read(0, @dots{})} is requested by the target, or debugging
28438 is stopped at the user's request.
28441 @node List of Supported Calls
28442 @subsection List of Supported Calls
28443 @cindex list of supported file-i/o calls
28460 @unnumberedsubsubsec open
28461 @cindex open, file-i/o system call
28466 int open(const char *pathname, int flags);
28467 int open(const char *pathname, int flags, mode_t mode);
28471 @samp{Fopen,@var{pathptr}/@var{len},@var{flags},@var{mode}}
28474 @var{flags} is the bitwise @code{OR} of the following values:
28478 If the file does not exist it will be created. The host
28479 rules apply as far as file ownership and time stamps
28483 When used with @code{O_CREAT}, if the file already exists it is
28484 an error and open() fails.
28487 If the file already exists and the open mode allows
28488 writing (@code{O_RDWR} or @code{O_WRONLY} is given) it will be
28489 truncated to zero length.
28492 The file is opened in append mode.
28495 The file is opened for reading only.
28498 The file is opened for writing only.
28501 The file is opened for reading and writing.
28505 Other bits are silently ignored.
28509 @var{mode} is the bitwise @code{OR} of the following values:
28513 User has read permission.
28516 User has write permission.
28519 Group has read permission.
28522 Group has write permission.
28525 Others have read permission.
28528 Others have write permission.
28532 Other bits are silently ignored.
28535 @item Return value:
28536 @code{open} returns the new file descriptor or -1 if an error
28543 @var{pathname} already exists and @code{O_CREAT} and @code{O_EXCL} were used.
28546 @var{pathname} refers to a directory.
28549 The requested access is not allowed.
28552 @var{pathname} was too long.
28555 A directory component in @var{pathname} does not exist.
28558 @var{pathname} refers to a device, pipe, named pipe or socket.
28561 @var{pathname} refers to a file on a read-only filesystem and
28562 write access was requested.
28565 @var{pathname} is an invalid pointer value.
28568 No space on device to create the file.
28571 The process already has the maximum number of files open.
28574 The limit on the total number of files open on the system
28578 The call was interrupted by the user.
28584 @unnumberedsubsubsec close
28585 @cindex close, file-i/o system call
28594 @samp{Fclose,@var{fd}}
28596 @item Return value:
28597 @code{close} returns zero on success, or -1 if an error occurred.
28603 @var{fd} isn't a valid open file descriptor.
28606 The call was interrupted by the user.
28612 @unnumberedsubsubsec read
28613 @cindex read, file-i/o system call
28618 int read(int fd, void *buf, unsigned int count);
28622 @samp{Fread,@var{fd},@var{bufptr},@var{count}}
28624 @item Return value:
28625 On success, the number of bytes read is returned.
28626 Zero indicates end of file. If count is zero, read
28627 returns zero as well. On error, -1 is returned.
28633 @var{fd} is not a valid file descriptor or is not open for
28637 @var{bufptr} is an invalid pointer value.
28640 The call was interrupted by the user.
28646 @unnumberedsubsubsec write
28647 @cindex write, file-i/o system call
28652 int write(int fd, const void *buf, unsigned int count);
28656 @samp{Fwrite,@var{fd},@var{bufptr},@var{count}}
28658 @item Return value:
28659 On success, the number of bytes written are returned.
28660 Zero indicates nothing was written. On error, -1
28667 @var{fd} is not a valid file descriptor or is not open for
28671 @var{bufptr} is an invalid pointer value.
28674 An attempt was made to write a file that exceeds the
28675 host-specific maximum file size allowed.
28678 No space on device to write the data.
28681 The call was interrupted by the user.
28687 @unnumberedsubsubsec lseek
28688 @cindex lseek, file-i/o system call
28693 long lseek (int fd, long offset, int flag);
28697 @samp{Flseek,@var{fd},@var{offset},@var{flag}}
28699 @var{flag} is one of:
28703 The offset is set to @var{offset} bytes.
28706 The offset is set to its current location plus @var{offset}
28710 The offset is set to the size of the file plus @var{offset}
28714 @item Return value:
28715 On success, the resulting unsigned offset in bytes from
28716 the beginning of the file is returned. Otherwise, a
28717 value of -1 is returned.
28723 @var{fd} is not a valid open file descriptor.
28726 @var{fd} is associated with the @value{GDBN} console.
28729 @var{flag} is not a proper value.
28732 The call was interrupted by the user.
28738 @unnumberedsubsubsec rename
28739 @cindex rename, file-i/o system call
28744 int rename(const char *oldpath, const char *newpath);
28748 @samp{Frename,@var{oldpathptr}/@var{len},@var{newpathptr}/@var{len}}
28750 @item Return value:
28751 On success, zero is returned. On error, -1 is returned.
28757 @var{newpath} is an existing directory, but @var{oldpath} is not a
28761 @var{newpath} is a non-empty directory.
28764 @var{oldpath} or @var{newpath} is a directory that is in use by some
28768 An attempt was made to make a directory a subdirectory
28772 A component used as a directory in @var{oldpath} or new
28773 path is not a directory. Or @var{oldpath} is a directory
28774 and @var{newpath} exists but is not a directory.
28777 @var{oldpathptr} or @var{newpathptr} are invalid pointer values.
28780 No access to the file or the path of the file.
28784 @var{oldpath} or @var{newpath} was too long.
28787 A directory component in @var{oldpath} or @var{newpath} does not exist.
28790 The file is on a read-only filesystem.
28793 The device containing the file has no room for the new
28797 The call was interrupted by the user.
28803 @unnumberedsubsubsec unlink
28804 @cindex unlink, file-i/o system call
28809 int unlink(const char *pathname);
28813 @samp{Funlink,@var{pathnameptr}/@var{len}}
28815 @item Return value:
28816 On success, zero is returned. On error, -1 is returned.
28822 No access to the file or the path of the file.
28825 The system does not allow unlinking of directories.
28828 The file @var{pathname} cannot be unlinked because it's
28829 being used by another process.
28832 @var{pathnameptr} is an invalid pointer value.
28835 @var{pathname} was too long.
28838 A directory component in @var{pathname} does not exist.
28841 A component of the path is not a directory.
28844 The file is on a read-only filesystem.
28847 The call was interrupted by the user.
28853 @unnumberedsubsubsec stat/fstat
28854 @cindex fstat, file-i/o system call
28855 @cindex stat, file-i/o system call
28860 int stat(const char *pathname, struct stat *buf);
28861 int fstat(int fd, struct stat *buf);
28865 @samp{Fstat,@var{pathnameptr}/@var{len},@var{bufptr}}@*
28866 @samp{Ffstat,@var{fd},@var{bufptr}}
28868 @item Return value:
28869 On success, zero is returned. On error, -1 is returned.
28875 @var{fd} is not a valid open file.
28878 A directory component in @var{pathname} does not exist or the
28879 path is an empty string.
28882 A component of the path is not a directory.
28885 @var{pathnameptr} is an invalid pointer value.
28888 No access to the file or the path of the file.
28891 @var{pathname} was too long.
28894 The call was interrupted by the user.
28900 @unnumberedsubsubsec gettimeofday
28901 @cindex gettimeofday, file-i/o system call
28906 int gettimeofday(struct timeval *tv, void *tz);
28910 @samp{Fgettimeofday,@var{tvptr},@var{tzptr}}
28912 @item Return value:
28913 On success, 0 is returned, -1 otherwise.
28919 @var{tz} is a non-NULL pointer.
28922 @var{tvptr} and/or @var{tzptr} is an invalid pointer value.
28928 @unnumberedsubsubsec isatty
28929 @cindex isatty, file-i/o system call
28934 int isatty(int fd);
28938 @samp{Fisatty,@var{fd}}
28940 @item Return value:
28941 Returns 1 if @var{fd} refers to the @value{GDBN} console, 0 otherwise.
28947 The call was interrupted by the user.
28952 Note that the @code{isatty} call is treated as a special case: it returns
28953 1 to the target if the file descriptor is attached
28954 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
28955 would require implementing @code{ioctl} and would be more complex than
28960 @unnumberedsubsubsec system
28961 @cindex system, file-i/o system call
28966 int system(const char *command);
28970 @samp{Fsystem,@var{commandptr}/@var{len}}
28972 @item Return value:
28973 If @var{len} is zero, the return value indicates whether a shell is
28974 available. A zero return value indicates a shell is not available.
28975 For non-zero @var{len}, the value returned is -1 on error and the
28976 return status of the command otherwise. Only the exit status of the
28977 command is returned, which is extracted from the host's @code{system}
28978 return value by calling @code{WEXITSTATUS(retval)}. In case
28979 @file{/bin/sh} could not be executed, 127 is returned.
28985 The call was interrupted by the user.
28990 @value{GDBN} takes over the full task of calling the necessary host calls
28991 to perform the @code{system} call. The return value of @code{system} on
28992 the host is simplified before it's returned
28993 to the target. Any termination signal information from the child process
28994 is discarded, and the return value consists
28995 entirely of the exit status of the called command.
28997 Due to security concerns, the @code{system} call is by default refused
28998 by @value{GDBN}. The user has to allow this call explicitly with the
28999 @code{set remote system-call-allowed 1} command.
29002 @item set remote system-call-allowed
29003 @kindex set remote system-call-allowed
29004 Control whether to allow the @code{system} calls in the File I/O
29005 protocol for the remote target. The default is zero (disabled).
29007 @item show remote system-call-allowed
29008 @kindex show remote system-call-allowed
29009 Show whether the @code{system} calls are allowed in the File I/O
29013 @node Protocol-specific Representation of Datatypes
29014 @subsection Protocol-specific Representation of Datatypes
29015 @cindex protocol-specific representation of datatypes, in file-i/o protocol
29018 * Integral Datatypes::
29020 * Memory Transfer::
29025 @node Integral Datatypes
29026 @unnumberedsubsubsec Integral Datatypes
29027 @cindex integral datatypes, in file-i/o protocol
29029 The integral datatypes used in the system calls are @code{int},
29030 @code{unsigned int}, @code{long}, @code{unsigned long},
29031 @code{mode_t}, and @code{time_t}.
29033 @code{int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
29034 implemented as 32 bit values in this protocol.
29036 @code{long} and @code{unsigned long} are implemented as 64 bit types.
29038 @xref{Limits}, for corresponding MIN and MAX values (similar to those
29039 in @file{limits.h}) to allow range checking on host and target.
29041 @code{time_t} datatypes are defined as seconds since the Epoch.
29043 All integral datatypes transferred as part of a memory read or write of a
29044 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
29047 @node Pointer Values
29048 @unnumberedsubsubsec Pointer Values
29049 @cindex pointer values, in file-i/o protocol
29051 Pointers to target data are transmitted as they are. An exception
29052 is made for pointers to buffers for which the length isn't
29053 transmitted as part of the function call, namely strings. Strings
29054 are transmitted as a pointer/length pair, both as hex values, e.g.@:
29061 which is a pointer to data of length 18 bytes at position 0x1aaf.
29062 The length is defined as the full string length in bytes, including
29063 the trailing null byte. For example, the string @code{"hello world"}
29064 at address 0x123456 is transmitted as
29070 @node Memory Transfer
29071 @unnumberedsubsubsec Memory Transfer
29072 @cindex memory transfer, in file-i/o protocol
29074 Structured data which is transferred using a memory read or write (for
29075 example, a @code{struct stat}) is expected to be in a protocol-specific format
29076 with all scalar multibyte datatypes being big endian. Translation to
29077 this representation needs to be done both by the target before the @code{F}
29078 packet is sent, and by @value{GDBN} before
29079 it transfers memory to the target. Transferred pointers to structured
29080 data should point to the already-coerced data at any time.
29084 @unnumberedsubsubsec struct stat
29085 @cindex struct stat, in file-i/o protocol
29087 The buffer of type @code{struct stat} used by the target and @value{GDBN}
29088 is defined as follows:
29092 unsigned int st_dev; /* device */
29093 unsigned int st_ino; /* inode */
29094 mode_t st_mode; /* protection */
29095 unsigned int st_nlink; /* number of hard links */
29096 unsigned int st_uid; /* user ID of owner */
29097 unsigned int st_gid; /* group ID of owner */
29098 unsigned int st_rdev; /* device type (if inode device) */
29099 unsigned long st_size; /* total size, in bytes */
29100 unsigned long st_blksize; /* blocksize for filesystem I/O */
29101 unsigned long st_blocks; /* number of blocks allocated */
29102 time_t st_atime; /* time of last access */
29103 time_t st_mtime; /* time of last modification */
29104 time_t st_ctime; /* time of last change */
29108 The integral datatypes conform to the definitions given in the
29109 appropriate section (see @ref{Integral Datatypes}, for details) so this
29110 structure is of size 64 bytes.
29112 The values of several fields have a restricted meaning and/or
29118 A value of 0 represents a file, 1 the console.
29121 No valid meaning for the target. Transmitted unchanged.
29124 Valid mode bits are described in @ref{Constants}. Any other
29125 bits have currently no meaning for the target.
29130 No valid meaning for the target. Transmitted unchanged.
29135 These values have a host and file system dependent
29136 accuracy. Especially on Windows hosts, the file system may not
29137 support exact timing values.
29140 The target gets a @code{struct stat} of the above representation and is
29141 responsible for coercing it to the target representation before
29144 Note that due to size differences between the host, target, and protocol
29145 representations of @code{struct stat} members, these members could eventually
29146 get truncated on the target.
29148 @node struct timeval
29149 @unnumberedsubsubsec struct timeval
29150 @cindex struct timeval, in file-i/o protocol
29152 The buffer of type @code{struct timeval} used by the File-I/O protocol
29153 is defined as follows:
29157 time_t tv_sec; /* second */
29158 long tv_usec; /* microsecond */
29162 The integral datatypes conform to the definitions given in the
29163 appropriate section (see @ref{Integral Datatypes}, for details) so this
29164 structure is of size 8 bytes.
29167 @subsection Constants
29168 @cindex constants, in file-i/o protocol
29170 The following values are used for the constants inside of the
29171 protocol. @value{GDBN} and target are responsible for translating these
29172 values before and after the call as needed.
29183 @unnumberedsubsubsec Open Flags
29184 @cindex open flags, in file-i/o protocol
29186 All values are given in hexadecimal representation.
29198 @node mode_t Values
29199 @unnumberedsubsubsec mode_t Values
29200 @cindex mode_t values, in file-i/o protocol
29202 All values are given in octal representation.
29219 @unnumberedsubsubsec Errno Values
29220 @cindex errno values, in file-i/o protocol
29222 All values are given in decimal representation.
29247 @code{EUNKNOWN} is used as a fallback error value if a host system returns
29248 any error value not in the list of supported error numbers.
29251 @unnumberedsubsubsec Lseek Flags
29252 @cindex lseek flags, in file-i/o protocol
29261 @unnumberedsubsubsec Limits
29262 @cindex limits, in file-i/o protocol
29264 All values are given in decimal representation.
29267 INT_MIN -2147483648
29269 UINT_MAX 4294967295
29270 LONG_MIN -9223372036854775808
29271 LONG_MAX 9223372036854775807
29272 ULONG_MAX 18446744073709551615
29275 @node File-I/O Examples
29276 @subsection File-I/O Examples
29277 @cindex file-i/o examples
29279 Example sequence of a write call, file descriptor 3, buffer is at target
29280 address 0x1234, 6 bytes should be written:
29283 <- @code{Fwrite,3,1234,6}
29284 @emph{request memory read from target}
29287 @emph{return "6 bytes written"}
29291 Example sequence of a read call, file descriptor 3, buffer is at target
29292 address 0x1234, 6 bytes should be read:
29295 <- @code{Fread,3,1234,6}
29296 @emph{request memory write to target}
29297 -> @code{X1234,6:XXXXXX}
29298 @emph{return "6 bytes read"}
29302 Example sequence of a read call, call fails on the host due to invalid
29303 file descriptor (@code{EBADF}):
29306 <- @code{Fread,3,1234,6}
29310 Example sequence of a read call, user presses @kbd{Ctrl-c} before syscall on
29314 <- @code{Fread,3,1234,6}
29319 Example sequence of a read call, user presses @kbd{Ctrl-c} after syscall on
29323 <- @code{Fread,3,1234,6}
29324 -> @code{X1234,6:XXXXXX}
29328 @node Library List Format
29329 @section Library List Format
29330 @cindex library list format, remote protocol
29332 On some platforms, a dynamic loader (e.g.@: @file{ld.so}) runs in the
29333 same process as your application to manage libraries. In this case,
29334 @value{GDBN} can use the loader's symbol table and normal memory
29335 operations to maintain a list of shared libraries. On other
29336 platforms, the operating system manages loaded libraries.
29337 @value{GDBN} can not retrieve the list of currently loaded libraries
29338 through memory operations, so it uses the @samp{qXfer:libraries:read}
29339 packet (@pxref{qXfer library list read}) instead. The remote stub
29340 queries the target's operating system and reports which libraries
29343 The @samp{qXfer:libraries:read} packet returns an XML document which
29344 lists loaded libraries and their offsets. Each library has an
29345 associated name and one or more segment or section base addresses,
29346 which report where the library was loaded in memory.
29348 For the common case of libraries that are fully linked binaries, the
29349 library should have a list of segments. If the target supports
29350 dynamic linking of a relocatable object file, its library XML element
29351 should instead include a list of allocated sections. The segment or
29352 section bases are start addresses, not relocation offsets; they do not
29353 depend on the library's link-time base addresses.
29355 @value{GDBN} must be linked with the Expat library to support XML
29356 library lists. @xref{Expat}.
29358 A simple memory map, with one loaded library relocated by a single
29359 offset, looks like this:
29363 <library name="/lib/libc.so.6">
29364 <segment address="0x10000000"/>
29369 Another simple memory map, with one loaded library with three
29370 allocated sections (.text, .data, .bss), looks like this:
29374 <library name="sharedlib.o">
29375 <section address="0x10000000"/>
29376 <section address="0x20000000"/>
29377 <section address="0x30000000"/>
29382 The format of a library list is described by this DTD:
29385 <!-- library-list: Root element with versioning -->
29386 <!ELEMENT library-list (library)*>
29387 <!ATTLIST library-list version CDATA #FIXED "1.0">
29388 <!ELEMENT library (segment*, section*)>
29389 <!ATTLIST library name CDATA #REQUIRED>
29390 <!ELEMENT segment EMPTY>
29391 <!ATTLIST segment address CDATA #REQUIRED>
29392 <!ELEMENT section EMPTY>
29393 <!ATTLIST section address CDATA #REQUIRED>
29396 In addition, segments and section descriptors cannot be mixed within a
29397 single library element, and you must supply at least one segment or
29398 section for each library.
29400 @node Memory Map Format
29401 @section Memory Map Format
29402 @cindex memory map format
29404 To be able to write into flash memory, @value{GDBN} needs to obtain a
29405 memory map from the target. This section describes the format of the
29408 The memory map is obtained using the @samp{qXfer:memory-map:read}
29409 (@pxref{qXfer memory map read}) packet and is an XML document that
29410 lists memory regions.
29412 @value{GDBN} must be linked with the Expat library to support XML
29413 memory maps. @xref{Expat}.
29415 The top-level structure of the document is shown below:
29418 <?xml version="1.0"?>
29419 <!DOCTYPE memory-map
29420 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
29421 "http://sourceware.org/gdb/gdb-memory-map.dtd">
29427 Each region can be either:
29432 A region of RAM starting at @var{addr} and extending for @var{length}
29436 <memory type="ram" start="@var{addr}" length="@var{length}"/>
29441 A region of read-only memory:
29444 <memory type="rom" start="@var{addr}" length="@var{length}"/>
29449 A region of flash memory, with erasure blocks @var{blocksize}
29453 <memory type="flash" start="@var{addr}" length="@var{length}">
29454 <property name="blocksize">@var{blocksize}</property>
29460 Regions must not overlap. @value{GDBN} assumes that areas of memory not covered
29461 by the memory map are RAM, and uses the ordinary @samp{M} and @samp{X}
29462 packets to write to addresses in such ranges.
29464 The formal DTD for memory map format is given below:
29467 <!-- ................................................... -->
29468 <!-- Memory Map XML DTD ................................ -->
29469 <!-- File: memory-map.dtd .............................. -->
29470 <!-- .................................... .............. -->
29471 <!-- memory-map.dtd -->
29472 <!-- memory-map: Root element with versioning -->
29473 <!ELEMENT memory-map (memory | property)>
29474 <!ATTLIST memory-map version CDATA #FIXED "1.0.0">
29475 <!ELEMENT memory (property)>
29476 <!-- memory: Specifies a memory region,
29477 and its type, or device. -->
29478 <!ATTLIST memory type CDATA #REQUIRED
29479 start CDATA #REQUIRED
29480 length CDATA #REQUIRED
29481 device CDATA #IMPLIED>
29482 <!-- property: Generic attribute tag -->
29483 <!ELEMENT property (#PCDATA | property)*>
29484 <!ATTLIST property name CDATA #REQUIRED>
29487 @include agentexpr.texi
29489 @node Target Descriptions
29490 @appendix Target Descriptions
29491 @cindex target descriptions
29493 @strong{Warning:} target descriptions are still under active development,
29494 and the contents and format may change between @value{GDBN} releases.
29495 The format is expected to stabilize in the future.
29497 One of the challenges of using @value{GDBN} to debug embedded systems
29498 is that there are so many minor variants of each processor
29499 architecture in use. It is common practice for vendors to start with
29500 a standard processor core --- ARM, PowerPC, or MIPS, for example ---
29501 and then make changes to adapt it to a particular market niche. Some
29502 architectures have hundreds of variants, available from dozens of
29503 vendors. This leads to a number of problems:
29507 With so many different customized processors, it is difficult for
29508 the @value{GDBN} maintainers to keep up with the changes.
29510 Since individual variants may have short lifetimes or limited
29511 audiences, it may not be worthwhile to carry information about every
29512 variant in the @value{GDBN} source tree.
29514 When @value{GDBN} does support the architecture of the embedded system
29515 at hand, the task of finding the correct architecture name to give the
29516 @command{set architecture} command can be error-prone.
29519 To address these problems, the @value{GDBN} remote protocol allows a
29520 target system to not only identify itself to @value{GDBN}, but to
29521 actually describe its own features. This lets @value{GDBN} support
29522 processor variants it has never seen before --- to the extent that the
29523 descriptions are accurate, and that @value{GDBN} understands them.
29525 @value{GDBN} must be linked with the Expat library to support XML
29526 target descriptions. @xref{Expat}.
29529 * Retrieving Descriptions:: How descriptions are fetched from a target.
29530 * Target Description Format:: The contents of a target description.
29531 * Predefined Target Types:: Standard types available for target
29533 * Standard Target Features:: Features @value{GDBN} knows about.
29536 @node Retrieving Descriptions
29537 @section Retrieving Descriptions
29539 Target descriptions can be read from the target automatically, or
29540 specified by the user manually. The default behavior is to read the
29541 description from the target. @value{GDBN} retrieves it via the remote
29542 protocol using @samp{qXfer} requests (@pxref{General Query Packets,
29543 qXfer}). The @var{annex} in the @samp{qXfer} packet will be
29544 @samp{target.xml}. The contents of the @samp{target.xml} annex are an
29545 XML document, of the form described in @ref{Target Description
29548 Alternatively, you can specify a file to read for the target description.
29549 If a file is set, the target will not be queried. The commands to
29550 specify a file are:
29553 @cindex set tdesc filename
29554 @item set tdesc filename @var{path}
29555 Read the target description from @var{path}.
29557 @cindex unset tdesc filename
29558 @item unset tdesc filename
29559 Do not read the XML target description from a file. @value{GDBN}
29560 will use the description supplied by the current target.
29562 @cindex show tdesc filename
29563 @item show tdesc filename
29564 Show the filename to read for a target description, if any.
29568 @node Target Description Format
29569 @section Target Description Format
29570 @cindex target descriptions, XML format
29572 A target description annex is an @uref{http://www.w3.org/XML/, XML}
29573 document which complies with the Document Type Definition provided in
29574 the @value{GDBN} sources in @file{gdb/features/gdb-target.dtd}. This
29575 means you can use generally available tools like @command{xmllint} to
29576 check that your feature descriptions are well-formed and valid.
29577 However, to help people unfamiliar with XML write descriptions for
29578 their targets, we also describe the grammar here.
29580 Target descriptions can identify the architecture of the remote target
29581 and (for some architectures) provide information about custom register
29582 sets. @value{GDBN} can use this information to autoconfigure for your
29583 target, or to warn you if you connect to an unsupported target.
29585 Here is a simple target description:
29588 <target version="1.0">
29589 <architecture>i386:x86-64</architecture>
29594 This minimal description only says that the target uses
29595 the x86-64 architecture.
29597 A target description has the following overall form, with [ ] marking
29598 optional elements and @dots{} marking repeatable elements. The elements
29599 are explained further below.
29602 <?xml version="1.0"?>
29603 <!DOCTYPE target SYSTEM "gdb-target.dtd">
29604 <target version="1.0">
29605 @r{[}@var{architecture}@r{]}
29606 @r{[}@var{feature}@dots{}@r{]}
29611 The description is generally insensitive to whitespace and line
29612 breaks, under the usual common-sense rules. The XML version
29613 declaration and document type declaration can generally be omitted
29614 (@value{GDBN} does not require them), but specifying them may be
29615 useful for XML validation tools. The @samp{version} attribute for
29616 @samp{<target>} may also be omitted, but we recommend
29617 including it; if future versions of @value{GDBN} use an incompatible
29618 revision of @file{gdb-target.dtd}, they will detect and report
29619 the version mismatch.
29621 @subsection Inclusion
29622 @cindex target descriptions, inclusion
29625 @cindex <xi:include>
29628 It can sometimes be valuable to split a target description up into
29629 several different annexes, either for organizational purposes, or to
29630 share files between different possible target descriptions. You can
29631 divide a description into multiple files by replacing any element of
29632 the target description with an inclusion directive of the form:
29635 <xi:include href="@var{document}"/>
29639 When @value{GDBN} encounters an element of this form, it will retrieve
29640 the named XML @var{document}, and replace the inclusion directive with
29641 the contents of that document. If the current description was read
29642 using @samp{qXfer}, then so will be the included document;
29643 @var{document} will be interpreted as the name of an annex. If the
29644 current description was read from a file, @value{GDBN} will look for
29645 @var{document} as a file in the same directory where it found the
29646 original description.
29648 @subsection Architecture
29649 @cindex <architecture>
29651 An @samp{<architecture>} element has this form:
29654 <architecture>@var{arch}</architecture>
29657 @var{arch} is an architecture name from the same selection
29658 accepted by @code{set architecture} (@pxref{Targets, ,Specifying a
29659 Debugging Target}).
29661 @subsection Features
29664 Each @samp{<feature>} describes some logical portion of the target
29665 system. Features are currently used to describe available CPU
29666 registers and the types of their contents. A @samp{<feature>} element
29670 <feature name="@var{name}">
29671 @r{[}@var{type}@dots{}@r{]}
29677 Each feature's name should be unique within the description. The name
29678 of a feature does not matter unless @value{GDBN} has some special
29679 knowledge of the contents of that feature; if it does, the feature
29680 should have its standard name. @xref{Standard Target Features}.
29684 Any register's value is a collection of bits which @value{GDBN} must
29685 interpret. The default interpretation is a two's complement integer,
29686 but other types can be requested by name in the register description.
29687 Some predefined types are provided by @value{GDBN} (@pxref{Predefined
29688 Target Types}), and the description can define additional composite types.
29690 Each type element must have an @samp{id} attribute, which gives
29691 a unique (within the containing @samp{<feature>}) name to the type.
29692 Types must be defined before they are used.
29695 Some targets offer vector registers, which can be treated as arrays
29696 of scalar elements. These types are written as @samp{<vector>} elements,
29697 specifying the array element type, @var{type}, and the number of elements,
29701 <vector id="@var{id}" type="@var{type}" count="@var{count}"/>
29705 If a register's value is usefully viewed in multiple ways, define it
29706 with a union type containing the useful representations. The
29707 @samp{<union>} element contains one or more @samp{<field>} elements,
29708 each of which has a @var{name} and a @var{type}:
29711 <union id="@var{id}">
29712 <field name="@var{name}" type="@var{type}"/>
29717 @subsection Registers
29720 Each register is represented as an element with this form:
29723 <reg name="@var{name}"
29724 bitsize="@var{size}"
29725 @r{[}regnum="@var{num}"@r{]}
29726 @r{[}save-restore="@var{save-restore}"@r{]}
29727 @r{[}type="@var{type}"@r{]}
29728 @r{[}group="@var{group}"@r{]}/>
29732 The components are as follows:
29737 The register's name; it must be unique within the target description.
29740 The register's size, in bits.
29743 The register's number. If omitted, a register's number is one greater
29744 than that of the previous register (either in the current feature or in
29745 a preceeding feature); the first register in the target description
29746 defaults to zero. This register number is used to read or write
29747 the register; e.g.@: it is used in the remote @code{p} and @code{P}
29748 packets, and registers appear in the @code{g} and @code{G} packets
29749 in order of increasing register number.
29752 Whether the register should be preserved across inferior function
29753 calls; this must be either @code{yes} or @code{no}. The default is
29754 @code{yes}, which is appropriate for most registers except for
29755 some system control registers; this is not related to the target's
29759 The type of the register. @var{type} may be a predefined type, a type
29760 defined in the current feature, or one of the special types @code{int}
29761 and @code{float}. @code{int} is an integer type of the correct size
29762 for @var{bitsize}, and @code{float} is a floating point type (in the
29763 architecture's normal floating point format) of the correct size for
29764 @var{bitsize}. The default is @code{int}.
29767 The register group to which this register belongs. @var{group} must
29768 be either @code{general}, @code{float}, or @code{vector}. If no
29769 @var{group} is specified, @value{GDBN} will not display the register
29770 in @code{info registers}.
29774 @node Predefined Target Types
29775 @section Predefined Target Types
29776 @cindex target descriptions, predefined types
29778 Type definitions in the self-description can build up composite types
29779 from basic building blocks, but can not define fundamental types. Instead,
29780 standard identifiers are provided by @value{GDBN} for the fundamental
29781 types. The currently supported types are:
29790 Signed integer types holding the specified number of bits.
29797 Unsigned integer types holding the specified number of bits.
29801 Pointers to unspecified code and data. The program counter and
29802 any dedicated return address register may be marked as code
29803 pointers; printing a code pointer converts it into a symbolic
29804 address. The stack pointer and any dedicated address registers
29805 may be marked as data pointers.
29808 Single precision IEEE floating point.
29811 Double precision IEEE floating point.
29814 The 12-byte extended precision format used by ARM FPA registers.
29818 @node Standard Target Features
29819 @section Standard Target Features
29820 @cindex target descriptions, standard features
29822 A target description must contain either no registers or all the
29823 target's registers. If the description contains no registers, then
29824 @value{GDBN} will assume a default register layout, selected based on
29825 the architecture. If the description contains any registers, the
29826 default layout will not be used; the standard registers must be
29827 described in the target description, in such a way that @value{GDBN}
29828 can recognize them.
29830 This is accomplished by giving specific names to feature elements
29831 which contain standard registers. @value{GDBN} will look for features
29832 with those names and verify that they contain the expected registers;
29833 if any known feature is missing required registers, or if any required
29834 feature is missing, @value{GDBN} will reject the target
29835 description. You can add additional registers to any of the
29836 standard features --- @value{GDBN} will display them just as if
29837 they were added to an unrecognized feature.
29839 This section lists the known features and their expected contents.
29840 Sample XML documents for these features are included in the
29841 @value{GDBN} source tree, in the directory @file{gdb/features}.
29843 Names recognized by @value{GDBN} should include the name of the
29844 company or organization which selected the name, and the overall
29845 architecture to which the feature applies; so e.g.@: the feature
29846 containing ARM core registers is named @samp{org.gnu.gdb.arm.core}.
29848 The names of registers are not case sensitive for the purpose
29849 of recognizing standard features, but @value{GDBN} will only display
29850 registers using the capitalization used in the description.
29856 * PowerPC Features::
29861 @subsection ARM Features
29862 @cindex target descriptions, ARM features
29864 The @samp{org.gnu.gdb.arm.core} feature is required for ARM targets.
29865 It should contain registers @samp{r0} through @samp{r13}, @samp{sp},
29866 @samp{lr}, @samp{pc}, and @samp{cpsr}.
29868 The @samp{org.gnu.gdb.arm.fpa} feature is optional. If present, it
29869 should contain registers @samp{f0} through @samp{f7} and @samp{fps}.
29871 The @samp{org.gnu.gdb.xscale.iwmmxt} feature is optional. If present,
29872 it should contain at least registers @samp{wR0} through @samp{wR15} and
29873 @samp{wCGR0} through @samp{wCGR3}. The @samp{wCID}, @samp{wCon},
29874 @samp{wCSSF}, and @samp{wCASF} registers are optional.
29876 @node MIPS Features
29877 @subsection MIPS Features
29878 @cindex target descriptions, MIPS features
29880 The @samp{org.gnu.gdb.mips.cpu} feature is required for MIPS targets.
29881 It should contain registers @samp{r0} through @samp{r31}, @samp{lo},
29882 @samp{hi}, and @samp{pc}. They may be 32-bit or 64-bit depending
29885 The @samp{org.gnu.gdb.mips.cp0} feature is also required. It should
29886 contain at least the @samp{status}, @samp{badvaddr}, and @samp{cause}
29887 registers. They may be 32-bit or 64-bit depending on the target.
29889 The @samp{org.gnu.gdb.mips.fpu} feature is currently required, though
29890 it may be optional in a future version of @value{GDBN}. It should
29891 contain registers @samp{f0} through @samp{f31}, @samp{fcsr}, and
29892 @samp{fir}. They may be 32-bit or 64-bit depending on the target.
29894 The @samp{org.gnu.gdb.mips.linux} feature is optional. It should
29895 contain a single register, @samp{restart}, which is used by the
29896 Linux kernel to control restartable syscalls.
29898 @node M68K Features
29899 @subsection M68K Features
29900 @cindex target descriptions, M68K features
29903 @item @samp{org.gnu.gdb.m68k.core}
29904 @itemx @samp{org.gnu.gdb.coldfire.core}
29905 @itemx @samp{org.gnu.gdb.fido.core}
29906 One of those features must be always present.
29907 The feature that is present determines which flavor of m68k is
29908 used. The feature that is present should contain registers
29909 @samp{d0} through @samp{d7}, @samp{a0} through @samp{a5}, @samp{fp},
29910 @samp{sp}, @samp{ps} and @samp{pc}.
29912 @item @samp{org.gnu.gdb.coldfire.fp}
29913 This feature is optional. If present, it should contain registers
29914 @samp{fp0} through @samp{fp7}, @samp{fpcontrol}, @samp{fpstatus} and
29918 @node PowerPC Features
29919 @subsection PowerPC Features
29920 @cindex target descriptions, PowerPC features
29922 The @samp{org.gnu.gdb.power.core} feature is required for PowerPC
29923 targets. It should contain registers @samp{r0} through @samp{r31},
29924 @samp{pc}, @samp{msr}, @samp{cr}, @samp{lr}, @samp{ctr}, and
29925 @samp{xer}. They may be 32-bit or 64-bit depending on the target.
29927 The @samp{org.gnu.gdb.power.fpu} feature is optional. It should
29928 contain registers @samp{f0} through @samp{f31} and @samp{fpscr}.
29930 The @samp{org.gnu.gdb.power.altivec} feature is optional. It should
29931 contain registers @samp{vr0} through @samp{vr31}, @samp{vscr},
29934 The @samp{org.gnu.gdb.power.vsx} feature is optional. It should
29935 contain registers @samp{vs0h} through @samp{vs31h}. @value{GDBN}
29936 will combine these registers with the floating point registers
29937 (@samp{f0} through @samp{f31}) and the altivec registers (@samp{vr0}
29938 through @samp{vr31}) to present the 128-bit wide registers @samp{vs0}
29939 through @samp{vs63}, the set of vector registers for POWER7.
29941 The @samp{org.gnu.gdb.power.spe} feature is optional. It should
29942 contain registers @samp{ev0h} through @samp{ev31h}, @samp{acc}, and
29943 @samp{spefscr}. SPE targets should provide 32-bit registers in
29944 @samp{org.gnu.gdb.power.core} and provide the upper halves in
29945 @samp{ev0h} through @samp{ev31h}. @value{GDBN} will combine
29946 these to present registers @samp{ev0} through @samp{ev31} to the
29949 @node Operating System Information
29950 @appendix Operating System Information
29951 @cindex operating system information
29957 Users of @value{GDBN} often wish to obtain information about the state of
29958 the operating system running on the target---for example the list of
29959 processes, or the list of open files. This section describes the
29960 mechanism that makes it possible. This mechanism is similar to the
29961 target features mechanism (@pxref{Target Descriptions}), but focuses
29962 on a different aspect of target.
29964 Operating system information is retrived from the target via the
29965 remote protocol, using @samp{qXfer} requests (@pxref{qXfer osdata
29966 read}). The object name in the request should be @samp{osdata}, and
29967 the @var{annex} identifies the data to be fetched.
29970 @appendixsection Process list
29971 @cindex operating system information, process list
29973 When requesting the process list, the @var{annex} field in the
29974 @samp{qXfer} request should be @samp{processes}. The returned data is
29975 an XML document. The formal syntax of this document is defined in
29976 @file{gdb/features/osdata.dtd}.
29978 An example document is:
29981 <?xml version="1.0"?>
29982 <!DOCTYPE target SYSTEM "osdata.dtd">
29983 <osdata type="processes">
29985 <column name="pid">1</column>
29986 <column name="user">root</column>
29987 <column name="command">/sbin/init</column>
29992 Each item should include a column whose name is @samp{pid}. The value
29993 of that column should identify the process on the target. The
29994 @samp{user} and @samp{command} columns are optional, and will be
29995 displayed by @value{GDBN}. Target may provide additional columns,
29996 which @value{GDBN} currently ignores.
30010 % I think something like @colophon should be in texinfo. In the
30012 \long\def\colophon{\hbox to0pt{}\vfill
30013 \centerline{The body of this manual is set in}
30014 \centerline{\fontname\tenrm,}
30015 \centerline{with headings in {\bf\fontname\tenbf}}
30016 \centerline{and examples in {\tt\fontname\tentt}.}
30017 \centerline{{\it\fontname\tenit\/},}
30018 \centerline{{\bf\fontname\tenbf}, and}
30019 \centerline{{\sl\fontname\tensl\/}}
30020 \centerline{are used for emphasis.}\vfill}
30022 % Blame: doc@cygnus.com, 1991.