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
3055 When called without any arguments, @code{break} sets a breakpoint at
3056 the next instruction to be executed in the selected stack frame
3057 (@pxref{Stack, ,Examining the Stack}). In any selected frame but the
3058 innermost, this makes your program stop as soon as control
3059 returns to that frame. This is similar to the effect of a
3060 @code{finish} command in the frame inside the selected frame---except
3061 that @code{finish} does not leave an active breakpoint. If you use
3062 @code{break} without an argument in the innermost frame, @value{GDBN} stops
3063 the next time it reaches the current location; this may be useful
3066 @value{GDBN} normally ignores breakpoints when it resumes execution, until at
3067 least one instruction has been executed. If it did not do this, you
3068 would be unable to proceed past a breakpoint without first disabling the
3069 breakpoint. This rule applies whether or not the breakpoint already
3070 existed when your program stopped.
3072 @item break @dots{} if @var{cond}
3073 Set a breakpoint with condition @var{cond}; evaluate the expression
3074 @var{cond} each time the breakpoint is reached, and stop only if the
3075 value is nonzero---that is, if @var{cond} evaluates as true.
3076 @samp{@dots{}} stands for one of the possible arguments described
3077 above (or no argument) specifying where to break. @xref{Conditions,
3078 ,Break Conditions}, for more information on breakpoint conditions.
3081 @item tbreak @var{args}
3082 Set a breakpoint enabled only for one stop. @var{args} are the
3083 same as for the @code{break} command, and the breakpoint is set in the same
3084 way, but the breakpoint is automatically deleted after the first time your
3085 program stops there. @xref{Disabling, ,Disabling Breakpoints}.
3088 @cindex hardware breakpoints
3089 @item hbreak @var{args}
3090 Set a hardware-assisted breakpoint. @var{args} are the same as for the
3091 @code{break} command and the breakpoint is set in the same way, but the
3092 breakpoint requires hardware support and some target hardware may not
3093 have this support. The main purpose of this is EPROM/ROM code
3094 debugging, so you can set a breakpoint at an instruction without
3095 changing the instruction. This can be used with the new trap-generation
3096 provided by SPARClite DSU and most x86-based targets. These targets
3097 will generate traps when a program accesses some data or instruction
3098 address that is assigned to the debug registers. However the hardware
3099 breakpoint registers can take a limited number of breakpoints. For
3100 example, on the DSU, only two data breakpoints can be set at a time, and
3101 @value{GDBN} will reject this command if more than two are used. Delete
3102 or disable unused hardware breakpoints before setting new ones
3103 (@pxref{Disabling, ,Disabling Breakpoints}).
3104 @xref{Conditions, ,Break Conditions}.
3105 For remote targets, you can restrict the number of hardware
3106 breakpoints @value{GDBN} will use, see @ref{set remote
3107 hardware-breakpoint-limit}.
3110 @item thbreak @var{args}
3111 Set a hardware-assisted breakpoint enabled only for one stop. @var{args}
3112 are the same as for the @code{hbreak} command and the breakpoint is set in
3113 the same way. However, like the @code{tbreak} command,
3114 the breakpoint is automatically deleted after the
3115 first time your program stops there. Also, like the @code{hbreak}
3116 command, the breakpoint requires hardware support and some target hardware
3117 may not have this support. @xref{Disabling, ,Disabling Breakpoints}.
3118 See also @ref{Conditions, ,Break Conditions}.
3121 @cindex regular expression
3122 @cindex breakpoints in functions matching a regexp
3123 @cindex set breakpoints in many functions
3124 @item rbreak @var{regex}
3125 Set breakpoints on all functions matching the regular expression
3126 @var{regex}. This command sets an unconditional breakpoint on all
3127 matches, printing a list of all breakpoints it set. Once these
3128 breakpoints are set, they are treated just like the breakpoints set with
3129 the @code{break} command. You can delete them, disable them, or make
3130 them conditional the same way as any other breakpoint.
3132 The syntax of the regular expression is the standard one used with tools
3133 like @file{grep}. Note that this is different from the syntax used by
3134 shells, so for instance @code{foo*} matches all functions that include
3135 an @code{fo} followed by zero or more @code{o}s. There is an implicit
3136 @code{.*} leading and trailing the regular expression you supply, so to
3137 match only functions that begin with @code{foo}, use @code{^foo}.
3139 @cindex non-member C@t{++} functions, set breakpoint in
3140 When debugging C@t{++} programs, @code{rbreak} is useful for setting
3141 breakpoints on overloaded functions that are not members of any special
3144 @cindex set breakpoints on all functions
3145 The @code{rbreak} command can be used to set breakpoints in
3146 @strong{all} the functions in a program, like this:
3149 (@value{GDBP}) rbreak .
3152 @kindex info breakpoints
3153 @cindex @code{$_} and @code{info breakpoints}
3154 @item info breakpoints @r{[}@var{n}@r{]}
3155 @itemx info break @r{[}@var{n}@r{]}
3156 @itemx info watchpoints @r{[}@var{n}@r{]}
3157 Print a table of all breakpoints, watchpoints, and catchpoints set and
3158 not deleted. Optional argument @var{n} means print information only
3159 about the specified breakpoint (or watchpoint or catchpoint). For
3160 each breakpoint, following columns are printed:
3163 @item Breakpoint Numbers
3165 Breakpoint, watchpoint, or catchpoint.
3167 Whether the breakpoint is marked to be disabled or deleted when hit.
3168 @item Enabled or Disabled
3169 Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints
3170 that are not enabled.
3172 Where the breakpoint is in your program, as a memory address. For a
3173 pending breakpoint whose address is not yet known, this field will
3174 contain @samp{<PENDING>}. Such breakpoint won't fire until a shared
3175 library that has the symbol or line referred by breakpoint is loaded.
3176 See below for details. A breakpoint with several locations will
3177 have @samp{<MULTIPLE>} in this field---see below for details.
3179 Where the breakpoint is in the source for your program, as a file and
3180 line number. For a pending breakpoint, the original string passed to
3181 the breakpoint command will be listed as it cannot be resolved until
3182 the appropriate shared library is loaded in the future.
3186 If a breakpoint is conditional, @code{info break} shows the condition on
3187 the line following the affected breakpoint; breakpoint commands, if any,
3188 are listed after that. A pending breakpoint is allowed to have a condition
3189 specified for it. The condition is not parsed for validity until a shared
3190 library is loaded that allows the pending breakpoint to resolve to a
3194 @code{info break} with a breakpoint
3195 number @var{n} as argument lists only that breakpoint. The
3196 convenience variable @code{$_} and the default examining-address for
3197 the @code{x} command are set to the address of the last breakpoint
3198 listed (@pxref{Memory, ,Examining Memory}).
3201 @code{info break} displays a count of the number of times the breakpoint
3202 has been hit. This is especially useful in conjunction with the
3203 @code{ignore} command. You can ignore a large number of breakpoint
3204 hits, look at the breakpoint info to see how many times the breakpoint
3205 was hit, and then run again, ignoring one less than that number. This
3206 will get you quickly to the last hit of that breakpoint.
3209 @value{GDBN} allows you to set any number of breakpoints at the same place in
3210 your program. There is nothing silly or meaningless about this. When
3211 the breakpoints are conditional, this is even useful
3212 (@pxref{Conditions, ,Break Conditions}).
3214 @cindex multiple locations, breakpoints
3215 @cindex breakpoints, multiple locations
3216 It is possible that a breakpoint corresponds to several locations
3217 in your program. Examples of this situation are:
3221 For a C@t{++} constructor, the @value{NGCC} compiler generates several
3222 instances of the function body, used in different cases.
3225 For a C@t{++} template function, a given line in the function can
3226 correspond to any number of instantiations.
3229 For an inlined function, a given source line can correspond to
3230 several places where that function is inlined.
3233 In all those cases, @value{GDBN} will insert a breakpoint at all
3234 the relevant locations@footnote{
3235 As of this writing, multiple-location breakpoints work only if there's
3236 line number information for all the locations. This means that they
3237 will generally not work in system libraries, unless you have debug
3238 info with line numbers for them.}.
3240 A breakpoint with multiple locations is displayed in the breakpoint
3241 table using several rows---one header row, followed by one row for
3242 each breakpoint location. The header row has @samp{<MULTIPLE>} in the
3243 address column. The rows for individual locations contain the actual
3244 addresses for locations, and show the functions to which those
3245 locations belong. The number column for a location is of the form
3246 @var{breakpoint-number}.@var{location-number}.
3251 Num Type Disp Enb Address What
3252 1 breakpoint keep y <MULTIPLE>
3254 breakpoint already hit 1 time
3255 1.1 y 0x080486a2 in void foo<int>() at t.cc:8
3256 1.2 y 0x080486ca in void foo<double>() at t.cc:8
3259 Each location can be individually enabled or disabled by passing
3260 @var{breakpoint-number}.@var{location-number} as argument to the
3261 @code{enable} and @code{disable} commands. Note that you cannot
3262 delete the individual locations from the list, you can only delete the
3263 entire list of locations that belong to their parent breakpoint (with
3264 the @kbd{delete @var{num}} command, where @var{num} is the number of
3265 the parent breakpoint, 1 in the above example). Disabling or enabling
3266 the parent breakpoint (@pxref{Disabling}) affects all of the locations
3267 that belong to that breakpoint.
3269 @cindex pending breakpoints
3270 It's quite common to have a breakpoint inside a shared library.
3271 Shared libraries can be loaded and unloaded explicitly,
3272 and possibly repeatedly, as the program is executed. To support
3273 this use case, @value{GDBN} updates breakpoint locations whenever
3274 any shared library is loaded or unloaded. Typically, you would
3275 set a breakpoint in a shared library at the beginning of your
3276 debugging session, when the library is not loaded, and when the
3277 symbols from the library are not available. When you try to set
3278 breakpoint, @value{GDBN} will ask you if you want to set
3279 a so called @dfn{pending breakpoint}---breakpoint whose address
3280 is not yet resolved.
3282 After the program is run, whenever a new shared library is loaded,
3283 @value{GDBN} reevaluates all the breakpoints. When a newly loaded
3284 shared library contains the symbol or line referred to by some
3285 pending breakpoint, that breakpoint is resolved and becomes an
3286 ordinary breakpoint. When a library is unloaded, all breakpoints
3287 that refer to its symbols or source lines become pending again.
3289 This logic works for breakpoints with multiple locations, too. For
3290 example, if you have a breakpoint in a C@t{++} template function, and
3291 a newly loaded shared library has an instantiation of that template,
3292 a new location is added to the list of locations for the breakpoint.
3294 Except for having unresolved address, pending breakpoints do not
3295 differ from regular breakpoints. You can set conditions or commands,
3296 enable and disable them and perform other breakpoint operations.
3298 @value{GDBN} provides some additional commands for controlling what
3299 happens when the @samp{break} command cannot resolve breakpoint
3300 address specification to an address:
3302 @kindex set breakpoint pending
3303 @kindex show breakpoint pending
3305 @item set breakpoint pending auto
3306 This is the default behavior. When @value{GDBN} cannot find the breakpoint
3307 location, it queries you whether a pending breakpoint should be created.
3309 @item set breakpoint pending on
3310 This indicates that an unrecognized breakpoint location should automatically
3311 result in a pending breakpoint being created.
3313 @item set breakpoint pending off
3314 This indicates that pending breakpoints are not to be created. Any
3315 unrecognized breakpoint location results in an error. This setting does
3316 not affect any pending breakpoints previously created.
3318 @item show breakpoint pending
3319 Show the current behavior setting for creating pending breakpoints.
3322 The settings above only affect the @code{break} command and its
3323 variants. Once breakpoint is set, it will be automatically updated
3324 as shared libraries are loaded and unloaded.
3326 @cindex automatic hardware breakpoints
3327 For some targets, @value{GDBN} can automatically decide if hardware or
3328 software breakpoints should be used, depending on whether the
3329 breakpoint address is read-only or read-write. This applies to
3330 breakpoints set with the @code{break} command as well as to internal
3331 breakpoints set by commands like @code{next} and @code{finish}. For
3332 breakpoints set with @code{hbreak}, @value{GDBN} will always use hardware
3335 You can control this automatic behaviour with the following commands::
3337 @kindex set breakpoint auto-hw
3338 @kindex show breakpoint auto-hw
3340 @item set breakpoint auto-hw on
3341 This is the default behavior. When @value{GDBN} sets a breakpoint, it
3342 will try to use the target memory map to decide if software or hardware
3343 breakpoint must be used.
3345 @item set breakpoint auto-hw off
3346 This indicates @value{GDBN} should not automatically select breakpoint
3347 type. If the target provides a memory map, @value{GDBN} will warn when
3348 trying to set software breakpoint at a read-only address.
3351 @value{GDBN} normally implements breakpoints by replacing the program code
3352 at the breakpoint address with a special instruction, which, when
3353 executed, given control to the debugger. By default, the program
3354 code is so modified only when the program is resumed. As soon as
3355 the program stops, @value{GDBN} restores the original instructions. This
3356 behaviour guards against leaving breakpoints inserted in the
3357 target should gdb abrubptly disconnect. However, with slow remote
3358 targets, inserting and removing breakpoint can reduce the performance.
3359 This behavior can be controlled with the following commands::
3361 @kindex set breakpoint always-inserted
3362 @kindex show breakpoint always-inserted
3364 @item set breakpoint always-inserted off
3365 All breakpoints, including newly added by the user, are inserted in
3366 the target only when the target is resumed. All breakpoints are
3367 removed from the target when it stops.
3369 @item set breakpoint always-inserted on
3370 Causes all breakpoints to be inserted in the target at all times. If
3371 the user adds a new breakpoint, or changes an existing breakpoint, the
3372 breakpoints in the target are updated immediately. A breakpoint is
3373 removed from the target only when breakpoint itself is removed.
3375 @cindex non-stop mode, and @code{breakpoint always-inserted}
3376 @item set breakpoint always-inserted auto
3377 This is the default mode. If @value{GDBN} is controlling the inferior
3378 in non-stop mode (@pxref{Non-Stop Mode}), gdb behaves as if
3379 @code{breakpoint always-inserted} mode is on. If @value{GDBN} is
3380 controlling the inferior in all-stop mode, @value{GDBN} behaves as if
3381 @code{breakpoint always-inserted} mode is off.
3384 @cindex negative breakpoint numbers
3385 @cindex internal @value{GDBN} breakpoints
3386 @value{GDBN} itself sometimes sets breakpoints in your program for
3387 special purposes, such as proper handling of @code{longjmp} (in C
3388 programs). These internal breakpoints are assigned negative numbers,
3389 starting with @code{-1}; @samp{info breakpoints} does not display them.
3390 You can see these breakpoints with the @value{GDBN} maintenance command
3391 @samp{maint info breakpoints} (@pxref{maint info breakpoints}).
3394 @node Set Watchpoints
3395 @subsection Setting Watchpoints
3397 @cindex setting watchpoints
3398 You can use a watchpoint to stop execution whenever the value of an
3399 expression changes, without having to predict a particular place where
3400 this may happen. (This is sometimes called a @dfn{data breakpoint}.)
3401 The expression may be as simple as the value of a single variable, or
3402 as complex as many variables combined by operators. Examples include:
3406 A reference to the value of a single variable.
3409 An address cast to an appropriate data type. For example,
3410 @samp{*(int *)0x12345678} will watch a 4-byte region at the specified
3411 address (assuming an @code{int} occupies 4 bytes).
3414 An arbitrarily complex expression, such as @samp{a*b + c/d}. The
3415 expression can use any operators valid in the program's native
3416 language (@pxref{Languages}).
3419 You can set a watchpoint on an expression even if the expression can
3420 not be evaluated yet. For instance, you can set a watchpoint on
3421 @samp{*global_ptr} before @samp{global_ptr} is initialized.
3422 @value{GDBN} will stop when your program sets @samp{global_ptr} and
3423 the expression produces a valid value. If the expression becomes
3424 valid in some other way than changing a variable (e.g.@: if the memory
3425 pointed to by @samp{*global_ptr} becomes readable as the result of a
3426 @code{malloc} call), @value{GDBN} may not stop until the next time
3427 the expression changes.
3429 @cindex software watchpoints
3430 @cindex hardware watchpoints
3431 Depending on your system, watchpoints may be implemented in software or
3432 hardware. @value{GDBN} does software watchpointing by single-stepping your
3433 program and testing the variable's value each time, which is hundreds of
3434 times slower than normal execution. (But this may still be worth it, to
3435 catch errors where you have no clue what part of your program is the
3438 On some systems, such as HP-UX, PowerPC, @sc{gnu}/Linux and most other
3439 x86-based targets, @value{GDBN} includes support for hardware
3440 watchpoints, which do not slow down the running of your program.
3444 @item watch @var{expr} @r{[}thread @var{threadnum}@r{]}
3445 Set a watchpoint for an expression. @value{GDBN} will break when the
3446 expression @var{expr} is written into by the program and its value
3447 changes. The simplest (and the most popular) use of this command is
3448 to watch the value of a single variable:
3451 (@value{GDBP}) watch foo
3454 If the command includes a @code{@r{[}thread @var{threadnum}@r{]}}
3455 clause, @value{GDBN} breaks only when the thread identified by
3456 @var{threadnum} changes the value of @var{expr}. If any other threads
3457 change the value of @var{expr}, @value{GDBN} will not break. Note
3458 that watchpoints restricted to a single thread in this way only work
3459 with Hardware Watchpoints.
3462 @item rwatch @var{expr} @r{[}thread @var{threadnum}@r{]}
3463 Set a watchpoint that will break when the value of @var{expr} is read
3467 @item awatch @var{expr} @r{[}thread @var{threadnum}@r{]}
3468 Set a watchpoint that will break when @var{expr} is either read from
3469 or written into by the program.
3471 @kindex info watchpoints @r{[}@var{n}@r{]}
3472 @item info watchpoints
3473 This command prints a list of watchpoints, breakpoints, and catchpoints;
3474 it is the same as @code{info break} (@pxref{Set Breaks}).
3477 @value{GDBN} sets a @dfn{hardware watchpoint} if possible. Hardware
3478 watchpoints execute very quickly, and the debugger reports a change in
3479 value at the exact instruction where the change occurs. If @value{GDBN}
3480 cannot set a hardware watchpoint, it sets a software watchpoint, which
3481 executes more slowly and reports the change in value at the next
3482 @emph{statement}, not the instruction, after the change occurs.
3484 @cindex use only software watchpoints
3485 You can force @value{GDBN} to use only software watchpoints with the
3486 @kbd{set can-use-hw-watchpoints 0} command. With this variable set to
3487 zero, @value{GDBN} will never try to use hardware watchpoints, even if
3488 the underlying system supports them. (Note that hardware-assisted
3489 watchpoints that were set @emph{before} setting
3490 @code{can-use-hw-watchpoints} to zero will still use the hardware
3491 mechanism of watching expression values.)
3494 @item set can-use-hw-watchpoints
3495 @kindex set can-use-hw-watchpoints
3496 Set whether or not to use hardware watchpoints.
3498 @item show can-use-hw-watchpoints
3499 @kindex show can-use-hw-watchpoints
3500 Show the current mode of using hardware watchpoints.
3503 For remote targets, you can restrict the number of hardware
3504 watchpoints @value{GDBN} will use, see @ref{set remote
3505 hardware-breakpoint-limit}.
3507 When you issue the @code{watch} command, @value{GDBN} reports
3510 Hardware watchpoint @var{num}: @var{expr}
3514 if it was able to set a hardware watchpoint.
3516 Currently, the @code{awatch} and @code{rwatch} commands can only set
3517 hardware watchpoints, because accesses to data that don't change the
3518 value of the watched expression cannot be detected without examining
3519 every instruction as it is being executed, and @value{GDBN} does not do
3520 that currently. If @value{GDBN} finds that it is unable to set a
3521 hardware breakpoint with the @code{awatch} or @code{rwatch} command, it
3522 will print a message like this:
3525 Expression cannot be implemented with read/access watchpoint.
3528 Sometimes, @value{GDBN} cannot set a hardware watchpoint because the
3529 data type of the watched expression is wider than what a hardware
3530 watchpoint on the target machine can handle. For example, some systems
3531 can only watch regions that are up to 4 bytes wide; on such systems you
3532 cannot set hardware watchpoints for an expression that yields a
3533 double-precision floating-point number (which is typically 8 bytes
3534 wide). As a work-around, it might be possible to break the large region
3535 into a series of smaller ones and watch them with separate watchpoints.
3537 If you set too many hardware watchpoints, @value{GDBN} might be unable
3538 to insert all of them when you resume the execution of your program.
3539 Since the precise number of active watchpoints is unknown until such
3540 time as the program is about to be resumed, @value{GDBN} might not be
3541 able to warn you about this when you set the watchpoints, and the
3542 warning will be printed only when the program is resumed:
3545 Hardware watchpoint @var{num}: Could not insert watchpoint
3549 If this happens, delete or disable some of the watchpoints.
3551 Watching complex expressions that reference many variables can also
3552 exhaust the resources available for hardware-assisted watchpoints.
3553 That's because @value{GDBN} needs to watch every variable in the
3554 expression with separately allocated resources.
3556 If you call a function interactively using @code{print} or @code{call},
3557 any watchpoints you have set will be inactive until @value{GDBN} reaches another
3558 kind of breakpoint or the call completes.
3560 @value{GDBN} automatically deletes watchpoints that watch local
3561 (automatic) variables, or expressions that involve such variables, when
3562 they go out of scope, that is, when the execution leaves the block in
3563 which these variables were defined. In particular, when the program
3564 being debugged terminates, @emph{all} local variables go out of scope,
3565 and so only watchpoints that watch global variables remain set. If you
3566 rerun the program, you will need to set all such watchpoints again. One
3567 way of doing that would be to set a code breakpoint at the entry to the
3568 @code{main} function and when it breaks, set all the watchpoints.
3570 @cindex watchpoints and threads
3571 @cindex threads and watchpoints
3572 In multi-threaded programs, watchpoints will detect changes to the
3573 watched expression from every thread.
3576 @emph{Warning:} In multi-threaded programs, software watchpoints
3577 have only limited usefulness. If @value{GDBN} creates a software
3578 watchpoint, it can only watch the value of an expression @emph{in a
3579 single thread}. If you are confident that the expression can only
3580 change due to the current thread's activity (and if you are also
3581 confident that no other thread can become current), then you can use
3582 software watchpoints as usual. However, @value{GDBN} may not notice
3583 when a non-current thread's activity changes the expression. (Hardware
3584 watchpoints, in contrast, watch an expression in all threads.)
3587 @xref{set remote hardware-watchpoint-limit}.
3589 @node Set Catchpoints
3590 @subsection Setting Catchpoints
3591 @cindex catchpoints, setting
3592 @cindex exception handlers
3593 @cindex event handling
3595 You can use @dfn{catchpoints} to cause the debugger to stop for certain
3596 kinds of program events, such as C@t{++} exceptions or the loading of a
3597 shared library. Use the @code{catch} command to set a catchpoint.
3601 @item catch @var{event}
3602 Stop when @var{event} occurs. @var{event} can be any of the following:
3605 @cindex stop on C@t{++} exceptions
3606 The throwing of a C@t{++} exception.
3609 The catching of a C@t{++} exception.
3612 @cindex Ada exception catching
3613 @cindex catch Ada exceptions
3614 An Ada exception being raised. If an exception name is specified
3615 at the end of the command (eg @code{catch exception Program_Error}),
3616 the debugger will stop only when this specific exception is raised.
3617 Otherwise, the debugger stops execution when any Ada exception is raised.
3619 When inserting an exception catchpoint on a user-defined exception whose
3620 name is identical to one of the exceptions defined by the language, the
3621 fully qualified name must be used as the exception name. Otherwise,
3622 @value{GDBN} will assume that it should stop on the pre-defined exception
3623 rather than the user-defined one. For instance, assuming an exception
3624 called @code{Constraint_Error} is defined in package @code{Pck}, then
3625 the command to use to catch such exceptions is @kbd{catch exception
3626 Pck.Constraint_Error}.
3628 @item exception unhandled
3629 An exception that was raised but is not handled by the program.
3632 A failed Ada assertion.
3635 @cindex break on fork/exec
3636 A call to @code{exec}. This is currently only available for HP-UX
3640 A call to @code{fork}. This is currently only available for HP-UX
3644 A call to @code{vfork}. This is currently only available for HP-UX
3649 @item tcatch @var{event}
3650 Set a catchpoint that is enabled only for one stop. The catchpoint is
3651 automatically deleted after the first time the event is caught.
3655 Use the @code{info break} command to list the current catchpoints.
3657 There are currently some limitations to C@t{++} exception handling
3658 (@code{catch throw} and @code{catch catch}) in @value{GDBN}:
3662 If you call a function interactively, @value{GDBN} normally returns
3663 control to you when the function has finished executing. If the call
3664 raises an exception, however, the call may bypass the mechanism that
3665 returns control to you and cause your program either to abort or to
3666 simply continue running until it hits a breakpoint, catches a signal
3667 that @value{GDBN} is listening for, or exits. This is the case even if
3668 you set a catchpoint for the exception; catchpoints on exceptions are
3669 disabled within interactive calls.
3672 You cannot raise an exception interactively.
3675 You cannot install an exception handler interactively.
3678 @cindex raise exceptions
3679 Sometimes @code{catch} is not the best way to debug exception handling:
3680 if you need to know exactly where an exception is raised, it is better to
3681 stop @emph{before} the exception handler is called, since that way you
3682 can see the stack before any unwinding takes place. If you set a
3683 breakpoint in an exception handler instead, it may not be easy to find
3684 out where the exception was raised.
3686 To stop just before an exception handler is called, you need some
3687 knowledge of the implementation. In the case of @sc{gnu} C@t{++}, exceptions are
3688 raised by calling a library function named @code{__raise_exception}
3689 which has the following ANSI C interface:
3692 /* @var{addr} is where the exception identifier is stored.
3693 @var{id} is the exception identifier. */
3694 void __raise_exception (void **addr, void *id);
3698 To make the debugger catch all exceptions before any stack
3699 unwinding takes place, set a breakpoint on @code{__raise_exception}
3700 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Exceptions}).
3702 With a conditional breakpoint (@pxref{Conditions, ,Break Conditions})
3703 that depends on the value of @var{id}, you can stop your program when
3704 a specific exception is raised. You can use multiple conditional
3705 breakpoints to stop your program when any of a number of exceptions are
3710 @subsection Deleting Breakpoints
3712 @cindex clearing breakpoints, watchpoints, catchpoints
3713 @cindex deleting breakpoints, watchpoints, catchpoints
3714 It is often necessary to eliminate a breakpoint, watchpoint, or
3715 catchpoint once it has done its job and you no longer want your program
3716 to stop there. This is called @dfn{deleting} the breakpoint. A
3717 breakpoint that has been deleted no longer exists; it is forgotten.
3719 With the @code{clear} command you can delete breakpoints according to
3720 where they are in your program. With the @code{delete} command you can
3721 delete individual breakpoints, watchpoints, or catchpoints by specifying
3722 their breakpoint numbers.
3724 It is not necessary to delete a breakpoint to proceed past it. @value{GDBN}
3725 automatically ignores breakpoints on the first instruction to be executed
3726 when you continue execution without changing the execution address.
3731 Delete any breakpoints at the next instruction to be executed in the
3732 selected stack frame (@pxref{Selection, ,Selecting a Frame}). When
3733 the innermost frame is selected, this is a good way to delete a
3734 breakpoint where your program just stopped.
3736 @item clear @var{location}
3737 Delete any breakpoints set at the specified @var{location}.
3738 @xref{Specify Location}, for the various forms of @var{location}; the
3739 most useful ones are listed below:
3742 @item clear @var{function}
3743 @itemx clear @var{filename}:@var{function}
3744 Delete any breakpoints set at entry to the named @var{function}.
3746 @item clear @var{linenum}
3747 @itemx clear @var{filename}:@var{linenum}
3748 Delete any breakpoints set at or within the code of the specified
3749 @var{linenum} of the specified @var{filename}.
3752 @cindex delete breakpoints
3754 @kindex d @r{(@code{delete})}
3755 @item delete @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
3756 Delete the breakpoints, watchpoints, or catchpoints of the breakpoint
3757 ranges specified as arguments. If no argument is specified, delete all
3758 breakpoints (@value{GDBN} asks confirmation, unless you have @code{set
3759 confirm off}). You can abbreviate this command as @code{d}.
3763 @subsection Disabling Breakpoints
3765 @cindex enable/disable a breakpoint
3766 Rather than deleting a breakpoint, watchpoint, or catchpoint, you might
3767 prefer to @dfn{disable} it. This makes the breakpoint inoperative as if
3768 it had been deleted, but remembers the information on the breakpoint so
3769 that you can @dfn{enable} it again later.
3771 You disable and enable breakpoints, watchpoints, and catchpoints with
3772 the @code{enable} and @code{disable} commands, optionally specifying one
3773 or more breakpoint numbers as arguments. Use @code{info break} or
3774 @code{info watch} to print a list of breakpoints, watchpoints, and
3775 catchpoints if you do not know which numbers to use.
3777 Disabling and enabling a breakpoint that has multiple locations
3778 affects all of its locations.
3780 A breakpoint, watchpoint, or catchpoint can have any of four different
3781 states of enablement:
3785 Enabled. The breakpoint stops your program. A breakpoint set
3786 with the @code{break} command starts out in this state.
3788 Disabled. The breakpoint has no effect on your program.
3790 Enabled once. The breakpoint stops your program, but then becomes
3793 Enabled for deletion. The breakpoint stops your program, but
3794 immediately after it does so it is deleted permanently. A breakpoint
3795 set with the @code{tbreak} command starts out in this state.
3798 You can use the following commands to enable or disable breakpoints,
3799 watchpoints, and catchpoints:
3803 @kindex dis @r{(@code{disable})}
3804 @item disable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
3805 Disable the specified breakpoints---or all breakpoints, if none are
3806 listed. A disabled breakpoint has no effect but is not forgotten. All
3807 options such as ignore-counts, conditions and commands are remembered in
3808 case the breakpoint is enabled again later. You may abbreviate
3809 @code{disable} as @code{dis}.
3812 @item enable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
3813 Enable the specified breakpoints (or all defined breakpoints). They
3814 become effective once again in stopping your program.
3816 @item enable @r{[}breakpoints@r{]} once @var{range}@dots{}
3817 Enable the specified breakpoints temporarily. @value{GDBN} disables any
3818 of these breakpoints immediately after stopping your program.
3820 @item enable @r{[}breakpoints@r{]} delete @var{range}@dots{}
3821 Enable the specified breakpoints to work once, then die. @value{GDBN}
3822 deletes any of these breakpoints as soon as your program stops there.
3823 Breakpoints set by the @code{tbreak} command start out in this state.
3826 @c FIXME: I think the following ``Except for [...] @code{tbreak}'' is
3827 @c confusing: tbreak is also initially enabled.
3828 Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks,
3829 ,Setting Breakpoints}), breakpoints that you set are initially enabled;
3830 subsequently, they become disabled or enabled only when you use one of
3831 the commands above. (The command @code{until} can set and delete a
3832 breakpoint of its own, but it does not change the state of your other
3833 breakpoints; see @ref{Continuing and Stepping, ,Continuing and
3837 @subsection Break Conditions
3838 @cindex conditional breakpoints
3839 @cindex breakpoint conditions
3841 @c FIXME what is scope of break condition expr? Context where wanted?
3842 @c in particular for a watchpoint?
3843 The simplest sort of breakpoint breaks every time your program reaches a
3844 specified place. You can also specify a @dfn{condition} for a
3845 breakpoint. A condition is just a Boolean expression in your
3846 programming language (@pxref{Expressions, ,Expressions}). A breakpoint with
3847 a condition evaluates the expression each time your program reaches it,
3848 and your program stops only if the condition is @emph{true}.
3850 This is the converse of using assertions for program validation; in that
3851 situation, you want to stop when the assertion is violated---that is,
3852 when the condition is false. In C, if you want to test an assertion expressed
3853 by the condition @var{assert}, you should set the condition
3854 @samp{! @var{assert}} on the appropriate breakpoint.
3856 Conditions are also accepted for watchpoints; you may not need them,
3857 since a watchpoint is inspecting the value of an expression anyhow---but
3858 it might be simpler, say, to just set a watchpoint on a variable name,
3859 and specify a condition that tests whether the new value is an interesting
3862 Break conditions can have side effects, and may even call functions in
3863 your program. This can be useful, for example, to activate functions
3864 that log program progress, or to use your own print functions to
3865 format special data structures. The effects are completely predictable
3866 unless there is another enabled breakpoint at the same address. (In
3867 that case, @value{GDBN} might see the other breakpoint first and stop your
3868 program without checking the condition of this one.) Note that
3869 breakpoint commands are usually more convenient and flexible than break
3871 purpose of performing side effects when a breakpoint is reached
3872 (@pxref{Break Commands, ,Breakpoint Command Lists}).
3874 Break conditions can be specified when a breakpoint is set, by using
3875 @samp{if} in the arguments to the @code{break} command. @xref{Set
3876 Breaks, ,Setting Breakpoints}. They can also be changed at any time
3877 with the @code{condition} command.
3879 You can also use the @code{if} keyword with the @code{watch} command.
3880 The @code{catch} command does not recognize the @code{if} keyword;
3881 @code{condition} is the only way to impose a further condition on a
3886 @item condition @var{bnum} @var{expression}
3887 Specify @var{expression} as the break condition for breakpoint,
3888 watchpoint, or catchpoint number @var{bnum}. After you set a condition,
3889 breakpoint @var{bnum} stops your program only if the value of
3890 @var{expression} is true (nonzero, in C). When you use
3891 @code{condition}, @value{GDBN} checks @var{expression} immediately for
3892 syntactic correctness, and to determine whether symbols in it have
3893 referents in the context of your breakpoint. If @var{expression} uses
3894 symbols not referenced in the context of the breakpoint, @value{GDBN}
3895 prints an error message:
3898 No symbol "foo" in current context.
3903 not actually evaluate @var{expression} at the time the @code{condition}
3904 command (or a command that sets a breakpoint with a condition, like
3905 @code{break if @dots{}}) is given, however. @xref{Expressions, ,Expressions}.
3907 @item condition @var{bnum}
3908 Remove the condition from breakpoint number @var{bnum}. It becomes
3909 an ordinary unconditional breakpoint.
3912 @cindex ignore count (of breakpoint)
3913 A special case of a breakpoint condition is to stop only when the
3914 breakpoint has been reached a certain number of times. This is so
3915 useful that there is a special way to do it, using the @dfn{ignore
3916 count} of the breakpoint. Every breakpoint has an ignore count, which
3917 is an integer. Most of the time, the ignore count is zero, and
3918 therefore has no effect. But if your program reaches a breakpoint whose
3919 ignore count is positive, then instead of stopping, it just decrements
3920 the ignore count by one and continues. As a result, if the ignore count
3921 value is @var{n}, the breakpoint does not stop the next @var{n} times
3922 your program reaches it.
3926 @item ignore @var{bnum} @var{count}
3927 Set the ignore count of breakpoint number @var{bnum} to @var{count}.
3928 The next @var{count} times the breakpoint is reached, your program's
3929 execution does not stop; other than to decrement the ignore count, @value{GDBN}
3932 To make the breakpoint stop the next time it is reached, specify
3935 When you use @code{continue} to resume execution of your program from a
3936 breakpoint, you can specify an ignore count directly as an argument to
3937 @code{continue}, rather than using @code{ignore}. @xref{Continuing and
3938 Stepping,,Continuing and Stepping}.
3940 If a breakpoint has a positive ignore count and a condition, the
3941 condition is not checked. Once the ignore count reaches zero,
3942 @value{GDBN} resumes checking the condition.
3944 You could achieve the effect of the ignore count with a condition such
3945 as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that
3946 is decremented each time. @xref{Convenience Vars, ,Convenience
3950 Ignore counts apply to breakpoints, watchpoints, and catchpoints.
3953 @node Break Commands
3954 @subsection Breakpoint Command Lists
3956 @cindex breakpoint commands
3957 You can give any breakpoint (or watchpoint or catchpoint) a series of
3958 commands to execute when your program stops due to that breakpoint. For
3959 example, you might want to print the values of certain expressions, or
3960 enable other breakpoints.
3964 @kindex end@r{ (breakpoint commands)}
3965 @item commands @r{[}@var{bnum}@r{]}
3966 @itemx @dots{} @var{command-list} @dots{}
3968 Specify a list of commands for breakpoint number @var{bnum}. The commands
3969 themselves appear on the following lines. Type a line containing just
3970 @code{end} to terminate the commands.
3972 To remove all commands from a breakpoint, type @code{commands} and
3973 follow it immediately with @code{end}; that is, give no commands.
3975 With no @var{bnum} argument, @code{commands} refers to the last
3976 breakpoint, watchpoint, or catchpoint set (not to the breakpoint most
3977 recently encountered).
3980 Pressing @key{RET} as a means of repeating the last @value{GDBN} command is
3981 disabled within a @var{command-list}.
3983 You can use breakpoint commands to start your program up again. Simply
3984 use the @code{continue} command, or @code{step}, or any other command
3985 that resumes execution.
3987 Any other commands in the command list, after a command that resumes
3988 execution, are ignored. This is because any time you resume execution
3989 (even with a simple @code{next} or @code{step}), you may encounter
3990 another breakpoint---which could have its own command list, leading to
3991 ambiguities about which list to execute.
3994 If the first command you specify in a command list is @code{silent}, the
3995 usual message about stopping at a breakpoint is not printed. This may
3996 be desirable for breakpoints that are to print a specific message and
3997 then continue. If none of the remaining commands print anything, you
3998 see no sign that the breakpoint was reached. @code{silent} is
3999 meaningful only at the beginning of a breakpoint command list.
4001 The commands @code{echo}, @code{output}, and @code{printf} allow you to
4002 print precisely controlled output, and are often useful in silent
4003 breakpoints. @xref{Output, ,Commands for Controlled Output}.
4005 For example, here is how you could use breakpoint commands to print the
4006 value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
4012 printf "x is %d\n",x
4017 One application for breakpoint commands is to compensate for one bug so
4018 you can test for another. Put a breakpoint just after the erroneous line
4019 of code, give it a condition to detect the case in which something
4020 erroneous has been done, and give it commands to assign correct values
4021 to any variables that need them. End with the @code{continue} command
4022 so that your program does not stop, and start with the @code{silent}
4023 command so that no output is produced. Here is an example:
4034 @c @ifclear BARETARGET
4035 @node Error in Breakpoints
4036 @subsection ``Cannot insert breakpoints''
4038 If you request too many active hardware-assisted breakpoints and
4039 watchpoints, you will see this error message:
4041 @c FIXME: the precise wording of this message may change; the relevant
4042 @c source change is not committed yet (Sep 3, 1999).
4044 Stopped; cannot insert breakpoints.
4045 You may have requested too many hardware breakpoints and watchpoints.
4049 This message is printed when you attempt to resume the program, since
4050 only then @value{GDBN} knows exactly how many hardware breakpoints and
4051 watchpoints it needs to insert.
4053 When this message is printed, you need to disable or remove some of the
4054 hardware-assisted breakpoints and watchpoints, and then continue.
4056 @node Breakpoint-related Warnings
4057 @subsection ``Breakpoint address adjusted...''
4058 @cindex breakpoint address adjusted
4060 Some processor architectures place constraints on the addresses at
4061 which breakpoints may be placed. For architectures thus constrained,
4062 @value{GDBN} will attempt to adjust the breakpoint's address to comply
4063 with the constraints dictated by the architecture.
4065 One example of such an architecture is the Fujitsu FR-V. The FR-V is
4066 a VLIW architecture in which a number of RISC-like instructions may be
4067 bundled together for parallel execution. The FR-V architecture
4068 constrains the location of a breakpoint instruction within such a
4069 bundle to the instruction with the lowest address. @value{GDBN}
4070 honors this constraint by adjusting a breakpoint's address to the
4071 first in the bundle.
4073 It is not uncommon for optimized code to have bundles which contain
4074 instructions from different source statements, thus it may happen that
4075 a breakpoint's address will be adjusted from one source statement to
4076 another. Since this adjustment may significantly alter @value{GDBN}'s
4077 breakpoint related behavior from what the user expects, a warning is
4078 printed when the breakpoint is first set and also when the breakpoint
4081 A warning like the one below is printed when setting a breakpoint
4082 that's been subject to address adjustment:
4085 warning: Breakpoint address adjusted from 0x00010414 to 0x00010410.
4088 Such warnings are printed both for user settable and @value{GDBN}'s
4089 internal breakpoints. If you see one of these warnings, you should
4090 verify that a breakpoint set at the adjusted address will have the
4091 desired affect. If not, the breakpoint in question may be removed and
4092 other breakpoints may be set which will have the desired behavior.
4093 E.g., it may be sufficient to place the breakpoint at a later
4094 instruction. A conditional breakpoint may also be useful in some
4095 cases to prevent the breakpoint from triggering too often.
4097 @value{GDBN} will also issue a warning when stopping at one of these
4098 adjusted breakpoints:
4101 warning: Breakpoint 1 address previously adjusted from 0x00010414
4105 When this warning is encountered, it may be too late to take remedial
4106 action except in cases where the breakpoint is hit earlier or more
4107 frequently than expected.
4109 @node Continuing and Stepping
4110 @section Continuing and Stepping
4114 @cindex resuming execution
4115 @dfn{Continuing} means resuming program execution until your program
4116 completes normally. In contrast, @dfn{stepping} means executing just
4117 one more ``step'' of your program, where ``step'' may mean either one
4118 line of source code, or one machine instruction (depending on what
4119 particular command you use). Either when continuing or when stepping,
4120 your program may stop even sooner, due to a breakpoint or a signal. (If
4121 it stops due to a signal, you may want to use @code{handle}, or use
4122 @samp{signal 0} to resume execution. @xref{Signals, ,Signals}.)
4126 @kindex c @r{(@code{continue})}
4127 @kindex fg @r{(resume foreground execution)}
4128 @item continue @r{[}@var{ignore-count}@r{]}
4129 @itemx c @r{[}@var{ignore-count}@r{]}
4130 @itemx fg @r{[}@var{ignore-count}@r{]}
4131 Resume program execution, at the address where your program last stopped;
4132 any breakpoints set at that address are bypassed. The optional argument
4133 @var{ignore-count} allows you to specify a further number of times to
4134 ignore a breakpoint at this location; its effect is like that of
4135 @code{ignore} (@pxref{Conditions, ,Break Conditions}).
4137 The argument @var{ignore-count} is meaningful only when your program
4138 stopped due to a breakpoint. At other times, the argument to
4139 @code{continue} is ignored.
4141 The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the
4142 debugged program is deemed to be the foreground program) are provided
4143 purely for convenience, and have exactly the same behavior as
4147 To resume execution at a different place, you can use @code{return}
4148 (@pxref{Returning, ,Returning from a Function}) to go back to the
4149 calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
4150 Different Address}) to go to an arbitrary location in your program.
4152 A typical technique for using stepping is to set a breakpoint
4153 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Catchpoints}) at the
4154 beginning of the function or the section of your program where a problem
4155 is believed to lie, run your program until it stops at that breakpoint,
4156 and then step through the suspect area, examining the variables that are
4157 interesting, until you see the problem happen.
4161 @kindex s @r{(@code{step})}
4163 Continue running your program until control reaches a different source
4164 line, then stop it and return control to @value{GDBN}. This command is
4165 abbreviated @code{s}.
4168 @c "without debugging information" is imprecise; actually "without line
4169 @c numbers in the debugging information". (gcc -g1 has debugging info but
4170 @c not line numbers). But it seems complex to try to make that
4171 @c distinction here.
4172 @emph{Warning:} If you use the @code{step} command while control is
4173 within a function that was compiled without debugging information,
4174 execution proceeds until control reaches a function that does have
4175 debugging information. Likewise, it will not step into a function which
4176 is compiled without debugging information. To step through functions
4177 without debugging information, use the @code{stepi} command, described
4181 The @code{step} command only stops at the first instruction of a source
4182 line. This prevents the multiple stops that could otherwise occur in
4183 @code{switch} statements, @code{for} loops, etc. @code{step} continues
4184 to stop if a function that has debugging information is called within
4185 the line. In other words, @code{step} @emph{steps inside} any functions
4186 called within the line.
4188 Also, the @code{step} command only enters a function if there is line
4189 number information for the function. Otherwise it acts like the
4190 @code{next} command. This avoids problems when using @code{cc -gl}
4191 on MIPS machines. Previously, @code{step} entered subroutines if there
4192 was any debugging information about the routine.
4194 @item step @var{count}
4195 Continue running as in @code{step}, but do so @var{count} times. If a
4196 breakpoint is reached, or a signal not related to stepping occurs before
4197 @var{count} steps, stepping stops right away.
4200 @kindex n @r{(@code{next})}
4201 @item next @r{[}@var{count}@r{]}
4202 Continue to the next source line in the current (innermost) stack frame.
4203 This is similar to @code{step}, but function calls that appear within
4204 the line of code are executed without stopping. Execution stops when
4205 control reaches a different line of code at the original stack level
4206 that was executing when you gave the @code{next} command. This command
4207 is abbreviated @code{n}.
4209 An argument @var{count} is a repeat count, as for @code{step}.
4212 @c FIX ME!! Do we delete this, or is there a way it fits in with
4213 @c the following paragraph? --- Vctoria
4215 @c @code{next} within a function that lacks debugging information acts like
4216 @c @code{step}, but any function calls appearing within the code of the
4217 @c function are executed without stopping.
4219 The @code{next} command only stops at the first instruction of a
4220 source line. This prevents multiple stops that could otherwise occur in
4221 @code{switch} statements, @code{for} loops, etc.
4223 @kindex set step-mode
4225 @cindex functions without line info, and stepping
4226 @cindex stepping into functions with no line info
4227 @itemx set step-mode on
4228 The @code{set step-mode on} command causes the @code{step} command to
4229 stop at the first instruction of a function which contains no debug line
4230 information rather than stepping over it.
4232 This is useful in cases where you may be interested in inspecting the
4233 machine instructions of a function which has no symbolic info and do not
4234 want @value{GDBN} to automatically skip over this function.
4236 @item set step-mode off
4237 Causes the @code{step} command to step over any functions which contains no
4238 debug information. This is the default.
4240 @item show step-mode
4241 Show whether @value{GDBN} will stop in or step over functions without
4242 source line debug information.
4245 @kindex fin @r{(@code{finish})}
4247 Continue running until just after function in the selected stack frame
4248 returns. Print the returned value (if any). This command can be
4249 abbreviated as @code{fin}.
4251 Contrast this with the @code{return} command (@pxref{Returning,
4252 ,Returning from a Function}).
4255 @kindex u @r{(@code{until})}
4256 @cindex run until specified location
4259 Continue running until a source line past the current line, in the
4260 current stack frame, is reached. This command is used to avoid single
4261 stepping through a loop more than once. It is like the @code{next}
4262 command, except that when @code{until} encounters a jump, it
4263 automatically continues execution until the program counter is greater
4264 than the address of the jump.
4266 This means that when you reach the end of a loop after single stepping
4267 though it, @code{until} makes your program continue execution until it
4268 exits the loop. In contrast, a @code{next} command at the end of a loop
4269 simply steps back to the beginning of the loop, which forces you to step
4270 through the next iteration.
4272 @code{until} always stops your program if it attempts to exit the current
4275 @code{until} may produce somewhat counterintuitive results if the order
4276 of machine code does not match the order of the source lines. For
4277 example, in the following excerpt from a debugging session, the @code{f}
4278 (@code{frame}) command shows that execution is stopped at line
4279 @code{206}; yet when we use @code{until}, we get to line @code{195}:
4283 #0 main (argc=4, argv=0xf7fffae8) at m4.c:206
4285 (@value{GDBP}) until
4286 195 for ( ; argc > 0; NEXTARG) @{
4289 This happened because, for execution efficiency, the compiler had
4290 generated code for the loop closure test at the end, rather than the
4291 start, of the loop---even though the test in a C @code{for}-loop is
4292 written before the body of the loop. The @code{until} command appeared
4293 to step back to the beginning of the loop when it advanced to this
4294 expression; however, it has not really gone to an earlier
4295 statement---not in terms of the actual machine code.
4297 @code{until} with no argument works by means of single
4298 instruction stepping, and hence is slower than @code{until} with an
4301 @item until @var{location}
4302 @itemx u @var{location}
4303 Continue running your program until either the specified location is
4304 reached, or the current stack frame returns. @var{location} is any of
4305 the forms described in @ref{Specify Location}.
4306 This form of the command uses temporary breakpoints, and
4307 hence is quicker than @code{until} without an argument. The specified
4308 location is actually reached only if it is in the current frame. This
4309 implies that @code{until} can be used to skip over recursive function
4310 invocations. For instance in the code below, if the current location is
4311 line @code{96}, issuing @code{until 99} will execute the program up to
4312 line @code{99} in the same invocation of factorial, i.e., after the inner
4313 invocations have returned.
4316 94 int factorial (int value)
4318 96 if (value > 1) @{
4319 97 value *= factorial (value - 1);
4326 @kindex advance @var{location}
4327 @itemx advance @var{location}
4328 Continue running the program up to the given @var{location}. An argument is
4329 required, which should be of one of the forms described in
4330 @ref{Specify Location}.
4331 Execution will also stop upon exit from the current stack
4332 frame. This command is similar to @code{until}, but @code{advance} will
4333 not skip over recursive function calls, and the target location doesn't
4334 have to be in the same frame as the current one.
4338 @kindex si @r{(@code{stepi})}
4340 @itemx stepi @var{arg}
4342 Execute one machine instruction, then stop and return to the debugger.
4344 It is often useful to do @samp{display/i $pc} when stepping by machine
4345 instructions. This makes @value{GDBN} automatically display the next
4346 instruction to be executed, each time your program stops. @xref{Auto
4347 Display,, Automatic Display}.
4349 An argument is a repeat count, as in @code{step}.
4353 @kindex ni @r{(@code{nexti})}
4355 @itemx nexti @var{arg}
4357 Execute one machine instruction, but if it is a function call,
4358 proceed until the function returns.
4360 An argument is a repeat count, as in @code{next}.
4367 A signal is an asynchronous event that can happen in a program. The
4368 operating system defines the possible kinds of signals, and gives each
4369 kind a name and a number. For example, in Unix @code{SIGINT} is the
4370 signal a program gets when you type an interrupt character (often @kbd{Ctrl-c});
4371 @code{SIGSEGV} is the signal a program gets from referencing a place in
4372 memory far away from all the areas in use; @code{SIGALRM} occurs when
4373 the alarm clock timer goes off (which happens only if your program has
4374 requested an alarm).
4376 @cindex fatal signals
4377 Some signals, including @code{SIGALRM}, are a normal part of the
4378 functioning of your program. Others, such as @code{SIGSEGV}, indicate
4379 errors; these signals are @dfn{fatal} (they kill your program immediately) if the
4380 program has not specified in advance some other way to handle the signal.
4381 @code{SIGINT} does not indicate an error in your program, but it is normally
4382 fatal so it can carry out the purpose of the interrupt: to kill the program.
4384 @value{GDBN} has the ability to detect any occurrence of a signal in your
4385 program. You can tell @value{GDBN} in advance what to do for each kind of
4388 @cindex handling signals
4389 Normally, @value{GDBN} is set up to let the non-erroneous signals like
4390 @code{SIGALRM} be silently passed to your program
4391 (so as not to interfere with their role in the program's functioning)
4392 but to stop your program immediately whenever an error signal happens.
4393 You can change these settings with the @code{handle} command.
4396 @kindex info signals
4400 Print a table of all the kinds of signals and how @value{GDBN} has been told to
4401 handle each one. You can use this to see the signal numbers of all
4402 the defined types of signals.
4404 @item info signals @var{sig}
4405 Similar, but print information only about the specified signal number.
4407 @code{info handle} is an alias for @code{info signals}.
4410 @item handle @var{signal} @r{[}@var{keywords}@dots{}@r{]}
4411 Change the way @value{GDBN} handles signal @var{signal}. @var{signal}
4412 can be the number of a signal or its name (with or without the
4413 @samp{SIG} at the beginning); a list of signal numbers of the form
4414 @samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the
4415 known signals. Optional arguments @var{keywords}, described below,
4416 say what change to make.
4420 The keywords allowed by the @code{handle} command can be abbreviated.
4421 Their full names are:
4425 @value{GDBN} should not stop your program when this signal happens. It may
4426 still print a message telling you that the signal has come in.
4429 @value{GDBN} should stop your program when this signal happens. This implies
4430 the @code{print} keyword as well.
4433 @value{GDBN} should print a message when this signal happens.
4436 @value{GDBN} should not mention the occurrence of the signal at all. This
4437 implies the @code{nostop} keyword as well.
4441 @value{GDBN} should allow your program to see this signal; your program
4442 can handle the signal, or else it may terminate if the signal is fatal
4443 and not handled. @code{pass} and @code{noignore} are synonyms.
4447 @value{GDBN} should not allow your program to see this signal.
4448 @code{nopass} and @code{ignore} are synonyms.
4452 When a signal stops your program, the signal is not visible to the
4454 continue. Your program sees the signal then, if @code{pass} is in
4455 effect for the signal in question @emph{at that time}. In other words,
4456 after @value{GDBN} reports a signal, you can use the @code{handle}
4457 command with @code{pass} or @code{nopass} to control whether your
4458 program sees that signal when you continue.
4460 The default is set to @code{nostop}, @code{noprint}, @code{pass} for
4461 non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and
4462 @code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the
4465 You can also use the @code{signal} command to prevent your program from
4466 seeing a signal, or cause it to see a signal it normally would not see,
4467 or to give it any signal at any time. For example, if your program stopped
4468 due to some sort of memory reference error, you might store correct
4469 values into the erroneous variables and continue, hoping to see more
4470 execution; but your program would probably terminate immediately as
4471 a result of the fatal signal once it saw the signal. To prevent this,
4472 you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
4475 @cindex extra signal information
4476 @anchor{extra signal information}
4478 On some targets, @value{GDBN} can inspect extra signal information
4479 associated with the intercepted signal, before it is actually
4480 delivered to the program being debugged. This information is exported
4481 by the convenience variable @code{$_siginfo}, and consists of data
4482 that is passed by the kernel to the signal handler at the time of the
4483 receipt of a signal. The data type of the information itself is
4484 target dependent. You can see the data type using the @code{ptype
4485 $_siginfo} command. On Unix systems, it typically corresponds to the
4486 standard @code{siginfo_t} type, as defined in the @file{signal.h}
4489 Here's an example, on a @sc{gnu}/Linux system, printing the stray
4490 referenced address that raised a segmentation fault.
4494 (@value{GDBP}) continue
4495 Program received signal SIGSEGV, Segmentation fault.
4496 0x0000000000400766 in main ()
4498 (@value{GDBP}) ptype $_siginfo
4505 struct @{...@} _kill;
4506 struct @{...@} _timer;
4508 struct @{...@} _sigchld;
4509 struct @{...@} _sigfault;
4510 struct @{...@} _sigpoll;
4513 (@value{GDBP}) ptype $_siginfo._sifields._sigfault
4517 (@value{GDBP}) p $_siginfo._sifields._sigfault.si_addr
4518 $1 = (void *) 0x7ffff7ff7000
4522 Depending on target support, @code{$_siginfo} may also be writable.
4525 @section Stopping and Starting Multi-thread Programs
4527 @cindex stopped threads
4528 @cindex threads, stopped
4530 @cindex continuing threads
4531 @cindex threads, continuing
4533 @value{GDBN} supports debugging programs with multiple threads
4534 (@pxref{Threads,, Debugging Programs with Multiple Threads}). There
4535 are two modes of controlling execution of your program within the
4536 debugger. In the default mode, referred to as @dfn{all-stop mode},
4537 when any thread in your program stops (for example, at a breakpoint
4538 or while being stepped), all other threads in the program are also stopped by
4539 @value{GDBN}. On some targets, @value{GDBN} also supports
4540 @dfn{non-stop mode}, in which other threads can continue to run freely while
4541 you examine the stopped thread in the debugger.
4544 * All-Stop Mode:: All threads stop when GDB takes control
4545 * Non-Stop Mode:: Other threads continue to execute
4546 * Background Execution:: Running your program asynchronously
4547 * Thread-Specific Breakpoints:: Controlling breakpoints
4548 * Interrupted System Calls:: GDB may interfere with system calls
4552 @subsection All-Stop Mode
4554 @cindex all-stop mode
4556 In all-stop mode, whenever your program stops under @value{GDBN} for any reason,
4557 @emph{all} threads of execution stop, not just the current thread. This
4558 allows you to examine the overall state of the program, including
4559 switching between threads, without worrying that things may change
4562 Conversely, whenever you restart the program, @emph{all} threads start
4563 executing. @emph{This is true even when single-stepping} with commands
4564 like @code{step} or @code{next}.
4566 In particular, @value{GDBN} cannot single-step all threads in lockstep.
4567 Since thread scheduling is up to your debugging target's operating
4568 system (not controlled by @value{GDBN}), other threads may
4569 execute more than one statement while the current thread completes a
4570 single step. Moreover, in general other threads stop in the middle of a
4571 statement, rather than at a clean statement boundary, when the program
4574 You might even find your program stopped in another thread after
4575 continuing or even single-stepping. This happens whenever some other
4576 thread runs into a breakpoint, a signal, or an exception before the
4577 first thread completes whatever you requested.
4579 @cindex automatic thread selection
4580 @cindex switching threads automatically
4581 @cindex threads, automatic switching
4582 Whenever @value{GDBN} stops your program, due to a breakpoint or a
4583 signal, it automatically selects the thread where that breakpoint or
4584 signal happened. @value{GDBN} alerts you to the context switch with a
4585 message such as @samp{[Switching to Thread @var{n}]} to identify the
4588 On some OSes, you can modify @value{GDBN}'s default behavior by
4589 locking the OS scheduler to allow only a single thread to run.
4592 @item set scheduler-locking @var{mode}
4593 @cindex scheduler locking mode
4594 @cindex lock scheduler
4595 Set the scheduler locking mode. If it is @code{off}, then there is no
4596 locking and any thread may run at any time. If @code{on}, then only the
4597 current thread may run when the inferior is resumed. The @code{step}
4598 mode optimizes for single-stepping; it prevents other threads
4599 from preempting the current thread while you are stepping, so that
4600 the focus of debugging does not change unexpectedly.
4601 Other threads only rarely (or never) get a chance to run
4602 when you step. They are more likely to run when you @samp{next} over a
4603 function call, and they are completely free to run when you use commands
4604 like @samp{continue}, @samp{until}, or @samp{finish}. However, unless another
4605 thread hits a breakpoint during its timeslice, @value{GDBN} does not change
4606 the current thread away from the thread that you are debugging.
4608 @item show scheduler-locking
4609 Display the current scheduler locking mode.
4613 @subsection Non-Stop Mode
4615 @cindex non-stop mode
4617 @c This section is really only a place-holder, and needs to be expanded
4618 @c with more details.
4620 For some multi-threaded targets, @value{GDBN} supports an optional
4621 mode of operation in which you can examine stopped program threads in
4622 the debugger while other threads continue to execute freely. This
4623 minimizes intrusion when debugging live systems, such as programs
4624 where some threads have real-time constraints or must continue to
4625 respond to external events. This is referred to as @dfn{non-stop} mode.
4627 In non-stop mode, when a thread stops to report a debugging event,
4628 @emph{only} that thread is stopped; @value{GDBN} does not stop other
4629 threads as well, in contrast to the all-stop mode behavior. Additionally,
4630 execution commands such as @code{continue} and @code{step} apply by default
4631 only to the current thread in non-stop mode, rather than all threads as
4632 in all-stop mode. This allows you to control threads explicitly in
4633 ways that are not possible in all-stop mode --- for example, stepping
4634 one thread while allowing others to run freely, stepping
4635 one thread while holding all others stopped, or stepping several threads
4636 independently and simultaneously.
4638 To enter non-stop mode, use this sequence of commands before you run
4639 or attach to your program:
4642 # Enable the async interface.
4645 # If using the CLI, pagination breaks non-stop.
4648 # Finally, turn it on!
4652 You can use these commands to manipulate the non-stop mode setting:
4655 @kindex set non-stop
4656 @item set non-stop on
4657 Enable selection of non-stop mode.
4658 @item set non-stop off
4659 Disable selection of non-stop mode.
4660 @kindex show non-stop
4662 Show the current non-stop enablement setting.
4665 Note these commands only reflect whether non-stop mode is enabled,
4666 not whether the currently-executing program is being run in non-stop mode.
4667 In particular, the @code{set non-stop} preference is only consulted when
4668 @value{GDBN} starts or connects to the target program, and it is generally
4669 not possible to switch modes once debugging has started. Furthermore,
4670 since not all targets support non-stop mode, even when you have enabled
4671 non-stop mode, @value{GDBN} may still fall back to all-stop operation by
4674 In non-stop mode, all execution commands apply only to the current thread
4675 by default. That is, @code{continue} only continues one thread.
4676 To continue all threads, issue @code{continue -a} or @code{c -a}.
4678 You can use @value{GDBN}'s background execution commands
4679 (@pxref{Background Execution}) to run some threads in the background
4680 while you continue to examine or step others from @value{GDBN}.
4681 The MI execution commands (@pxref{GDB/MI Program Execution}) are
4682 always executed asynchronously in non-stop mode.
4684 Suspending execution is done with the @code{interrupt} command when
4685 running in the background, or @kbd{Ctrl-c} during foreground execution.
4686 In all-stop mode, this stops the whole process;
4687 but in non-stop mode the interrupt applies only to the current thread.
4688 To stop the whole program, use @code{interrupt -a}.
4690 Other execution commands do not currently support the @code{-a} option.
4692 In non-stop mode, when a thread stops, @value{GDBN} doesn't automatically make
4693 that thread current, as it does in all-stop mode. This is because the
4694 thread stop notifications are asynchronous with respect to @value{GDBN}'s
4695 command interpreter, and it would be confusing if @value{GDBN} unexpectedly
4696 changed to a different thread just as you entered a command to operate on the
4697 previously current thread.
4699 @node Background Execution
4700 @subsection Background Execution
4702 @cindex foreground execution
4703 @cindex background execution
4704 @cindex asynchronous execution
4705 @cindex execution, foreground, background and asynchronous
4707 @value{GDBN}'s execution commands have two variants: the normal
4708 foreground (synchronous) behavior, and a background
4709 (asynchronous) behavior. In foreground execution, @value{GDBN} waits for
4710 the program to report that some thread has stopped before prompting for
4711 another command. In background execution, @value{GDBN} immediately gives
4712 a command prompt so that you can issue other commands while your program runs.
4714 You need to explicitly enable asynchronous mode before you can use
4715 background execution commands. You can use these commands to
4716 manipulate the asynchronous mode setting:
4719 @kindex set target-async
4720 @item set target-async on
4721 Enable asynchronous mode.
4722 @item set target-async off
4723 Disable asynchronous mode.
4724 @kindex show target-async
4725 @item show target-async
4726 Show the current target-async setting.
4729 If the target doesn't support async mode, @value{GDBN} issues an error
4730 message if you attempt to use the background execution commands.
4732 To specify background execution, add a @code{&} to the command. For example,
4733 the background form of the @code{continue} command is @code{continue&}, or
4734 just @code{c&}. The execution commands that accept background execution
4740 @xref{Starting, , Starting your Program}.
4744 @xref{Attach, , Debugging an Already-running Process}.
4748 @xref{Continuing and Stepping, step}.
4752 @xref{Continuing and Stepping, stepi}.
4756 @xref{Continuing and Stepping, next}.
4760 @xref{Continuing and Stepping, nexti}.
4764 @xref{Continuing and Stepping, continue}.
4768 @xref{Continuing and Stepping, finish}.
4772 @xref{Continuing and Stepping, until}.
4776 Background execution is especially useful in conjunction with non-stop
4777 mode for debugging programs with multiple threads; see @ref{Non-Stop Mode}.
4778 However, you can also use these commands in the normal all-stop mode with
4779 the restriction that you cannot issue another execution command until the
4780 previous one finishes. Examples of commands that are valid in all-stop
4781 mode while the program is running include @code{help} and @code{info break}.
4783 You can interrupt your program while it is running in the background by
4784 using the @code{interrupt} command.
4791 Suspend execution of the running program. In all-stop mode,
4792 @code{interrupt} stops the whole process, but in non-stop mode, it stops
4793 only the current thread. To stop the whole program in non-stop mode,
4794 use @code{interrupt -a}.
4797 @node Thread-Specific Breakpoints
4798 @subsection Thread-Specific Breakpoints
4800 When your program has multiple threads (@pxref{Threads,, Debugging
4801 Programs with Multiple Threads}), you can choose whether to set
4802 breakpoints on all threads, or on a particular thread.
4805 @cindex breakpoints and threads
4806 @cindex thread breakpoints
4807 @kindex break @dots{} thread @var{threadno}
4808 @item break @var{linespec} thread @var{threadno}
4809 @itemx break @var{linespec} thread @var{threadno} if @dots{}
4810 @var{linespec} specifies source lines; there are several ways of
4811 writing them (@pxref{Specify Location}), but the effect is always to
4812 specify some source line.
4814 Use the qualifier @samp{thread @var{threadno}} with a breakpoint command
4815 to specify that you only want @value{GDBN} to stop the program when a
4816 particular thread reaches this breakpoint. @var{threadno} is one of the
4817 numeric thread identifiers assigned by @value{GDBN}, shown in the first
4818 column of the @samp{info threads} display.
4820 If you do not specify @samp{thread @var{threadno}} when you set a
4821 breakpoint, the breakpoint applies to @emph{all} threads of your
4824 You can use the @code{thread} qualifier on conditional breakpoints as
4825 well; in this case, place @samp{thread @var{threadno}} before the
4826 breakpoint condition, like this:
4829 (@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
4834 @node Interrupted System Calls
4835 @subsection Interrupted System Calls
4837 @cindex thread breakpoints and system calls
4838 @cindex system calls and thread breakpoints
4839 @cindex premature return from system calls
4840 There is an unfortunate side effect when using @value{GDBN} to debug
4841 multi-threaded programs. If one thread stops for a
4842 breakpoint, or for some other reason, and another thread is blocked in a
4843 system call, then the system call may return prematurely. This is a
4844 consequence of the interaction between multiple threads and the signals
4845 that @value{GDBN} uses to implement breakpoints and other events that
4848 To handle this problem, your program should check the return value of
4849 each system call and react appropriately. This is good programming
4852 For example, do not write code like this:
4858 The call to @code{sleep} will return early if a different thread stops
4859 at a breakpoint or for some other reason.
4861 Instead, write this:
4866 unslept = sleep (unslept);
4869 A system call is allowed to return early, so the system is still
4870 conforming to its specification. But @value{GDBN} does cause your
4871 multi-threaded program to behave differently than it would without
4874 Also, @value{GDBN} uses internal breakpoints in the thread library to
4875 monitor certain events such as thread creation and thread destruction.
4876 When such an event happens, a system call in another thread may return
4877 prematurely, even though your program does not appear to stop.
4880 @node Reverse Execution
4881 @chapter Running programs backward
4882 @cindex reverse execution
4883 @cindex running programs backward
4885 When you are debugging a program, it is not unusual to realize that
4886 you have gone too far, and some event of interest has already happened.
4887 If the target environment supports it, @value{GDBN} can allow you to
4888 ``rewind'' the program by running it backward.
4890 A target environment that supports reverse execution should be able
4891 to ``undo'' the changes in machine state that have taken place as the
4892 program was executing normally. Variables, registers etc.@: should
4893 revert to their previous values. Obviously this requires a great
4894 deal of sophistication on the part of the target environment; not
4895 all target environments can support reverse execution.
4897 When a program is executed in reverse, the instructions that
4898 have most recently been executed are ``un-executed'', in reverse
4899 order. The program counter runs backward, following the previous
4900 thread of execution in reverse. As each instruction is ``un-executed'',
4901 the values of memory and/or registers that were changed by that
4902 instruction are reverted to their previous states. After executing
4903 a piece of source code in reverse, all side effects of that code
4904 should be ``undone'', and all variables should be returned to their
4905 prior values@footnote{
4906 Note that some side effects are easier to undo than others. For instance,
4907 memory and registers are relatively easy, but device I/O is hard. Some
4908 targets may be able undo things like device I/O, and some may not.
4910 The contract between @value{GDBN} and the reverse executing target
4911 requires only that the target do something reasonable when
4912 @value{GDBN} tells it to execute backwards, and then report the
4913 results back to @value{GDBN}. Whatever the target reports back to
4914 @value{GDBN}, @value{GDBN} will report back to the user. @value{GDBN}
4915 assumes that the memory and registers that the target reports are in a
4916 consistant state, but @value{GDBN} accepts whatever it is given.
4919 If you are debugging in a target environment that supports
4920 reverse execution, @value{GDBN} provides the following commands.
4923 @kindex reverse-continue
4924 @kindex rc @r{(@code{reverse-continue})}
4925 @item reverse-continue @r{[}@var{ignore-count}@r{]}
4926 @itemx rc @r{[}@var{ignore-count}@r{]}
4927 Beginning at the point where your program last stopped, start executing
4928 in reverse. Reverse execution will stop for breakpoints and synchronous
4929 exceptions (signals), just like normal execution. Behavior of
4930 asynchronous signals depends on the target environment.
4932 @kindex reverse-step
4933 @kindex rs @r{(@code{step})}
4934 @item reverse-step @r{[}@var{count}@r{]}
4935 Run the program backward until control reaches the start of a
4936 different source line; then stop it, and return control to @value{GDBN}.
4938 Like the @code{step} command, @code{reverse-step} will only stop
4939 at the beginning of a source line. It ``un-executes'' the previously
4940 executed source line. If the previous source line included calls to
4941 debuggable functions, @code{reverse-step} will step (backward) into
4942 the called function, stopping at the beginning of the @emph{last}
4943 statement in the called function (typically a return statement).
4945 Also, as with the @code{step} command, if non-debuggable functions are
4946 called, @code{reverse-step} will run thru them backward without stopping.
4948 @kindex reverse-stepi
4949 @kindex rsi @r{(@code{reverse-stepi})}
4950 @item reverse-stepi @r{[}@var{count}@r{]}
4951 Reverse-execute one machine instruction. Note that the instruction
4952 to be reverse-executed is @emph{not} the one pointed to by the program
4953 counter, but the instruction executed prior to that one. For instance,
4954 if the last instruction was a jump, @code{reverse-stepi} will take you
4955 back from the destination of the jump to the jump instruction itself.
4957 @kindex reverse-next
4958 @kindex rn @r{(@code{reverse-next})}
4959 @item reverse-next @r{[}@var{count}@r{]}
4960 Run backward to the beginning of the previous line executed in
4961 the current (innermost) stack frame. If the line contains function
4962 calls, they will be ``un-executed'' without stopping. Starting from
4963 the first line of a function, @code{reverse-next} will take you back
4964 to the caller of that function, @emph{before} the function was called,
4965 just as the normal @code{next} command would take you from the last
4966 line of a function back to its return to its caller
4967 @footnote{Unles the code is too heavily optimized.}.
4969 @kindex reverse-nexti
4970 @kindex rni @r{(@code{reverse-nexti})}
4971 @item reverse-nexti @r{[}@var{count}@r{]}
4972 Like @code{nexti}, @code{reverse-nexti} executes a single instruction
4973 in reverse, except that called functions are ``un-executed'' atomically.
4974 That is, if the previously executed instruction was a return from
4975 another instruction, @code{reverse-nexti} will continue to execute
4976 in reverse until the call to that function (from the current stack
4979 @kindex reverse-finish
4980 @item reverse-finish
4981 Just as the @code{finish} command takes you to the point where the
4982 current function returns, @code{reverse-finish} takes you to the point
4983 where it was called. Instead of ending up at the end of the current
4984 function invocation, you end up at the beginning.
4986 @kindex set exec-direction
4987 @item set exec-direction
4988 Set the direction of target execution.
4989 @itemx set exec-direction reverse
4990 @cindex execute forward or backward in time
4991 @value{GDBN} will perform all execution commands in reverse, until the
4992 exec-direction mode is changed to ``forward''. Affected commands include
4993 @code{step, stepi, next, nexti, continue, and finish}. The @code{return}
4994 command cannot be used in reverse mode.
4995 @item set exec-direction forward
4996 @value{GDBN} will perform all execution commands in the normal fashion.
4997 This is the default.
5002 @chapter Examining the Stack
5004 When your program has stopped, the first thing you need to know is where it
5005 stopped and how it got there.
5008 Each time your program performs a function call, information about the call
5010 That information includes the location of the call in your program,
5011 the arguments of the call,
5012 and the local variables of the function being called.
5013 The information is saved in a block of data called a @dfn{stack frame}.
5014 The stack frames are allocated in a region of memory called the @dfn{call
5017 When your program stops, the @value{GDBN} commands for examining the
5018 stack allow you to see all of this information.
5020 @cindex selected frame
5021 One of the stack frames is @dfn{selected} by @value{GDBN} and many
5022 @value{GDBN} commands refer implicitly to the selected frame. In
5023 particular, whenever you ask @value{GDBN} for the value of a variable in
5024 your program, the value is found in the selected frame. There are
5025 special @value{GDBN} commands to select whichever frame you are
5026 interested in. @xref{Selection, ,Selecting a Frame}.
5028 When your program stops, @value{GDBN} automatically selects the
5029 currently executing frame and describes it briefly, similar to the
5030 @code{frame} command (@pxref{Frame Info, ,Information about a Frame}).
5033 * Frames:: Stack frames
5034 * Backtrace:: Backtraces
5035 * Selection:: Selecting a frame
5036 * Frame Info:: Information on a frame
5041 @section Stack Frames
5043 @cindex frame, definition
5045 The call stack is divided up into contiguous pieces called @dfn{stack
5046 frames}, or @dfn{frames} for short; each frame is the data associated
5047 with one call to one function. The frame contains the arguments given
5048 to the function, the function's local variables, and the address at
5049 which the function is executing.
5051 @cindex initial frame
5052 @cindex outermost frame
5053 @cindex innermost frame
5054 When your program is started, the stack has only one frame, that of the
5055 function @code{main}. This is called the @dfn{initial} frame or the
5056 @dfn{outermost} frame. Each time a function is called, a new frame is
5057 made. Each time a function returns, the frame for that function invocation
5058 is eliminated. If a function is recursive, there can be many frames for
5059 the same function. The frame for the function in which execution is
5060 actually occurring is called the @dfn{innermost} frame. This is the most
5061 recently created of all the stack frames that still exist.
5063 @cindex frame pointer
5064 Inside your program, stack frames are identified by their addresses. A
5065 stack frame consists of many bytes, each of which has its own address; each
5066 kind of computer has a convention for choosing one byte whose
5067 address serves as the address of the frame. Usually this address is kept
5068 in a register called the @dfn{frame pointer register}
5069 (@pxref{Registers, $fp}) while execution is going on in that frame.
5071 @cindex frame number
5072 @value{GDBN} assigns numbers to all existing stack frames, starting with
5073 zero for the innermost frame, one for the frame that called it,
5074 and so on upward. These numbers do not really exist in your program;
5075 they are assigned by @value{GDBN} to give you a way of designating stack
5076 frames in @value{GDBN} commands.
5078 @c The -fomit-frame-pointer below perennially causes hbox overflow
5079 @c underflow problems.
5080 @cindex frameless execution
5081 Some compilers provide a way to compile functions so that they operate
5082 without stack frames. (For example, the @value{NGCC} option
5084 @samp{-fomit-frame-pointer}
5086 generates functions without a frame.)
5087 This is occasionally done with heavily used library functions to save
5088 the frame setup time. @value{GDBN} has limited facilities for dealing
5089 with these function invocations. If the innermost function invocation
5090 has no stack frame, @value{GDBN} nevertheless regards it as though
5091 it had a separate frame, which is numbered zero as usual, allowing
5092 correct tracing of the function call chain. However, @value{GDBN} has
5093 no provision for frameless functions elsewhere in the stack.
5096 @kindex frame@r{, command}
5097 @cindex current stack frame
5098 @item frame @var{args}
5099 The @code{frame} command allows you to move from one stack frame to another,
5100 and to print the stack frame you select. @var{args} may be either the
5101 address of the frame or the stack frame number. Without an argument,
5102 @code{frame} prints the current stack frame.
5104 @kindex select-frame
5105 @cindex selecting frame silently
5107 The @code{select-frame} command allows you to move from one stack frame
5108 to another without printing the frame. This is the silent version of
5116 @cindex call stack traces
5117 A backtrace is a summary of how your program got where it is. It shows one
5118 line per frame, for many frames, starting with the currently executing
5119 frame (frame zero), followed by its caller (frame one), and on up the
5124 @kindex bt @r{(@code{backtrace})}
5127 Print a backtrace of the entire stack: one line per frame for all
5128 frames in the stack.
5130 You can stop the backtrace at any time by typing the system interrupt
5131 character, normally @kbd{Ctrl-c}.
5133 @item backtrace @var{n}
5135 Similar, but print only the innermost @var{n} frames.
5137 @item backtrace -@var{n}
5139 Similar, but print only the outermost @var{n} frames.
5141 @item backtrace full
5143 @itemx bt full @var{n}
5144 @itemx bt full -@var{n}
5145 Print the values of the local variables also. @var{n} specifies the
5146 number of frames to print, as described above.
5151 The names @code{where} and @code{info stack} (abbreviated @code{info s})
5152 are additional aliases for @code{backtrace}.
5154 @cindex multiple threads, backtrace
5155 In a multi-threaded program, @value{GDBN} by default shows the
5156 backtrace only for the current thread. To display the backtrace for
5157 several or all of the threads, use the command @code{thread apply}
5158 (@pxref{Threads, thread apply}). For example, if you type @kbd{thread
5159 apply all backtrace}, @value{GDBN} will display the backtrace for all
5160 the threads; this is handy when you debug a core dump of a
5161 multi-threaded program.
5163 Each line in the backtrace shows the frame number and the function name.
5164 The program counter value is also shown---unless you use @code{set
5165 print address off}. The backtrace also shows the source file name and
5166 line number, as well as the arguments to the function. The program
5167 counter value is omitted if it is at the beginning of the code for that
5170 Here is an example of a backtrace. It was made with the command
5171 @samp{bt 3}, so it shows the innermost three frames.
5175 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
5177 #1 0x6e38 in expand_macro (sym=0x2b600) at macro.c:242
5178 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
5180 (More stack frames follow...)
5185 The display for frame zero does not begin with a program counter
5186 value, indicating that your program has stopped at the beginning of the
5187 code for line @code{993} of @code{builtin.c}.
5189 @cindex value optimized out, in backtrace
5190 @cindex function call arguments, optimized out
5191 If your program was compiled with optimizations, some compilers will
5192 optimize away arguments passed to functions if those arguments are
5193 never used after the call. Such optimizations generate code that
5194 passes arguments through registers, but doesn't store those arguments
5195 in the stack frame. @value{GDBN} has no way of displaying such
5196 arguments in stack frames other than the innermost one. Here's what
5197 such a backtrace might look like:
5201 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
5203 #1 0x6e38 in expand_macro (sym=<value optimized out>) at macro.c:242
5204 #2 0x6840 in expand_token (obs=0x0, t=<value optimized out>, td=0xf7fffb08)
5206 (More stack frames follow...)
5211 The values of arguments that were not saved in their stack frames are
5212 shown as @samp{<value optimized out>}.
5214 If you need to display the values of such optimized-out arguments,
5215 either deduce that from other variables whose values depend on the one
5216 you are interested in, or recompile without optimizations.
5218 @cindex backtrace beyond @code{main} function
5219 @cindex program entry point
5220 @cindex startup code, and backtrace
5221 Most programs have a standard user entry point---a place where system
5222 libraries and startup code transition into user code. For C this is
5223 @code{main}@footnote{
5224 Note that embedded programs (the so-called ``free-standing''
5225 environment) are not required to have a @code{main} function as the
5226 entry point. They could even have multiple entry points.}.
5227 When @value{GDBN} finds the entry function in a backtrace
5228 it will terminate the backtrace, to avoid tracing into highly
5229 system-specific (and generally uninteresting) code.
5231 If you need to examine the startup code, or limit the number of levels
5232 in a backtrace, you can change this behavior:
5235 @item set backtrace past-main
5236 @itemx set backtrace past-main on
5237 @kindex set backtrace
5238 Backtraces will continue past the user entry point.
5240 @item set backtrace past-main off
5241 Backtraces will stop when they encounter the user entry point. This is the
5244 @item show backtrace past-main
5245 @kindex show backtrace
5246 Display the current user entry point backtrace policy.
5248 @item set backtrace past-entry
5249 @itemx set backtrace past-entry on
5250 Backtraces will continue past the internal entry point of an application.
5251 This entry point is encoded by the linker when the application is built,
5252 and is likely before the user entry point @code{main} (or equivalent) is called.
5254 @item set backtrace past-entry off
5255 Backtraces will stop when they encounter the internal entry point of an
5256 application. This is the default.
5258 @item show backtrace past-entry
5259 Display the current internal entry point backtrace policy.
5261 @item set backtrace limit @var{n}
5262 @itemx set backtrace limit 0
5263 @cindex backtrace limit
5264 Limit the backtrace to @var{n} levels. A value of zero means
5267 @item show backtrace limit
5268 Display the current limit on backtrace levels.
5272 @section Selecting a Frame
5274 Most commands for examining the stack and other data in your program work on
5275 whichever stack frame is selected at the moment. Here are the commands for
5276 selecting a stack frame; all of them finish by printing a brief description
5277 of the stack frame just selected.
5280 @kindex frame@r{, selecting}
5281 @kindex f @r{(@code{frame})}
5284 Select frame number @var{n}. Recall that frame zero is the innermost
5285 (currently executing) frame, frame one is the frame that called the
5286 innermost one, and so on. The highest-numbered frame is the one for
5289 @item frame @var{addr}
5291 Select the frame at address @var{addr}. This is useful mainly if the
5292 chaining of stack frames has been damaged by a bug, making it
5293 impossible for @value{GDBN} to assign numbers properly to all frames. In
5294 addition, this can be useful when your program has multiple stacks and
5295 switches between them.
5297 On the SPARC architecture, @code{frame} needs two addresses to
5298 select an arbitrary frame: a frame pointer and a stack pointer.
5300 On the MIPS and Alpha architecture, it needs two addresses: a stack
5301 pointer and a program counter.
5303 On the 29k architecture, it needs three addresses: a register stack
5304 pointer, a program counter, and a memory stack pointer.
5308 Move @var{n} frames up the stack. For positive numbers @var{n}, this
5309 advances toward the outermost frame, to higher frame numbers, to frames
5310 that have existed longer. @var{n} defaults to one.
5313 @kindex do @r{(@code{down})}
5315 Move @var{n} frames down the stack. For positive numbers @var{n}, this
5316 advances toward the innermost frame, to lower frame numbers, to frames
5317 that were created more recently. @var{n} defaults to one. You may
5318 abbreviate @code{down} as @code{do}.
5321 All of these commands end by printing two lines of output describing the
5322 frame. The first line shows the frame number, the function name, the
5323 arguments, and the source file and line number of execution in that
5324 frame. The second line shows the text of that source line.
5332 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
5334 10 read_input_file (argv[i]);
5338 After such a printout, the @code{list} command with no arguments
5339 prints ten lines centered on the point of execution in the frame.
5340 You can also edit the program at the point of execution with your favorite
5341 editing program by typing @code{edit}.
5342 @xref{List, ,Printing Source Lines},
5346 @kindex down-silently
5348 @item up-silently @var{n}
5349 @itemx down-silently @var{n}
5350 These two commands are variants of @code{up} and @code{down},
5351 respectively; they differ in that they do their work silently, without
5352 causing display of the new frame. They are intended primarily for use
5353 in @value{GDBN} command scripts, where the output might be unnecessary and
5358 @section Information About a Frame
5360 There are several other commands to print information about the selected
5366 When used without any argument, this command does not change which
5367 frame is selected, but prints a brief description of the currently
5368 selected stack frame. It can be abbreviated @code{f}. With an
5369 argument, this command is used to select a stack frame.
5370 @xref{Selection, ,Selecting a Frame}.
5373 @kindex info f @r{(@code{info frame})}
5376 This command prints a verbose description of the selected stack frame,
5381 the address of the frame
5383 the address of the next frame down (called by this frame)
5385 the address of the next frame up (caller of this frame)
5387 the language in which the source code corresponding to this frame is written
5389 the address of the frame's arguments
5391 the address of the frame's local variables
5393 the program counter saved in it (the address of execution in the caller frame)
5395 which registers were saved in the frame
5398 @noindent The verbose description is useful when
5399 something has gone wrong that has made the stack format fail to fit
5400 the usual conventions.
5402 @item info frame @var{addr}
5403 @itemx info f @var{addr}
5404 Print a verbose description of the frame at address @var{addr}, without
5405 selecting that frame. The selected frame remains unchanged by this
5406 command. This requires the same kind of address (more than one for some
5407 architectures) that you specify in the @code{frame} command.
5408 @xref{Selection, ,Selecting a Frame}.
5412 Print the arguments of the selected frame, each on a separate line.
5416 Print the local variables of the selected frame, each on a separate
5417 line. These are all variables (declared either static or automatic)
5418 accessible at the point of execution of the selected frame.
5421 @cindex catch exceptions, list active handlers
5422 @cindex exception handlers, how to list
5424 Print a list of all the exception handlers that are active in the
5425 current stack frame at the current point of execution. To see other
5426 exception handlers, visit the associated frame (using the @code{up},
5427 @code{down}, or @code{frame} commands); then type @code{info catch}.
5428 @xref{Set Catchpoints, , Setting Catchpoints}.
5434 @chapter Examining Source Files
5436 @value{GDBN} can print parts of your program's source, since the debugging
5437 information recorded in the program tells @value{GDBN} what source files were
5438 used to build it. When your program stops, @value{GDBN} spontaneously prints
5439 the line where it stopped. Likewise, when you select a stack frame
5440 (@pxref{Selection, ,Selecting a Frame}), @value{GDBN} prints the line where
5441 execution in that frame has stopped. You can print other portions of
5442 source files by explicit command.
5444 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
5445 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
5446 @value{GDBN} under @sc{gnu} Emacs}.
5449 * List:: Printing source lines
5450 * Specify Location:: How to specify code locations
5451 * Edit:: Editing source files
5452 * Search:: Searching source files
5453 * Source Path:: Specifying source directories
5454 * Machine Code:: Source and machine code
5458 @section Printing Source Lines
5461 @kindex l @r{(@code{list})}
5462 To print lines from a source file, use the @code{list} command
5463 (abbreviated @code{l}). By default, ten lines are printed.
5464 There are several ways to specify what part of the file you want to
5465 print; see @ref{Specify Location}, for the full list.
5467 Here are the forms of the @code{list} command most commonly used:
5470 @item list @var{linenum}
5471 Print lines centered around line number @var{linenum} in the
5472 current source file.
5474 @item list @var{function}
5475 Print lines centered around the beginning of function
5479 Print more lines. If the last lines printed were printed with a
5480 @code{list} command, this prints lines following the last lines
5481 printed; however, if the last line printed was a solitary line printed
5482 as part of displaying a stack frame (@pxref{Stack, ,Examining the
5483 Stack}), this prints lines centered around that line.
5486 Print lines just before the lines last printed.
5489 @cindex @code{list}, how many lines to display
5490 By default, @value{GDBN} prints ten source lines with any of these forms of
5491 the @code{list} command. You can change this using @code{set listsize}:
5494 @kindex set listsize
5495 @item set listsize @var{count}
5496 Make the @code{list} command display @var{count} source lines (unless
5497 the @code{list} argument explicitly specifies some other number).
5499 @kindex show listsize
5501 Display the number of lines that @code{list} prints.
5504 Repeating a @code{list} command with @key{RET} discards the argument,
5505 so it is equivalent to typing just @code{list}. This is more useful
5506 than listing the same lines again. An exception is made for an
5507 argument of @samp{-}; that argument is preserved in repetition so that
5508 each repetition moves up in the source file.
5510 In general, the @code{list} command expects you to supply zero, one or two
5511 @dfn{linespecs}. Linespecs specify source lines; there are several ways
5512 of writing them (@pxref{Specify Location}), but the effect is always
5513 to specify some source line.
5515 Here is a complete description of the possible arguments for @code{list}:
5518 @item list @var{linespec}
5519 Print lines centered around the line specified by @var{linespec}.
5521 @item list @var{first},@var{last}
5522 Print lines from @var{first} to @var{last}. Both arguments are
5523 linespecs. When a @code{list} command has two linespecs, and the
5524 source file of the second linespec is omitted, this refers to
5525 the same source file as the first linespec.
5527 @item list ,@var{last}
5528 Print lines ending with @var{last}.
5530 @item list @var{first},
5531 Print lines starting with @var{first}.
5534 Print lines just after the lines last printed.
5537 Print lines just before the lines last printed.
5540 As described in the preceding table.
5543 @node Specify Location
5544 @section Specifying a Location
5545 @cindex specifying location
5548 Several @value{GDBN} commands accept arguments that specify a location
5549 of your program's code. Since @value{GDBN} is a source-level
5550 debugger, a location usually specifies some line in the source code;
5551 for that reason, locations are also known as @dfn{linespecs}.
5553 Here are all the different ways of specifying a code location that
5554 @value{GDBN} understands:
5558 Specifies the line number @var{linenum} of the current source file.
5561 @itemx +@var{offset}
5562 Specifies the line @var{offset} lines before or after the @dfn{current
5563 line}. For the @code{list} command, the current line is the last one
5564 printed; for the breakpoint commands, this is the line at which
5565 execution stopped in the currently selected @dfn{stack frame}
5566 (@pxref{Frames, ,Frames}, for a description of stack frames.) When
5567 used as the second of the two linespecs in a @code{list} command,
5568 this specifies the line @var{offset} lines up or down from the first
5571 @item @var{filename}:@var{linenum}
5572 Specifies the line @var{linenum} in the source file @var{filename}.
5574 @item @var{function}
5575 Specifies the line that begins the body of the function @var{function}.
5576 For example, in C, this is the line with the open brace.
5578 @item @var{filename}:@var{function}
5579 Specifies the line that begins the body of the function @var{function}
5580 in the file @var{filename}. You only need the file name with a
5581 function name to avoid ambiguity when there are identically named
5582 functions in different source files.
5584 @item *@var{address}
5585 Specifies the program address @var{address}. For line-oriented
5586 commands, such as @code{list} and @code{edit}, this specifies a source
5587 line that contains @var{address}. For @code{break} and other
5588 breakpoint oriented commands, this can be used to set breakpoints in
5589 parts of your program which do not have debugging information or
5592 Here @var{address} may be any expression valid in the current working
5593 language (@pxref{Languages, working language}) that specifies a code
5594 address. In addition, as a convenience, @value{GDBN} extends the
5595 semantics of expressions used in locations to cover the situations
5596 that frequently happen during debugging. Here are the various forms
5600 @item @var{expression}
5601 Any expression valid in the current working language.
5603 @item @var{funcaddr}
5604 An address of a function or procedure derived from its name. In C,
5605 C@t{++}, Java, Objective-C, Fortran, minimal, and assembly, this is
5606 simply the function's name @var{function} (and actually a special case
5607 of a valid expression). In Pascal and Modula-2, this is
5608 @code{&@var{function}}. In Ada, this is @code{@var{function}'Address}
5609 (although the Pascal form also works).
5611 This form specifies the address of the function's first instruction,
5612 before the stack frame and arguments have been set up.
5614 @item '@var{filename}'::@var{funcaddr}
5615 Like @var{funcaddr} above, but also specifies the name of the source
5616 file explicitly. This is useful if the name of the function does not
5617 specify the function unambiguously, e.g., if there are several
5618 functions with identical names in different source files.
5625 @section Editing Source Files
5626 @cindex editing source files
5629 @kindex e @r{(@code{edit})}
5630 To edit the lines in a source file, use the @code{edit} command.
5631 The editing program of your choice
5632 is invoked with the current line set to
5633 the active line in the program.
5634 Alternatively, there are several ways to specify what part of the file you
5635 want to print if you want to see other parts of the program:
5638 @item edit @var{location}
5639 Edit the source file specified by @code{location}. Editing starts at
5640 that @var{location}, e.g., at the specified source line of the
5641 specified file. @xref{Specify Location}, for all the possible forms
5642 of the @var{location} argument; here are the forms of the @code{edit}
5643 command most commonly used:
5646 @item edit @var{number}
5647 Edit the current source file with @var{number} as the active line number.
5649 @item edit @var{function}
5650 Edit the file containing @var{function} at the beginning of its definition.
5655 @subsection Choosing your Editor
5656 You can customize @value{GDBN} to use any editor you want
5658 The only restriction is that your editor (say @code{ex}), recognizes the
5659 following command-line syntax:
5661 ex +@var{number} file
5663 The optional numeric value +@var{number} specifies the number of the line in
5664 the file where to start editing.}.
5665 By default, it is @file{@value{EDITOR}}, but you can change this
5666 by setting the environment variable @code{EDITOR} before using
5667 @value{GDBN}. For example, to configure @value{GDBN} to use the
5668 @code{vi} editor, you could use these commands with the @code{sh} shell:
5674 or in the @code{csh} shell,
5676 setenv EDITOR /usr/bin/vi
5681 @section Searching Source Files
5682 @cindex searching source files
5684 There are two commands for searching through the current source file for a
5689 @kindex forward-search
5690 @item forward-search @var{regexp}
5691 @itemx search @var{regexp}
5692 The command @samp{forward-search @var{regexp}} checks each line,
5693 starting with the one following the last line listed, for a match for
5694 @var{regexp}. It lists the line that is found. You can use the
5695 synonym @samp{search @var{regexp}} or abbreviate the command name as
5698 @kindex reverse-search
5699 @item reverse-search @var{regexp}
5700 The command @samp{reverse-search @var{regexp}} checks each line, starting
5701 with the one before the last line listed and going backward, for a match
5702 for @var{regexp}. It lists the line that is found. You can abbreviate
5703 this command as @code{rev}.
5707 @section Specifying Source Directories
5710 @cindex directories for source files
5711 Executable programs sometimes do not record the directories of the source
5712 files from which they were compiled, just the names. Even when they do,
5713 the directories could be moved between the compilation and your debugging
5714 session. @value{GDBN} has a list of directories to search for source files;
5715 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
5716 it tries all the directories in the list, in the order they are present
5717 in the list, until it finds a file with the desired name.
5719 For example, suppose an executable references the file
5720 @file{/usr/src/foo-1.0/lib/foo.c}, and our source path is
5721 @file{/mnt/cross}. The file is first looked up literally; if this
5722 fails, @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c} is tried; if this
5723 fails, @file{/mnt/cross/foo.c} is opened; if this fails, an error
5724 message is printed. @value{GDBN} does not look up the parts of the
5725 source file name, such as @file{/mnt/cross/src/foo-1.0/lib/foo.c}.
5726 Likewise, the subdirectories of the source path are not searched: if
5727 the source path is @file{/mnt/cross}, and the binary refers to
5728 @file{foo.c}, @value{GDBN} would not find it under
5729 @file{/mnt/cross/usr/src/foo-1.0/lib}.
5731 Plain file names, relative file names with leading directories, file
5732 names containing dots, etc.@: are all treated as described above; for
5733 instance, if the source path is @file{/mnt/cross}, and the source file
5734 is recorded as @file{../lib/foo.c}, @value{GDBN} would first try
5735 @file{../lib/foo.c}, then @file{/mnt/cross/../lib/foo.c}, and after
5736 that---@file{/mnt/cross/foo.c}.
5738 Note that the executable search path is @emph{not} used to locate the
5741 Whenever you reset or rearrange the source path, @value{GDBN} clears out
5742 any information it has cached about where source files are found and where
5743 each line is in the file.
5747 When you start @value{GDBN}, its source path includes only @samp{cdir}
5748 and @samp{cwd}, in that order.
5749 To add other directories, use the @code{directory} command.
5751 The search path is used to find both program source files and @value{GDBN}
5752 script files (read using the @samp{-command} option and @samp{source} command).
5754 In addition to the source path, @value{GDBN} provides a set of commands
5755 that manage a list of source path substitution rules. A @dfn{substitution
5756 rule} specifies how to rewrite source directories stored in the program's
5757 debug information in case the sources were moved to a different
5758 directory between compilation and debugging. A rule is made of
5759 two strings, the first specifying what needs to be rewritten in
5760 the path, and the second specifying how it should be rewritten.
5761 In @ref{set substitute-path}, we name these two parts @var{from} and
5762 @var{to} respectively. @value{GDBN} does a simple string replacement
5763 of @var{from} with @var{to} at the start of the directory part of the
5764 source file name, and uses that result instead of the original file
5765 name to look up the sources.
5767 Using the previous example, suppose the @file{foo-1.0} tree has been
5768 moved from @file{/usr/src} to @file{/mnt/cross}, then you can tell
5769 @value{GDBN} to replace @file{/usr/src} in all source path names with
5770 @file{/mnt/cross}. The first lookup will then be
5771 @file{/mnt/cross/foo-1.0/lib/foo.c} in place of the original location
5772 of @file{/usr/src/foo-1.0/lib/foo.c}. To define a source path
5773 substitution rule, use the @code{set substitute-path} command
5774 (@pxref{set substitute-path}).
5776 To avoid unexpected substitution results, a rule is applied only if the
5777 @var{from} part of the directory name ends at a directory separator.
5778 For instance, a rule substituting @file{/usr/source} into
5779 @file{/mnt/cross} will be applied to @file{/usr/source/foo-1.0} but
5780 not to @file{/usr/sourceware/foo-2.0}. And because the substitution
5781 is applied only at the beginning of the directory name, this rule will
5782 not be applied to @file{/root/usr/source/baz.c} either.
5784 In many cases, you can achieve the same result using the @code{directory}
5785 command. However, @code{set substitute-path} can be more efficient in
5786 the case where the sources are organized in a complex tree with multiple
5787 subdirectories. With the @code{directory} command, you need to add each
5788 subdirectory of your project. If you moved the entire tree while
5789 preserving its internal organization, then @code{set substitute-path}
5790 allows you to direct the debugger to all the sources with one single
5793 @code{set substitute-path} is also more than just a shortcut command.
5794 The source path is only used if the file at the original location no
5795 longer exists. On the other hand, @code{set substitute-path} modifies
5796 the debugger behavior to look at the rewritten location instead. So, if
5797 for any reason a source file that is not relevant to your executable is
5798 located at the original location, a substitution rule is the only
5799 method available to point @value{GDBN} at the new location.
5802 @item directory @var{dirname} @dots{}
5803 @item dir @var{dirname} @dots{}
5804 Add directory @var{dirname} to the front of the source path. Several
5805 directory names may be given to this command, separated by @samp{:}
5806 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
5807 part of absolute file names) or
5808 whitespace. You may specify a directory that is already in the source
5809 path; this moves it forward, so @value{GDBN} searches it sooner.
5813 @vindex $cdir@r{, convenience variable}
5814 @vindex $cwd@r{, convenience variable}
5815 @cindex compilation directory
5816 @cindex current directory
5817 @cindex working directory
5818 @cindex directory, current
5819 @cindex directory, compilation
5820 You can use the string @samp{$cdir} to refer to the compilation
5821 directory (if one is recorded), and @samp{$cwd} to refer to the current
5822 working directory. @samp{$cwd} is not the same as @samp{.}---the former
5823 tracks the current working directory as it changes during your @value{GDBN}
5824 session, while the latter is immediately expanded to the current
5825 directory at the time you add an entry to the source path.
5828 Reset the source path to its default value (@samp{$cdir:$cwd} on Unix systems). This requires confirmation.
5830 @c RET-repeat for @code{directory} is explicitly disabled, but since
5831 @c repeating it would be a no-op we do not say that. (thanks to RMS)
5833 @item show directories
5834 @kindex show directories
5835 Print the source path: show which directories it contains.
5837 @anchor{set substitute-path}
5838 @item set substitute-path @var{from} @var{to}
5839 @kindex set substitute-path
5840 Define a source path substitution rule, and add it at the end of the
5841 current list of existing substitution rules. If a rule with the same
5842 @var{from} was already defined, then the old rule is also deleted.
5844 For example, if the file @file{/foo/bar/baz.c} was moved to
5845 @file{/mnt/cross/baz.c}, then the command
5848 (@value{GDBP}) set substitute-path /usr/src /mnt/cross
5852 will tell @value{GDBN} to replace @samp{/usr/src} with
5853 @samp{/mnt/cross}, which will allow @value{GDBN} to find the file
5854 @file{baz.c} even though it was moved.
5856 In the case when more than one substitution rule have been defined,
5857 the rules are evaluated one by one in the order where they have been
5858 defined. The first one matching, if any, is selected to perform
5861 For instance, if we had entered the following commands:
5864 (@value{GDBP}) set substitute-path /usr/src/include /mnt/include
5865 (@value{GDBP}) set substitute-path /usr/src /mnt/src
5869 @value{GDBN} would then rewrite @file{/usr/src/include/defs.h} into
5870 @file{/mnt/include/defs.h} by using the first rule. However, it would
5871 use the second rule to rewrite @file{/usr/src/lib/foo.c} into
5872 @file{/mnt/src/lib/foo.c}.
5875 @item unset substitute-path [path]
5876 @kindex unset substitute-path
5877 If a path is specified, search the current list of substitution rules
5878 for a rule that would rewrite that path. Delete that rule if found.
5879 A warning is emitted by the debugger if no rule could be found.
5881 If no path is specified, then all substitution rules are deleted.
5883 @item show substitute-path [path]
5884 @kindex show substitute-path
5885 If a path is specified, then print the source path substitution rule
5886 which would rewrite that path, if any.
5888 If no path is specified, then print all existing source path substitution
5893 If your source path is cluttered with directories that are no longer of
5894 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
5895 versions of source. You can correct the situation as follows:
5899 Use @code{directory} with no argument to reset the source path to its default value.
5902 Use @code{directory} with suitable arguments to reinstall the
5903 directories you want in the source path. You can add all the
5904 directories in one command.
5908 @section Source and Machine Code
5909 @cindex source line and its code address
5911 You can use the command @code{info line} to map source lines to program
5912 addresses (and vice versa), and the command @code{disassemble} to display
5913 a range of addresses as machine instructions. You can use the command
5914 @code{set disassemble-next-line} to set whether to disassemble next
5915 source line when execution stops. When run under @sc{gnu} Emacs
5916 mode, the @code{info line} command causes the arrow to point to the
5917 line specified. Also, @code{info line} prints addresses in symbolic form as
5922 @item info line @var{linespec}
5923 Print the starting and ending addresses of the compiled code for
5924 source line @var{linespec}. You can specify source lines in any of
5925 the ways documented in @ref{Specify Location}.
5928 For example, we can use @code{info line} to discover the location of
5929 the object code for the first line of function
5930 @code{m4_changequote}:
5932 @c FIXME: I think this example should also show the addresses in
5933 @c symbolic form, as they usually would be displayed.
5935 (@value{GDBP}) info line m4_changequote
5936 Line 895 of "builtin.c" starts at pc 0x634c and ends at 0x6350.
5940 @cindex code address and its source line
5941 We can also inquire (using @code{*@var{addr}} as the form for
5942 @var{linespec}) what source line covers a particular address:
5944 (@value{GDBP}) info line *0x63ff
5945 Line 926 of "builtin.c" starts at pc 0x63e4 and ends at 0x6404.
5948 @cindex @code{$_} and @code{info line}
5949 @cindex @code{x} command, default address
5950 @kindex x@r{(examine), and} info line
5951 After @code{info line}, the default address for the @code{x} command
5952 is changed to the starting address of the line, so that @samp{x/i} is
5953 sufficient to begin examining the machine code (@pxref{Memory,
5954 ,Examining Memory}). Also, this address is saved as the value of the
5955 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
5960 @cindex assembly instructions
5961 @cindex instructions, assembly
5962 @cindex machine instructions
5963 @cindex listing machine instructions
5965 @itemx disassemble /m
5966 This specialized command dumps a range of memory as machine
5967 instructions. It can also print mixed source+disassembly by specifying
5968 the @code{/m} modifier.
5969 The default memory range is the function surrounding the
5970 program counter of the selected frame. A single argument to this
5971 command is a program counter value; @value{GDBN} dumps the function
5972 surrounding this value. Two arguments specify a range of addresses
5973 (first inclusive, second exclusive) to dump.
5976 The following example shows the disassembly of a range of addresses of
5977 HP PA-RISC 2.0 code:
5980 (@value{GDBP}) disas 0x32c4 0x32e4
5981 Dump of assembler code from 0x32c4 to 0x32e4:
5982 0x32c4 <main+204>: addil 0,dp
5983 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
5984 0x32cc <main+212>: ldil 0x3000,r31
5985 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
5986 0x32d4 <main+220>: ldo 0(r31),rp
5987 0x32d8 <main+224>: addil -0x800,dp
5988 0x32dc <main+228>: ldo 0x588(r1),r26
5989 0x32e0 <main+232>: ldil 0x3000,r31
5990 End of assembler dump.
5993 Here is an example showing mixed source+assembly for Intel x86:
5996 (@value{GDBP}) disas /m main
5997 Dump of assembler code for function main:
5999 0x08048330 <main+0>: push %ebp
6000 0x08048331 <main+1>: mov %esp,%ebp
6001 0x08048333 <main+3>: sub $0x8,%esp
6002 0x08048336 <main+6>: and $0xfffffff0,%esp
6003 0x08048339 <main+9>: sub $0x10,%esp
6005 6 printf ("Hello.\n");
6006 0x0804833c <main+12>: movl $0x8048440,(%esp)
6007 0x08048343 <main+19>: call 0x8048284 <puts@@plt>
6011 0x08048348 <main+24>: mov $0x0,%eax
6012 0x0804834d <main+29>: leave
6013 0x0804834e <main+30>: ret
6015 End of assembler dump.
6018 Some architectures have more than one commonly-used set of instruction
6019 mnemonics or other syntax.
6021 For programs that were dynamically linked and use shared libraries,
6022 instructions that call functions or branch to locations in the shared
6023 libraries might show a seemingly bogus location---it's actually a
6024 location of the relocation table. On some architectures, @value{GDBN}
6025 might be able to resolve these to actual function names.
6028 @kindex set disassembly-flavor
6029 @cindex Intel disassembly flavor
6030 @cindex AT&T disassembly flavor
6031 @item set disassembly-flavor @var{instruction-set}
6032 Select the instruction set to use when disassembling the
6033 program via the @code{disassemble} or @code{x/i} commands.
6035 Currently this command is only defined for the Intel x86 family. You
6036 can set @var{instruction-set} to either @code{intel} or @code{att}.
6037 The default is @code{att}, the AT&T flavor used by default by Unix
6038 assemblers for x86-based targets.
6040 @kindex show disassembly-flavor
6041 @item show disassembly-flavor
6042 Show the current setting of the disassembly flavor.
6046 @kindex set disassemble-next-line
6047 @kindex show disassemble-next-line
6048 @item set disassemble-next-line
6049 @itemx show disassemble-next-line
6050 Control whether or not @value{GDBN} will disassemble next source line
6051 when execution stops. If ON, GDB will display disassembly of the next
6052 source line when execution of the program being debugged stops.
6053 If AUTO (which is the default), or there's no line info to determine
6054 the source line of the next instruction, display disassembly of next
6055 instruction instead.
6060 @chapter Examining Data
6062 @cindex printing data
6063 @cindex examining data
6066 @c "inspect" is not quite a synonym if you are using Epoch, which we do not
6067 @c document because it is nonstandard... Under Epoch it displays in a
6068 @c different window or something like that.
6069 The usual way to examine data in your program is with the @code{print}
6070 command (abbreviated @code{p}), or its synonym @code{inspect}. It
6071 evaluates and prints the value of an expression of the language your
6072 program is written in (@pxref{Languages, ,Using @value{GDBN} with
6073 Different Languages}).
6076 @item print @var{expr}
6077 @itemx print /@var{f} @var{expr}
6078 @var{expr} is an expression (in the source language). By default the
6079 value of @var{expr} is printed in a format appropriate to its data type;
6080 you can choose a different format by specifying @samp{/@var{f}}, where
6081 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
6085 @itemx print /@var{f}
6086 @cindex reprint the last value
6087 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
6088 @dfn{value history}; @pxref{Value History, ,Value History}). This allows you to
6089 conveniently inspect the same value in an alternative format.
6092 A more low-level way of examining data is with the @code{x} command.
6093 It examines data in memory at a specified address and prints it in a
6094 specified format. @xref{Memory, ,Examining Memory}.
6096 If you are interested in information about types, or about how the
6097 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
6098 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
6102 * Expressions:: Expressions
6103 * Ambiguous Expressions:: Ambiguous Expressions
6104 * Variables:: Program variables
6105 * Arrays:: Artificial arrays
6106 * Output Formats:: Output formats
6107 * Memory:: Examining memory
6108 * Auto Display:: Automatic display
6109 * Print Settings:: Print settings
6110 * Value History:: Value history
6111 * Convenience Vars:: Convenience variables
6112 * Registers:: Registers
6113 * Floating Point Hardware:: Floating point hardware
6114 * Vector Unit:: Vector Unit
6115 * OS Information:: Auxiliary data provided by operating system
6116 * Memory Region Attributes:: Memory region attributes
6117 * Dump/Restore Files:: Copy between memory and a file
6118 * Core File Generation:: Cause a program dump its core
6119 * Character Sets:: Debugging programs that use a different
6120 character set than GDB does
6121 * Caching Remote Data:: Data caching for remote targets
6122 * Searching Memory:: Searching memory for a sequence of bytes
6126 @section Expressions
6129 @code{print} and many other @value{GDBN} commands accept an expression and
6130 compute its value. Any kind of constant, variable or operator defined
6131 by the programming language you are using is valid in an expression in
6132 @value{GDBN}. This includes conditional expressions, function calls,
6133 casts, and string constants. It also includes preprocessor macros, if
6134 you compiled your program to include this information; see
6137 @cindex arrays in expressions
6138 @value{GDBN} supports array constants in expressions input by
6139 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
6140 you can use the command @code{print @{1, 2, 3@}} to create an array
6141 of three integers. If you pass an array to a function or assign it
6142 to a program variable, @value{GDBN} copies the array to memory that
6143 is @code{malloc}ed in the target program.
6145 Because C is so widespread, most of the expressions shown in examples in
6146 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
6147 Languages}, for information on how to use expressions in other
6150 In this section, we discuss operators that you can use in @value{GDBN}
6151 expressions regardless of your programming language.
6153 @cindex casts, in expressions
6154 Casts are supported in all languages, not just in C, because it is so
6155 useful to cast a number into a pointer in order to examine a structure
6156 at that address in memory.
6157 @c FIXME: casts supported---Mod2 true?
6159 @value{GDBN} supports these operators, in addition to those common
6160 to programming languages:
6164 @samp{@@} is a binary operator for treating parts of memory as arrays.
6165 @xref{Arrays, ,Artificial Arrays}, for more information.
6168 @samp{::} allows you to specify a variable in terms of the file or
6169 function where it is defined. @xref{Variables, ,Program Variables}.
6171 @cindex @{@var{type}@}
6172 @cindex type casting memory
6173 @cindex memory, viewing as typed object
6174 @cindex casts, to view memory
6175 @item @{@var{type}@} @var{addr}
6176 Refers to an object of type @var{type} stored at address @var{addr} in
6177 memory. @var{addr} may be any expression whose value is an integer or
6178 pointer (but parentheses are required around binary operators, just as in
6179 a cast). This construct is allowed regardless of what kind of data is
6180 normally supposed to reside at @var{addr}.
6183 @node Ambiguous Expressions
6184 @section Ambiguous Expressions
6185 @cindex ambiguous expressions
6187 Expressions can sometimes contain some ambiguous elements. For instance,
6188 some programming languages (notably Ada, C@t{++} and Objective-C) permit
6189 a single function name to be defined several times, for application in
6190 different contexts. This is called @dfn{overloading}. Another example
6191 involving Ada is generics. A @dfn{generic package} is similar to C@t{++}
6192 templates and is typically instantiated several times, resulting in
6193 the same function name being defined in different contexts.
6195 In some cases and depending on the language, it is possible to adjust
6196 the expression to remove the ambiguity. For instance in C@t{++}, you
6197 can specify the signature of the function you want to break on, as in
6198 @kbd{break @var{function}(@var{types})}. In Ada, using the fully
6199 qualified name of your function often makes the expression unambiguous
6202 When an ambiguity that needs to be resolved is detected, the debugger
6203 has the capability to display a menu of numbered choices for each
6204 possibility, and then waits for the selection with the prompt @samp{>}.
6205 The first option is always @samp{[0] cancel}, and typing @kbd{0 @key{RET}}
6206 aborts the current command. If the command in which the expression was
6207 used allows more than one choice to be selected, the next option in the
6208 menu is @samp{[1] all}, and typing @kbd{1 @key{RET}} selects all possible
6211 For example, the following session excerpt shows an attempt to set a
6212 breakpoint at the overloaded symbol @code{String::after}.
6213 We choose three particular definitions of that function name:
6215 @c FIXME! This is likely to change to show arg type lists, at least
6218 (@value{GDBP}) b String::after
6221 [2] file:String.cc; line number:867
6222 [3] file:String.cc; line number:860
6223 [4] file:String.cc; line number:875
6224 [5] file:String.cc; line number:853
6225 [6] file:String.cc; line number:846
6226 [7] file:String.cc; line number:735
6228 Breakpoint 1 at 0xb26c: file String.cc, line 867.
6229 Breakpoint 2 at 0xb344: file String.cc, line 875.
6230 Breakpoint 3 at 0xafcc: file String.cc, line 846.
6231 Multiple breakpoints were set.
6232 Use the "delete" command to delete unwanted
6239 @kindex set multiple-symbols
6240 @item set multiple-symbols @var{mode}
6241 @cindex multiple-symbols menu
6243 This option allows you to adjust the debugger behavior when an expression
6246 By default, @var{mode} is set to @code{all}. If the command with which
6247 the expression is used allows more than one choice, then @value{GDBN}
6248 automatically selects all possible choices. For instance, inserting
6249 a breakpoint on a function using an ambiguous name results in a breakpoint
6250 inserted on each possible match. However, if a unique choice must be made,
6251 then @value{GDBN} uses the menu to help you disambiguate the expression.
6252 For instance, printing the address of an overloaded function will result
6253 in the use of the menu.
6255 When @var{mode} is set to @code{ask}, the debugger always uses the menu
6256 when an ambiguity is detected.
6258 Finally, when @var{mode} is set to @code{cancel}, the debugger reports
6259 an error due to the ambiguity and the command is aborted.
6261 @kindex show multiple-symbols
6262 @item show multiple-symbols
6263 Show the current value of the @code{multiple-symbols} setting.
6267 @section Program Variables
6269 The most common kind of expression to use is the name of a variable
6272 Variables in expressions are understood in the selected stack frame
6273 (@pxref{Selection, ,Selecting a Frame}); they must be either:
6277 global (or file-static)
6284 visible according to the scope rules of the
6285 programming language from the point of execution in that frame
6288 @noindent This means that in the function
6303 you can examine and use the variable @code{a} whenever your program is
6304 executing within the function @code{foo}, but you can only use or
6305 examine the variable @code{b} while your program is executing inside
6306 the block where @code{b} is declared.
6308 @cindex variable name conflict
6309 There is an exception: you can refer to a variable or function whose
6310 scope is a single source file even if the current execution point is not
6311 in this file. But it is possible to have more than one such variable or
6312 function with the same name (in different source files). If that
6313 happens, referring to that name has unpredictable effects. If you wish,
6314 you can specify a static variable in a particular function or file,
6315 using the colon-colon (@code{::}) notation:
6317 @cindex colon-colon, context for variables/functions
6319 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
6320 @cindex @code{::}, context for variables/functions
6323 @var{file}::@var{variable}
6324 @var{function}::@var{variable}
6328 Here @var{file} or @var{function} is the name of the context for the
6329 static @var{variable}. In the case of file names, you can use quotes to
6330 make sure @value{GDBN} parses the file name as a single word---for example,
6331 to print a global value of @code{x} defined in @file{f2.c}:
6334 (@value{GDBP}) p 'f2.c'::x
6337 @cindex C@t{++} scope resolution
6338 This use of @samp{::} is very rarely in conflict with the very similar
6339 use of the same notation in C@t{++}. @value{GDBN} also supports use of the C@t{++}
6340 scope resolution operator in @value{GDBN} expressions.
6341 @c FIXME: Um, so what happens in one of those rare cases where it's in
6344 @cindex wrong values
6345 @cindex variable values, wrong
6346 @cindex function entry/exit, wrong values of variables
6347 @cindex optimized code, wrong values of variables
6349 @emph{Warning:} Occasionally, a local variable may appear to have the
6350 wrong value at certain points in a function---just after entry to a new
6351 scope, and just before exit.
6353 You may see this problem when you are stepping by machine instructions.
6354 This is because, on most machines, it takes more than one instruction to
6355 set up a stack frame (including local variable definitions); if you are
6356 stepping by machine instructions, variables may appear to have the wrong
6357 values until the stack frame is completely built. On exit, it usually
6358 also takes more than one machine instruction to destroy a stack frame;
6359 after you begin stepping through that group of instructions, local
6360 variable definitions may be gone.
6362 This may also happen when the compiler does significant optimizations.
6363 To be sure of always seeing accurate values, turn off all optimization
6366 @cindex ``No symbol "foo" in current context''
6367 Another possible effect of compiler optimizations is to optimize
6368 unused variables out of existence, or assign variables to registers (as
6369 opposed to memory addresses). Depending on the support for such cases
6370 offered by the debug info format used by the compiler, @value{GDBN}
6371 might not be able to display values for such local variables. If that
6372 happens, @value{GDBN} will print a message like this:
6375 No symbol "foo" in current context.
6378 To solve such problems, either recompile without optimizations, or use a
6379 different debug info format, if the compiler supports several such
6380 formats. For example, @value{NGCC}, the @sc{gnu} C/C@t{++} compiler,
6381 usually supports the @option{-gstabs+} option. @option{-gstabs+}
6382 produces debug info in a format that is superior to formats such as
6383 COFF. You may be able to use DWARF 2 (@option{-gdwarf-2}), which is also
6384 an effective form for debug info. @xref{Debugging Options,,Options
6385 for Debugging Your Program or GCC, gcc.info, Using the @sc{gnu}
6386 Compiler Collection (GCC)}.
6387 @xref{C, ,C and C@t{++}}, for more information about debug info formats
6388 that are best suited to C@t{++} programs.
6390 If you ask to print an object whose contents are unknown to
6391 @value{GDBN}, e.g., because its data type is not completely specified
6392 by the debug information, @value{GDBN} will say @samp{<incomplete
6393 type>}. @xref{Symbols, incomplete type}, for more about this.
6395 Strings are identified as arrays of @code{char} values without specified
6396 signedness. Arrays of either @code{signed char} or @code{unsigned char} get
6397 printed as arrays of 1 byte sized integers. @code{-fsigned-char} or
6398 @code{-funsigned-char} @value{NGCC} options have no effect as @value{GDBN}
6399 defines literal string type @code{"char"} as @code{char} without a sign.
6404 signed char var1[] = "A";
6407 You get during debugging
6412 $2 = @{65 'A', 0 '\0'@}
6416 @section Artificial Arrays
6418 @cindex artificial array
6420 @kindex @@@r{, referencing memory as an array}
6421 It is often useful to print out several successive objects of the
6422 same type in memory; a section of an array, or an array of
6423 dynamically determined size for which only a pointer exists in the
6426 You can do this by referring to a contiguous span of memory as an
6427 @dfn{artificial array}, using the binary operator @samp{@@}. The left
6428 operand of @samp{@@} should be the first element of the desired array
6429 and be an individual object. The right operand should be the desired length
6430 of the array. The result is an array value whose elements are all of
6431 the type of the left argument. The first element is actually the left
6432 argument; the second element comes from bytes of memory immediately
6433 following those that hold the first element, and so on. Here is an
6434 example. If a program says
6437 int *array = (int *) malloc (len * sizeof (int));
6441 you can print the contents of @code{array} with
6447 The left operand of @samp{@@} must reside in memory. Array values made
6448 with @samp{@@} in this way behave just like other arrays in terms of
6449 subscripting, and are coerced to pointers when used in expressions.
6450 Artificial arrays most often appear in expressions via the value history
6451 (@pxref{Value History, ,Value History}), after printing one out.
6453 Another way to create an artificial array is to use a cast.
6454 This re-interprets a value as if it were an array.
6455 The value need not be in memory:
6457 (@value{GDBP}) p/x (short[2])0x12345678
6458 $1 = @{0x1234, 0x5678@}
6461 As a convenience, if you leave the array length out (as in
6462 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
6463 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
6465 (@value{GDBP}) p/x (short[])0x12345678
6466 $2 = @{0x1234, 0x5678@}
6469 Sometimes the artificial array mechanism is not quite enough; in
6470 moderately complex data structures, the elements of interest may not
6471 actually be adjacent---for example, if you are interested in the values
6472 of pointers in an array. One useful work-around in this situation is
6473 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
6474 Variables}) as a counter in an expression that prints the first
6475 interesting value, and then repeat that expression via @key{RET}. For
6476 instance, suppose you have an array @code{dtab} of pointers to
6477 structures, and you are interested in the values of a field @code{fv}
6478 in each structure. Here is an example of what you might type:
6488 @node Output Formats
6489 @section Output Formats
6491 @cindex formatted output
6492 @cindex output formats
6493 By default, @value{GDBN} prints a value according to its data type. Sometimes
6494 this is not what you want. For example, you might want to print a number
6495 in hex, or a pointer in decimal. Or you might want to view data in memory
6496 at a certain address as a character string or as an instruction. To do
6497 these things, specify an @dfn{output format} when you print a value.
6499 The simplest use of output formats is to say how to print a value
6500 already computed. This is done by starting the arguments of the
6501 @code{print} command with a slash and a format letter. The format
6502 letters supported are:
6506 Regard the bits of the value as an integer, and print the integer in
6510 Print as integer in signed decimal.
6513 Print as integer in unsigned decimal.
6516 Print as integer in octal.
6519 Print as integer in binary. The letter @samp{t} stands for ``two''.
6520 @footnote{@samp{b} cannot be used because these format letters are also
6521 used with the @code{x} command, where @samp{b} stands for ``byte'';
6522 see @ref{Memory,,Examining Memory}.}
6525 @cindex unknown address, locating
6526 @cindex locate address
6527 Print as an address, both absolute in hexadecimal and as an offset from
6528 the nearest preceding symbol. You can use this format used to discover
6529 where (in what function) an unknown address is located:
6532 (@value{GDBP}) p/a 0x54320
6533 $3 = 0x54320 <_initialize_vx+396>
6537 The command @code{info symbol 0x54320} yields similar results.
6538 @xref{Symbols, info symbol}.
6541 Regard as an integer and print it as a character constant. This
6542 prints both the numerical value and its character representation. The
6543 character representation is replaced with the octal escape @samp{\nnn}
6544 for characters outside the 7-bit @sc{ascii} range.
6546 Without this format, @value{GDBN} displays @code{char},
6547 @w{@code{unsigned char}}, and @w{@code{signed char}} data as character
6548 constants. Single-byte members of vectors are displayed as integer
6552 Regard the bits of the value as a floating point number and print
6553 using typical floating point syntax.
6556 @cindex printing strings
6557 @cindex printing byte arrays
6558 Regard as a string, if possible. With this format, pointers to single-byte
6559 data are displayed as null-terminated strings and arrays of single-byte data
6560 are displayed as fixed-length strings. Other values are displayed in their
6563 Without this format, @value{GDBN} displays pointers to and arrays of
6564 @code{char}, @w{@code{unsigned char}}, and @w{@code{signed char}} as
6565 strings. Single-byte members of a vector are displayed as an integer
6569 For example, to print the program counter in hex (@pxref{Registers}), type
6576 Note that no space is required before the slash; this is because command
6577 names in @value{GDBN} cannot contain a slash.
6579 To reprint the last value in the value history with a different format,
6580 you can use the @code{print} command with just a format and no
6581 expression. For example, @samp{p/x} reprints the last value in hex.
6584 @section Examining Memory
6586 You can use the command @code{x} (for ``examine'') to examine memory in
6587 any of several formats, independently of your program's data types.
6589 @cindex examining memory
6591 @kindex x @r{(examine memory)}
6592 @item x/@var{nfu} @var{addr}
6595 Use the @code{x} command to examine memory.
6598 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
6599 much memory to display and how to format it; @var{addr} is an
6600 expression giving the address where you want to start displaying memory.
6601 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
6602 Several commands set convenient defaults for @var{addr}.
6605 @item @var{n}, the repeat count
6606 The repeat count is a decimal integer; the default is 1. It specifies
6607 how much memory (counting by units @var{u}) to display.
6608 @c This really is **decimal**; unaffected by 'set radix' as of GDB
6611 @item @var{f}, the display format
6612 The display format is one of the formats used by @code{print}
6613 (@samp{x}, @samp{d}, @samp{u}, @samp{o}, @samp{t}, @samp{a}, @samp{c},
6614 @samp{f}, @samp{s}), and in addition @samp{i} (for machine instructions).
6615 The default is @samp{x} (hexadecimal) initially. The default changes
6616 each time you use either @code{x} or @code{print}.
6618 @item @var{u}, the unit size
6619 The unit size is any of
6625 Halfwords (two bytes).
6627 Words (four bytes). This is the initial default.
6629 Giant words (eight bytes).
6632 Each time you specify a unit size with @code{x}, that size becomes the
6633 default unit the next time you use @code{x}. (For the @samp{s} and
6634 @samp{i} formats, the unit size is ignored and is normally not written.)
6636 @item @var{addr}, starting display address
6637 @var{addr} is the address where you want @value{GDBN} to begin displaying
6638 memory. The expression need not have a pointer value (though it may);
6639 it is always interpreted as an integer address of a byte of memory.
6640 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
6641 @var{addr} is usually just after the last address examined---but several
6642 other commands also set the default address: @code{info breakpoints} (to
6643 the address of the last breakpoint listed), @code{info line} (to the
6644 starting address of a line), and @code{print} (if you use it to display
6645 a value from memory).
6648 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
6649 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
6650 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
6651 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
6652 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
6654 Since the letters indicating unit sizes are all distinct from the
6655 letters specifying output formats, you do not have to remember whether
6656 unit size or format comes first; either order works. The output
6657 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
6658 (However, the count @var{n} must come first; @samp{wx4} does not work.)
6660 Even though the unit size @var{u} is ignored for the formats @samp{s}
6661 and @samp{i}, you might still want to use a count @var{n}; for example,
6662 @samp{3i} specifies that you want to see three machine instructions,
6663 including any operands. For convenience, especially when used with
6664 the @code{display} command, the @samp{i} format also prints branch delay
6665 slot instructions, if any, beyond the count specified, which immediately
6666 follow the last instruction that is within the count. The command
6667 @code{disassemble} gives an alternative way of inspecting machine
6668 instructions; see @ref{Machine Code,,Source and Machine Code}.
6670 All the defaults for the arguments to @code{x} are designed to make it
6671 easy to continue scanning memory with minimal specifications each time
6672 you use @code{x}. For example, after you have inspected three machine
6673 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
6674 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
6675 the repeat count @var{n} is used again; the other arguments default as
6676 for successive uses of @code{x}.
6678 @cindex @code{$_}, @code{$__}, and value history
6679 The addresses and contents printed by the @code{x} command are not saved
6680 in the value history because there is often too much of them and they
6681 would get in the way. Instead, @value{GDBN} makes these values available for
6682 subsequent use in expressions as values of the convenience variables
6683 @code{$_} and @code{$__}. After an @code{x} command, the last address
6684 examined is available for use in expressions in the convenience variable
6685 @code{$_}. The contents of that address, as examined, are available in
6686 the convenience variable @code{$__}.
6688 If the @code{x} command has a repeat count, the address and contents saved
6689 are from the last memory unit printed; this is not the same as the last
6690 address printed if several units were printed on the last line of output.
6692 @cindex remote memory comparison
6693 @cindex verify remote memory image
6694 When you are debugging a program running on a remote target machine
6695 (@pxref{Remote Debugging}), you may wish to verify the program's image in the
6696 remote machine's memory against the executable file you downloaded to
6697 the target. The @code{compare-sections} command is provided for such
6701 @kindex compare-sections
6702 @item compare-sections @r{[}@var{section-name}@r{]}
6703 Compare the data of a loadable section @var{section-name} in the
6704 executable file of the program being debugged with the same section in
6705 the remote machine's memory, and report any mismatches. With no
6706 arguments, compares all loadable sections. This command's
6707 availability depends on the target's support for the @code{"qCRC"}
6712 @section Automatic Display
6713 @cindex automatic display
6714 @cindex display of expressions
6716 If you find that you want to print the value of an expression frequently
6717 (to see how it changes), you might want to add it to the @dfn{automatic
6718 display list} so that @value{GDBN} prints its value each time your program stops.
6719 Each expression added to the list is given a number to identify it;
6720 to remove an expression from the list, you specify that number.
6721 The automatic display looks like this:
6725 3: bar[5] = (struct hack *) 0x3804
6729 This display shows item numbers, expressions and their current values. As with
6730 displays you request manually using @code{x} or @code{print}, you can
6731 specify the output format you prefer; in fact, @code{display} decides
6732 whether to use @code{print} or @code{x} depending your format
6733 specification---it uses @code{x} if you specify either the @samp{i}
6734 or @samp{s} format, or a unit size; otherwise it uses @code{print}.
6738 @item display @var{expr}
6739 Add the expression @var{expr} to the list of expressions to display
6740 each time your program stops. @xref{Expressions, ,Expressions}.
6742 @code{display} does not repeat if you press @key{RET} again after using it.
6744 @item display/@var{fmt} @var{expr}
6745 For @var{fmt} specifying only a display format and not a size or
6746 count, add the expression @var{expr} to the auto-display list but
6747 arrange to display it each time in the specified format @var{fmt}.
6748 @xref{Output Formats,,Output Formats}.
6750 @item display/@var{fmt} @var{addr}
6751 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
6752 number of units, add the expression @var{addr} as a memory address to
6753 be examined each time your program stops. Examining means in effect
6754 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining Memory}.
6757 For example, @samp{display/i $pc} can be helpful, to see the machine
6758 instruction about to be executed each time execution stops (@samp{$pc}
6759 is a common name for the program counter; @pxref{Registers, ,Registers}).
6762 @kindex delete display
6764 @item undisplay @var{dnums}@dots{}
6765 @itemx delete display @var{dnums}@dots{}
6766 Remove item numbers @var{dnums} from the list of expressions to display.
6768 @code{undisplay} does not repeat if you press @key{RET} after using it.
6769 (Otherwise you would just get the error @samp{No display number @dots{}}.)
6771 @kindex disable display
6772 @item disable display @var{dnums}@dots{}
6773 Disable the display of item numbers @var{dnums}. A disabled display
6774 item is not printed automatically, but is not forgotten. It may be
6775 enabled again later.
6777 @kindex enable display
6778 @item enable display @var{dnums}@dots{}
6779 Enable display of item numbers @var{dnums}. It becomes effective once
6780 again in auto display of its expression, until you specify otherwise.
6783 Display the current values of the expressions on the list, just as is
6784 done when your program stops.
6786 @kindex info display
6788 Print the list of expressions previously set up to display
6789 automatically, each one with its item number, but without showing the
6790 values. This includes disabled expressions, which are marked as such.
6791 It also includes expressions which would not be displayed right now
6792 because they refer to automatic variables not currently available.
6795 @cindex display disabled out of scope
6796 If a display expression refers to local variables, then it does not make
6797 sense outside the lexical context for which it was set up. Such an
6798 expression is disabled when execution enters a context where one of its
6799 variables is not defined. For example, if you give the command
6800 @code{display last_char} while inside a function with an argument
6801 @code{last_char}, @value{GDBN} displays this argument while your program
6802 continues to stop inside that function. When it stops elsewhere---where
6803 there is no variable @code{last_char}---the display is disabled
6804 automatically. The next time your program stops where @code{last_char}
6805 is meaningful, you can enable the display expression once again.
6807 @node Print Settings
6808 @section Print Settings
6810 @cindex format options
6811 @cindex print settings
6812 @value{GDBN} provides the following ways to control how arrays, structures,
6813 and symbols are printed.
6816 These settings are useful for debugging programs in any language:
6820 @item set print address
6821 @itemx set print address on
6822 @cindex print/don't print memory addresses
6823 @value{GDBN} prints memory addresses showing the location of stack
6824 traces, structure values, pointer values, breakpoints, and so forth,
6825 even when it also displays the contents of those addresses. The default
6826 is @code{on}. For example, this is what a stack frame display looks like with
6827 @code{set print address on}:
6832 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
6834 530 if (lquote != def_lquote)
6838 @item set print address off
6839 Do not print addresses when displaying their contents. For example,
6840 this is the same stack frame displayed with @code{set print address off}:
6844 (@value{GDBP}) set print addr off
6846 #0 set_quotes (lq="<<", rq=">>") at input.c:530
6847 530 if (lquote != def_lquote)
6851 You can use @samp{set print address off} to eliminate all machine
6852 dependent displays from the @value{GDBN} interface. For example, with
6853 @code{print address off}, you should get the same text for backtraces on
6854 all machines---whether or not they involve pointer arguments.
6857 @item show print address
6858 Show whether or not addresses are to be printed.
6861 When @value{GDBN} prints a symbolic address, it normally prints the
6862 closest earlier symbol plus an offset. If that symbol does not uniquely
6863 identify the address (for example, it is a name whose scope is a single
6864 source file), you may need to clarify. One way to do this is with
6865 @code{info line}, for example @samp{info line *0x4537}. Alternately,
6866 you can set @value{GDBN} to print the source file and line number when
6867 it prints a symbolic address:
6870 @item set print symbol-filename on
6871 @cindex source file and line of a symbol
6872 @cindex symbol, source file and line
6873 Tell @value{GDBN} to print the source file name and line number of a
6874 symbol in the symbolic form of an address.
6876 @item set print symbol-filename off
6877 Do not print source file name and line number of a symbol. This is the
6880 @item show print symbol-filename
6881 Show whether or not @value{GDBN} will print the source file name and
6882 line number of a symbol in the symbolic form of an address.
6885 Another situation where it is helpful to show symbol filenames and line
6886 numbers is when disassembling code; @value{GDBN} shows you the line
6887 number and source file that corresponds to each instruction.
6889 Also, you may wish to see the symbolic form only if the address being
6890 printed is reasonably close to the closest earlier symbol:
6893 @item set print max-symbolic-offset @var{max-offset}
6894 @cindex maximum value for offset of closest symbol
6895 Tell @value{GDBN} to only display the symbolic form of an address if the
6896 offset between the closest earlier symbol and the address is less than
6897 @var{max-offset}. The default is 0, which tells @value{GDBN}
6898 to always print the symbolic form of an address if any symbol precedes it.
6900 @item show print max-symbolic-offset
6901 Ask how large the maximum offset is that @value{GDBN} prints in a
6905 @cindex wild pointer, interpreting
6906 @cindex pointer, finding referent
6907 If you have a pointer and you are not sure where it points, try
6908 @samp{set print symbol-filename on}. Then you can determine the name
6909 and source file location of the variable where it points, using
6910 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
6911 For example, here @value{GDBN} shows that a variable @code{ptt} points
6912 at another variable @code{t}, defined in @file{hi2.c}:
6915 (@value{GDBP}) set print symbol-filename on
6916 (@value{GDBP}) p/a ptt
6917 $4 = 0xe008 <t in hi2.c>
6921 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
6922 does not show the symbol name and filename of the referent, even with
6923 the appropriate @code{set print} options turned on.
6926 Other settings control how different kinds of objects are printed:
6929 @item set print array
6930 @itemx set print array on
6931 @cindex pretty print arrays
6932 Pretty print arrays. This format is more convenient to read,
6933 but uses more space. The default is off.
6935 @item set print array off
6936 Return to compressed format for arrays.
6938 @item show print array
6939 Show whether compressed or pretty format is selected for displaying
6942 @cindex print array indexes
6943 @item set print array-indexes
6944 @itemx set print array-indexes on
6945 Print the index of each element when displaying arrays. May be more
6946 convenient to locate a given element in the array or quickly find the
6947 index of a given element in that printed array. The default is off.
6949 @item set print array-indexes off
6950 Stop printing element indexes when displaying arrays.
6952 @item show print array-indexes
6953 Show whether the index of each element is printed when displaying
6956 @item set print elements @var{number-of-elements}
6957 @cindex number of array elements to print
6958 @cindex limit on number of printed array elements
6959 Set a limit on how many elements of an array @value{GDBN} will print.
6960 If @value{GDBN} is printing a large array, it stops printing after it has
6961 printed the number of elements set by the @code{set print elements} command.
6962 This limit also applies to the display of strings.
6963 When @value{GDBN} starts, this limit is set to 200.
6964 Setting @var{number-of-elements} to zero means that the printing is unlimited.
6966 @item show print elements
6967 Display the number of elements of a large array that @value{GDBN} will print.
6968 If the number is 0, then the printing is unlimited.
6970 @item set print frame-arguments @var{value}
6971 @cindex printing frame argument values
6972 @cindex print all frame argument values
6973 @cindex print frame argument values for scalars only
6974 @cindex do not print frame argument values
6975 This command allows to control how the values of arguments are printed
6976 when the debugger prints a frame (@pxref{Frames}). The possible
6981 The values of all arguments are printed. This is the default.
6984 Print the value of an argument only if it is a scalar. The value of more
6985 complex arguments such as arrays, structures, unions, etc, is replaced
6986 by @code{@dots{}}. Here is an example where only scalar arguments are shown:
6989 #1 0x08048361 in call_me (i=3, s=@dots{}, ss=0xbf8d508c, u=@dots{}, e=green)
6994 None of the argument values are printed. Instead, the value of each argument
6995 is replaced by @code{@dots{}}. In this case, the example above now becomes:
6998 #1 0x08048361 in call_me (i=@dots{}, s=@dots{}, ss=@dots{}, u=@dots{}, e=@dots{})
7003 By default, all argument values are always printed. But this command
7004 can be useful in several cases. For instance, it can be used to reduce
7005 the amount of information printed in each frame, making the backtrace
7006 more readable. Also, this command can be used to improve performance
7007 when displaying Ada frames, because the computation of large arguments
7008 can sometimes be CPU-intensive, especiallly in large applications.
7009 Setting @code{print frame-arguments} to @code{scalars} or @code{none}
7010 avoids this computation, thus speeding up the display of each Ada frame.
7012 @item show print frame-arguments
7013 Show how the value of arguments should be displayed when printing a frame.
7015 @item set print repeats
7016 @cindex repeated array elements
7017 Set the threshold for suppressing display of repeated array
7018 elements. When the number of consecutive identical elements of an
7019 array exceeds the threshold, @value{GDBN} prints the string
7020 @code{"<repeats @var{n} times>"}, where @var{n} is the number of
7021 identical repetitions, instead of displaying the identical elements
7022 themselves. Setting the threshold to zero will cause all elements to
7023 be individually printed. The default threshold is 10.
7025 @item show print repeats
7026 Display the current threshold for printing repeated identical
7029 @item set print null-stop
7030 @cindex @sc{null} elements in arrays
7031 Cause @value{GDBN} to stop printing the characters of an array when the first
7032 @sc{null} is encountered. This is useful when large arrays actually
7033 contain only short strings.
7036 @item show print null-stop
7037 Show whether @value{GDBN} stops printing an array on the first
7038 @sc{null} character.
7040 @item set print pretty on
7041 @cindex print structures in indented form
7042 @cindex indentation in structure display
7043 Cause @value{GDBN} to print structures in an indented format with one member
7044 per line, like this:
7059 @item set print pretty off
7060 Cause @value{GDBN} to print structures in a compact format, like this:
7064 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
7065 meat = 0x54 "Pork"@}
7070 This is the default format.
7072 @item show print pretty
7073 Show which format @value{GDBN} is using to print structures.
7075 @item set print sevenbit-strings on
7076 @cindex eight-bit characters in strings
7077 @cindex octal escapes in strings
7078 Print using only seven-bit characters; if this option is set,
7079 @value{GDBN} displays any eight-bit characters (in strings or
7080 character values) using the notation @code{\}@var{nnn}. This setting is
7081 best if you are working in English (@sc{ascii}) and you use the
7082 high-order bit of characters as a marker or ``meta'' bit.
7084 @item set print sevenbit-strings off
7085 Print full eight-bit characters. This allows the use of more
7086 international character sets, and is the default.
7088 @item show print sevenbit-strings
7089 Show whether or not @value{GDBN} is printing only seven-bit characters.
7091 @item set print union on
7092 @cindex unions in structures, printing
7093 Tell @value{GDBN} to print unions which are contained in structures
7094 and other unions. This is the default setting.
7096 @item set print union off
7097 Tell @value{GDBN} not to print unions which are contained in
7098 structures and other unions. @value{GDBN} will print @code{"@{...@}"}
7101 @item show print union
7102 Ask @value{GDBN} whether or not it will print unions which are contained in
7103 structures and other unions.
7105 For example, given the declarations
7108 typedef enum @{Tree, Bug@} Species;
7109 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
7110 typedef enum @{Caterpillar, Cocoon, Butterfly@}
7121 struct thing foo = @{Tree, @{Acorn@}@};
7125 with @code{set print union on} in effect @samp{p foo} would print
7128 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
7132 and with @code{set print union off} in effect it would print
7135 $1 = @{it = Tree, form = @{...@}@}
7139 @code{set print union} affects programs written in C-like languages
7145 These settings are of interest when debugging C@t{++} programs:
7148 @cindex demangling C@t{++} names
7149 @item set print demangle
7150 @itemx set print demangle on
7151 Print C@t{++} names in their source form rather than in the encoded
7152 (``mangled'') form passed to the assembler and linker for type-safe
7153 linkage. The default is on.
7155 @item show print demangle
7156 Show whether C@t{++} names are printed in mangled or demangled form.
7158 @item set print asm-demangle
7159 @itemx set print asm-demangle on
7160 Print C@t{++} names in their source form rather than their mangled form, even
7161 in assembler code printouts such as instruction disassemblies.
7164 @item show print asm-demangle
7165 Show whether C@t{++} names in assembly listings are printed in mangled
7168 @cindex C@t{++} symbol decoding style
7169 @cindex symbol decoding style, C@t{++}
7170 @kindex set demangle-style
7171 @item set demangle-style @var{style}
7172 Choose among several encoding schemes used by different compilers to
7173 represent C@t{++} names. The choices for @var{style} are currently:
7177 Allow @value{GDBN} to choose a decoding style by inspecting your program.
7180 Decode based on the @sc{gnu} C@t{++} compiler (@code{g++}) encoding algorithm.
7181 This is the default.
7184 Decode based on the HP ANSI C@t{++} (@code{aCC}) encoding algorithm.
7187 Decode based on the Lucid C@t{++} compiler (@code{lcc}) encoding algorithm.
7190 Decode using the algorithm in the @cite{C@t{++} Annotated Reference Manual}.
7191 @strong{Warning:} this setting alone is not sufficient to allow
7192 debugging @code{cfront}-generated executables. @value{GDBN} would
7193 require further enhancement to permit that.
7196 If you omit @var{style}, you will see a list of possible formats.
7198 @item show demangle-style
7199 Display the encoding style currently in use for decoding C@t{++} symbols.
7201 @item set print object
7202 @itemx set print object on
7203 @cindex derived type of an object, printing
7204 @cindex display derived types
7205 When displaying a pointer to an object, identify the @emph{actual}
7206 (derived) type of the object rather than the @emph{declared} type, using
7207 the virtual function table.
7209 @item set print object off
7210 Display only the declared type of objects, without reference to the
7211 virtual function table. This is the default setting.
7213 @item show print object
7214 Show whether actual, or declared, object types are displayed.
7216 @item set print static-members
7217 @itemx set print static-members on
7218 @cindex static members of C@t{++} objects
7219 Print static members when displaying a C@t{++} object. The default is on.
7221 @item set print static-members off
7222 Do not print static members when displaying a C@t{++} object.
7224 @item show print static-members
7225 Show whether C@t{++} static members are printed or not.
7227 @item set print pascal_static-members
7228 @itemx set print pascal_static-members on
7229 @cindex static members of Pascal objects
7230 @cindex Pascal objects, static members display
7231 Print static members when displaying a Pascal object. The default is on.
7233 @item set print pascal_static-members off
7234 Do not print static members when displaying a Pascal object.
7236 @item show print pascal_static-members
7237 Show whether Pascal static members are printed or not.
7239 @c These don't work with HP ANSI C++ yet.
7240 @item set print vtbl
7241 @itemx set print vtbl on
7242 @cindex pretty print C@t{++} virtual function tables
7243 @cindex virtual functions (C@t{++}) display
7244 @cindex VTBL display
7245 Pretty print C@t{++} virtual function tables. The default is off.
7246 (The @code{vtbl} commands do not work on programs compiled with the HP
7247 ANSI C@t{++} compiler (@code{aCC}).)
7249 @item set print vtbl off
7250 Do not pretty print C@t{++} virtual function tables.
7252 @item show print vtbl
7253 Show whether C@t{++} virtual function tables are pretty printed, or not.
7257 @section Value History
7259 @cindex value history
7260 @cindex history of values printed by @value{GDBN}
7261 Values printed by the @code{print} command are saved in the @value{GDBN}
7262 @dfn{value history}. This allows you to refer to them in other expressions.
7263 Values are kept until the symbol table is re-read or discarded
7264 (for example with the @code{file} or @code{symbol-file} commands).
7265 When the symbol table changes, the value history is discarded,
7266 since the values may contain pointers back to the types defined in the
7271 @cindex history number
7272 The values printed are given @dfn{history numbers} by which you can
7273 refer to them. These are successive integers starting with one.
7274 @code{print} shows you the history number assigned to a value by
7275 printing @samp{$@var{num} = } before the value; here @var{num} is the
7278 To refer to any previous value, use @samp{$} followed by the value's
7279 history number. The way @code{print} labels its output is designed to
7280 remind you of this. Just @code{$} refers to the most recent value in
7281 the history, and @code{$$} refers to the value before that.
7282 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
7283 is the value just prior to @code{$$}, @code{$$1} is equivalent to
7284 @code{$$}, and @code{$$0} is equivalent to @code{$}.
7286 For example, suppose you have just printed a pointer to a structure and
7287 want to see the contents of the structure. It suffices to type
7293 If you have a chain of structures where the component @code{next} points
7294 to the next one, you can print the contents of the next one with this:
7301 You can print successive links in the chain by repeating this
7302 command---which you can do by just typing @key{RET}.
7304 Note that the history records values, not expressions. If the value of
7305 @code{x} is 4 and you type these commands:
7313 then the value recorded in the value history by the @code{print} command
7314 remains 4 even though the value of @code{x} has changed.
7319 Print the last ten values in the value history, with their item numbers.
7320 This is like @samp{p@ $$9} repeated ten times, except that @code{show
7321 values} does not change the history.
7323 @item show values @var{n}
7324 Print ten history values centered on history item number @var{n}.
7327 Print ten history values just after the values last printed. If no more
7328 values are available, @code{show values +} produces no display.
7331 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
7332 same effect as @samp{show values +}.
7334 @node Convenience Vars
7335 @section Convenience Variables
7337 @cindex convenience variables
7338 @cindex user-defined variables
7339 @value{GDBN} provides @dfn{convenience variables} that you can use within
7340 @value{GDBN} to hold on to a value and refer to it later. These variables
7341 exist entirely within @value{GDBN}; they are not part of your program, and
7342 setting a convenience variable has no direct effect on further execution
7343 of your program. That is why you can use them freely.
7345 Convenience variables are prefixed with @samp{$}. Any name preceded by
7346 @samp{$} can be used for a convenience variable, unless it is one of
7347 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
7348 (Value history references, in contrast, are @emph{numbers} preceded
7349 by @samp{$}. @xref{Value History, ,Value History}.)
7351 You can save a value in a convenience variable with an assignment
7352 expression, just as you would set a variable in your program.
7356 set $foo = *object_ptr
7360 would save in @code{$foo} the value contained in the object pointed to by
7363 Using a convenience variable for the first time creates it, but its
7364 value is @code{void} until you assign a new value. You can alter the
7365 value with another assignment at any time.
7367 Convenience variables have no fixed types. You can assign a convenience
7368 variable any type of value, including structures and arrays, even if
7369 that variable already has a value of a different type. The convenience
7370 variable, when used as an expression, has the type of its current value.
7373 @kindex show convenience
7374 @cindex show all user variables
7375 @item show convenience
7376 Print a list of convenience variables used so far, and their values.
7377 Abbreviated @code{show conv}.
7379 @kindex init-if-undefined
7380 @cindex convenience variables, initializing
7381 @item init-if-undefined $@var{variable} = @var{expression}
7382 Set a convenience variable if it has not already been set. This is useful
7383 for user-defined commands that keep some state. It is similar, in concept,
7384 to using local static variables with initializers in C (except that
7385 convenience variables are global). It can also be used to allow users to
7386 override default values used in a command script.
7388 If the variable is already defined then the expression is not evaluated so
7389 any side-effects do not occur.
7392 One of the ways to use a convenience variable is as a counter to be
7393 incremented or a pointer to be advanced. For example, to print
7394 a field from successive elements of an array of structures:
7398 print bar[$i++]->contents
7402 Repeat that command by typing @key{RET}.
7404 Some convenience variables are created automatically by @value{GDBN} and given
7405 values likely to be useful.
7408 @vindex $_@r{, convenience variable}
7410 The variable @code{$_} is automatically set by the @code{x} command to
7411 the last address examined (@pxref{Memory, ,Examining Memory}). Other
7412 commands which provide a default address for @code{x} to examine also
7413 set @code{$_} to that address; these commands include @code{info line}
7414 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
7415 except when set by the @code{x} command, in which case it is a pointer
7416 to the type of @code{$__}.
7418 @vindex $__@r{, convenience variable}
7420 The variable @code{$__} is automatically set by the @code{x} command
7421 to the value found in the last address examined. Its type is chosen
7422 to match the format in which the data was printed.
7425 @vindex $_exitcode@r{, convenience variable}
7426 The variable @code{$_exitcode} is automatically set to the exit code when
7427 the program being debugged terminates.
7430 @vindex $_siginfo@r{, convenience variable}
7431 The variable @code{$_siginfo} is bound to extra signal information
7432 inspection (@pxref{extra signal information}).
7435 On HP-UX systems, if you refer to a function or variable name that
7436 begins with a dollar sign, @value{GDBN} searches for a user or system
7437 name first, before it searches for a convenience variable.
7443 You can refer to machine register contents, in expressions, as variables
7444 with names starting with @samp{$}. The names of registers are different
7445 for each machine; use @code{info registers} to see the names used on
7449 @kindex info registers
7450 @item info registers
7451 Print the names and values of all registers except floating-point
7452 and vector registers (in the selected stack frame).
7454 @kindex info all-registers
7455 @cindex floating point registers
7456 @item info all-registers
7457 Print the names and values of all registers, including floating-point
7458 and vector registers (in the selected stack frame).
7460 @item info registers @var{regname} @dots{}
7461 Print the @dfn{relativized} value of each specified register @var{regname}.
7462 As discussed in detail below, register values are normally relative to
7463 the selected stack frame. @var{regname} may be any register name valid on
7464 the machine you are using, with or without the initial @samp{$}.
7467 @cindex stack pointer register
7468 @cindex program counter register
7469 @cindex process status register
7470 @cindex frame pointer register
7471 @cindex standard registers
7472 @value{GDBN} has four ``standard'' register names that are available (in
7473 expressions) on most machines---whenever they do not conflict with an
7474 architecture's canonical mnemonics for registers. The register names
7475 @code{$pc} and @code{$sp} are used for the program counter register and
7476 the stack pointer. @code{$fp} is used for a register that contains a
7477 pointer to the current stack frame, and @code{$ps} is used for a
7478 register that contains the processor status. For example,
7479 you could print the program counter in hex with
7486 or print the instruction to be executed next with
7493 or add four to the stack pointer@footnote{This is a way of removing
7494 one word from the stack, on machines where stacks grow downward in
7495 memory (most machines, nowadays). This assumes that the innermost
7496 stack frame is selected; setting @code{$sp} is not allowed when other
7497 stack frames are selected. To pop entire frames off the stack,
7498 regardless of machine architecture, use @code{return};
7499 see @ref{Returning, ,Returning from a Function}.} with
7505 Whenever possible, these four standard register names are available on
7506 your machine even though the machine has different canonical mnemonics,
7507 so long as there is no conflict. The @code{info registers} command
7508 shows the canonical names. For example, on the SPARC, @code{info
7509 registers} displays the processor status register as @code{$psr} but you
7510 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
7511 is an alias for the @sc{eflags} register.
7513 @value{GDBN} always considers the contents of an ordinary register as an
7514 integer when the register is examined in this way. Some machines have
7515 special registers which can hold nothing but floating point; these
7516 registers are considered to have floating point values. There is no way
7517 to refer to the contents of an ordinary register as floating point value
7518 (although you can @emph{print} it as a floating point value with
7519 @samp{print/f $@var{regname}}).
7521 Some registers have distinct ``raw'' and ``virtual'' data formats. This
7522 means that the data format in which the register contents are saved by
7523 the operating system is not the same one that your program normally
7524 sees. For example, the registers of the 68881 floating point
7525 coprocessor are always saved in ``extended'' (raw) format, but all C
7526 programs expect to work with ``double'' (virtual) format. In such
7527 cases, @value{GDBN} normally works with the virtual format only (the format
7528 that makes sense for your program), but the @code{info registers} command
7529 prints the data in both formats.
7531 @cindex SSE registers (x86)
7532 @cindex MMX registers (x86)
7533 Some machines have special registers whose contents can be interpreted
7534 in several different ways. For example, modern x86-based machines
7535 have SSE and MMX registers that can hold several values packed
7536 together in several different formats. @value{GDBN} refers to such
7537 registers in @code{struct} notation:
7540 (@value{GDBP}) print $xmm1
7542 v4_float = @{0, 3.43859137e-038, 1.54142831e-044, 1.821688e-044@},
7543 v2_double = @{9.92129282474342e-303, 2.7585945287983262e-313@},
7544 v16_int8 = "\000\000\000\000\3706;\001\v\000\000\000\r\000\000",
7545 v8_int16 = @{0, 0, 14072, 315, 11, 0, 13, 0@},
7546 v4_int32 = @{0, 20657912, 11, 13@},
7547 v2_int64 = @{88725056443645952, 55834574859@},
7548 uint128 = 0x0000000d0000000b013b36f800000000
7553 To set values of such registers, you need to tell @value{GDBN} which
7554 view of the register you wish to change, as if you were assigning
7555 value to a @code{struct} member:
7558 (@value{GDBP}) set $xmm1.uint128 = 0x000000000000000000000000FFFFFFFF
7561 Normally, register values are relative to the selected stack frame
7562 (@pxref{Selection, ,Selecting a Frame}). This means that you get the
7563 value that the register would contain if all stack frames farther in
7564 were exited and their saved registers restored. In order to see the
7565 true contents of hardware registers, you must select the innermost
7566 frame (with @samp{frame 0}).
7568 However, @value{GDBN} must deduce where registers are saved, from the machine
7569 code generated by your compiler. If some registers are not saved, or if
7570 @value{GDBN} is unable to locate the saved registers, the selected stack
7571 frame makes no difference.
7573 @node Floating Point Hardware
7574 @section Floating Point Hardware
7575 @cindex floating point
7577 Depending on the configuration, @value{GDBN} may be able to give
7578 you more information about the status of the floating point hardware.
7583 Display hardware-dependent information about the floating
7584 point unit. The exact contents and layout vary depending on the
7585 floating point chip. Currently, @samp{info float} is supported on
7586 the ARM and x86 machines.
7590 @section Vector Unit
7593 Depending on the configuration, @value{GDBN} may be able to give you
7594 more information about the status of the vector unit.
7599 Display information about the vector unit. The exact contents and
7600 layout vary depending on the hardware.
7603 @node OS Information
7604 @section Operating System Auxiliary Information
7605 @cindex OS information
7607 @value{GDBN} provides interfaces to useful OS facilities that can help
7608 you debug your program.
7610 @cindex @code{ptrace} system call
7611 @cindex @code{struct user} contents
7612 When @value{GDBN} runs on a @dfn{Posix system} (such as GNU or Unix
7613 machines), it interfaces with the inferior via the @code{ptrace}
7614 system call. The operating system creates a special sata structure,
7615 called @code{struct user}, for this interface. You can use the
7616 command @code{info udot} to display the contents of this data
7622 Display the contents of the @code{struct user} maintained by the OS
7623 kernel for the program being debugged. @value{GDBN} displays the
7624 contents of @code{struct user} as a list of hex numbers, similar to
7625 the @code{examine} command.
7628 @cindex auxiliary vector
7629 @cindex vector, auxiliary
7630 Some operating systems supply an @dfn{auxiliary vector} to programs at
7631 startup. This is akin to the arguments and environment that you
7632 specify for a program, but contains a system-dependent variety of
7633 binary values that tell system libraries important details about the
7634 hardware, operating system, and process. Each value's purpose is
7635 identified by an integer tag; the meanings are well-known but system-specific.
7636 Depending on the configuration and operating system facilities,
7637 @value{GDBN} may be able to show you this information. For remote
7638 targets, this functionality may further depend on the remote stub's
7639 support of the @samp{qXfer:auxv:read} packet, see
7640 @ref{qXfer auxiliary vector read}.
7645 Display the auxiliary vector of the inferior, which can be either a
7646 live process or a core dump file. @value{GDBN} prints each tag value
7647 numerically, and also shows names and text descriptions for recognized
7648 tags. Some values in the vector are numbers, some bit masks, and some
7649 pointers to strings or other data. @value{GDBN} displays each value in the
7650 most appropriate form for a recognized tag, and in hexadecimal for
7651 an unrecognized tag.
7654 On some targets, @value{GDBN} can access operating-system-specific information
7655 and display it to user, without interpretation. For remote targets,
7656 this functionality depends on the remote stub's support of the
7657 @samp{qXfer:osdata:read} packet, see @ref{qXfer osdata read}.
7660 @kindex info os processes
7661 @item info os processes
7662 Display the list of processes on the target. For each process,
7663 @value{GDBN} prints the process identifier, the name of the user, and
7664 the command corresponding to the process.
7667 @node Memory Region Attributes
7668 @section Memory Region Attributes
7669 @cindex memory region attributes
7671 @dfn{Memory region attributes} allow you to describe special handling
7672 required by regions of your target's memory. @value{GDBN} uses
7673 attributes to determine whether to allow certain types of memory
7674 accesses; whether to use specific width accesses; and whether to cache
7675 target memory. By default the description of memory regions is
7676 fetched from the target (if the current target supports this), but the
7677 user can override the fetched regions.
7679 Defined memory regions can be individually enabled and disabled. When a
7680 memory region is disabled, @value{GDBN} uses the default attributes when
7681 accessing memory in that region. Similarly, if no memory regions have
7682 been defined, @value{GDBN} uses the default attributes when accessing
7685 When a memory region is defined, it is given a number to identify it;
7686 to enable, disable, or remove a memory region, you specify that number.
7690 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
7691 Define a memory region bounded by @var{lower} and @var{upper} with
7692 attributes @var{attributes}@dots{}, and add it to the list of regions
7693 monitored by @value{GDBN}. Note that @var{upper} == 0 is a special
7694 case: it is treated as the target's maximum memory address.
7695 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
7698 Discard any user changes to the memory regions and use target-supplied
7699 regions, if available, or no regions if the target does not support.
7702 @item delete mem @var{nums}@dots{}
7703 Remove memory regions @var{nums}@dots{} from the list of regions
7704 monitored by @value{GDBN}.
7707 @item disable mem @var{nums}@dots{}
7708 Disable monitoring of memory regions @var{nums}@dots{}.
7709 A disabled memory region is not forgotten.
7710 It may be enabled again later.
7713 @item enable mem @var{nums}@dots{}
7714 Enable monitoring of memory regions @var{nums}@dots{}.
7718 Print a table of all defined memory regions, with the following columns
7722 @item Memory Region Number
7723 @item Enabled or Disabled.
7724 Enabled memory regions are marked with @samp{y}.
7725 Disabled memory regions are marked with @samp{n}.
7728 The address defining the inclusive lower bound of the memory region.
7731 The address defining the exclusive upper bound of the memory region.
7734 The list of attributes set for this memory region.
7739 @subsection Attributes
7741 @subsubsection Memory Access Mode
7742 The access mode attributes set whether @value{GDBN} may make read or
7743 write accesses to a memory region.
7745 While these attributes prevent @value{GDBN} from performing invalid
7746 memory accesses, they do nothing to prevent the target system, I/O DMA,
7747 etc.@: from accessing memory.
7751 Memory is read only.
7753 Memory is write only.
7755 Memory is read/write. This is the default.
7758 @subsubsection Memory Access Size
7759 The access size attribute tells @value{GDBN} to use specific sized
7760 accesses in the memory region. Often memory mapped device registers
7761 require specific sized accesses. If no access size attribute is
7762 specified, @value{GDBN} may use accesses of any size.
7766 Use 8 bit memory accesses.
7768 Use 16 bit memory accesses.
7770 Use 32 bit memory accesses.
7772 Use 64 bit memory accesses.
7775 @c @subsubsection Hardware/Software Breakpoints
7776 @c The hardware/software breakpoint attributes set whether @value{GDBN}
7777 @c will use hardware or software breakpoints for the internal breakpoints
7778 @c used by the step, next, finish, until, etc. commands.
7782 @c Always use hardware breakpoints
7783 @c @item swbreak (default)
7786 @subsubsection Data Cache
7787 The data cache attributes set whether @value{GDBN} will cache target
7788 memory. While this generally improves performance by reducing debug
7789 protocol overhead, it can lead to incorrect results because @value{GDBN}
7790 does not know about volatile variables or memory mapped device
7795 Enable @value{GDBN} to cache target memory.
7797 Disable @value{GDBN} from caching target memory. This is the default.
7800 @subsection Memory Access Checking
7801 @value{GDBN} can be instructed to refuse accesses to memory that is
7802 not explicitly described. This can be useful if accessing such
7803 regions has undesired effects for a specific target, or to provide
7804 better error checking. The following commands control this behaviour.
7807 @kindex set mem inaccessible-by-default
7808 @item set mem inaccessible-by-default [on|off]
7809 If @code{on} is specified, make @value{GDBN} treat memory not
7810 explicitly described by the memory ranges as non-existent and refuse accesses
7811 to such memory. The checks are only performed if there's at least one
7812 memory range defined. If @code{off} is specified, make @value{GDBN}
7813 treat the memory not explicitly described by the memory ranges as RAM.
7814 The default value is @code{on}.
7815 @kindex show mem inaccessible-by-default
7816 @item show mem inaccessible-by-default
7817 Show the current handling of accesses to unknown memory.
7821 @c @subsubsection Memory Write Verification
7822 @c The memory write verification attributes set whether @value{GDBN}
7823 @c will re-reads data after each write to verify the write was successful.
7827 @c @item noverify (default)
7830 @node Dump/Restore Files
7831 @section Copy Between Memory and a File
7832 @cindex dump/restore files
7833 @cindex append data to a file
7834 @cindex dump data to a file
7835 @cindex restore data from a file
7837 You can use the commands @code{dump}, @code{append}, and
7838 @code{restore} to copy data between target memory and a file. The
7839 @code{dump} and @code{append} commands write data to a file, and the
7840 @code{restore} command reads data from a file back into the inferior's
7841 memory. Files may be in binary, Motorola S-record, Intel hex, or
7842 Tektronix Hex format; however, @value{GDBN} can only append to binary
7848 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
7849 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
7850 Dump the contents of memory from @var{start_addr} to @var{end_addr},
7851 or the value of @var{expr}, to @var{filename} in the given format.
7853 The @var{format} parameter may be any one of:
7860 Motorola S-record format.
7862 Tektronix Hex format.
7865 @value{GDBN} uses the same definitions of these formats as the
7866 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
7867 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
7871 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
7872 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
7873 Append the contents of memory from @var{start_addr} to @var{end_addr},
7874 or the value of @var{expr}, to the file @var{filename}, in raw binary form.
7875 (@value{GDBN} can only append data to files in raw binary form.)
7878 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
7879 Restore the contents of file @var{filename} into memory. The
7880 @code{restore} command can automatically recognize any known @sc{bfd}
7881 file format, except for raw binary. To restore a raw binary file you
7882 must specify the optional keyword @code{binary} after the filename.
7884 If @var{bias} is non-zero, its value will be added to the addresses
7885 contained in the file. Binary files always start at address zero, so
7886 they will be restored at address @var{bias}. Other bfd files have
7887 a built-in location; they will be restored at offset @var{bias}
7890 If @var{start} and/or @var{end} are non-zero, then only data between
7891 file offset @var{start} and file offset @var{end} will be restored.
7892 These offsets are relative to the addresses in the file, before
7893 the @var{bias} argument is applied.
7897 @node Core File Generation
7898 @section How to Produce a Core File from Your Program
7899 @cindex dump core from inferior
7901 A @dfn{core file} or @dfn{core dump} is a file that records the memory
7902 image of a running process and its process status (register values
7903 etc.). Its primary use is post-mortem debugging of a program that
7904 crashed while it ran outside a debugger. A program that crashes
7905 automatically produces a core file, unless this feature is disabled by
7906 the user. @xref{Files}, for information on invoking @value{GDBN} in
7907 the post-mortem debugging mode.
7909 Occasionally, you may wish to produce a core file of the program you
7910 are debugging in order to preserve a snapshot of its state.
7911 @value{GDBN} has a special command for that.
7915 @kindex generate-core-file
7916 @item generate-core-file [@var{file}]
7917 @itemx gcore [@var{file}]
7918 Produce a core dump of the inferior process. The optional argument
7919 @var{file} specifies the file name where to put the core dump. If not
7920 specified, the file name defaults to @file{core.@var{pid}}, where
7921 @var{pid} is the inferior process ID.
7923 Note that this command is implemented only for some systems (as of
7924 this writing, @sc{gnu}/Linux, FreeBSD, Solaris, Unixware, and S390).
7927 @node Character Sets
7928 @section Character Sets
7929 @cindex character sets
7931 @cindex translating between character sets
7932 @cindex host character set
7933 @cindex target character set
7935 If the program you are debugging uses a different character set to
7936 represent characters and strings than the one @value{GDBN} uses itself,
7937 @value{GDBN} can automatically translate between the character sets for
7938 you. The character set @value{GDBN} uses we call the @dfn{host
7939 character set}; the one the inferior program uses we call the
7940 @dfn{target character set}.
7942 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
7943 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
7944 remote protocol (@pxref{Remote Debugging}) to debug a program
7945 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
7946 then the host character set is Latin-1, and the target character set is
7947 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
7948 target-charset EBCDIC-US}, then @value{GDBN} translates between
7949 @sc{ebcdic} and Latin 1 as you print character or string values, or use
7950 character and string literals in expressions.
7952 @value{GDBN} has no way to automatically recognize which character set
7953 the inferior program uses; you must tell it, using the @code{set
7954 target-charset} command, described below.
7956 Here are the commands for controlling @value{GDBN}'s character set
7960 @item set target-charset @var{charset}
7961 @kindex set target-charset
7962 Set the current target character set to @var{charset}. If you type
7963 @code{set target-charset} followed by @key{TAB}@key{TAB}, @value{GDBN}
7964 will list the target character sets it supports.
7966 @item set target-wide-charset @var{charset}
7967 @kindex set target-wide-charset
7968 Set the current target wide character set to @var{charset}. The
7969 target wide character set is the character set used by @code{wchar_t}.
7970 If you type @code{set target-charset} followed by @key{TAB}@key{TAB},
7971 @value{GDBN} will list the target character sets it supports.
7973 @item set host-charset @var{charset}
7974 @kindex set host-charset
7975 Set the current host character set to @var{charset}.
7977 By default, @value{GDBN} uses a host character set appropriate to the
7978 system it is running on; you can override that default using the
7979 @code{set host-charset} command.
7981 @value{GDBN} can only use certain character sets as its host character
7982 set. If you type @code{set target-charset} followed by
7983 @key{TAB}@key{TAB}, @value{GDBN} will list the host character sets it
7986 @item set charset @var{charset}
7988 Set the current host and target character sets to @var{charset}. As
7989 above, if you type @code{set charset} followed by @key{TAB}@key{TAB},
7990 @value{GDBN} will list the name of the character sets that can be used
7991 for both host and target.
7995 @kindex show charset
7996 Show the names of the current host and target charsets.
7998 @itemx show host-charset
7999 @kindex show host-charset
8000 Show the name of the current host charset.
8002 @itemx show target-charset
8003 @kindex show target-charset
8004 Show the name of the current target charset.
8008 Here is an example of @value{GDBN}'s character set support in action.
8009 Assume that the following source code has been placed in the file
8010 @file{charset-test.c}:
8016 = @{72, 101, 108, 108, 111, 44, 32, 119,
8017 111, 114, 108, 100, 33, 10, 0@};
8018 char ibm1047_hello[]
8019 = @{200, 133, 147, 147, 150, 107, 64, 166,
8020 150, 153, 147, 132, 90, 37, 0@};
8024 printf ("Hello, world!\n");
8028 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
8029 containing the string @samp{Hello, world!} followed by a newline,
8030 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
8032 We compile the program, and invoke the debugger on it:
8035 $ gcc -g charset-test.c -o charset-test
8036 $ gdb -nw charset-test
8037 GNU gdb 2001-12-19-cvs
8038 Copyright 2001 Free Software Foundation, Inc.
8043 We can use the @code{show charset} command to see what character sets
8044 @value{GDBN} is currently using to interpret and display characters and
8048 (@value{GDBP}) show charset
8049 The current host and target character set is `ISO-8859-1'.
8053 For the sake of printing this manual, let's use @sc{ascii} as our
8054 initial character set:
8056 (@value{GDBP}) set charset ASCII
8057 (@value{GDBP}) show charset
8058 The current host and target character set is `ASCII'.
8062 Let's assume that @sc{ascii} is indeed the correct character set for our
8063 host system --- in other words, let's assume that if @value{GDBN} prints
8064 characters using the @sc{ascii} character set, our terminal will display
8065 them properly. Since our current target character set is also
8066 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
8069 (@value{GDBP}) print ascii_hello
8070 $1 = 0x401698 "Hello, world!\n"
8071 (@value{GDBP}) print ascii_hello[0]
8076 @value{GDBN} uses the target character set for character and string
8077 literals you use in expressions:
8080 (@value{GDBP}) print '+'
8085 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
8088 @value{GDBN} relies on the user to tell it which character set the
8089 target program uses. If we print @code{ibm1047_hello} while our target
8090 character set is still @sc{ascii}, we get jibberish:
8093 (@value{GDBP}) print ibm1047_hello
8094 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
8095 (@value{GDBP}) print ibm1047_hello[0]
8100 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
8101 @value{GDBN} tells us the character sets it supports:
8104 (@value{GDBP}) set target-charset
8105 ASCII EBCDIC-US IBM1047 ISO-8859-1
8106 (@value{GDBP}) set target-charset
8109 We can select @sc{ibm1047} as our target character set, and examine the
8110 program's strings again. Now the @sc{ascii} string is wrong, but
8111 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
8112 target character set, @sc{ibm1047}, to the host character set,
8113 @sc{ascii}, and they display correctly:
8116 (@value{GDBP}) set target-charset IBM1047
8117 (@value{GDBP}) show charset
8118 The current host character set is `ASCII'.
8119 The current target character set is `IBM1047'.
8120 (@value{GDBP}) print ascii_hello
8121 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
8122 (@value{GDBP}) print ascii_hello[0]
8124 (@value{GDBP}) print ibm1047_hello
8125 $8 = 0x4016a8 "Hello, world!\n"
8126 (@value{GDBP}) print ibm1047_hello[0]
8131 As above, @value{GDBN} uses the target character set for character and
8132 string literals you use in expressions:
8135 (@value{GDBP}) print '+'
8140 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
8143 @node Caching Remote Data
8144 @section Caching Data of Remote Targets
8145 @cindex caching data of remote targets
8147 @value{GDBN} can cache data exchanged between the debugger and a
8148 remote target (@pxref{Remote Debugging}). Such caching generally improves
8149 performance, because it reduces the overhead of the remote protocol by
8150 bundling memory reads and writes into large chunks. Unfortunately,
8151 @value{GDBN} does not currently know anything about volatile
8152 registers, and thus data caching will produce incorrect results when
8153 volatile registers are in use.
8156 @kindex set remotecache
8157 @item set remotecache on
8158 @itemx set remotecache off
8159 Set caching state for remote targets. When @code{ON}, use data
8160 caching. By default, this option is @code{OFF}.
8162 @kindex show remotecache
8163 @item show remotecache
8164 Show the current state of data caching for remote targets.
8168 Print the information about the data cache performance. The
8169 information displayed includes: the dcache width and depth; and for
8170 each cache line, how many times it was referenced, and its data and
8171 state (invalid, dirty, valid). This command is useful for debugging
8172 the data cache operation.
8175 @node Searching Memory
8176 @section Search Memory
8177 @cindex searching memory
8179 Memory can be searched for a particular sequence of bytes with the
8180 @code{find} command.
8184 @item find @r{[}/@var{sn}@r{]} @var{start_addr}, +@var{len}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
8185 @itemx find @r{[}/@var{sn}@r{]} @var{start_addr}, @var{end_addr}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
8186 Search memory for the sequence of bytes specified by @var{val1}, @var{val2},
8187 etc. The search begins at address @var{start_addr} and continues for either
8188 @var{len} bytes or through to @var{end_addr} inclusive.
8191 @var{s} and @var{n} are optional parameters.
8192 They may be specified in either order, apart or together.
8195 @item @var{s}, search query size
8196 The size of each search query value.
8202 halfwords (two bytes)
8206 giant words (eight bytes)
8209 All values are interpreted in the current language.
8210 This means, for example, that if the current source language is C/C@t{++}
8211 then searching for the string ``hello'' includes the trailing '\0'.
8213 If the value size is not specified, it is taken from the
8214 value's type in the current language.
8215 This is useful when one wants to specify the search
8216 pattern as a mixture of types.
8217 Note that this means, for example, that in the case of C-like languages
8218 a search for an untyped 0x42 will search for @samp{(int) 0x42}
8219 which is typically four bytes.
8221 @item @var{n}, maximum number of finds
8222 The maximum number of matches to print. The default is to print all finds.
8225 You can use strings as search values. Quote them with double-quotes
8227 The string value is copied into the search pattern byte by byte,
8228 regardless of the endianness of the target and the size specification.
8230 The address of each match found is printed as well as a count of the
8231 number of matches found.
8233 The address of the last value found is stored in convenience variable
8235 A count of the number of matches is stored in @samp{$numfound}.
8237 For example, if stopped at the @code{printf} in this function:
8243 static char hello[] = "hello-hello";
8244 static struct @{ char c; short s; int i; @}
8245 __attribute__ ((packed)) mixed
8246 = @{ 'c', 0x1234, 0x87654321 @};
8247 printf ("%s\n", hello);
8252 you get during debugging:
8255 (gdb) find &hello[0], +sizeof(hello), "hello"
8256 0x804956d <hello.1620+6>
8258 (gdb) find &hello[0], +sizeof(hello), 'h', 'e', 'l', 'l', 'o'
8259 0x8049567 <hello.1620>
8260 0x804956d <hello.1620+6>
8262 (gdb) find /b1 &hello[0], +sizeof(hello), 'h', 0x65, 'l'
8263 0x8049567 <hello.1620>
8265 (gdb) find &mixed, +sizeof(mixed), (char) 'c', (short) 0x1234, (int) 0x87654321
8266 0x8049560 <mixed.1625>
8268 (gdb) print $numfound
8271 $2 = (void *) 0x8049560
8275 @chapter C Preprocessor Macros
8277 Some languages, such as C and C@t{++}, provide a way to define and invoke
8278 ``preprocessor macros'' which expand into strings of tokens.
8279 @value{GDBN} can evaluate expressions containing macro invocations, show
8280 the result of macro expansion, and show a macro's definition, including
8281 where it was defined.
8283 You may need to compile your program specially to provide @value{GDBN}
8284 with information about preprocessor macros. Most compilers do not
8285 include macros in their debugging information, even when you compile
8286 with the @option{-g} flag. @xref{Compilation}.
8288 A program may define a macro at one point, remove that definition later,
8289 and then provide a different definition after that. Thus, at different
8290 points in the program, a macro may have different definitions, or have
8291 no definition at all. If there is a current stack frame, @value{GDBN}
8292 uses the macros in scope at that frame's source code line. Otherwise,
8293 @value{GDBN} uses the macros in scope at the current listing location;
8296 Whenever @value{GDBN} evaluates an expression, it always expands any
8297 macro invocations present in the expression. @value{GDBN} also provides
8298 the following commands for working with macros explicitly.
8302 @kindex macro expand
8303 @cindex macro expansion, showing the results of preprocessor
8304 @cindex preprocessor macro expansion, showing the results of
8305 @cindex expanding preprocessor macros
8306 @item macro expand @var{expression}
8307 @itemx macro exp @var{expression}
8308 Show the results of expanding all preprocessor macro invocations in
8309 @var{expression}. Since @value{GDBN} simply expands macros, but does
8310 not parse the result, @var{expression} need not be a valid expression;
8311 it can be any string of tokens.
8314 @item macro expand-once @var{expression}
8315 @itemx macro exp1 @var{expression}
8316 @cindex expand macro once
8317 @i{(This command is not yet implemented.)} Show the results of
8318 expanding those preprocessor macro invocations that appear explicitly in
8319 @var{expression}. Macro invocations appearing in that expansion are
8320 left unchanged. This command allows you to see the effect of a
8321 particular macro more clearly, without being confused by further
8322 expansions. Since @value{GDBN} simply expands macros, but does not
8323 parse the result, @var{expression} need not be a valid expression; it
8324 can be any string of tokens.
8327 @cindex macro definition, showing
8328 @cindex definition, showing a macro's
8329 @item info macro @var{macro}
8330 Show the definition of the macro named @var{macro}, and describe the
8331 source location where that definition was established.
8333 @kindex macro define
8334 @cindex user-defined macros
8335 @cindex defining macros interactively
8336 @cindex macros, user-defined
8337 @item macro define @var{macro} @var{replacement-list}
8338 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
8339 Introduce a definition for a preprocessor macro named @var{macro},
8340 invocations of which are replaced by the tokens given in
8341 @var{replacement-list}. The first form of this command defines an
8342 ``object-like'' macro, which takes no arguments; the second form
8343 defines a ``function-like'' macro, which takes the arguments given in
8346 A definition introduced by this command is in scope in every
8347 expression evaluated in @value{GDBN}, until it is removed with the
8348 @code{macro undef} command, described below. The definition overrides
8349 all definitions for @var{macro} present in the program being debugged,
8350 as well as any previous user-supplied definition.
8353 @item macro undef @var{macro}
8354 Remove any user-supplied definition for the macro named @var{macro}.
8355 This command only affects definitions provided with the @code{macro
8356 define} command, described above; it cannot remove definitions present
8357 in the program being debugged.
8361 List all the macros defined using the @code{macro define} command.
8364 @cindex macros, example of debugging with
8365 Here is a transcript showing the above commands in action. First, we
8366 show our source files:
8374 #define ADD(x) (M + x)
8379 printf ("Hello, world!\n");
8381 printf ("We're so creative.\n");
8383 printf ("Goodbye, world!\n");
8390 Now, we compile the program using the @sc{gnu} C compiler, @value{NGCC}.
8391 We pass the @option{-gdwarf-2} and @option{-g3} flags to ensure the
8392 compiler includes information about preprocessor macros in the debugging
8396 $ gcc -gdwarf-2 -g3 sample.c -o sample
8400 Now, we start @value{GDBN} on our sample program:
8404 GNU gdb 2002-05-06-cvs
8405 Copyright 2002 Free Software Foundation, Inc.
8406 GDB is free software, @dots{}
8410 We can expand macros and examine their definitions, even when the
8411 program is not running. @value{GDBN} uses the current listing position
8412 to decide which macro definitions are in scope:
8415 (@value{GDBP}) list main
8418 5 #define ADD(x) (M + x)
8423 10 printf ("Hello, world!\n");
8425 12 printf ("We're so creative.\n");
8426 (@value{GDBP}) info macro ADD
8427 Defined at /home/jimb/gdb/macros/play/sample.c:5
8428 #define ADD(x) (M + x)
8429 (@value{GDBP}) info macro Q
8430 Defined at /home/jimb/gdb/macros/play/sample.h:1
8431 included at /home/jimb/gdb/macros/play/sample.c:2
8433 (@value{GDBP}) macro expand ADD(1)
8434 expands to: (42 + 1)
8435 (@value{GDBP}) macro expand-once ADD(1)
8436 expands to: once (M + 1)
8440 In the example above, note that @code{macro expand-once} expands only
8441 the macro invocation explicit in the original text --- the invocation of
8442 @code{ADD} --- but does not expand the invocation of the macro @code{M},
8443 which was introduced by @code{ADD}.
8445 Once the program is running, @value{GDBN} uses the macro definitions in
8446 force at the source line of the current stack frame:
8449 (@value{GDBP}) break main
8450 Breakpoint 1 at 0x8048370: file sample.c, line 10.
8452 Starting program: /home/jimb/gdb/macros/play/sample
8454 Breakpoint 1, main () at sample.c:10
8455 10 printf ("Hello, world!\n");
8459 At line 10, the definition of the macro @code{N} at line 9 is in force:
8462 (@value{GDBP}) info macro N
8463 Defined at /home/jimb/gdb/macros/play/sample.c:9
8465 (@value{GDBP}) macro expand N Q M
8467 (@value{GDBP}) print N Q M
8472 As we step over directives that remove @code{N}'s definition, and then
8473 give it a new definition, @value{GDBN} finds the definition (or lack
8474 thereof) in force at each point:
8479 12 printf ("We're so creative.\n");
8480 (@value{GDBP}) info macro N
8481 The symbol `N' has no definition as a C/C++ preprocessor macro
8482 at /home/jimb/gdb/macros/play/sample.c:12
8485 14 printf ("Goodbye, world!\n");
8486 (@value{GDBP}) info macro N
8487 Defined at /home/jimb/gdb/macros/play/sample.c:13
8489 (@value{GDBP}) macro expand N Q M
8490 expands to: 1729 < 42
8491 (@value{GDBP}) print N Q M
8498 @chapter Tracepoints
8499 @c This chapter is based on the documentation written by Michael
8500 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
8503 In some applications, it is not feasible for the debugger to interrupt
8504 the program's execution long enough for the developer to learn
8505 anything helpful about its behavior. If the program's correctness
8506 depends on its real-time behavior, delays introduced by a debugger
8507 might cause the program to change its behavior drastically, or perhaps
8508 fail, even when the code itself is correct. It is useful to be able
8509 to observe the program's behavior without interrupting it.
8511 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
8512 specify locations in the program, called @dfn{tracepoints}, and
8513 arbitrary expressions to evaluate when those tracepoints are reached.
8514 Later, using the @code{tfind} command, you can examine the values
8515 those expressions had when the program hit the tracepoints. The
8516 expressions may also denote objects in memory---structures or arrays,
8517 for example---whose values @value{GDBN} should record; while visiting
8518 a particular tracepoint, you may inspect those objects as if they were
8519 in memory at that moment. However, because @value{GDBN} records these
8520 values without interacting with you, it can do so quickly and
8521 unobtrusively, hopefully not disturbing the program's behavior.
8523 The tracepoint facility is currently available only for remote
8524 targets. @xref{Targets}. In addition, your remote target must know
8525 how to collect trace data. This functionality is implemented in the
8526 remote stub; however, none of the stubs distributed with @value{GDBN}
8527 support tracepoints as of this writing. The format of the remote
8528 packets used to implement tracepoints are described in @ref{Tracepoint
8531 This chapter describes the tracepoint commands and features.
8535 * Analyze Collected Data::
8536 * Tracepoint Variables::
8539 @node Set Tracepoints
8540 @section Commands to Set Tracepoints
8542 Before running such a @dfn{trace experiment}, an arbitrary number of
8543 tracepoints can be set. Like a breakpoint (@pxref{Set Breaks}), a
8544 tracepoint has a number assigned to it by @value{GDBN}. Like with
8545 breakpoints, tracepoint numbers are successive integers starting from
8546 one. Many of the commands associated with tracepoints take the
8547 tracepoint number as their argument, to identify which tracepoint to
8550 For each tracepoint, you can specify, in advance, some arbitrary set
8551 of data that you want the target to collect in the trace buffer when
8552 it hits that tracepoint. The collected data can include registers,
8553 local variables, or global data. Later, you can use @value{GDBN}
8554 commands to examine the values these data had at the time the
8557 This section describes commands to set tracepoints and associated
8558 conditions and actions.
8561 * Create and Delete Tracepoints::
8562 * Enable and Disable Tracepoints::
8563 * Tracepoint Passcounts::
8564 * Tracepoint Actions::
8565 * Listing Tracepoints::
8566 * Starting and Stopping Trace Experiments::
8569 @node Create and Delete Tracepoints
8570 @subsection Create and Delete Tracepoints
8573 @cindex set tracepoint
8576 The @code{trace} command is very similar to the @code{break} command.
8577 Its argument can be a source line, a function name, or an address in
8578 the target program. @xref{Set Breaks}. The @code{trace} command
8579 defines a tracepoint, which is a point in the target program where the
8580 debugger will briefly stop, collect some data, and then allow the
8581 program to continue. Setting a tracepoint or changing its commands
8582 doesn't take effect until the next @code{tstart} command; thus, you
8583 cannot change the tracepoint attributes once a trace experiment is
8586 Here are some examples of using the @code{trace} command:
8589 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
8591 (@value{GDBP}) @b{trace +2} // 2 lines forward
8593 (@value{GDBP}) @b{trace my_function} // first source line of function
8595 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
8597 (@value{GDBP}) @b{trace *0x2117c4} // an address
8601 You can abbreviate @code{trace} as @code{tr}.
8604 @cindex last tracepoint number
8605 @cindex recent tracepoint number
8606 @cindex tracepoint number
8607 The convenience variable @code{$tpnum} records the tracepoint number
8608 of the most recently set tracepoint.
8610 @kindex delete tracepoint
8611 @cindex tracepoint deletion
8612 @item delete tracepoint @r{[}@var{num}@r{]}
8613 Permanently delete one or more tracepoints. With no argument, the
8614 default is to delete all tracepoints.
8619 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
8621 (@value{GDBP}) @b{delete trace} // remove all tracepoints
8625 You can abbreviate this command as @code{del tr}.
8628 @node Enable and Disable Tracepoints
8629 @subsection Enable and Disable Tracepoints
8632 @kindex disable tracepoint
8633 @item disable tracepoint @r{[}@var{num}@r{]}
8634 Disable tracepoint @var{num}, or all tracepoints if no argument
8635 @var{num} is given. A disabled tracepoint will have no effect during
8636 the next trace experiment, but it is not forgotten. You can re-enable
8637 a disabled tracepoint using the @code{enable tracepoint} command.
8639 @kindex enable tracepoint
8640 @item enable tracepoint @r{[}@var{num}@r{]}
8641 Enable tracepoint @var{num}, or all tracepoints. The enabled
8642 tracepoints will become effective the next time a trace experiment is
8646 @node Tracepoint Passcounts
8647 @subsection Tracepoint Passcounts
8651 @cindex tracepoint pass count
8652 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
8653 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
8654 automatically stop a trace experiment. If a tracepoint's passcount is
8655 @var{n}, then the trace experiment will be automatically stopped on
8656 the @var{n}'th time that tracepoint is hit. If the tracepoint number
8657 @var{num} is not specified, the @code{passcount} command sets the
8658 passcount of the most recently defined tracepoint. If no passcount is
8659 given, the trace experiment will run until stopped explicitly by the
8665 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
8666 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
8668 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
8669 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
8670 (@value{GDBP}) @b{trace foo}
8671 (@value{GDBP}) @b{pass 3}
8672 (@value{GDBP}) @b{trace bar}
8673 (@value{GDBP}) @b{pass 2}
8674 (@value{GDBP}) @b{trace baz}
8675 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
8676 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
8677 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
8678 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
8682 @node Tracepoint Actions
8683 @subsection Tracepoint Action Lists
8687 @cindex tracepoint actions
8688 @item actions @r{[}@var{num}@r{]}
8689 This command will prompt for a list of actions to be taken when the
8690 tracepoint is hit. If the tracepoint number @var{num} is not
8691 specified, this command sets the actions for the one that was most
8692 recently defined (so that you can define a tracepoint and then say
8693 @code{actions} without bothering about its number). You specify the
8694 actions themselves on the following lines, one action at a time, and
8695 terminate the actions list with a line containing just @code{end}. So
8696 far, the only defined actions are @code{collect} and
8697 @code{while-stepping}.
8699 @cindex remove actions from a tracepoint
8700 To remove all actions from a tracepoint, type @samp{actions @var{num}}
8701 and follow it immediately with @samp{end}.
8704 (@value{GDBP}) @b{collect @var{data}} // collect some data
8706 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
8708 (@value{GDBP}) @b{end} // signals the end of actions.
8711 In the following example, the action list begins with @code{collect}
8712 commands indicating the things to be collected when the tracepoint is
8713 hit. Then, in order to single-step and collect additional data
8714 following the tracepoint, a @code{while-stepping} command is used,
8715 followed by the list of things to be collected while stepping. The
8716 @code{while-stepping} command is terminated by its own separate
8717 @code{end} command. Lastly, the action list is terminated by an
8721 (@value{GDBP}) @b{trace foo}
8722 (@value{GDBP}) @b{actions}
8723 Enter actions for tracepoint 1, one per line:
8732 @kindex collect @r{(tracepoints)}
8733 @item collect @var{expr1}, @var{expr2}, @dots{}
8734 Collect values of the given expressions when the tracepoint is hit.
8735 This command accepts a comma-separated list of any valid expressions.
8736 In addition to global, static, or local variables, the following
8737 special arguments are supported:
8741 collect all registers
8744 collect all function arguments
8747 collect all local variables.
8750 You can give several consecutive @code{collect} commands, each one
8751 with a single argument, or one @code{collect} command with several
8752 arguments separated by commas: the effect is the same.
8754 The command @code{info scope} (@pxref{Symbols, info scope}) is
8755 particularly useful for figuring out what data to collect.
8757 @kindex while-stepping @r{(tracepoints)}
8758 @item while-stepping @var{n}
8759 Perform @var{n} single-step traces after the tracepoint, collecting
8760 new data at each step. The @code{while-stepping} command is
8761 followed by the list of what to collect while stepping (followed by
8762 its own @code{end} command):
8766 > collect $regs, myglobal
8772 You may abbreviate @code{while-stepping} as @code{ws} or
8776 @node Listing Tracepoints
8777 @subsection Listing Tracepoints
8780 @kindex info tracepoints
8782 @cindex information about tracepoints
8783 @item info tracepoints @r{[}@var{num}@r{]}
8784 Display information about the tracepoint @var{num}. If you don't specify
8785 a tracepoint number, displays information about all the tracepoints
8786 defined so far. For each tracepoint, the following information is
8793 whether it is enabled or disabled
8797 its passcount as given by the @code{passcount @var{n}} command
8799 its step count as given by the @code{while-stepping @var{n}} command
8801 where in the source files is the tracepoint set
8803 its action list as given by the @code{actions} command
8807 (@value{GDBP}) @b{info trace}
8808 Num Enb Address PassC StepC What
8809 1 y 0x002117c4 0 0 <gdb_asm>
8810 2 y 0x0020dc64 0 0 in g_test at g_test.c:1375
8811 3 y 0x0020b1f4 0 0 in get_data at ../foo.c:41
8816 This command can be abbreviated @code{info tp}.
8819 @node Starting and Stopping Trace Experiments
8820 @subsection Starting and Stopping Trace Experiments
8824 @cindex start a new trace experiment
8825 @cindex collected data discarded
8827 This command takes no arguments. It starts the trace experiment, and
8828 begins collecting data. This has the side effect of discarding all
8829 the data collected in the trace buffer during the previous trace
8833 @cindex stop a running trace experiment
8835 This command takes no arguments. It ends the trace experiment, and
8836 stops collecting data.
8838 @strong{Note}: a trace experiment and data collection may stop
8839 automatically if any tracepoint's passcount is reached
8840 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
8843 @cindex status of trace data collection
8844 @cindex trace experiment, status of
8846 This command displays the status of the current trace data
8850 Here is an example of the commands we described so far:
8853 (@value{GDBP}) @b{trace gdb_c_test}
8854 (@value{GDBP}) @b{actions}
8855 Enter actions for tracepoint #1, one per line.
8856 > collect $regs,$locals,$args
8861 (@value{GDBP}) @b{tstart}
8862 [time passes @dots{}]
8863 (@value{GDBP}) @b{tstop}
8867 @node Analyze Collected Data
8868 @section Using the Collected Data
8870 After the tracepoint experiment ends, you use @value{GDBN} commands
8871 for examining the trace data. The basic idea is that each tracepoint
8872 collects a trace @dfn{snapshot} every time it is hit and another
8873 snapshot every time it single-steps. All these snapshots are
8874 consecutively numbered from zero and go into a buffer, and you can
8875 examine them later. The way you examine them is to @dfn{focus} on a
8876 specific trace snapshot. When the remote stub is focused on a trace
8877 snapshot, it will respond to all @value{GDBN} requests for memory and
8878 registers by reading from the buffer which belongs to that snapshot,
8879 rather than from @emph{real} memory or registers of the program being
8880 debugged. This means that @strong{all} @value{GDBN} commands
8881 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
8882 behave as if we were currently debugging the program state as it was
8883 when the tracepoint occurred. Any requests for data that are not in
8884 the buffer will fail.
8887 * tfind:: How to select a trace snapshot
8888 * tdump:: How to display all data for a snapshot
8889 * save-tracepoints:: How to save tracepoints for a future run
8893 @subsection @code{tfind @var{n}}
8896 @cindex select trace snapshot
8897 @cindex find trace snapshot
8898 The basic command for selecting a trace snapshot from the buffer is
8899 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
8900 counting from zero. If no argument @var{n} is given, the next
8901 snapshot is selected.
8903 Here are the various forms of using the @code{tfind} command.
8907 Find the first snapshot in the buffer. This is a synonym for
8908 @code{tfind 0} (since 0 is the number of the first snapshot).
8911 Stop debugging trace snapshots, resume @emph{live} debugging.
8914 Same as @samp{tfind none}.
8917 No argument means find the next trace snapshot.
8920 Find the previous trace snapshot before the current one. This permits
8921 retracing earlier steps.
8923 @item tfind tracepoint @var{num}
8924 Find the next snapshot associated with tracepoint @var{num}. Search
8925 proceeds forward from the last examined trace snapshot. If no
8926 argument @var{num} is given, it means find the next snapshot collected
8927 for the same tracepoint as the current snapshot.
8929 @item tfind pc @var{addr}
8930 Find the next snapshot associated with the value @var{addr} of the
8931 program counter. Search proceeds forward from the last examined trace
8932 snapshot. If no argument @var{addr} is given, it means find the next
8933 snapshot with the same value of PC as the current snapshot.
8935 @item tfind outside @var{addr1}, @var{addr2}
8936 Find the next snapshot whose PC is outside the given range of
8939 @item tfind range @var{addr1}, @var{addr2}
8940 Find the next snapshot whose PC is between @var{addr1} and
8941 @var{addr2}. @c FIXME: Is the range inclusive or exclusive?
8943 @item tfind line @r{[}@var{file}:@r{]}@var{n}
8944 Find the next snapshot associated with the source line @var{n}. If
8945 the optional argument @var{file} is given, refer to line @var{n} in
8946 that source file. Search proceeds forward from the last examined
8947 trace snapshot. If no argument @var{n} is given, it means find the
8948 next line other than the one currently being examined; thus saying
8949 @code{tfind line} repeatedly can appear to have the same effect as
8950 stepping from line to line in a @emph{live} debugging session.
8953 The default arguments for the @code{tfind} commands are specifically
8954 designed to make it easy to scan through the trace buffer. For
8955 instance, @code{tfind} with no argument selects the next trace
8956 snapshot, and @code{tfind -} with no argument selects the previous
8957 trace snapshot. So, by giving one @code{tfind} command, and then
8958 simply hitting @key{RET} repeatedly you can examine all the trace
8959 snapshots in order. Or, by saying @code{tfind -} and then hitting
8960 @key{RET} repeatedly you can examine the snapshots in reverse order.
8961 The @code{tfind line} command with no argument selects the snapshot
8962 for the next source line executed. The @code{tfind pc} command with
8963 no argument selects the next snapshot with the same program counter
8964 (PC) as the current frame. The @code{tfind tracepoint} command with
8965 no argument selects the next trace snapshot collected by the same
8966 tracepoint as the current one.
8968 In addition to letting you scan through the trace buffer manually,
8969 these commands make it easy to construct @value{GDBN} scripts that
8970 scan through the trace buffer and print out whatever collected data
8971 you are interested in. Thus, if we want to examine the PC, FP, and SP
8972 registers from each trace frame in the buffer, we can say this:
8975 (@value{GDBP}) @b{tfind start}
8976 (@value{GDBP}) @b{while ($trace_frame != -1)}
8977 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
8978 $trace_frame, $pc, $sp, $fp
8982 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
8983 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
8984 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
8985 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
8986 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
8987 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
8988 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
8989 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
8990 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
8991 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
8992 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
8995 Or, if we want to examine the variable @code{X} at each source line in
8999 (@value{GDBP}) @b{tfind start}
9000 (@value{GDBP}) @b{while ($trace_frame != -1)}
9001 > printf "Frame %d, X == %d\n", $trace_frame, X
9011 @subsection @code{tdump}
9013 @cindex dump all data collected at tracepoint
9014 @cindex tracepoint data, display
9016 This command takes no arguments. It prints all the data collected at
9017 the current trace snapshot.
9020 (@value{GDBP}) @b{trace 444}
9021 (@value{GDBP}) @b{actions}
9022 Enter actions for tracepoint #2, one per line:
9023 > collect $regs, $locals, $args, gdb_long_test
9026 (@value{GDBP}) @b{tstart}
9028 (@value{GDBP}) @b{tfind line 444}
9029 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
9031 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
9033 (@value{GDBP}) @b{tdump}
9034 Data collected at tracepoint 2, trace frame 1:
9035 d0 0xc4aa0085 -995491707
9039 d4 0x71aea3d 119204413
9044 a1 0x3000668 50333288
9047 a4 0x3000698 50333336
9049 fp 0x30bf3c 0x30bf3c
9050 sp 0x30bf34 0x30bf34
9052 pc 0x20b2c8 0x20b2c8
9056 p = 0x20e5b4 "gdb-test"
9063 gdb_long_test = 17 '\021'
9068 @node save-tracepoints
9069 @subsection @code{save-tracepoints @var{filename}}
9070 @kindex save-tracepoints
9071 @cindex save tracepoints for future sessions
9073 This command saves all current tracepoint definitions together with
9074 their actions and passcounts, into a file @file{@var{filename}}
9075 suitable for use in a later debugging session. To read the saved
9076 tracepoint definitions, use the @code{source} command (@pxref{Command
9079 @node Tracepoint Variables
9080 @section Convenience Variables for Tracepoints
9081 @cindex tracepoint variables
9082 @cindex convenience variables for tracepoints
9085 @vindex $trace_frame
9086 @item (int) $trace_frame
9087 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
9088 snapshot is selected.
9091 @item (int) $tracepoint
9092 The tracepoint for the current trace snapshot.
9095 @item (int) $trace_line
9096 The line number for the current trace snapshot.
9099 @item (char []) $trace_file
9100 The source file for the current trace snapshot.
9103 @item (char []) $trace_func
9104 The name of the function containing @code{$tracepoint}.
9107 Note: @code{$trace_file} is not suitable for use in @code{printf},
9108 use @code{output} instead.
9110 Here's a simple example of using these convenience variables for
9111 stepping through all the trace snapshots and printing some of their
9115 (@value{GDBP}) @b{tfind start}
9117 (@value{GDBP}) @b{while $trace_frame != -1}
9118 > output $trace_file
9119 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
9125 @chapter Debugging Programs That Use Overlays
9128 If your program is too large to fit completely in your target system's
9129 memory, you can sometimes use @dfn{overlays} to work around this
9130 problem. @value{GDBN} provides some support for debugging programs that
9134 * How Overlays Work:: A general explanation of overlays.
9135 * Overlay Commands:: Managing overlays in @value{GDBN}.
9136 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
9137 mapped by asking the inferior.
9138 * Overlay Sample Program:: A sample program using overlays.
9141 @node How Overlays Work
9142 @section How Overlays Work
9143 @cindex mapped overlays
9144 @cindex unmapped overlays
9145 @cindex load address, overlay's
9146 @cindex mapped address
9147 @cindex overlay area
9149 Suppose you have a computer whose instruction address space is only 64
9150 kilobytes long, but which has much more memory which can be accessed by
9151 other means: special instructions, segment registers, or memory
9152 management hardware, for example. Suppose further that you want to
9153 adapt a program which is larger than 64 kilobytes to run on this system.
9155 One solution is to identify modules of your program which are relatively
9156 independent, and need not call each other directly; call these modules
9157 @dfn{overlays}. Separate the overlays from the main program, and place
9158 their machine code in the larger memory. Place your main program in
9159 instruction memory, but leave at least enough space there to hold the
9160 largest overlay as well.
9162 Now, to call a function located in an overlay, you must first copy that
9163 overlay's machine code from the large memory into the space set aside
9164 for it in the instruction memory, and then jump to its entry point
9167 @c NB: In the below the mapped area's size is greater or equal to the
9168 @c size of all overlays. This is intentional to remind the developer
9169 @c that overlays don't necessarily need to be the same size.
9173 Data Instruction Larger
9174 Address Space Address Space Address Space
9175 +-----------+ +-----------+ +-----------+
9177 +-----------+ +-----------+ +-----------+<-- overlay 1
9178 | program | | main | .----| overlay 1 | load address
9179 | variables | | program | | +-----------+
9180 | and heap | | | | | |
9181 +-----------+ | | | +-----------+<-- overlay 2
9182 | | +-----------+ | | | load address
9183 +-----------+ | | | .-| overlay 2 |
9185 mapped --->+-----------+ | | +-----------+
9187 | overlay | <-' | | |
9188 | area | <---' +-----------+<-- overlay 3
9189 | | <---. | | load address
9190 +-----------+ `--| overlay 3 |
9197 @anchor{A code overlay}A code overlay
9201 The diagram (@pxref{A code overlay}) shows a system with separate data
9202 and instruction address spaces. To map an overlay, the program copies
9203 its code from the larger address space to the instruction address space.
9204 Since the overlays shown here all use the same mapped address, only one
9205 may be mapped at a time. For a system with a single address space for
9206 data and instructions, the diagram would be similar, except that the
9207 program variables and heap would share an address space with the main
9208 program and the overlay area.
9210 An overlay loaded into instruction memory and ready for use is called a
9211 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
9212 instruction memory. An overlay not present (or only partially present)
9213 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
9214 is its address in the larger memory. The mapped address is also called
9215 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
9216 called the @dfn{load memory address}, or @dfn{LMA}.
9218 Unfortunately, overlays are not a completely transparent way to adapt a
9219 program to limited instruction memory. They introduce a new set of
9220 global constraints you must keep in mind as you design your program:
9225 Before calling or returning to a function in an overlay, your program
9226 must make sure that overlay is actually mapped. Otherwise, the call or
9227 return will transfer control to the right address, but in the wrong
9228 overlay, and your program will probably crash.
9231 If the process of mapping an overlay is expensive on your system, you
9232 will need to choose your overlays carefully to minimize their effect on
9233 your program's performance.
9236 The executable file you load onto your system must contain each
9237 overlay's instructions, appearing at the overlay's load address, not its
9238 mapped address. However, each overlay's instructions must be relocated
9239 and its symbols defined as if the overlay were at its mapped address.
9240 You can use GNU linker scripts to specify different load and relocation
9241 addresses for pieces of your program; see @ref{Overlay Description,,,
9242 ld.info, Using ld: the GNU linker}.
9245 The procedure for loading executable files onto your system must be able
9246 to load their contents into the larger address space as well as the
9247 instruction and data spaces.
9251 The overlay system described above is rather simple, and could be
9252 improved in many ways:
9257 If your system has suitable bank switch registers or memory management
9258 hardware, you could use those facilities to make an overlay's load area
9259 contents simply appear at their mapped address in instruction space.
9260 This would probably be faster than copying the overlay to its mapped
9261 area in the usual way.
9264 If your overlays are small enough, you could set aside more than one
9265 overlay area, and have more than one overlay mapped at a time.
9268 You can use overlays to manage data, as well as instructions. In
9269 general, data overlays are even less transparent to your design than
9270 code overlays: whereas code overlays only require care when you call or
9271 return to functions, data overlays require care every time you access
9272 the data. Also, if you change the contents of a data overlay, you
9273 must copy its contents back out to its load address before you can copy a
9274 different data overlay into the same mapped area.
9279 @node Overlay Commands
9280 @section Overlay Commands
9282 To use @value{GDBN}'s overlay support, each overlay in your program must
9283 correspond to a separate section of the executable file. The section's
9284 virtual memory address and load memory address must be the overlay's
9285 mapped and load addresses. Identifying overlays with sections allows
9286 @value{GDBN} to determine the appropriate address of a function or
9287 variable, depending on whether the overlay is mapped or not.
9289 @value{GDBN}'s overlay commands all start with the word @code{overlay};
9290 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
9295 Disable @value{GDBN}'s overlay support. When overlay support is
9296 disabled, @value{GDBN} assumes that all functions and variables are
9297 always present at their mapped addresses. By default, @value{GDBN}'s
9298 overlay support is disabled.
9300 @item overlay manual
9301 @cindex manual overlay debugging
9302 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
9303 relies on you to tell it which overlays are mapped, and which are not,
9304 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
9305 commands described below.
9307 @item overlay map-overlay @var{overlay}
9308 @itemx overlay map @var{overlay}
9309 @cindex map an overlay
9310 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
9311 be the name of the object file section containing the overlay. When an
9312 overlay is mapped, @value{GDBN} assumes it can find the overlay's
9313 functions and variables at their mapped addresses. @value{GDBN} assumes
9314 that any other overlays whose mapped ranges overlap that of
9315 @var{overlay} are now unmapped.
9317 @item overlay unmap-overlay @var{overlay}
9318 @itemx overlay unmap @var{overlay}
9319 @cindex unmap an overlay
9320 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
9321 must be the name of the object file section containing the overlay.
9322 When an overlay is unmapped, @value{GDBN} assumes it can find the
9323 overlay's functions and variables at their load addresses.
9326 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
9327 consults a data structure the overlay manager maintains in the inferior
9328 to see which overlays are mapped. For details, see @ref{Automatic
9331 @item overlay load-target
9333 @cindex reloading the overlay table
9334 Re-read the overlay table from the inferior. Normally, @value{GDBN}
9335 re-reads the table @value{GDBN} automatically each time the inferior
9336 stops, so this command should only be necessary if you have changed the
9337 overlay mapping yourself using @value{GDBN}. This command is only
9338 useful when using automatic overlay debugging.
9340 @item overlay list-overlays
9342 @cindex listing mapped overlays
9343 Display a list of the overlays currently mapped, along with their mapped
9344 addresses, load addresses, and sizes.
9348 Normally, when @value{GDBN} prints a code address, it includes the name
9349 of the function the address falls in:
9352 (@value{GDBP}) print main
9353 $3 = @{int ()@} 0x11a0 <main>
9356 When overlay debugging is enabled, @value{GDBN} recognizes code in
9357 unmapped overlays, and prints the names of unmapped functions with
9358 asterisks around them. For example, if @code{foo} is a function in an
9359 unmapped overlay, @value{GDBN} prints it this way:
9362 (@value{GDBP}) overlay list
9363 No sections are mapped.
9364 (@value{GDBP}) print foo
9365 $5 = @{int (int)@} 0x100000 <*foo*>
9368 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
9372 (@value{GDBP}) overlay list
9373 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
9374 mapped at 0x1016 - 0x104a
9375 (@value{GDBP}) print foo
9376 $6 = @{int (int)@} 0x1016 <foo>
9379 When overlay debugging is enabled, @value{GDBN} can find the correct
9380 address for functions and variables in an overlay, whether or not the
9381 overlay is mapped. This allows most @value{GDBN} commands, like
9382 @code{break} and @code{disassemble}, to work normally, even on unmapped
9383 code. However, @value{GDBN}'s breakpoint support has some limitations:
9387 @cindex breakpoints in overlays
9388 @cindex overlays, setting breakpoints in
9389 You can set breakpoints in functions in unmapped overlays, as long as
9390 @value{GDBN} can write to the overlay at its load address.
9392 @value{GDBN} can not set hardware or simulator-based breakpoints in
9393 unmapped overlays. However, if you set a breakpoint at the end of your
9394 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
9395 you are using manual overlay management), @value{GDBN} will re-set its
9396 breakpoints properly.
9400 @node Automatic Overlay Debugging
9401 @section Automatic Overlay Debugging
9402 @cindex automatic overlay debugging
9404 @value{GDBN} can automatically track which overlays are mapped and which
9405 are not, given some simple co-operation from the overlay manager in the
9406 inferior. If you enable automatic overlay debugging with the
9407 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
9408 looks in the inferior's memory for certain variables describing the
9409 current state of the overlays.
9411 Here are the variables your overlay manager must define to support
9412 @value{GDBN}'s automatic overlay debugging:
9416 @item @code{_ovly_table}:
9417 This variable must be an array of the following structures:
9422 /* The overlay's mapped address. */
9425 /* The size of the overlay, in bytes. */
9428 /* The overlay's load address. */
9431 /* Non-zero if the overlay is currently mapped;
9433 unsigned long mapped;
9437 @item @code{_novlys}:
9438 This variable must be a four-byte signed integer, holding the total
9439 number of elements in @code{_ovly_table}.
9443 To decide whether a particular overlay is mapped or not, @value{GDBN}
9444 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
9445 @code{lma} members equal the VMA and LMA of the overlay's section in the
9446 executable file. When @value{GDBN} finds a matching entry, it consults
9447 the entry's @code{mapped} member to determine whether the overlay is
9450 In addition, your overlay manager may define a function called
9451 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
9452 will silently set a breakpoint there. If the overlay manager then
9453 calls this function whenever it has changed the overlay table, this
9454 will enable @value{GDBN} to accurately keep track of which overlays
9455 are in program memory, and update any breakpoints that may be set
9456 in overlays. This will allow breakpoints to work even if the
9457 overlays are kept in ROM or other non-writable memory while they
9458 are not being executed.
9460 @node Overlay Sample Program
9461 @section Overlay Sample Program
9462 @cindex overlay example program
9464 When linking a program which uses overlays, you must place the overlays
9465 at their load addresses, while relocating them to run at their mapped
9466 addresses. To do this, you must write a linker script (@pxref{Overlay
9467 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
9468 since linker scripts are specific to a particular host system, target
9469 architecture, and target memory layout, this manual cannot provide
9470 portable sample code demonstrating @value{GDBN}'s overlay support.
9472 However, the @value{GDBN} source distribution does contain an overlaid
9473 program, with linker scripts for a few systems, as part of its test
9474 suite. The program consists of the following files from
9475 @file{gdb/testsuite/gdb.base}:
9479 The main program file.
9481 A simple overlay manager, used by @file{overlays.c}.
9486 Overlay modules, loaded and used by @file{overlays.c}.
9489 Linker scripts for linking the test program on the @code{d10v-elf}
9490 and @code{m32r-elf} targets.
9493 You can build the test program using the @code{d10v-elf} GCC
9494 cross-compiler like this:
9497 $ d10v-elf-gcc -g -c overlays.c
9498 $ d10v-elf-gcc -g -c ovlymgr.c
9499 $ d10v-elf-gcc -g -c foo.c
9500 $ d10v-elf-gcc -g -c bar.c
9501 $ d10v-elf-gcc -g -c baz.c
9502 $ d10v-elf-gcc -g -c grbx.c
9503 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
9504 baz.o grbx.o -Wl,-Td10v.ld -o overlays
9507 The build process is identical for any other architecture, except that
9508 you must substitute the appropriate compiler and linker script for the
9509 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
9513 @chapter Using @value{GDBN} with Different Languages
9516 Although programming languages generally have common aspects, they are
9517 rarely expressed in the same manner. For instance, in ANSI C,
9518 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
9519 Modula-2, it is accomplished by @code{p^}. Values can also be
9520 represented (and displayed) differently. Hex numbers in C appear as
9521 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
9523 @cindex working language
9524 Language-specific information is built into @value{GDBN} for some languages,
9525 allowing you to express operations like the above in your program's
9526 native language, and allowing @value{GDBN} to output values in a manner
9527 consistent with the syntax of your program's native language. The
9528 language you use to build expressions is called the @dfn{working
9532 * Setting:: Switching between source languages
9533 * Show:: Displaying the language
9534 * Checks:: Type and range checks
9535 * Supported Languages:: Supported languages
9536 * Unsupported Languages:: Unsupported languages
9540 @section Switching Between Source Languages
9542 There are two ways to control the working language---either have @value{GDBN}
9543 set it automatically, or select it manually yourself. You can use the
9544 @code{set language} command for either purpose. On startup, @value{GDBN}
9545 defaults to setting the language automatically. The working language is
9546 used to determine how expressions you type are interpreted, how values
9549 In addition to the working language, every source file that
9550 @value{GDBN} knows about has its own working language. For some object
9551 file formats, the compiler might indicate which language a particular
9552 source file is in. However, most of the time @value{GDBN} infers the
9553 language from the name of the file. The language of a source file
9554 controls whether C@t{++} names are demangled---this way @code{backtrace} can
9555 show each frame appropriately for its own language. There is no way to
9556 set the language of a source file from within @value{GDBN}, but you can
9557 set the language associated with a filename extension. @xref{Show, ,
9558 Displaying the Language}.
9560 This is most commonly a problem when you use a program, such
9561 as @code{cfront} or @code{f2c}, that generates C but is written in
9562 another language. In that case, make the
9563 program use @code{#line} directives in its C output; that way
9564 @value{GDBN} will know the correct language of the source code of the original
9565 program, and will display that source code, not the generated C code.
9568 * Filenames:: Filename extensions and languages.
9569 * Manually:: Setting the working language manually
9570 * Automatically:: Having @value{GDBN} infer the source language
9574 @subsection List of Filename Extensions and Languages
9576 If a source file name ends in one of the following extensions, then
9577 @value{GDBN} infers that its language is the one indicated.
9598 Objective-C source file
9605 Modula-2 source file
9609 Assembler source file. This actually behaves almost like C, but
9610 @value{GDBN} does not skip over function prologues when stepping.
9613 In addition, you may set the language associated with a filename
9614 extension. @xref{Show, , Displaying the Language}.
9617 @subsection Setting the Working Language
9619 If you allow @value{GDBN} to set the language automatically,
9620 expressions are interpreted the same way in your debugging session and
9623 @kindex set language
9624 If you wish, you may set the language manually. To do this, issue the
9625 command @samp{set language @var{lang}}, where @var{lang} is the name of
9627 @code{c} or @code{modula-2}.
9628 For a list of the supported languages, type @samp{set language}.
9630 Setting the language manually prevents @value{GDBN} from updating the working
9631 language automatically. This can lead to confusion if you try
9632 to debug a program when the working language is not the same as the
9633 source language, when an expression is acceptable to both
9634 languages---but means different things. For instance, if the current
9635 source file were written in C, and @value{GDBN} was parsing Modula-2, a
9643 might not have the effect you intended. In C, this means to add
9644 @code{b} and @code{c} and place the result in @code{a}. The result
9645 printed would be the value of @code{a}. In Modula-2, this means to compare
9646 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
9649 @subsection Having @value{GDBN} Infer the Source Language
9651 To have @value{GDBN} set the working language automatically, use
9652 @samp{set language local} or @samp{set language auto}. @value{GDBN}
9653 then infers the working language. That is, when your program stops in a
9654 frame (usually by encountering a breakpoint), @value{GDBN} sets the
9655 working language to the language recorded for the function in that
9656 frame. If the language for a frame is unknown (that is, if the function
9657 or block corresponding to the frame was defined in a source file that
9658 does not have a recognized extension), the current working language is
9659 not changed, and @value{GDBN} issues a warning.
9661 This may not seem necessary for most programs, which are written
9662 entirely in one source language. However, program modules and libraries
9663 written in one source language can be used by a main program written in
9664 a different source language. Using @samp{set language auto} in this
9665 case frees you from having to set the working language manually.
9668 @section Displaying the Language
9670 The following commands help you find out which language is the
9671 working language, and also what language source files were written in.
9675 @kindex show language
9676 Display the current working language. This is the
9677 language you can use with commands such as @code{print} to
9678 build and compute expressions that may involve variables in your program.
9681 @kindex info frame@r{, show the source language}
9682 Display the source language for this frame. This language becomes the
9683 working language if you use an identifier from this frame.
9684 @xref{Frame Info, ,Information about a Frame}, to identify the other
9685 information listed here.
9688 @kindex info source@r{, show the source language}
9689 Display the source language of this source file.
9690 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
9691 information listed here.
9694 In unusual circumstances, you may have source files with extensions
9695 not in the standard list. You can then set the extension associated
9696 with a language explicitly:
9699 @item set extension-language @var{ext} @var{language}
9700 @kindex set extension-language
9701 Tell @value{GDBN} that source files with extension @var{ext} are to be
9702 assumed as written in the source language @var{language}.
9704 @item info extensions
9705 @kindex info extensions
9706 List all the filename extensions and the associated languages.
9710 @section Type and Range Checking
9713 @emph{Warning:} In this release, the @value{GDBN} commands for type and range
9714 checking are included, but they do not yet have any effect. This
9715 section documents the intended facilities.
9717 @c FIXME remove warning when type/range code added
9719 Some languages are designed to guard you against making seemingly common
9720 errors through a series of compile- and run-time checks. These include
9721 checking the type of arguments to functions and operators, and making
9722 sure mathematical overflows are caught at run time. Checks such as
9723 these help to ensure a program's correctness once it has been compiled
9724 by eliminating type mismatches, and providing active checks for range
9725 errors when your program is running.
9727 @value{GDBN} can check for conditions like the above if you wish.
9728 Although @value{GDBN} does not check the statements in your program,
9729 it can check expressions entered directly into @value{GDBN} for
9730 evaluation via the @code{print} command, for example. As with the
9731 working language, @value{GDBN} can also decide whether or not to check
9732 automatically based on your program's source language.
9733 @xref{Supported Languages, ,Supported Languages}, for the default
9734 settings of supported languages.
9737 * Type Checking:: An overview of type checking
9738 * Range Checking:: An overview of range checking
9741 @cindex type checking
9742 @cindex checks, type
9744 @subsection An Overview of Type Checking
9746 Some languages, such as Modula-2, are strongly typed, meaning that the
9747 arguments to operators and functions have to be of the correct type,
9748 otherwise an error occurs. These checks prevent type mismatch
9749 errors from ever causing any run-time problems. For example,
9757 The second example fails because the @code{CARDINAL} 1 is not
9758 type-compatible with the @code{REAL} 2.3.
9760 For the expressions you use in @value{GDBN} commands, you can tell the
9761 @value{GDBN} type checker to skip checking;
9762 to treat any mismatches as errors and abandon the expression;
9763 or to only issue warnings when type mismatches occur,
9764 but evaluate the expression anyway. When you choose the last of
9765 these, @value{GDBN} evaluates expressions like the second example above, but
9766 also issues a warning.
9768 Even if you turn type checking off, there may be other reasons
9769 related to type that prevent @value{GDBN} from evaluating an expression.
9770 For instance, @value{GDBN} does not know how to add an @code{int} and
9771 a @code{struct foo}. These particular type errors have nothing to do
9772 with the language in use, and usually arise from expressions, such as
9773 the one described above, which make little sense to evaluate anyway.
9775 Each language defines to what degree it is strict about type. For
9776 instance, both Modula-2 and C require the arguments to arithmetical
9777 operators to be numbers. In C, enumerated types and pointers can be
9778 represented as numbers, so that they are valid arguments to mathematical
9779 operators. @xref{Supported Languages, ,Supported Languages}, for further
9780 details on specific languages.
9782 @value{GDBN} provides some additional commands for controlling the type checker:
9784 @kindex set check type
9785 @kindex show check type
9787 @item set check type auto
9788 Set type checking on or off based on the current working language.
9789 @xref{Supported Languages, ,Supported Languages}, for the default settings for
9792 @item set check type on
9793 @itemx set check type off
9794 Set type checking on or off, overriding the default setting for the
9795 current working language. Issue a warning if the setting does not
9796 match the language default. If any type mismatches occur in
9797 evaluating an expression while type checking is on, @value{GDBN} prints a
9798 message and aborts evaluation of the expression.
9800 @item set check type warn
9801 Cause the type checker to issue warnings, but to always attempt to
9802 evaluate the expression. Evaluating the expression may still
9803 be impossible for other reasons. For example, @value{GDBN} cannot add
9804 numbers and structures.
9807 Show the current setting of the type checker, and whether or not @value{GDBN}
9808 is setting it automatically.
9811 @cindex range checking
9812 @cindex checks, range
9813 @node Range Checking
9814 @subsection An Overview of Range Checking
9816 In some languages (such as Modula-2), it is an error to exceed the
9817 bounds of a type; this is enforced with run-time checks. Such range
9818 checking is meant to ensure program correctness by making sure
9819 computations do not overflow, or indices on an array element access do
9820 not exceed the bounds of the array.
9822 For expressions you use in @value{GDBN} commands, you can tell
9823 @value{GDBN} to treat range errors in one of three ways: ignore them,
9824 always treat them as errors and abandon the expression, or issue
9825 warnings but evaluate the expression anyway.
9827 A range error can result from numerical overflow, from exceeding an
9828 array index bound, or when you type a constant that is not a member
9829 of any type. Some languages, however, do not treat overflows as an
9830 error. In many implementations of C, mathematical overflow causes the
9831 result to ``wrap around'' to lower values---for example, if @var{m} is
9832 the largest integer value, and @var{s} is the smallest, then
9835 @var{m} + 1 @result{} @var{s}
9838 This, too, is specific to individual languages, and in some cases
9839 specific to individual compilers or machines. @xref{Supported Languages, ,
9840 Supported Languages}, for further details on specific languages.
9842 @value{GDBN} provides some additional commands for controlling the range checker:
9844 @kindex set check range
9845 @kindex show check range
9847 @item set check range auto
9848 Set range checking on or off based on the current working language.
9849 @xref{Supported Languages, ,Supported Languages}, for the default settings for
9852 @item set check range on
9853 @itemx set check range off
9854 Set range checking on or off, overriding the default setting for the
9855 current working language. A warning is issued if the setting does not
9856 match the language default. If a range error occurs and range checking is on,
9857 then a message is printed and evaluation of the expression is aborted.
9859 @item set check range warn
9860 Output messages when the @value{GDBN} range checker detects a range error,
9861 but attempt to evaluate the expression anyway. Evaluating the
9862 expression may still be impossible for other reasons, such as accessing
9863 memory that the process does not own (a typical example from many Unix
9867 Show the current setting of the range checker, and whether or not it is
9868 being set automatically by @value{GDBN}.
9871 @node Supported Languages
9872 @section Supported Languages
9874 @value{GDBN} supports C, C@t{++}, Objective-C, Fortran, Java, Pascal,
9875 assembly, Modula-2, and Ada.
9876 @c This is false ...
9877 Some @value{GDBN} features may be used in expressions regardless of the
9878 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
9879 and the @samp{@{type@}addr} construct (@pxref{Expressions,
9880 ,Expressions}) can be used with the constructs of any supported
9883 The following sections detail to what degree each source language is
9884 supported by @value{GDBN}. These sections are not meant to be language
9885 tutorials or references, but serve only as a reference guide to what the
9886 @value{GDBN} expression parser accepts, and what input and output
9887 formats should look like for different languages. There are many good
9888 books written on each of these languages; please look to these for a
9889 language reference or tutorial.
9893 * Objective-C:: Objective-C
9896 * Modula-2:: Modula-2
9901 @subsection C and C@t{++}
9903 @cindex C and C@t{++}
9904 @cindex expressions in C or C@t{++}
9906 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
9907 to both languages. Whenever this is the case, we discuss those languages
9911 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
9912 @cindex @sc{gnu} C@t{++}
9913 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
9914 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
9915 effectively, you must compile your C@t{++} programs with a supported
9916 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
9917 compiler (@code{aCC}).
9919 For best results when using @sc{gnu} C@t{++}, use the DWARF 2 debugging
9920 format; if it doesn't work on your system, try the stabs+ debugging
9921 format. You can select those formats explicitly with the @code{g++}
9922 command-line options @option{-gdwarf-2} and @option{-gstabs+}.
9923 @xref{Debugging Options,,Options for Debugging Your Program or GCC,
9924 gcc.info, Using the @sc{gnu} Compiler Collection (GCC)}.
9927 * C Operators:: C and C@t{++} operators
9928 * C Constants:: C and C@t{++} constants
9929 * C Plus Plus Expressions:: C@t{++} expressions
9930 * C Defaults:: Default settings for C and C@t{++}
9931 * C Checks:: C and C@t{++} type and range checks
9932 * Debugging C:: @value{GDBN} and C
9933 * Debugging C Plus Plus:: @value{GDBN} features for C@t{++}
9934 * Decimal Floating Point:: Numbers in Decimal Floating Point format
9938 @subsubsection C and C@t{++} Operators
9940 @cindex C and C@t{++} operators
9942 Operators must be defined on values of specific types. For instance,
9943 @code{+} is defined on numbers, but not on structures. Operators are
9944 often defined on groups of types.
9946 For the purposes of C and C@t{++}, the following definitions hold:
9951 @emph{Integral types} include @code{int} with any of its storage-class
9952 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
9955 @emph{Floating-point types} include @code{float}, @code{double}, and
9956 @code{long double} (if supported by the target platform).
9959 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
9962 @emph{Scalar types} include all of the above.
9967 The following operators are supported. They are listed here
9968 in order of increasing precedence:
9972 The comma or sequencing operator. Expressions in a comma-separated list
9973 are evaluated from left to right, with the result of the entire
9974 expression being the last expression evaluated.
9977 Assignment. The value of an assignment expression is the value
9978 assigned. Defined on scalar types.
9981 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
9982 and translated to @w{@code{@var{a} = @var{a op b}}}.
9983 @w{@code{@var{op}=}} and @code{=} have the same precedence.
9984 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
9985 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
9988 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
9989 of as: if @var{a} then @var{b} else @var{c}. @var{a} should be of an
9993 Logical @sc{or}. Defined on integral types.
9996 Logical @sc{and}. Defined on integral types.
9999 Bitwise @sc{or}. Defined on integral types.
10002 Bitwise exclusive-@sc{or}. Defined on integral types.
10005 Bitwise @sc{and}. Defined on integral types.
10008 Equality and inequality. Defined on scalar types. The value of these
10009 expressions is 0 for false and non-zero for true.
10011 @item <@r{, }>@r{, }<=@r{, }>=
10012 Less than, greater than, less than or equal, greater than or equal.
10013 Defined on scalar types. The value of these expressions is 0 for false
10014 and non-zero for true.
10017 left shift, and right shift. Defined on integral types.
10020 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
10023 Addition and subtraction. Defined on integral types, floating-point types and
10026 @item *@r{, }/@r{, }%
10027 Multiplication, division, and modulus. Multiplication and division are
10028 defined on integral and floating-point types. Modulus is defined on
10032 Increment and decrement. When appearing before a variable, the
10033 operation is performed before the variable is used in an expression;
10034 when appearing after it, the variable's value is used before the
10035 operation takes place.
10038 Pointer dereferencing. Defined on pointer types. Same precedence as
10042 Address operator. Defined on variables. Same precedence as @code{++}.
10044 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
10045 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
10046 to examine the address
10047 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
10051 Negative. Defined on integral and floating-point types. Same
10052 precedence as @code{++}.
10055 Logical negation. Defined on integral types. Same precedence as
10059 Bitwise complement operator. Defined on integral types. Same precedence as
10064 Structure member, and pointer-to-structure member. For convenience,
10065 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
10066 pointer based on the stored type information.
10067 Defined on @code{struct} and @code{union} data.
10070 Dereferences of pointers to members.
10073 Array indexing. @code{@var{a}[@var{i}]} is defined as
10074 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
10077 Function parameter list. Same precedence as @code{->}.
10080 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
10081 and @code{class} types.
10084 Doubled colons also represent the @value{GDBN} scope operator
10085 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
10089 If an operator is redefined in the user code, @value{GDBN} usually
10090 attempts to invoke the redefined version instead of using the operator's
10091 predefined meaning.
10094 @subsubsection C and C@t{++} Constants
10096 @cindex C and C@t{++} constants
10098 @value{GDBN} allows you to express the constants of C and C@t{++} in the
10103 Integer constants are a sequence of digits. Octal constants are
10104 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
10105 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
10106 @samp{l}, specifying that the constant should be treated as a
10110 Floating point constants are a sequence of digits, followed by a decimal
10111 point, followed by a sequence of digits, and optionally followed by an
10112 exponent. An exponent is of the form:
10113 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
10114 sequence of digits. The @samp{+} is optional for positive exponents.
10115 A floating-point constant may also end with a letter @samp{f} or
10116 @samp{F}, specifying that the constant should be treated as being of
10117 the @code{float} (as opposed to the default @code{double}) type; or with
10118 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
10122 Enumerated constants consist of enumerated identifiers, or their
10123 integral equivalents.
10126 Character constants are a single character surrounded by single quotes
10127 (@code{'}), or a number---the ordinal value of the corresponding character
10128 (usually its @sc{ascii} value). Within quotes, the single character may
10129 be represented by a letter or by @dfn{escape sequences}, which are of
10130 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
10131 of the character's ordinal value; or of the form @samp{\@var{x}}, where
10132 @samp{@var{x}} is a predefined special character---for example,
10133 @samp{\n} for newline.
10136 String constants are a sequence of character constants surrounded by
10137 double quotes (@code{"}). Any valid character constant (as described
10138 above) may appear. Double quotes within the string must be preceded by
10139 a backslash, so for instance @samp{"a\"b'c"} is a string of five
10143 Pointer constants are an integral value. You can also write pointers
10144 to constants using the C operator @samp{&}.
10147 Array constants are comma-separated lists surrounded by braces @samp{@{}
10148 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
10149 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
10150 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
10153 @node C Plus Plus Expressions
10154 @subsubsection C@t{++} Expressions
10156 @cindex expressions in C@t{++}
10157 @value{GDBN} expression handling can interpret most C@t{++} expressions.
10159 @cindex debugging C@t{++} programs
10160 @cindex C@t{++} compilers
10161 @cindex debug formats and C@t{++}
10162 @cindex @value{NGCC} and C@t{++}
10164 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use the
10165 proper compiler and the proper debug format. Currently, @value{GDBN}
10166 works best when debugging C@t{++} code that is compiled with
10167 @value{NGCC} 2.95.3 or with @value{NGCC} 3.1 or newer, using the options
10168 @option{-gdwarf-2} or @option{-gstabs+}. DWARF 2 is preferred over
10169 stabs+. Most configurations of @value{NGCC} emit either DWARF 2 or
10170 stabs+ as their default debug format, so you usually don't need to
10171 specify a debug format explicitly. Other compilers and/or debug formats
10172 are likely to work badly or not at all when using @value{GDBN} to debug
10178 @cindex member functions
10180 Member function calls are allowed; you can use expressions like
10183 count = aml->GetOriginal(x, y)
10186 @vindex this@r{, inside C@t{++} member functions}
10187 @cindex namespace in C@t{++}
10189 While a member function is active (in the selected stack frame), your
10190 expressions have the same namespace available as the member function;
10191 that is, @value{GDBN} allows implicit references to the class instance
10192 pointer @code{this} following the same rules as C@t{++}.
10194 @cindex call overloaded functions
10195 @cindex overloaded functions, calling
10196 @cindex type conversions in C@t{++}
10198 You can call overloaded functions; @value{GDBN} resolves the function
10199 call to the right definition, with some restrictions. @value{GDBN} does not
10200 perform overload resolution involving user-defined type conversions,
10201 calls to constructors, or instantiations of templates that do not exist
10202 in the program. It also cannot handle ellipsis argument lists or
10205 It does perform integral conversions and promotions, floating-point
10206 promotions, arithmetic conversions, pointer conversions, conversions of
10207 class objects to base classes, and standard conversions such as those of
10208 functions or arrays to pointers; it requires an exact match on the
10209 number of function arguments.
10211 Overload resolution is always performed, unless you have specified
10212 @code{set overload-resolution off}. @xref{Debugging C Plus Plus,
10213 ,@value{GDBN} Features for C@t{++}}.
10215 You must specify @code{set overload-resolution off} in order to use an
10216 explicit function signature to call an overloaded function, as in
10218 p 'foo(char,int)'('x', 13)
10221 The @value{GDBN} command-completion facility can simplify this;
10222 see @ref{Completion, ,Command Completion}.
10224 @cindex reference declarations
10226 @value{GDBN} understands variables declared as C@t{++} references; you can use
10227 them in expressions just as you do in C@t{++} source---they are automatically
10230 In the parameter list shown when @value{GDBN} displays a frame, the values of
10231 reference variables are not displayed (unlike other variables); this
10232 avoids clutter, since references are often used for large structures.
10233 The @emph{address} of a reference variable is always shown, unless
10234 you have specified @samp{set print address off}.
10237 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
10238 expressions can use it just as expressions in your program do. Since
10239 one scope may be defined in another, you can use @code{::} repeatedly if
10240 necessary, for example in an expression like
10241 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
10242 resolving name scope by reference to source files, in both C and C@t{++}
10243 debugging (@pxref{Variables, ,Program Variables}).
10246 In addition, when used with HP's C@t{++} compiler, @value{GDBN} supports
10247 calling virtual functions correctly, printing out virtual bases of
10248 objects, calling functions in a base subobject, casting objects, and
10249 invoking user-defined operators.
10252 @subsubsection C and C@t{++} Defaults
10254 @cindex C and C@t{++} defaults
10256 If you allow @value{GDBN} to set type and range checking automatically, they
10257 both default to @code{off} whenever the working language changes to
10258 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
10259 selects the working language.
10261 If you allow @value{GDBN} to set the language automatically, it
10262 recognizes source files whose names end with @file{.c}, @file{.C}, or
10263 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
10264 these files, it sets the working language to C or C@t{++}.
10265 @xref{Automatically, ,Having @value{GDBN} Infer the Source Language},
10266 for further details.
10268 @c Type checking is (a) primarily motivated by Modula-2, and (b)
10269 @c unimplemented. If (b) changes, it might make sense to let this node
10270 @c appear even if Mod-2 does not, but meanwhile ignore it. roland 16jul93.
10273 @subsubsection C and C@t{++} Type and Range Checks
10275 @cindex C and C@t{++} checks
10277 By default, when @value{GDBN} parses C or C@t{++} expressions, type checking
10278 is not used. However, if you turn type checking on, @value{GDBN}
10279 considers two variables type equivalent if:
10283 The two variables are structured and have the same structure, union, or
10287 The two variables have the same type name, or types that have been
10288 declared equivalent through @code{typedef}.
10291 @c leaving this out because neither J Gilmore nor R Pesch understand it.
10294 The two @code{struct}, @code{union}, or @code{enum} variables are
10295 declared in the same declaration. (Note: this may not be true for all C
10300 Range checking, if turned on, is done on mathematical operations. Array
10301 indices are not checked, since they are often used to index a pointer
10302 that is not itself an array.
10305 @subsubsection @value{GDBN} and C
10307 The @code{set print union} and @code{show print union} commands apply to
10308 the @code{union} type. When set to @samp{on}, any @code{union} that is
10309 inside a @code{struct} or @code{class} is also printed. Otherwise, it
10310 appears as @samp{@{...@}}.
10312 The @code{@@} operator aids in the debugging of dynamic arrays, formed
10313 with pointers and a memory allocation function. @xref{Expressions,
10316 @node Debugging C Plus Plus
10317 @subsubsection @value{GDBN} Features for C@t{++}
10319 @cindex commands for C@t{++}
10321 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
10322 designed specifically for use with C@t{++}. Here is a summary:
10325 @cindex break in overloaded functions
10326 @item @r{breakpoint menus}
10327 When you want a breakpoint in a function whose name is overloaded,
10328 @value{GDBN} has the capability to display a menu of possible breakpoint
10329 locations to help you specify which function definition you want.
10330 @xref{Ambiguous Expressions,,Ambiguous Expressions}.
10332 @cindex overloading in C@t{++}
10333 @item rbreak @var{regex}
10334 Setting breakpoints using regular expressions is helpful for setting
10335 breakpoints on overloaded functions that are not members of any special
10337 @xref{Set Breaks, ,Setting Breakpoints}.
10339 @cindex C@t{++} exception handling
10342 Debug C@t{++} exception handling using these commands. @xref{Set
10343 Catchpoints, , Setting Catchpoints}.
10345 @cindex inheritance
10346 @item ptype @var{typename}
10347 Print inheritance relationships as well as other information for type
10349 @xref{Symbols, ,Examining the Symbol Table}.
10351 @cindex C@t{++} symbol display
10352 @item set print demangle
10353 @itemx show print demangle
10354 @itemx set print asm-demangle
10355 @itemx show print asm-demangle
10356 Control whether C@t{++} symbols display in their source form, both when
10357 displaying code as C@t{++} source and when displaying disassemblies.
10358 @xref{Print Settings, ,Print Settings}.
10360 @item set print object
10361 @itemx show print object
10362 Choose whether to print derived (actual) or declared types of objects.
10363 @xref{Print Settings, ,Print Settings}.
10365 @item set print vtbl
10366 @itemx show print vtbl
10367 Control the format for printing virtual function tables.
10368 @xref{Print Settings, ,Print Settings}.
10369 (The @code{vtbl} commands do not work on programs compiled with the HP
10370 ANSI C@t{++} compiler (@code{aCC}).)
10372 @kindex set overload-resolution
10373 @cindex overloaded functions, overload resolution
10374 @item set overload-resolution on
10375 Enable overload resolution for C@t{++} expression evaluation. The default
10376 is on. For overloaded functions, @value{GDBN} evaluates the arguments
10377 and searches for a function whose signature matches the argument types,
10378 using the standard C@t{++} conversion rules (see @ref{C Plus Plus
10379 Expressions, ,C@t{++} Expressions}, for details).
10380 If it cannot find a match, it emits a message.
10382 @item set overload-resolution off
10383 Disable overload resolution for C@t{++} expression evaluation. For
10384 overloaded functions that are not class member functions, @value{GDBN}
10385 chooses the first function of the specified name that it finds in the
10386 symbol table, whether or not its arguments are of the correct type. For
10387 overloaded functions that are class member functions, @value{GDBN}
10388 searches for a function whose signature @emph{exactly} matches the
10391 @kindex show overload-resolution
10392 @item show overload-resolution
10393 Show the current setting of overload resolution.
10395 @item @r{Overloaded symbol names}
10396 You can specify a particular definition of an overloaded symbol, using
10397 the same notation that is used to declare such symbols in C@t{++}: type
10398 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
10399 also use the @value{GDBN} command-line word completion facilities to list the
10400 available choices, or to finish the type list for you.
10401 @xref{Completion,, Command Completion}, for details on how to do this.
10404 @node Decimal Floating Point
10405 @subsubsection Decimal Floating Point format
10406 @cindex decimal floating point format
10408 @value{GDBN} can examine, set and perform computations with numbers in
10409 decimal floating point format, which in the C language correspond to the
10410 @code{_Decimal32}, @code{_Decimal64} and @code{_Decimal128} types as
10411 specified by the extension to support decimal floating-point arithmetic.
10413 There are two encodings in use, depending on the architecture: BID (Binary
10414 Integer Decimal) for x86 and x86-64, and DPD (Densely Packed Decimal) for
10415 PowerPC. @value{GDBN} will use the appropriate encoding for the configured
10418 Because of a limitation in @file{libdecnumber}, the library used by @value{GDBN}
10419 to manipulate decimal floating point numbers, it is not possible to convert
10420 (using a cast, for example) integers wider than 32-bit to decimal float.
10422 In addition, in order to imitate @value{GDBN}'s behaviour with binary floating
10423 point computations, error checking in decimal float operations ignores
10424 underflow, overflow and divide by zero exceptions.
10426 In the PowerPC architecture, @value{GDBN} provides a set of pseudo-registers
10427 to inspect @code{_Decimal128} values stored in floating point registers. See
10428 @ref{PowerPC,,PowerPC} for more details.
10431 @subsection Objective-C
10433 @cindex Objective-C
10434 This section provides information about some commands and command
10435 options that are useful for debugging Objective-C code. See also
10436 @ref{Symbols, info classes}, and @ref{Symbols, info selectors}, for a
10437 few more commands specific to Objective-C support.
10440 * Method Names in Commands::
10441 * The Print Command with Objective-C::
10444 @node Method Names in Commands
10445 @subsubsection Method Names in Commands
10447 The following commands have been extended to accept Objective-C method
10448 names as line specifications:
10450 @kindex clear@r{, and Objective-C}
10451 @kindex break@r{, and Objective-C}
10452 @kindex info line@r{, and Objective-C}
10453 @kindex jump@r{, and Objective-C}
10454 @kindex list@r{, and Objective-C}
10458 @item @code{info line}
10463 A fully qualified Objective-C method name is specified as
10466 -[@var{Class} @var{methodName}]
10469 where the minus sign is used to indicate an instance method and a
10470 plus sign (not shown) is used to indicate a class method. The class
10471 name @var{Class} and method name @var{methodName} are enclosed in
10472 brackets, similar to the way messages are specified in Objective-C
10473 source code. For example, to set a breakpoint at the @code{create}
10474 instance method of class @code{Fruit} in the program currently being
10478 break -[Fruit create]
10481 To list ten program lines around the @code{initialize} class method,
10485 list +[NSText initialize]
10488 In the current version of @value{GDBN}, the plus or minus sign is
10489 required. In future versions of @value{GDBN}, the plus or minus
10490 sign will be optional, but you can use it to narrow the search. It
10491 is also possible to specify just a method name:
10497 You must specify the complete method name, including any colons. If
10498 your program's source files contain more than one @code{create} method,
10499 you'll be presented with a numbered list of classes that implement that
10500 method. Indicate your choice by number, or type @samp{0} to exit if
10503 As another example, to clear a breakpoint established at the
10504 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
10507 clear -[NSWindow makeKeyAndOrderFront:]
10510 @node The Print Command with Objective-C
10511 @subsubsection The Print Command With Objective-C
10512 @cindex Objective-C, print objects
10513 @kindex print-object
10514 @kindex po @r{(@code{print-object})}
10516 The print command has also been extended to accept methods. For example:
10519 print -[@var{object} hash]
10522 @cindex print an Objective-C object description
10523 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
10525 will tell @value{GDBN} to send the @code{hash} message to @var{object}
10526 and print the result. Also, an additional command has been added,
10527 @code{print-object} or @code{po} for short, which is meant to print
10528 the description of an object. However, this command may only work
10529 with certain Objective-C libraries that have a particular hook
10530 function, @code{_NSPrintForDebugger}, defined.
10533 @subsection Fortran
10534 @cindex Fortran-specific support in @value{GDBN}
10536 @value{GDBN} can be used to debug programs written in Fortran, but it
10537 currently supports only the features of Fortran 77 language.
10539 @cindex trailing underscore, in Fortran symbols
10540 Some Fortran compilers (@sc{gnu} Fortran 77 and Fortran 95 compilers
10541 among them) append an underscore to the names of variables and
10542 functions. When you debug programs compiled by those compilers, you
10543 will need to refer to variables and functions with a trailing
10547 * Fortran Operators:: Fortran operators and expressions
10548 * Fortran Defaults:: Default settings for Fortran
10549 * Special Fortran Commands:: Special @value{GDBN} commands for Fortran
10552 @node Fortran Operators
10553 @subsubsection Fortran Operators and Expressions
10555 @cindex Fortran operators and expressions
10557 Operators must be defined on values of specific types. For instance,
10558 @code{+} is defined on numbers, but not on characters or other non-
10559 arithmetic types. Operators are often defined on groups of types.
10563 The exponentiation operator. It raises the first operand to the power
10567 The range operator. Normally used in the form of array(low:high) to
10568 represent a section of array.
10571 The access component operator. Normally used to access elements in derived
10572 types. Also suitable for unions. As unions aren't part of regular Fortran,
10573 this can only happen when accessing a register that uses a gdbarch-defined
10577 @node Fortran Defaults
10578 @subsubsection Fortran Defaults
10580 @cindex Fortran Defaults
10582 Fortran symbols are usually case-insensitive, so @value{GDBN} by
10583 default uses case-insensitive matches for Fortran symbols. You can
10584 change that with the @samp{set case-insensitive} command, see
10585 @ref{Symbols}, for the details.
10587 @node Special Fortran Commands
10588 @subsubsection Special Fortran Commands
10590 @cindex Special Fortran commands
10592 @value{GDBN} has some commands to support Fortran-specific features,
10593 such as displaying common blocks.
10596 @cindex @code{COMMON} blocks, Fortran
10597 @kindex info common
10598 @item info common @r{[}@var{common-name}@r{]}
10599 This command prints the values contained in the Fortran @code{COMMON}
10600 block whose name is @var{common-name}. With no argument, the names of
10601 all @code{COMMON} blocks visible at the current program location are
10608 @cindex Pascal support in @value{GDBN}, limitations
10609 Debugging Pascal programs which use sets, subranges, file variables, or
10610 nested functions does not currently work. @value{GDBN} does not support
10611 entering expressions, printing values, or similar features using Pascal
10614 The Pascal-specific command @code{set print pascal_static-members}
10615 controls whether static members of Pascal objects are displayed.
10616 @xref{Print Settings, pascal_static-members}.
10619 @subsection Modula-2
10621 @cindex Modula-2, @value{GDBN} support
10623 The extensions made to @value{GDBN} to support Modula-2 only support
10624 output from the @sc{gnu} Modula-2 compiler (which is currently being
10625 developed). Other Modula-2 compilers are not currently supported, and
10626 attempting to debug executables produced by them is most likely
10627 to give an error as @value{GDBN} reads in the executable's symbol
10630 @cindex expressions in Modula-2
10632 * M2 Operators:: Built-in operators
10633 * Built-In Func/Proc:: Built-in functions and procedures
10634 * M2 Constants:: Modula-2 constants
10635 * M2 Types:: Modula-2 types
10636 * M2 Defaults:: Default settings for Modula-2
10637 * Deviations:: Deviations from standard Modula-2
10638 * M2 Checks:: Modula-2 type and range checks
10639 * M2 Scope:: The scope operators @code{::} and @code{.}
10640 * GDB/M2:: @value{GDBN} and Modula-2
10644 @subsubsection Operators
10645 @cindex Modula-2 operators
10647 Operators must be defined on values of specific types. For instance,
10648 @code{+} is defined on numbers, but not on structures. Operators are
10649 often defined on groups of types. For the purposes of Modula-2, the
10650 following definitions hold:
10655 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
10659 @emph{Character types} consist of @code{CHAR} and its subranges.
10662 @emph{Floating-point types} consist of @code{REAL}.
10665 @emph{Pointer types} consist of anything declared as @code{POINTER TO
10669 @emph{Scalar types} consist of all of the above.
10672 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
10675 @emph{Boolean types} consist of @code{BOOLEAN}.
10679 The following operators are supported, and appear in order of
10680 increasing precedence:
10684 Function argument or array index separator.
10687 Assignment. The value of @var{var} @code{:=} @var{value} is
10691 Less than, greater than on integral, floating-point, or enumerated
10695 Less than or equal to, greater than or equal to
10696 on integral, floating-point and enumerated types, or set inclusion on
10697 set types. Same precedence as @code{<}.
10699 @item =@r{, }<>@r{, }#
10700 Equality and two ways of expressing inequality, valid on scalar types.
10701 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
10702 available for inequality, since @code{#} conflicts with the script
10706 Set membership. Defined on set types and the types of their members.
10707 Same precedence as @code{<}.
10710 Boolean disjunction. Defined on boolean types.
10713 Boolean conjunction. Defined on boolean types.
10716 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
10719 Addition and subtraction on integral and floating-point types, or union
10720 and difference on set types.
10723 Multiplication on integral and floating-point types, or set intersection
10727 Division on floating-point types, or symmetric set difference on set
10728 types. Same precedence as @code{*}.
10731 Integer division and remainder. Defined on integral types. Same
10732 precedence as @code{*}.
10735 Negative. Defined on @code{INTEGER} and @code{REAL} data.
10738 Pointer dereferencing. Defined on pointer types.
10741 Boolean negation. Defined on boolean types. Same precedence as
10745 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
10746 precedence as @code{^}.
10749 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
10752 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
10756 @value{GDBN} and Modula-2 scope operators.
10760 @emph{Warning:} Set expressions and their operations are not yet supported, so @value{GDBN}
10761 treats the use of the operator @code{IN}, or the use of operators
10762 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
10763 @code{<=}, and @code{>=} on sets as an error.
10767 @node Built-In Func/Proc
10768 @subsubsection Built-in Functions and Procedures
10769 @cindex Modula-2 built-ins
10771 Modula-2 also makes available several built-in procedures and functions.
10772 In describing these, the following metavariables are used:
10777 represents an @code{ARRAY} variable.
10780 represents a @code{CHAR} constant or variable.
10783 represents a variable or constant of integral type.
10786 represents an identifier that belongs to a set. Generally used in the
10787 same function with the metavariable @var{s}. The type of @var{s} should
10788 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
10791 represents a variable or constant of integral or floating-point type.
10794 represents a variable or constant of floating-point type.
10800 represents a variable.
10803 represents a variable or constant of one of many types. See the
10804 explanation of the function for details.
10807 All Modula-2 built-in procedures also return a result, described below.
10811 Returns the absolute value of @var{n}.
10814 If @var{c} is a lower case letter, it returns its upper case
10815 equivalent, otherwise it returns its argument.
10818 Returns the character whose ordinal value is @var{i}.
10821 Decrements the value in the variable @var{v} by one. Returns the new value.
10823 @item DEC(@var{v},@var{i})
10824 Decrements the value in the variable @var{v} by @var{i}. Returns the
10827 @item EXCL(@var{m},@var{s})
10828 Removes the element @var{m} from the set @var{s}. Returns the new
10831 @item FLOAT(@var{i})
10832 Returns the floating point equivalent of the integer @var{i}.
10834 @item HIGH(@var{a})
10835 Returns the index of the last member of @var{a}.
10838 Increments the value in the variable @var{v} by one. Returns the new value.
10840 @item INC(@var{v},@var{i})
10841 Increments the value in the variable @var{v} by @var{i}. Returns the
10844 @item INCL(@var{m},@var{s})
10845 Adds the element @var{m} to the set @var{s} if it is not already
10846 there. Returns the new set.
10849 Returns the maximum value of the type @var{t}.
10852 Returns the minimum value of the type @var{t}.
10855 Returns boolean TRUE if @var{i} is an odd number.
10858 Returns the ordinal value of its argument. For example, the ordinal
10859 value of a character is its @sc{ascii} value (on machines supporting the
10860 @sc{ascii} character set). @var{x} must be of an ordered type, which include
10861 integral, character and enumerated types.
10863 @item SIZE(@var{x})
10864 Returns the size of its argument. @var{x} can be a variable or a type.
10866 @item TRUNC(@var{r})
10867 Returns the integral part of @var{r}.
10869 @item TSIZE(@var{x})
10870 Returns the size of its argument. @var{x} can be a variable or a type.
10872 @item VAL(@var{t},@var{i})
10873 Returns the member of the type @var{t} whose ordinal value is @var{i}.
10877 @emph{Warning:} Sets and their operations are not yet supported, so
10878 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
10882 @cindex Modula-2 constants
10884 @subsubsection Constants
10886 @value{GDBN} allows you to express the constants of Modula-2 in the following
10892 Integer constants are simply a sequence of digits. When used in an
10893 expression, a constant is interpreted to be type-compatible with the
10894 rest of the expression. Hexadecimal integers are specified by a
10895 trailing @samp{H}, and octal integers by a trailing @samp{B}.
10898 Floating point constants appear as a sequence of digits, followed by a
10899 decimal point and another sequence of digits. An optional exponent can
10900 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
10901 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
10902 digits of the floating point constant must be valid decimal (base 10)
10906 Character constants consist of a single character enclosed by a pair of
10907 like quotes, either single (@code{'}) or double (@code{"}). They may
10908 also be expressed by their ordinal value (their @sc{ascii} value, usually)
10909 followed by a @samp{C}.
10912 String constants consist of a sequence of characters enclosed by a
10913 pair of like quotes, either single (@code{'}) or double (@code{"}).
10914 Escape sequences in the style of C are also allowed. @xref{C
10915 Constants, ,C and C@t{++} Constants}, for a brief explanation of escape
10919 Enumerated constants consist of an enumerated identifier.
10922 Boolean constants consist of the identifiers @code{TRUE} and
10926 Pointer constants consist of integral values only.
10929 Set constants are not yet supported.
10933 @subsubsection Modula-2 Types
10934 @cindex Modula-2 types
10936 Currently @value{GDBN} can print the following data types in Modula-2
10937 syntax: array types, record types, set types, pointer types, procedure
10938 types, enumerated types, subrange types and base types. You can also
10939 print the contents of variables declared using these type.
10940 This section gives a number of simple source code examples together with
10941 sample @value{GDBN} sessions.
10943 The first example contains the following section of code:
10952 and you can request @value{GDBN} to interrogate the type and value of
10953 @code{r} and @code{s}.
10956 (@value{GDBP}) print s
10958 (@value{GDBP}) ptype s
10960 (@value{GDBP}) print r
10962 (@value{GDBP}) ptype r
10967 Likewise if your source code declares @code{s} as:
10971 s: SET ['A'..'Z'] ;
10975 then you may query the type of @code{s} by:
10978 (@value{GDBP}) ptype s
10979 type = SET ['A'..'Z']
10983 Note that at present you cannot interactively manipulate set
10984 expressions using the debugger.
10986 The following example shows how you might declare an array in Modula-2
10987 and how you can interact with @value{GDBN} to print its type and contents:
10991 s: ARRAY [-10..10] OF CHAR ;
10995 (@value{GDBP}) ptype s
10996 ARRAY [-10..10] OF CHAR
10999 Note that the array handling is not yet complete and although the type
11000 is printed correctly, expression handling still assumes that all
11001 arrays have a lower bound of zero and not @code{-10} as in the example
11004 Here are some more type related Modula-2 examples:
11008 colour = (blue, red, yellow, green) ;
11009 t = [blue..yellow] ;
11017 The @value{GDBN} interaction shows how you can query the data type
11018 and value of a variable.
11021 (@value{GDBP}) print s
11023 (@value{GDBP}) ptype t
11024 type = [blue..yellow]
11028 In this example a Modula-2 array is declared and its contents
11029 displayed. Observe that the contents are written in the same way as
11030 their @code{C} counterparts.
11034 s: ARRAY [1..5] OF CARDINAL ;
11040 (@value{GDBP}) print s
11041 $1 = @{1, 0, 0, 0, 0@}
11042 (@value{GDBP}) ptype s
11043 type = ARRAY [1..5] OF CARDINAL
11046 The Modula-2 language interface to @value{GDBN} also understands
11047 pointer types as shown in this example:
11051 s: POINTER TO ARRAY [1..5] OF CARDINAL ;
11058 and you can request that @value{GDBN} describes the type of @code{s}.
11061 (@value{GDBP}) ptype s
11062 type = POINTER TO ARRAY [1..5] OF CARDINAL
11065 @value{GDBN} handles compound types as we can see in this example.
11066 Here we combine array types, record types, pointer types and subrange
11077 myarray = ARRAY myrange OF CARDINAL ;
11078 myrange = [-2..2] ;
11080 s: POINTER TO ARRAY myrange OF foo ;
11084 and you can ask @value{GDBN} to describe the type of @code{s} as shown
11088 (@value{GDBP}) ptype s
11089 type = POINTER TO ARRAY [-2..2] OF foo = RECORD
11092 f3 : ARRAY [-2..2] OF CARDINAL;
11097 @subsubsection Modula-2 Defaults
11098 @cindex Modula-2 defaults
11100 If type and range checking are set automatically by @value{GDBN}, they
11101 both default to @code{on} whenever the working language changes to
11102 Modula-2. This happens regardless of whether you or @value{GDBN}
11103 selected the working language.
11105 If you allow @value{GDBN} to set the language automatically, then entering
11106 code compiled from a file whose name ends with @file{.mod} sets the
11107 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN}
11108 Infer the Source Language}, for further details.
11111 @subsubsection Deviations from Standard Modula-2
11112 @cindex Modula-2, deviations from
11114 A few changes have been made to make Modula-2 programs easier to debug.
11115 This is done primarily via loosening its type strictness:
11119 Unlike in standard Modula-2, pointer constants can be formed by
11120 integers. This allows you to modify pointer variables during
11121 debugging. (In standard Modula-2, the actual address contained in a
11122 pointer variable is hidden from you; it can only be modified
11123 through direct assignment to another pointer variable or expression that
11124 returned a pointer.)
11127 C escape sequences can be used in strings and characters to represent
11128 non-printable characters. @value{GDBN} prints out strings with these
11129 escape sequences embedded. Single non-printable characters are
11130 printed using the @samp{CHR(@var{nnn})} format.
11133 The assignment operator (@code{:=}) returns the value of its right-hand
11137 All built-in procedures both modify @emph{and} return their argument.
11141 @subsubsection Modula-2 Type and Range Checks
11142 @cindex Modula-2 checks
11145 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
11148 @c FIXME remove warning when type/range checks added
11150 @value{GDBN} considers two Modula-2 variables type equivalent if:
11154 They are of types that have been declared equivalent via a @code{TYPE
11155 @var{t1} = @var{t2}} statement
11158 They have been declared on the same line. (Note: This is true of the
11159 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
11162 As long as type checking is enabled, any attempt to combine variables
11163 whose types are not equivalent is an error.
11165 Range checking is done on all mathematical operations, assignment, array
11166 index bounds, and all built-in functions and procedures.
11169 @subsubsection The Scope Operators @code{::} and @code{.}
11171 @cindex @code{.}, Modula-2 scope operator
11172 @cindex colon, doubled as scope operator
11174 @vindex colon-colon@r{, in Modula-2}
11175 @c Info cannot handle :: but TeX can.
11178 @vindex ::@r{, in Modula-2}
11181 There are a few subtle differences between the Modula-2 scope operator
11182 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
11187 @var{module} . @var{id}
11188 @var{scope} :: @var{id}
11192 where @var{scope} is the name of a module or a procedure,
11193 @var{module} the name of a module, and @var{id} is any declared
11194 identifier within your program, except another module.
11196 Using the @code{::} operator makes @value{GDBN} search the scope
11197 specified by @var{scope} for the identifier @var{id}. If it is not
11198 found in the specified scope, then @value{GDBN} searches all scopes
11199 enclosing the one specified by @var{scope}.
11201 Using the @code{.} operator makes @value{GDBN} search the current scope for
11202 the identifier specified by @var{id} that was imported from the
11203 definition module specified by @var{module}. With this operator, it is
11204 an error if the identifier @var{id} was not imported from definition
11205 module @var{module}, or if @var{id} is not an identifier in
11209 @subsubsection @value{GDBN} and Modula-2
11211 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
11212 Five subcommands of @code{set print} and @code{show print} apply
11213 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
11214 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
11215 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
11216 analogue in Modula-2.
11218 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
11219 with any language, is not useful with Modula-2. Its
11220 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
11221 created in Modula-2 as they can in C or C@t{++}. However, because an
11222 address can be specified by an integral constant, the construct
11223 @samp{@{@var{type}@}@var{adrexp}} is still useful.
11225 @cindex @code{#} in Modula-2
11226 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
11227 interpreted as the beginning of a comment. Use @code{<>} instead.
11233 The extensions made to @value{GDBN} for Ada only support
11234 output from the @sc{gnu} Ada (GNAT) compiler.
11235 Other Ada compilers are not currently supported, and
11236 attempting to debug executables produced by them is most likely
11240 @cindex expressions in Ada
11242 * Ada Mode Intro:: General remarks on the Ada syntax
11243 and semantics supported by Ada mode
11245 * Omissions from Ada:: Restrictions on the Ada expression syntax.
11246 * Additions to Ada:: Extensions of the Ada expression syntax.
11247 * Stopping Before Main Program:: Debugging the program during elaboration.
11248 * Ada Tasks:: Listing and setting breakpoints in tasks.
11249 * Ada Tasks and Core Files:: Tasking Support when Debugging Core Files
11250 * Ada Glitches:: Known peculiarities of Ada mode.
11253 @node Ada Mode Intro
11254 @subsubsection Introduction
11255 @cindex Ada mode, general
11257 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
11258 syntax, with some extensions.
11259 The philosophy behind the design of this subset is
11263 That @value{GDBN} should provide basic literals and access to operations for
11264 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
11265 leaving more sophisticated computations to subprograms written into the
11266 program (which therefore may be called from @value{GDBN}).
11269 That type safety and strict adherence to Ada language restrictions
11270 are not particularly important to the @value{GDBN} user.
11273 That brevity is important to the @value{GDBN} user.
11276 Thus, for brevity, the debugger acts as if all names declared in
11277 user-written packages are directly visible, even if they are not visible
11278 according to Ada rules, thus making it unnecessary to fully qualify most
11279 names with their packages, regardless of context. Where this causes
11280 ambiguity, @value{GDBN} asks the user's intent.
11282 The debugger will start in Ada mode if it detects an Ada main program.
11283 As for other languages, it will enter Ada mode when stopped in a program that
11284 was translated from an Ada source file.
11286 While in Ada mode, you may use `@t{--}' for comments. This is useful
11287 mostly for documenting command files. The standard @value{GDBN} comment
11288 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
11289 middle (to allow based literals).
11291 The debugger supports limited overloading. Given a subprogram call in which
11292 the function symbol has multiple definitions, it will use the number of
11293 actual parameters and some information about their types to attempt to narrow
11294 the set of definitions. It also makes very limited use of context, preferring
11295 procedures to functions in the context of the @code{call} command, and
11296 functions to procedures elsewhere.
11298 @node Omissions from Ada
11299 @subsubsection Omissions from Ada
11300 @cindex Ada, omissions from
11302 Here are the notable omissions from the subset:
11306 Only a subset of the attributes are supported:
11310 @t{'First}, @t{'Last}, and @t{'Length}
11311 on array objects (not on types and subtypes).
11314 @t{'Min} and @t{'Max}.
11317 @t{'Pos} and @t{'Val}.
11323 @t{'Range} on array objects (not subtypes), but only as the right
11324 operand of the membership (@code{in}) operator.
11327 @t{'Access}, @t{'Unchecked_Access}, and
11328 @t{'Unrestricted_Access} (a GNAT extension).
11336 @code{Characters.Latin_1} are not available and
11337 concatenation is not implemented. Thus, escape characters in strings are
11338 not currently available.
11341 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
11342 equality of representations. They will generally work correctly
11343 for strings and arrays whose elements have integer or enumeration types.
11344 They may not work correctly for arrays whose element
11345 types have user-defined equality, for arrays of real values
11346 (in particular, IEEE-conformant floating point, because of negative
11347 zeroes and NaNs), and for arrays whose elements contain unused bits with
11348 indeterminate values.
11351 The other component-by-component array operations (@code{and}, @code{or},
11352 @code{xor}, @code{not}, and relational tests other than equality)
11353 are not implemented.
11356 @cindex array aggregates (Ada)
11357 @cindex record aggregates (Ada)
11358 @cindex aggregates (Ada)
11359 There is limited support for array and record aggregates. They are
11360 permitted only on the right sides of assignments, as in these examples:
11363 (@value{GDBP}) set An_Array := (1, 2, 3, 4, 5, 6)
11364 (@value{GDBP}) set An_Array := (1, others => 0)
11365 (@value{GDBP}) set An_Array := (0|4 => 1, 1..3 => 2, 5 => 6)
11366 (@value{GDBP}) set A_2D_Array := ((1, 2, 3), (4, 5, 6), (7, 8, 9))
11367 (@value{GDBP}) set A_Record := (1, "Peter", True);
11368 (@value{GDBP}) set A_Record := (Name => "Peter", Id => 1, Alive => True)
11372 discriminant's value by assigning an aggregate has an
11373 undefined effect if that discriminant is used within the record.
11374 However, you can first modify discriminants by directly assigning to
11375 them (which normally would not be allowed in Ada), and then performing an
11376 aggregate assignment. For example, given a variable @code{A_Rec}
11377 declared to have a type such as:
11380 type Rec (Len : Small_Integer := 0) is record
11382 Vals : IntArray (1 .. Len);
11386 you can assign a value with a different size of @code{Vals} with two
11390 (@value{GDBP}) set A_Rec.Len := 4
11391 (@value{GDBP}) set A_Rec := (Id => 42, Vals => (1, 2, 3, 4))
11394 As this example also illustrates, @value{GDBN} is very loose about the usual
11395 rules concerning aggregates. You may leave out some of the
11396 components of an array or record aggregate (such as the @code{Len}
11397 component in the assignment to @code{A_Rec} above); they will retain their
11398 original values upon assignment. You may freely use dynamic values as
11399 indices in component associations. You may even use overlapping or
11400 redundant component associations, although which component values are
11401 assigned in such cases is not defined.
11404 Calls to dispatching subprograms are not implemented.
11407 The overloading algorithm is much more limited (i.e., less selective)
11408 than that of real Ada. It makes only limited use of the context in
11409 which a subexpression appears to resolve its meaning, and it is much
11410 looser in its rules for allowing type matches. As a result, some
11411 function calls will be ambiguous, and the user will be asked to choose
11412 the proper resolution.
11415 The @code{new} operator is not implemented.
11418 Entry calls are not implemented.
11421 Aside from printing, arithmetic operations on the native VAX floating-point
11422 formats are not supported.
11425 It is not possible to slice a packed array.
11428 The names @code{True} and @code{False}, when not part of a qualified name,
11429 are interpreted as if implicitly prefixed by @code{Standard}, regardless of
11431 Should your program
11432 redefine these names in a package or procedure (at best a dubious practice),
11433 you will have to use fully qualified names to access their new definitions.
11436 @node Additions to Ada
11437 @subsubsection Additions to Ada
11438 @cindex Ada, deviations from
11440 As it does for other languages, @value{GDBN} makes certain generic
11441 extensions to Ada (@pxref{Expressions}):
11445 If the expression @var{E} is a variable residing in memory (typically
11446 a local variable or array element) and @var{N} is a positive integer,
11447 then @code{@var{E}@@@var{N}} displays the values of @var{E} and the
11448 @var{N}-1 adjacent variables following it in memory as an array. In
11449 Ada, this operator is generally not necessary, since its prime use is
11450 in displaying parts of an array, and slicing will usually do this in
11451 Ada. However, there are occasional uses when debugging programs in
11452 which certain debugging information has been optimized away.
11455 @code{@var{B}::@var{var}} means ``the variable named @var{var} that
11456 appears in function or file @var{B}.'' When @var{B} is a file name,
11457 you must typically surround it in single quotes.
11460 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
11461 @var{type} that appears at address @var{addr}.''
11464 A name starting with @samp{$} is a convenience variable
11465 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
11468 In addition, @value{GDBN} provides a few other shortcuts and outright
11469 additions specific to Ada:
11473 The assignment statement is allowed as an expression, returning
11474 its right-hand operand as its value. Thus, you may enter
11477 (@value{GDBP}) set x := y + 3
11478 (@value{GDBP}) print A(tmp := y + 1)
11482 The semicolon is allowed as an ``operator,'' returning as its value
11483 the value of its right-hand operand.
11484 This allows, for example,
11485 complex conditional breaks:
11488 (@value{GDBP}) break f
11489 (@value{GDBP}) condition 1 (report(i); k += 1; A(k) > 100)
11493 Rather than use catenation and symbolic character names to introduce special
11494 characters into strings, one may instead use a special bracket notation,
11495 which is also used to print strings. A sequence of characters of the form
11496 @samp{["@var{XX}"]} within a string or character literal denotes the
11497 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
11498 sequence of characters @samp{["""]} also denotes a single quotation mark
11499 in strings. For example,
11501 "One line.["0a"]Next line.["0a"]"
11504 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF})
11508 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
11509 @t{'Max} is optional (and is ignored in any case). For example, it is valid
11513 (@value{GDBP}) print 'max(x, y)
11517 When printing arrays, @value{GDBN} uses positional notation when the
11518 array has a lower bound of 1, and uses a modified named notation otherwise.
11519 For example, a one-dimensional array of three integers with a lower bound
11520 of 3 might print as
11527 That is, in contrast to valid Ada, only the first component has a @code{=>}
11531 You may abbreviate attributes in expressions with any unique,
11532 multi-character subsequence of
11533 their names (an exact match gets preference).
11534 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
11535 in place of @t{a'length}.
11538 @cindex quoting Ada internal identifiers
11539 Since Ada is case-insensitive, the debugger normally maps identifiers you type
11540 to lower case. The GNAT compiler uses upper-case characters for
11541 some of its internal identifiers, which are normally of no interest to users.
11542 For the rare occasions when you actually have to look at them,
11543 enclose them in angle brackets to avoid the lower-case mapping.
11546 (@value{GDBP}) print <JMPBUF_SAVE>[0]
11550 Printing an object of class-wide type or dereferencing an
11551 access-to-class-wide value will display all the components of the object's
11552 specific type (as indicated by its run-time tag). Likewise, component
11553 selection on such a value will operate on the specific type of the
11558 @node Stopping Before Main Program
11559 @subsubsection Stopping at the Very Beginning
11561 @cindex breakpointing Ada elaboration code
11562 It is sometimes necessary to debug the program during elaboration, and
11563 before reaching the main procedure.
11564 As defined in the Ada Reference
11565 Manual, the elaboration code is invoked from a procedure called
11566 @code{adainit}. To run your program up to the beginning of
11567 elaboration, simply use the following two commands:
11568 @code{tbreak adainit} and @code{run}.
11571 @subsubsection Extensions for Ada Tasks
11572 @cindex Ada, tasking
11574 Support for Ada tasks is analogous to that for threads (@pxref{Threads}).
11575 @value{GDBN} provides the following task-related commands:
11580 This command shows a list of current Ada tasks, as in the following example:
11587 (@value{GDBP}) info tasks
11588 ID TID P-ID Pri State Name
11589 1 8088000 0 15 Child Activation Wait main_task
11590 2 80a4000 1 15 Accept Statement b
11591 3 809a800 1 15 Child Activation Wait a
11592 * 4 80ae800 3 15 Running c
11597 In this listing, the asterisk before the last task indicates it to be the
11598 task currently being inspected.
11602 Represents @value{GDBN}'s internal task number.
11608 The parent's task ID (@value{GDBN}'s internal task number).
11611 The base priority of the task.
11614 Current state of the task.
11618 The task has been created but has not been activated. It cannot be
11622 The task currently running.
11625 The task is not blocked for any reason known to Ada. (It may be waiting
11626 for a mutex, though.) It is conceptually "executing" in normal mode.
11629 The task is terminated, in the sense of ARM 9.3 (5). Any dependents
11630 that were waiting on terminate alternatives have been awakened and have
11631 terminated themselves.
11633 @item Child Activation Wait
11634 The task is waiting for created tasks to complete activation.
11636 @item Accept Statement
11637 The task is waiting on an accept or selective wait statement.
11639 @item Waiting on entry call
11640 The task is waiting on an entry call.
11642 @item Async Select Wait
11643 The task is waiting to start the abortable part of an asynchronous
11647 The task is waiting on a select statement with only a delay
11650 @item Child Termination Wait
11651 The task is sleeping having completed a master within itself, and is
11652 waiting for the tasks dependent on that master to become terminated or
11653 waiting on a terminate Phase.
11655 @item Wait Child in Term Alt
11656 The task is sleeping waiting for tasks on terminate alternatives to
11657 finish terminating.
11659 @item Accepting RV with @var{taskno}
11660 The task is accepting a rendez-vous with the task @var{taskno}.
11664 Name of the task in the program.
11668 @kindex info task @var{taskno}
11669 @item info task @var{taskno}
11670 This command shows detailled informations on the specified task, as in
11671 the following example:
11676 (@value{GDBP}) info tasks
11677 ID TID P-ID Pri State Name
11678 1 8077880 0 15 Child Activation Wait main_task
11679 * 2 807c468 1 15 Running task_1
11680 (@value{GDBP}) info task 2
11681 Ada Task: 0x807c468
11684 Parent: 1 (main_task)
11690 @kindex task@r{ (Ada)}
11691 @cindex current Ada task ID
11692 This command prints the ID of the current task.
11698 (@value{GDBP}) info tasks
11699 ID TID P-ID Pri State Name
11700 1 8077870 0 15 Child Activation Wait main_task
11701 * 2 807c458 1 15 Running t
11702 (@value{GDBP}) task
11703 [Current task is 2]
11706 @item task @var{taskno}
11707 @cindex Ada task switching
11708 This command is like the @code{thread @var{threadno}}
11709 command (@pxref{Threads}). It switches the context of debugging
11710 from the current task to the given task.
11716 (@value{GDBP}) info tasks
11717 ID TID P-ID Pri State Name
11718 1 8077870 0 15 Child Activation Wait main_task
11719 * 2 807c458 1 15 Running t
11720 (@value{GDBP}) task 1
11721 [Switching to task 1]
11722 #0 0x8067726 in pthread_cond_wait ()
11724 #0 0x8067726 in pthread_cond_wait ()
11725 #1 0x8056714 in system.os_interface.pthread_cond_wait ()
11726 #2 0x805cb63 in system.task_primitives.operations.sleep ()
11727 #3 0x806153e in system.tasking.stages.activate_tasks ()
11728 #4 0x804aacc in un () at un.adb:5
11733 @node Ada Tasks and Core Files
11734 @subsubsection Tasking Support when Debugging Core Files
11735 @cindex Ada tasking and core file debugging
11737 When inspecting a core file, as opposed to debugging a live program,
11738 tasking support may be limited or even unavailable, depending on
11739 the platform being used.
11740 For instance, on x86-linux, the list of tasks is available, but task
11741 switching is not supported. On Tru64, however, task switching will work
11744 On certain platforms, including Tru64, the debugger needs to perform some
11745 memory writes in order to provide Ada tasking support. When inspecting
11746 a core file, this means that the core file must be opened with read-write
11747 privileges, using the command @samp{"set write on"} (@pxref{Patching}).
11748 Under these circumstances, you should make a backup copy of the core
11749 file before inspecting it with @value{GDBN}.
11752 @subsubsection Known Peculiarities of Ada Mode
11753 @cindex Ada, problems
11755 Besides the omissions listed previously (@pxref{Omissions from Ada}),
11756 we know of several problems with and limitations of Ada mode in
11758 some of which will be fixed with planned future releases of the debugger
11759 and the GNU Ada compiler.
11763 Currently, the debugger
11764 has insufficient information to determine whether certain pointers represent
11765 pointers to objects or the objects themselves.
11766 Thus, the user may have to tack an extra @code{.all} after an expression
11767 to get it printed properly.
11770 Static constants that the compiler chooses not to materialize as objects in
11771 storage are invisible to the debugger.
11774 Named parameter associations in function argument lists are ignored (the
11775 argument lists are treated as positional).
11778 Many useful library packages are currently invisible to the debugger.
11781 Fixed-point arithmetic, conversions, input, and output is carried out using
11782 floating-point arithmetic, and may give results that only approximate those on
11786 The GNAT compiler never generates the prefix @code{Standard} for any of
11787 the standard symbols defined by the Ada language. @value{GDBN} knows about
11788 this: it will strip the prefix from names when you use it, and will never
11789 look for a name you have so qualified among local symbols, nor match against
11790 symbols in other packages or subprograms. If you have
11791 defined entities anywhere in your program other than parameters and
11792 local variables whose simple names match names in @code{Standard},
11793 GNAT's lack of qualification here can cause confusion. When this happens,
11794 you can usually resolve the confusion
11795 by qualifying the problematic names with package
11796 @code{Standard} explicitly.
11799 @node Unsupported Languages
11800 @section Unsupported Languages
11802 @cindex unsupported languages
11803 @cindex minimal language
11804 In addition to the other fully-supported programming languages,
11805 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
11806 It does not represent a real programming language, but provides a set
11807 of capabilities close to what the C or assembly languages provide.
11808 This should allow most simple operations to be performed while debugging
11809 an application that uses a language currently not supported by @value{GDBN}.
11811 If the language is set to @code{auto}, @value{GDBN} will automatically
11812 select this language if the current frame corresponds to an unsupported
11816 @chapter Examining the Symbol Table
11818 The commands described in this chapter allow you to inquire about the
11819 symbols (names of variables, functions and types) defined in your
11820 program. This information is inherent in the text of your program and
11821 does not change as your program executes. @value{GDBN} finds it in your
11822 program's symbol table, in the file indicated when you started @value{GDBN}
11823 (@pxref{File Options, ,Choosing Files}), or by one of the
11824 file-management commands (@pxref{Files, ,Commands to Specify Files}).
11826 @cindex symbol names
11827 @cindex names of symbols
11828 @cindex quoting names
11829 Occasionally, you may need to refer to symbols that contain unusual
11830 characters, which @value{GDBN} ordinarily treats as word delimiters. The
11831 most frequent case is in referring to static variables in other
11832 source files (@pxref{Variables,,Program Variables}). File names
11833 are recorded in object files as debugging symbols, but @value{GDBN} would
11834 ordinarily parse a typical file name, like @file{foo.c}, as the three words
11835 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
11836 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
11843 looks up the value of @code{x} in the scope of the file @file{foo.c}.
11846 @cindex case-insensitive symbol names
11847 @cindex case sensitivity in symbol names
11848 @kindex set case-sensitive
11849 @item set case-sensitive on
11850 @itemx set case-sensitive off
11851 @itemx set case-sensitive auto
11852 Normally, when @value{GDBN} looks up symbols, it matches their names
11853 with case sensitivity determined by the current source language.
11854 Occasionally, you may wish to control that. The command @code{set
11855 case-sensitive} lets you do that by specifying @code{on} for
11856 case-sensitive matches or @code{off} for case-insensitive ones. If
11857 you specify @code{auto}, case sensitivity is reset to the default
11858 suitable for the source language. The default is case-sensitive
11859 matches for all languages except for Fortran, for which the default is
11860 case-insensitive matches.
11862 @kindex show case-sensitive
11863 @item show case-sensitive
11864 This command shows the current setting of case sensitivity for symbols
11867 @kindex info address
11868 @cindex address of a symbol
11869 @item info address @var{symbol}
11870 Describe where the data for @var{symbol} is stored. For a register
11871 variable, this says which register it is kept in. For a non-register
11872 local variable, this prints the stack-frame offset at which the variable
11875 Note the contrast with @samp{print &@var{symbol}}, which does not work
11876 at all for a register variable, and for a stack local variable prints
11877 the exact address of the current instantiation of the variable.
11879 @kindex info symbol
11880 @cindex symbol from address
11881 @cindex closest symbol and offset for an address
11882 @item info symbol @var{addr}
11883 Print the name of a symbol which is stored at the address @var{addr}.
11884 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
11885 nearest symbol and an offset from it:
11888 (@value{GDBP}) info symbol 0x54320
11889 _initialize_vx + 396 in section .text
11893 This is the opposite of the @code{info address} command. You can use
11894 it to find out the name of a variable or a function given its address.
11896 For dynamically linked executables, the name of executable or shared
11897 library containing the symbol is also printed:
11900 (@value{GDBP}) info symbol 0x400225
11901 _start + 5 in section .text of /tmp/a.out
11902 (@value{GDBP}) info symbol 0x2aaaac2811cf
11903 __read_nocancel + 6 in section .text of /usr/lib64/libc.so.6
11907 @item whatis [@var{arg}]
11908 Print the data type of @var{arg}, which can be either an expression or
11909 a data type. With no argument, print the data type of @code{$}, the
11910 last value in the value history. If @var{arg} is an expression, it is
11911 not actually evaluated, and any side-effecting operations (such as
11912 assignments or function calls) inside it do not take place. If
11913 @var{arg} is a type name, it may be the name of a type or typedef, or
11914 for C code it may have the form @samp{class @var{class-name}},
11915 @samp{struct @var{struct-tag}}, @samp{union @var{union-tag}} or
11916 @samp{enum @var{enum-tag}}.
11917 @xref{Expressions, ,Expressions}.
11920 @item ptype [@var{arg}]
11921 @code{ptype} accepts the same arguments as @code{whatis}, but prints a
11922 detailed description of the type, instead of just the name of the type.
11923 @xref{Expressions, ,Expressions}.
11925 For example, for this variable declaration:
11928 struct complex @{double real; double imag;@} v;
11932 the two commands give this output:
11936 (@value{GDBP}) whatis v
11937 type = struct complex
11938 (@value{GDBP}) ptype v
11939 type = struct complex @{
11947 As with @code{whatis}, using @code{ptype} without an argument refers to
11948 the type of @code{$}, the last value in the value history.
11950 @cindex incomplete type
11951 Sometimes, programs use opaque data types or incomplete specifications
11952 of complex data structure. If the debug information included in the
11953 program does not allow @value{GDBN} to display a full declaration of
11954 the data type, it will say @samp{<incomplete type>}. For example,
11955 given these declarations:
11959 struct foo *fooptr;
11963 but no definition for @code{struct foo} itself, @value{GDBN} will say:
11966 (@value{GDBP}) ptype foo
11967 $1 = <incomplete type>
11971 ``Incomplete type'' is C terminology for data types that are not
11972 completely specified.
11975 @item info types @var{regexp}
11977 Print a brief description of all types whose names match the regular
11978 expression @var{regexp} (or all types in your program, if you supply
11979 no argument). Each complete typename is matched as though it were a
11980 complete line; thus, @samp{i type value} gives information on all
11981 types in your program whose names include the string @code{value}, but
11982 @samp{i type ^value$} gives information only on types whose complete
11983 name is @code{value}.
11985 This command differs from @code{ptype} in two ways: first, like
11986 @code{whatis}, it does not print a detailed description; second, it
11987 lists all source files where a type is defined.
11990 @cindex local variables
11991 @item info scope @var{location}
11992 List all the variables local to a particular scope. This command
11993 accepts a @var{location} argument---a function name, a source line, or
11994 an address preceded by a @samp{*}, and prints all the variables local
11995 to the scope defined by that location. (@xref{Specify Location}, for
11996 details about supported forms of @var{location}.) For example:
11999 (@value{GDBP}) @b{info scope command_line_handler}
12000 Scope for command_line_handler:
12001 Symbol rl is an argument at stack/frame offset 8, length 4.
12002 Symbol linebuffer is in static storage at address 0x150a18, length 4.
12003 Symbol linelength is in static storage at address 0x150a1c, length 4.
12004 Symbol p is a local variable in register $esi, length 4.
12005 Symbol p1 is a local variable in register $ebx, length 4.
12006 Symbol nline is a local variable in register $edx, length 4.
12007 Symbol repeat is a local variable at frame offset -8, length 4.
12011 This command is especially useful for determining what data to collect
12012 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
12015 @kindex info source
12017 Show information about the current source file---that is, the source file for
12018 the function containing the current point of execution:
12021 the name of the source file, and the directory containing it,
12023 the directory it was compiled in,
12025 its length, in lines,
12027 which programming language it is written in,
12029 whether the executable includes debugging information for that file, and
12030 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
12032 whether the debugging information includes information about
12033 preprocessor macros.
12037 @kindex info sources
12039 Print the names of all source files in your program for which there is
12040 debugging information, organized into two lists: files whose symbols
12041 have already been read, and files whose symbols will be read when needed.
12043 @kindex info functions
12044 @item info functions
12045 Print the names and data types of all defined functions.
12047 @item info functions @var{regexp}
12048 Print the names and data types of all defined functions
12049 whose names contain a match for regular expression @var{regexp}.
12050 Thus, @samp{info fun step} finds all functions whose names
12051 include @code{step}; @samp{info fun ^step} finds those whose names
12052 start with @code{step}. If a function name contains characters
12053 that conflict with the regular expression language (e.g.@:
12054 @samp{operator*()}), they may be quoted with a backslash.
12056 @kindex info variables
12057 @item info variables
12058 Print the names and data types of all variables that are declared
12059 outside of functions (i.e.@: excluding local variables).
12061 @item info variables @var{regexp}
12062 Print the names and data types of all variables (except for local
12063 variables) whose names contain a match for regular expression
12066 @kindex info classes
12067 @cindex Objective-C, classes and selectors
12069 @itemx info classes @var{regexp}
12070 Display all Objective-C classes in your program, or
12071 (with the @var{regexp} argument) all those matching a particular regular
12074 @kindex info selectors
12075 @item info selectors
12076 @itemx info selectors @var{regexp}
12077 Display all Objective-C selectors in your program, or
12078 (with the @var{regexp} argument) all those matching a particular regular
12082 This was never implemented.
12083 @kindex info methods
12085 @itemx info methods @var{regexp}
12086 The @code{info methods} command permits the user to examine all defined
12087 methods within C@t{++} program, or (with the @var{regexp} argument) a
12088 specific set of methods found in the various C@t{++} classes. Many
12089 C@t{++} classes provide a large number of methods. Thus, the output
12090 from the @code{ptype} command can be overwhelming and hard to use. The
12091 @code{info-methods} command filters the methods, printing only those
12092 which match the regular-expression @var{regexp}.
12095 @cindex reloading symbols
12096 Some systems allow individual object files that make up your program to
12097 be replaced without stopping and restarting your program. For example,
12098 in VxWorks you can simply recompile a defective object file and keep on
12099 running. If you are running on one of these systems, you can allow
12100 @value{GDBN} to reload the symbols for automatically relinked modules:
12103 @kindex set symbol-reloading
12104 @item set symbol-reloading on
12105 Replace symbol definitions for the corresponding source file when an
12106 object file with a particular name is seen again.
12108 @item set symbol-reloading off
12109 Do not replace symbol definitions when encountering object files of the
12110 same name more than once. This is the default state; if you are not
12111 running on a system that permits automatic relinking of modules, you
12112 should leave @code{symbol-reloading} off, since otherwise @value{GDBN}
12113 may discard symbols when linking large programs, that may contain
12114 several modules (from different directories or libraries) with the same
12117 @kindex show symbol-reloading
12118 @item show symbol-reloading
12119 Show the current @code{on} or @code{off} setting.
12122 @cindex opaque data types
12123 @kindex set opaque-type-resolution
12124 @item set opaque-type-resolution on
12125 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
12126 declared as a pointer to a @code{struct}, @code{class}, or
12127 @code{union}---for example, @code{struct MyType *}---that is used in one
12128 source file although the full declaration of @code{struct MyType} is in
12129 another source file. The default is on.
12131 A change in the setting of this subcommand will not take effect until
12132 the next time symbols for a file are loaded.
12134 @item set opaque-type-resolution off
12135 Tell @value{GDBN} not to resolve opaque types. In this case, the type
12136 is printed as follows:
12138 @{<no data fields>@}
12141 @kindex show opaque-type-resolution
12142 @item show opaque-type-resolution
12143 Show whether opaque types are resolved or not.
12145 @kindex set print symbol-loading
12146 @cindex print messages when symbols are loaded
12147 @item set print symbol-loading
12148 @itemx set print symbol-loading on
12149 @itemx set print symbol-loading off
12150 The @code{set print symbol-loading} command allows you to enable or
12151 disable printing of messages when @value{GDBN} loads symbols.
12152 By default, these messages will be printed, and normally this is what
12153 you want. Disabling these messages is useful when debugging applications
12154 with lots of shared libraries where the quantity of output can be more
12155 annoying than useful.
12157 @kindex show print symbol-loading
12158 @item show print symbol-loading
12159 Show whether messages will be printed when @value{GDBN} loads symbols.
12161 @kindex maint print symbols
12162 @cindex symbol dump
12163 @kindex maint print psymbols
12164 @cindex partial symbol dump
12165 @item maint print symbols @var{filename}
12166 @itemx maint print psymbols @var{filename}
12167 @itemx maint print msymbols @var{filename}
12168 Write a dump of debugging symbol data into the file @var{filename}.
12169 These commands are used to debug the @value{GDBN} symbol-reading code. Only
12170 symbols with debugging data are included. If you use @samp{maint print
12171 symbols}, @value{GDBN} includes all the symbols for which it has already
12172 collected full details: that is, @var{filename} reflects symbols for
12173 only those files whose symbols @value{GDBN} has read. You can use the
12174 command @code{info sources} to find out which files these are. If you
12175 use @samp{maint print psymbols} instead, the dump shows information about
12176 symbols that @value{GDBN} only knows partially---that is, symbols defined in
12177 files that @value{GDBN} has skimmed, but not yet read completely. Finally,
12178 @samp{maint print msymbols} dumps just the minimal symbol information
12179 required for each object file from which @value{GDBN} has read some symbols.
12180 @xref{Files, ,Commands to Specify Files}, for a discussion of how
12181 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
12183 @kindex maint info symtabs
12184 @kindex maint info psymtabs
12185 @cindex listing @value{GDBN}'s internal symbol tables
12186 @cindex symbol tables, listing @value{GDBN}'s internal
12187 @cindex full symbol tables, listing @value{GDBN}'s internal
12188 @cindex partial symbol tables, listing @value{GDBN}'s internal
12189 @item maint info symtabs @r{[} @var{regexp} @r{]}
12190 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
12192 List the @code{struct symtab} or @code{struct partial_symtab}
12193 structures whose names match @var{regexp}. If @var{regexp} is not
12194 given, list them all. The output includes expressions which you can
12195 copy into a @value{GDBN} debugging this one to examine a particular
12196 structure in more detail. For example:
12199 (@value{GDBP}) maint info psymtabs dwarf2read
12200 @{ objfile /home/gnu/build/gdb/gdb
12201 ((struct objfile *) 0x82e69d0)
12202 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
12203 ((struct partial_symtab *) 0x8474b10)
12206 text addresses 0x814d3c8 -- 0x8158074
12207 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
12208 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
12209 dependencies (none)
12212 (@value{GDBP}) maint info symtabs
12216 We see that there is one partial symbol table whose filename contains
12217 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
12218 and we see that @value{GDBN} has not read in any symtabs yet at all.
12219 If we set a breakpoint on a function, that will cause @value{GDBN} to
12220 read the symtab for the compilation unit containing that function:
12223 (@value{GDBP}) break dwarf2_psymtab_to_symtab
12224 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
12226 (@value{GDBP}) maint info symtabs
12227 @{ objfile /home/gnu/build/gdb/gdb
12228 ((struct objfile *) 0x82e69d0)
12229 @{ symtab /home/gnu/src/gdb/dwarf2read.c
12230 ((struct symtab *) 0x86c1f38)
12233 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
12234 linetable ((struct linetable *) 0x8370fa0)
12235 debugformat DWARF 2
12244 @chapter Altering Execution
12246 Once you think you have found an error in your program, you might want to
12247 find out for certain whether correcting the apparent error would lead to
12248 correct results in the rest of the run. You can find the answer by
12249 experiment, using the @value{GDBN} features for altering execution of the
12252 For example, you can store new values into variables or memory
12253 locations, give your program a signal, restart it at a different
12254 address, or even return prematurely from a function.
12257 * Assignment:: Assignment to variables
12258 * Jumping:: Continuing at a different address
12259 * Signaling:: Giving your program a signal
12260 * Returning:: Returning from a function
12261 * Calling:: Calling your program's functions
12262 * Patching:: Patching your program
12266 @section Assignment to Variables
12269 @cindex setting variables
12270 To alter the value of a variable, evaluate an assignment expression.
12271 @xref{Expressions, ,Expressions}. For example,
12278 stores the value 4 into the variable @code{x}, and then prints the
12279 value of the assignment expression (which is 4).
12280 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
12281 information on operators in supported languages.
12283 @kindex set variable
12284 @cindex variables, setting
12285 If you are not interested in seeing the value of the assignment, use the
12286 @code{set} command instead of the @code{print} command. @code{set} is
12287 really the same as @code{print} except that the expression's value is
12288 not printed and is not put in the value history (@pxref{Value History,
12289 ,Value History}). The expression is evaluated only for its effects.
12291 If the beginning of the argument string of the @code{set} command
12292 appears identical to a @code{set} subcommand, use the @code{set
12293 variable} command instead of just @code{set}. This command is identical
12294 to @code{set} except for its lack of subcommands. For example, if your
12295 program has a variable @code{width}, you get an error if you try to set
12296 a new value with just @samp{set width=13}, because @value{GDBN} has the
12297 command @code{set width}:
12300 (@value{GDBP}) whatis width
12302 (@value{GDBP}) p width
12304 (@value{GDBP}) set width=47
12305 Invalid syntax in expression.
12309 The invalid expression, of course, is @samp{=47}. In
12310 order to actually set the program's variable @code{width}, use
12313 (@value{GDBP}) set var width=47
12316 Because the @code{set} command has many subcommands that can conflict
12317 with the names of program variables, it is a good idea to use the
12318 @code{set variable} command instead of just @code{set}. For example, if
12319 your program has a variable @code{g}, you run into problems if you try
12320 to set a new value with just @samp{set g=4}, because @value{GDBN} has
12321 the command @code{set gnutarget}, abbreviated @code{set g}:
12325 (@value{GDBP}) whatis g
12329 (@value{GDBP}) set g=4
12333 The program being debugged has been started already.
12334 Start it from the beginning? (y or n) y
12335 Starting program: /home/smith/cc_progs/a.out
12336 "/home/smith/cc_progs/a.out": can't open to read symbols:
12337 Invalid bfd target.
12338 (@value{GDBP}) show g
12339 The current BFD target is "=4".
12344 The program variable @code{g} did not change, and you silently set the
12345 @code{gnutarget} to an invalid value. In order to set the variable
12349 (@value{GDBP}) set var g=4
12352 @value{GDBN} allows more implicit conversions in assignments than C; you can
12353 freely store an integer value into a pointer variable or vice versa,
12354 and you can convert any structure to any other structure that is the
12355 same length or shorter.
12356 @comment FIXME: how do structs align/pad in these conversions?
12357 @comment /doc@cygnus.com 18dec1990
12359 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
12360 construct to generate a value of specified type at a specified address
12361 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
12362 to memory location @code{0x83040} as an integer (which implies a certain size
12363 and representation in memory), and
12366 set @{int@}0x83040 = 4
12370 stores the value 4 into that memory location.
12373 @section Continuing at a Different Address
12375 Ordinarily, when you continue your program, you do so at the place where
12376 it stopped, with the @code{continue} command. You can instead continue at
12377 an address of your own choosing, with the following commands:
12381 @item jump @var{linespec}
12382 @itemx jump @var{location}
12383 Resume execution at line @var{linespec} or at address given by
12384 @var{location}. Execution stops again immediately if there is a
12385 breakpoint there. @xref{Specify Location}, for a description of the
12386 different forms of @var{linespec} and @var{location}. It is common
12387 practice to use the @code{tbreak} command in conjunction with
12388 @code{jump}. @xref{Set Breaks, ,Setting Breakpoints}.
12390 The @code{jump} command does not change the current stack frame, or
12391 the stack pointer, or the contents of any memory location or any
12392 register other than the program counter. If line @var{linespec} is in
12393 a different function from the one currently executing, the results may
12394 be bizarre if the two functions expect different patterns of arguments or
12395 of local variables. For this reason, the @code{jump} command requests
12396 confirmation if the specified line is not in the function currently
12397 executing. However, even bizarre results are predictable if you are
12398 well acquainted with the machine-language code of your program.
12401 @c Doesn't work on HP-UX; have to set $pcoqh and $pcoqt.
12402 On many systems, you can get much the same effect as the @code{jump}
12403 command by storing a new value into the register @code{$pc}. The
12404 difference is that this does not start your program running; it only
12405 changes the address of where it @emph{will} run when you continue. For
12413 makes the next @code{continue} command or stepping command execute at
12414 address @code{0x485}, rather than at the address where your program stopped.
12415 @xref{Continuing and Stepping, ,Continuing and Stepping}.
12417 The most common occasion to use the @code{jump} command is to back
12418 up---perhaps with more breakpoints set---over a portion of a program
12419 that has already executed, in order to examine its execution in more
12424 @section Giving your Program a Signal
12425 @cindex deliver a signal to a program
12429 @item signal @var{signal}
12430 Resume execution where your program stopped, but immediately give it the
12431 signal @var{signal}. @var{signal} can be the name or the number of a
12432 signal. For example, on many systems @code{signal 2} and @code{signal
12433 SIGINT} are both ways of sending an interrupt signal.
12435 Alternatively, if @var{signal} is zero, continue execution without
12436 giving a signal. This is useful when your program stopped on account of
12437 a signal and would ordinary see the signal when resumed with the
12438 @code{continue} command; @samp{signal 0} causes it to resume without a
12441 @code{signal} does not repeat when you press @key{RET} a second time
12442 after executing the command.
12446 Invoking the @code{signal} command is not the same as invoking the
12447 @code{kill} utility from the shell. Sending a signal with @code{kill}
12448 causes @value{GDBN} to decide what to do with the signal depending on
12449 the signal handling tables (@pxref{Signals}). The @code{signal} command
12450 passes the signal directly to your program.
12454 @section Returning from a Function
12457 @cindex returning from a function
12460 @itemx return @var{expression}
12461 You can cancel execution of a function call with the @code{return}
12462 command. If you give an
12463 @var{expression} argument, its value is used as the function's return
12467 When you use @code{return}, @value{GDBN} discards the selected stack frame
12468 (and all frames within it). You can think of this as making the
12469 discarded frame return prematurely. If you wish to specify a value to
12470 be returned, give that value as the argument to @code{return}.
12472 This pops the selected stack frame (@pxref{Selection, ,Selecting a
12473 Frame}), and any other frames inside of it, leaving its caller as the
12474 innermost remaining frame. That frame becomes selected. The
12475 specified value is stored in the registers used for returning values
12478 The @code{return} command does not resume execution; it leaves the
12479 program stopped in the state that would exist if the function had just
12480 returned. In contrast, the @code{finish} command (@pxref{Continuing
12481 and Stepping, ,Continuing and Stepping}) resumes execution until the
12482 selected stack frame returns naturally.
12484 @value{GDBN} needs to know how the @var{expression} argument should be set for
12485 the inferior. The concrete registers assignment depends on the OS ABI and the
12486 type being returned by the selected stack frame. For example it is common for
12487 OS ABI to return floating point values in FPU registers while integer values in
12488 CPU registers. Still some ABIs return even floating point values in CPU
12489 registers. Larger integer widths (such as @code{long long int}) also have
12490 specific placement rules. @value{GDBN} already knows the OS ABI from its
12491 current target so it needs to find out also the type being returned to make the
12492 assignment into the right register(s).
12494 Normally, the selected stack frame has debug info. @value{GDBN} will always
12495 use the debug info instead of the implicit type of @var{expression} when the
12496 debug info is available. For example, if you type @kbd{return -1}, and the
12497 function in the current stack frame is declared to return a @code{long long
12498 int}, @value{GDBN} transparently converts the implicit @code{int} value of -1
12499 into a @code{long long int}:
12502 Breakpoint 1, func () at gdb.base/return-nodebug.c:29
12504 (@value{GDBP}) return -1
12505 Make func return now? (y or n) y
12506 #0 0x004004f6 in main () at gdb.base/return-nodebug.c:43
12507 43 printf ("result=%lld\n", func ());
12511 However, if the selected stack frame does not have a debug info, e.g., if the
12512 function was compiled without debug info, @value{GDBN} has to find out the type
12513 to return from user. Specifying a different type by mistake may set the value
12514 in different inferior registers than the caller code expects. For example,
12515 typing @kbd{return -1} with its implicit type @code{int} would set only a part
12516 of a @code{long long int} result for a debug info less function (on 32-bit
12517 architectures). Therefore the user is required to specify the return type by
12518 an appropriate cast explicitly:
12521 Breakpoint 2, 0x0040050b in func ()
12522 (@value{GDBP}) return -1
12523 Return value type not available for selected stack frame.
12524 Please use an explicit cast of the value to return.
12525 (@value{GDBP}) return (long long int) -1
12526 Make selected stack frame return now? (y or n) y
12527 #0 0x00400526 in main ()
12532 @section Calling Program Functions
12535 @cindex calling functions
12536 @cindex inferior functions, calling
12537 @item print @var{expr}
12538 Evaluate the expression @var{expr} and display the resulting value.
12539 @var{expr} may include calls to functions in the program being
12543 @item call @var{expr}
12544 Evaluate the expression @var{expr} without displaying @code{void}
12547 You can use this variant of the @code{print} command if you want to
12548 execute a function from your program that does not return anything
12549 (a.k.a.@: @dfn{a void function}), but without cluttering the output
12550 with @code{void} returned values that @value{GDBN} will otherwise
12551 print. If the result is not void, it is printed and saved in the
12555 It is possible for the function you call via the @code{print} or
12556 @code{call} command to generate a signal (e.g., if there's a bug in
12557 the function, or if you passed it incorrect arguments). What happens
12558 in that case is controlled by the @code{set unwindonsignal} command.
12561 @item set unwindonsignal
12562 @kindex set unwindonsignal
12563 @cindex unwind stack in called functions
12564 @cindex call dummy stack unwinding
12565 Set unwinding of the stack if a signal is received while in a function
12566 that @value{GDBN} called in the program being debugged. If set to on,
12567 @value{GDBN} unwinds the stack it created for the call and restores
12568 the context to what it was before the call. If set to off (the
12569 default), @value{GDBN} stops in the frame where the signal was
12572 @item show unwindonsignal
12573 @kindex show unwindonsignal
12574 Show the current setting of stack unwinding in the functions called by
12578 @cindex weak alias functions
12579 Sometimes, a function you wish to call is actually a @dfn{weak alias}
12580 for another function. In such case, @value{GDBN} might not pick up
12581 the type information, including the types of the function arguments,
12582 which causes @value{GDBN} to call the inferior function incorrectly.
12583 As a result, the called function will function erroneously and may
12584 even crash. A solution to that is to use the name of the aliased
12588 @section Patching Programs
12590 @cindex patching binaries
12591 @cindex writing into executables
12592 @cindex writing into corefiles
12594 By default, @value{GDBN} opens the file containing your program's
12595 executable code (or the corefile) read-only. This prevents accidental
12596 alterations to machine code; but it also prevents you from intentionally
12597 patching your program's binary.
12599 If you'd like to be able to patch the binary, you can specify that
12600 explicitly with the @code{set write} command. For example, you might
12601 want to turn on internal debugging flags, or even to make emergency
12607 @itemx set write off
12608 If you specify @samp{set write on}, @value{GDBN} opens executable and
12609 core files for both reading and writing; if you specify @kbd{set write
12610 off} (the default), @value{GDBN} opens them read-only.
12612 If you have already loaded a file, you must load it again (using the
12613 @code{exec-file} or @code{core-file} command) after changing @code{set
12614 write}, for your new setting to take effect.
12618 Display whether executable files and core files are opened for writing
12619 as well as reading.
12623 @chapter @value{GDBN} Files
12625 @value{GDBN} needs to know the file name of the program to be debugged,
12626 both in order to read its symbol table and in order to start your
12627 program. To debug a core dump of a previous run, you must also tell
12628 @value{GDBN} the name of the core dump file.
12631 * Files:: Commands to specify files
12632 * Separate Debug Files:: Debugging information in separate files
12633 * Symbol Errors:: Errors reading symbol files
12637 @section Commands to Specify Files
12639 @cindex symbol table
12640 @cindex core dump file
12642 You may want to specify executable and core dump file names. The usual
12643 way to do this is at start-up time, using the arguments to
12644 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
12645 Out of @value{GDBN}}).
12647 Occasionally it is necessary to change to a different file during a
12648 @value{GDBN} session. Or you may run @value{GDBN} and forget to
12649 specify a file you want to use. Or you are debugging a remote target
12650 via @code{gdbserver} (@pxref{Server, file, Using the @code{gdbserver}
12651 Program}). In these situations the @value{GDBN} commands to specify
12652 new files are useful.
12655 @cindex executable file
12657 @item file @var{filename}
12658 Use @var{filename} as the program to be debugged. It is read for its
12659 symbols and for the contents of pure memory. It is also the program
12660 executed when you use the @code{run} command. If you do not specify a
12661 directory and the file is not found in the @value{GDBN} working directory,
12662 @value{GDBN} uses the environment variable @code{PATH} as a list of
12663 directories to search, just as the shell does when looking for a program
12664 to run. You can change the value of this variable, for both @value{GDBN}
12665 and your program, using the @code{path} command.
12667 @cindex unlinked object files
12668 @cindex patching object files
12669 You can load unlinked object @file{.o} files into @value{GDBN} using
12670 the @code{file} command. You will not be able to ``run'' an object
12671 file, but you can disassemble functions and inspect variables. Also,
12672 if the underlying BFD functionality supports it, you could use
12673 @kbd{gdb -write} to patch object files using this technique. Note
12674 that @value{GDBN} can neither interpret nor modify relocations in this
12675 case, so branches and some initialized variables will appear to go to
12676 the wrong place. But this feature is still handy from time to time.
12679 @code{file} with no argument makes @value{GDBN} discard any information it
12680 has on both executable file and the symbol table.
12683 @item exec-file @r{[} @var{filename} @r{]}
12684 Specify that the program to be run (but not the symbol table) is found
12685 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
12686 if necessary to locate your program. Omitting @var{filename} means to
12687 discard information on the executable file.
12689 @kindex symbol-file
12690 @item symbol-file @r{[} @var{filename} @r{]}
12691 Read symbol table information from file @var{filename}. @code{PATH} is
12692 searched when necessary. Use the @code{file} command to get both symbol
12693 table and program to run from the same file.
12695 @code{symbol-file} with no argument clears out @value{GDBN} information on your
12696 program's symbol table.
12698 The @code{symbol-file} command causes @value{GDBN} to forget the contents of
12699 some breakpoints and auto-display expressions. This is because they may
12700 contain pointers to the internal data recording symbols and data types,
12701 which are part of the old symbol table data being discarded inside
12704 @code{symbol-file} does not repeat if you press @key{RET} again after
12707 When @value{GDBN} is configured for a particular environment, it
12708 understands debugging information in whatever format is the standard
12709 generated for that environment; you may use either a @sc{gnu} compiler, or
12710 other compilers that adhere to the local conventions.
12711 Best results are usually obtained from @sc{gnu} compilers; for example,
12712 using @code{@value{NGCC}} you can generate debugging information for
12715 For most kinds of object files, with the exception of old SVR3 systems
12716 using COFF, the @code{symbol-file} command does not normally read the
12717 symbol table in full right away. Instead, it scans the symbol table
12718 quickly to find which source files and which symbols are present. The
12719 details are read later, one source file at a time, as they are needed.
12721 The purpose of this two-stage reading strategy is to make @value{GDBN}
12722 start up faster. For the most part, it is invisible except for
12723 occasional pauses while the symbol table details for a particular source
12724 file are being read. (The @code{set verbose} command can turn these
12725 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
12726 Warnings and Messages}.)
12728 We have not implemented the two-stage strategy for COFF yet. When the
12729 symbol table is stored in COFF format, @code{symbol-file} reads the
12730 symbol table data in full right away. Note that ``stabs-in-COFF''
12731 still does the two-stage strategy, since the debug info is actually
12735 @cindex reading symbols immediately
12736 @cindex symbols, reading immediately
12737 @item symbol-file @var{filename} @r{[} -readnow @r{]}
12738 @itemx file @var{filename} @r{[} -readnow @r{]}
12739 You can override the @value{GDBN} two-stage strategy for reading symbol
12740 tables by using the @samp{-readnow} option with any of the commands that
12741 load symbol table information, if you want to be sure @value{GDBN} has the
12742 entire symbol table available.
12744 @c FIXME: for now no mention of directories, since this seems to be in
12745 @c flux. 13mar1992 status is that in theory GDB would look either in
12746 @c current dir or in same dir as myprog; but issues like competing
12747 @c GDB's, or clutter in system dirs, mean that in practice right now
12748 @c only current dir is used. FFish says maybe a special GDB hierarchy
12749 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
12753 @item core-file @r{[}@var{filename}@r{]}
12755 Specify the whereabouts of a core dump file to be used as the ``contents
12756 of memory''. Traditionally, core files contain only some parts of the
12757 address space of the process that generated them; @value{GDBN} can access the
12758 executable file itself for other parts.
12760 @code{core-file} with no argument specifies that no core file is
12763 Note that the core file is ignored when your program is actually running
12764 under @value{GDBN}. So, if you have been running your program and you
12765 wish to debug a core file instead, you must kill the subprocess in which
12766 the program is running. To do this, use the @code{kill} command
12767 (@pxref{Kill Process, ,Killing the Child Process}).
12769 @kindex add-symbol-file
12770 @cindex dynamic linking
12771 @item add-symbol-file @var{filename} @var{address}
12772 @itemx add-symbol-file @var{filename} @var{address} @r{[} -readnow @r{]}
12773 @itemx add-symbol-file @var{filename} @r{-s}@var{section} @var{address} @dots{}
12774 The @code{add-symbol-file} command reads additional symbol table
12775 information from the file @var{filename}. You would use this command
12776 when @var{filename} has been dynamically loaded (by some other means)
12777 into the program that is running. @var{address} should be the memory
12778 address at which the file has been loaded; @value{GDBN} cannot figure
12779 this out for itself. You can additionally specify an arbitrary number
12780 of @samp{@r{-s}@var{section} @var{address}} pairs, to give an explicit
12781 section name and base address for that section. You can specify any
12782 @var{address} as an expression.
12784 The symbol table of the file @var{filename} is added to the symbol table
12785 originally read with the @code{symbol-file} command. You can use the
12786 @code{add-symbol-file} command any number of times; the new symbol data
12787 thus read keeps adding to the old. To discard all old symbol data
12788 instead, use the @code{symbol-file} command without any arguments.
12790 @cindex relocatable object files, reading symbols from
12791 @cindex object files, relocatable, reading symbols from
12792 @cindex reading symbols from relocatable object files
12793 @cindex symbols, reading from relocatable object files
12794 @cindex @file{.o} files, reading symbols from
12795 Although @var{filename} is typically a shared library file, an
12796 executable file, or some other object file which has been fully
12797 relocated for loading into a process, you can also load symbolic
12798 information from relocatable @file{.o} files, as long as:
12802 the file's symbolic information refers only to linker symbols defined in
12803 that file, not to symbols defined by other object files,
12805 every section the file's symbolic information refers to has actually
12806 been loaded into the inferior, as it appears in the file, and
12808 you can determine the address at which every section was loaded, and
12809 provide these to the @code{add-symbol-file} command.
12813 Some embedded operating systems, like Sun Chorus and VxWorks, can load
12814 relocatable files into an already running program; such systems
12815 typically make the requirements above easy to meet. However, it's
12816 important to recognize that many native systems use complex link
12817 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
12818 assembly, for example) that make the requirements difficult to meet. In
12819 general, one cannot assume that using @code{add-symbol-file} to read a
12820 relocatable object file's symbolic information will have the same effect
12821 as linking the relocatable object file into the program in the normal
12824 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
12826 @kindex add-symbol-file-from-memory
12827 @cindex @code{syscall DSO}
12828 @cindex load symbols from memory
12829 @item add-symbol-file-from-memory @var{address}
12830 Load symbols from the given @var{address} in a dynamically loaded
12831 object file whose image is mapped directly into the inferior's memory.
12832 For example, the Linux kernel maps a @code{syscall DSO} into each
12833 process's address space; this DSO provides kernel-specific code for
12834 some system calls. The argument can be any expression whose
12835 evaluation yields the address of the file's shared object file header.
12836 For this command to work, you must have used @code{symbol-file} or
12837 @code{exec-file} commands in advance.
12839 @kindex add-shared-symbol-files
12841 @item add-shared-symbol-files @var{library-file}
12842 @itemx assf @var{library-file}
12843 The @code{add-shared-symbol-files} command can currently be used only
12844 in the Cygwin build of @value{GDBN} on MS-Windows OS, where it is an
12845 alias for the @code{dll-symbols} command (@pxref{Cygwin Native}).
12846 @value{GDBN} automatically looks for shared libraries, however if
12847 @value{GDBN} does not find yours, you can invoke
12848 @code{add-shared-symbol-files}. It takes one argument: the shared
12849 library's file name. @code{assf} is a shorthand alias for
12850 @code{add-shared-symbol-files}.
12853 @item section @var{section} @var{addr}
12854 The @code{section} command changes the base address of the named
12855 @var{section} of the exec file to @var{addr}. This can be used if the
12856 exec file does not contain section addresses, (such as in the
12857 @code{a.out} format), or when the addresses specified in the file
12858 itself are wrong. Each section must be changed separately. The
12859 @code{info files} command, described below, lists all the sections and
12863 @kindex info target
12866 @code{info files} and @code{info target} are synonymous; both print the
12867 current target (@pxref{Targets, ,Specifying a Debugging Target}),
12868 including the names of the executable and core dump files currently in
12869 use by @value{GDBN}, and the files from which symbols were loaded. The
12870 command @code{help target} lists all possible targets rather than
12873 @kindex maint info sections
12874 @item maint info sections
12875 Another command that can give you extra information about program sections
12876 is @code{maint info sections}. In addition to the section information
12877 displayed by @code{info files}, this command displays the flags and file
12878 offset of each section in the executable and core dump files. In addition,
12879 @code{maint info sections} provides the following command options (which
12880 may be arbitrarily combined):
12884 Display sections for all loaded object files, including shared libraries.
12885 @item @var{sections}
12886 Display info only for named @var{sections}.
12887 @item @var{section-flags}
12888 Display info only for sections for which @var{section-flags} are true.
12889 The section flags that @value{GDBN} currently knows about are:
12892 Section will have space allocated in the process when loaded.
12893 Set for all sections except those containing debug information.
12895 Section will be loaded from the file into the child process memory.
12896 Set for pre-initialized code and data, clear for @code{.bss} sections.
12898 Section needs to be relocated before loading.
12900 Section cannot be modified by the child process.
12902 Section contains executable code only.
12904 Section contains data only (no executable code).
12906 Section will reside in ROM.
12908 Section contains data for constructor/destructor lists.
12910 Section is not empty.
12912 An instruction to the linker to not output the section.
12913 @item COFF_SHARED_LIBRARY
12914 A notification to the linker that the section contains
12915 COFF shared library information.
12917 Section contains common symbols.
12920 @kindex set trust-readonly-sections
12921 @cindex read-only sections
12922 @item set trust-readonly-sections on
12923 Tell @value{GDBN} that readonly sections in your object file
12924 really are read-only (i.e.@: that their contents will not change).
12925 In that case, @value{GDBN} can fetch values from these sections
12926 out of the object file, rather than from the target program.
12927 For some targets (notably embedded ones), this can be a significant
12928 enhancement to debugging performance.
12930 The default is off.
12932 @item set trust-readonly-sections off
12933 Tell @value{GDBN} not to trust readonly sections. This means that
12934 the contents of the section might change while the program is running,
12935 and must therefore be fetched from the target when needed.
12937 @item show trust-readonly-sections
12938 Show the current setting of trusting readonly sections.
12941 All file-specifying commands allow both absolute and relative file names
12942 as arguments. @value{GDBN} always converts the file name to an absolute file
12943 name and remembers it that way.
12945 @cindex shared libraries
12946 @anchor{Shared Libraries}
12947 @value{GDBN} supports @sc{gnu}/Linux, MS-Windows, HP-UX, SunOS, SVr4, Irix,
12948 and IBM RS/6000 AIX shared libraries.
12950 On MS-Windows @value{GDBN} must be linked with the Expat library to support
12951 shared libraries. @xref{Expat}.
12953 @value{GDBN} automatically loads symbol definitions from shared libraries
12954 when you use the @code{run} command, or when you examine a core file.
12955 (Before you issue the @code{run} command, @value{GDBN} does not understand
12956 references to a function in a shared library, however---unless you are
12957 debugging a core file).
12959 On HP-UX, if the program loads a library explicitly, @value{GDBN}
12960 automatically loads the symbols at the time of the @code{shl_load} call.
12962 @c FIXME: some @value{GDBN} release may permit some refs to undef
12963 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
12964 @c FIXME...lib; check this from time to time when updating manual
12966 There are times, however, when you may wish to not automatically load
12967 symbol definitions from shared libraries, such as when they are
12968 particularly large or there are many of them.
12970 To control the automatic loading of shared library symbols, use the
12974 @kindex set auto-solib-add
12975 @item set auto-solib-add @var{mode}
12976 If @var{mode} is @code{on}, symbols from all shared object libraries
12977 will be loaded automatically when the inferior begins execution, you
12978 attach to an independently started inferior, or when the dynamic linker
12979 informs @value{GDBN} that a new library has been loaded. If @var{mode}
12980 is @code{off}, symbols must be loaded manually, using the
12981 @code{sharedlibrary} command. The default value is @code{on}.
12983 @cindex memory used for symbol tables
12984 If your program uses lots of shared libraries with debug info that
12985 takes large amounts of memory, you can decrease the @value{GDBN}
12986 memory footprint by preventing it from automatically loading the
12987 symbols from shared libraries. To that end, type @kbd{set
12988 auto-solib-add off} before running the inferior, then load each
12989 library whose debug symbols you do need with @kbd{sharedlibrary
12990 @var{regexp}}, where @var{regexp} is a regular expression that matches
12991 the libraries whose symbols you want to be loaded.
12993 @kindex show auto-solib-add
12994 @item show auto-solib-add
12995 Display the current autoloading mode.
12998 @cindex load shared library
12999 To explicitly load shared library symbols, use the @code{sharedlibrary}
13003 @kindex info sharedlibrary
13006 @itemx info sharedlibrary
13007 Print the names of the shared libraries which are currently loaded.
13009 @kindex sharedlibrary
13011 @item sharedlibrary @var{regex}
13012 @itemx share @var{regex}
13013 Load shared object library symbols for files matching a
13014 Unix regular expression.
13015 As with files loaded automatically, it only loads shared libraries
13016 required by your program for a core file or after typing @code{run}. If
13017 @var{regex} is omitted all shared libraries required by your program are
13020 @item nosharedlibrary
13021 @kindex nosharedlibrary
13022 @cindex unload symbols from shared libraries
13023 Unload all shared object library symbols. This discards all symbols
13024 that have been loaded from all shared libraries. Symbols from shared
13025 libraries that were loaded by explicit user requests are not
13029 Sometimes you may wish that @value{GDBN} stops and gives you control
13030 when any of shared library events happen. Use the @code{set
13031 stop-on-solib-events} command for this:
13034 @item set stop-on-solib-events
13035 @kindex set stop-on-solib-events
13036 This command controls whether @value{GDBN} should give you control
13037 when the dynamic linker notifies it about some shared library event.
13038 The most common event of interest is loading or unloading of a new
13041 @item show stop-on-solib-events
13042 @kindex show stop-on-solib-events
13043 Show whether @value{GDBN} stops and gives you control when shared
13044 library events happen.
13047 Shared libraries are also supported in many cross or remote debugging
13048 configurations. @value{GDBN} needs to have access to the target's libraries;
13049 this can be accomplished either by providing copies of the libraries
13050 on the host system, or by asking @value{GDBN} to automatically retrieve the
13051 libraries from the target. If copies of the target libraries are
13052 provided, they need to be the same as the target libraries, although the
13053 copies on the target can be stripped as long as the copies on the host are
13056 @cindex where to look for shared libraries
13057 For remote debugging, you need to tell @value{GDBN} where the target
13058 libraries are, so that it can load the correct copies---otherwise, it
13059 may try to load the host's libraries. @value{GDBN} has two variables
13060 to specify the search directories for target libraries.
13063 @cindex prefix for shared library file names
13064 @cindex system root, alternate
13065 @kindex set solib-absolute-prefix
13066 @kindex set sysroot
13067 @item set sysroot @var{path}
13068 Use @var{path} as the system root for the program being debugged. Any
13069 absolute shared library paths will be prefixed with @var{path}; many
13070 runtime loaders store the absolute paths to the shared library in the
13071 target program's memory. If you use @code{set sysroot} to find shared
13072 libraries, they need to be laid out in the same way that they are on
13073 the target, with e.g.@: a @file{/lib} and @file{/usr/lib} hierarchy
13076 If @var{path} starts with the sequence @file{remote:}, @value{GDBN} will
13077 retrieve the target libraries from the remote system. This is only
13078 supported when using a remote target that supports the @code{remote get}
13079 command (@pxref{File Transfer,,Sending files to a remote system}).
13080 The part of @var{path} following the initial @file{remote:}
13081 (if present) is used as system root prefix on the remote file system.
13082 @footnote{If you want to specify a local system root using a directory
13083 that happens to be named @file{remote:}, you need to use some equivalent
13084 variant of the name like @file{./remote:}.}
13086 The @code{set solib-absolute-prefix} command is an alias for @code{set
13089 @cindex default system root
13090 @cindex @samp{--with-sysroot}
13091 You can set the default system root by using the configure-time
13092 @samp{--with-sysroot} option. If the system root is inside
13093 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
13094 @samp{--exec-prefix}), then the default system root will be updated
13095 automatically if the installed @value{GDBN} is moved to a new
13098 @kindex show sysroot
13100 Display the current shared library prefix.
13102 @kindex set solib-search-path
13103 @item set solib-search-path @var{path}
13104 If this variable is set, @var{path} is a colon-separated list of
13105 directories to search for shared libraries. @samp{solib-search-path}
13106 is used after @samp{sysroot} fails to locate the library, or if the
13107 path to the library is relative instead of absolute. If you want to
13108 use @samp{solib-search-path} instead of @samp{sysroot}, be sure to set
13109 @samp{sysroot} to a nonexistent directory to prevent @value{GDBN} from
13110 finding your host's libraries. @samp{sysroot} is preferred; setting
13111 it to a nonexistent directory may interfere with automatic loading
13112 of shared library symbols.
13114 @kindex show solib-search-path
13115 @item show solib-search-path
13116 Display the current shared library search path.
13120 @node Separate Debug Files
13121 @section Debugging Information in Separate Files
13122 @cindex separate debugging information files
13123 @cindex debugging information in separate files
13124 @cindex @file{.debug} subdirectories
13125 @cindex debugging information directory, global
13126 @cindex global debugging information directory
13127 @cindex build ID, and separate debugging files
13128 @cindex @file{.build-id} directory
13130 @value{GDBN} allows you to put a program's debugging information in a
13131 file separate from the executable itself, in a way that allows
13132 @value{GDBN} to find and load the debugging information automatically.
13133 Since debugging information can be very large---sometimes larger
13134 than the executable code itself---some systems distribute debugging
13135 information for their executables in separate files, which users can
13136 install only when they need to debug a problem.
13138 @value{GDBN} supports two ways of specifying the separate debug info
13143 The executable contains a @dfn{debug link} that specifies the name of
13144 the separate debug info file. The separate debug file's name is
13145 usually @file{@var{executable}.debug}, where @var{executable} is the
13146 name of the corresponding executable file without leading directories
13147 (e.g., @file{ls.debug} for @file{/usr/bin/ls}). In addition, the
13148 debug link specifies a CRC32 checksum for the debug file, which
13149 @value{GDBN} uses to validate that the executable and the debug file
13150 came from the same build.
13153 The executable contains a @dfn{build ID}, a unique bit string that is
13154 also present in the corresponding debug info file. (This is supported
13155 only on some operating systems, notably those which use the ELF format
13156 for binary files and the @sc{gnu} Binutils.) For more details about
13157 this feature, see the description of the @option{--build-id}
13158 command-line option in @ref{Options, , Command Line Options, ld.info,
13159 The GNU Linker}. The debug info file's name is not specified
13160 explicitly by the build ID, but can be computed from the build ID, see
13164 Depending on the way the debug info file is specified, @value{GDBN}
13165 uses two different methods of looking for the debug file:
13169 For the ``debug link'' method, @value{GDBN} looks up the named file in
13170 the directory of the executable file, then in a subdirectory of that
13171 directory named @file{.debug}, and finally under the global debug
13172 directory, in a subdirectory whose name is identical to the leading
13173 directories of the executable's absolute file name.
13176 For the ``build ID'' method, @value{GDBN} looks in the
13177 @file{.build-id} subdirectory of the global debug directory for a file
13178 named @file{@var{nn}/@var{nnnnnnnn}.debug}, where @var{nn} are the
13179 first 2 hex characters of the build ID bit string, and @var{nnnnnnnn}
13180 are the rest of the bit string. (Real build ID strings are 32 or more
13181 hex characters, not 10.)
13184 So, for example, suppose you ask @value{GDBN} to debug
13185 @file{/usr/bin/ls}, which has a debug link that specifies the
13186 file @file{ls.debug}, and a build ID whose value in hex is
13187 @code{abcdef1234}. If the global debug directory is
13188 @file{/usr/lib/debug}, then @value{GDBN} will look for the following
13189 debug information files, in the indicated order:
13193 @file{/usr/lib/debug/.build-id/ab/cdef1234.debug}
13195 @file{/usr/bin/ls.debug}
13197 @file{/usr/bin/.debug/ls.debug}
13199 @file{/usr/lib/debug/usr/bin/ls.debug}.
13202 You can set the global debugging info directory's name, and view the
13203 name @value{GDBN} is currently using.
13207 @kindex set debug-file-directory
13208 @item set debug-file-directory @var{directory}
13209 Set the directory which @value{GDBN} searches for separate debugging
13210 information files to @var{directory}.
13212 @kindex show debug-file-directory
13213 @item show debug-file-directory
13214 Show the directory @value{GDBN} searches for separate debugging
13219 @cindex @code{.gnu_debuglink} sections
13220 @cindex debug link sections
13221 A debug link is a special section of the executable file named
13222 @code{.gnu_debuglink}. The section must contain:
13226 A filename, with any leading directory components removed, followed by
13229 zero to three bytes of padding, as needed to reach the next four-byte
13230 boundary within the section, and
13232 a four-byte CRC checksum, stored in the same endianness used for the
13233 executable file itself. The checksum is computed on the debugging
13234 information file's full contents by the function given below, passing
13235 zero as the @var{crc} argument.
13238 Any executable file format can carry a debug link, as long as it can
13239 contain a section named @code{.gnu_debuglink} with the contents
13242 @cindex @code{.note.gnu.build-id} sections
13243 @cindex build ID sections
13244 The build ID is a special section in the executable file (and in other
13245 ELF binary files that @value{GDBN} may consider). This section is
13246 often named @code{.note.gnu.build-id}, but that name is not mandatory.
13247 It contains unique identification for the built files---the ID remains
13248 the same across multiple builds of the same build tree. The default
13249 algorithm SHA1 produces 160 bits (40 hexadecimal characters) of the
13250 content for the build ID string. The same section with an identical
13251 value is present in the original built binary with symbols, in its
13252 stripped variant, and in the separate debugging information file.
13254 The debugging information file itself should be an ordinary
13255 executable, containing a full set of linker symbols, sections, and
13256 debugging information. The sections of the debugging information file
13257 should have the same names, addresses, and sizes as the original file,
13258 but they need not contain any data---much like a @code{.bss} section
13259 in an ordinary executable.
13261 The @sc{gnu} binary utilities (Binutils) package includes the
13262 @samp{objcopy} utility that can produce
13263 the separated executable / debugging information file pairs using the
13264 following commands:
13267 @kbd{objcopy --only-keep-debug foo foo.debug}
13272 These commands remove the debugging
13273 information from the executable file @file{foo} and place it in the file
13274 @file{foo.debug}. You can use the first, second or both methods to link the
13279 The debug link method needs the following additional command to also leave
13280 behind a debug link in @file{foo}:
13283 @kbd{objcopy --add-gnu-debuglink=foo.debug foo}
13286 Ulrich Drepper's @file{elfutils} package, starting with version 0.53, contains
13287 a version of the @code{strip} command such that the command @kbd{strip foo -f
13288 foo.debug} has the same functionality as the two @code{objcopy} commands and
13289 the @code{ln -s} command above, together.
13292 Build ID gets embedded into the main executable using @code{ld --build-id} or
13293 the @value{NGCC} counterpart @code{gcc -Wl,--build-id}. Build ID support plus
13294 compatibility fixes for debug files separation are present in @sc{gnu} binary
13295 utilities (Binutils) package since version 2.18.
13300 Since there are many different ways to compute CRC's for the debug
13301 link (different polynomials, reversals, byte ordering, etc.), the
13302 simplest way to describe the CRC used in @code{.gnu_debuglink}
13303 sections is to give the complete code for a function that computes it:
13305 @kindex gnu_debuglink_crc32
13308 gnu_debuglink_crc32 (unsigned long crc,
13309 unsigned char *buf, size_t len)
13311 static const unsigned long crc32_table[256] =
13313 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
13314 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
13315 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
13316 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
13317 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
13318 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
13319 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
13320 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
13321 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
13322 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
13323 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
13324 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
13325 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
13326 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
13327 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
13328 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
13329 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
13330 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
13331 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
13332 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
13333 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
13334 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
13335 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
13336 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
13337 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
13338 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
13339 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
13340 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
13341 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
13342 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
13343 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
13344 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
13345 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
13346 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
13347 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
13348 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
13349 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
13350 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
13351 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
13352 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
13353 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
13354 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
13355 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
13356 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
13357 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
13358 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
13359 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
13360 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
13361 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
13362 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
13363 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
13366 unsigned char *end;
13368 crc = ~crc & 0xffffffff;
13369 for (end = buf + len; buf < end; ++buf)
13370 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
13371 return ~crc & 0xffffffff;
13376 This computation does not apply to the ``build ID'' method.
13379 @node Symbol Errors
13380 @section Errors Reading Symbol Files
13382 While reading a symbol file, @value{GDBN} occasionally encounters problems,
13383 such as symbol types it does not recognize, or known bugs in compiler
13384 output. By default, @value{GDBN} does not notify you of such problems, since
13385 they are relatively common and primarily of interest to people
13386 debugging compilers. If you are interested in seeing information
13387 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
13388 only one message about each such type of problem, no matter how many
13389 times the problem occurs; or you can ask @value{GDBN} to print more messages,
13390 to see how many times the problems occur, with the @code{set
13391 complaints} command (@pxref{Messages/Warnings, ,Optional Warnings and
13394 The messages currently printed, and their meanings, include:
13397 @item inner block not inside outer block in @var{symbol}
13399 The symbol information shows where symbol scopes begin and end
13400 (such as at the start of a function or a block of statements). This
13401 error indicates that an inner scope block is not fully contained
13402 in its outer scope blocks.
13404 @value{GDBN} circumvents the problem by treating the inner block as if it had
13405 the same scope as the outer block. In the error message, @var{symbol}
13406 may be shown as ``@code{(don't know)}'' if the outer block is not a
13409 @item block at @var{address} out of order
13411 The symbol information for symbol scope blocks should occur in
13412 order of increasing addresses. This error indicates that it does not
13415 @value{GDBN} does not circumvent this problem, and has trouble
13416 locating symbols in the source file whose symbols it is reading. (You
13417 can often determine what source file is affected by specifying
13418 @code{set verbose on}. @xref{Messages/Warnings, ,Optional Warnings and
13421 @item bad block start address patched
13423 The symbol information for a symbol scope block has a start address
13424 smaller than the address of the preceding source line. This is known
13425 to occur in the SunOS 4.1.1 (and earlier) C compiler.
13427 @value{GDBN} circumvents the problem by treating the symbol scope block as
13428 starting on the previous source line.
13430 @item bad string table offset in symbol @var{n}
13433 Symbol number @var{n} contains a pointer into the string table which is
13434 larger than the size of the string table.
13436 @value{GDBN} circumvents the problem by considering the symbol to have the
13437 name @code{foo}, which may cause other problems if many symbols end up
13440 @item unknown symbol type @code{0x@var{nn}}
13442 The symbol information contains new data types that @value{GDBN} does
13443 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
13444 uncomprehended information, in hexadecimal.
13446 @value{GDBN} circumvents the error by ignoring this symbol information.
13447 This usually allows you to debug your program, though certain symbols
13448 are not accessible. If you encounter such a problem and feel like
13449 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
13450 on @code{complain}, then go up to the function @code{read_dbx_symtab}
13451 and examine @code{*bufp} to see the symbol.
13453 @item stub type has NULL name
13455 @value{GDBN} could not find the full definition for a struct or class.
13457 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
13458 The symbol information for a C@t{++} member function is missing some
13459 information that recent versions of the compiler should have output for
13462 @item info mismatch between compiler and debugger
13464 @value{GDBN} could not parse a type specification output by the compiler.
13469 @chapter Specifying a Debugging Target
13471 @cindex debugging target
13472 A @dfn{target} is the execution environment occupied by your program.
13474 Often, @value{GDBN} runs in the same host environment as your program;
13475 in that case, the debugging target is specified as a side effect when
13476 you use the @code{file} or @code{core} commands. When you need more
13477 flexibility---for example, running @value{GDBN} on a physically separate
13478 host, or controlling a standalone system over a serial port or a
13479 realtime system over a TCP/IP connection---you can use the @code{target}
13480 command to specify one of the target types configured for @value{GDBN}
13481 (@pxref{Target Commands, ,Commands for Managing Targets}).
13483 @cindex target architecture
13484 It is possible to build @value{GDBN} for several different @dfn{target
13485 architectures}. When @value{GDBN} is built like that, you can choose
13486 one of the available architectures with the @kbd{set architecture}
13490 @kindex set architecture
13491 @kindex show architecture
13492 @item set architecture @var{arch}
13493 This command sets the current target architecture to @var{arch}. The
13494 value of @var{arch} can be @code{"auto"}, in addition to one of the
13495 supported architectures.
13497 @item show architecture
13498 Show the current target architecture.
13500 @item set processor
13502 @kindex set processor
13503 @kindex show processor
13504 These are alias commands for, respectively, @code{set architecture}
13505 and @code{show architecture}.
13509 * Active Targets:: Active targets
13510 * Target Commands:: Commands for managing targets
13511 * Byte Order:: Choosing target byte order
13514 @node Active Targets
13515 @section Active Targets
13517 @cindex stacking targets
13518 @cindex active targets
13519 @cindex multiple targets
13521 There are three classes of targets: processes, core files, and
13522 executable files. @value{GDBN} can work concurrently on up to three
13523 active targets, one in each class. This allows you to (for example)
13524 start a process and inspect its activity without abandoning your work on
13527 For example, if you execute @samp{gdb a.out}, then the executable file
13528 @code{a.out} is the only active target. If you designate a core file as
13529 well---presumably from a prior run that crashed and coredumped---then
13530 @value{GDBN} has two active targets and uses them in tandem, looking
13531 first in the corefile target, then in the executable file, to satisfy
13532 requests for memory addresses. (Typically, these two classes of target
13533 are complementary, since core files contain only a program's
13534 read-write memory---variables and so on---plus machine status, while
13535 executable files contain only the program text and initialized data.)
13537 When you type @code{run}, your executable file becomes an active process
13538 target as well. When a process target is active, all @value{GDBN}
13539 commands requesting memory addresses refer to that target; addresses in
13540 an active core file or executable file target are obscured while the
13541 process target is active.
13543 Use the @code{core-file} and @code{exec-file} commands to select a new
13544 core file or executable target (@pxref{Files, ,Commands to Specify
13545 Files}). To specify as a target a process that is already running, use
13546 the @code{attach} command (@pxref{Attach, ,Debugging an Already-running
13549 @node Target Commands
13550 @section Commands for Managing Targets
13553 @item target @var{type} @var{parameters}
13554 Connects the @value{GDBN} host environment to a target machine or
13555 process. A target is typically a protocol for talking to debugging
13556 facilities. You use the argument @var{type} to specify the type or
13557 protocol of the target machine.
13559 Further @var{parameters} are interpreted by the target protocol, but
13560 typically include things like device names or host names to connect
13561 with, process numbers, and baud rates.
13563 The @code{target} command does not repeat if you press @key{RET} again
13564 after executing the command.
13566 @kindex help target
13568 Displays the names of all targets available. To display targets
13569 currently selected, use either @code{info target} or @code{info files}
13570 (@pxref{Files, ,Commands to Specify Files}).
13572 @item help target @var{name}
13573 Describe a particular target, including any parameters necessary to
13576 @kindex set gnutarget
13577 @item set gnutarget @var{args}
13578 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
13579 knows whether it is reading an @dfn{executable},
13580 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
13581 with the @code{set gnutarget} command. Unlike most @code{target} commands,
13582 with @code{gnutarget} the @code{target} refers to a program, not a machine.
13585 @emph{Warning:} To specify a file format with @code{set gnutarget},
13586 you must know the actual BFD name.
13590 @xref{Files, , Commands to Specify Files}.
13592 @kindex show gnutarget
13593 @item show gnutarget
13594 Use the @code{show gnutarget} command to display what file format
13595 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
13596 @value{GDBN} will determine the file format for each file automatically,
13597 and @code{show gnutarget} displays @samp{The current BDF target is "auto"}.
13600 @cindex common targets
13601 Here are some common targets (available, or not, depending on the GDB
13606 @item target exec @var{program}
13607 @cindex executable file target
13608 An executable file. @samp{target exec @var{program}} is the same as
13609 @samp{exec-file @var{program}}.
13611 @item target core @var{filename}
13612 @cindex core dump file target
13613 A core dump file. @samp{target core @var{filename}} is the same as
13614 @samp{core-file @var{filename}}.
13616 @item target remote @var{medium}
13617 @cindex remote target
13618 A remote system connected to @value{GDBN} via a serial line or network
13619 connection. This command tells @value{GDBN} to use its own remote
13620 protocol over @var{medium} for debugging. @xref{Remote Debugging}.
13622 For example, if you have a board connected to @file{/dev/ttya} on the
13623 machine running @value{GDBN}, you could say:
13626 target remote /dev/ttya
13629 @code{target remote} supports the @code{load} command. This is only
13630 useful if you have some other way of getting the stub to the target
13631 system, and you can put it somewhere in memory where it won't get
13632 clobbered by the download.
13635 @cindex built-in simulator target
13636 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
13644 works; however, you cannot assume that a specific memory map, device
13645 drivers, or even basic I/O is available, although some simulators do
13646 provide these. For info about any processor-specific simulator details,
13647 see the appropriate section in @ref{Embedded Processors, ,Embedded
13652 Some configurations may include these targets as well:
13656 @item target nrom @var{dev}
13657 @cindex NetROM ROM emulator target
13658 NetROM ROM emulator. This target only supports downloading.
13662 Different targets are available on different configurations of @value{GDBN};
13663 your configuration may have more or fewer targets.
13665 Many remote targets require you to download the executable's code once
13666 you've successfully established a connection. You may wish to control
13667 various aspects of this process.
13672 @kindex set hash@r{, for remote monitors}
13673 @cindex hash mark while downloading
13674 This command controls whether a hash mark @samp{#} is displayed while
13675 downloading a file to the remote monitor. If on, a hash mark is
13676 displayed after each S-record is successfully downloaded to the
13680 @kindex show hash@r{, for remote monitors}
13681 Show the current status of displaying the hash mark.
13683 @item set debug monitor
13684 @kindex set debug monitor
13685 @cindex display remote monitor communications
13686 Enable or disable display of communications messages between
13687 @value{GDBN} and the remote monitor.
13689 @item show debug monitor
13690 @kindex show debug monitor
13691 Show the current status of displaying communications between
13692 @value{GDBN} and the remote monitor.
13697 @kindex load @var{filename}
13698 @item load @var{filename}
13700 Depending on what remote debugging facilities are configured into
13701 @value{GDBN}, the @code{load} command may be available. Where it exists, it
13702 is meant to make @var{filename} (an executable) available for debugging
13703 on the remote system---by downloading, or dynamic linking, for example.
13704 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
13705 the @code{add-symbol-file} command.
13707 If your @value{GDBN} does not have a @code{load} command, attempting to
13708 execute it gets the error message ``@code{You can't do that when your
13709 target is @dots{}}''
13711 The file is loaded at whatever address is specified in the executable.
13712 For some object file formats, you can specify the load address when you
13713 link the program; for other formats, like a.out, the object file format
13714 specifies a fixed address.
13715 @c FIXME! This would be a good place for an xref to the GNU linker doc.
13717 Depending on the remote side capabilities, @value{GDBN} may be able to
13718 load programs into flash memory.
13720 @code{load} does not repeat if you press @key{RET} again after using it.
13724 @section Choosing Target Byte Order
13726 @cindex choosing target byte order
13727 @cindex target byte order
13729 Some types of processors, such as the MIPS, PowerPC, and Renesas SH,
13730 offer the ability to run either big-endian or little-endian byte
13731 orders. Usually the executable or symbol will include a bit to
13732 designate the endian-ness, and you will not need to worry about
13733 which to use. However, you may still find it useful to adjust
13734 @value{GDBN}'s idea of processor endian-ness manually.
13738 @item set endian big
13739 Instruct @value{GDBN} to assume the target is big-endian.
13741 @item set endian little
13742 Instruct @value{GDBN} to assume the target is little-endian.
13744 @item set endian auto
13745 Instruct @value{GDBN} to use the byte order associated with the
13749 Display @value{GDBN}'s current idea of the target byte order.
13753 Note that these commands merely adjust interpretation of symbolic
13754 data on the host, and that they have absolutely no effect on the
13758 @node Remote Debugging
13759 @chapter Debugging Remote Programs
13760 @cindex remote debugging
13762 If you are trying to debug a program running on a machine that cannot run
13763 @value{GDBN} in the usual way, it is often useful to use remote debugging.
13764 For example, you might use remote debugging on an operating system kernel,
13765 or on a small system which does not have a general purpose operating system
13766 powerful enough to run a full-featured debugger.
13768 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
13769 to make this work with particular debugging targets. In addition,
13770 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
13771 but not specific to any particular target system) which you can use if you
13772 write the remote stubs---the code that runs on the remote system to
13773 communicate with @value{GDBN}.
13775 Other remote targets may be available in your
13776 configuration of @value{GDBN}; use @code{help target} to list them.
13779 * Connecting:: Connecting to a remote target
13780 * File Transfer:: Sending files to a remote system
13781 * Server:: Using the gdbserver program
13782 * Remote Configuration:: Remote configuration
13783 * Remote Stub:: Implementing a remote stub
13787 @section Connecting to a Remote Target
13789 On the @value{GDBN} host machine, you will need an unstripped copy of
13790 your program, since @value{GDBN} needs symbol and debugging information.
13791 Start up @value{GDBN} as usual, using the name of the local copy of your
13792 program as the first argument.
13794 @cindex @code{target remote}
13795 @value{GDBN} can communicate with the target over a serial line, or
13796 over an @acronym{IP} network using @acronym{TCP} or @acronym{UDP}. In
13797 each case, @value{GDBN} uses the same protocol for debugging your
13798 program; only the medium carrying the debugging packets varies. The
13799 @code{target remote} command establishes a connection to the target.
13800 Its arguments indicate which medium to use:
13804 @item target remote @var{serial-device}
13805 @cindex serial line, @code{target remote}
13806 Use @var{serial-device} to communicate with the target. For example,
13807 to use a serial line connected to the device named @file{/dev/ttyb}:
13810 target remote /dev/ttyb
13813 If you're using a serial line, you may want to give @value{GDBN} the
13814 @w{@samp{--baud}} option, or use the @code{set remotebaud} command
13815 (@pxref{Remote Configuration, set remotebaud}) before the
13816 @code{target} command.
13818 @item target remote @code{@var{host}:@var{port}}
13819 @itemx target remote @code{tcp:@var{host}:@var{port}}
13820 @cindex @acronym{TCP} port, @code{target remote}
13821 Debug using a @acronym{TCP} connection to @var{port} on @var{host}.
13822 The @var{host} may be either a host name or a numeric @acronym{IP}
13823 address; @var{port} must be a decimal number. The @var{host} could be
13824 the target machine itself, if it is directly connected to the net, or
13825 it might be a terminal server which in turn has a serial line to the
13828 For example, to connect to port 2828 on a terminal server named
13832 target remote manyfarms:2828
13835 If your remote target is actually running on the same machine as your
13836 debugger session (e.g.@: a simulator for your target running on the
13837 same host), you can omit the hostname. For example, to connect to
13838 port 1234 on your local machine:
13841 target remote :1234
13845 Note that the colon is still required here.
13847 @item target remote @code{udp:@var{host}:@var{port}}
13848 @cindex @acronym{UDP} port, @code{target remote}
13849 Debug using @acronym{UDP} packets to @var{port} on @var{host}. For example, to
13850 connect to @acronym{UDP} port 2828 on a terminal server named @code{manyfarms}:
13853 target remote udp:manyfarms:2828
13856 When using a @acronym{UDP} connection for remote debugging, you should
13857 keep in mind that the `U' stands for ``Unreliable''. @acronym{UDP}
13858 can silently drop packets on busy or unreliable networks, which will
13859 cause havoc with your debugging session.
13861 @item target remote | @var{command}
13862 @cindex pipe, @code{target remote} to
13863 Run @var{command} in the background and communicate with it using a
13864 pipe. The @var{command} is a shell command, to be parsed and expanded
13865 by the system's command shell, @code{/bin/sh}; it should expect remote
13866 protocol packets on its standard input, and send replies on its
13867 standard output. You could use this to run a stand-alone simulator
13868 that speaks the remote debugging protocol, to make net connections
13869 using programs like @code{ssh}, or for other similar tricks.
13871 If @var{command} closes its standard output (perhaps by exiting),
13872 @value{GDBN} will try to send it a @code{SIGTERM} signal. (If the
13873 program has already exited, this will have no effect.)
13877 Once the connection has been established, you can use all the usual
13878 commands to examine and change data. The remote program is already
13879 running; you can use @kbd{step} and @kbd{continue}, and you do not
13880 need to use @kbd{run}.
13882 @cindex interrupting remote programs
13883 @cindex remote programs, interrupting
13884 Whenever @value{GDBN} is waiting for the remote program, if you type the
13885 interrupt character (often @kbd{Ctrl-c}), @value{GDBN} attempts to stop the
13886 program. This may or may not succeed, depending in part on the hardware
13887 and the serial drivers the remote system uses. If you type the
13888 interrupt character once again, @value{GDBN} displays this prompt:
13891 Interrupted while waiting for the program.
13892 Give up (and stop debugging it)? (y or n)
13895 If you type @kbd{y}, @value{GDBN} abandons the remote debugging session.
13896 (If you decide you want to try again later, you can use @samp{target
13897 remote} again to connect once more.) If you type @kbd{n}, @value{GDBN}
13898 goes back to waiting.
13901 @kindex detach (remote)
13903 When you have finished debugging the remote program, you can use the
13904 @code{detach} command to release it from @value{GDBN} control.
13905 Detaching from the target normally resumes its execution, but the results
13906 will depend on your particular remote stub. After the @code{detach}
13907 command, @value{GDBN} is free to connect to another target.
13911 The @code{disconnect} command behaves like @code{detach}, except that
13912 the target is generally not resumed. It will wait for @value{GDBN}
13913 (this instance or another one) to connect and continue debugging. After
13914 the @code{disconnect} command, @value{GDBN} is again free to connect to
13917 @cindex send command to remote monitor
13918 @cindex extend @value{GDBN} for remote targets
13919 @cindex add new commands for external monitor
13921 @item monitor @var{cmd}
13922 This command allows you to send arbitrary commands directly to the
13923 remote monitor. Since @value{GDBN} doesn't care about the commands it
13924 sends like this, this command is the way to extend @value{GDBN}---you
13925 can add new commands that only the external monitor will understand
13929 @node File Transfer
13930 @section Sending files to a remote system
13931 @cindex remote target, file transfer
13932 @cindex file transfer
13933 @cindex sending files to remote systems
13935 Some remote targets offer the ability to transfer files over the same
13936 connection used to communicate with @value{GDBN}. This is convenient
13937 for targets accessible through other means, e.g.@: @sc{gnu}/Linux systems
13938 running @code{gdbserver} over a network interface. For other targets,
13939 e.g.@: embedded devices with only a single serial port, this may be
13940 the only way to upload or download files.
13942 Not all remote targets support these commands.
13946 @item remote put @var{hostfile} @var{targetfile}
13947 Copy file @var{hostfile} from the host system (the machine running
13948 @value{GDBN}) to @var{targetfile} on the target system.
13951 @item remote get @var{targetfile} @var{hostfile}
13952 Copy file @var{targetfile} from the target system to @var{hostfile}
13953 on the host system.
13955 @kindex remote delete
13956 @item remote delete @var{targetfile}
13957 Delete @var{targetfile} from the target system.
13962 @section Using the @code{gdbserver} Program
13965 @cindex remote connection without stubs
13966 @code{gdbserver} is a control program for Unix-like systems, which
13967 allows you to connect your program with a remote @value{GDBN} via
13968 @code{target remote}---but without linking in the usual debugging stub.
13970 @code{gdbserver} is not a complete replacement for the debugging stubs,
13971 because it requires essentially the same operating-system facilities
13972 that @value{GDBN} itself does. In fact, a system that can run
13973 @code{gdbserver} to connect to a remote @value{GDBN} could also run
13974 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
13975 because it is a much smaller program than @value{GDBN} itself. It is
13976 also easier to port than all of @value{GDBN}, so you may be able to get
13977 started more quickly on a new system by using @code{gdbserver}.
13978 Finally, if you develop code for real-time systems, you may find that
13979 the tradeoffs involved in real-time operation make it more convenient to
13980 do as much development work as possible on another system, for example
13981 by cross-compiling. You can use @code{gdbserver} to make a similar
13982 choice for debugging.
13984 @value{GDBN} and @code{gdbserver} communicate via either a serial line
13985 or a TCP connection, using the standard @value{GDBN} remote serial
13989 @emph{Warning:} @code{gdbserver} does not have any built-in security.
13990 Do not run @code{gdbserver} connected to any public network; a
13991 @value{GDBN} connection to @code{gdbserver} provides access to the
13992 target system with the same privileges as the user running
13996 @subsection Running @code{gdbserver}
13997 @cindex arguments, to @code{gdbserver}
13999 Run @code{gdbserver} on the target system. You need a copy of the
14000 program you want to debug, including any libraries it requires.
14001 @code{gdbserver} does not need your program's symbol table, so you can
14002 strip the program if necessary to save space. @value{GDBN} on the host
14003 system does all the symbol handling.
14005 To use the server, you must tell it how to communicate with @value{GDBN};
14006 the name of your program; and the arguments for your program. The usual
14010 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
14013 @var{comm} is either a device name (to use a serial line) or a TCP
14014 hostname and portnumber. For example, to debug Emacs with the argument
14015 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
14019 target> gdbserver /dev/com1 emacs foo.txt
14022 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
14025 To use a TCP connection instead of a serial line:
14028 target> gdbserver host:2345 emacs foo.txt
14031 The only difference from the previous example is the first argument,
14032 specifying that you are communicating with the host @value{GDBN} via
14033 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
14034 expect a TCP connection from machine @samp{host} to local TCP port 2345.
14035 (Currently, the @samp{host} part is ignored.) You can choose any number
14036 you want for the port number as long as it does not conflict with any
14037 TCP ports already in use on the target system (for example, @code{23} is
14038 reserved for @code{telnet}).@footnote{If you choose a port number that
14039 conflicts with another service, @code{gdbserver} prints an error message
14040 and exits.} You must use the same port number with the host @value{GDBN}
14041 @code{target remote} command.
14043 @subsubsection Attaching to a Running Program
14045 On some targets, @code{gdbserver} can also attach to running programs.
14046 This is accomplished via the @code{--attach} argument. The syntax is:
14049 target> gdbserver --attach @var{comm} @var{pid}
14052 @var{pid} is the process ID of a currently running process. It isn't necessary
14053 to point @code{gdbserver} at a binary for the running process.
14056 @cindex attach to a program by name
14057 You can debug processes by name instead of process ID if your target has the
14058 @code{pidof} utility:
14061 target> gdbserver --attach @var{comm} `pidof @var{program}`
14064 In case more than one copy of @var{program} is running, or @var{program}
14065 has multiple threads, most versions of @code{pidof} support the
14066 @code{-s} option to only return the first process ID.
14068 @subsubsection Multi-Process Mode for @code{gdbserver}
14069 @cindex gdbserver, multiple processes
14070 @cindex multiple processes with gdbserver
14072 When you connect to @code{gdbserver} using @code{target remote},
14073 @code{gdbserver} debugs the specified program only once. When the
14074 program exits, or you detach from it, @value{GDBN} closes the connection
14075 and @code{gdbserver} exits.
14077 If you connect using @kbd{target extended-remote}, @code{gdbserver}
14078 enters multi-process mode. When the debugged program exits, or you
14079 detach from it, @value{GDBN} stays connected to @code{gdbserver} even
14080 though no program is running. The @code{run} and @code{attach}
14081 commands instruct @code{gdbserver} to run or attach to a new program.
14082 The @code{run} command uses @code{set remote exec-file} (@pxref{set
14083 remote exec-file}) to select the program to run. Command line
14084 arguments are supported, except for wildcard expansion and I/O
14085 redirection (@pxref{Arguments}).
14087 To start @code{gdbserver} without supplying an initial command to run
14088 or process ID to attach, use the @option{--multi} command line option.
14089 Then you can connect using @kbd{target extended-remote} and start
14090 the program you want to debug.
14092 @code{gdbserver} does not automatically exit in multi-process mode.
14093 You can terminate it by using @code{monitor exit}
14094 (@pxref{Monitor Commands for gdbserver}).
14096 @subsubsection Other Command-Line Arguments for @code{gdbserver}
14098 The @option{--debug} option tells @code{gdbserver} to display extra
14099 status information about the debugging process. The
14100 @option{--remote-debug} option tells @code{gdbserver} to display
14101 remote protocol debug output. These options are intended for
14102 @code{gdbserver} development and for bug reports to the developers.
14104 The @option{--wrapper} option specifies a wrapper to launch programs
14105 for debugging. The option should be followed by the name of the
14106 wrapper, then any command-line arguments to pass to the wrapper, then
14107 @kbd{--} indicating the end of the wrapper arguments.
14109 @code{gdbserver} runs the specified wrapper program with a combined
14110 command line including the wrapper arguments, then the name of the
14111 program to debug, then any arguments to the program. The wrapper
14112 runs until it executes your program, and then @value{GDBN} gains control.
14114 You can use any program that eventually calls @code{execve} with
14115 its arguments as a wrapper. Several standard Unix utilities do
14116 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
14117 with @code{exec "$@@"} will also work.
14119 For example, you can use @code{env} to pass an environment variable to
14120 the debugged program, without setting the variable in @code{gdbserver}'s
14124 $ gdbserver --wrapper env LD_PRELOAD=libtest.so -- :2222 ./testprog
14127 @subsection Connecting to @code{gdbserver}
14129 Run @value{GDBN} on the host system.
14131 First make sure you have the necessary symbol files. Load symbols for
14132 your application using the @code{file} command before you connect. Use
14133 @code{set sysroot} to locate target libraries (unless your @value{GDBN}
14134 was compiled with the correct sysroot using @code{--with-sysroot}).
14136 The symbol file and target libraries must exactly match the executable
14137 and libraries on the target, with one exception: the files on the host
14138 system should not be stripped, even if the files on the target system
14139 are. Mismatched or missing files will lead to confusing results
14140 during debugging. On @sc{gnu}/Linux targets, mismatched or missing
14141 files may also prevent @code{gdbserver} from debugging multi-threaded
14144 Connect to your target (@pxref{Connecting,,Connecting to a Remote Target}).
14145 For TCP connections, you must start up @code{gdbserver} prior to using
14146 the @code{target remote} command. Otherwise you may get an error whose
14147 text depends on the host system, but which usually looks something like
14148 @samp{Connection refused}. Don't use the @code{load}
14149 command in @value{GDBN} when using @code{gdbserver}, since the program is
14150 already on the target.
14152 @subsection Monitor Commands for @code{gdbserver}
14153 @cindex monitor commands, for @code{gdbserver}
14154 @anchor{Monitor Commands for gdbserver}
14156 During a @value{GDBN} session using @code{gdbserver}, you can use the
14157 @code{monitor} command to send special requests to @code{gdbserver}.
14158 Here are the available commands.
14162 List the available monitor commands.
14164 @item monitor set debug 0
14165 @itemx monitor set debug 1
14166 Disable or enable general debugging messages.
14168 @item monitor set remote-debug 0
14169 @itemx monitor set remote-debug 1
14170 Disable or enable specific debugging messages associated with the remote
14171 protocol (@pxref{Remote Protocol}).
14174 Tell gdbserver to exit immediately. This command should be followed by
14175 @code{disconnect} to close the debugging session. @code{gdbserver} will
14176 detach from any attached processes and kill any processes it created.
14177 Use @code{monitor exit} to terminate @code{gdbserver} at the end
14178 of a multi-process mode debug session.
14182 @node Remote Configuration
14183 @section Remote Configuration
14186 @kindex show remote
14187 This section documents the configuration options available when
14188 debugging remote programs. For the options related to the File I/O
14189 extensions of the remote protocol, see @ref{system,
14190 system-call-allowed}.
14193 @item set remoteaddresssize @var{bits}
14194 @cindex address size for remote targets
14195 @cindex bits in remote address
14196 Set the maximum size of address in a memory packet to the specified
14197 number of bits. @value{GDBN} will mask off the address bits above
14198 that number, when it passes addresses to the remote target. The
14199 default value is the number of bits in the target's address.
14201 @item show remoteaddresssize
14202 Show the current value of remote address size in bits.
14204 @item set remotebaud @var{n}
14205 @cindex baud rate for remote targets
14206 Set the baud rate for the remote serial I/O to @var{n} baud. The
14207 value is used to set the speed of the serial port used for debugging
14210 @item show remotebaud
14211 Show the current speed of the remote connection.
14213 @item set remotebreak
14214 @cindex interrupt remote programs
14215 @cindex BREAK signal instead of Ctrl-C
14216 @anchor{set remotebreak}
14217 If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote
14218 when you type @kbd{Ctrl-c} to interrupt the program running
14219 on the remote. If set to off, @value{GDBN} sends the @samp{Ctrl-C}
14220 character instead. The default is off, since most remote systems
14221 expect to see @samp{Ctrl-C} as the interrupt signal.
14223 @item show remotebreak
14224 Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to
14225 interrupt the remote program.
14227 @item set remoteflow on
14228 @itemx set remoteflow off
14229 @kindex set remoteflow
14230 Enable or disable hardware flow control (@code{RTS}/@code{CTS})
14231 on the serial port used to communicate to the remote target.
14233 @item show remoteflow
14234 @kindex show remoteflow
14235 Show the current setting of hardware flow control.
14237 @item set remotelogbase @var{base}
14238 Set the base (a.k.a.@: radix) of logging serial protocol
14239 communications to @var{base}. Supported values of @var{base} are:
14240 @code{ascii}, @code{octal}, and @code{hex}. The default is
14243 @item show remotelogbase
14244 Show the current setting of the radix for logging remote serial
14247 @item set remotelogfile @var{file}
14248 @cindex record serial communications on file
14249 Record remote serial communications on the named @var{file}. The
14250 default is not to record at all.
14252 @item show remotelogfile.
14253 Show the current setting of the file name on which to record the
14254 serial communications.
14256 @item set remotetimeout @var{num}
14257 @cindex timeout for serial communications
14258 @cindex remote timeout
14259 Set the timeout limit to wait for the remote target to respond to
14260 @var{num} seconds. The default is 2 seconds.
14262 @item show remotetimeout
14263 Show the current number of seconds to wait for the remote target
14266 @cindex limit hardware breakpoints and watchpoints
14267 @cindex remote target, limit break- and watchpoints
14268 @anchor{set remote hardware-watchpoint-limit}
14269 @anchor{set remote hardware-breakpoint-limit}
14270 @item set remote hardware-watchpoint-limit @var{limit}
14271 @itemx set remote hardware-breakpoint-limit @var{limit}
14272 Restrict @value{GDBN} to using @var{limit} remote hardware breakpoint or
14273 watchpoints. A limit of -1, the default, is treated as unlimited.
14275 @item set remote exec-file @var{filename}
14276 @itemx show remote exec-file
14277 @anchor{set remote exec-file}
14278 @cindex executable file, for remote target
14279 Select the file used for @code{run} with @code{target
14280 extended-remote}. This should be set to a filename valid on the
14281 target system. If it is not set, the target will use a default
14282 filename (e.g.@: the last program run).
14286 @item set tcp auto-retry on
14287 @cindex auto-retry, for remote TCP target
14288 Enable auto-retry for remote TCP connections. This is useful if the remote
14289 debugging agent is launched in parallel with @value{GDBN}; there is a race
14290 condition because the agent may not become ready to accept the connection
14291 before @value{GDBN} attempts to connect. When auto-retry is
14292 enabled, if the initial attempt to connect fails, @value{GDBN} reattempts
14293 to establish the connection using the timeout specified by
14294 @code{set tcp connect-timeout}.
14296 @item set tcp auto-retry off
14297 Do not auto-retry failed TCP connections.
14299 @item show tcp auto-retry
14300 Show the current auto-retry setting.
14302 @item set tcp connect-timeout @var{seconds}
14303 @cindex connection timeout, for remote TCP target
14304 @cindex timeout, for remote target connection
14305 Set the timeout for establishing a TCP connection to the remote target to
14306 @var{seconds}. The timeout affects both polling to retry failed connections
14307 (enabled by @code{set tcp auto-retry on}) and waiting for connections
14308 that are merely slow to complete, and represents an approximate cumulative
14311 @item show tcp connect-timeout
14312 Show the current connection timeout setting.
14315 @cindex remote packets, enabling and disabling
14316 The @value{GDBN} remote protocol autodetects the packets supported by
14317 your debugging stub. If you need to override the autodetection, you
14318 can use these commands to enable or disable individual packets. Each
14319 packet can be set to @samp{on} (the remote target supports this
14320 packet), @samp{off} (the remote target does not support this packet),
14321 or @samp{auto} (detect remote target support for this packet). They
14322 all default to @samp{auto}. For more information about each packet,
14323 see @ref{Remote Protocol}.
14325 During normal use, you should not have to use any of these commands.
14326 If you do, that may be a bug in your remote debugging stub, or a bug
14327 in @value{GDBN}. You may want to report the problem to the
14328 @value{GDBN} developers.
14330 For each packet @var{name}, the command to enable or disable the
14331 packet is @code{set remote @var{name}-packet}. The available settings
14334 @multitable @columnfractions 0.28 0.32 0.25
14337 @tab Related Features
14339 @item @code{fetch-register}
14341 @tab @code{info registers}
14343 @item @code{set-register}
14347 @item @code{binary-download}
14349 @tab @code{load}, @code{set}
14351 @item @code{read-aux-vector}
14352 @tab @code{qXfer:auxv:read}
14353 @tab @code{info auxv}
14355 @item @code{symbol-lookup}
14356 @tab @code{qSymbol}
14357 @tab Detecting multiple threads
14359 @item @code{attach}
14360 @tab @code{vAttach}
14363 @item @code{verbose-resume}
14365 @tab Stepping or resuming multiple threads
14371 @item @code{software-breakpoint}
14375 @item @code{hardware-breakpoint}
14379 @item @code{write-watchpoint}
14383 @item @code{read-watchpoint}
14387 @item @code{access-watchpoint}
14391 @item @code{target-features}
14392 @tab @code{qXfer:features:read}
14393 @tab @code{set architecture}
14395 @item @code{library-info}
14396 @tab @code{qXfer:libraries:read}
14397 @tab @code{info sharedlibrary}
14399 @item @code{memory-map}
14400 @tab @code{qXfer:memory-map:read}
14401 @tab @code{info mem}
14403 @item @code{read-spu-object}
14404 @tab @code{qXfer:spu:read}
14405 @tab @code{info spu}
14407 @item @code{write-spu-object}
14408 @tab @code{qXfer:spu:write}
14409 @tab @code{info spu}
14411 @item @code{read-siginfo-object}
14412 @tab @code{qXfer:siginfo:read}
14413 @tab @code{print $_siginfo}
14415 @item @code{write-siginfo-object}
14416 @tab @code{qXfer:siginfo:write}
14417 @tab @code{set $_siginfo}
14419 @item @code{get-thread-local-@*storage-address}
14420 @tab @code{qGetTLSAddr}
14421 @tab Displaying @code{__thread} variables
14423 @item @code{search-memory}
14424 @tab @code{qSearch:memory}
14427 @item @code{supported-packets}
14428 @tab @code{qSupported}
14429 @tab Remote communications parameters
14431 @item @code{pass-signals}
14432 @tab @code{QPassSignals}
14433 @tab @code{handle @var{signal}}
14435 @item @code{hostio-close-packet}
14436 @tab @code{vFile:close}
14437 @tab @code{remote get}, @code{remote put}
14439 @item @code{hostio-open-packet}
14440 @tab @code{vFile:open}
14441 @tab @code{remote get}, @code{remote put}
14443 @item @code{hostio-pread-packet}
14444 @tab @code{vFile:pread}
14445 @tab @code{remote get}, @code{remote put}
14447 @item @code{hostio-pwrite-packet}
14448 @tab @code{vFile:pwrite}
14449 @tab @code{remote get}, @code{remote put}
14451 @item @code{hostio-unlink-packet}
14452 @tab @code{vFile:unlink}
14453 @tab @code{remote delete}
14455 @item @code{noack-packet}
14456 @tab @code{QStartNoAckMode}
14457 @tab Packet acknowledgment
14459 @item @code{osdata}
14460 @tab @code{qXfer:osdata:read}
14461 @tab @code{info os}
14463 @item @code{query-attached}
14464 @tab @code{qAttached}
14465 @tab Querying remote process attach state.
14469 @section Implementing a Remote Stub
14471 @cindex debugging stub, example
14472 @cindex remote stub, example
14473 @cindex stub example, remote debugging
14474 The stub files provided with @value{GDBN} implement the target side of the
14475 communication protocol, and the @value{GDBN} side is implemented in the
14476 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
14477 these subroutines to communicate, and ignore the details. (If you're
14478 implementing your own stub file, you can still ignore the details: start
14479 with one of the existing stub files. @file{sparc-stub.c} is the best
14480 organized, and therefore the easiest to read.)
14482 @cindex remote serial debugging, overview
14483 To debug a program running on another machine (the debugging
14484 @dfn{target} machine), you must first arrange for all the usual
14485 prerequisites for the program to run by itself. For example, for a C
14490 A startup routine to set up the C runtime environment; these usually
14491 have a name like @file{crt0}. The startup routine may be supplied by
14492 your hardware supplier, or you may have to write your own.
14495 A C subroutine library to support your program's
14496 subroutine calls, notably managing input and output.
14499 A way of getting your program to the other machine---for example, a
14500 download program. These are often supplied by the hardware
14501 manufacturer, but you may have to write your own from hardware
14505 The next step is to arrange for your program to use a serial port to
14506 communicate with the machine where @value{GDBN} is running (the @dfn{host}
14507 machine). In general terms, the scheme looks like this:
14511 @value{GDBN} already understands how to use this protocol; when everything
14512 else is set up, you can simply use the @samp{target remote} command
14513 (@pxref{Targets,,Specifying a Debugging Target}).
14515 @item On the target,
14516 you must link with your program a few special-purpose subroutines that
14517 implement the @value{GDBN} remote serial protocol. The file containing these
14518 subroutines is called a @dfn{debugging stub}.
14520 On certain remote targets, you can use an auxiliary program
14521 @code{gdbserver} instead of linking a stub into your program.
14522 @xref{Server,,Using the @code{gdbserver} Program}, for details.
14525 The debugging stub is specific to the architecture of the remote
14526 machine; for example, use @file{sparc-stub.c} to debug programs on
14529 @cindex remote serial stub list
14530 These working remote stubs are distributed with @value{GDBN}:
14535 @cindex @file{i386-stub.c}
14538 For Intel 386 and compatible architectures.
14541 @cindex @file{m68k-stub.c}
14542 @cindex Motorola 680x0
14544 For Motorola 680x0 architectures.
14547 @cindex @file{sh-stub.c}
14550 For Renesas SH architectures.
14553 @cindex @file{sparc-stub.c}
14555 For @sc{sparc} architectures.
14557 @item sparcl-stub.c
14558 @cindex @file{sparcl-stub.c}
14561 For Fujitsu @sc{sparclite} architectures.
14565 The @file{README} file in the @value{GDBN} distribution may list other
14566 recently added stubs.
14569 * Stub Contents:: What the stub can do for you
14570 * Bootstrapping:: What you must do for the stub
14571 * Debug Session:: Putting it all together
14574 @node Stub Contents
14575 @subsection What the Stub Can Do for You
14577 @cindex remote serial stub
14578 The debugging stub for your architecture supplies these three
14582 @item set_debug_traps
14583 @findex set_debug_traps
14584 @cindex remote serial stub, initialization
14585 This routine arranges for @code{handle_exception} to run when your
14586 program stops. You must call this subroutine explicitly near the
14587 beginning of your program.
14589 @item handle_exception
14590 @findex handle_exception
14591 @cindex remote serial stub, main routine
14592 This is the central workhorse, but your program never calls it
14593 explicitly---the setup code arranges for @code{handle_exception} to
14594 run when a trap is triggered.
14596 @code{handle_exception} takes control when your program stops during
14597 execution (for example, on a breakpoint), and mediates communications
14598 with @value{GDBN} on the host machine. This is where the communications
14599 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
14600 representative on the target machine. It begins by sending summary
14601 information on the state of your program, then continues to execute,
14602 retrieving and transmitting any information @value{GDBN} needs, until you
14603 execute a @value{GDBN} command that makes your program resume; at that point,
14604 @code{handle_exception} returns control to your own code on the target
14608 @cindex @code{breakpoint} subroutine, remote
14609 Use this auxiliary subroutine to make your program contain a
14610 breakpoint. Depending on the particular situation, this may be the only
14611 way for @value{GDBN} to get control. For instance, if your target
14612 machine has some sort of interrupt button, you won't need to call this;
14613 pressing the interrupt button transfers control to
14614 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
14615 simply receiving characters on the serial port may also trigger a trap;
14616 again, in that situation, you don't need to call @code{breakpoint} from
14617 your own program---simply running @samp{target remote} from the host
14618 @value{GDBN} session gets control.
14620 Call @code{breakpoint} if none of these is true, or if you simply want
14621 to make certain your program stops at a predetermined point for the
14622 start of your debugging session.
14625 @node Bootstrapping
14626 @subsection What You Must Do for the Stub
14628 @cindex remote stub, support routines
14629 The debugging stubs that come with @value{GDBN} are set up for a particular
14630 chip architecture, but they have no information about the rest of your
14631 debugging target machine.
14633 First of all you need to tell the stub how to communicate with the
14637 @item int getDebugChar()
14638 @findex getDebugChar
14639 Write this subroutine to read a single character from the serial port.
14640 It may be identical to @code{getchar} for your target system; a
14641 different name is used to allow you to distinguish the two if you wish.
14643 @item void putDebugChar(int)
14644 @findex putDebugChar
14645 Write this subroutine to write a single character to the serial port.
14646 It may be identical to @code{putchar} for your target system; a
14647 different name is used to allow you to distinguish the two if you wish.
14650 @cindex control C, and remote debugging
14651 @cindex interrupting remote targets
14652 If you want @value{GDBN} to be able to stop your program while it is
14653 running, you need to use an interrupt-driven serial driver, and arrange
14654 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
14655 character). That is the character which @value{GDBN} uses to tell the
14656 remote system to stop.
14658 Getting the debugging target to return the proper status to @value{GDBN}
14659 probably requires changes to the standard stub; one quick and dirty way
14660 is to just execute a breakpoint instruction (the ``dirty'' part is that
14661 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
14663 Other routines you need to supply are:
14666 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
14667 @findex exceptionHandler
14668 Write this function to install @var{exception_address} in the exception
14669 handling tables. You need to do this because the stub does not have any
14670 way of knowing what the exception handling tables on your target system
14671 are like (for example, the processor's table might be in @sc{rom},
14672 containing entries which point to a table in @sc{ram}).
14673 @var{exception_number} is the exception number which should be changed;
14674 its meaning is architecture-dependent (for example, different numbers
14675 might represent divide by zero, misaligned access, etc). When this
14676 exception occurs, control should be transferred directly to
14677 @var{exception_address}, and the processor state (stack, registers,
14678 and so on) should be just as it is when a processor exception occurs. So if
14679 you want to use a jump instruction to reach @var{exception_address}, it
14680 should be a simple jump, not a jump to subroutine.
14682 For the 386, @var{exception_address} should be installed as an interrupt
14683 gate so that interrupts are masked while the handler runs. The gate
14684 should be at privilege level 0 (the most privileged level). The
14685 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
14686 help from @code{exceptionHandler}.
14688 @item void flush_i_cache()
14689 @findex flush_i_cache
14690 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
14691 instruction cache, if any, on your target machine. If there is no
14692 instruction cache, this subroutine may be a no-op.
14694 On target machines that have instruction caches, @value{GDBN} requires this
14695 function to make certain that the state of your program is stable.
14699 You must also make sure this library routine is available:
14702 @item void *memset(void *, int, int)
14704 This is the standard library function @code{memset} that sets an area of
14705 memory to a known value. If you have one of the free versions of
14706 @code{libc.a}, @code{memset} can be found there; otherwise, you must
14707 either obtain it from your hardware manufacturer, or write your own.
14710 If you do not use the GNU C compiler, you may need other standard
14711 library subroutines as well; this varies from one stub to another,
14712 but in general the stubs are likely to use any of the common library
14713 subroutines which @code{@value{NGCC}} generates as inline code.
14716 @node Debug Session
14717 @subsection Putting it All Together
14719 @cindex remote serial debugging summary
14720 In summary, when your program is ready to debug, you must follow these
14725 Make sure you have defined the supporting low-level routines
14726 (@pxref{Bootstrapping,,What You Must Do for the Stub}):
14728 @code{getDebugChar}, @code{putDebugChar},
14729 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
14733 Insert these lines near the top of your program:
14741 For the 680x0 stub only, you need to provide a variable called
14742 @code{exceptionHook}. Normally you just use:
14745 void (*exceptionHook)() = 0;
14749 but if before calling @code{set_debug_traps}, you set it to point to a
14750 function in your program, that function is called when
14751 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
14752 error). The function indicated by @code{exceptionHook} is called with
14753 one parameter: an @code{int} which is the exception number.
14756 Compile and link together: your program, the @value{GDBN} debugging stub for
14757 your target architecture, and the supporting subroutines.
14760 Make sure you have a serial connection between your target machine and
14761 the @value{GDBN} host, and identify the serial port on the host.
14764 @c The "remote" target now provides a `load' command, so we should
14765 @c document that. FIXME.
14766 Download your program to your target machine (or get it there by
14767 whatever means the manufacturer provides), and start it.
14770 Start @value{GDBN} on the host, and connect to the target
14771 (@pxref{Connecting,,Connecting to a Remote Target}).
14775 @node Configurations
14776 @chapter Configuration-Specific Information
14778 While nearly all @value{GDBN} commands are available for all native and
14779 cross versions of the debugger, there are some exceptions. This chapter
14780 describes things that are only available in certain configurations.
14782 There are three major categories of configurations: native
14783 configurations, where the host and target are the same, embedded
14784 operating system configurations, which are usually the same for several
14785 different processor architectures, and bare embedded processors, which
14786 are quite different from each other.
14791 * Embedded Processors::
14798 This section describes details specific to particular native
14803 * BSD libkvm Interface:: Debugging BSD kernel memory images
14804 * SVR4 Process Information:: SVR4 process information
14805 * DJGPP Native:: Features specific to the DJGPP port
14806 * Cygwin Native:: Features specific to the Cygwin port
14807 * Hurd Native:: Features specific to @sc{gnu} Hurd
14808 * Neutrino:: Features specific to QNX Neutrino
14809 * Darwin:: Features specific to Darwin
14815 On HP-UX systems, if you refer to a function or variable name that
14816 begins with a dollar sign, @value{GDBN} searches for a user or system
14817 name first, before it searches for a convenience variable.
14820 @node BSD libkvm Interface
14821 @subsection BSD libkvm Interface
14824 @cindex kernel memory image
14825 @cindex kernel crash dump
14827 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
14828 interface that provides a uniform interface for accessing kernel virtual
14829 memory images, including live systems and crash dumps. @value{GDBN}
14830 uses this interface to allow you to debug live kernels and kernel crash
14831 dumps on many native BSD configurations. This is implemented as a
14832 special @code{kvm} debugging target. For debugging a live system, load
14833 the currently running kernel into @value{GDBN} and connect to the
14837 (@value{GDBP}) @b{target kvm}
14840 For debugging crash dumps, provide the file name of the crash dump as an
14844 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
14847 Once connected to the @code{kvm} target, the following commands are
14853 Set current context from the @dfn{Process Control Block} (PCB) address.
14856 Set current context from proc address. This command isn't available on
14857 modern FreeBSD systems.
14860 @node SVR4 Process Information
14861 @subsection SVR4 Process Information
14863 @cindex examine process image
14864 @cindex process info via @file{/proc}
14866 Many versions of SVR4 and compatible systems provide a facility called
14867 @samp{/proc} that can be used to examine the image of a running
14868 process using file-system subroutines. If @value{GDBN} is configured
14869 for an operating system with this facility, the command @code{info
14870 proc} is available to report information about the process running
14871 your program, or about any process running on your system. @code{info
14872 proc} works only on SVR4 systems that include the @code{procfs} code.
14873 This includes, as of this writing, @sc{gnu}/Linux, OSF/1 (Digital
14874 Unix), Solaris, Irix, and Unixware, but not HP-UX, for example.
14880 @itemx info proc @var{process-id}
14881 Summarize available information about any running process. If a
14882 process ID is specified by @var{process-id}, display information about
14883 that process; otherwise display information about the program being
14884 debugged. The summary includes the debugged process ID, the command
14885 line used to invoke it, its current working directory, and its
14886 executable file's absolute file name.
14888 On some systems, @var{process-id} can be of the form
14889 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
14890 within a process. If the optional @var{pid} part is missing, it means
14891 a thread from the process being debugged (the leading @samp{/} still
14892 needs to be present, or else @value{GDBN} will interpret the number as
14893 a process ID rather than a thread ID).
14895 @item info proc mappings
14896 @cindex memory address space mappings
14897 Report the memory address space ranges accessible in the program, with
14898 information on whether the process has read, write, or execute access
14899 rights to each range. On @sc{gnu}/Linux systems, each memory range
14900 includes the object file which is mapped to that range, instead of the
14901 memory access rights to that range.
14903 @item info proc stat
14904 @itemx info proc status
14905 @cindex process detailed status information
14906 These subcommands are specific to @sc{gnu}/Linux systems. They show
14907 the process-related information, including the user ID and group ID;
14908 how many threads are there in the process; its virtual memory usage;
14909 the signals that are pending, blocked, and ignored; its TTY; its
14910 consumption of system and user time; its stack size; its @samp{nice}
14911 value; etc. For more information, see the @samp{proc} man page
14912 (type @kbd{man 5 proc} from your shell prompt).
14914 @item info proc all
14915 Show all the information about the process described under all of the
14916 above @code{info proc} subcommands.
14919 @comment These sub-options of 'info proc' were not included when
14920 @comment procfs.c was re-written. Keep their descriptions around
14921 @comment against the day when someone finds the time to put them back in.
14922 @kindex info proc times
14923 @item info proc times
14924 Starting time, user CPU time, and system CPU time for your program and
14927 @kindex info proc id
14929 Report on the process IDs related to your program: its own process ID,
14930 the ID of its parent, the process group ID, and the session ID.
14933 @item set procfs-trace
14934 @kindex set procfs-trace
14935 @cindex @code{procfs} API calls
14936 This command enables and disables tracing of @code{procfs} API calls.
14938 @item show procfs-trace
14939 @kindex show procfs-trace
14940 Show the current state of @code{procfs} API call tracing.
14942 @item set procfs-file @var{file}
14943 @kindex set procfs-file
14944 Tell @value{GDBN} to write @code{procfs} API trace to the named
14945 @var{file}. @value{GDBN} appends the trace info to the previous
14946 contents of the file. The default is to display the trace on the
14949 @item show procfs-file
14950 @kindex show procfs-file
14951 Show the file to which @code{procfs} API trace is written.
14953 @item proc-trace-entry
14954 @itemx proc-trace-exit
14955 @itemx proc-untrace-entry
14956 @itemx proc-untrace-exit
14957 @kindex proc-trace-entry
14958 @kindex proc-trace-exit
14959 @kindex proc-untrace-entry
14960 @kindex proc-untrace-exit
14961 These commands enable and disable tracing of entries into and exits
14962 from the @code{syscall} interface.
14965 @kindex info pidlist
14966 @cindex process list, QNX Neutrino
14967 For QNX Neutrino only, this command displays the list of all the
14968 processes and all the threads within each process.
14971 @kindex info meminfo
14972 @cindex mapinfo list, QNX Neutrino
14973 For QNX Neutrino only, this command displays the list of all mapinfos.
14977 @subsection Features for Debugging @sc{djgpp} Programs
14978 @cindex @sc{djgpp} debugging
14979 @cindex native @sc{djgpp} debugging
14980 @cindex MS-DOS-specific commands
14983 @sc{djgpp} is a port of the @sc{gnu} development tools to MS-DOS and
14984 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
14985 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
14986 top of real-mode DOS systems and their emulations.
14988 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
14989 defines a few commands specific to the @sc{djgpp} port. This
14990 subsection describes those commands.
14995 This is a prefix of @sc{djgpp}-specific commands which print
14996 information about the target system and important OS structures.
14999 @cindex MS-DOS system info
15000 @cindex free memory information (MS-DOS)
15001 @item info dos sysinfo
15002 This command displays assorted information about the underlying
15003 platform: the CPU type and features, the OS version and flavor, the
15004 DPMI version, and the available conventional and DPMI memory.
15009 @cindex segment descriptor tables
15010 @cindex descriptor tables display
15012 @itemx info dos ldt
15013 @itemx info dos idt
15014 These 3 commands display entries from, respectively, Global, Local,
15015 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
15016 tables are data structures which store a descriptor for each segment
15017 that is currently in use. The segment's selector is an index into a
15018 descriptor table; the table entry for that index holds the
15019 descriptor's base address and limit, and its attributes and access
15022 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
15023 segment (used for both data and the stack), and a DOS segment (which
15024 allows access to DOS/BIOS data structures and absolute addresses in
15025 conventional memory). However, the DPMI host will usually define
15026 additional segments in order to support the DPMI environment.
15028 @cindex garbled pointers
15029 These commands allow to display entries from the descriptor tables.
15030 Without an argument, all entries from the specified table are
15031 displayed. An argument, which should be an integer expression, means
15032 display a single entry whose index is given by the argument. For
15033 example, here's a convenient way to display information about the
15034 debugged program's data segment:
15037 @exdent @code{(@value{GDBP}) info dos ldt $ds}
15038 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
15042 This comes in handy when you want to see whether a pointer is outside
15043 the data segment's limit (i.e.@: @dfn{garbled}).
15045 @cindex page tables display (MS-DOS)
15047 @itemx info dos pte
15048 These two commands display entries from, respectively, the Page
15049 Directory and the Page Tables. Page Directories and Page Tables are
15050 data structures which control how virtual memory addresses are mapped
15051 into physical addresses. A Page Table includes an entry for every
15052 page of memory that is mapped into the program's address space; there
15053 may be several Page Tables, each one holding up to 4096 entries. A
15054 Page Directory has up to 4096 entries, one each for every Page Table
15055 that is currently in use.
15057 Without an argument, @kbd{info dos pde} displays the entire Page
15058 Directory, and @kbd{info dos pte} displays all the entries in all of
15059 the Page Tables. An argument, an integer expression, given to the
15060 @kbd{info dos pde} command means display only that entry from the Page
15061 Directory table. An argument given to the @kbd{info dos pte} command
15062 means display entries from a single Page Table, the one pointed to by
15063 the specified entry in the Page Directory.
15065 @cindex direct memory access (DMA) on MS-DOS
15066 These commands are useful when your program uses @dfn{DMA} (Direct
15067 Memory Access), which needs physical addresses to program the DMA
15070 These commands are supported only with some DPMI servers.
15072 @cindex physical address from linear address
15073 @item info dos address-pte @var{addr}
15074 This command displays the Page Table entry for a specified linear
15075 address. The argument @var{addr} is a linear address which should
15076 already have the appropriate segment's base address added to it,
15077 because this command accepts addresses which may belong to @emph{any}
15078 segment. For example, here's how to display the Page Table entry for
15079 the page where a variable @code{i} is stored:
15082 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
15083 @exdent @code{Page Table entry for address 0x11a00d30:}
15084 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
15088 This says that @code{i} is stored at offset @code{0xd30} from the page
15089 whose physical base address is @code{0x02698000}, and shows all the
15090 attributes of that page.
15092 Note that you must cast the addresses of variables to a @code{char *},
15093 since otherwise the value of @code{__djgpp_base_address}, the base
15094 address of all variables and functions in a @sc{djgpp} program, will
15095 be added using the rules of C pointer arithmetics: if @code{i} is
15096 declared an @code{int}, @value{GDBN} will add 4 times the value of
15097 @code{__djgpp_base_address} to the address of @code{i}.
15099 Here's another example, it displays the Page Table entry for the
15103 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
15104 @exdent @code{Page Table entry for address 0x29110:}
15105 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
15109 (The @code{+ 3} offset is because the transfer buffer's address is the
15110 3rd member of the @code{_go32_info_block} structure.) The output
15111 clearly shows that this DPMI server maps the addresses in conventional
15112 memory 1:1, i.e.@: the physical (@code{0x00029000} + @code{0x110}) and
15113 linear (@code{0x29110}) addresses are identical.
15115 This command is supported only with some DPMI servers.
15118 @cindex DOS serial data link, remote debugging
15119 In addition to native debugging, the DJGPP port supports remote
15120 debugging via a serial data link. The following commands are specific
15121 to remote serial debugging in the DJGPP port of @value{GDBN}.
15124 @kindex set com1base
15125 @kindex set com1irq
15126 @kindex set com2base
15127 @kindex set com2irq
15128 @kindex set com3base
15129 @kindex set com3irq
15130 @kindex set com4base
15131 @kindex set com4irq
15132 @item set com1base @var{addr}
15133 This command sets the base I/O port address of the @file{COM1} serial
15136 @item set com1irq @var{irq}
15137 This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use
15138 for the @file{COM1} serial port.
15140 There are similar commands @samp{set com2base}, @samp{set com3irq},
15141 etc.@: for setting the port address and the @code{IRQ} lines for the
15144 @kindex show com1base
15145 @kindex show com1irq
15146 @kindex show com2base
15147 @kindex show com2irq
15148 @kindex show com3base
15149 @kindex show com3irq
15150 @kindex show com4base
15151 @kindex show com4irq
15152 The related commands @samp{show com1base}, @samp{show com1irq} etc.@:
15153 display the current settings of the base address and the @code{IRQ}
15154 lines used by the COM ports.
15157 @kindex info serial
15158 @cindex DOS serial port status
15159 This command prints the status of the 4 DOS serial ports. For each
15160 port, it prints whether it's active or not, its I/O base address and
15161 IRQ number, whether it uses a 16550-style FIFO, its baudrate, and the
15162 counts of various errors encountered so far.
15166 @node Cygwin Native
15167 @subsection Features for Debugging MS Windows PE Executables
15168 @cindex MS Windows debugging
15169 @cindex native Cygwin debugging
15170 @cindex Cygwin-specific commands
15172 @value{GDBN} supports native debugging of MS Windows programs, including
15173 DLLs with and without symbolic debugging information. There are various
15174 additional Cygwin-specific commands, described in this section.
15175 Working with DLLs that have no debugging symbols is described in
15176 @ref{Non-debug DLL Symbols}.
15181 This is a prefix of MS Windows-specific commands which print
15182 information about the target system and important OS structures.
15184 @item info w32 selector
15185 This command displays information returned by
15186 the Win32 API @code{GetThreadSelectorEntry} function.
15187 It takes an optional argument that is evaluated to
15188 a long value to give the information about this given selector.
15189 Without argument, this command displays information
15190 about the six segment registers.
15194 This is a Cygwin-specific alias of @code{info shared}.
15196 @kindex dll-symbols
15198 This command loads symbols from a dll similarly to
15199 add-sym command but without the need to specify a base address.
15201 @kindex set cygwin-exceptions
15202 @cindex debugging the Cygwin DLL
15203 @cindex Cygwin DLL, debugging
15204 @item set cygwin-exceptions @var{mode}
15205 If @var{mode} is @code{on}, @value{GDBN} will break on exceptions that
15206 happen inside the Cygwin DLL. If @var{mode} is @code{off},
15207 @value{GDBN} will delay recognition of exceptions, and may ignore some
15208 exceptions which seem to be caused by internal Cygwin DLL
15209 ``bookkeeping''. This option is meant primarily for debugging the
15210 Cygwin DLL itself; the default value is @code{off} to avoid annoying
15211 @value{GDBN} users with false @code{SIGSEGV} signals.
15213 @kindex show cygwin-exceptions
15214 @item show cygwin-exceptions
15215 Displays whether @value{GDBN} will break on exceptions that happen
15216 inside the Cygwin DLL itself.
15218 @kindex set new-console
15219 @item set new-console @var{mode}
15220 If @var{mode} is @code{on} the debuggee will
15221 be started in a new console on next start.
15222 If @var{mode} is @code{off}i, the debuggee will
15223 be started in the same console as the debugger.
15225 @kindex show new-console
15226 @item show new-console
15227 Displays whether a new console is used
15228 when the debuggee is started.
15230 @kindex set new-group
15231 @item set new-group @var{mode}
15232 This boolean value controls whether the debuggee should
15233 start a new group or stay in the same group as the debugger.
15234 This affects the way the Windows OS handles
15237 @kindex show new-group
15238 @item show new-group
15239 Displays current value of new-group boolean.
15241 @kindex set debugevents
15242 @item set debugevents
15243 This boolean value adds debug output concerning kernel events related
15244 to the debuggee seen by the debugger. This includes events that
15245 signal thread and process creation and exit, DLL loading and
15246 unloading, console interrupts, and debugging messages produced by the
15247 Windows @code{OutputDebugString} API call.
15249 @kindex set debugexec
15250 @item set debugexec
15251 This boolean value adds debug output concerning execute events
15252 (such as resume thread) seen by the debugger.
15254 @kindex set debugexceptions
15255 @item set debugexceptions
15256 This boolean value adds debug output concerning exceptions in the
15257 debuggee seen by the debugger.
15259 @kindex set debugmemory
15260 @item set debugmemory
15261 This boolean value adds debug output concerning debuggee memory reads
15262 and writes by the debugger.
15266 This boolean values specifies whether the debuggee is called
15267 via a shell or directly (default value is on).
15271 Displays if the debuggee will be started with a shell.
15276 * Non-debug DLL Symbols:: Support for DLLs without debugging symbols
15279 @node Non-debug DLL Symbols
15280 @subsubsection Support for DLLs without Debugging Symbols
15281 @cindex DLLs with no debugging symbols
15282 @cindex Minimal symbols and DLLs
15284 Very often on windows, some of the DLLs that your program relies on do
15285 not include symbolic debugging information (for example,
15286 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
15287 symbols in a DLL, it relies on the minimal amount of symbolic
15288 information contained in the DLL's export table. This section
15289 describes working with such symbols, known internally to @value{GDBN} as
15290 ``minimal symbols''.
15292 Note that before the debugged program has started execution, no DLLs
15293 will have been loaded. The easiest way around this problem is simply to
15294 start the program --- either by setting a breakpoint or letting the
15295 program run once to completion. It is also possible to force
15296 @value{GDBN} to load a particular DLL before starting the executable ---
15297 see the shared library information in @ref{Files}, or the
15298 @code{dll-symbols} command in @ref{Cygwin Native}. Currently,
15299 explicitly loading symbols from a DLL with no debugging information will
15300 cause the symbol names to be duplicated in @value{GDBN}'s lookup table,
15301 which may adversely affect symbol lookup performance.
15303 @subsubsection DLL Name Prefixes
15305 In keeping with the naming conventions used by the Microsoft debugging
15306 tools, DLL export symbols are made available with a prefix based on the
15307 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
15308 also entered into the symbol table, so @code{CreateFileA} is often
15309 sufficient. In some cases there will be name clashes within a program
15310 (particularly if the executable itself includes full debugging symbols)
15311 necessitating the use of the fully qualified name when referring to the
15312 contents of the DLL. Use single-quotes around the name to avoid the
15313 exclamation mark (``!'') being interpreted as a language operator.
15315 Note that the internal name of the DLL may be all upper-case, even
15316 though the file name of the DLL is lower-case, or vice-versa. Since
15317 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
15318 some confusion. If in doubt, try the @code{info functions} and
15319 @code{info variables} commands or even @code{maint print msymbols}
15320 (@pxref{Symbols}). Here's an example:
15323 (@value{GDBP}) info function CreateFileA
15324 All functions matching regular expression "CreateFileA":
15326 Non-debugging symbols:
15327 0x77e885f4 CreateFileA
15328 0x77e885f4 KERNEL32!CreateFileA
15332 (@value{GDBP}) info function !
15333 All functions matching regular expression "!":
15335 Non-debugging symbols:
15336 0x6100114c cygwin1!__assert
15337 0x61004034 cygwin1!_dll_crt0@@0
15338 0x61004240 cygwin1!dll_crt0(per_process *)
15342 @subsubsection Working with Minimal Symbols
15344 Symbols extracted from a DLL's export table do not contain very much
15345 type information. All that @value{GDBN} can do is guess whether a symbol
15346 refers to a function or variable depending on the linker section that
15347 contains the symbol. Also note that the actual contents of the memory
15348 contained in a DLL are not available unless the program is running. This
15349 means that you cannot examine the contents of a variable or disassemble
15350 a function within a DLL without a running program.
15352 Variables are generally treated as pointers and dereferenced
15353 automatically. For this reason, it is often necessary to prefix a
15354 variable name with the address-of operator (``&'') and provide explicit
15355 type information in the command. Here's an example of the type of
15359 (@value{GDBP}) print 'cygwin1!__argv'
15364 (@value{GDBP}) x 'cygwin1!__argv'
15365 0x10021610: "\230y\""
15368 And two possible solutions:
15371 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
15372 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
15376 (@value{GDBP}) x/2x &'cygwin1!__argv'
15377 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
15378 (@value{GDBP}) x/x 0x10021608
15379 0x10021608: 0x0022fd98
15380 (@value{GDBP}) x/s 0x0022fd98
15381 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
15384 Setting a break point within a DLL is possible even before the program
15385 starts execution. However, under these circumstances, @value{GDBN} can't
15386 examine the initial instructions of the function in order to skip the
15387 function's frame set-up code. You can work around this by using ``*&''
15388 to set the breakpoint at a raw memory address:
15391 (@value{GDBP}) break *&'python22!PyOS_Readline'
15392 Breakpoint 1 at 0x1e04eff0
15395 The author of these extensions is not entirely convinced that setting a
15396 break point within a shared DLL like @file{kernel32.dll} is completely
15400 @subsection Commands Specific to @sc{gnu} Hurd Systems
15401 @cindex @sc{gnu} Hurd debugging
15403 This subsection describes @value{GDBN} commands specific to the
15404 @sc{gnu} Hurd native debugging.
15409 @kindex set signals@r{, Hurd command}
15410 @kindex set sigs@r{, Hurd command}
15411 This command toggles the state of inferior signal interception by
15412 @value{GDBN}. Mach exceptions, such as breakpoint traps, are not
15413 affected by this command. @code{sigs} is a shorthand alias for
15418 @kindex show signals@r{, Hurd command}
15419 @kindex show sigs@r{, Hurd command}
15420 Show the current state of intercepting inferior's signals.
15422 @item set signal-thread
15423 @itemx set sigthread
15424 @kindex set signal-thread
15425 @kindex set sigthread
15426 This command tells @value{GDBN} which thread is the @code{libc} signal
15427 thread. That thread is run when a signal is delivered to a running
15428 process. @code{set sigthread} is the shorthand alias of @code{set
15431 @item show signal-thread
15432 @itemx show sigthread
15433 @kindex show signal-thread
15434 @kindex show sigthread
15435 These two commands show which thread will run when the inferior is
15436 delivered a signal.
15439 @kindex set stopped@r{, Hurd command}
15440 This commands tells @value{GDBN} that the inferior process is stopped,
15441 as with the @code{SIGSTOP} signal. The stopped process can be
15442 continued by delivering a signal to it.
15445 @kindex show stopped@r{, Hurd command}
15446 This command shows whether @value{GDBN} thinks the debuggee is
15449 @item set exceptions
15450 @kindex set exceptions@r{, Hurd command}
15451 Use this command to turn off trapping of exceptions in the inferior.
15452 When exception trapping is off, neither breakpoints nor
15453 single-stepping will work. To restore the default, set exception
15456 @item show exceptions
15457 @kindex show exceptions@r{, Hurd command}
15458 Show the current state of trapping exceptions in the inferior.
15460 @item set task pause
15461 @kindex set task@r{, Hurd commands}
15462 @cindex task attributes (@sc{gnu} Hurd)
15463 @cindex pause current task (@sc{gnu} Hurd)
15464 This command toggles task suspension when @value{GDBN} has control.
15465 Setting it to on takes effect immediately, and the task is suspended
15466 whenever @value{GDBN} gets control. Setting it to off will take
15467 effect the next time the inferior is continued. If this option is set
15468 to off, you can use @code{set thread default pause on} or @code{set
15469 thread pause on} (see below) to pause individual threads.
15471 @item show task pause
15472 @kindex show task@r{, Hurd commands}
15473 Show the current state of task suspension.
15475 @item set task detach-suspend-count
15476 @cindex task suspend count
15477 @cindex detach from task, @sc{gnu} Hurd
15478 This command sets the suspend count the task will be left with when
15479 @value{GDBN} detaches from it.
15481 @item show task detach-suspend-count
15482 Show the suspend count the task will be left with when detaching.
15484 @item set task exception-port
15485 @itemx set task excp
15486 @cindex task exception port, @sc{gnu} Hurd
15487 This command sets the task exception port to which @value{GDBN} will
15488 forward exceptions. The argument should be the value of the @dfn{send
15489 rights} of the task. @code{set task excp} is a shorthand alias.
15491 @item set noninvasive
15492 @cindex noninvasive task options
15493 This command switches @value{GDBN} to a mode that is the least
15494 invasive as far as interfering with the inferior is concerned. This
15495 is the same as using @code{set task pause}, @code{set exceptions}, and
15496 @code{set signals} to values opposite to the defaults.
15498 @item info send-rights
15499 @itemx info receive-rights
15500 @itemx info port-rights
15501 @itemx info port-sets
15502 @itemx info dead-names
15505 @cindex send rights, @sc{gnu} Hurd
15506 @cindex receive rights, @sc{gnu} Hurd
15507 @cindex port rights, @sc{gnu} Hurd
15508 @cindex port sets, @sc{gnu} Hurd
15509 @cindex dead names, @sc{gnu} Hurd
15510 These commands display information about, respectively, send rights,
15511 receive rights, port rights, port sets, and dead names of a task.
15512 There are also shorthand aliases: @code{info ports} for @code{info
15513 port-rights} and @code{info psets} for @code{info port-sets}.
15515 @item set thread pause
15516 @kindex set thread@r{, Hurd command}
15517 @cindex thread properties, @sc{gnu} Hurd
15518 @cindex pause current thread (@sc{gnu} Hurd)
15519 This command toggles current thread suspension when @value{GDBN} has
15520 control. Setting it to on takes effect immediately, and the current
15521 thread is suspended whenever @value{GDBN} gets control. Setting it to
15522 off will take effect the next time the inferior is continued.
15523 Normally, this command has no effect, since when @value{GDBN} has
15524 control, the whole task is suspended. However, if you used @code{set
15525 task pause off} (see above), this command comes in handy to suspend
15526 only the current thread.
15528 @item show thread pause
15529 @kindex show thread@r{, Hurd command}
15530 This command shows the state of current thread suspension.
15532 @item set thread run
15533 This command sets whether the current thread is allowed to run.
15535 @item show thread run
15536 Show whether the current thread is allowed to run.
15538 @item set thread detach-suspend-count
15539 @cindex thread suspend count, @sc{gnu} Hurd
15540 @cindex detach from thread, @sc{gnu} Hurd
15541 This command sets the suspend count @value{GDBN} will leave on a
15542 thread when detaching. This number is relative to the suspend count
15543 found by @value{GDBN} when it notices the thread; use @code{set thread
15544 takeover-suspend-count} to force it to an absolute value.
15546 @item show thread detach-suspend-count
15547 Show the suspend count @value{GDBN} will leave on the thread when
15550 @item set thread exception-port
15551 @itemx set thread excp
15552 Set the thread exception port to which to forward exceptions. This
15553 overrides the port set by @code{set task exception-port} (see above).
15554 @code{set thread excp} is the shorthand alias.
15556 @item set thread takeover-suspend-count
15557 Normally, @value{GDBN}'s thread suspend counts are relative to the
15558 value @value{GDBN} finds when it notices each thread. This command
15559 changes the suspend counts to be absolute instead.
15561 @item set thread default
15562 @itemx show thread default
15563 @cindex thread default settings, @sc{gnu} Hurd
15564 Each of the above @code{set thread} commands has a @code{set thread
15565 default} counterpart (e.g., @code{set thread default pause}, @code{set
15566 thread default exception-port}, etc.). The @code{thread default}
15567 variety of commands sets the default thread properties for all
15568 threads; you can then change the properties of individual threads with
15569 the non-default commands.
15574 @subsection QNX Neutrino
15575 @cindex QNX Neutrino
15577 @value{GDBN} provides the following commands specific to the QNX
15581 @item set debug nto-debug
15582 @kindex set debug nto-debug
15583 When set to on, enables debugging messages specific to the QNX
15586 @item show debug nto-debug
15587 @kindex show debug nto-debug
15588 Show the current state of QNX Neutrino messages.
15595 @value{GDBN} provides the following commands specific to the Darwin target:
15598 @item set debug darwin @var{num}
15599 @kindex set debug darwin
15600 When set to a non zero value, enables debugging messages specific to
15601 the Darwin support. Higher values produce more verbose output.
15603 @item show debug darwin
15604 @kindex show debug darwin
15605 Show the current state of Darwin messages.
15607 @item set debug mach-o @var{num}
15608 @kindex set debug mach-o
15609 When set to a non zero value, enables debugging messages while
15610 @value{GDBN} is reading Darwin object files. (@dfn{Mach-O} is the
15611 file format used on Darwin for object and executable files.) Higher
15612 values produce more verbose output. This is a command to diagnose
15613 problems internal to @value{GDBN} and should not be needed in normal
15616 @item show debug mach-o
15617 @kindex show debug mach-o
15618 Show the current state of Mach-O file messages.
15620 @item set mach-exceptions on
15621 @itemx set mach-exceptions off
15622 @kindex set mach-exceptions
15623 On Darwin, faults are first reported as a Mach exception and are then
15624 mapped to a Posix signal. Use this command to turn on trapping of
15625 Mach exceptions in the inferior. This might be sometimes useful to
15626 better understand the cause of a fault. The default is off.
15628 @item show mach-exceptions
15629 @kindex show mach-exceptions
15630 Show the current state of exceptions trapping.
15635 @section Embedded Operating Systems
15637 This section describes configurations involving the debugging of
15638 embedded operating systems that are available for several different
15642 * VxWorks:: Using @value{GDBN} with VxWorks
15645 @value{GDBN} includes the ability to debug programs running on
15646 various real-time operating systems.
15649 @subsection Using @value{GDBN} with VxWorks
15655 @kindex target vxworks
15656 @item target vxworks @var{machinename}
15657 A VxWorks system, attached via TCP/IP. The argument @var{machinename}
15658 is the target system's machine name or IP address.
15662 On VxWorks, @code{load} links @var{filename} dynamically on the
15663 current target system as well as adding its symbols in @value{GDBN}.
15665 @value{GDBN} enables developers to spawn and debug tasks running on networked
15666 VxWorks targets from a Unix host. Already-running tasks spawned from
15667 the VxWorks shell can also be debugged. @value{GDBN} uses code that runs on
15668 both the Unix host and on the VxWorks target. The program
15669 @code{@value{GDBP}} is installed and executed on the Unix host. (It may be
15670 installed with the name @code{vxgdb}, to distinguish it from a
15671 @value{GDBN} for debugging programs on the host itself.)
15674 @item VxWorks-timeout @var{args}
15675 @kindex vxworks-timeout
15676 All VxWorks-based targets now support the option @code{vxworks-timeout}.
15677 This option is set by the user, and @var{args} represents the number of
15678 seconds @value{GDBN} waits for responses to rpc's. You might use this if
15679 your VxWorks target is a slow software simulator or is on the far side
15680 of a thin network line.
15683 The following information on connecting to VxWorks was current when
15684 this manual was produced; newer releases of VxWorks may use revised
15687 @findex INCLUDE_RDB
15688 To use @value{GDBN} with VxWorks, you must rebuild your VxWorks kernel
15689 to include the remote debugging interface routines in the VxWorks
15690 library @file{rdb.a}. To do this, define @code{INCLUDE_RDB} in the
15691 VxWorks configuration file @file{configAll.h} and rebuild your VxWorks
15692 kernel. The resulting kernel contains @file{rdb.a}, and spawns the
15693 source debugging task @code{tRdbTask} when VxWorks is booted. For more
15694 information on configuring and remaking VxWorks, see the manufacturer's
15696 @c VxWorks, see the @cite{VxWorks Programmer's Guide}.
15698 Once you have included @file{rdb.a} in your VxWorks system image and set
15699 your Unix execution search path to find @value{GDBN}, you are ready to
15700 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}} (or
15701 @code{vxgdb}, depending on your installation).
15703 @value{GDBN} comes up showing the prompt:
15710 * VxWorks Connection:: Connecting to VxWorks
15711 * VxWorks Download:: VxWorks download
15712 * VxWorks Attach:: Running tasks
15715 @node VxWorks Connection
15716 @subsubsection Connecting to VxWorks
15718 The @value{GDBN} command @code{target} lets you connect to a VxWorks target on the
15719 network. To connect to a target whose host name is ``@code{tt}'', type:
15722 (vxgdb) target vxworks tt
15726 @value{GDBN} displays messages like these:
15729 Attaching remote machine across net...
15734 @value{GDBN} then attempts to read the symbol tables of any object modules
15735 loaded into the VxWorks target since it was last booted. @value{GDBN} locates
15736 these files by searching the directories listed in the command search
15737 path (@pxref{Environment, ,Your Program's Environment}); if it fails
15738 to find an object file, it displays a message such as:
15741 prog.o: No such file or directory.
15744 When this happens, add the appropriate directory to the search path with
15745 the @value{GDBN} command @code{path}, and execute the @code{target}
15748 @node VxWorks Download
15749 @subsubsection VxWorks Download
15751 @cindex download to VxWorks
15752 If you have connected to the VxWorks target and you want to debug an
15753 object that has not yet been loaded, you can use the @value{GDBN}
15754 @code{load} command to download a file from Unix to VxWorks
15755 incrementally. The object file given as an argument to the @code{load}
15756 command is actually opened twice: first by the VxWorks target in order
15757 to download the code, then by @value{GDBN} in order to read the symbol
15758 table. This can lead to problems if the current working directories on
15759 the two systems differ. If both systems have NFS mounted the same
15760 filesystems, you can avoid these problems by using absolute paths.
15761 Otherwise, it is simplest to set the working directory on both systems
15762 to the directory in which the object file resides, and then to reference
15763 the file by its name, without any path. For instance, a program
15764 @file{prog.o} may reside in @file{@var{vxpath}/vw/demo/rdb} in VxWorks
15765 and in @file{@var{hostpath}/vw/demo/rdb} on the host. To load this
15766 program, type this on VxWorks:
15769 -> cd "@var{vxpath}/vw/demo/rdb"
15773 Then, in @value{GDBN}, type:
15776 (vxgdb) cd @var{hostpath}/vw/demo/rdb
15777 (vxgdb) load prog.o
15780 @value{GDBN} displays a response similar to this:
15783 Reading symbol data from wherever/vw/demo/rdb/prog.o... done.
15786 You can also use the @code{load} command to reload an object module
15787 after editing and recompiling the corresponding source file. Note that
15788 this makes @value{GDBN} delete all currently-defined breakpoints,
15789 auto-displays, and convenience variables, and to clear the value
15790 history. (This is necessary in order to preserve the integrity of
15791 debugger's data structures that reference the target system's symbol
15794 @node VxWorks Attach
15795 @subsubsection Running Tasks
15797 @cindex running VxWorks tasks
15798 You can also attach to an existing task using the @code{attach} command as
15802 (vxgdb) attach @var{task}
15806 where @var{task} is the VxWorks hexadecimal task ID. The task can be running
15807 or suspended when you attach to it. Running tasks are suspended at
15808 the time of attachment.
15810 @node Embedded Processors
15811 @section Embedded Processors
15813 This section goes into details specific to particular embedded
15816 @cindex send command to simulator
15817 Whenever a specific embedded processor has a simulator, @value{GDBN}
15818 allows to send an arbitrary command to the simulator.
15821 @item sim @var{command}
15822 @kindex sim@r{, a command}
15823 Send an arbitrary @var{command} string to the simulator. Consult the
15824 documentation for the specific simulator in use for information about
15825 acceptable commands.
15831 * M32R/D:: Renesas M32R/D
15832 * M68K:: Motorola M68K
15833 * MIPS Embedded:: MIPS Embedded
15834 * OpenRISC 1000:: OpenRisc 1000
15835 * PA:: HP PA Embedded
15836 * PowerPC Embedded:: PowerPC Embedded
15837 * Sparclet:: Tsqware Sparclet
15838 * Sparclite:: Fujitsu Sparclite
15839 * Z8000:: Zilog Z8000
15842 * Super-H:: Renesas Super-H
15851 @item target rdi @var{dev}
15852 ARM Angel monitor, via RDI library interface to ADP protocol. You may
15853 use this target to communicate with both boards running the Angel
15854 monitor, or with the EmbeddedICE JTAG debug device.
15857 @item target rdp @var{dev}
15862 @value{GDBN} provides the following ARM-specific commands:
15865 @item set arm disassembler
15867 This commands selects from a list of disassembly styles. The
15868 @code{"std"} style is the standard style.
15870 @item show arm disassembler
15872 Show the current disassembly style.
15874 @item set arm apcs32
15875 @cindex ARM 32-bit mode
15876 This command toggles ARM operation mode between 32-bit and 26-bit.
15878 @item show arm apcs32
15879 Display the current usage of the ARM 32-bit mode.
15881 @item set arm fpu @var{fputype}
15882 This command sets the ARM floating-point unit (FPU) type. The
15883 argument @var{fputype} can be one of these:
15887 Determine the FPU type by querying the OS ABI.
15889 Software FPU, with mixed-endian doubles on little-endian ARM
15892 GCC-compiled FPA co-processor.
15894 Software FPU with pure-endian doubles.
15900 Show the current type of the FPU.
15903 This command forces @value{GDBN} to use the specified ABI.
15906 Show the currently used ABI.
15908 @item set arm fallback-mode (arm|thumb|auto)
15909 @value{GDBN} uses the symbol table, when available, to determine
15910 whether instructions are ARM or Thumb. This command controls
15911 @value{GDBN}'s default behavior when the symbol table is not
15912 available. The default is @samp{auto}, which causes @value{GDBN} to
15913 use the current execution mode (from the @code{T} bit in the @code{CPSR}
15916 @item show arm fallback-mode
15917 Show the current fallback instruction mode.
15919 @item set arm force-mode (arm|thumb|auto)
15920 This command overrides use of the symbol table to determine whether
15921 instructions are ARM or Thumb. The default is @samp{auto}, which
15922 causes @value{GDBN} to use the symbol table and then the setting
15923 of @samp{set arm fallback-mode}.
15925 @item show arm force-mode
15926 Show the current forced instruction mode.
15928 @item set debug arm
15929 Toggle whether to display ARM-specific debugging messages from the ARM
15930 target support subsystem.
15932 @item show debug arm
15933 Show whether ARM-specific debugging messages are enabled.
15936 The following commands are available when an ARM target is debugged
15937 using the RDI interface:
15940 @item rdilogfile @r{[}@var{file}@r{]}
15942 @cindex ADP (Angel Debugger Protocol) logging
15943 Set the filename for the ADP (Angel Debugger Protocol) packet log.
15944 With an argument, sets the log file to the specified @var{file}. With
15945 no argument, show the current log file name. The default log file is
15948 @item rdilogenable @r{[}@var{arg}@r{]}
15949 @kindex rdilogenable
15950 Control logging of ADP packets. With an argument of 1 or @code{"yes"}
15951 enables logging, with an argument 0 or @code{"no"} disables it. With
15952 no arguments displays the current setting. When logging is enabled,
15953 ADP packets exchanged between @value{GDBN} and the RDI target device
15954 are logged to a file.
15956 @item set rdiromatzero
15957 @kindex set rdiromatzero
15958 @cindex ROM at zero address, RDI
15959 Tell @value{GDBN} whether the target has ROM at address 0. If on,
15960 vector catching is disabled, so that zero address can be used. If off
15961 (the default), vector catching is enabled. For this command to take
15962 effect, it needs to be invoked prior to the @code{target rdi} command.
15964 @item show rdiromatzero
15965 @kindex show rdiromatzero
15966 Show the current setting of ROM at zero address.
15968 @item set rdiheartbeat
15969 @kindex set rdiheartbeat
15970 @cindex RDI heartbeat
15971 Enable or disable RDI heartbeat packets. It is not recommended to
15972 turn on this option, since it confuses ARM and EPI JTAG interface, as
15973 well as the Angel monitor.
15975 @item show rdiheartbeat
15976 @kindex show rdiheartbeat
15977 Show the setting of RDI heartbeat packets.
15982 @subsection Renesas M32R/D and M32R/SDI
15985 @kindex target m32r
15986 @item target m32r @var{dev}
15987 Renesas M32R/D ROM monitor.
15989 @kindex target m32rsdi
15990 @item target m32rsdi @var{dev}
15991 Renesas M32R SDI server, connected via parallel port to the board.
15994 The following @value{GDBN} commands are specific to the M32R monitor:
15997 @item set download-path @var{path}
15998 @kindex set download-path
15999 @cindex find downloadable @sc{srec} files (M32R)
16000 Set the default path for finding downloadable @sc{srec} files.
16002 @item show download-path
16003 @kindex show download-path
16004 Show the default path for downloadable @sc{srec} files.
16006 @item set board-address @var{addr}
16007 @kindex set board-address
16008 @cindex M32-EVA target board address
16009 Set the IP address for the M32R-EVA target board.
16011 @item show board-address
16012 @kindex show board-address
16013 Show the current IP address of the target board.
16015 @item set server-address @var{addr}
16016 @kindex set server-address
16017 @cindex download server address (M32R)
16018 Set the IP address for the download server, which is the @value{GDBN}'s
16021 @item show server-address
16022 @kindex show server-address
16023 Display the IP address of the download server.
16025 @item upload @r{[}@var{file}@r{]}
16026 @kindex upload@r{, M32R}
16027 Upload the specified @sc{srec} @var{file} via the monitor's Ethernet
16028 upload capability. If no @var{file} argument is given, the current
16029 executable file is uploaded.
16031 @item tload @r{[}@var{file}@r{]}
16032 @kindex tload@r{, M32R}
16033 Test the @code{upload} command.
16036 The following commands are available for M32R/SDI:
16041 @cindex reset SDI connection, M32R
16042 This command resets the SDI connection.
16046 This command shows the SDI connection status.
16049 @kindex debug_chaos
16050 @cindex M32R/Chaos debugging
16051 Instructs the remote that M32R/Chaos debugging is to be used.
16053 @item use_debug_dma
16054 @kindex use_debug_dma
16055 Instructs the remote to use the DEBUG_DMA method of accessing memory.
16058 @kindex use_mon_code
16059 Instructs the remote to use the MON_CODE method of accessing memory.
16062 @kindex use_ib_break
16063 Instructs the remote to set breakpoints by IB break.
16065 @item use_dbt_break
16066 @kindex use_dbt_break
16067 Instructs the remote to set breakpoints by DBT.
16073 The Motorola m68k configuration includes ColdFire support, and a
16074 target command for the following ROM monitor.
16078 @kindex target dbug
16079 @item target dbug @var{dev}
16080 dBUG ROM monitor for Motorola ColdFire.
16084 @node MIPS Embedded
16085 @subsection MIPS Embedded
16087 @cindex MIPS boards
16088 @value{GDBN} can use the MIPS remote debugging protocol to talk to a
16089 MIPS board attached to a serial line. This is available when
16090 you configure @value{GDBN} with @samp{--target=mips-idt-ecoff}.
16093 Use these @value{GDBN} commands to specify the connection to your target board:
16096 @item target mips @var{port}
16097 @kindex target mips @var{port}
16098 To run a program on the board, start up @code{@value{GDBP}} with the
16099 name of your program as the argument. To connect to the board, use the
16100 command @samp{target mips @var{port}}, where @var{port} is the name of
16101 the serial port connected to the board. If the program has not already
16102 been downloaded to the board, you may use the @code{load} command to
16103 download it. You can then use all the usual @value{GDBN} commands.
16105 For example, this sequence connects to the target board through a serial
16106 port, and loads and runs a program called @var{prog} through the
16110 host$ @value{GDBP} @var{prog}
16111 @value{GDBN} is free software and @dots{}
16112 (@value{GDBP}) target mips /dev/ttyb
16113 (@value{GDBP}) load @var{prog}
16117 @item target mips @var{hostname}:@var{portnumber}
16118 On some @value{GDBN} host configurations, you can specify a TCP
16119 connection (for instance, to a serial line managed by a terminal
16120 concentrator) instead of a serial port, using the syntax
16121 @samp{@var{hostname}:@var{portnumber}}.
16123 @item target pmon @var{port}
16124 @kindex target pmon @var{port}
16127 @item target ddb @var{port}
16128 @kindex target ddb @var{port}
16129 NEC's DDB variant of PMON for Vr4300.
16131 @item target lsi @var{port}
16132 @kindex target lsi @var{port}
16133 LSI variant of PMON.
16135 @kindex target r3900
16136 @item target r3900 @var{dev}
16137 Densan DVE-R3900 ROM monitor for Toshiba R3900 Mips.
16139 @kindex target array
16140 @item target array @var{dev}
16141 Array Tech LSI33K RAID controller board.
16147 @value{GDBN} also supports these special commands for MIPS targets:
16150 @item set mipsfpu double
16151 @itemx set mipsfpu single
16152 @itemx set mipsfpu none
16153 @itemx set mipsfpu auto
16154 @itemx show mipsfpu
16155 @kindex set mipsfpu
16156 @kindex show mipsfpu
16157 @cindex MIPS remote floating point
16158 @cindex floating point, MIPS remote
16159 If your target board does not support the MIPS floating point
16160 coprocessor, you should use the command @samp{set mipsfpu none} (if you
16161 need this, you may wish to put the command in your @value{GDBN} init
16162 file). This tells @value{GDBN} how to find the return value of
16163 functions which return floating point values. It also allows
16164 @value{GDBN} to avoid saving the floating point registers when calling
16165 functions on the board. If you are using a floating point coprocessor
16166 with only single precision floating point support, as on the @sc{r4650}
16167 processor, use the command @samp{set mipsfpu single}. The default
16168 double precision floating point coprocessor may be selected using
16169 @samp{set mipsfpu double}.
16171 In previous versions the only choices were double precision or no
16172 floating point, so @samp{set mipsfpu on} will select double precision
16173 and @samp{set mipsfpu off} will select no floating point.
16175 As usual, you can inquire about the @code{mipsfpu} variable with
16176 @samp{show mipsfpu}.
16178 @item set timeout @var{seconds}
16179 @itemx set retransmit-timeout @var{seconds}
16180 @itemx show timeout
16181 @itemx show retransmit-timeout
16182 @cindex @code{timeout}, MIPS protocol
16183 @cindex @code{retransmit-timeout}, MIPS protocol
16184 @kindex set timeout
16185 @kindex show timeout
16186 @kindex set retransmit-timeout
16187 @kindex show retransmit-timeout
16188 You can control the timeout used while waiting for a packet, in the MIPS
16189 remote protocol, with the @code{set timeout @var{seconds}} command. The
16190 default is 5 seconds. Similarly, you can control the timeout used while
16191 waiting for an acknowledgment of a packet with the @code{set
16192 retransmit-timeout @var{seconds}} command. The default is 3 seconds.
16193 You can inspect both values with @code{show timeout} and @code{show
16194 retransmit-timeout}. (These commands are @emph{only} available when
16195 @value{GDBN} is configured for @samp{--target=mips-idt-ecoff}.)
16197 The timeout set by @code{set timeout} does not apply when @value{GDBN}
16198 is waiting for your program to stop. In that case, @value{GDBN} waits
16199 forever because it has no way of knowing how long the program is going
16200 to run before stopping.
16202 @item set syn-garbage-limit @var{num}
16203 @kindex set syn-garbage-limit@r{, MIPS remote}
16204 @cindex synchronize with remote MIPS target
16205 Limit the maximum number of characters @value{GDBN} should ignore when
16206 it tries to synchronize with the remote target. The default is 10
16207 characters. Setting the limit to -1 means there's no limit.
16209 @item show syn-garbage-limit
16210 @kindex show syn-garbage-limit@r{, MIPS remote}
16211 Show the current limit on the number of characters to ignore when
16212 trying to synchronize with the remote system.
16214 @item set monitor-prompt @var{prompt}
16215 @kindex set monitor-prompt@r{, MIPS remote}
16216 @cindex remote monitor prompt
16217 Tell @value{GDBN} to expect the specified @var{prompt} string from the
16218 remote monitor. The default depends on the target:
16228 @item show monitor-prompt
16229 @kindex show monitor-prompt@r{, MIPS remote}
16230 Show the current strings @value{GDBN} expects as the prompt from the
16233 @item set monitor-warnings
16234 @kindex set monitor-warnings@r{, MIPS remote}
16235 Enable or disable monitor warnings about hardware breakpoints. This
16236 has effect only for the @code{lsi} target. When on, @value{GDBN} will
16237 display warning messages whose codes are returned by the @code{lsi}
16238 PMON monitor for breakpoint commands.
16240 @item show monitor-warnings
16241 @kindex show monitor-warnings@r{, MIPS remote}
16242 Show the current setting of printing monitor warnings.
16244 @item pmon @var{command}
16245 @kindex pmon@r{, MIPS remote}
16246 @cindex send PMON command
16247 This command allows sending an arbitrary @var{command} string to the
16248 monitor. The monitor must be in debug mode for this to work.
16251 @node OpenRISC 1000
16252 @subsection OpenRISC 1000
16253 @cindex OpenRISC 1000
16255 @cindex or1k boards
16256 See OR1k Architecture document (@uref{www.opencores.org}) for more information
16257 about platform and commands.
16261 @kindex target jtag
16262 @item target jtag jtag://@var{host}:@var{port}
16264 Connects to remote JTAG server.
16265 JTAG remote server can be either an or1ksim or JTAG server,
16266 connected via parallel port to the board.
16268 Example: @code{target jtag jtag://localhost:9999}
16271 @item or1ksim @var{command}
16272 If connected to @code{or1ksim} OpenRISC 1000 Architectural
16273 Simulator, proprietary commands can be executed.
16275 @kindex info or1k spr
16276 @item info or1k spr
16277 Displays spr groups.
16279 @item info or1k spr @var{group}
16280 @itemx info or1k spr @var{groupno}
16281 Displays register names in selected group.
16283 @item info or1k spr @var{group} @var{register}
16284 @itemx info or1k spr @var{register}
16285 @itemx info or1k spr @var{groupno} @var{registerno}
16286 @itemx info or1k spr @var{registerno}
16287 Shows information about specified spr register.
16290 @item spr @var{group} @var{register} @var{value}
16291 @itemx spr @var{register @var{value}}
16292 @itemx spr @var{groupno} @var{registerno @var{value}}
16293 @itemx spr @var{registerno @var{value}}
16294 Writes @var{value} to specified spr register.
16297 Some implementations of OpenRISC 1000 Architecture also have hardware trace.
16298 It is very similar to @value{GDBN} trace, except it does not interfere with normal
16299 program execution and is thus much faster. Hardware breakpoints/watchpoint
16300 triggers can be set using:
16303 Load effective address/data
16305 Store effective address/data
16307 Access effective address ($SEA or $LEA) or data ($SDATA/$LDATA)
16312 When triggered, it can capture low level data, like: @code{PC}, @code{LSEA},
16313 @code{LDATA}, @code{SDATA}, @code{READSPR}, @code{WRITESPR}, @code{INSTR}.
16315 @code{htrace} commands:
16316 @cindex OpenRISC 1000 htrace
16319 @item hwatch @var{conditional}
16320 Set hardware watchpoint on combination of Load/Store Effective Address(es)
16321 or Data. For example:
16323 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
16325 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
16329 Display information about current HW trace configuration.
16331 @item htrace trigger @var{conditional}
16332 Set starting criteria for HW trace.
16334 @item htrace qualifier @var{conditional}
16335 Set acquisition qualifier for HW trace.
16337 @item htrace stop @var{conditional}
16338 Set HW trace stopping criteria.
16340 @item htrace record [@var{data}]*
16341 Selects the data to be recorded, when qualifier is met and HW trace was
16344 @item htrace enable
16345 @itemx htrace disable
16346 Enables/disables the HW trace.
16348 @item htrace rewind [@var{filename}]
16349 Clears currently recorded trace data.
16351 If filename is specified, new trace file is made and any newly collected data
16352 will be written there.
16354 @item htrace print [@var{start} [@var{len}]]
16355 Prints trace buffer, using current record configuration.
16357 @item htrace mode continuous
16358 Set continuous trace mode.
16360 @item htrace mode suspend
16361 Set suspend trace mode.
16365 @node PowerPC Embedded
16366 @subsection PowerPC Embedded
16368 @value{GDBN} provides the following PowerPC-specific commands:
16371 @kindex set powerpc
16372 @item set powerpc soft-float
16373 @itemx show powerpc soft-float
16374 Force @value{GDBN} to use (or not use) a software floating point calling
16375 convention. By default, @value{GDBN} selects the calling convention based
16376 on the selected architecture and the provided executable file.
16378 @item set powerpc vector-abi
16379 @itemx show powerpc vector-abi
16380 Force @value{GDBN} to use the specified calling convention for vector
16381 arguments and return values. The valid options are @samp{auto};
16382 @samp{generic}, to avoid vector registers even if they are present;
16383 @samp{altivec}, to use AltiVec registers; and @samp{spe} to use SPE
16384 registers. By default, @value{GDBN} selects the calling convention
16385 based on the selected architecture and the provided executable file.
16387 @kindex target dink32
16388 @item target dink32 @var{dev}
16389 DINK32 ROM monitor.
16391 @kindex target ppcbug
16392 @item target ppcbug @var{dev}
16393 @kindex target ppcbug1
16394 @item target ppcbug1 @var{dev}
16395 PPCBUG ROM monitor for PowerPC.
16398 @item target sds @var{dev}
16399 SDS monitor, running on a PowerPC board (such as Motorola's ADS).
16402 @cindex SDS protocol
16403 The following commands specific to the SDS protocol are supported
16407 @item set sdstimeout @var{nsec}
16408 @kindex set sdstimeout
16409 Set the timeout for SDS protocol reads to be @var{nsec} seconds. The
16410 default is 2 seconds.
16412 @item show sdstimeout
16413 @kindex show sdstimeout
16414 Show the current value of the SDS timeout.
16416 @item sds @var{command}
16417 @kindex sds@r{, a command}
16418 Send the specified @var{command} string to the SDS monitor.
16423 @subsection HP PA Embedded
16427 @kindex target op50n
16428 @item target op50n @var{dev}
16429 OP50N monitor, running on an OKI HPPA board.
16431 @kindex target w89k
16432 @item target w89k @var{dev}
16433 W89K monitor, running on a Winbond HPPA board.
16438 @subsection Tsqware Sparclet
16442 @value{GDBN} enables developers to debug tasks running on
16443 Sparclet targets from a Unix host.
16444 @value{GDBN} uses code that runs on
16445 both the Unix host and on the Sparclet target. The program
16446 @code{@value{GDBP}} is installed and executed on the Unix host.
16449 @item remotetimeout @var{args}
16450 @kindex remotetimeout
16451 @value{GDBN} supports the option @code{remotetimeout}.
16452 This option is set by the user, and @var{args} represents the number of
16453 seconds @value{GDBN} waits for responses.
16456 @cindex compiling, on Sparclet
16457 When compiling for debugging, include the options @samp{-g} to get debug
16458 information and @samp{-Ttext} to relocate the program to where you wish to
16459 load it on the target. You may also want to add the options @samp{-n} or
16460 @samp{-N} in order to reduce the size of the sections. Example:
16463 sparclet-aout-gcc prog.c -Ttext 0x12010000 -g -o prog -N
16466 You can use @code{objdump} to verify that the addresses are what you intended:
16469 sparclet-aout-objdump --headers --syms prog
16472 @cindex running, on Sparclet
16474 your Unix execution search path to find @value{GDBN}, you are ready to
16475 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}}
16476 (or @code{sparclet-aout-gdb}, depending on your installation).
16478 @value{GDBN} comes up showing the prompt:
16485 * Sparclet File:: Setting the file to debug
16486 * Sparclet Connection:: Connecting to Sparclet
16487 * Sparclet Download:: Sparclet download
16488 * Sparclet Execution:: Running and debugging
16491 @node Sparclet File
16492 @subsubsection Setting File to Debug
16494 The @value{GDBN} command @code{file} lets you choose with program to debug.
16497 (gdbslet) file prog
16501 @value{GDBN} then attempts to read the symbol table of @file{prog}.
16502 @value{GDBN} locates
16503 the file by searching the directories listed in the command search
16505 If the file was compiled with debug information (option @samp{-g}), source
16506 files will be searched as well.
16507 @value{GDBN} locates
16508 the source files by searching the directories listed in the directory search
16509 path (@pxref{Environment, ,Your Program's Environment}).
16511 to find a file, it displays a message such as:
16514 prog: No such file or directory.
16517 When this happens, add the appropriate directories to the search paths with
16518 the @value{GDBN} commands @code{path} and @code{dir}, and execute the
16519 @code{target} command again.
16521 @node Sparclet Connection
16522 @subsubsection Connecting to Sparclet
16524 The @value{GDBN} command @code{target} lets you connect to a Sparclet target.
16525 To connect to a target on serial port ``@code{ttya}'', type:
16528 (gdbslet) target sparclet /dev/ttya
16529 Remote target sparclet connected to /dev/ttya
16530 main () at ../prog.c:3
16534 @value{GDBN} displays messages like these:
16540 @node Sparclet Download
16541 @subsubsection Sparclet Download
16543 @cindex download to Sparclet
16544 Once connected to the Sparclet target,
16545 you can use the @value{GDBN}
16546 @code{load} command to download the file from the host to the target.
16547 The file name and load offset should be given as arguments to the @code{load}
16549 Since the file format is aout, the program must be loaded to the starting
16550 address. You can use @code{objdump} to find out what this value is. The load
16551 offset is an offset which is added to the VMA (virtual memory address)
16552 of each of the file's sections.
16553 For instance, if the program
16554 @file{prog} was linked to text address 0x1201000, with data at 0x12010160
16555 and bss at 0x12010170, in @value{GDBN}, type:
16558 (gdbslet) load prog 0x12010000
16559 Loading section .text, size 0xdb0 vma 0x12010000
16562 If the code is loaded at a different address then what the program was linked
16563 to, you may need to use the @code{section} and @code{add-symbol-file} commands
16564 to tell @value{GDBN} where to map the symbol table.
16566 @node Sparclet Execution
16567 @subsubsection Running and Debugging
16569 @cindex running and debugging Sparclet programs
16570 You can now begin debugging the task using @value{GDBN}'s execution control
16571 commands, @code{b}, @code{step}, @code{run}, etc. See the @value{GDBN}
16572 manual for the list of commands.
16576 Breakpoint 1 at 0x12010000: file prog.c, line 3.
16578 Starting program: prog
16579 Breakpoint 1, main (argc=1, argv=0xeffff21c) at prog.c:3
16580 3 char *symarg = 0;
16582 4 char *execarg = "hello!";
16587 @subsection Fujitsu Sparclite
16591 @kindex target sparclite
16592 @item target sparclite @var{dev}
16593 Fujitsu sparclite boards, used only for the purpose of loading.
16594 You must use an additional command to debug the program.
16595 For example: target remote @var{dev} using @value{GDBN} standard
16601 @subsection Zilog Z8000
16604 @cindex simulator, Z8000
16605 @cindex Zilog Z8000 simulator
16607 When configured for debugging Zilog Z8000 targets, @value{GDBN} includes
16610 For the Z8000 family, @samp{target sim} simulates either the Z8002 (the
16611 unsegmented variant of the Z8000 architecture) or the Z8001 (the
16612 segmented variant). The simulator recognizes which architecture is
16613 appropriate by inspecting the object code.
16616 @item target sim @var{args}
16618 @kindex target sim@r{, with Z8000}
16619 Debug programs on a simulated CPU. If the simulator supports setup
16620 options, specify them via @var{args}.
16624 After specifying this target, you can debug programs for the simulated
16625 CPU in the same style as programs for your host computer; use the
16626 @code{file} command to load a new program image, the @code{run} command
16627 to run your program, and so on.
16629 As well as making available all the usual machine registers
16630 (@pxref{Registers, ,Registers}), the Z8000 simulator provides three
16631 additional items of information as specially named registers:
16636 Counts clock-ticks in the simulator.
16639 Counts instructions run in the simulator.
16642 Execution time in 60ths of a second.
16646 You can refer to these values in @value{GDBN} expressions with the usual
16647 conventions; for example, @w{@samp{b fputc if $cycles>5000}} sets a
16648 conditional breakpoint that suspends only after at least 5000
16649 simulated clock ticks.
16652 @subsection Atmel AVR
16655 When configured for debugging the Atmel AVR, @value{GDBN} supports the
16656 following AVR-specific commands:
16659 @item info io_registers
16660 @kindex info io_registers@r{, AVR}
16661 @cindex I/O registers (Atmel AVR)
16662 This command displays information about the AVR I/O registers. For
16663 each register, @value{GDBN} prints its number and value.
16670 When configured for debugging CRIS, @value{GDBN} provides the
16671 following CRIS-specific commands:
16674 @item set cris-version @var{ver}
16675 @cindex CRIS version
16676 Set the current CRIS version to @var{ver}, either @samp{10} or @samp{32}.
16677 The CRIS version affects register names and sizes. This command is useful in
16678 case autodetection of the CRIS version fails.
16680 @item show cris-version
16681 Show the current CRIS version.
16683 @item set cris-dwarf2-cfi
16684 @cindex DWARF-2 CFI and CRIS
16685 Set the usage of DWARF-2 CFI for CRIS debugging. The default is @samp{on}.
16686 Change to @samp{off} when using @code{gcc-cris} whose version is below
16689 @item show cris-dwarf2-cfi
16690 Show the current state of using DWARF-2 CFI.
16692 @item set cris-mode @var{mode}
16694 Set the current CRIS mode to @var{mode}. It should only be changed when
16695 debugging in guru mode, in which case it should be set to
16696 @samp{guru} (the default is @samp{normal}).
16698 @item show cris-mode
16699 Show the current CRIS mode.
16703 @subsection Renesas Super-H
16706 For the Renesas Super-H processor, @value{GDBN} provides these
16711 @kindex regs@r{, Super-H}
16712 Show the values of all Super-H registers.
16714 @item set sh calling-convention @var{convention}
16715 @kindex set sh calling-convention
16716 Set the calling-convention used when calling functions from @value{GDBN}.
16717 Allowed values are @samp{gcc}, which is the default setting, and @samp{renesas}.
16718 With the @samp{gcc} setting, functions are called using the @value{NGCC} calling
16719 convention. If the DWARF-2 information of the called function specifies
16720 that the function follows the Renesas calling convention, the function
16721 is called using the Renesas calling convention. If the calling convention
16722 is set to @samp{renesas}, the Renesas calling convention is always used,
16723 regardless of the DWARF-2 information. This can be used to override the
16724 default of @samp{gcc} if debug information is missing, or the compiler
16725 does not emit the DWARF-2 calling convention entry for a function.
16727 @item show sh calling-convention
16728 @kindex show sh calling-convention
16729 Show the current calling convention setting.
16734 @node Architectures
16735 @section Architectures
16737 This section describes characteristics of architectures that affect
16738 all uses of @value{GDBN} with the architecture, both native and cross.
16745 * HPPA:: HP PA architecture
16746 * SPU:: Cell Broadband Engine SPU architecture
16751 @subsection x86 Architecture-specific Issues
16754 @item set struct-convention @var{mode}
16755 @kindex set struct-convention
16756 @cindex struct return convention
16757 @cindex struct/union returned in registers
16758 Set the convention used by the inferior to return @code{struct}s and
16759 @code{union}s from functions to @var{mode}. Possible values of
16760 @var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the
16761 default). @code{"default"} or @code{"pcc"} means that @code{struct}s
16762 are returned on the stack, while @code{"reg"} means that a
16763 @code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will
16764 be returned in a register.
16766 @item show struct-convention
16767 @kindex show struct-convention
16768 Show the current setting of the convention to return @code{struct}s
16777 @kindex set rstack_high_address
16778 @cindex AMD 29K register stack
16779 @cindex register stack, AMD29K
16780 @item set rstack_high_address @var{address}
16781 On AMD 29000 family processors, registers are saved in a separate
16782 @dfn{register stack}. There is no way for @value{GDBN} to determine the
16783 extent of this stack. Normally, @value{GDBN} just assumes that the
16784 stack is ``large enough''. This may result in @value{GDBN} referencing
16785 memory locations that do not exist. If necessary, you can get around
16786 this problem by specifying the ending address of the register stack with
16787 the @code{set rstack_high_address} command. The argument should be an
16788 address, which you probably want to precede with @samp{0x} to specify in
16791 @kindex show rstack_high_address
16792 @item show rstack_high_address
16793 Display the current limit of the register stack, on AMD 29000 family
16801 See the following section.
16806 @cindex stack on Alpha
16807 @cindex stack on MIPS
16808 @cindex Alpha stack
16810 Alpha- and MIPS-based computers use an unusual stack frame, which
16811 sometimes requires @value{GDBN} to search backward in the object code to
16812 find the beginning of a function.
16814 @cindex response time, MIPS debugging
16815 To improve response time (especially for embedded applications, where
16816 @value{GDBN} may be restricted to a slow serial line for this search)
16817 you may want to limit the size of this search, using one of these
16821 @cindex @code{heuristic-fence-post} (Alpha, MIPS)
16822 @item set heuristic-fence-post @var{limit}
16823 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
16824 search for the beginning of a function. A value of @var{0} (the
16825 default) means there is no limit. However, except for @var{0}, the
16826 larger the limit the more bytes @code{heuristic-fence-post} must search
16827 and therefore the longer it takes to run. You should only need to use
16828 this command when debugging a stripped executable.
16830 @item show heuristic-fence-post
16831 Display the current limit.
16835 These commands are available @emph{only} when @value{GDBN} is configured
16836 for debugging programs on Alpha or MIPS processors.
16838 Several MIPS-specific commands are available when debugging MIPS
16842 @item set mips abi @var{arg}
16843 @kindex set mips abi
16844 @cindex set ABI for MIPS
16845 Tell @value{GDBN} which MIPS ABI is used by the inferior. Possible
16846 values of @var{arg} are:
16850 The default ABI associated with the current binary (this is the
16861 @item show mips abi
16862 @kindex show mips abi
16863 Show the MIPS ABI used by @value{GDBN} to debug the inferior.
16866 @itemx show mipsfpu
16867 @xref{MIPS Embedded, set mipsfpu}.
16869 @item set mips mask-address @var{arg}
16870 @kindex set mips mask-address
16871 @cindex MIPS addresses, masking
16872 This command determines whether the most-significant 32 bits of 64-bit
16873 MIPS addresses are masked off. The argument @var{arg} can be
16874 @samp{on}, @samp{off}, or @samp{auto}. The latter is the default
16875 setting, which lets @value{GDBN} determine the correct value.
16877 @item show mips mask-address
16878 @kindex show mips mask-address
16879 Show whether the upper 32 bits of MIPS addresses are masked off or
16882 @item set remote-mips64-transfers-32bit-regs
16883 @kindex set remote-mips64-transfers-32bit-regs
16884 This command controls compatibility with 64-bit MIPS targets that
16885 transfer data in 32-bit quantities. If you have an old MIPS 64 target
16886 that transfers 32 bits for some registers, like @sc{sr} and @sc{fsr},
16887 and 64 bits for other registers, set this option to @samp{on}.
16889 @item show remote-mips64-transfers-32bit-regs
16890 @kindex show remote-mips64-transfers-32bit-regs
16891 Show the current setting of compatibility with older MIPS 64 targets.
16893 @item set debug mips
16894 @kindex set debug mips
16895 This command turns on and off debugging messages for the MIPS-specific
16896 target code in @value{GDBN}.
16898 @item show debug mips
16899 @kindex show debug mips
16900 Show the current setting of MIPS debugging messages.
16906 @cindex HPPA support
16908 When @value{GDBN} is debugging the HP PA architecture, it provides the
16909 following special commands:
16912 @item set debug hppa
16913 @kindex set debug hppa
16914 This command determines whether HPPA architecture-specific debugging
16915 messages are to be displayed.
16917 @item show debug hppa
16918 Show whether HPPA debugging messages are displayed.
16920 @item maint print unwind @var{address}
16921 @kindex maint print unwind@r{, HPPA}
16922 This command displays the contents of the unwind table entry at the
16923 given @var{address}.
16929 @subsection Cell Broadband Engine SPU architecture
16930 @cindex Cell Broadband Engine
16933 When @value{GDBN} is debugging the Cell Broadband Engine SPU architecture,
16934 it provides the following special commands:
16937 @item info spu event
16939 Display SPU event facility status. Shows current event mask
16940 and pending event status.
16942 @item info spu signal
16943 Display SPU signal notification facility status. Shows pending
16944 signal-control word and signal notification mode of both signal
16945 notification channels.
16947 @item info spu mailbox
16948 Display SPU mailbox facility status. Shows all pending entries,
16949 in order of processing, in each of the SPU Write Outbound,
16950 SPU Write Outbound Interrupt, and SPU Read Inbound mailboxes.
16953 Display MFC DMA status. Shows all pending commands in the MFC
16954 DMA queue. For each entry, opcode, tag, class IDs, effective
16955 and local store addresses and transfer size are shown.
16957 @item info spu proxydma
16958 Display MFC Proxy-DMA status. Shows all pending commands in the MFC
16959 Proxy-DMA queue. For each entry, opcode, tag, class IDs, effective
16960 and local store addresses and transfer size are shown.
16965 @subsection PowerPC
16966 @cindex PowerPC architecture
16968 When @value{GDBN} is debugging the PowerPC architecture, it provides a set of
16969 pseudo-registers to enable inspection of 128-bit wide Decimal Floating Point
16970 numbers stored in the floating point registers. These values must be stored
16971 in two consecutive registers, always starting at an even register like
16972 @code{f0} or @code{f2}.
16974 The pseudo-registers go from @code{$dl0} through @code{$dl15}, and are formed
16975 by joining the even/odd register pairs @code{f0} and @code{f1} for @code{$dl0},
16976 @code{f2} and @code{f3} for @code{$dl1} and so on.
16978 For POWER7 processors, @value{GDBN} provides a set of pseudo-registers, the 64-bit
16979 wide Extended Floating Point Registers (@samp{f32} through @samp{f63}).
16982 @node Controlling GDB
16983 @chapter Controlling @value{GDBN}
16985 You can alter the way @value{GDBN} interacts with you by using the
16986 @code{set} command. For commands controlling how @value{GDBN} displays
16987 data, see @ref{Print Settings, ,Print Settings}. Other settings are
16992 * Editing:: Command editing
16993 * Command History:: Command history
16994 * Screen Size:: Screen size
16995 * Numbers:: Numbers
16996 * ABI:: Configuring the current ABI
16997 * Messages/Warnings:: Optional warnings and messages
16998 * Debugging Output:: Optional messages about internal happenings
17006 @value{GDBN} indicates its readiness to read a command by printing a string
17007 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
17008 can change the prompt string with the @code{set prompt} command. For
17009 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
17010 the prompt in one of the @value{GDBN} sessions so that you can always tell
17011 which one you are talking to.
17013 @emph{Note:} @code{set prompt} does not add a space for you after the
17014 prompt you set. This allows you to set a prompt which ends in a space
17015 or a prompt that does not.
17019 @item set prompt @var{newprompt}
17020 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
17022 @kindex show prompt
17024 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
17028 @section Command Editing
17030 @cindex command line editing
17032 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
17033 @sc{gnu} library provides consistent behavior for programs which provide a
17034 command line interface to the user. Advantages are @sc{gnu} Emacs-style
17035 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
17036 substitution, and a storage and recall of command history across
17037 debugging sessions.
17039 You may control the behavior of command line editing in @value{GDBN} with the
17040 command @code{set}.
17043 @kindex set editing
17046 @itemx set editing on
17047 Enable command line editing (enabled by default).
17049 @item set editing off
17050 Disable command line editing.
17052 @kindex show editing
17054 Show whether command line editing is enabled.
17057 @xref{Command Line Editing}, for more details about the Readline
17058 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
17059 encouraged to read that chapter.
17061 @node Command History
17062 @section Command History
17063 @cindex command history
17065 @value{GDBN} can keep track of the commands you type during your
17066 debugging sessions, so that you can be certain of precisely what
17067 happened. Use these commands to manage the @value{GDBN} command
17070 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
17071 package, to provide the history facility. @xref{Using History
17072 Interactively}, for the detailed description of the History library.
17074 To issue a command to @value{GDBN} without affecting certain aspects of
17075 the state which is seen by users, prefix it with @samp{server }
17076 (@pxref{Server Prefix}). This
17077 means that this command will not affect the command history, nor will it
17078 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
17079 pressed on a line by itself.
17081 @cindex @code{server}, command prefix
17082 The server prefix does not affect the recording of values into the value
17083 history; to print a value without recording it into the value history,
17084 use the @code{output} command instead of the @code{print} command.
17086 Here is the description of @value{GDBN} commands related to command
17090 @cindex history substitution
17091 @cindex history file
17092 @kindex set history filename
17093 @cindex @env{GDBHISTFILE}, environment variable
17094 @item set history filename @var{fname}
17095 Set the name of the @value{GDBN} command history file to @var{fname}.
17096 This is the file where @value{GDBN} reads an initial command history
17097 list, and where it writes the command history from this session when it
17098 exits. You can access this list through history expansion or through
17099 the history command editing characters listed below. This file defaults
17100 to the value of the environment variable @code{GDBHISTFILE}, or to
17101 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
17104 @cindex save command history
17105 @kindex set history save
17106 @item set history save
17107 @itemx set history save on
17108 Record command history in a file, whose name may be specified with the
17109 @code{set history filename} command. By default, this option is disabled.
17111 @item set history save off
17112 Stop recording command history in a file.
17114 @cindex history size
17115 @kindex set history size
17116 @cindex @env{HISTSIZE}, environment variable
17117 @item set history size @var{size}
17118 Set the number of commands which @value{GDBN} keeps in its history list.
17119 This defaults to the value of the environment variable
17120 @code{HISTSIZE}, or to 256 if this variable is not set.
17123 History expansion assigns special meaning to the character @kbd{!}.
17124 @xref{Event Designators}, for more details.
17126 @cindex history expansion, turn on/off
17127 Since @kbd{!} is also the logical not operator in C, history expansion
17128 is off by default. If you decide to enable history expansion with the
17129 @code{set history expansion on} command, you may sometimes need to
17130 follow @kbd{!} (when it is used as logical not, in an expression) with
17131 a space or a tab to prevent it from being expanded. The readline
17132 history facilities do not attempt substitution on the strings
17133 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
17135 The commands to control history expansion are:
17138 @item set history expansion on
17139 @itemx set history expansion
17140 @kindex set history expansion
17141 Enable history expansion. History expansion is off by default.
17143 @item set history expansion off
17144 Disable history expansion.
17147 @kindex show history
17149 @itemx show history filename
17150 @itemx show history save
17151 @itemx show history size
17152 @itemx show history expansion
17153 These commands display the state of the @value{GDBN} history parameters.
17154 @code{show history} by itself displays all four states.
17159 @kindex show commands
17160 @cindex show last commands
17161 @cindex display command history
17162 @item show commands
17163 Display the last ten commands in the command history.
17165 @item show commands @var{n}
17166 Print ten commands centered on command number @var{n}.
17168 @item show commands +
17169 Print ten commands just after the commands last printed.
17173 @section Screen Size
17174 @cindex size of screen
17175 @cindex pauses in output
17177 Certain commands to @value{GDBN} may produce large amounts of
17178 information output to the screen. To help you read all of it,
17179 @value{GDBN} pauses and asks you for input at the end of each page of
17180 output. Type @key{RET} when you want to continue the output, or @kbd{q}
17181 to discard the remaining output. Also, the screen width setting
17182 determines when to wrap lines of output. Depending on what is being
17183 printed, @value{GDBN} tries to break the line at a readable place,
17184 rather than simply letting it overflow onto the following line.
17186 Normally @value{GDBN} knows the size of the screen from the terminal
17187 driver software. For example, on Unix @value{GDBN} uses the termcap data base
17188 together with the value of the @code{TERM} environment variable and the
17189 @code{stty rows} and @code{stty cols} settings. If this is not correct,
17190 you can override it with the @code{set height} and @code{set
17197 @kindex show height
17198 @item set height @var{lpp}
17200 @itemx set width @var{cpl}
17202 These @code{set} commands specify a screen height of @var{lpp} lines and
17203 a screen width of @var{cpl} characters. The associated @code{show}
17204 commands display the current settings.
17206 If you specify a height of zero lines, @value{GDBN} does not pause during
17207 output no matter how long the output is. This is useful if output is to a
17208 file or to an editor buffer.
17210 Likewise, you can specify @samp{set width 0} to prevent @value{GDBN}
17211 from wrapping its output.
17213 @item set pagination on
17214 @itemx set pagination off
17215 @kindex set pagination
17216 Turn the output pagination on or off; the default is on. Turning
17217 pagination off is the alternative to @code{set height 0}.
17219 @item show pagination
17220 @kindex show pagination
17221 Show the current pagination mode.
17226 @cindex number representation
17227 @cindex entering numbers
17229 You can always enter numbers in octal, decimal, or hexadecimal in
17230 @value{GDBN} by the usual conventions: octal numbers begin with
17231 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
17232 begin with @samp{0x}. Numbers that neither begin with @samp{0} or
17233 @samp{0x}, nor end with a @samp{.} are, by default, entered in base
17234 10; likewise, the default display for numbers---when no particular
17235 format is specified---is base 10. You can change the default base for
17236 both input and output with the commands described below.
17239 @kindex set input-radix
17240 @item set input-radix @var{base}
17241 Set the default base for numeric input. Supported choices
17242 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
17243 specified either unambiguously or using the current input radix; for
17247 set input-radix 012
17248 set input-radix 10.
17249 set input-radix 0xa
17253 sets the input base to decimal. On the other hand, @samp{set input-radix 10}
17254 leaves the input radix unchanged, no matter what it was, since
17255 @samp{10}, being without any leading or trailing signs of its base, is
17256 interpreted in the current radix. Thus, if the current radix is 16,
17257 @samp{10} is interpreted in hex, i.e.@: as 16 decimal, which doesn't
17260 @kindex set output-radix
17261 @item set output-radix @var{base}
17262 Set the default base for numeric display. Supported choices
17263 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
17264 specified either unambiguously or using the current input radix.
17266 @kindex show input-radix
17267 @item show input-radix
17268 Display the current default base for numeric input.
17270 @kindex show output-radix
17271 @item show output-radix
17272 Display the current default base for numeric display.
17274 @item set radix @r{[}@var{base}@r{]}
17278 These commands set and show the default base for both input and output
17279 of numbers. @code{set radix} sets the radix of input and output to
17280 the same base; without an argument, it resets the radix back to its
17281 default value of 10.
17286 @section Configuring the Current ABI
17288 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
17289 application automatically. However, sometimes you need to override its
17290 conclusions. Use these commands to manage @value{GDBN}'s view of the
17297 One @value{GDBN} configuration can debug binaries for multiple operating
17298 system targets, either via remote debugging or native emulation.
17299 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
17300 but you can override its conclusion using the @code{set osabi} command.
17301 One example where this is useful is in debugging of binaries which use
17302 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
17303 not have the same identifying marks that the standard C library for your
17308 Show the OS ABI currently in use.
17311 With no argument, show the list of registered available OS ABI's.
17313 @item set osabi @var{abi}
17314 Set the current OS ABI to @var{abi}.
17317 @cindex float promotion
17319 Generally, the way that an argument of type @code{float} is passed to a
17320 function depends on whether the function is prototyped. For a prototyped
17321 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
17322 according to the architecture's convention for @code{float}. For unprototyped
17323 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
17324 @code{double} and then passed.
17326 Unfortunately, some forms of debug information do not reliably indicate whether
17327 a function is prototyped. If @value{GDBN} calls a function that is not marked
17328 as prototyped, it consults @kbd{set coerce-float-to-double}.
17331 @kindex set coerce-float-to-double
17332 @item set coerce-float-to-double
17333 @itemx set coerce-float-to-double on
17334 Arguments of type @code{float} will be promoted to @code{double} when passed
17335 to an unprototyped function. This is the default setting.
17337 @item set coerce-float-to-double off
17338 Arguments of type @code{float} will be passed directly to unprototyped
17341 @kindex show coerce-float-to-double
17342 @item show coerce-float-to-double
17343 Show the current setting of promoting @code{float} to @code{double}.
17347 @kindex show cp-abi
17348 @value{GDBN} needs to know the ABI used for your program's C@t{++}
17349 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
17350 used to build your application. @value{GDBN} only fully supports
17351 programs with a single C@t{++} ABI; if your program contains code using
17352 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
17353 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
17354 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
17355 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
17356 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
17357 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
17362 Show the C@t{++} ABI currently in use.
17365 With no argument, show the list of supported C@t{++} ABI's.
17367 @item set cp-abi @var{abi}
17368 @itemx set cp-abi auto
17369 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
17372 @node Messages/Warnings
17373 @section Optional Warnings and Messages
17375 @cindex verbose operation
17376 @cindex optional warnings
17377 By default, @value{GDBN} is silent about its inner workings. If you are
17378 running on a slow machine, you may want to use the @code{set verbose}
17379 command. This makes @value{GDBN} tell you when it does a lengthy
17380 internal operation, so you will not think it has crashed.
17382 Currently, the messages controlled by @code{set verbose} are those
17383 which announce that the symbol table for a source file is being read;
17384 see @code{symbol-file} in @ref{Files, ,Commands to Specify Files}.
17387 @kindex set verbose
17388 @item set verbose on
17389 Enables @value{GDBN} output of certain informational messages.
17391 @item set verbose off
17392 Disables @value{GDBN} output of certain informational messages.
17394 @kindex show verbose
17396 Displays whether @code{set verbose} is on or off.
17399 By default, if @value{GDBN} encounters bugs in the symbol table of an
17400 object file, it is silent; but if you are debugging a compiler, you may
17401 find this information useful (@pxref{Symbol Errors, ,Errors Reading
17406 @kindex set complaints
17407 @item set complaints @var{limit}
17408 Permits @value{GDBN} to output @var{limit} complaints about each type of
17409 unusual symbols before becoming silent about the problem. Set
17410 @var{limit} to zero to suppress all complaints; set it to a large number
17411 to prevent complaints from being suppressed.
17413 @kindex show complaints
17414 @item show complaints
17415 Displays how many symbol complaints @value{GDBN} is permitted to produce.
17419 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
17420 lot of stupid questions to confirm certain commands. For example, if
17421 you try to run a program which is already running:
17425 The program being debugged has been started already.
17426 Start it from the beginning? (y or n)
17429 If you are willing to unflinchingly face the consequences of your own
17430 commands, you can disable this ``feature'':
17434 @kindex set confirm
17436 @cindex confirmation
17437 @cindex stupid questions
17438 @item set confirm off
17439 Disables confirmation requests.
17441 @item set confirm on
17442 Enables confirmation requests (the default).
17444 @kindex show confirm
17446 Displays state of confirmation requests.
17450 @cindex command tracing
17451 If you need to debug user-defined commands or sourced files you may find it
17452 useful to enable @dfn{command tracing}. In this mode each command will be
17453 printed as it is executed, prefixed with one or more @samp{+} symbols, the
17454 quantity denoting the call depth of each command.
17457 @kindex set trace-commands
17458 @cindex command scripts, debugging
17459 @item set trace-commands on
17460 Enable command tracing.
17461 @item set trace-commands off
17462 Disable command tracing.
17463 @item show trace-commands
17464 Display the current state of command tracing.
17467 @node Debugging Output
17468 @section Optional Messages about Internal Happenings
17469 @cindex optional debugging messages
17471 @value{GDBN} has commands that enable optional debugging messages from
17472 various @value{GDBN} subsystems; normally these commands are of
17473 interest to @value{GDBN} maintainers, or when reporting a bug. This
17474 section documents those commands.
17477 @kindex set exec-done-display
17478 @item set exec-done-display
17479 Turns on or off the notification of asynchronous commands'
17480 completion. When on, @value{GDBN} will print a message when an
17481 asynchronous command finishes its execution. The default is off.
17482 @kindex show exec-done-display
17483 @item show exec-done-display
17484 Displays the current setting of asynchronous command completion
17487 @cindex gdbarch debugging info
17488 @cindex architecture debugging info
17489 @item set debug arch
17490 Turns on or off display of gdbarch debugging info. The default is off
17492 @item show debug arch
17493 Displays the current state of displaying gdbarch debugging info.
17494 @item set debug aix-thread
17495 @cindex AIX threads
17496 Display debugging messages about inner workings of the AIX thread
17498 @item show debug aix-thread
17499 Show the current state of AIX thread debugging info display.
17500 @item set debug dwarf2-die
17501 @cindex DWARF2 DIEs
17502 Dump DWARF2 DIEs after they are read in.
17503 The value is the number of nesting levels to print.
17504 A value of zero turns off the display.
17505 @item show debug dwarf2-die
17506 Show the current state of DWARF2 DIE debugging.
17507 @item set debug displaced
17508 @cindex displaced stepping debugging info
17509 Turns on or off display of @value{GDBN} debugging info for the
17510 displaced stepping support. The default is off.
17511 @item show debug displaced
17512 Displays the current state of displaying @value{GDBN} debugging info
17513 related to displaced stepping.
17514 @item set debug event
17515 @cindex event debugging info
17516 Turns on or off display of @value{GDBN} event debugging info. The
17518 @item show debug event
17519 Displays the current state of displaying @value{GDBN} event debugging
17521 @item set debug expression
17522 @cindex expression debugging info
17523 Turns on or off display of debugging info about @value{GDBN}
17524 expression parsing. The default is off.
17525 @item show debug expression
17526 Displays the current state of displaying debugging info about
17527 @value{GDBN} expression parsing.
17528 @item set debug frame
17529 @cindex frame debugging info
17530 Turns on or off display of @value{GDBN} frame debugging info. The
17532 @item show debug frame
17533 Displays the current state of displaying @value{GDBN} frame debugging
17535 @item set debug infrun
17536 @cindex inferior debugging info
17537 Turns on or off display of @value{GDBN} debugging info for running the inferior.
17538 The default is off. @file{infrun.c} contains GDB's runtime state machine used
17539 for implementing operations such as single-stepping the inferior.
17540 @item show debug infrun
17541 Displays the current state of @value{GDBN} inferior debugging.
17542 @item set debug lin-lwp
17543 @cindex @sc{gnu}/Linux LWP debug messages
17544 @cindex Linux lightweight processes
17545 Turns on or off debugging messages from the Linux LWP debug support.
17546 @item show debug lin-lwp
17547 Show the current state of Linux LWP debugging messages.
17548 @item set debug lin-lwp-async
17549 @cindex @sc{gnu}/Linux LWP async debug messages
17550 @cindex Linux lightweight processes
17551 Turns on or off debugging messages from the Linux LWP async debug support.
17552 @item show debug lin-lwp-async
17553 Show the current state of Linux LWP async debugging messages.
17554 @item set debug observer
17555 @cindex observer debugging info
17556 Turns on or off display of @value{GDBN} observer debugging. This
17557 includes info such as the notification of observable events.
17558 @item show debug observer
17559 Displays the current state of observer debugging.
17560 @item set debug overload
17561 @cindex C@t{++} overload debugging info
17562 Turns on or off display of @value{GDBN} C@t{++} overload debugging
17563 info. This includes info such as ranking of functions, etc. The default
17565 @item show debug overload
17566 Displays the current state of displaying @value{GDBN} C@t{++} overload
17568 @cindex packets, reporting on stdout
17569 @cindex serial connections, debugging
17570 @cindex debug remote protocol
17571 @cindex remote protocol debugging
17572 @cindex display remote packets
17573 @item set debug remote
17574 Turns on or off display of reports on all packets sent back and forth across
17575 the serial line to the remote machine. The info is printed on the
17576 @value{GDBN} standard output stream. The default is off.
17577 @item show debug remote
17578 Displays the state of display of remote packets.
17579 @item set debug serial
17580 Turns on or off display of @value{GDBN} serial debugging info. The
17582 @item show debug serial
17583 Displays the current state of displaying @value{GDBN} serial debugging
17585 @item set debug solib-frv
17586 @cindex FR-V shared-library debugging
17587 Turns on or off debugging messages for FR-V shared-library code.
17588 @item show debug solib-frv
17589 Display the current state of FR-V shared-library code debugging
17591 @item set debug target
17592 @cindex target debugging info
17593 Turns on or off display of @value{GDBN} target debugging info. This info
17594 includes what is going on at the target level of GDB, as it happens. The
17595 default is 0. Set it to 1 to track events, and to 2 to also track the
17596 value of large memory transfers. Changes to this flag do not take effect
17597 until the next time you connect to a target or use the @code{run} command.
17598 @item show debug target
17599 Displays the current state of displaying @value{GDBN} target debugging
17601 @item set debug timestamp
17602 @cindex timestampping debugging info
17603 Turns on or off display of timestamps with @value{GDBN} debugging info.
17604 When enabled, seconds and microseconds are displayed before each debugging
17606 @item show debug timestamp
17607 Displays the current state of displaying timestamps with @value{GDBN}
17609 @item set debugvarobj
17610 @cindex variable object debugging info
17611 Turns on or off display of @value{GDBN} variable object debugging
17612 info. The default is off.
17613 @item show debugvarobj
17614 Displays the current state of displaying @value{GDBN} variable object
17616 @item set debug xml
17617 @cindex XML parser debugging
17618 Turns on or off debugging messages for built-in XML parsers.
17619 @item show debug xml
17620 Displays the current state of XML debugging messages.
17623 @node Extending GDB
17624 @chapter Extending @value{GDBN}
17625 @cindex extending GDB
17627 @value{GDBN} provides two mechanisms for extension. The first is based
17628 on composition of @value{GDBN} commands, and the second is based on the
17629 Python scripting language.
17632 * Sequences:: Canned Sequences of Commands
17633 * Python:: Scripting @value{GDBN} using Python
17637 @section Canned Sequences of Commands
17639 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
17640 Command Lists}), @value{GDBN} provides two ways to store sequences of
17641 commands for execution as a unit: user-defined commands and command
17645 * Define:: How to define your own commands
17646 * Hooks:: Hooks for user-defined commands
17647 * Command Files:: How to write scripts of commands to be stored in a file
17648 * Output:: Commands for controlled output
17652 @subsection User-defined Commands
17654 @cindex user-defined command
17655 @cindex arguments, to user-defined commands
17656 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
17657 which you assign a new name as a command. This is done with the
17658 @code{define} command. User commands may accept up to 10 arguments
17659 separated by whitespace. Arguments are accessed within the user command
17660 via @code{$arg0@dots{}$arg9}. A trivial example:
17664 print $arg0 + $arg1 + $arg2
17669 To execute the command use:
17676 This defines the command @code{adder}, which prints the sum of
17677 its three arguments. Note the arguments are text substitutions, so they may
17678 reference variables, use complex expressions, or even perform inferior
17681 @cindex argument count in user-defined commands
17682 @cindex how many arguments (user-defined commands)
17683 In addition, @code{$argc} may be used to find out how many arguments have
17684 been passed. This expands to a number in the range 0@dots{}10.
17689 print $arg0 + $arg1
17692 print $arg0 + $arg1 + $arg2
17700 @item define @var{commandname}
17701 Define a command named @var{commandname}. If there is already a command
17702 by that name, you are asked to confirm that you want to redefine it.
17703 @var{commandname} may be a bare command name consisting of letters,
17704 numbers, dashes, and underscores. It may also start with any predefined
17705 prefix command. For example, @samp{define target my-target} creates
17706 a user-defined @samp{target my-target} command.
17708 The definition of the command is made up of other @value{GDBN} command lines,
17709 which are given following the @code{define} command. The end of these
17710 commands is marked by a line containing @code{end}.
17713 @kindex end@r{ (user-defined commands)}
17714 @item document @var{commandname}
17715 Document the user-defined command @var{commandname}, so that it can be
17716 accessed by @code{help}. The command @var{commandname} must already be
17717 defined. This command reads lines of documentation just as @code{define}
17718 reads the lines of the command definition, ending with @code{end}.
17719 After the @code{document} command is finished, @code{help} on command
17720 @var{commandname} displays the documentation you have written.
17722 You may use the @code{document} command again to change the
17723 documentation of a command. Redefining the command with @code{define}
17724 does not change the documentation.
17726 @kindex dont-repeat
17727 @cindex don't repeat command
17729 Used inside a user-defined command, this tells @value{GDBN} that this
17730 command should not be repeated when the user hits @key{RET}
17731 (@pxref{Command Syntax, repeat last command}).
17733 @kindex help user-defined
17734 @item help user-defined
17735 List all user-defined commands, with the first line of the documentation
17740 @itemx show user @var{commandname}
17741 Display the @value{GDBN} commands used to define @var{commandname} (but
17742 not its documentation). If no @var{commandname} is given, display the
17743 definitions for all user-defined commands.
17745 @cindex infinite recursion in user-defined commands
17746 @kindex show max-user-call-depth
17747 @kindex set max-user-call-depth
17748 @item show max-user-call-depth
17749 @itemx set max-user-call-depth
17750 The value of @code{max-user-call-depth} controls how many recursion
17751 levels are allowed in user-defined commands before @value{GDBN} suspects an
17752 infinite recursion and aborts the command.
17755 In addition to the above commands, user-defined commands frequently
17756 use control flow commands, described in @ref{Command Files}.
17758 When user-defined commands are executed, the
17759 commands of the definition are not printed. An error in any command
17760 stops execution of the user-defined command.
17762 If used interactively, commands that would ask for confirmation proceed
17763 without asking when used inside a user-defined command. Many @value{GDBN}
17764 commands that normally print messages to say what they are doing omit the
17765 messages when used in a user-defined command.
17768 @subsection User-defined Command Hooks
17769 @cindex command hooks
17770 @cindex hooks, for commands
17771 @cindex hooks, pre-command
17774 You may define @dfn{hooks}, which are a special kind of user-defined
17775 command. Whenever you run the command @samp{foo}, if the user-defined
17776 command @samp{hook-foo} exists, it is executed (with no arguments)
17777 before that command.
17779 @cindex hooks, post-command
17781 A hook may also be defined which is run after the command you executed.
17782 Whenever you run the command @samp{foo}, if the user-defined command
17783 @samp{hookpost-foo} exists, it is executed (with no arguments) after
17784 that command. Post-execution hooks may exist simultaneously with
17785 pre-execution hooks, for the same command.
17787 It is valid for a hook to call the command which it hooks. If this
17788 occurs, the hook is not re-executed, thereby avoiding infinite recursion.
17790 @c It would be nice if hookpost could be passed a parameter indicating
17791 @c if the command it hooks executed properly or not. FIXME!
17793 @kindex stop@r{, a pseudo-command}
17794 In addition, a pseudo-command, @samp{stop} exists. Defining
17795 (@samp{hook-stop}) makes the associated commands execute every time
17796 execution stops in your program: before breakpoint commands are run,
17797 displays are printed, or the stack frame is printed.
17799 For example, to ignore @code{SIGALRM} signals while
17800 single-stepping, but treat them normally during normal execution,
17805 handle SIGALRM nopass
17809 handle SIGALRM pass
17812 define hook-continue
17813 handle SIGALRM pass
17817 As a further example, to hook at the beginning and end of the @code{echo}
17818 command, and to add extra text to the beginning and end of the message,
17826 define hookpost-echo
17830 (@value{GDBP}) echo Hello World
17831 <<<---Hello World--->>>
17836 You can define a hook for any single-word command in @value{GDBN}, but
17837 not for command aliases; you should define a hook for the basic command
17838 name, e.g.@: @code{backtrace} rather than @code{bt}.
17839 @c FIXME! So how does Joe User discover whether a command is an alias
17841 You can hook a multi-word command by adding @code{hook-} or
17842 @code{hookpost-} to the last word of the command, e.g.@:
17843 @samp{define target hook-remote} to add a hook to @samp{target remote}.
17845 If an error occurs during the execution of your hook, execution of
17846 @value{GDBN} commands stops and @value{GDBN} issues a prompt
17847 (before the command that you actually typed had a chance to run).
17849 If you try to define a hook which does not match any known command, you
17850 get a warning from the @code{define} command.
17852 @node Command Files
17853 @subsection Command Files
17855 @cindex command files
17856 @cindex scripting commands
17857 A command file for @value{GDBN} is a text file made of lines that are
17858 @value{GDBN} commands. Comments (lines starting with @kbd{#}) may
17859 also be included. An empty line in a command file does nothing; it
17860 does not mean to repeat the last command, as it would from the
17863 You can request the execution of a command file with the @code{source}
17868 @cindex execute commands from a file
17869 @item source [@code{-v}] @var{filename}
17870 Execute the command file @var{filename}.
17873 The lines in a command file are generally executed sequentially,
17874 unless the order of execution is changed by one of the
17875 @emph{flow-control commands} described below. The commands are not
17876 printed as they are executed. An error in any command terminates
17877 execution of the command file and control is returned to the console.
17879 @value{GDBN} searches for @var{filename} in the current directory and then
17880 on the search path (specified with the @samp{directory} command).
17882 If @code{-v}, for verbose mode, is given then @value{GDBN} displays
17883 each command as it is executed. The option must be given before
17884 @var{filename}, and is interpreted as part of the filename anywhere else.
17886 Commands that would ask for confirmation if used interactively proceed
17887 without asking when used in a command file. Many @value{GDBN} commands that
17888 normally print messages to say what they are doing omit the messages
17889 when called from command files.
17891 @value{GDBN} also accepts command input from standard input. In this
17892 mode, normal output goes to standard output and error output goes to
17893 standard error. Errors in a command file supplied on standard input do
17894 not terminate execution of the command file---execution continues with
17898 gdb < cmds > log 2>&1
17901 (The syntax above will vary depending on the shell used.) This example
17902 will execute commands from the file @file{cmds}. All output and errors
17903 would be directed to @file{log}.
17905 Since commands stored on command files tend to be more general than
17906 commands typed interactively, they frequently need to deal with
17907 complicated situations, such as different or unexpected values of
17908 variables and symbols, changes in how the program being debugged is
17909 built, etc. @value{GDBN} provides a set of flow-control commands to
17910 deal with these complexities. Using these commands, you can write
17911 complex scripts that loop over data structures, execute commands
17912 conditionally, etc.
17919 This command allows to include in your script conditionally executed
17920 commands. The @code{if} command takes a single argument, which is an
17921 expression to evaluate. It is followed by a series of commands that
17922 are executed only if the expression is true (its value is nonzero).
17923 There can then optionally be an @code{else} line, followed by a series
17924 of commands that are only executed if the expression was false. The
17925 end of the list is marked by a line containing @code{end}.
17929 This command allows to write loops. Its syntax is similar to
17930 @code{if}: the command takes a single argument, which is an expression
17931 to evaluate, and must be followed by the commands to execute, one per
17932 line, terminated by an @code{end}. These commands are called the
17933 @dfn{body} of the loop. The commands in the body of @code{while} are
17934 executed repeatedly as long as the expression evaluates to true.
17938 This command exits the @code{while} loop in whose body it is included.
17939 Execution of the script continues after that @code{while}s @code{end}
17942 @kindex loop_continue
17943 @item loop_continue
17944 This command skips the execution of the rest of the body of commands
17945 in the @code{while} loop in whose body it is included. Execution
17946 branches to the beginning of the @code{while} loop, where it evaluates
17947 the controlling expression.
17949 @kindex end@r{ (if/else/while commands)}
17951 Terminate the block of commands that are the body of @code{if},
17952 @code{else}, or @code{while} flow-control commands.
17957 @subsection Commands for Controlled Output
17959 During the execution of a command file or a user-defined command, normal
17960 @value{GDBN} output is suppressed; the only output that appears is what is
17961 explicitly printed by the commands in the definition. This section
17962 describes three commands useful for generating exactly the output you
17967 @item echo @var{text}
17968 @c I do not consider backslash-space a standard C escape sequence
17969 @c because it is not in ANSI.
17970 Print @var{text}. Nonprinting characters can be included in
17971 @var{text} using C escape sequences, such as @samp{\n} to print a
17972 newline. @strong{No newline is printed unless you specify one.}
17973 In addition to the standard C escape sequences, a backslash followed
17974 by a space stands for a space. This is useful for displaying a
17975 string with spaces at the beginning or the end, since leading and
17976 trailing spaces are otherwise trimmed from all arguments.
17977 To print @samp{@w{ }and foo =@w{ }}, use the command
17978 @samp{echo \@w{ }and foo = \@w{ }}.
17980 A backslash at the end of @var{text} can be used, as in C, to continue
17981 the command onto subsequent lines. For example,
17984 echo This is some text\n\
17985 which is continued\n\
17986 onto several lines.\n
17989 produces the same output as
17992 echo This is some text\n
17993 echo which is continued\n
17994 echo onto several lines.\n
17998 @item output @var{expression}
17999 Print the value of @var{expression} and nothing but that value: no
18000 newlines, no @samp{$@var{nn} = }. The value is not entered in the
18001 value history either. @xref{Expressions, ,Expressions}, for more information
18004 @item output/@var{fmt} @var{expression}
18005 Print the value of @var{expression} in format @var{fmt}. You can use
18006 the same formats as for @code{print}. @xref{Output Formats,,Output
18007 Formats}, for more information.
18010 @item printf @var{template}, @var{expressions}@dots{}
18011 Print the values of one or more @var{expressions} under the control of
18012 the string @var{template}. To print several values, make
18013 @var{expressions} be a comma-separated list of individual expressions,
18014 which may be either numbers or pointers. Their values are printed as
18015 specified by @var{template}, exactly as a C program would do by
18016 executing the code below:
18019 printf (@var{template}, @var{expressions}@dots{});
18022 As in @code{C} @code{printf}, ordinary characters in @var{template}
18023 are printed verbatim, while @dfn{conversion specification} introduced
18024 by the @samp{%} character cause subsequent @var{expressions} to be
18025 evaluated, their values converted and formatted according to type and
18026 style information encoded in the conversion specifications, and then
18029 For example, you can print two values in hex like this:
18032 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
18035 @code{printf} supports all the standard @code{C} conversion
18036 specifications, including the flags and modifiers between the @samp{%}
18037 character and the conversion letter, with the following exceptions:
18041 The argument-ordering modifiers, such as @samp{2$}, are not supported.
18044 The modifier @samp{*} is not supported for specifying precision or
18048 The @samp{'} flag (for separation of digits into groups according to
18049 @code{LC_NUMERIC'}) is not supported.
18052 The type modifiers @samp{hh}, @samp{j}, @samp{t}, and @samp{z} are not
18056 The conversion letter @samp{n} (as in @samp{%n}) is not supported.
18059 The conversion letters @samp{a} and @samp{A} are not supported.
18063 Note that the @samp{ll} type modifier is supported only if the
18064 underlying @code{C} implementation used to build @value{GDBN} supports
18065 the @code{long long int} type, and the @samp{L} type modifier is
18066 supported only if @code{long double} type is available.
18068 As in @code{C}, @code{printf} supports simple backslash-escape
18069 sequences, such as @code{\n}, @samp{\t}, @samp{\\}, @samp{\"},
18070 @samp{\a}, and @samp{\f}, that consist of backslash followed by a
18071 single character. Octal and hexadecimal escape sequences are not
18074 Additionally, @code{printf} supports conversion specifications for DFP
18075 (@dfn{Decimal Floating Point}) types using the following length modifiers
18076 together with a floating point specifier.
18081 @samp{H} for printing @code{Decimal32} types.
18084 @samp{D} for printing @code{Decimal64} types.
18087 @samp{DD} for printing @code{Decimal128} types.
18090 If the underlying @code{C} implementation used to build @value{GDBN} has
18091 support for the three length modifiers for DFP types, other modifiers
18092 such as width and precision will also be available for @value{GDBN} to use.
18094 In case there is no such @code{C} support, no additional modifiers will be
18095 available and the value will be printed in the standard way.
18097 Here's an example of printing DFP types using the above conversion letters:
18099 printf "D32: %Hf - D64: %Df - D128: %DDf\n",1.2345df,1.2E10dd,1.2E1dl
18105 @section Scripting @value{GDBN} using Python
18106 @cindex python scripting
18107 @cindex scripting with python
18109 You can script @value{GDBN} using the @uref{http://www.python.org/,
18110 Python programming language}. This feature is available only if
18111 @value{GDBN} was configured using @option{--with-python}.
18114 * Python Commands:: Accessing Python from @value{GDBN}.
18115 * Python API:: Accessing @value{GDBN} from Python.
18118 @node Python Commands
18119 @subsection Python Commands
18120 @cindex python commands
18121 @cindex commands to access python
18123 @value{GDBN} provides one command for accessing the Python interpreter,
18124 and one related setting:
18128 @item python @r{[}@var{code}@r{]}
18129 The @code{python} command can be used to evaluate Python code.
18131 If given an argument, the @code{python} command will evaluate the
18132 argument as a Python command. For example:
18135 (@value{GDBP}) python print 23
18139 If you do not provide an argument to @code{python}, it will act as a
18140 multi-line command, like @code{define}. In this case, the Python
18141 script is made up of subsequent command lines, given after the
18142 @code{python} command. This command list is terminated using a line
18143 containing @code{end}. For example:
18146 (@value{GDBP}) python
18148 End with a line saying just "end".
18154 @kindex maint set python print-stack
18155 @item maint set python print-stack
18156 By default, @value{GDBN} will print a stack trace when an error occurs
18157 in a Python script. This can be controlled using @code{maint set
18158 python print-stack}: if @code{on}, the default, then Python stack
18159 printing is enabled; if @code{off}, then Python stack printing is
18164 @subsection Python API
18166 @cindex programming in python
18168 @cindex python stdout
18169 @cindex python pagination
18170 At startup, @value{GDBN} overrides Python's @code{sys.stdout} and
18171 @code{sys.stderr} to print using @value{GDBN}'s output-paging streams.
18172 A Python program which outputs to one of these streams may have its
18173 output interrupted by the user (@pxref{Screen Size}). In this
18174 situation, a Python @code{KeyboardInterrupt} exception is thrown.
18177 * Basic Python:: Basic Python Functions.
18178 * Exception Handling::
18179 * Values From Inferior::
18180 * Commands In Python:: Implementing new commands in Python.
18184 @subsubsection Basic Python
18186 @cindex python functions
18187 @cindex python module
18189 @value{GDBN} introduces a new Python module, named @code{gdb}. All
18190 methods and classes added by @value{GDBN} are placed in this module.
18191 @value{GDBN} automatically @code{import}s the @code{gdb} module for
18192 use in all scripts evaluated by the @code{python} command.
18194 @findex gdb.execute
18195 @defun execute command [from_tty]
18196 Evaluate @var{command}, a string, as a @value{GDBN} CLI command.
18197 If a GDB exception happens while @var{command} runs, it is
18198 translated as described in @ref{Exception Handling,,Exception Handling}.
18199 If no exceptions occur, this function returns @code{None}.
18201 @var{from_tty} specifies whether @value{GDBN} ought to consider this
18202 command as having originated from the user invoking it interactively.
18203 It must be a boolean value. If omitted, it defaults to @code{False}.
18206 @findex gdb.get_parameter
18207 @defun get_parameter parameter
18208 Return the value of a @value{GDBN} parameter. @var{parameter} is a
18209 string naming the parameter to look up; @var{parameter} may contain
18210 spaces if the parameter has a multi-part name. For example,
18211 @samp{print object} is a valid parameter name.
18213 If the named parameter does not exist, this function throws a
18214 @code{RuntimeError}. Otherwise, the parameter's value is converted to
18215 a Python value of the appropriate type, and returned.
18218 @findex gdb.history
18219 @defun history number
18220 Return a value from @value{GDBN}'s value history (@pxref{Value
18221 History}). @var{number} indicates which history element to return.
18222 If @var{number} is negative, then @value{GDBN} will take its absolute value
18223 and count backward from the last element (i.e., the most recent element) to
18224 find the value to return. If @var{number} is zero, then @value{GDBN} will
18225 return the most recent element. If the element specified by @var{number}
18226 doesn't exist in the value history, a @code{RuntimeError} exception will be
18229 If no exception is raised, the return value is always an instance of
18230 @code{gdb.Value} (@pxref{Values From Inferior}).
18234 @defun write string
18235 Print a string to @value{GDBN}'s paginated standard output stream.
18236 Writing to @code{sys.stdout} or @code{sys.stderr} will automatically
18237 call this function.
18242 Flush @value{GDBN}'s paginated standard output stream. Flushing
18243 @code{sys.stdout} or @code{sys.stderr} will automatically call this
18247 @node Exception Handling
18248 @subsubsection Exception Handling
18249 @cindex python exceptions
18250 @cindex exceptions, python
18252 When executing the @code{python} command, Python exceptions
18253 uncaught within the Python code are translated to calls to
18254 @value{GDBN} error-reporting mechanism. If the command that called
18255 @code{python} does not handle the error, @value{GDBN} will
18256 terminate it and print an error message containing the Python
18257 exception name, the associated value, and the Python call stack
18258 backtrace at the point where the exception was raised. Example:
18261 (@value{GDBP}) python print foo
18262 Traceback (most recent call last):
18263 File "<string>", line 1, in <module>
18264 NameError: name 'foo' is not defined
18267 @value{GDBN} errors that happen in @value{GDBN} commands invoked by Python
18268 code are converted to Python @code{RuntimeError} exceptions. User
18269 interrupt (via @kbd{C-c} or by typing @kbd{q} at a pagination
18270 prompt) is translated to a Python @code{KeyboardInterrupt}
18271 exception. If you catch these exceptions in your Python code, your
18272 exception handler will see @code{RuntimeError} or
18273 @code{KeyboardInterrupt} as the exception type, the @value{GDBN} error
18274 message as its value, and the Python call stack backtrace at the
18275 Python statement closest to where the @value{GDBN} error occured as the
18278 @node Values From Inferior
18279 @subsubsection Values From Inferior
18280 @cindex values from inferior, with Python
18281 @cindex python, working with values from inferior
18283 @cindex @code{gdb.Value}
18284 @value{GDBN} provides values it obtains from the inferior program in
18285 an object of type @code{gdb.Value}. @value{GDBN} uses this object
18286 for its internal bookkeeping of the inferior's values, and for
18287 fetching values when necessary.
18289 Inferior values that are simple scalars can be used directly in
18290 Python expressions that are valid for the value's data type. Here's
18291 an example for an integer or floating-point value @code{some_val}:
18298 As result of this, @code{bar} will also be a @code{gdb.Value} object
18299 whose values are of the same type as those of @code{some_val}.
18301 Inferior values that are structures or instances of some class can
18302 be accessed using the Python @dfn{dictionary syntax}. For example, if
18303 @code{some_val} is a @code{gdb.Value} instance holding a structure, you
18304 can access its @code{foo} element with:
18307 bar = some_val['foo']
18310 Again, @code{bar} will also be a @code{gdb.Value} object.
18312 For pointer data types, @code{gdb.Value} provides a method for
18313 dereferencing the pointer to obtain the object it points to.
18315 @defmethod Value dereference
18316 This method returns a new @code{gdb.Value} object whose contents is
18317 the object pointed to by the pointer. For example, if @code{foo} is
18318 a C pointer to an @code{int}, declared in your C program as
18325 then you can use the corresponding @code{gdb.Value} to access what
18326 @code{foo} points to like this:
18329 bar = foo.dereference ()
18332 The result @code{bar} will be a @code{gdb.Value} object holding the
18333 value pointed to by @code{foo}.
18336 @defmethod Value string @r{[}encoding @r{[}errors@r{]}@r{]}
18337 If this @code{gdb.Value} represents a string, then this method
18338 converts the contents to a Python string. Otherwise, this method will
18339 throw an exception.
18341 Strings are recognized in a language-specific way; whether a given
18342 @code{gdb.Value} represents a string is determined by the current
18345 For C-like languages, a value is a string if it is a pointer to or an
18346 array of characters or ints. The string is assumed to be terminated
18347 by a zero of the appropriate width.
18349 If the optional @var{encoding} argument is given, it must be a string
18350 naming the encoding of the string in the @code{gdb.Value}, such as
18351 @code{"ascii"}, @code{"iso-8859-6"} or @code{"utf-8"}. It accepts
18352 the same encodings as the corresponding argument to Python's
18353 @code{string.decode} method, and the Python codec machinery will be used
18354 to convert the string. If @var{encoding} is not given, or if
18355 @var{encoding} is the empty string, then either the @code{target-charset}
18356 (@pxref{Character Sets}) will be used, or a language-specific encoding
18357 will be used, if the current language is able to supply one.
18359 The optional @var{errors} argument is the same as the corresponding
18360 argument to Python's @code{string.decode} method.
18363 @node Commands In Python
18364 @subsubsection Commands In Python
18366 @cindex commands in python
18367 @cindex python commands
18368 You can implement new @value{GDBN} CLI commands in Python. A CLI
18369 command is implemented using an instance of the @code{gdb.Command}
18370 class, most commonly using a subclass.
18372 @defmethod Command __init__ name @var{command-class} @r{[}@var{completer-class} @var{prefix}@r{]}
18373 The object initializer for @code{Command} registers the new command
18374 with @value{GDBN}. This initializer is normally invoked from the
18375 subclass' own @code{__init__} method.
18377 @var{name} is the name of the command. If @var{name} consists of
18378 multiple words, then the initial words are looked for as prefix
18379 commands. In this case, if one of the prefix commands does not exist,
18380 an exception is raised.
18382 There is no support for multi-line commands.
18384 @var{command-class} should be one of the @samp{COMMAND_} constants
18385 defined below. This argument tells @value{GDBN} how to categorize the
18386 new command in the help system.
18388 @var{completer-class} is an optional argument. If given, it should be
18389 one of the @samp{COMPLETE_} constants defined below. This argument
18390 tells @value{GDBN} how to perform completion for this command. If not
18391 given, @value{GDBN} will attempt to complete using the object's
18392 @code{complete} method (see below); if no such method is found, an
18393 error will occur when completion is attempted.
18395 @var{prefix} is an optional argument. If @code{True}, then the new
18396 command is a prefix command; sub-commands of this command may be
18399 The help text for the new command is taken from the Python
18400 documentation string for the command's class, if there is one. If no
18401 documentation string is provided, the default value ``This command is
18402 not documented.'' is used.
18405 @cindex don't repeat Python command
18406 @defmethod Command dont_repeat
18407 By default, a @value{GDBN} command is repeated when the user enters a
18408 blank line at the command prompt. A command can suppress this
18409 behavior by invoking the @code{dont_repeat} method. This is similar
18410 to the user command @code{dont-repeat}, see @ref{Define, dont-repeat}.
18413 @defmethod Command invoke argument from_tty
18414 This method is called by @value{GDBN} when this command is invoked.
18416 @var{argument} is a string. It is the argument to the command, after
18417 leading and trailing whitespace has been stripped.
18419 @var{from_tty} is a boolean argument. When true, this means that the
18420 command was entered by the user at the terminal; when false it means
18421 that the command came from elsewhere.
18423 If this method throws an exception, it is turned into a @value{GDBN}
18424 @code{error} call. Otherwise, the return value is ignored.
18427 @cindex completion of Python commands
18428 @defmethod Command complete text word
18429 This method is called by @value{GDBN} when the user attempts
18430 completion on this command. All forms of completion are handled by
18431 this method, that is, the @key{TAB} and @key{M-?} key bindings
18432 (@pxref{Completion}), and the @code{complete} command (@pxref{Help,
18435 The arguments @var{text} and @var{word} are both strings. @var{text}
18436 holds the complete command line up to the cursor's location.
18437 @var{word} holds the last word of the command line; this is computed
18438 using a word-breaking heuristic.
18440 The @code{complete} method can return several values:
18443 If the return value is a sequence, the contents of the sequence are
18444 used as the completions. It is up to @code{complete} to ensure that the
18445 contents actually do complete the word. A zero-length sequence is
18446 allowed, it means that there were no completions available. Only
18447 string elements of the sequence are used; other elements in the
18448 sequence are ignored.
18451 If the return value is one of the @samp{COMPLETE_} constants defined
18452 below, then the corresponding @value{GDBN}-internal completion
18453 function is invoked, and its result is used.
18456 All other results are treated as though there were no available
18461 When a new command is registered, it must be declared as a member of
18462 some general class of commands. This is used to classify top-level
18463 commands in the on-line help system; note that prefix commands are not
18464 listed under their own category but rather that of their top-level
18465 command. The available classifications are represented by constants
18466 defined in the @code{gdb} module:
18469 @findex COMMAND_NONE
18470 @findex gdb.COMMAND_NONE
18472 The command does not belong to any particular class. A command in
18473 this category will not be displayed in any of the help categories.
18475 @findex COMMAND_RUNNING
18476 @findex gdb.COMMAND_RUNNING
18477 @item COMMAND_RUNNING
18478 The command is related to running the inferior. For example,
18479 @code{start}, @code{step}, and @code{continue} are in this category.
18480 Type @kbd{help running} at the @value{GDBN} prompt to see a list of
18481 commands in this category.
18483 @findex COMMAND_DATA
18484 @findex gdb.COMMAND_DATA
18486 The command is related to data or variables. For example,
18487 @code{call}, @code{find}, and @code{print} are in this category. Type
18488 @kbd{help data} at the @value{GDBN} prompt to see a list of commands
18491 @findex COMMAND_STACK
18492 @findex gdb.COMMAND_STACK
18493 @item COMMAND_STACK
18494 The command has to do with manipulation of the stack. For example,
18495 @code{backtrace}, @code{frame}, and @code{return} are in this
18496 category. Type @kbd{help stack} at the @value{GDBN} prompt to see a
18497 list of commands in this category.
18499 @findex COMMAND_FILES
18500 @findex gdb.COMMAND_FILES
18501 @item COMMAND_FILES
18502 This class is used for file-related commands. For example,
18503 @code{file}, @code{list} and @code{section} are in this category.
18504 Type @kbd{help files} at the @value{GDBN} prompt to see a list of
18505 commands in this category.
18507 @findex COMMAND_SUPPORT
18508 @findex gdb.COMMAND_SUPPORT
18509 @item COMMAND_SUPPORT
18510 This should be used for ``support facilities'', generally meaning
18511 things that are useful to the user when interacting with @value{GDBN},
18512 but not related to the state of the inferior. For example,
18513 @code{help}, @code{make}, and @code{shell} are in this category. Type
18514 @kbd{help support} at the @value{GDBN} prompt to see a list of
18515 commands in this category.
18517 @findex COMMAND_STATUS
18518 @findex gdb.COMMAND_STATUS
18519 @item COMMAND_STATUS
18520 The command is an @samp{info}-related command, that is, related to the
18521 state of @value{GDBN} itself. For example, @code{info}, @code{macro},
18522 and @code{show} are in this category. Type @kbd{help status} at the
18523 @value{GDBN} prompt to see a list of commands in this category.
18525 @findex COMMAND_BREAKPOINTS
18526 @findex gdb.COMMAND_BREAKPOINTS
18527 @item COMMAND_BREAKPOINTS
18528 The command has to do with breakpoints. For example, @code{break},
18529 @code{clear}, and @code{delete} are in this category. Type @kbd{help
18530 breakpoints} at the @value{GDBN} prompt to see a list of commands in
18533 @findex COMMAND_TRACEPOINTS
18534 @findex gdb.COMMAND_TRACEPOINTS
18535 @item COMMAND_TRACEPOINTS
18536 The command has to do with tracepoints. For example, @code{trace},
18537 @code{actions}, and @code{tfind} are in this category. Type
18538 @kbd{help tracepoints} at the @value{GDBN} prompt to see a list of
18539 commands in this category.
18541 @findex COMMAND_OBSCURE
18542 @findex gdb.COMMAND_OBSCURE
18543 @item COMMAND_OBSCURE
18544 The command is only used in unusual circumstances, or is not of
18545 general interest to users. For example, @code{checkpoint},
18546 @code{fork}, and @code{stop} are in this category. Type @kbd{help
18547 obscure} at the @value{GDBN} prompt to see a list of commands in this
18550 @findex COMMAND_MAINTENANCE
18551 @findex gdb.COMMAND_MAINTENANCE
18552 @item COMMAND_MAINTENANCE
18553 The command is only useful to @value{GDBN} maintainers. The
18554 @code{maintenance} and @code{flushregs} commands are in this category.
18555 Type @kbd{help internals} at the @value{GDBN} prompt to see a list of
18556 commands in this category.
18559 A new command can use a predefined completion function, either by
18560 specifying it via an argument at initialization, or by returning it
18561 from the @code{complete} method. These predefined completion
18562 constants are all defined in the @code{gdb} module:
18565 @findex COMPLETE_NONE
18566 @findex gdb.COMPLETE_NONE
18567 @item COMPLETE_NONE
18568 This constant means that no completion should be done.
18570 @findex COMPLETE_FILENAME
18571 @findex gdb.COMPLETE_FILENAME
18572 @item COMPLETE_FILENAME
18573 This constant means that filename completion should be performed.
18575 @findex COMPLETE_LOCATION
18576 @findex gdb.COMPLETE_LOCATION
18577 @item COMPLETE_LOCATION
18578 This constant means that location completion should be done.
18579 @xref{Specify Location}.
18581 @findex COMPLETE_COMMAND
18582 @findex gdb.COMPLETE_COMMAND
18583 @item COMPLETE_COMMAND
18584 This constant means that completion should examine @value{GDBN}
18587 @findex COMPLETE_SYMBOL
18588 @findex gdb.COMPLETE_SYMBOL
18589 @item COMPLETE_SYMBOL
18590 This constant means that completion should be done using symbol names
18594 The following code snippet shows how a trivial CLI command can be
18595 implemented in Python:
18598 class HelloWorld (gdb.Command):
18599 """Greet the whole world."""
18601 def __init__ (self):
18602 super (HelloWorld, self).__init__ ("hello-world", gdb.COMMAND_OBSCURE)
18604 def invoke (self, arg, from_tty):
18605 print "Hello, World!"
18610 The last line instantiates the class, and is necessary to trigger the
18611 registration of the command with @value{GDBN}. Depending on how the
18612 Python code is read into @value{GDBN}, you may need to import the
18613 @code{gdb} module explicitly.
18616 @chapter Command Interpreters
18617 @cindex command interpreters
18619 @value{GDBN} supports multiple command interpreters, and some command
18620 infrastructure to allow users or user interface writers to switch
18621 between interpreters or run commands in other interpreters.
18623 @value{GDBN} currently supports two command interpreters, the console
18624 interpreter (sometimes called the command-line interpreter or @sc{cli})
18625 and the machine interface interpreter (or @sc{gdb/mi}). This manual
18626 describes both of these interfaces in great detail.
18628 By default, @value{GDBN} will start with the console interpreter.
18629 However, the user may choose to start @value{GDBN} with another
18630 interpreter by specifying the @option{-i} or @option{--interpreter}
18631 startup options. Defined interpreters include:
18635 @cindex console interpreter
18636 The traditional console or command-line interpreter. This is the most often
18637 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
18638 @value{GDBN} will use this interpreter.
18641 @cindex mi interpreter
18642 The newest @sc{gdb/mi} interface (currently @code{mi2}). Used primarily
18643 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
18644 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
18648 @cindex mi2 interpreter
18649 The current @sc{gdb/mi} interface.
18652 @cindex mi1 interpreter
18653 The @sc{gdb/mi} interface included in @value{GDBN} 5.1, 5.2, and 5.3.
18657 @cindex invoke another interpreter
18658 The interpreter being used by @value{GDBN} may not be dynamically
18659 switched at runtime. Although possible, this could lead to a very
18660 precarious situation. Consider an IDE using @sc{gdb/mi}. If a user
18661 enters the command "interpreter-set console" in a console view,
18662 @value{GDBN} would switch to using the console interpreter, rendering
18663 the IDE inoperable!
18665 @kindex interpreter-exec
18666 Although you may only choose a single interpreter at startup, you may execute
18667 commands in any interpreter from the current interpreter using the appropriate
18668 command. If you are running the console interpreter, simply use the
18669 @code{interpreter-exec} command:
18672 interpreter-exec mi "-data-list-register-names"
18675 @sc{gdb/mi} has a similar command, although it is only available in versions of
18676 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
18679 @chapter @value{GDBN} Text User Interface
18681 @cindex Text User Interface
18684 * TUI Overview:: TUI overview
18685 * TUI Keys:: TUI key bindings
18686 * TUI Single Key Mode:: TUI single key mode
18687 * TUI Commands:: TUI-specific commands
18688 * TUI Configuration:: TUI configuration variables
18691 The @value{GDBN} Text User Interface (TUI) is a terminal
18692 interface which uses the @code{curses} library to show the source
18693 file, the assembly output, the program registers and @value{GDBN}
18694 commands in separate text windows. The TUI mode is supported only
18695 on platforms where a suitable version of the @code{curses} library
18698 @pindex @value{GDBTUI}
18699 The TUI mode is enabled by default when you invoke @value{GDBN} as
18700 either @samp{@value{GDBTUI}} or @samp{@value{GDBP} -tui}.
18701 You can also switch in and out of TUI mode while @value{GDBN} runs by
18702 using various TUI commands and key bindings, such as @kbd{C-x C-a}.
18703 @xref{TUI Keys, ,TUI Key Bindings}.
18706 @section TUI Overview
18708 In TUI mode, @value{GDBN} can display several text windows:
18712 This window is the @value{GDBN} command window with the @value{GDBN}
18713 prompt and the @value{GDBN} output. The @value{GDBN} input is still
18714 managed using readline.
18717 The source window shows the source file of the program. The current
18718 line and active breakpoints are displayed in this window.
18721 The assembly window shows the disassembly output of the program.
18724 This window shows the processor registers. Registers are highlighted
18725 when their values change.
18728 The source and assembly windows show the current program position
18729 by highlighting the current line and marking it with a @samp{>} marker.
18730 Breakpoints are indicated with two markers. The first marker
18731 indicates the breakpoint type:
18735 Breakpoint which was hit at least once.
18738 Breakpoint which was never hit.
18741 Hardware breakpoint which was hit at least once.
18744 Hardware breakpoint which was never hit.
18747 The second marker indicates whether the breakpoint is enabled or not:
18751 Breakpoint is enabled.
18754 Breakpoint is disabled.
18757 The source, assembly and register windows are updated when the current
18758 thread changes, when the frame changes, or when the program counter
18761 These windows are not all visible at the same time. The command
18762 window is always visible. The others can be arranged in several
18773 source and assembly,
18776 source and registers, or
18779 assembly and registers.
18782 A status line above the command window shows the following information:
18786 Indicates the current @value{GDBN} target.
18787 (@pxref{Targets, ,Specifying a Debugging Target}).
18790 Gives the current process or thread number.
18791 When no process is being debugged, this field is set to @code{No process}.
18794 Gives the current function name for the selected frame.
18795 The name is demangled if demangling is turned on (@pxref{Print Settings}).
18796 When there is no symbol corresponding to the current program counter,
18797 the string @code{??} is displayed.
18800 Indicates the current line number for the selected frame.
18801 When the current line number is not known, the string @code{??} is displayed.
18804 Indicates the current program counter address.
18808 @section TUI Key Bindings
18809 @cindex TUI key bindings
18811 The TUI installs several key bindings in the readline keymaps
18812 (@pxref{Command Line Editing}). The following key bindings
18813 are installed for both TUI mode and the @value{GDBN} standard mode.
18822 Enter or leave the TUI mode. When leaving the TUI mode,
18823 the curses window management stops and @value{GDBN} operates using
18824 its standard mode, writing on the terminal directly. When reentering
18825 the TUI mode, control is given back to the curses windows.
18826 The screen is then refreshed.
18830 Use a TUI layout with only one window. The layout will
18831 either be @samp{source} or @samp{assembly}. When the TUI mode
18832 is not active, it will switch to the TUI mode.
18834 Think of this key binding as the Emacs @kbd{C-x 1} binding.
18838 Use a TUI layout with at least two windows. When the current
18839 layout already has two windows, the next layout with two windows is used.
18840 When a new layout is chosen, one window will always be common to the
18841 previous layout and the new one.
18843 Think of it as the Emacs @kbd{C-x 2} binding.
18847 Change the active window. The TUI associates several key bindings
18848 (like scrolling and arrow keys) with the active window. This command
18849 gives the focus to the next TUI window.
18851 Think of it as the Emacs @kbd{C-x o} binding.
18855 Switch in and out of the TUI SingleKey mode that binds single
18856 keys to @value{GDBN} commands (@pxref{TUI Single Key Mode}).
18859 The following key bindings only work in the TUI mode:
18864 Scroll the active window one page up.
18868 Scroll the active window one page down.
18872 Scroll the active window one line up.
18876 Scroll the active window one line down.
18880 Scroll the active window one column left.
18884 Scroll the active window one column right.
18888 Refresh the screen.
18891 Because the arrow keys scroll the active window in the TUI mode, they
18892 are not available for their normal use by readline unless the command
18893 window has the focus. When another window is active, you must use
18894 other readline key bindings such as @kbd{C-p}, @kbd{C-n}, @kbd{C-b}
18895 and @kbd{C-f} to control the command window.
18897 @node TUI Single Key Mode
18898 @section TUI Single Key Mode
18899 @cindex TUI single key mode
18901 The TUI also provides a @dfn{SingleKey} mode, which binds several
18902 frequently used @value{GDBN} commands to single keys. Type @kbd{C-x s} to
18903 switch into this mode, where the following key bindings are used:
18906 @kindex c @r{(SingleKey TUI key)}
18910 @kindex d @r{(SingleKey TUI key)}
18914 @kindex f @r{(SingleKey TUI key)}
18918 @kindex n @r{(SingleKey TUI key)}
18922 @kindex q @r{(SingleKey TUI key)}
18924 exit the SingleKey mode.
18926 @kindex r @r{(SingleKey TUI key)}
18930 @kindex s @r{(SingleKey TUI key)}
18934 @kindex u @r{(SingleKey TUI key)}
18938 @kindex v @r{(SingleKey TUI key)}
18942 @kindex w @r{(SingleKey TUI key)}
18947 Other keys temporarily switch to the @value{GDBN} command prompt.
18948 The key that was pressed is inserted in the editing buffer so that
18949 it is possible to type most @value{GDBN} commands without interaction
18950 with the TUI SingleKey mode. Once the command is entered the TUI
18951 SingleKey mode is restored. The only way to permanently leave
18952 this mode is by typing @kbd{q} or @kbd{C-x s}.
18956 @section TUI-specific Commands
18957 @cindex TUI commands
18959 The TUI has specific commands to control the text windows.
18960 These commands are always available, even when @value{GDBN} is not in
18961 the TUI mode. When @value{GDBN} is in the standard mode, most
18962 of these commands will automatically switch to the TUI mode.
18967 List and give the size of all displayed windows.
18971 Display the next layout.
18974 Display the previous layout.
18977 Display the source window only.
18980 Display the assembly window only.
18983 Display the source and assembly window.
18986 Display the register window together with the source or assembly window.
18990 Make the next window active for scrolling.
18993 Make the previous window active for scrolling.
18996 Make the source window active for scrolling.
18999 Make the assembly window active for scrolling.
19002 Make the register window active for scrolling.
19005 Make the command window active for scrolling.
19009 Refresh the screen. This is similar to typing @kbd{C-L}.
19011 @item tui reg float
19013 Show the floating point registers in the register window.
19015 @item tui reg general
19016 Show the general registers in the register window.
19019 Show the next register group. The list of register groups as well as
19020 their order is target specific. The predefined register groups are the
19021 following: @code{general}, @code{float}, @code{system}, @code{vector},
19022 @code{all}, @code{save}, @code{restore}.
19024 @item tui reg system
19025 Show the system registers in the register window.
19029 Update the source window and the current execution point.
19031 @item winheight @var{name} +@var{count}
19032 @itemx winheight @var{name} -@var{count}
19034 Change the height of the window @var{name} by @var{count}
19035 lines. Positive counts increase the height, while negative counts
19038 @item tabset @var{nchars}
19040 Set the width of tab stops to be @var{nchars} characters.
19043 @node TUI Configuration
19044 @section TUI Configuration Variables
19045 @cindex TUI configuration variables
19047 Several configuration variables control the appearance of TUI windows.
19050 @item set tui border-kind @var{kind}
19051 @kindex set tui border-kind
19052 Select the border appearance for the source, assembly and register windows.
19053 The possible values are the following:
19056 Use a space character to draw the border.
19059 Use @sc{ascii} characters @samp{+}, @samp{-} and @samp{|} to draw the border.
19062 Use the Alternate Character Set to draw the border. The border is
19063 drawn using character line graphics if the terminal supports them.
19066 @item set tui border-mode @var{mode}
19067 @kindex set tui border-mode
19068 @itemx set tui active-border-mode @var{mode}
19069 @kindex set tui active-border-mode
19070 Select the display attributes for the borders of the inactive windows
19071 or the active window. The @var{mode} can be one of the following:
19074 Use normal attributes to display the border.
19080 Use reverse video mode.
19083 Use half bright mode.
19085 @item half-standout
19086 Use half bright and standout mode.
19089 Use extra bright or bold mode.
19091 @item bold-standout
19092 Use extra bright or bold and standout mode.
19097 @chapter Using @value{GDBN} under @sc{gnu} Emacs
19100 @cindex @sc{gnu} Emacs
19101 A special interface allows you to use @sc{gnu} Emacs to view (and
19102 edit) the source files for the program you are debugging with
19105 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
19106 executable file you want to debug as an argument. This command starts
19107 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
19108 created Emacs buffer.
19109 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
19111 Running @value{GDBN} under Emacs can be just like running @value{GDBN} normally except for two
19116 All ``terminal'' input and output goes through an Emacs buffer, called
19119 This applies both to @value{GDBN} commands and their output, and to the input
19120 and output done by the program you are debugging.
19122 This is useful because it means that you can copy the text of previous
19123 commands and input them again; you can even use parts of the output
19126 All the facilities of Emacs' Shell mode are available for interacting
19127 with your program. In particular, you can send signals the usual
19128 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
19132 @value{GDBN} displays source code through Emacs.
19134 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
19135 source file for that frame and puts an arrow (@samp{=>}) at the
19136 left margin of the current line. Emacs uses a separate buffer for
19137 source display, and splits the screen to show both your @value{GDBN} session
19140 Explicit @value{GDBN} @code{list} or search commands still produce output as
19141 usual, but you probably have no reason to use them from Emacs.
19144 We call this @dfn{text command mode}. Emacs 22.1, and later, also uses
19145 a graphical mode, enabled by default, which provides further buffers
19146 that can control the execution and describe the state of your program.
19147 @xref{GDB Graphical Interface,,, Emacs, The @sc{gnu} Emacs Manual}.
19149 If you specify an absolute file name when prompted for the @kbd{M-x
19150 gdb} argument, then Emacs sets your current working directory to where
19151 your program resides. If you only specify the file name, then Emacs
19152 sets your current working directory to to the directory associated
19153 with the previous buffer. In this case, @value{GDBN} may find your
19154 program by searching your environment's @code{PATH} variable, but on
19155 some operating systems it might not find the source. So, although the
19156 @value{GDBN} input and output session proceeds normally, the auxiliary
19157 buffer does not display the current source and line of execution.
19159 The initial working directory of @value{GDBN} is printed on the top
19160 line of the GUD buffer and this serves as a default for the commands
19161 that specify files for @value{GDBN} to operate on. @xref{Files,
19162 ,Commands to Specify Files}.
19164 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
19165 need to call @value{GDBN} by a different name (for example, if you
19166 keep several configurations around, with different names) you can
19167 customize the Emacs variable @code{gud-gdb-command-name} to run the
19170 In the GUD buffer, you can use these special Emacs commands in
19171 addition to the standard Shell mode commands:
19175 Describe the features of Emacs' GUD Mode.
19178 Execute to another source line, like the @value{GDBN} @code{step} command; also
19179 update the display window to show the current file and location.
19182 Execute to next source line in this function, skipping all function
19183 calls, like the @value{GDBN} @code{next} command. Then update the display window
19184 to show the current file and location.
19187 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
19188 display window accordingly.
19191 Execute until exit from the selected stack frame, like the @value{GDBN}
19192 @code{finish} command.
19195 Continue execution of your program, like the @value{GDBN} @code{continue}
19199 Go up the number of frames indicated by the numeric argument
19200 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
19201 like the @value{GDBN} @code{up} command.
19204 Go down the number of frames indicated by the numeric argument, like the
19205 @value{GDBN} @code{down} command.
19208 In any source file, the Emacs command @kbd{C-x @key{SPC}} (@code{gud-break})
19209 tells @value{GDBN} to set a breakpoint on the source line point is on.
19211 In text command mode, if you type @kbd{M-x speedbar}, Emacs displays a
19212 separate frame which shows a backtrace when the GUD buffer is current.
19213 Move point to any frame in the stack and type @key{RET} to make it
19214 become the current frame and display the associated source in the
19215 source buffer. Alternatively, click @kbd{Mouse-2} to make the
19216 selected frame become the current one. In graphical mode, the
19217 speedbar displays watch expressions.
19219 If you accidentally delete the source-display buffer, an easy way to get
19220 it back is to type the command @code{f} in the @value{GDBN} buffer, to
19221 request a frame display; when you run under Emacs, this recreates
19222 the source buffer if necessary to show you the context of the current
19225 The source files displayed in Emacs are in ordinary Emacs buffers
19226 which are visiting the source files in the usual way. You can edit
19227 the files with these buffers if you wish; but keep in mind that @value{GDBN}
19228 communicates with Emacs in terms of line numbers. If you add or
19229 delete lines from the text, the line numbers that @value{GDBN} knows cease
19230 to correspond properly with the code.
19232 A more detailed description of Emacs' interaction with @value{GDBN} is
19233 given in the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu}
19236 @c The following dropped because Epoch is nonstandard. Reactivate
19237 @c if/when v19 does something similar. ---doc@cygnus.com 19dec1990
19239 @kindex Emacs Epoch environment
19243 Version 18 of @sc{gnu} Emacs has a built-in window system
19244 called the @code{epoch}
19245 environment. Users of this environment can use a new command,
19246 @code{inspect} which performs identically to @code{print} except that
19247 each value is printed in its own window.
19252 @chapter The @sc{gdb/mi} Interface
19254 @unnumberedsec Function and Purpose
19256 @cindex @sc{gdb/mi}, its purpose
19257 @sc{gdb/mi} is a line based machine oriented text interface to
19258 @value{GDBN} and is activated by specifying using the
19259 @option{--interpreter} command line option (@pxref{Mode Options}). It
19260 is specifically intended to support the development of systems which
19261 use the debugger as just one small component of a larger system.
19263 This chapter is a specification of the @sc{gdb/mi} interface. It is written
19264 in the form of a reference manual.
19266 Note that @sc{gdb/mi} is still under construction, so some of the
19267 features described below are incomplete and subject to change
19268 (@pxref{GDB/MI Development and Front Ends, , @sc{gdb/mi} Development and Front Ends}).
19270 @unnumberedsec Notation and Terminology
19272 @cindex notational conventions, for @sc{gdb/mi}
19273 This chapter uses the following notation:
19277 @code{|} separates two alternatives.
19280 @code{[ @var{something} ]} indicates that @var{something} is optional:
19281 it may or may not be given.
19284 @code{( @var{group} )*} means that @var{group} inside the parentheses
19285 may repeat zero or more times.
19288 @code{( @var{group} )+} means that @var{group} inside the parentheses
19289 may repeat one or more times.
19292 @code{"@var{string}"} means a literal @var{string}.
19296 @heading Dependencies
19300 * GDB/MI General Design::
19301 * GDB/MI Command Syntax::
19302 * GDB/MI Compatibility with CLI::
19303 * GDB/MI Development and Front Ends::
19304 * GDB/MI Output Records::
19305 * GDB/MI Simple Examples::
19306 * GDB/MI Command Description Format::
19307 * GDB/MI Breakpoint Commands::
19308 * GDB/MI Program Context::
19309 * GDB/MI Thread Commands::
19310 * GDB/MI Program Execution::
19311 * GDB/MI Stack Manipulation::
19312 * GDB/MI Variable Objects::
19313 * GDB/MI Data Manipulation::
19314 * GDB/MI Tracepoint Commands::
19315 * GDB/MI Symbol Query::
19316 * GDB/MI File Commands::
19318 * GDB/MI Kod Commands::
19319 * GDB/MI Memory Overlay Commands::
19320 * GDB/MI Signal Handling Commands::
19322 * GDB/MI Target Manipulation::
19323 * GDB/MI File Transfer Commands::
19324 * GDB/MI Miscellaneous Commands::
19327 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19328 @node GDB/MI General Design
19329 @section @sc{gdb/mi} General Design
19330 @cindex GDB/MI General Design
19332 Interaction of a @sc{GDB/MI} frontend with @value{GDBN} involves three
19333 parts---commands sent to @value{GDBN}, responses to those commands
19334 and notifications. Each command results in exactly one response,
19335 indicating either successful completion of the command, or an error.
19336 For the commands that do not resume the target, the response contains the
19337 requested information. For the commands that resume the target, the
19338 response only indicates whether the target was successfully resumed.
19339 Notifications is the mechanism for reporting changes in the state of the
19340 target, or in @value{GDBN} state, that cannot conveniently be associated with
19341 a command and reported as part of that command response.
19343 The important examples of notifications are:
19347 Exec notifications. These are used to report changes in
19348 target state---when a target is resumed, or stopped. It would not
19349 be feasible to include this information in response of resuming
19350 commands, because one resume commands can result in multiple events in
19351 different threads. Also, quite some time may pass before any event
19352 happens in the target, while a frontend needs to know whether the resuming
19353 command itself was successfully executed.
19356 Console output, and status notifications. Console output
19357 notifications are used to report output of CLI commands, as well as
19358 diagnostics for other commands. Status notifications are used to
19359 report the progress of a long-running operation. Naturally, including
19360 this information in command response would mean no output is produced
19361 until the command is finished, which is undesirable.
19364 General notifications. Commands may have various side effects on
19365 the @value{GDBN} or target state beyond their official purpose. For example,
19366 a command may change the selected thread. Although such changes can
19367 be included in command response, using notification allows for more
19368 orthogonal frontend design.
19372 There's no guarantee that whenever an MI command reports an error,
19373 @value{GDBN} or the target are in any specific state, and especially,
19374 the state is not reverted to the state before the MI command was
19375 processed. Therefore, whenever an MI command results in an error,
19376 we recommend that the frontend refreshes all the information shown in
19377 the user interface.
19379 @subsection Context management
19381 In most cases when @value{GDBN} accesses the target, this access is
19382 done in context of a specific thread and frame (@pxref{Frames}).
19383 Often, even when accessing global data, the target requires that a thread
19384 be specified. The CLI interface maintains the selected thread and frame,
19385 and supplies them to target on each command. This is convenient,
19386 because a command line user would not want to specify that information
19387 explicitly on each command, and because user interacts with
19388 @value{GDBN} via a single terminal, so no confusion is possible as
19389 to what thread and frame are the current ones.
19391 In the case of MI, the concept of selected thread and frame is less
19392 useful. First, a frontend can easily remember this information
19393 itself. Second, a graphical frontend can have more than one window,
19394 each one used for debugging a different thread, and the frontend might
19395 want to access additional threads for internal purposes. This
19396 increases the risk that by relying on implicitly selected thread, the
19397 frontend may be operating on a wrong one. Therefore, each MI command
19398 should explicitly specify which thread and frame to operate on. To
19399 make it possible, each MI command accepts the @samp{--thread} and
19400 @samp{--frame} options, the value to each is @value{GDBN} identifier
19401 for thread and frame to operate on.
19403 Usually, each top-level window in a frontend allows the user to select
19404 a thread and a frame, and remembers the user selection for further
19405 operations. However, in some cases @value{GDBN} may suggest that the
19406 current thread be changed. For example, when stopping on a breakpoint
19407 it is reasonable to switch to the thread where breakpoint is hit. For
19408 another example, if the user issues the CLI @samp{thread} command via
19409 the frontend, it is desirable to change the frontend's selected thread to the
19410 one specified by user. @value{GDBN} communicates the suggestion to
19411 change current thread using the @samp{=thread-selected} notification.
19412 No such notification is available for the selected frame at the moment.
19414 Note that historically, MI shares the selected thread with CLI, so
19415 frontends used the @code{-thread-select} to execute commands in the
19416 right context. However, getting this to work right is cumbersome. The
19417 simplest way is for frontend to emit @code{-thread-select} command
19418 before every command. This doubles the number of commands that need
19419 to be sent. The alternative approach is to suppress @code{-thread-select}
19420 if the selected thread in @value{GDBN} is supposed to be identical to the
19421 thread the frontend wants to operate on. However, getting this
19422 optimization right can be tricky. In particular, if the frontend
19423 sends several commands to @value{GDBN}, and one of the commands changes the
19424 selected thread, then the behaviour of subsequent commands will
19425 change. So, a frontend should either wait for response from such
19426 problematic commands, or explicitly add @code{-thread-select} for
19427 all subsequent commands. No frontend is known to do this exactly
19428 right, so it is suggested to just always pass the @samp{--thread} and
19429 @samp{--frame} options.
19431 @subsection Asynchronous command execution and non-stop mode
19433 On some targets, @value{GDBN} is capable of processing MI commands
19434 even while the target is running. This is called @dfn{asynchronous
19435 command execution} (@pxref{Background Execution}). The frontend may
19436 specify a preferrence for asynchronous execution using the
19437 @code{-gdb-set target-async 1} command, which should be emitted before
19438 either running the executable or attaching to the target. After the
19439 frontend has started the executable or attached to the target, it can
19440 find if asynchronous execution is enabled using the
19441 @code{-list-target-features} command.
19443 Even if @value{GDBN} can accept a command while target is running,
19444 many commands that access the target do not work when the target is
19445 running. Therefore, asynchronous command execution is most useful
19446 when combined with non-stop mode (@pxref{Non-Stop Mode}). Then,
19447 it is possible to examine the state of one thread, while other threads
19450 When a given thread is running, MI commands that try to access the
19451 target in the context of that thread may not work, or may work only on
19452 some targets. In particular, commands that try to operate on thread's
19453 stack will not work, on any target. Commands that read memory, or
19454 modify breakpoints, may work or not work, depending on the target. Note
19455 that even commands that operate on global state, such as @code{print},
19456 @code{set}, and breakpoint commands, still access the target in the
19457 context of a specific thread, so frontend should try to find a
19458 stopped thread and perform the operation on that thread (using the
19459 @samp{--thread} option).
19461 Which commands will work in the context of a running thread is
19462 highly target dependent. However, the two commands
19463 @code{-exec-interrupt}, to stop a thread, and @code{-thread-info},
19464 to find the state of a thread, will always work.
19466 @subsection Thread groups
19467 @value{GDBN} may be used to debug several processes at the same time.
19468 On some platfroms, @value{GDBN} may support debugging of several
19469 hardware systems, each one having several cores with several different
19470 processes running on each core. This section describes the MI
19471 mechanism to support such debugging scenarios.
19473 The key observation is that regardless of the structure of the
19474 target, MI can have a global list of threads, because most commands that
19475 accept the @samp{--thread} option do not need to know what process that
19476 thread belongs to. Therefore, it is not necessary to introduce
19477 neither additional @samp{--process} option, nor an notion of the
19478 current process in the MI interface. The only strictly new feature
19479 that is required is the ability to find how the threads are grouped
19482 To allow the user to discover such grouping, and to support arbitrary
19483 hierarchy of machines/cores/processes, MI introduces the concept of a
19484 @dfn{thread group}. Thread group is a collection of threads and other
19485 thread groups. A thread group always has a string identifier, a type,
19486 and may have additional attributes specific to the type. A new
19487 command, @code{-list-thread-groups}, returns the list of top-level
19488 thread groups, which correspond to processes that @value{GDBN} is
19489 debugging at the moment. By passing an identifier of a thread group
19490 to the @code{-list-thread-groups} command, it is possible to obtain
19491 the members of specific thread group.
19493 To allow the user to easily discover processes, and other objects, he
19494 wishes to debug, a concept of @dfn{available thread group} is
19495 introduced. Available thread group is an thread group that
19496 @value{GDBN} is not debugging, but that can be attached to, using the
19497 @code{-target-attach} command. The list of available top-level thread
19498 groups can be obtained using @samp{-list-thread-groups --available}.
19499 In general, the content of a thread group may be only retrieved only
19500 after attaching to that thread group.
19502 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19503 @node GDB/MI Command Syntax
19504 @section @sc{gdb/mi} Command Syntax
19507 * GDB/MI Input Syntax::
19508 * GDB/MI Output Syntax::
19511 @node GDB/MI Input Syntax
19512 @subsection @sc{gdb/mi} Input Syntax
19514 @cindex input syntax for @sc{gdb/mi}
19515 @cindex @sc{gdb/mi}, input syntax
19517 @item @var{command} @expansion{}
19518 @code{@var{cli-command} | @var{mi-command}}
19520 @item @var{cli-command} @expansion{}
19521 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
19522 @var{cli-command} is any existing @value{GDBN} CLI command.
19524 @item @var{mi-command} @expansion{}
19525 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
19526 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
19528 @item @var{token} @expansion{}
19529 "any sequence of digits"
19531 @item @var{option} @expansion{}
19532 @code{"-" @var{parameter} [ " " @var{parameter} ]}
19534 @item @var{parameter} @expansion{}
19535 @code{@var{non-blank-sequence} | @var{c-string}}
19537 @item @var{operation} @expansion{}
19538 @emph{any of the operations described in this chapter}
19540 @item @var{non-blank-sequence} @expansion{}
19541 @emph{anything, provided it doesn't contain special characters such as
19542 "-", @var{nl}, """ and of course " "}
19544 @item @var{c-string} @expansion{}
19545 @code{""" @var{seven-bit-iso-c-string-content} """}
19547 @item @var{nl} @expansion{}
19556 The CLI commands are still handled by the @sc{mi} interpreter; their
19557 output is described below.
19560 The @code{@var{token}}, when present, is passed back when the command
19564 Some @sc{mi} commands accept optional arguments as part of the parameter
19565 list. Each option is identified by a leading @samp{-} (dash) and may be
19566 followed by an optional argument parameter. Options occur first in the
19567 parameter list and can be delimited from normal parameters using
19568 @samp{--} (this is useful when some parameters begin with a dash).
19575 We want easy access to the existing CLI syntax (for debugging).
19578 We want it to be easy to spot a @sc{mi} operation.
19581 @node GDB/MI Output Syntax
19582 @subsection @sc{gdb/mi} Output Syntax
19584 @cindex output syntax of @sc{gdb/mi}
19585 @cindex @sc{gdb/mi}, output syntax
19586 The output from @sc{gdb/mi} consists of zero or more out-of-band records
19587 followed, optionally, by a single result record. This result record
19588 is for the most recent command. The sequence of output records is
19589 terminated by @samp{(gdb)}.
19591 If an input command was prefixed with a @code{@var{token}} then the
19592 corresponding output for that command will also be prefixed by that same
19596 @item @var{output} @expansion{}
19597 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(gdb)" @var{nl}}
19599 @item @var{result-record} @expansion{}
19600 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
19602 @item @var{out-of-band-record} @expansion{}
19603 @code{@var{async-record} | @var{stream-record}}
19605 @item @var{async-record} @expansion{}
19606 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
19608 @item @var{exec-async-output} @expansion{}
19609 @code{[ @var{token} ] "*" @var{async-output}}
19611 @item @var{status-async-output} @expansion{}
19612 @code{[ @var{token} ] "+" @var{async-output}}
19614 @item @var{notify-async-output} @expansion{}
19615 @code{[ @var{token} ] "=" @var{async-output}}
19617 @item @var{async-output} @expansion{}
19618 @code{@var{async-class} ( "," @var{result} )* @var{nl}}
19620 @item @var{result-class} @expansion{}
19621 @code{"done" | "running" | "connected" | "error" | "exit"}
19623 @item @var{async-class} @expansion{}
19624 @code{"stopped" | @var{others}} (where @var{others} will be added
19625 depending on the needs---this is still in development).
19627 @item @var{result} @expansion{}
19628 @code{ @var{variable} "=" @var{value}}
19630 @item @var{variable} @expansion{}
19631 @code{ @var{string} }
19633 @item @var{value} @expansion{}
19634 @code{ @var{const} | @var{tuple} | @var{list} }
19636 @item @var{const} @expansion{}
19637 @code{@var{c-string}}
19639 @item @var{tuple} @expansion{}
19640 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
19642 @item @var{list} @expansion{}
19643 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
19644 @var{result} ( "," @var{result} )* "]" }
19646 @item @var{stream-record} @expansion{}
19647 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
19649 @item @var{console-stream-output} @expansion{}
19650 @code{"~" @var{c-string}}
19652 @item @var{target-stream-output} @expansion{}
19653 @code{"@@" @var{c-string}}
19655 @item @var{log-stream-output} @expansion{}
19656 @code{"&" @var{c-string}}
19658 @item @var{nl} @expansion{}
19661 @item @var{token} @expansion{}
19662 @emph{any sequence of digits}.
19670 All output sequences end in a single line containing a period.
19673 The @code{@var{token}} is from the corresponding request. Note that
19674 for all async output, while the token is allowed by the grammar and
19675 may be output by future versions of @value{GDBN} for select async
19676 output messages, it is generally omitted. Frontends should treat
19677 all async output as reporting general changes in the state of the
19678 target and there should be no need to associate async output to any
19682 @cindex status output in @sc{gdb/mi}
19683 @var{status-async-output} contains on-going status information about the
19684 progress of a slow operation. It can be discarded. All status output is
19685 prefixed by @samp{+}.
19688 @cindex async output in @sc{gdb/mi}
19689 @var{exec-async-output} contains asynchronous state change on the target
19690 (stopped, started, disappeared). All async output is prefixed by
19694 @cindex notify output in @sc{gdb/mi}
19695 @var{notify-async-output} contains supplementary information that the
19696 client should handle (e.g., a new breakpoint information). All notify
19697 output is prefixed by @samp{=}.
19700 @cindex console output in @sc{gdb/mi}
19701 @var{console-stream-output} is output that should be displayed as is in the
19702 console. It is the textual response to a CLI command. All the console
19703 output is prefixed by @samp{~}.
19706 @cindex target output in @sc{gdb/mi}
19707 @var{target-stream-output} is the output produced by the target program.
19708 All the target output is prefixed by @samp{@@}.
19711 @cindex log output in @sc{gdb/mi}
19712 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
19713 instance messages that should be displayed as part of an error log. All
19714 the log output is prefixed by @samp{&}.
19717 @cindex list output in @sc{gdb/mi}
19718 New @sc{gdb/mi} commands should only output @var{lists} containing
19724 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
19725 details about the various output records.
19727 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19728 @node GDB/MI Compatibility with CLI
19729 @section @sc{gdb/mi} Compatibility with CLI
19731 @cindex compatibility, @sc{gdb/mi} and CLI
19732 @cindex @sc{gdb/mi}, compatibility with CLI
19734 For the developers convenience CLI commands can be entered directly,
19735 but there may be some unexpected behaviour. For example, commands
19736 that query the user will behave as if the user replied yes, breakpoint
19737 command lists are not executed and some CLI commands, such as
19738 @code{if}, @code{when} and @code{define}, prompt for further input with
19739 @samp{>}, which is not valid MI output.
19741 This feature may be removed at some stage in the future and it is
19742 recommended that front ends use the @code{-interpreter-exec} command
19743 (@pxref{-interpreter-exec}).
19745 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19746 @node GDB/MI Development and Front Ends
19747 @section @sc{gdb/mi} Development and Front Ends
19748 @cindex @sc{gdb/mi} development
19750 The application which takes the MI output and presents the state of the
19751 program being debugged to the user is called a @dfn{front end}.
19753 Although @sc{gdb/mi} is still incomplete, it is currently being used
19754 by a variety of front ends to @value{GDBN}. This makes it difficult
19755 to introduce new functionality without breaking existing usage. This
19756 section tries to minimize the problems by describing how the protocol
19759 Some changes in MI need not break a carefully designed front end, and
19760 for these the MI version will remain unchanged. The following is a
19761 list of changes that may occur within one level, so front ends should
19762 parse MI output in a way that can handle them:
19766 New MI commands may be added.
19769 New fields may be added to the output of any MI command.
19772 The range of values for fields with specified values, e.g.,
19773 @code{in_scope} (@pxref{-var-update}) may be extended.
19775 @c The format of field's content e.g type prefix, may change so parse it
19776 @c at your own risk. Yes, in general?
19778 @c The order of fields may change? Shouldn't really matter but it might
19779 @c resolve inconsistencies.
19782 If the changes are likely to break front ends, the MI version level
19783 will be increased by one. This will allow the front end to parse the
19784 output according to the MI version. Apart from mi0, new versions of
19785 @value{GDBN} will not support old versions of MI and it will be the
19786 responsibility of the front end to work with the new one.
19788 @c Starting with mi3, add a new command -mi-version that prints the MI
19791 The best way to avoid unexpected changes in MI that might break your front
19792 end is to make your project known to @value{GDBN} developers and
19793 follow development on @email{gdb@@sourceware.org} and
19794 @email{gdb-patches@@sourceware.org}.
19795 @cindex mailing lists
19797 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19798 @node GDB/MI Output Records
19799 @section @sc{gdb/mi} Output Records
19802 * GDB/MI Result Records::
19803 * GDB/MI Stream Records::
19804 * GDB/MI Async Records::
19805 * GDB/MI Frame Information::
19808 @node GDB/MI Result Records
19809 @subsection @sc{gdb/mi} Result Records
19811 @cindex result records in @sc{gdb/mi}
19812 @cindex @sc{gdb/mi}, result records
19813 In addition to a number of out-of-band notifications, the response to a
19814 @sc{gdb/mi} command includes one of the following result indications:
19818 @item "^done" [ "," @var{results} ]
19819 The synchronous operation was successful, @code{@var{results}} are the return
19824 @c Is this one correct? Should it be an out-of-band notification?
19825 The asynchronous operation was successfully started. The target is
19830 @value{GDBN} has connected to a remote target.
19832 @item "^error" "," @var{c-string}
19834 The operation failed. The @code{@var{c-string}} contains the corresponding
19839 @value{GDBN} has terminated.
19843 @node GDB/MI Stream Records
19844 @subsection @sc{gdb/mi} Stream Records
19846 @cindex @sc{gdb/mi}, stream records
19847 @cindex stream records in @sc{gdb/mi}
19848 @value{GDBN} internally maintains a number of output streams: the console, the
19849 target, and the log. The output intended for each of these streams is
19850 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
19852 Each stream record begins with a unique @dfn{prefix character} which
19853 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
19854 Syntax}). In addition to the prefix, each stream record contains a
19855 @code{@var{string-output}}. This is either raw text (with an implicit new
19856 line) or a quoted C string (which does not contain an implicit newline).
19859 @item "~" @var{string-output}
19860 The console output stream contains text that should be displayed in the
19861 CLI console window. It contains the textual responses to CLI commands.
19863 @item "@@" @var{string-output}
19864 The target output stream contains any textual output from the running
19865 target. This is only present when GDB's event loop is truly
19866 asynchronous, which is currently only the case for remote targets.
19868 @item "&" @var{string-output}
19869 The log stream contains debugging messages being produced by @value{GDBN}'s
19873 @node GDB/MI Async Records
19874 @subsection @sc{gdb/mi} Async Records
19876 @cindex async records in @sc{gdb/mi}
19877 @cindex @sc{gdb/mi}, async records
19878 @dfn{Async} records are used to notify the @sc{gdb/mi} client of
19879 additional changes that have occurred. Those changes can either be a
19880 consequence of @sc{gdb/mi} commands (e.g., a breakpoint modified) or a result of
19881 target activity (e.g., target stopped).
19883 The following is the list of possible async records:
19887 @item *running,thread-id="@var{thread}"
19888 The target is now running. The @var{thread} field tells which
19889 specific thread is now running, and can be @samp{all} if all threads
19890 are running. The frontend should assume that no interaction with a
19891 running thread is possible after this notification is produced.
19892 The frontend should not assume that this notification is output
19893 only once for any command. @value{GDBN} may emit this notification
19894 several times, either for different threads, because it cannot resume
19895 all threads together, or even for a single thread, if the thread must
19896 be stepped though some code before letting it run freely.
19898 @item *stopped,reason="@var{reason}",thread-id="@var{id}",stopped-threads="@var{stopped}"
19899 The target has stopped. The @var{reason} field can have one of the
19903 @item breakpoint-hit
19904 A breakpoint was reached.
19905 @item watchpoint-trigger
19906 A watchpoint was triggered.
19907 @item read-watchpoint-trigger
19908 A read watchpoint was triggered.
19909 @item access-watchpoint-trigger
19910 An access watchpoint was triggered.
19911 @item function-finished
19912 An -exec-finish or similar CLI command was accomplished.
19913 @item location-reached
19914 An -exec-until or similar CLI command was accomplished.
19915 @item watchpoint-scope
19916 A watchpoint has gone out of scope.
19917 @item end-stepping-range
19918 An -exec-next, -exec-next-instruction, -exec-step, -exec-step-instruction or
19919 similar CLI command was accomplished.
19920 @item exited-signalled
19921 The inferior exited because of a signal.
19923 The inferior exited.
19924 @item exited-normally
19925 The inferior exited normally.
19926 @item signal-received
19927 A signal was received by the inferior.
19930 The @var{id} field identifies the thread that directly caused the stop
19931 -- for example by hitting a breakpoint. Depending on whether all-stop
19932 mode is in effect (@pxref{All-Stop Mode}), @value{GDBN} may either
19933 stop all threads, or only the thread that directly triggered the stop.
19934 If all threads are stopped, the @var{stopped} field will have the
19935 value of @code{"all"}. Otherwise, the value of the @var{stopped}
19936 field will be a list of thread identifiers. Presently, this list will
19937 always include a single thread, but frontend should be prepared to see
19938 several threads in the list.
19940 @item =thread-group-created,id="@var{id}"
19941 @itemx =thread-group-exited,id="@var{id}"
19942 A thread thread group either was attached to, or has exited/detached
19943 from. The @var{id} field contains the @value{GDBN} identifier of the
19946 @item =thread-created,id="@var{id}",group-id="@var{gid}"
19947 @itemx =thread-exited,id="@var{id}",group-id="@var{gid}"
19948 A thread either was created, or has exited. The @var{id} field
19949 contains the @value{GDBN} identifier of the thread. The @var{gid}
19950 field identifies the thread group this thread belongs to.
19952 @item =thread-selected,id="@var{id}"
19953 Informs that the selected thread was changed as result of the last
19954 command. This notification is not emitted as result of @code{-thread-select}
19955 command but is emitted whenever an MI command that is not documented
19956 to change the selected thread actually changes it. In particular,
19957 invoking, directly or indirectly (via user-defined command), the CLI
19958 @code{thread} command, will generate this notification.
19960 We suggest that in response to this notification, front ends
19961 highlight the selected thread and cause subsequent commands to apply to
19964 @item =library-loaded,...
19965 Reports that a new library file was loaded by the program. This
19966 notification has 4 fields---@var{id}, @var{target-name},
19967 @var{host-name}, and @var{symbols-loaded}. The @var{id} field is an
19968 opaque identifier of the library. For remote debugging case,
19969 @var{target-name} and @var{host-name} fields give the name of the
19970 library file on the target, and on the host respectively. For native
19971 debugging, both those fields have the same value. The
19972 @var{symbols-loaded} field reports if the debug symbols for this
19973 library are loaded.
19975 @item =library-unloaded,...
19976 Reports that a library was unloaded by the program. This notification
19977 has 3 fields---@var{id}, @var{target-name} and @var{host-name} with
19978 the same meaning as for the @code{=library-loaded} notification
19982 @node GDB/MI Frame Information
19983 @subsection @sc{gdb/mi} Frame Information
19985 Response from many MI commands includes an information about stack
19986 frame. This information is a tuple that may have the following
19991 The level of the stack frame. The innermost frame has the level of
19992 zero. This field is always present.
19995 The name of the function corresponding to the frame. This field may
19996 be absent if @value{GDBN} is unable to determine the function name.
19999 The code address for the frame. This field is always present.
20002 The name of the source files that correspond to the frame's code
20003 address. This field may be absent.
20006 The source line corresponding to the frames' code address. This field
20010 The name of the binary file (either executable or shared library) the
20011 corresponds to the frame's code address. This field may be absent.
20016 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20017 @node GDB/MI Simple Examples
20018 @section Simple Examples of @sc{gdb/mi} Interaction
20019 @cindex @sc{gdb/mi}, simple examples
20021 This subsection presents several simple examples of interaction using
20022 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
20023 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
20024 the output received from @sc{gdb/mi}.
20026 Note the line breaks shown in the examples are here only for
20027 readability, they don't appear in the real output.
20029 @subheading Setting a Breakpoint
20031 Setting a breakpoint generates synchronous output which contains detailed
20032 information of the breakpoint.
20035 -> -break-insert main
20036 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
20037 enabled="y",addr="0x08048564",func="main",file="myprog.c",
20038 fullname="/home/nickrob/myprog.c",line="68",times="0"@}
20042 @subheading Program Execution
20044 Program execution generates asynchronous records and MI gives the
20045 reason that execution stopped.
20051 <- *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
20052 frame=@{addr="0x08048564",func="main",
20053 args=[@{name="argc",value="1"@},@{name="argv",value="0xbfc4d4d4"@}],
20054 file="myprog.c",fullname="/home/nickrob/myprog.c",line="68"@}
20059 <- *stopped,reason="exited-normally"
20063 @subheading Quitting @value{GDBN}
20065 Quitting @value{GDBN} just prints the result class @samp{^exit}.
20073 @subheading A Bad Command
20075 Here's what happens if you pass a non-existent command:
20079 <- ^error,msg="Undefined MI command: rubbish"
20084 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20085 @node GDB/MI Command Description Format
20086 @section @sc{gdb/mi} Command Description Format
20088 The remaining sections describe blocks of commands. Each block of
20089 commands is laid out in a fashion similar to this section.
20091 @subheading Motivation
20093 The motivation for this collection of commands.
20095 @subheading Introduction
20097 A brief introduction to this collection of commands as a whole.
20099 @subheading Commands
20101 For each command in the block, the following is described:
20103 @subsubheading Synopsis
20106 -command @var{args}@dots{}
20109 @subsubheading Result
20111 @subsubheading @value{GDBN} Command
20113 The corresponding @value{GDBN} CLI command(s), if any.
20115 @subsubheading Example
20117 Example(s) formatted for readability. Some of the described commands have
20118 not been implemented yet and these are labeled N.A.@: (not available).
20121 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20122 @node GDB/MI Breakpoint Commands
20123 @section @sc{gdb/mi} Breakpoint Commands
20125 @cindex breakpoint commands for @sc{gdb/mi}
20126 @cindex @sc{gdb/mi}, breakpoint commands
20127 This section documents @sc{gdb/mi} commands for manipulating
20130 @subheading The @code{-break-after} Command
20131 @findex -break-after
20133 @subsubheading Synopsis
20136 -break-after @var{number} @var{count}
20139 The breakpoint number @var{number} is not in effect until it has been
20140 hit @var{count} times. To see how this is reflected in the output of
20141 the @samp{-break-list} command, see the description of the
20142 @samp{-break-list} command below.
20144 @subsubheading @value{GDBN} Command
20146 The corresponding @value{GDBN} command is @samp{ignore}.
20148 @subsubheading Example
20153 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
20154 enabled="y",addr="0x000100d0",func="main",file="hello.c",
20155 fullname="/home/foo/hello.c",line="5",times="0"@}
20162 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
20163 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
20164 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
20165 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
20166 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
20167 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
20168 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
20169 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
20170 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
20171 line="5",times="0",ignore="3"@}]@}
20176 @subheading The @code{-break-catch} Command
20177 @findex -break-catch
20179 @subheading The @code{-break-commands} Command
20180 @findex -break-commands
20184 @subheading The @code{-break-condition} Command
20185 @findex -break-condition
20187 @subsubheading Synopsis
20190 -break-condition @var{number} @var{expr}
20193 Breakpoint @var{number} will stop the program only if the condition in
20194 @var{expr} is true. The condition becomes part of the
20195 @samp{-break-list} output (see the description of the @samp{-break-list}
20198 @subsubheading @value{GDBN} Command
20200 The corresponding @value{GDBN} command is @samp{condition}.
20202 @subsubheading Example
20206 -break-condition 1 1
20210 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
20211 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
20212 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
20213 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
20214 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
20215 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
20216 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
20217 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
20218 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
20219 line="5",cond="1",times="0",ignore="3"@}]@}
20223 @subheading The @code{-break-delete} Command
20224 @findex -break-delete
20226 @subsubheading Synopsis
20229 -break-delete ( @var{breakpoint} )+
20232 Delete the breakpoint(s) whose number(s) are specified in the argument
20233 list. This is obviously reflected in the breakpoint list.
20235 @subsubheading @value{GDBN} Command
20237 The corresponding @value{GDBN} command is @samp{delete}.
20239 @subsubheading Example
20247 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
20248 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
20249 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
20250 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
20251 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
20252 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
20253 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
20258 @subheading The @code{-break-disable} Command
20259 @findex -break-disable
20261 @subsubheading Synopsis
20264 -break-disable ( @var{breakpoint} )+
20267 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
20268 break list is now set to @samp{n} for the named @var{breakpoint}(s).
20270 @subsubheading @value{GDBN} Command
20272 The corresponding @value{GDBN} command is @samp{disable}.
20274 @subsubheading Example
20282 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
20283 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
20284 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
20285 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
20286 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
20287 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
20288 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
20289 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
20290 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
20291 line="5",times="0"@}]@}
20295 @subheading The @code{-break-enable} Command
20296 @findex -break-enable
20298 @subsubheading Synopsis
20301 -break-enable ( @var{breakpoint} )+
20304 Enable (previously disabled) @var{breakpoint}(s).
20306 @subsubheading @value{GDBN} Command
20308 The corresponding @value{GDBN} command is @samp{enable}.
20310 @subsubheading Example
20318 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
20319 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
20320 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
20321 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
20322 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
20323 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
20324 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
20325 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
20326 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
20327 line="5",times="0"@}]@}
20331 @subheading The @code{-break-info} Command
20332 @findex -break-info
20334 @subsubheading Synopsis
20337 -break-info @var{breakpoint}
20341 Get information about a single breakpoint.
20343 @subsubheading @value{GDBN} Command
20345 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
20347 @subsubheading Example
20350 @subheading The @code{-break-insert} Command
20351 @findex -break-insert
20353 @subsubheading Synopsis
20356 -break-insert [ -t ] [ -h ] [ -f ] [ -d ]
20357 [ -c @var{condition} ] [ -i @var{ignore-count} ]
20358 [ -p @var{thread} ] [ @var{location} ]
20362 If specified, @var{location}, can be one of:
20369 @item filename:linenum
20370 @item filename:function
20374 The possible optional parameters of this command are:
20378 Insert a temporary breakpoint.
20380 Insert a hardware breakpoint.
20381 @item -c @var{condition}
20382 Make the breakpoint conditional on @var{condition}.
20383 @item -i @var{ignore-count}
20384 Initialize the @var{ignore-count}.
20386 If @var{location} cannot be parsed (for example if it
20387 refers to unknown files or functions), create a pending
20388 breakpoint. Without this flag, @value{GDBN} will report
20389 an error, and won't create a breakpoint, if @var{location}
20392 Create a disabled breakpoint.
20395 @subsubheading Result
20397 The result is in the form:
20400 ^done,bkpt=@{number="@var{number}",type="@var{type}",disp="del"|"keep",
20401 enabled="y"|"n",addr="@var{hex}",func="@var{funcname}",file="@var{filename}",
20402 fullname="@var{full_filename}",line="@var{lineno}",[thread="@var{threadno},]
20403 times="@var{times}"@}
20407 where @var{number} is the @value{GDBN} number for this breakpoint,
20408 @var{funcname} is the name of the function where the breakpoint was
20409 inserted, @var{filename} is the name of the source file which contains
20410 this function, @var{lineno} is the source line number within that file
20411 and @var{times} the number of times that the breakpoint has been hit
20412 (always 0 for -break-insert but may be greater for -break-info or -break-list
20413 which use the same output).
20415 Note: this format is open to change.
20416 @c An out-of-band breakpoint instead of part of the result?
20418 @subsubheading @value{GDBN} Command
20420 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
20421 @samp{hbreak}, @samp{thbreak}, and @samp{rbreak}.
20423 @subsubheading Example
20428 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",
20429 fullname="/home/foo/recursive2.c,line="4",times="0"@}
20431 -break-insert -t foo
20432 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",
20433 fullname="/home/foo/recursive2.c,line="11",times="0"@}
20436 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
20437 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
20438 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
20439 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
20440 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
20441 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
20442 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
20443 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
20444 addr="0x0001072c", func="main",file="recursive2.c",
20445 fullname="/home/foo/recursive2.c,"line="4",times="0"@},
20446 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
20447 addr="0x00010774",func="foo",file="recursive2.c",
20448 fullname="/home/foo/recursive2.c",line="11",times="0"@}]@}
20450 -break-insert -r foo.*
20451 ~int foo(int, int);
20452 ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c,
20453 "fullname="/home/foo/recursive2.c",line="11",times="0"@}
20457 @subheading The @code{-break-list} Command
20458 @findex -break-list
20460 @subsubheading Synopsis
20466 Displays the list of inserted breakpoints, showing the following fields:
20470 number of the breakpoint
20472 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
20474 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
20477 is the breakpoint enabled or no: @samp{y} or @samp{n}
20479 memory location at which the breakpoint is set
20481 logical location of the breakpoint, expressed by function name, file
20484 number of times the breakpoint has been hit
20487 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
20488 @code{body} field is an empty list.
20490 @subsubheading @value{GDBN} Command
20492 The corresponding @value{GDBN} command is @samp{info break}.
20494 @subsubheading Example
20499 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
20500 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
20501 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
20502 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
20503 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
20504 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
20505 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
20506 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
20507 addr="0x000100d0",func="main",file="hello.c",line="5",times="0"@},
20508 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
20509 addr="0x00010114",func="foo",file="hello.c",fullname="/home/foo/hello.c",
20510 line="13",times="0"@}]@}
20514 Here's an example of the result when there are no breakpoints:
20519 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
20520 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
20521 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
20522 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
20523 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
20524 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
20525 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
20530 @subheading The @code{-break-watch} Command
20531 @findex -break-watch
20533 @subsubheading Synopsis
20536 -break-watch [ -a | -r ]
20539 Create a watchpoint. With the @samp{-a} option it will create an
20540 @dfn{access} watchpoint, i.e., a watchpoint that triggers either on a
20541 read from or on a write to the memory location. With the @samp{-r}
20542 option, the watchpoint created is a @dfn{read} watchpoint, i.e., it will
20543 trigger only when the memory location is accessed for reading. Without
20544 either of the options, the watchpoint created is a regular watchpoint,
20545 i.e., it will trigger when the memory location is accessed for writing.
20546 @xref{Set Watchpoints, , Setting Watchpoints}.
20548 Note that @samp{-break-list} will report a single list of watchpoints and
20549 breakpoints inserted.
20551 @subsubheading @value{GDBN} Command
20553 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
20556 @subsubheading Example
20558 Setting a watchpoint on a variable in the @code{main} function:
20563 ^done,wpt=@{number="2",exp="x"@}
20568 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
20569 value=@{old="-268439212",new="55"@},
20570 frame=@{func="main",args=[],file="recursive2.c",
20571 fullname="/home/foo/bar/recursive2.c",line="5"@}
20575 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
20576 the program execution twice: first for the variable changing value, then
20577 for the watchpoint going out of scope.
20582 ^done,wpt=@{number="5",exp="C"@}
20587 *stopped,reason="watchpoint-trigger",
20588 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
20589 frame=@{func="callee4",args=[],
20590 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
20591 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
20596 *stopped,reason="watchpoint-scope",wpnum="5",
20597 frame=@{func="callee3",args=[@{name="strarg",
20598 value="0x11940 \"A string argument.\""@}],
20599 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
20600 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
20604 Listing breakpoints and watchpoints, at different points in the program
20605 execution. Note that once the watchpoint goes out of scope, it is
20611 ^done,wpt=@{number="2",exp="C"@}
20614 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
20615 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
20616 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
20617 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
20618 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
20619 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
20620 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
20621 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
20622 addr="0x00010734",func="callee4",
20623 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
20624 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c"line="8",times="1"@},
20625 bkpt=@{number="2",type="watchpoint",disp="keep",
20626 enabled="y",addr="",what="C",times="0"@}]@}
20631 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
20632 value=@{old="-276895068",new="3"@},
20633 frame=@{func="callee4",args=[],
20634 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
20635 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
20638 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
20639 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
20640 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
20641 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
20642 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
20643 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
20644 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
20645 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
20646 addr="0x00010734",func="callee4",
20647 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
20648 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",times="1"@},
20649 bkpt=@{number="2",type="watchpoint",disp="keep",
20650 enabled="y",addr="",what="C",times="-5"@}]@}
20654 ^done,reason="watchpoint-scope",wpnum="2",
20655 frame=@{func="callee3",args=[@{name="strarg",
20656 value="0x11940 \"A string argument.\""@}],
20657 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
20658 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
20661 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
20662 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
20663 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
20664 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
20665 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
20666 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
20667 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
20668 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
20669 addr="0x00010734",func="callee4",
20670 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
20671 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
20676 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20677 @node GDB/MI Program Context
20678 @section @sc{gdb/mi} Program Context
20680 @subheading The @code{-exec-arguments} Command
20681 @findex -exec-arguments
20684 @subsubheading Synopsis
20687 -exec-arguments @var{args}
20690 Set the inferior program arguments, to be used in the next
20693 @subsubheading @value{GDBN} Command
20695 The corresponding @value{GDBN} command is @samp{set args}.
20697 @subsubheading Example
20701 -exec-arguments -v word
20707 @subheading The @code{-exec-show-arguments} Command
20708 @findex -exec-show-arguments
20710 @subsubheading Synopsis
20713 -exec-show-arguments
20716 Print the arguments of the program.
20718 @subsubheading @value{GDBN} Command
20720 The corresponding @value{GDBN} command is @samp{show args}.
20722 @subsubheading Example
20726 @subheading The @code{-environment-cd} Command
20727 @findex -environment-cd
20729 @subsubheading Synopsis
20732 -environment-cd @var{pathdir}
20735 Set @value{GDBN}'s working directory.
20737 @subsubheading @value{GDBN} Command
20739 The corresponding @value{GDBN} command is @samp{cd}.
20741 @subsubheading Example
20745 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
20751 @subheading The @code{-environment-directory} Command
20752 @findex -environment-directory
20754 @subsubheading Synopsis
20757 -environment-directory [ -r ] [ @var{pathdir} ]+
20760 Add directories @var{pathdir} to beginning of search path for source files.
20761 If the @samp{-r} option is used, the search path is reset to the default
20762 search path. If directories @var{pathdir} are supplied in addition to the
20763 @samp{-r} option, the search path is first reset and then addition
20765 Multiple directories may be specified, separated by blanks. Specifying
20766 multiple directories in a single command
20767 results in the directories added to the beginning of the
20768 search path in the same order they were presented in the command.
20769 If blanks are needed as
20770 part of a directory name, double-quotes should be used around
20771 the name. In the command output, the path will show up separated
20772 by the system directory-separator character. The directory-separator
20773 character must not be used
20774 in any directory name.
20775 If no directories are specified, the current search path is displayed.
20777 @subsubheading @value{GDBN} Command
20779 The corresponding @value{GDBN} command is @samp{dir}.
20781 @subsubheading Example
20785 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
20786 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
20788 -environment-directory ""
20789 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
20791 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
20792 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
20794 -environment-directory -r
20795 ^done,source-path="$cdir:$cwd"
20800 @subheading The @code{-environment-path} Command
20801 @findex -environment-path
20803 @subsubheading Synopsis
20806 -environment-path [ -r ] [ @var{pathdir} ]+
20809 Add directories @var{pathdir} to beginning of search path for object files.
20810 If the @samp{-r} option is used, the search path is reset to the original
20811 search path that existed at gdb start-up. If directories @var{pathdir} are
20812 supplied in addition to the
20813 @samp{-r} option, the search path is first reset and then addition
20815 Multiple directories may be specified, separated by blanks. Specifying
20816 multiple directories in a single command
20817 results in the directories added to the beginning of the
20818 search path in the same order they were presented in the command.
20819 If blanks are needed as
20820 part of a directory name, double-quotes should be used around
20821 the name. In the command output, the path will show up separated
20822 by the system directory-separator character. The directory-separator
20823 character must not be used
20824 in any directory name.
20825 If no directories are specified, the current path is displayed.
20828 @subsubheading @value{GDBN} Command
20830 The corresponding @value{GDBN} command is @samp{path}.
20832 @subsubheading Example
20837 ^done,path="/usr/bin"
20839 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
20840 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
20842 -environment-path -r /usr/local/bin
20843 ^done,path="/usr/local/bin:/usr/bin"
20848 @subheading The @code{-environment-pwd} Command
20849 @findex -environment-pwd
20851 @subsubheading Synopsis
20857 Show the current working directory.
20859 @subsubheading @value{GDBN} Command
20861 The corresponding @value{GDBN} command is @samp{pwd}.
20863 @subsubheading Example
20868 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
20872 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20873 @node GDB/MI Thread Commands
20874 @section @sc{gdb/mi} Thread Commands
20877 @subheading The @code{-thread-info} Command
20878 @findex -thread-info
20880 @subsubheading Synopsis
20883 -thread-info [ @var{thread-id} ]
20886 Reports information about either a specific thread, if
20887 the @var{thread-id} parameter is present, or about all
20888 threads. When printing information about all threads,
20889 also reports the current thread.
20891 @subsubheading @value{GDBN} Command
20893 The @samp{info thread} command prints the same information
20896 @subsubheading Example
20901 @{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
20902 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},state="running"@},
20903 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
20904 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
20905 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},state="running"@}],
20906 current-thread-id="1"
20910 The @samp{state} field may have the following values:
20914 The thread is stopped. Frame information is available for stopped
20918 The thread is running. There's no frame information for running
20923 @subheading The @code{-thread-list-ids} Command
20924 @findex -thread-list-ids
20926 @subsubheading Synopsis
20932 Produces a list of the currently known @value{GDBN} thread ids. At the
20933 end of the list it also prints the total number of such threads.
20935 This command is retained for historical reasons, the
20936 @code{-thread-info} command should be used instead.
20938 @subsubheading @value{GDBN} Command
20940 Part of @samp{info threads} supplies the same information.
20942 @subsubheading Example
20947 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
20948 current-thread-id="1",number-of-threads="3"
20953 @subheading The @code{-thread-select} Command
20954 @findex -thread-select
20956 @subsubheading Synopsis
20959 -thread-select @var{threadnum}
20962 Make @var{threadnum} the current thread. It prints the number of the new
20963 current thread, and the topmost frame for that thread.
20965 This command is deprecated in favor of explicitly using the
20966 @samp{--thread} option to each command.
20968 @subsubheading @value{GDBN} Command
20970 The corresponding @value{GDBN} command is @samp{thread}.
20972 @subsubheading Example
20979 *stopped,reason="end-stepping-range",thread-id="2",line="187",
20980 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
20984 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
20985 number-of-threads="3"
20988 ^done,new-thread-id="3",
20989 frame=@{level="0",func="vprintf",
20990 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
20991 @{name="arg",value="0x2"@}],file="vprintf.c",line="31"@}
20995 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20996 @node GDB/MI Program Execution
20997 @section @sc{gdb/mi} Program Execution
20999 These are the asynchronous commands which generate the out-of-band
21000 record @samp{*stopped}. Currently @value{GDBN} only really executes
21001 asynchronously with remote targets and this interaction is mimicked in
21004 @subheading The @code{-exec-continue} Command
21005 @findex -exec-continue
21007 @subsubheading Synopsis
21010 -exec-continue [--all|--thread-group N]
21013 Resumes the execution of the inferior program until a breakpoint is
21014 encountered, or until the inferior exits. In all-stop mode
21015 (@pxref{All-Stop Mode}), may resume only one thread, or all threads,
21016 depending on the value of the @samp{scheduler-locking} variable. In
21017 non-stop mode (@pxref{Non-Stop Mode}), if the @samp{--all} is not
21018 specified, only the thread specified with the @samp{--thread} option
21019 (or current thread, if no @samp{--thread} is provided) is resumed. If
21020 @samp{--all} is specified, all threads will be resumed. The
21021 @samp{--all} option is ignored in all-stop mode. If the
21022 @samp{--thread-group} options is specified, then all threads in that
21023 thread group are resumed.
21025 @subsubheading @value{GDBN} Command
21027 The corresponding @value{GDBN} corresponding is @samp{continue}.
21029 @subsubheading Example
21036 *stopped,reason="breakpoint-hit",disp="keep",bkptno="2",frame=@{
21037 func="foo",args=[],file="hello.c",fullname="/home/foo/bar/hello.c",
21043 @subheading The @code{-exec-finish} Command
21044 @findex -exec-finish
21046 @subsubheading Synopsis
21052 Resumes the execution of the inferior program until the current
21053 function is exited. Displays the results returned by the function.
21055 @subsubheading @value{GDBN} Command
21057 The corresponding @value{GDBN} command is @samp{finish}.
21059 @subsubheading Example
21061 Function returning @code{void}.
21068 *stopped,reason="function-finished",frame=@{func="main",args=[],
21069 file="hello.c",fullname="/home/foo/bar/hello.c",line="7"@}
21073 Function returning other than @code{void}. The name of the internal
21074 @value{GDBN} variable storing the result is printed, together with the
21081 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
21082 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
21083 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
21084 gdb-result-var="$1",return-value="0"
21089 @subheading The @code{-exec-interrupt} Command
21090 @findex -exec-interrupt
21092 @subsubheading Synopsis
21095 -exec-interrupt [--all|--thread-group N]
21098 Interrupts the background execution of the target. Note how the token
21099 associated with the stop message is the one for the execution command
21100 that has been interrupted. The token for the interrupt itself only
21101 appears in the @samp{^done} output. If the user is trying to
21102 interrupt a non-running program, an error message will be printed.
21104 Note that when asynchronous execution is enabled, this command is
21105 asynchronous just like other execution commands. That is, first the
21106 @samp{^done} response will be printed, and the target stop will be
21107 reported after that using the @samp{*stopped} notification.
21109 In non-stop mode, only the context thread is interrupted by default.
21110 All threads will be interrupted if the @samp{--all} option is
21111 specified. If the @samp{--thread-group} option is specified, all
21112 threads in that group will be interrupted.
21114 @subsubheading @value{GDBN} Command
21116 The corresponding @value{GDBN} command is @samp{interrupt}.
21118 @subsubheading Example
21129 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
21130 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",
21131 fullname="/home/foo/bar/try.c",line="13"@}
21136 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
21141 @subheading The @code{-exec-next} Command
21144 @subsubheading Synopsis
21150 Resumes execution of the inferior program, stopping when the beginning
21151 of the next source line is reached.
21153 @subsubheading @value{GDBN} Command
21155 The corresponding @value{GDBN} command is @samp{next}.
21157 @subsubheading Example
21163 *stopped,reason="end-stepping-range",line="8",file="hello.c"
21168 @subheading The @code{-exec-next-instruction} Command
21169 @findex -exec-next-instruction
21171 @subsubheading Synopsis
21174 -exec-next-instruction
21177 Executes one machine instruction. If the instruction is a function
21178 call, continues until the function returns. If the program stops at an
21179 instruction in the middle of a source line, the address will be
21182 @subsubheading @value{GDBN} Command
21184 The corresponding @value{GDBN} command is @samp{nexti}.
21186 @subsubheading Example
21190 -exec-next-instruction
21194 *stopped,reason="end-stepping-range",
21195 addr="0x000100d4",line="5",file="hello.c"
21200 @subheading The @code{-exec-return} Command
21201 @findex -exec-return
21203 @subsubheading Synopsis
21209 Makes current function return immediately. Doesn't execute the inferior.
21210 Displays the new current frame.
21212 @subsubheading @value{GDBN} Command
21214 The corresponding @value{GDBN} command is @samp{return}.
21216 @subsubheading Example
21220 200-break-insert callee4
21221 200^done,bkpt=@{number="1",addr="0x00010734",
21222 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
21227 000*stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
21228 frame=@{func="callee4",args=[],
21229 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
21230 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
21236 111^done,frame=@{level="0",func="callee3",
21237 args=[@{name="strarg",
21238 value="0x11940 \"A string argument.\""@}],
21239 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
21240 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
21245 @subheading The @code{-exec-run} Command
21248 @subsubheading Synopsis
21254 Starts execution of the inferior from the beginning. The inferior
21255 executes until either a breakpoint is encountered or the program
21256 exits. In the latter case the output will include an exit code, if
21257 the program has exited exceptionally.
21259 @subsubheading @value{GDBN} Command
21261 The corresponding @value{GDBN} command is @samp{run}.
21263 @subsubheading Examples
21268 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
21273 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
21274 frame=@{func="main",args=[],file="recursive2.c",
21275 fullname="/home/foo/bar/recursive2.c",line="4"@}
21280 Program exited normally:
21288 *stopped,reason="exited-normally"
21293 Program exited exceptionally:
21301 *stopped,reason="exited",exit-code="01"
21305 Another way the program can terminate is if it receives a signal such as
21306 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
21310 *stopped,reason="exited-signalled",signal-name="SIGINT",
21311 signal-meaning="Interrupt"
21315 @c @subheading -exec-signal
21318 @subheading The @code{-exec-step} Command
21321 @subsubheading Synopsis
21327 Resumes execution of the inferior program, stopping when the beginning
21328 of the next source line is reached, if the next source line is not a
21329 function call. If it is, stop at the first instruction of the called
21332 @subsubheading @value{GDBN} Command
21334 The corresponding @value{GDBN} command is @samp{step}.
21336 @subsubheading Example
21338 Stepping into a function:
21344 *stopped,reason="end-stepping-range",
21345 frame=@{func="foo",args=[@{name="a",value="10"@},
21346 @{name="b",value="0"@}],file="recursive2.c",
21347 fullname="/home/foo/bar/recursive2.c",line="11"@}
21357 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
21362 @subheading The @code{-exec-step-instruction} Command
21363 @findex -exec-step-instruction
21365 @subsubheading Synopsis
21368 -exec-step-instruction
21371 Resumes the inferior which executes one machine instruction. The
21372 output, once @value{GDBN} has stopped, will vary depending on whether
21373 we have stopped in the middle of a source line or not. In the former
21374 case, the address at which the program stopped will be printed as
21377 @subsubheading @value{GDBN} Command
21379 The corresponding @value{GDBN} command is @samp{stepi}.
21381 @subsubheading Example
21385 -exec-step-instruction
21389 *stopped,reason="end-stepping-range",
21390 frame=@{func="foo",args=[],file="try.c",
21391 fullname="/home/foo/bar/try.c",line="10"@}
21393 -exec-step-instruction
21397 *stopped,reason="end-stepping-range",
21398 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",
21399 fullname="/home/foo/bar/try.c",line="10"@}
21404 @subheading The @code{-exec-until} Command
21405 @findex -exec-until
21407 @subsubheading Synopsis
21410 -exec-until [ @var{location} ]
21413 Executes the inferior until the @var{location} specified in the
21414 argument is reached. If there is no argument, the inferior executes
21415 until a source line greater than the current one is reached. The
21416 reason for stopping in this case will be @samp{location-reached}.
21418 @subsubheading @value{GDBN} Command
21420 The corresponding @value{GDBN} command is @samp{until}.
21422 @subsubheading Example
21426 -exec-until recursive2.c:6
21430 *stopped,reason="location-reached",frame=@{func="main",args=[],
21431 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="6"@}
21436 @subheading -file-clear
21437 Is this going away????
21440 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
21441 @node GDB/MI Stack Manipulation
21442 @section @sc{gdb/mi} Stack Manipulation Commands
21445 @subheading The @code{-stack-info-frame} Command
21446 @findex -stack-info-frame
21448 @subsubheading Synopsis
21454 Get info on the selected frame.
21456 @subsubheading @value{GDBN} Command
21458 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
21459 (without arguments).
21461 @subsubheading Example
21466 ^done,frame=@{level="1",addr="0x0001076c",func="callee3",
21467 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
21468 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@}
21472 @subheading The @code{-stack-info-depth} Command
21473 @findex -stack-info-depth
21475 @subsubheading Synopsis
21478 -stack-info-depth [ @var{max-depth} ]
21481 Return the depth of the stack. If the integer argument @var{max-depth}
21482 is specified, do not count beyond @var{max-depth} frames.
21484 @subsubheading @value{GDBN} Command
21486 There's no equivalent @value{GDBN} command.
21488 @subsubheading Example
21490 For a stack with frame levels 0 through 11:
21497 -stack-info-depth 4
21500 -stack-info-depth 12
21503 -stack-info-depth 11
21506 -stack-info-depth 13
21511 @subheading The @code{-stack-list-arguments} Command
21512 @findex -stack-list-arguments
21514 @subsubheading Synopsis
21517 -stack-list-arguments @var{show-values}
21518 [ @var{low-frame} @var{high-frame} ]
21521 Display a list of the arguments for the frames between @var{low-frame}
21522 and @var{high-frame} (inclusive). If @var{low-frame} and
21523 @var{high-frame} are not provided, list the arguments for the whole
21524 call stack. If the two arguments are equal, show the single frame
21525 at the corresponding level. It is an error if @var{low-frame} is
21526 larger than the actual number of frames. On the other hand,
21527 @var{high-frame} may be larger than the actual number of frames, in
21528 which case only existing frames will be returned.
21530 The @var{show-values} argument must have a value of 0 or 1. A value of
21531 0 means that only the names of the arguments are listed, a value of 1
21532 means that both names and values of the arguments are printed.
21534 @subsubheading @value{GDBN} Command
21536 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
21537 @samp{gdb_get_args} command which partially overlaps with the
21538 functionality of @samp{-stack-list-arguments}.
21540 @subsubheading Example
21547 frame=@{level="0",addr="0x00010734",func="callee4",
21548 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
21549 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@},
21550 frame=@{level="1",addr="0x0001076c",func="callee3",
21551 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
21552 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@},
21553 frame=@{level="2",addr="0x0001078c",func="callee2",
21554 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
21555 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="22"@},
21556 frame=@{level="3",addr="0x000107b4",func="callee1",
21557 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
21558 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="27"@},
21559 frame=@{level="4",addr="0x000107e0",func="main",
21560 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
21561 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="32"@}]
21563 -stack-list-arguments 0
21566 frame=@{level="0",args=[]@},
21567 frame=@{level="1",args=[name="strarg"]@},
21568 frame=@{level="2",args=[name="intarg",name="strarg"]@},
21569 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
21570 frame=@{level="4",args=[]@}]
21572 -stack-list-arguments 1
21575 frame=@{level="0",args=[]@},
21577 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
21578 frame=@{level="2",args=[
21579 @{name="intarg",value="2"@},
21580 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
21581 @{frame=@{level="3",args=[
21582 @{name="intarg",value="2"@},
21583 @{name="strarg",value="0x11940 \"A string argument.\""@},
21584 @{name="fltarg",value="3.5"@}]@},
21585 frame=@{level="4",args=[]@}]
21587 -stack-list-arguments 0 2 2
21588 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
21590 -stack-list-arguments 1 2 2
21591 ^done,stack-args=[frame=@{level="2",
21592 args=[@{name="intarg",value="2"@},
21593 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
21597 @c @subheading -stack-list-exception-handlers
21600 @subheading The @code{-stack-list-frames} Command
21601 @findex -stack-list-frames
21603 @subsubheading Synopsis
21606 -stack-list-frames [ @var{low-frame} @var{high-frame} ]
21609 List the frames currently on the stack. For each frame it displays the
21614 The frame number, 0 being the topmost frame, i.e., the innermost function.
21616 The @code{$pc} value for that frame.
21620 File name of the source file where the function lives.
21622 Line number corresponding to the @code{$pc}.
21625 If invoked without arguments, this command prints a backtrace for the
21626 whole stack. If given two integer arguments, it shows the frames whose
21627 levels are between the two arguments (inclusive). If the two arguments
21628 are equal, it shows the single frame at the corresponding level. It is
21629 an error if @var{low-frame} is larger than the actual number of
21630 frames. On the other hand, @var{high-frame} may be larger than the
21631 actual number of frames, in which case only existing frames will be returned.
21633 @subsubheading @value{GDBN} Command
21635 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
21637 @subsubheading Example
21639 Full stack backtrace:
21645 [frame=@{level="0",addr="0x0001076c",func="foo",
21646 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="11"@},
21647 frame=@{level="1",addr="0x000107a4",func="foo",
21648 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
21649 frame=@{level="2",addr="0x000107a4",func="foo",
21650 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
21651 frame=@{level="3",addr="0x000107a4",func="foo",
21652 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
21653 frame=@{level="4",addr="0x000107a4",func="foo",
21654 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
21655 frame=@{level="5",addr="0x000107a4",func="foo",
21656 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
21657 frame=@{level="6",addr="0x000107a4",func="foo",
21658 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
21659 frame=@{level="7",addr="0x000107a4",func="foo",
21660 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
21661 frame=@{level="8",addr="0x000107a4",func="foo",
21662 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
21663 frame=@{level="9",addr="0x000107a4",func="foo",
21664 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
21665 frame=@{level="10",addr="0x000107a4",func="foo",
21666 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
21667 frame=@{level="11",addr="0x00010738",func="main",
21668 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="4"@}]
21672 Show frames between @var{low_frame} and @var{high_frame}:
21676 -stack-list-frames 3 5
21678 [frame=@{level="3",addr="0x000107a4",func="foo",
21679 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
21680 frame=@{level="4",addr="0x000107a4",func="foo",
21681 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
21682 frame=@{level="5",addr="0x000107a4",func="foo",
21683 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
21687 Show a single frame:
21691 -stack-list-frames 3 3
21693 [frame=@{level="3",addr="0x000107a4",func="foo",
21694 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
21699 @subheading The @code{-stack-list-locals} Command
21700 @findex -stack-list-locals
21702 @subsubheading Synopsis
21705 -stack-list-locals @var{print-values}
21708 Display the local variable names for the selected frame. If
21709 @var{print-values} is 0 or @code{--no-values}, print only the names of
21710 the variables; if it is 1 or @code{--all-values}, print also their
21711 values; and if it is 2 or @code{--simple-values}, print the name,
21712 type and value for simple data types and the name and type for arrays,
21713 structures and unions. In this last case, a frontend can immediately
21714 display the value of simple data types and create variable objects for
21715 other data types when the user wishes to explore their values in
21718 @subsubheading @value{GDBN} Command
21720 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
21722 @subsubheading Example
21726 -stack-list-locals 0
21727 ^done,locals=[name="A",name="B",name="C"]
21729 -stack-list-locals --all-values
21730 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
21731 @{name="C",value="@{1, 2, 3@}"@}]
21732 -stack-list-locals --simple-values
21733 ^done,locals=[@{name="A",type="int",value="1"@},
21734 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
21739 @subheading The @code{-stack-select-frame} Command
21740 @findex -stack-select-frame
21742 @subsubheading Synopsis
21745 -stack-select-frame @var{framenum}
21748 Change the selected frame. Select a different frame @var{framenum} on
21751 This command in deprecated in favor of passing the @samp{--frame}
21752 option to every command.
21754 @subsubheading @value{GDBN} Command
21756 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
21757 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
21759 @subsubheading Example
21763 -stack-select-frame 2
21768 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
21769 @node GDB/MI Variable Objects
21770 @section @sc{gdb/mi} Variable Objects
21774 @subheading Motivation for Variable Objects in @sc{gdb/mi}
21776 For the implementation of a variable debugger window (locals, watched
21777 expressions, etc.), we are proposing the adaptation of the existing code
21778 used by @code{Insight}.
21780 The two main reasons for that are:
21784 It has been proven in practice (it is already on its second generation).
21787 It will shorten development time (needless to say how important it is
21791 The original interface was designed to be used by Tcl code, so it was
21792 slightly changed so it could be used through @sc{gdb/mi}. This section
21793 describes the @sc{gdb/mi} operations that will be available and gives some
21794 hints about their use.
21796 @emph{Note}: In addition to the set of operations described here, we
21797 expect the @sc{gui} implementation of a variable window to require, at
21798 least, the following operations:
21801 @item @code{-gdb-show} @code{output-radix}
21802 @item @code{-stack-list-arguments}
21803 @item @code{-stack-list-locals}
21804 @item @code{-stack-select-frame}
21809 @subheading Introduction to Variable Objects
21811 @cindex variable objects in @sc{gdb/mi}
21813 Variable objects are "object-oriented" MI interface for examining and
21814 changing values of expressions. Unlike some other MI interfaces that
21815 work with expressions, variable objects are specifically designed for
21816 simple and efficient presentation in the frontend. A variable object
21817 is identified by string name. When a variable object is created, the
21818 frontend specifies the expression for that variable object. The
21819 expression can be a simple variable, or it can be an arbitrary complex
21820 expression, and can even involve CPU registers. After creating a
21821 variable object, the frontend can invoke other variable object
21822 operations---for example to obtain or change the value of a variable
21823 object, or to change display format.
21825 Variable objects have hierarchical tree structure. Any variable object
21826 that corresponds to a composite type, such as structure in C, has
21827 a number of child variable objects, for example corresponding to each
21828 element of a structure. A child variable object can itself have
21829 children, recursively. Recursion ends when we reach
21830 leaf variable objects, which always have built-in types. Child variable
21831 objects are created only by explicit request, so if a frontend
21832 is not interested in the children of a particular variable object, no
21833 child will be created.
21835 For a leaf variable object it is possible to obtain its value as a
21836 string, or set the value from a string. String value can be also
21837 obtained for a non-leaf variable object, but it's generally a string
21838 that only indicates the type of the object, and does not list its
21839 contents. Assignment to a non-leaf variable object is not allowed.
21841 A frontend does not need to read the values of all variable objects each time
21842 the program stops. Instead, MI provides an update command that lists all
21843 variable objects whose values has changed since the last update
21844 operation. This considerably reduces the amount of data that must
21845 be transferred to the frontend. As noted above, children variable
21846 objects are created on demand, and only leaf variable objects have a
21847 real value. As result, gdb will read target memory only for leaf
21848 variables that frontend has created.
21850 The automatic update is not always desirable. For example, a frontend
21851 might want to keep a value of some expression for future reference,
21852 and never update it. For another example, fetching memory is
21853 relatively slow for embedded targets, so a frontend might want
21854 to disable automatic update for the variables that are either not
21855 visible on the screen, or ``closed''. This is possible using so
21856 called ``frozen variable objects''. Such variable objects are never
21857 implicitly updated.
21859 Variable objects can be either @dfn{fixed} or @dfn{floating}. For the
21860 fixed variable object, the expression is parsed when the variable
21861 object is created, including associating identifiers to specific
21862 variables. The meaning of expression never changes. For a floating
21863 variable object the values of variables whose names appear in the
21864 expressions are re-evaluated every time in the context of the current
21865 frame. Consider this example:
21870 struct work_state state;
21877 If a fixed variable object for the @code{state} variable is created in
21878 this function, and we enter the recursive call, the the variable
21879 object will report the value of @code{state} in the top-level
21880 @code{do_work} invocation. On the other hand, a floating variable
21881 object will report the value of @code{state} in the current frame.
21883 If an expression specified when creating a fixed variable object
21884 refers to a local variable, the variable object becomes bound to the
21885 thread and frame in which the variable object is created. When such
21886 variable object is updated, @value{GDBN} makes sure that the
21887 thread/frame combination the variable object is bound to still exists,
21888 and re-evaluates the variable object in context of that thread/frame.
21890 The following is the complete set of @sc{gdb/mi} operations defined to
21891 access this functionality:
21893 @multitable @columnfractions .4 .6
21894 @item @strong{Operation}
21895 @tab @strong{Description}
21897 @item @code{-var-create}
21898 @tab create a variable object
21899 @item @code{-var-delete}
21900 @tab delete the variable object and/or its children
21901 @item @code{-var-set-format}
21902 @tab set the display format of this variable
21903 @item @code{-var-show-format}
21904 @tab show the display format of this variable
21905 @item @code{-var-info-num-children}
21906 @tab tells how many children this object has
21907 @item @code{-var-list-children}
21908 @tab return a list of the object's children
21909 @item @code{-var-info-type}
21910 @tab show the type of this variable object
21911 @item @code{-var-info-expression}
21912 @tab print parent-relative expression that this variable object represents
21913 @item @code{-var-info-path-expression}
21914 @tab print full expression that this variable object represents
21915 @item @code{-var-show-attributes}
21916 @tab is this variable editable? does it exist here?
21917 @item @code{-var-evaluate-expression}
21918 @tab get the value of this variable
21919 @item @code{-var-assign}
21920 @tab set the value of this variable
21921 @item @code{-var-update}
21922 @tab update the variable and its children
21923 @item @code{-var-set-frozen}
21924 @tab set frozeness attribute
21927 In the next subsection we describe each operation in detail and suggest
21928 how it can be used.
21930 @subheading Description And Use of Operations on Variable Objects
21932 @subheading The @code{-var-create} Command
21933 @findex -var-create
21935 @subsubheading Synopsis
21938 -var-create @{@var{name} | "-"@}
21939 @{@var{frame-addr} | "*" | "@@"@} @var{expression}
21942 This operation creates a variable object, which allows the monitoring of
21943 a variable, the result of an expression, a memory cell or a CPU
21946 The @var{name} parameter is the string by which the object can be
21947 referenced. It must be unique. If @samp{-} is specified, the varobj
21948 system will generate a string ``varNNNNNN'' automatically. It will be
21949 unique provided that one does not specify @var{name} of that format.
21950 The command fails if a duplicate name is found.
21952 The frame under which the expression should be evaluated can be
21953 specified by @var{frame-addr}. A @samp{*} indicates that the current
21954 frame should be used. A @samp{@@} indicates that a floating variable
21955 object must be created.
21957 @var{expression} is any expression valid on the current language set (must not
21958 begin with a @samp{*}), or one of the following:
21962 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
21965 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
21968 @samp{$@var{regname}} --- a CPU register name
21971 @subsubheading Result
21973 This operation returns the name, number of children and the type of the
21974 object created. Type is returned as a string as the ones generated by
21975 the @value{GDBN} CLI. If a fixed variable object is bound to a
21976 specific thread, the thread is is also printed:
21979 name="@var{name}",numchild="@var{N}",type="@var{type}",thread-id="@var{M}"
21983 @subheading The @code{-var-delete} Command
21984 @findex -var-delete
21986 @subsubheading Synopsis
21989 -var-delete [ -c ] @var{name}
21992 Deletes a previously created variable object and all of its children.
21993 With the @samp{-c} option, just deletes the children.
21995 Returns an error if the object @var{name} is not found.
21998 @subheading The @code{-var-set-format} Command
21999 @findex -var-set-format
22001 @subsubheading Synopsis
22004 -var-set-format @var{name} @var{format-spec}
22007 Sets the output format for the value of the object @var{name} to be
22010 @anchor{-var-set-format}
22011 The syntax for the @var{format-spec} is as follows:
22014 @var{format-spec} @expansion{}
22015 @{binary | decimal | hexadecimal | octal | natural@}
22018 The natural format is the default format choosen automatically
22019 based on the variable type (like decimal for an @code{int}, hex
22020 for pointers, etc.).
22022 For a variable with children, the format is set only on the
22023 variable itself, and the children are not affected.
22025 @subheading The @code{-var-show-format} Command
22026 @findex -var-show-format
22028 @subsubheading Synopsis
22031 -var-show-format @var{name}
22034 Returns the format used to display the value of the object @var{name}.
22037 @var{format} @expansion{}
22042 @subheading The @code{-var-info-num-children} Command
22043 @findex -var-info-num-children
22045 @subsubheading Synopsis
22048 -var-info-num-children @var{name}
22051 Returns the number of children of a variable object @var{name}:
22058 @subheading The @code{-var-list-children} Command
22059 @findex -var-list-children
22061 @subsubheading Synopsis
22064 -var-list-children [@var{print-values}] @var{name}
22066 @anchor{-var-list-children}
22068 Return a list of the children of the specified variable object and
22069 create variable objects for them, if they do not already exist. With
22070 a single argument or if @var{print-values} has a value for of 0 or
22071 @code{--no-values}, print only the names of the variables; if
22072 @var{print-values} is 1 or @code{--all-values}, also print their
22073 values; and if it is 2 or @code{--simple-values} print the name and
22074 value for simple data types and just the name for arrays, structures
22077 @subsubheading Example
22081 -var-list-children n
22082 ^done,numchild=@var{n},children=[@{name=@var{name},
22083 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
22085 -var-list-children --all-values n
22086 ^done,numchild=@var{n},children=[@{name=@var{name},
22087 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
22091 @subheading The @code{-var-info-type} Command
22092 @findex -var-info-type
22094 @subsubheading Synopsis
22097 -var-info-type @var{name}
22100 Returns the type of the specified variable @var{name}. The type is
22101 returned as a string in the same format as it is output by the
22105 type=@var{typename}
22109 @subheading The @code{-var-info-expression} Command
22110 @findex -var-info-expression
22112 @subsubheading Synopsis
22115 -var-info-expression @var{name}
22118 Returns a string that is suitable for presenting this
22119 variable object in user interface. The string is generally
22120 not valid expression in the current language, and cannot be evaluated.
22122 For example, if @code{a} is an array, and variable object
22123 @code{A} was created for @code{a}, then we'll get this output:
22126 (gdb) -var-info-expression A.1
22127 ^done,lang="C",exp="1"
22131 Here, the values of @code{lang} can be @code{@{"C" | "C++" | "Java"@}}.
22133 Note that the output of the @code{-var-list-children} command also
22134 includes those expressions, so the @code{-var-info-expression} command
22137 @subheading The @code{-var-info-path-expression} Command
22138 @findex -var-info-path-expression
22140 @subsubheading Synopsis
22143 -var-info-path-expression @var{name}
22146 Returns an expression that can be evaluated in the current
22147 context and will yield the same value that a variable object has.
22148 Compare this with the @code{-var-info-expression} command, which
22149 result can be used only for UI presentation. Typical use of
22150 the @code{-var-info-path-expression} command is creating a
22151 watchpoint from a variable object.
22153 For example, suppose @code{C} is a C@t{++} class, derived from class
22154 @code{Base}, and that the @code{Base} class has a member called
22155 @code{m_size}. Assume a variable @code{c} is has the type of
22156 @code{C} and a variable object @code{C} was created for variable
22157 @code{c}. Then, we'll get this output:
22159 (gdb) -var-info-path-expression C.Base.public.m_size
22160 ^done,path_expr=((Base)c).m_size)
22163 @subheading The @code{-var-show-attributes} Command
22164 @findex -var-show-attributes
22166 @subsubheading Synopsis
22169 -var-show-attributes @var{name}
22172 List attributes of the specified variable object @var{name}:
22175 status=@var{attr} [ ( ,@var{attr} )* ]
22179 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
22181 @subheading The @code{-var-evaluate-expression} Command
22182 @findex -var-evaluate-expression
22184 @subsubheading Synopsis
22187 -var-evaluate-expression [-f @var{format-spec}] @var{name}
22190 Evaluates the expression that is represented by the specified variable
22191 object and returns its value as a string. The format of the string
22192 can be specified with the @samp{-f} option. The possible values of
22193 this option are the same as for @code{-var-set-format}
22194 (@pxref{-var-set-format}). If the @samp{-f} option is not specified,
22195 the current display format will be used. The current display format
22196 can be changed using the @code{-var-set-format} command.
22202 Note that one must invoke @code{-var-list-children} for a variable
22203 before the value of a child variable can be evaluated.
22205 @subheading The @code{-var-assign} Command
22206 @findex -var-assign
22208 @subsubheading Synopsis
22211 -var-assign @var{name} @var{expression}
22214 Assigns the value of @var{expression} to the variable object specified
22215 by @var{name}. The object must be @samp{editable}. If the variable's
22216 value is altered by the assign, the variable will show up in any
22217 subsequent @code{-var-update} list.
22219 @subsubheading Example
22227 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
22231 @subheading The @code{-var-update} Command
22232 @findex -var-update
22234 @subsubheading Synopsis
22237 -var-update [@var{print-values}] @{@var{name} | "*"@}
22240 Reevaluate the expressions corresponding to the variable object
22241 @var{name} and all its direct and indirect children, and return the
22242 list of variable objects whose values have changed; @var{name} must
22243 be a root variable object. Here, ``changed'' means that the result of
22244 @code{-var-evaluate-expression} before and after the
22245 @code{-var-update} is different. If @samp{*} is used as the variable
22246 object names, all existing variable objects are updated, except
22247 for frozen ones (@pxref{-var-set-frozen}). The option
22248 @var{print-values} determines whether both names and values, or just
22249 names are printed. The possible values of this option are the same
22250 as for @code{-var-list-children} (@pxref{-var-list-children}). It is
22251 recommended to use the @samp{--all-values} option, to reduce the
22252 number of MI commands needed on each program stop.
22254 With the @samp{*} parameter, if a variable object is bound to a
22255 currently running thread, it will not be updated, without any
22258 @subsubheading Example
22265 -var-update --all-values var1
22266 ^done,changelist=[@{name="var1",value="3",in_scope="true",
22267 type_changed="false"@}]
22271 @anchor{-var-update}
22272 The field in_scope may take three values:
22276 The variable object's current value is valid.
22279 The variable object does not currently hold a valid value but it may
22280 hold one in the future if its associated expression comes back into
22284 The variable object no longer holds a valid value.
22285 This can occur when the executable file being debugged has changed,
22286 either through recompilation or by using the @value{GDBN} @code{file}
22287 command. The front end should normally choose to delete these variable
22291 In the future new values may be added to this list so the front should
22292 be prepared for this possibility. @xref{GDB/MI Development and Front Ends, ,@sc{GDB/MI} Development and Front Ends}.
22294 @subheading The @code{-var-set-frozen} Command
22295 @findex -var-set-frozen
22296 @anchor{-var-set-frozen}
22298 @subsubheading Synopsis
22301 -var-set-frozen @var{name} @var{flag}
22304 Set the frozenness flag on the variable object @var{name}. The
22305 @var{flag} parameter should be either @samp{1} to make the variable
22306 frozen or @samp{0} to make it unfrozen. If a variable object is
22307 frozen, then neither itself, nor any of its children, are
22308 implicitly updated by @code{-var-update} of
22309 a parent variable or by @code{-var-update *}. Only
22310 @code{-var-update} of the variable itself will update its value and
22311 values of its children. After a variable object is unfrozen, it is
22312 implicitly updated by all subsequent @code{-var-update} operations.
22313 Unfreezing a variable does not update it, only subsequent
22314 @code{-var-update} does.
22316 @subsubheading Example
22320 -var-set-frozen V 1
22326 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
22327 @node GDB/MI Data Manipulation
22328 @section @sc{gdb/mi} Data Manipulation
22330 @cindex data manipulation, in @sc{gdb/mi}
22331 @cindex @sc{gdb/mi}, data manipulation
22332 This section describes the @sc{gdb/mi} commands that manipulate data:
22333 examine memory and registers, evaluate expressions, etc.
22335 @c REMOVED FROM THE INTERFACE.
22336 @c @subheading -data-assign
22337 @c Change the value of a program variable. Plenty of side effects.
22338 @c @subsubheading GDB Command
22340 @c @subsubheading Example
22343 @subheading The @code{-data-disassemble} Command
22344 @findex -data-disassemble
22346 @subsubheading Synopsis
22350 [ -s @var{start-addr} -e @var{end-addr} ]
22351 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
22359 @item @var{start-addr}
22360 is the beginning address (or @code{$pc})
22361 @item @var{end-addr}
22363 @item @var{filename}
22364 is the name of the file to disassemble
22365 @item @var{linenum}
22366 is the line number to disassemble around
22368 is the number of disassembly lines to be produced. If it is -1,
22369 the whole function will be disassembled, in case no @var{end-addr} is
22370 specified. If @var{end-addr} is specified as a non-zero value, and
22371 @var{lines} is lower than the number of disassembly lines between
22372 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
22373 displayed; if @var{lines} is higher than the number of lines between
22374 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
22377 is either 0 (meaning only disassembly) or 1 (meaning mixed source and
22381 @subsubheading Result
22383 The output for each instruction is composed of four fields:
22392 Note that whatever included in the instruction field, is not manipulated
22393 directly by @sc{gdb/mi}, i.e., it is not possible to adjust its format.
22395 @subsubheading @value{GDBN} Command
22397 There's no direct mapping from this command to the CLI.
22399 @subsubheading Example
22401 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
22405 -data-disassemble -s $pc -e "$pc + 20" -- 0
22408 @{address="0x000107c0",func-name="main",offset="4",
22409 inst="mov 2, %o0"@},
22410 @{address="0x000107c4",func-name="main",offset="8",
22411 inst="sethi %hi(0x11800), %o2"@},
22412 @{address="0x000107c8",func-name="main",offset="12",
22413 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
22414 @{address="0x000107cc",func-name="main",offset="16",
22415 inst="sethi %hi(0x11800), %o2"@},
22416 @{address="0x000107d0",func-name="main",offset="20",
22417 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
22421 Disassemble the whole @code{main} function. Line 32 is part of
22425 -data-disassemble -f basics.c -l 32 -- 0
22427 @{address="0x000107bc",func-name="main",offset="0",
22428 inst="save %sp, -112, %sp"@},
22429 @{address="0x000107c0",func-name="main",offset="4",
22430 inst="mov 2, %o0"@},
22431 @{address="0x000107c4",func-name="main",offset="8",
22432 inst="sethi %hi(0x11800), %o2"@},
22434 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
22435 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
22439 Disassemble 3 instructions from the start of @code{main}:
22443 -data-disassemble -f basics.c -l 32 -n 3 -- 0
22445 @{address="0x000107bc",func-name="main",offset="0",
22446 inst="save %sp, -112, %sp"@},
22447 @{address="0x000107c0",func-name="main",offset="4",
22448 inst="mov 2, %o0"@},
22449 @{address="0x000107c4",func-name="main",offset="8",
22450 inst="sethi %hi(0x11800), %o2"@}]
22454 Disassemble 3 instructions from the start of @code{main} in mixed mode:
22458 -data-disassemble -f basics.c -l 32 -n 3 -- 1
22460 src_and_asm_line=@{line="31",
22461 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
22462 testsuite/gdb.mi/basics.c",line_asm_insn=[
22463 @{address="0x000107bc",func-name="main",offset="0",
22464 inst="save %sp, -112, %sp"@}]@},
22465 src_and_asm_line=@{line="32",
22466 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
22467 testsuite/gdb.mi/basics.c",line_asm_insn=[
22468 @{address="0x000107c0",func-name="main",offset="4",
22469 inst="mov 2, %o0"@},
22470 @{address="0x000107c4",func-name="main",offset="8",
22471 inst="sethi %hi(0x11800), %o2"@}]@}]
22476 @subheading The @code{-data-evaluate-expression} Command
22477 @findex -data-evaluate-expression
22479 @subsubheading Synopsis
22482 -data-evaluate-expression @var{expr}
22485 Evaluate @var{expr} as an expression. The expression could contain an
22486 inferior function call. The function call will execute synchronously.
22487 If the expression contains spaces, it must be enclosed in double quotes.
22489 @subsubheading @value{GDBN} Command
22491 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
22492 @samp{call}. In @code{gdbtk} only, there's a corresponding
22493 @samp{gdb_eval} command.
22495 @subsubheading Example
22497 In the following example, the numbers that precede the commands are the
22498 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
22499 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
22503 211-data-evaluate-expression A
22506 311-data-evaluate-expression &A
22507 311^done,value="0xefffeb7c"
22509 411-data-evaluate-expression A+3
22512 511-data-evaluate-expression "A + 3"
22518 @subheading The @code{-data-list-changed-registers} Command
22519 @findex -data-list-changed-registers
22521 @subsubheading Synopsis
22524 -data-list-changed-registers
22527 Display a list of the registers that have changed.
22529 @subsubheading @value{GDBN} Command
22531 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
22532 has the corresponding command @samp{gdb_changed_register_list}.
22534 @subsubheading Example
22536 On a PPC MBX board:
22544 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",frame=@{
22545 func="main",args=[],file="try.c",fullname="/home/foo/bar/try.c",
22548 -data-list-changed-registers
22549 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
22550 "10","11","13","14","15","16","17","18","19","20","21","22","23",
22551 "24","25","26","27","28","30","31","64","65","66","67","69"]
22556 @subheading The @code{-data-list-register-names} Command
22557 @findex -data-list-register-names
22559 @subsubheading Synopsis
22562 -data-list-register-names [ ( @var{regno} )+ ]
22565 Show a list of register names for the current target. If no arguments
22566 are given, it shows a list of the names of all the registers. If
22567 integer numbers are given as arguments, it will print a list of the
22568 names of the registers corresponding to the arguments. To ensure
22569 consistency between a register name and its number, the output list may
22570 include empty register names.
22572 @subsubheading @value{GDBN} Command
22574 @value{GDBN} does not have a command which corresponds to
22575 @samp{-data-list-register-names}. In @code{gdbtk} there is a
22576 corresponding command @samp{gdb_regnames}.
22578 @subsubheading Example
22580 For the PPC MBX board:
22583 -data-list-register-names
22584 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
22585 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
22586 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
22587 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
22588 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
22589 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
22590 "", "pc","ps","cr","lr","ctr","xer"]
22592 -data-list-register-names 1 2 3
22593 ^done,register-names=["r1","r2","r3"]
22597 @subheading The @code{-data-list-register-values} Command
22598 @findex -data-list-register-values
22600 @subsubheading Synopsis
22603 -data-list-register-values @var{fmt} [ ( @var{regno} )*]
22606 Display the registers' contents. @var{fmt} is the format according to
22607 which the registers' contents are to be returned, followed by an optional
22608 list of numbers specifying the registers to display. A missing list of
22609 numbers indicates that the contents of all the registers must be returned.
22611 Allowed formats for @var{fmt} are:
22628 @subsubheading @value{GDBN} Command
22630 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
22631 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
22633 @subsubheading Example
22635 For a PPC MBX board (note: line breaks are for readability only, they
22636 don't appear in the actual output):
22640 -data-list-register-values r 64 65
22641 ^done,register-values=[@{number="64",value="0xfe00a300"@},
22642 @{number="65",value="0x00029002"@}]
22644 -data-list-register-values x
22645 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
22646 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
22647 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
22648 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
22649 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
22650 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
22651 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
22652 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
22653 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
22654 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
22655 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
22656 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
22657 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
22658 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
22659 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
22660 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
22661 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
22662 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
22663 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
22664 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
22665 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
22666 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
22667 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
22668 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
22669 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
22670 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
22671 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
22672 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
22673 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
22674 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
22675 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
22676 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
22677 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
22678 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
22679 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
22680 @{number="69",value="0x20002b03"@}]
22685 @subheading The @code{-data-read-memory} Command
22686 @findex -data-read-memory
22688 @subsubheading Synopsis
22691 -data-read-memory [ -o @var{byte-offset} ]
22692 @var{address} @var{word-format} @var{word-size}
22693 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
22700 @item @var{address}
22701 An expression specifying the address of the first memory word to be
22702 read. Complex expressions containing embedded white space should be
22703 quoted using the C convention.
22705 @item @var{word-format}
22706 The format to be used to print the memory words. The notation is the
22707 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
22710 @item @var{word-size}
22711 The size of each memory word in bytes.
22713 @item @var{nr-rows}
22714 The number of rows in the output table.
22716 @item @var{nr-cols}
22717 The number of columns in the output table.
22720 If present, indicates that each row should include an @sc{ascii} dump. The
22721 value of @var{aschar} is used as a padding character when a byte is not a
22722 member of the printable @sc{ascii} character set (printable @sc{ascii}
22723 characters are those whose code is between 32 and 126, inclusively).
22725 @item @var{byte-offset}
22726 An offset to add to the @var{address} before fetching memory.
22729 This command displays memory contents as a table of @var{nr-rows} by
22730 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
22731 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
22732 (returned as @samp{total-bytes}). Should less than the requested number
22733 of bytes be returned by the target, the missing words are identified
22734 using @samp{N/A}. The number of bytes read from the target is returned
22735 in @samp{nr-bytes} and the starting address used to read memory in
22738 The address of the next/previous row or page is available in
22739 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
22742 @subsubheading @value{GDBN} Command
22744 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
22745 @samp{gdb_get_mem} memory read command.
22747 @subsubheading Example
22749 Read six bytes of memory starting at @code{bytes+6} but then offset by
22750 @code{-6} bytes. Format as three rows of two columns. One byte per
22751 word. Display each word in hex.
22755 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
22756 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
22757 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
22758 prev-page="0x0000138a",memory=[
22759 @{addr="0x00001390",data=["0x00","0x01"]@},
22760 @{addr="0x00001392",data=["0x02","0x03"]@},
22761 @{addr="0x00001394",data=["0x04","0x05"]@}]
22765 Read two bytes of memory starting at address @code{shorts + 64} and
22766 display as a single word formatted in decimal.
22770 5-data-read-memory shorts+64 d 2 1 1
22771 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
22772 next-row="0x00001512",prev-row="0x0000150e",
22773 next-page="0x00001512",prev-page="0x0000150e",memory=[
22774 @{addr="0x00001510",data=["128"]@}]
22778 Read thirty two bytes of memory starting at @code{bytes+16} and format
22779 as eight rows of four columns. Include a string encoding with @samp{x}
22780 used as the non-printable character.
22784 4-data-read-memory bytes+16 x 1 8 4 x
22785 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
22786 next-row="0x000013c0",prev-row="0x0000139c",
22787 next-page="0x000013c0",prev-page="0x00001380",memory=[
22788 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
22789 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
22790 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
22791 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
22792 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
22793 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
22794 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
22795 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
22799 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
22800 @node GDB/MI Tracepoint Commands
22801 @section @sc{gdb/mi} Tracepoint Commands
22803 The tracepoint commands are not yet implemented.
22805 @c @subheading -trace-actions
22807 @c @subheading -trace-delete
22809 @c @subheading -trace-disable
22811 @c @subheading -trace-dump
22813 @c @subheading -trace-enable
22815 @c @subheading -trace-exists
22817 @c @subheading -trace-find
22819 @c @subheading -trace-frame-number
22821 @c @subheading -trace-info
22823 @c @subheading -trace-insert
22825 @c @subheading -trace-list
22827 @c @subheading -trace-pass-count
22829 @c @subheading -trace-save
22831 @c @subheading -trace-start
22833 @c @subheading -trace-stop
22836 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
22837 @node GDB/MI Symbol Query
22838 @section @sc{gdb/mi} Symbol Query Commands
22841 @subheading The @code{-symbol-info-address} Command
22842 @findex -symbol-info-address
22844 @subsubheading Synopsis
22847 -symbol-info-address @var{symbol}
22850 Describe where @var{symbol} is stored.
22852 @subsubheading @value{GDBN} Command
22854 The corresponding @value{GDBN} command is @samp{info address}.
22856 @subsubheading Example
22860 @subheading The @code{-symbol-info-file} Command
22861 @findex -symbol-info-file
22863 @subsubheading Synopsis
22869 Show the file for the symbol.
22871 @subsubheading @value{GDBN} Command
22873 There's no equivalent @value{GDBN} command. @code{gdbtk} has
22874 @samp{gdb_find_file}.
22876 @subsubheading Example
22880 @subheading The @code{-symbol-info-function} Command
22881 @findex -symbol-info-function
22883 @subsubheading Synopsis
22886 -symbol-info-function
22889 Show which function the symbol lives in.
22891 @subsubheading @value{GDBN} Command
22893 @samp{gdb_get_function} in @code{gdbtk}.
22895 @subsubheading Example
22899 @subheading The @code{-symbol-info-line} Command
22900 @findex -symbol-info-line
22902 @subsubheading Synopsis
22908 Show the core addresses of the code for a source line.
22910 @subsubheading @value{GDBN} Command
22912 The corresponding @value{GDBN} command is @samp{info line}.
22913 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
22915 @subsubheading Example
22919 @subheading The @code{-symbol-info-symbol} Command
22920 @findex -symbol-info-symbol
22922 @subsubheading Synopsis
22925 -symbol-info-symbol @var{addr}
22928 Describe what symbol is at location @var{addr}.
22930 @subsubheading @value{GDBN} Command
22932 The corresponding @value{GDBN} command is @samp{info symbol}.
22934 @subsubheading Example
22938 @subheading The @code{-symbol-list-functions} Command
22939 @findex -symbol-list-functions
22941 @subsubheading Synopsis
22944 -symbol-list-functions
22947 List the functions in the executable.
22949 @subsubheading @value{GDBN} Command
22951 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
22952 @samp{gdb_search} in @code{gdbtk}.
22954 @subsubheading Example
22958 @subheading The @code{-symbol-list-lines} Command
22959 @findex -symbol-list-lines
22961 @subsubheading Synopsis
22964 -symbol-list-lines @var{filename}
22967 Print the list of lines that contain code and their associated program
22968 addresses for the given source filename. The entries are sorted in
22969 ascending PC order.
22971 @subsubheading @value{GDBN} Command
22973 There is no corresponding @value{GDBN} command.
22975 @subsubheading Example
22978 -symbol-list-lines basics.c
22979 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
22984 @subheading The @code{-symbol-list-types} Command
22985 @findex -symbol-list-types
22987 @subsubheading Synopsis
22993 List all the type names.
22995 @subsubheading @value{GDBN} Command
22997 The corresponding commands are @samp{info types} in @value{GDBN},
22998 @samp{gdb_search} in @code{gdbtk}.
23000 @subsubheading Example
23004 @subheading The @code{-symbol-list-variables} Command
23005 @findex -symbol-list-variables
23007 @subsubheading Synopsis
23010 -symbol-list-variables
23013 List all the global and static variable names.
23015 @subsubheading @value{GDBN} Command
23017 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
23019 @subsubheading Example
23023 @subheading The @code{-symbol-locate} Command
23024 @findex -symbol-locate
23026 @subsubheading Synopsis
23032 @subsubheading @value{GDBN} Command
23034 @samp{gdb_loc} in @code{gdbtk}.
23036 @subsubheading Example
23040 @subheading The @code{-symbol-type} Command
23041 @findex -symbol-type
23043 @subsubheading Synopsis
23046 -symbol-type @var{variable}
23049 Show type of @var{variable}.
23051 @subsubheading @value{GDBN} Command
23053 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
23054 @samp{gdb_obj_variable}.
23056 @subsubheading Example
23060 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
23061 @node GDB/MI File Commands
23062 @section @sc{gdb/mi} File Commands
23064 This section describes the GDB/MI commands to specify executable file names
23065 and to read in and obtain symbol table information.
23067 @subheading The @code{-file-exec-and-symbols} Command
23068 @findex -file-exec-and-symbols
23070 @subsubheading Synopsis
23073 -file-exec-and-symbols @var{file}
23076 Specify the executable file to be debugged. This file is the one from
23077 which the symbol table is also read. If no file is specified, the
23078 command clears the executable and symbol information. If breakpoints
23079 are set when using this command with no arguments, @value{GDBN} will produce
23080 error messages. Otherwise, no output is produced, except a completion
23083 @subsubheading @value{GDBN} Command
23085 The corresponding @value{GDBN} command is @samp{file}.
23087 @subsubheading Example
23091 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
23097 @subheading The @code{-file-exec-file} Command
23098 @findex -file-exec-file
23100 @subsubheading Synopsis
23103 -file-exec-file @var{file}
23106 Specify the executable file to be debugged. Unlike
23107 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
23108 from this file. If used without argument, @value{GDBN} clears the information
23109 about the executable file. No output is produced, except a completion
23112 @subsubheading @value{GDBN} Command
23114 The corresponding @value{GDBN} command is @samp{exec-file}.
23116 @subsubheading Example
23120 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
23126 @subheading The @code{-file-list-exec-sections} Command
23127 @findex -file-list-exec-sections
23129 @subsubheading Synopsis
23132 -file-list-exec-sections
23135 List the sections of the current executable file.
23137 @subsubheading @value{GDBN} Command
23139 The @value{GDBN} command @samp{info file} shows, among the rest, the same
23140 information as this command. @code{gdbtk} has a corresponding command
23141 @samp{gdb_load_info}.
23143 @subsubheading Example
23147 @subheading The @code{-file-list-exec-source-file} Command
23148 @findex -file-list-exec-source-file
23150 @subsubheading Synopsis
23153 -file-list-exec-source-file
23156 List the line number, the current source file, and the absolute path
23157 to the current source file for the current executable. The macro
23158 information field has a value of @samp{1} or @samp{0} depending on
23159 whether or not the file includes preprocessor macro information.
23161 @subsubheading @value{GDBN} Command
23163 The @value{GDBN} equivalent is @samp{info source}
23165 @subsubheading Example
23169 123-file-list-exec-source-file
23170 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c,macro-info="1"
23175 @subheading The @code{-file-list-exec-source-files} Command
23176 @findex -file-list-exec-source-files
23178 @subsubheading Synopsis
23181 -file-list-exec-source-files
23184 List the source files for the current executable.
23186 It will always output the filename, but only when @value{GDBN} can find
23187 the absolute file name of a source file, will it output the fullname.
23189 @subsubheading @value{GDBN} Command
23191 The @value{GDBN} equivalent is @samp{info sources}.
23192 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
23194 @subsubheading Example
23197 -file-list-exec-source-files
23199 @{file=foo.c,fullname=/home/foo.c@},
23200 @{file=/home/bar.c,fullname=/home/bar.c@},
23201 @{file=gdb_could_not_find_fullpath.c@}]
23205 @subheading The @code{-file-list-shared-libraries} Command
23206 @findex -file-list-shared-libraries
23208 @subsubheading Synopsis
23211 -file-list-shared-libraries
23214 List the shared libraries in the program.
23216 @subsubheading @value{GDBN} Command
23218 The corresponding @value{GDBN} command is @samp{info shared}.
23220 @subsubheading Example
23224 @subheading The @code{-file-list-symbol-files} Command
23225 @findex -file-list-symbol-files
23227 @subsubheading Synopsis
23230 -file-list-symbol-files
23235 @subsubheading @value{GDBN} Command
23237 The corresponding @value{GDBN} command is @samp{info file} (part of it).
23239 @subsubheading Example
23243 @subheading The @code{-file-symbol-file} Command
23244 @findex -file-symbol-file
23246 @subsubheading Synopsis
23249 -file-symbol-file @var{file}
23252 Read symbol table info from the specified @var{file} argument. When
23253 used without arguments, clears @value{GDBN}'s symbol table info. No output is
23254 produced, except for a completion notification.
23256 @subsubheading @value{GDBN} Command
23258 The corresponding @value{GDBN} command is @samp{symbol-file}.
23260 @subsubheading Example
23264 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
23270 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
23271 @node GDB/MI Memory Overlay Commands
23272 @section @sc{gdb/mi} Memory Overlay Commands
23274 The memory overlay commands are not implemented.
23276 @c @subheading -overlay-auto
23278 @c @subheading -overlay-list-mapping-state
23280 @c @subheading -overlay-list-overlays
23282 @c @subheading -overlay-map
23284 @c @subheading -overlay-off
23286 @c @subheading -overlay-on
23288 @c @subheading -overlay-unmap
23290 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
23291 @node GDB/MI Signal Handling Commands
23292 @section @sc{gdb/mi} Signal Handling Commands
23294 Signal handling commands are not implemented.
23296 @c @subheading -signal-handle
23298 @c @subheading -signal-list-handle-actions
23300 @c @subheading -signal-list-signal-types
23304 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
23305 @node GDB/MI Target Manipulation
23306 @section @sc{gdb/mi} Target Manipulation Commands
23309 @subheading The @code{-target-attach} Command
23310 @findex -target-attach
23312 @subsubheading Synopsis
23315 -target-attach @var{pid} | @var{gid} | @var{file}
23318 Attach to a process @var{pid} or a file @var{file} outside of
23319 @value{GDBN}, or a thread group @var{gid}. If attaching to a thread
23320 group, the id previously returned by
23321 @samp{-list-thread-groups --available} must be used.
23323 @subsubheading @value{GDBN} Command
23325 The corresponding @value{GDBN} command is @samp{attach}.
23327 @subsubheading Example
23331 =thread-created,id="1"
23332 *stopped,thread-id="1",frame=@{addr="0xb7f7e410",func="bar",args=[]@}
23337 @subheading The @code{-target-compare-sections} Command
23338 @findex -target-compare-sections
23340 @subsubheading Synopsis
23343 -target-compare-sections [ @var{section} ]
23346 Compare data of section @var{section} on target to the exec file.
23347 Without the argument, all sections are compared.
23349 @subsubheading @value{GDBN} Command
23351 The @value{GDBN} equivalent is @samp{compare-sections}.
23353 @subsubheading Example
23357 @subheading The @code{-target-detach} Command
23358 @findex -target-detach
23360 @subsubheading Synopsis
23363 -target-detach [ @var{pid} | @var{gid} ]
23366 Detach from the remote target which normally resumes its execution.
23367 If either @var{pid} or @var{gid} is specified, detaches from either
23368 the specified process, or specified thread group. There's no output.
23370 @subsubheading @value{GDBN} Command
23372 The corresponding @value{GDBN} command is @samp{detach}.
23374 @subsubheading Example
23384 @subheading The @code{-target-disconnect} Command
23385 @findex -target-disconnect
23387 @subsubheading Synopsis
23393 Disconnect from the remote target. There's no output and the target is
23394 generally not resumed.
23396 @subsubheading @value{GDBN} Command
23398 The corresponding @value{GDBN} command is @samp{disconnect}.
23400 @subsubheading Example
23410 @subheading The @code{-target-download} Command
23411 @findex -target-download
23413 @subsubheading Synopsis
23419 Loads the executable onto the remote target.
23420 It prints out an update message every half second, which includes the fields:
23424 The name of the section.
23426 The size of what has been sent so far for that section.
23428 The size of the section.
23430 The total size of what was sent so far (the current and the previous sections).
23432 The size of the overall executable to download.
23436 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
23437 @sc{gdb/mi} Output Syntax}).
23439 In addition, it prints the name and size of the sections, as they are
23440 downloaded. These messages include the following fields:
23444 The name of the section.
23446 The size of the section.
23448 The size of the overall executable to download.
23452 At the end, a summary is printed.
23454 @subsubheading @value{GDBN} Command
23456 The corresponding @value{GDBN} command is @samp{load}.
23458 @subsubheading Example
23460 Note: each status message appears on a single line. Here the messages
23461 have been broken down so that they can fit onto a page.
23466 +download,@{section=".text",section-size="6668",total-size="9880"@}
23467 +download,@{section=".text",section-sent="512",section-size="6668",
23468 total-sent="512",total-size="9880"@}
23469 +download,@{section=".text",section-sent="1024",section-size="6668",
23470 total-sent="1024",total-size="9880"@}
23471 +download,@{section=".text",section-sent="1536",section-size="6668",
23472 total-sent="1536",total-size="9880"@}
23473 +download,@{section=".text",section-sent="2048",section-size="6668",
23474 total-sent="2048",total-size="9880"@}
23475 +download,@{section=".text",section-sent="2560",section-size="6668",
23476 total-sent="2560",total-size="9880"@}
23477 +download,@{section=".text",section-sent="3072",section-size="6668",
23478 total-sent="3072",total-size="9880"@}
23479 +download,@{section=".text",section-sent="3584",section-size="6668",
23480 total-sent="3584",total-size="9880"@}
23481 +download,@{section=".text",section-sent="4096",section-size="6668",
23482 total-sent="4096",total-size="9880"@}
23483 +download,@{section=".text",section-sent="4608",section-size="6668",
23484 total-sent="4608",total-size="9880"@}
23485 +download,@{section=".text",section-sent="5120",section-size="6668",
23486 total-sent="5120",total-size="9880"@}
23487 +download,@{section=".text",section-sent="5632",section-size="6668",
23488 total-sent="5632",total-size="9880"@}
23489 +download,@{section=".text",section-sent="6144",section-size="6668",
23490 total-sent="6144",total-size="9880"@}
23491 +download,@{section=".text",section-sent="6656",section-size="6668",
23492 total-sent="6656",total-size="9880"@}
23493 +download,@{section=".init",section-size="28",total-size="9880"@}
23494 +download,@{section=".fini",section-size="28",total-size="9880"@}
23495 +download,@{section=".data",section-size="3156",total-size="9880"@}
23496 +download,@{section=".data",section-sent="512",section-size="3156",
23497 total-sent="7236",total-size="9880"@}
23498 +download,@{section=".data",section-sent="1024",section-size="3156",
23499 total-sent="7748",total-size="9880"@}
23500 +download,@{section=".data",section-sent="1536",section-size="3156",
23501 total-sent="8260",total-size="9880"@}
23502 +download,@{section=".data",section-sent="2048",section-size="3156",
23503 total-sent="8772",total-size="9880"@}
23504 +download,@{section=".data",section-sent="2560",section-size="3156",
23505 total-sent="9284",total-size="9880"@}
23506 +download,@{section=".data",section-sent="3072",section-size="3156",
23507 total-sent="9796",total-size="9880"@}
23508 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
23514 @subheading The @code{-target-exec-status} Command
23515 @findex -target-exec-status
23517 @subsubheading Synopsis
23520 -target-exec-status
23523 Provide information on the state of the target (whether it is running or
23524 not, for instance).
23526 @subsubheading @value{GDBN} Command
23528 There's no equivalent @value{GDBN} command.
23530 @subsubheading Example
23534 @subheading The @code{-target-list-available-targets} Command
23535 @findex -target-list-available-targets
23537 @subsubheading Synopsis
23540 -target-list-available-targets
23543 List the possible targets to connect to.
23545 @subsubheading @value{GDBN} Command
23547 The corresponding @value{GDBN} command is @samp{help target}.
23549 @subsubheading Example
23553 @subheading The @code{-target-list-current-targets} Command
23554 @findex -target-list-current-targets
23556 @subsubheading Synopsis
23559 -target-list-current-targets
23562 Describe the current target.
23564 @subsubheading @value{GDBN} Command
23566 The corresponding information is printed by @samp{info file} (among
23569 @subsubheading Example
23573 @subheading The @code{-target-list-parameters} Command
23574 @findex -target-list-parameters
23576 @subsubheading Synopsis
23579 -target-list-parameters
23584 @subsubheading @value{GDBN} Command
23588 @subsubheading Example
23592 @subheading The @code{-target-select} Command
23593 @findex -target-select
23595 @subsubheading Synopsis
23598 -target-select @var{type} @var{parameters @dots{}}
23601 Connect @value{GDBN} to the remote target. This command takes two args:
23605 The type of target, for instance @samp{remote}, etc.
23606 @item @var{parameters}
23607 Device names, host names and the like. @xref{Target Commands, ,
23608 Commands for Managing Targets}, for more details.
23611 The output is a connection notification, followed by the address at
23612 which the target program is, in the following form:
23615 ^connected,addr="@var{address}",func="@var{function name}",
23616 args=[@var{arg list}]
23619 @subsubheading @value{GDBN} Command
23621 The corresponding @value{GDBN} command is @samp{target}.
23623 @subsubheading Example
23627 -target-select remote /dev/ttya
23628 ^connected,addr="0xfe00a300",func="??",args=[]
23632 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
23633 @node GDB/MI File Transfer Commands
23634 @section @sc{gdb/mi} File Transfer Commands
23637 @subheading The @code{-target-file-put} Command
23638 @findex -target-file-put
23640 @subsubheading Synopsis
23643 -target-file-put @var{hostfile} @var{targetfile}
23646 Copy file @var{hostfile} from the host system (the machine running
23647 @value{GDBN}) to @var{targetfile} on the target system.
23649 @subsubheading @value{GDBN} Command
23651 The corresponding @value{GDBN} command is @samp{remote put}.
23653 @subsubheading Example
23657 -target-file-put localfile remotefile
23663 @subheading The @code{-target-file-get} Command
23664 @findex -target-file-get
23666 @subsubheading Synopsis
23669 -target-file-get @var{targetfile} @var{hostfile}
23672 Copy file @var{targetfile} from the target system to @var{hostfile}
23673 on the host system.
23675 @subsubheading @value{GDBN} Command
23677 The corresponding @value{GDBN} command is @samp{remote get}.
23679 @subsubheading Example
23683 -target-file-get remotefile localfile
23689 @subheading The @code{-target-file-delete} Command
23690 @findex -target-file-delete
23692 @subsubheading Synopsis
23695 -target-file-delete @var{targetfile}
23698 Delete @var{targetfile} from the target system.
23700 @subsubheading @value{GDBN} Command
23702 The corresponding @value{GDBN} command is @samp{remote delete}.
23704 @subsubheading Example
23708 -target-file-delete remotefile
23714 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
23715 @node GDB/MI Miscellaneous Commands
23716 @section Miscellaneous @sc{gdb/mi} Commands
23718 @c @subheading -gdb-complete
23720 @subheading The @code{-gdb-exit} Command
23723 @subsubheading Synopsis
23729 Exit @value{GDBN} immediately.
23731 @subsubheading @value{GDBN} Command
23733 Approximately corresponds to @samp{quit}.
23735 @subsubheading Example
23744 @subheading The @code{-exec-abort} Command
23745 @findex -exec-abort
23747 @subsubheading Synopsis
23753 Kill the inferior running program.
23755 @subsubheading @value{GDBN} Command
23757 The corresponding @value{GDBN} command is @samp{kill}.
23759 @subsubheading Example
23763 @subheading The @code{-gdb-set} Command
23766 @subsubheading Synopsis
23772 Set an internal @value{GDBN} variable.
23773 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
23775 @subsubheading @value{GDBN} Command
23777 The corresponding @value{GDBN} command is @samp{set}.
23779 @subsubheading Example
23789 @subheading The @code{-gdb-show} Command
23792 @subsubheading Synopsis
23798 Show the current value of a @value{GDBN} variable.
23800 @subsubheading @value{GDBN} Command
23802 The corresponding @value{GDBN} command is @samp{show}.
23804 @subsubheading Example
23813 @c @subheading -gdb-source
23816 @subheading The @code{-gdb-version} Command
23817 @findex -gdb-version
23819 @subsubheading Synopsis
23825 Show version information for @value{GDBN}. Used mostly in testing.
23827 @subsubheading @value{GDBN} Command
23829 The @value{GDBN} equivalent is @samp{show version}. @value{GDBN} by
23830 default shows this information when you start an interactive session.
23832 @subsubheading Example
23834 @c This example modifies the actual output from GDB to avoid overfull
23840 ~Copyright 2000 Free Software Foundation, Inc.
23841 ~GDB is free software, covered by the GNU General Public License, and
23842 ~you are welcome to change it and/or distribute copies of it under
23843 ~ certain conditions.
23844 ~Type "show copying" to see the conditions.
23845 ~There is absolutely no warranty for GDB. Type "show warranty" for
23847 ~This GDB was configured as
23848 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
23853 @subheading The @code{-list-features} Command
23854 @findex -list-features
23856 Returns a list of particular features of the MI protocol that
23857 this version of gdb implements. A feature can be a command,
23858 or a new field in an output of some command, or even an
23859 important bugfix. While a frontend can sometimes detect presence
23860 of a feature at runtime, it is easier to perform detection at debugger
23863 The command returns a list of strings, with each string naming an
23864 available feature. Each returned string is just a name, it does not
23865 have any internal structure. The list of possible feature names
23871 (gdb) -list-features
23872 ^done,result=["feature1","feature2"]
23875 The current list of features is:
23878 @item frozen-varobjs
23879 Indicates presence of the @code{-var-set-frozen} command, as well
23880 as possible presense of the @code{frozen} field in the output
23881 of @code{-varobj-create}.
23882 @item pending-breakpoints
23883 Indicates presence of the @option{-f} option to the @code{-break-insert} command.
23885 Indicates presence of the @code{-thread-info} command.
23889 @subheading The @code{-list-target-features} Command
23890 @findex -list-target-features
23892 Returns a list of particular features that are supported by the
23893 target. Those features affect the permitted MI commands, but
23894 unlike the features reported by the @code{-list-features} command, the
23895 features depend on which target GDB is using at the moment. Whenever
23896 a target can change, due to commands such as @code{-target-select},
23897 @code{-target-attach} or @code{-exec-run}, the list of target features
23898 may change, and the frontend should obtain it again.
23902 (gdb) -list-features
23903 ^done,result=["async"]
23906 The current list of features is:
23910 Indicates that the target is capable of asynchronous command
23911 execution, which means that @value{GDBN} will accept further commands
23912 while the target is running.
23916 @subheading The @code{-list-thread-groups} Command
23917 @findex -list-thread-groups
23919 @subheading Synopsis
23922 -list-thread-groups [ --available ] [ @var{group} ]
23925 When used without the @var{group} parameter, lists top-level thread
23926 groups that are being debugged. When used with the @var{group}
23927 parameter, the children of the specified group are listed. The
23928 children can be either threads, or other groups. At present,
23929 @value{GDBN} will not report both threads and groups as children at
23930 the same time, but it may change in future.
23932 With the @samp{--available} option, instead of reporting groups that
23933 are been debugged, GDB will report all thread groups available on the
23934 target. Using the @samp{--available} option together with @var{group}
23937 @subheading Example
23941 -list-thread-groups
23942 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2"@}]
23943 -list-thread-groups 17
23944 ^done,threads=[@{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
23945 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},state="running"@},
23946 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
23947 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
23948 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},state="running"@}]]
23951 @subheading The @code{-interpreter-exec} Command
23952 @findex -interpreter-exec
23954 @subheading Synopsis
23957 -interpreter-exec @var{interpreter} @var{command}
23959 @anchor{-interpreter-exec}
23961 Execute the specified @var{command} in the given @var{interpreter}.
23963 @subheading @value{GDBN} Command
23965 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
23967 @subheading Example
23971 -interpreter-exec console "break main"
23972 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
23973 &"During symbol reading, bad structure-type format.\n"
23974 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
23979 @subheading The @code{-inferior-tty-set} Command
23980 @findex -inferior-tty-set
23982 @subheading Synopsis
23985 -inferior-tty-set /dev/pts/1
23988 Set terminal for future runs of the program being debugged.
23990 @subheading @value{GDBN} Command
23992 The corresponding @value{GDBN} command is @samp{set inferior-tty} /dev/pts/1.
23994 @subheading Example
23998 -inferior-tty-set /dev/pts/1
24003 @subheading The @code{-inferior-tty-show} Command
24004 @findex -inferior-tty-show
24006 @subheading Synopsis
24012 Show terminal for future runs of program being debugged.
24014 @subheading @value{GDBN} Command
24016 The corresponding @value{GDBN} command is @samp{show inferior-tty}.
24018 @subheading Example
24022 -inferior-tty-set /dev/pts/1
24026 ^done,inferior_tty_terminal="/dev/pts/1"
24030 @subheading The @code{-enable-timings} Command
24031 @findex -enable-timings
24033 @subheading Synopsis
24036 -enable-timings [yes | no]
24039 Toggle the printing of the wallclock, user and system times for an MI
24040 command as a field in its output. This command is to help frontend
24041 developers optimize the performance of their code. No argument is
24042 equivalent to @samp{yes}.
24044 @subheading @value{GDBN} Command
24048 @subheading Example
24056 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
24057 addr="0x080484ed",func="main",file="myprog.c",
24058 fullname="/home/nickrob/myprog.c",line="73",times="0"@},
24059 time=@{wallclock="0.05185",user="0.00800",system="0.00000"@}
24067 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
24068 frame=@{addr="0x080484ed",func="main",args=[@{name="argc",value="1"@},
24069 @{name="argv",value="0xbfb60364"@}],file="myprog.c",
24070 fullname="/home/nickrob/myprog.c",line="73"@}
24075 @chapter @value{GDBN} Annotations
24077 This chapter describes annotations in @value{GDBN}. Annotations were
24078 designed to interface @value{GDBN} to graphical user interfaces or other
24079 similar programs which want to interact with @value{GDBN} at a
24080 relatively high level.
24082 The annotation mechanism has largely been superseded by @sc{gdb/mi}
24086 This is Edition @value{EDITION}, @value{DATE}.
24090 * Annotations Overview:: What annotations are; the general syntax.
24091 * Server Prefix:: Issuing a command without affecting user state.
24092 * Prompting:: Annotations marking @value{GDBN}'s need for input.
24093 * Errors:: Annotations for error messages.
24094 * Invalidation:: Some annotations describe things now invalid.
24095 * Annotations for Running::
24096 Whether the program is running, how it stopped, etc.
24097 * Source Annotations:: Annotations describing source code.
24100 @node Annotations Overview
24101 @section What is an Annotation?
24102 @cindex annotations
24104 Annotations start with a newline character, two @samp{control-z}
24105 characters, and the name of the annotation. If there is no additional
24106 information associated with this annotation, the name of the annotation
24107 is followed immediately by a newline. If there is additional
24108 information, the name of the annotation is followed by a space, the
24109 additional information, and a newline. The additional information
24110 cannot contain newline characters.
24112 Any output not beginning with a newline and two @samp{control-z}
24113 characters denotes literal output from @value{GDBN}. Currently there is
24114 no need for @value{GDBN} to output a newline followed by two
24115 @samp{control-z} characters, but if there was such a need, the
24116 annotations could be extended with an @samp{escape} annotation which
24117 means those three characters as output.
24119 The annotation @var{level}, which is specified using the
24120 @option{--annotate} command line option (@pxref{Mode Options}), controls
24121 how much information @value{GDBN} prints together with its prompt,
24122 values of expressions, source lines, and other types of output. Level 0
24123 is for no annotations, level 1 is for use when @value{GDBN} is run as a
24124 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
24125 for programs that control @value{GDBN}, and level 2 annotations have
24126 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
24127 Interface, annotate, GDB's Obsolete Annotations}).
24130 @kindex set annotate
24131 @item set annotate @var{level}
24132 The @value{GDBN} command @code{set annotate} sets the level of
24133 annotations to the specified @var{level}.
24135 @item show annotate
24136 @kindex show annotate
24137 Show the current annotation level.
24140 This chapter describes level 3 annotations.
24142 A simple example of starting up @value{GDBN} with annotations is:
24145 $ @kbd{gdb --annotate=3}
24147 Copyright 2003 Free Software Foundation, Inc.
24148 GDB is free software, covered by the GNU General Public License,
24149 and you are welcome to change it and/or distribute copies of it
24150 under certain conditions.
24151 Type "show copying" to see the conditions.
24152 There is absolutely no warranty for GDB. Type "show warranty"
24154 This GDB was configured as "i386-pc-linux-gnu"
24165 Here @samp{quit} is input to @value{GDBN}; the rest is output from
24166 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
24167 denotes a @samp{control-z} character) are annotations; the rest is
24168 output from @value{GDBN}.
24170 @node Server Prefix
24171 @section The Server Prefix
24172 @cindex server prefix
24174 If you prefix a command with @samp{server } then it will not affect
24175 the command history, nor will it affect @value{GDBN}'s notion of which
24176 command to repeat if @key{RET} is pressed on a line by itself. This
24177 means that commands can be run behind a user's back by a front-end in
24178 a transparent manner.
24180 The server prefix does not affect the recording of values into the value
24181 history; to print a value without recording it into the value history,
24182 use the @code{output} command instead of the @code{print} command.
24185 @section Annotation for @value{GDBN} Input
24187 @cindex annotations for prompts
24188 When @value{GDBN} prompts for input, it annotates this fact so it is possible
24189 to know when to send output, when the output from a given command is
24192 Different kinds of input each have a different @dfn{input type}. Each
24193 input type has three annotations: a @code{pre-} annotation, which
24194 denotes the beginning of any prompt which is being output, a plain
24195 annotation, which denotes the end of the prompt, and then a @code{post-}
24196 annotation which denotes the end of any echo which may (or may not) be
24197 associated with the input. For example, the @code{prompt} input type
24198 features the following annotations:
24206 The input types are
24209 @findex pre-prompt annotation
24210 @findex prompt annotation
24211 @findex post-prompt annotation
24213 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
24215 @findex pre-commands annotation
24216 @findex commands annotation
24217 @findex post-commands annotation
24219 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
24220 command. The annotations are repeated for each command which is input.
24222 @findex pre-overload-choice annotation
24223 @findex overload-choice annotation
24224 @findex post-overload-choice annotation
24225 @item overload-choice
24226 When @value{GDBN} wants the user to select between various overloaded functions.
24228 @findex pre-query annotation
24229 @findex query annotation
24230 @findex post-query annotation
24232 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
24234 @findex pre-prompt-for-continue annotation
24235 @findex prompt-for-continue annotation
24236 @findex post-prompt-for-continue annotation
24237 @item prompt-for-continue
24238 When @value{GDBN} is asking the user to press return to continue. Note: Don't
24239 expect this to work well; instead use @code{set height 0} to disable
24240 prompting. This is because the counting of lines is buggy in the
24241 presence of annotations.
24246 @cindex annotations for errors, warnings and interrupts
24248 @findex quit annotation
24253 This annotation occurs right before @value{GDBN} responds to an interrupt.
24255 @findex error annotation
24260 This annotation occurs right before @value{GDBN} responds to an error.
24262 Quit and error annotations indicate that any annotations which @value{GDBN} was
24263 in the middle of may end abruptly. For example, if a
24264 @code{value-history-begin} annotation is followed by a @code{error}, one
24265 cannot expect to receive the matching @code{value-history-end}. One
24266 cannot expect not to receive it either, however; an error annotation
24267 does not necessarily mean that @value{GDBN} is immediately returning all the way
24270 @findex error-begin annotation
24271 A quit or error annotation may be preceded by
24277 Any output between that and the quit or error annotation is the error
24280 Warning messages are not yet annotated.
24281 @c If we want to change that, need to fix warning(), type_error(),
24282 @c range_error(), and possibly other places.
24285 @section Invalidation Notices
24287 @cindex annotations for invalidation messages
24288 The following annotations say that certain pieces of state may have
24292 @findex frames-invalid annotation
24293 @item ^Z^Zframes-invalid
24295 The frames (for example, output from the @code{backtrace} command) may
24298 @findex breakpoints-invalid annotation
24299 @item ^Z^Zbreakpoints-invalid
24301 The breakpoints may have changed. For example, the user just added or
24302 deleted a breakpoint.
24305 @node Annotations for Running
24306 @section Running the Program
24307 @cindex annotations for running programs
24309 @findex starting annotation
24310 @findex stopping annotation
24311 When the program starts executing due to a @value{GDBN} command such as
24312 @code{step} or @code{continue},
24318 is output. When the program stops,
24324 is output. Before the @code{stopped} annotation, a variety of
24325 annotations describe how the program stopped.
24328 @findex exited annotation
24329 @item ^Z^Zexited @var{exit-status}
24330 The program exited, and @var{exit-status} is the exit status (zero for
24331 successful exit, otherwise nonzero).
24333 @findex signalled annotation
24334 @findex signal-name annotation
24335 @findex signal-name-end annotation
24336 @findex signal-string annotation
24337 @findex signal-string-end annotation
24338 @item ^Z^Zsignalled
24339 The program exited with a signal. After the @code{^Z^Zsignalled}, the
24340 annotation continues:
24346 ^Z^Zsignal-name-end
24350 ^Z^Zsignal-string-end
24355 where @var{name} is the name of the signal, such as @code{SIGILL} or
24356 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
24357 as @code{Illegal Instruction} or @code{Segmentation fault}.
24358 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
24359 user's benefit and have no particular format.
24361 @findex signal annotation
24363 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
24364 just saying that the program received the signal, not that it was
24365 terminated with it.
24367 @findex breakpoint annotation
24368 @item ^Z^Zbreakpoint @var{number}
24369 The program hit breakpoint number @var{number}.
24371 @findex watchpoint annotation
24372 @item ^Z^Zwatchpoint @var{number}
24373 The program hit watchpoint number @var{number}.
24376 @node Source Annotations
24377 @section Displaying Source
24378 @cindex annotations for source display
24380 @findex source annotation
24381 The following annotation is used instead of displaying source code:
24384 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
24387 where @var{filename} is an absolute file name indicating which source
24388 file, @var{line} is the line number within that file (where 1 is the
24389 first line in the file), @var{character} is the character position
24390 within the file (where 0 is the first character in the file) (for most
24391 debug formats this will necessarily point to the beginning of a line),
24392 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
24393 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
24394 @var{addr} is the address in the target program associated with the
24395 source which is being displayed. @var{addr} is in the form @samp{0x}
24396 followed by one or more lowercase hex digits (note that this does not
24397 depend on the language).
24400 @chapter Reporting Bugs in @value{GDBN}
24401 @cindex bugs in @value{GDBN}
24402 @cindex reporting bugs in @value{GDBN}
24404 Your bug reports play an essential role in making @value{GDBN} reliable.
24406 Reporting a bug may help you by bringing a solution to your problem, or it
24407 may not. But in any case the principal function of a bug report is to help
24408 the entire community by making the next version of @value{GDBN} work better. Bug
24409 reports are your contribution to the maintenance of @value{GDBN}.
24411 In order for a bug report to serve its purpose, you must include the
24412 information that enables us to fix the bug.
24415 * Bug Criteria:: Have you found a bug?
24416 * Bug Reporting:: How to report bugs
24420 @section Have You Found a Bug?
24421 @cindex bug criteria
24423 If you are not sure whether you have found a bug, here are some guidelines:
24426 @cindex fatal signal
24427 @cindex debugger crash
24428 @cindex crash of debugger
24430 If the debugger gets a fatal signal, for any input whatever, that is a
24431 @value{GDBN} bug. Reliable debuggers never crash.
24433 @cindex error on valid input
24435 If @value{GDBN} produces an error message for valid input, that is a
24436 bug. (Note that if you're cross debugging, the problem may also be
24437 somewhere in the connection to the target.)
24439 @cindex invalid input
24441 If @value{GDBN} does not produce an error message for invalid input,
24442 that is a bug. However, you should note that your idea of
24443 ``invalid input'' might be our idea of ``an extension'' or ``support
24444 for traditional practice''.
24447 If you are an experienced user of debugging tools, your suggestions
24448 for improvement of @value{GDBN} are welcome in any case.
24451 @node Bug Reporting
24452 @section How to Report Bugs
24453 @cindex bug reports
24454 @cindex @value{GDBN} bugs, reporting
24456 A number of companies and individuals offer support for @sc{gnu} products.
24457 If you obtained @value{GDBN} from a support organization, we recommend you
24458 contact that organization first.
24460 You can find contact information for many support companies and
24461 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
24463 @c should add a web page ref...
24466 @ifset BUGURL_DEFAULT
24467 In any event, we also recommend that you submit bug reports for
24468 @value{GDBN}. The preferred method is to submit them directly using
24469 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
24470 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
24473 @strong{Do not send bug reports to @samp{info-gdb}, or to
24474 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
24475 not want to receive bug reports. Those that do have arranged to receive
24478 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
24479 serves as a repeater. The mailing list and the newsgroup carry exactly
24480 the same messages. Often people think of posting bug reports to the
24481 newsgroup instead of mailing them. This appears to work, but it has one
24482 problem which can be crucial: a newsgroup posting often lacks a mail
24483 path back to the sender. Thus, if we need to ask for more information,
24484 we may be unable to reach you. For this reason, it is better to send
24485 bug reports to the mailing list.
24487 @ifclear BUGURL_DEFAULT
24488 In any event, we also recommend that you submit bug reports for
24489 @value{GDBN} to @value{BUGURL}.
24493 The fundamental principle of reporting bugs usefully is this:
24494 @strong{report all the facts}. If you are not sure whether to state a
24495 fact or leave it out, state it!
24497 Often people omit facts because they think they know what causes the
24498 problem and assume that some details do not matter. Thus, you might
24499 assume that the name of the variable you use in an example does not matter.
24500 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
24501 stray memory reference which happens to fetch from the location where that
24502 name is stored in memory; perhaps, if the name were different, the contents
24503 of that location would fool the debugger into doing the right thing despite
24504 the bug. Play it safe and give a specific, complete example. That is the
24505 easiest thing for you to do, and the most helpful.
24507 Keep in mind that the purpose of a bug report is to enable us to fix the
24508 bug. It may be that the bug has been reported previously, but neither
24509 you nor we can know that unless your bug report is complete and
24512 Sometimes people give a few sketchy facts and ask, ``Does this ring a
24513 bell?'' Those bug reports are useless, and we urge everyone to
24514 @emph{refuse to respond to them} except to chide the sender to report
24517 To enable us to fix the bug, you should include all these things:
24521 The version of @value{GDBN}. @value{GDBN} announces it if you start
24522 with no arguments; you can also print it at any time using @code{show
24525 Without this, we will not know whether there is any point in looking for
24526 the bug in the current version of @value{GDBN}.
24529 The type of machine you are using, and the operating system name and
24533 What compiler (and its version) was used to compile @value{GDBN}---e.g.@:
24534 ``@value{GCC}--2.8.1''.
24537 What compiler (and its version) was used to compile the program you are
24538 debugging---e.g.@: ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
24539 C Compiler''. For @value{NGCC}, you can say @kbd{@value{GCC} --version}
24540 to get this information; for other compilers, see the documentation for
24544 The command arguments you gave the compiler to compile your example and
24545 observe the bug. For example, did you use @samp{-O}? To guarantee
24546 you will not omit something important, list them all. A copy of the
24547 Makefile (or the output from make) is sufficient.
24549 If we were to try to guess the arguments, we would probably guess wrong
24550 and then we might not encounter the bug.
24553 A complete input script, and all necessary source files, that will
24557 A description of what behavior you observe that you believe is
24558 incorrect. For example, ``It gets a fatal signal.''
24560 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
24561 will certainly notice it. But if the bug is incorrect output, we might
24562 not notice unless it is glaringly wrong. You might as well not give us
24563 a chance to make a mistake.
24565 Even if the problem you experience is a fatal signal, you should still
24566 say so explicitly. Suppose something strange is going on, such as, your
24567 copy of @value{GDBN} is out of synch, or you have encountered a bug in
24568 the C library on your system. (This has happened!) Your copy might
24569 crash and ours would not. If you told us to expect a crash, then when
24570 ours fails to crash, we would know that the bug was not happening for
24571 us. If you had not told us to expect a crash, then we would not be able
24572 to draw any conclusion from our observations.
24575 @cindex recording a session script
24576 To collect all this information, you can use a session recording program
24577 such as @command{script}, which is available on many Unix systems.
24578 Just run your @value{GDBN} session inside @command{script} and then
24579 include the @file{typescript} file with your bug report.
24581 Another way to record a @value{GDBN} session is to run @value{GDBN}
24582 inside Emacs and then save the entire buffer to a file.
24585 If you wish to suggest changes to the @value{GDBN} source, send us context
24586 diffs. If you even discuss something in the @value{GDBN} source, refer to
24587 it by context, not by line number.
24589 The line numbers in our development sources will not match those in your
24590 sources. Your line numbers would convey no useful information to us.
24594 Here are some things that are not necessary:
24598 A description of the envelope of the bug.
24600 Often people who encounter a bug spend a lot of time investigating
24601 which changes to the input file will make the bug go away and which
24602 changes will not affect it.
24604 This is often time consuming and not very useful, because the way we
24605 will find the bug is by running a single example under the debugger
24606 with breakpoints, not by pure deduction from a series of examples.
24607 We recommend that you save your time for something else.
24609 Of course, if you can find a simpler example to report @emph{instead}
24610 of the original one, that is a convenience for us. Errors in the
24611 output will be easier to spot, running under the debugger will take
24612 less time, and so on.
24614 However, simplification is not vital; if you do not want to do this,
24615 report the bug anyway and send us the entire test case you used.
24618 A patch for the bug.
24620 A patch for the bug does help us if it is a good one. But do not omit
24621 the necessary information, such as the test case, on the assumption that
24622 a patch is all we need. We might see problems with your patch and decide
24623 to fix the problem another way, or we might not understand it at all.
24625 Sometimes with a program as complicated as @value{GDBN} it is very hard to
24626 construct an example that will make the program follow a certain path
24627 through the code. If you do not send us the example, we will not be able
24628 to construct one, so we will not be able to verify that the bug is fixed.
24630 And if we cannot understand what bug you are trying to fix, or why your
24631 patch should be an improvement, we will not install it. A test case will
24632 help us to understand.
24635 A guess about what the bug is or what it depends on.
24637 Such guesses are usually wrong. Even we cannot guess right about such
24638 things without first using the debugger to find the facts.
24641 @c The readline documentation is distributed with the readline code
24642 @c and consists of the two following files:
24644 @c inc-hist.texinfo
24645 @c Use -I with makeinfo to point to the appropriate directory,
24646 @c environment var TEXINPUTS with TeX.
24647 @include rluser.texi
24648 @include inc-hist.texinfo
24651 @node Formatting Documentation
24652 @appendix Formatting Documentation
24654 @cindex @value{GDBN} reference card
24655 @cindex reference card
24656 The @value{GDBN} 4 release includes an already-formatted reference card, ready
24657 for printing with PostScript or Ghostscript, in the @file{gdb}
24658 subdirectory of the main source directory@footnote{In
24659 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
24660 release.}. If you can use PostScript or Ghostscript with your printer,
24661 you can print the reference card immediately with @file{refcard.ps}.
24663 The release also includes the source for the reference card. You
24664 can format it, using @TeX{}, by typing:
24670 The @value{GDBN} reference card is designed to print in @dfn{landscape}
24671 mode on US ``letter'' size paper;
24672 that is, on a sheet 11 inches wide by 8.5 inches
24673 high. You will need to specify this form of printing as an option to
24674 your @sc{dvi} output program.
24676 @cindex documentation
24678 All the documentation for @value{GDBN} comes as part of the machine-readable
24679 distribution. The documentation is written in Texinfo format, which is
24680 a documentation system that uses a single source file to produce both
24681 on-line information and a printed manual. You can use one of the Info
24682 formatting commands to create the on-line version of the documentation
24683 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
24685 @value{GDBN} includes an already formatted copy of the on-line Info
24686 version of this manual in the @file{gdb} subdirectory. The main Info
24687 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
24688 subordinate files matching @samp{gdb.info*} in the same directory. If
24689 necessary, you can print out these files, or read them with any editor;
24690 but they are easier to read using the @code{info} subsystem in @sc{gnu}
24691 Emacs or the standalone @code{info} program, available as part of the
24692 @sc{gnu} Texinfo distribution.
24694 If you want to format these Info files yourself, you need one of the
24695 Info formatting programs, such as @code{texinfo-format-buffer} or
24698 If you have @code{makeinfo} installed, and are in the top level
24699 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
24700 version @value{GDBVN}), you can make the Info file by typing:
24707 If you want to typeset and print copies of this manual, you need @TeX{},
24708 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
24709 Texinfo definitions file.
24711 @TeX{} is a typesetting program; it does not print files directly, but
24712 produces output files called @sc{dvi} files. To print a typeset
24713 document, you need a program to print @sc{dvi} files. If your system
24714 has @TeX{} installed, chances are it has such a program. The precise
24715 command to use depends on your system; @kbd{lpr -d} is common; another
24716 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
24717 require a file name without any extension or a @samp{.dvi} extension.
24719 @TeX{} also requires a macro definitions file called
24720 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
24721 written in Texinfo format. On its own, @TeX{} cannot either read or
24722 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
24723 and is located in the @file{gdb-@var{version-number}/texinfo}
24726 If you have @TeX{} and a @sc{dvi} printer program installed, you can
24727 typeset and print this manual. First switch to the @file{gdb}
24728 subdirectory of the main source directory (for example, to
24729 @file{gdb-@value{GDBVN}/gdb}) and type:
24735 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
24737 @node Installing GDB
24738 @appendix Installing @value{GDBN}
24739 @cindex installation
24742 * Requirements:: Requirements for building @value{GDBN}
24743 * Running Configure:: Invoking the @value{GDBN} @file{configure} script
24744 * Separate Objdir:: Compiling @value{GDBN} in another directory
24745 * Config Names:: Specifying names for hosts and targets
24746 * Configure Options:: Summary of options for configure
24747 * System-wide configuration:: Having a system-wide init file
24751 @section Requirements for Building @value{GDBN}
24752 @cindex building @value{GDBN}, requirements for
24754 Building @value{GDBN} requires various tools and packages to be available.
24755 Other packages will be used only if they are found.
24757 @heading Tools/Packages Necessary for Building @value{GDBN}
24759 @item ISO C90 compiler
24760 @value{GDBN} is written in ISO C90. It should be buildable with any
24761 working C90 compiler, e.g.@: GCC.
24765 @heading Tools/Packages Optional for Building @value{GDBN}
24769 @value{GDBN} can use the Expat XML parsing library. This library may be
24770 included with your operating system distribution; if it is not, you
24771 can get the latest version from @url{http://expat.sourceforge.net}.
24772 The @file{configure} script will search for this library in several
24773 standard locations; if it is installed in an unusual path, you can
24774 use the @option{--with-libexpat-prefix} option to specify its location.
24780 Remote protocol memory maps (@pxref{Memory Map Format})
24782 Target descriptions (@pxref{Target Descriptions})
24784 Remote shared library lists (@pxref{Library List Format})
24786 MS-Windows shared libraries (@pxref{Shared Libraries})
24790 @cindex compressed debug sections
24791 @value{GDBN} will use the @samp{zlib} library, if available, to read
24792 compressed debug sections. Some linkers, such as GNU gold, are capable
24793 of producing binaries with compressed debug sections. If @value{GDBN}
24794 is compiled with @samp{zlib}, it will be able to read the debug
24795 information in such binaries.
24797 The @samp{zlib} library is likely included with your operating system
24798 distribution; if it is not, you can get the latest version from
24799 @url{http://zlib.net}.
24802 @value{GDBN}'s features related to character sets (@pxref{Character
24803 Sets}) require a functioning @code{iconv} implementation. If you are
24804 on a GNU system, then this is provided by the GNU C Library. Some
24805 other systems also provide a working @code{iconv}.
24807 On systems with @code{iconv}, you can install GNU Libiconv. If you
24808 have previously installed Libiconv, you can use the
24809 @option{--with-libiconv-prefix} option to configure.
24811 @value{GDBN}'s top-level @file{configure} and @file{Makefile} will
24812 arrange to build Libiconv if a directory named @file{libiconv} appears
24813 in the top-most source directory. If Libiconv is built this way, and
24814 if the operating system does not provide a suitable @code{iconv}
24815 implementation, then the just-built library will automatically be used
24816 by @value{GDBN}. One easy way to set this up is to download GNU
24817 Libiconv, unpack it, and then rename the directory holding the
24818 Libiconv source code to @samp{libiconv}.
24821 @node Running Configure
24822 @section Invoking the @value{GDBN} @file{configure} Script
24823 @cindex configuring @value{GDBN}
24824 @value{GDBN} comes with a @file{configure} script that automates the process
24825 of preparing @value{GDBN} for installation; you can then use @code{make} to
24826 build the @code{gdb} program.
24828 @c irrelevant in info file; it's as current as the code it lives with.
24829 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
24830 look at the @file{README} file in the sources; we may have improved the
24831 installation procedures since publishing this manual.}
24834 The @value{GDBN} distribution includes all the source code you need for
24835 @value{GDBN} in a single directory, whose name is usually composed by
24836 appending the version number to @samp{gdb}.
24838 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
24839 @file{gdb-@value{GDBVN}} directory. That directory contains:
24842 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
24843 script for configuring @value{GDBN} and all its supporting libraries
24845 @item gdb-@value{GDBVN}/gdb
24846 the source specific to @value{GDBN} itself
24848 @item gdb-@value{GDBVN}/bfd
24849 source for the Binary File Descriptor library
24851 @item gdb-@value{GDBVN}/include
24852 @sc{gnu} include files
24854 @item gdb-@value{GDBVN}/libiberty
24855 source for the @samp{-liberty} free software library
24857 @item gdb-@value{GDBVN}/opcodes
24858 source for the library of opcode tables and disassemblers
24860 @item gdb-@value{GDBVN}/readline
24861 source for the @sc{gnu} command-line interface
24863 @item gdb-@value{GDBVN}/glob
24864 source for the @sc{gnu} filename pattern-matching subroutine
24866 @item gdb-@value{GDBVN}/mmalloc
24867 source for the @sc{gnu} memory-mapped malloc package
24870 The simplest way to configure and build @value{GDBN} is to run @file{configure}
24871 from the @file{gdb-@var{version-number}} source directory, which in
24872 this example is the @file{gdb-@value{GDBVN}} directory.
24874 First switch to the @file{gdb-@var{version-number}} source directory
24875 if you are not already in it; then run @file{configure}. Pass the
24876 identifier for the platform on which @value{GDBN} will run as an
24882 cd gdb-@value{GDBVN}
24883 ./configure @var{host}
24888 where @var{host} is an identifier such as @samp{sun4} or
24889 @samp{decstation}, that identifies the platform where @value{GDBN} will run.
24890 (You can often leave off @var{host}; @file{configure} tries to guess the
24891 correct value by examining your system.)
24893 Running @samp{configure @var{host}} and then running @code{make} builds the
24894 @file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty}
24895 libraries, then @code{gdb} itself. The configured source files, and the
24896 binaries, are left in the corresponding source directories.
24899 @file{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
24900 system does not recognize this automatically when you run a different
24901 shell, you may need to run @code{sh} on it explicitly:
24904 sh configure @var{host}
24907 If you run @file{configure} from a directory that contains source
24908 directories for multiple libraries or programs, such as the
24909 @file{gdb-@value{GDBVN}} source directory for version @value{GDBVN},
24911 creates configuration files for every directory level underneath (unless
24912 you tell it not to, with the @samp{--norecursion} option).
24914 You should run the @file{configure} script from the top directory in the
24915 source tree, the @file{gdb-@var{version-number}} directory. If you run
24916 @file{configure} from one of the subdirectories, you will configure only
24917 that subdirectory. That is usually not what you want. In particular,
24918 if you run the first @file{configure} from the @file{gdb} subdirectory
24919 of the @file{gdb-@var{version-number}} directory, you will omit the
24920 configuration of @file{bfd}, @file{readline}, and other sibling
24921 directories of the @file{gdb} subdirectory. This leads to build errors
24922 about missing include files such as @file{bfd/bfd.h}.
24924 You can install @code{@value{GDBP}} anywhere; it has no hardwired paths.
24925 However, you should make sure that the shell on your path (named by
24926 the @samp{SHELL} environment variable) is publicly readable. Remember
24927 that @value{GDBN} uses the shell to start your program---some systems refuse to
24928 let @value{GDBN} debug child processes whose programs are not readable.
24930 @node Separate Objdir
24931 @section Compiling @value{GDBN} in Another Directory
24933 If you want to run @value{GDBN} versions for several host or target machines,
24934 you need a different @code{gdb} compiled for each combination of
24935 host and target. @file{configure} is designed to make this easy by
24936 allowing you to generate each configuration in a separate subdirectory,
24937 rather than in the source directory. If your @code{make} program
24938 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
24939 @code{make} in each of these directories builds the @code{gdb}
24940 program specified there.
24942 To build @code{gdb} in a separate directory, run @file{configure}
24943 with the @samp{--srcdir} option to specify where to find the source.
24944 (You also need to specify a path to find @file{configure}
24945 itself from your working directory. If the path to @file{configure}
24946 would be the same as the argument to @samp{--srcdir}, you can leave out
24947 the @samp{--srcdir} option; it is assumed.)
24949 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
24950 separate directory for a Sun 4 like this:
24954 cd gdb-@value{GDBVN}
24957 ../gdb-@value{GDBVN}/configure sun4
24962 When @file{configure} builds a configuration using a remote source
24963 directory, it creates a tree for the binaries with the same structure
24964 (and using the same names) as the tree under the source directory. In
24965 the example, you'd find the Sun 4 library @file{libiberty.a} in the
24966 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
24967 @file{gdb-sun4/gdb}.
24969 Make sure that your path to the @file{configure} script has just one
24970 instance of @file{gdb} in it. If your path to @file{configure} looks
24971 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
24972 one subdirectory of @value{GDBN}, not the whole package. This leads to
24973 build errors about missing include files such as @file{bfd/bfd.h}.
24975 One popular reason to build several @value{GDBN} configurations in separate
24976 directories is to configure @value{GDBN} for cross-compiling (where
24977 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
24978 programs that run on another machine---the @dfn{target}).
24979 You specify a cross-debugging target by
24980 giving the @samp{--target=@var{target}} option to @file{configure}.
24982 When you run @code{make} to build a program or library, you must run
24983 it in a configured directory---whatever directory you were in when you
24984 called @file{configure} (or one of its subdirectories).
24986 The @code{Makefile} that @file{configure} generates in each source
24987 directory also runs recursively. If you type @code{make} in a source
24988 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
24989 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
24990 will build all the required libraries, and then build GDB.
24992 When you have multiple hosts or targets configured in separate
24993 directories, you can run @code{make} on them in parallel (for example,
24994 if they are NFS-mounted on each of the hosts); they will not interfere
24998 @section Specifying Names for Hosts and Targets
25000 The specifications used for hosts and targets in the @file{configure}
25001 script are based on a three-part naming scheme, but some short predefined
25002 aliases are also supported. The full naming scheme encodes three pieces
25003 of information in the following pattern:
25006 @var{architecture}-@var{vendor}-@var{os}
25009 For example, you can use the alias @code{sun4} as a @var{host} argument,
25010 or as the value for @var{target} in a @code{--target=@var{target}}
25011 option. The equivalent full name is @samp{sparc-sun-sunos4}.
25013 The @file{configure} script accompanying @value{GDBN} does not provide
25014 any query facility to list all supported host and target names or
25015 aliases. @file{configure} calls the Bourne shell script
25016 @code{config.sub} to map abbreviations to full names; you can read the
25017 script, if you wish, or you can use it to test your guesses on
25018 abbreviations---for example:
25021 % sh config.sub i386-linux
25023 % sh config.sub alpha-linux
25024 alpha-unknown-linux-gnu
25025 % sh config.sub hp9k700
25027 % sh config.sub sun4
25028 sparc-sun-sunos4.1.1
25029 % sh config.sub sun3
25030 m68k-sun-sunos4.1.1
25031 % sh config.sub i986v
25032 Invalid configuration `i986v': machine `i986v' not recognized
25036 @code{config.sub} is also distributed in the @value{GDBN} source
25037 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
25039 @node Configure Options
25040 @section @file{configure} Options
25042 Here is a summary of the @file{configure} options and arguments that
25043 are most often useful for building @value{GDBN}. @file{configure} also has
25044 several other options not listed here. @inforef{What Configure
25045 Does,,configure.info}, for a full explanation of @file{configure}.
25048 configure @r{[}--help@r{]}
25049 @r{[}--prefix=@var{dir}@r{]}
25050 @r{[}--exec-prefix=@var{dir}@r{]}
25051 @r{[}--srcdir=@var{dirname}@r{]}
25052 @r{[}--norecursion@r{]} @r{[}--rm@r{]}
25053 @r{[}--target=@var{target}@r{]}
25058 You may introduce options with a single @samp{-} rather than
25059 @samp{--} if you prefer; but you may abbreviate option names if you use
25064 Display a quick summary of how to invoke @file{configure}.
25066 @item --prefix=@var{dir}
25067 Configure the source to install programs and files under directory
25070 @item --exec-prefix=@var{dir}
25071 Configure the source to install programs under directory
25074 @c avoid splitting the warning from the explanation:
25076 @item --srcdir=@var{dirname}
25077 @strong{Warning: using this option requires @sc{gnu} @code{make}, or another
25078 @code{make} that implements the @code{VPATH} feature.}@*
25079 Use this option to make configurations in directories separate from the
25080 @value{GDBN} source directories. Among other things, you can use this to
25081 build (or maintain) several configurations simultaneously, in separate
25082 directories. @file{configure} writes configuration-specific files in
25083 the current directory, but arranges for them to use the source in the
25084 directory @var{dirname}. @file{configure} creates directories under
25085 the working directory in parallel to the source directories below
25088 @item --norecursion
25089 Configure only the directory level where @file{configure} is executed; do not
25090 propagate configuration to subdirectories.
25092 @item --target=@var{target}
25093 Configure @value{GDBN} for cross-debugging programs running on the specified
25094 @var{target}. Without this option, @value{GDBN} is configured to debug
25095 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
25097 There is no convenient way to generate a list of all available targets.
25099 @item @var{host} @dots{}
25100 Configure @value{GDBN} to run on the specified @var{host}.
25102 There is no convenient way to generate a list of all available hosts.
25105 There are many other options available as well, but they are generally
25106 needed for special purposes only.
25108 @node System-wide configuration
25109 @section System-wide configuration and settings
25110 @cindex system-wide init file
25112 @value{GDBN} can be configured to have a system-wide init file;
25113 this file will be read and executed at startup (@pxref{Startup, , What
25114 @value{GDBN} does during startup}).
25116 Here is the corresponding configure option:
25119 @item --with-system-gdbinit=@var{file}
25120 Specify that the default location of the system-wide init file is
25124 If @value{GDBN} has been configured with the option @option{--prefix=$prefix},
25125 it may be subject to relocation. Two possible cases:
25129 If the default location of this init file contains @file{$prefix},
25130 it will be subject to relocation. Suppose that the configure options
25131 are @option{--prefix=$prefix --with-system-gdbinit=$prefix/etc/gdbinit};
25132 if @value{GDBN} is moved from @file{$prefix} to @file{$install}, the system
25133 init file is looked for as @file{$install/etc/gdbinit} instead of
25134 @file{$prefix/etc/gdbinit}.
25137 By contrast, if the default location does not contain the prefix,
25138 it will not be relocated. E.g.@: if @value{GDBN} has been configured with
25139 @option{--prefix=/usr/local --with-system-gdbinit=/usr/share/gdb/gdbinit},
25140 then @value{GDBN} will always look for @file{/usr/share/gdb/gdbinit},
25141 wherever @value{GDBN} is installed.
25144 @node Maintenance Commands
25145 @appendix Maintenance Commands
25146 @cindex maintenance commands
25147 @cindex internal commands
25149 In addition to commands intended for @value{GDBN} users, @value{GDBN}
25150 includes a number of commands intended for @value{GDBN} developers,
25151 that are not documented elsewhere in this manual. These commands are
25152 provided here for reference. (For commands that turn on debugging
25153 messages, see @ref{Debugging Output}.)
25156 @kindex maint agent
25157 @item maint agent @var{expression}
25158 Translate the given @var{expression} into remote agent bytecodes.
25159 This command is useful for debugging the Agent Expression mechanism
25160 (@pxref{Agent Expressions}).
25162 @kindex maint info breakpoints
25163 @item @anchor{maint info breakpoints}maint info breakpoints
25164 Using the same format as @samp{info breakpoints}, display both the
25165 breakpoints you've set explicitly, and those @value{GDBN} is using for
25166 internal purposes. Internal breakpoints are shown with negative
25167 breakpoint numbers. The type column identifies what kind of breakpoint
25172 Normal, explicitly set breakpoint.
25175 Normal, explicitly set watchpoint.
25178 Internal breakpoint, used to handle correctly stepping through
25179 @code{longjmp} calls.
25181 @item longjmp resume
25182 Internal breakpoint at the target of a @code{longjmp}.
25185 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
25188 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
25191 Shared library events.
25195 @kindex set displaced-stepping
25196 @kindex show displaced-stepping
25197 @cindex displaced stepping support
25198 @cindex out-of-line single-stepping
25199 @item set displaced-stepping
25200 @itemx show displaced-stepping
25201 Control whether or not @value{GDBN} will do @dfn{displaced stepping}
25202 if the target supports it. Displaced stepping is a way to single-step
25203 over breakpoints without removing them from the inferior, by executing
25204 an out-of-line copy of the instruction that was originally at the
25205 breakpoint location. It is also known as out-of-line single-stepping.
25208 @item set displaced-stepping on
25209 If the target architecture supports it, @value{GDBN} will use
25210 displaced stepping to step over breakpoints.
25212 @item set displaced-stepping off
25213 @value{GDBN} will not use displaced stepping to step over breakpoints,
25214 even if such is supported by the target architecture.
25216 @cindex non-stop mode, and @samp{set displaced-stepping}
25217 @item set displaced-stepping auto
25218 This is the default mode. @value{GDBN} will use displaced stepping
25219 only if non-stop mode is active (@pxref{Non-Stop Mode}) and the target
25220 architecture supports displaced stepping.
25223 @kindex maint check-symtabs
25224 @item maint check-symtabs
25225 Check the consistency of psymtabs and symtabs.
25227 @kindex maint cplus first_component
25228 @item maint cplus first_component @var{name}
25229 Print the first C@t{++} class/namespace component of @var{name}.
25231 @kindex maint cplus namespace
25232 @item maint cplus namespace
25233 Print the list of possible C@t{++} namespaces.
25235 @kindex maint demangle
25236 @item maint demangle @var{name}
25237 Demangle a C@t{++} or Objective-C mangled @var{name}.
25239 @kindex maint deprecate
25240 @kindex maint undeprecate
25241 @cindex deprecated commands
25242 @item maint deprecate @var{command} @r{[}@var{replacement}@r{]}
25243 @itemx maint undeprecate @var{command}
25244 Deprecate or undeprecate the named @var{command}. Deprecated commands
25245 cause @value{GDBN} to issue a warning when you use them. The optional
25246 argument @var{replacement} says which newer command should be used in
25247 favor of the deprecated one; if it is given, @value{GDBN} will mention
25248 the replacement as part of the warning.
25250 @kindex maint dump-me
25251 @item maint dump-me
25252 @cindex @code{SIGQUIT} signal, dump core of @value{GDBN}
25253 Cause a fatal signal in the debugger and force it to dump its core.
25254 This is supported only on systems which support aborting a program
25255 with the @code{SIGQUIT} signal.
25257 @kindex maint internal-error
25258 @kindex maint internal-warning
25259 @item maint internal-error @r{[}@var{message-text}@r{]}
25260 @itemx maint internal-warning @r{[}@var{message-text}@r{]}
25261 Cause @value{GDBN} to call the internal function @code{internal_error}
25262 or @code{internal_warning} and hence behave as though an internal error
25263 or internal warning has been detected. In addition to reporting the
25264 internal problem, these functions give the user the opportunity to
25265 either quit @value{GDBN} or create a core file of the current
25266 @value{GDBN} session.
25268 These commands take an optional parameter @var{message-text} that is
25269 used as the text of the error or warning message.
25271 Here's an example of using @code{internal-error}:
25274 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
25275 @dots{}/maint.c:121: internal-error: testing, 1, 2
25276 A problem internal to GDB has been detected. Further
25277 debugging may prove unreliable.
25278 Quit this debugging session? (y or n) @kbd{n}
25279 Create a core file? (y or n) @kbd{n}
25283 @cindex @value{GDBN} internal error
25284 @cindex internal errors, control of @value{GDBN} behavior
25286 @kindex maint set internal-error
25287 @kindex maint show internal-error
25288 @kindex maint set internal-warning
25289 @kindex maint show internal-warning
25290 @item maint set internal-error @var{action} [ask|yes|no]
25291 @itemx maint show internal-error @var{action}
25292 @itemx maint set internal-warning @var{action} [ask|yes|no]
25293 @itemx maint show internal-warning @var{action}
25294 When @value{GDBN} reports an internal problem (error or warning) it
25295 gives the user the opportunity to both quit @value{GDBN} and create a
25296 core file of the current @value{GDBN} session. These commands let you
25297 override the default behaviour for each particular @var{action},
25298 described in the table below.
25302 You can specify that @value{GDBN} should always (yes) or never (no)
25303 quit. The default is to ask the user what to do.
25306 You can specify that @value{GDBN} should always (yes) or never (no)
25307 create a core file. The default is to ask the user what to do.
25310 @kindex maint packet
25311 @item maint packet @var{text}
25312 If @value{GDBN} is talking to an inferior via the serial protocol,
25313 then this command sends the string @var{text} to the inferior, and
25314 displays the response packet. @value{GDBN} supplies the initial
25315 @samp{$} character, the terminating @samp{#} character, and the
25318 @kindex maint print architecture
25319 @item maint print architecture @r{[}@var{file}@r{]}
25320 Print the entire architecture configuration. The optional argument
25321 @var{file} names the file where the output goes.
25323 @kindex maint print c-tdesc
25324 @item maint print c-tdesc
25325 Print the current target description (@pxref{Target Descriptions}) as
25326 a C source file. The created source file can be used in @value{GDBN}
25327 when an XML parser is not available to parse the description.
25329 @kindex maint print dummy-frames
25330 @item maint print dummy-frames
25331 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
25334 (@value{GDBP}) @kbd{b add}
25336 (@value{GDBP}) @kbd{print add(2,3)}
25337 Breakpoint 2, add (a=2, b=3) at @dots{}
25339 The program being debugged stopped while in a function called from GDB.
25341 (@value{GDBP}) @kbd{maint print dummy-frames}
25342 0x1a57c80: pc=0x01014068 fp=0x0200bddc sp=0x0200bdd6
25343 top=0x0200bdd4 id=@{stack=0x200bddc,code=0x101405c@}
25344 call_lo=0x01014000 call_hi=0x01014001
25348 Takes an optional file parameter.
25350 @kindex maint print registers
25351 @kindex maint print raw-registers
25352 @kindex maint print cooked-registers
25353 @kindex maint print register-groups
25354 @item maint print registers @r{[}@var{file}@r{]}
25355 @itemx maint print raw-registers @r{[}@var{file}@r{]}
25356 @itemx maint print cooked-registers @r{[}@var{file}@r{]}
25357 @itemx maint print register-groups @r{[}@var{file}@r{]}
25358 Print @value{GDBN}'s internal register data structures.
25360 The command @code{maint print raw-registers} includes the contents of
25361 the raw register cache; the command @code{maint print cooked-registers}
25362 includes the (cooked) value of all registers; and the command
25363 @code{maint print register-groups} includes the groups that each
25364 register is a member of. @xref{Registers,, Registers, gdbint,
25365 @value{GDBN} Internals}.
25367 These commands take an optional parameter, a file name to which to
25368 write the information.
25370 @kindex maint print reggroups
25371 @item maint print reggroups @r{[}@var{file}@r{]}
25372 Print @value{GDBN}'s internal register group data structures. The
25373 optional argument @var{file} tells to what file to write the
25376 The register groups info looks like this:
25379 (@value{GDBP}) @kbd{maint print reggroups}
25392 This command forces @value{GDBN} to flush its internal register cache.
25394 @kindex maint print objfiles
25395 @cindex info for known object files
25396 @item maint print objfiles
25397 Print a dump of all known object files. For each object file, this
25398 command prints its name, address in memory, and all of its psymtabs
25401 @kindex maint print statistics
25402 @cindex bcache statistics
25403 @item maint print statistics
25404 This command prints, for each object file in the program, various data
25405 about that object file followed by the byte cache (@dfn{bcache})
25406 statistics for the object file. The objfile data includes the number
25407 of minimal, partial, full, and stabs symbols, the number of types
25408 defined by the objfile, the number of as yet unexpanded psym tables,
25409 the number of line tables and string tables, and the amount of memory
25410 used by the various tables. The bcache statistics include the counts,
25411 sizes, and counts of duplicates of all and unique objects, max,
25412 average, and median entry size, total memory used and its overhead and
25413 savings, and various measures of the hash table size and chain
25416 @kindex maint print target-stack
25417 @cindex target stack description
25418 @item maint print target-stack
25419 A @dfn{target} is an interface between the debugger and a particular
25420 kind of file or process. Targets can be stacked in @dfn{strata},
25421 so that more than one target can potentially respond to a request.
25422 In particular, memory accesses will walk down the stack of targets
25423 until they find a target that is interested in handling that particular
25426 This command prints a short description of each layer that was pushed on
25427 the @dfn{target stack}, starting from the top layer down to the bottom one.
25429 @kindex maint print type
25430 @cindex type chain of a data type
25431 @item maint print type @var{expr}
25432 Print the type chain for a type specified by @var{expr}. The argument
25433 can be either a type name or a symbol. If it is a symbol, the type of
25434 that symbol is described. The type chain produced by this command is
25435 a recursive definition of the data type as stored in @value{GDBN}'s
25436 data structures, including its flags and contained types.
25438 @kindex maint set dwarf2 max-cache-age
25439 @kindex maint show dwarf2 max-cache-age
25440 @item maint set dwarf2 max-cache-age
25441 @itemx maint show dwarf2 max-cache-age
25442 Control the DWARF 2 compilation unit cache.
25444 @cindex DWARF 2 compilation units cache
25445 In object files with inter-compilation-unit references, such as those
25446 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF 2
25447 reader needs to frequently refer to previously read compilation units.
25448 This setting controls how long a compilation unit will remain in the
25449 cache if it is not referenced. A higher limit means that cached
25450 compilation units will be stored in memory longer, and more total
25451 memory will be used. Setting it to zero disables caching, which will
25452 slow down @value{GDBN} startup, but reduce memory consumption.
25454 @kindex maint set profile
25455 @kindex maint show profile
25456 @cindex profiling GDB
25457 @item maint set profile
25458 @itemx maint show profile
25459 Control profiling of @value{GDBN}.
25461 Profiling will be disabled until you use the @samp{maint set profile}
25462 command to enable it. When you enable profiling, the system will begin
25463 collecting timing and execution count data; when you disable profiling or
25464 exit @value{GDBN}, the results will be written to a log file. Remember that
25465 if you use profiling, @value{GDBN} will overwrite the profiling log file
25466 (often called @file{gmon.out}). If you have a record of important profiling
25467 data in a @file{gmon.out} file, be sure to move it to a safe location.
25469 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
25470 compiled with the @samp{-pg} compiler option.
25472 @kindex maint show-debug-regs
25473 @cindex x86 hardware debug registers
25474 @item maint show-debug-regs
25475 Control whether to show variables that mirror the x86 hardware debug
25476 registers. Use @code{ON} to enable, @code{OFF} to disable. If
25477 enabled, the debug registers values are shown when @value{GDBN} inserts or
25478 removes a hardware breakpoint or watchpoint, and when the inferior
25479 triggers a hardware-assisted breakpoint or watchpoint.
25481 @kindex maint space
25482 @cindex memory used by commands
25484 Control whether to display memory usage for each command. If set to a
25485 nonzero value, @value{GDBN} will display how much memory each command
25486 took, following the command's own output. This can also be requested
25487 by invoking @value{GDBN} with the @option{--statistics} command-line
25488 switch (@pxref{Mode Options}).
25491 @cindex time of command execution
25493 Control whether to display the execution time for each command. If
25494 set to a nonzero value, @value{GDBN} will display how much time it
25495 took to execute each command, following the command's own output.
25496 The time is not printed for the commands that run the target, since
25497 there's no mechanism currently to compute how much time was spend
25498 by @value{GDBN} and how much time was spend by the program been debugged.
25499 it's not possibly currently
25500 This can also be requested by invoking @value{GDBN} with the
25501 @option{--statistics} command-line switch (@pxref{Mode Options}).
25503 @kindex maint translate-address
25504 @item maint translate-address @r{[}@var{section}@r{]} @var{addr}
25505 Find the symbol stored at the location specified by the address
25506 @var{addr} and an optional section name @var{section}. If found,
25507 @value{GDBN} prints the name of the closest symbol and an offset from
25508 the symbol's location to the specified address. This is similar to
25509 the @code{info address} command (@pxref{Symbols}), except that this
25510 command also allows to find symbols in other sections.
25512 If section was not specified, the section in which the symbol was found
25513 is also printed. For dynamically linked executables, the name of
25514 executable or shared library containing the symbol is printed as well.
25518 The following command is useful for non-interactive invocations of
25519 @value{GDBN}, such as in the test suite.
25522 @item set watchdog @var{nsec}
25523 @kindex set watchdog
25524 @cindex watchdog timer
25525 @cindex timeout for commands
25526 Set the maximum number of seconds @value{GDBN} will wait for the
25527 target operation to finish. If this time expires, @value{GDBN}
25528 reports and error and the command is aborted.
25530 @item show watchdog
25531 Show the current setting of the target wait timeout.
25534 @node Remote Protocol
25535 @appendix @value{GDBN} Remote Serial Protocol
25540 * Stop Reply Packets::
25541 * General Query Packets::
25542 * Register Packet Format::
25543 * Tracepoint Packets::
25544 * Host I/O Packets::
25546 * Notification Packets::
25547 * Remote Non-Stop::
25548 * Packet Acknowledgment::
25550 * File-I/O Remote Protocol Extension::
25551 * Library List Format::
25552 * Memory Map Format::
25558 There may be occasions when you need to know something about the
25559 protocol---for example, if there is only one serial port to your target
25560 machine, you might want your program to do something special if it
25561 recognizes a packet meant for @value{GDBN}.
25563 In the examples below, @samp{->} and @samp{<-} are used to indicate
25564 transmitted and received data, respectively.
25566 @cindex protocol, @value{GDBN} remote serial
25567 @cindex serial protocol, @value{GDBN} remote
25568 @cindex remote serial protocol
25569 All @value{GDBN} commands and responses (other than acknowledgments
25570 and notifications, see @ref{Notification Packets}) are sent as a
25571 @var{packet}. A @var{packet} is introduced with the character
25572 @samp{$}, the actual @var{packet-data}, and the terminating character
25573 @samp{#} followed by a two-digit @var{checksum}:
25576 @code{$}@var{packet-data}@code{#}@var{checksum}
25580 @cindex checksum, for @value{GDBN} remote
25582 The two-digit @var{checksum} is computed as the modulo 256 sum of all
25583 characters between the leading @samp{$} and the trailing @samp{#} (an
25584 eight bit unsigned checksum).
25586 Implementors should note that prior to @value{GDBN} 5.0 the protocol
25587 specification also included an optional two-digit @var{sequence-id}:
25590 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
25593 @cindex sequence-id, for @value{GDBN} remote
25595 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
25596 has never output @var{sequence-id}s. Stubs that handle packets added
25597 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
25599 When either the host or the target machine receives a packet, the first
25600 response expected is an acknowledgment: either @samp{+} (to indicate
25601 the package was received correctly) or @samp{-} (to request
25605 -> @code{$}@var{packet-data}@code{#}@var{checksum}
25610 The @samp{+}/@samp{-} acknowledgments can be disabled
25611 once a connection is established.
25612 @xref{Packet Acknowledgment}, for details.
25614 The host (@value{GDBN}) sends @var{command}s, and the target (the
25615 debugging stub incorporated in your program) sends a @var{response}. In
25616 the case of step and continue @var{command}s, the response is only sent
25617 when the operation has completed, and the target has again stopped all
25618 threads in all attached processes. This is the default all-stop mode
25619 behavior, but the remote protocol also supports @value{GDBN}'s non-stop
25620 execution mode; see @ref{Remote Non-Stop}, for details.
25622 @var{packet-data} consists of a sequence of characters with the
25623 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
25626 @cindex remote protocol, field separator
25627 Fields within the packet should be separated using @samp{,} @samp{;} or
25628 @samp{:}. Except where otherwise noted all numbers are represented in
25629 @sc{hex} with leading zeros suppressed.
25631 Implementors should note that prior to @value{GDBN} 5.0, the character
25632 @samp{:} could not appear as the third character in a packet (as it
25633 would potentially conflict with the @var{sequence-id}).
25635 @cindex remote protocol, binary data
25636 @anchor{Binary Data}
25637 Binary data in most packets is encoded either as two hexadecimal
25638 digits per byte of binary data. This allowed the traditional remote
25639 protocol to work over connections which were only seven-bit clean.
25640 Some packets designed more recently assume an eight-bit clean
25641 connection, and use a more efficient encoding to send and receive
25644 The binary data representation uses @code{7d} (@sc{ascii} @samp{@}})
25645 as an escape character. Any escaped byte is transmitted as the escape
25646 character followed by the original character XORed with @code{0x20}.
25647 For example, the byte @code{0x7d} would be transmitted as the two
25648 bytes @code{0x7d 0x5d}. The bytes @code{0x23} (@sc{ascii} @samp{#}),
25649 @code{0x24} (@sc{ascii} @samp{$}), and @code{0x7d} (@sc{ascii}
25650 @samp{@}}) must always be escaped. Responses sent by the stub
25651 must also escape @code{0x2a} (@sc{ascii} @samp{*}), so that it
25652 is not interpreted as the start of a run-length encoded sequence
25655 Response @var{data} can be run-length encoded to save space.
25656 Run-length encoding replaces runs of identical characters with one
25657 instance of the repeated character, followed by a @samp{*} and a
25658 repeat count. The repeat count is itself sent encoded, to avoid
25659 binary characters in @var{data}: a value of @var{n} is sent as
25660 @code{@var{n}+29}. For a repeat count greater or equal to 3, this
25661 produces a printable @sc{ascii} character, e.g.@: a space (@sc{ascii}
25662 code 32) for a repeat count of 3. (This is because run-length
25663 encoding starts to win for counts 3 or more.) Thus, for example,
25664 @samp{0* } is a run-length encoding of ``0000'': the space character
25665 after @samp{*} means repeat the leading @code{0} @w{@code{32 - 29 =
25668 The printable characters @samp{#} and @samp{$} or with a numeric value
25669 greater than 126 must not be used. Runs of six repeats (@samp{#}) or
25670 seven repeats (@samp{$}) can be expanded using a repeat count of only
25671 five (@samp{"}). For example, @samp{00000000} can be encoded as
25674 The error response returned for some packets includes a two character
25675 error number. That number is not well defined.
25677 @cindex empty response, for unsupported packets
25678 For any @var{command} not supported by the stub, an empty response
25679 (@samp{$#00}) should be returned. That way it is possible to extend the
25680 protocol. A newer @value{GDBN} can tell if a packet is supported based
25683 A stub is required to support the @samp{g}, @samp{G}, @samp{m}, @samp{M},
25684 @samp{c}, and @samp{s} @var{command}s. All other @var{command}s are
25690 The following table provides a complete list of all currently defined
25691 @var{command}s and their corresponding response @var{data}.
25692 @xref{File-I/O Remote Protocol Extension}, for details about the File
25693 I/O extension of the remote protocol.
25695 Each packet's description has a template showing the packet's overall
25696 syntax, followed by an explanation of the packet's meaning. We
25697 include spaces in some of the templates for clarity; these are not
25698 part of the packet's syntax. No @value{GDBN} packet uses spaces to
25699 separate its components. For example, a template like @samp{foo
25700 @var{bar} @var{baz}} describes a packet beginning with the three ASCII
25701 bytes @samp{foo}, followed by a @var{bar}, followed directly by a
25702 @var{baz}. @value{GDBN} does not transmit a space character between the
25703 @samp{foo} and the @var{bar}, or between the @var{bar} and the
25706 @cindex @var{thread-id}, in remote protocol
25707 @anchor{thread-id syntax}
25708 Several packets and replies include a @var{thread-id} field to identify
25709 a thread. Normally these are positive numbers with a target-specific
25710 interpretation, formatted as big-endian hex strings. A @var{thread-id}
25711 can also be a literal @samp{-1} to indicate all threads, or @samp{0} to
25714 In addition, the remote protocol supports a multiprocess feature in
25715 which the @var{thread-id} syntax is extended to optionally include both
25716 process and thread ID fields, as @samp{p@var{pid}.@var{tid}}.
25717 The @var{pid} (process) and @var{tid} (thread) components each have the
25718 format described above: a positive number with target-specific
25719 interpretation formatted as a big-endian hex string, literal @samp{-1}
25720 to indicate all processes or threads (respectively), or @samp{0} to
25721 indicate an arbitrary process or thread. Specifying just a process, as
25722 @samp{p@var{pid}}, is equivalent to @samp{p@var{pid}.-1}. It is an
25723 error to specify all processes but a specific thread, such as
25724 @samp{p-1.@var{tid}}. Note that the @samp{p} prefix is @emph{not} used
25725 for those packets and replies explicitly documented to include a process
25726 ID, rather than a @var{thread-id}.
25728 The multiprocess @var{thread-id} syntax extensions are only used if both
25729 @value{GDBN} and the stub report support for the @samp{multiprocess}
25730 feature using @samp{qSupported}. @xref{multiprocess extensions}, for
25733 Note that all packet forms beginning with an upper- or lower-case
25734 letter, other than those described here, are reserved for future use.
25736 Here are the packet descriptions.
25741 @cindex @samp{!} packet
25742 @anchor{extended mode}
25743 Enable extended mode. In extended mode, the remote server is made
25744 persistent. The @samp{R} packet is used to restart the program being
25750 The remote target both supports and has enabled extended mode.
25754 @cindex @samp{?} packet
25755 Indicate the reason the target halted. The reply is the same as for
25756 step and continue. This packet has a special interpretation when the
25757 target is in non-stop mode; see @ref{Remote Non-Stop}.
25760 @xref{Stop Reply Packets}, for the reply specifications.
25762 @item A @var{arglen},@var{argnum},@var{arg},@dots{}
25763 @cindex @samp{A} packet
25764 Initialized @code{argv[]} array passed into program. @var{arglen}
25765 specifies the number of bytes in the hex encoded byte stream
25766 @var{arg}. See @code{gdbserver} for more details.
25771 The arguments were set.
25777 @cindex @samp{b} packet
25778 (Don't use this packet; its behavior is not well-defined.)
25779 Change the serial line speed to @var{baud}.
25781 JTC: @emph{When does the transport layer state change? When it's
25782 received, or after the ACK is transmitted. In either case, there are
25783 problems if the command or the acknowledgment packet is dropped.}
25785 Stan: @emph{If people really wanted to add something like this, and get
25786 it working for the first time, they ought to modify ser-unix.c to send
25787 some kind of out-of-band message to a specially-setup stub and have the
25788 switch happen "in between" packets, so that from remote protocol's point
25789 of view, nothing actually happened.}
25791 @item B @var{addr},@var{mode}
25792 @cindex @samp{B} packet
25793 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
25794 breakpoint at @var{addr}.
25796 Don't use this packet. Use the @samp{Z} and @samp{z} packets instead
25797 (@pxref{insert breakpoint or watchpoint packet}).
25800 @cindex @samp{bc} packet
25801 Backward continue. Execute the target system in reverse. No parameter.
25802 @xref{Reverse Execution}, for more information.
25805 @xref{Stop Reply Packets}, for the reply specifications.
25808 @cindex @samp{bs} packet
25809 Backward single step. Execute one instruction in reverse. No parameter.
25810 @xref{Reverse Execution}, for more information.
25813 @xref{Stop Reply Packets}, for the reply specifications.
25815 @item c @r{[}@var{addr}@r{]}
25816 @cindex @samp{c} packet
25817 Continue. @var{addr} is address to resume. If @var{addr} is omitted,
25818 resume at current address.
25821 @xref{Stop Reply Packets}, for the reply specifications.
25823 @item C @var{sig}@r{[};@var{addr}@r{]}
25824 @cindex @samp{C} packet
25825 Continue with signal @var{sig} (hex signal number). If
25826 @samp{;@var{addr}} is omitted, resume at same address.
25829 @xref{Stop Reply Packets}, for the reply specifications.
25832 @cindex @samp{d} packet
25835 Don't use this packet; instead, define a general set packet
25836 (@pxref{General Query Packets}).
25840 @cindex @samp{D} packet
25841 The first form of the packet is used to detach @value{GDBN} from the
25842 remote system. It is sent to the remote target
25843 before @value{GDBN} disconnects via the @code{detach} command.
25845 The second form, including a process ID, is used when multiprocess
25846 protocol extensions are enabled (@pxref{multiprocess extensions}), to
25847 detach only a specific process. The @var{pid} is specified as a
25848 big-endian hex string.
25858 @item F @var{RC},@var{EE},@var{CF};@var{XX}
25859 @cindex @samp{F} packet
25860 A reply from @value{GDBN} to an @samp{F} packet sent by the target.
25861 This is part of the File-I/O protocol extension. @xref{File-I/O
25862 Remote Protocol Extension}, for the specification.
25865 @anchor{read registers packet}
25866 @cindex @samp{g} packet
25867 Read general registers.
25871 @item @var{XX@dots{}}
25872 Each byte of register data is described by two hex digits. The bytes
25873 with the register are transmitted in target byte order. The size of
25874 each register and their position within the @samp{g} packet are
25875 determined by the @value{GDBN} internal gdbarch functions
25876 @code{DEPRECATED_REGISTER_RAW_SIZE} and @code{gdbarch_register_name}. The
25877 specification of several standard @samp{g} packets is specified below.
25882 @item G @var{XX@dots{}}
25883 @cindex @samp{G} packet
25884 Write general registers. @xref{read registers packet}, for a
25885 description of the @var{XX@dots{}} data.
25895 @item H @var{c} @var{thread-id}
25896 @cindex @samp{H} packet
25897 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
25898 @samp{G}, et.al.). @var{c} depends on the operation to be performed: it
25899 should be @samp{c} for step and continue operations, @samp{g} for other
25900 operations. The thread designator @var{thread-id} has the format and
25901 interpretation described in @ref{thread-id syntax}.
25912 @c 'H': How restrictive (or permissive) is the thread model. If a
25913 @c thread is selected and stopped, are other threads allowed
25914 @c to continue to execute? As I mentioned above, I think the
25915 @c semantics of each command when a thread is selected must be
25916 @c described. For example:
25918 @c 'g': If the stub supports threads and a specific thread is
25919 @c selected, returns the register block from that thread;
25920 @c otherwise returns current registers.
25922 @c 'G' If the stub supports threads and a specific thread is
25923 @c selected, sets the registers of the register block of
25924 @c that thread; otherwise sets current registers.
25926 @item i @r{[}@var{addr}@r{[},@var{nnn}@r{]]}
25927 @anchor{cycle step packet}
25928 @cindex @samp{i} packet
25929 Step the remote target by a single clock cycle. If @samp{,@var{nnn}} is
25930 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
25931 step starting at that address.
25934 @cindex @samp{I} packet
25935 Signal, then cycle step. @xref{step with signal packet}. @xref{cycle
25939 @cindex @samp{k} packet
25942 FIXME: @emph{There is no description of how to operate when a specific
25943 thread context has been selected (i.e.@: does 'k' kill only that
25946 @item m @var{addr},@var{length}
25947 @cindex @samp{m} packet
25948 Read @var{length} bytes of memory starting at address @var{addr}.
25949 Note that @var{addr} may not be aligned to any particular boundary.
25951 The stub need not use any particular size or alignment when gathering
25952 data from memory for the response; even if @var{addr} is word-aligned
25953 and @var{length} is a multiple of the word size, the stub is free to
25954 use byte accesses, or not. For this reason, this packet may not be
25955 suitable for accessing memory-mapped I/O devices.
25956 @cindex alignment of remote memory accesses
25957 @cindex size of remote memory accesses
25958 @cindex memory, alignment and size of remote accesses
25962 @item @var{XX@dots{}}
25963 Memory contents; each byte is transmitted as a two-digit hexadecimal
25964 number. The reply may contain fewer bytes than requested if the
25965 server was able to read only part of the region of memory.
25970 @item M @var{addr},@var{length}:@var{XX@dots{}}
25971 @cindex @samp{M} packet
25972 Write @var{length} bytes of memory starting at address @var{addr}.
25973 @var{XX@dots{}} is the data; each byte is transmitted as a two-digit
25974 hexadecimal number.
25981 for an error (this includes the case where only part of the data was
25986 @cindex @samp{p} packet
25987 Read the value of register @var{n}; @var{n} is in hex.
25988 @xref{read registers packet}, for a description of how the returned
25989 register value is encoded.
25993 @item @var{XX@dots{}}
25994 the register's value
25998 Indicating an unrecognized @var{query}.
26001 @item P @var{n@dots{}}=@var{r@dots{}}
26002 @anchor{write register packet}
26003 @cindex @samp{P} packet
26004 Write register @var{n@dots{}} with value @var{r@dots{}}. The register
26005 number @var{n} is in hexadecimal, and @var{r@dots{}} contains two hex
26006 digits for each byte in the register (target byte order).
26016 @item q @var{name} @var{params}@dots{}
26017 @itemx Q @var{name} @var{params}@dots{}
26018 @cindex @samp{q} packet
26019 @cindex @samp{Q} packet
26020 General query (@samp{q}) and set (@samp{Q}). These packets are
26021 described fully in @ref{General Query Packets}.
26024 @cindex @samp{r} packet
26025 Reset the entire system.
26027 Don't use this packet; use the @samp{R} packet instead.
26030 @cindex @samp{R} packet
26031 Restart the program being debugged. @var{XX}, while needed, is ignored.
26032 This packet is only available in extended mode (@pxref{extended mode}).
26034 The @samp{R} packet has no reply.
26036 @item s @r{[}@var{addr}@r{]}
26037 @cindex @samp{s} packet
26038 Single step. @var{addr} is the address at which to resume. If
26039 @var{addr} is omitted, resume at same address.
26042 @xref{Stop Reply Packets}, for the reply specifications.
26044 @item S @var{sig}@r{[};@var{addr}@r{]}
26045 @anchor{step with signal packet}
26046 @cindex @samp{S} packet
26047 Step with signal. This is analogous to the @samp{C} packet, but
26048 requests a single-step, rather than a normal resumption of execution.
26051 @xref{Stop Reply Packets}, for the reply specifications.
26053 @item t @var{addr}:@var{PP},@var{MM}
26054 @cindex @samp{t} packet
26055 Search backwards starting at address @var{addr} for a match with pattern
26056 @var{PP} and mask @var{MM}. @var{PP} and @var{MM} are 4 bytes.
26057 @var{addr} must be at least 3 digits.
26059 @item T @var{thread-id}
26060 @cindex @samp{T} packet
26061 Find out if the thread @var{thread-id} is alive. @xref{thread-id syntax}.
26066 thread is still alive
26072 Packets starting with @samp{v} are identified by a multi-letter name,
26073 up to the first @samp{;} or @samp{?} (or the end of the packet).
26075 @item vAttach;@var{pid}
26076 @cindex @samp{vAttach} packet
26077 Attach to a new process with the specified process ID @var{pid}.
26078 The process ID is a
26079 hexadecimal integer identifying the process. In all-stop mode, all
26080 threads in the attached process are stopped; in non-stop mode, it may be
26081 attached without being stopped if that is supported by the target.
26083 @c In non-stop mode, on a successful vAttach, the stub should set the
26084 @c current thread to a thread of the newly-attached process. After
26085 @c attaching, GDB queries for the attached process's thread ID with qC.
26086 @c Also note that, from a user perspective, whether or not the
26087 @c target is stopped on attach in non-stop mode depends on whether you
26088 @c use the foreground or background version of the attach command, not
26089 @c on what vAttach does; GDB does the right thing with respect to either
26090 @c stopping or restarting threads.
26092 This packet is only available in extended mode (@pxref{extended mode}).
26098 @item @r{Any stop packet}
26099 for success in all-stop mode (@pxref{Stop Reply Packets})
26101 for success in non-stop mode (@pxref{Remote Non-Stop})
26104 @item vCont@r{[};@var{action}@r{[}:@var{thread-id}@r{]]}@dots{}
26105 @cindex @samp{vCont} packet
26106 Resume the inferior, specifying different actions for each thread.
26107 If an action is specified with no @var{thread-id}, then it is applied to any
26108 threads that don't have a specific action specified; if no default action is
26109 specified then other threads should remain stopped in all-stop mode and
26110 in their current state in non-stop mode.
26111 Specifying multiple
26112 default actions is an error; specifying no actions is also an error.
26113 Thread IDs are specified using the syntax described in @ref{thread-id syntax}.
26115 Currently supported actions are:
26121 Continue with signal @var{sig}. The signal @var{sig} should be two hex digits.
26125 Step with signal @var{sig}. The signal @var{sig} should be two hex digits.
26129 Stop with signal @var{sig}. The signal @var{sig} should be two hex digits.
26132 The optional argument @var{addr} normally associated with the
26133 @samp{c}, @samp{C}, @samp{s}, and @samp{S} packets is
26134 not supported in @samp{vCont}.
26136 The @samp{t} and @samp{T} actions are only relevant in non-stop mode
26137 (@pxref{Remote Non-Stop}) and may be ignored by the stub otherwise.
26138 A stop reply should be generated for any affected thread not already stopped.
26139 When a thread is stopped by means of a @samp{t} action,
26140 the corresponding stop reply should indicate that the thread has stopped with
26141 signal @samp{0}, regardless of whether the target uses some other signal
26142 as an implementation detail.
26145 @xref{Stop Reply Packets}, for the reply specifications.
26148 @cindex @samp{vCont?} packet
26149 Request a list of actions supported by the @samp{vCont} packet.
26153 @item vCont@r{[};@var{action}@dots{}@r{]}
26154 The @samp{vCont} packet is supported. Each @var{action} is a supported
26155 command in the @samp{vCont} packet.
26157 The @samp{vCont} packet is not supported.
26160 @item vFile:@var{operation}:@var{parameter}@dots{}
26161 @cindex @samp{vFile} packet
26162 Perform a file operation on the target system. For details,
26163 see @ref{Host I/O Packets}.
26165 @item vFlashErase:@var{addr},@var{length}
26166 @cindex @samp{vFlashErase} packet
26167 Direct the stub to erase @var{length} bytes of flash starting at
26168 @var{addr}. The region may enclose any number of flash blocks, but
26169 its start and end must fall on block boundaries, as indicated by the
26170 flash block size appearing in the memory map (@pxref{Memory Map
26171 Format}). @value{GDBN} groups flash memory programming operations
26172 together, and sends a @samp{vFlashDone} request after each group; the
26173 stub is allowed to delay erase operation until the @samp{vFlashDone}
26174 packet is received.
26176 The stub must support @samp{vCont} if it reports support for
26177 multiprocess extensions (@pxref{multiprocess extensions}). Note that in
26178 this case @samp{vCont} actions can be specified to apply to all threads
26179 in a process by using the @samp{p@var{pid}.-1} form of the
26190 @item vFlashWrite:@var{addr}:@var{XX@dots{}}
26191 @cindex @samp{vFlashWrite} packet
26192 Direct the stub to write data to flash address @var{addr}. The data
26193 is passed in binary form using the same encoding as for the @samp{X}
26194 packet (@pxref{Binary Data}). The memory ranges specified by
26195 @samp{vFlashWrite} packets preceding a @samp{vFlashDone} packet must
26196 not overlap, and must appear in order of increasing addresses
26197 (although @samp{vFlashErase} packets for higher addresses may already
26198 have been received; the ordering is guaranteed only between
26199 @samp{vFlashWrite} packets). If a packet writes to an address that was
26200 neither erased by a preceding @samp{vFlashErase} packet nor by some other
26201 target-specific method, the results are unpredictable.
26209 for vFlashWrite addressing non-flash memory
26215 @cindex @samp{vFlashDone} packet
26216 Indicate to the stub that flash programming operation is finished.
26217 The stub is permitted to delay or batch the effects of a group of
26218 @samp{vFlashErase} and @samp{vFlashWrite} packets until a
26219 @samp{vFlashDone} packet is received. The contents of the affected
26220 regions of flash memory are unpredictable until the @samp{vFlashDone}
26221 request is completed.
26223 @item vKill;@var{pid}
26224 @cindex @samp{vKill} packet
26225 Kill the process with the specified process ID. @var{pid} is a
26226 hexadecimal integer identifying the process. This packet is used in
26227 preference to @samp{k} when multiprocess protocol extensions are
26228 supported; see @ref{multiprocess extensions}.
26238 @item vRun;@var{filename}@r{[};@var{argument}@r{]}@dots{}
26239 @cindex @samp{vRun} packet
26240 Run the program @var{filename}, passing it each @var{argument} on its
26241 command line. The file and arguments are hex-encoded strings. If
26242 @var{filename} is an empty string, the stub may use a default program
26243 (e.g.@: the last program run). The program is created in the stopped
26246 @c FIXME: What about non-stop mode?
26248 This packet is only available in extended mode (@pxref{extended mode}).
26254 @item @r{Any stop packet}
26255 for success (@pxref{Stop Reply Packets})
26259 @anchor{vStopped packet}
26260 @cindex @samp{vStopped} packet
26262 In non-stop mode (@pxref{Remote Non-Stop}), acknowledge a previous stop
26263 reply and prompt for the stub to report another one.
26267 @item @r{Any stop packet}
26268 if there is another unreported stop event (@pxref{Stop Reply Packets})
26270 if there are no unreported stop events
26273 @item X @var{addr},@var{length}:@var{XX@dots{}}
26275 @cindex @samp{X} packet
26276 Write data to memory, where the data is transmitted in binary.
26277 @var{addr} is address, @var{length} is number of bytes,
26278 @samp{@var{XX}@dots{}} is binary data (@pxref{Binary Data}).
26288 @item z @var{type},@var{addr},@var{length}
26289 @itemx Z @var{type},@var{addr},@var{length}
26290 @anchor{insert breakpoint or watchpoint packet}
26291 @cindex @samp{z} packet
26292 @cindex @samp{Z} packets
26293 Insert (@samp{Z}) or remove (@samp{z}) a @var{type} breakpoint or
26294 watchpoint starting at address @var{address} and covering the next
26295 @var{length} bytes.
26297 Each breakpoint and watchpoint packet @var{type} is documented
26300 @emph{Implementation notes: A remote target shall return an empty string
26301 for an unrecognized breakpoint or watchpoint packet @var{type}. A
26302 remote target shall support either both or neither of a given
26303 @samp{Z@var{type}@dots{}} and @samp{z@var{type}@dots{}} packet pair. To
26304 avoid potential problems with duplicate packets, the operations should
26305 be implemented in an idempotent way.}
26307 @item z0,@var{addr},@var{length}
26308 @itemx Z0,@var{addr},@var{length}
26309 @cindex @samp{z0} packet
26310 @cindex @samp{Z0} packet
26311 Insert (@samp{Z0}) or remove (@samp{z0}) a memory breakpoint at address
26312 @var{addr} of size @var{length}.
26314 A memory breakpoint is implemented by replacing the instruction at
26315 @var{addr} with a software breakpoint or trap instruction. The
26316 @var{length} is used by targets that indicates the size of the
26317 breakpoint (in bytes) that should be inserted (e.g., the @sc{arm} and
26318 @sc{mips} can insert either a 2 or 4 byte breakpoint).
26320 @emph{Implementation note: It is possible for a target to copy or move
26321 code that contains memory breakpoints (e.g., when implementing
26322 overlays). The behavior of this packet, in the presence of such a
26323 target, is not defined.}
26335 @item z1,@var{addr},@var{length}
26336 @itemx Z1,@var{addr},@var{length}
26337 @cindex @samp{z1} packet
26338 @cindex @samp{Z1} packet
26339 Insert (@samp{Z1}) or remove (@samp{z1}) a hardware breakpoint at
26340 address @var{addr} of size @var{length}.
26342 A hardware breakpoint is implemented using a mechanism that is not
26343 dependant on being able to modify the target's memory.
26345 @emph{Implementation note: A hardware breakpoint is not affected by code
26358 @item z2,@var{addr},@var{length}
26359 @itemx Z2,@var{addr},@var{length}
26360 @cindex @samp{z2} packet
26361 @cindex @samp{Z2} packet
26362 Insert (@samp{Z2}) or remove (@samp{z2}) a write watchpoint.
26374 @item z3,@var{addr},@var{length}
26375 @itemx Z3,@var{addr},@var{length}
26376 @cindex @samp{z3} packet
26377 @cindex @samp{Z3} packet
26378 Insert (@samp{Z3}) or remove (@samp{z3}) a read watchpoint.
26390 @item z4,@var{addr},@var{length}
26391 @itemx Z4,@var{addr},@var{length}
26392 @cindex @samp{z4} packet
26393 @cindex @samp{Z4} packet
26394 Insert (@samp{Z4}) or remove (@samp{z4}) an access watchpoint.
26408 @node Stop Reply Packets
26409 @section Stop Reply Packets
26410 @cindex stop reply packets
26412 The @samp{C}, @samp{c}, @samp{S}, @samp{s}, @samp{vCont},
26413 @samp{vAttach}, @samp{vRun}, @samp{vStopped}, and @samp{?} packets can
26414 receive any of the below as a reply. Except for @samp{?}
26415 and @samp{vStopped}, that reply is only returned
26416 when the target halts. In the below the exact meaning of @dfn{signal
26417 number} is defined by the header @file{include/gdb/signals.h} in the
26418 @value{GDBN} source code.
26420 As in the description of request packets, we include spaces in the
26421 reply templates for clarity; these are not part of the reply packet's
26422 syntax. No @value{GDBN} stop reply packet uses spaces to separate its
26428 The program received signal number @var{AA} (a two-digit hexadecimal
26429 number). This is equivalent to a @samp{T} response with no
26430 @var{n}:@var{r} pairs.
26432 @item T @var{AA} @var{n1}:@var{r1};@var{n2}:@var{r2};@dots{}
26433 @cindex @samp{T} packet reply
26434 The program received signal number @var{AA} (a two-digit hexadecimal
26435 number). This is equivalent to an @samp{S} response, except that the
26436 @samp{@var{n}:@var{r}} pairs can carry values of important registers
26437 and other information directly in the stop reply packet, reducing
26438 round-trip latency. Single-step and breakpoint traps are reported
26439 this way. Each @samp{@var{n}:@var{r}} pair is interpreted as follows:
26443 If @var{n} is a hexadecimal number, it is a register number, and the
26444 corresponding @var{r} gives that register's value. @var{r} is a
26445 series of bytes in target byte order, with each byte given by a
26446 two-digit hex number.
26449 If @var{n} is @samp{thread}, then @var{r} is the @var{thread-id} of
26450 the stopped thread, as specified in @ref{thread-id syntax}.
26453 If @var{n} is a recognized @dfn{stop reason}, it describes a more
26454 specific event that stopped the target. The currently defined stop
26455 reasons are listed below. @var{aa} should be @samp{05}, the trap
26456 signal. At most one stop reason should be present.
26459 Otherwise, @value{GDBN} should ignore this @samp{@var{n}:@var{r}} pair
26460 and go on to the next; this allows us to extend the protocol in the
26464 The currently defined stop reasons are:
26470 The packet indicates a watchpoint hit, and @var{r} is the data address, in
26473 @cindex shared library events, remote reply
26475 The packet indicates that the loaded libraries have changed.
26476 @value{GDBN} should use @samp{qXfer:libraries:read} to fetch a new
26477 list of loaded libraries. @var{r} is ignored.
26479 @cindex replay log events, remote reply
26481 The packet indicates that the target cannot continue replaying
26482 logged execution events, because it has reached the end (or the
26483 beginning when executing backward) of the log. The value of @var{r}
26484 will be either @samp{begin} or @samp{end}. @xref{Reverse Execution},
26485 for more information.
26491 @itemx W @var{AA} ; process:@var{pid}
26492 The process exited, and @var{AA} is the exit status. This is only
26493 applicable to certain targets.
26495 The second form of the response, including the process ID of the exited
26496 process, can be used only when @value{GDBN} has reported support for
26497 multiprocess protocol extensions; see @ref{multiprocess extensions}.
26498 The @var{pid} is formatted as a big-endian hex string.
26501 @itemx X @var{AA} ; process:@var{pid}
26502 The process terminated with signal @var{AA}.
26504 The second form of the response, including the process ID of the
26505 terminated process, can be used only when @value{GDBN} has reported
26506 support for multiprocess protocol extensions; see @ref{multiprocess
26507 extensions}. The @var{pid} is formatted as a big-endian hex string.
26509 @item O @var{XX}@dots{}
26510 @samp{@var{XX}@dots{}} is hex encoding of @sc{ascii} data, to be
26511 written as the program's console output. This can happen at any time
26512 while the program is running and the debugger should continue to wait
26513 for @samp{W}, @samp{T}, etc. This reply is not permitted in non-stop mode.
26515 @item F @var{call-id},@var{parameter}@dots{}
26516 @var{call-id} is the identifier which says which host system call should
26517 be called. This is just the name of the function. Translation into the
26518 correct system call is only applicable as it's defined in @value{GDBN}.
26519 @xref{File-I/O Remote Protocol Extension}, for a list of implemented
26522 @samp{@var{parameter}@dots{}} is a list of parameters as defined for
26523 this very system call.
26525 The target replies with this packet when it expects @value{GDBN} to
26526 call a host system call on behalf of the target. @value{GDBN} replies
26527 with an appropriate @samp{F} packet and keeps up waiting for the next
26528 reply packet from the target. The latest @samp{C}, @samp{c}, @samp{S}
26529 or @samp{s} action is expected to be continued. @xref{File-I/O Remote
26530 Protocol Extension}, for more details.
26534 @node General Query Packets
26535 @section General Query Packets
26536 @cindex remote query requests
26538 Packets starting with @samp{q} are @dfn{general query packets};
26539 packets starting with @samp{Q} are @dfn{general set packets}. General
26540 query and set packets are a semi-unified form for retrieving and
26541 sending information to and from the stub.
26543 The initial letter of a query or set packet is followed by a name
26544 indicating what sort of thing the packet applies to. For example,
26545 @value{GDBN} may use a @samp{qSymbol} packet to exchange symbol
26546 definitions with the stub. These packet names follow some
26551 The name must not contain commas, colons or semicolons.
26553 Most @value{GDBN} query and set packets have a leading upper case
26556 The names of custom vendor packets should use a company prefix, in
26557 lower case, followed by a period. For example, packets designed at
26558 the Acme Corporation might begin with @samp{qacme.foo} (for querying
26559 foos) or @samp{Qacme.bar} (for setting bars).
26562 The name of a query or set packet should be separated from any
26563 parameters by a @samp{:}; the parameters themselves should be
26564 separated by @samp{,} or @samp{;}. Stubs must be careful to match the
26565 full packet name, and check for a separator or the end of the packet,
26566 in case two packet names share a common prefix. New packets should not begin
26567 with @samp{qC}, @samp{qP}, or @samp{qL}@footnote{The @samp{qP} and @samp{qL}
26568 packets predate these conventions, and have arguments without any terminator
26569 for the packet name; we suspect they are in widespread use in places that
26570 are difficult to upgrade. The @samp{qC} packet has no arguments, but some
26571 existing stubs (e.g.@: RedBoot) are known to not check for the end of the
26574 Like the descriptions of the other packets, each description here
26575 has a template showing the packet's overall syntax, followed by an
26576 explanation of the packet's meaning. We include spaces in some of the
26577 templates for clarity; these are not part of the packet's syntax. No
26578 @value{GDBN} packet uses spaces to separate its components.
26580 Here are the currently defined query and set packets:
26585 @cindex current thread, remote request
26586 @cindex @samp{qC} packet
26587 Return the current thread ID.
26591 @item QC @var{thread-id}
26592 Where @var{thread-id} is a thread ID as documented in
26593 @ref{thread-id syntax}.
26594 @item @r{(anything else)}
26595 Any other reply implies the old thread ID.
26598 @item qCRC:@var{addr},@var{length}
26599 @cindex CRC of memory block, remote request
26600 @cindex @samp{qCRC} packet
26601 Compute the CRC checksum of a block of memory.
26605 An error (such as memory fault)
26606 @item C @var{crc32}
26607 The specified memory region's checksum is @var{crc32}.
26611 @itemx qsThreadInfo
26612 @cindex list active threads, remote request
26613 @cindex @samp{qfThreadInfo} packet
26614 @cindex @samp{qsThreadInfo} packet
26615 Obtain a list of all active thread IDs from the target (OS). Since there
26616 may be too many active threads to fit into one reply packet, this query
26617 works iteratively: it may require more than one query/reply sequence to
26618 obtain the entire list of threads. The first query of the sequence will
26619 be the @samp{qfThreadInfo} query; subsequent queries in the
26620 sequence will be the @samp{qsThreadInfo} query.
26622 NOTE: This packet replaces the @samp{qL} query (see below).
26626 @item m @var{thread-id}
26628 @item m @var{thread-id},@var{thread-id}@dots{}
26629 a comma-separated list of thread IDs
26631 (lower case letter @samp{L}) denotes end of list.
26634 In response to each query, the target will reply with a list of one or
26635 more thread IDs, separated by commas.
26636 @value{GDBN} will respond to each reply with a request for more thread
26637 ids (using the @samp{qs} form of the query), until the target responds
26638 with @samp{l} (lower-case el, for @dfn{last}).
26639 Refer to @ref{thread-id syntax}, for the format of the @var{thread-id}
26642 @item qGetTLSAddr:@var{thread-id},@var{offset},@var{lm}
26643 @cindex get thread-local storage address, remote request
26644 @cindex @samp{qGetTLSAddr} packet
26645 Fetch the address associated with thread local storage specified
26646 by @var{thread-id}, @var{offset}, and @var{lm}.
26648 @var{thread-id} is the thread ID associated with the
26649 thread for which to fetch the TLS address. @xref{thread-id syntax}.
26651 @var{offset} is the (big endian, hex encoded) offset associated with the
26652 thread local variable. (This offset is obtained from the debug
26653 information associated with the variable.)
26655 @var{lm} is the (big endian, hex encoded) OS/ABI-specific encoding of the
26656 the load module associated with the thread local storage. For example,
26657 a @sc{gnu}/Linux system will pass the link map address of the shared
26658 object associated with the thread local storage under consideration.
26659 Other operating environments may choose to represent the load module
26660 differently, so the precise meaning of this parameter will vary.
26664 @item @var{XX}@dots{}
26665 Hex encoded (big endian) bytes representing the address of the thread
26666 local storage requested.
26669 An error occurred. @var{nn} are hex digits.
26672 An empty reply indicates that @samp{qGetTLSAddr} is not supported by the stub.
26675 @item qL @var{startflag} @var{threadcount} @var{nextthread}
26676 Obtain thread information from RTOS. Where: @var{startflag} (one hex
26677 digit) is one to indicate the first query and zero to indicate a
26678 subsequent query; @var{threadcount} (two hex digits) is the maximum
26679 number of threads the response packet can contain; and @var{nextthread}
26680 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
26681 returned in the response as @var{argthread}.
26683 Don't use this packet; use the @samp{qfThreadInfo} query instead (see above).
26687 @item qM @var{count} @var{done} @var{argthread} @var{thread}@dots{}
26688 Where: @var{count} (two hex digits) is the number of threads being
26689 returned; @var{done} (one hex digit) is zero to indicate more threads
26690 and one indicates no further threads; @var{argthreadid} (eight hex
26691 digits) is @var{nextthread} from the request packet; @var{thread}@dots{}
26692 is a sequence of thread IDs from the target. @var{threadid} (eight hex
26693 digits). See @code{remote.c:parse_threadlist_response()}.
26697 @cindex section offsets, remote request
26698 @cindex @samp{qOffsets} packet
26699 Get section offsets that the target used when relocating the downloaded
26704 @item Text=@var{xxx};Data=@var{yyy}@r{[};Bss=@var{zzz}@r{]}
26705 Relocate the @code{Text} section by @var{xxx} from its original address.
26706 Relocate the @code{Data} section by @var{yyy} from its original address.
26707 If the object file format provides segment information (e.g.@: @sc{elf}
26708 @samp{PT_LOAD} program headers), @value{GDBN} will relocate entire
26709 segments by the supplied offsets.
26711 @emph{Note: while a @code{Bss} offset may be included in the response,
26712 @value{GDBN} ignores this and instead applies the @code{Data} offset
26713 to the @code{Bss} section.}
26715 @item TextSeg=@var{xxx}@r{[};DataSeg=@var{yyy}@r{]}
26716 Relocate the first segment of the object file, which conventionally
26717 contains program code, to a starting address of @var{xxx}. If
26718 @samp{DataSeg} is specified, relocate the second segment, which
26719 conventionally contains modifiable data, to a starting address of
26720 @var{yyy}. @value{GDBN} will report an error if the object file
26721 does not contain segment information, or does not contain at least
26722 as many segments as mentioned in the reply. Extra segments are
26723 kept at fixed offsets relative to the last relocated segment.
26726 @item qP @var{mode} @var{thread-id}
26727 @cindex thread information, remote request
26728 @cindex @samp{qP} packet
26729 Returns information on @var{thread-id}. Where: @var{mode} is a hex
26730 encoded 32 bit mode; @var{thread-id} is a thread ID
26731 (@pxref{thread-id syntax}).
26733 Don't use this packet; use the @samp{qThreadExtraInfo} query instead
26736 Reply: see @code{remote.c:remote_unpack_thread_info_response()}.
26740 @cindex non-stop mode, remote request
26741 @cindex @samp{QNonStop} packet
26743 Enter non-stop (@samp{QNonStop:1}) or all-stop (@samp{QNonStop:0}) mode.
26744 @xref{Remote Non-Stop}, for more information.
26749 The request succeeded.
26752 An error occurred. @var{nn} are hex digits.
26755 An empty reply indicates that @samp{QNonStop} is not supported by
26759 This packet is not probed by default; the remote stub must request it,
26760 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
26761 Use of this packet is controlled by the @code{set non-stop} command;
26762 @pxref{Non-Stop Mode}.
26764 @item QPassSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
26765 @cindex pass signals to inferior, remote request
26766 @cindex @samp{QPassSignals} packet
26767 @anchor{QPassSignals}
26768 Each listed @var{signal} should be passed directly to the inferior process.
26769 Signals are numbered identically to continue packets and stop replies
26770 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
26771 strictly greater than the previous item. These signals do not need to stop
26772 the inferior, or be reported to @value{GDBN}. All other signals should be
26773 reported to @value{GDBN}. Multiple @samp{QPassSignals} packets do not
26774 combine; any earlier @samp{QPassSignals} list is completely replaced by the
26775 new list. This packet improves performance when using @samp{handle
26776 @var{signal} nostop noprint pass}.
26781 The request succeeded.
26784 An error occurred. @var{nn} are hex digits.
26787 An empty reply indicates that @samp{QPassSignals} is not supported by
26791 Use of this packet is controlled by the @code{set remote pass-signals}
26792 command (@pxref{Remote Configuration, set remote pass-signals}).
26793 This packet is not probed by default; the remote stub must request it,
26794 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
26796 @item qRcmd,@var{command}
26797 @cindex execute remote command, remote request
26798 @cindex @samp{qRcmd} packet
26799 @var{command} (hex encoded) is passed to the local interpreter for
26800 execution. Invalid commands should be reported using the output
26801 string. Before the final result packet, the target may also respond
26802 with a number of intermediate @samp{O@var{output}} console output
26803 packets. @emph{Implementors should note that providing access to a
26804 stubs's interpreter may have security implications}.
26809 A command response with no output.
26811 A command response with the hex encoded output string @var{OUTPUT}.
26813 Indicate a badly formed request.
26815 An empty reply indicates that @samp{qRcmd} is not recognized.
26818 (Note that the @code{qRcmd} packet's name is separated from the
26819 command by a @samp{,}, not a @samp{:}, contrary to the naming
26820 conventions above. Please don't use this packet as a model for new
26823 @item qSearch:memory:@var{address};@var{length};@var{search-pattern}
26824 @cindex searching memory, in remote debugging
26825 @cindex @samp{qSearch:memory} packet
26826 @anchor{qSearch memory}
26827 Search @var{length} bytes at @var{address} for @var{search-pattern}.
26828 @var{address} and @var{length} are encoded in hex.
26829 @var{search-pattern} is a sequence of bytes, hex encoded.
26834 The pattern was not found.
26836 The pattern was found at @var{address}.
26838 A badly formed request or an error was encountered while searching memory.
26840 An empty reply indicates that @samp{qSearch:memory} is not recognized.
26843 @item QStartNoAckMode
26844 @cindex @samp{QStartNoAckMode} packet
26845 @anchor{QStartNoAckMode}
26846 Request that the remote stub disable the normal @samp{+}/@samp{-}
26847 protocol acknowledgments (@pxref{Packet Acknowledgment}).
26852 The stub has switched to no-acknowledgment mode.
26853 @value{GDBN} acknowledges this reponse,
26854 but neither the stub nor @value{GDBN} shall send or expect further
26855 @samp{+}/@samp{-} acknowledgments in the current connection.
26857 An empty reply indicates that the stub does not support no-acknowledgment mode.
26860 @item qSupported @r{[}:@var{gdbfeature} @r{[};@var{gdbfeature}@r{]}@dots{} @r{]}
26861 @cindex supported packets, remote query
26862 @cindex features of the remote protocol
26863 @cindex @samp{qSupported} packet
26864 @anchor{qSupported}
26865 Tell the remote stub about features supported by @value{GDBN}, and
26866 query the stub for features it supports. This packet allows
26867 @value{GDBN} and the remote stub to take advantage of each others'
26868 features. @samp{qSupported} also consolidates multiple feature probes
26869 at startup, to improve @value{GDBN} performance---a single larger
26870 packet performs better than multiple smaller probe packets on
26871 high-latency links. Some features may enable behavior which must not
26872 be on by default, e.g.@: because it would confuse older clients or
26873 stubs. Other features may describe packets which could be
26874 automatically probed for, but are not. These features must be
26875 reported before @value{GDBN} will use them. This ``default
26876 unsupported'' behavior is not appropriate for all packets, but it
26877 helps to keep the initial connection time under control with new
26878 versions of @value{GDBN} which support increasing numbers of packets.
26882 @item @var{stubfeature} @r{[};@var{stubfeature}@r{]}@dots{}
26883 The stub supports or does not support each returned @var{stubfeature},
26884 depending on the form of each @var{stubfeature} (see below for the
26887 An empty reply indicates that @samp{qSupported} is not recognized,
26888 or that no features needed to be reported to @value{GDBN}.
26891 The allowed forms for each feature (either a @var{gdbfeature} in the
26892 @samp{qSupported} packet, or a @var{stubfeature} in the response)
26896 @item @var{name}=@var{value}
26897 The remote protocol feature @var{name} is supported, and associated
26898 with the specified @var{value}. The format of @var{value} depends
26899 on the feature, but it must not include a semicolon.
26901 The remote protocol feature @var{name} is supported, and does not
26902 need an associated value.
26904 The remote protocol feature @var{name} is not supported.
26906 The remote protocol feature @var{name} may be supported, and
26907 @value{GDBN} should auto-detect support in some other way when it is
26908 needed. This form will not be used for @var{gdbfeature} notifications,
26909 but may be used for @var{stubfeature} responses.
26912 Whenever the stub receives a @samp{qSupported} request, the
26913 supplied set of @value{GDBN} features should override any previous
26914 request. This allows @value{GDBN} to put the stub in a known
26915 state, even if the stub had previously been communicating with
26916 a different version of @value{GDBN}.
26918 The following values of @var{gdbfeature} (for the packet sent by @value{GDBN})
26923 This feature indicates whether @value{GDBN} supports multiprocess
26924 extensions to the remote protocol. @value{GDBN} does not use such
26925 extensions unless the stub also reports that it supports them by
26926 including @samp{multiprocess+} in its @samp{qSupported} reply.
26927 @xref{multiprocess extensions}, for details.
26930 Stubs should ignore any unknown values for
26931 @var{gdbfeature}. Any @value{GDBN} which sends a @samp{qSupported}
26932 packet supports receiving packets of unlimited length (earlier
26933 versions of @value{GDBN} may reject overly long responses). Additional values
26934 for @var{gdbfeature} may be defined in the future to let the stub take
26935 advantage of new features in @value{GDBN}, e.g.@: incompatible
26936 improvements in the remote protocol---the @samp{multiprocess} feature is
26937 an example of such a feature. The stub's reply should be independent
26938 of the @var{gdbfeature} entries sent by @value{GDBN}; first @value{GDBN}
26939 describes all the features it supports, and then the stub replies with
26940 all the features it supports.
26942 Similarly, @value{GDBN} will silently ignore unrecognized stub feature
26943 responses, as long as each response uses one of the standard forms.
26945 Some features are flags. A stub which supports a flag feature
26946 should respond with a @samp{+} form response. Other features
26947 require values, and the stub should respond with an @samp{=}
26950 Each feature has a default value, which @value{GDBN} will use if
26951 @samp{qSupported} is not available or if the feature is not mentioned
26952 in the @samp{qSupported} response. The default values are fixed; a
26953 stub is free to omit any feature responses that match the defaults.
26955 Not all features can be probed, but for those which can, the probing
26956 mechanism is useful: in some cases, a stub's internal
26957 architecture may not allow the protocol layer to know some information
26958 about the underlying target in advance. This is especially common in
26959 stubs which may be configured for multiple targets.
26961 These are the currently defined stub features and their properties:
26963 @multitable @columnfractions 0.35 0.2 0.12 0.2
26964 @c NOTE: The first row should be @headitem, but we do not yet require
26965 @c a new enough version of Texinfo (4.7) to use @headitem.
26967 @tab Value Required
26971 @item @samp{PacketSize}
26976 @item @samp{qXfer:auxv:read}
26981 @item @samp{qXfer:features:read}
26986 @item @samp{qXfer:libraries:read}
26991 @item @samp{qXfer:memory-map:read}
26996 @item @samp{qXfer:spu:read}
27001 @item @samp{qXfer:spu:write}
27006 @item @samp{qXfer:siginfo:read}
27011 @item @samp{qXfer:siginfo:write}
27016 @item @samp{QNonStop}
27021 @item @samp{QPassSignals}
27026 @item @samp{QStartNoAckMode}
27031 @item @samp{multiprocess}
27038 These are the currently defined stub features, in more detail:
27041 @cindex packet size, remote protocol
27042 @item PacketSize=@var{bytes}
27043 The remote stub can accept packets up to at least @var{bytes} in
27044 length. @value{GDBN} will send packets up to this size for bulk
27045 transfers, and will never send larger packets. This is a limit on the
27046 data characters in the packet, including the frame and checksum.
27047 There is no trailing NUL byte in a remote protocol packet; if the stub
27048 stores packets in a NUL-terminated format, it should allow an extra
27049 byte in its buffer for the NUL. If this stub feature is not supported,
27050 @value{GDBN} guesses based on the size of the @samp{g} packet response.
27052 @item qXfer:auxv:read
27053 The remote stub understands the @samp{qXfer:auxv:read} packet
27054 (@pxref{qXfer auxiliary vector read}).
27056 @item qXfer:features:read
27057 The remote stub understands the @samp{qXfer:features:read} packet
27058 (@pxref{qXfer target description read}).
27060 @item qXfer:libraries:read
27061 The remote stub understands the @samp{qXfer:libraries:read} packet
27062 (@pxref{qXfer library list read}).
27064 @item qXfer:memory-map:read
27065 The remote stub understands the @samp{qXfer:memory-map:read} packet
27066 (@pxref{qXfer memory map read}).
27068 @item qXfer:spu:read
27069 The remote stub understands the @samp{qXfer:spu:read} packet
27070 (@pxref{qXfer spu read}).
27072 @item qXfer:spu:write
27073 The remote stub understands the @samp{qXfer:spu:write} packet
27074 (@pxref{qXfer spu write}).
27076 @item qXfer:siginfo:read
27077 The remote stub understands the @samp{qXfer:siginfo:read} packet
27078 (@pxref{qXfer siginfo read}).
27080 @item qXfer:siginfo:write
27081 The remote stub understands the @samp{qXfer:siginfo:write} packet
27082 (@pxref{qXfer siginfo write}).
27085 The remote stub understands the @samp{QNonStop} packet
27086 (@pxref{QNonStop}).
27089 The remote stub understands the @samp{QPassSignals} packet
27090 (@pxref{QPassSignals}).
27092 @item QStartNoAckMode
27093 The remote stub understands the @samp{QStartNoAckMode} packet and
27094 prefers to operate in no-acknowledgment mode. @xref{Packet Acknowledgment}.
27097 @anchor{multiprocess extensions}
27098 @cindex multiprocess extensions, in remote protocol
27099 The remote stub understands the multiprocess extensions to the remote
27100 protocol syntax. The multiprocess extensions affect the syntax of
27101 thread IDs in both packets and replies (@pxref{thread-id syntax}), and
27102 add process IDs to the @samp{D} packet and @samp{W} and @samp{X}
27103 replies. Note that reporting this feature indicates support for the
27104 syntactic extensions only, not that the stub necessarily supports
27105 debugging of more than one process at a time. The stub must not use
27106 multiprocess extensions in packet replies unless @value{GDBN} has also
27107 indicated it supports them in its @samp{qSupported} request.
27109 @item qXfer:osdata:read
27110 The remote stub understands the @samp{qXfer:osdata:read} packet
27111 ((@pxref{qXfer osdata read}).
27116 @cindex symbol lookup, remote request
27117 @cindex @samp{qSymbol} packet
27118 Notify the target that @value{GDBN} is prepared to serve symbol lookup
27119 requests. Accept requests from the target for the values of symbols.
27124 The target does not need to look up any (more) symbols.
27125 @item qSymbol:@var{sym_name}
27126 The target requests the value of symbol @var{sym_name} (hex encoded).
27127 @value{GDBN} may provide the value by using the
27128 @samp{qSymbol:@var{sym_value}:@var{sym_name}} message, described
27132 @item qSymbol:@var{sym_value}:@var{sym_name}
27133 Set the value of @var{sym_name} to @var{sym_value}.
27135 @var{sym_name} (hex encoded) is the name of a symbol whose value the
27136 target has previously requested.
27138 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
27139 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
27145 The target does not need to look up any (more) symbols.
27146 @item qSymbol:@var{sym_name}
27147 The target requests the value of a new symbol @var{sym_name} (hex
27148 encoded). @value{GDBN} will continue to supply the values of symbols
27149 (if available), until the target ceases to request them.
27154 @xref{Tracepoint Packets}.
27156 @item qThreadExtraInfo,@var{thread-id}
27157 @cindex thread attributes info, remote request
27158 @cindex @samp{qThreadExtraInfo} packet
27159 Obtain a printable string description of a thread's attributes from
27160 the target OS. @var{thread-id} is a thread ID;
27161 see @ref{thread-id syntax}. This
27162 string may contain anything that the target OS thinks is interesting
27163 for @value{GDBN} to tell the user about the thread. The string is
27164 displayed in @value{GDBN}'s @code{info threads} display. Some
27165 examples of possible thread extra info strings are @samp{Runnable}, or
27166 @samp{Blocked on Mutex}.
27170 @item @var{XX}@dots{}
27171 Where @samp{@var{XX}@dots{}} is a hex encoding of @sc{ascii} data,
27172 comprising the printable string containing the extra information about
27173 the thread's attributes.
27176 (Note that the @code{qThreadExtraInfo} packet's name is separated from
27177 the command by a @samp{,}, not a @samp{:}, contrary to the naming
27178 conventions above. Please don't use this packet as a model for new
27186 @xref{Tracepoint Packets}.
27188 @item qXfer:@var{object}:read:@var{annex}:@var{offset},@var{length}
27189 @cindex read special object, remote request
27190 @cindex @samp{qXfer} packet
27191 @anchor{qXfer read}
27192 Read uninterpreted bytes from the target's special data area
27193 identified by the keyword @var{object}. Request @var{length} bytes
27194 starting at @var{offset} bytes into the data. The content and
27195 encoding of @var{annex} is specific to @var{object}; it can supply
27196 additional details about what data to access.
27198 Here are the specific requests of this form defined so far. All
27199 @samp{qXfer:@var{object}:read:@dots{}} requests use the same reply
27200 formats, listed below.
27203 @item qXfer:auxv:read::@var{offset},@var{length}
27204 @anchor{qXfer auxiliary vector read}
27205 Access the target's @dfn{auxiliary vector}. @xref{OS Information,
27206 auxiliary vector}. Note @var{annex} must be empty.
27208 This packet is not probed by default; the remote stub must request it,
27209 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
27211 @item qXfer:features:read:@var{annex}:@var{offset},@var{length}
27212 @anchor{qXfer target description read}
27213 Access the @dfn{target description}. @xref{Target Descriptions}. The
27214 annex specifies which XML document to access. The main description is
27215 always loaded from the @samp{target.xml} annex.
27217 This packet is not probed by default; the remote stub must request it,
27218 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
27220 @item qXfer:libraries:read:@var{annex}:@var{offset},@var{length}
27221 @anchor{qXfer library list read}
27222 Access the target's list of loaded libraries. @xref{Library List Format}.
27223 The annex part of the generic @samp{qXfer} packet must be empty
27224 (@pxref{qXfer read}).
27226 Targets which maintain a list of libraries in the program's memory do
27227 not need to implement this packet; it is designed for platforms where
27228 the operating system manages the list of loaded libraries.
27230 This packet is not probed by default; the remote stub must request it,
27231 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
27233 @item qXfer:memory-map:read::@var{offset},@var{length}
27234 @anchor{qXfer memory map read}
27235 Access the target's @dfn{memory-map}. @xref{Memory Map Format}. The
27236 annex part of the generic @samp{qXfer} packet must be empty
27237 (@pxref{qXfer read}).
27239 This packet is not probed by default; the remote stub must request it,
27240 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
27242 @item qXfer:siginfo:read::@var{offset},@var{length}
27243 @anchor{qXfer siginfo read}
27244 Read contents of the extra signal information on the target
27245 system. The annex part of the generic @samp{qXfer} packet must be
27246 empty (@pxref{qXfer read}).
27248 This packet is not probed by default; the remote stub must request it,
27249 by supplying an appropriate @samp{qSupported} response
27250 (@pxref{qSupported}).
27252 @item qXfer:spu:read:@var{annex}:@var{offset},@var{length}
27253 @anchor{qXfer spu read}
27254 Read contents of an @code{spufs} file on the target system. The
27255 annex specifies which file to read; it must be of the form
27256 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
27257 in the target process, and @var{name} identifes the @code{spufs} file
27258 in that context to be accessed.
27260 This packet is not probed by default; the remote stub must request it,
27261 by supplying an appropriate @samp{qSupported} response
27262 (@pxref{qSupported}).
27264 @item qXfer:osdata:read::@var{offset},@var{length}
27265 @anchor{qXfer osdata read}
27266 Access the target's @dfn{operating system information}.
27267 @xref{Operating System Information}.
27274 Data @var{data} (@pxref{Binary Data}) has been read from the
27275 target. There may be more data at a higher address (although
27276 it is permitted to return @samp{m} even for the last valid
27277 block of data, as long as at least one byte of data was read).
27278 @var{data} may have fewer bytes than the @var{length} in the
27282 Data @var{data} (@pxref{Binary Data}) has been read from the target.
27283 There is no more data to be read. @var{data} may have fewer bytes
27284 than the @var{length} in the request.
27287 The @var{offset} in the request is at the end of the data.
27288 There is no more data to be read.
27291 The request was malformed, or @var{annex} was invalid.
27294 The offset was invalid, or there was an error encountered reading the data.
27295 @var{nn} is a hex-encoded @code{errno} value.
27298 An empty reply indicates the @var{object} string was not recognized by
27299 the stub, or that the object does not support reading.
27302 @item qXfer:@var{object}:write:@var{annex}:@var{offset}:@var{data}@dots{}
27303 @cindex write data into object, remote request
27304 @anchor{qXfer write}
27305 Write uninterpreted bytes into the target's special data area
27306 identified by the keyword @var{object}, starting at @var{offset} bytes
27307 into the data. @var{data}@dots{} is the binary-encoded data
27308 (@pxref{Binary Data}) to be written. The content and encoding of @var{annex}
27309 is specific to @var{object}; it can supply additional details about what data
27312 Here are the specific requests of this form defined so far. All
27313 @samp{qXfer:@var{object}:write:@dots{}} requests use the same reply
27314 formats, listed below.
27317 @item qXfer:siginfo:write::@var{offset}:@var{data}@dots{}
27318 @anchor{qXfer siginfo write}
27319 Write @var{data} to the extra signal information on the target system.
27320 The annex part of the generic @samp{qXfer} packet must be
27321 empty (@pxref{qXfer write}).
27323 This packet is not probed by default; the remote stub must request it,
27324 by supplying an appropriate @samp{qSupported} response
27325 (@pxref{qSupported}).
27327 @item qXfer:spu:write:@var{annex}:@var{offset}:@var{data}@dots{}
27328 @anchor{qXfer spu write}
27329 Write @var{data} to an @code{spufs} file on the target system. The
27330 annex specifies which file to write; it must be of the form
27331 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
27332 in the target process, and @var{name} identifes the @code{spufs} file
27333 in that context to be accessed.
27335 This packet is not probed by default; the remote stub must request it,
27336 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
27342 @var{nn} (hex encoded) is the number of bytes written.
27343 This may be fewer bytes than supplied in the request.
27346 The request was malformed, or @var{annex} was invalid.
27349 The offset was invalid, or there was an error encountered writing the data.
27350 @var{nn} is a hex-encoded @code{errno} value.
27353 An empty reply indicates the @var{object} string was not
27354 recognized by the stub, or that the object does not support writing.
27357 @item qXfer:@var{object}:@var{operation}:@dots{}
27358 Requests of this form may be added in the future. When a stub does
27359 not recognize the @var{object} keyword, or its support for
27360 @var{object} does not recognize the @var{operation} keyword, the stub
27361 must respond with an empty packet.
27363 @item qAttached:@var{pid}
27364 @cindex query attached, remote request
27365 @cindex @samp{qAttached} packet
27366 Return an indication of whether the remote server attached to an
27367 existing process or created a new process. When the multiprocess
27368 protocol extensions are supported (@pxref{multiprocess extensions}),
27369 @var{pid} is an integer in hexadecimal format identifying the target
27370 process. Otherwise, @value{GDBN} will omit the @var{pid} field and
27371 the query packet will be simplified as @samp{qAttached}.
27373 This query is used, for example, to know whether the remote process
27374 should be detached or killed when a @value{GDBN} session is ended with
27375 the @code{quit} command.
27380 The remote server attached to an existing process.
27382 The remote server created a new process.
27384 A badly formed request or an error was encountered.
27389 @node Register Packet Format
27390 @section Register Packet Format
27392 The following @code{g}/@code{G} packets have previously been defined.
27393 In the below, some thirty-two bit registers are transferred as
27394 sixty-four bits. Those registers should be zero/sign extended (which?)
27395 to fill the space allocated. Register bytes are transferred in target
27396 byte order. The two nibbles within a register byte are transferred
27397 most-significant - least-significant.
27403 All registers are transferred as thirty-two bit quantities in the order:
27404 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
27405 registers; fsr; fir; fp.
27409 All registers are transferred as sixty-four bit quantities (including
27410 thirty-two bit registers such as @code{sr}). The ordering is the same
27415 @node Tracepoint Packets
27416 @section Tracepoint Packets
27417 @cindex tracepoint packets
27418 @cindex packets, tracepoint
27420 Here we describe the packets @value{GDBN} uses to implement
27421 tracepoints (@pxref{Tracepoints}).
27425 @item QTDP:@var{n}:@var{addr}:@var{ena}:@var{step}:@var{pass}@r{[}-@r{]}
27426 Create a new tracepoint, number @var{n}, at @var{addr}. If @var{ena}
27427 is @samp{E}, then the tracepoint is enabled; if it is @samp{D}, then
27428 the tracepoint is disabled. @var{step} is the tracepoint's step
27429 count, and @var{pass} is its pass count. If the trailing @samp{-} is
27430 present, further @samp{QTDP} packets will follow to specify this
27431 tracepoint's actions.
27436 The packet was understood and carried out.
27438 The packet was not recognized.
27441 @item QTDP:-@var{n}:@var{addr}:@r{[}S@r{]}@var{action}@dots{}@r{[}-@r{]}
27442 Define actions to be taken when a tracepoint is hit. @var{n} and
27443 @var{addr} must be the same as in the initial @samp{QTDP} packet for
27444 this tracepoint. This packet may only be sent immediately after
27445 another @samp{QTDP} packet that ended with a @samp{-}. If the
27446 trailing @samp{-} is present, further @samp{QTDP} packets will follow,
27447 specifying more actions for this tracepoint.
27449 In the series of action packets for a given tracepoint, at most one
27450 can have an @samp{S} before its first @var{action}. If such a packet
27451 is sent, it and the following packets define ``while-stepping''
27452 actions. Any prior packets define ordinary actions --- that is, those
27453 taken when the tracepoint is first hit. If no action packet has an
27454 @samp{S}, then all the packets in the series specify ordinary
27455 tracepoint actions.
27457 The @samp{@var{action}@dots{}} portion of the packet is a series of
27458 actions, concatenated without separators. Each action has one of the
27464 Collect the registers whose bits are set in @var{mask}. @var{mask} is
27465 a hexadecimal number whose @var{i}'th bit is set if register number
27466 @var{i} should be collected. (The least significant bit is numbered
27467 zero.) Note that @var{mask} may be any number of digits long; it may
27468 not fit in a 32-bit word.
27470 @item M @var{basereg},@var{offset},@var{len}
27471 Collect @var{len} bytes of memory starting at the address in register
27472 number @var{basereg}, plus @var{offset}. If @var{basereg} is
27473 @samp{-1}, then the range has a fixed address: @var{offset} is the
27474 address of the lowest byte to collect. The @var{basereg},
27475 @var{offset}, and @var{len} parameters are all unsigned hexadecimal
27476 values (the @samp{-1} value for @var{basereg} is a special case).
27478 @item X @var{len},@var{expr}
27479 Evaluate @var{expr}, whose length is @var{len}, and collect memory as
27480 it directs. @var{expr} is an agent expression, as described in
27481 @ref{Agent Expressions}. Each byte of the expression is encoded as a
27482 two-digit hex number in the packet; @var{len} is the number of bytes
27483 in the expression (and thus one-half the number of hex digits in the
27488 Any number of actions may be packed together in a single @samp{QTDP}
27489 packet, as long as the packet does not exceed the maximum packet
27490 length (400 bytes, for many stubs). There may be only one @samp{R}
27491 action per tracepoint, and it must precede any @samp{M} or @samp{X}
27492 actions. Any registers referred to by @samp{M} and @samp{X} actions
27493 must be collected by a preceding @samp{R} action. (The
27494 ``while-stepping'' actions are treated as if they were attached to a
27495 separate tracepoint, as far as these restrictions are concerned.)
27500 The packet was understood and carried out.
27502 The packet was not recognized.
27505 @item QTFrame:@var{n}
27506 Select the @var{n}'th tracepoint frame from the buffer, and use the
27507 register and memory contents recorded there to answer subsequent
27508 request packets from @value{GDBN}.
27510 A successful reply from the stub indicates that the stub has found the
27511 requested frame. The response is a series of parts, concatenated
27512 without separators, describing the frame we selected. Each part has
27513 one of the following forms:
27517 The selected frame is number @var{n} in the trace frame buffer;
27518 @var{f} is a hexadecimal number. If @var{f} is @samp{-1}, then there
27519 was no frame matching the criteria in the request packet.
27522 The selected trace frame records a hit of tracepoint number @var{t};
27523 @var{t} is a hexadecimal number.
27527 @item QTFrame:pc:@var{addr}
27528 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
27529 currently selected frame whose PC is @var{addr};
27530 @var{addr} is a hexadecimal number.
27532 @item QTFrame:tdp:@var{t}
27533 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
27534 currently selected frame that is a hit of tracepoint @var{t}; @var{t}
27535 is a hexadecimal number.
27537 @item QTFrame:range:@var{start}:@var{end}
27538 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
27539 currently selected frame whose PC is between @var{start} (inclusive)
27540 and @var{end} (exclusive); @var{start} and @var{end} are hexadecimal
27543 @item QTFrame:outside:@var{start}:@var{end}
27544 Like @samp{QTFrame:range:@var{start}:@var{end}}, but select the first
27545 frame @emph{outside} the given range of addresses.
27548 Begin the tracepoint experiment. Begin collecting data from tracepoint
27549 hits in the trace frame buffer.
27552 End the tracepoint experiment. Stop collecting trace frames.
27555 Clear the table of tracepoints, and empty the trace frame buffer.
27557 @item QTro:@var{start1},@var{end1}:@var{start2},@var{end2}:@dots{}
27558 Establish the given ranges of memory as ``transparent''. The stub
27559 will answer requests for these ranges from memory's current contents,
27560 if they were not collected as part of the tracepoint hit.
27562 @value{GDBN} uses this to mark read-only regions of memory, like those
27563 containing program code. Since these areas never change, they should
27564 still have the same contents they did when the tracepoint was hit, so
27565 there's no reason for the stub to refuse to provide their contents.
27568 Ask the stub if there is a trace experiment running right now.
27573 There is no trace experiment running.
27575 There is a trace experiment running.
27581 @node Host I/O Packets
27582 @section Host I/O Packets
27583 @cindex Host I/O, remote protocol
27584 @cindex file transfer, remote protocol
27586 The @dfn{Host I/O} packets allow @value{GDBN} to perform I/O
27587 operations on the far side of a remote link. For example, Host I/O is
27588 used to upload and download files to a remote target with its own
27589 filesystem. Host I/O uses the same constant values and data structure
27590 layout as the target-initiated File-I/O protocol. However, the
27591 Host I/O packets are structured differently. The target-initiated
27592 protocol relies on target memory to store parameters and buffers.
27593 Host I/O requests are initiated by @value{GDBN}, and the
27594 target's memory is not involved. @xref{File-I/O Remote Protocol
27595 Extension}, for more details on the target-initiated protocol.
27597 The Host I/O request packets all encode a single operation along with
27598 its arguments. They have this format:
27602 @item vFile:@var{operation}: @var{parameter}@dots{}
27603 @var{operation} is the name of the particular request; the target
27604 should compare the entire packet name up to the second colon when checking
27605 for a supported operation. The format of @var{parameter} depends on
27606 the operation. Numbers are always passed in hexadecimal. Negative
27607 numbers have an explicit minus sign (i.e.@: two's complement is not
27608 used). Strings (e.g.@: filenames) are encoded as a series of
27609 hexadecimal bytes. The last argument to a system call may be a
27610 buffer of escaped binary data (@pxref{Binary Data}).
27614 The valid responses to Host I/O packets are:
27618 @item F @var{result} [, @var{errno}] [; @var{attachment}]
27619 @var{result} is the integer value returned by this operation, usually
27620 non-negative for success and -1 for errors. If an error has occured,
27621 @var{errno} will be included in the result. @var{errno} will have a
27622 value defined by the File-I/O protocol (@pxref{Errno Values}). For
27623 operations which return data, @var{attachment} supplies the data as a
27624 binary buffer. Binary buffers in response packets are escaped in the
27625 normal way (@pxref{Binary Data}). See the individual packet
27626 documentation for the interpretation of @var{result} and
27630 An empty response indicates that this operation is not recognized.
27634 These are the supported Host I/O operations:
27637 @item vFile:open: @var{pathname}, @var{flags}, @var{mode}
27638 Open a file at @var{pathname} and return a file descriptor for it, or
27639 return -1 if an error occurs. @var{pathname} is a string,
27640 @var{flags} is an integer indicating a mask of open flags
27641 (@pxref{Open Flags}), and @var{mode} is an integer indicating a mask
27642 of mode bits to use if the file is created (@pxref{mode_t Values}).
27643 @xref{open}, for details of the open flags and mode values.
27645 @item vFile:close: @var{fd}
27646 Close the open file corresponding to @var{fd} and return 0, or
27647 -1 if an error occurs.
27649 @item vFile:pread: @var{fd}, @var{count}, @var{offset}
27650 Read data from the open file corresponding to @var{fd}. Up to
27651 @var{count} bytes will be read from the file, starting at @var{offset}
27652 relative to the start of the file. The target may read fewer bytes;
27653 common reasons include packet size limits and an end-of-file
27654 condition. The number of bytes read is returned. Zero should only be
27655 returned for a successful read at the end of the file, or if
27656 @var{count} was zero.
27658 The data read should be returned as a binary attachment on success.
27659 If zero bytes were read, the response should include an empty binary
27660 attachment (i.e.@: a trailing semicolon). The return value is the
27661 number of target bytes read; the binary attachment may be longer if
27662 some characters were escaped.
27664 @item vFile:pwrite: @var{fd}, @var{offset}, @var{data}
27665 Write @var{data} (a binary buffer) to the open file corresponding
27666 to @var{fd}. Start the write at @var{offset} from the start of the
27667 file. Unlike many @code{write} system calls, there is no
27668 separate @var{count} argument; the length of @var{data} in the
27669 packet is used. @samp{vFile:write} returns the number of bytes written,
27670 which may be shorter than the length of @var{data}, or -1 if an
27673 @item vFile:unlink: @var{pathname}
27674 Delete the file at @var{pathname} on the target. Return 0,
27675 or -1 if an error occurs. @var{pathname} is a string.
27680 @section Interrupts
27681 @cindex interrupts (remote protocol)
27683 When a program on the remote target is running, @value{GDBN} may
27684 attempt to interrupt it by sending a @samp{Ctrl-C} or a @code{BREAK},
27685 control of which is specified via @value{GDBN}'s @samp{remotebreak}
27686 setting (@pxref{set remotebreak}).
27688 The precise meaning of @code{BREAK} is defined by the transport
27689 mechanism and may, in fact, be undefined. @value{GDBN} does not
27690 currently define a @code{BREAK} mechanism for any of the network
27691 interfaces except for TCP, in which case @value{GDBN} sends the
27692 @code{telnet} BREAK sequence.
27694 @samp{Ctrl-C}, on the other hand, is defined and implemented for all
27695 transport mechanisms. It is represented by sending the single byte
27696 @code{0x03} without any of the usual packet overhead described in
27697 the Overview section (@pxref{Overview}). When a @code{0x03} byte is
27698 transmitted as part of a packet, it is considered to be packet data
27699 and does @emph{not} represent an interrupt. E.g., an @samp{X} packet
27700 (@pxref{X packet}), used for binary downloads, may include an unescaped
27701 @code{0x03} as part of its packet.
27703 Stubs are not required to recognize these interrupt mechanisms and the
27704 precise meaning associated with receipt of the interrupt is
27705 implementation defined. If the target supports debugging of multiple
27706 threads and/or processes, it should attempt to interrupt all
27707 currently-executing threads and processes.
27708 If the stub is successful at interrupting the
27709 running program, it should send one of the stop
27710 reply packets (@pxref{Stop Reply Packets}) to @value{GDBN} as a result
27711 of successfully stopping the program in all-stop mode, and a stop reply
27712 for each stopped thread in non-stop mode.
27713 Interrupts received while the
27714 program is stopped are discarded.
27716 @node Notification Packets
27717 @section Notification Packets
27718 @cindex notification packets
27719 @cindex packets, notification
27721 The @value{GDBN} remote serial protocol includes @dfn{notifications},
27722 packets that require no acknowledgment. Both the GDB and the stub
27723 may send notifications (although the only notifications defined at
27724 present are sent by the stub). Notifications carry information
27725 without incurring the round-trip latency of an acknowledgment, and so
27726 are useful for low-impact communications where occasional packet loss
27729 A notification packet has the form @samp{% @var{data} #
27730 @var{checksum}}, where @var{data} is the content of the notification,
27731 and @var{checksum} is a checksum of @var{data}, computed and formatted
27732 as for ordinary @value{GDBN} packets. A notification's @var{data}
27733 never contains @samp{$}, @samp{%} or @samp{#} characters. Upon
27734 receiving a notification, the recipient sends no @samp{+} or @samp{-}
27735 to acknowledge the notification's receipt or to report its corruption.
27737 Every notification's @var{data} begins with a name, which contains no
27738 colon characters, followed by a colon character.
27740 Recipients should silently ignore corrupted notifications and
27741 notifications they do not understand. Recipients should restart
27742 timeout periods on receipt of a well-formed notification, whether or
27743 not they understand it.
27745 Senders should only send the notifications described here when this
27746 protocol description specifies that they are permitted. In the
27747 future, we may extend the protocol to permit existing notifications in
27748 new contexts; this rule helps older senders avoid confusing newer
27751 (Older versions of @value{GDBN} ignore bytes received until they see
27752 the @samp{$} byte that begins an ordinary packet, so new stubs may
27753 transmit notifications without fear of confusing older clients. There
27754 are no notifications defined for @value{GDBN} to send at the moment, but we
27755 assume that most older stubs would ignore them, as well.)
27757 The following notification packets from the stub to @value{GDBN} are
27761 @item Stop: @var{reply}
27762 Report an asynchronous stop event in non-stop mode.
27763 The @var{reply} has the form of a stop reply, as
27764 described in @ref{Stop Reply Packets}. Refer to @ref{Remote Non-Stop},
27765 for information on how these notifications are acknowledged by
27769 @node Remote Non-Stop
27770 @section Remote Protocol Support for Non-Stop Mode
27772 @value{GDBN}'s remote protocol supports non-stop debugging of
27773 multi-threaded programs, as described in @ref{Non-Stop Mode}. If the stub
27774 supports non-stop mode, it should report that to @value{GDBN} by including
27775 @samp{QNonStop+} in its @samp{qSupported} response (@pxref{qSupported}).
27777 @value{GDBN} typically sends a @samp{QNonStop} packet only when
27778 establishing a new connection with the stub. Entering non-stop mode
27779 does not alter the state of any currently-running threads, but targets
27780 must stop all threads in any already-attached processes when entering
27781 all-stop mode. @value{GDBN} uses the @samp{?} packet as necessary to
27782 probe the target state after a mode change.
27784 In non-stop mode, when an attached process encounters an event that
27785 would otherwise be reported with a stop reply, it uses the
27786 asynchronous notification mechanism (@pxref{Notification Packets}) to
27787 inform @value{GDBN}. In contrast to all-stop mode, where all threads
27788 in all processes are stopped when a stop reply is sent, in non-stop
27789 mode only the thread reporting the stop event is stopped. That is,
27790 when reporting a @samp{S} or @samp{T} response to indicate completion
27791 of a step operation, hitting a breakpoint, or a fault, only the
27792 affected thread is stopped; any other still-running threads continue
27793 to run. When reporting a @samp{W} or @samp{X} response, all running
27794 threads belonging to other attached processes continue to run.
27796 Only one stop reply notification at a time may be pending; if
27797 additional stop events occur before @value{GDBN} has acknowledged the
27798 previous notification, they must be queued by the stub for later
27799 synchronous transmission in response to @samp{vStopped} packets from
27800 @value{GDBN}. Because the notification mechanism is unreliable,
27801 the stub is permitted to resend a stop reply notification
27802 if it believes @value{GDBN} may not have received it. @value{GDBN}
27803 ignores additional stop reply notifications received before it has
27804 finished processing a previous notification and the stub has completed
27805 sending any queued stop events.
27807 Otherwise, @value{GDBN} must be prepared to receive a stop reply
27808 notification at any time. Specifically, they may appear when
27809 @value{GDBN} is not otherwise reading input from the stub, or when
27810 @value{GDBN} is expecting to read a normal synchronous response or a
27811 @samp{+}/@samp{-} acknowledgment to a packet it has sent.
27812 Notification packets are distinct from any other communication from
27813 the stub so there is no ambiguity.
27815 After receiving a stop reply notification, @value{GDBN} shall
27816 acknowledge it by sending a @samp{vStopped} packet (@pxref{vStopped packet})
27817 as a regular, synchronous request to the stub. Such acknowledgment
27818 is not required to happen immediately, as @value{GDBN} is permitted to
27819 send other, unrelated packets to the stub first, which the stub should
27822 Upon receiving a @samp{vStopped} packet, if the stub has other queued
27823 stop events to report to @value{GDBN}, it shall respond by sending a
27824 normal stop reply response. @value{GDBN} shall then send another
27825 @samp{vStopped} packet to solicit further responses; again, it is
27826 permitted to send other, unrelated packets as well which the stub
27827 should process normally.
27829 If the stub receives a @samp{vStopped} packet and there are no
27830 additional stop events to report, the stub shall return an @samp{OK}
27831 response. At this point, if further stop events occur, the stub shall
27832 send a new stop reply notification, @value{GDBN} shall accept the
27833 notification, and the process shall be repeated.
27835 In non-stop mode, the target shall respond to the @samp{?} packet as
27836 follows. First, any incomplete stop reply notification/@samp{vStopped}
27837 sequence in progress is abandoned. The target must begin a new
27838 sequence reporting stop events for all stopped threads, whether or not
27839 it has previously reported those events to @value{GDBN}. The first
27840 stop reply is sent as a synchronous reply to the @samp{?} packet, and
27841 subsequent stop replies are sent as responses to @samp{vStopped} packets
27842 using the mechanism described above. The target must not send
27843 asynchronous stop reply notifications until the sequence is complete.
27844 If all threads are running when the target receives the @samp{?} packet,
27845 or if the target is not attached to any process, it shall respond
27848 @node Packet Acknowledgment
27849 @section Packet Acknowledgment
27851 @cindex acknowledgment, for @value{GDBN} remote
27852 @cindex packet acknowledgment, for @value{GDBN} remote
27853 By default, when either the host or the target machine receives a packet,
27854 the first response expected is an acknowledgment: either @samp{+} (to indicate
27855 the package was received correctly) or @samp{-} (to request retransmission).
27856 This mechanism allows the @value{GDBN} remote protocol to operate over
27857 unreliable transport mechanisms, such as a serial line.
27859 In cases where the transport mechanism is itself reliable (such as a pipe or
27860 TCP connection), the @samp{+}/@samp{-} acknowledgments are redundant.
27861 It may be desirable to disable them in that case to reduce communication
27862 overhead, or for other reasons. This can be accomplished by means of the
27863 @samp{QStartNoAckMode} packet; @pxref{QStartNoAckMode}.
27865 When in no-acknowledgment mode, neither the stub nor @value{GDBN} shall send or
27866 expect @samp{+}/@samp{-} protocol acknowledgments. The packet
27867 and response format still includes the normal checksum, as described in
27868 @ref{Overview}, but the checksum may be ignored by the receiver.
27870 If the stub supports @samp{QStartNoAckMode} and prefers to operate in
27871 no-acknowledgment mode, it should report that to @value{GDBN}
27872 by including @samp{QStartNoAckMode+} in its response to @samp{qSupported};
27873 @pxref{qSupported}.
27874 If @value{GDBN} also supports @samp{QStartNoAckMode} and it has not been
27875 disabled via the @code{set remote noack-packet off} command
27876 (@pxref{Remote Configuration}),
27877 @value{GDBN} may then send a @samp{QStartNoAckMode} packet to the stub.
27878 Only then may the stub actually turn off packet acknowledgments.
27879 @value{GDBN} sends a final @samp{+} acknowledgment of the stub's @samp{OK}
27880 response, which can be safely ignored by the stub.
27882 Note that @code{set remote noack-packet} command only affects negotiation
27883 between @value{GDBN} and the stub when subsequent connections are made;
27884 it does not affect the protocol acknowledgment state for any current
27886 Since @samp{+}/@samp{-} acknowledgments are enabled by default when a
27887 new connection is established,
27888 there is also no protocol request to re-enable the acknowledgments
27889 for the current connection, once disabled.
27894 Example sequence of a target being re-started. Notice how the restart
27895 does not get any direct output:
27900 @emph{target restarts}
27903 <- @code{T001:1234123412341234}
27907 Example sequence of a target being stepped by a single instruction:
27910 -> @code{G1445@dots{}}
27915 <- @code{T001:1234123412341234}
27919 <- @code{1455@dots{}}
27923 @node File-I/O Remote Protocol Extension
27924 @section File-I/O Remote Protocol Extension
27925 @cindex File-I/O remote protocol extension
27928 * File-I/O Overview::
27929 * Protocol Basics::
27930 * The F Request Packet::
27931 * The F Reply Packet::
27932 * The Ctrl-C Message::
27934 * List of Supported Calls::
27935 * Protocol-specific Representation of Datatypes::
27937 * File-I/O Examples::
27940 @node File-I/O Overview
27941 @subsection File-I/O Overview
27942 @cindex file-i/o overview
27944 The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the
27945 target to use the host's file system and console I/O to perform various
27946 system calls. System calls on the target system are translated into a
27947 remote protocol packet to the host system, which then performs the needed
27948 actions and returns a response packet to the target system.
27949 This simulates file system operations even on targets that lack file systems.
27951 The protocol is defined to be independent of both the host and target systems.
27952 It uses its own internal representation of datatypes and values. Both
27953 @value{GDBN} and the target's @value{GDBN} stub are responsible for
27954 translating the system-dependent value representations into the internal
27955 protocol representations when data is transmitted.
27957 The communication is synchronous. A system call is possible only when
27958 @value{GDBN} is waiting for a response from the @samp{C}, @samp{c}, @samp{S}
27959 or @samp{s} packets. While @value{GDBN} handles the request for a system call,
27960 the target is stopped to allow deterministic access to the target's
27961 memory. Therefore File-I/O is not interruptible by target signals. On
27962 the other hand, it is possible to interrupt File-I/O by a user interrupt
27963 (@samp{Ctrl-C}) within @value{GDBN}.
27965 The target's request to perform a host system call does not finish
27966 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
27967 after finishing the system call, the target returns to continuing the
27968 previous activity (continue, step). No additional continue or step
27969 request from @value{GDBN} is required.
27972 (@value{GDBP}) continue
27973 <- target requests 'system call X'
27974 target is stopped, @value{GDBN} executes system call
27975 -> @value{GDBN} returns result
27976 ... target continues, @value{GDBN} returns to wait for the target
27977 <- target hits breakpoint and sends a Txx packet
27980 The protocol only supports I/O on the console and to regular files on
27981 the host file system. Character or block special devices, pipes,
27982 named pipes, sockets or any other communication method on the host
27983 system are not supported by this protocol.
27985 File I/O is not supported in non-stop mode.
27987 @node Protocol Basics
27988 @subsection Protocol Basics
27989 @cindex protocol basics, file-i/o
27991 The File-I/O protocol uses the @code{F} packet as the request as well
27992 as reply packet. Since a File-I/O system call can only occur when
27993 @value{GDBN} is waiting for a response from the continuing or stepping target,
27994 the File-I/O request is a reply that @value{GDBN} has to expect as a result
27995 of a previous @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
27996 This @code{F} packet contains all information needed to allow @value{GDBN}
27997 to call the appropriate host system call:
28001 A unique identifier for the requested system call.
28004 All parameters to the system call. Pointers are given as addresses
28005 in the target memory address space. Pointers to strings are given as
28006 pointer/length pair. Numerical values are given as they are.
28007 Numerical control flags are given in a protocol-specific representation.
28011 At this point, @value{GDBN} has to perform the following actions.
28015 If the parameters include pointer values to data needed as input to a
28016 system call, @value{GDBN} requests this data from the target with a
28017 standard @code{m} packet request. This additional communication has to be
28018 expected by the target implementation and is handled as any other @code{m}
28022 @value{GDBN} translates all value from protocol representation to host
28023 representation as needed. Datatypes are coerced into the host types.
28026 @value{GDBN} calls the system call.
28029 It then coerces datatypes back to protocol representation.
28032 If the system call is expected to return data in buffer space specified
28033 by pointer parameters to the call, the data is transmitted to the
28034 target using a @code{M} or @code{X} packet. This packet has to be expected
28035 by the target implementation and is handled as any other @code{M} or @code{X}
28040 Eventually @value{GDBN} replies with another @code{F} packet which contains all
28041 necessary information for the target to continue. This at least contains
28048 @code{errno}, if has been changed by the system call.
28055 After having done the needed type and value coercion, the target continues
28056 the latest continue or step action.
28058 @node The F Request Packet
28059 @subsection The @code{F} Request Packet
28060 @cindex file-i/o request packet
28061 @cindex @code{F} request packet
28063 The @code{F} request packet has the following format:
28066 @item F@var{call-id},@var{parameter@dots{}}
28068 @var{call-id} is the identifier to indicate the host system call to be called.
28069 This is just the name of the function.
28071 @var{parameter@dots{}} are the parameters to the system call.
28072 Parameters are hexadecimal integer values, either the actual values in case
28073 of scalar datatypes, pointers to target buffer space in case of compound
28074 datatypes and unspecified memory areas, or pointer/length pairs in case
28075 of string parameters. These are appended to the @var{call-id} as a
28076 comma-delimited list. All values are transmitted in ASCII
28077 string representation, pointer/length pairs separated by a slash.
28083 @node The F Reply Packet
28084 @subsection The @code{F} Reply Packet
28085 @cindex file-i/o reply packet
28086 @cindex @code{F} reply packet
28088 The @code{F} reply packet has the following format:
28092 @item F@var{retcode},@var{errno},@var{Ctrl-C flag};@var{call-specific attachment}
28094 @var{retcode} is the return code of the system call as hexadecimal value.
28096 @var{errno} is the @code{errno} set by the call, in protocol-specific
28098 This parameter can be omitted if the call was successful.
28100 @var{Ctrl-C flag} is only sent if the user requested a break. In this
28101 case, @var{errno} must be sent as well, even if the call was successful.
28102 The @var{Ctrl-C flag} itself consists of the character @samp{C}:
28109 or, if the call was interrupted before the host call has been performed:
28116 assuming 4 is the protocol-specific representation of @code{EINTR}.
28121 @node The Ctrl-C Message
28122 @subsection The @samp{Ctrl-C} Message
28123 @cindex ctrl-c message, in file-i/o protocol
28125 If the @samp{Ctrl-C} flag is set in the @value{GDBN}
28126 reply packet (@pxref{The F Reply Packet}),
28127 the target should behave as if it had
28128 gotten a break message. The meaning for the target is ``system call
28129 interrupted by @code{SIGINT}''. Consequentially, the target should actually stop
28130 (as with a break message) and return to @value{GDBN} with a @code{T02}
28133 It's important for the target to know in which
28134 state the system call was interrupted. There are two possible cases:
28138 The system call hasn't been performed on the host yet.
28141 The system call on the host has been finished.
28145 These two states can be distinguished by the target by the value of the
28146 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
28147 call hasn't been performed. This is equivalent to the @code{EINTR} handling
28148 on POSIX systems. In any other case, the target may presume that the
28149 system call has been finished --- successfully or not --- and should behave
28150 as if the break message arrived right after the system call.
28152 @value{GDBN} must behave reliably. If the system call has not been called
28153 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
28154 @code{errno} in the packet. If the system call on the host has been finished
28155 before the user requests a break, the full action must be finished by
28156 @value{GDBN}. This requires sending @code{M} or @code{X} packets as necessary.
28157 The @code{F} packet may only be sent when either nothing has happened
28158 or the full action has been completed.
28161 @subsection Console I/O
28162 @cindex console i/o as part of file-i/o
28164 By default and if not explicitly closed by the target system, the file
28165 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
28166 on the @value{GDBN} console is handled as any other file output operation
28167 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
28168 by @value{GDBN} so that after the target read request from file descriptor
28169 0 all following typing is buffered until either one of the following
28174 The user types @kbd{Ctrl-c}. The behaviour is as explained above, and the
28176 system call is treated as finished.
28179 The user presses @key{RET}. This is treated as end of input with a trailing
28183 The user types @kbd{Ctrl-d}. This is treated as end of input. No trailing
28184 character (neither newline nor @samp{Ctrl-D}) is appended to the input.
28188 If the user has typed more characters than fit in the buffer given to
28189 the @code{read} call, the trailing characters are buffered in @value{GDBN} until
28190 either another @code{read(0, @dots{})} is requested by the target, or debugging
28191 is stopped at the user's request.
28194 @node List of Supported Calls
28195 @subsection List of Supported Calls
28196 @cindex list of supported file-i/o calls
28213 @unnumberedsubsubsec open
28214 @cindex open, file-i/o system call
28219 int open(const char *pathname, int flags);
28220 int open(const char *pathname, int flags, mode_t mode);
28224 @samp{Fopen,@var{pathptr}/@var{len},@var{flags},@var{mode}}
28227 @var{flags} is the bitwise @code{OR} of the following values:
28231 If the file does not exist it will be created. The host
28232 rules apply as far as file ownership and time stamps
28236 When used with @code{O_CREAT}, if the file already exists it is
28237 an error and open() fails.
28240 If the file already exists and the open mode allows
28241 writing (@code{O_RDWR} or @code{O_WRONLY} is given) it will be
28242 truncated to zero length.
28245 The file is opened in append mode.
28248 The file is opened for reading only.
28251 The file is opened for writing only.
28254 The file is opened for reading and writing.
28258 Other bits are silently ignored.
28262 @var{mode} is the bitwise @code{OR} of the following values:
28266 User has read permission.
28269 User has write permission.
28272 Group has read permission.
28275 Group has write permission.
28278 Others have read permission.
28281 Others have write permission.
28285 Other bits are silently ignored.
28288 @item Return value:
28289 @code{open} returns the new file descriptor or -1 if an error
28296 @var{pathname} already exists and @code{O_CREAT} and @code{O_EXCL} were used.
28299 @var{pathname} refers to a directory.
28302 The requested access is not allowed.
28305 @var{pathname} was too long.
28308 A directory component in @var{pathname} does not exist.
28311 @var{pathname} refers to a device, pipe, named pipe or socket.
28314 @var{pathname} refers to a file on a read-only filesystem and
28315 write access was requested.
28318 @var{pathname} is an invalid pointer value.
28321 No space on device to create the file.
28324 The process already has the maximum number of files open.
28327 The limit on the total number of files open on the system
28331 The call was interrupted by the user.
28337 @unnumberedsubsubsec close
28338 @cindex close, file-i/o system call
28347 @samp{Fclose,@var{fd}}
28349 @item Return value:
28350 @code{close} returns zero on success, or -1 if an error occurred.
28356 @var{fd} isn't a valid open file descriptor.
28359 The call was interrupted by the user.
28365 @unnumberedsubsubsec read
28366 @cindex read, file-i/o system call
28371 int read(int fd, void *buf, unsigned int count);
28375 @samp{Fread,@var{fd},@var{bufptr},@var{count}}
28377 @item Return value:
28378 On success, the number of bytes read is returned.
28379 Zero indicates end of file. If count is zero, read
28380 returns zero as well. On error, -1 is returned.
28386 @var{fd} is not a valid file descriptor or is not open for
28390 @var{bufptr} is an invalid pointer value.
28393 The call was interrupted by the user.
28399 @unnumberedsubsubsec write
28400 @cindex write, file-i/o system call
28405 int write(int fd, const void *buf, unsigned int count);
28409 @samp{Fwrite,@var{fd},@var{bufptr},@var{count}}
28411 @item Return value:
28412 On success, the number of bytes written are returned.
28413 Zero indicates nothing was written. On error, -1
28420 @var{fd} is not a valid file descriptor or is not open for
28424 @var{bufptr} is an invalid pointer value.
28427 An attempt was made to write a file that exceeds the
28428 host-specific maximum file size allowed.
28431 No space on device to write the data.
28434 The call was interrupted by the user.
28440 @unnumberedsubsubsec lseek
28441 @cindex lseek, file-i/o system call
28446 long lseek (int fd, long offset, int flag);
28450 @samp{Flseek,@var{fd},@var{offset},@var{flag}}
28452 @var{flag} is one of:
28456 The offset is set to @var{offset} bytes.
28459 The offset is set to its current location plus @var{offset}
28463 The offset is set to the size of the file plus @var{offset}
28467 @item Return value:
28468 On success, the resulting unsigned offset in bytes from
28469 the beginning of the file is returned. Otherwise, a
28470 value of -1 is returned.
28476 @var{fd} is not a valid open file descriptor.
28479 @var{fd} is associated with the @value{GDBN} console.
28482 @var{flag} is not a proper value.
28485 The call was interrupted by the user.
28491 @unnumberedsubsubsec rename
28492 @cindex rename, file-i/o system call
28497 int rename(const char *oldpath, const char *newpath);
28501 @samp{Frename,@var{oldpathptr}/@var{len},@var{newpathptr}/@var{len}}
28503 @item Return value:
28504 On success, zero is returned. On error, -1 is returned.
28510 @var{newpath} is an existing directory, but @var{oldpath} is not a
28514 @var{newpath} is a non-empty directory.
28517 @var{oldpath} or @var{newpath} is a directory that is in use by some
28521 An attempt was made to make a directory a subdirectory
28525 A component used as a directory in @var{oldpath} or new
28526 path is not a directory. Or @var{oldpath} is a directory
28527 and @var{newpath} exists but is not a directory.
28530 @var{oldpathptr} or @var{newpathptr} are invalid pointer values.
28533 No access to the file or the path of the file.
28537 @var{oldpath} or @var{newpath} was too long.
28540 A directory component in @var{oldpath} or @var{newpath} does not exist.
28543 The file is on a read-only filesystem.
28546 The device containing the file has no room for the new
28550 The call was interrupted by the user.
28556 @unnumberedsubsubsec unlink
28557 @cindex unlink, file-i/o system call
28562 int unlink(const char *pathname);
28566 @samp{Funlink,@var{pathnameptr}/@var{len}}
28568 @item Return value:
28569 On success, zero is returned. On error, -1 is returned.
28575 No access to the file or the path of the file.
28578 The system does not allow unlinking of directories.
28581 The file @var{pathname} cannot be unlinked because it's
28582 being used by another process.
28585 @var{pathnameptr} is an invalid pointer value.
28588 @var{pathname} was too long.
28591 A directory component in @var{pathname} does not exist.
28594 A component of the path is not a directory.
28597 The file is on a read-only filesystem.
28600 The call was interrupted by the user.
28606 @unnumberedsubsubsec stat/fstat
28607 @cindex fstat, file-i/o system call
28608 @cindex stat, file-i/o system call
28613 int stat(const char *pathname, struct stat *buf);
28614 int fstat(int fd, struct stat *buf);
28618 @samp{Fstat,@var{pathnameptr}/@var{len},@var{bufptr}}@*
28619 @samp{Ffstat,@var{fd},@var{bufptr}}
28621 @item Return value:
28622 On success, zero is returned. On error, -1 is returned.
28628 @var{fd} is not a valid open file.
28631 A directory component in @var{pathname} does not exist or the
28632 path is an empty string.
28635 A component of the path is not a directory.
28638 @var{pathnameptr} is an invalid pointer value.
28641 No access to the file or the path of the file.
28644 @var{pathname} was too long.
28647 The call was interrupted by the user.
28653 @unnumberedsubsubsec gettimeofday
28654 @cindex gettimeofday, file-i/o system call
28659 int gettimeofday(struct timeval *tv, void *tz);
28663 @samp{Fgettimeofday,@var{tvptr},@var{tzptr}}
28665 @item Return value:
28666 On success, 0 is returned, -1 otherwise.
28672 @var{tz} is a non-NULL pointer.
28675 @var{tvptr} and/or @var{tzptr} is an invalid pointer value.
28681 @unnumberedsubsubsec isatty
28682 @cindex isatty, file-i/o system call
28687 int isatty(int fd);
28691 @samp{Fisatty,@var{fd}}
28693 @item Return value:
28694 Returns 1 if @var{fd} refers to the @value{GDBN} console, 0 otherwise.
28700 The call was interrupted by the user.
28705 Note that the @code{isatty} call is treated as a special case: it returns
28706 1 to the target if the file descriptor is attached
28707 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
28708 would require implementing @code{ioctl} and would be more complex than
28713 @unnumberedsubsubsec system
28714 @cindex system, file-i/o system call
28719 int system(const char *command);
28723 @samp{Fsystem,@var{commandptr}/@var{len}}
28725 @item Return value:
28726 If @var{len} is zero, the return value indicates whether a shell is
28727 available. A zero return value indicates a shell is not available.
28728 For non-zero @var{len}, the value returned is -1 on error and the
28729 return status of the command otherwise. Only the exit status of the
28730 command is returned, which is extracted from the host's @code{system}
28731 return value by calling @code{WEXITSTATUS(retval)}. In case
28732 @file{/bin/sh} could not be executed, 127 is returned.
28738 The call was interrupted by the user.
28743 @value{GDBN} takes over the full task of calling the necessary host calls
28744 to perform the @code{system} call. The return value of @code{system} on
28745 the host is simplified before it's returned
28746 to the target. Any termination signal information from the child process
28747 is discarded, and the return value consists
28748 entirely of the exit status of the called command.
28750 Due to security concerns, the @code{system} call is by default refused
28751 by @value{GDBN}. The user has to allow this call explicitly with the
28752 @code{set remote system-call-allowed 1} command.
28755 @item set remote system-call-allowed
28756 @kindex set remote system-call-allowed
28757 Control whether to allow the @code{system} calls in the File I/O
28758 protocol for the remote target. The default is zero (disabled).
28760 @item show remote system-call-allowed
28761 @kindex show remote system-call-allowed
28762 Show whether the @code{system} calls are allowed in the File I/O
28766 @node Protocol-specific Representation of Datatypes
28767 @subsection Protocol-specific Representation of Datatypes
28768 @cindex protocol-specific representation of datatypes, in file-i/o protocol
28771 * Integral Datatypes::
28773 * Memory Transfer::
28778 @node Integral Datatypes
28779 @unnumberedsubsubsec Integral Datatypes
28780 @cindex integral datatypes, in file-i/o protocol
28782 The integral datatypes used in the system calls are @code{int},
28783 @code{unsigned int}, @code{long}, @code{unsigned long},
28784 @code{mode_t}, and @code{time_t}.
28786 @code{int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
28787 implemented as 32 bit values in this protocol.
28789 @code{long} and @code{unsigned long} are implemented as 64 bit types.
28791 @xref{Limits}, for corresponding MIN and MAX values (similar to those
28792 in @file{limits.h}) to allow range checking on host and target.
28794 @code{time_t} datatypes are defined as seconds since the Epoch.
28796 All integral datatypes transferred as part of a memory read or write of a
28797 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
28800 @node Pointer Values
28801 @unnumberedsubsubsec Pointer Values
28802 @cindex pointer values, in file-i/o protocol
28804 Pointers to target data are transmitted as they are. An exception
28805 is made for pointers to buffers for which the length isn't
28806 transmitted as part of the function call, namely strings. Strings
28807 are transmitted as a pointer/length pair, both as hex values, e.g.@:
28814 which is a pointer to data of length 18 bytes at position 0x1aaf.
28815 The length is defined as the full string length in bytes, including
28816 the trailing null byte. For example, the string @code{"hello world"}
28817 at address 0x123456 is transmitted as
28823 @node Memory Transfer
28824 @unnumberedsubsubsec Memory Transfer
28825 @cindex memory transfer, in file-i/o protocol
28827 Structured data which is transferred using a memory read or write (for
28828 example, a @code{struct stat}) is expected to be in a protocol-specific format
28829 with all scalar multibyte datatypes being big endian. Translation to
28830 this representation needs to be done both by the target before the @code{F}
28831 packet is sent, and by @value{GDBN} before
28832 it transfers memory to the target. Transferred pointers to structured
28833 data should point to the already-coerced data at any time.
28837 @unnumberedsubsubsec struct stat
28838 @cindex struct stat, in file-i/o protocol
28840 The buffer of type @code{struct stat} used by the target and @value{GDBN}
28841 is defined as follows:
28845 unsigned int st_dev; /* device */
28846 unsigned int st_ino; /* inode */
28847 mode_t st_mode; /* protection */
28848 unsigned int st_nlink; /* number of hard links */
28849 unsigned int st_uid; /* user ID of owner */
28850 unsigned int st_gid; /* group ID of owner */
28851 unsigned int st_rdev; /* device type (if inode device) */
28852 unsigned long st_size; /* total size, in bytes */
28853 unsigned long st_blksize; /* blocksize for filesystem I/O */
28854 unsigned long st_blocks; /* number of blocks allocated */
28855 time_t st_atime; /* time of last access */
28856 time_t st_mtime; /* time of last modification */
28857 time_t st_ctime; /* time of last change */
28861 The integral datatypes conform to the definitions given in the
28862 appropriate section (see @ref{Integral Datatypes}, for details) so this
28863 structure is of size 64 bytes.
28865 The values of several fields have a restricted meaning and/or
28871 A value of 0 represents a file, 1 the console.
28874 No valid meaning for the target. Transmitted unchanged.
28877 Valid mode bits are described in @ref{Constants}. Any other
28878 bits have currently no meaning for the target.
28883 No valid meaning for the target. Transmitted unchanged.
28888 These values have a host and file system dependent
28889 accuracy. Especially on Windows hosts, the file system may not
28890 support exact timing values.
28893 The target gets a @code{struct stat} of the above representation and is
28894 responsible for coercing it to the target representation before
28897 Note that due to size differences between the host, target, and protocol
28898 representations of @code{struct stat} members, these members could eventually
28899 get truncated on the target.
28901 @node struct timeval
28902 @unnumberedsubsubsec struct timeval
28903 @cindex struct timeval, in file-i/o protocol
28905 The buffer of type @code{struct timeval} used by the File-I/O protocol
28906 is defined as follows:
28910 time_t tv_sec; /* second */
28911 long tv_usec; /* microsecond */
28915 The integral datatypes conform to the definitions given in the
28916 appropriate section (see @ref{Integral Datatypes}, for details) so this
28917 structure is of size 8 bytes.
28920 @subsection Constants
28921 @cindex constants, in file-i/o protocol
28923 The following values are used for the constants inside of the
28924 protocol. @value{GDBN} and target are responsible for translating these
28925 values before and after the call as needed.
28936 @unnumberedsubsubsec Open Flags
28937 @cindex open flags, in file-i/o protocol
28939 All values are given in hexadecimal representation.
28951 @node mode_t Values
28952 @unnumberedsubsubsec mode_t Values
28953 @cindex mode_t values, in file-i/o protocol
28955 All values are given in octal representation.
28972 @unnumberedsubsubsec Errno Values
28973 @cindex errno values, in file-i/o protocol
28975 All values are given in decimal representation.
29000 @code{EUNKNOWN} is used as a fallback error value if a host system returns
29001 any error value not in the list of supported error numbers.
29004 @unnumberedsubsubsec Lseek Flags
29005 @cindex lseek flags, in file-i/o protocol
29014 @unnumberedsubsubsec Limits
29015 @cindex limits, in file-i/o protocol
29017 All values are given in decimal representation.
29020 INT_MIN -2147483648
29022 UINT_MAX 4294967295
29023 LONG_MIN -9223372036854775808
29024 LONG_MAX 9223372036854775807
29025 ULONG_MAX 18446744073709551615
29028 @node File-I/O Examples
29029 @subsection File-I/O Examples
29030 @cindex file-i/o examples
29032 Example sequence of a write call, file descriptor 3, buffer is at target
29033 address 0x1234, 6 bytes should be written:
29036 <- @code{Fwrite,3,1234,6}
29037 @emph{request memory read from target}
29040 @emph{return "6 bytes written"}
29044 Example sequence of a read call, file descriptor 3, buffer is at target
29045 address 0x1234, 6 bytes should be read:
29048 <- @code{Fread,3,1234,6}
29049 @emph{request memory write to target}
29050 -> @code{X1234,6:XXXXXX}
29051 @emph{return "6 bytes read"}
29055 Example sequence of a read call, call fails on the host due to invalid
29056 file descriptor (@code{EBADF}):
29059 <- @code{Fread,3,1234,6}
29063 Example sequence of a read call, user presses @kbd{Ctrl-c} before syscall on
29067 <- @code{Fread,3,1234,6}
29072 Example sequence of a read call, user presses @kbd{Ctrl-c} after syscall on
29076 <- @code{Fread,3,1234,6}
29077 -> @code{X1234,6:XXXXXX}
29081 @node Library List Format
29082 @section Library List Format
29083 @cindex library list format, remote protocol
29085 On some platforms, a dynamic loader (e.g.@: @file{ld.so}) runs in the
29086 same process as your application to manage libraries. In this case,
29087 @value{GDBN} can use the loader's symbol table and normal memory
29088 operations to maintain a list of shared libraries. On other
29089 platforms, the operating system manages loaded libraries.
29090 @value{GDBN} can not retrieve the list of currently loaded libraries
29091 through memory operations, so it uses the @samp{qXfer:libraries:read}
29092 packet (@pxref{qXfer library list read}) instead. The remote stub
29093 queries the target's operating system and reports which libraries
29096 The @samp{qXfer:libraries:read} packet returns an XML document which
29097 lists loaded libraries and their offsets. Each library has an
29098 associated name and one or more segment or section base addresses,
29099 which report where the library was loaded in memory.
29101 For the common case of libraries that are fully linked binaries, the
29102 library should have a list of segments. If the target supports
29103 dynamic linking of a relocatable object file, its library XML element
29104 should instead include a list of allocated sections. The segment or
29105 section bases are start addresses, not relocation offsets; they do not
29106 depend on the library's link-time base addresses.
29108 @value{GDBN} must be linked with the Expat library to support XML
29109 library lists. @xref{Expat}.
29111 A simple memory map, with one loaded library relocated by a single
29112 offset, looks like this:
29116 <library name="/lib/libc.so.6">
29117 <segment address="0x10000000"/>
29122 Another simple memory map, with one loaded library with three
29123 allocated sections (.text, .data, .bss), looks like this:
29127 <library name="sharedlib.o">
29128 <section address="0x10000000"/>
29129 <section address="0x20000000"/>
29130 <section address="0x30000000"/>
29135 The format of a library list is described by this DTD:
29138 <!-- library-list: Root element with versioning -->
29139 <!ELEMENT library-list (library)*>
29140 <!ATTLIST library-list version CDATA #FIXED "1.0">
29141 <!ELEMENT library (segment*, section*)>
29142 <!ATTLIST library name CDATA #REQUIRED>
29143 <!ELEMENT segment EMPTY>
29144 <!ATTLIST segment address CDATA #REQUIRED>
29145 <!ELEMENT section EMPTY>
29146 <!ATTLIST section address CDATA #REQUIRED>
29149 In addition, segments and section descriptors cannot be mixed within a
29150 single library element, and you must supply at least one segment or
29151 section for each library.
29153 @node Memory Map Format
29154 @section Memory Map Format
29155 @cindex memory map format
29157 To be able to write into flash memory, @value{GDBN} needs to obtain a
29158 memory map from the target. This section describes the format of the
29161 The memory map is obtained using the @samp{qXfer:memory-map:read}
29162 (@pxref{qXfer memory map read}) packet and is an XML document that
29163 lists memory regions.
29165 @value{GDBN} must be linked with the Expat library to support XML
29166 memory maps. @xref{Expat}.
29168 The top-level structure of the document is shown below:
29171 <?xml version="1.0"?>
29172 <!DOCTYPE memory-map
29173 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
29174 "http://sourceware.org/gdb/gdb-memory-map.dtd">
29180 Each region can be either:
29185 A region of RAM starting at @var{addr} and extending for @var{length}
29189 <memory type="ram" start="@var{addr}" length="@var{length}"/>
29194 A region of read-only memory:
29197 <memory type="rom" start="@var{addr}" length="@var{length}"/>
29202 A region of flash memory, with erasure blocks @var{blocksize}
29206 <memory type="flash" start="@var{addr}" length="@var{length}">
29207 <property name="blocksize">@var{blocksize}</property>
29213 Regions must not overlap. @value{GDBN} assumes that areas of memory not covered
29214 by the memory map are RAM, and uses the ordinary @samp{M} and @samp{X}
29215 packets to write to addresses in such ranges.
29217 The formal DTD for memory map format is given below:
29220 <!-- ................................................... -->
29221 <!-- Memory Map XML DTD ................................ -->
29222 <!-- File: memory-map.dtd .............................. -->
29223 <!-- .................................... .............. -->
29224 <!-- memory-map.dtd -->
29225 <!-- memory-map: Root element with versioning -->
29226 <!ELEMENT memory-map (memory | property)>
29227 <!ATTLIST memory-map version CDATA #FIXED "1.0.0">
29228 <!ELEMENT memory (property)>
29229 <!-- memory: Specifies a memory region,
29230 and its type, or device. -->
29231 <!ATTLIST memory type CDATA #REQUIRED
29232 start CDATA #REQUIRED
29233 length CDATA #REQUIRED
29234 device CDATA #IMPLIED>
29235 <!-- property: Generic attribute tag -->
29236 <!ELEMENT property (#PCDATA | property)*>
29237 <!ATTLIST property name CDATA #REQUIRED>
29240 @include agentexpr.texi
29242 @node Target Descriptions
29243 @appendix Target Descriptions
29244 @cindex target descriptions
29246 @strong{Warning:} target descriptions are still under active development,
29247 and the contents and format may change between @value{GDBN} releases.
29248 The format is expected to stabilize in the future.
29250 One of the challenges of using @value{GDBN} to debug embedded systems
29251 is that there are so many minor variants of each processor
29252 architecture in use. It is common practice for vendors to start with
29253 a standard processor core --- ARM, PowerPC, or MIPS, for example ---
29254 and then make changes to adapt it to a particular market niche. Some
29255 architectures have hundreds of variants, available from dozens of
29256 vendors. This leads to a number of problems:
29260 With so many different customized processors, it is difficult for
29261 the @value{GDBN} maintainers to keep up with the changes.
29263 Since individual variants may have short lifetimes or limited
29264 audiences, it may not be worthwhile to carry information about every
29265 variant in the @value{GDBN} source tree.
29267 When @value{GDBN} does support the architecture of the embedded system
29268 at hand, the task of finding the correct architecture name to give the
29269 @command{set architecture} command can be error-prone.
29272 To address these problems, the @value{GDBN} remote protocol allows a
29273 target system to not only identify itself to @value{GDBN}, but to
29274 actually describe its own features. This lets @value{GDBN} support
29275 processor variants it has never seen before --- to the extent that the
29276 descriptions are accurate, and that @value{GDBN} understands them.
29278 @value{GDBN} must be linked with the Expat library to support XML
29279 target descriptions. @xref{Expat}.
29282 * Retrieving Descriptions:: How descriptions are fetched from a target.
29283 * Target Description Format:: The contents of a target description.
29284 * Predefined Target Types:: Standard types available for target
29286 * Standard Target Features:: Features @value{GDBN} knows about.
29289 @node Retrieving Descriptions
29290 @section Retrieving Descriptions
29292 Target descriptions can be read from the target automatically, or
29293 specified by the user manually. The default behavior is to read the
29294 description from the target. @value{GDBN} retrieves it via the remote
29295 protocol using @samp{qXfer} requests (@pxref{General Query Packets,
29296 qXfer}). The @var{annex} in the @samp{qXfer} packet will be
29297 @samp{target.xml}. The contents of the @samp{target.xml} annex are an
29298 XML document, of the form described in @ref{Target Description
29301 Alternatively, you can specify a file to read for the target description.
29302 If a file is set, the target will not be queried. The commands to
29303 specify a file are:
29306 @cindex set tdesc filename
29307 @item set tdesc filename @var{path}
29308 Read the target description from @var{path}.
29310 @cindex unset tdesc filename
29311 @item unset tdesc filename
29312 Do not read the XML target description from a file. @value{GDBN}
29313 will use the description supplied by the current target.
29315 @cindex show tdesc filename
29316 @item show tdesc filename
29317 Show the filename to read for a target description, if any.
29321 @node Target Description Format
29322 @section Target Description Format
29323 @cindex target descriptions, XML format
29325 A target description annex is an @uref{http://www.w3.org/XML/, XML}
29326 document which complies with the Document Type Definition provided in
29327 the @value{GDBN} sources in @file{gdb/features/gdb-target.dtd}. This
29328 means you can use generally available tools like @command{xmllint} to
29329 check that your feature descriptions are well-formed and valid.
29330 However, to help people unfamiliar with XML write descriptions for
29331 their targets, we also describe the grammar here.
29333 Target descriptions can identify the architecture of the remote target
29334 and (for some architectures) provide information about custom register
29335 sets. @value{GDBN} can use this information to autoconfigure for your
29336 target, or to warn you if you connect to an unsupported target.
29338 Here is a simple target description:
29341 <target version="1.0">
29342 <architecture>i386:x86-64</architecture>
29347 This minimal description only says that the target uses
29348 the x86-64 architecture.
29350 A target description has the following overall form, with [ ] marking
29351 optional elements and @dots{} marking repeatable elements. The elements
29352 are explained further below.
29355 <?xml version="1.0"?>
29356 <!DOCTYPE target SYSTEM "gdb-target.dtd">
29357 <target version="1.0">
29358 @r{[}@var{architecture}@r{]}
29359 @r{[}@var{feature}@dots{}@r{]}
29364 The description is generally insensitive to whitespace and line
29365 breaks, under the usual common-sense rules. The XML version
29366 declaration and document type declaration can generally be omitted
29367 (@value{GDBN} does not require them), but specifying them may be
29368 useful for XML validation tools. The @samp{version} attribute for
29369 @samp{<target>} may also be omitted, but we recommend
29370 including it; if future versions of @value{GDBN} use an incompatible
29371 revision of @file{gdb-target.dtd}, they will detect and report
29372 the version mismatch.
29374 @subsection Inclusion
29375 @cindex target descriptions, inclusion
29378 @cindex <xi:include>
29381 It can sometimes be valuable to split a target description up into
29382 several different annexes, either for organizational purposes, or to
29383 share files between different possible target descriptions. You can
29384 divide a description into multiple files by replacing any element of
29385 the target description with an inclusion directive of the form:
29388 <xi:include href="@var{document}"/>
29392 When @value{GDBN} encounters an element of this form, it will retrieve
29393 the named XML @var{document}, and replace the inclusion directive with
29394 the contents of that document. If the current description was read
29395 using @samp{qXfer}, then so will be the included document;
29396 @var{document} will be interpreted as the name of an annex. If the
29397 current description was read from a file, @value{GDBN} will look for
29398 @var{document} as a file in the same directory where it found the
29399 original description.
29401 @subsection Architecture
29402 @cindex <architecture>
29404 An @samp{<architecture>} element has this form:
29407 <architecture>@var{arch}</architecture>
29410 @var{arch} is an architecture name from the same selection
29411 accepted by @code{set architecture} (@pxref{Targets, ,Specifying a
29412 Debugging Target}).
29414 @subsection Features
29417 Each @samp{<feature>} describes some logical portion of the target
29418 system. Features are currently used to describe available CPU
29419 registers and the types of their contents. A @samp{<feature>} element
29423 <feature name="@var{name}">
29424 @r{[}@var{type}@dots{}@r{]}
29430 Each feature's name should be unique within the description. The name
29431 of a feature does not matter unless @value{GDBN} has some special
29432 knowledge of the contents of that feature; if it does, the feature
29433 should have its standard name. @xref{Standard Target Features}.
29437 Any register's value is a collection of bits which @value{GDBN} must
29438 interpret. The default interpretation is a two's complement integer,
29439 but other types can be requested by name in the register description.
29440 Some predefined types are provided by @value{GDBN} (@pxref{Predefined
29441 Target Types}), and the description can define additional composite types.
29443 Each type element must have an @samp{id} attribute, which gives
29444 a unique (within the containing @samp{<feature>}) name to the type.
29445 Types must be defined before they are used.
29448 Some targets offer vector registers, which can be treated as arrays
29449 of scalar elements. These types are written as @samp{<vector>} elements,
29450 specifying the array element type, @var{type}, and the number of elements,
29454 <vector id="@var{id}" type="@var{type}" count="@var{count}"/>
29458 If a register's value is usefully viewed in multiple ways, define it
29459 with a union type containing the useful representations. The
29460 @samp{<union>} element contains one or more @samp{<field>} elements,
29461 each of which has a @var{name} and a @var{type}:
29464 <union id="@var{id}">
29465 <field name="@var{name}" type="@var{type}"/>
29470 @subsection Registers
29473 Each register is represented as an element with this form:
29476 <reg name="@var{name}"
29477 bitsize="@var{size}"
29478 @r{[}regnum="@var{num}"@r{]}
29479 @r{[}save-restore="@var{save-restore}"@r{]}
29480 @r{[}type="@var{type}"@r{]}
29481 @r{[}group="@var{group}"@r{]}/>
29485 The components are as follows:
29490 The register's name; it must be unique within the target description.
29493 The register's size, in bits.
29496 The register's number. If omitted, a register's number is one greater
29497 than that of the previous register (either in the current feature or in
29498 a preceeding feature); the first register in the target description
29499 defaults to zero. This register number is used to read or write
29500 the register; e.g.@: it is used in the remote @code{p} and @code{P}
29501 packets, and registers appear in the @code{g} and @code{G} packets
29502 in order of increasing register number.
29505 Whether the register should be preserved across inferior function
29506 calls; this must be either @code{yes} or @code{no}. The default is
29507 @code{yes}, which is appropriate for most registers except for
29508 some system control registers; this is not related to the target's
29512 The type of the register. @var{type} may be a predefined type, a type
29513 defined in the current feature, or one of the special types @code{int}
29514 and @code{float}. @code{int} is an integer type of the correct size
29515 for @var{bitsize}, and @code{float} is a floating point type (in the
29516 architecture's normal floating point format) of the correct size for
29517 @var{bitsize}. The default is @code{int}.
29520 The register group to which this register belongs. @var{group} must
29521 be either @code{general}, @code{float}, or @code{vector}. If no
29522 @var{group} is specified, @value{GDBN} will not display the register
29523 in @code{info registers}.
29527 @node Predefined Target Types
29528 @section Predefined Target Types
29529 @cindex target descriptions, predefined types
29531 Type definitions in the self-description can build up composite types
29532 from basic building blocks, but can not define fundamental types. Instead,
29533 standard identifiers are provided by @value{GDBN} for the fundamental
29534 types. The currently supported types are:
29543 Signed integer types holding the specified number of bits.
29550 Unsigned integer types holding the specified number of bits.
29554 Pointers to unspecified code and data. The program counter and
29555 any dedicated return address register may be marked as code
29556 pointers; printing a code pointer converts it into a symbolic
29557 address. The stack pointer and any dedicated address registers
29558 may be marked as data pointers.
29561 Single precision IEEE floating point.
29564 Double precision IEEE floating point.
29567 The 12-byte extended precision format used by ARM FPA registers.
29571 @node Standard Target Features
29572 @section Standard Target Features
29573 @cindex target descriptions, standard features
29575 A target description must contain either no registers or all the
29576 target's registers. If the description contains no registers, then
29577 @value{GDBN} will assume a default register layout, selected based on
29578 the architecture. If the description contains any registers, the
29579 default layout will not be used; the standard registers must be
29580 described in the target description, in such a way that @value{GDBN}
29581 can recognize them.
29583 This is accomplished by giving specific names to feature elements
29584 which contain standard registers. @value{GDBN} will look for features
29585 with those names and verify that they contain the expected registers;
29586 if any known feature is missing required registers, or if any required
29587 feature is missing, @value{GDBN} will reject the target
29588 description. You can add additional registers to any of the
29589 standard features --- @value{GDBN} will display them just as if
29590 they were added to an unrecognized feature.
29592 This section lists the known features and their expected contents.
29593 Sample XML documents for these features are included in the
29594 @value{GDBN} source tree, in the directory @file{gdb/features}.
29596 Names recognized by @value{GDBN} should include the name of the
29597 company or organization which selected the name, and the overall
29598 architecture to which the feature applies; so e.g.@: the feature
29599 containing ARM core registers is named @samp{org.gnu.gdb.arm.core}.
29601 The names of registers are not case sensitive for the purpose
29602 of recognizing standard features, but @value{GDBN} will only display
29603 registers using the capitalization used in the description.
29609 * PowerPC Features::
29614 @subsection ARM Features
29615 @cindex target descriptions, ARM features
29617 The @samp{org.gnu.gdb.arm.core} feature is required for ARM targets.
29618 It should contain registers @samp{r0} through @samp{r13}, @samp{sp},
29619 @samp{lr}, @samp{pc}, and @samp{cpsr}.
29621 The @samp{org.gnu.gdb.arm.fpa} feature is optional. If present, it
29622 should contain registers @samp{f0} through @samp{f7} and @samp{fps}.
29624 The @samp{org.gnu.gdb.xscale.iwmmxt} feature is optional. If present,
29625 it should contain at least registers @samp{wR0} through @samp{wR15} and
29626 @samp{wCGR0} through @samp{wCGR3}. The @samp{wCID}, @samp{wCon},
29627 @samp{wCSSF}, and @samp{wCASF} registers are optional.
29629 @node MIPS Features
29630 @subsection MIPS Features
29631 @cindex target descriptions, MIPS features
29633 The @samp{org.gnu.gdb.mips.cpu} feature is required for MIPS targets.
29634 It should contain registers @samp{r0} through @samp{r31}, @samp{lo},
29635 @samp{hi}, and @samp{pc}. They may be 32-bit or 64-bit depending
29638 The @samp{org.gnu.gdb.mips.cp0} feature is also required. It should
29639 contain at least the @samp{status}, @samp{badvaddr}, and @samp{cause}
29640 registers. They may be 32-bit or 64-bit depending on the target.
29642 The @samp{org.gnu.gdb.mips.fpu} feature is currently required, though
29643 it may be optional in a future version of @value{GDBN}. It should
29644 contain registers @samp{f0} through @samp{f31}, @samp{fcsr}, and
29645 @samp{fir}. They may be 32-bit or 64-bit depending on the target.
29647 The @samp{org.gnu.gdb.mips.linux} feature is optional. It should
29648 contain a single register, @samp{restart}, which is used by the
29649 Linux kernel to control restartable syscalls.
29651 @node M68K Features
29652 @subsection M68K Features
29653 @cindex target descriptions, M68K features
29656 @item @samp{org.gnu.gdb.m68k.core}
29657 @itemx @samp{org.gnu.gdb.coldfire.core}
29658 @itemx @samp{org.gnu.gdb.fido.core}
29659 One of those features must be always present.
29660 The feature that is present determines which flavor of m68k is
29661 used. The feature that is present should contain registers
29662 @samp{d0} through @samp{d7}, @samp{a0} through @samp{a5}, @samp{fp},
29663 @samp{sp}, @samp{ps} and @samp{pc}.
29665 @item @samp{org.gnu.gdb.coldfire.fp}
29666 This feature is optional. If present, it should contain registers
29667 @samp{fp0} through @samp{fp7}, @samp{fpcontrol}, @samp{fpstatus} and
29671 @node PowerPC Features
29672 @subsection PowerPC Features
29673 @cindex target descriptions, PowerPC features
29675 The @samp{org.gnu.gdb.power.core} feature is required for PowerPC
29676 targets. It should contain registers @samp{r0} through @samp{r31},
29677 @samp{pc}, @samp{msr}, @samp{cr}, @samp{lr}, @samp{ctr}, and
29678 @samp{xer}. They may be 32-bit or 64-bit depending on the target.
29680 The @samp{org.gnu.gdb.power.fpu} feature is optional. It should
29681 contain registers @samp{f0} through @samp{f31} and @samp{fpscr}.
29683 The @samp{org.gnu.gdb.power.altivec} feature is optional. It should
29684 contain registers @samp{vr0} through @samp{vr31}, @samp{vscr},
29687 The @samp{org.gnu.gdb.power.vsx} feature is optional. It should
29688 contain registers @samp{vs0h} through @samp{vs31h}. @value{GDBN}
29689 will combine these registers with the floating point registers
29690 (@samp{f0} through @samp{f31}) and the altivec registers (@samp{vr0}
29691 through @samp{vr31}) to present the 128-bit wide registers @samp{vs0}
29692 through @samp{vs63}, the set of vector registers for POWER7.
29694 The @samp{org.gnu.gdb.power.spe} feature is optional. It should
29695 contain registers @samp{ev0h} through @samp{ev31h}, @samp{acc}, and
29696 @samp{spefscr}. SPE targets should provide 32-bit registers in
29697 @samp{org.gnu.gdb.power.core} and provide the upper halves in
29698 @samp{ev0h} through @samp{ev31h}. @value{GDBN} will combine
29699 these to present registers @samp{ev0} through @samp{ev31} to the
29702 @node Operating System Information
29703 @appendix Operating System Information
29704 @cindex operating system information
29710 Users of @value{GDBN} often wish to obtain information about the state of
29711 the operating system running on the target---for example the list of
29712 processes, or the list of open files. This section describes the
29713 mechanism that makes it possible. This mechanism is similar to the
29714 target features mechanism (@pxref{Target Descriptions}), but focuses
29715 on a different aspect of target.
29717 Operating system information is retrived from the target via the
29718 remote protocol, using @samp{qXfer} requests (@pxref{qXfer osdata
29719 read}). The object name in the request should be @samp{osdata}, and
29720 the @var{annex} identifies the data to be fetched.
29723 @appendixsection Process list
29724 @cindex operating system information, process list
29726 When requesting the process list, the @var{annex} field in the
29727 @samp{qXfer} request should be @samp{processes}. The returned data is
29728 an XML document. The formal syntax of this document is defined in
29729 @file{gdb/features/osdata.dtd}.
29731 An example document is:
29734 <?xml version="1.0"?>
29735 <!DOCTYPE target SYSTEM "osdata.dtd">
29736 <osdata type="processes">
29738 <column name="pid">1</column>
29739 <column name="user">root</column>
29740 <column name="command">/sbin/init</column>
29745 Each item should include a column whose name is @samp{pid}. The value
29746 of that column should identify the process on the target. The
29747 @samp{user} and @samp{command} columns are optional, and will be
29748 displayed by @value{GDBN}. Target may provide additional columns,
29749 which @value{GDBN} currently ignores.
29763 % I think something like @colophon should be in texinfo. In the
29765 \long\def\colophon{\hbox to0pt{}\vfill
29766 \centerline{The body of this manual is set in}
29767 \centerline{\fontname\tenrm,}
29768 \centerline{with headings in {\bf\fontname\tenbf}}
29769 \centerline{and examples in {\tt\fontname\tentt}.}
29770 \centerline{{\it\fontname\tenit\/},}
29771 \centerline{{\bf\fontname\tenbf}, and}
29772 \centerline{{\sl\fontname\tensl\/}}
29773 \centerline{are used for emphasis.}\vfill}
29775 % Blame: doc@cygnus.com, 1991.