1 \input texinfo @c -*-texinfo-*-
2 @c Copyright (C) 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995, 1996, 1998,
3 @c 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009
4 @c Free Software Foundation, Inc.
7 @c makeinfo ignores cmds prev to setfilename, so its arg cannot make use
8 @c of @set vars. However, you can override filename with makeinfo -o.
13 @settitle Debugging with @value{GDBN}
14 @setchapternewpage odd
26 @c readline appendices use @vindex, @findex and @ftable,
27 @c annotate.texi and gdbmi use @findex.
31 @c !!set GDB manual's edition---not the same as GDB version!
32 @c This is updated by GNU Press.
35 @c !!set GDB edit command default editor
38 @c THIS MANUAL REQUIRES TEXINFO 4.0 OR LATER.
40 @c This is a dir.info fragment to support semi-automated addition of
41 @c manuals to an info tree.
42 @dircategory Software development
44 * Gdb: (gdb). The GNU debugger.
48 Copyright @copyright{} 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995, 1996,
49 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009
50 Free Software Foundation, Inc.
52 Permission is granted to copy, distribute and/or modify this document
53 under the terms of the GNU Free Documentation License, Version 1.1 or
54 any later version published by the Free Software Foundation; with the
55 Invariant Sections being ``Free Software'' and ``Free Software Needs
56 Free Documentation'', with the Front-Cover Texts being ``A GNU Manual,''
57 and with the Back-Cover Texts as in (a) below.
59 (a) The FSF's Back-Cover Text is: ``You are free to copy and modify
60 this GNU Manual. Buying copies from GNU Press supports the FSF in
61 developing GNU and promoting software freedom.''
65 This file documents the @sc{gnu} debugger @value{GDBN}.
67 This is the @value{EDITION} Edition, of @cite{Debugging with
68 @value{GDBN}: the @sc{gnu} Source-Level Debugger} for @value{GDBN}
69 @ifset VERSION_PACKAGE
70 @value{VERSION_PACKAGE}
72 Version @value{GDBVN}.
78 @title Debugging with @value{GDBN}
79 @subtitle The @sc{gnu} Source-Level Debugger
81 @subtitle @value{EDITION} Edition, for @value{GDBN} version @value{GDBVN}
82 @ifset VERSION_PACKAGE
84 @subtitle @value{VERSION_PACKAGE}
86 @author Richard Stallman, Roland Pesch, Stan Shebs, et al.
90 \hfill (Send bugs and comments on @value{GDBN} to @value{BUGURL}.)\par
91 \hfill {\it Debugging with @value{GDBN}}\par
92 \hfill \TeX{}info \texinfoversion\par
96 @vskip 0pt plus 1filll
97 Published by the Free Software Foundation @*
98 51 Franklin Street, Fifth Floor,
99 Boston, MA 02110-1301, USA@*
100 ISBN 1-882114-77-9 @*
104 This edition of the GDB manual is dedicated to the memory of Fred
105 Fish. Fred was a long-standing contributor to GDB and to Free
106 software in general. We will miss him.
111 @node Top, Summary, (dir), (dir)
113 @top Debugging with @value{GDBN}
115 This file describes @value{GDBN}, the @sc{gnu} symbolic debugger.
117 This is the @value{EDITION} Edition, for @value{GDBN}
118 @ifset VERSION_PACKAGE
119 @value{VERSION_PACKAGE}
121 Version @value{GDBVN}.
123 Copyright (C) 1988-2009 Free Software Foundation, Inc.
125 This edition of the GDB manual is dedicated to the memory of Fred
126 Fish. Fred was a long-standing contributor to GDB and to Free
127 software in general. We will miss him.
130 * Summary:: Summary of @value{GDBN}
131 * Sample Session:: A sample @value{GDBN} session
133 * Invocation:: Getting in and out of @value{GDBN}
134 * Commands:: @value{GDBN} commands
135 * Running:: Running programs under @value{GDBN}
136 * Stopping:: Stopping and continuing
137 * Reverse Execution:: Running programs backward
138 * Process Record and Replay:: Recording inferior's execution and replaying it
139 * Stack:: Examining the stack
140 * Source:: Examining source files
141 * Data:: Examining data
142 * Optimized Code:: Debugging optimized code
143 * Macros:: Preprocessor Macros
144 * Tracepoints:: Debugging remote targets non-intrusively
145 * Overlays:: Debugging programs that use overlays
147 * Languages:: Using @value{GDBN} with different languages
149 * Symbols:: Examining the symbol table
150 * Altering:: Altering execution
151 * GDB Files:: @value{GDBN} files
152 * Targets:: Specifying a debugging target
153 * Remote Debugging:: Debugging remote programs
154 * Configurations:: Configuration-specific information
155 * Controlling GDB:: Controlling @value{GDBN}
156 * Extending GDB:: Extending @value{GDBN}
157 * Interpreters:: Command Interpreters
158 * TUI:: @value{GDBN} Text User Interface
159 * Emacs:: Using @value{GDBN} under @sc{gnu} Emacs
160 * GDB/MI:: @value{GDBN}'s Machine Interface.
161 * Annotations:: @value{GDBN}'s annotation interface.
162 * JIT Interface:: Using the JIT debugging interface.
164 * GDB Bugs:: Reporting bugs in @value{GDBN}
166 * Command Line Editing:: Command Line Editing
167 * Using History Interactively:: Using History Interactively
168 * Formatting Documentation:: How to format and print @value{GDBN} documentation
169 * Installing GDB:: Installing GDB
170 * Maintenance Commands:: Maintenance Commands
171 * Remote Protocol:: GDB Remote Serial Protocol
172 * Agent Expressions:: The GDB Agent Expression Mechanism
173 * Target Descriptions:: How targets can describe themselves to
175 * Operating System Information:: Getting additional information from
177 * Copying:: GNU General Public License says
178 how you can copy and share GDB
179 * GNU Free Documentation License:: The license for this documentation
188 @unnumbered Summary of @value{GDBN}
190 The purpose of a debugger such as @value{GDBN} is to allow you to see what is
191 going on ``inside'' another program while it executes---or what another
192 program was doing at the moment it crashed.
194 @value{GDBN} can do four main kinds of things (plus other things in support of
195 these) to help you catch bugs in the act:
199 Start your program, specifying anything that might affect its behavior.
202 Make your program stop on specified conditions.
205 Examine what has happened, when your program has stopped.
208 Change things in your program, so you can experiment with correcting the
209 effects of one bug and go on to learn about another.
212 You can use @value{GDBN} to debug programs written in C and C@t{++}.
213 For more information, see @ref{Supported Languages,,Supported Languages}.
214 For more information, see @ref{C,,C and C++}.
217 Support for Modula-2 is partial. For information on Modula-2, see
218 @ref{Modula-2,,Modula-2}.
221 Debugging Pascal programs which use sets, subranges, file variables, or
222 nested functions does not currently work. @value{GDBN} does not support
223 entering expressions, printing values, or similar features using Pascal
227 @value{GDBN} can be used to debug programs written in Fortran, although
228 it may be necessary to refer to some variables with a trailing
231 @value{GDBN} can be used to debug programs written in Objective-C,
232 using either the Apple/NeXT or the GNU Objective-C runtime.
235 * Free Software:: Freely redistributable software
236 * Contributors:: Contributors to GDB
240 @unnumberedsec Free Software
242 @value{GDBN} is @dfn{free software}, protected by the @sc{gnu}
243 General Public License
244 (GPL). The GPL gives you the freedom to copy or adapt a licensed
245 program---but every person getting a copy also gets with it the
246 freedom to modify that copy (which means that they must get access to
247 the source code), and the freedom to distribute further copies.
248 Typical software companies use copyrights to limit your freedoms; the
249 Free Software Foundation uses the GPL to preserve these freedoms.
251 Fundamentally, the General Public License is a license which says that
252 you have these freedoms and that you cannot take these freedoms away
255 @unnumberedsec Free Software Needs Free Documentation
257 The biggest deficiency in the free software community today is not in
258 the software---it is the lack of good free documentation that we can
259 include with the free software. Many of our most important
260 programs do not come with free reference manuals and free introductory
261 texts. Documentation is an essential part of any software package;
262 when an important free software package does not come with a free
263 manual and a free tutorial, that is a major gap. We have many such
266 Consider Perl, for instance. The tutorial manuals that people
267 normally use are non-free. How did this come about? Because the
268 authors of those manuals published them with restrictive terms---no
269 copying, no modification, source files not available---which exclude
270 them from the free software world.
272 That wasn't the first time this sort of thing happened, and it was far
273 from the last. Many times we have heard a GNU user eagerly describe a
274 manual that he is writing, his intended contribution to the community,
275 only to learn that he had ruined everything by signing a publication
276 contract to make it non-free.
278 Free documentation, like free software, is a matter of freedom, not
279 price. The problem with the non-free manual is not that publishers
280 charge a price for printed copies---that in itself is fine. (The Free
281 Software Foundation sells printed copies of manuals, too.) The
282 problem is the restrictions on the use of the manual. Free manuals
283 are available in source code form, and give you permission to copy and
284 modify. Non-free manuals do not allow this.
286 The criteria of freedom for a free manual are roughly the same as for
287 free software. Redistribution (including the normal kinds of
288 commercial redistribution) must be permitted, so that the manual can
289 accompany every copy of the program, both on-line and on paper.
291 Permission for modification of the technical content is crucial too.
292 When people modify the software, adding or changing features, if they
293 are conscientious they will change the manual too---so they can
294 provide accurate and clear documentation for the modified program. A
295 manual that leaves you no choice but to write a new manual to document
296 a changed version of the program is not really available to our
299 Some kinds of limits on the way modification is handled are
300 acceptable. For example, requirements to preserve the original
301 author's copyright notice, the distribution terms, or the list of
302 authors, are ok. It is also no problem to require modified versions
303 to include notice that they were modified. Even entire sections that
304 may not be deleted or changed are acceptable, as long as they deal
305 with nontechnical topics (like this one). These kinds of restrictions
306 are acceptable because they don't obstruct the community's normal use
309 However, it must be possible to modify all the @emph{technical}
310 content of the manual, and then distribute the result in all the usual
311 media, through all the usual channels. Otherwise, the restrictions
312 obstruct the use of the manual, it is not free, and we need another
313 manual to replace it.
315 Please spread the word about this issue. Our community continues to
316 lose manuals to proprietary publishing. If we spread the word that
317 free software needs free reference manuals and free tutorials, perhaps
318 the next person who wants to contribute by writing documentation will
319 realize, before it is too late, that only free manuals contribute to
320 the free software community.
322 If you are writing documentation, please insist on publishing it under
323 the GNU Free Documentation License or another free documentation
324 license. Remember that this decision requires your approval---you
325 don't have to let the publisher decide. Some commercial publishers
326 will use a free license if you insist, but they will not propose the
327 option; it is up to you to raise the issue and say firmly that this is
328 what you want. If the publisher you are dealing with refuses, please
329 try other publishers. If you're not sure whether a proposed license
330 is free, write to @email{licensing@@gnu.org}.
332 You can encourage commercial publishers to sell more free, copylefted
333 manuals and tutorials by buying them, and particularly by buying
334 copies from the publishers that paid for their writing or for major
335 improvements. Meanwhile, try to avoid buying non-free documentation
336 at all. Check the distribution terms of a manual before you buy it,
337 and insist that whoever seeks your business must respect your freedom.
338 Check the history of the book, and try to reward the publishers that
339 have paid or pay the authors to work on it.
341 The Free Software Foundation maintains a list of free documentation
342 published by other publishers, at
343 @url{http://www.fsf.org/doc/other-free-books.html}.
346 @unnumberedsec Contributors to @value{GDBN}
348 Richard Stallman was the original author of @value{GDBN}, and of many
349 other @sc{gnu} programs. Many others have contributed to its
350 development. This section attempts to credit major contributors. One
351 of the virtues of free software is that everyone is free to contribute
352 to it; with regret, we cannot actually acknowledge everyone here. The
353 file @file{ChangeLog} in the @value{GDBN} distribution approximates a
354 blow-by-blow account.
356 Changes much prior to version 2.0 are lost in the mists of time.
359 @emph{Plea:} Additions to this section are particularly welcome. If you
360 or your friends (or enemies, to be evenhanded) have been unfairly
361 omitted from this list, we would like to add your names!
364 So that they may not regard their many labors as thankless, we
365 particularly thank those who shepherded @value{GDBN} through major
367 Andrew Cagney (releases 6.3, 6.2, 6.1, 6.0, 5.3, 5.2, 5.1 and 5.0);
368 Jim Blandy (release 4.18);
369 Jason Molenda (release 4.17);
370 Stan Shebs (release 4.14);
371 Fred Fish (releases 4.16, 4.15, 4.13, 4.12, 4.11, 4.10, and 4.9);
372 Stu Grossman and John Gilmore (releases 4.8, 4.7, 4.6, 4.5, and 4.4);
373 John Gilmore (releases 4.3, 4.2, 4.1, 4.0, and 3.9);
374 Jim Kingdon (releases 3.5, 3.4, and 3.3);
375 and Randy Smith (releases 3.2, 3.1, and 3.0).
377 Richard Stallman, assisted at various times by Peter TerMaat, Chris
378 Hanson, and Richard Mlynarik, handled releases through 2.8.
380 Michael Tiemann is the author of most of the @sc{gnu} C@t{++} support
381 in @value{GDBN}, with significant additional contributions from Per
382 Bothner and Daniel Berlin. James Clark wrote the @sc{gnu} C@t{++}
383 demangler. Early work on C@t{++} was by Peter TerMaat (who also did
384 much general update work leading to release 3.0).
386 @value{GDBN} uses the BFD subroutine library to examine multiple
387 object-file formats; BFD was a joint project of David V.
388 Henkel-Wallace, Rich Pixley, Steve Chamberlain, and John Gilmore.
390 David Johnson wrote the original COFF support; Pace Willison did
391 the original support for encapsulated COFF.
393 Brent Benson of Harris Computer Systems contributed DWARF 2 support.
395 Adam de Boor and Bradley Davis contributed the ISI Optimum V support.
396 Per Bothner, Noboyuki Hikichi, and Alessandro Forin contributed MIPS
398 Jean-Daniel Fekete contributed Sun 386i support.
399 Chris Hanson improved the HP9000 support.
400 Noboyuki Hikichi and Tomoyuki Hasei contributed Sony/News OS 3 support.
401 David Johnson contributed Encore Umax support.
402 Jyrki Kuoppala contributed Altos 3068 support.
403 Jeff Law contributed HP PA and SOM support.
404 Keith Packard contributed NS32K support.
405 Doug Rabson contributed Acorn Risc Machine support.
406 Bob Rusk contributed Harris Nighthawk CX-UX support.
407 Chris Smith contributed Convex support (and Fortran debugging).
408 Jonathan Stone contributed Pyramid support.
409 Michael Tiemann contributed SPARC support.
410 Tim Tucker contributed support for the Gould NP1 and Gould Powernode.
411 Pace Willison contributed Intel 386 support.
412 Jay Vosburgh contributed Symmetry support.
413 Marko Mlinar contributed OpenRISC 1000 support.
415 Andreas Schwab contributed M68K @sc{gnu}/Linux support.
417 Rich Schaefer and Peter Schauer helped with support of SunOS shared
420 Jay Fenlason and Roland McGrath ensured that @value{GDBN} and GAS agree
421 about several machine instruction sets.
423 Patrick Duval, Ted Goldstein, Vikram Koka and Glenn Engel helped develop
424 remote debugging. Intel Corporation, Wind River Systems, AMD, and ARM
425 contributed remote debugging modules for the i960, VxWorks, A29K UDI,
426 and RDI targets, respectively.
428 Brian Fox is the author of the readline libraries providing
429 command-line editing and command history.
431 Andrew Beers of SUNY Buffalo wrote the language-switching code, the
432 Modula-2 support, and contributed the Languages chapter of this manual.
434 Fred Fish wrote most of the support for Unix System Vr4.
435 He also enhanced the command-completion support to cover C@t{++} overloaded
438 Hitachi America (now Renesas America), Ltd. sponsored the support for
439 H8/300, H8/500, and Super-H processors.
441 NEC sponsored the support for the v850, Vr4xxx, and Vr5xxx processors.
443 Mitsubishi (now Renesas) sponsored the support for D10V, D30V, and M32R/D
446 Toshiba sponsored the support for the TX39 Mips processor.
448 Matsushita sponsored the support for the MN10200 and MN10300 processors.
450 Fujitsu sponsored the support for SPARClite and FR30 processors.
452 Kung Hsu, Jeff Law, and Rick Sladkey added support for hardware
455 Michael Snyder added support for tracepoints.
457 Stu Grossman wrote gdbserver.
459 Jim Kingdon, Peter Schauer, Ian Taylor, and Stu Grossman made
460 nearly innumerable bug fixes and cleanups throughout @value{GDBN}.
462 The following people at the Hewlett-Packard Company contributed
463 support for the PA-RISC 2.0 architecture, HP-UX 10.20, 10.30, and 11.0
464 (narrow mode), HP's implementation of kernel threads, HP's aC@t{++}
465 compiler, and the Text User Interface (nee Terminal User Interface):
466 Ben Krepp, Richard Title, John Bishop, Susan Macchia, Kathy Mann,
467 Satish Pai, India Paul, Steve Rehrauer, and Elena Zannoni. Kim Haase
468 provided HP-specific information in this manual.
470 DJ Delorie ported @value{GDBN} to MS-DOS, for the DJGPP project.
471 Robert Hoehne made significant contributions to the DJGPP port.
473 Cygnus Solutions has sponsored @value{GDBN} maintenance and much of its
474 development since 1991. Cygnus engineers who have worked on @value{GDBN}
475 fulltime include Mark Alexander, Jim Blandy, Per Bothner, Kevin
476 Buettner, Edith Epstein, Chris Faylor, Fred Fish, Martin Hunt, Jim
477 Ingham, John Gilmore, Stu Grossman, Kung Hsu, Jim Kingdon, John Metzler,
478 Fernando Nasser, Geoffrey Noer, Dawn Perchik, Rich Pixley, Zdenek
479 Radouch, Keith Seitz, Stan Shebs, David Taylor, and Elena Zannoni. In
480 addition, Dave Brolley, Ian Carmichael, Steve Chamberlain, Nick Clifton,
481 JT Conklin, Stan Cox, DJ Delorie, Ulrich Drepper, Frank Eigler, Doug
482 Evans, Sean Fagan, David Henkel-Wallace, Richard Henderson, Jeff
483 Holcomb, Jeff Law, Jim Lemke, Tom Lord, Bob Manson, Michael Meissner,
484 Jason Merrill, Catherine Moore, Drew Moseley, Ken Raeburn, Gavin
485 Romig-Koch, Rob Savoye, Jamie Smith, Mike Stump, Ian Taylor, Angela
486 Thomas, Michael Tiemann, Tom Tromey, Ron Unrau, Jim Wilson, and David
487 Zuhn have made contributions both large and small.
489 Andrew Cagney, Fernando Nasser, and Elena Zannoni, while working for
490 Cygnus Solutions, implemented the original @sc{gdb/mi} interface.
492 Jim Blandy added support for preprocessor macros, while working for Red
495 Andrew Cagney designed @value{GDBN}'s architecture vector. Many
496 people including Andrew Cagney, Stephane Carrez, Randolph Chung, Nick
497 Duffek, Richard Henderson, Mark Kettenis, Grace Sainsbury, Kei
498 Sakamoto, Yoshinori Sato, Michael Snyder, Andreas Schwab, Jason
499 Thorpe, Corinna Vinschen, Ulrich Weigand, and Elena Zannoni, helped
500 with the migration of old architectures to this new framework.
502 Andrew Cagney completely re-designed and re-implemented @value{GDBN}'s
503 unwinder framework, this consisting of a fresh new design featuring
504 frame IDs, independent frame sniffers, and the sentinel frame. Mark
505 Kettenis implemented the @sc{dwarf 2} unwinder, Jeff Johnston the
506 libunwind unwinder, and Andrew Cagney the dummy, sentinel, tramp, and
507 trad unwinders. The architecture-specific changes, each involving a
508 complete rewrite of the architecture's frame code, were carried out by
509 Jim Blandy, Joel Brobecker, Kevin Buettner, Andrew Cagney, Stephane
510 Carrez, Randolph Chung, Orjan Friberg, Richard Henderson, Daniel
511 Jacobowitz, Jeff Johnston, Mark Kettenis, Theodore A. Roth, Kei
512 Sakamoto, Yoshinori Sato, Michael Snyder, Corinna Vinschen, and Ulrich
515 Christian Zankel, Ross Morley, Bob Wilson, and Maxim Grigoriev from
516 Tensilica, Inc.@: contributed support for Xtensa processors. Others
517 who have worked on the Xtensa port of @value{GDBN} in the past include
518 Steve Tjiang, John Newlin, and Scott Foehner.
521 @chapter A Sample @value{GDBN} Session
523 You can use this manual at your leisure to read all about @value{GDBN}.
524 However, a handful of commands are enough to get started using the
525 debugger. This chapter illustrates those commands.
528 In this sample session, we emphasize user input like this: @b{input},
529 to make it easier to pick out from the surrounding output.
532 @c FIXME: this example may not be appropriate for some configs, where
533 @c FIXME...primary interest is in remote use.
535 One of the preliminary versions of @sc{gnu} @code{m4} (a generic macro
536 processor) exhibits the following bug: sometimes, when we change its
537 quote strings from the default, the commands used to capture one macro
538 definition within another stop working. In the following short @code{m4}
539 session, we define a macro @code{foo} which expands to @code{0000}; we
540 then use the @code{m4} built-in @code{defn} to define @code{bar} as the
541 same thing. However, when we change the open quote string to
542 @code{<QUOTE>} and the close quote string to @code{<UNQUOTE>}, the same
543 procedure fails to define a new synonym @code{baz}:
552 @b{define(bar,defn(`foo'))}
556 @b{changequote(<QUOTE>,<UNQUOTE>)}
558 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
561 m4: End of input: 0: fatal error: EOF in string
565 Let us use @value{GDBN} to try to see what is going on.
568 $ @b{@value{GDBP} m4}
569 @c FIXME: this falsifies the exact text played out, to permit smallbook
570 @c FIXME... format to come out better.
571 @value{GDBN} is free software and you are welcome to distribute copies
572 of it under certain conditions; type "show copying" to see
574 There is absolutely no warranty for @value{GDBN}; type "show warranty"
577 @value{GDBN} @value{GDBVN}, Copyright 1999 Free Software Foundation, Inc...
582 @value{GDBN} reads only enough symbol data to know where to find the
583 rest when needed; as a result, the first prompt comes up very quickly.
584 We now tell @value{GDBN} to use a narrower display width than usual, so
585 that examples fit in this manual.
588 (@value{GDBP}) @b{set width 70}
592 We need to see how the @code{m4} built-in @code{changequote} works.
593 Having looked at the source, we know the relevant subroutine is
594 @code{m4_changequote}, so we set a breakpoint there with the @value{GDBN}
595 @code{break} command.
598 (@value{GDBP}) @b{break m4_changequote}
599 Breakpoint 1 at 0x62f4: file builtin.c, line 879.
603 Using the @code{run} command, we start @code{m4} running under @value{GDBN}
604 control; as long as control does not reach the @code{m4_changequote}
605 subroutine, the program runs as usual:
608 (@value{GDBP}) @b{run}
609 Starting program: /work/Editorial/gdb/gnu/m4/m4
617 To trigger the breakpoint, we call @code{changequote}. @value{GDBN}
618 suspends execution of @code{m4}, displaying information about the
619 context where it stops.
622 @b{changequote(<QUOTE>,<UNQUOTE>)}
624 Breakpoint 1, m4_changequote (argc=3, argv=0x33c70)
626 879 if (bad_argc(TOKEN_DATA_TEXT(argv[0]),argc,1,3))
630 Now we use the command @code{n} (@code{next}) to advance execution to
631 the next line of the current function.
635 882 set_quotes((argc >= 2) ? TOKEN_DATA_TEXT(argv[1])\
640 @code{set_quotes} looks like a promising subroutine. We can go into it
641 by using the command @code{s} (@code{step}) instead of @code{next}.
642 @code{step} goes to the next line to be executed in @emph{any}
643 subroutine, so it steps into @code{set_quotes}.
647 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
649 530 if (lquote != def_lquote)
653 The display that shows the subroutine where @code{m4} is now
654 suspended (and its arguments) is called a stack frame display. It
655 shows a summary of the stack. We can use the @code{backtrace}
656 command (which can also be spelled @code{bt}), to see where we are
657 in the stack as a whole: the @code{backtrace} command displays a
658 stack frame for each active subroutine.
661 (@value{GDBP}) @b{bt}
662 #0 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
664 #1 0x6344 in m4_changequote (argc=3, argv=0x33c70)
666 #2 0x8174 in expand_macro (sym=0x33320) at macro.c:242
667 #3 0x7a88 in expand_token (obs=0x0, t=209696, td=0xf7fffa30)
669 #4 0x79dc in expand_input () at macro.c:40
670 #5 0x2930 in main (argc=0, argv=0xf7fffb20) at m4.c:195
674 We step through a few more lines to see what happens. The first two
675 times, we can use @samp{s}; the next two times we use @code{n} to avoid
676 falling into the @code{xstrdup} subroutine.
680 0x3b5c 532 if (rquote != def_rquote)
682 0x3b80 535 lquote = (lq == nil || *lq == '\0') ? \
683 def_lquote : xstrdup(lq);
685 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
688 538 len_lquote = strlen(rquote);
692 The last line displayed looks a little odd; we can examine the variables
693 @code{lquote} and @code{rquote} to see if they are in fact the new left
694 and right quotes we specified. We use the command @code{p}
695 (@code{print}) to see their values.
698 (@value{GDBP}) @b{p lquote}
699 $1 = 0x35d40 "<QUOTE>"
700 (@value{GDBP}) @b{p rquote}
701 $2 = 0x35d50 "<UNQUOTE>"
705 @code{lquote} and @code{rquote} are indeed the new left and right quotes.
706 To look at some context, we can display ten lines of source
707 surrounding the current line with the @code{l} (@code{list}) command.
713 535 lquote = (lq == nil || *lq == '\0') ? def_lquote\
715 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
718 538 len_lquote = strlen(rquote);
719 539 len_rquote = strlen(lquote);
726 Let us step past the two lines that set @code{len_lquote} and
727 @code{len_rquote}, and then examine the values of those variables.
731 539 len_rquote = strlen(lquote);
734 (@value{GDBP}) @b{p len_lquote}
736 (@value{GDBP}) @b{p len_rquote}
741 That certainly looks wrong, assuming @code{len_lquote} and
742 @code{len_rquote} are meant to be the lengths of @code{lquote} and
743 @code{rquote} respectively. We can set them to better values using
744 the @code{p} command, since it can print the value of
745 any expression---and that expression can include subroutine calls and
749 (@value{GDBP}) @b{p len_lquote=strlen(lquote)}
751 (@value{GDBP}) @b{p len_rquote=strlen(rquote)}
756 Is that enough to fix the problem of using the new quotes with the
757 @code{m4} built-in @code{defn}? We can allow @code{m4} to continue
758 executing with the @code{c} (@code{continue}) command, and then try the
759 example that caused trouble initially:
765 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
772 Success! The new quotes now work just as well as the default ones. The
773 problem seems to have been just the two typos defining the wrong
774 lengths. We allow @code{m4} exit by giving it an EOF as input:
778 Program exited normally.
782 The message @samp{Program exited normally.} is from @value{GDBN}; it
783 indicates @code{m4} has finished executing. We can end our @value{GDBN}
784 session with the @value{GDBN} @code{quit} command.
787 (@value{GDBP}) @b{quit}
791 @chapter Getting In and Out of @value{GDBN}
793 This chapter discusses how to start @value{GDBN}, and how to get out of it.
797 type @samp{@value{GDBP}} to start @value{GDBN}.
799 type @kbd{quit} or @kbd{Ctrl-d} to exit.
803 * Invoking GDB:: How to start @value{GDBN}
804 * Quitting GDB:: How to quit @value{GDBN}
805 * Shell Commands:: How to use shell commands inside @value{GDBN}
806 * Logging Output:: How to log @value{GDBN}'s output to a file
810 @section Invoking @value{GDBN}
812 Invoke @value{GDBN} by running the program @code{@value{GDBP}}. Once started,
813 @value{GDBN} reads commands from the terminal until you tell it to exit.
815 You can also run @code{@value{GDBP}} with a variety of arguments and options,
816 to specify more of your debugging environment at the outset.
818 The command-line options described here are designed
819 to cover a variety of situations; in some environments, some of these
820 options may effectively be unavailable.
822 The most usual way to start @value{GDBN} is with one argument,
823 specifying an executable program:
826 @value{GDBP} @var{program}
830 You can also start with both an executable program and a core file
834 @value{GDBP} @var{program} @var{core}
837 You can, instead, specify a process ID as a second argument, if you want
838 to debug a running process:
841 @value{GDBP} @var{program} 1234
845 would attach @value{GDBN} to process @code{1234} (unless you also have a file
846 named @file{1234}; @value{GDBN} does check for a core file first).
848 Taking advantage of the second command-line argument requires a fairly
849 complete operating system; when you use @value{GDBN} as a remote
850 debugger attached to a bare board, there may not be any notion of
851 ``process'', and there is often no way to get a core dump. @value{GDBN}
852 will warn you if it is unable to attach or to read core dumps.
854 You can optionally have @code{@value{GDBP}} pass any arguments after the
855 executable file to the inferior using @code{--args}. This option stops
858 @value{GDBP} --args gcc -O2 -c foo.c
860 This will cause @code{@value{GDBP}} to debug @code{gcc}, and to set
861 @code{gcc}'s command-line arguments (@pxref{Arguments}) to @samp{-O2 -c foo.c}.
863 You can run @code{@value{GDBP}} without printing the front material, which describes
864 @value{GDBN}'s non-warranty, by specifying @code{-silent}:
871 You can further control how @value{GDBN} starts up by using command-line
872 options. @value{GDBN} itself can remind you of the options available.
882 to display all available options and briefly describe their use
883 (@samp{@value{GDBP} -h} is a shorter equivalent).
885 All options and command line arguments you give are processed
886 in sequential order. The order makes a difference when the
887 @samp{-x} option is used.
891 * File Options:: Choosing files
892 * Mode Options:: Choosing modes
893 * Startup:: What @value{GDBN} does during startup
897 @subsection Choosing Files
899 When @value{GDBN} starts, it reads any arguments other than options as
900 specifying an executable file and core file (or process ID). This is
901 the same as if the arguments were specified by the @samp{-se} and
902 @samp{-c} (or @samp{-p}) options respectively. (@value{GDBN} reads the
903 first argument that does not have an associated option flag as
904 equivalent to the @samp{-se} option followed by that argument; and the
905 second argument that does not have an associated option flag, if any, as
906 equivalent to the @samp{-c}/@samp{-p} option followed by that argument.)
907 If the second argument begins with a decimal digit, @value{GDBN} will
908 first attempt to attach to it as a process, and if that fails, attempt
909 to open it as a corefile. If you have a corefile whose name begins with
910 a digit, you can prevent @value{GDBN} from treating it as a pid by
911 prefixing it with @file{./}, e.g.@: @file{./12345}.
913 If @value{GDBN} has not been configured to included core file support,
914 such as for most embedded targets, then it will complain about a second
915 argument and ignore it.
917 Many options have both long and short forms; both are shown in the
918 following list. @value{GDBN} also recognizes the long forms if you truncate
919 them, so long as enough of the option is present to be unambiguous.
920 (If you prefer, you can flag option arguments with @samp{--} rather
921 than @samp{-}, though we illustrate the more usual convention.)
923 @c NOTE: the @cindex entries here use double dashes ON PURPOSE. This
924 @c way, both those who look for -foo and --foo in the index, will find
928 @item -symbols @var{file}
930 @cindex @code{--symbols}
932 Read symbol table from file @var{file}.
934 @item -exec @var{file}
936 @cindex @code{--exec}
938 Use file @var{file} as the executable file to execute when appropriate,
939 and for examining pure data in conjunction with a core dump.
943 Read symbol table from file @var{file} and use it as the executable
946 @item -core @var{file}
948 @cindex @code{--core}
950 Use file @var{file} as a core dump to examine.
952 @item -pid @var{number}
953 @itemx -p @var{number}
956 Connect to process ID @var{number}, as with the @code{attach} command.
958 @item -command @var{file}
960 @cindex @code{--command}
962 Execute @value{GDBN} commands from file @var{file}. @xref{Command
963 Files,, Command files}.
965 @item -eval-command @var{command}
966 @itemx -ex @var{command}
967 @cindex @code{--eval-command}
969 Execute a single @value{GDBN} command.
971 This option may be used multiple times to call multiple commands. It may
972 also be interleaved with @samp{-command} as required.
975 @value{GDBP} -ex 'target sim' -ex 'load' \
976 -x setbreakpoints -ex 'run' a.out
979 @item -directory @var{directory}
980 @itemx -d @var{directory}
981 @cindex @code{--directory}
983 Add @var{directory} to the path to search for source and script files.
987 @cindex @code{--readnow}
989 Read each symbol file's entire symbol table immediately, rather than
990 the default, which is to read it incrementally as it is needed.
991 This makes startup slower, but makes future operations faster.
996 @subsection Choosing Modes
998 You can run @value{GDBN} in various alternative modes---for example, in
999 batch mode or quiet mode.
1006 Do not execute commands found in any initialization files. Normally,
1007 @value{GDBN} executes the commands in these files after all the command
1008 options and arguments have been processed. @xref{Command Files,,Command
1014 @cindex @code{--quiet}
1015 @cindex @code{--silent}
1017 ``Quiet''. Do not print the introductory and copyright messages. These
1018 messages are also suppressed in batch mode.
1021 @cindex @code{--batch}
1022 Run in batch mode. Exit with status @code{0} after processing all the
1023 command files specified with @samp{-x} (and all commands from
1024 initialization files, if not inhibited with @samp{-n}). Exit with
1025 nonzero status if an error occurs in executing the @value{GDBN} commands
1026 in the command files.
1028 Batch mode may be useful for running @value{GDBN} as a filter, for
1029 example to download and run a program on another computer; in order to
1030 make this more useful, the message
1033 Program exited normally.
1037 (which is ordinarily issued whenever a program running under
1038 @value{GDBN} control terminates) is not issued when running in batch
1042 @cindex @code{--batch-silent}
1043 Run in batch mode exactly like @samp{-batch}, but totally silently. All
1044 @value{GDBN} output to @code{stdout} is prevented (@code{stderr} is
1045 unaffected). This is much quieter than @samp{-silent} and would be useless
1046 for an interactive session.
1048 This is particularly useful when using targets that give @samp{Loading section}
1049 messages, for example.
1051 Note that targets that give their output via @value{GDBN}, as opposed to
1052 writing directly to @code{stdout}, will also be made silent.
1054 @item -return-child-result
1055 @cindex @code{--return-child-result}
1056 The return code from @value{GDBN} will be the return code from the child
1057 process (the process being debugged), with the following exceptions:
1061 @value{GDBN} exits abnormally. E.g., due to an incorrect argument or an
1062 internal error. In this case the exit code is the same as it would have been
1063 without @samp{-return-child-result}.
1065 The user quits with an explicit value. E.g., @samp{quit 1}.
1067 The child process never runs, or is not allowed to terminate, in which case
1068 the exit code will be -1.
1071 This option is useful in conjunction with @samp{-batch} or @samp{-batch-silent},
1072 when @value{GDBN} is being used as a remote program loader or simulator
1077 @cindex @code{--nowindows}
1079 ``No windows''. If @value{GDBN} comes with a graphical user interface
1080 (GUI) built in, then this option tells @value{GDBN} to only use the command-line
1081 interface. If no GUI is available, this option has no effect.
1085 @cindex @code{--windows}
1087 If @value{GDBN} includes a GUI, then this option requires it to be
1090 @item -cd @var{directory}
1092 Run @value{GDBN} using @var{directory} as its working directory,
1093 instead of the current directory.
1097 @cindex @code{--fullname}
1099 @sc{gnu} Emacs sets this option when it runs @value{GDBN} as a
1100 subprocess. It tells @value{GDBN} to output the full file name and line
1101 number in a standard, recognizable fashion each time a stack frame is
1102 displayed (which includes each time your program stops). This
1103 recognizable format looks like two @samp{\032} characters, followed by
1104 the file name, line number and character position separated by colons,
1105 and a newline. The Emacs-to-@value{GDBN} interface program uses the two
1106 @samp{\032} characters as a signal to display the source code for the
1110 @cindex @code{--epoch}
1111 The Epoch Emacs-@value{GDBN} interface sets this option when it runs
1112 @value{GDBN} as a subprocess. It tells @value{GDBN} to modify its print
1113 routines so as to allow Epoch to display values of expressions in a
1116 @item -annotate @var{level}
1117 @cindex @code{--annotate}
1118 This option sets the @dfn{annotation level} inside @value{GDBN}. Its
1119 effect is identical to using @samp{set annotate @var{level}}
1120 (@pxref{Annotations}). The annotation @var{level} controls how much
1121 information @value{GDBN} prints together with its prompt, values of
1122 expressions, source lines, and other types of output. Level 0 is the
1123 normal, level 1 is for use when @value{GDBN} is run as a subprocess of
1124 @sc{gnu} Emacs, level 3 is the maximum annotation suitable for programs
1125 that control @value{GDBN}, and level 2 has been deprecated.
1127 The annotation mechanism has largely been superseded by @sc{gdb/mi}
1131 @cindex @code{--args}
1132 Change interpretation of command line so that arguments following the
1133 executable file are passed as command line arguments to the inferior.
1134 This option stops option processing.
1136 @item -baud @var{bps}
1138 @cindex @code{--baud}
1140 Set the line speed (baud rate or bits per second) of any serial
1141 interface used by @value{GDBN} for remote debugging.
1143 @item -l @var{timeout}
1145 Set the timeout (in seconds) of any communication used by @value{GDBN}
1146 for remote debugging.
1148 @item -tty @var{device}
1149 @itemx -t @var{device}
1150 @cindex @code{--tty}
1152 Run using @var{device} for your program's standard input and output.
1153 @c FIXME: kingdon thinks there is more to -tty. Investigate.
1155 @c resolve the situation of these eventually
1157 @cindex @code{--tui}
1158 Activate the @dfn{Text User Interface} when starting. The Text User
1159 Interface manages several text windows on the terminal, showing
1160 source, assembly, registers and @value{GDBN} command outputs
1161 (@pxref{TUI, ,@value{GDBN} Text User Interface}). Alternatively, the
1162 Text User Interface can be enabled by invoking the program
1163 @samp{@value{GDBTUI}}. Do not use this option if you run @value{GDBN} from
1164 Emacs (@pxref{Emacs, ,Using @value{GDBN} under @sc{gnu} Emacs}).
1167 @c @cindex @code{--xdb}
1168 @c Run in XDB compatibility mode, allowing the use of certain XDB commands.
1169 @c For information, see the file @file{xdb_trans.html}, which is usually
1170 @c installed in the directory @code{/opt/langtools/wdb/doc} on HP-UX
1173 @item -interpreter @var{interp}
1174 @cindex @code{--interpreter}
1175 Use the interpreter @var{interp} for interface with the controlling
1176 program or device. This option is meant to be set by programs which
1177 communicate with @value{GDBN} using it as a back end.
1178 @xref{Interpreters, , Command Interpreters}.
1180 @samp{--interpreter=mi} (or @samp{--interpreter=mi2}) causes
1181 @value{GDBN} to use the @dfn{@sc{gdb/mi} interface} (@pxref{GDB/MI, ,
1182 The @sc{gdb/mi} Interface}) included since @value{GDBN} version 6.0. The
1183 previous @sc{gdb/mi} interface, included in @value{GDBN} version 5.3 and
1184 selected with @samp{--interpreter=mi1}, is deprecated. Earlier
1185 @sc{gdb/mi} interfaces are no longer supported.
1188 @cindex @code{--write}
1189 Open the executable and core files for both reading and writing. This
1190 is equivalent to the @samp{set write on} command inside @value{GDBN}
1194 @cindex @code{--statistics}
1195 This option causes @value{GDBN} to print statistics about time and
1196 memory usage after it completes each command and returns to the prompt.
1199 @cindex @code{--version}
1200 This option causes @value{GDBN} to print its version number and
1201 no-warranty blurb, and exit.
1206 @subsection What @value{GDBN} Does During Startup
1207 @cindex @value{GDBN} startup
1209 Here's the description of what @value{GDBN} does during session startup:
1213 Sets up the command interpreter as specified by the command line
1214 (@pxref{Mode Options, interpreter}).
1218 Reads the system-wide @dfn{init file} (if @option{--with-system-gdbinit} was
1219 used when building @value{GDBN}; @pxref{System-wide configuration,
1220 ,System-wide configuration and settings}) and executes all the commands in
1224 Reads the init file (if any) in your home directory@footnote{On
1225 DOS/Windows systems, the home directory is the one pointed to by the
1226 @code{HOME} environment variable.} and executes all the commands in
1230 Processes command line options and operands.
1233 Reads and executes the commands from init file (if any) in the current
1234 working directory. This is only done if the current directory is
1235 different from your home directory. Thus, you can have more than one
1236 init file, one generic in your home directory, and another, specific
1237 to the program you are debugging, in the directory where you invoke
1241 Reads command files specified by the @samp{-x} option. @xref{Command
1242 Files}, for more details about @value{GDBN} command files.
1245 Reads the command history recorded in the @dfn{history file}.
1246 @xref{Command History}, for more details about the command history and the
1247 files where @value{GDBN} records it.
1250 Init files use the same syntax as @dfn{command files} (@pxref{Command
1251 Files}) and are processed by @value{GDBN} in the same way. The init
1252 file in your home directory can set options (such as @samp{set
1253 complaints}) that affect subsequent processing of command line options
1254 and operands. Init files are not executed if you use the @samp{-nx}
1255 option (@pxref{Mode Options, ,Choosing Modes}).
1257 To display the list of init files loaded by gdb at startup, you
1258 can use @kbd{gdb --help}.
1260 @cindex init file name
1261 @cindex @file{.gdbinit}
1262 @cindex @file{gdb.ini}
1263 The @value{GDBN} init files are normally called @file{.gdbinit}.
1264 The DJGPP port of @value{GDBN} uses the name @file{gdb.ini}, due to
1265 the limitations of file names imposed by DOS filesystems. The Windows
1266 ports of @value{GDBN} use the standard name, but if they find a
1267 @file{gdb.ini} file, they warn you about that and suggest to rename
1268 the file to the standard name.
1272 @section Quitting @value{GDBN}
1273 @cindex exiting @value{GDBN}
1274 @cindex leaving @value{GDBN}
1277 @kindex quit @r{[}@var{expression}@r{]}
1278 @kindex q @r{(@code{quit})}
1279 @item quit @r{[}@var{expression}@r{]}
1281 To exit @value{GDBN}, use the @code{quit} command (abbreviated
1282 @code{q}), or type an end-of-file character (usually @kbd{Ctrl-d}). If you
1283 do not supply @var{expression}, @value{GDBN} will terminate normally;
1284 otherwise it will terminate using the result of @var{expression} as the
1289 An interrupt (often @kbd{Ctrl-c}) does not exit from @value{GDBN}, but rather
1290 terminates the action of any @value{GDBN} command that is in progress and
1291 returns to @value{GDBN} command level. It is safe to type the interrupt
1292 character at any time because @value{GDBN} does not allow it to take effect
1293 until a time when it is safe.
1295 If you have been using @value{GDBN} to control an attached process or
1296 device, you can release it with the @code{detach} command
1297 (@pxref{Attach, ,Debugging an Already-running Process}).
1299 @node Shell Commands
1300 @section Shell Commands
1302 If you need to execute occasional shell commands during your
1303 debugging session, there is no need to leave or suspend @value{GDBN}; you can
1304 just use the @code{shell} command.
1308 @cindex shell escape
1309 @item shell @var{command string}
1310 Invoke a standard shell to execute @var{command string}.
1311 If it exists, the environment variable @code{SHELL} determines which
1312 shell to run. Otherwise @value{GDBN} uses the default shell
1313 (@file{/bin/sh} on Unix systems, @file{COMMAND.COM} on MS-DOS, etc.).
1316 The utility @code{make} is often needed in development environments.
1317 You do not have to use the @code{shell} command for this purpose in
1322 @cindex calling make
1323 @item make @var{make-args}
1324 Execute the @code{make} program with the specified
1325 arguments. This is equivalent to @samp{shell make @var{make-args}}.
1328 @node Logging Output
1329 @section Logging Output
1330 @cindex logging @value{GDBN} output
1331 @cindex save @value{GDBN} output to a file
1333 You may want to save the output of @value{GDBN} commands to a file.
1334 There are several commands to control @value{GDBN}'s logging.
1338 @item set logging on
1340 @item set logging off
1342 @cindex logging file name
1343 @item set logging file @var{file}
1344 Change the name of the current logfile. The default logfile is @file{gdb.txt}.
1345 @item set logging overwrite [on|off]
1346 By default, @value{GDBN} will append to the logfile. Set @code{overwrite} if
1347 you want @code{set logging on} to overwrite the logfile instead.
1348 @item set logging redirect [on|off]
1349 By default, @value{GDBN} output will go to both the terminal and the logfile.
1350 Set @code{redirect} if you want output to go only to the log file.
1351 @kindex show logging
1353 Show the current values of the logging settings.
1357 @chapter @value{GDBN} Commands
1359 You can abbreviate a @value{GDBN} command to the first few letters of the command
1360 name, if that abbreviation is unambiguous; and you can repeat certain
1361 @value{GDBN} commands by typing just @key{RET}. You can also use the @key{TAB}
1362 key to get @value{GDBN} to fill out the rest of a word in a command (or to
1363 show you the alternatives available, if there is more than one possibility).
1366 * Command Syntax:: How to give commands to @value{GDBN}
1367 * Completion:: Command completion
1368 * Help:: How to ask @value{GDBN} for help
1371 @node Command Syntax
1372 @section Command Syntax
1374 A @value{GDBN} command is a single line of input. There is no limit on
1375 how long it can be. It starts with a command name, which is followed by
1376 arguments whose meaning depends on the command name. For example, the
1377 command @code{step} accepts an argument which is the number of times to
1378 step, as in @samp{step 5}. You can also use the @code{step} command
1379 with no arguments. Some commands do not allow any arguments.
1381 @cindex abbreviation
1382 @value{GDBN} command names may always be truncated if that abbreviation is
1383 unambiguous. Other possible command abbreviations are listed in the
1384 documentation for individual commands. In some cases, even ambiguous
1385 abbreviations are allowed; for example, @code{s} is specially defined as
1386 equivalent to @code{step} even though there are other commands whose
1387 names start with @code{s}. You can test abbreviations by using them as
1388 arguments to the @code{help} command.
1390 @cindex repeating commands
1391 @kindex RET @r{(repeat last command)}
1392 A blank line as input to @value{GDBN} (typing just @key{RET}) means to
1393 repeat the previous command. Certain commands (for example, @code{run})
1394 will not repeat this way; these are commands whose unintentional
1395 repetition might cause trouble and which you are unlikely to want to
1396 repeat. User-defined commands can disable this feature; see
1397 @ref{Define, dont-repeat}.
1399 The @code{list} and @code{x} commands, when you repeat them with
1400 @key{RET}, construct new arguments rather than repeating
1401 exactly as typed. This permits easy scanning of source or memory.
1403 @value{GDBN} can also use @key{RET} in another way: to partition lengthy
1404 output, in a way similar to the common utility @code{more}
1405 (@pxref{Screen Size,,Screen Size}). Since it is easy to press one
1406 @key{RET} too many in this situation, @value{GDBN} disables command
1407 repetition after any command that generates this sort of display.
1409 @kindex # @r{(a comment)}
1411 Any text from a @kbd{#} to the end of the line is a comment; it does
1412 nothing. This is useful mainly in command files (@pxref{Command
1413 Files,,Command Files}).
1415 @cindex repeating command sequences
1416 @kindex Ctrl-o @r{(operate-and-get-next)}
1417 The @kbd{Ctrl-o} binding is useful for repeating a complex sequence of
1418 commands. This command accepts the current line, like @key{RET}, and
1419 then fetches the next line relative to the current line from the history
1423 @section Command Completion
1426 @cindex word completion
1427 @value{GDBN} can fill in the rest of a word in a command for you, if there is
1428 only one possibility; it can also show you what the valid possibilities
1429 are for the next word in a command, at any time. This works for @value{GDBN}
1430 commands, @value{GDBN} subcommands, and the names of symbols in your program.
1432 Press the @key{TAB} key whenever you want @value{GDBN} to fill out the rest
1433 of a word. If there is only one possibility, @value{GDBN} fills in the
1434 word, and waits for you to finish the command (or press @key{RET} to
1435 enter it). For example, if you type
1437 @c FIXME "@key" does not distinguish its argument sufficiently to permit
1438 @c complete accuracy in these examples; space introduced for clarity.
1439 @c If texinfo enhancements make it unnecessary, it would be nice to
1440 @c replace " @key" by "@key" in the following...
1442 (@value{GDBP}) info bre @key{TAB}
1446 @value{GDBN} fills in the rest of the word @samp{breakpoints}, since that is
1447 the only @code{info} subcommand beginning with @samp{bre}:
1450 (@value{GDBP}) info breakpoints
1454 You can either press @key{RET} at this point, to run the @code{info
1455 breakpoints} command, or backspace and enter something else, if
1456 @samp{breakpoints} does not look like the command you expected. (If you
1457 were sure you wanted @code{info breakpoints} in the first place, you
1458 might as well just type @key{RET} immediately after @samp{info bre},
1459 to exploit command abbreviations rather than command completion).
1461 If there is more than one possibility for the next word when you press
1462 @key{TAB}, @value{GDBN} sounds a bell. You can either supply more
1463 characters and try again, or just press @key{TAB} a second time;
1464 @value{GDBN} displays all the possible completions for that word. For
1465 example, you might want to set a breakpoint on a subroutine whose name
1466 begins with @samp{make_}, but when you type @kbd{b make_@key{TAB}} @value{GDBN}
1467 just sounds the bell. Typing @key{TAB} again displays all the
1468 function names in your program that begin with those characters, for
1472 (@value{GDBP}) b make_ @key{TAB}
1473 @exdent @value{GDBN} sounds bell; press @key{TAB} again, to see:
1474 make_a_section_from_file make_environ
1475 make_abs_section make_function_type
1476 make_blockvector make_pointer_type
1477 make_cleanup make_reference_type
1478 make_command make_symbol_completion_list
1479 (@value{GDBP}) b make_
1483 After displaying the available possibilities, @value{GDBN} copies your
1484 partial input (@samp{b make_} in the example) so you can finish the
1487 If you just want to see the list of alternatives in the first place, you
1488 can press @kbd{M-?} rather than pressing @key{TAB} twice. @kbd{M-?}
1489 means @kbd{@key{META} ?}. You can type this either by holding down a
1490 key designated as the @key{META} shift on your keyboard (if there is
1491 one) while typing @kbd{?}, or as @key{ESC} followed by @kbd{?}.
1493 @cindex quotes in commands
1494 @cindex completion of quoted strings
1495 Sometimes the string you need, while logically a ``word'', may contain
1496 parentheses or other characters that @value{GDBN} normally excludes from
1497 its notion of a word. To permit word completion to work in this
1498 situation, you may enclose words in @code{'} (single quote marks) in
1499 @value{GDBN} commands.
1501 The most likely situation where you might need this is in typing the
1502 name of a C@t{++} function. This is because C@t{++} allows function
1503 overloading (multiple definitions of the same function, distinguished
1504 by argument type). For example, when you want to set a breakpoint you
1505 may need to distinguish whether you mean the version of @code{name}
1506 that takes an @code{int} parameter, @code{name(int)}, or the version
1507 that takes a @code{float} parameter, @code{name(float)}. To use the
1508 word-completion facilities in this situation, type a single quote
1509 @code{'} at the beginning of the function name. This alerts
1510 @value{GDBN} that it may need to consider more information than usual
1511 when you press @key{TAB} or @kbd{M-?} to request word completion:
1514 (@value{GDBP}) b 'bubble( @kbd{M-?}
1515 bubble(double,double) bubble(int,int)
1516 (@value{GDBP}) b 'bubble(
1519 In some cases, @value{GDBN} can tell that completing a name requires using
1520 quotes. When this happens, @value{GDBN} inserts the quote for you (while
1521 completing as much as it can) if you do not type the quote in the first
1525 (@value{GDBP}) b bub @key{TAB}
1526 @exdent @value{GDBN} alters your input line to the following, and rings a bell:
1527 (@value{GDBP}) b 'bubble(
1531 In general, @value{GDBN} can tell that a quote is needed (and inserts it) if
1532 you have not yet started typing the argument list when you ask for
1533 completion on an overloaded symbol.
1535 For more information about overloaded functions, see @ref{C Plus Plus
1536 Expressions, ,C@t{++} Expressions}. You can use the command @code{set
1537 overload-resolution off} to disable overload resolution;
1538 see @ref{Debugging C Plus Plus, ,@value{GDBN} Features for C@t{++}}.
1540 @cindex completion of structure field names
1541 @cindex structure field name completion
1542 @cindex completion of union field names
1543 @cindex union field name completion
1544 When completing in an expression which looks up a field in a
1545 structure, @value{GDBN} also tries@footnote{The completer can be
1546 confused by certain kinds of invalid expressions. Also, it only
1547 examines the static type of the expression, not the dynamic type.} to
1548 limit completions to the field names available in the type of the
1552 (@value{GDBP}) p gdb_stdout.@kbd{M-?}
1553 magic to_delete to_fputs to_put to_rewind
1554 to_data to_flush to_isatty to_read to_write
1558 This is because the @code{gdb_stdout} is a variable of the type
1559 @code{struct ui_file} that is defined in @value{GDBN} sources as
1566 ui_file_flush_ftype *to_flush;
1567 ui_file_write_ftype *to_write;
1568 ui_file_fputs_ftype *to_fputs;
1569 ui_file_read_ftype *to_read;
1570 ui_file_delete_ftype *to_delete;
1571 ui_file_isatty_ftype *to_isatty;
1572 ui_file_rewind_ftype *to_rewind;
1573 ui_file_put_ftype *to_put;
1580 @section Getting Help
1581 @cindex online documentation
1584 You can always ask @value{GDBN} itself for information on its commands,
1585 using the command @code{help}.
1588 @kindex h @r{(@code{help})}
1591 You can use @code{help} (abbreviated @code{h}) with no arguments to
1592 display a short list of named classes of commands:
1596 List of classes of commands:
1598 aliases -- Aliases of other commands
1599 breakpoints -- Making program stop at certain points
1600 data -- Examining data
1601 files -- Specifying and examining files
1602 internals -- Maintenance commands
1603 obscure -- Obscure features
1604 running -- Running the program
1605 stack -- Examining the stack
1606 status -- Status inquiries
1607 support -- Support facilities
1608 tracepoints -- Tracing of program execution without
1609 stopping the program
1610 user-defined -- User-defined commands
1612 Type "help" followed by a class name for a list of
1613 commands in that class.
1614 Type "help" followed by command name for full
1616 Command name abbreviations are allowed if unambiguous.
1619 @c the above line break eliminates huge line overfull...
1621 @item help @var{class}
1622 Using one of the general help classes as an argument, you can get a
1623 list of the individual commands in that class. For example, here is the
1624 help display for the class @code{status}:
1627 (@value{GDBP}) help status
1632 @c Line break in "show" line falsifies real output, but needed
1633 @c to fit in smallbook page size.
1634 info -- Generic command for showing things
1635 about the program being debugged
1636 show -- Generic command for showing things
1639 Type "help" followed by command name for full
1641 Command name abbreviations are allowed if unambiguous.
1645 @item help @var{command}
1646 With a command name as @code{help} argument, @value{GDBN} displays a
1647 short paragraph on how to use that command.
1650 @item apropos @var{args}
1651 The @code{apropos} command searches through all of the @value{GDBN}
1652 commands, and their documentation, for the regular expression specified in
1653 @var{args}. It prints out all matches found. For example:
1664 set symbol-reloading -- Set dynamic symbol table reloading
1665 multiple times in one run
1666 show symbol-reloading -- Show dynamic symbol table reloading
1667 multiple times in one run
1672 @item complete @var{args}
1673 The @code{complete @var{args}} command lists all the possible completions
1674 for the beginning of a command. Use @var{args} to specify the beginning of the
1675 command you want completed. For example:
1681 @noindent results in:
1692 @noindent This is intended for use by @sc{gnu} Emacs.
1695 In addition to @code{help}, you can use the @value{GDBN} commands @code{info}
1696 and @code{show} to inquire about the state of your program, or the state
1697 of @value{GDBN} itself. Each command supports many topics of inquiry; this
1698 manual introduces each of them in the appropriate context. The listings
1699 under @code{info} and under @code{show} in the Index point to
1700 all the sub-commands. @xref{Index}.
1705 @kindex i @r{(@code{info})}
1707 This command (abbreviated @code{i}) is for describing the state of your
1708 program. For example, you can show the arguments passed to a function
1709 with @code{info args}, list the registers currently in use with @code{info
1710 registers}, or list the breakpoints you have set with @code{info breakpoints}.
1711 You can get a complete list of the @code{info} sub-commands with
1712 @w{@code{help info}}.
1716 You can assign the result of an expression to an environment variable with
1717 @code{set}. For example, you can set the @value{GDBN} prompt to a $-sign with
1718 @code{set prompt $}.
1722 In contrast to @code{info}, @code{show} is for describing the state of
1723 @value{GDBN} itself.
1724 You can change most of the things you can @code{show}, by using the
1725 related command @code{set}; for example, you can control what number
1726 system is used for displays with @code{set radix}, or simply inquire
1727 which is currently in use with @code{show radix}.
1730 To display all the settable parameters and their current
1731 values, you can use @code{show} with no arguments; you may also use
1732 @code{info set}. Both commands produce the same display.
1733 @c FIXME: "info set" violates the rule that "info" is for state of
1734 @c FIXME...program. Ck w/ GNU: "info set" to be called something else,
1735 @c FIXME...or change desc of rule---eg "state of prog and debugging session"?
1739 Here are three miscellaneous @code{show} subcommands, all of which are
1740 exceptional in lacking corresponding @code{set} commands:
1743 @kindex show version
1744 @cindex @value{GDBN} version number
1746 Show what version of @value{GDBN} is running. You should include this
1747 information in @value{GDBN} bug-reports. If multiple versions of
1748 @value{GDBN} are in use at your site, you may need to determine which
1749 version of @value{GDBN} you are running; as @value{GDBN} evolves, new
1750 commands are introduced, and old ones may wither away. Also, many
1751 system vendors ship variant versions of @value{GDBN}, and there are
1752 variant versions of @value{GDBN} in @sc{gnu}/Linux distributions as well.
1753 The version number is the same as the one announced when you start
1756 @kindex show copying
1757 @kindex info copying
1758 @cindex display @value{GDBN} copyright
1761 Display information about permission for copying @value{GDBN}.
1763 @kindex show warranty
1764 @kindex info warranty
1766 @itemx info warranty
1767 Display the @sc{gnu} ``NO WARRANTY'' statement, or a warranty,
1768 if your version of @value{GDBN} comes with one.
1773 @chapter Running Programs Under @value{GDBN}
1775 When you run a program under @value{GDBN}, you must first generate
1776 debugging information when you compile it.
1778 You may start @value{GDBN} with its arguments, if any, in an environment
1779 of your choice. If you are doing native debugging, you may redirect
1780 your program's input and output, debug an already running process, or
1781 kill a child process.
1784 * Compilation:: Compiling for debugging
1785 * Starting:: Starting your program
1786 * Arguments:: Your program's arguments
1787 * Environment:: Your program's environment
1789 * Working Directory:: Your program's working directory
1790 * Input/Output:: Your program's input and output
1791 * Attach:: Debugging an already-running process
1792 * Kill Process:: Killing the child process
1794 * Inferiors:: Debugging multiple inferiors
1795 * Threads:: Debugging programs with multiple threads
1796 * Processes:: Debugging programs with multiple processes
1797 * Checkpoint/Restart:: Setting a @emph{bookmark} to return to later
1801 @section Compiling for Debugging
1803 In order to debug a program effectively, you need to generate
1804 debugging information when you compile it. This debugging information
1805 is stored in the object file; it describes the data type of each
1806 variable or function and the correspondence between source line numbers
1807 and addresses in the executable code.
1809 To request debugging information, specify the @samp{-g} option when you run
1812 Programs that are to be shipped to your customers are compiled with
1813 optimizations, using the @samp{-O} compiler option. However, some
1814 compilers are unable to handle the @samp{-g} and @samp{-O} options
1815 together. Using those compilers, you cannot generate optimized
1816 executables containing debugging information.
1818 @value{NGCC}, the @sc{gnu} C/C@t{++} compiler, supports @samp{-g} with or
1819 without @samp{-O}, making it possible to debug optimized code. We
1820 recommend that you @emph{always} use @samp{-g} whenever you compile a
1821 program. You may think your program is correct, but there is no sense
1822 in pushing your luck. For more information, see @ref{Optimized Code}.
1824 Older versions of the @sc{gnu} C compiler permitted a variant option
1825 @w{@samp{-gg}} for debugging information. @value{GDBN} no longer supports this
1826 format; if your @sc{gnu} C compiler has this option, do not use it.
1828 @value{GDBN} knows about preprocessor macros and can show you their
1829 expansion (@pxref{Macros}). Most compilers do not include information
1830 about preprocessor macros in the debugging information if you specify
1831 the @option{-g} flag alone, because this information is rather large.
1832 Version 3.1 and later of @value{NGCC}, the @sc{gnu} C compiler,
1833 provides macro information if you specify the options
1834 @option{-gdwarf-2} and @option{-g3}; the former option requests
1835 debugging information in the Dwarf 2 format, and the latter requests
1836 ``extra information''. In the future, we hope to find more compact
1837 ways to represent macro information, so that it can be included with
1842 @section Starting your Program
1848 @kindex r @r{(@code{run})}
1851 Use the @code{run} command to start your program under @value{GDBN}.
1852 You must first specify the program name (except on VxWorks) with an
1853 argument to @value{GDBN} (@pxref{Invocation, ,Getting In and Out of
1854 @value{GDBN}}), or by using the @code{file} or @code{exec-file} command
1855 (@pxref{Files, ,Commands to Specify Files}).
1859 If you are running your program in an execution environment that
1860 supports processes, @code{run} creates an inferior process and makes
1861 that process run your program. In some environments without processes,
1862 @code{run} jumps to the start of your program. Other targets,
1863 like @samp{remote}, are always running. If you get an error
1864 message like this one:
1867 The "remote" target does not support "run".
1868 Try "help target" or "continue".
1872 then use @code{continue} to run your program. You may need @code{load}
1873 first (@pxref{load}).
1875 The execution of a program is affected by certain information it
1876 receives from its superior. @value{GDBN} provides ways to specify this
1877 information, which you must do @emph{before} starting your program. (You
1878 can change it after starting your program, but such changes only affect
1879 your program the next time you start it.) This information may be
1880 divided into four categories:
1883 @item The @emph{arguments.}
1884 Specify the arguments to give your program as the arguments of the
1885 @code{run} command. If a shell is available on your target, the shell
1886 is used to pass the arguments, so that you may use normal conventions
1887 (such as wildcard expansion or variable substitution) in describing
1889 In Unix systems, you can control which shell is used with the
1890 @code{SHELL} environment variable.
1891 @xref{Arguments, ,Your Program's Arguments}.
1893 @item The @emph{environment.}
1894 Your program normally inherits its environment from @value{GDBN}, but you can
1895 use the @value{GDBN} commands @code{set environment} and @code{unset
1896 environment} to change parts of the environment that affect
1897 your program. @xref{Environment, ,Your Program's Environment}.
1899 @item The @emph{working directory.}
1900 Your program inherits its working directory from @value{GDBN}. You can set
1901 the @value{GDBN} working directory with the @code{cd} command in @value{GDBN}.
1902 @xref{Working Directory, ,Your Program's Working Directory}.
1904 @item The @emph{standard input and output.}
1905 Your program normally uses the same device for standard input and
1906 standard output as @value{GDBN} is using. You can redirect input and output
1907 in the @code{run} command line, or you can use the @code{tty} command to
1908 set a different device for your program.
1909 @xref{Input/Output, ,Your Program's Input and Output}.
1912 @emph{Warning:} While input and output redirection work, you cannot use
1913 pipes to pass the output of the program you are debugging to another
1914 program; if you attempt this, @value{GDBN} is likely to wind up debugging the
1918 When you issue the @code{run} command, your program begins to execute
1919 immediately. @xref{Stopping, ,Stopping and Continuing}, for discussion
1920 of how to arrange for your program to stop. Once your program has
1921 stopped, you may call functions in your program, using the @code{print}
1922 or @code{call} commands. @xref{Data, ,Examining Data}.
1924 If the modification time of your symbol file has changed since the last
1925 time @value{GDBN} read its symbols, @value{GDBN} discards its symbol
1926 table, and reads it again. When it does this, @value{GDBN} tries to retain
1927 your current breakpoints.
1932 @cindex run to main procedure
1933 The name of the main procedure can vary from language to language.
1934 With C or C@t{++}, the main procedure name is always @code{main}, but
1935 other languages such as Ada do not require a specific name for their
1936 main procedure. The debugger provides a convenient way to start the
1937 execution of the program and to stop at the beginning of the main
1938 procedure, depending on the language used.
1940 The @samp{start} command does the equivalent of setting a temporary
1941 breakpoint at the beginning of the main procedure and then invoking
1942 the @samp{run} command.
1944 @cindex elaboration phase
1945 Some programs contain an @dfn{elaboration} phase where some startup code is
1946 executed before the main procedure is called. This depends on the
1947 languages used to write your program. In C@t{++}, for instance,
1948 constructors for static and global objects are executed before
1949 @code{main} is called. It is therefore possible that the debugger stops
1950 before reaching the main procedure. However, the temporary breakpoint
1951 will remain to halt execution.
1953 Specify the arguments to give to your program as arguments to the
1954 @samp{start} command. These arguments will be given verbatim to the
1955 underlying @samp{run} command. Note that the same arguments will be
1956 reused if no argument is provided during subsequent calls to
1957 @samp{start} or @samp{run}.
1959 It is sometimes necessary to debug the program during elaboration. In
1960 these cases, using the @code{start} command would stop the execution of
1961 your program too late, as the program would have already completed the
1962 elaboration phase. Under these circumstances, insert breakpoints in your
1963 elaboration code before running your program.
1965 @kindex set exec-wrapper
1966 @item set exec-wrapper @var{wrapper}
1967 @itemx show exec-wrapper
1968 @itemx unset exec-wrapper
1969 When @samp{exec-wrapper} is set, the specified wrapper is used to
1970 launch programs for debugging. @value{GDBN} starts your program
1971 with a shell command of the form @kbd{exec @var{wrapper}
1972 @var{program}}. Quoting is added to @var{program} and its
1973 arguments, but not to @var{wrapper}, so you should add quotes if
1974 appropriate for your shell. The wrapper runs until it executes
1975 your program, and then @value{GDBN} takes control.
1977 You can use any program that eventually calls @code{execve} with
1978 its arguments as a wrapper. Several standard Unix utilities do
1979 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
1980 with @code{exec "$@@"} will also work.
1982 For example, you can use @code{env} to pass an environment variable to
1983 the debugged program, without setting the variable in your shell's
1987 (@value{GDBP}) set exec-wrapper env 'LD_PRELOAD=libtest.so'
1991 This command is available when debugging locally on most targets, excluding
1992 @sc{djgpp}, Cygwin, MS Windows, and QNX Neutrino.
1994 @kindex set disable-randomization
1995 @item set disable-randomization
1996 @itemx set disable-randomization on
1997 This option (enabled by default in @value{GDBN}) will turn off the native
1998 randomization of the virtual address space of the started program. This option
1999 is useful for multiple debugging sessions to make the execution better
2000 reproducible and memory addresses reusable across debugging sessions.
2002 This feature is implemented only on @sc{gnu}/Linux. You can get the same
2006 (@value{GDBP}) set exec-wrapper setarch `uname -m` -R
2009 @item set disable-randomization off
2010 Leave the behavior of the started executable unchanged. Some bugs rear their
2011 ugly heads only when the program is loaded at certain addresses. If your bug
2012 disappears when you run the program under @value{GDBN}, that might be because
2013 @value{GDBN} by default disables the address randomization on platforms, such
2014 as @sc{gnu}/Linux, which do that for stand-alone programs. Use @kbd{set
2015 disable-randomization off} to try to reproduce such elusive bugs.
2017 The virtual address space randomization is implemented only on @sc{gnu}/Linux.
2018 It protects the programs against some kinds of security attacks. In these
2019 cases the attacker needs to know the exact location of a concrete executable
2020 code. Randomizing its location makes it impossible to inject jumps misusing
2021 a code at its expected addresses.
2023 Prelinking shared libraries provides a startup performance advantage but it
2024 makes addresses in these libraries predictable for privileged processes by
2025 having just unprivileged access at the target system. Reading the shared
2026 library binary gives enough information for assembling the malicious code
2027 misusing it. Still even a prelinked shared library can get loaded at a new
2028 random address just requiring the regular relocation process during the
2029 startup. Shared libraries not already prelinked are always loaded at
2030 a randomly chosen address.
2032 Position independent executables (PIE) contain position independent code
2033 similar to the shared libraries and therefore such executables get loaded at
2034 a randomly chosen address upon startup. PIE executables always load even
2035 already prelinked shared libraries at a random address. You can build such
2036 executable using @command{gcc -fPIE -pie}.
2038 Heap (malloc storage), stack and custom mmap areas are always placed randomly
2039 (as long as the randomization is enabled).
2041 @item show disable-randomization
2042 Show the current setting of the explicit disable of the native randomization of
2043 the virtual address space of the started program.
2048 @section Your Program's Arguments
2050 @cindex arguments (to your program)
2051 The arguments to your program can be specified by the arguments of the
2053 They are passed to a shell, which expands wildcard characters and
2054 performs redirection of I/O, and thence to your program. Your
2055 @code{SHELL} environment variable (if it exists) specifies what shell
2056 @value{GDBN} uses. If you do not define @code{SHELL}, @value{GDBN} uses
2057 the default shell (@file{/bin/sh} on Unix).
2059 On non-Unix systems, the program is usually invoked directly by
2060 @value{GDBN}, which emulates I/O redirection via the appropriate system
2061 calls, and the wildcard characters are expanded by the startup code of
2062 the program, not by the shell.
2064 @code{run} with no arguments uses the same arguments used by the previous
2065 @code{run}, or those set by the @code{set args} command.
2070 Specify the arguments to be used the next time your program is run. If
2071 @code{set args} has no arguments, @code{run} executes your program
2072 with no arguments. Once you have run your program with arguments,
2073 using @code{set args} before the next @code{run} is the only way to run
2074 it again without arguments.
2078 Show the arguments to give your program when it is started.
2082 @section Your Program's Environment
2084 @cindex environment (of your program)
2085 The @dfn{environment} consists of a set of environment variables and
2086 their values. Environment variables conventionally record such things as
2087 your user name, your home directory, your terminal type, and your search
2088 path for programs to run. Usually you set up environment variables with
2089 the shell and they are inherited by all the other programs you run. When
2090 debugging, it can be useful to try running your program with a modified
2091 environment without having to start @value{GDBN} over again.
2095 @item path @var{directory}
2096 Add @var{directory} to the front of the @code{PATH} environment variable
2097 (the search path for executables) that will be passed to your program.
2098 The value of @code{PATH} used by @value{GDBN} does not change.
2099 You may specify several directory names, separated by whitespace or by a
2100 system-dependent separator character (@samp{:} on Unix, @samp{;} on
2101 MS-DOS and MS-Windows). If @var{directory} is already in the path, it
2102 is moved to the front, so it is searched sooner.
2104 You can use the string @samp{$cwd} to refer to whatever is the current
2105 working directory at the time @value{GDBN} searches the path. If you
2106 use @samp{.} instead, it refers to the directory where you executed the
2107 @code{path} command. @value{GDBN} replaces @samp{.} in the
2108 @var{directory} argument (with the current path) before adding
2109 @var{directory} to the search path.
2110 @c 'path' is explicitly nonrepeatable, but RMS points out it is silly to
2111 @c document that, since repeating it would be a no-op.
2115 Display the list of search paths for executables (the @code{PATH}
2116 environment variable).
2118 @kindex show environment
2119 @item show environment @r{[}@var{varname}@r{]}
2120 Print the value of environment variable @var{varname} to be given to
2121 your program when it starts. If you do not supply @var{varname},
2122 print the names and values of all environment variables to be given to
2123 your program. You can abbreviate @code{environment} as @code{env}.
2125 @kindex set environment
2126 @item set environment @var{varname} @r{[}=@var{value}@r{]}
2127 Set environment variable @var{varname} to @var{value}. The value
2128 changes for your program only, not for @value{GDBN} itself. @var{value} may
2129 be any string; the values of environment variables are just strings, and
2130 any interpretation is supplied by your program itself. The @var{value}
2131 parameter is optional; if it is eliminated, the variable is set to a
2133 @c "any string" here does not include leading, trailing
2134 @c blanks. Gnu asks: does anyone care?
2136 For example, this command:
2143 tells the debugged program, when subsequently run, that its user is named
2144 @samp{foo}. (The spaces around @samp{=} are used for clarity here; they
2145 are not actually required.)
2147 @kindex unset environment
2148 @item unset environment @var{varname}
2149 Remove variable @var{varname} from the environment to be passed to your
2150 program. This is different from @samp{set env @var{varname} =};
2151 @code{unset environment} removes the variable from the environment,
2152 rather than assigning it an empty value.
2155 @emph{Warning:} On Unix systems, @value{GDBN} runs your program using
2157 by your @code{SHELL} environment variable if it exists (or
2158 @code{/bin/sh} if not). If your @code{SHELL} variable names a shell
2159 that runs an initialization file---such as @file{.cshrc} for C-shell, or
2160 @file{.bashrc} for BASH---any variables you set in that file affect
2161 your program. You may wish to move setting of environment variables to
2162 files that are only run when you sign on, such as @file{.login} or
2165 @node Working Directory
2166 @section Your Program's Working Directory
2168 @cindex working directory (of your program)
2169 Each time you start your program with @code{run}, it inherits its
2170 working directory from the current working directory of @value{GDBN}.
2171 The @value{GDBN} working directory is initially whatever it inherited
2172 from its parent process (typically the shell), but you can specify a new
2173 working directory in @value{GDBN} with the @code{cd} command.
2175 The @value{GDBN} working directory also serves as a default for the commands
2176 that specify files for @value{GDBN} to operate on. @xref{Files, ,Commands to
2181 @cindex change working directory
2182 @item cd @var{directory}
2183 Set the @value{GDBN} working directory to @var{directory}.
2187 Print the @value{GDBN} working directory.
2190 It is generally impossible to find the current working directory of
2191 the process being debugged (since a program can change its directory
2192 during its run). If you work on a system where @value{GDBN} is
2193 configured with the @file{/proc} support, you can use the @code{info
2194 proc} command (@pxref{SVR4 Process Information}) to find out the
2195 current working directory of the debuggee.
2198 @section Your Program's Input and Output
2203 By default, the program you run under @value{GDBN} does input and output to
2204 the same terminal that @value{GDBN} uses. @value{GDBN} switches the terminal
2205 to its own terminal modes to interact with you, but it records the terminal
2206 modes your program was using and switches back to them when you continue
2207 running your program.
2210 @kindex info terminal
2212 Displays information recorded by @value{GDBN} about the terminal modes your
2216 You can redirect your program's input and/or output using shell
2217 redirection with the @code{run} command. For example,
2224 starts your program, diverting its output to the file @file{outfile}.
2227 @cindex controlling terminal
2228 Another way to specify where your program should do input and output is
2229 with the @code{tty} command. This command accepts a file name as
2230 argument, and causes this file to be the default for future @code{run}
2231 commands. It also resets the controlling terminal for the child
2232 process, for future @code{run} commands. For example,
2239 directs that processes started with subsequent @code{run} commands
2240 default to do input and output on the terminal @file{/dev/ttyb} and have
2241 that as their controlling terminal.
2243 An explicit redirection in @code{run} overrides the @code{tty} command's
2244 effect on the input/output device, but not its effect on the controlling
2247 When you use the @code{tty} command or redirect input in the @code{run}
2248 command, only the input @emph{for your program} is affected. The input
2249 for @value{GDBN} still comes from your terminal. @code{tty} is an alias
2250 for @code{set inferior-tty}.
2252 @cindex inferior tty
2253 @cindex set inferior controlling terminal
2254 You can use the @code{show inferior-tty} command to tell @value{GDBN} to
2255 display the name of the terminal that will be used for future runs of your
2259 @item set inferior-tty /dev/ttyb
2260 @kindex set inferior-tty
2261 Set the tty for the program being debugged to /dev/ttyb.
2263 @item show inferior-tty
2264 @kindex show inferior-tty
2265 Show the current tty for the program being debugged.
2269 @section Debugging an Already-running Process
2274 @item attach @var{process-id}
2275 This command attaches to a running process---one that was started
2276 outside @value{GDBN}. (@code{info files} shows your active
2277 targets.) The command takes as argument a process ID. The usual way to
2278 find out the @var{process-id} of a Unix process is with the @code{ps} utility,
2279 or with the @samp{jobs -l} shell command.
2281 @code{attach} does not repeat if you press @key{RET} a second time after
2282 executing the command.
2285 To use @code{attach}, your program must be running in an environment
2286 which supports processes; for example, @code{attach} does not work for
2287 programs on bare-board targets that lack an operating system. You must
2288 also have permission to send the process a signal.
2290 When you use @code{attach}, the debugger finds the program running in
2291 the process first by looking in the current working directory, then (if
2292 the program is not found) by using the source file search path
2293 (@pxref{Source Path, ,Specifying Source Directories}). You can also use
2294 the @code{file} command to load the program. @xref{Files, ,Commands to
2297 The first thing @value{GDBN} does after arranging to debug the specified
2298 process is to stop it. You can examine and modify an attached process
2299 with all the @value{GDBN} commands that are ordinarily available when
2300 you start processes with @code{run}. You can insert breakpoints; you
2301 can step and continue; you can modify storage. If you would rather the
2302 process continue running, you may use the @code{continue} command after
2303 attaching @value{GDBN} to the process.
2308 When you have finished debugging the attached process, you can use the
2309 @code{detach} command to release it from @value{GDBN} control. Detaching
2310 the process continues its execution. After the @code{detach} command,
2311 that process and @value{GDBN} become completely independent once more, and you
2312 are ready to @code{attach} another process or start one with @code{run}.
2313 @code{detach} does not repeat if you press @key{RET} again after
2314 executing the command.
2317 If you exit @value{GDBN} while you have an attached process, you detach
2318 that process. If you use the @code{run} command, you kill that process.
2319 By default, @value{GDBN} asks for confirmation if you try to do either of these
2320 things; you can control whether or not you need to confirm by using the
2321 @code{set confirm} command (@pxref{Messages/Warnings, ,Optional Warnings and
2325 @section Killing the Child Process
2330 Kill the child process in which your program is running under @value{GDBN}.
2333 This command is useful if you wish to debug a core dump instead of a
2334 running process. @value{GDBN} ignores any core dump file while your program
2337 On some operating systems, a program cannot be executed outside @value{GDBN}
2338 while you have breakpoints set on it inside @value{GDBN}. You can use the
2339 @code{kill} command in this situation to permit running your program
2340 outside the debugger.
2342 The @code{kill} command is also useful if you wish to recompile and
2343 relink your program, since on many systems it is impossible to modify an
2344 executable file while it is running in a process. In this case, when you
2345 next type @code{run}, @value{GDBN} notices that the file has changed, and
2346 reads the symbol table again (while trying to preserve your current
2347 breakpoint settings).
2350 @section Debugging Multiple Inferiors
2352 Some @value{GDBN} targets are able to run multiple processes created
2353 from a single executable. This can happen, for instance, with an
2354 embedded system reporting back several processes via the remote
2358 @value{GDBN} represents the state of each program execution with an
2359 object called an @dfn{inferior}. An inferior typically corresponds to
2360 a process, but is more general and applies also to targets that do not
2361 have processes. Inferiors may be created before a process runs, and
2362 may (in future) be retained after a process exits. Each run of an
2363 executable creates a new inferior, as does each attachment to an
2364 existing process. Inferiors have unique identifiers that are
2365 different from process ids, and may optionally be named as well.
2366 Usually each inferior will also have its own distinct address space,
2367 although some embedded targets may have several inferiors running in
2368 different parts of a single space.
2370 Each inferior may in turn have multiple threads running in it.
2372 To find out what inferiors exist at any moment, use @code{info inferiors}:
2375 @kindex info inferiors
2376 @item info inferiors
2377 Print a list of all inferiors currently being managed by @value{GDBN}.
2379 @value{GDBN} displays for each inferior (in this order):
2383 the inferior number assigned by @value{GDBN}
2386 the target system's inferior identifier
2390 An asterisk @samp{*} preceding the @value{GDBN} inferior number
2391 indicates the current inferior.
2395 @c end table here to get a little more width for example
2398 (@value{GDBP}) info inferiors
2404 To switch focus between inferiors, use the @code{inferior} command:
2407 @kindex inferior @var{infno}
2408 @item inferior @var{infno}
2409 Make inferior number @var{infno} the current inferior. The argument
2410 @var{infno} is the inferior number assigned by @value{GDBN}, as shown
2411 in the first field of the @samp{info inferiors} display.
2414 To quit debugging one of the inferiors, you can either detach from it
2415 by using the @w{@code{detach inferior}} command (allowing it to run
2416 independently), or kill it using the @w{@code{kill inferior}} command:
2419 @kindex detach inferior @var{infno}
2420 @item detach inferior @var{infno}
2421 Detach from the inferior identified by @value{GDBN} inferior number
2422 @var{infno}, and remove it from the inferior list.
2424 @kindex kill inferior @var{infno}
2425 @item kill inferior @var{infno}
2426 Kill the inferior identified by @value{GDBN} inferior number
2427 @var{infno}, and remove it from the inferior list.
2430 To be notified when inferiors are started or exit under @value{GDBN}'s
2431 control use @w{@code{set print inferior-events}}:
2434 @kindex set print inferior-events
2435 @cindex print messages on inferior start and exit
2436 @item set print inferior-events
2437 @itemx set print inferior-events on
2438 @itemx set print inferior-events off
2439 The @code{set print inferior-events} command allows you to enable or
2440 disable printing of messages when @value{GDBN} notices that new
2441 inferiors have started or that inferiors have exited or have been
2442 detached. By default, these messages will not be printed.
2444 @kindex show print inferior-events
2445 @item show print inferior-events
2446 Show whether messages will be printed when @value{GDBN} detects that
2447 inferiors have started, exited or have been detached.
2451 @section Debugging Programs with Multiple Threads
2453 @cindex threads of execution
2454 @cindex multiple threads
2455 @cindex switching threads
2456 In some operating systems, such as HP-UX and Solaris, a single program
2457 may have more than one @dfn{thread} of execution. The precise semantics
2458 of threads differ from one operating system to another, but in general
2459 the threads of a single program are akin to multiple processes---except
2460 that they share one address space (that is, they can all examine and
2461 modify the same variables). On the other hand, each thread has its own
2462 registers and execution stack, and perhaps private memory.
2464 @value{GDBN} provides these facilities for debugging multi-thread
2468 @item automatic notification of new threads
2469 @item @samp{thread @var{threadno}}, a command to switch among threads
2470 @item @samp{info threads}, a command to inquire about existing threads
2471 @item @samp{thread apply [@var{threadno}] [@var{all}] @var{args}},
2472 a command to apply a command to a list of threads
2473 @item thread-specific breakpoints
2474 @item @samp{set print thread-events}, which controls printing of
2475 messages on thread start and exit.
2476 @item @samp{set libthread-db-search-path @var{path}}, which lets
2477 the user specify which @code{libthread_db} to use if the default choice
2478 isn't compatible with the program.
2482 @emph{Warning:} These facilities are not yet available on every
2483 @value{GDBN} configuration where the operating system supports threads.
2484 If your @value{GDBN} does not support threads, these commands have no
2485 effect. For example, a system without thread support shows no output
2486 from @samp{info threads}, and always rejects the @code{thread} command,
2490 (@value{GDBP}) info threads
2491 (@value{GDBP}) thread 1
2492 Thread ID 1 not known. Use the "info threads" command to
2493 see the IDs of currently known threads.
2495 @c FIXME to implementors: how hard would it be to say "sorry, this GDB
2496 @c doesn't support threads"?
2499 @cindex focus of debugging
2500 @cindex current thread
2501 The @value{GDBN} thread debugging facility allows you to observe all
2502 threads while your program runs---but whenever @value{GDBN} takes
2503 control, one thread in particular is always the focus of debugging.
2504 This thread is called the @dfn{current thread}. Debugging commands show
2505 program information from the perspective of the current thread.
2507 @cindex @code{New} @var{systag} message
2508 @cindex thread identifier (system)
2509 @c FIXME-implementors!! It would be more helpful if the [New...] message
2510 @c included GDB's numeric thread handle, so you could just go to that
2511 @c thread without first checking `info threads'.
2512 Whenever @value{GDBN} detects a new thread in your program, it displays
2513 the target system's identification for the thread with a message in the
2514 form @samp{[New @var{systag}]}. @var{systag} is a thread identifier
2515 whose form varies depending on the particular system. For example, on
2516 @sc{gnu}/Linux, you might see
2519 [New Thread 46912507313328 (LWP 25582)]
2523 when @value{GDBN} notices a new thread. In contrast, on an SGI system,
2524 the @var{systag} is simply something like @samp{process 368}, with no
2527 @c FIXME!! (1) Does the [New...] message appear even for the very first
2528 @c thread of a program, or does it only appear for the
2529 @c second---i.e.@: when it becomes obvious we have a multithread
2531 @c (2) *Is* there necessarily a first thread always? Or do some
2532 @c multithread systems permit starting a program with multiple
2533 @c threads ab initio?
2535 @cindex thread number
2536 @cindex thread identifier (GDB)
2537 For debugging purposes, @value{GDBN} associates its own thread
2538 number---always a single integer---with each thread in your program.
2541 @kindex info threads
2543 Display a summary of all threads currently in your
2544 program. @value{GDBN} displays for each thread (in this order):
2548 the thread number assigned by @value{GDBN}
2551 the target system's thread identifier (@var{systag})
2554 the current stack frame summary for that thread
2558 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2559 indicates the current thread.
2563 @c end table here to get a little more width for example
2566 (@value{GDBP}) info threads
2567 3 process 35 thread 27 0x34e5 in sigpause ()
2568 2 process 35 thread 23 0x34e5 in sigpause ()
2569 * 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
2575 @cindex debugging multithreaded programs (on HP-UX)
2576 @cindex thread identifier (GDB), on HP-UX
2577 For debugging purposes, @value{GDBN} associates its own thread
2578 number---a small integer assigned in thread-creation order---with each
2579 thread in your program.
2581 @cindex @code{New} @var{systag} message, on HP-UX
2582 @cindex thread identifier (system), on HP-UX
2583 @c FIXME-implementors!! It would be more helpful if the [New...] message
2584 @c included GDB's numeric thread handle, so you could just go to that
2585 @c thread without first checking `info threads'.
2586 Whenever @value{GDBN} detects a new thread in your program, it displays
2587 both @value{GDBN}'s thread number and the target system's identification for the thread with a message in the
2588 form @samp{[New @var{systag}]}. @var{systag} is a thread identifier
2589 whose form varies depending on the particular system. For example, on
2593 [New thread 2 (system thread 26594)]
2597 when @value{GDBN} notices a new thread.
2600 @kindex info threads (HP-UX)
2602 Display a summary of all threads currently in your
2603 program. @value{GDBN} displays for each thread (in this order):
2606 @item the thread number assigned by @value{GDBN}
2608 @item the target system's thread identifier (@var{systag})
2610 @item the current stack frame summary for that thread
2614 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2615 indicates the current thread.
2619 @c end table here to get a little more width for example
2622 (@value{GDBP}) info threads
2623 * 3 system thread 26607 worker (wptr=0x7b09c318 "@@") \@*
2625 2 system thread 26606 0x7b0030d8 in __ksleep () \@*
2626 from /usr/lib/libc.2
2627 1 system thread 27905 0x7b003498 in _brk () \@*
2628 from /usr/lib/libc.2
2631 On Solaris, you can display more information about user threads with a
2632 Solaris-specific command:
2635 @item maint info sol-threads
2636 @kindex maint info sol-threads
2637 @cindex thread info (Solaris)
2638 Display info on Solaris user threads.
2642 @kindex thread @var{threadno}
2643 @item thread @var{threadno}
2644 Make thread number @var{threadno} the current thread. The command
2645 argument @var{threadno} is the internal @value{GDBN} thread number, as
2646 shown in the first field of the @samp{info threads} display.
2647 @value{GDBN} responds by displaying the system identifier of the thread
2648 you selected, and its current stack frame summary:
2651 @c FIXME!! This example made up; find a @value{GDBN} w/threads and get real one
2652 (@value{GDBP}) thread 2
2653 [Switching to process 35 thread 23]
2654 0x34e5 in sigpause ()
2658 As with the @samp{[New @dots{}]} message, the form of the text after
2659 @samp{Switching to} depends on your system's conventions for identifying
2662 @kindex thread apply
2663 @cindex apply command to several threads
2664 @item thread apply [@var{threadno}] [@var{all}] @var{command}
2665 The @code{thread apply} command allows you to apply the named
2666 @var{command} to one or more threads. Specify the numbers of the
2667 threads that you want affected with the command argument
2668 @var{threadno}. It can be a single thread number, one of the numbers
2669 shown in the first field of the @samp{info threads} display; or it
2670 could be a range of thread numbers, as in @code{2-4}. To apply a
2671 command to all threads, type @kbd{thread apply all @var{command}}.
2673 @kindex set print thread-events
2674 @cindex print messages on thread start and exit
2675 @item set print thread-events
2676 @itemx set print thread-events on
2677 @itemx set print thread-events off
2678 The @code{set print thread-events} command allows you to enable or
2679 disable printing of messages when @value{GDBN} notices that new threads have
2680 started or that threads have exited. By default, these messages will
2681 be printed if detection of these events is supported by the target.
2682 Note that these messages cannot be disabled on all targets.
2684 @kindex show print thread-events
2685 @item show print thread-events
2686 Show whether messages will be printed when @value{GDBN} detects that threads
2687 have started and exited.
2690 @xref{Thread Stops,,Stopping and Starting Multi-thread Programs}, for
2691 more information about how @value{GDBN} behaves when you stop and start
2692 programs with multiple threads.
2694 @xref{Set Watchpoints,,Setting Watchpoints}, for information about
2695 watchpoints in programs with multiple threads.
2698 @kindex set libthread-db-search-path
2699 @cindex search path for @code{libthread_db}
2700 @item set libthread-db-search-path @r{[}@var{path}@r{]}
2701 If this variable is set, @var{path} is a colon-separated list of
2702 directories @value{GDBN} will use to search for @code{libthread_db}.
2703 If you omit @var{path}, @samp{libthread-db-search-path} will be reset to
2706 On @sc{gnu}/Linux and Solaris systems, @value{GDBN} uses a ``helper''
2707 @code{libthread_db} library to obtain information about threads in the
2708 inferior process. @value{GDBN} will use @samp{libthread-db-search-path}
2709 to find @code{libthread_db}. If that fails, @value{GDBN} will continue
2710 with default system shared library directories, and finally the directory
2711 from which @code{libpthread} was loaded in the inferior process.
2713 For any @code{libthread_db} library @value{GDBN} finds in above directories,
2714 @value{GDBN} attempts to initialize it with the current inferior process.
2715 If this initialization fails (which could happen because of a version
2716 mismatch between @code{libthread_db} and @code{libpthread}), @value{GDBN}
2717 will unload @code{libthread_db}, and continue with the next directory.
2718 If none of @code{libthread_db} libraries initialize successfully,
2719 @value{GDBN} will issue a warning and thread debugging will be disabled.
2721 Setting @code{libthread-db-search-path} is currently implemented
2722 only on some platforms.
2724 @kindex show libthread-db-search-path
2725 @item show libthread-db-search-path
2726 Display current libthread_db search path.
2730 @section Debugging Programs with Multiple Processes
2732 @cindex fork, debugging programs which call
2733 @cindex multiple processes
2734 @cindex processes, multiple
2735 On most systems, @value{GDBN} has no special support for debugging
2736 programs which create additional processes using the @code{fork}
2737 function. When a program forks, @value{GDBN} will continue to debug the
2738 parent process and the child process will run unimpeded. If you have
2739 set a breakpoint in any code which the child then executes, the child
2740 will get a @code{SIGTRAP} signal which (unless it catches the signal)
2741 will cause it to terminate.
2743 However, if you want to debug the child process there is a workaround
2744 which isn't too painful. Put a call to @code{sleep} in the code which
2745 the child process executes after the fork. It may be useful to sleep
2746 only if a certain environment variable is set, or a certain file exists,
2747 so that the delay need not occur when you don't want to run @value{GDBN}
2748 on the child. While the child is sleeping, use the @code{ps} program to
2749 get its process ID. Then tell @value{GDBN} (a new invocation of
2750 @value{GDBN} if you are also debugging the parent process) to attach to
2751 the child process (@pxref{Attach}). From that point on you can debug
2752 the child process just like any other process which you attached to.
2754 On some systems, @value{GDBN} provides support for debugging programs that
2755 create additional processes using the @code{fork} or @code{vfork} functions.
2756 Currently, the only platforms with this feature are HP-UX (11.x and later
2757 only?) and @sc{gnu}/Linux (kernel version 2.5.60 and later).
2759 By default, when a program forks, @value{GDBN} will continue to debug
2760 the parent process and the child process will run unimpeded.
2762 If you want to follow the child process instead of the parent process,
2763 use the command @w{@code{set follow-fork-mode}}.
2766 @kindex set follow-fork-mode
2767 @item set follow-fork-mode @var{mode}
2768 Set the debugger response to a program call of @code{fork} or
2769 @code{vfork}. A call to @code{fork} or @code{vfork} creates a new
2770 process. The @var{mode} argument can be:
2774 The original process is debugged after a fork. The child process runs
2775 unimpeded. This is the default.
2778 The new process is debugged after a fork. The parent process runs
2783 @kindex show follow-fork-mode
2784 @item show follow-fork-mode
2785 Display the current debugger response to a @code{fork} or @code{vfork} call.
2788 @cindex debugging multiple processes
2789 On Linux, if you want to debug both the parent and child processes, use the
2790 command @w{@code{set detach-on-fork}}.
2793 @kindex set detach-on-fork
2794 @item set detach-on-fork @var{mode}
2795 Tells gdb whether to detach one of the processes after a fork, or
2796 retain debugger control over them both.
2800 The child process (or parent process, depending on the value of
2801 @code{follow-fork-mode}) will be detached and allowed to run
2802 independently. This is the default.
2805 Both processes will be held under the control of @value{GDBN}.
2806 One process (child or parent, depending on the value of
2807 @code{follow-fork-mode}) is debugged as usual, while the other
2812 @kindex show detach-on-fork
2813 @item show detach-on-fork
2814 Show whether detach-on-fork mode is on/off.
2817 If you choose to set @samp{detach-on-fork} mode off, then @value{GDBN}
2818 will retain control of all forked processes (including nested forks).
2819 You can list the forked processes under the control of @value{GDBN} by
2820 using the @w{@code{info inferiors}} command, and switch from one fork
2821 to another by using the @code{inferior} command (@pxref{Inferiors,
2822 ,Debugging Multiple Inferiors}).
2824 To quit debugging one of the forked processes, you can either detach
2825 from it by using the @w{@code{detach inferior}} command (allowing it
2826 to run independently), or kill it using the @w{@code{kill inferior}}
2827 command. @xref{Inferiors, ,Debugging Multiple Inferiors}.
2829 If you ask to debug a child process and a @code{vfork} is followed by an
2830 @code{exec}, @value{GDBN} executes the new target up to the first
2831 breakpoint in the new target. If you have a breakpoint set on
2832 @code{main} in your original program, the breakpoint will also be set on
2833 the child process's @code{main}.
2835 On some systems, when a child process is spawned by @code{vfork}, you
2836 cannot debug the child or parent until an @code{exec} call completes.
2838 If you issue a @code{run} command to @value{GDBN} after an @code{exec}
2839 call executes, the new target restarts. To restart the parent process,
2840 use the @code{file} command with the parent executable name as its
2843 You can use the @code{catch} command to make @value{GDBN} stop whenever
2844 a @code{fork}, @code{vfork}, or @code{exec} call is made. @xref{Set
2845 Catchpoints, ,Setting Catchpoints}.
2847 @node Checkpoint/Restart
2848 @section Setting a @emph{Bookmark} to Return to Later
2853 @cindex snapshot of a process
2854 @cindex rewind program state
2856 On certain operating systems@footnote{Currently, only
2857 @sc{gnu}/Linux.}, @value{GDBN} is able to save a @dfn{snapshot} of a
2858 program's state, called a @dfn{checkpoint}, and come back to it
2861 Returning to a checkpoint effectively undoes everything that has
2862 happened in the program since the @code{checkpoint} was saved. This
2863 includes changes in memory, registers, and even (within some limits)
2864 system state. Effectively, it is like going back in time to the
2865 moment when the checkpoint was saved.
2867 Thus, if you're stepping thru a program and you think you're
2868 getting close to the point where things go wrong, you can save
2869 a checkpoint. Then, if you accidentally go too far and miss
2870 the critical statement, instead of having to restart your program
2871 from the beginning, you can just go back to the checkpoint and
2872 start again from there.
2874 This can be especially useful if it takes a lot of time or
2875 steps to reach the point where you think the bug occurs.
2877 To use the @code{checkpoint}/@code{restart} method of debugging:
2882 Save a snapshot of the debugged program's current execution state.
2883 The @code{checkpoint} command takes no arguments, but each checkpoint
2884 is assigned a small integer id, similar to a breakpoint id.
2886 @kindex info checkpoints
2887 @item info checkpoints
2888 List the checkpoints that have been saved in the current debugging
2889 session. For each checkpoint, the following information will be
2896 @item Source line, or label
2899 @kindex restart @var{checkpoint-id}
2900 @item restart @var{checkpoint-id}
2901 Restore the program state that was saved as checkpoint number
2902 @var{checkpoint-id}. All program variables, registers, stack frames
2903 etc.@: will be returned to the values that they had when the checkpoint
2904 was saved. In essence, gdb will ``wind back the clock'' to the point
2905 in time when the checkpoint was saved.
2907 Note that breakpoints, @value{GDBN} variables, command history etc.
2908 are not affected by restoring a checkpoint. In general, a checkpoint
2909 only restores things that reside in the program being debugged, not in
2912 @kindex delete checkpoint @var{checkpoint-id}
2913 @item delete checkpoint @var{checkpoint-id}
2914 Delete the previously-saved checkpoint identified by @var{checkpoint-id}.
2918 Returning to a previously saved checkpoint will restore the user state
2919 of the program being debugged, plus a significant subset of the system
2920 (OS) state, including file pointers. It won't ``un-write'' data from
2921 a file, but it will rewind the file pointer to the previous location,
2922 so that the previously written data can be overwritten. For files
2923 opened in read mode, the pointer will also be restored so that the
2924 previously read data can be read again.
2926 Of course, characters that have been sent to a printer (or other
2927 external device) cannot be ``snatched back'', and characters received
2928 from eg.@: a serial device can be removed from internal program buffers,
2929 but they cannot be ``pushed back'' into the serial pipeline, ready to
2930 be received again. Similarly, the actual contents of files that have
2931 been changed cannot be restored (at this time).
2933 However, within those constraints, you actually can ``rewind'' your
2934 program to a previously saved point in time, and begin debugging it
2935 again --- and you can change the course of events so as to debug a
2936 different execution path this time.
2938 @cindex checkpoints and process id
2939 Finally, there is one bit of internal program state that will be
2940 different when you return to a checkpoint --- the program's process
2941 id. Each checkpoint will have a unique process id (or @var{pid}),
2942 and each will be different from the program's original @var{pid}.
2943 If your program has saved a local copy of its process id, this could
2944 potentially pose a problem.
2946 @subsection A Non-obvious Benefit of Using Checkpoints
2948 On some systems such as @sc{gnu}/Linux, address space randomization
2949 is performed on new processes for security reasons. This makes it
2950 difficult or impossible to set a breakpoint, or watchpoint, on an
2951 absolute address if you have to restart the program, since the
2952 absolute location of a symbol will change from one execution to the
2955 A checkpoint, however, is an @emph{identical} copy of a process.
2956 Therefore if you create a checkpoint at (eg.@:) the start of main,
2957 and simply return to that checkpoint instead of restarting the
2958 process, you can avoid the effects of address randomization and
2959 your symbols will all stay in the same place.
2962 @chapter Stopping and Continuing
2964 The principal purposes of using a debugger are so that you can stop your
2965 program before it terminates; or so that, if your program runs into
2966 trouble, you can investigate and find out why.
2968 Inside @value{GDBN}, your program may stop for any of several reasons,
2969 such as a signal, a breakpoint, or reaching a new line after a
2970 @value{GDBN} command such as @code{step}. You may then examine and
2971 change variables, set new breakpoints or remove old ones, and then
2972 continue execution. Usually, the messages shown by @value{GDBN} provide
2973 ample explanation of the status of your program---but you can also
2974 explicitly request this information at any time.
2977 @kindex info program
2979 Display information about the status of your program: whether it is
2980 running or not, what process it is, and why it stopped.
2984 * Breakpoints:: Breakpoints, watchpoints, and catchpoints
2985 * Continuing and Stepping:: Resuming execution
2987 * Thread Stops:: Stopping and starting multi-thread programs
2991 @section Breakpoints, Watchpoints, and Catchpoints
2994 A @dfn{breakpoint} makes your program stop whenever a certain point in
2995 the program is reached. For each breakpoint, you can add conditions to
2996 control in finer detail whether your program stops. You can set
2997 breakpoints with the @code{break} command and its variants (@pxref{Set
2998 Breaks, ,Setting Breakpoints}), to specify the place where your program
2999 should stop by line number, function name or exact address in the
3002 On some systems, you can set breakpoints in shared libraries before
3003 the executable is run. There is a minor limitation on HP-UX systems:
3004 you must wait until the executable is run in order to set breakpoints
3005 in shared library routines that are not called directly by the program
3006 (for example, routines that are arguments in a @code{pthread_create}
3010 @cindex data breakpoints
3011 @cindex memory tracing
3012 @cindex breakpoint on memory address
3013 @cindex breakpoint on variable modification
3014 A @dfn{watchpoint} is a special breakpoint that stops your program
3015 when the value of an expression changes. The expression may be a value
3016 of a variable, or it could involve values of one or more variables
3017 combined by operators, such as @samp{a + b}. This is sometimes called
3018 @dfn{data breakpoints}. You must use a different command to set
3019 watchpoints (@pxref{Set Watchpoints, ,Setting Watchpoints}), but aside
3020 from that, you can manage a watchpoint like any other breakpoint: you
3021 enable, disable, and delete both breakpoints and watchpoints using the
3024 You can arrange to have values from your program displayed automatically
3025 whenever @value{GDBN} stops at a breakpoint. @xref{Auto Display,,
3029 @cindex breakpoint on events
3030 A @dfn{catchpoint} is another special breakpoint that stops your program
3031 when a certain kind of event occurs, such as the throwing of a C@t{++}
3032 exception or the loading of a library. As with watchpoints, you use a
3033 different command to set a catchpoint (@pxref{Set Catchpoints, ,Setting
3034 Catchpoints}), but aside from that, you can manage a catchpoint like any
3035 other breakpoint. (To stop when your program receives a signal, use the
3036 @code{handle} command; see @ref{Signals, ,Signals}.)
3038 @cindex breakpoint numbers
3039 @cindex numbers for breakpoints
3040 @value{GDBN} assigns a number to each breakpoint, watchpoint, or
3041 catchpoint when you create it; these numbers are successive integers
3042 starting with one. In many of the commands for controlling various
3043 features of breakpoints you use the breakpoint number to say which
3044 breakpoint you want to change. Each breakpoint may be @dfn{enabled} or
3045 @dfn{disabled}; if disabled, it has no effect on your program until you
3048 @cindex breakpoint ranges
3049 @cindex ranges of breakpoints
3050 Some @value{GDBN} commands accept a range of breakpoints on which to
3051 operate. A breakpoint range is either a single breakpoint number, like
3052 @samp{5}, or two such numbers, in increasing order, separated by a
3053 hyphen, like @samp{5-7}. When a breakpoint range is given to a command,
3054 all breakpoints in that range are operated on.
3057 * Set Breaks:: Setting breakpoints
3058 * Set Watchpoints:: Setting watchpoints
3059 * Set Catchpoints:: Setting catchpoints
3060 * Delete Breaks:: Deleting breakpoints
3061 * Disabling:: Disabling breakpoints
3062 * Conditions:: Break conditions
3063 * Break Commands:: Breakpoint command lists
3064 * Error in Breakpoints:: ``Cannot insert breakpoints''
3065 * Breakpoint-related Warnings:: ``Breakpoint address adjusted...''
3069 @subsection Setting Breakpoints
3071 @c FIXME LMB what does GDB do if no code on line of breakpt?
3072 @c consider in particular declaration with/without initialization.
3074 @c FIXME 2 is there stuff on this already? break at fun start, already init?
3077 @kindex b @r{(@code{break})}
3078 @vindex $bpnum@r{, convenience variable}
3079 @cindex latest breakpoint
3080 Breakpoints are set with the @code{break} command (abbreviated
3081 @code{b}). The debugger convenience variable @samp{$bpnum} records the
3082 number of the breakpoint you've set most recently; see @ref{Convenience
3083 Vars,, Convenience Variables}, for a discussion of what you can do with
3084 convenience variables.
3087 @item break @var{location}
3088 Set a breakpoint at the given @var{location}, which can specify a
3089 function name, a line number, or an address of an instruction.
3090 (@xref{Specify Location}, for a list of all the possible ways to
3091 specify a @var{location}.) The breakpoint will stop your program just
3092 before it executes any of the code in the specified @var{location}.
3094 When using source languages that permit overloading of symbols, such as
3095 C@t{++}, a function name may refer to more than one possible place to break.
3096 @xref{Ambiguous Expressions,,Ambiguous Expressions}, for a discussion of
3099 It is also possible to insert a breakpoint that will stop the program
3100 only if a specific thread (@pxref{Thread-Specific Breakpoints})
3101 or a specific task (@pxref{Ada Tasks}) hits that breakpoint.
3104 When called without any arguments, @code{break} sets a breakpoint at
3105 the next instruction to be executed in the selected stack frame
3106 (@pxref{Stack, ,Examining the Stack}). In any selected frame but the
3107 innermost, this makes your program stop as soon as control
3108 returns to that frame. This is similar to the effect of a
3109 @code{finish} command in the frame inside the selected frame---except
3110 that @code{finish} does not leave an active breakpoint. If you use
3111 @code{break} without an argument in the innermost frame, @value{GDBN} stops
3112 the next time it reaches the current location; this may be useful
3115 @value{GDBN} normally ignores breakpoints when it resumes execution, until at
3116 least one instruction has been executed. If it did not do this, you
3117 would be unable to proceed past a breakpoint without first disabling the
3118 breakpoint. This rule applies whether or not the breakpoint already
3119 existed when your program stopped.
3121 @item break @dots{} if @var{cond}
3122 Set a breakpoint with condition @var{cond}; evaluate the expression
3123 @var{cond} each time the breakpoint is reached, and stop only if the
3124 value is nonzero---that is, if @var{cond} evaluates as true.
3125 @samp{@dots{}} stands for one of the possible arguments described
3126 above (or no argument) specifying where to break. @xref{Conditions,
3127 ,Break Conditions}, for more information on breakpoint conditions.
3130 @item tbreak @var{args}
3131 Set a breakpoint enabled only for one stop. @var{args} are the
3132 same as for the @code{break} command, and the breakpoint is set in the same
3133 way, but the breakpoint is automatically deleted after the first time your
3134 program stops there. @xref{Disabling, ,Disabling Breakpoints}.
3137 @cindex hardware breakpoints
3138 @item hbreak @var{args}
3139 Set a hardware-assisted breakpoint. @var{args} are the same as for the
3140 @code{break} command and the breakpoint is set in the same way, but the
3141 breakpoint requires hardware support and some target hardware may not
3142 have this support. The main purpose of this is EPROM/ROM code
3143 debugging, so you can set a breakpoint at an instruction without
3144 changing the instruction. This can be used with the new trap-generation
3145 provided by SPARClite DSU and most x86-based targets. These targets
3146 will generate traps when a program accesses some data or instruction
3147 address that is assigned to the debug registers. However the hardware
3148 breakpoint registers can take a limited number of breakpoints. For
3149 example, on the DSU, only two data breakpoints can be set at a time, and
3150 @value{GDBN} will reject this command if more than two are used. Delete
3151 or disable unused hardware breakpoints before setting new ones
3152 (@pxref{Disabling, ,Disabling Breakpoints}).
3153 @xref{Conditions, ,Break Conditions}.
3154 For remote targets, you can restrict the number of hardware
3155 breakpoints @value{GDBN} will use, see @ref{set remote
3156 hardware-breakpoint-limit}.
3159 @item thbreak @var{args}
3160 Set a hardware-assisted breakpoint enabled only for one stop. @var{args}
3161 are the same as for the @code{hbreak} command and the breakpoint is set in
3162 the same way. However, like the @code{tbreak} command,
3163 the breakpoint is automatically deleted after the
3164 first time your program stops there. Also, like the @code{hbreak}
3165 command, the breakpoint requires hardware support and some target hardware
3166 may not have this support. @xref{Disabling, ,Disabling Breakpoints}.
3167 See also @ref{Conditions, ,Break Conditions}.
3170 @cindex regular expression
3171 @cindex breakpoints in functions matching a regexp
3172 @cindex set breakpoints in many functions
3173 @item rbreak @var{regex}
3174 Set breakpoints on all functions matching the regular expression
3175 @var{regex}. This command sets an unconditional breakpoint on all
3176 matches, printing a list of all breakpoints it set. Once these
3177 breakpoints are set, they are treated just like the breakpoints set with
3178 the @code{break} command. You can delete them, disable them, or make
3179 them conditional the same way as any other breakpoint.
3181 The syntax of the regular expression is the standard one used with tools
3182 like @file{grep}. Note that this is different from the syntax used by
3183 shells, so for instance @code{foo*} matches all functions that include
3184 an @code{fo} followed by zero or more @code{o}s. There is an implicit
3185 @code{.*} leading and trailing the regular expression you supply, so to
3186 match only functions that begin with @code{foo}, use @code{^foo}.
3188 @cindex non-member C@t{++} functions, set breakpoint in
3189 When debugging C@t{++} programs, @code{rbreak} is useful for setting
3190 breakpoints on overloaded functions that are not members of any special
3193 @cindex set breakpoints on all functions
3194 The @code{rbreak} command can be used to set breakpoints in
3195 @strong{all} the functions in a program, like this:
3198 (@value{GDBP}) rbreak .
3201 @kindex info breakpoints
3202 @cindex @code{$_} and @code{info breakpoints}
3203 @item info breakpoints @r{[}@var{n}@r{]}
3204 @itemx info break @r{[}@var{n}@r{]}
3205 @itemx info watchpoints @r{[}@var{n}@r{]}
3206 Print a table of all breakpoints, watchpoints, and catchpoints set and
3207 not deleted. Optional argument @var{n} means print information only
3208 about the specified breakpoint (or watchpoint or catchpoint). For
3209 each breakpoint, following columns are printed:
3212 @item Breakpoint Numbers
3214 Breakpoint, watchpoint, or catchpoint.
3216 Whether the breakpoint is marked to be disabled or deleted when hit.
3217 @item Enabled or Disabled
3218 Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints
3219 that are not enabled.
3221 Where the breakpoint is in your program, as a memory address. For a
3222 pending breakpoint whose address is not yet known, this field will
3223 contain @samp{<PENDING>}. Such breakpoint won't fire until a shared
3224 library that has the symbol or line referred by breakpoint is loaded.
3225 See below for details. A breakpoint with several locations will
3226 have @samp{<MULTIPLE>} in this field---see below for details.
3228 Where the breakpoint is in the source for your program, as a file and
3229 line number. For a pending breakpoint, the original string passed to
3230 the breakpoint command will be listed as it cannot be resolved until
3231 the appropriate shared library is loaded in the future.
3235 If a breakpoint is conditional, @code{info break} shows the condition on
3236 the line following the affected breakpoint; breakpoint commands, if any,
3237 are listed after that. A pending breakpoint is allowed to have a condition
3238 specified for it. The condition is not parsed for validity until a shared
3239 library is loaded that allows the pending breakpoint to resolve to a
3243 @code{info break} with a breakpoint
3244 number @var{n} as argument lists only that breakpoint. The
3245 convenience variable @code{$_} and the default examining-address for
3246 the @code{x} command are set to the address of the last breakpoint
3247 listed (@pxref{Memory, ,Examining Memory}).
3250 @code{info break} displays a count of the number of times the breakpoint
3251 has been hit. This is especially useful in conjunction with the
3252 @code{ignore} command. You can ignore a large number of breakpoint
3253 hits, look at the breakpoint info to see how many times the breakpoint
3254 was hit, and then run again, ignoring one less than that number. This
3255 will get you quickly to the last hit of that breakpoint.
3258 @value{GDBN} allows you to set any number of breakpoints at the same place in
3259 your program. There is nothing silly or meaningless about this. When
3260 the breakpoints are conditional, this is even useful
3261 (@pxref{Conditions, ,Break Conditions}).
3263 @cindex multiple locations, breakpoints
3264 @cindex breakpoints, multiple locations
3265 It is possible that a breakpoint corresponds to several locations
3266 in your program. Examples of this situation are:
3270 For a C@t{++} constructor, the @value{NGCC} compiler generates several
3271 instances of the function body, used in different cases.
3274 For a C@t{++} template function, a given line in the function can
3275 correspond to any number of instantiations.
3278 For an inlined function, a given source line can correspond to
3279 several places where that function is inlined.
3282 In all those cases, @value{GDBN} will insert a breakpoint at all
3283 the relevant locations@footnote{
3284 As of this writing, multiple-location breakpoints work only if there's
3285 line number information for all the locations. This means that they
3286 will generally not work in system libraries, unless you have debug
3287 info with line numbers for them.}.
3289 A breakpoint with multiple locations is displayed in the breakpoint
3290 table using several rows---one header row, followed by one row for
3291 each breakpoint location. The header row has @samp{<MULTIPLE>} in the
3292 address column. The rows for individual locations contain the actual
3293 addresses for locations, and show the functions to which those
3294 locations belong. The number column for a location is of the form
3295 @var{breakpoint-number}.@var{location-number}.
3300 Num Type Disp Enb Address What
3301 1 breakpoint keep y <MULTIPLE>
3303 breakpoint already hit 1 time
3304 1.1 y 0x080486a2 in void foo<int>() at t.cc:8
3305 1.2 y 0x080486ca in void foo<double>() at t.cc:8
3308 Each location can be individually enabled or disabled by passing
3309 @var{breakpoint-number}.@var{location-number} as argument to the
3310 @code{enable} and @code{disable} commands. Note that you cannot
3311 delete the individual locations from the list, you can only delete the
3312 entire list of locations that belong to their parent breakpoint (with
3313 the @kbd{delete @var{num}} command, where @var{num} is the number of
3314 the parent breakpoint, 1 in the above example). Disabling or enabling
3315 the parent breakpoint (@pxref{Disabling}) affects all of the locations
3316 that belong to that breakpoint.
3318 @cindex pending breakpoints
3319 It's quite common to have a breakpoint inside a shared library.
3320 Shared libraries can be loaded and unloaded explicitly,
3321 and possibly repeatedly, as the program is executed. To support
3322 this use case, @value{GDBN} updates breakpoint locations whenever
3323 any shared library is loaded or unloaded. Typically, you would
3324 set a breakpoint in a shared library at the beginning of your
3325 debugging session, when the library is not loaded, and when the
3326 symbols from the library are not available. When you try to set
3327 breakpoint, @value{GDBN} will ask you if you want to set
3328 a so called @dfn{pending breakpoint}---breakpoint whose address
3329 is not yet resolved.
3331 After the program is run, whenever a new shared library is loaded,
3332 @value{GDBN} reevaluates all the breakpoints. When a newly loaded
3333 shared library contains the symbol or line referred to by some
3334 pending breakpoint, that breakpoint is resolved and becomes an
3335 ordinary breakpoint. When a library is unloaded, all breakpoints
3336 that refer to its symbols or source lines become pending again.
3338 This logic works for breakpoints with multiple locations, too. For
3339 example, if you have a breakpoint in a C@t{++} template function, and
3340 a newly loaded shared library has an instantiation of that template,
3341 a new location is added to the list of locations for the breakpoint.
3343 Except for having unresolved address, pending breakpoints do not
3344 differ from regular breakpoints. You can set conditions or commands,
3345 enable and disable them and perform other breakpoint operations.
3347 @value{GDBN} provides some additional commands for controlling what
3348 happens when the @samp{break} command cannot resolve breakpoint
3349 address specification to an address:
3351 @kindex set breakpoint pending
3352 @kindex show breakpoint pending
3354 @item set breakpoint pending auto
3355 This is the default behavior. When @value{GDBN} cannot find the breakpoint
3356 location, it queries you whether a pending breakpoint should be created.
3358 @item set breakpoint pending on
3359 This indicates that an unrecognized breakpoint location should automatically
3360 result in a pending breakpoint being created.
3362 @item set breakpoint pending off
3363 This indicates that pending breakpoints are not to be created. Any
3364 unrecognized breakpoint location results in an error. This setting does
3365 not affect any pending breakpoints previously created.
3367 @item show breakpoint pending
3368 Show the current behavior setting for creating pending breakpoints.
3371 The settings above only affect the @code{break} command and its
3372 variants. Once breakpoint is set, it will be automatically updated
3373 as shared libraries are loaded and unloaded.
3375 @cindex automatic hardware breakpoints
3376 For some targets, @value{GDBN} can automatically decide if hardware or
3377 software breakpoints should be used, depending on whether the
3378 breakpoint address is read-only or read-write. This applies to
3379 breakpoints set with the @code{break} command as well as to internal
3380 breakpoints set by commands like @code{next} and @code{finish}. For
3381 breakpoints set with @code{hbreak}, @value{GDBN} will always use hardware
3384 You can control this automatic behaviour with the following commands::
3386 @kindex set breakpoint auto-hw
3387 @kindex show breakpoint auto-hw
3389 @item set breakpoint auto-hw on
3390 This is the default behavior. When @value{GDBN} sets a breakpoint, it
3391 will try to use the target memory map to decide if software or hardware
3392 breakpoint must be used.
3394 @item set breakpoint auto-hw off
3395 This indicates @value{GDBN} should not automatically select breakpoint
3396 type. If the target provides a memory map, @value{GDBN} will warn when
3397 trying to set software breakpoint at a read-only address.
3400 @value{GDBN} normally implements breakpoints by replacing the program code
3401 at the breakpoint address with a special instruction, which, when
3402 executed, given control to the debugger. By default, the program
3403 code is so modified only when the program is resumed. As soon as
3404 the program stops, @value{GDBN} restores the original instructions. This
3405 behaviour guards against leaving breakpoints inserted in the
3406 target should gdb abrubptly disconnect. However, with slow remote
3407 targets, inserting and removing breakpoint can reduce the performance.
3408 This behavior can be controlled with the following commands::
3410 @kindex set breakpoint always-inserted
3411 @kindex show breakpoint always-inserted
3413 @item set breakpoint always-inserted off
3414 All breakpoints, including newly added by the user, are inserted in
3415 the target only when the target is resumed. All breakpoints are
3416 removed from the target when it stops.
3418 @item set breakpoint always-inserted on
3419 Causes all breakpoints to be inserted in the target at all times. If
3420 the user adds a new breakpoint, or changes an existing breakpoint, the
3421 breakpoints in the target are updated immediately. A breakpoint is
3422 removed from the target only when breakpoint itself is removed.
3424 @cindex non-stop mode, and @code{breakpoint always-inserted}
3425 @item set breakpoint always-inserted auto
3426 This is the default mode. If @value{GDBN} is controlling the inferior
3427 in non-stop mode (@pxref{Non-Stop Mode}), gdb behaves as if
3428 @code{breakpoint always-inserted} mode is on. If @value{GDBN} is
3429 controlling the inferior in all-stop mode, @value{GDBN} behaves as if
3430 @code{breakpoint always-inserted} mode is off.
3433 @cindex negative breakpoint numbers
3434 @cindex internal @value{GDBN} breakpoints
3435 @value{GDBN} itself sometimes sets breakpoints in your program for
3436 special purposes, such as proper handling of @code{longjmp} (in C
3437 programs). These internal breakpoints are assigned negative numbers,
3438 starting with @code{-1}; @samp{info breakpoints} does not display them.
3439 You can see these breakpoints with the @value{GDBN} maintenance command
3440 @samp{maint info breakpoints} (@pxref{maint info breakpoints}).
3443 @node Set Watchpoints
3444 @subsection Setting Watchpoints
3446 @cindex setting watchpoints
3447 You can use a watchpoint to stop execution whenever the value of an
3448 expression changes, without having to predict a particular place where
3449 this may happen. (This is sometimes called a @dfn{data breakpoint}.)
3450 The expression may be as simple as the value of a single variable, or
3451 as complex as many variables combined by operators. Examples include:
3455 A reference to the value of a single variable.
3458 An address cast to an appropriate data type. For example,
3459 @samp{*(int *)0x12345678} will watch a 4-byte region at the specified
3460 address (assuming an @code{int} occupies 4 bytes).
3463 An arbitrarily complex expression, such as @samp{a*b + c/d}. The
3464 expression can use any operators valid in the program's native
3465 language (@pxref{Languages}).
3468 You can set a watchpoint on an expression even if the expression can
3469 not be evaluated yet. For instance, you can set a watchpoint on
3470 @samp{*global_ptr} before @samp{global_ptr} is initialized.
3471 @value{GDBN} will stop when your program sets @samp{global_ptr} and
3472 the expression produces a valid value. If the expression becomes
3473 valid in some other way than changing a variable (e.g.@: if the memory
3474 pointed to by @samp{*global_ptr} becomes readable as the result of a
3475 @code{malloc} call), @value{GDBN} may not stop until the next time
3476 the expression changes.
3478 @cindex software watchpoints
3479 @cindex hardware watchpoints
3480 Depending on your system, watchpoints may be implemented in software or
3481 hardware. @value{GDBN} does software watchpointing by single-stepping your
3482 program and testing the variable's value each time, which is hundreds of
3483 times slower than normal execution. (But this may still be worth it, to
3484 catch errors where you have no clue what part of your program is the
3487 On some systems, such as HP-UX, PowerPC, @sc{gnu}/Linux and most other
3488 x86-based targets, @value{GDBN} includes support for hardware
3489 watchpoints, which do not slow down the running of your program.
3493 @item watch @var{expr} @r{[}thread @var{threadnum}@r{]}
3494 Set a watchpoint for an expression. @value{GDBN} will break when the
3495 expression @var{expr} is written into by the program and its value
3496 changes. The simplest (and the most popular) use of this command is
3497 to watch the value of a single variable:
3500 (@value{GDBP}) watch foo
3503 If the command includes a @code{@r{[}thread @var{threadnum}@r{]}}
3504 clause, @value{GDBN} breaks only when the thread identified by
3505 @var{threadnum} changes the value of @var{expr}. If any other threads
3506 change the value of @var{expr}, @value{GDBN} will not break. Note
3507 that watchpoints restricted to a single thread in this way only work
3508 with Hardware Watchpoints.
3511 @item rwatch @var{expr} @r{[}thread @var{threadnum}@r{]}
3512 Set a watchpoint that will break when the value of @var{expr} is read
3516 @item awatch @var{expr} @r{[}thread @var{threadnum}@r{]}
3517 Set a watchpoint that will break when @var{expr} is either read from
3518 or written into by the program.
3520 @kindex info watchpoints @r{[}@var{n}@r{]}
3521 @item info watchpoints
3522 This command prints a list of watchpoints, breakpoints, and catchpoints;
3523 it is the same as @code{info break} (@pxref{Set Breaks}).
3526 @value{GDBN} sets a @dfn{hardware watchpoint} if possible. Hardware
3527 watchpoints execute very quickly, and the debugger reports a change in
3528 value at the exact instruction where the change occurs. If @value{GDBN}
3529 cannot set a hardware watchpoint, it sets a software watchpoint, which
3530 executes more slowly and reports the change in value at the next
3531 @emph{statement}, not the instruction, after the change occurs.
3533 @cindex use only software watchpoints
3534 You can force @value{GDBN} to use only software watchpoints with the
3535 @kbd{set can-use-hw-watchpoints 0} command. With this variable set to
3536 zero, @value{GDBN} will never try to use hardware watchpoints, even if
3537 the underlying system supports them. (Note that hardware-assisted
3538 watchpoints that were set @emph{before} setting
3539 @code{can-use-hw-watchpoints} to zero will still use the hardware
3540 mechanism of watching expression values.)
3543 @item set can-use-hw-watchpoints
3544 @kindex set can-use-hw-watchpoints
3545 Set whether or not to use hardware watchpoints.
3547 @item show can-use-hw-watchpoints
3548 @kindex show can-use-hw-watchpoints
3549 Show the current mode of using hardware watchpoints.
3552 For remote targets, you can restrict the number of hardware
3553 watchpoints @value{GDBN} will use, see @ref{set remote
3554 hardware-breakpoint-limit}.
3556 When you issue the @code{watch} command, @value{GDBN} reports
3559 Hardware watchpoint @var{num}: @var{expr}
3563 if it was able to set a hardware watchpoint.
3565 Currently, the @code{awatch} and @code{rwatch} commands can only set
3566 hardware watchpoints, because accesses to data that don't change the
3567 value of the watched expression cannot be detected without examining
3568 every instruction as it is being executed, and @value{GDBN} does not do
3569 that currently. If @value{GDBN} finds that it is unable to set a
3570 hardware breakpoint with the @code{awatch} or @code{rwatch} command, it
3571 will print a message like this:
3574 Expression cannot be implemented with read/access watchpoint.
3577 Sometimes, @value{GDBN} cannot set a hardware watchpoint because the
3578 data type of the watched expression is wider than what a hardware
3579 watchpoint on the target machine can handle. For example, some systems
3580 can only watch regions that are up to 4 bytes wide; on such systems you
3581 cannot set hardware watchpoints for an expression that yields a
3582 double-precision floating-point number (which is typically 8 bytes
3583 wide). As a work-around, it might be possible to break the large region
3584 into a series of smaller ones and watch them with separate watchpoints.
3586 If you set too many hardware watchpoints, @value{GDBN} might be unable
3587 to insert all of them when you resume the execution of your program.
3588 Since the precise number of active watchpoints is unknown until such
3589 time as the program is about to be resumed, @value{GDBN} might not be
3590 able to warn you about this when you set the watchpoints, and the
3591 warning will be printed only when the program is resumed:
3594 Hardware watchpoint @var{num}: Could not insert watchpoint
3598 If this happens, delete or disable some of the watchpoints.
3600 Watching complex expressions that reference many variables can also
3601 exhaust the resources available for hardware-assisted watchpoints.
3602 That's because @value{GDBN} needs to watch every variable in the
3603 expression with separately allocated resources.
3605 If you call a function interactively using @code{print} or @code{call},
3606 any watchpoints you have set will be inactive until @value{GDBN} reaches another
3607 kind of breakpoint or the call completes.
3609 @value{GDBN} automatically deletes watchpoints that watch local
3610 (automatic) variables, or expressions that involve such variables, when
3611 they go out of scope, that is, when the execution leaves the block in
3612 which these variables were defined. In particular, when the program
3613 being debugged terminates, @emph{all} local variables go out of scope,
3614 and so only watchpoints that watch global variables remain set. If you
3615 rerun the program, you will need to set all such watchpoints again. One
3616 way of doing that would be to set a code breakpoint at the entry to the
3617 @code{main} function and when it breaks, set all the watchpoints.
3619 @cindex watchpoints and threads
3620 @cindex threads and watchpoints
3621 In multi-threaded programs, watchpoints will detect changes to the
3622 watched expression from every thread.
3625 @emph{Warning:} In multi-threaded programs, software watchpoints
3626 have only limited usefulness. If @value{GDBN} creates a software
3627 watchpoint, it can only watch the value of an expression @emph{in a
3628 single thread}. If you are confident that the expression can only
3629 change due to the current thread's activity (and if you are also
3630 confident that no other thread can become current), then you can use
3631 software watchpoints as usual. However, @value{GDBN} may not notice
3632 when a non-current thread's activity changes the expression. (Hardware
3633 watchpoints, in contrast, watch an expression in all threads.)
3636 @xref{set remote hardware-watchpoint-limit}.
3638 @node Set Catchpoints
3639 @subsection Setting Catchpoints
3640 @cindex catchpoints, setting
3641 @cindex exception handlers
3642 @cindex event handling
3644 You can use @dfn{catchpoints} to cause the debugger to stop for certain
3645 kinds of program events, such as C@t{++} exceptions or the loading of a
3646 shared library. Use the @code{catch} command to set a catchpoint.
3650 @item catch @var{event}
3651 Stop when @var{event} occurs. @var{event} can be any of the following:
3654 @cindex stop on C@t{++} exceptions
3655 The throwing of a C@t{++} exception.
3658 The catching of a C@t{++} exception.
3661 @cindex Ada exception catching
3662 @cindex catch Ada exceptions
3663 An Ada exception being raised. If an exception name is specified
3664 at the end of the command (eg @code{catch exception Program_Error}),
3665 the debugger will stop only when this specific exception is raised.
3666 Otherwise, the debugger stops execution when any Ada exception is raised.
3668 When inserting an exception catchpoint on a user-defined exception whose
3669 name is identical to one of the exceptions defined by the language, the
3670 fully qualified name must be used as the exception name. Otherwise,
3671 @value{GDBN} will assume that it should stop on the pre-defined exception
3672 rather than the user-defined one. For instance, assuming an exception
3673 called @code{Constraint_Error} is defined in package @code{Pck}, then
3674 the command to use to catch such exceptions is @kbd{catch exception
3675 Pck.Constraint_Error}.
3677 @item exception unhandled
3678 An exception that was raised but is not handled by the program.
3681 A failed Ada assertion.
3684 @cindex break on fork/exec
3685 A call to @code{exec}. This is currently only available for HP-UX
3689 @itemx syscall @r{[}@var{name} @r{|} @var{number}@r{]} @r{...}
3690 @cindex break on a system call.
3691 A call to or return from a system call, a.k.a.@: @dfn{syscall}. A
3692 syscall is a mechanism for application programs to request a service
3693 from the operating system (OS) or one of the OS system services.
3694 @value{GDBN} can catch some or all of the syscalls issued by the
3695 debuggee, and show the related information for each syscall. If no
3696 argument is specified, calls to and returns from all system calls
3699 @var{name} can be any system call name that is valid for the
3700 underlying OS. Just what syscalls are valid depends on the OS. On
3701 GNU and Unix systems, you can find the full list of valid syscall
3702 names on @file{/usr/include/asm/unistd.h}.
3704 @c For MS-Windows, the syscall names and the corresponding numbers
3705 @c can be found, e.g., on this URL:
3706 @c http://www.metasploit.com/users/opcode/syscalls.html
3707 @c but we don't support Windows syscalls yet.
3709 Normally, @value{GDBN} knows in advance which syscalls are valid for
3710 each OS, so you can use the @value{GDBN} command-line completion
3711 facilities (@pxref{Completion,, command completion}) to list the
3714 You may also specify the system call numerically. A syscall's
3715 number is the value passed to the OS's syscall dispatcher to
3716 identify the requested service. When you specify the syscall by its
3717 name, @value{GDBN} uses its database of syscalls to convert the name
3718 into the corresponding numeric code, but using the number directly
3719 may be useful if @value{GDBN}'s database does not have the complete
3720 list of syscalls on your system (e.g., because @value{GDBN} lags
3721 behind the OS upgrades).
3723 The example below illustrates how this command works if you don't provide
3727 (@value{GDBP}) catch syscall
3728 Catchpoint 1 (syscall)
3730 Starting program: /tmp/catch-syscall
3732 Catchpoint 1 (call to syscall 'close'), \
3733 0xffffe424 in __kernel_vsyscall ()
3737 Catchpoint 1 (returned from syscall 'close'), \
3738 0xffffe424 in __kernel_vsyscall ()
3742 Here is an example of catching a system call by name:
3745 (@value{GDBP}) catch syscall chroot
3746 Catchpoint 1 (syscall 'chroot' [61])
3748 Starting program: /tmp/catch-syscall
3750 Catchpoint 1 (call to syscall 'chroot'), \
3751 0xffffe424 in __kernel_vsyscall ()
3755 Catchpoint 1 (returned from syscall 'chroot'), \
3756 0xffffe424 in __kernel_vsyscall ()
3760 An example of specifying a system call numerically. In the case
3761 below, the syscall number has a corresponding entry in the XML
3762 file, so @value{GDBN} finds its name and prints it:
3765 (@value{GDBP}) catch syscall 252
3766 Catchpoint 1 (syscall(s) 'exit_group')
3768 Starting program: /tmp/catch-syscall
3770 Catchpoint 1 (call to syscall 'exit_group'), \
3771 0xffffe424 in __kernel_vsyscall ()
3775 Program exited normally.
3779 However, there can be situations when there is no corresponding name
3780 in XML file for that syscall number. In this case, @value{GDBN} prints
3781 a warning message saying that it was not able to find the syscall name,
3782 but the catchpoint will be set anyway. See the example below:
3785 (@value{GDBP}) catch syscall 764
3786 warning: The number '764' does not represent a known syscall.
3787 Catchpoint 2 (syscall 764)
3791 If you configure @value{GDBN} using the @samp{--without-expat} option,
3792 it will not be able to display syscall names. Also, if your
3793 architecture does not have an XML file describing its system calls,
3794 you will not be able to see the syscall names. It is important to
3795 notice that these two features are used for accessing the syscall
3796 name database. In either case, you will see a warning like this:
3799 (@value{GDBP}) catch syscall
3800 warning: Could not open "syscalls/i386-linux.xml"
3801 warning: Could not load the syscall XML file 'syscalls/i386-linux.xml'.
3802 GDB will not be able to display syscall names.
3803 Catchpoint 1 (syscall)
3807 Of course, the file name will change depending on your architecture and system.
3809 Still using the example above, you can also try to catch a syscall by its
3810 number. In this case, you would see something like:
3813 (@value{GDBP}) catch syscall 252
3814 Catchpoint 1 (syscall(s) 252)
3817 Again, in this case @value{GDBN} would not be able to display syscall's names.
3820 A call to @code{fork}. This is currently only available for HP-UX
3824 A call to @code{vfork}. This is currently only available for HP-UX
3829 @item tcatch @var{event}
3830 Set a catchpoint that is enabled only for one stop. The catchpoint is
3831 automatically deleted after the first time the event is caught.
3835 Use the @code{info break} command to list the current catchpoints.
3837 There are currently some limitations to C@t{++} exception handling
3838 (@code{catch throw} and @code{catch catch}) in @value{GDBN}:
3842 If you call a function interactively, @value{GDBN} normally returns
3843 control to you when the function has finished executing. If the call
3844 raises an exception, however, the call may bypass the mechanism that
3845 returns control to you and cause your program either to abort or to
3846 simply continue running until it hits a breakpoint, catches a signal
3847 that @value{GDBN} is listening for, or exits. This is the case even if
3848 you set a catchpoint for the exception; catchpoints on exceptions are
3849 disabled within interactive calls.
3852 You cannot raise an exception interactively.
3855 You cannot install an exception handler interactively.
3858 @cindex raise exceptions
3859 Sometimes @code{catch} is not the best way to debug exception handling:
3860 if you need to know exactly where an exception is raised, it is better to
3861 stop @emph{before} the exception handler is called, since that way you
3862 can see the stack before any unwinding takes place. If you set a
3863 breakpoint in an exception handler instead, it may not be easy to find
3864 out where the exception was raised.
3866 To stop just before an exception handler is called, you need some
3867 knowledge of the implementation. In the case of @sc{gnu} C@t{++}, exceptions are
3868 raised by calling a library function named @code{__raise_exception}
3869 which has the following ANSI C interface:
3872 /* @var{addr} is where the exception identifier is stored.
3873 @var{id} is the exception identifier. */
3874 void __raise_exception (void **addr, void *id);
3878 To make the debugger catch all exceptions before any stack
3879 unwinding takes place, set a breakpoint on @code{__raise_exception}
3880 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Exceptions}).
3882 With a conditional breakpoint (@pxref{Conditions, ,Break Conditions})
3883 that depends on the value of @var{id}, you can stop your program when
3884 a specific exception is raised. You can use multiple conditional
3885 breakpoints to stop your program when any of a number of exceptions are
3890 @subsection Deleting Breakpoints
3892 @cindex clearing breakpoints, watchpoints, catchpoints
3893 @cindex deleting breakpoints, watchpoints, catchpoints
3894 It is often necessary to eliminate a breakpoint, watchpoint, or
3895 catchpoint once it has done its job and you no longer want your program
3896 to stop there. This is called @dfn{deleting} the breakpoint. A
3897 breakpoint that has been deleted no longer exists; it is forgotten.
3899 With the @code{clear} command you can delete breakpoints according to
3900 where they are in your program. With the @code{delete} command you can
3901 delete individual breakpoints, watchpoints, or catchpoints by specifying
3902 their breakpoint numbers.
3904 It is not necessary to delete a breakpoint to proceed past it. @value{GDBN}
3905 automatically ignores breakpoints on the first instruction to be executed
3906 when you continue execution without changing the execution address.
3911 Delete any breakpoints at the next instruction to be executed in the
3912 selected stack frame (@pxref{Selection, ,Selecting a Frame}). When
3913 the innermost frame is selected, this is a good way to delete a
3914 breakpoint where your program just stopped.
3916 @item clear @var{location}
3917 Delete any breakpoints set at the specified @var{location}.
3918 @xref{Specify Location}, for the various forms of @var{location}; the
3919 most useful ones are listed below:
3922 @item clear @var{function}
3923 @itemx clear @var{filename}:@var{function}
3924 Delete any breakpoints set at entry to the named @var{function}.
3926 @item clear @var{linenum}
3927 @itemx clear @var{filename}:@var{linenum}
3928 Delete any breakpoints set at or within the code of the specified
3929 @var{linenum} of the specified @var{filename}.
3932 @cindex delete breakpoints
3934 @kindex d @r{(@code{delete})}
3935 @item delete @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
3936 Delete the breakpoints, watchpoints, or catchpoints of the breakpoint
3937 ranges specified as arguments. If no argument is specified, delete all
3938 breakpoints (@value{GDBN} asks confirmation, unless you have @code{set
3939 confirm off}). You can abbreviate this command as @code{d}.
3943 @subsection Disabling Breakpoints
3945 @cindex enable/disable a breakpoint
3946 Rather than deleting a breakpoint, watchpoint, or catchpoint, you might
3947 prefer to @dfn{disable} it. This makes the breakpoint inoperative as if
3948 it had been deleted, but remembers the information on the breakpoint so
3949 that you can @dfn{enable} it again later.
3951 You disable and enable breakpoints, watchpoints, and catchpoints with
3952 the @code{enable} and @code{disable} commands, optionally specifying one
3953 or more breakpoint numbers as arguments. Use @code{info break} or
3954 @code{info watch} to print a list of breakpoints, watchpoints, and
3955 catchpoints if you do not know which numbers to use.
3957 Disabling and enabling a breakpoint that has multiple locations
3958 affects all of its locations.
3960 A breakpoint, watchpoint, or catchpoint can have any of four different
3961 states of enablement:
3965 Enabled. The breakpoint stops your program. A breakpoint set
3966 with the @code{break} command starts out in this state.
3968 Disabled. The breakpoint has no effect on your program.
3970 Enabled once. The breakpoint stops your program, but then becomes
3973 Enabled for deletion. The breakpoint stops your program, but
3974 immediately after it does so it is deleted permanently. A breakpoint
3975 set with the @code{tbreak} command starts out in this state.
3978 You can use the following commands to enable or disable breakpoints,
3979 watchpoints, and catchpoints:
3983 @kindex dis @r{(@code{disable})}
3984 @item disable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
3985 Disable the specified breakpoints---or all breakpoints, if none are
3986 listed. A disabled breakpoint has no effect but is not forgotten. All
3987 options such as ignore-counts, conditions and commands are remembered in
3988 case the breakpoint is enabled again later. You may abbreviate
3989 @code{disable} as @code{dis}.
3992 @item enable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
3993 Enable the specified breakpoints (or all defined breakpoints). They
3994 become effective once again in stopping your program.
3996 @item enable @r{[}breakpoints@r{]} once @var{range}@dots{}
3997 Enable the specified breakpoints temporarily. @value{GDBN} disables any
3998 of these breakpoints immediately after stopping your program.
4000 @item enable @r{[}breakpoints@r{]} delete @var{range}@dots{}
4001 Enable the specified breakpoints to work once, then die. @value{GDBN}
4002 deletes any of these breakpoints as soon as your program stops there.
4003 Breakpoints set by the @code{tbreak} command start out in this state.
4006 @c FIXME: I think the following ``Except for [...] @code{tbreak}'' is
4007 @c confusing: tbreak is also initially enabled.
4008 Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks,
4009 ,Setting Breakpoints}), breakpoints that you set are initially enabled;
4010 subsequently, they become disabled or enabled only when you use one of
4011 the commands above. (The command @code{until} can set and delete a
4012 breakpoint of its own, but it does not change the state of your other
4013 breakpoints; see @ref{Continuing and Stepping, ,Continuing and
4017 @subsection Break Conditions
4018 @cindex conditional breakpoints
4019 @cindex breakpoint conditions
4021 @c FIXME what is scope of break condition expr? Context where wanted?
4022 @c in particular for a watchpoint?
4023 The simplest sort of breakpoint breaks every time your program reaches a
4024 specified place. You can also specify a @dfn{condition} for a
4025 breakpoint. A condition is just a Boolean expression in your
4026 programming language (@pxref{Expressions, ,Expressions}). A breakpoint with
4027 a condition evaluates the expression each time your program reaches it,
4028 and your program stops only if the condition is @emph{true}.
4030 This is the converse of using assertions for program validation; in that
4031 situation, you want to stop when the assertion is violated---that is,
4032 when the condition is false. In C, if you want to test an assertion expressed
4033 by the condition @var{assert}, you should set the condition
4034 @samp{! @var{assert}} on the appropriate breakpoint.
4036 Conditions are also accepted for watchpoints; you may not need them,
4037 since a watchpoint is inspecting the value of an expression anyhow---but
4038 it might be simpler, say, to just set a watchpoint on a variable name,
4039 and specify a condition that tests whether the new value is an interesting
4042 Break conditions can have side effects, and may even call functions in
4043 your program. This can be useful, for example, to activate functions
4044 that log program progress, or to use your own print functions to
4045 format special data structures. The effects are completely predictable
4046 unless there is another enabled breakpoint at the same address. (In
4047 that case, @value{GDBN} might see the other breakpoint first and stop your
4048 program without checking the condition of this one.) Note that
4049 breakpoint commands are usually more convenient and flexible than break
4051 purpose of performing side effects when a breakpoint is reached
4052 (@pxref{Break Commands, ,Breakpoint Command Lists}).
4054 Break conditions can be specified when a breakpoint is set, by using
4055 @samp{if} in the arguments to the @code{break} command. @xref{Set
4056 Breaks, ,Setting Breakpoints}. They can also be changed at any time
4057 with the @code{condition} command.
4059 You can also use the @code{if} keyword with the @code{watch} command.
4060 The @code{catch} command does not recognize the @code{if} keyword;
4061 @code{condition} is the only way to impose a further condition on a
4066 @item condition @var{bnum} @var{expression}
4067 Specify @var{expression} as the break condition for breakpoint,
4068 watchpoint, or catchpoint number @var{bnum}. After you set a condition,
4069 breakpoint @var{bnum} stops your program only if the value of
4070 @var{expression} is true (nonzero, in C). When you use
4071 @code{condition}, @value{GDBN} checks @var{expression} immediately for
4072 syntactic correctness, and to determine whether symbols in it have
4073 referents in the context of your breakpoint. If @var{expression} uses
4074 symbols not referenced in the context of the breakpoint, @value{GDBN}
4075 prints an error message:
4078 No symbol "foo" in current context.
4083 not actually evaluate @var{expression} at the time the @code{condition}
4084 command (or a command that sets a breakpoint with a condition, like
4085 @code{break if @dots{}}) is given, however. @xref{Expressions, ,Expressions}.
4087 @item condition @var{bnum}
4088 Remove the condition from breakpoint number @var{bnum}. It becomes
4089 an ordinary unconditional breakpoint.
4092 @cindex ignore count (of breakpoint)
4093 A special case of a breakpoint condition is to stop only when the
4094 breakpoint has been reached a certain number of times. This is so
4095 useful that there is a special way to do it, using the @dfn{ignore
4096 count} of the breakpoint. Every breakpoint has an ignore count, which
4097 is an integer. Most of the time, the ignore count is zero, and
4098 therefore has no effect. But if your program reaches a breakpoint whose
4099 ignore count is positive, then instead of stopping, it just decrements
4100 the ignore count by one and continues. As a result, if the ignore count
4101 value is @var{n}, the breakpoint does not stop the next @var{n} times
4102 your program reaches it.
4106 @item ignore @var{bnum} @var{count}
4107 Set the ignore count of breakpoint number @var{bnum} to @var{count}.
4108 The next @var{count} times the breakpoint is reached, your program's
4109 execution does not stop; other than to decrement the ignore count, @value{GDBN}
4112 To make the breakpoint stop the next time it is reached, specify
4115 When you use @code{continue} to resume execution of your program from a
4116 breakpoint, you can specify an ignore count directly as an argument to
4117 @code{continue}, rather than using @code{ignore}. @xref{Continuing and
4118 Stepping,,Continuing and Stepping}.
4120 If a breakpoint has a positive ignore count and a condition, the
4121 condition is not checked. Once the ignore count reaches zero,
4122 @value{GDBN} resumes checking the condition.
4124 You could achieve the effect of the ignore count with a condition such
4125 as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that
4126 is decremented each time. @xref{Convenience Vars, ,Convenience
4130 Ignore counts apply to breakpoints, watchpoints, and catchpoints.
4133 @node Break Commands
4134 @subsection Breakpoint Command Lists
4136 @cindex breakpoint commands
4137 You can give any breakpoint (or watchpoint or catchpoint) a series of
4138 commands to execute when your program stops due to that breakpoint. For
4139 example, you might want to print the values of certain expressions, or
4140 enable other breakpoints.
4144 @kindex end@r{ (breakpoint commands)}
4145 @item commands @r{[}@var{bnum}@r{]}
4146 @itemx @dots{} @var{command-list} @dots{}
4148 Specify a list of commands for breakpoint number @var{bnum}. The commands
4149 themselves appear on the following lines. Type a line containing just
4150 @code{end} to terminate the commands.
4152 To remove all commands from a breakpoint, type @code{commands} and
4153 follow it immediately with @code{end}; that is, give no commands.
4155 With no @var{bnum} argument, @code{commands} refers to the last
4156 breakpoint, watchpoint, or catchpoint set (not to the breakpoint most
4157 recently encountered).
4160 Pressing @key{RET} as a means of repeating the last @value{GDBN} command is
4161 disabled within a @var{command-list}.
4163 You can use breakpoint commands to start your program up again. Simply
4164 use the @code{continue} command, or @code{step}, or any other command
4165 that resumes execution.
4167 Any other commands in the command list, after a command that resumes
4168 execution, are ignored. This is because any time you resume execution
4169 (even with a simple @code{next} or @code{step}), you may encounter
4170 another breakpoint---which could have its own command list, leading to
4171 ambiguities about which list to execute.
4174 If the first command you specify in a command list is @code{silent}, the
4175 usual message about stopping at a breakpoint is not printed. This may
4176 be desirable for breakpoints that are to print a specific message and
4177 then continue. If none of the remaining commands print anything, you
4178 see no sign that the breakpoint was reached. @code{silent} is
4179 meaningful only at the beginning of a breakpoint command list.
4181 The commands @code{echo}, @code{output}, and @code{printf} allow you to
4182 print precisely controlled output, and are often useful in silent
4183 breakpoints. @xref{Output, ,Commands for Controlled Output}.
4185 For example, here is how you could use breakpoint commands to print the
4186 value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
4192 printf "x is %d\n",x
4197 One application for breakpoint commands is to compensate for one bug so
4198 you can test for another. Put a breakpoint just after the erroneous line
4199 of code, give it a condition to detect the case in which something
4200 erroneous has been done, and give it commands to assign correct values
4201 to any variables that need them. End with the @code{continue} command
4202 so that your program does not stop, and start with the @code{silent}
4203 command so that no output is produced. Here is an example:
4214 @c @ifclear BARETARGET
4215 @node Error in Breakpoints
4216 @subsection ``Cannot insert breakpoints''
4218 If you request too many active hardware-assisted breakpoints and
4219 watchpoints, you will see this error message:
4221 @c FIXME: the precise wording of this message may change; the relevant
4222 @c source change is not committed yet (Sep 3, 1999).
4224 Stopped; cannot insert breakpoints.
4225 You may have requested too many hardware breakpoints and watchpoints.
4229 This message is printed when you attempt to resume the program, since
4230 only then @value{GDBN} knows exactly how many hardware breakpoints and
4231 watchpoints it needs to insert.
4233 When this message is printed, you need to disable or remove some of the
4234 hardware-assisted breakpoints and watchpoints, and then continue.
4236 @node Breakpoint-related Warnings
4237 @subsection ``Breakpoint address adjusted...''
4238 @cindex breakpoint address adjusted
4240 Some processor architectures place constraints on the addresses at
4241 which breakpoints may be placed. For architectures thus constrained,
4242 @value{GDBN} will attempt to adjust the breakpoint's address to comply
4243 with the constraints dictated by the architecture.
4245 One example of such an architecture is the Fujitsu FR-V. The FR-V is
4246 a VLIW architecture in which a number of RISC-like instructions may be
4247 bundled together for parallel execution. The FR-V architecture
4248 constrains the location of a breakpoint instruction within such a
4249 bundle to the instruction with the lowest address. @value{GDBN}
4250 honors this constraint by adjusting a breakpoint's address to the
4251 first in the bundle.
4253 It is not uncommon for optimized code to have bundles which contain
4254 instructions from different source statements, thus it may happen that
4255 a breakpoint's address will be adjusted from one source statement to
4256 another. Since this adjustment may significantly alter @value{GDBN}'s
4257 breakpoint related behavior from what the user expects, a warning is
4258 printed when the breakpoint is first set and also when the breakpoint
4261 A warning like the one below is printed when setting a breakpoint
4262 that's been subject to address adjustment:
4265 warning: Breakpoint address adjusted from 0x00010414 to 0x00010410.
4268 Such warnings are printed both for user settable and @value{GDBN}'s
4269 internal breakpoints. If you see one of these warnings, you should
4270 verify that a breakpoint set at the adjusted address will have the
4271 desired affect. If not, the breakpoint in question may be removed and
4272 other breakpoints may be set which will have the desired behavior.
4273 E.g., it may be sufficient to place the breakpoint at a later
4274 instruction. A conditional breakpoint may also be useful in some
4275 cases to prevent the breakpoint from triggering too often.
4277 @value{GDBN} will also issue a warning when stopping at one of these
4278 adjusted breakpoints:
4281 warning: Breakpoint 1 address previously adjusted from 0x00010414
4285 When this warning is encountered, it may be too late to take remedial
4286 action except in cases where the breakpoint is hit earlier or more
4287 frequently than expected.
4289 @node Continuing and Stepping
4290 @section Continuing and Stepping
4294 @cindex resuming execution
4295 @dfn{Continuing} means resuming program execution until your program
4296 completes normally. In contrast, @dfn{stepping} means executing just
4297 one more ``step'' of your program, where ``step'' may mean either one
4298 line of source code, or one machine instruction (depending on what
4299 particular command you use). Either when continuing or when stepping,
4300 your program may stop even sooner, due to a breakpoint or a signal. (If
4301 it stops due to a signal, you may want to use @code{handle}, or use
4302 @samp{signal 0} to resume execution. @xref{Signals, ,Signals}.)
4306 @kindex c @r{(@code{continue})}
4307 @kindex fg @r{(resume foreground execution)}
4308 @item continue @r{[}@var{ignore-count}@r{]}
4309 @itemx c @r{[}@var{ignore-count}@r{]}
4310 @itemx fg @r{[}@var{ignore-count}@r{]}
4311 Resume program execution, at the address where your program last stopped;
4312 any breakpoints set at that address are bypassed. The optional argument
4313 @var{ignore-count} allows you to specify a further number of times to
4314 ignore a breakpoint at this location; its effect is like that of
4315 @code{ignore} (@pxref{Conditions, ,Break Conditions}).
4317 The argument @var{ignore-count} is meaningful only when your program
4318 stopped due to a breakpoint. At other times, the argument to
4319 @code{continue} is ignored.
4321 The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the
4322 debugged program is deemed to be the foreground program) are provided
4323 purely for convenience, and have exactly the same behavior as
4327 To resume execution at a different place, you can use @code{return}
4328 (@pxref{Returning, ,Returning from a Function}) to go back to the
4329 calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
4330 Different Address}) to go to an arbitrary location in your program.
4332 A typical technique for using stepping is to set a breakpoint
4333 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Catchpoints}) at the
4334 beginning of the function or the section of your program where a problem
4335 is believed to lie, run your program until it stops at that breakpoint,
4336 and then step through the suspect area, examining the variables that are
4337 interesting, until you see the problem happen.
4341 @kindex s @r{(@code{step})}
4343 Continue running your program until control reaches a different source
4344 line, then stop it and return control to @value{GDBN}. This command is
4345 abbreviated @code{s}.
4348 @c "without debugging information" is imprecise; actually "without line
4349 @c numbers in the debugging information". (gcc -g1 has debugging info but
4350 @c not line numbers). But it seems complex to try to make that
4351 @c distinction here.
4352 @emph{Warning:} If you use the @code{step} command while control is
4353 within a function that was compiled without debugging information,
4354 execution proceeds until control reaches a function that does have
4355 debugging information. Likewise, it will not step into a function which
4356 is compiled without debugging information. To step through functions
4357 without debugging information, use the @code{stepi} command, described
4361 The @code{step} command only stops at the first instruction of a source
4362 line. This prevents the multiple stops that could otherwise occur in
4363 @code{switch} statements, @code{for} loops, etc. @code{step} continues
4364 to stop if a function that has debugging information is called within
4365 the line. In other words, @code{step} @emph{steps inside} any functions
4366 called within the line.
4368 Also, the @code{step} command only enters a function if there is line
4369 number information for the function. Otherwise it acts like the
4370 @code{next} command. This avoids problems when using @code{cc -gl}
4371 on MIPS machines. Previously, @code{step} entered subroutines if there
4372 was any debugging information about the routine.
4374 @item step @var{count}
4375 Continue running as in @code{step}, but do so @var{count} times. If a
4376 breakpoint is reached, or a signal not related to stepping occurs before
4377 @var{count} steps, stepping stops right away.
4380 @kindex n @r{(@code{next})}
4381 @item next @r{[}@var{count}@r{]}
4382 Continue to the next source line in the current (innermost) stack frame.
4383 This is similar to @code{step}, but function calls that appear within
4384 the line of code are executed without stopping. Execution stops when
4385 control reaches a different line of code at the original stack level
4386 that was executing when you gave the @code{next} command. This command
4387 is abbreviated @code{n}.
4389 An argument @var{count} is a repeat count, as for @code{step}.
4392 @c FIX ME!! Do we delete this, or is there a way it fits in with
4393 @c the following paragraph? --- Vctoria
4395 @c @code{next} within a function that lacks debugging information acts like
4396 @c @code{step}, but any function calls appearing within the code of the
4397 @c function are executed without stopping.
4399 The @code{next} command only stops at the first instruction of a
4400 source line. This prevents multiple stops that could otherwise occur in
4401 @code{switch} statements, @code{for} loops, etc.
4403 @kindex set step-mode
4405 @cindex functions without line info, and stepping
4406 @cindex stepping into functions with no line info
4407 @itemx set step-mode on
4408 The @code{set step-mode on} command causes the @code{step} command to
4409 stop at the first instruction of a function which contains no debug line
4410 information rather than stepping over it.
4412 This is useful in cases where you may be interested in inspecting the
4413 machine instructions of a function which has no symbolic info and do not
4414 want @value{GDBN} to automatically skip over this function.
4416 @item set step-mode off
4417 Causes the @code{step} command to step over any functions which contains no
4418 debug information. This is the default.
4420 @item show step-mode
4421 Show whether @value{GDBN} will stop in or step over functions without
4422 source line debug information.
4425 @kindex fin @r{(@code{finish})}
4427 Continue running until just after function in the selected stack frame
4428 returns. Print the returned value (if any). This command can be
4429 abbreviated as @code{fin}.
4431 Contrast this with the @code{return} command (@pxref{Returning,
4432 ,Returning from a Function}).
4435 @kindex u @r{(@code{until})}
4436 @cindex run until specified location
4439 Continue running until a source line past the current line, in the
4440 current stack frame, is reached. This command is used to avoid single
4441 stepping through a loop more than once. It is like the @code{next}
4442 command, except that when @code{until} encounters a jump, it
4443 automatically continues execution until the program counter is greater
4444 than the address of the jump.
4446 This means that when you reach the end of a loop after single stepping
4447 though it, @code{until} makes your program continue execution until it
4448 exits the loop. In contrast, a @code{next} command at the end of a loop
4449 simply steps back to the beginning of the loop, which forces you to step
4450 through the next iteration.
4452 @code{until} always stops your program if it attempts to exit the current
4455 @code{until} may produce somewhat counterintuitive results if the order
4456 of machine code does not match the order of the source lines. For
4457 example, in the following excerpt from a debugging session, the @code{f}
4458 (@code{frame}) command shows that execution is stopped at line
4459 @code{206}; yet when we use @code{until}, we get to line @code{195}:
4463 #0 main (argc=4, argv=0xf7fffae8) at m4.c:206
4465 (@value{GDBP}) until
4466 195 for ( ; argc > 0; NEXTARG) @{
4469 This happened because, for execution efficiency, the compiler had
4470 generated code for the loop closure test at the end, rather than the
4471 start, of the loop---even though the test in a C @code{for}-loop is
4472 written before the body of the loop. The @code{until} command appeared
4473 to step back to the beginning of the loop when it advanced to this
4474 expression; however, it has not really gone to an earlier
4475 statement---not in terms of the actual machine code.
4477 @code{until} with no argument works by means of single
4478 instruction stepping, and hence is slower than @code{until} with an
4481 @item until @var{location}
4482 @itemx u @var{location}
4483 Continue running your program until either the specified location is
4484 reached, or the current stack frame returns. @var{location} is any of
4485 the forms described in @ref{Specify Location}.
4486 This form of the command uses temporary breakpoints, and
4487 hence is quicker than @code{until} without an argument. The specified
4488 location is actually reached only if it is in the current frame. This
4489 implies that @code{until} can be used to skip over recursive function
4490 invocations. For instance in the code below, if the current location is
4491 line @code{96}, issuing @code{until 99} will execute the program up to
4492 line @code{99} in the same invocation of factorial, i.e., after the inner
4493 invocations have returned.
4496 94 int factorial (int value)
4498 96 if (value > 1) @{
4499 97 value *= factorial (value - 1);
4506 @kindex advance @var{location}
4507 @itemx advance @var{location}
4508 Continue running the program up to the given @var{location}. An argument is
4509 required, which should be of one of the forms described in
4510 @ref{Specify Location}.
4511 Execution will also stop upon exit from the current stack
4512 frame. This command is similar to @code{until}, but @code{advance} will
4513 not skip over recursive function calls, and the target location doesn't
4514 have to be in the same frame as the current one.
4518 @kindex si @r{(@code{stepi})}
4520 @itemx stepi @var{arg}
4522 Execute one machine instruction, then stop and return to the debugger.
4524 It is often useful to do @samp{display/i $pc} when stepping by machine
4525 instructions. This makes @value{GDBN} automatically display the next
4526 instruction to be executed, each time your program stops. @xref{Auto
4527 Display,, Automatic Display}.
4529 An argument is a repeat count, as in @code{step}.
4533 @kindex ni @r{(@code{nexti})}
4535 @itemx nexti @var{arg}
4537 Execute one machine instruction, but if it is a function call,
4538 proceed until the function returns.
4540 An argument is a repeat count, as in @code{next}.
4547 A signal is an asynchronous event that can happen in a program. The
4548 operating system defines the possible kinds of signals, and gives each
4549 kind a name and a number. For example, in Unix @code{SIGINT} is the
4550 signal a program gets when you type an interrupt character (often @kbd{Ctrl-c});
4551 @code{SIGSEGV} is the signal a program gets from referencing a place in
4552 memory far away from all the areas in use; @code{SIGALRM} occurs when
4553 the alarm clock timer goes off (which happens only if your program has
4554 requested an alarm).
4556 @cindex fatal signals
4557 Some signals, including @code{SIGALRM}, are a normal part of the
4558 functioning of your program. Others, such as @code{SIGSEGV}, indicate
4559 errors; these signals are @dfn{fatal} (they kill your program immediately) if the
4560 program has not specified in advance some other way to handle the signal.
4561 @code{SIGINT} does not indicate an error in your program, but it is normally
4562 fatal so it can carry out the purpose of the interrupt: to kill the program.
4564 @value{GDBN} has the ability to detect any occurrence of a signal in your
4565 program. You can tell @value{GDBN} in advance what to do for each kind of
4568 @cindex handling signals
4569 Normally, @value{GDBN} is set up to let the non-erroneous signals like
4570 @code{SIGALRM} be silently passed to your program
4571 (so as not to interfere with their role in the program's functioning)
4572 but to stop your program immediately whenever an error signal happens.
4573 You can change these settings with the @code{handle} command.
4576 @kindex info signals
4580 Print a table of all the kinds of signals and how @value{GDBN} has been told to
4581 handle each one. You can use this to see the signal numbers of all
4582 the defined types of signals.
4584 @item info signals @var{sig}
4585 Similar, but print information only about the specified signal number.
4587 @code{info handle} is an alias for @code{info signals}.
4590 @item handle @var{signal} @r{[}@var{keywords}@dots{}@r{]}
4591 Change the way @value{GDBN} handles signal @var{signal}. @var{signal}
4592 can be the number of a signal or its name (with or without the
4593 @samp{SIG} at the beginning); a list of signal numbers of the form
4594 @samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the
4595 known signals. Optional arguments @var{keywords}, described below,
4596 say what change to make.
4600 The keywords allowed by the @code{handle} command can be abbreviated.
4601 Their full names are:
4605 @value{GDBN} should not stop your program when this signal happens. It may
4606 still print a message telling you that the signal has come in.
4609 @value{GDBN} should stop your program when this signal happens. This implies
4610 the @code{print} keyword as well.
4613 @value{GDBN} should print a message when this signal happens.
4616 @value{GDBN} should not mention the occurrence of the signal at all. This
4617 implies the @code{nostop} keyword as well.
4621 @value{GDBN} should allow your program to see this signal; your program
4622 can handle the signal, or else it may terminate if the signal is fatal
4623 and not handled. @code{pass} and @code{noignore} are synonyms.
4627 @value{GDBN} should not allow your program to see this signal.
4628 @code{nopass} and @code{ignore} are synonyms.
4632 When a signal stops your program, the signal is not visible to the
4634 continue. Your program sees the signal then, if @code{pass} is in
4635 effect for the signal in question @emph{at that time}. In other words,
4636 after @value{GDBN} reports a signal, you can use the @code{handle}
4637 command with @code{pass} or @code{nopass} to control whether your
4638 program sees that signal when you continue.
4640 The default is set to @code{nostop}, @code{noprint}, @code{pass} for
4641 non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and
4642 @code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the
4645 You can also use the @code{signal} command to prevent your program from
4646 seeing a signal, or cause it to see a signal it normally would not see,
4647 or to give it any signal at any time. For example, if your program stopped
4648 due to some sort of memory reference error, you might store correct
4649 values into the erroneous variables and continue, hoping to see more
4650 execution; but your program would probably terminate immediately as
4651 a result of the fatal signal once it saw the signal. To prevent this,
4652 you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
4655 @cindex extra signal information
4656 @anchor{extra signal information}
4658 On some targets, @value{GDBN} can inspect extra signal information
4659 associated with the intercepted signal, before it is actually
4660 delivered to the program being debugged. This information is exported
4661 by the convenience variable @code{$_siginfo}, and consists of data
4662 that is passed by the kernel to the signal handler at the time of the
4663 receipt of a signal. The data type of the information itself is
4664 target dependent. You can see the data type using the @code{ptype
4665 $_siginfo} command. On Unix systems, it typically corresponds to the
4666 standard @code{siginfo_t} type, as defined in the @file{signal.h}
4669 Here's an example, on a @sc{gnu}/Linux system, printing the stray
4670 referenced address that raised a segmentation fault.
4674 (@value{GDBP}) continue
4675 Program received signal SIGSEGV, Segmentation fault.
4676 0x0000000000400766 in main ()
4678 (@value{GDBP}) ptype $_siginfo
4685 struct @{...@} _kill;
4686 struct @{...@} _timer;
4688 struct @{...@} _sigchld;
4689 struct @{...@} _sigfault;
4690 struct @{...@} _sigpoll;
4693 (@value{GDBP}) ptype $_siginfo._sifields._sigfault
4697 (@value{GDBP}) p $_siginfo._sifields._sigfault.si_addr
4698 $1 = (void *) 0x7ffff7ff7000
4702 Depending on target support, @code{$_siginfo} may also be writable.
4705 @section Stopping and Starting Multi-thread Programs
4707 @cindex stopped threads
4708 @cindex threads, stopped
4710 @cindex continuing threads
4711 @cindex threads, continuing
4713 @value{GDBN} supports debugging programs with multiple threads
4714 (@pxref{Threads,, Debugging Programs with Multiple Threads}). There
4715 are two modes of controlling execution of your program within the
4716 debugger. In the default mode, referred to as @dfn{all-stop mode},
4717 when any thread in your program stops (for example, at a breakpoint
4718 or while being stepped), all other threads in the program are also stopped by
4719 @value{GDBN}. On some targets, @value{GDBN} also supports
4720 @dfn{non-stop mode}, in which other threads can continue to run freely while
4721 you examine the stopped thread in the debugger.
4724 * All-Stop Mode:: All threads stop when GDB takes control
4725 * Non-Stop Mode:: Other threads continue to execute
4726 * Background Execution:: Running your program asynchronously
4727 * Thread-Specific Breakpoints:: Controlling breakpoints
4728 * Interrupted System Calls:: GDB may interfere with system calls
4732 @subsection All-Stop Mode
4734 @cindex all-stop mode
4736 In all-stop mode, whenever your program stops under @value{GDBN} for any reason,
4737 @emph{all} threads of execution stop, not just the current thread. This
4738 allows you to examine the overall state of the program, including
4739 switching between threads, without worrying that things may change
4742 Conversely, whenever you restart the program, @emph{all} threads start
4743 executing. @emph{This is true even when single-stepping} with commands
4744 like @code{step} or @code{next}.
4746 In particular, @value{GDBN} cannot single-step all threads in lockstep.
4747 Since thread scheduling is up to your debugging target's operating
4748 system (not controlled by @value{GDBN}), other threads may
4749 execute more than one statement while the current thread completes a
4750 single step. Moreover, in general other threads stop in the middle of a
4751 statement, rather than at a clean statement boundary, when the program
4754 You might even find your program stopped in another thread after
4755 continuing or even single-stepping. This happens whenever some other
4756 thread runs into a breakpoint, a signal, or an exception before the
4757 first thread completes whatever you requested.
4759 @cindex automatic thread selection
4760 @cindex switching threads automatically
4761 @cindex threads, automatic switching
4762 Whenever @value{GDBN} stops your program, due to a breakpoint or a
4763 signal, it automatically selects the thread where that breakpoint or
4764 signal happened. @value{GDBN} alerts you to the context switch with a
4765 message such as @samp{[Switching to Thread @var{n}]} to identify the
4768 On some OSes, you can modify @value{GDBN}'s default behavior by
4769 locking the OS scheduler to allow only a single thread to run.
4772 @item set scheduler-locking @var{mode}
4773 @cindex scheduler locking mode
4774 @cindex lock scheduler
4775 Set the scheduler locking mode. If it is @code{off}, then there is no
4776 locking and any thread may run at any time. If @code{on}, then only the
4777 current thread may run when the inferior is resumed. The @code{step}
4778 mode optimizes for single-stepping; it prevents other threads
4779 from preempting the current thread while you are stepping, so that
4780 the focus of debugging does not change unexpectedly.
4781 Other threads only rarely (or never) get a chance to run
4782 when you step. They are more likely to run when you @samp{next} over a
4783 function call, and they are completely free to run when you use commands
4784 like @samp{continue}, @samp{until}, or @samp{finish}. However, unless another
4785 thread hits a breakpoint during its timeslice, @value{GDBN} does not change
4786 the current thread away from the thread that you are debugging.
4788 @item show scheduler-locking
4789 Display the current scheduler locking mode.
4792 @cindex resume threads of multiple processes simultaneously
4793 By default, when you issue one of the execution commands such as
4794 @code{continue}, @code{next} or @code{step}, @value{GDBN} allows only
4795 threads of the current inferior to run. For example, if @value{GDBN}
4796 is attached to two inferiors, each with two threads, the
4797 @code{continue} command resumes only the two threads of the current
4798 inferior. This is useful, for example, when you debug a program that
4799 forks and you want to hold the parent stopped (so that, for instance,
4800 it doesn't run to exit), while you debug the child. In other
4801 situations, you may not be interested in inspecting the current state
4802 of any of the processes @value{GDBN} is attached to, and you may want
4803 to resume them all until some breakpoint is hit. In the latter case,
4804 you can instruct @value{GDBN} to allow all threads of all the
4805 inferiors to run with the @w{@code{set schedule-multiple}} command.
4808 @kindex set schedule-multiple
4809 @item set schedule-multiple
4810 Set the mode for allowing threads of multiple processes to be resumed
4811 when an execution command is issued. When @code{on}, all threads of
4812 all processes are allowed to run. When @code{off}, only the threads
4813 of the current process are resumed. The default is @code{off}. The
4814 @code{scheduler-locking} mode takes precedence when set to @code{on},
4815 or while you are stepping and set to @code{step}.
4817 @item show schedule-multiple
4818 Display the current mode for resuming the execution of threads of
4823 @subsection Non-Stop Mode
4825 @cindex non-stop mode
4827 @c This section is really only a place-holder, and needs to be expanded
4828 @c with more details.
4830 For some multi-threaded targets, @value{GDBN} supports an optional
4831 mode of operation in which you can examine stopped program threads in
4832 the debugger while other threads continue to execute freely. This
4833 minimizes intrusion when debugging live systems, such as programs
4834 where some threads have real-time constraints or must continue to
4835 respond to external events. This is referred to as @dfn{non-stop} mode.
4837 In non-stop mode, when a thread stops to report a debugging event,
4838 @emph{only} that thread is stopped; @value{GDBN} does not stop other
4839 threads as well, in contrast to the all-stop mode behavior. Additionally,
4840 execution commands such as @code{continue} and @code{step} apply by default
4841 only to the current thread in non-stop mode, rather than all threads as
4842 in all-stop mode. This allows you to control threads explicitly in
4843 ways that are not possible in all-stop mode --- for example, stepping
4844 one thread while allowing others to run freely, stepping
4845 one thread while holding all others stopped, or stepping several threads
4846 independently and simultaneously.
4848 To enter non-stop mode, use this sequence of commands before you run
4849 or attach to your program:
4852 # Enable the async interface.
4855 # If using the CLI, pagination breaks non-stop.
4858 # Finally, turn it on!
4862 You can use these commands to manipulate the non-stop mode setting:
4865 @kindex set non-stop
4866 @item set non-stop on
4867 Enable selection of non-stop mode.
4868 @item set non-stop off
4869 Disable selection of non-stop mode.
4870 @kindex show non-stop
4872 Show the current non-stop enablement setting.
4875 Note these commands only reflect whether non-stop mode is enabled,
4876 not whether the currently-executing program is being run in non-stop mode.
4877 In particular, the @code{set non-stop} preference is only consulted when
4878 @value{GDBN} starts or connects to the target program, and it is generally
4879 not possible to switch modes once debugging has started. Furthermore,
4880 since not all targets support non-stop mode, even when you have enabled
4881 non-stop mode, @value{GDBN} may still fall back to all-stop operation by
4884 In non-stop mode, all execution commands apply only to the current thread
4885 by default. That is, @code{continue} only continues one thread.
4886 To continue all threads, issue @code{continue -a} or @code{c -a}.
4888 You can use @value{GDBN}'s background execution commands
4889 (@pxref{Background Execution}) to run some threads in the background
4890 while you continue to examine or step others from @value{GDBN}.
4891 The MI execution commands (@pxref{GDB/MI Program Execution}) are
4892 always executed asynchronously in non-stop mode.
4894 Suspending execution is done with the @code{interrupt} command when
4895 running in the background, or @kbd{Ctrl-c} during foreground execution.
4896 In all-stop mode, this stops the whole process;
4897 but in non-stop mode the interrupt applies only to the current thread.
4898 To stop the whole program, use @code{interrupt -a}.
4900 Other execution commands do not currently support the @code{-a} option.
4902 In non-stop mode, when a thread stops, @value{GDBN} doesn't automatically make
4903 that thread current, as it does in all-stop mode. This is because the
4904 thread stop notifications are asynchronous with respect to @value{GDBN}'s
4905 command interpreter, and it would be confusing if @value{GDBN} unexpectedly
4906 changed to a different thread just as you entered a command to operate on the
4907 previously current thread.
4909 @node Background Execution
4910 @subsection Background Execution
4912 @cindex foreground execution
4913 @cindex background execution
4914 @cindex asynchronous execution
4915 @cindex execution, foreground, background and asynchronous
4917 @value{GDBN}'s execution commands have two variants: the normal
4918 foreground (synchronous) behavior, and a background
4919 (asynchronous) behavior. In foreground execution, @value{GDBN} waits for
4920 the program to report that some thread has stopped before prompting for
4921 another command. In background execution, @value{GDBN} immediately gives
4922 a command prompt so that you can issue other commands while your program runs.
4924 You need to explicitly enable asynchronous mode before you can use
4925 background execution commands. You can use these commands to
4926 manipulate the asynchronous mode setting:
4929 @kindex set target-async
4930 @item set target-async on
4931 Enable asynchronous mode.
4932 @item set target-async off
4933 Disable asynchronous mode.
4934 @kindex show target-async
4935 @item show target-async
4936 Show the current target-async setting.
4939 If the target doesn't support async mode, @value{GDBN} issues an error
4940 message if you attempt to use the background execution commands.
4942 To specify background execution, add a @code{&} to the command. For example,
4943 the background form of the @code{continue} command is @code{continue&}, or
4944 just @code{c&}. The execution commands that accept background execution
4950 @xref{Starting, , Starting your Program}.
4954 @xref{Attach, , Debugging an Already-running Process}.
4958 @xref{Continuing and Stepping, step}.
4962 @xref{Continuing and Stepping, stepi}.
4966 @xref{Continuing and Stepping, next}.
4970 @xref{Continuing and Stepping, nexti}.
4974 @xref{Continuing and Stepping, continue}.
4978 @xref{Continuing and Stepping, finish}.
4982 @xref{Continuing and Stepping, until}.
4986 Background execution is especially useful in conjunction with non-stop
4987 mode for debugging programs with multiple threads; see @ref{Non-Stop Mode}.
4988 However, you can also use these commands in the normal all-stop mode with
4989 the restriction that you cannot issue another execution command until the
4990 previous one finishes. Examples of commands that are valid in all-stop
4991 mode while the program is running include @code{help} and @code{info break}.
4993 You can interrupt your program while it is running in the background by
4994 using the @code{interrupt} command.
5001 Suspend execution of the running program. In all-stop mode,
5002 @code{interrupt} stops the whole process, but in non-stop mode, it stops
5003 only the current thread. To stop the whole program in non-stop mode,
5004 use @code{interrupt -a}.
5007 @node Thread-Specific Breakpoints
5008 @subsection Thread-Specific Breakpoints
5010 When your program has multiple threads (@pxref{Threads,, Debugging
5011 Programs with Multiple Threads}), you can choose whether to set
5012 breakpoints on all threads, or on a particular thread.
5015 @cindex breakpoints and threads
5016 @cindex thread breakpoints
5017 @kindex break @dots{} thread @var{threadno}
5018 @item break @var{linespec} thread @var{threadno}
5019 @itemx break @var{linespec} thread @var{threadno} if @dots{}
5020 @var{linespec} specifies source lines; there are several ways of
5021 writing them (@pxref{Specify Location}), but the effect is always to
5022 specify some source line.
5024 Use the qualifier @samp{thread @var{threadno}} with a breakpoint command
5025 to specify that you only want @value{GDBN} to stop the program when a
5026 particular thread reaches this breakpoint. @var{threadno} is one of the
5027 numeric thread identifiers assigned by @value{GDBN}, shown in the first
5028 column of the @samp{info threads} display.
5030 If you do not specify @samp{thread @var{threadno}} when you set a
5031 breakpoint, the breakpoint applies to @emph{all} threads of your
5034 You can use the @code{thread} qualifier on conditional breakpoints as
5035 well; in this case, place @samp{thread @var{threadno}} before the
5036 breakpoint condition, like this:
5039 (@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
5044 @node Interrupted System Calls
5045 @subsection Interrupted System Calls
5047 @cindex thread breakpoints and system calls
5048 @cindex system calls and thread breakpoints
5049 @cindex premature return from system calls
5050 There is an unfortunate side effect when using @value{GDBN} to debug
5051 multi-threaded programs. If one thread stops for a
5052 breakpoint, or for some other reason, and another thread is blocked in a
5053 system call, then the system call may return prematurely. This is a
5054 consequence of the interaction between multiple threads and the signals
5055 that @value{GDBN} uses to implement breakpoints and other events that
5058 To handle this problem, your program should check the return value of
5059 each system call and react appropriately. This is good programming
5062 For example, do not write code like this:
5068 The call to @code{sleep} will return early if a different thread stops
5069 at a breakpoint or for some other reason.
5071 Instead, write this:
5076 unslept = sleep (unslept);
5079 A system call is allowed to return early, so the system is still
5080 conforming to its specification. But @value{GDBN} does cause your
5081 multi-threaded program to behave differently than it would without
5084 Also, @value{GDBN} uses internal breakpoints in the thread library to
5085 monitor certain events such as thread creation and thread destruction.
5086 When such an event happens, a system call in another thread may return
5087 prematurely, even though your program does not appear to stop.
5090 @node Reverse Execution
5091 @chapter Running programs backward
5092 @cindex reverse execution
5093 @cindex running programs backward
5095 When you are debugging a program, it is not unusual to realize that
5096 you have gone too far, and some event of interest has already happened.
5097 If the target environment supports it, @value{GDBN} can allow you to
5098 ``rewind'' the program by running it backward.
5100 A target environment that supports reverse execution should be able
5101 to ``undo'' the changes in machine state that have taken place as the
5102 program was executing normally. Variables, registers etc.@: should
5103 revert to their previous values. Obviously this requires a great
5104 deal of sophistication on the part of the target environment; not
5105 all target environments can support reverse execution.
5107 When a program is executed in reverse, the instructions that
5108 have most recently been executed are ``un-executed'', in reverse
5109 order. The program counter runs backward, following the previous
5110 thread of execution in reverse. As each instruction is ``un-executed'',
5111 the values of memory and/or registers that were changed by that
5112 instruction are reverted to their previous states. After executing
5113 a piece of source code in reverse, all side effects of that code
5114 should be ``undone'', and all variables should be returned to their
5115 prior values@footnote{
5116 Note that some side effects are easier to undo than others. For instance,
5117 memory and registers are relatively easy, but device I/O is hard. Some
5118 targets may be able undo things like device I/O, and some may not.
5120 The contract between @value{GDBN} and the reverse executing target
5121 requires only that the target do something reasonable when
5122 @value{GDBN} tells it to execute backwards, and then report the
5123 results back to @value{GDBN}. Whatever the target reports back to
5124 @value{GDBN}, @value{GDBN} will report back to the user. @value{GDBN}
5125 assumes that the memory and registers that the target reports are in a
5126 consistant state, but @value{GDBN} accepts whatever it is given.
5129 If you are debugging in a target environment that supports
5130 reverse execution, @value{GDBN} provides the following commands.
5133 @kindex reverse-continue
5134 @kindex rc @r{(@code{reverse-continue})}
5135 @item reverse-continue @r{[}@var{ignore-count}@r{]}
5136 @itemx rc @r{[}@var{ignore-count}@r{]}
5137 Beginning at the point where your program last stopped, start executing
5138 in reverse. Reverse execution will stop for breakpoints and synchronous
5139 exceptions (signals), just like normal execution. Behavior of
5140 asynchronous signals depends on the target environment.
5142 @kindex reverse-step
5143 @kindex rs @r{(@code{step})}
5144 @item reverse-step @r{[}@var{count}@r{]}
5145 Run the program backward until control reaches the start of a
5146 different source line; then stop it, and return control to @value{GDBN}.
5148 Like the @code{step} command, @code{reverse-step} will only stop
5149 at the beginning of a source line. It ``un-executes'' the previously
5150 executed source line. If the previous source line included calls to
5151 debuggable functions, @code{reverse-step} will step (backward) into
5152 the called function, stopping at the beginning of the @emph{last}
5153 statement in the called function (typically a return statement).
5155 Also, as with the @code{step} command, if non-debuggable functions are
5156 called, @code{reverse-step} will run thru them backward without stopping.
5158 @kindex reverse-stepi
5159 @kindex rsi @r{(@code{reverse-stepi})}
5160 @item reverse-stepi @r{[}@var{count}@r{]}
5161 Reverse-execute one machine instruction. Note that the instruction
5162 to be reverse-executed is @emph{not} the one pointed to by the program
5163 counter, but the instruction executed prior to that one. For instance,
5164 if the last instruction was a jump, @code{reverse-stepi} will take you
5165 back from the destination of the jump to the jump instruction itself.
5167 @kindex reverse-next
5168 @kindex rn @r{(@code{reverse-next})}
5169 @item reverse-next @r{[}@var{count}@r{]}
5170 Run backward to the beginning of the previous line executed in
5171 the current (innermost) stack frame. If the line contains function
5172 calls, they will be ``un-executed'' without stopping. Starting from
5173 the first line of a function, @code{reverse-next} will take you back
5174 to the caller of that function, @emph{before} the function was called,
5175 just as the normal @code{next} command would take you from the last
5176 line of a function back to its return to its caller
5177 @footnote{Unles the code is too heavily optimized.}.
5179 @kindex reverse-nexti
5180 @kindex rni @r{(@code{reverse-nexti})}
5181 @item reverse-nexti @r{[}@var{count}@r{]}
5182 Like @code{nexti}, @code{reverse-nexti} executes a single instruction
5183 in reverse, except that called functions are ``un-executed'' atomically.
5184 That is, if the previously executed instruction was a return from
5185 another instruction, @code{reverse-nexti} will continue to execute
5186 in reverse until the call to that function (from the current stack
5189 @kindex reverse-finish
5190 @item reverse-finish
5191 Just as the @code{finish} command takes you to the point where the
5192 current function returns, @code{reverse-finish} takes you to the point
5193 where it was called. Instead of ending up at the end of the current
5194 function invocation, you end up at the beginning.
5196 @kindex set exec-direction
5197 @item set exec-direction
5198 Set the direction of target execution.
5199 @itemx set exec-direction reverse
5200 @cindex execute forward or backward in time
5201 @value{GDBN} will perform all execution commands in reverse, until the
5202 exec-direction mode is changed to ``forward''. Affected commands include
5203 @code{step, stepi, next, nexti, continue, and finish}. The @code{return}
5204 command cannot be used in reverse mode.
5205 @item set exec-direction forward
5206 @value{GDBN} will perform all execution commands in the normal fashion.
5207 This is the default.
5211 @node Process Record and Replay
5212 @chapter Recording Inferior's Execution and Replaying It
5213 @cindex process record and replay
5214 @cindex recording inferior's execution and replaying it
5216 On some platforms, @value{GDBN} provides a special @dfn{process record
5217 and replay} target that can record a log of the process execution, and
5218 replay it later with both forward and reverse execution commands.
5221 When this target is in use, if the execution log includes the record
5222 for the next instruction, @value{GDBN} will debug in @dfn{replay
5223 mode}. In the replay mode, the inferior does not really execute code
5224 instructions. Instead, all the events that normally happen during
5225 code execution are taken from the execution log. While code is not
5226 really executed in replay mode, the values of registers (including the
5227 program counter register) and the memory of the inferior are still
5228 changed as they normally would. Their contents are taken from the
5232 If the record for the next instruction is not in the execution log,
5233 @value{GDBN} will debug in @dfn{record mode}. In this mode, the
5234 inferior executes normally, and @value{GDBN} records the execution log
5237 The process record and replay target supports reverse execution
5238 (@pxref{Reverse Execution}), even if the platform on which the
5239 inferior runs does not. However, the reverse execution is limited in
5240 this case by the range of the instructions recorded in the execution
5241 log. In other words, reverse execution on platforms that don't
5242 support it directly can only be done in the replay mode.
5244 When debugging in the reverse direction, @value{GDBN} will work in
5245 replay mode as long as the execution log includes the record for the
5246 previous instruction; otherwise, it will work in record mode, if the
5247 platform supports reverse execution, or stop if not.
5249 For architecture environments that support process record and replay,
5250 @value{GDBN} provides the following commands:
5253 @kindex target record
5257 This command starts the process record and replay target. The process
5258 record and replay target can only debug a process that is already
5259 running. Therefore, you need first to start the process with the
5260 @kbd{run} or @kbd{start} commands, and then start the recording with
5261 the @kbd{target record} command.
5263 Both @code{record} and @code{rec} are aliases of @code{target record}.
5265 @cindex displaced stepping, and process record and replay
5266 Displaced stepping (@pxref{Maintenance Commands,, displaced stepping})
5267 will be automatically disabled when process record and replay target
5268 is started. That's because the process record and replay target
5269 doesn't support displaced stepping.
5271 @cindex non-stop mode, and process record and replay
5272 @cindex asynchronous execution, and process record and replay
5273 If the inferior is in the non-stop mode (@pxref{Non-Stop Mode}) or in
5274 the asynchronous execution mode (@pxref{Background Execution}), the
5275 process record and replay target cannot be started because it doesn't
5276 support these two modes.
5281 Stop the process record and replay target. When process record and
5282 replay target stops, the entire execution log will be deleted and the
5283 inferior will either be terminated, or will remain in its final state.
5285 When you stop the process record and replay target in record mode (at
5286 the end of the execution log), the inferior will be stopped at the
5287 next instruction that would have been recorded. In other words, if
5288 you record for a while and then stop recording, the inferior process
5289 will be left in the same state as if the recording never happened.
5291 On the other hand, if the process record and replay target is stopped
5292 while in replay mode (that is, not at the end of the execution log,
5293 but at some earlier point), the inferior process will become ``live''
5294 at that earlier state, and it will then be possible to continue the
5295 usual ``live'' debugging of the process from that state.
5297 When the inferior process exits, or @value{GDBN} detaches from it,
5298 process record and replay target will automatically stop itself.
5300 @kindex set record insn-number-max
5301 @item set record insn-number-max @var{limit}
5302 Set the limit of instructions to be recorded. Default value is 200000.
5304 If @var{limit} is a positive number, then @value{GDBN} will start
5305 deleting instructions from the log once the number of the record
5306 instructions becomes greater than @var{limit}. For every new recorded
5307 instruction, @value{GDBN} will delete the earliest recorded
5308 instruction to keep the number of recorded instructions at the limit.
5309 (Since deleting recorded instructions loses information, @value{GDBN}
5310 lets you control what happens when the limit is reached, by means of
5311 the @code{stop-at-limit} option, described below.)
5313 If @var{limit} is zero, @value{GDBN} will never delete recorded
5314 instructions from the execution log. The number of recorded
5315 instructions is unlimited in this case.
5317 @kindex show record insn-number-max
5318 @item show record insn-number-max
5319 Show the limit of instructions to be recorded.
5321 @kindex set record stop-at-limit
5322 @item set record stop-at-limit
5323 Control the behavior when the number of recorded instructions reaches
5324 the limit. If ON (the default), @value{GDBN} will stop when the limit
5325 is reached for the first time and ask you whether you want to stop the
5326 inferior or continue running it and recording the execution log. If
5327 you decide to continue recording, each new recorded instruction will
5328 cause the oldest one to be deleted.
5330 If this option is OFF, @value{GDBN} will automatically delete the
5331 oldest record to make room for each new one, without asking.
5333 @kindex show record stop-at-limit
5334 @item show record stop-at-limit
5335 Show the current setting of @code{stop-at-limit}.
5337 @kindex info record insn-number
5338 @item info record insn-number
5339 Show the current number of recorded instructions.
5341 @kindex record delete
5344 When record target runs in replay mode (``in the past''), delete the
5345 subsequent execution log and begin to record a new execution log starting
5346 from the current address. This means you will abandon the previously
5347 recorded ``future'' and begin recording a new ``future''.
5352 @chapter Examining the Stack
5354 When your program has stopped, the first thing you need to know is where it
5355 stopped and how it got there.
5358 Each time your program performs a function call, information about the call
5360 That information includes the location of the call in your program,
5361 the arguments of the call,
5362 and the local variables of the function being called.
5363 The information is saved in a block of data called a @dfn{stack frame}.
5364 The stack frames are allocated in a region of memory called the @dfn{call
5367 When your program stops, the @value{GDBN} commands for examining the
5368 stack allow you to see all of this information.
5370 @cindex selected frame
5371 One of the stack frames is @dfn{selected} by @value{GDBN} and many
5372 @value{GDBN} commands refer implicitly to the selected frame. In
5373 particular, whenever you ask @value{GDBN} for the value of a variable in
5374 your program, the value is found in the selected frame. There are
5375 special @value{GDBN} commands to select whichever frame you are
5376 interested in. @xref{Selection, ,Selecting a Frame}.
5378 When your program stops, @value{GDBN} automatically selects the
5379 currently executing frame and describes it briefly, similar to the
5380 @code{frame} command (@pxref{Frame Info, ,Information about a Frame}).
5383 * Frames:: Stack frames
5384 * Backtrace:: Backtraces
5385 * Selection:: Selecting a frame
5386 * Frame Info:: Information on a frame
5391 @section Stack Frames
5393 @cindex frame, definition
5395 The call stack is divided up into contiguous pieces called @dfn{stack
5396 frames}, or @dfn{frames} for short; each frame is the data associated
5397 with one call to one function. The frame contains the arguments given
5398 to the function, the function's local variables, and the address at
5399 which the function is executing.
5401 @cindex initial frame
5402 @cindex outermost frame
5403 @cindex innermost frame
5404 When your program is started, the stack has only one frame, that of the
5405 function @code{main}. This is called the @dfn{initial} frame or the
5406 @dfn{outermost} frame. Each time a function is called, a new frame is
5407 made. Each time a function returns, the frame for that function invocation
5408 is eliminated. If a function is recursive, there can be many frames for
5409 the same function. The frame for the function in which execution is
5410 actually occurring is called the @dfn{innermost} frame. This is the most
5411 recently created of all the stack frames that still exist.
5413 @cindex frame pointer
5414 Inside your program, stack frames are identified by their addresses. A
5415 stack frame consists of many bytes, each of which has its own address; each
5416 kind of computer has a convention for choosing one byte whose
5417 address serves as the address of the frame. Usually this address is kept
5418 in a register called the @dfn{frame pointer register}
5419 (@pxref{Registers, $fp}) while execution is going on in that frame.
5421 @cindex frame number
5422 @value{GDBN} assigns numbers to all existing stack frames, starting with
5423 zero for the innermost frame, one for the frame that called it,
5424 and so on upward. These numbers do not really exist in your program;
5425 they are assigned by @value{GDBN} to give you a way of designating stack
5426 frames in @value{GDBN} commands.
5428 @c The -fomit-frame-pointer below perennially causes hbox overflow
5429 @c underflow problems.
5430 @cindex frameless execution
5431 Some compilers provide a way to compile functions so that they operate
5432 without stack frames. (For example, the @value{NGCC} option
5434 @samp{-fomit-frame-pointer}
5436 generates functions without a frame.)
5437 This is occasionally done with heavily used library functions to save
5438 the frame setup time. @value{GDBN} has limited facilities for dealing
5439 with these function invocations. If the innermost function invocation
5440 has no stack frame, @value{GDBN} nevertheless regards it as though
5441 it had a separate frame, which is numbered zero as usual, allowing
5442 correct tracing of the function call chain. However, @value{GDBN} has
5443 no provision for frameless functions elsewhere in the stack.
5446 @kindex frame@r{, command}
5447 @cindex current stack frame
5448 @item frame @var{args}
5449 The @code{frame} command allows you to move from one stack frame to another,
5450 and to print the stack frame you select. @var{args} may be either the
5451 address of the frame or the stack frame number. Without an argument,
5452 @code{frame} prints the current stack frame.
5454 @kindex select-frame
5455 @cindex selecting frame silently
5457 The @code{select-frame} command allows you to move from one stack frame
5458 to another without printing the frame. This is the silent version of
5466 @cindex call stack traces
5467 A backtrace is a summary of how your program got where it is. It shows one
5468 line per frame, for many frames, starting with the currently executing
5469 frame (frame zero), followed by its caller (frame one), and on up the
5474 @kindex bt @r{(@code{backtrace})}
5477 Print a backtrace of the entire stack: one line per frame for all
5478 frames in the stack.
5480 You can stop the backtrace at any time by typing the system interrupt
5481 character, normally @kbd{Ctrl-c}.
5483 @item backtrace @var{n}
5485 Similar, but print only the innermost @var{n} frames.
5487 @item backtrace -@var{n}
5489 Similar, but print only the outermost @var{n} frames.
5491 @item backtrace full
5493 @itemx bt full @var{n}
5494 @itemx bt full -@var{n}
5495 Print the values of the local variables also. @var{n} specifies the
5496 number of frames to print, as described above.
5501 The names @code{where} and @code{info stack} (abbreviated @code{info s})
5502 are additional aliases for @code{backtrace}.
5504 @cindex multiple threads, backtrace
5505 In a multi-threaded program, @value{GDBN} by default shows the
5506 backtrace only for the current thread. To display the backtrace for
5507 several or all of the threads, use the command @code{thread apply}
5508 (@pxref{Threads, thread apply}). For example, if you type @kbd{thread
5509 apply all backtrace}, @value{GDBN} will display the backtrace for all
5510 the threads; this is handy when you debug a core dump of a
5511 multi-threaded program.
5513 Each line in the backtrace shows the frame number and the function name.
5514 The program counter value is also shown---unless you use @code{set
5515 print address off}. The backtrace also shows the source file name and
5516 line number, as well as the arguments to the function. The program
5517 counter value is omitted if it is at the beginning of the code for that
5520 Here is an example of a backtrace. It was made with the command
5521 @samp{bt 3}, so it shows the innermost three frames.
5525 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
5527 #1 0x6e38 in expand_macro (sym=0x2b600, data=...) at macro.c:242
5528 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
5530 (More stack frames follow...)
5535 The display for frame zero does not begin with a program counter
5536 value, indicating that your program has stopped at the beginning of the
5537 code for line @code{993} of @code{builtin.c}.
5540 The value of parameter @code{data} in frame 1 has been replaced by
5541 @code{@dots{}}. By default, @value{GDBN} prints the value of a parameter
5542 only if it is a scalar (integer, pointer, enumeration, etc). See command
5543 @kbd{set print frame-arguments} in @ref{Print Settings} for more details
5544 on how to configure the way function parameter values are printed.
5546 @cindex value optimized out, in backtrace
5547 @cindex function call arguments, optimized out
5548 If your program was compiled with optimizations, some compilers will
5549 optimize away arguments passed to functions if those arguments are
5550 never used after the call. Such optimizations generate code that
5551 passes arguments through registers, but doesn't store those arguments
5552 in the stack frame. @value{GDBN} has no way of displaying such
5553 arguments in stack frames other than the innermost one. Here's what
5554 such a backtrace might look like:
5558 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
5560 #1 0x6e38 in expand_macro (sym=<value optimized out>) at macro.c:242
5561 #2 0x6840 in expand_token (obs=0x0, t=<value optimized out>, td=0xf7fffb08)
5563 (More stack frames follow...)
5568 The values of arguments that were not saved in their stack frames are
5569 shown as @samp{<value optimized out>}.
5571 If you need to display the values of such optimized-out arguments,
5572 either deduce that from other variables whose values depend on the one
5573 you are interested in, or recompile without optimizations.
5575 @cindex backtrace beyond @code{main} function
5576 @cindex program entry point
5577 @cindex startup code, and backtrace
5578 Most programs have a standard user entry point---a place where system
5579 libraries and startup code transition into user code. For C this is
5580 @code{main}@footnote{
5581 Note that embedded programs (the so-called ``free-standing''
5582 environment) are not required to have a @code{main} function as the
5583 entry point. They could even have multiple entry points.}.
5584 When @value{GDBN} finds the entry function in a backtrace
5585 it will terminate the backtrace, to avoid tracing into highly
5586 system-specific (and generally uninteresting) code.
5588 If you need to examine the startup code, or limit the number of levels
5589 in a backtrace, you can change this behavior:
5592 @item set backtrace past-main
5593 @itemx set backtrace past-main on
5594 @kindex set backtrace
5595 Backtraces will continue past the user entry point.
5597 @item set backtrace past-main off
5598 Backtraces will stop when they encounter the user entry point. This is the
5601 @item show backtrace past-main
5602 @kindex show backtrace
5603 Display the current user entry point backtrace policy.
5605 @item set backtrace past-entry
5606 @itemx set backtrace past-entry on
5607 Backtraces will continue past the internal entry point of an application.
5608 This entry point is encoded by the linker when the application is built,
5609 and is likely before the user entry point @code{main} (or equivalent) is called.
5611 @item set backtrace past-entry off
5612 Backtraces will stop when they encounter the internal entry point of an
5613 application. This is the default.
5615 @item show backtrace past-entry
5616 Display the current internal entry point backtrace policy.
5618 @item set backtrace limit @var{n}
5619 @itemx set backtrace limit 0
5620 @cindex backtrace limit
5621 Limit the backtrace to @var{n} levels. A value of zero means
5624 @item show backtrace limit
5625 Display the current limit on backtrace levels.
5629 @section Selecting a Frame
5631 Most commands for examining the stack and other data in your program work on
5632 whichever stack frame is selected at the moment. Here are the commands for
5633 selecting a stack frame; all of them finish by printing a brief description
5634 of the stack frame just selected.
5637 @kindex frame@r{, selecting}
5638 @kindex f @r{(@code{frame})}
5641 Select frame number @var{n}. Recall that frame zero is the innermost
5642 (currently executing) frame, frame one is the frame that called the
5643 innermost one, and so on. The highest-numbered frame is the one for
5646 @item frame @var{addr}
5648 Select the frame at address @var{addr}. This is useful mainly if the
5649 chaining of stack frames has been damaged by a bug, making it
5650 impossible for @value{GDBN} to assign numbers properly to all frames. In
5651 addition, this can be useful when your program has multiple stacks and
5652 switches between them.
5654 On the SPARC architecture, @code{frame} needs two addresses to
5655 select an arbitrary frame: a frame pointer and a stack pointer.
5657 On the MIPS and Alpha architecture, it needs two addresses: a stack
5658 pointer and a program counter.
5660 On the 29k architecture, it needs three addresses: a register stack
5661 pointer, a program counter, and a memory stack pointer.
5665 Move @var{n} frames up the stack. For positive numbers @var{n}, this
5666 advances toward the outermost frame, to higher frame numbers, to frames
5667 that have existed longer. @var{n} defaults to one.
5670 @kindex do @r{(@code{down})}
5672 Move @var{n} frames down the stack. For positive numbers @var{n}, this
5673 advances toward the innermost frame, to lower frame numbers, to frames
5674 that were created more recently. @var{n} defaults to one. You may
5675 abbreviate @code{down} as @code{do}.
5678 All of these commands end by printing two lines of output describing the
5679 frame. The first line shows the frame number, the function name, the
5680 arguments, and the source file and line number of execution in that
5681 frame. The second line shows the text of that source line.
5689 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
5691 10 read_input_file (argv[i]);
5695 After such a printout, the @code{list} command with no arguments
5696 prints ten lines centered on the point of execution in the frame.
5697 You can also edit the program at the point of execution with your favorite
5698 editing program by typing @code{edit}.
5699 @xref{List, ,Printing Source Lines},
5703 @kindex down-silently
5705 @item up-silently @var{n}
5706 @itemx down-silently @var{n}
5707 These two commands are variants of @code{up} and @code{down},
5708 respectively; they differ in that they do their work silently, without
5709 causing display of the new frame. They are intended primarily for use
5710 in @value{GDBN} command scripts, where the output might be unnecessary and
5715 @section Information About a Frame
5717 There are several other commands to print information about the selected
5723 When used without any argument, this command does not change which
5724 frame is selected, but prints a brief description of the currently
5725 selected stack frame. It can be abbreviated @code{f}. With an
5726 argument, this command is used to select a stack frame.
5727 @xref{Selection, ,Selecting a Frame}.
5730 @kindex info f @r{(@code{info frame})}
5733 This command prints a verbose description of the selected stack frame,
5738 the address of the frame
5740 the address of the next frame down (called by this frame)
5742 the address of the next frame up (caller of this frame)
5744 the language in which the source code corresponding to this frame is written
5746 the address of the frame's arguments
5748 the address of the frame's local variables
5750 the program counter saved in it (the address of execution in the caller frame)
5752 which registers were saved in the frame
5755 @noindent The verbose description is useful when
5756 something has gone wrong that has made the stack format fail to fit
5757 the usual conventions.
5759 @item info frame @var{addr}
5760 @itemx info f @var{addr}
5761 Print a verbose description of the frame at address @var{addr}, without
5762 selecting that frame. The selected frame remains unchanged by this
5763 command. This requires the same kind of address (more than one for some
5764 architectures) that you specify in the @code{frame} command.
5765 @xref{Selection, ,Selecting a Frame}.
5769 Print the arguments of the selected frame, each on a separate line.
5773 Print the local variables of the selected frame, each on a separate
5774 line. These are all variables (declared either static or automatic)
5775 accessible at the point of execution of the selected frame.
5778 @cindex catch exceptions, list active handlers
5779 @cindex exception handlers, how to list
5781 Print a list of all the exception handlers that are active in the
5782 current stack frame at the current point of execution. To see other
5783 exception handlers, visit the associated frame (using the @code{up},
5784 @code{down}, or @code{frame} commands); then type @code{info catch}.
5785 @xref{Set Catchpoints, , Setting Catchpoints}.
5791 @chapter Examining Source Files
5793 @value{GDBN} can print parts of your program's source, since the debugging
5794 information recorded in the program tells @value{GDBN} what source files were
5795 used to build it. When your program stops, @value{GDBN} spontaneously prints
5796 the line where it stopped. Likewise, when you select a stack frame
5797 (@pxref{Selection, ,Selecting a Frame}), @value{GDBN} prints the line where
5798 execution in that frame has stopped. You can print other portions of
5799 source files by explicit command.
5801 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
5802 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
5803 @value{GDBN} under @sc{gnu} Emacs}.
5806 * List:: Printing source lines
5807 * Specify Location:: How to specify code locations
5808 * Edit:: Editing source files
5809 * Search:: Searching source files
5810 * Source Path:: Specifying source directories
5811 * Machine Code:: Source and machine code
5815 @section Printing Source Lines
5818 @kindex l @r{(@code{list})}
5819 To print lines from a source file, use the @code{list} command
5820 (abbreviated @code{l}). By default, ten lines are printed.
5821 There are several ways to specify what part of the file you want to
5822 print; see @ref{Specify Location}, for the full list.
5824 Here are the forms of the @code{list} command most commonly used:
5827 @item list @var{linenum}
5828 Print lines centered around line number @var{linenum} in the
5829 current source file.
5831 @item list @var{function}
5832 Print lines centered around the beginning of function
5836 Print more lines. If the last lines printed were printed with a
5837 @code{list} command, this prints lines following the last lines
5838 printed; however, if the last line printed was a solitary line printed
5839 as part of displaying a stack frame (@pxref{Stack, ,Examining the
5840 Stack}), this prints lines centered around that line.
5843 Print lines just before the lines last printed.
5846 @cindex @code{list}, how many lines to display
5847 By default, @value{GDBN} prints ten source lines with any of these forms of
5848 the @code{list} command. You can change this using @code{set listsize}:
5851 @kindex set listsize
5852 @item set listsize @var{count}
5853 Make the @code{list} command display @var{count} source lines (unless
5854 the @code{list} argument explicitly specifies some other number).
5856 @kindex show listsize
5858 Display the number of lines that @code{list} prints.
5861 Repeating a @code{list} command with @key{RET} discards the argument,
5862 so it is equivalent to typing just @code{list}. This is more useful
5863 than listing the same lines again. An exception is made for an
5864 argument of @samp{-}; that argument is preserved in repetition so that
5865 each repetition moves up in the source file.
5867 In general, the @code{list} command expects you to supply zero, one or two
5868 @dfn{linespecs}. Linespecs specify source lines; there are several ways
5869 of writing them (@pxref{Specify Location}), but the effect is always
5870 to specify some source line.
5872 Here is a complete description of the possible arguments for @code{list}:
5875 @item list @var{linespec}
5876 Print lines centered around the line specified by @var{linespec}.
5878 @item list @var{first},@var{last}
5879 Print lines from @var{first} to @var{last}. Both arguments are
5880 linespecs. When a @code{list} command has two linespecs, and the
5881 source file of the second linespec is omitted, this refers to
5882 the same source file as the first linespec.
5884 @item list ,@var{last}
5885 Print lines ending with @var{last}.
5887 @item list @var{first},
5888 Print lines starting with @var{first}.
5891 Print lines just after the lines last printed.
5894 Print lines just before the lines last printed.
5897 As described in the preceding table.
5900 @node Specify Location
5901 @section Specifying a Location
5902 @cindex specifying location
5905 Several @value{GDBN} commands accept arguments that specify a location
5906 of your program's code. Since @value{GDBN} is a source-level
5907 debugger, a location usually specifies some line in the source code;
5908 for that reason, locations are also known as @dfn{linespecs}.
5910 Here are all the different ways of specifying a code location that
5911 @value{GDBN} understands:
5915 Specifies the line number @var{linenum} of the current source file.
5918 @itemx +@var{offset}
5919 Specifies the line @var{offset} lines before or after the @dfn{current
5920 line}. For the @code{list} command, the current line is the last one
5921 printed; for the breakpoint commands, this is the line at which
5922 execution stopped in the currently selected @dfn{stack frame}
5923 (@pxref{Frames, ,Frames}, for a description of stack frames.) When
5924 used as the second of the two linespecs in a @code{list} command,
5925 this specifies the line @var{offset} lines up or down from the first
5928 @item @var{filename}:@var{linenum}
5929 Specifies the line @var{linenum} in the source file @var{filename}.
5931 @item @var{function}
5932 Specifies the line that begins the body of the function @var{function}.
5933 For example, in C, this is the line with the open brace.
5935 @item @var{filename}:@var{function}
5936 Specifies the line that begins the body of the function @var{function}
5937 in the file @var{filename}. You only need the file name with a
5938 function name to avoid ambiguity when there are identically named
5939 functions in different source files.
5941 @item *@var{address}
5942 Specifies the program address @var{address}. For line-oriented
5943 commands, such as @code{list} and @code{edit}, this specifies a source
5944 line that contains @var{address}. For @code{break} and other
5945 breakpoint oriented commands, this can be used to set breakpoints in
5946 parts of your program which do not have debugging information or
5949 Here @var{address} may be any expression valid in the current working
5950 language (@pxref{Languages, working language}) that specifies a code
5951 address. In addition, as a convenience, @value{GDBN} extends the
5952 semantics of expressions used in locations to cover the situations
5953 that frequently happen during debugging. Here are the various forms
5957 @item @var{expression}
5958 Any expression valid in the current working language.
5960 @item @var{funcaddr}
5961 An address of a function or procedure derived from its name. In C,
5962 C@t{++}, Java, Objective-C, Fortran, minimal, and assembly, this is
5963 simply the function's name @var{function} (and actually a special case
5964 of a valid expression). In Pascal and Modula-2, this is
5965 @code{&@var{function}}. In Ada, this is @code{@var{function}'Address}
5966 (although the Pascal form also works).
5968 This form specifies the address of the function's first instruction,
5969 before the stack frame and arguments have been set up.
5971 @item '@var{filename}'::@var{funcaddr}
5972 Like @var{funcaddr} above, but also specifies the name of the source
5973 file explicitly. This is useful if the name of the function does not
5974 specify the function unambiguously, e.g., if there are several
5975 functions with identical names in different source files.
5982 @section Editing Source Files
5983 @cindex editing source files
5986 @kindex e @r{(@code{edit})}
5987 To edit the lines in a source file, use the @code{edit} command.
5988 The editing program of your choice
5989 is invoked with the current line set to
5990 the active line in the program.
5991 Alternatively, there are several ways to specify what part of the file you
5992 want to print if you want to see other parts of the program:
5995 @item edit @var{location}
5996 Edit the source file specified by @code{location}. Editing starts at
5997 that @var{location}, e.g., at the specified source line of the
5998 specified file. @xref{Specify Location}, for all the possible forms
5999 of the @var{location} argument; here are the forms of the @code{edit}
6000 command most commonly used:
6003 @item edit @var{number}
6004 Edit the current source file with @var{number} as the active line number.
6006 @item edit @var{function}
6007 Edit the file containing @var{function} at the beginning of its definition.
6012 @subsection Choosing your Editor
6013 You can customize @value{GDBN} to use any editor you want
6015 The only restriction is that your editor (say @code{ex}), recognizes the
6016 following command-line syntax:
6018 ex +@var{number} file
6020 The optional numeric value +@var{number} specifies the number of the line in
6021 the file where to start editing.}.
6022 By default, it is @file{@value{EDITOR}}, but you can change this
6023 by setting the environment variable @code{EDITOR} before using
6024 @value{GDBN}. For example, to configure @value{GDBN} to use the
6025 @code{vi} editor, you could use these commands with the @code{sh} shell:
6031 or in the @code{csh} shell,
6033 setenv EDITOR /usr/bin/vi
6038 @section Searching Source Files
6039 @cindex searching source files
6041 There are two commands for searching through the current source file for a
6046 @kindex forward-search
6047 @item forward-search @var{regexp}
6048 @itemx search @var{regexp}
6049 The command @samp{forward-search @var{regexp}} checks each line,
6050 starting with the one following the last line listed, for a match for
6051 @var{regexp}. It lists the line that is found. You can use the
6052 synonym @samp{search @var{regexp}} or abbreviate the command name as
6055 @kindex reverse-search
6056 @item reverse-search @var{regexp}
6057 The command @samp{reverse-search @var{regexp}} checks each line, starting
6058 with the one before the last line listed and going backward, for a match
6059 for @var{regexp}. It lists the line that is found. You can abbreviate
6060 this command as @code{rev}.
6064 @section Specifying Source Directories
6067 @cindex directories for source files
6068 Executable programs sometimes do not record the directories of the source
6069 files from which they were compiled, just the names. Even when they do,
6070 the directories could be moved between the compilation and your debugging
6071 session. @value{GDBN} has a list of directories to search for source files;
6072 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
6073 it tries all the directories in the list, in the order they are present
6074 in the list, until it finds a file with the desired name.
6076 For example, suppose an executable references the file
6077 @file{/usr/src/foo-1.0/lib/foo.c}, and our source path is
6078 @file{/mnt/cross}. The file is first looked up literally; if this
6079 fails, @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c} is tried; if this
6080 fails, @file{/mnt/cross/foo.c} is opened; if this fails, an error
6081 message is printed. @value{GDBN} does not look up the parts of the
6082 source file name, such as @file{/mnt/cross/src/foo-1.0/lib/foo.c}.
6083 Likewise, the subdirectories of the source path are not searched: if
6084 the source path is @file{/mnt/cross}, and the binary refers to
6085 @file{foo.c}, @value{GDBN} would not find it under
6086 @file{/mnt/cross/usr/src/foo-1.0/lib}.
6088 Plain file names, relative file names with leading directories, file
6089 names containing dots, etc.@: are all treated as described above; for
6090 instance, if the source path is @file{/mnt/cross}, and the source file
6091 is recorded as @file{../lib/foo.c}, @value{GDBN} would first try
6092 @file{../lib/foo.c}, then @file{/mnt/cross/../lib/foo.c}, and after
6093 that---@file{/mnt/cross/foo.c}.
6095 Note that the executable search path is @emph{not} used to locate the
6098 Whenever you reset or rearrange the source path, @value{GDBN} clears out
6099 any information it has cached about where source files are found and where
6100 each line is in the file.
6104 When you start @value{GDBN}, its source path includes only @samp{cdir}
6105 and @samp{cwd}, in that order.
6106 To add other directories, use the @code{directory} command.
6108 The search path is used to find both program source files and @value{GDBN}
6109 script files (read using the @samp{-command} option and @samp{source} command).
6111 In addition to the source path, @value{GDBN} provides a set of commands
6112 that manage a list of source path substitution rules. A @dfn{substitution
6113 rule} specifies how to rewrite source directories stored in the program's
6114 debug information in case the sources were moved to a different
6115 directory between compilation and debugging. A rule is made of
6116 two strings, the first specifying what needs to be rewritten in
6117 the path, and the second specifying how it should be rewritten.
6118 In @ref{set substitute-path}, we name these two parts @var{from} and
6119 @var{to} respectively. @value{GDBN} does a simple string replacement
6120 of @var{from} with @var{to} at the start of the directory part of the
6121 source file name, and uses that result instead of the original file
6122 name to look up the sources.
6124 Using the previous example, suppose the @file{foo-1.0} tree has been
6125 moved from @file{/usr/src} to @file{/mnt/cross}, then you can tell
6126 @value{GDBN} to replace @file{/usr/src} in all source path names with
6127 @file{/mnt/cross}. The first lookup will then be
6128 @file{/mnt/cross/foo-1.0/lib/foo.c} in place of the original location
6129 of @file{/usr/src/foo-1.0/lib/foo.c}. To define a source path
6130 substitution rule, use the @code{set substitute-path} command
6131 (@pxref{set substitute-path}).
6133 To avoid unexpected substitution results, a rule is applied only if the
6134 @var{from} part of the directory name ends at a directory separator.
6135 For instance, a rule substituting @file{/usr/source} into
6136 @file{/mnt/cross} will be applied to @file{/usr/source/foo-1.0} but
6137 not to @file{/usr/sourceware/foo-2.0}. And because the substitution
6138 is applied only at the beginning of the directory name, this rule will
6139 not be applied to @file{/root/usr/source/baz.c} either.
6141 In many cases, you can achieve the same result using the @code{directory}
6142 command. However, @code{set substitute-path} can be more efficient in
6143 the case where the sources are organized in a complex tree with multiple
6144 subdirectories. With the @code{directory} command, you need to add each
6145 subdirectory of your project. If you moved the entire tree while
6146 preserving its internal organization, then @code{set substitute-path}
6147 allows you to direct the debugger to all the sources with one single
6150 @code{set substitute-path} is also more than just a shortcut command.
6151 The source path is only used if the file at the original location no
6152 longer exists. On the other hand, @code{set substitute-path} modifies
6153 the debugger behavior to look at the rewritten location instead. So, if
6154 for any reason a source file that is not relevant to your executable is
6155 located at the original location, a substitution rule is the only
6156 method available to point @value{GDBN} at the new location.
6158 @cindex @samp{--with-relocated-sources}
6159 @cindex default source path substitution
6160 You can configure a default source path substitution rule by
6161 configuring @value{GDBN} with the
6162 @samp{--with-relocated-sources=@var{dir}} option. The @var{dir}
6163 should be the name of a directory under @value{GDBN}'s configured
6164 prefix (set with @samp{--prefix} or @samp{--exec-prefix}), and
6165 directory names in debug information under @var{dir} will be adjusted
6166 automatically if the installed @value{GDBN} is moved to a new
6167 location. This is useful if @value{GDBN}, libraries or executables
6168 with debug information and corresponding source code are being moved
6172 @item directory @var{dirname} @dots{}
6173 @item dir @var{dirname} @dots{}
6174 Add directory @var{dirname} to the front of the source path. Several
6175 directory names may be given to this command, separated by @samp{:}
6176 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
6177 part of absolute file names) or
6178 whitespace. You may specify a directory that is already in the source
6179 path; this moves it forward, so @value{GDBN} searches it sooner.
6183 @vindex $cdir@r{, convenience variable}
6184 @vindex $cwd@r{, convenience variable}
6185 @cindex compilation directory
6186 @cindex current directory
6187 @cindex working directory
6188 @cindex directory, current
6189 @cindex directory, compilation
6190 You can use the string @samp{$cdir} to refer to the compilation
6191 directory (if one is recorded), and @samp{$cwd} to refer to the current
6192 working directory. @samp{$cwd} is not the same as @samp{.}---the former
6193 tracks the current working directory as it changes during your @value{GDBN}
6194 session, while the latter is immediately expanded to the current
6195 directory at the time you add an entry to the source path.
6198 Reset the source path to its default value (@samp{$cdir:$cwd} on Unix systems). This requires confirmation.
6200 @c RET-repeat for @code{directory} is explicitly disabled, but since
6201 @c repeating it would be a no-op we do not say that. (thanks to RMS)
6203 @item show directories
6204 @kindex show directories
6205 Print the source path: show which directories it contains.
6207 @anchor{set substitute-path}
6208 @item set substitute-path @var{from} @var{to}
6209 @kindex set substitute-path
6210 Define a source path substitution rule, and add it at the end of the
6211 current list of existing substitution rules. If a rule with the same
6212 @var{from} was already defined, then the old rule is also deleted.
6214 For example, if the file @file{/foo/bar/baz.c} was moved to
6215 @file{/mnt/cross/baz.c}, then the command
6218 (@value{GDBP}) set substitute-path /usr/src /mnt/cross
6222 will tell @value{GDBN} to replace @samp{/usr/src} with
6223 @samp{/mnt/cross}, which will allow @value{GDBN} to find the file
6224 @file{baz.c} even though it was moved.
6226 In the case when more than one substitution rule have been defined,
6227 the rules are evaluated one by one in the order where they have been
6228 defined. The first one matching, if any, is selected to perform
6231 For instance, if we had entered the following commands:
6234 (@value{GDBP}) set substitute-path /usr/src/include /mnt/include
6235 (@value{GDBP}) set substitute-path /usr/src /mnt/src
6239 @value{GDBN} would then rewrite @file{/usr/src/include/defs.h} into
6240 @file{/mnt/include/defs.h} by using the first rule. However, it would
6241 use the second rule to rewrite @file{/usr/src/lib/foo.c} into
6242 @file{/mnt/src/lib/foo.c}.
6245 @item unset substitute-path [path]
6246 @kindex unset substitute-path
6247 If a path is specified, search the current list of substitution rules
6248 for a rule that would rewrite that path. Delete that rule if found.
6249 A warning is emitted by the debugger if no rule could be found.
6251 If no path is specified, then all substitution rules are deleted.
6253 @item show substitute-path [path]
6254 @kindex show substitute-path
6255 If a path is specified, then print the source path substitution rule
6256 which would rewrite that path, if any.
6258 If no path is specified, then print all existing source path substitution
6263 If your source path is cluttered with directories that are no longer of
6264 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
6265 versions of source. You can correct the situation as follows:
6269 Use @code{directory} with no argument to reset the source path to its default value.
6272 Use @code{directory} with suitable arguments to reinstall the
6273 directories you want in the source path. You can add all the
6274 directories in one command.
6278 @section Source and Machine Code
6279 @cindex source line and its code address
6281 You can use the command @code{info line} to map source lines to program
6282 addresses (and vice versa), and the command @code{disassemble} to display
6283 a range of addresses as machine instructions. You can use the command
6284 @code{set disassemble-next-line} to set whether to disassemble next
6285 source line when execution stops. When run under @sc{gnu} Emacs
6286 mode, the @code{info line} command causes the arrow to point to the
6287 line specified. Also, @code{info line} prints addresses in symbolic form as
6292 @item info line @var{linespec}
6293 Print the starting and ending addresses of the compiled code for
6294 source line @var{linespec}. You can specify source lines in any of
6295 the ways documented in @ref{Specify Location}.
6298 For example, we can use @code{info line} to discover the location of
6299 the object code for the first line of function
6300 @code{m4_changequote}:
6302 @c FIXME: I think this example should also show the addresses in
6303 @c symbolic form, as they usually would be displayed.
6305 (@value{GDBP}) info line m4_changequote
6306 Line 895 of "builtin.c" starts at pc 0x634c and ends at 0x6350.
6310 @cindex code address and its source line
6311 We can also inquire (using @code{*@var{addr}} as the form for
6312 @var{linespec}) what source line covers a particular address:
6314 (@value{GDBP}) info line *0x63ff
6315 Line 926 of "builtin.c" starts at pc 0x63e4 and ends at 0x6404.
6318 @cindex @code{$_} and @code{info line}
6319 @cindex @code{x} command, default address
6320 @kindex x@r{(examine), and} info line
6321 After @code{info line}, the default address for the @code{x} command
6322 is changed to the starting address of the line, so that @samp{x/i} is
6323 sufficient to begin examining the machine code (@pxref{Memory,
6324 ,Examining Memory}). Also, this address is saved as the value of the
6325 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
6330 @cindex assembly instructions
6331 @cindex instructions, assembly
6332 @cindex machine instructions
6333 @cindex listing machine instructions
6335 @itemx disassemble /m
6336 @itemx disassemble /r
6337 This specialized command dumps a range of memory as machine
6338 instructions. It can also print mixed source+disassembly by specifying
6339 the @code{/m} modifier and print the raw instructions in hex as well as
6340 in symbolic form by specifying the @code{/r}.
6341 The default memory range is the function surrounding the
6342 program counter of the selected frame. A single argument to this
6343 command is a program counter value; @value{GDBN} dumps the function
6344 surrounding this value. Two arguments specify a range of addresses
6345 (first inclusive, second exclusive) to dump.
6348 The following example shows the disassembly of a range of addresses of
6349 HP PA-RISC 2.0 code:
6352 (@value{GDBP}) disas 0x32c4 0x32e4
6353 Dump of assembler code from 0x32c4 to 0x32e4:
6354 0x32c4 <main+204>: addil 0,dp
6355 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
6356 0x32cc <main+212>: ldil 0x3000,r31
6357 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
6358 0x32d4 <main+220>: ldo 0(r31),rp
6359 0x32d8 <main+224>: addil -0x800,dp
6360 0x32dc <main+228>: ldo 0x588(r1),r26
6361 0x32e0 <main+232>: ldil 0x3000,r31
6362 End of assembler dump.
6365 Here is an example showing mixed source+assembly for Intel x86:
6368 (@value{GDBP}) disas /m main
6369 Dump of assembler code for function main:
6371 0x08048330 <main+0>: push %ebp
6372 0x08048331 <main+1>: mov %esp,%ebp
6373 0x08048333 <main+3>: sub $0x8,%esp
6374 0x08048336 <main+6>: and $0xfffffff0,%esp
6375 0x08048339 <main+9>: sub $0x10,%esp
6377 6 printf ("Hello.\n");
6378 0x0804833c <main+12>: movl $0x8048440,(%esp)
6379 0x08048343 <main+19>: call 0x8048284 <puts@@plt>
6383 0x08048348 <main+24>: mov $0x0,%eax
6384 0x0804834d <main+29>: leave
6385 0x0804834e <main+30>: ret
6387 End of assembler dump.
6390 Some architectures have more than one commonly-used set of instruction
6391 mnemonics or other syntax.
6393 For programs that were dynamically linked and use shared libraries,
6394 instructions that call functions or branch to locations in the shared
6395 libraries might show a seemingly bogus location---it's actually a
6396 location of the relocation table. On some architectures, @value{GDBN}
6397 might be able to resolve these to actual function names.
6400 @kindex set disassembly-flavor
6401 @cindex Intel disassembly flavor
6402 @cindex AT&T disassembly flavor
6403 @item set disassembly-flavor @var{instruction-set}
6404 Select the instruction set to use when disassembling the
6405 program via the @code{disassemble} or @code{x/i} commands.
6407 Currently this command is only defined for the Intel x86 family. You
6408 can set @var{instruction-set} to either @code{intel} or @code{att}.
6409 The default is @code{att}, the AT&T flavor used by default by Unix
6410 assemblers for x86-based targets.
6412 @kindex show disassembly-flavor
6413 @item show disassembly-flavor
6414 Show the current setting of the disassembly flavor.
6418 @kindex set disassemble-next-line
6419 @kindex show disassemble-next-line
6420 @item set disassemble-next-line
6421 @itemx show disassemble-next-line
6422 Control whether or not @value{GDBN} will disassemble the next source
6423 line or instruction when execution stops. If ON, @value{GDBN} will
6424 display disassembly of the next source line when execution of the
6425 program being debugged stops. This is @emph{in addition} to
6426 displaying the source line itself, which @value{GDBN} always does if
6427 possible. If the next source line cannot be displayed for some reason
6428 (e.g., if @value{GDBN} cannot find the source file, or there's no line
6429 info in the debug info), @value{GDBN} will display disassembly of the
6430 next @emph{instruction} instead of showing the next source line. If
6431 AUTO, @value{GDBN} will display disassembly of next instruction only
6432 if the source line cannot be displayed. This setting causes
6433 @value{GDBN} to display some feedback when you step through a function
6434 with no line info or whose source file is unavailable. The default is
6435 OFF, which means never display the disassembly of the next line or
6441 @chapter Examining Data
6443 @cindex printing data
6444 @cindex examining data
6447 @c "inspect" is not quite a synonym if you are using Epoch, which we do not
6448 @c document because it is nonstandard... Under Epoch it displays in a
6449 @c different window or something like that.
6450 The usual way to examine data in your program is with the @code{print}
6451 command (abbreviated @code{p}), or its synonym @code{inspect}. It
6452 evaluates and prints the value of an expression of the language your
6453 program is written in (@pxref{Languages, ,Using @value{GDBN} with
6454 Different Languages}).
6457 @item print @var{expr}
6458 @itemx print /@var{f} @var{expr}
6459 @var{expr} is an expression (in the source language). By default the
6460 value of @var{expr} is printed in a format appropriate to its data type;
6461 you can choose a different format by specifying @samp{/@var{f}}, where
6462 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
6466 @itemx print /@var{f}
6467 @cindex reprint the last value
6468 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
6469 @dfn{value history}; @pxref{Value History, ,Value History}). This allows you to
6470 conveniently inspect the same value in an alternative format.
6473 A more low-level way of examining data is with the @code{x} command.
6474 It examines data in memory at a specified address and prints it in a
6475 specified format. @xref{Memory, ,Examining Memory}.
6477 If you are interested in information about types, or about how the
6478 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
6479 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
6483 * Expressions:: Expressions
6484 * Ambiguous Expressions:: Ambiguous Expressions
6485 * Variables:: Program variables
6486 * Arrays:: Artificial arrays
6487 * Output Formats:: Output formats
6488 * Memory:: Examining memory
6489 * Auto Display:: Automatic display
6490 * Print Settings:: Print settings
6491 * Value History:: Value history
6492 * Convenience Vars:: Convenience variables
6493 * Registers:: Registers
6494 * Floating Point Hardware:: Floating point hardware
6495 * Vector Unit:: Vector Unit
6496 * OS Information:: Auxiliary data provided by operating system
6497 * Memory Region Attributes:: Memory region attributes
6498 * Dump/Restore Files:: Copy between memory and a file
6499 * Core File Generation:: Cause a program dump its core
6500 * Character Sets:: Debugging programs that use a different
6501 character set than GDB does
6502 * Caching Remote Data:: Data caching for remote targets
6503 * Searching Memory:: Searching memory for a sequence of bytes
6507 @section Expressions
6510 @code{print} and many other @value{GDBN} commands accept an expression and
6511 compute its value. Any kind of constant, variable or operator defined
6512 by the programming language you are using is valid in an expression in
6513 @value{GDBN}. This includes conditional expressions, function calls,
6514 casts, and string constants. It also includes preprocessor macros, if
6515 you compiled your program to include this information; see
6518 @cindex arrays in expressions
6519 @value{GDBN} supports array constants in expressions input by
6520 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
6521 you can use the command @code{print @{1, 2, 3@}} to create an array
6522 of three integers. If you pass an array to a function or assign it
6523 to a program variable, @value{GDBN} copies the array to memory that
6524 is @code{malloc}ed in the target program.
6526 Because C is so widespread, most of the expressions shown in examples in
6527 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
6528 Languages}, for information on how to use expressions in other
6531 In this section, we discuss operators that you can use in @value{GDBN}
6532 expressions regardless of your programming language.
6534 @cindex casts, in expressions
6535 Casts are supported in all languages, not just in C, because it is so
6536 useful to cast a number into a pointer in order to examine a structure
6537 at that address in memory.
6538 @c FIXME: casts supported---Mod2 true?
6540 @value{GDBN} supports these operators, in addition to those common
6541 to programming languages:
6545 @samp{@@} is a binary operator for treating parts of memory as arrays.
6546 @xref{Arrays, ,Artificial Arrays}, for more information.
6549 @samp{::} allows you to specify a variable in terms of the file or
6550 function where it is defined. @xref{Variables, ,Program Variables}.
6552 @cindex @{@var{type}@}
6553 @cindex type casting memory
6554 @cindex memory, viewing as typed object
6555 @cindex casts, to view memory
6556 @item @{@var{type}@} @var{addr}
6557 Refers to an object of type @var{type} stored at address @var{addr} in
6558 memory. @var{addr} may be any expression whose value is an integer or
6559 pointer (but parentheses are required around binary operators, just as in
6560 a cast). This construct is allowed regardless of what kind of data is
6561 normally supposed to reside at @var{addr}.
6564 @node Ambiguous Expressions
6565 @section Ambiguous Expressions
6566 @cindex ambiguous expressions
6568 Expressions can sometimes contain some ambiguous elements. For instance,
6569 some programming languages (notably Ada, C@t{++} and Objective-C) permit
6570 a single function name to be defined several times, for application in
6571 different contexts. This is called @dfn{overloading}. Another example
6572 involving Ada is generics. A @dfn{generic package} is similar to C@t{++}
6573 templates and is typically instantiated several times, resulting in
6574 the same function name being defined in different contexts.
6576 In some cases and depending on the language, it is possible to adjust
6577 the expression to remove the ambiguity. For instance in C@t{++}, you
6578 can specify the signature of the function you want to break on, as in
6579 @kbd{break @var{function}(@var{types})}. In Ada, using the fully
6580 qualified name of your function often makes the expression unambiguous
6583 When an ambiguity that needs to be resolved is detected, the debugger
6584 has the capability to display a menu of numbered choices for each
6585 possibility, and then waits for the selection with the prompt @samp{>}.
6586 The first option is always @samp{[0] cancel}, and typing @kbd{0 @key{RET}}
6587 aborts the current command. If the command in which the expression was
6588 used allows more than one choice to be selected, the next option in the
6589 menu is @samp{[1] all}, and typing @kbd{1 @key{RET}} selects all possible
6592 For example, the following session excerpt shows an attempt to set a
6593 breakpoint at the overloaded symbol @code{String::after}.
6594 We choose three particular definitions of that function name:
6596 @c FIXME! This is likely to change to show arg type lists, at least
6599 (@value{GDBP}) b String::after
6602 [2] file:String.cc; line number:867
6603 [3] file:String.cc; line number:860
6604 [4] file:String.cc; line number:875
6605 [5] file:String.cc; line number:853
6606 [6] file:String.cc; line number:846
6607 [7] file:String.cc; line number:735
6609 Breakpoint 1 at 0xb26c: file String.cc, line 867.
6610 Breakpoint 2 at 0xb344: file String.cc, line 875.
6611 Breakpoint 3 at 0xafcc: file String.cc, line 846.
6612 Multiple breakpoints were set.
6613 Use the "delete" command to delete unwanted
6620 @kindex set multiple-symbols
6621 @item set multiple-symbols @var{mode}
6622 @cindex multiple-symbols menu
6624 This option allows you to adjust the debugger behavior when an expression
6627 By default, @var{mode} is set to @code{all}. If the command with which
6628 the expression is used allows more than one choice, then @value{GDBN}
6629 automatically selects all possible choices. For instance, inserting
6630 a breakpoint on a function using an ambiguous name results in a breakpoint
6631 inserted on each possible match. However, if a unique choice must be made,
6632 then @value{GDBN} uses the menu to help you disambiguate the expression.
6633 For instance, printing the address of an overloaded function will result
6634 in the use of the menu.
6636 When @var{mode} is set to @code{ask}, the debugger always uses the menu
6637 when an ambiguity is detected.
6639 Finally, when @var{mode} is set to @code{cancel}, the debugger reports
6640 an error due to the ambiguity and the command is aborted.
6642 @kindex show multiple-symbols
6643 @item show multiple-symbols
6644 Show the current value of the @code{multiple-symbols} setting.
6648 @section Program Variables
6650 The most common kind of expression to use is the name of a variable
6653 Variables in expressions are understood in the selected stack frame
6654 (@pxref{Selection, ,Selecting a Frame}); they must be either:
6658 global (or file-static)
6665 visible according to the scope rules of the
6666 programming language from the point of execution in that frame
6669 @noindent This means that in the function
6684 you can examine and use the variable @code{a} whenever your program is
6685 executing within the function @code{foo}, but you can only use or
6686 examine the variable @code{b} while your program is executing inside
6687 the block where @code{b} is declared.
6689 @cindex variable name conflict
6690 There is an exception: you can refer to a variable or function whose
6691 scope is a single source file even if the current execution point is not
6692 in this file. But it is possible to have more than one such variable or
6693 function with the same name (in different source files). If that
6694 happens, referring to that name has unpredictable effects. If you wish,
6695 you can specify a static variable in a particular function or file,
6696 using the colon-colon (@code{::}) notation:
6698 @cindex colon-colon, context for variables/functions
6700 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
6701 @cindex @code{::}, context for variables/functions
6704 @var{file}::@var{variable}
6705 @var{function}::@var{variable}
6709 Here @var{file} or @var{function} is the name of the context for the
6710 static @var{variable}. In the case of file names, you can use quotes to
6711 make sure @value{GDBN} parses the file name as a single word---for example,
6712 to print a global value of @code{x} defined in @file{f2.c}:
6715 (@value{GDBP}) p 'f2.c'::x
6718 @cindex C@t{++} scope resolution
6719 This use of @samp{::} is very rarely in conflict with the very similar
6720 use of the same notation in C@t{++}. @value{GDBN} also supports use of the C@t{++}
6721 scope resolution operator in @value{GDBN} expressions.
6722 @c FIXME: Um, so what happens in one of those rare cases where it's in
6725 @cindex wrong values
6726 @cindex variable values, wrong
6727 @cindex function entry/exit, wrong values of variables
6728 @cindex optimized code, wrong values of variables
6730 @emph{Warning:} Occasionally, a local variable may appear to have the
6731 wrong value at certain points in a function---just after entry to a new
6732 scope, and just before exit.
6734 You may see this problem when you are stepping by machine instructions.
6735 This is because, on most machines, it takes more than one instruction to
6736 set up a stack frame (including local variable definitions); if you are
6737 stepping by machine instructions, variables may appear to have the wrong
6738 values until the stack frame is completely built. On exit, it usually
6739 also takes more than one machine instruction to destroy a stack frame;
6740 after you begin stepping through that group of instructions, local
6741 variable definitions may be gone.
6743 This may also happen when the compiler does significant optimizations.
6744 To be sure of always seeing accurate values, turn off all optimization
6747 @cindex ``No symbol "foo" in current context''
6748 Another possible effect of compiler optimizations is to optimize
6749 unused variables out of existence, or assign variables to registers (as
6750 opposed to memory addresses). Depending on the support for such cases
6751 offered by the debug info format used by the compiler, @value{GDBN}
6752 might not be able to display values for such local variables. If that
6753 happens, @value{GDBN} will print a message like this:
6756 No symbol "foo" in current context.
6759 To solve such problems, either recompile without optimizations, or use a
6760 different debug info format, if the compiler supports several such
6761 formats. For example, @value{NGCC}, the @sc{gnu} C/C@t{++} compiler,
6762 usually supports the @option{-gstabs+} option. @option{-gstabs+}
6763 produces debug info in a format that is superior to formats such as
6764 COFF. You may be able to use DWARF 2 (@option{-gdwarf-2}), which is also
6765 an effective form for debug info. @xref{Debugging Options,,Options
6766 for Debugging Your Program or GCC, gcc.info, Using the @sc{gnu}
6767 Compiler Collection (GCC)}.
6768 @xref{C, ,C and C@t{++}}, for more information about debug info formats
6769 that are best suited to C@t{++} programs.
6771 If you ask to print an object whose contents are unknown to
6772 @value{GDBN}, e.g., because its data type is not completely specified
6773 by the debug information, @value{GDBN} will say @samp{<incomplete
6774 type>}. @xref{Symbols, incomplete type}, for more about this.
6776 Strings are identified as arrays of @code{char} values without specified
6777 signedness. Arrays of either @code{signed char} or @code{unsigned char} get
6778 printed as arrays of 1 byte sized integers. @code{-fsigned-char} or
6779 @code{-funsigned-char} @value{NGCC} options have no effect as @value{GDBN}
6780 defines literal string type @code{"char"} as @code{char} without a sign.
6785 signed char var1[] = "A";
6788 You get during debugging
6793 $2 = @{65 'A', 0 '\0'@}
6797 @section Artificial Arrays
6799 @cindex artificial array
6801 @kindex @@@r{, referencing memory as an array}
6802 It is often useful to print out several successive objects of the
6803 same type in memory; a section of an array, or an array of
6804 dynamically determined size for which only a pointer exists in the
6807 You can do this by referring to a contiguous span of memory as an
6808 @dfn{artificial array}, using the binary operator @samp{@@}. The left
6809 operand of @samp{@@} should be the first element of the desired array
6810 and be an individual object. The right operand should be the desired length
6811 of the array. The result is an array value whose elements are all of
6812 the type of the left argument. The first element is actually the left
6813 argument; the second element comes from bytes of memory immediately
6814 following those that hold the first element, and so on. Here is an
6815 example. If a program says
6818 int *array = (int *) malloc (len * sizeof (int));
6822 you can print the contents of @code{array} with
6828 The left operand of @samp{@@} must reside in memory. Array values made
6829 with @samp{@@} in this way behave just like other arrays in terms of
6830 subscripting, and are coerced to pointers when used in expressions.
6831 Artificial arrays most often appear in expressions via the value history
6832 (@pxref{Value History, ,Value History}), after printing one out.
6834 Another way to create an artificial array is to use a cast.
6835 This re-interprets a value as if it were an array.
6836 The value need not be in memory:
6838 (@value{GDBP}) p/x (short[2])0x12345678
6839 $1 = @{0x1234, 0x5678@}
6842 As a convenience, if you leave the array length out (as in
6843 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
6844 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
6846 (@value{GDBP}) p/x (short[])0x12345678
6847 $2 = @{0x1234, 0x5678@}
6850 Sometimes the artificial array mechanism is not quite enough; in
6851 moderately complex data structures, the elements of interest may not
6852 actually be adjacent---for example, if you are interested in the values
6853 of pointers in an array. One useful work-around in this situation is
6854 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
6855 Variables}) as a counter in an expression that prints the first
6856 interesting value, and then repeat that expression via @key{RET}. For
6857 instance, suppose you have an array @code{dtab} of pointers to
6858 structures, and you are interested in the values of a field @code{fv}
6859 in each structure. Here is an example of what you might type:
6869 @node Output Formats
6870 @section Output Formats
6872 @cindex formatted output
6873 @cindex output formats
6874 By default, @value{GDBN} prints a value according to its data type. Sometimes
6875 this is not what you want. For example, you might want to print a number
6876 in hex, or a pointer in decimal. Or you might want to view data in memory
6877 at a certain address as a character string or as an instruction. To do
6878 these things, specify an @dfn{output format} when you print a value.
6880 The simplest use of output formats is to say how to print a value
6881 already computed. This is done by starting the arguments of the
6882 @code{print} command with a slash and a format letter. The format
6883 letters supported are:
6887 Regard the bits of the value as an integer, and print the integer in
6891 Print as integer in signed decimal.
6894 Print as integer in unsigned decimal.
6897 Print as integer in octal.
6900 Print as integer in binary. The letter @samp{t} stands for ``two''.
6901 @footnote{@samp{b} cannot be used because these format letters are also
6902 used with the @code{x} command, where @samp{b} stands for ``byte'';
6903 see @ref{Memory,,Examining Memory}.}
6906 @cindex unknown address, locating
6907 @cindex locate address
6908 Print as an address, both absolute in hexadecimal and as an offset from
6909 the nearest preceding symbol. You can use this format used to discover
6910 where (in what function) an unknown address is located:
6913 (@value{GDBP}) p/a 0x54320
6914 $3 = 0x54320 <_initialize_vx+396>
6918 The command @code{info symbol 0x54320} yields similar results.
6919 @xref{Symbols, info symbol}.
6922 Regard as an integer and print it as a character constant. This
6923 prints both the numerical value and its character representation. The
6924 character representation is replaced with the octal escape @samp{\nnn}
6925 for characters outside the 7-bit @sc{ascii} range.
6927 Without this format, @value{GDBN} displays @code{char},
6928 @w{@code{unsigned char}}, and @w{@code{signed char}} data as character
6929 constants. Single-byte members of vectors are displayed as integer
6933 Regard the bits of the value as a floating point number and print
6934 using typical floating point syntax.
6937 @cindex printing strings
6938 @cindex printing byte arrays
6939 Regard as a string, if possible. With this format, pointers to single-byte
6940 data are displayed as null-terminated strings and arrays of single-byte data
6941 are displayed as fixed-length strings. Other values are displayed in their
6944 Without this format, @value{GDBN} displays pointers to and arrays of
6945 @code{char}, @w{@code{unsigned char}}, and @w{@code{signed char}} as
6946 strings. Single-byte members of a vector are displayed as an integer
6950 @cindex raw printing
6951 Print using the @samp{raw} formatting. By default, @value{GDBN} will
6952 use a type-specific pretty-printer. The @samp{r} format bypasses any
6953 pretty-printer which might exist for the value's type.
6956 For example, to print the program counter in hex (@pxref{Registers}), type
6963 Note that no space is required before the slash; this is because command
6964 names in @value{GDBN} cannot contain a slash.
6966 To reprint the last value in the value history with a different format,
6967 you can use the @code{print} command with just a format and no
6968 expression. For example, @samp{p/x} reprints the last value in hex.
6971 @section Examining Memory
6973 You can use the command @code{x} (for ``examine'') to examine memory in
6974 any of several formats, independently of your program's data types.
6976 @cindex examining memory
6978 @kindex x @r{(examine memory)}
6979 @item x/@var{nfu} @var{addr}
6982 Use the @code{x} command to examine memory.
6985 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
6986 much memory to display and how to format it; @var{addr} is an
6987 expression giving the address where you want to start displaying memory.
6988 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
6989 Several commands set convenient defaults for @var{addr}.
6992 @item @var{n}, the repeat count
6993 The repeat count is a decimal integer; the default is 1. It specifies
6994 how much memory (counting by units @var{u}) to display.
6995 @c This really is **decimal**; unaffected by 'set radix' as of GDB
6998 @item @var{f}, the display format
6999 The display format is one of the formats used by @code{print}
7000 (@samp{x}, @samp{d}, @samp{u}, @samp{o}, @samp{t}, @samp{a}, @samp{c},
7001 @samp{f}, @samp{s}), and in addition @samp{i} (for machine instructions).
7002 The default is @samp{x} (hexadecimal) initially. The default changes
7003 each time you use either @code{x} or @code{print}.
7005 @item @var{u}, the unit size
7006 The unit size is any of
7012 Halfwords (two bytes).
7014 Words (four bytes). This is the initial default.
7016 Giant words (eight bytes).
7019 Each time you specify a unit size with @code{x}, that size becomes the
7020 default unit the next time you use @code{x}. (For the @samp{s} and
7021 @samp{i} formats, the unit size is ignored and is normally not written.)
7023 @item @var{addr}, starting display address
7024 @var{addr} is the address where you want @value{GDBN} to begin displaying
7025 memory. The expression need not have a pointer value (though it may);
7026 it is always interpreted as an integer address of a byte of memory.
7027 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
7028 @var{addr} is usually just after the last address examined---but several
7029 other commands also set the default address: @code{info breakpoints} (to
7030 the address of the last breakpoint listed), @code{info line} (to the
7031 starting address of a line), and @code{print} (if you use it to display
7032 a value from memory).
7035 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
7036 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
7037 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
7038 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
7039 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
7041 Since the letters indicating unit sizes are all distinct from the
7042 letters specifying output formats, you do not have to remember whether
7043 unit size or format comes first; either order works. The output
7044 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
7045 (However, the count @var{n} must come first; @samp{wx4} does not work.)
7047 Even though the unit size @var{u} is ignored for the formats @samp{s}
7048 and @samp{i}, you might still want to use a count @var{n}; for example,
7049 @samp{3i} specifies that you want to see three machine instructions,
7050 including any operands. For convenience, especially when used with
7051 the @code{display} command, the @samp{i} format also prints branch delay
7052 slot instructions, if any, beyond the count specified, which immediately
7053 follow the last instruction that is within the count. The command
7054 @code{disassemble} gives an alternative way of inspecting machine
7055 instructions; see @ref{Machine Code,,Source and Machine Code}.
7057 All the defaults for the arguments to @code{x} are designed to make it
7058 easy to continue scanning memory with minimal specifications each time
7059 you use @code{x}. For example, after you have inspected three machine
7060 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
7061 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
7062 the repeat count @var{n} is used again; the other arguments default as
7063 for successive uses of @code{x}.
7065 @cindex @code{$_}, @code{$__}, and value history
7066 The addresses and contents printed by the @code{x} command are not saved
7067 in the value history because there is often too much of them and they
7068 would get in the way. Instead, @value{GDBN} makes these values available for
7069 subsequent use in expressions as values of the convenience variables
7070 @code{$_} and @code{$__}. After an @code{x} command, the last address
7071 examined is available for use in expressions in the convenience variable
7072 @code{$_}. The contents of that address, as examined, are available in
7073 the convenience variable @code{$__}.
7075 If the @code{x} command has a repeat count, the address and contents saved
7076 are from the last memory unit printed; this is not the same as the last
7077 address printed if several units were printed on the last line of output.
7079 @cindex remote memory comparison
7080 @cindex verify remote memory image
7081 When you are debugging a program running on a remote target machine
7082 (@pxref{Remote Debugging}), you may wish to verify the program's image in the
7083 remote machine's memory against the executable file you downloaded to
7084 the target. The @code{compare-sections} command is provided for such
7088 @kindex compare-sections
7089 @item compare-sections @r{[}@var{section-name}@r{]}
7090 Compare the data of a loadable section @var{section-name} in the
7091 executable file of the program being debugged with the same section in
7092 the remote machine's memory, and report any mismatches. With no
7093 arguments, compares all loadable sections. This command's
7094 availability depends on the target's support for the @code{"qCRC"}
7099 @section Automatic Display
7100 @cindex automatic display
7101 @cindex display of expressions
7103 If you find that you want to print the value of an expression frequently
7104 (to see how it changes), you might want to add it to the @dfn{automatic
7105 display list} so that @value{GDBN} prints its value each time your program stops.
7106 Each expression added to the list is given a number to identify it;
7107 to remove an expression from the list, you specify that number.
7108 The automatic display looks like this:
7112 3: bar[5] = (struct hack *) 0x3804
7116 This display shows item numbers, expressions and their current values. As with
7117 displays you request manually using @code{x} or @code{print}, you can
7118 specify the output format you prefer; in fact, @code{display} decides
7119 whether to use @code{print} or @code{x} depending your format
7120 specification---it uses @code{x} if you specify either the @samp{i}
7121 or @samp{s} format, or a unit size; otherwise it uses @code{print}.
7125 @item display @var{expr}
7126 Add the expression @var{expr} to the list of expressions to display
7127 each time your program stops. @xref{Expressions, ,Expressions}.
7129 @code{display} does not repeat if you press @key{RET} again after using it.
7131 @item display/@var{fmt} @var{expr}
7132 For @var{fmt} specifying only a display format and not a size or
7133 count, add the expression @var{expr} to the auto-display list but
7134 arrange to display it each time in the specified format @var{fmt}.
7135 @xref{Output Formats,,Output Formats}.
7137 @item display/@var{fmt} @var{addr}
7138 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
7139 number of units, add the expression @var{addr} as a memory address to
7140 be examined each time your program stops. Examining means in effect
7141 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining Memory}.
7144 For example, @samp{display/i $pc} can be helpful, to see the machine
7145 instruction about to be executed each time execution stops (@samp{$pc}
7146 is a common name for the program counter; @pxref{Registers, ,Registers}).
7149 @kindex delete display
7151 @item undisplay @var{dnums}@dots{}
7152 @itemx delete display @var{dnums}@dots{}
7153 Remove item numbers @var{dnums} from the list of expressions to display.
7155 @code{undisplay} does not repeat if you press @key{RET} after using it.
7156 (Otherwise you would just get the error @samp{No display number @dots{}}.)
7158 @kindex disable display
7159 @item disable display @var{dnums}@dots{}
7160 Disable the display of item numbers @var{dnums}. A disabled display
7161 item is not printed automatically, but is not forgotten. It may be
7162 enabled again later.
7164 @kindex enable display
7165 @item enable display @var{dnums}@dots{}
7166 Enable display of item numbers @var{dnums}. It becomes effective once
7167 again in auto display of its expression, until you specify otherwise.
7170 Display the current values of the expressions on the list, just as is
7171 done when your program stops.
7173 @kindex info display
7175 Print the list of expressions previously set up to display
7176 automatically, each one with its item number, but without showing the
7177 values. This includes disabled expressions, which are marked as such.
7178 It also includes expressions which would not be displayed right now
7179 because they refer to automatic variables not currently available.
7182 @cindex display disabled out of scope
7183 If a display expression refers to local variables, then it does not make
7184 sense outside the lexical context for which it was set up. Such an
7185 expression is disabled when execution enters a context where one of its
7186 variables is not defined. For example, if you give the command
7187 @code{display last_char} while inside a function with an argument
7188 @code{last_char}, @value{GDBN} displays this argument while your program
7189 continues to stop inside that function. When it stops elsewhere---where
7190 there is no variable @code{last_char}---the display is disabled
7191 automatically. The next time your program stops where @code{last_char}
7192 is meaningful, you can enable the display expression once again.
7194 @node Print Settings
7195 @section Print Settings
7197 @cindex format options
7198 @cindex print settings
7199 @value{GDBN} provides the following ways to control how arrays, structures,
7200 and symbols are printed.
7203 These settings are useful for debugging programs in any language:
7207 @item set print address
7208 @itemx set print address on
7209 @cindex print/don't print memory addresses
7210 @value{GDBN} prints memory addresses showing the location of stack
7211 traces, structure values, pointer values, breakpoints, and so forth,
7212 even when it also displays the contents of those addresses. The default
7213 is @code{on}. For example, this is what a stack frame display looks like with
7214 @code{set print address on}:
7219 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
7221 530 if (lquote != def_lquote)
7225 @item set print address off
7226 Do not print addresses when displaying their contents. For example,
7227 this is the same stack frame displayed with @code{set print address off}:
7231 (@value{GDBP}) set print addr off
7233 #0 set_quotes (lq="<<", rq=">>") at input.c:530
7234 530 if (lquote != def_lquote)
7238 You can use @samp{set print address off} to eliminate all machine
7239 dependent displays from the @value{GDBN} interface. For example, with
7240 @code{print address off}, you should get the same text for backtraces on
7241 all machines---whether or not they involve pointer arguments.
7244 @item show print address
7245 Show whether or not addresses are to be printed.
7248 When @value{GDBN} prints a symbolic address, it normally prints the
7249 closest earlier symbol plus an offset. If that symbol does not uniquely
7250 identify the address (for example, it is a name whose scope is a single
7251 source file), you may need to clarify. One way to do this is with
7252 @code{info line}, for example @samp{info line *0x4537}. Alternately,
7253 you can set @value{GDBN} to print the source file and line number when
7254 it prints a symbolic address:
7257 @item set print symbol-filename on
7258 @cindex source file and line of a symbol
7259 @cindex symbol, source file and line
7260 Tell @value{GDBN} to print the source file name and line number of a
7261 symbol in the symbolic form of an address.
7263 @item set print symbol-filename off
7264 Do not print source file name and line number of a symbol. This is the
7267 @item show print symbol-filename
7268 Show whether or not @value{GDBN} will print the source file name and
7269 line number of a symbol in the symbolic form of an address.
7272 Another situation where it is helpful to show symbol filenames and line
7273 numbers is when disassembling code; @value{GDBN} shows you the line
7274 number and source file that corresponds to each instruction.
7276 Also, you may wish to see the symbolic form only if the address being
7277 printed is reasonably close to the closest earlier symbol:
7280 @item set print max-symbolic-offset @var{max-offset}
7281 @cindex maximum value for offset of closest symbol
7282 Tell @value{GDBN} to only display the symbolic form of an address if the
7283 offset between the closest earlier symbol and the address is less than
7284 @var{max-offset}. The default is 0, which tells @value{GDBN}
7285 to always print the symbolic form of an address if any symbol precedes it.
7287 @item show print max-symbolic-offset
7288 Ask how large the maximum offset is that @value{GDBN} prints in a
7292 @cindex wild pointer, interpreting
7293 @cindex pointer, finding referent
7294 If you have a pointer and you are not sure where it points, try
7295 @samp{set print symbol-filename on}. Then you can determine the name
7296 and source file location of the variable where it points, using
7297 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
7298 For example, here @value{GDBN} shows that a variable @code{ptt} points
7299 at another variable @code{t}, defined in @file{hi2.c}:
7302 (@value{GDBP}) set print symbol-filename on
7303 (@value{GDBP}) p/a ptt
7304 $4 = 0xe008 <t in hi2.c>
7308 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
7309 does not show the symbol name and filename of the referent, even with
7310 the appropriate @code{set print} options turned on.
7313 Other settings control how different kinds of objects are printed:
7316 @item set print array
7317 @itemx set print array on
7318 @cindex pretty print arrays
7319 Pretty print arrays. This format is more convenient to read,
7320 but uses more space. The default is off.
7322 @item set print array off
7323 Return to compressed format for arrays.
7325 @item show print array
7326 Show whether compressed or pretty format is selected for displaying
7329 @cindex print array indexes
7330 @item set print array-indexes
7331 @itemx set print array-indexes on
7332 Print the index of each element when displaying arrays. May be more
7333 convenient to locate a given element in the array or quickly find the
7334 index of a given element in that printed array. The default is off.
7336 @item set print array-indexes off
7337 Stop printing element indexes when displaying arrays.
7339 @item show print array-indexes
7340 Show whether the index of each element is printed when displaying
7343 @item set print elements @var{number-of-elements}
7344 @cindex number of array elements to print
7345 @cindex limit on number of printed array elements
7346 Set a limit on how many elements of an array @value{GDBN} will print.
7347 If @value{GDBN} is printing a large array, it stops printing after it has
7348 printed the number of elements set by the @code{set print elements} command.
7349 This limit also applies to the display of strings.
7350 When @value{GDBN} starts, this limit is set to 200.
7351 Setting @var{number-of-elements} to zero means that the printing is unlimited.
7353 @item show print elements
7354 Display the number of elements of a large array that @value{GDBN} will print.
7355 If the number is 0, then the printing is unlimited.
7357 @item set print frame-arguments @var{value}
7358 @kindex set print frame-arguments
7359 @cindex printing frame argument values
7360 @cindex print all frame argument values
7361 @cindex print frame argument values for scalars only
7362 @cindex do not print frame argument values
7363 This command allows to control how the values of arguments are printed
7364 when the debugger prints a frame (@pxref{Frames}). The possible
7369 The values of all arguments are printed.
7372 Print the value of an argument only if it is a scalar. The value of more
7373 complex arguments such as arrays, structures, unions, etc, is replaced
7374 by @code{@dots{}}. This is the default. Here is an example where
7375 only scalar arguments are shown:
7378 #1 0x08048361 in call_me (i=3, s=@dots{}, ss=0xbf8d508c, u=@dots{}, e=green)
7383 None of the argument values are printed. Instead, the value of each argument
7384 is replaced by @code{@dots{}}. In this case, the example above now becomes:
7387 #1 0x08048361 in call_me (i=@dots{}, s=@dots{}, ss=@dots{}, u=@dots{}, e=@dots{})
7392 By default, only scalar arguments are printed. This command can be used
7393 to configure the debugger to print the value of all arguments, regardless
7394 of their type. However, it is often advantageous to not print the value
7395 of more complex parameters. For instance, it reduces the amount of
7396 information printed in each frame, making the backtrace more readable.
7397 Also, it improves performance when displaying Ada frames, because
7398 the computation of large arguments can sometimes be CPU-intensive,
7399 especially in large applications. Setting @code{print frame-arguments}
7400 to @code{scalars} (the default) or @code{none} avoids this computation,
7401 thus speeding up the display of each Ada frame.
7403 @item show print frame-arguments
7404 Show how the value of arguments should be displayed when printing a frame.
7406 @item set print repeats
7407 @cindex repeated array elements
7408 Set the threshold for suppressing display of repeated array
7409 elements. When the number of consecutive identical elements of an
7410 array exceeds the threshold, @value{GDBN} prints the string
7411 @code{"<repeats @var{n} times>"}, where @var{n} is the number of
7412 identical repetitions, instead of displaying the identical elements
7413 themselves. Setting the threshold to zero will cause all elements to
7414 be individually printed. The default threshold is 10.
7416 @item show print repeats
7417 Display the current threshold for printing repeated identical
7420 @item set print null-stop
7421 @cindex @sc{null} elements in arrays
7422 Cause @value{GDBN} to stop printing the characters of an array when the first
7423 @sc{null} is encountered. This is useful when large arrays actually
7424 contain only short strings.
7427 @item show print null-stop
7428 Show whether @value{GDBN} stops printing an array on the first
7429 @sc{null} character.
7431 @item set print pretty on
7432 @cindex print structures in indented form
7433 @cindex indentation in structure display
7434 Cause @value{GDBN} to print structures in an indented format with one member
7435 per line, like this:
7450 @item set print pretty off
7451 Cause @value{GDBN} to print structures in a compact format, like this:
7455 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
7456 meat = 0x54 "Pork"@}
7461 This is the default format.
7463 @item show print pretty
7464 Show which format @value{GDBN} is using to print structures.
7466 @item set print sevenbit-strings on
7467 @cindex eight-bit characters in strings
7468 @cindex octal escapes in strings
7469 Print using only seven-bit characters; if this option is set,
7470 @value{GDBN} displays any eight-bit characters (in strings or
7471 character values) using the notation @code{\}@var{nnn}. This setting is
7472 best if you are working in English (@sc{ascii}) and you use the
7473 high-order bit of characters as a marker or ``meta'' bit.
7475 @item set print sevenbit-strings off
7476 Print full eight-bit characters. This allows the use of more
7477 international character sets, and is the default.
7479 @item show print sevenbit-strings
7480 Show whether or not @value{GDBN} is printing only seven-bit characters.
7482 @item set print union on
7483 @cindex unions in structures, printing
7484 Tell @value{GDBN} to print unions which are contained in structures
7485 and other unions. This is the default setting.
7487 @item set print union off
7488 Tell @value{GDBN} not to print unions which are contained in
7489 structures and other unions. @value{GDBN} will print @code{"@{...@}"}
7492 @item show print union
7493 Ask @value{GDBN} whether or not it will print unions which are contained in
7494 structures and other unions.
7496 For example, given the declarations
7499 typedef enum @{Tree, Bug@} Species;
7500 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
7501 typedef enum @{Caterpillar, Cocoon, Butterfly@}
7512 struct thing foo = @{Tree, @{Acorn@}@};
7516 with @code{set print union on} in effect @samp{p foo} would print
7519 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
7523 and with @code{set print union off} in effect it would print
7526 $1 = @{it = Tree, form = @{...@}@}
7530 @code{set print union} affects programs written in C-like languages
7536 These settings are of interest when debugging C@t{++} programs:
7539 @cindex demangling C@t{++} names
7540 @item set print demangle
7541 @itemx set print demangle on
7542 Print C@t{++} names in their source form rather than in the encoded
7543 (``mangled'') form passed to the assembler and linker for type-safe
7544 linkage. The default is on.
7546 @item show print demangle
7547 Show whether C@t{++} names are printed in mangled or demangled form.
7549 @item set print asm-demangle
7550 @itemx set print asm-demangle on
7551 Print C@t{++} names in their source form rather than their mangled form, even
7552 in assembler code printouts such as instruction disassemblies.
7555 @item show print asm-demangle
7556 Show whether C@t{++} names in assembly listings are printed in mangled
7559 @cindex C@t{++} symbol decoding style
7560 @cindex symbol decoding style, C@t{++}
7561 @kindex set demangle-style
7562 @item set demangle-style @var{style}
7563 Choose among several encoding schemes used by different compilers to
7564 represent C@t{++} names. The choices for @var{style} are currently:
7568 Allow @value{GDBN} to choose a decoding style by inspecting your program.
7571 Decode based on the @sc{gnu} C@t{++} compiler (@code{g++}) encoding algorithm.
7572 This is the default.
7575 Decode based on the HP ANSI C@t{++} (@code{aCC}) encoding algorithm.
7578 Decode based on the Lucid C@t{++} compiler (@code{lcc}) encoding algorithm.
7581 Decode using the algorithm in the @cite{C@t{++} Annotated Reference Manual}.
7582 @strong{Warning:} this setting alone is not sufficient to allow
7583 debugging @code{cfront}-generated executables. @value{GDBN} would
7584 require further enhancement to permit that.
7587 If you omit @var{style}, you will see a list of possible formats.
7589 @item show demangle-style
7590 Display the encoding style currently in use for decoding C@t{++} symbols.
7592 @item set print object
7593 @itemx set print object on
7594 @cindex derived type of an object, printing
7595 @cindex display derived types
7596 When displaying a pointer to an object, identify the @emph{actual}
7597 (derived) type of the object rather than the @emph{declared} type, using
7598 the virtual function table.
7600 @item set print object off
7601 Display only the declared type of objects, without reference to the
7602 virtual function table. This is the default setting.
7604 @item show print object
7605 Show whether actual, or declared, object types are displayed.
7607 @item set print static-members
7608 @itemx set print static-members on
7609 @cindex static members of C@t{++} objects
7610 Print static members when displaying a C@t{++} object. The default is on.
7612 @item set print static-members off
7613 Do not print static members when displaying a C@t{++} object.
7615 @item show print static-members
7616 Show whether C@t{++} static members are printed or not.
7618 @item set print pascal_static-members
7619 @itemx set print pascal_static-members on
7620 @cindex static members of Pascal objects
7621 @cindex Pascal objects, static members display
7622 Print static members when displaying a Pascal object. The default is on.
7624 @item set print pascal_static-members off
7625 Do not print static members when displaying a Pascal object.
7627 @item show print pascal_static-members
7628 Show whether Pascal static members are printed or not.
7630 @c These don't work with HP ANSI C++ yet.
7631 @item set print vtbl
7632 @itemx set print vtbl on
7633 @cindex pretty print C@t{++} virtual function tables
7634 @cindex virtual functions (C@t{++}) display
7635 @cindex VTBL display
7636 Pretty print C@t{++} virtual function tables. The default is off.
7637 (The @code{vtbl} commands do not work on programs compiled with the HP
7638 ANSI C@t{++} compiler (@code{aCC}).)
7640 @item set print vtbl off
7641 Do not pretty print C@t{++} virtual function tables.
7643 @item show print vtbl
7644 Show whether C@t{++} virtual function tables are pretty printed, or not.
7648 @section Value History
7650 @cindex value history
7651 @cindex history of values printed by @value{GDBN}
7652 Values printed by the @code{print} command are saved in the @value{GDBN}
7653 @dfn{value history}. This allows you to refer to them in other expressions.
7654 Values are kept until the symbol table is re-read or discarded
7655 (for example with the @code{file} or @code{symbol-file} commands).
7656 When the symbol table changes, the value history is discarded,
7657 since the values may contain pointers back to the types defined in the
7662 @cindex history number
7663 The values printed are given @dfn{history numbers} by which you can
7664 refer to them. These are successive integers starting with one.
7665 @code{print} shows you the history number assigned to a value by
7666 printing @samp{$@var{num} = } before the value; here @var{num} is the
7669 To refer to any previous value, use @samp{$} followed by the value's
7670 history number. The way @code{print} labels its output is designed to
7671 remind you of this. Just @code{$} refers to the most recent value in
7672 the history, and @code{$$} refers to the value before that.
7673 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
7674 is the value just prior to @code{$$}, @code{$$1} is equivalent to
7675 @code{$$}, and @code{$$0} is equivalent to @code{$}.
7677 For example, suppose you have just printed a pointer to a structure and
7678 want to see the contents of the structure. It suffices to type
7684 If you have a chain of structures where the component @code{next} points
7685 to the next one, you can print the contents of the next one with this:
7692 You can print successive links in the chain by repeating this
7693 command---which you can do by just typing @key{RET}.
7695 Note that the history records values, not expressions. If the value of
7696 @code{x} is 4 and you type these commands:
7704 then the value recorded in the value history by the @code{print} command
7705 remains 4 even though the value of @code{x} has changed.
7710 Print the last ten values in the value history, with their item numbers.
7711 This is like @samp{p@ $$9} repeated ten times, except that @code{show
7712 values} does not change the history.
7714 @item show values @var{n}
7715 Print ten history values centered on history item number @var{n}.
7718 Print ten history values just after the values last printed. If no more
7719 values are available, @code{show values +} produces no display.
7722 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
7723 same effect as @samp{show values +}.
7725 @node Convenience Vars
7726 @section Convenience Variables
7728 @cindex convenience variables
7729 @cindex user-defined variables
7730 @value{GDBN} provides @dfn{convenience variables} that you can use within
7731 @value{GDBN} to hold on to a value and refer to it later. These variables
7732 exist entirely within @value{GDBN}; they are not part of your program, and
7733 setting a convenience variable has no direct effect on further execution
7734 of your program. That is why you can use them freely.
7736 Convenience variables are prefixed with @samp{$}. Any name preceded by
7737 @samp{$} can be used for a convenience variable, unless it is one of
7738 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
7739 (Value history references, in contrast, are @emph{numbers} preceded
7740 by @samp{$}. @xref{Value History, ,Value History}.)
7742 You can save a value in a convenience variable with an assignment
7743 expression, just as you would set a variable in your program.
7747 set $foo = *object_ptr
7751 would save in @code{$foo} the value contained in the object pointed to by
7754 Using a convenience variable for the first time creates it, but its
7755 value is @code{void} until you assign a new value. You can alter the
7756 value with another assignment at any time.
7758 Convenience variables have no fixed types. You can assign a convenience
7759 variable any type of value, including structures and arrays, even if
7760 that variable already has a value of a different type. The convenience
7761 variable, when used as an expression, has the type of its current value.
7764 @kindex show convenience
7765 @cindex show all user variables
7766 @item show convenience
7767 Print a list of convenience variables used so far, and their values.
7768 Abbreviated @code{show conv}.
7770 @kindex init-if-undefined
7771 @cindex convenience variables, initializing
7772 @item init-if-undefined $@var{variable} = @var{expression}
7773 Set a convenience variable if it has not already been set. This is useful
7774 for user-defined commands that keep some state. It is similar, in concept,
7775 to using local static variables with initializers in C (except that
7776 convenience variables are global). It can also be used to allow users to
7777 override default values used in a command script.
7779 If the variable is already defined then the expression is not evaluated so
7780 any side-effects do not occur.
7783 One of the ways to use a convenience variable is as a counter to be
7784 incremented or a pointer to be advanced. For example, to print
7785 a field from successive elements of an array of structures:
7789 print bar[$i++]->contents
7793 Repeat that command by typing @key{RET}.
7795 Some convenience variables are created automatically by @value{GDBN} and given
7796 values likely to be useful.
7799 @vindex $_@r{, convenience variable}
7801 The variable @code{$_} is automatically set by the @code{x} command to
7802 the last address examined (@pxref{Memory, ,Examining Memory}). Other
7803 commands which provide a default address for @code{x} to examine also
7804 set @code{$_} to that address; these commands include @code{info line}
7805 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
7806 except when set by the @code{x} command, in which case it is a pointer
7807 to the type of @code{$__}.
7809 @vindex $__@r{, convenience variable}
7811 The variable @code{$__} is automatically set by the @code{x} command
7812 to the value found in the last address examined. Its type is chosen
7813 to match the format in which the data was printed.
7816 @vindex $_exitcode@r{, convenience variable}
7817 The variable @code{$_exitcode} is automatically set to the exit code when
7818 the program being debugged terminates.
7821 @vindex $_siginfo@r{, convenience variable}
7822 The variable @code{$_siginfo} is bound to extra signal information
7823 inspection (@pxref{extra signal information}).
7826 On HP-UX systems, if you refer to a function or variable name that
7827 begins with a dollar sign, @value{GDBN} searches for a user or system
7828 name first, before it searches for a convenience variable.
7830 @cindex convenience functions
7831 @value{GDBN} also supplies some @dfn{convenience functions}. These
7832 have a syntax similar to convenience variables. A convenience
7833 function can be used in an expression just like an ordinary function;
7834 however, a convenience function is implemented internally to
7839 @kindex help function
7840 @cindex show all convenience functions
7841 Print a list of all convenience functions.
7848 You can refer to machine register contents, in expressions, as variables
7849 with names starting with @samp{$}. The names of registers are different
7850 for each machine; use @code{info registers} to see the names used on
7854 @kindex info registers
7855 @item info registers
7856 Print the names and values of all registers except floating-point
7857 and vector registers (in the selected stack frame).
7859 @kindex info all-registers
7860 @cindex floating point registers
7861 @item info all-registers
7862 Print the names and values of all registers, including floating-point
7863 and vector registers (in the selected stack frame).
7865 @item info registers @var{regname} @dots{}
7866 Print the @dfn{relativized} value of each specified register @var{regname}.
7867 As discussed in detail below, register values are normally relative to
7868 the selected stack frame. @var{regname} may be any register name valid on
7869 the machine you are using, with or without the initial @samp{$}.
7872 @cindex stack pointer register
7873 @cindex program counter register
7874 @cindex process status register
7875 @cindex frame pointer register
7876 @cindex standard registers
7877 @value{GDBN} has four ``standard'' register names that are available (in
7878 expressions) on most machines---whenever they do not conflict with an
7879 architecture's canonical mnemonics for registers. The register names
7880 @code{$pc} and @code{$sp} are used for the program counter register and
7881 the stack pointer. @code{$fp} is used for a register that contains a
7882 pointer to the current stack frame, and @code{$ps} is used for a
7883 register that contains the processor status. For example,
7884 you could print the program counter in hex with
7891 or print the instruction to be executed next with
7898 or add four to the stack pointer@footnote{This is a way of removing
7899 one word from the stack, on machines where stacks grow downward in
7900 memory (most machines, nowadays). This assumes that the innermost
7901 stack frame is selected; setting @code{$sp} is not allowed when other
7902 stack frames are selected. To pop entire frames off the stack,
7903 regardless of machine architecture, use @code{return};
7904 see @ref{Returning, ,Returning from a Function}.} with
7910 Whenever possible, these four standard register names are available on
7911 your machine even though the machine has different canonical mnemonics,
7912 so long as there is no conflict. The @code{info registers} command
7913 shows the canonical names. For example, on the SPARC, @code{info
7914 registers} displays the processor status register as @code{$psr} but you
7915 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
7916 is an alias for the @sc{eflags} register.
7918 @value{GDBN} always considers the contents of an ordinary register as an
7919 integer when the register is examined in this way. Some machines have
7920 special registers which can hold nothing but floating point; these
7921 registers are considered to have floating point values. There is no way
7922 to refer to the contents of an ordinary register as floating point value
7923 (although you can @emph{print} it as a floating point value with
7924 @samp{print/f $@var{regname}}).
7926 Some registers have distinct ``raw'' and ``virtual'' data formats. This
7927 means that the data format in which the register contents are saved by
7928 the operating system is not the same one that your program normally
7929 sees. For example, the registers of the 68881 floating point
7930 coprocessor are always saved in ``extended'' (raw) format, but all C
7931 programs expect to work with ``double'' (virtual) format. In such
7932 cases, @value{GDBN} normally works with the virtual format only (the format
7933 that makes sense for your program), but the @code{info registers} command
7934 prints the data in both formats.
7936 @cindex SSE registers (x86)
7937 @cindex MMX registers (x86)
7938 Some machines have special registers whose contents can be interpreted
7939 in several different ways. For example, modern x86-based machines
7940 have SSE and MMX registers that can hold several values packed
7941 together in several different formats. @value{GDBN} refers to such
7942 registers in @code{struct} notation:
7945 (@value{GDBP}) print $xmm1
7947 v4_float = @{0, 3.43859137e-038, 1.54142831e-044, 1.821688e-044@},
7948 v2_double = @{9.92129282474342e-303, 2.7585945287983262e-313@},
7949 v16_int8 = "\000\000\000\000\3706;\001\v\000\000\000\r\000\000",
7950 v8_int16 = @{0, 0, 14072, 315, 11, 0, 13, 0@},
7951 v4_int32 = @{0, 20657912, 11, 13@},
7952 v2_int64 = @{88725056443645952, 55834574859@},
7953 uint128 = 0x0000000d0000000b013b36f800000000
7958 To set values of such registers, you need to tell @value{GDBN} which
7959 view of the register you wish to change, as if you were assigning
7960 value to a @code{struct} member:
7963 (@value{GDBP}) set $xmm1.uint128 = 0x000000000000000000000000FFFFFFFF
7966 Normally, register values are relative to the selected stack frame
7967 (@pxref{Selection, ,Selecting a Frame}). This means that you get the
7968 value that the register would contain if all stack frames farther in
7969 were exited and their saved registers restored. In order to see the
7970 true contents of hardware registers, you must select the innermost
7971 frame (with @samp{frame 0}).
7973 However, @value{GDBN} must deduce where registers are saved, from the machine
7974 code generated by your compiler. If some registers are not saved, or if
7975 @value{GDBN} is unable to locate the saved registers, the selected stack
7976 frame makes no difference.
7978 @node Floating Point Hardware
7979 @section Floating Point Hardware
7980 @cindex floating point
7982 Depending on the configuration, @value{GDBN} may be able to give
7983 you more information about the status of the floating point hardware.
7988 Display hardware-dependent information about the floating
7989 point unit. The exact contents and layout vary depending on the
7990 floating point chip. Currently, @samp{info float} is supported on
7991 the ARM and x86 machines.
7995 @section Vector Unit
7998 Depending on the configuration, @value{GDBN} may be able to give you
7999 more information about the status of the vector unit.
8004 Display information about the vector unit. The exact contents and
8005 layout vary depending on the hardware.
8008 @node OS Information
8009 @section Operating System Auxiliary Information
8010 @cindex OS information
8012 @value{GDBN} provides interfaces to useful OS facilities that can help
8013 you debug your program.
8015 @cindex @code{ptrace} system call
8016 @cindex @code{struct user} contents
8017 When @value{GDBN} runs on a @dfn{Posix system} (such as GNU or Unix
8018 machines), it interfaces with the inferior via the @code{ptrace}
8019 system call. The operating system creates a special sata structure,
8020 called @code{struct user}, for this interface. You can use the
8021 command @code{info udot} to display the contents of this data
8027 Display the contents of the @code{struct user} maintained by the OS
8028 kernel for the program being debugged. @value{GDBN} displays the
8029 contents of @code{struct user} as a list of hex numbers, similar to
8030 the @code{examine} command.
8033 @cindex auxiliary vector
8034 @cindex vector, auxiliary
8035 Some operating systems supply an @dfn{auxiliary vector} to programs at
8036 startup. This is akin to the arguments and environment that you
8037 specify for a program, but contains a system-dependent variety of
8038 binary values that tell system libraries important details about the
8039 hardware, operating system, and process. Each value's purpose is
8040 identified by an integer tag; the meanings are well-known but system-specific.
8041 Depending on the configuration and operating system facilities,
8042 @value{GDBN} may be able to show you this information. For remote
8043 targets, this functionality may further depend on the remote stub's
8044 support of the @samp{qXfer:auxv:read} packet, see
8045 @ref{qXfer auxiliary vector read}.
8050 Display the auxiliary vector of the inferior, which can be either a
8051 live process or a core dump file. @value{GDBN} prints each tag value
8052 numerically, and also shows names and text descriptions for recognized
8053 tags. Some values in the vector are numbers, some bit masks, and some
8054 pointers to strings or other data. @value{GDBN} displays each value in the
8055 most appropriate form for a recognized tag, and in hexadecimal for
8056 an unrecognized tag.
8059 On some targets, @value{GDBN} can access operating-system-specific information
8060 and display it to user, without interpretation. For remote targets,
8061 this functionality depends on the remote stub's support of the
8062 @samp{qXfer:osdata:read} packet, see @ref{qXfer osdata read}.
8065 @kindex info os processes
8066 @item info os processes
8067 Display the list of processes on the target. For each process,
8068 @value{GDBN} prints the process identifier, the name of the user, and
8069 the command corresponding to the process.
8072 @node Memory Region Attributes
8073 @section Memory Region Attributes
8074 @cindex memory region attributes
8076 @dfn{Memory region attributes} allow you to describe special handling
8077 required by regions of your target's memory. @value{GDBN} uses
8078 attributes to determine whether to allow certain types of memory
8079 accesses; whether to use specific width accesses; and whether to cache
8080 target memory. By default the description of memory regions is
8081 fetched from the target (if the current target supports this), but the
8082 user can override the fetched regions.
8084 Defined memory regions can be individually enabled and disabled. When a
8085 memory region is disabled, @value{GDBN} uses the default attributes when
8086 accessing memory in that region. Similarly, if no memory regions have
8087 been defined, @value{GDBN} uses the default attributes when accessing
8090 When a memory region is defined, it is given a number to identify it;
8091 to enable, disable, or remove a memory region, you specify that number.
8095 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
8096 Define a memory region bounded by @var{lower} and @var{upper} with
8097 attributes @var{attributes}@dots{}, and add it to the list of regions
8098 monitored by @value{GDBN}. Note that @var{upper} == 0 is a special
8099 case: it is treated as the target's maximum memory address.
8100 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
8103 Discard any user changes to the memory regions and use target-supplied
8104 regions, if available, or no regions if the target does not support.
8107 @item delete mem @var{nums}@dots{}
8108 Remove memory regions @var{nums}@dots{} from the list of regions
8109 monitored by @value{GDBN}.
8112 @item disable mem @var{nums}@dots{}
8113 Disable monitoring of memory regions @var{nums}@dots{}.
8114 A disabled memory region is not forgotten.
8115 It may be enabled again later.
8118 @item enable mem @var{nums}@dots{}
8119 Enable monitoring of memory regions @var{nums}@dots{}.
8123 Print a table of all defined memory regions, with the following columns
8127 @item Memory Region Number
8128 @item Enabled or Disabled.
8129 Enabled memory regions are marked with @samp{y}.
8130 Disabled memory regions are marked with @samp{n}.
8133 The address defining the inclusive lower bound of the memory region.
8136 The address defining the exclusive upper bound of the memory region.
8139 The list of attributes set for this memory region.
8144 @subsection Attributes
8146 @subsubsection Memory Access Mode
8147 The access mode attributes set whether @value{GDBN} may make read or
8148 write accesses to a memory region.
8150 While these attributes prevent @value{GDBN} from performing invalid
8151 memory accesses, they do nothing to prevent the target system, I/O DMA,
8152 etc.@: from accessing memory.
8156 Memory is read only.
8158 Memory is write only.
8160 Memory is read/write. This is the default.
8163 @subsubsection Memory Access Size
8164 The access size attribute tells @value{GDBN} to use specific sized
8165 accesses in the memory region. Often memory mapped device registers
8166 require specific sized accesses. If no access size attribute is
8167 specified, @value{GDBN} may use accesses of any size.
8171 Use 8 bit memory accesses.
8173 Use 16 bit memory accesses.
8175 Use 32 bit memory accesses.
8177 Use 64 bit memory accesses.
8180 @c @subsubsection Hardware/Software Breakpoints
8181 @c The hardware/software breakpoint attributes set whether @value{GDBN}
8182 @c will use hardware or software breakpoints for the internal breakpoints
8183 @c used by the step, next, finish, until, etc. commands.
8187 @c Always use hardware breakpoints
8188 @c @item swbreak (default)
8191 @subsubsection Data Cache
8192 The data cache attributes set whether @value{GDBN} will cache target
8193 memory. While this generally improves performance by reducing debug
8194 protocol overhead, it can lead to incorrect results because @value{GDBN}
8195 does not know about volatile variables or memory mapped device
8200 Enable @value{GDBN} to cache target memory.
8202 Disable @value{GDBN} from caching target memory. This is the default.
8205 @subsection Memory Access Checking
8206 @value{GDBN} can be instructed to refuse accesses to memory that is
8207 not explicitly described. This can be useful if accessing such
8208 regions has undesired effects for a specific target, or to provide
8209 better error checking. The following commands control this behaviour.
8212 @kindex set mem inaccessible-by-default
8213 @item set mem inaccessible-by-default [on|off]
8214 If @code{on} is specified, make @value{GDBN} treat memory not
8215 explicitly described by the memory ranges as non-existent and refuse accesses
8216 to such memory. The checks are only performed if there's at least one
8217 memory range defined. If @code{off} is specified, make @value{GDBN}
8218 treat the memory not explicitly described by the memory ranges as RAM.
8219 The default value is @code{on}.
8220 @kindex show mem inaccessible-by-default
8221 @item show mem inaccessible-by-default
8222 Show the current handling of accesses to unknown memory.
8226 @c @subsubsection Memory Write Verification
8227 @c The memory write verification attributes set whether @value{GDBN}
8228 @c will re-reads data after each write to verify the write was successful.
8232 @c @item noverify (default)
8235 @node Dump/Restore Files
8236 @section Copy Between Memory and a File
8237 @cindex dump/restore files
8238 @cindex append data to a file
8239 @cindex dump data to a file
8240 @cindex restore data from a file
8242 You can use the commands @code{dump}, @code{append}, and
8243 @code{restore} to copy data between target memory and a file. The
8244 @code{dump} and @code{append} commands write data to a file, and the
8245 @code{restore} command reads data from a file back into the inferior's
8246 memory. Files may be in binary, Motorola S-record, Intel hex, or
8247 Tektronix Hex format; however, @value{GDBN} can only append to binary
8253 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
8254 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
8255 Dump the contents of memory from @var{start_addr} to @var{end_addr},
8256 or the value of @var{expr}, to @var{filename} in the given format.
8258 The @var{format} parameter may be any one of:
8265 Motorola S-record format.
8267 Tektronix Hex format.
8270 @value{GDBN} uses the same definitions of these formats as the
8271 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
8272 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
8276 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
8277 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
8278 Append the contents of memory from @var{start_addr} to @var{end_addr},
8279 or the value of @var{expr}, to the file @var{filename}, in raw binary form.
8280 (@value{GDBN} can only append data to files in raw binary form.)
8283 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
8284 Restore the contents of file @var{filename} into memory. The
8285 @code{restore} command can automatically recognize any known @sc{bfd}
8286 file format, except for raw binary. To restore a raw binary file you
8287 must specify the optional keyword @code{binary} after the filename.
8289 If @var{bias} is non-zero, its value will be added to the addresses
8290 contained in the file. Binary files always start at address zero, so
8291 they will be restored at address @var{bias}. Other bfd files have
8292 a built-in location; they will be restored at offset @var{bias}
8295 If @var{start} and/or @var{end} are non-zero, then only data between
8296 file offset @var{start} and file offset @var{end} will be restored.
8297 These offsets are relative to the addresses in the file, before
8298 the @var{bias} argument is applied.
8302 @node Core File Generation
8303 @section How to Produce a Core File from Your Program
8304 @cindex dump core from inferior
8306 A @dfn{core file} or @dfn{core dump} is a file that records the memory
8307 image of a running process and its process status (register values
8308 etc.). Its primary use is post-mortem debugging of a program that
8309 crashed while it ran outside a debugger. A program that crashes
8310 automatically produces a core file, unless this feature is disabled by
8311 the user. @xref{Files}, for information on invoking @value{GDBN} in
8312 the post-mortem debugging mode.
8314 Occasionally, you may wish to produce a core file of the program you
8315 are debugging in order to preserve a snapshot of its state.
8316 @value{GDBN} has a special command for that.
8320 @kindex generate-core-file
8321 @item generate-core-file [@var{file}]
8322 @itemx gcore [@var{file}]
8323 Produce a core dump of the inferior process. The optional argument
8324 @var{file} specifies the file name where to put the core dump. If not
8325 specified, the file name defaults to @file{core.@var{pid}}, where
8326 @var{pid} is the inferior process ID.
8328 Note that this command is implemented only for some systems (as of
8329 this writing, @sc{gnu}/Linux, FreeBSD, Solaris, Unixware, and S390).
8332 @node Character Sets
8333 @section Character Sets
8334 @cindex character sets
8336 @cindex translating between character sets
8337 @cindex host character set
8338 @cindex target character set
8340 If the program you are debugging uses a different character set to
8341 represent characters and strings than the one @value{GDBN} uses itself,
8342 @value{GDBN} can automatically translate between the character sets for
8343 you. The character set @value{GDBN} uses we call the @dfn{host
8344 character set}; the one the inferior program uses we call the
8345 @dfn{target character set}.
8347 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
8348 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
8349 remote protocol (@pxref{Remote Debugging}) to debug a program
8350 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
8351 then the host character set is Latin-1, and the target character set is
8352 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
8353 target-charset EBCDIC-US}, then @value{GDBN} translates between
8354 @sc{ebcdic} and Latin 1 as you print character or string values, or use
8355 character and string literals in expressions.
8357 @value{GDBN} has no way to automatically recognize which character set
8358 the inferior program uses; you must tell it, using the @code{set
8359 target-charset} command, described below.
8361 Here are the commands for controlling @value{GDBN}'s character set
8365 @item set target-charset @var{charset}
8366 @kindex set target-charset
8367 Set the current target character set to @var{charset}. To display the
8368 list of supported target character sets, type
8369 @kbd{@w{set target-charset @key{TAB}@key{TAB}}}.
8371 @item set host-charset @var{charset}
8372 @kindex set host-charset
8373 Set the current host character set to @var{charset}.
8375 By default, @value{GDBN} uses a host character set appropriate to the
8376 system it is running on; you can override that default using the
8377 @code{set host-charset} command. On some systems, @value{GDBN} cannot
8378 automatically determine the appropriate host character set. In this
8379 case, @value{GDBN} uses @samp{UTF-8}.
8381 @value{GDBN} can only use certain character sets as its host character
8382 set. If you type @kbd{@w{set target-charset @key{TAB}@key{TAB}}},
8383 @value{GDBN} will list the host character sets it supports.
8385 @item set charset @var{charset}
8387 Set the current host and target character sets to @var{charset}. As
8388 above, if you type @kbd{@w{set charset @key{TAB}@key{TAB}}},
8389 @value{GDBN} will list the names of the character sets that can be used
8390 for both host and target.
8393 @kindex show charset
8394 Show the names of the current host and target character sets.
8396 @item show host-charset
8397 @kindex show host-charset
8398 Show the name of the current host character set.
8400 @item show target-charset
8401 @kindex show target-charset
8402 Show the name of the current target character set.
8404 @item set target-wide-charset @var{charset}
8405 @kindex set target-wide-charset
8406 Set the current target's wide character set to @var{charset}. This is
8407 the character set used by the target's @code{wchar_t} type. To
8408 display the list of supported wide character sets, type
8409 @kbd{@w{set target-wide-charset @key{TAB}@key{TAB}}}.
8411 @item show target-wide-charset
8412 @kindex show target-wide-charset
8413 Show the name of the current target's wide character set.
8416 Here is an example of @value{GDBN}'s character set support in action.
8417 Assume that the following source code has been placed in the file
8418 @file{charset-test.c}:
8424 = @{72, 101, 108, 108, 111, 44, 32, 119,
8425 111, 114, 108, 100, 33, 10, 0@};
8426 char ibm1047_hello[]
8427 = @{200, 133, 147, 147, 150, 107, 64, 166,
8428 150, 153, 147, 132, 90, 37, 0@};
8432 printf ("Hello, world!\n");
8436 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
8437 containing the string @samp{Hello, world!} followed by a newline,
8438 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
8440 We compile the program, and invoke the debugger on it:
8443 $ gcc -g charset-test.c -o charset-test
8444 $ gdb -nw charset-test
8445 GNU gdb 2001-12-19-cvs
8446 Copyright 2001 Free Software Foundation, Inc.
8451 We can use the @code{show charset} command to see what character sets
8452 @value{GDBN} is currently using to interpret and display characters and
8456 (@value{GDBP}) show charset
8457 The current host and target character set is `ISO-8859-1'.
8461 For the sake of printing this manual, let's use @sc{ascii} as our
8462 initial character set:
8464 (@value{GDBP}) set charset ASCII
8465 (@value{GDBP}) show charset
8466 The current host and target character set is `ASCII'.
8470 Let's assume that @sc{ascii} is indeed the correct character set for our
8471 host system --- in other words, let's assume that if @value{GDBN} prints
8472 characters using the @sc{ascii} character set, our terminal will display
8473 them properly. Since our current target character set is also
8474 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
8477 (@value{GDBP}) print ascii_hello
8478 $1 = 0x401698 "Hello, world!\n"
8479 (@value{GDBP}) print ascii_hello[0]
8484 @value{GDBN} uses the target character set for character and string
8485 literals you use in expressions:
8488 (@value{GDBP}) print '+'
8493 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
8496 @value{GDBN} relies on the user to tell it which character set the
8497 target program uses. If we print @code{ibm1047_hello} while our target
8498 character set is still @sc{ascii}, we get jibberish:
8501 (@value{GDBP}) print ibm1047_hello
8502 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
8503 (@value{GDBP}) print ibm1047_hello[0]
8508 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
8509 @value{GDBN} tells us the character sets it supports:
8512 (@value{GDBP}) set target-charset
8513 ASCII EBCDIC-US IBM1047 ISO-8859-1
8514 (@value{GDBP}) set target-charset
8517 We can select @sc{ibm1047} as our target character set, and examine the
8518 program's strings again. Now the @sc{ascii} string is wrong, but
8519 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
8520 target character set, @sc{ibm1047}, to the host character set,
8521 @sc{ascii}, and they display correctly:
8524 (@value{GDBP}) set target-charset IBM1047
8525 (@value{GDBP}) show charset
8526 The current host character set is `ASCII'.
8527 The current target character set is `IBM1047'.
8528 (@value{GDBP}) print ascii_hello
8529 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
8530 (@value{GDBP}) print ascii_hello[0]
8532 (@value{GDBP}) print ibm1047_hello
8533 $8 = 0x4016a8 "Hello, world!\n"
8534 (@value{GDBP}) print ibm1047_hello[0]
8539 As above, @value{GDBN} uses the target character set for character and
8540 string literals you use in expressions:
8543 (@value{GDBP}) print '+'
8548 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
8551 @node Caching Remote Data
8552 @section Caching Data of Remote Targets
8553 @cindex caching data of remote targets
8555 @value{GDBN} caches data exchanged between the debugger and a
8556 remote target (@pxref{Remote Debugging}). Such caching generally improves
8557 performance, because it reduces the overhead of the remote protocol by
8558 bundling memory reads and writes into large chunks. Unfortunately, simply
8559 caching everything would lead to incorrect results, since @value{GDBN}
8560 does not necessarily know anything about volatile values, memory-mapped I/O
8561 addresses, etc. Furthermore, in non-stop mode (@pxref{Non-Stop Mode})
8562 memory can be changed @emph{while} a gdb command is executing.
8563 Therefore, by default, @value{GDBN} only caches data
8564 known to be on the stack@footnote{In non-stop mode, it is moderately
8565 rare for a running thread to modify the stack of a stopped thread
8566 in a way that would interfere with a backtrace, and caching of
8567 stack reads provides a significant speed up of remote backtraces.}.
8568 Other regions of memory can be explicitly marked as
8569 cacheable; see @pxref{Memory Region Attributes}.
8572 @kindex set remotecache
8573 @item set remotecache on
8574 @itemx set remotecache off
8575 This option no longer does anything; it exists for compatibility
8578 @kindex show remotecache
8579 @item show remotecache
8580 Show the current state of the obsolete remotecache flag.
8582 @kindex set stack-cache
8583 @item set stack-cache on
8584 @itemx set stack-cache off
8585 Enable or disable caching of stack accesses. When @code{ON}, use
8586 caching. By default, this option is @code{ON}.
8588 @kindex show stack-cache
8589 @item show stack-cache
8590 Show the current state of data caching for memory accesses.
8593 @item info dcache @r{[}line@r{]}
8594 Print the information about the data cache performance. The
8595 information displayed includes the dcache width and depth, and for
8596 each cache line, its number, address, and how many times it was
8597 referenced. This command is useful for debugging the data cache
8600 If a line number is specified, the contents of that line will be
8604 @node Searching Memory
8605 @section Search Memory
8606 @cindex searching memory
8608 Memory can be searched for a particular sequence of bytes with the
8609 @code{find} command.
8613 @item find @r{[}/@var{sn}@r{]} @var{start_addr}, +@var{len}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
8614 @itemx find @r{[}/@var{sn}@r{]} @var{start_addr}, @var{end_addr}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
8615 Search memory for the sequence of bytes specified by @var{val1}, @var{val2},
8616 etc. The search begins at address @var{start_addr} and continues for either
8617 @var{len} bytes or through to @var{end_addr} inclusive.
8620 @var{s} and @var{n} are optional parameters.
8621 They may be specified in either order, apart or together.
8624 @item @var{s}, search query size
8625 The size of each search query value.
8631 halfwords (two bytes)
8635 giant words (eight bytes)
8638 All values are interpreted in the current language.
8639 This means, for example, that if the current source language is C/C@t{++}
8640 then searching for the string ``hello'' includes the trailing '\0'.
8642 If the value size is not specified, it is taken from the
8643 value's type in the current language.
8644 This is useful when one wants to specify the search
8645 pattern as a mixture of types.
8646 Note that this means, for example, that in the case of C-like languages
8647 a search for an untyped 0x42 will search for @samp{(int) 0x42}
8648 which is typically four bytes.
8650 @item @var{n}, maximum number of finds
8651 The maximum number of matches to print. The default is to print all finds.
8654 You can use strings as search values. Quote them with double-quotes
8656 The string value is copied into the search pattern byte by byte,
8657 regardless of the endianness of the target and the size specification.
8659 The address of each match found is printed as well as a count of the
8660 number of matches found.
8662 The address of the last value found is stored in convenience variable
8664 A count of the number of matches is stored in @samp{$numfound}.
8666 For example, if stopped at the @code{printf} in this function:
8672 static char hello[] = "hello-hello";
8673 static struct @{ char c; short s; int i; @}
8674 __attribute__ ((packed)) mixed
8675 = @{ 'c', 0x1234, 0x87654321 @};
8676 printf ("%s\n", hello);
8681 you get during debugging:
8684 (gdb) find &hello[0], +sizeof(hello), "hello"
8685 0x804956d <hello.1620+6>
8687 (gdb) find &hello[0], +sizeof(hello), 'h', 'e', 'l', 'l', 'o'
8688 0x8049567 <hello.1620>
8689 0x804956d <hello.1620+6>
8691 (gdb) find /b1 &hello[0], +sizeof(hello), 'h', 0x65, 'l'
8692 0x8049567 <hello.1620>
8694 (gdb) find &mixed, +sizeof(mixed), (char) 'c', (short) 0x1234, (int) 0x87654321
8695 0x8049560 <mixed.1625>
8697 (gdb) print $numfound
8700 $2 = (void *) 0x8049560
8703 @node Optimized Code
8704 @chapter Debugging Optimized Code
8705 @cindex optimized code, debugging
8706 @cindex debugging optimized code
8708 Almost all compilers support optimization. With optimization
8709 disabled, the compiler generates assembly code that corresponds
8710 directly to your source code, in a simplistic way. As the compiler
8711 applies more powerful optimizations, the generated assembly code
8712 diverges from your original source code. With help from debugging
8713 information generated by the compiler, @value{GDBN} can map from
8714 the running program back to constructs from your original source.
8716 @value{GDBN} is more accurate with optimization disabled. If you
8717 can recompile without optimization, it is easier to follow the
8718 progress of your program during debugging. But, there are many cases
8719 where you may need to debug an optimized version.
8721 When you debug a program compiled with @samp{-g -O}, remember that the
8722 optimizer has rearranged your code; the debugger shows you what is
8723 really there. Do not be too surprised when the execution path does not
8724 exactly match your source file! An extreme example: if you define a
8725 variable, but never use it, @value{GDBN} never sees that
8726 variable---because the compiler optimizes it out of existence.
8728 Some things do not work as well with @samp{-g -O} as with just
8729 @samp{-g}, particularly on machines with instruction scheduling. If in
8730 doubt, recompile with @samp{-g} alone, and if this fixes the problem,
8731 please report it to us as a bug (including a test case!).
8732 @xref{Variables}, for more information about debugging optimized code.
8735 * Inline Functions:: How @value{GDBN} presents inlining
8738 @node Inline Functions
8739 @section Inline Functions
8740 @cindex inline functions, debugging
8742 @dfn{Inlining} is an optimization that inserts a copy of the function
8743 body directly at each call site, instead of jumping to a shared
8744 routine. @value{GDBN} displays inlined functions just like
8745 non-inlined functions. They appear in backtraces. You can view their
8746 arguments and local variables, step into them with @code{step}, skip
8747 them with @code{next}, and escape from them with @code{finish}.
8748 You can check whether a function was inlined by using the
8749 @code{info frame} command.
8751 For @value{GDBN} to support inlined functions, the compiler must
8752 record information about inlining in the debug information ---
8753 @value{NGCC} using the @sc{dwarf 2} format does this, and several
8754 other compilers do also. @value{GDBN} only supports inlined functions
8755 when using @sc{dwarf 2}. Versions of @value{NGCC} before 4.1
8756 do not emit two required attributes (@samp{DW_AT_call_file} and
8757 @samp{DW_AT_call_line}); @value{GDBN} does not display inlined
8758 function calls with earlier versions of @value{NGCC}. It instead
8759 displays the arguments and local variables of inlined functions as
8760 local variables in the caller.
8762 The body of an inlined function is directly included at its call site;
8763 unlike a non-inlined function, there are no instructions devoted to
8764 the call. @value{GDBN} still pretends that the call site and the
8765 start of the inlined function are different instructions. Stepping to
8766 the call site shows the call site, and then stepping again shows
8767 the first line of the inlined function, even though no additional
8768 instructions are executed.
8770 This makes source-level debugging much clearer; you can see both the
8771 context of the call and then the effect of the call. Only stepping by
8772 a single instruction using @code{stepi} or @code{nexti} does not do
8773 this; single instruction steps always show the inlined body.
8775 There are some ways that @value{GDBN} does not pretend that inlined
8776 function calls are the same as normal calls:
8780 You cannot set breakpoints on inlined functions. @value{GDBN}
8781 either reports that there is no symbol with that name, or else sets the
8782 breakpoint only on non-inlined copies of the function. This limitation
8783 will be removed in a future version of @value{GDBN}; until then,
8784 set a breakpoint by line number on the first line of the inlined
8788 Setting breakpoints at the call site of an inlined function may not
8789 work, because the call site does not contain any code. @value{GDBN}
8790 may incorrectly move the breakpoint to the next line of the enclosing
8791 function, after the call. This limitation will be removed in a future
8792 version of @value{GDBN}; until then, set a breakpoint on an earlier line
8793 or inside the inlined function instead.
8796 @value{GDBN} cannot locate the return value of inlined calls after
8797 using the @code{finish} command. This is a limitation of compiler-generated
8798 debugging information; after @code{finish}, you can step to the next line
8799 and print a variable where your program stored the return value.
8805 @chapter C Preprocessor Macros
8807 Some languages, such as C and C@t{++}, provide a way to define and invoke
8808 ``preprocessor macros'' which expand into strings of tokens.
8809 @value{GDBN} can evaluate expressions containing macro invocations, show
8810 the result of macro expansion, and show a macro's definition, including
8811 where it was defined.
8813 You may need to compile your program specially to provide @value{GDBN}
8814 with information about preprocessor macros. Most compilers do not
8815 include macros in their debugging information, even when you compile
8816 with the @option{-g} flag. @xref{Compilation}.
8818 A program may define a macro at one point, remove that definition later,
8819 and then provide a different definition after that. Thus, at different
8820 points in the program, a macro may have different definitions, or have
8821 no definition at all. If there is a current stack frame, @value{GDBN}
8822 uses the macros in scope at that frame's source code line. Otherwise,
8823 @value{GDBN} uses the macros in scope at the current listing location;
8826 Whenever @value{GDBN} evaluates an expression, it always expands any
8827 macro invocations present in the expression. @value{GDBN} also provides
8828 the following commands for working with macros explicitly.
8832 @kindex macro expand
8833 @cindex macro expansion, showing the results of preprocessor
8834 @cindex preprocessor macro expansion, showing the results of
8835 @cindex expanding preprocessor macros
8836 @item macro expand @var{expression}
8837 @itemx macro exp @var{expression}
8838 Show the results of expanding all preprocessor macro invocations in
8839 @var{expression}. Since @value{GDBN} simply expands macros, but does
8840 not parse the result, @var{expression} need not be a valid expression;
8841 it can be any string of tokens.
8844 @item macro expand-once @var{expression}
8845 @itemx macro exp1 @var{expression}
8846 @cindex expand macro once
8847 @i{(This command is not yet implemented.)} Show the results of
8848 expanding those preprocessor macro invocations that appear explicitly in
8849 @var{expression}. Macro invocations appearing in that expansion are
8850 left unchanged. This command allows you to see the effect of a
8851 particular macro more clearly, without being confused by further
8852 expansions. Since @value{GDBN} simply expands macros, but does not
8853 parse the result, @var{expression} need not be a valid expression; it
8854 can be any string of tokens.
8857 @cindex macro definition, showing
8858 @cindex definition, showing a macro's
8859 @item info macro @var{macro}
8860 Show the definition of the macro named @var{macro}, and describe the
8861 source location or compiler command-line where that definition was established.
8863 @kindex macro define
8864 @cindex user-defined macros
8865 @cindex defining macros interactively
8866 @cindex macros, user-defined
8867 @item macro define @var{macro} @var{replacement-list}
8868 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
8869 Introduce a definition for a preprocessor macro named @var{macro},
8870 invocations of which are replaced by the tokens given in
8871 @var{replacement-list}. The first form of this command defines an
8872 ``object-like'' macro, which takes no arguments; the second form
8873 defines a ``function-like'' macro, which takes the arguments given in
8876 A definition introduced by this command is in scope in every
8877 expression evaluated in @value{GDBN}, until it is removed with the
8878 @code{macro undef} command, described below. The definition overrides
8879 all definitions for @var{macro} present in the program being debugged,
8880 as well as any previous user-supplied definition.
8883 @item macro undef @var{macro}
8884 Remove any user-supplied definition for the macro named @var{macro}.
8885 This command only affects definitions provided with the @code{macro
8886 define} command, described above; it cannot remove definitions present
8887 in the program being debugged.
8891 List all the macros defined using the @code{macro define} command.
8894 @cindex macros, example of debugging with
8895 Here is a transcript showing the above commands in action. First, we
8896 show our source files:
8904 #define ADD(x) (M + x)
8909 printf ("Hello, world!\n");
8911 printf ("We're so creative.\n");
8913 printf ("Goodbye, world!\n");
8920 Now, we compile the program using the @sc{gnu} C compiler, @value{NGCC}.
8921 We pass the @option{-gdwarf-2} and @option{-g3} flags to ensure the
8922 compiler includes information about preprocessor macros in the debugging
8926 $ gcc -gdwarf-2 -g3 sample.c -o sample
8930 Now, we start @value{GDBN} on our sample program:
8934 GNU gdb 2002-05-06-cvs
8935 Copyright 2002 Free Software Foundation, Inc.
8936 GDB is free software, @dots{}
8940 We can expand macros and examine their definitions, even when the
8941 program is not running. @value{GDBN} uses the current listing position
8942 to decide which macro definitions are in scope:
8945 (@value{GDBP}) list main
8948 5 #define ADD(x) (M + x)
8953 10 printf ("Hello, world!\n");
8955 12 printf ("We're so creative.\n");
8956 (@value{GDBP}) info macro ADD
8957 Defined at /home/jimb/gdb/macros/play/sample.c:5
8958 #define ADD(x) (M + x)
8959 (@value{GDBP}) info macro Q
8960 Defined at /home/jimb/gdb/macros/play/sample.h:1
8961 included at /home/jimb/gdb/macros/play/sample.c:2
8963 (@value{GDBP}) macro expand ADD(1)
8964 expands to: (42 + 1)
8965 (@value{GDBP}) macro expand-once ADD(1)
8966 expands to: once (M + 1)
8970 In the example above, note that @code{macro expand-once} expands only
8971 the macro invocation explicit in the original text --- the invocation of
8972 @code{ADD} --- but does not expand the invocation of the macro @code{M},
8973 which was introduced by @code{ADD}.
8975 Once the program is running, @value{GDBN} uses the macro definitions in
8976 force at the source line of the current stack frame:
8979 (@value{GDBP}) break main
8980 Breakpoint 1 at 0x8048370: file sample.c, line 10.
8982 Starting program: /home/jimb/gdb/macros/play/sample
8984 Breakpoint 1, main () at sample.c:10
8985 10 printf ("Hello, world!\n");
8989 At line 10, the definition of the macro @code{N} at line 9 is in force:
8992 (@value{GDBP}) info macro N
8993 Defined at /home/jimb/gdb/macros/play/sample.c:9
8995 (@value{GDBP}) macro expand N Q M
8997 (@value{GDBP}) print N Q M
9002 As we step over directives that remove @code{N}'s definition, and then
9003 give it a new definition, @value{GDBN} finds the definition (or lack
9004 thereof) in force at each point:
9009 12 printf ("We're so creative.\n");
9010 (@value{GDBP}) info macro N
9011 The symbol `N' has no definition as a C/C++ preprocessor macro
9012 at /home/jimb/gdb/macros/play/sample.c:12
9015 14 printf ("Goodbye, world!\n");
9016 (@value{GDBP}) info macro N
9017 Defined at /home/jimb/gdb/macros/play/sample.c:13
9019 (@value{GDBP}) macro expand N Q M
9020 expands to: 1729 < 42
9021 (@value{GDBP}) print N Q M
9026 In addition to source files, macros can be defined on the compilation command
9027 line using the @option{-D@var{name}=@var{value}} syntax. For macros defined in
9028 such a way, @value{GDBN} displays the location of their definition as line zero
9029 of the source file submitted to the compiler.
9032 (@value{GDBP}) info macro __STDC__
9033 Defined at /home/jimb/gdb/macros/play/sample.c:0
9040 @chapter Tracepoints
9041 @c This chapter is based on the documentation written by Michael
9042 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
9045 In some applications, it is not feasible for the debugger to interrupt
9046 the program's execution long enough for the developer to learn
9047 anything helpful about its behavior. If the program's correctness
9048 depends on its real-time behavior, delays introduced by a debugger
9049 might cause the program to change its behavior drastically, or perhaps
9050 fail, even when the code itself is correct. It is useful to be able
9051 to observe the program's behavior without interrupting it.
9053 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
9054 specify locations in the program, called @dfn{tracepoints}, and
9055 arbitrary expressions to evaluate when those tracepoints are reached.
9056 Later, using the @code{tfind} command, you can examine the values
9057 those expressions had when the program hit the tracepoints. The
9058 expressions may also denote objects in memory---structures or arrays,
9059 for example---whose values @value{GDBN} should record; while visiting
9060 a particular tracepoint, you may inspect those objects as if they were
9061 in memory at that moment. However, because @value{GDBN} records these
9062 values without interacting with you, it can do so quickly and
9063 unobtrusively, hopefully not disturbing the program's behavior.
9065 The tracepoint facility is currently available only for remote
9066 targets. @xref{Targets}. In addition, your remote target must know
9067 how to collect trace data. This functionality is implemented in the
9068 remote stub; however, none of the stubs distributed with @value{GDBN}
9069 support tracepoints as of this writing. The format of the remote
9070 packets used to implement tracepoints are described in @ref{Tracepoint
9073 This chapter describes the tracepoint commands and features.
9077 * Analyze Collected Data::
9078 * Tracepoint Variables::
9081 @node Set Tracepoints
9082 @section Commands to Set Tracepoints
9084 Before running such a @dfn{trace experiment}, an arbitrary number of
9085 tracepoints can be set. A tracepoint is actually a special type of
9086 breakpoint (@pxref{Set Breaks}), so you can manipulate it using
9087 standard breakpoint commands. For instance, as with breakpoints,
9088 tracepoint numbers are successive integers starting from one, and many
9089 of the commands associated with tracepoints take the tracepoint number
9090 as their argument, to identify which tracepoint to work on.
9092 For each tracepoint, you can specify, in advance, some arbitrary set
9093 of data that you want the target to collect in the trace buffer when
9094 it hits that tracepoint. The collected data can include registers,
9095 local variables, or global data. Later, you can use @value{GDBN}
9096 commands to examine the values these data had at the time the
9099 Tracepoints do not support every breakpoint feature. Conditional
9100 expressions and ignore counts on tracepoints have no effect, and
9101 tracepoints cannot run @value{GDBN} commands when they are
9102 hit. Tracepoints may not be thread-specific either.
9104 This section describes commands to set tracepoints and associated
9105 conditions and actions.
9108 * Create and Delete Tracepoints::
9109 * Enable and Disable Tracepoints::
9110 * Tracepoint Passcounts::
9111 * Tracepoint Conditions::
9112 * Tracepoint Actions::
9113 * Listing Tracepoints::
9114 * Starting and Stopping Trace Experiments::
9117 @node Create and Delete Tracepoints
9118 @subsection Create and Delete Tracepoints
9121 @cindex set tracepoint
9123 @item trace @var{location}
9124 The @code{trace} command is very similar to the @code{break} command.
9125 Its argument @var{location} can be a source line, a function name, or
9126 an address in the target program. @xref{Specify Location}. The
9127 @code{trace} command defines a tracepoint, which is a point in the
9128 target program where the debugger will briefly stop, collect some
9129 data, and then allow the program to continue. Setting a tracepoint or
9130 changing its actions doesn't take effect until the next @code{tstart}
9131 command, and once a trace experiment is running, further changes will
9132 not have any effect until the next trace experiment starts.
9134 Here are some examples of using the @code{trace} command:
9137 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
9139 (@value{GDBP}) @b{trace +2} // 2 lines forward
9141 (@value{GDBP}) @b{trace my_function} // first source line of function
9143 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
9145 (@value{GDBP}) @b{trace *0x2117c4} // an address
9149 You can abbreviate @code{trace} as @code{tr}.
9151 @item trace @var{location} if @var{cond}
9152 Set a tracepoint with condition @var{cond}; evaluate the expression
9153 @var{cond} each time the tracepoint is reached, and collect data only
9154 if the value is nonzero---that is, if @var{cond} evaluates as true.
9155 @xref{Tracepoint Conditions, ,Tracepoint Conditions}, for more
9156 information on tracepoint conditions.
9159 @cindex last tracepoint number
9160 @cindex recent tracepoint number
9161 @cindex tracepoint number
9162 The convenience variable @code{$tpnum} records the tracepoint number
9163 of the most recently set tracepoint.
9165 @kindex delete tracepoint
9166 @cindex tracepoint deletion
9167 @item delete tracepoint @r{[}@var{num}@r{]}
9168 Permanently delete one or more tracepoints. With no argument, the
9169 default is to delete all tracepoints. Note that the regular
9170 @code{delete} command can remove tracepoints also.
9175 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
9177 (@value{GDBP}) @b{delete trace} // remove all tracepoints
9181 You can abbreviate this command as @code{del tr}.
9184 @node Enable and Disable Tracepoints
9185 @subsection Enable and Disable Tracepoints
9187 These commands are deprecated; they are equivalent to plain @code{disable} and @code{enable}.
9190 @kindex disable tracepoint
9191 @item disable tracepoint @r{[}@var{num}@r{]}
9192 Disable tracepoint @var{num}, or all tracepoints if no argument
9193 @var{num} is given. A disabled tracepoint will have no effect during
9194 the next trace experiment, but it is not forgotten. You can re-enable
9195 a disabled tracepoint using the @code{enable tracepoint} command.
9197 @kindex enable tracepoint
9198 @item enable tracepoint @r{[}@var{num}@r{]}
9199 Enable tracepoint @var{num}, or all tracepoints. The enabled
9200 tracepoints will become effective the next time a trace experiment is
9204 @node Tracepoint Passcounts
9205 @subsection Tracepoint Passcounts
9209 @cindex tracepoint pass count
9210 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
9211 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
9212 automatically stop a trace experiment. If a tracepoint's passcount is
9213 @var{n}, then the trace experiment will be automatically stopped on
9214 the @var{n}'th time that tracepoint is hit. If the tracepoint number
9215 @var{num} is not specified, the @code{passcount} command sets the
9216 passcount of the most recently defined tracepoint. If no passcount is
9217 given, the trace experiment will run until stopped explicitly by the
9223 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
9224 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
9226 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
9227 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
9228 (@value{GDBP}) @b{trace foo}
9229 (@value{GDBP}) @b{pass 3}
9230 (@value{GDBP}) @b{trace bar}
9231 (@value{GDBP}) @b{pass 2}
9232 (@value{GDBP}) @b{trace baz}
9233 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
9234 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
9235 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
9236 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
9240 @node Tracepoint Conditions
9241 @subsection Tracepoint Conditions
9242 @cindex conditional tracepoints
9243 @cindex tracepoint conditions
9245 The simplest sort of tracepoint collects data every time your program
9246 reaches a specified place. You can also specify a @dfn{condition} for
9247 a tracepoint. A condition is just a Boolean expression in your
9248 programming language (@pxref{Expressions, ,Expressions}). A
9249 tracepoint with a condition evaluates the expression each time your
9250 program reaches it, and data collection happens only if the condition
9253 Tracepoint conditions can be specified when a tracepoint is set, by
9254 using @samp{if} in the arguments to the @code{trace} command.
9255 @xref{Create and Delete Tracepoints, ,Setting Tracepoints}. They can
9256 also be set or changed at any time with the @code{condition} command,
9257 just as with breakpoints.
9259 Unlike breakpoint conditions, @value{GDBN} does not actually evaluate
9260 the conditional expression itself. Instead, @value{GDBN} encodes the
9261 expression into an agent expression (@pxref{Agent Expressions}
9262 suitable for execution on the target, independently of @value{GDBN}.
9263 Global variables become raw memory locations, locals become stack
9264 accesses, and so forth.
9266 For instance, suppose you have a function that is usually called
9267 frequently, but should not be called after an error has occurred. You
9268 could use the following tracepoint command to collect data about calls
9269 of that function that happen while the error code is propagating
9270 through the program; an unconditional tracepoint could end up
9271 collecting thousands of useless trace frames that you would have to
9275 (@value{GDBP}) @kbd{trace normal_operation if errcode > 0}
9278 @node Tracepoint Actions
9279 @subsection Tracepoint Action Lists
9283 @cindex tracepoint actions
9284 @item actions @r{[}@var{num}@r{]}
9285 This command will prompt for a list of actions to be taken when the
9286 tracepoint is hit. If the tracepoint number @var{num} is not
9287 specified, this command sets the actions for the one that was most
9288 recently defined (so that you can define a tracepoint and then say
9289 @code{actions} without bothering about its number). You specify the
9290 actions themselves on the following lines, one action at a time, and
9291 terminate the actions list with a line containing just @code{end}. So
9292 far, the only defined actions are @code{collect} and
9293 @code{while-stepping}.
9295 @cindex remove actions from a tracepoint
9296 To remove all actions from a tracepoint, type @samp{actions @var{num}}
9297 and follow it immediately with @samp{end}.
9300 (@value{GDBP}) @b{collect @var{data}} // collect some data
9302 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
9304 (@value{GDBP}) @b{end} // signals the end of actions.
9307 In the following example, the action list begins with @code{collect}
9308 commands indicating the things to be collected when the tracepoint is
9309 hit. Then, in order to single-step and collect additional data
9310 following the tracepoint, a @code{while-stepping} command is used,
9311 followed by the list of things to be collected while stepping. The
9312 @code{while-stepping} command is terminated by its own separate
9313 @code{end} command. Lastly, the action list is terminated by an
9317 (@value{GDBP}) @b{trace foo}
9318 (@value{GDBP}) @b{actions}
9319 Enter actions for tracepoint 1, one per line:
9328 @kindex collect @r{(tracepoints)}
9329 @item collect @var{expr1}, @var{expr2}, @dots{}
9330 Collect values of the given expressions when the tracepoint is hit.
9331 This command accepts a comma-separated list of any valid expressions.
9332 In addition to global, static, or local variables, the following
9333 special arguments are supported:
9337 collect all registers
9340 collect all function arguments
9343 collect all local variables.
9346 You can give several consecutive @code{collect} commands, each one
9347 with a single argument, or one @code{collect} command with several
9348 arguments separated by commas: the effect is the same.
9350 The command @code{info scope} (@pxref{Symbols, info scope}) is
9351 particularly useful for figuring out what data to collect.
9353 @kindex while-stepping @r{(tracepoints)}
9354 @item while-stepping @var{n}
9355 Perform @var{n} single-step traces after the tracepoint, collecting
9356 new data at each step. The @code{while-stepping} command is
9357 followed by the list of what to collect while stepping (followed by
9358 its own @code{end} command):
9362 > collect $regs, myglobal
9368 You may abbreviate @code{while-stepping} as @code{ws} or
9372 @node Listing Tracepoints
9373 @subsection Listing Tracepoints
9376 @kindex info tracepoints
9378 @cindex information about tracepoints
9379 @item info tracepoints @r{[}@var{num}@r{]}
9380 Display information about the tracepoint @var{num}. If you don't
9381 specify a tracepoint number, displays information about all the
9382 tracepoints defined so far. The format is similar to that used for
9383 @code{info breakpoints}; in fact, @code{info tracepoints} is the same
9384 command, simply restricting itself to tracepoints.
9386 A tracepoint's listing may include additional information specific to
9391 its passcount as given by the @code{passcount @var{n}} command
9393 its step count as given by the @code{while-stepping @var{n}} command
9395 its action list as given by the @code{actions} command. The actions
9396 are prefixed with an @samp{A} so as to distinguish them from commands.
9400 (@value{GDBP}) @b{info trace}
9401 Num Type Disp Enb Address What
9402 1 tracepoint keep y 0x0804ab57 in foo() at main.cxx:7
9406 A collect globfoo, $regs
9414 This command can be abbreviated @code{info tp}.
9417 @node Starting and Stopping Trace Experiments
9418 @subsection Starting and Stopping Trace Experiments
9422 @cindex start a new trace experiment
9423 @cindex collected data discarded
9425 This command takes no arguments. It starts the trace experiment, and
9426 begins collecting data. This has the side effect of discarding all
9427 the data collected in the trace buffer during the previous trace
9431 @cindex stop a running trace experiment
9433 This command takes no arguments. It ends the trace experiment, and
9434 stops collecting data.
9436 @strong{Note}: a trace experiment and data collection may stop
9437 automatically if any tracepoint's passcount is reached
9438 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
9441 @cindex status of trace data collection
9442 @cindex trace experiment, status of
9444 This command displays the status of the current trace data
9448 Here is an example of the commands we described so far:
9451 (@value{GDBP}) @b{trace gdb_c_test}
9452 (@value{GDBP}) @b{actions}
9453 Enter actions for tracepoint #1, one per line.
9454 > collect $regs,$locals,$args
9459 (@value{GDBP}) @b{tstart}
9460 [time passes @dots{}]
9461 (@value{GDBP}) @b{tstop}
9465 @node Analyze Collected Data
9466 @section Using the Collected Data
9468 After the tracepoint experiment ends, you use @value{GDBN} commands
9469 for examining the trace data. The basic idea is that each tracepoint
9470 collects a trace @dfn{snapshot} every time it is hit and another
9471 snapshot every time it single-steps. All these snapshots are
9472 consecutively numbered from zero and go into a buffer, and you can
9473 examine them later. The way you examine them is to @dfn{focus} on a
9474 specific trace snapshot. When the remote stub is focused on a trace
9475 snapshot, it will respond to all @value{GDBN} requests for memory and
9476 registers by reading from the buffer which belongs to that snapshot,
9477 rather than from @emph{real} memory or registers of the program being
9478 debugged. This means that @strong{all} @value{GDBN} commands
9479 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
9480 behave as if we were currently debugging the program state as it was
9481 when the tracepoint occurred. Any requests for data that are not in
9482 the buffer will fail.
9485 * tfind:: How to select a trace snapshot
9486 * tdump:: How to display all data for a snapshot
9487 * save-tracepoints:: How to save tracepoints for a future run
9491 @subsection @code{tfind @var{n}}
9494 @cindex select trace snapshot
9495 @cindex find trace snapshot
9496 The basic command for selecting a trace snapshot from the buffer is
9497 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
9498 counting from zero. If no argument @var{n} is given, the next
9499 snapshot is selected.
9501 Here are the various forms of using the @code{tfind} command.
9505 Find the first snapshot in the buffer. This is a synonym for
9506 @code{tfind 0} (since 0 is the number of the first snapshot).
9509 Stop debugging trace snapshots, resume @emph{live} debugging.
9512 Same as @samp{tfind none}.
9515 No argument means find the next trace snapshot.
9518 Find the previous trace snapshot before the current one. This permits
9519 retracing earlier steps.
9521 @item tfind tracepoint @var{num}
9522 Find the next snapshot associated with tracepoint @var{num}. Search
9523 proceeds forward from the last examined trace snapshot. If no
9524 argument @var{num} is given, it means find the next snapshot collected
9525 for the same tracepoint as the current snapshot.
9527 @item tfind pc @var{addr}
9528 Find the next snapshot associated with the value @var{addr} of the
9529 program counter. Search proceeds forward from the last examined trace
9530 snapshot. If no argument @var{addr} is given, it means find the next
9531 snapshot with the same value of PC as the current snapshot.
9533 @item tfind outside @var{addr1}, @var{addr2}
9534 Find the next snapshot whose PC is outside the given range of
9537 @item tfind range @var{addr1}, @var{addr2}
9538 Find the next snapshot whose PC is between @var{addr1} and
9539 @var{addr2}. @c FIXME: Is the range inclusive or exclusive?
9541 @item tfind line @r{[}@var{file}:@r{]}@var{n}
9542 Find the next snapshot associated with the source line @var{n}. If
9543 the optional argument @var{file} is given, refer to line @var{n} in
9544 that source file. Search proceeds forward from the last examined
9545 trace snapshot. If no argument @var{n} is given, it means find the
9546 next line other than the one currently being examined; thus saying
9547 @code{tfind line} repeatedly can appear to have the same effect as
9548 stepping from line to line in a @emph{live} debugging session.
9551 The default arguments for the @code{tfind} commands are specifically
9552 designed to make it easy to scan through the trace buffer. For
9553 instance, @code{tfind} with no argument selects the next trace
9554 snapshot, and @code{tfind -} with no argument selects the previous
9555 trace snapshot. So, by giving one @code{tfind} command, and then
9556 simply hitting @key{RET} repeatedly you can examine all the trace
9557 snapshots in order. Or, by saying @code{tfind -} and then hitting
9558 @key{RET} repeatedly you can examine the snapshots in reverse order.
9559 The @code{tfind line} command with no argument selects the snapshot
9560 for the next source line executed. The @code{tfind pc} command with
9561 no argument selects the next snapshot with the same program counter
9562 (PC) as the current frame. The @code{tfind tracepoint} command with
9563 no argument selects the next trace snapshot collected by the same
9564 tracepoint as the current one.
9566 In addition to letting you scan through the trace buffer manually,
9567 these commands make it easy to construct @value{GDBN} scripts that
9568 scan through the trace buffer and print out whatever collected data
9569 you are interested in. Thus, if we want to examine the PC, FP, and SP
9570 registers from each trace frame in the buffer, we can say this:
9573 (@value{GDBP}) @b{tfind start}
9574 (@value{GDBP}) @b{while ($trace_frame != -1)}
9575 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
9576 $trace_frame, $pc, $sp, $fp
9580 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
9581 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
9582 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
9583 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
9584 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
9585 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
9586 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
9587 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
9588 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
9589 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
9590 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
9593 Or, if we want to examine the variable @code{X} at each source line in
9597 (@value{GDBP}) @b{tfind start}
9598 (@value{GDBP}) @b{while ($trace_frame != -1)}
9599 > printf "Frame %d, X == %d\n", $trace_frame, X
9609 @subsection @code{tdump}
9611 @cindex dump all data collected at tracepoint
9612 @cindex tracepoint data, display
9614 This command takes no arguments. It prints all the data collected at
9615 the current trace snapshot.
9618 (@value{GDBP}) @b{trace 444}
9619 (@value{GDBP}) @b{actions}
9620 Enter actions for tracepoint #2, one per line:
9621 > collect $regs, $locals, $args, gdb_long_test
9624 (@value{GDBP}) @b{tstart}
9626 (@value{GDBP}) @b{tfind line 444}
9627 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
9629 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
9631 (@value{GDBP}) @b{tdump}
9632 Data collected at tracepoint 2, trace frame 1:
9633 d0 0xc4aa0085 -995491707
9637 d4 0x71aea3d 119204413
9642 a1 0x3000668 50333288
9645 a4 0x3000698 50333336
9647 fp 0x30bf3c 0x30bf3c
9648 sp 0x30bf34 0x30bf34
9650 pc 0x20b2c8 0x20b2c8
9654 p = 0x20e5b4 "gdb-test"
9661 gdb_long_test = 17 '\021'
9666 @node save-tracepoints
9667 @subsection @code{save-tracepoints @var{filename}}
9668 @kindex save-tracepoints
9669 @cindex save tracepoints for future sessions
9671 This command saves all current tracepoint definitions together with
9672 their actions and passcounts, into a file @file{@var{filename}}
9673 suitable for use in a later debugging session. To read the saved
9674 tracepoint definitions, use the @code{source} command (@pxref{Command
9677 @node Tracepoint Variables
9678 @section Convenience Variables for Tracepoints
9679 @cindex tracepoint variables
9680 @cindex convenience variables for tracepoints
9683 @vindex $trace_frame
9684 @item (int) $trace_frame
9685 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
9686 snapshot is selected.
9689 @item (int) $tracepoint
9690 The tracepoint for the current trace snapshot.
9693 @item (int) $trace_line
9694 The line number for the current trace snapshot.
9697 @item (char []) $trace_file
9698 The source file for the current trace snapshot.
9701 @item (char []) $trace_func
9702 The name of the function containing @code{$tracepoint}.
9705 Note: @code{$trace_file} is not suitable for use in @code{printf},
9706 use @code{output} instead.
9708 Here's a simple example of using these convenience variables for
9709 stepping through all the trace snapshots and printing some of their
9713 (@value{GDBP}) @b{tfind start}
9715 (@value{GDBP}) @b{while $trace_frame != -1}
9716 > output $trace_file
9717 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
9723 @chapter Debugging Programs That Use Overlays
9726 If your program is too large to fit completely in your target system's
9727 memory, you can sometimes use @dfn{overlays} to work around this
9728 problem. @value{GDBN} provides some support for debugging programs that
9732 * How Overlays Work:: A general explanation of overlays.
9733 * Overlay Commands:: Managing overlays in @value{GDBN}.
9734 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
9735 mapped by asking the inferior.
9736 * Overlay Sample Program:: A sample program using overlays.
9739 @node How Overlays Work
9740 @section How Overlays Work
9741 @cindex mapped overlays
9742 @cindex unmapped overlays
9743 @cindex load address, overlay's
9744 @cindex mapped address
9745 @cindex overlay area
9747 Suppose you have a computer whose instruction address space is only 64
9748 kilobytes long, but which has much more memory which can be accessed by
9749 other means: special instructions, segment registers, or memory
9750 management hardware, for example. Suppose further that you want to
9751 adapt a program which is larger than 64 kilobytes to run on this system.
9753 One solution is to identify modules of your program which are relatively
9754 independent, and need not call each other directly; call these modules
9755 @dfn{overlays}. Separate the overlays from the main program, and place
9756 their machine code in the larger memory. Place your main program in
9757 instruction memory, but leave at least enough space there to hold the
9758 largest overlay as well.
9760 Now, to call a function located in an overlay, you must first copy that
9761 overlay's machine code from the large memory into the space set aside
9762 for it in the instruction memory, and then jump to its entry point
9765 @c NB: In the below the mapped area's size is greater or equal to the
9766 @c size of all overlays. This is intentional to remind the developer
9767 @c that overlays don't necessarily need to be the same size.
9771 Data Instruction Larger
9772 Address Space Address Space Address Space
9773 +-----------+ +-----------+ +-----------+
9775 +-----------+ +-----------+ +-----------+<-- overlay 1
9776 | program | | main | .----| overlay 1 | load address
9777 | variables | | program | | +-----------+
9778 | and heap | | | | | |
9779 +-----------+ | | | +-----------+<-- overlay 2
9780 | | +-----------+ | | | load address
9781 +-----------+ | | | .-| overlay 2 |
9783 mapped --->+-----------+ | | +-----------+
9785 | overlay | <-' | | |
9786 | area | <---' +-----------+<-- overlay 3
9787 | | <---. | | load address
9788 +-----------+ `--| overlay 3 |
9795 @anchor{A code overlay}A code overlay
9799 The diagram (@pxref{A code overlay}) shows a system with separate data
9800 and instruction address spaces. To map an overlay, the program copies
9801 its code from the larger address space to the instruction address space.
9802 Since the overlays shown here all use the same mapped address, only one
9803 may be mapped at a time. For a system with a single address space for
9804 data and instructions, the diagram would be similar, except that the
9805 program variables and heap would share an address space with the main
9806 program and the overlay area.
9808 An overlay loaded into instruction memory and ready for use is called a
9809 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
9810 instruction memory. An overlay not present (or only partially present)
9811 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
9812 is its address in the larger memory. The mapped address is also called
9813 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
9814 called the @dfn{load memory address}, or @dfn{LMA}.
9816 Unfortunately, overlays are not a completely transparent way to adapt a
9817 program to limited instruction memory. They introduce a new set of
9818 global constraints you must keep in mind as you design your program:
9823 Before calling or returning to a function in an overlay, your program
9824 must make sure that overlay is actually mapped. Otherwise, the call or
9825 return will transfer control to the right address, but in the wrong
9826 overlay, and your program will probably crash.
9829 If the process of mapping an overlay is expensive on your system, you
9830 will need to choose your overlays carefully to minimize their effect on
9831 your program's performance.
9834 The executable file you load onto your system must contain each
9835 overlay's instructions, appearing at the overlay's load address, not its
9836 mapped address. However, each overlay's instructions must be relocated
9837 and its symbols defined as if the overlay were at its mapped address.
9838 You can use GNU linker scripts to specify different load and relocation
9839 addresses for pieces of your program; see @ref{Overlay Description,,,
9840 ld.info, Using ld: the GNU linker}.
9843 The procedure for loading executable files onto your system must be able
9844 to load their contents into the larger address space as well as the
9845 instruction and data spaces.
9849 The overlay system described above is rather simple, and could be
9850 improved in many ways:
9855 If your system has suitable bank switch registers or memory management
9856 hardware, you could use those facilities to make an overlay's load area
9857 contents simply appear at their mapped address in instruction space.
9858 This would probably be faster than copying the overlay to its mapped
9859 area in the usual way.
9862 If your overlays are small enough, you could set aside more than one
9863 overlay area, and have more than one overlay mapped at a time.
9866 You can use overlays to manage data, as well as instructions. In
9867 general, data overlays are even less transparent to your design than
9868 code overlays: whereas code overlays only require care when you call or
9869 return to functions, data overlays require care every time you access
9870 the data. Also, if you change the contents of a data overlay, you
9871 must copy its contents back out to its load address before you can copy a
9872 different data overlay into the same mapped area.
9877 @node Overlay Commands
9878 @section Overlay Commands
9880 To use @value{GDBN}'s overlay support, each overlay in your program must
9881 correspond to a separate section of the executable file. The section's
9882 virtual memory address and load memory address must be the overlay's
9883 mapped and load addresses. Identifying overlays with sections allows
9884 @value{GDBN} to determine the appropriate address of a function or
9885 variable, depending on whether the overlay is mapped or not.
9887 @value{GDBN}'s overlay commands all start with the word @code{overlay};
9888 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
9893 Disable @value{GDBN}'s overlay support. When overlay support is
9894 disabled, @value{GDBN} assumes that all functions and variables are
9895 always present at their mapped addresses. By default, @value{GDBN}'s
9896 overlay support is disabled.
9898 @item overlay manual
9899 @cindex manual overlay debugging
9900 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
9901 relies on you to tell it which overlays are mapped, and which are not,
9902 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
9903 commands described below.
9905 @item overlay map-overlay @var{overlay}
9906 @itemx overlay map @var{overlay}
9907 @cindex map an overlay
9908 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
9909 be the name of the object file section containing the overlay. When an
9910 overlay is mapped, @value{GDBN} assumes it can find the overlay's
9911 functions and variables at their mapped addresses. @value{GDBN} assumes
9912 that any other overlays whose mapped ranges overlap that of
9913 @var{overlay} are now unmapped.
9915 @item overlay unmap-overlay @var{overlay}
9916 @itemx overlay unmap @var{overlay}
9917 @cindex unmap an overlay
9918 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
9919 must be the name of the object file section containing the overlay.
9920 When an overlay is unmapped, @value{GDBN} assumes it can find the
9921 overlay's functions and variables at their load addresses.
9924 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
9925 consults a data structure the overlay manager maintains in the inferior
9926 to see which overlays are mapped. For details, see @ref{Automatic
9929 @item overlay load-target
9931 @cindex reloading the overlay table
9932 Re-read the overlay table from the inferior. Normally, @value{GDBN}
9933 re-reads the table @value{GDBN} automatically each time the inferior
9934 stops, so this command should only be necessary if you have changed the
9935 overlay mapping yourself using @value{GDBN}. This command is only
9936 useful when using automatic overlay debugging.
9938 @item overlay list-overlays
9940 @cindex listing mapped overlays
9941 Display a list of the overlays currently mapped, along with their mapped
9942 addresses, load addresses, and sizes.
9946 Normally, when @value{GDBN} prints a code address, it includes the name
9947 of the function the address falls in:
9950 (@value{GDBP}) print main
9951 $3 = @{int ()@} 0x11a0 <main>
9954 When overlay debugging is enabled, @value{GDBN} recognizes code in
9955 unmapped overlays, and prints the names of unmapped functions with
9956 asterisks around them. For example, if @code{foo} is a function in an
9957 unmapped overlay, @value{GDBN} prints it this way:
9960 (@value{GDBP}) overlay list
9961 No sections are mapped.
9962 (@value{GDBP}) print foo
9963 $5 = @{int (int)@} 0x100000 <*foo*>
9966 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
9970 (@value{GDBP}) overlay list
9971 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
9972 mapped at 0x1016 - 0x104a
9973 (@value{GDBP}) print foo
9974 $6 = @{int (int)@} 0x1016 <foo>
9977 When overlay debugging is enabled, @value{GDBN} can find the correct
9978 address for functions and variables in an overlay, whether or not the
9979 overlay is mapped. This allows most @value{GDBN} commands, like
9980 @code{break} and @code{disassemble}, to work normally, even on unmapped
9981 code. However, @value{GDBN}'s breakpoint support has some limitations:
9985 @cindex breakpoints in overlays
9986 @cindex overlays, setting breakpoints in
9987 You can set breakpoints in functions in unmapped overlays, as long as
9988 @value{GDBN} can write to the overlay at its load address.
9990 @value{GDBN} can not set hardware or simulator-based breakpoints in
9991 unmapped overlays. However, if you set a breakpoint at the end of your
9992 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
9993 you are using manual overlay management), @value{GDBN} will re-set its
9994 breakpoints properly.
9998 @node Automatic Overlay Debugging
9999 @section Automatic Overlay Debugging
10000 @cindex automatic overlay debugging
10002 @value{GDBN} can automatically track which overlays are mapped and which
10003 are not, given some simple co-operation from the overlay manager in the
10004 inferior. If you enable automatic overlay debugging with the
10005 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
10006 looks in the inferior's memory for certain variables describing the
10007 current state of the overlays.
10009 Here are the variables your overlay manager must define to support
10010 @value{GDBN}'s automatic overlay debugging:
10014 @item @code{_ovly_table}:
10015 This variable must be an array of the following structures:
10020 /* The overlay's mapped address. */
10023 /* The size of the overlay, in bytes. */
10024 unsigned long size;
10026 /* The overlay's load address. */
10029 /* Non-zero if the overlay is currently mapped;
10031 unsigned long mapped;
10035 @item @code{_novlys}:
10036 This variable must be a four-byte signed integer, holding the total
10037 number of elements in @code{_ovly_table}.
10041 To decide whether a particular overlay is mapped or not, @value{GDBN}
10042 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
10043 @code{lma} members equal the VMA and LMA of the overlay's section in the
10044 executable file. When @value{GDBN} finds a matching entry, it consults
10045 the entry's @code{mapped} member to determine whether the overlay is
10048 In addition, your overlay manager may define a function called
10049 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
10050 will silently set a breakpoint there. If the overlay manager then
10051 calls this function whenever it has changed the overlay table, this
10052 will enable @value{GDBN} to accurately keep track of which overlays
10053 are in program memory, and update any breakpoints that may be set
10054 in overlays. This will allow breakpoints to work even if the
10055 overlays are kept in ROM or other non-writable memory while they
10056 are not being executed.
10058 @node Overlay Sample Program
10059 @section Overlay Sample Program
10060 @cindex overlay example program
10062 When linking a program which uses overlays, you must place the overlays
10063 at their load addresses, while relocating them to run at their mapped
10064 addresses. To do this, you must write a linker script (@pxref{Overlay
10065 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
10066 since linker scripts are specific to a particular host system, target
10067 architecture, and target memory layout, this manual cannot provide
10068 portable sample code demonstrating @value{GDBN}'s overlay support.
10070 However, the @value{GDBN} source distribution does contain an overlaid
10071 program, with linker scripts for a few systems, as part of its test
10072 suite. The program consists of the following files from
10073 @file{gdb/testsuite/gdb.base}:
10077 The main program file.
10079 A simple overlay manager, used by @file{overlays.c}.
10084 Overlay modules, loaded and used by @file{overlays.c}.
10087 Linker scripts for linking the test program on the @code{d10v-elf}
10088 and @code{m32r-elf} targets.
10091 You can build the test program using the @code{d10v-elf} GCC
10092 cross-compiler like this:
10095 $ d10v-elf-gcc -g -c overlays.c
10096 $ d10v-elf-gcc -g -c ovlymgr.c
10097 $ d10v-elf-gcc -g -c foo.c
10098 $ d10v-elf-gcc -g -c bar.c
10099 $ d10v-elf-gcc -g -c baz.c
10100 $ d10v-elf-gcc -g -c grbx.c
10101 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
10102 baz.o grbx.o -Wl,-Td10v.ld -o overlays
10105 The build process is identical for any other architecture, except that
10106 you must substitute the appropriate compiler and linker script for the
10107 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
10111 @chapter Using @value{GDBN} with Different Languages
10114 Although programming languages generally have common aspects, they are
10115 rarely expressed in the same manner. For instance, in ANSI C,
10116 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
10117 Modula-2, it is accomplished by @code{p^}. Values can also be
10118 represented (and displayed) differently. Hex numbers in C appear as
10119 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
10121 @cindex working language
10122 Language-specific information is built into @value{GDBN} for some languages,
10123 allowing you to express operations like the above in your program's
10124 native language, and allowing @value{GDBN} to output values in a manner
10125 consistent with the syntax of your program's native language. The
10126 language you use to build expressions is called the @dfn{working
10130 * Setting:: Switching between source languages
10131 * Show:: Displaying the language
10132 * Checks:: Type and range checks
10133 * Supported Languages:: Supported languages
10134 * Unsupported Languages:: Unsupported languages
10138 @section Switching Between Source Languages
10140 There are two ways to control the working language---either have @value{GDBN}
10141 set it automatically, or select it manually yourself. You can use the
10142 @code{set language} command for either purpose. On startup, @value{GDBN}
10143 defaults to setting the language automatically. The working language is
10144 used to determine how expressions you type are interpreted, how values
10147 In addition to the working language, every source file that
10148 @value{GDBN} knows about has its own working language. For some object
10149 file formats, the compiler might indicate which language a particular
10150 source file is in. However, most of the time @value{GDBN} infers the
10151 language from the name of the file. The language of a source file
10152 controls whether C@t{++} names are demangled---this way @code{backtrace} can
10153 show each frame appropriately for its own language. There is no way to
10154 set the language of a source file from within @value{GDBN}, but you can
10155 set the language associated with a filename extension. @xref{Show, ,
10156 Displaying the Language}.
10158 This is most commonly a problem when you use a program, such
10159 as @code{cfront} or @code{f2c}, that generates C but is written in
10160 another language. In that case, make the
10161 program use @code{#line} directives in its C output; that way
10162 @value{GDBN} will know the correct language of the source code of the original
10163 program, and will display that source code, not the generated C code.
10166 * Filenames:: Filename extensions and languages.
10167 * Manually:: Setting the working language manually
10168 * Automatically:: Having @value{GDBN} infer the source language
10172 @subsection List of Filename Extensions and Languages
10174 If a source file name ends in one of the following extensions, then
10175 @value{GDBN} infers that its language is the one indicated.
10193 C@t{++} source file
10196 Objective-C source file
10200 Fortran source file
10203 Modula-2 source file
10207 Assembler source file. This actually behaves almost like C, but
10208 @value{GDBN} does not skip over function prologues when stepping.
10211 In addition, you may set the language associated with a filename
10212 extension. @xref{Show, , Displaying the Language}.
10215 @subsection Setting the Working Language
10217 If you allow @value{GDBN} to set the language automatically,
10218 expressions are interpreted the same way in your debugging session and
10221 @kindex set language
10222 If you wish, you may set the language manually. To do this, issue the
10223 command @samp{set language @var{lang}}, where @var{lang} is the name of
10224 a language, such as
10225 @code{c} or @code{modula-2}.
10226 For a list of the supported languages, type @samp{set language}.
10228 Setting the language manually prevents @value{GDBN} from updating the working
10229 language automatically. This can lead to confusion if you try
10230 to debug a program when the working language is not the same as the
10231 source language, when an expression is acceptable to both
10232 languages---but means different things. For instance, if the current
10233 source file were written in C, and @value{GDBN} was parsing Modula-2, a
10241 might not have the effect you intended. In C, this means to add
10242 @code{b} and @code{c} and place the result in @code{a}. The result
10243 printed would be the value of @code{a}. In Modula-2, this means to compare
10244 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
10246 @node Automatically
10247 @subsection Having @value{GDBN} Infer the Source Language
10249 To have @value{GDBN} set the working language automatically, use
10250 @samp{set language local} or @samp{set language auto}. @value{GDBN}
10251 then infers the working language. That is, when your program stops in a
10252 frame (usually by encountering a breakpoint), @value{GDBN} sets the
10253 working language to the language recorded for the function in that
10254 frame. If the language for a frame is unknown (that is, if the function
10255 or block corresponding to the frame was defined in a source file that
10256 does not have a recognized extension), the current working language is
10257 not changed, and @value{GDBN} issues a warning.
10259 This may not seem necessary for most programs, which are written
10260 entirely in one source language. However, program modules and libraries
10261 written in one source language can be used by a main program written in
10262 a different source language. Using @samp{set language auto} in this
10263 case frees you from having to set the working language manually.
10266 @section Displaying the Language
10268 The following commands help you find out which language is the
10269 working language, and also what language source files were written in.
10272 @item show language
10273 @kindex show language
10274 Display the current working language. This is the
10275 language you can use with commands such as @code{print} to
10276 build and compute expressions that may involve variables in your program.
10279 @kindex info frame@r{, show the source language}
10280 Display the source language for this frame. This language becomes the
10281 working language if you use an identifier from this frame.
10282 @xref{Frame Info, ,Information about a Frame}, to identify the other
10283 information listed here.
10286 @kindex info source@r{, show the source language}
10287 Display the source language of this source file.
10288 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
10289 information listed here.
10292 In unusual circumstances, you may have source files with extensions
10293 not in the standard list. You can then set the extension associated
10294 with a language explicitly:
10297 @item set extension-language @var{ext} @var{language}
10298 @kindex set extension-language
10299 Tell @value{GDBN} that source files with extension @var{ext} are to be
10300 assumed as written in the source language @var{language}.
10302 @item info extensions
10303 @kindex info extensions
10304 List all the filename extensions and the associated languages.
10308 @section Type and Range Checking
10311 @emph{Warning:} In this release, the @value{GDBN} commands for type and range
10312 checking are included, but they do not yet have any effect. This
10313 section documents the intended facilities.
10315 @c FIXME remove warning when type/range code added
10317 Some languages are designed to guard you against making seemingly common
10318 errors through a series of compile- and run-time checks. These include
10319 checking the type of arguments to functions and operators, and making
10320 sure mathematical overflows are caught at run time. Checks such as
10321 these help to ensure a program's correctness once it has been compiled
10322 by eliminating type mismatches, and providing active checks for range
10323 errors when your program is running.
10325 @value{GDBN} can check for conditions like the above if you wish.
10326 Although @value{GDBN} does not check the statements in your program,
10327 it can check expressions entered directly into @value{GDBN} for
10328 evaluation via the @code{print} command, for example. As with the
10329 working language, @value{GDBN} can also decide whether or not to check
10330 automatically based on your program's source language.
10331 @xref{Supported Languages, ,Supported Languages}, for the default
10332 settings of supported languages.
10335 * Type Checking:: An overview of type checking
10336 * Range Checking:: An overview of range checking
10339 @cindex type checking
10340 @cindex checks, type
10341 @node Type Checking
10342 @subsection An Overview of Type Checking
10344 Some languages, such as Modula-2, are strongly typed, meaning that the
10345 arguments to operators and functions have to be of the correct type,
10346 otherwise an error occurs. These checks prevent type mismatch
10347 errors from ever causing any run-time problems. For example,
10355 The second example fails because the @code{CARDINAL} 1 is not
10356 type-compatible with the @code{REAL} 2.3.
10358 For the expressions you use in @value{GDBN} commands, you can tell the
10359 @value{GDBN} type checker to skip checking;
10360 to treat any mismatches as errors and abandon the expression;
10361 or to only issue warnings when type mismatches occur,
10362 but evaluate the expression anyway. When you choose the last of
10363 these, @value{GDBN} evaluates expressions like the second example above, but
10364 also issues a warning.
10366 Even if you turn type checking off, there may be other reasons
10367 related to type that prevent @value{GDBN} from evaluating an expression.
10368 For instance, @value{GDBN} does not know how to add an @code{int} and
10369 a @code{struct foo}. These particular type errors have nothing to do
10370 with the language in use, and usually arise from expressions, such as
10371 the one described above, which make little sense to evaluate anyway.
10373 Each language defines to what degree it is strict about type. For
10374 instance, both Modula-2 and C require the arguments to arithmetical
10375 operators to be numbers. In C, enumerated types and pointers can be
10376 represented as numbers, so that they are valid arguments to mathematical
10377 operators. @xref{Supported Languages, ,Supported Languages}, for further
10378 details on specific languages.
10380 @value{GDBN} provides some additional commands for controlling the type checker:
10382 @kindex set check type
10383 @kindex show check type
10385 @item set check type auto
10386 Set type checking on or off based on the current working language.
10387 @xref{Supported Languages, ,Supported Languages}, for the default settings for
10390 @item set check type on
10391 @itemx set check type off
10392 Set type checking on or off, overriding the default setting for the
10393 current working language. Issue a warning if the setting does not
10394 match the language default. If any type mismatches occur in
10395 evaluating an expression while type checking is on, @value{GDBN} prints a
10396 message and aborts evaluation of the expression.
10398 @item set check type warn
10399 Cause the type checker to issue warnings, but to always attempt to
10400 evaluate the expression. Evaluating the expression may still
10401 be impossible for other reasons. For example, @value{GDBN} cannot add
10402 numbers and structures.
10405 Show the current setting of the type checker, and whether or not @value{GDBN}
10406 is setting it automatically.
10409 @cindex range checking
10410 @cindex checks, range
10411 @node Range Checking
10412 @subsection An Overview of Range Checking
10414 In some languages (such as Modula-2), it is an error to exceed the
10415 bounds of a type; this is enforced with run-time checks. Such range
10416 checking is meant to ensure program correctness by making sure
10417 computations do not overflow, or indices on an array element access do
10418 not exceed the bounds of the array.
10420 For expressions you use in @value{GDBN} commands, you can tell
10421 @value{GDBN} to treat range errors in one of three ways: ignore them,
10422 always treat them as errors and abandon the expression, or issue
10423 warnings but evaluate the expression anyway.
10425 A range error can result from numerical overflow, from exceeding an
10426 array index bound, or when you type a constant that is not a member
10427 of any type. Some languages, however, do not treat overflows as an
10428 error. In many implementations of C, mathematical overflow causes the
10429 result to ``wrap around'' to lower values---for example, if @var{m} is
10430 the largest integer value, and @var{s} is the smallest, then
10433 @var{m} + 1 @result{} @var{s}
10436 This, too, is specific to individual languages, and in some cases
10437 specific to individual compilers or machines. @xref{Supported Languages, ,
10438 Supported Languages}, for further details on specific languages.
10440 @value{GDBN} provides some additional commands for controlling the range checker:
10442 @kindex set check range
10443 @kindex show check range
10445 @item set check range auto
10446 Set range checking on or off based on the current working language.
10447 @xref{Supported Languages, ,Supported Languages}, for the default settings for
10450 @item set check range on
10451 @itemx set check range off
10452 Set range checking on or off, overriding the default setting for the
10453 current working language. A warning is issued if the setting does not
10454 match the language default. If a range error occurs and range checking is on,
10455 then a message is printed and evaluation of the expression is aborted.
10457 @item set check range warn
10458 Output messages when the @value{GDBN} range checker detects a range error,
10459 but attempt to evaluate the expression anyway. Evaluating the
10460 expression may still be impossible for other reasons, such as accessing
10461 memory that the process does not own (a typical example from many Unix
10465 Show the current setting of the range checker, and whether or not it is
10466 being set automatically by @value{GDBN}.
10469 @node Supported Languages
10470 @section Supported Languages
10472 @value{GDBN} supports C, C@t{++}, Objective-C, Fortran, Java, Pascal,
10473 assembly, Modula-2, and Ada.
10474 @c This is false ...
10475 Some @value{GDBN} features may be used in expressions regardless of the
10476 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
10477 and the @samp{@{type@}addr} construct (@pxref{Expressions,
10478 ,Expressions}) can be used with the constructs of any supported
10481 The following sections detail to what degree each source language is
10482 supported by @value{GDBN}. These sections are not meant to be language
10483 tutorials or references, but serve only as a reference guide to what the
10484 @value{GDBN} expression parser accepts, and what input and output
10485 formats should look like for different languages. There are many good
10486 books written on each of these languages; please look to these for a
10487 language reference or tutorial.
10490 * C:: C and C@t{++}
10491 * Objective-C:: Objective-C
10492 * Fortran:: Fortran
10494 * Modula-2:: Modula-2
10499 @subsection C and C@t{++}
10501 @cindex C and C@t{++}
10502 @cindex expressions in C or C@t{++}
10504 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
10505 to both languages. Whenever this is the case, we discuss those languages
10509 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
10510 @cindex @sc{gnu} C@t{++}
10511 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
10512 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
10513 effectively, you must compile your C@t{++} programs with a supported
10514 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
10515 compiler (@code{aCC}).
10517 For best results when using @sc{gnu} C@t{++}, use the DWARF 2 debugging
10518 format; if it doesn't work on your system, try the stabs+ debugging
10519 format. You can select those formats explicitly with the @code{g++}
10520 command-line options @option{-gdwarf-2} and @option{-gstabs+}.
10521 @xref{Debugging Options,,Options for Debugging Your Program or GCC,
10522 gcc.info, Using the @sc{gnu} Compiler Collection (GCC)}.
10525 * C Operators:: C and C@t{++} operators
10526 * C Constants:: C and C@t{++} constants
10527 * C Plus Plus Expressions:: C@t{++} expressions
10528 * C Defaults:: Default settings for C and C@t{++}
10529 * C Checks:: C and C@t{++} type and range checks
10530 * Debugging C:: @value{GDBN} and C
10531 * Debugging C Plus Plus:: @value{GDBN} features for C@t{++}
10532 * Decimal Floating Point:: Numbers in Decimal Floating Point format
10536 @subsubsection C and C@t{++} Operators
10538 @cindex C and C@t{++} operators
10540 Operators must be defined on values of specific types. For instance,
10541 @code{+} is defined on numbers, but not on structures. Operators are
10542 often defined on groups of types.
10544 For the purposes of C and C@t{++}, the following definitions hold:
10549 @emph{Integral types} include @code{int} with any of its storage-class
10550 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
10553 @emph{Floating-point types} include @code{float}, @code{double}, and
10554 @code{long double} (if supported by the target platform).
10557 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
10560 @emph{Scalar types} include all of the above.
10565 The following operators are supported. They are listed here
10566 in order of increasing precedence:
10570 The comma or sequencing operator. Expressions in a comma-separated list
10571 are evaluated from left to right, with the result of the entire
10572 expression being the last expression evaluated.
10575 Assignment. The value of an assignment expression is the value
10576 assigned. Defined on scalar types.
10579 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
10580 and translated to @w{@code{@var{a} = @var{a op b}}}.
10581 @w{@code{@var{op}=}} and @code{=} have the same precedence.
10582 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
10583 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
10586 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
10587 of as: if @var{a} then @var{b} else @var{c}. @var{a} should be of an
10591 Logical @sc{or}. Defined on integral types.
10594 Logical @sc{and}. Defined on integral types.
10597 Bitwise @sc{or}. Defined on integral types.
10600 Bitwise exclusive-@sc{or}. Defined on integral types.
10603 Bitwise @sc{and}. Defined on integral types.
10606 Equality and inequality. Defined on scalar types. The value of these
10607 expressions is 0 for false and non-zero for true.
10609 @item <@r{, }>@r{, }<=@r{, }>=
10610 Less than, greater than, less than or equal, greater than or equal.
10611 Defined on scalar types. The value of these expressions is 0 for false
10612 and non-zero for true.
10615 left shift, and right shift. Defined on integral types.
10618 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
10621 Addition and subtraction. Defined on integral types, floating-point types and
10624 @item *@r{, }/@r{, }%
10625 Multiplication, division, and modulus. Multiplication and division are
10626 defined on integral and floating-point types. Modulus is defined on
10630 Increment and decrement. When appearing before a variable, the
10631 operation is performed before the variable is used in an expression;
10632 when appearing after it, the variable's value is used before the
10633 operation takes place.
10636 Pointer dereferencing. Defined on pointer types. Same precedence as
10640 Address operator. Defined on variables. Same precedence as @code{++}.
10642 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
10643 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
10644 to examine the address
10645 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
10649 Negative. Defined on integral and floating-point types. Same
10650 precedence as @code{++}.
10653 Logical negation. Defined on integral types. Same precedence as
10657 Bitwise complement operator. Defined on integral types. Same precedence as
10662 Structure member, and pointer-to-structure member. For convenience,
10663 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
10664 pointer based on the stored type information.
10665 Defined on @code{struct} and @code{union} data.
10668 Dereferences of pointers to members.
10671 Array indexing. @code{@var{a}[@var{i}]} is defined as
10672 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
10675 Function parameter list. Same precedence as @code{->}.
10678 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
10679 and @code{class} types.
10682 Doubled colons also represent the @value{GDBN} scope operator
10683 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
10687 If an operator is redefined in the user code, @value{GDBN} usually
10688 attempts to invoke the redefined version instead of using the operator's
10689 predefined meaning.
10692 @subsubsection C and C@t{++} Constants
10694 @cindex C and C@t{++} constants
10696 @value{GDBN} allows you to express the constants of C and C@t{++} in the
10701 Integer constants are a sequence of digits. Octal constants are
10702 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
10703 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
10704 @samp{l}, specifying that the constant should be treated as a
10708 Floating point constants are a sequence of digits, followed by a decimal
10709 point, followed by a sequence of digits, and optionally followed by an
10710 exponent. An exponent is of the form:
10711 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
10712 sequence of digits. The @samp{+} is optional for positive exponents.
10713 A floating-point constant may also end with a letter @samp{f} or
10714 @samp{F}, specifying that the constant should be treated as being of
10715 the @code{float} (as opposed to the default @code{double}) type; or with
10716 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
10720 Enumerated constants consist of enumerated identifiers, or their
10721 integral equivalents.
10724 Character constants are a single character surrounded by single quotes
10725 (@code{'}), or a number---the ordinal value of the corresponding character
10726 (usually its @sc{ascii} value). Within quotes, the single character may
10727 be represented by a letter or by @dfn{escape sequences}, which are of
10728 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
10729 of the character's ordinal value; or of the form @samp{\@var{x}}, where
10730 @samp{@var{x}} is a predefined special character---for example,
10731 @samp{\n} for newline.
10734 String constants are a sequence of character constants surrounded by
10735 double quotes (@code{"}). Any valid character constant (as described
10736 above) may appear. Double quotes within the string must be preceded by
10737 a backslash, so for instance @samp{"a\"b'c"} is a string of five
10741 Pointer constants are an integral value. You can also write pointers
10742 to constants using the C operator @samp{&}.
10745 Array constants are comma-separated lists surrounded by braces @samp{@{}
10746 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
10747 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
10748 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
10751 @node C Plus Plus Expressions
10752 @subsubsection C@t{++} Expressions
10754 @cindex expressions in C@t{++}
10755 @value{GDBN} expression handling can interpret most C@t{++} expressions.
10757 @cindex debugging C@t{++} programs
10758 @cindex C@t{++} compilers
10759 @cindex debug formats and C@t{++}
10760 @cindex @value{NGCC} and C@t{++}
10762 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use the
10763 proper compiler and the proper debug format. Currently, @value{GDBN}
10764 works best when debugging C@t{++} code that is compiled with
10765 @value{NGCC} 2.95.3 or with @value{NGCC} 3.1 or newer, using the options
10766 @option{-gdwarf-2} or @option{-gstabs+}. DWARF 2 is preferred over
10767 stabs+. Most configurations of @value{NGCC} emit either DWARF 2 or
10768 stabs+ as their default debug format, so you usually don't need to
10769 specify a debug format explicitly. Other compilers and/or debug formats
10770 are likely to work badly or not at all when using @value{GDBN} to debug
10776 @cindex member functions
10778 Member function calls are allowed; you can use expressions like
10781 count = aml->GetOriginal(x, y)
10784 @vindex this@r{, inside C@t{++} member functions}
10785 @cindex namespace in C@t{++}
10787 While a member function is active (in the selected stack frame), your
10788 expressions have the same namespace available as the member function;
10789 that is, @value{GDBN} allows implicit references to the class instance
10790 pointer @code{this} following the same rules as C@t{++}.
10792 @cindex call overloaded functions
10793 @cindex overloaded functions, calling
10794 @cindex type conversions in C@t{++}
10796 You can call overloaded functions; @value{GDBN} resolves the function
10797 call to the right definition, with some restrictions. @value{GDBN} does not
10798 perform overload resolution involving user-defined type conversions,
10799 calls to constructors, or instantiations of templates that do not exist
10800 in the program. It also cannot handle ellipsis argument lists or
10803 It does perform integral conversions and promotions, floating-point
10804 promotions, arithmetic conversions, pointer conversions, conversions of
10805 class objects to base classes, and standard conversions such as those of
10806 functions or arrays to pointers; it requires an exact match on the
10807 number of function arguments.
10809 Overload resolution is always performed, unless you have specified
10810 @code{set overload-resolution off}. @xref{Debugging C Plus Plus,
10811 ,@value{GDBN} Features for C@t{++}}.
10813 You must specify @code{set overload-resolution off} in order to use an
10814 explicit function signature to call an overloaded function, as in
10816 p 'foo(char,int)'('x', 13)
10819 The @value{GDBN} command-completion facility can simplify this;
10820 see @ref{Completion, ,Command Completion}.
10822 @cindex reference declarations
10824 @value{GDBN} understands variables declared as C@t{++} references; you can use
10825 them in expressions just as you do in C@t{++} source---they are automatically
10828 In the parameter list shown when @value{GDBN} displays a frame, the values of
10829 reference variables are not displayed (unlike other variables); this
10830 avoids clutter, since references are often used for large structures.
10831 The @emph{address} of a reference variable is always shown, unless
10832 you have specified @samp{set print address off}.
10835 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
10836 expressions can use it just as expressions in your program do. Since
10837 one scope may be defined in another, you can use @code{::} repeatedly if
10838 necessary, for example in an expression like
10839 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
10840 resolving name scope by reference to source files, in both C and C@t{++}
10841 debugging (@pxref{Variables, ,Program Variables}).
10844 In addition, when used with HP's C@t{++} compiler, @value{GDBN} supports
10845 calling virtual functions correctly, printing out virtual bases of
10846 objects, calling functions in a base subobject, casting objects, and
10847 invoking user-defined operators.
10850 @subsubsection C and C@t{++} Defaults
10852 @cindex C and C@t{++} defaults
10854 If you allow @value{GDBN} to set type and range checking automatically, they
10855 both default to @code{off} whenever the working language changes to
10856 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
10857 selects the working language.
10859 If you allow @value{GDBN} to set the language automatically, it
10860 recognizes source files whose names end with @file{.c}, @file{.C}, or
10861 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
10862 these files, it sets the working language to C or C@t{++}.
10863 @xref{Automatically, ,Having @value{GDBN} Infer the Source Language},
10864 for further details.
10866 @c Type checking is (a) primarily motivated by Modula-2, and (b)
10867 @c unimplemented. If (b) changes, it might make sense to let this node
10868 @c appear even if Mod-2 does not, but meanwhile ignore it. roland 16jul93.
10871 @subsubsection C and C@t{++} Type and Range Checks
10873 @cindex C and C@t{++} checks
10875 By default, when @value{GDBN} parses C or C@t{++} expressions, type checking
10876 is not used. However, if you turn type checking on, @value{GDBN}
10877 considers two variables type equivalent if:
10881 The two variables are structured and have the same structure, union, or
10885 The two variables have the same type name, or types that have been
10886 declared equivalent through @code{typedef}.
10889 @c leaving this out because neither J Gilmore nor R Pesch understand it.
10892 The two @code{struct}, @code{union}, or @code{enum} variables are
10893 declared in the same declaration. (Note: this may not be true for all C
10898 Range checking, if turned on, is done on mathematical operations. Array
10899 indices are not checked, since they are often used to index a pointer
10900 that is not itself an array.
10903 @subsubsection @value{GDBN} and C
10905 The @code{set print union} and @code{show print union} commands apply to
10906 the @code{union} type. When set to @samp{on}, any @code{union} that is
10907 inside a @code{struct} or @code{class} is also printed. Otherwise, it
10908 appears as @samp{@{...@}}.
10910 The @code{@@} operator aids in the debugging of dynamic arrays, formed
10911 with pointers and a memory allocation function. @xref{Expressions,
10914 @node Debugging C Plus Plus
10915 @subsubsection @value{GDBN} Features for C@t{++}
10917 @cindex commands for C@t{++}
10919 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
10920 designed specifically for use with C@t{++}. Here is a summary:
10923 @cindex break in overloaded functions
10924 @item @r{breakpoint menus}
10925 When you want a breakpoint in a function whose name is overloaded,
10926 @value{GDBN} has the capability to display a menu of possible breakpoint
10927 locations to help you specify which function definition you want.
10928 @xref{Ambiguous Expressions,,Ambiguous Expressions}.
10930 @cindex overloading in C@t{++}
10931 @item rbreak @var{regex}
10932 Setting breakpoints using regular expressions is helpful for setting
10933 breakpoints on overloaded functions that are not members of any special
10935 @xref{Set Breaks, ,Setting Breakpoints}.
10937 @cindex C@t{++} exception handling
10940 Debug C@t{++} exception handling using these commands. @xref{Set
10941 Catchpoints, , Setting Catchpoints}.
10943 @cindex inheritance
10944 @item ptype @var{typename}
10945 Print inheritance relationships as well as other information for type
10947 @xref{Symbols, ,Examining the Symbol Table}.
10949 @cindex C@t{++} symbol display
10950 @item set print demangle
10951 @itemx show print demangle
10952 @itemx set print asm-demangle
10953 @itemx show print asm-demangle
10954 Control whether C@t{++} symbols display in their source form, both when
10955 displaying code as C@t{++} source and when displaying disassemblies.
10956 @xref{Print Settings, ,Print Settings}.
10958 @item set print object
10959 @itemx show print object
10960 Choose whether to print derived (actual) or declared types of objects.
10961 @xref{Print Settings, ,Print Settings}.
10963 @item set print vtbl
10964 @itemx show print vtbl
10965 Control the format for printing virtual function tables.
10966 @xref{Print Settings, ,Print Settings}.
10967 (The @code{vtbl} commands do not work on programs compiled with the HP
10968 ANSI C@t{++} compiler (@code{aCC}).)
10970 @kindex set overload-resolution
10971 @cindex overloaded functions, overload resolution
10972 @item set overload-resolution on
10973 Enable overload resolution for C@t{++} expression evaluation. The default
10974 is on. For overloaded functions, @value{GDBN} evaluates the arguments
10975 and searches for a function whose signature matches the argument types,
10976 using the standard C@t{++} conversion rules (see @ref{C Plus Plus
10977 Expressions, ,C@t{++} Expressions}, for details).
10978 If it cannot find a match, it emits a message.
10980 @item set overload-resolution off
10981 Disable overload resolution for C@t{++} expression evaluation. For
10982 overloaded functions that are not class member functions, @value{GDBN}
10983 chooses the first function of the specified name that it finds in the
10984 symbol table, whether or not its arguments are of the correct type. For
10985 overloaded functions that are class member functions, @value{GDBN}
10986 searches for a function whose signature @emph{exactly} matches the
10989 @kindex show overload-resolution
10990 @item show overload-resolution
10991 Show the current setting of overload resolution.
10993 @item @r{Overloaded symbol names}
10994 You can specify a particular definition of an overloaded symbol, using
10995 the same notation that is used to declare such symbols in C@t{++}: type
10996 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
10997 also use the @value{GDBN} command-line word completion facilities to list the
10998 available choices, or to finish the type list for you.
10999 @xref{Completion,, Command Completion}, for details on how to do this.
11002 @node Decimal Floating Point
11003 @subsubsection Decimal Floating Point format
11004 @cindex decimal floating point format
11006 @value{GDBN} can examine, set and perform computations with numbers in
11007 decimal floating point format, which in the C language correspond to the
11008 @code{_Decimal32}, @code{_Decimal64} and @code{_Decimal128} types as
11009 specified by the extension to support decimal floating-point arithmetic.
11011 There are two encodings in use, depending on the architecture: BID (Binary
11012 Integer Decimal) for x86 and x86-64, and DPD (Densely Packed Decimal) for
11013 PowerPC. @value{GDBN} will use the appropriate encoding for the configured
11016 Because of a limitation in @file{libdecnumber}, the library used by @value{GDBN}
11017 to manipulate decimal floating point numbers, it is not possible to convert
11018 (using a cast, for example) integers wider than 32-bit to decimal float.
11020 In addition, in order to imitate @value{GDBN}'s behaviour with binary floating
11021 point computations, error checking in decimal float operations ignores
11022 underflow, overflow and divide by zero exceptions.
11024 In the PowerPC architecture, @value{GDBN} provides a set of pseudo-registers
11025 to inspect @code{_Decimal128} values stored in floating point registers.
11026 See @ref{PowerPC,,PowerPC} for more details.
11029 @subsection Objective-C
11031 @cindex Objective-C
11032 This section provides information about some commands and command
11033 options that are useful for debugging Objective-C code. See also
11034 @ref{Symbols, info classes}, and @ref{Symbols, info selectors}, for a
11035 few more commands specific to Objective-C support.
11038 * Method Names in Commands::
11039 * The Print Command with Objective-C::
11042 @node Method Names in Commands
11043 @subsubsection Method Names in Commands
11045 The following commands have been extended to accept Objective-C method
11046 names as line specifications:
11048 @kindex clear@r{, and Objective-C}
11049 @kindex break@r{, and Objective-C}
11050 @kindex info line@r{, and Objective-C}
11051 @kindex jump@r{, and Objective-C}
11052 @kindex list@r{, and Objective-C}
11056 @item @code{info line}
11061 A fully qualified Objective-C method name is specified as
11064 -[@var{Class} @var{methodName}]
11067 where the minus sign is used to indicate an instance method and a
11068 plus sign (not shown) is used to indicate a class method. The class
11069 name @var{Class} and method name @var{methodName} are enclosed in
11070 brackets, similar to the way messages are specified in Objective-C
11071 source code. For example, to set a breakpoint at the @code{create}
11072 instance method of class @code{Fruit} in the program currently being
11076 break -[Fruit create]
11079 To list ten program lines around the @code{initialize} class method,
11083 list +[NSText initialize]
11086 In the current version of @value{GDBN}, the plus or minus sign is
11087 required. In future versions of @value{GDBN}, the plus or minus
11088 sign will be optional, but you can use it to narrow the search. It
11089 is also possible to specify just a method name:
11095 You must specify the complete method name, including any colons. If
11096 your program's source files contain more than one @code{create} method,
11097 you'll be presented with a numbered list of classes that implement that
11098 method. Indicate your choice by number, or type @samp{0} to exit if
11101 As another example, to clear a breakpoint established at the
11102 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
11105 clear -[NSWindow makeKeyAndOrderFront:]
11108 @node The Print Command with Objective-C
11109 @subsubsection The Print Command With Objective-C
11110 @cindex Objective-C, print objects
11111 @kindex print-object
11112 @kindex po @r{(@code{print-object})}
11114 The print command has also been extended to accept methods. For example:
11117 print -[@var{object} hash]
11120 @cindex print an Objective-C object description
11121 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
11123 will tell @value{GDBN} to send the @code{hash} message to @var{object}
11124 and print the result. Also, an additional command has been added,
11125 @code{print-object} or @code{po} for short, which is meant to print
11126 the description of an object. However, this command may only work
11127 with certain Objective-C libraries that have a particular hook
11128 function, @code{_NSPrintForDebugger}, defined.
11131 @subsection Fortran
11132 @cindex Fortran-specific support in @value{GDBN}
11134 @value{GDBN} can be used to debug programs written in Fortran, but it
11135 currently supports only the features of Fortran 77 language.
11137 @cindex trailing underscore, in Fortran symbols
11138 Some Fortran compilers (@sc{gnu} Fortran 77 and Fortran 95 compilers
11139 among them) append an underscore to the names of variables and
11140 functions. When you debug programs compiled by those compilers, you
11141 will need to refer to variables and functions with a trailing
11145 * Fortran Operators:: Fortran operators and expressions
11146 * Fortran Defaults:: Default settings for Fortran
11147 * Special Fortran Commands:: Special @value{GDBN} commands for Fortran
11150 @node Fortran Operators
11151 @subsubsection Fortran Operators and Expressions
11153 @cindex Fortran operators and expressions
11155 Operators must be defined on values of specific types. For instance,
11156 @code{+} is defined on numbers, but not on characters or other non-
11157 arithmetic types. Operators are often defined on groups of types.
11161 The exponentiation operator. It raises the first operand to the power
11165 The range operator. Normally used in the form of array(low:high) to
11166 represent a section of array.
11169 The access component operator. Normally used to access elements in derived
11170 types. Also suitable for unions. As unions aren't part of regular Fortran,
11171 this can only happen when accessing a register that uses a gdbarch-defined
11175 @node Fortran Defaults
11176 @subsubsection Fortran Defaults
11178 @cindex Fortran Defaults
11180 Fortran symbols are usually case-insensitive, so @value{GDBN} by
11181 default uses case-insensitive matches for Fortran symbols. You can
11182 change that with the @samp{set case-insensitive} command, see
11183 @ref{Symbols}, for the details.
11185 @node Special Fortran Commands
11186 @subsubsection Special Fortran Commands
11188 @cindex Special Fortran commands
11190 @value{GDBN} has some commands to support Fortran-specific features,
11191 such as displaying common blocks.
11194 @cindex @code{COMMON} blocks, Fortran
11195 @kindex info common
11196 @item info common @r{[}@var{common-name}@r{]}
11197 This command prints the values contained in the Fortran @code{COMMON}
11198 block whose name is @var{common-name}. With no argument, the names of
11199 all @code{COMMON} blocks visible at the current program location are
11206 @cindex Pascal support in @value{GDBN}, limitations
11207 Debugging Pascal programs which use sets, subranges, file variables, or
11208 nested functions does not currently work. @value{GDBN} does not support
11209 entering expressions, printing values, or similar features using Pascal
11212 The Pascal-specific command @code{set print pascal_static-members}
11213 controls whether static members of Pascal objects are displayed.
11214 @xref{Print Settings, pascal_static-members}.
11217 @subsection Modula-2
11219 @cindex Modula-2, @value{GDBN} support
11221 The extensions made to @value{GDBN} to support Modula-2 only support
11222 output from the @sc{gnu} Modula-2 compiler (which is currently being
11223 developed). Other Modula-2 compilers are not currently supported, and
11224 attempting to debug executables produced by them is most likely
11225 to give an error as @value{GDBN} reads in the executable's symbol
11228 @cindex expressions in Modula-2
11230 * M2 Operators:: Built-in operators
11231 * Built-In Func/Proc:: Built-in functions and procedures
11232 * M2 Constants:: Modula-2 constants
11233 * M2 Types:: Modula-2 types
11234 * M2 Defaults:: Default settings for Modula-2
11235 * Deviations:: Deviations from standard Modula-2
11236 * M2 Checks:: Modula-2 type and range checks
11237 * M2 Scope:: The scope operators @code{::} and @code{.}
11238 * GDB/M2:: @value{GDBN} and Modula-2
11242 @subsubsection Operators
11243 @cindex Modula-2 operators
11245 Operators must be defined on values of specific types. For instance,
11246 @code{+} is defined on numbers, but not on structures. Operators are
11247 often defined on groups of types. For the purposes of Modula-2, the
11248 following definitions hold:
11253 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
11257 @emph{Character types} consist of @code{CHAR} and its subranges.
11260 @emph{Floating-point types} consist of @code{REAL}.
11263 @emph{Pointer types} consist of anything declared as @code{POINTER TO
11267 @emph{Scalar types} consist of all of the above.
11270 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
11273 @emph{Boolean types} consist of @code{BOOLEAN}.
11277 The following operators are supported, and appear in order of
11278 increasing precedence:
11282 Function argument or array index separator.
11285 Assignment. The value of @var{var} @code{:=} @var{value} is
11289 Less than, greater than on integral, floating-point, or enumerated
11293 Less than or equal to, greater than or equal to
11294 on integral, floating-point and enumerated types, or set inclusion on
11295 set types. Same precedence as @code{<}.
11297 @item =@r{, }<>@r{, }#
11298 Equality and two ways of expressing inequality, valid on scalar types.
11299 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
11300 available for inequality, since @code{#} conflicts with the script
11304 Set membership. Defined on set types and the types of their members.
11305 Same precedence as @code{<}.
11308 Boolean disjunction. Defined on boolean types.
11311 Boolean conjunction. Defined on boolean types.
11314 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
11317 Addition and subtraction on integral and floating-point types, or union
11318 and difference on set types.
11321 Multiplication on integral and floating-point types, or set intersection
11325 Division on floating-point types, or symmetric set difference on set
11326 types. Same precedence as @code{*}.
11329 Integer division and remainder. Defined on integral types. Same
11330 precedence as @code{*}.
11333 Negative. Defined on @code{INTEGER} and @code{REAL} data.
11336 Pointer dereferencing. Defined on pointer types.
11339 Boolean negation. Defined on boolean types. Same precedence as
11343 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
11344 precedence as @code{^}.
11347 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
11350 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
11354 @value{GDBN} and Modula-2 scope operators.
11358 @emph{Warning:} Set expressions and their operations are not yet supported, so @value{GDBN}
11359 treats the use of the operator @code{IN}, or the use of operators
11360 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
11361 @code{<=}, and @code{>=} on sets as an error.
11365 @node Built-In Func/Proc
11366 @subsubsection Built-in Functions and Procedures
11367 @cindex Modula-2 built-ins
11369 Modula-2 also makes available several built-in procedures and functions.
11370 In describing these, the following metavariables are used:
11375 represents an @code{ARRAY} variable.
11378 represents a @code{CHAR} constant or variable.
11381 represents a variable or constant of integral type.
11384 represents an identifier that belongs to a set. Generally used in the
11385 same function with the metavariable @var{s}. The type of @var{s} should
11386 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
11389 represents a variable or constant of integral or floating-point type.
11392 represents a variable or constant of floating-point type.
11398 represents a variable.
11401 represents a variable or constant of one of many types. See the
11402 explanation of the function for details.
11405 All Modula-2 built-in procedures also return a result, described below.
11409 Returns the absolute value of @var{n}.
11412 If @var{c} is a lower case letter, it returns its upper case
11413 equivalent, otherwise it returns its argument.
11416 Returns the character whose ordinal value is @var{i}.
11419 Decrements the value in the variable @var{v} by one. Returns the new value.
11421 @item DEC(@var{v},@var{i})
11422 Decrements the value in the variable @var{v} by @var{i}. Returns the
11425 @item EXCL(@var{m},@var{s})
11426 Removes the element @var{m} from the set @var{s}. Returns the new
11429 @item FLOAT(@var{i})
11430 Returns the floating point equivalent of the integer @var{i}.
11432 @item HIGH(@var{a})
11433 Returns the index of the last member of @var{a}.
11436 Increments the value in the variable @var{v} by one. Returns the new value.
11438 @item INC(@var{v},@var{i})
11439 Increments the value in the variable @var{v} by @var{i}. Returns the
11442 @item INCL(@var{m},@var{s})
11443 Adds the element @var{m} to the set @var{s} if it is not already
11444 there. Returns the new set.
11447 Returns the maximum value of the type @var{t}.
11450 Returns the minimum value of the type @var{t}.
11453 Returns boolean TRUE if @var{i} is an odd number.
11456 Returns the ordinal value of its argument. For example, the ordinal
11457 value of a character is its @sc{ascii} value (on machines supporting the
11458 @sc{ascii} character set). @var{x} must be of an ordered type, which include
11459 integral, character and enumerated types.
11461 @item SIZE(@var{x})
11462 Returns the size of its argument. @var{x} can be a variable or a type.
11464 @item TRUNC(@var{r})
11465 Returns the integral part of @var{r}.
11467 @item TSIZE(@var{x})
11468 Returns the size of its argument. @var{x} can be a variable or a type.
11470 @item VAL(@var{t},@var{i})
11471 Returns the member of the type @var{t} whose ordinal value is @var{i}.
11475 @emph{Warning:} Sets and their operations are not yet supported, so
11476 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
11480 @cindex Modula-2 constants
11482 @subsubsection Constants
11484 @value{GDBN} allows you to express the constants of Modula-2 in the following
11490 Integer constants are simply a sequence of digits. When used in an
11491 expression, a constant is interpreted to be type-compatible with the
11492 rest of the expression. Hexadecimal integers are specified by a
11493 trailing @samp{H}, and octal integers by a trailing @samp{B}.
11496 Floating point constants appear as a sequence of digits, followed by a
11497 decimal point and another sequence of digits. An optional exponent can
11498 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
11499 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
11500 digits of the floating point constant must be valid decimal (base 10)
11504 Character constants consist of a single character enclosed by a pair of
11505 like quotes, either single (@code{'}) or double (@code{"}). They may
11506 also be expressed by their ordinal value (their @sc{ascii} value, usually)
11507 followed by a @samp{C}.
11510 String constants consist of a sequence of characters enclosed by a
11511 pair of like quotes, either single (@code{'}) or double (@code{"}).
11512 Escape sequences in the style of C are also allowed. @xref{C
11513 Constants, ,C and C@t{++} Constants}, for a brief explanation of escape
11517 Enumerated constants consist of an enumerated identifier.
11520 Boolean constants consist of the identifiers @code{TRUE} and
11524 Pointer constants consist of integral values only.
11527 Set constants are not yet supported.
11531 @subsubsection Modula-2 Types
11532 @cindex Modula-2 types
11534 Currently @value{GDBN} can print the following data types in Modula-2
11535 syntax: array types, record types, set types, pointer types, procedure
11536 types, enumerated types, subrange types and base types. You can also
11537 print the contents of variables declared using these type.
11538 This section gives a number of simple source code examples together with
11539 sample @value{GDBN} sessions.
11541 The first example contains the following section of code:
11550 and you can request @value{GDBN} to interrogate the type and value of
11551 @code{r} and @code{s}.
11554 (@value{GDBP}) print s
11556 (@value{GDBP}) ptype s
11558 (@value{GDBP}) print r
11560 (@value{GDBP}) ptype r
11565 Likewise if your source code declares @code{s} as:
11569 s: SET ['A'..'Z'] ;
11573 then you may query the type of @code{s} by:
11576 (@value{GDBP}) ptype s
11577 type = SET ['A'..'Z']
11581 Note that at present you cannot interactively manipulate set
11582 expressions using the debugger.
11584 The following example shows how you might declare an array in Modula-2
11585 and how you can interact with @value{GDBN} to print its type and contents:
11589 s: ARRAY [-10..10] OF CHAR ;
11593 (@value{GDBP}) ptype s
11594 ARRAY [-10..10] OF CHAR
11597 Note that the array handling is not yet complete and although the type
11598 is printed correctly, expression handling still assumes that all
11599 arrays have a lower bound of zero and not @code{-10} as in the example
11602 Here are some more type related Modula-2 examples:
11606 colour = (blue, red, yellow, green) ;
11607 t = [blue..yellow] ;
11615 The @value{GDBN} interaction shows how you can query the data type
11616 and value of a variable.
11619 (@value{GDBP}) print s
11621 (@value{GDBP}) ptype t
11622 type = [blue..yellow]
11626 In this example a Modula-2 array is declared and its contents
11627 displayed. Observe that the contents are written in the same way as
11628 their @code{C} counterparts.
11632 s: ARRAY [1..5] OF CARDINAL ;
11638 (@value{GDBP}) print s
11639 $1 = @{1, 0, 0, 0, 0@}
11640 (@value{GDBP}) ptype s
11641 type = ARRAY [1..5] OF CARDINAL
11644 The Modula-2 language interface to @value{GDBN} also understands
11645 pointer types as shown in this example:
11649 s: POINTER TO ARRAY [1..5] OF CARDINAL ;
11656 and you can request that @value{GDBN} describes the type of @code{s}.
11659 (@value{GDBP}) ptype s
11660 type = POINTER TO ARRAY [1..5] OF CARDINAL
11663 @value{GDBN} handles compound types as we can see in this example.
11664 Here we combine array types, record types, pointer types and subrange
11675 myarray = ARRAY myrange OF CARDINAL ;
11676 myrange = [-2..2] ;
11678 s: POINTER TO ARRAY myrange OF foo ;
11682 and you can ask @value{GDBN} to describe the type of @code{s} as shown
11686 (@value{GDBP}) ptype s
11687 type = POINTER TO ARRAY [-2..2] OF foo = RECORD
11690 f3 : ARRAY [-2..2] OF CARDINAL;
11695 @subsubsection Modula-2 Defaults
11696 @cindex Modula-2 defaults
11698 If type and range checking are set automatically by @value{GDBN}, they
11699 both default to @code{on} whenever the working language changes to
11700 Modula-2. This happens regardless of whether you or @value{GDBN}
11701 selected the working language.
11703 If you allow @value{GDBN} to set the language automatically, then entering
11704 code compiled from a file whose name ends with @file{.mod} sets the
11705 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN}
11706 Infer the Source Language}, for further details.
11709 @subsubsection Deviations from Standard Modula-2
11710 @cindex Modula-2, deviations from
11712 A few changes have been made to make Modula-2 programs easier to debug.
11713 This is done primarily via loosening its type strictness:
11717 Unlike in standard Modula-2, pointer constants can be formed by
11718 integers. This allows you to modify pointer variables during
11719 debugging. (In standard Modula-2, the actual address contained in a
11720 pointer variable is hidden from you; it can only be modified
11721 through direct assignment to another pointer variable or expression that
11722 returned a pointer.)
11725 C escape sequences can be used in strings and characters to represent
11726 non-printable characters. @value{GDBN} prints out strings with these
11727 escape sequences embedded. Single non-printable characters are
11728 printed using the @samp{CHR(@var{nnn})} format.
11731 The assignment operator (@code{:=}) returns the value of its right-hand
11735 All built-in procedures both modify @emph{and} return their argument.
11739 @subsubsection Modula-2 Type and Range Checks
11740 @cindex Modula-2 checks
11743 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
11746 @c FIXME remove warning when type/range checks added
11748 @value{GDBN} considers two Modula-2 variables type equivalent if:
11752 They are of types that have been declared equivalent via a @code{TYPE
11753 @var{t1} = @var{t2}} statement
11756 They have been declared on the same line. (Note: This is true of the
11757 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
11760 As long as type checking is enabled, any attempt to combine variables
11761 whose types are not equivalent is an error.
11763 Range checking is done on all mathematical operations, assignment, array
11764 index bounds, and all built-in functions and procedures.
11767 @subsubsection The Scope Operators @code{::} and @code{.}
11769 @cindex @code{.}, Modula-2 scope operator
11770 @cindex colon, doubled as scope operator
11772 @vindex colon-colon@r{, in Modula-2}
11773 @c Info cannot handle :: but TeX can.
11776 @vindex ::@r{, in Modula-2}
11779 There are a few subtle differences between the Modula-2 scope operator
11780 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
11785 @var{module} . @var{id}
11786 @var{scope} :: @var{id}
11790 where @var{scope} is the name of a module or a procedure,
11791 @var{module} the name of a module, and @var{id} is any declared
11792 identifier within your program, except another module.
11794 Using the @code{::} operator makes @value{GDBN} search the scope
11795 specified by @var{scope} for the identifier @var{id}. If it is not
11796 found in the specified scope, then @value{GDBN} searches all scopes
11797 enclosing the one specified by @var{scope}.
11799 Using the @code{.} operator makes @value{GDBN} search the current scope for
11800 the identifier specified by @var{id} that was imported from the
11801 definition module specified by @var{module}. With this operator, it is
11802 an error if the identifier @var{id} was not imported from definition
11803 module @var{module}, or if @var{id} is not an identifier in
11807 @subsubsection @value{GDBN} and Modula-2
11809 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
11810 Five subcommands of @code{set print} and @code{show print} apply
11811 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
11812 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
11813 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
11814 analogue in Modula-2.
11816 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
11817 with any language, is not useful with Modula-2. Its
11818 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
11819 created in Modula-2 as they can in C or C@t{++}. However, because an
11820 address can be specified by an integral constant, the construct
11821 @samp{@{@var{type}@}@var{adrexp}} is still useful.
11823 @cindex @code{#} in Modula-2
11824 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
11825 interpreted as the beginning of a comment. Use @code{<>} instead.
11831 The extensions made to @value{GDBN} for Ada only support
11832 output from the @sc{gnu} Ada (GNAT) compiler.
11833 Other Ada compilers are not currently supported, and
11834 attempting to debug executables produced by them is most likely
11838 @cindex expressions in Ada
11840 * Ada Mode Intro:: General remarks on the Ada syntax
11841 and semantics supported by Ada mode
11843 * Omissions from Ada:: Restrictions on the Ada expression syntax.
11844 * Additions to Ada:: Extensions of the Ada expression syntax.
11845 * Stopping Before Main Program:: Debugging the program during elaboration.
11846 * Ada Tasks:: Listing and setting breakpoints in tasks.
11847 * Ada Tasks and Core Files:: Tasking Support when Debugging Core Files
11848 * Ada Glitches:: Known peculiarities of Ada mode.
11851 @node Ada Mode Intro
11852 @subsubsection Introduction
11853 @cindex Ada mode, general
11855 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
11856 syntax, with some extensions.
11857 The philosophy behind the design of this subset is
11861 That @value{GDBN} should provide basic literals and access to operations for
11862 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
11863 leaving more sophisticated computations to subprograms written into the
11864 program (which therefore may be called from @value{GDBN}).
11867 That type safety and strict adherence to Ada language restrictions
11868 are not particularly important to the @value{GDBN} user.
11871 That brevity is important to the @value{GDBN} user.
11874 Thus, for brevity, the debugger acts as if all names declared in
11875 user-written packages are directly visible, even if they are not visible
11876 according to Ada rules, thus making it unnecessary to fully qualify most
11877 names with their packages, regardless of context. Where this causes
11878 ambiguity, @value{GDBN} asks the user's intent.
11880 The debugger will start in Ada mode if it detects an Ada main program.
11881 As for other languages, it will enter Ada mode when stopped in a program that
11882 was translated from an Ada source file.
11884 While in Ada mode, you may use `@t{--}' for comments. This is useful
11885 mostly for documenting command files. The standard @value{GDBN} comment
11886 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
11887 middle (to allow based literals).
11889 The debugger supports limited overloading. Given a subprogram call in which
11890 the function symbol has multiple definitions, it will use the number of
11891 actual parameters and some information about their types to attempt to narrow
11892 the set of definitions. It also makes very limited use of context, preferring
11893 procedures to functions in the context of the @code{call} command, and
11894 functions to procedures elsewhere.
11896 @node Omissions from Ada
11897 @subsubsection Omissions from Ada
11898 @cindex Ada, omissions from
11900 Here are the notable omissions from the subset:
11904 Only a subset of the attributes are supported:
11908 @t{'First}, @t{'Last}, and @t{'Length}
11909 on array objects (not on types and subtypes).
11912 @t{'Min} and @t{'Max}.
11915 @t{'Pos} and @t{'Val}.
11921 @t{'Range} on array objects (not subtypes), but only as the right
11922 operand of the membership (@code{in}) operator.
11925 @t{'Access}, @t{'Unchecked_Access}, and
11926 @t{'Unrestricted_Access} (a GNAT extension).
11934 @code{Characters.Latin_1} are not available and
11935 concatenation is not implemented. Thus, escape characters in strings are
11936 not currently available.
11939 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
11940 equality of representations. They will generally work correctly
11941 for strings and arrays whose elements have integer or enumeration types.
11942 They may not work correctly for arrays whose element
11943 types have user-defined equality, for arrays of real values
11944 (in particular, IEEE-conformant floating point, because of negative
11945 zeroes and NaNs), and for arrays whose elements contain unused bits with
11946 indeterminate values.
11949 The other component-by-component array operations (@code{and}, @code{or},
11950 @code{xor}, @code{not}, and relational tests other than equality)
11951 are not implemented.
11954 @cindex array aggregates (Ada)
11955 @cindex record aggregates (Ada)
11956 @cindex aggregates (Ada)
11957 There is limited support for array and record aggregates. They are
11958 permitted only on the right sides of assignments, as in these examples:
11961 (@value{GDBP}) set An_Array := (1, 2, 3, 4, 5, 6)
11962 (@value{GDBP}) set An_Array := (1, others => 0)
11963 (@value{GDBP}) set An_Array := (0|4 => 1, 1..3 => 2, 5 => 6)
11964 (@value{GDBP}) set A_2D_Array := ((1, 2, 3), (4, 5, 6), (7, 8, 9))
11965 (@value{GDBP}) set A_Record := (1, "Peter", True);
11966 (@value{GDBP}) set A_Record := (Name => "Peter", Id => 1, Alive => True)
11970 discriminant's value by assigning an aggregate has an
11971 undefined effect if that discriminant is used within the record.
11972 However, you can first modify discriminants by directly assigning to
11973 them (which normally would not be allowed in Ada), and then performing an
11974 aggregate assignment. For example, given a variable @code{A_Rec}
11975 declared to have a type such as:
11978 type Rec (Len : Small_Integer := 0) is record
11980 Vals : IntArray (1 .. Len);
11984 you can assign a value with a different size of @code{Vals} with two
11988 (@value{GDBP}) set A_Rec.Len := 4
11989 (@value{GDBP}) set A_Rec := (Id => 42, Vals => (1, 2, 3, 4))
11992 As this example also illustrates, @value{GDBN} is very loose about the usual
11993 rules concerning aggregates. You may leave out some of the
11994 components of an array or record aggregate (such as the @code{Len}
11995 component in the assignment to @code{A_Rec} above); they will retain their
11996 original values upon assignment. You may freely use dynamic values as
11997 indices in component associations. You may even use overlapping or
11998 redundant component associations, although which component values are
11999 assigned in such cases is not defined.
12002 Calls to dispatching subprograms are not implemented.
12005 The overloading algorithm is much more limited (i.e., less selective)
12006 than that of real Ada. It makes only limited use of the context in
12007 which a subexpression appears to resolve its meaning, and it is much
12008 looser in its rules for allowing type matches. As a result, some
12009 function calls will be ambiguous, and the user will be asked to choose
12010 the proper resolution.
12013 The @code{new} operator is not implemented.
12016 Entry calls are not implemented.
12019 Aside from printing, arithmetic operations on the native VAX floating-point
12020 formats are not supported.
12023 It is not possible to slice a packed array.
12026 The names @code{True} and @code{False}, when not part of a qualified name,
12027 are interpreted as if implicitly prefixed by @code{Standard}, regardless of
12029 Should your program
12030 redefine these names in a package or procedure (at best a dubious practice),
12031 you will have to use fully qualified names to access their new definitions.
12034 @node Additions to Ada
12035 @subsubsection Additions to Ada
12036 @cindex Ada, deviations from
12038 As it does for other languages, @value{GDBN} makes certain generic
12039 extensions to Ada (@pxref{Expressions}):
12043 If the expression @var{E} is a variable residing in memory (typically
12044 a local variable or array element) and @var{N} is a positive integer,
12045 then @code{@var{E}@@@var{N}} displays the values of @var{E} and the
12046 @var{N}-1 adjacent variables following it in memory as an array. In
12047 Ada, this operator is generally not necessary, since its prime use is
12048 in displaying parts of an array, and slicing will usually do this in
12049 Ada. However, there are occasional uses when debugging programs in
12050 which certain debugging information has been optimized away.
12053 @code{@var{B}::@var{var}} means ``the variable named @var{var} that
12054 appears in function or file @var{B}.'' When @var{B} is a file name,
12055 you must typically surround it in single quotes.
12058 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
12059 @var{type} that appears at address @var{addr}.''
12062 A name starting with @samp{$} is a convenience variable
12063 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
12066 In addition, @value{GDBN} provides a few other shortcuts and outright
12067 additions specific to Ada:
12071 The assignment statement is allowed as an expression, returning
12072 its right-hand operand as its value. Thus, you may enter
12075 (@value{GDBP}) set x := y + 3
12076 (@value{GDBP}) print A(tmp := y + 1)
12080 The semicolon is allowed as an ``operator,'' returning as its value
12081 the value of its right-hand operand.
12082 This allows, for example,
12083 complex conditional breaks:
12086 (@value{GDBP}) break f
12087 (@value{GDBP}) condition 1 (report(i); k += 1; A(k) > 100)
12091 Rather than use catenation and symbolic character names to introduce special
12092 characters into strings, one may instead use a special bracket notation,
12093 which is also used to print strings. A sequence of characters of the form
12094 @samp{["@var{XX}"]} within a string or character literal denotes the
12095 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
12096 sequence of characters @samp{["""]} also denotes a single quotation mark
12097 in strings. For example,
12099 "One line.["0a"]Next line.["0a"]"
12102 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF})
12106 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
12107 @t{'Max} is optional (and is ignored in any case). For example, it is valid
12111 (@value{GDBP}) print 'max(x, y)
12115 When printing arrays, @value{GDBN} uses positional notation when the
12116 array has a lower bound of 1, and uses a modified named notation otherwise.
12117 For example, a one-dimensional array of three integers with a lower bound
12118 of 3 might print as
12125 That is, in contrast to valid Ada, only the first component has a @code{=>}
12129 You may abbreviate attributes in expressions with any unique,
12130 multi-character subsequence of
12131 their names (an exact match gets preference).
12132 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
12133 in place of @t{a'length}.
12136 @cindex quoting Ada internal identifiers
12137 Since Ada is case-insensitive, the debugger normally maps identifiers you type
12138 to lower case. The GNAT compiler uses upper-case characters for
12139 some of its internal identifiers, which are normally of no interest to users.
12140 For the rare occasions when you actually have to look at them,
12141 enclose them in angle brackets to avoid the lower-case mapping.
12144 (@value{GDBP}) print <JMPBUF_SAVE>[0]
12148 Printing an object of class-wide type or dereferencing an
12149 access-to-class-wide value will display all the components of the object's
12150 specific type (as indicated by its run-time tag). Likewise, component
12151 selection on such a value will operate on the specific type of the
12156 @node Stopping Before Main Program
12157 @subsubsection Stopping at the Very Beginning
12159 @cindex breakpointing Ada elaboration code
12160 It is sometimes necessary to debug the program during elaboration, and
12161 before reaching the main procedure.
12162 As defined in the Ada Reference
12163 Manual, the elaboration code is invoked from a procedure called
12164 @code{adainit}. To run your program up to the beginning of
12165 elaboration, simply use the following two commands:
12166 @code{tbreak adainit} and @code{run}.
12169 @subsubsection Extensions for Ada Tasks
12170 @cindex Ada, tasking
12172 Support for Ada tasks is analogous to that for threads (@pxref{Threads}).
12173 @value{GDBN} provides the following task-related commands:
12178 This command shows a list of current Ada tasks, as in the following example:
12185 (@value{GDBP}) info tasks
12186 ID TID P-ID Pri State Name
12187 1 8088000 0 15 Child Activation Wait main_task
12188 2 80a4000 1 15 Accept Statement b
12189 3 809a800 1 15 Child Activation Wait a
12190 * 4 80ae800 3 15 Runnable c
12195 In this listing, the asterisk before the last task indicates it to be the
12196 task currently being inspected.
12200 Represents @value{GDBN}'s internal task number.
12206 The parent's task ID (@value{GDBN}'s internal task number).
12209 The base priority of the task.
12212 Current state of the task.
12216 The task has been created but has not been activated. It cannot be
12220 The task is not blocked for any reason known to Ada. (It may be waiting
12221 for a mutex, though.) It is conceptually "executing" in normal mode.
12224 The task is terminated, in the sense of ARM 9.3 (5). Any dependents
12225 that were waiting on terminate alternatives have been awakened and have
12226 terminated themselves.
12228 @item Child Activation Wait
12229 The task is waiting for created tasks to complete activation.
12231 @item Accept Statement
12232 The task is waiting on an accept or selective wait statement.
12234 @item Waiting on entry call
12235 The task is waiting on an entry call.
12237 @item Async Select Wait
12238 The task is waiting to start the abortable part of an asynchronous
12242 The task is waiting on a select statement with only a delay
12245 @item Child Termination Wait
12246 The task is sleeping having completed a master within itself, and is
12247 waiting for the tasks dependent on that master to become terminated or
12248 waiting on a terminate Phase.
12250 @item Wait Child in Term Alt
12251 The task is sleeping waiting for tasks on terminate alternatives to
12252 finish terminating.
12254 @item Accepting RV with @var{taskno}
12255 The task is accepting a rendez-vous with the task @var{taskno}.
12259 Name of the task in the program.
12263 @kindex info task @var{taskno}
12264 @item info task @var{taskno}
12265 This command shows detailled informations on the specified task, as in
12266 the following example:
12271 (@value{GDBP}) info tasks
12272 ID TID P-ID Pri State Name
12273 1 8077880 0 15 Child Activation Wait main_task
12274 * 2 807c468 1 15 Runnable task_1
12275 (@value{GDBP}) info task 2
12276 Ada Task: 0x807c468
12279 Parent: 1 (main_task)
12285 @kindex task@r{ (Ada)}
12286 @cindex current Ada task ID
12287 This command prints the ID of the current task.
12293 (@value{GDBP}) info tasks
12294 ID TID P-ID Pri State Name
12295 1 8077870 0 15 Child Activation Wait main_task
12296 * 2 807c458 1 15 Runnable t
12297 (@value{GDBP}) task
12298 [Current task is 2]
12301 @item task @var{taskno}
12302 @cindex Ada task switching
12303 This command is like the @code{thread @var{threadno}}
12304 command (@pxref{Threads}). It switches the context of debugging
12305 from the current task to the given task.
12311 (@value{GDBP}) info tasks
12312 ID TID P-ID Pri State Name
12313 1 8077870 0 15 Child Activation Wait main_task
12314 * 2 807c458 1 15 Runnable t
12315 (@value{GDBP}) task 1
12316 [Switching to task 1]
12317 #0 0x8067726 in pthread_cond_wait ()
12319 #0 0x8067726 in pthread_cond_wait ()
12320 #1 0x8056714 in system.os_interface.pthread_cond_wait ()
12321 #2 0x805cb63 in system.task_primitives.operations.sleep ()
12322 #3 0x806153e in system.tasking.stages.activate_tasks ()
12323 #4 0x804aacc in un () at un.adb:5
12326 @item break @var{linespec} task @var{taskno}
12327 @itemx break @var{linespec} task @var{taskno} if @dots{}
12328 @cindex breakpoints and tasks, in Ada
12329 @cindex task breakpoints, in Ada
12330 @kindex break @dots{} task @var{taskno}@r{ (Ada)}
12331 These commands are like the @code{break @dots{} thread @dots{}}
12332 command (@pxref{Thread Stops}).
12333 @var{linespec} specifies source lines, as described
12334 in @ref{Specify Location}.
12336 Use the qualifier @samp{task @var{taskno}} with a breakpoint command
12337 to specify that you only want @value{GDBN} to stop the program when a
12338 particular Ada task reaches this breakpoint. @var{taskno} is one of the
12339 numeric task identifiers assigned by @value{GDBN}, shown in the first
12340 column of the @samp{info tasks} display.
12342 If you do not specify @samp{task @var{taskno}} when you set a
12343 breakpoint, the breakpoint applies to @emph{all} tasks of your
12346 You can use the @code{task} qualifier on conditional breakpoints as
12347 well; in this case, place @samp{task @var{taskno}} before the
12348 breakpoint condition (before the @code{if}).
12356 (@value{GDBP}) info tasks
12357 ID TID P-ID Pri State Name
12358 1 140022020 0 15 Child Activation Wait main_task
12359 2 140045060 1 15 Accept/Select Wait t2
12360 3 140044840 1 15 Runnable t1
12361 * 4 140056040 1 15 Runnable t3
12362 (@value{GDBP}) b 15 task 2
12363 Breakpoint 5 at 0x120044cb0: file test_task_debug.adb, line 15.
12364 (@value{GDBP}) cont
12369 Breakpoint 5, test_task_debug () at test_task_debug.adb:15
12371 (@value{GDBP}) info tasks
12372 ID TID P-ID Pri State Name
12373 1 140022020 0 15 Child Activation Wait main_task
12374 * 2 140045060 1 15 Runnable t2
12375 3 140044840 1 15 Runnable t1
12376 4 140056040 1 15 Delay Sleep t3
12380 @node Ada Tasks and Core Files
12381 @subsubsection Tasking Support when Debugging Core Files
12382 @cindex Ada tasking and core file debugging
12384 When inspecting a core file, as opposed to debugging a live program,
12385 tasking support may be limited or even unavailable, depending on
12386 the platform being used.
12387 For instance, on x86-linux, the list of tasks is available, but task
12388 switching is not supported. On Tru64, however, task switching will work
12391 On certain platforms, including Tru64, the debugger needs to perform some
12392 memory writes in order to provide Ada tasking support. When inspecting
12393 a core file, this means that the core file must be opened with read-write
12394 privileges, using the command @samp{"set write on"} (@pxref{Patching}).
12395 Under these circumstances, you should make a backup copy of the core
12396 file before inspecting it with @value{GDBN}.
12399 @subsubsection Known Peculiarities of Ada Mode
12400 @cindex Ada, problems
12402 Besides the omissions listed previously (@pxref{Omissions from Ada}),
12403 we know of several problems with and limitations of Ada mode in
12405 some of which will be fixed with planned future releases of the debugger
12406 and the GNU Ada compiler.
12410 Currently, the debugger
12411 has insufficient information to determine whether certain pointers represent
12412 pointers to objects or the objects themselves.
12413 Thus, the user may have to tack an extra @code{.all} after an expression
12414 to get it printed properly.
12417 Static constants that the compiler chooses not to materialize as objects in
12418 storage are invisible to the debugger.
12421 Named parameter associations in function argument lists are ignored (the
12422 argument lists are treated as positional).
12425 Many useful library packages are currently invisible to the debugger.
12428 Fixed-point arithmetic, conversions, input, and output is carried out using
12429 floating-point arithmetic, and may give results that only approximate those on
12433 The GNAT compiler never generates the prefix @code{Standard} for any of
12434 the standard symbols defined by the Ada language. @value{GDBN} knows about
12435 this: it will strip the prefix from names when you use it, and will never
12436 look for a name you have so qualified among local symbols, nor match against
12437 symbols in other packages or subprograms. If you have
12438 defined entities anywhere in your program other than parameters and
12439 local variables whose simple names match names in @code{Standard},
12440 GNAT's lack of qualification here can cause confusion. When this happens,
12441 you can usually resolve the confusion
12442 by qualifying the problematic names with package
12443 @code{Standard} explicitly.
12446 @node Unsupported Languages
12447 @section Unsupported Languages
12449 @cindex unsupported languages
12450 @cindex minimal language
12451 In addition to the other fully-supported programming languages,
12452 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
12453 It does not represent a real programming language, but provides a set
12454 of capabilities close to what the C or assembly languages provide.
12455 This should allow most simple operations to be performed while debugging
12456 an application that uses a language currently not supported by @value{GDBN}.
12458 If the language is set to @code{auto}, @value{GDBN} will automatically
12459 select this language if the current frame corresponds to an unsupported
12463 @chapter Examining the Symbol Table
12465 The commands described in this chapter allow you to inquire about the
12466 symbols (names of variables, functions and types) defined in your
12467 program. This information is inherent in the text of your program and
12468 does not change as your program executes. @value{GDBN} finds it in your
12469 program's symbol table, in the file indicated when you started @value{GDBN}
12470 (@pxref{File Options, ,Choosing Files}), or by one of the
12471 file-management commands (@pxref{Files, ,Commands to Specify Files}).
12473 @cindex symbol names
12474 @cindex names of symbols
12475 @cindex quoting names
12476 Occasionally, you may need to refer to symbols that contain unusual
12477 characters, which @value{GDBN} ordinarily treats as word delimiters. The
12478 most frequent case is in referring to static variables in other
12479 source files (@pxref{Variables,,Program Variables}). File names
12480 are recorded in object files as debugging symbols, but @value{GDBN} would
12481 ordinarily parse a typical file name, like @file{foo.c}, as the three words
12482 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
12483 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
12490 looks up the value of @code{x} in the scope of the file @file{foo.c}.
12493 @cindex case-insensitive symbol names
12494 @cindex case sensitivity in symbol names
12495 @kindex set case-sensitive
12496 @item set case-sensitive on
12497 @itemx set case-sensitive off
12498 @itemx set case-sensitive auto
12499 Normally, when @value{GDBN} looks up symbols, it matches their names
12500 with case sensitivity determined by the current source language.
12501 Occasionally, you may wish to control that. The command @code{set
12502 case-sensitive} lets you do that by specifying @code{on} for
12503 case-sensitive matches or @code{off} for case-insensitive ones. If
12504 you specify @code{auto}, case sensitivity is reset to the default
12505 suitable for the source language. The default is case-sensitive
12506 matches for all languages except for Fortran, for which the default is
12507 case-insensitive matches.
12509 @kindex show case-sensitive
12510 @item show case-sensitive
12511 This command shows the current setting of case sensitivity for symbols
12514 @kindex info address
12515 @cindex address of a symbol
12516 @item info address @var{symbol}
12517 Describe where the data for @var{symbol} is stored. For a register
12518 variable, this says which register it is kept in. For a non-register
12519 local variable, this prints the stack-frame offset at which the variable
12522 Note the contrast with @samp{print &@var{symbol}}, which does not work
12523 at all for a register variable, and for a stack local variable prints
12524 the exact address of the current instantiation of the variable.
12526 @kindex info symbol
12527 @cindex symbol from address
12528 @cindex closest symbol and offset for an address
12529 @item info symbol @var{addr}
12530 Print the name of a symbol which is stored at the address @var{addr}.
12531 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
12532 nearest symbol and an offset from it:
12535 (@value{GDBP}) info symbol 0x54320
12536 _initialize_vx + 396 in section .text
12540 This is the opposite of the @code{info address} command. You can use
12541 it to find out the name of a variable or a function given its address.
12543 For dynamically linked executables, the name of executable or shared
12544 library containing the symbol is also printed:
12547 (@value{GDBP}) info symbol 0x400225
12548 _start + 5 in section .text of /tmp/a.out
12549 (@value{GDBP}) info symbol 0x2aaaac2811cf
12550 __read_nocancel + 6 in section .text of /usr/lib64/libc.so.6
12554 @item whatis [@var{arg}]
12555 Print the data type of @var{arg}, which can be either an expression or
12556 a data type. With no argument, print the data type of @code{$}, the
12557 last value in the value history. If @var{arg} is an expression, it is
12558 not actually evaluated, and any side-effecting operations (such as
12559 assignments or function calls) inside it do not take place. If
12560 @var{arg} is a type name, it may be the name of a type or typedef, or
12561 for C code it may have the form @samp{class @var{class-name}},
12562 @samp{struct @var{struct-tag}}, @samp{union @var{union-tag}} or
12563 @samp{enum @var{enum-tag}}.
12564 @xref{Expressions, ,Expressions}.
12567 @item ptype [@var{arg}]
12568 @code{ptype} accepts the same arguments as @code{whatis}, but prints a
12569 detailed description of the type, instead of just the name of the type.
12570 @xref{Expressions, ,Expressions}.
12572 For example, for this variable declaration:
12575 struct complex @{double real; double imag;@} v;
12579 the two commands give this output:
12583 (@value{GDBP}) whatis v
12584 type = struct complex
12585 (@value{GDBP}) ptype v
12586 type = struct complex @{
12594 As with @code{whatis}, using @code{ptype} without an argument refers to
12595 the type of @code{$}, the last value in the value history.
12597 @cindex incomplete type
12598 Sometimes, programs use opaque data types or incomplete specifications
12599 of complex data structure. If the debug information included in the
12600 program does not allow @value{GDBN} to display a full declaration of
12601 the data type, it will say @samp{<incomplete type>}. For example,
12602 given these declarations:
12606 struct foo *fooptr;
12610 but no definition for @code{struct foo} itself, @value{GDBN} will say:
12613 (@value{GDBP}) ptype foo
12614 $1 = <incomplete type>
12618 ``Incomplete type'' is C terminology for data types that are not
12619 completely specified.
12622 @item info types @var{regexp}
12624 Print a brief description of all types whose names match the regular
12625 expression @var{regexp} (or all types in your program, if you supply
12626 no argument). Each complete typename is matched as though it were a
12627 complete line; thus, @samp{i type value} gives information on all
12628 types in your program whose names include the string @code{value}, but
12629 @samp{i type ^value$} gives information only on types whose complete
12630 name is @code{value}.
12632 This command differs from @code{ptype} in two ways: first, like
12633 @code{whatis}, it does not print a detailed description; second, it
12634 lists all source files where a type is defined.
12637 @cindex local variables
12638 @item info scope @var{location}
12639 List all the variables local to a particular scope. This command
12640 accepts a @var{location} argument---a function name, a source line, or
12641 an address preceded by a @samp{*}, and prints all the variables local
12642 to the scope defined by that location. (@xref{Specify Location}, for
12643 details about supported forms of @var{location}.) For example:
12646 (@value{GDBP}) @b{info scope command_line_handler}
12647 Scope for command_line_handler:
12648 Symbol rl is an argument at stack/frame offset 8, length 4.
12649 Symbol linebuffer is in static storage at address 0x150a18, length 4.
12650 Symbol linelength is in static storage at address 0x150a1c, length 4.
12651 Symbol p is a local variable in register $esi, length 4.
12652 Symbol p1 is a local variable in register $ebx, length 4.
12653 Symbol nline is a local variable in register $edx, length 4.
12654 Symbol repeat is a local variable at frame offset -8, length 4.
12658 This command is especially useful for determining what data to collect
12659 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
12662 @kindex info source
12664 Show information about the current source file---that is, the source file for
12665 the function containing the current point of execution:
12668 the name of the source file, and the directory containing it,
12670 the directory it was compiled in,
12672 its length, in lines,
12674 which programming language it is written in,
12676 whether the executable includes debugging information for that file, and
12677 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
12679 whether the debugging information includes information about
12680 preprocessor macros.
12684 @kindex info sources
12686 Print the names of all source files in your program for which there is
12687 debugging information, organized into two lists: files whose symbols
12688 have already been read, and files whose symbols will be read when needed.
12690 @kindex info functions
12691 @item info functions
12692 Print the names and data types of all defined functions.
12694 @item info functions @var{regexp}
12695 Print the names and data types of all defined functions
12696 whose names contain a match for regular expression @var{regexp}.
12697 Thus, @samp{info fun step} finds all functions whose names
12698 include @code{step}; @samp{info fun ^step} finds those whose names
12699 start with @code{step}. If a function name contains characters
12700 that conflict with the regular expression language (e.g.@:
12701 @samp{operator*()}), they may be quoted with a backslash.
12703 @kindex info variables
12704 @item info variables
12705 Print the names and data types of all variables that are declared
12706 outside of functions (i.e.@: excluding local variables).
12708 @item info variables @var{regexp}
12709 Print the names and data types of all variables (except for local
12710 variables) whose names contain a match for regular expression
12713 @kindex info classes
12714 @cindex Objective-C, classes and selectors
12716 @itemx info classes @var{regexp}
12717 Display all Objective-C classes in your program, or
12718 (with the @var{regexp} argument) all those matching a particular regular
12721 @kindex info selectors
12722 @item info selectors
12723 @itemx info selectors @var{regexp}
12724 Display all Objective-C selectors in your program, or
12725 (with the @var{regexp} argument) all those matching a particular regular
12729 This was never implemented.
12730 @kindex info methods
12732 @itemx info methods @var{regexp}
12733 The @code{info methods} command permits the user to examine all defined
12734 methods within C@t{++} program, or (with the @var{regexp} argument) a
12735 specific set of methods found in the various C@t{++} classes. Many
12736 C@t{++} classes provide a large number of methods. Thus, the output
12737 from the @code{ptype} command can be overwhelming and hard to use. The
12738 @code{info-methods} command filters the methods, printing only those
12739 which match the regular-expression @var{regexp}.
12742 @cindex reloading symbols
12743 Some systems allow individual object files that make up your program to
12744 be replaced without stopping and restarting your program. For example,
12745 in VxWorks you can simply recompile a defective object file and keep on
12746 running. If you are running on one of these systems, you can allow
12747 @value{GDBN} to reload the symbols for automatically relinked modules:
12750 @kindex set symbol-reloading
12751 @item set symbol-reloading on
12752 Replace symbol definitions for the corresponding source file when an
12753 object file with a particular name is seen again.
12755 @item set symbol-reloading off
12756 Do not replace symbol definitions when encountering object files of the
12757 same name more than once. This is the default state; if you are not
12758 running on a system that permits automatic relinking of modules, you
12759 should leave @code{symbol-reloading} off, since otherwise @value{GDBN}
12760 may discard symbols when linking large programs, that may contain
12761 several modules (from different directories or libraries) with the same
12764 @kindex show symbol-reloading
12765 @item show symbol-reloading
12766 Show the current @code{on} or @code{off} setting.
12769 @cindex opaque data types
12770 @kindex set opaque-type-resolution
12771 @item set opaque-type-resolution on
12772 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
12773 declared as a pointer to a @code{struct}, @code{class}, or
12774 @code{union}---for example, @code{struct MyType *}---that is used in one
12775 source file although the full declaration of @code{struct MyType} is in
12776 another source file. The default is on.
12778 A change in the setting of this subcommand will not take effect until
12779 the next time symbols for a file are loaded.
12781 @item set opaque-type-resolution off
12782 Tell @value{GDBN} not to resolve opaque types. In this case, the type
12783 is printed as follows:
12785 @{<no data fields>@}
12788 @kindex show opaque-type-resolution
12789 @item show opaque-type-resolution
12790 Show whether opaque types are resolved or not.
12792 @kindex maint print symbols
12793 @cindex symbol dump
12794 @kindex maint print psymbols
12795 @cindex partial symbol dump
12796 @item maint print symbols @var{filename}
12797 @itemx maint print psymbols @var{filename}
12798 @itemx maint print msymbols @var{filename}
12799 Write a dump of debugging symbol data into the file @var{filename}.
12800 These commands are used to debug the @value{GDBN} symbol-reading code. Only
12801 symbols with debugging data are included. If you use @samp{maint print
12802 symbols}, @value{GDBN} includes all the symbols for which it has already
12803 collected full details: that is, @var{filename} reflects symbols for
12804 only those files whose symbols @value{GDBN} has read. You can use the
12805 command @code{info sources} to find out which files these are. If you
12806 use @samp{maint print psymbols} instead, the dump shows information about
12807 symbols that @value{GDBN} only knows partially---that is, symbols defined in
12808 files that @value{GDBN} has skimmed, but not yet read completely. Finally,
12809 @samp{maint print msymbols} dumps just the minimal symbol information
12810 required for each object file from which @value{GDBN} has read some symbols.
12811 @xref{Files, ,Commands to Specify Files}, for a discussion of how
12812 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
12814 @kindex maint info symtabs
12815 @kindex maint info psymtabs
12816 @cindex listing @value{GDBN}'s internal symbol tables
12817 @cindex symbol tables, listing @value{GDBN}'s internal
12818 @cindex full symbol tables, listing @value{GDBN}'s internal
12819 @cindex partial symbol tables, listing @value{GDBN}'s internal
12820 @item maint info symtabs @r{[} @var{regexp} @r{]}
12821 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
12823 List the @code{struct symtab} or @code{struct partial_symtab}
12824 structures whose names match @var{regexp}. If @var{regexp} is not
12825 given, list them all. The output includes expressions which you can
12826 copy into a @value{GDBN} debugging this one to examine a particular
12827 structure in more detail. For example:
12830 (@value{GDBP}) maint info psymtabs dwarf2read
12831 @{ objfile /home/gnu/build/gdb/gdb
12832 ((struct objfile *) 0x82e69d0)
12833 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
12834 ((struct partial_symtab *) 0x8474b10)
12837 text addresses 0x814d3c8 -- 0x8158074
12838 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
12839 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
12840 dependencies (none)
12843 (@value{GDBP}) maint info symtabs
12847 We see that there is one partial symbol table whose filename contains
12848 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
12849 and we see that @value{GDBN} has not read in any symtabs yet at all.
12850 If we set a breakpoint on a function, that will cause @value{GDBN} to
12851 read the symtab for the compilation unit containing that function:
12854 (@value{GDBP}) break dwarf2_psymtab_to_symtab
12855 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
12857 (@value{GDBP}) maint info symtabs
12858 @{ objfile /home/gnu/build/gdb/gdb
12859 ((struct objfile *) 0x82e69d0)
12860 @{ symtab /home/gnu/src/gdb/dwarf2read.c
12861 ((struct symtab *) 0x86c1f38)
12864 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
12865 linetable ((struct linetable *) 0x8370fa0)
12866 debugformat DWARF 2
12875 @chapter Altering Execution
12877 Once you think you have found an error in your program, you might want to
12878 find out for certain whether correcting the apparent error would lead to
12879 correct results in the rest of the run. You can find the answer by
12880 experiment, using the @value{GDBN} features for altering execution of the
12883 For example, you can store new values into variables or memory
12884 locations, give your program a signal, restart it at a different
12885 address, or even return prematurely from a function.
12888 * Assignment:: Assignment to variables
12889 * Jumping:: Continuing at a different address
12890 * Signaling:: Giving your program a signal
12891 * Returning:: Returning from a function
12892 * Calling:: Calling your program's functions
12893 * Patching:: Patching your program
12897 @section Assignment to Variables
12900 @cindex setting variables
12901 To alter the value of a variable, evaluate an assignment expression.
12902 @xref{Expressions, ,Expressions}. For example,
12909 stores the value 4 into the variable @code{x}, and then prints the
12910 value of the assignment expression (which is 4).
12911 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
12912 information on operators in supported languages.
12914 @kindex set variable
12915 @cindex variables, setting
12916 If you are not interested in seeing the value of the assignment, use the
12917 @code{set} command instead of the @code{print} command. @code{set} is
12918 really the same as @code{print} except that the expression's value is
12919 not printed and is not put in the value history (@pxref{Value History,
12920 ,Value History}). The expression is evaluated only for its effects.
12922 If the beginning of the argument string of the @code{set} command
12923 appears identical to a @code{set} subcommand, use the @code{set
12924 variable} command instead of just @code{set}. This command is identical
12925 to @code{set} except for its lack of subcommands. For example, if your
12926 program has a variable @code{width}, you get an error if you try to set
12927 a new value with just @samp{set width=13}, because @value{GDBN} has the
12928 command @code{set width}:
12931 (@value{GDBP}) whatis width
12933 (@value{GDBP}) p width
12935 (@value{GDBP}) set width=47
12936 Invalid syntax in expression.
12940 The invalid expression, of course, is @samp{=47}. In
12941 order to actually set the program's variable @code{width}, use
12944 (@value{GDBP}) set var width=47
12947 Because the @code{set} command has many subcommands that can conflict
12948 with the names of program variables, it is a good idea to use the
12949 @code{set variable} command instead of just @code{set}. For example, if
12950 your program has a variable @code{g}, you run into problems if you try
12951 to set a new value with just @samp{set g=4}, because @value{GDBN} has
12952 the command @code{set gnutarget}, abbreviated @code{set g}:
12956 (@value{GDBP}) whatis g
12960 (@value{GDBP}) set g=4
12964 The program being debugged has been started already.
12965 Start it from the beginning? (y or n) y
12966 Starting program: /home/smith/cc_progs/a.out
12967 "/home/smith/cc_progs/a.out": can't open to read symbols:
12968 Invalid bfd target.
12969 (@value{GDBP}) show g
12970 The current BFD target is "=4".
12975 The program variable @code{g} did not change, and you silently set the
12976 @code{gnutarget} to an invalid value. In order to set the variable
12980 (@value{GDBP}) set var g=4
12983 @value{GDBN} allows more implicit conversions in assignments than C; you can
12984 freely store an integer value into a pointer variable or vice versa,
12985 and you can convert any structure to any other structure that is the
12986 same length or shorter.
12987 @comment FIXME: how do structs align/pad in these conversions?
12988 @comment /doc@cygnus.com 18dec1990
12990 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
12991 construct to generate a value of specified type at a specified address
12992 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
12993 to memory location @code{0x83040} as an integer (which implies a certain size
12994 and representation in memory), and
12997 set @{int@}0x83040 = 4
13001 stores the value 4 into that memory location.
13004 @section Continuing at a Different Address
13006 Ordinarily, when you continue your program, you do so at the place where
13007 it stopped, with the @code{continue} command. You can instead continue at
13008 an address of your own choosing, with the following commands:
13012 @item jump @var{linespec}
13013 @itemx jump @var{location}
13014 Resume execution at line @var{linespec} or at address given by
13015 @var{location}. Execution stops again immediately if there is a
13016 breakpoint there. @xref{Specify Location}, for a description of the
13017 different forms of @var{linespec} and @var{location}. It is common
13018 practice to use the @code{tbreak} command in conjunction with
13019 @code{jump}. @xref{Set Breaks, ,Setting Breakpoints}.
13021 The @code{jump} command does not change the current stack frame, or
13022 the stack pointer, or the contents of any memory location or any
13023 register other than the program counter. If line @var{linespec} is in
13024 a different function from the one currently executing, the results may
13025 be bizarre if the two functions expect different patterns of arguments or
13026 of local variables. For this reason, the @code{jump} command requests
13027 confirmation if the specified line is not in the function currently
13028 executing. However, even bizarre results are predictable if you are
13029 well acquainted with the machine-language code of your program.
13032 @c Doesn't work on HP-UX; have to set $pcoqh and $pcoqt.
13033 On many systems, you can get much the same effect as the @code{jump}
13034 command by storing a new value into the register @code{$pc}. The
13035 difference is that this does not start your program running; it only
13036 changes the address of where it @emph{will} run when you continue. For
13044 makes the next @code{continue} command or stepping command execute at
13045 address @code{0x485}, rather than at the address where your program stopped.
13046 @xref{Continuing and Stepping, ,Continuing and Stepping}.
13048 The most common occasion to use the @code{jump} command is to back
13049 up---perhaps with more breakpoints set---over a portion of a program
13050 that has already executed, in order to examine its execution in more
13055 @section Giving your Program a Signal
13056 @cindex deliver a signal to a program
13060 @item signal @var{signal}
13061 Resume execution where your program stopped, but immediately give it the
13062 signal @var{signal}. @var{signal} can be the name or the number of a
13063 signal. For example, on many systems @code{signal 2} and @code{signal
13064 SIGINT} are both ways of sending an interrupt signal.
13066 Alternatively, if @var{signal} is zero, continue execution without
13067 giving a signal. This is useful when your program stopped on account of
13068 a signal and would ordinary see the signal when resumed with the
13069 @code{continue} command; @samp{signal 0} causes it to resume without a
13072 @code{signal} does not repeat when you press @key{RET} a second time
13073 after executing the command.
13077 Invoking the @code{signal} command is not the same as invoking the
13078 @code{kill} utility from the shell. Sending a signal with @code{kill}
13079 causes @value{GDBN} to decide what to do with the signal depending on
13080 the signal handling tables (@pxref{Signals}). The @code{signal} command
13081 passes the signal directly to your program.
13085 @section Returning from a Function
13088 @cindex returning from a function
13091 @itemx return @var{expression}
13092 You can cancel execution of a function call with the @code{return}
13093 command. If you give an
13094 @var{expression} argument, its value is used as the function's return
13098 When you use @code{return}, @value{GDBN} discards the selected stack frame
13099 (and all frames within it). You can think of this as making the
13100 discarded frame return prematurely. If you wish to specify a value to
13101 be returned, give that value as the argument to @code{return}.
13103 This pops the selected stack frame (@pxref{Selection, ,Selecting a
13104 Frame}), and any other frames inside of it, leaving its caller as the
13105 innermost remaining frame. That frame becomes selected. The
13106 specified value is stored in the registers used for returning values
13109 The @code{return} command does not resume execution; it leaves the
13110 program stopped in the state that would exist if the function had just
13111 returned. In contrast, the @code{finish} command (@pxref{Continuing
13112 and Stepping, ,Continuing and Stepping}) resumes execution until the
13113 selected stack frame returns naturally.
13115 @value{GDBN} needs to know how the @var{expression} argument should be set for
13116 the inferior. The concrete registers assignment depends on the OS ABI and the
13117 type being returned by the selected stack frame. For example it is common for
13118 OS ABI to return floating point values in FPU registers while integer values in
13119 CPU registers. Still some ABIs return even floating point values in CPU
13120 registers. Larger integer widths (such as @code{long long int}) also have
13121 specific placement rules. @value{GDBN} already knows the OS ABI from its
13122 current target so it needs to find out also the type being returned to make the
13123 assignment into the right register(s).
13125 Normally, the selected stack frame has debug info. @value{GDBN} will always
13126 use the debug info instead of the implicit type of @var{expression} when the
13127 debug info is available. For example, if you type @kbd{return -1}, and the
13128 function in the current stack frame is declared to return a @code{long long
13129 int}, @value{GDBN} transparently converts the implicit @code{int} value of -1
13130 into a @code{long long int}:
13133 Breakpoint 1, func () at gdb.base/return-nodebug.c:29
13135 (@value{GDBP}) return -1
13136 Make func return now? (y or n) y
13137 #0 0x004004f6 in main () at gdb.base/return-nodebug.c:43
13138 43 printf ("result=%lld\n", func ());
13142 However, if the selected stack frame does not have a debug info, e.g., if the
13143 function was compiled without debug info, @value{GDBN} has to find out the type
13144 to return from user. Specifying a different type by mistake may set the value
13145 in different inferior registers than the caller code expects. For example,
13146 typing @kbd{return -1} with its implicit type @code{int} would set only a part
13147 of a @code{long long int} result for a debug info less function (on 32-bit
13148 architectures). Therefore the user is required to specify the return type by
13149 an appropriate cast explicitly:
13152 Breakpoint 2, 0x0040050b in func ()
13153 (@value{GDBP}) return -1
13154 Return value type not available for selected stack frame.
13155 Please use an explicit cast of the value to return.
13156 (@value{GDBP}) return (long long int) -1
13157 Make selected stack frame return now? (y or n) y
13158 #0 0x00400526 in main ()
13163 @section Calling Program Functions
13166 @cindex calling functions
13167 @cindex inferior functions, calling
13168 @item print @var{expr}
13169 Evaluate the expression @var{expr} and display the resulting value.
13170 @var{expr} may include calls to functions in the program being
13174 @item call @var{expr}
13175 Evaluate the expression @var{expr} without displaying @code{void}
13178 You can use this variant of the @code{print} command if you want to
13179 execute a function from your program that does not return anything
13180 (a.k.a.@: @dfn{a void function}), but without cluttering the output
13181 with @code{void} returned values that @value{GDBN} will otherwise
13182 print. If the result is not void, it is printed and saved in the
13186 It is possible for the function you call via the @code{print} or
13187 @code{call} command to generate a signal (e.g., if there's a bug in
13188 the function, or if you passed it incorrect arguments). What happens
13189 in that case is controlled by the @code{set unwindonsignal} command.
13191 Similarly, with a C@t{++} program it is possible for the function you
13192 call via the @code{print} or @code{call} command to generate an
13193 exception that is not handled due to the constraints of the dummy
13194 frame. In this case, any exception that is raised in the frame, but has
13195 an out-of-frame exception handler will not be found. GDB builds a
13196 dummy-frame for the inferior function call, and the unwinder cannot
13197 seek for exception handlers outside of this dummy-frame. What happens
13198 in that case is controlled by the
13199 @code{set unwind-on-terminating-exception} command.
13202 @item set unwindonsignal
13203 @kindex set unwindonsignal
13204 @cindex unwind stack in called functions
13205 @cindex call dummy stack unwinding
13206 Set unwinding of the stack if a signal is received while in a function
13207 that @value{GDBN} called in the program being debugged. If set to on,
13208 @value{GDBN} unwinds the stack it created for the call and restores
13209 the context to what it was before the call. If set to off (the
13210 default), @value{GDBN} stops in the frame where the signal was
13213 @item show unwindonsignal
13214 @kindex show unwindonsignal
13215 Show the current setting of stack unwinding in the functions called by
13218 @item set unwind-on-terminating-exception
13219 @kindex set unwind-on-terminating-exception
13220 @cindex unwind stack in called functions with unhandled exceptions
13221 @cindex call dummy stack unwinding on unhandled exception.
13222 Set unwinding of the stack if a C@t{++} exception is raised, but left
13223 unhandled while in a function that @value{GDBN} called in the program being
13224 debugged. If set to on (the default), @value{GDBN} unwinds the stack
13225 it created for the call and restores the context to what it was before
13226 the call. If set to off, @value{GDBN} the exception is delivered to
13227 the default C@t{++} exception handler and the inferior terminated.
13229 @item show unwind-on-terminating-exception
13230 @kindex show unwind-on-terminating-exception
13231 Show the current setting of stack unwinding in the functions called by
13236 @cindex weak alias functions
13237 Sometimes, a function you wish to call is actually a @dfn{weak alias}
13238 for another function. In such case, @value{GDBN} might not pick up
13239 the type information, including the types of the function arguments,
13240 which causes @value{GDBN} to call the inferior function incorrectly.
13241 As a result, the called function will function erroneously and may
13242 even crash. A solution to that is to use the name of the aliased
13246 @section Patching Programs
13248 @cindex patching binaries
13249 @cindex writing into executables
13250 @cindex writing into corefiles
13252 By default, @value{GDBN} opens the file containing your program's
13253 executable code (or the corefile) read-only. This prevents accidental
13254 alterations to machine code; but it also prevents you from intentionally
13255 patching your program's binary.
13257 If you'd like to be able to patch the binary, you can specify that
13258 explicitly with the @code{set write} command. For example, you might
13259 want to turn on internal debugging flags, or even to make emergency
13265 @itemx set write off
13266 If you specify @samp{set write on}, @value{GDBN} opens executable and
13267 core files for both reading and writing; if you specify @kbd{set write
13268 off} (the default), @value{GDBN} opens them read-only.
13270 If you have already loaded a file, you must load it again (using the
13271 @code{exec-file} or @code{core-file} command) after changing @code{set
13272 write}, for your new setting to take effect.
13276 Display whether executable files and core files are opened for writing
13277 as well as reading.
13281 @chapter @value{GDBN} Files
13283 @value{GDBN} needs to know the file name of the program to be debugged,
13284 both in order to read its symbol table and in order to start your
13285 program. To debug a core dump of a previous run, you must also tell
13286 @value{GDBN} the name of the core dump file.
13289 * Files:: Commands to specify files
13290 * Separate Debug Files:: Debugging information in separate files
13291 * Symbol Errors:: Errors reading symbol files
13292 * Data Files:: GDB data files
13296 @section Commands to Specify Files
13298 @cindex symbol table
13299 @cindex core dump file
13301 You may want to specify executable and core dump file names. The usual
13302 way to do this is at start-up time, using the arguments to
13303 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
13304 Out of @value{GDBN}}).
13306 Occasionally it is necessary to change to a different file during a
13307 @value{GDBN} session. Or you may run @value{GDBN} and forget to
13308 specify a file you want to use. Or you are debugging a remote target
13309 via @code{gdbserver} (@pxref{Server, file, Using the @code{gdbserver}
13310 Program}). In these situations the @value{GDBN} commands to specify
13311 new files are useful.
13314 @cindex executable file
13316 @item file @var{filename}
13317 Use @var{filename} as the program to be debugged. It is read for its
13318 symbols and for the contents of pure memory. It is also the program
13319 executed when you use the @code{run} command. If you do not specify a
13320 directory and the file is not found in the @value{GDBN} working directory,
13321 @value{GDBN} uses the environment variable @code{PATH} as a list of
13322 directories to search, just as the shell does when looking for a program
13323 to run. You can change the value of this variable, for both @value{GDBN}
13324 and your program, using the @code{path} command.
13326 @cindex unlinked object files
13327 @cindex patching object files
13328 You can load unlinked object @file{.o} files into @value{GDBN} using
13329 the @code{file} command. You will not be able to ``run'' an object
13330 file, but you can disassemble functions and inspect variables. Also,
13331 if the underlying BFD functionality supports it, you could use
13332 @kbd{gdb -write} to patch object files using this technique. Note
13333 that @value{GDBN} can neither interpret nor modify relocations in this
13334 case, so branches and some initialized variables will appear to go to
13335 the wrong place. But this feature is still handy from time to time.
13338 @code{file} with no argument makes @value{GDBN} discard any information it
13339 has on both executable file and the symbol table.
13342 @item exec-file @r{[} @var{filename} @r{]}
13343 Specify that the program to be run (but not the symbol table) is found
13344 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
13345 if necessary to locate your program. Omitting @var{filename} means to
13346 discard information on the executable file.
13348 @kindex symbol-file
13349 @item symbol-file @r{[} @var{filename} @r{]}
13350 Read symbol table information from file @var{filename}. @code{PATH} is
13351 searched when necessary. Use the @code{file} command to get both symbol
13352 table and program to run from the same file.
13354 @code{symbol-file} with no argument clears out @value{GDBN} information on your
13355 program's symbol table.
13357 The @code{symbol-file} command causes @value{GDBN} to forget the contents of
13358 some breakpoints and auto-display expressions. This is because they may
13359 contain pointers to the internal data recording symbols and data types,
13360 which are part of the old symbol table data being discarded inside
13363 @code{symbol-file} does not repeat if you press @key{RET} again after
13366 When @value{GDBN} is configured for a particular environment, it
13367 understands debugging information in whatever format is the standard
13368 generated for that environment; you may use either a @sc{gnu} compiler, or
13369 other compilers that adhere to the local conventions.
13370 Best results are usually obtained from @sc{gnu} compilers; for example,
13371 using @code{@value{NGCC}} you can generate debugging information for
13374 For most kinds of object files, with the exception of old SVR3 systems
13375 using COFF, the @code{symbol-file} command does not normally read the
13376 symbol table in full right away. Instead, it scans the symbol table
13377 quickly to find which source files and which symbols are present. The
13378 details are read later, one source file at a time, as they are needed.
13380 The purpose of this two-stage reading strategy is to make @value{GDBN}
13381 start up faster. For the most part, it is invisible except for
13382 occasional pauses while the symbol table details for a particular source
13383 file are being read. (The @code{set verbose} command can turn these
13384 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
13385 Warnings and Messages}.)
13387 We have not implemented the two-stage strategy for COFF yet. When the
13388 symbol table is stored in COFF format, @code{symbol-file} reads the
13389 symbol table data in full right away. Note that ``stabs-in-COFF''
13390 still does the two-stage strategy, since the debug info is actually
13394 @cindex reading symbols immediately
13395 @cindex symbols, reading immediately
13396 @item symbol-file @var{filename} @r{[} -readnow @r{]}
13397 @itemx file @var{filename} @r{[} -readnow @r{]}
13398 You can override the @value{GDBN} two-stage strategy for reading symbol
13399 tables by using the @samp{-readnow} option with any of the commands that
13400 load symbol table information, if you want to be sure @value{GDBN} has the
13401 entire symbol table available.
13403 @c FIXME: for now no mention of directories, since this seems to be in
13404 @c flux. 13mar1992 status is that in theory GDB would look either in
13405 @c current dir or in same dir as myprog; but issues like competing
13406 @c GDB's, or clutter in system dirs, mean that in practice right now
13407 @c only current dir is used. FFish says maybe a special GDB hierarchy
13408 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
13412 @item core-file @r{[}@var{filename}@r{]}
13414 Specify the whereabouts of a core dump file to be used as the ``contents
13415 of memory''. Traditionally, core files contain only some parts of the
13416 address space of the process that generated them; @value{GDBN} can access the
13417 executable file itself for other parts.
13419 @code{core-file} with no argument specifies that no core file is
13422 Note that the core file is ignored when your program is actually running
13423 under @value{GDBN}. So, if you have been running your program and you
13424 wish to debug a core file instead, you must kill the subprocess in which
13425 the program is running. To do this, use the @code{kill} command
13426 (@pxref{Kill Process, ,Killing the Child Process}).
13428 @kindex add-symbol-file
13429 @cindex dynamic linking
13430 @item add-symbol-file @var{filename} @var{address}
13431 @itemx add-symbol-file @var{filename} @var{address} @r{[} -readnow @r{]}
13432 @itemx add-symbol-file @var{filename} @r{-s}@var{section} @var{address} @dots{}
13433 The @code{add-symbol-file} command reads additional symbol table
13434 information from the file @var{filename}. You would use this command
13435 when @var{filename} has been dynamically loaded (by some other means)
13436 into the program that is running. @var{address} should be the memory
13437 address at which the file has been loaded; @value{GDBN} cannot figure
13438 this out for itself. You can additionally specify an arbitrary number
13439 of @samp{@r{-s}@var{section} @var{address}} pairs, to give an explicit
13440 section name and base address for that section. You can specify any
13441 @var{address} as an expression.
13443 The symbol table of the file @var{filename} is added to the symbol table
13444 originally read with the @code{symbol-file} command. You can use the
13445 @code{add-symbol-file} command any number of times; the new symbol data
13446 thus read keeps adding to the old. To discard all old symbol data
13447 instead, use the @code{symbol-file} command without any arguments.
13449 @cindex relocatable object files, reading symbols from
13450 @cindex object files, relocatable, reading symbols from
13451 @cindex reading symbols from relocatable object files
13452 @cindex symbols, reading from relocatable object files
13453 @cindex @file{.o} files, reading symbols from
13454 Although @var{filename} is typically a shared library file, an
13455 executable file, or some other object file which has been fully
13456 relocated for loading into a process, you can also load symbolic
13457 information from relocatable @file{.o} files, as long as:
13461 the file's symbolic information refers only to linker symbols defined in
13462 that file, not to symbols defined by other object files,
13464 every section the file's symbolic information refers to has actually
13465 been loaded into the inferior, as it appears in the file, and
13467 you can determine the address at which every section was loaded, and
13468 provide these to the @code{add-symbol-file} command.
13472 Some embedded operating systems, like Sun Chorus and VxWorks, can load
13473 relocatable files into an already running program; such systems
13474 typically make the requirements above easy to meet. However, it's
13475 important to recognize that many native systems use complex link
13476 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
13477 assembly, for example) that make the requirements difficult to meet. In
13478 general, one cannot assume that using @code{add-symbol-file} to read a
13479 relocatable object file's symbolic information will have the same effect
13480 as linking the relocatable object file into the program in the normal
13483 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
13485 @kindex add-symbol-file-from-memory
13486 @cindex @code{syscall DSO}
13487 @cindex load symbols from memory
13488 @item add-symbol-file-from-memory @var{address}
13489 Load symbols from the given @var{address} in a dynamically loaded
13490 object file whose image is mapped directly into the inferior's memory.
13491 For example, the Linux kernel maps a @code{syscall DSO} into each
13492 process's address space; this DSO provides kernel-specific code for
13493 some system calls. The argument can be any expression whose
13494 evaluation yields the address of the file's shared object file header.
13495 For this command to work, you must have used @code{symbol-file} or
13496 @code{exec-file} commands in advance.
13498 @kindex add-shared-symbol-files
13500 @item add-shared-symbol-files @var{library-file}
13501 @itemx assf @var{library-file}
13502 The @code{add-shared-symbol-files} command can currently be used only
13503 in the Cygwin build of @value{GDBN} on MS-Windows OS, where it is an
13504 alias for the @code{dll-symbols} command (@pxref{Cygwin Native}).
13505 @value{GDBN} automatically looks for shared libraries, however if
13506 @value{GDBN} does not find yours, you can invoke
13507 @code{add-shared-symbol-files}. It takes one argument: the shared
13508 library's file name. @code{assf} is a shorthand alias for
13509 @code{add-shared-symbol-files}.
13512 @item section @var{section} @var{addr}
13513 The @code{section} command changes the base address of the named
13514 @var{section} of the exec file to @var{addr}. This can be used if the
13515 exec file does not contain section addresses, (such as in the
13516 @code{a.out} format), or when the addresses specified in the file
13517 itself are wrong. Each section must be changed separately. The
13518 @code{info files} command, described below, lists all the sections and
13522 @kindex info target
13525 @code{info files} and @code{info target} are synonymous; both print the
13526 current target (@pxref{Targets, ,Specifying a Debugging Target}),
13527 including the names of the executable and core dump files currently in
13528 use by @value{GDBN}, and the files from which symbols were loaded. The
13529 command @code{help target} lists all possible targets rather than
13532 @kindex maint info sections
13533 @item maint info sections
13534 Another command that can give you extra information about program sections
13535 is @code{maint info sections}. In addition to the section information
13536 displayed by @code{info files}, this command displays the flags and file
13537 offset of each section in the executable and core dump files. In addition,
13538 @code{maint info sections} provides the following command options (which
13539 may be arbitrarily combined):
13543 Display sections for all loaded object files, including shared libraries.
13544 @item @var{sections}
13545 Display info only for named @var{sections}.
13546 @item @var{section-flags}
13547 Display info only for sections for which @var{section-flags} are true.
13548 The section flags that @value{GDBN} currently knows about are:
13551 Section will have space allocated in the process when loaded.
13552 Set for all sections except those containing debug information.
13554 Section will be loaded from the file into the child process memory.
13555 Set for pre-initialized code and data, clear for @code{.bss} sections.
13557 Section needs to be relocated before loading.
13559 Section cannot be modified by the child process.
13561 Section contains executable code only.
13563 Section contains data only (no executable code).
13565 Section will reside in ROM.
13567 Section contains data for constructor/destructor lists.
13569 Section is not empty.
13571 An instruction to the linker to not output the section.
13572 @item COFF_SHARED_LIBRARY
13573 A notification to the linker that the section contains
13574 COFF shared library information.
13576 Section contains common symbols.
13579 @kindex set trust-readonly-sections
13580 @cindex read-only sections
13581 @item set trust-readonly-sections on
13582 Tell @value{GDBN} that readonly sections in your object file
13583 really are read-only (i.e.@: that their contents will not change).
13584 In that case, @value{GDBN} can fetch values from these sections
13585 out of the object file, rather than from the target program.
13586 For some targets (notably embedded ones), this can be a significant
13587 enhancement to debugging performance.
13589 The default is off.
13591 @item set trust-readonly-sections off
13592 Tell @value{GDBN} not to trust readonly sections. This means that
13593 the contents of the section might change while the program is running,
13594 and must therefore be fetched from the target when needed.
13596 @item show trust-readonly-sections
13597 Show the current setting of trusting readonly sections.
13600 All file-specifying commands allow both absolute and relative file names
13601 as arguments. @value{GDBN} always converts the file name to an absolute file
13602 name and remembers it that way.
13604 @cindex shared libraries
13605 @anchor{Shared Libraries}
13606 @value{GDBN} supports @sc{gnu}/Linux, MS-Windows, HP-UX, SunOS, SVr4, Irix,
13607 and IBM RS/6000 AIX shared libraries.
13609 On MS-Windows @value{GDBN} must be linked with the Expat library to support
13610 shared libraries. @xref{Expat}.
13612 @value{GDBN} automatically loads symbol definitions from shared libraries
13613 when you use the @code{run} command, or when you examine a core file.
13614 (Before you issue the @code{run} command, @value{GDBN} does not understand
13615 references to a function in a shared library, however---unless you are
13616 debugging a core file).
13618 On HP-UX, if the program loads a library explicitly, @value{GDBN}
13619 automatically loads the symbols at the time of the @code{shl_load} call.
13621 @c FIXME: some @value{GDBN} release may permit some refs to undef
13622 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
13623 @c FIXME...lib; check this from time to time when updating manual
13625 There are times, however, when you may wish to not automatically load
13626 symbol definitions from shared libraries, such as when they are
13627 particularly large or there are many of them.
13629 To control the automatic loading of shared library symbols, use the
13633 @kindex set auto-solib-add
13634 @item set auto-solib-add @var{mode}
13635 If @var{mode} is @code{on}, symbols from all shared object libraries
13636 will be loaded automatically when the inferior begins execution, you
13637 attach to an independently started inferior, or when the dynamic linker
13638 informs @value{GDBN} that a new library has been loaded. If @var{mode}
13639 is @code{off}, symbols must be loaded manually, using the
13640 @code{sharedlibrary} command. The default value is @code{on}.
13642 @cindex memory used for symbol tables
13643 If your program uses lots of shared libraries with debug info that
13644 takes large amounts of memory, you can decrease the @value{GDBN}
13645 memory footprint by preventing it from automatically loading the
13646 symbols from shared libraries. To that end, type @kbd{set
13647 auto-solib-add off} before running the inferior, then load each
13648 library whose debug symbols you do need with @kbd{sharedlibrary
13649 @var{regexp}}, where @var{regexp} is a regular expression that matches
13650 the libraries whose symbols you want to be loaded.
13652 @kindex show auto-solib-add
13653 @item show auto-solib-add
13654 Display the current autoloading mode.
13657 @cindex load shared library
13658 To explicitly load shared library symbols, use the @code{sharedlibrary}
13662 @kindex info sharedlibrary
13664 @item info share @var{regex}
13665 @itemx info sharedlibrary @var{regex}
13666 Print the names of the shared libraries which are currently loaded
13667 that match @var{regex}. If @var{regex} is omitted then print
13668 all shared libraries that are loaded.
13670 @kindex sharedlibrary
13672 @item sharedlibrary @var{regex}
13673 @itemx share @var{regex}
13674 Load shared object library symbols for files matching a
13675 Unix regular expression.
13676 As with files loaded automatically, it only loads shared libraries
13677 required by your program for a core file or after typing @code{run}. If
13678 @var{regex} is omitted all shared libraries required by your program are
13681 @item nosharedlibrary
13682 @kindex nosharedlibrary
13683 @cindex unload symbols from shared libraries
13684 Unload all shared object library symbols. This discards all symbols
13685 that have been loaded from all shared libraries. Symbols from shared
13686 libraries that were loaded by explicit user requests are not
13690 Sometimes you may wish that @value{GDBN} stops and gives you control
13691 when any of shared library events happen. Use the @code{set
13692 stop-on-solib-events} command for this:
13695 @item set stop-on-solib-events
13696 @kindex set stop-on-solib-events
13697 This command controls whether @value{GDBN} should give you control
13698 when the dynamic linker notifies it about some shared library event.
13699 The most common event of interest is loading or unloading of a new
13702 @item show stop-on-solib-events
13703 @kindex show stop-on-solib-events
13704 Show whether @value{GDBN} stops and gives you control when shared
13705 library events happen.
13708 Shared libraries are also supported in many cross or remote debugging
13709 configurations. @value{GDBN} needs to have access to the target's libraries;
13710 this can be accomplished either by providing copies of the libraries
13711 on the host system, or by asking @value{GDBN} to automatically retrieve the
13712 libraries from the target. If copies of the target libraries are
13713 provided, they need to be the same as the target libraries, although the
13714 copies on the target can be stripped as long as the copies on the host are
13717 @cindex where to look for shared libraries
13718 For remote debugging, you need to tell @value{GDBN} where the target
13719 libraries are, so that it can load the correct copies---otherwise, it
13720 may try to load the host's libraries. @value{GDBN} has two variables
13721 to specify the search directories for target libraries.
13724 @cindex prefix for shared library file names
13725 @cindex system root, alternate
13726 @kindex set solib-absolute-prefix
13727 @kindex set sysroot
13728 @item set sysroot @var{path}
13729 Use @var{path} as the system root for the program being debugged. Any
13730 absolute shared library paths will be prefixed with @var{path}; many
13731 runtime loaders store the absolute paths to the shared library in the
13732 target program's memory. If you use @code{set sysroot} to find shared
13733 libraries, they need to be laid out in the same way that they are on
13734 the target, with e.g.@: a @file{/lib} and @file{/usr/lib} hierarchy
13737 If @var{path} starts with the sequence @file{remote:}, @value{GDBN} will
13738 retrieve the target libraries from the remote system. This is only
13739 supported when using a remote target that supports the @code{remote get}
13740 command (@pxref{File Transfer,,Sending files to a remote system}).
13741 The part of @var{path} following the initial @file{remote:}
13742 (if present) is used as system root prefix on the remote file system.
13743 @footnote{If you want to specify a local system root using a directory
13744 that happens to be named @file{remote:}, you need to use some equivalent
13745 variant of the name like @file{./remote:}.}
13747 The @code{set solib-absolute-prefix} command is an alias for @code{set
13750 @cindex default system root
13751 @cindex @samp{--with-sysroot}
13752 You can set the default system root by using the configure-time
13753 @samp{--with-sysroot} option. If the system root is inside
13754 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
13755 @samp{--exec-prefix}), then the default system root will be updated
13756 automatically if the installed @value{GDBN} is moved to a new
13759 @kindex show sysroot
13761 Display the current shared library prefix.
13763 @kindex set solib-search-path
13764 @item set solib-search-path @var{path}
13765 If this variable is set, @var{path} is a colon-separated list of
13766 directories to search for shared libraries. @samp{solib-search-path}
13767 is used after @samp{sysroot} fails to locate the library, or if the
13768 path to the library is relative instead of absolute. If you want to
13769 use @samp{solib-search-path} instead of @samp{sysroot}, be sure to set
13770 @samp{sysroot} to a nonexistent directory to prevent @value{GDBN} from
13771 finding your host's libraries. @samp{sysroot} is preferred; setting
13772 it to a nonexistent directory may interfere with automatic loading
13773 of shared library symbols.
13775 @kindex show solib-search-path
13776 @item show solib-search-path
13777 Display the current shared library search path.
13781 @node Separate Debug Files
13782 @section Debugging Information in Separate Files
13783 @cindex separate debugging information files
13784 @cindex debugging information in separate files
13785 @cindex @file{.debug} subdirectories
13786 @cindex debugging information directory, global
13787 @cindex global debugging information directory
13788 @cindex build ID, and separate debugging files
13789 @cindex @file{.build-id} directory
13791 @value{GDBN} allows you to put a program's debugging information in a
13792 file separate from the executable itself, in a way that allows
13793 @value{GDBN} to find and load the debugging information automatically.
13794 Since debugging information can be very large---sometimes larger
13795 than the executable code itself---some systems distribute debugging
13796 information for their executables in separate files, which users can
13797 install only when they need to debug a problem.
13799 @value{GDBN} supports two ways of specifying the separate debug info
13804 The executable contains a @dfn{debug link} that specifies the name of
13805 the separate debug info file. The separate debug file's name is
13806 usually @file{@var{executable}.debug}, where @var{executable} is the
13807 name of the corresponding executable file without leading directories
13808 (e.g., @file{ls.debug} for @file{/usr/bin/ls}). In addition, the
13809 debug link specifies a 32-bit @dfn{Cyclic Redundancy Check} (CRC)
13810 checksum for the debug file, which @value{GDBN} uses to validate that
13811 the executable and the debug file came from the same build.
13814 The executable contains a @dfn{build ID}, a unique bit string that is
13815 also present in the corresponding debug info file. (This is supported
13816 only on some operating systems, notably those which use the ELF format
13817 for binary files and the @sc{gnu} Binutils.) For more details about
13818 this feature, see the description of the @option{--build-id}
13819 command-line option in @ref{Options, , Command Line Options, ld.info,
13820 The GNU Linker}. The debug info file's name is not specified
13821 explicitly by the build ID, but can be computed from the build ID, see
13825 Depending on the way the debug info file is specified, @value{GDBN}
13826 uses two different methods of looking for the debug file:
13830 For the ``debug link'' method, @value{GDBN} looks up the named file in
13831 the directory of the executable file, then in a subdirectory of that
13832 directory named @file{.debug}, and finally under the global debug
13833 directory, in a subdirectory whose name is identical to the leading
13834 directories of the executable's absolute file name.
13837 For the ``build ID'' method, @value{GDBN} looks in the
13838 @file{.build-id} subdirectory of the global debug directory for a file
13839 named @file{@var{nn}/@var{nnnnnnnn}.debug}, where @var{nn} are the
13840 first 2 hex characters of the build ID bit string, and @var{nnnnnnnn}
13841 are the rest of the bit string. (Real build ID strings are 32 or more
13842 hex characters, not 10.)
13845 So, for example, suppose you ask @value{GDBN} to debug
13846 @file{/usr/bin/ls}, which has a debug link that specifies the
13847 file @file{ls.debug}, and a build ID whose value in hex is
13848 @code{abcdef1234}. If the global debug directory is
13849 @file{/usr/lib/debug}, then @value{GDBN} will look for the following
13850 debug information files, in the indicated order:
13854 @file{/usr/lib/debug/.build-id/ab/cdef1234.debug}
13856 @file{/usr/bin/ls.debug}
13858 @file{/usr/bin/.debug/ls.debug}
13860 @file{/usr/lib/debug/usr/bin/ls.debug}.
13863 You can set the global debugging info directory's name, and view the
13864 name @value{GDBN} is currently using.
13868 @kindex set debug-file-directory
13869 @item set debug-file-directory @var{directory}
13870 Set the directory which @value{GDBN} searches for separate debugging
13871 information files to @var{directory}.
13873 @kindex show debug-file-directory
13874 @item show debug-file-directory
13875 Show the directory @value{GDBN} searches for separate debugging
13880 @cindex @code{.gnu_debuglink} sections
13881 @cindex debug link sections
13882 A debug link is a special section of the executable file named
13883 @code{.gnu_debuglink}. The section must contain:
13887 A filename, with any leading directory components removed, followed by
13890 zero to three bytes of padding, as needed to reach the next four-byte
13891 boundary within the section, and
13893 a four-byte CRC checksum, stored in the same endianness used for the
13894 executable file itself. The checksum is computed on the debugging
13895 information file's full contents by the function given below, passing
13896 zero as the @var{crc} argument.
13899 Any executable file format can carry a debug link, as long as it can
13900 contain a section named @code{.gnu_debuglink} with the contents
13903 @cindex @code{.note.gnu.build-id} sections
13904 @cindex build ID sections
13905 The build ID is a special section in the executable file (and in other
13906 ELF binary files that @value{GDBN} may consider). This section is
13907 often named @code{.note.gnu.build-id}, but that name is not mandatory.
13908 It contains unique identification for the built files---the ID remains
13909 the same across multiple builds of the same build tree. The default
13910 algorithm SHA1 produces 160 bits (40 hexadecimal characters) of the
13911 content for the build ID string. The same section with an identical
13912 value is present in the original built binary with symbols, in its
13913 stripped variant, and in the separate debugging information file.
13915 The debugging information file itself should be an ordinary
13916 executable, containing a full set of linker symbols, sections, and
13917 debugging information. The sections of the debugging information file
13918 should have the same names, addresses, and sizes as the original file,
13919 but they need not contain any data---much like a @code{.bss} section
13920 in an ordinary executable.
13922 The @sc{gnu} binary utilities (Binutils) package includes the
13923 @samp{objcopy} utility that can produce
13924 the separated executable / debugging information file pairs using the
13925 following commands:
13928 @kbd{objcopy --only-keep-debug foo foo.debug}
13933 These commands remove the debugging
13934 information from the executable file @file{foo} and place it in the file
13935 @file{foo.debug}. You can use the first, second or both methods to link the
13940 The debug link method needs the following additional command to also leave
13941 behind a debug link in @file{foo}:
13944 @kbd{objcopy --add-gnu-debuglink=foo.debug foo}
13947 Ulrich Drepper's @file{elfutils} package, starting with version 0.53, contains
13948 a version of the @code{strip} command such that the command @kbd{strip foo -f
13949 foo.debug} has the same functionality as the two @code{objcopy} commands and
13950 the @code{ln -s} command above, together.
13953 Build ID gets embedded into the main executable using @code{ld --build-id} or
13954 the @value{NGCC} counterpart @code{gcc -Wl,--build-id}. Build ID support plus
13955 compatibility fixes for debug files separation are present in @sc{gnu} binary
13956 utilities (Binutils) package since version 2.18.
13961 @cindex CRC algorithm definition
13962 The CRC used in @code{.gnu_debuglink} is the CRC-32 defined in
13963 IEEE 802.3 using the polynomial:
13965 @c TexInfo requires naked braces for multi-digit exponents for Tex
13966 @c output, but this causes HTML output to barf. HTML has to be set using
13967 @c raw commands. So we end up having to specify this equation in 2
13972 <em>x</em><sup>32</sup> + <em>x</em><sup>26</sup> + <em>x</em><sup>23</sup> + <em>x</em><sup>22</sup> + <em>x</em><sup>16</sup> + <em>x</em><sup>12</sup> + <em>x</em><sup>11</sup>
13973 + <em>x</em><sup>10</sup> + <em>x</em><sup>8</sup> + <em>x</em><sup>7</sup> + <em>x</em><sup>5</sup> + <em>x</em><sup>4</sup> + <em>x</em><sup>2</sup> + <em>x</em> + 1
13979 @math{x^{32} + x^{26} + x^{23} + x^{22} + x^{16} + x^{12} + x^{11}}
13980 @math{+ x^{10} + x^8 + x^7 + x^5 + x^4 + x^2 + x + 1}
13984 The function is computed byte at a time, taking the least
13985 significant bit of each byte first. The initial pattern
13986 @code{0xffffffff} is used, to ensure leading zeros affect the CRC and
13987 the final result is inverted to ensure trailing zeros also affect the
13990 @emph{Note:} This is the same CRC polynomial as used in handling the
13991 @dfn{Remote Serial Protocol} @code{qCRC} packet (@pxref{Remote Protocol,
13992 , @value{GDBN} Remote Serial Protocol}). However in the
13993 case of the Remote Serial Protocol, the CRC is computed @emph{most}
13994 significant bit first, and the result is not inverted, so trailing
13995 zeros have no effect on the CRC value.
13997 To complete the description, we show below the code of the function
13998 which produces the CRC used in @code{.gnu_debuglink}. Inverting the
13999 initially supplied @code{crc} argument means that an initial call to
14000 this function passing in zero will start computing the CRC using
14003 @kindex gnu_debuglink_crc32
14006 gnu_debuglink_crc32 (unsigned long crc,
14007 unsigned char *buf, size_t len)
14009 static const unsigned long crc32_table[256] =
14011 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
14012 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
14013 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
14014 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
14015 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
14016 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
14017 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
14018 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
14019 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
14020 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
14021 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
14022 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
14023 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
14024 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
14025 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
14026 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
14027 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
14028 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
14029 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
14030 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
14031 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
14032 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
14033 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
14034 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
14035 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
14036 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
14037 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
14038 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
14039 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
14040 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
14041 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
14042 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
14043 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
14044 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
14045 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
14046 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
14047 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
14048 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
14049 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
14050 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
14051 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
14052 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
14053 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
14054 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
14055 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
14056 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
14057 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
14058 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
14059 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
14060 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
14061 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
14064 unsigned char *end;
14066 crc = ~crc & 0xffffffff;
14067 for (end = buf + len; buf < end; ++buf)
14068 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
14069 return ~crc & 0xffffffff;
14074 This computation does not apply to the ``build ID'' method.
14077 @node Symbol Errors
14078 @section Errors Reading Symbol Files
14080 While reading a symbol file, @value{GDBN} occasionally encounters problems,
14081 such as symbol types it does not recognize, or known bugs in compiler
14082 output. By default, @value{GDBN} does not notify you of such problems, since
14083 they are relatively common and primarily of interest to people
14084 debugging compilers. If you are interested in seeing information
14085 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
14086 only one message about each such type of problem, no matter how many
14087 times the problem occurs; or you can ask @value{GDBN} to print more messages,
14088 to see how many times the problems occur, with the @code{set
14089 complaints} command (@pxref{Messages/Warnings, ,Optional Warnings and
14092 The messages currently printed, and their meanings, include:
14095 @item inner block not inside outer block in @var{symbol}
14097 The symbol information shows where symbol scopes begin and end
14098 (such as at the start of a function or a block of statements). This
14099 error indicates that an inner scope block is not fully contained
14100 in its outer scope blocks.
14102 @value{GDBN} circumvents the problem by treating the inner block as if it had
14103 the same scope as the outer block. In the error message, @var{symbol}
14104 may be shown as ``@code{(don't know)}'' if the outer block is not a
14107 @item block at @var{address} out of order
14109 The symbol information for symbol scope blocks should occur in
14110 order of increasing addresses. This error indicates that it does not
14113 @value{GDBN} does not circumvent this problem, and has trouble
14114 locating symbols in the source file whose symbols it is reading. (You
14115 can often determine what source file is affected by specifying
14116 @code{set verbose on}. @xref{Messages/Warnings, ,Optional Warnings and
14119 @item bad block start address patched
14121 The symbol information for a symbol scope block has a start address
14122 smaller than the address of the preceding source line. This is known
14123 to occur in the SunOS 4.1.1 (and earlier) C compiler.
14125 @value{GDBN} circumvents the problem by treating the symbol scope block as
14126 starting on the previous source line.
14128 @item bad string table offset in symbol @var{n}
14131 Symbol number @var{n} contains a pointer into the string table which is
14132 larger than the size of the string table.
14134 @value{GDBN} circumvents the problem by considering the symbol to have the
14135 name @code{foo}, which may cause other problems if many symbols end up
14138 @item unknown symbol type @code{0x@var{nn}}
14140 The symbol information contains new data types that @value{GDBN} does
14141 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
14142 uncomprehended information, in hexadecimal.
14144 @value{GDBN} circumvents the error by ignoring this symbol information.
14145 This usually allows you to debug your program, though certain symbols
14146 are not accessible. If you encounter such a problem and feel like
14147 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
14148 on @code{complain}, then go up to the function @code{read_dbx_symtab}
14149 and examine @code{*bufp} to see the symbol.
14151 @item stub type has NULL name
14153 @value{GDBN} could not find the full definition for a struct or class.
14155 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
14156 The symbol information for a C@t{++} member function is missing some
14157 information that recent versions of the compiler should have output for
14160 @item info mismatch between compiler and debugger
14162 @value{GDBN} could not parse a type specification output by the compiler.
14167 @section GDB Data Files
14169 @cindex prefix for data files
14170 @value{GDBN} will sometimes read an auxiliary data file. These files
14171 are kept in a directory known as the @dfn{data directory}.
14173 You can set the data directory's name, and view the name @value{GDBN}
14174 is currently using.
14177 @kindex set data-directory
14178 @item set data-directory @var{directory}
14179 Set the directory which @value{GDBN} searches for auxiliary data files
14180 to @var{directory}.
14182 @kindex show data-directory
14183 @item show data-directory
14184 Show the directory @value{GDBN} searches for auxiliary data files.
14187 @cindex default data directory
14188 @cindex @samp{--with-gdb-datadir}
14189 You can set the default data directory by using the configure-time
14190 @samp{--with-gdb-datadir} option. If the data directory is inside
14191 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
14192 @samp{--exec-prefix}), then the default data directory will be updated
14193 automatically if the installed @value{GDBN} is moved to a new
14197 @chapter Specifying a Debugging Target
14199 @cindex debugging target
14200 A @dfn{target} is the execution environment occupied by your program.
14202 Often, @value{GDBN} runs in the same host environment as your program;
14203 in that case, the debugging target is specified as a side effect when
14204 you use the @code{file} or @code{core} commands. When you need more
14205 flexibility---for example, running @value{GDBN} on a physically separate
14206 host, or controlling a standalone system over a serial port or a
14207 realtime system over a TCP/IP connection---you can use the @code{target}
14208 command to specify one of the target types configured for @value{GDBN}
14209 (@pxref{Target Commands, ,Commands for Managing Targets}).
14211 @cindex target architecture
14212 It is possible to build @value{GDBN} for several different @dfn{target
14213 architectures}. When @value{GDBN} is built like that, you can choose
14214 one of the available architectures with the @kbd{set architecture}
14218 @kindex set architecture
14219 @kindex show architecture
14220 @item set architecture @var{arch}
14221 This command sets the current target architecture to @var{arch}. The
14222 value of @var{arch} can be @code{"auto"}, in addition to one of the
14223 supported architectures.
14225 @item show architecture
14226 Show the current target architecture.
14228 @item set processor
14230 @kindex set processor
14231 @kindex show processor
14232 These are alias commands for, respectively, @code{set architecture}
14233 and @code{show architecture}.
14237 * Active Targets:: Active targets
14238 * Target Commands:: Commands for managing targets
14239 * Byte Order:: Choosing target byte order
14242 @node Active Targets
14243 @section Active Targets
14245 @cindex stacking targets
14246 @cindex active targets
14247 @cindex multiple targets
14249 There are three classes of targets: processes, core files, and
14250 executable files. @value{GDBN} can work concurrently on up to three
14251 active targets, one in each class. This allows you to (for example)
14252 start a process and inspect its activity without abandoning your work on
14255 For example, if you execute @samp{gdb a.out}, then the executable file
14256 @code{a.out} is the only active target. If you designate a core file as
14257 well---presumably from a prior run that crashed and coredumped---then
14258 @value{GDBN} has two active targets and uses them in tandem, looking
14259 first in the corefile target, then in the executable file, to satisfy
14260 requests for memory addresses. (Typically, these two classes of target
14261 are complementary, since core files contain only a program's
14262 read-write memory---variables and so on---plus machine status, while
14263 executable files contain only the program text and initialized data.)
14265 When you type @code{run}, your executable file becomes an active process
14266 target as well. When a process target is active, all @value{GDBN}
14267 commands requesting memory addresses refer to that target; addresses in
14268 an active core file or executable file target are obscured while the
14269 process target is active.
14271 Use the @code{core-file} and @code{exec-file} commands to select a new
14272 core file or executable target (@pxref{Files, ,Commands to Specify
14273 Files}). To specify as a target a process that is already running, use
14274 the @code{attach} command (@pxref{Attach, ,Debugging an Already-running
14277 @node Target Commands
14278 @section Commands for Managing Targets
14281 @item target @var{type} @var{parameters}
14282 Connects the @value{GDBN} host environment to a target machine or
14283 process. A target is typically a protocol for talking to debugging
14284 facilities. You use the argument @var{type} to specify the type or
14285 protocol of the target machine.
14287 Further @var{parameters} are interpreted by the target protocol, but
14288 typically include things like device names or host names to connect
14289 with, process numbers, and baud rates.
14291 The @code{target} command does not repeat if you press @key{RET} again
14292 after executing the command.
14294 @kindex help target
14296 Displays the names of all targets available. To display targets
14297 currently selected, use either @code{info target} or @code{info files}
14298 (@pxref{Files, ,Commands to Specify Files}).
14300 @item help target @var{name}
14301 Describe a particular target, including any parameters necessary to
14304 @kindex set gnutarget
14305 @item set gnutarget @var{args}
14306 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
14307 knows whether it is reading an @dfn{executable},
14308 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
14309 with the @code{set gnutarget} command. Unlike most @code{target} commands,
14310 with @code{gnutarget} the @code{target} refers to a program, not a machine.
14313 @emph{Warning:} To specify a file format with @code{set gnutarget},
14314 you must know the actual BFD name.
14318 @xref{Files, , Commands to Specify Files}.
14320 @kindex show gnutarget
14321 @item show gnutarget
14322 Use the @code{show gnutarget} command to display what file format
14323 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
14324 @value{GDBN} will determine the file format for each file automatically,
14325 and @code{show gnutarget} displays @samp{The current BDF target is "auto"}.
14328 @cindex common targets
14329 Here are some common targets (available, or not, depending on the GDB
14334 @item target exec @var{program}
14335 @cindex executable file target
14336 An executable file. @samp{target exec @var{program}} is the same as
14337 @samp{exec-file @var{program}}.
14339 @item target core @var{filename}
14340 @cindex core dump file target
14341 A core dump file. @samp{target core @var{filename}} is the same as
14342 @samp{core-file @var{filename}}.
14344 @item target remote @var{medium}
14345 @cindex remote target
14346 A remote system connected to @value{GDBN} via a serial line or network
14347 connection. This command tells @value{GDBN} to use its own remote
14348 protocol over @var{medium} for debugging. @xref{Remote Debugging}.
14350 For example, if you have a board connected to @file{/dev/ttya} on the
14351 machine running @value{GDBN}, you could say:
14354 target remote /dev/ttya
14357 @code{target remote} supports the @code{load} command. This is only
14358 useful if you have some other way of getting the stub to the target
14359 system, and you can put it somewhere in memory where it won't get
14360 clobbered by the download.
14363 @cindex built-in simulator target
14364 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
14372 works; however, you cannot assume that a specific memory map, device
14373 drivers, or even basic I/O is available, although some simulators do
14374 provide these. For info about any processor-specific simulator details,
14375 see the appropriate section in @ref{Embedded Processors, ,Embedded
14380 Some configurations may include these targets as well:
14384 @item target nrom @var{dev}
14385 @cindex NetROM ROM emulator target
14386 NetROM ROM emulator. This target only supports downloading.
14390 Different targets are available on different configurations of @value{GDBN};
14391 your configuration may have more or fewer targets.
14393 Many remote targets require you to download the executable's code once
14394 you've successfully established a connection. You may wish to control
14395 various aspects of this process.
14400 @kindex set hash@r{, for remote monitors}
14401 @cindex hash mark while downloading
14402 This command controls whether a hash mark @samp{#} is displayed while
14403 downloading a file to the remote monitor. If on, a hash mark is
14404 displayed after each S-record is successfully downloaded to the
14408 @kindex show hash@r{, for remote monitors}
14409 Show the current status of displaying the hash mark.
14411 @item set debug monitor
14412 @kindex set debug monitor
14413 @cindex display remote monitor communications
14414 Enable or disable display of communications messages between
14415 @value{GDBN} and the remote monitor.
14417 @item show debug monitor
14418 @kindex show debug monitor
14419 Show the current status of displaying communications between
14420 @value{GDBN} and the remote monitor.
14425 @kindex load @var{filename}
14426 @item load @var{filename}
14428 Depending on what remote debugging facilities are configured into
14429 @value{GDBN}, the @code{load} command may be available. Where it exists, it
14430 is meant to make @var{filename} (an executable) available for debugging
14431 on the remote system---by downloading, or dynamic linking, for example.
14432 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
14433 the @code{add-symbol-file} command.
14435 If your @value{GDBN} does not have a @code{load} command, attempting to
14436 execute it gets the error message ``@code{You can't do that when your
14437 target is @dots{}}''
14439 The file is loaded at whatever address is specified in the executable.
14440 For some object file formats, you can specify the load address when you
14441 link the program; for other formats, like a.out, the object file format
14442 specifies a fixed address.
14443 @c FIXME! This would be a good place for an xref to the GNU linker doc.
14445 Depending on the remote side capabilities, @value{GDBN} may be able to
14446 load programs into flash memory.
14448 @code{load} does not repeat if you press @key{RET} again after using it.
14452 @section Choosing Target Byte Order
14454 @cindex choosing target byte order
14455 @cindex target byte order
14457 Some types of processors, such as the MIPS, PowerPC, and Renesas SH,
14458 offer the ability to run either big-endian or little-endian byte
14459 orders. Usually the executable or symbol will include a bit to
14460 designate the endian-ness, and you will not need to worry about
14461 which to use. However, you may still find it useful to adjust
14462 @value{GDBN}'s idea of processor endian-ness manually.
14466 @item set endian big
14467 Instruct @value{GDBN} to assume the target is big-endian.
14469 @item set endian little
14470 Instruct @value{GDBN} to assume the target is little-endian.
14472 @item set endian auto
14473 Instruct @value{GDBN} to use the byte order associated with the
14477 Display @value{GDBN}'s current idea of the target byte order.
14481 Note that these commands merely adjust interpretation of symbolic
14482 data on the host, and that they have absolutely no effect on the
14486 @node Remote Debugging
14487 @chapter Debugging Remote Programs
14488 @cindex remote debugging
14490 If you are trying to debug a program running on a machine that cannot run
14491 @value{GDBN} in the usual way, it is often useful to use remote debugging.
14492 For example, you might use remote debugging on an operating system kernel,
14493 or on a small system which does not have a general purpose operating system
14494 powerful enough to run a full-featured debugger.
14496 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
14497 to make this work with particular debugging targets. In addition,
14498 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
14499 but not specific to any particular target system) which you can use if you
14500 write the remote stubs---the code that runs on the remote system to
14501 communicate with @value{GDBN}.
14503 Other remote targets may be available in your
14504 configuration of @value{GDBN}; use @code{help target} to list them.
14507 * Connecting:: Connecting to a remote target
14508 * File Transfer:: Sending files to a remote system
14509 * Server:: Using the gdbserver program
14510 * Remote Configuration:: Remote configuration
14511 * Remote Stub:: Implementing a remote stub
14515 @section Connecting to a Remote Target
14517 On the @value{GDBN} host machine, you will need an unstripped copy of
14518 your program, since @value{GDBN} needs symbol and debugging information.
14519 Start up @value{GDBN} as usual, using the name of the local copy of your
14520 program as the first argument.
14522 @cindex @code{target remote}
14523 @value{GDBN} can communicate with the target over a serial line, or
14524 over an @acronym{IP} network using @acronym{TCP} or @acronym{UDP}. In
14525 each case, @value{GDBN} uses the same protocol for debugging your
14526 program; only the medium carrying the debugging packets varies. The
14527 @code{target remote} command establishes a connection to the target.
14528 Its arguments indicate which medium to use:
14532 @item target remote @var{serial-device}
14533 @cindex serial line, @code{target remote}
14534 Use @var{serial-device} to communicate with the target. For example,
14535 to use a serial line connected to the device named @file{/dev/ttyb}:
14538 target remote /dev/ttyb
14541 If you're using a serial line, you may want to give @value{GDBN} the
14542 @w{@samp{--baud}} option, or use the @code{set remotebaud} command
14543 (@pxref{Remote Configuration, set remotebaud}) before the
14544 @code{target} command.
14546 @item target remote @code{@var{host}:@var{port}}
14547 @itemx target remote @code{tcp:@var{host}:@var{port}}
14548 @cindex @acronym{TCP} port, @code{target remote}
14549 Debug using a @acronym{TCP} connection to @var{port} on @var{host}.
14550 The @var{host} may be either a host name or a numeric @acronym{IP}
14551 address; @var{port} must be a decimal number. The @var{host} could be
14552 the target machine itself, if it is directly connected to the net, or
14553 it might be a terminal server which in turn has a serial line to the
14556 For example, to connect to port 2828 on a terminal server named
14560 target remote manyfarms:2828
14563 If your remote target is actually running on the same machine as your
14564 debugger session (e.g.@: a simulator for your target running on the
14565 same host), you can omit the hostname. For example, to connect to
14566 port 1234 on your local machine:
14569 target remote :1234
14573 Note that the colon is still required here.
14575 @item target remote @code{udp:@var{host}:@var{port}}
14576 @cindex @acronym{UDP} port, @code{target remote}
14577 Debug using @acronym{UDP} packets to @var{port} on @var{host}. For example, to
14578 connect to @acronym{UDP} port 2828 on a terminal server named @code{manyfarms}:
14581 target remote udp:manyfarms:2828
14584 When using a @acronym{UDP} connection for remote debugging, you should
14585 keep in mind that the `U' stands for ``Unreliable''. @acronym{UDP}
14586 can silently drop packets on busy or unreliable networks, which will
14587 cause havoc with your debugging session.
14589 @item target remote | @var{command}
14590 @cindex pipe, @code{target remote} to
14591 Run @var{command} in the background and communicate with it using a
14592 pipe. The @var{command} is a shell command, to be parsed and expanded
14593 by the system's command shell, @code{/bin/sh}; it should expect remote
14594 protocol packets on its standard input, and send replies on its
14595 standard output. You could use this to run a stand-alone simulator
14596 that speaks the remote debugging protocol, to make net connections
14597 using programs like @code{ssh}, or for other similar tricks.
14599 If @var{command} closes its standard output (perhaps by exiting),
14600 @value{GDBN} will try to send it a @code{SIGTERM} signal. (If the
14601 program has already exited, this will have no effect.)
14605 Once the connection has been established, you can use all the usual
14606 commands to examine and change data. The remote program is already
14607 running; you can use @kbd{step} and @kbd{continue}, and you do not
14608 need to use @kbd{run}.
14610 @cindex interrupting remote programs
14611 @cindex remote programs, interrupting
14612 Whenever @value{GDBN} is waiting for the remote program, if you type the
14613 interrupt character (often @kbd{Ctrl-c}), @value{GDBN} attempts to stop the
14614 program. This may or may not succeed, depending in part on the hardware
14615 and the serial drivers the remote system uses. If you type the
14616 interrupt character once again, @value{GDBN} displays this prompt:
14619 Interrupted while waiting for the program.
14620 Give up (and stop debugging it)? (y or n)
14623 If you type @kbd{y}, @value{GDBN} abandons the remote debugging session.
14624 (If you decide you want to try again later, you can use @samp{target
14625 remote} again to connect once more.) If you type @kbd{n}, @value{GDBN}
14626 goes back to waiting.
14629 @kindex detach (remote)
14631 When you have finished debugging the remote program, you can use the
14632 @code{detach} command to release it from @value{GDBN} control.
14633 Detaching from the target normally resumes its execution, but the results
14634 will depend on your particular remote stub. After the @code{detach}
14635 command, @value{GDBN} is free to connect to another target.
14639 The @code{disconnect} command behaves like @code{detach}, except that
14640 the target is generally not resumed. It will wait for @value{GDBN}
14641 (this instance or another one) to connect and continue debugging. After
14642 the @code{disconnect} command, @value{GDBN} is again free to connect to
14645 @cindex send command to remote monitor
14646 @cindex extend @value{GDBN} for remote targets
14647 @cindex add new commands for external monitor
14649 @item monitor @var{cmd}
14650 This command allows you to send arbitrary commands directly to the
14651 remote monitor. Since @value{GDBN} doesn't care about the commands it
14652 sends like this, this command is the way to extend @value{GDBN}---you
14653 can add new commands that only the external monitor will understand
14657 @node File Transfer
14658 @section Sending files to a remote system
14659 @cindex remote target, file transfer
14660 @cindex file transfer
14661 @cindex sending files to remote systems
14663 Some remote targets offer the ability to transfer files over the same
14664 connection used to communicate with @value{GDBN}. This is convenient
14665 for targets accessible through other means, e.g.@: @sc{gnu}/Linux systems
14666 running @code{gdbserver} over a network interface. For other targets,
14667 e.g.@: embedded devices with only a single serial port, this may be
14668 the only way to upload or download files.
14670 Not all remote targets support these commands.
14674 @item remote put @var{hostfile} @var{targetfile}
14675 Copy file @var{hostfile} from the host system (the machine running
14676 @value{GDBN}) to @var{targetfile} on the target system.
14679 @item remote get @var{targetfile} @var{hostfile}
14680 Copy file @var{targetfile} from the target system to @var{hostfile}
14681 on the host system.
14683 @kindex remote delete
14684 @item remote delete @var{targetfile}
14685 Delete @var{targetfile} from the target system.
14690 @section Using the @code{gdbserver} Program
14693 @cindex remote connection without stubs
14694 @code{gdbserver} is a control program for Unix-like systems, which
14695 allows you to connect your program with a remote @value{GDBN} via
14696 @code{target remote}---but without linking in the usual debugging stub.
14698 @code{gdbserver} is not a complete replacement for the debugging stubs,
14699 because it requires essentially the same operating-system facilities
14700 that @value{GDBN} itself does. In fact, a system that can run
14701 @code{gdbserver} to connect to a remote @value{GDBN} could also run
14702 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
14703 because it is a much smaller program than @value{GDBN} itself. It is
14704 also easier to port than all of @value{GDBN}, so you may be able to get
14705 started more quickly on a new system by using @code{gdbserver}.
14706 Finally, if you develop code for real-time systems, you may find that
14707 the tradeoffs involved in real-time operation make it more convenient to
14708 do as much development work as possible on another system, for example
14709 by cross-compiling. You can use @code{gdbserver} to make a similar
14710 choice for debugging.
14712 @value{GDBN} and @code{gdbserver} communicate via either a serial line
14713 or a TCP connection, using the standard @value{GDBN} remote serial
14717 @emph{Warning:} @code{gdbserver} does not have any built-in security.
14718 Do not run @code{gdbserver} connected to any public network; a
14719 @value{GDBN} connection to @code{gdbserver} provides access to the
14720 target system with the same privileges as the user running
14724 @subsection Running @code{gdbserver}
14725 @cindex arguments, to @code{gdbserver}
14727 Run @code{gdbserver} on the target system. You need a copy of the
14728 program you want to debug, including any libraries it requires.
14729 @code{gdbserver} does not need your program's symbol table, so you can
14730 strip the program if necessary to save space. @value{GDBN} on the host
14731 system does all the symbol handling.
14733 To use the server, you must tell it how to communicate with @value{GDBN};
14734 the name of your program; and the arguments for your program. The usual
14738 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
14741 @var{comm} is either a device name (to use a serial line) or a TCP
14742 hostname and portnumber. For example, to debug Emacs with the argument
14743 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
14747 target> gdbserver /dev/com1 emacs foo.txt
14750 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
14753 To use a TCP connection instead of a serial line:
14756 target> gdbserver host:2345 emacs foo.txt
14759 The only difference from the previous example is the first argument,
14760 specifying that you are communicating with the host @value{GDBN} via
14761 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
14762 expect a TCP connection from machine @samp{host} to local TCP port 2345.
14763 (Currently, the @samp{host} part is ignored.) You can choose any number
14764 you want for the port number as long as it does not conflict with any
14765 TCP ports already in use on the target system (for example, @code{23} is
14766 reserved for @code{telnet}).@footnote{If you choose a port number that
14767 conflicts with another service, @code{gdbserver} prints an error message
14768 and exits.} You must use the same port number with the host @value{GDBN}
14769 @code{target remote} command.
14771 @subsubsection Attaching to a Running Program
14773 On some targets, @code{gdbserver} can also attach to running programs.
14774 This is accomplished via the @code{--attach} argument. The syntax is:
14777 target> gdbserver --attach @var{comm} @var{pid}
14780 @var{pid} is the process ID of a currently running process. It isn't necessary
14781 to point @code{gdbserver} at a binary for the running process.
14784 @cindex attach to a program by name
14785 You can debug processes by name instead of process ID if your target has the
14786 @code{pidof} utility:
14789 target> gdbserver --attach @var{comm} `pidof @var{program}`
14792 In case more than one copy of @var{program} is running, or @var{program}
14793 has multiple threads, most versions of @code{pidof} support the
14794 @code{-s} option to only return the first process ID.
14796 @subsubsection Multi-Process Mode for @code{gdbserver}
14797 @cindex gdbserver, multiple processes
14798 @cindex multiple processes with gdbserver
14800 When you connect to @code{gdbserver} using @code{target remote},
14801 @code{gdbserver} debugs the specified program only once. When the
14802 program exits, or you detach from it, @value{GDBN} closes the connection
14803 and @code{gdbserver} exits.
14805 If you connect using @kbd{target extended-remote}, @code{gdbserver}
14806 enters multi-process mode. When the debugged program exits, or you
14807 detach from it, @value{GDBN} stays connected to @code{gdbserver} even
14808 though no program is running. The @code{run} and @code{attach}
14809 commands instruct @code{gdbserver} to run or attach to a new program.
14810 The @code{run} command uses @code{set remote exec-file} (@pxref{set
14811 remote exec-file}) to select the program to run. Command line
14812 arguments are supported, except for wildcard expansion and I/O
14813 redirection (@pxref{Arguments}).
14815 To start @code{gdbserver} without supplying an initial command to run
14816 or process ID to attach, use the @option{--multi} command line option.
14817 Then you can connect using @kbd{target extended-remote} and start
14818 the program you want to debug.
14820 @code{gdbserver} does not automatically exit in multi-process mode.
14821 You can terminate it by using @code{monitor exit}
14822 (@pxref{Monitor Commands for gdbserver}).
14824 @subsubsection Other Command-Line Arguments for @code{gdbserver}
14826 The @option{--debug} option tells @code{gdbserver} to display extra
14827 status information about the debugging process. The
14828 @option{--remote-debug} option tells @code{gdbserver} to display
14829 remote protocol debug output. These options are intended for
14830 @code{gdbserver} development and for bug reports to the developers.
14832 The @option{--wrapper} option specifies a wrapper to launch programs
14833 for debugging. The option should be followed by the name of the
14834 wrapper, then any command-line arguments to pass to the wrapper, then
14835 @kbd{--} indicating the end of the wrapper arguments.
14837 @code{gdbserver} runs the specified wrapper program with a combined
14838 command line including the wrapper arguments, then the name of the
14839 program to debug, then any arguments to the program. The wrapper
14840 runs until it executes your program, and then @value{GDBN} gains control.
14842 You can use any program that eventually calls @code{execve} with
14843 its arguments as a wrapper. Several standard Unix utilities do
14844 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
14845 with @code{exec "$@@"} will also work.
14847 For example, you can use @code{env} to pass an environment variable to
14848 the debugged program, without setting the variable in @code{gdbserver}'s
14852 $ gdbserver --wrapper env LD_PRELOAD=libtest.so -- :2222 ./testprog
14855 @subsection Connecting to @code{gdbserver}
14857 Run @value{GDBN} on the host system.
14859 First make sure you have the necessary symbol files. Load symbols for
14860 your application using the @code{file} command before you connect. Use
14861 @code{set sysroot} to locate target libraries (unless your @value{GDBN}
14862 was compiled with the correct sysroot using @code{--with-sysroot}).
14864 The symbol file and target libraries must exactly match the executable
14865 and libraries on the target, with one exception: the files on the host
14866 system should not be stripped, even if the files on the target system
14867 are. Mismatched or missing files will lead to confusing results
14868 during debugging. On @sc{gnu}/Linux targets, mismatched or missing
14869 files may also prevent @code{gdbserver} from debugging multi-threaded
14872 Connect to your target (@pxref{Connecting,,Connecting to a Remote Target}).
14873 For TCP connections, you must start up @code{gdbserver} prior to using
14874 the @code{target remote} command. Otherwise you may get an error whose
14875 text depends on the host system, but which usually looks something like
14876 @samp{Connection refused}. Don't use the @code{load}
14877 command in @value{GDBN} when using @code{gdbserver}, since the program is
14878 already on the target.
14880 @subsection Monitor Commands for @code{gdbserver}
14881 @cindex monitor commands, for @code{gdbserver}
14882 @anchor{Monitor Commands for gdbserver}
14884 During a @value{GDBN} session using @code{gdbserver}, you can use the
14885 @code{monitor} command to send special requests to @code{gdbserver}.
14886 Here are the available commands.
14890 List the available monitor commands.
14892 @item monitor set debug 0
14893 @itemx monitor set debug 1
14894 Disable or enable general debugging messages.
14896 @item monitor set remote-debug 0
14897 @itemx monitor set remote-debug 1
14898 Disable or enable specific debugging messages associated with the remote
14899 protocol (@pxref{Remote Protocol}).
14902 Tell gdbserver to exit immediately. This command should be followed by
14903 @code{disconnect} to close the debugging session. @code{gdbserver} will
14904 detach from any attached processes and kill any processes it created.
14905 Use @code{monitor exit} to terminate @code{gdbserver} at the end
14906 of a multi-process mode debug session.
14910 @node Remote Configuration
14911 @section Remote Configuration
14914 @kindex show remote
14915 This section documents the configuration options available when
14916 debugging remote programs. For the options related to the File I/O
14917 extensions of the remote protocol, see @ref{system,
14918 system-call-allowed}.
14921 @item set remoteaddresssize @var{bits}
14922 @cindex address size for remote targets
14923 @cindex bits in remote address
14924 Set the maximum size of address in a memory packet to the specified
14925 number of bits. @value{GDBN} will mask off the address bits above
14926 that number, when it passes addresses to the remote target. The
14927 default value is the number of bits in the target's address.
14929 @item show remoteaddresssize
14930 Show the current value of remote address size in bits.
14932 @item set remotebaud @var{n}
14933 @cindex baud rate for remote targets
14934 Set the baud rate for the remote serial I/O to @var{n} baud. The
14935 value is used to set the speed of the serial port used for debugging
14938 @item show remotebaud
14939 Show the current speed of the remote connection.
14941 @item set remotebreak
14942 @cindex interrupt remote programs
14943 @cindex BREAK signal instead of Ctrl-C
14944 @anchor{set remotebreak}
14945 If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote
14946 when you type @kbd{Ctrl-c} to interrupt the program running
14947 on the remote. If set to off, @value{GDBN} sends the @samp{Ctrl-C}
14948 character instead. The default is off, since most remote systems
14949 expect to see @samp{Ctrl-C} as the interrupt signal.
14951 @item show remotebreak
14952 Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to
14953 interrupt the remote program.
14955 @item set remoteflow on
14956 @itemx set remoteflow off
14957 @kindex set remoteflow
14958 Enable or disable hardware flow control (@code{RTS}/@code{CTS})
14959 on the serial port used to communicate to the remote target.
14961 @item show remoteflow
14962 @kindex show remoteflow
14963 Show the current setting of hardware flow control.
14965 @item set remotelogbase @var{base}
14966 Set the base (a.k.a.@: radix) of logging serial protocol
14967 communications to @var{base}. Supported values of @var{base} are:
14968 @code{ascii}, @code{octal}, and @code{hex}. The default is
14971 @item show remotelogbase
14972 Show the current setting of the radix for logging remote serial
14975 @item set remotelogfile @var{file}
14976 @cindex record serial communications on file
14977 Record remote serial communications on the named @var{file}. The
14978 default is not to record at all.
14980 @item show remotelogfile.
14981 Show the current setting of the file name on which to record the
14982 serial communications.
14984 @item set remotetimeout @var{num}
14985 @cindex timeout for serial communications
14986 @cindex remote timeout
14987 Set the timeout limit to wait for the remote target to respond to
14988 @var{num} seconds. The default is 2 seconds.
14990 @item show remotetimeout
14991 Show the current number of seconds to wait for the remote target
14994 @cindex limit hardware breakpoints and watchpoints
14995 @cindex remote target, limit break- and watchpoints
14996 @anchor{set remote hardware-watchpoint-limit}
14997 @anchor{set remote hardware-breakpoint-limit}
14998 @item set remote hardware-watchpoint-limit @var{limit}
14999 @itemx set remote hardware-breakpoint-limit @var{limit}
15000 Restrict @value{GDBN} to using @var{limit} remote hardware breakpoint or
15001 watchpoints. A limit of -1, the default, is treated as unlimited.
15003 @item set remote exec-file @var{filename}
15004 @itemx show remote exec-file
15005 @anchor{set remote exec-file}
15006 @cindex executable file, for remote target
15007 Select the file used for @code{run} with @code{target
15008 extended-remote}. This should be set to a filename valid on the
15009 target system. If it is not set, the target will use a default
15010 filename (e.g.@: the last program run).
15014 @item set tcp auto-retry on
15015 @cindex auto-retry, for remote TCP target
15016 Enable auto-retry for remote TCP connections. This is useful if the remote
15017 debugging agent is launched in parallel with @value{GDBN}; there is a race
15018 condition because the agent may not become ready to accept the connection
15019 before @value{GDBN} attempts to connect. When auto-retry is
15020 enabled, if the initial attempt to connect fails, @value{GDBN} reattempts
15021 to establish the connection using the timeout specified by
15022 @code{set tcp connect-timeout}.
15024 @item set tcp auto-retry off
15025 Do not auto-retry failed TCP connections.
15027 @item show tcp auto-retry
15028 Show the current auto-retry setting.
15030 @item set tcp connect-timeout @var{seconds}
15031 @cindex connection timeout, for remote TCP target
15032 @cindex timeout, for remote target connection
15033 Set the timeout for establishing a TCP connection to the remote target to
15034 @var{seconds}. The timeout affects both polling to retry failed connections
15035 (enabled by @code{set tcp auto-retry on}) and waiting for connections
15036 that are merely slow to complete, and represents an approximate cumulative
15039 @item show tcp connect-timeout
15040 Show the current connection timeout setting.
15043 @cindex remote packets, enabling and disabling
15044 The @value{GDBN} remote protocol autodetects the packets supported by
15045 your debugging stub. If you need to override the autodetection, you
15046 can use these commands to enable or disable individual packets. Each
15047 packet can be set to @samp{on} (the remote target supports this
15048 packet), @samp{off} (the remote target does not support this packet),
15049 or @samp{auto} (detect remote target support for this packet). They
15050 all default to @samp{auto}. For more information about each packet,
15051 see @ref{Remote Protocol}.
15053 During normal use, you should not have to use any of these commands.
15054 If you do, that may be a bug in your remote debugging stub, or a bug
15055 in @value{GDBN}. You may want to report the problem to the
15056 @value{GDBN} developers.
15058 For each packet @var{name}, the command to enable or disable the
15059 packet is @code{set remote @var{name}-packet}. The available settings
15062 @multitable @columnfractions 0.28 0.32 0.25
15065 @tab Related Features
15067 @item @code{fetch-register}
15069 @tab @code{info registers}
15071 @item @code{set-register}
15075 @item @code{binary-download}
15077 @tab @code{load}, @code{set}
15079 @item @code{read-aux-vector}
15080 @tab @code{qXfer:auxv:read}
15081 @tab @code{info auxv}
15083 @item @code{symbol-lookup}
15084 @tab @code{qSymbol}
15085 @tab Detecting multiple threads
15087 @item @code{attach}
15088 @tab @code{vAttach}
15091 @item @code{verbose-resume}
15093 @tab Stepping or resuming multiple threads
15099 @item @code{software-breakpoint}
15103 @item @code{hardware-breakpoint}
15107 @item @code{write-watchpoint}
15111 @item @code{read-watchpoint}
15115 @item @code{access-watchpoint}
15119 @item @code{target-features}
15120 @tab @code{qXfer:features:read}
15121 @tab @code{set architecture}
15123 @item @code{library-info}
15124 @tab @code{qXfer:libraries:read}
15125 @tab @code{info sharedlibrary}
15127 @item @code{memory-map}
15128 @tab @code{qXfer:memory-map:read}
15129 @tab @code{info mem}
15131 @item @code{read-spu-object}
15132 @tab @code{qXfer:spu:read}
15133 @tab @code{info spu}
15135 @item @code{write-spu-object}
15136 @tab @code{qXfer:spu:write}
15137 @tab @code{info spu}
15139 @item @code{read-siginfo-object}
15140 @tab @code{qXfer:siginfo:read}
15141 @tab @code{print $_siginfo}
15143 @item @code{write-siginfo-object}
15144 @tab @code{qXfer:siginfo:write}
15145 @tab @code{set $_siginfo}
15147 @item @code{get-thread-local-@*storage-address}
15148 @tab @code{qGetTLSAddr}
15149 @tab Displaying @code{__thread} variables
15151 @item @code{search-memory}
15152 @tab @code{qSearch:memory}
15155 @item @code{supported-packets}
15156 @tab @code{qSupported}
15157 @tab Remote communications parameters
15159 @item @code{pass-signals}
15160 @tab @code{QPassSignals}
15161 @tab @code{handle @var{signal}}
15163 @item @code{hostio-close-packet}
15164 @tab @code{vFile:close}
15165 @tab @code{remote get}, @code{remote put}
15167 @item @code{hostio-open-packet}
15168 @tab @code{vFile:open}
15169 @tab @code{remote get}, @code{remote put}
15171 @item @code{hostio-pread-packet}
15172 @tab @code{vFile:pread}
15173 @tab @code{remote get}, @code{remote put}
15175 @item @code{hostio-pwrite-packet}
15176 @tab @code{vFile:pwrite}
15177 @tab @code{remote get}, @code{remote put}
15179 @item @code{hostio-unlink-packet}
15180 @tab @code{vFile:unlink}
15181 @tab @code{remote delete}
15183 @item @code{noack-packet}
15184 @tab @code{QStartNoAckMode}
15185 @tab Packet acknowledgment
15187 @item @code{osdata}
15188 @tab @code{qXfer:osdata:read}
15189 @tab @code{info os}
15191 @item @code{query-attached}
15192 @tab @code{qAttached}
15193 @tab Querying remote process attach state.
15197 @section Implementing a Remote Stub
15199 @cindex debugging stub, example
15200 @cindex remote stub, example
15201 @cindex stub example, remote debugging
15202 The stub files provided with @value{GDBN} implement the target side of the
15203 communication protocol, and the @value{GDBN} side is implemented in the
15204 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
15205 these subroutines to communicate, and ignore the details. (If you're
15206 implementing your own stub file, you can still ignore the details: start
15207 with one of the existing stub files. @file{sparc-stub.c} is the best
15208 organized, and therefore the easiest to read.)
15210 @cindex remote serial debugging, overview
15211 To debug a program running on another machine (the debugging
15212 @dfn{target} machine), you must first arrange for all the usual
15213 prerequisites for the program to run by itself. For example, for a C
15218 A startup routine to set up the C runtime environment; these usually
15219 have a name like @file{crt0}. The startup routine may be supplied by
15220 your hardware supplier, or you may have to write your own.
15223 A C subroutine library to support your program's
15224 subroutine calls, notably managing input and output.
15227 A way of getting your program to the other machine---for example, a
15228 download program. These are often supplied by the hardware
15229 manufacturer, but you may have to write your own from hardware
15233 The next step is to arrange for your program to use a serial port to
15234 communicate with the machine where @value{GDBN} is running (the @dfn{host}
15235 machine). In general terms, the scheme looks like this:
15239 @value{GDBN} already understands how to use this protocol; when everything
15240 else is set up, you can simply use the @samp{target remote} command
15241 (@pxref{Targets,,Specifying a Debugging Target}).
15243 @item On the target,
15244 you must link with your program a few special-purpose subroutines that
15245 implement the @value{GDBN} remote serial protocol. The file containing these
15246 subroutines is called a @dfn{debugging stub}.
15248 On certain remote targets, you can use an auxiliary program
15249 @code{gdbserver} instead of linking a stub into your program.
15250 @xref{Server,,Using the @code{gdbserver} Program}, for details.
15253 The debugging stub is specific to the architecture of the remote
15254 machine; for example, use @file{sparc-stub.c} to debug programs on
15257 @cindex remote serial stub list
15258 These working remote stubs are distributed with @value{GDBN}:
15263 @cindex @file{i386-stub.c}
15266 For Intel 386 and compatible architectures.
15269 @cindex @file{m68k-stub.c}
15270 @cindex Motorola 680x0
15272 For Motorola 680x0 architectures.
15275 @cindex @file{sh-stub.c}
15278 For Renesas SH architectures.
15281 @cindex @file{sparc-stub.c}
15283 For @sc{sparc} architectures.
15285 @item sparcl-stub.c
15286 @cindex @file{sparcl-stub.c}
15289 For Fujitsu @sc{sparclite} architectures.
15293 The @file{README} file in the @value{GDBN} distribution may list other
15294 recently added stubs.
15297 * Stub Contents:: What the stub can do for you
15298 * Bootstrapping:: What you must do for the stub
15299 * Debug Session:: Putting it all together
15302 @node Stub Contents
15303 @subsection What the Stub Can Do for You
15305 @cindex remote serial stub
15306 The debugging stub for your architecture supplies these three
15310 @item set_debug_traps
15311 @findex set_debug_traps
15312 @cindex remote serial stub, initialization
15313 This routine arranges for @code{handle_exception} to run when your
15314 program stops. You must call this subroutine explicitly near the
15315 beginning of your program.
15317 @item handle_exception
15318 @findex handle_exception
15319 @cindex remote serial stub, main routine
15320 This is the central workhorse, but your program never calls it
15321 explicitly---the setup code arranges for @code{handle_exception} to
15322 run when a trap is triggered.
15324 @code{handle_exception} takes control when your program stops during
15325 execution (for example, on a breakpoint), and mediates communications
15326 with @value{GDBN} on the host machine. This is where the communications
15327 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
15328 representative on the target machine. It begins by sending summary
15329 information on the state of your program, then continues to execute,
15330 retrieving and transmitting any information @value{GDBN} needs, until you
15331 execute a @value{GDBN} command that makes your program resume; at that point,
15332 @code{handle_exception} returns control to your own code on the target
15336 @cindex @code{breakpoint} subroutine, remote
15337 Use this auxiliary subroutine to make your program contain a
15338 breakpoint. Depending on the particular situation, this may be the only
15339 way for @value{GDBN} to get control. For instance, if your target
15340 machine has some sort of interrupt button, you won't need to call this;
15341 pressing the interrupt button transfers control to
15342 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
15343 simply receiving characters on the serial port may also trigger a trap;
15344 again, in that situation, you don't need to call @code{breakpoint} from
15345 your own program---simply running @samp{target remote} from the host
15346 @value{GDBN} session gets control.
15348 Call @code{breakpoint} if none of these is true, or if you simply want
15349 to make certain your program stops at a predetermined point for the
15350 start of your debugging session.
15353 @node Bootstrapping
15354 @subsection What You Must Do for the Stub
15356 @cindex remote stub, support routines
15357 The debugging stubs that come with @value{GDBN} are set up for a particular
15358 chip architecture, but they have no information about the rest of your
15359 debugging target machine.
15361 First of all you need to tell the stub how to communicate with the
15365 @item int getDebugChar()
15366 @findex getDebugChar
15367 Write this subroutine to read a single character from the serial port.
15368 It may be identical to @code{getchar} for your target system; a
15369 different name is used to allow you to distinguish the two if you wish.
15371 @item void putDebugChar(int)
15372 @findex putDebugChar
15373 Write this subroutine to write a single character to the serial port.
15374 It may be identical to @code{putchar} for your target system; a
15375 different name is used to allow you to distinguish the two if you wish.
15378 @cindex control C, and remote debugging
15379 @cindex interrupting remote targets
15380 If you want @value{GDBN} to be able to stop your program while it is
15381 running, you need to use an interrupt-driven serial driver, and arrange
15382 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
15383 character). That is the character which @value{GDBN} uses to tell the
15384 remote system to stop.
15386 Getting the debugging target to return the proper status to @value{GDBN}
15387 probably requires changes to the standard stub; one quick and dirty way
15388 is to just execute a breakpoint instruction (the ``dirty'' part is that
15389 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
15391 Other routines you need to supply are:
15394 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
15395 @findex exceptionHandler
15396 Write this function to install @var{exception_address} in the exception
15397 handling tables. You need to do this because the stub does not have any
15398 way of knowing what the exception handling tables on your target system
15399 are like (for example, the processor's table might be in @sc{rom},
15400 containing entries which point to a table in @sc{ram}).
15401 @var{exception_number} is the exception number which should be changed;
15402 its meaning is architecture-dependent (for example, different numbers
15403 might represent divide by zero, misaligned access, etc). When this
15404 exception occurs, control should be transferred directly to
15405 @var{exception_address}, and the processor state (stack, registers,
15406 and so on) should be just as it is when a processor exception occurs. So if
15407 you want to use a jump instruction to reach @var{exception_address}, it
15408 should be a simple jump, not a jump to subroutine.
15410 For the 386, @var{exception_address} should be installed as an interrupt
15411 gate so that interrupts are masked while the handler runs. The gate
15412 should be at privilege level 0 (the most privileged level). The
15413 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
15414 help from @code{exceptionHandler}.
15416 @item void flush_i_cache()
15417 @findex flush_i_cache
15418 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
15419 instruction cache, if any, on your target machine. If there is no
15420 instruction cache, this subroutine may be a no-op.
15422 On target machines that have instruction caches, @value{GDBN} requires this
15423 function to make certain that the state of your program is stable.
15427 You must also make sure this library routine is available:
15430 @item void *memset(void *, int, int)
15432 This is the standard library function @code{memset} that sets an area of
15433 memory to a known value. If you have one of the free versions of
15434 @code{libc.a}, @code{memset} can be found there; otherwise, you must
15435 either obtain it from your hardware manufacturer, or write your own.
15438 If you do not use the GNU C compiler, you may need other standard
15439 library subroutines as well; this varies from one stub to another,
15440 but in general the stubs are likely to use any of the common library
15441 subroutines which @code{@value{NGCC}} generates as inline code.
15444 @node Debug Session
15445 @subsection Putting it All Together
15447 @cindex remote serial debugging summary
15448 In summary, when your program is ready to debug, you must follow these
15453 Make sure you have defined the supporting low-level routines
15454 (@pxref{Bootstrapping,,What You Must Do for the Stub}):
15456 @code{getDebugChar}, @code{putDebugChar},
15457 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
15461 Insert these lines near the top of your program:
15469 For the 680x0 stub only, you need to provide a variable called
15470 @code{exceptionHook}. Normally you just use:
15473 void (*exceptionHook)() = 0;
15477 but if before calling @code{set_debug_traps}, you set it to point to a
15478 function in your program, that function is called when
15479 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
15480 error). The function indicated by @code{exceptionHook} is called with
15481 one parameter: an @code{int} which is the exception number.
15484 Compile and link together: your program, the @value{GDBN} debugging stub for
15485 your target architecture, and the supporting subroutines.
15488 Make sure you have a serial connection between your target machine and
15489 the @value{GDBN} host, and identify the serial port on the host.
15492 @c The "remote" target now provides a `load' command, so we should
15493 @c document that. FIXME.
15494 Download your program to your target machine (or get it there by
15495 whatever means the manufacturer provides), and start it.
15498 Start @value{GDBN} on the host, and connect to the target
15499 (@pxref{Connecting,,Connecting to a Remote Target}).
15503 @node Configurations
15504 @chapter Configuration-Specific Information
15506 While nearly all @value{GDBN} commands are available for all native and
15507 cross versions of the debugger, there are some exceptions. This chapter
15508 describes things that are only available in certain configurations.
15510 There are three major categories of configurations: native
15511 configurations, where the host and target are the same, embedded
15512 operating system configurations, which are usually the same for several
15513 different processor architectures, and bare embedded processors, which
15514 are quite different from each other.
15519 * Embedded Processors::
15526 This section describes details specific to particular native
15531 * BSD libkvm Interface:: Debugging BSD kernel memory images
15532 * SVR4 Process Information:: SVR4 process information
15533 * DJGPP Native:: Features specific to the DJGPP port
15534 * Cygwin Native:: Features specific to the Cygwin port
15535 * Hurd Native:: Features specific to @sc{gnu} Hurd
15536 * Neutrino:: Features specific to QNX Neutrino
15537 * Darwin:: Features specific to Darwin
15543 On HP-UX systems, if you refer to a function or variable name that
15544 begins with a dollar sign, @value{GDBN} searches for a user or system
15545 name first, before it searches for a convenience variable.
15548 @node BSD libkvm Interface
15549 @subsection BSD libkvm Interface
15552 @cindex kernel memory image
15553 @cindex kernel crash dump
15555 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
15556 interface that provides a uniform interface for accessing kernel virtual
15557 memory images, including live systems and crash dumps. @value{GDBN}
15558 uses this interface to allow you to debug live kernels and kernel crash
15559 dumps on many native BSD configurations. This is implemented as a
15560 special @code{kvm} debugging target. For debugging a live system, load
15561 the currently running kernel into @value{GDBN} and connect to the
15565 (@value{GDBP}) @b{target kvm}
15568 For debugging crash dumps, provide the file name of the crash dump as an
15572 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
15575 Once connected to the @code{kvm} target, the following commands are
15581 Set current context from the @dfn{Process Control Block} (PCB) address.
15584 Set current context from proc address. This command isn't available on
15585 modern FreeBSD systems.
15588 @node SVR4 Process Information
15589 @subsection SVR4 Process Information
15591 @cindex examine process image
15592 @cindex process info via @file{/proc}
15594 Many versions of SVR4 and compatible systems provide a facility called
15595 @samp{/proc} that can be used to examine the image of a running
15596 process using file-system subroutines. If @value{GDBN} is configured
15597 for an operating system with this facility, the command @code{info
15598 proc} is available to report information about the process running
15599 your program, or about any process running on your system. @code{info
15600 proc} works only on SVR4 systems that include the @code{procfs} code.
15601 This includes, as of this writing, @sc{gnu}/Linux, OSF/1 (Digital
15602 Unix), Solaris, Irix, and Unixware, but not HP-UX, for example.
15608 @itemx info proc @var{process-id}
15609 Summarize available information about any running process. If a
15610 process ID is specified by @var{process-id}, display information about
15611 that process; otherwise display information about the program being
15612 debugged. The summary includes the debugged process ID, the command
15613 line used to invoke it, its current working directory, and its
15614 executable file's absolute file name.
15616 On some systems, @var{process-id} can be of the form
15617 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
15618 within a process. If the optional @var{pid} part is missing, it means
15619 a thread from the process being debugged (the leading @samp{/} still
15620 needs to be present, or else @value{GDBN} will interpret the number as
15621 a process ID rather than a thread ID).
15623 @item info proc mappings
15624 @cindex memory address space mappings
15625 Report the memory address space ranges accessible in the program, with
15626 information on whether the process has read, write, or execute access
15627 rights to each range. On @sc{gnu}/Linux systems, each memory range
15628 includes the object file which is mapped to that range, instead of the
15629 memory access rights to that range.
15631 @item info proc stat
15632 @itemx info proc status
15633 @cindex process detailed status information
15634 These subcommands are specific to @sc{gnu}/Linux systems. They show
15635 the process-related information, including the user ID and group ID;
15636 how many threads are there in the process; its virtual memory usage;
15637 the signals that are pending, blocked, and ignored; its TTY; its
15638 consumption of system and user time; its stack size; its @samp{nice}
15639 value; etc. For more information, see the @samp{proc} man page
15640 (type @kbd{man 5 proc} from your shell prompt).
15642 @item info proc all
15643 Show all the information about the process described under all of the
15644 above @code{info proc} subcommands.
15647 @comment These sub-options of 'info proc' were not included when
15648 @comment procfs.c was re-written. Keep their descriptions around
15649 @comment against the day when someone finds the time to put them back in.
15650 @kindex info proc times
15651 @item info proc times
15652 Starting time, user CPU time, and system CPU time for your program and
15655 @kindex info proc id
15657 Report on the process IDs related to your program: its own process ID,
15658 the ID of its parent, the process group ID, and the session ID.
15661 @item set procfs-trace
15662 @kindex set procfs-trace
15663 @cindex @code{procfs} API calls
15664 This command enables and disables tracing of @code{procfs} API calls.
15666 @item show procfs-trace
15667 @kindex show procfs-trace
15668 Show the current state of @code{procfs} API call tracing.
15670 @item set procfs-file @var{file}
15671 @kindex set procfs-file
15672 Tell @value{GDBN} to write @code{procfs} API trace to the named
15673 @var{file}. @value{GDBN} appends the trace info to the previous
15674 contents of the file. The default is to display the trace on the
15677 @item show procfs-file
15678 @kindex show procfs-file
15679 Show the file to which @code{procfs} API trace is written.
15681 @item proc-trace-entry
15682 @itemx proc-trace-exit
15683 @itemx proc-untrace-entry
15684 @itemx proc-untrace-exit
15685 @kindex proc-trace-entry
15686 @kindex proc-trace-exit
15687 @kindex proc-untrace-entry
15688 @kindex proc-untrace-exit
15689 These commands enable and disable tracing of entries into and exits
15690 from the @code{syscall} interface.
15693 @kindex info pidlist
15694 @cindex process list, QNX Neutrino
15695 For QNX Neutrino only, this command displays the list of all the
15696 processes and all the threads within each process.
15699 @kindex info meminfo
15700 @cindex mapinfo list, QNX Neutrino
15701 For QNX Neutrino only, this command displays the list of all mapinfos.
15705 @subsection Features for Debugging @sc{djgpp} Programs
15706 @cindex @sc{djgpp} debugging
15707 @cindex native @sc{djgpp} debugging
15708 @cindex MS-DOS-specific commands
15711 @sc{djgpp} is a port of the @sc{gnu} development tools to MS-DOS and
15712 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
15713 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
15714 top of real-mode DOS systems and their emulations.
15716 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
15717 defines a few commands specific to the @sc{djgpp} port. This
15718 subsection describes those commands.
15723 This is a prefix of @sc{djgpp}-specific commands which print
15724 information about the target system and important OS structures.
15727 @cindex MS-DOS system info
15728 @cindex free memory information (MS-DOS)
15729 @item info dos sysinfo
15730 This command displays assorted information about the underlying
15731 platform: the CPU type and features, the OS version and flavor, the
15732 DPMI version, and the available conventional and DPMI memory.
15737 @cindex segment descriptor tables
15738 @cindex descriptor tables display
15740 @itemx info dos ldt
15741 @itemx info dos idt
15742 These 3 commands display entries from, respectively, Global, Local,
15743 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
15744 tables are data structures which store a descriptor for each segment
15745 that is currently in use. The segment's selector is an index into a
15746 descriptor table; the table entry for that index holds the
15747 descriptor's base address and limit, and its attributes and access
15750 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
15751 segment (used for both data and the stack), and a DOS segment (which
15752 allows access to DOS/BIOS data structures and absolute addresses in
15753 conventional memory). However, the DPMI host will usually define
15754 additional segments in order to support the DPMI environment.
15756 @cindex garbled pointers
15757 These commands allow to display entries from the descriptor tables.
15758 Without an argument, all entries from the specified table are
15759 displayed. An argument, which should be an integer expression, means
15760 display a single entry whose index is given by the argument. For
15761 example, here's a convenient way to display information about the
15762 debugged program's data segment:
15765 @exdent @code{(@value{GDBP}) info dos ldt $ds}
15766 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
15770 This comes in handy when you want to see whether a pointer is outside
15771 the data segment's limit (i.e.@: @dfn{garbled}).
15773 @cindex page tables display (MS-DOS)
15775 @itemx info dos pte
15776 These two commands display entries from, respectively, the Page
15777 Directory and the Page Tables. Page Directories and Page Tables are
15778 data structures which control how virtual memory addresses are mapped
15779 into physical addresses. A Page Table includes an entry for every
15780 page of memory that is mapped into the program's address space; there
15781 may be several Page Tables, each one holding up to 4096 entries. A
15782 Page Directory has up to 4096 entries, one each for every Page Table
15783 that is currently in use.
15785 Without an argument, @kbd{info dos pde} displays the entire Page
15786 Directory, and @kbd{info dos pte} displays all the entries in all of
15787 the Page Tables. An argument, an integer expression, given to the
15788 @kbd{info dos pde} command means display only that entry from the Page
15789 Directory table. An argument given to the @kbd{info dos pte} command
15790 means display entries from a single Page Table, the one pointed to by
15791 the specified entry in the Page Directory.
15793 @cindex direct memory access (DMA) on MS-DOS
15794 These commands are useful when your program uses @dfn{DMA} (Direct
15795 Memory Access), which needs physical addresses to program the DMA
15798 These commands are supported only with some DPMI servers.
15800 @cindex physical address from linear address
15801 @item info dos address-pte @var{addr}
15802 This command displays the Page Table entry for a specified linear
15803 address. The argument @var{addr} is a linear address which should
15804 already have the appropriate segment's base address added to it,
15805 because this command accepts addresses which may belong to @emph{any}
15806 segment. For example, here's how to display the Page Table entry for
15807 the page where a variable @code{i} is stored:
15810 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
15811 @exdent @code{Page Table entry for address 0x11a00d30:}
15812 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
15816 This says that @code{i} is stored at offset @code{0xd30} from the page
15817 whose physical base address is @code{0x02698000}, and shows all the
15818 attributes of that page.
15820 Note that you must cast the addresses of variables to a @code{char *},
15821 since otherwise the value of @code{__djgpp_base_address}, the base
15822 address of all variables and functions in a @sc{djgpp} program, will
15823 be added using the rules of C pointer arithmetics: if @code{i} is
15824 declared an @code{int}, @value{GDBN} will add 4 times the value of
15825 @code{__djgpp_base_address} to the address of @code{i}.
15827 Here's another example, it displays the Page Table entry for the
15831 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
15832 @exdent @code{Page Table entry for address 0x29110:}
15833 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
15837 (The @code{+ 3} offset is because the transfer buffer's address is the
15838 3rd member of the @code{_go32_info_block} structure.) The output
15839 clearly shows that this DPMI server maps the addresses in conventional
15840 memory 1:1, i.e.@: the physical (@code{0x00029000} + @code{0x110}) and
15841 linear (@code{0x29110}) addresses are identical.
15843 This command is supported only with some DPMI servers.
15846 @cindex DOS serial data link, remote debugging
15847 In addition to native debugging, the DJGPP port supports remote
15848 debugging via a serial data link. The following commands are specific
15849 to remote serial debugging in the DJGPP port of @value{GDBN}.
15852 @kindex set com1base
15853 @kindex set com1irq
15854 @kindex set com2base
15855 @kindex set com2irq
15856 @kindex set com3base
15857 @kindex set com3irq
15858 @kindex set com4base
15859 @kindex set com4irq
15860 @item set com1base @var{addr}
15861 This command sets the base I/O port address of the @file{COM1} serial
15864 @item set com1irq @var{irq}
15865 This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use
15866 for the @file{COM1} serial port.
15868 There are similar commands @samp{set com2base}, @samp{set com3irq},
15869 etc.@: for setting the port address and the @code{IRQ} lines for the
15872 @kindex show com1base
15873 @kindex show com1irq
15874 @kindex show com2base
15875 @kindex show com2irq
15876 @kindex show com3base
15877 @kindex show com3irq
15878 @kindex show com4base
15879 @kindex show com4irq
15880 The related commands @samp{show com1base}, @samp{show com1irq} etc.@:
15881 display the current settings of the base address and the @code{IRQ}
15882 lines used by the COM ports.
15885 @kindex info serial
15886 @cindex DOS serial port status
15887 This command prints the status of the 4 DOS serial ports. For each
15888 port, it prints whether it's active or not, its I/O base address and
15889 IRQ number, whether it uses a 16550-style FIFO, its baudrate, and the
15890 counts of various errors encountered so far.
15894 @node Cygwin Native
15895 @subsection Features for Debugging MS Windows PE Executables
15896 @cindex MS Windows debugging
15897 @cindex native Cygwin debugging
15898 @cindex Cygwin-specific commands
15900 @value{GDBN} supports native debugging of MS Windows programs, including
15901 DLLs with and without symbolic debugging information. There are various
15902 additional Cygwin-specific commands, described in this section.
15903 Working with DLLs that have no debugging symbols is described in
15904 @ref{Non-debug DLL Symbols}.
15909 This is a prefix of MS Windows-specific commands which print
15910 information about the target system and important OS structures.
15912 @item info w32 selector
15913 This command displays information returned by
15914 the Win32 API @code{GetThreadSelectorEntry} function.
15915 It takes an optional argument that is evaluated to
15916 a long value to give the information about this given selector.
15917 Without argument, this command displays information
15918 about the six segment registers.
15922 This is a Cygwin-specific alias of @code{info shared}.
15924 @kindex dll-symbols
15926 This command loads symbols from a dll similarly to
15927 add-sym command but without the need to specify a base address.
15929 @kindex set cygwin-exceptions
15930 @cindex debugging the Cygwin DLL
15931 @cindex Cygwin DLL, debugging
15932 @item set cygwin-exceptions @var{mode}
15933 If @var{mode} is @code{on}, @value{GDBN} will break on exceptions that
15934 happen inside the Cygwin DLL. If @var{mode} is @code{off},
15935 @value{GDBN} will delay recognition of exceptions, and may ignore some
15936 exceptions which seem to be caused by internal Cygwin DLL
15937 ``bookkeeping''. This option is meant primarily for debugging the
15938 Cygwin DLL itself; the default value is @code{off} to avoid annoying
15939 @value{GDBN} users with false @code{SIGSEGV} signals.
15941 @kindex show cygwin-exceptions
15942 @item show cygwin-exceptions
15943 Displays whether @value{GDBN} will break on exceptions that happen
15944 inside the Cygwin DLL itself.
15946 @kindex set new-console
15947 @item set new-console @var{mode}
15948 If @var{mode} is @code{on} the debuggee will
15949 be started in a new console on next start.
15950 If @var{mode} is @code{off}i, the debuggee will
15951 be started in the same console as the debugger.
15953 @kindex show new-console
15954 @item show new-console
15955 Displays whether a new console is used
15956 when the debuggee is started.
15958 @kindex set new-group
15959 @item set new-group @var{mode}
15960 This boolean value controls whether the debuggee should
15961 start a new group or stay in the same group as the debugger.
15962 This affects the way the Windows OS handles
15965 @kindex show new-group
15966 @item show new-group
15967 Displays current value of new-group boolean.
15969 @kindex set debugevents
15970 @item set debugevents
15971 This boolean value adds debug output concerning kernel events related
15972 to the debuggee seen by the debugger. This includes events that
15973 signal thread and process creation and exit, DLL loading and
15974 unloading, console interrupts, and debugging messages produced by the
15975 Windows @code{OutputDebugString} API call.
15977 @kindex set debugexec
15978 @item set debugexec
15979 This boolean value adds debug output concerning execute events
15980 (such as resume thread) seen by the debugger.
15982 @kindex set debugexceptions
15983 @item set debugexceptions
15984 This boolean value adds debug output concerning exceptions in the
15985 debuggee seen by the debugger.
15987 @kindex set debugmemory
15988 @item set debugmemory
15989 This boolean value adds debug output concerning debuggee memory reads
15990 and writes by the debugger.
15994 This boolean values specifies whether the debuggee is called
15995 via a shell or directly (default value is on).
15999 Displays if the debuggee will be started with a shell.
16004 * Non-debug DLL Symbols:: Support for DLLs without debugging symbols
16007 @node Non-debug DLL Symbols
16008 @subsubsection Support for DLLs without Debugging Symbols
16009 @cindex DLLs with no debugging symbols
16010 @cindex Minimal symbols and DLLs
16012 Very often on windows, some of the DLLs that your program relies on do
16013 not include symbolic debugging information (for example,
16014 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
16015 symbols in a DLL, it relies on the minimal amount of symbolic
16016 information contained in the DLL's export table. This section
16017 describes working with such symbols, known internally to @value{GDBN} as
16018 ``minimal symbols''.
16020 Note that before the debugged program has started execution, no DLLs
16021 will have been loaded. The easiest way around this problem is simply to
16022 start the program --- either by setting a breakpoint or letting the
16023 program run once to completion. It is also possible to force
16024 @value{GDBN} to load a particular DLL before starting the executable ---
16025 see the shared library information in @ref{Files}, or the
16026 @code{dll-symbols} command in @ref{Cygwin Native}. Currently,
16027 explicitly loading symbols from a DLL with no debugging information will
16028 cause the symbol names to be duplicated in @value{GDBN}'s lookup table,
16029 which may adversely affect symbol lookup performance.
16031 @subsubsection DLL Name Prefixes
16033 In keeping with the naming conventions used by the Microsoft debugging
16034 tools, DLL export symbols are made available with a prefix based on the
16035 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
16036 also entered into the symbol table, so @code{CreateFileA} is often
16037 sufficient. In some cases there will be name clashes within a program
16038 (particularly if the executable itself includes full debugging symbols)
16039 necessitating the use of the fully qualified name when referring to the
16040 contents of the DLL. Use single-quotes around the name to avoid the
16041 exclamation mark (``!'') being interpreted as a language operator.
16043 Note that the internal name of the DLL may be all upper-case, even
16044 though the file name of the DLL is lower-case, or vice-versa. Since
16045 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
16046 some confusion. If in doubt, try the @code{info functions} and
16047 @code{info variables} commands or even @code{maint print msymbols}
16048 (@pxref{Symbols}). Here's an example:
16051 (@value{GDBP}) info function CreateFileA
16052 All functions matching regular expression "CreateFileA":
16054 Non-debugging symbols:
16055 0x77e885f4 CreateFileA
16056 0x77e885f4 KERNEL32!CreateFileA
16060 (@value{GDBP}) info function !
16061 All functions matching regular expression "!":
16063 Non-debugging symbols:
16064 0x6100114c cygwin1!__assert
16065 0x61004034 cygwin1!_dll_crt0@@0
16066 0x61004240 cygwin1!dll_crt0(per_process *)
16070 @subsubsection Working with Minimal Symbols
16072 Symbols extracted from a DLL's export table do not contain very much
16073 type information. All that @value{GDBN} can do is guess whether a symbol
16074 refers to a function or variable depending on the linker section that
16075 contains the symbol. Also note that the actual contents of the memory
16076 contained in a DLL are not available unless the program is running. This
16077 means that you cannot examine the contents of a variable or disassemble
16078 a function within a DLL without a running program.
16080 Variables are generally treated as pointers and dereferenced
16081 automatically. For this reason, it is often necessary to prefix a
16082 variable name with the address-of operator (``&'') and provide explicit
16083 type information in the command. Here's an example of the type of
16087 (@value{GDBP}) print 'cygwin1!__argv'
16092 (@value{GDBP}) x 'cygwin1!__argv'
16093 0x10021610: "\230y\""
16096 And two possible solutions:
16099 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
16100 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
16104 (@value{GDBP}) x/2x &'cygwin1!__argv'
16105 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
16106 (@value{GDBP}) x/x 0x10021608
16107 0x10021608: 0x0022fd98
16108 (@value{GDBP}) x/s 0x0022fd98
16109 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
16112 Setting a break point within a DLL is possible even before the program
16113 starts execution. However, under these circumstances, @value{GDBN} can't
16114 examine the initial instructions of the function in order to skip the
16115 function's frame set-up code. You can work around this by using ``*&''
16116 to set the breakpoint at a raw memory address:
16119 (@value{GDBP}) break *&'python22!PyOS_Readline'
16120 Breakpoint 1 at 0x1e04eff0
16123 The author of these extensions is not entirely convinced that setting a
16124 break point within a shared DLL like @file{kernel32.dll} is completely
16128 @subsection Commands Specific to @sc{gnu} Hurd Systems
16129 @cindex @sc{gnu} Hurd debugging
16131 This subsection describes @value{GDBN} commands specific to the
16132 @sc{gnu} Hurd native debugging.
16137 @kindex set signals@r{, Hurd command}
16138 @kindex set sigs@r{, Hurd command}
16139 This command toggles the state of inferior signal interception by
16140 @value{GDBN}. Mach exceptions, such as breakpoint traps, are not
16141 affected by this command. @code{sigs} is a shorthand alias for
16146 @kindex show signals@r{, Hurd command}
16147 @kindex show sigs@r{, Hurd command}
16148 Show the current state of intercepting inferior's signals.
16150 @item set signal-thread
16151 @itemx set sigthread
16152 @kindex set signal-thread
16153 @kindex set sigthread
16154 This command tells @value{GDBN} which thread is the @code{libc} signal
16155 thread. That thread is run when a signal is delivered to a running
16156 process. @code{set sigthread} is the shorthand alias of @code{set
16159 @item show signal-thread
16160 @itemx show sigthread
16161 @kindex show signal-thread
16162 @kindex show sigthread
16163 These two commands show which thread will run when the inferior is
16164 delivered a signal.
16167 @kindex set stopped@r{, Hurd command}
16168 This commands tells @value{GDBN} that the inferior process is stopped,
16169 as with the @code{SIGSTOP} signal. The stopped process can be
16170 continued by delivering a signal to it.
16173 @kindex show stopped@r{, Hurd command}
16174 This command shows whether @value{GDBN} thinks the debuggee is
16177 @item set exceptions
16178 @kindex set exceptions@r{, Hurd command}
16179 Use this command to turn off trapping of exceptions in the inferior.
16180 When exception trapping is off, neither breakpoints nor
16181 single-stepping will work. To restore the default, set exception
16184 @item show exceptions
16185 @kindex show exceptions@r{, Hurd command}
16186 Show the current state of trapping exceptions in the inferior.
16188 @item set task pause
16189 @kindex set task@r{, Hurd commands}
16190 @cindex task attributes (@sc{gnu} Hurd)
16191 @cindex pause current task (@sc{gnu} Hurd)
16192 This command toggles task suspension when @value{GDBN} has control.
16193 Setting it to on takes effect immediately, and the task is suspended
16194 whenever @value{GDBN} gets control. Setting it to off will take
16195 effect the next time the inferior is continued. If this option is set
16196 to off, you can use @code{set thread default pause on} or @code{set
16197 thread pause on} (see below) to pause individual threads.
16199 @item show task pause
16200 @kindex show task@r{, Hurd commands}
16201 Show the current state of task suspension.
16203 @item set task detach-suspend-count
16204 @cindex task suspend count
16205 @cindex detach from task, @sc{gnu} Hurd
16206 This command sets the suspend count the task will be left with when
16207 @value{GDBN} detaches from it.
16209 @item show task detach-suspend-count
16210 Show the suspend count the task will be left with when detaching.
16212 @item set task exception-port
16213 @itemx set task excp
16214 @cindex task exception port, @sc{gnu} Hurd
16215 This command sets the task exception port to which @value{GDBN} will
16216 forward exceptions. The argument should be the value of the @dfn{send
16217 rights} of the task. @code{set task excp} is a shorthand alias.
16219 @item set noninvasive
16220 @cindex noninvasive task options
16221 This command switches @value{GDBN} to a mode that is the least
16222 invasive as far as interfering with the inferior is concerned. This
16223 is the same as using @code{set task pause}, @code{set exceptions}, and
16224 @code{set signals} to values opposite to the defaults.
16226 @item info send-rights
16227 @itemx info receive-rights
16228 @itemx info port-rights
16229 @itemx info port-sets
16230 @itemx info dead-names
16233 @cindex send rights, @sc{gnu} Hurd
16234 @cindex receive rights, @sc{gnu} Hurd
16235 @cindex port rights, @sc{gnu} Hurd
16236 @cindex port sets, @sc{gnu} Hurd
16237 @cindex dead names, @sc{gnu} Hurd
16238 These commands display information about, respectively, send rights,
16239 receive rights, port rights, port sets, and dead names of a task.
16240 There are also shorthand aliases: @code{info ports} for @code{info
16241 port-rights} and @code{info psets} for @code{info port-sets}.
16243 @item set thread pause
16244 @kindex set thread@r{, Hurd command}
16245 @cindex thread properties, @sc{gnu} Hurd
16246 @cindex pause current thread (@sc{gnu} Hurd)
16247 This command toggles current thread suspension when @value{GDBN} has
16248 control. Setting it to on takes effect immediately, and the current
16249 thread is suspended whenever @value{GDBN} gets control. Setting it to
16250 off will take effect the next time the inferior is continued.
16251 Normally, this command has no effect, since when @value{GDBN} has
16252 control, the whole task is suspended. However, if you used @code{set
16253 task pause off} (see above), this command comes in handy to suspend
16254 only the current thread.
16256 @item show thread pause
16257 @kindex show thread@r{, Hurd command}
16258 This command shows the state of current thread suspension.
16260 @item set thread run
16261 This command sets whether the current thread is allowed to run.
16263 @item show thread run
16264 Show whether the current thread is allowed to run.
16266 @item set thread detach-suspend-count
16267 @cindex thread suspend count, @sc{gnu} Hurd
16268 @cindex detach from thread, @sc{gnu} Hurd
16269 This command sets the suspend count @value{GDBN} will leave on a
16270 thread when detaching. This number is relative to the suspend count
16271 found by @value{GDBN} when it notices the thread; use @code{set thread
16272 takeover-suspend-count} to force it to an absolute value.
16274 @item show thread detach-suspend-count
16275 Show the suspend count @value{GDBN} will leave on the thread when
16278 @item set thread exception-port
16279 @itemx set thread excp
16280 Set the thread exception port to which to forward exceptions. This
16281 overrides the port set by @code{set task exception-port} (see above).
16282 @code{set thread excp} is the shorthand alias.
16284 @item set thread takeover-suspend-count
16285 Normally, @value{GDBN}'s thread suspend counts are relative to the
16286 value @value{GDBN} finds when it notices each thread. This command
16287 changes the suspend counts to be absolute instead.
16289 @item set thread default
16290 @itemx show thread default
16291 @cindex thread default settings, @sc{gnu} Hurd
16292 Each of the above @code{set thread} commands has a @code{set thread
16293 default} counterpart (e.g., @code{set thread default pause}, @code{set
16294 thread default exception-port}, etc.). The @code{thread default}
16295 variety of commands sets the default thread properties for all
16296 threads; you can then change the properties of individual threads with
16297 the non-default commands.
16302 @subsection QNX Neutrino
16303 @cindex QNX Neutrino
16305 @value{GDBN} provides the following commands specific to the QNX
16309 @item set debug nto-debug
16310 @kindex set debug nto-debug
16311 When set to on, enables debugging messages specific to the QNX
16314 @item show debug nto-debug
16315 @kindex show debug nto-debug
16316 Show the current state of QNX Neutrino messages.
16323 @value{GDBN} provides the following commands specific to the Darwin target:
16326 @item set debug darwin @var{num}
16327 @kindex set debug darwin
16328 When set to a non zero value, enables debugging messages specific to
16329 the Darwin support. Higher values produce more verbose output.
16331 @item show debug darwin
16332 @kindex show debug darwin
16333 Show the current state of Darwin messages.
16335 @item set debug mach-o @var{num}
16336 @kindex set debug mach-o
16337 When set to a non zero value, enables debugging messages while
16338 @value{GDBN} is reading Darwin object files. (@dfn{Mach-O} is the
16339 file format used on Darwin for object and executable files.) Higher
16340 values produce more verbose output. This is a command to diagnose
16341 problems internal to @value{GDBN} and should not be needed in normal
16344 @item show debug mach-o
16345 @kindex show debug mach-o
16346 Show the current state of Mach-O file messages.
16348 @item set mach-exceptions on
16349 @itemx set mach-exceptions off
16350 @kindex set mach-exceptions
16351 On Darwin, faults are first reported as a Mach exception and are then
16352 mapped to a Posix signal. Use this command to turn on trapping of
16353 Mach exceptions in the inferior. This might be sometimes useful to
16354 better understand the cause of a fault. The default is off.
16356 @item show mach-exceptions
16357 @kindex show mach-exceptions
16358 Show the current state of exceptions trapping.
16363 @section Embedded Operating Systems
16365 This section describes configurations involving the debugging of
16366 embedded operating systems that are available for several different
16370 * VxWorks:: Using @value{GDBN} with VxWorks
16373 @value{GDBN} includes the ability to debug programs running on
16374 various real-time operating systems.
16377 @subsection Using @value{GDBN} with VxWorks
16383 @kindex target vxworks
16384 @item target vxworks @var{machinename}
16385 A VxWorks system, attached via TCP/IP. The argument @var{machinename}
16386 is the target system's machine name or IP address.
16390 On VxWorks, @code{load} links @var{filename} dynamically on the
16391 current target system as well as adding its symbols in @value{GDBN}.
16393 @value{GDBN} enables developers to spawn and debug tasks running on networked
16394 VxWorks targets from a Unix host. Already-running tasks spawned from
16395 the VxWorks shell can also be debugged. @value{GDBN} uses code that runs on
16396 both the Unix host and on the VxWorks target. The program
16397 @code{@value{GDBP}} is installed and executed on the Unix host. (It may be
16398 installed with the name @code{vxgdb}, to distinguish it from a
16399 @value{GDBN} for debugging programs on the host itself.)
16402 @item VxWorks-timeout @var{args}
16403 @kindex vxworks-timeout
16404 All VxWorks-based targets now support the option @code{vxworks-timeout}.
16405 This option is set by the user, and @var{args} represents the number of
16406 seconds @value{GDBN} waits for responses to rpc's. You might use this if
16407 your VxWorks target is a slow software simulator or is on the far side
16408 of a thin network line.
16411 The following information on connecting to VxWorks was current when
16412 this manual was produced; newer releases of VxWorks may use revised
16415 @findex INCLUDE_RDB
16416 To use @value{GDBN} with VxWorks, you must rebuild your VxWorks kernel
16417 to include the remote debugging interface routines in the VxWorks
16418 library @file{rdb.a}. To do this, define @code{INCLUDE_RDB} in the
16419 VxWorks configuration file @file{configAll.h} and rebuild your VxWorks
16420 kernel. The resulting kernel contains @file{rdb.a}, and spawns the
16421 source debugging task @code{tRdbTask} when VxWorks is booted. For more
16422 information on configuring and remaking VxWorks, see the manufacturer's
16424 @c VxWorks, see the @cite{VxWorks Programmer's Guide}.
16426 Once you have included @file{rdb.a} in your VxWorks system image and set
16427 your Unix execution search path to find @value{GDBN}, you are ready to
16428 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}} (or
16429 @code{vxgdb}, depending on your installation).
16431 @value{GDBN} comes up showing the prompt:
16438 * VxWorks Connection:: Connecting to VxWorks
16439 * VxWorks Download:: VxWorks download
16440 * VxWorks Attach:: Running tasks
16443 @node VxWorks Connection
16444 @subsubsection Connecting to VxWorks
16446 The @value{GDBN} command @code{target} lets you connect to a VxWorks target on the
16447 network. To connect to a target whose host name is ``@code{tt}'', type:
16450 (vxgdb) target vxworks tt
16454 @value{GDBN} displays messages like these:
16457 Attaching remote machine across net...
16462 @value{GDBN} then attempts to read the symbol tables of any object modules
16463 loaded into the VxWorks target since it was last booted. @value{GDBN} locates
16464 these files by searching the directories listed in the command search
16465 path (@pxref{Environment, ,Your Program's Environment}); if it fails
16466 to find an object file, it displays a message such as:
16469 prog.o: No such file or directory.
16472 When this happens, add the appropriate directory to the search path with
16473 the @value{GDBN} command @code{path}, and execute the @code{target}
16476 @node VxWorks Download
16477 @subsubsection VxWorks Download
16479 @cindex download to VxWorks
16480 If you have connected to the VxWorks target and you want to debug an
16481 object that has not yet been loaded, you can use the @value{GDBN}
16482 @code{load} command to download a file from Unix to VxWorks
16483 incrementally. The object file given as an argument to the @code{load}
16484 command is actually opened twice: first by the VxWorks target in order
16485 to download the code, then by @value{GDBN} in order to read the symbol
16486 table. This can lead to problems if the current working directories on
16487 the two systems differ. If both systems have NFS mounted the same
16488 filesystems, you can avoid these problems by using absolute paths.
16489 Otherwise, it is simplest to set the working directory on both systems
16490 to the directory in which the object file resides, and then to reference
16491 the file by its name, without any path. For instance, a program
16492 @file{prog.o} may reside in @file{@var{vxpath}/vw/demo/rdb} in VxWorks
16493 and in @file{@var{hostpath}/vw/demo/rdb} on the host. To load this
16494 program, type this on VxWorks:
16497 -> cd "@var{vxpath}/vw/demo/rdb"
16501 Then, in @value{GDBN}, type:
16504 (vxgdb) cd @var{hostpath}/vw/demo/rdb
16505 (vxgdb) load prog.o
16508 @value{GDBN} displays a response similar to this:
16511 Reading symbol data from wherever/vw/demo/rdb/prog.o... done.
16514 You can also use the @code{load} command to reload an object module
16515 after editing and recompiling the corresponding source file. Note that
16516 this makes @value{GDBN} delete all currently-defined breakpoints,
16517 auto-displays, and convenience variables, and to clear the value
16518 history. (This is necessary in order to preserve the integrity of
16519 debugger's data structures that reference the target system's symbol
16522 @node VxWorks Attach
16523 @subsubsection Running Tasks
16525 @cindex running VxWorks tasks
16526 You can also attach to an existing task using the @code{attach} command as
16530 (vxgdb) attach @var{task}
16534 where @var{task} is the VxWorks hexadecimal task ID. The task can be running
16535 or suspended when you attach to it. Running tasks are suspended at
16536 the time of attachment.
16538 @node Embedded Processors
16539 @section Embedded Processors
16541 This section goes into details specific to particular embedded
16544 @cindex send command to simulator
16545 Whenever a specific embedded processor has a simulator, @value{GDBN}
16546 allows to send an arbitrary command to the simulator.
16549 @item sim @var{command}
16550 @kindex sim@r{, a command}
16551 Send an arbitrary @var{command} string to the simulator. Consult the
16552 documentation for the specific simulator in use for information about
16553 acceptable commands.
16559 * M32R/D:: Renesas M32R/D
16560 * M68K:: Motorola M68K
16561 * MIPS Embedded:: MIPS Embedded
16562 * OpenRISC 1000:: OpenRisc 1000
16563 * PA:: HP PA Embedded
16564 * PowerPC Embedded:: PowerPC Embedded
16565 * Sparclet:: Tsqware Sparclet
16566 * Sparclite:: Fujitsu Sparclite
16567 * Z8000:: Zilog Z8000
16570 * Super-H:: Renesas Super-H
16579 @item target rdi @var{dev}
16580 ARM Angel monitor, via RDI library interface to ADP protocol. You may
16581 use this target to communicate with both boards running the Angel
16582 monitor, or with the EmbeddedICE JTAG debug device.
16585 @item target rdp @var{dev}
16590 @value{GDBN} provides the following ARM-specific commands:
16593 @item set arm disassembler
16595 This commands selects from a list of disassembly styles. The
16596 @code{"std"} style is the standard style.
16598 @item show arm disassembler
16600 Show the current disassembly style.
16602 @item set arm apcs32
16603 @cindex ARM 32-bit mode
16604 This command toggles ARM operation mode between 32-bit and 26-bit.
16606 @item show arm apcs32
16607 Display the current usage of the ARM 32-bit mode.
16609 @item set arm fpu @var{fputype}
16610 This command sets the ARM floating-point unit (FPU) type. The
16611 argument @var{fputype} can be one of these:
16615 Determine the FPU type by querying the OS ABI.
16617 Software FPU, with mixed-endian doubles on little-endian ARM
16620 GCC-compiled FPA co-processor.
16622 Software FPU with pure-endian doubles.
16628 Show the current type of the FPU.
16631 This command forces @value{GDBN} to use the specified ABI.
16634 Show the currently used ABI.
16636 @item set arm fallback-mode (arm|thumb|auto)
16637 @value{GDBN} uses the symbol table, when available, to determine
16638 whether instructions are ARM or Thumb. This command controls
16639 @value{GDBN}'s default behavior when the symbol table is not
16640 available. The default is @samp{auto}, which causes @value{GDBN} to
16641 use the current execution mode (from the @code{T} bit in the @code{CPSR}
16644 @item show arm fallback-mode
16645 Show the current fallback instruction mode.
16647 @item set arm force-mode (arm|thumb|auto)
16648 This command overrides use of the symbol table to determine whether
16649 instructions are ARM or Thumb. The default is @samp{auto}, which
16650 causes @value{GDBN} to use the symbol table and then the setting
16651 of @samp{set arm fallback-mode}.
16653 @item show arm force-mode
16654 Show the current forced instruction mode.
16656 @item set debug arm
16657 Toggle whether to display ARM-specific debugging messages from the ARM
16658 target support subsystem.
16660 @item show debug arm
16661 Show whether ARM-specific debugging messages are enabled.
16664 The following commands are available when an ARM target is debugged
16665 using the RDI interface:
16668 @item rdilogfile @r{[}@var{file}@r{]}
16670 @cindex ADP (Angel Debugger Protocol) logging
16671 Set the filename for the ADP (Angel Debugger Protocol) packet log.
16672 With an argument, sets the log file to the specified @var{file}. With
16673 no argument, show the current log file name. The default log file is
16676 @item rdilogenable @r{[}@var{arg}@r{]}
16677 @kindex rdilogenable
16678 Control logging of ADP packets. With an argument of 1 or @code{"yes"}
16679 enables logging, with an argument 0 or @code{"no"} disables it. With
16680 no arguments displays the current setting. When logging is enabled,
16681 ADP packets exchanged between @value{GDBN} and the RDI target device
16682 are logged to a file.
16684 @item set rdiromatzero
16685 @kindex set rdiromatzero
16686 @cindex ROM at zero address, RDI
16687 Tell @value{GDBN} whether the target has ROM at address 0. If on,
16688 vector catching is disabled, so that zero address can be used. If off
16689 (the default), vector catching is enabled. For this command to take
16690 effect, it needs to be invoked prior to the @code{target rdi} command.
16692 @item show rdiromatzero
16693 @kindex show rdiromatzero
16694 Show the current setting of ROM at zero address.
16696 @item set rdiheartbeat
16697 @kindex set rdiheartbeat
16698 @cindex RDI heartbeat
16699 Enable or disable RDI heartbeat packets. It is not recommended to
16700 turn on this option, since it confuses ARM and EPI JTAG interface, as
16701 well as the Angel monitor.
16703 @item show rdiheartbeat
16704 @kindex show rdiheartbeat
16705 Show the setting of RDI heartbeat packets.
16710 @subsection Renesas M32R/D and M32R/SDI
16713 @kindex target m32r
16714 @item target m32r @var{dev}
16715 Renesas M32R/D ROM monitor.
16717 @kindex target m32rsdi
16718 @item target m32rsdi @var{dev}
16719 Renesas M32R SDI server, connected via parallel port to the board.
16722 The following @value{GDBN} commands are specific to the M32R monitor:
16725 @item set download-path @var{path}
16726 @kindex set download-path
16727 @cindex find downloadable @sc{srec} files (M32R)
16728 Set the default path for finding downloadable @sc{srec} files.
16730 @item show download-path
16731 @kindex show download-path
16732 Show the default path for downloadable @sc{srec} files.
16734 @item set board-address @var{addr}
16735 @kindex set board-address
16736 @cindex M32-EVA target board address
16737 Set the IP address for the M32R-EVA target board.
16739 @item show board-address
16740 @kindex show board-address
16741 Show the current IP address of the target board.
16743 @item set server-address @var{addr}
16744 @kindex set server-address
16745 @cindex download server address (M32R)
16746 Set the IP address for the download server, which is the @value{GDBN}'s
16749 @item show server-address
16750 @kindex show server-address
16751 Display the IP address of the download server.
16753 @item upload @r{[}@var{file}@r{]}
16754 @kindex upload@r{, M32R}
16755 Upload the specified @sc{srec} @var{file} via the monitor's Ethernet
16756 upload capability. If no @var{file} argument is given, the current
16757 executable file is uploaded.
16759 @item tload @r{[}@var{file}@r{]}
16760 @kindex tload@r{, M32R}
16761 Test the @code{upload} command.
16764 The following commands are available for M32R/SDI:
16769 @cindex reset SDI connection, M32R
16770 This command resets the SDI connection.
16774 This command shows the SDI connection status.
16777 @kindex debug_chaos
16778 @cindex M32R/Chaos debugging
16779 Instructs the remote that M32R/Chaos debugging is to be used.
16781 @item use_debug_dma
16782 @kindex use_debug_dma
16783 Instructs the remote to use the DEBUG_DMA method of accessing memory.
16786 @kindex use_mon_code
16787 Instructs the remote to use the MON_CODE method of accessing memory.
16790 @kindex use_ib_break
16791 Instructs the remote to set breakpoints by IB break.
16793 @item use_dbt_break
16794 @kindex use_dbt_break
16795 Instructs the remote to set breakpoints by DBT.
16801 The Motorola m68k configuration includes ColdFire support, and a
16802 target command for the following ROM monitor.
16806 @kindex target dbug
16807 @item target dbug @var{dev}
16808 dBUG ROM monitor for Motorola ColdFire.
16812 @node MIPS Embedded
16813 @subsection MIPS Embedded
16815 @cindex MIPS boards
16816 @value{GDBN} can use the MIPS remote debugging protocol to talk to a
16817 MIPS board attached to a serial line. This is available when
16818 you configure @value{GDBN} with @samp{--target=mips-idt-ecoff}.
16821 Use these @value{GDBN} commands to specify the connection to your target board:
16824 @item target mips @var{port}
16825 @kindex target mips @var{port}
16826 To run a program on the board, start up @code{@value{GDBP}} with the
16827 name of your program as the argument. To connect to the board, use the
16828 command @samp{target mips @var{port}}, where @var{port} is the name of
16829 the serial port connected to the board. If the program has not already
16830 been downloaded to the board, you may use the @code{load} command to
16831 download it. You can then use all the usual @value{GDBN} commands.
16833 For example, this sequence connects to the target board through a serial
16834 port, and loads and runs a program called @var{prog} through the
16838 host$ @value{GDBP} @var{prog}
16839 @value{GDBN} is free software and @dots{}
16840 (@value{GDBP}) target mips /dev/ttyb
16841 (@value{GDBP}) load @var{prog}
16845 @item target mips @var{hostname}:@var{portnumber}
16846 On some @value{GDBN} host configurations, you can specify a TCP
16847 connection (for instance, to a serial line managed by a terminal
16848 concentrator) instead of a serial port, using the syntax
16849 @samp{@var{hostname}:@var{portnumber}}.
16851 @item target pmon @var{port}
16852 @kindex target pmon @var{port}
16855 @item target ddb @var{port}
16856 @kindex target ddb @var{port}
16857 NEC's DDB variant of PMON for Vr4300.
16859 @item target lsi @var{port}
16860 @kindex target lsi @var{port}
16861 LSI variant of PMON.
16863 @kindex target r3900
16864 @item target r3900 @var{dev}
16865 Densan DVE-R3900 ROM monitor for Toshiba R3900 Mips.
16867 @kindex target array
16868 @item target array @var{dev}
16869 Array Tech LSI33K RAID controller board.
16875 @value{GDBN} also supports these special commands for MIPS targets:
16878 @item set mipsfpu double
16879 @itemx set mipsfpu single
16880 @itemx set mipsfpu none
16881 @itemx set mipsfpu auto
16882 @itemx show mipsfpu
16883 @kindex set mipsfpu
16884 @kindex show mipsfpu
16885 @cindex MIPS remote floating point
16886 @cindex floating point, MIPS remote
16887 If your target board does not support the MIPS floating point
16888 coprocessor, you should use the command @samp{set mipsfpu none} (if you
16889 need this, you may wish to put the command in your @value{GDBN} init
16890 file). This tells @value{GDBN} how to find the return value of
16891 functions which return floating point values. It also allows
16892 @value{GDBN} to avoid saving the floating point registers when calling
16893 functions on the board. If you are using a floating point coprocessor
16894 with only single precision floating point support, as on the @sc{r4650}
16895 processor, use the command @samp{set mipsfpu single}. The default
16896 double precision floating point coprocessor may be selected using
16897 @samp{set mipsfpu double}.
16899 In previous versions the only choices were double precision or no
16900 floating point, so @samp{set mipsfpu on} will select double precision
16901 and @samp{set mipsfpu off} will select no floating point.
16903 As usual, you can inquire about the @code{mipsfpu} variable with
16904 @samp{show mipsfpu}.
16906 @item set timeout @var{seconds}
16907 @itemx set retransmit-timeout @var{seconds}
16908 @itemx show timeout
16909 @itemx show retransmit-timeout
16910 @cindex @code{timeout}, MIPS protocol
16911 @cindex @code{retransmit-timeout}, MIPS protocol
16912 @kindex set timeout
16913 @kindex show timeout
16914 @kindex set retransmit-timeout
16915 @kindex show retransmit-timeout
16916 You can control the timeout used while waiting for a packet, in the MIPS
16917 remote protocol, with the @code{set timeout @var{seconds}} command. The
16918 default is 5 seconds. Similarly, you can control the timeout used while
16919 waiting for an acknowledgment of a packet with the @code{set
16920 retransmit-timeout @var{seconds}} command. The default is 3 seconds.
16921 You can inspect both values with @code{show timeout} and @code{show
16922 retransmit-timeout}. (These commands are @emph{only} available when
16923 @value{GDBN} is configured for @samp{--target=mips-idt-ecoff}.)
16925 The timeout set by @code{set timeout} does not apply when @value{GDBN}
16926 is waiting for your program to stop. In that case, @value{GDBN} waits
16927 forever because it has no way of knowing how long the program is going
16928 to run before stopping.
16930 @item set syn-garbage-limit @var{num}
16931 @kindex set syn-garbage-limit@r{, MIPS remote}
16932 @cindex synchronize with remote MIPS target
16933 Limit the maximum number of characters @value{GDBN} should ignore when
16934 it tries to synchronize with the remote target. The default is 10
16935 characters. Setting the limit to -1 means there's no limit.
16937 @item show syn-garbage-limit
16938 @kindex show syn-garbage-limit@r{, MIPS remote}
16939 Show the current limit on the number of characters to ignore when
16940 trying to synchronize with the remote system.
16942 @item set monitor-prompt @var{prompt}
16943 @kindex set monitor-prompt@r{, MIPS remote}
16944 @cindex remote monitor prompt
16945 Tell @value{GDBN} to expect the specified @var{prompt} string from the
16946 remote monitor. The default depends on the target:
16956 @item show monitor-prompt
16957 @kindex show monitor-prompt@r{, MIPS remote}
16958 Show the current strings @value{GDBN} expects as the prompt from the
16961 @item set monitor-warnings
16962 @kindex set monitor-warnings@r{, MIPS remote}
16963 Enable or disable monitor warnings about hardware breakpoints. This
16964 has effect only for the @code{lsi} target. When on, @value{GDBN} will
16965 display warning messages whose codes are returned by the @code{lsi}
16966 PMON monitor for breakpoint commands.
16968 @item show monitor-warnings
16969 @kindex show monitor-warnings@r{, MIPS remote}
16970 Show the current setting of printing monitor warnings.
16972 @item pmon @var{command}
16973 @kindex pmon@r{, MIPS remote}
16974 @cindex send PMON command
16975 This command allows sending an arbitrary @var{command} string to the
16976 monitor. The monitor must be in debug mode for this to work.
16979 @node OpenRISC 1000
16980 @subsection OpenRISC 1000
16981 @cindex OpenRISC 1000
16983 @cindex or1k boards
16984 See OR1k Architecture document (@uref{www.opencores.org}) for more information
16985 about platform and commands.
16989 @kindex target jtag
16990 @item target jtag jtag://@var{host}:@var{port}
16992 Connects to remote JTAG server.
16993 JTAG remote server can be either an or1ksim or JTAG server,
16994 connected via parallel port to the board.
16996 Example: @code{target jtag jtag://localhost:9999}
16999 @item or1ksim @var{command}
17000 If connected to @code{or1ksim} OpenRISC 1000 Architectural
17001 Simulator, proprietary commands can be executed.
17003 @kindex info or1k spr
17004 @item info or1k spr
17005 Displays spr groups.
17007 @item info or1k spr @var{group}
17008 @itemx info or1k spr @var{groupno}
17009 Displays register names in selected group.
17011 @item info or1k spr @var{group} @var{register}
17012 @itemx info or1k spr @var{register}
17013 @itemx info or1k spr @var{groupno} @var{registerno}
17014 @itemx info or1k spr @var{registerno}
17015 Shows information about specified spr register.
17018 @item spr @var{group} @var{register} @var{value}
17019 @itemx spr @var{register @var{value}}
17020 @itemx spr @var{groupno} @var{registerno @var{value}}
17021 @itemx spr @var{registerno @var{value}}
17022 Writes @var{value} to specified spr register.
17025 Some implementations of OpenRISC 1000 Architecture also have hardware trace.
17026 It is very similar to @value{GDBN} trace, except it does not interfere with normal
17027 program execution and is thus much faster. Hardware breakpoints/watchpoint
17028 triggers can be set using:
17031 Load effective address/data
17033 Store effective address/data
17035 Access effective address ($SEA or $LEA) or data ($SDATA/$LDATA)
17040 When triggered, it can capture low level data, like: @code{PC}, @code{LSEA},
17041 @code{LDATA}, @code{SDATA}, @code{READSPR}, @code{WRITESPR}, @code{INSTR}.
17043 @code{htrace} commands:
17044 @cindex OpenRISC 1000 htrace
17047 @item hwatch @var{conditional}
17048 Set hardware watchpoint on combination of Load/Store Effective Address(es)
17049 or Data. For example:
17051 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
17053 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
17057 Display information about current HW trace configuration.
17059 @item htrace trigger @var{conditional}
17060 Set starting criteria for HW trace.
17062 @item htrace qualifier @var{conditional}
17063 Set acquisition qualifier for HW trace.
17065 @item htrace stop @var{conditional}
17066 Set HW trace stopping criteria.
17068 @item htrace record [@var{data}]*
17069 Selects the data to be recorded, when qualifier is met and HW trace was
17072 @item htrace enable
17073 @itemx htrace disable
17074 Enables/disables the HW trace.
17076 @item htrace rewind [@var{filename}]
17077 Clears currently recorded trace data.
17079 If filename is specified, new trace file is made and any newly collected data
17080 will be written there.
17082 @item htrace print [@var{start} [@var{len}]]
17083 Prints trace buffer, using current record configuration.
17085 @item htrace mode continuous
17086 Set continuous trace mode.
17088 @item htrace mode suspend
17089 Set suspend trace mode.
17093 @node PowerPC Embedded
17094 @subsection PowerPC Embedded
17096 @value{GDBN} provides the following PowerPC-specific commands:
17099 @kindex set powerpc
17100 @item set powerpc soft-float
17101 @itemx show powerpc soft-float
17102 Force @value{GDBN} to use (or not use) a software floating point calling
17103 convention. By default, @value{GDBN} selects the calling convention based
17104 on the selected architecture and the provided executable file.
17106 @item set powerpc vector-abi
17107 @itemx show powerpc vector-abi
17108 Force @value{GDBN} to use the specified calling convention for vector
17109 arguments and return values. The valid options are @samp{auto};
17110 @samp{generic}, to avoid vector registers even if they are present;
17111 @samp{altivec}, to use AltiVec registers; and @samp{spe} to use SPE
17112 registers. By default, @value{GDBN} selects the calling convention
17113 based on the selected architecture and the provided executable file.
17115 @kindex target dink32
17116 @item target dink32 @var{dev}
17117 DINK32 ROM monitor.
17119 @kindex target ppcbug
17120 @item target ppcbug @var{dev}
17121 @kindex target ppcbug1
17122 @item target ppcbug1 @var{dev}
17123 PPCBUG ROM monitor for PowerPC.
17126 @item target sds @var{dev}
17127 SDS monitor, running on a PowerPC board (such as Motorola's ADS).
17130 @cindex SDS protocol
17131 The following commands specific to the SDS protocol are supported
17135 @item set sdstimeout @var{nsec}
17136 @kindex set sdstimeout
17137 Set the timeout for SDS protocol reads to be @var{nsec} seconds. The
17138 default is 2 seconds.
17140 @item show sdstimeout
17141 @kindex show sdstimeout
17142 Show the current value of the SDS timeout.
17144 @item sds @var{command}
17145 @kindex sds@r{, a command}
17146 Send the specified @var{command} string to the SDS monitor.
17151 @subsection HP PA Embedded
17155 @kindex target op50n
17156 @item target op50n @var{dev}
17157 OP50N monitor, running on an OKI HPPA board.
17159 @kindex target w89k
17160 @item target w89k @var{dev}
17161 W89K monitor, running on a Winbond HPPA board.
17166 @subsection Tsqware Sparclet
17170 @value{GDBN} enables developers to debug tasks running on
17171 Sparclet targets from a Unix host.
17172 @value{GDBN} uses code that runs on
17173 both the Unix host and on the Sparclet target. The program
17174 @code{@value{GDBP}} is installed and executed on the Unix host.
17177 @item remotetimeout @var{args}
17178 @kindex remotetimeout
17179 @value{GDBN} supports the option @code{remotetimeout}.
17180 This option is set by the user, and @var{args} represents the number of
17181 seconds @value{GDBN} waits for responses.
17184 @cindex compiling, on Sparclet
17185 When compiling for debugging, include the options @samp{-g} to get debug
17186 information and @samp{-Ttext} to relocate the program to where you wish to
17187 load it on the target. You may also want to add the options @samp{-n} or
17188 @samp{-N} in order to reduce the size of the sections. Example:
17191 sparclet-aout-gcc prog.c -Ttext 0x12010000 -g -o prog -N
17194 You can use @code{objdump} to verify that the addresses are what you intended:
17197 sparclet-aout-objdump --headers --syms prog
17200 @cindex running, on Sparclet
17202 your Unix execution search path to find @value{GDBN}, you are ready to
17203 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}}
17204 (or @code{sparclet-aout-gdb}, depending on your installation).
17206 @value{GDBN} comes up showing the prompt:
17213 * Sparclet File:: Setting the file to debug
17214 * Sparclet Connection:: Connecting to Sparclet
17215 * Sparclet Download:: Sparclet download
17216 * Sparclet Execution:: Running and debugging
17219 @node Sparclet File
17220 @subsubsection Setting File to Debug
17222 The @value{GDBN} command @code{file} lets you choose with program to debug.
17225 (gdbslet) file prog
17229 @value{GDBN} then attempts to read the symbol table of @file{prog}.
17230 @value{GDBN} locates
17231 the file by searching the directories listed in the command search
17233 If the file was compiled with debug information (option @samp{-g}), source
17234 files will be searched as well.
17235 @value{GDBN} locates
17236 the source files by searching the directories listed in the directory search
17237 path (@pxref{Environment, ,Your Program's Environment}).
17239 to find a file, it displays a message such as:
17242 prog: No such file or directory.
17245 When this happens, add the appropriate directories to the search paths with
17246 the @value{GDBN} commands @code{path} and @code{dir}, and execute the
17247 @code{target} command again.
17249 @node Sparclet Connection
17250 @subsubsection Connecting to Sparclet
17252 The @value{GDBN} command @code{target} lets you connect to a Sparclet target.
17253 To connect to a target on serial port ``@code{ttya}'', type:
17256 (gdbslet) target sparclet /dev/ttya
17257 Remote target sparclet connected to /dev/ttya
17258 main () at ../prog.c:3
17262 @value{GDBN} displays messages like these:
17268 @node Sparclet Download
17269 @subsubsection Sparclet Download
17271 @cindex download to Sparclet
17272 Once connected to the Sparclet target,
17273 you can use the @value{GDBN}
17274 @code{load} command to download the file from the host to the target.
17275 The file name and load offset should be given as arguments to the @code{load}
17277 Since the file format is aout, the program must be loaded to the starting
17278 address. You can use @code{objdump} to find out what this value is. The load
17279 offset is an offset which is added to the VMA (virtual memory address)
17280 of each of the file's sections.
17281 For instance, if the program
17282 @file{prog} was linked to text address 0x1201000, with data at 0x12010160
17283 and bss at 0x12010170, in @value{GDBN}, type:
17286 (gdbslet) load prog 0x12010000
17287 Loading section .text, size 0xdb0 vma 0x12010000
17290 If the code is loaded at a different address then what the program was linked
17291 to, you may need to use the @code{section} and @code{add-symbol-file} commands
17292 to tell @value{GDBN} where to map the symbol table.
17294 @node Sparclet Execution
17295 @subsubsection Running and Debugging
17297 @cindex running and debugging Sparclet programs
17298 You can now begin debugging the task using @value{GDBN}'s execution control
17299 commands, @code{b}, @code{step}, @code{run}, etc. See the @value{GDBN}
17300 manual for the list of commands.
17304 Breakpoint 1 at 0x12010000: file prog.c, line 3.
17306 Starting program: prog
17307 Breakpoint 1, main (argc=1, argv=0xeffff21c) at prog.c:3
17308 3 char *symarg = 0;
17310 4 char *execarg = "hello!";
17315 @subsection Fujitsu Sparclite
17319 @kindex target sparclite
17320 @item target sparclite @var{dev}
17321 Fujitsu sparclite boards, used only for the purpose of loading.
17322 You must use an additional command to debug the program.
17323 For example: target remote @var{dev} using @value{GDBN} standard
17329 @subsection Zilog Z8000
17332 @cindex simulator, Z8000
17333 @cindex Zilog Z8000 simulator
17335 When configured for debugging Zilog Z8000 targets, @value{GDBN} includes
17338 For the Z8000 family, @samp{target sim} simulates either the Z8002 (the
17339 unsegmented variant of the Z8000 architecture) or the Z8001 (the
17340 segmented variant). The simulator recognizes which architecture is
17341 appropriate by inspecting the object code.
17344 @item target sim @var{args}
17346 @kindex target sim@r{, with Z8000}
17347 Debug programs on a simulated CPU. If the simulator supports setup
17348 options, specify them via @var{args}.
17352 After specifying this target, you can debug programs for the simulated
17353 CPU in the same style as programs for your host computer; use the
17354 @code{file} command to load a new program image, the @code{run} command
17355 to run your program, and so on.
17357 As well as making available all the usual machine registers
17358 (@pxref{Registers, ,Registers}), the Z8000 simulator provides three
17359 additional items of information as specially named registers:
17364 Counts clock-ticks in the simulator.
17367 Counts instructions run in the simulator.
17370 Execution time in 60ths of a second.
17374 You can refer to these values in @value{GDBN} expressions with the usual
17375 conventions; for example, @w{@samp{b fputc if $cycles>5000}} sets a
17376 conditional breakpoint that suspends only after at least 5000
17377 simulated clock ticks.
17380 @subsection Atmel AVR
17383 When configured for debugging the Atmel AVR, @value{GDBN} supports the
17384 following AVR-specific commands:
17387 @item info io_registers
17388 @kindex info io_registers@r{, AVR}
17389 @cindex I/O registers (Atmel AVR)
17390 This command displays information about the AVR I/O registers. For
17391 each register, @value{GDBN} prints its number and value.
17398 When configured for debugging CRIS, @value{GDBN} provides the
17399 following CRIS-specific commands:
17402 @item set cris-version @var{ver}
17403 @cindex CRIS version
17404 Set the current CRIS version to @var{ver}, either @samp{10} or @samp{32}.
17405 The CRIS version affects register names and sizes. This command is useful in
17406 case autodetection of the CRIS version fails.
17408 @item show cris-version
17409 Show the current CRIS version.
17411 @item set cris-dwarf2-cfi
17412 @cindex DWARF-2 CFI and CRIS
17413 Set the usage of DWARF-2 CFI for CRIS debugging. The default is @samp{on}.
17414 Change to @samp{off} when using @code{gcc-cris} whose version is below
17417 @item show cris-dwarf2-cfi
17418 Show the current state of using DWARF-2 CFI.
17420 @item set cris-mode @var{mode}
17422 Set the current CRIS mode to @var{mode}. It should only be changed when
17423 debugging in guru mode, in which case it should be set to
17424 @samp{guru} (the default is @samp{normal}).
17426 @item show cris-mode
17427 Show the current CRIS mode.
17431 @subsection Renesas Super-H
17434 For the Renesas Super-H processor, @value{GDBN} provides these
17439 @kindex regs@r{, Super-H}
17440 Show the values of all Super-H registers.
17442 @item set sh calling-convention @var{convention}
17443 @kindex set sh calling-convention
17444 Set the calling-convention used when calling functions from @value{GDBN}.
17445 Allowed values are @samp{gcc}, which is the default setting, and @samp{renesas}.
17446 With the @samp{gcc} setting, functions are called using the @value{NGCC} calling
17447 convention. If the DWARF-2 information of the called function specifies
17448 that the function follows the Renesas calling convention, the function
17449 is called using the Renesas calling convention. If the calling convention
17450 is set to @samp{renesas}, the Renesas calling convention is always used,
17451 regardless of the DWARF-2 information. This can be used to override the
17452 default of @samp{gcc} if debug information is missing, or the compiler
17453 does not emit the DWARF-2 calling convention entry for a function.
17455 @item show sh calling-convention
17456 @kindex show sh calling-convention
17457 Show the current calling convention setting.
17462 @node Architectures
17463 @section Architectures
17465 This section describes characteristics of architectures that affect
17466 all uses of @value{GDBN} with the architecture, both native and cross.
17473 * HPPA:: HP PA architecture
17474 * SPU:: Cell Broadband Engine SPU architecture
17479 @subsection x86 Architecture-specific Issues
17482 @item set struct-convention @var{mode}
17483 @kindex set struct-convention
17484 @cindex struct return convention
17485 @cindex struct/union returned in registers
17486 Set the convention used by the inferior to return @code{struct}s and
17487 @code{union}s from functions to @var{mode}. Possible values of
17488 @var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the
17489 default). @code{"default"} or @code{"pcc"} means that @code{struct}s
17490 are returned on the stack, while @code{"reg"} means that a
17491 @code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will
17492 be returned in a register.
17494 @item show struct-convention
17495 @kindex show struct-convention
17496 Show the current setting of the convention to return @code{struct}s
17505 @kindex set rstack_high_address
17506 @cindex AMD 29K register stack
17507 @cindex register stack, AMD29K
17508 @item set rstack_high_address @var{address}
17509 On AMD 29000 family processors, registers are saved in a separate
17510 @dfn{register stack}. There is no way for @value{GDBN} to determine the
17511 extent of this stack. Normally, @value{GDBN} just assumes that the
17512 stack is ``large enough''. This may result in @value{GDBN} referencing
17513 memory locations that do not exist. If necessary, you can get around
17514 this problem by specifying the ending address of the register stack with
17515 the @code{set rstack_high_address} command. The argument should be an
17516 address, which you probably want to precede with @samp{0x} to specify in
17519 @kindex show rstack_high_address
17520 @item show rstack_high_address
17521 Display the current limit of the register stack, on AMD 29000 family
17529 See the following section.
17534 @cindex stack on Alpha
17535 @cindex stack on MIPS
17536 @cindex Alpha stack
17538 Alpha- and MIPS-based computers use an unusual stack frame, which
17539 sometimes requires @value{GDBN} to search backward in the object code to
17540 find the beginning of a function.
17542 @cindex response time, MIPS debugging
17543 To improve response time (especially for embedded applications, where
17544 @value{GDBN} may be restricted to a slow serial line for this search)
17545 you may want to limit the size of this search, using one of these
17549 @cindex @code{heuristic-fence-post} (Alpha, MIPS)
17550 @item set heuristic-fence-post @var{limit}
17551 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
17552 search for the beginning of a function. A value of @var{0} (the
17553 default) means there is no limit. However, except for @var{0}, the
17554 larger the limit the more bytes @code{heuristic-fence-post} must search
17555 and therefore the longer it takes to run. You should only need to use
17556 this command when debugging a stripped executable.
17558 @item show heuristic-fence-post
17559 Display the current limit.
17563 These commands are available @emph{only} when @value{GDBN} is configured
17564 for debugging programs on Alpha or MIPS processors.
17566 Several MIPS-specific commands are available when debugging MIPS
17570 @item set mips abi @var{arg}
17571 @kindex set mips abi
17572 @cindex set ABI for MIPS
17573 Tell @value{GDBN} which MIPS ABI is used by the inferior. Possible
17574 values of @var{arg} are:
17578 The default ABI associated with the current binary (this is the
17589 @item show mips abi
17590 @kindex show mips abi
17591 Show the MIPS ABI used by @value{GDBN} to debug the inferior.
17594 @itemx show mipsfpu
17595 @xref{MIPS Embedded, set mipsfpu}.
17597 @item set mips mask-address @var{arg}
17598 @kindex set mips mask-address
17599 @cindex MIPS addresses, masking
17600 This command determines whether the most-significant 32 bits of 64-bit
17601 MIPS addresses are masked off. The argument @var{arg} can be
17602 @samp{on}, @samp{off}, or @samp{auto}. The latter is the default
17603 setting, which lets @value{GDBN} determine the correct value.
17605 @item show mips mask-address
17606 @kindex show mips mask-address
17607 Show whether the upper 32 bits of MIPS addresses are masked off or
17610 @item set remote-mips64-transfers-32bit-regs
17611 @kindex set remote-mips64-transfers-32bit-regs
17612 This command controls compatibility with 64-bit MIPS targets that
17613 transfer data in 32-bit quantities. If you have an old MIPS 64 target
17614 that transfers 32 bits for some registers, like @sc{sr} and @sc{fsr},
17615 and 64 bits for other registers, set this option to @samp{on}.
17617 @item show remote-mips64-transfers-32bit-regs
17618 @kindex show remote-mips64-transfers-32bit-regs
17619 Show the current setting of compatibility with older MIPS 64 targets.
17621 @item set debug mips
17622 @kindex set debug mips
17623 This command turns on and off debugging messages for the MIPS-specific
17624 target code in @value{GDBN}.
17626 @item show debug mips
17627 @kindex show debug mips
17628 Show the current setting of MIPS debugging messages.
17634 @cindex HPPA support
17636 When @value{GDBN} is debugging the HP PA architecture, it provides the
17637 following special commands:
17640 @item set debug hppa
17641 @kindex set debug hppa
17642 This command determines whether HPPA architecture-specific debugging
17643 messages are to be displayed.
17645 @item show debug hppa
17646 Show whether HPPA debugging messages are displayed.
17648 @item maint print unwind @var{address}
17649 @kindex maint print unwind@r{, HPPA}
17650 This command displays the contents of the unwind table entry at the
17651 given @var{address}.
17657 @subsection Cell Broadband Engine SPU architecture
17658 @cindex Cell Broadband Engine
17661 When @value{GDBN} is debugging the Cell Broadband Engine SPU architecture,
17662 it provides the following special commands:
17665 @item info spu event
17667 Display SPU event facility status. Shows current event mask
17668 and pending event status.
17670 @item info spu signal
17671 Display SPU signal notification facility status. Shows pending
17672 signal-control word and signal notification mode of both signal
17673 notification channels.
17675 @item info spu mailbox
17676 Display SPU mailbox facility status. Shows all pending entries,
17677 in order of processing, in each of the SPU Write Outbound,
17678 SPU Write Outbound Interrupt, and SPU Read Inbound mailboxes.
17681 Display MFC DMA status. Shows all pending commands in the MFC
17682 DMA queue. For each entry, opcode, tag, class IDs, effective
17683 and local store addresses and transfer size are shown.
17685 @item info spu proxydma
17686 Display MFC Proxy-DMA status. Shows all pending commands in the MFC
17687 Proxy-DMA queue. For each entry, opcode, tag, class IDs, effective
17688 and local store addresses and transfer size are shown.
17692 When @value{GDBN} is debugging a combined PowerPC/SPU application
17693 on the Cell Broadband Engine, it provides in addition the following
17697 @item set spu stop-on-load @var{arg}
17699 Set whether to stop for new SPE threads. When set to @code{on}, @value{GDBN}
17700 will give control to the user when a new SPE thread enters its @code{main}
17701 function. The default is @code{off}.
17703 @item show spu stop-on-load
17705 Show whether to stop for new SPE threads.
17707 @item set spu auto-flush-cache @var{arg}
17708 Set whether to automatically flush the software-managed cache. When set to
17709 @code{on}, @value{GDBN} will automatically cause the SPE software-managed
17710 cache to be flushed whenever SPE execution stops. This provides a consistent
17711 view of PowerPC memory that is accessed via the cache. If an application
17712 does not use the software-managed cache, this option has no effect.
17714 @item show spu auto-flush-cache
17715 Show whether to automatically flush the software-managed cache.
17720 @subsection PowerPC
17721 @cindex PowerPC architecture
17723 When @value{GDBN} is debugging the PowerPC architecture, it provides a set of
17724 pseudo-registers to enable inspection of 128-bit wide Decimal Floating Point
17725 numbers stored in the floating point registers. These values must be stored
17726 in two consecutive registers, always starting at an even register like
17727 @code{f0} or @code{f2}.
17729 The pseudo-registers go from @code{$dl0} through @code{$dl15}, and are formed
17730 by joining the even/odd register pairs @code{f0} and @code{f1} for @code{$dl0},
17731 @code{f2} and @code{f3} for @code{$dl1} and so on.
17733 For POWER7 processors, @value{GDBN} provides a set of pseudo-registers, the 64-bit
17734 wide Extended Floating Point Registers (@samp{f32} through @samp{f63}).
17737 @node Controlling GDB
17738 @chapter Controlling @value{GDBN}
17740 You can alter the way @value{GDBN} interacts with you by using the
17741 @code{set} command. For commands controlling how @value{GDBN} displays
17742 data, see @ref{Print Settings, ,Print Settings}. Other settings are
17747 * Editing:: Command editing
17748 * Command History:: Command history
17749 * Screen Size:: Screen size
17750 * Numbers:: Numbers
17751 * ABI:: Configuring the current ABI
17752 * Messages/Warnings:: Optional warnings and messages
17753 * Debugging Output:: Optional messages about internal happenings
17754 * Other Misc Settings:: Other Miscellaneous Settings
17762 @value{GDBN} indicates its readiness to read a command by printing a string
17763 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
17764 can change the prompt string with the @code{set prompt} command. For
17765 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
17766 the prompt in one of the @value{GDBN} sessions so that you can always tell
17767 which one you are talking to.
17769 @emph{Note:} @code{set prompt} does not add a space for you after the
17770 prompt you set. This allows you to set a prompt which ends in a space
17771 or a prompt that does not.
17775 @item set prompt @var{newprompt}
17776 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
17778 @kindex show prompt
17780 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
17784 @section Command Editing
17786 @cindex command line editing
17788 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
17789 @sc{gnu} library provides consistent behavior for programs which provide a
17790 command line interface to the user. Advantages are @sc{gnu} Emacs-style
17791 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
17792 substitution, and a storage and recall of command history across
17793 debugging sessions.
17795 You may control the behavior of command line editing in @value{GDBN} with the
17796 command @code{set}.
17799 @kindex set editing
17802 @itemx set editing on
17803 Enable command line editing (enabled by default).
17805 @item set editing off
17806 Disable command line editing.
17808 @kindex show editing
17810 Show whether command line editing is enabled.
17813 @xref{Command Line Editing}, for more details about the Readline
17814 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
17815 encouraged to read that chapter.
17817 @node Command History
17818 @section Command History
17819 @cindex command history
17821 @value{GDBN} can keep track of the commands you type during your
17822 debugging sessions, so that you can be certain of precisely what
17823 happened. Use these commands to manage the @value{GDBN} command
17826 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
17827 package, to provide the history facility. @xref{Using History
17828 Interactively}, for the detailed description of the History library.
17830 To issue a command to @value{GDBN} without affecting certain aspects of
17831 the state which is seen by users, prefix it with @samp{server }
17832 (@pxref{Server Prefix}). This
17833 means that this command will not affect the command history, nor will it
17834 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
17835 pressed on a line by itself.
17837 @cindex @code{server}, command prefix
17838 The server prefix does not affect the recording of values into the value
17839 history; to print a value without recording it into the value history,
17840 use the @code{output} command instead of the @code{print} command.
17842 Here is the description of @value{GDBN} commands related to command
17846 @cindex history substitution
17847 @cindex history file
17848 @kindex set history filename
17849 @cindex @env{GDBHISTFILE}, environment variable
17850 @item set history filename @var{fname}
17851 Set the name of the @value{GDBN} command history file to @var{fname}.
17852 This is the file where @value{GDBN} reads an initial command history
17853 list, and where it writes the command history from this session when it
17854 exits. You can access this list through history expansion or through
17855 the history command editing characters listed below. This file defaults
17856 to the value of the environment variable @code{GDBHISTFILE}, or to
17857 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
17860 @cindex save command history
17861 @kindex set history save
17862 @item set history save
17863 @itemx set history save on
17864 Record command history in a file, whose name may be specified with the
17865 @code{set history filename} command. By default, this option is disabled.
17867 @item set history save off
17868 Stop recording command history in a file.
17870 @cindex history size
17871 @kindex set history size
17872 @cindex @env{HISTSIZE}, environment variable
17873 @item set history size @var{size}
17874 Set the number of commands which @value{GDBN} keeps in its history list.
17875 This defaults to the value of the environment variable
17876 @code{HISTSIZE}, or to 256 if this variable is not set.
17879 History expansion assigns special meaning to the character @kbd{!}.
17880 @xref{Event Designators}, for more details.
17882 @cindex history expansion, turn on/off
17883 Since @kbd{!} is also the logical not operator in C, history expansion
17884 is off by default. If you decide to enable history expansion with the
17885 @code{set history expansion on} command, you may sometimes need to
17886 follow @kbd{!} (when it is used as logical not, in an expression) with
17887 a space or a tab to prevent it from being expanded. The readline
17888 history facilities do not attempt substitution on the strings
17889 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
17891 The commands to control history expansion are:
17894 @item set history expansion on
17895 @itemx set history expansion
17896 @kindex set history expansion
17897 Enable history expansion. History expansion is off by default.
17899 @item set history expansion off
17900 Disable history expansion.
17903 @kindex show history
17905 @itemx show history filename
17906 @itemx show history save
17907 @itemx show history size
17908 @itemx show history expansion
17909 These commands display the state of the @value{GDBN} history parameters.
17910 @code{show history} by itself displays all four states.
17915 @kindex show commands
17916 @cindex show last commands
17917 @cindex display command history
17918 @item show commands
17919 Display the last ten commands in the command history.
17921 @item show commands @var{n}
17922 Print ten commands centered on command number @var{n}.
17924 @item show commands +
17925 Print ten commands just after the commands last printed.
17929 @section Screen Size
17930 @cindex size of screen
17931 @cindex pauses in output
17933 Certain commands to @value{GDBN} may produce large amounts of
17934 information output to the screen. To help you read all of it,
17935 @value{GDBN} pauses and asks you for input at the end of each page of
17936 output. Type @key{RET} when you want to continue the output, or @kbd{q}
17937 to discard the remaining output. Also, the screen width setting
17938 determines when to wrap lines of output. Depending on what is being
17939 printed, @value{GDBN} tries to break the line at a readable place,
17940 rather than simply letting it overflow onto the following line.
17942 Normally @value{GDBN} knows the size of the screen from the terminal
17943 driver software. For example, on Unix @value{GDBN} uses the termcap data base
17944 together with the value of the @code{TERM} environment variable and the
17945 @code{stty rows} and @code{stty cols} settings. If this is not correct,
17946 you can override it with the @code{set height} and @code{set
17953 @kindex show height
17954 @item set height @var{lpp}
17956 @itemx set width @var{cpl}
17958 These @code{set} commands specify a screen height of @var{lpp} lines and
17959 a screen width of @var{cpl} characters. The associated @code{show}
17960 commands display the current settings.
17962 If you specify a height of zero lines, @value{GDBN} does not pause during
17963 output no matter how long the output is. This is useful if output is to a
17964 file or to an editor buffer.
17966 Likewise, you can specify @samp{set width 0} to prevent @value{GDBN}
17967 from wrapping its output.
17969 @item set pagination on
17970 @itemx set pagination off
17971 @kindex set pagination
17972 Turn the output pagination on or off; the default is on. Turning
17973 pagination off is the alternative to @code{set height 0}.
17975 @item show pagination
17976 @kindex show pagination
17977 Show the current pagination mode.
17982 @cindex number representation
17983 @cindex entering numbers
17985 You can always enter numbers in octal, decimal, or hexadecimal in
17986 @value{GDBN} by the usual conventions: octal numbers begin with
17987 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
17988 begin with @samp{0x}. Numbers that neither begin with @samp{0} or
17989 @samp{0x}, nor end with a @samp{.} are, by default, entered in base
17990 10; likewise, the default display for numbers---when no particular
17991 format is specified---is base 10. You can change the default base for
17992 both input and output with the commands described below.
17995 @kindex set input-radix
17996 @item set input-radix @var{base}
17997 Set the default base for numeric input. Supported choices
17998 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
17999 specified either unambiguously or using the current input radix; for
18003 set input-radix 012
18004 set input-radix 10.
18005 set input-radix 0xa
18009 sets the input base to decimal. On the other hand, @samp{set input-radix 10}
18010 leaves the input radix unchanged, no matter what it was, since
18011 @samp{10}, being without any leading or trailing signs of its base, is
18012 interpreted in the current radix. Thus, if the current radix is 16,
18013 @samp{10} is interpreted in hex, i.e.@: as 16 decimal, which doesn't
18016 @kindex set output-radix
18017 @item set output-radix @var{base}
18018 Set the default base for numeric display. Supported choices
18019 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
18020 specified either unambiguously or using the current input radix.
18022 @kindex show input-radix
18023 @item show input-radix
18024 Display the current default base for numeric input.
18026 @kindex show output-radix
18027 @item show output-radix
18028 Display the current default base for numeric display.
18030 @item set radix @r{[}@var{base}@r{]}
18034 These commands set and show the default base for both input and output
18035 of numbers. @code{set radix} sets the radix of input and output to
18036 the same base; without an argument, it resets the radix back to its
18037 default value of 10.
18042 @section Configuring the Current ABI
18044 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
18045 application automatically. However, sometimes you need to override its
18046 conclusions. Use these commands to manage @value{GDBN}'s view of the
18053 One @value{GDBN} configuration can debug binaries for multiple operating
18054 system targets, either via remote debugging or native emulation.
18055 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
18056 but you can override its conclusion using the @code{set osabi} command.
18057 One example where this is useful is in debugging of binaries which use
18058 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
18059 not have the same identifying marks that the standard C library for your
18064 Show the OS ABI currently in use.
18067 With no argument, show the list of registered available OS ABI's.
18069 @item set osabi @var{abi}
18070 Set the current OS ABI to @var{abi}.
18073 @cindex float promotion
18075 Generally, the way that an argument of type @code{float} is passed to a
18076 function depends on whether the function is prototyped. For a prototyped
18077 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
18078 according to the architecture's convention for @code{float}. For unprototyped
18079 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
18080 @code{double} and then passed.
18082 Unfortunately, some forms of debug information do not reliably indicate whether
18083 a function is prototyped. If @value{GDBN} calls a function that is not marked
18084 as prototyped, it consults @kbd{set coerce-float-to-double}.
18087 @kindex set coerce-float-to-double
18088 @item set coerce-float-to-double
18089 @itemx set coerce-float-to-double on
18090 Arguments of type @code{float} will be promoted to @code{double} when passed
18091 to an unprototyped function. This is the default setting.
18093 @item set coerce-float-to-double off
18094 Arguments of type @code{float} will be passed directly to unprototyped
18097 @kindex show coerce-float-to-double
18098 @item show coerce-float-to-double
18099 Show the current setting of promoting @code{float} to @code{double}.
18103 @kindex show cp-abi
18104 @value{GDBN} needs to know the ABI used for your program's C@t{++}
18105 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
18106 used to build your application. @value{GDBN} only fully supports
18107 programs with a single C@t{++} ABI; if your program contains code using
18108 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
18109 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
18110 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
18111 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
18112 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
18113 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
18118 Show the C@t{++} ABI currently in use.
18121 With no argument, show the list of supported C@t{++} ABI's.
18123 @item set cp-abi @var{abi}
18124 @itemx set cp-abi auto
18125 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
18128 @node Messages/Warnings
18129 @section Optional Warnings and Messages
18131 @cindex verbose operation
18132 @cindex optional warnings
18133 By default, @value{GDBN} is silent about its inner workings. If you are
18134 running on a slow machine, you may want to use the @code{set verbose}
18135 command. This makes @value{GDBN} tell you when it does a lengthy
18136 internal operation, so you will not think it has crashed.
18138 Currently, the messages controlled by @code{set verbose} are those
18139 which announce that the symbol table for a source file is being read;
18140 see @code{symbol-file} in @ref{Files, ,Commands to Specify Files}.
18143 @kindex set verbose
18144 @item set verbose on
18145 Enables @value{GDBN} output of certain informational messages.
18147 @item set verbose off
18148 Disables @value{GDBN} output of certain informational messages.
18150 @kindex show verbose
18152 Displays whether @code{set verbose} is on or off.
18155 By default, if @value{GDBN} encounters bugs in the symbol table of an
18156 object file, it is silent; but if you are debugging a compiler, you may
18157 find this information useful (@pxref{Symbol Errors, ,Errors Reading
18162 @kindex set complaints
18163 @item set complaints @var{limit}
18164 Permits @value{GDBN} to output @var{limit} complaints about each type of
18165 unusual symbols before becoming silent about the problem. Set
18166 @var{limit} to zero to suppress all complaints; set it to a large number
18167 to prevent complaints from being suppressed.
18169 @kindex show complaints
18170 @item show complaints
18171 Displays how many symbol complaints @value{GDBN} is permitted to produce.
18175 @anchor{confirmation requests}
18176 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
18177 lot of stupid questions to confirm certain commands. For example, if
18178 you try to run a program which is already running:
18182 The program being debugged has been started already.
18183 Start it from the beginning? (y or n)
18186 If you are willing to unflinchingly face the consequences of your own
18187 commands, you can disable this ``feature'':
18191 @kindex set confirm
18193 @cindex confirmation
18194 @cindex stupid questions
18195 @item set confirm off
18196 Disables confirmation requests.
18198 @item set confirm on
18199 Enables confirmation requests (the default).
18201 @kindex show confirm
18203 Displays state of confirmation requests.
18207 @cindex command tracing
18208 If you need to debug user-defined commands or sourced files you may find it
18209 useful to enable @dfn{command tracing}. In this mode each command will be
18210 printed as it is executed, prefixed with one or more @samp{+} symbols, the
18211 quantity denoting the call depth of each command.
18214 @kindex set trace-commands
18215 @cindex command scripts, debugging
18216 @item set trace-commands on
18217 Enable command tracing.
18218 @item set trace-commands off
18219 Disable command tracing.
18220 @item show trace-commands
18221 Display the current state of command tracing.
18224 @node Debugging Output
18225 @section Optional Messages about Internal Happenings
18226 @cindex optional debugging messages
18228 @value{GDBN} has commands that enable optional debugging messages from
18229 various @value{GDBN} subsystems; normally these commands are of
18230 interest to @value{GDBN} maintainers, or when reporting a bug. This
18231 section documents those commands.
18234 @kindex set exec-done-display
18235 @item set exec-done-display
18236 Turns on or off the notification of asynchronous commands'
18237 completion. When on, @value{GDBN} will print a message when an
18238 asynchronous command finishes its execution. The default is off.
18239 @kindex show exec-done-display
18240 @item show exec-done-display
18241 Displays the current setting of asynchronous command completion
18244 @cindex gdbarch debugging info
18245 @cindex architecture debugging info
18246 @item set debug arch
18247 Turns on or off display of gdbarch debugging info. The default is off
18249 @item show debug arch
18250 Displays the current state of displaying gdbarch debugging info.
18251 @item set debug aix-thread
18252 @cindex AIX threads
18253 Display debugging messages about inner workings of the AIX thread
18255 @item show debug aix-thread
18256 Show the current state of AIX thread debugging info display.
18257 @item set debug dwarf2-die
18258 @cindex DWARF2 DIEs
18259 Dump DWARF2 DIEs after they are read in.
18260 The value is the number of nesting levels to print.
18261 A value of zero turns off the display.
18262 @item show debug dwarf2-die
18263 Show the current state of DWARF2 DIE debugging.
18264 @item set debug displaced
18265 @cindex displaced stepping debugging info
18266 Turns on or off display of @value{GDBN} debugging info for the
18267 displaced stepping support. The default is off.
18268 @item show debug displaced
18269 Displays the current state of displaying @value{GDBN} debugging info
18270 related to displaced stepping.
18271 @item set debug event
18272 @cindex event debugging info
18273 Turns on or off display of @value{GDBN} event debugging info. The
18275 @item show debug event
18276 Displays the current state of displaying @value{GDBN} event debugging
18278 @item set debug expression
18279 @cindex expression debugging info
18280 Turns on or off display of debugging info about @value{GDBN}
18281 expression parsing. The default is off.
18282 @item show debug expression
18283 Displays the current state of displaying debugging info about
18284 @value{GDBN} expression parsing.
18285 @item set debug frame
18286 @cindex frame debugging info
18287 Turns on or off display of @value{GDBN} frame debugging info. The
18289 @item show debug frame
18290 Displays the current state of displaying @value{GDBN} frame debugging
18292 @item set debug gnu-nat
18293 @cindex @sc{gnu}/Hurd debug messages
18294 Turns on or off debugging messages from the @sc{gnu}/Hurd debug support.
18295 @item show debug gnu-nat
18296 Show the current state of @sc{gnu}/Hurd debugging messages.
18297 @item set debug infrun
18298 @cindex inferior debugging info
18299 Turns on or off display of @value{GDBN} debugging info for running the inferior.
18300 The default is off. @file{infrun.c} contains GDB's runtime state machine used
18301 for implementing operations such as single-stepping the inferior.
18302 @item show debug infrun
18303 Displays the current state of @value{GDBN} inferior debugging.
18304 @item set debug lin-lwp
18305 @cindex @sc{gnu}/Linux LWP debug messages
18306 @cindex Linux lightweight processes
18307 Turns on or off debugging messages from the Linux LWP debug support.
18308 @item show debug lin-lwp
18309 Show the current state of Linux LWP debugging messages.
18310 @item set debug lin-lwp-async
18311 @cindex @sc{gnu}/Linux LWP async debug messages
18312 @cindex Linux lightweight processes
18313 Turns on or off debugging messages from the Linux LWP async debug support.
18314 @item show debug lin-lwp-async
18315 Show the current state of Linux LWP async debugging messages.
18316 @item set debug observer
18317 @cindex observer debugging info
18318 Turns on or off display of @value{GDBN} observer debugging. This
18319 includes info such as the notification of observable events.
18320 @item show debug observer
18321 Displays the current state of observer debugging.
18322 @item set debug overload
18323 @cindex C@t{++} overload debugging info
18324 Turns on or off display of @value{GDBN} C@t{++} overload debugging
18325 info. This includes info such as ranking of functions, etc. The default
18327 @item show debug overload
18328 Displays the current state of displaying @value{GDBN} C@t{++} overload
18330 @cindex packets, reporting on stdout
18331 @cindex serial connections, debugging
18332 @cindex debug remote protocol
18333 @cindex remote protocol debugging
18334 @cindex display remote packets
18335 @item set debug remote
18336 Turns on or off display of reports on all packets sent back and forth across
18337 the serial line to the remote machine. The info is printed on the
18338 @value{GDBN} standard output stream. The default is off.
18339 @item show debug remote
18340 Displays the state of display of remote packets.
18341 @item set debug serial
18342 Turns on or off display of @value{GDBN} serial debugging info. The
18344 @item show debug serial
18345 Displays the current state of displaying @value{GDBN} serial debugging
18347 @item set debug solib-frv
18348 @cindex FR-V shared-library debugging
18349 Turns on or off debugging messages for FR-V shared-library code.
18350 @item show debug solib-frv
18351 Display the current state of FR-V shared-library code debugging
18353 @item set debug target
18354 @cindex target debugging info
18355 Turns on or off display of @value{GDBN} target debugging info. This info
18356 includes what is going on at the target level of GDB, as it happens. The
18357 default is 0. Set it to 1 to track events, and to 2 to also track the
18358 value of large memory transfers. Changes to this flag do not take effect
18359 until the next time you connect to a target or use the @code{run} command.
18360 @item show debug target
18361 Displays the current state of displaying @value{GDBN} target debugging
18363 @item set debug timestamp
18364 @cindex timestampping debugging info
18365 Turns on or off display of timestamps with @value{GDBN} debugging info.
18366 When enabled, seconds and microseconds are displayed before each debugging
18368 @item show debug timestamp
18369 Displays the current state of displaying timestamps with @value{GDBN}
18371 @item set debugvarobj
18372 @cindex variable object debugging info
18373 Turns on or off display of @value{GDBN} variable object debugging
18374 info. The default is off.
18375 @item show debugvarobj
18376 Displays the current state of displaying @value{GDBN} variable object
18378 @item set debug xml
18379 @cindex XML parser debugging
18380 Turns on or off debugging messages for built-in XML parsers.
18381 @item show debug xml
18382 Displays the current state of XML debugging messages.
18385 @node Other Misc Settings
18386 @section Other Miscellaneous Settings
18387 @cindex miscellaneous settings
18390 @kindex set interactive-mode
18391 @item set interactive-mode
18392 If @code{on}, forces @value{GDBN} to operate interactively.
18393 If @code{off}, forces @value{GDBN} to operate non-interactively,
18394 If @code{auto} (the default), @value{GDBN} guesses which mode to use,
18395 based on whether the debugger was started in a terminal or not.
18397 In the vast majority of cases, the debugger should be able to guess
18398 correctly which mode should be used. But this setting can be useful
18399 in certain specific cases, such as running a MinGW @value{GDBN}
18400 inside a cygwin window.
18402 @kindex show interactive-mode
18403 @item show interactive-mode
18404 Displays whether the debugger is operating in interactive mode or not.
18407 @node Extending GDB
18408 @chapter Extending @value{GDBN}
18409 @cindex extending GDB
18411 @value{GDBN} provides two mechanisms for extension. The first is based
18412 on composition of @value{GDBN} commands, and the second is based on the
18413 Python scripting language.
18416 * Sequences:: Canned Sequences of Commands
18417 * Python:: Scripting @value{GDBN} using Python
18421 @section Canned Sequences of Commands
18423 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
18424 Command Lists}), @value{GDBN} provides two ways to store sequences of
18425 commands for execution as a unit: user-defined commands and command
18429 * Define:: How to define your own commands
18430 * Hooks:: Hooks for user-defined commands
18431 * Command Files:: How to write scripts of commands to be stored in a file
18432 * Output:: Commands for controlled output
18436 @subsection User-defined Commands
18438 @cindex user-defined command
18439 @cindex arguments, to user-defined commands
18440 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
18441 which you assign a new name as a command. This is done with the
18442 @code{define} command. User commands may accept up to 10 arguments
18443 separated by whitespace. Arguments are accessed within the user command
18444 via @code{$arg0@dots{}$arg9}. A trivial example:
18448 print $arg0 + $arg1 + $arg2
18453 To execute the command use:
18460 This defines the command @code{adder}, which prints the sum of
18461 its three arguments. Note the arguments are text substitutions, so they may
18462 reference variables, use complex expressions, or even perform inferior
18465 @cindex argument count in user-defined commands
18466 @cindex how many arguments (user-defined commands)
18467 In addition, @code{$argc} may be used to find out how many arguments have
18468 been passed. This expands to a number in the range 0@dots{}10.
18473 print $arg0 + $arg1
18476 print $arg0 + $arg1 + $arg2
18484 @item define @var{commandname}
18485 Define a command named @var{commandname}. If there is already a command
18486 by that name, you are asked to confirm that you want to redefine it.
18487 @var{commandname} may be a bare command name consisting of letters,
18488 numbers, dashes, and underscores. It may also start with any predefined
18489 prefix command. For example, @samp{define target my-target} creates
18490 a user-defined @samp{target my-target} command.
18492 The definition of the command is made up of other @value{GDBN} command lines,
18493 which are given following the @code{define} command. The end of these
18494 commands is marked by a line containing @code{end}.
18497 @kindex end@r{ (user-defined commands)}
18498 @item document @var{commandname}
18499 Document the user-defined command @var{commandname}, so that it can be
18500 accessed by @code{help}. The command @var{commandname} must already be
18501 defined. This command reads lines of documentation just as @code{define}
18502 reads the lines of the command definition, ending with @code{end}.
18503 After the @code{document} command is finished, @code{help} on command
18504 @var{commandname} displays the documentation you have written.
18506 You may use the @code{document} command again to change the
18507 documentation of a command. Redefining the command with @code{define}
18508 does not change the documentation.
18510 @kindex dont-repeat
18511 @cindex don't repeat command
18513 Used inside a user-defined command, this tells @value{GDBN} that this
18514 command should not be repeated when the user hits @key{RET}
18515 (@pxref{Command Syntax, repeat last command}).
18517 @kindex help user-defined
18518 @item help user-defined
18519 List all user-defined commands, with the first line of the documentation
18524 @itemx show user @var{commandname}
18525 Display the @value{GDBN} commands used to define @var{commandname} (but
18526 not its documentation). If no @var{commandname} is given, display the
18527 definitions for all user-defined commands.
18529 @cindex infinite recursion in user-defined commands
18530 @kindex show max-user-call-depth
18531 @kindex set max-user-call-depth
18532 @item show max-user-call-depth
18533 @itemx set max-user-call-depth
18534 The value of @code{max-user-call-depth} controls how many recursion
18535 levels are allowed in user-defined commands before @value{GDBN} suspects an
18536 infinite recursion and aborts the command.
18539 In addition to the above commands, user-defined commands frequently
18540 use control flow commands, described in @ref{Command Files}.
18542 When user-defined commands are executed, the
18543 commands of the definition are not printed. An error in any command
18544 stops execution of the user-defined command.
18546 If used interactively, commands that would ask for confirmation proceed
18547 without asking when used inside a user-defined command. Many @value{GDBN}
18548 commands that normally print messages to say what they are doing omit the
18549 messages when used in a user-defined command.
18552 @subsection User-defined Command Hooks
18553 @cindex command hooks
18554 @cindex hooks, for commands
18555 @cindex hooks, pre-command
18558 You may define @dfn{hooks}, which are a special kind of user-defined
18559 command. Whenever you run the command @samp{foo}, if the user-defined
18560 command @samp{hook-foo} exists, it is executed (with no arguments)
18561 before that command.
18563 @cindex hooks, post-command
18565 A hook may also be defined which is run after the command you executed.
18566 Whenever you run the command @samp{foo}, if the user-defined command
18567 @samp{hookpost-foo} exists, it is executed (with no arguments) after
18568 that command. Post-execution hooks may exist simultaneously with
18569 pre-execution hooks, for the same command.
18571 It is valid for a hook to call the command which it hooks. If this
18572 occurs, the hook is not re-executed, thereby avoiding infinite recursion.
18574 @c It would be nice if hookpost could be passed a parameter indicating
18575 @c if the command it hooks executed properly or not. FIXME!
18577 @kindex stop@r{, a pseudo-command}
18578 In addition, a pseudo-command, @samp{stop} exists. Defining
18579 (@samp{hook-stop}) makes the associated commands execute every time
18580 execution stops in your program: before breakpoint commands are run,
18581 displays are printed, or the stack frame is printed.
18583 For example, to ignore @code{SIGALRM} signals while
18584 single-stepping, but treat them normally during normal execution,
18589 handle SIGALRM nopass
18593 handle SIGALRM pass
18596 define hook-continue
18597 handle SIGALRM pass
18601 As a further example, to hook at the beginning and end of the @code{echo}
18602 command, and to add extra text to the beginning and end of the message,
18610 define hookpost-echo
18614 (@value{GDBP}) echo Hello World
18615 <<<---Hello World--->>>
18620 You can define a hook for any single-word command in @value{GDBN}, but
18621 not for command aliases; you should define a hook for the basic command
18622 name, e.g.@: @code{backtrace} rather than @code{bt}.
18623 @c FIXME! So how does Joe User discover whether a command is an alias
18625 You can hook a multi-word command by adding @code{hook-} or
18626 @code{hookpost-} to the last word of the command, e.g.@:
18627 @samp{define target hook-remote} to add a hook to @samp{target remote}.
18629 If an error occurs during the execution of your hook, execution of
18630 @value{GDBN} commands stops and @value{GDBN} issues a prompt
18631 (before the command that you actually typed had a chance to run).
18633 If you try to define a hook which does not match any known command, you
18634 get a warning from the @code{define} command.
18636 @node Command Files
18637 @subsection Command Files
18639 @cindex command files
18640 @cindex scripting commands
18641 A command file for @value{GDBN} is a text file made of lines that are
18642 @value{GDBN} commands. Comments (lines starting with @kbd{#}) may
18643 also be included. An empty line in a command file does nothing; it
18644 does not mean to repeat the last command, as it would from the
18647 You can request the execution of a command file with the @code{source}
18652 @cindex execute commands from a file
18653 @item source [@code{-v}] @var{filename}
18654 Execute the command file @var{filename}.
18657 The lines in a command file are generally executed sequentially,
18658 unless the order of execution is changed by one of the
18659 @emph{flow-control commands} described below. The commands are not
18660 printed as they are executed. An error in any command terminates
18661 execution of the command file and control is returned to the console.
18663 @value{GDBN} searches for @var{filename} in the current directory and then
18664 on the search path (specified with the @samp{directory} command).
18666 If @code{-v}, for verbose mode, is given then @value{GDBN} displays
18667 each command as it is executed. The option must be given before
18668 @var{filename}, and is interpreted as part of the filename anywhere else.
18670 Commands that would ask for confirmation if used interactively proceed
18671 without asking when used in a command file. Many @value{GDBN} commands that
18672 normally print messages to say what they are doing omit the messages
18673 when called from command files.
18675 @value{GDBN} also accepts command input from standard input. In this
18676 mode, normal output goes to standard output and error output goes to
18677 standard error. Errors in a command file supplied on standard input do
18678 not terminate execution of the command file---execution continues with
18682 gdb < cmds > log 2>&1
18685 (The syntax above will vary depending on the shell used.) This example
18686 will execute commands from the file @file{cmds}. All output and errors
18687 would be directed to @file{log}.
18689 Since commands stored on command files tend to be more general than
18690 commands typed interactively, they frequently need to deal with
18691 complicated situations, such as different or unexpected values of
18692 variables and symbols, changes in how the program being debugged is
18693 built, etc. @value{GDBN} provides a set of flow-control commands to
18694 deal with these complexities. Using these commands, you can write
18695 complex scripts that loop over data structures, execute commands
18696 conditionally, etc.
18703 This command allows to include in your script conditionally executed
18704 commands. The @code{if} command takes a single argument, which is an
18705 expression to evaluate. It is followed by a series of commands that
18706 are executed only if the expression is true (its value is nonzero).
18707 There can then optionally be an @code{else} line, followed by a series
18708 of commands that are only executed if the expression was false. The
18709 end of the list is marked by a line containing @code{end}.
18713 This command allows to write loops. Its syntax is similar to
18714 @code{if}: the command takes a single argument, which is an expression
18715 to evaluate, and must be followed by the commands to execute, one per
18716 line, terminated by an @code{end}. These commands are called the
18717 @dfn{body} of the loop. The commands in the body of @code{while} are
18718 executed repeatedly as long as the expression evaluates to true.
18722 This command exits the @code{while} loop in whose body it is included.
18723 Execution of the script continues after that @code{while}s @code{end}
18726 @kindex loop_continue
18727 @item loop_continue
18728 This command skips the execution of the rest of the body of commands
18729 in the @code{while} loop in whose body it is included. Execution
18730 branches to the beginning of the @code{while} loop, where it evaluates
18731 the controlling expression.
18733 @kindex end@r{ (if/else/while commands)}
18735 Terminate the block of commands that are the body of @code{if},
18736 @code{else}, or @code{while} flow-control commands.
18741 @subsection Commands for Controlled Output
18743 During the execution of a command file or a user-defined command, normal
18744 @value{GDBN} output is suppressed; the only output that appears is what is
18745 explicitly printed by the commands in the definition. This section
18746 describes three commands useful for generating exactly the output you
18751 @item echo @var{text}
18752 @c I do not consider backslash-space a standard C escape sequence
18753 @c because it is not in ANSI.
18754 Print @var{text}. Nonprinting characters can be included in
18755 @var{text} using C escape sequences, such as @samp{\n} to print a
18756 newline. @strong{No newline is printed unless you specify one.}
18757 In addition to the standard C escape sequences, a backslash followed
18758 by a space stands for a space. This is useful for displaying a
18759 string with spaces at the beginning or the end, since leading and
18760 trailing spaces are otherwise trimmed from all arguments.
18761 To print @samp{@w{ }and foo =@w{ }}, use the command
18762 @samp{echo \@w{ }and foo = \@w{ }}.
18764 A backslash at the end of @var{text} can be used, as in C, to continue
18765 the command onto subsequent lines. For example,
18768 echo This is some text\n\
18769 which is continued\n\
18770 onto several lines.\n
18773 produces the same output as
18776 echo This is some text\n
18777 echo which is continued\n
18778 echo onto several lines.\n
18782 @item output @var{expression}
18783 Print the value of @var{expression} and nothing but that value: no
18784 newlines, no @samp{$@var{nn} = }. The value is not entered in the
18785 value history either. @xref{Expressions, ,Expressions}, for more information
18788 @item output/@var{fmt} @var{expression}
18789 Print the value of @var{expression} in format @var{fmt}. You can use
18790 the same formats as for @code{print}. @xref{Output Formats,,Output
18791 Formats}, for more information.
18794 @item printf @var{template}, @var{expressions}@dots{}
18795 Print the values of one or more @var{expressions} under the control of
18796 the string @var{template}. To print several values, make
18797 @var{expressions} be a comma-separated list of individual expressions,
18798 which may be either numbers or pointers. Their values are printed as
18799 specified by @var{template}, exactly as a C program would do by
18800 executing the code below:
18803 printf (@var{template}, @var{expressions}@dots{});
18806 As in @code{C} @code{printf}, ordinary characters in @var{template}
18807 are printed verbatim, while @dfn{conversion specification} introduced
18808 by the @samp{%} character cause subsequent @var{expressions} to be
18809 evaluated, their values converted and formatted according to type and
18810 style information encoded in the conversion specifications, and then
18813 For example, you can print two values in hex like this:
18816 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
18819 @code{printf} supports all the standard @code{C} conversion
18820 specifications, including the flags and modifiers between the @samp{%}
18821 character and the conversion letter, with the following exceptions:
18825 The argument-ordering modifiers, such as @samp{2$}, are not supported.
18828 The modifier @samp{*} is not supported for specifying precision or
18832 The @samp{'} flag (for separation of digits into groups according to
18833 @code{LC_NUMERIC'}) is not supported.
18836 The type modifiers @samp{hh}, @samp{j}, @samp{t}, and @samp{z} are not
18840 The conversion letter @samp{n} (as in @samp{%n}) is not supported.
18843 The conversion letters @samp{a} and @samp{A} are not supported.
18847 Note that the @samp{ll} type modifier is supported only if the
18848 underlying @code{C} implementation used to build @value{GDBN} supports
18849 the @code{long long int} type, and the @samp{L} type modifier is
18850 supported only if @code{long double} type is available.
18852 As in @code{C}, @code{printf} supports simple backslash-escape
18853 sequences, such as @code{\n}, @samp{\t}, @samp{\\}, @samp{\"},
18854 @samp{\a}, and @samp{\f}, that consist of backslash followed by a
18855 single character. Octal and hexadecimal escape sequences are not
18858 Additionally, @code{printf} supports conversion specifications for DFP
18859 (@dfn{Decimal Floating Point}) types using the following length modifiers
18860 together with a floating point specifier.
18865 @samp{H} for printing @code{Decimal32} types.
18868 @samp{D} for printing @code{Decimal64} types.
18871 @samp{DD} for printing @code{Decimal128} types.
18874 If the underlying @code{C} implementation used to build @value{GDBN} has
18875 support for the three length modifiers for DFP types, other modifiers
18876 such as width and precision will also be available for @value{GDBN} to use.
18878 In case there is no such @code{C} support, no additional modifiers will be
18879 available and the value will be printed in the standard way.
18881 Here's an example of printing DFP types using the above conversion letters:
18883 printf "D32: %Hf - D64: %Df - D128: %DDf\n",1.2345df,1.2E10dd,1.2E1dl
18889 @section Scripting @value{GDBN} using Python
18890 @cindex python scripting
18891 @cindex scripting with python
18893 You can script @value{GDBN} using the @uref{http://www.python.org/,
18894 Python programming language}. This feature is available only if
18895 @value{GDBN} was configured using @option{--with-python}.
18898 * Python Commands:: Accessing Python from @value{GDBN}.
18899 * Python API:: Accessing @value{GDBN} from Python.
18902 @node Python Commands
18903 @subsection Python Commands
18904 @cindex python commands
18905 @cindex commands to access python
18907 @value{GDBN} provides one command for accessing the Python interpreter,
18908 and one related setting:
18912 @item python @r{[}@var{code}@r{]}
18913 The @code{python} command can be used to evaluate Python code.
18915 If given an argument, the @code{python} command will evaluate the
18916 argument as a Python command. For example:
18919 (@value{GDBP}) python print 23
18923 If you do not provide an argument to @code{python}, it will act as a
18924 multi-line command, like @code{define}. In this case, the Python
18925 script is made up of subsequent command lines, given after the
18926 @code{python} command. This command list is terminated using a line
18927 containing @code{end}. For example:
18930 (@value{GDBP}) python
18932 End with a line saying just "end".
18938 @kindex maint set python print-stack
18939 @item maint set python print-stack
18940 By default, @value{GDBN} will print a stack trace when an error occurs
18941 in a Python script. This can be controlled using @code{maint set
18942 python print-stack}: if @code{on}, the default, then Python stack
18943 printing is enabled; if @code{off}, then Python stack printing is
18948 @subsection Python API
18950 @cindex programming in python
18952 @cindex python stdout
18953 @cindex python pagination
18954 At startup, @value{GDBN} overrides Python's @code{sys.stdout} and
18955 @code{sys.stderr} to print using @value{GDBN}'s output-paging streams.
18956 A Python program which outputs to one of these streams may have its
18957 output interrupted by the user (@pxref{Screen Size}). In this
18958 situation, a Python @code{KeyboardInterrupt} exception is thrown.
18961 * Basic Python:: Basic Python Functions.
18962 * Exception Handling::
18963 * Auto-loading:: Automatically loading Python code.
18964 * Values From Inferior::
18965 * Types In Python:: Python representation of types.
18966 * Pretty Printing:: Pretty-printing values.
18967 * Selecting Pretty-Printers:: How GDB chooses a pretty-printer.
18968 * Commands In Python:: Implementing new commands in Python.
18969 * Functions In Python:: Writing new convenience functions.
18970 * Objfiles In Python:: Object files.
18971 * Frames In Python:: Acessing inferior stack frames from Python.
18975 @subsubsection Basic Python
18977 @cindex python functions
18978 @cindex python module
18980 @value{GDBN} introduces a new Python module, named @code{gdb}. All
18981 methods and classes added by @value{GDBN} are placed in this module.
18982 @value{GDBN} automatically @code{import}s the @code{gdb} module for
18983 use in all scripts evaluated by the @code{python} command.
18985 @findex gdb.execute
18986 @defun execute command [from_tty]
18987 Evaluate @var{command}, a string, as a @value{GDBN} CLI command.
18988 If a GDB exception happens while @var{command} runs, it is
18989 translated as described in @ref{Exception Handling,,Exception Handling}.
18990 If no exceptions occur, this function returns @code{None}.
18992 @var{from_tty} specifies whether @value{GDBN} ought to consider this
18993 command as having originated from the user invoking it interactively.
18994 It must be a boolean value. If omitted, it defaults to @code{False}.
18997 @findex gdb.parameter
18998 @defun parameter parameter
18999 Return the value of a @value{GDBN} parameter. @var{parameter} is a
19000 string naming the parameter to look up; @var{parameter} may contain
19001 spaces if the parameter has a multi-part name. For example,
19002 @samp{print object} is a valid parameter name.
19004 If the named parameter does not exist, this function throws a
19005 @code{RuntimeError}. Otherwise, the parameter's value is converted to
19006 a Python value of the appropriate type, and returned.
19009 @findex gdb.history
19010 @defun history number
19011 Return a value from @value{GDBN}'s value history (@pxref{Value
19012 History}). @var{number} indicates which history element to return.
19013 If @var{number} is negative, then @value{GDBN} will take its absolute value
19014 and count backward from the last element (i.e., the most recent element) to
19015 find the value to return. If @var{number} is zero, then @value{GDBN} will
19016 return the most recent element. If the element specified by @var{number}
19017 doesn't exist in the value history, a @code{RuntimeError} exception will be
19020 If no exception is raised, the return value is always an instance of
19021 @code{gdb.Value} (@pxref{Values From Inferior}).
19025 @defun write string
19026 Print a string to @value{GDBN}'s paginated standard output stream.
19027 Writing to @code{sys.stdout} or @code{sys.stderr} will automatically
19028 call this function.
19033 Flush @value{GDBN}'s paginated standard output stream. Flushing
19034 @code{sys.stdout} or @code{sys.stderr} will automatically call this
19038 @node Exception Handling
19039 @subsubsection Exception Handling
19040 @cindex python exceptions
19041 @cindex exceptions, python
19043 When executing the @code{python} command, Python exceptions
19044 uncaught within the Python code are translated to calls to
19045 @value{GDBN} error-reporting mechanism. If the command that called
19046 @code{python} does not handle the error, @value{GDBN} will
19047 terminate it and print an error message containing the Python
19048 exception name, the associated value, and the Python call stack
19049 backtrace at the point where the exception was raised. Example:
19052 (@value{GDBP}) python print foo
19053 Traceback (most recent call last):
19054 File "<string>", line 1, in <module>
19055 NameError: name 'foo' is not defined
19058 @value{GDBN} errors that happen in @value{GDBN} commands invoked by Python
19059 code are converted to Python @code{RuntimeError} exceptions. User
19060 interrupt (via @kbd{C-c} or by typing @kbd{q} at a pagination
19061 prompt) is translated to a Python @code{KeyboardInterrupt}
19062 exception. If you catch these exceptions in your Python code, your
19063 exception handler will see @code{RuntimeError} or
19064 @code{KeyboardInterrupt} as the exception type, the @value{GDBN} error
19065 message as its value, and the Python call stack backtrace at the
19066 Python statement closest to where the @value{GDBN} error occured as the
19070 @subsubsection Auto-loading
19071 @cindex auto-loading, Python
19073 When a new object file is read (for example, due to the @code{file}
19074 command, or because the inferior has loaded a shared library),
19075 @value{GDBN} will look for a file named @file{@var{objfile}-gdb.py},
19076 where @var{objfile} is the object file's real name, formed by ensuring
19077 that the file name is absolute, following all symlinks, and resolving
19078 @code{.} and @code{..} components. If this file exists and is
19079 readable, @value{GDBN} will evaluate it as a Python script.
19081 If this file does not exist, and if the parameter
19082 @code{debug-file-directory} is set (@pxref{Separate Debug Files}),
19083 then @value{GDBN} will use the file named
19084 @file{@var{debug-file-directory}/@var{real-name}}, where
19085 @var{real-name} is the object file's real name, as described above.
19087 Finally, if this file does not exist, then @value{GDBN} will look for
19088 a file named @file{@var{data-directory}/python/auto-load/@var{real-name}}, where
19089 @var{data-directory} is @value{GDBN}'s data directory (available via
19090 @code{show data-directory}, @pxref{Data Files}), and @var{real-name}
19091 is the object file's real name, as described above.
19093 When reading an auto-loaded file, @value{GDBN} sets the ``current
19094 objfile''. This is available via the @code{gdb.current_objfile}
19095 function (@pxref{Objfiles In Python}). This can be useful for
19096 registering objfile-specific pretty-printers.
19098 The auto-loading feature is useful for supplying application-specific
19099 debugging commands and scripts. You can enable or disable this
19100 feature, and view its current state.
19103 @kindex maint set python auto-load
19104 @item maint set python auto-load [yes|no]
19105 Enable or disable the Python auto-loading feature.
19107 @kindex show python auto-load
19108 @item show python auto-load
19109 Show whether Python auto-loading is enabled or disabled.
19112 @value{GDBN} does not track which files it has already auto-loaded.
19113 So, your @samp{-gdb.py} file should take care to ensure that it may be
19114 evaluated multiple times without error.
19116 @node Values From Inferior
19117 @subsubsection Values From Inferior
19118 @cindex values from inferior, with Python
19119 @cindex python, working with values from inferior
19121 @cindex @code{gdb.Value}
19122 @value{GDBN} provides values it obtains from the inferior program in
19123 an object of type @code{gdb.Value}. @value{GDBN} uses this object
19124 for its internal bookkeeping of the inferior's values, and for
19125 fetching values when necessary.
19127 Inferior values that are simple scalars can be used directly in
19128 Python expressions that are valid for the value's data type. Here's
19129 an example for an integer or floating-point value @code{some_val}:
19136 As result of this, @code{bar} will also be a @code{gdb.Value} object
19137 whose values are of the same type as those of @code{some_val}.
19139 Inferior values that are structures or instances of some class can
19140 be accessed using the Python @dfn{dictionary syntax}. For example, if
19141 @code{some_val} is a @code{gdb.Value} instance holding a structure, you
19142 can access its @code{foo} element with:
19145 bar = some_val['foo']
19148 Again, @code{bar} will also be a @code{gdb.Value} object.
19150 The following attributes are provided:
19153 @defivar Value address
19154 If this object is addressable, this read-only attribute holds a
19155 @code{gdb.Value} object representing the address. Otherwise,
19156 this attribute holds @code{None}.
19159 @cindex optimized out value in Python
19160 @defivar Value is_optimized_out
19161 This read-only boolean attribute is true if the compiler optimized out
19162 this value, thus it is not available for fetching from the inferior.
19165 @defivar Value type
19166 The type of this @code{gdb.Value}. The value of this attribute is a
19167 @code{gdb.Type} object.
19171 The following methods are provided:
19174 @defmethod Value dereference
19175 For pointer data types, this method returns a new @code{gdb.Value} object
19176 whose contents is the object pointed to by the pointer. For example, if
19177 @code{foo} is a C pointer to an @code{int}, declared in your C program as
19184 then you can use the corresponding @code{gdb.Value} to access what
19185 @code{foo} points to like this:
19188 bar = foo.dereference ()
19191 The result @code{bar} will be a @code{gdb.Value} object holding the
19192 value pointed to by @code{foo}.
19195 @defmethod Value string @r{[}encoding@r{]} @r{[}errors@r{]} @r{[}length@r{]}
19196 If this @code{gdb.Value} represents a string, then this method
19197 converts the contents to a Python string. Otherwise, this method will
19198 throw an exception.
19200 Strings are recognized in a language-specific way; whether a given
19201 @code{gdb.Value} represents a string is determined by the current
19204 For C-like languages, a value is a string if it is a pointer to or an
19205 array of characters or ints. The string is assumed to be terminated
19206 by a zero of the appropriate width. However if the optional length
19207 argument is given, the string will be converted to that given length,
19208 ignoring any embedded zeros that the string may contain.
19210 If the optional @var{encoding} argument is given, it must be a string
19211 naming the encoding of the string in the @code{gdb.Value}, such as
19212 @code{"ascii"}, @code{"iso-8859-6"} or @code{"utf-8"}. It accepts
19213 the same encodings as the corresponding argument to Python's
19214 @code{string.decode} method, and the Python codec machinery will be used
19215 to convert the string. If @var{encoding} is not given, or if
19216 @var{encoding} is the empty string, then either the @code{target-charset}
19217 (@pxref{Character Sets}) will be used, or a language-specific encoding
19218 will be used, if the current language is able to supply one.
19220 The optional @var{errors} argument is the same as the corresponding
19221 argument to Python's @code{string.decode} method.
19223 If the optional @var{length} argument is given, the string will be
19224 fetched and converted to the given length.
19228 @node Types In Python
19229 @subsubsection Types In Python
19230 @cindex types in Python
19231 @cindex Python, working with types
19234 @value{GDBN} represents types from the inferior using the class
19237 The following type-related functions are available in the @code{gdb}
19240 @findex gdb.lookup_type
19241 @defun lookup_type name [block]
19242 This function looks up a type by name. @var{name} is the name of the
19243 type to look up. It must be a string.
19245 Ordinarily, this function will return an instance of @code{gdb.Type}.
19246 If the named type cannot be found, it will throw an exception.
19249 An instance of @code{Type} has the following attributes:
19253 The type code for this type. The type code will be one of the
19254 @code{TYPE_CODE_} constants defined below.
19257 @defivar Type sizeof
19258 The size of this type, in target @code{char} units. Usually, a
19259 target's @code{char} type will be an 8-bit byte. However, on some
19260 unusual platforms, this type may have a different size.
19264 The tag name for this type. The tag name is the name after
19265 @code{struct}, @code{union}, or @code{enum} in C and C@t{++}; not all
19266 languages have this concept. If this type has no tag name, then
19267 @code{None} is returned.
19271 The following methods are provided:
19274 @defmethod Type fields
19275 For structure and union types, this method returns the fields. Range
19276 types have two fields, the minimum and maximum values. Enum types
19277 have one field per enum constant. Function and method types have one
19278 field per parameter. The base types of C@t{++} classes are also
19279 represented as fields. If the type has no fields, or does not fit
19280 into one of these categories, an empty sequence will be returned.
19282 Each field is an object, with some pre-defined attributes:
19285 This attribute is not available for @code{static} fields (as in
19286 C@t{++} or Java). For non-@code{static} fields, the value is the bit
19287 position of the field.
19290 The name of the field, or @code{None} for anonymous fields.
19293 This is @code{True} if the field is artificial, usually meaning that
19294 it was provided by the compiler and not the user. This attribute is
19295 always provided, and is @code{False} if the field is not artificial.
19298 If the field is packed, or is a bitfield, then this will have a
19299 non-zero value, which is the size of the field in bits. Otherwise,
19300 this will be zero; in this case the field's size is given by its type.
19303 The type of the field. This is usually an instance of @code{Type},
19304 but it can be @code{None} in some situations.
19308 @defmethod Type const
19309 Return a new @code{gdb.Type} object which represents a
19310 @code{const}-qualified variant of this type.
19313 @defmethod Type volatile
19314 Return a new @code{gdb.Type} object which represents a
19315 @code{volatile}-qualified variant of this type.
19318 @defmethod Type unqualified
19319 Return a new @code{gdb.Type} object which represents an unqualified
19320 variant of this type. That is, the result is neither @code{const} nor
19324 @defmethod Type reference
19325 Return a new @code{gdb.Type} object which represents a reference to this
19329 @defmethod Type strip_typedefs
19330 Return a new @code{gdb.Type} that represents the real type,
19331 after removing all layers of typedefs.
19334 @defmethod Type target
19335 Return a new @code{gdb.Type} object which represents the target type
19338 For a pointer type, the target type is the type of the pointed-to
19339 object. For an array type (meaning C-like arrays), the target type is
19340 the type of the elements of the array. For a function or method type,
19341 the target type is the type of the return value. For a complex type,
19342 the target type is the type of the elements. For a typedef, the
19343 target type is the aliased type.
19345 If the type does not have a target, this method will throw an
19349 @defmethod Type template_argument n
19350 If this @code{gdb.Type} is an instantiation of a template, this will
19351 return a new @code{gdb.Type} which represents the type of the
19352 @var{n}th template argument.
19354 If this @code{gdb.Type} is not a template type, this will throw an
19355 exception. Ordinarily, only C@t{++} code will have template types.
19357 @var{name} is searched for globally.
19362 Each type has a code, which indicates what category this type falls
19363 into. The available type categories are represented by constants
19364 defined in the @code{gdb} module:
19367 @findex TYPE_CODE_PTR
19368 @findex gdb.TYPE_CODE_PTR
19369 @item TYPE_CODE_PTR
19370 The type is a pointer.
19372 @findex TYPE_CODE_ARRAY
19373 @findex gdb.TYPE_CODE_ARRAY
19374 @item TYPE_CODE_ARRAY
19375 The type is an array.
19377 @findex TYPE_CODE_STRUCT
19378 @findex gdb.TYPE_CODE_STRUCT
19379 @item TYPE_CODE_STRUCT
19380 The type is a structure.
19382 @findex TYPE_CODE_UNION
19383 @findex gdb.TYPE_CODE_UNION
19384 @item TYPE_CODE_UNION
19385 The type is a union.
19387 @findex TYPE_CODE_ENUM
19388 @findex gdb.TYPE_CODE_ENUM
19389 @item TYPE_CODE_ENUM
19390 The type is an enum.
19392 @findex TYPE_CODE_FLAGS
19393 @findex gdb.TYPE_CODE_FLAGS
19394 @item TYPE_CODE_FLAGS
19395 A bit flags type, used for things such as status registers.
19397 @findex TYPE_CODE_FUNC
19398 @findex gdb.TYPE_CODE_FUNC
19399 @item TYPE_CODE_FUNC
19400 The type is a function.
19402 @findex TYPE_CODE_INT
19403 @findex gdb.TYPE_CODE_INT
19404 @item TYPE_CODE_INT
19405 The type is an integer type.
19407 @findex TYPE_CODE_FLT
19408 @findex gdb.TYPE_CODE_FLT
19409 @item TYPE_CODE_FLT
19410 A floating point type.
19412 @findex TYPE_CODE_VOID
19413 @findex gdb.TYPE_CODE_VOID
19414 @item TYPE_CODE_VOID
19415 The special type @code{void}.
19417 @findex TYPE_CODE_SET
19418 @findex gdb.TYPE_CODE_SET
19419 @item TYPE_CODE_SET
19422 @findex TYPE_CODE_RANGE
19423 @findex gdb.TYPE_CODE_RANGE
19424 @item TYPE_CODE_RANGE
19425 A range type, that is, an integer type with bounds.
19427 @findex TYPE_CODE_STRING
19428 @findex gdb.TYPE_CODE_STRING
19429 @item TYPE_CODE_STRING
19430 A string type. Note that this is only used for certain languages with
19431 language-defined string types; C strings are not represented this way.
19433 @findex TYPE_CODE_BITSTRING
19434 @findex gdb.TYPE_CODE_BITSTRING
19435 @item TYPE_CODE_BITSTRING
19438 @findex TYPE_CODE_ERROR
19439 @findex gdb.TYPE_CODE_ERROR
19440 @item TYPE_CODE_ERROR
19441 An unknown or erroneous type.
19443 @findex TYPE_CODE_METHOD
19444 @findex gdb.TYPE_CODE_METHOD
19445 @item TYPE_CODE_METHOD
19446 A method type, as found in C@t{++} or Java.
19448 @findex TYPE_CODE_METHODPTR
19449 @findex gdb.TYPE_CODE_METHODPTR
19450 @item TYPE_CODE_METHODPTR
19451 A pointer-to-member-function.
19453 @findex TYPE_CODE_MEMBERPTR
19454 @findex gdb.TYPE_CODE_MEMBERPTR
19455 @item TYPE_CODE_MEMBERPTR
19456 A pointer-to-member.
19458 @findex TYPE_CODE_REF
19459 @findex gdb.TYPE_CODE_REF
19460 @item TYPE_CODE_REF
19463 @findex TYPE_CODE_CHAR
19464 @findex gdb.TYPE_CODE_CHAR
19465 @item TYPE_CODE_CHAR
19468 @findex TYPE_CODE_BOOL
19469 @findex gdb.TYPE_CODE_BOOL
19470 @item TYPE_CODE_BOOL
19473 @findex TYPE_CODE_COMPLEX
19474 @findex gdb.TYPE_CODE_COMPLEX
19475 @item TYPE_CODE_COMPLEX
19476 A complex float type.
19478 @findex TYPE_CODE_TYPEDEF
19479 @findex gdb.TYPE_CODE_TYPEDEF
19480 @item TYPE_CODE_TYPEDEF
19481 A typedef to some other type.
19483 @findex TYPE_CODE_NAMESPACE
19484 @findex gdb.TYPE_CODE_NAMESPACE
19485 @item TYPE_CODE_NAMESPACE
19486 A C@t{++} namespace.
19488 @findex TYPE_CODE_DECFLOAT
19489 @findex gdb.TYPE_CODE_DECFLOAT
19490 @item TYPE_CODE_DECFLOAT
19491 A decimal floating point type.
19493 @findex TYPE_CODE_INTERNAL_FUNCTION
19494 @findex gdb.TYPE_CODE_INTERNAL_FUNCTION
19495 @item TYPE_CODE_INTERNAL_FUNCTION
19496 A function internal to @value{GDBN}. This is the type used to represent
19497 convenience functions.
19500 @node Pretty Printing
19501 @subsubsection Pretty Printing
19503 @value{GDBN} provides a mechanism to allow pretty-printing of values
19504 using Python code. The pretty-printer API allows application-specific
19505 code to greatly simplify the display of complex objects. This
19506 mechanism works for both MI and the CLI.
19508 For example, here is how a C@t{++} @code{std::string} looks without a
19512 (@value{GDBP}) print s
19514 static npos = 4294967295,
19516 <std::allocator<char>> = @{
19517 <__gnu_cxx::new_allocator<char>> = @{<No data fields>@}, <No data fields>@},
19518 members of std::basic_string<char, std::char_traits<char>, std::allocator<char> >::_Alloc_hider:
19519 _M_p = 0x804a014 "abcd"
19524 After a pretty-printer for @code{std::string} has been installed, only
19525 the contents are printed:
19528 (@value{GDBP}) print s
19532 A pretty-printer is just an object that holds a value and implements a
19533 specific interface, defined here.
19535 @defop Operation {pretty printer} children (self)
19536 @value{GDBN} will call this method on a pretty-printer to compute the
19537 children of the pretty-printer's value.
19539 This method must return an object conforming to the Python iterator
19540 protocol. Each item returned by the iterator must be a tuple holding
19541 two elements. The first element is the ``name'' of the child; the
19542 second element is the child's value. The value can be any Python
19543 object which is convertible to a @value{GDBN} value.
19545 This method is optional. If it does not exist, @value{GDBN} will act
19546 as though the value has no children.
19549 @defop Operation {pretty printer} display_hint (self)
19550 The CLI may call this method and use its result to change the
19551 formatting of a value. The result will also be supplied to an MI
19552 consumer as a @samp{displayhint} attribute of the variable being
19555 This method is optional. If it does exist, this method must return a
19558 Some display hints are predefined by @value{GDBN}:
19562 Indicate that the object being printed is ``array-like''. The CLI
19563 uses this to respect parameters such as @code{set print elements} and
19564 @code{set print array}.
19567 Indicate that the object being printed is ``map-like'', and that the
19568 children of this value can be assumed to alternate between keys and
19572 Indicate that the object being printed is ``string-like''. If the
19573 printer's @code{to_string} method returns a Python string of some
19574 kind, then @value{GDBN} will call its internal language-specific
19575 string-printing function to format the string. For the CLI this means
19576 adding quotation marks, possibly escaping some characters, respecting
19577 @code{set print elements}, and the like.
19581 @defop Operation {pretty printer} to_string (self)
19582 @value{GDBN} will call this method to display the string
19583 representation of the value passed to the object's constructor.
19585 When printing from the CLI, if the @code{to_string} method exists,
19586 then @value{GDBN} will prepend its result to the values returned by
19587 @code{children}. Exactly how this formatting is done is dependent on
19588 the display hint, and may change as more hints are added. Also,
19589 depending on the print settings (@pxref{Print Settings}), the CLI may
19590 print just the result of @code{to_string} in a stack trace, omitting
19591 the result of @code{children}.
19593 If this method returns a string, it is printed verbatim.
19595 Otherwise, if this method returns an instance of @code{gdb.Value},
19596 then @value{GDBN} prints this value. This may result in a call to
19597 another pretty-printer.
19599 If instead the method returns a Python value which is convertible to a
19600 @code{gdb.Value}, then @value{GDBN} performs the conversion and prints
19601 the resulting value. Again, this may result in a call to another
19602 pretty-printer. Python scalars (integers, floats, and booleans) and
19603 strings are convertible to @code{gdb.Value}; other types are not.
19605 If the result is not one of these types, an exception is raised.
19608 @node Selecting Pretty-Printers
19609 @subsubsection Selecting Pretty-Printers
19611 The Python list @code{gdb.pretty_printers} contains an array of
19612 functions that have been registered via addition as a pretty-printer.
19613 Each @code{gdb.Objfile} also contains a @code{pretty_printers}
19616 A function on one of these lists is passed a single @code{gdb.Value}
19617 argument and should return a pretty-printer object conforming to the
19618 interface definition above (@pxref{Pretty Printing}). If a function
19619 cannot create a pretty-printer for the value, it should return
19622 @value{GDBN} first checks the @code{pretty_printers} attribute of each
19623 @code{gdb.Objfile} and iteratively calls each function in the list for
19624 that @code{gdb.Objfile} until it receives a pretty-printer object.
19625 After these lists have been exhausted, it tries the global
19626 @code{gdb.pretty-printers} list, again calling each function until an
19627 object is returned.
19629 The order in which the objfiles are searched is not specified. For a
19630 given list, functions are always invoked from the head of the list,
19631 and iterated over sequentially until the end of the list, or a printer
19632 object is returned.
19634 Here is an example showing how a @code{std::string} printer might be
19638 class StdStringPrinter:
19639 "Print a std::string"
19641 def __init__ (self, val):
19644 def to_string (self):
19645 return self.val['_M_dataplus']['_M_p']
19647 def display_hint (self):
19651 And here is an example showing how a lookup function for the printer
19652 example above might be written.
19655 def str_lookup_function (val):
19657 lookup_tag = val.type.tag
19658 regex = re.compile ("^std::basic_string<char,.*>$")
19659 if lookup_tag == None:
19661 if regex.match (lookup_tag):
19662 return StdStringPrinter (val)
19667 The example lookup function extracts the value's type, and attempts to
19668 match it to a type that it can pretty-print. If it is a type the
19669 printer can pretty-print, it will return a printer object. If not, it
19670 returns @code{None}.
19672 We recommend that you put your core pretty-printers into a Python
19673 package. If your pretty-printers are for use with a library, we
19674 further recommend embedding a version number into the package name.
19675 This practice will enable @value{GDBN} to load multiple versions of
19676 your pretty-printers at the same time, because they will have
19679 You should write auto-loaded code (@pxref{Auto-loading}) such that it
19680 can be evaluated multiple times without changing its meaning. An
19681 ideal auto-load file will consist solely of @code{import}s of your
19682 printer modules, followed by a call to a register pretty-printers with
19683 the current objfile.
19685 Taken as a whole, this approach will scale nicely to multiple
19686 inferiors, each potentially using a different library version.
19687 Embedding a version number in the Python package name will ensure that
19688 @value{GDBN} is able to load both sets of printers simultaneously.
19689 Then, because the search for pretty-printers is done by objfile, and
19690 because your auto-loaded code took care to register your library's
19691 printers with a specific objfile, @value{GDBN} will find the correct
19692 printers for the specific version of the library used by each
19695 To continue the @code{std::string} example (@pxref{Pretty Printing}),
19696 this code might appear in @code{gdb.libstdcxx.v6}:
19699 def register_printers (objfile):
19700 objfile.pretty_printers.add (str_lookup_function)
19704 And then the corresponding contents of the auto-load file would be:
19707 import gdb.libstdcxx.v6
19708 gdb.libstdcxx.v6.register_printers (gdb.current_objfile ())
19711 @node Commands In Python
19712 @subsubsection Commands In Python
19714 @cindex commands in python
19715 @cindex python commands
19716 You can implement new @value{GDBN} CLI commands in Python. A CLI
19717 command is implemented using an instance of the @code{gdb.Command}
19718 class, most commonly using a subclass.
19720 @defmethod Command __init__ name @var{command_class} @r{[}@var{completer_class}@r{]} @r{[}@var{prefix}@r{]}
19721 The object initializer for @code{Command} registers the new command
19722 with @value{GDBN}. This initializer is normally invoked from the
19723 subclass' own @code{__init__} method.
19725 @var{name} is the name of the command. If @var{name} consists of
19726 multiple words, then the initial words are looked for as prefix
19727 commands. In this case, if one of the prefix commands does not exist,
19728 an exception is raised.
19730 There is no support for multi-line commands.
19732 @var{command_class} should be one of the @samp{COMMAND_} constants
19733 defined below. This argument tells @value{GDBN} how to categorize the
19734 new command in the help system.
19736 @var{completer_class} is an optional argument. If given, it should be
19737 one of the @samp{COMPLETE_} constants defined below. This argument
19738 tells @value{GDBN} how to perform completion for this command. If not
19739 given, @value{GDBN} will attempt to complete using the object's
19740 @code{complete} method (see below); if no such method is found, an
19741 error will occur when completion is attempted.
19743 @var{prefix} is an optional argument. If @code{True}, then the new
19744 command is a prefix command; sub-commands of this command may be
19747 The help text for the new command is taken from the Python
19748 documentation string for the command's class, if there is one. If no
19749 documentation string is provided, the default value ``This command is
19750 not documented.'' is used.
19753 @cindex don't repeat Python command
19754 @defmethod Command dont_repeat
19755 By default, a @value{GDBN} command is repeated when the user enters a
19756 blank line at the command prompt. A command can suppress this
19757 behavior by invoking the @code{dont_repeat} method. This is similar
19758 to the user command @code{dont-repeat}, see @ref{Define, dont-repeat}.
19761 @defmethod Command invoke argument from_tty
19762 This method is called by @value{GDBN} when this command is invoked.
19764 @var{argument} is a string. It is the argument to the command, after
19765 leading and trailing whitespace has been stripped.
19767 @var{from_tty} is a boolean argument. When true, this means that the
19768 command was entered by the user at the terminal; when false it means
19769 that the command came from elsewhere.
19771 If this method throws an exception, it is turned into a @value{GDBN}
19772 @code{error} call. Otherwise, the return value is ignored.
19775 @cindex completion of Python commands
19776 @defmethod Command complete text word
19777 This method is called by @value{GDBN} when the user attempts
19778 completion on this command. All forms of completion are handled by
19779 this method, that is, the @key{TAB} and @key{M-?} key bindings
19780 (@pxref{Completion}), and the @code{complete} command (@pxref{Help,
19783 The arguments @var{text} and @var{word} are both strings. @var{text}
19784 holds the complete command line up to the cursor's location.
19785 @var{word} holds the last word of the command line; this is computed
19786 using a word-breaking heuristic.
19788 The @code{complete} method can return several values:
19791 If the return value is a sequence, the contents of the sequence are
19792 used as the completions. It is up to @code{complete} to ensure that the
19793 contents actually do complete the word. A zero-length sequence is
19794 allowed, it means that there were no completions available. Only
19795 string elements of the sequence are used; other elements in the
19796 sequence are ignored.
19799 If the return value is one of the @samp{COMPLETE_} constants defined
19800 below, then the corresponding @value{GDBN}-internal completion
19801 function is invoked, and its result is used.
19804 All other results are treated as though there were no available
19809 When a new command is registered, it must be declared as a member of
19810 some general class of commands. This is used to classify top-level
19811 commands in the on-line help system; note that prefix commands are not
19812 listed under their own category but rather that of their top-level
19813 command. The available classifications are represented by constants
19814 defined in the @code{gdb} module:
19817 @findex COMMAND_NONE
19818 @findex gdb.COMMAND_NONE
19820 The command does not belong to any particular class. A command in
19821 this category will not be displayed in any of the help categories.
19823 @findex COMMAND_RUNNING
19824 @findex gdb.COMMAND_RUNNING
19825 @item COMMAND_RUNNING
19826 The command is related to running the inferior. For example,
19827 @code{start}, @code{step}, and @code{continue} are in this category.
19828 Type @kbd{help running} at the @value{GDBN} prompt to see a list of
19829 commands in this category.
19831 @findex COMMAND_DATA
19832 @findex gdb.COMMAND_DATA
19834 The command is related to data or variables. For example,
19835 @code{call}, @code{find}, and @code{print} are in this category. Type
19836 @kbd{help data} at the @value{GDBN} prompt to see a list of commands
19839 @findex COMMAND_STACK
19840 @findex gdb.COMMAND_STACK
19841 @item COMMAND_STACK
19842 The command has to do with manipulation of the stack. For example,
19843 @code{backtrace}, @code{frame}, and @code{return} are in this
19844 category. Type @kbd{help stack} at the @value{GDBN} prompt to see a
19845 list of commands in this category.
19847 @findex COMMAND_FILES
19848 @findex gdb.COMMAND_FILES
19849 @item COMMAND_FILES
19850 This class is used for file-related commands. For example,
19851 @code{file}, @code{list} and @code{section} are in this category.
19852 Type @kbd{help files} at the @value{GDBN} prompt to see a list of
19853 commands in this category.
19855 @findex COMMAND_SUPPORT
19856 @findex gdb.COMMAND_SUPPORT
19857 @item COMMAND_SUPPORT
19858 This should be used for ``support facilities'', generally meaning
19859 things that are useful to the user when interacting with @value{GDBN},
19860 but not related to the state of the inferior. For example,
19861 @code{help}, @code{make}, and @code{shell} are in this category. Type
19862 @kbd{help support} at the @value{GDBN} prompt to see a list of
19863 commands in this category.
19865 @findex COMMAND_STATUS
19866 @findex gdb.COMMAND_STATUS
19867 @item COMMAND_STATUS
19868 The command is an @samp{info}-related command, that is, related to the
19869 state of @value{GDBN} itself. For example, @code{info}, @code{macro},
19870 and @code{show} are in this category. Type @kbd{help status} at the
19871 @value{GDBN} prompt to see a list of commands in this category.
19873 @findex COMMAND_BREAKPOINTS
19874 @findex gdb.COMMAND_BREAKPOINTS
19875 @item COMMAND_BREAKPOINTS
19876 The command has to do with breakpoints. For example, @code{break},
19877 @code{clear}, and @code{delete} are in this category. Type @kbd{help
19878 breakpoints} at the @value{GDBN} prompt to see a list of commands in
19881 @findex COMMAND_TRACEPOINTS
19882 @findex gdb.COMMAND_TRACEPOINTS
19883 @item COMMAND_TRACEPOINTS
19884 The command has to do with tracepoints. For example, @code{trace},
19885 @code{actions}, and @code{tfind} are in this category. Type
19886 @kbd{help tracepoints} at the @value{GDBN} prompt to see a list of
19887 commands in this category.
19889 @findex COMMAND_OBSCURE
19890 @findex gdb.COMMAND_OBSCURE
19891 @item COMMAND_OBSCURE
19892 The command is only used in unusual circumstances, or is not of
19893 general interest to users. For example, @code{checkpoint},
19894 @code{fork}, and @code{stop} are in this category. Type @kbd{help
19895 obscure} at the @value{GDBN} prompt to see a list of commands in this
19898 @findex COMMAND_MAINTENANCE
19899 @findex gdb.COMMAND_MAINTENANCE
19900 @item COMMAND_MAINTENANCE
19901 The command is only useful to @value{GDBN} maintainers. The
19902 @code{maintenance} and @code{flushregs} commands are in this category.
19903 Type @kbd{help internals} at the @value{GDBN} prompt to see a list of
19904 commands in this category.
19907 A new command can use a predefined completion function, either by
19908 specifying it via an argument at initialization, or by returning it
19909 from the @code{complete} method. These predefined completion
19910 constants are all defined in the @code{gdb} module:
19913 @findex COMPLETE_NONE
19914 @findex gdb.COMPLETE_NONE
19915 @item COMPLETE_NONE
19916 This constant means that no completion should be done.
19918 @findex COMPLETE_FILENAME
19919 @findex gdb.COMPLETE_FILENAME
19920 @item COMPLETE_FILENAME
19921 This constant means that filename completion should be performed.
19923 @findex COMPLETE_LOCATION
19924 @findex gdb.COMPLETE_LOCATION
19925 @item COMPLETE_LOCATION
19926 This constant means that location completion should be done.
19927 @xref{Specify Location}.
19929 @findex COMPLETE_COMMAND
19930 @findex gdb.COMPLETE_COMMAND
19931 @item COMPLETE_COMMAND
19932 This constant means that completion should examine @value{GDBN}
19935 @findex COMPLETE_SYMBOL
19936 @findex gdb.COMPLETE_SYMBOL
19937 @item COMPLETE_SYMBOL
19938 This constant means that completion should be done using symbol names
19942 The following code snippet shows how a trivial CLI command can be
19943 implemented in Python:
19946 class HelloWorld (gdb.Command):
19947 """Greet the whole world."""
19949 def __init__ (self):
19950 super (HelloWorld, self).__init__ ("hello-world", gdb.COMMAND_OBSCURE)
19952 def invoke (self, arg, from_tty):
19953 print "Hello, World!"
19958 The last line instantiates the class, and is necessary to trigger the
19959 registration of the command with @value{GDBN}. Depending on how the
19960 Python code is read into @value{GDBN}, you may need to import the
19961 @code{gdb} module explicitly.
19963 @node Functions In Python
19964 @subsubsection Writing new convenience functions
19966 @cindex writing convenience functions
19967 @cindex convenience functions in python
19968 @cindex python convenience functions
19969 @tindex gdb.Function
19971 You can implement new convenience functions (@pxref{Convenience Vars})
19972 in Python. A convenience function is an instance of a subclass of the
19973 class @code{gdb.Function}.
19975 @defmethod Function __init__ name
19976 The initializer for @code{Function} registers the new function with
19977 @value{GDBN}. The argument @var{name} is the name of the function,
19978 a string. The function will be visible to the user as a convenience
19979 variable of type @code{internal function}, whose name is the same as
19980 the given @var{name}.
19982 The documentation for the new function is taken from the documentation
19983 string for the new class.
19986 @defmethod Function invoke @var{*args}
19987 When a convenience function is evaluated, its arguments are converted
19988 to instances of @code{gdb.Value}, and then the function's
19989 @code{invoke} method is called. Note that @value{GDBN} does not
19990 predetermine the arity of convenience functions. Instead, all
19991 available arguments are passed to @code{invoke}, following the
19992 standard Python calling convention. In particular, a convenience
19993 function can have default values for parameters without ill effect.
19995 The return value of this method is used as its value in the enclosing
19996 expression. If an ordinary Python value is returned, it is converted
19997 to a @code{gdb.Value} following the usual rules.
20000 The following code snippet shows how a trivial convenience function can
20001 be implemented in Python:
20004 class Greet (gdb.Function):
20005 """Return string to greet someone.
20006 Takes a name as argument."""
20008 def __init__ (self):
20009 super (Greet, self).__init__ ("greet")
20011 def invoke (self, name):
20012 return "Hello, %s!" % name.string ()
20017 The last line instantiates the class, and is necessary to trigger the
20018 registration of the function with @value{GDBN}. Depending on how the
20019 Python code is read into @value{GDBN}, you may need to import the
20020 @code{gdb} module explicitly.
20022 @node Objfiles In Python
20023 @subsubsection Objfiles In Python
20025 @cindex objfiles in python
20026 @tindex gdb.Objfile
20028 @value{GDBN} loads symbols for an inferior from various
20029 symbol-containing files (@pxref{Files}). These include the primary
20030 executable file, any shared libraries used by the inferior, and any
20031 separate debug info files (@pxref{Separate Debug Files}).
20032 @value{GDBN} calls these symbol-containing files @dfn{objfiles}.
20034 The following objfile-related functions are available in the
20037 @findex gdb.current_objfile
20038 @defun current_objfile
20039 When auto-loading a Python script (@pxref{Auto-loading}), @value{GDBN}
20040 sets the ``current objfile'' to the corresponding objfile. This
20041 function returns the current objfile. If there is no current objfile,
20042 this function returns @code{None}.
20045 @findex gdb.objfiles
20047 Return a sequence of all the objfiles current known to @value{GDBN}.
20048 @xref{Objfiles In Python}.
20051 Each objfile is represented by an instance of the @code{gdb.Objfile}
20054 @defivar Objfile filename
20055 The file name of the objfile as a string.
20058 @defivar Objfile pretty_printers
20059 The @code{pretty_printers} attribute is a list of functions. It is
20060 used to look up pretty-printers. A @code{Value} is passed to each
20061 function in order; if the function returns @code{None}, then the
20062 search continues. Otherwise, the return value should be an object
20063 which is used to format the value. @xref{Pretty Printing}, for more
20067 @node Frames In Python
20068 @subsubsection Acessing inferior stack frames from Python.
20070 @cindex frames in python
20071 When the debugged program stops, @value{GDBN} is able to analyze its call
20072 stack (@pxref{Frames,,Stack frames}). The @code{gdb.Frame} class
20073 represents a frame in the stack. A @code{gdb.Frame} object is only valid
20074 while its corresponding frame exists in the inferior's stack. If you try
20075 to use an invalid frame object, @value{GDBN} will throw a @code{RuntimeError}
20078 Two @code{gdb.Frame} objects can be compared for equality with the @code{==}
20082 (@value{GDBP}) python print gdb.newest_frame() == gdb.selected_frame ()
20086 The following frame-related functions are available in the @code{gdb} module:
20088 @findex gdb.selected_frame
20089 @defun selected_frame
20090 Return the selected frame object. (@pxref{Selection,,Selecting a Frame}).
20093 @defun frame_stop_reason_string reason
20094 Return a string explaining the reason why @value{GDBN} stopped unwinding
20095 frames, as expressed by the given @var{reason} code (an integer, see the
20096 @code{unwind_stop_reason} method further down in this section).
20099 A @code{gdb.Frame} object has the following methods:
20102 @defmethod Frame is_valid
20103 Returns true if the @code{gdb.Frame} object is valid, false if not.
20104 A frame object can become invalid if the frame it refers to doesn't
20105 exist anymore in the inferior. All @code{gdb.Frame} methods will throw
20106 an exception if it is invalid at the time the method is called.
20109 @defmethod Frame name
20110 Returns the function name of the frame, or @code{None} if it can't be
20114 @defmethod Frame type
20115 Returns the type of the frame. The value can be one of
20116 @code{gdb.NORMAL_FRAME}, @code{gdb.DUMMY_FRAME}, @code{gdb.SIGTRAMP_FRAME}
20117 or @code{gdb.SENTINEL_FRAME}.
20120 @defmethod Frame unwind_stop_reason
20121 Return an integer representing the reason why it's not possible to find
20122 more frames toward the outermost frame. Use
20123 @code{gdb.frame_stop_reason_string} to convert the value returned by this
20124 function to a string.
20127 @defmethod Frame pc
20128 Returns the frame's resume address.
20131 @defmethod Frame older
20132 Return the frame that called this frame.
20135 @defmethod Frame newer
20136 Return the frame called by this frame.
20139 @defmethod Frame read_var variable
20140 Return the value of the given variable in this frame. @var{variable} must
20146 @chapter Command Interpreters
20147 @cindex command interpreters
20149 @value{GDBN} supports multiple command interpreters, and some command
20150 infrastructure to allow users or user interface writers to switch
20151 between interpreters or run commands in other interpreters.
20153 @value{GDBN} currently supports two command interpreters, the console
20154 interpreter (sometimes called the command-line interpreter or @sc{cli})
20155 and the machine interface interpreter (or @sc{gdb/mi}). This manual
20156 describes both of these interfaces in great detail.
20158 By default, @value{GDBN} will start with the console interpreter.
20159 However, the user may choose to start @value{GDBN} with another
20160 interpreter by specifying the @option{-i} or @option{--interpreter}
20161 startup options. Defined interpreters include:
20165 @cindex console interpreter
20166 The traditional console or command-line interpreter. This is the most often
20167 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
20168 @value{GDBN} will use this interpreter.
20171 @cindex mi interpreter
20172 The newest @sc{gdb/mi} interface (currently @code{mi2}). Used primarily
20173 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
20174 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
20178 @cindex mi2 interpreter
20179 The current @sc{gdb/mi} interface.
20182 @cindex mi1 interpreter
20183 The @sc{gdb/mi} interface included in @value{GDBN} 5.1, 5.2, and 5.3.
20187 @cindex invoke another interpreter
20188 The interpreter being used by @value{GDBN} may not be dynamically
20189 switched at runtime. Although possible, this could lead to a very
20190 precarious situation. Consider an IDE using @sc{gdb/mi}. If a user
20191 enters the command "interpreter-set console" in a console view,
20192 @value{GDBN} would switch to using the console interpreter, rendering
20193 the IDE inoperable!
20195 @kindex interpreter-exec
20196 Although you may only choose a single interpreter at startup, you may execute
20197 commands in any interpreter from the current interpreter using the appropriate
20198 command. If you are running the console interpreter, simply use the
20199 @code{interpreter-exec} command:
20202 interpreter-exec mi "-data-list-register-names"
20205 @sc{gdb/mi} has a similar command, although it is only available in versions of
20206 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
20209 @chapter @value{GDBN} Text User Interface
20211 @cindex Text User Interface
20214 * TUI Overview:: TUI overview
20215 * TUI Keys:: TUI key bindings
20216 * TUI Single Key Mode:: TUI single key mode
20217 * TUI Commands:: TUI-specific commands
20218 * TUI Configuration:: TUI configuration variables
20221 The @value{GDBN} Text User Interface (TUI) is a terminal
20222 interface which uses the @code{curses} library to show the source
20223 file, the assembly output, the program registers and @value{GDBN}
20224 commands in separate text windows. The TUI mode is supported only
20225 on platforms where a suitable version of the @code{curses} library
20228 @pindex @value{GDBTUI}
20229 The TUI mode is enabled by default when you invoke @value{GDBN} as
20230 either @samp{@value{GDBTUI}} or @samp{@value{GDBP} -tui}.
20231 You can also switch in and out of TUI mode while @value{GDBN} runs by
20232 using various TUI commands and key bindings, such as @kbd{C-x C-a}.
20233 @xref{TUI Keys, ,TUI Key Bindings}.
20236 @section TUI Overview
20238 In TUI mode, @value{GDBN} can display several text windows:
20242 This window is the @value{GDBN} command window with the @value{GDBN}
20243 prompt and the @value{GDBN} output. The @value{GDBN} input is still
20244 managed using readline.
20247 The source window shows the source file of the program. The current
20248 line and active breakpoints are displayed in this window.
20251 The assembly window shows the disassembly output of the program.
20254 This window shows the processor registers. Registers are highlighted
20255 when their values change.
20258 The source and assembly windows show the current program position
20259 by highlighting the current line and marking it with a @samp{>} marker.
20260 Breakpoints are indicated with two markers. The first marker
20261 indicates the breakpoint type:
20265 Breakpoint which was hit at least once.
20268 Breakpoint which was never hit.
20271 Hardware breakpoint which was hit at least once.
20274 Hardware breakpoint which was never hit.
20277 The second marker indicates whether the breakpoint is enabled or not:
20281 Breakpoint is enabled.
20284 Breakpoint is disabled.
20287 The source, assembly and register windows are updated when the current
20288 thread changes, when the frame changes, or when the program counter
20291 These windows are not all visible at the same time. The command
20292 window is always visible. The others can be arranged in several
20303 source and assembly,
20306 source and registers, or
20309 assembly and registers.
20312 A status line above the command window shows the following information:
20316 Indicates the current @value{GDBN} target.
20317 (@pxref{Targets, ,Specifying a Debugging Target}).
20320 Gives the current process or thread number.
20321 When no process is being debugged, this field is set to @code{No process}.
20324 Gives the current function name for the selected frame.
20325 The name is demangled if demangling is turned on (@pxref{Print Settings}).
20326 When there is no symbol corresponding to the current program counter,
20327 the string @code{??} is displayed.
20330 Indicates the current line number for the selected frame.
20331 When the current line number is not known, the string @code{??} is displayed.
20334 Indicates the current program counter address.
20338 @section TUI Key Bindings
20339 @cindex TUI key bindings
20341 The TUI installs several key bindings in the readline keymaps
20342 (@pxref{Command Line Editing}). The following key bindings
20343 are installed for both TUI mode and the @value{GDBN} standard mode.
20352 Enter or leave the TUI mode. When leaving the TUI mode,
20353 the curses window management stops and @value{GDBN} operates using
20354 its standard mode, writing on the terminal directly. When reentering
20355 the TUI mode, control is given back to the curses windows.
20356 The screen is then refreshed.
20360 Use a TUI layout with only one window. The layout will
20361 either be @samp{source} or @samp{assembly}. When the TUI mode
20362 is not active, it will switch to the TUI mode.
20364 Think of this key binding as the Emacs @kbd{C-x 1} binding.
20368 Use a TUI layout with at least two windows. When the current
20369 layout already has two windows, the next layout with two windows is used.
20370 When a new layout is chosen, one window will always be common to the
20371 previous layout and the new one.
20373 Think of it as the Emacs @kbd{C-x 2} binding.
20377 Change the active window. The TUI associates several key bindings
20378 (like scrolling and arrow keys) with the active window. This command
20379 gives the focus to the next TUI window.
20381 Think of it as the Emacs @kbd{C-x o} binding.
20385 Switch in and out of the TUI SingleKey mode that binds single
20386 keys to @value{GDBN} commands (@pxref{TUI Single Key Mode}).
20389 The following key bindings only work in the TUI mode:
20394 Scroll the active window one page up.
20398 Scroll the active window one page down.
20402 Scroll the active window one line up.
20406 Scroll the active window one line down.
20410 Scroll the active window one column left.
20414 Scroll the active window one column right.
20418 Refresh the screen.
20421 Because the arrow keys scroll the active window in the TUI mode, they
20422 are not available for their normal use by readline unless the command
20423 window has the focus. When another window is active, you must use
20424 other readline key bindings such as @kbd{C-p}, @kbd{C-n}, @kbd{C-b}
20425 and @kbd{C-f} to control the command window.
20427 @node TUI Single Key Mode
20428 @section TUI Single Key Mode
20429 @cindex TUI single key mode
20431 The TUI also provides a @dfn{SingleKey} mode, which binds several
20432 frequently used @value{GDBN} commands to single keys. Type @kbd{C-x s} to
20433 switch into this mode, where the following key bindings are used:
20436 @kindex c @r{(SingleKey TUI key)}
20440 @kindex d @r{(SingleKey TUI key)}
20444 @kindex f @r{(SingleKey TUI key)}
20448 @kindex n @r{(SingleKey TUI key)}
20452 @kindex q @r{(SingleKey TUI key)}
20454 exit the SingleKey mode.
20456 @kindex r @r{(SingleKey TUI key)}
20460 @kindex s @r{(SingleKey TUI key)}
20464 @kindex u @r{(SingleKey TUI key)}
20468 @kindex v @r{(SingleKey TUI key)}
20472 @kindex w @r{(SingleKey TUI key)}
20477 Other keys temporarily switch to the @value{GDBN} command prompt.
20478 The key that was pressed is inserted in the editing buffer so that
20479 it is possible to type most @value{GDBN} commands without interaction
20480 with the TUI SingleKey mode. Once the command is entered the TUI
20481 SingleKey mode is restored. The only way to permanently leave
20482 this mode is by typing @kbd{q} or @kbd{C-x s}.
20486 @section TUI-specific Commands
20487 @cindex TUI commands
20489 The TUI has specific commands to control the text windows.
20490 These commands are always available, even when @value{GDBN} is not in
20491 the TUI mode. When @value{GDBN} is in the standard mode, most
20492 of these commands will automatically switch to the TUI mode.
20497 List and give the size of all displayed windows.
20501 Display the next layout.
20504 Display the previous layout.
20507 Display the source window only.
20510 Display the assembly window only.
20513 Display the source and assembly window.
20516 Display the register window together with the source or assembly window.
20520 Make the next window active for scrolling.
20523 Make the previous window active for scrolling.
20526 Make the source window active for scrolling.
20529 Make the assembly window active for scrolling.
20532 Make the register window active for scrolling.
20535 Make the command window active for scrolling.
20539 Refresh the screen. This is similar to typing @kbd{C-L}.
20541 @item tui reg float
20543 Show the floating point registers in the register window.
20545 @item tui reg general
20546 Show the general registers in the register window.
20549 Show the next register group. The list of register groups as well as
20550 their order is target specific. The predefined register groups are the
20551 following: @code{general}, @code{float}, @code{system}, @code{vector},
20552 @code{all}, @code{save}, @code{restore}.
20554 @item tui reg system
20555 Show the system registers in the register window.
20559 Update the source window and the current execution point.
20561 @item winheight @var{name} +@var{count}
20562 @itemx winheight @var{name} -@var{count}
20564 Change the height of the window @var{name} by @var{count}
20565 lines. Positive counts increase the height, while negative counts
20568 @item tabset @var{nchars}
20570 Set the width of tab stops to be @var{nchars} characters.
20573 @node TUI Configuration
20574 @section TUI Configuration Variables
20575 @cindex TUI configuration variables
20577 Several configuration variables control the appearance of TUI windows.
20580 @item set tui border-kind @var{kind}
20581 @kindex set tui border-kind
20582 Select the border appearance for the source, assembly and register windows.
20583 The possible values are the following:
20586 Use a space character to draw the border.
20589 Use @sc{ascii} characters @samp{+}, @samp{-} and @samp{|} to draw the border.
20592 Use the Alternate Character Set to draw the border. The border is
20593 drawn using character line graphics if the terminal supports them.
20596 @item set tui border-mode @var{mode}
20597 @kindex set tui border-mode
20598 @itemx set tui active-border-mode @var{mode}
20599 @kindex set tui active-border-mode
20600 Select the display attributes for the borders of the inactive windows
20601 or the active window. The @var{mode} can be one of the following:
20604 Use normal attributes to display the border.
20610 Use reverse video mode.
20613 Use half bright mode.
20615 @item half-standout
20616 Use half bright and standout mode.
20619 Use extra bright or bold mode.
20621 @item bold-standout
20622 Use extra bright or bold and standout mode.
20627 @chapter Using @value{GDBN} under @sc{gnu} Emacs
20630 @cindex @sc{gnu} Emacs
20631 A special interface allows you to use @sc{gnu} Emacs to view (and
20632 edit) the source files for the program you are debugging with
20635 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
20636 executable file you want to debug as an argument. This command starts
20637 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
20638 created Emacs buffer.
20639 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
20641 Running @value{GDBN} under Emacs can be just like running @value{GDBN} normally except for two
20646 All ``terminal'' input and output goes through an Emacs buffer, called
20649 This applies both to @value{GDBN} commands and their output, and to the input
20650 and output done by the program you are debugging.
20652 This is useful because it means that you can copy the text of previous
20653 commands and input them again; you can even use parts of the output
20656 All the facilities of Emacs' Shell mode are available for interacting
20657 with your program. In particular, you can send signals the usual
20658 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
20662 @value{GDBN} displays source code through Emacs.
20664 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
20665 source file for that frame and puts an arrow (@samp{=>}) at the
20666 left margin of the current line. Emacs uses a separate buffer for
20667 source display, and splits the screen to show both your @value{GDBN} session
20670 Explicit @value{GDBN} @code{list} or search commands still produce output as
20671 usual, but you probably have no reason to use them from Emacs.
20674 We call this @dfn{text command mode}. Emacs 22.1, and later, also uses
20675 a graphical mode, enabled by default, which provides further buffers
20676 that can control the execution and describe the state of your program.
20677 @xref{GDB Graphical Interface,,, Emacs, The @sc{gnu} Emacs Manual}.
20679 If you specify an absolute file name when prompted for the @kbd{M-x
20680 gdb} argument, then Emacs sets your current working directory to where
20681 your program resides. If you only specify the file name, then Emacs
20682 sets your current working directory to to the directory associated
20683 with the previous buffer. In this case, @value{GDBN} may find your
20684 program by searching your environment's @code{PATH} variable, but on
20685 some operating systems it might not find the source. So, although the
20686 @value{GDBN} input and output session proceeds normally, the auxiliary
20687 buffer does not display the current source and line of execution.
20689 The initial working directory of @value{GDBN} is printed on the top
20690 line of the GUD buffer and this serves as a default for the commands
20691 that specify files for @value{GDBN} to operate on. @xref{Files,
20692 ,Commands to Specify Files}.
20694 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
20695 need to call @value{GDBN} by a different name (for example, if you
20696 keep several configurations around, with different names) you can
20697 customize the Emacs variable @code{gud-gdb-command-name} to run the
20700 In the GUD buffer, you can use these special Emacs commands in
20701 addition to the standard Shell mode commands:
20705 Describe the features of Emacs' GUD Mode.
20708 Execute to another source line, like the @value{GDBN} @code{step} command; also
20709 update the display window to show the current file and location.
20712 Execute to next source line in this function, skipping all function
20713 calls, like the @value{GDBN} @code{next} command. Then update the display window
20714 to show the current file and location.
20717 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
20718 display window accordingly.
20721 Execute until exit from the selected stack frame, like the @value{GDBN}
20722 @code{finish} command.
20725 Continue execution of your program, like the @value{GDBN} @code{continue}
20729 Go up the number of frames indicated by the numeric argument
20730 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
20731 like the @value{GDBN} @code{up} command.
20734 Go down the number of frames indicated by the numeric argument, like the
20735 @value{GDBN} @code{down} command.
20738 In any source file, the Emacs command @kbd{C-x @key{SPC}} (@code{gud-break})
20739 tells @value{GDBN} to set a breakpoint on the source line point is on.
20741 In text command mode, if you type @kbd{M-x speedbar}, Emacs displays a
20742 separate frame which shows a backtrace when the GUD buffer is current.
20743 Move point to any frame in the stack and type @key{RET} to make it
20744 become the current frame and display the associated source in the
20745 source buffer. Alternatively, click @kbd{Mouse-2} to make the
20746 selected frame become the current one. In graphical mode, the
20747 speedbar displays watch expressions.
20749 If you accidentally delete the source-display buffer, an easy way to get
20750 it back is to type the command @code{f} in the @value{GDBN} buffer, to
20751 request a frame display; when you run under Emacs, this recreates
20752 the source buffer if necessary to show you the context of the current
20755 The source files displayed in Emacs are in ordinary Emacs buffers
20756 which are visiting the source files in the usual way. You can edit
20757 the files with these buffers if you wish; but keep in mind that @value{GDBN}
20758 communicates with Emacs in terms of line numbers. If you add or
20759 delete lines from the text, the line numbers that @value{GDBN} knows cease
20760 to correspond properly with the code.
20762 A more detailed description of Emacs' interaction with @value{GDBN} is
20763 given in the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu}
20766 @c The following dropped because Epoch is nonstandard. Reactivate
20767 @c if/when v19 does something similar. ---doc@cygnus.com 19dec1990
20769 @kindex Emacs Epoch environment
20773 Version 18 of @sc{gnu} Emacs has a built-in window system
20774 called the @code{epoch}
20775 environment. Users of this environment can use a new command,
20776 @code{inspect} which performs identically to @code{print} except that
20777 each value is printed in its own window.
20782 @chapter The @sc{gdb/mi} Interface
20784 @unnumberedsec Function and Purpose
20786 @cindex @sc{gdb/mi}, its purpose
20787 @sc{gdb/mi} is a line based machine oriented text interface to
20788 @value{GDBN} and is activated by specifying using the
20789 @option{--interpreter} command line option (@pxref{Mode Options}). It
20790 is specifically intended to support the development of systems which
20791 use the debugger as just one small component of a larger system.
20793 This chapter is a specification of the @sc{gdb/mi} interface. It is written
20794 in the form of a reference manual.
20796 Note that @sc{gdb/mi} is still under construction, so some of the
20797 features described below are incomplete and subject to change
20798 (@pxref{GDB/MI Development and Front Ends, , @sc{gdb/mi} Development and Front Ends}).
20800 @unnumberedsec Notation and Terminology
20802 @cindex notational conventions, for @sc{gdb/mi}
20803 This chapter uses the following notation:
20807 @code{|} separates two alternatives.
20810 @code{[ @var{something} ]} indicates that @var{something} is optional:
20811 it may or may not be given.
20814 @code{( @var{group} )*} means that @var{group} inside the parentheses
20815 may repeat zero or more times.
20818 @code{( @var{group} )+} means that @var{group} inside the parentheses
20819 may repeat one or more times.
20822 @code{"@var{string}"} means a literal @var{string}.
20826 @heading Dependencies
20830 * GDB/MI General Design::
20831 * GDB/MI Command Syntax::
20832 * GDB/MI Compatibility with CLI::
20833 * GDB/MI Development and Front Ends::
20834 * GDB/MI Output Records::
20835 * GDB/MI Simple Examples::
20836 * GDB/MI Command Description Format::
20837 * GDB/MI Breakpoint Commands::
20838 * GDB/MI Program Context::
20839 * GDB/MI Thread Commands::
20840 * GDB/MI Program Execution::
20841 * GDB/MI Stack Manipulation::
20842 * GDB/MI Variable Objects::
20843 * GDB/MI Data Manipulation::
20844 * GDB/MI Tracepoint Commands::
20845 * GDB/MI Symbol Query::
20846 * GDB/MI File Commands::
20848 * GDB/MI Kod Commands::
20849 * GDB/MI Memory Overlay Commands::
20850 * GDB/MI Signal Handling Commands::
20852 * GDB/MI Target Manipulation::
20853 * GDB/MI File Transfer Commands::
20854 * GDB/MI Miscellaneous Commands::
20857 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20858 @node GDB/MI General Design
20859 @section @sc{gdb/mi} General Design
20860 @cindex GDB/MI General Design
20862 Interaction of a @sc{GDB/MI} frontend with @value{GDBN} involves three
20863 parts---commands sent to @value{GDBN}, responses to those commands
20864 and notifications. Each command results in exactly one response,
20865 indicating either successful completion of the command, or an error.
20866 For the commands that do not resume the target, the response contains the
20867 requested information. For the commands that resume the target, the
20868 response only indicates whether the target was successfully resumed.
20869 Notifications is the mechanism for reporting changes in the state of the
20870 target, or in @value{GDBN} state, that cannot conveniently be associated with
20871 a command and reported as part of that command response.
20873 The important examples of notifications are:
20877 Exec notifications. These are used to report changes in
20878 target state---when a target is resumed, or stopped. It would not
20879 be feasible to include this information in response of resuming
20880 commands, because one resume commands can result in multiple events in
20881 different threads. Also, quite some time may pass before any event
20882 happens in the target, while a frontend needs to know whether the resuming
20883 command itself was successfully executed.
20886 Console output, and status notifications. Console output
20887 notifications are used to report output of CLI commands, as well as
20888 diagnostics for other commands. Status notifications are used to
20889 report the progress of a long-running operation. Naturally, including
20890 this information in command response would mean no output is produced
20891 until the command is finished, which is undesirable.
20894 General notifications. Commands may have various side effects on
20895 the @value{GDBN} or target state beyond their official purpose. For example,
20896 a command may change the selected thread. Although such changes can
20897 be included in command response, using notification allows for more
20898 orthogonal frontend design.
20902 There's no guarantee that whenever an MI command reports an error,
20903 @value{GDBN} or the target are in any specific state, and especially,
20904 the state is not reverted to the state before the MI command was
20905 processed. Therefore, whenever an MI command results in an error,
20906 we recommend that the frontend refreshes all the information shown in
20907 the user interface.
20911 * Context management::
20912 * Asynchronous and non-stop modes::
20916 @node Context management
20917 @subsection Context management
20919 In most cases when @value{GDBN} accesses the target, this access is
20920 done in context of a specific thread and frame (@pxref{Frames}).
20921 Often, even when accessing global data, the target requires that a thread
20922 be specified. The CLI interface maintains the selected thread and frame,
20923 and supplies them to target on each command. This is convenient,
20924 because a command line user would not want to specify that information
20925 explicitly on each command, and because user interacts with
20926 @value{GDBN} via a single terminal, so no confusion is possible as
20927 to what thread and frame are the current ones.
20929 In the case of MI, the concept of selected thread and frame is less
20930 useful. First, a frontend can easily remember this information
20931 itself. Second, a graphical frontend can have more than one window,
20932 each one used for debugging a different thread, and the frontend might
20933 want to access additional threads for internal purposes. This
20934 increases the risk that by relying on implicitly selected thread, the
20935 frontend may be operating on a wrong one. Therefore, each MI command
20936 should explicitly specify which thread and frame to operate on. To
20937 make it possible, each MI command accepts the @samp{--thread} and
20938 @samp{--frame} options, the value to each is @value{GDBN} identifier
20939 for thread and frame to operate on.
20941 Usually, each top-level window in a frontend allows the user to select
20942 a thread and a frame, and remembers the user selection for further
20943 operations. However, in some cases @value{GDBN} may suggest that the
20944 current thread be changed. For example, when stopping on a breakpoint
20945 it is reasonable to switch to the thread where breakpoint is hit. For
20946 another example, if the user issues the CLI @samp{thread} command via
20947 the frontend, it is desirable to change the frontend's selected thread to the
20948 one specified by user. @value{GDBN} communicates the suggestion to
20949 change current thread using the @samp{=thread-selected} notification.
20950 No such notification is available for the selected frame at the moment.
20952 Note that historically, MI shares the selected thread with CLI, so
20953 frontends used the @code{-thread-select} to execute commands in the
20954 right context. However, getting this to work right is cumbersome. The
20955 simplest way is for frontend to emit @code{-thread-select} command
20956 before every command. This doubles the number of commands that need
20957 to be sent. The alternative approach is to suppress @code{-thread-select}
20958 if the selected thread in @value{GDBN} is supposed to be identical to the
20959 thread the frontend wants to operate on. However, getting this
20960 optimization right can be tricky. In particular, if the frontend
20961 sends several commands to @value{GDBN}, and one of the commands changes the
20962 selected thread, then the behaviour of subsequent commands will
20963 change. So, a frontend should either wait for response from such
20964 problematic commands, or explicitly add @code{-thread-select} for
20965 all subsequent commands. No frontend is known to do this exactly
20966 right, so it is suggested to just always pass the @samp{--thread} and
20967 @samp{--frame} options.
20969 @node Asynchronous and non-stop modes
20970 @subsection Asynchronous command execution and non-stop mode
20972 On some targets, @value{GDBN} is capable of processing MI commands
20973 even while the target is running. This is called @dfn{asynchronous
20974 command execution} (@pxref{Background Execution}). The frontend may
20975 specify a preferrence for asynchronous execution using the
20976 @code{-gdb-set target-async 1} command, which should be emitted before
20977 either running the executable or attaching to the target. After the
20978 frontend has started the executable or attached to the target, it can
20979 find if asynchronous execution is enabled using the
20980 @code{-list-target-features} command.
20982 Even if @value{GDBN} can accept a command while target is running,
20983 many commands that access the target do not work when the target is
20984 running. Therefore, asynchronous command execution is most useful
20985 when combined with non-stop mode (@pxref{Non-Stop Mode}). Then,
20986 it is possible to examine the state of one thread, while other threads
20989 When a given thread is running, MI commands that try to access the
20990 target in the context of that thread may not work, or may work only on
20991 some targets. In particular, commands that try to operate on thread's
20992 stack will not work, on any target. Commands that read memory, or
20993 modify breakpoints, may work or not work, depending on the target. Note
20994 that even commands that operate on global state, such as @code{print},
20995 @code{set}, and breakpoint commands, still access the target in the
20996 context of a specific thread, so frontend should try to find a
20997 stopped thread and perform the operation on that thread (using the
20998 @samp{--thread} option).
21000 Which commands will work in the context of a running thread is
21001 highly target dependent. However, the two commands
21002 @code{-exec-interrupt}, to stop a thread, and @code{-thread-info},
21003 to find the state of a thread, will always work.
21005 @node Thread groups
21006 @subsection Thread groups
21007 @value{GDBN} may be used to debug several processes at the same time.
21008 On some platfroms, @value{GDBN} may support debugging of several
21009 hardware systems, each one having several cores with several different
21010 processes running on each core. This section describes the MI
21011 mechanism to support such debugging scenarios.
21013 The key observation is that regardless of the structure of the
21014 target, MI can have a global list of threads, because most commands that
21015 accept the @samp{--thread} option do not need to know what process that
21016 thread belongs to. Therefore, it is not necessary to introduce
21017 neither additional @samp{--process} option, nor an notion of the
21018 current process in the MI interface. The only strictly new feature
21019 that is required is the ability to find how the threads are grouped
21022 To allow the user to discover such grouping, and to support arbitrary
21023 hierarchy of machines/cores/processes, MI introduces the concept of a
21024 @dfn{thread group}. Thread group is a collection of threads and other
21025 thread groups. A thread group always has a string identifier, a type,
21026 and may have additional attributes specific to the type. A new
21027 command, @code{-list-thread-groups}, returns the list of top-level
21028 thread groups, which correspond to processes that @value{GDBN} is
21029 debugging at the moment. By passing an identifier of a thread group
21030 to the @code{-list-thread-groups} command, it is possible to obtain
21031 the members of specific thread group.
21033 To allow the user to easily discover processes, and other objects, he
21034 wishes to debug, a concept of @dfn{available thread group} is
21035 introduced. Available thread group is an thread group that
21036 @value{GDBN} is not debugging, but that can be attached to, using the
21037 @code{-target-attach} command. The list of available top-level thread
21038 groups can be obtained using @samp{-list-thread-groups --available}.
21039 In general, the content of a thread group may be only retrieved only
21040 after attaching to that thread group.
21042 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
21043 @node GDB/MI Command Syntax
21044 @section @sc{gdb/mi} Command Syntax
21047 * GDB/MI Input Syntax::
21048 * GDB/MI Output Syntax::
21051 @node GDB/MI Input Syntax
21052 @subsection @sc{gdb/mi} Input Syntax
21054 @cindex input syntax for @sc{gdb/mi}
21055 @cindex @sc{gdb/mi}, input syntax
21057 @item @var{command} @expansion{}
21058 @code{@var{cli-command} | @var{mi-command}}
21060 @item @var{cli-command} @expansion{}
21061 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
21062 @var{cli-command} is any existing @value{GDBN} CLI command.
21064 @item @var{mi-command} @expansion{}
21065 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
21066 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
21068 @item @var{token} @expansion{}
21069 "any sequence of digits"
21071 @item @var{option} @expansion{}
21072 @code{"-" @var{parameter} [ " " @var{parameter} ]}
21074 @item @var{parameter} @expansion{}
21075 @code{@var{non-blank-sequence} | @var{c-string}}
21077 @item @var{operation} @expansion{}
21078 @emph{any of the operations described in this chapter}
21080 @item @var{non-blank-sequence} @expansion{}
21081 @emph{anything, provided it doesn't contain special characters such as
21082 "-", @var{nl}, """ and of course " "}
21084 @item @var{c-string} @expansion{}
21085 @code{""" @var{seven-bit-iso-c-string-content} """}
21087 @item @var{nl} @expansion{}
21096 The CLI commands are still handled by the @sc{mi} interpreter; their
21097 output is described below.
21100 The @code{@var{token}}, when present, is passed back when the command
21104 Some @sc{mi} commands accept optional arguments as part of the parameter
21105 list. Each option is identified by a leading @samp{-} (dash) and may be
21106 followed by an optional argument parameter. Options occur first in the
21107 parameter list and can be delimited from normal parameters using
21108 @samp{--} (this is useful when some parameters begin with a dash).
21115 We want easy access to the existing CLI syntax (for debugging).
21118 We want it to be easy to spot a @sc{mi} operation.
21121 @node GDB/MI Output Syntax
21122 @subsection @sc{gdb/mi} Output Syntax
21124 @cindex output syntax of @sc{gdb/mi}
21125 @cindex @sc{gdb/mi}, output syntax
21126 The output from @sc{gdb/mi} consists of zero or more out-of-band records
21127 followed, optionally, by a single result record. This result record
21128 is for the most recent command. The sequence of output records is
21129 terminated by @samp{(gdb)}.
21131 If an input command was prefixed with a @code{@var{token}} then the
21132 corresponding output for that command will also be prefixed by that same
21136 @item @var{output} @expansion{}
21137 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(gdb)" @var{nl}}
21139 @item @var{result-record} @expansion{}
21140 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
21142 @item @var{out-of-band-record} @expansion{}
21143 @code{@var{async-record} | @var{stream-record}}
21145 @item @var{async-record} @expansion{}
21146 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
21148 @item @var{exec-async-output} @expansion{}
21149 @code{[ @var{token} ] "*" @var{async-output}}
21151 @item @var{status-async-output} @expansion{}
21152 @code{[ @var{token} ] "+" @var{async-output}}
21154 @item @var{notify-async-output} @expansion{}
21155 @code{[ @var{token} ] "=" @var{async-output}}
21157 @item @var{async-output} @expansion{}
21158 @code{@var{async-class} ( "," @var{result} )* @var{nl}}
21160 @item @var{result-class} @expansion{}
21161 @code{"done" | "running" | "connected" | "error" | "exit"}
21163 @item @var{async-class} @expansion{}
21164 @code{"stopped" | @var{others}} (where @var{others} will be added
21165 depending on the needs---this is still in development).
21167 @item @var{result} @expansion{}
21168 @code{ @var{variable} "=" @var{value}}
21170 @item @var{variable} @expansion{}
21171 @code{ @var{string} }
21173 @item @var{value} @expansion{}
21174 @code{ @var{const} | @var{tuple} | @var{list} }
21176 @item @var{const} @expansion{}
21177 @code{@var{c-string}}
21179 @item @var{tuple} @expansion{}
21180 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
21182 @item @var{list} @expansion{}
21183 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
21184 @var{result} ( "," @var{result} )* "]" }
21186 @item @var{stream-record} @expansion{}
21187 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
21189 @item @var{console-stream-output} @expansion{}
21190 @code{"~" @var{c-string}}
21192 @item @var{target-stream-output} @expansion{}
21193 @code{"@@" @var{c-string}}
21195 @item @var{log-stream-output} @expansion{}
21196 @code{"&" @var{c-string}}
21198 @item @var{nl} @expansion{}
21201 @item @var{token} @expansion{}
21202 @emph{any sequence of digits}.
21210 All output sequences end in a single line containing a period.
21213 The @code{@var{token}} is from the corresponding request. Note that
21214 for all async output, while the token is allowed by the grammar and
21215 may be output by future versions of @value{GDBN} for select async
21216 output messages, it is generally omitted. Frontends should treat
21217 all async output as reporting general changes in the state of the
21218 target and there should be no need to associate async output to any
21222 @cindex status output in @sc{gdb/mi}
21223 @var{status-async-output} contains on-going status information about the
21224 progress of a slow operation. It can be discarded. All status output is
21225 prefixed by @samp{+}.
21228 @cindex async output in @sc{gdb/mi}
21229 @var{exec-async-output} contains asynchronous state change on the target
21230 (stopped, started, disappeared). All async output is prefixed by
21234 @cindex notify output in @sc{gdb/mi}
21235 @var{notify-async-output} contains supplementary information that the
21236 client should handle (e.g., a new breakpoint information). All notify
21237 output is prefixed by @samp{=}.
21240 @cindex console output in @sc{gdb/mi}
21241 @var{console-stream-output} is output that should be displayed as is in the
21242 console. It is the textual response to a CLI command. All the console
21243 output is prefixed by @samp{~}.
21246 @cindex target output in @sc{gdb/mi}
21247 @var{target-stream-output} is the output produced by the target program.
21248 All the target output is prefixed by @samp{@@}.
21251 @cindex log output in @sc{gdb/mi}
21252 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
21253 instance messages that should be displayed as part of an error log. All
21254 the log output is prefixed by @samp{&}.
21257 @cindex list output in @sc{gdb/mi}
21258 New @sc{gdb/mi} commands should only output @var{lists} containing
21264 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
21265 details about the various output records.
21267 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
21268 @node GDB/MI Compatibility with CLI
21269 @section @sc{gdb/mi} Compatibility with CLI
21271 @cindex compatibility, @sc{gdb/mi} and CLI
21272 @cindex @sc{gdb/mi}, compatibility with CLI
21274 For the developers convenience CLI commands can be entered directly,
21275 but there may be some unexpected behaviour. For example, commands
21276 that query the user will behave as if the user replied yes, breakpoint
21277 command lists are not executed and some CLI commands, such as
21278 @code{if}, @code{when} and @code{define}, prompt for further input with
21279 @samp{>}, which is not valid MI output.
21281 This feature may be removed at some stage in the future and it is
21282 recommended that front ends use the @code{-interpreter-exec} command
21283 (@pxref{-interpreter-exec}).
21285 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
21286 @node GDB/MI Development and Front Ends
21287 @section @sc{gdb/mi} Development and Front Ends
21288 @cindex @sc{gdb/mi} development
21290 The application which takes the MI output and presents the state of the
21291 program being debugged to the user is called a @dfn{front end}.
21293 Although @sc{gdb/mi} is still incomplete, it is currently being used
21294 by a variety of front ends to @value{GDBN}. This makes it difficult
21295 to introduce new functionality without breaking existing usage. This
21296 section tries to minimize the problems by describing how the protocol
21299 Some changes in MI need not break a carefully designed front end, and
21300 for these the MI version will remain unchanged. The following is a
21301 list of changes that may occur within one level, so front ends should
21302 parse MI output in a way that can handle them:
21306 New MI commands may be added.
21309 New fields may be added to the output of any MI command.
21312 The range of values for fields with specified values, e.g.,
21313 @code{in_scope} (@pxref{-var-update}) may be extended.
21315 @c The format of field's content e.g type prefix, may change so parse it
21316 @c at your own risk. Yes, in general?
21318 @c The order of fields may change? Shouldn't really matter but it might
21319 @c resolve inconsistencies.
21322 If the changes are likely to break front ends, the MI version level
21323 will be increased by one. This will allow the front end to parse the
21324 output according to the MI version. Apart from mi0, new versions of
21325 @value{GDBN} will not support old versions of MI and it will be the
21326 responsibility of the front end to work with the new one.
21328 @c Starting with mi3, add a new command -mi-version that prints the MI
21331 The best way to avoid unexpected changes in MI that might break your front
21332 end is to make your project known to @value{GDBN} developers and
21333 follow development on @email{gdb@@sourceware.org} and
21334 @email{gdb-patches@@sourceware.org}.
21335 @cindex mailing lists
21337 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
21338 @node GDB/MI Output Records
21339 @section @sc{gdb/mi} Output Records
21342 * GDB/MI Result Records::
21343 * GDB/MI Stream Records::
21344 * GDB/MI Async Records::
21345 * GDB/MI Frame Information::
21348 @node GDB/MI Result Records
21349 @subsection @sc{gdb/mi} Result Records
21351 @cindex result records in @sc{gdb/mi}
21352 @cindex @sc{gdb/mi}, result records
21353 In addition to a number of out-of-band notifications, the response to a
21354 @sc{gdb/mi} command includes one of the following result indications:
21358 @item "^done" [ "," @var{results} ]
21359 The synchronous operation was successful, @code{@var{results}} are the return
21364 @c Is this one correct? Should it be an out-of-band notification?
21365 The asynchronous operation was successfully started. The target is
21370 @value{GDBN} has connected to a remote target.
21372 @item "^error" "," @var{c-string}
21374 The operation failed. The @code{@var{c-string}} contains the corresponding
21379 @value{GDBN} has terminated.
21383 @node GDB/MI Stream Records
21384 @subsection @sc{gdb/mi} Stream Records
21386 @cindex @sc{gdb/mi}, stream records
21387 @cindex stream records in @sc{gdb/mi}
21388 @value{GDBN} internally maintains a number of output streams: the console, the
21389 target, and the log. The output intended for each of these streams is
21390 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
21392 Each stream record begins with a unique @dfn{prefix character} which
21393 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
21394 Syntax}). In addition to the prefix, each stream record contains a
21395 @code{@var{string-output}}. This is either raw text (with an implicit new
21396 line) or a quoted C string (which does not contain an implicit newline).
21399 @item "~" @var{string-output}
21400 The console output stream contains text that should be displayed in the
21401 CLI console window. It contains the textual responses to CLI commands.
21403 @item "@@" @var{string-output}
21404 The target output stream contains any textual output from the running
21405 target. This is only present when GDB's event loop is truly
21406 asynchronous, which is currently only the case for remote targets.
21408 @item "&" @var{string-output}
21409 The log stream contains debugging messages being produced by @value{GDBN}'s
21413 @node GDB/MI Async Records
21414 @subsection @sc{gdb/mi} Async Records
21416 @cindex async records in @sc{gdb/mi}
21417 @cindex @sc{gdb/mi}, async records
21418 @dfn{Async} records are used to notify the @sc{gdb/mi} client of
21419 additional changes that have occurred. Those changes can either be a
21420 consequence of @sc{gdb/mi} commands (e.g., a breakpoint modified) or a result of
21421 target activity (e.g., target stopped).
21423 The following is the list of possible async records:
21427 @item *running,thread-id="@var{thread}"
21428 The target is now running. The @var{thread} field tells which
21429 specific thread is now running, and can be @samp{all} if all threads
21430 are running. The frontend should assume that no interaction with a
21431 running thread is possible after this notification is produced.
21432 The frontend should not assume that this notification is output
21433 only once for any command. @value{GDBN} may emit this notification
21434 several times, either for different threads, because it cannot resume
21435 all threads together, or even for a single thread, if the thread must
21436 be stepped though some code before letting it run freely.
21438 @item *stopped,reason="@var{reason}",thread-id="@var{id}",stopped-threads="@var{stopped}"
21439 The target has stopped. The @var{reason} field can have one of the
21443 @item breakpoint-hit
21444 A breakpoint was reached.
21445 @item watchpoint-trigger
21446 A watchpoint was triggered.
21447 @item read-watchpoint-trigger
21448 A read watchpoint was triggered.
21449 @item access-watchpoint-trigger
21450 An access watchpoint was triggered.
21451 @item function-finished
21452 An -exec-finish or similar CLI command was accomplished.
21453 @item location-reached
21454 An -exec-until or similar CLI command was accomplished.
21455 @item watchpoint-scope
21456 A watchpoint has gone out of scope.
21457 @item end-stepping-range
21458 An -exec-next, -exec-next-instruction, -exec-step, -exec-step-instruction or
21459 similar CLI command was accomplished.
21460 @item exited-signalled
21461 The inferior exited because of a signal.
21463 The inferior exited.
21464 @item exited-normally
21465 The inferior exited normally.
21466 @item signal-received
21467 A signal was received by the inferior.
21470 The @var{id} field identifies the thread that directly caused the stop
21471 -- for example by hitting a breakpoint. Depending on whether all-stop
21472 mode is in effect (@pxref{All-Stop Mode}), @value{GDBN} may either
21473 stop all threads, or only the thread that directly triggered the stop.
21474 If all threads are stopped, the @var{stopped} field will have the
21475 value of @code{"all"}. Otherwise, the value of the @var{stopped}
21476 field will be a list of thread identifiers. Presently, this list will
21477 always include a single thread, but frontend should be prepared to see
21478 several threads in the list.
21480 @item =thread-group-created,id="@var{id}"
21481 @itemx =thread-group-exited,id="@var{id}"
21482 A thread thread group either was attached to, or has exited/detached
21483 from. The @var{id} field contains the @value{GDBN} identifier of the
21486 @item =thread-created,id="@var{id}",group-id="@var{gid}"
21487 @itemx =thread-exited,id="@var{id}",group-id="@var{gid}"
21488 A thread either was created, or has exited. The @var{id} field
21489 contains the @value{GDBN} identifier of the thread. The @var{gid}
21490 field identifies the thread group this thread belongs to.
21492 @item =thread-selected,id="@var{id}"
21493 Informs that the selected thread was changed as result of the last
21494 command. This notification is not emitted as result of @code{-thread-select}
21495 command but is emitted whenever an MI command that is not documented
21496 to change the selected thread actually changes it. In particular,
21497 invoking, directly or indirectly (via user-defined command), the CLI
21498 @code{thread} command, will generate this notification.
21500 We suggest that in response to this notification, front ends
21501 highlight the selected thread and cause subsequent commands to apply to
21504 @item =library-loaded,...
21505 Reports that a new library file was loaded by the program. This
21506 notification has 4 fields---@var{id}, @var{target-name},
21507 @var{host-name}, and @var{symbols-loaded}. The @var{id} field is an
21508 opaque identifier of the library. For remote debugging case,
21509 @var{target-name} and @var{host-name} fields give the name of the
21510 library file on the target, and on the host respectively. For native
21511 debugging, both those fields have the same value. The
21512 @var{symbols-loaded} field reports if the debug symbols for this
21513 library are loaded.
21515 @item =library-unloaded,...
21516 Reports that a library was unloaded by the program. This notification
21517 has 3 fields---@var{id}, @var{target-name} and @var{host-name} with
21518 the same meaning as for the @code{=library-loaded} notification
21522 @node GDB/MI Frame Information
21523 @subsection @sc{gdb/mi} Frame Information
21525 Response from many MI commands includes an information about stack
21526 frame. This information is a tuple that may have the following
21531 The level of the stack frame. The innermost frame has the level of
21532 zero. This field is always present.
21535 The name of the function corresponding to the frame. This field may
21536 be absent if @value{GDBN} is unable to determine the function name.
21539 The code address for the frame. This field is always present.
21542 The name of the source files that correspond to the frame's code
21543 address. This field may be absent.
21546 The source line corresponding to the frames' code address. This field
21550 The name of the binary file (either executable or shared library) the
21551 corresponds to the frame's code address. This field may be absent.
21556 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
21557 @node GDB/MI Simple Examples
21558 @section Simple Examples of @sc{gdb/mi} Interaction
21559 @cindex @sc{gdb/mi}, simple examples
21561 This subsection presents several simple examples of interaction using
21562 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
21563 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
21564 the output received from @sc{gdb/mi}.
21566 Note the line breaks shown in the examples are here only for
21567 readability, they don't appear in the real output.
21569 @subheading Setting a Breakpoint
21571 Setting a breakpoint generates synchronous output which contains detailed
21572 information of the breakpoint.
21575 -> -break-insert main
21576 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
21577 enabled="y",addr="0x08048564",func="main",file="myprog.c",
21578 fullname="/home/nickrob/myprog.c",line="68",times="0"@}
21582 @subheading Program Execution
21584 Program execution generates asynchronous records and MI gives the
21585 reason that execution stopped.
21591 <- *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
21592 frame=@{addr="0x08048564",func="main",
21593 args=[@{name="argc",value="1"@},@{name="argv",value="0xbfc4d4d4"@}],
21594 file="myprog.c",fullname="/home/nickrob/myprog.c",line="68"@}
21599 <- *stopped,reason="exited-normally"
21603 @subheading Quitting @value{GDBN}
21605 Quitting @value{GDBN} just prints the result class @samp{^exit}.
21613 @subheading A Bad Command
21615 Here's what happens if you pass a non-existent command:
21619 <- ^error,msg="Undefined MI command: rubbish"
21624 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
21625 @node GDB/MI Command Description Format
21626 @section @sc{gdb/mi} Command Description Format
21628 The remaining sections describe blocks of commands. Each block of
21629 commands is laid out in a fashion similar to this section.
21631 @subheading Motivation
21633 The motivation for this collection of commands.
21635 @subheading Introduction
21637 A brief introduction to this collection of commands as a whole.
21639 @subheading Commands
21641 For each command in the block, the following is described:
21643 @subsubheading Synopsis
21646 -command @var{args}@dots{}
21649 @subsubheading Result
21651 @subsubheading @value{GDBN} Command
21653 The corresponding @value{GDBN} CLI command(s), if any.
21655 @subsubheading Example
21657 Example(s) formatted for readability. Some of the described commands have
21658 not been implemented yet and these are labeled N.A.@: (not available).
21661 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
21662 @node GDB/MI Breakpoint Commands
21663 @section @sc{gdb/mi} Breakpoint Commands
21665 @cindex breakpoint commands for @sc{gdb/mi}
21666 @cindex @sc{gdb/mi}, breakpoint commands
21667 This section documents @sc{gdb/mi} commands for manipulating
21670 @subheading The @code{-break-after} Command
21671 @findex -break-after
21673 @subsubheading Synopsis
21676 -break-after @var{number} @var{count}
21679 The breakpoint number @var{number} is not in effect until it has been
21680 hit @var{count} times. To see how this is reflected in the output of
21681 the @samp{-break-list} command, see the description of the
21682 @samp{-break-list} command below.
21684 @subsubheading @value{GDBN} Command
21686 The corresponding @value{GDBN} command is @samp{ignore}.
21688 @subsubheading Example
21693 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
21694 enabled="y",addr="0x000100d0",func="main",file="hello.c",
21695 fullname="/home/foo/hello.c",line="5",times="0"@}
21702 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
21703 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
21704 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
21705 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
21706 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
21707 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
21708 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
21709 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
21710 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
21711 line="5",times="0",ignore="3"@}]@}
21716 @subheading The @code{-break-catch} Command
21717 @findex -break-catch
21720 @subheading The @code{-break-commands} Command
21721 @findex -break-commands
21723 @subsubheading Synopsis
21726 -break-commands @var{number} [ @var{command1} ... @var{commandN} ]
21729 Specifies the CLI commands that should be executed when breakpoint
21730 @var{number} is hit. The parameters @var{command1} to @var{commandN}
21731 are the commands. If no command is specified, any previously-set
21732 commands are cleared. @xref{Break Commands}. Typical use of this
21733 functionality is tracing a program, that is, printing of values of
21734 some variables whenever breakpoint is hit and then continuing.
21736 @subsubheading @value{GDBN} Command
21738 The corresponding @value{GDBN} command is @samp{commands}.
21740 @subsubheading Example
21745 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
21746 enabled="y",addr="0x000100d0",func="main",file="hello.c",
21747 fullname="/home/foo/hello.c",line="5",times="0"@}
21749 -break-commands 1 "print v" "continue"
21754 @subheading The @code{-break-condition} Command
21755 @findex -break-condition
21757 @subsubheading Synopsis
21760 -break-condition @var{number} @var{expr}
21763 Breakpoint @var{number} will stop the program only if the condition in
21764 @var{expr} is true. The condition becomes part of the
21765 @samp{-break-list} output (see the description of the @samp{-break-list}
21768 @subsubheading @value{GDBN} Command
21770 The corresponding @value{GDBN} command is @samp{condition}.
21772 @subsubheading Example
21776 -break-condition 1 1
21780 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
21781 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
21782 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
21783 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
21784 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
21785 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
21786 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
21787 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
21788 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
21789 line="5",cond="1",times="0",ignore="3"@}]@}
21793 @subheading The @code{-break-delete} Command
21794 @findex -break-delete
21796 @subsubheading Synopsis
21799 -break-delete ( @var{breakpoint} )+
21802 Delete the breakpoint(s) whose number(s) are specified in the argument
21803 list. This is obviously reflected in the breakpoint list.
21805 @subsubheading @value{GDBN} Command
21807 The corresponding @value{GDBN} command is @samp{delete}.
21809 @subsubheading Example
21817 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
21818 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
21819 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
21820 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
21821 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
21822 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
21823 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
21828 @subheading The @code{-break-disable} Command
21829 @findex -break-disable
21831 @subsubheading Synopsis
21834 -break-disable ( @var{breakpoint} )+
21837 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
21838 break list is now set to @samp{n} for the named @var{breakpoint}(s).
21840 @subsubheading @value{GDBN} Command
21842 The corresponding @value{GDBN} command is @samp{disable}.
21844 @subsubheading Example
21852 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
21853 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
21854 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
21855 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
21856 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
21857 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
21858 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
21859 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
21860 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
21861 line="5",times="0"@}]@}
21865 @subheading The @code{-break-enable} Command
21866 @findex -break-enable
21868 @subsubheading Synopsis
21871 -break-enable ( @var{breakpoint} )+
21874 Enable (previously disabled) @var{breakpoint}(s).
21876 @subsubheading @value{GDBN} Command
21878 The corresponding @value{GDBN} command is @samp{enable}.
21880 @subsubheading Example
21888 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
21889 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
21890 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
21891 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
21892 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
21893 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
21894 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
21895 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
21896 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
21897 line="5",times="0"@}]@}
21901 @subheading The @code{-break-info} Command
21902 @findex -break-info
21904 @subsubheading Synopsis
21907 -break-info @var{breakpoint}
21911 Get information about a single breakpoint.
21913 @subsubheading @value{GDBN} Command
21915 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
21917 @subsubheading Example
21920 @subheading The @code{-break-insert} Command
21921 @findex -break-insert
21923 @subsubheading Synopsis
21926 -break-insert [ -t ] [ -h ] [ -f ] [ -d ]
21927 [ -c @var{condition} ] [ -i @var{ignore-count} ]
21928 [ -p @var{thread} ] [ @var{location} ]
21932 If specified, @var{location}, can be one of:
21939 @item filename:linenum
21940 @item filename:function
21944 The possible optional parameters of this command are:
21948 Insert a temporary breakpoint.
21950 Insert a hardware breakpoint.
21951 @item -c @var{condition}
21952 Make the breakpoint conditional on @var{condition}.
21953 @item -i @var{ignore-count}
21954 Initialize the @var{ignore-count}.
21956 If @var{location} cannot be parsed (for example if it
21957 refers to unknown files or functions), create a pending
21958 breakpoint. Without this flag, @value{GDBN} will report
21959 an error, and won't create a breakpoint, if @var{location}
21962 Create a disabled breakpoint.
21965 @subsubheading Result
21967 The result is in the form:
21970 ^done,bkpt=@{number="@var{number}",type="@var{type}",disp="del"|"keep",
21971 enabled="y"|"n",addr="@var{hex}",func="@var{funcname}",file="@var{filename}",
21972 fullname="@var{full_filename}",line="@var{lineno}",[thread="@var{threadno},]
21973 times="@var{times}"@}
21977 where @var{number} is the @value{GDBN} number for this breakpoint,
21978 @var{funcname} is the name of the function where the breakpoint was
21979 inserted, @var{filename} is the name of the source file which contains
21980 this function, @var{lineno} is the source line number within that file
21981 and @var{times} the number of times that the breakpoint has been hit
21982 (always 0 for -break-insert but may be greater for -break-info or -break-list
21983 which use the same output).
21985 Note: this format is open to change.
21986 @c An out-of-band breakpoint instead of part of the result?
21988 @subsubheading @value{GDBN} Command
21990 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
21991 @samp{hbreak}, @samp{thbreak}, and @samp{rbreak}.
21993 @subsubheading Example
21998 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",
21999 fullname="/home/foo/recursive2.c,line="4",times="0"@}
22001 -break-insert -t foo
22002 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",
22003 fullname="/home/foo/recursive2.c,line="11",times="0"@}
22006 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
22007 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
22008 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
22009 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
22010 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
22011 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
22012 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
22013 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
22014 addr="0x0001072c", func="main",file="recursive2.c",
22015 fullname="/home/foo/recursive2.c,"line="4",times="0"@},
22016 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
22017 addr="0x00010774",func="foo",file="recursive2.c",
22018 fullname="/home/foo/recursive2.c",line="11",times="0"@}]@}
22020 -break-insert -r foo.*
22021 ~int foo(int, int);
22022 ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c,
22023 "fullname="/home/foo/recursive2.c",line="11",times="0"@}
22027 @subheading The @code{-break-list} Command
22028 @findex -break-list
22030 @subsubheading Synopsis
22036 Displays the list of inserted breakpoints, showing the following fields:
22040 number of the breakpoint
22042 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
22044 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
22047 is the breakpoint enabled or no: @samp{y} or @samp{n}
22049 memory location at which the breakpoint is set
22051 logical location of the breakpoint, expressed by function name, file
22054 number of times the breakpoint has been hit
22057 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
22058 @code{body} field is an empty list.
22060 @subsubheading @value{GDBN} Command
22062 The corresponding @value{GDBN} command is @samp{info break}.
22064 @subsubheading Example
22069 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
22070 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
22071 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
22072 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
22073 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
22074 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
22075 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
22076 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
22077 addr="0x000100d0",func="main",file="hello.c",line="5",times="0"@},
22078 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
22079 addr="0x00010114",func="foo",file="hello.c",fullname="/home/foo/hello.c",
22080 line="13",times="0"@}]@}
22084 Here's an example of the result when there are no breakpoints:
22089 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
22090 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
22091 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
22092 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
22093 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
22094 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
22095 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
22100 @subheading The @code{-break-watch} Command
22101 @findex -break-watch
22103 @subsubheading Synopsis
22106 -break-watch [ -a | -r ]
22109 Create a watchpoint. With the @samp{-a} option it will create an
22110 @dfn{access} watchpoint, i.e., a watchpoint that triggers either on a
22111 read from or on a write to the memory location. With the @samp{-r}
22112 option, the watchpoint created is a @dfn{read} watchpoint, i.e., it will
22113 trigger only when the memory location is accessed for reading. Without
22114 either of the options, the watchpoint created is a regular watchpoint,
22115 i.e., it will trigger when the memory location is accessed for writing.
22116 @xref{Set Watchpoints, , Setting Watchpoints}.
22118 Note that @samp{-break-list} will report a single list of watchpoints and
22119 breakpoints inserted.
22121 @subsubheading @value{GDBN} Command
22123 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
22126 @subsubheading Example
22128 Setting a watchpoint on a variable in the @code{main} function:
22133 ^done,wpt=@{number="2",exp="x"@}
22138 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
22139 value=@{old="-268439212",new="55"@},
22140 frame=@{func="main",args=[],file="recursive2.c",
22141 fullname="/home/foo/bar/recursive2.c",line="5"@}
22145 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
22146 the program execution twice: first for the variable changing value, then
22147 for the watchpoint going out of scope.
22152 ^done,wpt=@{number="5",exp="C"@}
22157 *stopped,reason="watchpoint-trigger",
22158 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
22159 frame=@{func="callee4",args=[],
22160 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
22161 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
22166 *stopped,reason="watchpoint-scope",wpnum="5",
22167 frame=@{func="callee3",args=[@{name="strarg",
22168 value="0x11940 \"A string argument.\""@}],
22169 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
22170 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
22174 Listing breakpoints and watchpoints, at different points in the program
22175 execution. Note that once the watchpoint goes out of scope, it is
22181 ^done,wpt=@{number="2",exp="C"@}
22184 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
22185 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
22186 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
22187 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
22188 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
22189 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
22190 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
22191 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
22192 addr="0x00010734",func="callee4",
22193 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
22194 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c"line="8",times="1"@},
22195 bkpt=@{number="2",type="watchpoint",disp="keep",
22196 enabled="y",addr="",what="C",times="0"@}]@}
22201 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
22202 value=@{old="-276895068",new="3"@},
22203 frame=@{func="callee4",args=[],
22204 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
22205 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
22208 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
22209 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
22210 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
22211 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
22212 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
22213 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
22214 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
22215 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
22216 addr="0x00010734",func="callee4",
22217 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
22218 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",times="1"@},
22219 bkpt=@{number="2",type="watchpoint",disp="keep",
22220 enabled="y",addr="",what="C",times="-5"@}]@}
22224 ^done,reason="watchpoint-scope",wpnum="2",
22225 frame=@{func="callee3",args=[@{name="strarg",
22226 value="0x11940 \"A string argument.\""@}],
22227 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
22228 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
22231 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
22232 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
22233 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
22234 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
22235 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
22236 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
22237 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
22238 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
22239 addr="0x00010734",func="callee4",
22240 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
22241 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
22246 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
22247 @node GDB/MI Program Context
22248 @section @sc{gdb/mi} Program Context
22250 @subheading The @code{-exec-arguments} Command
22251 @findex -exec-arguments
22254 @subsubheading Synopsis
22257 -exec-arguments @var{args}
22260 Set the inferior program arguments, to be used in the next
22263 @subsubheading @value{GDBN} Command
22265 The corresponding @value{GDBN} command is @samp{set args}.
22267 @subsubheading Example
22271 -exec-arguments -v word
22278 @subheading The @code{-exec-show-arguments} Command
22279 @findex -exec-show-arguments
22281 @subsubheading Synopsis
22284 -exec-show-arguments
22287 Print the arguments of the program.
22289 @subsubheading @value{GDBN} Command
22291 The corresponding @value{GDBN} command is @samp{show args}.
22293 @subsubheading Example
22298 @subheading The @code{-environment-cd} Command
22299 @findex -environment-cd
22301 @subsubheading Synopsis
22304 -environment-cd @var{pathdir}
22307 Set @value{GDBN}'s working directory.
22309 @subsubheading @value{GDBN} Command
22311 The corresponding @value{GDBN} command is @samp{cd}.
22313 @subsubheading Example
22317 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
22323 @subheading The @code{-environment-directory} Command
22324 @findex -environment-directory
22326 @subsubheading Synopsis
22329 -environment-directory [ -r ] [ @var{pathdir} ]+
22332 Add directories @var{pathdir} to beginning of search path for source files.
22333 If the @samp{-r} option is used, the search path is reset to the default
22334 search path. If directories @var{pathdir} are supplied in addition to the
22335 @samp{-r} option, the search path is first reset and then addition
22337 Multiple directories may be specified, separated by blanks. Specifying
22338 multiple directories in a single command
22339 results in the directories added to the beginning of the
22340 search path in the same order they were presented in the command.
22341 If blanks are needed as
22342 part of a directory name, double-quotes should be used around
22343 the name. In the command output, the path will show up separated
22344 by the system directory-separator character. The directory-separator
22345 character must not be used
22346 in any directory name.
22347 If no directories are specified, the current search path is displayed.
22349 @subsubheading @value{GDBN} Command
22351 The corresponding @value{GDBN} command is @samp{dir}.
22353 @subsubheading Example
22357 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
22358 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
22360 -environment-directory ""
22361 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
22363 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
22364 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
22366 -environment-directory -r
22367 ^done,source-path="$cdir:$cwd"
22372 @subheading The @code{-environment-path} Command
22373 @findex -environment-path
22375 @subsubheading Synopsis
22378 -environment-path [ -r ] [ @var{pathdir} ]+
22381 Add directories @var{pathdir} to beginning of search path for object files.
22382 If the @samp{-r} option is used, the search path is reset to the original
22383 search path that existed at gdb start-up. If directories @var{pathdir} are
22384 supplied in addition to the
22385 @samp{-r} option, the search path is first reset and then addition
22387 Multiple directories may be specified, separated by blanks. Specifying
22388 multiple directories in a single command
22389 results in the directories added to the beginning of the
22390 search path in the same order they were presented in the command.
22391 If blanks are needed as
22392 part of a directory name, double-quotes should be used around
22393 the name. In the command output, the path will show up separated
22394 by the system directory-separator character. The directory-separator
22395 character must not be used
22396 in any directory name.
22397 If no directories are specified, the current path is displayed.
22400 @subsubheading @value{GDBN} Command
22402 The corresponding @value{GDBN} command is @samp{path}.
22404 @subsubheading Example
22409 ^done,path="/usr/bin"
22411 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
22412 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
22414 -environment-path -r /usr/local/bin
22415 ^done,path="/usr/local/bin:/usr/bin"
22420 @subheading The @code{-environment-pwd} Command
22421 @findex -environment-pwd
22423 @subsubheading Synopsis
22429 Show the current working directory.
22431 @subsubheading @value{GDBN} Command
22433 The corresponding @value{GDBN} command is @samp{pwd}.
22435 @subsubheading Example
22440 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
22444 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
22445 @node GDB/MI Thread Commands
22446 @section @sc{gdb/mi} Thread Commands
22449 @subheading The @code{-thread-info} Command
22450 @findex -thread-info
22452 @subsubheading Synopsis
22455 -thread-info [ @var{thread-id} ]
22458 Reports information about either a specific thread, if
22459 the @var{thread-id} parameter is present, or about all
22460 threads. When printing information about all threads,
22461 also reports the current thread.
22463 @subsubheading @value{GDBN} Command
22465 The @samp{info thread} command prints the same information
22468 @subsubheading Example
22473 @{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
22474 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},state="running"@},
22475 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
22476 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
22477 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},state="running"@}],
22478 current-thread-id="1"
22482 The @samp{state} field may have the following values:
22486 The thread is stopped. Frame information is available for stopped
22490 The thread is running. There's no frame information for running
22495 @subheading The @code{-thread-list-ids} Command
22496 @findex -thread-list-ids
22498 @subsubheading Synopsis
22504 Produces a list of the currently known @value{GDBN} thread ids. At the
22505 end of the list it also prints the total number of such threads.
22507 This command is retained for historical reasons, the
22508 @code{-thread-info} command should be used instead.
22510 @subsubheading @value{GDBN} Command
22512 Part of @samp{info threads} supplies the same information.
22514 @subsubheading Example
22519 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
22520 current-thread-id="1",number-of-threads="3"
22525 @subheading The @code{-thread-select} Command
22526 @findex -thread-select
22528 @subsubheading Synopsis
22531 -thread-select @var{threadnum}
22534 Make @var{threadnum} the current thread. It prints the number of the new
22535 current thread, and the topmost frame for that thread.
22537 This command is deprecated in favor of explicitly using the
22538 @samp{--thread} option to each command.
22540 @subsubheading @value{GDBN} Command
22542 The corresponding @value{GDBN} command is @samp{thread}.
22544 @subsubheading Example
22551 *stopped,reason="end-stepping-range",thread-id="2",line="187",
22552 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
22556 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
22557 number-of-threads="3"
22560 ^done,new-thread-id="3",
22561 frame=@{level="0",func="vprintf",
22562 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
22563 @{name="arg",value="0x2"@}],file="vprintf.c",line="31"@}
22567 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
22568 @node GDB/MI Program Execution
22569 @section @sc{gdb/mi} Program Execution
22571 These are the asynchronous commands which generate the out-of-band
22572 record @samp{*stopped}. Currently @value{GDBN} only really executes
22573 asynchronously with remote targets and this interaction is mimicked in
22576 @subheading The @code{-exec-continue} Command
22577 @findex -exec-continue
22579 @subsubheading Synopsis
22582 -exec-continue [--all|--thread-group N]
22585 Resumes the execution of the inferior program until a breakpoint is
22586 encountered, or until the inferior exits. In all-stop mode
22587 (@pxref{All-Stop Mode}), may resume only one thread, or all threads,
22588 depending on the value of the @samp{scheduler-locking} variable. In
22589 non-stop mode (@pxref{Non-Stop Mode}), if the @samp{--all} is not
22590 specified, only the thread specified with the @samp{--thread} option
22591 (or current thread, if no @samp{--thread} is provided) is resumed. If
22592 @samp{--all} is specified, all threads will be resumed. The
22593 @samp{--all} option is ignored in all-stop mode. If the
22594 @samp{--thread-group} options is specified, then all threads in that
22595 thread group are resumed.
22597 @subsubheading @value{GDBN} Command
22599 The corresponding @value{GDBN} corresponding is @samp{continue}.
22601 @subsubheading Example
22608 *stopped,reason="breakpoint-hit",disp="keep",bkptno="2",frame=@{
22609 func="foo",args=[],file="hello.c",fullname="/home/foo/bar/hello.c",
22615 @subheading The @code{-exec-finish} Command
22616 @findex -exec-finish
22618 @subsubheading Synopsis
22624 Resumes the execution of the inferior program until the current
22625 function is exited. Displays the results returned by the function.
22627 @subsubheading @value{GDBN} Command
22629 The corresponding @value{GDBN} command is @samp{finish}.
22631 @subsubheading Example
22633 Function returning @code{void}.
22640 *stopped,reason="function-finished",frame=@{func="main",args=[],
22641 file="hello.c",fullname="/home/foo/bar/hello.c",line="7"@}
22645 Function returning other than @code{void}. The name of the internal
22646 @value{GDBN} variable storing the result is printed, together with the
22653 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
22654 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
22655 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
22656 gdb-result-var="$1",return-value="0"
22661 @subheading The @code{-exec-interrupt} Command
22662 @findex -exec-interrupt
22664 @subsubheading Synopsis
22667 -exec-interrupt [--all|--thread-group N]
22670 Interrupts the background execution of the target. Note how the token
22671 associated with the stop message is the one for the execution command
22672 that has been interrupted. The token for the interrupt itself only
22673 appears in the @samp{^done} output. If the user is trying to
22674 interrupt a non-running program, an error message will be printed.
22676 Note that when asynchronous execution is enabled, this command is
22677 asynchronous just like other execution commands. That is, first the
22678 @samp{^done} response will be printed, and the target stop will be
22679 reported after that using the @samp{*stopped} notification.
22681 In non-stop mode, only the context thread is interrupted by default.
22682 All threads will be interrupted if the @samp{--all} option is
22683 specified. If the @samp{--thread-group} option is specified, all
22684 threads in that group will be interrupted.
22686 @subsubheading @value{GDBN} Command
22688 The corresponding @value{GDBN} command is @samp{interrupt}.
22690 @subsubheading Example
22701 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
22702 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",
22703 fullname="/home/foo/bar/try.c",line="13"@}
22708 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
22712 @subheading The @code{-exec-jump} Command
22715 @subsubheading Synopsis
22718 -exec-jump @var{location}
22721 Resumes execution of the inferior program at the location specified by
22722 parameter. @xref{Specify Location}, for a description of the
22723 different forms of @var{location}.
22725 @subsubheading @value{GDBN} Command
22727 The corresponding @value{GDBN} command is @samp{jump}.
22729 @subsubheading Example
22732 -exec-jump foo.c:10
22733 *running,thread-id="all"
22738 @subheading The @code{-exec-next} Command
22741 @subsubheading Synopsis
22747 Resumes execution of the inferior program, stopping when the beginning
22748 of the next source line is reached.
22750 @subsubheading @value{GDBN} Command
22752 The corresponding @value{GDBN} command is @samp{next}.
22754 @subsubheading Example
22760 *stopped,reason="end-stepping-range",line="8",file="hello.c"
22765 @subheading The @code{-exec-next-instruction} Command
22766 @findex -exec-next-instruction
22768 @subsubheading Synopsis
22771 -exec-next-instruction
22774 Executes one machine instruction. If the instruction is a function
22775 call, continues until the function returns. If the program stops at an
22776 instruction in the middle of a source line, the address will be
22779 @subsubheading @value{GDBN} Command
22781 The corresponding @value{GDBN} command is @samp{nexti}.
22783 @subsubheading Example
22787 -exec-next-instruction
22791 *stopped,reason="end-stepping-range",
22792 addr="0x000100d4",line="5",file="hello.c"
22797 @subheading The @code{-exec-return} Command
22798 @findex -exec-return
22800 @subsubheading Synopsis
22806 Makes current function return immediately. Doesn't execute the inferior.
22807 Displays the new current frame.
22809 @subsubheading @value{GDBN} Command
22811 The corresponding @value{GDBN} command is @samp{return}.
22813 @subsubheading Example
22817 200-break-insert callee4
22818 200^done,bkpt=@{number="1",addr="0x00010734",
22819 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
22824 000*stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
22825 frame=@{func="callee4",args=[],
22826 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
22827 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
22833 111^done,frame=@{level="0",func="callee3",
22834 args=[@{name="strarg",
22835 value="0x11940 \"A string argument.\""@}],
22836 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
22837 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
22842 @subheading The @code{-exec-run} Command
22845 @subsubheading Synopsis
22851 Starts execution of the inferior from the beginning. The inferior
22852 executes until either a breakpoint is encountered or the program
22853 exits. In the latter case the output will include an exit code, if
22854 the program has exited exceptionally.
22856 @subsubheading @value{GDBN} Command
22858 The corresponding @value{GDBN} command is @samp{run}.
22860 @subsubheading Examples
22865 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
22870 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
22871 frame=@{func="main",args=[],file="recursive2.c",
22872 fullname="/home/foo/bar/recursive2.c",line="4"@}
22877 Program exited normally:
22885 *stopped,reason="exited-normally"
22890 Program exited exceptionally:
22898 *stopped,reason="exited",exit-code="01"
22902 Another way the program can terminate is if it receives a signal such as
22903 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
22907 *stopped,reason="exited-signalled",signal-name="SIGINT",
22908 signal-meaning="Interrupt"
22912 @c @subheading -exec-signal
22915 @subheading The @code{-exec-step} Command
22918 @subsubheading Synopsis
22924 Resumes execution of the inferior program, stopping when the beginning
22925 of the next source line is reached, if the next source line is not a
22926 function call. If it is, stop at the first instruction of the called
22929 @subsubheading @value{GDBN} Command
22931 The corresponding @value{GDBN} command is @samp{step}.
22933 @subsubheading Example
22935 Stepping into a function:
22941 *stopped,reason="end-stepping-range",
22942 frame=@{func="foo",args=[@{name="a",value="10"@},
22943 @{name="b",value="0"@}],file="recursive2.c",
22944 fullname="/home/foo/bar/recursive2.c",line="11"@}
22954 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
22959 @subheading The @code{-exec-step-instruction} Command
22960 @findex -exec-step-instruction
22962 @subsubheading Synopsis
22965 -exec-step-instruction
22968 Resumes the inferior which executes one machine instruction. The
22969 output, once @value{GDBN} has stopped, will vary depending on whether
22970 we have stopped in the middle of a source line or not. In the former
22971 case, the address at which the program stopped will be printed as
22974 @subsubheading @value{GDBN} Command
22976 The corresponding @value{GDBN} command is @samp{stepi}.
22978 @subsubheading Example
22982 -exec-step-instruction
22986 *stopped,reason="end-stepping-range",
22987 frame=@{func="foo",args=[],file="try.c",
22988 fullname="/home/foo/bar/try.c",line="10"@}
22990 -exec-step-instruction
22994 *stopped,reason="end-stepping-range",
22995 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",
22996 fullname="/home/foo/bar/try.c",line="10"@}
23001 @subheading The @code{-exec-until} Command
23002 @findex -exec-until
23004 @subsubheading Synopsis
23007 -exec-until [ @var{location} ]
23010 Executes the inferior until the @var{location} specified in the
23011 argument is reached. If there is no argument, the inferior executes
23012 until a source line greater than the current one is reached. The
23013 reason for stopping in this case will be @samp{location-reached}.
23015 @subsubheading @value{GDBN} Command
23017 The corresponding @value{GDBN} command is @samp{until}.
23019 @subsubheading Example
23023 -exec-until recursive2.c:6
23027 *stopped,reason="location-reached",frame=@{func="main",args=[],
23028 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="6"@}
23033 @subheading -file-clear
23034 Is this going away????
23037 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
23038 @node GDB/MI Stack Manipulation
23039 @section @sc{gdb/mi} Stack Manipulation Commands
23042 @subheading The @code{-stack-info-frame} Command
23043 @findex -stack-info-frame
23045 @subsubheading Synopsis
23051 Get info on the selected frame.
23053 @subsubheading @value{GDBN} Command
23055 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
23056 (without arguments).
23058 @subsubheading Example
23063 ^done,frame=@{level="1",addr="0x0001076c",func="callee3",
23064 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
23065 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@}
23069 @subheading The @code{-stack-info-depth} Command
23070 @findex -stack-info-depth
23072 @subsubheading Synopsis
23075 -stack-info-depth [ @var{max-depth} ]
23078 Return the depth of the stack. If the integer argument @var{max-depth}
23079 is specified, do not count beyond @var{max-depth} frames.
23081 @subsubheading @value{GDBN} Command
23083 There's no equivalent @value{GDBN} command.
23085 @subsubheading Example
23087 For a stack with frame levels 0 through 11:
23094 -stack-info-depth 4
23097 -stack-info-depth 12
23100 -stack-info-depth 11
23103 -stack-info-depth 13
23108 @subheading The @code{-stack-list-arguments} Command
23109 @findex -stack-list-arguments
23111 @subsubheading Synopsis
23114 -stack-list-arguments @var{show-values}
23115 [ @var{low-frame} @var{high-frame} ]
23118 Display a list of the arguments for the frames between @var{low-frame}
23119 and @var{high-frame} (inclusive). If @var{low-frame} and
23120 @var{high-frame} are not provided, list the arguments for the whole
23121 call stack. If the two arguments are equal, show the single frame
23122 at the corresponding level. It is an error if @var{low-frame} is
23123 larger than the actual number of frames. On the other hand,
23124 @var{high-frame} may be larger than the actual number of frames, in
23125 which case only existing frames will be returned.
23127 The @var{show-values} argument must have a value of 0 or 1. A value of
23128 0 means that only the names of the arguments are listed, a value of 1
23129 means that both names and values of the arguments are printed.
23131 @subsubheading @value{GDBN} Command
23133 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
23134 @samp{gdb_get_args} command which partially overlaps with the
23135 functionality of @samp{-stack-list-arguments}.
23137 @subsubheading Example
23144 frame=@{level="0",addr="0x00010734",func="callee4",
23145 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
23146 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@},
23147 frame=@{level="1",addr="0x0001076c",func="callee3",
23148 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
23149 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@},
23150 frame=@{level="2",addr="0x0001078c",func="callee2",
23151 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
23152 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="22"@},
23153 frame=@{level="3",addr="0x000107b4",func="callee1",
23154 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
23155 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="27"@},
23156 frame=@{level="4",addr="0x000107e0",func="main",
23157 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
23158 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="32"@}]
23160 -stack-list-arguments 0
23163 frame=@{level="0",args=[]@},
23164 frame=@{level="1",args=[name="strarg"]@},
23165 frame=@{level="2",args=[name="intarg",name="strarg"]@},
23166 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
23167 frame=@{level="4",args=[]@}]
23169 -stack-list-arguments 1
23172 frame=@{level="0",args=[]@},
23174 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
23175 frame=@{level="2",args=[
23176 @{name="intarg",value="2"@},
23177 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
23178 @{frame=@{level="3",args=[
23179 @{name="intarg",value="2"@},
23180 @{name="strarg",value="0x11940 \"A string argument.\""@},
23181 @{name="fltarg",value="3.5"@}]@},
23182 frame=@{level="4",args=[]@}]
23184 -stack-list-arguments 0 2 2
23185 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
23187 -stack-list-arguments 1 2 2
23188 ^done,stack-args=[frame=@{level="2",
23189 args=[@{name="intarg",value="2"@},
23190 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
23194 @c @subheading -stack-list-exception-handlers
23197 @subheading The @code{-stack-list-frames} Command
23198 @findex -stack-list-frames
23200 @subsubheading Synopsis
23203 -stack-list-frames [ @var{low-frame} @var{high-frame} ]
23206 List the frames currently on the stack. For each frame it displays the
23211 The frame number, 0 being the topmost frame, i.e., the innermost function.
23213 The @code{$pc} value for that frame.
23217 File name of the source file where the function lives.
23219 Line number corresponding to the @code{$pc}.
23222 If invoked without arguments, this command prints a backtrace for the
23223 whole stack. If given two integer arguments, it shows the frames whose
23224 levels are between the two arguments (inclusive). If the two arguments
23225 are equal, it shows the single frame at the corresponding level. It is
23226 an error if @var{low-frame} is larger than the actual number of
23227 frames. On the other hand, @var{high-frame} may be larger than the
23228 actual number of frames, in which case only existing frames will be returned.
23230 @subsubheading @value{GDBN} Command
23232 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
23234 @subsubheading Example
23236 Full stack backtrace:
23242 [frame=@{level="0",addr="0x0001076c",func="foo",
23243 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="11"@},
23244 frame=@{level="1",addr="0x000107a4",func="foo",
23245 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
23246 frame=@{level="2",addr="0x000107a4",func="foo",
23247 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
23248 frame=@{level="3",addr="0x000107a4",func="foo",
23249 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
23250 frame=@{level="4",addr="0x000107a4",func="foo",
23251 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
23252 frame=@{level="5",addr="0x000107a4",func="foo",
23253 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
23254 frame=@{level="6",addr="0x000107a4",func="foo",
23255 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
23256 frame=@{level="7",addr="0x000107a4",func="foo",
23257 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
23258 frame=@{level="8",addr="0x000107a4",func="foo",
23259 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
23260 frame=@{level="9",addr="0x000107a4",func="foo",
23261 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
23262 frame=@{level="10",addr="0x000107a4",func="foo",
23263 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
23264 frame=@{level="11",addr="0x00010738",func="main",
23265 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="4"@}]
23269 Show frames between @var{low_frame} and @var{high_frame}:
23273 -stack-list-frames 3 5
23275 [frame=@{level="3",addr="0x000107a4",func="foo",
23276 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
23277 frame=@{level="4",addr="0x000107a4",func="foo",
23278 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
23279 frame=@{level="5",addr="0x000107a4",func="foo",
23280 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
23284 Show a single frame:
23288 -stack-list-frames 3 3
23290 [frame=@{level="3",addr="0x000107a4",func="foo",
23291 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
23296 @subheading The @code{-stack-list-locals} Command
23297 @findex -stack-list-locals
23299 @subsubheading Synopsis
23302 -stack-list-locals @var{print-values}
23305 Display the local variable names for the selected frame. If
23306 @var{print-values} is 0 or @code{--no-values}, print only the names of
23307 the variables; if it is 1 or @code{--all-values}, print also their
23308 values; and if it is 2 or @code{--simple-values}, print the name,
23309 type and value for simple data types and the name and type for arrays,
23310 structures and unions. In this last case, a frontend can immediately
23311 display the value of simple data types and create variable objects for
23312 other data types when the user wishes to explore their values in
23315 @subsubheading @value{GDBN} Command
23317 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
23319 @subsubheading Example
23323 -stack-list-locals 0
23324 ^done,locals=[name="A",name="B",name="C"]
23326 -stack-list-locals --all-values
23327 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
23328 @{name="C",value="@{1, 2, 3@}"@}]
23329 -stack-list-locals --simple-values
23330 ^done,locals=[@{name="A",type="int",value="1"@},
23331 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
23336 @subheading The @code{-stack-select-frame} Command
23337 @findex -stack-select-frame
23339 @subsubheading Synopsis
23342 -stack-select-frame @var{framenum}
23345 Change the selected frame. Select a different frame @var{framenum} on
23348 This command in deprecated in favor of passing the @samp{--frame}
23349 option to every command.
23351 @subsubheading @value{GDBN} Command
23353 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
23354 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
23356 @subsubheading Example
23360 -stack-select-frame 2
23365 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
23366 @node GDB/MI Variable Objects
23367 @section @sc{gdb/mi} Variable Objects
23371 @subheading Motivation for Variable Objects in @sc{gdb/mi}
23373 For the implementation of a variable debugger window (locals, watched
23374 expressions, etc.), we are proposing the adaptation of the existing code
23375 used by @code{Insight}.
23377 The two main reasons for that are:
23381 It has been proven in practice (it is already on its second generation).
23384 It will shorten development time (needless to say how important it is
23388 The original interface was designed to be used by Tcl code, so it was
23389 slightly changed so it could be used through @sc{gdb/mi}. This section
23390 describes the @sc{gdb/mi} operations that will be available and gives some
23391 hints about their use.
23393 @emph{Note}: In addition to the set of operations described here, we
23394 expect the @sc{gui} implementation of a variable window to require, at
23395 least, the following operations:
23398 @item @code{-gdb-show} @code{output-radix}
23399 @item @code{-stack-list-arguments}
23400 @item @code{-stack-list-locals}
23401 @item @code{-stack-select-frame}
23406 @subheading Introduction to Variable Objects
23408 @cindex variable objects in @sc{gdb/mi}
23410 Variable objects are "object-oriented" MI interface for examining and
23411 changing values of expressions. Unlike some other MI interfaces that
23412 work with expressions, variable objects are specifically designed for
23413 simple and efficient presentation in the frontend. A variable object
23414 is identified by string name. When a variable object is created, the
23415 frontend specifies the expression for that variable object. The
23416 expression can be a simple variable, or it can be an arbitrary complex
23417 expression, and can even involve CPU registers. After creating a
23418 variable object, the frontend can invoke other variable object
23419 operations---for example to obtain or change the value of a variable
23420 object, or to change display format.
23422 Variable objects have hierarchical tree structure. Any variable object
23423 that corresponds to a composite type, such as structure in C, has
23424 a number of child variable objects, for example corresponding to each
23425 element of a structure. A child variable object can itself have
23426 children, recursively. Recursion ends when we reach
23427 leaf variable objects, which always have built-in types. Child variable
23428 objects are created only by explicit request, so if a frontend
23429 is not interested in the children of a particular variable object, no
23430 child will be created.
23432 For a leaf variable object it is possible to obtain its value as a
23433 string, or set the value from a string. String value can be also
23434 obtained for a non-leaf variable object, but it's generally a string
23435 that only indicates the type of the object, and does not list its
23436 contents. Assignment to a non-leaf variable object is not allowed.
23438 A frontend does not need to read the values of all variable objects each time
23439 the program stops. Instead, MI provides an update command that lists all
23440 variable objects whose values has changed since the last update
23441 operation. This considerably reduces the amount of data that must
23442 be transferred to the frontend. As noted above, children variable
23443 objects are created on demand, and only leaf variable objects have a
23444 real value. As result, gdb will read target memory only for leaf
23445 variables that frontend has created.
23447 The automatic update is not always desirable. For example, a frontend
23448 might want to keep a value of some expression for future reference,
23449 and never update it. For another example, fetching memory is
23450 relatively slow for embedded targets, so a frontend might want
23451 to disable automatic update for the variables that are either not
23452 visible on the screen, or ``closed''. This is possible using so
23453 called ``frozen variable objects''. Such variable objects are never
23454 implicitly updated.
23456 Variable objects can be either @dfn{fixed} or @dfn{floating}. For the
23457 fixed variable object, the expression is parsed when the variable
23458 object is created, including associating identifiers to specific
23459 variables. The meaning of expression never changes. For a floating
23460 variable object the values of variables whose names appear in the
23461 expressions are re-evaluated every time in the context of the current
23462 frame. Consider this example:
23467 struct work_state state;
23474 If a fixed variable object for the @code{state} variable is created in
23475 this function, and we enter the recursive call, the the variable
23476 object will report the value of @code{state} in the top-level
23477 @code{do_work} invocation. On the other hand, a floating variable
23478 object will report the value of @code{state} in the current frame.
23480 If an expression specified when creating a fixed variable object
23481 refers to a local variable, the variable object becomes bound to the
23482 thread and frame in which the variable object is created. When such
23483 variable object is updated, @value{GDBN} makes sure that the
23484 thread/frame combination the variable object is bound to still exists,
23485 and re-evaluates the variable object in context of that thread/frame.
23487 The following is the complete set of @sc{gdb/mi} operations defined to
23488 access this functionality:
23490 @multitable @columnfractions .4 .6
23491 @item @strong{Operation}
23492 @tab @strong{Description}
23494 @item @code{-var-create}
23495 @tab create a variable object
23496 @item @code{-var-delete}
23497 @tab delete the variable object and/or its children
23498 @item @code{-var-set-format}
23499 @tab set the display format of this variable
23500 @item @code{-var-show-format}
23501 @tab show the display format of this variable
23502 @item @code{-var-info-num-children}
23503 @tab tells how many children this object has
23504 @item @code{-var-list-children}
23505 @tab return a list of the object's children
23506 @item @code{-var-info-type}
23507 @tab show the type of this variable object
23508 @item @code{-var-info-expression}
23509 @tab print parent-relative expression that this variable object represents
23510 @item @code{-var-info-path-expression}
23511 @tab print full expression that this variable object represents
23512 @item @code{-var-show-attributes}
23513 @tab is this variable editable? does it exist here?
23514 @item @code{-var-evaluate-expression}
23515 @tab get the value of this variable
23516 @item @code{-var-assign}
23517 @tab set the value of this variable
23518 @item @code{-var-update}
23519 @tab update the variable and its children
23520 @item @code{-var-set-frozen}
23521 @tab set frozeness attribute
23524 In the next subsection we describe each operation in detail and suggest
23525 how it can be used.
23527 @subheading Description And Use of Operations on Variable Objects
23529 @subheading The @code{-var-create} Command
23530 @findex -var-create
23532 @subsubheading Synopsis
23535 -var-create @{@var{name} | "-"@}
23536 @{@var{frame-addr} | "*" | "@@"@} @var{expression}
23539 This operation creates a variable object, which allows the monitoring of
23540 a variable, the result of an expression, a memory cell or a CPU
23543 The @var{name} parameter is the string by which the object can be
23544 referenced. It must be unique. If @samp{-} is specified, the varobj
23545 system will generate a string ``varNNNNNN'' automatically. It will be
23546 unique provided that one does not specify @var{name} of that format.
23547 The command fails if a duplicate name is found.
23549 The frame under which the expression should be evaluated can be
23550 specified by @var{frame-addr}. A @samp{*} indicates that the current
23551 frame should be used. A @samp{@@} indicates that a floating variable
23552 object must be created.
23554 @var{expression} is any expression valid on the current language set (must not
23555 begin with a @samp{*}), or one of the following:
23559 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
23562 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
23565 @samp{$@var{regname}} --- a CPU register name
23568 @subsubheading Result
23570 This operation returns the name, number of children and the type of the
23571 object created. Type is returned as a string as the ones generated by
23572 the @value{GDBN} CLI. If a fixed variable object is bound to a
23573 specific thread, the thread is is also printed:
23576 name="@var{name}",numchild="@var{N}",type="@var{type}",thread-id="@var{M}"
23580 @subheading The @code{-var-delete} Command
23581 @findex -var-delete
23583 @subsubheading Synopsis
23586 -var-delete [ -c ] @var{name}
23589 Deletes a previously created variable object and all of its children.
23590 With the @samp{-c} option, just deletes the children.
23592 Returns an error if the object @var{name} is not found.
23595 @subheading The @code{-var-set-format} Command
23596 @findex -var-set-format
23598 @subsubheading Synopsis
23601 -var-set-format @var{name} @var{format-spec}
23604 Sets the output format for the value of the object @var{name} to be
23607 @anchor{-var-set-format}
23608 The syntax for the @var{format-spec} is as follows:
23611 @var{format-spec} @expansion{}
23612 @{binary | decimal | hexadecimal | octal | natural@}
23615 The natural format is the default format choosen automatically
23616 based on the variable type (like decimal for an @code{int}, hex
23617 for pointers, etc.).
23619 For a variable with children, the format is set only on the
23620 variable itself, and the children are not affected.
23622 @subheading The @code{-var-show-format} Command
23623 @findex -var-show-format
23625 @subsubheading Synopsis
23628 -var-show-format @var{name}
23631 Returns the format used to display the value of the object @var{name}.
23634 @var{format} @expansion{}
23639 @subheading The @code{-var-info-num-children} Command
23640 @findex -var-info-num-children
23642 @subsubheading Synopsis
23645 -var-info-num-children @var{name}
23648 Returns the number of children of a variable object @var{name}:
23655 @subheading The @code{-var-list-children} Command
23656 @findex -var-list-children
23658 @subsubheading Synopsis
23661 -var-list-children [@var{print-values}] @var{name}
23663 @anchor{-var-list-children}
23665 Return a list of the children of the specified variable object and
23666 create variable objects for them, if they do not already exist. With
23667 a single argument or if @var{print-values} has a value for of 0 or
23668 @code{--no-values}, print only the names of the variables; if
23669 @var{print-values} is 1 or @code{--all-values}, also print their
23670 values; and if it is 2 or @code{--simple-values} print the name and
23671 value for simple data types and just the name for arrays, structures
23674 For each child the following results are returned:
23679 Name of the variable object created for this child.
23682 The expression to be shown to the user by the front end to designate this child.
23683 For example this may be the name of a structure member.
23685 For C/C@t{++} structures there are several pseudo children returned to
23686 designate access qualifiers. For these pseudo children @var{exp} is
23687 @samp{public}, @samp{private}, or @samp{protected}. In this case the
23688 type and value are not present.
23691 Number of children this child has.
23694 The type of the child.
23697 If values were requested, this is the value.
23700 If this variable object is associated with a thread, this is the thread id.
23701 Otherwise this result is not present.
23704 If the variable object is frozen, this variable will be present with a value of 1.
23707 @subsubheading Example
23711 -var-list-children n
23712 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
23713 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
23715 -var-list-children --all-values n
23716 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
23717 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
23721 @subheading The @code{-var-info-type} Command
23722 @findex -var-info-type
23724 @subsubheading Synopsis
23727 -var-info-type @var{name}
23730 Returns the type of the specified variable @var{name}. The type is
23731 returned as a string in the same format as it is output by the
23735 type=@var{typename}
23739 @subheading The @code{-var-info-expression} Command
23740 @findex -var-info-expression
23742 @subsubheading Synopsis
23745 -var-info-expression @var{name}
23748 Returns a string that is suitable for presenting this
23749 variable object in user interface. The string is generally
23750 not valid expression in the current language, and cannot be evaluated.
23752 For example, if @code{a} is an array, and variable object
23753 @code{A} was created for @code{a}, then we'll get this output:
23756 (gdb) -var-info-expression A.1
23757 ^done,lang="C",exp="1"
23761 Here, the values of @code{lang} can be @code{@{"C" | "C++" | "Java"@}}.
23763 Note that the output of the @code{-var-list-children} command also
23764 includes those expressions, so the @code{-var-info-expression} command
23767 @subheading The @code{-var-info-path-expression} Command
23768 @findex -var-info-path-expression
23770 @subsubheading Synopsis
23773 -var-info-path-expression @var{name}
23776 Returns an expression that can be evaluated in the current
23777 context and will yield the same value that a variable object has.
23778 Compare this with the @code{-var-info-expression} command, which
23779 result can be used only for UI presentation. Typical use of
23780 the @code{-var-info-path-expression} command is creating a
23781 watchpoint from a variable object.
23783 For example, suppose @code{C} is a C@t{++} class, derived from class
23784 @code{Base}, and that the @code{Base} class has a member called
23785 @code{m_size}. Assume a variable @code{c} is has the type of
23786 @code{C} and a variable object @code{C} was created for variable
23787 @code{c}. Then, we'll get this output:
23789 (gdb) -var-info-path-expression C.Base.public.m_size
23790 ^done,path_expr=((Base)c).m_size)
23793 @subheading The @code{-var-show-attributes} Command
23794 @findex -var-show-attributes
23796 @subsubheading Synopsis
23799 -var-show-attributes @var{name}
23802 List attributes of the specified variable object @var{name}:
23805 status=@var{attr} [ ( ,@var{attr} )* ]
23809 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
23811 @subheading The @code{-var-evaluate-expression} Command
23812 @findex -var-evaluate-expression
23814 @subsubheading Synopsis
23817 -var-evaluate-expression [-f @var{format-spec}] @var{name}
23820 Evaluates the expression that is represented by the specified variable
23821 object and returns its value as a string. The format of the string
23822 can be specified with the @samp{-f} option. The possible values of
23823 this option are the same as for @code{-var-set-format}
23824 (@pxref{-var-set-format}). If the @samp{-f} option is not specified,
23825 the current display format will be used. The current display format
23826 can be changed using the @code{-var-set-format} command.
23832 Note that one must invoke @code{-var-list-children} for a variable
23833 before the value of a child variable can be evaluated.
23835 @subheading The @code{-var-assign} Command
23836 @findex -var-assign
23838 @subsubheading Synopsis
23841 -var-assign @var{name} @var{expression}
23844 Assigns the value of @var{expression} to the variable object specified
23845 by @var{name}. The object must be @samp{editable}. If the variable's
23846 value is altered by the assign, the variable will show up in any
23847 subsequent @code{-var-update} list.
23849 @subsubheading Example
23857 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
23861 @subheading The @code{-var-update} Command
23862 @findex -var-update
23864 @subsubheading Synopsis
23867 -var-update [@var{print-values}] @{@var{name} | "*"@}
23870 Reevaluate the expressions corresponding to the variable object
23871 @var{name} and all its direct and indirect children, and return the
23872 list of variable objects whose values have changed; @var{name} must
23873 be a root variable object. Here, ``changed'' means that the result of
23874 @code{-var-evaluate-expression} before and after the
23875 @code{-var-update} is different. If @samp{*} is used as the variable
23876 object names, all existing variable objects are updated, except
23877 for frozen ones (@pxref{-var-set-frozen}). The option
23878 @var{print-values} determines whether both names and values, or just
23879 names are printed. The possible values of this option are the same
23880 as for @code{-var-list-children} (@pxref{-var-list-children}). It is
23881 recommended to use the @samp{--all-values} option, to reduce the
23882 number of MI commands needed on each program stop.
23884 With the @samp{*} parameter, if a variable object is bound to a
23885 currently running thread, it will not be updated, without any
23888 @subsubheading Example
23895 -var-update --all-values var1
23896 ^done,changelist=[@{name="var1",value="3",in_scope="true",
23897 type_changed="false"@}]
23901 @anchor{-var-update}
23902 The field in_scope may take three values:
23906 The variable object's current value is valid.
23909 The variable object does not currently hold a valid value but it may
23910 hold one in the future if its associated expression comes back into
23914 The variable object no longer holds a valid value.
23915 This can occur when the executable file being debugged has changed,
23916 either through recompilation or by using the @value{GDBN} @code{file}
23917 command. The front end should normally choose to delete these variable
23921 In the future new values may be added to this list so the front should
23922 be prepared for this possibility. @xref{GDB/MI Development and Front Ends, ,@sc{GDB/MI} Development and Front Ends}.
23924 @subheading The @code{-var-set-frozen} Command
23925 @findex -var-set-frozen
23926 @anchor{-var-set-frozen}
23928 @subsubheading Synopsis
23931 -var-set-frozen @var{name} @var{flag}
23934 Set the frozenness flag on the variable object @var{name}. The
23935 @var{flag} parameter should be either @samp{1} to make the variable
23936 frozen or @samp{0} to make it unfrozen. If a variable object is
23937 frozen, then neither itself, nor any of its children, are
23938 implicitly updated by @code{-var-update} of
23939 a parent variable or by @code{-var-update *}. Only
23940 @code{-var-update} of the variable itself will update its value and
23941 values of its children. After a variable object is unfrozen, it is
23942 implicitly updated by all subsequent @code{-var-update} operations.
23943 Unfreezing a variable does not update it, only subsequent
23944 @code{-var-update} does.
23946 @subsubheading Example
23950 -var-set-frozen V 1
23955 @subheading The @code{-var-set-visualizer} command
23956 @findex -var-set-visualizer
23957 @anchor{-var-set-visualizer}
23959 @subsubheading Synopsis
23962 -var-set-visualizer @var{name} @var{visualizer}
23965 Set a visualizer for the variable object @var{name}.
23967 @var{visualizer} is the visualizer to use. The special value
23968 @samp{None} means to disable any visualizer in use.
23970 If not @samp{None}, @var{visualizer} must be a Python expression.
23971 This expression must evaluate to a callable object which accepts a
23972 single argument. @value{GDBN} will call this object with the value of
23973 the varobj @var{name} as an argument (this is done so that the same
23974 Python pretty-printing code can be used for both the CLI and MI).
23975 When called, this object must return an object which conforms to the
23976 pretty-printing interface (@pxref{Pretty Printing}).
23978 The pre-defined function @code{gdb.default_visualizer} may be used to
23979 select a visualizer by following the built-in process
23980 (@pxref{Selecting Pretty-Printers}). This is done automatically when
23981 a varobj is created, and so ordinarily is not needed.
23983 This feature is only available if Python support is enabled. The MI
23984 command @code{-list-features} (@pxref{GDB/MI Miscellaneous Commands})
23985 can be used to check this.
23987 @subsubheading Example
23989 Resetting the visualizer:
23993 -var-set-visualizer V None
23997 Reselecting the default (type-based) visualizer:
24001 -var-set-visualizer V gdb.default_visualizer
24005 Suppose @code{SomeClass} is a visualizer class. A lambda expression
24006 can be used to instantiate this class for a varobj:
24010 -var-set-visualizer V "lambda val: SomeClass()"
24014 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
24015 @node GDB/MI Data Manipulation
24016 @section @sc{gdb/mi} Data Manipulation
24018 @cindex data manipulation, in @sc{gdb/mi}
24019 @cindex @sc{gdb/mi}, data manipulation
24020 This section describes the @sc{gdb/mi} commands that manipulate data:
24021 examine memory and registers, evaluate expressions, etc.
24023 @c REMOVED FROM THE INTERFACE.
24024 @c @subheading -data-assign
24025 @c Change the value of a program variable. Plenty of side effects.
24026 @c @subsubheading GDB Command
24028 @c @subsubheading Example
24031 @subheading The @code{-data-disassemble} Command
24032 @findex -data-disassemble
24034 @subsubheading Synopsis
24038 [ -s @var{start-addr} -e @var{end-addr} ]
24039 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
24047 @item @var{start-addr}
24048 is the beginning address (or @code{$pc})
24049 @item @var{end-addr}
24051 @item @var{filename}
24052 is the name of the file to disassemble
24053 @item @var{linenum}
24054 is the line number to disassemble around
24056 is the number of disassembly lines to be produced. If it is -1,
24057 the whole function will be disassembled, in case no @var{end-addr} is
24058 specified. If @var{end-addr} is specified as a non-zero value, and
24059 @var{lines} is lower than the number of disassembly lines between
24060 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
24061 displayed; if @var{lines} is higher than the number of lines between
24062 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
24065 is either 0 (meaning only disassembly) or 1 (meaning mixed source and
24069 @subsubheading Result
24071 The output for each instruction is composed of four fields:
24080 Note that whatever included in the instruction field, is not manipulated
24081 directly by @sc{gdb/mi}, i.e., it is not possible to adjust its format.
24083 @subsubheading @value{GDBN} Command
24085 There's no direct mapping from this command to the CLI.
24087 @subsubheading Example
24089 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
24093 -data-disassemble -s $pc -e "$pc + 20" -- 0
24096 @{address="0x000107c0",func-name="main",offset="4",
24097 inst="mov 2, %o0"@},
24098 @{address="0x000107c4",func-name="main",offset="8",
24099 inst="sethi %hi(0x11800), %o2"@},
24100 @{address="0x000107c8",func-name="main",offset="12",
24101 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
24102 @{address="0x000107cc",func-name="main",offset="16",
24103 inst="sethi %hi(0x11800), %o2"@},
24104 @{address="0x000107d0",func-name="main",offset="20",
24105 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
24109 Disassemble the whole @code{main} function. Line 32 is part of
24113 -data-disassemble -f basics.c -l 32 -- 0
24115 @{address="0x000107bc",func-name="main",offset="0",
24116 inst="save %sp, -112, %sp"@},
24117 @{address="0x000107c0",func-name="main",offset="4",
24118 inst="mov 2, %o0"@},
24119 @{address="0x000107c4",func-name="main",offset="8",
24120 inst="sethi %hi(0x11800), %o2"@},
24122 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
24123 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
24127 Disassemble 3 instructions from the start of @code{main}:
24131 -data-disassemble -f basics.c -l 32 -n 3 -- 0
24133 @{address="0x000107bc",func-name="main",offset="0",
24134 inst="save %sp, -112, %sp"@},
24135 @{address="0x000107c0",func-name="main",offset="4",
24136 inst="mov 2, %o0"@},
24137 @{address="0x000107c4",func-name="main",offset="8",
24138 inst="sethi %hi(0x11800), %o2"@}]
24142 Disassemble 3 instructions from the start of @code{main} in mixed mode:
24146 -data-disassemble -f basics.c -l 32 -n 3 -- 1
24148 src_and_asm_line=@{line="31",
24149 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
24150 testsuite/gdb.mi/basics.c",line_asm_insn=[
24151 @{address="0x000107bc",func-name="main",offset="0",
24152 inst="save %sp, -112, %sp"@}]@},
24153 src_and_asm_line=@{line="32",
24154 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
24155 testsuite/gdb.mi/basics.c",line_asm_insn=[
24156 @{address="0x000107c0",func-name="main",offset="4",
24157 inst="mov 2, %o0"@},
24158 @{address="0x000107c4",func-name="main",offset="8",
24159 inst="sethi %hi(0x11800), %o2"@}]@}]
24164 @subheading The @code{-data-evaluate-expression} Command
24165 @findex -data-evaluate-expression
24167 @subsubheading Synopsis
24170 -data-evaluate-expression @var{expr}
24173 Evaluate @var{expr} as an expression. The expression could contain an
24174 inferior function call. The function call will execute synchronously.
24175 If the expression contains spaces, it must be enclosed in double quotes.
24177 @subsubheading @value{GDBN} Command
24179 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
24180 @samp{call}. In @code{gdbtk} only, there's a corresponding
24181 @samp{gdb_eval} command.
24183 @subsubheading Example
24185 In the following example, the numbers that precede the commands are the
24186 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
24187 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
24191 211-data-evaluate-expression A
24194 311-data-evaluate-expression &A
24195 311^done,value="0xefffeb7c"
24197 411-data-evaluate-expression A+3
24200 511-data-evaluate-expression "A + 3"
24206 @subheading The @code{-data-list-changed-registers} Command
24207 @findex -data-list-changed-registers
24209 @subsubheading Synopsis
24212 -data-list-changed-registers
24215 Display a list of the registers that have changed.
24217 @subsubheading @value{GDBN} Command
24219 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
24220 has the corresponding command @samp{gdb_changed_register_list}.
24222 @subsubheading Example
24224 On a PPC MBX board:
24232 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",frame=@{
24233 func="main",args=[],file="try.c",fullname="/home/foo/bar/try.c",
24236 -data-list-changed-registers
24237 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
24238 "10","11","13","14","15","16","17","18","19","20","21","22","23",
24239 "24","25","26","27","28","30","31","64","65","66","67","69"]
24244 @subheading The @code{-data-list-register-names} Command
24245 @findex -data-list-register-names
24247 @subsubheading Synopsis
24250 -data-list-register-names [ ( @var{regno} )+ ]
24253 Show a list of register names for the current target. If no arguments
24254 are given, it shows a list of the names of all the registers. If
24255 integer numbers are given as arguments, it will print a list of the
24256 names of the registers corresponding to the arguments. To ensure
24257 consistency between a register name and its number, the output list may
24258 include empty register names.
24260 @subsubheading @value{GDBN} Command
24262 @value{GDBN} does not have a command which corresponds to
24263 @samp{-data-list-register-names}. In @code{gdbtk} there is a
24264 corresponding command @samp{gdb_regnames}.
24266 @subsubheading Example
24268 For the PPC MBX board:
24271 -data-list-register-names
24272 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
24273 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
24274 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
24275 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
24276 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
24277 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
24278 "", "pc","ps","cr","lr","ctr","xer"]
24280 -data-list-register-names 1 2 3
24281 ^done,register-names=["r1","r2","r3"]
24285 @subheading The @code{-data-list-register-values} Command
24286 @findex -data-list-register-values
24288 @subsubheading Synopsis
24291 -data-list-register-values @var{fmt} [ ( @var{regno} )*]
24294 Display the registers' contents. @var{fmt} is the format according to
24295 which the registers' contents are to be returned, followed by an optional
24296 list of numbers specifying the registers to display. A missing list of
24297 numbers indicates that the contents of all the registers must be returned.
24299 Allowed formats for @var{fmt} are:
24316 @subsubheading @value{GDBN} Command
24318 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
24319 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
24321 @subsubheading Example
24323 For a PPC MBX board (note: line breaks are for readability only, they
24324 don't appear in the actual output):
24328 -data-list-register-values r 64 65
24329 ^done,register-values=[@{number="64",value="0xfe00a300"@},
24330 @{number="65",value="0x00029002"@}]
24332 -data-list-register-values x
24333 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
24334 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
24335 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
24336 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
24337 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
24338 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
24339 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
24340 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
24341 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
24342 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
24343 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
24344 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
24345 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
24346 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
24347 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
24348 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
24349 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
24350 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
24351 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
24352 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
24353 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
24354 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
24355 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
24356 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
24357 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
24358 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
24359 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
24360 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
24361 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
24362 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
24363 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
24364 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
24365 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
24366 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
24367 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
24368 @{number="69",value="0x20002b03"@}]
24373 @subheading The @code{-data-read-memory} Command
24374 @findex -data-read-memory
24376 @subsubheading Synopsis
24379 -data-read-memory [ -o @var{byte-offset} ]
24380 @var{address} @var{word-format} @var{word-size}
24381 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
24388 @item @var{address}
24389 An expression specifying the address of the first memory word to be
24390 read. Complex expressions containing embedded white space should be
24391 quoted using the C convention.
24393 @item @var{word-format}
24394 The format to be used to print the memory words. The notation is the
24395 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
24398 @item @var{word-size}
24399 The size of each memory word in bytes.
24401 @item @var{nr-rows}
24402 The number of rows in the output table.
24404 @item @var{nr-cols}
24405 The number of columns in the output table.
24408 If present, indicates that each row should include an @sc{ascii} dump. The
24409 value of @var{aschar} is used as a padding character when a byte is not a
24410 member of the printable @sc{ascii} character set (printable @sc{ascii}
24411 characters are those whose code is between 32 and 126, inclusively).
24413 @item @var{byte-offset}
24414 An offset to add to the @var{address} before fetching memory.
24417 This command displays memory contents as a table of @var{nr-rows} by
24418 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
24419 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
24420 (returned as @samp{total-bytes}). Should less than the requested number
24421 of bytes be returned by the target, the missing words are identified
24422 using @samp{N/A}. The number of bytes read from the target is returned
24423 in @samp{nr-bytes} and the starting address used to read memory in
24426 The address of the next/previous row or page is available in
24427 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
24430 @subsubheading @value{GDBN} Command
24432 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
24433 @samp{gdb_get_mem} memory read command.
24435 @subsubheading Example
24437 Read six bytes of memory starting at @code{bytes+6} but then offset by
24438 @code{-6} bytes. Format as three rows of two columns. One byte per
24439 word. Display each word in hex.
24443 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
24444 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
24445 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
24446 prev-page="0x0000138a",memory=[
24447 @{addr="0x00001390",data=["0x00","0x01"]@},
24448 @{addr="0x00001392",data=["0x02","0x03"]@},
24449 @{addr="0x00001394",data=["0x04","0x05"]@}]
24453 Read two bytes of memory starting at address @code{shorts + 64} and
24454 display as a single word formatted in decimal.
24458 5-data-read-memory shorts+64 d 2 1 1
24459 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
24460 next-row="0x00001512",prev-row="0x0000150e",
24461 next-page="0x00001512",prev-page="0x0000150e",memory=[
24462 @{addr="0x00001510",data=["128"]@}]
24466 Read thirty two bytes of memory starting at @code{bytes+16} and format
24467 as eight rows of four columns. Include a string encoding with @samp{x}
24468 used as the non-printable character.
24472 4-data-read-memory bytes+16 x 1 8 4 x
24473 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
24474 next-row="0x000013c0",prev-row="0x0000139c",
24475 next-page="0x000013c0",prev-page="0x00001380",memory=[
24476 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
24477 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
24478 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
24479 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
24480 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
24481 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
24482 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
24483 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
24487 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
24488 @node GDB/MI Tracepoint Commands
24489 @section @sc{gdb/mi} Tracepoint Commands
24491 The tracepoint commands are not yet implemented.
24493 @c @subheading -trace-actions
24495 @c @subheading -trace-delete
24497 @c @subheading -trace-disable
24499 @c @subheading -trace-dump
24501 @c @subheading -trace-enable
24503 @c @subheading -trace-exists
24505 @c @subheading -trace-find
24507 @c @subheading -trace-frame-number
24509 @c @subheading -trace-info
24511 @c @subheading -trace-insert
24513 @c @subheading -trace-list
24515 @c @subheading -trace-pass-count
24517 @c @subheading -trace-save
24519 @c @subheading -trace-start
24521 @c @subheading -trace-stop
24524 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
24525 @node GDB/MI Symbol Query
24526 @section @sc{gdb/mi} Symbol Query Commands
24530 @subheading The @code{-symbol-info-address} Command
24531 @findex -symbol-info-address
24533 @subsubheading Synopsis
24536 -symbol-info-address @var{symbol}
24539 Describe where @var{symbol} is stored.
24541 @subsubheading @value{GDBN} Command
24543 The corresponding @value{GDBN} command is @samp{info address}.
24545 @subsubheading Example
24549 @subheading The @code{-symbol-info-file} Command
24550 @findex -symbol-info-file
24552 @subsubheading Synopsis
24558 Show the file for the symbol.
24560 @subsubheading @value{GDBN} Command
24562 There's no equivalent @value{GDBN} command. @code{gdbtk} has
24563 @samp{gdb_find_file}.
24565 @subsubheading Example
24569 @subheading The @code{-symbol-info-function} Command
24570 @findex -symbol-info-function
24572 @subsubheading Synopsis
24575 -symbol-info-function
24578 Show which function the symbol lives in.
24580 @subsubheading @value{GDBN} Command
24582 @samp{gdb_get_function} in @code{gdbtk}.
24584 @subsubheading Example
24588 @subheading The @code{-symbol-info-line} Command
24589 @findex -symbol-info-line
24591 @subsubheading Synopsis
24597 Show the core addresses of the code for a source line.
24599 @subsubheading @value{GDBN} Command
24601 The corresponding @value{GDBN} command is @samp{info line}.
24602 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
24604 @subsubheading Example
24608 @subheading The @code{-symbol-info-symbol} Command
24609 @findex -symbol-info-symbol
24611 @subsubheading Synopsis
24614 -symbol-info-symbol @var{addr}
24617 Describe what symbol is at location @var{addr}.
24619 @subsubheading @value{GDBN} Command
24621 The corresponding @value{GDBN} command is @samp{info symbol}.
24623 @subsubheading Example
24627 @subheading The @code{-symbol-list-functions} Command
24628 @findex -symbol-list-functions
24630 @subsubheading Synopsis
24633 -symbol-list-functions
24636 List the functions in the executable.
24638 @subsubheading @value{GDBN} Command
24640 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
24641 @samp{gdb_search} in @code{gdbtk}.
24643 @subsubheading Example
24648 @subheading The @code{-symbol-list-lines} Command
24649 @findex -symbol-list-lines
24651 @subsubheading Synopsis
24654 -symbol-list-lines @var{filename}
24657 Print the list of lines that contain code and their associated program
24658 addresses for the given source filename. The entries are sorted in
24659 ascending PC order.
24661 @subsubheading @value{GDBN} Command
24663 There is no corresponding @value{GDBN} command.
24665 @subsubheading Example
24668 -symbol-list-lines basics.c
24669 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
24675 @subheading The @code{-symbol-list-types} Command
24676 @findex -symbol-list-types
24678 @subsubheading Synopsis
24684 List all the type names.
24686 @subsubheading @value{GDBN} Command
24688 The corresponding commands are @samp{info types} in @value{GDBN},
24689 @samp{gdb_search} in @code{gdbtk}.
24691 @subsubheading Example
24695 @subheading The @code{-symbol-list-variables} Command
24696 @findex -symbol-list-variables
24698 @subsubheading Synopsis
24701 -symbol-list-variables
24704 List all the global and static variable names.
24706 @subsubheading @value{GDBN} Command
24708 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
24710 @subsubheading Example
24714 @subheading The @code{-symbol-locate} Command
24715 @findex -symbol-locate
24717 @subsubheading Synopsis
24723 @subsubheading @value{GDBN} Command
24725 @samp{gdb_loc} in @code{gdbtk}.
24727 @subsubheading Example
24731 @subheading The @code{-symbol-type} Command
24732 @findex -symbol-type
24734 @subsubheading Synopsis
24737 -symbol-type @var{variable}
24740 Show type of @var{variable}.
24742 @subsubheading @value{GDBN} Command
24744 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
24745 @samp{gdb_obj_variable}.
24747 @subsubheading Example
24752 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
24753 @node GDB/MI File Commands
24754 @section @sc{gdb/mi} File Commands
24756 This section describes the GDB/MI commands to specify executable file names
24757 and to read in and obtain symbol table information.
24759 @subheading The @code{-file-exec-and-symbols} Command
24760 @findex -file-exec-and-symbols
24762 @subsubheading Synopsis
24765 -file-exec-and-symbols @var{file}
24768 Specify the executable file to be debugged. This file is the one from
24769 which the symbol table is also read. If no file is specified, the
24770 command clears the executable and symbol information. If breakpoints
24771 are set when using this command with no arguments, @value{GDBN} will produce
24772 error messages. Otherwise, no output is produced, except a completion
24775 @subsubheading @value{GDBN} Command
24777 The corresponding @value{GDBN} command is @samp{file}.
24779 @subsubheading Example
24783 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
24789 @subheading The @code{-file-exec-file} Command
24790 @findex -file-exec-file
24792 @subsubheading Synopsis
24795 -file-exec-file @var{file}
24798 Specify the executable file to be debugged. Unlike
24799 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
24800 from this file. If used without argument, @value{GDBN} clears the information
24801 about the executable file. No output is produced, except a completion
24804 @subsubheading @value{GDBN} Command
24806 The corresponding @value{GDBN} command is @samp{exec-file}.
24808 @subsubheading Example
24812 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
24819 @subheading The @code{-file-list-exec-sections} Command
24820 @findex -file-list-exec-sections
24822 @subsubheading Synopsis
24825 -file-list-exec-sections
24828 List the sections of the current executable file.
24830 @subsubheading @value{GDBN} Command
24832 The @value{GDBN} command @samp{info file} shows, among the rest, the same
24833 information as this command. @code{gdbtk} has a corresponding command
24834 @samp{gdb_load_info}.
24836 @subsubheading Example
24841 @subheading The @code{-file-list-exec-source-file} Command
24842 @findex -file-list-exec-source-file
24844 @subsubheading Synopsis
24847 -file-list-exec-source-file
24850 List the line number, the current source file, and the absolute path
24851 to the current source file for the current executable. The macro
24852 information field has a value of @samp{1} or @samp{0} depending on
24853 whether or not the file includes preprocessor macro information.
24855 @subsubheading @value{GDBN} Command
24857 The @value{GDBN} equivalent is @samp{info source}
24859 @subsubheading Example
24863 123-file-list-exec-source-file
24864 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c,macro-info="1"
24869 @subheading The @code{-file-list-exec-source-files} Command
24870 @findex -file-list-exec-source-files
24872 @subsubheading Synopsis
24875 -file-list-exec-source-files
24878 List the source files for the current executable.
24880 It will always output the filename, but only when @value{GDBN} can find
24881 the absolute file name of a source file, will it output the fullname.
24883 @subsubheading @value{GDBN} Command
24885 The @value{GDBN} equivalent is @samp{info sources}.
24886 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
24888 @subsubheading Example
24891 -file-list-exec-source-files
24893 @{file=foo.c,fullname=/home/foo.c@},
24894 @{file=/home/bar.c,fullname=/home/bar.c@},
24895 @{file=gdb_could_not_find_fullpath.c@}]
24900 @subheading The @code{-file-list-shared-libraries} Command
24901 @findex -file-list-shared-libraries
24903 @subsubheading Synopsis
24906 -file-list-shared-libraries
24909 List the shared libraries in the program.
24911 @subsubheading @value{GDBN} Command
24913 The corresponding @value{GDBN} command is @samp{info shared}.
24915 @subsubheading Example
24919 @subheading The @code{-file-list-symbol-files} Command
24920 @findex -file-list-symbol-files
24922 @subsubheading Synopsis
24925 -file-list-symbol-files
24930 @subsubheading @value{GDBN} Command
24932 The corresponding @value{GDBN} command is @samp{info file} (part of it).
24934 @subsubheading Example
24939 @subheading The @code{-file-symbol-file} Command
24940 @findex -file-symbol-file
24942 @subsubheading Synopsis
24945 -file-symbol-file @var{file}
24948 Read symbol table info from the specified @var{file} argument. When
24949 used without arguments, clears @value{GDBN}'s symbol table info. No output is
24950 produced, except for a completion notification.
24952 @subsubheading @value{GDBN} Command
24954 The corresponding @value{GDBN} command is @samp{symbol-file}.
24956 @subsubheading Example
24960 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
24966 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
24967 @node GDB/MI Memory Overlay Commands
24968 @section @sc{gdb/mi} Memory Overlay Commands
24970 The memory overlay commands are not implemented.
24972 @c @subheading -overlay-auto
24974 @c @subheading -overlay-list-mapping-state
24976 @c @subheading -overlay-list-overlays
24978 @c @subheading -overlay-map
24980 @c @subheading -overlay-off
24982 @c @subheading -overlay-on
24984 @c @subheading -overlay-unmap
24986 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
24987 @node GDB/MI Signal Handling Commands
24988 @section @sc{gdb/mi} Signal Handling Commands
24990 Signal handling commands are not implemented.
24992 @c @subheading -signal-handle
24994 @c @subheading -signal-list-handle-actions
24996 @c @subheading -signal-list-signal-types
25000 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25001 @node GDB/MI Target Manipulation
25002 @section @sc{gdb/mi} Target Manipulation Commands
25005 @subheading The @code{-target-attach} Command
25006 @findex -target-attach
25008 @subsubheading Synopsis
25011 -target-attach @var{pid} | @var{gid} | @var{file}
25014 Attach to a process @var{pid} or a file @var{file} outside of
25015 @value{GDBN}, or a thread group @var{gid}. If attaching to a thread
25016 group, the id previously returned by
25017 @samp{-list-thread-groups --available} must be used.
25019 @subsubheading @value{GDBN} Command
25021 The corresponding @value{GDBN} command is @samp{attach}.
25023 @subsubheading Example
25027 =thread-created,id="1"
25028 *stopped,thread-id="1",frame=@{addr="0xb7f7e410",func="bar",args=[]@}
25034 @subheading The @code{-target-compare-sections} Command
25035 @findex -target-compare-sections
25037 @subsubheading Synopsis
25040 -target-compare-sections [ @var{section} ]
25043 Compare data of section @var{section} on target to the exec file.
25044 Without the argument, all sections are compared.
25046 @subsubheading @value{GDBN} Command
25048 The @value{GDBN} equivalent is @samp{compare-sections}.
25050 @subsubheading Example
25055 @subheading The @code{-target-detach} Command
25056 @findex -target-detach
25058 @subsubheading Synopsis
25061 -target-detach [ @var{pid} | @var{gid} ]
25064 Detach from the remote target which normally resumes its execution.
25065 If either @var{pid} or @var{gid} is specified, detaches from either
25066 the specified process, or specified thread group. There's no output.
25068 @subsubheading @value{GDBN} Command
25070 The corresponding @value{GDBN} command is @samp{detach}.
25072 @subsubheading Example
25082 @subheading The @code{-target-disconnect} Command
25083 @findex -target-disconnect
25085 @subsubheading Synopsis
25091 Disconnect from the remote target. There's no output and the target is
25092 generally not resumed.
25094 @subsubheading @value{GDBN} Command
25096 The corresponding @value{GDBN} command is @samp{disconnect}.
25098 @subsubheading Example
25108 @subheading The @code{-target-download} Command
25109 @findex -target-download
25111 @subsubheading Synopsis
25117 Loads the executable onto the remote target.
25118 It prints out an update message every half second, which includes the fields:
25122 The name of the section.
25124 The size of what has been sent so far for that section.
25126 The size of the section.
25128 The total size of what was sent so far (the current and the previous sections).
25130 The size of the overall executable to download.
25134 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
25135 @sc{gdb/mi} Output Syntax}).
25137 In addition, it prints the name and size of the sections, as they are
25138 downloaded. These messages include the following fields:
25142 The name of the section.
25144 The size of the section.
25146 The size of the overall executable to download.
25150 At the end, a summary is printed.
25152 @subsubheading @value{GDBN} Command
25154 The corresponding @value{GDBN} command is @samp{load}.
25156 @subsubheading Example
25158 Note: each status message appears on a single line. Here the messages
25159 have been broken down so that they can fit onto a page.
25164 +download,@{section=".text",section-size="6668",total-size="9880"@}
25165 +download,@{section=".text",section-sent="512",section-size="6668",
25166 total-sent="512",total-size="9880"@}
25167 +download,@{section=".text",section-sent="1024",section-size="6668",
25168 total-sent="1024",total-size="9880"@}
25169 +download,@{section=".text",section-sent="1536",section-size="6668",
25170 total-sent="1536",total-size="9880"@}
25171 +download,@{section=".text",section-sent="2048",section-size="6668",
25172 total-sent="2048",total-size="9880"@}
25173 +download,@{section=".text",section-sent="2560",section-size="6668",
25174 total-sent="2560",total-size="9880"@}
25175 +download,@{section=".text",section-sent="3072",section-size="6668",
25176 total-sent="3072",total-size="9880"@}
25177 +download,@{section=".text",section-sent="3584",section-size="6668",
25178 total-sent="3584",total-size="9880"@}
25179 +download,@{section=".text",section-sent="4096",section-size="6668",
25180 total-sent="4096",total-size="9880"@}
25181 +download,@{section=".text",section-sent="4608",section-size="6668",
25182 total-sent="4608",total-size="9880"@}
25183 +download,@{section=".text",section-sent="5120",section-size="6668",
25184 total-sent="5120",total-size="9880"@}
25185 +download,@{section=".text",section-sent="5632",section-size="6668",
25186 total-sent="5632",total-size="9880"@}
25187 +download,@{section=".text",section-sent="6144",section-size="6668",
25188 total-sent="6144",total-size="9880"@}
25189 +download,@{section=".text",section-sent="6656",section-size="6668",
25190 total-sent="6656",total-size="9880"@}
25191 +download,@{section=".init",section-size="28",total-size="9880"@}
25192 +download,@{section=".fini",section-size="28",total-size="9880"@}
25193 +download,@{section=".data",section-size="3156",total-size="9880"@}
25194 +download,@{section=".data",section-sent="512",section-size="3156",
25195 total-sent="7236",total-size="9880"@}
25196 +download,@{section=".data",section-sent="1024",section-size="3156",
25197 total-sent="7748",total-size="9880"@}
25198 +download,@{section=".data",section-sent="1536",section-size="3156",
25199 total-sent="8260",total-size="9880"@}
25200 +download,@{section=".data",section-sent="2048",section-size="3156",
25201 total-sent="8772",total-size="9880"@}
25202 +download,@{section=".data",section-sent="2560",section-size="3156",
25203 total-sent="9284",total-size="9880"@}
25204 +download,@{section=".data",section-sent="3072",section-size="3156",
25205 total-sent="9796",total-size="9880"@}
25206 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
25213 @subheading The @code{-target-exec-status} Command
25214 @findex -target-exec-status
25216 @subsubheading Synopsis
25219 -target-exec-status
25222 Provide information on the state of the target (whether it is running or
25223 not, for instance).
25225 @subsubheading @value{GDBN} Command
25227 There's no equivalent @value{GDBN} command.
25229 @subsubheading Example
25233 @subheading The @code{-target-list-available-targets} Command
25234 @findex -target-list-available-targets
25236 @subsubheading Synopsis
25239 -target-list-available-targets
25242 List the possible targets to connect to.
25244 @subsubheading @value{GDBN} Command
25246 The corresponding @value{GDBN} command is @samp{help target}.
25248 @subsubheading Example
25252 @subheading The @code{-target-list-current-targets} Command
25253 @findex -target-list-current-targets
25255 @subsubheading Synopsis
25258 -target-list-current-targets
25261 Describe the current target.
25263 @subsubheading @value{GDBN} Command
25265 The corresponding information is printed by @samp{info file} (among
25268 @subsubheading Example
25272 @subheading The @code{-target-list-parameters} Command
25273 @findex -target-list-parameters
25275 @subsubheading Synopsis
25278 -target-list-parameters
25284 @subsubheading @value{GDBN} Command
25288 @subsubheading Example
25292 @subheading The @code{-target-select} Command
25293 @findex -target-select
25295 @subsubheading Synopsis
25298 -target-select @var{type} @var{parameters @dots{}}
25301 Connect @value{GDBN} to the remote target. This command takes two args:
25305 The type of target, for instance @samp{remote}, etc.
25306 @item @var{parameters}
25307 Device names, host names and the like. @xref{Target Commands, ,
25308 Commands for Managing Targets}, for more details.
25311 The output is a connection notification, followed by the address at
25312 which the target program is, in the following form:
25315 ^connected,addr="@var{address}",func="@var{function name}",
25316 args=[@var{arg list}]
25319 @subsubheading @value{GDBN} Command
25321 The corresponding @value{GDBN} command is @samp{target}.
25323 @subsubheading Example
25327 -target-select remote /dev/ttya
25328 ^connected,addr="0xfe00a300",func="??",args=[]
25332 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25333 @node GDB/MI File Transfer Commands
25334 @section @sc{gdb/mi} File Transfer Commands
25337 @subheading The @code{-target-file-put} Command
25338 @findex -target-file-put
25340 @subsubheading Synopsis
25343 -target-file-put @var{hostfile} @var{targetfile}
25346 Copy file @var{hostfile} from the host system (the machine running
25347 @value{GDBN}) to @var{targetfile} on the target system.
25349 @subsubheading @value{GDBN} Command
25351 The corresponding @value{GDBN} command is @samp{remote put}.
25353 @subsubheading Example
25357 -target-file-put localfile remotefile
25363 @subheading The @code{-target-file-get} Command
25364 @findex -target-file-get
25366 @subsubheading Synopsis
25369 -target-file-get @var{targetfile} @var{hostfile}
25372 Copy file @var{targetfile} from the target system to @var{hostfile}
25373 on the host system.
25375 @subsubheading @value{GDBN} Command
25377 The corresponding @value{GDBN} command is @samp{remote get}.
25379 @subsubheading Example
25383 -target-file-get remotefile localfile
25389 @subheading The @code{-target-file-delete} Command
25390 @findex -target-file-delete
25392 @subsubheading Synopsis
25395 -target-file-delete @var{targetfile}
25398 Delete @var{targetfile} from the target system.
25400 @subsubheading @value{GDBN} Command
25402 The corresponding @value{GDBN} command is @samp{remote delete}.
25404 @subsubheading Example
25408 -target-file-delete remotefile
25414 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25415 @node GDB/MI Miscellaneous Commands
25416 @section Miscellaneous @sc{gdb/mi} Commands
25418 @c @subheading -gdb-complete
25420 @subheading The @code{-gdb-exit} Command
25423 @subsubheading Synopsis
25429 Exit @value{GDBN} immediately.
25431 @subsubheading @value{GDBN} Command
25433 Approximately corresponds to @samp{quit}.
25435 @subsubheading Example
25445 @subheading The @code{-exec-abort} Command
25446 @findex -exec-abort
25448 @subsubheading Synopsis
25454 Kill the inferior running program.
25456 @subsubheading @value{GDBN} Command
25458 The corresponding @value{GDBN} command is @samp{kill}.
25460 @subsubheading Example
25465 @subheading The @code{-gdb-set} Command
25468 @subsubheading Synopsis
25474 Set an internal @value{GDBN} variable.
25475 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
25477 @subsubheading @value{GDBN} Command
25479 The corresponding @value{GDBN} command is @samp{set}.
25481 @subsubheading Example
25491 @subheading The @code{-gdb-show} Command
25494 @subsubheading Synopsis
25500 Show the current value of a @value{GDBN} variable.
25502 @subsubheading @value{GDBN} Command
25504 The corresponding @value{GDBN} command is @samp{show}.
25506 @subsubheading Example
25515 @c @subheading -gdb-source
25518 @subheading The @code{-gdb-version} Command
25519 @findex -gdb-version
25521 @subsubheading Synopsis
25527 Show version information for @value{GDBN}. Used mostly in testing.
25529 @subsubheading @value{GDBN} Command
25531 The @value{GDBN} equivalent is @samp{show version}. @value{GDBN} by
25532 default shows this information when you start an interactive session.
25534 @subsubheading Example
25536 @c This example modifies the actual output from GDB to avoid overfull
25542 ~Copyright 2000 Free Software Foundation, Inc.
25543 ~GDB is free software, covered by the GNU General Public License, and
25544 ~you are welcome to change it and/or distribute copies of it under
25545 ~ certain conditions.
25546 ~Type "show copying" to see the conditions.
25547 ~There is absolutely no warranty for GDB. Type "show warranty" for
25549 ~This GDB was configured as
25550 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
25555 @subheading The @code{-list-features} Command
25556 @findex -list-features
25558 Returns a list of particular features of the MI protocol that
25559 this version of gdb implements. A feature can be a command,
25560 or a new field in an output of some command, or even an
25561 important bugfix. While a frontend can sometimes detect presence
25562 of a feature at runtime, it is easier to perform detection at debugger
25565 The command returns a list of strings, with each string naming an
25566 available feature. Each returned string is just a name, it does not
25567 have any internal structure. The list of possible feature names
25573 (gdb) -list-features
25574 ^done,result=["feature1","feature2"]
25577 The current list of features is:
25580 @item frozen-varobjs
25581 Indicates presence of the @code{-var-set-frozen} command, as well
25582 as possible presense of the @code{frozen} field in the output
25583 of @code{-varobj-create}.
25584 @item pending-breakpoints
25585 Indicates presence of the @option{-f} option to the @code{-break-insert} command.
25587 Indicates presence of Python scripting support, Python-based
25588 pretty-printing commands, and possible presence of the
25589 @samp{display_hint} field in the output of @code{-var-list-children}
25591 Indicates presence of the @code{-thread-info} command.
25595 @subheading The @code{-list-target-features} Command
25596 @findex -list-target-features
25598 Returns a list of particular features that are supported by the
25599 target. Those features affect the permitted MI commands, but
25600 unlike the features reported by the @code{-list-features} command, the
25601 features depend on which target GDB is using at the moment. Whenever
25602 a target can change, due to commands such as @code{-target-select},
25603 @code{-target-attach} or @code{-exec-run}, the list of target features
25604 may change, and the frontend should obtain it again.
25608 (gdb) -list-features
25609 ^done,result=["async"]
25612 The current list of features is:
25616 Indicates that the target is capable of asynchronous command
25617 execution, which means that @value{GDBN} will accept further commands
25618 while the target is running.
25622 @subheading The @code{-list-thread-groups} Command
25623 @findex -list-thread-groups
25625 @subheading Synopsis
25628 -list-thread-groups [ --available ] [ @var{group} ]
25631 When used without the @var{group} parameter, lists top-level thread
25632 groups that are being debugged. When used with the @var{group}
25633 parameter, the children of the specified group are listed. The
25634 children can be either threads, or other groups. At present,
25635 @value{GDBN} will not report both threads and groups as children at
25636 the same time, but it may change in future.
25638 With the @samp{--available} option, instead of reporting groups that
25639 are been debugged, GDB will report all thread groups available on the
25640 target. Using the @samp{--available} option together with @var{group}
25643 @subheading Example
25647 -list-thread-groups
25648 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2"@}]
25649 -list-thread-groups 17
25650 ^done,threads=[@{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
25651 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},state="running"@},
25652 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
25653 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
25654 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},state="running"@}]]
25657 @subheading The @code{-interpreter-exec} Command
25658 @findex -interpreter-exec
25660 @subheading Synopsis
25663 -interpreter-exec @var{interpreter} @var{command}
25665 @anchor{-interpreter-exec}
25667 Execute the specified @var{command} in the given @var{interpreter}.
25669 @subheading @value{GDBN} Command
25671 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
25673 @subheading Example
25677 -interpreter-exec console "break main"
25678 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
25679 &"During symbol reading, bad structure-type format.\n"
25680 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
25685 @subheading The @code{-inferior-tty-set} Command
25686 @findex -inferior-tty-set
25688 @subheading Synopsis
25691 -inferior-tty-set /dev/pts/1
25694 Set terminal for future runs of the program being debugged.
25696 @subheading @value{GDBN} Command
25698 The corresponding @value{GDBN} command is @samp{set inferior-tty} /dev/pts/1.
25700 @subheading Example
25704 -inferior-tty-set /dev/pts/1
25709 @subheading The @code{-inferior-tty-show} Command
25710 @findex -inferior-tty-show
25712 @subheading Synopsis
25718 Show terminal for future runs of program being debugged.
25720 @subheading @value{GDBN} Command
25722 The corresponding @value{GDBN} command is @samp{show inferior-tty}.
25724 @subheading Example
25728 -inferior-tty-set /dev/pts/1
25732 ^done,inferior_tty_terminal="/dev/pts/1"
25736 @subheading The @code{-enable-timings} Command
25737 @findex -enable-timings
25739 @subheading Synopsis
25742 -enable-timings [yes | no]
25745 Toggle the printing of the wallclock, user and system times for an MI
25746 command as a field in its output. This command is to help frontend
25747 developers optimize the performance of their code. No argument is
25748 equivalent to @samp{yes}.
25750 @subheading @value{GDBN} Command
25754 @subheading Example
25762 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
25763 addr="0x080484ed",func="main",file="myprog.c",
25764 fullname="/home/nickrob/myprog.c",line="73",times="0"@},
25765 time=@{wallclock="0.05185",user="0.00800",system="0.00000"@}
25773 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
25774 frame=@{addr="0x080484ed",func="main",args=[@{name="argc",value="1"@},
25775 @{name="argv",value="0xbfb60364"@}],file="myprog.c",
25776 fullname="/home/nickrob/myprog.c",line="73"@}
25781 @chapter @value{GDBN} Annotations
25783 This chapter describes annotations in @value{GDBN}. Annotations were
25784 designed to interface @value{GDBN} to graphical user interfaces or other
25785 similar programs which want to interact with @value{GDBN} at a
25786 relatively high level.
25788 The annotation mechanism has largely been superseded by @sc{gdb/mi}
25792 This is Edition @value{EDITION}, @value{DATE}.
25796 * Annotations Overview:: What annotations are; the general syntax.
25797 * Server Prefix:: Issuing a command without affecting user state.
25798 * Prompting:: Annotations marking @value{GDBN}'s need for input.
25799 * Errors:: Annotations for error messages.
25800 * Invalidation:: Some annotations describe things now invalid.
25801 * Annotations for Running::
25802 Whether the program is running, how it stopped, etc.
25803 * Source Annotations:: Annotations describing source code.
25806 @node Annotations Overview
25807 @section What is an Annotation?
25808 @cindex annotations
25810 Annotations start with a newline character, two @samp{control-z}
25811 characters, and the name of the annotation. If there is no additional
25812 information associated with this annotation, the name of the annotation
25813 is followed immediately by a newline. If there is additional
25814 information, the name of the annotation is followed by a space, the
25815 additional information, and a newline. The additional information
25816 cannot contain newline characters.
25818 Any output not beginning with a newline and two @samp{control-z}
25819 characters denotes literal output from @value{GDBN}. Currently there is
25820 no need for @value{GDBN} to output a newline followed by two
25821 @samp{control-z} characters, but if there was such a need, the
25822 annotations could be extended with an @samp{escape} annotation which
25823 means those three characters as output.
25825 The annotation @var{level}, which is specified using the
25826 @option{--annotate} command line option (@pxref{Mode Options}), controls
25827 how much information @value{GDBN} prints together with its prompt,
25828 values of expressions, source lines, and other types of output. Level 0
25829 is for no annotations, level 1 is for use when @value{GDBN} is run as a
25830 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
25831 for programs that control @value{GDBN}, and level 2 annotations have
25832 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
25833 Interface, annotate, GDB's Obsolete Annotations}).
25836 @kindex set annotate
25837 @item set annotate @var{level}
25838 The @value{GDBN} command @code{set annotate} sets the level of
25839 annotations to the specified @var{level}.
25841 @item show annotate
25842 @kindex show annotate
25843 Show the current annotation level.
25846 This chapter describes level 3 annotations.
25848 A simple example of starting up @value{GDBN} with annotations is:
25851 $ @kbd{gdb --annotate=3}
25853 Copyright 2003 Free Software Foundation, Inc.
25854 GDB is free software, covered by the GNU General Public License,
25855 and you are welcome to change it and/or distribute copies of it
25856 under certain conditions.
25857 Type "show copying" to see the conditions.
25858 There is absolutely no warranty for GDB. Type "show warranty"
25860 This GDB was configured as "i386-pc-linux-gnu"
25871 Here @samp{quit} is input to @value{GDBN}; the rest is output from
25872 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
25873 denotes a @samp{control-z} character) are annotations; the rest is
25874 output from @value{GDBN}.
25876 @node Server Prefix
25877 @section The Server Prefix
25878 @cindex server prefix
25880 If you prefix a command with @samp{server } then it will not affect
25881 the command history, nor will it affect @value{GDBN}'s notion of which
25882 command to repeat if @key{RET} is pressed on a line by itself. This
25883 means that commands can be run behind a user's back by a front-end in
25884 a transparent manner.
25886 The @code{server } prefix does not affect the recording of values into
25887 the value history; to print a value without recording it into the
25888 value history, use the @code{output} command instead of the
25889 @code{print} command.
25891 Using this prefix also disables confirmation requests
25892 (@pxref{confirmation requests}).
25895 @section Annotation for @value{GDBN} Input
25897 @cindex annotations for prompts
25898 When @value{GDBN} prompts for input, it annotates this fact so it is possible
25899 to know when to send output, when the output from a given command is
25902 Different kinds of input each have a different @dfn{input type}. Each
25903 input type has three annotations: a @code{pre-} annotation, which
25904 denotes the beginning of any prompt which is being output, a plain
25905 annotation, which denotes the end of the prompt, and then a @code{post-}
25906 annotation which denotes the end of any echo which may (or may not) be
25907 associated with the input. For example, the @code{prompt} input type
25908 features the following annotations:
25916 The input types are
25919 @findex pre-prompt annotation
25920 @findex prompt annotation
25921 @findex post-prompt annotation
25923 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
25925 @findex pre-commands annotation
25926 @findex commands annotation
25927 @findex post-commands annotation
25929 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
25930 command. The annotations are repeated for each command which is input.
25932 @findex pre-overload-choice annotation
25933 @findex overload-choice annotation
25934 @findex post-overload-choice annotation
25935 @item overload-choice
25936 When @value{GDBN} wants the user to select between various overloaded functions.
25938 @findex pre-query annotation
25939 @findex query annotation
25940 @findex post-query annotation
25942 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
25944 @findex pre-prompt-for-continue annotation
25945 @findex prompt-for-continue annotation
25946 @findex post-prompt-for-continue annotation
25947 @item prompt-for-continue
25948 When @value{GDBN} is asking the user to press return to continue. Note: Don't
25949 expect this to work well; instead use @code{set height 0} to disable
25950 prompting. This is because the counting of lines is buggy in the
25951 presence of annotations.
25956 @cindex annotations for errors, warnings and interrupts
25958 @findex quit annotation
25963 This annotation occurs right before @value{GDBN} responds to an interrupt.
25965 @findex error annotation
25970 This annotation occurs right before @value{GDBN} responds to an error.
25972 Quit and error annotations indicate that any annotations which @value{GDBN} was
25973 in the middle of may end abruptly. For example, if a
25974 @code{value-history-begin} annotation is followed by a @code{error}, one
25975 cannot expect to receive the matching @code{value-history-end}. One
25976 cannot expect not to receive it either, however; an error annotation
25977 does not necessarily mean that @value{GDBN} is immediately returning all the way
25980 @findex error-begin annotation
25981 A quit or error annotation may be preceded by
25987 Any output between that and the quit or error annotation is the error
25990 Warning messages are not yet annotated.
25991 @c If we want to change that, need to fix warning(), type_error(),
25992 @c range_error(), and possibly other places.
25995 @section Invalidation Notices
25997 @cindex annotations for invalidation messages
25998 The following annotations say that certain pieces of state may have
26002 @findex frames-invalid annotation
26003 @item ^Z^Zframes-invalid
26005 The frames (for example, output from the @code{backtrace} command) may
26008 @findex breakpoints-invalid annotation
26009 @item ^Z^Zbreakpoints-invalid
26011 The breakpoints may have changed. For example, the user just added or
26012 deleted a breakpoint.
26015 @node Annotations for Running
26016 @section Running the Program
26017 @cindex annotations for running programs
26019 @findex starting annotation
26020 @findex stopping annotation
26021 When the program starts executing due to a @value{GDBN} command such as
26022 @code{step} or @code{continue},
26028 is output. When the program stops,
26034 is output. Before the @code{stopped} annotation, a variety of
26035 annotations describe how the program stopped.
26038 @findex exited annotation
26039 @item ^Z^Zexited @var{exit-status}
26040 The program exited, and @var{exit-status} is the exit status (zero for
26041 successful exit, otherwise nonzero).
26043 @findex signalled annotation
26044 @findex signal-name annotation
26045 @findex signal-name-end annotation
26046 @findex signal-string annotation
26047 @findex signal-string-end annotation
26048 @item ^Z^Zsignalled
26049 The program exited with a signal. After the @code{^Z^Zsignalled}, the
26050 annotation continues:
26056 ^Z^Zsignal-name-end
26060 ^Z^Zsignal-string-end
26065 where @var{name} is the name of the signal, such as @code{SIGILL} or
26066 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
26067 as @code{Illegal Instruction} or @code{Segmentation fault}.
26068 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
26069 user's benefit and have no particular format.
26071 @findex signal annotation
26073 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
26074 just saying that the program received the signal, not that it was
26075 terminated with it.
26077 @findex breakpoint annotation
26078 @item ^Z^Zbreakpoint @var{number}
26079 The program hit breakpoint number @var{number}.
26081 @findex watchpoint annotation
26082 @item ^Z^Zwatchpoint @var{number}
26083 The program hit watchpoint number @var{number}.
26086 @node Source Annotations
26087 @section Displaying Source
26088 @cindex annotations for source display
26090 @findex source annotation
26091 The following annotation is used instead of displaying source code:
26094 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
26097 where @var{filename} is an absolute file name indicating which source
26098 file, @var{line} is the line number within that file (where 1 is the
26099 first line in the file), @var{character} is the character position
26100 within the file (where 0 is the first character in the file) (for most
26101 debug formats this will necessarily point to the beginning of a line),
26102 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
26103 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
26104 @var{addr} is the address in the target program associated with the
26105 source which is being displayed. @var{addr} is in the form @samp{0x}
26106 followed by one or more lowercase hex digits (note that this does not
26107 depend on the language).
26109 @node JIT Interface
26110 @chapter JIT Compilation Interface
26111 @cindex just-in-time compilation
26112 @cindex JIT compilation interface
26114 This chapter documents @value{GDBN}'s @dfn{just-in-time} (JIT) compilation
26115 interface. A JIT compiler is a program or library that generates native
26116 executable code at runtime and executes it, usually in order to achieve good
26117 performance while maintaining platform independence.
26119 Programs that use JIT compilation are normally difficult to debug because
26120 portions of their code are generated at runtime, instead of being loaded from
26121 object files, which is where @value{GDBN} normally finds the program's symbols
26122 and debug information. In order to debug programs that use JIT compilation,
26123 @value{GDBN} has an interface that allows the program to register in-memory
26124 symbol files with @value{GDBN} at runtime.
26126 If you are using @value{GDBN} to debug a program that uses this interface, then
26127 it should work transparently so long as you have not stripped the binary. If
26128 you are developing a JIT compiler, then the interface is documented in the rest
26129 of this chapter. At this time, the only known client of this interface is the
26132 Broadly speaking, the JIT interface mirrors the dynamic loader interface. The
26133 JIT compiler communicates with @value{GDBN} by writing data into a global
26134 variable and calling a fuction at a well-known symbol. When @value{GDBN}
26135 attaches, it reads a linked list of symbol files from the global variable to
26136 find existing code, and puts a breakpoint in the function so that it can find
26137 out about additional code.
26140 * Declarations:: Relevant C struct declarations
26141 * Registering Code:: Steps to register code
26142 * Unregistering Code:: Steps to unregister code
26146 @section JIT Declarations
26148 These are the relevant struct declarations that a C program should include to
26149 implement the interface:
26159 struct jit_code_entry
26161 struct jit_code_entry *next_entry;
26162 struct jit_code_entry *prev_entry;
26163 const char *symfile_addr;
26164 uint64_t symfile_size;
26167 struct jit_descriptor
26170 /* This type should be jit_actions_t, but we use uint32_t
26171 to be explicit about the bitwidth. */
26172 uint32_t action_flag;
26173 struct jit_code_entry *relevant_entry;
26174 struct jit_code_entry *first_entry;
26177 /* GDB puts a breakpoint in this function. */
26178 void __attribute__((noinline)) __jit_debug_register_code() @{ @};
26180 /* Make sure to specify the version statically, because the
26181 debugger may check the version before we can set it. */
26182 struct jit_descriptor __jit_debug_descriptor = @{ 1, 0, 0, 0 @};
26185 If the JIT is multi-threaded, then it is important that the JIT synchronize any
26186 modifications to this global data properly, which can easily be done by putting
26187 a global mutex around modifications to these structures.
26189 @node Registering Code
26190 @section Registering Code
26192 To register code with @value{GDBN}, the JIT should follow this protocol:
26196 Generate an object file in memory with symbols and other desired debug
26197 information. The file must include the virtual addresses of the sections.
26200 Create a code entry for the file, which gives the start and size of the symbol
26204 Add it to the linked list in the JIT descriptor.
26207 Point the relevant_entry field of the descriptor at the entry.
26210 Set @code{action_flag} to @code{JIT_REGISTER} and call
26211 @code{__jit_debug_register_code}.
26214 When @value{GDBN} is attached and the breakpoint fires, @value{GDBN} uses the
26215 @code{relevant_entry} pointer so it doesn't have to walk the list looking for
26216 new code. However, the linked list must still be maintained in order to allow
26217 @value{GDBN} to attach to a running process and still find the symbol files.
26219 @node Unregistering Code
26220 @section Unregistering Code
26222 If code is freed, then the JIT should use the following protocol:
26226 Remove the code entry corresponding to the code from the linked list.
26229 Point the @code{relevant_entry} field of the descriptor at the code entry.
26232 Set @code{action_flag} to @code{JIT_UNREGISTER} and call
26233 @code{__jit_debug_register_code}.
26236 If the JIT frees or recompiles code without unregistering it, then @value{GDBN}
26237 and the JIT will leak the memory used for the associated symbol files.
26240 @chapter Reporting Bugs in @value{GDBN}
26241 @cindex bugs in @value{GDBN}
26242 @cindex reporting bugs in @value{GDBN}
26244 Your bug reports play an essential role in making @value{GDBN} reliable.
26246 Reporting a bug may help you by bringing a solution to your problem, or it
26247 may not. But in any case the principal function of a bug report is to help
26248 the entire community by making the next version of @value{GDBN} work better. Bug
26249 reports are your contribution to the maintenance of @value{GDBN}.
26251 In order for a bug report to serve its purpose, you must include the
26252 information that enables us to fix the bug.
26255 * Bug Criteria:: Have you found a bug?
26256 * Bug Reporting:: How to report bugs
26260 @section Have You Found a Bug?
26261 @cindex bug criteria
26263 If you are not sure whether you have found a bug, here are some guidelines:
26266 @cindex fatal signal
26267 @cindex debugger crash
26268 @cindex crash of debugger
26270 If the debugger gets a fatal signal, for any input whatever, that is a
26271 @value{GDBN} bug. Reliable debuggers never crash.
26273 @cindex error on valid input
26275 If @value{GDBN} produces an error message for valid input, that is a
26276 bug. (Note that if you're cross debugging, the problem may also be
26277 somewhere in the connection to the target.)
26279 @cindex invalid input
26281 If @value{GDBN} does not produce an error message for invalid input,
26282 that is a bug. However, you should note that your idea of
26283 ``invalid input'' might be our idea of ``an extension'' or ``support
26284 for traditional practice''.
26287 If you are an experienced user of debugging tools, your suggestions
26288 for improvement of @value{GDBN} are welcome in any case.
26291 @node Bug Reporting
26292 @section How to Report Bugs
26293 @cindex bug reports
26294 @cindex @value{GDBN} bugs, reporting
26296 A number of companies and individuals offer support for @sc{gnu} products.
26297 If you obtained @value{GDBN} from a support organization, we recommend you
26298 contact that organization first.
26300 You can find contact information for many support companies and
26301 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
26303 @c should add a web page ref...
26306 @ifset BUGURL_DEFAULT
26307 In any event, we also recommend that you submit bug reports for
26308 @value{GDBN}. The preferred method is to submit them directly using
26309 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
26310 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
26313 @strong{Do not send bug reports to @samp{info-gdb}, or to
26314 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
26315 not want to receive bug reports. Those that do have arranged to receive
26318 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
26319 serves as a repeater. The mailing list and the newsgroup carry exactly
26320 the same messages. Often people think of posting bug reports to the
26321 newsgroup instead of mailing them. This appears to work, but it has one
26322 problem which can be crucial: a newsgroup posting often lacks a mail
26323 path back to the sender. Thus, if we need to ask for more information,
26324 we may be unable to reach you. For this reason, it is better to send
26325 bug reports to the mailing list.
26327 @ifclear BUGURL_DEFAULT
26328 In any event, we also recommend that you submit bug reports for
26329 @value{GDBN} to @value{BUGURL}.
26333 The fundamental principle of reporting bugs usefully is this:
26334 @strong{report all the facts}. If you are not sure whether to state a
26335 fact or leave it out, state it!
26337 Often people omit facts because they think they know what causes the
26338 problem and assume that some details do not matter. Thus, you might
26339 assume that the name of the variable you use in an example does not matter.
26340 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
26341 stray memory reference which happens to fetch from the location where that
26342 name is stored in memory; perhaps, if the name were different, the contents
26343 of that location would fool the debugger into doing the right thing despite
26344 the bug. Play it safe and give a specific, complete example. That is the
26345 easiest thing for you to do, and the most helpful.
26347 Keep in mind that the purpose of a bug report is to enable us to fix the
26348 bug. It may be that the bug has been reported previously, but neither
26349 you nor we can know that unless your bug report is complete and
26352 Sometimes people give a few sketchy facts and ask, ``Does this ring a
26353 bell?'' Those bug reports are useless, and we urge everyone to
26354 @emph{refuse to respond to them} except to chide the sender to report
26357 To enable us to fix the bug, you should include all these things:
26361 The version of @value{GDBN}. @value{GDBN} announces it if you start
26362 with no arguments; you can also print it at any time using @code{show
26365 Without this, we will not know whether there is any point in looking for
26366 the bug in the current version of @value{GDBN}.
26369 The type of machine you are using, and the operating system name and
26373 What compiler (and its version) was used to compile @value{GDBN}---e.g.@:
26374 ``@value{GCC}--2.8.1''.
26377 What compiler (and its version) was used to compile the program you are
26378 debugging---e.g.@: ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
26379 C Compiler''. For @value{NGCC}, you can say @kbd{@value{GCC} --version}
26380 to get this information; for other compilers, see the documentation for
26384 The command arguments you gave the compiler to compile your example and
26385 observe the bug. For example, did you use @samp{-O}? To guarantee
26386 you will not omit something important, list them all. A copy of the
26387 Makefile (or the output from make) is sufficient.
26389 If we were to try to guess the arguments, we would probably guess wrong
26390 and then we might not encounter the bug.
26393 A complete input script, and all necessary source files, that will
26397 A description of what behavior you observe that you believe is
26398 incorrect. For example, ``It gets a fatal signal.''
26400 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
26401 will certainly notice it. But if the bug is incorrect output, we might
26402 not notice unless it is glaringly wrong. You might as well not give us
26403 a chance to make a mistake.
26405 Even if the problem you experience is a fatal signal, you should still
26406 say so explicitly. Suppose something strange is going on, such as, your
26407 copy of @value{GDBN} is out of synch, or you have encountered a bug in
26408 the C library on your system. (This has happened!) Your copy might
26409 crash and ours would not. If you told us to expect a crash, then when
26410 ours fails to crash, we would know that the bug was not happening for
26411 us. If you had not told us to expect a crash, then we would not be able
26412 to draw any conclusion from our observations.
26415 @cindex recording a session script
26416 To collect all this information, you can use a session recording program
26417 such as @command{script}, which is available on many Unix systems.
26418 Just run your @value{GDBN} session inside @command{script} and then
26419 include the @file{typescript} file with your bug report.
26421 Another way to record a @value{GDBN} session is to run @value{GDBN}
26422 inside Emacs and then save the entire buffer to a file.
26425 If you wish to suggest changes to the @value{GDBN} source, send us context
26426 diffs. If you even discuss something in the @value{GDBN} source, refer to
26427 it by context, not by line number.
26429 The line numbers in our development sources will not match those in your
26430 sources. Your line numbers would convey no useful information to us.
26434 Here are some things that are not necessary:
26438 A description of the envelope of the bug.
26440 Often people who encounter a bug spend a lot of time investigating
26441 which changes to the input file will make the bug go away and which
26442 changes will not affect it.
26444 This is often time consuming and not very useful, because the way we
26445 will find the bug is by running a single example under the debugger
26446 with breakpoints, not by pure deduction from a series of examples.
26447 We recommend that you save your time for something else.
26449 Of course, if you can find a simpler example to report @emph{instead}
26450 of the original one, that is a convenience for us. Errors in the
26451 output will be easier to spot, running under the debugger will take
26452 less time, and so on.
26454 However, simplification is not vital; if you do not want to do this,
26455 report the bug anyway and send us the entire test case you used.
26458 A patch for the bug.
26460 A patch for the bug does help us if it is a good one. But do not omit
26461 the necessary information, such as the test case, on the assumption that
26462 a patch is all we need. We might see problems with your patch and decide
26463 to fix the problem another way, or we might not understand it at all.
26465 Sometimes with a program as complicated as @value{GDBN} it is very hard to
26466 construct an example that will make the program follow a certain path
26467 through the code. If you do not send us the example, we will not be able
26468 to construct one, so we will not be able to verify that the bug is fixed.
26470 And if we cannot understand what bug you are trying to fix, or why your
26471 patch should be an improvement, we will not install it. A test case will
26472 help us to understand.
26475 A guess about what the bug is or what it depends on.
26477 Such guesses are usually wrong. Even we cannot guess right about such
26478 things without first using the debugger to find the facts.
26481 @c The readline documentation is distributed with the readline code
26482 @c and consists of the two following files:
26484 @c inc-hist.texinfo
26485 @c Use -I with makeinfo to point to the appropriate directory,
26486 @c environment var TEXINPUTS with TeX.
26487 @include rluser.texi
26488 @include inc-hist.texinfo
26491 @node Formatting Documentation
26492 @appendix Formatting Documentation
26494 @cindex @value{GDBN} reference card
26495 @cindex reference card
26496 The @value{GDBN} 4 release includes an already-formatted reference card, ready
26497 for printing with PostScript or Ghostscript, in the @file{gdb}
26498 subdirectory of the main source directory@footnote{In
26499 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
26500 release.}. If you can use PostScript or Ghostscript with your printer,
26501 you can print the reference card immediately with @file{refcard.ps}.
26503 The release also includes the source for the reference card. You
26504 can format it, using @TeX{}, by typing:
26510 The @value{GDBN} reference card is designed to print in @dfn{landscape}
26511 mode on US ``letter'' size paper;
26512 that is, on a sheet 11 inches wide by 8.5 inches
26513 high. You will need to specify this form of printing as an option to
26514 your @sc{dvi} output program.
26516 @cindex documentation
26518 All the documentation for @value{GDBN} comes as part of the machine-readable
26519 distribution. The documentation is written in Texinfo format, which is
26520 a documentation system that uses a single source file to produce both
26521 on-line information and a printed manual. You can use one of the Info
26522 formatting commands to create the on-line version of the documentation
26523 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
26525 @value{GDBN} includes an already formatted copy of the on-line Info
26526 version of this manual in the @file{gdb} subdirectory. The main Info
26527 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
26528 subordinate files matching @samp{gdb.info*} in the same directory. If
26529 necessary, you can print out these files, or read them with any editor;
26530 but they are easier to read using the @code{info} subsystem in @sc{gnu}
26531 Emacs or the standalone @code{info} program, available as part of the
26532 @sc{gnu} Texinfo distribution.
26534 If you want to format these Info files yourself, you need one of the
26535 Info formatting programs, such as @code{texinfo-format-buffer} or
26538 If you have @code{makeinfo} installed, and are in the top level
26539 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
26540 version @value{GDBVN}), you can make the Info file by typing:
26547 If you want to typeset and print copies of this manual, you need @TeX{},
26548 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
26549 Texinfo definitions file.
26551 @TeX{} is a typesetting program; it does not print files directly, but
26552 produces output files called @sc{dvi} files. To print a typeset
26553 document, you need a program to print @sc{dvi} files. If your system
26554 has @TeX{} installed, chances are it has such a program. The precise
26555 command to use depends on your system; @kbd{lpr -d} is common; another
26556 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
26557 require a file name without any extension or a @samp{.dvi} extension.
26559 @TeX{} also requires a macro definitions file called
26560 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
26561 written in Texinfo format. On its own, @TeX{} cannot either read or
26562 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
26563 and is located in the @file{gdb-@var{version-number}/texinfo}
26566 If you have @TeX{} and a @sc{dvi} printer program installed, you can
26567 typeset and print this manual. First switch to the @file{gdb}
26568 subdirectory of the main source directory (for example, to
26569 @file{gdb-@value{GDBVN}/gdb}) and type:
26575 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
26577 @node Installing GDB
26578 @appendix Installing @value{GDBN}
26579 @cindex installation
26582 * Requirements:: Requirements for building @value{GDBN}
26583 * Running Configure:: Invoking the @value{GDBN} @file{configure} script
26584 * Separate Objdir:: Compiling @value{GDBN} in another directory
26585 * Config Names:: Specifying names for hosts and targets
26586 * Configure Options:: Summary of options for configure
26587 * System-wide configuration:: Having a system-wide init file
26591 @section Requirements for Building @value{GDBN}
26592 @cindex building @value{GDBN}, requirements for
26594 Building @value{GDBN} requires various tools and packages to be available.
26595 Other packages will be used only if they are found.
26597 @heading Tools/Packages Necessary for Building @value{GDBN}
26599 @item ISO C90 compiler
26600 @value{GDBN} is written in ISO C90. It should be buildable with any
26601 working C90 compiler, e.g.@: GCC.
26605 @heading Tools/Packages Optional for Building @value{GDBN}
26609 @value{GDBN} can use the Expat XML parsing library. This library may be
26610 included with your operating system distribution; if it is not, you
26611 can get the latest version from @url{http://expat.sourceforge.net}.
26612 The @file{configure} script will search for this library in several
26613 standard locations; if it is installed in an unusual path, you can
26614 use the @option{--with-libexpat-prefix} option to specify its location.
26620 Remote protocol memory maps (@pxref{Memory Map Format})
26622 Target descriptions (@pxref{Target Descriptions})
26624 Remote shared library lists (@pxref{Library List Format})
26626 MS-Windows shared libraries (@pxref{Shared Libraries})
26630 @cindex compressed debug sections
26631 @value{GDBN} will use the @samp{zlib} library, if available, to read
26632 compressed debug sections. Some linkers, such as GNU gold, are capable
26633 of producing binaries with compressed debug sections. If @value{GDBN}
26634 is compiled with @samp{zlib}, it will be able to read the debug
26635 information in such binaries.
26637 The @samp{zlib} library is likely included with your operating system
26638 distribution; if it is not, you can get the latest version from
26639 @url{http://zlib.net}.
26642 @value{GDBN}'s features related to character sets (@pxref{Character
26643 Sets}) require a functioning @code{iconv} implementation. If you are
26644 on a GNU system, then this is provided by the GNU C Library. Some
26645 other systems also provide a working @code{iconv}.
26647 On systems with @code{iconv}, you can install GNU Libiconv. If you
26648 have previously installed Libiconv, you can use the
26649 @option{--with-libiconv-prefix} option to configure.
26651 @value{GDBN}'s top-level @file{configure} and @file{Makefile} will
26652 arrange to build Libiconv if a directory named @file{libiconv} appears
26653 in the top-most source directory. If Libiconv is built this way, and
26654 if the operating system does not provide a suitable @code{iconv}
26655 implementation, then the just-built library will automatically be used
26656 by @value{GDBN}. One easy way to set this up is to download GNU
26657 Libiconv, unpack it, and then rename the directory holding the
26658 Libiconv source code to @samp{libiconv}.
26661 @node Running Configure
26662 @section Invoking the @value{GDBN} @file{configure} Script
26663 @cindex configuring @value{GDBN}
26664 @value{GDBN} comes with a @file{configure} script that automates the process
26665 of preparing @value{GDBN} for installation; you can then use @code{make} to
26666 build the @code{gdb} program.
26668 @c irrelevant in info file; it's as current as the code it lives with.
26669 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
26670 look at the @file{README} file in the sources; we may have improved the
26671 installation procedures since publishing this manual.}
26674 The @value{GDBN} distribution includes all the source code you need for
26675 @value{GDBN} in a single directory, whose name is usually composed by
26676 appending the version number to @samp{gdb}.
26678 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
26679 @file{gdb-@value{GDBVN}} directory. That directory contains:
26682 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
26683 script for configuring @value{GDBN} and all its supporting libraries
26685 @item gdb-@value{GDBVN}/gdb
26686 the source specific to @value{GDBN} itself
26688 @item gdb-@value{GDBVN}/bfd
26689 source for the Binary File Descriptor library
26691 @item gdb-@value{GDBVN}/include
26692 @sc{gnu} include files
26694 @item gdb-@value{GDBVN}/libiberty
26695 source for the @samp{-liberty} free software library
26697 @item gdb-@value{GDBVN}/opcodes
26698 source for the library of opcode tables and disassemblers
26700 @item gdb-@value{GDBVN}/readline
26701 source for the @sc{gnu} command-line interface
26703 @item gdb-@value{GDBVN}/glob
26704 source for the @sc{gnu} filename pattern-matching subroutine
26706 @item gdb-@value{GDBVN}/mmalloc
26707 source for the @sc{gnu} memory-mapped malloc package
26710 The simplest way to configure and build @value{GDBN} is to run @file{configure}
26711 from the @file{gdb-@var{version-number}} source directory, which in
26712 this example is the @file{gdb-@value{GDBVN}} directory.
26714 First switch to the @file{gdb-@var{version-number}} source directory
26715 if you are not already in it; then run @file{configure}. Pass the
26716 identifier for the platform on which @value{GDBN} will run as an
26722 cd gdb-@value{GDBVN}
26723 ./configure @var{host}
26728 where @var{host} is an identifier such as @samp{sun4} or
26729 @samp{decstation}, that identifies the platform where @value{GDBN} will run.
26730 (You can often leave off @var{host}; @file{configure} tries to guess the
26731 correct value by examining your system.)
26733 Running @samp{configure @var{host}} and then running @code{make} builds the
26734 @file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty}
26735 libraries, then @code{gdb} itself. The configured source files, and the
26736 binaries, are left in the corresponding source directories.
26739 @file{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
26740 system does not recognize this automatically when you run a different
26741 shell, you may need to run @code{sh} on it explicitly:
26744 sh configure @var{host}
26747 If you run @file{configure} from a directory that contains source
26748 directories for multiple libraries or programs, such as the
26749 @file{gdb-@value{GDBVN}} source directory for version @value{GDBVN},
26751 creates configuration files for every directory level underneath (unless
26752 you tell it not to, with the @samp{--norecursion} option).
26754 You should run the @file{configure} script from the top directory in the
26755 source tree, the @file{gdb-@var{version-number}} directory. If you run
26756 @file{configure} from one of the subdirectories, you will configure only
26757 that subdirectory. That is usually not what you want. In particular,
26758 if you run the first @file{configure} from the @file{gdb} subdirectory
26759 of the @file{gdb-@var{version-number}} directory, you will omit the
26760 configuration of @file{bfd}, @file{readline}, and other sibling
26761 directories of the @file{gdb} subdirectory. This leads to build errors
26762 about missing include files such as @file{bfd/bfd.h}.
26764 You can install @code{@value{GDBP}} anywhere; it has no hardwired paths.
26765 However, you should make sure that the shell on your path (named by
26766 the @samp{SHELL} environment variable) is publicly readable. Remember
26767 that @value{GDBN} uses the shell to start your program---some systems refuse to
26768 let @value{GDBN} debug child processes whose programs are not readable.
26770 @node Separate Objdir
26771 @section Compiling @value{GDBN} in Another Directory
26773 If you want to run @value{GDBN} versions for several host or target machines,
26774 you need a different @code{gdb} compiled for each combination of
26775 host and target. @file{configure} is designed to make this easy by
26776 allowing you to generate each configuration in a separate subdirectory,
26777 rather than in the source directory. If your @code{make} program
26778 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
26779 @code{make} in each of these directories builds the @code{gdb}
26780 program specified there.
26782 To build @code{gdb} in a separate directory, run @file{configure}
26783 with the @samp{--srcdir} option to specify where to find the source.
26784 (You also need to specify a path to find @file{configure}
26785 itself from your working directory. If the path to @file{configure}
26786 would be the same as the argument to @samp{--srcdir}, you can leave out
26787 the @samp{--srcdir} option; it is assumed.)
26789 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
26790 separate directory for a Sun 4 like this:
26794 cd gdb-@value{GDBVN}
26797 ../gdb-@value{GDBVN}/configure sun4
26802 When @file{configure} builds a configuration using a remote source
26803 directory, it creates a tree for the binaries with the same structure
26804 (and using the same names) as the tree under the source directory. In
26805 the example, you'd find the Sun 4 library @file{libiberty.a} in the
26806 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
26807 @file{gdb-sun4/gdb}.
26809 Make sure that your path to the @file{configure} script has just one
26810 instance of @file{gdb} in it. If your path to @file{configure} looks
26811 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
26812 one subdirectory of @value{GDBN}, not the whole package. This leads to
26813 build errors about missing include files such as @file{bfd/bfd.h}.
26815 One popular reason to build several @value{GDBN} configurations in separate
26816 directories is to configure @value{GDBN} for cross-compiling (where
26817 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
26818 programs that run on another machine---the @dfn{target}).
26819 You specify a cross-debugging target by
26820 giving the @samp{--target=@var{target}} option to @file{configure}.
26822 When you run @code{make} to build a program or library, you must run
26823 it in a configured directory---whatever directory you were in when you
26824 called @file{configure} (or one of its subdirectories).
26826 The @code{Makefile} that @file{configure} generates in each source
26827 directory also runs recursively. If you type @code{make} in a source
26828 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
26829 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
26830 will build all the required libraries, and then build GDB.
26832 When you have multiple hosts or targets configured in separate
26833 directories, you can run @code{make} on them in parallel (for example,
26834 if they are NFS-mounted on each of the hosts); they will not interfere
26838 @section Specifying Names for Hosts and Targets
26840 The specifications used for hosts and targets in the @file{configure}
26841 script are based on a three-part naming scheme, but some short predefined
26842 aliases are also supported. The full naming scheme encodes three pieces
26843 of information in the following pattern:
26846 @var{architecture}-@var{vendor}-@var{os}
26849 For example, you can use the alias @code{sun4} as a @var{host} argument,
26850 or as the value for @var{target} in a @code{--target=@var{target}}
26851 option. The equivalent full name is @samp{sparc-sun-sunos4}.
26853 The @file{configure} script accompanying @value{GDBN} does not provide
26854 any query facility to list all supported host and target names or
26855 aliases. @file{configure} calls the Bourne shell script
26856 @code{config.sub} to map abbreviations to full names; you can read the
26857 script, if you wish, or you can use it to test your guesses on
26858 abbreviations---for example:
26861 % sh config.sub i386-linux
26863 % sh config.sub alpha-linux
26864 alpha-unknown-linux-gnu
26865 % sh config.sub hp9k700
26867 % sh config.sub sun4
26868 sparc-sun-sunos4.1.1
26869 % sh config.sub sun3
26870 m68k-sun-sunos4.1.1
26871 % sh config.sub i986v
26872 Invalid configuration `i986v': machine `i986v' not recognized
26876 @code{config.sub} is also distributed in the @value{GDBN} source
26877 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
26879 @node Configure Options
26880 @section @file{configure} Options
26882 Here is a summary of the @file{configure} options and arguments that
26883 are most often useful for building @value{GDBN}. @file{configure} also has
26884 several other options not listed here. @inforef{What Configure
26885 Does,,configure.info}, for a full explanation of @file{configure}.
26888 configure @r{[}--help@r{]}
26889 @r{[}--prefix=@var{dir}@r{]}
26890 @r{[}--exec-prefix=@var{dir}@r{]}
26891 @r{[}--srcdir=@var{dirname}@r{]}
26892 @r{[}--norecursion@r{]} @r{[}--rm@r{]}
26893 @r{[}--target=@var{target}@r{]}
26898 You may introduce options with a single @samp{-} rather than
26899 @samp{--} if you prefer; but you may abbreviate option names if you use
26904 Display a quick summary of how to invoke @file{configure}.
26906 @item --prefix=@var{dir}
26907 Configure the source to install programs and files under directory
26910 @item --exec-prefix=@var{dir}
26911 Configure the source to install programs under directory
26914 @c avoid splitting the warning from the explanation:
26916 @item --srcdir=@var{dirname}
26917 @strong{Warning: using this option requires @sc{gnu} @code{make}, or another
26918 @code{make} that implements the @code{VPATH} feature.}@*
26919 Use this option to make configurations in directories separate from the
26920 @value{GDBN} source directories. Among other things, you can use this to
26921 build (or maintain) several configurations simultaneously, in separate
26922 directories. @file{configure} writes configuration-specific files in
26923 the current directory, but arranges for them to use the source in the
26924 directory @var{dirname}. @file{configure} creates directories under
26925 the working directory in parallel to the source directories below
26928 @item --norecursion
26929 Configure only the directory level where @file{configure} is executed; do not
26930 propagate configuration to subdirectories.
26932 @item --target=@var{target}
26933 Configure @value{GDBN} for cross-debugging programs running on the specified
26934 @var{target}. Without this option, @value{GDBN} is configured to debug
26935 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
26937 There is no convenient way to generate a list of all available targets.
26939 @item @var{host} @dots{}
26940 Configure @value{GDBN} to run on the specified @var{host}.
26942 There is no convenient way to generate a list of all available hosts.
26945 There are many other options available as well, but they are generally
26946 needed for special purposes only.
26948 @node System-wide configuration
26949 @section System-wide configuration and settings
26950 @cindex system-wide init file
26952 @value{GDBN} can be configured to have a system-wide init file;
26953 this file will be read and executed at startup (@pxref{Startup, , What
26954 @value{GDBN} does during startup}).
26956 Here is the corresponding configure option:
26959 @item --with-system-gdbinit=@var{file}
26960 Specify that the default location of the system-wide init file is
26964 If @value{GDBN} has been configured with the option @option{--prefix=$prefix},
26965 it may be subject to relocation. Two possible cases:
26969 If the default location of this init file contains @file{$prefix},
26970 it will be subject to relocation. Suppose that the configure options
26971 are @option{--prefix=$prefix --with-system-gdbinit=$prefix/etc/gdbinit};
26972 if @value{GDBN} is moved from @file{$prefix} to @file{$install}, the system
26973 init file is looked for as @file{$install/etc/gdbinit} instead of
26974 @file{$prefix/etc/gdbinit}.
26977 By contrast, if the default location does not contain the prefix,
26978 it will not be relocated. E.g.@: if @value{GDBN} has been configured with
26979 @option{--prefix=/usr/local --with-system-gdbinit=/usr/share/gdb/gdbinit},
26980 then @value{GDBN} will always look for @file{/usr/share/gdb/gdbinit},
26981 wherever @value{GDBN} is installed.
26984 @node Maintenance Commands
26985 @appendix Maintenance Commands
26986 @cindex maintenance commands
26987 @cindex internal commands
26989 In addition to commands intended for @value{GDBN} users, @value{GDBN}
26990 includes a number of commands intended for @value{GDBN} developers,
26991 that are not documented elsewhere in this manual. These commands are
26992 provided here for reference. (For commands that turn on debugging
26993 messages, see @ref{Debugging Output}.)
26996 @kindex maint agent
26997 @kindex maint agent-eval
26998 @item maint agent @var{expression}
26999 @itemx maint agent-eval @var{expression}
27000 Translate the given @var{expression} into remote agent bytecodes.
27001 This command is useful for debugging the Agent Expression mechanism
27002 (@pxref{Agent Expressions}). The @samp{agent} version produces an
27003 expression useful for data collection, such as by tracepoints, while
27004 @samp{maint agent-eval} produces an expression that evaluates directly
27005 to a result. For instance, a collection expression for @code{globa +
27006 globb} will include bytecodes to record four bytes of memory at each
27007 of the addresses of @code{globa} and @code{globb}, while discarding
27008 the result of the addition, while an evaluation expression will do the
27009 addition and return the sum.
27011 @kindex maint info breakpoints
27012 @item @anchor{maint info breakpoints}maint info breakpoints
27013 Using the same format as @samp{info breakpoints}, display both the
27014 breakpoints you've set explicitly, and those @value{GDBN} is using for
27015 internal purposes. Internal breakpoints are shown with negative
27016 breakpoint numbers. The type column identifies what kind of breakpoint
27021 Normal, explicitly set breakpoint.
27024 Normal, explicitly set watchpoint.
27027 Internal breakpoint, used to handle correctly stepping through
27028 @code{longjmp} calls.
27030 @item longjmp resume
27031 Internal breakpoint at the target of a @code{longjmp}.
27034 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
27037 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
27040 Shared library events.
27044 @kindex set displaced-stepping
27045 @kindex show displaced-stepping
27046 @cindex displaced stepping support
27047 @cindex out-of-line single-stepping
27048 @item set displaced-stepping
27049 @itemx show displaced-stepping
27050 Control whether or not @value{GDBN} will do @dfn{displaced stepping}
27051 if the target supports it. Displaced stepping is a way to single-step
27052 over breakpoints without removing them from the inferior, by executing
27053 an out-of-line copy of the instruction that was originally at the
27054 breakpoint location. It is also known as out-of-line single-stepping.
27057 @item set displaced-stepping on
27058 If the target architecture supports it, @value{GDBN} will use
27059 displaced stepping to step over breakpoints.
27061 @item set displaced-stepping off
27062 @value{GDBN} will not use displaced stepping to step over breakpoints,
27063 even if such is supported by the target architecture.
27065 @cindex non-stop mode, and @samp{set displaced-stepping}
27066 @item set displaced-stepping auto
27067 This is the default mode. @value{GDBN} will use displaced stepping
27068 only if non-stop mode is active (@pxref{Non-Stop Mode}) and the target
27069 architecture supports displaced stepping.
27072 @kindex maint check-symtabs
27073 @item maint check-symtabs
27074 Check the consistency of psymtabs and symtabs.
27076 @kindex maint cplus first_component
27077 @item maint cplus first_component @var{name}
27078 Print the first C@t{++} class/namespace component of @var{name}.
27080 @kindex maint cplus namespace
27081 @item maint cplus namespace
27082 Print the list of possible C@t{++} namespaces.
27084 @kindex maint demangle
27085 @item maint demangle @var{name}
27086 Demangle a C@t{++} or Objective-C mangled @var{name}.
27088 @kindex maint deprecate
27089 @kindex maint undeprecate
27090 @cindex deprecated commands
27091 @item maint deprecate @var{command} @r{[}@var{replacement}@r{]}
27092 @itemx maint undeprecate @var{command}
27093 Deprecate or undeprecate the named @var{command}. Deprecated commands
27094 cause @value{GDBN} to issue a warning when you use them. The optional
27095 argument @var{replacement} says which newer command should be used in
27096 favor of the deprecated one; if it is given, @value{GDBN} will mention
27097 the replacement as part of the warning.
27099 @kindex maint dump-me
27100 @item maint dump-me
27101 @cindex @code{SIGQUIT} signal, dump core of @value{GDBN}
27102 Cause a fatal signal in the debugger and force it to dump its core.
27103 This is supported only on systems which support aborting a program
27104 with the @code{SIGQUIT} signal.
27106 @kindex maint internal-error
27107 @kindex maint internal-warning
27108 @item maint internal-error @r{[}@var{message-text}@r{]}
27109 @itemx maint internal-warning @r{[}@var{message-text}@r{]}
27110 Cause @value{GDBN} to call the internal function @code{internal_error}
27111 or @code{internal_warning} and hence behave as though an internal error
27112 or internal warning has been detected. In addition to reporting the
27113 internal problem, these functions give the user the opportunity to
27114 either quit @value{GDBN} or create a core file of the current
27115 @value{GDBN} session.
27117 These commands take an optional parameter @var{message-text} that is
27118 used as the text of the error or warning message.
27120 Here's an example of using @code{internal-error}:
27123 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
27124 @dots{}/maint.c:121: internal-error: testing, 1, 2
27125 A problem internal to GDB has been detected. Further
27126 debugging may prove unreliable.
27127 Quit this debugging session? (y or n) @kbd{n}
27128 Create a core file? (y or n) @kbd{n}
27132 @cindex @value{GDBN} internal error
27133 @cindex internal errors, control of @value{GDBN} behavior
27135 @kindex maint set internal-error
27136 @kindex maint show internal-error
27137 @kindex maint set internal-warning
27138 @kindex maint show internal-warning
27139 @item maint set internal-error @var{action} [ask|yes|no]
27140 @itemx maint show internal-error @var{action}
27141 @itemx maint set internal-warning @var{action} [ask|yes|no]
27142 @itemx maint show internal-warning @var{action}
27143 When @value{GDBN} reports an internal problem (error or warning) it
27144 gives the user the opportunity to both quit @value{GDBN} and create a
27145 core file of the current @value{GDBN} session. These commands let you
27146 override the default behaviour for each particular @var{action},
27147 described in the table below.
27151 You can specify that @value{GDBN} should always (yes) or never (no)
27152 quit. The default is to ask the user what to do.
27155 You can specify that @value{GDBN} should always (yes) or never (no)
27156 create a core file. The default is to ask the user what to do.
27159 @kindex maint packet
27160 @item maint packet @var{text}
27161 If @value{GDBN} is talking to an inferior via the serial protocol,
27162 then this command sends the string @var{text} to the inferior, and
27163 displays the response packet. @value{GDBN} supplies the initial
27164 @samp{$} character, the terminating @samp{#} character, and the
27167 @kindex maint print architecture
27168 @item maint print architecture @r{[}@var{file}@r{]}
27169 Print the entire architecture configuration. The optional argument
27170 @var{file} names the file where the output goes.
27172 @kindex maint print c-tdesc
27173 @item maint print c-tdesc
27174 Print the current target description (@pxref{Target Descriptions}) as
27175 a C source file. The created source file can be used in @value{GDBN}
27176 when an XML parser is not available to parse the description.
27178 @kindex maint print dummy-frames
27179 @item maint print dummy-frames
27180 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
27183 (@value{GDBP}) @kbd{b add}
27185 (@value{GDBP}) @kbd{print add(2,3)}
27186 Breakpoint 2, add (a=2, b=3) at @dots{}
27188 The program being debugged stopped while in a function called from GDB.
27190 (@value{GDBP}) @kbd{maint print dummy-frames}
27191 0x1a57c80: pc=0x01014068 fp=0x0200bddc sp=0x0200bdd6
27192 top=0x0200bdd4 id=@{stack=0x200bddc,code=0x101405c@}
27193 call_lo=0x01014000 call_hi=0x01014001
27197 Takes an optional file parameter.
27199 @kindex maint print registers
27200 @kindex maint print raw-registers
27201 @kindex maint print cooked-registers
27202 @kindex maint print register-groups
27203 @item maint print registers @r{[}@var{file}@r{]}
27204 @itemx maint print raw-registers @r{[}@var{file}@r{]}
27205 @itemx maint print cooked-registers @r{[}@var{file}@r{]}
27206 @itemx maint print register-groups @r{[}@var{file}@r{]}
27207 Print @value{GDBN}'s internal register data structures.
27209 The command @code{maint print raw-registers} includes the contents of
27210 the raw register cache; the command @code{maint print cooked-registers}
27211 includes the (cooked) value of all registers; and the command
27212 @code{maint print register-groups} includes the groups that each
27213 register is a member of. @xref{Registers,, Registers, gdbint,
27214 @value{GDBN} Internals}.
27216 These commands take an optional parameter, a file name to which to
27217 write the information.
27219 @kindex maint print reggroups
27220 @item maint print reggroups @r{[}@var{file}@r{]}
27221 Print @value{GDBN}'s internal register group data structures. The
27222 optional argument @var{file} tells to what file to write the
27225 The register groups info looks like this:
27228 (@value{GDBP}) @kbd{maint print reggroups}
27241 This command forces @value{GDBN} to flush its internal register cache.
27243 @kindex maint print objfiles
27244 @cindex info for known object files
27245 @item maint print objfiles
27246 Print a dump of all known object files. For each object file, this
27247 command prints its name, address in memory, and all of its psymtabs
27250 @kindex maint print statistics
27251 @cindex bcache statistics
27252 @item maint print statistics
27253 This command prints, for each object file in the program, various data
27254 about that object file followed by the byte cache (@dfn{bcache})
27255 statistics for the object file. The objfile data includes the number
27256 of minimal, partial, full, and stabs symbols, the number of types
27257 defined by the objfile, the number of as yet unexpanded psym tables,
27258 the number of line tables and string tables, and the amount of memory
27259 used by the various tables. The bcache statistics include the counts,
27260 sizes, and counts of duplicates of all and unique objects, max,
27261 average, and median entry size, total memory used and its overhead and
27262 savings, and various measures of the hash table size and chain
27265 @kindex maint print target-stack
27266 @cindex target stack description
27267 @item maint print target-stack
27268 A @dfn{target} is an interface between the debugger and a particular
27269 kind of file or process. Targets can be stacked in @dfn{strata},
27270 so that more than one target can potentially respond to a request.
27271 In particular, memory accesses will walk down the stack of targets
27272 until they find a target that is interested in handling that particular
27275 This command prints a short description of each layer that was pushed on
27276 the @dfn{target stack}, starting from the top layer down to the bottom one.
27278 @kindex maint print type
27279 @cindex type chain of a data type
27280 @item maint print type @var{expr}
27281 Print the type chain for a type specified by @var{expr}. The argument
27282 can be either a type name or a symbol. If it is a symbol, the type of
27283 that symbol is described. The type chain produced by this command is
27284 a recursive definition of the data type as stored in @value{GDBN}'s
27285 data structures, including its flags and contained types.
27287 @kindex maint set dwarf2 max-cache-age
27288 @kindex maint show dwarf2 max-cache-age
27289 @item maint set dwarf2 max-cache-age
27290 @itemx maint show dwarf2 max-cache-age
27291 Control the DWARF 2 compilation unit cache.
27293 @cindex DWARF 2 compilation units cache
27294 In object files with inter-compilation-unit references, such as those
27295 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF 2
27296 reader needs to frequently refer to previously read compilation units.
27297 This setting controls how long a compilation unit will remain in the
27298 cache if it is not referenced. A higher limit means that cached
27299 compilation units will be stored in memory longer, and more total
27300 memory will be used. Setting it to zero disables caching, which will
27301 slow down @value{GDBN} startup, but reduce memory consumption.
27303 @kindex maint set profile
27304 @kindex maint show profile
27305 @cindex profiling GDB
27306 @item maint set profile
27307 @itemx maint show profile
27308 Control profiling of @value{GDBN}.
27310 Profiling will be disabled until you use the @samp{maint set profile}
27311 command to enable it. When you enable profiling, the system will begin
27312 collecting timing and execution count data; when you disable profiling or
27313 exit @value{GDBN}, the results will be written to a log file. Remember that
27314 if you use profiling, @value{GDBN} will overwrite the profiling log file
27315 (often called @file{gmon.out}). If you have a record of important profiling
27316 data in a @file{gmon.out} file, be sure to move it to a safe location.
27318 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
27319 compiled with the @samp{-pg} compiler option.
27321 @kindex maint set show-debug-regs
27322 @kindex maint show show-debug-regs
27323 @cindex hardware debug registers
27324 @item maint set show-debug-regs
27325 @itemx maint show show-debug-regs
27326 Control whether to show variables that mirror the hardware debug
27327 registers. Use @code{ON} to enable, @code{OFF} to disable. If
27328 enabled, the debug registers values are shown when @value{GDBN} inserts or
27329 removes a hardware breakpoint or watchpoint, and when the inferior
27330 triggers a hardware-assisted breakpoint or watchpoint.
27332 @kindex maint space
27333 @cindex memory used by commands
27335 Control whether to display memory usage for each command. If set to a
27336 nonzero value, @value{GDBN} will display how much memory each command
27337 took, following the command's own output. This can also be requested
27338 by invoking @value{GDBN} with the @option{--statistics} command-line
27339 switch (@pxref{Mode Options}).
27342 @cindex time of command execution
27344 Control whether to display the execution time for each command. If
27345 set to a nonzero value, @value{GDBN} will display how much time it
27346 took to execute each command, following the command's own output.
27347 The time is not printed for the commands that run the target, since
27348 there's no mechanism currently to compute how much time was spend
27349 by @value{GDBN} and how much time was spend by the program been debugged.
27350 it's not possibly currently
27351 This can also be requested by invoking @value{GDBN} with the
27352 @option{--statistics} command-line switch (@pxref{Mode Options}).
27354 @kindex maint translate-address
27355 @item maint translate-address @r{[}@var{section}@r{]} @var{addr}
27356 Find the symbol stored at the location specified by the address
27357 @var{addr} and an optional section name @var{section}. If found,
27358 @value{GDBN} prints the name of the closest symbol and an offset from
27359 the symbol's location to the specified address. This is similar to
27360 the @code{info address} command (@pxref{Symbols}), except that this
27361 command also allows to find symbols in other sections.
27363 If section was not specified, the section in which the symbol was found
27364 is also printed. For dynamically linked executables, the name of
27365 executable or shared library containing the symbol is printed as well.
27369 The following command is useful for non-interactive invocations of
27370 @value{GDBN}, such as in the test suite.
27373 @item set watchdog @var{nsec}
27374 @kindex set watchdog
27375 @cindex watchdog timer
27376 @cindex timeout for commands
27377 Set the maximum number of seconds @value{GDBN} will wait for the
27378 target operation to finish. If this time expires, @value{GDBN}
27379 reports and error and the command is aborted.
27381 @item show watchdog
27382 Show the current setting of the target wait timeout.
27385 @node Remote Protocol
27386 @appendix @value{GDBN} Remote Serial Protocol
27391 * Stop Reply Packets::
27392 * General Query Packets::
27393 * Register Packet Format::
27394 * Tracepoint Packets::
27395 * Host I/O Packets::
27397 * Notification Packets::
27398 * Remote Non-Stop::
27399 * Packet Acknowledgment::
27401 * File-I/O Remote Protocol Extension::
27402 * Library List Format::
27403 * Memory Map Format::
27409 There may be occasions when you need to know something about the
27410 protocol---for example, if there is only one serial port to your target
27411 machine, you might want your program to do something special if it
27412 recognizes a packet meant for @value{GDBN}.
27414 In the examples below, @samp{->} and @samp{<-} are used to indicate
27415 transmitted and received data, respectively.
27417 @cindex protocol, @value{GDBN} remote serial
27418 @cindex serial protocol, @value{GDBN} remote
27419 @cindex remote serial protocol
27420 All @value{GDBN} commands and responses (other than acknowledgments
27421 and notifications, see @ref{Notification Packets}) are sent as a
27422 @var{packet}. A @var{packet} is introduced with the character
27423 @samp{$}, the actual @var{packet-data}, and the terminating character
27424 @samp{#} followed by a two-digit @var{checksum}:
27427 @code{$}@var{packet-data}@code{#}@var{checksum}
27431 @cindex checksum, for @value{GDBN} remote
27433 The two-digit @var{checksum} is computed as the modulo 256 sum of all
27434 characters between the leading @samp{$} and the trailing @samp{#} (an
27435 eight bit unsigned checksum).
27437 Implementors should note that prior to @value{GDBN} 5.0 the protocol
27438 specification also included an optional two-digit @var{sequence-id}:
27441 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
27444 @cindex sequence-id, for @value{GDBN} remote
27446 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
27447 has never output @var{sequence-id}s. Stubs that handle packets added
27448 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
27450 When either the host or the target machine receives a packet, the first
27451 response expected is an acknowledgment: either @samp{+} (to indicate
27452 the package was received correctly) or @samp{-} (to request
27456 -> @code{$}@var{packet-data}@code{#}@var{checksum}
27461 The @samp{+}/@samp{-} acknowledgments can be disabled
27462 once a connection is established.
27463 @xref{Packet Acknowledgment}, for details.
27465 The host (@value{GDBN}) sends @var{command}s, and the target (the
27466 debugging stub incorporated in your program) sends a @var{response}. In
27467 the case of step and continue @var{command}s, the response is only sent
27468 when the operation has completed, and the target has again stopped all
27469 threads in all attached processes. This is the default all-stop mode
27470 behavior, but the remote protocol also supports @value{GDBN}'s non-stop
27471 execution mode; see @ref{Remote Non-Stop}, for details.
27473 @var{packet-data} consists of a sequence of characters with the
27474 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
27477 @cindex remote protocol, field separator
27478 Fields within the packet should be separated using @samp{,} @samp{;} or
27479 @samp{:}. Except where otherwise noted all numbers are represented in
27480 @sc{hex} with leading zeros suppressed.
27482 Implementors should note that prior to @value{GDBN} 5.0, the character
27483 @samp{:} could not appear as the third character in a packet (as it
27484 would potentially conflict with the @var{sequence-id}).
27486 @cindex remote protocol, binary data
27487 @anchor{Binary Data}
27488 Binary data in most packets is encoded either as two hexadecimal
27489 digits per byte of binary data. This allowed the traditional remote
27490 protocol to work over connections which were only seven-bit clean.
27491 Some packets designed more recently assume an eight-bit clean
27492 connection, and use a more efficient encoding to send and receive
27495 The binary data representation uses @code{7d} (@sc{ascii} @samp{@}})
27496 as an escape character. Any escaped byte is transmitted as the escape
27497 character followed by the original character XORed with @code{0x20}.
27498 For example, the byte @code{0x7d} would be transmitted as the two
27499 bytes @code{0x7d 0x5d}. The bytes @code{0x23} (@sc{ascii} @samp{#}),
27500 @code{0x24} (@sc{ascii} @samp{$}), and @code{0x7d} (@sc{ascii}
27501 @samp{@}}) must always be escaped. Responses sent by the stub
27502 must also escape @code{0x2a} (@sc{ascii} @samp{*}), so that it
27503 is not interpreted as the start of a run-length encoded sequence
27506 Response @var{data} can be run-length encoded to save space.
27507 Run-length encoding replaces runs of identical characters with one
27508 instance of the repeated character, followed by a @samp{*} and a
27509 repeat count. The repeat count is itself sent encoded, to avoid
27510 binary characters in @var{data}: a value of @var{n} is sent as
27511 @code{@var{n}+29}. For a repeat count greater or equal to 3, this
27512 produces a printable @sc{ascii} character, e.g.@: a space (@sc{ascii}
27513 code 32) for a repeat count of 3. (This is because run-length
27514 encoding starts to win for counts 3 or more.) Thus, for example,
27515 @samp{0* } is a run-length encoding of ``0000'': the space character
27516 after @samp{*} means repeat the leading @code{0} @w{@code{32 - 29 =
27519 The printable characters @samp{#} and @samp{$} or with a numeric value
27520 greater than 126 must not be used. Runs of six repeats (@samp{#}) or
27521 seven repeats (@samp{$}) can be expanded using a repeat count of only
27522 five (@samp{"}). For example, @samp{00000000} can be encoded as
27525 The error response returned for some packets includes a two character
27526 error number. That number is not well defined.
27528 @cindex empty response, for unsupported packets
27529 For any @var{command} not supported by the stub, an empty response
27530 (@samp{$#00}) should be returned. That way it is possible to extend the
27531 protocol. A newer @value{GDBN} can tell if a packet is supported based
27534 A stub is required to support the @samp{g}, @samp{G}, @samp{m}, @samp{M},
27535 @samp{c}, and @samp{s} @var{command}s. All other @var{command}s are
27541 The following table provides a complete list of all currently defined
27542 @var{command}s and their corresponding response @var{data}.
27543 @xref{File-I/O Remote Protocol Extension}, for details about the File
27544 I/O extension of the remote protocol.
27546 Each packet's description has a template showing the packet's overall
27547 syntax, followed by an explanation of the packet's meaning. We
27548 include spaces in some of the templates for clarity; these are not
27549 part of the packet's syntax. No @value{GDBN} packet uses spaces to
27550 separate its components. For example, a template like @samp{foo
27551 @var{bar} @var{baz}} describes a packet beginning with the three ASCII
27552 bytes @samp{foo}, followed by a @var{bar}, followed directly by a
27553 @var{baz}. @value{GDBN} does not transmit a space character between the
27554 @samp{foo} and the @var{bar}, or between the @var{bar} and the
27557 @cindex @var{thread-id}, in remote protocol
27558 @anchor{thread-id syntax}
27559 Several packets and replies include a @var{thread-id} field to identify
27560 a thread. Normally these are positive numbers with a target-specific
27561 interpretation, formatted as big-endian hex strings. A @var{thread-id}
27562 can also be a literal @samp{-1} to indicate all threads, or @samp{0} to
27565 In addition, the remote protocol supports a multiprocess feature in
27566 which the @var{thread-id} syntax is extended to optionally include both
27567 process and thread ID fields, as @samp{p@var{pid}.@var{tid}}.
27568 The @var{pid} (process) and @var{tid} (thread) components each have the
27569 format described above: a positive number with target-specific
27570 interpretation formatted as a big-endian hex string, literal @samp{-1}
27571 to indicate all processes or threads (respectively), or @samp{0} to
27572 indicate an arbitrary process or thread. Specifying just a process, as
27573 @samp{p@var{pid}}, is equivalent to @samp{p@var{pid}.-1}. It is an
27574 error to specify all processes but a specific thread, such as
27575 @samp{p-1.@var{tid}}. Note that the @samp{p} prefix is @emph{not} used
27576 for those packets and replies explicitly documented to include a process
27577 ID, rather than a @var{thread-id}.
27579 The multiprocess @var{thread-id} syntax extensions are only used if both
27580 @value{GDBN} and the stub report support for the @samp{multiprocess}
27581 feature using @samp{qSupported}. @xref{multiprocess extensions}, for
27584 Note that all packet forms beginning with an upper- or lower-case
27585 letter, other than those described here, are reserved for future use.
27587 Here are the packet descriptions.
27592 @cindex @samp{!} packet
27593 @anchor{extended mode}
27594 Enable extended mode. In extended mode, the remote server is made
27595 persistent. The @samp{R} packet is used to restart the program being
27601 The remote target both supports and has enabled extended mode.
27605 @cindex @samp{?} packet
27606 Indicate the reason the target halted. The reply is the same as for
27607 step and continue. This packet has a special interpretation when the
27608 target is in non-stop mode; see @ref{Remote Non-Stop}.
27611 @xref{Stop Reply Packets}, for the reply specifications.
27613 @item A @var{arglen},@var{argnum},@var{arg},@dots{}
27614 @cindex @samp{A} packet
27615 Initialized @code{argv[]} array passed into program. @var{arglen}
27616 specifies the number of bytes in the hex encoded byte stream
27617 @var{arg}. See @code{gdbserver} for more details.
27622 The arguments were set.
27628 @cindex @samp{b} packet
27629 (Don't use this packet; its behavior is not well-defined.)
27630 Change the serial line speed to @var{baud}.
27632 JTC: @emph{When does the transport layer state change? When it's
27633 received, or after the ACK is transmitted. In either case, there are
27634 problems if the command or the acknowledgment packet is dropped.}
27636 Stan: @emph{If people really wanted to add something like this, and get
27637 it working for the first time, they ought to modify ser-unix.c to send
27638 some kind of out-of-band message to a specially-setup stub and have the
27639 switch happen "in between" packets, so that from remote protocol's point
27640 of view, nothing actually happened.}
27642 @item B @var{addr},@var{mode}
27643 @cindex @samp{B} packet
27644 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
27645 breakpoint at @var{addr}.
27647 Don't use this packet. Use the @samp{Z} and @samp{z} packets instead
27648 (@pxref{insert breakpoint or watchpoint packet}).
27650 @cindex @samp{bc} packet
27653 Backward continue. Execute the target system in reverse. No parameter.
27654 @xref{Reverse Execution}, for more information.
27657 @xref{Stop Reply Packets}, for the reply specifications.
27659 @cindex @samp{bs} packet
27662 Backward single step. Execute one instruction in reverse. No parameter.
27663 @xref{Reverse Execution}, for more information.
27666 @xref{Stop Reply Packets}, for the reply specifications.
27668 @item c @r{[}@var{addr}@r{]}
27669 @cindex @samp{c} packet
27670 Continue. @var{addr} is address to resume. If @var{addr} is omitted,
27671 resume at current address.
27674 @xref{Stop Reply Packets}, for the reply specifications.
27676 @item C @var{sig}@r{[};@var{addr}@r{]}
27677 @cindex @samp{C} packet
27678 Continue with signal @var{sig} (hex signal number). If
27679 @samp{;@var{addr}} is omitted, resume at same address.
27682 @xref{Stop Reply Packets}, for the reply specifications.
27685 @cindex @samp{d} packet
27688 Don't use this packet; instead, define a general set packet
27689 (@pxref{General Query Packets}).
27693 @cindex @samp{D} packet
27694 The first form of the packet is used to detach @value{GDBN} from the
27695 remote system. It is sent to the remote target
27696 before @value{GDBN} disconnects via the @code{detach} command.
27698 The second form, including a process ID, is used when multiprocess
27699 protocol extensions are enabled (@pxref{multiprocess extensions}), to
27700 detach only a specific process. The @var{pid} is specified as a
27701 big-endian hex string.
27711 @item F @var{RC},@var{EE},@var{CF};@var{XX}
27712 @cindex @samp{F} packet
27713 A reply from @value{GDBN} to an @samp{F} packet sent by the target.
27714 This is part of the File-I/O protocol extension. @xref{File-I/O
27715 Remote Protocol Extension}, for the specification.
27718 @anchor{read registers packet}
27719 @cindex @samp{g} packet
27720 Read general registers.
27724 @item @var{XX@dots{}}
27725 Each byte of register data is described by two hex digits. The bytes
27726 with the register are transmitted in target byte order. The size of
27727 each register and their position within the @samp{g} packet are
27728 determined by the @value{GDBN} internal gdbarch functions
27729 @code{DEPRECATED_REGISTER_RAW_SIZE} and @code{gdbarch_register_name}. The
27730 specification of several standard @samp{g} packets is specified below.
27735 @item G @var{XX@dots{}}
27736 @cindex @samp{G} packet
27737 Write general registers. @xref{read registers packet}, for a
27738 description of the @var{XX@dots{}} data.
27748 @item H @var{c} @var{thread-id}
27749 @cindex @samp{H} packet
27750 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
27751 @samp{G}, et.al.). @var{c} depends on the operation to be performed: it
27752 should be @samp{c} for step and continue operations, @samp{g} for other
27753 operations. The thread designator @var{thread-id} has the format and
27754 interpretation described in @ref{thread-id syntax}.
27765 @c 'H': How restrictive (or permissive) is the thread model. If a
27766 @c thread is selected and stopped, are other threads allowed
27767 @c to continue to execute? As I mentioned above, I think the
27768 @c semantics of each command when a thread is selected must be
27769 @c described. For example:
27771 @c 'g': If the stub supports threads and a specific thread is
27772 @c selected, returns the register block from that thread;
27773 @c otherwise returns current registers.
27775 @c 'G' If the stub supports threads and a specific thread is
27776 @c selected, sets the registers of the register block of
27777 @c that thread; otherwise sets current registers.
27779 @item i @r{[}@var{addr}@r{[},@var{nnn}@r{]]}
27780 @anchor{cycle step packet}
27781 @cindex @samp{i} packet
27782 Step the remote target by a single clock cycle. If @samp{,@var{nnn}} is
27783 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
27784 step starting at that address.
27787 @cindex @samp{I} packet
27788 Signal, then cycle step. @xref{step with signal packet}. @xref{cycle
27792 @cindex @samp{k} packet
27795 FIXME: @emph{There is no description of how to operate when a specific
27796 thread context has been selected (i.e.@: does 'k' kill only that
27799 @item m @var{addr},@var{length}
27800 @cindex @samp{m} packet
27801 Read @var{length} bytes of memory starting at address @var{addr}.
27802 Note that @var{addr} may not be aligned to any particular boundary.
27804 The stub need not use any particular size or alignment when gathering
27805 data from memory for the response; even if @var{addr} is word-aligned
27806 and @var{length} is a multiple of the word size, the stub is free to
27807 use byte accesses, or not. For this reason, this packet may not be
27808 suitable for accessing memory-mapped I/O devices.
27809 @cindex alignment of remote memory accesses
27810 @cindex size of remote memory accesses
27811 @cindex memory, alignment and size of remote accesses
27815 @item @var{XX@dots{}}
27816 Memory contents; each byte is transmitted as a two-digit hexadecimal
27817 number. The reply may contain fewer bytes than requested if the
27818 server was able to read only part of the region of memory.
27823 @item M @var{addr},@var{length}:@var{XX@dots{}}
27824 @cindex @samp{M} packet
27825 Write @var{length} bytes of memory starting at address @var{addr}.
27826 @var{XX@dots{}} is the data; each byte is transmitted as a two-digit
27827 hexadecimal number.
27834 for an error (this includes the case where only part of the data was
27839 @cindex @samp{p} packet
27840 Read the value of register @var{n}; @var{n} is in hex.
27841 @xref{read registers packet}, for a description of how the returned
27842 register value is encoded.
27846 @item @var{XX@dots{}}
27847 the register's value
27851 Indicating an unrecognized @var{query}.
27854 @item P @var{n@dots{}}=@var{r@dots{}}
27855 @anchor{write register packet}
27856 @cindex @samp{P} packet
27857 Write register @var{n@dots{}} with value @var{r@dots{}}. The register
27858 number @var{n} is in hexadecimal, and @var{r@dots{}} contains two hex
27859 digits for each byte in the register (target byte order).
27869 @item q @var{name} @var{params}@dots{}
27870 @itemx Q @var{name} @var{params}@dots{}
27871 @cindex @samp{q} packet
27872 @cindex @samp{Q} packet
27873 General query (@samp{q}) and set (@samp{Q}). These packets are
27874 described fully in @ref{General Query Packets}.
27877 @cindex @samp{r} packet
27878 Reset the entire system.
27880 Don't use this packet; use the @samp{R} packet instead.
27883 @cindex @samp{R} packet
27884 Restart the program being debugged. @var{XX}, while needed, is ignored.
27885 This packet is only available in extended mode (@pxref{extended mode}).
27887 The @samp{R} packet has no reply.
27889 @item s @r{[}@var{addr}@r{]}
27890 @cindex @samp{s} packet
27891 Single step. @var{addr} is the address at which to resume. If
27892 @var{addr} is omitted, resume at same address.
27895 @xref{Stop Reply Packets}, for the reply specifications.
27897 @item S @var{sig}@r{[};@var{addr}@r{]}
27898 @anchor{step with signal packet}
27899 @cindex @samp{S} packet
27900 Step with signal. This is analogous to the @samp{C} packet, but
27901 requests a single-step, rather than a normal resumption of execution.
27904 @xref{Stop Reply Packets}, for the reply specifications.
27906 @item t @var{addr}:@var{PP},@var{MM}
27907 @cindex @samp{t} packet
27908 Search backwards starting at address @var{addr} for a match with pattern
27909 @var{PP} and mask @var{MM}. @var{PP} and @var{MM} are 4 bytes.
27910 @var{addr} must be at least 3 digits.
27912 @item T @var{thread-id}
27913 @cindex @samp{T} packet
27914 Find out if the thread @var{thread-id} is alive. @xref{thread-id syntax}.
27919 thread is still alive
27925 Packets starting with @samp{v} are identified by a multi-letter name,
27926 up to the first @samp{;} or @samp{?} (or the end of the packet).
27928 @item vAttach;@var{pid}
27929 @cindex @samp{vAttach} packet
27930 Attach to a new process with the specified process ID @var{pid}.
27931 The process ID is a
27932 hexadecimal integer identifying the process. In all-stop mode, all
27933 threads in the attached process are stopped; in non-stop mode, it may be
27934 attached without being stopped if that is supported by the target.
27936 @c In non-stop mode, on a successful vAttach, the stub should set the
27937 @c current thread to a thread of the newly-attached process. After
27938 @c attaching, GDB queries for the attached process's thread ID with qC.
27939 @c Also note that, from a user perspective, whether or not the
27940 @c target is stopped on attach in non-stop mode depends on whether you
27941 @c use the foreground or background version of the attach command, not
27942 @c on what vAttach does; GDB does the right thing with respect to either
27943 @c stopping or restarting threads.
27945 This packet is only available in extended mode (@pxref{extended mode}).
27951 @item @r{Any stop packet}
27952 for success in all-stop mode (@pxref{Stop Reply Packets})
27954 for success in non-stop mode (@pxref{Remote Non-Stop})
27957 @item vCont@r{[};@var{action}@r{[}:@var{thread-id}@r{]]}@dots{}
27958 @cindex @samp{vCont} packet
27959 Resume the inferior, specifying different actions for each thread.
27960 If an action is specified with no @var{thread-id}, then it is applied to any
27961 threads that don't have a specific action specified; if no default action is
27962 specified then other threads should remain stopped in all-stop mode and
27963 in their current state in non-stop mode.
27964 Specifying multiple
27965 default actions is an error; specifying no actions is also an error.
27966 Thread IDs are specified using the syntax described in @ref{thread-id syntax}.
27968 Currently supported actions are:
27974 Continue with signal @var{sig}. The signal @var{sig} should be two hex digits.
27978 Step with signal @var{sig}. The signal @var{sig} should be two hex digits.
27982 Stop with signal @var{sig}. The signal @var{sig} should be two hex digits.
27985 The optional argument @var{addr} normally associated with the
27986 @samp{c}, @samp{C}, @samp{s}, and @samp{S} packets is
27987 not supported in @samp{vCont}.
27989 The @samp{t} and @samp{T} actions are only relevant in non-stop mode
27990 (@pxref{Remote Non-Stop}) and may be ignored by the stub otherwise.
27991 A stop reply should be generated for any affected thread not already stopped.
27992 When a thread is stopped by means of a @samp{t} action,
27993 the corresponding stop reply should indicate that the thread has stopped with
27994 signal @samp{0}, regardless of whether the target uses some other signal
27995 as an implementation detail.
27998 @xref{Stop Reply Packets}, for the reply specifications.
28001 @cindex @samp{vCont?} packet
28002 Request a list of actions supported by the @samp{vCont} packet.
28006 @item vCont@r{[};@var{action}@dots{}@r{]}
28007 The @samp{vCont} packet is supported. Each @var{action} is a supported
28008 command in the @samp{vCont} packet.
28010 The @samp{vCont} packet is not supported.
28013 @item vFile:@var{operation}:@var{parameter}@dots{}
28014 @cindex @samp{vFile} packet
28015 Perform a file operation on the target system. For details,
28016 see @ref{Host I/O Packets}.
28018 @item vFlashErase:@var{addr},@var{length}
28019 @cindex @samp{vFlashErase} packet
28020 Direct the stub to erase @var{length} bytes of flash starting at
28021 @var{addr}. The region may enclose any number of flash blocks, but
28022 its start and end must fall on block boundaries, as indicated by the
28023 flash block size appearing in the memory map (@pxref{Memory Map
28024 Format}). @value{GDBN} groups flash memory programming operations
28025 together, and sends a @samp{vFlashDone} request after each group; the
28026 stub is allowed to delay erase operation until the @samp{vFlashDone}
28027 packet is received.
28029 The stub must support @samp{vCont} if it reports support for
28030 multiprocess extensions (@pxref{multiprocess extensions}). Note that in
28031 this case @samp{vCont} actions can be specified to apply to all threads
28032 in a process by using the @samp{p@var{pid}.-1} form of the
28043 @item vFlashWrite:@var{addr}:@var{XX@dots{}}
28044 @cindex @samp{vFlashWrite} packet
28045 Direct the stub to write data to flash address @var{addr}. The data
28046 is passed in binary form using the same encoding as for the @samp{X}
28047 packet (@pxref{Binary Data}). The memory ranges specified by
28048 @samp{vFlashWrite} packets preceding a @samp{vFlashDone} packet must
28049 not overlap, and must appear in order of increasing addresses
28050 (although @samp{vFlashErase} packets for higher addresses may already
28051 have been received; the ordering is guaranteed only between
28052 @samp{vFlashWrite} packets). If a packet writes to an address that was
28053 neither erased by a preceding @samp{vFlashErase} packet nor by some other
28054 target-specific method, the results are unpredictable.
28062 for vFlashWrite addressing non-flash memory
28068 @cindex @samp{vFlashDone} packet
28069 Indicate to the stub that flash programming operation is finished.
28070 The stub is permitted to delay or batch the effects of a group of
28071 @samp{vFlashErase} and @samp{vFlashWrite} packets until a
28072 @samp{vFlashDone} packet is received. The contents of the affected
28073 regions of flash memory are unpredictable until the @samp{vFlashDone}
28074 request is completed.
28076 @item vKill;@var{pid}
28077 @cindex @samp{vKill} packet
28078 Kill the process with the specified process ID. @var{pid} is a
28079 hexadecimal integer identifying the process. This packet is used in
28080 preference to @samp{k} when multiprocess protocol extensions are
28081 supported; see @ref{multiprocess extensions}.
28091 @item vRun;@var{filename}@r{[};@var{argument}@r{]}@dots{}
28092 @cindex @samp{vRun} packet
28093 Run the program @var{filename}, passing it each @var{argument} on its
28094 command line. The file and arguments are hex-encoded strings. If
28095 @var{filename} is an empty string, the stub may use a default program
28096 (e.g.@: the last program run). The program is created in the stopped
28099 @c FIXME: What about non-stop mode?
28101 This packet is only available in extended mode (@pxref{extended mode}).
28107 @item @r{Any stop packet}
28108 for success (@pxref{Stop Reply Packets})
28112 @anchor{vStopped packet}
28113 @cindex @samp{vStopped} packet
28115 In non-stop mode (@pxref{Remote Non-Stop}), acknowledge a previous stop
28116 reply and prompt for the stub to report another one.
28120 @item @r{Any stop packet}
28121 if there is another unreported stop event (@pxref{Stop Reply Packets})
28123 if there are no unreported stop events
28126 @item X @var{addr},@var{length}:@var{XX@dots{}}
28128 @cindex @samp{X} packet
28129 Write data to memory, where the data is transmitted in binary.
28130 @var{addr} is address, @var{length} is number of bytes,
28131 @samp{@var{XX}@dots{}} is binary data (@pxref{Binary Data}).
28141 @item z @var{type},@var{addr},@var{length}
28142 @itemx Z @var{type},@var{addr},@var{length}
28143 @anchor{insert breakpoint or watchpoint packet}
28144 @cindex @samp{z} packet
28145 @cindex @samp{Z} packets
28146 Insert (@samp{Z}) or remove (@samp{z}) a @var{type} breakpoint or
28147 watchpoint starting at address @var{address} and covering the next
28148 @var{length} bytes.
28150 Each breakpoint and watchpoint packet @var{type} is documented
28153 @emph{Implementation notes: A remote target shall return an empty string
28154 for an unrecognized breakpoint or watchpoint packet @var{type}. A
28155 remote target shall support either both or neither of a given
28156 @samp{Z@var{type}@dots{}} and @samp{z@var{type}@dots{}} packet pair. To
28157 avoid potential problems with duplicate packets, the operations should
28158 be implemented in an idempotent way.}
28160 @item z0,@var{addr},@var{length}
28161 @itemx Z0,@var{addr},@var{length}
28162 @cindex @samp{z0} packet
28163 @cindex @samp{Z0} packet
28164 Insert (@samp{Z0}) or remove (@samp{z0}) a memory breakpoint at address
28165 @var{addr} of size @var{length}.
28167 A memory breakpoint is implemented by replacing the instruction at
28168 @var{addr} with a software breakpoint or trap instruction. The
28169 @var{length} is used by targets that indicates the size of the
28170 breakpoint (in bytes) that should be inserted (e.g., the @sc{arm} and
28171 @sc{mips} can insert either a 2 or 4 byte breakpoint).
28173 @emph{Implementation note: It is possible for a target to copy or move
28174 code that contains memory breakpoints (e.g., when implementing
28175 overlays). The behavior of this packet, in the presence of such a
28176 target, is not defined.}
28188 @item z1,@var{addr},@var{length}
28189 @itemx Z1,@var{addr},@var{length}
28190 @cindex @samp{z1} packet
28191 @cindex @samp{Z1} packet
28192 Insert (@samp{Z1}) or remove (@samp{z1}) a hardware breakpoint at
28193 address @var{addr} of size @var{length}.
28195 A hardware breakpoint is implemented using a mechanism that is not
28196 dependant on being able to modify the target's memory.
28198 @emph{Implementation note: A hardware breakpoint is not affected by code
28211 @item z2,@var{addr},@var{length}
28212 @itemx Z2,@var{addr},@var{length}
28213 @cindex @samp{z2} packet
28214 @cindex @samp{Z2} packet
28215 Insert (@samp{Z2}) or remove (@samp{z2}) a write watchpoint.
28227 @item z3,@var{addr},@var{length}
28228 @itemx Z3,@var{addr},@var{length}
28229 @cindex @samp{z3} packet
28230 @cindex @samp{Z3} packet
28231 Insert (@samp{Z3}) or remove (@samp{z3}) a read watchpoint.
28243 @item z4,@var{addr},@var{length}
28244 @itemx Z4,@var{addr},@var{length}
28245 @cindex @samp{z4} packet
28246 @cindex @samp{Z4} packet
28247 Insert (@samp{Z4}) or remove (@samp{z4}) an access watchpoint.
28261 @node Stop Reply Packets
28262 @section Stop Reply Packets
28263 @cindex stop reply packets
28265 The @samp{C}, @samp{c}, @samp{S}, @samp{s}, @samp{vCont},
28266 @samp{vAttach}, @samp{vRun}, @samp{vStopped}, and @samp{?} packets can
28267 receive any of the below as a reply. Except for @samp{?}
28268 and @samp{vStopped}, that reply is only returned
28269 when the target halts. In the below the exact meaning of @dfn{signal
28270 number} is defined by the header @file{include/gdb/signals.h} in the
28271 @value{GDBN} source code.
28273 As in the description of request packets, we include spaces in the
28274 reply templates for clarity; these are not part of the reply packet's
28275 syntax. No @value{GDBN} stop reply packet uses spaces to separate its
28281 The program received signal number @var{AA} (a two-digit hexadecimal
28282 number). This is equivalent to a @samp{T} response with no
28283 @var{n}:@var{r} pairs.
28285 @item T @var{AA} @var{n1}:@var{r1};@var{n2}:@var{r2};@dots{}
28286 @cindex @samp{T} packet reply
28287 The program received signal number @var{AA} (a two-digit hexadecimal
28288 number). This is equivalent to an @samp{S} response, except that the
28289 @samp{@var{n}:@var{r}} pairs can carry values of important registers
28290 and other information directly in the stop reply packet, reducing
28291 round-trip latency. Single-step and breakpoint traps are reported
28292 this way. Each @samp{@var{n}:@var{r}} pair is interpreted as follows:
28296 If @var{n} is a hexadecimal number, it is a register number, and the
28297 corresponding @var{r} gives that register's value. @var{r} is a
28298 series of bytes in target byte order, with each byte given by a
28299 two-digit hex number.
28302 If @var{n} is @samp{thread}, then @var{r} is the @var{thread-id} of
28303 the stopped thread, as specified in @ref{thread-id syntax}.
28306 If @var{n} is a recognized @dfn{stop reason}, it describes a more
28307 specific event that stopped the target. The currently defined stop
28308 reasons are listed below. @var{aa} should be @samp{05}, the trap
28309 signal. At most one stop reason should be present.
28312 Otherwise, @value{GDBN} should ignore this @samp{@var{n}:@var{r}} pair
28313 and go on to the next; this allows us to extend the protocol in the
28317 The currently defined stop reasons are:
28323 The packet indicates a watchpoint hit, and @var{r} is the data address, in
28326 @cindex shared library events, remote reply
28328 The packet indicates that the loaded libraries have changed.
28329 @value{GDBN} should use @samp{qXfer:libraries:read} to fetch a new
28330 list of loaded libraries. @var{r} is ignored.
28332 @cindex replay log events, remote reply
28334 The packet indicates that the target cannot continue replaying
28335 logged execution events, because it has reached the end (or the
28336 beginning when executing backward) of the log. The value of @var{r}
28337 will be either @samp{begin} or @samp{end}. @xref{Reverse Execution},
28338 for more information.
28344 @itemx W @var{AA} ; process:@var{pid}
28345 The process exited, and @var{AA} is the exit status. This is only
28346 applicable to certain targets.
28348 The second form of the response, including the process ID of the exited
28349 process, can be used only when @value{GDBN} has reported support for
28350 multiprocess protocol extensions; see @ref{multiprocess extensions}.
28351 The @var{pid} is formatted as a big-endian hex string.
28354 @itemx X @var{AA} ; process:@var{pid}
28355 The process terminated with signal @var{AA}.
28357 The second form of the response, including the process ID of the
28358 terminated process, can be used only when @value{GDBN} has reported
28359 support for multiprocess protocol extensions; see @ref{multiprocess
28360 extensions}. The @var{pid} is formatted as a big-endian hex string.
28362 @item O @var{XX}@dots{}
28363 @samp{@var{XX}@dots{}} is hex encoding of @sc{ascii} data, to be
28364 written as the program's console output. This can happen at any time
28365 while the program is running and the debugger should continue to wait
28366 for @samp{W}, @samp{T}, etc. This reply is not permitted in non-stop mode.
28368 @item F @var{call-id},@var{parameter}@dots{}
28369 @var{call-id} is the identifier which says which host system call should
28370 be called. This is just the name of the function. Translation into the
28371 correct system call is only applicable as it's defined in @value{GDBN}.
28372 @xref{File-I/O Remote Protocol Extension}, for a list of implemented
28375 @samp{@var{parameter}@dots{}} is a list of parameters as defined for
28376 this very system call.
28378 The target replies with this packet when it expects @value{GDBN} to
28379 call a host system call on behalf of the target. @value{GDBN} replies
28380 with an appropriate @samp{F} packet and keeps up waiting for the next
28381 reply packet from the target. The latest @samp{C}, @samp{c}, @samp{S}
28382 or @samp{s} action is expected to be continued. @xref{File-I/O Remote
28383 Protocol Extension}, for more details.
28387 @node General Query Packets
28388 @section General Query Packets
28389 @cindex remote query requests
28391 Packets starting with @samp{q} are @dfn{general query packets};
28392 packets starting with @samp{Q} are @dfn{general set packets}. General
28393 query and set packets are a semi-unified form for retrieving and
28394 sending information to and from the stub.
28396 The initial letter of a query or set packet is followed by a name
28397 indicating what sort of thing the packet applies to. For example,
28398 @value{GDBN} may use a @samp{qSymbol} packet to exchange symbol
28399 definitions with the stub. These packet names follow some
28404 The name must not contain commas, colons or semicolons.
28406 Most @value{GDBN} query and set packets have a leading upper case
28409 The names of custom vendor packets should use a company prefix, in
28410 lower case, followed by a period. For example, packets designed at
28411 the Acme Corporation might begin with @samp{qacme.foo} (for querying
28412 foos) or @samp{Qacme.bar} (for setting bars).
28415 The name of a query or set packet should be separated from any
28416 parameters by a @samp{:}; the parameters themselves should be
28417 separated by @samp{,} or @samp{;}. Stubs must be careful to match the
28418 full packet name, and check for a separator or the end of the packet,
28419 in case two packet names share a common prefix. New packets should not begin
28420 with @samp{qC}, @samp{qP}, or @samp{qL}@footnote{The @samp{qP} and @samp{qL}
28421 packets predate these conventions, and have arguments without any terminator
28422 for the packet name; we suspect they are in widespread use in places that
28423 are difficult to upgrade. The @samp{qC} packet has no arguments, but some
28424 existing stubs (e.g.@: RedBoot) are known to not check for the end of the
28427 Like the descriptions of the other packets, each description here
28428 has a template showing the packet's overall syntax, followed by an
28429 explanation of the packet's meaning. We include spaces in some of the
28430 templates for clarity; these are not part of the packet's syntax. No
28431 @value{GDBN} packet uses spaces to separate its components.
28433 Here are the currently defined query and set packets:
28438 @cindex current thread, remote request
28439 @cindex @samp{qC} packet
28440 Return the current thread ID.
28444 @item QC @var{thread-id}
28445 Where @var{thread-id} is a thread ID as documented in
28446 @ref{thread-id syntax}.
28447 @item @r{(anything else)}
28448 Any other reply implies the old thread ID.
28451 @item qCRC:@var{addr},@var{length}
28452 @cindex CRC of memory block, remote request
28453 @cindex @samp{qCRC} packet
28454 Compute the CRC checksum of a block of memory using CRC-32 defined in
28455 IEEE 802.3. The CRC is computed byte at a time, taking the most
28456 significant bit of each byte first. The initial pattern code
28457 @code{0xffffffff} is used to ensure leading zeros affect the CRC.
28459 @emph{Note:} This is the same CRC used in validating separate debug
28460 files (@pxref{Separate Debug Files, , Debugging Information in Separate
28461 Files}). However the algorithm is slightly different. When validating
28462 separate debug files, the CRC is computed taking the @emph{least}
28463 significant bit of each byte first, and the final result is inverted to
28464 detect trailing zeros.
28469 An error (such as memory fault)
28470 @item C @var{crc32}
28471 The specified memory region's checksum is @var{crc32}.
28475 @itemx qsThreadInfo
28476 @cindex list active threads, remote request
28477 @cindex @samp{qfThreadInfo} packet
28478 @cindex @samp{qsThreadInfo} packet
28479 Obtain a list of all active thread IDs from the target (OS). Since there
28480 may be too many active threads to fit into one reply packet, this query
28481 works iteratively: it may require more than one query/reply sequence to
28482 obtain the entire list of threads. The first query of the sequence will
28483 be the @samp{qfThreadInfo} query; subsequent queries in the
28484 sequence will be the @samp{qsThreadInfo} query.
28486 NOTE: This packet replaces the @samp{qL} query (see below).
28490 @item m @var{thread-id}
28492 @item m @var{thread-id},@var{thread-id}@dots{}
28493 a comma-separated list of thread IDs
28495 (lower case letter @samp{L}) denotes end of list.
28498 In response to each query, the target will reply with a list of one or
28499 more thread IDs, separated by commas.
28500 @value{GDBN} will respond to each reply with a request for more thread
28501 ids (using the @samp{qs} form of the query), until the target responds
28502 with @samp{l} (lower-case el, for @dfn{last}).
28503 Refer to @ref{thread-id syntax}, for the format of the @var{thread-id}
28506 @item qGetTLSAddr:@var{thread-id},@var{offset},@var{lm}
28507 @cindex get thread-local storage address, remote request
28508 @cindex @samp{qGetTLSAddr} packet
28509 Fetch the address associated with thread local storage specified
28510 by @var{thread-id}, @var{offset}, and @var{lm}.
28512 @var{thread-id} is the thread ID associated with the
28513 thread for which to fetch the TLS address. @xref{thread-id syntax}.
28515 @var{offset} is the (big endian, hex encoded) offset associated with the
28516 thread local variable. (This offset is obtained from the debug
28517 information associated with the variable.)
28519 @var{lm} is the (big endian, hex encoded) OS/ABI-specific encoding of the
28520 the load module associated with the thread local storage. For example,
28521 a @sc{gnu}/Linux system will pass the link map address of the shared
28522 object associated with the thread local storage under consideration.
28523 Other operating environments may choose to represent the load module
28524 differently, so the precise meaning of this parameter will vary.
28528 @item @var{XX}@dots{}
28529 Hex encoded (big endian) bytes representing the address of the thread
28530 local storage requested.
28533 An error occurred. @var{nn} are hex digits.
28536 An empty reply indicates that @samp{qGetTLSAddr} is not supported by the stub.
28539 @item qL @var{startflag} @var{threadcount} @var{nextthread}
28540 Obtain thread information from RTOS. Where: @var{startflag} (one hex
28541 digit) is one to indicate the first query and zero to indicate a
28542 subsequent query; @var{threadcount} (two hex digits) is the maximum
28543 number of threads the response packet can contain; and @var{nextthread}
28544 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
28545 returned in the response as @var{argthread}.
28547 Don't use this packet; use the @samp{qfThreadInfo} query instead (see above).
28551 @item qM @var{count} @var{done} @var{argthread} @var{thread}@dots{}
28552 Where: @var{count} (two hex digits) is the number of threads being
28553 returned; @var{done} (one hex digit) is zero to indicate more threads
28554 and one indicates no further threads; @var{argthreadid} (eight hex
28555 digits) is @var{nextthread} from the request packet; @var{thread}@dots{}
28556 is a sequence of thread IDs from the target. @var{threadid} (eight hex
28557 digits). See @code{remote.c:parse_threadlist_response()}.
28561 @cindex section offsets, remote request
28562 @cindex @samp{qOffsets} packet
28563 Get section offsets that the target used when relocating the downloaded
28568 @item Text=@var{xxx};Data=@var{yyy}@r{[};Bss=@var{zzz}@r{]}
28569 Relocate the @code{Text} section by @var{xxx} from its original address.
28570 Relocate the @code{Data} section by @var{yyy} from its original address.
28571 If the object file format provides segment information (e.g.@: @sc{elf}
28572 @samp{PT_LOAD} program headers), @value{GDBN} will relocate entire
28573 segments by the supplied offsets.
28575 @emph{Note: while a @code{Bss} offset may be included in the response,
28576 @value{GDBN} ignores this and instead applies the @code{Data} offset
28577 to the @code{Bss} section.}
28579 @item TextSeg=@var{xxx}@r{[};DataSeg=@var{yyy}@r{]}
28580 Relocate the first segment of the object file, which conventionally
28581 contains program code, to a starting address of @var{xxx}. If
28582 @samp{DataSeg} is specified, relocate the second segment, which
28583 conventionally contains modifiable data, to a starting address of
28584 @var{yyy}. @value{GDBN} will report an error if the object file
28585 does not contain segment information, or does not contain at least
28586 as many segments as mentioned in the reply. Extra segments are
28587 kept at fixed offsets relative to the last relocated segment.
28590 @item qP @var{mode} @var{thread-id}
28591 @cindex thread information, remote request
28592 @cindex @samp{qP} packet
28593 Returns information on @var{thread-id}. Where: @var{mode} is a hex
28594 encoded 32 bit mode; @var{thread-id} is a thread ID
28595 (@pxref{thread-id syntax}).
28597 Don't use this packet; use the @samp{qThreadExtraInfo} query instead
28600 Reply: see @code{remote.c:remote_unpack_thread_info_response()}.
28604 @cindex non-stop mode, remote request
28605 @cindex @samp{QNonStop} packet
28607 Enter non-stop (@samp{QNonStop:1}) or all-stop (@samp{QNonStop:0}) mode.
28608 @xref{Remote Non-Stop}, for more information.
28613 The request succeeded.
28616 An error occurred. @var{nn} are hex digits.
28619 An empty reply indicates that @samp{QNonStop} is not supported by
28623 This packet is not probed by default; the remote stub must request it,
28624 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
28625 Use of this packet is controlled by the @code{set non-stop} command;
28626 @pxref{Non-Stop Mode}.
28628 @item QPassSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
28629 @cindex pass signals to inferior, remote request
28630 @cindex @samp{QPassSignals} packet
28631 @anchor{QPassSignals}
28632 Each listed @var{signal} should be passed directly to the inferior process.
28633 Signals are numbered identically to continue packets and stop replies
28634 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
28635 strictly greater than the previous item. These signals do not need to stop
28636 the inferior, or be reported to @value{GDBN}. All other signals should be
28637 reported to @value{GDBN}. Multiple @samp{QPassSignals} packets do not
28638 combine; any earlier @samp{QPassSignals} list is completely replaced by the
28639 new list. This packet improves performance when using @samp{handle
28640 @var{signal} nostop noprint pass}.
28645 The request succeeded.
28648 An error occurred. @var{nn} are hex digits.
28651 An empty reply indicates that @samp{QPassSignals} is not supported by
28655 Use of this packet is controlled by the @code{set remote pass-signals}
28656 command (@pxref{Remote Configuration, set remote pass-signals}).
28657 This packet is not probed by default; the remote stub must request it,
28658 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
28660 @item qRcmd,@var{command}
28661 @cindex execute remote command, remote request
28662 @cindex @samp{qRcmd} packet
28663 @var{command} (hex encoded) is passed to the local interpreter for
28664 execution. Invalid commands should be reported using the output
28665 string. Before the final result packet, the target may also respond
28666 with a number of intermediate @samp{O@var{output}} console output
28667 packets. @emph{Implementors should note that providing access to a
28668 stubs's interpreter may have security implications}.
28673 A command response with no output.
28675 A command response with the hex encoded output string @var{OUTPUT}.
28677 Indicate a badly formed request.
28679 An empty reply indicates that @samp{qRcmd} is not recognized.
28682 (Note that the @code{qRcmd} packet's name is separated from the
28683 command by a @samp{,}, not a @samp{:}, contrary to the naming
28684 conventions above. Please don't use this packet as a model for new
28687 @item qSearch:memory:@var{address};@var{length};@var{search-pattern}
28688 @cindex searching memory, in remote debugging
28689 @cindex @samp{qSearch:memory} packet
28690 @anchor{qSearch memory}
28691 Search @var{length} bytes at @var{address} for @var{search-pattern}.
28692 @var{address} and @var{length} are encoded in hex.
28693 @var{search-pattern} is a sequence of bytes, hex encoded.
28698 The pattern was not found.
28700 The pattern was found at @var{address}.
28702 A badly formed request or an error was encountered while searching memory.
28704 An empty reply indicates that @samp{qSearch:memory} is not recognized.
28707 @item QStartNoAckMode
28708 @cindex @samp{QStartNoAckMode} packet
28709 @anchor{QStartNoAckMode}
28710 Request that the remote stub disable the normal @samp{+}/@samp{-}
28711 protocol acknowledgments (@pxref{Packet Acknowledgment}).
28716 The stub has switched to no-acknowledgment mode.
28717 @value{GDBN} acknowledges this reponse,
28718 but neither the stub nor @value{GDBN} shall send or expect further
28719 @samp{+}/@samp{-} acknowledgments in the current connection.
28721 An empty reply indicates that the stub does not support no-acknowledgment mode.
28724 @item qSupported @r{[}:@var{gdbfeature} @r{[};@var{gdbfeature}@r{]}@dots{} @r{]}
28725 @cindex supported packets, remote query
28726 @cindex features of the remote protocol
28727 @cindex @samp{qSupported} packet
28728 @anchor{qSupported}
28729 Tell the remote stub about features supported by @value{GDBN}, and
28730 query the stub for features it supports. This packet allows
28731 @value{GDBN} and the remote stub to take advantage of each others'
28732 features. @samp{qSupported} also consolidates multiple feature probes
28733 at startup, to improve @value{GDBN} performance---a single larger
28734 packet performs better than multiple smaller probe packets on
28735 high-latency links. Some features may enable behavior which must not
28736 be on by default, e.g.@: because it would confuse older clients or
28737 stubs. Other features may describe packets which could be
28738 automatically probed for, but are not. These features must be
28739 reported before @value{GDBN} will use them. This ``default
28740 unsupported'' behavior is not appropriate for all packets, but it
28741 helps to keep the initial connection time under control with new
28742 versions of @value{GDBN} which support increasing numbers of packets.
28746 @item @var{stubfeature} @r{[};@var{stubfeature}@r{]}@dots{}
28747 The stub supports or does not support each returned @var{stubfeature},
28748 depending on the form of each @var{stubfeature} (see below for the
28751 An empty reply indicates that @samp{qSupported} is not recognized,
28752 or that no features needed to be reported to @value{GDBN}.
28755 The allowed forms for each feature (either a @var{gdbfeature} in the
28756 @samp{qSupported} packet, or a @var{stubfeature} in the response)
28760 @item @var{name}=@var{value}
28761 The remote protocol feature @var{name} is supported, and associated
28762 with the specified @var{value}. The format of @var{value} depends
28763 on the feature, but it must not include a semicolon.
28765 The remote protocol feature @var{name} is supported, and does not
28766 need an associated value.
28768 The remote protocol feature @var{name} is not supported.
28770 The remote protocol feature @var{name} may be supported, and
28771 @value{GDBN} should auto-detect support in some other way when it is
28772 needed. This form will not be used for @var{gdbfeature} notifications,
28773 but may be used for @var{stubfeature} responses.
28776 Whenever the stub receives a @samp{qSupported} request, the
28777 supplied set of @value{GDBN} features should override any previous
28778 request. This allows @value{GDBN} to put the stub in a known
28779 state, even if the stub had previously been communicating with
28780 a different version of @value{GDBN}.
28782 The following values of @var{gdbfeature} (for the packet sent by @value{GDBN})
28787 This feature indicates whether @value{GDBN} supports multiprocess
28788 extensions to the remote protocol. @value{GDBN} does not use such
28789 extensions unless the stub also reports that it supports them by
28790 including @samp{multiprocess+} in its @samp{qSupported} reply.
28791 @xref{multiprocess extensions}, for details.
28794 Stubs should ignore any unknown values for
28795 @var{gdbfeature}. Any @value{GDBN} which sends a @samp{qSupported}
28796 packet supports receiving packets of unlimited length (earlier
28797 versions of @value{GDBN} may reject overly long responses). Additional values
28798 for @var{gdbfeature} may be defined in the future to let the stub take
28799 advantage of new features in @value{GDBN}, e.g.@: incompatible
28800 improvements in the remote protocol---the @samp{multiprocess} feature is
28801 an example of such a feature. The stub's reply should be independent
28802 of the @var{gdbfeature} entries sent by @value{GDBN}; first @value{GDBN}
28803 describes all the features it supports, and then the stub replies with
28804 all the features it supports.
28806 Similarly, @value{GDBN} will silently ignore unrecognized stub feature
28807 responses, as long as each response uses one of the standard forms.
28809 Some features are flags. A stub which supports a flag feature
28810 should respond with a @samp{+} form response. Other features
28811 require values, and the stub should respond with an @samp{=}
28814 Each feature has a default value, which @value{GDBN} will use if
28815 @samp{qSupported} is not available or if the feature is not mentioned
28816 in the @samp{qSupported} response. The default values are fixed; a
28817 stub is free to omit any feature responses that match the defaults.
28819 Not all features can be probed, but for those which can, the probing
28820 mechanism is useful: in some cases, a stub's internal
28821 architecture may not allow the protocol layer to know some information
28822 about the underlying target in advance. This is especially common in
28823 stubs which may be configured for multiple targets.
28825 These are the currently defined stub features and their properties:
28827 @multitable @columnfractions 0.35 0.2 0.12 0.2
28828 @c NOTE: The first row should be @headitem, but we do not yet require
28829 @c a new enough version of Texinfo (4.7) to use @headitem.
28831 @tab Value Required
28835 @item @samp{PacketSize}
28840 @item @samp{qXfer:auxv:read}
28845 @item @samp{qXfer:features:read}
28850 @item @samp{qXfer:libraries:read}
28855 @item @samp{qXfer:memory-map:read}
28860 @item @samp{qXfer:spu:read}
28865 @item @samp{qXfer:spu:write}
28870 @item @samp{qXfer:siginfo:read}
28875 @item @samp{qXfer:siginfo:write}
28880 @item @samp{QNonStop}
28885 @item @samp{QPassSignals}
28890 @item @samp{QStartNoAckMode}
28895 @item @samp{multiprocess}
28900 @item @samp{ConditionalTracepoints}
28905 @item @samp{ReverseContinue}
28910 @item @samp{ReverseStep}
28917 These are the currently defined stub features, in more detail:
28920 @cindex packet size, remote protocol
28921 @item PacketSize=@var{bytes}
28922 The remote stub can accept packets up to at least @var{bytes} in
28923 length. @value{GDBN} will send packets up to this size for bulk
28924 transfers, and will never send larger packets. This is a limit on the
28925 data characters in the packet, including the frame and checksum.
28926 There is no trailing NUL byte in a remote protocol packet; if the stub
28927 stores packets in a NUL-terminated format, it should allow an extra
28928 byte in its buffer for the NUL. If this stub feature is not supported,
28929 @value{GDBN} guesses based on the size of the @samp{g} packet response.
28931 @item qXfer:auxv:read
28932 The remote stub understands the @samp{qXfer:auxv:read} packet
28933 (@pxref{qXfer auxiliary vector read}).
28935 @item qXfer:features:read
28936 The remote stub understands the @samp{qXfer:features:read} packet
28937 (@pxref{qXfer target description read}).
28939 @item qXfer:libraries:read
28940 The remote stub understands the @samp{qXfer:libraries:read} packet
28941 (@pxref{qXfer library list read}).
28943 @item qXfer:memory-map:read
28944 The remote stub understands the @samp{qXfer:memory-map:read} packet
28945 (@pxref{qXfer memory map read}).
28947 @item qXfer:spu:read
28948 The remote stub understands the @samp{qXfer:spu:read} packet
28949 (@pxref{qXfer spu read}).
28951 @item qXfer:spu:write
28952 The remote stub understands the @samp{qXfer:spu:write} packet
28953 (@pxref{qXfer spu write}).
28955 @item qXfer:siginfo:read
28956 The remote stub understands the @samp{qXfer:siginfo:read} packet
28957 (@pxref{qXfer siginfo read}).
28959 @item qXfer:siginfo:write
28960 The remote stub understands the @samp{qXfer:siginfo:write} packet
28961 (@pxref{qXfer siginfo write}).
28964 The remote stub understands the @samp{QNonStop} packet
28965 (@pxref{QNonStop}).
28968 The remote stub understands the @samp{QPassSignals} packet
28969 (@pxref{QPassSignals}).
28971 @item QStartNoAckMode
28972 The remote stub understands the @samp{QStartNoAckMode} packet and
28973 prefers to operate in no-acknowledgment mode. @xref{Packet Acknowledgment}.
28976 @anchor{multiprocess extensions}
28977 @cindex multiprocess extensions, in remote protocol
28978 The remote stub understands the multiprocess extensions to the remote
28979 protocol syntax. The multiprocess extensions affect the syntax of
28980 thread IDs in both packets and replies (@pxref{thread-id syntax}), and
28981 add process IDs to the @samp{D} packet and @samp{W} and @samp{X}
28982 replies. Note that reporting this feature indicates support for the
28983 syntactic extensions only, not that the stub necessarily supports
28984 debugging of more than one process at a time. The stub must not use
28985 multiprocess extensions in packet replies unless @value{GDBN} has also
28986 indicated it supports them in its @samp{qSupported} request.
28988 @item qXfer:osdata:read
28989 The remote stub understands the @samp{qXfer:osdata:read} packet
28990 ((@pxref{qXfer osdata read}).
28992 @item ConditionalTracepoints
28993 The remote stub accepts and implements conditional expressions defined
28994 for tracepoints (@pxref{Tracepoint Conditions}).
28996 @item ReverseContinue
28997 The remote stub accepts and implements the reverse continue packet
29001 The remote stub accepts and implements the reverse step packet
29007 @cindex symbol lookup, remote request
29008 @cindex @samp{qSymbol} packet
29009 Notify the target that @value{GDBN} is prepared to serve symbol lookup
29010 requests. Accept requests from the target for the values of symbols.
29015 The target does not need to look up any (more) symbols.
29016 @item qSymbol:@var{sym_name}
29017 The target requests the value of symbol @var{sym_name} (hex encoded).
29018 @value{GDBN} may provide the value by using the
29019 @samp{qSymbol:@var{sym_value}:@var{sym_name}} message, described
29023 @item qSymbol:@var{sym_value}:@var{sym_name}
29024 Set the value of @var{sym_name} to @var{sym_value}.
29026 @var{sym_name} (hex encoded) is the name of a symbol whose value the
29027 target has previously requested.
29029 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
29030 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
29036 The target does not need to look up any (more) symbols.
29037 @item qSymbol:@var{sym_name}
29038 The target requests the value of a new symbol @var{sym_name} (hex
29039 encoded). @value{GDBN} will continue to supply the values of symbols
29040 (if available), until the target ceases to request them.
29045 @xref{Tracepoint Packets}.
29047 @item qThreadExtraInfo,@var{thread-id}
29048 @cindex thread attributes info, remote request
29049 @cindex @samp{qThreadExtraInfo} packet
29050 Obtain a printable string description of a thread's attributes from
29051 the target OS. @var{thread-id} is a thread ID;
29052 see @ref{thread-id syntax}. This
29053 string may contain anything that the target OS thinks is interesting
29054 for @value{GDBN} to tell the user about the thread. The string is
29055 displayed in @value{GDBN}'s @code{info threads} display. Some
29056 examples of possible thread extra info strings are @samp{Runnable}, or
29057 @samp{Blocked on Mutex}.
29061 @item @var{XX}@dots{}
29062 Where @samp{@var{XX}@dots{}} is a hex encoding of @sc{ascii} data,
29063 comprising the printable string containing the extra information about
29064 the thread's attributes.
29067 (Note that the @code{qThreadExtraInfo} packet's name is separated from
29068 the command by a @samp{,}, not a @samp{:}, contrary to the naming
29069 conventions above. Please don't use this packet as a model for new
29077 @xref{Tracepoint Packets}.
29079 @item qXfer:@var{object}:read:@var{annex}:@var{offset},@var{length}
29080 @cindex read special object, remote request
29081 @cindex @samp{qXfer} packet
29082 @anchor{qXfer read}
29083 Read uninterpreted bytes from the target's special data area
29084 identified by the keyword @var{object}. Request @var{length} bytes
29085 starting at @var{offset} bytes into the data. The content and
29086 encoding of @var{annex} is specific to @var{object}; it can supply
29087 additional details about what data to access.
29089 Here are the specific requests of this form defined so far. All
29090 @samp{qXfer:@var{object}:read:@dots{}} requests use the same reply
29091 formats, listed below.
29094 @item qXfer:auxv:read::@var{offset},@var{length}
29095 @anchor{qXfer auxiliary vector read}
29096 Access the target's @dfn{auxiliary vector}. @xref{OS Information,
29097 auxiliary vector}. Note @var{annex} must be empty.
29099 This packet is not probed by default; the remote stub must request it,
29100 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
29102 @item qXfer:features:read:@var{annex}:@var{offset},@var{length}
29103 @anchor{qXfer target description read}
29104 Access the @dfn{target description}. @xref{Target Descriptions}. The
29105 annex specifies which XML document to access. The main description is
29106 always loaded from the @samp{target.xml} annex.
29108 This packet is not probed by default; the remote stub must request it,
29109 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
29111 @item qXfer:libraries:read:@var{annex}:@var{offset},@var{length}
29112 @anchor{qXfer library list read}
29113 Access the target's list of loaded libraries. @xref{Library List Format}.
29114 The annex part of the generic @samp{qXfer} packet must be empty
29115 (@pxref{qXfer read}).
29117 Targets which maintain a list of libraries in the program's memory do
29118 not need to implement this packet; it is designed for platforms where
29119 the operating system manages the list of loaded libraries.
29121 This packet is not probed by default; the remote stub must request it,
29122 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
29124 @item qXfer:memory-map:read::@var{offset},@var{length}
29125 @anchor{qXfer memory map read}
29126 Access the target's @dfn{memory-map}. @xref{Memory Map Format}. The
29127 annex part of the generic @samp{qXfer} packet must be empty
29128 (@pxref{qXfer read}).
29130 This packet is not probed by default; the remote stub must request it,
29131 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
29133 @item qXfer:siginfo:read::@var{offset},@var{length}
29134 @anchor{qXfer siginfo read}
29135 Read contents of the extra signal information on the target
29136 system. The annex part of the generic @samp{qXfer} packet must be
29137 empty (@pxref{qXfer read}).
29139 This packet is not probed by default; the remote stub must request it,
29140 by supplying an appropriate @samp{qSupported} response
29141 (@pxref{qSupported}).
29143 @item qXfer:spu:read:@var{annex}:@var{offset},@var{length}
29144 @anchor{qXfer spu read}
29145 Read contents of an @code{spufs} file on the target system. The
29146 annex specifies which file to read; it must be of the form
29147 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
29148 in the target process, and @var{name} identifes the @code{spufs} file
29149 in that context to be accessed.
29151 This packet is not probed by default; the remote stub must request it,
29152 by supplying an appropriate @samp{qSupported} response
29153 (@pxref{qSupported}).
29155 @item qXfer:osdata:read::@var{offset},@var{length}
29156 @anchor{qXfer osdata read}
29157 Access the target's @dfn{operating system information}.
29158 @xref{Operating System Information}.
29165 Data @var{data} (@pxref{Binary Data}) has been read from the
29166 target. There may be more data at a higher address (although
29167 it is permitted to return @samp{m} even for the last valid
29168 block of data, as long as at least one byte of data was read).
29169 @var{data} may have fewer bytes than the @var{length} in the
29173 Data @var{data} (@pxref{Binary Data}) has been read from the target.
29174 There is no more data to be read. @var{data} may have fewer bytes
29175 than the @var{length} in the request.
29178 The @var{offset} in the request is at the end of the data.
29179 There is no more data to be read.
29182 The request was malformed, or @var{annex} was invalid.
29185 The offset was invalid, or there was an error encountered reading the data.
29186 @var{nn} is a hex-encoded @code{errno} value.
29189 An empty reply indicates the @var{object} string was not recognized by
29190 the stub, or that the object does not support reading.
29193 @item qXfer:@var{object}:write:@var{annex}:@var{offset}:@var{data}@dots{}
29194 @cindex write data into object, remote request
29195 @anchor{qXfer write}
29196 Write uninterpreted bytes into the target's special data area
29197 identified by the keyword @var{object}, starting at @var{offset} bytes
29198 into the data. @var{data}@dots{} is the binary-encoded data
29199 (@pxref{Binary Data}) to be written. The content and encoding of @var{annex}
29200 is specific to @var{object}; it can supply additional details about what data
29203 Here are the specific requests of this form defined so far. All
29204 @samp{qXfer:@var{object}:write:@dots{}} requests use the same reply
29205 formats, listed below.
29208 @item qXfer:siginfo:write::@var{offset}:@var{data}@dots{}
29209 @anchor{qXfer siginfo write}
29210 Write @var{data} to the extra signal information on the target system.
29211 The annex part of the generic @samp{qXfer} packet must be
29212 empty (@pxref{qXfer write}).
29214 This packet is not probed by default; the remote stub must request it,
29215 by supplying an appropriate @samp{qSupported} response
29216 (@pxref{qSupported}).
29218 @item qXfer:spu:write:@var{annex}:@var{offset}:@var{data}@dots{}
29219 @anchor{qXfer spu write}
29220 Write @var{data} to an @code{spufs} file on the target system. The
29221 annex specifies which file to write; it must be of the form
29222 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
29223 in the target process, and @var{name} identifes the @code{spufs} file
29224 in that context to be accessed.
29226 This packet is not probed by default; the remote stub must request it,
29227 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
29233 @var{nn} (hex encoded) is the number of bytes written.
29234 This may be fewer bytes than supplied in the request.
29237 The request was malformed, or @var{annex} was invalid.
29240 The offset was invalid, or there was an error encountered writing the data.
29241 @var{nn} is a hex-encoded @code{errno} value.
29244 An empty reply indicates the @var{object} string was not
29245 recognized by the stub, or that the object does not support writing.
29248 @item qXfer:@var{object}:@var{operation}:@dots{}
29249 Requests of this form may be added in the future. When a stub does
29250 not recognize the @var{object} keyword, or its support for
29251 @var{object} does not recognize the @var{operation} keyword, the stub
29252 must respond with an empty packet.
29254 @item qAttached:@var{pid}
29255 @cindex query attached, remote request
29256 @cindex @samp{qAttached} packet
29257 Return an indication of whether the remote server attached to an
29258 existing process or created a new process. When the multiprocess
29259 protocol extensions are supported (@pxref{multiprocess extensions}),
29260 @var{pid} is an integer in hexadecimal format identifying the target
29261 process. Otherwise, @value{GDBN} will omit the @var{pid} field and
29262 the query packet will be simplified as @samp{qAttached}.
29264 This query is used, for example, to know whether the remote process
29265 should be detached or killed when a @value{GDBN} session is ended with
29266 the @code{quit} command.
29271 The remote server attached to an existing process.
29273 The remote server created a new process.
29275 A badly formed request or an error was encountered.
29280 @node Register Packet Format
29281 @section Register Packet Format
29283 The following @code{g}/@code{G} packets have previously been defined.
29284 In the below, some thirty-two bit registers are transferred as
29285 sixty-four bits. Those registers should be zero/sign extended (which?)
29286 to fill the space allocated. Register bytes are transferred in target
29287 byte order. The two nibbles within a register byte are transferred
29288 most-significant - least-significant.
29294 All registers are transferred as thirty-two bit quantities in the order:
29295 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
29296 registers; fsr; fir; fp.
29300 All registers are transferred as sixty-four bit quantities (including
29301 thirty-two bit registers such as @code{sr}). The ordering is the same
29306 @node Tracepoint Packets
29307 @section Tracepoint Packets
29308 @cindex tracepoint packets
29309 @cindex packets, tracepoint
29311 Here we describe the packets @value{GDBN} uses to implement
29312 tracepoints (@pxref{Tracepoints}).
29316 @item QTDP:@var{n}:@var{addr}:@var{ena}:@var{step}:@var{pass}[:X@var{len},@var{bytes}]@r{[}-@r{]}
29317 Create a new tracepoint, number @var{n}, at @var{addr}. If @var{ena}
29318 is @samp{E}, then the tracepoint is enabled; if it is @samp{D}, then
29319 the tracepoint is disabled. @var{step} is the tracepoint's step
29320 count, and @var{pass} is its pass count. If an @samp{X} is present,
29321 it introduces a tracepoint condition, which consists of a hexadecimal
29322 length, followed by a comma and hex-encoded bytes, in a manner similar
29323 to action encodings as described below. If the trailing @samp{-} is
29324 present, further @samp{QTDP} packets will follow to specify this
29325 tracepoint's actions.
29330 The packet was understood and carried out.
29332 The packet was not recognized.
29335 @item QTDP:-@var{n}:@var{addr}:@r{[}S@r{]}@var{action}@dots{}@r{[}-@r{]}
29336 Define actions to be taken when a tracepoint is hit. @var{n} and
29337 @var{addr} must be the same as in the initial @samp{QTDP} packet for
29338 this tracepoint. This packet may only be sent immediately after
29339 another @samp{QTDP} packet that ended with a @samp{-}. If the
29340 trailing @samp{-} is present, further @samp{QTDP} packets will follow,
29341 specifying more actions for this tracepoint.
29343 In the series of action packets for a given tracepoint, at most one
29344 can have an @samp{S} before its first @var{action}. If such a packet
29345 is sent, it and the following packets define ``while-stepping''
29346 actions. Any prior packets define ordinary actions --- that is, those
29347 taken when the tracepoint is first hit. If no action packet has an
29348 @samp{S}, then all the packets in the series specify ordinary
29349 tracepoint actions.
29351 The @samp{@var{action}@dots{}} portion of the packet is a series of
29352 actions, concatenated without separators. Each action has one of the
29358 Collect the registers whose bits are set in @var{mask}. @var{mask} is
29359 a hexadecimal number whose @var{i}'th bit is set if register number
29360 @var{i} should be collected. (The least significant bit is numbered
29361 zero.) Note that @var{mask} may be any number of digits long; it may
29362 not fit in a 32-bit word.
29364 @item M @var{basereg},@var{offset},@var{len}
29365 Collect @var{len} bytes of memory starting at the address in register
29366 number @var{basereg}, plus @var{offset}. If @var{basereg} is
29367 @samp{-1}, then the range has a fixed address: @var{offset} is the
29368 address of the lowest byte to collect. The @var{basereg},
29369 @var{offset}, and @var{len} parameters are all unsigned hexadecimal
29370 values (the @samp{-1} value for @var{basereg} is a special case).
29372 @item X @var{len},@var{expr}
29373 Evaluate @var{expr}, whose length is @var{len}, and collect memory as
29374 it directs. @var{expr} is an agent expression, as described in
29375 @ref{Agent Expressions}. Each byte of the expression is encoded as a
29376 two-digit hex number in the packet; @var{len} is the number of bytes
29377 in the expression (and thus one-half the number of hex digits in the
29382 Any number of actions may be packed together in a single @samp{QTDP}
29383 packet, as long as the packet does not exceed the maximum packet
29384 length (400 bytes, for many stubs). There may be only one @samp{R}
29385 action per tracepoint, and it must precede any @samp{M} or @samp{X}
29386 actions. Any registers referred to by @samp{M} and @samp{X} actions
29387 must be collected by a preceding @samp{R} action. (The
29388 ``while-stepping'' actions are treated as if they were attached to a
29389 separate tracepoint, as far as these restrictions are concerned.)
29394 The packet was understood and carried out.
29396 The packet was not recognized.
29399 @item QTFrame:@var{n}
29400 Select the @var{n}'th tracepoint frame from the buffer, and use the
29401 register and memory contents recorded there to answer subsequent
29402 request packets from @value{GDBN}.
29404 A successful reply from the stub indicates that the stub has found the
29405 requested frame. The response is a series of parts, concatenated
29406 without separators, describing the frame we selected. Each part has
29407 one of the following forms:
29411 The selected frame is number @var{n} in the trace frame buffer;
29412 @var{f} is a hexadecimal number. If @var{f} is @samp{-1}, then there
29413 was no frame matching the criteria in the request packet.
29416 The selected trace frame records a hit of tracepoint number @var{t};
29417 @var{t} is a hexadecimal number.
29421 @item QTFrame:pc:@var{addr}
29422 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
29423 currently selected frame whose PC is @var{addr};
29424 @var{addr} is a hexadecimal number.
29426 @item QTFrame:tdp:@var{t}
29427 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
29428 currently selected frame that is a hit of tracepoint @var{t}; @var{t}
29429 is a hexadecimal number.
29431 @item QTFrame:range:@var{start}:@var{end}
29432 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
29433 currently selected frame whose PC is between @var{start} (inclusive)
29434 and @var{end} (exclusive); @var{start} and @var{end} are hexadecimal
29437 @item QTFrame:outside:@var{start}:@var{end}
29438 Like @samp{QTFrame:range:@var{start}:@var{end}}, but select the first
29439 frame @emph{outside} the given range of addresses.
29442 Begin the tracepoint experiment. Begin collecting data from tracepoint
29443 hits in the trace frame buffer.
29446 End the tracepoint experiment. Stop collecting trace frames.
29449 Clear the table of tracepoints, and empty the trace frame buffer.
29451 @item QTro:@var{start1},@var{end1}:@var{start2},@var{end2}:@dots{}
29452 Establish the given ranges of memory as ``transparent''. The stub
29453 will answer requests for these ranges from memory's current contents,
29454 if they were not collected as part of the tracepoint hit.
29456 @value{GDBN} uses this to mark read-only regions of memory, like those
29457 containing program code. Since these areas never change, they should
29458 still have the same contents they did when the tracepoint was hit, so
29459 there's no reason for the stub to refuse to provide their contents.
29462 Ask the stub if there is a trace experiment running right now.
29467 There is no trace experiment running.
29469 There is a trace experiment running.
29475 @node Host I/O Packets
29476 @section Host I/O Packets
29477 @cindex Host I/O, remote protocol
29478 @cindex file transfer, remote protocol
29480 The @dfn{Host I/O} packets allow @value{GDBN} to perform I/O
29481 operations on the far side of a remote link. For example, Host I/O is
29482 used to upload and download files to a remote target with its own
29483 filesystem. Host I/O uses the same constant values and data structure
29484 layout as the target-initiated File-I/O protocol. However, the
29485 Host I/O packets are structured differently. The target-initiated
29486 protocol relies on target memory to store parameters and buffers.
29487 Host I/O requests are initiated by @value{GDBN}, and the
29488 target's memory is not involved. @xref{File-I/O Remote Protocol
29489 Extension}, for more details on the target-initiated protocol.
29491 The Host I/O request packets all encode a single operation along with
29492 its arguments. They have this format:
29496 @item vFile:@var{operation}: @var{parameter}@dots{}
29497 @var{operation} is the name of the particular request; the target
29498 should compare the entire packet name up to the second colon when checking
29499 for a supported operation. The format of @var{parameter} depends on
29500 the operation. Numbers are always passed in hexadecimal. Negative
29501 numbers have an explicit minus sign (i.e.@: two's complement is not
29502 used). Strings (e.g.@: filenames) are encoded as a series of
29503 hexadecimal bytes. The last argument to a system call may be a
29504 buffer of escaped binary data (@pxref{Binary Data}).
29508 The valid responses to Host I/O packets are:
29512 @item F @var{result} [, @var{errno}] [; @var{attachment}]
29513 @var{result} is the integer value returned by this operation, usually
29514 non-negative for success and -1 for errors. If an error has occured,
29515 @var{errno} will be included in the result. @var{errno} will have a
29516 value defined by the File-I/O protocol (@pxref{Errno Values}). For
29517 operations which return data, @var{attachment} supplies the data as a
29518 binary buffer. Binary buffers in response packets are escaped in the
29519 normal way (@pxref{Binary Data}). See the individual packet
29520 documentation for the interpretation of @var{result} and
29524 An empty response indicates that this operation is not recognized.
29528 These are the supported Host I/O operations:
29531 @item vFile:open: @var{pathname}, @var{flags}, @var{mode}
29532 Open a file at @var{pathname} and return a file descriptor for it, or
29533 return -1 if an error occurs. @var{pathname} is a string,
29534 @var{flags} is an integer indicating a mask of open flags
29535 (@pxref{Open Flags}), and @var{mode} is an integer indicating a mask
29536 of mode bits to use if the file is created (@pxref{mode_t Values}).
29537 @xref{open}, for details of the open flags and mode values.
29539 @item vFile:close: @var{fd}
29540 Close the open file corresponding to @var{fd} and return 0, or
29541 -1 if an error occurs.
29543 @item vFile:pread: @var{fd}, @var{count}, @var{offset}
29544 Read data from the open file corresponding to @var{fd}. Up to
29545 @var{count} bytes will be read from the file, starting at @var{offset}
29546 relative to the start of the file. The target may read fewer bytes;
29547 common reasons include packet size limits and an end-of-file
29548 condition. The number of bytes read is returned. Zero should only be
29549 returned for a successful read at the end of the file, or if
29550 @var{count} was zero.
29552 The data read should be returned as a binary attachment on success.
29553 If zero bytes were read, the response should include an empty binary
29554 attachment (i.e.@: a trailing semicolon). The return value is the
29555 number of target bytes read; the binary attachment may be longer if
29556 some characters were escaped.
29558 @item vFile:pwrite: @var{fd}, @var{offset}, @var{data}
29559 Write @var{data} (a binary buffer) to the open file corresponding
29560 to @var{fd}. Start the write at @var{offset} from the start of the
29561 file. Unlike many @code{write} system calls, there is no
29562 separate @var{count} argument; the length of @var{data} in the
29563 packet is used. @samp{vFile:write} returns the number of bytes written,
29564 which may be shorter than the length of @var{data}, or -1 if an
29567 @item vFile:unlink: @var{pathname}
29568 Delete the file at @var{pathname} on the target. Return 0,
29569 or -1 if an error occurs. @var{pathname} is a string.
29574 @section Interrupts
29575 @cindex interrupts (remote protocol)
29577 When a program on the remote target is running, @value{GDBN} may
29578 attempt to interrupt it by sending a @samp{Ctrl-C} or a @code{BREAK},
29579 control of which is specified via @value{GDBN}'s @samp{remotebreak}
29580 setting (@pxref{set remotebreak}).
29582 The precise meaning of @code{BREAK} is defined by the transport
29583 mechanism and may, in fact, be undefined. @value{GDBN} does not
29584 currently define a @code{BREAK} mechanism for any of the network
29585 interfaces except for TCP, in which case @value{GDBN} sends the
29586 @code{telnet} BREAK sequence.
29588 @samp{Ctrl-C}, on the other hand, is defined and implemented for all
29589 transport mechanisms. It is represented by sending the single byte
29590 @code{0x03} without any of the usual packet overhead described in
29591 the Overview section (@pxref{Overview}). When a @code{0x03} byte is
29592 transmitted as part of a packet, it is considered to be packet data
29593 and does @emph{not} represent an interrupt. E.g., an @samp{X} packet
29594 (@pxref{X packet}), used for binary downloads, may include an unescaped
29595 @code{0x03} as part of its packet.
29597 Stubs are not required to recognize these interrupt mechanisms and the
29598 precise meaning associated with receipt of the interrupt is
29599 implementation defined. If the target supports debugging of multiple
29600 threads and/or processes, it should attempt to interrupt all
29601 currently-executing threads and processes.
29602 If the stub is successful at interrupting the
29603 running program, it should send one of the stop
29604 reply packets (@pxref{Stop Reply Packets}) to @value{GDBN} as a result
29605 of successfully stopping the program in all-stop mode, and a stop reply
29606 for each stopped thread in non-stop mode.
29607 Interrupts received while the
29608 program is stopped are discarded.
29610 @node Notification Packets
29611 @section Notification Packets
29612 @cindex notification packets
29613 @cindex packets, notification
29615 The @value{GDBN} remote serial protocol includes @dfn{notifications},
29616 packets that require no acknowledgment. Both the GDB and the stub
29617 may send notifications (although the only notifications defined at
29618 present are sent by the stub). Notifications carry information
29619 without incurring the round-trip latency of an acknowledgment, and so
29620 are useful for low-impact communications where occasional packet loss
29623 A notification packet has the form @samp{% @var{data} #
29624 @var{checksum}}, where @var{data} is the content of the notification,
29625 and @var{checksum} is a checksum of @var{data}, computed and formatted
29626 as for ordinary @value{GDBN} packets. A notification's @var{data}
29627 never contains @samp{$}, @samp{%} or @samp{#} characters. Upon
29628 receiving a notification, the recipient sends no @samp{+} or @samp{-}
29629 to acknowledge the notification's receipt or to report its corruption.
29631 Every notification's @var{data} begins with a name, which contains no
29632 colon characters, followed by a colon character.
29634 Recipients should silently ignore corrupted notifications and
29635 notifications they do not understand. Recipients should restart
29636 timeout periods on receipt of a well-formed notification, whether or
29637 not they understand it.
29639 Senders should only send the notifications described here when this
29640 protocol description specifies that they are permitted. In the
29641 future, we may extend the protocol to permit existing notifications in
29642 new contexts; this rule helps older senders avoid confusing newer
29645 (Older versions of @value{GDBN} ignore bytes received until they see
29646 the @samp{$} byte that begins an ordinary packet, so new stubs may
29647 transmit notifications without fear of confusing older clients. There
29648 are no notifications defined for @value{GDBN} to send at the moment, but we
29649 assume that most older stubs would ignore them, as well.)
29651 The following notification packets from the stub to @value{GDBN} are
29655 @item Stop: @var{reply}
29656 Report an asynchronous stop event in non-stop mode.
29657 The @var{reply} has the form of a stop reply, as
29658 described in @ref{Stop Reply Packets}. Refer to @ref{Remote Non-Stop},
29659 for information on how these notifications are acknowledged by
29663 @node Remote Non-Stop
29664 @section Remote Protocol Support for Non-Stop Mode
29666 @value{GDBN}'s remote protocol supports non-stop debugging of
29667 multi-threaded programs, as described in @ref{Non-Stop Mode}. If the stub
29668 supports non-stop mode, it should report that to @value{GDBN} by including
29669 @samp{QNonStop+} in its @samp{qSupported} response (@pxref{qSupported}).
29671 @value{GDBN} typically sends a @samp{QNonStop} packet only when
29672 establishing a new connection with the stub. Entering non-stop mode
29673 does not alter the state of any currently-running threads, but targets
29674 must stop all threads in any already-attached processes when entering
29675 all-stop mode. @value{GDBN} uses the @samp{?} packet as necessary to
29676 probe the target state after a mode change.
29678 In non-stop mode, when an attached process encounters an event that
29679 would otherwise be reported with a stop reply, it uses the
29680 asynchronous notification mechanism (@pxref{Notification Packets}) to
29681 inform @value{GDBN}. In contrast to all-stop mode, where all threads
29682 in all processes are stopped when a stop reply is sent, in non-stop
29683 mode only the thread reporting the stop event is stopped. That is,
29684 when reporting a @samp{S} or @samp{T} response to indicate completion
29685 of a step operation, hitting a breakpoint, or a fault, only the
29686 affected thread is stopped; any other still-running threads continue
29687 to run. When reporting a @samp{W} or @samp{X} response, all running
29688 threads belonging to other attached processes continue to run.
29690 Only one stop reply notification at a time may be pending; if
29691 additional stop events occur before @value{GDBN} has acknowledged the
29692 previous notification, they must be queued by the stub for later
29693 synchronous transmission in response to @samp{vStopped} packets from
29694 @value{GDBN}. Because the notification mechanism is unreliable,
29695 the stub is permitted to resend a stop reply notification
29696 if it believes @value{GDBN} may not have received it. @value{GDBN}
29697 ignores additional stop reply notifications received before it has
29698 finished processing a previous notification and the stub has completed
29699 sending any queued stop events.
29701 Otherwise, @value{GDBN} must be prepared to receive a stop reply
29702 notification at any time. Specifically, they may appear when
29703 @value{GDBN} is not otherwise reading input from the stub, or when
29704 @value{GDBN} is expecting to read a normal synchronous response or a
29705 @samp{+}/@samp{-} acknowledgment to a packet it has sent.
29706 Notification packets are distinct from any other communication from
29707 the stub so there is no ambiguity.
29709 After receiving a stop reply notification, @value{GDBN} shall
29710 acknowledge it by sending a @samp{vStopped} packet (@pxref{vStopped packet})
29711 as a regular, synchronous request to the stub. Such acknowledgment
29712 is not required to happen immediately, as @value{GDBN} is permitted to
29713 send other, unrelated packets to the stub first, which the stub should
29716 Upon receiving a @samp{vStopped} packet, if the stub has other queued
29717 stop events to report to @value{GDBN}, it shall respond by sending a
29718 normal stop reply response. @value{GDBN} shall then send another
29719 @samp{vStopped} packet to solicit further responses; again, it is
29720 permitted to send other, unrelated packets as well which the stub
29721 should process normally.
29723 If the stub receives a @samp{vStopped} packet and there are no
29724 additional stop events to report, the stub shall return an @samp{OK}
29725 response. At this point, if further stop events occur, the stub shall
29726 send a new stop reply notification, @value{GDBN} shall accept the
29727 notification, and the process shall be repeated.
29729 In non-stop mode, the target shall respond to the @samp{?} packet as
29730 follows. First, any incomplete stop reply notification/@samp{vStopped}
29731 sequence in progress is abandoned. The target must begin a new
29732 sequence reporting stop events for all stopped threads, whether or not
29733 it has previously reported those events to @value{GDBN}. The first
29734 stop reply is sent as a synchronous reply to the @samp{?} packet, and
29735 subsequent stop replies are sent as responses to @samp{vStopped} packets
29736 using the mechanism described above. The target must not send
29737 asynchronous stop reply notifications until the sequence is complete.
29738 If all threads are running when the target receives the @samp{?} packet,
29739 or if the target is not attached to any process, it shall respond
29742 @node Packet Acknowledgment
29743 @section Packet Acknowledgment
29745 @cindex acknowledgment, for @value{GDBN} remote
29746 @cindex packet acknowledgment, for @value{GDBN} remote
29747 By default, when either the host or the target machine receives a packet,
29748 the first response expected is an acknowledgment: either @samp{+} (to indicate
29749 the package was received correctly) or @samp{-} (to request retransmission).
29750 This mechanism allows the @value{GDBN} remote protocol to operate over
29751 unreliable transport mechanisms, such as a serial line.
29753 In cases where the transport mechanism is itself reliable (such as a pipe or
29754 TCP connection), the @samp{+}/@samp{-} acknowledgments are redundant.
29755 It may be desirable to disable them in that case to reduce communication
29756 overhead, or for other reasons. This can be accomplished by means of the
29757 @samp{QStartNoAckMode} packet; @pxref{QStartNoAckMode}.
29759 When in no-acknowledgment mode, neither the stub nor @value{GDBN} shall send or
29760 expect @samp{+}/@samp{-} protocol acknowledgments. The packet
29761 and response format still includes the normal checksum, as described in
29762 @ref{Overview}, but the checksum may be ignored by the receiver.
29764 If the stub supports @samp{QStartNoAckMode} and prefers to operate in
29765 no-acknowledgment mode, it should report that to @value{GDBN}
29766 by including @samp{QStartNoAckMode+} in its response to @samp{qSupported};
29767 @pxref{qSupported}.
29768 If @value{GDBN} also supports @samp{QStartNoAckMode} and it has not been
29769 disabled via the @code{set remote noack-packet off} command
29770 (@pxref{Remote Configuration}),
29771 @value{GDBN} may then send a @samp{QStartNoAckMode} packet to the stub.
29772 Only then may the stub actually turn off packet acknowledgments.
29773 @value{GDBN} sends a final @samp{+} acknowledgment of the stub's @samp{OK}
29774 response, which can be safely ignored by the stub.
29776 Note that @code{set remote noack-packet} command only affects negotiation
29777 between @value{GDBN} and the stub when subsequent connections are made;
29778 it does not affect the protocol acknowledgment state for any current
29780 Since @samp{+}/@samp{-} acknowledgments are enabled by default when a
29781 new connection is established,
29782 there is also no protocol request to re-enable the acknowledgments
29783 for the current connection, once disabled.
29788 Example sequence of a target being re-started. Notice how the restart
29789 does not get any direct output:
29794 @emph{target restarts}
29797 <- @code{T001:1234123412341234}
29801 Example sequence of a target being stepped by a single instruction:
29804 -> @code{G1445@dots{}}
29809 <- @code{T001:1234123412341234}
29813 <- @code{1455@dots{}}
29817 @node File-I/O Remote Protocol Extension
29818 @section File-I/O Remote Protocol Extension
29819 @cindex File-I/O remote protocol extension
29822 * File-I/O Overview::
29823 * Protocol Basics::
29824 * The F Request Packet::
29825 * The F Reply Packet::
29826 * The Ctrl-C Message::
29828 * List of Supported Calls::
29829 * Protocol-specific Representation of Datatypes::
29831 * File-I/O Examples::
29834 @node File-I/O Overview
29835 @subsection File-I/O Overview
29836 @cindex file-i/o overview
29838 The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the
29839 target to use the host's file system and console I/O to perform various
29840 system calls. System calls on the target system are translated into a
29841 remote protocol packet to the host system, which then performs the needed
29842 actions and returns a response packet to the target system.
29843 This simulates file system operations even on targets that lack file systems.
29845 The protocol is defined to be independent of both the host and target systems.
29846 It uses its own internal representation of datatypes and values. Both
29847 @value{GDBN} and the target's @value{GDBN} stub are responsible for
29848 translating the system-dependent value representations into the internal
29849 protocol representations when data is transmitted.
29851 The communication is synchronous. A system call is possible only when
29852 @value{GDBN} is waiting for a response from the @samp{C}, @samp{c}, @samp{S}
29853 or @samp{s} packets. While @value{GDBN} handles the request for a system call,
29854 the target is stopped to allow deterministic access to the target's
29855 memory. Therefore File-I/O is not interruptible by target signals. On
29856 the other hand, it is possible to interrupt File-I/O by a user interrupt
29857 (@samp{Ctrl-C}) within @value{GDBN}.
29859 The target's request to perform a host system call does not finish
29860 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
29861 after finishing the system call, the target returns to continuing the
29862 previous activity (continue, step). No additional continue or step
29863 request from @value{GDBN} is required.
29866 (@value{GDBP}) continue
29867 <- target requests 'system call X'
29868 target is stopped, @value{GDBN} executes system call
29869 -> @value{GDBN} returns result
29870 ... target continues, @value{GDBN} returns to wait for the target
29871 <- target hits breakpoint and sends a Txx packet
29874 The protocol only supports I/O on the console and to regular files on
29875 the host file system. Character or block special devices, pipes,
29876 named pipes, sockets or any other communication method on the host
29877 system are not supported by this protocol.
29879 File I/O is not supported in non-stop mode.
29881 @node Protocol Basics
29882 @subsection Protocol Basics
29883 @cindex protocol basics, file-i/o
29885 The File-I/O protocol uses the @code{F} packet as the request as well
29886 as reply packet. Since a File-I/O system call can only occur when
29887 @value{GDBN} is waiting for a response from the continuing or stepping target,
29888 the File-I/O request is a reply that @value{GDBN} has to expect as a result
29889 of a previous @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
29890 This @code{F} packet contains all information needed to allow @value{GDBN}
29891 to call the appropriate host system call:
29895 A unique identifier for the requested system call.
29898 All parameters to the system call. Pointers are given as addresses
29899 in the target memory address space. Pointers to strings are given as
29900 pointer/length pair. Numerical values are given as they are.
29901 Numerical control flags are given in a protocol-specific representation.
29905 At this point, @value{GDBN} has to perform the following actions.
29909 If the parameters include pointer values to data needed as input to a
29910 system call, @value{GDBN} requests this data from the target with a
29911 standard @code{m} packet request. This additional communication has to be
29912 expected by the target implementation and is handled as any other @code{m}
29916 @value{GDBN} translates all value from protocol representation to host
29917 representation as needed. Datatypes are coerced into the host types.
29920 @value{GDBN} calls the system call.
29923 It then coerces datatypes back to protocol representation.
29926 If the system call is expected to return data in buffer space specified
29927 by pointer parameters to the call, the data is transmitted to the
29928 target using a @code{M} or @code{X} packet. This packet has to be expected
29929 by the target implementation and is handled as any other @code{M} or @code{X}
29934 Eventually @value{GDBN} replies with another @code{F} packet which contains all
29935 necessary information for the target to continue. This at least contains
29942 @code{errno}, if has been changed by the system call.
29949 After having done the needed type and value coercion, the target continues
29950 the latest continue or step action.
29952 @node The F Request Packet
29953 @subsection The @code{F} Request Packet
29954 @cindex file-i/o request packet
29955 @cindex @code{F} request packet
29957 The @code{F} request packet has the following format:
29960 @item F@var{call-id},@var{parameter@dots{}}
29962 @var{call-id} is the identifier to indicate the host system call to be called.
29963 This is just the name of the function.
29965 @var{parameter@dots{}} are the parameters to the system call.
29966 Parameters are hexadecimal integer values, either the actual values in case
29967 of scalar datatypes, pointers to target buffer space in case of compound
29968 datatypes and unspecified memory areas, or pointer/length pairs in case
29969 of string parameters. These are appended to the @var{call-id} as a
29970 comma-delimited list. All values are transmitted in ASCII
29971 string representation, pointer/length pairs separated by a slash.
29977 @node The F Reply Packet
29978 @subsection The @code{F} Reply Packet
29979 @cindex file-i/o reply packet
29980 @cindex @code{F} reply packet
29982 The @code{F} reply packet has the following format:
29986 @item F@var{retcode},@var{errno},@var{Ctrl-C flag};@var{call-specific attachment}
29988 @var{retcode} is the return code of the system call as hexadecimal value.
29990 @var{errno} is the @code{errno} set by the call, in protocol-specific
29992 This parameter can be omitted if the call was successful.
29994 @var{Ctrl-C flag} is only sent if the user requested a break. In this
29995 case, @var{errno} must be sent as well, even if the call was successful.
29996 The @var{Ctrl-C flag} itself consists of the character @samp{C}:
30003 or, if the call was interrupted before the host call has been performed:
30010 assuming 4 is the protocol-specific representation of @code{EINTR}.
30015 @node The Ctrl-C Message
30016 @subsection The @samp{Ctrl-C} Message
30017 @cindex ctrl-c message, in file-i/o protocol
30019 If the @samp{Ctrl-C} flag is set in the @value{GDBN}
30020 reply packet (@pxref{The F Reply Packet}),
30021 the target should behave as if it had
30022 gotten a break message. The meaning for the target is ``system call
30023 interrupted by @code{SIGINT}''. Consequentially, the target should actually stop
30024 (as with a break message) and return to @value{GDBN} with a @code{T02}
30027 It's important for the target to know in which
30028 state the system call was interrupted. There are two possible cases:
30032 The system call hasn't been performed on the host yet.
30035 The system call on the host has been finished.
30039 These two states can be distinguished by the target by the value of the
30040 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
30041 call hasn't been performed. This is equivalent to the @code{EINTR} handling
30042 on POSIX systems. In any other case, the target may presume that the
30043 system call has been finished --- successfully or not --- and should behave
30044 as if the break message arrived right after the system call.
30046 @value{GDBN} must behave reliably. If the system call has not been called
30047 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
30048 @code{errno} in the packet. If the system call on the host has been finished
30049 before the user requests a break, the full action must be finished by
30050 @value{GDBN}. This requires sending @code{M} or @code{X} packets as necessary.
30051 The @code{F} packet may only be sent when either nothing has happened
30052 or the full action has been completed.
30055 @subsection Console I/O
30056 @cindex console i/o as part of file-i/o
30058 By default and if not explicitly closed by the target system, the file
30059 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
30060 on the @value{GDBN} console is handled as any other file output operation
30061 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
30062 by @value{GDBN} so that after the target read request from file descriptor
30063 0 all following typing is buffered until either one of the following
30068 The user types @kbd{Ctrl-c}. The behaviour is as explained above, and the
30070 system call is treated as finished.
30073 The user presses @key{RET}. This is treated as end of input with a trailing
30077 The user types @kbd{Ctrl-d}. This is treated as end of input. No trailing
30078 character (neither newline nor @samp{Ctrl-D}) is appended to the input.
30082 If the user has typed more characters than fit in the buffer given to
30083 the @code{read} call, the trailing characters are buffered in @value{GDBN} until
30084 either another @code{read(0, @dots{})} is requested by the target, or debugging
30085 is stopped at the user's request.
30088 @node List of Supported Calls
30089 @subsection List of Supported Calls
30090 @cindex list of supported file-i/o calls
30107 @unnumberedsubsubsec open
30108 @cindex open, file-i/o system call
30113 int open(const char *pathname, int flags);
30114 int open(const char *pathname, int flags, mode_t mode);
30118 @samp{Fopen,@var{pathptr}/@var{len},@var{flags},@var{mode}}
30121 @var{flags} is the bitwise @code{OR} of the following values:
30125 If the file does not exist it will be created. The host
30126 rules apply as far as file ownership and time stamps
30130 When used with @code{O_CREAT}, if the file already exists it is
30131 an error and open() fails.
30134 If the file already exists and the open mode allows
30135 writing (@code{O_RDWR} or @code{O_WRONLY} is given) it will be
30136 truncated to zero length.
30139 The file is opened in append mode.
30142 The file is opened for reading only.
30145 The file is opened for writing only.
30148 The file is opened for reading and writing.
30152 Other bits are silently ignored.
30156 @var{mode} is the bitwise @code{OR} of the following values:
30160 User has read permission.
30163 User has write permission.
30166 Group has read permission.
30169 Group has write permission.
30172 Others have read permission.
30175 Others have write permission.
30179 Other bits are silently ignored.
30182 @item Return value:
30183 @code{open} returns the new file descriptor or -1 if an error
30190 @var{pathname} already exists and @code{O_CREAT} and @code{O_EXCL} were used.
30193 @var{pathname} refers to a directory.
30196 The requested access is not allowed.
30199 @var{pathname} was too long.
30202 A directory component in @var{pathname} does not exist.
30205 @var{pathname} refers to a device, pipe, named pipe or socket.
30208 @var{pathname} refers to a file on a read-only filesystem and
30209 write access was requested.
30212 @var{pathname} is an invalid pointer value.
30215 No space on device to create the file.
30218 The process already has the maximum number of files open.
30221 The limit on the total number of files open on the system
30225 The call was interrupted by the user.
30231 @unnumberedsubsubsec close
30232 @cindex close, file-i/o system call
30241 @samp{Fclose,@var{fd}}
30243 @item Return value:
30244 @code{close} returns zero on success, or -1 if an error occurred.
30250 @var{fd} isn't a valid open file descriptor.
30253 The call was interrupted by the user.
30259 @unnumberedsubsubsec read
30260 @cindex read, file-i/o system call
30265 int read(int fd, void *buf, unsigned int count);
30269 @samp{Fread,@var{fd},@var{bufptr},@var{count}}
30271 @item Return value:
30272 On success, the number of bytes read is returned.
30273 Zero indicates end of file. If count is zero, read
30274 returns zero as well. On error, -1 is returned.
30280 @var{fd} is not a valid file descriptor or is not open for
30284 @var{bufptr} is an invalid pointer value.
30287 The call was interrupted by the user.
30293 @unnumberedsubsubsec write
30294 @cindex write, file-i/o system call
30299 int write(int fd, const void *buf, unsigned int count);
30303 @samp{Fwrite,@var{fd},@var{bufptr},@var{count}}
30305 @item Return value:
30306 On success, the number of bytes written are returned.
30307 Zero indicates nothing was written. On error, -1
30314 @var{fd} is not a valid file descriptor or is not open for
30318 @var{bufptr} is an invalid pointer value.
30321 An attempt was made to write a file that exceeds the
30322 host-specific maximum file size allowed.
30325 No space on device to write the data.
30328 The call was interrupted by the user.
30334 @unnumberedsubsubsec lseek
30335 @cindex lseek, file-i/o system call
30340 long lseek (int fd, long offset, int flag);
30344 @samp{Flseek,@var{fd},@var{offset},@var{flag}}
30346 @var{flag} is one of:
30350 The offset is set to @var{offset} bytes.
30353 The offset is set to its current location plus @var{offset}
30357 The offset is set to the size of the file plus @var{offset}
30361 @item Return value:
30362 On success, the resulting unsigned offset in bytes from
30363 the beginning of the file is returned. Otherwise, a
30364 value of -1 is returned.
30370 @var{fd} is not a valid open file descriptor.
30373 @var{fd} is associated with the @value{GDBN} console.
30376 @var{flag} is not a proper value.
30379 The call was interrupted by the user.
30385 @unnumberedsubsubsec rename
30386 @cindex rename, file-i/o system call
30391 int rename(const char *oldpath, const char *newpath);
30395 @samp{Frename,@var{oldpathptr}/@var{len},@var{newpathptr}/@var{len}}
30397 @item Return value:
30398 On success, zero is returned. On error, -1 is returned.
30404 @var{newpath} is an existing directory, but @var{oldpath} is not a
30408 @var{newpath} is a non-empty directory.
30411 @var{oldpath} or @var{newpath} is a directory that is in use by some
30415 An attempt was made to make a directory a subdirectory
30419 A component used as a directory in @var{oldpath} or new
30420 path is not a directory. Or @var{oldpath} is a directory
30421 and @var{newpath} exists but is not a directory.
30424 @var{oldpathptr} or @var{newpathptr} are invalid pointer values.
30427 No access to the file or the path of the file.
30431 @var{oldpath} or @var{newpath} was too long.
30434 A directory component in @var{oldpath} or @var{newpath} does not exist.
30437 The file is on a read-only filesystem.
30440 The device containing the file has no room for the new
30444 The call was interrupted by the user.
30450 @unnumberedsubsubsec unlink
30451 @cindex unlink, file-i/o system call
30456 int unlink(const char *pathname);
30460 @samp{Funlink,@var{pathnameptr}/@var{len}}
30462 @item Return value:
30463 On success, zero is returned. On error, -1 is returned.
30469 No access to the file or the path of the file.
30472 The system does not allow unlinking of directories.
30475 The file @var{pathname} cannot be unlinked because it's
30476 being used by another process.
30479 @var{pathnameptr} is an invalid pointer value.
30482 @var{pathname} was too long.
30485 A directory component in @var{pathname} does not exist.
30488 A component of the path is not a directory.
30491 The file is on a read-only filesystem.
30494 The call was interrupted by the user.
30500 @unnumberedsubsubsec stat/fstat
30501 @cindex fstat, file-i/o system call
30502 @cindex stat, file-i/o system call
30507 int stat(const char *pathname, struct stat *buf);
30508 int fstat(int fd, struct stat *buf);
30512 @samp{Fstat,@var{pathnameptr}/@var{len},@var{bufptr}}@*
30513 @samp{Ffstat,@var{fd},@var{bufptr}}
30515 @item Return value:
30516 On success, zero is returned. On error, -1 is returned.
30522 @var{fd} is not a valid open file.
30525 A directory component in @var{pathname} does not exist or the
30526 path is an empty string.
30529 A component of the path is not a directory.
30532 @var{pathnameptr} is an invalid pointer value.
30535 No access to the file or the path of the file.
30538 @var{pathname} was too long.
30541 The call was interrupted by the user.
30547 @unnumberedsubsubsec gettimeofday
30548 @cindex gettimeofday, file-i/o system call
30553 int gettimeofday(struct timeval *tv, void *tz);
30557 @samp{Fgettimeofday,@var{tvptr},@var{tzptr}}
30559 @item Return value:
30560 On success, 0 is returned, -1 otherwise.
30566 @var{tz} is a non-NULL pointer.
30569 @var{tvptr} and/or @var{tzptr} is an invalid pointer value.
30575 @unnumberedsubsubsec isatty
30576 @cindex isatty, file-i/o system call
30581 int isatty(int fd);
30585 @samp{Fisatty,@var{fd}}
30587 @item Return value:
30588 Returns 1 if @var{fd} refers to the @value{GDBN} console, 0 otherwise.
30594 The call was interrupted by the user.
30599 Note that the @code{isatty} call is treated as a special case: it returns
30600 1 to the target if the file descriptor is attached
30601 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
30602 would require implementing @code{ioctl} and would be more complex than
30607 @unnumberedsubsubsec system
30608 @cindex system, file-i/o system call
30613 int system(const char *command);
30617 @samp{Fsystem,@var{commandptr}/@var{len}}
30619 @item Return value:
30620 If @var{len} is zero, the return value indicates whether a shell is
30621 available. A zero return value indicates a shell is not available.
30622 For non-zero @var{len}, the value returned is -1 on error and the
30623 return status of the command otherwise. Only the exit status of the
30624 command is returned, which is extracted from the host's @code{system}
30625 return value by calling @code{WEXITSTATUS(retval)}. In case
30626 @file{/bin/sh} could not be executed, 127 is returned.
30632 The call was interrupted by the user.
30637 @value{GDBN} takes over the full task of calling the necessary host calls
30638 to perform the @code{system} call. The return value of @code{system} on
30639 the host is simplified before it's returned
30640 to the target. Any termination signal information from the child process
30641 is discarded, and the return value consists
30642 entirely of the exit status of the called command.
30644 Due to security concerns, the @code{system} call is by default refused
30645 by @value{GDBN}. The user has to allow this call explicitly with the
30646 @code{set remote system-call-allowed 1} command.
30649 @item set remote system-call-allowed
30650 @kindex set remote system-call-allowed
30651 Control whether to allow the @code{system} calls in the File I/O
30652 protocol for the remote target. The default is zero (disabled).
30654 @item show remote system-call-allowed
30655 @kindex show remote system-call-allowed
30656 Show whether the @code{system} calls are allowed in the File I/O
30660 @node Protocol-specific Representation of Datatypes
30661 @subsection Protocol-specific Representation of Datatypes
30662 @cindex protocol-specific representation of datatypes, in file-i/o protocol
30665 * Integral Datatypes::
30667 * Memory Transfer::
30672 @node Integral Datatypes
30673 @unnumberedsubsubsec Integral Datatypes
30674 @cindex integral datatypes, in file-i/o protocol
30676 The integral datatypes used in the system calls are @code{int},
30677 @code{unsigned int}, @code{long}, @code{unsigned long},
30678 @code{mode_t}, and @code{time_t}.
30680 @code{int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
30681 implemented as 32 bit values in this protocol.
30683 @code{long} and @code{unsigned long} are implemented as 64 bit types.
30685 @xref{Limits}, for corresponding MIN and MAX values (similar to those
30686 in @file{limits.h}) to allow range checking on host and target.
30688 @code{time_t} datatypes are defined as seconds since the Epoch.
30690 All integral datatypes transferred as part of a memory read or write of a
30691 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
30694 @node Pointer Values
30695 @unnumberedsubsubsec Pointer Values
30696 @cindex pointer values, in file-i/o protocol
30698 Pointers to target data are transmitted as they are. An exception
30699 is made for pointers to buffers for which the length isn't
30700 transmitted as part of the function call, namely strings. Strings
30701 are transmitted as a pointer/length pair, both as hex values, e.g.@:
30708 which is a pointer to data of length 18 bytes at position 0x1aaf.
30709 The length is defined as the full string length in bytes, including
30710 the trailing null byte. For example, the string @code{"hello world"}
30711 at address 0x123456 is transmitted as
30717 @node Memory Transfer
30718 @unnumberedsubsubsec Memory Transfer
30719 @cindex memory transfer, in file-i/o protocol
30721 Structured data which is transferred using a memory read or write (for
30722 example, a @code{struct stat}) is expected to be in a protocol-specific format
30723 with all scalar multibyte datatypes being big endian. Translation to
30724 this representation needs to be done both by the target before the @code{F}
30725 packet is sent, and by @value{GDBN} before
30726 it transfers memory to the target. Transferred pointers to structured
30727 data should point to the already-coerced data at any time.
30731 @unnumberedsubsubsec struct stat
30732 @cindex struct stat, in file-i/o protocol
30734 The buffer of type @code{struct stat} used by the target and @value{GDBN}
30735 is defined as follows:
30739 unsigned int st_dev; /* device */
30740 unsigned int st_ino; /* inode */
30741 mode_t st_mode; /* protection */
30742 unsigned int st_nlink; /* number of hard links */
30743 unsigned int st_uid; /* user ID of owner */
30744 unsigned int st_gid; /* group ID of owner */
30745 unsigned int st_rdev; /* device type (if inode device) */
30746 unsigned long st_size; /* total size, in bytes */
30747 unsigned long st_blksize; /* blocksize for filesystem I/O */
30748 unsigned long st_blocks; /* number of blocks allocated */
30749 time_t st_atime; /* time of last access */
30750 time_t st_mtime; /* time of last modification */
30751 time_t st_ctime; /* time of last change */
30755 The integral datatypes conform to the definitions given in the
30756 appropriate section (see @ref{Integral Datatypes}, for details) so this
30757 structure is of size 64 bytes.
30759 The values of several fields have a restricted meaning and/or
30765 A value of 0 represents a file, 1 the console.
30768 No valid meaning for the target. Transmitted unchanged.
30771 Valid mode bits are described in @ref{Constants}. Any other
30772 bits have currently no meaning for the target.
30777 No valid meaning for the target. Transmitted unchanged.
30782 These values have a host and file system dependent
30783 accuracy. Especially on Windows hosts, the file system may not
30784 support exact timing values.
30787 The target gets a @code{struct stat} of the above representation and is
30788 responsible for coercing it to the target representation before
30791 Note that due to size differences between the host, target, and protocol
30792 representations of @code{struct stat} members, these members could eventually
30793 get truncated on the target.
30795 @node struct timeval
30796 @unnumberedsubsubsec struct timeval
30797 @cindex struct timeval, in file-i/o protocol
30799 The buffer of type @code{struct timeval} used by the File-I/O protocol
30800 is defined as follows:
30804 time_t tv_sec; /* second */
30805 long tv_usec; /* microsecond */
30809 The integral datatypes conform to the definitions given in the
30810 appropriate section (see @ref{Integral Datatypes}, for details) so this
30811 structure is of size 8 bytes.
30814 @subsection Constants
30815 @cindex constants, in file-i/o protocol
30817 The following values are used for the constants inside of the
30818 protocol. @value{GDBN} and target are responsible for translating these
30819 values before and after the call as needed.
30830 @unnumberedsubsubsec Open Flags
30831 @cindex open flags, in file-i/o protocol
30833 All values are given in hexadecimal representation.
30845 @node mode_t Values
30846 @unnumberedsubsubsec mode_t Values
30847 @cindex mode_t values, in file-i/o protocol
30849 All values are given in octal representation.
30866 @unnumberedsubsubsec Errno Values
30867 @cindex errno values, in file-i/o protocol
30869 All values are given in decimal representation.
30894 @code{EUNKNOWN} is used as a fallback error value if a host system returns
30895 any error value not in the list of supported error numbers.
30898 @unnumberedsubsubsec Lseek Flags
30899 @cindex lseek flags, in file-i/o protocol
30908 @unnumberedsubsubsec Limits
30909 @cindex limits, in file-i/o protocol
30911 All values are given in decimal representation.
30914 INT_MIN -2147483648
30916 UINT_MAX 4294967295
30917 LONG_MIN -9223372036854775808
30918 LONG_MAX 9223372036854775807
30919 ULONG_MAX 18446744073709551615
30922 @node File-I/O Examples
30923 @subsection File-I/O Examples
30924 @cindex file-i/o examples
30926 Example sequence of a write call, file descriptor 3, buffer is at target
30927 address 0x1234, 6 bytes should be written:
30930 <- @code{Fwrite,3,1234,6}
30931 @emph{request memory read from target}
30934 @emph{return "6 bytes written"}
30938 Example sequence of a read call, file descriptor 3, buffer is at target
30939 address 0x1234, 6 bytes should be read:
30942 <- @code{Fread,3,1234,6}
30943 @emph{request memory write to target}
30944 -> @code{X1234,6:XXXXXX}
30945 @emph{return "6 bytes read"}
30949 Example sequence of a read call, call fails on the host due to invalid
30950 file descriptor (@code{EBADF}):
30953 <- @code{Fread,3,1234,6}
30957 Example sequence of a read call, user presses @kbd{Ctrl-c} before syscall on
30961 <- @code{Fread,3,1234,6}
30966 Example sequence of a read call, user presses @kbd{Ctrl-c} after syscall on
30970 <- @code{Fread,3,1234,6}
30971 -> @code{X1234,6:XXXXXX}
30975 @node Library List Format
30976 @section Library List Format
30977 @cindex library list format, remote protocol
30979 On some platforms, a dynamic loader (e.g.@: @file{ld.so}) runs in the
30980 same process as your application to manage libraries. In this case,
30981 @value{GDBN} can use the loader's symbol table and normal memory
30982 operations to maintain a list of shared libraries. On other
30983 platforms, the operating system manages loaded libraries.
30984 @value{GDBN} can not retrieve the list of currently loaded libraries
30985 through memory operations, so it uses the @samp{qXfer:libraries:read}
30986 packet (@pxref{qXfer library list read}) instead. The remote stub
30987 queries the target's operating system and reports which libraries
30990 The @samp{qXfer:libraries:read} packet returns an XML document which
30991 lists loaded libraries and their offsets. Each library has an
30992 associated name and one or more segment or section base addresses,
30993 which report where the library was loaded in memory.
30995 For the common case of libraries that are fully linked binaries, the
30996 library should have a list of segments. If the target supports
30997 dynamic linking of a relocatable object file, its library XML element
30998 should instead include a list of allocated sections. The segment or
30999 section bases are start addresses, not relocation offsets; they do not
31000 depend on the library's link-time base addresses.
31002 @value{GDBN} must be linked with the Expat library to support XML
31003 library lists. @xref{Expat}.
31005 A simple memory map, with one loaded library relocated by a single
31006 offset, looks like this:
31010 <library name="/lib/libc.so.6">
31011 <segment address="0x10000000"/>
31016 Another simple memory map, with one loaded library with three
31017 allocated sections (.text, .data, .bss), looks like this:
31021 <library name="sharedlib.o">
31022 <section address="0x10000000"/>
31023 <section address="0x20000000"/>
31024 <section address="0x30000000"/>
31029 The format of a library list is described by this DTD:
31032 <!-- library-list: Root element with versioning -->
31033 <!ELEMENT library-list (library)*>
31034 <!ATTLIST library-list version CDATA #FIXED "1.0">
31035 <!ELEMENT library (segment*, section*)>
31036 <!ATTLIST library name CDATA #REQUIRED>
31037 <!ELEMENT segment EMPTY>
31038 <!ATTLIST segment address CDATA #REQUIRED>
31039 <!ELEMENT section EMPTY>
31040 <!ATTLIST section address CDATA #REQUIRED>
31043 In addition, segments and section descriptors cannot be mixed within a
31044 single library element, and you must supply at least one segment or
31045 section for each library.
31047 @node Memory Map Format
31048 @section Memory Map Format
31049 @cindex memory map format
31051 To be able to write into flash memory, @value{GDBN} needs to obtain a
31052 memory map from the target. This section describes the format of the
31055 The memory map is obtained using the @samp{qXfer:memory-map:read}
31056 (@pxref{qXfer memory map read}) packet and is an XML document that
31057 lists memory regions.
31059 @value{GDBN} must be linked with the Expat library to support XML
31060 memory maps. @xref{Expat}.
31062 The top-level structure of the document is shown below:
31065 <?xml version="1.0"?>
31066 <!DOCTYPE memory-map
31067 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
31068 "http://sourceware.org/gdb/gdb-memory-map.dtd">
31074 Each region can be either:
31079 A region of RAM starting at @var{addr} and extending for @var{length}
31083 <memory type="ram" start="@var{addr}" length="@var{length}"/>
31088 A region of read-only memory:
31091 <memory type="rom" start="@var{addr}" length="@var{length}"/>
31096 A region of flash memory, with erasure blocks @var{blocksize}
31100 <memory type="flash" start="@var{addr}" length="@var{length}">
31101 <property name="blocksize">@var{blocksize}</property>
31107 Regions must not overlap. @value{GDBN} assumes that areas of memory not covered
31108 by the memory map are RAM, and uses the ordinary @samp{M} and @samp{X}
31109 packets to write to addresses in such ranges.
31111 The formal DTD for memory map format is given below:
31114 <!-- ................................................... -->
31115 <!-- Memory Map XML DTD ................................ -->
31116 <!-- File: memory-map.dtd .............................. -->
31117 <!-- .................................... .............. -->
31118 <!-- memory-map.dtd -->
31119 <!-- memory-map: Root element with versioning -->
31120 <!ELEMENT memory-map (memory | property)>
31121 <!ATTLIST memory-map version CDATA #FIXED "1.0.0">
31122 <!ELEMENT memory (property)>
31123 <!-- memory: Specifies a memory region,
31124 and its type, or device. -->
31125 <!ATTLIST memory type CDATA #REQUIRED
31126 start CDATA #REQUIRED
31127 length CDATA #REQUIRED
31128 device CDATA #IMPLIED>
31129 <!-- property: Generic attribute tag -->
31130 <!ELEMENT property (#PCDATA | property)*>
31131 <!ATTLIST property name CDATA #REQUIRED>
31134 @include agentexpr.texi
31136 @node Target Descriptions
31137 @appendix Target Descriptions
31138 @cindex target descriptions
31140 @strong{Warning:} target descriptions are still under active development,
31141 and the contents and format may change between @value{GDBN} releases.
31142 The format is expected to stabilize in the future.
31144 One of the challenges of using @value{GDBN} to debug embedded systems
31145 is that there are so many minor variants of each processor
31146 architecture in use. It is common practice for vendors to start with
31147 a standard processor core --- ARM, PowerPC, or MIPS, for example ---
31148 and then make changes to adapt it to a particular market niche. Some
31149 architectures have hundreds of variants, available from dozens of
31150 vendors. This leads to a number of problems:
31154 With so many different customized processors, it is difficult for
31155 the @value{GDBN} maintainers to keep up with the changes.
31157 Since individual variants may have short lifetimes or limited
31158 audiences, it may not be worthwhile to carry information about every
31159 variant in the @value{GDBN} source tree.
31161 When @value{GDBN} does support the architecture of the embedded system
31162 at hand, the task of finding the correct architecture name to give the
31163 @command{set architecture} command can be error-prone.
31166 To address these problems, the @value{GDBN} remote protocol allows a
31167 target system to not only identify itself to @value{GDBN}, but to
31168 actually describe its own features. This lets @value{GDBN} support
31169 processor variants it has never seen before --- to the extent that the
31170 descriptions are accurate, and that @value{GDBN} understands them.
31172 @value{GDBN} must be linked with the Expat library to support XML
31173 target descriptions. @xref{Expat}.
31176 * Retrieving Descriptions:: How descriptions are fetched from a target.
31177 * Target Description Format:: The contents of a target description.
31178 * Predefined Target Types:: Standard types available for target
31180 * Standard Target Features:: Features @value{GDBN} knows about.
31183 @node Retrieving Descriptions
31184 @section Retrieving Descriptions
31186 Target descriptions can be read from the target automatically, or
31187 specified by the user manually. The default behavior is to read the
31188 description from the target. @value{GDBN} retrieves it via the remote
31189 protocol using @samp{qXfer} requests (@pxref{General Query Packets,
31190 qXfer}). The @var{annex} in the @samp{qXfer} packet will be
31191 @samp{target.xml}. The contents of the @samp{target.xml} annex are an
31192 XML document, of the form described in @ref{Target Description
31195 Alternatively, you can specify a file to read for the target description.
31196 If a file is set, the target will not be queried. The commands to
31197 specify a file are:
31200 @cindex set tdesc filename
31201 @item set tdesc filename @var{path}
31202 Read the target description from @var{path}.
31204 @cindex unset tdesc filename
31205 @item unset tdesc filename
31206 Do not read the XML target description from a file. @value{GDBN}
31207 will use the description supplied by the current target.
31209 @cindex show tdesc filename
31210 @item show tdesc filename
31211 Show the filename to read for a target description, if any.
31215 @node Target Description Format
31216 @section Target Description Format
31217 @cindex target descriptions, XML format
31219 A target description annex is an @uref{http://www.w3.org/XML/, XML}
31220 document which complies with the Document Type Definition provided in
31221 the @value{GDBN} sources in @file{gdb/features/gdb-target.dtd}. This
31222 means you can use generally available tools like @command{xmllint} to
31223 check that your feature descriptions are well-formed and valid.
31224 However, to help people unfamiliar with XML write descriptions for
31225 their targets, we also describe the grammar here.
31227 Target descriptions can identify the architecture of the remote target
31228 and (for some architectures) provide information about custom register
31229 sets. They can also identify the OS ABI of the remote target.
31230 @value{GDBN} can use this information to autoconfigure for your
31231 target, or to warn you if you connect to an unsupported target.
31233 Here is a simple target description:
31236 <target version="1.0">
31237 <architecture>i386:x86-64</architecture>
31242 This minimal description only says that the target uses
31243 the x86-64 architecture.
31245 A target description has the following overall form, with [ ] marking
31246 optional elements and @dots{} marking repeatable elements. The elements
31247 are explained further below.
31250 <?xml version="1.0"?>
31251 <!DOCTYPE target SYSTEM "gdb-target.dtd">
31252 <target version="1.0">
31253 @r{[}@var{architecture}@r{]}
31254 @r{[}@var{osabi}@r{]}
31255 @r{[}@var{compatible}@r{]}
31256 @r{[}@var{feature}@dots{}@r{]}
31261 The description is generally insensitive to whitespace and line
31262 breaks, under the usual common-sense rules. The XML version
31263 declaration and document type declaration can generally be omitted
31264 (@value{GDBN} does not require them), but specifying them may be
31265 useful for XML validation tools. The @samp{version} attribute for
31266 @samp{<target>} may also be omitted, but we recommend
31267 including it; if future versions of @value{GDBN} use an incompatible
31268 revision of @file{gdb-target.dtd}, they will detect and report
31269 the version mismatch.
31271 @subsection Inclusion
31272 @cindex target descriptions, inclusion
31275 @cindex <xi:include>
31278 It can sometimes be valuable to split a target description up into
31279 several different annexes, either for organizational purposes, or to
31280 share files between different possible target descriptions. You can
31281 divide a description into multiple files by replacing any element of
31282 the target description with an inclusion directive of the form:
31285 <xi:include href="@var{document}"/>
31289 When @value{GDBN} encounters an element of this form, it will retrieve
31290 the named XML @var{document}, and replace the inclusion directive with
31291 the contents of that document. If the current description was read
31292 using @samp{qXfer}, then so will be the included document;
31293 @var{document} will be interpreted as the name of an annex. If the
31294 current description was read from a file, @value{GDBN} will look for
31295 @var{document} as a file in the same directory where it found the
31296 original description.
31298 @subsection Architecture
31299 @cindex <architecture>
31301 An @samp{<architecture>} element has this form:
31304 <architecture>@var{arch}</architecture>
31307 @var{arch} is one of the architectures from the set accepted by
31308 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
31311 @cindex @code{<osabi>}
31313 This optional field was introduced in @value{GDBN} version 7.0.
31314 Previous versions of @value{GDBN} ignore it.
31316 An @samp{<osabi>} element has this form:
31319 <osabi>@var{abi-name}</osabi>
31322 @var{abi-name} is an OS ABI name from the same selection accepted by
31323 @w{@code{set osabi}} (@pxref{ABI, ,Configuring the Current ABI}).
31325 @subsection Compatible Architecture
31326 @cindex @code{<compatible>}
31328 This optional field was introduced in @value{GDBN} version 7.0.
31329 Previous versions of @value{GDBN} ignore it.
31331 A @samp{<compatible>} element has this form:
31334 <compatible>@var{arch}</compatible>
31337 @var{arch} is one of the architectures from the set accepted by
31338 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
31340 A @samp{<compatible>} element is used to specify that the target
31341 is able to run binaries in some other than the main target architecture
31342 given by the @samp{<architecture>} element. For example, on the
31343 Cell Broadband Engine, the main architecture is @code{powerpc:common}
31344 or @code{powerpc:common64}, but the system is able to run binaries
31345 in the @code{spu} architecture as well. The way to describe this
31346 capability with @samp{<compatible>} is as follows:
31349 <architecture>powerpc:common</architecture>
31350 <compatible>spu</compatible>
31353 @subsection Features
31356 Each @samp{<feature>} describes some logical portion of the target
31357 system. Features are currently used to describe available CPU
31358 registers and the types of their contents. A @samp{<feature>} element
31362 <feature name="@var{name}">
31363 @r{[}@var{type}@dots{}@r{]}
31369 Each feature's name should be unique within the description. The name
31370 of a feature does not matter unless @value{GDBN} has some special
31371 knowledge of the contents of that feature; if it does, the feature
31372 should have its standard name. @xref{Standard Target Features}.
31376 Any register's value is a collection of bits which @value{GDBN} must
31377 interpret. The default interpretation is a two's complement integer,
31378 but other types can be requested by name in the register description.
31379 Some predefined types are provided by @value{GDBN} (@pxref{Predefined
31380 Target Types}), and the description can define additional composite types.
31382 Each type element must have an @samp{id} attribute, which gives
31383 a unique (within the containing @samp{<feature>}) name to the type.
31384 Types must be defined before they are used.
31387 Some targets offer vector registers, which can be treated as arrays
31388 of scalar elements. These types are written as @samp{<vector>} elements,
31389 specifying the array element type, @var{type}, and the number of elements,
31393 <vector id="@var{id}" type="@var{type}" count="@var{count}"/>
31397 If a register's value is usefully viewed in multiple ways, define it
31398 with a union type containing the useful representations. The
31399 @samp{<union>} element contains one or more @samp{<field>} elements,
31400 each of which has a @var{name} and a @var{type}:
31403 <union id="@var{id}">
31404 <field name="@var{name}" type="@var{type}"/>
31409 @subsection Registers
31412 Each register is represented as an element with this form:
31415 <reg name="@var{name}"
31416 bitsize="@var{size}"
31417 @r{[}regnum="@var{num}"@r{]}
31418 @r{[}save-restore="@var{save-restore}"@r{]}
31419 @r{[}type="@var{type}"@r{]}
31420 @r{[}group="@var{group}"@r{]}/>
31424 The components are as follows:
31429 The register's name; it must be unique within the target description.
31432 The register's size, in bits.
31435 The register's number. If omitted, a register's number is one greater
31436 than that of the previous register (either in the current feature or in
31437 a preceeding feature); the first register in the target description
31438 defaults to zero. This register number is used to read or write
31439 the register; e.g.@: it is used in the remote @code{p} and @code{P}
31440 packets, and registers appear in the @code{g} and @code{G} packets
31441 in order of increasing register number.
31444 Whether the register should be preserved across inferior function
31445 calls; this must be either @code{yes} or @code{no}. The default is
31446 @code{yes}, which is appropriate for most registers except for
31447 some system control registers; this is not related to the target's
31451 The type of the register. @var{type} may be a predefined type, a type
31452 defined in the current feature, or one of the special types @code{int}
31453 and @code{float}. @code{int} is an integer type of the correct size
31454 for @var{bitsize}, and @code{float} is a floating point type (in the
31455 architecture's normal floating point format) of the correct size for
31456 @var{bitsize}. The default is @code{int}.
31459 The register group to which this register belongs. @var{group} must
31460 be either @code{general}, @code{float}, or @code{vector}. If no
31461 @var{group} is specified, @value{GDBN} will not display the register
31462 in @code{info registers}.
31466 @node Predefined Target Types
31467 @section Predefined Target Types
31468 @cindex target descriptions, predefined types
31470 Type definitions in the self-description can build up composite types
31471 from basic building blocks, but can not define fundamental types. Instead,
31472 standard identifiers are provided by @value{GDBN} for the fundamental
31473 types. The currently supported types are:
31482 Signed integer types holding the specified number of bits.
31489 Unsigned integer types holding the specified number of bits.
31493 Pointers to unspecified code and data. The program counter and
31494 any dedicated return address register may be marked as code
31495 pointers; printing a code pointer converts it into a symbolic
31496 address. The stack pointer and any dedicated address registers
31497 may be marked as data pointers.
31500 Single precision IEEE floating point.
31503 Double precision IEEE floating point.
31506 The 12-byte extended precision format used by ARM FPA registers.
31510 @node Standard Target Features
31511 @section Standard Target Features
31512 @cindex target descriptions, standard features
31514 A target description must contain either no registers or all the
31515 target's registers. If the description contains no registers, then
31516 @value{GDBN} will assume a default register layout, selected based on
31517 the architecture. If the description contains any registers, the
31518 default layout will not be used; the standard registers must be
31519 described in the target description, in such a way that @value{GDBN}
31520 can recognize them.
31522 This is accomplished by giving specific names to feature elements
31523 which contain standard registers. @value{GDBN} will look for features
31524 with those names and verify that they contain the expected registers;
31525 if any known feature is missing required registers, or if any required
31526 feature is missing, @value{GDBN} will reject the target
31527 description. You can add additional registers to any of the
31528 standard features --- @value{GDBN} will display them just as if
31529 they were added to an unrecognized feature.
31531 This section lists the known features and their expected contents.
31532 Sample XML documents for these features are included in the
31533 @value{GDBN} source tree, in the directory @file{gdb/features}.
31535 Names recognized by @value{GDBN} should include the name of the
31536 company or organization which selected the name, and the overall
31537 architecture to which the feature applies; so e.g.@: the feature
31538 containing ARM core registers is named @samp{org.gnu.gdb.arm.core}.
31540 The names of registers are not case sensitive for the purpose
31541 of recognizing standard features, but @value{GDBN} will only display
31542 registers using the capitalization used in the description.
31548 * PowerPC Features::
31553 @subsection ARM Features
31554 @cindex target descriptions, ARM features
31556 The @samp{org.gnu.gdb.arm.core} feature is required for ARM targets.
31557 It should contain registers @samp{r0} through @samp{r13}, @samp{sp},
31558 @samp{lr}, @samp{pc}, and @samp{cpsr}.
31560 The @samp{org.gnu.gdb.arm.fpa} feature is optional. If present, it
31561 should contain registers @samp{f0} through @samp{f7} and @samp{fps}.
31563 The @samp{org.gnu.gdb.xscale.iwmmxt} feature is optional. If present,
31564 it should contain at least registers @samp{wR0} through @samp{wR15} and
31565 @samp{wCGR0} through @samp{wCGR3}. The @samp{wCID}, @samp{wCon},
31566 @samp{wCSSF}, and @samp{wCASF} registers are optional.
31568 The @samp{org.gnu.gdb.arm.vfp} feature is optional. If present, it
31569 should contain at least registers @samp{d0} through @samp{d15}. If
31570 they are present, @samp{d16} through @samp{d31} should also be included.
31571 @value{GDBN} will synthesize the single-precision registers from
31572 halves of the double-precision registers.
31574 The @samp{org.gnu.gdb.arm.neon} feature is optional. It does not
31575 need to contain registers; it instructs @value{GDBN} to display the
31576 VFP double-precision registers as vectors and to synthesize the
31577 quad-precision registers from pairs of double-precision registers.
31578 If this feature is present, @samp{org.gnu.gdb.arm.vfp} must also
31579 be present and include 32 double-precision registers.
31581 @node MIPS Features
31582 @subsection MIPS Features
31583 @cindex target descriptions, MIPS features
31585 The @samp{org.gnu.gdb.mips.cpu} feature is required for MIPS targets.
31586 It should contain registers @samp{r0} through @samp{r31}, @samp{lo},
31587 @samp{hi}, and @samp{pc}. They may be 32-bit or 64-bit depending
31590 The @samp{org.gnu.gdb.mips.cp0} feature is also required. It should
31591 contain at least the @samp{status}, @samp{badvaddr}, and @samp{cause}
31592 registers. They may be 32-bit or 64-bit depending on the target.
31594 The @samp{org.gnu.gdb.mips.fpu} feature is currently required, though
31595 it may be optional in a future version of @value{GDBN}. It should
31596 contain registers @samp{f0} through @samp{f31}, @samp{fcsr}, and
31597 @samp{fir}. They may be 32-bit or 64-bit depending on the target.
31599 The @samp{org.gnu.gdb.mips.linux} feature is optional. It should
31600 contain a single register, @samp{restart}, which is used by the
31601 Linux kernel to control restartable syscalls.
31603 @node M68K Features
31604 @subsection M68K Features
31605 @cindex target descriptions, M68K features
31608 @item @samp{org.gnu.gdb.m68k.core}
31609 @itemx @samp{org.gnu.gdb.coldfire.core}
31610 @itemx @samp{org.gnu.gdb.fido.core}
31611 One of those features must be always present.
31612 The feature that is present determines which flavor of m68k is
31613 used. The feature that is present should contain registers
31614 @samp{d0} through @samp{d7}, @samp{a0} through @samp{a5}, @samp{fp},
31615 @samp{sp}, @samp{ps} and @samp{pc}.
31617 @item @samp{org.gnu.gdb.coldfire.fp}
31618 This feature is optional. If present, it should contain registers
31619 @samp{fp0} through @samp{fp7}, @samp{fpcontrol}, @samp{fpstatus} and
31623 @node PowerPC Features
31624 @subsection PowerPC Features
31625 @cindex target descriptions, PowerPC features
31627 The @samp{org.gnu.gdb.power.core} feature is required for PowerPC
31628 targets. It should contain registers @samp{r0} through @samp{r31},
31629 @samp{pc}, @samp{msr}, @samp{cr}, @samp{lr}, @samp{ctr}, and
31630 @samp{xer}. They may be 32-bit or 64-bit depending on the target.
31632 The @samp{org.gnu.gdb.power.fpu} feature is optional. It should
31633 contain registers @samp{f0} through @samp{f31} and @samp{fpscr}.
31635 The @samp{org.gnu.gdb.power.altivec} feature is optional. It should
31636 contain registers @samp{vr0} through @samp{vr31}, @samp{vscr},
31639 The @samp{org.gnu.gdb.power.vsx} feature is optional. It should
31640 contain registers @samp{vs0h} through @samp{vs31h}. @value{GDBN}
31641 will combine these registers with the floating point registers
31642 (@samp{f0} through @samp{f31}) and the altivec registers (@samp{vr0}
31643 through @samp{vr31}) to present the 128-bit wide registers @samp{vs0}
31644 through @samp{vs63}, the set of vector registers for POWER7.
31646 The @samp{org.gnu.gdb.power.spe} feature is optional. It should
31647 contain registers @samp{ev0h} through @samp{ev31h}, @samp{acc}, and
31648 @samp{spefscr}. SPE targets should provide 32-bit registers in
31649 @samp{org.gnu.gdb.power.core} and provide the upper halves in
31650 @samp{ev0h} through @samp{ev31h}. @value{GDBN} will combine
31651 these to present registers @samp{ev0} through @samp{ev31} to the
31654 @node Operating System Information
31655 @appendix Operating System Information
31656 @cindex operating system information
31662 Users of @value{GDBN} often wish to obtain information about the state of
31663 the operating system running on the target---for example the list of
31664 processes, or the list of open files. This section describes the
31665 mechanism that makes it possible. This mechanism is similar to the
31666 target features mechanism (@pxref{Target Descriptions}), but focuses
31667 on a different aspect of target.
31669 Operating system information is retrived from the target via the
31670 remote protocol, using @samp{qXfer} requests (@pxref{qXfer osdata
31671 read}). The object name in the request should be @samp{osdata}, and
31672 the @var{annex} identifies the data to be fetched.
31675 @appendixsection Process list
31676 @cindex operating system information, process list
31678 When requesting the process list, the @var{annex} field in the
31679 @samp{qXfer} request should be @samp{processes}. The returned data is
31680 an XML document. The formal syntax of this document is defined in
31681 @file{gdb/features/osdata.dtd}.
31683 An example document is:
31686 <?xml version="1.0"?>
31687 <!DOCTYPE target SYSTEM "osdata.dtd">
31688 <osdata type="processes">
31690 <column name="pid">1</column>
31691 <column name="user">root</column>
31692 <column name="command">/sbin/init</column>
31697 Each item should include a column whose name is @samp{pid}. The value
31698 of that column should identify the process on the target. The
31699 @samp{user} and @samp{command} columns are optional, and will be
31700 displayed by @value{GDBN}. Target may provide additional columns,
31701 which @value{GDBN} currently ignores.
31715 % I think something like @colophon should be in texinfo. In the
31717 \long\def\colophon{\hbox to0pt{}\vfill
31718 \centerline{The body of this manual is set in}
31719 \centerline{\fontname\tenrm,}
31720 \centerline{with headings in {\bf\fontname\tenbf}}
31721 \centerline{and examples in {\tt\fontname\tentt}.}
31722 \centerline{{\it\fontname\tenit\/},}
31723 \centerline{{\bf\fontname\tenbf}, and}
31724 \centerline{{\sl\fontname\tensl\/}}
31725 \centerline{are used for emphasis.}\vfill}
31727 % Blame: doc@cygnus.com, 1991.