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, 2010
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, 2010
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) 1988-2010 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 * Trace File Format:: GDB trace file format
178 * Copying:: GNU General Public License says
179 how you can copy and share GDB
180 * GNU Free Documentation License:: The license for this documentation
189 @unnumbered Summary of @value{GDBN}
191 The purpose of a debugger such as @value{GDBN} is to allow you to see what is
192 going on ``inside'' another program while it executes---or what another
193 program was doing at the moment it crashed.
195 @value{GDBN} can do four main kinds of things (plus other things in support of
196 these) to help you catch bugs in the act:
200 Start your program, specifying anything that might affect its behavior.
203 Make your program stop on specified conditions.
206 Examine what has happened, when your program has stopped.
209 Change things in your program, so you can experiment with correcting the
210 effects of one bug and go on to learn about another.
213 You can use @value{GDBN} to debug programs written in C and C@t{++}.
214 For more information, see @ref{Supported Languages,,Supported Languages}.
215 For more information, see @ref{C,,C and C++}.
217 Support for D is partial. For information on D, see
221 Support for Modula-2 is partial. For information on Modula-2, see
222 @ref{Modula-2,,Modula-2}.
225 Debugging Pascal programs which use sets, subranges, file variables, or
226 nested functions does not currently work. @value{GDBN} does not support
227 entering expressions, printing values, or similar features using Pascal
231 @value{GDBN} can be used to debug programs written in Fortran, although
232 it may be necessary to refer to some variables with a trailing
235 @value{GDBN} can be used to debug programs written in Objective-C,
236 using either the Apple/NeXT or the GNU Objective-C runtime.
239 * Free Software:: Freely redistributable software
240 * Contributors:: Contributors to GDB
244 @unnumberedsec Free Software
246 @value{GDBN} is @dfn{free software}, protected by the @sc{gnu}
247 General Public License
248 (GPL). The GPL gives you the freedom to copy or adapt a licensed
249 program---but every person getting a copy also gets with it the
250 freedom to modify that copy (which means that they must get access to
251 the source code), and the freedom to distribute further copies.
252 Typical software companies use copyrights to limit your freedoms; the
253 Free Software Foundation uses the GPL to preserve these freedoms.
255 Fundamentally, the General Public License is a license which says that
256 you have these freedoms and that you cannot take these freedoms away
259 @unnumberedsec Free Software Needs Free Documentation
261 The biggest deficiency in the free software community today is not in
262 the software---it is the lack of good free documentation that we can
263 include with the free software. Many of our most important
264 programs do not come with free reference manuals and free introductory
265 texts. Documentation is an essential part of any software package;
266 when an important free software package does not come with a free
267 manual and a free tutorial, that is a major gap. We have many such
270 Consider Perl, for instance. The tutorial manuals that people
271 normally use are non-free. How did this come about? Because the
272 authors of those manuals published them with restrictive terms---no
273 copying, no modification, source files not available---which exclude
274 them from the free software world.
276 That wasn't the first time this sort of thing happened, and it was far
277 from the last. Many times we have heard a GNU user eagerly describe a
278 manual that he is writing, his intended contribution to the community,
279 only to learn that he had ruined everything by signing a publication
280 contract to make it non-free.
282 Free documentation, like free software, is a matter of freedom, not
283 price. The problem with the non-free manual is not that publishers
284 charge a price for printed copies---that in itself is fine. (The Free
285 Software Foundation sells printed copies of manuals, too.) The
286 problem is the restrictions on the use of the manual. Free manuals
287 are available in source code form, and give you permission to copy and
288 modify. Non-free manuals do not allow this.
290 The criteria of freedom for a free manual are roughly the same as for
291 free software. Redistribution (including the normal kinds of
292 commercial redistribution) must be permitted, so that the manual can
293 accompany every copy of the program, both on-line and on paper.
295 Permission for modification of the technical content is crucial too.
296 When people modify the software, adding or changing features, if they
297 are conscientious they will change the manual too---so they can
298 provide accurate and clear documentation for the modified program. A
299 manual that leaves you no choice but to write a new manual to document
300 a changed version of the program is not really available to our
303 Some kinds of limits on the way modification is handled are
304 acceptable. For example, requirements to preserve the original
305 author's copyright notice, the distribution terms, or the list of
306 authors, are ok. It is also no problem to require modified versions
307 to include notice that they were modified. Even entire sections that
308 may not be deleted or changed are acceptable, as long as they deal
309 with nontechnical topics (like this one). These kinds of restrictions
310 are acceptable because they don't obstruct the community's normal use
313 However, it must be possible to modify all the @emph{technical}
314 content of the manual, and then distribute the result in all the usual
315 media, through all the usual channels. Otherwise, the restrictions
316 obstruct the use of the manual, it is not free, and we need another
317 manual to replace it.
319 Please spread the word about this issue. Our community continues to
320 lose manuals to proprietary publishing. If we spread the word that
321 free software needs free reference manuals and free tutorials, perhaps
322 the next person who wants to contribute by writing documentation will
323 realize, before it is too late, that only free manuals contribute to
324 the free software community.
326 If you are writing documentation, please insist on publishing it under
327 the GNU Free Documentation License or another free documentation
328 license. Remember that this decision requires your approval---you
329 don't have to let the publisher decide. Some commercial publishers
330 will use a free license if you insist, but they will not propose the
331 option; it is up to you to raise the issue and say firmly that this is
332 what you want. If the publisher you are dealing with refuses, please
333 try other publishers. If you're not sure whether a proposed license
334 is free, write to @email{licensing@@gnu.org}.
336 You can encourage commercial publishers to sell more free, copylefted
337 manuals and tutorials by buying them, and particularly by buying
338 copies from the publishers that paid for their writing or for major
339 improvements. Meanwhile, try to avoid buying non-free documentation
340 at all. Check the distribution terms of a manual before you buy it,
341 and insist that whoever seeks your business must respect your freedom.
342 Check the history of the book, and try to reward the publishers that
343 have paid or pay the authors to work on it.
345 The Free Software Foundation maintains a list of free documentation
346 published by other publishers, at
347 @url{http://www.fsf.org/doc/other-free-books.html}.
350 @unnumberedsec Contributors to @value{GDBN}
352 Richard Stallman was the original author of @value{GDBN}, and of many
353 other @sc{gnu} programs. Many others have contributed to its
354 development. This section attempts to credit major contributors. One
355 of the virtues of free software is that everyone is free to contribute
356 to it; with regret, we cannot actually acknowledge everyone here. The
357 file @file{ChangeLog} in the @value{GDBN} distribution approximates a
358 blow-by-blow account.
360 Changes much prior to version 2.0 are lost in the mists of time.
363 @emph{Plea:} Additions to this section are particularly welcome. If you
364 or your friends (or enemies, to be evenhanded) have been unfairly
365 omitted from this list, we would like to add your names!
368 So that they may not regard their many labors as thankless, we
369 particularly thank those who shepherded @value{GDBN} through major
371 Andrew Cagney (releases 6.3, 6.2, 6.1, 6.0, 5.3, 5.2, 5.1 and 5.0);
372 Jim Blandy (release 4.18);
373 Jason Molenda (release 4.17);
374 Stan Shebs (release 4.14);
375 Fred Fish (releases 4.16, 4.15, 4.13, 4.12, 4.11, 4.10, and 4.9);
376 Stu Grossman and John Gilmore (releases 4.8, 4.7, 4.6, 4.5, and 4.4);
377 John Gilmore (releases 4.3, 4.2, 4.1, 4.0, and 3.9);
378 Jim Kingdon (releases 3.5, 3.4, and 3.3);
379 and Randy Smith (releases 3.2, 3.1, and 3.0).
381 Richard Stallman, assisted at various times by Peter TerMaat, Chris
382 Hanson, and Richard Mlynarik, handled releases through 2.8.
384 Michael Tiemann is the author of most of the @sc{gnu} C@t{++} support
385 in @value{GDBN}, with significant additional contributions from Per
386 Bothner and Daniel Berlin. James Clark wrote the @sc{gnu} C@t{++}
387 demangler. Early work on C@t{++} was by Peter TerMaat (who also did
388 much general update work leading to release 3.0).
390 @value{GDBN} uses the BFD subroutine library to examine multiple
391 object-file formats; BFD was a joint project of David V.
392 Henkel-Wallace, Rich Pixley, Steve Chamberlain, and John Gilmore.
394 David Johnson wrote the original COFF support; Pace Willison did
395 the original support for encapsulated COFF.
397 Brent Benson of Harris Computer Systems contributed DWARF 2 support.
399 Adam de Boor and Bradley Davis contributed the ISI Optimum V support.
400 Per Bothner, Noboyuki Hikichi, and Alessandro Forin contributed MIPS
402 Jean-Daniel Fekete contributed Sun 386i support.
403 Chris Hanson improved the HP9000 support.
404 Noboyuki Hikichi and Tomoyuki Hasei contributed Sony/News OS 3 support.
405 David Johnson contributed Encore Umax support.
406 Jyrki Kuoppala contributed Altos 3068 support.
407 Jeff Law contributed HP PA and SOM support.
408 Keith Packard contributed NS32K support.
409 Doug Rabson contributed Acorn Risc Machine support.
410 Bob Rusk contributed Harris Nighthawk CX-UX support.
411 Chris Smith contributed Convex support (and Fortran debugging).
412 Jonathan Stone contributed Pyramid support.
413 Michael Tiemann contributed SPARC support.
414 Tim Tucker contributed support for the Gould NP1 and Gould Powernode.
415 Pace Willison contributed Intel 386 support.
416 Jay Vosburgh contributed Symmetry support.
417 Marko Mlinar contributed OpenRISC 1000 support.
419 Andreas Schwab contributed M68K @sc{gnu}/Linux support.
421 Rich Schaefer and Peter Schauer helped with support of SunOS shared
424 Jay Fenlason and Roland McGrath ensured that @value{GDBN} and GAS agree
425 about several machine instruction sets.
427 Patrick Duval, Ted Goldstein, Vikram Koka and Glenn Engel helped develop
428 remote debugging. Intel Corporation, Wind River Systems, AMD, and ARM
429 contributed remote debugging modules for the i960, VxWorks, A29K UDI,
430 and RDI targets, respectively.
432 Brian Fox is the author of the readline libraries providing
433 command-line editing and command history.
435 Andrew Beers of SUNY Buffalo wrote the language-switching code, the
436 Modula-2 support, and contributed the Languages chapter of this manual.
438 Fred Fish wrote most of the support for Unix System Vr4.
439 He also enhanced the command-completion support to cover C@t{++} overloaded
442 Hitachi America (now Renesas America), Ltd. sponsored the support for
443 H8/300, H8/500, and Super-H processors.
445 NEC sponsored the support for the v850, Vr4xxx, and Vr5xxx processors.
447 Mitsubishi (now Renesas) sponsored the support for D10V, D30V, and M32R/D
450 Toshiba sponsored the support for the TX39 Mips processor.
452 Matsushita sponsored the support for the MN10200 and MN10300 processors.
454 Fujitsu sponsored the support for SPARClite and FR30 processors.
456 Kung Hsu, Jeff Law, and Rick Sladkey added support for hardware
459 Michael Snyder added support for tracepoints.
461 Stu Grossman wrote gdbserver.
463 Jim Kingdon, Peter Schauer, Ian Taylor, and Stu Grossman made
464 nearly innumerable bug fixes and cleanups throughout @value{GDBN}.
466 The following people at the Hewlett-Packard Company contributed
467 support for the PA-RISC 2.0 architecture, HP-UX 10.20, 10.30, and 11.0
468 (narrow mode), HP's implementation of kernel threads, HP's aC@t{++}
469 compiler, and the Text User Interface (nee Terminal User Interface):
470 Ben Krepp, Richard Title, John Bishop, Susan Macchia, Kathy Mann,
471 Satish Pai, India Paul, Steve Rehrauer, and Elena Zannoni. Kim Haase
472 provided HP-specific information in this manual.
474 DJ Delorie ported @value{GDBN} to MS-DOS, for the DJGPP project.
475 Robert Hoehne made significant contributions to the DJGPP port.
477 Cygnus Solutions has sponsored @value{GDBN} maintenance and much of its
478 development since 1991. Cygnus engineers who have worked on @value{GDBN}
479 fulltime include Mark Alexander, Jim Blandy, Per Bothner, Kevin
480 Buettner, Edith Epstein, Chris Faylor, Fred Fish, Martin Hunt, Jim
481 Ingham, John Gilmore, Stu Grossman, Kung Hsu, Jim Kingdon, John Metzler,
482 Fernando Nasser, Geoffrey Noer, Dawn Perchik, Rich Pixley, Zdenek
483 Radouch, Keith Seitz, Stan Shebs, David Taylor, and Elena Zannoni. In
484 addition, Dave Brolley, Ian Carmichael, Steve Chamberlain, Nick Clifton,
485 JT Conklin, Stan Cox, DJ Delorie, Ulrich Drepper, Frank Eigler, Doug
486 Evans, Sean Fagan, David Henkel-Wallace, Richard Henderson, Jeff
487 Holcomb, Jeff Law, Jim Lemke, Tom Lord, Bob Manson, Michael Meissner,
488 Jason Merrill, Catherine Moore, Drew Moseley, Ken Raeburn, Gavin
489 Romig-Koch, Rob Savoye, Jamie Smith, Mike Stump, Ian Taylor, Angela
490 Thomas, Michael Tiemann, Tom Tromey, Ron Unrau, Jim Wilson, and David
491 Zuhn have made contributions both large and small.
493 Andrew Cagney, Fernando Nasser, and Elena Zannoni, while working for
494 Cygnus Solutions, implemented the original @sc{gdb/mi} interface.
496 Jim Blandy added support for preprocessor macros, while working for Red
499 Andrew Cagney designed @value{GDBN}'s architecture vector. Many
500 people including Andrew Cagney, Stephane Carrez, Randolph Chung, Nick
501 Duffek, Richard Henderson, Mark Kettenis, Grace Sainsbury, Kei
502 Sakamoto, Yoshinori Sato, Michael Snyder, Andreas Schwab, Jason
503 Thorpe, Corinna Vinschen, Ulrich Weigand, and Elena Zannoni, helped
504 with the migration of old architectures to this new framework.
506 Andrew Cagney completely re-designed and re-implemented @value{GDBN}'s
507 unwinder framework, this consisting of a fresh new design featuring
508 frame IDs, independent frame sniffers, and the sentinel frame. Mark
509 Kettenis implemented the @sc{dwarf 2} unwinder, Jeff Johnston the
510 libunwind unwinder, and Andrew Cagney the dummy, sentinel, tramp, and
511 trad unwinders. The architecture-specific changes, each involving a
512 complete rewrite of the architecture's frame code, were carried out by
513 Jim Blandy, Joel Brobecker, Kevin Buettner, Andrew Cagney, Stephane
514 Carrez, Randolph Chung, Orjan Friberg, Richard Henderson, Daniel
515 Jacobowitz, Jeff Johnston, Mark Kettenis, Theodore A. Roth, Kei
516 Sakamoto, Yoshinori Sato, Michael Snyder, Corinna Vinschen, and Ulrich
519 Christian Zankel, Ross Morley, Bob Wilson, and Maxim Grigoriev from
520 Tensilica, Inc.@: contributed support for Xtensa processors. Others
521 who have worked on the Xtensa port of @value{GDBN} in the past include
522 Steve Tjiang, John Newlin, and Scott Foehner.
524 Michael Eager and staff of Xilinx, Inc., contributed support for the
525 Xilinx MicroBlaze architecture.
528 @chapter A Sample @value{GDBN} Session
530 You can use this manual at your leisure to read all about @value{GDBN}.
531 However, a handful of commands are enough to get started using the
532 debugger. This chapter illustrates those commands.
535 In this sample session, we emphasize user input like this: @b{input},
536 to make it easier to pick out from the surrounding output.
539 @c FIXME: this example may not be appropriate for some configs, where
540 @c FIXME...primary interest is in remote use.
542 One of the preliminary versions of @sc{gnu} @code{m4} (a generic macro
543 processor) exhibits the following bug: sometimes, when we change its
544 quote strings from the default, the commands used to capture one macro
545 definition within another stop working. In the following short @code{m4}
546 session, we define a macro @code{foo} which expands to @code{0000}; we
547 then use the @code{m4} built-in @code{defn} to define @code{bar} as the
548 same thing. However, when we change the open quote string to
549 @code{<QUOTE>} and the close quote string to @code{<UNQUOTE>}, the same
550 procedure fails to define a new synonym @code{baz}:
559 @b{define(bar,defn(`foo'))}
563 @b{changequote(<QUOTE>,<UNQUOTE>)}
565 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
568 m4: End of input: 0: fatal error: EOF in string
572 Let us use @value{GDBN} to try to see what is going on.
575 $ @b{@value{GDBP} m4}
576 @c FIXME: this falsifies the exact text played out, to permit smallbook
577 @c FIXME... format to come out better.
578 @value{GDBN} is free software and you are welcome to distribute copies
579 of it under certain conditions; type "show copying" to see
581 There is absolutely no warranty for @value{GDBN}; type "show warranty"
584 @value{GDBN} @value{GDBVN}, Copyright 1999 Free Software Foundation, Inc...
589 @value{GDBN} reads only enough symbol data to know where to find the
590 rest when needed; as a result, the first prompt comes up very quickly.
591 We now tell @value{GDBN} to use a narrower display width than usual, so
592 that examples fit in this manual.
595 (@value{GDBP}) @b{set width 70}
599 We need to see how the @code{m4} built-in @code{changequote} works.
600 Having looked at the source, we know the relevant subroutine is
601 @code{m4_changequote}, so we set a breakpoint there with the @value{GDBN}
602 @code{break} command.
605 (@value{GDBP}) @b{break m4_changequote}
606 Breakpoint 1 at 0x62f4: file builtin.c, line 879.
610 Using the @code{run} command, we start @code{m4} running under @value{GDBN}
611 control; as long as control does not reach the @code{m4_changequote}
612 subroutine, the program runs as usual:
615 (@value{GDBP}) @b{run}
616 Starting program: /work/Editorial/gdb/gnu/m4/m4
624 To trigger the breakpoint, we call @code{changequote}. @value{GDBN}
625 suspends execution of @code{m4}, displaying information about the
626 context where it stops.
629 @b{changequote(<QUOTE>,<UNQUOTE>)}
631 Breakpoint 1, m4_changequote (argc=3, argv=0x33c70)
633 879 if (bad_argc(TOKEN_DATA_TEXT(argv[0]),argc,1,3))
637 Now we use the command @code{n} (@code{next}) to advance execution to
638 the next line of the current function.
642 882 set_quotes((argc >= 2) ? TOKEN_DATA_TEXT(argv[1])\
647 @code{set_quotes} looks like a promising subroutine. We can go into it
648 by using the command @code{s} (@code{step}) instead of @code{next}.
649 @code{step} goes to the next line to be executed in @emph{any}
650 subroutine, so it steps into @code{set_quotes}.
654 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
656 530 if (lquote != def_lquote)
660 The display that shows the subroutine where @code{m4} is now
661 suspended (and its arguments) is called a stack frame display. It
662 shows a summary of the stack. We can use the @code{backtrace}
663 command (which can also be spelled @code{bt}), to see where we are
664 in the stack as a whole: the @code{backtrace} command displays a
665 stack frame for each active subroutine.
668 (@value{GDBP}) @b{bt}
669 #0 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
671 #1 0x6344 in m4_changequote (argc=3, argv=0x33c70)
673 #2 0x8174 in expand_macro (sym=0x33320) at macro.c:242
674 #3 0x7a88 in expand_token (obs=0x0, t=209696, td=0xf7fffa30)
676 #4 0x79dc in expand_input () at macro.c:40
677 #5 0x2930 in main (argc=0, argv=0xf7fffb20) at m4.c:195
681 We step through a few more lines to see what happens. The first two
682 times, we can use @samp{s}; the next two times we use @code{n} to avoid
683 falling into the @code{xstrdup} subroutine.
687 0x3b5c 532 if (rquote != def_rquote)
689 0x3b80 535 lquote = (lq == nil || *lq == '\0') ? \
690 def_lquote : xstrdup(lq);
692 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
695 538 len_lquote = strlen(rquote);
699 The last line displayed looks a little odd; we can examine the variables
700 @code{lquote} and @code{rquote} to see if they are in fact the new left
701 and right quotes we specified. We use the command @code{p}
702 (@code{print}) to see their values.
705 (@value{GDBP}) @b{p lquote}
706 $1 = 0x35d40 "<QUOTE>"
707 (@value{GDBP}) @b{p rquote}
708 $2 = 0x35d50 "<UNQUOTE>"
712 @code{lquote} and @code{rquote} are indeed the new left and right quotes.
713 To look at some context, we can display ten lines of source
714 surrounding the current line with the @code{l} (@code{list}) command.
720 535 lquote = (lq == nil || *lq == '\0') ? def_lquote\
722 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
725 538 len_lquote = strlen(rquote);
726 539 len_rquote = strlen(lquote);
733 Let us step past the two lines that set @code{len_lquote} and
734 @code{len_rquote}, and then examine the values of those variables.
738 539 len_rquote = strlen(lquote);
741 (@value{GDBP}) @b{p len_lquote}
743 (@value{GDBP}) @b{p len_rquote}
748 That certainly looks wrong, assuming @code{len_lquote} and
749 @code{len_rquote} are meant to be the lengths of @code{lquote} and
750 @code{rquote} respectively. We can set them to better values using
751 the @code{p} command, since it can print the value of
752 any expression---and that expression can include subroutine calls and
756 (@value{GDBP}) @b{p len_lquote=strlen(lquote)}
758 (@value{GDBP}) @b{p len_rquote=strlen(rquote)}
763 Is that enough to fix the problem of using the new quotes with the
764 @code{m4} built-in @code{defn}? We can allow @code{m4} to continue
765 executing with the @code{c} (@code{continue}) command, and then try the
766 example that caused trouble initially:
772 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
779 Success! The new quotes now work just as well as the default ones. The
780 problem seems to have been just the two typos defining the wrong
781 lengths. We allow @code{m4} exit by giving it an EOF as input:
785 Program exited normally.
789 The message @samp{Program exited normally.} is from @value{GDBN}; it
790 indicates @code{m4} has finished executing. We can end our @value{GDBN}
791 session with the @value{GDBN} @code{quit} command.
794 (@value{GDBP}) @b{quit}
798 @chapter Getting In and Out of @value{GDBN}
800 This chapter discusses how to start @value{GDBN}, and how to get out of it.
804 type @samp{@value{GDBP}} to start @value{GDBN}.
806 type @kbd{quit} or @kbd{Ctrl-d} to exit.
810 * Invoking GDB:: How to start @value{GDBN}
811 * Quitting GDB:: How to quit @value{GDBN}
812 * Shell Commands:: How to use shell commands inside @value{GDBN}
813 * Logging Output:: How to log @value{GDBN}'s output to a file
817 @section Invoking @value{GDBN}
819 Invoke @value{GDBN} by running the program @code{@value{GDBP}}. Once started,
820 @value{GDBN} reads commands from the terminal until you tell it to exit.
822 You can also run @code{@value{GDBP}} with a variety of arguments and options,
823 to specify more of your debugging environment at the outset.
825 The command-line options described here are designed
826 to cover a variety of situations; in some environments, some of these
827 options may effectively be unavailable.
829 The most usual way to start @value{GDBN} is with one argument,
830 specifying an executable program:
833 @value{GDBP} @var{program}
837 You can also start with both an executable program and a core file
841 @value{GDBP} @var{program} @var{core}
844 You can, instead, specify a process ID as a second argument, if you want
845 to debug a running process:
848 @value{GDBP} @var{program} 1234
852 would attach @value{GDBN} to process @code{1234} (unless you also have a file
853 named @file{1234}; @value{GDBN} does check for a core file first).
855 Taking advantage of the second command-line argument requires a fairly
856 complete operating system; when you use @value{GDBN} as a remote
857 debugger attached to a bare board, there may not be any notion of
858 ``process'', and there is often no way to get a core dump. @value{GDBN}
859 will warn you if it is unable to attach or to read core dumps.
861 You can optionally have @code{@value{GDBP}} pass any arguments after the
862 executable file to the inferior using @code{--args}. This option stops
865 @value{GDBP} --args gcc -O2 -c foo.c
867 This will cause @code{@value{GDBP}} to debug @code{gcc}, and to set
868 @code{gcc}'s command-line arguments (@pxref{Arguments}) to @samp{-O2 -c foo.c}.
870 You can run @code{@value{GDBP}} without printing the front material, which describes
871 @value{GDBN}'s non-warranty, by specifying @code{-silent}:
878 You can further control how @value{GDBN} starts up by using command-line
879 options. @value{GDBN} itself can remind you of the options available.
889 to display all available options and briefly describe their use
890 (@samp{@value{GDBP} -h} is a shorter equivalent).
892 All options and command line arguments you give are processed
893 in sequential order. The order makes a difference when the
894 @samp{-x} option is used.
898 * File Options:: Choosing files
899 * Mode Options:: Choosing modes
900 * Startup:: What @value{GDBN} does during startup
904 @subsection Choosing Files
906 When @value{GDBN} starts, it reads any arguments other than options as
907 specifying an executable file and core file (or process ID). This is
908 the same as if the arguments were specified by the @samp{-se} and
909 @samp{-c} (or @samp{-p}) options respectively. (@value{GDBN} reads the
910 first argument that does not have an associated option flag as
911 equivalent to the @samp{-se} option followed by that argument; and the
912 second argument that does not have an associated option flag, if any, as
913 equivalent to the @samp{-c}/@samp{-p} option followed by that argument.)
914 If the second argument begins with a decimal digit, @value{GDBN} will
915 first attempt to attach to it as a process, and if that fails, attempt
916 to open it as a corefile. If you have a corefile whose name begins with
917 a digit, you can prevent @value{GDBN} from treating it as a pid by
918 prefixing it with @file{./}, e.g.@: @file{./12345}.
920 If @value{GDBN} has not been configured to included core file support,
921 such as for most embedded targets, then it will complain about a second
922 argument and ignore it.
924 Many options have both long and short forms; both are shown in the
925 following list. @value{GDBN} also recognizes the long forms if you truncate
926 them, so long as enough of the option is present to be unambiguous.
927 (If you prefer, you can flag option arguments with @samp{--} rather
928 than @samp{-}, though we illustrate the more usual convention.)
930 @c NOTE: the @cindex entries here use double dashes ON PURPOSE. This
931 @c way, both those who look for -foo and --foo in the index, will find
935 @item -symbols @var{file}
937 @cindex @code{--symbols}
939 Read symbol table from file @var{file}.
941 @item -exec @var{file}
943 @cindex @code{--exec}
945 Use file @var{file} as the executable file to execute when appropriate,
946 and for examining pure data in conjunction with a core dump.
950 Read symbol table from file @var{file} and use it as the executable
953 @item -core @var{file}
955 @cindex @code{--core}
957 Use file @var{file} as a core dump to examine.
959 @item -pid @var{number}
960 @itemx -p @var{number}
963 Connect to process ID @var{number}, as with the @code{attach} command.
965 @item -command @var{file}
967 @cindex @code{--command}
969 Execute commands from file @var{file}. The contents of this file is
970 evaluated exactly as the @code{source} command would.
971 @xref{Command Files,, Command files}.
973 @item -eval-command @var{command}
974 @itemx -ex @var{command}
975 @cindex @code{--eval-command}
977 Execute a single @value{GDBN} command.
979 This option may be used multiple times to call multiple commands. It may
980 also be interleaved with @samp{-command} as required.
983 @value{GDBP} -ex 'target sim' -ex 'load' \
984 -x setbreakpoints -ex 'run' a.out
987 @item -directory @var{directory}
988 @itemx -d @var{directory}
989 @cindex @code{--directory}
991 Add @var{directory} to the path to search for source and script files.
995 @cindex @code{--readnow}
997 Read each symbol file's entire symbol table immediately, rather than
998 the default, which is to read it incrementally as it is needed.
999 This makes startup slower, but makes future operations faster.
1004 @subsection Choosing Modes
1006 You can run @value{GDBN} in various alternative modes---for example, in
1007 batch mode or quiet mode.
1014 Do not execute commands found in any initialization files. Normally,
1015 @value{GDBN} executes the commands in these files after all the command
1016 options and arguments have been processed. @xref{Command Files,,Command
1022 @cindex @code{--quiet}
1023 @cindex @code{--silent}
1025 ``Quiet''. Do not print the introductory and copyright messages. These
1026 messages are also suppressed in batch mode.
1029 @cindex @code{--batch}
1030 Run in batch mode. Exit with status @code{0} after processing all the
1031 command files specified with @samp{-x} (and all commands from
1032 initialization files, if not inhibited with @samp{-n}). Exit with
1033 nonzero status if an error occurs in executing the @value{GDBN} commands
1034 in the command files. Batch mode also disables pagination;
1035 @pxref{Screen Size} and acts as if @kbd{set confirm off} were in
1036 effect (@pxref{Messages/Warnings}).
1038 Batch mode may be useful for running @value{GDBN} as a filter, for
1039 example to download and run a program on another computer; in order to
1040 make this more useful, the message
1043 Program exited normally.
1047 (which is ordinarily issued whenever a program running under
1048 @value{GDBN} control terminates) is not issued when running in batch
1052 @cindex @code{--batch-silent}
1053 Run in batch mode exactly like @samp{-batch}, but totally silently. All
1054 @value{GDBN} output to @code{stdout} is prevented (@code{stderr} is
1055 unaffected). This is much quieter than @samp{-silent} and would be useless
1056 for an interactive session.
1058 This is particularly useful when using targets that give @samp{Loading section}
1059 messages, for example.
1061 Note that targets that give their output via @value{GDBN}, as opposed to
1062 writing directly to @code{stdout}, will also be made silent.
1064 @item -return-child-result
1065 @cindex @code{--return-child-result}
1066 The return code from @value{GDBN} will be the return code from the child
1067 process (the process being debugged), with the following exceptions:
1071 @value{GDBN} exits abnormally. E.g., due to an incorrect argument or an
1072 internal error. In this case the exit code is the same as it would have been
1073 without @samp{-return-child-result}.
1075 The user quits with an explicit value. E.g., @samp{quit 1}.
1077 The child process never runs, or is not allowed to terminate, in which case
1078 the exit code will be -1.
1081 This option is useful in conjunction with @samp{-batch} or @samp{-batch-silent},
1082 when @value{GDBN} is being used as a remote program loader or simulator
1087 @cindex @code{--nowindows}
1089 ``No windows''. If @value{GDBN} comes with a graphical user interface
1090 (GUI) built in, then this option tells @value{GDBN} to only use the command-line
1091 interface. If no GUI is available, this option has no effect.
1095 @cindex @code{--windows}
1097 If @value{GDBN} includes a GUI, then this option requires it to be
1100 @item -cd @var{directory}
1102 Run @value{GDBN} using @var{directory} as its working directory,
1103 instead of the current directory.
1107 @cindex @code{--fullname}
1109 @sc{gnu} Emacs sets this option when it runs @value{GDBN} as a
1110 subprocess. It tells @value{GDBN} to output the full file name and line
1111 number in a standard, recognizable fashion each time a stack frame is
1112 displayed (which includes each time your program stops). This
1113 recognizable format looks like two @samp{\032} characters, followed by
1114 the file name, line number and character position separated by colons,
1115 and a newline. The Emacs-to-@value{GDBN} interface program uses the two
1116 @samp{\032} characters as a signal to display the source code for the
1120 @cindex @code{--epoch}
1121 The Epoch Emacs-@value{GDBN} interface sets this option when it runs
1122 @value{GDBN} as a subprocess. It tells @value{GDBN} to modify its print
1123 routines so as to allow Epoch to display values of expressions in a
1126 @item -annotate @var{level}
1127 @cindex @code{--annotate}
1128 This option sets the @dfn{annotation level} inside @value{GDBN}. Its
1129 effect is identical to using @samp{set annotate @var{level}}
1130 (@pxref{Annotations}). The annotation @var{level} controls how much
1131 information @value{GDBN} prints together with its prompt, values of
1132 expressions, source lines, and other types of output. Level 0 is the
1133 normal, level 1 is for use when @value{GDBN} is run as a subprocess of
1134 @sc{gnu} Emacs, level 3 is the maximum annotation suitable for programs
1135 that control @value{GDBN}, and level 2 has been deprecated.
1137 The annotation mechanism has largely been superseded by @sc{gdb/mi}
1141 @cindex @code{--args}
1142 Change interpretation of command line so that arguments following the
1143 executable file are passed as command line arguments to the inferior.
1144 This option stops option processing.
1146 @item -baud @var{bps}
1148 @cindex @code{--baud}
1150 Set the line speed (baud rate or bits per second) of any serial
1151 interface used by @value{GDBN} for remote debugging.
1153 @item -l @var{timeout}
1155 Set the timeout (in seconds) of any communication used by @value{GDBN}
1156 for remote debugging.
1158 @item -tty @var{device}
1159 @itemx -t @var{device}
1160 @cindex @code{--tty}
1162 Run using @var{device} for your program's standard input and output.
1163 @c FIXME: kingdon thinks there is more to -tty. Investigate.
1165 @c resolve the situation of these eventually
1167 @cindex @code{--tui}
1168 Activate the @dfn{Text User Interface} when starting. The Text User
1169 Interface manages several text windows on the terminal, showing
1170 source, assembly, registers and @value{GDBN} command outputs
1171 (@pxref{TUI, ,@value{GDBN} Text User Interface}). Alternatively, the
1172 Text User Interface can be enabled by invoking the program
1173 @samp{@value{GDBTUI}}. Do not use this option if you run @value{GDBN} from
1174 Emacs (@pxref{Emacs, ,Using @value{GDBN} under @sc{gnu} Emacs}).
1177 @c @cindex @code{--xdb}
1178 @c Run in XDB compatibility mode, allowing the use of certain XDB commands.
1179 @c For information, see the file @file{xdb_trans.html}, which is usually
1180 @c installed in the directory @code{/opt/langtools/wdb/doc} on HP-UX
1183 @item -interpreter @var{interp}
1184 @cindex @code{--interpreter}
1185 Use the interpreter @var{interp} for interface with the controlling
1186 program or device. This option is meant to be set by programs which
1187 communicate with @value{GDBN} using it as a back end.
1188 @xref{Interpreters, , Command Interpreters}.
1190 @samp{--interpreter=mi} (or @samp{--interpreter=mi2}) causes
1191 @value{GDBN} to use the @dfn{@sc{gdb/mi} interface} (@pxref{GDB/MI, ,
1192 The @sc{gdb/mi} Interface}) included since @value{GDBN} version 6.0. The
1193 previous @sc{gdb/mi} interface, included in @value{GDBN} version 5.3 and
1194 selected with @samp{--interpreter=mi1}, is deprecated. Earlier
1195 @sc{gdb/mi} interfaces are no longer supported.
1198 @cindex @code{--write}
1199 Open the executable and core files for both reading and writing. This
1200 is equivalent to the @samp{set write on} command inside @value{GDBN}
1204 @cindex @code{--statistics}
1205 This option causes @value{GDBN} to print statistics about time and
1206 memory usage after it completes each command and returns to the prompt.
1209 @cindex @code{--version}
1210 This option causes @value{GDBN} to print its version number and
1211 no-warranty blurb, and exit.
1216 @subsection What @value{GDBN} Does During Startup
1217 @cindex @value{GDBN} startup
1219 Here's the description of what @value{GDBN} does during session startup:
1223 Sets up the command interpreter as specified by the command line
1224 (@pxref{Mode Options, interpreter}).
1228 Reads the system-wide @dfn{init file} (if @option{--with-system-gdbinit} was
1229 used when building @value{GDBN}; @pxref{System-wide configuration,
1230 ,System-wide configuration and settings}) and executes all the commands in
1234 Reads the init file (if any) in your home directory@footnote{On
1235 DOS/Windows systems, the home directory is the one pointed to by the
1236 @code{HOME} environment variable.} and executes all the commands in
1240 Processes command line options and operands.
1243 Reads and executes the commands from init file (if any) in the current
1244 working directory. This is only done if the current directory is
1245 different from your home directory. Thus, you can have more than one
1246 init file, one generic in your home directory, and another, specific
1247 to the program you are debugging, in the directory where you invoke
1251 Reads command files specified by the @samp{-x} option. @xref{Command
1252 Files}, for more details about @value{GDBN} command files.
1255 Reads the command history recorded in the @dfn{history file}.
1256 @xref{Command History}, for more details about the command history and the
1257 files where @value{GDBN} records it.
1260 Init files use the same syntax as @dfn{command files} (@pxref{Command
1261 Files}) and are processed by @value{GDBN} in the same way. The init
1262 file in your home directory can set options (such as @samp{set
1263 complaints}) that affect subsequent processing of command line options
1264 and operands. Init files are not executed if you use the @samp{-nx}
1265 option (@pxref{Mode Options, ,Choosing Modes}).
1267 To display the list of init files loaded by gdb at startup, you
1268 can use @kbd{gdb --help}.
1270 @cindex init file name
1271 @cindex @file{.gdbinit}
1272 @cindex @file{gdb.ini}
1273 The @value{GDBN} init files are normally called @file{.gdbinit}.
1274 The DJGPP port of @value{GDBN} uses the name @file{gdb.ini}, due to
1275 the limitations of file names imposed by DOS filesystems. The Windows
1276 ports of @value{GDBN} use the standard name, but if they find a
1277 @file{gdb.ini} file, they warn you about that and suggest to rename
1278 the file to the standard name.
1282 @section Quitting @value{GDBN}
1283 @cindex exiting @value{GDBN}
1284 @cindex leaving @value{GDBN}
1287 @kindex quit @r{[}@var{expression}@r{]}
1288 @kindex q @r{(@code{quit})}
1289 @item quit @r{[}@var{expression}@r{]}
1291 To exit @value{GDBN}, use the @code{quit} command (abbreviated
1292 @code{q}), or type an end-of-file character (usually @kbd{Ctrl-d}). If you
1293 do not supply @var{expression}, @value{GDBN} will terminate normally;
1294 otherwise it will terminate using the result of @var{expression} as the
1299 An interrupt (often @kbd{Ctrl-c}) does not exit from @value{GDBN}, but rather
1300 terminates the action of any @value{GDBN} command that is in progress and
1301 returns to @value{GDBN} command level. It is safe to type the interrupt
1302 character at any time because @value{GDBN} does not allow it to take effect
1303 until a time when it is safe.
1305 If you have been using @value{GDBN} to control an attached process or
1306 device, you can release it with the @code{detach} command
1307 (@pxref{Attach, ,Debugging an Already-running Process}).
1309 @node Shell Commands
1310 @section Shell Commands
1312 If you need to execute occasional shell commands during your
1313 debugging session, there is no need to leave or suspend @value{GDBN}; you can
1314 just use the @code{shell} command.
1318 @cindex shell escape
1319 @item shell @var{command string}
1320 Invoke a standard shell to execute @var{command string}.
1321 If it exists, the environment variable @code{SHELL} determines which
1322 shell to run. Otherwise @value{GDBN} uses the default shell
1323 (@file{/bin/sh} on Unix systems, @file{COMMAND.COM} on MS-DOS, etc.).
1326 The utility @code{make} is often needed in development environments.
1327 You do not have to use the @code{shell} command for this purpose in
1332 @cindex calling make
1333 @item make @var{make-args}
1334 Execute the @code{make} program with the specified
1335 arguments. This is equivalent to @samp{shell make @var{make-args}}.
1338 @node Logging Output
1339 @section Logging Output
1340 @cindex logging @value{GDBN} output
1341 @cindex save @value{GDBN} output to a file
1343 You may want to save the output of @value{GDBN} commands to a file.
1344 There are several commands to control @value{GDBN}'s logging.
1348 @item set logging on
1350 @item set logging off
1352 @cindex logging file name
1353 @item set logging file @var{file}
1354 Change the name of the current logfile. The default logfile is @file{gdb.txt}.
1355 @item set logging overwrite [on|off]
1356 By default, @value{GDBN} will append to the logfile. Set @code{overwrite} if
1357 you want @code{set logging on} to overwrite the logfile instead.
1358 @item set logging redirect [on|off]
1359 By default, @value{GDBN} output will go to both the terminal and the logfile.
1360 Set @code{redirect} if you want output to go only to the log file.
1361 @kindex show logging
1363 Show the current values of the logging settings.
1367 @chapter @value{GDBN} Commands
1369 You can abbreviate a @value{GDBN} command to the first few letters of the command
1370 name, if that abbreviation is unambiguous; and you can repeat certain
1371 @value{GDBN} commands by typing just @key{RET}. You can also use the @key{TAB}
1372 key to get @value{GDBN} to fill out the rest of a word in a command (or to
1373 show you the alternatives available, if there is more than one possibility).
1376 * Command Syntax:: How to give commands to @value{GDBN}
1377 * Completion:: Command completion
1378 * Help:: How to ask @value{GDBN} for help
1381 @node Command Syntax
1382 @section Command Syntax
1384 A @value{GDBN} command is a single line of input. There is no limit on
1385 how long it can be. It starts with a command name, which is followed by
1386 arguments whose meaning depends on the command name. For example, the
1387 command @code{step} accepts an argument which is the number of times to
1388 step, as in @samp{step 5}. You can also use the @code{step} command
1389 with no arguments. Some commands do not allow any arguments.
1391 @cindex abbreviation
1392 @value{GDBN} command names may always be truncated if that abbreviation is
1393 unambiguous. Other possible command abbreviations are listed in the
1394 documentation for individual commands. In some cases, even ambiguous
1395 abbreviations are allowed; for example, @code{s} is specially defined as
1396 equivalent to @code{step} even though there are other commands whose
1397 names start with @code{s}. You can test abbreviations by using them as
1398 arguments to the @code{help} command.
1400 @cindex repeating commands
1401 @kindex RET @r{(repeat last command)}
1402 A blank line as input to @value{GDBN} (typing just @key{RET}) means to
1403 repeat the previous command. Certain commands (for example, @code{run})
1404 will not repeat this way; these are commands whose unintentional
1405 repetition might cause trouble and which you are unlikely to want to
1406 repeat. User-defined commands can disable this feature; see
1407 @ref{Define, dont-repeat}.
1409 The @code{list} and @code{x} commands, when you repeat them with
1410 @key{RET}, construct new arguments rather than repeating
1411 exactly as typed. This permits easy scanning of source or memory.
1413 @value{GDBN} can also use @key{RET} in another way: to partition lengthy
1414 output, in a way similar to the common utility @code{more}
1415 (@pxref{Screen Size,,Screen Size}). Since it is easy to press one
1416 @key{RET} too many in this situation, @value{GDBN} disables command
1417 repetition after any command that generates this sort of display.
1419 @kindex # @r{(a comment)}
1421 Any text from a @kbd{#} to the end of the line is a comment; it does
1422 nothing. This is useful mainly in command files (@pxref{Command
1423 Files,,Command Files}).
1425 @cindex repeating command sequences
1426 @kindex Ctrl-o @r{(operate-and-get-next)}
1427 The @kbd{Ctrl-o} binding is useful for repeating a complex sequence of
1428 commands. This command accepts the current line, like @key{RET}, and
1429 then fetches the next line relative to the current line from the history
1433 @section Command Completion
1436 @cindex word completion
1437 @value{GDBN} can fill in the rest of a word in a command for you, if there is
1438 only one possibility; it can also show you what the valid possibilities
1439 are for the next word in a command, at any time. This works for @value{GDBN}
1440 commands, @value{GDBN} subcommands, and the names of symbols in your program.
1442 Press the @key{TAB} key whenever you want @value{GDBN} to fill out the rest
1443 of a word. If there is only one possibility, @value{GDBN} fills in the
1444 word, and waits for you to finish the command (or press @key{RET} to
1445 enter it). For example, if you type
1447 @c FIXME "@key" does not distinguish its argument sufficiently to permit
1448 @c complete accuracy in these examples; space introduced for clarity.
1449 @c If texinfo enhancements make it unnecessary, it would be nice to
1450 @c replace " @key" by "@key" in the following...
1452 (@value{GDBP}) info bre @key{TAB}
1456 @value{GDBN} fills in the rest of the word @samp{breakpoints}, since that is
1457 the only @code{info} subcommand beginning with @samp{bre}:
1460 (@value{GDBP}) info breakpoints
1464 You can either press @key{RET} at this point, to run the @code{info
1465 breakpoints} command, or backspace and enter something else, if
1466 @samp{breakpoints} does not look like the command you expected. (If you
1467 were sure you wanted @code{info breakpoints} in the first place, you
1468 might as well just type @key{RET} immediately after @samp{info bre},
1469 to exploit command abbreviations rather than command completion).
1471 If there is more than one possibility for the next word when you press
1472 @key{TAB}, @value{GDBN} sounds a bell. You can either supply more
1473 characters and try again, or just press @key{TAB} a second time;
1474 @value{GDBN} displays all the possible completions for that word. For
1475 example, you might want to set a breakpoint on a subroutine whose name
1476 begins with @samp{make_}, but when you type @kbd{b make_@key{TAB}} @value{GDBN}
1477 just sounds the bell. Typing @key{TAB} again displays all the
1478 function names in your program that begin with those characters, for
1482 (@value{GDBP}) b make_ @key{TAB}
1483 @exdent @value{GDBN} sounds bell; press @key{TAB} again, to see:
1484 make_a_section_from_file make_environ
1485 make_abs_section make_function_type
1486 make_blockvector make_pointer_type
1487 make_cleanup make_reference_type
1488 make_command make_symbol_completion_list
1489 (@value{GDBP}) b make_
1493 After displaying the available possibilities, @value{GDBN} copies your
1494 partial input (@samp{b make_} in the example) so you can finish the
1497 If you just want to see the list of alternatives in the first place, you
1498 can press @kbd{M-?} rather than pressing @key{TAB} twice. @kbd{M-?}
1499 means @kbd{@key{META} ?}. You can type this either by holding down a
1500 key designated as the @key{META} shift on your keyboard (if there is
1501 one) while typing @kbd{?}, or as @key{ESC} followed by @kbd{?}.
1503 @cindex quotes in commands
1504 @cindex completion of quoted strings
1505 Sometimes the string you need, while logically a ``word'', may contain
1506 parentheses or other characters that @value{GDBN} normally excludes from
1507 its notion of a word. To permit word completion to work in this
1508 situation, you may enclose words in @code{'} (single quote marks) in
1509 @value{GDBN} commands.
1511 The most likely situation where you might need this is in typing the
1512 name of a C@t{++} function. This is because C@t{++} allows function
1513 overloading (multiple definitions of the same function, distinguished
1514 by argument type). For example, when you want to set a breakpoint you
1515 may need to distinguish whether you mean the version of @code{name}
1516 that takes an @code{int} parameter, @code{name(int)}, or the version
1517 that takes a @code{float} parameter, @code{name(float)}. To use the
1518 word-completion facilities in this situation, type a single quote
1519 @code{'} at the beginning of the function name. This alerts
1520 @value{GDBN} that it may need to consider more information than usual
1521 when you press @key{TAB} or @kbd{M-?} to request word completion:
1524 (@value{GDBP}) b 'bubble( @kbd{M-?}
1525 bubble(double,double) bubble(int,int)
1526 (@value{GDBP}) b 'bubble(
1529 In some cases, @value{GDBN} can tell that completing a name requires using
1530 quotes. When this happens, @value{GDBN} inserts the quote for you (while
1531 completing as much as it can) if you do not type the quote in the first
1535 (@value{GDBP}) b bub @key{TAB}
1536 @exdent @value{GDBN} alters your input line to the following, and rings a bell:
1537 (@value{GDBP}) b 'bubble(
1541 In general, @value{GDBN} can tell that a quote is needed (and inserts it) if
1542 you have not yet started typing the argument list when you ask for
1543 completion on an overloaded symbol.
1545 For more information about overloaded functions, see @ref{C Plus Plus
1546 Expressions, ,C@t{++} Expressions}. You can use the command @code{set
1547 overload-resolution off} to disable overload resolution;
1548 see @ref{Debugging C Plus Plus, ,@value{GDBN} Features for C@t{++}}.
1550 @cindex completion of structure field names
1551 @cindex structure field name completion
1552 @cindex completion of union field names
1553 @cindex union field name completion
1554 When completing in an expression which looks up a field in a
1555 structure, @value{GDBN} also tries@footnote{The completer can be
1556 confused by certain kinds of invalid expressions. Also, it only
1557 examines the static type of the expression, not the dynamic type.} to
1558 limit completions to the field names available in the type of the
1562 (@value{GDBP}) p gdb_stdout.@kbd{M-?}
1563 magic to_delete to_fputs to_put to_rewind
1564 to_data to_flush to_isatty to_read to_write
1568 This is because the @code{gdb_stdout} is a variable of the type
1569 @code{struct ui_file} that is defined in @value{GDBN} sources as
1576 ui_file_flush_ftype *to_flush;
1577 ui_file_write_ftype *to_write;
1578 ui_file_fputs_ftype *to_fputs;
1579 ui_file_read_ftype *to_read;
1580 ui_file_delete_ftype *to_delete;
1581 ui_file_isatty_ftype *to_isatty;
1582 ui_file_rewind_ftype *to_rewind;
1583 ui_file_put_ftype *to_put;
1590 @section Getting Help
1591 @cindex online documentation
1594 You can always ask @value{GDBN} itself for information on its commands,
1595 using the command @code{help}.
1598 @kindex h @r{(@code{help})}
1601 You can use @code{help} (abbreviated @code{h}) with no arguments to
1602 display a short list of named classes of commands:
1606 List of classes of commands:
1608 aliases -- Aliases of other commands
1609 breakpoints -- Making program stop at certain points
1610 data -- Examining data
1611 files -- Specifying and examining files
1612 internals -- Maintenance commands
1613 obscure -- Obscure features
1614 running -- Running the program
1615 stack -- Examining the stack
1616 status -- Status inquiries
1617 support -- Support facilities
1618 tracepoints -- Tracing of program execution without
1619 stopping the program
1620 user-defined -- User-defined commands
1622 Type "help" followed by a class name for a list of
1623 commands in that class.
1624 Type "help" followed by command name for full
1626 Command name abbreviations are allowed if unambiguous.
1629 @c the above line break eliminates huge line overfull...
1631 @item help @var{class}
1632 Using one of the general help classes as an argument, you can get a
1633 list of the individual commands in that class. For example, here is the
1634 help display for the class @code{status}:
1637 (@value{GDBP}) help status
1642 @c Line break in "show" line falsifies real output, but needed
1643 @c to fit in smallbook page size.
1644 info -- Generic command for showing things
1645 about the program being debugged
1646 show -- Generic command for showing things
1649 Type "help" followed by command name for full
1651 Command name abbreviations are allowed if unambiguous.
1655 @item help @var{command}
1656 With a command name as @code{help} argument, @value{GDBN} displays a
1657 short paragraph on how to use that command.
1660 @item apropos @var{args}
1661 The @code{apropos} command searches through all of the @value{GDBN}
1662 commands, and their documentation, for the regular expression specified in
1663 @var{args}. It prints out all matches found. For example:
1674 set symbol-reloading -- Set dynamic symbol table reloading
1675 multiple times in one run
1676 show symbol-reloading -- Show dynamic symbol table reloading
1677 multiple times in one run
1682 @item complete @var{args}
1683 The @code{complete @var{args}} command lists all the possible completions
1684 for the beginning of a command. Use @var{args} to specify the beginning of the
1685 command you want completed. For example:
1691 @noindent results in:
1702 @noindent This is intended for use by @sc{gnu} Emacs.
1705 In addition to @code{help}, you can use the @value{GDBN} commands @code{info}
1706 and @code{show} to inquire about the state of your program, or the state
1707 of @value{GDBN} itself. Each command supports many topics of inquiry; this
1708 manual introduces each of them in the appropriate context. The listings
1709 under @code{info} and under @code{show} in the Index point to
1710 all the sub-commands. @xref{Index}.
1715 @kindex i @r{(@code{info})}
1717 This command (abbreviated @code{i}) is for describing the state of your
1718 program. For example, you can show the arguments passed to a function
1719 with @code{info args}, list the registers currently in use with @code{info
1720 registers}, or list the breakpoints you have set with @code{info breakpoints}.
1721 You can get a complete list of the @code{info} sub-commands with
1722 @w{@code{help info}}.
1726 You can assign the result of an expression to an environment variable with
1727 @code{set}. For example, you can set the @value{GDBN} prompt to a $-sign with
1728 @code{set prompt $}.
1732 In contrast to @code{info}, @code{show} is for describing the state of
1733 @value{GDBN} itself.
1734 You can change most of the things you can @code{show}, by using the
1735 related command @code{set}; for example, you can control what number
1736 system is used for displays with @code{set radix}, or simply inquire
1737 which is currently in use with @code{show radix}.
1740 To display all the settable parameters and their current
1741 values, you can use @code{show} with no arguments; you may also use
1742 @code{info set}. Both commands produce the same display.
1743 @c FIXME: "info set" violates the rule that "info" is for state of
1744 @c FIXME...program. Ck w/ GNU: "info set" to be called something else,
1745 @c FIXME...or change desc of rule---eg "state of prog and debugging session"?
1749 Here are three miscellaneous @code{show} subcommands, all of which are
1750 exceptional in lacking corresponding @code{set} commands:
1753 @kindex show version
1754 @cindex @value{GDBN} version number
1756 Show what version of @value{GDBN} is running. You should include this
1757 information in @value{GDBN} bug-reports. If multiple versions of
1758 @value{GDBN} are in use at your site, you may need to determine which
1759 version of @value{GDBN} you are running; as @value{GDBN} evolves, new
1760 commands are introduced, and old ones may wither away. Also, many
1761 system vendors ship variant versions of @value{GDBN}, and there are
1762 variant versions of @value{GDBN} in @sc{gnu}/Linux distributions as well.
1763 The version number is the same as the one announced when you start
1766 @kindex show copying
1767 @kindex info copying
1768 @cindex display @value{GDBN} copyright
1771 Display information about permission for copying @value{GDBN}.
1773 @kindex show warranty
1774 @kindex info warranty
1776 @itemx info warranty
1777 Display the @sc{gnu} ``NO WARRANTY'' statement, or a warranty,
1778 if your version of @value{GDBN} comes with one.
1783 @chapter Running Programs Under @value{GDBN}
1785 When you run a program under @value{GDBN}, you must first generate
1786 debugging information when you compile it.
1788 You may start @value{GDBN} with its arguments, if any, in an environment
1789 of your choice. If you are doing native debugging, you may redirect
1790 your program's input and output, debug an already running process, or
1791 kill a child process.
1794 * Compilation:: Compiling for debugging
1795 * Starting:: Starting your program
1796 * Arguments:: Your program's arguments
1797 * Environment:: Your program's environment
1799 * Working Directory:: Your program's working directory
1800 * Input/Output:: Your program's input and output
1801 * Attach:: Debugging an already-running process
1802 * Kill Process:: Killing the child process
1804 * Inferiors and Programs:: Debugging multiple inferiors and programs
1805 * Threads:: Debugging programs with multiple threads
1806 * Forks:: Debugging forks
1807 * Checkpoint/Restart:: Setting a @emph{bookmark} to return to later
1811 @section Compiling for Debugging
1813 In order to debug a program effectively, you need to generate
1814 debugging information when you compile it. This debugging information
1815 is stored in the object file; it describes the data type of each
1816 variable or function and the correspondence between source line numbers
1817 and addresses in the executable code.
1819 To request debugging information, specify the @samp{-g} option when you run
1822 Programs that are to be shipped to your customers are compiled with
1823 optimizations, using the @samp{-O} compiler option. However, some
1824 compilers are unable to handle the @samp{-g} and @samp{-O} options
1825 together. Using those compilers, you cannot generate optimized
1826 executables containing debugging information.
1828 @value{NGCC}, the @sc{gnu} C/C@t{++} compiler, supports @samp{-g} with or
1829 without @samp{-O}, making it possible to debug optimized code. We
1830 recommend that you @emph{always} use @samp{-g} whenever you compile a
1831 program. You may think your program is correct, but there is no sense
1832 in pushing your luck. For more information, see @ref{Optimized Code}.
1834 Older versions of the @sc{gnu} C compiler permitted a variant option
1835 @w{@samp{-gg}} for debugging information. @value{GDBN} no longer supports this
1836 format; if your @sc{gnu} C compiler has this option, do not use it.
1838 @value{GDBN} knows about preprocessor macros and can show you their
1839 expansion (@pxref{Macros}). Most compilers do not include information
1840 about preprocessor macros in the debugging information if you specify
1841 the @option{-g} flag alone, because this information is rather large.
1842 Version 3.1 and later of @value{NGCC}, the @sc{gnu} C compiler,
1843 provides macro information if you specify the options
1844 @option{-gdwarf-2} and @option{-g3}; the former option requests
1845 debugging information in the Dwarf 2 format, and the latter requests
1846 ``extra information''. In the future, we hope to find more compact
1847 ways to represent macro information, so that it can be included with
1852 @section Starting your Program
1858 @kindex r @r{(@code{run})}
1861 Use the @code{run} command to start your program under @value{GDBN}.
1862 You must first specify the program name (except on VxWorks) with an
1863 argument to @value{GDBN} (@pxref{Invocation, ,Getting In and Out of
1864 @value{GDBN}}), or by using the @code{file} or @code{exec-file} command
1865 (@pxref{Files, ,Commands to Specify Files}).
1869 If you are running your program in an execution environment that
1870 supports processes, @code{run} creates an inferior process and makes
1871 that process run your program. In some environments without processes,
1872 @code{run} jumps to the start of your program. Other targets,
1873 like @samp{remote}, are always running. If you get an error
1874 message like this one:
1877 The "remote" target does not support "run".
1878 Try "help target" or "continue".
1882 then use @code{continue} to run your program. You may need @code{load}
1883 first (@pxref{load}).
1885 The execution of a program is affected by certain information it
1886 receives from its superior. @value{GDBN} provides ways to specify this
1887 information, which you must do @emph{before} starting your program. (You
1888 can change it after starting your program, but such changes only affect
1889 your program the next time you start it.) This information may be
1890 divided into four categories:
1893 @item The @emph{arguments.}
1894 Specify the arguments to give your program as the arguments of the
1895 @code{run} command. If a shell is available on your target, the shell
1896 is used to pass the arguments, so that you may use normal conventions
1897 (such as wildcard expansion or variable substitution) in describing
1899 In Unix systems, you can control which shell is used with the
1900 @code{SHELL} environment variable.
1901 @xref{Arguments, ,Your Program's Arguments}.
1903 @item The @emph{environment.}
1904 Your program normally inherits its environment from @value{GDBN}, but you can
1905 use the @value{GDBN} commands @code{set environment} and @code{unset
1906 environment} to change parts of the environment that affect
1907 your program. @xref{Environment, ,Your Program's Environment}.
1909 @item The @emph{working directory.}
1910 Your program inherits its working directory from @value{GDBN}. You can set
1911 the @value{GDBN} working directory with the @code{cd} command in @value{GDBN}.
1912 @xref{Working Directory, ,Your Program's Working Directory}.
1914 @item The @emph{standard input and output.}
1915 Your program normally uses the same device for standard input and
1916 standard output as @value{GDBN} is using. You can redirect input and output
1917 in the @code{run} command line, or you can use the @code{tty} command to
1918 set a different device for your program.
1919 @xref{Input/Output, ,Your Program's Input and Output}.
1922 @emph{Warning:} While input and output redirection work, you cannot use
1923 pipes to pass the output of the program you are debugging to another
1924 program; if you attempt this, @value{GDBN} is likely to wind up debugging the
1928 When you issue the @code{run} command, your program begins to execute
1929 immediately. @xref{Stopping, ,Stopping and Continuing}, for discussion
1930 of how to arrange for your program to stop. Once your program has
1931 stopped, you may call functions in your program, using the @code{print}
1932 or @code{call} commands. @xref{Data, ,Examining Data}.
1934 If the modification time of your symbol file has changed since the last
1935 time @value{GDBN} read its symbols, @value{GDBN} discards its symbol
1936 table, and reads it again. When it does this, @value{GDBN} tries to retain
1937 your current breakpoints.
1942 @cindex run to main procedure
1943 The name of the main procedure can vary from language to language.
1944 With C or C@t{++}, the main procedure name is always @code{main}, but
1945 other languages such as Ada do not require a specific name for their
1946 main procedure. The debugger provides a convenient way to start the
1947 execution of the program and to stop at the beginning of the main
1948 procedure, depending on the language used.
1950 The @samp{start} command does the equivalent of setting a temporary
1951 breakpoint at the beginning of the main procedure and then invoking
1952 the @samp{run} command.
1954 @cindex elaboration phase
1955 Some programs contain an @dfn{elaboration} phase where some startup code is
1956 executed before the main procedure is called. This depends on the
1957 languages used to write your program. In C@t{++}, for instance,
1958 constructors for static and global objects are executed before
1959 @code{main} is called. It is therefore possible that the debugger stops
1960 before reaching the main procedure. However, the temporary breakpoint
1961 will remain to halt execution.
1963 Specify the arguments to give to your program as arguments to the
1964 @samp{start} command. These arguments will be given verbatim to the
1965 underlying @samp{run} command. Note that the same arguments will be
1966 reused if no argument is provided during subsequent calls to
1967 @samp{start} or @samp{run}.
1969 It is sometimes necessary to debug the program during elaboration. In
1970 these cases, using the @code{start} command would stop the execution of
1971 your program too late, as the program would have already completed the
1972 elaboration phase. Under these circumstances, insert breakpoints in your
1973 elaboration code before running your program.
1975 @kindex set exec-wrapper
1976 @item set exec-wrapper @var{wrapper}
1977 @itemx show exec-wrapper
1978 @itemx unset exec-wrapper
1979 When @samp{exec-wrapper} is set, the specified wrapper is used to
1980 launch programs for debugging. @value{GDBN} starts your program
1981 with a shell command of the form @kbd{exec @var{wrapper}
1982 @var{program}}. Quoting is added to @var{program} and its
1983 arguments, but not to @var{wrapper}, so you should add quotes if
1984 appropriate for your shell. The wrapper runs until it executes
1985 your program, and then @value{GDBN} takes control.
1987 You can use any program that eventually calls @code{execve} with
1988 its arguments as a wrapper. Several standard Unix utilities do
1989 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
1990 with @code{exec "$@@"} will also work.
1992 For example, you can use @code{env} to pass an environment variable to
1993 the debugged program, without setting the variable in your shell's
1997 (@value{GDBP}) set exec-wrapper env 'LD_PRELOAD=libtest.so'
2001 This command is available when debugging locally on most targets, excluding
2002 @sc{djgpp}, Cygwin, MS Windows, and QNX Neutrino.
2004 @kindex set disable-randomization
2005 @item set disable-randomization
2006 @itemx set disable-randomization on
2007 This option (enabled by default in @value{GDBN}) will turn off the native
2008 randomization of the virtual address space of the started program. This option
2009 is useful for multiple debugging sessions to make the execution better
2010 reproducible and memory addresses reusable across debugging sessions.
2012 This feature is implemented only on @sc{gnu}/Linux. You can get the same
2016 (@value{GDBP}) set exec-wrapper setarch `uname -m` -R
2019 @item set disable-randomization off
2020 Leave the behavior of the started executable unchanged. Some bugs rear their
2021 ugly heads only when the program is loaded at certain addresses. If your bug
2022 disappears when you run the program under @value{GDBN}, that might be because
2023 @value{GDBN} by default disables the address randomization on platforms, such
2024 as @sc{gnu}/Linux, which do that for stand-alone programs. Use @kbd{set
2025 disable-randomization off} to try to reproduce such elusive bugs.
2027 The virtual address space randomization is implemented only on @sc{gnu}/Linux.
2028 It protects the programs against some kinds of security attacks. In these
2029 cases the attacker needs to know the exact location of a concrete executable
2030 code. Randomizing its location makes it impossible to inject jumps misusing
2031 a code at its expected addresses.
2033 Prelinking shared libraries provides a startup performance advantage but it
2034 makes addresses in these libraries predictable for privileged processes by
2035 having just unprivileged access at the target system. Reading the shared
2036 library binary gives enough information for assembling the malicious code
2037 misusing it. Still even a prelinked shared library can get loaded at a new
2038 random address just requiring the regular relocation process during the
2039 startup. Shared libraries not already prelinked are always loaded at
2040 a randomly chosen address.
2042 Position independent executables (PIE) contain position independent code
2043 similar to the shared libraries and therefore such executables get loaded at
2044 a randomly chosen address upon startup. PIE executables always load even
2045 already prelinked shared libraries at a random address. You can build such
2046 executable using @command{gcc -fPIE -pie}.
2048 Heap (malloc storage), stack and custom mmap areas are always placed randomly
2049 (as long as the randomization is enabled).
2051 @item show disable-randomization
2052 Show the current setting of the explicit disable of the native randomization of
2053 the virtual address space of the started program.
2058 @section Your Program's Arguments
2060 @cindex arguments (to your program)
2061 The arguments to your program can be specified by the arguments of the
2063 They are passed to a shell, which expands wildcard characters and
2064 performs redirection of I/O, and thence to your program. Your
2065 @code{SHELL} environment variable (if it exists) specifies what shell
2066 @value{GDBN} uses. If you do not define @code{SHELL}, @value{GDBN} uses
2067 the default shell (@file{/bin/sh} on Unix).
2069 On non-Unix systems, the program is usually invoked directly by
2070 @value{GDBN}, which emulates I/O redirection via the appropriate system
2071 calls, and the wildcard characters are expanded by the startup code of
2072 the program, not by the shell.
2074 @code{run} with no arguments uses the same arguments used by the previous
2075 @code{run}, or those set by the @code{set args} command.
2080 Specify the arguments to be used the next time your program is run. If
2081 @code{set args} has no arguments, @code{run} executes your program
2082 with no arguments. Once you have run your program with arguments,
2083 using @code{set args} before the next @code{run} is the only way to run
2084 it again without arguments.
2088 Show the arguments to give your program when it is started.
2092 @section Your Program's Environment
2094 @cindex environment (of your program)
2095 The @dfn{environment} consists of a set of environment variables and
2096 their values. Environment variables conventionally record such things as
2097 your user name, your home directory, your terminal type, and your search
2098 path for programs to run. Usually you set up environment variables with
2099 the shell and they are inherited by all the other programs you run. When
2100 debugging, it can be useful to try running your program with a modified
2101 environment without having to start @value{GDBN} over again.
2105 @item path @var{directory}
2106 Add @var{directory} to the front of the @code{PATH} environment variable
2107 (the search path for executables) that will be passed to your program.
2108 The value of @code{PATH} used by @value{GDBN} does not change.
2109 You may specify several directory names, separated by whitespace or by a
2110 system-dependent separator character (@samp{:} on Unix, @samp{;} on
2111 MS-DOS and MS-Windows). If @var{directory} is already in the path, it
2112 is moved to the front, so it is searched sooner.
2114 You can use the string @samp{$cwd} to refer to whatever is the current
2115 working directory at the time @value{GDBN} searches the path. If you
2116 use @samp{.} instead, it refers to the directory where you executed the
2117 @code{path} command. @value{GDBN} replaces @samp{.} in the
2118 @var{directory} argument (with the current path) before adding
2119 @var{directory} to the search path.
2120 @c 'path' is explicitly nonrepeatable, but RMS points out it is silly to
2121 @c document that, since repeating it would be a no-op.
2125 Display the list of search paths for executables (the @code{PATH}
2126 environment variable).
2128 @kindex show environment
2129 @item show environment @r{[}@var{varname}@r{]}
2130 Print the value of environment variable @var{varname} to be given to
2131 your program when it starts. If you do not supply @var{varname},
2132 print the names and values of all environment variables to be given to
2133 your program. You can abbreviate @code{environment} as @code{env}.
2135 @kindex set environment
2136 @item set environment @var{varname} @r{[}=@var{value}@r{]}
2137 Set environment variable @var{varname} to @var{value}. The value
2138 changes for your program only, not for @value{GDBN} itself. @var{value} may
2139 be any string; the values of environment variables are just strings, and
2140 any interpretation is supplied by your program itself. The @var{value}
2141 parameter is optional; if it is eliminated, the variable is set to a
2143 @c "any string" here does not include leading, trailing
2144 @c blanks. Gnu asks: does anyone care?
2146 For example, this command:
2153 tells the debugged program, when subsequently run, that its user is named
2154 @samp{foo}. (The spaces around @samp{=} are used for clarity here; they
2155 are not actually required.)
2157 @kindex unset environment
2158 @item unset environment @var{varname}
2159 Remove variable @var{varname} from the environment to be passed to your
2160 program. This is different from @samp{set env @var{varname} =};
2161 @code{unset environment} removes the variable from the environment,
2162 rather than assigning it an empty value.
2165 @emph{Warning:} On Unix systems, @value{GDBN} runs your program using
2167 by your @code{SHELL} environment variable if it exists (or
2168 @code{/bin/sh} if not). If your @code{SHELL} variable names a shell
2169 that runs an initialization file---such as @file{.cshrc} for C-shell, or
2170 @file{.bashrc} for BASH---any variables you set in that file affect
2171 your program. You may wish to move setting of environment variables to
2172 files that are only run when you sign on, such as @file{.login} or
2175 @node Working Directory
2176 @section Your Program's Working Directory
2178 @cindex working directory (of your program)
2179 Each time you start your program with @code{run}, it inherits its
2180 working directory from the current working directory of @value{GDBN}.
2181 The @value{GDBN} working directory is initially whatever it inherited
2182 from its parent process (typically the shell), but you can specify a new
2183 working directory in @value{GDBN} with the @code{cd} command.
2185 The @value{GDBN} working directory also serves as a default for the commands
2186 that specify files for @value{GDBN} to operate on. @xref{Files, ,Commands to
2191 @cindex change working directory
2192 @item cd @var{directory}
2193 Set the @value{GDBN} working directory to @var{directory}.
2197 Print the @value{GDBN} working directory.
2200 It is generally impossible to find the current working directory of
2201 the process being debugged (since a program can change its directory
2202 during its run). If you work on a system where @value{GDBN} is
2203 configured with the @file{/proc} support, you can use the @code{info
2204 proc} command (@pxref{SVR4 Process Information}) to find out the
2205 current working directory of the debuggee.
2208 @section Your Program's Input and Output
2213 By default, the program you run under @value{GDBN} does input and output to
2214 the same terminal that @value{GDBN} uses. @value{GDBN} switches the terminal
2215 to its own terminal modes to interact with you, but it records the terminal
2216 modes your program was using and switches back to them when you continue
2217 running your program.
2220 @kindex info terminal
2222 Displays information recorded by @value{GDBN} about the terminal modes your
2226 You can redirect your program's input and/or output using shell
2227 redirection with the @code{run} command. For example,
2234 starts your program, diverting its output to the file @file{outfile}.
2237 @cindex controlling terminal
2238 Another way to specify where your program should do input and output is
2239 with the @code{tty} command. This command accepts a file name as
2240 argument, and causes this file to be the default for future @code{run}
2241 commands. It also resets the controlling terminal for the child
2242 process, for future @code{run} commands. For example,
2249 directs that processes started with subsequent @code{run} commands
2250 default to do input and output on the terminal @file{/dev/ttyb} and have
2251 that as their controlling terminal.
2253 An explicit redirection in @code{run} overrides the @code{tty} command's
2254 effect on the input/output device, but not its effect on the controlling
2257 When you use the @code{tty} command or redirect input in the @code{run}
2258 command, only the input @emph{for your program} is affected. The input
2259 for @value{GDBN} still comes from your terminal. @code{tty} is an alias
2260 for @code{set inferior-tty}.
2262 @cindex inferior tty
2263 @cindex set inferior controlling terminal
2264 You can use the @code{show inferior-tty} command to tell @value{GDBN} to
2265 display the name of the terminal that will be used for future runs of your
2269 @item set inferior-tty /dev/ttyb
2270 @kindex set inferior-tty
2271 Set the tty for the program being debugged to /dev/ttyb.
2273 @item show inferior-tty
2274 @kindex show inferior-tty
2275 Show the current tty for the program being debugged.
2279 @section Debugging an Already-running Process
2284 @item attach @var{process-id}
2285 This command attaches to a running process---one that was started
2286 outside @value{GDBN}. (@code{info files} shows your active
2287 targets.) The command takes as argument a process ID. The usual way to
2288 find out the @var{process-id} of a Unix process is with the @code{ps} utility,
2289 or with the @samp{jobs -l} shell command.
2291 @code{attach} does not repeat if you press @key{RET} a second time after
2292 executing the command.
2295 To use @code{attach}, your program must be running in an environment
2296 which supports processes; for example, @code{attach} does not work for
2297 programs on bare-board targets that lack an operating system. You must
2298 also have permission to send the process a signal.
2300 When you use @code{attach}, the debugger finds the program running in
2301 the process first by looking in the current working directory, then (if
2302 the program is not found) by using the source file search path
2303 (@pxref{Source Path, ,Specifying Source Directories}). You can also use
2304 the @code{file} command to load the program. @xref{Files, ,Commands to
2307 The first thing @value{GDBN} does after arranging to debug the specified
2308 process is to stop it. You can examine and modify an attached process
2309 with all the @value{GDBN} commands that are ordinarily available when
2310 you start processes with @code{run}. You can insert breakpoints; you
2311 can step and continue; you can modify storage. If you would rather the
2312 process continue running, you may use the @code{continue} command after
2313 attaching @value{GDBN} to the process.
2318 When you have finished debugging the attached process, you can use the
2319 @code{detach} command to release it from @value{GDBN} control. Detaching
2320 the process continues its execution. After the @code{detach} command,
2321 that process and @value{GDBN} become completely independent once more, and you
2322 are ready to @code{attach} another process or start one with @code{run}.
2323 @code{detach} does not repeat if you press @key{RET} again after
2324 executing the command.
2327 If you exit @value{GDBN} while you have an attached process, you detach
2328 that process. If you use the @code{run} command, you kill that process.
2329 By default, @value{GDBN} asks for confirmation if you try to do either of these
2330 things; you can control whether or not you need to confirm by using the
2331 @code{set confirm} command (@pxref{Messages/Warnings, ,Optional Warnings and
2335 @section Killing the Child Process
2340 Kill the child process in which your program is running under @value{GDBN}.
2343 This command is useful if you wish to debug a core dump instead of a
2344 running process. @value{GDBN} ignores any core dump file while your program
2347 On some operating systems, a program cannot be executed outside @value{GDBN}
2348 while you have breakpoints set on it inside @value{GDBN}. You can use the
2349 @code{kill} command in this situation to permit running your program
2350 outside the debugger.
2352 The @code{kill} command is also useful if you wish to recompile and
2353 relink your program, since on many systems it is impossible to modify an
2354 executable file while it is running in a process. In this case, when you
2355 next type @code{run}, @value{GDBN} notices that the file has changed, and
2356 reads the symbol table again (while trying to preserve your current
2357 breakpoint settings).
2359 @node Inferiors and Programs
2360 @section Debugging Multiple Inferiors and Programs
2362 @value{GDBN} lets you run and debug multiple programs in a single
2363 session. In addition, @value{GDBN} on some systems may let you run
2364 several programs simultaneously (otherwise you have to exit from one
2365 before starting another). In the most general case, you can have
2366 multiple threads of execution in each of multiple processes, launched
2367 from multiple executables.
2370 @value{GDBN} represents the state of each program execution with an
2371 object called an @dfn{inferior}. An inferior typically corresponds to
2372 a process, but is more general and applies also to targets that do not
2373 have processes. Inferiors may be created before a process runs, and
2374 may be retained after a process exits. Inferiors have unique
2375 identifiers that are different from process ids. Usually each
2376 inferior will also have its own distinct address space, although some
2377 embedded targets may have several inferiors running in different parts
2378 of a single address space. Each inferior may in turn have multiple
2379 threads running in it.
2381 To find out what inferiors exist at any moment, use @w{@code{info
2385 @kindex info inferiors
2386 @item info inferiors
2387 Print a list of all inferiors currently being managed by @value{GDBN}.
2389 @value{GDBN} displays for each inferior (in this order):
2393 the inferior number assigned by @value{GDBN}
2396 the target system's inferior identifier
2399 the name of the executable the inferior is running.
2404 An asterisk @samp{*} preceding the @value{GDBN} inferior number
2405 indicates the current inferior.
2409 @c end table here to get a little more width for example
2412 (@value{GDBP}) info inferiors
2413 Num Description Executable
2414 2 process 2307 hello
2415 * 1 process 3401 goodbye
2418 To switch focus between inferiors, use the @code{inferior} command:
2421 @kindex inferior @var{infno}
2422 @item inferior @var{infno}
2423 Make inferior number @var{infno} the current inferior. The argument
2424 @var{infno} is the inferior number assigned by @value{GDBN}, as shown
2425 in the first field of the @samp{info inferiors} display.
2429 You can get multiple executables into a debugging session via the
2430 @code{add-inferior} and @w{@code{clone-inferior}} commands. On some
2431 systems @value{GDBN} can add inferiors to the debug session
2432 automatically by following calls to @code{fork} and @code{exec}. To
2433 remove inferiors from the debugging session use the
2434 @w{@code{remove-inferior}} command.
2437 @kindex add-inferior
2438 @item add-inferior [ -copies @var{n} ] [ -exec @var{executable} ]
2439 Adds @var{n} inferiors to be run using @var{executable} as the
2440 executable. @var{n} defaults to 1. If no executable is specified,
2441 the inferiors begins empty, with no program. You can still assign or
2442 change the program assigned to the inferior at any time by using the
2443 @code{file} command with the executable name as its argument.
2445 @kindex clone-inferior
2446 @item clone-inferior [ -copies @var{n} ] [ @var{infno} ]
2447 Adds @var{n} inferiors ready to execute the same program as inferior
2448 @var{infno}. @var{n} defaults to 1. @var{infno} defaults to the
2449 number of the current inferior. This is a convenient command when you
2450 want to run another instance of the inferior you are debugging.
2453 (@value{GDBP}) info inferiors
2454 Num Description Executable
2455 * 1 process 29964 helloworld
2456 (@value{GDBP}) clone-inferior
2459 (@value{GDBP}) info inferiors
2460 Num Description Executable
2462 * 1 process 29964 helloworld
2465 You can now simply switch focus to inferior 2 and run it.
2467 @kindex remove-inferior
2468 @item remove-inferior @var{infno}
2469 Removes the inferior @var{infno}. It is not possible to remove an
2470 inferior that is running with this command. For those, use the
2471 @code{kill} or @code{detach} command first.
2475 To quit debugging one of the running inferiors that is not the current
2476 inferior, you can either detach from it by using the @w{@code{detach
2477 inferior}} command (allowing it to run independently), or kill it
2478 using the @w{@code{kill inferior}} command:
2481 @kindex detach inferior @var{infno}
2482 @item detach inferior @var{infno}
2483 Detach from the inferior identified by @value{GDBN} inferior number
2484 @var{infno}, and remove it from the inferior list.
2486 @kindex kill inferior @var{infno}
2487 @item kill inferior @var{infno}
2488 Kill the inferior identified by @value{GDBN} inferior number
2489 @var{infno}, and remove it from the inferior list.
2492 After the successful completion of a command such as @code{detach},
2493 @code{detach inferior}, @code{kill} or @code{kill inferior}, or after
2494 a normal process exit, the inferior is still valid and listed with
2495 @code{info inferiors}, ready to be restarted.
2498 To be notified when inferiors are started or exit under @value{GDBN}'s
2499 control use @w{@code{set print inferior-events}}:
2502 @kindex set print inferior-events
2503 @cindex print messages on inferior start and exit
2504 @item set print inferior-events
2505 @itemx set print inferior-events on
2506 @itemx set print inferior-events off
2507 The @code{set print inferior-events} command allows you to enable or
2508 disable printing of messages when @value{GDBN} notices that new
2509 inferiors have started or that inferiors have exited or have been
2510 detached. By default, these messages will not be printed.
2512 @kindex show print inferior-events
2513 @item show print inferior-events
2514 Show whether messages will be printed when @value{GDBN} detects that
2515 inferiors have started, exited or have been detached.
2518 Many commands will work the same with multiple programs as with a
2519 single program: e.g., @code{print myglobal} will simply display the
2520 value of @code{myglobal} in the current inferior.
2523 Occasionaly, when debugging @value{GDBN} itself, it may be useful to
2524 get more info about the relationship of inferiors, programs, address
2525 spaces in a debug session. You can do that with the @w{@code{maint
2526 info program-spaces}} command.
2529 @kindex maint info program-spaces
2530 @item maint info program-spaces
2531 Print a list of all program spaces currently being managed by
2534 @value{GDBN} displays for each program space (in this order):
2538 the program space number assigned by @value{GDBN}
2541 the name of the executable loaded into the program space, with e.g.,
2542 the @code{file} command.
2547 An asterisk @samp{*} preceding the @value{GDBN} program space number
2548 indicates the current program space.
2550 In addition, below each program space line, @value{GDBN} prints extra
2551 information that isn't suitable to display in tabular form. For
2552 example, the list of inferiors bound to the program space.
2555 (@value{GDBP}) maint info program-spaces
2558 Bound inferiors: ID 1 (process 21561)
2562 Here we can see that no inferior is running the program @code{hello},
2563 while @code{process 21561} is running the program @code{goodbye}. On
2564 some targets, it is possible that multiple inferiors are bound to the
2565 same program space. The most common example is that of debugging both
2566 the parent and child processes of a @code{vfork} call. For example,
2569 (@value{GDBP}) maint info program-spaces
2572 Bound inferiors: ID 2 (process 18050), ID 1 (process 18045)
2575 Here, both inferior 2 and inferior 1 are running in the same program
2576 space as a result of inferior 1 having executed a @code{vfork} call.
2580 @section Debugging Programs with Multiple Threads
2582 @cindex threads of execution
2583 @cindex multiple threads
2584 @cindex switching threads
2585 In some operating systems, such as HP-UX and Solaris, a single program
2586 may have more than one @dfn{thread} of execution. The precise semantics
2587 of threads differ from one operating system to another, but in general
2588 the threads of a single program are akin to multiple processes---except
2589 that they share one address space (that is, they can all examine and
2590 modify the same variables). On the other hand, each thread has its own
2591 registers and execution stack, and perhaps private memory.
2593 @value{GDBN} provides these facilities for debugging multi-thread
2597 @item automatic notification of new threads
2598 @item @samp{thread @var{threadno}}, a command to switch among threads
2599 @item @samp{info threads}, a command to inquire about existing threads
2600 @item @samp{thread apply [@var{threadno}] [@var{all}] @var{args}},
2601 a command to apply a command to a list of threads
2602 @item thread-specific breakpoints
2603 @item @samp{set print thread-events}, which controls printing of
2604 messages on thread start and exit.
2605 @item @samp{set libthread-db-search-path @var{path}}, which lets
2606 the user specify which @code{libthread_db} to use if the default choice
2607 isn't compatible with the program.
2611 @emph{Warning:} These facilities are not yet available on every
2612 @value{GDBN} configuration where the operating system supports threads.
2613 If your @value{GDBN} does not support threads, these commands have no
2614 effect. For example, a system without thread support shows no output
2615 from @samp{info threads}, and always rejects the @code{thread} command,
2619 (@value{GDBP}) info threads
2620 (@value{GDBP}) thread 1
2621 Thread ID 1 not known. Use the "info threads" command to
2622 see the IDs of currently known threads.
2624 @c FIXME to implementors: how hard would it be to say "sorry, this GDB
2625 @c doesn't support threads"?
2628 @cindex focus of debugging
2629 @cindex current thread
2630 The @value{GDBN} thread debugging facility allows you to observe all
2631 threads while your program runs---but whenever @value{GDBN} takes
2632 control, one thread in particular is always the focus of debugging.
2633 This thread is called the @dfn{current thread}. Debugging commands show
2634 program information from the perspective of the current thread.
2636 @cindex @code{New} @var{systag} message
2637 @cindex thread identifier (system)
2638 @c FIXME-implementors!! It would be more helpful if the [New...] message
2639 @c included GDB's numeric thread handle, so you could just go to that
2640 @c thread without first checking `info threads'.
2641 Whenever @value{GDBN} detects a new thread in your program, it displays
2642 the target system's identification for the thread with a message in the
2643 form @samp{[New @var{systag}]}. @var{systag} is a thread identifier
2644 whose form varies depending on the particular system. For example, on
2645 @sc{gnu}/Linux, you might see
2648 [New Thread 46912507313328 (LWP 25582)]
2652 when @value{GDBN} notices a new thread. In contrast, on an SGI system,
2653 the @var{systag} is simply something like @samp{process 368}, with no
2656 @c FIXME!! (1) Does the [New...] message appear even for the very first
2657 @c thread of a program, or does it only appear for the
2658 @c second---i.e.@: when it becomes obvious we have a multithread
2660 @c (2) *Is* there necessarily a first thread always? Or do some
2661 @c multithread systems permit starting a program with multiple
2662 @c threads ab initio?
2664 @cindex thread number
2665 @cindex thread identifier (GDB)
2666 For debugging purposes, @value{GDBN} associates its own thread
2667 number---always a single integer---with each thread in your program.
2670 @kindex info threads
2672 Display a summary of all threads currently in your
2673 program. @value{GDBN} displays for each thread (in this order):
2677 the thread number assigned by @value{GDBN}
2680 the target system's thread identifier (@var{systag})
2683 the current stack frame summary for that thread
2687 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2688 indicates the current thread.
2692 @c end table here to get a little more width for example
2695 (@value{GDBP}) info threads
2696 3 process 35 thread 27 0x34e5 in sigpause ()
2697 2 process 35 thread 23 0x34e5 in sigpause ()
2698 * 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
2704 @cindex debugging multithreaded programs (on HP-UX)
2705 @cindex thread identifier (GDB), on HP-UX
2706 For debugging purposes, @value{GDBN} associates its own thread
2707 number---a small integer assigned in thread-creation order---with each
2708 thread in your program.
2710 @cindex @code{New} @var{systag} message, on HP-UX
2711 @cindex thread identifier (system), on HP-UX
2712 @c FIXME-implementors!! It would be more helpful if the [New...] message
2713 @c included GDB's numeric thread handle, so you could just go to that
2714 @c thread without first checking `info threads'.
2715 Whenever @value{GDBN} detects a new thread in your program, it displays
2716 both @value{GDBN}'s thread number and the target system's identification for the thread with a message in the
2717 form @samp{[New @var{systag}]}. @var{systag} is a thread identifier
2718 whose form varies depending on the particular system. For example, on
2722 [New thread 2 (system thread 26594)]
2726 when @value{GDBN} notices a new thread.
2729 @kindex info threads (HP-UX)
2731 Display a summary of all threads currently in your
2732 program. @value{GDBN} displays for each thread (in this order):
2735 @item the thread number assigned by @value{GDBN}
2737 @item the target system's thread identifier (@var{systag})
2739 @item the current stack frame summary for that thread
2743 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2744 indicates the current thread.
2748 @c end table here to get a little more width for example
2751 (@value{GDBP}) info threads
2752 * 3 system thread 26607 worker (wptr=0x7b09c318 "@@") \@*
2754 2 system thread 26606 0x7b0030d8 in __ksleep () \@*
2755 from /usr/lib/libc.2
2756 1 system thread 27905 0x7b003498 in _brk () \@*
2757 from /usr/lib/libc.2
2760 On Solaris, you can display more information about user threads with a
2761 Solaris-specific command:
2764 @item maint info sol-threads
2765 @kindex maint info sol-threads
2766 @cindex thread info (Solaris)
2767 Display info on Solaris user threads.
2771 @kindex thread @var{threadno}
2772 @item thread @var{threadno}
2773 Make thread number @var{threadno} the current thread. The command
2774 argument @var{threadno} is the internal @value{GDBN} thread number, as
2775 shown in the first field of the @samp{info threads} display.
2776 @value{GDBN} responds by displaying the system identifier of the thread
2777 you selected, and its current stack frame summary:
2780 @c FIXME!! This example made up; find a @value{GDBN} w/threads and get real one
2781 (@value{GDBP}) thread 2
2782 [Switching to process 35 thread 23]
2783 0x34e5 in sigpause ()
2787 As with the @samp{[New @dots{}]} message, the form of the text after
2788 @samp{Switching to} depends on your system's conventions for identifying
2791 @kindex thread apply
2792 @cindex apply command to several threads
2793 @item thread apply [@var{threadno}] [@var{all}] @var{command}
2794 The @code{thread apply} command allows you to apply the named
2795 @var{command} to one or more threads. Specify the numbers of the
2796 threads that you want affected with the command argument
2797 @var{threadno}. It can be a single thread number, one of the numbers
2798 shown in the first field of the @samp{info threads} display; or it
2799 could be a range of thread numbers, as in @code{2-4}. To apply a
2800 command to all threads, type @kbd{thread apply all @var{command}}.
2802 @kindex set print thread-events
2803 @cindex print messages on thread start and exit
2804 @item set print thread-events
2805 @itemx set print thread-events on
2806 @itemx set print thread-events off
2807 The @code{set print thread-events} command allows you to enable or
2808 disable printing of messages when @value{GDBN} notices that new threads have
2809 started or that threads have exited. By default, these messages will
2810 be printed if detection of these events is supported by the target.
2811 Note that these messages cannot be disabled on all targets.
2813 @kindex show print thread-events
2814 @item show print thread-events
2815 Show whether messages will be printed when @value{GDBN} detects that threads
2816 have started and exited.
2819 @xref{Thread Stops,,Stopping and Starting Multi-thread Programs}, for
2820 more information about how @value{GDBN} behaves when you stop and start
2821 programs with multiple threads.
2823 @xref{Set Watchpoints,,Setting Watchpoints}, for information about
2824 watchpoints in programs with multiple threads.
2827 @kindex set libthread-db-search-path
2828 @cindex search path for @code{libthread_db}
2829 @item set libthread-db-search-path @r{[}@var{path}@r{]}
2830 If this variable is set, @var{path} is a colon-separated list of
2831 directories @value{GDBN} will use to search for @code{libthread_db}.
2832 If you omit @var{path}, @samp{libthread-db-search-path} will be reset to
2835 On @sc{gnu}/Linux and Solaris systems, @value{GDBN} uses a ``helper''
2836 @code{libthread_db} library to obtain information about threads in the
2837 inferior process. @value{GDBN} will use @samp{libthread-db-search-path}
2838 to find @code{libthread_db}. If that fails, @value{GDBN} will continue
2839 with default system shared library directories, and finally the directory
2840 from which @code{libpthread} was loaded in the inferior process.
2842 For any @code{libthread_db} library @value{GDBN} finds in above directories,
2843 @value{GDBN} attempts to initialize it with the current inferior process.
2844 If this initialization fails (which could happen because of a version
2845 mismatch between @code{libthread_db} and @code{libpthread}), @value{GDBN}
2846 will unload @code{libthread_db}, and continue with the next directory.
2847 If none of @code{libthread_db} libraries initialize successfully,
2848 @value{GDBN} will issue a warning and thread debugging will be disabled.
2850 Setting @code{libthread-db-search-path} is currently implemented
2851 only on some platforms.
2853 @kindex show libthread-db-search-path
2854 @item show libthread-db-search-path
2855 Display current libthread_db search path.
2859 @section Debugging Forks
2861 @cindex fork, debugging programs which call
2862 @cindex multiple processes
2863 @cindex processes, multiple
2864 On most systems, @value{GDBN} has no special support for debugging
2865 programs which create additional processes using the @code{fork}
2866 function. When a program forks, @value{GDBN} will continue to debug the
2867 parent process and the child process will run unimpeded. If you have
2868 set a breakpoint in any code which the child then executes, the child
2869 will get a @code{SIGTRAP} signal which (unless it catches the signal)
2870 will cause it to terminate.
2872 However, if you want to debug the child process there is a workaround
2873 which isn't too painful. Put a call to @code{sleep} in the code which
2874 the child process executes after the fork. It may be useful to sleep
2875 only if a certain environment variable is set, or a certain file exists,
2876 so that the delay need not occur when you don't want to run @value{GDBN}
2877 on the child. While the child is sleeping, use the @code{ps} program to
2878 get its process ID. Then tell @value{GDBN} (a new invocation of
2879 @value{GDBN} if you are also debugging the parent process) to attach to
2880 the child process (@pxref{Attach}). From that point on you can debug
2881 the child process just like any other process which you attached to.
2883 On some systems, @value{GDBN} provides support for debugging programs that
2884 create additional processes using the @code{fork} or @code{vfork} functions.
2885 Currently, the only platforms with this feature are HP-UX (11.x and later
2886 only?) and @sc{gnu}/Linux (kernel version 2.5.60 and later).
2888 By default, when a program forks, @value{GDBN} will continue to debug
2889 the parent process and the child process will run unimpeded.
2891 If you want to follow the child process instead of the parent process,
2892 use the command @w{@code{set follow-fork-mode}}.
2895 @kindex set follow-fork-mode
2896 @item set follow-fork-mode @var{mode}
2897 Set the debugger response to a program call of @code{fork} or
2898 @code{vfork}. A call to @code{fork} or @code{vfork} creates a new
2899 process. The @var{mode} argument can be:
2903 The original process is debugged after a fork. The child process runs
2904 unimpeded. This is the default.
2907 The new process is debugged after a fork. The parent process runs
2912 @kindex show follow-fork-mode
2913 @item show follow-fork-mode
2914 Display the current debugger response to a @code{fork} or @code{vfork} call.
2917 @cindex debugging multiple processes
2918 On Linux, if you want to debug both the parent and child processes, use the
2919 command @w{@code{set detach-on-fork}}.
2922 @kindex set detach-on-fork
2923 @item set detach-on-fork @var{mode}
2924 Tells gdb whether to detach one of the processes after a fork, or
2925 retain debugger control over them both.
2929 The child process (or parent process, depending on the value of
2930 @code{follow-fork-mode}) will be detached and allowed to run
2931 independently. This is the default.
2934 Both processes will be held under the control of @value{GDBN}.
2935 One process (child or parent, depending on the value of
2936 @code{follow-fork-mode}) is debugged as usual, while the other
2941 @kindex show detach-on-fork
2942 @item show detach-on-fork
2943 Show whether detach-on-fork mode is on/off.
2946 If you choose to set @samp{detach-on-fork} mode off, then @value{GDBN}
2947 will retain control of all forked processes (including nested forks).
2948 You can list the forked processes under the control of @value{GDBN} by
2949 using the @w{@code{info inferiors}} command, and switch from one fork
2950 to another by using the @code{inferior} command (@pxref{Inferiors and
2951 Programs, ,Debugging Multiple Inferiors and Programs}).
2953 To quit debugging one of the forked processes, you can either detach
2954 from it by using the @w{@code{detach inferior}} command (allowing it
2955 to run independently), or kill it using the @w{@code{kill inferior}}
2956 command. @xref{Inferiors and Programs, ,Debugging Multiple Inferiors
2959 If you ask to debug a child process and a @code{vfork} is followed by an
2960 @code{exec}, @value{GDBN} executes the new target up to the first
2961 breakpoint in the new target. If you have a breakpoint set on
2962 @code{main} in your original program, the breakpoint will also be set on
2963 the child process's @code{main}.
2965 On some systems, when a child process is spawned by @code{vfork}, you
2966 cannot debug the child or parent until an @code{exec} call completes.
2968 If you issue a @code{run} command to @value{GDBN} after an @code{exec}
2969 call executes, the new target restarts. To restart the parent
2970 process, use the @code{file} command with the parent executable name
2971 as its argument. By default, after an @code{exec} call executes,
2972 @value{GDBN} discards the symbols of the previous executable image.
2973 You can change this behaviour with the @w{@code{set follow-exec-mode}}
2977 @kindex set follow-exec-mode
2978 @item set follow-exec-mode @var{mode}
2980 Set debugger response to a program call of @code{exec}. An
2981 @code{exec} call replaces the program image of a process.
2983 @code{follow-exec-mode} can be:
2987 @value{GDBN} creates a new inferior and rebinds the process to this
2988 new inferior. The program the process was running before the
2989 @code{exec} call can be restarted afterwards by restarting the
2995 (@value{GDBP}) info inferiors
2997 Id Description Executable
3000 process 12020 is executing new program: prog2
3001 Program exited normally.
3002 (@value{GDBP}) info inferiors
3003 Id Description Executable
3009 @value{GDBN} keeps the process bound to the same inferior. The new
3010 executable image replaces the previous executable loaded in the
3011 inferior. Restarting the inferior after the @code{exec} call, with
3012 e.g., the @code{run} command, restarts the executable the process was
3013 running after the @code{exec} call. This is the default mode.
3018 (@value{GDBP}) info inferiors
3019 Id Description Executable
3022 process 12020 is executing new program: prog2
3023 Program exited normally.
3024 (@value{GDBP}) info inferiors
3025 Id Description Executable
3032 You can use the @code{catch} command to make @value{GDBN} stop whenever
3033 a @code{fork}, @code{vfork}, or @code{exec} call is made. @xref{Set
3034 Catchpoints, ,Setting Catchpoints}.
3036 @node Checkpoint/Restart
3037 @section Setting a @emph{Bookmark} to Return to Later
3042 @cindex snapshot of a process
3043 @cindex rewind program state
3045 On certain operating systems@footnote{Currently, only
3046 @sc{gnu}/Linux.}, @value{GDBN} is able to save a @dfn{snapshot} of a
3047 program's state, called a @dfn{checkpoint}, and come back to it
3050 Returning to a checkpoint effectively undoes everything that has
3051 happened in the program since the @code{checkpoint} was saved. This
3052 includes changes in memory, registers, and even (within some limits)
3053 system state. Effectively, it is like going back in time to the
3054 moment when the checkpoint was saved.
3056 Thus, if you're stepping thru a program and you think you're
3057 getting close to the point where things go wrong, you can save
3058 a checkpoint. Then, if you accidentally go too far and miss
3059 the critical statement, instead of having to restart your program
3060 from the beginning, you can just go back to the checkpoint and
3061 start again from there.
3063 This can be especially useful if it takes a lot of time or
3064 steps to reach the point where you think the bug occurs.
3066 To use the @code{checkpoint}/@code{restart} method of debugging:
3071 Save a snapshot of the debugged program's current execution state.
3072 The @code{checkpoint} command takes no arguments, but each checkpoint
3073 is assigned a small integer id, similar to a breakpoint id.
3075 @kindex info checkpoints
3076 @item info checkpoints
3077 List the checkpoints that have been saved in the current debugging
3078 session. For each checkpoint, the following information will be
3085 @item Source line, or label
3088 @kindex restart @var{checkpoint-id}
3089 @item restart @var{checkpoint-id}
3090 Restore the program state that was saved as checkpoint number
3091 @var{checkpoint-id}. All program variables, registers, stack frames
3092 etc.@: will be returned to the values that they had when the checkpoint
3093 was saved. In essence, gdb will ``wind back the clock'' to the point
3094 in time when the checkpoint was saved.
3096 Note that breakpoints, @value{GDBN} variables, command history etc.
3097 are not affected by restoring a checkpoint. In general, a checkpoint
3098 only restores things that reside in the program being debugged, not in
3101 @kindex delete checkpoint @var{checkpoint-id}
3102 @item delete checkpoint @var{checkpoint-id}
3103 Delete the previously-saved checkpoint identified by @var{checkpoint-id}.
3107 Returning to a previously saved checkpoint will restore the user state
3108 of the program being debugged, plus a significant subset of the system
3109 (OS) state, including file pointers. It won't ``un-write'' data from
3110 a file, but it will rewind the file pointer to the previous location,
3111 so that the previously written data can be overwritten. For files
3112 opened in read mode, the pointer will also be restored so that the
3113 previously read data can be read again.
3115 Of course, characters that have been sent to a printer (or other
3116 external device) cannot be ``snatched back'', and characters received
3117 from eg.@: a serial device can be removed from internal program buffers,
3118 but they cannot be ``pushed back'' into the serial pipeline, ready to
3119 be received again. Similarly, the actual contents of files that have
3120 been changed cannot be restored (at this time).
3122 However, within those constraints, you actually can ``rewind'' your
3123 program to a previously saved point in time, and begin debugging it
3124 again --- and you can change the course of events so as to debug a
3125 different execution path this time.
3127 @cindex checkpoints and process id
3128 Finally, there is one bit of internal program state that will be
3129 different when you return to a checkpoint --- the program's process
3130 id. Each checkpoint will have a unique process id (or @var{pid}),
3131 and each will be different from the program's original @var{pid}.
3132 If your program has saved a local copy of its process id, this could
3133 potentially pose a problem.
3135 @subsection A Non-obvious Benefit of Using Checkpoints
3137 On some systems such as @sc{gnu}/Linux, address space randomization
3138 is performed on new processes for security reasons. This makes it
3139 difficult or impossible to set a breakpoint, or watchpoint, on an
3140 absolute address if you have to restart the program, since the
3141 absolute location of a symbol will change from one execution to the
3144 A checkpoint, however, is an @emph{identical} copy of a process.
3145 Therefore if you create a checkpoint at (eg.@:) the start of main,
3146 and simply return to that checkpoint instead of restarting the
3147 process, you can avoid the effects of address randomization and
3148 your symbols will all stay in the same place.
3151 @chapter Stopping and Continuing
3153 The principal purposes of using a debugger are so that you can stop your
3154 program before it terminates; or so that, if your program runs into
3155 trouble, you can investigate and find out why.
3157 Inside @value{GDBN}, your program may stop for any of several reasons,
3158 such as a signal, a breakpoint, or reaching a new line after a
3159 @value{GDBN} command such as @code{step}. You may then examine and
3160 change variables, set new breakpoints or remove old ones, and then
3161 continue execution. Usually, the messages shown by @value{GDBN} provide
3162 ample explanation of the status of your program---but you can also
3163 explicitly request this information at any time.
3166 @kindex info program
3168 Display information about the status of your program: whether it is
3169 running or not, what process it is, and why it stopped.
3173 * Breakpoints:: Breakpoints, watchpoints, and catchpoints
3174 * Continuing and Stepping:: Resuming execution
3176 * Thread Stops:: Stopping and starting multi-thread programs
3180 @section Breakpoints, Watchpoints, and Catchpoints
3183 A @dfn{breakpoint} makes your program stop whenever a certain point in
3184 the program is reached. For each breakpoint, you can add conditions to
3185 control in finer detail whether your program stops. You can set
3186 breakpoints with the @code{break} command and its variants (@pxref{Set
3187 Breaks, ,Setting Breakpoints}), to specify the place where your program
3188 should stop by line number, function name or exact address in the
3191 On some systems, you can set breakpoints in shared libraries before
3192 the executable is run. There is a minor limitation on HP-UX systems:
3193 you must wait until the executable is run in order to set breakpoints
3194 in shared library routines that are not called directly by the program
3195 (for example, routines that are arguments in a @code{pthread_create}
3199 @cindex data breakpoints
3200 @cindex memory tracing
3201 @cindex breakpoint on memory address
3202 @cindex breakpoint on variable modification
3203 A @dfn{watchpoint} is a special breakpoint that stops your program
3204 when the value of an expression changes. The expression may be a value
3205 of a variable, or it could involve values of one or more variables
3206 combined by operators, such as @samp{a + b}. This is sometimes called
3207 @dfn{data breakpoints}. You must use a different command to set
3208 watchpoints (@pxref{Set Watchpoints, ,Setting Watchpoints}), but aside
3209 from that, you can manage a watchpoint like any other breakpoint: you
3210 enable, disable, and delete both breakpoints and watchpoints using the
3213 You can arrange to have values from your program displayed automatically
3214 whenever @value{GDBN} stops at a breakpoint. @xref{Auto Display,,
3218 @cindex breakpoint on events
3219 A @dfn{catchpoint} is another special breakpoint that stops your program
3220 when a certain kind of event occurs, such as the throwing of a C@t{++}
3221 exception or the loading of a library. As with watchpoints, you use a
3222 different command to set a catchpoint (@pxref{Set Catchpoints, ,Setting
3223 Catchpoints}), but aside from that, you can manage a catchpoint like any
3224 other breakpoint. (To stop when your program receives a signal, use the
3225 @code{handle} command; see @ref{Signals, ,Signals}.)
3227 @cindex breakpoint numbers
3228 @cindex numbers for breakpoints
3229 @value{GDBN} assigns a number to each breakpoint, watchpoint, or
3230 catchpoint when you create it; these numbers are successive integers
3231 starting with one. In many of the commands for controlling various
3232 features of breakpoints you use the breakpoint number to say which
3233 breakpoint you want to change. Each breakpoint may be @dfn{enabled} or
3234 @dfn{disabled}; if disabled, it has no effect on your program until you
3237 @cindex breakpoint ranges
3238 @cindex ranges of breakpoints
3239 Some @value{GDBN} commands accept a range of breakpoints on which to
3240 operate. A breakpoint range is either a single breakpoint number, like
3241 @samp{5}, or two such numbers, in increasing order, separated by a
3242 hyphen, like @samp{5-7}. When a breakpoint range is given to a command,
3243 all breakpoints in that range are operated on.
3246 * Set Breaks:: Setting breakpoints
3247 * Set Watchpoints:: Setting watchpoints
3248 * Set Catchpoints:: Setting catchpoints
3249 * Delete Breaks:: Deleting breakpoints
3250 * Disabling:: Disabling breakpoints
3251 * Conditions:: Break conditions
3252 * Break Commands:: Breakpoint command lists
3253 * Save Breakpoints:: How to save breakpoints in a file
3254 * Error in Breakpoints:: ``Cannot insert breakpoints''
3255 * Breakpoint-related Warnings:: ``Breakpoint address adjusted...''
3259 @subsection Setting Breakpoints
3261 @c FIXME LMB what does GDB do if no code on line of breakpt?
3262 @c consider in particular declaration with/without initialization.
3264 @c FIXME 2 is there stuff on this already? break at fun start, already init?
3267 @kindex b @r{(@code{break})}
3268 @vindex $bpnum@r{, convenience variable}
3269 @cindex latest breakpoint
3270 Breakpoints are set with the @code{break} command (abbreviated
3271 @code{b}). The debugger convenience variable @samp{$bpnum} records the
3272 number of the breakpoint you've set most recently; see @ref{Convenience
3273 Vars,, Convenience Variables}, for a discussion of what you can do with
3274 convenience variables.
3277 @item break @var{location}
3278 Set a breakpoint at the given @var{location}, which can specify a
3279 function name, a line number, or an address of an instruction.
3280 (@xref{Specify Location}, for a list of all the possible ways to
3281 specify a @var{location}.) The breakpoint will stop your program just
3282 before it executes any of the code in the specified @var{location}.
3284 When using source languages that permit overloading of symbols, such as
3285 C@t{++}, a function name may refer to more than one possible place to break.
3286 @xref{Ambiguous Expressions,,Ambiguous Expressions}, for a discussion of
3289 It is also possible to insert a breakpoint that will stop the program
3290 only if a specific thread (@pxref{Thread-Specific Breakpoints})
3291 or a specific task (@pxref{Ada Tasks}) hits that breakpoint.
3294 When called without any arguments, @code{break} sets a breakpoint at
3295 the next instruction to be executed in the selected stack frame
3296 (@pxref{Stack, ,Examining the Stack}). In any selected frame but the
3297 innermost, this makes your program stop as soon as control
3298 returns to that frame. This is similar to the effect of a
3299 @code{finish} command in the frame inside the selected frame---except
3300 that @code{finish} does not leave an active breakpoint. If you use
3301 @code{break} without an argument in the innermost frame, @value{GDBN} stops
3302 the next time it reaches the current location; this may be useful
3305 @value{GDBN} normally ignores breakpoints when it resumes execution, until at
3306 least one instruction has been executed. If it did not do this, you
3307 would be unable to proceed past a breakpoint without first disabling the
3308 breakpoint. This rule applies whether or not the breakpoint already
3309 existed when your program stopped.
3311 @item break @dots{} if @var{cond}
3312 Set a breakpoint with condition @var{cond}; evaluate the expression
3313 @var{cond} each time the breakpoint is reached, and stop only if the
3314 value is nonzero---that is, if @var{cond} evaluates as true.
3315 @samp{@dots{}} stands for one of the possible arguments described
3316 above (or no argument) specifying where to break. @xref{Conditions,
3317 ,Break Conditions}, for more information on breakpoint conditions.
3320 @item tbreak @var{args}
3321 Set a breakpoint enabled only for one stop. @var{args} are the
3322 same as for the @code{break} command, and the breakpoint is set in the same
3323 way, but the breakpoint is automatically deleted after the first time your
3324 program stops there. @xref{Disabling, ,Disabling Breakpoints}.
3327 @cindex hardware breakpoints
3328 @item hbreak @var{args}
3329 Set a hardware-assisted breakpoint. @var{args} are the same as for the
3330 @code{break} command and the breakpoint is set in the same way, but the
3331 breakpoint requires hardware support and some target hardware may not
3332 have this support. The main purpose of this is EPROM/ROM code
3333 debugging, so you can set a breakpoint at an instruction without
3334 changing the instruction. This can be used with the new trap-generation
3335 provided by SPARClite DSU and most x86-based targets. These targets
3336 will generate traps when a program accesses some data or instruction
3337 address that is assigned to the debug registers. However the hardware
3338 breakpoint registers can take a limited number of breakpoints. For
3339 example, on the DSU, only two data breakpoints can be set at a time, and
3340 @value{GDBN} will reject this command if more than two are used. Delete
3341 or disable unused hardware breakpoints before setting new ones
3342 (@pxref{Disabling, ,Disabling Breakpoints}).
3343 @xref{Conditions, ,Break Conditions}.
3344 For remote targets, you can restrict the number of hardware
3345 breakpoints @value{GDBN} will use, see @ref{set remote
3346 hardware-breakpoint-limit}.
3349 @item thbreak @var{args}
3350 Set a hardware-assisted breakpoint enabled only for one stop. @var{args}
3351 are the same as for the @code{hbreak} command and the breakpoint is set in
3352 the same way. However, like the @code{tbreak} command,
3353 the breakpoint is automatically deleted after the
3354 first time your program stops there. Also, like the @code{hbreak}
3355 command, the breakpoint requires hardware support and some target hardware
3356 may not have this support. @xref{Disabling, ,Disabling Breakpoints}.
3357 See also @ref{Conditions, ,Break Conditions}.
3360 @cindex regular expression
3361 @cindex breakpoints at functions matching a regexp
3362 @cindex set breakpoints in many functions
3363 @item rbreak @var{regex}
3364 Set breakpoints on all functions matching the regular expression
3365 @var{regex}. This command sets an unconditional breakpoint on all
3366 matches, printing a list of all breakpoints it set. Once these
3367 breakpoints are set, they are treated just like the breakpoints set with
3368 the @code{break} command. You can delete them, disable them, or make
3369 them conditional the same way as any other breakpoint.
3371 The syntax of the regular expression is the standard one used with tools
3372 like @file{grep}. Note that this is different from the syntax used by
3373 shells, so for instance @code{foo*} matches all functions that include
3374 an @code{fo} followed by zero or more @code{o}s. There is an implicit
3375 @code{.*} leading and trailing the regular expression you supply, so to
3376 match only functions that begin with @code{foo}, use @code{^foo}.
3378 @cindex non-member C@t{++} functions, set breakpoint in
3379 When debugging C@t{++} programs, @code{rbreak} is useful for setting
3380 breakpoints on overloaded functions that are not members of any special
3383 @cindex set breakpoints on all functions
3384 The @code{rbreak} command can be used to set breakpoints in
3385 @strong{all} the functions in a program, like this:
3388 (@value{GDBP}) rbreak .
3391 @item rbreak @var{file}:@var{regex}
3392 If @code{rbreak} is called with a filename qualification, it limits
3393 the search for functions matching the given regular expression to the
3394 specified @var{file}. This can be used, for example, to set breakpoints on
3395 every function in a given file:
3398 (@value{GDBP}) rbreak file.c:.
3401 The colon separating the filename qualifier from the regex may
3402 optionally be surrounded by spaces.
3404 @kindex info breakpoints
3405 @cindex @code{$_} and @code{info breakpoints}
3406 @item info breakpoints @r{[}@var{n}@r{]}
3407 @itemx info break @r{[}@var{n}@r{]}
3408 Print a table of all breakpoints, watchpoints, and catchpoints set and
3409 not deleted. Optional argument @var{n} means print information only
3410 about the specified breakpoint (or watchpoint or catchpoint). For
3411 each breakpoint, following columns are printed:
3414 @item Breakpoint Numbers
3416 Breakpoint, watchpoint, or catchpoint.
3418 Whether the breakpoint is marked to be disabled or deleted when hit.
3419 @item Enabled or Disabled
3420 Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints
3421 that are not enabled.
3423 Where the breakpoint is in your program, as a memory address. For a
3424 pending breakpoint whose address is not yet known, this field will
3425 contain @samp{<PENDING>}. Such breakpoint won't fire until a shared
3426 library that has the symbol or line referred by breakpoint is loaded.
3427 See below for details. A breakpoint with several locations will
3428 have @samp{<MULTIPLE>} in this field---see below for details.
3430 Where the breakpoint is in the source for your program, as a file and
3431 line number. For a pending breakpoint, the original string passed to
3432 the breakpoint command will be listed as it cannot be resolved until
3433 the appropriate shared library is loaded in the future.
3437 If a breakpoint is conditional, @code{info break} shows the condition on
3438 the line following the affected breakpoint; breakpoint commands, if any,
3439 are listed after that. A pending breakpoint is allowed to have a condition
3440 specified for it. The condition is not parsed for validity until a shared
3441 library is loaded that allows the pending breakpoint to resolve to a
3445 @code{info break} with a breakpoint
3446 number @var{n} as argument lists only that breakpoint. The
3447 convenience variable @code{$_} and the default examining-address for
3448 the @code{x} command are set to the address of the last breakpoint
3449 listed (@pxref{Memory, ,Examining Memory}).
3452 @code{info break} displays a count of the number of times the breakpoint
3453 has been hit. This is especially useful in conjunction with the
3454 @code{ignore} command. You can ignore a large number of breakpoint
3455 hits, look at the breakpoint info to see how many times the breakpoint
3456 was hit, and then run again, ignoring one less than that number. This
3457 will get you quickly to the last hit of that breakpoint.
3460 @value{GDBN} allows you to set any number of breakpoints at the same place in
3461 your program. There is nothing silly or meaningless about this. When
3462 the breakpoints are conditional, this is even useful
3463 (@pxref{Conditions, ,Break Conditions}).
3465 @cindex multiple locations, breakpoints
3466 @cindex breakpoints, multiple locations
3467 It is possible that a breakpoint corresponds to several locations
3468 in your program. Examples of this situation are:
3472 For a C@t{++} constructor, the @value{NGCC} compiler generates several
3473 instances of the function body, used in different cases.
3476 For a C@t{++} template function, a given line in the function can
3477 correspond to any number of instantiations.
3480 For an inlined function, a given source line can correspond to
3481 several places where that function is inlined.
3484 In all those cases, @value{GDBN} will insert a breakpoint at all
3485 the relevant locations@footnote{
3486 As of this writing, multiple-location breakpoints work only if there's
3487 line number information for all the locations. This means that they
3488 will generally not work in system libraries, unless you have debug
3489 info with line numbers for them.}.
3491 A breakpoint with multiple locations is displayed in the breakpoint
3492 table using several rows---one header row, followed by one row for
3493 each breakpoint location. The header row has @samp{<MULTIPLE>} in the
3494 address column. The rows for individual locations contain the actual
3495 addresses for locations, and show the functions to which those
3496 locations belong. The number column for a location is of the form
3497 @var{breakpoint-number}.@var{location-number}.
3502 Num Type Disp Enb Address What
3503 1 breakpoint keep y <MULTIPLE>
3505 breakpoint already hit 1 time
3506 1.1 y 0x080486a2 in void foo<int>() at t.cc:8
3507 1.2 y 0x080486ca in void foo<double>() at t.cc:8
3510 Each location can be individually enabled or disabled by passing
3511 @var{breakpoint-number}.@var{location-number} as argument to the
3512 @code{enable} and @code{disable} commands. Note that you cannot
3513 delete the individual locations from the list, you can only delete the
3514 entire list of locations that belong to their parent breakpoint (with
3515 the @kbd{delete @var{num}} command, where @var{num} is the number of
3516 the parent breakpoint, 1 in the above example). Disabling or enabling
3517 the parent breakpoint (@pxref{Disabling}) affects all of the locations
3518 that belong to that breakpoint.
3520 @cindex pending breakpoints
3521 It's quite common to have a breakpoint inside a shared library.
3522 Shared libraries can be loaded and unloaded explicitly,
3523 and possibly repeatedly, as the program is executed. To support
3524 this use case, @value{GDBN} updates breakpoint locations whenever
3525 any shared library is loaded or unloaded. Typically, you would
3526 set a breakpoint in a shared library at the beginning of your
3527 debugging session, when the library is not loaded, and when the
3528 symbols from the library are not available. When you try to set
3529 breakpoint, @value{GDBN} will ask you if you want to set
3530 a so called @dfn{pending breakpoint}---breakpoint whose address
3531 is not yet resolved.
3533 After the program is run, whenever a new shared library is loaded,
3534 @value{GDBN} reevaluates all the breakpoints. When a newly loaded
3535 shared library contains the symbol or line referred to by some
3536 pending breakpoint, that breakpoint is resolved and becomes an
3537 ordinary breakpoint. When a library is unloaded, all breakpoints
3538 that refer to its symbols or source lines become pending again.
3540 This logic works for breakpoints with multiple locations, too. For
3541 example, if you have a breakpoint in a C@t{++} template function, and
3542 a newly loaded shared library has an instantiation of that template,
3543 a new location is added to the list of locations for the breakpoint.
3545 Except for having unresolved address, pending breakpoints do not
3546 differ from regular breakpoints. You can set conditions or commands,
3547 enable and disable them and perform other breakpoint operations.
3549 @value{GDBN} provides some additional commands for controlling what
3550 happens when the @samp{break} command cannot resolve breakpoint
3551 address specification to an address:
3553 @kindex set breakpoint pending
3554 @kindex show breakpoint pending
3556 @item set breakpoint pending auto
3557 This is the default behavior. When @value{GDBN} cannot find the breakpoint
3558 location, it queries you whether a pending breakpoint should be created.
3560 @item set breakpoint pending on
3561 This indicates that an unrecognized breakpoint location should automatically
3562 result in a pending breakpoint being created.
3564 @item set breakpoint pending off
3565 This indicates that pending breakpoints are not to be created. Any
3566 unrecognized breakpoint location results in an error. This setting does
3567 not affect any pending breakpoints previously created.
3569 @item show breakpoint pending
3570 Show the current behavior setting for creating pending breakpoints.
3573 The settings above only affect the @code{break} command and its
3574 variants. Once breakpoint is set, it will be automatically updated
3575 as shared libraries are loaded and unloaded.
3577 @cindex automatic hardware breakpoints
3578 For some targets, @value{GDBN} can automatically decide if hardware or
3579 software breakpoints should be used, depending on whether the
3580 breakpoint address is read-only or read-write. This applies to
3581 breakpoints set with the @code{break} command as well as to internal
3582 breakpoints set by commands like @code{next} and @code{finish}. For
3583 breakpoints set with @code{hbreak}, @value{GDBN} will always use hardware
3586 You can control this automatic behaviour with the following commands::
3588 @kindex set breakpoint auto-hw
3589 @kindex show breakpoint auto-hw
3591 @item set breakpoint auto-hw on
3592 This is the default behavior. When @value{GDBN} sets a breakpoint, it
3593 will try to use the target memory map to decide if software or hardware
3594 breakpoint must be used.
3596 @item set breakpoint auto-hw off
3597 This indicates @value{GDBN} should not automatically select breakpoint
3598 type. If the target provides a memory map, @value{GDBN} will warn when
3599 trying to set software breakpoint at a read-only address.
3602 @value{GDBN} normally implements breakpoints by replacing the program code
3603 at the breakpoint address with a special instruction, which, when
3604 executed, given control to the debugger. By default, the program
3605 code is so modified only when the program is resumed. As soon as
3606 the program stops, @value{GDBN} restores the original instructions. This
3607 behaviour guards against leaving breakpoints inserted in the
3608 target should gdb abrubptly disconnect. However, with slow remote
3609 targets, inserting and removing breakpoint can reduce the performance.
3610 This behavior can be controlled with the following commands::
3612 @kindex set breakpoint always-inserted
3613 @kindex show breakpoint always-inserted
3615 @item set breakpoint always-inserted off
3616 All breakpoints, including newly added by the user, are inserted in
3617 the target only when the target is resumed. All breakpoints are
3618 removed from the target when it stops.
3620 @item set breakpoint always-inserted on
3621 Causes all breakpoints to be inserted in the target at all times. If
3622 the user adds a new breakpoint, or changes an existing breakpoint, the
3623 breakpoints in the target are updated immediately. A breakpoint is
3624 removed from the target only when breakpoint itself is removed.
3626 @cindex non-stop mode, and @code{breakpoint always-inserted}
3627 @item set breakpoint always-inserted auto
3628 This is the default mode. If @value{GDBN} is controlling the inferior
3629 in non-stop mode (@pxref{Non-Stop Mode}), gdb behaves as if
3630 @code{breakpoint always-inserted} mode is on. If @value{GDBN} is
3631 controlling the inferior in all-stop mode, @value{GDBN} behaves as if
3632 @code{breakpoint always-inserted} mode is off.
3635 @cindex negative breakpoint numbers
3636 @cindex internal @value{GDBN} breakpoints
3637 @value{GDBN} itself sometimes sets breakpoints in your program for
3638 special purposes, such as proper handling of @code{longjmp} (in C
3639 programs). These internal breakpoints are assigned negative numbers,
3640 starting with @code{-1}; @samp{info breakpoints} does not display them.
3641 You can see these breakpoints with the @value{GDBN} maintenance command
3642 @samp{maint info breakpoints} (@pxref{maint info breakpoints}).
3645 @node Set Watchpoints
3646 @subsection Setting Watchpoints
3648 @cindex setting watchpoints
3649 You can use a watchpoint to stop execution whenever the value of an
3650 expression changes, without having to predict a particular place where
3651 this may happen. (This is sometimes called a @dfn{data breakpoint}.)
3652 The expression may be as simple as the value of a single variable, or
3653 as complex as many variables combined by operators. Examples include:
3657 A reference to the value of a single variable.
3660 An address cast to an appropriate data type. For example,
3661 @samp{*(int *)0x12345678} will watch a 4-byte region at the specified
3662 address (assuming an @code{int} occupies 4 bytes).
3665 An arbitrarily complex expression, such as @samp{a*b + c/d}. The
3666 expression can use any operators valid in the program's native
3667 language (@pxref{Languages}).
3670 You can set a watchpoint on an expression even if the expression can
3671 not be evaluated yet. For instance, you can set a watchpoint on
3672 @samp{*global_ptr} before @samp{global_ptr} is initialized.
3673 @value{GDBN} will stop when your program sets @samp{global_ptr} and
3674 the expression produces a valid value. If the expression becomes
3675 valid in some other way than changing a variable (e.g.@: if the memory
3676 pointed to by @samp{*global_ptr} becomes readable as the result of a
3677 @code{malloc} call), @value{GDBN} may not stop until the next time
3678 the expression changes.
3680 @cindex software watchpoints
3681 @cindex hardware watchpoints
3682 Depending on your system, watchpoints may be implemented in software or
3683 hardware. @value{GDBN} does software watchpointing by single-stepping your
3684 program and testing the variable's value each time, which is hundreds of
3685 times slower than normal execution. (But this may still be worth it, to
3686 catch errors where you have no clue what part of your program is the
3689 On some systems, such as HP-UX, PowerPC, @sc{gnu}/Linux and most other
3690 x86-based targets, @value{GDBN} includes support for hardware
3691 watchpoints, which do not slow down the running of your program.
3695 @item watch @var{expr} @r{[}thread @var{threadnum}@r{]}
3696 Set a watchpoint for an expression. @value{GDBN} will break when the
3697 expression @var{expr} is written into by the program and its value
3698 changes. The simplest (and the most popular) use of this command is
3699 to watch the value of a single variable:
3702 (@value{GDBP}) watch foo
3705 If the command includes a @code{@r{[}thread @var{threadnum}@r{]}}
3706 clause, @value{GDBN} breaks only when the thread identified by
3707 @var{threadnum} changes the value of @var{expr}. If any other threads
3708 change the value of @var{expr}, @value{GDBN} will not break. Note
3709 that watchpoints restricted to a single thread in this way only work
3710 with Hardware Watchpoints.
3713 @item rwatch @var{expr} @r{[}thread @var{threadnum}@r{]}
3714 Set a watchpoint that will break when the value of @var{expr} is read
3718 @item awatch @var{expr} @r{[}thread @var{threadnum}@r{]}
3719 Set a watchpoint that will break when @var{expr} is either read from
3720 or written into by the program.
3722 @kindex info watchpoints @r{[}@var{n}@r{]}
3723 @item info watchpoints
3724 This command prints a list of watchpoints, using the same format as
3725 @code{info break} (@pxref{Set Breaks}).
3728 @value{GDBN} sets a @dfn{hardware watchpoint} if possible. Hardware
3729 watchpoints execute very quickly, and the debugger reports a change in
3730 value at the exact instruction where the change occurs. If @value{GDBN}
3731 cannot set a hardware watchpoint, it sets a software watchpoint, which
3732 executes more slowly and reports the change in value at the next
3733 @emph{statement}, not the instruction, after the change occurs.
3735 @cindex use only software watchpoints
3736 You can force @value{GDBN} to use only software watchpoints with the
3737 @kbd{set can-use-hw-watchpoints 0} command. With this variable set to
3738 zero, @value{GDBN} will never try to use hardware watchpoints, even if
3739 the underlying system supports them. (Note that hardware-assisted
3740 watchpoints that were set @emph{before} setting
3741 @code{can-use-hw-watchpoints} to zero will still use the hardware
3742 mechanism of watching expression values.)
3745 @item set can-use-hw-watchpoints
3746 @kindex set can-use-hw-watchpoints
3747 Set whether or not to use hardware watchpoints.
3749 @item show can-use-hw-watchpoints
3750 @kindex show can-use-hw-watchpoints
3751 Show the current mode of using hardware watchpoints.
3754 For remote targets, you can restrict the number of hardware
3755 watchpoints @value{GDBN} will use, see @ref{set remote
3756 hardware-breakpoint-limit}.
3758 When you issue the @code{watch} command, @value{GDBN} reports
3761 Hardware watchpoint @var{num}: @var{expr}
3765 if it was able to set a hardware watchpoint.
3767 Currently, the @code{awatch} and @code{rwatch} commands can only set
3768 hardware watchpoints, because accesses to data that don't change the
3769 value of the watched expression cannot be detected without examining
3770 every instruction as it is being executed, and @value{GDBN} does not do
3771 that currently. If @value{GDBN} finds that it is unable to set a
3772 hardware breakpoint with the @code{awatch} or @code{rwatch} command, it
3773 will print a message like this:
3776 Expression cannot be implemented with read/access watchpoint.
3779 Sometimes, @value{GDBN} cannot set a hardware watchpoint because the
3780 data type of the watched expression is wider than what a hardware
3781 watchpoint on the target machine can handle. For example, some systems
3782 can only watch regions that are up to 4 bytes wide; on such systems you
3783 cannot set hardware watchpoints for an expression that yields a
3784 double-precision floating-point number (which is typically 8 bytes
3785 wide). As a work-around, it might be possible to break the large region
3786 into a series of smaller ones and watch them with separate watchpoints.
3788 If you set too many hardware watchpoints, @value{GDBN} might be unable
3789 to insert all of them when you resume the execution of your program.
3790 Since the precise number of active watchpoints is unknown until such
3791 time as the program is about to be resumed, @value{GDBN} might not be
3792 able to warn you about this when you set the watchpoints, and the
3793 warning will be printed only when the program is resumed:
3796 Hardware watchpoint @var{num}: Could not insert watchpoint
3800 If this happens, delete or disable some of the watchpoints.
3802 Watching complex expressions that reference many variables can also
3803 exhaust the resources available for hardware-assisted watchpoints.
3804 That's because @value{GDBN} needs to watch every variable in the
3805 expression with separately allocated resources.
3807 If you call a function interactively using @code{print} or @code{call},
3808 any watchpoints you have set will be inactive until @value{GDBN} reaches another
3809 kind of breakpoint or the call completes.
3811 @value{GDBN} automatically deletes watchpoints that watch local
3812 (automatic) variables, or expressions that involve such variables, when
3813 they go out of scope, that is, when the execution leaves the block in
3814 which these variables were defined. In particular, when the program
3815 being debugged terminates, @emph{all} local variables go out of scope,
3816 and so only watchpoints that watch global variables remain set. If you
3817 rerun the program, you will need to set all such watchpoints again. One
3818 way of doing that would be to set a code breakpoint at the entry to the
3819 @code{main} function and when it breaks, set all the watchpoints.
3821 @cindex watchpoints and threads
3822 @cindex threads and watchpoints
3823 In multi-threaded programs, watchpoints will detect changes to the
3824 watched expression from every thread.
3827 @emph{Warning:} In multi-threaded programs, software watchpoints
3828 have only limited usefulness. If @value{GDBN} creates a software
3829 watchpoint, it can only watch the value of an expression @emph{in a
3830 single thread}. If you are confident that the expression can only
3831 change due to the current thread's activity (and if you are also
3832 confident that no other thread can become current), then you can use
3833 software watchpoints as usual. However, @value{GDBN} may not notice
3834 when a non-current thread's activity changes the expression. (Hardware
3835 watchpoints, in contrast, watch an expression in all threads.)
3838 @xref{set remote hardware-watchpoint-limit}.
3840 @node Set Catchpoints
3841 @subsection Setting Catchpoints
3842 @cindex catchpoints, setting
3843 @cindex exception handlers
3844 @cindex event handling
3846 You can use @dfn{catchpoints} to cause the debugger to stop for certain
3847 kinds of program events, such as C@t{++} exceptions or the loading of a
3848 shared library. Use the @code{catch} command to set a catchpoint.
3852 @item catch @var{event}
3853 Stop when @var{event} occurs. @var{event} can be any of the following:
3856 @cindex stop on C@t{++} exceptions
3857 The throwing of a C@t{++} exception.
3860 The catching of a C@t{++} exception.
3863 @cindex Ada exception catching
3864 @cindex catch Ada exceptions
3865 An Ada exception being raised. If an exception name is specified
3866 at the end of the command (eg @code{catch exception Program_Error}),
3867 the debugger will stop only when this specific exception is raised.
3868 Otherwise, the debugger stops execution when any Ada exception is raised.
3870 When inserting an exception catchpoint on a user-defined exception whose
3871 name is identical to one of the exceptions defined by the language, the
3872 fully qualified name must be used as the exception name. Otherwise,
3873 @value{GDBN} will assume that it should stop on the pre-defined exception
3874 rather than the user-defined one. For instance, assuming an exception
3875 called @code{Constraint_Error} is defined in package @code{Pck}, then
3876 the command to use to catch such exceptions is @kbd{catch exception
3877 Pck.Constraint_Error}.
3879 @item exception unhandled
3880 An exception that was raised but is not handled by the program.
3883 A failed Ada assertion.
3886 @cindex break on fork/exec
3887 A call to @code{exec}. This is currently only available for HP-UX
3891 @itemx syscall @r{[}@var{name} @r{|} @var{number}@r{]} @dots{}
3892 @cindex break on a system call.
3893 A call to or return from a system call, a.k.a.@: @dfn{syscall}. A
3894 syscall is a mechanism for application programs to request a service
3895 from the operating system (OS) or one of the OS system services.
3896 @value{GDBN} can catch some or all of the syscalls issued by the
3897 debuggee, and show the related information for each syscall. If no
3898 argument is specified, calls to and returns from all system calls
3901 @var{name} can be any system call name that is valid for the
3902 underlying OS. Just what syscalls are valid depends on the OS. On
3903 GNU and Unix systems, you can find the full list of valid syscall
3904 names on @file{/usr/include/asm/unistd.h}.
3906 @c For MS-Windows, the syscall names and the corresponding numbers
3907 @c can be found, e.g., on this URL:
3908 @c http://www.metasploit.com/users/opcode/syscalls.html
3909 @c but we don't support Windows syscalls yet.
3911 Normally, @value{GDBN} knows in advance which syscalls are valid for
3912 each OS, so you can use the @value{GDBN} command-line completion
3913 facilities (@pxref{Completion,, command completion}) to list the
3916 You may also specify the system call numerically. A syscall's
3917 number is the value passed to the OS's syscall dispatcher to
3918 identify the requested service. When you specify the syscall by its
3919 name, @value{GDBN} uses its database of syscalls to convert the name
3920 into the corresponding numeric code, but using the number directly
3921 may be useful if @value{GDBN}'s database does not have the complete
3922 list of syscalls on your system (e.g., because @value{GDBN} lags
3923 behind the OS upgrades).
3925 The example below illustrates how this command works if you don't provide
3929 (@value{GDBP}) catch syscall
3930 Catchpoint 1 (syscall)
3932 Starting program: /tmp/catch-syscall
3934 Catchpoint 1 (call to syscall 'close'), \
3935 0xffffe424 in __kernel_vsyscall ()
3939 Catchpoint 1 (returned from syscall 'close'), \
3940 0xffffe424 in __kernel_vsyscall ()
3944 Here is an example of catching a system call by name:
3947 (@value{GDBP}) catch syscall chroot
3948 Catchpoint 1 (syscall 'chroot' [61])
3950 Starting program: /tmp/catch-syscall
3952 Catchpoint 1 (call to syscall 'chroot'), \
3953 0xffffe424 in __kernel_vsyscall ()
3957 Catchpoint 1 (returned from syscall 'chroot'), \
3958 0xffffe424 in __kernel_vsyscall ()
3962 An example of specifying a system call numerically. In the case
3963 below, the syscall number has a corresponding entry in the XML
3964 file, so @value{GDBN} finds its name and prints it:
3967 (@value{GDBP}) catch syscall 252
3968 Catchpoint 1 (syscall(s) 'exit_group')
3970 Starting program: /tmp/catch-syscall
3972 Catchpoint 1 (call to syscall 'exit_group'), \
3973 0xffffe424 in __kernel_vsyscall ()
3977 Program exited normally.
3981 However, there can be situations when there is no corresponding name
3982 in XML file for that syscall number. In this case, @value{GDBN} prints
3983 a warning message saying that it was not able to find the syscall name,
3984 but the catchpoint will be set anyway. See the example below:
3987 (@value{GDBP}) catch syscall 764
3988 warning: The number '764' does not represent a known syscall.
3989 Catchpoint 2 (syscall 764)
3993 If you configure @value{GDBN} using the @samp{--without-expat} option,
3994 it will not be able to display syscall names. Also, if your
3995 architecture does not have an XML file describing its system calls,
3996 you will not be able to see the syscall names. It is important to
3997 notice that these two features are used for accessing the syscall
3998 name database. In either case, you will see a warning like this:
4001 (@value{GDBP}) catch syscall
4002 warning: Could not open "syscalls/i386-linux.xml"
4003 warning: Could not load the syscall XML file 'syscalls/i386-linux.xml'.
4004 GDB will not be able to display syscall names.
4005 Catchpoint 1 (syscall)
4009 Of course, the file name will change depending on your architecture and system.
4011 Still using the example above, you can also try to catch a syscall by its
4012 number. In this case, you would see something like:
4015 (@value{GDBP}) catch syscall 252
4016 Catchpoint 1 (syscall(s) 252)
4019 Again, in this case @value{GDBN} would not be able to display syscall's names.
4022 A call to @code{fork}. This is currently only available for HP-UX
4026 A call to @code{vfork}. This is currently only available for HP-UX
4031 @item tcatch @var{event}
4032 Set a catchpoint that is enabled only for one stop. The catchpoint is
4033 automatically deleted after the first time the event is caught.
4037 Use the @code{info break} command to list the current catchpoints.
4039 There are currently some limitations to C@t{++} exception handling
4040 (@code{catch throw} and @code{catch catch}) in @value{GDBN}:
4044 If you call a function interactively, @value{GDBN} normally returns
4045 control to you when the function has finished executing. If the call
4046 raises an exception, however, the call may bypass the mechanism that
4047 returns control to you and cause your program either to abort or to
4048 simply continue running until it hits a breakpoint, catches a signal
4049 that @value{GDBN} is listening for, or exits. This is the case even if
4050 you set a catchpoint for the exception; catchpoints on exceptions are
4051 disabled within interactive calls.
4054 You cannot raise an exception interactively.
4057 You cannot install an exception handler interactively.
4060 @cindex raise exceptions
4061 Sometimes @code{catch} is not the best way to debug exception handling:
4062 if you need to know exactly where an exception is raised, it is better to
4063 stop @emph{before} the exception handler is called, since that way you
4064 can see the stack before any unwinding takes place. If you set a
4065 breakpoint in an exception handler instead, it may not be easy to find
4066 out where the exception was raised.
4068 To stop just before an exception handler is called, you need some
4069 knowledge of the implementation. In the case of @sc{gnu} C@t{++}, exceptions are
4070 raised by calling a library function named @code{__raise_exception}
4071 which has the following ANSI C interface:
4074 /* @var{addr} is where the exception identifier is stored.
4075 @var{id} is the exception identifier. */
4076 void __raise_exception (void **addr, void *id);
4080 To make the debugger catch all exceptions before any stack
4081 unwinding takes place, set a breakpoint on @code{__raise_exception}
4082 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Exceptions}).
4084 With a conditional breakpoint (@pxref{Conditions, ,Break Conditions})
4085 that depends on the value of @var{id}, you can stop your program when
4086 a specific exception is raised. You can use multiple conditional
4087 breakpoints to stop your program when any of a number of exceptions are
4092 @subsection Deleting Breakpoints
4094 @cindex clearing breakpoints, watchpoints, catchpoints
4095 @cindex deleting breakpoints, watchpoints, catchpoints
4096 It is often necessary to eliminate a breakpoint, watchpoint, or
4097 catchpoint once it has done its job and you no longer want your program
4098 to stop there. This is called @dfn{deleting} the breakpoint. A
4099 breakpoint that has been deleted no longer exists; it is forgotten.
4101 With the @code{clear} command you can delete breakpoints according to
4102 where they are in your program. With the @code{delete} command you can
4103 delete individual breakpoints, watchpoints, or catchpoints by specifying
4104 their breakpoint numbers.
4106 It is not necessary to delete a breakpoint to proceed past it. @value{GDBN}
4107 automatically ignores breakpoints on the first instruction to be executed
4108 when you continue execution without changing the execution address.
4113 Delete any breakpoints at the next instruction to be executed in the
4114 selected stack frame (@pxref{Selection, ,Selecting a Frame}). When
4115 the innermost frame is selected, this is a good way to delete a
4116 breakpoint where your program just stopped.
4118 @item clear @var{location}
4119 Delete any breakpoints set at the specified @var{location}.
4120 @xref{Specify Location}, for the various forms of @var{location}; the
4121 most useful ones are listed below:
4124 @item clear @var{function}
4125 @itemx clear @var{filename}:@var{function}
4126 Delete any breakpoints set at entry to the named @var{function}.
4128 @item clear @var{linenum}
4129 @itemx clear @var{filename}:@var{linenum}
4130 Delete any breakpoints set at or within the code of the specified
4131 @var{linenum} of the specified @var{filename}.
4134 @cindex delete breakpoints
4136 @kindex d @r{(@code{delete})}
4137 @item delete @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4138 Delete the breakpoints, watchpoints, or catchpoints of the breakpoint
4139 ranges specified as arguments. If no argument is specified, delete all
4140 breakpoints (@value{GDBN} asks confirmation, unless you have @code{set
4141 confirm off}). You can abbreviate this command as @code{d}.
4145 @subsection Disabling Breakpoints
4147 @cindex enable/disable a breakpoint
4148 Rather than deleting a breakpoint, watchpoint, or catchpoint, you might
4149 prefer to @dfn{disable} it. This makes the breakpoint inoperative as if
4150 it had been deleted, but remembers the information on the breakpoint so
4151 that you can @dfn{enable} it again later.
4153 You disable and enable breakpoints, watchpoints, and catchpoints with
4154 the @code{enable} and @code{disable} commands, optionally specifying
4155 one or more breakpoint numbers as arguments. Use @code{info break} to
4156 print a list of all breakpoints, watchpoints, and catchpoints if you
4157 do not know which numbers to use.
4159 Disabling and enabling a breakpoint that has multiple locations
4160 affects all of its locations.
4162 A breakpoint, watchpoint, or catchpoint can have any of four different
4163 states of enablement:
4167 Enabled. The breakpoint stops your program. A breakpoint set
4168 with the @code{break} command starts out in this state.
4170 Disabled. The breakpoint has no effect on your program.
4172 Enabled once. The breakpoint stops your program, but then becomes
4175 Enabled for deletion. The breakpoint stops your program, but
4176 immediately after it does so it is deleted permanently. A breakpoint
4177 set with the @code{tbreak} command starts out in this state.
4180 You can use the following commands to enable or disable breakpoints,
4181 watchpoints, and catchpoints:
4185 @kindex dis @r{(@code{disable})}
4186 @item disable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4187 Disable the specified breakpoints---or all breakpoints, if none are
4188 listed. A disabled breakpoint has no effect but is not forgotten. All
4189 options such as ignore-counts, conditions and commands are remembered in
4190 case the breakpoint is enabled again later. You may abbreviate
4191 @code{disable} as @code{dis}.
4194 @item enable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4195 Enable the specified breakpoints (or all defined breakpoints). They
4196 become effective once again in stopping your program.
4198 @item enable @r{[}breakpoints@r{]} once @var{range}@dots{}
4199 Enable the specified breakpoints temporarily. @value{GDBN} disables any
4200 of these breakpoints immediately after stopping your program.
4202 @item enable @r{[}breakpoints@r{]} delete @var{range}@dots{}
4203 Enable the specified breakpoints to work once, then die. @value{GDBN}
4204 deletes any of these breakpoints as soon as your program stops there.
4205 Breakpoints set by the @code{tbreak} command start out in this state.
4208 @c FIXME: I think the following ``Except for [...] @code{tbreak}'' is
4209 @c confusing: tbreak is also initially enabled.
4210 Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks,
4211 ,Setting Breakpoints}), breakpoints that you set are initially enabled;
4212 subsequently, they become disabled or enabled only when you use one of
4213 the commands above. (The command @code{until} can set and delete a
4214 breakpoint of its own, but it does not change the state of your other
4215 breakpoints; see @ref{Continuing and Stepping, ,Continuing and
4219 @subsection Break Conditions
4220 @cindex conditional breakpoints
4221 @cindex breakpoint conditions
4223 @c FIXME what is scope of break condition expr? Context where wanted?
4224 @c in particular for a watchpoint?
4225 The simplest sort of breakpoint breaks every time your program reaches a
4226 specified place. You can also specify a @dfn{condition} for a
4227 breakpoint. A condition is just a Boolean expression in your
4228 programming language (@pxref{Expressions, ,Expressions}). A breakpoint with
4229 a condition evaluates the expression each time your program reaches it,
4230 and your program stops only if the condition is @emph{true}.
4232 This is the converse of using assertions for program validation; in that
4233 situation, you want to stop when the assertion is violated---that is,
4234 when the condition is false. In C, if you want to test an assertion expressed
4235 by the condition @var{assert}, you should set the condition
4236 @samp{! @var{assert}} on the appropriate breakpoint.
4238 Conditions are also accepted for watchpoints; you may not need them,
4239 since a watchpoint is inspecting the value of an expression anyhow---but
4240 it might be simpler, say, to just set a watchpoint on a variable name,
4241 and specify a condition that tests whether the new value is an interesting
4244 Break conditions can have side effects, and may even call functions in
4245 your program. This can be useful, for example, to activate functions
4246 that log program progress, or to use your own print functions to
4247 format special data structures. The effects are completely predictable
4248 unless there is another enabled breakpoint at the same address. (In
4249 that case, @value{GDBN} might see the other breakpoint first and stop your
4250 program without checking the condition of this one.) Note that
4251 breakpoint commands are usually more convenient and flexible than break
4253 purpose of performing side effects when a breakpoint is reached
4254 (@pxref{Break Commands, ,Breakpoint Command Lists}).
4256 Break conditions can be specified when a breakpoint is set, by using
4257 @samp{if} in the arguments to the @code{break} command. @xref{Set
4258 Breaks, ,Setting Breakpoints}. They can also be changed at any time
4259 with the @code{condition} command.
4261 You can also use the @code{if} keyword with the @code{watch} command.
4262 The @code{catch} command does not recognize the @code{if} keyword;
4263 @code{condition} is the only way to impose a further condition on a
4268 @item condition @var{bnum} @var{expression}
4269 Specify @var{expression} as the break condition for breakpoint,
4270 watchpoint, or catchpoint number @var{bnum}. After you set a condition,
4271 breakpoint @var{bnum} stops your program only if the value of
4272 @var{expression} is true (nonzero, in C). When you use
4273 @code{condition}, @value{GDBN} checks @var{expression} immediately for
4274 syntactic correctness, and to determine whether symbols in it have
4275 referents in the context of your breakpoint. If @var{expression} uses
4276 symbols not referenced in the context of the breakpoint, @value{GDBN}
4277 prints an error message:
4280 No symbol "foo" in current context.
4285 not actually evaluate @var{expression} at the time the @code{condition}
4286 command (or a command that sets a breakpoint with a condition, like
4287 @code{break if @dots{}}) is given, however. @xref{Expressions, ,Expressions}.
4289 @item condition @var{bnum}
4290 Remove the condition from breakpoint number @var{bnum}. It becomes
4291 an ordinary unconditional breakpoint.
4294 @cindex ignore count (of breakpoint)
4295 A special case of a breakpoint condition is to stop only when the
4296 breakpoint has been reached a certain number of times. This is so
4297 useful that there is a special way to do it, using the @dfn{ignore
4298 count} of the breakpoint. Every breakpoint has an ignore count, which
4299 is an integer. Most of the time, the ignore count is zero, and
4300 therefore has no effect. But if your program reaches a breakpoint whose
4301 ignore count is positive, then instead of stopping, it just decrements
4302 the ignore count by one and continues. As a result, if the ignore count
4303 value is @var{n}, the breakpoint does not stop the next @var{n} times
4304 your program reaches it.
4308 @item ignore @var{bnum} @var{count}
4309 Set the ignore count of breakpoint number @var{bnum} to @var{count}.
4310 The next @var{count} times the breakpoint is reached, your program's
4311 execution does not stop; other than to decrement the ignore count, @value{GDBN}
4314 To make the breakpoint stop the next time it is reached, specify
4317 When you use @code{continue} to resume execution of your program from a
4318 breakpoint, you can specify an ignore count directly as an argument to
4319 @code{continue}, rather than using @code{ignore}. @xref{Continuing and
4320 Stepping,,Continuing and Stepping}.
4322 If a breakpoint has a positive ignore count and a condition, the
4323 condition is not checked. Once the ignore count reaches zero,
4324 @value{GDBN} resumes checking the condition.
4326 You could achieve the effect of the ignore count with a condition such
4327 as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that
4328 is decremented each time. @xref{Convenience Vars, ,Convenience
4332 Ignore counts apply to breakpoints, watchpoints, and catchpoints.
4335 @node Break Commands
4336 @subsection Breakpoint Command Lists
4338 @cindex breakpoint commands
4339 You can give any breakpoint (or watchpoint or catchpoint) a series of
4340 commands to execute when your program stops due to that breakpoint. For
4341 example, you might want to print the values of certain expressions, or
4342 enable other breakpoints.
4346 @kindex end@r{ (breakpoint commands)}
4347 @item commands @r{[}@var{range}@dots{}@r{]}
4348 @itemx @dots{} @var{command-list} @dots{}
4350 Specify a list of commands for the given breakpoints. The commands
4351 themselves appear on the following lines. Type a line containing just
4352 @code{end} to terminate the commands.
4354 To remove all commands from a breakpoint, type @code{commands} and
4355 follow it immediately with @code{end}; that is, give no commands.
4357 With no argument, @code{commands} refers to the last breakpoint,
4358 watchpoint, or catchpoint set (not to the breakpoint most recently
4359 encountered). If the most recent breakpoints were set with a single
4360 command, then the @code{commands} will apply to all the breakpoints
4361 set by that command. This applies to breakpoints set by
4362 @code{rbreak}, and also applies when a single @code{break} command
4363 creates multiple breakpoints (@pxref{Ambiguous Expressions,,Ambiguous
4367 Pressing @key{RET} as a means of repeating the last @value{GDBN} command is
4368 disabled within a @var{command-list}.
4370 You can use breakpoint commands to start your program up again. Simply
4371 use the @code{continue} command, or @code{step}, or any other command
4372 that resumes execution.
4374 Any other commands in the command list, after a command that resumes
4375 execution, are ignored. This is because any time you resume execution
4376 (even with a simple @code{next} or @code{step}), you may encounter
4377 another breakpoint---which could have its own command list, leading to
4378 ambiguities about which list to execute.
4381 If the first command you specify in a command list is @code{silent}, the
4382 usual message about stopping at a breakpoint is not printed. This may
4383 be desirable for breakpoints that are to print a specific message and
4384 then continue. If none of the remaining commands print anything, you
4385 see no sign that the breakpoint was reached. @code{silent} is
4386 meaningful only at the beginning of a breakpoint command list.
4388 The commands @code{echo}, @code{output}, and @code{printf} allow you to
4389 print precisely controlled output, and are often useful in silent
4390 breakpoints. @xref{Output, ,Commands for Controlled Output}.
4392 For example, here is how you could use breakpoint commands to print the
4393 value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
4399 printf "x is %d\n",x
4404 One application for breakpoint commands is to compensate for one bug so
4405 you can test for another. Put a breakpoint just after the erroneous line
4406 of code, give it a condition to detect the case in which something
4407 erroneous has been done, and give it commands to assign correct values
4408 to any variables that need them. End with the @code{continue} command
4409 so that your program does not stop, and start with the @code{silent}
4410 command so that no output is produced. Here is an example:
4421 @node Save Breakpoints
4422 @subsection How to save breakpoints to a file
4424 To save breakpoint definitions to a file use the @w{@code{save
4425 breakpoints}} command.
4428 @kindex save breakpoints
4429 @cindex save breakpoints to a file for future sessions
4430 @item save breakpoints [@var{filename}]
4431 This command saves all current breakpoint definitions together with
4432 their commands and ignore counts, into a file @file{@var{filename}}
4433 suitable for use in a later debugging session. This includes all
4434 types of breakpoints (breakpoints, watchpoints, catchpoints,
4435 tracepoints). To read the saved breakpoint definitions, use the
4436 @code{source} command (@pxref{Command Files}). Note that watchpoints
4437 with expressions involving local variables may fail to be recreated
4438 because it may not be possible to access the context where the
4439 watchpoint is valid anymore. Because the saved breakpoint definitions
4440 are simply a sequence of @value{GDBN} commands that recreate the
4441 breakpoints, you can edit the file in your favorite editing program,
4442 and remove the breakpoint definitions you're not interested in, or
4443 that can no longer be recreated.
4446 @c @ifclear BARETARGET
4447 @node Error in Breakpoints
4448 @subsection ``Cannot insert breakpoints''
4450 If you request too many active hardware-assisted breakpoints and
4451 watchpoints, you will see this error message:
4453 @c FIXME: the precise wording of this message may change; the relevant
4454 @c source change is not committed yet (Sep 3, 1999).
4456 Stopped; cannot insert breakpoints.
4457 You may have requested too many hardware breakpoints and watchpoints.
4461 This message is printed when you attempt to resume the program, since
4462 only then @value{GDBN} knows exactly how many hardware breakpoints and
4463 watchpoints it needs to insert.
4465 When this message is printed, you need to disable or remove some of the
4466 hardware-assisted breakpoints and watchpoints, and then continue.
4468 @node Breakpoint-related Warnings
4469 @subsection ``Breakpoint address adjusted...''
4470 @cindex breakpoint address adjusted
4472 Some processor architectures place constraints on the addresses at
4473 which breakpoints may be placed. For architectures thus constrained,
4474 @value{GDBN} will attempt to adjust the breakpoint's address to comply
4475 with the constraints dictated by the architecture.
4477 One example of such an architecture is the Fujitsu FR-V. The FR-V is
4478 a VLIW architecture in which a number of RISC-like instructions may be
4479 bundled together for parallel execution. The FR-V architecture
4480 constrains the location of a breakpoint instruction within such a
4481 bundle to the instruction with the lowest address. @value{GDBN}
4482 honors this constraint by adjusting a breakpoint's address to the
4483 first in the bundle.
4485 It is not uncommon for optimized code to have bundles which contain
4486 instructions from different source statements, thus it may happen that
4487 a breakpoint's address will be adjusted from one source statement to
4488 another. Since this adjustment may significantly alter @value{GDBN}'s
4489 breakpoint related behavior from what the user expects, a warning is
4490 printed when the breakpoint is first set and also when the breakpoint
4493 A warning like the one below is printed when setting a breakpoint
4494 that's been subject to address adjustment:
4497 warning: Breakpoint address adjusted from 0x00010414 to 0x00010410.
4500 Such warnings are printed both for user settable and @value{GDBN}'s
4501 internal breakpoints. If you see one of these warnings, you should
4502 verify that a breakpoint set at the adjusted address will have the
4503 desired affect. If not, the breakpoint in question may be removed and
4504 other breakpoints may be set which will have the desired behavior.
4505 E.g., it may be sufficient to place the breakpoint at a later
4506 instruction. A conditional breakpoint may also be useful in some
4507 cases to prevent the breakpoint from triggering too often.
4509 @value{GDBN} will also issue a warning when stopping at one of these
4510 adjusted breakpoints:
4513 warning: Breakpoint 1 address previously adjusted from 0x00010414
4517 When this warning is encountered, it may be too late to take remedial
4518 action except in cases where the breakpoint is hit earlier or more
4519 frequently than expected.
4521 @node Continuing and Stepping
4522 @section Continuing and Stepping
4526 @cindex resuming execution
4527 @dfn{Continuing} means resuming program execution until your program
4528 completes normally. In contrast, @dfn{stepping} means executing just
4529 one more ``step'' of your program, where ``step'' may mean either one
4530 line of source code, or one machine instruction (depending on what
4531 particular command you use). Either when continuing or when stepping,
4532 your program may stop even sooner, due to a breakpoint or a signal. (If
4533 it stops due to a signal, you may want to use @code{handle}, or use
4534 @samp{signal 0} to resume execution. @xref{Signals, ,Signals}.)
4538 @kindex c @r{(@code{continue})}
4539 @kindex fg @r{(resume foreground execution)}
4540 @item continue @r{[}@var{ignore-count}@r{]}
4541 @itemx c @r{[}@var{ignore-count}@r{]}
4542 @itemx fg @r{[}@var{ignore-count}@r{]}
4543 Resume program execution, at the address where your program last stopped;
4544 any breakpoints set at that address are bypassed. The optional argument
4545 @var{ignore-count} allows you to specify a further number of times to
4546 ignore a breakpoint at this location; its effect is like that of
4547 @code{ignore} (@pxref{Conditions, ,Break Conditions}).
4549 The argument @var{ignore-count} is meaningful only when your program
4550 stopped due to a breakpoint. At other times, the argument to
4551 @code{continue} is ignored.
4553 The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the
4554 debugged program is deemed to be the foreground program) are provided
4555 purely for convenience, and have exactly the same behavior as
4559 To resume execution at a different place, you can use @code{return}
4560 (@pxref{Returning, ,Returning from a Function}) to go back to the
4561 calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
4562 Different Address}) to go to an arbitrary location in your program.
4564 A typical technique for using stepping is to set a breakpoint
4565 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Catchpoints}) at the
4566 beginning of the function or the section of your program where a problem
4567 is believed to lie, run your program until it stops at that breakpoint,
4568 and then step through the suspect area, examining the variables that are
4569 interesting, until you see the problem happen.
4573 @kindex s @r{(@code{step})}
4575 Continue running your program until control reaches a different source
4576 line, then stop it and return control to @value{GDBN}. This command is
4577 abbreviated @code{s}.
4580 @c "without debugging information" is imprecise; actually "without line
4581 @c numbers in the debugging information". (gcc -g1 has debugging info but
4582 @c not line numbers). But it seems complex to try to make that
4583 @c distinction here.
4584 @emph{Warning:} If you use the @code{step} command while control is
4585 within a function that was compiled without debugging information,
4586 execution proceeds until control reaches a function that does have
4587 debugging information. Likewise, it will not step into a function which
4588 is compiled without debugging information. To step through functions
4589 without debugging information, use the @code{stepi} command, described
4593 The @code{step} command only stops at the first instruction of a source
4594 line. This prevents the multiple stops that could otherwise occur in
4595 @code{switch} statements, @code{for} loops, etc. @code{step} continues
4596 to stop if a function that has debugging information is called within
4597 the line. In other words, @code{step} @emph{steps inside} any functions
4598 called within the line.
4600 Also, the @code{step} command only enters a function if there is line
4601 number information for the function. Otherwise it acts like the
4602 @code{next} command. This avoids problems when using @code{cc -gl}
4603 on MIPS machines. Previously, @code{step} entered subroutines if there
4604 was any debugging information about the routine.
4606 @item step @var{count}
4607 Continue running as in @code{step}, but do so @var{count} times. If a
4608 breakpoint is reached, or a signal not related to stepping occurs before
4609 @var{count} steps, stepping stops right away.
4612 @kindex n @r{(@code{next})}
4613 @item next @r{[}@var{count}@r{]}
4614 Continue to the next source line in the current (innermost) stack frame.
4615 This is similar to @code{step}, but function calls that appear within
4616 the line of code are executed without stopping. Execution stops when
4617 control reaches a different line of code at the original stack level
4618 that was executing when you gave the @code{next} command. This command
4619 is abbreviated @code{n}.
4621 An argument @var{count} is a repeat count, as for @code{step}.
4624 @c FIX ME!! Do we delete this, or is there a way it fits in with
4625 @c the following paragraph? --- Vctoria
4627 @c @code{next} within a function that lacks debugging information acts like
4628 @c @code{step}, but any function calls appearing within the code of the
4629 @c function are executed without stopping.
4631 The @code{next} command only stops at the first instruction of a
4632 source line. This prevents multiple stops that could otherwise occur in
4633 @code{switch} statements, @code{for} loops, etc.
4635 @kindex set step-mode
4637 @cindex functions without line info, and stepping
4638 @cindex stepping into functions with no line info
4639 @itemx set step-mode on
4640 The @code{set step-mode on} command causes the @code{step} command to
4641 stop at the first instruction of a function which contains no debug line
4642 information rather than stepping over it.
4644 This is useful in cases where you may be interested in inspecting the
4645 machine instructions of a function which has no symbolic info and do not
4646 want @value{GDBN} to automatically skip over this function.
4648 @item set step-mode off
4649 Causes the @code{step} command to step over any functions which contains no
4650 debug information. This is the default.
4652 @item show step-mode
4653 Show whether @value{GDBN} will stop in or step over functions without
4654 source line debug information.
4657 @kindex fin @r{(@code{finish})}
4659 Continue running until just after function in the selected stack frame
4660 returns. Print the returned value (if any). This command can be
4661 abbreviated as @code{fin}.
4663 Contrast this with the @code{return} command (@pxref{Returning,
4664 ,Returning from a Function}).
4667 @kindex u @r{(@code{until})}
4668 @cindex run until specified location
4671 Continue running until a source line past the current line, in the
4672 current stack frame, is reached. This command is used to avoid single
4673 stepping through a loop more than once. It is like the @code{next}
4674 command, except that when @code{until} encounters a jump, it
4675 automatically continues execution until the program counter is greater
4676 than the address of the jump.
4678 This means that when you reach the end of a loop after single stepping
4679 though it, @code{until} makes your program continue execution until it
4680 exits the loop. In contrast, a @code{next} command at the end of a loop
4681 simply steps back to the beginning of the loop, which forces you to step
4682 through the next iteration.
4684 @code{until} always stops your program if it attempts to exit the current
4687 @code{until} may produce somewhat counterintuitive results if the order
4688 of machine code does not match the order of the source lines. For
4689 example, in the following excerpt from a debugging session, the @code{f}
4690 (@code{frame}) command shows that execution is stopped at line
4691 @code{206}; yet when we use @code{until}, we get to line @code{195}:
4695 #0 main (argc=4, argv=0xf7fffae8) at m4.c:206
4697 (@value{GDBP}) until
4698 195 for ( ; argc > 0; NEXTARG) @{
4701 This happened because, for execution efficiency, the compiler had
4702 generated code for the loop closure test at the end, rather than the
4703 start, of the loop---even though the test in a C @code{for}-loop is
4704 written before the body of the loop. The @code{until} command appeared
4705 to step back to the beginning of the loop when it advanced to this
4706 expression; however, it has not really gone to an earlier
4707 statement---not in terms of the actual machine code.
4709 @code{until} with no argument works by means of single
4710 instruction stepping, and hence is slower than @code{until} with an
4713 @item until @var{location}
4714 @itemx u @var{location}
4715 Continue running your program until either the specified location is
4716 reached, or the current stack frame returns. @var{location} is any of
4717 the forms described in @ref{Specify Location}.
4718 This form of the command uses temporary breakpoints, and
4719 hence is quicker than @code{until} without an argument. The specified
4720 location is actually reached only if it is in the current frame. This
4721 implies that @code{until} can be used to skip over recursive function
4722 invocations. For instance in the code below, if the current location is
4723 line @code{96}, issuing @code{until 99} will execute the program up to
4724 line @code{99} in the same invocation of factorial, i.e., after the inner
4725 invocations have returned.
4728 94 int factorial (int value)
4730 96 if (value > 1) @{
4731 97 value *= factorial (value - 1);
4738 @kindex advance @var{location}
4739 @itemx advance @var{location}
4740 Continue running the program up to the given @var{location}. An argument is
4741 required, which should be of one of the forms described in
4742 @ref{Specify Location}.
4743 Execution will also stop upon exit from the current stack
4744 frame. This command is similar to @code{until}, but @code{advance} will
4745 not skip over recursive function calls, and the target location doesn't
4746 have to be in the same frame as the current one.
4750 @kindex si @r{(@code{stepi})}
4752 @itemx stepi @var{arg}
4754 Execute one machine instruction, then stop and return to the debugger.
4756 It is often useful to do @samp{display/i $pc} when stepping by machine
4757 instructions. This makes @value{GDBN} automatically display the next
4758 instruction to be executed, each time your program stops. @xref{Auto
4759 Display,, Automatic Display}.
4761 An argument is a repeat count, as in @code{step}.
4765 @kindex ni @r{(@code{nexti})}
4767 @itemx nexti @var{arg}
4769 Execute one machine instruction, but if it is a function call,
4770 proceed until the function returns.
4772 An argument is a repeat count, as in @code{next}.
4779 A signal is an asynchronous event that can happen in a program. The
4780 operating system defines the possible kinds of signals, and gives each
4781 kind a name and a number. For example, in Unix @code{SIGINT} is the
4782 signal a program gets when you type an interrupt character (often @kbd{Ctrl-c});
4783 @code{SIGSEGV} is the signal a program gets from referencing a place in
4784 memory far away from all the areas in use; @code{SIGALRM} occurs when
4785 the alarm clock timer goes off (which happens only if your program has
4786 requested an alarm).
4788 @cindex fatal signals
4789 Some signals, including @code{SIGALRM}, are a normal part of the
4790 functioning of your program. Others, such as @code{SIGSEGV}, indicate
4791 errors; these signals are @dfn{fatal} (they kill your program immediately) if the
4792 program has not specified in advance some other way to handle the signal.
4793 @code{SIGINT} does not indicate an error in your program, but it is normally
4794 fatal so it can carry out the purpose of the interrupt: to kill the program.
4796 @value{GDBN} has the ability to detect any occurrence of a signal in your
4797 program. You can tell @value{GDBN} in advance what to do for each kind of
4800 @cindex handling signals
4801 Normally, @value{GDBN} is set up to let the non-erroneous signals like
4802 @code{SIGALRM} be silently passed to your program
4803 (so as not to interfere with their role in the program's functioning)
4804 but to stop your program immediately whenever an error signal happens.
4805 You can change these settings with the @code{handle} command.
4808 @kindex info signals
4812 Print a table of all the kinds of signals and how @value{GDBN} has been told to
4813 handle each one. You can use this to see the signal numbers of all
4814 the defined types of signals.
4816 @item info signals @var{sig}
4817 Similar, but print information only about the specified signal number.
4819 @code{info handle} is an alias for @code{info signals}.
4822 @item handle @var{signal} @r{[}@var{keywords}@dots{}@r{]}
4823 Change the way @value{GDBN} handles signal @var{signal}. @var{signal}
4824 can be the number of a signal or its name (with or without the
4825 @samp{SIG} at the beginning); a list of signal numbers of the form
4826 @samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the
4827 known signals. Optional arguments @var{keywords}, described below,
4828 say what change to make.
4832 The keywords allowed by the @code{handle} command can be abbreviated.
4833 Their full names are:
4837 @value{GDBN} should not stop your program when this signal happens. It may
4838 still print a message telling you that the signal has come in.
4841 @value{GDBN} should stop your program when this signal happens. This implies
4842 the @code{print} keyword as well.
4845 @value{GDBN} should print a message when this signal happens.
4848 @value{GDBN} should not mention the occurrence of the signal at all. This
4849 implies the @code{nostop} keyword as well.
4853 @value{GDBN} should allow your program to see this signal; your program
4854 can handle the signal, or else it may terminate if the signal is fatal
4855 and not handled. @code{pass} and @code{noignore} are synonyms.
4859 @value{GDBN} should not allow your program to see this signal.
4860 @code{nopass} and @code{ignore} are synonyms.
4864 When a signal stops your program, the signal is not visible to the
4866 continue. Your program sees the signal then, if @code{pass} is in
4867 effect for the signal in question @emph{at that time}. In other words,
4868 after @value{GDBN} reports a signal, you can use the @code{handle}
4869 command with @code{pass} or @code{nopass} to control whether your
4870 program sees that signal when you continue.
4872 The default is set to @code{nostop}, @code{noprint}, @code{pass} for
4873 non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and
4874 @code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the
4877 You can also use the @code{signal} command to prevent your program from
4878 seeing a signal, or cause it to see a signal it normally would not see,
4879 or to give it any signal at any time. For example, if your program stopped
4880 due to some sort of memory reference error, you might store correct
4881 values into the erroneous variables and continue, hoping to see more
4882 execution; but your program would probably terminate immediately as
4883 a result of the fatal signal once it saw the signal. To prevent this,
4884 you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
4887 @cindex extra signal information
4888 @anchor{extra signal information}
4890 On some targets, @value{GDBN} can inspect extra signal information
4891 associated with the intercepted signal, before it is actually
4892 delivered to the program being debugged. This information is exported
4893 by the convenience variable @code{$_siginfo}, and consists of data
4894 that is passed by the kernel to the signal handler at the time of the
4895 receipt of a signal. The data type of the information itself is
4896 target dependent. You can see the data type using the @code{ptype
4897 $_siginfo} command. On Unix systems, it typically corresponds to the
4898 standard @code{siginfo_t} type, as defined in the @file{signal.h}
4901 Here's an example, on a @sc{gnu}/Linux system, printing the stray
4902 referenced address that raised a segmentation fault.
4906 (@value{GDBP}) continue
4907 Program received signal SIGSEGV, Segmentation fault.
4908 0x0000000000400766 in main ()
4910 (@value{GDBP}) ptype $_siginfo
4917 struct @{...@} _kill;
4918 struct @{...@} _timer;
4920 struct @{...@} _sigchld;
4921 struct @{...@} _sigfault;
4922 struct @{...@} _sigpoll;
4925 (@value{GDBP}) ptype $_siginfo._sifields._sigfault
4929 (@value{GDBP}) p $_siginfo._sifields._sigfault.si_addr
4930 $1 = (void *) 0x7ffff7ff7000
4934 Depending on target support, @code{$_siginfo} may also be writable.
4937 @section Stopping and Starting Multi-thread Programs
4939 @cindex stopped threads
4940 @cindex threads, stopped
4942 @cindex continuing threads
4943 @cindex threads, continuing
4945 @value{GDBN} supports debugging programs with multiple threads
4946 (@pxref{Threads,, Debugging Programs with Multiple Threads}). There
4947 are two modes of controlling execution of your program within the
4948 debugger. In the default mode, referred to as @dfn{all-stop mode},
4949 when any thread in your program stops (for example, at a breakpoint
4950 or while being stepped), all other threads in the program are also stopped by
4951 @value{GDBN}. On some targets, @value{GDBN} also supports
4952 @dfn{non-stop mode}, in which other threads can continue to run freely while
4953 you examine the stopped thread in the debugger.
4956 * All-Stop Mode:: All threads stop when GDB takes control
4957 * Non-Stop Mode:: Other threads continue to execute
4958 * Background Execution:: Running your program asynchronously
4959 * Thread-Specific Breakpoints:: Controlling breakpoints
4960 * Interrupted System Calls:: GDB may interfere with system calls
4964 @subsection All-Stop Mode
4966 @cindex all-stop mode
4968 In all-stop mode, whenever your program stops under @value{GDBN} for any reason,
4969 @emph{all} threads of execution stop, not just the current thread. This
4970 allows you to examine the overall state of the program, including
4971 switching between threads, without worrying that things may change
4974 Conversely, whenever you restart the program, @emph{all} threads start
4975 executing. @emph{This is true even when single-stepping} with commands
4976 like @code{step} or @code{next}.
4978 In particular, @value{GDBN} cannot single-step all threads in lockstep.
4979 Since thread scheduling is up to your debugging target's operating
4980 system (not controlled by @value{GDBN}), other threads may
4981 execute more than one statement while the current thread completes a
4982 single step. Moreover, in general other threads stop in the middle of a
4983 statement, rather than at a clean statement boundary, when the program
4986 You might even find your program stopped in another thread after
4987 continuing or even single-stepping. This happens whenever some other
4988 thread runs into a breakpoint, a signal, or an exception before the
4989 first thread completes whatever you requested.
4991 @cindex automatic thread selection
4992 @cindex switching threads automatically
4993 @cindex threads, automatic switching
4994 Whenever @value{GDBN} stops your program, due to a breakpoint or a
4995 signal, it automatically selects the thread where that breakpoint or
4996 signal happened. @value{GDBN} alerts you to the context switch with a
4997 message such as @samp{[Switching to Thread @var{n}]} to identify the
5000 On some OSes, you can modify @value{GDBN}'s default behavior by
5001 locking the OS scheduler to allow only a single thread to run.
5004 @item set scheduler-locking @var{mode}
5005 @cindex scheduler locking mode
5006 @cindex lock scheduler
5007 Set the scheduler locking mode. If it is @code{off}, then there is no
5008 locking and any thread may run at any time. If @code{on}, then only the
5009 current thread may run when the inferior is resumed. The @code{step}
5010 mode optimizes for single-stepping; it prevents other threads
5011 from preempting the current thread while you are stepping, so that
5012 the focus of debugging does not change unexpectedly.
5013 Other threads only rarely (or never) get a chance to run
5014 when you step. They are more likely to run when you @samp{next} over a
5015 function call, and they are completely free to run when you use commands
5016 like @samp{continue}, @samp{until}, or @samp{finish}. However, unless another
5017 thread hits a breakpoint during its timeslice, @value{GDBN} does not change
5018 the current thread away from the thread that you are debugging.
5020 @item show scheduler-locking
5021 Display the current scheduler locking mode.
5024 @cindex resume threads of multiple processes simultaneously
5025 By default, when you issue one of the execution commands such as
5026 @code{continue}, @code{next} or @code{step}, @value{GDBN} allows only
5027 threads of the current inferior to run. For example, if @value{GDBN}
5028 is attached to two inferiors, each with two threads, the
5029 @code{continue} command resumes only the two threads of the current
5030 inferior. This is useful, for example, when you debug a program that
5031 forks and you want to hold the parent stopped (so that, for instance,
5032 it doesn't run to exit), while you debug the child. In other
5033 situations, you may not be interested in inspecting the current state
5034 of any of the processes @value{GDBN} is attached to, and you may want
5035 to resume them all until some breakpoint is hit. In the latter case,
5036 you can instruct @value{GDBN} to allow all threads of all the
5037 inferiors to run with the @w{@code{set schedule-multiple}} command.
5040 @kindex set schedule-multiple
5041 @item set schedule-multiple
5042 Set the mode for allowing threads of multiple processes to be resumed
5043 when an execution command is issued. When @code{on}, all threads of
5044 all processes are allowed to run. When @code{off}, only the threads
5045 of the current process are resumed. The default is @code{off}. The
5046 @code{scheduler-locking} mode takes precedence when set to @code{on},
5047 or while you are stepping and set to @code{step}.
5049 @item show schedule-multiple
5050 Display the current mode for resuming the execution of threads of
5055 @subsection Non-Stop Mode
5057 @cindex non-stop mode
5059 @c This section is really only a place-holder, and needs to be expanded
5060 @c with more details.
5062 For some multi-threaded targets, @value{GDBN} supports an optional
5063 mode of operation in which you can examine stopped program threads in
5064 the debugger while other threads continue to execute freely. This
5065 minimizes intrusion when debugging live systems, such as programs
5066 where some threads have real-time constraints or must continue to
5067 respond to external events. This is referred to as @dfn{non-stop} mode.
5069 In non-stop mode, when a thread stops to report a debugging event,
5070 @emph{only} that thread is stopped; @value{GDBN} does not stop other
5071 threads as well, in contrast to the all-stop mode behavior. Additionally,
5072 execution commands such as @code{continue} and @code{step} apply by default
5073 only to the current thread in non-stop mode, rather than all threads as
5074 in all-stop mode. This allows you to control threads explicitly in
5075 ways that are not possible in all-stop mode --- for example, stepping
5076 one thread while allowing others to run freely, stepping
5077 one thread while holding all others stopped, or stepping several threads
5078 independently and simultaneously.
5080 To enter non-stop mode, use this sequence of commands before you run
5081 or attach to your program:
5084 # Enable the async interface.
5087 # If using the CLI, pagination breaks non-stop.
5090 # Finally, turn it on!
5094 You can use these commands to manipulate the non-stop mode setting:
5097 @kindex set non-stop
5098 @item set non-stop on
5099 Enable selection of non-stop mode.
5100 @item set non-stop off
5101 Disable selection of non-stop mode.
5102 @kindex show non-stop
5104 Show the current non-stop enablement setting.
5107 Note these commands only reflect whether non-stop mode is enabled,
5108 not whether the currently-executing program is being run in non-stop mode.
5109 In particular, the @code{set non-stop} preference is only consulted when
5110 @value{GDBN} starts or connects to the target program, and it is generally
5111 not possible to switch modes once debugging has started. Furthermore,
5112 since not all targets support non-stop mode, even when you have enabled
5113 non-stop mode, @value{GDBN} may still fall back to all-stop operation by
5116 In non-stop mode, all execution commands apply only to the current thread
5117 by default. That is, @code{continue} only continues one thread.
5118 To continue all threads, issue @code{continue -a} or @code{c -a}.
5120 You can use @value{GDBN}'s background execution commands
5121 (@pxref{Background Execution}) to run some threads in the background
5122 while you continue to examine or step others from @value{GDBN}.
5123 The MI execution commands (@pxref{GDB/MI Program Execution}) are
5124 always executed asynchronously in non-stop mode.
5126 Suspending execution is done with the @code{interrupt} command when
5127 running in the background, or @kbd{Ctrl-c} during foreground execution.
5128 In all-stop mode, this stops the whole process;
5129 but in non-stop mode the interrupt applies only to the current thread.
5130 To stop the whole program, use @code{interrupt -a}.
5132 Other execution commands do not currently support the @code{-a} option.
5134 In non-stop mode, when a thread stops, @value{GDBN} doesn't automatically make
5135 that thread current, as it does in all-stop mode. This is because the
5136 thread stop notifications are asynchronous with respect to @value{GDBN}'s
5137 command interpreter, and it would be confusing if @value{GDBN} unexpectedly
5138 changed to a different thread just as you entered a command to operate on the
5139 previously current thread.
5141 @node Background Execution
5142 @subsection Background Execution
5144 @cindex foreground execution
5145 @cindex background execution
5146 @cindex asynchronous execution
5147 @cindex execution, foreground, background and asynchronous
5149 @value{GDBN}'s execution commands have two variants: the normal
5150 foreground (synchronous) behavior, and a background
5151 (asynchronous) behavior. In foreground execution, @value{GDBN} waits for
5152 the program to report that some thread has stopped before prompting for
5153 another command. In background execution, @value{GDBN} immediately gives
5154 a command prompt so that you can issue other commands while your program runs.
5156 You need to explicitly enable asynchronous mode before you can use
5157 background execution commands. You can use these commands to
5158 manipulate the asynchronous mode setting:
5161 @kindex set target-async
5162 @item set target-async on
5163 Enable asynchronous mode.
5164 @item set target-async off
5165 Disable asynchronous mode.
5166 @kindex show target-async
5167 @item show target-async
5168 Show the current target-async setting.
5171 If the target doesn't support async mode, @value{GDBN} issues an error
5172 message if you attempt to use the background execution commands.
5174 To specify background execution, add a @code{&} to the command. For example,
5175 the background form of the @code{continue} command is @code{continue&}, or
5176 just @code{c&}. The execution commands that accept background execution
5182 @xref{Starting, , Starting your Program}.
5186 @xref{Attach, , Debugging an Already-running Process}.
5190 @xref{Continuing and Stepping, step}.
5194 @xref{Continuing and Stepping, stepi}.
5198 @xref{Continuing and Stepping, next}.
5202 @xref{Continuing and Stepping, nexti}.
5206 @xref{Continuing and Stepping, continue}.
5210 @xref{Continuing and Stepping, finish}.
5214 @xref{Continuing and Stepping, until}.
5218 Background execution is especially useful in conjunction with non-stop
5219 mode for debugging programs with multiple threads; see @ref{Non-Stop Mode}.
5220 However, you can also use these commands in the normal all-stop mode with
5221 the restriction that you cannot issue another execution command until the
5222 previous one finishes. Examples of commands that are valid in all-stop
5223 mode while the program is running include @code{help} and @code{info break}.
5225 You can interrupt your program while it is running in the background by
5226 using the @code{interrupt} command.
5233 Suspend execution of the running program. In all-stop mode,
5234 @code{interrupt} stops the whole process, but in non-stop mode, it stops
5235 only the current thread. To stop the whole program in non-stop mode,
5236 use @code{interrupt -a}.
5239 @node Thread-Specific Breakpoints
5240 @subsection Thread-Specific Breakpoints
5242 When your program has multiple threads (@pxref{Threads,, Debugging
5243 Programs with Multiple Threads}), you can choose whether to set
5244 breakpoints on all threads, or on a particular thread.
5247 @cindex breakpoints and threads
5248 @cindex thread breakpoints
5249 @kindex break @dots{} thread @var{threadno}
5250 @item break @var{linespec} thread @var{threadno}
5251 @itemx break @var{linespec} thread @var{threadno} if @dots{}
5252 @var{linespec} specifies source lines; there are several ways of
5253 writing them (@pxref{Specify Location}), but the effect is always to
5254 specify some source line.
5256 Use the qualifier @samp{thread @var{threadno}} with a breakpoint command
5257 to specify that you only want @value{GDBN} to stop the program when a
5258 particular thread reaches this breakpoint. @var{threadno} is one of the
5259 numeric thread identifiers assigned by @value{GDBN}, shown in the first
5260 column of the @samp{info threads} display.
5262 If you do not specify @samp{thread @var{threadno}} when you set a
5263 breakpoint, the breakpoint applies to @emph{all} threads of your
5266 You can use the @code{thread} qualifier on conditional breakpoints as
5267 well; in this case, place @samp{thread @var{threadno}} before or
5268 after the breakpoint condition, like this:
5271 (@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
5276 @node Interrupted System Calls
5277 @subsection Interrupted System Calls
5279 @cindex thread breakpoints and system calls
5280 @cindex system calls and thread breakpoints
5281 @cindex premature return from system calls
5282 There is an unfortunate side effect when using @value{GDBN} to debug
5283 multi-threaded programs. If one thread stops for a
5284 breakpoint, or for some other reason, and another thread is blocked in a
5285 system call, then the system call may return prematurely. This is a
5286 consequence of the interaction between multiple threads and the signals
5287 that @value{GDBN} uses to implement breakpoints and other events that
5290 To handle this problem, your program should check the return value of
5291 each system call and react appropriately. This is good programming
5294 For example, do not write code like this:
5300 The call to @code{sleep} will return early if a different thread stops
5301 at a breakpoint or for some other reason.
5303 Instead, write this:
5308 unslept = sleep (unslept);
5311 A system call is allowed to return early, so the system is still
5312 conforming to its specification. But @value{GDBN} does cause your
5313 multi-threaded program to behave differently than it would without
5316 Also, @value{GDBN} uses internal breakpoints in the thread library to
5317 monitor certain events such as thread creation and thread destruction.
5318 When such an event happens, a system call in another thread may return
5319 prematurely, even though your program does not appear to stop.
5322 @node Reverse Execution
5323 @chapter Running programs backward
5324 @cindex reverse execution
5325 @cindex running programs backward
5327 When you are debugging a program, it is not unusual to realize that
5328 you have gone too far, and some event of interest has already happened.
5329 If the target environment supports it, @value{GDBN} can allow you to
5330 ``rewind'' the program by running it backward.
5332 A target environment that supports reverse execution should be able
5333 to ``undo'' the changes in machine state that have taken place as the
5334 program was executing normally. Variables, registers etc.@: should
5335 revert to their previous values. Obviously this requires a great
5336 deal of sophistication on the part of the target environment; not
5337 all target environments can support reverse execution.
5339 When a program is executed in reverse, the instructions that
5340 have most recently been executed are ``un-executed'', in reverse
5341 order. The program counter runs backward, following the previous
5342 thread of execution in reverse. As each instruction is ``un-executed'',
5343 the values of memory and/or registers that were changed by that
5344 instruction are reverted to their previous states. After executing
5345 a piece of source code in reverse, all side effects of that code
5346 should be ``undone'', and all variables should be returned to their
5347 prior values@footnote{
5348 Note that some side effects are easier to undo than others. For instance,
5349 memory and registers are relatively easy, but device I/O is hard. Some
5350 targets may be able undo things like device I/O, and some may not.
5352 The contract between @value{GDBN} and the reverse executing target
5353 requires only that the target do something reasonable when
5354 @value{GDBN} tells it to execute backwards, and then report the
5355 results back to @value{GDBN}. Whatever the target reports back to
5356 @value{GDBN}, @value{GDBN} will report back to the user. @value{GDBN}
5357 assumes that the memory and registers that the target reports are in a
5358 consistant state, but @value{GDBN} accepts whatever it is given.
5361 If you are debugging in a target environment that supports
5362 reverse execution, @value{GDBN} provides the following commands.
5365 @kindex reverse-continue
5366 @kindex rc @r{(@code{reverse-continue})}
5367 @item reverse-continue @r{[}@var{ignore-count}@r{]}
5368 @itemx rc @r{[}@var{ignore-count}@r{]}
5369 Beginning at the point where your program last stopped, start executing
5370 in reverse. Reverse execution will stop for breakpoints and synchronous
5371 exceptions (signals), just like normal execution. Behavior of
5372 asynchronous signals depends on the target environment.
5374 @kindex reverse-step
5375 @kindex rs @r{(@code{step})}
5376 @item reverse-step @r{[}@var{count}@r{]}
5377 Run the program backward until control reaches the start of a
5378 different source line; then stop it, and return control to @value{GDBN}.
5380 Like the @code{step} command, @code{reverse-step} will only stop
5381 at the beginning of a source line. It ``un-executes'' the previously
5382 executed source line. If the previous source line included calls to
5383 debuggable functions, @code{reverse-step} will step (backward) into
5384 the called function, stopping at the beginning of the @emph{last}
5385 statement in the called function (typically a return statement).
5387 Also, as with the @code{step} command, if non-debuggable functions are
5388 called, @code{reverse-step} will run thru them backward without stopping.
5390 @kindex reverse-stepi
5391 @kindex rsi @r{(@code{reverse-stepi})}
5392 @item reverse-stepi @r{[}@var{count}@r{]}
5393 Reverse-execute one machine instruction. Note that the instruction
5394 to be reverse-executed is @emph{not} the one pointed to by the program
5395 counter, but the instruction executed prior to that one. For instance,
5396 if the last instruction was a jump, @code{reverse-stepi} will take you
5397 back from the destination of the jump to the jump instruction itself.
5399 @kindex reverse-next
5400 @kindex rn @r{(@code{reverse-next})}
5401 @item reverse-next @r{[}@var{count}@r{]}
5402 Run backward to the beginning of the previous line executed in
5403 the current (innermost) stack frame. If the line contains function
5404 calls, they will be ``un-executed'' without stopping. Starting from
5405 the first line of a function, @code{reverse-next} will take you back
5406 to the caller of that function, @emph{before} the function was called,
5407 just as the normal @code{next} command would take you from the last
5408 line of a function back to its return to its caller
5409 @footnote{Unless the code is too heavily optimized.}.
5411 @kindex reverse-nexti
5412 @kindex rni @r{(@code{reverse-nexti})}
5413 @item reverse-nexti @r{[}@var{count}@r{]}
5414 Like @code{nexti}, @code{reverse-nexti} executes a single instruction
5415 in reverse, except that called functions are ``un-executed'' atomically.
5416 That is, if the previously executed instruction was a return from
5417 another function, @code{reverse-nexti} will continue to execute
5418 in reverse until the call to that function (from the current stack
5421 @kindex reverse-finish
5422 @item reverse-finish
5423 Just as the @code{finish} command takes you to the point where the
5424 current function returns, @code{reverse-finish} takes you to the point
5425 where it was called. Instead of ending up at the end of the current
5426 function invocation, you end up at the beginning.
5428 @kindex set exec-direction
5429 @item set exec-direction
5430 Set the direction of target execution.
5431 @itemx set exec-direction reverse
5432 @cindex execute forward or backward in time
5433 @value{GDBN} will perform all execution commands in reverse, until the
5434 exec-direction mode is changed to ``forward''. Affected commands include
5435 @code{step, stepi, next, nexti, continue, and finish}. The @code{return}
5436 command cannot be used in reverse mode.
5437 @item set exec-direction forward
5438 @value{GDBN} will perform all execution commands in the normal fashion.
5439 This is the default.
5443 @node Process Record and Replay
5444 @chapter Recording Inferior's Execution and Replaying It
5445 @cindex process record and replay
5446 @cindex recording inferior's execution and replaying it
5448 On some platforms, @value{GDBN} provides a special @dfn{process record
5449 and replay} target that can record a log of the process execution, and
5450 replay it later with both forward and reverse execution commands.
5453 When this target is in use, if the execution log includes the record
5454 for the next instruction, @value{GDBN} will debug in @dfn{replay
5455 mode}. In the replay mode, the inferior does not really execute code
5456 instructions. Instead, all the events that normally happen during
5457 code execution are taken from the execution log. While code is not
5458 really executed in replay mode, the values of registers (including the
5459 program counter register) and the memory of the inferior are still
5460 changed as they normally would. Their contents are taken from the
5464 If the record for the next instruction is not in the execution log,
5465 @value{GDBN} will debug in @dfn{record mode}. In this mode, the
5466 inferior executes normally, and @value{GDBN} records the execution log
5469 The process record and replay target supports reverse execution
5470 (@pxref{Reverse Execution}), even if the platform on which the
5471 inferior runs does not. However, the reverse execution is limited in
5472 this case by the range of the instructions recorded in the execution
5473 log. In other words, reverse execution on platforms that don't
5474 support it directly can only be done in the replay mode.
5476 When debugging in the reverse direction, @value{GDBN} will work in
5477 replay mode as long as the execution log includes the record for the
5478 previous instruction; otherwise, it will work in record mode, if the
5479 platform supports reverse execution, or stop if not.
5481 For architecture environments that support process record and replay,
5482 @value{GDBN} provides the following commands:
5485 @kindex target record
5489 This command starts the process record and replay target. The process
5490 record and replay target can only debug a process that is already
5491 running. Therefore, you need first to start the process with the
5492 @kbd{run} or @kbd{start} commands, and then start the recording with
5493 the @kbd{target record} command.
5495 Both @code{record} and @code{rec} are aliases of @code{target record}.
5497 @cindex displaced stepping, and process record and replay
5498 Displaced stepping (@pxref{Maintenance Commands,, displaced stepping})
5499 will be automatically disabled when process record and replay target
5500 is started. That's because the process record and replay target
5501 doesn't support displaced stepping.
5503 @cindex non-stop mode, and process record and replay
5504 @cindex asynchronous execution, and process record and replay
5505 If the inferior is in the non-stop mode (@pxref{Non-Stop Mode}) or in
5506 the asynchronous execution mode (@pxref{Background Execution}), the
5507 process record and replay target cannot be started because it doesn't
5508 support these two modes.
5513 Stop the process record and replay target. When process record and
5514 replay target stops, the entire execution log will be deleted and the
5515 inferior will either be terminated, or will remain in its final state.
5517 When you stop the process record and replay target in record mode (at
5518 the end of the execution log), the inferior will be stopped at the
5519 next instruction that would have been recorded. In other words, if
5520 you record for a while and then stop recording, the inferior process
5521 will be left in the same state as if the recording never happened.
5523 On the other hand, if the process record and replay target is stopped
5524 while in replay mode (that is, not at the end of the execution log,
5525 but at some earlier point), the inferior process will become ``live''
5526 at that earlier state, and it will then be possible to continue the
5527 usual ``live'' debugging of the process from that state.
5529 When the inferior process exits, or @value{GDBN} detaches from it,
5530 process record and replay target will automatically stop itself.
5532 @kindex set record insn-number-max
5533 @item set record insn-number-max @var{limit}
5534 Set the limit of instructions to be recorded. Default value is 200000.
5536 If @var{limit} is a positive number, then @value{GDBN} will start
5537 deleting instructions from the log once the number of the record
5538 instructions becomes greater than @var{limit}. For every new recorded
5539 instruction, @value{GDBN} will delete the earliest recorded
5540 instruction to keep the number of recorded instructions at the limit.
5541 (Since deleting recorded instructions loses information, @value{GDBN}
5542 lets you control what happens when the limit is reached, by means of
5543 the @code{stop-at-limit} option, described below.)
5545 If @var{limit} is zero, @value{GDBN} will never delete recorded
5546 instructions from the execution log. The number of recorded
5547 instructions is unlimited in this case.
5549 @kindex show record insn-number-max
5550 @item show record insn-number-max
5551 Show the limit of instructions to be recorded.
5553 @kindex set record stop-at-limit
5554 @item set record stop-at-limit
5555 Control the behavior when the number of recorded instructions reaches
5556 the limit. If ON (the default), @value{GDBN} will stop when the limit
5557 is reached for the first time and ask you whether you want to stop the
5558 inferior or continue running it and recording the execution log. If
5559 you decide to continue recording, each new recorded instruction will
5560 cause the oldest one to be deleted.
5562 If this option is OFF, @value{GDBN} will automatically delete the
5563 oldest record to make room for each new one, without asking.
5565 @kindex show record stop-at-limit
5566 @item show record stop-at-limit
5567 Show the current setting of @code{stop-at-limit}.
5571 Show various statistics about the state of process record and its
5572 in-memory execution log buffer, including:
5576 Whether in record mode or replay mode.
5578 Lowest recorded instruction number (counting from when the current execution log started recording instructions).
5580 Highest recorded instruction number.
5582 Current instruction about to be replayed (if in replay mode).
5584 Number of instructions contained in the execution log.
5586 Maximum number of instructions that may be contained in the execution log.
5589 @kindex record delete
5592 When record target runs in replay mode (``in the past''), delete the
5593 subsequent execution log and begin to record a new execution log starting
5594 from the current address. This means you will abandon the previously
5595 recorded ``future'' and begin recording a new ``future''.
5600 @chapter Examining the Stack
5602 When your program has stopped, the first thing you need to know is where it
5603 stopped and how it got there.
5606 Each time your program performs a function call, information about the call
5608 That information includes the location of the call in your program,
5609 the arguments of the call,
5610 and the local variables of the function being called.
5611 The information is saved in a block of data called a @dfn{stack frame}.
5612 The stack frames are allocated in a region of memory called the @dfn{call
5615 When your program stops, the @value{GDBN} commands for examining the
5616 stack allow you to see all of this information.
5618 @cindex selected frame
5619 One of the stack frames is @dfn{selected} by @value{GDBN} and many
5620 @value{GDBN} commands refer implicitly to the selected frame. In
5621 particular, whenever you ask @value{GDBN} for the value of a variable in
5622 your program, the value is found in the selected frame. There are
5623 special @value{GDBN} commands to select whichever frame you are
5624 interested in. @xref{Selection, ,Selecting a Frame}.
5626 When your program stops, @value{GDBN} automatically selects the
5627 currently executing frame and describes it briefly, similar to the
5628 @code{frame} command (@pxref{Frame Info, ,Information about a Frame}).
5631 * Frames:: Stack frames
5632 * Backtrace:: Backtraces
5633 * Selection:: Selecting a frame
5634 * Frame Info:: Information on a frame
5639 @section Stack Frames
5641 @cindex frame, definition
5643 The call stack is divided up into contiguous pieces called @dfn{stack
5644 frames}, or @dfn{frames} for short; each frame is the data associated
5645 with one call to one function. The frame contains the arguments given
5646 to the function, the function's local variables, and the address at
5647 which the function is executing.
5649 @cindex initial frame
5650 @cindex outermost frame
5651 @cindex innermost frame
5652 When your program is started, the stack has only one frame, that of the
5653 function @code{main}. This is called the @dfn{initial} frame or the
5654 @dfn{outermost} frame. Each time a function is called, a new frame is
5655 made. Each time a function returns, the frame for that function invocation
5656 is eliminated. If a function is recursive, there can be many frames for
5657 the same function. The frame for the function in which execution is
5658 actually occurring is called the @dfn{innermost} frame. This is the most
5659 recently created of all the stack frames that still exist.
5661 @cindex frame pointer
5662 Inside your program, stack frames are identified by their addresses. A
5663 stack frame consists of many bytes, each of which has its own address; each
5664 kind of computer has a convention for choosing one byte whose
5665 address serves as the address of the frame. Usually this address is kept
5666 in a register called the @dfn{frame pointer register}
5667 (@pxref{Registers, $fp}) while execution is going on in that frame.
5669 @cindex frame number
5670 @value{GDBN} assigns numbers to all existing stack frames, starting with
5671 zero for the innermost frame, one for the frame that called it,
5672 and so on upward. These numbers do not really exist in your program;
5673 they are assigned by @value{GDBN} to give you a way of designating stack
5674 frames in @value{GDBN} commands.
5676 @c The -fomit-frame-pointer below perennially causes hbox overflow
5677 @c underflow problems.
5678 @cindex frameless execution
5679 Some compilers provide a way to compile functions so that they operate
5680 without stack frames. (For example, the @value{NGCC} option
5682 @samp{-fomit-frame-pointer}
5684 generates functions without a frame.)
5685 This is occasionally done with heavily used library functions to save
5686 the frame setup time. @value{GDBN} has limited facilities for dealing
5687 with these function invocations. If the innermost function invocation
5688 has no stack frame, @value{GDBN} nevertheless regards it as though
5689 it had a separate frame, which is numbered zero as usual, allowing
5690 correct tracing of the function call chain. However, @value{GDBN} has
5691 no provision for frameless functions elsewhere in the stack.
5694 @kindex frame@r{, command}
5695 @cindex current stack frame
5696 @item frame @var{args}
5697 The @code{frame} command allows you to move from one stack frame to another,
5698 and to print the stack frame you select. @var{args} may be either the
5699 address of the frame or the stack frame number. Without an argument,
5700 @code{frame} prints the current stack frame.
5702 @kindex select-frame
5703 @cindex selecting frame silently
5705 The @code{select-frame} command allows you to move from one stack frame
5706 to another without printing the frame. This is the silent version of
5714 @cindex call stack traces
5715 A backtrace is a summary of how your program got where it is. It shows one
5716 line per frame, for many frames, starting with the currently executing
5717 frame (frame zero), followed by its caller (frame one), and on up the
5722 @kindex bt @r{(@code{backtrace})}
5725 Print a backtrace of the entire stack: one line per frame for all
5726 frames in the stack.
5728 You can stop the backtrace at any time by typing the system interrupt
5729 character, normally @kbd{Ctrl-c}.
5731 @item backtrace @var{n}
5733 Similar, but print only the innermost @var{n} frames.
5735 @item backtrace -@var{n}
5737 Similar, but print only the outermost @var{n} frames.
5739 @item backtrace full
5741 @itemx bt full @var{n}
5742 @itemx bt full -@var{n}
5743 Print the values of the local variables also. @var{n} specifies the
5744 number of frames to print, as described above.
5749 The names @code{where} and @code{info stack} (abbreviated @code{info s})
5750 are additional aliases for @code{backtrace}.
5752 @cindex multiple threads, backtrace
5753 In a multi-threaded program, @value{GDBN} by default shows the
5754 backtrace only for the current thread. To display the backtrace for
5755 several or all of the threads, use the command @code{thread apply}
5756 (@pxref{Threads, thread apply}). For example, if you type @kbd{thread
5757 apply all backtrace}, @value{GDBN} will display the backtrace for all
5758 the threads; this is handy when you debug a core dump of a
5759 multi-threaded program.
5761 Each line in the backtrace shows the frame number and the function name.
5762 The program counter value is also shown---unless you use @code{set
5763 print address off}. The backtrace also shows the source file name and
5764 line number, as well as the arguments to the function. The program
5765 counter value is omitted if it is at the beginning of the code for that
5768 Here is an example of a backtrace. It was made with the command
5769 @samp{bt 3}, so it shows the innermost three frames.
5773 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
5775 #1 0x6e38 in expand_macro (sym=0x2b600, data=...) at macro.c:242
5776 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
5778 (More stack frames follow...)
5783 The display for frame zero does not begin with a program counter
5784 value, indicating that your program has stopped at the beginning of the
5785 code for line @code{993} of @code{builtin.c}.
5788 The value of parameter @code{data} in frame 1 has been replaced by
5789 @code{@dots{}}. By default, @value{GDBN} prints the value of a parameter
5790 only if it is a scalar (integer, pointer, enumeration, etc). See command
5791 @kbd{set print frame-arguments} in @ref{Print Settings} for more details
5792 on how to configure the way function parameter values are printed.
5794 @cindex value optimized out, in backtrace
5795 @cindex function call arguments, optimized out
5796 If your program was compiled with optimizations, some compilers will
5797 optimize away arguments passed to functions if those arguments are
5798 never used after the call. Such optimizations generate code that
5799 passes arguments through registers, but doesn't store those arguments
5800 in the stack frame. @value{GDBN} has no way of displaying such
5801 arguments in stack frames other than the innermost one. Here's what
5802 such a backtrace might look like:
5806 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
5808 #1 0x6e38 in expand_macro (sym=<value optimized out>) at macro.c:242
5809 #2 0x6840 in expand_token (obs=0x0, t=<value optimized out>, td=0xf7fffb08)
5811 (More stack frames follow...)
5816 The values of arguments that were not saved in their stack frames are
5817 shown as @samp{<value optimized out>}.
5819 If you need to display the values of such optimized-out arguments,
5820 either deduce that from other variables whose values depend on the one
5821 you are interested in, or recompile without optimizations.
5823 @cindex backtrace beyond @code{main} function
5824 @cindex program entry point
5825 @cindex startup code, and backtrace
5826 Most programs have a standard user entry point---a place where system
5827 libraries and startup code transition into user code. For C this is
5828 @code{main}@footnote{
5829 Note that embedded programs (the so-called ``free-standing''
5830 environment) are not required to have a @code{main} function as the
5831 entry point. They could even have multiple entry points.}.
5832 When @value{GDBN} finds the entry function in a backtrace
5833 it will terminate the backtrace, to avoid tracing into highly
5834 system-specific (and generally uninteresting) code.
5836 If you need to examine the startup code, or limit the number of levels
5837 in a backtrace, you can change this behavior:
5840 @item set backtrace past-main
5841 @itemx set backtrace past-main on
5842 @kindex set backtrace
5843 Backtraces will continue past the user entry point.
5845 @item set backtrace past-main off
5846 Backtraces will stop when they encounter the user entry point. This is the
5849 @item show backtrace past-main
5850 @kindex show backtrace
5851 Display the current user entry point backtrace policy.
5853 @item set backtrace past-entry
5854 @itemx set backtrace past-entry on
5855 Backtraces will continue past the internal entry point of an application.
5856 This entry point is encoded by the linker when the application is built,
5857 and is likely before the user entry point @code{main} (or equivalent) is called.
5859 @item set backtrace past-entry off
5860 Backtraces will stop when they encounter the internal entry point of an
5861 application. This is the default.
5863 @item show backtrace past-entry
5864 Display the current internal entry point backtrace policy.
5866 @item set backtrace limit @var{n}
5867 @itemx set backtrace limit 0
5868 @cindex backtrace limit
5869 Limit the backtrace to @var{n} levels. A value of zero means
5872 @item show backtrace limit
5873 Display the current limit on backtrace levels.
5877 @section Selecting a Frame
5879 Most commands for examining the stack and other data in your program work on
5880 whichever stack frame is selected at the moment. Here are the commands for
5881 selecting a stack frame; all of them finish by printing a brief description
5882 of the stack frame just selected.
5885 @kindex frame@r{, selecting}
5886 @kindex f @r{(@code{frame})}
5889 Select frame number @var{n}. Recall that frame zero is the innermost
5890 (currently executing) frame, frame one is the frame that called the
5891 innermost one, and so on. The highest-numbered frame is the one for
5894 @item frame @var{addr}
5896 Select the frame at address @var{addr}. This is useful mainly if the
5897 chaining of stack frames has been damaged by a bug, making it
5898 impossible for @value{GDBN} to assign numbers properly to all frames. In
5899 addition, this can be useful when your program has multiple stacks and
5900 switches between them.
5902 On the SPARC architecture, @code{frame} needs two addresses to
5903 select an arbitrary frame: a frame pointer and a stack pointer.
5905 On the MIPS and Alpha architecture, it needs two addresses: a stack
5906 pointer and a program counter.
5908 On the 29k architecture, it needs three addresses: a register stack
5909 pointer, a program counter, and a memory stack pointer.
5913 Move @var{n} frames up the stack. For positive numbers @var{n}, this
5914 advances toward the outermost frame, to higher frame numbers, to frames
5915 that have existed longer. @var{n} defaults to one.
5918 @kindex do @r{(@code{down})}
5920 Move @var{n} frames down the stack. For positive numbers @var{n}, this
5921 advances toward the innermost frame, to lower frame numbers, to frames
5922 that were created more recently. @var{n} defaults to one. You may
5923 abbreviate @code{down} as @code{do}.
5926 All of these commands end by printing two lines of output describing the
5927 frame. The first line shows the frame number, the function name, the
5928 arguments, and the source file and line number of execution in that
5929 frame. The second line shows the text of that source line.
5937 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
5939 10 read_input_file (argv[i]);
5943 After such a printout, the @code{list} command with no arguments
5944 prints ten lines centered on the point of execution in the frame.
5945 You can also edit the program at the point of execution with your favorite
5946 editing program by typing @code{edit}.
5947 @xref{List, ,Printing Source Lines},
5951 @kindex down-silently
5953 @item up-silently @var{n}
5954 @itemx down-silently @var{n}
5955 These two commands are variants of @code{up} and @code{down},
5956 respectively; they differ in that they do their work silently, without
5957 causing display of the new frame. They are intended primarily for use
5958 in @value{GDBN} command scripts, where the output might be unnecessary and
5963 @section Information About a Frame
5965 There are several other commands to print information about the selected
5971 When used without any argument, this command does not change which
5972 frame is selected, but prints a brief description of the currently
5973 selected stack frame. It can be abbreviated @code{f}. With an
5974 argument, this command is used to select a stack frame.
5975 @xref{Selection, ,Selecting a Frame}.
5978 @kindex info f @r{(@code{info frame})}
5981 This command prints a verbose description of the selected stack frame,
5986 the address of the frame
5988 the address of the next frame down (called by this frame)
5990 the address of the next frame up (caller of this frame)
5992 the language in which the source code corresponding to this frame is written
5994 the address of the frame's arguments
5996 the address of the frame's local variables
5998 the program counter saved in it (the address of execution in the caller frame)
6000 which registers were saved in the frame
6003 @noindent The verbose description is useful when
6004 something has gone wrong that has made the stack format fail to fit
6005 the usual conventions.
6007 @item info frame @var{addr}
6008 @itemx info f @var{addr}
6009 Print a verbose description of the frame at address @var{addr}, without
6010 selecting that frame. The selected frame remains unchanged by this
6011 command. This requires the same kind of address (more than one for some
6012 architectures) that you specify in the @code{frame} command.
6013 @xref{Selection, ,Selecting a Frame}.
6017 Print the arguments of the selected frame, each on a separate line.
6021 Print the local variables of the selected frame, each on a separate
6022 line. These are all variables (declared either static or automatic)
6023 accessible at the point of execution of the selected frame.
6026 @cindex catch exceptions, list active handlers
6027 @cindex exception handlers, how to list
6029 Print a list of all the exception handlers that are active in the
6030 current stack frame at the current point of execution. To see other
6031 exception handlers, visit the associated frame (using the @code{up},
6032 @code{down}, or @code{frame} commands); then type @code{info catch}.
6033 @xref{Set Catchpoints, , Setting Catchpoints}.
6039 @chapter Examining Source Files
6041 @value{GDBN} can print parts of your program's source, since the debugging
6042 information recorded in the program tells @value{GDBN} what source files were
6043 used to build it. When your program stops, @value{GDBN} spontaneously prints
6044 the line where it stopped. Likewise, when you select a stack frame
6045 (@pxref{Selection, ,Selecting a Frame}), @value{GDBN} prints the line where
6046 execution in that frame has stopped. You can print other portions of
6047 source files by explicit command.
6049 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
6050 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
6051 @value{GDBN} under @sc{gnu} Emacs}.
6054 * List:: Printing source lines
6055 * Specify Location:: How to specify code locations
6056 * Edit:: Editing source files
6057 * Search:: Searching source files
6058 * Source Path:: Specifying source directories
6059 * Machine Code:: Source and machine code
6063 @section Printing Source Lines
6066 @kindex l @r{(@code{list})}
6067 To print lines from a source file, use the @code{list} command
6068 (abbreviated @code{l}). By default, ten lines are printed.
6069 There are several ways to specify what part of the file you want to
6070 print; see @ref{Specify Location}, for the full list.
6072 Here are the forms of the @code{list} command most commonly used:
6075 @item list @var{linenum}
6076 Print lines centered around line number @var{linenum} in the
6077 current source file.
6079 @item list @var{function}
6080 Print lines centered around the beginning of function
6084 Print more lines. If the last lines printed were printed with a
6085 @code{list} command, this prints lines following the last lines
6086 printed; however, if the last line printed was a solitary line printed
6087 as part of displaying a stack frame (@pxref{Stack, ,Examining the
6088 Stack}), this prints lines centered around that line.
6091 Print lines just before the lines last printed.
6094 @cindex @code{list}, how many lines to display
6095 By default, @value{GDBN} prints ten source lines with any of these forms of
6096 the @code{list} command. You can change this using @code{set listsize}:
6099 @kindex set listsize
6100 @item set listsize @var{count}
6101 Make the @code{list} command display @var{count} source lines (unless
6102 the @code{list} argument explicitly specifies some other number).
6104 @kindex show listsize
6106 Display the number of lines that @code{list} prints.
6109 Repeating a @code{list} command with @key{RET} discards the argument,
6110 so it is equivalent to typing just @code{list}. This is more useful
6111 than listing the same lines again. An exception is made for an
6112 argument of @samp{-}; that argument is preserved in repetition so that
6113 each repetition moves up in the source file.
6115 In general, the @code{list} command expects you to supply zero, one or two
6116 @dfn{linespecs}. Linespecs specify source lines; there are several ways
6117 of writing them (@pxref{Specify Location}), but the effect is always
6118 to specify some source line.
6120 Here is a complete description of the possible arguments for @code{list}:
6123 @item list @var{linespec}
6124 Print lines centered around the line specified by @var{linespec}.
6126 @item list @var{first},@var{last}
6127 Print lines from @var{first} to @var{last}. Both arguments are
6128 linespecs. When a @code{list} command has two linespecs, and the
6129 source file of the second linespec is omitted, this refers to
6130 the same source file as the first linespec.
6132 @item list ,@var{last}
6133 Print lines ending with @var{last}.
6135 @item list @var{first},
6136 Print lines starting with @var{first}.
6139 Print lines just after the lines last printed.
6142 Print lines just before the lines last printed.
6145 As described in the preceding table.
6148 @node Specify Location
6149 @section Specifying a Location
6150 @cindex specifying location
6153 Several @value{GDBN} commands accept arguments that specify a location
6154 of your program's code. Since @value{GDBN} is a source-level
6155 debugger, a location usually specifies some line in the source code;
6156 for that reason, locations are also known as @dfn{linespecs}.
6158 Here are all the different ways of specifying a code location that
6159 @value{GDBN} understands:
6163 Specifies the line number @var{linenum} of the current source file.
6166 @itemx +@var{offset}
6167 Specifies the line @var{offset} lines before or after the @dfn{current
6168 line}. For the @code{list} command, the current line is the last one
6169 printed; for the breakpoint commands, this is the line at which
6170 execution stopped in the currently selected @dfn{stack frame}
6171 (@pxref{Frames, ,Frames}, for a description of stack frames.) When
6172 used as the second of the two linespecs in a @code{list} command,
6173 this specifies the line @var{offset} lines up or down from the first
6176 @item @var{filename}:@var{linenum}
6177 Specifies the line @var{linenum} in the source file @var{filename}.
6179 @item @var{function}
6180 Specifies the line that begins the body of the function @var{function}.
6181 For example, in C, this is the line with the open brace.
6183 @item @var{filename}:@var{function}
6184 Specifies the line that begins the body of the function @var{function}
6185 in the file @var{filename}. You only need the file name with a
6186 function name to avoid ambiguity when there are identically named
6187 functions in different source files.
6189 @item *@var{address}
6190 Specifies the program address @var{address}. For line-oriented
6191 commands, such as @code{list} and @code{edit}, this specifies a source
6192 line that contains @var{address}. For @code{break} and other
6193 breakpoint oriented commands, this can be used to set breakpoints in
6194 parts of your program which do not have debugging information or
6197 Here @var{address} may be any expression valid in the current working
6198 language (@pxref{Languages, working language}) that specifies a code
6199 address. In addition, as a convenience, @value{GDBN} extends the
6200 semantics of expressions used in locations to cover the situations
6201 that frequently happen during debugging. Here are the various forms
6205 @item @var{expression}
6206 Any expression valid in the current working language.
6208 @item @var{funcaddr}
6209 An address of a function or procedure derived from its name. In C,
6210 C@t{++}, Java, Objective-C, Fortran, minimal, and assembly, this is
6211 simply the function's name @var{function} (and actually a special case
6212 of a valid expression). In Pascal and Modula-2, this is
6213 @code{&@var{function}}. In Ada, this is @code{@var{function}'Address}
6214 (although the Pascal form also works).
6216 This form specifies the address of the function's first instruction,
6217 before the stack frame and arguments have been set up.
6219 @item '@var{filename}'::@var{funcaddr}
6220 Like @var{funcaddr} above, but also specifies the name of the source
6221 file explicitly. This is useful if the name of the function does not
6222 specify the function unambiguously, e.g., if there are several
6223 functions with identical names in different source files.
6230 @section Editing Source Files
6231 @cindex editing source files
6234 @kindex e @r{(@code{edit})}
6235 To edit the lines in a source file, use the @code{edit} command.
6236 The editing program of your choice
6237 is invoked with the current line set to
6238 the active line in the program.
6239 Alternatively, there are several ways to specify what part of the file you
6240 want to print if you want to see other parts of the program:
6243 @item edit @var{location}
6244 Edit the source file specified by @code{location}. Editing starts at
6245 that @var{location}, e.g., at the specified source line of the
6246 specified file. @xref{Specify Location}, for all the possible forms
6247 of the @var{location} argument; here are the forms of the @code{edit}
6248 command most commonly used:
6251 @item edit @var{number}
6252 Edit the current source file with @var{number} as the active line number.
6254 @item edit @var{function}
6255 Edit the file containing @var{function} at the beginning of its definition.
6260 @subsection Choosing your Editor
6261 You can customize @value{GDBN} to use any editor you want
6263 The only restriction is that your editor (say @code{ex}), recognizes the
6264 following command-line syntax:
6266 ex +@var{number} file
6268 The optional numeric value +@var{number} specifies the number of the line in
6269 the file where to start editing.}.
6270 By default, it is @file{@value{EDITOR}}, but you can change this
6271 by setting the environment variable @code{EDITOR} before using
6272 @value{GDBN}. For example, to configure @value{GDBN} to use the
6273 @code{vi} editor, you could use these commands with the @code{sh} shell:
6279 or in the @code{csh} shell,
6281 setenv EDITOR /usr/bin/vi
6286 @section Searching Source Files
6287 @cindex searching source files
6289 There are two commands for searching through the current source file for a
6294 @kindex forward-search
6295 @item forward-search @var{regexp}
6296 @itemx search @var{regexp}
6297 The command @samp{forward-search @var{regexp}} checks each line,
6298 starting with the one following the last line listed, for a match for
6299 @var{regexp}. It lists the line that is found. You can use the
6300 synonym @samp{search @var{regexp}} or abbreviate the command name as
6303 @kindex reverse-search
6304 @item reverse-search @var{regexp}
6305 The command @samp{reverse-search @var{regexp}} checks each line, starting
6306 with the one before the last line listed and going backward, for a match
6307 for @var{regexp}. It lists the line that is found. You can abbreviate
6308 this command as @code{rev}.
6312 @section Specifying Source Directories
6315 @cindex directories for source files
6316 Executable programs sometimes do not record the directories of the source
6317 files from which they were compiled, just the names. Even when they do,
6318 the directories could be moved between the compilation and your debugging
6319 session. @value{GDBN} has a list of directories to search for source files;
6320 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
6321 it tries all the directories in the list, in the order they are present
6322 in the list, until it finds a file with the desired name.
6324 For example, suppose an executable references the file
6325 @file{/usr/src/foo-1.0/lib/foo.c}, and our source path is
6326 @file{/mnt/cross}. The file is first looked up literally; if this
6327 fails, @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c} is tried; if this
6328 fails, @file{/mnt/cross/foo.c} is opened; if this fails, an error
6329 message is printed. @value{GDBN} does not look up the parts of the
6330 source file name, such as @file{/mnt/cross/src/foo-1.0/lib/foo.c}.
6331 Likewise, the subdirectories of the source path are not searched: if
6332 the source path is @file{/mnt/cross}, and the binary refers to
6333 @file{foo.c}, @value{GDBN} would not find it under
6334 @file{/mnt/cross/usr/src/foo-1.0/lib}.
6336 Plain file names, relative file names with leading directories, file
6337 names containing dots, etc.@: are all treated as described above; for
6338 instance, if the source path is @file{/mnt/cross}, and the source file
6339 is recorded as @file{../lib/foo.c}, @value{GDBN} would first try
6340 @file{../lib/foo.c}, then @file{/mnt/cross/../lib/foo.c}, and after
6341 that---@file{/mnt/cross/foo.c}.
6343 Note that the executable search path is @emph{not} used to locate the
6346 Whenever you reset or rearrange the source path, @value{GDBN} clears out
6347 any information it has cached about where source files are found and where
6348 each line is in the file.
6352 When you start @value{GDBN}, its source path includes only @samp{cdir}
6353 and @samp{cwd}, in that order.
6354 To add other directories, use the @code{directory} command.
6356 The search path is used to find both program source files and @value{GDBN}
6357 script files (read using the @samp{-command} option and @samp{source} command).
6359 In addition to the source path, @value{GDBN} provides a set of commands
6360 that manage a list of source path substitution rules. A @dfn{substitution
6361 rule} specifies how to rewrite source directories stored in the program's
6362 debug information in case the sources were moved to a different
6363 directory between compilation and debugging. A rule is made of
6364 two strings, the first specifying what needs to be rewritten in
6365 the path, and the second specifying how it should be rewritten.
6366 In @ref{set substitute-path}, we name these two parts @var{from} and
6367 @var{to} respectively. @value{GDBN} does a simple string replacement
6368 of @var{from} with @var{to} at the start of the directory part of the
6369 source file name, and uses that result instead of the original file
6370 name to look up the sources.
6372 Using the previous example, suppose the @file{foo-1.0} tree has been
6373 moved from @file{/usr/src} to @file{/mnt/cross}, then you can tell
6374 @value{GDBN} to replace @file{/usr/src} in all source path names with
6375 @file{/mnt/cross}. The first lookup will then be
6376 @file{/mnt/cross/foo-1.0/lib/foo.c} in place of the original location
6377 of @file{/usr/src/foo-1.0/lib/foo.c}. To define a source path
6378 substitution rule, use the @code{set substitute-path} command
6379 (@pxref{set substitute-path}).
6381 To avoid unexpected substitution results, a rule is applied only if the
6382 @var{from} part of the directory name ends at a directory separator.
6383 For instance, a rule substituting @file{/usr/source} into
6384 @file{/mnt/cross} will be applied to @file{/usr/source/foo-1.0} but
6385 not to @file{/usr/sourceware/foo-2.0}. And because the substitution
6386 is applied only at the beginning of the directory name, this rule will
6387 not be applied to @file{/root/usr/source/baz.c} either.
6389 In many cases, you can achieve the same result using the @code{directory}
6390 command. However, @code{set substitute-path} can be more efficient in
6391 the case where the sources are organized in a complex tree with multiple
6392 subdirectories. With the @code{directory} command, you need to add each
6393 subdirectory of your project. If you moved the entire tree while
6394 preserving its internal organization, then @code{set substitute-path}
6395 allows you to direct the debugger to all the sources with one single
6398 @code{set substitute-path} is also more than just a shortcut command.
6399 The source path is only used if the file at the original location no
6400 longer exists. On the other hand, @code{set substitute-path} modifies
6401 the debugger behavior to look at the rewritten location instead. So, if
6402 for any reason a source file that is not relevant to your executable is
6403 located at the original location, a substitution rule is the only
6404 method available to point @value{GDBN} at the new location.
6406 @cindex @samp{--with-relocated-sources}
6407 @cindex default source path substitution
6408 You can configure a default source path substitution rule by
6409 configuring @value{GDBN} with the
6410 @samp{--with-relocated-sources=@var{dir}} option. The @var{dir}
6411 should be the name of a directory under @value{GDBN}'s configured
6412 prefix (set with @samp{--prefix} or @samp{--exec-prefix}), and
6413 directory names in debug information under @var{dir} will be adjusted
6414 automatically if the installed @value{GDBN} is moved to a new
6415 location. This is useful if @value{GDBN}, libraries or executables
6416 with debug information and corresponding source code are being moved
6420 @item directory @var{dirname} @dots{}
6421 @item dir @var{dirname} @dots{}
6422 Add directory @var{dirname} to the front of the source path. Several
6423 directory names may be given to this command, separated by @samp{:}
6424 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
6425 part of absolute file names) or
6426 whitespace. You may specify a directory that is already in the source
6427 path; this moves it forward, so @value{GDBN} searches it sooner.
6431 @vindex $cdir@r{, convenience variable}
6432 @vindex $cwd@r{, convenience variable}
6433 @cindex compilation directory
6434 @cindex current directory
6435 @cindex working directory
6436 @cindex directory, current
6437 @cindex directory, compilation
6438 You can use the string @samp{$cdir} to refer to the compilation
6439 directory (if one is recorded), and @samp{$cwd} to refer to the current
6440 working directory. @samp{$cwd} is not the same as @samp{.}---the former
6441 tracks the current working directory as it changes during your @value{GDBN}
6442 session, while the latter is immediately expanded to the current
6443 directory at the time you add an entry to the source path.
6446 Reset the source path to its default value (@samp{$cdir:$cwd} on Unix systems). This requires confirmation.
6448 @c RET-repeat for @code{directory} is explicitly disabled, but since
6449 @c repeating it would be a no-op we do not say that. (thanks to RMS)
6451 @item show directories
6452 @kindex show directories
6453 Print the source path: show which directories it contains.
6455 @anchor{set substitute-path}
6456 @item set substitute-path @var{from} @var{to}
6457 @kindex set substitute-path
6458 Define a source path substitution rule, and add it at the end of the
6459 current list of existing substitution rules. If a rule with the same
6460 @var{from} was already defined, then the old rule is also deleted.
6462 For example, if the file @file{/foo/bar/baz.c} was moved to
6463 @file{/mnt/cross/baz.c}, then the command
6466 (@value{GDBP}) set substitute-path /usr/src /mnt/cross
6470 will tell @value{GDBN} to replace @samp{/usr/src} with
6471 @samp{/mnt/cross}, which will allow @value{GDBN} to find the file
6472 @file{baz.c} even though it was moved.
6474 In the case when more than one substitution rule have been defined,
6475 the rules are evaluated one by one in the order where they have been
6476 defined. The first one matching, if any, is selected to perform
6479 For instance, if we had entered the following commands:
6482 (@value{GDBP}) set substitute-path /usr/src/include /mnt/include
6483 (@value{GDBP}) set substitute-path /usr/src /mnt/src
6487 @value{GDBN} would then rewrite @file{/usr/src/include/defs.h} into
6488 @file{/mnt/include/defs.h} by using the first rule. However, it would
6489 use the second rule to rewrite @file{/usr/src/lib/foo.c} into
6490 @file{/mnt/src/lib/foo.c}.
6493 @item unset substitute-path [path]
6494 @kindex unset substitute-path
6495 If a path is specified, search the current list of substitution rules
6496 for a rule that would rewrite that path. Delete that rule if found.
6497 A warning is emitted by the debugger if no rule could be found.
6499 If no path is specified, then all substitution rules are deleted.
6501 @item show substitute-path [path]
6502 @kindex show substitute-path
6503 If a path is specified, then print the source path substitution rule
6504 which would rewrite that path, if any.
6506 If no path is specified, then print all existing source path substitution
6511 If your source path is cluttered with directories that are no longer of
6512 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
6513 versions of source. You can correct the situation as follows:
6517 Use @code{directory} with no argument to reset the source path to its default value.
6520 Use @code{directory} with suitable arguments to reinstall the
6521 directories you want in the source path. You can add all the
6522 directories in one command.
6526 @section Source and Machine Code
6527 @cindex source line and its code address
6529 You can use the command @code{info line} to map source lines to program
6530 addresses (and vice versa), and the command @code{disassemble} to display
6531 a range of addresses as machine instructions. You can use the command
6532 @code{set disassemble-next-line} to set whether to disassemble next
6533 source line when execution stops. When run under @sc{gnu} Emacs
6534 mode, the @code{info line} command causes the arrow to point to the
6535 line specified. Also, @code{info line} prints addresses in symbolic form as
6540 @item info line @var{linespec}
6541 Print the starting and ending addresses of the compiled code for
6542 source line @var{linespec}. You can specify source lines in any of
6543 the ways documented in @ref{Specify Location}.
6546 For example, we can use @code{info line} to discover the location of
6547 the object code for the first line of function
6548 @code{m4_changequote}:
6550 @c FIXME: I think this example should also show the addresses in
6551 @c symbolic form, as they usually would be displayed.
6553 (@value{GDBP}) info line m4_changequote
6554 Line 895 of "builtin.c" starts at pc 0x634c and ends at 0x6350.
6558 @cindex code address and its source line
6559 We can also inquire (using @code{*@var{addr}} as the form for
6560 @var{linespec}) what source line covers a particular address:
6562 (@value{GDBP}) info line *0x63ff
6563 Line 926 of "builtin.c" starts at pc 0x63e4 and ends at 0x6404.
6566 @cindex @code{$_} and @code{info line}
6567 @cindex @code{x} command, default address
6568 @kindex x@r{(examine), and} info line
6569 After @code{info line}, the default address for the @code{x} command
6570 is changed to the starting address of the line, so that @samp{x/i} is
6571 sufficient to begin examining the machine code (@pxref{Memory,
6572 ,Examining Memory}). Also, this address is saved as the value of the
6573 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
6578 @cindex assembly instructions
6579 @cindex instructions, assembly
6580 @cindex machine instructions
6581 @cindex listing machine instructions
6583 @itemx disassemble /m
6584 @itemx disassemble /r
6585 This specialized command dumps a range of memory as machine
6586 instructions. It can also print mixed source+disassembly by specifying
6587 the @code{/m} modifier and print the raw instructions in hex as well as
6588 in symbolic form by specifying the @code{/r}.
6589 The default memory range is the function surrounding the
6590 program counter of the selected frame. A single argument to this
6591 command is a program counter value; @value{GDBN} dumps the function
6592 surrounding this value. When two arguments are given, they should
6593 be separated by a comma, possibly surrounded by whitespace. The
6594 arguments specify a range of addresses (first inclusive, second exclusive)
6595 to dump. In that case, the name of the function is also printed (since
6596 there could be several functions in the given range).
6598 The argument(s) can be any expression yielding a numeric value, such as
6599 @samp{0x32c4}, @samp{&main+10} or @samp{$pc - 8}.
6601 If the range of memory being disassembled contains current program counter,
6602 the instruction at that location is shown with a @code{=>} marker.
6605 The following example shows the disassembly of a range of addresses of
6606 HP PA-RISC 2.0 code:
6609 (@value{GDBP}) disas 0x32c4, 0x32e4
6610 Dump of assembler code from 0x32c4 to 0x32e4:
6611 0x32c4 <main+204>: addil 0,dp
6612 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
6613 0x32cc <main+212>: ldil 0x3000,r31
6614 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
6615 0x32d4 <main+220>: ldo 0(r31),rp
6616 0x32d8 <main+224>: addil -0x800,dp
6617 0x32dc <main+228>: ldo 0x588(r1),r26
6618 0x32e0 <main+232>: ldil 0x3000,r31
6619 End of assembler dump.
6622 Here is an example showing mixed source+assembly for Intel x86, when the
6623 program is stopped just after function prologue:
6626 (@value{GDBP}) disas /m main
6627 Dump of assembler code for function main:
6629 0x08048330 <+0>: push %ebp
6630 0x08048331 <+1>: mov %esp,%ebp
6631 0x08048333 <+3>: sub $0x8,%esp
6632 0x08048336 <+6>: and $0xfffffff0,%esp
6633 0x08048339 <+9>: sub $0x10,%esp
6635 6 printf ("Hello.\n");
6636 => 0x0804833c <+12>: movl $0x8048440,(%esp)
6637 0x08048343 <+19>: call 0x8048284 <puts@@plt>
6641 0x08048348 <+24>: mov $0x0,%eax
6642 0x0804834d <+29>: leave
6643 0x0804834e <+30>: ret
6645 End of assembler dump.
6648 Some architectures have more than one commonly-used set of instruction
6649 mnemonics or other syntax.
6651 For programs that were dynamically linked and use shared libraries,
6652 instructions that call functions or branch to locations in the shared
6653 libraries might show a seemingly bogus location---it's actually a
6654 location of the relocation table. On some architectures, @value{GDBN}
6655 might be able to resolve these to actual function names.
6658 @kindex set disassembly-flavor
6659 @cindex Intel disassembly flavor
6660 @cindex AT&T disassembly flavor
6661 @item set disassembly-flavor @var{instruction-set}
6662 Select the instruction set to use when disassembling the
6663 program via the @code{disassemble} or @code{x/i} commands.
6665 Currently this command is only defined for the Intel x86 family. You
6666 can set @var{instruction-set} to either @code{intel} or @code{att}.
6667 The default is @code{att}, the AT&T flavor used by default by Unix
6668 assemblers for x86-based targets.
6670 @kindex show disassembly-flavor
6671 @item show disassembly-flavor
6672 Show the current setting of the disassembly flavor.
6676 @kindex set disassemble-next-line
6677 @kindex show disassemble-next-line
6678 @item set disassemble-next-line
6679 @itemx show disassemble-next-line
6680 Control whether or not @value{GDBN} will disassemble the next source
6681 line or instruction when execution stops. If ON, @value{GDBN} will
6682 display disassembly of the next source line when execution of the
6683 program being debugged stops. This is @emph{in addition} to
6684 displaying the source line itself, which @value{GDBN} always does if
6685 possible. If the next source line cannot be displayed for some reason
6686 (e.g., if @value{GDBN} cannot find the source file, or there's no line
6687 info in the debug info), @value{GDBN} will display disassembly of the
6688 next @emph{instruction} instead of showing the next source line. If
6689 AUTO, @value{GDBN} will display disassembly of next instruction only
6690 if the source line cannot be displayed. This setting causes
6691 @value{GDBN} to display some feedback when you step through a function
6692 with no line info or whose source file is unavailable. The default is
6693 OFF, which means never display the disassembly of the next line or
6699 @chapter Examining Data
6701 @cindex printing data
6702 @cindex examining data
6705 @c "inspect" is not quite a synonym if you are using Epoch, which we do not
6706 @c document because it is nonstandard... Under Epoch it displays in a
6707 @c different window or something like that.
6708 The usual way to examine data in your program is with the @code{print}
6709 command (abbreviated @code{p}), or its synonym @code{inspect}. It
6710 evaluates and prints the value of an expression of the language your
6711 program is written in (@pxref{Languages, ,Using @value{GDBN} with
6712 Different Languages}). It may also print the expression using a
6713 Python-based pretty-printer (@pxref{Pretty Printing}).
6716 @item print @var{expr}
6717 @itemx print /@var{f} @var{expr}
6718 @var{expr} is an expression (in the source language). By default the
6719 value of @var{expr} is printed in a format appropriate to its data type;
6720 you can choose a different format by specifying @samp{/@var{f}}, where
6721 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
6725 @itemx print /@var{f}
6726 @cindex reprint the last value
6727 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
6728 @dfn{value history}; @pxref{Value History, ,Value History}). This allows you to
6729 conveniently inspect the same value in an alternative format.
6732 A more low-level way of examining data is with the @code{x} command.
6733 It examines data in memory at a specified address and prints it in a
6734 specified format. @xref{Memory, ,Examining Memory}.
6736 If you are interested in information about types, or about how the
6737 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
6738 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
6742 * Expressions:: Expressions
6743 * Ambiguous Expressions:: Ambiguous Expressions
6744 * Variables:: Program variables
6745 * Arrays:: Artificial arrays
6746 * Output Formats:: Output formats
6747 * Memory:: Examining memory
6748 * Auto Display:: Automatic display
6749 * Print Settings:: Print settings
6750 * Pretty Printing:: Python pretty printing
6751 * Value History:: Value history
6752 * Convenience Vars:: Convenience variables
6753 * Registers:: Registers
6754 * Floating Point Hardware:: Floating point hardware
6755 * Vector Unit:: Vector Unit
6756 * OS Information:: Auxiliary data provided by operating system
6757 * Memory Region Attributes:: Memory region attributes
6758 * Dump/Restore Files:: Copy between memory and a file
6759 * Core File Generation:: Cause a program dump its core
6760 * Character Sets:: Debugging programs that use a different
6761 character set than GDB does
6762 * Caching Remote Data:: Data caching for remote targets
6763 * Searching Memory:: Searching memory for a sequence of bytes
6767 @section Expressions
6770 @code{print} and many other @value{GDBN} commands accept an expression and
6771 compute its value. Any kind of constant, variable or operator defined
6772 by the programming language you are using is valid in an expression in
6773 @value{GDBN}. This includes conditional expressions, function calls,
6774 casts, and string constants. It also includes preprocessor macros, if
6775 you compiled your program to include this information; see
6778 @cindex arrays in expressions
6779 @value{GDBN} supports array constants in expressions input by
6780 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
6781 you can use the command @code{print @{1, 2, 3@}} to create an array
6782 of three integers. If you pass an array to a function or assign it
6783 to a program variable, @value{GDBN} copies the array to memory that
6784 is @code{malloc}ed in the target program.
6786 Because C is so widespread, most of the expressions shown in examples in
6787 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
6788 Languages}, for information on how to use expressions in other
6791 In this section, we discuss operators that you can use in @value{GDBN}
6792 expressions regardless of your programming language.
6794 @cindex casts, in expressions
6795 Casts are supported in all languages, not just in C, because it is so
6796 useful to cast a number into a pointer in order to examine a structure
6797 at that address in memory.
6798 @c FIXME: casts supported---Mod2 true?
6800 @value{GDBN} supports these operators, in addition to those common
6801 to programming languages:
6805 @samp{@@} is a binary operator for treating parts of memory as arrays.
6806 @xref{Arrays, ,Artificial Arrays}, for more information.
6809 @samp{::} allows you to specify a variable in terms of the file or
6810 function where it is defined. @xref{Variables, ,Program Variables}.
6812 @cindex @{@var{type}@}
6813 @cindex type casting memory
6814 @cindex memory, viewing as typed object
6815 @cindex casts, to view memory
6816 @item @{@var{type}@} @var{addr}
6817 Refers to an object of type @var{type} stored at address @var{addr} in
6818 memory. @var{addr} may be any expression whose value is an integer or
6819 pointer (but parentheses are required around binary operators, just as in
6820 a cast). This construct is allowed regardless of what kind of data is
6821 normally supposed to reside at @var{addr}.
6824 @node Ambiguous Expressions
6825 @section Ambiguous Expressions
6826 @cindex ambiguous expressions
6828 Expressions can sometimes contain some ambiguous elements. For instance,
6829 some programming languages (notably Ada, C@t{++} and Objective-C) permit
6830 a single function name to be defined several times, for application in
6831 different contexts. This is called @dfn{overloading}. Another example
6832 involving Ada is generics. A @dfn{generic package} is similar to C@t{++}
6833 templates and is typically instantiated several times, resulting in
6834 the same function name being defined in different contexts.
6836 In some cases and depending on the language, it is possible to adjust
6837 the expression to remove the ambiguity. For instance in C@t{++}, you
6838 can specify the signature of the function you want to break on, as in
6839 @kbd{break @var{function}(@var{types})}. In Ada, using the fully
6840 qualified name of your function often makes the expression unambiguous
6843 When an ambiguity that needs to be resolved is detected, the debugger
6844 has the capability to display a menu of numbered choices for each
6845 possibility, and then waits for the selection with the prompt @samp{>}.
6846 The first option is always @samp{[0] cancel}, and typing @kbd{0 @key{RET}}
6847 aborts the current command. If the command in which the expression was
6848 used allows more than one choice to be selected, the next option in the
6849 menu is @samp{[1] all}, and typing @kbd{1 @key{RET}} selects all possible
6852 For example, the following session excerpt shows an attempt to set a
6853 breakpoint at the overloaded symbol @code{String::after}.
6854 We choose three particular definitions of that function name:
6856 @c FIXME! This is likely to change to show arg type lists, at least
6859 (@value{GDBP}) b String::after
6862 [2] file:String.cc; line number:867
6863 [3] file:String.cc; line number:860
6864 [4] file:String.cc; line number:875
6865 [5] file:String.cc; line number:853
6866 [6] file:String.cc; line number:846
6867 [7] file:String.cc; line number:735
6869 Breakpoint 1 at 0xb26c: file String.cc, line 867.
6870 Breakpoint 2 at 0xb344: file String.cc, line 875.
6871 Breakpoint 3 at 0xafcc: file String.cc, line 846.
6872 Multiple breakpoints were set.
6873 Use the "delete" command to delete unwanted
6880 @kindex set multiple-symbols
6881 @item set multiple-symbols @var{mode}
6882 @cindex multiple-symbols menu
6884 This option allows you to adjust the debugger behavior when an expression
6887 By default, @var{mode} is set to @code{all}. If the command with which
6888 the expression is used allows more than one choice, then @value{GDBN}
6889 automatically selects all possible choices. For instance, inserting
6890 a breakpoint on a function using an ambiguous name results in a breakpoint
6891 inserted on each possible match. However, if a unique choice must be made,
6892 then @value{GDBN} uses the menu to help you disambiguate the expression.
6893 For instance, printing the address of an overloaded function will result
6894 in the use of the menu.
6896 When @var{mode} is set to @code{ask}, the debugger always uses the menu
6897 when an ambiguity is detected.
6899 Finally, when @var{mode} is set to @code{cancel}, the debugger reports
6900 an error due to the ambiguity and the command is aborted.
6902 @kindex show multiple-symbols
6903 @item show multiple-symbols
6904 Show the current value of the @code{multiple-symbols} setting.
6908 @section Program Variables
6910 The most common kind of expression to use is the name of a variable
6913 Variables in expressions are understood in the selected stack frame
6914 (@pxref{Selection, ,Selecting a Frame}); they must be either:
6918 global (or file-static)
6925 visible according to the scope rules of the
6926 programming language from the point of execution in that frame
6929 @noindent This means that in the function
6944 you can examine and use the variable @code{a} whenever your program is
6945 executing within the function @code{foo}, but you can only use or
6946 examine the variable @code{b} while your program is executing inside
6947 the block where @code{b} is declared.
6949 @cindex variable name conflict
6950 There is an exception: you can refer to a variable or function whose
6951 scope is a single source file even if the current execution point is not
6952 in this file. But it is possible to have more than one such variable or
6953 function with the same name (in different source files). If that
6954 happens, referring to that name has unpredictable effects. If you wish,
6955 you can specify a static variable in a particular function or file,
6956 using the colon-colon (@code{::}) notation:
6958 @cindex colon-colon, context for variables/functions
6960 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
6961 @cindex @code{::}, context for variables/functions
6964 @var{file}::@var{variable}
6965 @var{function}::@var{variable}
6969 Here @var{file} or @var{function} is the name of the context for the
6970 static @var{variable}. In the case of file names, you can use quotes to
6971 make sure @value{GDBN} parses the file name as a single word---for example,
6972 to print a global value of @code{x} defined in @file{f2.c}:
6975 (@value{GDBP}) p 'f2.c'::x
6978 @cindex C@t{++} scope resolution
6979 This use of @samp{::} is very rarely in conflict with the very similar
6980 use of the same notation in C@t{++}. @value{GDBN} also supports use of the C@t{++}
6981 scope resolution operator in @value{GDBN} expressions.
6982 @c FIXME: Um, so what happens in one of those rare cases where it's in
6985 @cindex wrong values
6986 @cindex variable values, wrong
6987 @cindex function entry/exit, wrong values of variables
6988 @cindex optimized code, wrong values of variables
6990 @emph{Warning:} Occasionally, a local variable may appear to have the
6991 wrong value at certain points in a function---just after entry to a new
6992 scope, and just before exit.
6994 You may see this problem when you are stepping by machine instructions.
6995 This is because, on most machines, it takes more than one instruction to
6996 set up a stack frame (including local variable definitions); if you are
6997 stepping by machine instructions, variables may appear to have the wrong
6998 values until the stack frame is completely built. On exit, it usually
6999 also takes more than one machine instruction to destroy a stack frame;
7000 after you begin stepping through that group of instructions, local
7001 variable definitions may be gone.
7003 This may also happen when the compiler does significant optimizations.
7004 To be sure of always seeing accurate values, turn off all optimization
7007 @cindex ``No symbol "foo" in current context''
7008 Another possible effect of compiler optimizations is to optimize
7009 unused variables out of existence, or assign variables to registers (as
7010 opposed to memory addresses). Depending on the support for such cases
7011 offered by the debug info format used by the compiler, @value{GDBN}
7012 might not be able to display values for such local variables. If that
7013 happens, @value{GDBN} will print a message like this:
7016 No symbol "foo" in current context.
7019 To solve such problems, either recompile without optimizations, or use a
7020 different debug info format, if the compiler supports several such
7021 formats. For example, @value{NGCC}, the @sc{gnu} C/C@t{++} compiler,
7022 usually supports the @option{-gstabs+} option. @option{-gstabs+}
7023 produces debug info in a format that is superior to formats such as
7024 COFF. You may be able to use DWARF 2 (@option{-gdwarf-2}), which is also
7025 an effective form for debug info. @xref{Debugging Options,,Options
7026 for Debugging Your Program or GCC, gcc.info, Using the @sc{gnu}
7027 Compiler Collection (GCC)}.
7028 @xref{C, ,C and C@t{++}}, for more information about debug info formats
7029 that are best suited to C@t{++} programs.
7031 If you ask to print an object whose contents are unknown to
7032 @value{GDBN}, e.g., because its data type is not completely specified
7033 by the debug information, @value{GDBN} will say @samp{<incomplete
7034 type>}. @xref{Symbols, incomplete type}, for more about this.
7036 Strings are identified as arrays of @code{char} values without specified
7037 signedness. Arrays of either @code{signed char} or @code{unsigned char} get
7038 printed as arrays of 1 byte sized integers. @code{-fsigned-char} or
7039 @code{-funsigned-char} @value{NGCC} options have no effect as @value{GDBN}
7040 defines literal string type @code{"char"} as @code{char} without a sign.
7045 signed char var1[] = "A";
7048 You get during debugging
7053 $2 = @{65 'A', 0 '\0'@}
7057 @section Artificial Arrays
7059 @cindex artificial array
7061 @kindex @@@r{, referencing memory as an array}
7062 It is often useful to print out several successive objects of the
7063 same type in memory; a section of an array, or an array of
7064 dynamically determined size for which only a pointer exists in the
7067 You can do this by referring to a contiguous span of memory as an
7068 @dfn{artificial array}, using the binary operator @samp{@@}. The left
7069 operand of @samp{@@} should be the first element of the desired array
7070 and be an individual object. The right operand should be the desired length
7071 of the array. The result is an array value whose elements are all of
7072 the type of the left argument. The first element is actually the left
7073 argument; the second element comes from bytes of memory immediately
7074 following those that hold the first element, and so on. Here is an
7075 example. If a program says
7078 int *array = (int *) malloc (len * sizeof (int));
7082 you can print the contents of @code{array} with
7088 The left operand of @samp{@@} must reside in memory. Array values made
7089 with @samp{@@} in this way behave just like other arrays in terms of
7090 subscripting, and are coerced to pointers when used in expressions.
7091 Artificial arrays most often appear in expressions via the value history
7092 (@pxref{Value History, ,Value History}), after printing one out.
7094 Another way to create an artificial array is to use a cast.
7095 This re-interprets a value as if it were an array.
7096 The value need not be in memory:
7098 (@value{GDBP}) p/x (short[2])0x12345678
7099 $1 = @{0x1234, 0x5678@}
7102 As a convenience, if you leave the array length out (as in
7103 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
7104 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
7106 (@value{GDBP}) p/x (short[])0x12345678
7107 $2 = @{0x1234, 0x5678@}
7110 Sometimes the artificial array mechanism is not quite enough; in
7111 moderately complex data structures, the elements of interest may not
7112 actually be adjacent---for example, if you are interested in the values
7113 of pointers in an array. One useful work-around in this situation is
7114 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
7115 Variables}) as a counter in an expression that prints the first
7116 interesting value, and then repeat that expression via @key{RET}. For
7117 instance, suppose you have an array @code{dtab} of pointers to
7118 structures, and you are interested in the values of a field @code{fv}
7119 in each structure. Here is an example of what you might type:
7129 @node Output Formats
7130 @section Output Formats
7132 @cindex formatted output
7133 @cindex output formats
7134 By default, @value{GDBN} prints a value according to its data type. Sometimes
7135 this is not what you want. For example, you might want to print a number
7136 in hex, or a pointer in decimal. Or you might want to view data in memory
7137 at a certain address as a character string or as an instruction. To do
7138 these things, specify an @dfn{output format} when you print a value.
7140 The simplest use of output formats is to say how to print a value
7141 already computed. This is done by starting the arguments of the
7142 @code{print} command with a slash and a format letter. The format
7143 letters supported are:
7147 Regard the bits of the value as an integer, and print the integer in
7151 Print as integer in signed decimal.
7154 Print as integer in unsigned decimal.
7157 Print as integer in octal.
7160 Print as integer in binary. The letter @samp{t} stands for ``two''.
7161 @footnote{@samp{b} cannot be used because these format letters are also
7162 used with the @code{x} command, where @samp{b} stands for ``byte'';
7163 see @ref{Memory,,Examining Memory}.}
7166 @cindex unknown address, locating
7167 @cindex locate address
7168 Print as an address, both absolute in hexadecimal and as an offset from
7169 the nearest preceding symbol. You can use this format used to discover
7170 where (in what function) an unknown address is located:
7173 (@value{GDBP}) p/a 0x54320
7174 $3 = 0x54320 <_initialize_vx+396>
7178 The command @code{info symbol 0x54320} yields similar results.
7179 @xref{Symbols, info symbol}.
7182 Regard as an integer and print it as a character constant. This
7183 prints both the numerical value and its character representation. The
7184 character representation is replaced with the octal escape @samp{\nnn}
7185 for characters outside the 7-bit @sc{ascii} range.
7187 Without this format, @value{GDBN} displays @code{char},
7188 @w{@code{unsigned char}}, and @w{@code{signed char}} data as character
7189 constants. Single-byte members of vectors are displayed as integer
7193 Regard the bits of the value as a floating point number and print
7194 using typical floating point syntax.
7197 @cindex printing strings
7198 @cindex printing byte arrays
7199 Regard as a string, if possible. With this format, pointers to single-byte
7200 data are displayed as null-terminated strings and arrays of single-byte data
7201 are displayed as fixed-length strings. Other values are displayed in their
7204 Without this format, @value{GDBN} displays pointers to and arrays of
7205 @code{char}, @w{@code{unsigned char}}, and @w{@code{signed char}} as
7206 strings. Single-byte members of a vector are displayed as an integer
7210 @cindex raw printing
7211 Print using the @samp{raw} formatting. By default, @value{GDBN} will
7212 use a Python-based pretty-printer, if one is available (@pxref{Pretty
7213 Printing}). This typically results in a higher-level display of the
7214 value's contents. The @samp{r} format bypasses any Python
7215 pretty-printer which might exist.
7218 For example, to print the program counter in hex (@pxref{Registers}), type
7225 Note that no space is required before the slash; this is because command
7226 names in @value{GDBN} cannot contain a slash.
7228 To reprint the last value in the value history with a different format,
7229 you can use the @code{print} command with just a format and no
7230 expression. For example, @samp{p/x} reprints the last value in hex.
7233 @section Examining Memory
7235 You can use the command @code{x} (for ``examine'') to examine memory in
7236 any of several formats, independently of your program's data types.
7238 @cindex examining memory
7240 @kindex x @r{(examine memory)}
7241 @item x/@var{nfu} @var{addr}
7244 Use the @code{x} command to examine memory.
7247 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
7248 much memory to display and how to format it; @var{addr} is an
7249 expression giving the address where you want to start displaying memory.
7250 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
7251 Several commands set convenient defaults for @var{addr}.
7254 @item @var{n}, the repeat count
7255 The repeat count is a decimal integer; the default is 1. It specifies
7256 how much memory (counting by units @var{u}) to display.
7257 @c This really is **decimal**; unaffected by 'set radix' as of GDB
7260 @item @var{f}, the display format
7261 The display format is one of the formats used by @code{print}
7262 (@samp{x}, @samp{d}, @samp{u}, @samp{o}, @samp{t}, @samp{a}, @samp{c},
7263 @samp{f}, @samp{s}), and in addition @samp{i} (for machine instructions).
7264 The default is @samp{x} (hexadecimal) initially. The default changes
7265 each time you use either @code{x} or @code{print}.
7267 @item @var{u}, the unit size
7268 The unit size is any of
7274 Halfwords (two bytes).
7276 Words (four bytes). This is the initial default.
7278 Giant words (eight bytes).
7281 Each time you specify a unit size with @code{x}, that size becomes the
7282 default unit the next time you use @code{x}. For the @samp{i} format,
7283 the unit size is ignored and is normally not written. For the @samp{s} format,
7284 the unit size defaults to @samp{b}, unless it is explicitly given.
7285 Use @kbd{x /hs} to display 16-bit char strings and @kbd{x /ws} to display
7286 32-bit strings. The next use of @kbd{x /s} will again display 8-bit strings.
7287 Note that the results depend on the programming language of the
7288 current compilation unit. If the language is C, the @samp{s}
7289 modifier will use the UTF-16 encoding while @samp{w} will use
7290 UTF-32. The encoding is set by the programming language and cannot
7293 @item @var{addr}, starting display address
7294 @var{addr} is the address where you want @value{GDBN} to begin displaying
7295 memory. The expression need not have a pointer value (though it may);
7296 it is always interpreted as an integer address of a byte of memory.
7297 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
7298 @var{addr} is usually just after the last address examined---but several
7299 other commands also set the default address: @code{info breakpoints} (to
7300 the address of the last breakpoint listed), @code{info line} (to the
7301 starting address of a line), and @code{print} (if you use it to display
7302 a value from memory).
7305 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
7306 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
7307 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
7308 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
7309 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
7311 Since the letters indicating unit sizes are all distinct from the
7312 letters specifying output formats, you do not have to remember whether
7313 unit size or format comes first; either order works. The output
7314 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
7315 (However, the count @var{n} must come first; @samp{wx4} does not work.)
7317 Even though the unit size @var{u} is ignored for the formats @samp{s}
7318 and @samp{i}, you might still want to use a count @var{n}; for example,
7319 @samp{3i} specifies that you want to see three machine instructions,
7320 including any operands. For convenience, especially when used with
7321 the @code{display} command, the @samp{i} format also prints branch delay
7322 slot instructions, if any, beyond the count specified, which immediately
7323 follow the last instruction that is within the count. The command
7324 @code{disassemble} gives an alternative way of inspecting machine
7325 instructions; see @ref{Machine Code,,Source and Machine Code}.
7327 All the defaults for the arguments to @code{x} are designed to make it
7328 easy to continue scanning memory with minimal specifications each time
7329 you use @code{x}. For example, after you have inspected three machine
7330 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
7331 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
7332 the repeat count @var{n} is used again; the other arguments default as
7333 for successive uses of @code{x}.
7335 When examining machine instructions, the instruction at current program
7336 counter is shown with a @code{=>} marker. For example:
7339 (@value{GDBP}) x/5i $pc-6
7340 0x804837f <main+11>: mov %esp,%ebp
7341 0x8048381 <main+13>: push %ecx
7342 0x8048382 <main+14>: sub $0x4,%esp
7343 => 0x8048385 <main+17>: movl $0x8048460,(%esp)
7344 0x804838c <main+24>: call 0x80482d4 <puts@@plt>
7347 @cindex @code{$_}, @code{$__}, and value history
7348 The addresses and contents printed by the @code{x} command are not saved
7349 in the value history because there is often too much of them and they
7350 would get in the way. Instead, @value{GDBN} makes these values available for
7351 subsequent use in expressions as values of the convenience variables
7352 @code{$_} and @code{$__}. After an @code{x} command, the last address
7353 examined is available for use in expressions in the convenience variable
7354 @code{$_}. The contents of that address, as examined, are available in
7355 the convenience variable @code{$__}.
7357 If the @code{x} command has a repeat count, the address and contents saved
7358 are from the last memory unit printed; this is not the same as the last
7359 address printed if several units were printed on the last line of output.
7361 @cindex remote memory comparison
7362 @cindex verify remote memory image
7363 When you are debugging a program running on a remote target machine
7364 (@pxref{Remote Debugging}), you may wish to verify the program's image in the
7365 remote machine's memory against the executable file you downloaded to
7366 the target. The @code{compare-sections} command is provided for such
7370 @kindex compare-sections
7371 @item compare-sections @r{[}@var{section-name}@r{]}
7372 Compare the data of a loadable section @var{section-name} in the
7373 executable file of the program being debugged with the same section in
7374 the remote machine's memory, and report any mismatches. With no
7375 arguments, compares all loadable sections. This command's
7376 availability depends on the target's support for the @code{"qCRC"}
7381 @section Automatic Display
7382 @cindex automatic display
7383 @cindex display of expressions
7385 If you find that you want to print the value of an expression frequently
7386 (to see how it changes), you might want to add it to the @dfn{automatic
7387 display list} so that @value{GDBN} prints its value each time your program stops.
7388 Each expression added to the list is given a number to identify it;
7389 to remove an expression from the list, you specify that number.
7390 The automatic display looks like this:
7394 3: bar[5] = (struct hack *) 0x3804
7398 This display shows item numbers, expressions and their current values. As with
7399 displays you request manually using @code{x} or @code{print}, you can
7400 specify the output format you prefer; in fact, @code{display} decides
7401 whether to use @code{print} or @code{x} depending your format
7402 specification---it uses @code{x} if you specify either the @samp{i}
7403 or @samp{s} format, or a unit size; otherwise it uses @code{print}.
7407 @item display @var{expr}
7408 Add the expression @var{expr} to the list of expressions to display
7409 each time your program stops. @xref{Expressions, ,Expressions}.
7411 @code{display} does not repeat if you press @key{RET} again after using it.
7413 @item display/@var{fmt} @var{expr}
7414 For @var{fmt} specifying only a display format and not a size or
7415 count, add the expression @var{expr} to the auto-display list but
7416 arrange to display it each time in the specified format @var{fmt}.
7417 @xref{Output Formats,,Output Formats}.
7419 @item display/@var{fmt} @var{addr}
7420 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
7421 number of units, add the expression @var{addr} as a memory address to
7422 be examined each time your program stops. Examining means in effect
7423 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining Memory}.
7426 For example, @samp{display/i $pc} can be helpful, to see the machine
7427 instruction about to be executed each time execution stops (@samp{$pc}
7428 is a common name for the program counter; @pxref{Registers, ,Registers}).
7431 @kindex delete display
7433 @item undisplay @var{dnums}@dots{}
7434 @itemx delete display @var{dnums}@dots{}
7435 Remove item numbers @var{dnums} from the list of expressions to display.
7437 @code{undisplay} does not repeat if you press @key{RET} after using it.
7438 (Otherwise you would just get the error @samp{No display number @dots{}}.)
7440 @kindex disable display
7441 @item disable display @var{dnums}@dots{}
7442 Disable the display of item numbers @var{dnums}. A disabled display
7443 item is not printed automatically, but is not forgotten. It may be
7444 enabled again later.
7446 @kindex enable display
7447 @item enable display @var{dnums}@dots{}
7448 Enable display of item numbers @var{dnums}. It becomes effective once
7449 again in auto display of its expression, until you specify otherwise.
7452 Display the current values of the expressions on the list, just as is
7453 done when your program stops.
7455 @kindex info display
7457 Print the list of expressions previously set up to display
7458 automatically, each one with its item number, but without showing the
7459 values. This includes disabled expressions, which are marked as such.
7460 It also includes expressions which would not be displayed right now
7461 because they refer to automatic variables not currently available.
7464 @cindex display disabled out of scope
7465 If a display expression refers to local variables, then it does not make
7466 sense outside the lexical context for which it was set up. Such an
7467 expression is disabled when execution enters a context where one of its
7468 variables is not defined. For example, if you give the command
7469 @code{display last_char} while inside a function with an argument
7470 @code{last_char}, @value{GDBN} displays this argument while your program
7471 continues to stop inside that function. When it stops elsewhere---where
7472 there is no variable @code{last_char}---the display is disabled
7473 automatically. The next time your program stops where @code{last_char}
7474 is meaningful, you can enable the display expression once again.
7476 @node Print Settings
7477 @section Print Settings
7479 @cindex format options
7480 @cindex print settings
7481 @value{GDBN} provides the following ways to control how arrays, structures,
7482 and symbols are printed.
7485 These settings are useful for debugging programs in any language:
7489 @item set print address
7490 @itemx set print address on
7491 @cindex print/don't print memory addresses
7492 @value{GDBN} prints memory addresses showing the location of stack
7493 traces, structure values, pointer values, breakpoints, and so forth,
7494 even when it also displays the contents of those addresses. The default
7495 is @code{on}. For example, this is what a stack frame display looks like with
7496 @code{set print address on}:
7501 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
7503 530 if (lquote != def_lquote)
7507 @item set print address off
7508 Do not print addresses when displaying their contents. For example,
7509 this is the same stack frame displayed with @code{set print address off}:
7513 (@value{GDBP}) set print addr off
7515 #0 set_quotes (lq="<<", rq=">>") at input.c:530
7516 530 if (lquote != def_lquote)
7520 You can use @samp{set print address off} to eliminate all machine
7521 dependent displays from the @value{GDBN} interface. For example, with
7522 @code{print address off}, you should get the same text for backtraces on
7523 all machines---whether or not they involve pointer arguments.
7526 @item show print address
7527 Show whether or not addresses are to be printed.
7530 When @value{GDBN} prints a symbolic address, it normally prints the
7531 closest earlier symbol plus an offset. If that symbol does not uniquely
7532 identify the address (for example, it is a name whose scope is a single
7533 source file), you may need to clarify. One way to do this is with
7534 @code{info line}, for example @samp{info line *0x4537}. Alternately,
7535 you can set @value{GDBN} to print the source file and line number when
7536 it prints a symbolic address:
7539 @item set print symbol-filename on
7540 @cindex source file and line of a symbol
7541 @cindex symbol, source file and line
7542 Tell @value{GDBN} to print the source file name and line number of a
7543 symbol in the symbolic form of an address.
7545 @item set print symbol-filename off
7546 Do not print source file name and line number of a symbol. This is the
7549 @item show print symbol-filename
7550 Show whether or not @value{GDBN} will print the source file name and
7551 line number of a symbol in the symbolic form of an address.
7554 Another situation where it is helpful to show symbol filenames and line
7555 numbers is when disassembling code; @value{GDBN} shows you the line
7556 number and source file that corresponds to each instruction.
7558 Also, you may wish to see the symbolic form only if the address being
7559 printed is reasonably close to the closest earlier symbol:
7562 @item set print max-symbolic-offset @var{max-offset}
7563 @cindex maximum value for offset of closest symbol
7564 Tell @value{GDBN} to only display the symbolic form of an address if the
7565 offset between the closest earlier symbol and the address is less than
7566 @var{max-offset}. The default is 0, which tells @value{GDBN}
7567 to always print the symbolic form of an address if any symbol precedes it.
7569 @item show print max-symbolic-offset
7570 Ask how large the maximum offset is that @value{GDBN} prints in a
7574 @cindex wild pointer, interpreting
7575 @cindex pointer, finding referent
7576 If you have a pointer and you are not sure where it points, try
7577 @samp{set print symbol-filename on}. Then you can determine the name
7578 and source file location of the variable where it points, using
7579 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
7580 For example, here @value{GDBN} shows that a variable @code{ptt} points
7581 at another variable @code{t}, defined in @file{hi2.c}:
7584 (@value{GDBP}) set print symbol-filename on
7585 (@value{GDBP}) p/a ptt
7586 $4 = 0xe008 <t in hi2.c>
7590 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
7591 does not show the symbol name and filename of the referent, even with
7592 the appropriate @code{set print} options turned on.
7595 Other settings control how different kinds of objects are printed:
7598 @item set print array
7599 @itemx set print array on
7600 @cindex pretty print arrays
7601 Pretty print arrays. This format is more convenient to read,
7602 but uses more space. The default is off.
7604 @item set print array off
7605 Return to compressed format for arrays.
7607 @item show print array
7608 Show whether compressed or pretty format is selected for displaying
7611 @cindex print array indexes
7612 @item set print array-indexes
7613 @itemx set print array-indexes on
7614 Print the index of each element when displaying arrays. May be more
7615 convenient to locate a given element in the array or quickly find the
7616 index of a given element in that printed array. The default is off.
7618 @item set print array-indexes off
7619 Stop printing element indexes when displaying arrays.
7621 @item show print array-indexes
7622 Show whether the index of each element is printed when displaying
7625 @item set print elements @var{number-of-elements}
7626 @cindex number of array elements to print
7627 @cindex limit on number of printed array elements
7628 Set a limit on how many elements of an array @value{GDBN} will print.
7629 If @value{GDBN} is printing a large array, it stops printing after it has
7630 printed the number of elements set by the @code{set print elements} command.
7631 This limit also applies to the display of strings.
7632 When @value{GDBN} starts, this limit is set to 200.
7633 Setting @var{number-of-elements} to zero means that the printing is unlimited.
7635 @item show print elements
7636 Display the number of elements of a large array that @value{GDBN} will print.
7637 If the number is 0, then the printing is unlimited.
7639 @item set print frame-arguments @var{value}
7640 @kindex set print frame-arguments
7641 @cindex printing frame argument values
7642 @cindex print all frame argument values
7643 @cindex print frame argument values for scalars only
7644 @cindex do not print frame argument values
7645 This command allows to control how the values of arguments are printed
7646 when the debugger prints a frame (@pxref{Frames}). The possible
7651 The values of all arguments are printed.
7654 Print the value of an argument only if it is a scalar. The value of more
7655 complex arguments such as arrays, structures, unions, etc, is replaced
7656 by @code{@dots{}}. This is the default. Here is an example where
7657 only scalar arguments are shown:
7660 #1 0x08048361 in call_me (i=3, s=@dots{}, ss=0xbf8d508c, u=@dots{}, e=green)
7665 None of the argument values are printed. Instead, the value of each argument
7666 is replaced by @code{@dots{}}. In this case, the example above now becomes:
7669 #1 0x08048361 in call_me (i=@dots{}, s=@dots{}, ss=@dots{}, u=@dots{}, e=@dots{})
7674 By default, only scalar arguments are printed. This command can be used
7675 to configure the debugger to print the value of all arguments, regardless
7676 of their type. However, it is often advantageous to not print the value
7677 of more complex parameters. For instance, it reduces the amount of
7678 information printed in each frame, making the backtrace more readable.
7679 Also, it improves performance when displaying Ada frames, because
7680 the computation of large arguments can sometimes be CPU-intensive,
7681 especially in large applications. Setting @code{print frame-arguments}
7682 to @code{scalars} (the default) or @code{none} avoids this computation,
7683 thus speeding up the display of each Ada frame.
7685 @item show print frame-arguments
7686 Show how the value of arguments should be displayed when printing a frame.
7688 @item set print repeats
7689 @cindex repeated array elements
7690 Set the threshold for suppressing display of repeated array
7691 elements. When the number of consecutive identical elements of an
7692 array exceeds the threshold, @value{GDBN} prints the string
7693 @code{"<repeats @var{n} times>"}, where @var{n} is the number of
7694 identical repetitions, instead of displaying the identical elements
7695 themselves. Setting the threshold to zero will cause all elements to
7696 be individually printed. The default threshold is 10.
7698 @item show print repeats
7699 Display the current threshold for printing repeated identical
7702 @item set print null-stop
7703 @cindex @sc{null} elements in arrays
7704 Cause @value{GDBN} to stop printing the characters of an array when the first
7705 @sc{null} is encountered. This is useful when large arrays actually
7706 contain only short strings.
7709 @item show print null-stop
7710 Show whether @value{GDBN} stops printing an array on the first
7711 @sc{null} character.
7713 @item set print pretty on
7714 @cindex print structures in indented form
7715 @cindex indentation in structure display
7716 Cause @value{GDBN} to print structures in an indented format with one member
7717 per line, like this:
7732 @item set print pretty off
7733 Cause @value{GDBN} to print structures in a compact format, like this:
7737 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
7738 meat = 0x54 "Pork"@}
7743 This is the default format.
7745 @item show print pretty
7746 Show which format @value{GDBN} is using to print structures.
7748 @item set print sevenbit-strings on
7749 @cindex eight-bit characters in strings
7750 @cindex octal escapes in strings
7751 Print using only seven-bit characters; if this option is set,
7752 @value{GDBN} displays any eight-bit characters (in strings or
7753 character values) using the notation @code{\}@var{nnn}. This setting is
7754 best if you are working in English (@sc{ascii}) and you use the
7755 high-order bit of characters as a marker or ``meta'' bit.
7757 @item set print sevenbit-strings off
7758 Print full eight-bit characters. This allows the use of more
7759 international character sets, and is the default.
7761 @item show print sevenbit-strings
7762 Show whether or not @value{GDBN} is printing only seven-bit characters.
7764 @item set print union on
7765 @cindex unions in structures, printing
7766 Tell @value{GDBN} to print unions which are contained in structures
7767 and other unions. This is the default setting.
7769 @item set print union off
7770 Tell @value{GDBN} not to print unions which are contained in
7771 structures and other unions. @value{GDBN} will print @code{"@{...@}"}
7774 @item show print union
7775 Ask @value{GDBN} whether or not it will print unions which are contained in
7776 structures and other unions.
7778 For example, given the declarations
7781 typedef enum @{Tree, Bug@} Species;
7782 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
7783 typedef enum @{Caterpillar, Cocoon, Butterfly@}
7794 struct thing foo = @{Tree, @{Acorn@}@};
7798 with @code{set print union on} in effect @samp{p foo} would print
7801 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
7805 and with @code{set print union off} in effect it would print
7808 $1 = @{it = Tree, form = @{...@}@}
7812 @code{set print union} affects programs written in C-like languages
7818 These settings are of interest when debugging C@t{++} programs:
7821 @cindex demangling C@t{++} names
7822 @item set print demangle
7823 @itemx set print demangle on
7824 Print C@t{++} names in their source form rather than in the encoded
7825 (``mangled'') form passed to the assembler and linker for type-safe
7826 linkage. The default is on.
7828 @item show print demangle
7829 Show whether C@t{++} names are printed in mangled or demangled form.
7831 @item set print asm-demangle
7832 @itemx set print asm-demangle on
7833 Print C@t{++} names in their source form rather than their mangled form, even
7834 in assembler code printouts such as instruction disassemblies.
7837 @item show print asm-demangle
7838 Show whether C@t{++} names in assembly listings are printed in mangled
7841 @cindex C@t{++} symbol decoding style
7842 @cindex symbol decoding style, C@t{++}
7843 @kindex set demangle-style
7844 @item set demangle-style @var{style}
7845 Choose among several encoding schemes used by different compilers to
7846 represent C@t{++} names. The choices for @var{style} are currently:
7850 Allow @value{GDBN} to choose a decoding style by inspecting your program.
7853 Decode based on the @sc{gnu} C@t{++} compiler (@code{g++}) encoding algorithm.
7854 This is the default.
7857 Decode based on the HP ANSI C@t{++} (@code{aCC}) encoding algorithm.
7860 Decode based on the Lucid C@t{++} compiler (@code{lcc}) encoding algorithm.
7863 Decode using the algorithm in the @cite{C@t{++} Annotated Reference Manual}.
7864 @strong{Warning:} this setting alone is not sufficient to allow
7865 debugging @code{cfront}-generated executables. @value{GDBN} would
7866 require further enhancement to permit that.
7869 If you omit @var{style}, you will see a list of possible formats.
7871 @item show demangle-style
7872 Display the encoding style currently in use for decoding C@t{++} symbols.
7874 @item set print object
7875 @itemx set print object on
7876 @cindex derived type of an object, printing
7877 @cindex display derived types
7878 When displaying a pointer to an object, identify the @emph{actual}
7879 (derived) type of the object rather than the @emph{declared} type, using
7880 the virtual function table.
7882 @item set print object off
7883 Display only the declared type of objects, without reference to the
7884 virtual function table. This is the default setting.
7886 @item show print object
7887 Show whether actual, or declared, object types are displayed.
7889 @item set print static-members
7890 @itemx set print static-members on
7891 @cindex static members of C@t{++} objects
7892 Print static members when displaying a C@t{++} object. The default is on.
7894 @item set print static-members off
7895 Do not print static members when displaying a C@t{++} object.
7897 @item show print static-members
7898 Show whether C@t{++} static members are printed or not.
7900 @item set print pascal_static-members
7901 @itemx set print pascal_static-members on
7902 @cindex static members of Pascal objects
7903 @cindex Pascal objects, static members display
7904 Print static members when displaying a Pascal object. The default is on.
7906 @item set print pascal_static-members off
7907 Do not print static members when displaying a Pascal object.
7909 @item show print pascal_static-members
7910 Show whether Pascal static members are printed or not.
7912 @c These don't work with HP ANSI C++ yet.
7913 @item set print vtbl
7914 @itemx set print vtbl on
7915 @cindex pretty print C@t{++} virtual function tables
7916 @cindex virtual functions (C@t{++}) display
7917 @cindex VTBL display
7918 Pretty print C@t{++} virtual function tables. The default is off.
7919 (The @code{vtbl} commands do not work on programs compiled with the HP
7920 ANSI C@t{++} compiler (@code{aCC}).)
7922 @item set print vtbl off
7923 Do not pretty print C@t{++} virtual function tables.
7925 @item show print vtbl
7926 Show whether C@t{++} virtual function tables are pretty printed, or not.
7929 @node Pretty Printing
7930 @section Pretty Printing
7932 @value{GDBN} provides a mechanism to allow pretty-printing of values using
7933 Python code. It greatly simplifies the display of complex objects. This
7934 mechanism works for both MI and the CLI.
7936 For example, here is how a C@t{++} @code{std::string} looks without a
7940 (@value{GDBP}) print s
7942 static npos = 4294967295,
7944 <std::allocator<char>> = @{
7945 <__gnu_cxx::new_allocator<char>> = @{
7946 <No data fields>@}, <No data fields>
7948 members of std::basic_string<char, std::char_traits<char>,
7949 std::allocator<char> >::_Alloc_hider:
7950 _M_p = 0x804a014 "abcd"
7955 With a pretty-printer for @code{std::string} only the contents are printed:
7958 (@value{GDBP}) print s
7962 For implementing pretty printers for new types you should read the Python API
7963 details (@pxref{Pretty Printing API}).
7966 @section Value History
7968 @cindex value history
7969 @cindex history of values printed by @value{GDBN}
7970 Values printed by the @code{print} command are saved in the @value{GDBN}
7971 @dfn{value history}. This allows you to refer to them in other expressions.
7972 Values are kept until the symbol table is re-read or discarded
7973 (for example with the @code{file} or @code{symbol-file} commands).
7974 When the symbol table changes, the value history is discarded,
7975 since the values may contain pointers back to the types defined in the
7980 @cindex history number
7981 The values printed are given @dfn{history numbers} by which you can
7982 refer to them. These are successive integers starting with one.
7983 @code{print} shows you the history number assigned to a value by
7984 printing @samp{$@var{num} = } before the value; here @var{num} is the
7987 To refer to any previous value, use @samp{$} followed by the value's
7988 history number. The way @code{print} labels its output is designed to
7989 remind you of this. Just @code{$} refers to the most recent value in
7990 the history, and @code{$$} refers to the value before that.
7991 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
7992 is the value just prior to @code{$$}, @code{$$1} is equivalent to
7993 @code{$$}, and @code{$$0} is equivalent to @code{$}.
7995 For example, suppose you have just printed a pointer to a structure and
7996 want to see the contents of the structure. It suffices to type
8002 If you have a chain of structures where the component @code{next} points
8003 to the next one, you can print the contents of the next one with this:
8010 You can print successive links in the chain by repeating this
8011 command---which you can do by just typing @key{RET}.
8013 Note that the history records values, not expressions. If the value of
8014 @code{x} is 4 and you type these commands:
8022 then the value recorded in the value history by the @code{print} command
8023 remains 4 even though the value of @code{x} has changed.
8028 Print the last ten values in the value history, with their item numbers.
8029 This is like @samp{p@ $$9} repeated ten times, except that @code{show
8030 values} does not change the history.
8032 @item show values @var{n}
8033 Print ten history values centered on history item number @var{n}.
8036 Print ten history values just after the values last printed. If no more
8037 values are available, @code{show values +} produces no display.
8040 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
8041 same effect as @samp{show values +}.
8043 @node Convenience Vars
8044 @section Convenience Variables
8046 @cindex convenience variables
8047 @cindex user-defined variables
8048 @value{GDBN} provides @dfn{convenience variables} that you can use within
8049 @value{GDBN} to hold on to a value and refer to it later. These variables
8050 exist entirely within @value{GDBN}; they are not part of your program, and
8051 setting a convenience variable has no direct effect on further execution
8052 of your program. That is why you can use them freely.
8054 Convenience variables are prefixed with @samp{$}. Any name preceded by
8055 @samp{$} can be used for a convenience variable, unless it is one of
8056 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
8057 (Value history references, in contrast, are @emph{numbers} preceded
8058 by @samp{$}. @xref{Value History, ,Value History}.)
8060 You can save a value in a convenience variable with an assignment
8061 expression, just as you would set a variable in your program.
8065 set $foo = *object_ptr
8069 would save in @code{$foo} the value contained in the object pointed to by
8072 Using a convenience variable for the first time creates it, but its
8073 value is @code{void} until you assign a new value. You can alter the
8074 value with another assignment at any time.
8076 Convenience variables have no fixed types. You can assign a convenience
8077 variable any type of value, including structures and arrays, even if
8078 that variable already has a value of a different type. The convenience
8079 variable, when used as an expression, has the type of its current value.
8082 @kindex show convenience
8083 @cindex show all user variables
8084 @item show convenience
8085 Print a list of convenience variables used so far, and their values.
8086 Abbreviated @code{show conv}.
8088 @kindex init-if-undefined
8089 @cindex convenience variables, initializing
8090 @item init-if-undefined $@var{variable} = @var{expression}
8091 Set a convenience variable if it has not already been set. This is useful
8092 for user-defined commands that keep some state. It is similar, in concept,
8093 to using local static variables with initializers in C (except that
8094 convenience variables are global). It can also be used to allow users to
8095 override default values used in a command script.
8097 If the variable is already defined then the expression is not evaluated so
8098 any side-effects do not occur.
8101 One of the ways to use a convenience variable is as a counter to be
8102 incremented or a pointer to be advanced. For example, to print
8103 a field from successive elements of an array of structures:
8107 print bar[$i++]->contents
8111 Repeat that command by typing @key{RET}.
8113 Some convenience variables are created automatically by @value{GDBN} and given
8114 values likely to be useful.
8117 @vindex $_@r{, convenience variable}
8119 The variable @code{$_} is automatically set by the @code{x} command to
8120 the last address examined (@pxref{Memory, ,Examining Memory}). Other
8121 commands which provide a default address for @code{x} to examine also
8122 set @code{$_} to that address; these commands include @code{info line}
8123 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
8124 except when set by the @code{x} command, in which case it is a pointer
8125 to the type of @code{$__}.
8127 @vindex $__@r{, convenience variable}
8129 The variable @code{$__} is automatically set by the @code{x} command
8130 to the value found in the last address examined. Its type is chosen
8131 to match the format in which the data was printed.
8134 @vindex $_exitcode@r{, convenience variable}
8135 The variable @code{$_exitcode} is automatically set to the exit code when
8136 the program being debugged terminates.
8139 @vindex $_siginfo@r{, convenience variable}
8140 The variable @code{$_siginfo} contains extra signal information
8141 (@pxref{extra signal information}). Note that @code{$_siginfo}
8142 could be empty, if the application has not yet received any signals.
8143 For example, it will be empty before you execute the @code{run} command.
8146 @vindex $_tlb@r{, convenience variable}
8147 The variable @code{$_tlb} is automatically set when debugging
8148 applications running on MS-Windows in native mode or connected to
8149 gdbserver that supports the @code{qGetTIBAddr} request.
8150 @xref{General Query Packets}.
8151 This variable contains the address of the thread information block.
8155 On HP-UX systems, if you refer to a function or variable name that
8156 begins with a dollar sign, @value{GDBN} searches for a user or system
8157 name first, before it searches for a convenience variable.
8159 @cindex convenience functions
8160 @value{GDBN} also supplies some @dfn{convenience functions}. These
8161 have a syntax similar to convenience variables. A convenience
8162 function can be used in an expression just like an ordinary function;
8163 however, a convenience function is implemented internally to
8168 @kindex help function
8169 @cindex show all convenience functions
8170 Print a list of all convenience functions.
8177 You can refer to machine register contents, in expressions, as variables
8178 with names starting with @samp{$}. The names of registers are different
8179 for each machine; use @code{info registers} to see the names used on
8183 @kindex info registers
8184 @item info registers
8185 Print the names and values of all registers except floating-point
8186 and vector registers (in the selected stack frame).
8188 @kindex info all-registers
8189 @cindex floating point registers
8190 @item info all-registers
8191 Print the names and values of all registers, including floating-point
8192 and vector registers (in the selected stack frame).
8194 @item info registers @var{regname} @dots{}
8195 Print the @dfn{relativized} value of each specified register @var{regname}.
8196 As discussed in detail below, register values are normally relative to
8197 the selected stack frame. @var{regname} may be any register name valid on
8198 the machine you are using, with or without the initial @samp{$}.
8201 @cindex stack pointer register
8202 @cindex program counter register
8203 @cindex process status register
8204 @cindex frame pointer register
8205 @cindex standard registers
8206 @value{GDBN} has four ``standard'' register names that are available (in
8207 expressions) on most machines---whenever they do not conflict with an
8208 architecture's canonical mnemonics for registers. The register names
8209 @code{$pc} and @code{$sp} are used for the program counter register and
8210 the stack pointer. @code{$fp} is used for a register that contains a
8211 pointer to the current stack frame, and @code{$ps} is used for a
8212 register that contains the processor status. For example,
8213 you could print the program counter in hex with
8220 or print the instruction to be executed next with
8227 or add four to the stack pointer@footnote{This is a way of removing
8228 one word from the stack, on machines where stacks grow downward in
8229 memory (most machines, nowadays). This assumes that the innermost
8230 stack frame is selected; setting @code{$sp} is not allowed when other
8231 stack frames are selected. To pop entire frames off the stack,
8232 regardless of machine architecture, use @code{return};
8233 see @ref{Returning, ,Returning from a Function}.} with
8239 Whenever possible, these four standard register names are available on
8240 your machine even though the machine has different canonical mnemonics,
8241 so long as there is no conflict. The @code{info registers} command
8242 shows the canonical names. For example, on the SPARC, @code{info
8243 registers} displays the processor status register as @code{$psr} but you
8244 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
8245 is an alias for the @sc{eflags} register.
8247 @value{GDBN} always considers the contents of an ordinary register as an
8248 integer when the register is examined in this way. Some machines have
8249 special registers which can hold nothing but floating point; these
8250 registers are considered to have floating point values. There is no way
8251 to refer to the contents of an ordinary register as floating point value
8252 (although you can @emph{print} it as a floating point value with
8253 @samp{print/f $@var{regname}}).
8255 Some registers have distinct ``raw'' and ``virtual'' data formats. This
8256 means that the data format in which the register contents are saved by
8257 the operating system is not the same one that your program normally
8258 sees. For example, the registers of the 68881 floating point
8259 coprocessor are always saved in ``extended'' (raw) format, but all C
8260 programs expect to work with ``double'' (virtual) format. In such
8261 cases, @value{GDBN} normally works with the virtual format only (the format
8262 that makes sense for your program), but the @code{info registers} command
8263 prints the data in both formats.
8265 @cindex SSE registers (x86)
8266 @cindex MMX registers (x86)
8267 Some machines have special registers whose contents can be interpreted
8268 in several different ways. For example, modern x86-based machines
8269 have SSE and MMX registers that can hold several values packed
8270 together in several different formats. @value{GDBN} refers to such
8271 registers in @code{struct} notation:
8274 (@value{GDBP}) print $xmm1
8276 v4_float = @{0, 3.43859137e-038, 1.54142831e-044, 1.821688e-044@},
8277 v2_double = @{9.92129282474342e-303, 2.7585945287983262e-313@},
8278 v16_int8 = "\000\000\000\000\3706;\001\v\000\000\000\r\000\000",
8279 v8_int16 = @{0, 0, 14072, 315, 11, 0, 13, 0@},
8280 v4_int32 = @{0, 20657912, 11, 13@},
8281 v2_int64 = @{88725056443645952, 55834574859@},
8282 uint128 = 0x0000000d0000000b013b36f800000000
8287 To set values of such registers, you need to tell @value{GDBN} which
8288 view of the register you wish to change, as if you were assigning
8289 value to a @code{struct} member:
8292 (@value{GDBP}) set $xmm1.uint128 = 0x000000000000000000000000FFFFFFFF
8295 Normally, register values are relative to the selected stack frame
8296 (@pxref{Selection, ,Selecting a Frame}). This means that you get the
8297 value that the register would contain if all stack frames farther in
8298 were exited and their saved registers restored. In order to see the
8299 true contents of hardware registers, you must select the innermost
8300 frame (with @samp{frame 0}).
8302 However, @value{GDBN} must deduce where registers are saved, from the machine
8303 code generated by your compiler. If some registers are not saved, or if
8304 @value{GDBN} is unable to locate the saved registers, the selected stack
8305 frame makes no difference.
8307 @node Floating Point Hardware
8308 @section Floating Point Hardware
8309 @cindex floating point
8311 Depending on the configuration, @value{GDBN} may be able to give
8312 you more information about the status of the floating point hardware.
8317 Display hardware-dependent information about the floating
8318 point unit. The exact contents and layout vary depending on the
8319 floating point chip. Currently, @samp{info float} is supported on
8320 the ARM and x86 machines.
8324 @section Vector Unit
8327 Depending on the configuration, @value{GDBN} may be able to give you
8328 more information about the status of the vector unit.
8333 Display information about the vector unit. The exact contents and
8334 layout vary depending on the hardware.
8337 @node OS Information
8338 @section Operating System Auxiliary Information
8339 @cindex OS information
8341 @value{GDBN} provides interfaces to useful OS facilities that can help
8342 you debug your program.
8344 @cindex @code{ptrace} system call
8345 @cindex @code{struct user} contents
8346 When @value{GDBN} runs on a @dfn{Posix system} (such as GNU or Unix
8347 machines), it interfaces with the inferior via the @code{ptrace}
8348 system call. The operating system creates a special sata structure,
8349 called @code{struct user}, for this interface. You can use the
8350 command @code{info udot} to display the contents of this data
8356 Display the contents of the @code{struct user} maintained by the OS
8357 kernel for the program being debugged. @value{GDBN} displays the
8358 contents of @code{struct user} as a list of hex numbers, similar to
8359 the @code{examine} command.
8362 @cindex auxiliary vector
8363 @cindex vector, auxiliary
8364 Some operating systems supply an @dfn{auxiliary vector} to programs at
8365 startup. This is akin to the arguments and environment that you
8366 specify for a program, but contains a system-dependent variety of
8367 binary values that tell system libraries important details about the
8368 hardware, operating system, and process. Each value's purpose is
8369 identified by an integer tag; the meanings are well-known but system-specific.
8370 Depending on the configuration and operating system facilities,
8371 @value{GDBN} may be able to show you this information. For remote
8372 targets, this functionality may further depend on the remote stub's
8373 support of the @samp{qXfer:auxv:read} packet, see
8374 @ref{qXfer auxiliary vector read}.
8379 Display the auxiliary vector of the inferior, which can be either a
8380 live process or a core dump file. @value{GDBN} prints each tag value
8381 numerically, and also shows names and text descriptions for recognized
8382 tags. Some values in the vector are numbers, some bit masks, and some
8383 pointers to strings or other data. @value{GDBN} displays each value in the
8384 most appropriate form for a recognized tag, and in hexadecimal for
8385 an unrecognized tag.
8388 On some targets, @value{GDBN} can access operating-system-specific information
8389 and display it to user, without interpretation. For remote targets,
8390 this functionality depends on the remote stub's support of the
8391 @samp{qXfer:osdata:read} packet, see @ref{qXfer osdata read}.
8394 @kindex info os processes
8395 @item info os processes
8396 Display the list of processes on the target. For each process,
8397 @value{GDBN} prints the process identifier, the name of the user, and
8398 the command corresponding to the process.
8401 @node Memory Region Attributes
8402 @section Memory Region Attributes
8403 @cindex memory region attributes
8405 @dfn{Memory region attributes} allow you to describe special handling
8406 required by regions of your target's memory. @value{GDBN} uses
8407 attributes to determine whether to allow certain types of memory
8408 accesses; whether to use specific width accesses; and whether to cache
8409 target memory. By default the description of memory regions is
8410 fetched from the target (if the current target supports this), but the
8411 user can override the fetched regions.
8413 Defined memory regions can be individually enabled and disabled. When a
8414 memory region is disabled, @value{GDBN} uses the default attributes when
8415 accessing memory in that region. Similarly, if no memory regions have
8416 been defined, @value{GDBN} uses the default attributes when accessing
8419 When a memory region is defined, it is given a number to identify it;
8420 to enable, disable, or remove a memory region, you specify that number.
8424 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
8425 Define a memory region bounded by @var{lower} and @var{upper} with
8426 attributes @var{attributes}@dots{}, and add it to the list of regions
8427 monitored by @value{GDBN}. Note that @var{upper} == 0 is a special
8428 case: it is treated as the target's maximum memory address.
8429 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
8432 Discard any user changes to the memory regions and use target-supplied
8433 regions, if available, or no regions if the target does not support.
8436 @item delete mem @var{nums}@dots{}
8437 Remove memory regions @var{nums}@dots{} from the list of regions
8438 monitored by @value{GDBN}.
8441 @item disable mem @var{nums}@dots{}
8442 Disable monitoring of memory regions @var{nums}@dots{}.
8443 A disabled memory region is not forgotten.
8444 It may be enabled again later.
8447 @item enable mem @var{nums}@dots{}
8448 Enable monitoring of memory regions @var{nums}@dots{}.
8452 Print a table of all defined memory regions, with the following columns
8456 @item Memory Region Number
8457 @item Enabled or Disabled.
8458 Enabled memory regions are marked with @samp{y}.
8459 Disabled memory regions are marked with @samp{n}.
8462 The address defining the inclusive lower bound of the memory region.
8465 The address defining the exclusive upper bound of the memory region.
8468 The list of attributes set for this memory region.
8473 @subsection Attributes
8475 @subsubsection Memory Access Mode
8476 The access mode attributes set whether @value{GDBN} may make read or
8477 write accesses to a memory region.
8479 While these attributes prevent @value{GDBN} from performing invalid
8480 memory accesses, they do nothing to prevent the target system, I/O DMA,
8481 etc.@: from accessing memory.
8485 Memory is read only.
8487 Memory is write only.
8489 Memory is read/write. This is the default.
8492 @subsubsection Memory Access Size
8493 The access size attribute tells @value{GDBN} to use specific sized
8494 accesses in the memory region. Often memory mapped device registers
8495 require specific sized accesses. If no access size attribute is
8496 specified, @value{GDBN} may use accesses of any size.
8500 Use 8 bit memory accesses.
8502 Use 16 bit memory accesses.
8504 Use 32 bit memory accesses.
8506 Use 64 bit memory accesses.
8509 @c @subsubsection Hardware/Software Breakpoints
8510 @c The hardware/software breakpoint attributes set whether @value{GDBN}
8511 @c will use hardware or software breakpoints for the internal breakpoints
8512 @c used by the step, next, finish, until, etc. commands.
8516 @c Always use hardware breakpoints
8517 @c @item swbreak (default)
8520 @subsubsection Data Cache
8521 The data cache attributes set whether @value{GDBN} will cache target
8522 memory. While this generally improves performance by reducing debug
8523 protocol overhead, it can lead to incorrect results because @value{GDBN}
8524 does not know about volatile variables or memory mapped device
8529 Enable @value{GDBN} to cache target memory.
8531 Disable @value{GDBN} from caching target memory. This is the default.
8534 @subsection Memory Access Checking
8535 @value{GDBN} can be instructed to refuse accesses to memory that is
8536 not explicitly described. This can be useful if accessing such
8537 regions has undesired effects for a specific target, or to provide
8538 better error checking. The following commands control this behaviour.
8541 @kindex set mem inaccessible-by-default
8542 @item set mem inaccessible-by-default [on|off]
8543 If @code{on} is specified, make @value{GDBN} treat memory not
8544 explicitly described by the memory ranges as non-existent and refuse accesses
8545 to such memory. The checks are only performed if there's at least one
8546 memory range defined. If @code{off} is specified, make @value{GDBN}
8547 treat the memory not explicitly described by the memory ranges as RAM.
8548 The default value is @code{on}.
8549 @kindex show mem inaccessible-by-default
8550 @item show mem inaccessible-by-default
8551 Show the current handling of accesses to unknown memory.
8555 @c @subsubsection Memory Write Verification
8556 @c The memory write verification attributes set whether @value{GDBN}
8557 @c will re-reads data after each write to verify the write was successful.
8561 @c @item noverify (default)
8564 @node Dump/Restore Files
8565 @section Copy Between Memory and a File
8566 @cindex dump/restore files
8567 @cindex append data to a file
8568 @cindex dump data to a file
8569 @cindex restore data from a file
8571 You can use the commands @code{dump}, @code{append}, and
8572 @code{restore} to copy data between target memory and a file. The
8573 @code{dump} and @code{append} commands write data to a file, and the
8574 @code{restore} command reads data from a file back into the inferior's
8575 memory. Files may be in binary, Motorola S-record, Intel hex, or
8576 Tektronix Hex format; however, @value{GDBN} can only append to binary
8582 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
8583 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
8584 Dump the contents of memory from @var{start_addr} to @var{end_addr},
8585 or the value of @var{expr}, to @var{filename} in the given format.
8587 The @var{format} parameter may be any one of:
8594 Motorola S-record format.
8596 Tektronix Hex format.
8599 @value{GDBN} uses the same definitions of these formats as the
8600 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
8601 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
8605 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
8606 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
8607 Append the contents of memory from @var{start_addr} to @var{end_addr},
8608 or the value of @var{expr}, to the file @var{filename}, in raw binary form.
8609 (@value{GDBN} can only append data to files in raw binary form.)
8612 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
8613 Restore the contents of file @var{filename} into memory. The
8614 @code{restore} command can automatically recognize any known @sc{bfd}
8615 file format, except for raw binary. To restore a raw binary file you
8616 must specify the optional keyword @code{binary} after the filename.
8618 If @var{bias} is non-zero, its value will be added to the addresses
8619 contained in the file. Binary files always start at address zero, so
8620 they will be restored at address @var{bias}. Other bfd files have
8621 a built-in location; they will be restored at offset @var{bias}
8624 If @var{start} and/or @var{end} are non-zero, then only data between
8625 file offset @var{start} and file offset @var{end} will be restored.
8626 These offsets are relative to the addresses in the file, before
8627 the @var{bias} argument is applied.
8631 @node Core File Generation
8632 @section How to Produce a Core File from Your Program
8633 @cindex dump core from inferior
8635 A @dfn{core file} or @dfn{core dump} is a file that records the memory
8636 image of a running process and its process status (register values
8637 etc.). Its primary use is post-mortem debugging of a program that
8638 crashed while it ran outside a debugger. A program that crashes
8639 automatically produces a core file, unless this feature is disabled by
8640 the user. @xref{Files}, for information on invoking @value{GDBN} in
8641 the post-mortem debugging mode.
8643 Occasionally, you may wish to produce a core file of the program you
8644 are debugging in order to preserve a snapshot of its state.
8645 @value{GDBN} has a special command for that.
8649 @kindex generate-core-file
8650 @item generate-core-file [@var{file}]
8651 @itemx gcore [@var{file}]
8652 Produce a core dump of the inferior process. The optional argument
8653 @var{file} specifies the file name where to put the core dump. If not
8654 specified, the file name defaults to @file{core.@var{pid}}, where
8655 @var{pid} is the inferior process ID.
8657 Note that this command is implemented only for some systems (as of
8658 this writing, @sc{gnu}/Linux, FreeBSD, Solaris, Unixware, and S390).
8661 @node Character Sets
8662 @section Character Sets
8663 @cindex character sets
8665 @cindex translating between character sets
8666 @cindex host character set
8667 @cindex target character set
8669 If the program you are debugging uses a different character set to
8670 represent characters and strings than the one @value{GDBN} uses itself,
8671 @value{GDBN} can automatically translate between the character sets for
8672 you. The character set @value{GDBN} uses we call the @dfn{host
8673 character set}; the one the inferior program uses we call the
8674 @dfn{target character set}.
8676 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
8677 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
8678 remote protocol (@pxref{Remote Debugging}) to debug a program
8679 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
8680 then the host character set is Latin-1, and the target character set is
8681 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
8682 target-charset EBCDIC-US}, then @value{GDBN} translates between
8683 @sc{ebcdic} and Latin 1 as you print character or string values, or use
8684 character and string literals in expressions.
8686 @value{GDBN} has no way to automatically recognize which character set
8687 the inferior program uses; you must tell it, using the @code{set
8688 target-charset} command, described below.
8690 Here are the commands for controlling @value{GDBN}'s character set
8694 @item set target-charset @var{charset}
8695 @kindex set target-charset
8696 Set the current target character set to @var{charset}. To display the
8697 list of supported target character sets, type
8698 @kbd{@w{set target-charset @key{TAB}@key{TAB}}}.
8700 @item set host-charset @var{charset}
8701 @kindex set host-charset
8702 Set the current host character set to @var{charset}.
8704 By default, @value{GDBN} uses a host character set appropriate to the
8705 system it is running on; you can override that default using the
8706 @code{set host-charset} command. On some systems, @value{GDBN} cannot
8707 automatically determine the appropriate host character set. In this
8708 case, @value{GDBN} uses @samp{UTF-8}.
8710 @value{GDBN} can only use certain character sets as its host character
8711 set. If you type @kbd{@w{set target-charset @key{TAB}@key{TAB}}},
8712 @value{GDBN} will list the host character sets it supports.
8714 @item set charset @var{charset}
8716 Set the current host and target character sets to @var{charset}. As
8717 above, if you type @kbd{@w{set charset @key{TAB}@key{TAB}}},
8718 @value{GDBN} will list the names of the character sets that can be used
8719 for both host and target.
8722 @kindex show charset
8723 Show the names of the current host and target character sets.
8725 @item show host-charset
8726 @kindex show host-charset
8727 Show the name of the current host character set.
8729 @item show target-charset
8730 @kindex show target-charset
8731 Show the name of the current target character set.
8733 @item set target-wide-charset @var{charset}
8734 @kindex set target-wide-charset
8735 Set the current target's wide character set to @var{charset}. This is
8736 the character set used by the target's @code{wchar_t} type. To
8737 display the list of supported wide character sets, type
8738 @kbd{@w{set target-wide-charset @key{TAB}@key{TAB}}}.
8740 @item show target-wide-charset
8741 @kindex show target-wide-charset
8742 Show the name of the current target's wide character set.
8745 Here is an example of @value{GDBN}'s character set support in action.
8746 Assume that the following source code has been placed in the file
8747 @file{charset-test.c}:
8753 = @{72, 101, 108, 108, 111, 44, 32, 119,
8754 111, 114, 108, 100, 33, 10, 0@};
8755 char ibm1047_hello[]
8756 = @{200, 133, 147, 147, 150, 107, 64, 166,
8757 150, 153, 147, 132, 90, 37, 0@};
8761 printf ("Hello, world!\n");
8765 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
8766 containing the string @samp{Hello, world!} followed by a newline,
8767 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
8769 We compile the program, and invoke the debugger on it:
8772 $ gcc -g charset-test.c -o charset-test
8773 $ gdb -nw charset-test
8774 GNU gdb 2001-12-19-cvs
8775 Copyright 2001 Free Software Foundation, Inc.
8780 We can use the @code{show charset} command to see what character sets
8781 @value{GDBN} is currently using to interpret and display characters and
8785 (@value{GDBP}) show charset
8786 The current host and target character set is `ISO-8859-1'.
8790 For the sake of printing this manual, let's use @sc{ascii} as our
8791 initial character set:
8793 (@value{GDBP}) set charset ASCII
8794 (@value{GDBP}) show charset
8795 The current host and target character set is `ASCII'.
8799 Let's assume that @sc{ascii} is indeed the correct character set for our
8800 host system --- in other words, let's assume that if @value{GDBN} prints
8801 characters using the @sc{ascii} character set, our terminal will display
8802 them properly. Since our current target character set is also
8803 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
8806 (@value{GDBP}) print ascii_hello
8807 $1 = 0x401698 "Hello, world!\n"
8808 (@value{GDBP}) print ascii_hello[0]
8813 @value{GDBN} uses the target character set for character and string
8814 literals you use in expressions:
8817 (@value{GDBP}) print '+'
8822 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
8825 @value{GDBN} relies on the user to tell it which character set the
8826 target program uses. If we print @code{ibm1047_hello} while our target
8827 character set is still @sc{ascii}, we get jibberish:
8830 (@value{GDBP}) print ibm1047_hello
8831 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
8832 (@value{GDBP}) print ibm1047_hello[0]
8837 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
8838 @value{GDBN} tells us the character sets it supports:
8841 (@value{GDBP}) set target-charset
8842 ASCII EBCDIC-US IBM1047 ISO-8859-1
8843 (@value{GDBP}) set target-charset
8846 We can select @sc{ibm1047} as our target character set, and examine the
8847 program's strings again. Now the @sc{ascii} string is wrong, but
8848 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
8849 target character set, @sc{ibm1047}, to the host character set,
8850 @sc{ascii}, and they display correctly:
8853 (@value{GDBP}) set target-charset IBM1047
8854 (@value{GDBP}) show charset
8855 The current host character set is `ASCII'.
8856 The current target character set is `IBM1047'.
8857 (@value{GDBP}) print ascii_hello
8858 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
8859 (@value{GDBP}) print ascii_hello[0]
8861 (@value{GDBP}) print ibm1047_hello
8862 $8 = 0x4016a8 "Hello, world!\n"
8863 (@value{GDBP}) print ibm1047_hello[0]
8868 As above, @value{GDBN} uses the target character set for character and
8869 string literals you use in expressions:
8872 (@value{GDBP}) print '+'
8877 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
8880 @node Caching Remote Data
8881 @section Caching Data of Remote Targets
8882 @cindex caching data of remote targets
8884 @value{GDBN} caches data exchanged between the debugger and a
8885 remote target (@pxref{Remote Debugging}). Such caching generally improves
8886 performance, because it reduces the overhead of the remote protocol by
8887 bundling memory reads and writes into large chunks. Unfortunately, simply
8888 caching everything would lead to incorrect results, since @value{GDBN}
8889 does not necessarily know anything about volatile values, memory-mapped I/O
8890 addresses, etc. Furthermore, in non-stop mode (@pxref{Non-Stop Mode})
8891 memory can be changed @emph{while} a gdb command is executing.
8892 Therefore, by default, @value{GDBN} only caches data
8893 known to be on the stack@footnote{In non-stop mode, it is moderately
8894 rare for a running thread to modify the stack of a stopped thread
8895 in a way that would interfere with a backtrace, and caching of
8896 stack reads provides a significant speed up of remote backtraces.}.
8897 Other regions of memory can be explicitly marked as
8898 cacheable; see @pxref{Memory Region Attributes}.
8901 @kindex set remotecache
8902 @item set remotecache on
8903 @itemx set remotecache off
8904 This option no longer does anything; it exists for compatibility
8907 @kindex show remotecache
8908 @item show remotecache
8909 Show the current state of the obsolete remotecache flag.
8911 @kindex set stack-cache
8912 @item set stack-cache on
8913 @itemx set stack-cache off
8914 Enable or disable caching of stack accesses. When @code{ON}, use
8915 caching. By default, this option is @code{ON}.
8917 @kindex show stack-cache
8918 @item show stack-cache
8919 Show the current state of data caching for memory accesses.
8922 @item info dcache @r{[}line@r{]}
8923 Print the information about the data cache performance. The
8924 information displayed includes the dcache width and depth, and for
8925 each cache line, its number, address, and how many times it was
8926 referenced. This command is useful for debugging the data cache
8929 If a line number is specified, the contents of that line will be
8933 @node Searching Memory
8934 @section Search Memory
8935 @cindex searching memory
8937 Memory can be searched for a particular sequence of bytes with the
8938 @code{find} command.
8942 @item find @r{[}/@var{sn}@r{]} @var{start_addr}, +@var{len}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
8943 @itemx find @r{[}/@var{sn}@r{]} @var{start_addr}, @var{end_addr}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
8944 Search memory for the sequence of bytes specified by @var{val1}, @var{val2},
8945 etc. The search begins at address @var{start_addr} and continues for either
8946 @var{len} bytes or through to @var{end_addr} inclusive.
8949 @var{s} and @var{n} are optional parameters.
8950 They may be specified in either order, apart or together.
8953 @item @var{s}, search query size
8954 The size of each search query value.
8960 halfwords (two bytes)
8964 giant words (eight bytes)
8967 All values are interpreted in the current language.
8968 This means, for example, that if the current source language is C/C@t{++}
8969 then searching for the string ``hello'' includes the trailing '\0'.
8971 If the value size is not specified, it is taken from the
8972 value's type in the current language.
8973 This is useful when one wants to specify the search
8974 pattern as a mixture of types.
8975 Note that this means, for example, that in the case of C-like languages
8976 a search for an untyped 0x42 will search for @samp{(int) 0x42}
8977 which is typically four bytes.
8979 @item @var{n}, maximum number of finds
8980 The maximum number of matches to print. The default is to print all finds.
8983 You can use strings as search values. Quote them with double-quotes
8985 The string value is copied into the search pattern byte by byte,
8986 regardless of the endianness of the target and the size specification.
8988 The address of each match found is printed as well as a count of the
8989 number of matches found.
8991 The address of the last value found is stored in convenience variable
8993 A count of the number of matches is stored in @samp{$numfound}.
8995 For example, if stopped at the @code{printf} in this function:
9001 static char hello[] = "hello-hello";
9002 static struct @{ char c; short s; int i; @}
9003 __attribute__ ((packed)) mixed
9004 = @{ 'c', 0x1234, 0x87654321 @};
9005 printf ("%s\n", hello);
9010 you get during debugging:
9013 (gdb) find &hello[0], +sizeof(hello), "hello"
9014 0x804956d <hello.1620+6>
9016 (gdb) find &hello[0], +sizeof(hello), 'h', 'e', 'l', 'l', 'o'
9017 0x8049567 <hello.1620>
9018 0x804956d <hello.1620+6>
9020 (gdb) find /b1 &hello[0], +sizeof(hello), 'h', 0x65, 'l'
9021 0x8049567 <hello.1620>
9023 (gdb) find &mixed, +sizeof(mixed), (char) 'c', (short) 0x1234, (int) 0x87654321
9024 0x8049560 <mixed.1625>
9026 (gdb) print $numfound
9029 $2 = (void *) 0x8049560
9032 @node Optimized Code
9033 @chapter Debugging Optimized Code
9034 @cindex optimized code, debugging
9035 @cindex debugging optimized code
9037 Almost all compilers support optimization. With optimization
9038 disabled, the compiler generates assembly code that corresponds
9039 directly to your source code, in a simplistic way. As the compiler
9040 applies more powerful optimizations, the generated assembly code
9041 diverges from your original source code. With help from debugging
9042 information generated by the compiler, @value{GDBN} can map from
9043 the running program back to constructs from your original source.
9045 @value{GDBN} is more accurate with optimization disabled. If you
9046 can recompile without optimization, it is easier to follow the
9047 progress of your program during debugging. But, there are many cases
9048 where you may need to debug an optimized version.
9050 When you debug a program compiled with @samp{-g -O}, remember that the
9051 optimizer has rearranged your code; the debugger shows you what is
9052 really there. Do not be too surprised when the execution path does not
9053 exactly match your source file! An extreme example: if you define a
9054 variable, but never use it, @value{GDBN} never sees that
9055 variable---because the compiler optimizes it out of existence.
9057 Some things do not work as well with @samp{-g -O} as with just
9058 @samp{-g}, particularly on machines with instruction scheduling. If in
9059 doubt, recompile with @samp{-g} alone, and if this fixes the problem,
9060 please report it to us as a bug (including a test case!).
9061 @xref{Variables}, for more information about debugging optimized code.
9064 * Inline Functions:: How @value{GDBN} presents inlining
9067 @node Inline Functions
9068 @section Inline Functions
9069 @cindex inline functions, debugging
9071 @dfn{Inlining} is an optimization that inserts a copy of the function
9072 body directly at each call site, instead of jumping to a shared
9073 routine. @value{GDBN} displays inlined functions just like
9074 non-inlined functions. They appear in backtraces. You can view their
9075 arguments and local variables, step into them with @code{step}, skip
9076 them with @code{next}, and escape from them with @code{finish}.
9077 You can check whether a function was inlined by using the
9078 @code{info frame} command.
9080 For @value{GDBN} to support inlined functions, the compiler must
9081 record information about inlining in the debug information ---
9082 @value{NGCC} using the @sc{dwarf 2} format does this, and several
9083 other compilers do also. @value{GDBN} only supports inlined functions
9084 when using @sc{dwarf 2}. Versions of @value{NGCC} before 4.1
9085 do not emit two required attributes (@samp{DW_AT_call_file} and
9086 @samp{DW_AT_call_line}); @value{GDBN} does not display inlined
9087 function calls with earlier versions of @value{NGCC}. It instead
9088 displays the arguments and local variables of inlined functions as
9089 local variables in the caller.
9091 The body of an inlined function is directly included at its call site;
9092 unlike a non-inlined function, there are no instructions devoted to
9093 the call. @value{GDBN} still pretends that the call site and the
9094 start of the inlined function are different instructions. Stepping to
9095 the call site shows the call site, and then stepping again shows
9096 the first line of the inlined function, even though no additional
9097 instructions are executed.
9099 This makes source-level debugging much clearer; you can see both the
9100 context of the call and then the effect of the call. Only stepping by
9101 a single instruction using @code{stepi} or @code{nexti} does not do
9102 this; single instruction steps always show the inlined body.
9104 There are some ways that @value{GDBN} does not pretend that inlined
9105 function calls are the same as normal calls:
9109 You cannot set breakpoints on inlined functions. @value{GDBN}
9110 either reports that there is no symbol with that name, or else sets the
9111 breakpoint only on non-inlined copies of the function. This limitation
9112 will be removed in a future version of @value{GDBN}; until then,
9113 set a breakpoint by line number on the first line of the inlined
9117 Setting breakpoints at the call site of an inlined function may not
9118 work, because the call site does not contain any code. @value{GDBN}
9119 may incorrectly move the breakpoint to the next line of the enclosing
9120 function, after the call. This limitation will be removed in a future
9121 version of @value{GDBN}; until then, set a breakpoint on an earlier line
9122 or inside the inlined function instead.
9125 @value{GDBN} cannot locate the return value of inlined calls after
9126 using the @code{finish} command. This is a limitation of compiler-generated
9127 debugging information; after @code{finish}, you can step to the next line
9128 and print a variable where your program stored the return value.
9134 @chapter C Preprocessor Macros
9136 Some languages, such as C and C@t{++}, provide a way to define and invoke
9137 ``preprocessor macros'' which expand into strings of tokens.
9138 @value{GDBN} can evaluate expressions containing macro invocations, show
9139 the result of macro expansion, and show a macro's definition, including
9140 where it was defined.
9142 You may need to compile your program specially to provide @value{GDBN}
9143 with information about preprocessor macros. Most compilers do not
9144 include macros in their debugging information, even when you compile
9145 with the @option{-g} flag. @xref{Compilation}.
9147 A program may define a macro at one point, remove that definition later,
9148 and then provide a different definition after that. Thus, at different
9149 points in the program, a macro may have different definitions, or have
9150 no definition at all. If there is a current stack frame, @value{GDBN}
9151 uses the macros in scope at that frame's source code line. Otherwise,
9152 @value{GDBN} uses the macros in scope at the current listing location;
9155 Whenever @value{GDBN} evaluates an expression, it always expands any
9156 macro invocations present in the expression. @value{GDBN} also provides
9157 the following commands for working with macros explicitly.
9161 @kindex macro expand
9162 @cindex macro expansion, showing the results of preprocessor
9163 @cindex preprocessor macro expansion, showing the results of
9164 @cindex expanding preprocessor macros
9165 @item macro expand @var{expression}
9166 @itemx macro exp @var{expression}
9167 Show the results of expanding all preprocessor macro invocations in
9168 @var{expression}. Since @value{GDBN} simply expands macros, but does
9169 not parse the result, @var{expression} need not be a valid expression;
9170 it can be any string of tokens.
9173 @item macro expand-once @var{expression}
9174 @itemx macro exp1 @var{expression}
9175 @cindex expand macro once
9176 @i{(This command is not yet implemented.)} Show the results of
9177 expanding those preprocessor macro invocations that appear explicitly in
9178 @var{expression}. Macro invocations appearing in that expansion are
9179 left unchanged. This command allows you to see the effect of a
9180 particular macro more clearly, without being confused by further
9181 expansions. Since @value{GDBN} simply expands macros, but does not
9182 parse the result, @var{expression} need not be a valid expression; it
9183 can be any string of tokens.
9186 @cindex macro definition, showing
9187 @cindex definition, showing a macro's
9188 @item info macro @var{macro}
9189 Show the definition of the macro named @var{macro}, and describe the
9190 source location or compiler command-line where that definition was established.
9192 @kindex macro define
9193 @cindex user-defined macros
9194 @cindex defining macros interactively
9195 @cindex macros, user-defined
9196 @item macro define @var{macro} @var{replacement-list}
9197 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
9198 Introduce a definition for a preprocessor macro named @var{macro},
9199 invocations of which are replaced by the tokens given in
9200 @var{replacement-list}. The first form of this command defines an
9201 ``object-like'' macro, which takes no arguments; the second form
9202 defines a ``function-like'' macro, which takes the arguments given in
9205 A definition introduced by this command is in scope in every
9206 expression evaluated in @value{GDBN}, until it is removed with the
9207 @code{macro undef} command, described below. The definition overrides
9208 all definitions for @var{macro} present in the program being debugged,
9209 as well as any previous user-supplied definition.
9212 @item macro undef @var{macro}
9213 Remove any user-supplied definition for the macro named @var{macro}.
9214 This command only affects definitions provided with the @code{macro
9215 define} command, described above; it cannot remove definitions present
9216 in the program being debugged.
9220 List all the macros defined using the @code{macro define} command.
9223 @cindex macros, example of debugging with
9224 Here is a transcript showing the above commands in action. First, we
9225 show our source files:
9233 #define ADD(x) (M + x)
9238 printf ("Hello, world!\n");
9240 printf ("We're so creative.\n");
9242 printf ("Goodbye, world!\n");
9249 Now, we compile the program using the @sc{gnu} C compiler, @value{NGCC}.
9250 We pass the @option{-gdwarf-2} and @option{-g3} flags to ensure the
9251 compiler includes information about preprocessor macros in the debugging
9255 $ gcc -gdwarf-2 -g3 sample.c -o sample
9259 Now, we start @value{GDBN} on our sample program:
9263 GNU gdb 2002-05-06-cvs
9264 Copyright 2002 Free Software Foundation, Inc.
9265 GDB is free software, @dots{}
9269 We can expand macros and examine their definitions, even when the
9270 program is not running. @value{GDBN} uses the current listing position
9271 to decide which macro definitions are in scope:
9274 (@value{GDBP}) list main
9277 5 #define ADD(x) (M + x)
9282 10 printf ("Hello, world!\n");
9284 12 printf ("We're so creative.\n");
9285 (@value{GDBP}) info macro ADD
9286 Defined at /home/jimb/gdb/macros/play/sample.c:5
9287 #define ADD(x) (M + x)
9288 (@value{GDBP}) info macro Q
9289 Defined at /home/jimb/gdb/macros/play/sample.h:1
9290 included at /home/jimb/gdb/macros/play/sample.c:2
9292 (@value{GDBP}) macro expand ADD(1)
9293 expands to: (42 + 1)
9294 (@value{GDBP}) macro expand-once ADD(1)
9295 expands to: once (M + 1)
9299 In the example above, note that @code{macro expand-once} expands only
9300 the macro invocation explicit in the original text --- the invocation of
9301 @code{ADD} --- but does not expand the invocation of the macro @code{M},
9302 which was introduced by @code{ADD}.
9304 Once the program is running, @value{GDBN} uses the macro definitions in
9305 force at the source line of the current stack frame:
9308 (@value{GDBP}) break main
9309 Breakpoint 1 at 0x8048370: file sample.c, line 10.
9311 Starting program: /home/jimb/gdb/macros/play/sample
9313 Breakpoint 1, main () at sample.c:10
9314 10 printf ("Hello, world!\n");
9318 At line 10, the definition of the macro @code{N} at line 9 is in force:
9321 (@value{GDBP}) info macro N
9322 Defined at /home/jimb/gdb/macros/play/sample.c:9
9324 (@value{GDBP}) macro expand N Q M
9326 (@value{GDBP}) print N Q M
9331 As we step over directives that remove @code{N}'s definition, and then
9332 give it a new definition, @value{GDBN} finds the definition (or lack
9333 thereof) in force at each point:
9338 12 printf ("We're so creative.\n");
9339 (@value{GDBP}) info macro N
9340 The symbol `N' has no definition as a C/C++ preprocessor macro
9341 at /home/jimb/gdb/macros/play/sample.c:12
9344 14 printf ("Goodbye, world!\n");
9345 (@value{GDBP}) info macro N
9346 Defined at /home/jimb/gdb/macros/play/sample.c:13
9348 (@value{GDBP}) macro expand N Q M
9349 expands to: 1729 < 42
9350 (@value{GDBP}) print N Q M
9355 In addition to source files, macros can be defined on the compilation command
9356 line using the @option{-D@var{name}=@var{value}} syntax. For macros defined in
9357 such a way, @value{GDBN} displays the location of their definition as line zero
9358 of the source file submitted to the compiler.
9361 (@value{GDBP}) info macro __STDC__
9362 Defined at /home/jimb/gdb/macros/play/sample.c:0
9369 @chapter Tracepoints
9370 @c This chapter is based on the documentation written by Michael
9371 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
9374 In some applications, it is not feasible for the debugger to interrupt
9375 the program's execution long enough for the developer to learn
9376 anything helpful about its behavior. If the program's correctness
9377 depends on its real-time behavior, delays introduced by a debugger
9378 might cause the program to change its behavior drastically, or perhaps
9379 fail, even when the code itself is correct. It is useful to be able
9380 to observe the program's behavior without interrupting it.
9382 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
9383 specify locations in the program, called @dfn{tracepoints}, and
9384 arbitrary expressions to evaluate when those tracepoints are reached.
9385 Later, using the @code{tfind} command, you can examine the values
9386 those expressions had when the program hit the tracepoints. The
9387 expressions may also denote objects in memory---structures or arrays,
9388 for example---whose values @value{GDBN} should record; while visiting
9389 a particular tracepoint, you may inspect those objects as if they were
9390 in memory at that moment. However, because @value{GDBN} records these
9391 values without interacting with you, it can do so quickly and
9392 unobtrusively, hopefully not disturbing the program's behavior.
9394 The tracepoint facility is currently available only for remote
9395 targets. @xref{Targets}. In addition, your remote target must know
9396 how to collect trace data. This functionality is implemented in the
9397 remote stub; however, none of the stubs distributed with @value{GDBN}
9398 support tracepoints as of this writing. The format of the remote
9399 packets used to implement tracepoints are described in @ref{Tracepoint
9402 It is also possible to get trace data from a file, in a manner reminiscent
9403 of corefiles; you specify the filename, and use @code{tfind} to search
9404 through the file. @xref{Trace Files}, for more details.
9406 This chapter describes the tracepoint commands and features.
9410 * Analyze Collected Data::
9411 * Tracepoint Variables::
9415 @node Set Tracepoints
9416 @section Commands to Set Tracepoints
9418 Before running such a @dfn{trace experiment}, an arbitrary number of
9419 tracepoints can be set. A tracepoint is actually a special type of
9420 breakpoint (@pxref{Set Breaks}), so you can manipulate it using
9421 standard breakpoint commands. For instance, as with breakpoints,
9422 tracepoint numbers are successive integers starting from one, and many
9423 of the commands associated with tracepoints take the tracepoint number
9424 as their argument, to identify which tracepoint to work on.
9426 For each tracepoint, you can specify, in advance, some arbitrary set
9427 of data that you want the target to collect in the trace buffer when
9428 it hits that tracepoint. The collected data can include registers,
9429 local variables, or global data. Later, you can use @value{GDBN}
9430 commands to examine the values these data had at the time the
9433 Tracepoints do not support every breakpoint feature. Ignore counts on
9434 tracepoints have no effect, and tracepoints cannot run @value{GDBN}
9435 commands when they are hit. Tracepoints may not be thread-specific
9438 @cindex fast tracepoints
9439 Some targets may support @dfn{fast tracepoints}, which are inserted in
9440 a different way (such as with a jump instead of a trap), that is
9441 faster but possibly restricted in where they may be installed.
9443 This section describes commands to set tracepoints and associated
9444 conditions and actions.
9447 * Create and Delete Tracepoints::
9448 * Enable and Disable Tracepoints::
9449 * Tracepoint Passcounts::
9450 * Tracepoint Conditions::
9451 * Trace State Variables::
9452 * Tracepoint Actions::
9453 * Listing Tracepoints::
9454 * Starting and Stopping Trace Experiments::
9455 * Tracepoint Restrictions::
9458 @node Create and Delete Tracepoints
9459 @subsection Create and Delete Tracepoints
9462 @cindex set tracepoint
9464 @item trace @var{location}
9465 The @code{trace} command is very similar to the @code{break} command.
9466 Its argument @var{location} can be a source line, a function name, or
9467 an address in the target program. @xref{Specify Location}. The
9468 @code{trace} command defines a tracepoint, which is a point in the
9469 target program where the debugger will briefly stop, collect some
9470 data, and then allow the program to continue. Setting a tracepoint or
9471 changing its actions doesn't take effect until the next @code{tstart}
9472 command, and once a trace experiment is running, further changes will
9473 not have any effect until the next trace experiment starts.
9475 Here are some examples of using the @code{trace} command:
9478 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
9480 (@value{GDBP}) @b{trace +2} // 2 lines forward
9482 (@value{GDBP}) @b{trace my_function} // first source line of function
9484 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
9486 (@value{GDBP}) @b{trace *0x2117c4} // an address
9490 You can abbreviate @code{trace} as @code{tr}.
9492 @item trace @var{location} if @var{cond}
9493 Set a tracepoint with condition @var{cond}; evaluate the expression
9494 @var{cond} each time the tracepoint is reached, and collect data only
9495 if the value is nonzero---that is, if @var{cond} evaluates as true.
9496 @xref{Tracepoint Conditions, ,Tracepoint Conditions}, for more
9497 information on tracepoint conditions.
9499 @item ftrace @var{location} [ if @var{cond} ]
9500 @cindex set fast tracepoint
9502 The @code{ftrace} command sets a fast tracepoint. For targets that
9503 support them, fast tracepoints will use a more efficient but possibly
9504 less general technique to trigger data collection, such as a jump
9505 instruction instead of a trap, or some sort of hardware support. It
9506 may not be possible to create a fast tracepoint at the desired
9507 location, in which case the command will exit with an explanatory
9510 @value{GDBN} handles arguments to @code{ftrace} exactly as for
9514 @cindex last tracepoint number
9515 @cindex recent tracepoint number
9516 @cindex tracepoint number
9517 The convenience variable @code{$tpnum} records the tracepoint number
9518 of the most recently set tracepoint.
9520 @kindex delete tracepoint
9521 @cindex tracepoint deletion
9522 @item delete tracepoint @r{[}@var{num}@r{]}
9523 Permanently delete one or more tracepoints. With no argument, the
9524 default is to delete all tracepoints. Note that the regular
9525 @code{delete} command can remove tracepoints also.
9530 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
9532 (@value{GDBP}) @b{delete trace} // remove all tracepoints
9536 You can abbreviate this command as @code{del tr}.
9539 @node Enable and Disable Tracepoints
9540 @subsection Enable and Disable Tracepoints
9542 These commands are deprecated; they are equivalent to plain @code{disable} and @code{enable}.
9545 @kindex disable tracepoint
9546 @item disable tracepoint @r{[}@var{num}@r{]}
9547 Disable tracepoint @var{num}, or all tracepoints if no argument
9548 @var{num} is given. A disabled tracepoint will have no effect during
9549 the next trace experiment, but it is not forgotten. You can re-enable
9550 a disabled tracepoint using the @code{enable tracepoint} command.
9552 @kindex enable tracepoint
9553 @item enable tracepoint @r{[}@var{num}@r{]}
9554 Enable tracepoint @var{num}, or all tracepoints. The enabled
9555 tracepoints will become effective the next time a trace experiment is
9559 @node Tracepoint Passcounts
9560 @subsection Tracepoint Passcounts
9564 @cindex tracepoint pass count
9565 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
9566 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
9567 automatically stop a trace experiment. If a tracepoint's passcount is
9568 @var{n}, then the trace experiment will be automatically stopped on
9569 the @var{n}'th time that tracepoint is hit. If the tracepoint number
9570 @var{num} is not specified, the @code{passcount} command sets the
9571 passcount of the most recently defined tracepoint. If no passcount is
9572 given, the trace experiment will run until stopped explicitly by the
9578 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
9579 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
9581 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
9582 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
9583 (@value{GDBP}) @b{trace foo}
9584 (@value{GDBP}) @b{pass 3}
9585 (@value{GDBP}) @b{trace bar}
9586 (@value{GDBP}) @b{pass 2}
9587 (@value{GDBP}) @b{trace baz}
9588 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
9589 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
9590 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
9591 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
9595 @node Tracepoint Conditions
9596 @subsection Tracepoint Conditions
9597 @cindex conditional tracepoints
9598 @cindex tracepoint conditions
9600 The simplest sort of tracepoint collects data every time your program
9601 reaches a specified place. You can also specify a @dfn{condition} for
9602 a tracepoint. A condition is just a Boolean expression in your
9603 programming language (@pxref{Expressions, ,Expressions}). A
9604 tracepoint with a condition evaluates the expression each time your
9605 program reaches it, and data collection happens only if the condition
9608 Tracepoint conditions can be specified when a tracepoint is set, by
9609 using @samp{if} in the arguments to the @code{trace} command.
9610 @xref{Create and Delete Tracepoints, ,Setting Tracepoints}. They can
9611 also be set or changed at any time with the @code{condition} command,
9612 just as with breakpoints.
9614 Unlike breakpoint conditions, @value{GDBN} does not actually evaluate
9615 the conditional expression itself. Instead, @value{GDBN} encodes the
9616 expression into an agent expression (@pxref{Agent Expressions}
9617 suitable for execution on the target, independently of @value{GDBN}.
9618 Global variables become raw memory locations, locals become stack
9619 accesses, and so forth.
9621 For instance, suppose you have a function that is usually called
9622 frequently, but should not be called after an error has occurred. You
9623 could use the following tracepoint command to collect data about calls
9624 of that function that happen while the error code is propagating
9625 through the program; an unconditional tracepoint could end up
9626 collecting thousands of useless trace frames that you would have to
9630 (@value{GDBP}) @kbd{trace normal_operation if errcode > 0}
9633 @node Trace State Variables
9634 @subsection Trace State Variables
9635 @cindex trace state variables
9637 A @dfn{trace state variable} is a special type of variable that is
9638 created and managed by target-side code. The syntax is the same as
9639 that for GDB's convenience variables (a string prefixed with ``$''),
9640 but they are stored on the target. They must be created explicitly,
9641 using a @code{tvariable} command. They are always 64-bit signed
9644 Trace state variables are remembered by @value{GDBN}, and downloaded
9645 to the target along with tracepoint information when the trace
9646 experiment starts. There are no intrinsic limits on the number of
9647 trace state variables, beyond memory limitations of the target.
9649 @cindex convenience variables, and trace state variables
9650 Although trace state variables are managed by the target, you can use
9651 them in print commands and expressions as if they were convenience
9652 variables; @value{GDBN} will get the current value from the target
9653 while the trace experiment is running. Trace state variables share
9654 the same namespace as other ``$'' variables, which means that you
9655 cannot have trace state variables with names like @code{$23} or
9656 @code{$pc}, nor can you have a trace state variable and a convenience
9657 variable with the same name.
9661 @item tvariable $@var{name} [ = @var{expression} ]
9663 The @code{tvariable} command creates a new trace state variable named
9664 @code{$@var{name}}, and optionally gives it an initial value of
9665 @var{expression}. @var{expression} is evaluated when this command is
9666 entered; the result will be converted to an integer if possible,
9667 otherwise @value{GDBN} will report an error. A subsequent
9668 @code{tvariable} command specifying the same name does not create a
9669 variable, but instead assigns the supplied initial value to the
9670 existing variable of that name, overwriting any previous initial
9671 value. The default initial value is 0.
9673 @item info tvariables
9674 @kindex info tvariables
9675 List all the trace state variables along with their initial values.
9676 Their current values may also be displayed, if the trace experiment is
9679 @item delete tvariable @r{[} $@var{name} @dots{} @r{]}
9680 @kindex delete tvariable
9681 Delete the given trace state variables, or all of them if no arguments
9686 @node Tracepoint Actions
9687 @subsection Tracepoint Action Lists
9691 @cindex tracepoint actions
9692 @item actions @r{[}@var{num}@r{]}
9693 This command will prompt for a list of actions to be taken when the
9694 tracepoint is hit. If the tracepoint number @var{num} is not
9695 specified, this command sets the actions for the one that was most
9696 recently defined (so that you can define a tracepoint and then say
9697 @code{actions} without bothering about its number). You specify the
9698 actions themselves on the following lines, one action at a time, and
9699 terminate the actions list with a line containing just @code{end}. So
9700 far, the only defined actions are @code{collect}, @code{teval}, and
9701 @code{while-stepping}.
9703 @code{actions} is actually equivalent to @code{commands} (@pxref{Break
9704 Commands, ,Breakpoint Command Lists}), except that only the defined
9705 actions are allowed; any other @value{GDBN} command is rejected.
9707 @cindex remove actions from a tracepoint
9708 To remove all actions from a tracepoint, type @samp{actions @var{num}}
9709 and follow it immediately with @samp{end}.
9712 (@value{GDBP}) @b{collect @var{data}} // collect some data
9714 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
9716 (@value{GDBP}) @b{end} // signals the end of actions.
9719 In the following example, the action list begins with @code{collect}
9720 commands indicating the things to be collected when the tracepoint is
9721 hit. Then, in order to single-step and collect additional data
9722 following the tracepoint, a @code{while-stepping} command is used,
9723 followed by the list of things to be collected after each step in a
9724 sequence of single steps. The @code{while-stepping} command is
9725 terminated by its own separate @code{end} command. Lastly, the action
9726 list is terminated by an @code{end} command.
9729 (@value{GDBP}) @b{trace foo}
9730 (@value{GDBP}) @b{actions}
9731 Enter actions for tracepoint 1, one per line:
9735 > collect $pc, arr[i]
9740 @kindex collect @r{(tracepoints)}
9741 @item collect @var{expr1}, @var{expr2}, @dots{}
9742 Collect values of the given expressions when the tracepoint is hit.
9743 This command accepts a comma-separated list of any valid expressions.
9744 In addition to global, static, or local variables, the following
9745 special arguments are supported:
9749 collect all registers
9752 collect all function arguments
9755 collect all local variables.
9758 You can give several consecutive @code{collect} commands, each one
9759 with a single argument, or one @code{collect} command with several
9760 arguments separated by commas; the effect is the same.
9762 The command @code{info scope} (@pxref{Symbols, info scope}) is
9763 particularly useful for figuring out what data to collect.
9765 @kindex teval @r{(tracepoints)}
9766 @item teval @var{expr1}, @var{expr2}, @dots{}
9767 Evaluate the given expressions when the tracepoint is hit. This
9768 command accepts a comma-separated list of expressions. The results
9769 are discarded, so this is mainly useful for assigning values to trace
9770 state variables (@pxref{Trace State Variables}) without adding those
9771 values to the trace buffer, as would be the case if the @code{collect}
9774 @kindex while-stepping @r{(tracepoints)}
9775 @item while-stepping @var{n}
9776 Perform @var{n} single-step instruction traces after the tracepoint,
9777 collecting new data after each step. The @code{while-stepping}
9778 command is followed by the list of what to collect while stepping
9779 (followed by its own @code{end} command):
9783 > collect $regs, myglobal
9789 Note that @code{$pc} is not automatically collected by
9790 @code{while-stepping}; you need to explicitly collect that register if
9791 you need it. You may abbreviate @code{while-stepping} as @code{ws} or
9794 @item set default-collect @var{expr1}, @var{expr2}, @dots{}
9795 @kindex set default-collect
9796 @cindex default collection action
9797 This variable is a list of expressions to collect at each tracepoint
9798 hit. It is effectively an additional @code{collect} action prepended
9799 to every tracepoint action list. The expressions are parsed
9800 individually for each tracepoint, so for instance a variable named
9801 @code{xyz} may be interpreted as a global for one tracepoint, and a
9802 local for another, as appropriate to the tracepoint's location.
9804 @item show default-collect
9805 @kindex show default-collect
9806 Show the list of expressions that are collected by default at each
9811 @node Listing Tracepoints
9812 @subsection Listing Tracepoints
9815 @kindex info tracepoints
9817 @cindex information about tracepoints
9818 @item info tracepoints @r{[}@var{num}@r{]}
9819 Display information about the tracepoint @var{num}. If you don't
9820 specify a tracepoint number, displays information about all the
9821 tracepoints defined so far. The format is similar to that used for
9822 @code{info breakpoints}; in fact, @code{info tracepoints} is the same
9823 command, simply restricting itself to tracepoints.
9825 A tracepoint's listing may include additional information specific to
9830 its passcount as given by the @code{passcount @var{n}} command
9834 (@value{GDBP}) @b{info trace}
9835 Num Type Disp Enb Address What
9836 1 tracepoint keep y 0x0804ab57 in foo() at main.cxx:7
9838 collect globfoo, $regs
9847 This command can be abbreviated @code{info tp}.
9850 @node Starting and Stopping Trace Experiments
9851 @subsection Starting and Stopping Trace Experiments
9855 @cindex start a new trace experiment
9856 @cindex collected data discarded
9858 This command takes no arguments. It starts the trace experiment, and
9859 begins collecting data. This has the side effect of discarding all
9860 the data collected in the trace buffer during the previous trace
9864 @cindex stop a running trace experiment
9866 This command takes no arguments. It ends the trace experiment, and
9867 stops collecting data.
9869 @strong{Note}: a trace experiment and data collection may stop
9870 automatically if any tracepoint's passcount is reached
9871 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
9874 @cindex status of trace data collection
9875 @cindex trace experiment, status of
9877 This command displays the status of the current trace data
9881 Here is an example of the commands we described so far:
9884 (@value{GDBP}) @b{trace gdb_c_test}
9885 (@value{GDBP}) @b{actions}
9886 Enter actions for tracepoint #1, one per line.
9887 > collect $regs,$locals,$args
9892 (@value{GDBP}) @b{tstart}
9893 [time passes @dots{}]
9894 (@value{GDBP}) @b{tstop}
9897 @cindex disconnected tracing
9898 You can choose to continue running the trace experiment even if
9899 @value{GDBN} disconnects from the target, voluntarily or
9900 involuntarily. For commands such as @code{detach}, the debugger will
9901 ask what you want to do with the trace. But for unexpected
9902 terminations (@value{GDBN} crash, network outage), it would be
9903 unfortunate to lose hard-won trace data, so the variable
9904 @code{disconnected-tracing} lets you decide whether the trace should
9905 continue running without @value{GDBN}.
9908 @item set disconnected-tracing on
9909 @itemx set disconnected-tracing off
9910 @kindex set disconnected-tracing
9911 Choose whether a tracing run should continue to run if @value{GDBN}
9912 has disconnected from the target. Note that @code{detach} or
9913 @code{quit} will ask you directly what to do about a running trace no
9914 matter what this variable's setting, so the variable is mainly useful
9915 for handling unexpected situations, such as loss of the network.
9917 @item show disconnected-tracing
9918 @kindex show disconnected-tracing
9919 Show the current choice for disconnected tracing.
9923 When you reconnect to the target, the trace experiment may or may not
9924 still be running; it might have filled the trace buffer in the
9925 meantime, or stopped for one of the other reasons. If it is running,
9926 it will continue after reconnection.
9928 Upon reconnection, the target will upload information about the
9929 tracepoints in effect. @value{GDBN} will then compare that
9930 information to the set of tracepoints currently defined, and attempt
9931 to match them up, allowing for the possibility that the numbers may
9932 have changed due to creation and deletion in the meantime. If one of
9933 the target's tracepoints does not match any in @value{GDBN}, the
9934 debugger will create a new tracepoint, so that you have a number with
9935 which to specify that tracepoint. This matching-up process is
9936 necessarily heuristic, and it may result in useless tracepoints being
9937 created; you may simply delete them if they are of no use.
9939 @cindex circular trace buffer
9940 If your target agent supports a @dfn{circular trace buffer}, then you
9941 can run a trace experiment indefinitely without filling the trace
9942 buffer; when space runs out, the agent deletes already-collected trace
9943 frames, oldest first, until there is enough room to continue
9944 collecting. This is especially useful if your tracepoints are being
9945 hit too often, and your trace gets terminated prematurely because the
9946 buffer is full. To ask for a circular trace buffer, simply set
9947 @samp{circular_trace_buffer} to on. You can set this at any time,
9948 including during tracing; if the agent can do it, it will change
9949 buffer handling on the fly, otherwise it will not take effect until
9953 @item set circular-trace-buffer on
9954 @itemx set circular-trace-buffer off
9955 @kindex set circular-trace-buffer
9956 Choose whether a tracing run should use a linear or circular buffer
9957 for trace data. A linear buffer will not lose any trace data, but may
9958 fill up prematurely, while a circular buffer will discard old trace
9959 data, but it will have always room for the latest tracepoint hits.
9961 @item show circular-trace-buffer
9962 @kindex show circular-trace-buffer
9963 Show the current choice for the trace buffer. Note that this may not
9964 match the agent's current buffer handling, nor is it guaranteed to
9965 match the setting that might have been in effect during a past run,
9966 for instance if you are looking at frames from a trace file.
9970 @node Tracepoint Restrictions
9971 @subsection Tracepoint Restrictions
9973 @cindex tracepoint restrictions
9974 There are a number of restrictions on the use of tracepoints. As
9975 described above, tracepoint data gathering occurs on the target
9976 without interaction from @value{GDBN}. Thus the full capabilities of
9977 the debugger are not available during data gathering, and then at data
9978 examination time, you will be limited by only having what was
9979 collected. The following items describe some common problems, but it
9980 is not exhaustive, and you may run into additional difficulties not
9986 Tracepoint expressions are intended to gather objects (lvalues). Thus
9987 the full flexibility of GDB's expression evaluator is not available.
9988 You cannot call functions, cast objects to aggregate types, access
9989 convenience variables or modify values (except by assignment to trace
9990 state variables). Some language features may implicitly call
9991 functions (for instance Objective-C fields with accessors), and therefore
9992 cannot be collected either.
9995 Collection of local variables, either individually or in bulk with
9996 @code{$locals} or @code{$args}, during @code{while-stepping} may
9997 behave erratically. The stepping action may enter a new scope (for
9998 instance by stepping into a function), or the location of the variable
9999 may change (for instance it is loaded into a register). The
10000 tracepoint data recorded uses the location information for the
10001 variables that is correct for the tracepoint location. When the
10002 tracepoint is created, it is not possible, in general, to determine
10003 where the steps of a @code{while-stepping} sequence will advance the
10004 program---particularly if a conditional branch is stepped.
10007 Collection of an incompletely-initialized or partially-destroyed object
10008 may result in something that @value{GDBN} cannot display, or displays
10009 in a misleading way.
10012 When @value{GDBN} displays a pointer to character it automatically
10013 dereferences the pointer to also display characters of the string
10014 being pointed to. However, collecting the pointer during tracing does
10015 not automatically collect the string. You need to explicitly
10016 dereference the pointer and provide size information if you want to
10017 collect not only the pointer, but the memory pointed to. For example,
10018 @code{*ptr@@50} can be used to collect the 50 element array pointed to
10022 It is not possible to collect a complete stack backtrace at a
10023 tracepoint. Instead, you may collect the registers and a few hundred
10024 bytes from the stack pointer with something like @code{*$esp@@300}
10025 (adjust to use the name of the actual stack pointer register on your
10026 target architecture, and the amount of stack you wish to capture).
10027 Then the @code{backtrace} command will show a partial backtrace when
10028 using a trace frame. The number of stack frames that can be examined
10029 depends on the sizes of the frames in the collected stack. Note that
10030 if you ask for a block so large that it goes past the bottom of the
10031 stack, the target agent may report an error trying to read from an
10035 If you do not collect registers at a tracepoint, @value{GDBN} can
10036 infer that the value of @code{$pc} must be the same as the address of
10037 the tracepoint and use that when you are looking at a trace frame
10038 for that tracepoint. However, this cannot work if the tracepoint has
10039 multiple locations (for instance if it was set in a function that was
10040 inlined), or if it has a @code{while-stepping} loop. In those cases
10041 @value{GDBN} will warn you that it can't infer @code{$pc}, and default
10046 @node Analyze Collected Data
10047 @section Using the Collected Data
10049 After the tracepoint experiment ends, you use @value{GDBN} commands
10050 for examining the trace data. The basic idea is that each tracepoint
10051 collects a trace @dfn{snapshot} every time it is hit and another
10052 snapshot every time it single-steps. All these snapshots are
10053 consecutively numbered from zero and go into a buffer, and you can
10054 examine them later. The way you examine them is to @dfn{focus} on a
10055 specific trace snapshot. When the remote stub is focused on a trace
10056 snapshot, it will respond to all @value{GDBN} requests for memory and
10057 registers by reading from the buffer which belongs to that snapshot,
10058 rather than from @emph{real} memory or registers of the program being
10059 debugged. This means that @strong{all} @value{GDBN} commands
10060 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
10061 behave as if we were currently debugging the program state as it was
10062 when the tracepoint occurred. Any requests for data that are not in
10063 the buffer will fail.
10066 * tfind:: How to select a trace snapshot
10067 * tdump:: How to display all data for a snapshot
10068 * save tracepoints:: How to save tracepoints for a future run
10072 @subsection @code{tfind @var{n}}
10075 @cindex select trace snapshot
10076 @cindex find trace snapshot
10077 The basic command for selecting a trace snapshot from the buffer is
10078 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
10079 counting from zero. If no argument @var{n} is given, the next
10080 snapshot is selected.
10082 Here are the various forms of using the @code{tfind} command.
10086 Find the first snapshot in the buffer. This is a synonym for
10087 @code{tfind 0} (since 0 is the number of the first snapshot).
10090 Stop debugging trace snapshots, resume @emph{live} debugging.
10093 Same as @samp{tfind none}.
10096 No argument means find the next trace snapshot.
10099 Find the previous trace snapshot before the current one. This permits
10100 retracing earlier steps.
10102 @item tfind tracepoint @var{num}
10103 Find the next snapshot associated with tracepoint @var{num}. Search
10104 proceeds forward from the last examined trace snapshot. If no
10105 argument @var{num} is given, it means find the next snapshot collected
10106 for the same tracepoint as the current snapshot.
10108 @item tfind pc @var{addr}
10109 Find the next snapshot associated with the value @var{addr} of the
10110 program counter. Search proceeds forward from the last examined trace
10111 snapshot. If no argument @var{addr} is given, it means find the next
10112 snapshot with the same value of PC as the current snapshot.
10114 @item tfind outside @var{addr1}, @var{addr2}
10115 Find the next snapshot whose PC is outside the given range of
10116 addresses (exclusive).
10118 @item tfind range @var{addr1}, @var{addr2}
10119 Find the next snapshot whose PC is between @var{addr1} and
10120 @var{addr2} (inclusive).
10122 @item tfind line @r{[}@var{file}:@r{]}@var{n}
10123 Find the next snapshot associated with the source line @var{n}. If
10124 the optional argument @var{file} is given, refer to line @var{n} in
10125 that source file. Search proceeds forward from the last examined
10126 trace snapshot. If no argument @var{n} is given, it means find the
10127 next line other than the one currently being examined; thus saying
10128 @code{tfind line} repeatedly can appear to have the same effect as
10129 stepping from line to line in a @emph{live} debugging session.
10132 The default arguments for the @code{tfind} commands are specifically
10133 designed to make it easy to scan through the trace buffer. For
10134 instance, @code{tfind} with no argument selects the next trace
10135 snapshot, and @code{tfind -} with no argument selects the previous
10136 trace snapshot. So, by giving one @code{tfind} command, and then
10137 simply hitting @key{RET} repeatedly you can examine all the trace
10138 snapshots in order. Or, by saying @code{tfind -} and then hitting
10139 @key{RET} repeatedly you can examine the snapshots in reverse order.
10140 The @code{tfind line} command with no argument selects the snapshot
10141 for the next source line executed. The @code{tfind pc} command with
10142 no argument selects the next snapshot with the same program counter
10143 (PC) as the current frame. The @code{tfind tracepoint} command with
10144 no argument selects the next trace snapshot collected by the same
10145 tracepoint as the current one.
10147 In addition to letting you scan through the trace buffer manually,
10148 these commands make it easy to construct @value{GDBN} scripts that
10149 scan through the trace buffer and print out whatever collected data
10150 you are interested in. Thus, if we want to examine the PC, FP, and SP
10151 registers from each trace frame in the buffer, we can say this:
10154 (@value{GDBP}) @b{tfind start}
10155 (@value{GDBP}) @b{while ($trace_frame != -1)}
10156 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
10157 $trace_frame, $pc, $sp, $fp
10161 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
10162 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
10163 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
10164 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
10165 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
10166 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
10167 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
10168 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
10169 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
10170 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
10171 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
10174 Or, if we want to examine the variable @code{X} at each source line in
10178 (@value{GDBP}) @b{tfind start}
10179 (@value{GDBP}) @b{while ($trace_frame != -1)}
10180 > printf "Frame %d, X == %d\n", $trace_frame, X
10190 @subsection @code{tdump}
10192 @cindex dump all data collected at tracepoint
10193 @cindex tracepoint data, display
10195 This command takes no arguments. It prints all the data collected at
10196 the current trace snapshot.
10199 (@value{GDBP}) @b{trace 444}
10200 (@value{GDBP}) @b{actions}
10201 Enter actions for tracepoint #2, one per line:
10202 > collect $regs, $locals, $args, gdb_long_test
10205 (@value{GDBP}) @b{tstart}
10207 (@value{GDBP}) @b{tfind line 444}
10208 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
10210 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
10212 (@value{GDBP}) @b{tdump}
10213 Data collected at tracepoint 2, trace frame 1:
10214 d0 0xc4aa0085 -995491707
10218 d4 0x71aea3d 119204413
10221 d7 0x380035 3670069
10222 a0 0x19e24a 1696330
10223 a1 0x3000668 50333288
10225 a3 0x322000 3284992
10226 a4 0x3000698 50333336
10227 a5 0x1ad3cc 1758156
10228 fp 0x30bf3c 0x30bf3c
10229 sp 0x30bf34 0x30bf34
10231 pc 0x20b2c8 0x20b2c8
10235 p = 0x20e5b4 "gdb-test"
10242 gdb_long_test = 17 '\021'
10247 @code{tdump} works by scanning the tracepoint's current collection
10248 actions and printing the value of each expression listed. So
10249 @code{tdump} can fail, if after a run, you change the tracepoint's
10250 actions to mention variables that were not collected during the run.
10252 Also, for tracepoints with @code{while-stepping} loops, @code{tdump}
10253 uses the collected value of @code{$pc} to distinguish between trace
10254 frames that were collected at the tracepoint hit, and frames that were
10255 collected while stepping. This allows it to correctly choose whether
10256 to display the basic list of collections, or the collections from the
10257 body of the while-stepping loop. However, if @code{$pc} was not collected,
10258 then @code{tdump} will always attempt to dump using the basic collection
10259 list, and may fail if a while-stepping frame does not include all the
10260 same data that is collected at the tracepoint hit.
10261 @c This is getting pretty arcane, example would be good.
10263 @node save tracepoints
10264 @subsection @code{save tracepoints @var{filename}}
10265 @kindex save tracepoints
10266 @kindex save-tracepoints
10267 @cindex save tracepoints for future sessions
10269 This command saves all current tracepoint definitions together with
10270 their actions and passcounts, into a file @file{@var{filename}}
10271 suitable for use in a later debugging session. To read the saved
10272 tracepoint definitions, use the @code{source} command (@pxref{Command
10273 Files}). The @w{@code{save-tracepoints}} command is a deprecated
10274 alias for @w{@code{save tracepoints}}
10276 @node Tracepoint Variables
10277 @section Convenience Variables for Tracepoints
10278 @cindex tracepoint variables
10279 @cindex convenience variables for tracepoints
10282 @vindex $trace_frame
10283 @item (int) $trace_frame
10284 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
10285 snapshot is selected.
10287 @vindex $tracepoint
10288 @item (int) $tracepoint
10289 The tracepoint for the current trace snapshot.
10291 @vindex $trace_line
10292 @item (int) $trace_line
10293 The line number for the current trace snapshot.
10295 @vindex $trace_file
10296 @item (char []) $trace_file
10297 The source file for the current trace snapshot.
10299 @vindex $trace_func
10300 @item (char []) $trace_func
10301 The name of the function containing @code{$tracepoint}.
10304 Note: @code{$trace_file} is not suitable for use in @code{printf},
10305 use @code{output} instead.
10307 Here's a simple example of using these convenience variables for
10308 stepping through all the trace snapshots and printing some of their
10309 data. Note that these are not the same as trace state variables,
10310 which are managed by the target.
10313 (@value{GDBP}) @b{tfind start}
10315 (@value{GDBP}) @b{while $trace_frame != -1}
10316 > output $trace_file
10317 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
10323 @section Using Trace Files
10324 @cindex trace files
10326 In some situations, the target running a trace experiment may no
10327 longer be available; perhaps it crashed, or the hardware was needed
10328 for a different activity. To handle these cases, you can arrange to
10329 dump the trace data into a file, and later use that file as a source
10330 of trace data, via the @code{target tfile} command.
10335 @item tsave [ -r ] @var{filename}
10336 Save the trace data to @var{filename}. By default, this command
10337 assumes that @var{filename} refers to the host filesystem, so if
10338 necessary @value{GDBN} will copy raw trace data up from the target and
10339 then save it. If the target supports it, you can also supply the
10340 optional argument @code{-r} (``remote'') to direct the target to save
10341 the data directly into @var{filename} in its own filesystem, which may be
10342 more efficient if the trace buffer is very large. (Note, however, that
10343 @code{target tfile} can only read from files accessible to the host.)
10345 @kindex target tfile
10347 @item target tfile @var{filename}
10348 Use the file named @var{filename} as a source of trace data. Commands
10349 that examine data work as they do with a live target, but it is not
10350 possible to run any new trace experiments. @code{tstatus} will report
10351 the state of the trace run at the moment the data was saved, as well
10352 as the current trace frame you are examining. @var{filename} must be
10353 on a filesystem accessible to the host.
10358 @chapter Debugging Programs That Use Overlays
10361 If your program is too large to fit completely in your target system's
10362 memory, you can sometimes use @dfn{overlays} to work around this
10363 problem. @value{GDBN} provides some support for debugging programs that
10367 * How Overlays Work:: A general explanation of overlays.
10368 * Overlay Commands:: Managing overlays in @value{GDBN}.
10369 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
10370 mapped by asking the inferior.
10371 * Overlay Sample Program:: A sample program using overlays.
10374 @node How Overlays Work
10375 @section How Overlays Work
10376 @cindex mapped overlays
10377 @cindex unmapped overlays
10378 @cindex load address, overlay's
10379 @cindex mapped address
10380 @cindex overlay area
10382 Suppose you have a computer whose instruction address space is only 64
10383 kilobytes long, but which has much more memory which can be accessed by
10384 other means: special instructions, segment registers, or memory
10385 management hardware, for example. Suppose further that you want to
10386 adapt a program which is larger than 64 kilobytes to run on this system.
10388 One solution is to identify modules of your program which are relatively
10389 independent, and need not call each other directly; call these modules
10390 @dfn{overlays}. Separate the overlays from the main program, and place
10391 their machine code in the larger memory. Place your main program in
10392 instruction memory, but leave at least enough space there to hold the
10393 largest overlay as well.
10395 Now, to call a function located in an overlay, you must first copy that
10396 overlay's machine code from the large memory into the space set aside
10397 for it in the instruction memory, and then jump to its entry point
10400 @c NB: In the below the mapped area's size is greater or equal to the
10401 @c size of all overlays. This is intentional to remind the developer
10402 @c that overlays don't necessarily need to be the same size.
10406 Data Instruction Larger
10407 Address Space Address Space Address Space
10408 +-----------+ +-----------+ +-----------+
10410 +-----------+ +-----------+ +-----------+<-- overlay 1
10411 | program | | main | .----| overlay 1 | load address
10412 | variables | | program | | +-----------+
10413 | and heap | | | | | |
10414 +-----------+ | | | +-----------+<-- overlay 2
10415 | | +-----------+ | | | load address
10416 +-----------+ | | | .-| overlay 2 |
10418 mapped --->+-----------+ | | +-----------+
10419 address | | | | | |
10420 | overlay | <-' | | |
10421 | area | <---' +-----------+<-- overlay 3
10422 | | <---. | | load address
10423 +-----------+ `--| overlay 3 |
10430 @anchor{A code overlay}A code overlay
10434 The diagram (@pxref{A code overlay}) shows a system with separate data
10435 and instruction address spaces. To map an overlay, the program copies
10436 its code from the larger address space to the instruction address space.
10437 Since the overlays shown here all use the same mapped address, only one
10438 may be mapped at a time. For a system with a single address space for
10439 data and instructions, the diagram would be similar, except that the
10440 program variables and heap would share an address space with the main
10441 program and the overlay area.
10443 An overlay loaded into instruction memory and ready for use is called a
10444 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
10445 instruction memory. An overlay not present (or only partially present)
10446 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
10447 is its address in the larger memory. The mapped address is also called
10448 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
10449 called the @dfn{load memory address}, or @dfn{LMA}.
10451 Unfortunately, overlays are not a completely transparent way to adapt a
10452 program to limited instruction memory. They introduce a new set of
10453 global constraints you must keep in mind as you design your program:
10458 Before calling or returning to a function in an overlay, your program
10459 must make sure that overlay is actually mapped. Otherwise, the call or
10460 return will transfer control to the right address, but in the wrong
10461 overlay, and your program will probably crash.
10464 If the process of mapping an overlay is expensive on your system, you
10465 will need to choose your overlays carefully to minimize their effect on
10466 your program's performance.
10469 The executable file you load onto your system must contain each
10470 overlay's instructions, appearing at the overlay's load address, not its
10471 mapped address. However, each overlay's instructions must be relocated
10472 and its symbols defined as if the overlay were at its mapped address.
10473 You can use GNU linker scripts to specify different load and relocation
10474 addresses for pieces of your program; see @ref{Overlay Description,,,
10475 ld.info, Using ld: the GNU linker}.
10478 The procedure for loading executable files onto your system must be able
10479 to load their contents into the larger address space as well as the
10480 instruction and data spaces.
10484 The overlay system described above is rather simple, and could be
10485 improved in many ways:
10490 If your system has suitable bank switch registers or memory management
10491 hardware, you could use those facilities to make an overlay's load area
10492 contents simply appear at their mapped address in instruction space.
10493 This would probably be faster than copying the overlay to its mapped
10494 area in the usual way.
10497 If your overlays are small enough, you could set aside more than one
10498 overlay area, and have more than one overlay mapped at a time.
10501 You can use overlays to manage data, as well as instructions. In
10502 general, data overlays are even less transparent to your design than
10503 code overlays: whereas code overlays only require care when you call or
10504 return to functions, data overlays require care every time you access
10505 the data. Also, if you change the contents of a data overlay, you
10506 must copy its contents back out to its load address before you can copy a
10507 different data overlay into the same mapped area.
10512 @node Overlay Commands
10513 @section Overlay Commands
10515 To use @value{GDBN}'s overlay support, each overlay in your program must
10516 correspond to a separate section of the executable file. The section's
10517 virtual memory address and load memory address must be the overlay's
10518 mapped and load addresses. Identifying overlays with sections allows
10519 @value{GDBN} to determine the appropriate address of a function or
10520 variable, depending on whether the overlay is mapped or not.
10522 @value{GDBN}'s overlay commands all start with the word @code{overlay};
10523 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
10528 Disable @value{GDBN}'s overlay support. When overlay support is
10529 disabled, @value{GDBN} assumes that all functions and variables are
10530 always present at their mapped addresses. By default, @value{GDBN}'s
10531 overlay support is disabled.
10533 @item overlay manual
10534 @cindex manual overlay debugging
10535 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
10536 relies on you to tell it which overlays are mapped, and which are not,
10537 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
10538 commands described below.
10540 @item overlay map-overlay @var{overlay}
10541 @itemx overlay map @var{overlay}
10542 @cindex map an overlay
10543 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
10544 be the name of the object file section containing the overlay. When an
10545 overlay is mapped, @value{GDBN} assumes it can find the overlay's
10546 functions and variables at their mapped addresses. @value{GDBN} assumes
10547 that any other overlays whose mapped ranges overlap that of
10548 @var{overlay} are now unmapped.
10550 @item overlay unmap-overlay @var{overlay}
10551 @itemx overlay unmap @var{overlay}
10552 @cindex unmap an overlay
10553 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
10554 must be the name of the object file section containing the overlay.
10555 When an overlay is unmapped, @value{GDBN} assumes it can find the
10556 overlay's functions and variables at their load addresses.
10559 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
10560 consults a data structure the overlay manager maintains in the inferior
10561 to see which overlays are mapped. For details, see @ref{Automatic
10562 Overlay Debugging}.
10564 @item overlay load-target
10565 @itemx overlay load
10566 @cindex reloading the overlay table
10567 Re-read the overlay table from the inferior. Normally, @value{GDBN}
10568 re-reads the table @value{GDBN} automatically each time the inferior
10569 stops, so this command should only be necessary if you have changed the
10570 overlay mapping yourself using @value{GDBN}. This command is only
10571 useful when using automatic overlay debugging.
10573 @item overlay list-overlays
10574 @itemx overlay list
10575 @cindex listing mapped overlays
10576 Display a list of the overlays currently mapped, along with their mapped
10577 addresses, load addresses, and sizes.
10581 Normally, when @value{GDBN} prints a code address, it includes the name
10582 of the function the address falls in:
10585 (@value{GDBP}) print main
10586 $3 = @{int ()@} 0x11a0 <main>
10589 When overlay debugging is enabled, @value{GDBN} recognizes code in
10590 unmapped overlays, and prints the names of unmapped functions with
10591 asterisks around them. For example, if @code{foo} is a function in an
10592 unmapped overlay, @value{GDBN} prints it this way:
10595 (@value{GDBP}) overlay list
10596 No sections are mapped.
10597 (@value{GDBP}) print foo
10598 $5 = @{int (int)@} 0x100000 <*foo*>
10601 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
10605 (@value{GDBP}) overlay list
10606 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
10607 mapped at 0x1016 - 0x104a
10608 (@value{GDBP}) print foo
10609 $6 = @{int (int)@} 0x1016 <foo>
10612 When overlay debugging is enabled, @value{GDBN} can find the correct
10613 address for functions and variables in an overlay, whether or not the
10614 overlay is mapped. This allows most @value{GDBN} commands, like
10615 @code{break} and @code{disassemble}, to work normally, even on unmapped
10616 code. However, @value{GDBN}'s breakpoint support has some limitations:
10620 @cindex breakpoints in overlays
10621 @cindex overlays, setting breakpoints in
10622 You can set breakpoints in functions in unmapped overlays, as long as
10623 @value{GDBN} can write to the overlay at its load address.
10625 @value{GDBN} can not set hardware or simulator-based breakpoints in
10626 unmapped overlays. However, if you set a breakpoint at the end of your
10627 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
10628 you are using manual overlay management), @value{GDBN} will re-set its
10629 breakpoints properly.
10633 @node Automatic Overlay Debugging
10634 @section Automatic Overlay Debugging
10635 @cindex automatic overlay debugging
10637 @value{GDBN} can automatically track which overlays are mapped and which
10638 are not, given some simple co-operation from the overlay manager in the
10639 inferior. If you enable automatic overlay debugging with the
10640 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
10641 looks in the inferior's memory for certain variables describing the
10642 current state of the overlays.
10644 Here are the variables your overlay manager must define to support
10645 @value{GDBN}'s automatic overlay debugging:
10649 @item @code{_ovly_table}:
10650 This variable must be an array of the following structures:
10655 /* The overlay's mapped address. */
10658 /* The size of the overlay, in bytes. */
10659 unsigned long size;
10661 /* The overlay's load address. */
10664 /* Non-zero if the overlay is currently mapped;
10666 unsigned long mapped;
10670 @item @code{_novlys}:
10671 This variable must be a four-byte signed integer, holding the total
10672 number of elements in @code{_ovly_table}.
10676 To decide whether a particular overlay is mapped or not, @value{GDBN}
10677 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
10678 @code{lma} members equal the VMA and LMA of the overlay's section in the
10679 executable file. When @value{GDBN} finds a matching entry, it consults
10680 the entry's @code{mapped} member to determine whether the overlay is
10683 In addition, your overlay manager may define a function called
10684 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
10685 will silently set a breakpoint there. If the overlay manager then
10686 calls this function whenever it has changed the overlay table, this
10687 will enable @value{GDBN} to accurately keep track of which overlays
10688 are in program memory, and update any breakpoints that may be set
10689 in overlays. This will allow breakpoints to work even if the
10690 overlays are kept in ROM or other non-writable memory while they
10691 are not being executed.
10693 @node Overlay Sample Program
10694 @section Overlay Sample Program
10695 @cindex overlay example program
10697 When linking a program which uses overlays, you must place the overlays
10698 at their load addresses, while relocating them to run at their mapped
10699 addresses. To do this, you must write a linker script (@pxref{Overlay
10700 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
10701 since linker scripts are specific to a particular host system, target
10702 architecture, and target memory layout, this manual cannot provide
10703 portable sample code demonstrating @value{GDBN}'s overlay support.
10705 However, the @value{GDBN} source distribution does contain an overlaid
10706 program, with linker scripts for a few systems, as part of its test
10707 suite. The program consists of the following files from
10708 @file{gdb/testsuite/gdb.base}:
10712 The main program file.
10714 A simple overlay manager, used by @file{overlays.c}.
10719 Overlay modules, loaded and used by @file{overlays.c}.
10722 Linker scripts for linking the test program on the @code{d10v-elf}
10723 and @code{m32r-elf} targets.
10726 You can build the test program using the @code{d10v-elf} GCC
10727 cross-compiler like this:
10730 $ d10v-elf-gcc -g -c overlays.c
10731 $ d10v-elf-gcc -g -c ovlymgr.c
10732 $ d10v-elf-gcc -g -c foo.c
10733 $ d10v-elf-gcc -g -c bar.c
10734 $ d10v-elf-gcc -g -c baz.c
10735 $ d10v-elf-gcc -g -c grbx.c
10736 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
10737 baz.o grbx.o -Wl,-Td10v.ld -o overlays
10740 The build process is identical for any other architecture, except that
10741 you must substitute the appropriate compiler and linker script for the
10742 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
10746 @chapter Using @value{GDBN} with Different Languages
10749 Although programming languages generally have common aspects, they are
10750 rarely expressed in the same manner. For instance, in ANSI C,
10751 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
10752 Modula-2, it is accomplished by @code{p^}. Values can also be
10753 represented (and displayed) differently. Hex numbers in C appear as
10754 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
10756 @cindex working language
10757 Language-specific information is built into @value{GDBN} for some languages,
10758 allowing you to express operations like the above in your program's
10759 native language, and allowing @value{GDBN} to output values in a manner
10760 consistent with the syntax of your program's native language. The
10761 language you use to build expressions is called the @dfn{working
10765 * Setting:: Switching between source languages
10766 * Show:: Displaying the language
10767 * Checks:: Type and range checks
10768 * Supported Languages:: Supported languages
10769 * Unsupported Languages:: Unsupported languages
10773 @section Switching Between Source Languages
10775 There are two ways to control the working language---either have @value{GDBN}
10776 set it automatically, or select it manually yourself. You can use the
10777 @code{set language} command for either purpose. On startup, @value{GDBN}
10778 defaults to setting the language automatically. The working language is
10779 used to determine how expressions you type are interpreted, how values
10782 In addition to the working language, every source file that
10783 @value{GDBN} knows about has its own working language. For some object
10784 file formats, the compiler might indicate which language a particular
10785 source file is in. However, most of the time @value{GDBN} infers the
10786 language from the name of the file. The language of a source file
10787 controls whether C@t{++} names are demangled---this way @code{backtrace} can
10788 show each frame appropriately for its own language. There is no way to
10789 set the language of a source file from within @value{GDBN}, but you can
10790 set the language associated with a filename extension. @xref{Show, ,
10791 Displaying the Language}.
10793 This is most commonly a problem when you use a program, such
10794 as @code{cfront} or @code{f2c}, that generates C but is written in
10795 another language. In that case, make the
10796 program use @code{#line} directives in its C output; that way
10797 @value{GDBN} will know the correct language of the source code of the original
10798 program, and will display that source code, not the generated C code.
10801 * Filenames:: Filename extensions and languages.
10802 * Manually:: Setting the working language manually
10803 * Automatically:: Having @value{GDBN} infer the source language
10807 @subsection List of Filename Extensions and Languages
10809 If a source file name ends in one of the following extensions, then
10810 @value{GDBN} infers that its language is the one indicated.
10828 C@t{++} source file
10834 Objective-C source file
10838 Fortran source file
10841 Modula-2 source file
10845 Assembler source file. This actually behaves almost like C, but
10846 @value{GDBN} does not skip over function prologues when stepping.
10849 In addition, you may set the language associated with a filename
10850 extension. @xref{Show, , Displaying the Language}.
10853 @subsection Setting the Working Language
10855 If you allow @value{GDBN} to set the language automatically,
10856 expressions are interpreted the same way in your debugging session and
10859 @kindex set language
10860 If you wish, you may set the language manually. To do this, issue the
10861 command @samp{set language @var{lang}}, where @var{lang} is the name of
10862 a language, such as
10863 @code{c} or @code{modula-2}.
10864 For a list of the supported languages, type @samp{set language}.
10866 Setting the language manually prevents @value{GDBN} from updating the working
10867 language automatically. This can lead to confusion if you try
10868 to debug a program when the working language is not the same as the
10869 source language, when an expression is acceptable to both
10870 languages---but means different things. For instance, if the current
10871 source file were written in C, and @value{GDBN} was parsing Modula-2, a
10879 might not have the effect you intended. In C, this means to add
10880 @code{b} and @code{c} and place the result in @code{a}. The result
10881 printed would be the value of @code{a}. In Modula-2, this means to compare
10882 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
10884 @node Automatically
10885 @subsection Having @value{GDBN} Infer the Source Language
10887 To have @value{GDBN} set the working language automatically, use
10888 @samp{set language local} or @samp{set language auto}. @value{GDBN}
10889 then infers the working language. That is, when your program stops in a
10890 frame (usually by encountering a breakpoint), @value{GDBN} sets the
10891 working language to the language recorded for the function in that
10892 frame. If the language for a frame is unknown (that is, if the function
10893 or block corresponding to the frame was defined in a source file that
10894 does not have a recognized extension), the current working language is
10895 not changed, and @value{GDBN} issues a warning.
10897 This may not seem necessary for most programs, which are written
10898 entirely in one source language. However, program modules and libraries
10899 written in one source language can be used by a main program written in
10900 a different source language. Using @samp{set language auto} in this
10901 case frees you from having to set the working language manually.
10904 @section Displaying the Language
10906 The following commands help you find out which language is the
10907 working language, and also what language source files were written in.
10910 @item show language
10911 @kindex show language
10912 Display the current working language. This is the
10913 language you can use with commands such as @code{print} to
10914 build and compute expressions that may involve variables in your program.
10917 @kindex info frame@r{, show the source language}
10918 Display the source language for this frame. This language becomes the
10919 working language if you use an identifier from this frame.
10920 @xref{Frame Info, ,Information about a Frame}, to identify the other
10921 information listed here.
10924 @kindex info source@r{, show the source language}
10925 Display the source language of this source file.
10926 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
10927 information listed here.
10930 In unusual circumstances, you may have source files with extensions
10931 not in the standard list. You can then set the extension associated
10932 with a language explicitly:
10935 @item set extension-language @var{ext} @var{language}
10936 @kindex set extension-language
10937 Tell @value{GDBN} that source files with extension @var{ext} are to be
10938 assumed as written in the source language @var{language}.
10940 @item info extensions
10941 @kindex info extensions
10942 List all the filename extensions and the associated languages.
10946 @section Type and Range Checking
10949 @emph{Warning:} In this release, the @value{GDBN} commands for type and range
10950 checking are included, but they do not yet have any effect. This
10951 section documents the intended facilities.
10953 @c FIXME remove warning when type/range code added
10955 Some languages are designed to guard you against making seemingly common
10956 errors through a series of compile- and run-time checks. These include
10957 checking the type of arguments to functions and operators, and making
10958 sure mathematical overflows are caught at run time. Checks such as
10959 these help to ensure a program's correctness once it has been compiled
10960 by eliminating type mismatches, and providing active checks for range
10961 errors when your program is running.
10963 @value{GDBN} can check for conditions like the above if you wish.
10964 Although @value{GDBN} does not check the statements in your program,
10965 it can check expressions entered directly into @value{GDBN} for
10966 evaluation via the @code{print} command, for example. As with the
10967 working language, @value{GDBN} can also decide whether or not to check
10968 automatically based on your program's source language.
10969 @xref{Supported Languages, ,Supported Languages}, for the default
10970 settings of supported languages.
10973 * Type Checking:: An overview of type checking
10974 * Range Checking:: An overview of range checking
10977 @cindex type checking
10978 @cindex checks, type
10979 @node Type Checking
10980 @subsection An Overview of Type Checking
10982 Some languages, such as Modula-2, are strongly typed, meaning that the
10983 arguments to operators and functions have to be of the correct type,
10984 otherwise an error occurs. These checks prevent type mismatch
10985 errors from ever causing any run-time problems. For example,
10993 The second example fails because the @code{CARDINAL} 1 is not
10994 type-compatible with the @code{REAL} 2.3.
10996 For the expressions you use in @value{GDBN} commands, you can tell the
10997 @value{GDBN} type checker to skip checking;
10998 to treat any mismatches as errors and abandon the expression;
10999 or to only issue warnings when type mismatches occur,
11000 but evaluate the expression anyway. When you choose the last of
11001 these, @value{GDBN} evaluates expressions like the second example above, but
11002 also issues a warning.
11004 Even if you turn type checking off, there may be other reasons
11005 related to type that prevent @value{GDBN} from evaluating an expression.
11006 For instance, @value{GDBN} does not know how to add an @code{int} and
11007 a @code{struct foo}. These particular type errors have nothing to do
11008 with the language in use, and usually arise from expressions, such as
11009 the one described above, which make little sense to evaluate anyway.
11011 Each language defines to what degree it is strict about type. For
11012 instance, both Modula-2 and C require the arguments to arithmetical
11013 operators to be numbers. In C, enumerated types and pointers can be
11014 represented as numbers, so that they are valid arguments to mathematical
11015 operators. @xref{Supported Languages, ,Supported Languages}, for further
11016 details on specific languages.
11018 @value{GDBN} provides some additional commands for controlling the type checker:
11020 @kindex set check type
11021 @kindex show check type
11023 @item set check type auto
11024 Set type checking on or off based on the current working language.
11025 @xref{Supported Languages, ,Supported Languages}, for the default settings for
11028 @item set check type on
11029 @itemx set check type off
11030 Set type checking on or off, overriding the default setting for the
11031 current working language. Issue a warning if the setting does not
11032 match the language default. If any type mismatches occur in
11033 evaluating an expression while type checking is on, @value{GDBN} prints a
11034 message and aborts evaluation of the expression.
11036 @item set check type warn
11037 Cause the type checker to issue warnings, but to always attempt to
11038 evaluate the expression. Evaluating the expression may still
11039 be impossible for other reasons. For example, @value{GDBN} cannot add
11040 numbers and structures.
11043 Show the current setting of the type checker, and whether or not @value{GDBN}
11044 is setting it automatically.
11047 @cindex range checking
11048 @cindex checks, range
11049 @node Range Checking
11050 @subsection An Overview of Range Checking
11052 In some languages (such as Modula-2), it is an error to exceed the
11053 bounds of a type; this is enforced with run-time checks. Such range
11054 checking is meant to ensure program correctness by making sure
11055 computations do not overflow, or indices on an array element access do
11056 not exceed the bounds of the array.
11058 For expressions you use in @value{GDBN} commands, you can tell
11059 @value{GDBN} to treat range errors in one of three ways: ignore them,
11060 always treat them as errors and abandon the expression, or issue
11061 warnings but evaluate the expression anyway.
11063 A range error can result from numerical overflow, from exceeding an
11064 array index bound, or when you type a constant that is not a member
11065 of any type. Some languages, however, do not treat overflows as an
11066 error. In many implementations of C, mathematical overflow causes the
11067 result to ``wrap around'' to lower values---for example, if @var{m} is
11068 the largest integer value, and @var{s} is the smallest, then
11071 @var{m} + 1 @result{} @var{s}
11074 This, too, is specific to individual languages, and in some cases
11075 specific to individual compilers or machines. @xref{Supported Languages, ,
11076 Supported Languages}, for further details on specific languages.
11078 @value{GDBN} provides some additional commands for controlling the range checker:
11080 @kindex set check range
11081 @kindex show check range
11083 @item set check range auto
11084 Set range checking on or off based on the current working language.
11085 @xref{Supported Languages, ,Supported Languages}, for the default settings for
11088 @item set check range on
11089 @itemx set check range off
11090 Set range checking on or off, overriding the default setting for the
11091 current working language. A warning is issued if the setting does not
11092 match the language default. If a range error occurs and range checking is on,
11093 then a message is printed and evaluation of the expression is aborted.
11095 @item set check range warn
11096 Output messages when the @value{GDBN} range checker detects a range error,
11097 but attempt to evaluate the expression anyway. Evaluating the
11098 expression may still be impossible for other reasons, such as accessing
11099 memory that the process does not own (a typical example from many Unix
11103 Show the current setting of the range checker, and whether or not it is
11104 being set automatically by @value{GDBN}.
11107 @node Supported Languages
11108 @section Supported Languages
11110 @value{GDBN} supports C, C@t{++}, D, Objective-C, Fortran, Java, Pascal,
11111 assembly, Modula-2, and Ada.
11112 @c This is false ...
11113 Some @value{GDBN} features may be used in expressions regardless of the
11114 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
11115 and the @samp{@{type@}addr} construct (@pxref{Expressions,
11116 ,Expressions}) can be used with the constructs of any supported
11119 The following sections detail to what degree each source language is
11120 supported by @value{GDBN}. These sections are not meant to be language
11121 tutorials or references, but serve only as a reference guide to what the
11122 @value{GDBN} expression parser accepts, and what input and output
11123 formats should look like for different languages. There are many good
11124 books written on each of these languages; please look to these for a
11125 language reference or tutorial.
11128 * C:: C and C@t{++}
11130 * Objective-C:: Objective-C
11131 * Fortran:: Fortran
11133 * Modula-2:: Modula-2
11138 @subsection C and C@t{++}
11140 @cindex C and C@t{++}
11141 @cindex expressions in C or C@t{++}
11143 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
11144 to both languages. Whenever this is the case, we discuss those languages
11148 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
11149 @cindex @sc{gnu} C@t{++}
11150 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
11151 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
11152 effectively, you must compile your C@t{++} programs with a supported
11153 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
11154 compiler (@code{aCC}).
11156 For best results when using @sc{gnu} C@t{++}, use the DWARF 2 debugging
11157 format; if it doesn't work on your system, try the stabs+ debugging
11158 format. You can select those formats explicitly with the @code{g++}
11159 command-line options @option{-gdwarf-2} and @option{-gstabs+}.
11160 @xref{Debugging Options,,Options for Debugging Your Program or GCC,
11161 gcc.info, Using the @sc{gnu} Compiler Collection (GCC)}.
11164 * C Operators:: C and C@t{++} operators
11165 * C Constants:: C and C@t{++} constants
11166 * C Plus Plus Expressions:: C@t{++} expressions
11167 * C Defaults:: Default settings for C and C@t{++}
11168 * C Checks:: C and C@t{++} type and range checks
11169 * Debugging C:: @value{GDBN} and C
11170 * Debugging C Plus Plus:: @value{GDBN} features for C@t{++}
11171 * Decimal Floating Point:: Numbers in Decimal Floating Point format
11175 @subsubsection C and C@t{++} Operators
11177 @cindex C and C@t{++} operators
11179 Operators must be defined on values of specific types. For instance,
11180 @code{+} is defined on numbers, but not on structures. Operators are
11181 often defined on groups of types.
11183 For the purposes of C and C@t{++}, the following definitions hold:
11188 @emph{Integral types} include @code{int} with any of its storage-class
11189 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
11192 @emph{Floating-point types} include @code{float}, @code{double}, and
11193 @code{long double} (if supported by the target platform).
11196 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
11199 @emph{Scalar types} include all of the above.
11204 The following operators are supported. They are listed here
11205 in order of increasing precedence:
11209 The comma or sequencing operator. Expressions in a comma-separated list
11210 are evaluated from left to right, with the result of the entire
11211 expression being the last expression evaluated.
11214 Assignment. The value of an assignment expression is the value
11215 assigned. Defined on scalar types.
11218 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
11219 and translated to @w{@code{@var{a} = @var{a op b}}}.
11220 @w{@code{@var{op}=}} and @code{=} have the same precedence.
11221 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
11222 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
11225 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
11226 of as: if @var{a} then @var{b} else @var{c}. @var{a} should be of an
11230 Logical @sc{or}. Defined on integral types.
11233 Logical @sc{and}. Defined on integral types.
11236 Bitwise @sc{or}. Defined on integral types.
11239 Bitwise exclusive-@sc{or}. Defined on integral types.
11242 Bitwise @sc{and}. Defined on integral types.
11245 Equality and inequality. Defined on scalar types. The value of these
11246 expressions is 0 for false and non-zero for true.
11248 @item <@r{, }>@r{, }<=@r{, }>=
11249 Less than, greater than, less than or equal, greater than or equal.
11250 Defined on scalar types. The value of these expressions is 0 for false
11251 and non-zero for true.
11254 left shift, and right shift. Defined on integral types.
11257 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
11260 Addition and subtraction. Defined on integral types, floating-point types and
11263 @item *@r{, }/@r{, }%
11264 Multiplication, division, and modulus. Multiplication and division are
11265 defined on integral and floating-point types. Modulus is defined on
11269 Increment and decrement. When appearing before a variable, the
11270 operation is performed before the variable is used in an expression;
11271 when appearing after it, the variable's value is used before the
11272 operation takes place.
11275 Pointer dereferencing. Defined on pointer types. Same precedence as
11279 Address operator. Defined on variables. Same precedence as @code{++}.
11281 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
11282 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
11283 to examine the address
11284 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
11288 Negative. Defined on integral and floating-point types. Same
11289 precedence as @code{++}.
11292 Logical negation. Defined on integral types. Same precedence as
11296 Bitwise complement operator. Defined on integral types. Same precedence as
11301 Structure member, and pointer-to-structure member. For convenience,
11302 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
11303 pointer based on the stored type information.
11304 Defined on @code{struct} and @code{union} data.
11307 Dereferences of pointers to members.
11310 Array indexing. @code{@var{a}[@var{i}]} is defined as
11311 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
11314 Function parameter list. Same precedence as @code{->}.
11317 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
11318 and @code{class} types.
11321 Doubled colons also represent the @value{GDBN} scope operator
11322 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
11326 If an operator is redefined in the user code, @value{GDBN} usually
11327 attempts to invoke the redefined version instead of using the operator's
11328 predefined meaning.
11331 @subsubsection C and C@t{++} Constants
11333 @cindex C and C@t{++} constants
11335 @value{GDBN} allows you to express the constants of C and C@t{++} in the
11340 Integer constants are a sequence of digits. Octal constants are
11341 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
11342 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
11343 @samp{l}, specifying that the constant should be treated as a
11347 Floating point constants are a sequence of digits, followed by a decimal
11348 point, followed by a sequence of digits, and optionally followed by an
11349 exponent. An exponent is of the form:
11350 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
11351 sequence of digits. The @samp{+} is optional for positive exponents.
11352 A floating-point constant may also end with a letter @samp{f} or
11353 @samp{F}, specifying that the constant should be treated as being of
11354 the @code{float} (as opposed to the default @code{double}) type; or with
11355 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
11359 Enumerated constants consist of enumerated identifiers, or their
11360 integral equivalents.
11363 Character constants are a single character surrounded by single quotes
11364 (@code{'}), or a number---the ordinal value of the corresponding character
11365 (usually its @sc{ascii} value). Within quotes, the single character may
11366 be represented by a letter or by @dfn{escape sequences}, which are of
11367 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
11368 of the character's ordinal value; or of the form @samp{\@var{x}}, where
11369 @samp{@var{x}} is a predefined special character---for example,
11370 @samp{\n} for newline.
11373 String constants are a sequence of character constants surrounded by
11374 double quotes (@code{"}). Any valid character constant (as described
11375 above) may appear. Double quotes within the string must be preceded by
11376 a backslash, so for instance @samp{"a\"b'c"} is a string of five
11380 Pointer constants are an integral value. You can also write pointers
11381 to constants using the C operator @samp{&}.
11384 Array constants are comma-separated lists surrounded by braces @samp{@{}
11385 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
11386 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
11387 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
11390 @node C Plus Plus Expressions
11391 @subsubsection C@t{++} Expressions
11393 @cindex expressions in C@t{++}
11394 @value{GDBN} expression handling can interpret most C@t{++} expressions.
11396 @cindex debugging C@t{++} programs
11397 @cindex C@t{++} compilers
11398 @cindex debug formats and C@t{++}
11399 @cindex @value{NGCC} and C@t{++}
11401 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use the
11402 proper compiler and the proper debug format. Currently, @value{GDBN}
11403 works best when debugging C@t{++} code that is compiled with
11404 @value{NGCC} 2.95.3 or with @value{NGCC} 3.1 or newer, using the options
11405 @option{-gdwarf-2} or @option{-gstabs+}. DWARF 2 is preferred over
11406 stabs+. Most configurations of @value{NGCC} emit either DWARF 2 or
11407 stabs+ as their default debug format, so you usually don't need to
11408 specify a debug format explicitly. Other compilers and/or debug formats
11409 are likely to work badly or not at all when using @value{GDBN} to debug
11415 @cindex member functions
11417 Member function calls are allowed; you can use expressions like
11420 count = aml->GetOriginal(x, y)
11423 @vindex this@r{, inside C@t{++} member functions}
11424 @cindex namespace in C@t{++}
11426 While a member function is active (in the selected stack frame), your
11427 expressions have the same namespace available as the member function;
11428 that is, @value{GDBN} allows implicit references to the class instance
11429 pointer @code{this} following the same rules as C@t{++}.
11431 @cindex call overloaded functions
11432 @cindex overloaded functions, calling
11433 @cindex type conversions in C@t{++}
11435 You can call overloaded functions; @value{GDBN} resolves the function
11436 call to the right definition, with some restrictions. @value{GDBN} does not
11437 perform overload resolution involving user-defined type conversions,
11438 calls to constructors, or instantiations of templates that do not exist
11439 in the program. It also cannot handle ellipsis argument lists or
11442 It does perform integral conversions and promotions, floating-point
11443 promotions, arithmetic conversions, pointer conversions, conversions of
11444 class objects to base classes, and standard conversions such as those of
11445 functions or arrays to pointers; it requires an exact match on the
11446 number of function arguments.
11448 Overload resolution is always performed, unless you have specified
11449 @code{set overload-resolution off}. @xref{Debugging C Plus Plus,
11450 ,@value{GDBN} Features for C@t{++}}.
11452 You must specify @code{set overload-resolution off} in order to use an
11453 explicit function signature to call an overloaded function, as in
11455 p 'foo(char,int)'('x', 13)
11458 The @value{GDBN} command-completion facility can simplify this;
11459 see @ref{Completion, ,Command Completion}.
11461 @cindex reference declarations
11463 @value{GDBN} understands variables declared as C@t{++} references; you can use
11464 them in expressions just as you do in C@t{++} source---they are automatically
11467 In the parameter list shown when @value{GDBN} displays a frame, the values of
11468 reference variables are not displayed (unlike other variables); this
11469 avoids clutter, since references are often used for large structures.
11470 The @emph{address} of a reference variable is always shown, unless
11471 you have specified @samp{set print address off}.
11474 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
11475 expressions can use it just as expressions in your program do. Since
11476 one scope may be defined in another, you can use @code{::} repeatedly if
11477 necessary, for example in an expression like
11478 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
11479 resolving name scope by reference to source files, in both C and C@t{++}
11480 debugging (@pxref{Variables, ,Program Variables}).
11483 In addition, when used with HP's C@t{++} compiler, @value{GDBN} supports
11484 calling virtual functions correctly, printing out virtual bases of
11485 objects, calling functions in a base subobject, casting objects, and
11486 invoking user-defined operators.
11489 @subsubsection C and C@t{++} Defaults
11491 @cindex C and C@t{++} defaults
11493 If you allow @value{GDBN} to set type and range checking automatically, they
11494 both default to @code{off} whenever the working language changes to
11495 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
11496 selects the working language.
11498 If you allow @value{GDBN} to set the language automatically, it
11499 recognizes source files whose names end with @file{.c}, @file{.C}, or
11500 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
11501 these files, it sets the working language to C or C@t{++}.
11502 @xref{Automatically, ,Having @value{GDBN} Infer the Source Language},
11503 for further details.
11505 @c Type checking is (a) primarily motivated by Modula-2, and (b)
11506 @c unimplemented. If (b) changes, it might make sense to let this node
11507 @c appear even if Mod-2 does not, but meanwhile ignore it. roland 16jul93.
11510 @subsubsection C and C@t{++} Type and Range Checks
11512 @cindex C and C@t{++} checks
11514 By default, when @value{GDBN} parses C or C@t{++} expressions, type checking
11515 is not used. However, if you turn type checking on, @value{GDBN}
11516 considers two variables type equivalent if:
11520 The two variables are structured and have the same structure, union, or
11524 The two variables have the same type name, or types that have been
11525 declared equivalent through @code{typedef}.
11528 @c leaving this out because neither J Gilmore nor R Pesch understand it.
11531 The two @code{struct}, @code{union}, or @code{enum} variables are
11532 declared in the same declaration. (Note: this may not be true for all C
11537 Range checking, if turned on, is done on mathematical operations. Array
11538 indices are not checked, since they are often used to index a pointer
11539 that is not itself an array.
11542 @subsubsection @value{GDBN} and C
11544 The @code{set print union} and @code{show print union} commands apply to
11545 the @code{union} type. When set to @samp{on}, any @code{union} that is
11546 inside a @code{struct} or @code{class} is also printed. Otherwise, it
11547 appears as @samp{@{...@}}.
11549 The @code{@@} operator aids in the debugging of dynamic arrays, formed
11550 with pointers and a memory allocation function. @xref{Expressions,
11553 @node Debugging C Plus Plus
11554 @subsubsection @value{GDBN} Features for C@t{++}
11556 @cindex commands for C@t{++}
11558 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
11559 designed specifically for use with C@t{++}. Here is a summary:
11562 @cindex break in overloaded functions
11563 @item @r{breakpoint menus}
11564 When you want a breakpoint in a function whose name is overloaded,
11565 @value{GDBN} has the capability to display a menu of possible breakpoint
11566 locations to help you specify which function definition you want.
11567 @xref{Ambiguous Expressions,,Ambiguous Expressions}.
11569 @cindex overloading in C@t{++}
11570 @item rbreak @var{regex}
11571 Setting breakpoints using regular expressions is helpful for setting
11572 breakpoints on overloaded functions that are not members of any special
11574 @xref{Set Breaks, ,Setting Breakpoints}.
11576 @cindex C@t{++} exception handling
11579 Debug C@t{++} exception handling using these commands. @xref{Set
11580 Catchpoints, , Setting Catchpoints}.
11582 @cindex inheritance
11583 @item ptype @var{typename}
11584 Print inheritance relationships as well as other information for type
11586 @xref{Symbols, ,Examining the Symbol Table}.
11588 @cindex C@t{++} symbol display
11589 @item set print demangle
11590 @itemx show print demangle
11591 @itemx set print asm-demangle
11592 @itemx show print asm-demangle
11593 Control whether C@t{++} symbols display in their source form, both when
11594 displaying code as C@t{++} source and when displaying disassemblies.
11595 @xref{Print Settings, ,Print Settings}.
11597 @item set print object
11598 @itemx show print object
11599 Choose whether to print derived (actual) or declared types of objects.
11600 @xref{Print Settings, ,Print Settings}.
11602 @item set print vtbl
11603 @itemx show print vtbl
11604 Control the format for printing virtual function tables.
11605 @xref{Print Settings, ,Print Settings}.
11606 (The @code{vtbl} commands do not work on programs compiled with the HP
11607 ANSI C@t{++} compiler (@code{aCC}).)
11609 @kindex set overload-resolution
11610 @cindex overloaded functions, overload resolution
11611 @item set overload-resolution on
11612 Enable overload resolution for C@t{++} expression evaluation. The default
11613 is on. For overloaded functions, @value{GDBN} evaluates the arguments
11614 and searches for a function whose signature matches the argument types,
11615 using the standard C@t{++} conversion rules (see @ref{C Plus Plus
11616 Expressions, ,C@t{++} Expressions}, for details).
11617 If it cannot find a match, it emits a message.
11619 @item set overload-resolution off
11620 Disable overload resolution for C@t{++} expression evaluation. For
11621 overloaded functions that are not class member functions, @value{GDBN}
11622 chooses the first function of the specified name that it finds in the
11623 symbol table, whether or not its arguments are of the correct type. For
11624 overloaded functions that are class member functions, @value{GDBN}
11625 searches for a function whose signature @emph{exactly} matches the
11628 @kindex show overload-resolution
11629 @item show overload-resolution
11630 Show the current setting of overload resolution.
11632 @item @r{Overloaded symbol names}
11633 You can specify a particular definition of an overloaded symbol, using
11634 the same notation that is used to declare such symbols in C@t{++}: type
11635 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
11636 also use the @value{GDBN} command-line word completion facilities to list the
11637 available choices, or to finish the type list for you.
11638 @xref{Completion,, Command Completion}, for details on how to do this.
11641 @node Decimal Floating Point
11642 @subsubsection Decimal Floating Point format
11643 @cindex decimal floating point format
11645 @value{GDBN} can examine, set and perform computations with numbers in
11646 decimal floating point format, which in the C language correspond to the
11647 @code{_Decimal32}, @code{_Decimal64} and @code{_Decimal128} types as
11648 specified by the extension to support decimal floating-point arithmetic.
11650 There are two encodings in use, depending on the architecture: BID (Binary
11651 Integer Decimal) for x86 and x86-64, and DPD (Densely Packed Decimal) for
11652 PowerPC. @value{GDBN} will use the appropriate encoding for the configured
11655 Because of a limitation in @file{libdecnumber}, the library used by @value{GDBN}
11656 to manipulate decimal floating point numbers, it is not possible to convert
11657 (using a cast, for example) integers wider than 32-bit to decimal float.
11659 In addition, in order to imitate @value{GDBN}'s behaviour with binary floating
11660 point computations, error checking in decimal float operations ignores
11661 underflow, overflow and divide by zero exceptions.
11663 In the PowerPC architecture, @value{GDBN} provides a set of pseudo-registers
11664 to inspect @code{_Decimal128} values stored in floating point registers.
11665 See @ref{PowerPC,,PowerPC} for more details.
11671 @value{GDBN} can be used to debug programs written in D and compiled with
11672 GDC, LDC or DMD compilers. Currently @value{GDBN} supports only one D
11673 specific feature --- dynamic arrays.
11676 @subsection Objective-C
11678 @cindex Objective-C
11679 This section provides information about some commands and command
11680 options that are useful for debugging Objective-C code. See also
11681 @ref{Symbols, info classes}, and @ref{Symbols, info selectors}, for a
11682 few more commands specific to Objective-C support.
11685 * Method Names in Commands::
11686 * The Print Command with Objective-C::
11689 @node Method Names in Commands
11690 @subsubsection Method Names in Commands
11692 The following commands have been extended to accept Objective-C method
11693 names as line specifications:
11695 @kindex clear@r{, and Objective-C}
11696 @kindex break@r{, and Objective-C}
11697 @kindex info line@r{, and Objective-C}
11698 @kindex jump@r{, and Objective-C}
11699 @kindex list@r{, and Objective-C}
11703 @item @code{info line}
11708 A fully qualified Objective-C method name is specified as
11711 -[@var{Class} @var{methodName}]
11714 where the minus sign is used to indicate an instance method and a
11715 plus sign (not shown) is used to indicate a class method. The class
11716 name @var{Class} and method name @var{methodName} are enclosed in
11717 brackets, similar to the way messages are specified in Objective-C
11718 source code. For example, to set a breakpoint at the @code{create}
11719 instance method of class @code{Fruit} in the program currently being
11723 break -[Fruit create]
11726 To list ten program lines around the @code{initialize} class method,
11730 list +[NSText initialize]
11733 In the current version of @value{GDBN}, the plus or minus sign is
11734 required. In future versions of @value{GDBN}, the plus or minus
11735 sign will be optional, but you can use it to narrow the search. It
11736 is also possible to specify just a method name:
11742 You must specify the complete method name, including any colons. If
11743 your program's source files contain more than one @code{create} method,
11744 you'll be presented with a numbered list of classes that implement that
11745 method. Indicate your choice by number, or type @samp{0} to exit if
11748 As another example, to clear a breakpoint established at the
11749 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
11752 clear -[NSWindow makeKeyAndOrderFront:]
11755 @node The Print Command with Objective-C
11756 @subsubsection The Print Command With Objective-C
11757 @cindex Objective-C, print objects
11758 @kindex print-object
11759 @kindex po @r{(@code{print-object})}
11761 The print command has also been extended to accept methods. For example:
11764 print -[@var{object} hash]
11767 @cindex print an Objective-C object description
11768 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
11770 will tell @value{GDBN} to send the @code{hash} message to @var{object}
11771 and print the result. Also, an additional command has been added,
11772 @code{print-object} or @code{po} for short, which is meant to print
11773 the description of an object. However, this command may only work
11774 with certain Objective-C libraries that have a particular hook
11775 function, @code{_NSPrintForDebugger}, defined.
11778 @subsection Fortran
11779 @cindex Fortran-specific support in @value{GDBN}
11781 @value{GDBN} can be used to debug programs written in Fortran, but it
11782 currently supports only the features of Fortran 77 language.
11784 @cindex trailing underscore, in Fortran symbols
11785 Some Fortran compilers (@sc{gnu} Fortran 77 and Fortran 95 compilers
11786 among them) append an underscore to the names of variables and
11787 functions. When you debug programs compiled by those compilers, you
11788 will need to refer to variables and functions with a trailing
11792 * Fortran Operators:: Fortran operators and expressions
11793 * Fortran Defaults:: Default settings for Fortran
11794 * Special Fortran Commands:: Special @value{GDBN} commands for Fortran
11797 @node Fortran Operators
11798 @subsubsection Fortran Operators and Expressions
11800 @cindex Fortran operators and expressions
11802 Operators must be defined on values of specific types. For instance,
11803 @code{+} is defined on numbers, but not on characters or other non-
11804 arithmetic types. Operators are often defined on groups of types.
11808 The exponentiation operator. It raises the first operand to the power
11812 The range operator. Normally used in the form of array(low:high) to
11813 represent a section of array.
11816 The access component operator. Normally used to access elements in derived
11817 types. Also suitable for unions. As unions aren't part of regular Fortran,
11818 this can only happen when accessing a register that uses a gdbarch-defined
11822 @node Fortran Defaults
11823 @subsubsection Fortran Defaults
11825 @cindex Fortran Defaults
11827 Fortran symbols are usually case-insensitive, so @value{GDBN} by
11828 default uses case-insensitive matches for Fortran symbols. You can
11829 change that with the @samp{set case-insensitive} command, see
11830 @ref{Symbols}, for the details.
11832 @node Special Fortran Commands
11833 @subsubsection Special Fortran Commands
11835 @cindex Special Fortran commands
11837 @value{GDBN} has some commands to support Fortran-specific features,
11838 such as displaying common blocks.
11841 @cindex @code{COMMON} blocks, Fortran
11842 @kindex info common
11843 @item info common @r{[}@var{common-name}@r{]}
11844 This command prints the values contained in the Fortran @code{COMMON}
11845 block whose name is @var{common-name}. With no argument, the names of
11846 all @code{COMMON} blocks visible at the current program location are
11853 @cindex Pascal support in @value{GDBN}, limitations
11854 Debugging Pascal programs which use sets, subranges, file variables, or
11855 nested functions does not currently work. @value{GDBN} does not support
11856 entering expressions, printing values, or similar features using Pascal
11859 The Pascal-specific command @code{set print pascal_static-members}
11860 controls whether static members of Pascal objects are displayed.
11861 @xref{Print Settings, pascal_static-members}.
11864 @subsection Modula-2
11866 @cindex Modula-2, @value{GDBN} support
11868 The extensions made to @value{GDBN} to support Modula-2 only support
11869 output from the @sc{gnu} Modula-2 compiler (which is currently being
11870 developed). Other Modula-2 compilers are not currently supported, and
11871 attempting to debug executables produced by them is most likely
11872 to give an error as @value{GDBN} reads in the executable's symbol
11875 @cindex expressions in Modula-2
11877 * M2 Operators:: Built-in operators
11878 * Built-In Func/Proc:: Built-in functions and procedures
11879 * M2 Constants:: Modula-2 constants
11880 * M2 Types:: Modula-2 types
11881 * M2 Defaults:: Default settings for Modula-2
11882 * Deviations:: Deviations from standard Modula-2
11883 * M2 Checks:: Modula-2 type and range checks
11884 * M2 Scope:: The scope operators @code{::} and @code{.}
11885 * GDB/M2:: @value{GDBN} and Modula-2
11889 @subsubsection Operators
11890 @cindex Modula-2 operators
11892 Operators must be defined on values of specific types. For instance,
11893 @code{+} is defined on numbers, but not on structures. Operators are
11894 often defined on groups of types. For the purposes of Modula-2, the
11895 following definitions hold:
11900 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
11904 @emph{Character types} consist of @code{CHAR} and its subranges.
11907 @emph{Floating-point types} consist of @code{REAL}.
11910 @emph{Pointer types} consist of anything declared as @code{POINTER TO
11914 @emph{Scalar types} consist of all of the above.
11917 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
11920 @emph{Boolean types} consist of @code{BOOLEAN}.
11924 The following operators are supported, and appear in order of
11925 increasing precedence:
11929 Function argument or array index separator.
11932 Assignment. The value of @var{var} @code{:=} @var{value} is
11936 Less than, greater than on integral, floating-point, or enumerated
11940 Less than or equal to, greater than or equal to
11941 on integral, floating-point and enumerated types, or set inclusion on
11942 set types. Same precedence as @code{<}.
11944 @item =@r{, }<>@r{, }#
11945 Equality and two ways of expressing inequality, valid on scalar types.
11946 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
11947 available for inequality, since @code{#} conflicts with the script
11951 Set membership. Defined on set types and the types of their members.
11952 Same precedence as @code{<}.
11955 Boolean disjunction. Defined on boolean types.
11958 Boolean conjunction. Defined on boolean types.
11961 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
11964 Addition and subtraction on integral and floating-point types, or union
11965 and difference on set types.
11968 Multiplication on integral and floating-point types, or set intersection
11972 Division on floating-point types, or symmetric set difference on set
11973 types. Same precedence as @code{*}.
11976 Integer division and remainder. Defined on integral types. Same
11977 precedence as @code{*}.
11980 Negative. Defined on @code{INTEGER} and @code{REAL} data.
11983 Pointer dereferencing. Defined on pointer types.
11986 Boolean negation. Defined on boolean types. Same precedence as
11990 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
11991 precedence as @code{^}.
11994 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
11997 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
12001 @value{GDBN} and Modula-2 scope operators.
12005 @emph{Warning:} Set expressions and their operations are not yet supported, so @value{GDBN}
12006 treats the use of the operator @code{IN}, or the use of operators
12007 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
12008 @code{<=}, and @code{>=} on sets as an error.
12012 @node Built-In Func/Proc
12013 @subsubsection Built-in Functions and Procedures
12014 @cindex Modula-2 built-ins
12016 Modula-2 also makes available several built-in procedures and functions.
12017 In describing these, the following metavariables are used:
12022 represents an @code{ARRAY} variable.
12025 represents a @code{CHAR} constant or variable.
12028 represents a variable or constant of integral type.
12031 represents an identifier that belongs to a set. Generally used in the
12032 same function with the metavariable @var{s}. The type of @var{s} should
12033 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
12036 represents a variable or constant of integral or floating-point type.
12039 represents a variable or constant of floating-point type.
12045 represents a variable.
12048 represents a variable or constant of one of many types. See the
12049 explanation of the function for details.
12052 All Modula-2 built-in procedures also return a result, described below.
12056 Returns the absolute value of @var{n}.
12059 If @var{c} is a lower case letter, it returns its upper case
12060 equivalent, otherwise it returns its argument.
12063 Returns the character whose ordinal value is @var{i}.
12066 Decrements the value in the variable @var{v} by one. Returns the new value.
12068 @item DEC(@var{v},@var{i})
12069 Decrements the value in the variable @var{v} by @var{i}. Returns the
12072 @item EXCL(@var{m},@var{s})
12073 Removes the element @var{m} from the set @var{s}. Returns the new
12076 @item FLOAT(@var{i})
12077 Returns the floating point equivalent of the integer @var{i}.
12079 @item HIGH(@var{a})
12080 Returns the index of the last member of @var{a}.
12083 Increments the value in the variable @var{v} by one. Returns the new value.
12085 @item INC(@var{v},@var{i})
12086 Increments the value in the variable @var{v} by @var{i}. Returns the
12089 @item INCL(@var{m},@var{s})
12090 Adds the element @var{m} to the set @var{s} if it is not already
12091 there. Returns the new set.
12094 Returns the maximum value of the type @var{t}.
12097 Returns the minimum value of the type @var{t}.
12100 Returns boolean TRUE if @var{i} is an odd number.
12103 Returns the ordinal value of its argument. For example, the ordinal
12104 value of a character is its @sc{ascii} value (on machines supporting the
12105 @sc{ascii} character set). @var{x} must be of an ordered type, which include
12106 integral, character and enumerated types.
12108 @item SIZE(@var{x})
12109 Returns the size of its argument. @var{x} can be a variable or a type.
12111 @item TRUNC(@var{r})
12112 Returns the integral part of @var{r}.
12114 @item TSIZE(@var{x})
12115 Returns the size of its argument. @var{x} can be a variable or a type.
12117 @item VAL(@var{t},@var{i})
12118 Returns the member of the type @var{t} whose ordinal value is @var{i}.
12122 @emph{Warning:} Sets and their operations are not yet supported, so
12123 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
12127 @cindex Modula-2 constants
12129 @subsubsection Constants
12131 @value{GDBN} allows you to express the constants of Modula-2 in the following
12137 Integer constants are simply a sequence of digits. When used in an
12138 expression, a constant is interpreted to be type-compatible with the
12139 rest of the expression. Hexadecimal integers are specified by a
12140 trailing @samp{H}, and octal integers by a trailing @samp{B}.
12143 Floating point constants appear as a sequence of digits, followed by a
12144 decimal point and another sequence of digits. An optional exponent can
12145 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
12146 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
12147 digits of the floating point constant must be valid decimal (base 10)
12151 Character constants consist of a single character enclosed by a pair of
12152 like quotes, either single (@code{'}) or double (@code{"}). They may
12153 also be expressed by their ordinal value (their @sc{ascii} value, usually)
12154 followed by a @samp{C}.
12157 String constants consist of a sequence of characters enclosed by a
12158 pair of like quotes, either single (@code{'}) or double (@code{"}).
12159 Escape sequences in the style of C are also allowed. @xref{C
12160 Constants, ,C and C@t{++} Constants}, for a brief explanation of escape
12164 Enumerated constants consist of an enumerated identifier.
12167 Boolean constants consist of the identifiers @code{TRUE} and
12171 Pointer constants consist of integral values only.
12174 Set constants are not yet supported.
12178 @subsubsection Modula-2 Types
12179 @cindex Modula-2 types
12181 Currently @value{GDBN} can print the following data types in Modula-2
12182 syntax: array types, record types, set types, pointer types, procedure
12183 types, enumerated types, subrange types and base types. You can also
12184 print the contents of variables declared using these type.
12185 This section gives a number of simple source code examples together with
12186 sample @value{GDBN} sessions.
12188 The first example contains the following section of code:
12197 and you can request @value{GDBN} to interrogate the type and value of
12198 @code{r} and @code{s}.
12201 (@value{GDBP}) print s
12203 (@value{GDBP}) ptype s
12205 (@value{GDBP}) print r
12207 (@value{GDBP}) ptype r
12212 Likewise if your source code declares @code{s} as:
12216 s: SET ['A'..'Z'] ;
12220 then you may query the type of @code{s} by:
12223 (@value{GDBP}) ptype s
12224 type = SET ['A'..'Z']
12228 Note that at present you cannot interactively manipulate set
12229 expressions using the debugger.
12231 The following example shows how you might declare an array in Modula-2
12232 and how you can interact with @value{GDBN} to print its type and contents:
12236 s: ARRAY [-10..10] OF CHAR ;
12240 (@value{GDBP}) ptype s
12241 ARRAY [-10..10] OF CHAR
12244 Note that the array handling is not yet complete and although the type
12245 is printed correctly, expression handling still assumes that all
12246 arrays have a lower bound of zero and not @code{-10} as in the example
12249 Here are some more type related Modula-2 examples:
12253 colour = (blue, red, yellow, green) ;
12254 t = [blue..yellow] ;
12262 The @value{GDBN} interaction shows how you can query the data type
12263 and value of a variable.
12266 (@value{GDBP}) print s
12268 (@value{GDBP}) ptype t
12269 type = [blue..yellow]
12273 In this example a Modula-2 array is declared and its contents
12274 displayed. Observe that the contents are written in the same way as
12275 their @code{C} counterparts.
12279 s: ARRAY [1..5] OF CARDINAL ;
12285 (@value{GDBP}) print s
12286 $1 = @{1, 0, 0, 0, 0@}
12287 (@value{GDBP}) ptype s
12288 type = ARRAY [1..5] OF CARDINAL
12291 The Modula-2 language interface to @value{GDBN} also understands
12292 pointer types as shown in this example:
12296 s: POINTER TO ARRAY [1..5] OF CARDINAL ;
12303 and you can request that @value{GDBN} describes the type of @code{s}.
12306 (@value{GDBP}) ptype s
12307 type = POINTER TO ARRAY [1..5] OF CARDINAL
12310 @value{GDBN} handles compound types as we can see in this example.
12311 Here we combine array types, record types, pointer types and subrange
12322 myarray = ARRAY myrange OF CARDINAL ;
12323 myrange = [-2..2] ;
12325 s: POINTER TO ARRAY myrange OF foo ;
12329 and you can ask @value{GDBN} to describe the type of @code{s} as shown
12333 (@value{GDBP}) ptype s
12334 type = POINTER TO ARRAY [-2..2] OF foo = RECORD
12337 f3 : ARRAY [-2..2] OF CARDINAL;
12342 @subsubsection Modula-2 Defaults
12343 @cindex Modula-2 defaults
12345 If type and range checking are set automatically by @value{GDBN}, they
12346 both default to @code{on} whenever the working language changes to
12347 Modula-2. This happens regardless of whether you or @value{GDBN}
12348 selected the working language.
12350 If you allow @value{GDBN} to set the language automatically, then entering
12351 code compiled from a file whose name ends with @file{.mod} sets the
12352 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN}
12353 Infer the Source Language}, for further details.
12356 @subsubsection Deviations from Standard Modula-2
12357 @cindex Modula-2, deviations from
12359 A few changes have been made to make Modula-2 programs easier to debug.
12360 This is done primarily via loosening its type strictness:
12364 Unlike in standard Modula-2, pointer constants can be formed by
12365 integers. This allows you to modify pointer variables during
12366 debugging. (In standard Modula-2, the actual address contained in a
12367 pointer variable is hidden from you; it can only be modified
12368 through direct assignment to another pointer variable or expression that
12369 returned a pointer.)
12372 C escape sequences can be used in strings and characters to represent
12373 non-printable characters. @value{GDBN} prints out strings with these
12374 escape sequences embedded. Single non-printable characters are
12375 printed using the @samp{CHR(@var{nnn})} format.
12378 The assignment operator (@code{:=}) returns the value of its right-hand
12382 All built-in procedures both modify @emph{and} return their argument.
12386 @subsubsection Modula-2 Type and Range Checks
12387 @cindex Modula-2 checks
12390 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
12393 @c FIXME remove warning when type/range checks added
12395 @value{GDBN} considers two Modula-2 variables type equivalent if:
12399 They are of types that have been declared equivalent via a @code{TYPE
12400 @var{t1} = @var{t2}} statement
12403 They have been declared on the same line. (Note: This is true of the
12404 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
12407 As long as type checking is enabled, any attempt to combine variables
12408 whose types are not equivalent is an error.
12410 Range checking is done on all mathematical operations, assignment, array
12411 index bounds, and all built-in functions and procedures.
12414 @subsubsection The Scope Operators @code{::} and @code{.}
12416 @cindex @code{.}, Modula-2 scope operator
12417 @cindex colon, doubled as scope operator
12419 @vindex colon-colon@r{, in Modula-2}
12420 @c Info cannot handle :: but TeX can.
12423 @vindex ::@r{, in Modula-2}
12426 There are a few subtle differences between the Modula-2 scope operator
12427 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
12432 @var{module} . @var{id}
12433 @var{scope} :: @var{id}
12437 where @var{scope} is the name of a module or a procedure,
12438 @var{module} the name of a module, and @var{id} is any declared
12439 identifier within your program, except another module.
12441 Using the @code{::} operator makes @value{GDBN} search the scope
12442 specified by @var{scope} for the identifier @var{id}. If it is not
12443 found in the specified scope, then @value{GDBN} searches all scopes
12444 enclosing the one specified by @var{scope}.
12446 Using the @code{.} operator makes @value{GDBN} search the current scope for
12447 the identifier specified by @var{id} that was imported from the
12448 definition module specified by @var{module}. With this operator, it is
12449 an error if the identifier @var{id} was not imported from definition
12450 module @var{module}, or if @var{id} is not an identifier in
12454 @subsubsection @value{GDBN} and Modula-2
12456 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
12457 Five subcommands of @code{set print} and @code{show print} apply
12458 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
12459 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
12460 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
12461 analogue in Modula-2.
12463 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
12464 with any language, is not useful with Modula-2. Its
12465 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
12466 created in Modula-2 as they can in C or C@t{++}. However, because an
12467 address can be specified by an integral constant, the construct
12468 @samp{@{@var{type}@}@var{adrexp}} is still useful.
12470 @cindex @code{#} in Modula-2
12471 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
12472 interpreted as the beginning of a comment. Use @code{<>} instead.
12478 The extensions made to @value{GDBN} for Ada only support
12479 output from the @sc{gnu} Ada (GNAT) compiler.
12480 Other Ada compilers are not currently supported, and
12481 attempting to debug executables produced by them is most likely
12485 @cindex expressions in Ada
12487 * Ada Mode Intro:: General remarks on the Ada syntax
12488 and semantics supported by Ada mode
12490 * Omissions from Ada:: Restrictions on the Ada expression syntax.
12491 * Additions to Ada:: Extensions of the Ada expression syntax.
12492 * Stopping Before Main Program:: Debugging the program during elaboration.
12493 * Ada Tasks:: Listing and setting breakpoints in tasks.
12494 * Ada Tasks and Core Files:: Tasking Support when Debugging Core Files
12495 * Ada Glitches:: Known peculiarities of Ada mode.
12498 @node Ada Mode Intro
12499 @subsubsection Introduction
12500 @cindex Ada mode, general
12502 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
12503 syntax, with some extensions.
12504 The philosophy behind the design of this subset is
12508 That @value{GDBN} should provide basic literals and access to operations for
12509 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
12510 leaving more sophisticated computations to subprograms written into the
12511 program (which therefore may be called from @value{GDBN}).
12514 That type safety and strict adherence to Ada language restrictions
12515 are not particularly important to the @value{GDBN} user.
12518 That brevity is important to the @value{GDBN} user.
12521 Thus, for brevity, the debugger acts as if all names declared in
12522 user-written packages are directly visible, even if they are not visible
12523 according to Ada rules, thus making it unnecessary to fully qualify most
12524 names with their packages, regardless of context. Where this causes
12525 ambiguity, @value{GDBN} asks the user's intent.
12527 The debugger will start in Ada mode if it detects an Ada main program.
12528 As for other languages, it will enter Ada mode when stopped in a program that
12529 was translated from an Ada source file.
12531 While in Ada mode, you may use `@t{--}' for comments. This is useful
12532 mostly for documenting command files. The standard @value{GDBN} comment
12533 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
12534 middle (to allow based literals).
12536 The debugger supports limited overloading. Given a subprogram call in which
12537 the function symbol has multiple definitions, it will use the number of
12538 actual parameters and some information about their types to attempt to narrow
12539 the set of definitions. It also makes very limited use of context, preferring
12540 procedures to functions in the context of the @code{call} command, and
12541 functions to procedures elsewhere.
12543 @node Omissions from Ada
12544 @subsubsection Omissions from Ada
12545 @cindex Ada, omissions from
12547 Here are the notable omissions from the subset:
12551 Only a subset of the attributes are supported:
12555 @t{'First}, @t{'Last}, and @t{'Length}
12556 on array objects (not on types and subtypes).
12559 @t{'Min} and @t{'Max}.
12562 @t{'Pos} and @t{'Val}.
12568 @t{'Range} on array objects (not subtypes), but only as the right
12569 operand of the membership (@code{in}) operator.
12572 @t{'Access}, @t{'Unchecked_Access}, and
12573 @t{'Unrestricted_Access} (a GNAT extension).
12581 @code{Characters.Latin_1} are not available and
12582 concatenation is not implemented. Thus, escape characters in strings are
12583 not currently available.
12586 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
12587 equality of representations. They will generally work correctly
12588 for strings and arrays whose elements have integer or enumeration types.
12589 They may not work correctly for arrays whose element
12590 types have user-defined equality, for arrays of real values
12591 (in particular, IEEE-conformant floating point, because of negative
12592 zeroes and NaNs), and for arrays whose elements contain unused bits with
12593 indeterminate values.
12596 The other component-by-component array operations (@code{and}, @code{or},
12597 @code{xor}, @code{not}, and relational tests other than equality)
12598 are not implemented.
12601 @cindex array aggregates (Ada)
12602 @cindex record aggregates (Ada)
12603 @cindex aggregates (Ada)
12604 There is limited support for array and record aggregates. They are
12605 permitted only on the right sides of assignments, as in these examples:
12608 (@value{GDBP}) set An_Array := (1, 2, 3, 4, 5, 6)
12609 (@value{GDBP}) set An_Array := (1, others => 0)
12610 (@value{GDBP}) set An_Array := (0|4 => 1, 1..3 => 2, 5 => 6)
12611 (@value{GDBP}) set A_2D_Array := ((1, 2, 3), (4, 5, 6), (7, 8, 9))
12612 (@value{GDBP}) set A_Record := (1, "Peter", True);
12613 (@value{GDBP}) set A_Record := (Name => "Peter", Id => 1, Alive => True)
12617 discriminant's value by assigning an aggregate has an
12618 undefined effect if that discriminant is used within the record.
12619 However, you can first modify discriminants by directly assigning to
12620 them (which normally would not be allowed in Ada), and then performing an
12621 aggregate assignment. For example, given a variable @code{A_Rec}
12622 declared to have a type such as:
12625 type Rec (Len : Small_Integer := 0) is record
12627 Vals : IntArray (1 .. Len);
12631 you can assign a value with a different size of @code{Vals} with two
12635 (@value{GDBP}) set A_Rec.Len := 4
12636 (@value{GDBP}) set A_Rec := (Id => 42, Vals => (1, 2, 3, 4))
12639 As this example also illustrates, @value{GDBN} is very loose about the usual
12640 rules concerning aggregates. You may leave out some of the
12641 components of an array or record aggregate (such as the @code{Len}
12642 component in the assignment to @code{A_Rec} above); they will retain their
12643 original values upon assignment. You may freely use dynamic values as
12644 indices in component associations. You may even use overlapping or
12645 redundant component associations, although which component values are
12646 assigned in such cases is not defined.
12649 Calls to dispatching subprograms are not implemented.
12652 The overloading algorithm is much more limited (i.e., less selective)
12653 than that of real Ada. It makes only limited use of the context in
12654 which a subexpression appears to resolve its meaning, and it is much
12655 looser in its rules for allowing type matches. As a result, some
12656 function calls will be ambiguous, and the user will be asked to choose
12657 the proper resolution.
12660 The @code{new} operator is not implemented.
12663 Entry calls are not implemented.
12666 Aside from printing, arithmetic operations on the native VAX floating-point
12667 formats are not supported.
12670 It is not possible to slice a packed array.
12673 The names @code{True} and @code{False}, when not part of a qualified name,
12674 are interpreted as if implicitly prefixed by @code{Standard}, regardless of
12676 Should your program
12677 redefine these names in a package or procedure (at best a dubious practice),
12678 you will have to use fully qualified names to access their new definitions.
12681 @node Additions to Ada
12682 @subsubsection Additions to Ada
12683 @cindex Ada, deviations from
12685 As it does for other languages, @value{GDBN} makes certain generic
12686 extensions to Ada (@pxref{Expressions}):
12690 If the expression @var{E} is a variable residing in memory (typically
12691 a local variable or array element) and @var{N} is a positive integer,
12692 then @code{@var{E}@@@var{N}} displays the values of @var{E} and the
12693 @var{N}-1 adjacent variables following it in memory as an array. In
12694 Ada, this operator is generally not necessary, since its prime use is
12695 in displaying parts of an array, and slicing will usually do this in
12696 Ada. However, there are occasional uses when debugging programs in
12697 which certain debugging information has been optimized away.
12700 @code{@var{B}::@var{var}} means ``the variable named @var{var} that
12701 appears in function or file @var{B}.'' When @var{B} is a file name,
12702 you must typically surround it in single quotes.
12705 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
12706 @var{type} that appears at address @var{addr}.''
12709 A name starting with @samp{$} is a convenience variable
12710 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
12713 In addition, @value{GDBN} provides a few other shortcuts and outright
12714 additions specific to Ada:
12718 The assignment statement is allowed as an expression, returning
12719 its right-hand operand as its value. Thus, you may enter
12722 (@value{GDBP}) set x := y + 3
12723 (@value{GDBP}) print A(tmp := y + 1)
12727 The semicolon is allowed as an ``operator,'' returning as its value
12728 the value of its right-hand operand.
12729 This allows, for example,
12730 complex conditional breaks:
12733 (@value{GDBP}) break f
12734 (@value{GDBP}) condition 1 (report(i); k += 1; A(k) > 100)
12738 Rather than use catenation and symbolic character names to introduce special
12739 characters into strings, one may instead use a special bracket notation,
12740 which is also used to print strings. A sequence of characters of the form
12741 @samp{["@var{XX}"]} within a string or character literal denotes the
12742 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
12743 sequence of characters @samp{["""]} also denotes a single quotation mark
12744 in strings. For example,
12746 "One line.["0a"]Next line.["0a"]"
12749 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF})
12753 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
12754 @t{'Max} is optional (and is ignored in any case). For example, it is valid
12758 (@value{GDBP}) print 'max(x, y)
12762 When printing arrays, @value{GDBN} uses positional notation when the
12763 array has a lower bound of 1, and uses a modified named notation otherwise.
12764 For example, a one-dimensional array of three integers with a lower bound
12765 of 3 might print as
12772 That is, in contrast to valid Ada, only the first component has a @code{=>}
12776 You may abbreviate attributes in expressions with any unique,
12777 multi-character subsequence of
12778 their names (an exact match gets preference).
12779 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
12780 in place of @t{a'length}.
12783 @cindex quoting Ada internal identifiers
12784 Since Ada is case-insensitive, the debugger normally maps identifiers you type
12785 to lower case. The GNAT compiler uses upper-case characters for
12786 some of its internal identifiers, which are normally of no interest to users.
12787 For the rare occasions when you actually have to look at them,
12788 enclose them in angle brackets to avoid the lower-case mapping.
12791 (@value{GDBP}) print <JMPBUF_SAVE>[0]
12795 Printing an object of class-wide type or dereferencing an
12796 access-to-class-wide value will display all the components of the object's
12797 specific type (as indicated by its run-time tag). Likewise, component
12798 selection on such a value will operate on the specific type of the
12803 @node Stopping Before Main Program
12804 @subsubsection Stopping at the Very Beginning
12806 @cindex breakpointing Ada elaboration code
12807 It is sometimes necessary to debug the program during elaboration, and
12808 before reaching the main procedure.
12809 As defined in the Ada Reference
12810 Manual, the elaboration code is invoked from a procedure called
12811 @code{adainit}. To run your program up to the beginning of
12812 elaboration, simply use the following two commands:
12813 @code{tbreak adainit} and @code{run}.
12816 @subsubsection Extensions for Ada Tasks
12817 @cindex Ada, tasking
12819 Support for Ada tasks is analogous to that for threads (@pxref{Threads}).
12820 @value{GDBN} provides the following task-related commands:
12825 This command shows a list of current Ada tasks, as in the following example:
12832 (@value{GDBP}) info tasks
12833 ID TID P-ID Pri State Name
12834 1 8088000 0 15 Child Activation Wait main_task
12835 2 80a4000 1 15 Accept Statement b
12836 3 809a800 1 15 Child Activation Wait a
12837 * 4 80ae800 3 15 Runnable c
12842 In this listing, the asterisk before the last task indicates it to be the
12843 task currently being inspected.
12847 Represents @value{GDBN}'s internal task number.
12853 The parent's task ID (@value{GDBN}'s internal task number).
12856 The base priority of the task.
12859 Current state of the task.
12863 The task has been created but has not been activated. It cannot be
12867 The task is not blocked for any reason known to Ada. (It may be waiting
12868 for a mutex, though.) It is conceptually "executing" in normal mode.
12871 The task is terminated, in the sense of ARM 9.3 (5). Any dependents
12872 that were waiting on terminate alternatives have been awakened and have
12873 terminated themselves.
12875 @item Child Activation Wait
12876 The task is waiting for created tasks to complete activation.
12878 @item Accept Statement
12879 The task is waiting on an accept or selective wait statement.
12881 @item Waiting on entry call
12882 The task is waiting on an entry call.
12884 @item Async Select Wait
12885 The task is waiting to start the abortable part of an asynchronous
12889 The task is waiting on a select statement with only a delay
12892 @item Child Termination Wait
12893 The task is sleeping having completed a master within itself, and is
12894 waiting for the tasks dependent on that master to become terminated or
12895 waiting on a terminate Phase.
12897 @item Wait Child in Term Alt
12898 The task is sleeping waiting for tasks on terminate alternatives to
12899 finish terminating.
12901 @item Accepting RV with @var{taskno}
12902 The task is accepting a rendez-vous with the task @var{taskno}.
12906 Name of the task in the program.
12910 @kindex info task @var{taskno}
12911 @item info task @var{taskno}
12912 This command shows detailled informations on the specified task, as in
12913 the following example:
12918 (@value{GDBP}) info tasks
12919 ID TID P-ID Pri State Name
12920 1 8077880 0 15 Child Activation Wait main_task
12921 * 2 807c468 1 15 Runnable task_1
12922 (@value{GDBP}) info task 2
12923 Ada Task: 0x807c468
12926 Parent: 1 (main_task)
12932 @kindex task@r{ (Ada)}
12933 @cindex current Ada task ID
12934 This command prints the ID of the current task.
12940 (@value{GDBP}) info tasks
12941 ID TID P-ID Pri State Name
12942 1 8077870 0 15 Child Activation Wait main_task
12943 * 2 807c458 1 15 Runnable t
12944 (@value{GDBP}) task
12945 [Current task is 2]
12948 @item task @var{taskno}
12949 @cindex Ada task switching
12950 This command is like the @code{thread @var{threadno}}
12951 command (@pxref{Threads}). It switches the context of debugging
12952 from the current task to the given task.
12958 (@value{GDBP}) info tasks
12959 ID TID P-ID Pri State Name
12960 1 8077870 0 15 Child Activation Wait main_task
12961 * 2 807c458 1 15 Runnable t
12962 (@value{GDBP}) task 1
12963 [Switching to task 1]
12964 #0 0x8067726 in pthread_cond_wait ()
12966 #0 0x8067726 in pthread_cond_wait ()
12967 #1 0x8056714 in system.os_interface.pthread_cond_wait ()
12968 #2 0x805cb63 in system.task_primitives.operations.sleep ()
12969 #3 0x806153e in system.tasking.stages.activate_tasks ()
12970 #4 0x804aacc in un () at un.adb:5
12973 @item break @var{linespec} task @var{taskno}
12974 @itemx break @var{linespec} task @var{taskno} if @dots{}
12975 @cindex breakpoints and tasks, in Ada
12976 @cindex task breakpoints, in Ada
12977 @kindex break @dots{} task @var{taskno}@r{ (Ada)}
12978 These commands are like the @code{break @dots{} thread @dots{}}
12979 command (@pxref{Thread Stops}).
12980 @var{linespec} specifies source lines, as described
12981 in @ref{Specify Location}.
12983 Use the qualifier @samp{task @var{taskno}} with a breakpoint command
12984 to specify that you only want @value{GDBN} to stop the program when a
12985 particular Ada task reaches this breakpoint. @var{taskno} is one of the
12986 numeric task identifiers assigned by @value{GDBN}, shown in the first
12987 column of the @samp{info tasks} display.
12989 If you do not specify @samp{task @var{taskno}} when you set a
12990 breakpoint, the breakpoint applies to @emph{all} tasks of your
12993 You can use the @code{task} qualifier on conditional breakpoints as
12994 well; in this case, place @samp{task @var{taskno}} before the
12995 breakpoint condition (before the @code{if}).
13003 (@value{GDBP}) info tasks
13004 ID TID P-ID Pri State Name
13005 1 140022020 0 15 Child Activation Wait main_task
13006 2 140045060 1 15 Accept/Select Wait t2
13007 3 140044840 1 15 Runnable t1
13008 * 4 140056040 1 15 Runnable t3
13009 (@value{GDBP}) b 15 task 2
13010 Breakpoint 5 at 0x120044cb0: file test_task_debug.adb, line 15.
13011 (@value{GDBP}) cont
13016 Breakpoint 5, test_task_debug () at test_task_debug.adb:15
13018 (@value{GDBP}) info tasks
13019 ID TID P-ID Pri State Name
13020 1 140022020 0 15 Child Activation Wait main_task
13021 * 2 140045060 1 15 Runnable t2
13022 3 140044840 1 15 Runnable t1
13023 4 140056040 1 15 Delay Sleep t3
13027 @node Ada Tasks and Core Files
13028 @subsubsection Tasking Support when Debugging Core Files
13029 @cindex Ada tasking and core file debugging
13031 When inspecting a core file, as opposed to debugging a live program,
13032 tasking support may be limited or even unavailable, depending on
13033 the platform being used.
13034 For instance, on x86-linux, the list of tasks is available, but task
13035 switching is not supported. On Tru64, however, task switching will work
13038 On certain platforms, including Tru64, the debugger needs to perform some
13039 memory writes in order to provide Ada tasking support. When inspecting
13040 a core file, this means that the core file must be opened with read-write
13041 privileges, using the command @samp{"set write on"} (@pxref{Patching}).
13042 Under these circumstances, you should make a backup copy of the core
13043 file before inspecting it with @value{GDBN}.
13046 @subsubsection Known Peculiarities of Ada Mode
13047 @cindex Ada, problems
13049 Besides the omissions listed previously (@pxref{Omissions from Ada}),
13050 we know of several problems with and limitations of Ada mode in
13052 some of which will be fixed with planned future releases of the debugger
13053 and the GNU Ada compiler.
13057 Currently, the debugger
13058 has insufficient information to determine whether certain pointers represent
13059 pointers to objects or the objects themselves.
13060 Thus, the user may have to tack an extra @code{.all} after an expression
13061 to get it printed properly.
13064 Static constants that the compiler chooses not to materialize as objects in
13065 storage are invisible to the debugger.
13068 Named parameter associations in function argument lists are ignored (the
13069 argument lists are treated as positional).
13072 Many useful library packages are currently invisible to the debugger.
13075 Fixed-point arithmetic, conversions, input, and output is carried out using
13076 floating-point arithmetic, and may give results that only approximate those on
13080 The GNAT compiler never generates the prefix @code{Standard} for any of
13081 the standard symbols defined by the Ada language. @value{GDBN} knows about
13082 this: it will strip the prefix from names when you use it, and will never
13083 look for a name you have so qualified among local symbols, nor match against
13084 symbols in other packages or subprograms. If you have
13085 defined entities anywhere in your program other than parameters and
13086 local variables whose simple names match names in @code{Standard},
13087 GNAT's lack of qualification here can cause confusion. When this happens,
13088 you can usually resolve the confusion
13089 by qualifying the problematic names with package
13090 @code{Standard} explicitly.
13093 Older versions of the compiler sometimes generate erroneous debugging
13094 information, resulting in the debugger incorrectly printing the value
13095 of affected entities. In some cases, the debugger is able to work
13096 around an issue automatically. In other cases, the debugger is able
13097 to work around the issue, but the work-around has to be specifically
13100 @kindex set ada trust-PAD-over-XVS
13101 @kindex show ada trust-PAD-over-XVS
13104 @item set ada trust-PAD-over-XVS on
13105 Configure GDB to strictly follow the GNAT encoding when computing the
13106 value of Ada entities, particularly when @code{PAD} and @code{PAD___XVS}
13107 types are involved (see @code{ada/exp_dbug.ads} in the GCC sources for
13108 a complete description of the encoding used by the GNAT compiler).
13109 This is the default.
13111 @item set ada trust-PAD-over-XVS off
13112 This is related to the encoding using by the GNAT compiler. If @value{GDBN}
13113 sometimes prints the wrong value for certain entities, changing @code{ada
13114 trust-PAD-over-XVS} to @code{off} activates a work-around which may fix
13115 the issue. It is always safe to set @code{ada trust-PAD-over-XVS} to
13116 @code{off}, but this incurs a slight performance penalty, so it is
13117 recommended to leave this setting to @code{on} unless necessary.
13121 @node Unsupported Languages
13122 @section Unsupported Languages
13124 @cindex unsupported languages
13125 @cindex minimal language
13126 In addition to the other fully-supported programming languages,
13127 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
13128 It does not represent a real programming language, but provides a set
13129 of capabilities close to what the C or assembly languages provide.
13130 This should allow most simple operations to be performed while debugging
13131 an application that uses a language currently not supported by @value{GDBN}.
13133 If the language is set to @code{auto}, @value{GDBN} will automatically
13134 select this language if the current frame corresponds to an unsupported
13138 @chapter Examining the Symbol Table
13140 The commands described in this chapter allow you to inquire about the
13141 symbols (names of variables, functions and types) defined in your
13142 program. This information is inherent in the text of your program and
13143 does not change as your program executes. @value{GDBN} finds it in your
13144 program's symbol table, in the file indicated when you started @value{GDBN}
13145 (@pxref{File Options, ,Choosing Files}), or by one of the
13146 file-management commands (@pxref{Files, ,Commands to Specify Files}).
13148 @cindex symbol names
13149 @cindex names of symbols
13150 @cindex quoting names
13151 Occasionally, you may need to refer to symbols that contain unusual
13152 characters, which @value{GDBN} ordinarily treats as word delimiters. The
13153 most frequent case is in referring to static variables in other
13154 source files (@pxref{Variables,,Program Variables}). File names
13155 are recorded in object files as debugging symbols, but @value{GDBN} would
13156 ordinarily parse a typical file name, like @file{foo.c}, as the three words
13157 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
13158 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
13165 looks up the value of @code{x} in the scope of the file @file{foo.c}.
13168 @cindex case-insensitive symbol names
13169 @cindex case sensitivity in symbol names
13170 @kindex set case-sensitive
13171 @item set case-sensitive on
13172 @itemx set case-sensitive off
13173 @itemx set case-sensitive auto
13174 Normally, when @value{GDBN} looks up symbols, it matches their names
13175 with case sensitivity determined by the current source language.
13176 Occasionally, you may wish to control that. The command @code{set
13177 case-sensitive} lets you do that by specifying @code{on} for
13178 case-sensitive matches or @code{off} for case-insensitive ones. If
13179 you specify @code{auto}, case sensitivity is reset to the default
13180 suitable for the source language. The default is case-sensitive
13181 matches for all languages except for Fortran, for which the default is
13182 case-insensitive matches.
13184 @kindex show case-sensitive
13185 @item show case-sensitive
13186 This command shows the current setting of case sensitivity for symbols
13189 @kindex info address
13190 @cindex address of a symbol
13191 @item info address @var{symbol}
13192 Describe where the data for @var{symbol} is stored. For a register
13193 variable, this says which register it is kept in. For a non-register
13194 local variable, this prints the stack-frame offset at which the variable
13197 Note the contrast with @samp{print &@var{symbol}}, which does not work
13198 at all for a register variable, and for a stack local variable prints
13199 the exact address of the current instantiation of the variable.
13201 @kindex info symbol
13202 @cindex symbol from address
13203 @cindex closest symbol and offset for an address
13204 @item info symbol @var{addr}
13205 Print the name of a symbol which is stored at the address @var{addr}.
13206 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
13207 nearest symbol and an offset from it:
13210 (@value{GDBP}) info symbol 0x54320
13211 _initialize_vx + 396 in section .text
13215 This is the opposite of the @code{info address} command. You can use
13216 it to find out the name of a variable or a function given its address.
13218 For dynamically linked executables, the name of executable or shared
13219 library containing the symbol is also printed:
13222 (@value{GDBP}) info symbol 0x400225
13223 _start + 5 in section .text of /tmp/a.out
13224 (@value{GDBP}) info symbol 0x2aaaac2811cf
13225 __read_nocancel + 6 in section .text of /usr/lib64/libc.so.6
13229 @item whatis [@var{arg}]
13230 Print the data type of @var{arg}, which can be either an expression or
13231 a data type. With no argument, print the data type of @code{$}, the
13232 last value in the value history. If @var{arg} is an expression, it is
13233 not actually evaluated, and any side-effecting operations (such as
13234 assignments or function calls) inside it do not take place. If
13235 @var{arg} is a type name, it may be the name of a type or typedef, or
13236 for C code it may have the form @samp{class @var{class-name}},
13237 @samp{struct @var{struct-tag}}, @samp{union @var{union-tag}} or
13238 @samp{enum @var{enum-tag}}.
13239 @xref{Expressions, ,Expressions}.
13242 @item ptype [@var{arg}]
13243 @code{ptype} accepts the same arguments as @code{whatis}, but prints a
13244 detailed description of the type, instead of just the name of the type.
13245 @xref{Expressions, ,Expressions}.
13247 For example, for this variable declaration:
13250 struct complex @{double real; double imag;@} v;
13254 the two commands give this output:
13258 (@value{GDBP}) whatis v
13259 type = struct complex
13260 (@value{GDBP}) ptype v
13261 type = struct complex @{
13269 As with @code{whatis}, using @code{ptype} without an argument refers to
13270 the type of @code{$}, the last value in the value history.
13272 @cindex incomplete type
13273 Sometimes, programs use opaque data types or incomplete specifications
13274 of complex data structure. If the debug information included in the
13275 program does not allow @value{GDBN} to display a full declaration of
13276 the data type, it will say @samp{<incomplete type>}. For example,
13277 given these declarations:
13281 struct foo *fooptr;
13285 but no definition for @code{struct foo} itself, @value{GDBN} will say:
13288 (@value{GDBP}) ptype foo
13289 $1 = <incomplete type>
13293 ``Incomplete type'' is C terminology for data types that are not
13294 completely specified.
13297 @item info types @var{regexp}
13299 Print a brief description of all types whose names match the regular
13300 expression @var{regexp} (or all types in your program, if you supply
13301 no argument). Each complete typename is matched as though it were a
13302 complete line; thus, @samp{i type value} gives information on all
13303 types in your program whose names include the string @code{value}, but
13304 @samp{i type ^value$} gives information only on types whose complete
13305 name is @code{value}.
13307 This command differs from @code{ptype} in two ways: first, like
13308 @code{whatis}, it does not print a detailed description; second, it
13309 lists all source files where a type is defined.
13312 @cindex local variables
13313 @item info scope @var{location}
13314 List all the variables local to a particular scope. This command
13315 accepts a @var{location} argument---a function name, a source line, or
13316 an address preceded by a @samp{*}, and prints all the variables local
13317 to the scope defined by that location. (@xref{Specify Location}, for
13318 details about supported forms of @var{location}.) For example:
13321 (@value{GDBP}) @b{info scope command_line_handler}
13322 Scope for command_line_handler:
13323 Symbol rl is an argument at stack/frame offset 8, length 4.
13324 Symbol linebuffer is in static storage at address 0x150a18, length 4.
13325 Symbol linelength is in static storage at address 0x150a1c, length 4.
13326 Symbol p is a local variable in register $esi, length 4.
13327 Symbol p1 is a local variable in register $ebx, length 4.
13328 Symbol nline is a local variable in register $edx, length 4.
13329 Symbol repeat is a local variable at frame offset -8, length 4.
13333 This command is especially useful for determining what data to collect
13334 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
13337 @kindex info source
13339 Show information about the current source file---that is, the source file for
13340 the function containing the current point of execution:
13343 the name of the source file, and the directory containing it,
13345 the directory it was compiled in,
13347 its length, in lines,
13349 which programming language it is written in,
13351 whether the executable includes debugging information for that file, and
13352 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
13354 whether the debugging information includes information about
13355 preprocessor macros.
13359 @kindex info sources
13361 Print the names of all source files in your program for which there is
13362 debugging information, organized into two lists: files whose symbols
13363 have already been read, and files whose symbols will be read when needed.
13365 @kindex info functions
13366 @item info functions
13367 Print the names and data types of all defined functions.
13369 @item info functions @var{regexp}
13370 Print the names and data types of all defined functions
13371 whose names contain a match for regular expression @var{regexp}.
13372 Thus, @samp{info fun step} finds all functions whose names
13373 include @code{step}; @samp{info fun ^step} finds those whose names
13374 start with @code{step}. If a function name contains characters
13375 that conflict with the regular expression language (e.g.@:
13376 @samp{operator*()}), they may be quoted with a backslash.
13378 @kindex info variables
13379 @item info variables
13380 Print the names and data types of all variables that are defined
13381 outside of functions (i.e.@: excluding local variables).
13383 @item info variables @var{regexp}
13384 Print the names and data types of all variables (except for local
13385 variables) whose names contain a match for regular expression
13388 @kindex info classes
13389 @cindex Objective-C, classes and selectors
13391 @itemx info classes @var{regexp}
13392 Display all Objective-C classes in your program, or
13393 (with the @var{regexp} argument) all those matching a particular regular
13396 @kindex info selectors
13397 @item info selectors
13398 @itemx info selectors @var{regexp}
13399 Display all Objective-C selectors in your program, or
13400 (with the @var{regexp} argument) all those matching a particular regular
13404 This was never implemented.
13405 @kindex info methods
13407 @itemx info methods @var{regexp}
13408 The @code{info methods} command permits the user to examine all defined
13409 methods within C@t{++} program, or (with the @var{regexp} argument) a
13410 specific set of methods found in the various C@t{++} classes. Many
13411 C@t{++} classes provide a large number of methods. Thus, the output
13412 from the @code{ptype} command can be overwhelming and hard to use. The
13413 @code{info-methods} command filters the methods, printing only those
13414 which match the regular-expression @var{regexp}.
13417 @cindex reloading symbols
13418 Some systems allow individual object files that make up your program to
13419 be replaced without stopping and restarting your program. For example,
13420 in VxWorks you can simply recompile a defective object file and keep on
13421 running. If you are running on one of these systems, you can allow
13422 @value{GDBN} to reload the symbols for automatically relinked modules:
13425 @kindex set symbol-reloading
13426 @item set symbol-reloading on
13427 Replace symbol definitions for the corresponding source file when an
13428 object file with a particular name is seen again.
13430 @item set symbol-reloading off
13431 Do not replace symbol definitions when encountering object files of the
13432 same name more than once. This is the default state; if you are not
13433 running on a system that permits automatic relinking of modules, you
13434 should leave @code{symbol-reloading} off, since otherwise @value{GDBN}
13435 may discard symbols when linking large programs, that may contain
13436 several modules (from different directories or libraries) with the same
13439 @kindex show symbol-reloading
13440 @item show symbol-reloading
13441 Show the current @code{on} or @code{off} setting.
13444 @cindex opaque data types
13445 @kindex set opaque-type-resolution
13446 @item set opaque-type-resolution on
13447 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
13448 declared as a pointer to a @code{struct}, @code{class}, or
13449 @code{union}---for example, @code{struct MyType *}---that is used in one
13450 source file although the full declaration of @code{struct MyType} is in
13451 another source file. The default is on.
13453 A change in the setting of this subcommand will not take effect until
13454 the next time symbols for a file are loaded.
13456 @item set opaque-type-resolution off
13457 Tell @value{GDBN} not to resolve opaque types. In this case, the type
13458 is printed as follows:
13460 @{<no data fields>@}
13463 @kindex show opaque-type-resolution
13464 @item show opaque-type-resolution
13465 Show whether opaque types are resolved or not.
13467 @kindex maint print symbols
13468 @cindex symbol dump
13469 @kindex maint print psymbols
13470 @cindex partial symbol dump
13471 @item maint print symbols @var{filename}
13472 @itemx maint print psymbols @var{filename}
13473 @itemx maint print msymbols @var{filename}
13474 Write a dump of debugging symbol data into the file @var{filename}.
13475 These commands are used to debug the @value{GDBN} symbol-reading code. Only
13476 symbols with debugging data are included. If you use @samp{maint print
13477 symbols}, @value{GDBN} includes all the symbols for which it has already
13478 collected full details: that is, @var{filename} reflects symbols for
13479 only those files whose symbols @value{GDBN} has read. You can use the
13480 command @code{info sources} to find out which files these are. If you
13481 use @samp{maint print psymbols} instead, the dump shows information about
13482 symbols that @value{GDBN} only knows partially---that is, symbols defined in
13483 files that @value{GDBN} has skimmed, but not yet read completely. Finally,
13484 @samp{maint print msymbols} dumps just the minimal symbol information
13485 required for each object file from which @value{GDBN} has read some symbols.
13486 @xref{Files, ,Commands to Specify Files}, for a discussion of how
13487 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
13489 @kindex maint info symtabs
13490 @kindex maint info psymtabs
13491 @cindex listing @value{GDBN}'s internal symbol tables
13492 @cindex symbol tables, listing @value{GDBN}'s internal
13493 @cindex full symbol tables, listing @value{GDBN}'s internal
13494 @cindex partial symbol tables, listing @value{GDBN}'s internal
13495 @item maint info symtabs @r{[} @var{regexp} @r{]}
13496 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
13498 List the @code{struct symtab} or @code{struct partial_symtab}
13499 structures whose names match @var{regexp}. If @var{regexp} is not
13500 given, list them all. The output includes expressions which you can
13501 copy into a @value{GDBN} debugging this one to examine a particular
13502 structure in more detail. For example:
13505 (@value{GDBP}) maint info psymtabs dwarf2read
13506 @{ objfile /home/gnu/build/gdb/gdb
13507 ((struct objfile *) 0x82e69d0)
13508 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
13509 ((struct partial_symtab *) 0x8474b10)
13512 text addresses 0x814d3c8 -- 0x8158074
13513 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
13514 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
13515 dependencies (none)
13518 (@value{GDBP}) maint info symtabs
13522 We see that there is one partial symbol table whose filename contains
13523 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
13524 and we see that @value{GDBN} has not read in any symtabs yet at all.
13525 If we set a breakpoint on a function, that will cause @value{GDBN} to
13526 read the symtab for the compilation unit containing that function:
13529 (@value{GDBP}) break dwarf2_psymtab_to_symtab
13530 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
13532 (@value{GDBP}) maint info symtabs
13533 @{ objfile /home/gnu/build/gdb/gdb
13534 ((struct objfile *) 0x82e69d0)
13535 @{ symtab /home/gnu/src/gdb/dwarf2read.c
13536 ((struct symtab *) 0x86c1f38)
13539 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
13540 linetable ((struct linetable *) 0x8370fa0)
13541 debugformat DWARF 2
13550 @chapter Altering Execution
13552 Once you think you have found an error in your program, you might want to
13553 find out for certain whether correcting the apparent error would lead to
13554 correct results in the rest of the run. You can find the answer by
13555 experiment, using the @value{GDBN} features for altering execution of the
13558 For example, you can store new values into variables or memory
13559 locations, give your program a signal, restart it at a different
13560 address, or even return prematurely from a function.
13563 * Assignment:: Assignment to variables
13564 * Jumping:: Continuing at a different address
13565 * Signaling:: Giving your program a signal
13566 * Returning:: Returning from a function
13567 * Calling:: Calling your program's functions
13568 * Patching:: Patching your program
13572 @section Assignment to Variables
13575 @cindex setting variables
13576 To alter the value of a variable, evaluate an assignment expression.
13577 @xref{Expressions, ,Expressions}. For example,
13584 stores the value 4 into the variable @code{x}, and then prints the
13585 value of the assignment expression (which is 4).
13586 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
13587 information on operators in supported languages.
13589 @kindex set variable
13590 @cindex variables, setting
13591 If you are not interested in seeing the value of the assignment, use the
13592 @code{set} command instead of the @code{print} command. @code{set} is
13593 really the same as @code{print} except that the expression's value is
13594 not printed and is not put in the value history (@pxref{Value History,
13595 ,Value History}). The expression is evaluated only for its effects.
13597 If the beginning of the argument string of the @code{set} command
13598 appears identical to a @code{set} subcommand, use the @code{set
13599 variable} command instead of just @code{set}. This command is identical
13600 to @code{set} except for its lack of subcommands. For example, if your
13601 program has a variable @code{width}, you get an error if you try to set
13602 a new value with just @samp{set width=13}, because @value{GDBN} has the
13603 command @code{set width}:
13606 (@value{GDBP}) whatis width
13608 (@value{GDBP}) p width
13610 (@value{GDBP}) set width=47
13611 Invalid syntax in expression.
13615 The invalid expression, of course, is @samp{=47}. In
13616 order to actually set the program's variable @code{width}, use
13619 (@value{GDBP}) set var width=47
13622 Because the @code{set} command has many subcommands that can conflict
13623 with the names of program variables, it is a good idea to use the
13624 @code{set variable} command instead of just @code{set}. For example, if
13625 your program has a variable @code{g}, you run into problems if you try
13626 to set a new value with just @samp{set g=4}, because @value{GDBN} has
13627 the command @code{set gnutarget}, abbreviated @code{set g}:
13631 (@value{GDBP}) whatis g
13635 (@value{GDBP}) set g=4
13639 The program being debugged has been started already.
13640 Start it from the beginning? (y or n) y
13641 Starting program: /home/smith/cc_progs/a.out
13642 "/home/smith/cc_progs/a.out": can't open to read symbols:
13643 Invalid bfd target.
13644 (@value{GDBP}) show g
13645 The current BFD target is "=4".
13650 The program variable @code{g} did not change, and you silently set the
13651 @code{gnutarget} to an invalid value. In order to set the variable
13655 (@value{GDBP}) set var g=4
13658 @value{GDBN} allows more implicit conversions in assignments than C; you can
13659 freely store an integer value into a pointer variable or vice versa,
13660 and you can convert any structure to any other structure that is the
13661 same length or shorter.
13662 @comment FIXME: how do structs align/pad in these conversions?
13663 @comment /doc@cygnus.com 18dec1990
13665 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
13666 construct to generate a value of specified type at a specified address
13667 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
13668 to memory location @code{0x83040} as an integer (which implies a certain size
13669 and representation in memory), and
13672 set @{int@}0x83040 = 4
13676 stores the value 4 into that memory location.
13679 @section Continuing at a Different Address
13681 Ordinarily, when you continue your program, you do so at the place where
13682 it stopped, with the @code{continue} command. You can instead continue at
13683 an address of your own choosing, with the following commands:
13687 @item jump @var{linespec}
13688 @itemx jump @var{location}
13689 Resume execution at line @var{linespec} or at address given by
13690 @var{location}. Execution stops again immediately if there is a
13691 breakpoint there. @xref{Specify Location}, for a description of the
13692 different forms of @var{linespec} and @var{location}. It is common
13693 practice to use the @code{tbreak} command in conjunction with
13694 @code{jump}. @xref{Set Breaks, ,Setting Breakpoints}.
13696 The @code{jump} command does not change the current stack frame, or
13697 the stack pointer, or the contents of any memory location or any
13698 register other than the program counter. If line @var{linespec} is in
13699 a different function from the one currently executing, the results may
13700 be bizarre if the two functions expect different patterns of arguments or
13701 of local variables. For this reason, the @code{jump} command requests
13702 confirmation if the specified line is not in the function currently
13703 executing. However, even bizarre results are predictable if you are
13704 well acquainted with the machine-language code of your program.
13707 @c Doesn't work on HP-UX; have to set $pcoqh and $pcoqt.
13708 On many systems, you can get much the same effect as the @code{jump}
13709 command by storing a new value into the register @code{$pc}. The
13710 difference is that this does not start your program running; it only
13711 changes the address of where it @emph{will} run when you continue. For
13719 makes the next @code{continue} command or stepping command execute at
13720 address @code{0x485}, rather than at the address where your program stopped.
13721 @xref{Continuing and Stepping, ,Continuing and Stepping}.
13723 The most common occasion to use the @code{jump} command is to back
13724 up---perhaps with more breakpoints set---over a portion of a program
13725 that has already executed, in order to examine its execution in more
13730 @section Giving your Program a Signal
13731 @cindex deliver a signal to a program
13735 @item signal @var{signal}
13736 Resume execution where your program stopped, but immediately give it the
13737 signal @var{signal}. @var{signal} can be the name or the number of a
13738 signal. For example, on many systems @code{signal 2} and @code{signal
13739 SIGINT} are both ways of sending an interrupt signal.
13741 Alternatively, if @var{signal} is zero, continue execution without
13742 giving a signal. This is useful when your program stopped on account of
13743 a signal and would ordinary see the signal when resumed with the
13744 @code{continue} command; @samp{signal 0} causes it to resume without a
13747 @code{signal} does not repeat when you press @key{RET} a second time
13748 after executing the command.
13752 Invoking the @code{signal} command is not the same as invoking the
13753 @code{kill} utility from the shell. Sending a signal with @code{kill}
13754 causes @value{GDBN} to decide what to do with the signal depending on
13755 the signal handling tables (@pxref{Signals}). The @code{signal} command
13756 passes the signal directly to your program.
13760 @section Returning from a Function
13763 @cindex returning from a function
13766 @itemx return @var{expression}
13767 You can cancel execution of a function call with the @code{return}
13768 command. If you give an
13769 @var{expression} argument, its value is used as the function's return
13773 When you use @code{return}, @value{GDBN} discards the selected stack frame
13774 (and all frames within it). You can think of this as making the
13775 discarded frame return prematurely. If you wish to specify a value to
13776 be returned, give that value as the argument to @code{return}.
13778 This pops the selected stack frame (@pxref{Selection, ,Selecting a
13779 Frame}), and any other frames inside of it, leaving its caller as the
13780 innermost remaining frame. That frame becomes selected. The
13781 specified value is stored in the registers used for returning values
13784 The @code{return} command does not resume execution; it leaves the
13785 program stopped in the state that would exist if the function had just
13786 returned. In contrast, the @code{finish} command (@pxref{Continuing
13787 and Stepping, ,Continuing and Stepping}) resumes execution until the
13788 selected stack frame returns naturally.
13790 @value{GDBN} needs to know how the @var{expression} argument should be set for
13791 the inferior. The concrete registers assignment depends on the OS ABI and the
13792 type being returned by the selected stack frame. For example it is common for
13793 OS ABI to return floating point values in FPU registers while integer values in
13794 CPU registers. Still some ABIs return even floating point values in CPU
13795 registers. Larger integer widths (such as @code{long long int}) also have
13796 specific placement rules. @value{GDBN} already knows the OS ABI from its
13797 current target so it needs to find out also the type being returned to make the
13798 assignment into the right register(s).
13800 Normally, the selected stack frame has debug info. @value{GDBN} will always
13801 use the debug info instead of the implicit type of @var{expression} when the
13802 debug info is available. For example, if you type @kbd{return -1}, and the
13803 function in the current stack frame is declared to return a @code{long long
13804 int}, @value{GDBN} transparently converts the implicit @code{int} value of -1
13805 into a @code{long long int}:
13808 Breakpoint 1, func () at gdb.base/return-nodebug.c:29
13810 (@value{GDBP}) return -1
13811 Make func return now? (y or n) y
13812 #0 0x004004f6 in main () at gdb.base/return-nodebug.c:43
13813 43 printf ("result=%lld\n", func ());
13817 However, if the selected stack frame does not have a debug info, e.g., if the
13818 function was compiled without debug info, @value{GDBN} has to find out the type
13819 to return from user. Specifying a different type by mistake may set the value
13820 in different inferior registers than the caller code expects. For example,
13821 typing @kbd{return -1} with its implicit type @code{int} would set only a part
13822 of a @code{long long int} result for a debug info less function (on 32-bit
13823 architectures). Therefore the user is required to specify the return type by
13824 an appropriate cast explicitly:
13827 Breakpoint 2, 0x0040050b in func ()
13828 (@value{GDBP}) return -1
13829 Return value type not available for selected stack frame.
13830 Please use an explicit cast of the value to return.
13831 (@value{GDBP}) return (long long int) -1
13832 Make selected stack frame return now? (y or n) y
13833 #0 0x00400526 in main ()
13838 @section Calling Program Functions
13841 @cindex calling functions
13842 @cindex inferior functions, calling
13843 @item print @var{expr}
13844 Evaluate the expression @var{expr} and display the resulting value.
13845 @var{expr} may include calls to functions in the program being
13849 @item call @var{expr}
13850 Evaluate the expression @var{expr} without displaying @code{void}
13853 You can use this variant of the @code{print} command if you want to
13854 execute a function from your program that does not return anything
13855 (a.k.a.@: @dfn{a void function}), but without cluttering the output
13856 with @code{void} returned values that @value{GDBN} will otherwise
13857 print. If the result is not void, it is printed and saved in the
13861 It is possible for the function you call via the @code{print} or
13862 @code{call} command to generate a signal (e.g., if there's a bug in
13863 the function, or if you passed it incorrect arguments). What happens
13864 in that case is controlled by the @code{set unwindonsignal} command.
13866 Similarly, with a C@t{++} program it is possible for the function you
13867 call via the @code{print} or @code{call} command to generate an
13868 exception that is not handled due to the constraints of the dummy
13869 frame. In this case, any exception that is raised in the frame, but has
13870 an out-of-frame exception handler will not be found. GDB builds a
13871 dummy-frame for the inferior function call, and the unwinder cannot
13872 seek for exception handlers outside of this dummy-frame. What happens
13873 in that case is controlled by the
13874 @code{set unwind-on-terminating-exception} command.
13877 @item set unwindonsignal
13878 @kindex set unwindonsignal
13879 @cindex unwind stack in called functions
13880 @cindex call dummy stack unwinding
13881 Set unwinding of the stack if a signal is received while in a function
13882 that @value{GDBN} called in the program being debugged. If set to on,
13883 @value{GDBN} unwinds the stack it created for the call and restores
13884 the context to what it was before the call. If set to off (the
13885 default), @value{GDBN} stops in the frame where the signal was
13888 @item show unwindonsignal
13889 @kindex show unwindonsignal
13890 Show the current setting of stack unwinding in the functions called by
13893 @item set unwind-on-terminating-exception
13894 @kindex set unwind-on-terminating-exception
13895 @cindex unwind stack in called functions with unhandled exceptions
13896 @cindex call dummy stack unwinding on unhandled exception.
13897 Set unwinding of the stack if a C@t{++} exception is raised, but left
13898 unhandled while in a function that @value{GDBN} called in the program being
13899 debugged. If set to on (the default), @value{GDBN} unwinds the stack
13900 it created for the call and restores the context to what it was before
13901 the call. If set to off, @value{GDBN} the exception is delivered to
13902 the default C@t{++} exception handler and the inferior terminated.
13904 @item show unwind-on-terminating-exception
13905 @kindex show unwind-on-terminating-exception
13906 Show the current setting of stack unwinding in the functions called by
13911 @cindex weak alias functions
13912 Sometimes, a function you wish to call is actually a @dfn{weak alias}
13913 for another function. In such case, @value{GDBN} might not pick up
13914 the type information, including the types of the function arguments,
13915 which causes @value{GDBN} to call the inferior function incorrectly.
13916 As a result, the called function will function erroneously and may
13917 even crash. A solution to that is to use the name of the aliased
13921 @section Patching Programs
13923 @cindex patching binaries
13924 @cindex writing into executables
13925 @cindex writing into corefiles
13927 By default, @value{GDBN} opens the file containing your program's
13928 executable code (or the corefile) read-only. This prevents accidental
13929 alterations to machine code; but it also prevents you from intentionally
13930 patching your program's binary.
13932 If you'd like to be able to patch the binary, you can specify that
13933 explicitly with the @code{set write} command. For example, you might
13934 want to turn on internal debugging flags, or even to make emergency
13940 @itemx set write off
13941 If you specify @samp{set write on}, @value{GDBN} opens executable and
13942 core files for both reading and writing; if you specify @kbd{set write
13943 off} (the default), @value{GDBN} opens them read-only.
13945 If you have already loaded a file, you must load it again (using the
13946 @code{exec-file} or @code{core-file} command) after changing @code{set
13947 write}, for your new setting to take effect.
13951 Display whether executable files and core files are opened for writing
13952 as well as reading.
13956 @chapter @value{GDBN} Files
13958 @value{GDBN} needs to know the file name of the program to be debugged,
13959 both in order to read its symbol table and in order to start your
13960 program. To debug a core dump of a previous run, you must also tell
13961 @value{GDBN} the name of the core dump file.
13964 * Files:: Commands to specify files
13965 * Separate Debug Files:: Debugging information in separate files
13966 * Symbol Errors:: Errors reading symbol files
13967 * Data Files:: GDB data files
13971 @section Commands to Specify Files
13973 @cindex symbol table
13974 @cindex core dump file
13976 You may want to specify executable and core dump file names. The usual
13977 way to do this is at start-up time, using the arguments to
13978 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
13979 Out of @value{GDBN}}).
13981 Occasionally it is necessary to change to a different file during a
13982 @value{GDBN} session. Or you may run @value{GDBN} and forget to
13983 specify a file you want to use. Or you are debugging a remote target
13984 via @code{gdbserver} (@pxref{Server, file, Using the @code{gdbserver}
13985 Program}). In these situations the @value{GDBN} commands to specify
13986 new files are useful.
13989 @cindex executable file
13991 @item file @var{filename}
13992 Use @var{filename} as the program to be debugged. It is read for its
13993 symbols and for the contents of pure memory. It is also the program
13994 executed when you use the @code{run} command. If you do not specify a
13995 directory and the file is not found in the @value{GDBN} working directory,
13996 @value{GDBN} uses the environment variable @code{PATH} as a list of
13997 directories to search, just as the shell does when looking for a program
13998 to run. You can change the value of this variable, for both @value{GDBN}
13999 and your program, using the @code{path} command.
14001 @cindex unlinked object files
14002 @cindex patching object files
14003 You can load unlinked object @file{.o} files into @value{GDBN} using
14004 the @code{file} command. You will not be able to ``run'' an object
14005 file, but you can disassemble functions and inspect variables. Also,
14006 if the underlying BFD functionality supports it, you could use
14007 @kbd{gdb -write} to patch object files using this technique. Note
14008 that @value{GDBN} can neither interpret nor modify relocations in this
14009 case, so branches and some initialized variables will appear to go to
14010 the wrong place. But this feature is still handy from time to time.
14013 @code{file} with no argument makes @value{GDBN} discard any information it
14014 has on both executable file and the symbol table.
14017 @item exec-file @r{[} @var{filename} @r{]}
14018 Specify that the program to be run (but not the symbol table) is found
14019 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
14020 if necessary to locate your program. Omitting @var{filename} means to
14021 discard information on the executable file.
14023 @kindex symbol-file
14024 @item symbol-file @r{[} @var{filename} @r{]}
14025 Read symbol table information from file @var{filename}. @code{PATH} is
14026 searched when necessary. Use the @code{file} command to get both symbol
14027 table and program to run from the same file.
14029 @code{symbol-file} with no argument clears out @value{GDBN} information on your
14030 program's symbol table.
14032 The @code{symbol-file} command causes @value{GDBN} to forget the contents of
14033 some breakpoints and auto-display expressions. This is because they may
14034 contain pointers to the internal data recording symbols and data types,
14035 which are part of the old symbol table data being discarded inside
14038 @code{symbol-file} does not repeat if you press @key{RET} again after
14041 When @value{GDBN} is configured for a particular environment, it
14042 understands debugging information in whatever format is the standard
14043 generated for that environment; you may use either a @sc{gnu} compiler, or
14044 other compilers that adhere to the local conventions.
14045 Best results are usually obtained from @sc{gnu} compilers; for example,
14046 using @code{@value{NGCC}} you can generate debugging information for
14049 For most kinds of object files, with the exception of old SVR3 systems
14050 using COFF, the @code{symbol-file} command does not normally read the
14051 symbol table in full right away. Instead, it scans the symbol table
14052 quickly to find which source files and which symbols are present. The
14053 details are read later, one source file at a time, as they are needed.
14055 The purpose of this two-stage reading strategy is to make @value{GDBN}
14056 start up faster. For the most part, it is invisible except for
14057 occasional pauses while the symbol table details for a particular source
14058 file are being read. (The @code{set verbose} command can turn these
14059 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
14060 Warnings and Messages}.)
14062 We have not implemented the two-stage strategy for COFF yet. When the
14063 symbol table is stored in COFF format, @code{symbol-file} reads the
14064 symbol table data in full right away. Note that ``stabs-in-COFF''
14065 still does the two-stage strategy, since the debug info is actually
14069 @cindex reading symbols immediately
14070 @cindex symbols, reading immediately
14071 @item symbol-file @r{[} -readnow @r{]} @var{filename}
14072 @itemx file @r{[} -readnow @r{]} @var{filename}
14073 You can override the @value{GDBN} two-stage strategy for reading symbol
14074 tables by using the @samp{-readnow} option with any of the commands that
14075 load symbol table information, if you want to be sure @value{GDBN} has the
14076 entire symbol table available.
14078 @c FIXME: for now no mention of directories, since this seems to be in
14079 @c flux. 13mar1992 status is that in theory GDB would look either in
14080 @c current dir or in same dir as myprog; but issues like competing
14081 @c GDB's, or clutter in system dirs, mean that in practice right now
14082 @c only current dir is used. FFish says maybe a special GDB hierarchy
14083 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
14087 @item core-file @r{[}@var{filename}@r{]}
14089 Specify the whereabouts of a core dump file to be used as the ``contents
14090 of memory''. Traditionally, core files contain only some parts of the
14091 address space of the process that generated them; @value{GDBN} can access the
14092 executable file itself for other parts.
14094 @code{core-file} with no argument specifies that no core file is
14097 Note that the core file is ignored when your program is actually running
14098 under @value{GDBN}. So, if you have been running your program and you
14099 wish to debug a core file instead, you must kill the subprocess in which
14100 the program is running. To do this, use the @code{kill} command
14101 (@pxref{Kill Process, ,Killing the Child Process}).
14103 @kindex add-symbol-file
14104 @cindex dynamic linking
14105 @item add-symbol-file @var{filename} @var{address}
14106 @itemx add-symbol-file @var{filename} @var{address} @r{[} -readnow @r{]}
14107 @itemx add-symbol-file @var{filename} @r{-s}@var{section} @var{address} @dots{}
14108 The @code{add-symbol-file} command reads additional symbol table
14109 information from the file @var{filename}. You would use this command
14110 when @var{filename} has been dynamically loaded (by some other means)
14111 into the program that is running. @var{address} should be the memory
14112 address at which the file has been loaded; @value{GDBN} cannot figure
14113 this out for itself. You can additionally specify an arbitrary number
14114 of @samp{@r{-s}@var{section} @var{address}} pairs, to give an explicit
14115 section name and base address for that section. You can specify any
14116 @var{address} as an expression.
14118 The symbol table of the file @var{filename} is added to the symbol table
14119 originally read with the @code{symbol-file} command. You can use the
14120 @code{add-symbol-file} command any number of times; the new symbol data
14121 thus read keeps adding to the old. To discard all old symbol data
14122 instead, use the @code{symbol-file} command without any arguments.
14124 @cindex relocatable object files, reading symbols from
14125 @cindex object files, relocatable, reading symbols from
14126 @cindex reading symbols from relocatable object files
14127 @cindex symbols, reading from relocatable object files
14128 @cindex @file{.o} files, reading symbols from
14129 Although @var{filename} is typically a shared library file, an
14130 executable file, or some other object file which has been fully
14131 relocated for loading into a process, you can also load symbolic
14132 information from relocatable @file{.o} files, as long as:
14136 the file's symbolic information refers only to linker symbols defined in
14137 that file, not to symbols defined by other object files,
14139 every section the file's symbolic information refers to has actually
14140 been loaded into the inferior, as it appears in the file, and
14142 you can determine the address at which every section was loaded, and
14143 provide these to the @code{add-symbol-file} command.
14147 Some embedded operating systems, like Sun Chorus and VxWorks, can load
14148 relocatable files into an already running program; such systems
14149 typically make the requirements above easy to meet. However, it's
14150 important to recognize that many native systems use complex link
14151 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
14152 assembly, for example) that make the requirements difficult to meet. In
14153 general, one cannot assume that using @code{add-symbol-file} to read a
14154 relocatable object file's symbolic information will have the same effect
14155 as linking the relocatable object file into the program in the normal
14158 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
14160 @kindex add-symbol-file-from-memory
14161 @cindex @code{syscall DSO}
14162 @cindex load symbols from memory
14163 @item add-symbol-file-from-memory @var{address}
14164 Load symbols from the given @var{address} in a dynamically loaded
14165 object file whose image is mapped directly into the inferior's memory.
14166 For example, the Linux kernel maps a @code{syscall DSO} into each
14167 process's address space; this DSO provides kernel-specific code for
14168 some system calls. The argument can be any expression whose
14169 evaluation yields the address of the file's shared object file header.
14170 For this command to work, you must have used @code{symbol-file} or
14171 @code{exec-file} commands in advance.
14173 @kindex add-shared-symbol-files
14175 @item add-shared-symbol-files @var{library-file}
14176 @itemx assf @var{library-file}
14177 The @code{add-shared-symbol-files} command can currently be used only
14178 in the Cygwin build of @value{GDBN} on MS-Windows OS, where it is an
14179 alias for the @code{dll-symbols} command (@pxref{Cygwin Native}).
14180 @value{GDBN} automatically looks for shared libraries, however if
14181 @value{GDBN} does not find yours, you can invoke
14182 @code{add-shared-symbol-files}. It takes one argument: the shared
14183 library's file name. @code{assf} is a shorthand alias for
14184 @code{add-shared-symbol-files}.
14187 @item section @var{section} @var{addr}
14188 The @code{section} command changes the base address of the named
14189 @var{section} of the exec file to @var{addr}. This can be used if the
14190 exec file does not contain section addresses, (such as in the
14191 @code{a.out} format), or when the addresses specified in the file
14192 itself are wrong. Each section must be changed separately. The
14193 @code{info files} command, described below, lists all the sections and
14197 @kindex info target
14200 @code{info files} and @code{info target} are synonymous; both print the
14201 current target (@pxref{Targets, ,Specifying a Debugging Target}),
14202 including the names of the executable and core dump files currently in
14203 use by @value{GDBN}, and the files from which symbols were loaded. The
14204 command @code{help target} lists all possible targets rather than
14207 @kindex maint info sections
14208 @item maint info sections
14209 Another command that can give you extra information about program sections
14210 is @code{maint info sections}. In addition to the section information
14211 displayed by @code{info files}, this command displays the flags and file
14212 offset of each section in the executable and core dump files. In addition,
14213 @code{maint info sections} provides the following command options (which
14214 may be arbitrarily combined):
14218 Display sections for all loaded object files, including shared libraries.
14219 @item @var{sections}
14220 Display info only for named @var{sections}.
14221 @item @var{section-flags}
14222 Display info only for sections for which @var{section-flags} are true.
14223 The section flags that @value{GDBN} currently knows about are:
14226 Section will have space allocated in the process when loaded.
14227 Set for all sections except those containing debug information.
14229 Section will be loaded from the file into the child process memory.
14230 Set for pre-initialized code and data, clear for @code{.bss} sections.
14232 Section needs to be relocated before loading.
14234 Section cannot be modified by the child process.
14236 Section contains executable code only.
14238 Section contains data only (no executable code).
14240 Section will reside in ROM.
14242 Section contains data for constructor/destructor lists.
14244 Section is not empty.
14246 An instruction to the linker to not output the section.
14247 @item COFF_SHARED_LIBRARY
14248 A notification to the linker that the section contains
14249 COFF shared library information.
14251 Section contains common symbols.
14254 @kindex set trust-readonly-sections
14255 @cindex read-only sections
14256 @item set trust-readonly-sections on
14257 Tell @value{GDBN} that readonly sections in your object file
14258 really are read-only (i.e.@: that their contents will not change).
14259 In that case, @value{GDBN} can fetch values from these sections
14260 out of the object file, rather than from the target program.
14261 For some targets (notably embedded ones), this can be a significant
14262 enhancement to debugging performance.
14264 The default is off.
14266 @item set trust-readonly-sections off
14267 Tell @value{GDBN} not to trust readonly sections. This means that
14268 the contents of the section might change while the program is running,
14269 and must therefore be fetched from the target when needed.
14271 @item show trust-readonly-sections
14272 Show the current setting of trusting readonly sections.
14275 All file-specifying commands allow both absolute and relative file names
14276 as arguments. @value{GDBN} always converts the file name to an absolute file
14277 name and remembers it that way.
14279 @cindex shared libraries
14280 @anchor{Shared Libraries}
14281 @value{GDBN} supports @sc{gnu}/Linux, MS-Windows, HP-UX, SunOS, SVr4, Irix,
14282 and IBM RS/6000 AIX shared libraries.
14284 On MS-Windows @value{GDBN} must be linked with the Expat library to support
14285 shared libraries. @xref{Expat}.
14287 @value{GDBN} automatically loads symbol definitions from shared libraries
14288 when you use the @code{run} command, or when you examine a core file.
14289 (Before you issue the @code{run} command, @value{GDBN} does not understand
14290 references to a function in a shared library, however---unless you are
14291 debugging a core file).
14293 On HP-UX, if the program loads a library explicitly, @value{GDBN}
14294 automatically loads the symbols at the time of the @code{shl_load} call.
14296 @c FIXME: some @value{GDBN} release may permit some refs to undef
14297 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
14298 @c FIXME...lib; check this from time to time when updating manual
14300 There are times, however, when you may wish to not automatically load
14301 symbol definitions from shared libraries, such as when they are
14302 particularly large or there are many of them.
14304 To control the automatic loading of shared library symbols, use the
14308 @kindex set auto-solib-add
14309 @item set auto-solib-add @var{mode}
14310 If @var{mode} is @code{on}, symbols from all shared object libraries
14311 will be loaded automatically when the inferior begins execution, you
14312 attach to an independently started inferior, or when the dynamic linker
14313 informs @value{GDBN} that a new library has been loaded. If @var{mode}
14314 is @code{off}, symbols must be loaded manually, using the
14315 @code{sharedlibrary} command. The default value is @code{on}.
14317 @cindex memory used for symbol tables
14318 If your program uses lots of shared libraries with debug info that
14319 takes large amounts of memory, you can decrease the @value{GDBN}
14320 memory footprint by preventing it from automatically loading the
14321 symbols from shared libraries. To that end, type @kbd{set
14322 auto-solib-add off} before running the inferior, then load each
14323 library whose debug symbols you do need with @kbd{sharedlibrary
14324 @var{regexp}}, where @var{regexp} is a regular expression that matches
14325 the libraries whose symbols you want to be loaded.
14327 @kindex show auto-solib-add
14328 @item show auto-solib-add
14329 Display the current autoloading mode.
14332 @cindex load shared library
14333 To explicitly load shared library symbols, use the @code{sharedlibrary}
14337 @kindex info sharedlibrary
14339 @item info share @var{regex}
14340 @itemx info sharedlibrary @var{regex}
14341 Print the names of the shared libraries which are currently loaded
14342 that match @var{regex}. If @var{regex} is omitted then print
14343 all shared libraries that are loaded.
14345 @kindex sharedlibrary
14347 @item sharedlibrary @var{regex}
14348 @itemx share @var{regex}
14349 Load shared object library symbols for files matching a
14350 Unix regular expression.
14351 As with files loaded automatically, it only loads shared libraries
14352 required by your program for a core file or after typing @code{run}. If
14353 @var{regex} is omitted all shared libraries required by your program are
14356 @item nosharedlibrary
14357 @kindex nosharedlibrary
14358 @cindex unload symbols from shared libraries
14359 Unload all shared object library symbols. This discards all symbols
14360 that have been loaded from all shared libraries. Symbols from shared
14361 libraries that were loaded by explicit user requests are not
14365 Sometimes you may wish that @value{GDBN} stops and gives you control
14366 when any of shared library events happen. Use the @code{set
14367 stop-on-solib-events} command for this:
14370 @item set stop-on-solib-events
14371 @kindex set stop-on-solib-events
14372 This command controls whether @value{GDBN} should give you control
14373 when the dynamic linker notifies it about some shared library event.
14374 The most common event of interest is loading or unloading of a new
14377 @item show stop-on-solib-events
14378 @kindex show stop-on-solib-events
14379 Show whether @value{GDBN} stops and gives you control when shared
14380 library events happen.
14383 Shared libraries are also supported in many cross or remote debugging
14384 configurations. @value{GDBN} needs to have access to the target's libraries;
14385 this can be accomplished either by providing copies of the libraries
14386 on the host system, or by asking @value{GDBN} to automatically retrieve the
14387 libraries from the target. If copies of the target libraries are
14388 provided, they need to be the same as the target libraries, although the
14389 copies on the target can be stripped as long as the copies on the host are
14392 @cindex where to look for shared libraries
14393 For remote debugging, you need to tell @value{GDBN} where the target
14394 libraries are, so that it can load the correct copies---otherwise, it
14395 may try to load the host's libraries. @value{GDBN} has two variables
14396 to specify the search directories for target libraries.
14399 @cindex prefix for shared library file names
14400 @cindex system root, alternate
14401 @kindex set solib-absolute-prefix
14402 @kindex set sysroot
14403 @item set sysroot @var{path}
14404 Use @var{path} as the system root for the program being debugged. Any
14405 absolute shared library paths will be prefixed with @var{path}; many
14406 runtime loaders store the absolute paths to the shared library in the
14407 target program's memory. If you use @code{set sysroot} to find shared
14408 libraries, they need to be laid out in the same way that they are on
14409 the target, with e.g.@: a @file{/lib} and @file{/usr/lib} hierarchy
14412 If @var{path} starts with the sequence @file{remote:}, @value{GDBN} will
14413 retrieve the target libraries from the remote system. This is only
14414 supported when using a remote target that supports the @code{remote get}
14415 command (@pxref{File Transfer,,Sending files to a remote system}).
14416 The part of @var{path} following the initial @file{remote:}
14417 (if present) is used as system root prefix on the remote file system.
14418 @footnote{If you want to specify a local system root using a directory
14419 that happens to be named @file{remote:}, you need to use some equivalent
14420 variant of the name like @file{./remote:}.}
14422 For targets with an MS-DOS based filesystem, such as MS-Windows and
14423 SymbianOS, @value{GDBN} tries prefixing a few variants of the target
14424 absolute file name with @var{path}. But first, on Unix hosts,
14425 @value{GDBN} converts all backslash directory separators into forward
14426 slashes, because the backslash is not a directory separator on Unix:
14429 c:\foo\bar.dll @result{} c:/foo/bar.dll
14432 Then, @value{GDBN} attempts prefixing the target file name with
14433 @var{path}, and looks for the resulting file name in the host file
14437 c:/foo/bar.dll @result{} /path/to/sysroot/c:/foo/bar.dll
14440 If that does not find the shared library, @value{GDBN} tries removing
14441 the @samp{:} character from the drive spec, both for convenience, and,
14442 for the case of the host file system not supporting file names with
14446 c:/foo/bar.dll @result{} /path/to/sysroot/c/foo/bar.dll
14449 This makes it possible to have a system root that mirrors a target
14450 with more than one drive. E.g., you may want to setup your local
14451 copies of the target system shared libraries like so (note @samp{c} vs
14455 @file{/path/to/sysroot/c/sys/bin/foo.dll}
14456 @file{/path/to/sysroot/c/sys/bin/bar.dll}
14457 @file{/path/to/sysroot/z/sys/bin/bar.dll}
14461 and point the system root at @file{/path/to/sysroot}, so that
14462 @value{GDBN} can find the correct copies of both
14463 @file{c:\sys\bin\foo.dll}, and @file{z:\sys\bin\bar.dll}.
14465 If that still does not find the shared library, @value{GDBN} tries
14466 removing the whole drive spec from the target file name:
14469 c:/foo/bar.dll @result{} /path/to/sysroot/foo/bar.dll
14472 This last lookup makes it possible to not care about the drive name,
14473 if you don't want or need to.
14475 The @code{set solib-absolute-prefix} command is an alias for @code{set
14478 @cindex default system root
14479 @cindex @samp{--with-sysroot}
14480 You can set the default system root by using the configure-time
14481 @samp{--with-sysroot} option. If the system root is inside
14482 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
14483 @samp{--exec-prefix}), then the default system root will be updated
14484 automatically if the installed @value{GDBN} is moved to a new
14487 @kindex show sysroot
14489 Display the current shared library prefix.
14491 @kindex set solib-search-path
14492 @item set solib-search-path @var{path}
14493 If this variable is set, @var{path} is a colon-separated list of
14494 directories to search for shared libraries. @samp{solib-search-path}
14495 is used after @samp{sysroot} fails to locate the library, or if the
14496 path to the library is relative instead of absolute. If you want to
14497 use @samp{solib-search-path} instead of @samp{sysroot}, be sure to set
14498 @samp{sysroot} to a nonexistent directory to prevent @value{GDBN} from
14499 finding your host's libraries. @samp{sysroot} is preferred; setting
14500 it to a nonexistent directory may interfere with automatic loading
14501 of shared library symbols.
14503 @kindex show solib-search-path
14504 @item show solib-search-path
14505 Display the current shared library search path.
14507 @cindex DOS file-name semantics of file names.
14508 @kindex set target-file-system-kind (unix|dos-based|auto)
14509 @kindex show target-file-system-kind
14510 @item set target-file-system-kind @var{kind}
14511 Set assumed file system kind for target reported file names.
14513 Shared library file names as reported by the target system may not
14514 make sense as is on the system @value{GDBN} is running on. For
14515 example, when remote debugging a target that has MS-DOS based file
14516 system semantics, from a Unix host, the target may be reporting to
14517 @value{GDBN} a list of loaded shared libraries with file names such as
14518 @file{c:\Windows\kernel32.dll}. On Unix hosts, there's no concept of
14519 drive letters, so the @samp{c:\} prefix is not normally understood as
14520 indicating an absolute file name, and neither is the backslash
14521 normally considered a directory separator character. In that case,
14522 the native file system would interpret this whole absolute file name
14523 as a relative file name with no directory components. This would make
14524 it impossible to point @value{GDBN} at a copy of the remote target's
14525 shared libraries on the host using @code{set sysroot}, and impractical
14526 with @code{set solib-search-path}. Setting
14527 @code{target-file-system-kind} to @code{dos-based} tells @value{GDBN}
14528 to interpret such file names similarly to how the target would, and to
14529 map them to file names valid on @value{GDBN}'s native file system
14530 semantics. The value of @var{kind} can be @code{"auto"}, in addition
14531 to one of the supported file system kinds. In that case, @value{GDBN}
14532 tries to determine the appropriate file system variant based on the
14533 current target's operating system (@pxref{ABI, ,Configuring the
14534 Current ABI}). The supported file system settings are:
14538 Instruct @value{GDBN} to assume the target file system is of Unix
14539 kind. Only file names starting the forward slash (@samp{/}) character
14540 are considered absolute, and the directory separator character is also
14544 Instruct @value{GDBN} to assume the target file system is DOS based.
14545 File names starting with either a forward slash, or a drive letter
14546 followed by a colon (e.g., @samp{c:}), are considered absolute, and
14547 both the slash (@samp{/}) and the backslash (@samp{\\}) characters are
14548 considered directory separators.
14551 Instruct @value{GDBN} to use the file system kind associated with the
14552 target operating system (@pxref{ABI, ,Configuring the Current ABI}).
14553 This is the default.
14558 @node Separate Debug Files
14559 @section Debugging Information in Separate Files
14560 @cindex separate debugging information files
14561 @cindex debugging information in separate files
14562 @cindex @file{.debug} subdirectories
14563 @cindex debugging information directory, global
14564 @cindex global debugging information directory
14565 @cindex build ID, and separate debugging files
14566 @cindex @file{.build-id} directory
14568 @value{GDBN} allows you to put a program's debugging information in a
14569 file separate from the executable itself, in a way that allows
14570 @value{GDBN} to find and load the debugging information automatically.
14571 Since debugging information can be very large---sometimes larger
14572 than the executable code itself---some systems distribute debugging
14573 information for their executables in separate files, which users can
14574 install only when they need to debug a problem.
14576 @value{GDBN} supports two ways of specifying the separate debug info
14581 The executable contains a @dfn{debug link} that specifies the name of
14582 the separate debug info file. The separate debug file's name is
14583 usually @file{@var{executable}.debug}, where @var{executable} is the
14584 name of the corresponding executable file without leading directories
14585 (e.g., @file{ls.debug} for @file{/usr/bin/ls}). In addition, the
14586 debug link specifies a 32-bit @dfn{Cyclic Redundancy Check} (CRC)
14587 checksum for the debug file, which @value{GDBN} uses to validate that
14588 the executable and the debug file came from the same build.
14591 The executable contains a @dfn{build ID}, a unique bit string that is
14592 also present in the corresponding debug info file. (This is supported
14593 only on some operating systems, notably those which use the ELF format
14594 for binary files and the @sc{gnu} Binutils.) For more details about
14595 this feature, see the description of the @option{--build-id}
14596 command-line option in @ref{Options, , Command Line Options, ld.info,
14597 The GNU Linker}. The debug info file's name is not specified
14598 explicitly by the build ID, but can be computed from the build ID, see
14602 Depending on the way the debug info file is specified, @value{GDBN}
14603 uses two different methods of looking for the debug file:
14607 For the ``debug link'' method, @value{GDBN} looks up the named file in
14608 the directory of the executable file, then in a subdirectory of that
14609 directory named @file{.debug}, and finally under the global debug
14610 directory, in a subdirectory whose name is identical to the leading
14611 directories of the executable's absolute file name.
14614 For the ``build ID'' method, @value{GDBN} looks in the
14615 @file{.build-id} subdirectory of the global debug directory for a file
14616 named @file{@var{nn}/@var{nnnnnnnn}.debug}, where @var{nn} are the
14617 first 2 hex characters of the build ID bit string, and @var{nnnnnnnn}
14618 are the rest of the bit string. (Real build ID strings are 32 or more
14619 hex characters, not 10.)
14622 So, for example, suppose you ask @value{GDBN} to debug
14623 @file{/usr/bin/ls}, which has a debug link that specifies the
14624 file @file{ls.debug}, and a build ID whose value in hex is
14625 @code{abcdef1234}. If the global debug directory is
14626 @file{/usr/lib/debug}, then @value{GDBN} will look for the following
14627 debug information files, in the indicated order:
14631 @file{/usr/lib/debug/.build-id/ab/cdef1234.debug}
14633 @file{/usr/bin/ls.debug}
14635 @file{/usr/bin/.debug/ls.debug}
14637 @file{/usr/lib/debug/usr/bin/ls.debug}.
14640 You can set the global debugging info directory's name, and view the
14641 name @value{GDBN} is currently using.
14645 @kindex set debug-file-directory
14646 @item set debug-file-directory @var{directories}
14647 Set the directories which @value{GDBN} searches for separate debugging
14648 information files to @var{directory}. Multiple directory components can be set
14649 concatenating them by a directory separator.
14651 @kindex show debug-file-directory
14652 @item show debug-file-directory
14653 Show the directories @value{GDBN} searches for separate debugging
14658 @cindex @code{.gnu_debuglink} sections
14659 @cindex debug link sections
14660 A debug link is a special section of the executable file named
14661 @code{.gnu_debuglink}. The section must contain:
14665 A filename, with any leading directory components removed, followed by
14668 zero to three bytes of padding, as needed to reach the next four-byte
14669 boundary within the section, and
14671 a four-byte CRC checksum, stored in the same endianness used for the
14672 executable file itself. The checksum is computed on the debugging
14673 information file's full contents by the function given below, passing
14674 zero as the @var{crc} argument.
14677 Any executable file format can carry a debug link, as long as it can
14678 contain a section named @code{.gnu_debuglink} with the contents
14681 @cindex @code{.note.gnu.build-id} sections
14682 @cindex build ID sections
14683 The build ID is a special section in the executable file (and in other
14684 ELF binary files that @value{GDBN} may consider). This section is
14685 often named @code{.note.gnu.build-id}, but that name is not mandatory.
14686 It contains unique identification for the built files---the ID remains
14687 the same across multiple builds of the same build tree. The default
14688 algorithm SHA1 produces 160 bits (40 hexadecimal characters) of the
14689 content for the build ID string. The same section with an identical
14690 value is present in the original built binary with symbols, in its
14691 stripped variant, and in the separate debugging information file.
14693 The debugging information file itself should be an ordinary
14694 executable, containing a full set of linker symbols, sections, and
14695 debugging information. The sections of the debugging information file
14696 should have the same names, addresses, and sizes as the original file,
14697 but they need not contain any data---much like a @code{.bss} section
14698 in an ordinary executable.
14700 The @sc{gnu} binary utilities (Binutils) package includes the
14701 @samp{objcopy} utility that can produce
14702 the separated executable / debugging information file pairs using the
14703 following commands:
14706 @kbd{objcopy --only-keep-debug foo foo.debug}
14711 These commands remove the debugging
14712 information from the executable file @file{foo} and place it in the file
14713 @file{foo.debug}. You can use the first, second or both methods to link the
14718 The debug link method needs the following additional command to also leave
14719 behind a debug link in @file{foo}:
14722 @kbd{objcopy --add-gnu-debuglink=foo.debug foo}
14725 Ulrich Drepper's @file{elfutils} package, starting with version 0.53, contains
14726 a version of the @code{strip} command such that the command @kbd{strip foo -f
14727 foo.debug} has the same functionality as the two @code{objcopy} commands and
14728 the @code{ln -s} command above, together.
14731 Build ID gets embedded into the main executable using @code{ld --build-id} or
14732 the @value{NGCC} counterpart @code{gcc -Wl,--build-id}. Build ID support plus
14733 compatibility fixes for debug files separation are present in @sc{gnu} binary
14734 utilities (Binutils) package since version 2.18.
14739 @cindex CRC algorithm definition
14740 The CRC used in @code{.gnu_debuglink} is the CRC-32 defined in
14741 IEEE 802.3 using the polynomial:
14743 @c TexInfo requires naked braces for multi-digit exponents for Tex
14744 @c output, but this causes HTML output to barf. HTML has to be set using
14745 @c raw commands. So we end up having to specify this equation in 2
14750 <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>
14751 + <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
14757 @math{x^{32} + x^{26} + x^{23} + x^{22} + x^{16} + x^{12} + x^{11}}
14758 @math{+ x^{10} + x^8 + x^7 + x^5 + x^4 + x^2 + x + 1}
14762 The function is computed byte at a time, taking the least
14763 significant bit of each byte first. The initial pattern
14764 @code{0xffffffff} is used, to ensure leading zeros affect the CRC and
14765 the final result is inverted to ensure trailing zeros also affect the
14768 @emph{Note:} This is the same CRC polynomial as used in handling the
14769 @dfn{Remote Serial Protocol} @code{qCRC} packet (@pxref{Remote Protocol,
14770 , @value{GDBN} Remote Serial Protocol}). However in the
14771 case of the Remote Serial Protocol, the CRC is computed @emph{most}
14772 significant bit first, and the result is not inverted, so trailing
14773 zeros have no effect on the CRC value.
14775 To complete the description, we show below the code of the function
14776 which produces the CRC used in @code{.gnu_debuglink}. Inverting the
14777 initially supplied @code{crc} argument means that an initial call to
14778 this function passing in zero will start computing the CRC using
14781 @kindex gnu_debuglink_crc32
14784 gnu_debuglink_crc32 (unsigned long crc,
14785 unsigned char *buf, size_t len)
14787 static const unsigned long crc32_table[256] =
14789 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
14790 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
14791 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
14792 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
14793 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
14794 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
14795 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
14796 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
14797 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
14798 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
14799 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
14800 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
14801 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
14802 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
14803 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
14804 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
14805 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
14806 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
14807 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
14808 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
14809 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
14810 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
14811 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
14812 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
14813 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
14814 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
14815 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
14816 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
14817 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
14818 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
14819 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
14820 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
14821 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
14822 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
14823 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
14824 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
14825 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
14826 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
14827 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
14828 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
14829 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
14830 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
14831 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
14832 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
14833 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
14834 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
14835 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
14836 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
14837 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
14838 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
14839 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
14842 unsigned char *end;
14844 crc = ~crc & 0xffffffff;
14845 for (end = buf + len; buf < end; ++buf)
14846 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
14847 return ~crc & 0xffffffff;
14852 This computation does not apply to the ``build ID'' method.
14855 @node Symbol Errors
14856 @section Errors Reading Symbol Files
14858 While reading a symbol file, @value{GDBN} occasionally encounters problems,
14859 such as symbol types it does not recognize, or known bugs in compiler
14860 output. By default, @value{GDBN} does not notify you of such problems, since
14861 they are relatively common and primarily of interest to people
14862 debugging compilers. If you are interested in seeing information
14863 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
14864 only one message about each such type of problem, no matter how many
14865 times the problem occurs; or you can ask @value{GDBN} to print more messages,
14866 to see how many times the problems occur, with the @code{set
14867 complaints} command (@pxref{Messages/Warnings, ,Optional Warnings and
14870 The messages currently printed, and their meanings, include:
14873 @item inner block not inside outer block in @var{symbol}
14875 The symbol information shows where symbol scopes begin and end
14876 (such as at the start of a function or a block of statements). This
14877 error indicates that an inner scope block is not fully contained
14878 in its outer scope blocks.
14880 @value{GDBN} circumvents the problem by treating the inner block as if it had
14881 the same scope as the outer block. In the error message, @var{symbol}
14882 may be shown as ``@code{(don't know)}'' if the outer block is not a
14885 @item block at @var{address} out of order
14887 The symbol information for symbol scope blocks should occur in
14888 order of increasing addresses. This error indicates that it does not
14891 @value{GDBN} does not circumvent this problem, and has trouble
14892 locating symbols in the source file whose symbols it is reading. (You
14893 can often determine what source file is affected by specifying
14894 @code{set verbose on}. @xref{Messages/Warnings, ,Optional Warnings and
14897 @item bad block start address patched
14899 The symbol information for a symbol scope block has a start address
14900 smaller than the address of the preceding source line. This is known
14901 to occur in the SunOS 4.1.1 (and earlier) C compiler.
14903 @value{GDBN} circumvents the problem by treating the symbol scope block as
14904 starting on the previous source line.
14906 @item bad string table offset in symbol @var{n}
14909 Symbol number @var{n} contains a pointer into the string table which is
14910 larger than the size of the string table.
14912 @value{GDBN} circumvents the problem by considering the symbol to have the
14913 name @code{foo}, which may cause other problems if many symbols end up
14916 @item unknown symbol type @code{0x@var{nn}}
14918 The symbol information contains new data types that @value{GDBN} does
14919 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
14920 uncomprehended information, in hexadecimal.
14922 @value{GDBN} circumvents the error by ignoring this symbol information.
14923 This usually allows you to debug your program, though certain symbols
14924 are not accessible. If you encounter such a problem and feel like
14925 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
14926 on @code{complain}, then go up to the function @code{read_dbx_symtab}
14927 and examine @code{*bufp} to see the symbol.
14929 @item stub type has NULL name
14931 @value{GDBN} could not find the full definition for a struct or class.
14933 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
14934 The symbol information for a C@t{++} member function is missing some
14935 information that recent versions of the compiler should have output for
14938 @item info mismatch between compiler and debugger
14940 @value{GDBN} could not parse a type specification output by the compiler.
14945 @section GDB Data Files
14947 @cindex prefix for data files
14948 @value{GDBN} will sometimes read an auxiliary data file. These files
14949 are kept in a directory known as the @dfn{data directory}.
14951 You can set the data directory's name, and view the name @value{GDBN}
14952 is currently using.
14955 @kindex set data-directory
14956 @item set data-directory @var{directory}
14957 Set the directory which @value{GDBN} searches for auxiliary data files
14958 to @var{directory}.
14960 @kindex show data-directory
14961 @item show data-directory
14962 Show the directory @value{GDBN} searches for auxiliary data files.
14965 @cindex default data directory
14966 @cindex @samp{--with-gdb-datadir}
14967 You can set the default data directory by using the configure-time
14968 @samp{--with-gdb-datadir} option. If the data directory is inside
14969 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
14970 @samp{--exec-prefix}), then the default data directory will be updated
14971 automatically if the installed @value{GDBN} is moved to a new
14975 @chapter Specifying a Debugging Target
14977 @cindex debugging target
14978 A @dfn{target} is the execution environment occupied by your program.
14980 Often, @value{GDBN} runs in the same host environment as your program;
14981 in that case, the debugging target is specified as a side effect when
14982 you use the @code{file} or @code{core} commands. When you need more
14983 flexibility---for example, running @value{GDBN} on a physically separate
14984 host, or controlling a standalone system over a serial port or a
14985 realtime system over a TCP/IP connection---you can use the @code{target}
14986 command to specify one of the target types configured for @value{GDBN}
14987 (@pxref{Target Commands, ,Commands for Managing Targets}).
14989 @cindex target architecture
14990 It is possible to build @value{GDBN} for several different @dfn{target
14991 architectures}. When @value{GDBN} is built like that, you can choose
14992 one of the available architectures with the @kbd{set architecture}
14996 @kindex set architecture
14997 @kindex show architecture
14998 @item set architecture @var{arch}
14999 This command sets the current target architecture to @var{arch}. The
15000 value of @var{arch} can be @code{"auto"}, in addition to one of the
15001 supported architectures.
15003 @item show architecture
15004 Show the current target architecture.
15006 @item set processor
15008 @kindex set processor
15009 @kindex show processor
15010 These are alias commands for, respectively, @code{set architecture}
15011 and @code{show architecture}.
15015 * Active Targets:: Active targets
15016 * Target Commands:: Commands for managing targets
15017 * Byte Order:: Choosing target byte order
15020 @node Active Targets
15021 @section Active Targets
15023 @cindex stacking targets
15024 @cindex active targets
15025 @cindex multiple targets
15027 There are three classes of targets: processes, core files, and
15028 executable files. @value{GDBN} can work concurrently on up to three
15029 active targets, one in each class. This allows you to (for example)
15030 start a process and inspect its activity without abandoning your work on
15033 For example, if you execute @samp{gdb a.out}, then the executable file
15034 @code{a.out} is the only active target. If you designate a core file as
15035 well---presumably from a prior run that crashed and coredumped---then
15036 @value{GDBN} has two active targets and uses them in tandem, looking
15037 first in the corefile target, then in the executable file, to satisfy
15038 requests for memory addresses. (Typically, these two classes of target
15039 are complementary, since core files contain only a program's
15040 read-write memory---variables and so on---plus machine status, while
15041 executable files contain only the program text and initialized data.)
15043 When you type @code{run}, your executable file becomes an active process
15044 target as well. When a process target is active, all @value{GDBN}
15045 commands requesting memory addresses refer to that target; addresses in
15046 an active core file or executable file target are obscured while the
15047 process target is active.
15049 Use the @code{core-file} and @code{exec-file} commands to select a new
15050 core file or executable target (@pxref{Files, ,Commands to Specify
15051 Files}). To specify as a target a process that is already running, use
15052 the @code{attach} command (@pxref{Attach, ,Debugging an Already-running
15055 @node Target Commands
15056 @section Commands for Managing Targets
15059 @item target @var{type} @var{parameters}
15060 Connects the @value{GDBN} host environment to a target machine or
15061 process. A target is typically a protocol for talking to debugging
15062 facilities. You use the argument @var{type} to specify the type or
15063 protocol of the target machine.
15065 Further @var{parameters} are interpreted by the target protocol, but
15066 typically include things like device names or host names to connect
15067 with, process numbers, and baud rates.
15069 The @code{target} command does not repeat if you press @key{RET} again
15070 after executing the command.
15072 @kindex help target
15074 Displays the names of all targets available. To display targets
15075 currently selected, use either @code{info target} or @code{info files}
15076 (@pxref{Files, ,Commands to Specify Files}).
15078 @item help target @var{name}
15079 Describe a particular target, including any parameters necessary to
15082 @kindex set gnutarget
15083 @item set gnutarget @var{args}
15084 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
15085 knows whether it is reading an @dfn{executable},
15086 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
15087 with the @code{set gnutarget} command. Unlike most @code{target} commands,
15088 with @code{gnutarget} the @code{target} refers to a program, not a machine.
15091 @emph{Warning:} To specify a file format with @code{set gnutarget},
15092 you must know the actual BFD name.
15096 @xref{Files, , Commands to Specify Files}.
15098 @kindex show gnutarget
15099 @item show gnutarget
15100 Use the @code{show gnutarget} command to display what file format
15101 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
15102 @value{GDBN} will determine the file format for each file automatically,
15103 and @code{show gnutarget} displays @samp{The current BDF target is "auto"}.
15106 @cindex common targets
15107 Here are some common targets (available, or not, depending on the GDB
15112 @item target exec @var{program}
15113 @cindex executable file target
15114 An executable file. @samp{target exec @var{program}} is the same as
15115 @samp{exec-file @var{program}}.
15117 @item target core @var{filename}
15118 @cindex core dump file target
15119 A core dump file. @samp{target core @var{filename}} is the same as
15120 @samp{core-file @var{filename}}.
15122 @item target remote @var{medium}
15123 @cindex remote target
15124 A remote system connected to @value{GDBN} via a serial line or network
15125 connection. This command tells @value{GDBN} to use its own remote
15126 protocol over @var{medium} for debugging. @xref{Remote Debugging}.
15128 For example, if you have a board connected to @file{/dev/ttya} on the
15129 machine running @value{GDBN}, you could say:
15132 target remote /dev/ttya
15135 @code{target remote} supports the @code{load} command. This is only
15136 useful if you have some other way of getting the stub to the target
15137 system, and you can put it somewhere in memory where it won't get
15138 clobbered by the download.
15140 @item target sim @r{[}@var{simargs}@r{]} @dots{}
15141 @cindex built-in simulator target
15142 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
15150 works; however, you cannot assume that a specific memory map, device
15151 drivers, or even basic I/O is available, although some simulators do
15152 provide these. For info about any processor-specific simulator details,
15153 see the appropriate section in @ref{Embedded Processors, ,Embedded
15158 Some configurations may include these targets as well:
15162 @item target nrom @var{dev}
15163 @cindex NetROM ROM emulator target
15164 NetROM ROM emulator. This target only supports downloading.
15168 Different targets are available on different configurations of @value{GDBN};
15169 your configuration may have more or fewer targets.
15171 Many remote targets require you to download the executable's code once
15172 you've successfully established a connection. You may wish to control
15173 various aspects of this process.
15178 @kindex set hash@r{, for remote monitors}
15179 @cindex hash mark while downloading
15180 This command controls whether a hash mark @samp{#} is displayed while
15181 downloading a file to the remote monitor. If on, a hash mark is
15182 displayed after each S-record is successfully downloaded to the
15186 @kindex show hash@r{, for remote monitors}
15187 Show the current status of displaying the hash mark.
15189 @item set debug monitor
15190 @kindex set debug monitor
15191 @cindex display remote monitor communications
15192 Enable or disable display of communications messages between
15193 @value{GDBN} and the remote monitor.
15195 @item show debug monitor
15196 @kindex show debug monitor
15197 Show the current status of displaying communications between
15198 @value{GDBN} and the remote monitor.
15203 @kindex load @var{filename}
15204 @item load @var{filename}
15206 Depending on what remote debugging facilities are configured into
15207 @value{GDBN}, the @code{load} command may be available. Where it exists, it
15208 is meant to make @var{filename} (an executable) available for debugging
15209 on the remote system---by downloading, or dynamic linking, for example.
15210 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
15211 the @code{add-symbol-file} command.
15213 If your @value{GDBN} does not have a @code{load} command, attempting to
15214 execute it gets the error message ``@code{You can't do that when your
15215 target is @dots{}}''
15217 The file is loaded at whatever address is specified in the executable.
15218 For some object file formats, you can specify the load address when you
15219 link the program; for other formats, like a.out, the object file format
15220 specifies a fixed address.
15221 @c FIXME! This would be a good place for an xref to the GNU linker doc.
15223 Depending on the remote side capabilities, @value{GDBN} may be able to
15224 load programs into flash memory.
15226 @code{load} does not repeat if you press @key{RET} again after using it.
15230 @section Choosing Target Byte Order
15232 @cindex choosing target byte order
15233 @cindex target byte order
15235 Some types of processors, such as the MIPS, PowerPC, and Renesas SH,
15236 offer the ability to run either big-endian or little-endian byte
15237 orders. Usually the executable or symbol will include a bit to
15238 designate the endian-ness, and you will not need to worry about
15239 which to use. However, you may still find it useful to adjust
15240 @value{GDBN}'s idea of processor endian-ness manually.
15244 @item set endian big
15245 Instruct @value{GDBN} to assume the target is big-endian.
15247 @item set endian little
15248 Instruct @value{GDBN} to assume the target is little-endian.
15250 @item set endian auto
15251 Instruct @value{GDBN} to use the byte order associated with the
15255 Display @value{GDBN}'s current idea of the target byte order.
15259 Note that these commands merely adjust interpretation of symbolic
15260 data on the host, and that they have absolutely no effect on the
15264 @node Remote Debugging
15265 @chapter Debugging Remote Programs
15266 @cindex remote debugging
15268 If you are trying to debug a program running on a machine that cannot run
15269 @value{GDBN} in the usual way, it is often useful to use remote debugging.
15270 For example, you might use remote debugging on an operating system kernel,
15271 or on a small system which does not have a general purpose operating system
15272 powerful enough to run a full-featured debugger.
15274 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
15275 to make this work with particular debugging targets. In addition,
15276 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
15277 but not specific to any particular target system) which you can use if you
15278 write the remote stubs---the code that runs on the remote system to
15279 communicate with @value{GDBN}.
15281 Other remote targets may be available in your
15282 configuration of @value{GDBN}; use @code{help target} to list them.
15285 * Connecting:: Connecting to a remote target
15286 * File Transfer:: Sending files to a remote system
15287 * Server:: Using the gdbserver program
15288 * Remote Configuration:: Remote configuration
15289 * Remote Stub:: Implementing a remote stub
15293 @section Connecting to a Remote Target
15295 On the @value{GDBN} host machine, you will need an unstripped copy of
15296 your program, since @value{GDBN} needs symbol and debugging information.
15297 Start up @value{GDBN} as usual, using the name of the local copy of your
15298 program as the first argument.
15300 @cindex @code{target remote}
15301 @value{GDBN} can communicate with the target over a serial line, or
15302 over an @acronym{IP} network using @acronym{TCP} or @acronym{UDP}. In
15303 each case, @value{GDBN} uses the same protocol for debugging your
15304 program; only the medium carrying the debugging packets varies. The
15305 @code{target remote} command establishes a connection to the target.
15306 Its arguments indicate which medium to use:
15310 @item target remote @var{serial-device}
15311 @cindex serial line, @code{target remote}
15312 Use @var{serial-device} to communicate with the target. For example,
15313 to use a serial line connected to the device named @file{/dev/ttyb}:
15316 target remote /dev/ttyb
15319 If you're using a serial line, you may want to give @value{GDBN} the
15320 @w{@samp{--baud}} option, or use the @code{set remotebaud} command
15321 (@pxref{Remote Configuration, set remotebaud}) before the
15322 @code{target} command.
15324 @item target remote @code{@var{host}:@var{port}}
15325 @itemx target remote @code{tcp:@var{host}:@var{port}}
15326 @cindex @acronym{TCP} port, @code{target remote}
15327 Debug using a @acronym{TCP} connection to @var{port} on @var{host}.
15328 The @var{host} may be either a host name or a numeric @acronym{IP}
15329 address; @var{port} must be a decimal number. The @var{host} could be
15330 the target machine itself, if it is directly connected to the net, or
15331 it might be a terminal server which in turn has a serial line to the
15334 For example, to connect to port 2828 on a terminal server named
15338 target remote manyfarms:2828
15341 If your remote target is actually running on the same machine as your
15342 debugger session (e.g.@: a simulator for your target running on the
15343 same host), you can omit the hostname. For example, to connect to
15344 port 1234 on your local machine:
15347 target remote :1234
15351 Note that the colon is still required here.
15353 @item target remote @code{udp:@var{host}:@var{port}}
15354 @cindex @acronym{UDP} port, @code{target remote}
15355 Debug using @acronym{UDP} packets to @var{port} on @var{host}. For example, to
15356 connect to @acronym{UDP} port 2828 on a terminal server named @code{manyfarms}:
15359 target remote udp:manyfarms:2828
15362 When using a @acronym{UDP} connection for remote debugging, you should
15363 keep in mind that the `U' stands for ``Unreliable''. @acronym{UDP}
15364 can silently drop packets on busy or unreliable networks, which will
15365 cause havoc with your debugging session.
15367 @item target remote | @var{command}
15368 @cindex pipe, @code{target remote} to
15369 Run @var{command} in the background and communicate with it using a
15370 pipe. The @var{command} is a shell command, to be parsed and expanded
15371 by the system's command shell, @code{/bin/sh}; it should expect remote
15372 protocol packets on its standard input, and send replies on its
15373 standard output. You could use this to run a stand-alone simulator
15374 that speaks the remote debugging protocol, to make net connections
15375 using programs like @code{ssh}, or for other similar tricks.
15377 If @var{command} closes its standard output (perhaps by exiting),
15378 @value{GDBN} will try to send it a @code{SIGTERM} signal. (If the
15379 program has already exited, this will have no effect.)
15383 Once the connection has been established, you can use all the usual
15384 commands to examine and change data. The remote program is already
15385 running; you can use @kbd{step} and @kbd{continue}, and you do not
15386 need to use @kbd{run}.
15388 @cindex interrupting remote programs
15389 @cindex remote programs, interrupting
15390 Whenever @value{GDBN} is waiting for the remote program, if you type the
15391 interrupt character (often @kbd{Ctrl-c}), @value{GDBN} attempts to stop the
15392 program. This may or may not succeed, depending in part on the hardware
15393 and the serial drivers the remote system uses. If you type the
15394 interrupt character once again, @value{GDBN} displays this prompt:
15397 Interrupted while waiting for the program.
15398 Give up (and stop debugging it)? (y or n)
15401 If you type @kbd{y}, @value{GDBN} abandons the remote debugging session.
15402 (If you decide you want to try again later, you can use @samp{target
15403 remote} again to connect once more.) If you type @kbd{n}, @value{GDBN}
15404 goes back to waiting.
15407 @kindex detach (remote)
15409 When you have finished debugging the remote program, you can use the
15410 @code{detach} command to release it from @value{GDBN} control.
15411 Detaching from the target normally resumes its execution, but the results
15412 will depend on your particular remote stub. After the @code{detach}
15413 command, @value{GDBN} is free to connect to another target.
15417 The @code{disconnect} command behaves like @code{detach}, except that
15418 the target is generally not resumed. It will wait for @value{GDBN}
15419 (this instance or another one) to connect and continue debugging. After
15420 the @code{disconnect} command, @value{GDBN} is again free to connect to
15423 @cindex send command to remote monitor
15424 @cindex extend @value{GDBN} for remote targets
15425 @cindex add new commands for external monitor
15427 @item monitor @var{cmd}
15428 This command allows you to send arbitrary commands directly to the
15429 remote monitor. Since @value{GDBN} doesn't care about the commands it
15430 sends like this, this command is the way to extend @value{GDBN}---you
15431 can add new commands that only the external monitor will understand
15435 @node File Transfer
15436 @section Sending files to a remote system
15437 @cindex remote target, file transfer
15438 @cindex file transfer
15439 @cindex sending files to remote systems
15441 Some remote targets offer the ability to transfer files over the same
15442 connection used to communicate with @value{GDBN}. This is convenient
15443 for targets accessible through other means, e.g.@: @sc{gnu}/Linux systems
15444 running @code{gdbserver} over a network interface. For other targets,
15445 e.g.@: embedded devices with only a single serial port, this may be
15446 the only way to upload or download files.
15448 Not all remote targets support these commands.
15452 @item remote put @var{hostfile} @var{targetfile}
15453 Copy file @var{hostfile} from the host system (the machine running
15454 @value{GDBN}) to @var{targetfile} on the target system.
15457 @item remote get @var{targetfile} @var{hostfile}
15458 Copy file @var{targetfile} from the target system to @var{hostfile}
15459 on the host system.
15461 @kindex remote delete
15462 @item remote delete @var{targetfile}
15463 Delete @var{targetfile} from the target system.
15468 @section Using the @code{gdbserver} Program
15471 @cindex remote connection without stubs
15472 @code{gdbserver} is a control program for Unix-like systems, which
15473 allows you to connect your program with a remote @value{GDBN} via
15474 @code{target remote}---but without linking in the usual debugging stub.
15476 @code{gdbserver} is not a complete replacement for the debugging stubs,
15477 because it requires essentially the same operating-system facilities
15478 that @value{GDBN} itself does. In fact, a system that can run
15479 @code{gdbserver} to connect to a remote @value{GDBN} could also run
15480 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
15481 because it is a much smaller program than @value{GDBN} itself. It is
15482 also easier to port than all of @value{GDBN}, so you may be able to get
15483 started more quickly on a new system by using @code{gdbserver}.
15484 Finally, if you develop code for real-time systems, you may find that
15485 the tradeoffs involved in real-time operation make it more convenient to
15486 do as much development work as possible on another system, for example
15487 by cross-compiling. You can use @code{gdbserver} to make a similar
15488 choice for debugging.
15490 @value{GDBN} and @code{gdbserver} communicate via either a serial line
15491 or a TCP connection, using the standard @value{GDBN} remote serial
15495 @emph{Warning:} @code{gdbserver} does not have any built-in security.
15496 Do not run @code{gdbserver} connected to any public network; a
15497 @value{GDBN} connection to @code{gdbserver} provides access to the
15498 target system with the same privileges as the user running
15502 @subsection Running @code{gdbserver}
15503 @cindex arguments, to @code{gdbserver}
15505 Run @code{gdbserver} on the target system. You need a copy of the
15506 program you want to debug, including any libraries it requires.
15507 @code{gdbserver} does not need your program's symbol table, so you can
15508 strip the program if necessary to save space. @value{GDBN} on the host
15509 system does all the symbol handling.
15511 To use the server, you must tell it how to communicate with @value{GDBN};
15512 the name of your program; and the arguments for your program. The usual
15516 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
15519 @var{comm} is either a device name (to use a serial line) or a TCP
15520 hostname and portnumber. For example, to debug Emacs with the argument
15521 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
15525 target> gdbserver /dev/com1 emacs foo.txt
15528 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
15531 To use a TCP connection instead of a serial line:
15534 target> gdbserver host:2345 emacs foo.txt
15537 The only difference from the previous example is the first argument,
15538 specifying that you are communicating with the host @value{GDBN} via
15539 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
15540 expect a TCP connection from machine @samp{host} to local TCP port 2345.
15541 (Currently, the @samp{host} part is ignored.) You can choose any number
15542 you want for the port number as long as it does not conflict with any
15543 TCP ports already in use on the target system (for example, @code{23} is
15544 reserved for @code{telnet}).@footnote{If you choose a port number that
15545 conflicts with another service, @code{gdbserver} prints an error message
15546 and exits.} You must use the same port number with the host @value{GDBN}
15547 @code{target remote} command.
15549 @subsubsection Attaching to a Running Program
15551 On some targets, @code{gdbserver} can also attach to running programs.
15552 This is accomplished via the @code{--attach} argument. The syntax is:
15555 target> gdbserver --attach @var{comm} @var{pid}
15558 @var{pid} is the process ID of a currently running process. It isn't necessary
15559 to point @code{gdbserver} at a binary for the running process.
15562 @cindex attach to a program by name
15563 You can debug processes by name instead of process ID if your target has the
15564 @code{pidof} utility:
15567 target> gdbserver --attach @var{comm} `pidof @var{program}`
15570 In case more than one copy of @var{program} is running, or @var{program}
15571 has multiple threads, most versions of @code{pidof} support the
15572 @code{-s} option to only return the first process ID.
15574 @subsubsection Multi-Process Mode for @code{gdbserver}
15575 @cindex gdbserver, multiple processes
15576 @cindex multiple processes with gdbserver
15578 When you connect to @code{gdbserver} using @code{target remote},
15579 @code{gdbserver} debugs the specified program only once. When the
15580 program exits, or you detach from it, @value{GDBN} closes the connection
15581 and @code{gdbserver} exits.
15583 If you connect using @kbd{target extended-remote}, @code{gdbserver}
15584 enters multi-process mode. When the debugged program exits, or you
15585 detach from it, @value{GDBN} stays connected to @code{gdbserver} even
15586 though no program is running. The @code{run} and @code{attach}
15587 commands instruct @code{gdbserver} to run or attach to a new program.
15588 The @code{run} command uses @code{set remote exec-file} (@pxref{set
15589 remote exec-file}) to select the program to run. Command line
15590 arguments are supported, except for wildcard expansion and I/O
15591 redirection (@pxref{Arguments}).
15593 To start @code{gdbserver} without supplying an initial command to run
15594 or process ID to attach, use the @option{--multi} command line option.
15595 Then you can connect using @kbd{target extended-remote} and start
15596 the program you want to debug.
15598 @code{gdbserver} does not automatically exit in multi-process mode.
15599 You can terminate it by using @code{monitor exit}
15600 (@pxref{Monitor Commands for gdbserver}).
15602 @subsubsection Other Command-Line Arguments for @code{gdbserver}
15604 The @option{--debug} option tells @code{gdbserver} to display extra
15605 status information about the debugging process. The
15606 @option{--remote-debug} option tells @code{gdbserver} to display
15607 remote protocol debug output. These options are intended for
15608 @code{gdbserver} development and for bug reports to the developers.
15610 The @option{--wrapper} option specifies a wrapper to launch programs
15611 for debugging. The option should be followed by the name of the
15612 wrapper, then any command-line arguments to pass to the wrapper, then
15613 @kbd{--} indicating the end of the wrapper arguments.
15615 @code{gdbserver} runs the specified wrapper program with a combined
15616 command line including the wrapper arguments, then the name of the
15617 program to debug, then any arguments to the program. The wrapper
15618 runs until it executes your program, and then @value{GDBN} gains control.
15620 You can use any program that eventually calls @code{execve} with
15621 its arguments as a wrapper. Several standard Unix utilities do
15622 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
15623 with @code{exec "$@@"} will also work.
15625 For example, you can use @code{env} to pass an environment variable to
15626 the debugged program, without setting the variable in @code{gdbserver}'s
15630 $ gdbserver --wrapper env LD_PRELOAD=libtest.so -- :2222 ./testprog
15633 @subsection Connecting to @code{gdbserver}
15635 Run @value{GDBN} on the host system.
15637 First make sure you have the necessary symbol files. Load symbols for
15638 your application using the @code{file} command before you connect. Use
15639 @code{set sysroot} to locate target libraries (unless your @value{GDBN}
15640 was compiled with the correct sysroot using @code{--with-sysroot}).
15642 The symbol file and target libraries must exactly match the executable
15643 and libraries on the target, with one exception: the files on the host
15644 system should not be stripped, even if the files on the target system
15645 are. Mismatched or missing files will lead to confusing results
15646 during debugging. On @sc{gnu}/Linux targets, mismatched or missing
15647 files may also prevent @code{gdbserver} from debugging multi-threaded
15650 Connect to your target (@pxref{Connecting,,Connecting to a Remote Target}).
15651 For TCP connections, you must start up @code{gdbserver} prior to using
15652 the @code{target remote} command. Otherwise you may get an error whose
15653 text depends on the host system, but which usually looks something like
15654 @samp{Connection refused}. Don't use the @code{load}
15655 command in @value{GDBN} when using @code{gdbserver}, since the program is
15656 already on the target.
15658 @subsection Monitor Commands for @code{gdbserver}
15659 @cindex monitor commands, for @code{gdbserver}
15660 @anchor{Monitor Commands for gdbserver}
15662 During a @value{GDBN} session using @code{gdbserver}, you can use the
15663 @code{monitor} command to send special requests to @code{gdbserver}.
15664 Here are the available commands.
15668 List the available monitor commands.
15670 @item monitor set debug 0
15671 @itemx monitor set debug 1
15672 Disable or enable general debugging messages.
15674 @item monitor set remote-debug 0
15675 @itemx monitor set remote-debug 1
15676 Disable or enable specific debugging messages associated with the remote
15677 protocol (@pxref{Remote Protocol}).
15679 @item monitor set libthread-db-search-path [PATH]
15680 @cindex gdbserver, search path for @code{libthread_db}
15681 When this command is issued, @var{path} is a colon-separated list of
15682 directories to search for @code{libthread_db} (@pxref{Threads,,set
15683 libthread-db-search-path}). If you omit @var{path},
15684 @samp{libthread-db-search-path} will be reset to an empty list.
15687 Tell gdbserver to exit immediately. This command should be followed by
15688 @code{disconnect} to close the debugging session. @code{gdbserver} will
15689 detach from any attached processes and kill any processes it created.
15690 Use @code{monitor exit} to terminate @code{gdbserver} at the end
15691 of a multi-process mode debug session.
15695 @node Remote Configuration
15696 @section Remote Configuration
15699 @kindex show remote
15700 This section documents the configuration options available when
15701 debugging remote programs. For the options related to the File I/O
15702 extensions of the remote protocol, see @ref{system,
15703 system-call-allowed}.
15706 @item set remoteaddresssize @var{bits}
15707 @cindex address size for remote targets
15708 @cindex bits in remote address
15709 Set the maximum size of address in a memory packet to the specified
15710 number of bits. @value{GDBN} will mask off the address bits above
15711 that number, when it passes addresses to the remote target. The
15712 default value is the number of bits in the target's address.
15714 @item show remoteaddresssize
15715 Show the current value of remote address size in bits.
15717 @item set remotebaud @var{n}
15718 @cindex baud rate for remote targets
15719 Set the baud rate for the remote serial I/O to @var{n} baud. The
15720 value is used to set the speed of the serial port used for debugging
15723 @item show remotebaud
15724 Show the current speed of the remote connection.
15726 @item set remotebreak
15727 @cindex interrupt remote programs
15728 @cindex BREAK signal instead of Ctrl-C
15729 @anchor{set remotebreak}
15730 If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote
15731 when you type @kbd{Ctrl-c} to interrupt the program running
15732 on the remote. If set to off, @value{GDBN} sends the @samp{Ctrl-C}
15733 character instead. The default is off, since most remote systems
15734 expect to see @samp{Ctrl-C} as the interrupt signal.
15736 @item show remotebreak
15737 Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to
15738 interrupt the remote program.
15740 @item set remoteflow on
15741 @itemx set remoteflow off
15742 @kindex set remoteflow
15743 Enable or disable hardware flow control (@code{RTS}/@code{CTS})
15744 on the serial port used to communicate to the remote target.
15746 @item show remoteflow
15747 @kindex show remoteflow
15748 Show the current setting of hardware flow control.
15750 @item set remotelogbase @var{base}
15751 Set the base (a.k.a.@: radix) of logging serial protocol
15752 communications to @var{base}. Supported values of @var{base} are:
15753 @code{ascii}, @code{octal}, and @code{hex}. The default is
15756 @item show remotelogbase
15757 Show the current setting of the radix for logging remote serial
15760 @item set remotelogfile @var{file}
15761 @cindex record serial communications on file
15762 Record remote serial communications on the named @var{file}. The
15763 default is not to record at all.
15765 @item show remotelogfile.
15766 Show the current setting of the file name on which to record the
15767 serial communications.
15769 @item set remotetimeout @var{num}
15770 @cindex timeout for serial communications
15771 @cindex remote timeout
15772 Set the timeout limit to wait for the remote target to respond to
15773 @var{num} seconds. The default is 2 seconds.
15775 @item show remotetimeout
15776 Show the current number of seconds to wait for the remote target
15779 @cindex limit hardware breakpoints and watchpoints
15780 @cindex remote target, limit break- and watchpoints
15781 @anchor{set remote hardware-watchpoint-limit}
15782 @anchor{set remote hardware-breakpoint-limit}
15783 @item set remote hardware-watchpoint-limit @var{limit}
15784 @itemx set remote hardware-breakpoint-limit @var{limit}
15785 Restrict @value{GDBN} to using @var{limit} remote hardware breakpoint or
15786 watchpoints. A limit of -1, the default, is treated as unlimited.
15788 @item set remote exec-file @var{filename}
15789 @itemx show remote exec-file
15790 @anchor{set remote exec-file}
15791 @cindex executable file, for remote target
15792 Select the file used for @code{run} with @code{target
15793 extended-remote}. This should be set to a filename valid on the
15794 target system. If it is not set, the target will use a default
15795 filename (e.g.@: the last program run).
15797 @item set remote interrupt-sequence
15798 @cindex interrupt remote programs
15799 @cindex select Ctrl-C, BREAK or BREAK-g
15800 Allow the user to select one of @samp{Ctrl-C}, a @code{BREAK} or
15801 @samp{BREAK-g} as the
15802 sequence to the remote target in order to interrupt the execution.
15803 @samp{Ctrl-C} is a default. Some system prefers @code{BREAK} which
15804 is high level of serial line for some certain time.
15805 Linux kernel prefers @samp{BREAK-g}, a.k.a Magic SysRq g.
15806 It is @code{BREAK} signal followed by character @code{g}.
15808 @item show interrupt-sequence
15809 Show which of @samp{Ctrl-C}, @code{BREAK} or @code{BREAK-g}
15810 is sent by @value{GDBN} to interrupt the remote program.
15811 @code{BREAK-g} is BREAK signal followed by @code{g} and
15812 also known as Magic SysRq g.
15814 @item set remote interrupt-on-connect
15815 @cindex send interrupt-sequence on start
15816 Specify whether interrupt-sequence is sent to remote target when
15817 @value{GDBN} connects to it. This is mostly needed when you debug
15818 Linux kernel. Linux kernel expects @code{BREAK} followed by @code{g}
15819 which is known as Magic SysRq g in order to connect @value{GDBN}.
15821 @item show interrupt-on-connect
15822 Show whether interrupt-sequence is sent
15823 to remote target when @value{GDBN} connects to it.
15827 @item set tcp auto-retry on
15828 @cindex auto-retry, for remote TCP target
15829 Enable auto-retry for remote TCP connections. This is useful if the remote
15830 debugging agent is launched in parallel with @value{GDBN}; there is a race
15831 condition because the agent may not become ready to accept the connection
15832 before @value{GDBN} attempts to connect. When auto-retry is
15833 enabled, if the initial attempt to connect fails, @value{GDBN} reattempts
15834 to establish the connection using the timeout specified by
15835 @code{set tcp connect-timeout}.
15837 @item set tcp auto-retry off
15838 Do not auto-retry failed TCP connections.
15840 @item show tcp auto-retry
15841 Show the current auto-retry setting.
15843 @item set tcp connect-timeout @var{seconds}
15844 @cindex connection timeout, for remote TCP target
15845 @cindex timeout, for remote target connection
15846 Set the timeout for establishing a TCP connection to the remote target to
15847 @var{seconds}. The timeout affects both polling to retry failed connections
15848 (enabled by @code{set tcp auto-retry on}) and waiting for connections
15849 that are merely slow to complete, and represents an approximate cumulative
15852 @item show tcp connect-timeout
15853 Show the current connection timeout setting.
15856 @cindex remote packets, enabling and disabling
15857 The @value{GDBN} remote protocol autodetects the packets supported by
15858 your debugging stub. If you need to override the autodetection, you
15859 can use these commands to enable or disable individual packets. Each
15860 packet can be set to @samp{on} (the remote target supports this
15861 packet), @samp{off} (the remote target does not support this packet),
15862 or @samp{auto} (detect remote target support for this packet). They
15863 all default to @samp{auto}. For more information about each packet,
15864 see @ref{Remote Protocol}.
15866 During normal use, you should not have to use any of these commands.
15867 If you do, that may be a bug in your remote debugging stub, or a bug
15868 in @value{GDBN}. You may want to report the problem to the
15869 @value{GDBN} developers.
15871 For each packet @var{name}, the command to enable or disable the
15872 packet is @code{set remote @var{name}-packet}. The available settings
15875 @multitable @columnfractions 0.28 0.32 0.25
15878 @tab Related Features
15880 @item @code{fetch-register}
15882 @tab @code{info registers}
15884 @item @code{set-register}
15888 @item @code{binary-download}
15890 @tab @code{load}, @code{set}
15892 @item @code{read-aux-vector}
15893 @tab @code{qXfer:auxv:read}
15894 @tab @code{info auxv}
15896 @item @code{symbol-lookup}
15897 @tab @code{qSymbol}
15898 @tab Detecting multiple threads
15900 @item @code{attach}
15901 @tab @code{vAttach}
15904 @item @code{verbose-resume}
15906 @tab Stepping or resuming multiple threads
15912 @item @code{software-breakpoint}
15916 @item @code{hardware-breakpoint}
15920 @item @code{write-watchpoint}
15924 @item @code{read-watchpoint}
15928 @item @code{access-watchpoint}
15932 @item @code{target-features}
15933 @tab @code{qXfer:features:read}
15934 @tab @code{set architecture}
15936 @item @code{library-info}
15937 @tab @code{qXfer:libraries:read}
15938 @tab @code{info sharedlibrary}
15940 @item @code{memory-map}
15941 @tab @code{qXfer:memory-map:read}
15942 @tab @code{info mem}
15944 @item @code{read-spu-object}
15945 @tab @code{qXfer:spu:read}
15946 @tab @code{info spu}
15948 @item @code{write-spu-object}
15949 @tab @code{qXfer:spu:write}
15950 @tab @code{info spu}
15952 @item @code{read-siginfo-object}
15953 @tab @code{qXfer:siginfo:read}
15954 @tab @code{print $_siginfo}
15956 @item @code{write-siginfo-object}
15957 @tab @code{qXfer:siginfo:write}
15958 @tab @code{set $_siginfo}
15960 @item @code{threads}
15961 @tab @code{qXfer:threads:read}
15962 @tab @code{info threads}
15964 @item @code{get-thread-local-@*storage-address}
15965 @tab @code{qGetTLSAddr}
15966 @tab Displaying @code{__thread} variables
15968 @item @code{get-thread-information-block-address}
15969 @tab @code{qGetTIBAddr}
15970 @tab Display MS-Windows Thread Information Block.
15972 @item @code{search-memory}
15973 @tab @code{qSearch:memory}
15976 @item @code{supported-packets}
15977 @tab @code{qSupported}
15978 @tab Remote communications parameters
15980 @item @code{pass-signals}
15981 @tab @code{QPassSignals}
15982 @tab @code{handle @var{signal}}
15984 @item @code{hostio-close-packet}
15985 @tab @code{vFile:close}
15986 @tab @code{remote get}, @code{remote put}
15988 @item @code{hostio-open-packet}
15989 @tab @code{vFile:open}
15990 @tab @code{remote get}, @code{remote put}
15992 @item @code{hostio-pread-packet}
15993 @tab @code{vFile:pread}
15994 @tab @code{remote get}, @code{remote put}
15996 @item @code{hostio-pwrite-packet}
15997 @tab @code{vFile:pwrite}
15998 @tab @code{remote get}, @code{remote put}
16000 @item @code{hostio-unlink-packet}
16001 @tab @code{vFile:unlink}
16002 @tab @code{remote delete}
16004 @item @code{noack-packet}
16005 @tab @code{QStartNoAckMode}
16006 @tab Packet acknowledgment
16008 @item @code{osdata}
16009 @tab @code{qXfer:osdata:read}
16010 @tab @code{info os}
16012 @item @code{query-attached}
16013 @tab @code{qAttached}
16014 @tab Querying remote process attach state.
16018 @section Implementing a Remote Stub
16020 @cindex debugging stub, example
16021 @cindex remote stub, example
16022 @cindex stub example, remote debugging
16023 The stub files provided with @value{GDBN} implement the target side of the
16024 communication protocol, and the @value{GDBN} side is implemented in the
16025 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
16026 these subroutines to communicate, and ignore the details. (If you're
16027 implementing your own stub file, you can still ignore the details: start
16028 with one of the existing stub files. @file{sparc-stub.c} is the best
16029 organized, and therefore the easiest to read.)
16031 @cindex remote serial debugging, overview
16032 To debug a program running on another machine (the debugging
16033 @dfn{target} machine), you must first arrange for all the usual
16034 prerequisites for the program to run by itself. For example, for a C
16039 A startup routine to set up the C runtime environment; these usually
16040 have a name like @file{crt0}. The startup routine may be supplied by
16041 your hardware supplier, or you may have to write your own.
16044 A C subroutine library to support your program's
16045 subroutine calls, notably managing input and output.
16048 A way of getting your program to the other machine---for example, a
16049 download program. These are often supplied by the hardware
16050 manufacturer, but you may have to write your own from hardware
16054 The next step is to arrange for your program to use a serial port to
16055 communicate with the machine where @value{GDBN} is running (the @dfn{host}
16056 machine). In general terms, the scheme looks like this:
16060 @value{GDBN} already understands how to use this protocol; when everything
16061 else is set up, you can simply use the @samp{target remote} command
16062 (@pxref{Targets,,Specifying a Debugging Target}).
16064 @item On the target,
16065 you must link with your program a few special-purpose subroutines that
16066 implement the @value{GDBN} remote serial protocol. The file containing these
16067 subroutines is called a @dfn{debugging stub}.
16069 On certain remote targets, you can use an auxiliary program
16070 @code{gdbserver} instead of linking a stub into your program.
16071 @xref{Server,,Using the @code{gdbserver} Program}, for details.
16074 The debugging stub is specific to the architecture of the remote
16075 machine; for example, use @file{sparc-stub.c} to debug programs on
16078 @cindex remote serial stub list
16079 These working remote stubs are distributed with @value{GDBN}:
16084 @cindex @file{i386-stub.c}
16087 For Intel 386 and compatible architectures.
16090 @cindex @file{m68k-stub.c}
16091 @cindex Motorola 680x0
16093 For Motorola 680x0 architectures.
16096 @cindex @file{sh-stub.c}
16099 For Renesas SH architectures.
16102 @cindex @file{sparc-stub.c}
16104 For @sc{sparc} architectures.
16106 @item sparcl-stub.c
16107 @cindex @file{sparcl-stub.c}
16110 For Fujitsu @sc{sparclite} architectures.
16114 The @file{README} file in the @value{GDBN} distribution may list other
16115 recently added stubs.
16118 * Stub Contents:: What the stub can do for you
16119 * Bootstrapping:: What you must do for the stub
16120 * Debug Session:: Putting it all together
16123 @node Stub Contents
16124 @subsection What the Stub Can Do for You
16126 @cindex remote serial stub
16127 The debugging stub for your architecture supplies these three
16131 @item set_debug_traps
16132 @findex set_debug_traps
16133 @cindex remote serial stub, initialization
16134 This routine arranges for @code{handle_exception} to run when your
16135 program stops. You must call this subroutine explicitly near the
16136 beginning of your program.
16138 @item handle_exception
16139 @findex handle_exception
16140 @cindex remote serial stub, main routine
16141 This is the central workhorse, but your program never calls it
16142 explicitly---the setup code arranges for @code{handle_exception} to
16143 run when a trap is triggered.
16145 @code{handle_exception} takes control when your program stops during
16146 execution (for example, on a breakpoint), and mediates communications
16147 with @value{GDBN} on the host machine. This is where the communications
16148 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
16149 representative on the target machine. It begins by sending summary
16150 information on the state of your program, then continues to execute,
16151 retrieving and transmitting any information @value{GDBN} needs, until you
16152 execute a @value{GDBN} command that makes your program resume; at that point,
16153 @code{handle_exception} returns control to your own code on the target
16157 @cindex @code{breakpoint} subroutine, remote
16158 Use this auxiliary subroutine to make your program contain a
16159 breakpoint. Depending on the particular situation, this may be the only
16160 way for @value{GDBN} to get control. For instance, if your target
16161 machine has some sort of interrupt button, you won't need to call this;
16162 pressing the interrupt button transfers control to
16163 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
16164 simply receiving characters on the serial port may also trigger a trap;
16165 again, in that situation, you don't need to call @code{breakpoint} from
16166 your own program---simply running @samp{target remote} from the host
16167 @value{GDBN} session gets control.
16169 Call @code{breakpoint} if none of these is true, or if you simply want
16170 to make certain your program stops at a predetermined point for the
16171 start of your debugging session.
16174 @node Bootstrapping
16175 @subsection What You Must Do for the Stub
16177 @cindex remote stub, support routines
16178 The debugging stubs that come with @value{GDBN} are set up for a particular
16179 chip architecture, but they have no information about the rest of your
16180 debugging target machine.
16182 First of all you need to tell the stub how to communicate with the
16186 @item int getDebugChar()
16187 @findex getDebugChar
16188 Write this subroutine to read a single character from the serial port.
16189 It may be identical to @code{getchar} for your target system; a
16190 different name is used to allow you to distinguish the two if you wish.
16192 @item void putDebugChar(int)
16193 @findex putDebugChar
16194 Write this subroutine to write a single character to the serial port.
16195 It may be identical to @code{putchar} for your target system; a
16196 different name is used to allow you to distinguish the two if you wish.
16199 @cindex control C, and remote debugging
16200 @cindex interrupting remote targets
16201 If you want @value{GDBN} to be able to stop your program while it is
16202 running, you need to use an interrupt-driven serial driver, and arrange
16203 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
16204 character). That is the character which @value{GDBN} uses to tell the
16205 remote system to stop.
16207 Getting the debugging target to return the proper status to @value{GDBN}
16208 probably requires changes to the standard stub; one quick and dirty way
16209 is to just execute a breakpoint instruction (the ``dirty'' part is that
16210 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
16212 Other routines you need to supply are:
16215 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
16216 @findex exceptionHandler
16217 Write this function to install @var{exception_address} in the exception
16218 handling tables. You need to do this because the stub does not have any
16219 way of knowing what the exception handling tables on your target system
16220 are like (for example, the processor's table might be in @sc{rom},
16221 containing entries which point to a table in @sc{ram}).
16222 @var{exception_number} is the exception number which should be changed;
16223 its meaning is architecture-dependent (for example, different numbers
16224 might represent divide by zero, misaligned access, etc). When this
16225 exception occurs, control should be transferred directly to
16226 @var{exception_address}, and the processor state (stack, registers,
16227 and so on) should be just as it is when a processor exception occurs. So if
16228 you want to use a jump instruction to reach @var{exception_address}, it
16229 should be a simple jump, not a jump to subroutine.
16231 For the 386, @var{exception_address} should be installed as an interrupt
16232 gate so that interrupts are masked while the handler runs. The gate
16233 should be at privilege level 0 (the most privileged level). The
16234 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
16235 help from @code{exceptionHandler}.
16237 @item void flush_i_cache()
16238 @findex flush_i_cache
16239 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
16240 instruction cache, if any, on your target machine. If there is no
16241 instruction cache, this subroutine may be a no-op.
16243 On target machines that have instruction caches, @value{GDBN} requires this
16244 function to make certain that the state of your program is stable.
16248 You must also make sure this library routine is available:
16251 @item void *memset(void *, int, int)
16253 This is the standard library function @code{memset} that sets an area of
16254 memory to a known value. If you have one of the free versions of
16255 @code{libc.a}, @code{memset} can be found there; otherwise, you must
16256 either obtain it from your hardware manufacturer, or write your own.
16259 If you do not use the GNU C compiler, you may need other standard
16260 library subroutines as well; this varies from one stub to another,
16261 but in general the stubs are likely to use any of the common library
16262 subroutines which @code{@value{NGCC}} generates as inline code.
16265 @node Debug Session
16266 @subsection Putting it All Together
16268 @cindex remote serial debugging summary
16269 In summary, when your program is ready to debug, you must follow these
16274 Make sure you have defined the supporting low-level routines
16275 (@pxref{Bootstrapping,,What You Must Do for the Stub}):
16277 @code{getDebugChar}, @code{putDebugChar},
16278 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
16282 Insert these lines near the top of your program:
16290 For the 680x0 stub only, you need to provide a variable called
16291 @code{exceptionHook}. Normally you just use:
16294 void (*exceptionHook)() = 0;
16298 but if before calling @code{set_debug_traps}, you set it to point to a
16299 function in your program, that function is called when
16300 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
16301 error). The function indicated by @code{exceptionHook} is called with
16302 one parameter: an @code{int} which is the exception number.
16305 Compile and link together: your program, the @value{GDBN} debugging stub for
16306 your target architecture, and the supporting subroutines.
16309 Make sure you have a serial connection between your target machine and
16310 the @value{GDBN} host, and identify the serial port on the host.
16313 @c The "remote" target now provides a `load' command, so we should
16314 @c document that. FIXME.
16315 Download your program to your target machine (or get it there by
16316 whatever means the manufacturer provides), and start it.
16319 Start @value{GDBN} on the host, and connect to the target
16320 (@pxref{Connecting,,Connecting to a Remote Target}).
16324 @node Configurations
16325 @chapter Configuration-Specific Information
16327 While nearly all @value{GDBN} commands are available for all native and
16328 cross versions of the debugger, there are some exceptions. This chapter
16329 describes things that are only available in certain configurations.
16331 There are three major categories of configurations: native
16332 configurations, where the host and target are the same, embedded
16333 operating system configurations, which are usually the same for several
16334 different processor architectures, and bare embedded processors, which
16335 are quite different from each other.
16340 * Embedded Processors::
16347 This section describes details specific to particular native
16352 * BSD libkvm Interface:: Debugging BSD kernel memory images
16353 * SVR4 Process Information:: SVR4 process information
16354 * DJGPP Native:: Features specific to the DJGPP port
16355 * Cygwin Native:: Features specific to the Cygwin port
16356 * Hurd Native:: Features specific to @sc{gnu} Hurd
16357 * Neutrino:: Features specific to QNX Neutrino
16358 * Darwin:: Features specific to Darwin
16364 On HP-UX systems, if you refer to a function or variable name that
16365 begins with a dollar sign, @value{GDBN} searches for a user or system
16366 name first, before it searches for a convenience variable.
16369 @node BSD libkvm Interface
16370 @subsection BSD libkvm Interface
16373 @cindex kernel memory image
16374 @cindex kernel crash dump
16376 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
16377 interface that provides a uniform interface for accessing kernel virtual
16378 memory images, including live systems and crash dumps. @value{GDBN}
16379 uses this interface to allow you to debug live kernels and kernel crash
16380 dumps on many native BSD configurations. This is implemented as a
16381 special @code{kvm} debugging target. For debugging a live system, load
16382 the currently running kernel into @value{GDBN} and connect to the
16386 (@value{GDBP}) @b{target kvm}
16389 For debugging crash dumps, provide the file name of the crash dump as an
16393 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
16396 Once connected to the @code{kvm} target, the following commands are
16402 Set current context from the @dfn{Process Control Block} (PCB) address.
16405 Set current context from proc address. This command isn't available on
16406 modern FreeBSD systems.
16409 @node SVR4 Process Information
16410 @subsection SVR4 Process Information
16412 @cindex examine process image
16413 @cindex process info via @file{/proc}
16415 Many versions of SVR4 and compatible systems provide a facility called
16416 @samp{/proc} that can be used to examine the image of a running
16417 process using file-system subroutines. If @value{GDBN} is configured
16418 for an operating system with this facility, the command @code{info
16419 proc} is available to report information about the process running
16420 your program, or about any process running on your system. @code{info
16421 proc} works only on SVR4 systems that include the @code{procfs} code.
16422 This includes, as of this writing, @sc{gnu}/Linux, OSF/1 (Digital
16423 Unix), Solaris, Irix, and Unixware, but not HP-UX, for example.
16429 @itemx info proc @var{process-id}
16430 Summarize available information about any running process. If a
16431 process ID is specified by @var{process-id}, display information about
16432 that process; otherwise display information about the program being
16433 debugged. The summary includes the debugged process ID, the command
16434 line used to invoke it, its current working directory, and its
16435 executable file's absolute file name.
16437 On some systems, @var{process-id} can be of the form
16438 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
16439 within a process. If the optional @var{pid} part is missing, it means
16440 a thread from the process being debugged (the leading @samp{/} still
16441 needs to be present, or else @value{GDBN} will interpret the number as
16442 a process ID rather than a thread ID).
16444 @item info proc mappings
16445 @cindex memory address space mappings
16446 Report the memory address space ranges accessible in the program, with
16447 information on whether the process has read, write, or execute access
16448 rights to each range. On @sc{gnu}/Linux systems, each memory range
16449 includes the object file which is mapped to that range, instead of the
16450 memory access rights to that range.
16452 @item info proc stat
16453 @itemx info proc status
16454 @cindex process detailed status information
16455 These subcommands are specific to @sc{gnu}/Linux systems. They show
16456 the process-related information, including the user ID and group ID;
16457 how many threads are there in the process; its virtual memory usage;
16458 the signals that are pending, blocked, and ignored; its TTY; its
16459 consumption of system and user time; its stack size; its @samp{nice}
16460 value; etc. For more information, see the @samp{proc} man page
16461 (type @kbd{man 5 proc} from your shell prompt).
16463 @item info proc all
16464 Show all the information about the process described under all of the
16465 above @code{info proc} subcommands.
16468 @comment These sub-options of 'info proc' were not included when
16469 @comment procfs.c was re-written. Keep their descriptions around
16470 @comment against the day when someone finds the time to put them back in.
16471 @kindex info proc times
16472 @item info proc times
16473 Starting time, user CPU time, and system CPU time for your program and
16476 @kindex info proc id
16478 Report on the process IDs related to your program: its own process ID,
16479 the ID of its parent, the process group ID, and the session ID.
16482 @item set procfs-trace
16483 @kindex set procfs-trace
16484 @cindex @code{procfs} API calls
16485 This command enables and disables tracing of @code{procfs} API calls.
16487 @item show procfs-trace
16488 @kindex show procfs-trace
16489 Show the current state of @code{procfs} API call tracing.
16491 @item set procfs-file @var{file}
16492 @kindex set procfs-file
16493 Tell @value{GDBN} to write @code{procfs} API trace to the named
16494 @var{file}. @value{GDBN} appends the trace info to the previous
16495 contents of the file. The default is to display the trace on the
16498 @item show procfs-file
16499 @kindex show procfs-file
16500 Show the file to which @code{procfs} API trace is written.
16502 @item proc-trace-entry
16503 @itemx proc-trace-exit
16504 @itemx proc-untrace-entry
16505 @itemx proc-untrace-exit
16506 @kindex proc-trace-entry
16507 @kindex proc-trace-exit
16508 @kindex proc-untrace-entry
16509 @kindex proc-untrace-exit
16510 These commands enable and disable tracing of entries into and exits
16511 from the @code{syscall} interface.
16514 @kindex info pidlist
16515 @cindex process list, QNX Neutrino
16516 For QNX Neutrino only, this command displays the list of all the
16517 processes and all the threads within each process.
16520 @kindex info meminfo
16521 @cindex mapinfo list, QNX Neutrino
16522 For QNX Neutrino only, this command displays the list of all mapinfos.
16526 @subsection Features for Debugging @sc{djgpp} Programs
16527 @cindex @sc{djgpp} debugging
16528 @cindex native @sc{djgpp} debugging
16529 @cindex MS-DOS-specific commands
16532 @sc{djgpp} is a port of the @sc{gnu} development tools to MS-DOS and
16533 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
16534 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
16535 top of real-mode DOS systems and their emulations.
16537 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
16538 defines a few commands specific to the @sc{djgpp} port. This
16539 subsection describes those commands.
16544 This is a prefix of @sc{djgpp}-specific commands which print
16545 information about the target system and important OS structures.
16548 @cindex MS-DOS system info
16549 @cindex free memory information (MS-DOS)
16550 @item info dos sysinfo
16551 This command displays assorted information about the underlying
16552 platform: the CPU type and features, the OS version and flavor, the
16553 DPMI version, and the available conventional and DPMI memory.
16558 @cindex segment descriptor tables
16559 @cindex descriptor tables display
16561 @itemx info dos ldt
16562 @itemx info dos idt
16563 These 3 commands display entries from, respectively, Global, Local,
16564 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
16565 tables are data structures which store a descriptor for each segment
16566 that is currently in use. The segment's selector is an index into a
16567 descriptor table; the table entry for that index holds the
16568 descriptor's base address and limit, and its attributes and access
16571 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
16572 segment (used for both data and the stack), and a DOS segment (which
16573 allows access to DOS/BIOS data structures and absolute addresses in
16574 conventional memory). However, the DPMI host will usually define
16575 additional segments in order to support the DPMI environment.
16577 @cindex garbled pointers
16578 These commands allow to display entries from the descriptor tables.
16579 Without an argument, all entries from the specified table are
16580 displayed. An argument, which should be an integer expression, means
16581 display a single entry whose index is given by the argument. For
16582 example, here's a convenient way to display information about the
16583 debugged program's data segment:
16586 @exdent @code{(@value{GDBP}) info dos ldt $ds}
16587 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
16591 This comes in handy when you want to see whether a pointer is outside
16592 the data segment's limit (i.e.@: @dfn{garbled}).
16594 @cindex page tables display (MS-DOS)
16596 @itemx info dos pte
16597 These two commands display entries from, respectively, the Page
16598 Directory and the Page Tables. Page Directories and Page Tables are
16599 data structures which control how virtual memory addresses are mapped
16600 into physical addresses. A Page Table includes an entry for every
16601 page of memory that is mapped into the program's address space; there
16602 may be several Page Tables, each one holding up to 4096 entries. A
16603 Page Directory has up to 4096 entries, one each for every Page Table
16604 that is currently in use.
16606 Without an argument, @kbd{info dos pde} displays the entire Page
16607 Directory, and @kbd{info dos pte} displays all the entries in all of
16608 the Page Tables. An argument, an integer expression, given to the
16609 @kbd{info dos pde} command means display only that entry from the Page
16610 Directory table. An argument given to the @kbd{info dos pte} command
16611 means display entries from a single Page Table, the one pointed to by
16612 the specified entry in the Page Directory.
16614 @cindex direct memory access (DMA) on MS-DOS
16615 These commands are useful when your program uses @dfn{DMA} (Direct
16616 Memory Access), which needs physical addresses to program the DMA
16619 These commands are supported only with some DPMI servers.
16621 @cindex physical address from linear address
16622 @item info dos address-pte @var{addr}
16623 This command displays the Page Table entry for a specified linear
16624 address. The argument @var{addr} is a linear address which should
16625 already have the appropriate segment's base address added to it,
16626 because this command accepts addresses which may belong to @emph{any}
16627 segment. For example, here's how to display the Page Table entry for
16628 the page where a variable @code{i} is stored:
16631 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
16632 @exdent @code{Page Table entry for address 0x11a00d30:}
16633 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
16637 This says that @code{i} is stored at offset @code{0xd30} from the page
16638 whose physical base address is @code{0x02698000}, and shows all the
16639 attributes of that page.
16641 Note that you must cast the addresses of variables to a @code{char *},
16642 since otherwise the value of @code{__djgpp_base_address}, the base
16643 address of all variables and functions in a @sc{djgpp} program, will
16644 be added using the rules of C pointer arithmetics: if @code{i} is
16645 declared an @code{int}, @value{GDBN} will add 4 times the value of
16646 @code{__djgpp_base_address} to the address of @code{i}.
16648 Here's another example, it displays the Page Table entry for the
16652 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
16653 @exdent @code{Page Table entry for address 0x29110:}
16654 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
16658 (The @code{+ 3} offset is because the transfer buffer's address is the
16659 3rd member of the @code{_go32_info_block} structure.) The output
16660 clearly shows that this DPMI server maps the addresses in conventional
16661 memory 1:1, i.e.@: the physical (@code{0x00029000} + @code{0x110}) and
16662 linear (@code{0x29110}) addresses are identical.
16664 This command is supported only with some DPMI servers.
16667 @cindex DOS serial data link, remote debugging
16668 In addition to native debugging, the DJGPP port supports remote
16669 debugging via a serial data link. The following commands are specific
16670 to remote serial debugging in the DJGPP port of @value{GDBN}.
16673 @kindex set com1base
16674 @kindex set com1irq
16675 @kindex set com2base
16676 @kindex set com2irq
16677 @kindex set com3base
16678 @kindex set com3irq
16679 @kindex set com4base
16680 @kindex set com4irq
16681 @item set com1base @var{addr}
16682 This command sets the base I/O port address of the @file{COM1} serial
16685 @item set com1irq @var{irq}
16686 This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use
16687 for the @file{COM1} serial port.
16689 There are similar commands @samp{set com2base}, @samp{set com3irq},
16690 etc.@: for setting the port address and the @code{IRQ} lines for the
16693 @kindex show com1base
16694 @kindex show com1irq
16695 @kindex show com2base
16696 @kindex show com2irq
16697 @kindex show com3base
16698 @kindex show com3irq
16699 @kindex show com4base
16700 @kindex show com4irq
16701 The related commands @samp{show com1base}, @samp{show com1irq} etc.@:
16702 display the current settings of the base address and the @code{IRQ}
16703 lines used by the COM ports.
16706 @kindex info serial
16707 @cindex DOS serial port status
16708 This command prints the status of the 4 DOS serial ports. For each
16709 port, it prints whether it's active or not, its I/O base address and
16710 IRQ number, whether it uses a 16550-style FIFO, its baudrate, and the
16711 counts of various errors encountered so far.
16715 @node Cygwin Native
16716 @subsection Features for Debugging MS Windows PE Executables
16717 @cindex MS Windows debugging
16718 @cindex native Cygwin debugging
16719 @cindex Cygwin-specific commands
16721 @value{GDBN} supports native debugging of MS Windows programs, including
16722 DLLs with and without symbolic debugging information.
16724 @cindex Ctrl-BREAK, MS-Windows
16725 @cindex interrupt debuggee on MS-Windows
16726 MS-Windows programs that call @code{SetConsoleMode} to switch off the
16727 special meaning of the @samp{Ctrl-C} keystroke cannot be interrupted
16728 by typing @kbd{C-c}. For this reason, @value{GDBN} on MS-Windows
16729 supports @kbd{C-@key{BREAK}} as an alternative interrupt key
16730 sequence, which can be used to interrupt the debuggee even if it
16733 There are various additional Cygwin-specific commands, described in
16734 this section. Working with DLLs that have no debugging symbols is
16735 described in @ref{Non-debug DLL Symbols}.
16740 This is a prefix of MS Windows-specific commands which print
16741 information about the target system and important OS structures.
16743 @item info w32 selector
16744 This command displays information returned by
16745 the Win32 API @code{GetThreadSelectorEntry} function.
16746 It takes an optional argument that is evaluated to
16747 a long value to give the information about this given selector.
16748 Without argument, this command displays information
16749 about the six segment registers.
16751 @item info w32 thread-information-block
16752 This command displays thread specific information stored in the
16753 Thread Information Block (readable on the X86 CPU family using @code{$fs}
16754 selector for 32-bit programs and @code{$gs} for 64-bit programs).
16758 This is a Cygwin-specific alias of @code{info shared}.
16760 @kindex dll-symbols
16762 This command loads symbols from a dll similarly to
16763 add-sym command but without the need to specify a base address.
16765 @kindex set cygwin-exceptions
16766 @cindex debugging the Cygwin DLL
16767 @cindex Cygwin DLL, debugging
16768 @item set cygwin-exceptions @var{mode}
16769 If @var{mode} is @code{on}, @value{GDBN} will break on exceptions that
16770 happen inside the Cygwin DLL. If @var{mode} is @code{off},
16771 @value{GDBN} will delay recognition of exceptions, and may ignore some
16772 exceptions which seem to be caused by internal Cygwin DLL
16773 ``bookkeeping''. This option is meant primarily for debugging the
16774 Cygwin DLL itself; the default value is @code{off} to avoid annoying
16775 @value{GDBN} users with false @code{SIGSEGV} signals.
16777 @kindex show cygwin-exceptions
16778 @item show cygwin-exceptions
16779 Displays whether @value{GDBN} will break on exceptions that happen
16780 inside the Cygwin DLL itself.
16782 @kindex set new-console
16783 @item set new-console @var{mode}
16784 If @var{mode} is @code{on} the debuggee will
16785 be started in a new console on next start.
16786 If @var{mode} is @code{off}, the debuggee will
16787 be started in the same console as the debugger.
16789 @kindex show new-console
16790 @item show new-console
16791 Displays whether a new console is used
16792 when the debuggee is started.
16794 @kindex set new-group
16795 @item set new-group @var{mode}
16796 This boolean value controls whether the debuggee should
16797 start a new group or stay in the same group as the debugger.
16798 This affects the way the Windows OS handles
16801 @kindex show new-group
16802 @item show new-group
16803 Displays current value of new-group boolean.
16805 @kindex set debugevents
16806 @item set debugevents
16807 This boolean value adds debug output concerning kernel events related
16808 to the debuggee seen by the debugger. This includes events that
16809 signal thread and process creation and exit, DLL loading and
16810 unloading, console interrupts, and debugging messages produced by the
16811 Windows @code{OutputDebugString} API call.
16813 @kindex set debugexec
16814 @item set debugexec
16815 This boolean value adds debug output concerning execute events
16816 (such as resume thread) seen by the debugger.
16818 @kindex set debugexceptions
16819 @item set debugexceptions
16820 This boolean value adds debug output concerning exceptions in the
16821 debuggee seen by the debugger.
16823 @kindex set debugmemory
16824 @item set debugmemory
16825 This boolean value adds debug output concerning debuggee memory reads
16826 and writes by the debugger.
16830 This boolean values specifies whether the debuggee is called
16831 via a shell or directly (default value is on).
16835 Displays if the debuggee will be started with a shell.
16840 * Non-debug DLL Symbols:: Support for DLLs without debugging symbols
16843 @node Non-debug DLL Symbols
16844 @subsubsection Support for DLLs without Debugging Symbols
16845 @cindex DLLs with no debugging symbols
16846 @cindex Minimal symbols and DLLs
16848 Very often on windows, some of the DLLs that your program relies on do
16849 not include symbolic debugging information (for example,
16850 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
16851 symbols in a DLL, it relies on the minimal amount of symbolic
16852 information contained in the DLL's export table. This section
16853 describes working with such symbols, known internally to @value{GDBN} as
16854 ``minimal symbols''.
16856 Note that before the debugged program has started execution, no DLLs
16857 will have been loaded. The easiest way around this problem is simply to
16858 start the program --- either by setting a breakpoint or letting the
16859 program run once to completion. It is also possible to force
16860 @value{GDBN} to load a particular DLL before starting the executable ---
16861 see the shared library information in @ref{Files}, or the
16862 @code{dll-symbols} command in @ref{Cygwin Native}. Currently,
16863 explicitly loading symbols from a DLL with no debugging information will
16864 cause the symbol names to be duplicated in @value{GDBN}'s lookup table,
16865 which may adversely affect symbol lookup performance.
16867 @subsubsection DLL Name Prefixes
16869 In keeping with the naming conventions used by the Microsoft debugging
16870 tools, DLL export symbols are made available with a prefix based on the
16871 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
16872 also entered into the symbol table, so @code{CreateFileA} is often
16873 sufficient. In some cases there will be name clashes within a program
16874 (particularly if the executable itself includes full debugging symbols)
16875 necessitating the use of the fully qualified name when referring to the
16876 contents of the DLL. Use single-quotes around the name to avoid the
16877 exclamation mark (``!'') being interpreted as a language operator.
16879 Note that the internal name of the DLL may be all upper-case, even
16880 though the file name of the DLL is lower-case, or vice-versa. Since
16881 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
16882 some confusion. If in doubt, try the @code{info functions} and
16883 @code{info variables} commands or even @code{maint print msymbols}
16884 (@pxref{Symbols}). Here's an example:
16887 (@value{GDBP}) info function CreateFileA
16888 All functions matching regular expression "CreateFileA":
16890 Non-debugging symbols:
16891 0x77e885f4 CreateFileA
16892 0x77e885f4 KERNEL32!CreateFileA
16896 (@value{GDBP}) info function !
16897 All functions matching regular expression "!":
16899 Non-debugging symbols:
16900 0x6100114c cygwin1!__assert
16901 0x61004034 cygwin1!_dll_crt0@@0
16902 0x61004240 cygwin1!dll_crt0(per_process *)
16906 @subsubsection Working with Minimal Symbols
16908 Symbols extracted from a DLL's export table do not contain very much
16909 type information. All that @value{GDBN} can do is guess whether a symbol
16910 refers to a function or variable depending on the linker section that
16911 contains the symbol. Also note that the actual contents of the memory
16912 contained in a DLL are not available unless the program is running. This
16913 means that you cannot examine the contents of a variable or disassemble
16914 a function within a DLL without a running program.
16916 Variables are generally treated as pointers and dereferenced
16917 automatically. For this reason, it is often necessary to prefix a
16918 variable name with the address-of operator (``&'') and provide explicit
16919 type information in the command. Here's an example of the type of
16923 (@value{GDBP}) print 'cygwin1!__argv'
16928 (@value{GDBP}) x 'cygwin1!__argv'
16929 0x10021610: "\230y\""
16932 And two possible solutions:
16935 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
16936 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
16940 (@value{GDBP}) x/2x &'cygwin1!__argv'
16941 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
16942 (@value{GDBP}) x/x 0x10021608
16943 0x10021608: 0x0022fd98
16944 (@value{GDBP}) x/s 0x0022fd98
16945 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
16948 Setting a break point within a DLL is possible even before the program
16949 starts execution. However, under these circumstances, @value{GDBN} can't
16950 examine the initial instructions of the function in order to skip the
16951 function's frame set-up code. You can work around this by using ``*&''
16952 to set the breakpoint at a raw memory address:
16955 (@value{GDBP}) break *&'python22!PyOS_Readline'
16956 Breakpoint 1 at 0x1e04eff0
16959 The author of these extensions is not entirely convinced that setting a
16960 break point within a shared DLL like @file{kernel32.dll} is completely
16964 @subsection Commands Specific to @sc{gnu} Hurd Systems
16965 @cindex @sc{gnu} Hurd debugging
16967 This subsection describes @value{GDBN} commands specific to the
16968 @sc{gnu} Hurd native debugging.
16973 @kindex set signals@r{, Hurd command}
16974 @kindex set sigs@r{, Hurd command}
16975 This command toggles the state of inferior signal interception by
16976 @value{GDBN}. Mach exceptions, such as breakpoint traps, are not
16977 affected by this command. @code{sigs} is a shorthand alias for
16982 @kindex show signals@r{, Hurd command}
16983 @kindex show sigs@r{, Hurd command}
16984 Show the current state of intercepting inferior's signals.
16986 @item set signal-thread
16987 @itemx set sigthread
16988 @kindex set signal-thread
16989 @kindex set sigthread
16990 This command tells @value{GDBN} which thread is the @code{libc} signal
16991 thread. That thread is run when a signal is delivered to a running
16992 process. @code{set sigthread} is the shorthand alias of @code{set
16995 @item show signal-thread
16996 @itemx show sigthread
16997 @kindex show signal-thread
16998 @kindex show sigthread
16999 These two commands show which thread will run when the inferior is
17000 delivered a signal.
17003 @kindex set stopped@r{, Hurd command}
17004 This commands tells @value{GDBN} that the inferior process is stopped,
17005 as with the @code{SIGSTOP} signal. The stopped process can be
17006 continued by delivering a signal to it.
17009 @kindex show stopped@r{, Hurd command}
17010 This command shows whether @value{GDBN} thinks the debuggee is
17013 @item set exceptions
17014 @kindex set exceptions@r{, Hurd command}
17015 Use this command to turn off trapping of exceptions in the inferior.
17016 When exception trapping is off, neither breakpoints nor
17017 single-stepping will work. To restore the default, set exception
17020 @item show exceptions
17021 @kindex show exceptions@r{, Hurd command}
17022 Show the current state of trapping exceptions in the inferior.
17024 @item set task pause
17025 @kindex set task@r{, Hurd commands}
17026 @cindex task attributes (@sc{gnu} Hurd)
17027 @cindex pause current task (@sc{gnu} Hurd)
17028 This command toggles task suspension when @value{GDBN} has control.
17029 Setting it to on takes effect immediately, and the task is suspended
17030 whenever @value{GDBN} gets control. Setting it to off will take
17031 effect the next time the inferior is continued. If this option is set
17032 to off, you can use @code{set thread default pause on} or @code{set
17033 thread pause on} (see below) to pause individual threads.
17035 @item show task pause
17036 @kindex show task@r{, Hurd commands}
17037 Show the current state of task suspension.
17039 @item set task detach-suspend-count
17040 @cindex task suspend count
17041 @cindex detach from task, @sc{gnu} Hurd
17042 This command sets the suspend count the task will be left with when
17043 @value{GDBN} detaches from it.
17045 @item show task detach-suspend-count
17046 Show the suspend count the task will be left with when detaching.
17048 @item set task exception-port
17049 @itemx set task excp
17050 @cindex task exception port, @sc{gnu} Hurd
17051 This command sets the task exception port to which @value{GDBN} will
17052 forward exceptions. The argument should be the value of the @dfn{send
17053 rights} of the task. @code{set task excp} is a shorthand alias.
17055 @item set noninvasive
17056 @cindex noninvasive task options
17057 This command switches @value{GDBN} to a mode that is the least
17058 invasive as far as interfering with the inferior is concerned. This
17059 is the same as using @code{set task pause}, @code{set exceptions}, and
17060 @code{set signals} to values opposite to the defaults.
17062 @item info send-rights
17063 @itemx info receive-rights
17064 @itemx info port-rights
17065 @itemx info port-sets
17066 @itemx info dead-names
17069 @cindex send rights, @sc{gnu} Hurd
17070 @cindex receive rights, @sc{gnu} Hurd
17071 @cindex port rights, @sc{gnu} Hurd
17072 @cindex port sets, @sc{gnu} Hurd
17073 @cindex dead names, @sc{gnu} Hurd
17074 These commands display information about, respectively, send rights,
17075 receive rights, port rights, port sets, and dead names of a task.
17076 There are also shorthand aliases: @code{info ports} for @code{info
17077 port-rights} and @code{info psets} for @code{info port-sets}.
17079 @item set thread pause
17080 @kindex set thread@r{, Hurd command}
17081 @cindex thread properties, @sc{gnu} Hurd
17082 @cindex pause current thread (@sc{gnu} Hurd)
17083 This command toggles current thread suspension when @value{GDBN} has
17084 control. Setting it to on takes effect immediately, and the current
17085 thread is suspended whenever @value{GDBN} gets control. Setting it to
17086 off will take effect the next time the inferior is continued.
17087 Normally, this command has no effect, since when @value{GDBN} has
17088 control, the whole task is suspended. However, if you used @code{set
17089 task pause off} (see above), this command comes in handy to suspend
17090 only the current thread.
17092 @item show thread pause
17093 @kindex show thread@r{, Hurd command}
17094 This command shows the state of current thread suspension.
17096 @item set thread run
17097 This command sets whether the current thread is allowed to run.
17099 @item show thread run
17100 Show whether the current thread is allowed to run.
17102 @item set thread detach-suspend-count
17103 @cindex thread suspend count, @sc{gnu} Hurd
17104 @cindex detach from thread, @sc{gnu} Hurd
17105 This command sets the suspend count @value{GDBN} will leave on a
17106 thread when detaching. This number is relative to the suspend count
17107 found by @value{GDBN} when it notices the thread; use @code{set thread
17108 takeover-suspend-count} to force it to an absolute value.
17110 @item show thread detach-suspend-count
17111 Show the suspend count @value{GDBN} will leave on the thread when
17114 @item set thread exception-port
17115 @itemx set thread excp
17116 Set the thread exception port to which to forward exceptions. This
17117 overrides the port set by @code{set task exception-port} (see above).
17118 @code{set thread excp} is the shorthand alias.
17120 @item set thread takeover-suspend-count
17121 Normally, @value{GDBN}'s thread suspend counts are relative to the
17122 value @value{GDBN} finds when it notices each thread. This command
17123 changes the suspend counts to be absolute instead.
17125 @item set thread default
17126 @itemx show thread default
17127 @cindex thread default settings, @sc{gnu} Hurd
17128 Each of the above @code{set thread} commands has a @code{set thread
17129 default} counterpart (e.g., @code{set thread default pause}, @code{set
17130 thread default exception-port}, etc.). The @code{thread default}
17131 variety of commands sets the default thread properties for all
17132 threads; you can then change the properties of individual threads with
17133 the non-default commands.
17138 @subsection QNX Neutrino
17139 @cindex QNX Neutrino
17141 @value{GDBN} provides the following commands specific to the QNX
17145 @item set debug nto-debug
17146 @kindex set debug nto-debug
17147 When set to on, enables debugging messages specific to the QNX
17150 @item show debug nto-debug
17151 @kindex show debug nto-debug
17152 Show the current state of QNX Neutrino messages.
17159 @value{GDBN} provides the following commands specific to the Darwin target:
17162 @item set debug darwin @var{num}
17163 @kindex set debug darwin
17164 When set to a non zero value, enables debugging messages specific to
17165 the Darwin support. Higher values produce more verbose output.
17167 @item show debug darwin
17168 @kindex show debug darwin
17169 Show the current state of Darwin messages.
17171 @item set debug mach-o @var{num}
17172 @kindex set debug mach-o
17173 When set to a non zero value, enables debugging messages while
17174 @value{GDBN} is reading Darwin object files. (@dfn{Mach-O} is the
17175 file format used on Darwin for object and executable files.) Higher
17176 values produce more verbose output. This is a command to diagnose
17177 problems internal to @value{GDBN} and should not be needed in normal
17180 @item show debug mach-o
17181 @kindex show debug mach-o
17182 Show the current state of Mach-O file messages.
17184 @item set mach-exceptions on
17185 @itemx set mach-exceptions off
17186 @kindex set mach-exceptions
17187 On Darwin, faults are first reported as a Mach exception and are then
17188 mapped to a Posix signal. Use this command to turn on trapping of
17189 Mach exceptions in the inferior. This might be sometimes useful to
17190 better understand the cause of a fault. The default is off.
17192 @item show mach-exceptions
17193 @kindex show mach-exceptions
17194 Show the current state of exceptions trapping.
17199 @section Embedded Operating Systems
17201 This section describes configurations involving the debugging of
17202 embedded operating systems that are available for several different
17206 * VxWorks:: Using @value{GDBN} with VxWorks
17209 @value{GDBN} includes the ability to debug programs running on
17210 various real-time operating systems.
17213 @subsection Using @value{GDBN} with VxWorks
17219 @kindex target vxworks
17220 @item target vxworks @var{machinename}
17221 A VxWorks system, attached via TCP/IP. The argument @var{machinename}
17222 is the target system's machine name or IP address.
17226 On VxWorks, @code{load} links @var{filename} dynamically on the
17227 current target system as well as adding its symbols in @value{GDBN}.
17229 @value{GDBN} enables developers to spawn and debug tasks running on networked
17230 VxWorks targets from a Unix host. Already-running tasks spawned from
17231 the VxWorks shell can also be debugged. @value{GDBN} uses code that runs on
17232 both the Unix host and on the VxWorks target. The program
17233 @code{@value{GDBP}} is installed and executed on the Unix host. (It may be
17234 installed with the name @code{vxgdb}, to distinguish it from a
17235 @value{GDBN} for debugging programs on the host itself.)
17238 @item VxWorks-timeout @var{args}
17239 @kindex vxworks-timeout
17240 All VxWorks-based targets now support the option @code{vxworks-timeout}.
17241 This option is set by the user, and @var{args} represents the number of
17242 seconds @value{GDBN} waits for responses to rpc's. You might use this if
17243 your VxWorks target is a slow software simulator or is on the far side
17244 of a thin network line.
17247 The following information on connecting to VxWorks was current when
17248 this manual was produced; newer releases of VxWorks may use revised
17251 @findex INCLUDE_RDB
17252 To use @value{GDBN} with VxWorks, you must rebuild your VxWorks kernel
17253 to include the remote debugging interface routines in the VxWorks
17254 library @file{rdb.a}. To do this, define @code{INCLUDE_RDB} in the
17255 VxWorks configuration file @file{configAll.h} and rebuild your VxWorks
17256 kernel. The resulting kernel contains @file{rdb.a}, and spawns the
17257 source debugging task @code{tRdbTask} when VxWorks is booted. For more
17258 information on configuring and remaking VxWorks, see the manufacturer's
17260 @c VxWorks, see the @cite{VxWorks Programmer's Guide}.
17262 Once you have included @file{rdb.a} in your VxWorks system image and set
17263 your Unix execution search path to find @value{GDBN}, you are ready to
17264 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}} (or
17265 @code{vxgdb}, depending on your installation).
17267 @value{GDBN} comes up showing the prompt:
17274 * VxWorks Connection:: Connecting to VxWorks
17275 * VxWorks Download:: VxWorks download
17276 * VxWorks Attach:: Running tasks
17279 @node VxWorks Connection
17280 @subsubsection Connecting to VxWorks
17282 The @value{GDBN} command @code{target} lets you connect to a VxWorks target on the
17283 network. To connect to a target whose host name is ``@code{tt}'', type:
17286 (vxgdb) target vxworks tt
17290 @value{GDBN} displays messages like these:
17293 Attaching remote machine across net...
17298 @value{GDBN} then attempts to read the symbol tables of any object modules
17299 loaded into the VxWorks target since it was last booted. @value{GDBN} locates
17300 these files by searching the directories listed in the command search
17301 path (@pxref{Environment, ,Your Program's Environment}); if it fails
17302 to find an object file, it displays a message such as:
17305 prog.o: No such file or directory.
17308 When this happens, add the appropriate directory to the search path with
17309 the @value{GDBN} command @code{path}, and execute the @code{target}
17312 @node VxWorks Download
17313 @subsubsection VxWorks Download
17315 @cindex download to VxWorks
17316 If you have connected to the VxWorks target and you want to debug an
17317 object that has not yet been loaded, you can use the @value{GDBN}
17318 @code{load} command to download a file from Unix to VxWorks
17319 incrementally. The object file given as an argument to the @code{load}
17320 command is actually opened twice: first by the VxWorks target in order
17321 to download the code, then by @value{GDBN} in order to read the symbol
17322 table. This can lead to problems if the current working directories on
17323 the two systems differ. If both systems have NFS mounted the same
17324 filesystems, you can avoid these problems by using absolute paths.
17325 Otherwise, it is simplest to set the working directory on both systems
17326 to the directory in which the object file resides, and then to reference
17327 the file by its name, without any path. For instance, a program
17328 @file{prog.o} may reside in @file{@var{vxpath}/vw/demo/rdb} in VxWorks
17329 and in @file{@var{hostpath}/vw/demo/rdb} on the host. To load this
17330 program, type this on VxWorks:
17333 -> cd "@var{vxpath}/vw/demo/rdb"
17337 Then, in @value{GDBN}, type:
17340 (vxgdb) cd @var{hostpath}/vw/demo/rdb
17341 (vxgdb) load prog.o
17344 @value{GDBN} displays a response similar to this:
17347 Reading symbol data from wherever/vw/demo/rdb/prog.o... done.
17350 You can also use the @code{load} command to reload an object module
17351 after editing and recompiling the corresponding source file. Note that
17352 this makes @value{GDBN} delete all currently-defined breakpoints,
17353 auto-displays, and convenience variables, and to clear the value
17354 history. (This is necessary in order to preserve the integrity of
17355 debugger's data structures that reference the target system's symbol
17358 @node VxWorks Attach
17359 @subsubsection Running Tasks
17361 @cindex running VxWorks tasks
17362 You can also attach to an existing task using the @code{attach} command as
17366 (vxgdb) attach @var{task}
17370 where @var{task} is the VxWorks hexadecimal task ID. The task can be running
17371 or suspended when you attach to it. Running tasks are suspended at
17372 the time of attachment.
17374 @node Embedded Processors
17375 @section Embedded Processors
17377 This section goes into details specific to particular embedded
17380 @cindex send command to simulator
17381 Whenever a specific embedded processor has a simulator, @value{GDBN}
17382 allows to send an arbitrary command to the simulator.
17385 @item sim @var{command}
17386 @kindex sim@r{, a command}
17387 Send an arbitrary @var{command} string to the simulator. Consult the
17388 documentation for the specific simulator in use for information about
17389 acceptable commands.
17395 * M32R/D:: Renesas M32R/D
17396 * M68K:: Motorola M68K
17397 * MicroBlaze:: Xilinx MicroBlaze
17398 * MIPS Embedded:: MIPS Embedded
17399 * OpenRISC 1000:: OpenRisc 1000
17400 * PA:: HP PA Embedded
17401 * PowerPC Embedded:: PowerPC Embedded
17402 * Sparclet:: Tsqware Sparclet
17403 * Sparclite:: Fujitsu Sparclite
17404 * Z8000:: Zilog Z8000
17407 * Super-H:: Renesas Super-H
17416 @item target rdi @var{dev}
17417 ARM Angel monitor, via RDI library interface to ADP protocol. You may
17418 use this target to communicate with both boards running the Angel
17419 monitor, or with the EmbeddedICE JTAG debug device.
17422 @item target rdp @var{dev}
17427 @value{GDBN} provides the following ARM-specific commands:
17430 @item set arm disassembler
17432 This commands selects from a list of disassembly styles. The
17433 @code{"std"} style is the standard style.
17435 @item show arm disassembler
17437 Show the current disassembly style.
17439 @item set arm apcs32
17440 @cindex ARM 32-bit mode
17441 This command toggles ARM operation mode between 32-bit and 26-bit.
17443 @item show arm apcs32
17444 Display the current usage of the ARM 32-bit mode.
17446 @item set arm fpu @var{fputype}
17447 This command sets the ARM floating-point unit (FPU) type. The
17448 argument @var{fputype} can be one of these:
17452 Determine the FPU type by querying the OS ABI.
17454 Software FPU, with mixed-endian doubles on little-endian ARM
17457 GCC-compiled FPA co-processor.
17459 Software FPU with pure-endian doubles.
17465 Show the current type of the FPU.
17468 This command forces @value{GDBN} to use the specified ABI.
17471 Show the currently used ABI.
17473 @item set arm fallback-mode (arm|thumb|auto)
17474 @value{GDBN} uses the symbol table, when available, to determine
17475 whether instructions are ARM or Thumb. This command controls
17476 @value{GDBN}'s default behavior when the symbol table is not
17477 available. The default is @samp{auto}, which causes @value{GDBN} to
17478 use the current execution mode (from the @code{T} bit in the @code{CPSR}
17481 @item show arm fallback-mode
17482 Show the current fallback instruction mode.
17484 @item set arm force-mode (arm|thumb|auto)
17485 This command overrides use of the symbol table to determine whether
17486 instructions are ARM or Thumb. The default is @samp{auto}, which
17487 causes @value{GDBN} to use the symbol table and then the setting
17488 of @samp{set arm fallback-mode}.
17490 @item show arm force-mode
17491 Show the current forced instruction mode.
17493 @item set debug arm
17494 Toggle whether to display ARM-specific debugging messages from the ARM
17495 target support subsystem.
17497 @item show debug arm
17498 Show whether ARM-specific debugging messages are enabled.
17501 The following commands are available when an ARM target is debugged
17502 using the RDI interface:
17505 @item rdilogfile @r{[}@var{file}@r{]}
17507 @cindex ADP (Angel Debugger Protocol) logging
17508 Set the filename for the ADP (Angel Debugger Protocol) packet log.
17509 With an argument, sets the log file to the specified @var{file}. With
17510 no argument, show the current log file name. The default log file is
17513 @item rdilogenable @r{[}@var{arg}@r{]}
17514 @kindex rdilogenable
17515 Control logging of ADP packets. With an argument of 1 or @code{"yes"}
17516 enables logging, with an argument 0 or @code{"no"} disables it. With
17517 no arguments displays the current setting. When logging is enabled,
17518 ADP packets exchanged between @value{GDBN} and the RDI target device
17519 are logged to a file.
17521 @item set rdiromatzero
17522 @kindex set rdiromatzero
17523 @cindex ROM at zero address, RDI
17524 Tell @value{GDBN} whether the target has ROM at address 0. If on,
17525 vector catching is disabled, so that zero address can be used. If off
17526 (the default), vector catching is enabled. For this command to take
17527 effect, it needs to be invoked prior to the @code{target rdi} command.
17529 @item show rdiromatzero
17530 @kindex show rdiromatzero
17531 Show the current setting of ROM at zero address.
17533 @item set rdiheartbeat
17534 @kindex set rdiheartbeat
17535 @cindex RDI heartbeat
17536 Enable or disable RDI heartbeat packets. It is not recommended to
17537 turn on this option, since it confuses ARM and EPI JTAG interface, as
17538 well as the Angel monitor.
17540 @item show rdiheartbeat
17541 @kindex show rdiheartbeat
17542 Show the setting of RDI heartbeat packets.
17546 @item target sim @r{[}@var{simargs}@r{]} @dots{}
17547 The @value{GDBN} ARM simulator accepts the following optional arguments.
17550 @item --swi-support=@var{type}
17551 Tell the simulator which SWI interfaces to support.
17552 @var{type} may be a comma separated list of the following values.
17553 The default value is @code{all}.
17566 @subsection Renesas M32R/D and M32R/SDI
17569 @kindex target m32r
17570 @item target m32r @var{dev}
17571 Renesas M32R/D ROM monitor.
17573 @kindex target m32rsdi
17574 @item target m32rsdi @var{dev}
17575 Renesas M32R SDI server, connected via parallel port to the board.
17578 The following @value{GDBN} commands are specific to the M32R monitor:
17581 @item set download-path @var{path}
17582 @kindex set download-path
17583 @cindex find downloadable @sc{srec} files (M32R)
17584 Set the default path for finding downloadable @sc{srec} files.
17586 @item show download-path
17587 @kindex show download-path
17588 Show the default path for downloadable @sc{srec} files.
17590 @item set board-address @var{addr}
17591 @kindex set board-address
17592 @cindex M32-EVA target board address
17593 Set the IP address for the M32R-EVA target board.
17595 @item show board-address
17596 @kindex show board-address
17597 Show the current IP address of the target board.
17599 @item set server-address @var{addr}
17600 @kindex set server-address
17601 @cindex download server address (M32R)
17602 Set the IP address for the download server, which is the @value{GDBN}'s
17605 @item show server-address
17606 @kindex show server-address
17607 Display the IP address of the download server.
17609 @item upload @r{[}@var{file}@r{]}
17610 @kindex upload@r{, M32R}
17611 Upload the specified @sc{srec} @var{file} via the monitor's Ethernet
17612 upload capability. If no @var{file} argument is given, the current
17613 executable file is uploaded.
17615 @item tload @r{[}@var{file}@r{]}
17616 @kindex tload@r{, M32R}
17617 Test the @code{upload} command.
17620 The following commands are available for M32R/SDI:
17625 @cindex reset SDI connection, M32R
17626 This command resets the SDI connection.
17630 This command shows the SDI connection status.
17633 @kindex debug_chaos
17634 @cindex M32R/Chaos debugging
17635 Instructs the remote that M32R/Chaos debugging is to be used.
17637 @item use_debug_dma
17638 @kindex use_debug_dma
17639 Instructs the remote to use the DEBUG_DMA method of accessing memory.
17642 @kindex use_mon_code
17643 Instructs the remote to use the MON_CODE method of accessing memory.
17646 @kindex use_ib_break
17647 Instructs the remote to set breakpoints by IB break.
17649 @item use_dbt_break
17650 @kindex use_dbt_break
17651 Instructs the remote to set breakpoints by DBT.
17657 The Motorola m68k configuration includes ColdFire support, and a
17658 target command for the following ROM monitor.
17662 @kindex target dbug
17663 @item target dbug @var{dev}
17664 dBUG ROM monitor for Motorola ColdFire.
17669 @subsection MicroBlaze
17670 @cindex Xilinx MicroBlaze
17671 @cindex XMD, Xilinx Microprocessor Debugger
17673 The MicroBlaze is a soft-core processor supported on various Xilinx
17674 FPGAs, such as Spartan or Virtex series. Boards with these processors
17675 usually have JTAG ports which connect to a host system running the Xilinx
17676 Embedded Development Kit (EDK) or Software Development Kit (SDK).
17677 This host system is used to download the configuration bitstream to
17678 the target FPGA. The Xilinx Microprocessor Debugger (XMD) program
17679 communicates with the target board using the JTAG interface and
17680 presents a @code{gdbserver} interface to the board. By default
17681 @code{xmd} uses port @code{1234}. (While it is possible to change
17682 this default port, it requires the use of undocumented @code{xmd}
17683 commands. Contact Xilinx support if you need to do this.)
17685 Use these GDB commands to connect to the MicroBlaze target processor.
17688 @item target remote :1234
17689 Use this command to connect to the target if you are running @value{GDBN}
17690 on the same system as @code{xmd}.
17692 @item target remote @var{xmd-host}:1234
17693 Use this command to connect to the target if it is connected to @code{xmd}
17694 running on a different system named @var{xmd-host}.
17697 Use this command to download a program to the MicroBlaze target.
17699 @item set debug microblaze @var{n}
17700 Enable MicroBlaze-specific debugging messages if non-zero.
17702 @item show debug microblaze @var{n}
17703 Show MicroBlaze-specific debugging level.
17706 @node MIPS Embedded
17707 @subsection MIPS Embedded
17709 @cindex MIPS boards
17710 @value{GDBN} can use the MIPS remote debugging protocol to talk to a
17711 MIPS board attached to a serial line. This is available when
17712 you configure @value{GDBN} with @samp{--target=mips-idt-ecoff}.
17715 Use these @value{GDBN} commands to specify the connection to your target board:
17718 @item target mips @var{port}
17719 @kindex target mips @var{port}
17720 To run a program on the board, start up @code{@value{GDBP}} with the
17721 name of your program as the argument. To connect to the board, use the
17722 command @samp{target mips @var{port}}, where @var{port} is the name of
17723 the serial port connected to the board. If the program has not already
17724 been downloaded to the board, you may use the @code{load} command to
17725 download it. You can then use all the usual @value{GDBN} commands.
17727 For example, this sequence connects to the target board through a serial
17728 port, and loads and runs a program called @var{prog} through the
17732 host$ @value{GDBP} @var{prog}
17733 @value{GDBN} is free software and @dots{}
17734 (@value{GDBP}) target mips /dev/ttyb
17735 (@value{GDBP}) load @var{prog}
17739 @item target mips @var{hostname}:@var{portnumber}
17740 On some @value{GDBN} host configurations, you can specify a TCP
17741 connection (for instance, to a serial line managed by a terminal
17742 concentrator) instead of a serial port, using the syntax
17743 @samp{@var{hostname}:@var{portnumber}}.
17745 @item target pmon @var{port}
17746 @kindex target pmon @var{port}
17749 @item target ddb @var{port}
17750 @kindex target ddb @var{port}
17751 NEC's DDB variant of PMON for Vr4300.
17753 @item target lsi @var{port}
17754 @kindex target lsi @var{port}
17755 LSI variant of PMON.
17757 @kindex target r3900
17758 @item target r3900 @var{dev}
17759 Densan DVE-R3900 ROM monitor for Toshiba R3900 Mips.
17761 @kindex target array
17762 @item target array @var{dev}
17763 Array Tech LSI33K RAID controller board.
17769 @value{GDBN} also supports these special commands for MIPS targets:
17772 @item set mipsfpu double
17773 @itemx set mipsfpu single
17774 @itemx set mipsfpu none
17775 @itemx set mipsfpu auto
17776 @itemx show mipsfpu
17777 @kindex set mipsfpu
17778 @kindex show mipsfpu
17779 @cindex MIPS remote floating point
17780 @cindex floating point, MIPS remote
17781 If your target board does not support the MIPS floating point
17782 coprocessor, you should use the command @samp{set mipsfpu none} (if you
17783 need this, you may wish to put the command in your @value{GDBN} init
17784 file). This tells @value{GDBN} how to find the return value of
17785 functions which return floating point values. It also allows
17786 @value{GDBN} to avoid saving the floating point registers when calling
17787 functions on the board. If you are using a floating point coprocessor
17788 with only single precision floating point support, as on the @sc{r4650}
17789 processor, use the command @samp{set mipsfpu single}. The default
17790 double precision floating point coprocessor may be selected using
17791 @samp{set mipsfpu double}.
17793 In previous versions the only choices were double precision or no
17794 floating point, so @samp{set mipsfpu on} will select double precision
17795 and @samp{set mipsfpu off} will select no floating point.
17797 As usual, you can inquire about the @code{mipsfpu} variable with
17798 @samp{show mipsfpu}.
17800 @item set timeout @var{seconds}
17801 @itemx set retransmit-timeout @var{seconds}
17802 @itemx show timeout
17803 @itemx show retransmit-timeout
17804 @cindex @code{timeout}, MIPS protocol
17805 @cindex @code{retransmit-timeout}, MIPS protocol
17806 @kindex set timeout
17807 @kindex show timeout
17808 @kindex set retransmit-timeout
17809 @kindex show retransmit-timeout
17810 You can control the timeout used while waiting for a packet, in the MIPS
17811 remote protocol, with the @code{set timeout @var{seconds}} command. The
17812 default is 5 seconds. Similarly, you can control the timeout used while
17813 waiting for an acknowledgment of a packet with the @code{set
17814 retransmit-timeout @var{seconds}} command. The default is 3 seconds.
17815 You can inspect both values with @code{show timeout} and @code{show
17816 retransmit-timeout}. (These commands are @emph{only} available when
17817 @value{GDBN} is configured for @samp{--target=mips-idt-ecoff}.)
17819 The timeout set by @code{set timeout} does not apply when @value{GDBN}
17820 is waiting for your program to stop. In that case, @value{GDBN} waits
17821 forever because it has no way of knowing how long the program is going
17822 to run before stopping.
17824 @item set syn-garbage-limit @var{num}
17825 @kindex set syn-garbage-limit@r{, MIPS remote}
17826 @cindex synchronize with remote MIPS target
17827 Limit the maximum number of characters @value{GDBN} should ignore when
17828 it tries to synchronize with the remote target. The default is 10
17829 characters. Setting the limit to -1 means there's no limit.
17831 @item show syn-garbage-limit
17832 @kindex show syn-garbage-limit@r{, MIPS remote}
17833 Show the current limit on the number of characters to ignore when
17834 trying to synchronize with the remote system.
17836 @item set monitor-prompt @var{prompt}
17837 @kindex set monitor-prompt@r{, MIPS remote}
17838 @cindex remote monitor prompt
17839 Tell @value{GDBN} to expect the specified @var{prompt} string from the
17840 remote monitor. The default depends on the target:
17850 @item show monitor-prompt
17851 @kindex show monitor-prompt@r{, MIPS remote}
17852 Show the current strings @value{GDBN} expects as the prompt from the
17855 @item set monitor-warnings
17856 @kindex set monitor-warnings@r{, MIPS remote}
17857 Enable or disable monitor warnings about hardware breakpoints. This
17858 has effect only for the @code{lsi} target. When on, @value{GDBN} will
17859 display warning messages whose codes are returned by the @code{lsi}
17860 PMON monitor for breakpoint commands.
17862 @item show monitor-warnings
17863 @kindex show monitor-warnings@r{, MIPS remote}
17864 Show the current setting of printing monitor warnings.
17866 @item pmon @var{command}
17867 @kindex pmon@r{, MIPS remote}
17868 @cindex send PMON command
17869 This command allows sending an arbitrary @var{command} string to the
17870 monitor. The monitor must be in debug mode for this to work.
17873 @node OpenRISC 1000
17874 @subsection OpenRISC 1000
17875 @cindex OpenRISC 1000
17877 @cindex or1k boards
17878 See OR1k Architecture document (@uref{www.opencores.org}) for more information
17879 about platform and commands.
17883 @kindex target jtag
17884 @item target jtag jtag://@var{host}:@var{port}
17886 Connects to remote JTAG server.
17887 JTAG remote server can be either an or1ksim or JTAG server,
17888 connected via parallel port to the board.
17890 Example: @code{target jtag jtag://localhost:9999}
17893 @item or1ksim @var{command}
17894 If connected to @code{or1ksim} OpenRISC 1000 Architectural
17895 Simulator, proprietary commands can be executed.
17897 @kindex info or1k spr
17898 @item info or1k spr
17899 Displays spr groups.
17901 @item info or1k spr @var{group}
17902 @itemx info or1k spr @var{groupno}
17903 Displays register names in selected group.
17905 @item info or1k spr @var{group} @var{register}
17906 @itemx info or1k spr @var{register}
17907 @itemx info or1k spr @var{groupno} @var{registerno}
17908 @itemx info or1k spr @var{registerno}
17909 Shows information about specified spr register.
17912 @item spr @var{group} @var{register} @var{value}
17913 @itemx spr @var{register @var{value}}
17914 @itemx spr @var{groupno} @var{registerno @var{value}}
17915 @itemx spr @var{registerno @var{value}}
17916 Writes @var{value} to specified spr register.
17919 Some implementations of OpenRISC 1000 Architecture also have hardware trace.
17920 It is very similar to @value{GDBN} trace, except it does not interfere with normal
17921 program execution and is thus much faster. Hardware breakpoints/watchpoint
17922 triggers can be set using:
17925 Load effective address/data
17927 Store effective address/data
17929 Access effective address ($SEA or $LEA) or data ($SDATA/$LDATA)
17934 When triggered, it can capture low level data, like: @code{PC}, @code{LSEA},
17935 @code{LDATA}, @code{SDATA}, @code{READSPR}, @code{WRITESPR}, @code{INSTR}.
17937 @code{htrace} commands:
17938 @cindex OpenRISC 1000 htrace
17941 @item hwatch @var{conditional}
17942 Set hardware watchpoint on combination of Load/Store Effective Address(es)
17943 or Data. For example:
17945 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
17947 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
17951 Display information about current HW trace configuration.
17953 @item htrace trigger @var{conditional}
17954 Set starting criteria for HW trace.
17956 @item htrace qualifier @var{conditional}
17957 Set acquisition qualifier for HW trace.
17959 @item htrace stop @var{conditional}
17960 Set HW trace stopping criteria.
17962 @item htrace record [@var{data}]*
17963 Selects the data to be recorded, when qualifier is met and HW trace was
17966 @item htrace enable
17967 @itemx htrace disable
17968 Enables/disables the HW trace.
17970 @item htrace rewind [@var{filename}]
17971 Clears currently recorded trace data.
17973 If filename is specified, new trace file is made and any newly collected data
17974 will be written there.
17976 @item htrace print [@var{start} [@var{len}]]
17977 Prints trace buffer, using current record configuration.
17979 @item htrace mode continuous
17980 Set continuous trace mode.
17982 @item htrace mode suspend
17983 Set suspend trace mode.
17987 @node PowerPC Embedded
17988 @subsection PowerPC Embedded
17990 @value{GDBN} provides the following PowerPC-specific commands:
17993 @kindex set powerpc
17994 @item set powerpc soft-float
17995 @itemx show powerpc soft-float
17996 Force @value{GDBN} to use (or not use) a software floating point calling
17997 convention. By default, @value{GDBN} selects the calling convention based
17998 on the selected architecture and the provided executable file.
18000 @item set powerpc vector-abi
18001 @itemx show powerpc vector-abi
18002 Force @value{GDBN} to use the specified calling convention for vector
18003 arguments and return values. The valid options are @samp{auto};
18004 @samp{generic}, to avoid vector registers even if they are present;
18005 @samp{altivec}, to use AltiVec registers; and @samp{spe} to use SPE
18006 registers. By default, @value{GDBN} selects the calling convention
18007 based on the selected architecture and the provided executable file.
18009 @kindex target dink32
18010 @item target dink32 @var{dev}
18011 DINK32 ROM monitor.
18013 @kindex target ppcbug
18014 @item target ppcbug @var{dev}
18015 @kindex target ppcbug1
18016 @item target ppcbug1 @var{dev}
18017 PPCBUG ROM monitor for PowerPC.
18020 @item target sds @var{dev}
18021 SDS monitor, running on a PowerPC board (such as Motorola's ADS).
18024 @cindex SDS protocol
18025 The following commands specific to the SDS protocol are supported
18029 @item set sdstimeout @var{nsec}
18030 @kindex set sdstimeout
18031 Set the timeout for SDS protocol reads to be @var{nsec} seconds. The
18032 default is 2 seconds.
18034 @item show sdstimeout
18035 @kindex show sdstimeout
18036 Show the current value of the SDS timeout.
18038 @item sds @var{command}
18039 @kindex sds@r{, a command}
18040 Send the specified @var{command} string to the SDS monitor.
18045 @subsection HP PA Embedded
18049 @kindex target op50n
18050 @item target op50n @var{dev}
18051 OP50N monitor, running on an OKI HPPA board.
18053 @kindex target w89k
18054 @item target w89k @var{dev}
18055 W89K monitor, running on a Winbond HPPA board.
18060 @subsection Tsqware Sparclet
18064 @value{GDBN} enables developers to debug tasks running on
18065 Sparclet targets from a Unix host.
18066 @value{GDBN} uses code that runs on
18067 both the Unix host and on the Sparclet target. The program
18068 @code{@value{GDBP}} is installed and executed on the Unix host.
18071 @item remotetimeout @var{args}
18072 @kindex remotetimeout
18073 @value{GDBN} supports the option @code{remotetimeout}.
18074 This option is set by the user, and @var{args} represents the number of
18075 seconds @value{GDBN} waits for responses.
18078 @cindex compiling, on Sparclet
18079 When compiling for debugging, include the options @samp{-g} to get debug
18080 information and @samp{-Ttext} to relocate the program to where you wish to
18081 load it on the target. You may also want to add the options @samp{-n} or
18082 @samp{-N} in order to reduce the size of the sections. Example:
18085 sparclet-aout-gcc prog.c -Ttext 0x12010000 -g -o prog -N
18088 You can use @code{objdump} to verify that the addresses are what you intended:
18091 sparclet-aout-objdump --headers --syms prog
18094 @cindex running, on Sparclet
18096 your Unix execution search path to find @value{GDBN}, you are ready to
18097 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}}
18098 (or @code{sparclet-aout-gdb}, depending on your installation).
18100 @value{GDBN} comes up showing the prompt:
18107 * Sparclet File:: Setting the file to debug
18108 * Sparclet Connection:: Connecting to Sparclet
18109 * Sparclet Download:: Sparclet download
18110 * Sparclet Execution:: Running and debugging
18113 @node Sparclet File
18114 @subsubsection Setting File to Debug
18116 The @value{GDBN} command @code{file} lets you choose with program to debug.
18119 (gdbslet) file prog
18123 @value{GDBN} then attempts to read the symbol table of @file{prog}.
18124 @value{GDBN} locates
18125 the file by searching the directories listed in the command search
18127 If the file was compiled with debug information (option @samp{-g}), source
18128 files will be searched as well.
18129 @value{GDBN} locates
18130 the source files by searching the directories listed in the directory search
18131 path (@pxref{Environment, ,Your Program's Environment}).
18133 to find a file, it displays a message such as:
18136 prog: No such file or directory.
18139 When this happens, add the appropriate directories to the search paths with
18140 the @value{GDBN} commands @code{path} and @code{dir}, and execute the
18141 @code{target} command again.
18143 @node Sparclet Connection
18144 @subsubsection Connecting to Sparclet
18146 The @value{GDBN} command @code{target} lets you connect to a Sparclet target.
18147 To connect to a target on serial port ``@code{ttya}'', type:
18150 (gdbslet) target sparclet /dev/ttya
18151 Remote target sparclet connected to /dev/ttya
18152 main () at ../prog.c:3
18156 @value{GDBN} displays messages like these:
18162 @node Sparclet Download
18163 @subsubsection Sparclet Download
18165 @cindex download to Sparclet
18166 Once connected to the Sparclet target,
18167 you can use the @value{GDBN}
18168 @code{load} command to download the file from the host to the target.
18169 The file name and load offset should be given as arguments to the @code{load}
18171 Since the file format is aout, the program must be loaded to the starting
18172 address. You can use @code{objdump} to find out what this value is. The load
18173 offset is an offset which is added to the VMA (virtual memory address)
18174 of each of the file's sections.
18175 For instance, if the program
18176 @file{prog} was linked to text address 0x1201000, with data at 0x12010160
18177 and bss at 0x12010170, in @value{GDBN}, type:
18180 (gdbslet) load prog 0x12010000
18181 Loading section .text, size 0xdb0 vma 0x12010000
18184 If the code is loaded at a different address then what the program was linked
18185 to, you may need to use the @code{section} and @code{add-symbol-file} commands
18186 to tell @value{GDBN} where to map the symbol table.
18188 @node Sparclet Execution
18189 @subsubsection Running and Debugging
18191 @cindex running and debugging Sparclet programs
18192 You can now begin debugging the task using @value{GDBN}'s execution control
18193 commands, @code{b}, @code{step}, @code{run}, etc. See the @value{GDBN}
18194 manual for the list of commands.
18198 Breakpoint 1 at 0x12010000: file prog.c, line 3.
18200 Starting program: prog
18201 Breakpoint 1, main (argc=1, argv=0xeffff21c) at prog.c:3
18202 3 char *symarg = 0;
18204 4 char *execarg = "hello!";
18209 @subsection Fujitsu Sparclite
18213 @kindex target sparclite
18214 @item target sparclite @var{dev}
18215 Fujitsu sparclite boards, used only for the purpose of loading.
18216 You must use an additional command to debug the program.
18217 For example: target remote @var{dev} using @value{GDBN} standard
18223 @subsection Zilog Z8000
18226 @cindex simulator, Z8000
18227 @cindex Zilog Z8000 simulator
18229 When configured for debugging Zilog Z8000 targets, @value{GDBN} includes
18232 For the Z8000 family, @samp{target sim} simulates either the Z8002 (the
18233 unsegmented variant of the Z8000 architecture) or the Z8001 (the
18234 segmented variant). The simulator recognizes which architecture is
18235 appropriate by inspecting the object code.
18238 @item target sim @var{args}
18240 @kindex target sim@r{, with Z8000}
18241 Debug programs on a simulated CPU. If the simulator supports setup
18242 options, specify them via @var{args}.
18246 After specifying this target, you can debug programs for the simulated
18247 CPU in the same style as programs for your host computer; use the
18248 @code{file} command to load a new program image, the @code{run} command
18249 to run your program, and so on.
18251 As well as making available all the usual machine registers
18252 (@pxref{Registers, ,Registers}), the Z8000 simulator provides three
18253 additional items of information as specially named registers:
18258 Counts clock-ticks in the simulator.
18261 Counts instructions run in the simulator.
18264 Execution time in 60ths of a second.
18268 You can refer to these values in @value{GDBN} expressions with the usual
18269 conventions; for example, @w{@samp{b fputc if $cycles>5000}} sets a
18270 conditional breakpoint that suspends only after at least 5000
18271 simulated clock ticks.
18274 @subsection Atmel AVR
18277 When configured for debugging the Atmel AVR, @value{GDBN} supports the
18278 following AVR-specific commands:
18281 @item info io_registers
18282 @kindex info io_registers@r{, AVR}
18283 @cindex I/O registers (Atmel AVR)
18284 This command displays information about the AVR I/O registers. For
18285 each register, @value{GDBN} prints its number and value.
18292 When configured for debugging CRIS, @value{GDBN} provides the
18293 following CRIS-specific commands:
18296 @item set cris-version @var{ver}
18297 @cindex CRIS version
18298 Set the current CRIS version to @var{ver}, either @samp{10} or @samp{32}.
18299 The CRIS version affects register names and sizes. This command is useful in
18300 case autodetection of the CRIS version fails.
18302 @item show cris-version
18303 Show the current CRIS version.
18305 @item set cris-dwarf2-cfi
18306 @cindex DWARF-2 CFI and CRIS
18307 Set the usage of DWARF-2 CFI for CRIS debugging. The default is @samp{on}.
18308 Change to @samp{off} when using @code{gcc-cris} whose version is below
18311 @item show cris-dwarf2-cfi
18312 Show the current state of using DWARF-2 CFI.
18314 @item set cris-mode @var{mode}
18316 Set the current CRIS mode to @var{mode}. It should only be changed when
18317 debugging in guru mode, in which case it should be set to
18318 @samp{guru} (the default is @samp{normal}).
18320 @item show cris-mode
18321 Show the current CRIS mode.
18325 @subsection Renesas Super-H
18328 For the Renesas Super-H processor, @value{GDBN} provides these
18333 @kindex regs@r{, Super-H}
18334 Show the values of all Super-H registers.
18336 @item set sh calling-convention @var{convention}
18337 @kindex set sh calling-convention
18338 Set the calling-convention used when calling functions from @value{GDBN}.
18339 Allowed values are @samp{gcc}, which is the default setting, and @samp{renesas}.
18340 With the @samp{gcc} setting, functions are called using the @value{NGCC} calling
18341 convention. If the DWARF-2 information of the called function specifies
18342 that the function follows the Renesas calling convention, the function
18343 is called using the Renesas calling convention. If the calling convention
18344 is set to @samp{renesas}, the Renesas calling convention is always used,
18345 regardless of the DWARF-2 information. This can be used to override the
18346 default of @samp{gcc} if debug information is missing, or the compiler
18347 does not emit the DWARF-2 calling convention entry for a function.
18349 @item show sh calling-convention
18350 @kindex show sh calling-convention
18351 Show the current calling convention setting.
18356 @node Architectures
18357 @section Architectures
18359 This section describes characteristics of architectures that affect
18360 all uses of @value{GDBN} with the architecture, both native and cross.
18367 * HPPA:: HP PA architecture
18368 * SPU:: Cell Broadband Engine SPU architecture
18373 @subsection x86 Architecture-specific Issues
18376 @item set struct-convention @var{mode}
18377 @kindex set struct-convention
18378 @cindex struct return convention
18379 @cindex struct/union returned in registers
18380 Set the convention used by the inferior to return @code{struct}s and
18381 @code{union}s from functions to @var{mode}. Possible values of
18382 @var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the
18383 default). @code{"default"} or @code{"pcc"} means that @code{struct}s
18384 are returned on the stack, while @code{"reg"} means that a
18385 @code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will
18386 be returned in a register.
18388 @item show struct-convention
18389 @kindex show struct-convention
18390 Show the current setting of the convention to return @code{struct}s
18399 @kindex set rstack_high_address
18400 @cindex AMD 29K register stack
18401 @cindex register stack, AMD29K
18402 @item set rstack_high_address @var{address}
18403 On AMD 29000 family processors, registers are saved in a separate
18404 @dfn{register stack}. There is no way for @value{GDBN} to determine the
18405 extent of this stack. Normally, @value{GDBN} just assumes that the
18406 stack is ``large enough''. This may result in @value{GDBN} referencing
18407 memory locations that do not exist. If necessary, you can get around
18408 this problem by specifying the ending address of the register stack with
18409 the @code{set rstack_high_address} command. The argument should be an
18410 address, which you probably want to precede with @samp{0x} to specify in
18413 @kindex show rstack_high_address
18414 @item show rstack_high_address
18415 Display the current limit of the register stack, on AMD 29000 family
18423 See the following section.
18428 @cindex stack on Alpha
18429 @cindex stack on MIPS
18430 @cindex Alpha stack
18432 Alpha- and MIPS-based computers use an unusual stack frame, which
18433 sometimes requires @value{GDBN} to search backward in the object code to
18434 find the beginning of a function.
18436 @cindex response time, MIPS debugging
18437 To improve response time (especially for embedded applications, where
18438 @value{GDBN} may be restricted to a slow serial line for this search)
18439 you may want to limit the size of this search, using one of these
18443 @cindex @code{heuristic-fence-post} (Alpha, MIPS)
18444 @item set heuristic-fence-post @var{limit}
18445 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
18446 search for the beginning of a function. A value of @var{0} (the
18447 default) means there is no limit. However, except for @var{0}, the
18448 larger the limit the more bytes @code{heuristic-fence-post} must search
18449 and therefore the longer it takes to run. You should only need to use
18450 this command when debugging a stripped executable.
18452 @item show heuristic-fence-post
18453 Display the current limit.
18457 These commands are available @emph{only} when @value{GDBN} is configured
18458 for debugging programs on Alpha or MIPS processors.
18460 Several MIPS-specific commands are available when debugging MIPS
18464 @item set mips abi @var{arg}
18465 @kindex set mips abi
18466 @cindex set ABI for MIPS
18467 Tell @value{GDBN} which MIPS ABI is used by the inferior. Possible
18468 values of @var{arg} are:
18472 The default ABI associated with the current binary (this is the
18483 @item show mips abi
18484 @kindex show mips abi
18485 Show the MIPS ABI used by @value{GDBN} to debug the inferior.
18488 @itemx show mipsfpu
18489 @xref{MIPS Embedded, set mipsfpu}.
18491 @item set mips mask-address @var{arg}
18492 @kindex set mips mask-address
18493 @cindex MIPS addresses, masking
18494 This command determines whether the most-significant 32 bits of 64-bit
18495 MIPS addresses are masked off. The argument @var{arg} can be
18496 @samp{on}, @samp{off}, or @samp{auto}. The latter is the default
18497 setting, which lets @value{GDBN} determine the correct value.
18499 @item show mips mask-address
18500 @kindex show mips mask-address
18501 Show whether the upper 32 bits of MIPS addresses are masked off or
18504 @item set remote-mips64-transfers-32bit-regs
18505 @kindex set remote-mips64-transfers-32bit-regs
18506 This command controls compatibility with 64-bit MIPS targets that
18507 transfer data in 32-bit quantities. If you have an old MIPS 64 target
18508 that transfers 32 bits for some registers, like @sc{sr} and @sc{fsr},
18509 and 64 bits for other registers, set this option to @samp{on}.
18511 @item show remote-mips64-transfers-32bit-regs
18512 @kindex show remote-mips64-transfers-32bit-regs
18513 Show the current setting of compatibility with older MIPS 64 targets.
18515 @item set debug mips
18516 @kindex set debug mips
18517 This command turns on and off debugging messages for the MIPS-specific
18518 target code in @value{GDBN}.
18520 @item show debug mips
18521 @kindex show debug mips
18522 Show the current setting of MIPS debugging messages.
18528 @cindex HPPA support
18530 When @value{GDBN} is debugging the HP PA architecture, it provides the
18531 following special commands:
18534 @item set debug hppa
18535 @kindex set debug hppa
18536 This command determines whether HPPA architecture-specific debugging
18537 messages are to be displayed.
18539 @item show debug hppa
18540 Show whether HPPA debugging messages are displayed.
18542 @item maint print unwind @var{address}
18543 @kindex maint print unwind@r{, HPPA}
18544 This command displays the contents of the unwind table entry at the
18545 given @var{address}.
18551 @subsection Cell Broadband Engine SPU architecture
18552 @cindex Cell Broadband Engine
18555 When @value{GDBN} is debugging the Cell Broadband Engine SPU architecture,
18556 it provides the following special commands:
18559 @item info spu event
18561 Display SPU event facility status. Shows current event mask
18562 and pending event status.
18564 @item info spu signal
18565 Display SPU signal notification facility status. Shows pending
18566 signal-control word and signal notification mode of both signal
18567 notification channels.
18569 @item info spu mailbox
18570 Display SPU mailbox facility status. Shows all pending entries,
18571 in order of processing, in each of the SPU Write Outbound,
18572 SPU Write Outbound Interrupt, and SPU Read Inbound mailboxes.
18575 Display MFC DMA status. Shows all pending commands in the MFC
18576 DMA queue. For each entry, opcode, tag, class IDs, effective
18577 and local store addresses and transfer size are shown.
18579 @item info spu proxydma
18580 Display MFC Proxy-DMA status. Shows all pending commands in the MFC
18581 Proxy-DMA queue. For each entry, opcode, tag, class IDs, effective
18582 and local store addresses and transfer size are shown.
18586 When @value{GDBN} is debugging a combined PowerPC/SPU application
18587 on the Cell Broadband Engine, it provides in addition the following
18591 @item set spu stop-on-load @var{arg}
18593 Set whether to stop for new SPE threads. When set to @code{on}, @value{GDBN}
18594 will give control to the user when a new SPE thread enters its @code{main}
18595 function. The default is @code{off}.
18597 @item show spu stop-on-load
18599 Show whether to stop for new SPE threads.
18601 @item set spu auto-flush-cache @var{arg}
18602 Set whether to automatically flush the software-managed cache. When set to
18603 @code{on}, @value{GDBN} will automatically cause the SPE software-managed
18604 cache to be flushed whenever SPE execution stops. This provides a consistent
18605 view of PowerPC memory that is accessed via the cache. If an application
18606 does not use the software-managed cache, this option has no effect.
18608 @item show spu auto-flush-cache
18609 Show whether to automatically flush the software-managed cache.
18614 @subsection PowerPC
18615 @cindex PowerPC architecture
18617 When @value{GDBN} is debugging the PowerPC architecture, it provides a set of
18618 pseudo-registers to enable inspection of 128-bit wide Decimal Floating Point
18619 numbers stored in the floating point registers. These values must be stored
18620 in two consecutive registers, always starting at an even register like
18621 @code{f0} or @code{f2}.
18623 The pseudo-registers go from @code{$dl0} through @code{$dl15}, and are formed
18624 by joining the even/odd register pairs @code{f0} and @code{f1} for @code{$dl0},
18625 @code{f2} and @code{f3} for @code{$dl1} and so on.
18627 For POWER7 processors, @value{GDBN} provides a set of pseudo-registers, the 64-bit
18628 wide Extended Floating Point Registers (@samp{f32} through @samp{f63}).
18631 @node Controlling GDB
18632 @chapter Controlling @value{GDBN}
18634 You can alter the way @value{GDBN} interacts with you by using the
18635 @code{set} command. For commands controlling how @value{GDBN} displays
18636 data, see @ref{Print Settings, ,Print Settings}. Other settings are
18641 * Editing:: Command editing
18642 * Command History:: Command history
18643 * Screen Size:: Screen size
18644 * Numbers:: Numbers
18645 * ABI:: Configuring the current ABI
18646 * Messages/Warnings:: Optional warnings and messages
18647 * Debugging Output:: Optional messages about internal happenings
18648 * Other Misc Settings:: Other Miscellaneous Settings
18656 @value{GDBN} indicates its readiness to read a command by printing a string
18657 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
18658 can change the prompt string with the @code{set prompt} command. For
18659 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
18660 the prompt in one of the @value{GDBN} sessions so that you can always tell
18661 which one you are talking to.
18663 @emph{Note:} @code{set prompt} does not add a space for you after the
18664 prompt you set. This allows you to set a prompt which ends in a space
18665 or a prompt that does not.
18669 @item set prompt @var{newprompt}
18670 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
18672 @kindex show prompt
18674 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
18678 @section Command Editing
18680 @cindex command line editing
18682 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
18683 @sc{gnu} library provides consistent behavior for programs which provide a
18684 command line interface to the user. Advantages are @sc{gnu} Emacs-style
18685 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
18686 substitution, and a storage and recall of command history across
18687 debugging sessions.
18689 You may control the behavior of command line editing in @value{GDBN} with the
18690 command @code{set}.
18693 @kindex set editing
18696 @itemx set editing on
18697 Enable command line editing (enabled by default).
18699 @item set editing off
18700 Disable command line editing.
18702 @kindex show editing
18704 Show whether command line editing is enabled.
18707 @xref{Command Line Editing}, for more details about the Readline
18708 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
18709 encouraged to read that chapter.
18711 @node Command History
18712 @section Command History
18713 @cindex command history
18715 @value{GDBN} can keep track of the commands you type during your
18716 debugging sessions, so that you can be certain of precisely what
18717 happened. Use these commands to manage the @value{GDBN} command
18720 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
18721 package, to provide the history facility. @xref{Using History
18722 Interactively}, for the detailed description of the History library.
18724 To issue a command to @value{GDBN} without affecting certain aspects of
18725 the state which is seen by users, prefix it with @samp{server }
18726 (@pxref{Server Prefix}). This
18727 means that this command will not affect the command history, nor will it
18728 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
18729 pressed on a line by itself.
18731 @cindex @code{server}, command prefix
18732 The server prefix does not affect the recording of values into the value
18733 history; to print a value without recording it into the value history,
18734 use the @code{output} command instead of the @code{print} command.
18736 Here is the description of @value{GDBN} commands related to command
18740 @cindex history substitution
18741 @cindex history file
18742 @kindex set history filename
18743 @cindex @env{GDBHISTFILE}, environment variable
18744 @item set history filename @var{fname}
18745 Set the name of the @value{GDBN} command history file to @var{fname}.
18746 This is the file where @value{GDBN} reads an initial command history
18747 list, and where it writes the command history from this session when it
18748 exits. You can access this list through history expansion or through
18749 the history command editing characters listed below. This file defaults
18750 to the value of the environment variable @code{GDBHISTFILE}, or to
18751 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
18754 @cindex save command history
18755 @kindex set history save
18756 @item set history save
18757 @itemx set history save on
18758 Record command history in a file, whose name may be specified with the
18759 @code{set history filename} command. By default, this option is disabled.
18761 @item set history save off
18762 Stop recording command history in a file.
18764 @cindex history size
18765 @kindex set history size
18766 @cindex @env{HISTSIZE}, environment variable
18767 @item set history size @var{size}
18768 Set the number of commands which @value{GDBN} keeps in its history list.
18769 This defaults to the value of the environment variable
18770 @code{HISTSIZE}, or to 256 if this variable is not set.
18773 History expansion assigns special meaning to the character @kbd{!}.
18774 @xref{Event Designators}, for more details.
18776 @cindex history expansion, turn on/off
18777 Since @kbd{!} is also the logical not operator in C, history expansion
18778 is off by default. If you decide to enable history expansion with the
18779 @code{set history expansion on} command, you may sometimes need to
18780 follow @kbd{!} (when it is used as logical not, in an expression) with
18781 a space or a tab to prevent it from being expanded. The readline
18782 history facilities do not attempt substitution on the strings
18783 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
18785 The commands to control history expansion are:
18788 @item set history expansion on
18789 @itemx set history expansion
18790 @kindex set history expansion
18791 Enable history expansion. History expansion is off by default.
18793 @item set history expansion off
18794 Disable history expansion.
18797 @kindex show history
18799 @itemx show history filename
18800 @itemx show history save
18801 @itemx show history size
18802 @itemx show history expansion
18803 These commands display the state of the @value{GDBN} history parameters.
18804 @code{show history} by itself displays all four states.
18809 @kindex show commands
18810 @cindex show last commands
18811 @cindex display command history
18812 @item show commands
18813 Display the last ten commands in the command history.
18815 @item show commands @var{n}
18816 Print ten commands centered on command number @var{n}.
18818 @item show commands +
18819 Print ten commands just after the commands last printed.
18823 @section Screen Size
18824 @cindex size of screen
18825 @cindex pauses in output
18827 Certain commands to @value{GDBN} may produce large amounts of
18828 information output to the screen. To help you read all of it,
18829 @value{GDBN} pauses and asks you for input at the end of each page of
18830 output. Type @key{RET} when you want to continue the output, or @kbd{q}
18831 to discard the remaining output. Also, the screen width setting
18832 determines when to wrap lines of output. Depending on what is being
18833 printed, @value{GDBN} tries to break the line at a readable place,
18834 rather than simply letting it overflow onto the following line.
18836 Normally @value{GDBN} knows the size of the screen from the terminal
18837 driver software. For example, on Unix @value{GDBN} uses the termcap data base
18838 together with the value of the @code{TERM} environment variable and the
18839 @code{stty rows} and @code{stty cols} settings. If this is not correct,
18840 you can override it with the @code{set height} and @code{set
18847 @kindex show height
18848 @item set height @var{lpp}
18850 @itemx set width @var{cpl}
18852 These @code{set} commands specify a screen height of @var{lpp} lines and
18853 a screen width of @var{cpl} characters. The associated @code{show}
18854 commands display the current settings.
18856 If you specify a height of zero lines, @value{GDBN} does not pause during
18857 output no matter how long the output is. This is useful if output is to a
18858 file or to an editor buffer.
18860 Likewise, you can specify @samp{set width 0} to prevent @value{GDBN}
18861 from wrapping its output.
18863 @item set pagination on
18864 @itemx set pagination off
18865 @kindex set pagination
18866 Turn the output pagination on or off; the default is on. Turning
18867 pagination off is the alternative to @code{set height 0}. Note that
18868 running @value{GDBN} with the @option{--batch} option (@pxref{Mode
18869 Options, -batch}) also automatically disables pagination.
18871 @item show pagination
18872 @kindex show pagination
18873 Show the current pagination mode.
18878 @cindex number representation
18879 @cindex entering numbers
18881 You can always enter numbers in octal, decimal, or hexadecimal in
18882 @value{GDBN} by the usual conventions: octal numbers begin with
18883 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
18884 begin with @samp{0x}. Numbers that neither begin with @samp{0} or
18885 @samp{0x}, nor end with a @samp{.} are, by default, entered in base
18886 10; likewise, the default display for numbers---when no particular
18887 format is specified---is base 10. You can change the default base for
18888 both input and output with the commands described below.
18891 @kindex set input-radix
18892 @item set input-radix @var{base}
18893 Set the default base for numeric input. Supported choices
18894 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
18895 specified either unambiguously or using the current input radix; for
18899 set input-radix 012
18900 set input-radix 10.
18901 set input-radix 0xa
18905 sets the input base to decimal. On the other hand, @samp{set input-radix 10}
18906 leaves the input radix unchanged, no matter what it was, since
18907 @samp{10}, being without any leading or trailing signs of its base, is
18908 interpreted in the current radix. Thus, if the current radix is 16,
18909 @samp{10} is interpreted in hex, i.e.@: as 16 decimal, which doesn't
18912 @kindex set output-radix
18913 @item set output-radix @var{base}
18914 Set the default base for numeric display. Supported choices
18915 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
18916 specified either unambiguously or using the current input radix.
18918 @kindex show input-radix
18919 @item show input-radix
18920 Display the current default base for numeric input.
18922 @kindex show output-radix
18923 @item show output-radix
18924 Display the current default base for numeric display.
18926 @item set radix @r{[}@var{base}@r{]}
18930 These commands set and show the default base for both input and output
18931 of numbers. @code{set radix} sets the radix of input and output to
18932 the same base; without an argument, it resets the radix back to its
18933 default value of 10.
18938 @section Configuring the Current ABI
18940 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
18941 application automatically. However, sometimes you need to override its
18942 conclusions. Use these commands to manage @value{GDBN}'s view of the
18949 One @value{GDBN} configuration can debug binaries for multiple operating
18950 system targets, either via remote debugging or native emulation.
18951 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
18952 but you can override its conclusion using the @code{set osabi} command.
18953 One example where this is useful is in debugging of binaries which use
18954 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
18955 not have the same identifying marks that the standard C library for your
18960 Show the OS ABI currently in use.
18963 With no argument, show the list of registered available OS ABI's.
18965 @item set osabi @var{abi}
18966 Set the current OS ABI to @var{abi}.
18969 @cindex float promotion
18971 Generally, the way that an argument of type @code{float} is passed to a
18972 function depends on whether the function is prototyped. For a prototyped
18973 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
18974 according to the architecture's convention for @code{float}. For unprototyped
18975 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
18976 @code{double} and then passed.
18978 Unfortunately, some forms of debug information do not reliably indicate whether
18979 a function is prototyped. If @value{GDBN} calls a function that is not marked
18980 as prototyped, it consults @kbd{set coerce-float-to-double}.
18983 @kindex set coerce-float-to-double
18984 @item set coerce-float-to-double
18985 @itemx set coerce-float-to-double on
18986 Arguments of type @code{float} will be promoted to @code{double} when passed
18987 to an unprototyped function. This is the default setting.
18989 @item set coerce-float-to-double off
18990 Arguments of type @code{float} will be passed directly to unprototyped
18993 @kindex show coerce-float-to-double
18994 @item show coerce-float-to-double
18995 Show the current setting of promoting @code{float} to @code{double}.
18999 @kindex show cp-abi
19000 @value{GDBN} needs to know the ABI used for your program's C@t{++}
19001 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
19002 used to build your application. @value{GDBN} only fully supports
19003 programs with a single C@t{++} ABI; if your program contains code using
19004 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
19005 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
19006 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
19007 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
19008 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
19009 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
19014 Show the C@t{++} ABI currently in use.
19017 With no argument, show the list of supported C@t{++} ABI's.
19019 @item set cp-abi @var{abi}
19020 @itemx set cp-abi auto
19021 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
19024 @node Messages/Warnings
19025 @section Optional Warnings and Messages
19027 @cindex verbose operation
19028 @cindex optional warnings
19029 By default, @value{GDBN} is silent about its inner workings. If you are
19030 running on a slow machine, you may want to use the @code{set verbose}
19031 command. This makes @value{GDBN} tell you when it does a lengthy
19032 internal operation, so you will not think it has crashed.
19034 Currently, the messages controlled by @code{set verbose} are those
19035 which announce that the symbol table for a source file is being read;
19036 see @code{symbol-file} in @ref{Files, ,Commands to Specify Files}.
19039 @kindex set verbose
19040 @item set verbose on
19041 Enables @value{GDBN} output of certain informational messages.
19043 @item set verbose off
19044 Disables @value{GDBN} output of certain informational messages.
19046 @kindex show verbose
19048 Displays whether @code{set verbose} is on or off.
19051 By default, if @value{GDBN} encounters bugs in the symbol table of an
19052 object file, it is silent; but if you are debugging a compiler, you may
19053 find this information useful (@pxref{Symbol Errors, ,Errors Reading
19058 @kindex set complaints
19059 @item set complaints @var{limit}
19060 Permits @value{GDBN} to output @var{limit} complaints about each type of
19061 unusual symbols before becoming silent about the problem. Set
19062 @var{limit} to zero to suppress all complaints; set it to a large number
19063 to prevent complaints from being suppressed.
19065 @kindex show complaints
19066 @item show complaints
19067 Displays how many symbol complaints @value{GDBN} is permitted to produce.
19071 @anchor{confirmation requests}
19072 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
19073 lot of stupid questions to confirm certain commands. For example, if
19074 you try to run a program which is already running:
19078 The program being debugged has been started already.
19079 Start it from the beginning? (y or n)
19082 If you are willing to unflinchingly face the consequences of your own
19083 commands, you can disable this ``feature'':
19087 @kindex set confirm
19089 @cindex confirmation
19090 @cindex stupid questions
19091 @item set confirm off
19092 Disables confirmation requests. Note that running @value{GDBN} with
19093 the @option{--batch} option (@pxref{Mode Options, -batch}) also
19094 automatically disables confirmation requests.
19096 @item set confirm on
19097 Enables confirmation requests (the default).
19099 @kindex show confirm
19101 Displays state of confirmation requests.
19105 @cindex command tracing
19106 If you need to debug user-defined commands or sourced files you may find it
19107 useful to enable @dfn{command tracing}. In this mode each command will be
19108 printed as it is executed, prefixed with one or more @samp{+} symbols, the
19109 quantity denoting the call depth of each command.
19112 @kindex set trace-commands
19113 @cindex command scripts, debugging
19114 @item set trace-commands on
19115 Enable command tracing.
19116 @item set trace-commands off
19117 Disable command tracing.
19118 @item show trace-commands
19119 Display the current state of command tracing.
19122 @node Debugging Output
19123 @section Optional Messages about Internal Happenings
19124 @cindex optional debugging messages
19126 @value{GDBN} has commands that enable optional debugging messages from
19127 various @value{GDBN} subsystems; normally these commands are of
19128 interest to @value{GDBN} maintainers, or when reporting a bug. This
19129 section documents those commands.
19132 @kindex set exec-done-display
19133 @item set exec-done-display
19134 Turns on or off the notification of asynchronous commands'
19135 completion. When on, @value{GDBN} will print a message when an
19136 asynchronous command finishes its execution. The default is off.
19137 @kindex show exec-done-display
19138 @item show exec-done-display
19139 Displays the current setting of asynchronous command completion
19142 @cindex gdbarch debugging info
19143 @cindex architecture debugging info
19144 @item set debug arch
19145 Turns on or off display of gdbarch debugging info. The default is off
19147 @item show debug arch
19148 Displays the current state of displaying gdbarch debugging info.
19149 @item set debug aix-thread
19150 @cindex AIX threads
19151 Display debugging messages about inner workings of the AIX thread
19153 @item show debug aix-thread
19154 Show the current state of AIX thread debugging info display.
19155 @item set debug dwarf2-die
19156 @cindex DWARF2 DIEs
19157 Dump DWARF2 DIEs after they are read in.
19158 The value is the number of nesting levels to print.
19159 A value of zero turns off the display.
19160 @item show debug dwarf2-die
19161 Show the current state of DWARF2 DIE debugging.
19162 @item set debug displaced
19163 @cindex displaced stepping debugging info
19164 Turns on or off display of @value{GDBN} debugging info for the
19165 displaced stepping support. The default is off.
19166 @item show debug displaced
19167 Displays the current state of displaying @value{GDBN} debugging info
19168 related to displaced stepping.
19169 @item set debug event
19170 @cindex event debugging info
19171 Turns on or off display of @value{GDBN} event debugging info. The
19173 @item show debug event
19174 Displays the current state of displaying @value{GDBN} event debugging
19176 @item set debug expression
19177 @cindex expression debugging info
19178 Turns on or off display of debugging info about @value{GDBN}
19179 expression parsing. The default is off.
19180 @item show debug expression
19181 Displays the current state of displaying debugging info about
19182 @value{GDBN} expression parsing.
19183 @item set debug frame
19184 @cindex frame debugging info
19185 Turns on or off display of @value{GDBN} frame debugging info. The
19187 @item show debug frame
19188 Displays the current state of displaying @value{GDBN} frame debugging
19190 @item set debug gnu-nat
19191 @cindex @sc{gnu}/Hurd debug messages
19192 Turns on or off debugging messages from the @sc{gnu}/Hurd debug support.
19193 @item show debug gnu-nat
19194 Show the current state of @sc{gnu}/Hurd debugging messages.
19195 @item set debug infrun
19196 @cindex inferior debugging info
19197 Turns on or off display of @value{GDBN} debugging info for running the inferior.
19198 The default is off. @file{infrun.c} contains GDB's runtime state machine used
19199 for implementing operations such as single-stepping the inferior.
19200 @item show debug infrun
19201 Displays the current state of @value{GDBN} inferior debugging.
19202 @item set debug lin-lwp
19203 @cindex @sc{gnu}/Linux LWP debug messages
19204 @cindex Linux lightweight processes
19205 Turns on or off debugging messages from the Linux LWP debug support.
19206 @item show debug lin-lwp
19207 Show the current state of Linux LWP debugging messages.
19208 @item set debug lin-lwp-async
19209 @cindex @sc{gnu}/Linux LWP async debug messages
19210 @cindex Linux lightweight processes
19211 Turns on or off debugging messages from the Linux LWP async debug support.
19212 @item show debug lin-lwp-async
19213 Show the current state of Linux LWP async debugging messages.
19214 @item set debug observer
19215 @cindex observer debugging info
19216 Turns on or off display of @value{GDBN} observer debugging. This
19217 includes info such as the notification of observable events.
19218 @item show debug observer
19219 Displays the current state of observer debugging.
19220 @item set debug overload
19221 @cindex C@t{++} overload debugging info
19222 Turns on or off display of @value{GDBN} C@t{++} overload debugging
19223 info. This includes info such as ranking of functions, etc. The default
19225 @item show debug overload
19226 Displays the current state of displaying @value{GDBN} C@t{++} overload
19228 @cindex expression parser, debugging info
19229 @cindex debug expression parser
19230 @item set debug parser
19231 Turns on or off the display of expression parser debugging output.
19232 Internally, this sets the @code{yydebug} variable in the expression
19233 parser. @xref{Tracing, , Tracing Your Parser, bison, Bison}, for
19234 details. The default is off.
19235 @item show debug parser
19236 Show the current state of expression parser debugging.
19237 @cindex packets, reporting on stdout
19238 @cindex serial connections, debugging
19239 @cindex debug remote protocol
19240 @cindex remote protocol debugging
19241 @cindex display remote packets
19242 @item set debug remote
19243 Turns on or off display of reports on all packets sent back and forth across
19244 the serial line to the remote machine. The info is printed on the
19245 @value{GDBN} standard output stream. The default is off.
19246 @item show debug remote
19247 Displays the state of display of remote packets.
19248 @item set debug serial
19249 Turns on or off display of @value{GDBN} serial debugging info. The
19251 @item show debug serial
19252 Displays the current state of displaying @value{GDBN} serial debugging
19254 @item set debug solib-frv
19255 @cindex FR-V shared-library debugging
19256 Turns on or off debugging messages for FR-V shared-library code.
19257 @item show debug solib-frv
19258 Display the current state of FR-V shared-library code debugging
19260 @item set debug target
19261 @cindex target debugging info
19262 Turns on or off display of @value{GDBN} target debugging info. This info
19263 includes what is going on at the target level of GDB, as it happens. The
19264 default is 0. Set it to 1 to track events, and to 2 to also track the
19265 value of large memory transfers. Changes to this flag do not take effect
19266 until the next time you connect to a target or use the @code{run} command.
19267 @item show debug target
19268 Displays the current state of displaying @value{GDBN} target debugging
19270 @item set debug timestamp
19271 @cindex timestampping debugging info
19272 Turns on or off display of timestamps with @value{GDBN} debugging info.
19273 When enabled, seconds and microseconds are displayed before each debugging
19275 @item show debug timestamp
19276 Displays the current state of displaying timestamps with @value{GDBN}
19278 @item set debugvarobj
19279 @cindex variable object debugging info
19280 Turns on or off display of @value{GDBN} variable object debugging
19281 info. The default is off.
19282 @item show debugvarobj
19283 Displays the current state of displaying @value{GDBN} variable object
19285 @item set debug xml
19286 @cindex XML parser debugging
19287 Turns on or off debugging messages for built-in XML parsers.
19288 @item show debug xml
19289 Displays the current state of XML debugging messages.
19292 @node Other Misc Settings
19293 @section Other Miscellaneous Settings
19294 @cindex miscellaneous settings
19297 @kindex set interactive-mode
19298 @item set interactive-mode
19299 If @code{on}, forces @value{GDBN} to operate interactively.
19300 If @code{off}, forces @value{GDBN} to operate non-interactively,
19301 If @code{auto} (the default), @value{GDBN} guesses which mode to use,
19302 based on whether the debugger was started in a terminal or not.
19304 In the vast majority of cases, the debugger should be able to guess
19305 correctly which mode should be used. But this setting can be useful
19306 in certain specific cases, such as running a MinGW @value{GDBN}
19307 inside a cygwin window.
19309 @kindex show interactive-mode
19310 @item show interactive-mode
19311 Displays whether the debugger is operating in interactive mode or not.
19314 @node Extending GDB
19315 @chapter Extending @value{GDBN}
19316 @cindex extending GDB
19318 @value{GDBN} provides two mechanisms for extension. The first is based
19319 on composition of @value{GDBN} commands, and the second is based on the
19320 Python scripting language.
19322 To facilitate the use of these extensions, @value{GDBN} is capable
19323 of evaluating the contents of a file. When doing so, @value{GDBN}
19324 can recognize which scripting language is being used by looking at
19325 the filename extension. Files with an unrecognized filename extension
19326 are always treated as a @value{GDBN} Command Files.
19327 @xref{Command Files,, Command files}.
19329 You can control how @value{GDBN} evaluates these files with the following
19333 @kindex set script-extension
19334 @kindex show script-extension
19335 @item set script-extension off
19336 All scripts are always evaluated as @value{GDBN} Command Files.
19338 @item set script-extension soft
19339 The debugger determines the scripting language based on filename
19340 extension. If this scripting language is supported, @value{GDBN}
19341 evaluates the script using that language. Otherwise, it evaluates
19342 the file as a @value{GDBN} Command File.
19344 @item set script-extension strict
19345 The debugger determines the scripting language based on filename
19346 extension, and evaluates the script using that language. If the
19347 language is not supported, then the evaluation fails.
19349 @item show script-extension
19350 Display the current value of the @code{script-extension} option.
19355 * Sequences:: Canned Sequences of Commands
19356 * Python:: Scripting @value{GDBN} using Python
19360 @section Canned Sequences of Commands
19362 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
19363 Command Lists}), @value{GDBN} provides two ways to store sequences of
19364 commands for execution as a unit: user-defined commands and command
19368 * Define:: How to define your own commands
19369 * Hooks:: Hooks for user-defined commands
19370 * Command Files:: How to write scripts of commands to be stored in a file
19371 * Output:: Commands for controlled output
19375 @subsection User-defined Commands
19377 @cindex user-defined command
19378 @cindex arguments, to user-defined commands
19379 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
19380 which you assign a new name as a command. This is done with the
19381 @code{define} command. User commands may accept up to 10 arguments
19382 separated by whitespace. Arguments are accessed within the user command
19383 via @code{$arg0@dots{}$arg9}. A trivial example:
19387 print $arg0 + $arg1 + $arg2
19392 To execute the command use:
19399 This defines the command @code{adder}, which prints the sum of
19400 its three arguments. Note the arguments are text substitutions, so they may
19401 reference variables, use complex expressions, or even perform inferior
19404 @cindex argument count in user-defined commands
19405 @cindex how many arguments (user-defined commands)
19406 In addition, @code{$argc} may be used to find out how many arguments have
19407 been passed. This expands to a number in the range 0@dots{}10.
19412 print $arg0 + $arg1
19415 print $arg0 + $arg1 + $arg2
19423 @item define @var{commandname}
19424 Define a command named @var{commandname}. If there is already a command
19425 by that name, you are asked to confirm that you want to redefine it.
19426 @var{commandname} may be a bare command name consisting of letters,
19427 numbers, dashes, and underscores. It may also start with any predefined
19428 prefix command. For example, @samp{define target my-target} creates
19429 a user-defined @samp{target my-target} command.
19431 The definition of the command is made up of other @value{GDBN} command lines,
19432 which are given following the @code{define} command. The end of these
19433 commands is marked by a line containing @code{end}.
19436 @kindex end@r{ (user-defined commands)}
19437 @item document @var{commandname}
19438 Document the user-defined command @var{commandname}, so that it can be
19439 accessed by @code{help}. The command @var{commandname} must already be
19440 defined. This command reads lines of documentation just as @code{define}
19441 reads the lines of the command definition, ending with @code{end}.
19442 After the @code{document} command is finished, @code{help} on command
19443 @var{commandname} displays the documentation you have written.
19445 You may use the @code{document} command again to change the
19446 documentation of a command. Redefining the command with @code{define}
19447 does not change the documentation.
19449 @kindex dont-repeat
19450 @cindex don't repeat command
19452 Used inside a user-defined command, this tells @value{GDBN} that this
19453 command should not be repeated when the user hits @key{RET}
19454 (@pxref{Command Syntax, repeat last command}).
19456 @kindex help user-defined
19457 @item help user-defined
19458 List all user-defined commands, with the first line of the documentation
19463 @itemx show user @var{commandname}
19464 Display the @value{GDBN} commands used to define @var{commandname} (but
19465 not its documentation). If no @var{commandname} is given, display the
19466 definitions for all user-defined commands.
19468 @cindex infinite recursion in user-defined commands
19469 @kindex show max-user-call-depth
19470 @kindex set max-user-call-depth
19471 @item show max-user-call-depth
19472 @itemx set max-user-call-depth
19473 The value of @code{max-user-call-depth} controls how many recursion
19474 levels are allowed in user-defined commands before @value{GDBN} suspects an
19475 infinite recursion and aborts the command.
19478 In addition to the above commands, user-defined commands frequently
19479 use control flow commands, described in @ref{Command Files}.
19481 When user-defined commands are executed, the
19482 commands of the definition are not printed. An error in any command
19483 stops execution of the user-defined command.
19485 If used interactively, commands that would ask for confirmation proceed
19486 without asking when used inside a user-defined command. Many @value{GDBN}
19487 commands that normally print messages to say what they are doing omit the
19488 messages when used in a user-defined command.
19491 @subsection User-defined Command Hooks
19492 @cindex command hooks
19493 @cindex hooks, for commands
19494 @cindex hooks, pre-command
19497 You may define @dfn{hooks}, which are a special kind of user-defined
19498 command. Whenever you run the command @samp{foo}, if the user-defined
19499 command @samp{hook-foo} exists, it is executed (with no arguments)
19500 before that command.
19502 @cindex hooks, post-command
19504 A hook may also be defined which is run after the command you executed.
19505 Whenever you run the command @samp{foo}, if the user-defined command
19506 @samp{hookpost-foo} exists, it is executed (with no arguments) after
19507 that command. Post-execution hooks may exist simultaneously with
19508 pre-execution hooks, for the same command.
19510 It is valid for a hook to call the command which it hooks. If this
19511 occurs, the hook is not re-executed, thereby avoiding infinite recursion.
19513 @c It would be nice if hookpost could be passed a parameter indicating
19514 @c if the command it hooks executed properly or not. FIXME!
19516 @kindex stop@r{, a pseudo-command}
19517 In addition, a pseudo-command, @samp{stop} exists. Defining
19518 (@samp{hook-stop}) makes the associated commands execute every time
19519 execution stops in your program: before breakpoint commands are run,
19520 displays are printed, or the stack frame is printed.
19522 For example, to ignore @code{SIGALRM} signals while
19523 single-stepping, but treat them normally during normal execution,
19528 handle SIGALRM nopass
19532 handle SIGALRM pass
19535 define hook-continue
19536 handle SIGALRM pass
19540 As a further example, to hook at the beginning and end of the @code{echo}
19541 command, and to add extra text to the beginning and end of the message,
19549 define hookpost-echo
19553 (@value{GDBP}) echo Hello World
19554 <<<---Hello World--->>>
19559 You can define a hook for any single-word command in @value{GDBN}, but
19560 not for command aliases; you should define a hook for the basic command
19561 name, e.g.@: @code{backtrace} rather than @code{bt}.
19562 @c FIXME! So how does Joe User discover whether a command is an alias
19564 You can hook a multi-word command by adding @code{hook-} or
19565 @code{hookpost-} to the last word of the command, e.g.@:
19566 @samp{define target hook-remote} to add a hook to @samp{target remote}.
19568 If an error occurs during the execution of your hook, execution of
19569 @value{GDBN} commands stops and @value{GDBN} issues a prompt
19570 (before the command that you actually typed had a chance to run).
19572 If you try to define a hook which does not match any known command, you
19573 get a warning from the @code{define} command.
19575 @node Command Files
19576 @subsection Command Files
19578 @cindex command files
19579 @cindex scripting commands
19580 A command file for @value{GDBN} is a text file made of lines that are
19581 @value{GDBN} commands. Comments (lines starting with @kbd{#}) may
19582 also be included. An empty line in a command file does nothing; it
19583 does not mean to repeat the last command, as it would from the
19586 You can request the execution of a command file with the @code{source}
19587 command. Note that the @code{source} command is also used to evaluate
19588 scripts that are not Command Files. The exact behavior can be configured
19589 using the @code{script-extension} setting.
19590 @xref{Extending GDB,, Extending GDB}.
19594 @cindex execute commands from a file
19595 @item source [-s] [-v] @var{filename}
19596 Execute the command file @var{filename}.
19599 The lines in a command file are generally executed sequentially,
19600 unless the order of execution is changed by one of the
19601 @emph{flow-control commands} described below. The commands are not
19602 printed as they are executed. An error in any command terminates
19603 execution of the command file and control is returned to the console.
19605 @value{GDBN} first searches for @var{filename} in the current directory.
19606 If the file is not found there, and @var{filename} does not specify a
19607 directory, then @value{GDBN} also looks for the file on the source search path
19608 (specified with the @samp{directory} command);
19609 except that @file{$cdir} is not searched because the compilation directory
19610 is not relevant to scripts.
19612 If @code{-s} is specified, then @value{GDBN} searches for @var{filename}
19613 on the search path even if @var{filename} specifies a directory.
19614 The search is done by appending @var{filename} to each element of the
19615 search path. So, for example, if @var{filename} is @file{mylib/myscript}
19616 and the search path contains @file{/home/user} then @value{GDBN} will
19617 look for the script @file{/home/user/mylib/myscript}.
19618 The search is also done if @var{filename} is an absolute path.
19619 For example, if @var{filename} is @file{/tmp/myscript} and
19620 the search path contains @file{/home/user} then @value{GDBN} will
19621 look for the script @file{/home/user/tmp/myscript}.
19622 For DOS-like systems, if @var{filename} contains a drive specification,
19623 it is stripped before concatenation. For example, if @var{filename} is
19624 @file{d:myscript} and the search path contains @file{c:/tmp} then @value{GDBN}
19625 will look for the script @file{c:/tmp/myscript}.
19627 If @code{-v}, for verbose mode, is given then @value{GDBN} displays
19628 each command as it is executed. The option must be given before
19629 @var{filename}, and is interpreted as part of the filename anywhere else.
19631 Commands that would ask for confirmation if used interactively proceed
19632 without asking when used in a command file. Many @value{GDBN} commands that
19633 normally print messages to say what they are doing omit the messages
19634 when called from command files.
19636 @value{GDBN} also accepts command input from standard input. In this
19637 mode, normal output goes to standard output and error output goes to
19638 standard error. Errors in a command file supplied on standard input do
19639 not terminate execution of the command file---execution continues with
19643 gdb < cmds > log 2>&1
19646 (The syntax above will vary depending on the shell used.) This example
19647 will execute commands from the file @file{cmds}. All output and errors
19648 would be directed to @file{log}.
19650 Since commands stored on command files tend to be more general than
19651 commands typed interactively, they frequently need to deal with
19652 complicated situations, such as different or unexpected values of
19653 variables and symbols, changes in how the program being debugged is
19654 built, etc. @value{GDBN} provides a set of flow-control commands to
19655 deal with these complexities. Using these commands, you can write
19656 complex scripts that loop over data structures, execute commands
19657 conditionally, etc.
19664 This command allows to include in your script conditionally executed
19665 commands. The @code{if} command takes a single argument, which is an
19666 expression to evaluate. It is followed by a series of commands that
19667 are executed only if the expression is true (its value is nonzero).
19668 There can then optionally be an @code{else} line, followed by a series
19669 of commands that are only executed if the expression was false. The
19670 end of the list is marked by a line containing @code{end}.
19674 This command allows to write loops. Its syntax is similar to
19675 @code{if}: the command takes a single argument, which is an expression
19676 to evaluate, and must be followed by the commands to execute, one per
19677 line, terminated by an @code{end}. These commands are called the
19678 @dfn{body} of the loop. The commands in the body of @code{while} are
19679 executed repeatedly as long as the expression evaluates to true.
19683 This command exits the @code{while} loop in whose body it is included.
19684 Execution of the script continues after that @code{while}s @code{end}
19687 @kindex loop_continue
19688 @item loop_continue
19689 This command skips the execution of the rest of the body of commands
19690 in the @code{while} loop in whose body it is included. Execution
19691 branches to the beginning of the @code{while} loop, where it evaluates
19692 the controlling expression.
19694 @kindex end@r{ (if/else/while commands)}
19696 Terminate the block of commands that are the body of @code{if},
19697 @code{else}, or @code{while} flow-control commands.
19702 @subsection Commands for Controlled Output
19704 During the execution of a command file or a user-defined command, normal
19705 @value{GDBN} output is suppressed; the only output that appears is what is
19706 explicitly printed by the commands in the definition. This section
19707 describes three commands useful for generating exactly the output you
19712 @item echo @var{text}
19713 @c I do not consider backslash-space a standard C escape sequence
19714 @c because it is not in ANSI.
19715 Print @var{text}. Nonprinting characters can be included in
19716 @var{text} using C escape sequences, such as @samp{\n} to print a
19717 newline. @strong{No newline is printed unless you specify one.}
19718 In addition to the standard C escape sequences, a backslash followed
19719 by a space stands for a space. This is useful for displaying a
19720 string with spaces at the beginning or the end, since leading and
19721 trailing spaces are otherwise trimmed from all arguments.
19722 To print @samp{@w{ }and foo =@w{ }}, use the command
19723 @samp{echo \@w{ }and foo = \@w{ }}.
19725 A backslash at the end of @var{text} can be used, as in C, to continue
19726 the command onto subsequent lines. For example,
19729 echo This is some text\n\
19730 which is continued\n\
19731 onto several lines.\n
19734 produces the same output as
19737 echo This is some text\n
19738 echo which is continued\n
19739 echo onto several lines.\n
19743 @item output @var{expression}
19744 Print the value of @var{expression} and nothing but that value: no
19745 newlines, no @samp{$@var{nn} = }. The value is not entered in the
19746 value history either. @xref{Expressions, ,Expressions}, for more information
19749 @item output/@var{fmt} @var{expression}
19750 Print the value of @var{expression} in format @var{fmt}. You can use
19751 the same formats as for @code{print}. @xref{Output Formats,,Output
19752 Formats}, for more information.
19755 @item printf @var{template}, @var{expressions}@dots{}
19756 Print the values of one or more @var{expressions} under the control of
19757 the string @var{template}. To print several values, make
19758 @var{expressions} be a comma-separated list of individual expressions,
19759 which may be either numbers or pointers. Their values are printed as
19760 specified by @var{template}, exactly as a C program would do by
19761 executing the code below:
19764 printf (@var{template}, @var{expressions}@dots{});
19767 As in @code{C} @code{printf}, ordinary characters in @var{template}
19768 are printed verbatim, while @dfn{conversion specification} introduced
19769 by the @samp{%} character cause subsequent @var{expressions} to be
19770 evaluated, their values converted and formatted according to type and
19771 style information encoded in the conversion specifications, and then
19774 For example, you can print two values in hex like this:
19777 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
19780 @code{printf} supports all the standard @code{C} conversion
19781 specifications, including the flags and modifiers between the @samp{%}
19782 character and the conversion letter, with the following exceptions:
19786 The argument-ordering modifiers, such as @samp{2$}, are not supported.
19789 The modifier @samp{*} is not supported for specifying precision or
19793 The @samp{'} flag (for separation of digits into groups according to
19794 @code{LC_NUMERIC'}) is not supported.
19797 The type modifiers @samp{hh}, @samp{j}, @samp{t}, and @samp{z} are not
19801 The conversion letter @samp{n} (as in @samp{%n}) is not supported.
19804 The conversion letters @samp{a} and @samp{A} are not supported.
19808 Note that the @samp{ll} type modifier is supported only if the
19809 underlying @code{C} implementation used to build @value{GDBN} supports
19810 the @code{long long int} type, and the @samp{L} type modifier is
19811 supported only if @code{long double} type is available.
19813 As in @code{C}, @code{printf} supports simple backslash-escape
19814 sequences, such as @code{\n}, @samp{\t}, @samp{\\}, @samp{\"},
19815 @samp{\a}, and @samp{\f}, that consist of backslash followed by a
19816 single character. Octal and hexadecimal escape sequences are not
19819 Additionally, @code{printf} supports conversion specifications for DFP
19820 (@dfn{Decimal Floating Point}) types using the following length modifiers
19821 together with a floating point specifier.
19826 @samp{H} for printing @code{Decimal32} types.
19829 @samp{D} for printing @code{Decimal64} types.
19832 @samp{DD} for printing @code{Decimal128} types.
19835 If the underlying @code{C} implementation used to build @value{GDBN} has
19836 support for the three length modifiers for DFP types, other modifiers
19837 such as width and precision will also be available for @value{GDBN} to use.
19839 In case there is no such @code{C} support, no additional modifiers will be
19840 available and the value will be printed in the standard way.
19842 Here's an example of printing DFP types using the above conversion letters:
19844 printf "D32: %Hf - D64: %Df - D128: %DDf\n",1.2345df,1.2E10dd,1.2E1dl
19850 @section Scripting @value{GDBN} using Python
19851 @cindex python scripting
19852 @cindex scripting with python
19854 You can script @value{GDBN} using the @uref{http://www.python.org/,
19855 Python programming language}. This feature is available only if
19856 @value{GDBN} was configured using @option{--with-python}.
19859 * Python Commands:: Accessing Python from @value{GDBN}.
19860 * Python API:: Accessing @value{GDBN} from Python.
19861 * Auto-loading:: Automatically loading Python code.
19864 @node Python Commands
19865 @subsection Python Commands
19866 @cindex python commands
19867 @cindex commands to access python
19869 @value{GDBN} provides one command for accessing the Python interpreter,
19870 and one related setting:
19874 @item python @r{[}@var{code}@r{]}
19875 The @code{python} command can be used to evaluate Python code.
19877 If given an argument, the @code{python} command will evaluate the
19878 argument as a Python command. For example:
19881 (@value{GDBP}) python print 23
19885 If you do not provide an argument to @code{python}, it will act as a
19886 multi-line command, like @code{define}. In this case, the Python
19887 script is made up of subsequent command lines, given after the
19888 @code{python} command. This command list is terminated using a line
19889 containing @code{end}. For example:
19892 (@value{GDBP}) python
19894 End with a line saying just "end".
19900 @kindex maint set python print-stack
19901 @item maint set python print-stack
19902 By default, @value{GDBN} will print a stack trace when an error occurs
19903 in a Python script. This can be controlled using @code{maint set
19904 python print-stack}: if @code{on}, the default, then Python stack
19905 printing is enabled; if @code{off}, then Python stack printing is
19909 It is also possible to execute a Python script from the @value{GDBN}
19913 @item source @file{script-name}
19914 The script name must end with @samp{.py} and @value{GDBN} must be configured
19915 to recognize the script language based on filename extension using
19916 the @code{script-extension} setting. @xref{Extending GDB, ,Extending GDB}.
19918 @item python execfile ("script-name")
19919 This method is based on the @code{execfile} Python built-in function,
19920 and thus is always available.
19924 @subsection Python API
19926 @cindex programming in python
19928 @cindex python stdout
19929 @cindex python pagination
19930 At startup, @value{GDBN} overrides Python's @code{sys.stdout} and
19931 @code{sys.stderr} to print using @value{GDBN}'s output-paging streams.
19932 A Python program which outputs to one of these streams may have its
19933 output interrupted by the user (@pxref{Screen Size}). In this
19934 situation, a Python @code{KeyboardInterrupt} exception is thrown.
19937 * Basic Python:: Basic Python Functions.
19938 * Exception Handling::
19939 * Values From Inferior::
19940 * Types In Python:: Python representation of types.
19941 * Pretty Printing API:: Pretty-printing values.
19942 * Selecting Pretty-Printers:: How GDB chooses a pretty-printer.
19943 * Commands In Python:: Implementing new commands in Python.
19944 * Parameters In Python:: Adding new @value{GDBN} parameters.
19945 * Functions In Python:: Writing new convenience functions.
19946 * Progspaces In Python:: Program spaces.
19947 * Objfiles In Python:: Object files.
19948 * Frames In Python:: Accessing inferior stack frames from Python.
19949 * Blocks In Python:: Accessing frame blocks from Python.
19950 * Symbols In Python:: Python representation of symbols.
19951 * Symbol Tables In Python:: Python representation of symbol tables.
19952 * Lazy Strings In Python:: Python representation of lazy strings.
19953 * Breakpoints In Python:: Manipulating breakpoints using Python.
19957 @subsubsection Basic Python
19959 @cindex python functions
19960 @cindex python module
19962 @value{GDBN} introduces a new Python module, named @code{gdb}. All
19963 methods and classes added by @value{GDBN} are placed in this module.
19964 @value{GDBN} automatically @code{import}s the @code{gdb} module for
19965 use in all scripts evaluated by the @code{python} command.
19967 @findex gdb.execute
19968 @defun execute command [from_tty]
19969 Evaluate @var{command}, a string, as a @value{GDBN} CLI command.
19970 If a GDB exception happens while @var{command} runs, it is
19971 translated as described in @ref{Exception Handling,,Exception Handling}.
19972 If no exceptions occur, this function returns @code{None}.
19974 @var{from_tty} specifies whether @value{GDBN} ought to consider this
19975 command as having originated from the user invoking it interactively.
19976 It must be a boolean value. If omitted, it defaults to @code{False}.
19979 @findex gdb.breakpoints
19981 Return a sequence holding all of @value{GDBN}'s breakpoints.
19982 @xref{Breakpoints In Python}, for more information.
19985 @findex gdb.parameter
19986 @defun parameter parameter
19987 Return the value of a @value{GDBN} parameter. @var{parameter} is a
19988 string naming the parameter to look up; @var{parameter} may contain
19989 spaces if the parameter has a multi-part name. For example,
19990 @samp{print object} is a valid parameter name.
19992 If the named parameter does not exist, this function throws a
19993 @code{RuntimeError}. Otherwise, the parameter's value is converted to
19994 a Python value of the appropriate type, and returned.
19997 @findex gdb.history
19998 @defun history number
19999 Return a value from @value{GDBN}'s value history (@pxref{Value
20000 History}). @var{number} indicates which history element to return.
20001 If @var{number} is negative, then @value{GDBN} will take its absolute value
20002 and count backward from the last element (i.e., the most recent element) to
20003 find the value to return. If @var{number} is zero, then @value{GDBN} will
20004 return the most recent element. If the element specified by @var{number}
20005 doesn't exist in the value history, a @code{RuntimeError} exception will be
20008 If no exception is raised, the return value is always an instance of
20009 @code{gdb.Value} (@pxref{Values From Inferior}).
20012 @findex gdb.parse_and_eval
20013 @defun parse_and_eval expression
20014 Parse @var{expression} as an expression in the current language,
20015 evaluate it, and return the result as a @code{gdb.Value}.
20016 @var{expression} must be a string.
20018 This function can be useful when implementing a new command
20019 (@pxref{Commands In Python}), as it provides a way to parse the
20020 command's argument as an expression. It is also useful simply to
20021 compute values, for example, it is the only way to get the value of a
20022 convenience variable (@pxref{Convenience Vars}) as a @code{gdb.Value}.
20026 @defun write string
20027 Print a string to @value{GDBN}'s paginated standard output stream.
20028 Writing to @code{sys.stdout} or @code{sys.stderr} will automatically
20029 call this function.
20034 Flush @value{GDBN}'s paginated standard output stream. Flushing
20035 @code{sys.stdout} or @code{sys.stderr} will automatically call this
20039 @findex gdb.target_charset
20040 @defun target_charset
20041 Return the name of the current target character set (@pxref{Character
20042 Sets}). This differs from @code{gdb.parameter('target-charset')} in
20043 that @samp{auto} is never returned.
20046 @findex gdb.target_wide_charset
20047 @defun target_wide_charset
20048 Return the name of the current target wide character set
20049 (@pxref{Character Sets}). This differs from
20050 @code{gdb.parameter('target-wide-charset')} in that @samp{auto} is
20054 @node Exception Handling
20055 @subsubsection Exception Handling
20056 @cindex python exceptions
20057 @cindex exceptions, python
20059 When executing the @code{python} command, Python exceptions
20060 uncaught within the Python code are translated to calls to
20061 @value{GDBN} error-reporting mechanism. If the command that called
20062 @code{python} does not handle the error, @value{GDBN} will
20063 terminate it and print an error message containing the Python
20064 exception name, the associated value, and the Python call stack
20065 backtrace at the point where the exception was raised. Example:
20068 (@value{GDBP}) python print foo
20069 Traceback (most recent call last):
20070 File "<string>", line 1, in <module>
20071 NameError: name 'foo' is not defined
20074 @value{GDBN} errors that happen in @value{GDBN} commands invoked by Python
20075 code are converted to Python @code{RuntimeError} exceptions. User
20076 interrupt (via @kbd{C-c} or by typing @kbd{q} at a pagination
20077 prompt) is translated to a Python @code{KeyboardInterrupt}
20078 exception. If you catch these exceptions in your Python code, your
20079 exception handler will see @code{RuntimeError} or
20080 @code{KeyboardInterrupt} as the exception type, the @value{GDBN} error
20081 message as its value, and the Python call stack backtrace at the
20082 Python statement closest to where the @value{GDBN} error occured as the
20085 @findex gdb.GdbError
20086 When implementing @value{GDBN} commands in Python via @code{gdb.Command},
20087 it is useful to be able to throw an exception that doesn't cause a
20088 traceback to be printed. For example, the user may have invoked the
20089 command incorrectly. Use the @code{gdb.GdbError} exception
20090 to handle this case. Example:
20094 >class HelloWorld (gdb.Command):
20095 > """Greet the whole world."""
20096 > def __init__ (self):
20097 > super (HelloWorld, self).__init__ ("hello-world", gdb.COMMAND_OBSCURE)
20098 > def invoke (self, args, from_tty):
20099 > argv = gdb.string_to_argv (args)
20100 > if len (argv) != 0:
20101 > raise gdb.GdbError ("hello-world takes no arguments")
20102 > print "Hello, World!"
20105 (gdb) hello-world 42
20106 hello-world takes no arguments
20109 @node Values From Inferior
20110 @subsubsection Values From Inferior
20111 @cindex values from inferior, with Python
20112 @cindex python, working with values from inferior
20114 @cindex @code{gdb.Value}
20115 @value{GDBN} provides values it obtains from the inferior program in
20116 an object of type @code{gdb.Value}. @value{GDBN} uses this object
20117 for its internal bookkeeping of the inferior's values, and for
20118 fetching values when necessary.
20120 Inferior values that are simple scalars can be used directly in
20121 Python expressions that are valid for the value's data type. Here's
20122 an example for an integer or floating-point value @code{some_val}:
20129 As result of this, @code{bar} will also be a @code{gdb.Value} object
20130 whose values are of the same type as those of @code{some_val}.
20132 Inferior values that are structures or instances of some class can
20133 be accessed using the Python @dfn{dictionary syntax}. For example, if
20134 @code{some_val} is a @code{gdb.Value} instance holding a structure, you
20135 can access its @code{foo} element with:
20138 bar = some_val['foo']
20141 Again, @code{bar} will also be a @code{gdb.Value} object.
20143 The following attributes are provided:
20146 @defivar Value address
20147 If this object is addressable, this read-only attribute holds a
20148 @code{gdb.Value} object representing the address. Otherwise,
20149 this attribute holds @code{None}.
20152 @cindex optimized out value in Python
20153 @defivar Value is_optimized_out
20154 This read-only boolean attribute is true if the compiler optimized out
20155 this value, thus it is not available for fetching from the inferior.
20158 @defivar Value type
20159 The type of this @code{gdb.Value}. The value of this attribute is a
20160 @code{gdb.Type} object.
20164 The following methods are provided:
20167 @defmethod Value cast type
20168 Return a new instance of @code{gdb.Value} that is the result of
20169 casting this instance to the type described by @var{type}, which must
20170 be a @code{gdb.Type} object. If the cast cannot be performed for some
20171 reason, this method throws an exception.
20174 @defmethod Value dereference
20175 For pointer data types, this method returns a new @code{gdb.Value} object
20176 whose contents is the object pointed to by the pointer. For example, if
20177 @code{foo} is a C pointer to an @code{int}, declared in your C program as
20184 then you can use the corresponding @code{gdb.Value} to access what
20185 @code{foo} points to like this:
20188 bar = foo.dereference ()
20191 The result @code{bar} will be a @code{gdb.Value} object holding the
20192 value pointed to by @code{foo}.
20195 @defmethod Value string @r{[}encoding@r{]} @r{[}errors@r{]} @r{[}length@r{]}
20196 If this @code{gdb.Value} represents a string, then this method
20197 converts the contents to a Python string. Otherwise, this method will
20198 throw an exception.
20200 Strings are recognized in a language-specific way; whether a given
20201 @code{gdb.Value} represents a string is determined by the current
20204 For C-like languages, a value is a string if it is a pointer to or an
20205 array of characters or ints. The string is assumed to be terminated
20206 by a zero of the appropriate width. However if the optional length
20207 argument is given, the string will be converted to that given length,
20208 ignoring any embedded zeros that the string may contain.
20210 If the optional @var{encoding} argument is given, it must be a string
20211 naming the encoding of the string in the @code{gdb.Value}, such as
20212 @code{"ascii"}, @code{"iso-8859-6"} or @code{"utf-8"}. It accepts
20213 the same encodings as the corresponding argument to Python's
20214 @code{string.decode} method, and the Python codec machinery will be used
20215 to convert the string. If @var{encoding} is not given, or if
20216 @var{encoding} is the empty string, then either the @code{target-charset}
20217 (@pxref{Character Sets}) will be used, or a language-specific encoding
20218 will be used, if the current language is able to supply one.
20220 The optional @var{errors} argument is the same as the corresponding
20221 argument to Python's @code{string.decode} method.
20223 If the optional @var{length} argument is given, the string will be
20224 fetched and converted to the given length.
20227 @defmethod Value lazy_string @r{[}encoding@r{]} @r{[}length@r{]}
20228 If this @code{gdb.Value} represents a string, then this method
20229 converts the contents to a @code{gdb.LazyString} (@pxref{Lazy Strings
20230 In Python}). Otherwise, this method will throw an exception.
20232 If the optional @var{encoding} argument is given, it must be a string
20233 naming the encoding of the @code{gdb.LazyString}. Some examples are:
20234 @samp{ascii}, @samp{iso-8859-6} or @samp{utf-8}. If the
20235 @var{encoding} argument is an encoding that @value{GDBN} does
20236 recognize, @value{GDBN} will raise an error.
20238 When a lazy string is printed, the @value{GDBN} encoding machinery is
20239 used to convert the string during printing. If the optional
20240 @var{encoding} argument is not provided, or is an empty string,
20241 @value{GDBN} will automatically select the encoding most suitable for
20242 the string type. For further information on encoding in @value{GDBN}
20243 please see @ref{Character Sets}.
20245 If the optional @var{length} argument is given, the string will be
20246 fetched and encoded to the length of characters specified. If
20247 the @var{length} argument is not provided, the string will be fetched
20248 and encoded until a null of appropriate width is found.
20252 @node Types In Python
20253 @subsubsection Types In Python
20254 @cindex types in Python
20255 @cindex Python, working with types
20258 @value{GDBN} represents types from the inferior using the class
20261 The following type-related functions are available in the @code{gdb}
20264 @findex gdb.lookup_type
20265 @defun lookup_type name [block]
20266 This function looks up a type by name. @var{name} is the name of the
20267 type to look up. It must be a string.
20269 If @var{block} is given, then @var{name} is looked up in that scope.
20270 Otherwise, it is searched for globally.
20272 Ordinarily, this function will return an instance of @code{gdb.Type}.
20273 If the named type cannot be found, it will throw an exception.
20276 An instance of @code{Type} has the following attributes:
20280 The type code for this type. The type code will be one of the
20281 @code{TYPE_CODE_} constants defined below.
20284 @defivar Type sizeof
20285 The size of this type, in target @code{char} units. Usually, a
20286 target's @code{char} type will be an 8-bit byte. However, on some
20287 unusual platforms, this type may have a different size.
20291 The tag name for this type. The tag name is the name after
20292 @code{struct}, @code{union}, or @code{enum} in C and C@t{++}; not all
20293 languages have this concept. If this type has no tag name, then
20294 @code{None} is returned.
20298 The following methods are provided:
20301 @defmethod Type fields
20302 For structure and union types, this method returns the fields. Range
20303 types have two fields, the minimum and maximum values. Enum types
20304 have one field per enum constant. Function and method types have one
20305 field per parameter. The base types of C@t{++} classes are also
20306 represented as fields. If the type has no fields, or does not fit
20307 into one of these categories, an empty sequence will be returned.
20309 Each field is an object, with some pre-defined attributes:
20312 This attribute is not available for @code{static} fields (as in
20313 C@t{++} or Java). For non-@code{static} fields, the value is the bit
20314 position of the field.
20317 The name of the field, or @code{None} for anonymous fields.
20320 This is @code{True} if the field is artificial, usually meaning that
20321 it was provided by the compiler and not the user. This attribute is
20322 always provided, and is @code{False} if the field is not artificial.
20324 @item is_base_class
20325 This is @code{True} if the field represents a base class of a C@t{++}
20326 structure. This attribute is always provided, and is @code{False}
20327 if the field is not a base class of the type that is the argument of
20328 @code{fields}, or if that type was not a C@t{++} class.
20331 If the field is packed, or is a bitfield, then this will have a
20332 non-zero value, which is the size of the field in bits. Otherwise,
20333 this will be zero; in this case the field's size is given by its type.
20336 The type of the field. This is usually an instance of @code{Type},
20337 but it can be @code{None} in some situations.
20341 @defmethod Type const
20342 Return a new @code{gdb.Type} object which represents a
20343 @code{const}-qualified variant of this type.
20346 @defmethod Type volatile
20347 Return a new @code{gdb.Type} object which represents a
20348 @code{volatile}-qualified variant of this type.
20351 @defmethod Type unqualified
20352 Return a new @code{gdb.Type} object which represents an unqualified
20353 variant of this type. That is, the result is neither @code{const} nor
20357 @defmethod Type range
20358 Return a Python @code{Tuple} object that contains two elements: the
20359 low bound of the argument type and the high bound of that type. If
20360 the type does not have a range, @value{GDBN} will raise a
20361 @code{RuntimeError} exception.
20364 @defmethod Type reference
20365 Return a new @code{gdb.Type} object which represents a reference to this
20369 @defmethod Type pointer
20370 Return a new @code{gdb.Type} object which represents a pointer to this
20374 @defmethod Type strip_typedefs
20375 Return a new @code{gdb.Type} that represents the real type,
20376 after removing all layers of typedefs.
20379 @defmethod Type target
20380 Return a new @code{gdb.Type} object which represents the target type
20383 For a pointer type, the target type is the type of the pointed-to
20384 object. For an array type (meaning C-like arrays), the target type is
20385 the type of the elements of the array. For a function or method type,
20386 the target type is the type of the return value. For a complex type,
20387 the target type is the type of the elements. For a typedef, the
20388 target type is the aliased type.
20390 If the type does not have a target, this method will throw an
20394 @defmethod Type template_argument n [block]
20395 If this @code{gdb.Type} is an instantiation of a template, this will
20396 return a new @code{gdb.Type} which represents the type of the
20397 @var{n}th template argument.
20399 If this @code{gdb.Type} is not a template type, this will throw an
20400 exception. Ordinarily, only C@t{++} code will have template types.
20402 If @var{block} is given, then @var{name} is looked up in that scope.
20403 Otherwise, it is searched for globally.
20408 Each type has a code, which indicates what category this type falls
20409 into. The available type categories are represented by constants
20410 defined in the @code{gdb} module:
20413 @findex TYPE_CODE_PTR
20414 @findex gdb.TYPE_CODE_PTR
20415 @item TYPE_CODE_PTR
20416 The type is a pointer.
20418 @findex TYPE_CODE_ARRAY
20419 @findex gdb.TYPE_CODE_ARRAY
20420 @item TYPE_CODE_ARRAY
20421 The type is an array.
20423 @findex TYPE_CODE_STRUCT
20424 @findex gdb.TYPE_CODE_STRUCT
20425 @item TYPE_CODE_STRUCT
20426 The type is a structure.
20428 @findex TYPE_CODE_UNION
20429 @findex gdb.TYPE_CODE_UNION
20430 @item TYPE_CODE_UNION
20431 The type is a union.
20433 @findex TYPE_CODE_ENUM
20434 @findex gdb.TYPE_CODE_ENUM
20435 @item TYPE_CODE_ENUM
20436 The type is an enum.
20438 @findex TYPE_CODE_FLAGS
20439 @findex gdb.TYPE_CODE_FLAGS
20440 @item TYPE_CODE_FLAGS
20441 A bit flags type, used for things such as status registers.
20443 @findex TYPE_CODE_FUNC
20444 @findex gdb.TYPE_CODE_FUNC
20445 @item TYPE_CODE_FUNC
20446 The type is a function.
20448 @findex TYPE_CODE_INT
20449 @findex gdb.TYPE_CODE_INT
20450 @item TYPE_CODE_INT
20451 The type is an integer type.
20453 @findex TYPE_CODE_FLT
20454 @findex gdb.TYPE_CODE_FLT
20455 @item TYPE_CODE_FLT
20456 A floating point type.
20458 @findex TYPE_CODE_VOID
20459 @findex gdb.TYPE_CODE_VOID
20460 @item TYPE_CODE_VOID
20461 The special type @code{void}.
20463 @findex TYPE_CODE_SET
20464 @findex gdb.TYPE_CODE_SET
20465 @item TYPE_CODE_SET
20468 @findex TYPE_CODE_RANGE
20469 @findex gdb.TYPE_CODE_RANGE
20470 @item TYPE_CODE_RANGE
20471 A range type, that is, an integer type with bounds.
20473 @findex TYPE_CODE_STRING
20474 @findex gdb.TYPE_CODE_STRING
20475 @item TYPE_CODE_STRING
20476 A string type. Note that this is only used for certain languages with
20477 language-defined string types; C strings are not represented this way.
20479 @findex TYPE_CODE_BITSTRING
20480 @findex gdb.TYPE_CODE_BITSTRING
20481 @item TYPE_CODE_BITSTRING
20484 @findex TYPE_CODE_ERROR
20485 @findex gdb.TYPE_CODE_ERROR
20486 @item TYPE_CODE_ERROR
20487 An unknown or erroneous type.
20489 @findex TYPE_CODE_METHOD
20490 @findex gdb.TYPE_CODE_METHOD
20491 @item TYPE_CODE_METHOD
20492 A method type, as found in C@t{++} or Java.
20494 @findex TYPE_CODE_METHODPTR
20495 @findex gdb.TYPE_CODE_METHODPTR
20496 @item TYPE_CODE_METHODPTR
20497 A pointer-to-member-function.
20499 @findex TYPE_CODE_MEMBERPTR
20500 @findex gdb.TYPE_CODE_MEMBERPTR
20501 @item TYPE_CODE_MEMBERPTR
20502 A pointer-to-member.
20504 @findex TYPE_CODE_REF
20505 @findex gdb.TYPE_CODE_REF
20506 @item TYPE_CODE_REF
20509 @findex TYPE_CODE_CHAR
20510 @findex gdb.TYPE_CODE_CHAR
20511 @item TYPE_CODE_CHAR
20514 @findex TYPE_CODE_BOOL
20515 @findex gdb.TYPE_CODE_BOOL
20516 @item TYPE_CODE_BOOL
20519 @findex TYPE_CODE_COMPLEX
20520 @findex gdb.TYPE_CODE_COMPLEX
20521 @item TYPE_CODE_COMPLEX
20522 A complex float type.
20524 @findex TYPE_CODE_TYPEDEF
20525 @findex gdb.TYPE_CODE_TYPEDEF
20526 @item TYPE_CODE_TYPEDEF
20527 A typedef to some other type.
20529 @findex TYPE_CODE_NAMESPACE
20530 @findex gdb.TYPE_CODE_NAMESPACE
20531 @item TYPE_CODE_NAMESPACE
20532 A C@t{++} namespace.
20534 @findex TYPE_CODE_DECFLOAT
20535 @findex gdb.TYPE_CODE_DECFLOAT
20536 @item TYPE_CODE_DECFLOAT
20537 A decimal floating point type.
20539 @findex TYPE_CODE_INTERNAL_FUNCTION
20540 @findex gdb.TYPE_CODE_INTERNAL_FUNCTION
20541 @item TYPE_CODE_INTERNAL_FUNCTION
20542 A function internal to @value{GDBN}. This is the type used to represent
20543 convenience functions.
20546 @node Pretty Printing API
20547 @subsubsection Pretty Printing API
20549 An example output is provided (@pxref{Pretty Printing}).
20551 A pretty-printer is just an object that holds a value and implements a
20552 specific interface, defined here.
20554 @defop Operation {pretty printer} children (self)
20555 @value{GDBN} will call this method on a pretty-printer to compute the
20556 children of the pretty-printer's value.
20558 This method must return an object conforming to the Python iterator
20559 protocol. Each item returned by the iterator must be a tuple holding
20560 two elements. The first element is the ``name'' of the child; the
20561 second element is the child's value. The value can be any Python
20562 object which is convertible to a @value{GDBN} value.
20564 This method is optional. If it does not exist, @value{GDBN} will act
20565 as though the value has no children.
20568 @defop Operation {pretty printer} display_hint (self)
20569 The CLI may call this method and use its result to change the
20570 formatting of a value. The result will also be supplied to an MI
20571 consumer as a @samp{displayhint} attribute of the variable being
20574 This method is optional. If it does exist, this method must return a
20577 Some display hints are predefined by @value{GDBN}:
20581 Indicate that the object being printed is ``array-like''. The CLI
20582 uses this to respect parameters such as @code{set print elements} and
20583 @code{set print array}.
20586 Indicate that the object being printed is ``map-like'', and that the
20587 children of this value can be assumed to alternate between keys and
20591 Indicate that the object being printed is ``string-like''. If the
20592 printer's @code{to_string} method returns a Python string of some
20593 kind, then @value{GDBN} will call its internal language-specific
20594 string-printing function to format the string. For the CLI this means
20595 adding quotation marks, possibly escaping some characters, respecting
20596 @code{set print elements}, and the like.
20600 @defop Operation {pretty printer} to_string (self)
20601 @value{GDBN} will call this method to display the string
20602 representation of the value passed to the object's constructor.
20604 When printing from the CLI, if the @code{to_string} method exists,
20605 then @value{GDBN} will prepend its result to the values returned by
20606 @code{children}. Exactly how this formatting is done is dependent on
20607 the display hint, and may change as more hints are added. Also,
20608 depending on the print settings (@pxref{Print Settings}), the CLI may
20609 print just the result of @code{to_string} in a stack trace, omitting
20610 the result of @code{children}.
20612 If this method returns a string, it is printed verbatim.
20614 Otherwise, if this method returns an instance of @code{gdb.Value},
20615 then @value{GDBN} prints this value. This may result in a call to
20616 another pretty-printer.
20618 If instead the method returns a Python value which is convertible to a
20619 @code{gdb.Value}, then @value{GDBN} performs the conversion and prints
20620 the resulting value. Again, this may result in a call to another
20621 pretty-printer. Python scalars (integers, floats, and booleans) and
20622 strings are convertible to @code{gdb.Value}; other types are not.
20624 Finally, if this method returns @code{None} then no further operations
20625 are peformed in this method and nothing is printed.
20627 If the result is not one of these types, an exception is raised.
20630 @node Selecting Pretty-Printers
20631 @subsubsection Selecting Pretty-Printers
20633 The Python list @code{gdb.pretty_printers} contains an array of
20634 functions that have been registered via addition as a pretty-printer.
20635 Each @code{gdb.Progspace} contains a @code{pretty_printers} attribute.
20636 Each @code{gdb.Objfile} also contains a @code{pretty_printers}
20639 A function on one of these lists is passed a single @code{gdb.Value}
20640 argument and should return a pretty-printer object conforming to the
20641 interface definition above (@pxref{Pretty Printing API}). If a function
20642 cannot create a pretty-printer for the value, it should return
20645 @value{GDBN} first checks the @code{pretty_printers} attribute of each
20646 @code{gdb.Objfile} in the current program space and iteratively calls
20647 each function in the list for that @code{gdb.Objfile} until it receives
20648 a pretty-printer object.
20649 If no pretty-printer is found in the objfile lists, @value{GDBN} then
20650 searches the pretty-printer list of the current program space,
20651 calling each function until an object is returned.
20652 After these lists have been exhausted, it tries the global
20653 @code{gdb.pretty-printers} list, again calling each function until an
20654 object is returned.
20656 The order in which the objfiles are searched is not specified. For a
20657 given list, functions are always invoked from the head of the list,
20658 and iterated over sequentially until the end of the list, or a printer
20659 object is returned.
20661 Here is an example showing how a @code{std::string} printer might be
20665 class StdStringPrinter:
20666 "Print a std::string"
20668 def __init__ (self, val):
20671 def to_string (self):
20672 return self.val['_M_dataplus']['_M_p']
20674 def display_hint (self):
20678 And here is an example showing how a lookup function for the printer
20679 example above might be written.
20682 def str_lookup_function (val):
20684 lookup_tag = val.type.tag
20685 regex = re.compile ("^std::basic_string<char,.*>$")
20686 if lookup_tag == None:
20688 if regex.match (lookup_tag):
20689 return StdStringPrinter (val)
20694 The example lookup function extracts the value's type, and attempts to
20695 match it to a type that it can pretty-print. If it is a type the
20696 printer can pretty-print, it will return a printer object. If not, it
20697 returns @code{None}.
20699 We recommend that you put your core pretty-printers into a Python
20700 package. If your pretty-printers are for use with a library, we
20701 further recommend embedding a version number into the package name.
20702 This practice will enable @value{GDBN} to load multiple versions of
20703 your pretty-printers at the same time, because they will have
20706 You should write auto-loaded code (@pxref{Auto-loading}) such that it
20707 can be evaluated multiple times without changing its meaning. An
20708 ideal auto-load file will consist solely of @code{import}s of your
20709 printer modules, followed by a call to a register pretty-printers with
20710 the current objfile.
20712 Taken as a whole, this approach will scale nicely to multiple
20713 inferiors, each potentially using a different library version.
20714 Embedding a version number in the Python package name will ensure that
20715 @value{GDBN} is able to load both sets of printers simultaneously.
20716 Then, because the search for pretty-printers is done by objfile, and
20717 because your auto-loaded code took care to register your library's
20718 printers with a specific objfile, @value{GDBN} will find the correct
20719 printers for the specific version of the library used by each
20722 To continue the @code{std::string} example (@pxref{Pretty Printing API}),
20723 this code might appear in @code{gdb.libstdcxx.v6}:
20726 def register_printers (objfile):
20727 objfile.pretty_printers.add (str_lookup_function)
20731 And then the corresponding contents of the auto-load file would be:
20734 import gdb.libstdcxx.v6
20735 gdb.libstdcxx.v6.register_printers (gdb.current_objfile ())
20738 @node Commands In Python
20739 @subsubsection Commands In Python
20741 @cindex commands in python
20742 @cindex python commands
20743 You can implement new @value{GDBN} CLI commands in Python. A CLI
20744 command is implemented using an instance of the @code{gdb.Command}
20745 class, most commonly using a subclass.
20747 @defmethod Command __init__ name @var{command_class} @r{[}@var{completer_class}@r{]} @r{[}@var{prefix}@r{]}
20748 The object initializer for @code{Command} registers the new command
20749 with @value{GDBN}. This initializer is normally invoked from the
20750 subclass' own @code{__init__} method.
20752 @var{name} is the name of the command. If @var{name} consists of
20753 multiple words, then the initial words are looked for as prefix
20754 commands. In this case, if one of the prefix commands does not exist,
20755 an exception is raised.
20757 There is no support for multi-line commands.
20759 @var{command_class} should be one of the @samp{COMMAND_} constants
20760 defined below. This argument tells @value{GDBN} how to categorize the
20761 new command in the help system.
20763 @var{completer_class} is an optional argument. If given, it should be
20764 one of the @samp{COMPLETE_} constants defined below. This argument
20765 tells @value{GDBN} how to perform completion for this command. If not
20766 given, @value{GDBN} will attempt to complete using the object's
20767 @code{complete} method (see below); if no such method is found, an
20768 error will occur when completion is attempted.
20770 @var{prefix} is an optional argument. If @code{True}, then the new
20771 command is a prefix command; sub-commands of this command may be
20774 The help text for the new command is taken from the Python
20775 documentation string for the command's class, if there is one. If no
20776 documentation string is provided, the default value ``This command is
20777 not documented.'' is used.
20780 @cindex don't repeat Python command
20781 @defmethod Command dont_repeat
20782 By default, a @value{GDBN} command is repeated when the user enters a
20783 blank line at the command prompt. A command can suppress this
20784 behavior by invoking the @code{dont_repeat} method. This is similar
20785 to the user command @code{dont-repeat}, see @ref{Define, dont-repeat}.
20788 @defmethod Command invoke argument from_tty
20789 This method is called by @value{GDBN} when this command is invoked.
20791 @var{argument} is a string. It is the argument to the command, after
20792 leading and trailing whitespace has been stripped.
20794 @var{from_tty} is a boolean argument. When true, this means that the
20795 command was entered by the user at the terminal; when false it means
20796 that the command came from elsewhere.
20798 If this method throws an exception, it is turned into a @value{GDBN}
20799 @code{error} call. Otherwise, the return value is ignored.
20801 @findex gdb.string_to_argv
20802 To break @var{argument} up into an argv-like string use
20803 @code{gdb.string_to_argv}. This function behaves identically to
20804 @value{GDBN}'s internal argument lexer @code{buildargv}.
20805 It is recommended to use this for consistency.
20806 Arguments are separated by spaces and may be quoted.
20810 print gdb.string_to_argv ("1 2\ \\\"3 '4 \"5' \"6 '7\"")
20811 ['1', '2 "3', '4 "5', "6 '7"]
20816 @cindex completion of Python commands
20817 @defmethod Command complete text word
20818 This method is called by @value{GDBN} when the user attempts
20819 completion on this command. All forms of completion are handled by
20820 this method, that is, the @key{TAB} and @key{M-?} key bindings
20821 (@pxref{Completion}), and the @code{complete} command (@pxref{Help,
20824 The arguments @var{text} and @var{word} are both strings. @var{text}
20825 holds the complete command line up to the cursor's location.
20826 @var{word} holds the last word of the command line; this is computed
20827 using a word-breaking heuristic.
20829 The @code{complete} method can return several values:
20832 If the return value is a sequence, the contents of the sequence are
20833 used as the completions. It is up to @code{complete} to ensure that the
20834 contents actually do complete the word. A zero-length sequence is
20835 allowed, it means that there were no completions available. Only
20836 string elements of the sequence are used; other elements in the
20837 sequence are ignored.
20840 If the return value is one of the @samp{COMPLETE_} constants defined
20841 below, then the corresponding @value{GDBN}-internal completion
20842 function is invoked, and its result is used.
20845 All other results are treated as though there were no available
20850 When a new command is registered, it must be declared as a member of
20851 some general class of commands. This is used to classify top-level
20852 commands in the on-line help system; note that prefix commands are not
20853 listed under their own category but rather that of their top-level
20854 command. The available classifications are represented by constants
20855 defined in the @code{gdb} module:
20858 @findex COMMAND_NONE
20859 @findex gdb.COMMAND_NONE
20861 The command does not belong to any particular class. A command in
20862 this category will not be displayed in any of the help categories.
20864 @findex COMMAND_RUNNING
20865 @findex gdb.COMMAND_RUNNING
20866 @item COMMAND_RUNNING
20867 The command is related to running the inferior. For example,
20868 @code{start}, @code{step}, and @code{continue} are in this category.
20869 Type @kbd{help running} at the @value{GDBN} prompt to see a list of
20870 commands in this category.
20872 @findex COMMAND_DATA
20873 @findex gdb.COMMAND_DATA
20875 The command is related to data or variables. For example,
20876 @code{call}, @code{find}, and @code{print} are in this category. Type
20877 @kbd{help data} at the @value{GDBN} prompt to see a list of commands
20880 @findex COMMAND_STACK
20881 @findex gdb.COMMAND_STACK
20882 @item COMMAND_STACK
20883 The command has to do with manipulation of the stack. For example,
20884 @code{backtrace}, @code{frame}, and @code{return} are in this
20885 category. Type @kbd{help stack} at the @value{GDBN} prompt to see a
20886 list of commands in this category.
20888 @findex COMMAND_FILES
20889 @findex gdb.COMMAND_FILES
20890 @item COMMAND_FILES
20891 This class is used for file-related commands. For example,
20892 @code{file}, @code{list} and @code{section} are in this category.
20893 Type @kbd{help files} at the @value{GDBN} prompt to see a list of
20894 commands in this category.
20896 @findex COMMAND_SUPPORT
20897 @findex gdb.COMMAND_SUPPORT
20898 @item COMMAND_SUPPORT
20899 This should be used for ``support facilities'', generally meaning
20900 things that are useful to the user when interacting with @value{GDBN},
20901 but not related to the state of the inferior. For example,
20902 @code{help}, @code{make}, and @code{shell} are in this category. Type
20903 @kbd{help support} at the @value{GDBN} prompt to see a list of
20904 commands in this category.
20906 @findex COMMAND_STATUS
20907 @findex gdb.COMMAND_STATUS
20908 @item COMMAND_STATUS
20909 The command is an @samp{info}-related command, that is, related to the
20910 state of @value{GDBN} itself. For example, @code{info}, @code{macro},
20911 and @code{show} are in this category. Type @kbd{help status} at the
20912 @value{GDBN} prompt to see a list of commands in this category.
20914 @findex COMMAND_BREAKPOINTS
20915 @findex gdb.COMMAND_BREAKPOINTS
20916 @item COMMAND_BREAKPOINTS
20917 The command has to do with breakpoints. For example, @code{break},
20918 @code{clear}, and @code{delete} are in this category. Type @kbd{help
20919 breakpoints} at the @value{GDBN} prompt to see a list of commands in
20922 @findex COMMAND_TRACEPOINTS
20923 @findex gdb.COMMAND_TRACEPOINTS
20924 @item COMMAND_TRACEPOINTS
20925 The command has to do with tracepoints. For example, @code{trace},
20926 @code{actions}, and @code{tfind} are in this category. Type
20927 @kbd{help tracepoints} at the @value{GDBN} prompt to see a list of
20928 commands in this category.
20930 @findex COMMAND_OBSCURE
20931 @findex gdb.COMMAND_OBSCURE
20932 @item COMMAND_OBSCURE
20933 The command is only used in unusual circumstances, or is not of
20934 general interest to users. For example, @code{checkpoint},
20935 @code{fork}, and @code{stop} are in this category. Type @kbd{help
20936 obscure} at the @value{GDBN} prompt to see a list of commands in this
20939 @findex COMMAND_MAINTENANCE
20940 @findex gdb.COMMAND_MAINTENANCE
20941 @item COMMAND_MAINTENANCE
20942 The command is only useful to @value{GDBN} maintainers. The
20943 @code{maintenance} and @code{flushregs} commands are in this category.
20944 Type @kbd{help internals} at the @value{GDBN} prompt to see a list of
20945 commands in this category.
20948 A new command can use a predefined completion function, either by
20949 specifying it via an argument at initialization, or by returning it
20950 from the @code{complete} method. These predefined completion
20951 constants are all defined in the @code{gdb} module:
20954 @findex COMPLETE_NONE
20955 @findex gdb.COMPLETE_NONE
20956 @item COMPLETE_NONE
20957 This constant means that no completion should be done.
20959 @findex COMPLETE_FILENAME
20960 @findex gdb.COMPLETE_FILENAME
20961 @item COMPLETE_FILENAME
20962 This constant means that filename completion should be performed.
20964 @findex COMPLETE_LOCATION
20965 @findex gdb.COMPLETE_LOCATION
20966 @item COMPLETE_LOCATION
20967 This constant means that location completion should be done.
20968 @xref{Specify Location}.
20970 @findex COMPLETE_COMMAND
20971 @findex gdb.COMPLETE_COMMAND
20972 @item COMPLETE_COMMAND
20973 This constant means that completion should examine @value{GDBN}
20976 @findex COMPLETE_SYMBOL
20977 @findex gdb.COMPLETE_SYMBOL
20978 @item COMPLETE_SYMBOL
20979 This constant means that completion should be done using symbol names
20983 The following code snippet shows how a trivial CLI command can be
20984 implemented in Python:
20987 class HelloWorld (gdb.Command):
20988 """Greet the whole world."""
20990 def __init__ (self):
20991 super (HelloWorld, self).__init__ ("hello-world", gdb.COMMAND_OBSCURE)
20993 def invoke (self, arg, from_tty):
20994 print "Hello, World!"
20999 The last line instantiates the class, and is necessary to trigger the
21000 registration of the command with @value{GDBN}. Depending on how the
21001 Python code is read into @value{GDBN}, you may need to import the
21002 @code{gdb} module explicitly.
21004 @node Parameters In Python
21005 @subsubsection Parameters In Python
21007 @cindex parameters in python
21008 @cindex python parameters
21009 @tindex gdb.Parameter
21011 You can implement new @value{GDBN} parameters using Python. A new
21012 parameter is implemented as an instance of the @code{gdb.Parameter}
21015 Parameters are exposed to the user via the @code{set} and
21016 @code{show} commands. @xref{Help}.
21018 There are many parameters that already exist and can be set in
21019 @value{GDBN}. Two examples are: @code{set follow fork} and
21020 @code{set charset}. Setting these parameters influences certain
21021 behavior in @value{GDBN}. Similarly, you can define parameters that
21022 can be used to influence behavior in custom Python scripts and commands.
21024 @defmethod Parameter __init__ name @var{command-class} @var{parameter-class} @r{[}@var{enum-sequence}@r{]}
21025 The object initializer for @code{Parameter} registers the new
21026 parameter with @value{GDBN}. This initializer is normally invoked
21027 from the subclass' own @code{__init__} method.
21029 @var{name} is the name of the new parameter. If @var{name} consists
21030 of multiple words, then the initial words are looked for as prefix
21031 parameters. An example of this can be illustrated with the
21032 @code{set print} set of parameters. If @var{name} is
21033 @code{print foo}, then @code{print} will be searched as the prefix
21034 parameter. In this case the parameter can subsequently be accessed in
21035 @value{GDBN} as @code{set print foo}.
21037 If @var{name} consists of multiple words, and no prefix parameter group
21038 can be found, an exception is raised.
21040 @var{command-class} should be one of the @samp{COMMAND_} constants
21041 (@pxref{Commands In Python}). This argument tells @value{GDBN} how to
21042 categorize the new parameter in the help system.
21044 @var{parameter-class} should be one of the @samp{PARAM_} constants
21045 defined below. This argument tells @value{GDBN} the type of the new
21046 parameter; this information is used for input validation and
21049 If @var{parameter-class} is @code{PARAM_ENUM}, then
21050 @var{enum-sequence} must be a sequence of strings. These strings
21051 represent the possible values for the parameter.
21053 If @var{parameter-class} is not @code{PARAM_ENUM}, then the presence
21054 of a fourth argument will cause an exception to be thrown.
21056 The help text for the new parameter is taken from the Python
21057 documentation string for the parameter's class, if there is one. If
21058 there is no documentation string, a default value is used.
21061 @defivar Parameter set_doc
21062 If this attribute exists, and is a string, then its value is used as
21063 the help text for this parameter's @code{set} command. The value is
21064 examined when @code{Parameter.__init__} is invoked; subsequent changes
21068 @defivar Parameter show_doc
21069 If this attribute exists, and is a string, then its value is used as
21070 the help text for this parameter's @code{show} command. The value is
21071 examined when @code{Parameter.__init__} is invoked; subsequent changes
21075 @defivar Parameter value
21076 The @code{value} attribute holds the underlying value of the
21077 parameter. It can be read and assigned to just as any other
21078 attribute. @value{GDBN} does validation when assignments are made.
21082 When a new parameter is defined, its type must be specified. The
21083 available types are represented by constants defined in the @code{gdb}
21087 @findex PARAM_BOOLEAN
21088 @findex gdb.PARAM_BOOLEAN
21089 @item PARAM_BOOLEAN
21090 The value is a plain boolean. The Python boolean values, @code{True}
21091 and @code{False} are the only valid values.
21093 @findex PARAM_AUTO_BOOLEAN
21094 @findex gdb.PARAM_AUTO_BOOLEAN
21095 @item PARAM_AUTO_BOOLEAN
21096 The value has three possible states: true, false, and @samp{auto}. In
21097 Python, true and false are represented using boolean constants, and
21098 @samp{auto} is represented using @code{None}.
21100 @findex PARAM_UINTEGER
21101 @findex gdb.PARAM_UINTEGER
21102 @item PARAM_UINTEGER
21103 The value is an unsigned integer. The value of 0 should be
21104 interpreted to mean ``unlimited''.
21106 @findex PARAM_INTEGER
21107 @findex gdb.PARAM_INTEGER
21108 @item PARAM_INTEGER
21109 The value is a signed integer. The value of 0 should be interpreted
21110 to mean ``unlimited''.
21112 @findex PARAM_STRING
21113 @findex gdb.PARAM_STRING
21115 The value is a string. When the user modifies the string, any escape
21116 sequences, such as @samp{\t}, @samp{\f}, and octal escapes, are
21117 translated into corresponding characters and encoded into the current
21120 @findex PARAM_STRING_NOESCAPE
21121 @findex gdb.PARAM_STRING_NOESCAPE
21122 @item PARAM_STRING_NOESCAPE
21123 The value is a string. When the user modifies the string, escapes are
21124 passed through untranslated.
21126 @findex PARAM_OPTIONAL_FILENAME
21127 @findex gdb.PARAM_OPTIONAL_FILENAME
21128 @item PARAM_OPTIONAL_FILENAME
21129 The value is a either a filename (a string), or @code{None}.
21131 @findex PARAM_FILENAME
21132 @findex gdb.PARAM_FILENAME
21133 @item PARAM_FILENAME
21134 The value is a filename. This is just like
21135 @code{PARAM_STRING_NOESCAPE}, but uses file names for completion.
21137 @findex PARAM_ZINTEGER
21138 @findex gdb.PARAM_ZINTEGER
21139 @item PARAM_ZINTEGER
21140 The value is an integer. This is like @code{PARAM_INTEGER}, except 0
21141 is interpreted as itself.
21144 @findex gdb.PARAM_ENUM
21146 The value is a string, which must be one of a collection string
21147 constants provided when the parameter is created.
21150 @node Functions In Python
21151 @subsubsection Writing new convenience functions
21153 @cindex writing convenience functions
21154 @cindex convenience functions in python
21155 @cindex python convenience functions
21156 @tindex gdb.Function
21158 You can implement new convenience functions (@pxref{Convenience Vars})
21159 in Python. A convenience function is an instance of a subclass of the
21160 class @code{gdb.Function}.
21162 @defmethod Function __init__ name
21163 The initializer for @code{Function} registers the new function with
21164 @value{GDBN}. The argument @var{name} is the name of the function,
21165 a string. The function will be visible to the user as a convenience
21166 variable of type @code{internal function}, whose name is the same as
21167 the given @var{name}.
21169 The documentation for the new function is taken from the documentation
21170 string for the new class.
21173 @defmethod Function invoke @var{*args}
21174 When a convenience function is evaluated, its arguments are converted
21175 to instances of @code{gdb.Value}, and then the function's
21176 @code{invoke} method is called. Note that @value{GDBN} does not
21177 predetermine the arity of convenience functions. Instead, all
21178 available arguments are passed to @code{invoke}, following the
21179 standard Python calling convention. In particular, a convenience
21180 function can have default values for parameters without ill effect.
21182 The return value of this method is used as its value in the enclosing
21183 expression. If an ordinary Python value is returned, it is converted
21184 to a @code{gdb.Value} following the usual rules.
21187 The following code snippet shows how a trivial convenience function can
21188 be implemented in Python:
21191 class Greet (gdb.Function):
21192 """Return string to greet someone.
21193 Takes a name as argument."""
21195 def __init__ (self):
21196 super (Greet, self).__init__ ("greet")
21198 def invoke (self, name):
21199 return "Hello, %s!" % name.string ()
21204 The last line instantiates the class, and is necessary to trigger the
21205 registration of the function with @value{GDBN}. Depending on how the
21206 Python code is read into @value{GDBN}, you may need to import the
21207 @code{gdb} module explicitly.
21209 @node Progspaces In Python
21210 @subsubsection Program Spaces In Python
21212 @cindex progspaces in python
21213 @tindex gdb.Progspace
21215 A program space, or @dfn{progspace}, represents a symbolic view
21216 of an address space.
21217 It consists of all of the objfiles of the program.
21218 @xref{Objfiles In Python}.
21219 @xref{Inferiors and Programs, program spaces}, for more details
21220 about program spaces.
21222 The following progspace-related functions are available in the
21225 @findex gdb.current_progspace
21226 @defun current_progspace
21227 This function returns the program space of the currently selected inferior.
21228 @xref{Inferiors and Programs}.
21231 @findex gdb.progspaces
21233 Return a sequence of all the progspaces currently known to @value{GDBN}.
21236 Each progspace is represented by an instance of the @code{gdb.Progspace}
21239 @defivar Progspace filename
21240 The file name of the progspace as a string.
21243 @defivar Progspace pretty_printers
21244 The @code{pretty_printers} attribute is a list of functions. It is
21245 used to look up pretty-printers. A @code{Value} is passed to each
21246 function in order; if the function returns @code{None}, then the
21247 search continues. Otherwise, the return value should be an object
21248 which is used to format the value. @xref{Pretty Printing API}, for more
21252 @node Objfiles In Python
21253 @subsubsection Objfiles In Python
21255 @cindex objfiles in python
21256 @tindex gdb.Objfile
21258 @value{GDBN} loads symbols for an inferior from various
21259 symbol-containing files (@pxref{Files}). These include the primary
21260 executable file, any shared libraries used by the inferior, and any
21261 separate debug info files (@pxref{Separate Debug Files}).
21262 @value{GDBN} calls these symbol-containing files @dfn{objfiles}.
21264 The following objfile-related functions are available in the
21267 @findex gdb.current_objfile
21268 @defun current_objfile
21269 When auto-loading a Python script (@pxref{Auto-loading}), @value{GDBN}
21270 sets the ``current objfile'' to the corresponding objfile. This
21271 function returns the current objfile. If there is no current objfile,
21272 this function returns @code{None}.
21275 @findex gdb.objfiles
21277 Return a sequence of all the objfiles current known to @value{GDBN}.
21278 @xref{Objfiles In Python}.
21281 Each objfile is represented by an instance of the @code{gdb.Objfile}
21284 @defivar Objfile filename
21285 The file name of the objfile as a string.
21288 @defivar Objfile pretty_printers
21289 The @code{pretty_printers} attribute is a list of functions. It is
21290 used to look up pretty-printers. A @code{Value} is passed to each
21291 function in order; if the function returns @code{None}, then the
21292 search continues. Otherwise, the return value should be an object
21293 which is used to format the value. @xref{Pretty Printing API}, for more
21297 @node Frames In Python
21298 @subsubsection Accessing inferior stack frames from Python.
21300 @cindex frames in python
21301 When the debugged program stops, @value{GDBN} is able to analyze its call
21302 stack (@pxref{Frames,,Stack frames}). The @code{gdb.Frame} class
21303 represents a frame in the stack. A @code{gdb.Frame} object is only valid
21304 while its corresponding frame exists in the inferior's stack. If you try
21305 to use an invalid frame object, @value{GDBN} will throw a @code{RuntimeError}
21308 Two @code{gdb.Frame} objects can be compared for equality with the @code{==}
21312 (@value{GDBP}) python print gdb.newest_frame() == gdb.selected_frame ()
21316 The following frame-related functions are available in the @code{gdb} module:
21318 @findex gdb.selected_frame
21319 @defun selected_frame
21320 Return the selected frame object. (@pxref{Selection,,Selecting a Frame}).
21323 @defun frame_stop_reason_string reason
21324 Return a string explaining the reason why @value{GDBN} stopped unwinding
21325 frames, as expressed by the given @var{reason} code (an integer, see the
21326 @code{unwind_stop_reason} method further down in this section).
21329 A @code{gdb.Frame} object has the following methods:
21332 @defmethod Frame is_valid
21333 Returns true if the @code{gdb.Frame} object is valid, false if not.
21334 A frame object can become invalid if the frame it refers to doesn't
21335 exist anymore in the inferior. All @code{gdb.Frame} methods will throw
21336 an exception if it is invalid at the time the method is called.
21339 @defmethod Frame name
21340 Returns the function name of the frame, or @code{None} if it can't be
21344 @defmethod Frame type
21345 Returns the type of the frame. The value can be one of
21346 @code{gdb.NORMAL_FRAME}, @code{gdb.DUMMY_FRAME}, @code{gdb.SIGTRAMP_FRAME}
21347 or @code{gdb.SENTINEL_FRAME}.
21350 @defmethod Frame unwind_stop_reason
21351 Return an integer representing the reason why it's not possible to find
21352 more frames toward the outermost frame. Use
21353 @code{gdb.frame_stop_reason_string} to convert the value returned by this
21354 function to a string.
21357 @defmethod Frame pc
21358 Returns the frame's resume address.
21361 @defmethod Frame block
21362 Return the frame's code block. @xref{Blocks In Python}.
21365 @defmethod Frame function
21366 Return the symbol for the function corresponding to this frame.
21367 @xref{Symbols In Python}.
21370 @defmethod Frame older
21371 Return the frame that called this frame.
21374 @defmethod Frame newer
21375 Return the frame called by this frame.
21378 @defmethod Frame find_sal
21379 Return the frame's symtab and line object.
21380 @xref{Symbol Tables In Python}.
21383 @defmethod Frame read_var variable @r{[}block@r{]}
21384 Return the value of @var{variable} in this frame. If the optional
21385 argument @var{block} is provided, search for the variable from that
21386 block; otherwise start at the frame's current block (which is
21387 determined by the frame's current program counter). @var{variable}
21388 must be a string or a @code{gdb.Symbol} object. @var{block} must be a
21389 @code{gdb.Block} object.
21392 @defmethod Frame select
21393 Set this frame to be the selected frame. @xref{Stack, ,Examining the
21398 @node Blocks In Python
21399 @subsubsection Accessing frame blocks from Python.
21401 @cindex blocks in python
21404 Within each frame, @value{GDBN} maintains information on each block
21405 stored in that frame. These blocks are organized hierarchically, and
21406 are represented individually in Python as a @code{gdb.Block}.
21407 Please see @ref{Frames In Python}, for a more in-depth discussion on
21408 frames. Furthermore, see @ref{Stack, ,Examining the Stack}, for more
21409 detailed technical information on @value{GDBN}'s book-keeping of the
21412 The following block-related functions are available in the @code{gdb}
21415 @findex gdb.block_for_pc
21416 @defun block_for_pc pc
21417 Return the @code{gdb.Block} containing the given @var{pc} value. If the
21418 block cannot be found for the @var{pc} value specified, the function
21419 will return @code{None}.
21422 A @code{gdb.Block} object has the following attributes:
21425 @defivar Block start
21426 The start address of the block. This attribute is not writable.
21430 The end address of the block. This attribute is not writable.
21433 @defivar Block function
21434 The name of the block represented as a @code{gdb.Symbol}. If the
21435 block is not named, then this attribute holds @code{None}. This
21436 attribute is not writable.
21439 @defivar Block superblock
21440 The block containing this block. If this parent block does not exist,
21441 this attribute holds @code{None}. This attribute is not writable.
21445 @node Symbols In Python
21446 @subsubsection Python representation of Symbols.
21448 @cindex symbols in python
21451 @value{GDBN} represents every variable, function and type as an
21452 entry in a symbol table. @xref{Symbols, ,Examining the Symbol Table}.
21453 Similarly, Python represents these symbols in @value{GDBN} with the
21454 @code{gdb.Symbol} object.
21456 The following symbol-related functions are available in the @code{gdb}
21459 @findex gdb.lookup_symbol
21460 @defun lookup_symbol name [block] [domain]
21461 This function searches for a symbol by name. The search scope can be
21462 restricted to the parameters defined in the optional domain and block
21465 @var{name} is the name of the symbol. It must be a string. The
21466 optional @var{block} argument restricts the search to symbols visible
21467 in that @var{block}. The @var{block} argument must be a
21468 @code{gdb.Block} object. The optional @var{domain} argument restricts
21469 the search to the domain type. The @var{domain} argument must be a
21470 domain constant defined in the @code{gdb} module and described later
21474 A @code{gdb.Symbol} object has the following attributes:
21477 @defivar Symbol symtab
21478 The symbol table in which the symbol appears. This attribute is
21479 represented as a @code{gdb.Symtab} object. @xref{Symbol Tables In
21480 Python}. This attribute is not writable.
21483 @defivar Symbol name
21484 The name of the symbol as a string. This attribute is not writable.
21487 @defivar Symbol linkage_name
21488 The name of the symbol, as used by the linker (i.e., may be mangled).
21489 This attribute is not writable.
21492 @defivar Symbol print_name
21493 The name of the symbol in a form suitable for output. This is either
21494 @code{name} or @code{linkage_name}, depending on whether the user
21495 asked @value{GDBN} to display demangled or mangled names.
21498 @defivar Symbol addr_class
21499 The address class of the symbol. This classifies how to find the value
21500 of a symbol. Each address class is a constant defined in the
21501 @code{gdb} module and described later in this chapter.
21504 @defivar Symbol is_argument
21505 @code{True} if the symbol is an argument of a function.
21508 @defivar Symbol is_constant
21509 @code{True} if the symbol is a constant.
21512 @defivar Symbol is_function
21513 @code{True} if the symbol is a function or a method.
21516 @defivar Symbol is_variable
21517 @code{True} if the symbol is a variable.
21521 The available domain categories in @code{gdb.Symbol} are represented
21522 as constants in the @code{gdb} module:
21525 @findex SYMBOL_UNDEF_DOMAIN
21526 @findex gdb.SYMBOL_UNDEF_DOMAIN
21527 @item SYMBOL_UNDEF_DOMAIN
21528 This is used when a domain has not been discovered or none of the
21529 following domains apply. This usually indicates an error either
21530 in the symbol information or in @value{GDBN}'s handling of symbols.
21531 @findex SYMBOL_VAR_DOMAIN
21532 @findex gdb.SYMBOL_VAR_DOMAIN
21533 @item SYMBOL_VAR_DOMAIN
21534 This domain contains variables, function names, typedef names and enum
21536 @findex SYMBOL_STRUCT_DOMAIN
21537 @findex gdb.SYMBOL_STRUCT_DOMAIN
21538 @item SYMBOL_STRUCT_DOMAIN
21539 This domain holds struct, union and enum type names.
21540 @findex SYMBOL_LABEL_DOMAIN
21541 @findex gdb.SYMBOL_LABEL_DOMAIN
21542 @item SYMBOL_LABEL_DOMAIN
21543 This domain contains names of labels (for gotos).
21544 @findex SYMBOL_VARIABLES_DOMAIN
21545 @findex gdb.SYMBOL_VARIABLES_DOMAIN
21546 @item SYMBOL_VARIABLES_DOMAIN
21547 This domain holds a subset of the @code{SYMBOLS_VAR_DOMAIN}; it
21548 contains everything minus functions and types.
21549 @findex SYMBOL_FUNCTIONS_DOMAIN
21550 @findex gdb.SYMBOL_FUNCTIONS_DOMAIN
21551 @item SYMBOL_FUNCTION_DOMAIN
21552 This domain contains all functions.
21553 @findex SYMBOL_TYPES_DOMAIN
21554 @findex gdb.SYMBOL_TYPES_DOMAIN
21555 @item SYMBOL_TYPES_DOMAIN
21556 This domain contains all types.
21559 The available address class categories in @code{gdb.Symbol} are represented
21560 as constants in the @code{gdb} module:
21563 @findex SYMBOL_LOC_UNDEF
21564 @findex gdb.SYMBOL_LOC_UNDEF
21565 @item SYMBOL_LOC_UNDEF
21566 If this is returned by address class, it indicates an error either in
21567 the symbol information or in @value{GDBN}'s handling of symbols.
21568 @findex SYMBOL_LOC_CONST
21569 @findex gdb.SYMBOL_LOC_CONST
21570 @item SYMBOL_LOC_CONST
21571 Value is constant int.
21572 @findex SYMBOL_LOC_STATIC
21573 @findex gdb.SYMBOL_LOC_STATIC
21574 @item SYMBOL_LOC_STATIC
21575 Value is at a fixed address.
21576 @findex SYMBOL_LOC_REGISTER
21577 @findex gdb.SYMBOL_LOC_REGISTER
21578 @item SYMBOL_LOC_REGISTER
21579 Value is in a register.
21580 @findex SYMBOL_LOC_ARG
21581 @findex gdb.SYMBOL_LOC_ARG
21582 @item SYMBOL_LOC_ARG
21583 Value is an argument. This value is at the offset stored within the
21584 symbol inside the frame's argument list.
21585 @findex SYMBOL_LOC_REF_ARG
21586 @findex gdb.SYMBOL_LOC_REF_ARG
21587 @item SYMBOL_LOC_REF_ARG
21588 Value address is stored in the frame's argument list. Just like
21589 @code{LOC_ARG} except that the value's address is stored at the
21590 offset, not the value itself.
21591 @findex SYMBOL_LOC_REGPARM_ADDR
21592 @findex gdb.SYMBOL_LOC_REGPARM_ADDR
21593 @item SYMBOL_LOC_REGPARM_ADDR
21594 Value is a specified register. Just like @code{LOC_REGISTER} except
21595 the register holds the address of the argument instead of the argument
21597 @findex SYMBOL_LOC_LOCAL
21598 @findex gdb.SYMBOL_LOC_LOCAL
21599 @item SYMBOL_LOC_LOCAL
21600 Value is a local variable.
21601 @findex SYMBOL_LOC_TYPEDEF
21602 @findex gdb.SYMBOL_LOC_TYPEDEF
21603 @item SYMBOL_LOC_TYPEDEF
21604 Value not used. Symbols in the domain @code{SYMBOL_STRUCT_DOMAIN} all
21606 @findex SYMBOL_LOC_BLOCK
21607 @findex gdb.SYMBOL_LOC_BLOCK
21608 @item SYMBOL_LOC_BLOCK
21610 @findex SYMBOL_LOC_CONST_BYTES
21611 @findex gdb.SYMBOL_LOC_CONST_BYTES
21612 @item SYMBOL_LOC_CONST_BYTES
21613 Value is a byte-sequence.
21614 @findex SYMBOL_LOC_UNRESOLVED
21615 @findex gdb.SYMBOL_LOC_UNRESOLVED
21616 @item SYMBOL_LOC_UNRESOLVED
21617 Value is at a fixed address, but the address of the variable has to be
21618 determined from the minimal symbol table whenever the variable is
21620 @findex SYMBOL_LOC_OPTIMIZED_OUT
21621 @findex gdb.SYMBOL_LOC_OPTIMIZED_OUT
21622 @item SYMBOL_LOC_OPTIMIZED_OUT
21623 The value does not actually exist in the program.
21624 @findex SYMBOL_LOC_COMPUTED
21625 @findex gdb.SYMBOL_LOC_COMPUTED
21626 @item SYMBOL_LOC_COMPUTED
21627 The value's address is a computed location.
21630 @node Symbol Tables In Python
21631 @subsubsection Symbol table representation in Python.
21633 @cindex symbol tables in python
21635 @tindex gdb.Symtab_and_line
21637 Access to symbol table data maintained by @value{GDBN} on the inferior
21638 is exposed to Python via two objects: @code{gdb.Symtab_and_line} and
21639 @code{gdb.Symtab}. Symbol table and line data for a frame is returned
21640 from the @code{find_sal} method in @code{gdb.Frame} object.
21641 @xref{Frames In Python}.
21643 For more information on @value{GDBN}'s symbol table management, see
21644 @ref{Symbols, ,Examining the Symbol Table}, for more information.
21646 A @code{gdb.Symtab_and_line} object has the following attributes:
21649 @defivar Symtab_and_line symtab
21650 The symbol table object (@code{gdb.Symtab}) for this frame.
21651 This attribute is not writable.
21654 @defivar Symtab_and_line pc
21655 Indicates the current program counter address. This attribute is not
21659 @defivar Symtab_and_line line
21660 Indicates the current line number for this object. This
21661 attribute is not writable.
21665 A @code{gdb.Symtab} object has the following attributes:
21668 @defivar Symtab filename
21669 The symbol table's source filename. This attribute is not writable.
21672 @defivar Symtab objfile
21673 The symbol table's backing object file. @xref{Objfiles In Python}.
21674 This attribute is not writable.
21678 The following methods are provided:
21681 @defmethod Symtab fullname
21682 Return the symbol table's source absolute file name.
21686 @node Breakpoints In Python
21687 @subsubsection Manipulating breakpoints using Python
21689 @cindex breakpoints in python
21690 @tindex gdb.Breakpoint
21692 Python code can manipulate breakpoints via the @code{gdb.Breakpoint}
21695 @defmethod Breakpoint __init__ spec @r{[}type@r{]} @r{[}wp_class@r{]}
21696 Create a new breakpoint. @var{spec} is a string naming the
21697 location of the breakpoint, or an expression that defines a
21698 watchpoint. The contents can be any location recognized by the
21699 @code{break} command, or in the case of a watchpoint, by the @code{watch}
21700 command. The optional @var{type} denotes the breakpoint to create
21701 from the types defined later in this chapter. This argument can be
21702 either: @code{BP_BREAKPOINT} or @code{BP_WATCHPOINT}. @var{type}
21703 defaults to @code{BP_BREAKPOINT}. The optional @var{wp_class}
21704 argument defines the class of watchpoint to create, if @var{type} is
21705 defined as @code{BP_WATCHPOINT}. If a watchpoint class is not
21706 provided, it is assumed to be a @var{WP_WRITE} class.
21709 The available watchpoint types represented by constants are defined in the
21714 @findex gdb.WP_READ
21716 Read only watchpoint.
21719 @findex gdb.WP_WRITE
21721 Write only watchpoint.
21724 @findex gdb.WP_ACCESS
21726 Read/Write watchpoint.
21729 @defmethod Breakpoint is_valid
21730 Return @code{True} if this @code{Breakpoint} object is valid,
21731 @code{False} otherwise. A @code{Breakpoint} object can become invalid
21732 if the user deletes the breakpoint. In this case, the object still
21733 exists, but the underlying breakpoint does not. In the cases of
21734 watchpoint scope, the watchpoint remains valid even if execution of the
21735 inferior leaves the scope of that watchpoint.
21738 @defivar Breakpoint enabled
21739 This attribute is @code{True} if the breakpoint is enabled, and
21740 @code{False} otherwise. This attribute is writable.
21743 @defivar Breakpoint silent
21744 This attribute is @code{True} if the breakpoint is silent, and
21745 @code{False} otherwise. This attribute is writable.
21747 Note that a breakpoint can also be silent if it has commands and the
21748 first command is @code{silent}. This is not reported by the
21749 @code{silent} attribute.
21752 @defivar Breakpoint thread
21753 If the breakpoint is thread-specific, this attribute holds the thread
21754 id. If the breakpoint is not thread-specific, this attribute is
21755 @code{None}. This attribute is writable.
21758 @defivar Breakpoint task
21759 If the breakpoint is Ada task-specific, this attribute holds the Ada task
21760 id. If the breakpoint is not task-specific (or the underlying
21761 language is not Ada), this attribute is @code{None}. This attribute
21765 @defivar Breakpoint ignore_count
21766 This attribute holds the ignore count for the breakpoint, an integer.
21767 This attribute is writable.
21770 @defivar Breakpoint number
21771 This attribute holds the breakpoint's number --- the identifier used by
21772 the user to manipulate the breakpoint. This attribute is not writable.
21775 @defivar Breakpoint type
21776 This attribute holds the breakpoint's type --- the identifier used to
21777 determine the actual breakpoint type or use-case. This attribute is not
21781 The available types are represented by constants defined in the @code{gdb}
21785 @findex BP_BREAKPOINT
21786 @findex gdb.BP_BREAKPOINT
21787 @item BP_BREAKPOINT
21788 Normal code breakpoint.
21790 @findex BP_WATCHPOINT
21791 @findex gdb.BP_WATCHPOINT
21792 @item BP_WATCHPOINT
21793 Watchpoint breakpoint.
21795 @findex BP_HARDWARE_WATCHPOINT
21796 @findex gdb.BP_HARDWARE_WATCHPOINT
21797 @item BP_HARDWARE_WATCHPOINT
21798 Hardware assisted watchpoint.
21800 @findex BP_READ_WATCHPOINT
21801 @findex gdb.BP_READ_WATCHPOINT
21802 @item BP_READ_WATCHPOINT
21803 Hardware assisted read watchpoint.
21805 @findex BP_ACCESS_WATCHPOINT
21806 @findex gdb.BP_ACCESS_WATCHPOINT
21807 @item BP_ACCESS_WATCHPOINT
21808 Hardware assisted access watchpoint.
21811 @defivar Breakpoint hit_count
21812 This attribute holds the hit count for the breakpoint, an integer.
21813 This attribute is writable, but currently it can only be set to zero.
21816 @defivar Breakpoint location
21817 This attribute holds the location of the breakpoint, as specified by
21818 the user. It is a string. If the breakpoint does not have a location
21819 (that is, it is a watchpoint) the attribute's value is @code{None}. This
21820 attribute is not writable.
21823 @defivar Breakpoint expression
21824 This attribute holds a breakpoint expression, as specified by
21825 the user. It is a string. If the breakpoint does not have an
21826 expression (the breakpoint is not a watchpoint) the attribute's value
21827 is @code{None}. This attribute is not writable.
21830 @defivar Breakpoint condition
21831 This attribute holds the condition of the breakpoint, as specified by
21832 the user. It is a string. If there is no condition, this attribute's
21833 value is @code{None}. This attribute is writable.
21836 @defivar Breakpoint commands
21837 This attribute holds the commands attached to the breakpoint. If
21838 there are commands, this attribute's value is a string holding all the
21839 commands, separated by newlines. If there are no commands, this
21840 attribute is @code{None}. This attribute is not writable.
21843 @node Lazy Strings In Python
21844 @subsubsection Python representation of lazy strings.
21846 @cindex lazy strings in python
21847 @tindex gdb.LazyString
21849 A @dfn{lazy string} is a string whose contents is not retrieved or
21850 encoded until it is needed.
21852 A @code{gdb.LazyString} is represented in @value{GDBN} as an
21853 @code{address} that points to a region of memory, an @code{encoding}
21854 that will be used to encode that region of memory, and a @code{length}
21855 to delimit the region of memory that represents the string. The
21856 difference between a @code{gdb.LazyString} and a string wrapped within
21857 a @code{gdb.Value} is that a @code{gdb.LazyString} will be treated
21858 differently by @value{GDBN} when printing. A @code{gdb.LazyString} is
21859 retrieved and encoded during printing, while a @code{gdb.Value}
21860 wrapping a string is immediately retrieved and encoded on creation.
21862 A @code{gdb.LazyString} object has the following functions:
21864 @defmethod LazyString value
21865 Convert the @code{gdb.LazyString} to a @code{gdb.Value}. This value
21866 will point to the string in memory, but will lose all the delayed
21867 retrieval, encoding and handling that @value{GDBN} applies to a
21868 @code{gdb.LazyString}.
21871 @defivar LazyString address
21872 This attribute holds the address of the string. This attribute is not
21876 @defivar LazyString length
21877 This attribute holds the length of the string in characters. If the
21878 length is -1, then the string will be fetched and encoded up to the
21879 first null of appropriate width. This attribute is not writable.
21882 @defivar LazyString encoding
21883 This attribute holds the encoding that will be applied to the string
21884 when the string is printed by @value{GDBN}. If the encoding is not
21885 set, or contains an empty string, then @value{GDBN} will select the
21886 most appropriate encoding when the string is printed. This attribute
21890 @defivar LazyString type
21891 This attribute holds the type that is represented by the lazy string's
21892 type. For a lazy string this will always be a pointer type. To
21893 resolve this to the lazy string's character type, use the type's
21894 @code{target} method. @xref{Types In Python}. This attribute is not
21899 @subsection Auto-loading
21900 @cindex auto-loading, Python
21902 When a new object file is read (for example, due to the @code{file}
21903 command, or because the inferior has loaded a shared library),
21904 @value{GDBN} will look for Python support scripts in several ways:
21905 @file{@var{objfile}-gdb.py} and @code{.debug_gdb_scripts} section.
21908 * objfile-gdb.py file:: The @file{@var{objfile}-gdb.py} file
21909 * .debug_gdb_scripts section:: The @code{.debug_gdb_scripts} section
21910 * Which flavor to choose?::
21913 The auto-loading feature is useful for supplying application-specific
21914 debugging commands and scripts.
21916 Auto-loading can be enabled or disabled.
21919 @kindex maint set python auto-load
21920 @item maint set python auto-load [yes|no]
21921 Enable or disable the Python auto-loading feature.
21923 @kindex maint show python auto-load
21924 @item maint show python auto-load
21925 Show whether Python auto-loading is enabled or disabled.
21928 When reading an auto-loaded file, @value{GDBN} sets the
21929 @dfn{current objfile}. This is available via the @code{gdb.current_objfile}
21930 function (@pxref{Objfiles In Python}). This can be useful for
21931 registering objfile-specific pretty-printers.
21933 @node objfile-gdb.py file
21934 @subsubsection The @file{@var{objfile}-gdb.py} file
21935 @cindex @file{@var{objfile}-gdb.py}
21937 When a new object file is read, @value{GDBN} looks for
21938 a file named @file{@var{objfile}-gdb.py},
21939 where @var{objfile} is the object file's real name, formed by ensuring
21940 that the file name is absolute, following all symlinks, and resolving
21941 @code{.} and @code{..} components. If this file exists and is
21942 readable, @value{GDBN} will evaluate it as a Python script.
21944 If this file does not exist, and if the parameter
21945 @code{debug-file-directory} is set (@pxref{Separate Debug Files}),
21946 then @value{GDBN} will look for @var{real-name} in all of the
21947 directories mentioned in the value of @code{debug-file-directory}.
21949 Finally, if this file does not exist, then @value{GDBN} will look for
21950 a file named @file{@var{data-directory}/python/auto-load/@var{real-name}}, where
21951 @var{data-directory} is @value{GDBN}'s data directory (available via
21952 @code{show data-directory}, @pxref{Data Files}), and @var{real-name}
21953 is the object file's real name, as described above.
21955 @value{GDBN} does not track which files it has already auto-loaded this way.
21956 @value{GDBN} will load the associated script every time the corresponding
21957 @var{objfile} is opened.
21958 So your @file{-gdb.py} file should be careful to avoid errors if it
21959 is evaluated more than once.
21961 @node .debug_gdb_scripts section
21962 @subsubsection The @code{.debug_gdb_scripts} section
21963 @cindex @code{.debug_gdb_scripts} section
21965 For systems using file formats like ELF and COFF,
21966 when @value{GDBN} loads a new object file
21967 it will look for a special section named @samp{.debug_gdb_scripts}.
21968 If this section exists, its contents is a list of names of scripts to load.
21970 @value{GDBN} will look for each specified script file first in the
21971 current directory and then along the source search path
21972 (@pxref{Source Path, ,Specifying Source Directories}),
21973 except that @file{$cdir} is not searched, since the compilation
21974 directory is not relevant to scripts.
21976 Entries can be placed in section @code{.debug_gdb_scripts} with,
21977 for example, this GCC macro:
21980 /* Note: The "MS" section flags are to remote duplicates. */
21981 #define DEFINE_GDB_SCRIPT(script_name) \
21983 .pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n\
21985 .asciz \"" script_name "\"\n\
21991 Then one can reference the macro in a header or source file like this:
21994 DEFINE_GDB_SCRIPT ("my-app-scripts.py")
21997 The script name may include directories if desired.
21999 If the macro is put in a header, any application or library
22000 using this header will get a reference to the specified script.
22002 @node Which flavor to choose?
22003 @subsubsection Which flavor to choose?
22005 Given the multiple ways of auto-loading Python scripts, it might not always
22006 be clear which one to choose. This section provides some guidance.
22008 Benefits of the @file{-gdb.py} way:
22012 Can be used with file formats that don't support multiple sections.
22015 Ease of finding scripts for public libraries.
22017 Scripts specified in the @code{.debug_gdb_scripts} section are searched for
22018 in the source search path.
22019 For publicly installed libraries, e.g., @file{libstdc++}, there typically
22020 isn't a source directory in which to find the script.
22023 Doesn't require source code additions.
22026 Benefits of the @code{.debug_gdb_scripts} way:
22030 Works with static linking.
22032 Scripts for libraries done the @file{-gdb.py} way require an objfile to
22033 trigger their loading. When an application is statically linked the only
22034 objfile available is the executable, and it is cumbersome to attach all the
22035 scripts from all the input libraries to the executable's @file{-gdb.py} script.
22038 Works with classes that are entirely inlined.
22040 Some classes can be entirely inlined, and thus there may not be an associated
22041 shared library to attach a @file{-gdb.py} script to.
22044 Scripts needn't be copied out of the source tree.
22046 In some circumstances, apps can be built out of large collections of internal
22047 libraries, and the build infrastructure necessary to install the
22048 @file{-gdb.py} scripts in a place where @value{GDBN} can find them is
22049 cumbersome. It may be easier to specify the scripts in the
22050 @code{.debug_gdb_scripts} section as relative paths, and add a path to the
22051 top of the source tree to the source search path.
22055 @chapter Command Interpreters
22056 @cindex command interpreters
22058 @value{GDBN} supports multiple command interpreters, and some command
22059 infrastructure to allow users or user interface writers to switch
22060 between interpreters or run commands in other interpreters.
22062 @value{GDBN} currently supports two command interpreters, the console
22063 interpreter (sometimes called the command-line interpreter or @sc{cli})
22064 and the machine interface interpreter (or @sc{gdb/mi}). This manual
22065 describes both of these interfaces in great detail.
22067 By default, @value{GDBN} will start with the console interpreter.
22068 However, the user may choose to start @value{GDBN} with another
22069 interpreter by specifying the @option{-i} or @option{--interpreter}
22070 startup options. Defined interpreters include:
22074 @cindex console interpreter
22075 The traditional console or command-line interpreter. This is the most often
22076 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
22077 @value{GDBN} will use this interpreter.
22080 @cindex mi interpreter
22081 The newest @sc{gdb/mi} interface (currently @code{mi2}). Used primarily
22082 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
22083 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
22087 @cindex mi2 interpreter
22088 The current @sc{gdb/mi} interface.
22091 @cindex mi1 interpreter
22092 The @sc{gdb/mi} interface included in @value{GDBN} 5.1, 5.2, and 5.3.
22096 @cindex invoke another interpreter
22097 The interpreter being used by @value{GDBN} may not be dynamically
22098 switched at runtime. Although possible, this could lead to a very
22099 precarious situation. Consider an IDE using @sc{gdb/mi}. If a user
22100 enters the command "interpreter-set console" in a console view,
22101 @value{GDBN} would switch to using the console interpreter, rendering
22102 the IDE inoperable!
22104 @kindex interpreter-exec
22105 Although you may only choose a single interpreter at startup, you may execute
22106 commands in any interpreter from the current interpreter using the appropriate
22107 command. If you are running the console interpreter, simply use the
22108 @code{interpreter-exec} command:
22111 interpreter-exec mi "-data-list-register-names"
22114 @sc{gdb/mi} has a similar command, although it is only available in versions of
22115 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
22118 @chapter @value{GDBN} Text User Interface
22120 @cindex Text User Interface
22123 * TUI Overview:: TUI overview
22124 * TUI Keys:: TUI key bindings
22125 * TUI Single Key Mode:: TUI single key mode
22126 * TUI Commands:: TUI-specific commands
22127 * TUI Configuration:: TUI configuration variables
22130 The @value{GDBN} Text User Interface (TUI) is a terminal
22131 interface which uses the @code{curses} library to show the source
22132 file, the assembly output, the program registers and @value{GDBN}
22133 commands in separate text windows. The TUI mode is supported only
22134 on platforms where a suitable version of the @code{curses} library
22137 @pindex @value{GDBTUI}
22138 The TUI mode is enabled by default when you invoke @value{GDBN} as
22139 either @samp{@value{GDBTUI}} or @samp{@value{GDBP} -tui}.
22140 You can also switch in and out of TUI mode while @value{GDBN} runs by
22141 using various TUI commands and key bindings, such as @kbd{C-x C-a}.
22142 @xref{TUI Keys, ,TUI Key Bindings}.
22145 @section TUI Overview
22147 In TUI mode, @value{GDBN} can display several text windows:
22151 This window is the @value{GDBN} command window with the @value{GDBN}
22152 prompt and the @value{GDBN} output. The @value{GDBN} input is still
22153 managed using readline.
22156 The source window shows the source file of the program. The current
22157 line and active breakpoints are displayed in this window.
22160 The assembly window shows the disassembly output of the program.
22163 This window shows the processor registers. Registers are highlighted
22164 when their values change.
22167 The source and assembly windows show the current program position
22168 by highlighting the current line and marking it with a @samp{>} marker.
22169 Breakpoints are indicated with two markers. The first marker
22170 indicates the breakpoint type:
22174 Breakpoint which was hit at least once.
22177 Breakpoint which was never hit.
22180 Hardware breakpoint which was hit at least once.
22183 Hardware breakpoint which was never hit.
22186 The second marker indicates whether the breakpoint is enabled or not:
22190 Breakpoint is enabled.
22193 Breakpoint is disabled.
22196 The source, assembly and register windows are updated when the current
22197 thread changes, when the frame changes, or when the program counter
22200 These windows are not all visible at the same time. The command
22201 window is always visible. The others can be arranged in several
22212 source and assembly,
22215 source and registers, or
22218 assembly and registers.
22221 A status line above the command window shows the following information:
22225 Indicates the current @value{GDBN} target.
22226 (@pxref{Targets, ,Specifying a Debugging Target}).
22229 Gives the current process or thread number.
22230 When no process is being debugged, this field is set to @code{No process}.
22233 Gives the current function name for the selected frame.
22234 The name is demangled if demangling is turned on (@pxref{Print Settings}).
22235 When there is no symbol corresponding to the current program counter,
22236 the string @code{??} is displayed.
22239 Indicates the current line number for the selected frame.
22240 When the current line number is not known, the string @code{??} is displayed.
22243 Indicates the current program counter address.
22247 @section TUI Key Bindings
22248 @cindex TUI key bindings
22250 The TUI installs several key bindings in the readline keymaps
22251 (@pxref{Command Line Editing}). The following key bindings
22252 are installed for both TUI mode and the @value{GDBN} standard mode.
22261 Enter or leave the TUI mode. When leaving the TUI mode,
22262 the curses window management stops and @value{GDBN} operates using
22263 its standard mode, writing on the terminal directly. When reentering
22264 the TUI mode, control is given back to the curses windows.
22265 The screen is then refreshed.
22269 Use a TUI layout with only one window. The layout will
22270 either be @samp{source} or @samp{assembly}. When the TUI mode
22271 is not active, it will switch to the TUI mode.
22273 Think of this key binding as the Emacs @kbd{C-x 1} binding.
22277 Use a TUI layout with at least two windows. When the current
22278 layout already has two windows, the next layout with two windows is used.
22279 When a new layout is chosen, one window will always be common to the
22280 previous layout and the new one.
22282 Think of it as the Emacs @kbd{C-x 2} binding.
22286 Change the active window. The TUI associates several key bindings
22287 (like scrolling and arrow keys) with the active window. This command
22288 gives the focus to the next TUI window.
22290 Think of it as the Emacs @kbd{C-x o} binding.
22294 Switch in and out of the TUI SingleKey mode that binds single
22295 keys to @value{GDBN} commands (@pxref{TUI Single Key Mode}).
22298 The following key bindings only work in the TUI mode:
22303 Scroll the active window one page up.
22307 Scroll the active window one page down.
22311 Scroll the active window one line up.
22315 Scroll the active window one line down.
22319 Scroll the active window one column left.
22323 Scroll the active window one column right.
22327 Refresh the screen.
22330 Because the arrow keys scroll the active window in the TUI mode, they
22331 are not available for their normal use by readline unless the command
22332 window has the focus. When another window is active, you must use
22333 other readline key bindings such as @kbd{C-p}, @kbd{C-n}, @kbd{C-b}
22334 and @kbd{C-f} to control the command window.
22336 @node TUI Single Key Mode
22337 @section TUI Single Key Mode
22338 @cindex TUI single key mode
22340 The TUI also provides a @dfn{SingleKey} mode, which binds several
22341 frequently used @value{GDBN} commands to single keys. Type @kbd{C-x s} to
22342 switch into this mode, where the following key bindings are used:
22345 @kindex c @r{(SingleKey TUI key)}
22349 @kindex d @r{(SingleKey TUI key)}
22353 @kindex f @r{(SingleKey TUI key)}
22357 @kindex n @r{(SingleKey TUI key)}
22361 @kindex q @r{(SingleKey TUI key)}
22363 exit the SingleKey mode.
22365 @kindex r @r{(SingleKey TUI key)}
22369 @kindex s @r{(SingleKey TUI key)}
22373 @kindex u @r{(SingleKey TUI key)}
22377 @kindex v @r{(SingleKey TUI key)}
22381 @kindex w @r{(SingleKey TUI key)}
22386 Other keys temporarily switch to the @value{GDBN} command prompt.
22387 The key that was pressed is inserted in the editing buffer so that
22388 it is possible to type most @value{GDBN} commands without interaction
22389 with the TUI SingleKey mode. Once the command is entered the TUI
22390 SingleKey mode is restored. The only way to permanently leave
22391 this mode is by typing @kbd{q} or @kbd{C-x s}.
22395 @section TUI-specific Commands
22396 @cindex TUI commands
22398 The TUI has specific commands to control the text windows.
22399 These commands are always available, even when @value{GDBN} is not in
22400 the TUI mode. When @value{GDBN} is in the standard mode, most
22401 of these commands will automatically switch to the TUI mode.
22403 Note that if @value{GDBN}'s @code{stdout} is not connected to a
22404 terminal, or @value{GDBN} has been started with the machine interface
22405 interpreter (@pxref{GDB/MI, ,The @sc{gdb/mi} Interface}), most of
22406 these commands will fail with an error, because it would not be
22407 possible or desirable to enable curses window management.
22412 List and give the size of all displayed windows.
22416 Display the next layout.
22419 Display the previous layout.
22422 Display the source window only.
22425 Display the assembly window only.
22428 Display the source and assembly window.
22431 Display the register window together with the source or assembly window.
22435 Make the next window active for scrolling.
22438 Make the previous window active for scrolling.
22441 Make the source window active for scrolling.
22444 Make the assembly window active for scrolling.
22447 Make the register window active for scrolling.
22450 Make the command window active for scrolling.
22454 Refresh the screen. This is similar to typing @kbd{C-L}.
22456 @item tui reg float
22458 Show the floating point registers in the register window.
22460 @item tui reg general
22461 Show the general registers in the register window.
22464 Show the next register group. The list of register groups as well as
22465 their order is target specific. The predefined register groups are the
22466 following: @code{general}, @code{float}, @code{system}, @code{vector},
22467 @code{all}, @code{save}, @code{restore}.
22469 @item tui reg system
22470 Show the system registers in the register window.
22474 Update the source window and the current execution point.
22476 @item winheight @var{name} +@var{count}
22477 @itemx winheight @var{name} -@var{count}
22479 Change the height of the window @var{name} by @var{count}
22480 lines. Positive counts increase the height, while negative counts
22483 @item tabset @var{nchars}
22485 Set the width of tab stops to be @var{nchars} characters.
22488 @node TUI Configuration
22489 @section TUI Configuration Variables
22490 @cindex TUI configuration variables
22492 Several configuration variables control the appearance of TUI windows.
22495 @item set tui border-kind @var{kind}
22496 @kindex set tui border-kind
22497 Select the border appearance for the source, assembly and register windows.
22498 The possible values are the following:
22501 Use a space character to draw the border.
22504 Use @sc{ascii} characters @samp{+}, @samp{-} and @samp{|} to draw the border.
22507 Use the Alternate Character Set to draw the border. The border is
22508 drawn using character line graphics if the terminal supports them.
22511 @item set tui border-mode @var{mode}
22512 @kindex set tui border-mode
22513 @itemx set tui active-border-mode @var{mode}
22514 @kindex set tui active-border-mode
22515 Select the display attributes for the borders of the inactive windows
22516 or the active window. The @var{mode} can be one of the following:
22519 Use normal attributes to display the border.
22525 Use reverse video mode.
22528 Use half bright mode.
22530 @item half-standout
22531 Use half bright and standout mode.
22534 Use extra bright or bold mode.
22536 @item bold-standout
22537 Use extra bright or bold and standout mode.
22542 @chapter Using @value{GDBN} under @sc{gnu} Emacs
22545 @cindex @sc{gnu} Emacs
22546 A special interface allows you to use @sc{gnu} Emacs to view (and
22547 edit) the source files for the program you are debugging with
22550 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
22551 executable file you want to debug as an argument. This command starts
22552 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
22553 created Emacs buffer.
22554 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
22556 Running @value{GDBN} under Emacs can be just like running @value{GDBN} normally except for two
22561 All ``terminal'' input and output goes through an Emacs buffer, called
22564 This applies both to @value{GDBN} commands and their output, and to the input
22565 and output done by the program you are debugging.
22567 This is useful because it means that you can copy the text of previous
22568 commands and input them again; you can even use parts of the output
22571 All the facilities of Emacs' Shell mode are available for interacting
22572 with your program. In particular, you can send signals the usual
22573 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
22577 @value{GDBN} displays source code through Emacs.
22579 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
22580 source file for that frame and puts an arrow (@samp{=>}) at the
22581 left margin of the current line. Emacs uses a separate buffer for
22582 source display, and splits the screen to show both your @value{GDBN} session
22585 Explicit @value{GDBN} @code{list} or search commands still produce output as
22586 usual, but you probably have no reason to use them from Emacs.
22589 We call this @dfn{text command mode}. Emacs 22.1, and later, also uses
22590 a graphical mode, enabled by default, which provides further buffers
22591 that can control the execution and describe the state of your program.
22592 @xref{GDB Graphical Interface,,, Emacs, The @sc{gnu} Emacs Manual}.
22594 If you specify an absolute file name when prompted for the @kbd{M-x
22595 gdb} argument, then Emacs sets your current working directory to where
22596 your program resides. If you only specify the file name, then Emacs
22597 sets your current working directory to to the directory associated
22598 with the previous buffer. In this case, @value{GDBN} may find your
22599 program by searching your environment's @code{PATH} variable, but on
22600 some operating systems it might not find the source. So, although the
22601 @value{GDBN} input and output session proceeds normally, the auxiliary
22602 buffer does not display the current source and line of execution.
22604 The initial working directory of @value{GDBN} is printed on the top
22605 line of the GUD buffer and this serves as a default for the commands
22606 that specify files for @value{GDBN} to operate on. @xref{Files,
22607 ,Commands to Specify Files}.
22609 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
22610 need to call @value{GDBN} by a different name (for example, if you
22611 keep several configurations around, with different names) you can
22612 customize the Emacs variable @code{gud-gdb-command-name} to run the
22615 In the GUD buffer, you can use these special Emacs commands in
22616 addition to the standard Shell mode commands:
22620 Describe the features of Emacs' GUD Mode.
22623 Execute to another source line, like the @value{GDBN} @code{step} command; also
22624 update the display window to show the current file and location.
22627 Execute to next source line in this function, skipping all function
22628 calls, like the @value{GDBN} @code{next} command. Then update the display window
22629 to show the current file and location.
22632 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
22633 display window accordingly.
22636 Execute until exit from the selected stack frame, like the @value{GDBN}
22637 @code{finish} command.
22640 Continue execution of your program, like the @value{GDBN} @code{continue}
22644 Go up the number of frames indicated by the numeric argument
22645 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
22646 like the @value{GDBN} @code{up} command.
22649 Go down the number of frames indicated by the numeric argument, like the
22650 @value{GDBN} @code{down} command.
22653 In any source file, the Emacs command @kbd{C-x @key{SPC}} (@code{gud-break})
22654 tells @value{GDBN} to set a breakpoint on the source line point is on.
22656 In text command mode, if you type @kbd{M-x speedbar}, Emacs displays a
22657 separate frame which shows a backtrace when the GUD buffer is current.
22658 Move point to any frame in the stack and type @key{RET} to make it
22659 become the current frame and display the associated source in the
22660 source buffer. Alternatively, click @kbd{Mouse-2} to make the
22661 selected frame become the current one. In graphical mode, the
22662 speedbar displays watch expressions.
22664 If you accidentally delete the source-display buffer, an easy way to get
22665 it back is to type the command @code{f} in the @value{GDBN} buffer, to
22666 request a frame display; when you run under Emacs, this recreates
22667 the source buffer if necessary to show you the context of the current
22670 The source files displayed in Emacs are in ordinary Emacs buffers
22671 which are visiting the source files in the usual way. You can edit
22672 the files with these buffers if you wish; but keep in mind that @value{GDBN}
22673 communicates with Emacs in terms of line numbers. If you add or
22674 delete lines from the text, the line numbers that @value{GDBN} knows cease
22675 to correspond properly with the code.
22677 A more detailed description of Emacs' interaction with @value{GDBN} is
22678 given in the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu}
22681 @c The following dropped because Epoch is nonstandard. Reactivate
22682 @c if/when v19 does something similar. ---doc@cygnus.com 19dec1990
22684 @kindex Emacs Epoch environment
22688 Version 18 of @sc{gnu} Emacs has a built-in window system
22689 called the @code{epoch}
22690 environment. Users of this environment can use a new command,
22691 @code{inspect} which performs identically to @code{print} except that
22692 each value is printed in its own window.
22697 @chapter The @sc{gdb/mi} Interface
22699 @unnumberedsec Function and Purpose
22701 @cindex @sc{gdb/mi}, its purpose
22702 @sc{gdb/mi} is a line based machine oriented text interface to
22703 @value{GDBN} and is activated by specifying using the
22704 @option{--interpreter} command line option (@pxref{Mode Options}). It
22705 is specifically intended to support the development of systems which
22706 use the debugger as just one small component of a larger system.
22708 This chapter is a specification of the @sc{gdb/mi} interface. It is written
22709 in the form of a reference manual.
22711 Note that @sc{gdb/mi} is still under construction, so some of the
22712 features described below are incomplete and subject to change
22713 (@pxref{GDB/MI Development and Front Ends, , @sc{gdb/mi} Development and Front Ends}).
22715 @unnumberedsec Notation and Terminology
22717 @cindex notational conventions, for @sc{gdb/mi}
22718 This chapter uses the following notation:
22722 @code{|} separates two alternatives.
22725 @code{[ @var{something} ]} indicates that @var{something} is optional:
22726 it may or may not be given.
22729 @code{( @var{group} )*} means that @var{group} inside the parentheses
22730 may repeat zero or more times.
22733 @code{( @var{group} )+} means that @var{group} inside the parentheses
22734 may repeat one or more times.
22737 @code{"@var{string}"} means a literal @var{string}.
22741 @heading Dependencies
22745 * GDB/MI General Design::
22746 * GDB/MI Command Syntax::
22747 * GDB/MI Compatibility with CLI::
22748 * GDB/MI Development and Front Ends::
22749 * GDB/MI Output Records::
22750 * GDB/MI Simple Examples::
22751 * GDB/MI Command Description Format::
22752 * GDB/MI Breakpoint Commands::
22753 * GDB/MI Program Context::
22754 * GDB/MI Thread Commands::
22755 * GDB/MI Program Execution::
22756 * GDB/MI Stack Manipulation::
22757 * GDB/MI Variable Objects::
22758 * GDB/MI Data Manipulation::
22759 * GDB/MI Tracepoint Commands::
22760 * GDB/MI Symbol Query::
22761 * GDB/MI File Commands::
22763 * GDB/MI Kod Commands::
22764 * GDB/MI Memory Overlay Commands::
22765 * GDB/MI Signal Handling Commands::
22767 * GDB/MI Target Manipulation::
22768 * GDB/MI File Transfer Commands::
22769 * GDB/MI Miscellaneous Commands::
22772 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
22773 @node GDB/MI General Design
22774 @section @sc{gdb/mi} General Design
22775 @cindex GDB/MI General Design
22777 Interaction of a @sc{GDB/MI} frontend with @value{GDBN} involves three
22778 parts---commands sent to @value{GDBN}, responses to those commands
22779 and notifications. Each command results in exactly one response,
22780 indicating either successful completion of the command, or an error.
22781 For the commands that do not resume the target, the response contains the
22782 requested information. For the commands that resume the target, the
22783 response only indicates whether the target was successfully resumed.
22784 Notifications is the mechanism for reporting changes in the state of the
22785 target, or in @value{GDBN} state, that cannot conveniently be associated with
22786 a command and reported as part of that command response.
22788 The important examples of notifications are:
22792 Exec notifications. These are used to report changes in
22793 target state---when a target is resumed, or stopped. It would not
22794 be feasible to include this information in response of resuming
22795 commands, because one resume commands can result in multiple events in
22796 different threads. Also, quite some time may pass before any event
22797 happens in the target, while a frontend needs to know whether the resuming
22798 command itself was successfully executed.
22801 Console output, and status notifications. Console output
22802 notifications are used to report output of CLI commands, as well as
22803 diagnostics for other commands. Status notifications are used to
22804 report the progress of a long-running operation. Naturally, including
22805 this information in command response would mean no output is produced
22806 until the command is finished, which is undesirable.
22809 General notifications. Commands may have various side effects on
22810 the @value{GDBN} or target state beyond their official purpose. For example,
22811 a command may change the selected thread. Although such changes can
22812 be included in command response, using notification allows for more
22813 orthogonal frontend design.
22817 There's no guarantee that whenever an MI command reports an error,
22818 @value{GDBN} or the target are in any specific state, and especially,
22819 the state is not reverted to the state before the MI command was
22820 processed. Therefore, whenever an MI command results in an error,
22821 we recommend that the frontend refreshes all the information shown in
22822 the user interface.
22826 * Context management::
22827 * Asynchronous and non-stop modes::
22831 @node Context management
22832 @subsection Context management
22834 In most cases when @value{GDBN} accesses the target, this access is
22835 done in context of a specific thread and frame (@pxref{Frames}).
22836 Often, even when accessing global data, the target requires that a thread
22837 be specified. The CLI interface maintains the selected thread and frame,
22838 and supplies them to target on each command. This is convenient,
22839 because a command line user would not want to specify that information
22840 explicitly on each command, and because user interacts with
22841 @value{GDBN} via a single terminal, so no confusion is possible as
22842 to what thread and frame are the current ones.
22844 In the case of MI, the concept of selected thread and frame is less
22845 useful. First, a frontend can easily remember this information
22846 itself. Second, a graphical frontend can have more than one window,
22847 each one used for debugging a different thread, and the frontend might
22848 want to access additional threads for internal purposes. This
22849 increases the risk that by relying on implicitly selected thread, the
22850 frontend may be operating on a wrong one. Therefore, each MI command
22851 should explicitly specify which thread and frame to operate on. To
22852 make it possible, each MI command accepts the @samp{--thread} and
22853 @samp{--frame} options, the value to each is @value{GDBN} identifier
22854 for thread and frame to operate on.
22856 Usually, each top-level window in a frontend allows the user to select
22857 a thread and a frame, and remembers the user selection for further
22858 operations. However, in some cases @value{GDBN} may suggest that the
22859 current thread be changed. For example, when stopping on a breakpoint
22860 it is reasonable to switch to the thread where breakpoint is hit. For
22861 another example, if the user issues the CLI @samp{thread} command via
22862 the frontend, it is desirable to change the frontend's selected thread to the
22863 one specified by user. @value{GDBN} communicates the suggestion to
22864 change current thread using the @samp{=thread-selected} notification.
22865 No such notification is available for the selected frame at the moment.
22867 Note that historically, MI shares the selected thread with CLI, so
22868 frontends used the @code{-thread-select} to execute commands in the
22869 right context. However, getting this to work right is cumbersome. The
22870 simplest way is for frontend to emit @code{-thread-select} command
22871 before every command. This doubles the number of commands that need
22872 to be sent. The alternative approach is to suppress @code{-thread-select}
22873 if the selected thread in @value{GDBN} is supposed to be identical to the
22874 thread the frontend wants to operate on. However, getting this
22875 optimization right can be tricky. In particular, if the frontend
22876 sends several commands to @value{GDBN}, and one of the commands changes the
22877 selected thread, then the behaviour of subsequent commands will
22878 change. So, a frontend should either wait for response from such
22879 problematic commands, or explicitly add @code{-thread-select} for
22880 all subsequent commands. No frontend is known to do this exactly
22881 right, so it is suggested to just always pass the @samp{--thread} and
22882 @samp{--frame} options.
22884 @node Asynchronous and non-stop modes
22885 @subsection Asynchronous command execution and non-stop mode
22887 On some targets, @value{GDBN} is capable of processing MI commands
22888 even while the target is running. This is called @dfn{asynchronous
22889 command execution} (@pxref{Background Execution}). The frontend may
22890 specify a preferrence for asynchronous execution using the
22891 @code{-gdb-set target-async 1} command, which should be emitted before
22892 either running the executable or attaching to the target. After the
22893 frontend has started the executable or attached to the target, it can
22894 find if asynchronous execution is enabled using the
22895 @code{-list-target-features} command.
22897 Even if @value{GDBN} can accept a command while target is running,
22898 many commands that access the target do not work when the target is
22899 running. Therefore, asynchronous command execution is most useful
22900 when combined with non-stop mode (@pxref{Non-Stop Mode}). Then,
22901 it is possible to examine the state of one thread, while other threads
22904 When a given thread is running, MI commands that try to access the
22905 target in the context of that thread may not work, or may work only on
22906 some targets. In particular, commands that try to operate on thread's
22907 stack will not work, on any target. Commands that read memory, or
22908 modify breakpoints, may work or not work, depending on the target. Note
22909 that even commands that operate on global state, such as @code{print},
22910 @code{set}, and breakpoint commands, still access the target in the
22911 context of a specific thread, so frontend should try to find a
22912 stopped thread and perform the operation on that thread (using the
22913 @samp{--thread} option).
22915 Which commands will work in the context of a running thread is
22916 highly target dependent. However, the two commands
22917 @code{-exec-interrupt}, to stop a thread, and @code{-thread-info},
22918 to find the state of a thread, will always work.
22920 @node Thread groups
22921 @subsection Thread groups
22922 @value{GDBN} may be used to debug several processes at the same time.
22923 On some platfroms, @value{GDBN} may support debugging of several
22924 hardware systems, each one having several cores with several different
22925 processes running on each core. This section describes the MI
22926 mechanism to support such debugging scenarios.
22928 The key observation is that regardless of the structure of the
22929 target, MI can have a global list of threads, because most commands that
22930 accept the @samp{--thread} option do not need to know what process that
22931 thread belongs to. Therefore, it is not necessary to introduce
22932 neither additional @samp{--process} option, nor an notion of the
22933 current process in the MI interface. The only strictly new feature
22934 that is required is the ability to find how the threads are grouped
22937 To allow the user to discover such grouping, and to support arbitrary
22938 hierarchy of machines/cores/processes, MI introduces the concept of a
22939 @dfn{thread group}. Thread group is a collection of threads and other
22940 thread groups. A thread group always has a string identifier, a type,
22941 and may have additional attributes specific to the type. A new
22942 command, @code{-list-thread-groups}, returns the list of top-level
22943 thread groups, which correspond to processes that @value{GDBN} is
22944 debugging at the moment. By passing an identifier of a thread group
22945 to the @code{-list-thread-groups} command, it is possible to obtain
22946 the members of specific thread group.
22948 To allow the user to easily discover processes, and other objects, he
22949 wishes to debug, a concept of @dfn{available thread group} is
22950 introduced. Available thread group is an thread group that
22951 @value{GDBN} is not debugging, but that can be attached to, using the
22952 @code{-target-attach} command. The list of available top-level thread
22953 groups can be obtained using @samp{-list-thread-groups --available}.
22954 In general, the content of a thread group may be only retrieved only
22955 after attaching to that thread group.
22957 Thread groups are related to inferiors (@pxref{Inferiors and
22958 Programs}). Each inferior corresponds to a thread group of a special
22959 type @samp{process}, and some additional operations are permitted on
22960 such thread groups.
22962 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
22963 @node GDB/MI Command Syntax
22964 @section @sc{gdb/mi} Command Syntax
22967 * GDB/MI Input Syntax::
22968 * GDB/MI Output Syntax::
22971 @node GDB/MI Input Syntax
22972 @subsection @sc{gdb/mi} Input Syntax
22974 @cindex input syntax for @sc{gdb/mi}
22975 @cindex @sc{gdb/mi}, input syntax
22977 @item @var{command} @expansion{}
22978 @code{@var{cli-command} | @var{mi-command}}
22980 @item @var{cli-command} @expansion{}
22981 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
22982 @var{cli-command} is any existing @value{GDBN} CLI command.
22984 @item @var{mi-command} @expansion{}
22985 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
22986 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
22988 @item @var{token} @expansion{}
22989 "any sequence of digits"
22991 @item @var{option} @expansion{}
22992 @code{"-" @var{parameter} [ " " @var{parameter} ]}
22994 @item @var{parameter} @expansion{}
22995 @code{@var{non-blank-sequence} | @var{c-string}}
22997 @item @var{operation} @expansion{}
22998 @emph{any of the operations described in this chapter}
23000 @item @var{non-blank-sequence} @expansion{}
23001 @emph{anything, provided it doesn't contain special characters such as
23002 "-", @var{nl}, """ and of course " "}
23004 @item @var{c-string} @expansion{}
23005 @code{""" @var{seven-bit-iso-c-string-content} """}
23007 @item @var{nl} @expansion{}
23016 The CLI commands are still handled by the @sc{mi} interpreter; their
23017 output is described below.
23020 The @code{@var{token}}, when present, is passed back when the command
23024 Some @sc{mi} commands accept optional arguments as part of the parameter
23025 list. Each option is identified by a leading @samp{-} (dash) and may be
23026 followed by an optional argument parameter. Options occur first in the
23027 parameter list and can be delimited from normal parameters using
23028 @samp{--} (this is useful when some parameters begin with a dash).
23035 We want easy access to the existing CLI syntax (for debugging).
23038 We want it to be easy to spot a @sc{mi} operation.
23041 @node GDB/MI Output Syntax
23042 @subsection @sc{gdb/mi} Output Syntax
23044 @cindex output syntax of @sc{gdb/mi}
23045 @cindex @sc{gdb/mi}, output syntax
23046 The output from @sc{gdb/mi} consists of zero or more out-of-band records
23047 followed, optionally, by a single result record. This result record
23048 is for the most recent command. The sequence of output records is
23049 terminated by @samp{(gdb)}.
23051 If an input command was prefixed with a @code{@var{token}} then the
23052 corresponding output for that command will also be prefixed by that same
23056 @item @var{output} @expansion{}
23057 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(gdb)" @var{nl}}
23059 @item @var{result-record} @expansion{}
23060 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
23062 @item @var{out-of-band-record} @expansion{}
23063 @code{@var{async-record} | @var{stream-record}}
23065 @item @var{async-record} @expansion{}
23066 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
23068 @item @var{exec-async-output} @expansion{}
23069 @code{[ @var{token} ] "*" @var{async-output}}
23071 @item @var{status-async-output} @expansion{}
23072 @code{[ @var{token} ] "+" @var{async-output}}
23074 @item @var{notify-async-output} @expansion{}
23075 @code{[ @var{token} ] "=" @var{async-output}}
23077 @item @var{async-output} @expansion{}
23078 @code{@var{async-class} ( "," @var{result} )* @var{nl}}
23080 @item @var{result-class} @expansion{}
23081 @code{"done" | "running" | "connected" | "error" | "exit"}
23083 @item @var{async-class} @expansion{}
23084 @code{"stopped" | @var{others}} (where @var{others} will be added
23085 depending on the needs---this is still in development).
23087 @item @var{result} @expansion{}
23088 @code{ @var{variable} "=" @var{value}}
23090 @item @var{variable} @expansion{}
23091 @code{ @var{string} }
23093 @item @var{value} @expansion{}
23094 @code{ @var{const} | @var{tuple} | @var{list} }
23096 @item @var{const} @expansion{}
23097 @code{@var{c-string}}
23099 @item @var{tuple} @expansion{}
23100 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
23102 @item @var{list} @expansion{}
23103 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
23104 @var{result} ( "," @var{result} )* "]" }
23106 @item @var{stream-record} @expansion{}
23107 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
23109 @item @var{console-stream-output} @expansion{}
23110 @code{"~" @var{c-string}}
23112 @item @var{target-stream-output} @expansion{}
23113 @code{"@@" @var{c-string}}
23115 @item @var{log-stream-output} @expansion{}
23116 @code{"&" @var{c-string}}
23118 @item @var{nl} @expansion{}
23121 @item @var{token} @expansion{}
23122 @emph{any sequence of digits}.
23130 All output sequences end in a single line containing a period.
23133 The @code{@var{token}} is from the corresponding request. Note that
23134 for all async output, while the token is allowed by the grammar and
23135 may be output by future versions of @value{GDBN} for select async
23136 output messages, it is generally omitted. Frontends should treat
23137 all async output as reporting general changes in the state of the
23138 target and there should be no need to associate async output to any
23142 @cindex status output in @sc{gdb/mi}
23143 @var{status-async-output} contains on-going status information about the
23144 progress of a slow operation. It can be discarded. All status output is
23145 prefixed by @samp{+}.
23148 @cindex async output in @sc{gdb/mi}
23149 @var{exec-async-output} contains asynchronous state change on the target
23150 (stopped, started, disappeared). All async output is prefixed by
23154 @cindex notify output in @sc{gdb/mi}
23155 @var{notify-async-output} contains supplementary information that the
23156 client should handle (e.g., a new breakpoint information). All notify
23157 output is prefixed by @samp{=}.
23160 @cindex console output in @sc{gdb/mi}
23161 @var{console-stream-output} is output that should be displayed as is in the
23162 console. It is the textual response to a CLI command. All the console
23163 output is prefixed by @samp{~}.
23166 @cindex target output in @sc{gdb/mi}
23167 @var{target-stream-output} is the output produced by the target program.
23168 All the target output is prefixed by @samp{@@}.
23171 @cindex log output in @sc{gdb/mi}
23172 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
23173 instance messages that should be displayed as part of an error log. All
23174 the log output is prefixed by @samp{&}.
23177 @cindex list output in @sc{gdb/mi}
23178 New @sc{gdb/mi} commands should only output @var{lists} containing
23184 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
23185 details about the various output records.
23187 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
23188 @node GDB/MI Compatibility with CLI
23189 @section @sc{gdb/mi} Compatibility with CLI
23191 @cindex compatibility, @sc{gdb/mi} and CLI
23192 @cindex @sc{gdb/mi}, compatibility with CLI
23194 For the developers convenience CLI commands can be entered directly,
23195 but there may be some unexpected behaviour. For example, commands
23196 that query the user will behave as if the user replied yes, breakpoint
23197 command lists are not executed and some CLI commands, such as
23198 @code{if}, @code{when} and @code{define}, prompt for further input with
23199 @samp{>}, which is not valid MI output.
23201 This feature may be removed at some stage in the future and it is
23202 recommended that front ends use the @code{-interpreter-exec} command
23203 (@pxref{-interpreter-exec}).
23205 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
23206 @node GDB/MI Development and Front Ends
23207 @section @sc{gdb/mi} Development and Front Ends
23208 @cindex @sc{gdb/mi} development
23210 The application which takes the MI output and presents the state of the
23211 program being debugged to the user is called a @dfn{front end}.
23213 Although @sc{gdb/mi} is still incomplete, it is currently being used
23214 by a variety of front ends to @value{GDBN}. This makes it difficult
23215 to introduce new functionality without breaking existing usage. This
23216 section tries to minimize the problems by describing how the protocol
23219 Some changes in MI need not break a carefully designed front end, and
23220 for these the MI version will remain unchanged. The following is a
23221 list of changes that may occur within one level, so front ends should
23222 parse MI output in a way that can handle them:
23226 New MI commands may be added.
23229 New fields may be added to the output of any MI command.
23232 The range of values for fields with specified values, e.g.,
23233 @code{in_scope} (@pxref{-var-update}) may be extended.
23235 @c The format of field's content e.g type prefix, may change so parse it
23236 @c at your own risk. Yes, in general?
23238 @c The order of fields may change? Shouldn't really matter but it might
23239 @c resolve inconsistencies.
23242 If the changes are likely to break front ends, the MI version level
23243 will be increased by one. This will allow the front end to parse the
23244 output according to the MI version. Apart from mi0, new versions of
23245 @value{GDBN} will not support old versions of MI and it will be the
23246 responsibility of the front end to work with the new one.
23248 @c Starting with mi3, add a new command -mi-version that prints the MI
23251 The best way to avoid unexpected changes in MI that might break your front
23252 end is to make your project known to @value{GDBN} developers and
23253 follow development on @email{gdb@@sourceware.org} and
23254 @email{gdb-patches@@sourceware.org}.
23255 @cindex mailing lists
23257 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
23258 @node GDB/MI Output Records
23259 @section @sc{gdb/mi} Output Records
23262 * GDB/MI Result Records::
23263 * GDB/MI Stream Records::
23264 * GDB/MI Async Records::
23265 * GDB/MI Frame Information::
23266 * GDB/MI Thread Information::
23269 @node GDB/MI Result Records
23270 @subsection @sc{gdb/mi} Result Records
23272 @cindex result records in @sc{gdb/mi}
23273 @cindex @sc{gdb/mi}, result records
23274 In addition to a number of out-of-band notifications, the response to a
23275 @sc{gdb/mi} command includes one of the following result indications:
23279 @item "^done" [ "," @var{results} ]
23280 The synchronous operation was successful, @code{@var{results}} are the return
23285 This result record is equivalent to @samp{^done}. Historically, it
23286 was output instead of @samp{^done} if the command has resumed the
23287 target. This behaviour is maintained for backward compatibility, but
23288 all frontends should treat @samp{^done} and @samp{^running}
23289 identically and rely on the @samp{*running} output record to determine
23290 which threads are resumed.
23294 @value{GDBN} has connected to a remote target.
23296 @item "^error" "," @var{c-string}
23298 The operation failed. The @code{@var{c-string}} contains the corresponding
23303 @value{GDBN} has terminated.
23307 @node GDB/MI Stream Records
23308 @subsection @sc{gdb/mi} Stream Records
23310 @cindex @sc{gdb/mi}, stream records
23311 @cindex stream records in @sc{gdb/mi}
23312 @value{GDBN} internally maintains a number of output streams: the console, the
23313 target, and the log. The output intended for each of these streams is
23314 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
23316 Each stream record begins with a unique @dfn{prefix character} which
23317 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
23318 Syntax}). In addition to the prefix, each stream record contains a
23319 @code{@var{string-output}}. This is either raw text (with an implicit new
23320 line) or a quoted C string (which does not contain an implicit newline).
23323 @item "~" @var{string-output}
23324 The console output stream contains text that should be displayed in the
23325 CLI console window. It contains the textual responses to CLI commands.
23327 @item "@@" @var{string-output}
23328 The target output stream contains any textual output from the running
23329 target. This is only present when GDB's event loop is truly
23330 asynchronous, which is currently only the case for remote targets.
23332 @item "&" @var{string-output}
23333 The log stream contains debugging messages being produced by @value{GDBN}'s
23337 @node GDB/MI Async Records
23338 @subsection @sc{gdb/mi} Async Records
23340 @cindex async records in @sc{gdb/mi}
23341 @cindex @sc{gdb/mi}, async records
23342 @dfn{Async} records are used to notify the @sc{gdb/mi} client of
23343 additional changes that have occurred. Those changes can either be a
23344 consequence of @sc{gdb/mi} commands (e.g., a breakpoint modified) or a result of
23345 target activity (e.g., target stopped).
23347 The following is the list of possible async records:
23351 @item *running,thread-id="@var{thread}"
23352 The target is now running. The @var{thread} field tells which
23353 specific thread is now running, and can be @samp{all} if all threads
23354 are running. The frontend should assume that no interaction with a
23355 running thread is possible after this notification is produced.
23356 The frontend should not assume that this notification is output
23357 only once for any command. @value{GDBN} may emit this notification
23358 several times, either for different threads, because it cannot resume
23359 all threads together, or even for a single thread, if the thread must
23360 be stepped though some code before letting it run freely.
23362 @item *stopped,reason="@var{reason}",thread-id="@var{id}",stopped-threads="@var{stopped}",core="@var{core}"
23363 The target has stopped. The @var{reason} field can have one of the
23367 @item breakpoint-hit
23368 A breakpoint was reached.
23369 @item watchpoint-trigger
23370 A watchpoint was triggered.
23371 @item read-watchpoint-trigger
23372 A read watchpoint was triggered.
23373 @item access-watchpoint-trigger
23374 An access watchpoint was triggered.
23375 @item function-finished
23376 An -exec-finish or similar CLI command was accomplished.
23377 @item location-reached
23378 An -exec-until or similar CLI command was accomplished.
23379 @item watchpoint-scope
23380 A watchpoint has gone out of scope.
23381 @item end-stepping-range
23382 An -exec-next, -exec-next-instruction, -exec-step, -exec-step-instruction or
23383 similar CLI command was accomplished.
23384 @item exited-signalled
23385 The inferior exited because of a signal.
23387 The inferior exited.
23388 @item exited-normally
23389 The inferior exited normally.
23390 @item signal-received
23391 A signal was received by the inferior.
23394 The @var{id} field identifies the thread that directly caused the stop
23395 -- for example by hitting a breakpoint. Depending on whether all-stop
23396 mode is in effect (@pxref{All-Stop Mode}), @value{GDBN} may either
23397 stop all threads, or only the thread that directly triggered the stop.
23398 If all threads are stopped, the @var{stopped} field will have the
23399 value of @code{"all"}. Otherwise, the value of the @var{stopped}
23400 field will be a list of thread identifiers. Presently, this list will
23401 always include a single thread, but frontend should be prepared to see
23402 several threads in the list. The @var{core} field reports the
23403 processor core on which the stop event has happened. This field may be absent
23404 if such information is not available.
23406 @item =thread-group-added,id="@var{id}"
23407 @itemx =thread-group-removed,id="@var{id}"
23408 A thread group was either added or removed. The @var{id} field
23409 contains the @value{GDBN} identifier of the thread group. When a thread
23410 group is added, it generally might not be associated with a running
23411 process. When a thread group is removed, its id becomes invalid and
23412 cannot be used in any way.
23414 @item =thread-group-started,id="@var{id}",pid="@var{pid}"
23415 A thread group became associated with a running program,
23416 either because the program was just started or the thread group
23417 was attached to a program. The @var{id} field contains the
23418 @value{GDBN} identifier of the thread group. The @var{pid} field
23419 contains process identifier, specific to the operating system.
23421 @itemx =thread-group-exited,id="@var{id}"
23422 A thread group is no longer associated with a running program,
23423 either because the program has exited, or because it was detached
23424 from. The @var{id} field contains the @value{GDBN} identifier of the
23427 @item =thread-created,id="@var{id}",group-id="@var{gid}"
23428 @itemx =thread-exited,id="@var{id}",group-id="@var{gid}"
23429 A thread either was created, or has exited. The @var{id} field
23430 contains the @value{GDBN} identifier of the thread. The @var{gid}
23431 field identifies the thread group this thread belongs to.
23433 @item =thread-selected,id="@var{id}"
23434 Informs that the selected thread was changed as result of the last
23435 command. This notification is not emitted as result of @code{-thread-select}
23436 command but is emitted whenever an MI command that is not documented
23437 to change the selected thread actually changes it. In particular,
23438 invoking, directly or indirectly (via user-defined command), the CLI
23439 @code{thread} command, will generate this notification.
23441 We suggest that in response to this notification, front ends
23442 highlight the selected thread and cause subsequent commands to apply to
23445 @item =library-loaded,...
23446 Reports that a new library file was loaded by the program. This
23447 notification has 4 fields---@var{id}, @var{target-name},
23448 @var{host-name}, and @var{symbols-loaded}. The @var{id} field is an
23449 opaque identifier of the library. For remote debugging case,
23450 @var{target-name} and @var{host-name} fields give the name of the
23451 library file on the target, and on the host respectively. For native
23452 debugging, both those fields have the same value. The
23453 @var{symbols-loaded} field reports if the debug symbols for this
23454 library are loaded. The @var{thread-group} field, if present,
23455 specifies the id of the thread group in whose context the library was loaded.
23456 If the field is absent, it means the library was loaded in the context
23457 of all present thread groups.
23459 @item =library-unloaded,...
23460 Reports that a library was unloaded by the program. This notification
23461 has 3 fields---@var{id}, @var{target-name} and @var{host-name} with
23462 the same meaning as for the @code{=library-loaded} notification.
23463 The @var{thread-group} field, if present, specifies the id of the
23464 thread group in whose context the library was unloaded. If the field is
23465 absent, it means the library was unloaded in the context of all present
23470 @node GDB/MI Frame Information
23471 @subsection @sc{gdb/mi} Frame Information
23473 Response from many MI commands includes an information about stack
23474 frame. This information is a tuple that may have the following
23479 The level of the stack frame. The innermost frame has the level of
23480 zero. This field is always present.
23483 The name of the function corresponding to the frame. This field may
23484 be absent if @value{GDBN} is unable to determine the function name.
23487 The code address for the frame. This field is always present.
23490 The name of the source files that correspond to the frame's code
23491 address. This field may be absent.
23494 The source line corresponding to the frames' code address. This field
23498 The name of the binary file (either executable or shared library) the
23499 corresponds to the frame's code address. This field may be absent.
23503 @node GDB/MI Thread Information
23504 @subsection @sc{gdb/mi} Thread Information
23506 Whenever @value{GDBN} has to report an information about a thread, it
23507 uses a tuple with the following fields:
23511 The numeric id assigned to the thread by @value{GDBN}. This field is
23515 Target-specific string identifying the thread. This field is always present.
23518 Additional information about the thread provided by the target.
23519 It is supposed to be human-readable and not interpreted by the
23520 frontend. This field is optional.
23523 Either @samp{stopped} or @samp{running}, depending on whether the
23524 thread is presently running. This field is always present.
23527 The value of this field is an integer number of the processor core the
23528 thread was last seen on. This field is optional.
23532 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
23533 @node GDB/MI Simple Examples
23534 @section Simple Examples of @sc{gdb/mi} Interaction
23535 @cindex @sc{gdb/mi}, simple examples
23537 This subsection presents several simple examples of interaction using
23538 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
23539 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
23540 the output received from @sc{gdb/mi}.
23542 Note the line breaks shown in the examples are here only for
23543 readability, they don't appear in the real output.
23545 @subheading Setting a Breakpoint
23547 Setting a breakpoint generates synchronous output which contains detailed
23548 information of the breakpoint.
23551 -> -break-insert main
23552 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
23553 enabled="y",addr="0x08048564",func="main",file="myprog.c",
23554 fullname="/home/nickrob/myprog.c",line="68",times="0"@}
23558 @subheading Program Execution
23560 Program execution generates asynchronous records and MI gives the
23561 reason that execution stopped.
23567 <- *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
23568 frame=@{addr="0x08048564",func="main",
23569 args=[@{name="argc",value="1"@},@{name="argv",value="0xbfc4d4d4"@}],
23570 file="myprog.c",fullname="/home/nickrob/myprog.c",line="68"@}
23575 <- *stopped,reason="exited-normally"
23579 @subheading Quitting @value{GDBN}
23581 Quitting @value{GDBN} just prints the result class @samp{^exit}.
23589 Please note that @samp{^exit} is printed immediately, but it might
23590 take some time for @value{GDBN} to actually exit. During that time, @value{GDBN}
23591 performs necessary cleanups, including killing programs being debugged
23592 or disconnecting from debug hardware, so the frontend should wait till
23593 @value{GDBN} exits and should only forcibly kill @value{GDBN} if it
23594 fails to exit in reasonable time.
23596 @subheading A Bad Command
23598 Here's what happens if you pass a non-existent command:
23602 <- ^error,msg="Undefined MI command: rubbish"
23607 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
23608 @node GDB/MI Command Description Format
23609 @section @sc{gdb/mi} Command Description Format
23611 The remaining sections describe blocks of commands. Each block of
23612 commands is laid out in a fashion similar to this section.
23614 @subheading Motivation
23616 The motivation for this collection of commands.
23618 @subheading Introduction
23620 A brief introduction to this collection of commands as a whole.
23622 @subheading Commands
23624 For each command in the block, the following is described:
23626 @subsubheading Synopsis
23629 -command @var{args}@dots{}
23632 @subsubheading Result
23634 @subsubheading @value{GDBN} Command
23636 The corresponding @value{GDBN} CLI command(s), if any.
23638 @subsubheading Example
23640 Example(s) formatted for readability. Some of the described commands have
23641 not been implemented yet and these are labeled N.A.@: (not available).
23644 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
23645 @node GDB/MI Breakpoint Commands
23646 @section @sc{gdb/mi} Breakpoint Commands
23648 @cindex breakpoint commands for @sc{gdb/mi}
23649 @cindex @sc{gdb/mi}, breakpoint commands
23650 This section documents @sc{gdb/mi} commands for manipulating
23653 @subheading The @code{-break-after} Command
23654 @findex -break-after
23656 @subsubheading Synopsis
23659 -break-after @var{number} @var{count}
23662 The breakpoint number @var{number} is not in effect until it has been
23663 hit @var{count} times. To see how this is reflected in the output of
23664 the @samp{-break-list} command, see the description of the
23665 @samp{-break-list} command below.
23667 @subsubheading @value{GDBN} Command
23669 The corresponding @value{GDBN} command is @samp{ignore}.
23671 @subsubheading Example
23676 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
23677 enabled="y",addr="0x000100d0",func="main",file="hello.c",
23678 fullname="/home/foo/hello.c",line="5",times="0"@}
23685 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
23686 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
23687 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
23688 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
23689 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
23690 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
23691 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
23692 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
23693 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
23694 line="5",times="0",ignore="3"@}]@}
23699 @subheading The @code{-break-catch} Command
23700 @findex -break-catch
23703 @subheading The @code{-break-commands} Command
23704 @findex -break-commands
23706 @subsubheading Synopsis
23709 -break-commands @var{number} [ @var{command1} ... @var{commandN} ]
23712 Specifies the CLI commands that should be executed when breakpoint
23713 @var{number} is hit. The parameters @var{command1} to @var{commandN}
23714 are the commands. If no command is specified, any previously-set
23715 commands are cleared. @xref{Break Commands}. Typical use of this
23716 functionality is tracing a program, that is, printing of values of
23717 some variables whenever breakpoint is hit and then continuing.
23719 @subsubheading @value{GDBN} Command
23721 The corresponding @value{GDBN} command is @samp{commands}.
23723 @subsubheading Example
23728 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
23729 enabled="y",addr="0x000100d0",func="main",file="hello.c",
23730 fullname="/home/foo/hello.c",line="5",times="0"@}
23732 -break-commands 1 "print v" "continue"
23737 @subheading The @code{-break-condition} Command
23738 @findex -break-condition
23740 @subsubheading Synopsis
23743 -break-condition @var{number} @var{expr}
23746 Breakpoint @var{number} will stop the program only if the condition in
23747 @var{expr} is true. The condition becomes part of the
23748 @samp{-break-list} output (see the description of the @samp{-break-list}
23751 @subsubheading @value{GDBN} Command
23753 The corresponding @value{GDBN} command is @samp{condition}.
23755 @subsubheading Example
23759 -break-condition 1 1
23763 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
23764 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
23765 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
23766 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
23767 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
23768 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
23769 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
23770 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
23771 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
23772 line="5",cond="1",times="0",ignore="3"@}]@}
23776 @subheading The @code{-break-delete} Command
23777 @findex -break-delete
23779 @subsubheading Synopsis
23782 -break-delete ( @var{breakpoint} )+
23785 Delete the breakpoint(s) whose number(s) are specified in the argument
23786 list. This is obviously reflected in the breakpoint list.
23788 @subsubheading @value{GDBN} Command
23790 The corresponding @value{GDBN} command is @samp{delete}.
23792 @subsubheading Example
23800 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
23801 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
23802 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
23803 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
23804 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
23805 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
23806 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
23811 @subheading The @code{-break-disable} Command
23812 @findex -break-disable
23814 @subsubheading Synopsis
23817 -break-disable ( @var{breakpoint} )+
23820 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
23821 break list is now set to @samp{n} for the named @var{breakpoint}(s).
23823 @subsubheading @value{GDBN} Command
23825 The corresponding @value{GDBN} command is @samp{disable}.
23827 @subsubheading Example
23835 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
23836 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
23837 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
23838 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
23839 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
23840 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
23841 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
23842 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
23843 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
23844 line="5",times="0"@}]@}
23848 @subheading The @code{-break-enable} Command
23849 @findex -break-enable
23851 @subsubheading Synopsis
23854 -break-enable ( @var{breakpoint} )+
23857 Enable (previously disabled) @var{breakpoint}(s).
23859 @subsubheading @value{GDBN} Command
23861 The corresponding @value{GDBN} command is @samp{enable}.
23863 @subsubheading Example
23871 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
23872 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
23873 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
23874 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
23875 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
23876 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
23877 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
23878 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
23879 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
23880 line="5",times="0"@}]@}
23884 @subheading The @code{-break-info} Command
23885 @findex -break-info
23887 @subsubheading Synopsis
23890 -break-info @var{breakpoint}
23894 Get information about a single breakpoint.
23896 @subsubheading @value{GDBN} Command
23898 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
23900 @subsubheading Example
23903 @subheading The @code{-break-insert} Command
23904 @findex -break-insert
23906 @subsubheading Synopsis
23909 -break-insert [ -t ] [ -h ] [ -f ] [ -d ] [ -a ]
23910 [ -c @var{condition} ] [ -i @var{ignore-count} ]
23911 [ -p @var{thread} ] [ @var{location} ]
23915 If specified, @var{location}, can be one of:
23922 @item filename:linenum
23923 @item filename:function
23927 The possible optional parameters of this command are:
23931 Insert a temporary breakpoint.
23933 Insert a hardware breakpoint.
23934 @item -c @var{condition}
23935 Make the breakpoint conditional on @var{condition}.
23936 @item -i @var{ignore-count}
23937 Initialize the @var{ignore-count}.
23939 If @var{location} cannot be parsed (for example if it
23940 refers to unknown files or functions), create a pending
23941 breakpoint. Without this flag, @value{GDBN} will report
23942 an error, and won't create a breakpoint, if @var{location}
23945 Create a disabled breakpoint.
23947 Create a tracepoint. @xref{Tracepoints}. When this parameter
23948 is used together with @samp{-h}, a fast tracepoint is created.
23951 @subsubheading Result
23953 The result is in the form:
23956 ^done,bkpt=@{number="@var{number}",type="@var{type}",disp="del"|"keep",
23957 enabled="y"|"n",addr="@var{hex}",func="@var{funcname}",file="@var{filename}",
23958 fullname="@var{full_filename}",line="@var{lineno}",[thread="@var{threadno},]
23959 times="@var{times}"@}
23963 where @var{number} is the @value{GDBN} number for this breakpoint,
23964 @var{funcname} is the name of the function where the breakpoint was
23965 inserted, @var{filename} is the name of the source file which contains
23966 this function, @var{lineno} is the source line number within that file
23967 and @var{times} the number of times that the breakpoint has been hit
23968 (always 0 for -break-insert but may be greater for -break-info or -break-list
23969 which use the same output).
23971 Note: this format is open to change.
23972 @c An out-of-band breakpoint instead of part of the result?
23974 @subsubheading @value{GDBN} Command
23976 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
23977 @samp{hbreak}, @samp{thbreak}, and @samp{rbreak}.
23979 @subsubheading Example
23984 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",
23985 fullname="/home/foo/recursive2.c,line="4",times="0"@}
23987 -break-insert -t foo
23988 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",
23989 fullname="/home/foo/recursive2.c,line="11",times="0"@}
23992 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
23993 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
23994 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
23995 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
23996 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
23997 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
23998 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
23999 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
24000 addr="0x0001072c", func="main",file="recursive2.c",
24001 fullname="/home/foo/recursive2.c,"line="4",times="0"@},
24002 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
24003 addr="0x00010774",func="foo",file="recursive2.c",
24004 fullname="/home/foo/recursive2.c",line="11",times="0"@}]@}
24006 -break-insert -r foo.*
24007 ~int foo(int, int);
24008 ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c,
24009 "fullname="/home/foo/recursive2.c",line="11",times="0"@}
24013 @subheading The @code{-break-list} Command
24014 @findex -break-list
24016 @subsubheading Synopsis
24022 Displays the list of inserted breakpoints, showing the following fields:
24026 number of the breakpoint
24028 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
24030 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
24033 is the breakpoint enabled or no: @samp{y} or @samp{n}
24035 memory location at which the breakpoint is set
24037 logical location of the breakpoint, expressed by function name, file
24040 number of times the breakpoint has been hit
24043 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
24044 @code{body} field is an empty list.
24046 @subsubheading @value{GDBN} Command
24048 The corresponding @value{GDBN} command is @samp{info break}.
24050 @subsubheading Example
24055 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
24056 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
24057 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
24058 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
24059 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
24060 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
24061 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
24062 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
24063 addr="0x000100d0",func="main",file="hello.c",line="5",times="0"@},
24064 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
24065 addr="0x00010114",func="foo",file="hello.c",fullname="/home/foo/hello.c",
24066 line="13",times="0"@}]@}
24070 Here's an example of the result when there are no breakpoints:
24075 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
24076 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
24077 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
24078 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
24079 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
24080 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
24081 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
24086 @subheading The @code{-break-passcount} Command
24087 @findex -break-passcount
24089 @subsubheading Synopsis
24092 -break-passcount @var{tracepoint-number} @var{passcount}
24095 Set the passcount for tracepoint @var{tracepoint-number} to
24096 @var{passcount}. If the breakpoint referred to by @var{tracepoint-number}
24097 is not a tracepoint, error is emitted. This corresponds to CLI
24098 command @samp{passcount}.
24100 @subheading The @code{-break-watch} Command
24101 @findex -break-watch
24103 @subsubheading Synopsis
24106 -break-watch [ -a | -r ]
24109 Create a watchpoint. With the @samp{-a} option it will create an
24110 @dfn{access} watchpoint, i.e., a watchpoint that triggers either on a
24111 read from or on a write to the memory location. With the @samp{-r}
24112 option, the watchpoint created is a @dfn{read} watchpoint, i.e., it will
24113 trigger only when the memory location is accessed for reading. Without
24114 either of the options, the watchpoint created is a regular watchpoint,
24115 i.e., it will trigger when the memory location is accessed for writing.
24116 @xref{Set Watchpoints, , Setting Watchpoints}.
24118 Note that @samp{-break-list} will report a single list of watchpoints and
24119 breakpoints inserted.
24121 @subsubheading @value{GDBN} Command
24123 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
24126 @subsubheading Example
24128 Setting a watchpoint on a variable in the @code{main} function:
24133 ^done,wpt=@{number="2",exp="x"@}
24138 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
24139 value=@{old="-268439212",new="55"@},
24140 frame=@{func="main",args=[],file="recursive2.c",
24141 fullname="/home/foo/bar/recursive2.c",line="5"@}
24145 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
24146 the program execution twice: first for the variable changing value, then
24147 for the watchpoint going out of scope.
24152 ^done,wpt=@{number="5",exp="C"@}
24157 *stopped,reason="watchpoint-trigger",
24158 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
24159 frame=@{func="callee4",args=[],
24160 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
24161 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
24166 *stopped,reason="watchpoint-scope",wpnum="5",
24167 frame=@{func="callee3",args=[@{name="strarg",
24168 value="0x11940 \"A string argument.\""@}],
24169 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
24170 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
24174 Listing breakpoints and watchpoints, at different points in the program
24175 execution. Note that once the watchpoint goes out of scope, it is
24181 ^done,wpt=@{number="2",exp="C"@}
24184 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
24185 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
24186 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
24187 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
24188 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
24189 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
24190 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
24191 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
24192 addr="0x00010734",func="callee4",
24193 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
24194 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c"line="8",times="1"@},
24195 bkpt=@{number="2",type="watchpoint",disp="keep",
24196 enabled="y",addr="",what="C",times="0"@}]@}
24201 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
24202 value=@{old="-276895068",new="3"@},
24203 frame=@{func="callee4",args=[],
24204 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
24205 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
24208 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
24209 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
24210 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
24211 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
24212 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
24213 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
24214 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
24215 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
24216 addr="0x00010734",func="callee4",
24217 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
24218 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",times="1"@},
24219 bkpt=@{number="2",type="watchpoint",disp="keep",
24220 enabled="y",addr="",what="C",times="-5"@}]@}
24224 ^done,reason="watchpoint-scope",wpnum="2",
24225 frame=@{func="callee3",args=[@{name="strarg",
24226 value="0x11940 \"A string argument.\""@}],
24227 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
24228 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
24231 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
24232 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
24233 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
24234 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
24235 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
24236 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
24237 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
24238 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
24239 addr="0x00010734",func="callee4",
24240 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
24241 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
24246 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
24247 @node GDB/MI Program Context
24248 @section @sc{gdb/mi} Program Context
24250 @subheading The @code{-exec-arguments} Command
24251 @findex -exec-arguments
24254 @subsubheading Synopsis
24257 -exec-arguments @var{args}
24260 Set the inferior program arguments, to be used in the next
24263 @subsubheading @value{GDBN} Command
24265 The corresponding @value{GDBN} command is @samp{set args}.
24267 @subsubheading Example
24271 -exec-arguments -v word
24278 @subheading The @code{-exec-show-arguments} Command
24279 @findex -exec-show-arguments
24281 @subsubheading Synopsis
24284 -exec-show-arguments
24287 Print the arguments of the program.
24289 @subsubheading @value{GDBN} Command
24291 The corresponding @value{GDBN} command is @samp{show args}.
24293 @subsubheading Example
24298 @subheading The @code{-environment-cd} Command
24299 @findex -environment-cd
24301 @subsubheading Synopsis
24304 -environment-cd @var{pathdir}
24307 Set @value{GDBN}'s working directory.
24309 @subsubheading @value{GDBN} Command
24311 The corresponding @value{GDBN} command is @samp{cd}.
24313 @subsubheading Example
24317 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
24323 @subheading The @code{-environment-directory} Command
24324 @findex -environment-directory
24326 @subsubheading Synopsis
24329 -environment-directory [ -r ] [ @var{pathdir} ]+
24332 Add directories @var{pathdir} to beginning of search path for source files.
24333 If the @samp{-r} option is used, the search path is reset to the default
24334 search path. If directories @var{pathdir} are supplied in addition to the
24335 @samp{-r} option, the search path is first reset and then addition
24337 Multiple directories may be specified, separated by blanks. Specifying
24338 multiple directories in a single command
24339 results in the directories added to the beginning of the
24340 search path in the same order they were presented in the command.
24341 If blanks are needed as
24342 part of a directory name, double-quotes should be used around
24343 the name. In the command output, the path will show up separated
24344 by the system directory-separator character. The directory-separator
24345 character must not be used
24346 in any directory name.
24347 If no directories are specified, the current search path is displayed.
24349 @subsubheading @value{GDBN} Command
24351 The corresponding @value{GDBN} command is @samp{dir}.
24353 @subsubheading Example
24357 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
24358 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
24360 -environment-directory ""
24361 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
24363 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
24364 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
24366 -environment-directory -r
24367 ^done,source-path="$cdir:$cwd"
24372 @subheading The @code{-environment-path} Command
24373 @findex -environment-path
24375 @subsubheading Synopsis
24378 -environment-path [ -r ] [ @var{pathdir} ]+
24381 Add directories @var{pathdir} to beginning of search path for object files.
24382 If the @samp{-r} option is used, the search path is reset to the original
24383 search path that existed at gdb start-up. If directories @var{pathdir} are
24384 supplied in addition to the
24385 @samp{-r} option, the search path is first reset and then addition
24387 Multiple directories may be specified, separated by blanks. Specifying
24388 multiple directories in a single command
24389 results in the directories added to the beginning of the
24390 search path in the same order they were presented in the command.
24391 If blanks are needed as
24392 part of a directory name, double-quotes should be used around
24393 the name. In the command output, the path will show up separated
24394 by the system directory-separator character. The directory-separator
24395 character must not be used
24396 in any directory name.
24397 If no directories are specified, the current path is displayed.
24400 @subsubheading @value{GDBN} Command
24402 The corresponding @value{GDBN} command is @samp{path}.
24404 @subsubheading Example
24409 ^done,path="/usr/bin"
24411 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
24412 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
24414 -environment-path -r /usr/local/bin
24415 ^done,path="/usr/local/bin:/usr/bin"
24420 @subheading The @code{-environment-pwd} Command
24421 @findex -environment-pwd
24423 @subsubheading Synopsis
24429 Show the current working directory.
24431 @subsubheading @value{GDBN} Command
24433 The corresponding @value{GDBN} command is @samp{pwd}.
24435 @subsubheading Example
24440 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
24444 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
24445 @node GDB/MI Thread Commands
24446 @section @sc{gdb/mi} Thread Commands
24449 @subheading The @code{-thread-info} Command
24450 @findex -thread-info
24452 @subsubheading Synopsis
24455 -thread-info [ @var{thread-id} ]
24458 Reports information about either a specific thread, if
24459 the @var{thread-id} parameter is present, or about all
24460 threads. When printing information about all threads,
24461 also reports the current thread.
24463 @subsubheading @value{GDBN} Command
24465 The @samp{info thread} command prints the same information
24468 @subsubheading Example
24473 @{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
24474 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},state="running"@},
24475 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
24476 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
24477 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},state="running"@}],
24478 current-thread-id="1"
24482 The @samp{state} field may have the following values:
24486 The thread is stopped. Frame information is available for stopped
24490 The thread is running. There's no frame information for running
24495 @subheading The @code{-thread-list-ids} Command
24496 @findex -thread-list-ids
24498 @subsubheading Synopsis
24504 Produces a list of the currently known @value{GDBN} thread ids. At the
24505 end of the list it also prints the total number of such threads.
24507 This command is retained for historical reasons, the
24508 @code{-thread-info} command should be used instead.
24510 @subsubheading @value{GDBN} Command
24512 Part of @samp{info threads} supplies the same information.
24514 @subsubheading Example
24519 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
24520 current-thread-id="1",number-of-threads="3"
24525 @subheading The @code{-thread-select} Command
24526 @findex -thread-select
24528 @subsubheading Synopsis
24531 -thread-select @var{threadnum}
24534 Make @var{threadnum} the current thread. It prints the number of the new
24535 current thread, and the topmost frame for that thread.
24537 This command is deprecated in favor of explicitly using the
24538 @samp{--thread} option to each command.
24540 @subsubheading @value{GDBN} Command
24542 The corresponding @value{GDBN} command is @samp{thread}.
24544 @subsubheading Example
24551 *stopped,reason="end-stepping-range",thread-id="2",line="187",
24552 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
24556 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
24557 number-of-threads="3"
24560 ^done,new-thread-id="3",
24561 frame=@{level="0",func="vprintf",
24562 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
24563 @{name="arg",value="0x2"@}],file="vprintf.c",line="31"@}
24567 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
24568 @node GDB/MI Program Execution
24569 @section @sc{gdb/mi} Program Execution
24571 These are the asynchronous commands which generate the out-of-band
24572 record @samp{*stopped}. Currently @value{GDBN} only really executes
24573 asynchronously with remote targets and this interaction is mimicked in
24576 @subheading The @code{-exec-continue} Command
24577 @findex -exec-continue
24579 @subsubheading Synopsis
24582 -exec-continue [--reverse] [--all|--thread-group N]
24585 Resumes the execution of the inferior program, which will continue
24586 to execute until it reaches a debugger stop event. If the
24587 @samp{--reverse} option is specified, execution resumes in reverse until
24588 it reaches a stop event. Stop events may include
24591 breakpoints or watchpoints
24593 signals or exceptions
24595 the end of the process (or its beginning under @samp{--reverse})
24597 the end or beginning of a replay log if one is being used.
24599 In all-stop mode (@pxref{All-Stop
24600 Mode}), may resume only one thread, or all threads, depending on the
24601 value of the @samp{scheduler-locking} variable. If @samp{--all} is
24602 specified, all threads (in all inferiors) will be resumed. The @samp{--all} option is
24603 ignored in all-stop mode. If the @samp{--thread-group} options is
24604 specified, then all threads in that thread group are resumed.
24606 @subsubheading @value{GDBN} Command
24608 The corresponding @value{GDBN} corresponding is @samp{continue}.
24610 @subsubheading Example
24617 *stopped,reason="breakpoint-hit",disp="keep",bkptno="2",frame=@{
24618 func="foo",args=[],file="hello.c",fullname="/home/foo/bar/hello.c",
24624 @subheading The @code{-exec-finish} Command
24625 @findex -exec-finish
24627 @subsubheading Synopsis
24630 -exec-finish [--reverse]
24633 Resumes the execution of the inferior program until the current
24634 function is exited. Displays the results returned by the function.
24635 If the @samp{--reverse} option is specified, resumes the reverse
24636 execution of the inferior program until the point where current
24637 function was called.
24639 @subsubheading @value{GDBN} Command
24641 The corresponding @value{GDBN} command is @samp{finish}.
24643 @subsubheading Example
24645 Function returning @code{void}.
24652 *stopped,reason="function-finished",frame=@{func="main",args=[],
24653 file="hello.c",fullname="/home/foo/bar/hello.c",line="7"@}
24657 Function returning other than @code{void}. The name of the internal
24658 @value{GDBN} variable storing the result is printed, together with the
24665 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
24666 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
24667 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
24668 gdb-result-var="$1",return-value="0"
24673 @subheading The @code{-exec-interrupt} Command
24674 @findex -exec-interrupt
24676 @subsubheading Synopsis
24679 -exec-interrupt [--all|--thread-group N]
24682 Interrupts the background execution of the target. Note how the token
24683 associated with the stop message is the one for the execution command
24684 that has been interrupted. The token for the interrupt itself only
24685 appears in the @samp{^done} output. If the user is trying to
24686 interrupt a non-running program, an error message will be printed.
24688 Note that when asynchronous execution is enabled, this command is
24689 asynchronous just like other execution commands. That is, first the
24690 @samp{^done} response will be printed, and the target stop will be
24691 reported after that using the @samp{*stopped} notification.
24693 In non-stop mode, only the context thread is interrupted by default.
24694 All threads (in all inferiors) will be interrupted if the
24695 @samp{--all} option is specified. If the @samp{--thread-group}
24696 option is specified, all threads in that group will be interrupted.
24698 @subsubheading @value{GDBN} Command
24700 The corresponding @value{GDBN} command is @samp{interrupt}.
24702 @subsubheading Example
24713 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
24714 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",
24715 fullname="/home/foo/bar/try.c",line="13"@}
24720 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
24724 @subheading The @code{-exec-jump} Command
24727 @subsubheading Synopsis
24730 -exec-jump @var{location}
24733 Resumes execution of the inferior program at the location specified by
24734 parameter. @xref{Specify Location}, for a description of the
24735 different forms of @var{location}.
24737 @subsubheading @value{GDBN} Command
24739 The corresponding @value{GDBN} command is @samp{jump}.
24741 @subsubheading Example
24744 -exec-jump foo.c:10
24745 *running,thread-id="all"
24750 @subheading The @code{-exec-next} Command
24753 @subsubheading Synopsis
24756 -exec-next [--reverse]
24759 Resumes execution of the inferior program, stopping when the beginning
24760 of the next source line is reached.
24762 If the @samp{--reverse} option is specified, resumes reverse execution
24763 of the inferior program, stopping at the beginning of the previous
24764 source line. If you issue this command on the first line of a
24765 function, it will take you back to the caller of that function, to the
24766 source line where the function was called.
24769 @subsubheading @value{GDBN} Command
24771 The corresponding @value{GDBN} command is @samp{next}.
24773 @subsubheading Example
24779 *stopped,reason="end-stepping-range",line="8",file="hello.c"
24784 @subheading The @code{-exec-next-instruction} Command
24785 @findex -exec-next-instruction
24787 @subsubheading Synopsis
24790 -exec-next-instruction [--reverse]
24793 Executes one machine instruction. If the instruction is a function
24794 call, continues until the function returns. If the program stops at an
24795 instruction in the middle of a source line, the address will be
24798 If the @samp{--reverse} option is specified, resumes reverse execution
24799 of the inferior program, stopping at the previous instruction. If the
24800 previously executed instruction was a return from another function,
24801 it will continue to execute in reverse until the call to that function
24802 (from the current stack frame) is reached.
24804 @subsubheading @value{GDBN} Command
24806 The corresponding @value{GDBN} command is @samp{nexti}.
24808 @subsubheading Example
24812 -exec-next-instruction
24816 *stopped,reason="end-stepping-range",
24817 addr="0x000100d4",line="5",file="hello.c"
24822 @subheading The @code{-exec-return} Command
24823 @findex -exec-return
24825 @subsubheading Synopsis
24831 Makes current function return immediately. Doesn't execute the inferior.
24832 Displays the new current frame.
24834 @subsubheading @value{GDBN} Command
24836 The corresponding @value{GDBN} command is @samp{return}.
24838 @subsubheading Example
24842 200-break-insert callee4
24843 200^done,bkpt=@{number="1",addr="0x00010734",
24844 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
24849 000*stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
24850 frame=@{func="callee4",args=[],
24851 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
24852 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
24858 111^done,frame=@{level="0",func="callee3",
24859 args=[@{name="strarg",
24860 value="0x11940 \"A string argument.\""@}],
24861 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
24862 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
24867 @subheading The @code{-exec-run} Command
24870 @subsubheading Synopsis
24873 -exec-run [--all | --thread-group N]
24876 Starts execution of the inferior from the beginning. The inferior
24877 executes until either a breakpoint is encountered or the program
24878 exits. In the latter case the output will include an exit code, if
24879 the program has exited exceptionally.
24881 When no option is specified, the current inferior is started. If the
24882 @samp{--thread-group} option is specified, it should refer to a thread
24883 group of type @samp{process}, and that thread group will be started.
24884 If the @samp{--all} option is specified, then all inferiors will be started.
24886 @subsubheading @value{GDBN} Command
24888 The corresponding @value{GDBN} command is @samp{run}.
24890 @subsubheading Examples
24895 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
24900 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
24901 frame=@{func="main",args=[],file="recursive2.c",
24902 fullname="/home/foo/bar/recursive2.c",line="4"@}
24907 Program exited normally:
24915 *stopped,reason="exited-normally"
24920 Program exited exceptionally:
24928 *stopped,reason="exited",exit-code="01"
24932 Another way the program can terminate is if it receives a signal such as
24933 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
24937 *stopped,reason="exited-signalled",signal-name="SIGINT",
24938 signal-meaning="Interrupt"
24942 @c @subheading -exec-signal
24945 @subheading The @code{-exec-step} Command
24948 @subsubheading Synopsis
24951 -exec-step [--reverse]
24954 Resumes execution of the inferior program, stopping when the beginning
24955 of the next source line is reached, if the next source line is not a
24956 function call. If it is, stop at the first instruction of the called
24957 function. If the @samp{--reverse} option is specified, resumes reverse
24958 execution of the inferior program, stopping at the beginning of the
24959 previously executed source line.
24961 @subsubheading @value{GDBN} Command
24963 The corresponding @value{GDBN} command is @samp{step}.
24965 @subsubheading Example
24967 Stepping into a function:
24973 *stopped,reason="end-stepping-range",
24974 frame=@{func="foo",args=[@{name="a",value="10"@},
24975 @{name="b",value="0"@}],file="recursive2.c",
24976 fullname="/home/foo/bar/recursive2.c",line="11"@}
24986 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
24991 @subheading The @code{-exec-step-instruction} Command
24992 @findex -exec-step-instruction
24994 @subsubheading Synopsis
24997 -exec-step-instruction [--reverse]
25000 Resumes the inferior which executes one machine instruction. If the
25001 @samp{--reverse} option is specified, resumes reverse execution of the
25002 inferior program, stopping at the previously executed instruction.
25003 The output, once @value{GDBN} has stopped, will vary depending on
25004 whether we have stopped in the middle of a source line or not. In the
25005 former case, the address at which the program stopped will be printed
25008 @subsubheading @value{GDBN} Command
25010 The corresponding @value{GDBN} command is @samp{stepi}.
25012 @subsubheading Example
25016 -exec-step-instruction
25020 *stopped,reason="end-stepping-range",
25021 frame=@{func="foo",args=[],file="try.c",
25022 fullname="/home/foo/bar/try.c",line="10"@}
25024 -exec-step-instruction
25028 *stopped,reason="end-stepping-range",
25029 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",
25030 fullname="/home/foo/bar/try.c",line="10"@}
25035 @subheading The @code{-exec-until} Command
25036 @findex -exec-until
25038 @subsubheading Synopsis
25041 -exec-until [ @var{location} ]
25044 Executes the inferior until the @var{location} specified in the
25045 argument is reached. If there is no argument, the inferior executes
25046 until a source line greater than the current one is reached. The
25047 reason for stopping in this case will be @samp{location-reached}.
25049 @subsubheading @value{GDBN} Command
25051 The corresponding @value{GDBN} command is @samp{until}.
25053 @subsubheading Example
25057 -exec-until recursive2.c:6
25061 *stopped,reason="location-reached",frame=@{func="main",args=[],
25062 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="6"@}
25067 @subheading -file-clear
25068 Is this going away????
25071 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25072 @node GDB/MI Stack Manipulation
25073 @section @sc{gdb/mi} Stack Manipulation Commands
25076 @subheading The @code{-stack-info-frame} Command
25077 @findex -stack-info-frame
25079 @subsubheading Synopsis
25085 Get info on the selected frame.
25087 @subsubheading @value{GDBN} Command
25089 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
25090 (without arguments).
25092 @subsubheading Example
25097 ^done,frame=@{level="1",addr="0x0001076c",func="callee3",
25098 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
25099 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@}
25103 @subheading The @code{-stack-info-depth} Command
25104 @findex -stack-info-depth
25106 @subsubheading Synopsis
25109 -stack-info-depth [ @var{max-depth} ]
25112 Return the depth of the stack. If the integer argument @var{max-depth}
25113 is specified, do not count beyond @var{max-depth} frames.
25115 @subsubheading @value{GDBN} Command
25117 There's no equivalent @value{GDBN} command.
25119 @subsubheading Example
25121 For a stack with frame levels 0 through 11:
25128 -stack-info-depth 4
25131 -stack-info-depth 12
25134 -stack-info-depth 11
25137 -stack-info-depth 13
25142 @subheading The @code{-stack-list-arguments} Command
25143 @findex -stack-list-arguments
25145 @subsubheading Synopsis
25148 -stack-list-arguments @var{print-values}
25149 [ @var{low-frame} @var{high-frame} ]
25152 Display a list of the arguments for the frames between @var{low-frame}
25153 and @var{high-frame} (inclusive). If @var{low-frame} and
25154 @var{high-frame} are not provided, list the arguments for the whole
25155 call stack. If the two arguments are equal, show the single frame
25156 at the corresponding level. It is an error if @var{low-frame} is
25157 larger than the actual number of frames. On the other hand,
25158 @var{high-frame} may be larger than the actual number of frames, in
25159 which case only existing frames will be returned.
25161 If @var{print-values} is 0 or @code{--no-values}, print only the names of
25162 the variables; if it is 1 or @code{--all-values}, print also their
25163 values; and if it is 2 or @code{--simple-values}, print the name,
25164 type and value for simple data types, and the name and type for arrays,
25165 structures and unions.
25167 Use of this command to obtain arguments in a single frame is
25168 deprecated in favor of the @samp{-stack-list-variables} command.
25170 @subsubheading @value{GDBN} Command
25172 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
25173 @samp{gdb_get_args} command which partially overlaps with the
25174 functionality of @samp{-stack-list-arguments}.
25176 @subsubheading Example
25183 frame=@{level="0",addr="0x00010734",func="callee4",
25184 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
25185 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@},
25186 frame=@{level="1",addr="0x0001076c",func="callee3",
25187 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
25188 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@},
25189 frame=@{level="2",addr="0x0001078c",func="callee2",
25190 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
25191 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="22"@},
25192 frame=@{level="3",addr="0x000107b4",func="callee1",
25193 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
25194 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="27"@},
25195 frame=@{level="4",addr="0x000107e0",func="main",
25196 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
25197 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="32"@}]
25199 -stack-list-arguments 0
25202 frame=@{level="0",args=[]@},
25203 frame=@{level="1",args=[name="strarg"]@},
25204 frame=@{level="2",args=[name="intarg",name="strarg"]@},
25205 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
25206 frame=@{level="4",args=[]@}]
25208 -stack-list-arguments 1
25211 frame=@{level="0",args=[]@},
25213 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
25214 frame=@{level="2",args=[
25215 @{name="intarg",value="2"@},
25216 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
25217 @{frame=@{level="3",args=[
25218 @{name="intarg",value="2"@},
25219 @{name="strarg",value="0x11940 \"A string argument.\""@},
25220 @{name="fltarg",value="3.5"@}]@},
25221 frame=@{level="4",args=[]@}]
25223 -stack-list-arguments 0 2 2
25224 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
25226 -stack-list-arguments 1 2 2
25227 ^done,stack-args=[frame=@{level="2",
25228 args=[@{name="intarg",value="2"@},
25229 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
25233 @c @subheading -stack-list-exception-handlers
25236 @subheading The @code{-stack-list-frames} Command
25237 @findex -stack-list-frames
25239 @subsubheading Synopsis
25242 -stack-list-frames [ @var{low-frame} @var{high-frame} ]
25245 List the frames currently on the stack. For each frame it displays the
25250 The frame number, 0 being the topmost frame, i.e., the innermost function.
25252 The @code{$pc} value for that frame.
25256 File name of the source file where the function lives.
25258 Line number corresponding to the @code{$pc}.
25261 If invoked without arguments, this command prints a backtrace for the
25262 whole stack. If given two integer arguments, it shows the frames whose
25263 levels are between the two arguments (inclusive). If the two arguments
25264 are equal, it shows the single frame at the corresponding level. It is
25265 an error if @var{low-frame} is larger than the actual number of
25266 frames. On the other hand, @var{high-frame} may be larger than the
25267 actual number of frames, in which case only existing frames will be returned.
25269 @subsubheading @value{GDBN} Command
25271 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
25273 @subsubheading Example
25275 Full stack backtrace:
25281 [frame=@{level="0",addr="0x0001076c",func="foo",
25282 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="11"@},
25283 frame=@{level="1",addr="0x000107a4",func="foo",
25284 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
25285 frame=@{level="2",addr="0x000107a4",func="foo",
25286 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
25287 frame=@{level="3",addr="0x000107a4",func="foo",
25288 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
25289 frame=@{level="4",addr="0x000107a4",func="foo",
25290 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
25291 frame=@{level="5",addr="0x000107a4",func="foo",
25292 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
25293 frame=@{level="6",addr="0x000107a4",func="foo",
25294 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
25295 frame=@{level="7",addr="0x000107a4",func="foo",
25296 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
25297 frame=@{level="8",addr="0x000107a4",func="foo",
25298 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
25299 frame=@{level="9",addr="0x000107a4",func="foo",
25300 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
25301 frame=@{level="10",addr="0x000107a4",func="foo",
25302 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
25303 frame=@{level="11",addr="0x00010738",func="main",
25304 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="4"@}]
25308 Show frames between @var{low_frame} and @var{high_frame}:
25312 -stack-list-frames 3 5
25314 [frame=@{level="3",addr="0x000107a4",func="foo",
25315 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
25316 frame=@{level="4",addr="0x000107a4",func="foo",
25317 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
25318 frame=@{level="5",addr="0x000107a4",func="foo",
25319 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
25323 Show a single frame:
25327 -stack-list-frames 3 3
25329 [frame=@{level="3",addr="0x000107a4",func="foo",
25330 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
25335 @subheading The @code{-stack-list-locals} Command
25336 @findex -stack-list-locals
25338 @subsubheading Synopsis
25341 -stack-list-locals @var{print-values}
25344 Display the local variable names for the selected frame. If
25345 @var{print-values} is 0 or @code{--no-values}, print only the names of
25346 the variables; if it is 1 or @code{--all-values}, print also their
25347 values; and if it is 2 or @code{--simple-values}, print the name,
25348 type and value for simple data types, and the name and type for arrays,
25349 structures and unions. In this last case, a frontend can immediately
25350 display the value of simple data types and create variable objects for
25351 other data types when the user wishes to explore their values in
25354 This command is deprecated in favor of the
25355 @samp{-stack-list-variables} command.
25357 @subsubheading @value{GDBN} Command
25359 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
25361 @subsubheading Example
25365 -stack-list-locals 0
25366 ^done,locals=[name="A",name="B",name="C"]
25368 -stack-list-locals --all-values
25369 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
25370 @{name="C",value="@{1, 2, 3@}"@}]
25371 -stack-list-locals --simple-values
25372 ^done,locals=[@{name="A",type="int",value="1"@},
25373 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
25377 @subheading The @code{-stack-list-variables} Command
25378 @findex -stack-list-variables
25380 @subsubheading Synopsis
25383 -stack-list-variables @var{print-values}
25386 Display the names of local variables and function arguments for the selected frame. If
25387 @var{print-values} is 0 or @code{--no-values}, print only the names of
25388 the variables; if it is 1 or @code{--all-values}, print also their
25389 values; and if it is 2 or @code{--simple-values}, print the name,
25390 type and value for simple data types, and the name and type for arrays,
25391 structures and unions.
25393 @subsubheading Example
25397 -stack-list-variables --thread 1 --frame 0 --all-values
25398 ^done,variables=[@{name="x",value="11"@},@{name="s",value="@{a = 1, b = 2@}"@}]
25403 @subheading The @code{-stack-select-frame} Command
25404 @findex -stack-select-frame
25406 @subsubheading Synopsis
25409 -stack-select-frame @var{framenum}
25412 Change the selected frame. Select a different frame @var{framenum} on
25415 This command in deprecated in favor of passing the @samp{--frame}
25416 option to every command.
25418 @subsubheading @value{GDBN} Command
25420 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
25421 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
25423 @subsubheading Example
25427 -stack-select-frame 2
25432 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25433 @node GDB/MI Variable Objects
25434 @section @sc{gdb/mi} Variable Objects
25438 @subheading Motivation for Variable Objects in @sc{gdb/mi}
25440 For the implementation of a variable debugger window (locals, watched
25441 expressions, etc.), we are proposing the adaptation of the existing code
25442 used by @code{Insight}.
25444 The two main reasons for that are:
25448 It has been proven in practice (it is already on its second generation).
25451 It will shorten development time (needless to say how important it is
25455 The original interface was designed to be used by Tcl code, so it was
25456 slightly changed so it could be used through @sc{gdb/mi}. This section
25457 describes the @sc{gdb/mi} operations that will be available and gives some
25458 hints about their use.
25460 @emph{Note}: In addition to the set of operations described here, we
25461 expect the @sc{gui} implementation of a variable window to require, at
25462 least, the following operations:
25465 @item @code{-gdb-show} @code{output-radix}
25466 @item @code{-stack-list-arguments}
25467 @item @code{-stack-list-locals}
25468 @item @code{-stack-select-frame}
25473 @subheading Introduction to Variable Objects
25475 @cindex variable objects in @sc{gdb/mi}
25477 Variable objects are "object-oriented" MI interface for examining and
25478 changing values of expressions. Unlike some other MI interfaces that
25479 work with expressions, variable objects are specifically designed for
25480 simple and efficient presentation in the frontend. A variable object
25481 is identified by string name. When a variable object is created, the
25482 frontend specifies the expression for that variable object. The
25483 expression can be a simple variable, or it can be an arbitrary complex
25484 expression, and can even involve CPU registers. After creating a
25485 variable object, the frontend can invoke other variable object
25486 operations---for example to obtain or change the value of a variable
25487 object, or to change display format.
25489 Variable objects have hierarchical tree structure. Any variable object
25490 that corresponds to a composite type, such as structure in C, has
25491 a number of child variable objects, for example corresponding to each
25492 element of a structure. A child variable object can itself have
25493 children, recursively. Recursion ends when we reach
25494 leaf variable objects, which always have built-in types. Child variable
25495 objects are created only by explicit request, so if a frontend
25496 is not interested in the children of a particular variable object, no
25497 child will be created.
25499 For a leaf variable object it is possible to obtain its value as a
25500 string, or set the value from a string. String value can be also
25501 obtained for a non-leaf variable object, but it's generally a string
25502 that only indicates the type of the object, and does not list its
25503 contents. Assignment to a non-leaf variable object is not allowed.
25505 A frontend does not need to read the values of all variable objects each time
25506 the program stops. Instead, MI provides an update command that lists all
25507 variable objects whose values has changed since the last update
25508 operation. This considerably reduces the amount of data that must
25509 be transferred to the frontend. As noted above, children variable
25510 objects are created on demand, and only leaf variable objects have a
25511 real value. As result, gdb will read target memory only for leaf
25512 variables that frontend has created.
25514 The automatic update is not always desirable. For example, a frontend
25515 might want to keep a value of some expression for future reference,
25516 and never update it. For another example, fetching memory is
25517 relatively slow for embedded targets, so a frontend might want
25518 to disable automatic update for the variables that are either not
25519 visible on the screen, or ``closed''. This is possible using so
25520 called ``frozen variable objects''. Such variable objects are never
25521 implicitly updated.
25523 Variable objects can be either @dfn{fixed} or @dfn{floating}. For the
25524 fixed variable object, the expression is parsed when the variable
25525 object is created, including associating identifiers to specific
25526 variables. The meaning of expression never changes. For a floating
25527 variable object the values of variables whose names appear in the
25528 expressions are re-evaluated every time in the context of the current
25529 frame. Consider this example:
25534 struct work_state state;
25541 If a fixed variable object for the @code{state} variable is created in
25542 this function, and we enter the recursive call, the the variable
25543 object will report the value of @code{state} in the top-level
25544 @code{do_work} invocation. On the other hand, a floating variable
25545 object will report the value of @code{state} in the current frame.
25547 If an expression specified when creating a fixed variable object
25548 refers to a local variable, the variable object becomes bound to the
25549 thread and frame in which the variable object is created. When such
25550 variable object is updated, @value{GDBN} makes sure that the
25551 thread/frame combination the variable object is bound to still exists,
25552 and re-evaluates the variable object in context of that thread/frame.
25554 The following is the complete set of @sc{gdb/mi} operations defined to
25555 access this functionality:
25557 @multitable @columnfractions .4 .6
25558 @item @strong{Operation}
25559 @tab @strong{Description}
25561 @item @code{-enable-pretty-printing}
25562 @tab enable Python-based pretty-printing
25563 @item @code{-var-create}
25564 @tab create a variable object
25565 @item @code{-var-delete}
25566 @tab delete the variable object and/or its children
25567 @item @code{-var-set-format}
25568 @tab set the display format of this variable
25569 @item @code{-var-show-format}
25570 @tab show the display format of this variable
25571 @item @code{-var-info-num-children}
25572 @tab tells how many children this object has
25573 @item @code{-var-list-children}
25574 @tab return a list of the object's children
25575 @item @code{-var-info-type}
25576 @tab show the type of this variable object
25577 @item @code{-var-info-expression}
25578 @tab print parent-relative expression that this variable object represents
25579 @item @code{-var-info-path-expression}
25580 @tab print full expression that this variable object represents
25581 @item @code{-var-show-attributes}
25582 @tab is this variable editable? does it exist here?
25583 @item @code{-var-evaluate-expression}
25584 @tab get the value of this variable
25585 @item @code{-var-assign}
25586 @tab set the value of this variable
25587 @item @code{-var-update}
25588 @tab update the variable and its children
25589 @item @code{-var-set-frozen}
25590 @tab set frozeness attribute
25591 @item @code{-var-set-update-range}
25592 @tab set range of children to display on update
25595 In the next subsection we describe each operation in detail and suggest
25596 how it can be used.
25598 @subheading Description And Use of Operations on Variable Objects
25600 @subheading The @code{-enable-pretty-printing} Command
25601 @findex -enable-pretty-printing
25604 -enable-pretty-printing
25607 @value{GDBN} allows Python-based visualizers to affect the output of the
25608 MI variable object commands. However, because there was no way to
25609 implement this in a fully backward-compatible way, a front end must
25610 request that this functionality be enabled.
25612 Once enabled, this feature cannot be disabled.
25614 Note that if Python support has not been compiled into @value{GDBN},
25615 this command will still succeed (and do nothing).
25617 This feature is currently (as of @value{GDBN} 7.0) experimental, and
25618 may work differently in future versions of @value{GDBN}.
25620 @subheading The @code{-var-create} Command
25621 @findex -var-create
25623 @subsubheading Synopsis
25626 -var-create @{@var{name} | "-"@}
25627 @{@var{frame-addr} | "*" | "@@"@} @var{expression}
25630 This operation creates a variable object, which allows the monitoring of
25631 a variable, the result of an expression, a memory cell or a CPU
25634 The @var{name} parameter is the string by which the object can be
25635 referenced. It must be unique. If @samp{-} is specified, the varobj
25636 system will generate a string ``varNNNNNN'' automatically. It will be
25637 unique provided that one does not specify @var{name} of that format.
25638 The command fails if a duplicate name is found.
25640 The frame under which the expression should be evaluated can be
25641 specified by @var{frame-addr}. A @samp{*} indicates that the current
25642 frame should be used. A @samp{@@} indicates that a floating variable
25643 object must be created.
25645 @var{expression} is any expression valid on the current language set (must not
25646 begin with a @samp{*}), or one of the following:
25650 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
25653 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
25656 @samp{$@var{regname}} --- a CPU register name
25659 @cindex dynamic varobj
25660 A varobj's contents may be provided by a Python-based pretty-printer. In this
25661 case the varobj is known as a @dfn{dynamic varobj}. Dynamic varobjs
25662 have slightly different semantics in some cases. If the
25663 @code{-enable-pretty-printing} command is not sent, then @value{GDBN}
25664 will never create a dynamic varobj. This ensures backward
25665 compatibility for existing clients.
25667 @subsubheading Result
25669 This operation returns attributes of the newly-created varobj. These
25674 The name of the varobj.
25677 The number of children of the varobj. This number is not necessarily
25678 reliable for a dynamic varobj. Instead, you must examine the
25679 @samp{has_more} attribute.
25682 The varobj's scalar value. For a varobj whose type is some sort of
25683 aggregate (e.g., a @code{struct}), or for a dynamic varobj, this value
25684 will not be interesting.
25687 The varobj's type. This is a string representation of the type, as
25688 would be printed by the @value{GDBN} CLI.
25691 If a variable object is bound to a specific thread, then this is the
25692 thread's identifier.
25695 For a dynamic varobj, this indicates whether there appear to be any
25696 children available. For a non-dynamic varobj, this will be 0.
25699 This attribute will be present and have the value @samp{1} if the
25700 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
25701 then this attribute will not be present.
25704 A dynamic varobj can supply a display hint to the front end. The
25705 value comes directly from the Python pretty-printer object's
25706 @code{display_hint} method. @xref{Pretty Printing API}.
25709 Typical output will look like this:
25712 name="@var{name}",numchild="@var{N}",type="@var{type}",thread-id="@var{M}",
25713 has_more="@var{has_more}"
25717 @subheading The @code{-var-delete} Command
25718 @findex -var-delete
25720 @subsubheading Synopsis
25723 -var-delete [ -c ] @var{name}
25726 Deletes a previously created variable object and all of its children.
25727 With the @samp{-c} option, just deletes the children.
25729 Returns an error if the object @var{name} is not found.
25732 @subheading The @code{-var-set-format} Command
25733 @findex -var-set-format
25735 @subsubheading Synopsis
25738 -var-set-format @var{name} @var{format-spec}
25741 Sets the output format for the value of the object @var{name} to be
25744 @anchor{-var-set-format}
25745 The syntax for the @var{format-spec} is as follows:
25748 @var{format-spec} @expansion{}
25749 @{binary | decimal | hexadecimal | octal | natural@}
25752 The natural format is the default format choosen automatically
25753 based on the variable type (like decimal for an @code{int}, hex
25754 for pointers, etc.).
25756 For a variable with children, the format is set only on the
25757 variable itself, and the children are not affected.
25759 @subheading The @code{-var-show-format} Command
25760 @findex -var-show-format
25762 @subsubheading Synopsis
25765 -var-show-format @var{name}
25768 Returns the format used to display the value of the object @var{name}.
25771 @var{format} @expansion{}
25776 @subheading The @code{-var-info-num-children} Command
25777 @findex -var-info-num-children
25779 @subsubheading Synopsis
25782 -var-info-num-children @var{name}
25785 Returns the number of children of a variable object @var{name}:
25791 Note that this number is not completely reliable for a dynamic varobj.
25792 It will return the current number of children, but more children may
25796 @subheading The @code{-var-list-children} Command
25797 @findex -var-list-children
25799 @subsubheading Synopsis
25802 -var-list-children [@var{print-values}] @var{name} [@var{from} @var{to}]
25804 @anchor{-var-list-children}
25806 Return a list of the children of the specified variable object and
25807 create variable objects for them, if they do not already exist. With
25808 a single argument or if @var{print-values} has a value for of 0 or
25809 @code{--no-values}, print only the names of the variables; if
25810 @var{print-values} is 1 or @code{--all-values}, also print their
25811 values; and if it is 2 or @code{--simple-values} print the name and
25812 value for simple data types and just the name for arrays, structures
25815 @var{from} and @var{to}, if specified, indicate the range of children
25816 to report. If @var{from} or @var{to} is less than zero, the range is
25817 reset and all children will be reported. Otherwise, children starting
25818 at @var{from} (zero-based) and up to and excluding @var{to} will be
25821 If a child range is requested, it will only affect the current call to
25822 @code{-var-list-children}, but not future calls to @code{-var-update}.
25823 For this, you must instead use @code{-var-set-update-range}. The
25824 intent of this approach is to enable a front end to implement any
25825 update approach it likes; for example, scrolling a view may cause the
25826 front end to request more children with @code{-var-list-children}, and
25827 then the front end could call @code{-var-set-update-range} with a
25828 different range to ensure that future updates are restricted to just
25831 For each child the following results are returned:
25836 Name of the variable object created for this child.
25839 The expression to be shown to the user by the front end to designate this child.
25840 For example this may be the name of a structure member.
25842 For a dynamic varobj, this value cannot be used to form an
25843 expression. There is no way to do this at all with a dynamic varobj.
25845 For C/C@t{++} structures there are several pseudo children returned to
25846 designate access qualifiers. For these pseudo children @var{exp} is
25847 @samp{public}, @samp{private}, or @samp{protected}. In this case the
25848 type and value are not present.
25850 A dynamic varobj will not report the access qualifying
25851 pseudo-children, regardless of the language. This information is not
25852 available at all with a dynamic varobj.
25855 Number of children this child has. For a dynamic varobj, this will be
25859 The type of the child.
25862 If values were requested, this is the value.
25865 If this variable object is associated with a thread, this is the thread id.
25866 Otherwise this result is not present.
25869 If the variable object is frozen, this variable will be present with a value of 1.
25872 The result may have its own attributes:
25876 A dynamic varobj can supply a display hint to the front end. The
25877 value comes directly from the Python pretty-printer object's
25878 @code{display_hint} method. @xref{Pretty Printing API}.
25881 This is an integer attribute which is nonzero if there are children
25882 remaining after the end of the selected range.
25885 @subsubheading Example
25889 -var-list-children n
25890 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
25891 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
25893 -var-list-children --all-values n
25894 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
25895 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
25899 @subheading The @code{-var-info-type} Command
25900 @findex -var-info-type
25902 @subsubheading Synopsis
25905 -var-info-type @var{name}
25908 Returns the type of the specified variable @var{name}. The type is
25909 returned as a string in the same format as it is output by the
25913 type=@var{typename}
25917 @subheading The @code{-var-info-expression} Command
25918 @findex -var-info-expression
25920 @subsubheading Synopsis
25923 -var-info-expression @var{name}
25926 Returns a string that is suitable for presenting this
25927 variable object in user interface. The string is generally
25928 not valid expression in the current language, and cannot be evaluated.
25930 For example, if @code{a} is an array, and variable object
25931 @code{A} was created for @code{a}, then we'll get this output:
25934 (gdb) -var-info-expression A.1
25935 ^done,lang="C",exp="1"
25939 Here, the values of @code{lang} can be @code{@{"C" | "C++" | "Java"@}}.
25941 Note that the output of the @code{-var-list-children} command also
25942 includes those expressions, so the @code{-var-info-expression} command
25945 @subheading The @code{-var-info-path-expression} Command
25946 @findex -var-info-path-expression
25948 @subsubheading Synopsis
25951 -var-info-path-expression @var{name}
25954 Returns an expression that can be evaluated in the current
25955 context and will yield the same value that a variable object has.
25956 Compare this with the @code{-var-info-expression} command, which
25957 result can be used only for UI presentation. Typical use of
25958 the @code{-var-info-path-expression} command is creating a
25959 watchpoint from a variable object.
25961 This command is currently not valid for children of a dynamic varobj,
25962 and will give an error when invoked on one.
25964 For example, suppose @code{C} is a C@t{++} class, derived from class
25965 @code{Base}, and that the @code{Base} class has a member called
25966 @code{m_size}. Assume a variable @code{c} is has the type of
25967 @code{C} and a variable object @code{C} was created for variable
25968 @code{c}. Then, we'll get this output:
25970 (gdb) -var-info-path-expression C.Base.public.m_size
25971 ^done,path_expr=((Base)c).m_size)
25974 @subheading The @code{-var-show-attributes} Command
25975 @findex -var-show-attributes
25977 @subsubheading Synopsis
25980 -var-show-attributes @var{name}
25983 List attributes of the specified variable object @var{name}:
25986 status=@var{attr} [ ( ,@var{attr} )* ]
25990 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
25992 @subheading The @code{-var-evaluate-expression} Command
25993 @findex -var-evaluate-expression
25995 @subsubheading Synopsis
25998 -var-evaluate-expression [-f @var{format-spec}] @var{name}
26001 Evaluates the expression that is represented by the specified variable
26002 object and returns its value as a string. The format of the string
26003 can be specified with the @samp{-f} option. The possible values of
26004 this option are the same as for @code{-var-set-format}
26005 (@pxref{-var-set-format}). If the @samp{-f} option is not specified,
26006 the current display format will be used. The current display format
26007 can be changed using the @code{-var-set-format} command.
26013 Note that one must invoke @code{-var-list-children} for a variable
26014 before the value of a child variable can be evaluated.
26016 @subheading The @code{-var-assign} Command
26017 @findex -var-assign
26019 @subsubheading Synopsis
26022 -var-assign @var{name} @var{expression}
26025 Assigns the value of @var{expression} to the variable object specified
26026 by @var{name}. The object must be @samp{editable}. If the variable's
26027 value is altered by the assign, the variable will show up in any
26028 subsequent @code{-var-update} list.
26030 @subsubheading Example
26038 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
26042 @subheading The @code{-var-update} Command
26043 @findex -var-update
26045 @subsubheading Synopsis
26048 -var-update [@var{print-values}] @{@var{name} | "*"@}
26051 Reevaluate the expressions corresponding to the variable object
26052 @var{name} and all its direct and indirect children, and return the
26053 list of variable objects whose values have changed; @var{name} must
26054 be a root variable object. Here, ``changed'' means that the result of
26055 @code{-var-evaluate-expression} before and after the
26056 @code{-var-update} is different. If @samp{*} is used as the variable
26057 object names, all existing variable objects are updated, except
26058 for frozen ones (@pxref{-var-set-frozen}). The option
26059 @var{print-values} determines whether both names and values, or just
26060 names are printed. The possible values of this option are the same
26061 as for @code{-var-list-children} (@pxref{-var-list-children}). It is
26062 recommended to use the @samp{--all-values} option, to reduce the
26063 number of MI commands needed on each program stop.
26065 With the @samp{*} parameter, if a variable object is bound to a
26066 currently running thread, it will not be updated, without any
26069 If @code{-var-set-update-range} was previously used on a varobj, then
26070 only the selected range of children will be reported.
26072 @code{-var-update} reports all the changed varobjs in a tuple named
26075 Each item in the change list is itself a tuple holding:
26079 The name of the varobj.
26082 If values were requested for this update, then this field will be
26083 present and will hold the value of the varobj.
26086 @anchor{-var-update}
26087 This field is a string which may take one of three values:
26091 The variable object's current value is valid.
26094 The variable object does not currently hold a valid value but it may
26095 hold one in the future if its associated expression comes back into
26099 The variable object no longer holds a valid value.
26100 This can occur when the executable file being debugged has changed,
26101 either through recompilation or by using the @value{GDBN} @code{file}
26102 command. The front end should normally choose to delete these variable
26106 In the future new values may be added to this list so the front should
26107 be prepared for this possibility. @xref{GDB/MI Development and Front Ends, ,@sc{GDB/MI} Development and Front Ends}.
26110 This is only present if the varobj is still valid. If the type
26111 changed, then this will be the string @samp{true}; otherwise it will
26115 If the varobj's type changed, then this field will be present and will
26118 @item new_num_children
26119 For a dynamic varobj, if the number of children changed, or if the
26120 type changed, this will be the new number of children.
26122 The @samp{numchild} field in other varobj responses is generally not
26123 valid for a dynamic varobj -- it will show the number of children that
26124 @value{GDBN} knows about, but because dynamic varobjs lazily
26125 instantiate their children, this will not reflect the number of
26126 children which may be available.
26128 The @samp{new_num_children} attribute only reports changes to the
26129 number of children known by @value{GDBN}. This is the only way to
26130 detect whether an update has removed children (which necessarily can
26131 only happen at the end of the update range).
26134 The display hint, if any.
26137 This is an integer value, which will be 1 if there are more children
26138 available outside the varobj's update range.
26141 This attribute will be present and have the value @samp{1} if the
26142 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
26143 then this attribute will not be present.
26146 If new children were added to a dynamic varobj within the selected
26147 update range (as set by @code{-var-set-update-range}), then they will
26148 be listed in this attribute.
26151 @subsubheading Example
26158 -var-update --all-values var1
26159 ^done,changelist=[@{name="var1",value="3",in_scope="true",
26160 type_changed="false"@}]
26164 @subheading The @code{-var-set-frozen} Command
26165 @findex -var-set-frozen
26166 @anchor{-var-set-frozen}
26168 @subsubheading Synopsis
26171 -var-set-frozen @var{name} @var{flag}
26174 Set the frozenness flag on the variable object @var{name}. The
26175 @var{flag} parameter should be either @samp{1} to make the variable
26176 frozen or @samp{0} to make it unfrozen. If a variable object is
26177 frozen, then neither itself, nor any of its children, are
26178 implicitly updated by @code{-var-update} of
26179 a parent variable or by @code{-var-update *}. Only
26180 @code{-var-update} of the variable itself will update its value and
26181 values of its children. After a variable object is unfrozen, it is
26182 implicitly updated by all subsequent @code{-var-update} operations.
26183 Unfreezing a variable does not update it, only subsequent
26184 @code{-var-update} does.
26186 @subsubheading Example
26190 -var-set-frozen V 1
26195 @subheading The @code{-var-set-update-range} command
26196 @findex -var-set-update-range
26197 @anchor{-var-set-update-range}
26199 @subsubheading Synopsis
26202 -var-set-update-range @var{name} @var{from} @var{to}
26205 Set the range of children to be returned by future invocations of
26206 @code{-var-update}.
26208 @var{from} and @var{to} indicate the range of children to report. If
26209 @var{from} or @var{to} is less than zero, the range is reset and all
26210 children will be reported. Otherwise, children starting at @var{from}
26211 (zero-based) and up to and excluding @var{to} will be reported.
26213 @subsubheading Example
26217 -var-set-update-range V 1 2
26221 @subheading The @code{-var-set-visualizer} command
26222 @findex -var-set-visualizer
26223 @anchor{-var-set-visualizer}
26225 @subsubheading Synopsis
26228 -var-set-visualizer @var{name} @var{visualizer}
26231 Set a visualizer for the variable object @var{name}.
26233 @var{visualizer} is the visualizer to use. The special value
26234 @samp{None} means to disable any visualizer in use.
26236 If not @samp{None}, @var{visualizer} must be a Python expression.
26237 This expression must evaluate to a callable object which accepts a
26238 single argument. @value{GDBN} will call this object with the value of
26239 the varobj @var{name} as an argument (this is done so that the same
26240 Python pretty-printing code can be used for both the CLI and MI).
26241 When called, this object must return an object which conforms to the
26242 pretty-printing interface (@pxref{Pretty Printing API}).
26244 The pre-defined function @code{gdb.default_visualizer} may be used to
26245 select a visualizer by following the built-in process
26246 (@pxref{Selecting Pretty-Printers}). This is done automatically when
26247 a varobj is created, and so ordinarily is not needed.
26249 This feature is only available if Python support is enabled. The MI
26250 command @code{-list-features} (@pxref{GDB/MI Miscellaneous Commands})
26251 can be used to check this.
26253 @subsubheading Example
26255 Resetting the visualizer:
26259 -var-set-visualizer V None
26263 Reselecting the default (type-based) visualizer:
26267 -var-set-visualizer V gdb.default_visualizer
26271 Suppose @code{SomeClass} is a visualizer class. A lambda expression
26272 can be used to instantiate this class for a varobj:
26276 -var-set-visualizer V "lambda val: SomeClass()"
26280 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26281 @node GDB/MI Data Manipulation
26282 @section @sc{gdb/mi} Data Manipulation
26284 @cindex data manipulation, in @sc{gdb/mi}
26285 @cindex @sc{gdb/mi}, data manipulation
26286 This section describes the @sc{gdb/mi} commands that manipulate data:
26287 examine memory and registers, evaluate expressions, etc.
26289 @c REMOVED FROM THE INTERFACE.
26290 @c @subheading -data-assign
26291 @c Change the value of a program variable. Plenty of side effects.
26292 @c @subsubheading GDB Command
26294 @c @subsubheading Example
26297 @subheading The @code{-data-disassemble} Command
26298 @findex -data-disassemble
26300 @subsubheading Synopsis
26304 [ -s @var{start-addr} -e @var{end-addr} ]
26305 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
26313 @item @var{start-addr}
26314 is the beginning address (or @code{$pc})
26315 @item @var{end-addr}
26317 @item @var{filename}
26318 is the name of the file to disassemble
26319 @item @var{linenum}
26320 is the line number to disassemble around
26322 is the number of disassembly lines to be produced. If it is -1,
26323 the whole function will be disassembled, in case no @var{end-addr} is
26324 specified. If @var{end-addr} is specified as a non-zero value, and
26325 @var{lines} is lower than the number of disassembly lines between
26326 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
26327 displayed; if @var{lines} is higher than the number of lines between
26328 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
26331 is either 0 (meaning only disassembly) or 1 (meaning mixed source and
26335 @subsubheading Result
26337 The output for each instruction is composed of four fields:
26346 Note that whatever included in the instruction field, is not manipulated
26347 directly by @sc{gdb/mi}, i.e., it is not possible to adjust its format.
26349 @subsubheading @value{GDBN} Command
26351 There's no direct mapping from this command to the CLI.
26353 @subsubheading Example
26355 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
26359 -data-disassemble -s $pc -e "$pc + 20" -- 0
26362 @{address="0x000107c0",func-name="main",offset="4",
26363 inst="mov 2, %o0"@},
26364 @{address="0x000107c4",func-name="main",offset="8",
26365 inst="sethi %hi(0x11800), %o2"@},
26366 @{address="0x000107c8",func-name="main",offset="12",
26367 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
26368 @{address="0x000107cc",func-name="main",offset="16",
26369 inst="sethi %hi(0x11800), %o2"@},
26370 @{address="0x000107d0",func-name="main",offset="20",
26371 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
26375 Disassemble the whole @code{main} function. Line 32 is part of
26379 -data-disassemble -f basics.c -l 32 -- 0
26381 @{address="0x000107bc",func-name="main",offset="0",
26382 inst="save %sp, -112, %sp"@},
26383 @{address="0x000107c0",func-name="main",offset="4",
26384 inst="mov 2, %o0"@},
26385 @{address="0x000107c4",func-name="main",offset="8",
26386 inst="sethi %hi(0x11800), %o2"@},
26388 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
26389 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
26393 Disassemble 3 instructions from the start of @code{main}:
26397 -data-disassemble -f basics.c -l 32 -n 3 -- 0
26399 @{address="0x000107bc",func-name="main",offset="0",
26400 inst="save %sp, -112, %sp"@},
26401 @{address="0x000107c0",func-name="main",offset="4",
26402 inst="mov 2, %o0"@},
26403 @{address="0x000107c4",func-name="main",offset="8",
26404 inst="sethi %hi(0x11800), %o2"@}]
26408 Disassemble 3 instructions from the start of @code{main} in mixed mode:
26412 -data-disassemble -f basics.c -l 32 -n 3 -- 1
26414 src_and_asm_line=@{line="31",
26415 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
26416 testsuite/gdb.mi/basics.c",line_asm_insn=[
26417 @{address="0x000107bc",func-name="main",offset="0",
26418 inst="save %sp, -112, %sp"@}]@},
26419 src_and_asm_line=@{line="32",
26420 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
26421 testsuite/gdb.mi/basics.c",line_asm_insn=[
26422 @{address="0x000107c0",func-name="main",offset="4",
26423 inst="mov 2, %o0"@},
26424 @{address="0x000107c4",func-name="main",offset="8",
26425 inst="sethi %hi(0x11800), %o2"@}]@}]
26430 @subheading The @code{-data-evaluate-expression} Command
26431 @findex -data-evaluate-expression
26433 @subsubheading Synopsis
26436 -data-evaluate-expression @var{expr}
26439 Evaluate @var{expr} as an expression. The expression could contain an
26440 inferior function call. The function call will execute synchronously.
26441 If the expression contains spaces, it must be enclosed in double quotes.
26443 @subsubheading @value{GDBN} Command
26445 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
26446 @samp{call}. In @code{gdbtk} only, there's a corresponding
26447 @samp{gdb_eval} command.
26449 @subsubheading Example
26451 In the following example, the numbers that precede the commands are the
26452 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
26453 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
26457 211-data-evaluate-expression A
26460 311-data-evaluate-expression &A
26461 311^done,value="0xefffeb7c"
26463 411-data-evaluate-expression A+3
26466 511-data-evaluate-expression "A + 3"
26472 @subheading The @code{-data-list-changed-registers} Command
26473 @findex -data-list-changed-registers
26475 @subsubheading Synopsis
26478 -data-list-changed-registers
26481 Display a list of the registers that have changed.
26483 @subsubheading @value{GDBN} Command
26485 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
26486 has the corresponding command @samp{gdb_changed_register_list}.
26488 @subsubheading Example
26490 On a PPC MBX board:
26498 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",frame=@{
26499 func="main",args=[],file="try.c",fullname="/home/foo/bar/try.c",
26502 -data-list-changed-registers
26503 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
26504 "10","11","13","14","15","16","17","18","19","20","21","22","23",
26505 "24","25","26","27","28","30","31","64","65","66","67","69"]
26510 @subheading The @code{-data-list-register-names} Command
26511 @findex -data-list-register-names
26513 @subsubheading Synopsis
26516 -data-list-register-names [ ( @var{regno} )+ ]
26519 Show a list of register names for the current target. If no arguments
26520 are given, it shows a list of the names of all the registers. If
26521 integer numbers are given as arguments, it will print a list of the
26522 names of the registers corresponding to the arguments. To ensure
26523 consistency between a register name and its number, the output list may
26524 include empty register names.
26526 @subsubheading @value{GDBN} Command
26528 @value{GDBN} does not have a command which corresponds to
26529 @samp{-data-list-register-names}. In @code{gdbtk} there is a
26530 corresponding command @samp{gdb_regnames}.
26532 @subsubheading Example
26534 For the PPC MBX board:
26537 -data-list-register-names
26538 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
26539 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
26540 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
26541 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
26542 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
26543 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
26544 "", "pc","ps","cr","lr","ctr","xer"]
26546 -data-list-register-names 1 2 3
26547 ^done,register-names=["r1","r2","r3"]
26551 @subheading The @code{-data-list-register-values} Command
26552 @findex -data-list-register-values
26554 @subsubheading Synopsis
26557 -data-list-register-values @var{fmt} [ ( @var{regno} )*]
26560 Display the registers' contents. @var{fmt} is the format according to
26561 which the registers' contents are to be returned, followed by an optional
26562 list of numbers specifying the registers to display. A missing list of
26563 numbers indicates that the contents of all the registers must be returned.
26565 Allowed formats for @var{fmt} are:
26582 @subsubheading @value{GDBN} Command
26584 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
26585 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
26587 @subsubheading Example
26589 For a PPC MBX board (note: line breaks are for readability only, they
26590 don't appear in the actual output):
26594 -data-list-register-values r 64 65
26595 ^done,register-values=[@{number="64",value="0xfe00a300"@},
26596 @{number="65",value="0x00029002"@}]
26598 -data-list-register-values x
26599 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
26600 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
26601 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
26602 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
26603 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
26604 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
26605 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
26606 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
26607 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
26608 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
26609 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
26610 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
26611 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
26612 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
26613 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
26614 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
26615 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
26616 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
26617 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
26618 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
26619 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
26620 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
26621 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
26622 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
26623 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
26624 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
26625 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
26626 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
26627 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
26628 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
26629 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
26630 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
26631 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
26632 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
26633 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
26634 @{number="69",value="0x20002b03"@}]
26639 @subheading The @code{-data-read-memory} Command
26640 @findex -data-read-memory
26642 @subsubheading Synopsis
26645 -data-read-memory [ -o @var{byte-offset} ]
26646 @var{address} @var{word-format} @var{word-size}
26647 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
26654 @item @var{address}
26655 An expression specifying the address of the first memory word to be
26656 read. Complex expressions containing embedded white space should be
26657 quoted using the C convention.
26659 @item @var{word-format}
26660 The format to be used to print the memory words. The notation is the
26661 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
26664 @item @var{word-size}
26665 The size of each memory word in bytes.
26667 @item @var{nr-rows}
26668 The number of rows in the output table.
26670 @item @var{nr-cols}
26671 The number of columns in the output table.
26674 If present, indicates that each row should include an @sc{ascii} dump. The
26675 value of @var{aschar} is used as a padding character when a byte is not a
26676 member of the printable @sc{ascii} character set (printable @sc{ascii}
26677 characters are those whose code is between 32 and 126, inclusively).
26679 @item @var{byte-offset}
26680 An offset to add to the @var{address} before fetching memory.
26683 This command displays memory contents as a table of @var{nr-rows} by
26684 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
26685 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
26686 (returned as @samp{total-bytes}). Should less than the requested number
26687 of bytes be returned by the target, the missing words are identified
26688 using @samp{N/A}. The number of bytes read from the target is returned
26689 in @samp{nr-bytes} and the starting address used to read memory in
26692 The address of the next/previous row or page is available in
26693 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
26696 @subsubheading @value{GDBN} Command
26698 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
26699 @samp{gdb_get_mem} memory read command.
26701 @subsubheading Example
26703 Read six bytes of memory starting at @code{bytes+6} but then offset by
26704 @code{-6} bytes. Format as three rows of two columns. One byte per
26705 word. Display each word in hex.
26709 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
26710 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
26711 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
26712 prev-page="0x0000138a",memory=[
26713 @{addr="0x00001390",data=["0x00","0x01"]@},
26714 @{addr="0x00001392",data=["0x02","0x03"]@},
26715 @{addr="0x00001394",data=["0x04","0x05"]@}]
26719 Read two bytes of memory starting at address @code{shorts + 64} and
26720 display as a single word formatted in decimal.
26724 5-data-read-memory shorts+64 d 2 1 1
26725 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
26726 next-row="0x00001512",prev-row="0x0000150e",
26727 next-page="0x00001512",prev-page="0x0000150e",memory=[
26728 @{addr="0x00001510",data=["128"]@}]
26732 Read thirty two bytes of memory starting at @code{bytes+16} and format
26733 as eight rows of four columns. Include a string encoding with @samp{x}
26734 used as the non-printable character.
26738 4-data-read-memory bytes+16 x 1 8 4 x
26739 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
26740 next-row="0x000013c0",prev-row="0x0000139c",
26741 next-page="0x000013c0",prev-page="0x00001380",memory=[
26742 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
26743 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
26744 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
26745 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
26746 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
26747 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
26748 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
26749 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
26753 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26754 @node GDB/MI Tracepoint Commands
26755 @section @sc{gdb/mi} Tracepoint Commands
26757 The commands defined in this section implement MI support for
26758 tracepoints. For detailed introduction, see @ref{Tracepoints}.
26760 @subheading The @code{-trace-find} Command
26761 @findex -trace-find
26763 @subsubheading Synopsis
26766 -trace-find @var{mode} [@var{parameters}@dots{}]
26769 Find a trace frame using criteria defined by @var{mode} and
26770 @var{parameters}. The following table lists permissible
26771 modes and their parameters. For details of operation, see @ref{tfind}.
26776 No parameters are required. Stops examining trace frames.
26779 An integer is required as parameter. Selects tracepoint frame with
26782 @item tracepoint-number
26783 An integer is required as parameter. Finds next
26784 trace frame that corresponds to tracepoint with the specified number.
26787 An address is required as parameter. Finds
26788 next trace frame that corresponds to any tracepoint at the specified
26791 @item pc-inside-range
26792 Two addresses are required as parameters. Finds next trace
26793 frame that corresponds to a tracepoint at an address inside the
26794 specified range. Both bounds are considered to be inside the range.
26796 @item pc-outside-range
26797 Two addresses are required as parameters. Finds
26798 next trace frame that corresponds to a tracepoint at an address outside
26799 the specified range. Both bounds are considered to be inside the range.
26802 Line specification is required as parameter. @xref{Specify Location}.
26803 Finds next trace frame that corresponds to a tracepoint at
26804 the specified location.
26808 If @samp{none} was passed as @var{mode}, the response does not
26809 have fields. Otherwise, the response may have the following fields:
26813 This field has either @samp{0} or @samp{1} as the value, depending
26814 on whether a matching tracepoint was found.
26817 The index of the found traceframe. This field is present iff
26818 the @samp{found} field has value of @samp{1}.
26821 The index of the found tracepoint. This field is present iff
26822 the @samp{found} field has value of @samp{1}.
26825 The information about the frame corresponding to the found trace
26826 frame. This field is present only if a trace frame was found.
26827 @xref{GDB/MI Frame Information}, for description of this field.
26831 @subsubheading @value{GDBN} Command
26833 The corresponding @value{GDBN} command is @samp{tfind}.
26835 @subheading -trace-define-variable
26836 @findex -trace-define-variable
26838 @subsubheading Synopsis
26841 -trace-define-variable @var{name} [ @var{value} ]
26844 Create trace variable @var{name} if it does not exist. If
26845 @var{value} is specified, sets the initial value of the specified
26846 trace variable to that value. Note that the @var{name} should start
26847 with the @samp{$} character.
26849 @subsubheading @value{GDBN} Command
26851 The corresponding @value{GDBN} command is @samp{tvariable}.
26853 @subheading -trace-list-variables
26854 @findex -trace-list-variables
26856 @subsubheading Synopsis
26859 -trace-list-variables
26862 Return a table of all defined trace variables. Each element of the
26863 table has the following fields:
26867 The name of the trace variable. This field is always present.
26870 The initial value. This is a 64-bit signed integer. This
26871 field is always present.
26874 The value the trace variable has at the moment. This is a 64-bit
26875 signed integer. This field is absent iff current value is
26876 not defined, for example if the trace was never run, or is
26881 @subsubheading @value{GDBN} Command
26883 The corresponding @value{GDBN} command is @samp{tvariables}.
26885 @subsubheading Example
26889 -trace-list-variables
26890 ^done,trace-variables=@{nr_rows="1",nr_cols="3",
26891 hdr=[@{width="15",alignment="-1",col_name="name",colhdr="Name"@},
26892 @{width="11",alignment="-1",col_name="initial",colhdr="Initial"@},
26893 @{width="11",alignment="-1",col_name="current",colhdr="Current"@}],
26894 body=[variable=@{name="$trace_timestamp",initial="0"@}
26895 variable=@{name="$foo",initial="10",current="15"@}]@}
26899 @subheading -trace-save
26900 @findex -trace-save
26902 @subsubheading Synopsis
26905 -trace-save [-r ] @var{filename}
26908 Saves the collected trace data to @var{filename}. Without the
26909 @samp{-r} option, the data is downloaded from the target and saved
26910 in a local file. With the @samp{-r} option the target is asked
26911 to perform the save.
26913 @subsubheading @value{GDBN} Command
26915 The corresponding @value{GDBN} command is @samp{tsave}.
26918 @subheading -trace-start
26919 @findex -trace-start
26921 @subsubheading Synopsis
26927 Starts a tracing experiments. The result of this command does not
26930 @subsubheading @value{GDBN} Command
26932 The corresponding @value{GDBN} command is @samp{tstart}.
26934 @subheading -trace-status
26935 @findex -trace-status
26937 @subsubheading Synopsis
26943 Obtains the status of a tracing experiment. The result may include
26944 the following fields:
26949 May have a value of either @samp{0}, when no tracing operations are
26950 supported, @samp{1}, when all tracing operations are supported, or
26951 @samp{file} when examining trace file. In the latter case, examining
26952 of trace frame is possible but new tracing experiement cannot be
26953 started. This field is always present.
26956 May have a value of either @samp{0} or @samp{1} depending on whether
26957 tracing experiement is in progress on target. This field is present
26958 if @samp{supported} field is not @samp{0}.
26961 Report the reason why the tracing was stopped last time. This field
26962 may be absent iff tracing was never stopped on target yet. The
26963 value of @samp{request} means the tracing was stopped as result of
26964 the @code{-trace-stop} command. The value of @samp{overflow} means
26965 the tracing buffer is full. The value of @samp{disconnection} means
26966 tracing was automatically stopped when @value{GDBN} has disconnected.
26967 The value of @samp{passcount} means tracing was stopped when a
26968 tracepoint was passed a maximal number of times for that tracepoint.
26969 This field is present if @samp{supported} field is not @samp{0}.
26971 @item stopping-tracepoint
26972 The number of tracepoint whose passcount as exceeded. This field is
26973 present iff the @samp{stop-reason} field has the value of
26977 @itemx frames-created
26978 The @samp{frames} field is a count of the total number of trace frames
26979 in the trace buffer, while @samp{frames-created} is the total created
26980 during the run, including ones that were discarded, such as when a
26981 circular trace buffer filled up. Both fields are optional.
26985 These fields tell the current size of the tracing buffer and the
26986 remaining space. These fields are optional.
26989 The value of the circular trace buffer flag. @code{1} means that the
26990 trace buffer is circular and old trace frames will be discarded if
26991 necessary to make room, @code{0} means that the trace buffer is linear
26995 The value of the disconnected tracing flag. @code{1} means that
26996 tracing will continue after @value{GDBN} disconnects, @code{0} means
26997 that the trace run will stop.
27001 @subsubheading @value{GDBN} Command
27003 The corresponding @value{GDBN} command is @samp{tstatus}.
27005 @subheading -trace-stop
27006 @findex -trace-stop
27008 @subsubheading Synopsis
27014 Stops a tracing experiment. The result of this command has the same
27015 fields as @code{-trace-status}, except that the @samp{supported} and
27016 @samp{running} fields are not output.
27018 @subsubheading @value{GDBN} Command
27020 The corresponding @value{GDBN} command is @samp{tstop}.
27023 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27024 @node GDB/MI Symbol Query
27025 @section @sc{gdb/mi} Symbol Query Commands
27029 @subheading The @code{-symbol-info-address} Command
27030 @findex -symbol-info-address
27032 @subsubheading Synopsis
27035 -symbol-info-address @var{symbol}
27038 Describe where @var{symbol} is stored.
27040 @subsubheading @value{GDBN} Command
27042 The corresponding @value{GDBN} command is @samp{info address}.
27044 @subsubheading Example
27048 @subheading The @code{-symbol-info-file} Command
27049 @findex -symbol-info-file
27051 @subsubheading Synopsis
27057 Show the file for the symbol.
27059 @subsubheading @value{GDBN} Command
27061 There's no equivalent @value{GDBN} command. @code{gdbtk} has
27062 @samp{gdb_find_file}.
27064 @subsubheading Example
27068 @subheading The @code{-symbol-info-function} Command
27069 @findex -symbol-info-function
27071 @subsubheading Synopsis
27074 -symbol-info-function
27077 Show which function the symbol lives in.
27079 @subsubheading @value{GDBN} Command
27081 @samp{gdb_get_function} in @code{gdbtk}.
27083 @subsubheading Example
27087 @subheading The @code{-symbol-info-line} Command
27088 @findex -symbol-info-line
27090 @subsubheading Synopsis
27096 Show the core addresses of the code for a source line.
27098 @subsubheading @value{GDBN} Command
27100 The corresponding @value{GDBN} command is @samp{info line}.
27101 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
27103 @subsubheading Example
27107 @subheading The @code{-symbol-info-symbol} Command
27108 @findex -symbol-info-symbol
27110 @subsubheading Synopsis
27113 -symbol-info-symbol @var{addr}
27116 Describe what symbol is at location @var{addr}.
27118 @subsubheading @value{GDBN} Command
27120 The corresponding @value{GDBN} command is @samp{info symbol}.
27122 @subsubheading Example
27126 @subheading The @code{-symbol-list-functions} Command
27127 @findex -symbol-list-functions
27129 @subsubheading Synopsis
27132 -symbol-list-functions
27135 List the functions in the executable.
27137 @subsubheading @value{GDBN} Command
27139 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
27140 @samp{gdb_search} in @code{gdbtk}.
27142 @subsubheading Example
27147 @subheading The @code{-symbol-list-lines} Command
27148 @findex -symbol-list-lines
27150 @subsubheading Synopsis
27153 -symbol-list-lines @var{filename}
27156 Print the list of lines that contain code and their associated program
27157 addresses for the given source filename. The entries are sorted in
27158 ascending PC order.
27160 @subsubheading @value{GDBN} Command
27162 There is no corresponding @value{GDBN} command.
27164 @subsubheading Example
27167 -symbol-list-lines basics.c
27168 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
27174 @subheading The @code{-symbol-list-types} Command
27175 @findex -symbol-list-types
27177 @subsubheading Synopsis
27183 List all the type names.
27185 @subsubheading @value{GDBN} Command
27187 The corresponding commands are @samp{info types} in @value{GDBN},
27188 @samp{gdb_search} in @code{gdbtk}.
27190 @subsubheading Example
27194 @subheading The @code{-symbol-list-variables} Command
27195 @findex -symbol-list-variables
27197 @subsubheading Synopsis
27200 -symbol-list-variables
27203 List all the global and static variable names.
27205 @subsubheading @value{GDBN} Command
27207 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
27209 @subsubheading Example
27213 @subheading The @code{-symbol-locate} Command
27214 @findex -symbol-locate
27216 @subsubheading Synopsis
27222 @subsubheading @value{GDBN} Command
27224 @samp{gdb_loc} in @code{gdbtk}.
27226 @subsubheading Example
27230 @subheading The @code{-symbol-type} Command
27231 @findex -symbol-type
27233 @subsubheading Synopsis
27236 -symbol-type @var{variable}
27239 Show type of @var{variable}.
27241 @subsubheading @value{GDBN} Command
27243 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
27244 @samp{gdb_obj_variable}.
27246 @subsubheading Example
27251 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27252 @node GDB/MI File Commands
27253 @section @sc{gdb/mi} File Commands
27255 This section describes the GDB/MI commands to specify executable file names
27256 and to read in and obtain symbol table information.
27258 @subheading The @code{-file-exec-and-symbols} Command
27259 @findex -file-exec-and-symbols
27261 @subsubheading Synopsis
27264 -file-exec-and-symbols @var{file}
27267 Specify the executable file to be debugged. This file is the one from
27268 which the symbol table is also read. If no file is specified, the
27269 command clears the executable and symbol information. If breakpoints
27270 are set when using this command with no arguments, @value{GDBN} will produce
27271 error messages. Otherwise, no output is produced, except a completion
27274 @subsubheading @value{GDBN} Command
27276 The corresponding @value{GDBN} command is @samp{file}.
27278 @subsubheading Example
27282 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
27288 @subheading The @code{-file-exec-file} Command
27289 @findex -file-exec-file
27291 @subsubheading Synopsis
27294 -file-exec-file @var{file}
27297 Specify the executable file to be debugged. Unlike
27298 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
27299 from this file. If used without argument, @value{GDBN} clears the information
27300 about the executable file. No output is produced, except a completion
27303 @subsubheading @value{GDBN} Command
27305 The corresponding @value{GDBN} command is @samp{exec-file}.
27307 @subsubheading Example
27311 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
27318 @subheading The @code{-file-list-exec-sections} Command
27319 @findex -file-list-exec-sections
27321 @subsubheading Synopsis
27324 -file-list-exec-sections
27327 List the sections of the current executable file.
27329 @subsubheading @value{GDBN} Command
27331 The @value{GDBN} command @samp{info file} shows, among the rest, the same
27332 information as this command. @code{gdbtk} has a corresponding command
27333 @samp{gdb_load_info}.
27335 @subsubheading Example
27340 @subheading The @code{-file-list-exec-source-file} Command
27341 @findex -file-list-exec-source-file
27343 @subsubheading Synopsis
27346 -file-list-exec-source-file
27349 List the line number, the current source file, and the absolute path
27350 to the current source file for the current executable. The macro
27351 information field has a value of @samp{1} or @samp{0} depending on
27352 whether or not the file includes preprocessor macro information.
27354 @subsubheading @value{GDBN} Command
27356 The @value{GDBN} equivalent is @samp{info source}
27358 @subsubheading Example
27362 123-file-list-exec-source-file
27363 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c,macro-info="1"
27368 @subheading The @code{-file-list-exec-source-files} Command
27369 @findex -file-list-exec-source-files
27371 @subsubheading Synopsis
27374 -file-list-exec-source-files
27377 List the source files for the current executable.
27379 It will always output the filename, but only when @value{GDBN} can find
27380 the absolute file name of a source file, will it output the fullname.
27382 @subsubheading @value{GDBN} Command
27384 The @value{GDBN} equivalent is @samp{info sources}.
27385 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
27387 @subsubheading Example
27390 -file-list-exec-source-files
27392 @{file=foo.c,fullname=/home/foo.c@},
27393 @{file=/home/bar.c,fullname=/home/bar.c@},
27394 @{file=gdb_could_not_find_fullpath.c@}]
27399 @subheading The @code{-file-list-shared-libraries} Command
27400 @findex -file-list-shared-libraries
27402 @subsubheading Synopsis
27405 -file-list-shared-libraries
27408 List the shared libraries in the program.
27410 @subsubheading @value{GDBN} Command
27412 The corresponding @value{GDBN} command is @samp{info shared}.
27414 @subsubheading Example
27418 @subheading The @code{-file-list-symbol-files} Command
27419 @findex -file-list-symbol-files
27421 @subsubheading Synopsis
27424 -file-list-symbol-files
27429 @subsubheading @value{GDBN} Command
27431 The corresponding @value{GDBN} command is @samp{info file} (part of it).
27433 @subsubheading Example
27438 @subheading The @code{-file-symbol-file} Command
27439 @findex -file-symbol-file
27441 @subsubheading Synopsis
27444 -file-symbol-file @var{file}
27447 Read symbol table info from the specified @var{file} argument. When
27448 used without arguments, clears @value{GDBN}'s symbol table info. No output is
27449 produced, except for a completion notification.
27451 @subsubheading @value{GDBN} Command
27453 The corresponding @value{GDBN} command is @samp{symbol-file}.
27455 @subsubheading Example
27459 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
27465 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27466 @node GDB/MI Memory Overlay Commands
27467 @section @sc{gdb/mi} Memory Overlay Commands
27469 The memory overlay commands are not implemented.
27471 @c @subheading -overlay-auto
27473 @c @subheading -overlay-list-mapping-state
27475 @c @subheading -overlay-list-overlays
27477 @c @subheading -overlay-map
27479 @c @subheading -overlay-off
27481 @c @subheading -overlay-on
27483 @c @subheading -overlay-unmap
27485 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27486 @node GDB/MI Signal Handling Commands
27487 @section @sc{gdb/mi} Signal Handling Commands
27489 Signal handling commands are not implemented.
27491 @c @subheading -signal-handle
27493 @c @subheading -signal-list-handle-actions
27495 @c @subheading -signal-list-signal-types
27499 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27500 @node GDB/MI Target Manipulation
27501 @section @sc{gdb/mi} Target Manipulation Commands
27504 @subheading The @code{-target-attach} Command
27505 @findex -target-attach
27507 @subsubheading Synopsis
27510 -target-attach @var{pid} | @var{gid} | @var{file}
27513 Attach to a process @var{pid} or a file @var{file} outside of
27514 @value{GDBN}, or a thread group @var{gid}. If attaching to a thread
27515 group, the id previously returned by
27516 @samp{-list-thread-groups --available} must be used.
27518 @subsubheading @value{GDBN} Command
27520 The corresponding @value{GDBN} command is @samp{attach}.
27522 @subsubheading Example
27526 =thread-created,id="1"
27527 *stopped,thread-id="1",frame=@{addr="0xb7f7e410",func="bar",args=[]@}
27533 @subheading The @code{-target-compare-sections} Command
27534 @findex -target-compare-sections
27536 @subsubheading Synopsis
27539 -target-compare-sections [ @var{section} ]
27542 Compare data of section @var{section} on target to the exec file.
27543 Without the argument, all sections are compared.
27545 @subsubheading @value{GDBN} Command
27547 The @value{GDBN} equivalent is @samp{compare-sections}.
27549 @subsubheading Example
27554 @subheading The @code{-target-detach} Command
27555 @findex -target-detach
27557 @subsubheading Synopsis
27560 -target-detach [ @var{pid} | @var{gid} ]
27563 Detach from the remote target which normally resumes its execution.
27564 If either @var{pid} or @var{gid} is specified, detaches from either
27565 the specified process, or specified thread group. There's no output.
27567 @subsubheading @value{GDBN} Command
27569 The corresponding @value{GDBN} command is @samp{detach}.
27571 @subsubheading Example
27581 @subheading The @code{-target-disconnect} Command
27582 @findex -target-disconnect
27584 @subsubheading Synopsis
27590 Disconnect from the remote target. There's no output and the target is
27591 generally not resumed.
27593 @subsubheading @value{GDBN} Command
27595 The corresponding @value{GDBN} command is @samp{disconnect}.
27597 @subsubheading Example
27607 @subheading The @code{-target-download} Command
27608 @findex -target-download
27610 @subsubheading Synopsis
27616 Loads the executable onto the remote target.
27617 It prints out an update message every half second, which includes the fields:
27621 The name of the section.
27623 The size of what has been sent so far for that section.
27625 The size of the section.
27627 The total size of what was sent so far (the current and the previous sections).
27629 The size of the overall executable to download.
27633 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
27634 @sc{gdb/mi} Output Syntax}).
27636 In addition, it prints the name and size of the sections, as they are
27637 downloaded. These messages include the following fields:
27641 The name of the section.
27643 The size of the section.
27645 The size of the overall executable to download.
27649 At the end, a summary is printed.
27651 @subsubheading @value{GDBN} Command
27653 The corresponding @value{GDBN} command is @samp{load}.
27655 @subsubheading Example
27657 Note: each status message appears on a single line. Here the messages
27658 have been broken down so that they can fit onto a page.
27663 +download,@{section=".text",section-size="6668",total-size="9880"@}
27664 +download,@{section=".text",section-sent="512",section-size="6668",
27665 total-sent="512",total-size="9880"@}
27666 +download,@{section=".text",section-sent="1024",section-size="6668",
27667 total-sent="1024",total-size="9880"@}
27668 +download,@{section=".text",section-sent="1536",section-size="6668",
27669 total-sent="1536",total-size="9880"@}
27670 +download,@{section=".text",section-sent="2048",section-size="6668",
27671 total-sent="2048",total-size="9880"@}
27672 +download,@{section=".text",section-sent="2560",section-size="6668",
27673 total-sent="2560",total-size="9880"@}
27674 +download,@{section=".text",section-sent="3072",section-size="6668",
27675 total-sent="3072",total-size="9880"@}
27676 +download,@{section=".text",section-sent="3584",section-size="6668",
27677 total-sent="3584",total-size="9880"@}
27678 +download,@{section=".text",section-sent="4096",section-size="6668",
27679 total-sent="4096",total-size="9880"@}
27680 +download,@{section=".text",section-sent="4608",section-size="6668",
27681 total-sent="4608",total-size="9880"@}
27682 +download,@{section=".text",section-sent="5120",section-size="6668",
27683 total-sent="5120",total-size="9880"@}
27684 +download,@{section=".text",section-sent="5632",section-size="6668",
27685 total-sent="5632",total-size="9880"@}
27686 +download,@{section=".text",section-sent="6144",section-size="6668",
27687 total-sent="6144",total-size="9880"@}
27688 +download,@{section=".text",section-sent="6656",section-size="6668",
27689 total-sent="6656",total-size="9880"@}
27690 +download,@{section=".init",section-size="28",total-size="9880"@}
27691 +download,@{section=".fini",section-size="28",total-size="9880"@}
27692 +download,@{section=".data",section-size="3156",total-size="9880"@}
27693 +download,@{section=".data",section-sent="512",section-size="3156",
27694 total-sent="7236",total-size="9880"@}
27695 +download,@{section=".data",section-sent="1024",section-size="3156",
27696 total-sent="7748",total-size="9880"@}
27697 +download,@{section=".data",section-sent="1536",section-size="3156",
27698 total-sent="8260",total-size="9880"@}
27699 +download,@{section=".data",section-sent="2048",section-size="3156",
27700 total-sent="8772",total-size="9880"@}
27701 +download,@{section=".data",section-sent="2560",section-size="3156",
27702 total-sent="9284",total-size="9880"@}
27703 +download,@{section=".data",section-sent="3072",section-size="3156",
27704 total-sent="9796",total-size="9880"@}
27705 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
27712 @subheading The @code{-target-exec-status} Command
27713 @findex -target-exec-status
27715 @subsubheading Synopsis
27718 -target-exec-status
27721 Provide information on the state of the target (whether it is running or
27722 not, for instance).
27724 @subsubheading @value{GDBN} Command
27726 There's no equivalent @value{GDBN} command.
27728 @subsubheading Example
27732 @subheading The @code{-target-list-available-targets} Command
27733 @findex -target-list-available-targets
27735 @subsubheading Synopsis
27738 -target-list-available-targets
27741 List the possible targets to connect to.
27743 @subsubheading @value{GDBN} Command
27745 The corresponding @value{GDBN} command is @samp{help target}.
27747 @subsubheading Example
27751 @subheading The @code{-target-list-current-targets} Command
27752 @findex -target-list-current-targets
27754 @subsubheading Synopsis
27757 -target-list-current-targets
27760 Describe the current target.
27762 @subsubheading @value{GDBN} Command
27764 The corresponding information is printed by @samp{info file} (among
27767 @subsubheading Example
27771 @subheading The @code{-target-list-parameters} Command
27772 @findex -target-list-parameters
27774 @subsubheading Synopsis
27777 -target-list-parameters
27783 @subsubheading @value{GDBN} Command
27787 @subsubheading Example
27791 @subheading The @code{-target-select} Command
27792 @findex -target-select
27794 @subsubheading Synopsis
27797 -target-select @var{type} @var{parameters @dots{}}
27800 Connect @value{GDBN} to the remote target. This command takes two args:
27804 The type of target, for instance @samp{remote}, etc.
27805 @item @var{parameters}
27806 Device names, host names and the like. @xref{Target Commands, ,
27807 Commands for Managing Targets}, for more details.
27810 The output is a connection notification, followed by the address at
27811 which the target program is, in the following form:
27814 ^connected,addr="@var{address}",func="@var{function name}",
27815 args=[@var{arg list}]
27818 @subsubheading @value{GDBN} Command
27820 The corresponding @value{GDBN} command is @samp{target}.
27822 @subsubheading Example
27826 -target-select remote /dev/ttya
27827 ^connected,addr="0xfe00a300",func="??",args=[]
27831 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27832 @node GDB/MI File Transfer Commands
27833 @section @sc{gdb/mi} File Transfer Commands
27836 @subheading The @code{-target-file-put} Command
27837 @findex -target-file-put
27839 @subsubheading Synopsis
27842 -target-file-put @var{hostfile} @var{targetfile}
27845 Copy file @var{hostfile} from the host system (the machine running
27846 @value{GDBN}) to @var{targetfile} on the target system.
27848 @subsubheading @value{GDBN} Command
27850 The corresponding @value{GDBN} command is @samp{remote put}.
27852 @subsubheading Example
27856 -target-file-put localfile remotefile
27862 @subheading The @code{-target-file-get} Command
27863 @findex -target-file-get
27865 @subsubheading Synopsis
27868 -target-file-get @var{targetfile} @var{hostfile}
27871 Copy file @var{targetfile} from the target system to @var{hostfile}
27872 on the host system.
27874 @subsubheading @value{GDBN} Command
27876 The corresponding @value{GDBN} command is @samp{remote get}.
27878 @subsubheading Example
27882 -target-file-get remotefile localfile
27888 @subheading The @code{-target-file-delete} Command
27889 @findex -target-file-delete
27891 @subsubheading Synopsis
27894 -target-file-delete @var{targetfile}
27897 Delete @var{targetfile} from the target system.
27899 @subsubheading @value{GDBN} Command
27901 The corresponding @value{GDBN} command is @samp{remote delete}.
27903 @subsubheading Example
27907 -target-file-delete remotefile
27913 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27914 @node GDB/MI Miscellaneous Commands
27915 @section Miscellaneous @sc{gdb/mi} Commands
27917 @c @subheading -gdb-complete
27919 @subheading The @code{-gdb-exit} Command
27922 @subsubheading Synopsis
27928 Exit @value{GDBN} immediately.
27930 @subsubheading @value{GDBN} Command
27932 Approximately corresponds to @samp{quit}.
27934 @subsubheading Example
27944 @subheading The @code{-exec-abort} Command
27945 @findex -exec-abort
27947 @subsubheading Synopsis
27953 Kill the inferior running program.
27955 @subsubheading @value{GDBN} Command
27957 The corresponding @value{GDBN} command is @samp{kill}.
27959 @subsubheading Example
27964 @subheading The @code{-gdb-set} Command
27967 @subsubheading Synopsis
27973 Set an internal @value{GDBN} variable.
27974 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
27976 @subsubheading @value{GDBN} Command
27978 The corresponding @value{GDBN} command is @samp{set}.
27980 @subsubheading Example
27990 @subheading The @code{-gdb-show} Command
27993 @subsubheading Synopsis
27999 Show the current value of a @value{GDBN} variable.
28001 @subsubheading @value{GDBN} Command
28003 The corresponding @value{GDBN} command is @samp{show}.
28005 @subsubheading Example
28014 @c @subheading -gdb-source
28017 @subheading The @code{-gdb-version} Command
28018 @findex -gdb-version
28020 @subsubheading Synopsis
28026 Show version information for @value{GDBN}. Used mostly in testing.
28028 @subsubheading @value{GDBN} Command
28030 The @value{GDBN} equivalent is @samp{show version}. @value{GDBN} by
28031 default shows this information when you start an interactive session.
28033 @subsubheading Example
28035 @c This example modifies the actual output from GDB to avoid overfull
28041 ~Copyright 2000 Free Software Foundation, Inc.
28042 ~GDB is free software, covered by the GNU General Public License, and
28043 ~you are welcome to change it and/or distribute copies of it under
28044 ~ certain conditions.
28045 ~Type "show copying" to see the conditions.
28046 ~There is absolutely no warranty for GDB. Type "show warranty" for
28048 ~This GDB was configured as
28049 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
28054 @subheading The @code{-list-features} Command
28055 @findex -list-features
28057 Returns a list of particular features of the MI protocol that
28058 this version of gdb implements. A feature can be a command,
28059 or a new field in an output of some command, or even an
28060 important bugfix. While a frontend can sometimes detect presence
28061 of a feature at runtime, it is easier to perform detection at debugger
28064 The command returns a list of strings, with each string naming an
28065 available feature. Each returned string is just a name, it does not
28066 have any internal structure. The list of possible feature names
28072 (gdb) -list-features
28073 ^done,result=["feature1","feature2"]
28076 The current list of features is:
28079 @item frozen-varobjs
28080 Indicates presence of the @code{-var-set-frozen} command, as well
28081 as possible presense of the @code{frozen} field in the output
28082 of @code{-varobj-create}.
28083 @item pending-breakpoints
28084 Indicates presence of the @option{-f} option to the @code{-break-insert} command.
28086 Indicates presence of Python scripting support, Python-based
28087 pretty-printing commands, and possible presence of the
28088 @samp{display_hint} field in the output of @code{-var-list-children}
28090 Indicates presence of the @code{-thread-info} command.
28094 @subheading The @code{-list-target-features} Command
28095 @findex -list-target-features
28097 Returns a list of particular features that are supported by the
28098 target. Those features affect the permitted MI commands, but
28099 unlike the features reported by the @code{-list-features} command, the
28100 features depend on which target GDB is using at the moment. Whenever
28101 a target can change, due to commands such as @code{-target-select},
28102 @code{-target-attach} or @code{-exec-run}, the list of target features
28103 may change, and the frontend should obtain it again.
28107 (gdb) -list-features
28108 ^done,result=["async"]
28111 The current list of features is:
28115 Indicates that the target is capable of asynchronous command
28116 execution, which means that @value{GDBN} will accept further commands
28117 while the target is running.
28121 @subheading The @code{-list-thread-groups} Command
28122 @findex -list-thread-groups
28124 @subheading Synopsis
28127 -list-thread-groups [ --available ] [ --recurse 1 ] [ @var{group} ... ]
28130 Lists thread groups (@pxref{Thread groups}). When a single thread
28131 group is passed as the argument, lists the children of that group.
28132 When several thread group are passed, lists information about those
28133 thread groups. Without any parameters, lists information about all
28134 top-level thread groups.
28136 Normally, thread groups that are being debugged are reported.
28137 With the @samp{--available} option, @value{GDBN} reports thread groups
28138 available on the target.
28140 The output of this command may have either a @samp{threads} result or
28141 a @samp{groups} result. The @samp{thread} result has a list of tuples
28142 as value, with each tuple describing a thread (@pxref{GDB/MI Thread
28143 Information}). The @samp{groups} result has a list of tuples as value,
28144 each tuple describing a thread group. If top-level groups are
28145 requested (that is, no parameter is passed), or when several groups
28146 are passed, the output always has a @samp{groups} result. The format
28147 of the @samp{group} result is described below.
28149 To reduce the number of roundtrips it's possible to list thread groups
28150 together with their children, by passing the @samp{--recurse} option
28151 and the recursion depth. Presently, only recursion depth of 1 is
28152 permitted. If this option is present, then every reported thread group
28153 will also include its children, either as @samp{group} or
28154 @samp{threads} field.
28156 In general, any combination of option and parameters is permitted, with
28157 the following caveats:
28161 When a single thread group is passed, the output will typically
28162 be the @samp{threads} result. Because threads may not contain
28163 anything, the @samp{recurse} option will be ignored.
28166 When the @samp{--available} option is passed, limited information may
28167 be available. In particular, the list of threads of a process might
28168 be inaccessible. Further, specifying specific thread groups might
28169 not give any performance advantage over listing all thread groups.
28170 The frontend should assume that @samp{-list-thread-groups --available}
28171 is always an expensive operation and cache the results.
28175 The @samp{groups} result is a list of tuples, where each tuple may
28176 have the following fields:
28180 Identifier of the thread group. This field is always present.
28181 The identifier is an opaque string; frontends should not try to
28182 convert it to an integer, even though it might look like one.
28185 The type of the thread group. At present, only @samp{process} is a
28189 The target-specific process identifier. This field is only present
28190 for thread groups of type @samp{process} and only if the process exists.
28193 The number of children this thread group has. This field may be
28194 absent for an available thread group.
28197 This field has a list of tuples as value, each tuple describing a
28198 thread. It may be present if the @samp{--recurse} option is
28199 specified, and it's actually possible to obtain the threads.
28202 This field is a list of integers, each identifying a core that one
28203 thread of the group is running on. This field may be absent if
28204 such information is not available.
28207 The name of the executable file that corresponds to this thread group.
28208 The field is only present for thread groups of type @samp{process},
28209 and only if there is a corresponding executable file.
28213 @subheading Example
28217 -list-thread-groups
28218 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2"@}]
28219 -list-thread-groups 17
28220 ^done,threads=[@{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
28221 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},state="running"@},
28222 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
28223 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
28224 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},state="running"@}]]
28225 -list-thread-groups --available
28226 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2",cores=[1,2]@}]
28227 -list-thread-groups --available --recurse 1
28228 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
28229 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
28230 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},..]
28231 -list-thread-groups --available --recurse 1 17 18
28232 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
28233 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
28234 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},...]
28238 @subheading The @code{-add-inferior} Command
28239 @findex -add-inferior
28241 @subheading Synopsis
28247 Creates a new inferior (@pxref{Inferiors and Programs}). The created
28248 inferior is not associated with any executable. Such association may
28249 be established with the @samp{-file-exec-and-symbols} command
28250 (@pxref{GDB/MI File Commands}). The command response has a single
28251 field, @samp{thread-group}, whose value is the identifier of the
28252 thread group corresponding to the new inferior.
28254 @subheading Example
28259 ^done,thread-group="i3"
28262 @subheading The @code{-interpreter-exec} Command
28263 @findex -interpreter-exec
28265 @subheading Synopsis
28268 -interpreter-exec @var{interpreter} @var{command}
28270 @anchor{-interpreter-exec}
28272 Execute the specified @var{command} in the given @var{interpreter}.
28274 @subheading @value{GDBN} Command
28276 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
28278 @subheading Example
28282 -interpreter-exec console "break main"
28283 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
28284 &"During symbol reading, bad structure-type format.\n"
28285 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
28290 @subheading The @code{-inferior-tty-set} Command
28291 @findex -inferior-tty-set
28293 @subheading Synopsis
28296 -inferior-tty-set /dev/pts/1
28299 Set terminal for future runs of the program being debugged.
28301 @subheading @value{GDBN} Command
28303 The corresponding @value{GDBN} command is @samp{set inferior-tty} /dev/pts/1.
28305 @subheading Example
28309 -inferior-tty-set /dev/pts/1
28314 @subheading The @code{-inferior-tty-show} Command
28315 @findex -inferior-tty-show
28317 @subheading Synopsis
28323 Show terminal for future runs of program being debugged.
28325 @subheading @value{GDBN} Command
28327 The corresponding @value{GDBN} command is @samp{show inferior-tty}.
28329 @subheading Example
28333 -inferior-tty-set /dev/pts/1
28337 ^done,inferior_tty_terminal="/dev/pts/1"
28341 @subheading The @code{-enable-timings} Command
28342 @findex -enable-timings
28344 @subheading Synopsis
28347 -enable-timings [yes | no]
28350 Toggle the printing of the wallclock, user and system times for an MI
28351 command as a field in its output. This command is to help frontend
28352 developers optimize the performance of their code. No argument is
28353 equivalent to @samp{yes}.
28355 @subheading @value{GDBN} Command
28359 @subheading Example
28367 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
28368 addr="0x080484ed",func="main",file="myprog.c",
28369 fullname="/home/nickrob/myprog.c",line="73",times="0"@},
28370 time=@{wallclock="0.05185",user="0.00800",system="0.00000"@}
28378 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
28379 frame=@{addr="0x080484ed",func="main",args=[@{name="argc",value="1"@},
28380 @{name="argv",value="0xbfb60364"@}],file="myprog.c",
28381 fullname="/home/nickrob/myprog.c",line="73"@}
28386 @chapter @value{GDBN} Annotations
28388 This chapter describes annotations in @value{GDBN}. Annotations were
28389 designed to interface @value{GDBN} to graphical user interfaces or other
28390 similar programs which want to interact with @value{GDBN} at a
28391 relatively high level.
28393 The annotation mechanism has largely been superseded by @sc{gdb/mi}
28397 This is Edition @value{EDITION}, @value{DATE}.
28401 * Annotations Overview:: What annotations are; the general syntax.
28402 * Server Prefix:: Issuing a command without affecting user state.
28403 * Prompting:: Annotations marking @value{GDBN}'s need for input.
28404 * Errors:: Annotations for error messages.
28405 * Invalidation:: Some annotations describe things now invalid.
28406 * Annotations for Running::
28407 Whether the program is running, how it stopped, etc.
28408 * Source Annotations:: Annotations describing source code.
28411 @node Annotations Overview
28412 @section What is an Annotation?
28413 @cindex annotations
28415 Annotations start with a newline character, two @samp{control-z}
28416 characters, and the name of the annotation. If there is no additional
28417 information associated with this annotation, the name of the annotation
28418 is followed immediately by a newline. If there is additional
28419 information, the name of the annotation is followed by a space, the
28420 additional information, and a newline. The additional information
28421 cannot contain newline characters.
28423 Any output not beginning with a newline and two @samp{control-z}
28424 characters denotes literal output from @value{GDBN}. Currently there is
28425 no need for @value{GDBN} to output a newline followed by two
28426 @samp{control-z} characters, but if there was such a need, the
28427 annotations could be extended with an @samp{escape} annotation which
28428 means those three characters as output.
28430 The annotation @var{level}, which is specified using the
28431 @option{--annotate} command line option (@pxref{Mode Options}), controls
28432 how much information @value{GDBN} prints together with its prompt,
28433 values of expressions, source lines, and other types of output. Level 0
28434 is for no annotations, level 1 is for use when @value{GDBN} is run as a
28435 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
28436 for programs that control @value{GDBN}, and level 2 annotations have
28437 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
28438 Interface, annotate, GDB's Obsolete Annotations}).
28441 @kindex set annotate
28442 @item set annotate @var{level}
28443 The @value{GDBN} command @code{set annotate} sets the level of
28444 annotations to the specified @var{level}.
28446 @item show annotate
28447 @kindex show annotate
28448 Show the current annotation level.
28451 This chapter describes level 3 annotations.
28453 A simple example of starting up @value{GDBN} with annotations is:
28456 $ @kbd{gdb --annotate=3}
28458 Copyright 2003 Free Software Foundation, Inc.
28459 GDB is free software, covered by the GNU General Public License,
28460 and you are welcome to change it and/or distribute copies of it
28461 under certain conditions.
28462 Type "show copying" to see the conditions.
28463 There is absolutely no warranty for GDB. Type "show warranty"
28465 This GDB was configured as "i386-pc-linux-gnu"
28476 Here @samp{quit} is input to @value{GDBN}; the rest is output from
28477 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
28478 denotes a @samp{control-z} character) are annotations; the rest is
28479 output from @value{GDBN}.
28481 @node Server Prefix
28482 @section The Server Prefix
28483 @cindex server prefix
28485 If you prefix a command with @samp{server } then it will not affect
28486 the command history, nor will it affect @value{GDBN}'s notion of which
28487 command to repeat if @key{RET} is pressed on a line by itself. This
28488 means that commands can be run behind a user's back by a front-end in
28489 a transparent manner.
28491 The @code{server } prefix does not affect the recording of values into
28492 the value history; to print a value without recording it into the
28493 value history, use the @code{output} command instead of the
28494 @code{print} command.
28496 Using this prefix also disables confirmation requests
28497 (@pxref{confirmation requests}).
28500 @section Annotation for @value{GDBN} Input
28502 @cindex annotations for prompts
28503 When @value{GDBN} prompts for input, it annotates this fact so it is possible
28504 to know when to send output, when the output from a given command is
28507 Different kinds of input each have a different @dfn{input type}. Each
28508 input type has three annotations: a @code{pre-} annotation, which
28509 denotes the beginning of any prompt which is being output, a plain
28510 annotation, which denotes the end of the prompt, and then a @code{post-}
28511 annotation which denotes the end of any echo which may (or may not) be
28512 associated with the input. For example, the @code{prompt} input type
28513 features the following annotations:
28521 The input types are
28524 @findex pre-prompt annotation
28525 @findex prompt annotation
28526 @findex post-prompt annotation
28528 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
28530 @findex pre-commands annotation
28531 @findex commands annotation
28532 @findex post-commands annotation
28534 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
28535 command. The annotations are repeated for each command which is input.
28537 @findex pre-overload-choice annotation
28538 @findex overload-choice annotation
28539 @findex post-overload-choice annotation
28540 @item overload-choice
28541 When @value{GDBN} wants the user to select between various overloaded functions.
28543 @findex pre-query annotation
28544 @findex query annotation
28545 @findex post-query annotation
28547 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
28549 @findex pre-prompt-for-continue annotation
28550 @findex prompt-for-continue annotation
28551 @findex post-prompt-for-continue annotation
28552 @item prompt-for-continue
28553 When @value{GDBN} is asking the user to press return to continue. Note: Don't
28554 expect this to work well; instead use @code{set height 0} to disable
28555 prompting. This is because the counting of lines is buggy in the
28556 presence of annotations.
28561 @cindex annotations for errors, warnings and interrupts
28563 @findex quit annotation
28568 This annotation occurs right before @value{GDBN} responds to an interrupt.
28570 @findex error annotation
28575 This annotation occurs right before @value{GDBN} responds to an error.
28577 Quit and error annotations indicate that any annotations which @value{GDBN} was
28578 in the middle of may end abruptly. For example, if a
28579 @code{value-history-begin} annotation is followed by a @code{error}, one
28580 cannot expect to receive the matching @code{value-history-end}. One
28581 cannot expect not to receive it either, however; an error annotation
28582 does not necessarily mean that @value{GDBN} is immediately returning all the way
28585 @findex error-begin annotation
28586 A quit or error annotation may be preceded by
28592 Any output between that and the quit or error annotation is the error
28595 Warning messages are not yet annotated.
28596 @c If we want to change that, need to fix warning(), type_error(),
28597 @c range_error(), and possibly other places.
28600 @section Invalidation Notices
28602 @cindex annotations for invalidation messages
28603 The following annotations say that certain pieces of state may have
28607 @findex frames-invalid annotation
28608 @item ^Z^Zframes-invalid
28610 The frames (for example, output from the @code{backtrace} command) may
28613 @findex breakpoints-invalid annotation
28614 @item ^Z^Zbreakpoints-invalid
28616 The breakpoints may have changed. For example, the user just added or
28617 deleted a breakpoint.
28620 @node Annotations for Running
28621 @section Running the Program
28622 @cindex annotations for running programs
28624 @findex starting annotation
28625 @findex stopping annotation
28626 When the program starts executing due to a @value{GDBN} command such as
28627 @code{step} or @code{continue},
28633 is output. When the program stops,
28639 is output. Before the @code{stopped} annotation, a variety of
28640 annotations describe how the program stopped.
28643 @findex exited annotation
28644 @item ^Z^Zexited @var{exit-status}
28645 The program exited, and @var{exit-status} is the exit status (zero for
28646 successful exit, otherwise nonzero).
28648 @findex signalled annotation
28649 @findex signal-name annotation
28650 @findex signal-name-end annotation
28651 @findex signal-string annotation
28652 @findex signal-string-end annotation
28653 @item ^Z^Zsignalled
28654 The program exited with a signal. After the @code{^Z^Zsignalled}, the
28655 annotation continues:
28661 ^Z^Zsignal-name-end
28665 ^Z^Zsignal-string-end
28670 where @var{name} is the name of the signal, such as @code{SIGILL} or
28671 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
28672 as @code{Illegal Instruction} or @code{Segmentation fault}.
28673 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
28674 user's benefit and have no particular format.
28676 @findex signal annotation
28678 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
28679 just saying that the program received the signal, not that it was
28680 terminated with it.
28682 @findex breakpoint annotation
28683 @item ^Z^Zbreakpoint @var{number}
28684 The program hit breakpoint number @var{number}.
28686 @findex watchpoint annotation
28687 @item ^Z^Zwatchpoint @var{number}
28688 The program hit watchpoint number @var{number}.
28691 @node Source Annotations
28692 @section Displaying Source
28693 @cindex annotations for source display
28695 @findex source annotation
28696 The following annotation is used instead of displaying source code:
28699 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
28702 where @var{filename} is an absolute file name indicating which source
28703 file, @var{line} is the line number within that file (where 1 is the
28704 first line in the file), @var{character} is the character position
28705 within the file (where 0 is the first character in the file) (for most
28706 debug formats this will necessarily point to the beginning of a line),
28707 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
28708 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
28709 @var{addr} is the address in the target program associated with the
28710 source which is being displayed. @var{addr} is in the form @samp{0x}
28711 followed by one or more lowercase hex digits (note that this does not
28712 depend on the language).
28714 @node JIT Interface
28715 @chapter JIT Compilation Interface
28716 @cindex just-in-time compilation
28717 @cindex JIT compilation interface
28719 This chapter documents @value{GDBN}'s @dfn{just-in-time} (JIT) compilation
28720 interface. A JIT compiler is a program or library that generates native
28721 executable code at runtime and executes it, usually in order to achieve good
28722 performance while maintaining platform independence.
28724 Programs that use JIT compilation are normally difficult to debug because
28725 portions of their code are generated at runtime, instead of being loaded from
28726 object files, which is where @value{GDBN} normally finds the program's symbols
28727 and debug information. In order to debug programs that use JIT compilation,
28728 @value{GDBN} has an interface that allows the program to register in-memory
28729 symbol files with @value{GDBN} at runtime.
28731 If you are using @value{GDBN} to debug a program that uses this interface, then
28732 it should work transparently so long as you have not stripped the binary. If
28733 you are developing a JIT compiler, then the interface is documented in the rest
28734 of this chapter. At this time, the only known client of this interface is the
28737 Broadly speaking, the JIT interface mirrors the dynamic loader interface. The
28738 JIT compiler communicates with @value{GDBN} by writing data into a global
28739 variable and calling a fuction at a well-known symbol. When @value{GDBN}
28740 attaches, it reads a linked list of symbol files from the global variable to
28741 find existing code, and puts a breakpoint in the function so that it can find
28742 out about additional code.
28745 * Declarations:: Relevant C struct declarations
28746 * Registering Code:: Steps to register code
28747 * Unregistering Code:: Steps to unregister code
28751 @section JIT Declarations
28753 These are the relevant struct declarations that a C program should include to
28754 implement the interface:
28764 struct jit_code_entry
28766 struct jit_code_entry *next_entry;
28767 struct jit_code_entry *prev_entry;
28768 const char *symfile_addr;
28769 uint64_t symfile_size;
28772 struct jit_descriptor
28775 /* This type should be jit_actions_t, but we use uint32_t
28776 to be explicit about the bitwidth. */
28777 uint32_t action_flag;
28778 struct jit_code_entry *relevant_entry;
28779 struct jit_code_entry *first_entry;
28782 /* GDB puts a breakpoint in this function. */
28783 void __attribute__((noinline)) __jit_debug_register_code() @{ @};
28785 /* Make sure to specify the version statically, because the
28786 debugger may check the version before we can set it. */
28787 struct jit_descriptor __jit_debug_descriptor = @{ 1, 0, 0, 0 @};
28790 If the JIT is multi-threaded, then it is important that the JIT synchronize any
28791 modifications to this global data properly, which can easily be done by putting
28792 a global mutex around modifications to these structures.
28794 @node Registering Code
28795 @section Registering Code
28797 To register code with @value{GDBN}, the JIT should follow this protocol:
28801 Generate an object file in memory with symbols and other desired debug
28802 information. The file must include the virtual addresses of the sections.
28805 Create a code entry for the file, which gives the start and size of the symbol
28809 Add it to the linked list in the JIT descriptor.
28812 Point the relevant_entry field of the descriptor at the entry.
28815 Set @code{action_flag} to @code{JIT_REGISTER} and call
28816 @code{__jit_debug_register_code}.
28819 When @value{GDBN} is attached and the breakpoint fires, @value{GDBN} uses the
28820 @code{relevant_entry} pointer so it doesn't have to walk the list looking for
28821 new code. However, the linked list must still be maintained in order to allow
28822 @value{GDBN} to attach to a running process and still find the symbol files.
28824 @node Unregistering Code
28825 @section Unregistering Code
28827 If code is freed, then the JIT should use the following protocol:
28831 Remove the code entry corresponding to the code from the linked list.
28834 Point the @code{relevant_entry} field of the descriptor at the code entry.
28837 Set @code{action_flag} to @code{JIT_UNREGISTER} and call
28838 @code{__jit_debug_register_code}.
28841 If the JIT frees or recompiles code without unregistering it, then @value{GDBN}
28842 and the JIT will leak the memory used for the associated symbol files.
28845 @chapter Reporting Bugs in @value{GDBN}
28846 @cindex bugs in @value{GDBN}
28847 @cindex reporting bugs in @value{GDBN}
28849 Your bug reports play an essential role in making @value{GDBN} reliable.
28851 Reporting a bug may help you by bringing a solution to your problem, or it
28852 may not. But in any case the principal function of a bug report is to help
28853 the entire community by making the next version of @value{GDBN} work better. Bug
28854 reports are your contribution to the maintenance of @value{GDBN}.
28856 In order for a bug report to serve its purpose, you must include the
28857 information that enables us to fix the bug.
28860 * Bug Criteria:: Have you found a bug?
28861 * Bug Reporting:: How to report bugs
28865 @section Have You Found a Bug?
28866 @cindex bug criteria
28868 If you are not sure whether you have found a bug, here are some guidelines:
28871 @cindex fatal signal
28872 @cindex debugger crash
28873 @cindex crash of debugger
28875 If the debugger gets a fatal signal, for any input whatever, that is a
28876 @value{GDBN} bug. Reliable debuggers never crash.
28878 @cindex error on valid input
28880 If @value{GDBN} produces an error message for valid input, that is a
28881 bug. (Note that if you're cross debugging, the problem may also be
28882 somewhere in the connection to the target.)
28884 @cindex invalid input
28886 If @value{GDBN} does not produce an error message for invalid input,
28887 that is a bug. However, you should note that your idea of
28888 ``invalid input'' might be our idea of ``an extension'' or ``support
28889 for traditional practice''.
28892 If you are an experienced user of debugging tools, your suggestions
28893 for improvement of @value{GDBN} are welcome in any case.
28896 @node Bug Reporting
28897 @section How to Report Bugs
28898 @cindex bug reports
28899 @cindex @value{GDBN} bugs, reporting
28901 A number of companies and individuals offer support for @sc{gnu} products.
28902 If you obtained @value{GDBN} from a support organization, we recommend you
28903 contact that organization first.
28905 You can find contact information for many support companies and
28906 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
28908 @c should add a web page ref...
28911 @ifset BUGURL_DEFAULT
28912 In any event, we also recommend that you submit bug reports for
28913 @value{GDBN}. The preferred method is to submit them directly using
28914 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
28915 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
28918 @strong{Do not send bug reports to @samp{info-gdb}, or to
28919 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
28920 not want to receive bug reports. Those that do have arranged to receive
28923 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
28924 serves as a repeater. The mailing list and the newsgroup carry exactly
28925 the same messages. Often people think of posting bug reports to the
28926 newsgroup instead of mailing them. This appears to work, but it has one
28927 problem which can be crucial: a newsgroup posting often lacks a mail
28928 path back to the sender. Thus, if we need to ask for more information,
28929 we may be unable to reach you. For this reason, it is better to send
28930 bug reports to the mailing list.
28932 @ifclear BUGURL_DEFAULT
28933 In any event, we also recommend that you submit bug reports for
28934 @value{GDBN} to @value{BUGURL}.
28938 The fundamental principle of reporting bugs usefully is this:
28939 @strong{report all the facts}. If you are not sure whether to state a
28940 fact or leave it out, state it!
28942 Often people omit facts because they think they know what causes the
28943 problem and assume that some details do not matter. Thus, you might
28944 assume that the name of the variable you use in an example does not matter.
28945 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
28946 stray memory reference which happens to fetch from the location where that
28947 name is stored in memory; perhaps, if the name were different, the contents
28948 of that location would fool the debugger into doing the right thing despite
28949 the bug. Play it safe and give a specific, complete example. That is the
28950 easiest thing for you to do, and the most helpful.
28952 Keep in mind that the purpose of a bug report is to enable us to fix the
28953 bug. It may be that the bug has been reported previously, but neither
28954 you nor we can know that unless your bug report is complete and
28957 Sometimes people give a few sketchy facts and ask, ``Does this ring a
28958 bell?'' Those bug reports are useless, and we urge everyone to
28959 @emph{refuse to respond to them} except to chide the sender to report
28962 To enable us to fix the bug, you should include all these things:
28966 The version of @value{GDBN}. @value{GDBN} announces it if you start
28967 with no arguments; you can also print it at any time using @code{show
28970 Without this, we will not know whether there is any point in looking for
28971 the bug in the current version of @value{GDBN}.
28974 The type of machine you are using, and the operating system name and
28978 What compiler (and its version) was used to compile @value{GDBN}---e.g.@:
28979 ``@value{GCC}--2.8.1''.
28982 What compiler (and its version) was used to compile the program you are
28983 debugging---e.g.@: ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
28984 C Compiler''. For @value{NGCC}, you can say @kbd{@value{GCC} --version}
28985 to get this information; for other compilers, see the documentation for
28989 The command arguments you gave the compiler to compile your example and
28990 observe the bug. For example, did you use @samp{-O}? To guarantee
28991 you will not omit something important, list them all. A copy of the
28992 Makefile (or the output from make) is sufficient.
28994 If we were to try to guess the arguments, we would probably guess wrong
28995 and then we might not encounter the bug.
28998 A complete input script, and all necessary source files, that will
29002 A description of what behavior you observe that you believe is
29003 incorrect. For example, ``It gets a fatal signal.''
29005 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
29006 will certainly notice it. But if the bug is incorrect output, we might
29007 not notice unless it is glaringly wrong. You might as well not give us
29008 a chance to make a mistake.
29010 Even if the problem you experience is a fatal signal, you should still
29011 say so explicitly. Suppose something strange is going on, such as, your
29012 copy of @value{GDBN} is out of synch, or you have encountered a bug in
29013 the C library on your system. (This has happened!) Your copy might
29014 crash and ours would not. If you told us to expect a crash, then when
29015 ours fails to crash, we would know that the bug was not happening for
29016 us. If you had not told us to expect a crash, then we would not be able
29017 to draw any conclusion from our observations.
29020 @cindex recording a session script
29021 To collect all this information, you can use a session recording program
29022 such as @command{script}, which is available on many Unix systems.
29023 Just run your @value{GDBN} session inside @command{script} and then
29024 include the @file{typescript} file with your bug report.
29026 Another way to record a @value{GDBN} session is to run @value{GDBN}
29027 inside Emacs and then save the entire buffer to a file.
29030 If you wish to suggest changes to the @value{GDBN} source, send us context
29031 diffs. If you even discuss something in the @value{GDBN} source, refer to
29032 it by context, not by line number.
29034 The line numbers in our development sources will not match those in your
29035 sources. Your line numbers would convey no useful information to us.
29039 Here are some things that are not necessary:
29043 A description of the envelope of the bug.
29045 Often people who encounter a bug spend a lot of time investigating
29046 which changes to the input file will make the bug go away and which
29047 changes will not affect it.
29049 This is often time consuming and not very useful, because the way we
29050 will find the bug is by running a single example under the debugger
29051 with breakpoints, not by pure deduction from a series of examples.
29052 We recommend that you save your time for something else.
29054 Of course, if you can find a simpler example to report @emph{instead}
29055 of the original one, that is a convenience for us. Errors in the
29056 output will be easier to spot, running under the debugger will take
29057 less time, and so on.
29059 However, simplification is not vital; if you do not want to do this,
29060 report the bug anyway and send us the entire test case you used.
29063 A patch for the bug.
29065 A patch for the bug does help us if it is a good one. But do not omit
29066 the necessary information, such as the test case, on the assumption that
29067 a patch is all we need. We might see problems with your patch and decide
29068 to fix the problem another way, or we might not understand it at all.
29070 Sometimes with a program as complicated as @value{GDBN} it is very hard to
29071 construct an example that will make the program follow a certain path
29072 through the code. If you do not send us the example, we will not be able
29073 to construct one, so we will not be able to verify that the bug is fixed.
29075 And if we cannot understand what bug you are trying to fix, or why your
29076 patch should be an improvement, we will not install it. A test case will
29077 help us to understand.
29080 A guess about what the bug is or what it depends on.
29082 Such guesses are usually wrong. Even we cannot guess right about such
29083 things without first using the debugger to find the facts.
29086 @c The readline documentation is distributed with the readline code
29087 @c and consists of the two following files:
29089 @c inc-hist.texinfo
29090 @c Use -I with makeinfo to point to the appropriate directory,
29091 @c environment var TEXINPUTS with TeX.
29092 @include rluser.texi
29093 @include inc-hist.texinfo
29096 @node Formatting Documentation
29097 @appendix Formatting Documentation
29099 @cindex @value{GDBN} reference card
29100 @cindex reference card
29101 The @value{GDBN} 4 release includes an already-formatted reference card, ready
29102 for printing with PostScript or Ghostscript, in the @file{gdb}
29103 subdirectory of the main source directory@footnote{In
29104 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
29105 release.}. If you can use PostScript or Ghostscript with your printer,
29106 you can print the reference card immediately with @file{refcard.ps}.
29108 The release also includes the source for the reference card. You
29109 can format it, using @TeX{}, by typing:
29115 The @value{GDBN} reference card is designed to print in @dfn{landscape}
29116 mode on US ``letter'' size paper;
29117 that is, on a sheet 11 inches wide by 8.5 inches
29118 high. You will need to specify this form of printing as an option to
29119 your @sc{dvi} output program.
29121 @cindex documentation
29123 All the documentation for @value{GDBN} comes as part of the machine-readable
29124 distribution. The documentation is written in Texinfo format, which is
29125 a documentation system that uses a single source file to produce both
29126 on-line information and a printed manual. You can use one of the Info
29127 formatting commands to create the on-line version of the documentation
29128 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
29130 @value{GDBN} includes an already formatted copy of the on-line Info
29131 version of this manual in the @file{gdb} subdirectory. The main Info
29132 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
29133 subordinate files matching @samp{gdb.info*} in the same directory. If
29134 necessary, you can print out these files, or read them with any editor;
29135 but they are easier to read using the @code{info} subsystem in @sc{gnu}
29136 Emacs or the standalone @code{info} program, available as part of the
29137 @sc{gnu} Texinfo distribution.
29139 If you want to format these Info files yourself, you need one of the
29140 Info formatting programs, such as @code{texinfo-format-buffer} or
29143 If you have @code{makeinfo} installed, and are in the top level
29144 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
29145 version @value{GDBVN}), you can make the Info file by typing:
29152 If you want to typeset and print copies of this manual, you need @TeX{},
29153 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
29154 Texinfo definitions file.
29156 @TeX{} is a typesetting program; it does not print files directly, but
29157 produces output files called @sc{dvi} files. To print a typeset
29158 document, you need a program to print @sc{dvi} files. If your system
29159 has @TeX{} installed, chances are it has such a program. The precise
29160 command to use depends on your system; @kbd{lpr -d} is common; another
29161 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
29162 require a file name without any extension or a @samp{.dvi} extension.
29164 @TeX{} also requires a macro definitions file called
29165 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
29166 written in Texinfo format. On its own, @TeX{} cannot either read or
29167 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
29168 and is located in the @file{gdb-@var{version-number}/texinfo}
29171 If you have @TeX{} and a @sc{dvi} printer program installed, you can
29172 typeset and print this manual. First switch to the @file{gdb}
29173 subdirectory of the main source directory (for example, to
29174 @file{gdb-@value{GDBVN}/gdb}) and type:
29180 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
29182 @node Installing GDB
29183 @appendix Installing @value{GDBN}
29184 @cindex installation
29187 * Requirements:: Requirements for building @value{GDBN}
29188 * Running Configure:: Invoking the @value{GDBN} @file{configure} script
29189 * Separate Objdir:: Compiling @value{GDBN} in another directory
29190 * Config Names:: Specifying names for hosts and targets
29191 * Configure Options:: Summary of options for configure
29192 * System-wide configuration:: Having a system-wide init file
29196 @section Requirements for Building @value{GDBN}
29197 @cindex building @value{GDBN}, requirements for
29199 Building @value{GDBN} requires various tools and packages to be available.
29200 Other packages will be used only if they are found.
29202 @heading Tools/Packages Necessary for Building @value{GDBN}
29204 @item ISO C90 compiler
29205 @value{GDBN} is written in ISO C90. It should be buildable with any
29206 working C90 compiler, e.g.@: GCC.
29210 @heading Tools/Packages Optional for Building @value{GDBN}
29214 @value{GDBN} can use the Expat XML parsing library. This library may be
29215 included with your operating system distribution; if it is not, you
29216 can get the latest version from @url{http://expat.sourceforge.net}.
29217 The @file{configure} script will search for this library in several
29218 standard locations; if it is installed in an unusual path, you can
29219 use the @option{--with-libexpat-prefix} option to specify its location.
29225 Remote protocol memory maps (@pxref{Memory Map Format})
29227 Target descriptions (@pxref{Target Descriptions})
29229 Remote shared library lists (@pxref{Library List Format})
29231 MS-Windows shared libraries (@pxref{Shared Libraries})
29235 @cindex compressed debug sections
29236 @value{GDBN} will use the @samp{zlib} library, if available, to read
29237 compressed debug sections. Some linkers, such as GNU gold, are capable
29238 of producing binaries with compressed debug sections. If @value{GDBN}
29239 is compiled with @samp{zlib}, it will be able to read the debug
29240 information in such binaries.
29242 The @samp{zlib} library is likely included with your operating system
29243 distribution; if it is not, you can get the latest version from
29244 @url{http://zlib.net}.
29247 @value{GDBN}'s features related to character sets (@pxref{Character
29248 Sets}) require a functioning @code{iconv} implementation. If you are
29249 on a GNU system, then this is provided by the GNU C Library. Some
29250 other systems also provide a working @code{iconv}.
29252 On systems with @code{iconv}, you can install GNU Libiconv. If you
29253 have previously installed Libiconv, you can use the
29254 @option{--with-libiconv-prefix} option to configure.
29256 @value{GDBN}'s top-level @file{configure} and @file{Makefile} will
29257 arrange to build Libiconv if a directory named @file{libiconv} appears
29258 in the top-most source directory. If Libiconv is built this way, and
29259 if the operating system does not provide a suitable @code{iconv}
29260 implementation, then the just-built library will automatically be used
29261 by @value{GDBN}. One easy way to set this up is to download GNU
29262 Libiconv, unpack it, and then rename the directory holding the
29263 Libiconv source code to @samp{libiconv}.
29266 @node Running Configure
29267 @section Invoking the @value{GDBN} @file{configure} Script
29268 @cindex configuring @value{GDBN}
29269 @value{GDBN} comes with a @file{configure} script that automates the process
29270 of preparing @value{GDBN} for installation; you can then use @code{make} to
29271 build the @code{gdb} program.
29273 @c irrelevant in info file; it's as current as the code it lives with.
29274 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
29275 look at the @file{README} file in the sources; we may have improved the
29276 installation procedures since publishing this manual.}
29279 The @value{GDBN} distribution includes all the source code you need for
29280 @value{GDBN} in a single directory, whose name is usually composed by
29281 appending the version number to @samp{gdb}.
29283 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
29284 @file{gdb-@value{GDBVN}} directory. That directory contains:
29287 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
29288 script for configuring @value{GDBN} and all its supporting libraries
29290 @item gdb-@value{GDBVN}/gdb
29291 the source specific to @value{GDBN} itself
29293 @item gdb-@value{GDBVN}/bfd
29294 source for the Binary File Descriptor library
29296 @item gdb-@value{GDBVN}/include
29297 @sc{gnu} include files
29299 @item gdb-@value{GDBVN}/libiberty
29300 source for the @samp{-liberty} free software library
29302 @item gdb-@value{GDBVN}/opcodes
29303 source for the library of opcode tables and disassemblers
29305 @item gdb-@value{GDBVN}/readline
29306 source for the @sc{gnu} command-line interface
29308 @item gdb-@value{GDBVN}/glob
29309 source for the @sc{gnu} filename pattern-matching subroutine
29311 @item gdb-@value{GDBVN}/mmalloc
29312 source for the @sc{gnu} memory-mapped malloc package
29315 The simplest way to configure and build @value{GDBN} is to run @file{configure}
29316 from the @file{gdb-@var{version-number}} source directory, which in
29317 this example is the @file{gdb-@value{GDBVN}} directory.
29319 First switch to the @file{gdb-@var{version-number}} source directory
29320 if you are not already in it; then run @file{configure}. Pass the
29321 identifier for the platform on which @value{GDBN} will run as an
29327 cd gdb-@value{GDBVN}
29328 ./configure @var{host}
29333 where @var{host} is an identifier such as @samp{sun4} or
29334 @samp{decstation}, that identifies the platform where @value{GDBN} will run.
29335 (You can often leave off @var{host}; @file{configure} tries to guess the
29336 correct value by examining your system.)
29338 Running @samp{configure @var{host}} and then running @code{make} builds the
29339 @file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty}
29340 libraries, then @code{gdb} itself. The configured source files, and the
29341 binaries, are left in the corresponding source directories.
29344 @file{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
29345 system does not recognize this automatically when you run a different
29346 shell, you may need to run @code{sh} on it explicitly:
29349 sh configure @var{host}
29352 If you run @file{configure} from a directory that contains source
29353 directories for multiple libraries or programs, such as the
29354 @file{gdb-@value{GDBVN}} source directory for version @value{GDBVN},
29356 creates configuration files for every directory level underneath (unless
29357 you tell it not to, with the @samp{--norecursion} option).
29359 You should run the @file{configure} script from the top directory in the
29360 source tree, the @file{gdb-@var{version-number}} directory. If you run
29361 @file{configure} from one of the subdirectories, you will configure only
29362 that subdirectory. That is usually not what you want. In particular,
29363 if you run the first @file{configure} from the @file{gdb} subdirectory
29364 of the @file{gdb-@var{version-number}} directory, you will omit the
29365 configuration of @file{bfd}, @file{readline}, and other sibling
29366 directories of the @file{gdb} subdirectory. This leads to build errors
29367 about missing include files such as @file{bfd/bfd.h}.
29369 You can install @code{@value{GDBP}} anywhere; it has no hardwired paths.
29370 However, you should make sure that the shell on your path (named by
29371 the @samp{SHELL} environment variable) is publicly readable. Remember
29372 that @value{GDBN} uses the shell to start your program---some systems refuse to
29373 let @value{GDBN} debug child processes whose programs are not readable.
29375 @node Separate Objdir
29376 @section Compiling @value{GDBN} in Another Directory
29378 If you want to run @value{GDBN} versions for several host or target machines,
29379 you need a different @code{gdb} compiled for each combination of
29380 host and target. @file{configure} is designed to make this easy by
29381 allowing you to generate each configuration in a separate subdirectory,
29382 rather than in the source directory. If your @code{make} program
29383 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
29384 @code{make} in each of these directories builds the @code{gdb}
29385 program specified there.
29387 To build @code{gdb} in a separate directory, run @file{configure}
29388 with the @samp{--srcdir} option to specify where to find the source.
29389 (You also need to specify a path to find @file{configure}
29390 itself from your working directory. If the path to @file{configure}
29391 would be the same as the argument to @samp{--srcdir}, you can leave out
29392 the @samp{--srcdir} option; it is assumed.)
29394 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
29395 separate directory for a Sun 4 like this:
29399 cd gdb-@value{GDBVN}
29402 ../gdb-@value{GDBVN}/configure sun4
29407 When @file{configure} builds a configuration using a remote source
29408 directory, it creates a tree for the binaries with the same structure
29409 (and using the same names) as the tree under the source directory. In
29410 the example, you'd find the Sun 4 library @file{libiberty.a} in the
29411 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
29412 @file{gdb-sun4/gdb}.
29414 Make sure that your path to the @file{configure} script has just one
29415 instance of @file{gdb} in it. If your path to @file{configure} looks
29416 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
29417 one subdirectory of @value{GDBN}, not the whole package. This leads to
29418 build errors about missing include files such as @file{bfd/bfd.h}.
29420 One popular reason to build several @value{GDBN} configurations in separate
29421 directories is to configure @value{GDBN} for cross-compiling (where
29422 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
29423 programs that run on another machine---the @dfn{target}).
29424 You specify a cross-debugging target by
29425 giving the @samp{--target=@var{target}} option to @file{configure}.
29427 When you run @code{make} to build a program or library, you must run
29428 it in a configured directory---whatever directory you were in when you
29429 called @file{configure} (or one of its subdirectories).
29431 The @code{Makefile} that @file{configure} generates in each source
29432 directory also runs recursively. If you type @code{make} in a source
29433 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
29434 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
29435 will build all the required libraries, and then build GDB.
29437 When you have multiple hosts or targets configured in separate
29438 directories, you can run @code{make} on them in parallel (for example,
29439 if they are NFS-mounted on each of the hosts); they will not interfere
29443 @section Specifying Names for Hosts and Targets
29445 The specifications used for hosts and targets in the @file{configure}
29446 script are based on a three-part naming scheme, but some short predefined
29447 aliases are also supported. The full naming scheme encodes three pieces
29448 of information in the following pattern:
29451 @var{architecture}-@var{vendor}-@var{os}
29454 For example, you can use the alias @code{sun4} as a @var{host} argument,
29455 or as the value for @var{target} in a @code{--target=@var{target}}
29456 option. The equivalent full name is @samp{sparc-sun-sunos4}.
29458 The @file{configure} script accompanying @value{GDBN} does not provide
29459 any query facility to list all supported host and target names or
29460 aliases. @file{configure} calls the Bourne shell script
29461 @code{config.sub} to map abbreviations to full names; you can read the
29462 script, if you wish, or you can use it to test your guesses on
29463 abbreviations---for example:
29466 % sh config.sub i386-linux
29468 % sh config.sub alpha-linux
29469 alpha-unknown-linux-gnu
29470 % sh config.sub hp9k700
29472 % sh config.sub sun4
29473 sparc-sun-sunos4.1.1
29474 % sh config.sub sun3
29475 m68k-sun-sunos4.1.1
29476 % sh config.sub i986v
29477 Invalid configuration `i986v': machine `i986v' not recognized
29481 @code{config.sub} is also distributed in the @value{GDBN} source
29482 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
29484 @node Configure Options
29485 @section @file{configure} Options
29487 Here is a summary of the @file{configure} options and arguments that
29488 are most often useful for building @value{GDBN}. @file{configure} also has
29489 several other options not listed here. @inforef{What Configure
29490 Does,,configure.info}, for a full explanation of @file{configure}.
29493 configure @r{[}--help@r{]}
29494 @r{[}--prefix=@var{dir}@r{]}
29495 @r{[}--exec-prefix=@var{dir}@r{]}
29496 @r{[}--srcdir=@var{dirname}@r{]}
29497 @r{[}--norecursion@r{]} @r{[}--rm@r{]}
29498 @r{[}--target=@var{target}@r{]}
29503 You may introduce options with a single @samp{-} rather than
29504 @samp{--} if you prefer; but you may abbreviate option names if you use
29509 Display a quick summary of how to invoke @file{configure}.
29511 @item --prefix=@var{dir}
29512 Configure the source to install programs and files under directory
29515 @item --exec-prefix=@var{dir}
29516 Configure the source to install programs under directory
29519 @c avoid splitting the warning from the explanation:
29521 @item --srcdir=@var{dirname}
29522 @strong{Warning: using this option requires @sc{gnu} @code{make}, or another
29523 @code{make} that implements the @code{VPATH} feature.}@*
29524 Use this option to make configurations in directories separate from the
29525 @value{GDBN} source directories. Among other things, you can use this to
29526 build (or maintain) several configurations simultaneously, in separate
29527 directories. @file{configure} writes configuration-specific files in
29528 the current directory, but arranges for them to use the source in the
29529 directory @var{dirname}. @file{configure} creates directories under
29530 the working directory in parallel to the source directories below
29533 @item --norecursion
29534 Configure only the directory level where @file{configure} is executed; do not
29535 propagate configuration to subdirectories.
29537 @item --target=@var{target}
29538 Configure @value{GDBN} for cross-debugging programs running on the specified
29539 @var{target}. Without this option, @value{GDBN} is configured to debug
29540 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
29542 There is no convenient way to generate a list of all available targets.
29544 @item @var{host} @dots{}
29545 Configure @value{GDBN} to run on the specified @var{host}.
29547 There is no convenient way to generate a list of all available hosts.
29550 There are many other options available as well, but they are generally
29551 needed for special purposes only.
29553 @node System-wide configuration
29554 @section System-wide configuration and settings
29555 @cindex system-wide init file
29557 @value{GDBN} can be configured to have a system-wide init file;
29558 this file will be read and executed at startup (@pxref{Startup, , What
29559 @value{GDBN} does during startup}).
29561 Here is the corresponding configure option:
29564 @item --with-system-gdbinit=@var{file}
29565 Specify that the default location of the system-wide init file is
29569 If @value{GDBN} has been configured with the option @option{--prefix=$prefix},
29570 it may be subject to relocation. Two possible cases:
29574 If the default location of this init file contains @file{$prefix},
29575 it will be subject to relocation. Suppose that the configure options
29576 are @option{--prefix=$prefix --with-system-gdbinit=$prefix/etc/gdbinit};
29577 if @value{GDBN} is moved from @file{$prefix} to @file{$install}, the system
29578 init file is looked for as @file{$install/etc/gdbinit} instead of
29579 @file{$prefix/etc/gdbinit}.
29582 By contrast, if the default location does not contain the prefix,
29583 it will not be relocated. E.g.@: if @value{GDBN} has been configured with
29584 @option{--prefix=/usr/local --with-system-gdbinit=/usr/share/gdb/gdbinit},
29585 then @value{GDBN} will always look for @file{/usr/share/gdb/gdbinit},
29586 wherever @value{GDBN} is installed.
29589 @node Maintenance Commands
29590 @appendix Maintenance Commands
29591 @cindex maintenance commands
29592 @cindex internal commands
29594 In addition to commands intended for @value{GDBN} users, @value{GDBN}
29595 includes a number of commands intended for @value{GDBN} developers,
29596 that are not documented elsewhere in this manual. These commands are
29597 provided here for reference. (For commands that turn on debugging
29598 messages, see @ref{Debugging Output}.)
29601 @kindex maint agent
29602 @kindex maint agent-eval
29603 @item maint agent @var{expression}
29604 @itemx maint agent-eval @var{expression}
29605 Translate the given @var{expression} into remote agent bytecodes.
29606 This command is useful for debugging the Agent Expression mechanism
29607 (@pxref{Agent Expressions}). The @samp{agent} version produces an
29608 expression useful for data collection, such as by tracepoints, while
29609 @samp{maint agent-eval} produces an expression that evaluates directly
29610 to a result. For instance, a collection expression for @code{globa +
29611 globb} will include bytecodes to record four bytes of memory at each
29612 of the addresses of @code{globa} and @code{globb}, while discarding
29613 the result of the addition, while an evaluation expression will do the
29614 addition and return the sum.
29616 @kindex maint info breakpoints
29617 @item @anchor{maint info breakpoints}maint info breakpoints
29618 Using the same format as @samp{info breakpoints}, display both the
29619 breakpoints you've set explicitly, and those @value{GDBN} is using for
29620 internal purposes. Internal breakpoints are shown with negative
29621 breakpoint numbers. The type column identifies what kind of breakpoint
29626 Normal, explicitly set breakpoint.
29629 Normal, explicitly set watchpoint.
29632 Internal breakpoint, used to handle correctly stepping through
29633 @code{longjmp} calls.
29635 @item longjmp resume
29636 Internal breakpoint at the target of a @code{longjmp}.
29639 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
29642 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
29645 Shared library events.
29649 @kindex set displaced-stepping
29650 @kindex show displaced-stepping
29651 @cindex displaced stepping support
29652 @cindex out-of-line single-stepping
29653 @item set displaced-stepping
29654 @itemx show displaced-stepping
29655 Control whether or not @value{GDBN} will do @dfn{displaced stepping}
29656 if the target supports it. Displaced stepping is a way to single-step
29657 over breakpoints without removing them from the inferior, by executing
29658 an out-of-line copy of the instruction that was originally at the
29659 breakpoint location. It is also known as out-of-line single-stepping.
29662 @item set displaced-stepping on
29663 If the target architecture supports it, @value{GDBN} will use
29664 displaced stepping to step over breakpoints.
29666 @item set displaced-stepping off
29667 @value{GDBN} will not use displaced stepping to step over breakpoints,
29668 even if such is supported by the target architecture.
29670 @cindex non-stop mode, and @samp{set displaced-stepping}
29671 @item set displaced-stepping auto
29672 This is the default mode. @value{GDBN} will use displaced stepping
29673 only if non-stop mode is active (@pxref{Non-Stop Mode}) and the target
29674 architecture supports displaced stepping.
29677 @kindex maint check-symtabs
29678 @item maint check-symtabs
29679 Check the consistency of psymtabs and symtabs.
29681 @kindex maint cplus first_component
29682 @item maint cplus first_component @var{name}
29683 Print the first C@t{++} class/namespace component of @var{name}.
29685 @kindex maint cplus namespace
29686 @item maint cplus namespace
29687 Print the list of possible C@t{++} namespaces.
29689 @kindex maint demangle
29690 @item maint demangle @var{name}
29691 Demangle a C@t{++} or Objective-C mangled @var{name}.
29693 @kindex maint deprecate
29694 @kindex maint undeprecate
29695 @cindex deprecated commands
29696 @item maint deprecate @var{command} @r{[}@var{replacement}@r{]}
29697 @itemx maint undeprecate @var{command}
29698 Deprecate or undeprecate the named @var{command}. Deprecated commands
29699 cause @value{GDBN} to issue a warning when you use them. The optional
29700 argument @var{replacement} says which newer command should be used in
29701 favor of the deprecated one; if it is given, @value{GDBN} will mention
29702 the replacement as part of the warning.
29704 @kindex maint dump-me
29705 @item maint dump-me
29706 @cindex @code{SIGQUIT} signal, dump core of @value{GDBN}
29707 Cause a fatal signal in the debugger and force it to dump its core.
29708 This is supported only on systems which support aborting a program
29709 with the @code{SIGQUIT} signal.
29711 @kindex maint internal-error
29712 @kindex maint internal-warning
29713 @item maint internal-error @r{[}@var{message-text}@r{]}
29714 @itemx maint internal-warning @r{[}@var{message-text}@r{]}
29715 Cause @value{GDBN} to call the internal function @code{internal_error}
29716 or @code{internal_warning} and hence behave as though an internal error
29717 or internal warning has been detected. In addition to reporting the
29718 internal problem, these functions give the user the opportunity to
29719 either quit @value{GDBN} or create a core file of the current
29720 @value{GDBN} session.
29722 These commands take an optional parameter @var{message-text} that is
29723 used as the text of the error or warning message.
29725 Here's an example of using @code{internal-error}:
29728 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
29729 @dots{}/maint.c:121: internal-error: testing, 1, 2
29730 A problem internal to GDB has been detected. Further
29731 debugging may prove unreliable.
29732 Quit this debugging session? (y or n) @kbd{n}
29733 Create a core file? (y or n) @kbd{n}
29737 @cindex @value{GDBN} internal error
29738 @cindex internal errors, control of @value{GDBN} behavior
29740 @kindex maint set internal-error
29741 @kindex maint show internal-error
29742 @kindex maint set internal-warning
29743 @kindex maint show internal-warning
29744 @item maint set internal-error @var{action} [ask|yes|no]
29745 @itemx maint show internal-error @var{action}
29746 @itemx maint set internal-warning @var{action} [ask|yes|no]
29747 @itemx maint show internal-warning @var{action}
29748 When @value{GDBN} reports an internal problem (error or warning) it
29749 gives the user the opportunity to both quit @value{GDBN} and create a
29750 core file of the current @value{GDBN} session. These commands let you
29751 override the default behaviour for each particular @var{action},
29752 described in the table below.
29756 You can specify that @value{GDBN} should always (yes) or never (no)
29757 quit. The default is to ask the user what to do.
29760 You can specify that @value{GDBN} should always (yes) or never (no)
29761 create a core file. The default is to ask the user what to do.
29764 @kindex maint packet
29765 @item maint packet @var{text}
29766 If @value{GDBN} is talking to an inferior via the serial protocol,
29767 then this command sends the string @var{text} to the inferior, and
29768 displays the response packet. @value{GDBN} supplies the initial
29769 @samp{$} character, the terminating @samp{#} character, and the
29772 @kindex maint print architecture
29773 @item maint print architecture @r{[}@var{file}@r{]}
29774 Print the entire architecture configuration. The optional argument
29775 @var{file} names the file where the output goes.
29777 @kindex maint print c-tdesc
29778 @item maint print c-tdesc
29779 Print the current target description (@pxref{Target Descriptions}) as
29780 a C source file. The created source file can be used in @value{GDBN}
29781 when an XML parser is not available to parse the description.
29783 @kindex maint print dummy-frames
29784 @item maint print dummy-frames
29785 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
29788 (@value{GDBP}) @kbd{b add}
29790 (@value{GDBP}) @kbd{print add(2,3)}
29791 Breakpoint 2, add (a=2, b=3) at @dots{}
29793 The program being debugged stopped while in a function called from GDB.
29795 (@value{GDBP}) @kbd{maint print dummy-frames}
29796 0x1a57c80: pc=0x01014068 fp=0x0200bddc sp=0x0200bdd6
29797 top=0x0200bdd4 id=@{stack=0x200bddc,code=0x101405c@}
29798 call_lo=0x01014000 call_hi=0x01014001
29802 Takes an optional file parameter.
29804 @kindex maint print registers
29805 @kindex maint print raw-registers
29806 @kindex maint print cooked-registers
29807 @kindex maint print register-groups
29808 @item maint print registers @r{[}@var{file}@r{]}
29809 @itemx maint print raw-registers @r{[}@var{file}@r{]}
29810 @itemx maint print cooked-registers @r{[}@var{file}@r{]}
29811 @itemx maint print register-groups @r{[}@var{file}@r{]}
29812 Print @value{GDBN}'s internal register data structures.
29814 The command @code{maint print raw-registers} includes the contents of
29815 the raw register cache; the command @code{maint print cooked-registers}
29816 includes the (cooked) value of all registers, including registers which
29817 aren't available on the target nor visible to user; and the
29818 command @code{maint print register-groups} includes the groups that each
29819 register is a member of. @xref{Registers,, Registers, gdbint,
29820 @value{GDBN} Internals}.
29822 These commands take an optional parameter, a file name to which to
29823 write the information.
29825 @kindex maint print reggroups
29826 @item maint print reggroups @r{[}@var{file}@r{]}
29827 Print @value{GDBN}'s internal register group data structures. The
29828 optional argument @var{file} tells to what file to write the
29831 The register groups info looks like this:
29834 (@value{GDBP}) @kbd{maint print reggroups}
29847 This command forces @value{GDBN} to flush its internal register cache.
29849 @kindex maint print objfiles
29850 @cindex info for known object files
29851 @item maint print objfiles
29852 Print a dump of all known object files. For each object file, this
29853 command prints its name, address in memory, and all of its psymtabs
29856 @kindex maint print section-scripts
29857 @cindex info for known .debug_gdb_scripts-loaded scripts
29858 @item maint print section-scripts [@var{regexp}]
29859 Print a dump of scripts specified in the @code{.debug_gdb_section} section.
29860 If @var{regexp} is specified, only print scripts loaded by object files
29861 matching @var{regexp}.
29862 For each script, this command prints its name as specified in the objfile,
29863 and the full path if known.
29864 @xref{.debug_gdb_scripts section}.
29866 @kindex maint print statistics
29867 @cindex bcache statistics
29868 @item maint print statistics
29869 This command prints, for each object file in the program, various data
29870 about that object file followed by the byte cache (@dfn{bcache})
29871 statistics for the object file. The objfile data includes the number
29872 of minimal, partial, full, and stabs symbols, the number of types
29873 defined by the objfile, the number of as yet unexpanded psym tables,
29874 the number of line tables and string tables, and the amount of memory
29875 used by the various tables. The bcache statistics include the counts,
29876 sizes, and counts of duplicates of all and unique objects, max,
29877 average, and median entry size, total memory used and its overhead and
29878 savings, and various measures of the hash table size and chain
29881 @kindex maint print target-stack
29882 @cindex target stack description
29883 @item maint print target-stack
29884 A @dfn{target} is an interface between the debugger and a particular
29885 kind of file or process. Targets can be stacked in @dfn{strata},
29886 so that more than one target can potentially respond to a request.
29887 In particular, memory accesses will walk down the stack of targets
29888 until they find a target that is interested in handling that particular
29891 This command prints a short description of each layer that was pushed on
29892 the @dfn{target stack}, starting from the top layer down to the bottom one.
29894 @kindex maint print type
29895 @cindex type chain of a data type
29896 @item maint print type @var{expr}
29897 Print the type chain for a type specified by @var{expr}. The argument
29898 can be either a type name or a symbol. If it is a symbol, the type of
29899 that symbol is described. The type chain produced by this command is
29900 a recursive definition of the data type as stored in @value{GDBN}'s
29901 data structures, including its flags and contained types.
29903 @kindex maint set dwarf2 max-cache-age
29904 @kindex maint show dwarf2 max-cache-age
29905 @item maint set dwarf2 max-cache-age
29906 @itemx maint show dwarf2 max-cache-age
29907 Control the DWARF 2 compilation unit cache.
29909 @cindex DWARF 2 compilation units cache
29910 In object files with inter-compilation-unit references, such as those
29911 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF 2
29912 reader needs to frequently refer to previously read compilation units.
29913 This setting controls how long a compilation unit will remain in the
29914 cache if it is not referenced. A higher limit means that cached
29915 compilation units will be stored in memory longer, and more total
29916 memory will be used. Setting it to zero disables caching, which will
29917 slow down @value{GDBN} startup, but reduce memory consumption.
29919 @kindex maint set profile
29920 @kindex maint show profile
29921 @cindex profiling GDB
29922 @item maint set profile
29923 @itemx maint show profile
29924 Control profiling of @value{GDBN}.
29926 Profiling will be disabled until you use the @samp{maint set profile}
29927 command to enable it. When you enable profiling, the system will begin
29928 collecting timing and execution count data; when you disable profiling or
29929 exit @value{GDBN}, the results will be written to a log file. Remember that
29930 if you use profiling, @value{GDBN} will overwrite the profiling log file
29931 (often called @file{gmon.out}). If you have a record of important profiling
29932 data in a @file{gmon.out} file, be sure to move it to a safe location.
29934 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
29935 compiled with the @samp{-pg} compiler option.
29937 @kindex maint set show-debug-regs
29938 @kindex maint show show-debug-regs
29939 @cindex hardware debug registers
29940 @item maint set show-debug-regs
29941 @itemx maint show show-debug-regs
29942 Control whether to show variables that mirror the hardware debug
29943 registers. Use @code{ON} to enable, @code{OFF} to disable. If
29944 enabled, the debug registers values are shown when @value{GDBN} inserts or
29945 removes a hardware breakpoint or watchpoint, and when the inferior
29946 triggers a hardware-assisted breakpoint or watchpoint.
29948 @kindex maint set show-all-tib
29949 @kindex maint show show-all-tib
29950 @item maint set show-all-tib
29951 @itemx maint show show-all-tib
29952 Control whether to show all non zero areas within a 1k block starting
29953 at thread local base, when using the @samp{info w32 thread-information-block}
29956 @kindex maint space
29957 @cindex memory used by commands
29959 Control whether to display memory usage for each command. If set to a
29960 nonzero value, @value{GDBN} will display how much memory each command
29961 took, following the command's own output. This can also be requested
29962 by invoking @value{GDBN} with the @option{--statistics} command-line
29963 switch (@pxref{Mode Options}).
29966 @cindex time of command execution
29968 Control whether to display the execution time for each command. If
29969 set to a nonzero value, @value{GDBN} will display how much time it
29970 took to execute each command, following the command's own output.
29971 The time is not printed for the commands that run the target, since
29972 there's no mechanism currently to compute how much time was spend
29973 by @value{GDBN} and how much time was spend by the program been debugged.
29974 it's not possibly currently
29975 This can also be requested by invoking @value{GDBN} with the
29976 @option{--statistics} command-line switch (@pxref{Mode Options}).
29978 @kindex maint translate-address
29979 @item maint translate-address @r{[}@var{section}@r{]} @var{addr}
29980 Find the symbol stored at the location specified by the address
29981 @var{addr} and an optional section name @var{section}. If found,
29982 @value{GDBN} prints the name of the closest symbol and an offset from
29983 the symbol's location to the specified address. This is similar to
29984 the @code{info address} command (@pxref{Symbols}), except that this
29985 command also allows to find symbols in other sections.
29987 If section was not specified, the section in which the symbol was found
29988 is also printed. For dynamically linked executables, the name of
29989 executable or shared library containing the symbol is printed as well.
29993 The following command is useful for non-interactive invocations of
29994 @value{GDBN}, such as in the test suite.
29997 @item set watchdog @var{nsec}
29998 @kindex set watchdog
29999 @cindex watchdog timer
30000 @cindex timeout for commands
30001 Set the maximum number of seconds @value{GDBN} will wait for the
30002 target operation to finish. If this time expires, @value{GDBN}
30003 reports and error and the command is aborted.
30005 @item show watchdog
30006 Show the current setting of the target wait timeout.
30009 @node Remote Protocol
30010 @appendix @value{GDBN} Remote Serial Protocol
30015 * Stop Reply Packets::
30016 * General Query Packets::
30017 * Architecture-Specific Protocol Details::
30018 * Tracepoint Packets::
30019 * Host I/O Packets::
30021 * Notification Packets::
30022 * Remote Non-Stop::
30023 * Packet Acknowledgment::
30025 * File-I/O Remote Protocol Extension::
30026 * Library List Format::
30027 * Memory Map Format::
30028 * Thread List Format::
30034 There may be occasions when you need to know something about the
30035 protocol---for example, if there is only one serial port to your target
30036 machine, you might want your program to do something special if it
30037 recognizes a packet meant for @value{GDBN}.
30039 In the examples below, @samp{->} and @samp{<-} are used to indicate
30040 transmitted and received data, respectively.
30042 @cindex protocol, @value{GDBN} remote serial
30043 @cindex serial protocol, @value{GDBN} remote
30044 @cindex remote serial protocol
30045 All @value{GDBN} commands and responses (other than acknowledgments
30046 and notifications, see @ref{Notification Packets}) are sent as a
30047 @var{packet}. A @var{packet} is introduced with the character
30048 @samp{$}, the actual @var{packet-data}, and the terminating character
30049 @samp{#} followed by a two-digit @var{checksum}:
30052 @code{$}@var{packet-data}@code{#}@var{checksum}
30056 @cindex checksum, for @value{GDBN} remote
30058 The two-digit @var{checksum} is computed as the modulo 256 sum of all
30059 characters between the leading @samp{$} and the trailing @samp{#} (an
30060 eight bit unsigned checksum).
30062 Implementors should note that prior to @value{GDBN} 5.0 the protocol
30063 specification also included an optional two-digit @var{sequence-id}:
30066 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
30069 @cindex sequence-id, for @value{GDBN} remote
30071 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
30072 has never output @var{sequence-id}s. Stubs that handle packets added
30073 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
30075 When either the host or the target machine receives a packet, the first
30076 response expected is an acknowledgment: either @samp{+} (to indicate
30077 the package was received correctly) or @samp{-} (to request
30081 -> @code{$}@var{packet-data}@code{#}@var{checksum}
30086 The @samp{+}/@samp{-} acknowledgments can be disabled
30087 once a connection is established.
30088 @xref{Packet Acknowledgment}, for details.
30090 The host (@value{GDBN}) sends @var{command}s, and the target (the
30091 debugging stub incorporated in your program) sends a @var{response}. In
30092 the case of step and continue @var{command}s, the response is only sent
30093 when the operation has completed, and the target has again stopped all
30094 threads in all attached processes. This is the default all-stop mode
30095 behavior, but the remote protocol also supports @value{GDBN}'s non-stop
30096 execution mode; see @ref{Remote Non-Stop}, for details.
30098 @var{packet-data} consists of a sequence of characters with the
30099 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
30102 @cindex remote protocol, field separator
30103 Fields within the packet should be separated using @samp{,} @samp{;} or
30104 @samp{:}. Except where otherwise noted all numbers are represented in
30105 @sc{hex} with leading zeros suppressed.
30107 Implementors should note that prior to @value{GDBN} 5.0, the character
30108 @samp{:} could not appear as the third character in a packet (as it
30109 would potentially conflict with the @var{sequence-id}).
30111 @cindex remote protocol, binary data
30112 @anchor{Binary Data}
30113 Binary data in most packets is encoded either as two hexadecimal
30114 digits per byte of binary data. This allowed the traditional remote
30115 protocol to work over connections which were only seven-bit clean.
30116 Some packets designed more recently assume an eight-bit clean
30117 connection, and use a more efficient encoding to send and receive
30120 The binary data representation uses @code{7d} (@sc{ascii} @samp{@}})
30121 as an escape character. Any escaped byte is transmitted as the escape
30122 character followed by the original character XORed with @code{0x20}.
30123 For example, the byte @code{0x7d} would be transmitted as the two
30124 bytes @code{0x7d 0x5d}. The bytes @code{0x23} (@sc{ascii} @samp{#}),
30125 @code{0x24} (@sc{ascii} @samp{$}), and @code{0x7d} (@sc{ascii}
30126 @samp{@}}) must always be escaped. Responses sent by the stub
30127 must also escape @code{0x2a} (@sc{ascii} @samp{*}), so that it
30128 is not interpreted as the start of a run-length encoded sequence
30131 Response @var{data} can be run-length encoded to save space.
30132 Run-length encoding replaces runs of identical characters with one
30133 instance of the repeated character, followed by a @samp{*} and a
30134 repeat count. The repeat count is itself sent encoded, to avoid
30135 binary characters in @var{data}: a value of @var{n} is sent as
30136 @code{@var{n}+29}. For a repeat count greater or equal to 3, this
30137 produces a printable @sc{ascii} character, e.g.@: a space (@sc{ascii}
30138 code 32) for a repeat count of 3. (This is because run-length
30139 encoding starts to win for counts 3 or more.) Thus, for example,
30140 @samp{0* } is a run-length encoding of ``0000'': the space character
30141 after @samp{*} means repeat the leading @code{0} @w{@code{32 - 29 =
30144 The printable characters @samp{#} and @samp{$} or with a numeric value
30145 greater than 126 must not be used. Runs of six repeats (@samp{#}) or
30146 seven repeats (@samp{$}) can be expanded using a repeat count of only
30147 five (@samp{"}). For example, @samp{00000000} can be encoded as
30150 The error response returned for some packets includes a two character
30151 error number. That number is not well defined.
30153 @cindex empty response, for unsupported packets
30154 For any @var{command} not supported by the stub, an empty response
30155 (@samp{$#00}) should be returned. That way it is possible to extend the
30156 protocol. A newer @value{GDBN} can tell if a packet is supported based
30159 A stub is required to support the @samp{g}, @samp{G}, @samp{m}, @samp{M},
30160 @samp{c}, and @samp{s} @var{command}s. All other @var{command}s are
30166 The following table provides a complete list of all currently defined
30167 @var{command}s and their corresponding response @var{data}.
30168 @xref{File-I/O Remote Protocol Extension}, for details about the File
30169 I/O extension of the remote protocol.
30171 Each packet's description has a template showing the packet's overall
30172 syntax, followed by an explanation of the packet's meaning. We
30173 include spaces in some of the templates for clarity; these are not
30174 part of the packet's syntax. No @value{GDBN} packet uses spaces to
30175 separate its components. For example, a template like @samp{foo
30176 @var{bar} @var{baz}} describes a packet beginning with the three ASCII
30177 bytes @samp{foo}, followed by a @var{bar}, followed directly by a
30178 @var{baz}. @value{GDBN} does not transmit a space character between the
30179 @samp{foo} and the @var{bar}, or between the @var{bar} and the
30182 @cindex @var{thread-id}, in remote protocol
30183 @anchor{thread-id syntax}
30184 Several packets and replies include a @var{thread-id} field to identify
30185 a thread. Normally these are positive numbers with a target-specific
30186 interpretation, formatted as big-endian hex strings. A @var{thread-id}
30187 can also be a literal @samp{-1} to indicate all threads, or @samp{0} to
30190 In addition, the remote protocol supports a multiprocess feature in
30191 which the @var{thread-id} syntax is extended to optionally include both
30192 process and thread ID fields, as @samp{p@var{pid}.@var{tid}}.
30193 The @var{pid} (process) and @var{tid} (thread) components each have the
30194 format described above: a positive number with target-specific
30195 interpretation formatted as a big-endian hex string, literal @samp{-1}
30196 to indicate all processes or threads (respectively), or @samp{0} to
30197 indicate an arbitrary process or thread. Specifying just a process, as
30198 @samp{p@var{pid}}, is equivalent to @samp{p@var{pid}.-1}. It is an
30199 error to specify all processes but a specific thread, such as
30200 @samp{p-1.@var{tid}}. Note that the @samp{p} prefix is @emph{not} used
30201 for those packets and replies explicitly documented to include a process
30202 ID, rather than a @var{thread-id}.
30204 The multiprocess @var{thread-id} syntax extensions are only used if both
30205 @value{GDBN} and the stub report support for the @samp{multiprocess}
30206 feature using @samp{qSupported}. @xref{multiprocess extensions}, for
30209 Note that all packet forms beginning with an upper- or lower-case
30210 letter, other than those described here, are reserved for future use.
30212 Here are the packet descriptions.
30217 @cindex @samp{!} packet
30218 @anchor{extended mode}
30219 Enable extended mode. In extended mode, the remote server is made
30220 persistent. The @samp{R} packet is used to restart the program being
30226 The remote target both supports and has enabled extended mode.
30230 @cindex @samp{?} packet
30231 Indicate the reason the target halted. The reply is the same as for
30232 step and continue. This packet has a special interpretation when the
30233 target is in non-stop mode; see @ref{Remote Non-Stop}.
30236 @xref{Stop Reply Packets}, for the reply specifications.
30238 @item A @var{arglen},@var{argnum},@var{arg},@dots{}
30239 @cindex @samp{A} packet
30240 Initialized @code{argv[]} array passed into program. @var{arglen}
30241 specifies the number of bytes in the hex encoded byte stream
30242 @var{arg}. See @code{gdbserver} for more details.
30247 The arguments were set.
30253 @cindex @samp{b} packet
30254 (Don't use this packet; its behavior is not well-defined.)
30255 Change the serial line speed to @var{baud}.
30257 JTC: @emph{When does the transport layer state change? When it's
30258 received, or after the ACK is transmitted. In either case, there are
30259 problems if the command or the acknowledgment packet is dropped.}
30261 Stan: @emph{If people really wanted to add something like this, and get
30262 it working for the first time, they ought to modify ser-unix.c to send
30263 some kind of out-of-band message to a specially-setup stub and have the
30264 switch happen "in between" packets, so that from remote protocol's point
30265 of view, nothing actually happened.}
30267 @item B @var{addr},@var{mode}
30268 @cindex @samp{B} packet
30269 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
30270 breakpoint at @var{addr}.
30272 Don't use this packet. Use the @samp{Z} and @samp{z} packets instead
30273 (@pxref{insert breakpoint or watchpoint packet}).
30275 @cindex @samp{bc} packet
30278 Backward continue. Execute the target system in reverse. No parameter.
30279 @xref{Reverse Execution}, for more information.
30282 @xref{Stop Reply Packets}, for the reply specifications.
30284 @cindex @samp{bs} packet
30287 Backward single step. Execute one instruction in reverse. No parameter.
30288 @xref{Reverse Execution}, for more information.
30291 @xref{Stop Reply Packets}, for the reply specifications.
30293 @item c @r{[}@var{addr}@r{]}
30294 @cindex @samp{c} packet
30295 Continue. @var{addr} is address to resume. If @var{addr} is omitted,
30296 resume at current address.
30299 @xref{Stop Reply Packets}, for the reply specifications.
30301 @item C @var{sig}@r{[};@var{addr}@r{]}
30302 @cindex @samp{C} packet
30303 Continue with signal @var{sig} (hex signal number). If
30304 @samp{;@var{addr}} is omitted, resume at same address.
30307 @xref{Stop Reply Packets}, for the reply specifications.
30310 @cindex @samp{d} packet
30313 Don't use this packet; instead, define a general set packet
30314 (@pxref{General Query Packets}).
30318 @cindex @samp{D} packet
30319 The first form of the packet is used to detach @value{GDBN} from the
30320 remote system. It is sent to the remote target
30321 before @value{GDBN} disconnects via the @code{detach} command.
30323 The second form, including a process ID, is used when multiprocess
30324 protocol extensions are enabled (@pxref{multiprocess extensions}), to
30325 detach only a specific process. The @var{pid} is specified as a
30326 big-endian hex string.
30336 @item F @var{RC},@var{EE},@var{CF};@var{XX}
30337 @cindex @samp{F} packet
30338 A reply from @value{GDBN} to an @samp{F} packet sent by the target.
30339 This is part of the File-I/O protocol extension. @xref{File-I/O
30340 Remote Protocol Extension}, for the specification.
30343 @anchor{read registers packet}
30344 @cindex @samp{g} packet
30345 Read general registers.
30349 @item @var{XX@dots{}}
30350 Each byte of register data is described by two hex digits. The bytes
30351 with the register are transmitted in target byte order. The size of
30352 each register and their position within the @samp{g} packet are
30353 determined by the @value{GDBN} internal gdbarch functions
30354 @code{DEPRECATED_REGISTER_RAW_SIZE} and @code{gdbarch_register_name}. The
30355 specification of several standard @samp{g} packets is specified below.
30360 @item G @var{XX@dots{}}
30361 @cindex @samp{G} packet
30362 Write general registers. @xref{read registers packet}, for a
30363 description of the @var{XX@dots{}} data.
30373 @item H @var{c} @var{thread-id}
30374 @cindex @samp{H} packet
30375 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
30376 @samp{G}, et.al.). @var{c} depends on the operation to be performed: it
30377 should be @samp{c} for step and continue operations, @samp{g} for other
30378 operations. The thread designator @var{thread-id} has the format and
30379 interpretation described in @ref{thread-id syntax}.
30390 @c 'H': How restrictive (or permissive) is the thread model. If a
30391 @c thread is selected and stopped, are other threads allowed
30392 @c to continue to execute? As I mentioned above, I think the
30393 @c semantics of each command when a thread is selected must be
30394 @c described. For example:
30396 @c 'g': If the stub supports threads and a specific thread is
30397 @c selected, returns the register block from that thread;
30398 @c otherwise returns current registers.
30400 @c 'G' If the stub supports threads and a specific thread is
30401 @c selected, sets the registers of the register block of
30402 @c that thread; otherwise sets current registers.
30404 @item i @r{[}@var{addr}@r{[},@var{nnn}@r{]]}
30405 @anchor{cycle step packet}
30406 @cindex @samp{i} packet
30407 Step the remote target by a single clock cycle. If @samp{,@var{nnn}} is
30408 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
30409 step starting at that address.
30412 @cindex @samp{I} packet
30413 Signal, then cycle step. @xref{step with signal packet}. @xref{cycle
30417 @cindex @samp{k} packet
30420 FIXME: @emph{There is no description of how to operate when a specific
30421 thread context has been selected (i.e.@: does 'k' kill only that
30424 @item m @var{addr},@var{length}
30425 @cindex @samp{m} packet
30426 Read @var{length} bytes of memory starting at address @var{addr}.
30427 Note that @var{addr} may not be aligned to any particular boundary.
30429 The stub need not use any particular size or alignment when gathering
30430 data from memory for the response; even if @var{addr} is word-aligned
30431 and @var{length} is a multiple of the word size, the stub is free to
30432 use byte accesses, or not. For this reason, this packet may not be
30433 suitable for accessing memory-mapped I/O devices.
30434 @cindex alignment of remote memory accesses
30435 @cindex size of remote memory accesses
30436 @cindex memory, alignment and size of remote accesses
30440 @item @var{XX@dots{}}
30441 Memory contents; each byte is transmitted as a two-digit hexadecimal
30442 number. The reply may contain fewer bytes than requested if the
30443 server was able to read only part of the region of memory.
30448 @item M @var{addr},@var{length}:@var{XX@dots{}}
30449 @cindex @samp{M} packet
30450 Write @var{length} bytes of memory starting at address @var{addr}.
30451 @var{XX@dots{}} is the data; each byte is transmitted as a two-digit
30452 hexadecimal number.
30459 for an error (this includes the case where only part of the data was
30464 @cindex @samp{p} packet
30465 Read the value of register @var{n}; @var{n} is in hex.
30466 @xref{read registers packet}, for a description of how the returned
30467 register value is encoded.
30471 @item @var{XX@dots{}}
30472 the register's value
30476 Indicating an unrecognized @var{query}.
30479 @item P @var{n@dots{}}=@var{r@dots{}}
30480 @anchor{write register packet}
30481 @cindex @samp{P} packet
30482 Write register @var{n@dots{}} with value @var{r@dots{}}. The register
30483 number @var{n} is in hexadecimal, and @var{r@dots{}} contains two hex
30484 digits for each byte in the register (target byte order).
30494 @item q @var{name} @var{params}@dots{}
30495 @itemx Q @var{name} @var{params}@dots{}
30496 @cindex @samp{q} packet
30497 @cindex @samp{Q} packet
30498 General query (@samp{q}) and set (@samp{Q}). These packets are
30499 described fully in @ref{General Query Packets}.
30502 @cindex @samp{r} packet
30503 Reset the entire system.
30505 Don't use this packet; use the @samp{R} packet instead.
30508 @cindex @samp{R} packet
30509 Restart the program being debugged. @var{XX}, while needed, is ignored.
30510 This packet is only available in extended mode (@pxref{extended mode}).
30512 The @samp{R} packet has no reply.
30514 @item s @r{[}@var{addr}@r{]}
30515 @cindex @samp{s} packet
30516 Single step. @var{addr} is the address at which to resume. If
30517 @var{addr} is omitted, resume at same address.
30520 @xref{Stop Reply Packets}, for the reply specifications.
30522 @item S @var{sig}@r{[};@var{addr}@r{]}
30523 @anchor{step with signal packet}
30524 @cindex @samp{S} packet
30525 Step with signal. This is analogous to the @samp{C} packet, but
30526 requests a single-step, rather than a normal resumption of execution.
30529 @xref{Stop Reply Packets}, for the reply specifications.
30531 @item t @var{addr}:@var{PP},@var{MM}
30532 @cindex @samp{t} packet
30533 Search backwards starting at address @var{addr} for a match with pattern
30534 @var{PP} and mask @var{MM}. @var{PP} and @var{MM} are 4 bytes.
30535 @var{addr} must be at least 3 digits.
30537 @item T @var{thread-id}
30538 @cindex @samp{T} packet
30539 Find out if the thread @var{thread-id} is alive. @xref{thread-id syntax}.
30544 thread is still alive
30550 Packets starting with @samp{v} are identified by a multi-letter name,
30551 up to the first @samp{;} or @samp{?} (or the end of the packet).
30553 @item vAttach;@var{pid}
30554 @cindex @samp{vAttach} packet
30555 Attach to a new process with the specified process ID @var{pid}.
30556 The process ID is a
30557 hexadecimal integer identifying the process. In all-stop mode, all
30558 threads in the attached process are stopped; in non-stop mode, it may be
30559 attached without being stopped if that is supported by the target.
30561 @c In non-stop mode, on a successful vAttach, the stub should set the
30562 @c current thread to a thread of the newly-attached process. After
30563 @c attaching, GDB queries for the attached process's thread ID with qC.
30564 @c Also note that, from a user perspective, whether or not the
30565 @c target is stopped on attach in non-stop mode depends on whether you
30566 @c use the foreground or background version of the attach command, not
30567 @c on what vAttach does; GDB does the right thing with respect to either
30568 @c stopping or restarting threads.
30570 This packet is only available in extended mode (@pxref{extended mode}).
30576 @item @r{Any stop packet}
30577 for success in all-stop mode (@pxref{Stop Reply Packets})
30579 for success in non-stop mode (@pxref{Remote Non-Stop})
30582 @item vCont@r{[};@var{action}@r{[}:@var{thread-id}@r{]]}@dots{}
30583 @cindex @samp{vCont} packet
30584 Resume the inferior, specifying different actions for each thread.
30585 If an action is specified with no @var{thread-id}, then it is applied to any
30586 threads that don't have a specific action specified; if no default action is
30587 specified then other threads should remain stopped in all-stop mode and
30588 in their current state in non-stop mode.
30589 Specifying multiple
30590 default actions is an error; specifying no actions is also an error.
30591 Thread IDs are specified using the syntax described in @ref{thread-id syntax}.
30593 Currently supported actions are:
30599 Continue with signal @var{sig}. The signal @var{sig} should be two hex digits.
30603 Step with signal @var{sig}. The signal @var{sig} should be two hex digits.
30608 The optional argument @var{addr} normally associated with the
30609 @samp{c}, @samp{C}, @samp{s}, and @samp{S} packets is
30610 not supported in @samp{vCont}.
30612 The @samp{t} action is only relevant in non-stop mode
30613 (@pxref{Remote Non-Stop}) and may be ignored by the stub otherwise.
30614 A stop reply should be generated for any affected thread not already stopped.
30615 When a thread is stopped by means of a @samp{t} action,
30616 the corresponding stop reply should indicate that the thread has stopped with
30617 signal @samp{0}, regardless of whether the target uses some other signal
30618 as an implementation detail.
30621 @xref{Stop Reply Packets}, for the reply specifications.
30624 @cindex @samp{vCont?} packet
30625 Request a list of actions supported by the @samp{vCont} packet.
30629 @item vCont@r{[};@var{action}@dots{}@r{]}
30630 The @samp{vCont} packet is supported. Each @var{action} is a supported
30631 command in the @samp{vCont} packet.
30633 The @samp{vCont} packet is not supported.
30636 @item vFile:@var{operation}:@var{parameter}@dots{}
30637 @cindex @samp{vFile} packet
30638 Perform a file operation on the target system. For details,
30639 see @ref{Host I/O Packets}.
30641 @item vFlashErase:@var{addr},@var{length}
30642 @cindex @samp{vFlashErase} packet
30643 Direct the stub to erase @var{length} bytes of flash starting at
30644 @var{addr}. The region may enclose any number of flash blocks, but
30645 its start and end must fall on block boundaries, as indicated by the
30646 flash block size appearing in the memory map (@pxref{Memory Map
30647 Format}). @value{GDBN} groups flash memory programming operations
30648 together, and sends a @samp{vFlashDone} request after each group; the
30649 stub is allowed to delay erase operation until the @samp{vFlashDone}
30650 packet is received.
30652 The stub must support @samp{vCont} if it reports support for
30653 multiprocess extensions (@pxref{multiprocess extensions}). Note that in
30654 this case @samp{vCont} actions can be specified to apply to all threads
30655 in a process by using the @samp{p@var{pid}.-1} form of the
30666 @item vFlashWrite:@var{addr}:@var{XX@dots{}}
30667 @cindex @samp{vFlashWrite} packet
30668 Direct the stub to write data to flash address @var{addr}. The data
30669 is passed in binary form using the same encoding as for the @samp{X}
30670 packet (@pxref{Binary Data}). The memory ranges specified by
30671 @samp{vFlashWrite} packets preceding a @samp{vFlashDone} packet must
30672 not overlap, and must appear in order of increasing addresses
30673 (although @samp{vFlashErase} packets for higher addresses may already
30674 have been received; the ordering is guaranteed only between
30675 @samp{vFlashWrite} packets). If a packet writes to an address that was
30676 neither erased by a preceding @samp{vFlashErase} packet nor by some other
30677 target-specific method, the results are unpredictable.
30685 for vFlashWrite addressing non-flash memory
30691 @cindex @samp{vFlashDone} packet
30692 Indicate to the stub that flash programming operation is finished.
30693 The stub is permitted to delay or batch the effects of a group of
30694 @samp{vFlashErase} and @samp{vFlashWrite} packets until a
30695 @samp{vFlashDone} packet is received. The contents of the affected
30696 regions of flash memory are unpredictable until the @samp{vFlashDone}
30697 request is completed.
30699 @item vKill;@var{pid}
30700 @cindex @samp{vKill} packet
30701 Kill the process with the specified process ID. @var{pid} is a
30702 hexadecimal integer identifying the process. This packet is used in
30703 preference to @samp{k} when multiprocess protocol extensions are
30704 supported; see @ref{multiprocess extensions}.
30714 @item vRun;@var{filename}@r{[};@var{argument}@r{]}@dots{}
30715 @cindex @samp{vRun} packet
30716 Run the program @var{filename}, passing it each @var{argument} on its
30717 command line. The file and arguments are hex-encoded strings. If
30718 @var{filename} is an empty string, the stub may use a default program
30719 (e.g.@: the last program run). The program is created in the stopped
30722 @c FIXME: What about non-stop mode?
30724 This packet is only available in extended mode (@pxref{extended mode}).
30730 @item @r{Any stop packet}
30731 for success (@pxref{Stop Reply Packets})
30735 @anchor{vStopped packet}
30736 @cindex @samp{vStopped} packet
30738 In non-stop mode (@pxref{Remote Non-Stop}), acknowledge a previous stop
30739 reply and prompt for the stub to report another one.
30743 @item @r{Any stop packet}
30744 if there is another unreported stop event (@pxref{Stop Reply Packets})
30746 if there are no unreported stop events
30749 @item X @var{addr},@var{length}:@var{XX@dots{}}
30751 @cindex @samp{X} packet
30752 Write data to memory, where the data is transmitted in binary.
30753 @var{addr} is address, @var{length} is number of bytes,
30754 @samp{@var{XX}@dots{}} is binary data (@pxref{Binary Data}).
30764 @item z @var{type},@var{addr},@var{kind}
30765 @itemx Z @var{type},@var{addr},@var{kind}
30766 @anchor{insert breakpoint or watchpoint packet}
30767 @cindex @samp{z} packet
30768 @cindex @samp{Z} packets
30769 Insert (@samp{Z}) or remove (@samp{z}) a @var{type} breakpoint or
30770 watchpoint starting at address @var{address} of kind @var{kind}.
30772 Each breakpoint and watchpoint packet @var{type} is documented
30775 @emph{Implementation notes: A remote target shall return an empty string
30776 for an unrecognized breakpoint or watchpoint packet @var{type}. A
30777 remote target shall support either both or neither of a given
30778 @samp{Z@var{type}@dots{}} and @samp{z@var{type}@dots{}} packet pair. To
30779 avoid potential problems with duplicate packets, the operations should
30780 be implemented in an idempotent way.}
30782 @item z0,@var{addr},@var{kind}
30783 @itemx Z0,@var{addr},@var{kind}
30784 @cindex @samp{z0} packet
30785 @cindex @samp{Z0} packet
30786 Insert (@samp{Z0}) or remove (@samp{z0}) a memory breakpoint at address
30787 @var{addr} of type @var{kind}.
30789 A memory breakpoint is implemented by replacing the instruction at
30790 @var{addr} with a software breakpoint or trap instruction. The
30791 @var{kind} is target-specific and typically indicates the size of
30792 the breakpoint in bytes that should be inserted. E.g., the @sc{arm}
30793 and @sc{mips} can insert either a 2 or 4 byte breakpoint. Some
30794 architectures have additional meanings for @var{kind};
30795 see @ref{Architecture-Specific Protocol Details}.
30797 @emph{Implementation note: It is possible for a target to copy or move
30798 code that contains memory breakpoints (e.g., when implementing
30799 overlays). The behavior of this packet, in the presence of such a
30800 target, is not defined.}
30812 @item z1,@var{addr},@var{kind}
30813 @itemx Z1,@var{addr},@var{kind}
30814 @cindex @samp{z1} packet
30815 @cindex @samp{Z1} packet
30816 Insert (@samp{Z1}) or remove (@samp{z1}) a hardware breakpoint at
30817 address @var{addr}.
30819 A hardware breakpoint is implemented using a mechanism that is not
30820 dependant on being able to modify the target's memory. @var{kind}
30821 has the same meaning as in @samp{Z0} packets.
30823 @emph{Implementation note: A hardware breakpoint is not affected by code
30836 @item z2,@var{addr},@var{kind}
30837 @itemx Z2,@var{addr},@var{kind}
30838 @cindex @samp{z2} packet
30839 @cindex @samp{Z2} packet
30840 Insert (@samp{Z2}) or remove (@samp{z2}) a write watchpoint at @var{addr}.
30841 @var{kind} is interpreted as the number of bytes to watch.
30853 @item z3,@var{addr},@var{kind}
30854 @itemx Z3,@var{addr},@var{kind}
30855 @cindex @samp{z3} packet
30856 @cindex @samp{Z3} packet
30857 Insert (@samp{Z3}) or remove (@samp{z3}) a read watchpoint at @var{addr}.
30858 @var{kind} is interpreted as the number of bytes to watch.
30870 @item z4,@var{addr},@var{kind}
30871 @itemx Z4,@var{addr},@var{kind}
30872 @cindex @samp{z4} packet
30873 @cindex @samp{Z4} packet
30874 Insert (@samp{Z4}) or remove (@samp{z4}) an access watchpoint at @var{addr}.
30875 @var{kind} is interpreted as the number of bytes to watch.
30889 @node Stop Reply Packets
30890 @section Stop Reply Packets
30891 @cindex stop reply packets
30893 The @samp{C}, @samp{c}, @samp{S}, @samp{s}, @samp{vCont},
30894 @samp{vAttach}, @samp{vRun}, @samp{vStopped}, and @samp{?} packets can
30895 receive any of the below as a reply. Except for @samp{?}
30896 and @samp{vStopped}, that reply is only returned
30897 when the target halts. In the below the exact meaning of @dfn{signal
30898 number} is defined by the header @file{include/gdb/signals.h} in the
30899 @value{GDBN} source code.
30901 As in the description of request packets, we include spaces in the
30902 reply templates for clarity; these are not part of the reply packet's
30903 syntax. No @value{GDBN} stop reply packet uses spaces to separate its
30909 The program received signal number @var{AA} (a two-digit hexadecimal
30910 number). This is equivalent to a @samp{T} response with no
30911 @var{n}:@var{r} pairs.
30913 @item T @var{AA} @var{n1}:@var{r1};@var{n2}:@var{r2};@dots{}
30914 @cindex @samp{T} packet reply
30915 The program received signal number @var{AA} (a two-digit hexadecimal
30916 number). This is equivalent to an @samp{S} response, except that the
30917 @samp{@var{n}:@var{r}} pairs can carry values of important registers
30918 and other information directly in the stop reply packet, reducing
30919 round-trip latency. Single-step and breakpoint traps are reported
30920 this way. Each @samp{@var{n}:@var{r}} pair is interpreted as follows:
30924 If @var{n} is a hexadecimal number, it is a register number, and the
30925 corresponding @var{r} gives that register's value. @var{r} is a
30926 series of bytes in target byte order, with each byte given by a
30927 two-digit hex number.
30930 If @var{n} is @samp{thread}, then @var{r} is the @var{thread-id} of
30931 the stopped thread, as specified in @ref{thread-id syntax}.
30934 If @var{n} is @samp{core}, then @var{r} is the hexadecimal number of
30935 the core on which the stop event was detected.
30938 If @var{n} is a recognized @dfn{stop reason}, it describes a more
30939 specific event that stopped the target. The currently defined stop
30940 reasons are listed below. @var{aa} should be @samp{05}, the trap
30941 signal. At most one stop reason should be present.
30944 Otherwise, @value{GDBN} should ignore this @samp{@var{n}:@var{r}} pair
30945 and go on to the next; this allows us to extend the protocol in the
30949 The currently defined stop reasons are:
30955 The packet indicates a watchpoint hit, and @var{r} is the data address, in
30958 @cindex shared library events, remote reply
30960 The packet indicates that the loaded libraries have changed.
30961 @value{GDBN} should use @samp{qXfer:libraries:read} to fetch a new
30962 list of loaded libraries. @var{r} is ignored.
30964 @cindex replay log events, remote reply
30966 The packet indicates that the target cannot continue replaying
30967 logged execution events, because it has reached the end (or the
30968 beginning when executing backward) of the log. The value of @var{r}
30969 will be either @samp{begin} or @samp{end}. @xref{Reverse Execution},
30970 for more information.
30974 @itemx W @var{AA} ; process:@var{pid}
30975 The process exited, and @var{AA} is the exit status. This is only
30976 applicable to certain targets.
30978 The second form of the response, including the process ID of the exited
30979 process, can be used only when @value{GDBN} has reported support for
30980 multiprocess protocol extensions; see @ref{multiprocess extensions}.
30981 The @var{pid} is formatted as a big-endian hex string.
30984 @itemx X @var{AA} ; process:@var{pid}
30985 The process terminated with signal @var{AA}.
30987 The second form of the response, including the process ID of the
30988 terminated process, can be used only when @value{GDBN} has reported
30989 support for multiprocess protocol extensions; see @ref{multiprocess
30990 extensions}. The @var{pid} is formatted as a big-endian hex string.
30992 @item O @var{XX}@dots{}
30993 @samp{@var{XX}@dots{}} is hex encoding of @sc{ascii} data, to be
30994 written as the program's console output. This can happen at any time
30995 while the program is running and the debugger should continue to wait
30996 for @samp{W}, @samp{T}, etc. This reply is not permitted in non-stop mode.
30998 @item F @var{call-id},@var{parameter}@dots{}
30999 @var{call-id} is the identifier which says which host system call should
31000 be called. This is just the name of the function. Translation into the
31001 correct system call is only applicable as it's defined in @value{GDBN}.
31002 @xref{File-I/O Remote Protocol Extension}, for a list of implemented
31005 @samp{@var{parameter}@dots{}} is a list of parameters as defined for
31006 this very system call.
31008 The target replies with this packet when it expects @value{GDBN} to
31009 call a host system call on behalf of the target. @value{GDBN} replies
31010 with an appropriate @samp{F} packet and keeps up waiting for the next
31011 reply packet from the target. The latest @samp{C}, @samp{c}, @samp{S}
31012 or @samp{s} action is expected to be continued. @xref{File-I/O Remote
31013 Protocol Extension}, for more details.
31017 @node General Query Packets
31018 @section General Query Packets
31019 @cindex remote query requests
31021 Packets starting with @samp{q} are @dfn{general query packets};
31022 packets starting with @samp{Q} are @dfn{general set packets}. General
31023 query and set packets are a semi-unified form for retrieving and
31024 sending information to and from the stub.
31026 The initial letter of a query or set packet is followed by a name
31027 indicating what sort of thing the packet applies to. For example,
31028 @value{GDBN} may use a @samp{qSymbol} packet to exchange symbol
31029 definitions with the stub. These packet names follow some
31034 The name must not contain commas, colons or semicolons.
31036 Most @value{GDBN} query and set packets have a leading upper case
31039 The names of custom vendor packets should use a company prefix, in
31040 lower case, followed by a period. For example, packets designed at
31041 the Acme Corporation might begin with @samp{qacme.foo} (for querying
31042 foos) or @samp{Qacme.bar} (for setting bars).
31045 The name of a query or set packet should be separated from any
31046 parameters by a @samp{:}; the parameters themselves should be
31047 separated by @samp{,} or @samp{;}. Stubs must be careful to match the
31048 full packet name, and check for a separator or the end of the packet,
31049 in case two packet names share a common prefix. New packets should not begin
31050 with @samp{qC}, @samp{qP}, or @samp{qL}@footnote{The @samp{qP} and @samp{qL}
31051 packets predate these conventions, and have arguments without any terminator
31052 for the packet name; we suspect they are in widespread use in places that
31053 are difficult to upgrade. The @samp{qC} packet has no arguments, but some
31054 existing stubs (e.g.@: RedBoot) are known to not check for the end of the
31057 Like the descriptions of the other packets, each description here
31058 has a template showing the packet's overall syntax, followed by an
31059 explanation of the packet's meaning. We include spaces in some of the
31060 templates for clarity; these are not part of the packet's syntax. No
31061 @value{GDBN} packet uses spaces to separate its components.
31063 Here are the currently defined query and set packets:
31068 @cindex current thread, remote request
31069 @cindex @samp{qC} packet
31070 Return the current thread ID.
31074 @item QC @var{thread-id}
31075 Where @var{thread-id} is a thread ID as documented in
31076 @ref{thread-id syntax}.
31077 @item @r{(anything else)}
31078 Any other reply implies the old thread ID.
31081 @item qCRC:@var{addr},@var{length}
31082 @cindex CRC of memory block, remote request
31083 @cindex @samp{qCRC} packet
31084 Compute the CRC checksum of a block of memory using CRC-32 defined in
31085 IEEE 802.3. The CRC is computed byte at a time, taking the most
31086 significant bit of each byte first. The initial pattern code
31087 @code{0xffffffff} is used to ensure leading zeros affect the CRC.
31089 @emph{Note:} This is the same CRC used in validating separate debug
31090 files (@pxref{Separate Debug Files, , Debugging Information in Separate
31091 Files}). However the algorithm is slightly different. When validating
31092 separate debug files, the CRC is computed taking the @emph{least}
31093 significant bit of each byte first, and the final result is inverted to
31094 detect trailing zeros.
31099 An error (such as memory fault)
31100 @item C @var{crc32}
31101 The specified memory region's checksum is @var{crc32}.
31105 @itemx qsThreadInfo
31106 @cindex list active threads, remote request
31107 @cindex @samp{qfThreadInfo} packet
31108 @cindex @samp{qsThreadInfo} packet
31109 Obtain a list of all active thread IDs from the target (OS). Since there
31110 may be too many active threads to fit into one reply packet, this query
31111 works iteratively: it may require more than one query/reply sequence to
31112 obtain the entire list of threads. The first query of the sequence will
31113 be the @samp{qfThreadInfo} query; subsequent queries in the
31114 sequence will be the @samp{qsThreadInfo} query.
31116 NOTE: This packet replaces the @samp{qL} query (see below).
31120 @item m @var{thread-id}
31122 @item m @var{thread-id},@var{thread-id}@dots{}
31123 a comma-separated list of thread IDs
31125 (lower case letter @samp{L}) denotes end of list.
31128 In response to each query, the target will reply with a list of one or
31129 more thread IDs, separated by commas.
31130 @value{GDBN} will respond to each reply with a request for more thread
31131 ids (using the @samp{qs} form of the query), until the target responds
31132 with @samp{l} (lower-case el, for @dfn{last}).
31133 Refer to @ref{thread-id syntax}, for the format of the @var{thread-id}
31136 @item qGetTLSAddr:@var{thread-id},@var{offset},@var{lm}
31137 @cindex get thread-local storage address, remote request
31138 @cindex @samp{qGetTLSAddr} packet
31139 Fetch the address associated with thread local storage specified
31140 by @var{thread-id}, @var{offset}, and @var{lm}.
31142 @var{thread-id} is the thread ID associated with the
31143 thread for which to fetch the TLS address. @xref{thread-id syntax}.
31145 @var{offset} is the (big endian, hex encoded) offset associated with the
31146 thread local variable. (This offset is obtained from the debug
31147 information associated with the variable.)
31149 @var{lm} is the (big endian, hex encoded) OS/ABI-specific encoding of the
31150 the load module associated with the thread local storage. For example,
31151 a @sc{gnu}/Linux system will pass the link map address of the shared
31152 object associated with the thread local storage under consideration.
31153 Other operating environments may choose to represent the load module
31154 differently, so the precise meaning of this parameter will vary.
31158 @item @var{XX}@dots{}
31159 Hex encoded (big endian) bytes representing the address of the thread
31160 local storage requested.
31163 An error occurred. @var{nn} are hex digits.
31166 An empty reply indicates that @samp{qGetTLSAddr} is not supported by the stub.
31169 @item qGetTIBAddr:@var{thread-id}
31170 @cindex get thread information block address
31171 @cindex @samp{qGetTIBAddr} packet
31172 Fetch address of the Windows OS specific Thread Information Block.
31174 @var{thread-id} is the thread ID associated with the thread.
31178 @item @var{XX}@dots{}
31179 Hex encoded (big endian) bytes representing the linear address of the
31180 thread information block.
31183 An error occured. This means that either the thread was not found, or the
31184 address could not be retrieved.
31187 An empty reply indicates that @samp{qGetTIBAddr} is not supported by the stub.
31190 @item qL @var{startflag} @var{threadcount} @var{nextthread}
31191 Obtain thread information from RTOS. Where: @var{startflag} (one hex
31192 digit) is one to indicate the first query and zero to indicate a
31193 subsequent query; @var{threadcount} (two hex digits) is the maximum
31194 number of threads the response packet can contain; and @var{nextthread}
31195 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
31196 returned in the response as @var{argthread}.
31198 Don't use this packet; use the @samp{qfThreadInfo} query instead (see above).
31202 @item qM @var{count} @var{done} @var{argthread} @var{thread}@dots{}
31203 Where: @var{count} (two hex digits) is the number of threads being
31204 returned; @var{done} (one hex digit) is zero to indicate more threads
31205 and one indicates no further threads; @var{argthreadid} (eight hex
31206 digits) is @var{nextthread} from the request packet; @var{thread}@dots{}
31207 is a sequence of thread IDs from the target. @var{threadid} (eight hex
31208 digits). See @code{remote.c:parse_threadlist_response()}.
31212 @cindex section offsets, remote request
31213 @cindex @samp{qOffsets} packet
31214 Get section offsets that the target used when relocating the downloaded
31219 @item Text=@var{xxx};Data=@var{yyy}@r{[};Bss=@var{zzz}@r{]}
31220 Relocate the @code{Text} section by @var{xxx} from its original address.
31221 Relocate the @code{Data} section by @var{yyy} from its original address.
31222 If the object file format provides segment information (e.g.@: @sc{elf}
31223 @samp{PT_LOAD} program headers), @value{GDBN} will relocate entire
31224 segments by the supplied offsets.
31226 @emph{Note: while a @code{Bss} offset may be included in the response,
31227 @value{GDBN} ignores this and instead applies the @code{Data} offset
31228 to the @code{Bss} section.}
31230 @item TextSeg=@var{xxx}@r{[};DataSeg=@var{yyy}@r{]}
31231 Relocate the first segment of the object file, which conventionally
31232 contains program code, to a starting address of @var{xxx}. If
31233 @samp{DataSeg} is specified, relocate the second segment, which
31234 conventionally contains modifiable data, to a starting address of
31235 @var{yyy}. @value{GDBN} will report an error if the object file
31236 does not contain segment information, or does not contain at least
31237 as many segments as mentioned in the reply. Extra segments are
31238 kept at fixed offsets relative to the last relocated segment.
31241 @item qP @var{mode} @var{thread-id}
31242 @cindex thread information, remote request
31243 @cindex @samp{qP} packet
31244 Returns information on @var{thread-id}. Where: @var{mode} is a hex
31245 encoded 32 bit mode; @var{thread-id} is a thread ID
31246 (@pxref{thread-id syntax}).
31248 Don't use this packet; use the @samp{qThreadExtraInfo} query instead
31251 Reply: see @code{remote.c:remote_unpack_thread_info_response()}.
31255 @cindex non-stop mode, remote request
31256 @cindex @samp{QNonStop} packet
31258 Enter non-stop (@samp{QNonStop:1}) or all-stop (@samp{QNonStop:0}) mode.
31259 @xref{Remote Non-Stop}, for more information.
31264 The request succeeded.
31267 An error occurred. @var{nn} are hex digits.
31270 An empty reply indicates that @samp{QNonStop} is not supported by
31274 This packet is not probed by default; the remote stub must request it,
31275 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
31276 Use of this packet is controlled by the @code{set non-stop} command;
31277 @pxref{Non-Stop Mode}.
31279 @item QPassSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
31280 @cindex pass signals to inferior, remote request
31281 @cindex @samp{QPassSignals} packet
31282 @anchor{QPassSignals}
31283 Each listed @var{signal} should be passed directly to the inferior process.
31284 Signals are numbered identically to continue packets and stop replies
31285 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
31286 strictly greater than the previous item. These signals do not need to stop
31287 the inferior, or be reported to @value{GDBN}. All other signals should be
31288 reported to @value{GDBN}. Multiple @samp{QPassSignals} packets do not
31289 combine; any earlier @samp{QPassSignals} list is completely replaced by the
31290 new list. This packet improves performance when using @samp{handle
31291 @var{signal} nostop noprint pass}.
31296 The request succeeded.
31299 An error occurred. @var{nn} are hex digits.
31302 An empty reply indicates that @samp{QPassSignals} is not supported by
31306 Use of this packet is controlled by the @code{set remote pass-signals}
31307 command (@pxref{Remote Configuration, set remote pass-signals}).
31308 This packet is not probed by default; the remote stub must request it,
31309 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
31311 @item qRcmd,@var{command}
31312 @cindex execute remote command, remote request
31313 @cindex @samp{qRcmd} packet
31314 @var{command} (hex encoded) is passed to the local interpreter for
31315 execution. Invalid commands should be reported using the output
31316 string. Before the final result packet, the target may also respond
31317 with a number of intermediate @samp{O@var{output}} console output
31318 packets. @emph{Implementors should note that providing access to a
31319 stubs's interpreter may have security implications}.
31324 A command response with no output.
31326 A command response with the hex encoded output string @var{OUTPUT}.
31328 Indicate a badly formed request.
31330 An empty reply indicates that @samp{qRcmd} is not recognized.
31333 (Note that the @code{qRcmd} packet's name is separated from the
31334 command by a @samp{,}, not a @samp{:}, contrary to the naming
31335 conventions above. Please don't use this packet as a model for new
31338 @item qSearch:memory:@var{address};@var{length};@var{search-pattern}
31339 @cindex searching memory, in remote debugging
31340 @cindex @samp{qSearch:memory} packet
31341 @anchor{qSearch memory}
31342 Search @var{length} bytes at @var{address} for @var{search-pattern}.
31343 @var{address} and @var{length} are encoded in hex.
31344 @var{search-pattern} is a sequence of bytes, hex encoded.
31349 The pattern was not found.
31351 The pattern was found at @var{address}.
31353 A badly formed request or an error was encountered while searching memory.
31355 An empty reply indicates that @samp{qSearch:memory} is not recognized.
31358 @item QStartNoAckMode
31359 @cindex @samp{QStartNoAckMode} packet
31360 @anchor{QStartNoAckMode}
31361 Request that the remote stub disable the normal @samp{+}/@samp{-}
31362 protocol acknowledgments (@pxref{Packet Acknowledgment}).
31367 The stub has switched to no-acknowledgment mode.
31368 @value{GDBN} acknowledges this reponse,
31369 but neither the stub nor @value{GDBN} shall send or expect further
31370 @samp{+}/@samp{-} acknowledgments in the current connection.
31372 An empty reply indicates that the stub does not support no-acknowledgment mode.
31375 @item qSupported @r{[}:@var{gdbfeature} @r{[};@var{gdbfeature}@r{]}@dots{} @r{]}
31376 @cindex supported packets, remote query
31377 @cindex features of the remote protocol
31378 @cindex @samp{qSupported} packet
31379 @anchor{qSupported}
31380 Tell the remote stub about features supported by @value{GDBN}, and
31381 query the stub for features it supports. This packet allows
31382 @value{GDBN} and the remote stub to take advantage of each others'
31383 features. @samp{qSupported} also consolidates multiple feature probes
31384 at startup, to improve @value{GDBN} performance---a single larger
31385 packet performs better than multiple smaller probe packets on
31386 high-latency links. Some features may enable behavior which must not
31387 be on by default, e.g.@: because it would confuse older clients or
31388 stubs. Other features may describe packets which could be
31389 automatically probed for, but are not. These features must be
31390 reported before @value{GDBN} will use them. This ``default
31391 unsupported'' behavior is not appropriate for all packets, but it
31392 helps to keep the initial connection time under control with new
31393 versions of @value{GDBN} which support increasing numbers of packets.
31397 @item @var{stubfeature} @r{[};@var{stubfeature}@r{]}@dots{}
31398 The stub supports or does not support each returned @var{stubfeature},
31399 depending on the form of each @var{stubfeature} (see below for the
31402 An empty reply indicates that @samp{qSupported} is not recognized,
31403 or that no features needed to be reported to @value{GDBN}.
31406 The allowed forms for each feature (either a @var{gdbfeature} in the
31407 @samp{qSupported} packet, or a @var{stubfeature} in the response)
31411 @item @var{name}=@var{value}
31412 The remote protocol feature @var{name} is supported, and associated
31413 with the specified @var{value}. The format of @var{value} depends
31414 on the feature, but it must not include a semicolon.
31416 The remote protocol feature @var{name} is supported, and does not
31417 need an associated value.
31419 The remote protocol feature @var{name} is not supported.
31421 The remote protocol feature @var{name} may be supported, and
31422 @value{GDBN} should auto-detect support in some other way when it is
31423 needed. This form will not be used for @var{gdbfeature} notifications,
31424 but may be used for @var{stubfeature} responses.
31427 Whenever the stub receives a @samp{qSupported} request, the
31428 supplied set of @value{GDBN} features should override any previous
31429 request. This allows @value{GDBN} to put the stub in a known
31430 state, even if the stub had previously been communicating with
31431 a different version of @value{GDBN}.
31433 The following values of @var{gdbfeature} (for the packet sent by @value{GDBN})
31438 This feature indicates whether @value{GDBN} supports multiprocess
31439 extensions to the remote protocol. @value{GDBN} does not use such
31440 extensions unless the stub also reports that it supports them by
31441 including @samp{multiprocess+} in its @samp{qSupported} reply.
31442 @xref{multiprocess extensions}, for details.
31445 This feature indicates that @value{GDBN} supports the XML target
31446 description. If the stub sees @samp{xmlRegisters=} with target
31447 specific strings separated by a comma, it will report register
31451 Stubs should ignore any unknown values for
31452 @var{gdbfeature}. Any @value{GDBN} which sends a @samp{qSupported}
31453 packet supports receiving packets of unlimited length (earlier
31454 versions of @value{GDBN} may reject overly long responses). Additional values
31455 for @var{gdbfeature} may be defined in the future to let the stub take
31456 advantage of new features in @value{GDBN}, e.g.@: incompatible
31457 improvements in the remote protocol---the @samp{multiprocess} feature is
31458 an example of such a feature. The stub's reply should be independent
31459 of the @var{gdbfeature} entries sent by @value{GDBN}; first @value{GDBN}
31460 describes all the features it supports, and then the stub replies with
31461 all the features it supports.
31463 Similarly, @value{GDBN} will silently ignore unrecognized stub feature
31464 responses, as long as each response uses one of the standard forms.
31466 Some features are flags. A stub which supports a flag feature
31467 should respond with a @samp{+} form response. Other features
31468 require values, and the stub should respond with an @samp{=}
31471 Each feature has a default value, which @value{GDBN} will use if
31472 @samp{qSupported} is not available or if the feature is not mentioned
31473 in the @samp{qSupported} response. The default values are fixed; a
31474 stub is free to omit any feature responses that match the defaults.
31476 Not all features can be probed, but for those which can, the probing
31477 mechanism is useful: in some cases, a stub's internal
31478 architecture may not allow the protocol layer to know some information
31479 about the underlying target in advance. This is especially common in
31480 stubs which may be configured for multiple targets.
31482 These are the currently defined stub features and their properties:
31484 @multitable @columnfractions 0.35 0.2 0.12 0.2
31485 @c NOTE: The first row should be @headitem, but we do not yet require
31486 @c a new enough version of Texinfo (4.7) to use @headitem.
31488 @tab Value Required
31492 @item @samp{PacketSize}
31497 @item @samp{qXfer:auxv:read}
31502 @item @samp{qXfer:features:read}
31507 @item @samp{qXfer:libraries:read}
31512 @item @samp{qXfer:memory-map:read}
31517 @item @samp{qXfer:spu:read}
31522 @item @samp{qXfer:spu:write}
31527 @item @samp{qXfer:siginfo:read}
31532 @item @samp{qXfer:siginfo:write}
31537 @item @samp{qXfer:threads:read}
31543 @item @samp{QNonStop}
31548 @item @samp{QPassSignals}
31553 @item @samp{QStartNoAckMode}
31558 @item @samp{multiprocess}
31563 @item @samp{ConditionalTracepoints}
31568 @item @samp{ReverseContinue}
31573 @item @samp{ReverseStep}
31578 @item @samp{TracepointSource}
31585 These are the currently defined stub features, in more detail:
31588 @cindex packet size, remote protocol
31589 @item PacketSize=@var{bytes}
31590 The remote stub can accept packets up to at least @var{bytes} in
31591 length. @value{GDBN} will send packets up to this size for bulk
31592 transfers, and will never send larger packets. This is a limit on the
31593 data characters in the packet, including the frame and checksum.
31594 There is no trailing NUL byte in a remote protocol packet; if the stub
31595 stores packets in a NUL-terminated format, it should allow an extra
31596 byte in its buffer for the NUL. If this stub feature is not supported,
31597 @value{GDBN} guesses based on the size of the @samp{g} packet response.
31599 @item qXfer:auxv:read
31600 The remote stub understands the @samp{qXfer:auxv:read} packet
31601 (@pxref{qXfer auxiliary vector read}).
31603 @item qXfer:features:read
31604 The remote stub understands the @samp{qXfer:features:read} packet
31605 (@pxref{qXfer target description read}).
31607 @item qXfer:libraries:read
31608 The remote stub understands the @samp{qXfer:libraries:read} packet
31609 (@pxref{qXfer library list read}).
31611 @item qXfer:memory-map:read
31612 The remote stub understands the @samp{qXfer:memory-map:read} packet
31613 (@pxref{qXfer memory map read}).
31615 @item qXfer:spu:read
31616 The remote stub understands the @samp{qXfer:spu:read} packet
31617 (@pxref{qXfer spu read}).
31619 @item qXfer:spu:write
31620 The remote stub understands the @samp{qXfer:spu:write} packet
31621 (@pxref{qXfer spu write}).
31623 @item qXfer:siginfo:read
31624 The remote stub understands the @samp{qXfer:siginfo:read} packet
31625 (@pxref{qXfer siginfo read}).
31627 @item qXfer:siginfo:write
31628 The remote stub understands the @samp{qXfer:siginfo:write} packet
31629 (@pxref{qXfer siginfo write}).
31631 @item qXfer:threads:read
31632 The remote stub understands the @samp{qXfer:threads:read} packet
31633 (@pxref{qXfer threads read}).
31636 The remote stub understands the @samp{QNonStop} packet
31637 (@pxref{QNonStop}).
31640 The remote stub understands the @samp{QPassSignals} packet
31641 (@pxref{QPassSignals}).
31643 @item QStartNoAckMode
31644 The remote stub understands the @samp{QStartNoAckMode} packet and
31645 prefers to operate in no-acknowledgment mode. @xref{Packet Acknowledgment}.
31648 @anchor{multiprocess extensions}
31649 @cindex multiprocess extensions, in remote protocol
31650 The remote stub understands the multiprocess extensions to the remote
31651 protocol syntax. The multiprocess extensions affect the syntax of
31652 thread IDs in both packets and replies (@pxref{thread-id syntax}), and
31653 add process IDs to the @samp{D} packet and @samp{W} and @samp{X}
31654 replies. Note that reporting this feature indicates support for the
31655 syntactic extensions only, not that the stub necessarily supports
31656 debugging of more than one process at a time. The stub must not use
31657 multiprocess extensions in packet replies unless @value{GDBN} has also
31658 indicated it supports them in its @samp{qSupported} request.
31660 @item qXfer:osdata:read
31661 The remote stub understands the @samp{qXfer:osdata:read} packet
31662 ((@pxref{qXfer osdata read}).
31664 @item ConditionalTracepoints
31665 The remote stub accepts and implements conditional expressions defined
31666 for tracepoints (@pxref{Tracepoint Conditions}).
31668 @item ReverseContinue
31669 The remote stub accepts and implements the reverse continue packet
31673 The remote stub accepts and implements the reverse step packet
31676 @item TracepointSource
31677 The remote stub understands the @samp{QTDPsrc} packet that supplies
31678 the source form of tracepoint definitions.
31683 @cindex symbol lookup, remote request
31684 @cindex @samp{qSymbol} packet
31685 Notify the target that @value{GDBN} is prepared to serve symbol lookup
31686 requests. Accept requests from the target for the values of symbols.
31691 The target does not need to look up any (more) symbols.
31692 @item qSymbol:@var{sym_name}
31693 The target requests the value of symbol @var{sym_name} (hex encoded).
31694 @value{GDBN} may provide the value by using the
31695 @samp{qSymbol:@var{sym_value}:@var{sym_name}} message, described
31699 @item qSymbol:@var{sym_value}:@var{sym_name}
31700 Set the value of @var{sym_name} to @var{sym_value}.
31702 @var{sym_name} (hex encoded) is the name of a symbol whose value the
31703 target has previously requested.
31705 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
31706 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
31712 The target does not need to look up any (more) symbols.
31713 @item qSymbol:@var{sym_name}
31714 The target requests the value of a new symbol @var{sym_name} (hex
31715 encoded). @value{GDBN} will continue to supply the values of symbols
31716 (if available), until the target ceases to request them.
31721 @item QTDisconnected
31728 @xref{Tracepoint Packets}.
31730 @item qThreadExtraInfo,@var{thread-id}
31731 @cindex thread attributes info, remote request
31732 @cindex @samp{qThreadExtraInfo} packet
31733 Obtain a printable string description of a thread's attributes from
31734 the target OS. @var{thread-id} is a thread ID;
31735 see @ref{thread-id syntax}. This
31736 string may contain anything that the target OS thinks is interesting
31737 for @value{GDBN} to tell the user about the thread. The string is
31738 displayed in @value{GDBN}'s @code{info threads} display. Some
31739 examples of possible thread extra info strings are @samp{Runnable}, or
31740 @samp{Blocked on Mutex}.
31744 @item @var{XX}@dots{}
31745 Where @samp{@var{XX}@dots{}} is a hex encoding of @sc{ascii} data,
31746 comprising the printable string containing the extra information about
31747 the thread's attributes.
31750 (Note that the @code{qThreadExtraInfo} packet's name is separated from
31751 the command by a @samp{,}, not a @samp{:}, contrary to the naming
31752 conventions above. Please don't use this packet as a model for new
31764 @xref{Tracepoint Packets}.
31766 @item qXfer:@var{object}:read:@var{annex}:@var{offset},@var{length}
31767 @cindex read special object, remote request
31768 @cindex @samp{qXfer} packet
31769 @anchor{qXfer read}
31770 Read uninterpreted bytes from the target's special data area
31771 identified by the keyword @var{object}. Request @var{length} bytes
31772 starting at @var{offset} bytes into the data. The content and
31773 encoding of @var{annex} is specific to @var{object}; it can supply
31774 additional details about what data to access.
31776 Here are the specific requests of this form defined so far. All
31777 @samp{qXfer:@var{object}:read:@dots{}} requests use the same reply
31778 formats, listed below.
31781 @item qXfer:auxv:read::@var{offset},@var{length}
31782 @anchor{qXfer auxiliary vector read}
31783 Access the target's @dfn{auxiliary vector}. @xref{OS Information,
31784 auxiliary vector}. Note @var{annex} must be empty.
31786 This packet is not probed by default; the remote stub must request it,
31787 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
31789 @item qXfer:features:read:@var{annex}:@var{offset},@var{length}
31790 @anchor{qXfer target description read}
31791 Access the @dfn{target description}. @xref{Target Descriptions}. The
31792 annex specifies which XML document to access. The main description is
31793 always loaded from the @samp{target.xml} annex.
31795 This packet is not probed by default; the remote stub must request it,
31796 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
31798 @item qXfer:libraries:read:@var{annex}:@var{offset},@var{length}
31799 @anchor{qXfer library list read}
31800 Access the target's list of loaded libraries. @xref{Library List Format}.
31801 The annex part of the generic @samp{qXfer} packet must be empty
31802 (@pxref{qXfer read}).
31804 Targets which maintain a list of libraries in the program's memory do
31805 not need to implement this packet; it is designed for platforms where
31806 the operating system manages the list of loaded libraries.
31808 This packet is not probed by default; the remote stub must request it,
31809 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
31811 @item qXfer:memory-map:read::@var{offset},@var{length}
31812 @anchor{qXfer memory map read}
31813 Access the target's @dfn{memory-map}. @xref{Memory Map Format}. The
31814 annex part of the generic @samp{qXfer} packet must be empty
31815 (@pxref{qXfer read}).
31817 This packet is not probed by default; the remote stub must request it,
31818 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
31820 @item qXfer:siginfo:read::@var{offset},@var{length}
31821 @anchor{qXfer siginfo read}
31822 Read contents of the extra signal information on the target
31823 system. The annex part of the generic @samp{qXfer} packet must be
31824 empty (@pxref{qXfer read}).
31826 This packet is not probed by default; the remote stub must request it,
31827 by supplying an appropriate @samp{qSupported} response
31828 (@pxref{qSupported}).
31830 @item qXfer:spu:read:@var{annex}:@var{offset},@var{length}
31831 @anchor{qXfer spu read}
31832 Read contents of an @code{spufs} file on the target system. The
31833 annex specifies which file to read; it must be of the form
31834 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
31835 in the target process, and @var{name} identifes the @code{spufs} file
31836 in that context to be accessed.
31838 This packet is not probed by default; the remote stub must request it,
31839 by supplying an appropriate @samp{qSupported} response
31840 (@pxref{qSupported}).
31842 @item qXfer:threads:read::@var{offset},@var{length}
31843 @anchor{qXfer threads read}
31844 Access the list of threads on target. @xref{Thread List Format}. The
31845 annex part of the generic @samp{qXfer} packet must be empty
31846 (@pxref{qXfer read}).
31848 This packet is not probed by default; the remote stub must request it,
31849 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
31851 @item qXfer:osdata:read::@var{offset},@var{length}
31852 @anchor{qXfer osdata read}
31853 Access the target's @dfn{operating system information}.
31854 @xref{Operating System Information}.
31861 Data @var{data} (@pxref{Binary Data}) has been read from the
31862 target. There may be more data at a higher address (although
31863 it is permitted to return @samp{m} even for the last valid
31864 block of data, as long as at least one byte of data was read).
31865 @var{data} may have fewer bytes than the @var{length} in the
31869 Data @var{data} (@pxref{Binary Data}) has been read from the target.
31870 There is no more data to be read. @var{data} may have fewer bytes
31871 than the @var{length} in the request.
31874 The @var{offset} in the request is at the end of the data.
31875 There is no more data to be read.
31878 The request was malformed, or @var{annex} was invalid.
31881 The offset was invalid, or there was an error encountered reading the data.
31882 @var{nn} is a hex-encoded @code{errno} value.
31885 An empty reply indicates the @var{object} string was not recognized by
31886 the stub, or that the object does not support reading.
31889 @item qXfer:@var{object}:write:@var{annex}:@var{offset}:@var{data}@dots{}
31890 @cindex write data into object, remote request
31891 @anchor{qXfer write}
31892 Write uninterpreted bytes into the target's special data area
31893 identified by the keyword @var{object}, starting at @var{offset} bytes
31894 into the data. @var{data}@dots{} is the binary-encoded data
31895 (@pxref{Binary Data}) to be written. The content and encoding of @var{annex}
31896 is specific to @var{object}; it can supply additional details about what data
31899 Here are the specific requests of this form defined so far. All
31900 @samp{qXfer:@var{object}:write:@dots{}} requests use the same reply
31901 formats, listed below.
31904 @item qXfer:siginfo:write::@var{offset}:@var{data}@dots{}
31905 @anchor{qXfer siginfo write}
31906 Write @var{data} to the extra signal information on the target system.
31907 The annex part of the generic @samp{qXfer} packet must be
31908 empty (@pxref{qXfer write}).
31910 This packet is not probed by default; the remote stub must request it,
31911 by supplying an appropriate @samp{qSupported} response
31912 (@pxref{qSupported}).
31914 @item qXfer:spu:write:@var{annex}:@var{offset}:@var{data}@dots{}
31915 @anchor{qXfer spu write}
31916 Write @var{data} to an @code{spufs} file on the target system. The
31917 annex specifies which file to write; it must be of the form
31918 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
31919 in the target process, and @var{name} identifes the @code{spufs} file
31920 in that context to be accessed.
31922 This packet is not probed by default; the remote stub must request it,
31923 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
31929 @var{nn} (hex encoded) is the number of bytes written.
31930 This may be fewer bytes than supplied in the request.
31933 The request was malformed, or @var{annex} was invalid.
31936 The offset was invalid, or there was an error encountered writing the data.
31937 @var{nn} is a hex-encoded @code{errno} value.
31940 An empty reply indicates the @var{object} string was not
31941 recognized by the stub, or that the object does not support writing.
31944 @item qXfer:@var{object}:@var{operation}:@dots{}
31945 Requests of this form may be added in the future. When a stub does
31946 not recognize the @var{object} keyword, or its support for
31947 @var{object} does not recognize the @var{operation} keyword, the stub
31948 must respond with an empty packet.
31950 @item qAttached:@var{pid}
31951 @cindex query attached, remote request
31952 @cindex @samp{qAttached} packet
31953 Return an indication of whether the remote server attached to an
31954 existing process or created a new process. When the multiprocess
31955 protocol extensions are supported (@pxref{multiprocess extensions}),
31956 @var{pid} is an integer in hexadecimal format identifying the target
31957 process. Otherwise, @value{GDBN} will omit the @var{pid} field and
31958 the query packet will be simplified as @samp{qAttached}.
31960 This query is used, for example, to know whether the remote process
31961 should be detached or killed when a @value{GDBN} session is ended with
31962 the @code{quit} command.
31967 The remote server attached to an existing process.
31969 The remote server created a new process.
31971 A badly formed request or an error was encountered.
31976 @node Architecture-Specific Protocol Details
31977 @section Architecture-Specific Protocol Details
31979 This section describes how the remote protocol is applied to specific
31980 target architectures. Also see @ref{Standard Target Features}, for
31981 details of XML target descriptions for each architecture.
31985 @subsubsection Breakpoint Kinds
31987 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
31992 16-bit Thumb mode breakpoint.
31995 32-bit Thumb mode (Thumb-2) breakpoint.
31998 32-bit ARM mode breakpoint.
32004 @subsubsection Register Packet Format
32006 The following @code{g}/@code{G} packets have previously been defined.
32007 In the below, some thirty-two bit registers are transferred as
32008 sixty-four bits. Those registers should be zero/sign extended (which?)
32009 to fill the space allocated. Register bytes are transferred in target
32010 byte order. The two nibbles within a register byte are transferred
32011 most-significant - least-significant.
32017 All registers are transferred as thirty-two bit quantities in the order:
32018 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
32019 registers; fsr; fir; fp.
32023 All registers are transferred as sixty-four bit quantities (including
32024 thirty-two bit registers such as @code{sr}). The ordering is the same
32029 @node Tracepoint Packets
32030 @section Tracepoint Packets
32031 @cindex tracepoint packets
32032 @cindex packets, tracepoint
32034 Here we describe the packets @value{GDBN} uses to implement
32035 tracepoints (@pxref{Tracepoints}).
32039 @item QTDP:@var{n}:@var{addr}:@var{ena}:@var{step}:@var{pass}[:F@var{flen}][:X@var{len},@var{bytes}]@r{[}-@r{]}
32040 Create a new tracepoint, number @var{n}, at @var{addr}. If @var{ena}
32041 is @samp{E}, then the tracepoint is enabled; if it is @samp{D}, then
32042 the tracepoint is disabled. @var{step} is the tracepoint's step
32043 count, and @var{pass} is its pass count. If an @samp{F} is present,
32044 then the tracepoint is to be a fast tracepoint, and the @var{flen} is
32045 the number of bytes that the target should copy elsewhere to make room
32046 for the tracepoint. If an @samp{X} is present, it introduces a
32047 tracepoint condition, which consists of a hexadecimal length, followed
32048 by a comma and hex-encoded bytes, in a manner similar to action
32049 encodings as described below. If the trailing @samp{-} is present,
32050 further @samp{QTDP} packets will follow to specify this tracepoint's
32056 The packet was understood and carried out.
32058 The packet was not recognized.
32061 @item QTDP:-@var{n}:@var{addr}:@r{[}S@r{]}@var{action}@dots{}@r{[}-@r{]}
32062 Define actions to be taken when a tracepoint is hit. @var{n} and
32063 @var{addr} must be the same as in the initial @samp{QTDP} packet for
32064 this tracepoint. This packet may only be sent immediately after
32065 another @samp{QTDP} packet that ended with a @samp{-}. If the
32066 trailing @samp{-} is present, further @samp{QTDP} packets will follow,
32067 specifying more actions for this tracepoint.
32069 In the series of action packets for a given tracepoint, at most one
32070 can have an @samp{S} before its first @var{action}. If such a packet
32071 is sent, it and the following packets define ``while-stepping''
32072 actions. Any prior packets define ordinary actions --- that is, those
32073 taken when the tracepoint is first hit. If no action packet has an
32074 @samp{S}, then all the packets in the series specify ordinary
32075 tracepoint actions.
32077 The @samp{@var{action}@dots{}} portion of the packet is a series of
32078 actions, concatenated without separators. Each action has one of the
32084 Collect the registers whose bits are set in @var{mask}. @var{mask} is
32085 a hexadecimal number whose @var{i}'th bit is set if register number
32086 @var{i} should be collected. (The least significant bit is numbered
32087 zero.) Note that @var{mask} may be any number of digits long; it may
32088 not fit in a 32-bit word.
32090 @item M @var{basereg},@var{offset},@var{len}
32091 Collect @var{len} bytes of memory starting at the address in register
32092 number @var{basereg}, plus @var{offset}. If @var{basereg} is
32093 @samp{-1}, then the range has a fixed address: @var{offset} is the
32094 address of the lowest byte to collect. The @var{basereg},
32095 @var{offset}, and @var{len} parameters are all unsigned hexadecimal
32096 values (the @samp{-1} value for @var{basereg} is a special case).
32098 @item X @var{len},@var{expr}
32099 Evaluate @var{expr}, whose length is @var{len}, and collect memory as
32100 it directs. @var{expr} is an agent expression, as described in
32101 @ref{Agent Expressions}. Each byte of the expression is encoded as a
32102 two-digit hex number in the packet; @var{len} is the number of bytes
32103 in the expression (and thus one-half the number of hex digits in the
32108 Any number of actions may be packed together in a single @samp{QTDP}
32109 packet, as long as the packet does not exceed the maximum packet
32110 length (400 bytes, for many stubs). There may be only one @samp{R}
32111 action per tracepoint, and it must precede any @samp{M} or @samp{X}
32112 actions. Any registers referred to by @samp{M} and @samp{X} actions
32113 must be collected by a preceding @samp{R} action. (The
32114 ``while-stepping'' actions are treated as if they were attached to a
32115 separate tracepoint, as far as these restrictions are concerned.)
32120 The packet was understood and carried out.
32122 The packet was not recognized.
32125 @item QTDPsrc:@var{n}:@var{addr}:@var{type}:@var{start}:@var{slen}:@var{bytes}
32126 @cindex @samp{QTDPsrc} packet
32127 Specify a source string of tracepoint @var{n} at address @var{addr}.
32128 This is useful to get accurate reproduction of the tracepoints
32129 originally downloaded at the beginning of the trace run. @var{type}
32130 is the name of the tracepoint part, such as @samp{cond} for the
32131 tracepoint's conditional expression (see below for a list of types), while
32132 @var{bytes} is the string, encoded in hexadecimal.
32134 @var{start} is the offset of the @var{bytes} within the overall source
32135 string, while @var{slen} is the total length of the source string.
32136 This is intended for handling source strings that are longer than will
32137 fit in a single packet.
32138 @c Add detailed example when this info is moved into a dedicated
32139 @c tracepoint descriptions section.
32141 The available string types are @samp{at} for the location,
32142 @samp{cond} for the conditional, and @samp{cmd} for an action command.
32143 @value{GDBN} sends a separate packet for each command in the action
32144 list, in the same order in which the commands are stored in the list.
32146 The target does not need to do anything with source strings except
32147 report them back as part of the replies to the @samp{qTfP}/@samp{qTsP}
32150 Although this packet is optional, and @value{GDBN} will only send it
32151 if the target replies with @samp{TracepointSource} @xref{General
32152 Query Packets}, it makes both disconnected tracing and trace files
32153 much easier to use. Otherwise the user must be careful that the
32154 tracepoints in effect while looking at trace frames are identical to
32155 the ones in effect during the trace run; even a small discrepancy
32156 could cause @samp{tdump} not to work, or a particular trace frame not
32159 @item QTDV:@var{n}:@var{value}
32160 @cindex define trace state variable, remote request
32161 @cindex @samp{QTDV} packet
32162 Create a new trace state variable, number @var{n}, with an initial
32163 value of @var{value}, which is a 64-bit signed integer. Both @var{n}
32164 and @var{value} are encoded as hexadecimal values. @value{GDBN} has
32165 the option of not using this packet for initial values of zero; the
32166 target should simply create the trace state variables as they are
32167 mentioned in expressions.
32169 @item QTFrame:@var{n}
32170 Select the @var{n}'th tracepoint frame from the buffer, and use the
32171 register and memory contents recorded there to answer subsequent
32172 request packets from @value{GDBN}.
32174 A successful reply from the stub indicates that the stub has found the
32175 requested frame. The response is a series of parts, concatenated
32176 without separators, describing the frame we selected. Each part has
32177 one of the following forms:
32181 The selected frame is number @var{n} in the trace frame buffer;
32182 @var{f} is a hexadecimal number. If @var{f} is @samp{-1}, then there
32183 was no frame matching the criteria in the request packet.
32186 The selected trace frame records a hit of tracepoint number @var{t};
32187 @var{t} is a hexadecimal number.
32191 @item QTFrame:pc:@var{addr}
32192 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
32193 currently selected frame whose PC is @var{addr};
32194 @var{addr} is a hexadecimal number.
32196 @item QTFrame:tdp:@var{t}
32197 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
32198 currently selected frame that is a hit of tracepoint @var{t}; @var{t}
32199 is a hexadecimal number.
32201 @item QTFrame:range:@var{start}:@var{end}
32202 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
32203 currently selected frame whose PC is between @var{start} (inclusive)
32204 and @var{end} (inclusive); @var{start} and @var{end} are hexadecimal
32207 @item QTFrame:outside:@var{start}:@var{end}
32208 Like @samp{QTFrame:range:@var{start}:@var{end}}, but select the first
32209 frame @emph{outside} the given range of addresses (exclusive).
32212 Begin the tracepoint experiment. Begin collecting data from tracepoint
32213 hits in the trace frame buffer.
32216 End the tracepoint experiment. Stop collecting trace frames.
32219 Clear the table of tracepoints, and empty the trace frame buffer.
32221 @item QTro:@var{start1},@var{end1}:@var{start2},@var{end2}:@dots{}
32222 Establish the given ranges of memory as ``transparent''. The stub
32223 will answer requests for these ranges from memory's current contents,
32224 if they were not collected as part of the tracepoint hit.
32226 @value{GDBN} uses this to mark read-only regions of memory, like those
32227 containing program code. Since these areas never change, they should
32228 still have the same contents they did when the tracepoint was hit, so
32229 there's no reason for the stub to refuse to provide their contents.
32231 @item QTDisconnected:@var{value}
32232 Set the choice to what to do with the tracing run when @value{GDBN}
32233 disconnects from the target. A @var{value} of 1 directs the target to
32234 continue the tracing run, while 0 tells the target to stop tracing if
32235 @value{GDBN} is no longer in the picture.
32238 Ask the stub if there is a trace experiment running right now.
32240 The reply has the form:
32244 @item T@var{running}@r{[};@var{field}@r{]}@dots{}
32245 @var{running} is a single digit @code{1} if the trace is presently
32246 running, or @code{0} if not. It is followed by semicolon-separated
32247 optional fields that an agent may use to report additional status.
32251 If the trace is not running, the agent may report any of several
32252 explanations as one of the optional fields:
32257 No trace has been run yet.
32260 The trace was stopped by a user-originated stop command.
32263 The trace stopped because the trace buffer filled up.
32265 @item tdisconnected:0
32266 The trace stopped because @value{GDBN} disconnected from the target.
32268 @item tpasscount:@var{tpnum}
32269 The trace stopped because tracepoint @var{tpnum} exceeded its pass count.
32271 @item terror:@var{text}:@var{tpnum}
32272 The trace stopped because tracepoint @var{tpnum} had an error. The
32273 string @var{text} is available to describe the nature of the error
32274 (for instance, a divide by zero in the condition expression).
32275 @var{text} is hex encoded.
32278 The trace stopped for some other reason.
32282 Additional optional fields supply statistical and other information.
32283 Although not required, they are extremely useful for users monitoring
32284 the progress of a trace run. If a trace has stopped, and these
32285 numbers are reported, they must reflect the state of the just-stopped
32290 @item tframes:@var{n}
32291 The number of trace frames in the buffer.
32293 @item tcreated:@var{n}
32294 The total number of trace frames created during the run. This may
32295 be larger than the trace frame count, if the buffer is circular.
32297 @item tsize:@var{n}
32298 The total size of the trace buffer, in bytes.
32300 @item tfree:@var{n}
32301 The number of bytes still unused in the buffer.
32303 @item circular:@var{n}
32304 The value of the circular trace buffer flag. @code{1} means that the
32305 trace buffer is circular and old trace frames will be discarded if
32306 necessary to make room, @code{0} means that the trace buffer is linear
32309 @item disconn:@var{n}
32310 The value of the disconnected tracing flag. @code{1} means that
32311 tracing will continue after @value{GDBN} disconnects, @code{0} means
32312 that the trace run will stop.
32316 @item qTV:@var{var}
32317 @cindex trace state variable value, remote request
32318 @cindex @samp{qTV} packet
32319 Ask the stub for the value of the trace state variable number @var{var}.
32324 The value of the variable is @var{value}. This will be the current
32325 value of the variable if the user is examining a running target, or a
32326 saved value if the variable was collected in the trace frame that the
32327 user is looking at. Note that multiple requests may result in
32328 different reply values, such as when requesting values while the
32329 program is running.
32332 The value of the variable is unknown. This would occur, for example,
32333 if the user is examining a trace frame in which the requested variable
32339 These packets request data about tracepoints that are being used by
32340 the target. @value{GDBN} sends @code{qTfP} to get the first piece
32341 of data, and multiple @code{qTsP} to get additional pieces. Replies
32342 to these packets generally take the form of the @code{QTDP} packets
32343 that define tracepoints. (FIXME add detailed syntax)
32347 These packets request data about trace state variables that are on the
32348 target. @value{GDBN} sends @code{qTfV} to get the first vari of data,
32349 and multiple @code{qTsV} to get additional variables. Replies to
32350 these packets follow the syntax of the @code{QTDV} packets that define
32351 trace state variables.
32353 @item QTSave:@var{filename}
32354 This packet directs the target to save trace data to the file name
32355 @var{filename} in the target's filesystem. @var{filename} is encoded
32356 as a hex string; the interpretation of the file name (relative vs
32357 absolute, wild cards, etc) is up to the target.
32359 @item qTBuffer:@var{offset},@var{len}
32360 Return up to @var{len} bytes of the current contents of trace buffer,
32361 starting at @var{offset}. The trace buffer is treated as if it were
32362 a contiguous collection of traceframes, as per the trace file format.
32363 The reply consists as many hex-encoded bytes as the target can deliver
32364 in a packet; it is not an error to return fewer than were asked for.
32365 A reply consisting of just @code{l} indicates that no bytes are
32368 @item QTBuffer:circular:@var{value}
32369 This packet directs the target to use a circular trace buffer if
32370 @var{value} is 1, or a linear buffer if the value is 0.
32374 @node Host I/O Packets
32375 @section Host I/O Packets
32376 @cindex Host I/O, remote protocol
32377 @cindex file transfer, remote protocol
32379 The @dfn{Host I/O} packets allow @value{GDBN} to perform I/O
32380 operations on the far side of a remote link. For example, Host I/O is
32381 used to upload and download files to a remote target with its own
32382 filesystem. Host I/O uses the same constant values and data structure
32383 layout as the target-initiated File-I/O protocol. However, the
32384 Host I/O packets are structured differently. The target-initiated
32385 protocol relies on target memory to store parameters and buffers.
32386 Host I/O requests are initiated by @value{GDBN}, and the
32387 target's memory is not involved. @xref{File-I/O Remote Protocol
32388 Extension}, for more details on the target-initiated protocol.
32390 The Host I/O request packets all encode a single operation along with
32391 its arguments. They have this format:
32395 @item vFile:@var{operation}: @var{parameter}@dots{}
32396 @var{operation} is the name of the particular request; the target
32397 should compare the entire packet name up to the second colon when checking
32398 for a supported operation. The format of @var{parameter} depends on
32399 the operation. Numbers are always passed in hexadecimal. Negative
32400 numbers have an explicit minus sign (i.e.@: two's complement is not
32401 used). Strings (e.g.@: filenames) are encoded as a series of
32402 hexadecimal bytes. The last argument to a system call may be a
32403 buffer of escaped binary data (@pxref{Binary Data}).
32407 The valid responses to Host I/O packets are:
32411 @item F @var{result} [, @var{errno}] [; @var{attachment}]
32412 @var{result} is the integer value returned by this operation, usually
32413 non-negative for success and -1 for errors. If an error has occured,
32414 @var{errno} will be included in the result. @var{errno} will have a
32415 value defined by the File-I/O protocol (@pxref{Errno Values}). For
32416 operations which return data, @var{attachment} supplies the data as a
32417 binary buffer. Binary buffers in response packets are escaped in the
32418 normal way (@pxref{Binary Data}). See the individual packet
32419 documentation for the interpretation of @var{result} and
32423 An empty response indicates that this operation is not recognized.
32427 These are the supported Host I/O operations:
32430 @item vFile:open: @var{pathname}, @var{flags}, @var{mode}
32431 Open a file at @var{pathname} and return a file descriptor for it, or
32432 return -1 if an error occurs. @var{pathname} is a string,
32433 @var{flags} is an integer indicating a mask of open flags
32434 (@pxref{Open Flags}), and @var{mode} is an integer indicating a mask
32435 of mode bits to use if the file is created (@pxref{mode_t Values}).
32436 @xref{open}, for details of the open flags and mode values.
32438 @item vFile:close: @var{fd}
32439 Close the open file corresponding to @var{fd} and return 0, or
32440 -1 if an error occurs.
32442 @item vFile:pread: @var{fd}, @var{count}, @var{offset}
32443 Read data from the open file corresponding to @var{fd}. Up to
32444 @var{count} bytes will be read from the file, starting at @var{offset}
32445 relative to the start of the file. The target may read fewer bytes;
32446 common reasons include packet size limits and an end-of-file
32447 condition. The number of bytes read is returned. Zero should only be
32448 returned for a successful read at the end of the file, or if
32449 @var{count} was zero.
32451 The data read should be returned as a binary attachment on success.
32452 If zero bytes were read, the response should include an empty binary
32453 attachment (i.e.@: a trailing semicolon). The return value is the
32454 number of target bytes read; the binary attachment may be longer if
32455 some characters were escaped.
32457 @item vFile:pwrite: @var{fd}, @var{offset}, @var{data}
32458 Write @var{data} (a binary buffer) to the open file corresponding
32459 to @var{fd}. Start the write at @var{offset} from the start of the
32460 file. Unlike many @code{write} system calls, there is no
32461 separate @var{count} argument; the length of @var{data} in the
32462 packet is used. @samp{vFile:write} returns the number of bytes written,
32463 which may be shorter than the length of @var{data}, or -1 if an
32466 @item vFile:unlink: @var{pathname}
32467 Delete the file at @var{pathname} on the target. Return 0,
32468 or -1 if an error occurs. @var{pathname} is a string.
32473 @section Interrupts
32474 @cindex interrupts (remote protocol)
32476 When a program on the remote target is running, @value{GDBN} may
32477 attempt to interrupt it by sending a @samp{Ctrl-C}, @code{BREAK} or
32478 a @code{BREAK} followed by @code{g},
32479 control of which is specified via @value{GDBN}'s @samp{interrupt-sequence}.
32481 The precise meaning of @code{BREAK} is defined by the transport
32482 mechanism and may, in fact, be undefined. @value{GDBN} does not
32483 currently define a @code{BREAK} mechanism for any of the network
32484 interfaces except for TCP, in which case @value{GDBN} sends the
32485 @code{telnet} BREAK sequence.
32487 @samp{Ctrl-C}, on the other hand, is defined and implemented for all
32488 transport mechanisms. It is represented by sending the single byte
32489 @code{0x03} without any of the usual packet overhead described in
32490 the Overview section (@pxref{Overview}). When a @code{0x03} byte is
32491 transmitted as part of a packet, it is considered to be packet data
32492 and does @emph{not} represent an interrupt. E.g., an @samp{X} packet
32493 (@pxref{X packet}), used for binary downloads, may include an unescaped
32494 @code{0x03} as part of its packet.
32496 @code{BREAK} followed by @code{g} is also known as Magic SysRq g.
32497 When Linux kernel receives this sequence from serial port,
32498 it stops execution and connects to gdb.
32500 Stubs are not required to recognize these interrupt mechanisms and the
32501 precise meaning associated with receipt of the interrupt is
32502 implementation defined. If the target supports debugging of multiple
32503 threads and/or processes, it should attempt to interrupt all
32504 currently-executing threads and processes.
32505 If the stub is successful at interrupting the
32506 running program, it should send one of the stop
32507 reply packets (@pxref{Stop Reply Packets}) to @value{GDBN} as a result
32508 of successfully stopping the program in all-stop mode, and a stop reply
32509 for each stopped thread in non-stop mode.
32510 Interrupts received while the
32511 program is stopped are discarded.
32513 @node Notification Packets
32514 @section Notification Packets
32515 @cindex notification packets
32516 @cindex packets, notification
32518 The @value{GDBN} remote serial protocol includes @dfn{notifications},
32519 packets that require no acknowledgment. Both the GDB and the stub
32520 may send notifications (although the only notifications defined at
32521 present are sent by the stub). Notifications carry information
32522 without incurring the round-trip latency of an acknowledgment, and so
32523 are useful for low-impact communications where occasional packet loss
32526 A notification packet has the form @samp{% @var{data} #
32527 @var{checksum}}, where @var{data} is the content of the notification,
32528 and @var{checksum} is a checksum of @var{data}, computed and formatted
32529 as for ordinary @value{GDBN} packets. A notification's @var{data}
32530 never contains @samp{$}, @samp{%} or @samp{#} characters. Upon
32531 receiving a notification, the recipient sends no @samp{+} or @samp{-}
32532 to acknowledge the notification's receipt or to report its corruption.
32534 Every notification's @var{data} begins with a name, which contains no
32535 colon characters, followed by a colon character.
32537 Recipients should silently ignore corrupted notifications and
32538 notifications they do not understand. Recipients should restart
32539 timeout periods on receipt of a well-formed notification, whether or
32540 not they understand it.
32542 Senders should only send the notifications described here when this
32543 protocol description specifies that they are permitted. In the
32544 future, we may extend the protocol to permit existing notifications in
32545 new contexts; this rule helps older senders avoid confusing newer
32548 (Older versions of @value{GDBN} ignore bytes received until they see
32549 the @samp{$} byte that begins an ordinary packet, so new stubs may
32550 transmit notifications without fear of confusing older clients. There
32551 are no notifications defined for @value{GDBN} to send at the moment, but we
32552 assume that most older stubs would ignore them, as well.)
32554 The following notification packets from the stub to @value{GDBN} are
32558 @item Stop: @var{reply}
32559 Report an asynchronous stop event in non-stop mode.
32560 The @var{reply} has the form of a stop reply, as
32561 described in @ref{Stop Reply Packets}. Refer to @ref{Remote Non-Stop},
32562 for information on how these notifications are acknowledged by
32566 @node Remote Non-Stop
32567 @section Remote Protocol Support for Non-Stop Mode
32569 @value{GDBN}'s remote protocol supports non-stop debugging of
32570 multi-threaded programs, as described in @ref{Non-Stop Mode}. If the stub
32571 supports non-stop mode, it should report that to @value{GDBN} by including
32572 @samp{QNonStop+} in its @samp{qSupported} response (@pxref{qSupported}).
32574 @value{GDBN} typically sends a @samp{QNonStop} packet only when
32575 establishing a new connection with the stub. Entering non-stop mode
32576 does not alter the state of any currently-running threads, but targets
32577 must stop all threads in any already-attached processes when entering
32578 all-stop mode. @value{GDBN} uses the @samp{?} packet as necessary to
32579 probe the target state after a mode change.
32581 In non-stop mode, when an attached process encounters an event that
32582 would otherwise be reported with a stop reply, it uses the
32583 asynchronous notification mechanism (@pxref{Notification Packets}) to
32584 inform @value{GDBN}. In contrast to all-stop mode, where all threads
32585 in all processes are stopped when a stop reply is sent, in non-stop
32586 mode only the thread reporting the stop event is stopped. That is,
32587 when reporting a @samp{S} or @samp{T} response to indicate completion
32588 of a step operation, hitting a breakpoint, or a fault, only the
32589 affected thread is stopped; any other still-running threads continue
32590 to run. When reporting a @samp{W} or @samp{X} response, all running
32591 threads belonging to other attached processes continue to run.
32593 Only one stop reply notification at a time may be pending; if
32594 additional stop events occur before @value{GDBN} has acknowledged the
32595 previous notification, they must be queued by the stub for later
32596 synchronous transmission in response to @samp{vStopped} packets from
32597 @value{GDBN}. Because the notification mechanism is unreliable,
32598 the stub is permitted to resend a stop reply notification
32599 if it believes @value{GDBN} may not have received it. @value{GDBN}
32600 ignores additional stop reply notifications received before it has
32601 finished processing a previous notification and the stub has completed
32602 sending any queued stop events.
32604 Otherwise, @value{GDBN} must be prepared to receive a stop reply
32605 notification at any time. Specifically, they may appear when
32606 @value{GDBN} is not otherwise reading input from the stub, or when
32607 @value{GDBN} is expecting to read a normal synchronous response or a
32608 @samp{+}/@samp{-} acknowledgment to a packet it has sent.
32609 Notification packets are distinct from any other communication from
32610 the stub so there is no ambiguity.
32612 After receiving a stop reply notification, @value{GDBN} shall
32613 acknowledge it by sending a @samp{vStopped} packet (@pxref{vStopped packet})
32614 as a regular, synchronous request to the stub. Such acknowledgment
32615 is not required to happen immediately, as @value{GDBN} is permitted to
32616 send other, unrelated packets to the stub first, which the stub should
32619 Upon receiving a @samp{vStopped} packet, if the stub has other queued
32620 stop events to report to @value{GDBN}, it shall respond by sending a
32621 normal stop reply response. @value{GDBN} shall then send another
32622 @samp{vStopped} packet to solicit further responses; again, it is
32623 permitted to send other, unrelated packets as well which the stub
32624 should process normally.
32626 If the stub receives a @samp{vStopped} packet and there are no
32627 additional stop events to report, the stub shall return an @samp{OK}
32628 response. At this point, if further stop events occur, the stub shall
32629 send a new stop reply notification, @value{GDBN} shall accept the
32630 notification, and the process shall be repeated.
32632 In non-stop mode, the target shall respond to the @samp{?} packet as
32633 follows. First, any incomplete stop reply notification/@samp{vStopped}
32634 sequence in progress is abandoned. The target must begin a new
32635 sequence reporting stop events for all stopped threads, whether or not
32636 it has previously reported those events to @value{GDBN}. The first
32637 stop reply is sent as a synchronous reply to the @samp{?} packet, and
32638 subsequent stop replies are sent as responses to @samp{vStopped} packets
32639 using the mechanism described above. The target must not send
32640 asynchronous stop reply notifications until the sequence is complete.
32641 If all threads are running when the target receives the @samp{?} packet,
32642 or if the target is not attached to any process, it shall respond
32645 @node Packet Acknowledgment
32646 @section Packet Acknowledgment
32648 @cindex acknowledgment, for @value{GDBN} remote
32649 @cindex packet acknowledgment, for @value{GDBN} remote
32650 By default, when either the host or the target machine receives a packet,
32651 the first response expected is an acknowledgment: either @samp{+} (to indicate
32652 the package was received correctly) or @samp{-} (to request retransmission).
32653 This mechanism allows the @value{GDBN} remote protocol to operate over
32654 unreliable transport mechanisms, such as a serial line.
32656 In cases where the transport mechanism is itself reliable (such as a pipe or
32657 TCP connection), the @samp{+}/@samp{-} acknowledgments are redundant.
32658 It may be desirable to disable them in that case to reduce communication
32659 overhead, or for other reasons. This can be accomplished by means of the
32660 @samp{QStartNoAckMode} packet; @pxref{QStartNoAckMode}.
32662 When in no-acknowledgment mode, neither the stub nor @value{GDBN} shall send or
32663 expect @samp{+}/@samp{-} protocol acknowledgments. The packet
32664 and response format still includes the normal checksum, as described in
32665 @ref{Overview}, but the checksum may be ignored by the receiver.
32667 If the stub supports @samp{QStartNoAckMode} and prefers to operate in
32668 no-acknowledgment mode, it should report that to @value{GDBN}
32669 by including @samp{QStartNoAckMode+} in its response to @samp{qSupported};
32670 @pxref{qSupported}.
32671 If @value{GDBN} also supports @samp{QStartNoAckMode} and it has not been
32672 disabled via the @code{set remote noack-packet off} command
32673 (@pxref{Remote Configuration}),
32674 @value{GDBN} may then send a @samp{QStartNoAckMode} packet to the stub.
32675 Only then may the stub actually turn off packet acknowledgments.
32676 @value{GDBN} sends a final @samp{+} acknowledgment of the stub's @samp{OK}
32677 response, which can be safely ignored by the stub.
32679 Note that @code{set remote noack-packet} command only affects negotiation
32680 between @value{GDBN} and the stub when subsequent connections are made;
32681 it does not affect the protocol acknowledgment state for any current
32683 Since @samp{+}/@samp{-} acknowledgments are enabled by default when a
32684 new connection is established,
32685 there is also no protocol request to re-enable the acknowledgments
32686 for the current connection, once disabled.
32691 Example sequence of a target being re-started. Notice how the restart
32692 does not get any direct output:
32697 @emph{target restarts}
32700 <- @code{T001:1234123412341234}
32704 Example sequence of a target being stepped by a single instruction:
32707 -> @code{G1445@dots{}}
32712 <- @code{T001:1234123412341234}
32716 <- @code{1455@dots{}}
32720 @node File-I/O Remote Protocol Extension
32721 @section File-I/O Remote Protocol Extension
32722 @cindex File-I/O remote protocol extension
32725 * File-I/O Overview::
32726 * Protocol Basics::
32727 * The F Request Packet::
32728 * The F Reply Packet::
32729 * The Ctrl-C Message::
32731 * List of Supported Calls::
32732 * Protocol-specific Representation of Datatypes::
32734 * File-I/O Examples::
32737 @node File-I/O Overview
32738 @subsection File-I/O Overview
32739 @cindex file-i/o overview
32741 The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the
32742 target to use the host's file system and console I/O to perform various
32743 system calls. System calls on the target system are translated into a
32744 remote protocol packet to the host system, which then performs the needed
32745 actions and returns a response packet to the target system.
32746 This simulates file system operations even on targets that lack file systems.
32748 The protocol is defined to be independent of both the host and target systems.
32749 It uses its own internal representation of datatypes and values. Both
32750 @value{GDBN} and the target's @value{GDBN} stub are responsible for
32751 translating the system-dependent value representations into the internal
32752 protocol representations when data is transmitted.
32754 The communication is synchronous. A system call is possible only when
32755 @value{GDBN} is waiting for a response from the @samp{C}, @samp{c}, @samp{S}
32756 or @samp{s} packets. While @value{GDBN} handles the request for a system call,
32757 the target is stopped to allow deterministic access to the target's
32758 memory. Therefore File-I/O is not interruptible by target signals. On
32759 the other hand, it is possible to interrupt File-I/O by a user interrupt
32760 (@samp{Ctrl-C}) within @value{GDBN}.
32762 The target's request to perform a host system call does not finish
32763 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
32764 after finishing the system call, the target returns to continuing the
32765 previous activity (continue, step). No additional continue or step
32766 request from @value{GDBN} is required.
32769 (@value{GDBP}) continue
32770 <- target requests 'system call X'
32771 target is stopped, @value{GDBN} executes system call
32772 -> @value{GDBN} returns result
32773 ... target continues, @value{GDBN} returns to wait for the target
32774 <- target hits breakpoint and sends a Txx packet
32777 The protocol only supports I/O on the console and to regular files on
32778 the host file system. Character or block special devices, pipes,
32779 named pipes, sockets or any other communication method on the host
32780 system are not supported by this protocol.
32782 File I/O is not supported in non-stop mode.
32784 @node Protocol Basics
32785 @subsection Protocol Basics
32786 @cindex protocol basics, file-i/o
32788 The File-I/O protocol uses the @code{F} packet as the request as well
32789 as reply packet. Since a File-I/O system call can only occur when
32790 @value{GDBN} is waiting for a response from the continuing or stepping target,
32791 the File-I/O request is a reply that @value{GDBN} has to expect as a result
32792 of a previous @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
32793 This @code{F} packet contains all information needed to allow @value{GDBN}
32794 to call the appropriate host system call:
32798 A unique identifier for the requested system call.
32801 All parameters to the system call. Pointers are given as addresses
32802 in the target memory address space. Pointers to strings are given as
32803 pointer/length pair. Numerical values are given as they are.
32804 Numerical control flags are given in a protocol-specific representation.
32808 At this point, @value{GDBN} has to perform the following actions.
32812 If the parameters include pointer values to data needed as input to a
32813 system call, @value{GDBN} requests this data from the target with a
32814 standard @code{m} packet request. This additional communication has to be
32815 expected by the target implementation and is handled as any other @code{m}
32819 @value{GDBN} translates all value from protocol representation to host
32820 representation as needed. Datatypes are coerced into the host types.
32823 @value{GDBN} calls the system call.
32826 It then coerces datatypes back to protocol representation.
32829 If the system call is expected to return data in buffer space specified
32830 by pointer parameters to the call, the data is transmitted to the
32831 target using a @code{M} or @code{X} packet. This packet has to be expected
32832 by the target implementation and is handled as any other @code{M} or @code{X}
32837 Eventually @value{GDBN} replies with another @code{F} packet which contains all
32838 necessary information for the target to continue. This at least contains
32845 @code{errno}, if has been changed by the system call.
32852 After having done the needed type and value coercion, the target continues
32853 the latest continue or step action.
32855 @node The F Request Packet
32856 @subsection The @code{F} Request Packet
32857 @cindex file-i/o request packet
32858 @cindex @code{F} request packet
32860 The @code{F} request packet has the following format:
32863 @item F@var{call-id},@var{parameter@dots{}}
32865 @var{call-id} is the identifier to indicate the host system call to be called.
32866 This is just the name of the function.
32868 @var{parameter@dots{}} are the parameters to the system call.
32869 Parameters are hexadecimal integer values, either the actual values in case
32870 of scalar datatypes, pointers to target buffer space in case of compound
32871 datatypes and unspecified memory areas, or pointer/length pairs in case
32872 of string parameters. These are appended to the @var{call-id} as a
32873 comma-delimited list. All values are transmitted in ASCII
32874 string representation, pointer/length pairs separated by a slash.
32880 @node The F Reply Packet
32881 @subsection The @code{F} Reply Packet
32882 @cindex file-i/o reply packet
32883 @cindex @code{F} reply packet
32885 The @code{F} reply packet has the following format:
32889 @item F@var{retcode},@var{errno},@var{Ctrl-C flag};@var{call-specific attachment}
32891 @var{retcode} is the return code of the system call as hexadecimal value.
32893 @var{errno} is the @code{errno} set by the call, in protocol-specific
32895 This parameter can be omitted if the call was successful.
32897 @var{Ctrl-C flag} is only sent if the user requested a break. In this
32898 case, @var{errno} must be sent as well, even if the call was successful.
32899 The @var{Ctrl-C flag} itself consists of the character @samp{C}:
32906 or, if the call was interrupted before the host call has been performed:
32913 assuming 4 is the protocol-specific representation of @code{EINTR}.
32918 @node The Ctrl-C Message
32919 @subsection The @samp{Ctrl-C} Message
32920 @cindex ctrl-c message, in file-i/o protocol
32922 If the @samp{Ctrl-C} flag is set in the @value{GDBN}
32923 reply packet (@pxref{The F Reply Packet}),
32924 the target should behave as if it had
32925 gotten a break message. The meaning for the target is ``system call
32926 interrupted by @code{SIGINT}''. Consequentially, the target should actually stop
32927 (as with a break message) and return to @value{GDBN} with a @code{T02}
32930 It's important for the target to know in which
32931 state the system call was interrupted. There are two possible cases:
32935 The system call hasn't been performed on the host yet.
32938 The system call on the host has been finished.
32942 These two states can be distinguished by the target by the value of the
32943 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
32944 call hasn't been performed. This is equivalent to the @code{EINTR} handling
32945 on POSIX systems. In any other case, the target may presume that the
32946 system call has been finished --- successfully or not --- and should behave
32947 as if the break message arrived right after the system call.
32949 @value{GDBN} must behave reliably. If the system call has not been called
32950 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
32951 @code{errno} in the packet. If the system call on the host has been finished
32952 before the user requests a break, the full action must be finished by
32953 @value{GDBN}. This requires sending @code{M} or @code{X} packets as necessary.
32954 The @code{F} packet may only be sent when either nothing has happened
32955 or the full action has been completed.
32958 @subsection Console I/O
32959 @cindex console i/o as part of file-i/o
32961 By default and if not explicitly closed by the target system, the file
32962 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
32963 on the @value{GDBN} console is handled as any other file output operation
32964 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
32965 by @value{GDBN} so that after the target read request from file descriptor
32966 0 all following typing is buffered until either one of the following
32971 The user types @kbd{Ctrl-c}. The behaviour is as explained above, and the
32973 system call is treated as finished.
32976 The user presses @key{RET}. This is treated as end of input with a trailing
32980 The user types @kbd{Ctrl-d}. This is treated as end of input. No trailing
32981 character (neither newline nor @samp{Ctrl-D}) is appended to the input.
32985 If the user has typed more characters than fit in the buffer given to
32986 the @code{read} call, the trailing characters are buffered in @value{GDBN} until
32987 either another @code{read(0, @dots{})} is requested by the target, or debugging
32988 is stopped at the user's request.
32991 @node List of Supported Calls
32992 @subsection List of Supported Calls
32993 @cindex list of supported file-i/o calls
33010 @unnumberedsubsubsec open
33011 @cindex open, file-i/o system call
33016 int open(const char *pathname, int flags);
33017 int open(const char *pathname, int flags, mode_t mode);
33021 @samp{Fopen,@var{pathptr}/@var{len},@var{flags},@var{mode}}
33024 @var{flags} is the bitwise @code{OR} of the following values:
33028 If the file does not exist it will be created. The host
33029 rules apply as far as file ownership and time stamps
33033 When used with @code{O_CREAT}, if the file already exists it is
33034 an error and open() fails.
33037 If the file already exists and the open mode allows
33038 writing (@code{O_RDWR} or @code{O_WRONLY} is given) it will be
33039 truncated to zero length.
33042 The file is opened in append mode.
33045 The file is opened for reading only.
33048 The file is opened for writing only.
33051 The file is opened for reading and writing.
33055 Other bits are silently ignored.
33059 @var{mode} is the bitwise @code{OR} of the following values:
33063 User has read permission.
33066 User has write permission.
33069 Group has read permission.
33072 Group has write permission.
33075 Others have read permission.
33078 Others have write permission.
33082 Other bits are silently ignored.
33085 @item Return value:
33086 @code{open} returns the new file descriptor or -1 if an error
33093 @var{pathname} already exists and @code{O_CREAT} and @code{O_EXCL} were used.
33096 @var{pathname} refers to a directory.
33099 The requested access is not allowed.
33102 @var{pathname} was too long.
33105 A directory component in @var{pathname} does not exist.
33108 @var{pathname} refers to a device, pipe, named pipe or socket.
33111 @var{pathname} refers to a file on a read-only filesystem and
33112 write access was requested.
33115 @var{pathname} is an invalid pointer value.
33118 No space on device to create the file.
33121 The process already has the maximum number of files open.
33124 The limit on the total number of files open on the system
33128 The call was interrupted by the user.
33134 @unnumberedsubsubsec close
33135 @cindex close, file-i/o system call
33144 @samp{Fclose,@var{fd}}
33146 @item Return value:
33147 @code{close} returns zero on success, or -1 if an error occurred.
33153 @var{fd} isn't a valid open file descriptor.
33156 The call was interrupted by the user.
33162 @unnumberedsubsubsec read
33163 @cindex read, file-i/o system call
33168 int read(int fd, void *buf, unsigned int count);
33172 @samp{Fread,@var{fd},@var{bufptr},@var{count}}
33174 @item Return value:
33175 On success, the number of bytes read is returned.
33176 Zero indicates end of file. If count is zero, read
33177 returns zero as well. On error, -1 is returned.
33183 @var{fd} is not a valid file descriptor or is not open for
33187 @var{bufptr} is an invalid pointer value.
33190 The call was interrupted by the user.
33196 @unnumberedsubsubsec write
33197 @cindex write, file-i/o system call
33202 int write(int fd, const void *buf, unsigned int count);
33206 @samp{Fwrite,@var{fd},@var{bufptr},@var{count}}
33208 @item Return value:
33209 On success, the number of bytes written are returned.
33210 Zero indicates nothing was written. On error, -1
33217 @var{fd} is not a valid file descriptor or is not open for
33221 @var{bufptr} is an invalid pointer value.
33224 An attempt was made to write a file that exceeds the
33225 host-specific maximum file size allowed.
33228 No space on device to write the data.
33231 The call was interrupted by the user.
33237 @unnumberedsubsubsec lseek
33238 @cindex lseek, file-i/o system call
33243 long lseek (int fd, long offset, int flag);
33247 @samp{Flseek,@var{fd},@var{offset},@var{flag}}
33249 @var{flag} is one of:
33253 The offset is set to @var{offset} bytes.
33256 The offset is set to its current location plus @var{offset}
33260 The offset is set to the size of the file plus @var{offset}
33264 @item Return value:
33265 On success, the resulting unsigned offset in bytes from
33266 the beginning of the file is returned. Otherwise, a
33267 value of -1 is returned.
33273 @var{fd} is not a valid open file descriptor.
33276 @var{fd} is associated with the @value{GDBN} console.
33279 @var{flag} is not a proper value.
33282 The call was interrupted by the user.
33288 @unnumberedsubsubsec rename
33289 @cindex rename, file-i/o system call
33294 int rename(const char *oldpath, const char *newpath);
33298 @samp{Frename,@var{oldpathptr}/@var{len},@var{newpathptr}/@var{len}}
33300 @item Return value:
33301 On success, zero is returned. On error, -1 is returned.
33307 @var{newpath} is an existing directory, but @var{oldpath} is not a
33311 @var{newpath} is a non-empty directory.
33314 @var{oldpath} or @var{newpath} is a directory that is in use by some
33318 An attempt was made to make a directory a subdirectory
33322 A component used as a directory in @var{oldpath} or new
33323 path is not a directory. Or @var{oldpath} is a directory
33324 and @var{newpath} exists but is not a directory.
33327 @var{oldpathptr} or @var{newpathptr} are invalid pointer values.
33330 No access to the file or the path of the file.
33334 @var{oldpath} or @var{newpath} was too long.
33337 A directory component in @var{oldpath} or @var{newpath} does not exist.
33340 The file is on a read-only filesystem.
33343 The device containing the file has no room for the new
33347 The call was interrupted by the user.
33353 @unnumberedsubsubsec unlink
33354 @cindex unlink, file-i/o system call
33359 int unlink(const char *pathname);
33363 @samp{Funlink,@var{pathnameptr}/@var{len}}
33365 @item Return value:
33366 On success, zero is returned. On error, -1 is returned.
33372 No access to the file or the path of the file.
33375 The system does not allow unlinking of directories.
33378 The file @var{pathname} cannot be unlinked because it's
33379 being used by another process.
33382 @var{pathnameptr} is an invalid pointer value.
33385 @var{pathname} was too long.
33388 A directory component in @var{pathname} does not exist.
33391 A component of the path is not a directory.
33394 The file is on a read-only filesystem.
33397 The call was interrupted by the user.
33403 @unnumberedsubsubsec stat/fstat
33404 @cindex fstat, file-i/o system call
33405 @cindex stat, file-i/o system call
33410 int stat(const char *pathname, struct stat *buf);
33411 int fstat(int fd, struct stat *buf);
33415 @samp{Fstat,@var{pathnameptr}/@var{len},@var{bufptr}}@*
33416 @samp{Ffstat,@var{fd},@var{bufptr}}
33418 @item Return value:
33419 On success, zero is returned. On error, -1 is returned.
33425 @var{fd} is not a valid open file.
33428 A directory component in @var{pathname} does not exist or the
33429 path is an empty string.
33432 A component of the path is not a directory.
33435 @var{pathnameptr} is an invalid pointer value.
33438 No access to the file or the path of the file.
33441 @var{pathname} was too long.
33444 The call was interrupted by the user.
33450 @unnumberedsubsubsec gettimeofday
33451 @cindex gettimeofday, file-i/o system call
33456 int gettimeofday(struct timeval *tv, void *tz);
33460 @samp{Fgettimeofday,@var{tvptr},@var{tzptr}}
33462 @item Return value:
33463 On success, 0 is returned, -1 otherwise.
33469 @var{tz} is a non-NULL pointer.
33472 @var{tvptr} and/or @var{tzptr} is an invalid pointer value.
33478 @unnumberedsubsubsec isatty
33479 @cindex isatty, file-i/o system call
33484 int isatty(int fd);
33488 @samp{Fisatty,@var{fd}}
33490 @item Return value:
33491 Returns 1 if @var{fd} refers to the @value{GDBN} console, 0 otherwise.
33497 The call was interrupted by the user.
33502 Note that the @code{isatty} call is treated as a special case: it returns
33503 1 to the target if the file descriptor is attached
33504 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
33505 would require implementing @code{ioctl} and would be more complex than
33510 @unnumberedsubsubsec system
33511 @cindex system, file-i/o system call
33516 int system(const char *command);
33520 @samp{Fsystem,@var{commandptr}/@var{len}}
33522 @item Return value:
33523 If @var{len} is zero, the return value indicates whether a shell is
33524 available. A zero return value indicates a shell is not available.
33525 For non-zero @var{len}, the value returned is -1 on error and the
33526 return status of the command otherwise. Only the exit status of the
33527 command is returned, which is extracted from the host's @code{system}
33528 return value by calling @code{WEXITSTATUS(retval)}. In case
33529 @file{/bin/sh} could not be executed, 127 is returned.
33535 The call was interrupted by the user.
33540 @value{GDBN} takes over the full task of calling the necessary host calls
33541 to perform the @code{system} call. The return value of @code{system} on
33542 the host is simplified before it's returned
33543 to the target. Any termination signal information from the child process
33544 is discarded, and the return value consists
33545 entirely of the exit status of the called command.
33547 Due to security concerns, the @code{system} call is by default refused
33548 by @value{GDBN}. The user has to allow this call explicitly with the
33549 @code{set remote system-call-allowed 1} command.
33552 @item set remote system-call-allowed
33553 @kindex set remote system-call-allowed
33554 Control whether to allow the @code{system} calls in the File I/O
33555 protocol for the remote target. The default is zero (disabled).
33557 @item show remote system-call-allowed
33558 @kindex show remote system-call-allowed
33559 Show whether the @code{system} calls are allowed in the File I/O
33563 @node Protocol-specific Representation of Datatypes
33564 @subsection Protocol-specific Representation of Datatypes
33565 @cindex protocol-specific representation of datatypes, in file-i/o protocol
33568 * Integral Datatypes::
33570 * Memory Transfer::
33575 @node Integral Datatypes
33576 @unnumberedsubsubsec Integral Datatypes
33577 @cindex integral datatypes, in file-i/o protocol
33579 The integral datatypes used in the system calls are @code{int},
33580 @code{unsigned int}, @code{long}, @code{unsigned long},
33581 @code{mode_t}, and @code{time_t}.
33583 @code{int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
33584 implemented as 32 bit values in this protocol.
33586 @code{long} and @code{unsigned long} are implemented as 64 bit types.
33588 @xref{Limits}, for corresponding MIN and MAX values (similar to those
33589 in @file{limits.h}) to allow range checking on host and target.
33591 @code{time_t} datatypes are defined as seconds since the Epoch.
33593 All integral datatypes transferred as part of a memory read or write of a
33594 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
33597 @node Pointer Values
33598 @unnumberedsubsubsec Pointer Values
33599 @cindex pointer values, in file-i/o protocol
33601 Pointers to target data are transmitted as they are. An exception
33602 is made for pointers to buffers for which the length isn't
33603 transmitted as part of the function call, namely strings. Strings
33604 are transmitted as a pointer/length pair, both as hex values, e.g.@:
33611 which is a pointer to data of length 18 bytes at position 0x1aaf.
33612 The length is defined as the full string length in bytes, including
33613 the trailing null byte. For example, the string @code{"hello world"}
33614 at address 0x123456 is transmitted as
33620 @node Memory Transfer
33621 @unnumberedsubsubsec Memory Transfer
33622 @cindex memory transfer, in file-i/o protocol
33624 Structured data which is transferred using a memory read or write (for
33625 example, a @code{struct stat}) is expected to be in a protocol-specific format
33626 with all scalar multibyte datatypes being big endian. Translation to
33627 this representation needs to be done both by the target before the @code{F}
33628 packet is sent, and by @value{GDBN} before
33629 it transfers memory to the target. Transferred pointers to structured
33630 data should point to the already-coerced data at any time.
33634 @unnumberedsubsubsec struct stat
33635 @cindex struct stat, in file-i/o protocol
33637 The buffer of type @code{struct stat} used by the target and @value{GDBN}
33638 is defined as follows:
33642 unsigned int st_dev; /* device */
33643 unsigned int st_ino; /* inode */
33644 mode_t st_mode; /* protection */
33645 unsigned int st_nlink; /* number of hard links */
33646 unsigned int st_uid; /* user ID of owner */
33647 unsigned int st_gid; /* group ID of owner */
33648 unsigned int st_rdev; /* device type (if inode device) */
33649 unsigned long st_size; /* total size, in bytes */
33650 unsigned long st_blksize; /* blocksize for filesystem I/O */
33651 unsigned long st_blocks; /* number of blocks allocated */
33652 time_t st_atime; /* time of last access */
33653 time_t st_mtime; /* time of last modification */
33654 time_t st_ctime; /* time of last change */
33658 The integral datatypes conform to the definitions given in the
33659 appropriate section (see @ref{Integral Datatypes}, for details) so this
33660 structure is of size 64 bytes.
33662 The values of several fields have a restricted meaning and/or
33668 A value of 0 represents a file, 1 the console.
33671 No valid meaning for the target. Transmitted unchanged.
33674 Valid mode bits are described in @ref{Constants}. Any other
33675 bits have currently no meaning for the target.
33680 No valid meaning for the target. Transmitted unchanged.
33685 These values have a host and file system dependent
33686 accuracy. Especially on Windows hosts, the file system may not
33687 support exact timing values.
33690 The target gets a @code{struct stat} of the above representation and is
33691 responsible for coercing it to the target representation before
33694 Note that due to size differences between the host, target, and protocol
33695 representations of @code{struct stat} members, these members could eventually
33696 get truncated on the target.
33698 @node struct timeval
33699 @unnumberedsubsubsec struct timeval
33700 @cindex struct timeval, in file-i/o protocol
33702 The buffer of type @code{struct timeval} used by the File-I/O protocol
33703 is defined as follows:
33707 time_t tv_sec; /* second */
33708 long tv_usec; /* microsecond */
33712 The integral datatypes conform to the definitions given in the
33713 appropriate section (see @ref{Integral Datatypes}, for details) so this
33714 structure is of size 8 bytes.
33717 @subsection Constants
33718 @cindex constants, in file-i/o protocol
33720 The following values are used for the constants inside of the
33721 protocol. @value{GDBN} and target are responsible for translating these
33722 values before and after the call as needed.
33733 @unnumberedsubsubsec Open Flags
33734 @cindex open flags, in file-i/o protocol
33736 All values are given in hexadecimal representation.
33748 @node mode_t Values
33749 @unnumberedsubsubsec mode_t Values
33750 @cindex mode_t values, in file-i/o protocol
33752 All values are given in octal representation.
33769 @unnumberedsubsubsec Errno Values
33770 @cindex errno values, in file-i/o protocol
33772 All values are given in decimal representation.
33797 @code{EUNKNOWN} is used as a fallback error value if a host system returns
33798 any error value not in the list of supported error numbers.
33801 @unnumberedsubsubsec Lseek Flags
33802 @cindex lseek flags, in file-i/o protocol
33811 @unnumberedsubsubsec Limits
33812 @cindex limits, in file-i/o protocol
33814 All values are given in decimal representation.
33817 INT_MIN -2147483648
33819 UINT_MAX 4294967295
33820 LONG_MIN -9223372036854775808
33821 LONG_MAX 9223372036854775807
33822 ULONG_MAX 18446744073709551615
33825 @node File-I/O Examples
33826 @subsection File-I/O Examples
33827 @cindex file-i/o examples
33829 Example sequence of a write call, file descriptor 3, buffer is at target
33830 address 0x1234, 6 bytes should be written:
33833 <- @code{Fwrite,3,1234,6}
33834 @emph{request memory read from target}
33837 @emph{return "6 bytes written"}
33841 Example sequence of a read call, file descriptor 3, buffer is at target
33842 address 0x1234, 6 bytes should be read:
33845 <- @code{Fread,3,1234,6}
33846 @emph{request memory write to target}
33847 -> @code{X1234,6:XXXXXX}
33848 @emph{return "6 bytes read"}
33852 Example sequence of a read call, call fails on the host due to invalid
33853 file descriptor (@code{EBADF}):
33856 <- @code{Fread,3,1234,6}
33860 Example sequence of a read call, user presses @kbd{Ctrl-c} before syscall on
33864 <- @code{Fread,3,1234,6}
33869 Example sequence of a read call, user presses @kbd{Ctrl-c} after syscall on
33873 <- @code{Fread,3,1234,6}
33874 -> @code{X1234,6:XXXXXX}
33878 @node Library List Format
33879 @section Library List Format
33880 @cindex library list format, remote protocol
33882 On some platforms, a dynamic loader (e.g.@: @file{ld.so}) runs in the
33883 same process as your application to manage libraries. In this case,
33884 @value{GDBN} can use the loader's symbol table and normal memory
33885 operations to maintain a list of shared libraries. On other
33886 platforms, the operating system manages loaded libraries.
33887 @value{GDBN} can not retrieve the list of currently loaded libraries
33888 through memory operations, so it uses the @samp{qXfer:libraries:read}
33889 packet (@pxref{qXfer library list read}) instead. The remote stub
33890 queries the target's operating system and reports which libraries
33893 The @samp{qXfer:libraries:read} packet returns an XML document which
33894 lists loaded libraries and their offsets. Each library has an
33895 associated name and one or more segment or section base addresses,
33896 which report where the library was loaded in memory.
33898 For the common case of libraries that are fully linked binaries, the
33899 library should have a list of segments. If the target supports
33900 dynamic linking of a relocatable object file, its library XML element
33901 should instead include a list of allocated sections. The segment or
33902 section bases are start addresses, not relocation offsets; they do not
33903 depend on the library's link-time base addresses.
33905 @value{GDBN} must be linked with the Expat library to support XML
33906 library lists. @xref{Expat}.
33908 A simple memory map, with one loaded library relocated by a single
33909 offset, looks like this:
33913 <library name="/lib/libc.so.6">
33914 <segment address="0x10000000"/>
33919 Another simple memory map, with one loaded library with three
33920 allocated sections (.text, .data, .bss), looks like this:
33924 <library name="sharedlib.o">
33925 <section address="0x10000000"/>
33926 <section address="0x20000000"/>
33927 <section address="0x30000000"/>
33932 The format of a library list is described by this DTD:
33935 <!-- library-list: Root element with versioning -->
33936 <!ELEMENT library-list (library)*>
33937 <!ATTLIST library-list version CDATA #FIXED "1.0">
33938 <!ELEMENT library (segment*, section*)>
33939 <!ATTLIST library name CDATA #REQUIRED>
33940 <!ELEMENT segment EMPTY>
33941 <!ATTLIST segment address CDATA #REQUIRED>
33942 <!ELEMENT section EMPTY>
33943 <!ATTLIST section address CDATA #REQUIRED>
33946 In addition, segments and section descriptors cannot be mixed within a
33947 single library element, and you must supply at least one segment or
33948 section for each library.
33950 @node Memory Map Format
33951 @section Memory Map Format
33952 @cindex memory map format
33954 To be able to write into flash memory, @value{GDBN} needs to obtain a
33955 memory map from the target. This section describes the format of the
33958 The memory map is obtained using the @samp{qXfer:memory-map:read}
33959 (@pxref{qXfer memory map read}) packet and is an XML document that
33960 lists memory regions.
33962 @value{GDBN} must be linked with the Expat library to support XML
33963 memory maps. @xref{Expat}.
33965 The top-level structure of the document is shown below:
33968 <?xml version="1.0"?>
33969 <!DOCTYPE memory-map
33970 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
33971 "http://sourceware.org/gdb/gdb-memory-map.dtd">
33977 Each region can be either:
33982 A region of RAM starting at @var{addr} and extending for @var{length}
33986 <memory type="ram" start="@var{addr}" length="@var{length}"/>
33991 A region of read-only memory:
33994 <memory type="rom" start="@var{addr}" length="@var{length}"/>
33999 A region of flash memory, with erasure blocks @var{blocksize}
34003 <memory type="flash" start="@var{addr}" length="@var{length}">
34004 <property name="blocksize">@var{blocksize}</property>
34010 Regions must not overlap. @value{GDBN} assumes that areas of memory not covered
34011 by the memory map are RAM, and uses the ordinary @samp{M} and @samp{X}
34012 packets to write to addresses in such ranges.
34014 The formal DTD for memory map format is given below:
34017 <!-- ................................................... -->
34018 <!-- Memory Map XML DTD ................................ -->
34019 <!-- File: memory-map.dtd .............................. -->
34020 <!-- .................................... .............. -->
34021 <!-- memory-map.dtd -->
34022 <!-- memory-map: Root element with versioning -->
34023 <!ELEMENT memory-map (memory | property)>
34024 <!ATTLIST memory-map version CDATA #FIXED "1.0.0">
34025 <!ELEMENT memory (property)>
34026 <!-- memory: Specifies a memory region,
34027 and its type, or device. -->
34028 <!ATTLIST memory type CDATA #REQUIRED
34029 start CDATA #REQUIRED
34030 length CDATA #REQUIRED
34031 device CDATA #IMPLIED>
34032 <!-- property: Generic attribute tag -->
34033 <!ELEMENT property (#PCDATA | property)*>
34034 <!ATTLIST property name CDATA #REQUIRED>
34037 @node Thread List Format
34038 @section Thread List Format
34039 @cindex thread list format
34041 To efficiently update the list of threads and their attributes,
34042 @value{GDBN} issues the @samp{qXfer:threads:read} packet
34043 (@pxref{qXfer threads read}) and obtains the XML document with
34044 the following structure:
34047 <?xml version="1.0"?>
34049 <thread id="id" core="0">
34050 ... description ...
34055 Each @samp{thread} element must have the @samp{id} attribute that
34056 identifies the thread (@pxref{thread-id syntax}). The
34057 @samp{core} attribute, if present, specifies which processor core
34058 the thread was last executing on. The content of the of @samp{thread}
34059 element is interpreted as human-readable auxilliary information.
34061 @include agentexpr.texi
34063 @node Trace File Format
34064 @appendix Trace File Format
34065 @cindex trace file format
34067 The trace file comes in three parts: a header, a textual description
34068 section, and a trace frame section with binary data.
34070 The header has the form @code{\x7fTRACE0\n}. The first byte is
34071 @code{0x7f} so as to indicate that the file contains binary data,
34072 while the @code{0} is a version number that may have different values
34075 The description section consists of multiple lines of @sc{ascii} text
34076 separated by newline characters (@code{0xa}). The lines may include a
34077 variety of optional descriptive or context-setting information, such
34078 as tracepoint definitions or register set size. @value{GDBN} will
34079 ignore any line that it does not recognize. An empty line marks the end
34082 @c FIXME add some specific types of data
34084 The trace frame section consists of a number of consecutive frames.
34085 Each frame begins with a two-byte tracepoint number, followed by a
34086 four-byte size giving the amount of data in the frame. The data in
34087 the frame consists of a number of blocks, each introduced by a
34088 character indicating its type (at least register, memory, and trace
34089 state variable). The data in this section is raw binary, not a
34090 hexadecimal or other encoding; its endianness matches the target's
34093 @c FIXME bi-arch may require endianness/arch info in description section
34096 @item R @var{bytes}
34097 Register block. The number and ordering of bytes matches that of a
34098 @code{g} packet in the remote protocol. Note that these are the
34099 actual bytes, in target order and @value{GDBN} register order, not a
34100 hexadecimal encoding.
34102 @item M @var{address} @var{length} @var{bytes}...
34103 Memory block. This is a contiguous block of memory, at the 8-byte
34104 address @var{address}, with a 2-byte length @var{length}, followed by
34105 @var{length} bytes.
34107 @item V @var{number} @var{value}
34108 Trace state variable block. This records the 8-byte signed value
34109 @var{value} of trace state variable numbered @var{number}.
34113 Future enhancements of the trace file format may include additional types
34116 @node Target Descriptions
34117 @appendix Target Descriptions
34118 @cindex target descriptions
34120 @strong{Warning:} target descriptions are still under active development,
34121 and the contents and format may change between @value{GDBN} releases.
34122 The format is expected to stabilize in the future.
34124 One of the challenges of using @value{GDBN} to debug embedded systems
34125 is that there are so many minor variants of each processor
34126 architecture in use. It is common practice for vendors to start with
34127 a standard processor core --- ARM, PowerPC, or MIPS, for example ---
34128 and then make changes to adapt it to a particular market niche. Some
34129 architectures have hundreds of variants, available from dozens of
34130 vendors. This leads to a number of problems:
34134 With so many different customized processors, it is difficult for
34135 the @value{GDBN} maintainers to keep up with the changes.
34137 Since individual variants may have short lifetimes or limited
34138 audiences, it may not be worthwhile to carry information about every
34139 variant in the @value{GDBN} source tree.
34141 When @value{GDBN} does support the architecture of the embedded system
34142 at hand, the task of finding the correct architecture name to give the
34143 @command{set architecture} command can be error-prone.
34146 To address these problems, the @value{GDBN} remote protocol allows a
34147 target system to not only identify itself to @value{GDBN}, but to
34148 actually describe its own features. This lets @value{GDBN} support
34149 processor variants it has never seen before --- to the extent that the
34150 descriptions are accurate, and that @value{GDBN} understands them.
34152 @value{GDBN} must be linked with the Expat library to support XML
34153 target descriptions. @xref{Expat}.
34156 * Retrieving Descriptions:: How descriptions are fetched from a target.
34157 * Target Description Format:: The contents of a target description.
34158 * Predefined Target Types:: Standard types available for target
34160 * Standard Target Features:: Features @value{GDBN} knows about.
34163 @node Retrieving Descriptions
34164 @section Retrieving Descriptions
34166 Target descriptions can be read from the target automatically, or
34167 specified by the user manually. The default behavior is to read the
34168 description from the target. @value{GDBN} retrieves it via the remote
34169 protocol using @samp{qXfer} requests (@pxref{General Query Packets,
34170 qXfer}). The @var{annex} in the @samp{qXfer} packet will be
34171 @samp{target.xml}. The contents of the @samp{target.xml} annex are an
34172 XML document, of the form described in @ref{Target Description
34175 Alternatively, you can specify a file to read for the target description.
34176 If a file is set, the target will not be queried. The commands to
34177 specify a file are:
34180 @cindex set tdesc filename
34181 @item set tdesc filename @var{path}
34182 Read the target description from @var{path}.
34184 @cindex unset tdesc filename
34185 @item unset tdesc filename
34186 Do not read the XML target description from a file. @value{GDBN}
34187 will use the description supplied by the current target.
34189 @cindex show tdesc filename
34190 @item show tdesc filename
34191 Show the filename to read for a target description, if any.
34195 @node Target Description Format
34196 @section Target Description Format
34197 @cindex target descriptions, XML format
34199 A target description annex is an @uref{http://www.w3.org/XML/, XML}
34200 document which complies with the Document Type Definition provided in
34201 the @value{GDBN} sources in @file{gdb/features/gdb-target.dtd}. This
34202 means you can use generally available tools like @command{xmllint} to
34203 check that your feature descriptions are well-formed and valid.
34204 However, to help people unfamiliar with XML write descriptions for
34205 their targets, we also describe the grammar here.
34207 Target descriptions can identify the architecture of the remote target
34208 and (for some architectures) provide information about custom register
34209 sets. They can also identify the OS ABI of the remote target.
34210 @value{GDBN} can use this information to autoconfigure for your
34211 target, or to warn you if you connect to an unsupported target.
34213 Here is a simple target description:
34216 <target version="1.0">
34217 <architecture>i386:x86-64</architecture>
34222 This minimal description only says that the target uses
34223 the x86-64 architecture.
34225 A target description has the following overall form, with [ ] marking
34226 optional elements and @dots{} marking repeatable elements. The elements
34227 are explained further below.
34230 <?xml version="1.0"?>
34231 <!DOCTYPE target SYSTEM "gdb-target.dtd">
34232 <target version="1.0">
34233 @r{[}@var{architecture}@r{]}
34234 @r{[}@var{osabi}@r{]}
34235 @r{[}@var{compatible}@r{]}
34236 @r{[}@var{feature}@dots{}@r{]}
34241 The description is generally insensitive to whitespace and line
34242 breaks, under the usual common-sense rules. The XML version
34243 declaration and document type declaration can generally be omitted
34244 (@value{GDBN} does not require them), but specifying them may be
34245 useful for XML validation tools. The @samp{version} attribute for
34246 @samp{<target>} may also be omitted, but we recommend
34247 including it; if future versions of @value{GDBN} use an incompatible
34248 revision of @file{gdb-target.dtd}, they will detect and report
34249 the version mismatch.
34251 @subsection Inclusion
34252 @cindex target descriptions, inclusion
34255 @cindex <xi:include>
34258 It can sometimes be valuable to split a target description up into
34259 several different annexes, either for organizational purposes, or to
34260 share files between different possible target descriptions. You can
34261 divide a description into multiple files by replacing any element of
34262 the target description with an inclusion directive of the form:
34265 <xi:include href="@var{document}"/>
34269 When @value{GDBN} encounters an element of this form, it will retrieve
34270 the named XML @var{document}, and replace the inclusion directive with
34271 the contents of that document. If the current description was read
34272 using @samp{qXfer}, then so will be the included document;
34273 @var{document} will be interpreted as the name of an annex. If the
34274 current description was read from a file, @value{GDBN} will look for
34275 @var{document} as a file in the same directory where it found the
34276 original description.
34278 @subsection Architecture
34279 @cindex <architecture>
34281 An @samp{<architecture>} element has this form:
34284 <architecture>@var{arch}</architecture>
34287 @var{arch} is one of the architectures from the set accepted by
34288 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
34291 @cindex @code{<osabi>}
34293 This optional field was introduced in @value{GDBN} version 7.0.
34294 Previous versions of @value{GDBN} ignore it.
34296 An @samp{<osabi>} element has this form:
34299 <osabi>@var{abi-name}</osabi>
34302 @var{abi-name} is an OS ABI name from the same selection accepted by
34303 @w{@code{set osabi}} (@pxref{ABI, ,Configuring the Current ABI}).
34305 @subsection Compatible Architecture
34306 @cindex @code{<compatible>}
34308 This optional field was introduced in @value{GDBN} version 7.0.
34309 Previous versions of @value{GDBN} ignore it.
34311 A @samp{<compatible>} element has this form:
34314 <compatible>@var{arch}</compatible>
34317 @var{arch} is one of the architectures from the set accepted by
34318 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
34320 A @samp{<compatible>} element is used to specify that the target
34321 is able to run binaries in some other than the main target architecture
34322 given by the @samp{<architecture>} element. For example, on the
34323 Cell Broadband Engine, the main architecture is @code{powerpc:common}
34324 or @code{powerpc:common64}, but the system is able to run binaries
34325 in the @code{spu} architecture as well. The way to describe this
34326 capability with @samp{<compatible>} is as follows:
34329 <architecture>powerpc:common</architecture>
34330 <compatible>spu</compatible>
34333 @subsection Features
34336 Each @samp{<feature>} describes some logical portion of the target
34337 system. Features are currently used to describe available CPU
34338 registers and the types of their contents. A @samp{<feature>} element
34342 <feature name="@var{name}">
34343 @r{[}@var{type}@dots{}@r{]}
34349 Each feature's name should be unique within the description. The name
34350 of a feature does not matter unless @value{GDBN} has some special
34351 knowledge of the contents of that feature; if it does, the feature
34352 should have its standard name. @xref{Standard Target Features}.
34356 Any register's value is a collection of bits which @value{GDBN} must
34357 interpret. The default interpretation is a two's complement integer,
34358 but other types can be requested by name in the register description.
34359 Some predefined types are provided by @value{GDBN} (@pxref{Predefined
34360 Target Types}), and the description can define additional composite types.
34362 Each type element must have an @samp{id} attribute, which gives
34363 a unique (within the containing @samp{<feature>}) name to the type.
34364 Types must be defined before they are used.
34367 Some targets offer vector registers, which can be treated as arrays
34368 of scalar elements. These types are written as @samp{<vector>} elements,
34369 specifying the array element type, @var{type}, and the number of elements,
34373 <vector id="@var{id}" type="@var{type}" count="@var{count}"/>
34377 If a register's value is usefully viewed in multiple ways, define it
34378 with a union type containing the useful representations. The
34379 @samp{<union>} element contains one or more @samp{<field>} elements,
34380 each of which has a @var{name} and a @var{type}:
34383 <union id="@var{id}">
34384 <field name="@var{name}" type="@var{type}"/>
34390 If a register's value is composed from several separate values, define
34391 it with a structure type. There are two forms of the @samp{<struct>}
34392 element; a @samp{<struct>} element must either contain only bitfields
34393 or contain no bitfields. If the structure contains only bitfields,
34394 its total size in bytes must be specified, each bitfield must have an
34395 explicit start and end, and bitfields are automatically assigned an
34396 integer type. The field's @var{start} should be less than or
34397 equal to its @var{end}, and zero represents the least significant bit.
34400 <struct id="@var{id}" size="@var{size}">
34401 <field name="@var{name}" start="@var{start}" end="@var{end}"/>
34406 If the structure contains no bitfields, then each field has an
34407 explicit type, and no implicit padding is added.
34410 <struct id="@var{id}">
34411 <field name="@var{name}" type="@var{type}"/>
34417 If a register's value is a series of single-bit flags, define it with
34418 a flags type. The @samp{<flags>} element has an explicit @var{size}
34419 and contains one or more @samp{<field>} elements. Each field has a
34420 @var{name}, a @var{start}, and an @var{end}. Only single-bit flags
34424 <flags id="@var{id}" size="@var{size}">
34425 <field name="@var{name}" start="@var{start}" end="@var{end}"/>
34430 @subsection Registers
34433 Each register is represented as an element with this form:
34436 <reg name="@var{name}"
34437 bitsize="@var{size}"
34438 @r{[}regnum="@var{num}"@r{]}
34439 @r{[}save-restore="@var{save-restore}"@r{]}
34440 @r{[}type="@var{type}"@r{]}
34441 @r{[}group="@var{group}"@r{]}/>
34445 The components are as follows:
34450 The register's name; it must be unique within the target description.
34453 The register's size, in bits.
34456 The register's number. If omitted, a register's number is one greater
34457 than that of the previous register (either in the current feature or in
34458 a preceeding feature); the first register in the target description
34459 defaults to zero. This register number is used to read or write
34460 the register; e.g.@: it is used in the remote @code{p} and @code{P}
34461 packets, and registers appear in the @code{g} and @code{G} packets
34462 in order of increasing register number.
34465 Whether the register should be preserved across inferior function
34466 calls; this must be either @code{yes} or @code{no}. The default is
34467 @code{yes}, which is appropriate for most registers except for
34468 some system control registers; this is not related to the target's
34472 The type of the register. @var{type} may be a predefined type, a type
34473 defined in the current feature, or one of the special types @code{int}
34474 and @code{float}. @code{int} is an integer type of the correct size
34475 for @var{bitsize}, and @code{float} is a floating point type (in the
34476 architecture's normal floating point format) of the correct size for
34477 @var{bitsize}. The default is @code{int}.
34480 The register group to which this register belongs. @var{group} must
34481 be either @code{general}, @code{float}, or @code{vector}. If no
34482 @var{group} is specified, @value{GDBN} will not display the register
34483 in @code{info registers}.
34487 @node Predefined Target Types
34488 @section Predefined Target Types
34489 @cindex target descriptions, predefined types
34491 Type definitions in the self-description can build up composite types
34492 from basic building blocks, but can not define fundamental types. Instead,
34493 standard identifiers are provided by @value{GDBN} for the fundamental
34494 types. The currently supported types are:
34503 Signed integer types holding the specified number of bits.
34510 Unsigned integer types holding the specified number of bits.
34514 Pointers to unspecified code and data. The program counter and
34515 any dedicated return address register may be marked as code
34516 pointers; printing a code pointer converts it into a symbolic
34517 address. The stack pointer and any dedicated address registers
34518 may be marked as data pointers.
34521 Single precision IEEE floating point.
34524 Double precision IEEE floating point.
34527 The 12-byte extended precision format used by ARM FPA registers.
34530 The 10-byte extended precision format used by x87 registers.
34533 32bit @sc{eflags} register used by x86.
34536 32bit @sc{mxcsr} register used by x86.
34540 @node Standard Target Features
34541 @section Standard Target Features
34542 @cindex target descriptions, standard features
34544 A target description must contain either no registers or all the
34545 target's registers. If the description contains no registers, then
34546 @value{GDBN} will assume a default register layout, selected based on
34547 the architecture. If the description contains any registers, the
34548 default layout will not be used; the standard registers must be
34549 described in the target description, in such a way that @value{GDBN}
34550 can recognize them.
34552 This is accomplished by giving specific names to feature elements
34553 which contain standard registers. @value{GDBN} will look for features
34554 with those names and verify that they contain the expected registers;
34555 if any known feature is missing required registers, or if any required
34556 feature is missing, @value{GDBN} will reject the target
34557 description. You can add additional registers to any of the
34558 standard features --- @value{GDBN} will display them just as if
34559 they were added to an unrecognized feature.
34561 This section lists the known features and their expected contents.
34562 Sample XML documents for these features are included in the
34563 @value{GDBN} source tree, in the directory @file{gdb/features}.
34565 Names recognized by @value{GDBN} should include the name of the
34566 company or organization which selected the name, and the overall
34567 architecture to which the feature applies; so e.g.@: the feature
34568 containing ARM core registers is named @samp{org.gnu.gdb.arm.core}.
34570 The names of registers are not case sensitive for the purpose
34571 of recognizing standard features, but @value{GDBN} will only display
34572 registers using the capitalization used in the description.
34579 * PowerPC Features::
34584 @subsection ARM Features
34585 @cindex target descriptions, ARM features
34587 The @samp{org.gnu.gdb.arm.core} feature is required for ARM targets.
34588 It should contain registers @samp{r0} through @samp{r13}, @samp{sp},
34589 @samp{lr}, @samp{pc}, and @samp{cpsr}.
34591 The @samp{org.gnu.gdb.arm.fpa} feature is optional. If present, it
34592 should contain registers @samp{f0} through @samp{f7} and @samp{fps}.
34594 The @samp{org.gnu.gdb.xscale.iwmmxt} feature is optional. If present,
34595 it should contain at least registers @samp{wR0} through @samp{wR15} and
34596 @samp{wCGR0} through @samp{wCGR3}. The @samp{wCID}, @samp{wCon},
34597 @samp{wCSSF}, and @samp{wCASF} registers are optional.
34599 The @samp{org.gnu.gdb.arm.vfp} feature is optional. If present, it
34600 should contain at least registers @samp{d0} through @samp{d15}. If
34601 they are present, @samp{d16} through @samp{d31} should also be included.
34602 @value{GDBN} will synthesize the single-precision registers from
34603 halves of the double-precision registers.
34605 The @samp{org.gnu.gdb.arm.neon} feature is optional. It does not
34606 need to contain registers; it instructs @value{GDBN} to display the
34607 VFP double-precision registers as vectors and to synthesize the
34608 quad-precision registers from pairs of double-precision registers.
34609 If this feature is present, @samp{org.gnu.gdb.arm.vfp} must also
34610 be present and include 32 double-precision registers.
34612 @node i386 Features
34613 @subsection i386 Features
34614 @cindex target descriptions, i386 features
34616 The @samp{org.gnu.gdb.i386.core} feature is required for i386/amd64
34617 targets. It should describe the following registers:
34621 @samp{eax} through @samp{edi} plus @samp{eip} for i386
34623 @samp{rax} through @samp{r15} plus @samp{rip} for amd64
34625 @samp{eflags}, @samp{cs}, @samp{ss}, @samp{ds}, @samp{es},
34626 @samp{fs}, @samp{gs}
34628 @samp{st0} through @samp{st7}
34630 @samp{fctrl}, @samp{fstat}, @samp{ftag}, @samp{fiseg}, @samp{fioff},
34631 @samp{foseg}, @samp{fooff} and @samp{fop}
34634 The register sets may be different, depending on the target.
34636 The @samp{org.gnu.gdb.i386.sse} feature is optional. It should
34637 describe registers:
34641 @samp{xmm0} through @samp{xmm7} for i386
34643 @samp{xmm0} through @samp{xmm15} for amd64
34648 The @samp{org.gnu.gdb.i386.avx} feature is optional and requires the
34649 @samp{org.gnu.gdb.i386.sse} feature. It should
34650 describe the upper 128 bits of @sc{ymm} registers:
34654 @samp{ymm0h} through @samp{ymm7h} for i386
34656 @samp{ymm0h} through @samp{ymm15h} for amd64
34660 The @samp{org.gnu.gdb.i386.linux} feature is optional. It should
34661 describe a single register, @samp{orig_eax}.
34663 @node MIPS Features
34664 @subsection MIPS Features
34665 @cindex target descriptions, MIPS features
34667 The @samp{org.gnu.gdb.mips.cpu} feature is required for MIPS targets.
34668 It should contain registers @samp{r0} through @samp{r31}, @samp{lo},
34669 @samp{hi}, and @samp{pc}. They may be 32-bit or 64-bit depending
34672 The @samp{org.gnu.gdb.mips.cp0} feature is also required. It should
34673 contain at least the @samp{status}, @samp{badvaddr}, and @samp{cause}
34674 registers. They may be 32-bit or 64-bit depending on the target.
34676 The @samp{org.gnu.gdb.mips.fpu} feature is currently required, though
34677 it may be optional in a future version of @value{GDBN}. It should
34678 contain registers @samp{f0} through @samp{f31}, @samp{fcsr}, and
34679 @samp{fir}. They may be 32-bit or 64-bit depending on the target.
34681 The @samp{org.gnu.gdb.mips.linux} feature is optional. It should
34682 contain a single register, @samp{restart}, which is used by the
34683 Linux kernel to control restartable syscalls.
34685 @node M68K Features
34686 @subsection M68K Features
34687 @cindex target descriptions, M68K features
34690 @item @samp{org.gnu.gdb.m68k.core}
34691 @itemx @samp{org.gnu.gdb.coldfire.core}
34692 @itemx @samp{org.gnu.gdb.fido.core}
34693 One of those features must be always present.
34694 The feature that is present determines which flavor of m68k is
34695 used. The feature that is present should contain registers
34696 @samp{d0} through @samp{d7}, @samp{a0} through @samp{a5}, @samp{fp},
34697 @samp{sp}, @samp{ps} and @samp{pc}.
34699 @item @samp{org.gnu.gdb.coldfire.fp}
34700 This feature is optional. If present, it should contain registers
34701 @samp{fp0} through @samp{fp7}, @samp{fpcontrol}, @samp{fpstatus} and
34705 @node PowerPC Features
34706 @subsection PowerPC Features
34707 @cindex target descriptions, PowerPC features
34709 The @samp{org.gnu.gdb.power.core} feature is required for PowerPC
34710 targets. It should contain registers @samp{r0} through @samp{r31},
34711 @samp{pc}, @samp{msr}, @samp{cr}, @samp{lr}, @samp{ctr}, and
34712 @samp{xer}. They may be 32-bit or 64-bit depending on the target.
34714 The @samp{org.gnu.gdb.power.fpu} feature is optional. It should
34715 contain registers @samp{f0} through @samp{f31} and @samp{fpscr}.
34717 The @samp{org.gnu.gdb.power.altivec} feature is optional. It should
34718 contain registers @samp{vr0} through @samp{vr31}, @samp{vscr},
34721 The @samp{org.gnu.gdb.power.vsx} feature is optional. It should
34722 contain registers @samp{vs0h} through @samp{vs31h}. @value{GDBN}
34723 will combine these registers with the floating point registers
34724 (@samp{f0} through @samp{f31}) and the altivec registers (@samp{vr0}
34725 through @samp{vr31}) to present the 128-bit wide registers @samp{vs0}
34726 through @samp{vs63}, the set of vector registers for POWER7.
34728 The @samp{org.gnu.gdb.power.spe} feature is optional. It should
34729 contain registers @samp{ev0h} through @samp{ev31h}, @samp{acc}, and
34730 @samp{spefscr}. SPE targets should provide 32-bit registers in
34731 @samp{org.gnu.gdb.power.core} and provide the upper halves in
34732 @samp{ev0h} through @samp{ev31h}. @value{GDBN} will combine
34733 these to present registers @samp{ev0} through @samp{ev31} to the
34736 @node Operating System Information
34737 @appendix Operating System Information
34738 @cindex operating system information
34744 Users of @value{GDBN} often wish to obtain information about the state of
34745 the operating system running on the target---for example the list of
34746 processes, or the list of open files. This section describes the
34747 mechanism that makes it possible. This mechanism is similar to the
34748 target features mechanism (@pxref{Target Descriptions}), but focuses
34749 on a different aspect of target.
34751 Operating system information is retrived from the target via the
34752 remote protocol, using @samp{qXfer} requests (@pxref{qXfer osdata
34753 read}). The object name in the request should be @samp{osdata}, and
34754 the @var{annex} identifies the data to be fetched.
34757 @appendixsection Process list
34758 @cindex operating system information, process list
34760 When requesting the process list, the @var{annex} field in the
34761 @samp{qXfer} request should be @samp{processes}. The returned data is
34762 an XML document. The formal syntax of this document is defined in
34763 @file{gdb/features/osdata.dtd}.
34765 An example document is:
34768 <?xml version="1.0"?>
34769 <!DOCTYPE target SYSTEM "osdata.dtd">
34770 <osdata type="processes">
34772 <column name="pid">1</column>
34773 <column name="user">root</column>
34774 <column name="command">/sbin/init</column>
34775 <column name="cores">1,2,3</column>
34780 Each item should include a column whose name is @samp{pid}. The value
34781 of that column should identify the process on the target. The
34782 @samp{user} and @samp{command} columns are optional, and will be
34783 displayed by @value{GDBN}. The @samp{cores} column, if present,
34784 should contain a comma-separated list of cores that this process
34785 is running on. Target may provide additional columns,
34786 which @value{GDBN} currently ignores.
34800 % I think something like @colophon should be in texinfo. In the
34802 \long\def\colophon{\hbox to0pt{}\vfill
34803 \centerline{The body of this manual is set in}
34804 \centerline{\fontname\tenrm,}
34805 \centerline{with headings in {\bf\fontname\tenbf}}
34806 \centerline{and examples in {\tt\fontname\tentt}.}
34807 \centerline{{\it\fontname\tenit\/},}
34808 \centerline{{\bf\fontname\tenbf}, and}
34809 \centerline{{\sl\fontname\tensl\/}}
34810 \centerline{are used for emphasis.}\vfill}
34812 % Blame: doc@cygnus.com, 1991.