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 1.3 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 @vindex $_thread@r{, convenience variable}
2792 The debugger convenience variable @samp{$_thread} contains the number
2793 of the current thread. You may find this useful in writing breakpoint
2794 conditional expressions, command scripts, and so forth. See
2795 @xref{Convenience Vars,, Convenience Variables}, for general
2796 information on convenience variables.
2798 @kindex thread apply
2799 @cindex apply command to several threads
2800 @item thread apply [@var{threadno}] [@var{all}] @var{command}
2801 The @code{thread apply} command allows you to apply the named
2802 @var{command} to one or more threads. Specify the numbers of the
2803 threads that you want affected with the command argument
2804 @var{threadno}. It can be a single thread number, one of the numbers
2805 shown in the first field of the @samp{info threads} display; or it
2806 could be a range of thread numbers, as in @code{2-4}. To apply a
2807 command to all threads, type @kbd{thread apply all @var{command}}.
2809 @kindex set print thread-events
2810 @cindex print messages on thread start and exit
2811 @item set print thread-events
2812 @itemx set print thread-events on
2813 @itemx set print thread-events off
2814 The @code{set print thread-events} command allows you to enable or
2815 disable printing of messages when @value{GDBN} notices that new threads have
2816 started or that threads have exited. By default, these messages will
2817 be printed if detection of these events is supported by the target.
2818 Note that these messages cannot be disabled on all targets.
2820 @kindex show print thread-events
2821 @item show print thread-events
2822 Show whether messages will be printed when @value{GDBN} detects that threads
2823 have started and exited.
2826 @xref{Thread Stops,,Stopping and Starting Multi-thread Programs}, for
2827 more information about how @value{GDBN} behaves when you stop and start
2828 programs with multiple threads.
2830 @xref{Set Watchpoints,,Setting Watchpoints}, for information about
2831 watchpoints in programs with multiple threads.
2834 @kindex set libthread-db-search-path
2835 @cindex search path for @code{libthread_db}
2836 @item set libthread-db-search-path @r{[}@var{path}@r{]}
2837 If this variable is set, @var{path} is a colon-separated list of
2838 directories @value{GDBN} will use to search for @code{libthread_db}.
2839 If you omit @var{path}, @samp{libthread-db-search-path} will be reset to
2842 On @sc{gnu}/Linux and Solaris systems, @value{GDBN} uses a ``helper''
2843 @code{libthread_db} library to obtain information about threads in the
2844 inferior process. @value{GDBN} will use @samp{libthread-db-search-path}
2845 to find @code{libthread_db}. If that fails, @value{GDBN} will continue
2846 with default system shared library directories, and finally the directory
2847 from which @code{libpthread} was loaded in the inferior process.
2849 For any @code{libthread_db} library @value{GDBN} finds in above directories,
2850 @value{GDBN} attempts to initialize it with the current inferior process.
2851 If this initialization fails (which could happen because of a version
2852 mismatch between @code{libthread_db} and @code{libpthread}), @value{GDBN}
2853 will unload @code{libthread_db}, and continue with the next directory.
2854 If none of @code{libthread_db} libraries initialize successfully,
2855 @value{GDBN} will issue a warning and thread debugging will be disabled.
2857 Setting @code{libthread-db-search-path} is currently implemented
2858 only on some platforms.
2860 @kindex show libthread-db-search-path
2861 @item show libthread-db-search-path
2862 Display current libthread_db search path.
2866 @section Debugging Forks
2868 @cindex fork, debugging programs which call
2869 @cindex multiple processes
2870 @cindex processes, multiple
2871 On most systems, @value{GDBN} has no special support for debugging
2872 programs which create additional processes using the @code{fork}
2873 function. When a program forks, @value{GDBN} will continue to debug the
2874 parent process and the child process will run unimpeded. If you have
2875 set a breakpoint in any code which the child then executes, the child
2876 will get a @code{SIGTRAP} signal which (unless it catches the signal)
2877 will cause it to terminate.
2879 However, if you want to debug the child process there is a workaround
2880 which isn't too painful. Put a call to @code{sleep} in the code which
2881 the child process executes after the fork. It may be useful to sleep
2882 only if a certain environment variable is set, or a certain file exists,
2883 so that the delay need not occur when you don't want to run @value{GDBN}
2884 on the child. While the child is sleeping, use the @code{ps} program to
2885 get its process ID. Then tell @value{GDBN} (a new invocation of
2886 @value{GDBN} if you are also debugging the parent process) to attach to
2887 the child process (@pxref{Attach}). From that point on you can debug
2888 the child process just like any other process which you attached to.
2890 On some systems, @value{GDBN} provides support for debugging programs that
2891 create additional processes using the @code{fork} or @code{vfork} functions.
2892 Currently, the only platforms with this feature are HP-UX (11.x and later
2893 only?) and @sc{gnu}/Linux (kernel version 2.5.60 and later).
2895 By default, when a program forks, @value{GDBN} will continue to debug
2896 the parent process and the child process will run unimpeded.
2898 If you want to follow the child process instead of the parent process,
2899 use the command @w{@code{set follow-fork-mode}}.
2902 @kindex set follow-fork-mode
2903 @item set follow-fork-mode @var{mode}
2904 Set the debugger response to a program call of @code{fork} or
2905 @code{vfork}. A call to @code{fork} or @code{vfork} creates a new
2906 process. The @var{mode} argument can be:
2910 The original process is debugged after a fork. The child process runs
2911 unimpeded. This is the default.
2914 The new process is debugged after a fork. The parent process runs
2919 @kindex show follow-fork-mode
2920 @item show follow-fork-mode
2921 Display the current debugger response to a @code{fork} or @code{vfork} call.
2924 @cindex debugging multiple processes
2925 On Linux, if you want to debug both the parent and child processes, use the
2926 command @w{@code{set detach-on-fork}}.
2929 @kindex set detach-on-fork
2930 @item set detach-on-fork @var{mode}
2931 Tells gdb whether to detach one of the processes after a fork, or
2932 retain debugger control over them both.
2936 The child process (or parent process, depending on the value of
2937 @code{follow-fork-mode}) will be detached and allowed to run
2938 independently. This is the default.
2941 Both processes will be held under the control of @value{GDBN}.
2942 One process (child or parent, depending on the value of
2943 @code{follow-fork-mode}) is debugged as usual, while the other
2948 @kindex show detach-on-fork
2949 @item show detach-on-fork
2950 Show whether detach-on-fork mode is on/off.
2953 If you choose to set @samp{detach-on-fork} mode off, then @value{GDBN}
2954 will retain control of all forked processes (including nested forks).
2955 You can list the forked processes under the control of @value{GDBN} by
2956 using the @w{@code{info inferiors}} command, and switch from one fork
2957 to another by using the @code{inferior} command (@pxref{Inferiors and
2958 Programs, ,Debugging Multiple Inferiors and Programs}).
2960 To quit debugging one of the forked processes, you can either detach
2961 from it by using the @w{@code{detach inferior}} command (allowing it
2962 to run independently), or kill it using the @w{@code{kill inferior}}
2963 command. @xref{Inferiors and Programs, ,Debugging Multiple Inferiors
2966 If you ask to debug a child process and a @code{vfork} is followed by an
2967 @code{exec}, @value{GDBN} executes the new target up to the first
2968 breakpoint in the new target. If you have a breakpoint set on
2969 @code{main} in your original program, the breakpoint will also be set on
2970 the child process's @code{main}.
2972 On some systems, when a child process is spawned by @code{vfork}, you
2973 cannot debug the child or parent until an @code{exec} call completes.
2975 If you issue a @code{run} command to @value{GDBN} after an @code{exec}
2976 call executes, the new target restarts. To restart the parent
2977 process, use the @code{file} command with the parent executable name
2978 as its argument. By default, after an @code{exec} call executes,
2979 @value{GDBN} discards the symbols of the previous executable image.
2980 You can change this behaviour with the @w{@code{set follow-exec-mode}}
2984 @kindex set follow-exec-mode
2985 @item set follow-exec-mode @var{mode}
2987 Set debugger response to a program call of @code{exec}. An
2988 @code{exec} call replaces the program image of a process.
2990 @code{follow-exec-mode} can be:
2994 @value{GDBN} creates a new inferior and rebinds the process to this
2995 new inferior. The program the process was running before the
2996 @code{exec} call can be restarted afterwards by restarting the
3002 (@value{GDBP}) info inferiors
3004 Id Description Executable
3007 process 12020 is executing new program: prog2
3008 Program exited normally.
3009 (@value{GDBP}) info inferiors
3010 Id Description Executable
3016 @value{GDBN} keeps the process bound to the same inferior. The new
3017 executable image replaces the previous executable loaded in the
3018 inferior. Restarting the inferior after the @code{exec} call, with
3019 e.g., the @code{run} command, restarts the executable the process was
3020 running after the @code{exec} call. This is the default mode.
3025 (@value{GDBP}) info inferiors
3026 Id Description Executable
3029 process 12020 is executing new program: prog2
3030 Program exited normally.
3031 (@value{GDBP}) info inferiors
3032 Id Description Executable
3039 You can use the @code{catch} command to make @value{GDBN} stop whenever
3040 a @code{fork}, @code{vfork}, or @code{exec} call is made. @xref{Set
3041 Catchpoints, ,Setting Catchpoints}.
3043 @node Checkpoint/Restart
3044 @section Setting a @emph{Bookmark} to Return to Later
3049 @cindex snapshot of a process
3050 @cindex rewind program state
3052 On certain operating systems@footnote{Currently, only
3053 @sc{gnu}/Linux.}, @value{GDBN} is able to save a @dfn{snapshot} of a
3054 program's state, called a @dfn{checkpoint}, and come back to it
3057 Returning to a checkpoint effectively undoes everything that has
3058 happened in the program since the @code{checkpoint} was saved. This
3059 includes changes in memory, registers, and even (within some limits)
3060 system state. Effectively, it is like going back in time to the
3061 moment when the checkpoint was saved.
3063 Thus, if you're stepping thru a program and you think you're
3064 getting close to the point where things go wrong, you can save
3065 a checkpoint. Then, if you accidentally go too far and miss
3066 the critical statement, instead of having to restart your program
3067 from the beginning, you can just go back to the checkpoint and
3068 start again from there.
3070 This can be especially useful if it takes a lot of time or
3071 steps to reach the point where you think the bug occurs.
3073 To use the @code{checkpoint}/@code{restart} method of debugging:
3078 Save a snapshot of the debugged program's current execution state.
3079 The @code{checkpoint} command takes no arguments, but each checkpoint
3080 is assigned a small integer id, similar to a breakpoint id.
3082 @kindex info checkpoints
3083 @item info checkpoints
3084 List the checkpoints that have been saved in the current debugging
3085 session. For each checkpoint, the following information will be
3092 @item Source line, or label
3095 @kindex restart @var{checkpoint-id}
3096 @item restart @var{checkpoint-id}
3097 Restore the program state that was saved as checkpoint number
3098 @var{checkpoint-id}. All program variables, registers, stack frames
3099 etc.@: will be returned to the values that they had when the checkpoint
3100 was saved. In essence, gdb will ``wind back the clock'' to the point
3101 in time when the checkpoint was saved.
3103 Note that breakpoints, @value{GDBN} variables, command history etc.
3104 are not affected by restoring a checkpoint. In general, a checkpoint
3105 only restores things that reside in the program being debugged, not in
3108 @kindex delete checkpoint @var{checkpoint-id}
3109 @item delete checkpoint @var{checkpoint-id}
3110 Delete the previously-saved checkpoint identified by @var{checkpoint-id}.
3114 Returning to a previously saved checkpoint will restore the user state
3115 of the program being debugged, plus a significant subset of the system
3116 (OS) state, including file pointers. It won't ``un-write'' data from
3117 a file, but it will rewind the file pointer to the previous location,
3118 so that the previously written data can be overwritten. For files
3119 opened in read mode, the pointer will also be restored so that the
3120 previously read data can be read again.
3122 Of course, characters that have been sent to a printer (or other
3123 external device) cannot be ``snatched back'', and characters received
3124 from eg.@: a serial device can be removed from internal program buffers,
3125 but they cannot be ``pushed back'' into the serial pipeline, ready to
3126 be received again. Similarly, the actual contents of files that have
3127 been changed cannot be restored (at this time).
3129 However, within those constraints, you actually can ``rewind'' your
3130 program to a previously saved point in time, and begin debugging it
3131 again --- and you can change the course of events so as to debug a
3132 different execution path this time.
3134 @cindex checkpoints and process id
3135 Finally, there is one bit of internal program state that will be
3136 different when you return to a checkpoint --- the program's process
3137 id. Each checkpoint will have a unique process id (or @var{pid}),
3138 and each will be different from the program's original @var{pid}.
3139 If your program has saved a local copy of its process id, this could
3140 potentially pose a problem.
3142 @subsection A Non-obvious Benefit of Using Checkpoints
3144 On some systems such as @sc{gnu}/Linux, address space randomization
3145 is performed on new processes for security reasons. This makes it
3146 difficult or impossible to set a breakpoint, or watchpoint, on an
3147 absolute address if you have to restart the program, since the
3148 absolute location of a symbol will change from one execution to the
3151 A checkpoint, however, is an @emph{identical} copy of a process.
3152 Therefore if you create a checkpoint at (eg.@:) the start of main,
3153 and simply return to that checkpoint instead of restarting the
3154 process, you can avoid the effects of address randomization and
3155 your symbols will all stay in the same place.
3158 @chapter Stopping and Continuing
3160 The principal purposes of using a debugger are so that you can stop your
3161 program before it terminates; or so that, if your program runs into
3162 trouble, you can investigate and find out why.
3164 Inside @value{GDBN}, your program may stop for any of several reasons,
3165 such as a signal, a breakpoint, or reaching a new line after a
3166 @value{GDBN} command such as @code{step}. You may then examine and
3167 change variables, set new breakpoints or remove old ones, and then
3168 continue execution. Usually, the messages shown by @value{GDBN} provide
3169 ample explanation of the status of your program---but you can also
3170 explicitly request this information at any time.
3173 @kindex info program
3175 Display information about the status of your program: whether it is
3176 running or not, what process it is, and why it stopped.
3180 * Breakpoints:: Breakpoints, watchpoints, and catchpoints
3181 * Continuing and Stepping:: Resuming execution
3183 * Thread Stops:: Stopping and starting multi-thread programs
3187 @section Breakpoints, Watchpoints, and Catchpoints
3190 A @dfn{breakpoint} makes your program stop whenever a certain point in
3191 the program is reached. For each breakpoint, you can add conditions to
3192 control in finer detail whether your program stops. You can set
3193 breakpoints with the @code{break} command and its variants (@pxref{Set
3194 Breaks, ,Setting Breakpoints}), to specify the place where your program
3195 should stop by line number, function name or exact address in the
3198 On some systems, you can set breakpoints in shared libraries before
3199 the executable is run. There is a minor limitation on HP-UX systems:
3200 you must wait until the executable is run in order to set breakpoints
3201 in shared library routines that are not called directly by the program
3202 (for example, routines that are arguments in a @code{pthread_create}
3206 @cindex data breakpoints
3207 @cindex memory tracing
3208 @cindex breakpoint on memory address
3209 @cindex breakpoint on variable modification
3210 A @dfn{watchpoint} is a special breakpoint that stops your program
3211 when the value of an expression changes. The expression may be a value
3212 of a variable, or it could involve values of one or more variables
3213 combined by operators, such as @samp{a + b}. This is sometimes called
3214 @dfn{data breakpoints}. You must use a different command to set
3215 watchpoints (@pxref{Set Watchpoints, ,Setting Watchpoints}), but aside
3216 from that, you can manage a watchpoint like any other breakpoint: you
3217 enable, disable, and delete both breakpoints and watchpoints using the
3220 You can arrange to have values from your program displayed automatically
3221 whenever @value{GDBN} stops at a breakpoint. @xref{Auto Display,,
3225 @cindex breakpoint on events
3226 A @dfn{catchpoint} is another special breakpoint that stops your program
3227 when a certain kind of event occurs, such as the throwing of a C@t{++}
3228 exception or the loading of a library. As with watchpoints, you use a
3229 different command to set a catchpoint (@pxref{Set Catchpoints, ,Setting
3230 Catchpoints}), but aside from that, you can manage a catchpoint like any
3231 other breakpoint. (To stop when your program receives a signal, use the
3232 @code{handle} command; see @ref{Signals, ,Signals}.)
3234 @cindex breakpoint numbers
3235 @cindex numbers for breakpoints
3236 @value{GDBN} assigns a number to each breakpoint, watchpoint, or
3237 catchpoint when you create it; these numbers are successive integers
3238 starting with one. In many of the commands for controlling various
3239 features of breakpoints you use the breakpoint number to say which
3240 breakpoint you want to change. Each breakpoint may be @dfn{enabled} or
3241 @dfn{disabled}; if disabled, it has no effect on your program until you
3244 @cindex breakpoint ranges
3245 @cindex ranges of breakpoints
3246 Some @value{GDBN} commands accept a range of breakpoints on which to
3247 operate. A breakpoint range is either a single breakpoint number, like
3248 @samp{5}, or two such numbers, in increasing order, separated by a
3249 hyphen, like @samp{5-7}. When a breakpoint range is given to a command,
3250 all breakpoints in that range are operated on.
3253 * Set Breaks:: Setting breakpoints
3254 * Set Watchpoints:: Setting watchpoints
3255 * Set Catchpoints:: Setting catchpoints
3256 * Delete Breaks:: Deleting breakpoints
3257 * Disabling:: Disabling breakpoints
3258 * Conditions:: Break conditions
3259 * Break Commands:: Breakpoint command lists
3260 * Save Breakpoints:: How to save breakpoints in a file
3261 * Error in Breakpoints:: ``Cannot insert breakpoints''
3262 * Breakpoint-related Warnings:: ``Breakpoint address adjusted...''
3266 @subsection Setting Breakpoints
3268 @c FIXME LMB what does GDB do if no code on line of breakpt?
3269 @c consider in particular declaration with/without initialization.
3271 @c FIXME 2 is there stuff on this already? break at fun start, already init?
3274 @kindex b @r{(@code{break})}
3275 @vindex $bpnum@r{, convenience variable}
3276 @cindex latest breakpoint
3277 Breakpoints are set with the @code{break} command (abbreviated
3278 @code{b}). The debugger convenience variable @samp{$bpnum} records the
3279 number of the breakpoint you've set most recently; see @ref{Convenience
3280 Vars,, Convenience Variables}, for a discussion of what you can do with
3281 convenience variables.
3284 @item break @var{location}
3285 Set a breakpoint at the given @var{location}, which can specify a
3286 function name, a line number, or an address of an instruction.
3287 (@xref{Specify Location}, for a list of all the possible ways to
3288 specify a @var{location}.) The breakpoint will stop your program just
3289 before it executes any of the code in the specified @var{location}.
3291 When using source languages that permit overloading of symbols, such as
3292 C@t{++}, a function name may refer to more than one possible place to break.
3293 @xref{Ambiguous Expressions,,Ambiguous Expressions}, for a discussion of
3296 It is also possible to insert a breakpoint that will stop the program
3297 only if a specific thread (@pxref{Thread-Specific Breakpoints})
3298 or a specific task (@pxref{Ada Tasks}) hits that breakpoint.
3301 When called without any arguments, @code{break} sets a breakpoint at
3302 the next instruction to be executed in the selected stack frame
3303 (@pxref{Stack, ,Examining the Stack}). In any selected frame but the
3304 innermost, this makes your program stop as soon as control
3305 returns to that frame. This is similar to the effect of a
3306 @code{finish} command in the frame inside the selected frame---except
3307 that @code{finish} does not leave an active breakpoint. If you use
3308 @code{break} without an argument in the innermost frame, @value{GDBN} stops
3309 the next time it reaches the current location; this may be useful
3312 @value{GDBN} normally ignores breakpoints when it resumes execution, until at
3313 least one instruction has been executed. If it did not do this, you
3314 would be unable to proceed past a breakpoint without first disabling the
3315 breakpoint. This rule applies whether or not the breakpoint already
3316 existed when your program stopped.
3318 @item break @dots{} if @var{cond}
3319 Set a breakpoint with condition @var{cond}; evaluate the expression
3320 @var{cond} each time the breakpoint is reached, and stop only if the
3321 value is nonzero---that is, if @var{cond} evaluates as true.
3322 @samp{@dots{}} stands for one of the possible arguments described
3323 above (or no argument) specifying where to break. @xref{Conditions,
3324 ,Break Conditions}, for more information on breakpoint conditions.
3327 @item tbreak @var{args}
3328 Set a breakpoint enabled only for one stop. @var{args} are the
3329 same as for the @code{break} command, and the breakpoint is set in the same
3330 way, but the breakpoint is automatically deleted after the first time your
3331 program stops there. @xref{Disabling, ,Disabling Breakpoints}.
3334 @cindex hardware breakpoints
3335 @item hbreak @var{args}
3336 Set a hardware-assisted breakpoint. @var{args} are the same as for the
3337 @code{break} command and the breakpoint is set in the same way, but the
3338 breakpoint requires hardware support and some target hardware may not
3339 have this support. The main purpose of this is EPROM/ROM code
3340 debugging, so you can set a breakpoint at an instruction without
3341 changing the instruction. This can be used with the new trap-generation
3342 provided by SPARClite DSU and most x86-based targets. These targets
3343 will generate traps when a program accesses some data or instruction
3344 address that is assigned to the debug registers. However the hardware
3345 breakpoint registers can take a limited number of breakpoints. For
3346 example, on the DSU, only two data breakpoints can be set at a time, and
3347 @value{GDBN} will reject this command if more than two are used. Delete
3348 or disable unused hardware breakpoints before setting new ones
3349 (@pxref{Disabling, ,Disabling Breakpoints}).
3350 @xref{Conditions, ,Break Conditions}.
3351 For remote targets, you can restrict the number of hardware
3352 breakpoints @value{GDBN} will use, see @ref{set remote
3353 hardware-breakpoint-limit}.
3356 @item thbreak @var{args}
3357 Set a hardware-assisted breakpoint enabled only for one stop. @var{args}
3358 are the same as for the @code{hbreak} command and the breakpoint is set in
3359 the same way. However, like the @code{tbreak} command,
3360 the breakpoint is automatically deleted after the
3361 first time your program stops there. Also, like the @code{hbreak}
3362 command, the breakpoint requires hardware support and some target hardware
3363 may not have this support. @xref{Disabling, ,Disabling Breakpoints}.
3364 See also @ref{Conditions, ,Break Conditions}.
3367 @cindex regular expression
3368 @cindex breakpoints at functions matching a regexp
3369 @cindex set breakpoints in many functions
3370 @item rbreak @var{regex}
3371 Set breakpoints on all functions matching the regular expression
3372 @var{regex}. This command sets an unconditional breakpoint on all
3373 matches, printing a list of all breakpoints it set. Once these
3374 breakpoints are set, they are treated just like the breakpoints set with
3375 the @code{break} command. You can delete them, disable them, or make
3376 them conditional the same way as any other breakpoint.
3378 The syntax of the regular expression is the standard one used with tools
3379 like @file{grep}. Note that this is different from the syntax used by
3380 shells, so for instance @code{foo*} matches all functions that include
3381 an @code{fo} followed by zero or more @code{o}s. There is an implicit
3382 @code{.*} leading and trailing the regular expression you supply, so to
3383 match only functions that begin with @code{foo}, use @code{^foo}.
3385 @cindex non-member C@t{++} functions, set breakpoint in
3386 When debugging C@t{++} programs, @code{rbreak} is useful for setting
3387 breakpoints on overloaded functions that are not members of any special
3390 @cindex set breakpoints on all functions
3391 The @code{rbreak} command can be used to set breakpoints in
3392 @strong{all} the functions in a program, like this:
3395 (@value{GDBP}) rbreak .
3398 @item rbreak @var{file}:@var{regex}
3399 If @code{rbreak} is called with a filename qualification, it limits
3400 the search for functions matching the given regular expression to the
3401 specified @var{file}. This can be used, for example, to set breakpoints on
3402 every function in a given file:
3405 (@value{GDBP}) rbreak file.c:.
3408 The colon separating the filename qualifier from the regex may
3409 optionally be surrounded by spaces.
3411 @kindex info breakpoints
3412 @cindex @code{$_} and @code{info breakpoints}
3413 @item info breakpoints @r{[}@var{n}@r{]}
3414 @itemx info break @r{[}@var{n}@r{]}
3415 Print a table of all breakpoints, watchpoints, and catchpoints set and
3416 not deleted. Optional argument @var{n} means print information only
3417 about the specified breakpoint (or watchpoint or catchpoint). For
3418 each breakpoint, following columns are printed:
3421 @item Breakpoint Numbers
3423 Breakpoint, watchpoint, or catchpoint.
3425 Whether the breakpoint is marked to be disabled or deleted when hit.
3426 @item Enabled or Disabled
3427 Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints
3428 that are not enabled.
3430 Where the breakpoint is in your program, as a memory address. For a
3431 pending breakpoint whose address is not yet known, this field will
3432 contain @samp{<PENDING>}. Such breakpoint won't fire until a shared
3433 library that has the symbol or line referred by breakpoint is loaded.
3434 See below for details. A breakpoint with several locations will
3435 have @samp{<MULTIPLE>} in this field---see below for details.
3437 Where the breakpoint is in the source for your program, as a file and
3438 line number. For a pending breakpoint, the original string passed to
3439 the breakpoint command will be listed as it cannot be resolved until
3440 the appropriate shared library is loaded in the future.
3444 If a breakpoint is conditional, @code{info break} shows the condition on
3445 the line following the affected breakpoint; breakpoint commands, if any,
3446 are listed after that. A pending breakpoint is allowed to have a condition
3447 specified for it. The condition is not parsed for validity until a shared
3448 library is loaded that allows the pending breakpoint to resolve to a
3452 @code{info break} with a breakpoint
3453 number @var{n} as argument lists only that breakpoint. The
3454 convenience variable @code{$_} and the default examining-address for
3455 the @code{x} command are set to the address of the last breakpoint
3456 listed (@pxref{Memory, ,Examining Memory}).
3459 @code{info break} displays a count of the number of times the breakpoint
3460 has been hit. This is especially useful in conjunction with the
3461 @code{ignore} command. You can ignore a large number of breakpoint
3462 hits, look at the breakpoint info to see how many times the breakpoint
3463 was hit, and then run again, ignoring one less than that number. This
3464 will get you quickly to the last hit of that breakpoint.
3467 @value{GDBN} allows you to set any number of breakpoints at the same place in
3468 your program. There is nothing silly or meaningless about this. When
3469 the breakpoints are conditional, this is even useful
3470 (@pxref{Conditions, ,Break Conditions}).
3472 @cindex multiple locations, breakpoints
3473 @cindex breakpoints, multiple locations
3474 It is possible that a breakpoint corresponds to several locations
3475 in your program. Examples of this situation are:
3479 For a C@t{++} constructor, the @value{NGCC} compiler generates several
3480 instances of the function body, used in different cases.
3483 For a C@t{++} template function, a given line in the function can
3484 correspond to any number of instantiations.
3487 For an inlined function, a given source line can correspond to
3488 several places where that function is inlined.
3491 In all those cases, @value{GDBN} will insert a breakpoint at all
3492 the relevant locations@footnote{
3493 As of this writing, multiple-location breakpoints work only if there's
3494 line number information for all the locations. This means that they
3495 will generally not work in system libraries, unless you have debug
3496 info with line numbers for them.}.
3498 A breakpoint with multiple locations is displayed in the breakpoint
3499 table using several rows---one header row, followed by one row for
3500 each breakpoint location. The header row has @samp{<MULTIPLE>} in the
3501 address column. The rows for individual locations contain the actual
3502 addresses for locations, and show the functions to which those
3503 locations belong. The number column for a location is of the form
3504 @var{breakpoint-number}.@var{location-number}.
3509 Num Type Disp Enb Address What
3510 1 breakpoint keep y <MULTIPLE>
3512 breakpoint already hit 1 time
3513 1.1 y 0x080486a2 in void foo<int>() at t.cc:8
3514 1.2 y 0x080486ca in void foo<double>() at t.cc:8
3517 Each location can be individually enabled or disabled by passing
3518 @var{breakpoint-number}.@var{location-number} as argument to the
3519 @code{enable} and @code{disable} commands. Note that you cannot
3520 delete the individual locations from the list, you can only delete the
3521 entire list of locations that belong to their parent breakpoint (with
3522 the @kbd{delete @var{num}} command, where @var{num} is the number of
3523 the parent breakpoint, 1 in the above example). Disabling or enabling
3524 the parent breakpoint (@pxref{Disabling}) affects all of the locations
3525 that belong to that breakpoint.
3527 @cindex pending breakpoints
3528 It's quite common to have a breakpoint inside a shared library.
3529 Shared libraries can be loaded and unloaded explicitly,
3530 and possibly repeatedly, as the program is executed. To support
3531 this use case, @value{GDBN} updates breakpoint locations whenever
3532 any shared library is loaded or unloaded. Typically, you would
3533 set a breakpoint in a shared library at the beginning of your
3534 debugging session, when the library is not loaded, and when the
3535 symbols from the library are not available. When you try to set
3536 breakpoint, @value{GDBN} will ask you if you want to set
3537 a so called @dfn{pending breakpoint}---breakpoint whose address
3538 is not yet resolved.
3540 After the program is run, whenever a new shared library is loaded,
3541 @value{GDBN} reevaluates all the breakpoints. When a newly loaded
3542 shared library contains the symbol or line referred to by some
3543 pending breakpoint, that breakpoint is resolved and becomes an
3544 ordinary breakpoint. When a library is unloaded, all breakpoints
3545 that refer to its symbols or source lines become pending again.
3547 This logic works for breakpoints with multiple locations, too. For
3548 example, if you have a breakpoint in a C@t{++} template function, and
3549 a newly loaded shared library has an instantiation of that template,
3550 a new location is added to the list of locations for the breakpoint.
3552 Except for having unresolved address, pending breakpoints do not
3553 differ from regular breakpoints. You can set conditions or commands,
3554 enable and disable them and perform other breakpoint operations.
3556 @value{GDBN} provides some additional commands for controlling what
3557 happens when the @samp{break} command cannot resolve breakpoint
3558 address specification to an address:
3560 @kindex set breakpoint pending
3561 @kindex show breakpoint pending
3563 @item set breakpoint pending auto
3564 This is the default behavior. When @value{GDBN} cannot find the breakpoint
3565 location, it queries you whether a pending breakpoint should be created.
3567 @item set breakpoint pending on
3568 This indicates that an unrecognized breakpoint location should automatically
3569 result in a pending breakpoint being created.
3571 @item set breakpoint pending off
3572 This indicates that pending breakpoints are not to be created. Any
3573 unrecognized breakpoint location results in an error. This setting does
3574 not affect any pending breakpoints previously created.
3576 @item show breakpoint pending
3577 Show the current behavior setting for creating pending breakpoints.
3580 The settings above only affect the @code{break} command and its
3581 variants. Once breakpoint is set, it will be automatically updated
3582 as shared libraries are loaded and unloaded.
3584 @cindex automatic hardware breakpoints
3585 For some targets, @value{GDBN} can automatically decide if hardware or
3586 software breakpoints should be used, depending on whether the
3587 breakpoint address is read-only or read-write. This applies to
3588 breakpoints set with the @code{break} command as well as to internal
3589 breakpoints set by commands like @code{next} and @code{finish}. For
3590 breakpoints set with @code{hbreak}, @value{GDBN} will always use hardware
3593 You can control this automatic behaviour with the following commands::
3595 @kindex set breakpoint auto-hw
3596 @kindex show breakpoint auto-hw
3598 @item set breakpoint auto-hw on
3599 This is the default behavior. When @value{GDBN} sets a breakpoint, it
3600 will try to use the target memory map to decide if software or hardware
3601 breakpoint must be used.
3603 @item set breakpoint auto-hw off
3604 This indicates @value{GDBN} should not automatically select breakpoint
3605 type. If the target provides a memory map, @value{GDBN} will warn when
3606 trying to set software breakpoint at a read-only address.
3609 @value{GDBN} normally implements breakpoints by replacing the program code
3610 at the breakpoint address with a special instruction, which, when
3611 executed, given control to the debugger. By default, the program
3612 code is so modified only when the program is resumed. As soon as
3613 the program stops, @value{GDBN} restores the original instructions. This
3614 behaviour guards against leaving breakpoints inserted in the
3615 target should gdb abrubptly disconnect. However, with slow remote
3616 targets, inserting and removing breakpoint can reduce the performance.
3617 This behavior can be controlled with the following commands::
3619 @kindex set breakpoint always-inserted
3620 @kindex show breakpoint always-inserted
3622 @item set breakpoint always-inserted off
3623 All breakpoints, including newly added by the user, are inserted in
3624 the target only when the target is resumed. All breakpoints are
3625 removed from the target when it stops.
3627 @item set breakpoint always-inserted on
3628 Causes all breakpoints to be inserted in the target at all times. If
3629 the user adds a new breakpoint, or changes an existing breakpoint, the
3630 breakpoints in the target are updated immediately. A breakpoint is
3631 removed from the target only when breakpoint itself is removed.
3633 @cindex non-stop mode, and @code{breakpoint always-inserted}
3634 @item set breakpoint always-inserted auto
3635 This is the default mode. If @value{GDBN} is controlling the inferior
3636 in non-stop mode (@pxref{Non-Stop Mode}), gdb behaves as if
3637 @code{breakpoint always-inserted} mode is on. If @value{GDBN} is
3638 controlling the inferior in all-stop mode, @value{GDBN} behaves as if
3639 @code{breakpoint always-inserted} mode is off.
3642 @cindex negative breakpoint numbers
3643 @cindex internal @value{GDBN} breakpoints
3644 @value{GDBN} itself sometimes sets breakpoints in your program for
3645 special purposes, such as proper handling of @code{longjmp} (in C
3646 programs). These internal breakpoints are assigned negative numbers,
3647 starting with @code{-1}; @samp{info breakpoints} does not display them.
3648 You can see these breakpoints with the @value{GDBN} maintenance command
3649 @samp{maint info breakpoints} (@pxref{maint info breakpoints}).
3652 @node Set Watchpoints
3653 @subsection Setting Watchpoints
3655 @cindex setting watchpoints
3656 You can use a watchpoint to stop execution whenever the value of an
3657 expression changes, without having to predict a particular place where
3658 this may happen. (This is sometimes called a @dfn{data breakpoint}.)
3659 The expression may be as simple as the value of a single variable, or
3660 as complex as many variables combined by operators. Examples include:
3664 A reference to the value of a single variable.
3667 An address cast to an appropriate data type. For example,
3668 @samp{*(int *)0x12345678} will watch a 4-byte region at the specified
3669 address (assuming an @code{int} occupies 4 bytes).
3672 An arbitrarily complex expression, such as @samp{a*b + c/d}. The
3673 expression can use any operators valid in the program's native
3674 language (@pxref{Languages}).
3677 You can set a watchpoint on an expression even if the expression can
3678 not be evaluated yet. For instance, you can set a watchpoint on
3679 @samp{*global_ptr} before @samp{global_ptr} is initialized.
3680 @value{GDBN} will stop when your program sets @samp{global_ptr} and
3681 the expression produces a valid value. If the expression becomes
3682 valid in some other way than changing a variable (e.g.@: if the memory
3683 pointed to by @samp{*global_ptr} becomes readable as the result of a
3684 @code{malloc} call), @value{GDBN} may not stop until the next time
3685 the expression changes.
3687 @cindex software watchpoints
3688 @cindex hardware watchpoints
3689 Depending on your system, watchpoints may be implemented in software or
3690 hardware. @value{GDBN} does software watchpointing by single-stepping your
3691 program and testing the variable's value each time, which is hundreds of
3692 times slower than normal execution. (But this may still be worth it, to
3693 catch errors where you have no clue what part of your program is the
3696 On some systems, such as HP-UX, PowerPC, @sc{gnu}/Linux and most other
3697 x86-based targets, @value{GDBN} includes support for hardware
3698 watchpoints, which do not slow down the running of your program.
3702 @item watch @var{expr} @r{[}thread @var{threadnum}@r{]}
3703 Set a watchpoint for an expression. @value{GDBN} will break when the
3704 expression @var{expr} is written into by the program and its value
3705 changes. The simplest (and the most popular) use of this command is
3706 to watch the value of a single variable:
3709 (@value{GDBP}) watch foo
3712 If the command includes a @code{@r{[}thread @var{threadnum}@r{]}}
3713 clause, @value{GDBN} breaks only when the thread identified by
3714 @var{threadnum} changes the value of @var{expr}. If any other threads
3715 change the value of @var{expr}, @value{GDBN} will not break. Note
3716 that watchpoints restricted to a single thread in this way only work
3717 with Hardware Watchpoints.
3720 @item rwatch @var{expr} @r{[}thread @var{threadnum}@r{]}
3721 Set a watchpoint that will break when the value of @var{expr} is read
3725 @item awatch @var{expr} @r{[}thread @var{threadnum}@r{]}
3726 Set a watchpoint that will break when @var{expr} is either read from
3727 or written into by the program.
3729 @kindex info watchpoints @r{[}@var{n}@r{]}
3730 @item info watchpoints
3731 This command prints a list of watchpoints, using the same format as
3732 @code{info break} (@pxref{Set Breaks}).
3735 If you watch for a change in a numerically entered address you need to
3736 dereference it, as the address itself is just a constant number which will
3737 never change. @value{GDBN} refuses to create a watchpoint that watches
3738 a never-changing value:
3741 (@value{GDBP}) watch 0x600850
3742 Cannot watch constant value 0x600850.
3743 (@value{GDBP}) watch *(int *) 0x600850
3744 Watchpoint 1: *(int *) 6293584
3747 @value{GDBN} sets a @dfn{hardware watchpoint} if possible. Hardware
3748 watchpoints execute very quickly, and the debugger reports a change in
3749 value at the exact instruction where the change occurs. If @value{GDBN}
3750 cannot set a hardware watchpoint, it sets a software watchpoint, which
3751 executes more slowly and reports the change in value at the next
3752 @emph{statement}, not the instruction, after the change occurs.
3754 @cindex use only software watchpoints
3755 You can force @value{GDBN} to use only software watchpoints with the
3756 @kbd{set can-use-hw-watchpoints 0} command. With this variable set to
3757 zero, @value{GDBN} will never try to use hardware watchpoints, even if
3758 the underlying system supports them. (Note that hardware-assisted
3759 watchpoints that were set @emph{before} setting
3760 @code{can-use-hw-watchpoints} to zero will still use the hardware
3761 mechanism of watching expression values.)
3764 @item set can-use-hw-watchpoints
3765 @kindex set can-use-hw-watchpoints
3766 Set whether or not to use hardware watchpoints.
3768 @item show can-use-hw-watchpoints
3769 @kindex show can-use-hw-watchpoints
3770 Show the current mode of using hardware watchpoints.
3773 For remote targets, you can restrict the number of hardware
3774 watchpoints @value{GDBN} will use, see @ref{set remote
3775 hardware-breakpoint-limit}.
3777 When you issue the @code{watch} command, @value{GDBN} reports
3780 Hardware watchpoint @var{num}: @var{expr}
3784 if it was able to set a hardware watchpoint.
3786 Currently, the @code{awatch} and @code{rwatch} commands can only set
3787 hardware watchpoints, because accesses to data that don't change the
3788 value of the watched expression cannot be detected without examining
3789 every instruction as it is being executed, and @value{GDBN} does not do
3790 that currently. If @value{GDBN} finds that it is unable to set a
3791 hardware breakpoint with the @code{awatch} or @code{rwatch} command, it
3792 will print a message like this:
3795 Expression cannot be implemented with read/access watchpoint.
3798 Sometimes, @value{GDBN} cannot set a hardware watchpoint because the
3799 data type of the watched expression is wider than what a hardware
3800 watchpoint on the target machine can handle. For example, some systems
3801 can only watch regions that are up to 4 bytes wide; on such systems you
3802 cannot set hardware watchpoints for an expression that yields a
3803 double-precision floating-point number (which is typically 8 bytes
3804 wide). As a work-around, it might be possible to break the large region
3805 into a series of smaller ones and watch them with separate watchpoints.
3807 If you set too many hardware watchpoints, @value{GDBN} might be unable
3808 to insert all of them when you resume the execution of your program.
3809 Since the precise number of active watchpoints is unknown until such
3810 time as the program is about to be resumed, @value{GDBN} might not be
3811 able to warn you about this when you set the watchpoints, and the
3812 warning will be printed only when the program is resumed:
3815 Hardware watchpoint @var{num}: Could not insert watchpoint
3819 If this happens, delete or disable some of the watchpoints.
3821 Watching complex expressions that reference many variables can also
3822 exhaust the resources available for hardware-assisted watchpoints.
3823 That's because @value{GDBN} needs to watch every variable in the
3824 expression with separately allocated resources.
3826 If you call a function interactively using @code{print} or @code{call},
3827 any watchpoints you have set will be inactive until @value{GDBN} reaches another
3828 kind of breakpoint or the call completes.
3830 @value{GDBN} automatically deletes watchpoints that watch local
3831 (automatic) variables, or expressions that involve such variables, when
3832 they go out of scope, that is, when the execution leaves the block in
3833 which these variables were defined. In particular, when the program
3834 being debugged terminates, @emph{all} local variables go out of scope,
3835 and so only watchpoints that watch global variables remain set. If you
3836 rerun the program, you will need to set all such watchpoints again. One
3837 way of doing that would be to set a code breakpoint at the entry to the
3838 @code{main} function and when it breaks, set all the watchpoints.
3840 @cindex watchpoints and threads
3841 @cindex threads and watchpoints
3842 In multi-threaded programs, watchpoints will detect changes to the
3843 watched expression from every thread.
3846 @emph{Warning:} In multi-threaded programs, software watchpoints
3847 have only limited usefulness. If @value{GDBN} creates a software
3848 watchpoint, it can only watch the value of an expression @emph{in a
3849 single thread}. If you are confident that the expression can only
3850 change due to the current thread's activity (and if you are also
3851 confident that no other thread can become current), then you can use
3852 software watchpoints as usual. However, @value{GDBN} may not notice
3853 when a non-current thread's activity changes the expression. (Hardware
3854 watchpoints, in contrast, watch an expression in all threads.)
3857 @xref{set remote hardware-watchpoint-limit}.
3859 @node Set Catchpoints
3860 @subsection Setting Catchpoints
3861 @cindex catchpoints, setting
3862 @cindex exception handlers
3863 @cindex event handling
3865 You can use @dfn{catchpoints} to cause the debugger to stop for certain
3866 kinds of program events, such as C@t{++} exceptions or the loading of a
3867 shared library. Use the @code{catch} command to set a catchpoint.
3871 @item catch @var{event}
3872 Stop when @var{event} occurs. @var{event} can be any of the following:
3875 @cindex stop on C@t{++} exceptions
3876 The throwing of a C@t{++} exception.
3879 The catching of a C@t{++} exception.
3882 @cindex Ada exception catching
3883 @cindex catch Ada exceptions
3884 An Ada exception being raised. If an exception name is specified
3885 at the end of the command (eg @code{catch exception Program_Error}),
3886 the debugger will stop only when this specific exception is raised.
3887 Otherwise, the debugger stops execution when any Ada exception is raised.
3889 When inserting an exception catchpoint on a user-defined exception whose
3890 name is identical to one of the exceptions defined by the language, the
3891 fully qualified name must be used as the exception name. Otherwise,
3892 @value{GDBN} will assume that it should stop on the pre-defined exception
3893 rather than the user-defined one. For instance, assuming an exception
3894 called @code{Constraint_Error} is defined in package @code{Pck}, then
3895 the command to use to catch such exceptions is @kbd{catch exception
3896 Pck.Constraint_Error}.
3898 @item exception unhandled
3899 An exception that was raised but is not handled by the program.
3902 A failed Ada assertion.
3905 @cindex break on fork/exec
3906 A call to @code{exec}. This is currently only available for HP-UX
3910 @itemx syscall @r{[}@var{name} @r{|} @var{number}@r{]} @dots{}
3911 @cindex break on a system call.
3912 A call to or return from a system call, a.k.a.@: @dfn{syscall}. A
3913 syscall is a mechanism for application programs to request a service
3914 from the operating system (OS) or one of the OS system services.
3915 @value{GDBN} can catch some or all of the syscalls issued by the
3916 debuggee, and show the related information for each syscall. If no
3917 argument is specified, calls to and returns from all system calls
3920 @var{name} can be any system call name that is valid for the
3921 underlying OS. Just what syscalls are valid depends on the OS. On
3922 GNU and Unix systems, you can find the full list of valid syscall
3923 names on @file{/usr/include/asm/unistd.h}.
3925 @c For MS-Windows, the syscall names and the corresponding numbers
3926 @c can be found, e.g., on this URL:
3927 @c http://www.metasploit.com/users/opcode/syscalls.html
3928 @c but we don't support Windows syscalls yet.
3930 Normally, @value{GDBN} knows in advance which syscalls are valid for
3931 each OS, so you can use the @value{GDBN} command-line completion
3932 facilities (@pxref{Completion,, command completion}) to list the
3935 You may also specify the system call numerically. A syscall's
3936 number is the value passed to the OS's syscall dispatcher to
3937 identify the requested service. When you specify the syscall by its
3938 name, @value{GDBN} uses its database of syscalls to convert the name
3939 into the corresponding numeric code, but using the number directly
3940 may be useful if @value{GDBN}'s database does not have the complete
3941 list of syscalls on your system (e.g., because @value{GDBN} lags
3942 behind the OS upgrades).
3944 The example below illustrates how this command works if you don't provide
3948 (@value{GDBP}) catch syscall
3949 Catchpoint 1 (syscall)
3951 Starting program: /tmp/catch-syscall
3953 Catchpoint 1 (call to syscall 'close'), \
3954 0xffffe424 in __kernel_vsyscall ()
3958 Catchpoint 1 (returned from syscall 'close'), \
3959 0xffffe424 in __kernel_vsyscall ()
3963 Here is an example of catching a system call by name:
3966 (@value{GDBP}) catch syscall chroot
3967 Catchpoint 1 (syscall 'chroot' [61])
3969 Starting program: /tmp/catch-syscall
3971 Catchpoint 1 (call to syscall 'chroot'), \
3972 0xffffe424 in __kernel_vsyscall ()
3976 Catchpoint 1 (returned from syscall 'chroot'), \
3977 0xffffe424 in __kernel_vsyscall ()
3981 An example of specifying a system call numerically. In the case
3982 below, the syscall number has a corresponding entry in the XML
3983 file, so @value{GDBN} finds its name and prints it:
3986 (@value{GDBP}) catch syscall 252
3987 Catchpoint 1 (syscall(s) 'exit_group')
3989 Starting program: /tmp/catch-syscall
3991 Catchpoint 1 (call to syscall 'exit_group'), \
3992 0xffffe424 in __kernel_vsyscall ()
3996 Program exited normally.
4000 However, there can be situations when there is no corresponding name
4001 in XML file for that syscall number. In this case, @value{GDBN} prints
4002 a warning message saying that it was not able to find the syscall name,
4003 but the catchpoint will be set anyway. See the example below:
4006 (@value{GDBP}) catch syscall 764
4007 warning: The number '764' does not represent a known syscall.
4008 Catchpoint 2 (syscall 764)
4012 If you configure @value{GDBN} using the @samp{--without-expat} option,
4013 it will not be able to display syscall names. Also, if your
4014 architecture does not have an XML file describing its system calls,
4015 you will not be able to see the syscall names. It is important to
4016 notice that these two features are used for accessing the syscall
4017 name database. In either case, you will see a warning like this:
4020 (@value{GDBP}) catch syscall
4021 warning: Could not open "syscalls/i386-linux.xml"
4022 warning: Could not load the syscall XML file 'syscalls/i386-linux.xml'.
4023 GDB will not be able to display syscall names.
4024 Catchpoint 1 (syscall)
4028 Of course, the file name will change depending on your architecture and system.
4030 Still using the example above, you can also try to catch a syscall by its
4031 number. In this case, you would see something like:
4034 (@value{GDBP}) catch syscall 252
4035 Catchpoint 1 (syscall(s) 252)
4038 Again, in this case @value{GDBN} would not be able to display syscall's names.
4041 A call to @code{fork}. This is currently only available for HP-UX
4045 A call to @code{vfork}. This is currently only available for HP-UX
4050 @item tcatch @var{event}
4051 Set a catchpoint that is enabled only for one stop. The catchpoint is
4052 automatically deleted after the first time the event is caught.
4056 Use the @code{info break} command to list the current catchpoints.
4058 There are currently some limitations to C@t{++} exception handling
4059 (@code{catch throw} and @code{catch catch}) in @value{GDBN}:
4063 If you call a function interactively, @value{GDBN} normally returns
4064 control to you when the function has finished executing. If the call
4065 raises an exception, however, the call may bypass the mechanism that
4066 returns control to you and cause your program either to abort or to
4067 simply continue running until it hits a breakpoint, catches a signal
4068 that @value{GDBN} is listening for, or exits. This is the case even if
4069 you set a catchpoint for the exception; catchpoints on exceptions are
4070 disabled within interactive calls.
4073 You cannot raise an exception interactively.
4076 You cannot install an exception handler interactively.
4079 @cindex raise exceptions
4080 Sometimes @code{catch} is not the best way to debug exception handling:
4081 if you need to know exactly where an exception is raised, it is better to
4082 stop @emph{before} the exception handler is called, since that way you
4083 can see the stack before any unwinding takes place. If you set a
4084 breakpoint in an exception handler instead, it may not be easy to find
4085 out where the exception was raised.
4087 To stop just before an exception handler is called, you need some
4088 knowledge of the implementation. In the case of @sc{gnu} C@t{++}, exceptions are
4089 raised by calling a library function named @code{__raise_exception}
4090 which has the following ANSI C interface:
4093 /* @var{addr} is where the exception identifier is stored.
4094 @var{id} is the exception identifier. */
4095 void __raise_exception (void **addr, void *id);
4099 To make the debugger catch all exceptions before any stack
4100 unwinding takes place, set a breakpoint on @code{__raise_exception}
4101 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Exceptions}).
4103 With a conditional breakpoint (@pxref{Conditions, ,Break Conditions})
4104 that depends on the value of @var{id}, you can stop your program when
4105 a specific exception is raised. You can use multiple conditional
4106 breakpoints to stop your program when any of a number of exceptions are
4111 @subsection Deleting Breakpoints
4113 @cindex clearing breakpoints, watchpoints, catchpoints
4114 @cindex deleting breakpoints, watchpoints, catchpoints
4115 It is often necessary to eliminate a breakpoint, watchpoint, or
4116 catchpoint once it has done its job and you no longer want your program
4117 to stop there. This is called @dfn{deleting} the breakpoint. A
4118 breakpoint that has been deleted no longer exists; it is forgotten.
4120 With the @code{clear} command you can delete breakpoints according to
4121 where they are in your program. With the @code{delete} command you can
4122 delete individual breakpoints, watchpoints, or catchpoints by specifying
4123 their breakpoint numbers.
4125 It is not necessary to delete a breakpoint to proceed past it. @value{GDBN}
4126 automatically ignores breakpoints on the first instruction to be executed
4127 when you continue execution without changing the execution address.
4132 Delete any breakpoints at the next instruction to be executed in the
4133 selected stack frame (@pxref{Selection, ,Selecting a Frame}). When
4134 the innermost frame is selected, this is a good way to delete a
4135 breakpoint where your program just stopped.
4137 @item clear @var{location}
4138 Delete any breakpoints set at the specified @var{location}.
4139 @xref{Specify Location}, for the various forms of @var{location}; the
4140 most useful ones are listed below:
4143 @item clear @var{function}
4144 @itemx clear @var{filename}:@var{function}
4145 Delete any breakpoints set at entry to the named @var{function}.
4147 @item clear @var{linenum}
4148 @itemx clear @var{filename}:@var{linenum}
4149 Delete any breakpoints set at or within the code of the specified
4150 @var{linenum} of the specified @var{filename}.
4153 @cindex delete breakpoints
4155 @kindex d @r{(@code{delete})}
4156 @item delete @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4157 Delete the breakpoints, watchpoints, or catchpoints of the breakpoint
4158 ranges specified as arguments. If no argument is specified, delete all
4159 breakpoints (@value{GDBN} asks confirmation, unless you have @code{set
4160 confirm off}). You can abbreviate this command as @code{d}.
4164 @subsection Disabling Breakpoints
4166 @cindex enable/disable a breakpoint
4167 Rather than deleting a breakpoint, watchpoint, or catchpoint, you might
4168 prefer to @dfn{disable} it. This makes the breakpoint inoperative as if
4169 it had been deleted, but remembers the information on the breakpoint so
4170 that you can @dfn{enable} it again later.
4172 You disable and enable breakpoints, watchpoints, and catchpoints with
4173 the @code{enable} and @code{disable} commands, optionally specifying
4174 one or more breakpoint numbers as arguments. Use @code{info break} to
4175 print a list of all breakpoints, watchpoints, and catchpoints if you
4176 do not know which numbers to use.
4178 Disabling and enabling a breakpoint that has multiple locations
4179 affects all of its locations.
4181 A breakpoint, watchpoint, or catchpoint can have any of four different
4182 states of enablement:
4186 Enabled. The breakpoint stops your program. A breakpoint set
4187 with the @code{break} command starts out in this state.
4189 Disabled. The breakpoint has no effect on your program.
4191 Enabled once. The breakpoint stops your program, but then becomes
4194 Enabled for deletion. The breakpoint stops your program, but
4195 immediately after it does so it is deleted permanently. A breakpoint
4196 set with the @code{tbreak} command starts out in this state.
4199 You can use the following commands to enable or disable breakpoints,
4200 watchpoints, and catchpoints:
4204 @kindex dis @r{(@code{disable})}
4205 @item disable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4206 Disable the specified breakpoints---or all breakpoints, if none are
4207 listed. A disabled breakpoint has no effect but is not forgotten. All
4208 options such as ignore-counts, conditions and commands are remembered in
4209 case the breakpoint is enabled again later. You may abbreviate
4210 @code{disable} as @code{dis}.
4213 @item enable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4214 Enable the specified breakpoints (or all defined breakpoints). They
4215 become effective once again in stopping your program.
4217 @item enable @r{[}breakpoints@r{]} once @var{range}@dots{}
4218 Enable the specified breakpoints temporarily. @value{GDBN} disables any
4219 of these breakpoints immediately after stopping your program.
4221 @item enable @r{[}breakpoints@r{]} delete @var{range}@dots{}
4222 Enable the specified breakpoints to work once, then die. @value{GDBN}
4223 deletes any of these breakpoints as soon as your program stops there.
4224 Breakpoints set by the @code{tbreak} command start out in this state.
4227 @c FIXME: I think the following ``Except for [...] @code{tbreak}'' is
4228 @c confusing: tbreak is also initially enabled.
4229 Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks,
4230 ,Setting Breakpoints}), breakpoints that you set are initially enabled;
4231 subsequently, they become disabled or enabled only when you use one of
4232 the commands above. (The command @code{until} can set and delete a
4233 breakpoint of its own, but it does not change the state of your other
4234 breakpoints; see @ref{Continuing and Stepping, ,Continuing and
4238 @subsection Break Conditions
4239 @cindex conditional breakpoints
4240 @cindex breakpoint conditions
4242 @c FIXME what is scope of break condition expr? Context where wanted?
4243 @c in particular for a watchpoint?
4244 The simplest sort of breakpoint breaks every time your program reaches a
4245 specified place. You can also specify a @dfn{condition} for a
4246 breakpoint. A condition is just a Boolean expression in your
4247 programming language (@pxref{Expressions, ,Expressions}). A breakpoint with
4248 a condition evaluates the expression each time your program reaches it,
4249 and your program stops only if the condition is @emph{true}.
4251 This is the converse of using assertions for program validation; in that
4252 situation, you want to stop when the assertion is violated---that is,
4253 when the condition is false. In C, if you want to test an assertion expressed
4254 by the condition @var{assert}, you should set the condition
4255 @samp{! @var{assert}} on the appropriate breakpoint.
4257 Conditions are also accepted for watchpoints; you may not need them,
4258 since a watchpoint is inspecting the value of an expression anyhow---but
4259 it might be simpler, say, to just set a watchpoint on a variable name,
4260 and specify a condition that tests whether the new value is an interesting
4263 Break conditions can have side effects, and may even call functions in
4264 your program. This can be useful, for example, to activate functions
4265 that log program progress, or to use your own print functions to
4266 format special data structures. The effects are completely predictable
4267 unless there is another enabled breakpoint at the same address. (In
4268 that case, @value{GDBN} might see the other breakpoint first and stop your
4269 program without checking the condition of this one.) Note that
4270 breakpoint commands are usually more convenient and flexible than break
4272 purpose of performing side effects when a breakpoint is reached
4273 (@pxref{Break Commands, ,Breakpoint Command Lists}).
4275 Break conditions can be specified when a breakpoint is set, by using
4276 @samp{if} in the arguments to the @code{break} command. @xref{Set
4277 Breaks, ,Setting Breakpoints}. They can also be changed at any time
4278 with the @code{condition} command.
4280 You can also use the @code{if} keyword with the @code{watch} command.
4281 The @code{catch} command does not recognize the @code{if} keyword;
4282 @code{condition} is the only way to impose a further condition on a
4287 @item condition @var{bnum} @var{expression}
4288 Specify @var{expression} as the break condition for breakpoint,
4289 watchpoint, or catchpoint number @var{bnum}. After you set a condition,
4290 breakpoint @var{bnum} stops your program only if the value of
4291 @var{expression} is true (nonzero, in C). When you use
4292 @code{condition}, @value{GDBN} checks @var{expression} immediately for
4293 syntactic correctness, and to determine whether symbols in it have
4294 referents in the context of your breakpoint. If @var{expression} uses
4295 symbols not referenced in the context of the breakpoint, @value{GDBN}
4296 prints an error message:
4299 No symbol "foo" in current context.
4304 not actually evaluate @var{expression} at the time the @code{condition}
4305 command (or a command that sets a breakpoint with a condition, like
4306 @code{break if @dots{}}) is given, however. @xref{Expressions, ,Expressions}.
4308 @item condition @var{bnum}
4309 Remove the condition from breakpoint number @var{bnum}. It becomes
4310 an ordinary unconditional breakpoint.
4313 @cindex ignore count (of breakpoint)
4314 A special case of a breakpoint condition is to stop only when the
4315 breakpoint has been reached a certain number of times. This is so
4316 useful that there is a special way to do it, using the @dfn{ignore
4317 count} of the breakpoint. Every breakpoint has an ignore count, which
4318 is an integer. Most of the time, the ignore count is zero, and
4319 therefore has no effect. But if your program reaches a breakpoint whose
4320 ignore count is positive, then instead of stopping, it just decrements
4321 the ignore count by one and continues. As a result, if the ignore count
4322 value is @var{n}, the breakpoint does not stop the next @var{n} times
4323 your program reaches it.
4327 @item ignore @var{bnum} @var{count}
4328 Set the ignore count of breakpoint number @var{bnum} to @var{count}.
4329 The next @var{count} times the breakpoint is reached, your program's
4330 execution does not stop; other than to decrement the ignore count, @value{GDBN}
4333 To make the breakpoint stop the next time it is reached, specify
4336 When you use @code{continue} to resume execution of your program from a
4337 breakpoint, you can specify an ignore count directly as an argument to
4338 @code{continue}, rather than using @code{ignore}. @xref{Continuing and
4339 Stepping,,Continuing and Stepping}.
4341 If a breakpoint has a positive ignore count and a condition, the
4342 condition is not checked. Once the ignore count reaches zero,
4343 @value{GDBN} resumes checking the condition.
4345 You could achieve the effect of the ignore count with a condition such
4346 as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that
4347 is decremented each time. @xref{Convenience Vars, ,Convenience
4351 Ignore counts apply to breakpoints, watchpoints, and catchpoints.
4354 @node Break Commands
4355 @subsection Breakpoint Command Lists
4357 @cindex breakpoint commands
4358 You can give any breakpoint (or watchpoint or catchpoint) a series of
4359 commands to execute when your program stops due to that breakpoint. For
4360 example, you might want to print the values of certain expressions, or
4361 enable other breakpoints.
4365 @kindex end@r{ (breakpoint commands)}
4366 @item commands @r{[}@var{range}@dots{}@r{]}
4367 @itemx @dots{} @var{command-list} @dots{}
4369 Specify a list of commands for the given breakpoints. The commands
4370 themselves appear on the following lines. Type a line containing just
4371 @code{end} to terminate the commands.
4373 To remove all commands from a breakpoint, type @code{commands} and
4374 follow it immediately with @code{end}; that is, give no commands.
4376 With no argument, @code{commands} refers to the last breakpoint,
4377 watchpoint, or catchpoint set (not to the breakpoint most recently
4378 encountered). If the most recent breakpoints were set with a single
4379 command, then the @code{commands} will apply to all the breakpoints
4380 set by that command. This applies to breakpoints set by
4381 @code{rbreak}, and also applies when a single @code{break} command
4382 creates multiple breakpoints (@pxref{Ambiguous Expressions,,Ambiguous
4386 Pressing @key{RET} as a means of repeating the last @value{GDBN} command is
4387 disabled within a @var{command-list}.
4389 You can use breakpoint commands to start your program up again. Simply
4390 use the @code{continue} command, or @code{step}, or any other command
4391 that resumes execution.
4393 Any other commands in the command list, after a command that resumes
4394 execution, are ignored. This is because any time you resume execution
4395 (even with a simple @code{next} or @code{step}), you may encounter
4396 another breakpoint---which could have its own command list, leading to
4397 ambiguities about which list to execute.
4400 If the first command you specify in a command list is @code{silent}, the
4401 usual message about stopping at a breakpoint is not printed. This may
4402 be desirable for breakpoints that are to print a specific message and
4403 then continue. If none of the remaining commands print anything, you
4404 see no sign that the breakpoint was reached. @code{silent} is
4405 meaningful only at the beginning of a breakpoint command list.
4407 The commands @code{echo}, @code{output}, and @code{printf} allow you to
4408 print precisely controlled output, and are often useful in silent
4409 breakpoints. @xref{Output, ,Commands for Controlled Output}.
4411 For example, here is how you could use breakpoint commands to print the
4412 value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
4418 printf "x is %d\n",x
4423 One application for breakpoint commands is to compensate for one bug so
4424 you can test for another. Put a breakpoint just after the erroneous line
4425 of code, give it a condition to detect the case in which something
4426 erroneous has been done, and give it commands to assign correct values
4427 to any variables that need them. End with the @code{continue} command
4428 so that your program does not stop, and start with the @code{silent}
4429 command so that no output is produced. Here is an example:
4440 @node Save Breakpoints
4441 @subsection How to save breakpoints to a file
4443 To save breakpoint definitions to a file use the @w{@code{save
4444 breakpoints}} command.
4447 @kindex save breakpoints
4448 @cindex save breakpoints to a file for future sessions
4449 @item save breakpoints [@var{filename}]
4450 This command saves all current breakpoint definitions together with
4451 their commands and ignore counts, into a file @file{@var{filename}}
4452 suitable for use in a later debugging session. This includes all
4453 types of breakpoints (breakpoints, watchpoints, catchpoints,
4454 tracepoints). To read the saved breakpoint definitions, use the
4455 @code{source} command (@pxref{Command Files}). Note that watchpoints
4456 with expressions involving local variables may fail to be recreated
4457 because it may not be possible to access the context where the
4458 watchpoint is valid anymore. Because the saved breakpoint definitions
4459 are simply a sequence of @value{GDBN} commands that recreate the
4460 breakpoints, you can edit the file in your favorite editing program,
4461 and remove the breakpoint definitions you're not interested in, or
4462 that can no longer be recreated.
4465 @c @ifclear BARETARGET
4466 @node Error in Breakpoints
4467 @subsection ``Cannot insert breakpoints''
4469 If you request too many active hardware-assisted breakpoints and
4470 watchpoints, you will see this error message:
4472 @c FIXME: the precise wording of this message may change; the relevant
4473 @c source change is not committed yet (Sep 3, 1999).
4475 Stopped; cannot insert breakpoints.
4476 You may have requested too many hardware breakpoints and watchpoints.
4480 This message is printed when you attempt to resume the program, since
4481 only then @value{GDBN} knows exactly how many hardware breakpoints and
4482 watchpoints it needs to insert.
4484 When this message is printed, you need to disable or remove some of the
4485 hardware-assisted breakpoints and watchpoints, and then continue.
4487 @node Breakpoint-related Warnings
4488 @subsection ``Breakpoint address adjusted...''
4489 @cindex breakpoint address adjusted
4491 Some processor architectures place constraints on the addresses at
4492 which breakpoints may be placed. For architectures thus constrained,
4493 @value{GDBN} will attempt to adjust the breakpoint's address to comply
4494 with the constraints dictated by the architecture.
4496 One example of such an architecture is the Fujitsu FR-V. The FR-V is
4497 a VLIW architecture in which a number of RISC-like instructions may be
4498 bundled together for parallel execution. The FR-V architecture
4499 constrains the location of a breakpoint instruction within such a
4500 bundle to the instruction with the lowest address. @value{GDBN}
4501 honors this constraint by adjusting a breakpoint's address to the
4502 first in the bundle.
4504 It is not uncommon for optimized code to have bundles which contain
4505 instructions from different source statements, thus it may happen that
4506 a breakpoint's address will be adjusted from one source statement to
4507 another. Since this adjustment may significantly alter @value{GDBN}'s
4508 breakpoint related behavior from what the user expects, a warning is
4509 printed when the breakpoint is first set and also when the breakpoint
4512 A warning like the one below is printed when setting a breakpoint
4513 that's been subject to address adjustment:
4516 warning: Breakpoint address adjusted from 0x00010414 to 0x00010410.
4519 Such warnings are printed both for user settable and @value{GDBN}'s
4520 internal breakpoints. If you see one of these warnings, you should
4521 verify that a breakpoint set at the adjusted address will have the
4522 desired affect. If not, the breakpoint in question may be removed and
4523 other breakpoints may be set which will have the desired behavior.
4524 E.g., it may be sufficient to place the breakpoint at a later
4525 instruction. A conditional breakpoint may also be useful in some
4526 cases to prevent the breakpoint from triggering too often.
4528 @value{GDBN} will also issue a warning when stopping at one of these
4529 adjusted breakpoints:
4532 warning: Breakpoint 1 address previously adjusted from 0x00010414
4536 When this warning is encountered, it may be too late to take remedial
4537 action except in cases where the breakpoint is hit earlier or more
4538 frequently than expected.
4540 @node Continuing and Stepping
4541 @section Continuing and Stepping
4545 @cindex resuming execution
4546 @dfn{Continuing} means resuming program execution until your program
4547 completes normally. In contrast, @dfn{stepping} means executing just
4548 one more ``step'' of your program, where ``step'' may mean either one
4549 line of source code, or one machine instruction (depending on what
4550 particular command you use). Either when continuing or when stepping,
4551 your program may stop even sooner, due to a breakpoint or a signal. (If
4552 it stops due to a signal, you may want to use @code{handle}, or use
4553 @samp{signal 0} to resume execution. @xref{Signals, ,Signals}.)
4557 @kindex c @r{(@code{continue})}
4558 @kindex fg @r{(resume foreground execution)}
4559 @item continue @r{[}@var{ignore-count}@r{]}
4560 @itemx c @r{[}@var{ignore-count}@r{]}
4561 @itemx fg @r{[}@var{ignore-count}@r{]}
4562 Resume program execution, at the address where your program last stopped;
4563 any breakpoints set at that address are bypassed. The optional argument
4564 @var{ignore-count} allows you to specify a further number of times to
4565 ignore a breakpoint at this location; its effect is like that of
4566 @code{ignore} (@pxref{Conditions, ,Break Conditions}).
4568 The argument @var{ignore-count} is meaningful only when your program
4569 stopped due to a breakpoint. At other times, the argument to
4570 @code{continue} is ignored.
4572 The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the
4573 debugged program is deemed to be the foreground program) are provided
4574 purely for convenience, and have exactly the same behavior as
4578 To resume execution at a different place, you can use @code{return}
4579 (@pxref{Returning, ,Returning from a Function}) to go back to the
4580 calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
4581 Different Address}) to go to an arbitrary location in your program.
4583 A typical technique for using stepping is to set a breakpoint
4584 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Catchpoints}) at the
4585 beginning of the function or the section of your program where a problem
4586 is believed to lie, run your program until it stops at that breakpoint,
4587 and then step through the suspect area, examining the variables that are
4588 interesting, until you see the problem happen.
4592 @kindex s @r{(@code{step})}
4594 Continue running your program until control reaches a different source
4595 line, then stop it and return control to @value{GDBN}. This command is
4596 abbreviated @code{s}.
4599 @c "without debugging information" is imprecise; actually "without line
4600 @c numbers in the debugging information". (gcc -g1 has debugging info but
4601 @c not line numbers). But it seems complex to try to make that
4602 @c distinction here.
4603 @emph{Warning:} If you use the @code{step} command while control is
4604 within a function that was compiled without debugging information,
4605 execution proceeds until control reaches a function that does have
4606 debugging information. Likewise, it will not step into a function which
4607 is compiled without debugging information. To step through functions
4608 without debugging information, use the @code{stepi} command, described
4612 The @code{step} command only stops at the first instruction of a source
4613 line. This prevents the multiple stops that could otherwise occur in
4614 @code{switch} statements, @code{for} loops, etc. @code{step} continues
4615 to stop if a function that has debugging information is called within
4616 the line. In other words, @code{step} @emph{steps inside} any functions
4617 called within the line.
4619 Also, the @code{step} command only enters a function if there is line
4620 number information for the function. Otherwise it acts like the
4621 @code{next} command. This avoids problems when using @code{cc -gl}
4622 on MIPS machines. Previously, @code{step} entered subroutines if there
4623 was any debugging information about the routine.
4625 @item step @var{count}
4626 Continue running as in @code{step}, but do so @var{count} times. If a
4627 breakpoint is reached, or a signal not related to stepping occurs before
4628 @var{count} steps, stepping stops right away.
4631 @kindex n @r{(@code{next})}
4632 @item next @r{[}@var{count}@r{]}
4633 Continue to the next source line in the current (innermost) stack frame.
4634 This is similar to @code{step}, but function calls that appear within
4635 the line of code are executed without stopping. Execution stops when
4636 control reaches a different line of code at the original stack level
4637 that was executing when you gave the @code{next} command. This command
4638 is abbreviated @code{n}.
4640 An argument @var{count} is a repeat count, as for @code{step}.
4643 @c FIX ME!! Do we delete this, or is there a way it fits in with
4644 @c the following paragraph? --- Vctoria
4646 @c @code{next} within a function that lacks debugging information acts like
4647 @c @code{step}, but any function calls appearing within the code of the
4648 @c function are executed without stopping.
4650 The @code{next} command only stops at the first instruction of a
4651 source line. This prevents multiple stops that could otherwise occur in
4652 @code{switch} statements, @code{for} loops, etc.
4654 @kindex set step-mode
4656 @cindex functions without line info, and stepping
4657 @cindex stepping into functions with no line info
4658 @itemx set step-mode on
4659 The @code{set step-mode on} command causes the @code{step} command to
4660 stop at the first instruction of a function which contains no debug line
4661 information rather than stepping over it.
4663 This is useful in cases where you may be interested in inspecting the
4664 machine instructions of a function which has no symbolic info and do not
4665 want @value{GDBN} to automatically skip over this function.
4667 @item set step-mode off
4668 Causes the @code{step} command to step over any functions which contains no
4669 debug information. This is the default.
4671 @item show step-mode
4672 Show whether @value{GDBN} will stop in or step over functions without
4673 source line debug information.
4676 @kindex fin @r{(@code{finish})}
4678 Continue running until just after function in the selected stack frame
4679 returns. Print the returned value (if any). This command can be
4680 abbreviated as @code{fin}.
4682 Contrast this with the @code{return} command (@pxref{Returning,
4683 ,Returning from a Function}).
4686 @kindex u @r{(@code{until})}
4687 @cindex run until specified location
4690 Continue running until a source line past the current line, in the
4691 current stack frame, is reached. This command is used to avoid single
4692 stepping through a loop more than once. It is like the @code{next}
4693 command, except that when @code{until} encounters a jump, it
4694 automatically continues execution until the program counter is greater
4695 than the address of the jump.
4697 This means that when you reach the end of a loop after single stepping
4698 though it, @code{until} makes your program continue execution until it
4699 exits the loop. In contrast, a @code{next} command at the end of a loop
4700 simply steps back to the beginning of the loop, which forces you to step
4701 through the next iteration.
4703 @code{until} always stops your program if it attempts to exit the current
4706 @code{until} may produce somewhat counterintuitive results if the order
4707 of machine code does not match the order of the source lines. For
4708 example, in the following excerpt from a debugging session, the @code{f}
4709 (@code{frame}) command shows that execution is stopped at line
4710 @code{206}; yet when we use @code{until}, we get to line @code{195}:
4714 #0 main (argc=4, argv=0xf7fffae8) at m4.c:206
4716 (@value{GDBP}) until
4717 195 for ( ; argc > 0; NEXTARG) @{
4720 This happened because, for execution efficiency, the compiler had
4721 generated code for the loop closure test at the end, rather than the
4722 start, of the loop---even though the test in a C @code{for}-loop is
4723 written before the body of the loop. The @code{until} command appeared
4724 to step back to the beginning of the loop when it advanced to this
4725 expression; however, it has not really gone to an earlier
4726 statement---not in terms of the actual machine code.
4728 @code{until} with no argument works by means of single
4729 instruction stepping, and hence is slower than @code{until} with an
4732 @item until @var{location}
4733 @itemx u @var{location}
4734 Continue running your program until either the specified location is
4735 reached, or the current stack frame returns. @var{location} is any of
4736 the forms described in @ref{Specify Location}.
4737 This form of the command uses temporary breakpoints, and
4738 hence is quicker than @code{until} without an argument. The specified
4739 location is actually reached only if it is in the current frame. This
4740 implies that @code{until} can be used to skip over recursive function
4741 invocations. For instance in the code below, if the current location is
4742 line @code{96}, issuing @code{until 99} will execute the program up to
4743 line @code{99} in the same invocation of factorial, i.e., after the inner
4744 invocations have returned.
4747 94 int factorial (int value)
4749 96 if (value > 1) @{
4750 97 value *= factorial (value - 1);
4757 @kindex advance @var{location}
4758 @itemx advance @var{location}
4759 Continue running the program up to the given @var{location}. An argument is
4760 required, which should be of one of the forms described in
4761 @ref{Specify Location}.
4762 Execution will also stop upon exit from the current stack
4763 frame. This command is similar to @code{until}, but @code{advance} will
4764 not skip over recursive function calls, and the target location doesn't
4765 have to be in the same frame as the current one.
4769 @kindex si @r{(@code{stepi})}
4771 @itemx stepi @var{arg}
4773 Execute one machine instruction, then stop and return to the debugger.
4775 It is often useful to do @samp{display/i $pc} when stepping by machine
4776 instructions. This makes @value{GDBN} automatically display the next
4777 instruction to be executed, each time your program stops. @xref{Auto
4778 Display,, Automatic Display}.
4780 An argument is a repeat count, as in @code{step}.
4784 @kindex ni @r{(@code{nexti})}
4786 @itemx nexti @var{arg}
4788 Execute one machine instruction, but if it is a function call,
4789 proceed until the function returns.
4791 An argument is a repeat count, as in @code{next}.
4798 A signal is an asynchronous event that can happen in a program. The
4799 operating system defines the possible kinds of signals, and gives each
4800 kind a name and a number. For example, in Unix @code{SIGINT} is the
4801 signal a program gets when you type an interrupt character (often @kbd{Ctrl-c});
4802 @code{SIGSEGV} is the signal a program gets from referencing a place in
4803 memory far away from all the areas in use; @code{SIGALRM} occurs when
4804 the alarm clock timer goes off (which happens only if your program has
4805 requested an alarm).
4807 @cindex fatal signals
4808 Some signals, including @code{SIGALRM}, are a normal part of the
4809 functioning of your program. Others, such as @code{SIGSEGV}, indicate
4810 errors; these signals are @dfn{fatal} (they kill your program immediately) if the
4811 program has not specified in advance some other way to handle the signal.
4812 @code{SIGINT} does not indicate an error in your program, but it is normally
4813 fatal so it can carry out the purpose of the interrupt: to kill the program.
4815 @value{GDBN} has the ability to detect any occurrence of a signal in your
4816 program. You can tell @value{GDBN} in advance what to do for each kind of
4819 @cindex handling signals
4820 Normally, @value{GDBN} is set up to let the non-erroneous signals like
4821 @code{SIGALRM} be silently passed to your program
4822 (so as not to interfere with their role in the program's functioning)
4823 but to stop your program immediately whenever an error signal happens.
4824 You can change these settings with the @code{handle} command.
4827 @kindex info signals
4831 Print a table of all the kinds of signals and how @value{GDBN} has been told to
4832 handle each one. You can use this to see the signal numbers of all
4833 the defined types of signals.
4835 @item info signals @var{sig}
4836 Similar, but print information only about the specified signal number.
4838 @code{info handle} is an alias for @code{info signals}.
4841 @item handle @var{signal} @r{[}@var{keywords}@dots{}@r{]}
4842 Change the way @value{GDBN} handles signal @var{signal}. @var{signal}
4843 can be the number of a signal or its name (with or without the
4844 @samp{SIG} at the beginning); a list of signal numbers of the form
4845 @samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the
4846 known signals. Optional arguments @var{keywords}, described below,
4847 say what change to make.
4851 The keywords allowed by the @code{handle} command can be abbreviated.
4852 Their full names are:
4856 @value{GDBN} should not stop your program when this signal happens. It may
4857 still print a message telling you that the signal has come in.
4860 @value{GDBN} should stop your program when this signal happens. This implies
4861 the @code{print} keyword as well.
4864 @value{GDBN} should print a message when this signal happens.
4867 @value{GDBN} should not mention the occurrence of the signal at all. This
4868 implies the @code{nostop} keyword as well.
4872 @value{GDBN} should allow your program to see this signal; your program
4873 can handle the signal, or else it may terminate if the signal is fatal
4874 and not handled. @code{pass} and @code{noignore} are synonyms.
4878 @value{GDBN} should not allow your program to see this signal.
4879 @code{nopass} and @code{ignore} are synonyms.
4883 When a signal stops your program, the signal is not visible to the
4885 continue. Your program sees the signal then, if @code{pass} is in
4886 effect for the signal in question @emph{at that time}. In other words,
4887 after @value{GDBN} reports a signal, you can use the @code{handle}
4888 command with @code{pass} or @code{nopass} to control whether your
4889 program sees that signal when you continue.
4891 The default is set to @code{nostop}, @code{noprint}, @code{pass} for
4892 non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and
4893 @code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the
4896 You can also use the @code{signal} command to prevent your program from
4897 seeing a signal, or cause it to see a signal it normally would not see,
4898 or to give it any signal at any time. For example, if your program stopped
4899 due to some sort of memory reference error, you might store correct
4900 values into the erroneous variables and continue, hoping to see more
4901 execution; but your program would probably terminate immediately as
4902 a result of the fatal signal once it saw the signal. To prevent this,
4903 you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
4906 @cindex extra signal information
4907 @anchor{extra signal information}
4909 On some targets, @value{GDBN} can inspect extra signal information
4910 associated with the intercepted signal, before it is actually
4911 delivered to the program being debugged. This information is exported
4912 by the convenience variable @code{$_siginfo}, and consists of data
4913 that is passed by the kernel to the signal handler at the time of the
4914 receipt of a signal. The data type of the information itself is
4915 target dependent. You can see the data type using the @code{ptype
4916 $_siginfo} command. On Unix systems, it typically corresponds to the
4917 standard @code{siginfo_t} type, as defined in the @file{signal.h}
4920 Here's an example, on a @sc{gnu}/Linux system, printing the stray
4921 referenced address that raised a segmentation fault.
4925 (@value{GDBP}) continue
4926 Program received signal SIGSEGV, Segmentation fault.
4927 0x0000000000400766 in main ()
4929 (@value{GDBP}) ptype $_siginfo
4936 struct @{...@} _kill;
4937 struct @{...@} _timer;
4939 struct @{...@} _sigchld;
4940 struct @{...@} _sigfault;
4941 struct @{...@} _sigpoll;
4944 (@value{GDBP}) ptype $_siginfo._sifields._sigfault
4948 (@value{GDBP}) p $_siginfo._sifields._sigfault.si_addr
4949 $1 = (void *) 0x7ffff7ff7000
4953 Depending on target support, @code{$_siginfo} may also be writable.
4956 @section Stopping and Starting Multi-thread Programs
4958 @cindex stopped threads
4959 @cindex threads, stopped
4961 @cindex continuing threads
4962 @cindex threads, continuing
4964 @value{GDBN} supports debugging programs with multiple threads
4965 (@pxref{Threads,, Debugging Programs with Multiple Threads}). There
4966 are two modes of controlling execution of your program within the
4967 debugger. In the default mode, referred to as @dfn{all-stop mode},
4968 when any thread in your program stops (for example, at a breakpoint
4969 or while being stepped), all other threads in the program are also stopped by
4970 @value{GDBN}. On some targets, @value{GDBN} also supports
4971 @dfn{non-stop mode}, in which other threads can continue to run freely while
4972 you examine the stopped thread in the debugger.
4975 * All-Stop Mode:: All threads stop when GDB takes control
4976 * Non-Stop Mode:: Other threads continue to execute
4977 * Background Execution:: Running your program asynchronously
4978 * Thread-Specific Breakpoints:: Controlling breakpoints
4979 * Interrupted System Calls:: GDB may interfere with system calls
4980 * Observer Mode:: GDB does not alter program behavior
4984 @subsection All-Stop Mode
4986 @cindex all-stop mode
4988 In all-stop mode, whenever your program stops under @value{GDBN} for any reason,
4989 @emph{all} threads of execution stop, not just the current thread. This
4990 allows you to examine the overall state of the program, including
4991 switching between threads, without worrying that things may change
4994 Conversely, whenever you restart the program, @emph{all} threads start
4995 executing. @emph{This is true even when single-stepping} with commands
4996 like @code{step} or @code{next}.
4998 In particular, @value{GDBN} cannot single-step all threads in lockstep.
4999 Since thread scheduling is up to your debugging target's operating
5000 system (not controlled by @value{GDBN}), other threads may
5001 execute more than one statement while the current thread completes a
5002 single step. Moreover, in general other threads stop in the middle of a
5003 statement, rather than at a clean statement boundary, when the program
5006 You might even find your program stopped in another thread after
5007 continuing or even single-stepping. This happens whenever some other
5008 thread runs into a breakpoint, a signal, or an exception before the
5009 first thread completes whatever you requested.
5011 @cindex automatic thread selection
5012 @cindex switching threads automatically
5013 @cindex threads, automatic switching
5014 Whenever @value{GDBN} stops your program, due to a breakpoint or a
5015 signal, it automatically selects the thread where that breakpoint or
5016 signal happened. @value{GDBN} alerts you to the context switch with a
5017 message such as @samp{[Switching to Thread @var{n}]} to identify the
5020 On some OSes, you can modify @value{GDBN}'s default behavior by
5021 locking the OS scheduler to allow only a single thread to run.
5024 @item set scheduler-locking @var{mode}
5025 @cindex scheduler locking mode
5026 @cindex lock scheduler
5027 Set the scheduler locking mode. If it is @code{off}, then there is no
5028 locking and any thread may run at any time. If @code{on}, then only the
5029 current thread may run when the inferior is resumed. The @code{step}
5030 mode optimizes for single-stepping; it prevents other threads
5031 from preempting the current thread while you are stepping, so that
5032 the focus of debugging does not change unexpectedly.
5033 Other threads only rarely (or never) get a chance to run
5034 when you step. They are more likely to run when you @samp{next} over a
5035 function call, and they are completely free to run when you use commands
5036 like @samp{continue}, @samp{until}, or @samp{finish}. However, unless another
5037 thread hits a breakpoint during its timeslice, @value{GDBN} does not change
5038 the current thread away from the thread that you are debugging.
5040 @item show scheduler-locking
5041 Display the current scheduler locking mode.
5044 @cindex resume threads of multiple processes simultaneously
5045 By default, when you issue one of the execution commands such as
5046 @code{continue}, @code{next} or @code{step}, @value{GDBN} allows only
5047 threads of the current inferior to run. For example, if @value{GDBN}
5048 is attached to two inferiors, each with two threads, the
5049 @code{continue} command resumes only the two threads of the current
5050 inferior. This is useful, for example, when you debug a program that
5051 forks and you want to hold the parent stopped (so that, for instance,
5052 it doesn't run to exit), while you debug the child. In other
5053 situations, you may not be interested in inspecting the current state
5054 of any of the processes @value{GDBN} is attached to, and you may want
5055 to resume them all until some breakpoint is hit. In the latter case,
5056 you can instruct @value{GDBN} to allow all threads of all the
5057 inferiors to run with the @w{@code{set schedule-multiple}} command.
5060 @kindex set schedule-multiple
5061 @item set schedule-multiple
5062 Set the mode for allowing threads of multiple processes to be resumed
5063 when an execution command is issued. When @code{on}, all threads of
5064 all processes are allowed to run. When @code{off}, only the threads
5065 of the current process are resumed. The default is @code{off}. The
5066 @code{scheduler-locking} mode takes precedence when set to @code{on},
5067 or while you are stepping and set to @code{step}.
5069 @item show schedule-multiple
5070 Display the current mode for resuming the execution of threads of
5075 @subsection Non-Stop Mode
5077 @cindex non-stop mode
5079 @c This section is really only a place-holder, and needs to be expanded
5080 @c with more details.
5082 For some multi-threaded targets, @value{GDBN} supports an optional
5083 mode of operation in which you can examine stopped program threads in
5084 the debugger while other threads continue to execute freely. This
5085 minimizes intrusion when debugging live systems, such as programs
5086 where some threads have real-time constraints or must continue to
5087 respond to external events. This is referred to as @dfn{non-stop} mode.
5089 In non-stop mode, when a thread stops to report a debugging event,
5090 @emph{only} that thread is stopped; @value{GDBN} does not stop other
5091 threads as well, in contrast to the all-stop mode behavior. Additionally,
5092 execution commands such as @code{continue} and @code{step} apply by default
5093 only to the current thread in non-stop mode, rather than all threads as
5094 in all-stop mode. This allows you to control threads explicitly in
5095 ways that are not possible in all-stop mode --- for example, stepping
5096 one thread while allowing others to run freely, stepping
5097 one thread while holding all others stopped, or stepping several threads
5098 independently and simultaneously.
5100 To enter non-stop mode, use this sequence of commands before you run
5101 or attach to your program:
5104 # Enable the async interface.
5107 # If using the CLI, pagination breaks non-stop.
5110 # Finally, turn it on!
5114 You can use these commands to manipulate the non-stop mode setting:
5117 @kindex set non-stop
5118 @item set non-stop on
5119 Enable selection of non-stop mode.
5120 @item set non-stop off
5121 Disable selection of non-stop mode.
5122 @kindex show non-stop
5124 Show the current non-stop enablement setting.
5127 Note these commands only reflect whether non-stop mode is enabled,
5128 not whether the currently-executing program is being run in non-stop mode.
5129 In particular, the @code{set non-stop} preference is only consulted when
5130 @value{GDBN} starts or connects to the target program, and it is generally
5131 not possible to switch modes once debugging has started. Furthermore,
5132 since not all targets support non-stop mode, even when you have enabled
5133 non-stop mode, @value{GDBN} may still fall back to all-stop operation by
5136 In non-stop mode, all execution commands apply only to the current thread
5137 by default. That is, @code{continue} only continues one thread.
5138 To continue all threads, issue @code{continue -a} or @code{c -a}.
5140 You can use @value{GDBN}'s background execution commands
5141 (@pxref{Background Execution}) to run some threads in the background
5142 while you continue to examine or step others from @value{GDBN}.
5143 The MI execution commands (@pxref{GDB/MI Program Execution}) are
5144 always executed asynchronously in non-stop mode.
5146 Suspending execution is done with the @code{interrupt} command when
5147 running in the background, or @kbd{Ctrl-c} during foreground execution.
5148 In all-stop mode, this stops the whole process;
5149 but in non-stop mode the interrupt applies only to the current thread.
5150 To stop the whole program, use @code{interrupt -a}.
5152 Other execution commands do not currently support the @code{-a} option.
5154 In non-stop mode, when a thread stops, @value{GDBN} doesn't automatically make
5155 that thread current, as it does in all-stop mode. This is because the
5156 thread stop notifications are asynchronous with respect to @value{GDBN}'s
5157 command interpreter, and it would be confusing if @value{GDBN} unexpectedly
5158 changed to a different thread just as you entered a command to operate on the
5159 previously current thread.
5161 @node Background Execution
5162 @subsection Background Execution
5164 @cindex foreground execution
5165 @cindex background execution
5166 @cindex asynchronous execution
5167 @cindex execution, foreground, background and asynchronous
5169 @value{GDBN}'s execution commands have two variants: the normal
5170 foreground (synchronous) behavior, and a background
5171 (asynchronous) behavior. In foreground execution, @value{GDBN} waits for
5172 the program to report that some thread has stopped before prompting for
5173 another command. In background execution, @value{GDBN} immediately gives
5174 a command prompt so that you can issue other commands while your program runs.
5176 You need to explicitly enable asynchronous mode before you can use
5177 background execution commands. You can use these commands to
5178 manipulate the asynchronous mode setting:
5181 @kindex set target-async
5182 @item set target-async on
5183 Enable asynchronous mode.
5184 @item set target-async off
5185 Disable asynchronous mode.
5186 @kindex show target-async
5187 @item show target-async
5188 Show the current target-async setting.
5191 If the target doesn't support async mode, @value{GDBN} issues an error
5192 message if you attempt to use the background execution commands.
5194 To specify background execution, add a @code{&} to the command. For example,
5195 the background form of the @code{continue} command is @code{continue&}, or
5196 just @code{c&}. The execution commands that accept background execution
5202 @xref{Starting, , Starting your Program}.
5206 @xref{Attach, , Debugging an Already-running Process}.
5210 @xref{Continuing and Stepping, step}.
5214 @xref{Continuing and Stepping, stepi}.
5218 @xref{Continuing and Stepping, next}.
5222 @xref{Continuing and Stepping, nexti}.
5226 @xref{Continuing and Stepping, continue}.
5230 @xref{Continuing and Stepping, finish}.
5234 @xref{Continuing and Stepping, until}.
5238 Background execution is especially useful in conjunction with non-stop
5239 mode for debugging programs with multiple threads; see @ref{Non-Stop Mode}.
5240 However, you can also use these commands in the normal all-stop mode with
5241 the restriction that you cannot issue another execution command until the
5242 previous one finishes. Examples of commands that are valid in all-stop
5243 mode while the program is running include @code{help} and @code{info break}.
5245 You can interrupt your program while it is running in the background by
5246 using the @code{interrupt} command.
5253 Suspend execution of the running program. In all-stop mode,
5254 @code{interrupt} stops the whole process, but in non-stop mode, it stops
5255 only the current thread. To stop the whole program in non-stop mode,
5256 use @code{interrupt -a}.
5259 @node Thread-Specific Breakpoints
5260 @subsection Thread-Specific Breakpoints
5262 When your program has multiple threads (@pxref{Threads,, Debugging
5263 Programs with Multiple Threads}), you can choose whether to set
5264 breakpoints on all threads, or on a particular thread.
5267 @cindex breakpoints and threads
5268 @cindex thread breakpoints
5269 @kindex break @dots{} thread @var{threadno}
5270 @item break @var{linespec} thread @var{threadno}
5271 @itemx break @var{linespec} thread @var{threadno} if @dots{}
5272 @var{linespec} specifies source lines; there are several ways of
5273 writing them (@pxref{Specify Location}), but the effect is always to
5274 specify some source line.
5276 Use the qualifier @samp{thread @var{threadno}} with a breakpoint command
5277 to specify that you only want @value{GDBN} to stop the program when a
5278 particular thread reaches this breakpoint. @var{threadno} is one of the
5279 numeric thread identifiers assigned by @value{GDBN}, shown in the first
5280 column of the @samp{info threads} display.
5282 If you do not specify @samp{thread @var{threadno}} when you set a
5283 breakpoint, the breakpoint applies to @emph{all} threads of your
5286 You can use the @code{thread} qualifier on conditional breakpoints as
5287 well; in this case, place @samp{thread @var{threadno}} before or
5288 after the breakpoint condition, like this:
5291 (@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
5296 @node Interrupted System Calls
5297 @subsection Interrupted System Calls
5299 @cindex thread breakpoints and system calls
5300 @cindex system calls and thread breakpoints
5301 @cindex premature return from system calls
5302 There is an unfortunate side effect when using @value{GDBN} to debug
5303 multi-threaded programs. If one thread stops for a
5304 breakpoint, or for some other reason, and another thread is blocked in a
5305 system call, then the system call may return prematurely. This is a
5306 consequence of the interaction between multiple threads and the signals
5307 that @value{GDBN} uses to implement breakpoints and other events that
5310 To handle this problem, your program should check the return value of
5311 each system call and react appropriately. This is good programming
5314 For example, do not write code like this:
5320 The call to @code{sleep} will return early if a different thread stops
5321 at a breakpoint or for some other reason.
5323 Instead, write this:
5328 unslept = sleep (unslept);
5331 A system call is allowed to return early, so the system is still
5332 conforming to its specification. But @value{GDBN} does cause your
5333 multi-threaded program to behave differently than it would without
5336 Also, @value{GDBN} uses internal breakpoints in the thread library to
5337 monitor certain events such as thread creation and thread destruction.
5338 When such an event happens, a system call in another thread may return
5339 prematurely, even though your program does not appear to stop.
5342 @subsection Observer Mode
5344 If you want to build on non-stop mode and observe program behavior
5345 without any chance of disruption by @value{GDBN}, you can set
5346 variables to disable all of the debugger's attempts to modify state,
5347 whether by writing memory, inserting breakpoints, etc. These operate
5348 at a low level, intercepting operations from all commands.
5350 When all of these are set to @code{off}, then @value{GDBN} is said to
5351 be @dfn{observer mode}. As a convenience, the variable
5352 @code{observer} can be set to disable these, plus enable non-stop
5355 Note that @value{GDBN} will not prevent you from making nonsensical
5356 combinations of these settings. For instance, if you have enabled
5357 @code{may-insert-breakpoints} but disabled @code{may-write-memory},
5358 then breakpoints that work by writing trap instructions into the code
5359 stream will still not be able to be placed.
5364 @item set observer on
5365 @itemx set observer off
5366 When set to @code{on}, this disables all the permission variables
5367 below (except for @code{insert-fast-tracepoints}), plus enables
5368 non-stop debugging. Setting this to @code{off} switches back to
5369 normal debugging, though remaining in non-stop mode.
5372 Show whether observer mode is on or off.
5374 @kindex may-write-registers
5375 @item set may-write-registers on
5376 @itemx set may-write-registers off
5377 This controls whether @value{GDBN} will attempt to alter the values of
5378 registers, such as with assignment expressions in @code{print}, or the
5379 @code{jump} command. It defaults to @code{on}.
5381 @item show may-write-registers
5382 Show the current permission to write registers.
5384 @kindex may-write-memory
5385 @item set may-write-memory on
5386 @itemx set may-write-memory off
5387 This controls whether @value{GDBN} will attempt to alter the contents
5388 of memory, such as with assignment expressions in @code{print}. It
5389 defaults to @code{on}.
5391 @item show may-write-memory
5392 Show the current permission to write memory.
5394 @kindex may-insert-breakpoints
5395 @item set may-insert-breakpoints on
5396 @itemx set may-insert-breakpoints off
5397 This controls whether @value{GDBN} will attempt to insert breakpoints.
5398 This affects all breakpoints, including internal breakpoints defined
5399 by @value{GDBN}. It defaults to @code{on}.
5401 @item show may-insert-breakpoints
5402 Show the current permission to insert breakpoints.
5404 @kindex may-insert-tracepoints
5405 @item set may-insert-tracepoints on
5406 @itemx set may-insert-tracepoints off
5407 This controls whether @value{GDBN} will attempt to insert (regular)
5408 tracepoints at the beginning of a tracing experiment. It affects only
5409 non-fast tracepoints, fast tracepoints being under the control of
5410 @code{may-insert-fast-tracepoints}. It defaults to @code{on}.
5412 @item show may-insert-tracepoints
5413 Show the current permission to insert tracepoints.
5415 @kindex may-insert-fast-tracepoints
5416 @item set may-insert-fast-tracepoints on
5417 @itemx set may-insert-fast-tracepoints off
5418 This controls whether @value{GDBN} will attempt to insert fast
5419 tracepoints at the beginning of a tracing experiment. It affects only
5420 fast tracepoints, regular (non-fast) tracepoints being under the
5421 control of @code{may-insert-tracepoints}. It defaults to @code{on}.
5423 @item show may-insert-fast-tracepoints
5424 Show the current permission to insert fast tracepoints.
5426 @kindex may-interrupt
5427 @item set may-interrupt on
5428 @itemx set may-interrupt off
5429 This controls whether @value{GDBN} will attempt to interrupt or stop
5430 program execution. When this variable is @code{off}, the
5431 @code{interrupt} command will have no effect, nor will
5432 @kbd{Ctrl-c}. It defaults to @code{on}.
5434 @item show may-interrupt
5435 Show the current permission to interrupt or stop the program.
5439 @node Reverse Execution
5440 @chapter Running programs backward
5441 @cindex reverse execution
5442 @cindex running programs backward
5444 When you are debugging a program, it is not unusual to realize that
5445 you have gone too far, and some event of interest has already happened.
5446 If the target environment supports it, @value{GDBN} can allow you to
5447 ``rewind'' the program by running it backward.
5449 A target environment that supports reverse execution should be able
5450 to ``undo'' the changes in machine state that have taken place as the
5451 program was executing normally. Variables, registers etc.@: should
5452 revert to their previous values. Obviously this requires a great
5453 deal of sophistication on the part of the target environment; not
5454 all target environments can support reverse execution.
5456 When a program is executed in reverse, the instructions that
5457 have most recently been executed are ``un-executed'', in reverse
5458 order. The program counter runs backward, following the previous
5459 thread of execution in reverse. As each instruction is ``un-executed'',
5460 the values of memory and/or registers that were changed by that
5461 instruction are reverted to their previous states. After executing
5462 a piece of source code in reverse, all side effects of that code
5463 should be ``undone'', and all variables should be returned to their
5464 prior values@footnote{
5465 Note that some side effects are easier to undo than others. For instance,
5466 memory and registers are relatively easy, but device I/O is hard. Some
5467 targets may be able undo things like device I/O, and some may not.
5469 The contract between @value{GDBN} and the reverse executing target
5470 requires only that the target do something reasonable when
5471 @value{GDBN} tells it to execute backwards, and then report the
5472 results back to @value{GDBN}. Whatever the target reports back to
5473 @value{GDBN}, @value{GDBN} will report back to the user. @value{GDBN}
5474 assumes that the memory and registers that the target reports are in a
5475 consistant state, but @value{GDBN} accepts whatever it is given.
5478 If you are debugging in a target environment that supports
5479 reverse execution, @value{GDBN} provides the following commands.
5482 @kindex reverse-continue
5483 @kindex rc @r{(@code{reverse-continue})}
5484 @item reverse-continue @r{[}@var{ignore-count}@r{]}
5485 @itemx rc @r{[}@var{ignore-count}@r{]}
5486 Beginning at the point where your program last stopped, start executing
5487 in reverse. Reverse execution will stop for breakpoints and synchronous
5488 exceptions (signals), just like normal execution. Behavior of
5489 asynchronous signals depends on the target environment.
5491 @kindex reverse-step
5492 @kindex rs @r{(@code{step})}
5493 @item reverse-step @r{[}@var{count}@r{]}
5494 Run the program backward until control reaches the start of a
5495 different source line; then stop it, and return control to @value{GDBN}.
5497 Like the @code{step} command, @code{reverse-step} will only stop
5498 at the beginning of a source line. It ``un-executes'' the previously
5499 executed source line. If the previous source line included calls to
5500 debuggable functions, @code{reverse-step} will step (backward) into
5501 the called function, stopping at the beginning of the @emph{last}
5502 statement in the called function (typically a return statement).
5504 Also, as with the @code{step} command, if non-debuggable functions are
5505 called, @code{reverse-step} will run thru them backward without stopping.
5507 @kindex reverse-stepi
5508 @kindex rsi @r{(@code{reverse-stepi})}
5509 @item reverse-stepi @r{[}@var{count}@r{]}
5510 Reverse-execute one machine instruction. Note that the instruction
5511 to be reverse-executed is @emph{not} the one pointed to by the program
5512 counter, but the instruction executed prior to that one. For instance,
5513 if the last instruction was a jump, @code{reverse-stepi} will take you
5514 back from the destination of the jump to the jump instruction itself.
5516 @kindex reverse-next
5517 @kindex rn @r{(@code{reverse-next})}
5518 @item reverse-next @r{[}@var{count}@r{]}
5519 Run backward to the beginning of the previous line executed in
5520 the current (innermost) stack frame. If the line contains function
5521 calls, they will be ``un-executed'' without stopping. Starting from
5522 the first line of a function, @code{reverse-next} will take you back
5523 to the caller of that function, @emph{before} the function was called,
5524 just as the normal @code{next} command would take you from the last
5525 line of a function back to its return to its caller
5526 @footnote{Unless the code is too heavily optimized.}.
5528 @kindex reverse-nexti
5529 @kindex rni @r{(@code{reverse-nexti})}
5530 @item reverse-nexti @r{[}@var{count}@r{]}
5531 Like @code{nexti}, @code{reverse-nexti} executes a single instruction
5532 in reverse, except that called functions are ``un-executed'' atomically.
5533 That is, if the previously executed instruction was a return from
5534 another function, @code{reverse-nexti} will continue to execute
5535 in reverse until the call to that function (from the current stack
5538 @kindex reverse-finish
5539 @item reverse-finish
5540 Just as the @code{finish} command takes you to the point where the
5541 current function returns, @code{reverse-finish} takes you to the point
5542 where it was called. Instead of ending up at the end of the current
5543 function invocation, you end up at the beginning.
5545 @kindex set exec-direction
5546 @item set exec-direction
5547 Set the direction of target execution.
5548 @itemx set exec-direction reverse
5549 @cindex execute forward or backward in time
5550 @value{GDBN} will perform all execution commands in reverse, until the
5551 exec-direction mode is changed to ``forward''. Affected commands include
5552 @code{step, stepi, next, nexti, continue, and finish}. The @code{return}
5553 command cannot be used in reverse mode.
5554 @item set exec-direction forward
5555 @value{GDBN} will perform all execution commands in the normal fashion.
5556 This is the default.
5560 @node Process Record and Replay
5561 @chapter Recording Inferior's Execution and Replaying It
5562 @cindex process record and replay
5563 @cindex recording inferior's execution and replaying it
5565 On some platforms, @value{GDBN} provides a special @dfn{process record
5566 and replay} target that can record a log of the process execution, and
5567 replay it later with both forward and reverse execution commands.
5570 When this target is in use, if the execution log includes the record
5571 for the next instruction, @value{GDBN} will debug in @dfn{replay
5572 mode}. In the replay mode, the inferior does not really execute code
5573 instructions. Instead, all the events that normally happen during
5574 code execution are taken from the execution log. While code is not
5575 really executed in replay mode, the values of registers (including the
5576 program counter register) and the memory of the inferior are still
5577 changed as they normally would. Their contents are taken from the
5581 If the record for the next instruction is not in the execution log,
5582 @value{GDBN} will debug in @dfn{record mode}. In this mode, the
5583 inferior executes normally, and @value{GDBN} records the execution log
5586 The process record and replay target supports reverse execution
5587 (@pxref{Reverse Execution}), even if the platform on which the
5588 inferior runs does not. However, the reverse execution is limited in
5589 this case by the range of the instructions recorded in the execution
5590 log. In other words, reverse execution on platforms that don't
5591 support it directly can only be done in the replay mode.
5593 When debugging in the reverse direction, @value{GDBN} will work in
5594 replay mode as long as the execution log includes the record for the
5595 previous instruction; otherwise, it will work in record mode, if the
5596 platform supports reverse execution, or stop if not.
5598 For architecture environments that support process record and replay,
5599 @value{GDBN} provides the following commands:
5602 @kindex target record
5606 This command starts the process record and replay target. The process
5607 record and replay target can only debug a process that is already
5608 running. Therefore, you need first to start the process with the
5609 @kbd{run} or @kbd{start} commands, and then start the recording with
5610 the @kbd{target record} command.
5612 Both @code{record} and @code{rec} are aliases of @code{target record}.
5614 @cindex displaced stepping, and process record and replay
5615 Displaced stepping (@pxref{Maintenance Commands,, displaced stepping})
5616 will be automatically disabled when process record and replay target
5617 is started. That's because the process record and replay target
5618 doesn't support displaced stepping.
5620 @cindex non-stop mode, and process record and replay
5621 @cindex asynchronous execution, and process record and replay
5622 If the inferior is in the non-stop mode (@pxref{Non-Stop Mode}) or in
5623 the asynchronous execution mode (@pxref{Background Execution}), the
5624 process record and replay target cannot be started because it doesn't
5625 support these two modes.
5630 Stop the process record and replay target. When process record and
5631 replay target stops, the entire execution log will be deleted and the
5632 inferior will either be terminated, or will remain in its final state.
5634 When you stop the process record and replay target in record mode (at
5635 the end of the execution log), the inferior will be stopped at the
5636 next instruction that would have been recorded. In other words, if
5637 you record for a while and then stop recording, the inferior process
5638 will be left in the same state as if the recording never happened.
5640 On the other hand, if the process record and replay target is stopped
5641 while in replay mode (that is, not at the end of the execution log,
5642 but at some earlier point), the inferior process will become ``live''
5643 at that earlier state, and it will then be possible to continue the
5644 usual ``live'' debugging of the process from that state.
5646 When the inferior process exits, or @value{GDBN} detaches from it,
5647 process record and replay target will automatically stop itself.
5650 @item record save @var{filename}
5651 Save the execution log to a file @file{@var{filename}}.
5652 Default filename is @file{gdb_record.@var{process_id}}, where
5653 @var{process_id} is the process ID of the inferior.
5655 @kindex record restore
5656 @item record restore @var{filename}
5657 Restore the execution log from a file @file{@var{filename}}.
5658 File must have been created with @code{record save}.
5660 @kindex set record insn-number-max
5661 @item set record insn-number-max @var{limit}
5662 Set the limit of instructions to be recorded. Default value is 200000.
5664 If @var{limit} is a positive number, then @value{GDBN} will start
5665 deleting instructions from the log once the number of the record
5666 instructions becomes greater than @var{limit}. For every new recorded
5667 instruction, @value{GDBN} will delete the earliest recorded
5668 instruction to keep the number of recorded instructions at the limit.
5669 (Since deleting recorded instructions loses information, @value{GDBN}
5670 lets you control what happens when the limit is reached, by means of
5671 the @code{stop-at-limit} option, described below.)
5673 If @var{limit} is zero, @value{GDBN} will never delete recorded
5674 instructions from the execution log. The number of recorded
5675 instructions is unlimited in this case.
5677 @kindex show record insn-number-max
5678 @item show record insn-number-max
5679 Show the limit of instructions to be recorded.
5681 @kindex set record stop-at-limit
5682 @item set record stop-at-limit
5683 Control the behavior when the number of recorded instructions reaches
5684 the limit. If ON (the default), @value{GDBN} will stop when the limit
5685 is reached for the first time and ask you whether you want to stop the
5686 inferior or continue running it and recording the execution log. If
5687 you decide to continue recording, each new recorded instruction will
5688 cause the oldest one to be deleted.
5690 If this option is OFF, @value{GDBN} will automatically delete the
5691 oldest record to make room for each new one, without asking.
5693 @kindex show record stop-at-limit
5694 @item show record stop-at-limit
5695 Show the current setting of @code{stop-at-limit}.
5697 @kindex set record memory-query
5698 @item set record memory-query
5699 Control the behavior when @value{GDBN} is unable to record memory
5700 changes caused by an instruction. If ON, @value{GDBN} will query
5701 whether to stop the inferior in that case.
5703 If this option is OFF (the default), @value{GDBN} will automatically
5704 ignore the effect of such instructions on memory. Later, when
5705 @value{GDBN} replays this execution log, it will mark the log of this
5706 instruction as not accessible, and it will not affect the replay
5709 @kindex show record memory-query
5710 @item show record memory-query
5711 Show the current setting of @code{memory-query}.
5715 Show various statistics about the state of process record and its
5716 in-memory execution log buffer, including:
5720 Whether in record mode or replay mode.
5722 Lowest recorded instruction number (counting from when the current execution log started recording instructions).
5724 Highest recorded instruction number.
5726 Current instruction about to be replayed (if in replay mode).
5728 Number of instructions contained in the execution log.
5730 Maximum number of instructions that may be contained in the execution log.
5733 @kindex record delete
5736 When record target runs in replay mode (``in the past''), delete the
5737 subsequent execution log and begin to record a new execution log starting
5738 from the current address. This means you will abandon the previously
5739 recorded ``future'' and begin recording a new ``future''.
5744 @chapter Examining the Stack
5746 When your program has stopped, the first thing you need to know is where it
5747 stopped and how it got there.
5750 Each time your program performs a function call, information about the call
5752 That information includes the location of the call in your program,
5753 the arguments of the call,
5754 and the local variables of the function being called.
5755 The information is saved in a block of data called a @dfn{stack frame}.
5756 The stack frames are allocated in a region of memory called the @dfn{call
5759 When your program stops, the @value{GDBN} commands for examining the
5760 stack allow you to see all of this information.
5762 @cindex selected frame
5763 One of the stack frames is @dfn{selected} by @value{GDBN} and many
5764 @value{GDBN} commands refer implicitly to the selected frame. In
5765 particular, whenever you ask @value{GDBN} for the value of a variable in
5766 your program, the value is found in the selected frame. There are
5767 special @value{GDBN} commands to select whichever frame you are
5768 interested in. @xref{Selection, ,Selecting a Frame}.
5770 When your program stops, @value{GDBN} automatically selects the
5771 currently executing frame and describes it briefly, similar to the
5772 @code{frame} command (@pxref{Frame Info, ,Information about a Frame}).
5775 * Frames:: Stack frames
5776 * Backtrace:: Backtraces
5777 * Selection:: Selecting a frame
5778 * Frame Info:: Information on a frame
5783 @section Stack Frames
5785 @cindex frame, definition
5787 The call stack is divided up into contiguous pieces called @dfn{stack
5788 frames}, or @dfn{frames} for short; each frame is the data associated
5789 with one call to one function. The frame contains the arguments given
5790 to the function, the function's local variables, and the address at
5791 which the function is executing.
5793 @cindex initial frame
5794 @cindex outermost frame
5795 @cindex innermost frame
5796 When your program is started, the stack has only one frame, that of the
5797 function @code{main}. This is called the @dfn{initial} frame or the
5798 @dfn{outermost} frame. Each time a function is called, a new frame is
5799 made. Each time a function returns, the frame for that function invocation
5800 is eliminated. If a function is recursive, there can be many frames for
5801 the same function. The frame for the function in which execution is
5802 actually occurring is called the @dfn{innermost} frame. This is the most
5803 recently created of all the stack frames that still exist.
5805 @cindex frame pointer
5806 Inside your program, stack frames are identified by their addresses. A
5807 stack frame consists of many bytes, each of which has its own address; each
5808 kind of computer has a convention for choosing one byte whose
5809 address serves as the address of the frame. Usually this address is kept
5810 in a register called the @dfn{frame pointer register}
5811 (@pxref{Registers, $fp}) while execution is going on in that frame.
5813 @cindex frame number
5814 @value{GDBN} assigns numbers to all existing stack frames, starting with
5815 zero for the innermost frame, one for the frame that called it,
5816 and so on upward. These numbers do not really exist in your program;
5817 they are assigned by @value{GDBN} to give you a way of designating stack
5818 frames in @value{GDBN} commands.
5820 @c The -fomit-frame-pointer below perennially causes hbox overflow
5821 @c underflow problems.
5822 @cindex frameless execution
5823 Some compilers provide a way to compile functions so that they operate
5824 without stack frames. (For example, the @value{NGCC} option
5826 @samp{-fomit-frame-pointer}
5828 generates functions without a frame.)
5829 This is occasionally done with heavily used library functions to save
5830 the frame setup time. @value{GDBN} has limited facilities for dealing
5831 with these function invocations. If the innermost function invocation
5832 has no stack frame, @value{GDBN} nevertheless regards it as though
5833 it had a separate frame, which is numbered zero as usual, allowing
5834 correct tracing of the function call chain. However, @value{GDBN} has
5835 no provision for frameless functions elsewhere in the stack.
5838 @kindex frame@r{, command}
5839 @cindex current stack frame
5840 @item frame @var{args}
5841 The @code{frame} command allows you to move from one stack frame to another,
5842 and to print the stack frame you select. @var{args} may be either the
5843 address of the frame or the stack frame number. Without an argument,
5844 @code{frame} prints the current stack frame.
5846 @kindex select-frame
5847 @cindex selecting frame silently
5849 The @code{select-frame} command allows you to move from one stack frame
5850 to another without printing the frame. This is the silent version of
5858 @cindex call stack traces
5859 A backtrace is a summary of how your program got where it is. It shows one
5860 line per frame, for many frames, starting with the currently executing
5861 frame (frame zero), followed by its caller (frame one), and on up the
5866 @kindex bt @r{(@code{backtrace})}
5869 Print a backtrace of the entire stack: one line per frame for all
5870 frames in the stack.
5872 You can stop the backtrace at any time by typing the system interrupt
5873 character, normally @kbd{Ctrl-c}.
5875 @item backtrace @var{n}
5877 Similar, but print only the innermost @var{n} frames.
5879 @item backtrace -@var{n}
5881 Similar, but print only the outermost @var{n} frames.
5883 @item backtrace full
5885 @itemx bt full @var{n}
5886 @itemx bt full -@var{n}
5887 Print the values of the local variables also. @var{n} specifies the
5888 number of frames to print, as described above.
5893 The names @code{where} and @code{info stack} (abbreviated @code{info s})
5894 are additional aliases for @code{backtrace}.
5896 @cindex multiple threads, backtrace
5897 In a multi-threaded program, @value{GDBN} by default shows the
5898 backtrace only for the current thread. To display the backtrace for
5899 several or all of the threads, use the command @code{thread apply}
5900 (@pxref{Threads, thread apply}). For example, if you type @kbd{thread
5901 apply all backtrace}, @value{GDBN} will display the backtrace for all
5902 the threads; this is handy when you debug a core dump of a
5903 multi-threaded program.
5905 Each line in the backtrace shows the frame number and the function name.
5906 The program counter value is also shown---unless you use @code{set
5907 print address off}. The backtrace also shows the source file name and
5908 line number, as well as the arguments to the function. The program
5909 counter value is omitted if it is at the beginning of the code for that
5912 Here is an example of a backtrace. It was made with the command
5913 @samp{bt 3}, so it shows the innermost three frames.
5917 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
5919 #1 0x6e38 in expand_macro (sym=0x2b600, data=...) at macro.c:242
5920 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
5922 (More stack frames follow...)
5927 The display for frame zero does not begin with a program counter
5928 value, indicating that your program has stopped at the beginning of the
5929 code for line @code{993} of @code{builtin.c}.
5932 The value of parameter @code{data} in frame 1 has been replaced by
5933 @code{@dots{}}. By default, @value{GDBN} prints the value of a parameter
5934 only if it is a scalar (integer, pointer, enumeration, etc). See command
5935 @kbd{set print frame-arguments} in @ref{Print Settings} for more details
5936 on how to configure the way function parameter values are printed.
5938 @cindex value optimized out, in backtrace
5939 @cindex function call arguments, optimized out
5940 If your program was compiled with optimizations, some compilers will
5941 optimize away arguments passed to functions if those arguments are
5942 never used after the call. Such optimizations generate code that
5943 passes arguments through registers, but doesn't store those arguments
5944 in the stack frame. @value{GDBN} has no way of displaying such
5945 arguments in stack frames other than the innermost one. Here's what
5946 such a backtrace might look like:
5950 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
5952 #1 0x6e38 in expand_macro (sym=<value optimized out>) at macro.c:242
5953 #2 0x6840 in expand_token (obs=0x0, t=<value optimized out>, td=0xf7fffb08)
5955 (More stack frames follow...)
5960 The values of arguments that were not saved in their stack frames are
5961 shown as @samp{<value optimized out>}.
5963 If you need to display the values of such optimized-out arguments,
5964 either deduce that from other variables whose values depend on the one
5965 you are interested in, or recompile without optimizations.
5967 @cindex backtrace beyond @code{main} function
5968 @cindex program entry point
5969 @cindex startup code, and backtrace
5970 Most programs have a standard user entry point---a place where system
5971 libraries and startup code transition into user code. For C this is
5972 @code{main}@footnote{
5973 Note that embedded programs (the so-called ``free-standing''
5974 environment) are not required to have a @code{main} function as the
5975 entry point. They could even have multiple entry points.}.
5976 When @value{GDBN} finds the entry function in a backtrace
5977 it will terminate the backtrace, to avoid tracing into highly
5978 system-specific (and generally uninteresting) code.
5980 If you need to examine the startup code, or limit the number of levels
5981 in a backtrace, you can change this behavior:
5984 @item set backtrace past-main
5985 @itemx set backtrace past-main on
5986 @kindex set backtrace
5987 Backtraces will continue past the user entry point.
5989 @item set backtrace past-main off
5990 Backtraces will stop when they encounter the user entry point. This is the
5993 @item show backtrace past-main
5994 @kindex show backtrace
5995 Display the current user entry point backtrace policy.
5997 @item set backtrace past-entry
5998 @itemx set backtrace past-entry on
5999 Backtraces will continue past the internal entry point of an application.
6000 This entry point is encoded by the linker when the application is built,
6001 and is likely before the user entry point @code{main} (or equivalent) is called.
6003 @item set backtrace past-entry off
6004 Backtraces will stop when they encounter the internal entry point of an
6005 application. This is the default.
6007 @item show backtrace past-entry
6008 Display the current internal entry point backtrace policy.
6010 @item set backtrace limit @var{n}
6011 @itemx set backtrace limit 0
6012 @cindex backtrace limit
6013 Limit the backtrace to @var{n} levels. A value of zero means
6016 @item show backtrace limit
6017 Display the current limit on backtrace levels.
6021 @section Selecting a Frame
6023 Most commands for examining the stack and other data in your program work on
6024 whichever stack frame is selected at the moment. Here are the commands for
6025 selecting a stack frame; all of them finish by printing a brief description
6026 of the stack frame just selected.
6029 @kindex frame@r{, selecting}
6030 @kindex f @r{(@code{frame})}
6033 Select frame number @var{n}. Recall that frame zero is the innermost
6034 (currently executing) frame, frame one is the frame that called the
6035 innermost one, and so on. The highest-numbered frame is the one for
6038 @item frame @var{addr}
6040 Select the frame at address @var{addr}. This is useful mainly if the
6041 chaining of stack frames has been damaged by a bug, making it
6042 impossible for @value{GDBN} to assign numbers properly to all frames. In
6043 addition, this can be useful when your program has multiple stacks and
6044 switches between them.
6046 On the SPARC architecture, @code{frame} needs two addresses to
6047 select an arbitrary frame: a frame pointer and a stack pointer.
6049 On the MIPS and Alpha architecture, it needs two addresses: a stack
6050 pointer and a program counter.
6052 On the 29k architecture, it needs three addresses: a register stack
6053 pointer, a program counter, and a memory stack pointer.
6057 Move @var{n} frames up the stack. For positive numbers @var{n}, this
6058 advances toward the outermost frame, to higher frame numbers, to frames
6059 that have existed longer. @var{n} defaults to one.
6062 @kindex do @r{(@code{down})}
6064 Move @var{n} frames down the stack. For positive numbers @var{n}, this
6065 advances toward the innermost frame, to lower frame numbers, to frames
6066 that were created more recently. @var{n} defaults to one. You may
6067 abbreviate @code{down} as @code{do}.
6070 All of these commands end by printing two lines of output describing the
6071 frame. The first line shows the frame number, the function name, the
6072 arguments, and the source file and line number of execution in that
6073 frame. The second line shows the text of that source line.
6081 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
6083 10 read_input_file (argv[i]);
6087 After such a printout, the @code{list} command with no arguments
6088 prints ten lines centered on the point of execution in the frame.
6089 You can also edit the program at the point of execution with your favorite
6090 editing program by typing @code{edit}.
6091 @xref{List, ,Printing Source Lines},
6095 @kindex down-silently
6097 @item up-silently @var{n}
6098 @itemx down-silently @var{n}
6099 These two commands are variants of @code{up} and @code{down},
6100 respectively; they differ in that they do their work silently, without
6101 causing display of the new frame. They are intended primarily for use
6102 in @value{GDBN} command scripts, where the output might be unnecessary and
6107 @section Information About a Frame
6109 There are several other commands to print information about the selected
6115 When used without any argument, this command does not change which
6116 frame is selected, but prints a brief description of the currently
6117 selected stack frame. It can be abbreviated @code{f}. With an
6118 argument, this command is used to select a stack frame.
6119 @xref{Selection, ,Selecting a Frame}.
6122 @kindex info f @r{(@code{info frame})}
6125 This command prints a verbose description of the selected stack frame,
6130 the address of the frame
6132 the address of the next frame down (called by this frame)
6134 the address of the next frame up (caller of this frame)
6136 the language in which the source code corresponding to this frame is written
6138 the address of the frame's arguments
6140 the address of the frame's local variables
6142 the program counter saved in it (the address of execution in the caller frame)
6144 which registers were saved in the frame
6147 @noindent The verbose description is useful when
6148 something has gone wrong that has made the stack format fail to fit
6149 the usual conventions.
6151 @item info frame @var{addr}
6152 @itemx info f @var{addr}
6153 Print a verbose description of the frame at address @var{addr}, without
6154 selecting that frame. The selected frame remains unchanged by this
6155 command. This requires the same kind of address (more than one for some
6156 architectures) that you specify in the @code{frame} command.
6157 @xref{Selection, ,Selecting a Frame}.
6161 Print the arguments of the selected frame, each on a separate line.
6165 Print the local variables of the selected frame, each on a separate
6166 line. These are all variables (declared either static or automatic)
6167 accessible at the point of execution of the selected frame.
6170 @cindex catch exceptions, list active handlers
6171 @cindex exception handlers, how to list
6173 Print a list of all the exception handlers that are active in the
6174 current stack frame at the current point of execution. To see other
6175 exception handlers, visit the associated frame (using the @code{up},
6176 @code{down}, or @code{frame} commands); then type @code{info catch}.
6177 @xref{Set Catchpoints, , Setting Catchpoints}.
6183 @chapter Examining Source Files
6185 @value{GDBN} can print parts of your program's source, since the debugging
6186 information recorded in the program tells @value{GDBN} what source files were
6187 used to build it. When your program stops, @value{GDBN} spontaneously prints
6188 the line where it stopped. Likewise, when you select a stack frame
6189 (@pxref{Selection, ,Selecting a Frame}), @value{GDBN} prints the line where
6190 execution in that frame has stopped. You can print other portions of
6191 source files by explicit command.
6193 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
6194 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
6195 @value{GDBN} under @sc{gnu} Emacs}.
6198 * List:: Printing source lines
6199 * Specify Location:: How to specify code locations
6200 * Edit:: Editing source files
6201 * Search:: Searching source files
6202 * Source Path:: Specifying source directories
6203 * Machine Code:: Source and machine code
6207 @section Printing Source Lines
6210 @kindex l @r{(@code{list})}
6211 To print lines from a source file, use the @code{list} command
6212 (abbreviated @code{l}). By default, ten lines are printed.
6213 There are several ways to specify what part of the file you want to
6214 print; see @ref{Specify Location}, for the full list.
6216 Here are the forms of the @code{list} command most commonly used:
6219 @item list @var{linenum}
6220 Print lines centered around line number @var{linenum} in the
6221 current source file.
6223 @item list @var{function}
6224 Print lines centered around the beginning of function
6228 Print more lines. If the last lines printed were printed with a
6229 @code{list} command, this prints lines following the last lines
6230 printed; however, if the last line printed was a solitary line printed
6231 as part of displaying a stack frame (@pxref{Stack, ,Examining the
6232 Stack}), this prints lines centered around that line.
6235 Print lines just before the lines last printed.
6238 @cindex @code{list}, how many lines to display
6239 By default, @value{GDBN} prints ten source lines with any of these forms of
6240 the @code{list} command. You can change this using @code{set listsize}:
6243 @kindex set listsize
6244 @item set listsize @var{count}
6245 Make the @code{list} command display @var{count} source lines (unless
6246 the @code{list} argument explicitly specifies some other number).
6248 @kindex show listsize
6250 Display the number of lines that @code{list} prints.
6253 Repeating a @code{list} command with @key{RET} discards the argument,
6254 so it is equivalent to typing just @code{list}. This is more useful
6255 than listing the same lines again. An exception is made for an
6256 argument of @samp{-}; that argument is preserved in repetition so that
6257 each repetition moves up in the source file.
6259 In general, the @code{list} command expects you to supply zero, one or two
6260 @dfn{linespecs}. Linespecs specify source lines; there are several ways
6261 of writing them (@pxref{Specify Location}), but the effect is always
6262 to specify some source line.
6264 Here is a complete description of the possible arguments for @code{list}:
6267 @item list @var{linespec}
6268 Print lines centered around the line specified by @var{linespec}.
6270 @item list @var{first},@var{last}
6271 Print lines from @var{first} to @var{last}. Both arguments are
6272 linespecs. When a @code{list} command has two linespecs, and the
6273 source file of the second linespec is omitted, this refers to
6274 the same source file as the first linespec.
6276 @item list ,@var{last}
6277 Print lines ending with @var{last}.
6279 @item list @var{first},
6280 Print lines starting with @var{first}.
6283 Print lines just after the lines last printed.
6286 Print lines just before the lines last printed.
6289 As described in the preceding table.
6292 @node Specify Location
6293 @section Specifying a Location
6294 @cindex specifying location
6297 Several @value{GDBN} commands accept arguments that specify a location
6298 of your program's code. Since @value{GDBN} is a source-level
6299 debugger, a location usually specifies some line in the source code;
6300 for that reason, locations are also known as @dfn{linespecs}.
6302 Here are all the different ways of specifying a code location that
6303 @value{GDBN} understands:
6307 Specifies the line number @var{linenum} of the current source file.
6310 @itemx +@var{offset}
6311 Specifies the line @var{offset} lines before or after the @dfn{current
6312 line}. For the @code{list} command, the current line is the last one
6313 printed; for the breakpoint commands, this is the line at which
6314 execution stopped in the currently selected @dfn{stack frame}
6315 (@pxref{Frames, ,Frames}, for a description of stack frames.) When
6316 used as the second of the two linespecs in a @code{list} command,
6317 this specifies the line @var{offset} lines up or down from the first
6320 @item @var{filename}:@var{linenum}
6321 Specifies the line @var{linenum} in the source file @var{filename}.
6323 @item @var{function}
6324 Specifies the line that begins the body of the function @var{function}.
6325 For example, in C, this is the line with the open brace.
6327 @item @var{filename}:@var{function}
6328 Specifies the line that begins the body of the function @var{function}
6329 in the file @var{filename}. You only need the file name with a
6330 function name to avoid ambiguity when there are identically named
6331 functions in different source files.
6334 Specifies the line at which the label named @var{label} appears.
6335 @value{GDBN} searches for the label in the function corresponding to
6336 the currently selected stack frame. If there is no current selected
6337 stack frame (for instance, if the inferior is not running), then
6338 @value{GDBN} will not search for a label.
6340 @item *@var{address}
6341 Specifies the program address @var{address}. For line-oriented
6342 commands, such as @code{list} and @code{edit}, this specifies a source
6343 line that contains @var{address}. For @code{break} and other
6344 breakpoint oriented commands, this can be used to set breakpoints in
6345 parts of your program which do not have debugging information or
6348 Here @var{address} may be any expression valid in the current working
6349 language (@pxref{Languages, working language}) that specifies a code
6350 address. In addition, as a convenience, @value{GDBN} extends the
6351 semantics of expressions used in locations to cover the situations
6352 that frequently happen during debugging. Here are the various forms
6356 @item @var{expression}
6357 Any expression valid in the current working language.
6359 @item @var{funcaddr}
6360 An address of a function or procedure derived from its name. In C,
6361 C@t{++}, Java, Objective-C, Fortran, minimal, and assembly, this is
6362 simply the function's name @var{function} (and actually a special case
6363 of a valid expression). In Pascal and Modula-2, this is
6364 @code{&@var{function}}. In Ada, this is @code{@var{function}'Address}
6365 (although the Pascal form also works).
6367 This form specifies the address of the function's first instruction,
6368 before the stack frame and arguments have been set up.
6370 @item '@var{filename}'::@var{funcaddr}
6371 Like @var{funcaddr} above, but also specifies the name of the source
6372 file explicitly. This is useful if the name of the function does not
6373 specify the function unambiguously, e.g., if there are several
6374 functions with identical names in different source files.
6381 @section Editing Source Files
6382 @cindex editing source files
6385 @kindex e @r{(@code{edit})}
6386 To edit the lines in a source file, use the @code{edit} command.
6387 The editing program of your choice
6388 is invoked with the current line set to
6389 the active line in the program.
6390 Alternatively, there are several ways to specify what part of the file you
6391 want to print if you want to see other parts of the program:
6394 @item edit @var{location}
6395 Edit the source file specified by @code{location}. Editing starts at
6396 that @var{location}, e.g., at the specified source line of the
6397 specified file. @xref{Specify Location}, for all the possible forms
6398 of the @var{location} argument; here are the forms of the @code{edit}
6399 command most commonly used:
6402 @item edit @var{number}
6403 Edit the current source file with @var{number} as the active line number.
6405 @item edit @var{function}
6406 Edit the file containing @var{function} at the beginning of its definition.
6411 @subsection Choosing your Editor
6412 You can customize @value{GDBN} to use any editor you want
6414 The only restriction is that your editor (say @code{ex}), recognizes the
6415 following command-line syntax:
6417 ex +@var{number} file
6419 The optional numeric value +@var{number} specifies the number of the line in
6420 the file where to start editing.}.
6421 By default, it is @file{@value{EDITOR}}, but you can change this
6422 by setting the environment variable @code{EDITOR} before using
6423 @value{GDBN}. For example, to configure @value{GDBN} to use the
6424 @code{vi} editor, you could use these commands with the @code{sh} shell:
6430 or in the @code{csh} shell,
6432 setenv EDITOR /usr/bin/vi
6437 @section Searching Source Files
6438 @cindex searching source files
6440 There are two commands for searching through the current source file for a
6445 @kindex forward-search
6446 @item forward-search @var{regexp}
6447 @itemx search @var{regexp}
6448 The command @samp{forward-search @var{regexp}} checks each line,
6449 starting with the one following the last line listed, for a match for
6450 @var{regexp}. It lists the line that is found. You can use the
6451 synonym @samp{search @var{regexp}} or abbreviate the command name as
6454 @kindex reverse-search
6455 @item reverse-search @var{regexp}
6456 The command @samp{reverse-search @var{regexp}} checks each line, starting
6457 with the one before the last line listed and going backward, for a match
6458 for @var{regexp}. It lists the line that is found. You can abbreviate
6459 this command as @code{rev}.
6463 @section Specifying Source Directories
6466 @cindex directories for source files
6467 Executable programs sometimes do not record the directories of the source
6468 files from which they were compiled, just the names. Even when they do,
6469 the directories could be moved between the compilation and your debugging
6470 session. @value{GDBN} has a list of directories to search for source files;
6471 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
6472 it tries all the directories in the list, in the order they are present
6473 in the list, until it finds a file with the desired name.
6475 For example, suppose an executable references the file
6476 @file{/usr/src/foo-1.0/lib/foo.c}, and our source path is
6477 @file{/mnt/cross}. The file is first looked up literally; if this
6478 fails, @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c} is tried; if this
6479 fails, @file{/mnt/cross/foo.c} is opened; if this fails, an error
6480 message is printed. @value{GDBN} does not look up the parts of the
6481 source file name, such as @file{/mnt/cross/src/foo-1.0/lib/foo.c}.
6482 Likewise, the subdirectories of the source path are not searched: if
6483 the source path is @file{/mnt/cross}, and the binary refers to
6484 @file{foo.c}, @value{GDBN} would not find it under
6485 @file{/mnt/cross/usr/src/foo-1.0/lib}.
6487 Plain file names, relative file names with leading directories, file
6488 names containing dots, etc.@: are all treated as described above; for
6489 instance, if the source path is @file{/mnt/cross}, and the source file
6490 is recorded as @file{../lib/foo.c}, @value{GDBN} would first try
6491 @file{../lib/foo.c}, then @file{/mnt/cross/../lib/foo.c}, and after
6492 that---@file{/mnt/cross/foo.c}.
6494 Note that the executable search path is @emph{not} used to locate the
6497 Whenever you reset or rearrange the source path, @value{GDBN} clears out
6498 any information it has cached about where source files are found and where
6499 each line is in the file.
6503 When you start @value{GDBN}, its source path includes only @samp{cdir}
6504 and @samp{cwd}, in that order.
6505 To add other directories, use the @code{directory} command.
6507 The search path is used to find both program source files and @value{GDBN}
6508 script files (read using the @samp{-command} option and @samp{source} command).
6510 In addition to the source path, @value{GDBN} provides a set of commands
6511 that manage a list of source path substitution rules. A @dfn{substitution
6512 rule} specifies how to rewrite source directories stored in the program's
6513 debug information in case the sources were moved to a different
6514 directory between compilation and debugging. A rule is made of
6515 two strings, the first specifying what needs to be rewritten in
6516 the path, and the second specifying how it should be rewritten.
6517 In @ref{set substitute-path}, we name these two parts @var{from} and
6518 @var{to} respectively. @value{GDBN} does a simple string replacement
6519 of @var{from} with @var{to} at the start of the directory part of the
6520 source file name, and uses that result instead of the original file
6521 name to look up the sources.
6523 Using the previous example, suppose the @file{foo-1.0} tree has been
6524 moved from @file{/usr/src} to @file{/mnt/cross}, then you can tell
6525 @value{GDBN} to replace @file{/usr/src} in all source path names with
6526 @file{/mnt/cross}. The first lookup will then be
6527 @file{/mnt/cross/foo-1.0/lib/foo.c} in place of the original location
6528 of @file{/usr/src/foo-1.0/lib/foo.c}. To define a source path
6529 substitution rule, use the @code{set substitute-path} command
6530 (@pxref{set substitute-path}).
6532 To avoid unexpected substitution results, a rule is applied only if the
6533 @var{from} part of the directory name ends at a directory separator.
6534 For instance, a rule substituting @file{/usr/source} into
6535 @file{/mnt/cross} will be applied to @file{/usr/source/foo-1.0} but
6536 not to @file{/usr/sourceware/foo-2.0}. And because the substitution
6537 is applied only at the beginning of the directory name, this rule will
6538 not be applied to @file{/root/usr/source/baz.c} either.
6540 In many cases, you can achieve the same result using the @code{directory}
6541 command. However, @code{set substitute-path} can be more efficient in
6542 the case where the sources are organized in a complex tree with multiple
6543 subdirectories. With the @code{directory} command, you need to add each
6544 subdirectory of your project. If you moved the entire tree while
6545 preserving its internal organization, then @code{set substitute-path}
6546 allows you to direct the debugger to all the sources with one single
6549 @code{set substitute-path} is also more than just a shortcut command.
6550 The source path is only used if the file at the original location no
6551 longer exists. On the other hand, @code{set substitute-path} modifies
6552 the debugger behavior to look at the rewritten location instead. So, if
6553 for any reason a source file that is not relevant to your executable is
6554 located at the original location, a substitution rule is the only
6555 method available to point @value{GDBN} at the new location.
6557 @cindex @samp{--with-relocated-sources}
6558 @cindex default source path substitution
6559 You can configure a default source path substitution rule by
6560 configuring @value{GDBN} with the
6561 @samp{--with-relocated-sources=@var{dir}} option. The @var{dir}
6562 should be the name of a directory under @value{GDBN}'s configured
6563 prefix (set with @samp{--prefix} or @samp{--exec-prefix}), and
6564 directory names in debug information under @var{dir} will be adjusted
6565 automatically if the installed @value{GDBN} is moved to a new
6566 location. This is useful if @value{GDBN}, libraries or executables
6567 with debug information and corresponding source code are being moved
6571 @item directory @var{dirname} @dots{}
6572 @item dir @var{dirname} @dots{}
6573 Add directory @var{dirname} to the front of the source path. Several
6574 directory names may be given to this command, separated by @samp{:}
6575 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
6576 part of absolute file names) or
6577 whitespace. You may specify a directory that is already in the source
6578 path; this moves it forward, so @value{GDBN} searches it sooner.
6582 @vindex $cdir@r{, convenience variable}
6583 @vindex $cwd@r{, convenience variable}
6584 @cindex compilation directory
6585 @cindex current directory
6586 @cindex working directory
6587 @cindex directory, current
6588 @cindex directory, compilation
6589 You can use the string @samp{$cdir} to refer to the compilation
6590 directory (if one is recorded), and @samp{$cwd} to refer to the current
6591 working directory. @samp{$cwd} is not the same as @samp{.}---the former
6592 tracks the current working directory as it changes during your @value{GDBN}
6593 session, while the latter is immediately expanded to the current
6594 directory at the time you add an entry to the source path.
6597 Reset the source path to its default value (@samp{$cdir:$cwd} on Unix systems). This requires confirmation.
6599 @c RET-repeat for @code{directory} is explicitly disabled, but since
6600 @c repeating it would be a no-op we do not say that. (thanks to RMS)
6602 @item show directories
6603 @kindex show directories
6604 Print the source path: show which directories it contains.
6606 @anchor{set substitute-path}
6607 @item set substitute-path @var{from} @var{to}
6608 @kindex set substitute-path
6609 Define a source path substitution rule, and add it at the end of the
6610 current list of existing substitution rules. If a rule with the same
6611 @var{from} was already defined, then the old rule is also deleted.
6613 For example, if the file @file{/foo/bar/baz.c} was moved to
6614 @file{/mnt/cross/baz.c}, then the command
6617 (@value{GDBP}) set substitute-path /usr/src /mnt/cross
6621 will tell @value{GDBN} to replace @samp{/usr/src} with
6622 @samp{/mnt/cross}, which will allow @value{GDBN} to find the file
6623 @file{baz.c} even though it was moved.
6625 In the case when more than one substitution rule have been defined,
6626 the rules are evaluated one by one in the order where they have been
6627 defined. The first one matching, if any, is selected to perform
6630 For instance, if we had entered the following commands:
6633 (@value{GDBP}) set substitute-path /usr/src/include /mnt/include
6634 (@value{GDBP}) set substitute-path /usr/src /mnt/src
6638 @value{GDBN} would then rewrite @file{/usr/src/include/defs.h} into
6639 @file{/mnt/include/defs.h} by using the first rule. However, it would
6640 use the second rule to rewrite @file{/usr/src/lib/foo.c} into
6641 @file{/mnt/src/lib/foo.c}.
6644 @item unset substitute-path [path]
6645 @kindex unset substitute-path
6646 If a path is specified, search the current list of substitution rules
6647 for a rule that would rewrite that path. Delete that rule if found.
6648 A warning is emitted by the debugger if no rule could be found.
6650 If no path is specified, then all substitution rules are deleted.
6652 @item show substitute-path [path]
6653 @kindex show substitute-path
6654 If a path is specified, then print the source path substitution rule
6655 which would rewrite that path, if any.
6657 If no path is specified, then print all existing source path substitution
6662 If your source path is cluttered with directories that are no longer of
6663 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
6664 versions of source. You can correct the situation as follows:
6668 Use @code{directory} with no argument to reset the source path to its default value.
6671 Use @code{directory} with suitable arguments to reinstall the
6672 directories you want in the source path. You can add all the
6673 directories in one command.
6677 @section Source and Machine Code
6678 @cindex source line and its code address
6680 You can use the command @code{info line} to map source lines to program
6681 addresses (and vice versa), and the command @code{disassemble} to display
6682 a range of addresses as machine instructions. You can use the command
6683 @code{set disassemble-next-line} to set whether to disassemble next
6684 source line when execution stops. When run under @sc{gnu} Emacs
6685 mode, the @code{info line} command causes the arrow to point to the
6686 line specified. Also, @code{info line} prints addresses in symbolic form as
6691 @item info line @var{linespec}
6692 Print the starting and ending addresses of the compiled code for
6693 source line @var{linespec}. You can specify source lines in any of
6694 the ways documented in @ref{Specify Location}.
6697 For example, we can use @code{info line} to discover the location of
6698 the object code for the first line of function
6699 @code{m4_changequote}:
6701 @c FIXME: I think this example should also show the addresses in
6702 @c symbolic form, as they usually would be displayed.
6704 (@value{GDBP}) info line m4_changequote
6705 Line 895 of "builtin.c" starts at pc 0x634c and ends at 0x6350.
6709 @cindex code address and its source line
6710 We can also inquire (using @code{*@var{addr}} as the form for
6711 @var{linespec}) what source line covers a particular address:
6713 (@value{GDBP}) info line *0x63ff
6714 Line 926 of "builtin.c" starts at pc 0x63e4 and ends at 0x6404.
6717 @cindex @code{$_} and @code{info line}
6718 @cindex @code{x} command, default address
6719 @kindex x@r{(examine), and} info line
6720 After @code{info line}, the default address for the @code{x} command
6721 is changed to the starting address of the line, so that @samp{x/i} is
6722 sufficient to begin examining the machine code (@pxref{Memory,
6723 ,Examining Memory}). Also, this address is saved as the value of the
6724 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
6729 @cindex assembly instructions
6730 @cindex instructions, assembly
6731 @cindex machine instructions
6732 @cindex listing machine instructions
6734 @itemx disassemble /m
6735 @itemx disassemble /r
6736 This specialized command dumps a range of memory as machine
6737 instructions. It can also print mixed source+disassembly by specifying
6738 the @code{/m} modifier and print the raw instructions in hex as well as
6739 in symbolic form by specifying the @code{/r}.
6740 The default memory range is the function surrounding the
6741 program counter of the selected frame. A single argument to this
6742 command is a program counter value; @value{GDBN} dumps the function
6743 surrounding this value. When two arguments are given, they should
6744 be separated by a comma, possibly surrounded by whitespace. The
6745 arguments specify a range of addresses (first inclusive, second exclusive)
6746 to dump. In that case, the name of the function is also printed (since
6747 there could be several functions in the given range).
6749 The argument(s) can be any expression yielding a numeric value, such as
6750 @samp{0x32c4}, @samp{&main+10} or @samp{$pc - 8}.
6752 If the range of memory being disassembled contains current program counter,
6753 the instruction at that location is shown with a @code{=>} marker.
6756 The following example shows the disassembly of a range of addresses of
6757 HP PA-RISC 2.0 code:
6760 (@value{GDBP}) disas 0x32c4, 0x32e4
6761 Dump of assembler code from 0x32c4 to 0x32e4:
6762 0x32c4 <main+204>: addil 0,dp
6763 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
6764 0x32cc <main+212>: ldil 0x3000,r31
6765 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
6766 0x32d4 <main+220>: ldo 0(r31),rp
6767 0x32d8 <main+224>: addil -0x800,dp
6768 0x32dc <main+228>: ldo 0x588(r1),r26
6769 0x32e0 <main+232>: ldil 0x3000,r31
6770 End of assembler dump.
6773 Here is an example showing mixed source+assembly for Intel x86, when the
6774 program is stopped just after function prologue:
6777 (@value{GDBP}) disas /m main
6778 Dump of assembler code for function main:
6780 0x08048330 <+0>: push %ebp
6781 0x08048331 <+1>: mov %esp,%ebp
6782 0x08048333 <+3>: sub $0x8,%esp
6783 0x08048336 <+6>: and $0xfffffff0,%esp
6784 0x08048339 <+9>: sub $0x10,%esp
6786 6 printf ("Hello.\n");
6787 => 0x0804833c <+12>: movl $0x8048440,(%esp)
6788 0x08048343 <+19>: call 0x8048284 <puts@@plt>
6792 0x08048348 <+24>: mov $0x0,%eax
6793 0x0804834d <+29>: leave
6794 0x0804834e <+30>: ret
6796 End of assembler dump.
6799 Some architectures have more than one commonly-used set of instruction
6800 mnemonics or other syntax.
6802 For programs that were dynamically linked and use shared libraries,
6803 instructions that call functions or branch to locations in the shared
6804 libraries might show a seemingly bogus location---it's actually a
6805 location of the relocation table. On some architectures, @value{GDBN}
6806 might be able to resolve these to actual function names.
6809 @kindex set disassembly-flavor
6810 @cindex Intel disassembly flavor
6811 @cindex AT&T disassembly flavor
6812 @item set disassembly-flavor @var{instruction-set}
6813 Select the instruction set to use when disassembling the
6814 program via the @code{disassemble} or @code{x/i} commands.
6816 Currently this command is only defined for the Intel x86 family. You
6817 can set @var{instruction-set} to either @code{intel} or @code{att}.
6818 The default is @code{att}, the AT&T flavor used by default by Unix
6819 assemblers for x86-based targets.
6821 @kindex show disassembly-flavor
6822 @item show disassembly-flavor
6823 Show the current setting of the disassembly flavor.
6827 @kindex set disassemble-next-line
6828 @kindex show disassemble-next-line
6829 @item set disassemble-next-line
6830 @itemx show disassemble-next-line
6831 Control whether or not @value{GDBN} will disassemble the next source
6832 line or instruction when execution stops. If ON, @value{GDBN} will
6833 display disassembly of the next source line when execution of the
6834 program being debugged stops. This is @emph{in addition} to
6835 displaying the source line itself, which @value{GDBN} always does if
6836 possible. If the next source line cannot be displayed for some reason
6837 (e.g., if @value{GDBN} cannot find the source file, or there's no line
6838 info in the debug info), @value{GDBN} will display disassembly of the
6839 next @emph{instruction} instead of showing the next source line. If
6840 AUTO, @value{GDBN} will display disassembly of next instruction only
6841 if the source line cannot be displayed. This setting causes
6842 @value{GDBN} to display some feedback when you step through a function
6843 with no line info or whose source file is unavailable. The default is
6844 OFF, which means never display the disassembly of the next line or
6850 @chapter Examining Data
6852 @cindex printing data
6853 @cindex examining data
6856 @c "inspect" is not quite a synonym if you are using Epoch, which we do not
6857 @c document because it is nonstandard... Under Epoch it displays in a
6858 @c different window or something like that.
6859 The usual way to examine data in your program is with the @code{print}
6860 command (abbreviated @code{p}), or its synonym @code{inspect}. It
6861 evaluates and prints the value of an expression of the language your
6862 program is written in (@pxref{Languages, ,Using @value{GDBN} with
6863 Different Languages}). It may also print the expression using a
6864 Python-based pretty-printer (@pxref{Pretty Printing}).
6867 @item print @var{expr}
6868 @itemx print /@var{f} @var{expr}
6869 @var{expr} is an expression (in the source language). By default the
6870 value of @var{expr} is printed in a format appropriate to its data type;
6871 you can choose a different format by specifying @samp{/@var{f}}, where
6872 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
6876 @itemx print /@var{f}
6877 @cindex reprint the last value
6878 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
6879 @dfn{value history}; @pxref{Value History, ,Value History}). This allows you to
6880 conveniently inspect the same value in an alternative format.
6883 A more low-level way of examining data is with the @code{x} command.
6884 It examines data in memory at a specified address and prints it in a
6885 specified format. @xref{Memory, ,Examining Memory}.
6887 If you are interested in information about types, or about how the
6888 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
6889 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
6893 * Expressions:: Expressions
6894 * Ambiguous Expressions:: Ambiguous Expressions
6895 * Variables:: Program variables
6896 * Arrays:: Artificial arrays
6897 * Output Formats:: Output formats
6898 * Memory:: Examining memory
6899 * Auto Display:: Automatic display
6900 * Print Settings:: Print settings
6901 * Pretty Printing:: Python pretty printing
6902 * Value History:: Value history
6903 * Convenience Vars:: Convenience variables
6904 * Registers:: Registers
6905 * Floating Point Hardware:: Floating point hardware
6906 * Vector Unit:: Vector Unit
6907 * OS Information:: Auxiliary data provided by operating system
6908 * Memory Region Attributes:: Memory region attributes
6909 * Dump/Restore Files:: Copy between memory and a file
6910 * Core File Generation:: Cause a program dump its core
6911 * Character Sets:: Debugging programs that use a different
6912 character set than GDB does
6913 * Caching Remote Data:: Data caching for remote targets
6914 * Searching Memory:: Searching memory for a sequence of bytes
6918 @section Expressions
6921 @code{print} and many other @value{GDBN} commands accept an expression and
6922 compute its value. Any kind of constant, variable or operator defined
6923 by the programming language you are using is valid in an expression in
6924 @value{GDBN}. This includes conditional expressions, function calls,
6925 casts, and string constants. It also includes preprocessor macros, if
6926 you compiled your program to include this information; see
6929 @cindex arrays in expressions
6930 @value{GDBN} supports array constants in expressions input by
6931 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
6932 you can use the command @code{print @{1, 2, 3@}} to create an array
6933 of three integers. If you pass an array to a function or assign it
6934 to a program variable, @value{GDBN} copies the array to memory that
6935 is @code{malloc}ed in the target program.
6937 Because C is so widespread, most of the expressions shown in examples in
6938 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
6939 Languages}, for information on how to use expressions in other
6942 In this section, we discuss operators that you can use in @value{GDBN}
6943 expressions regardless of your programming language.
6945 @cindex casts, in expressions
6946 Casts are supported in all languages, not just in C, because it is so
6947 useful to cast a number into a pointer in order to examine a structure
6948 at that address in memory.
6949 @c FIXME: casts supported---Mod2 true?
6951 @value{GDBN} supports these operators, in addition to those common
6952 to programming languages:
6956 @samp{@@} is a binary operator for treating parts of memory as arrays.
6957 @xref{Arrays, ,Artificial Arrays}, for more information.
6960 @samp{::} allows you to specify a variable in terms of the file or
6961 function where it is defined. @xref{Variables, ,Program Variables}.
6963 @cindex @{@var{type}@}
6964 @cindex type casting memory
6965 @cindex memory, viewing as typed object
6966 @cindex casts, to view memory
6967 @item @{@var{type}@} @var{addr}
6968 Refers to an object of type @var{type} stored at address @var{addr} in
6969 memory. @var{addr} may be any expression whose value is an integer or
6970 pointer (but parentheses are required around binary operators, just as in
6971 a cast). This construct is allowed regardless of what kind of data is
6972 normally supposed to reside at @var{addr}.
6975 @node Ambiguous Expressions
6976 @section Ambiguous Expressions
6977 @cindex ambiguous expressions
6979 Expressions can sometimes contain some ambiguous elements. For instance,
6980 some programming languages (notably Ada, C@t{++} and Objective-C) permit
6981 a single function name to be defined several times, for application in
6982 different contexts. This is called @dfn{overloading}. Another example
6983 involving Ada is generics. A @dfn{generic package} is similar to C@t{++}
6984 templates and is typically instantiated several times, resulting in
6985 the same function name being defined in different contexts.
6987 In some cases and depending on the language, it is possible to adjust
6988 the expression to remove the ambiguity. For instance in C@t{++}, you
6989 can specify the signature of the function you want to break on, as in
6990 @kbd{break @var{function}(@var{types})}. In Ada, using the fully
6991 qualified name of your function often makes the expression unambiguous
6994 When an ambiguity that needs to be resolved is detected, the debugger
6995 has the capability to display a menu of numbered choices for each
6996 possibility, and then waits for the selection with the prompt @samp{>}.
6997 The first option is always @samp{[0] cancel}, and typing @kbd{0 @key{RET}}
6998 aborts the current command. If the command in which the expression was
6999 used allows more than one choice to be selected, the next option in the
7000 menu is @samp{[1] all}, and typing @kbd{1 @key{RET}} selects all possible
7003 For example, the following session excerpt shows an attempt to set a
7004 breakpoint at the overloaded symbol @code{String::after}.
7005 We choose three particular definitions of that function name:
7007 @c FIXME! This is likely to change to show arg type lists, at least
7010 (@value{GDBP}) b String::after
7013 [2] file:String.cc; line number:867
7014 [3] file:String.cc; line number:860
7015 [4] file:String.cc; line number:875
7016 [5] file:String.cc; line number:853
7017 [6] file:String.cc; line number:846
7018 [7] file:String.cc; line number:735
7020 Breakpoint 1 at 0xb26c: file String.cc, line 867.
7021 Breakpoint 2 at 0xb344: file String.cc, line 875.
7022 Breakpoint 3 at 0xafcc: file String.cc, line 846.
7023 Multiple breakpoints were set.
7024 Use the "delete" command to delete unwanted
7031 @kindex set multiple-symbols
7032 @item set multiple-symbols @var{mode}
7033 @cindex multiple-symbols menu
7035 This option allows you to adjust the debugger behavior when an expression
7038 By default, @var{mode} is set to @code{all}. If the command with which
7039 the expression is used allows more than one choice, then @value{GDBN}
7040 automatically selects all possible choices. For instance, inserting
7041 a breakpoint on a function using an ambiguous name results in a breakpoint
7042 inserted on each possible match. However, if a unique choice must be made,
7043 then @value{GDBN} uses the menu to help you disambiguate the expression.
7044 For instance, printing the address of an overloaded function will result
7045 in the use of the menu.
7047 When @var{mode} is set to @code{ask}, the debugger always uses the menu
7048 when an ambiguity is detected.
7050 Finally, when @var{mode} is set to @code{cancel}, the debugger reports
7051 an error due to the ambiguity and the command is aborted.
7053 @kindex show multiple-symbols
7054 @item show multiple-symbols
7055 Show the current value of the @code{multiple-symbols} setting.
7059 @section Program Variables
7061 The most common kind of expression to use is the name of a variable
7064 Variables in expressions are understood in the selected stack frame
7065 (@pxref{Selection, ,Selecting a Frame}); they must be either:
7069 global (or file-static)
7076 visible according to the scope rules of the
7077 programming language from the point of execution in that frame
7080 @noindent This means that in the function
7095 you can examine and use the variable @code{a} whenever your program is
7096 executing within the function @code{foo}, but you can only use or
7097 examine the variable @code{b} while your program is executing inside
7098 the block where @code{b} is declared.
7100 @cindex variable name conflict
7101 There is an exception: you can refer to a variable or function whose
7102 scope is a single source file even if the current execution point is not
7103 in this file. But it is possible to have more than one such variable or
7104 function with the same name (in different source files). If that
7105 happens, referring to that name has unpredictable effects. If you wish,
7106 you can specify a static variable in a particular function or file,
7107 using the colon-colon (@code{::}) notation:
7109 @cindex colon-colon, context for variables/functions
7111 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
7112 @cindex @code{::}, context for variables/functions
7115 @var{file}::@var{variable}
7116 @var{function}::@var{variable}
7120 Here @var{file} or @var{function} is the name of the context for the
7121 static @var{variable}. In the case of file names, you can use quotes to
7122 make sure @value{GDBN} parses the file name as a single word---for example,
7123 to print a global value of @code{x} defined in @file{f2.c}:
7126 (@value{GDBP}) p 'f2.c'::x
7129 @cindex C@t{++} scope resolution
7130 This use of @samp{::} is very rarely in conflict with the very similar
7131 use of the same notation in C@t{++}. @value{GDBN} also supports use of the C@t{++}
7132 scope resolution operator in @value{GDBN} expressions.
7133 @c FIXME: Um, so what happens in one of those rare cases where it's in
7136 @cindex wrong values
7137 @cindex variable values, wrong
7138 @cindex function entry/exit, wrong values of variables
7139 @cindex optimized code, wrong values of variables
7141 @emph{Warning:} Occasionally, a local variable may appear to have the
7142 wrong value at certain points in a function---just after entry to a new
7143 scope, and just before exit.
7145 You may see this problem when you are stepping by machine instructions.
7146 This is because, on most machines, it takes more than one instruction to
7147 set up a stack frame (including local variable definitions); if you are
7148 stepping by machine instructions, variables may appear to have the wrong
7149 values until the stack frame is completely built. On exit, it usually
7150 also takes more than one machine instruction to destroy a stack frame;
7151 after you begin stepping through that group of instructions, local
7152 variable definitions may be gone.
7154 This may also happen when the compiler does significant optimizations.
7155 To be sure of always seeing accurate values, turn off all optimization
7158 @cindex ``No symbol "foo" in current context''
7159 Another possible effect of compiler optimizations is to optimize
7160 unused variables out of existence, or assign variables to registers (as
7161 opposed to memory addresses). Depending on the support for such cases
7162 offered by the debug info format used by the compiler, @value{GDBN}
7163 might not be able to display values for such local variables. If that
7164 happens, @value{GDBN} will print a message like this:
7167 No symbol "foo" in current context.
7170 To solve such problems, either recompile without optimizations, or use a
7171 different debug info format, if the compiler supports several such
7172 formats. For example, @value{NGCC}, the @sc{gnu} C/C@t{++} compiler,
7173 usually supports the @option{-gstabs+} option. @option{-gstabs+}
7174 produces debug info in a format that is superior to formats such as
7175 COFF. You may be able to use DWARF 2 (@option{-gdwarf-2}), which is also
7176 an effective form for debug info. @xref{Debugging Options,,Options
7177 for Debugging Your Program or GCC, gcc.info, Using the @sc{gnu}
7178 Compiler Collection (GCC)}.
7179 @xref{C, ,C and C@t{++}}, for more information about debug info formats
7180 that are best suited to C@t{++} programs.
7182 If you ask to print an object whose contents are unknown to
7183 @value{GDBN}, e.g., because its data type is not completely specified
7184 by the debug information, @value{GDBN} will say @samp{<incomplete
7185 type>}. @xref{Symbols, incomplete type}, for more about this.
7187 Strings are identified as arrays of @code{char} values without specified
7188 signedness. Arrays of either @code{signed char} or @code{unsigned char} get
7189 printed as arrays of 1 byte sized integers. @code{-fsigned-char} or
7190 @code{-funsigned-char} @value{NGCC} options have no effect as @value{GDBN}
7191 defines literal string type @code{"char"} as @code{char} without a sign.
7196 signed char var1[] = "A";
7199 You get during debugging
7204 $2 = @{65 'A', 0 '\0'@}
7208 @section Artificial Arrays
7210 @cindex artificial array
7212 @kindex @@@r{, referencing memory as an array}
7213 It is often useful to print out several successive objects of the
7214 same type in memory; a section of an array, or an array of
7215 dynamically determined size for which only a pointer exists in the
7218 You can do this by referring to a contiguous span of memory as an
7219 @dfn{artificial array}, using the binary operator @samp{@@}. The left
7220 operand of @samp{@@} should be the first element of the desired array
7221 and be an individual object. The right operand should be the desired length
7222 of the array. The result is an array value whose elements are all of
7223 the type of the left argument. The first element is actually the left
7224 argument; the second element comes from bytes of memory immediately
7225 following those that hold the first element, and so on. Here is an
7226 example. If a program says
7229 int *array = (int *) malloc (len * sizeof (int));
7233 you can print the contents of @code{array} with
7239 The left operand of @samp{@@} must reside in memory. Array values made
7240 with @samp{@@} in this way behave just like other arrays in terms of
7241 subscripting, and are coerced to pointers when used in expressions.
7242 Artificial arrays most often appear in expressions via the value history
7243 (@pxref{Value History, ,Value History}), after printing one out.
7245 Another way to create an artificial array is to use a cast.
7246 This re-interprets a value as if it were an array.
7247 The value need not be in memory:
7249 (@value{GDBP}) p/x (short[2])0x12345678
7250 $1 = @{0x1234, 0x5678@}
7253 As a convenience, if you leave the array length out (as in
7254 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
7255 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
7257 (@value{GDBP}) p/x (short[])0x12345678
7258 $2 = @{0x1234, 0x5678@}
7261 Sometimes the artificial array mechanism is not quite enough; in
7262 moderately complex data structures, the elements of interest may not
7263 actually be adjacent---for example, if you are interested in the values
7264 of pointers in an array. One useful work-around in this situation is
7265 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
7266 Variables}) as a counter in an expression that prints the first
7267 interesting value, and then repeat that expression via @key{RET}. For
7268 instance, suppose you have an array @code{dtab} of pointers to
7269 structures, and you are interested in the values of a field @code{fv}
7270 in each structure. Here is an example of what you might type:
7280 @node Output Formats
7281 @section Output Formats
7283 @cindex formatted output
7284 @cindex output formats
7285 By default, @value{GDBN} prints a value according to its data type. Sometimes
7286 this is not what you want. For example, you might want to print a number
7287 in hex, or a pointer in decimal. Or you might want to view data in memory
7288 at a certain address as a character string or as an instruction. To do
7289 these things, specify an @dfn{output format} when you print a value.
7291 The simplest use of output formats is to say how to print a value
7292 already computed. This is done by starting the arguments of the
7293 @code{print} command with a slash and a format letter. The format
7294 letters supported are:
7298 Regard the bits of the value as an integer, and print the integer in
7302 Print as integer in signed decimal.
7305 Print as integer in unsigned decimal.
7308 Print as integer in octal.
7311 Print as integer in binary. The letter @samp{t} stands for ``two''.
7312 @footnote{@samp{b} cannot be used because these format letters are also
7313 used with the @code{x} command, where @samp{b} stands for ``byte'';
7314 see @ref{Memory,,Examining Memory}.}
7317 @cindex unknown address, locating
7318 @cindex locate address
7319 Print as an address, both absolute in hexadecimal and as an offset from
7320 the nearest preceding symbol. You can use this format used to discover
7321 where (in what function) an unknown address is located:
7324 (@value{GDBP}) p/a 0x54320
7325 $3 = 0x54320 <_initialize_vx+396>
7329 The command @code{info symbol 0x54320} yields similar results.
7330 @xref{Symbols, info symbol}.
7333 Regard as an integer and print it as a character constant. This
7334 prints both the numerical value and its character representation. The
7335 character representation is replaced with the octal escape @samp{\nnn}
7336 for characters outside the 7-bit @sc{ascii} range.
7338 Without this format, @value{GDBN} displays @code{char},
7339 @w{@code{unsigned char}}, and @w{@code{signed char}} data as character
7340 constants. Single-byte members of vectors are displayed as integer
7344 Regard the bits of the value as a floating point number and print
7345 using typical floating point syntax.
7348 @cindex printing strings
7349 @cindex printing byte arrays
7350 Regard as a string, if possible. With this format, pointers to single-byte
7351 data are displayed as null-terminated strings and arrays of single-byte data
7352 are displayed as fixed-length strings. Other values are displayed in their
7355 Without this format, @value{GDBN} displays pointers to and arrays of
7356 @code{char}, @w{@code{unsigned char}}, and @w{@code{signed char}} as
7357 strings. Single-byte members of a vector are displayed as an integer
7361 @cindex raw printing
7362 Print using the @samp{raw} formatting. By default, @value{GDBN} will
7363 use a Python-based pretty-printer, if one is available (@pxref{Pretty
7364 Printing}). This typically results in a higher-level display of the
7365 value's contents. The @samp{r} format bypasses any Python
7366 pretty-printer which might exist.
7369 For example, to print the program counter in hex (@pxref{Registers}), type
7376 Note that no space is required before the slash; this is because command
7377 names in @value{GDBN} cannot contain a slash.
7379 To reprint the last value in the value history with a different format,
7380 you can use the @code{print} command with just a format and no
7381 expression. For example, @samp{p/x} reprints the last value in hex.
7384 @section Examining Memory
7386 You can use the command @code{x} (for ``examine'') to examine memory in
7387 any of several formats, independently of your program's data types.
7389 @cindex examining memory
7391 @kindex x @r{(examine memory)}
7392 @item x/@var{nfu} @var{addr}
7395 Use the @code{x} command to examine memory.
7398 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
7399 much memory to display and how to format it; @var{addr} is an
7400 expression giving the address where you want to start displaying memory.
7401 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
7402 Several commands set convenient defaults for @var{addr}.
7405 @item @var{n}, the repeat count
7406 The repeat count is a decimal integer; the default is 1. It specifies
7407 how much memory (counting by units @var{u}) to display.
7408 @c This really is **decimal**; unaffected by 'set radix' as of GDB
7411 @item @var{f}, the display format
7412 The display format is one of the formats used by @code{print}
7413 (@samp{x}, @samp{d}, @samp{u}, @samp{o}, @samp{t}, @samp{a}, @samp{c},
7414 @samp{f}, @samp{s}), and in addition @samp{i} (for machine instructions).
7415 The default is @samp{x} (hexadecimal) initially. The default changes
7416 each time you use either @code{x} or @code{print}.
7418 @item @var{u}, the unit size
7419 The unit size is any of
7425 Halfwords (two bytes).
7427 Words (four bytes). This is the initial default.
7429 Giant words (eight bytes).
7432 Each time you specify a unit size with @code{x}, that size becomes the
7433 default unit the next time you use @code{x}. For the @samp{i} format,
7434 the unit size is ignored and is normally not written. For the @samp{s} format,
7435 the unit size defaults to @samp{b}, unless it is explicitly given.
7436 Use @kbd{x /hs} to display 16-bit char strings and @kbd{x /ws} to display
7437 32-bit strings. The next use of @kbd{x /s} will again display 8-bit strings.
7438 Note that the results depend on the programming language of the
7439 current compilation unit. If the language is C, the @samp{s}
7440 modifier will use the UTF-16 encoding while @samp{w} will use
7441 UTF-32. The encoding is set by the programming language and cannot
7444 @item @var{addr}, starting display address
7445 @var{addr} is the address where you want @value{GDBN} to begin displaying
7446 memory. The expression need not have a pointer value (though it may);
7447 it is always interpreted as an integer address of a byte of memory.
7448 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
7449 @var{addr} is usually just after the last address examined---but several
7450 other commands also set the default address: @code{info breakpoints} (to
7451 the address of the last breakpoint listed), @code{info line} (to the
7452 starting address of a line), and @code{print} (if you use it to display
7453 a value from memory).
7456 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
7457 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
7458 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
7459 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
7460 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
7462 Since the letters indicating unit sizes are all distinct from the
7463 letters specifying output formats, you do not have to remember whether
7464 unit size or format comes first; either order works. The output
7465 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
7466 (However, the count @var{n} must come first; @samp{wx4} does not work.)
7468 Even though the unit size @var{u} is ignored for the formats @samp{s}
7469 and @samp{i}, you might still want to use a count @var{n}; for example,
7470 @samp{3i} specifies that you want to see three machine instructions,
7471 including any operands. For convenience, especially when used with
7472 the @code{display} command, the @samp{i} format also prints branch delay
7473 slot instructions, if any, beyond the count specified, which immediately
7474 follow the last instruction that is within the count. The command
7475 @code{disassemble} gives an alternative way of inspecting machine
7476 instructions; see @ref{Machine Code,,Source and Machine Code}.
7478 All the defaults for the arguments to @code{x} are designed to make it
7479 easy to continue scanning memory with minimal specifications each time
7480 you use @code{x}. For example, after you have inspected three machine
7481 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
7482 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
7483 the repeat count @var{n} is used again; the other arguments default as
7484 for successive uses of @code{x}.
7486 When examining machine instructions, the instruction at current program
7487 counter is shown with a @code{=>} marker. For example:
7490 (@value{GDBP}) x/5i $pc-6
7491 0x804837f <main+11>: mov %esp,%ebp
7492 0x8048381 <main+13>: push %ecx
7493 0x8048382 <main+14>: sub $0x4,%esp
7494 => 0x8048385 <main+17>: movl $0x8048460,(%esp)
7495 0x804838c <main+24>: call 0x80482d4 <puts@@plt>
7498 @cindex @code{$_}, @code{$__}, and value history
7499 The addresses and contents printed by the @code{x} command are not saved
7500 in the value history because there is often too much of them and they
7501 would get in the way. Instead, @value{GDBN} makes these values available for
7502 subsequent use in expressions as values of the convenience variables
7503 @code{$_} and @code{$__}. After an @code{x} command, the last address
7504 examined is available for use in expressions in the convenience variable
7505 @code{$_}. The contents of that address, as examined, are available in
7506 the convenience variable @code{$__}.
7508 If the @code{x} command has a repeat count, the address and contents saved
7509 are from the last memory unit printed; this is not the same as the last
7510 address printed if several units were printed on the last line of output.
7512 @cindex remote memory comparison
7513 @cindex verify remote memory image
7514 When you are debugging a program running on a remote target machine
7515 (@pxref{Remote Debugging}), you may wish to verify the program's image in the
7516 remote machine's memory against the executable file you downloaded to
7517 the target. The @code{compare-sections} command is provided for such
7521 @kindex compare-sections
7522 @item compare-sections @r{[}@var{section-name}@r{]}
7523 Compare the data of a loadable section @var{section-name} in the
7524 executable file of the program being debugged with the same section in
7525 the remote machine's memory, and report any mismatches. With no
7526 arguments, compares all loadable sections. This command's
7527 availability depends on the target's support for the @code{"qCRC"}
7532 @section Automatic Display
7533 @cindex automatic display
7534 @cindex display of expressions
7536 If you find that you want to print the value of an expression frequently
7537 (to see how it changes), you might want to add it to the @dfn{automatic
7538 display list} so that @value{GDBN} prints its value each time your program stops.
7539 Each expression added to the list is given a number to identify it;
7540 to remove an expression from the list, you specify that number.
7541 The automatic display looks like this:
7545 3: bar[5] = (struct hack *) 0x3804
7549 This display shows item numbers, expressions and their current values. As with
7550 displays you request manually using @code{x} or @code{print}, you can
7551 specify the output format you prefer; in fact, @code{display} decides
7552 whether to use @code{print} or @code{x} depending your format
7553 specification---it uses @code{x} if you specify either the @samp{i}
7554 or @samp{s} format, or a unit size; otherwise it uses @code{print}.
7558 @item display @var{expr}
7559 Add the expression @var{expr} to the list of expressions to display
7560 each time your program stops. @xref{Expressions, ,Expressions}.
7562 @code{display} does not repeat if you press @key{RET} again after using it.
7564 @item display/@var{fmt} @var{expr}
7565 For @var{fmt} specifying only a display format and not a size or
7566 count, add the expression @var{expr} to the auto-display list but
7567 arrange to display it each time in the specified format @var{fmt}.
7568 @xref{Output Formats,,Output Formats}.
7570 @item display/@var{fmt} @var{addr}
7571 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
7572 number of units, add the expression @var{addr} as a memory address to
7573 be examined each time your program stops. Examining means in effect
7574 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining Memory}.
7577 For example, @samp{display/i $pc} can be helpful, to see the machine
7578 instruction about to be executed each time execution stops (@samp{$pc}
7579 is a common name for the program counter; @pxref{Registers, ,Registers}).
7582 @kindex delete display
7584 @item undisplay @var{dnums}@dots{}
7585 @itemx delete display @var{dnums}@dots{}
7586 Remove item numbers @var{dnums} from the list of expressions to display.
7588 @code{undisplay} does not repeat if you press @key{RET} after using it.
7589 (Otherwise you would just get the error @samp{No display number @dots{}}.)
7591 @kindex disable display
7592 @item disable display @var{dnums}@dots{}
7593 Disable the display of item numbers @var{dnums}. A disabled display
7594 item is not printed automatically, but is not forgotten. It may be
7595 enabled again later.
7597 @kindex enable display
7598 @item enable display @var{dnums}@dots{}
7599 Enable display of item numbers @var{dnums}. It becomes effective once
7600 again in auto display of its expression, until you specify otherwise.
7603 Display the current values of the expressions on the list, just as is
7604 done when your program stops.
7606 @kindex info display
7608 Print the list of expressions previously set up to display
7609 automatically, each one with its item number, but without showing the
7610 values. This includes disabled expressions, which are marked as such.
7611 It also includes expressions which would not be displayed right now
7612 because they refer to automatic variables not currently available.
7615 @cindex display disabled out of scope
7616 If a display expression refers to local variables, then it does not make
7617 sense outside the lexical context for which it was set up. Such an
7618 expression is disabled when execution enters a context where one of its
7619 variables is not defined. For example, if you give the command
7620 @code{display last_char} while inside a function with an argument
7621 @code{last_char}, @value{GDBN} displays this argument while your program
7622 continues to stop inside that function. When it stops elsewhere---where
7623 there is no variable @code{last_char}---the display is disabled
7624 automatically. The next time your program stops where @code{last_char}
7625 is meaningful, you can enable the display expression once again.
7627 @node Print Settings
7628 @section Print Settings
7630 @cindex format options
7631 @cindex print settings
7632 @value{GDBN} provides the following ways to control how arrays, structures,
7633 and symbols are printed.
7636 These settings are useful for debugging programs in any language:
7640 @item set print address
7641 @itemx set print address on
7642 @cindex print/don't print memory addresses
7643 @value{GDBN} prints memory addresses showing the location of stack
7644 traces, structure values, pointer values, breakpoints, and so forth,
7645 even when it also displays the contents of those addresses. The default
7646 is @code{on}. For example, this is what a stack frame display looks like with
7647 @code{set print address on}:
7652 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
7654 530 if (lquote != def_lquote)
7658 @item set print address off
7659 Do not print addresses when displaying their contents. For example,
7660 this is the same stack frame displayed with @code{set print address off}:
7664 (@value{GDBP}) set print addr off
7666 #0 set_quotes (lq="<<", rq=">>") at input.c:530
7667 530 if (lquote != def_lquote)
7671 You can use @samp{set print address off} to eliminate all machine
7672 dependent displays from the @value{GDBN} interface. For example, with
7673 @code{print address off}, you should get the same text for backtraces on
7674 all machines---whether or not they involve pointer arguments.
7677 @item show print address
7678 Show whether or not addresses are to be printed.
7681 When @value{GDBN} prints a symbolic address, it normally prints the
7682 closest earlier symbol plus an offset. If that symbol does not uniquely
7683 identify the address (for example, it is a name whose scope is a single
7684 source file), you may need to clarify. One way to do this is with
7685 @code{info line}, for example @samp{info line *0x4537}. Alternately,
7686 you can set @value{GDBN} to print the source file and line number when
7687 it prints a symbolic address:
7690 @item set print symbol-filename on
7691 @cindex source file and line of a symbol
7692 @cindex symbol, source file and line
7693 Tell @value{GDBN} to print the source file name and line number of a
7694 symbol in the symbolic form of an address.
7696 @item set print symbol-filename off
7697 Do not print source file name and line number of a symbol. This is the
7700 @item show print symbol-filename
7701 Show whether or not @value{GDBN} will print the source file name and
7702 line number of a symbol in the symbolic form of an address.
7705 Another situation where it is helpful to show symbol filenames and line
7706 numbers is when disassembling code; @value{GDBN} shows you the line
7707 number and source file that corresponds to each instruction.
7709 Also, you may wish to see the symbolic form only if the address being
7710 printed is reasonably close to the closest earlier symbol:
7713 @item set print max-symbolic-offset @var{max-offset}
7714 @cindex maximum value for offset of closest symbol
7715 Tell @value{GDBN} to only display the symbolic form of an address if the
7716 offset between the closest earlier symbol and the address is less than
7717 @var{max-offset}. The default is 0, which tells @value{GDBN}
7718 to always print the symbolic form of an address if any symbol precedes it.
7720 @item show print max-symbolic-offset
7721 Ask how large the maximum offset is that @value{GDBN} prints in a
7725 @cindex wild pointer, interpreting
7726 @cindex pointer, finding referent
7727 If you have a pointer and you are not sure where it points, try
7728 @samp{set print symbol-filename on}. Then you can determine the name
7729 and source file location of the variable where it points, using
7730 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
7731 For example, here @value{GDBN} shows that a variable @code{ptt} points
7732 at another variable @code{t}, defined in @file{hi2.c}:
7735 (@value{GDBP}) set print symbol-filename on
7736 (@value{GDBP}) p/a ptt
7737 $4 = 0xe008 <t in hi2.c>
7741 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
7742 does not show the symbol name and filename of the referent, even with
7743 the appropriate @code{set print} options turned on.
7746 Other settings control how different kinds of objects are printed:
7749 @item set print array
7750 @itemx set print array on
7751 @cindex pretty print arrays
7752 Pretty print arrays. This format is more convenient to read,
7753 but uses more space. The default is off.
7755 @item set print array off
7756 Return to compressed format for arrays.
7758 @item show print array
7759 Show whether compressed or pretty format is selected for displaying
7762 @cindex print array indexes
7763 @item set print array-indexes
7764 @itemx set print array-indexes on
7765 Print the index of each element when displaying arrays. May be more
7766 convenient to locate a given element in the array or quickly find the
7767 index of a given element in that printed array. The default is off.
7769 @item set print array-indexes off
7770 Stop printing element indexes when displaying arrays.
7772 @item show print array-indexes
7773 Show whether the index of each element is printed when displaying
7776 @item set print elements @var{number-of-elements}
7777 @cindex number of array elements to print
7778 @cindex limit on number of printed array elements
7779 Set a limit on how many elements of an array @value{GDBN} will print.
7780 If @value{GDBN} is printing a large array, it stops printing after it has
7781 printed the number of elements set by the @code{set print elements} command.
7782 This limit also applies to the display of strings.
7783 When @value{GDBN} starts, this limit is set to 200.
7784 Setting @var{number-of-elements} to zero means that the printing is unlimited.
7786 @item show print elements
7787 Display the number of elements of a large array that @value{GDBN} will print.
7788 If the number is 0, then the printing is unlimited.
7790 @item set print frame-arguments @var{value}
7791 @kindex set print frame-arguments
7792 @cindex printing frame argument values
7793 @cindex print all frame argument values
7794 @cindex print frame argument values for scalars only
7795 @cindex do not print frame argument values
7796 This command allows to control how the values of arguments are printed
7797 when the debugger prints a frame (@pxref{Frames}). The possible
7802 The values of all arguments are printed.
7805 Print the value of an argument only if it is a scalar. The value of more
7806 complex arguments such as arrays, structures, unions, etc, is replaced
7807 by @code{@dots{}}. This is the default. Here is an example where
7808 only scalar arguments are shown:
7811 #1 0x08048361 in call_me (i=3, s=@dots{}, ss=0xbf8d508c, u=@dots{}, e=green)
7816 None of the argument values are printed. Instead, the value of each argument
7817 is replaced by @code{@dots{}}. In this case, the example above now becomes:
7820 #1 0x08048361 in call_me (i=@dots{}, s=@dots{}, ss=@dots{}, u=@dots{}, e=@dots{})
7825 By default, only scalar arguments are printed. This command can be used
7826 to configure the debugger to print the value of all arguments, regardless
7827 of their type. However, it is often advantageous to not print the value
7828 of more complex parameters. For instance, it reduces the amount of
7829 information printed in each frame, making the backtrace more readable.
7830 Also, it improves performance when displaying Ada frames, because
7831 the computation of large arguments can sometimes be CPU-intensive,
7832 especially in large applications. Setting @code{print frame-arguments}
7833 to @code{scalars} (the default) or @code{none} avoids this computation,
7834 thus speeding up the display of each Ada frame.
7836 @item show print frame-arguments
7837 Show how the value of arguments should be displayed when printing a frame.
7839 @item set print repeats
7840 @cindex repeated array elements
7841 Set the threshold for suppressing display of repeated array
7842 elements. When the number of consecutive identical elements of an
7843 array exceeds the threshold, @value{GDBN} prints the string
7844 @code{"<repeats @var{n} times>"}, where @var{n} is the number of
7845 identical repetitions, instead of displaying the identical elements
7846 themselves. Setting the threshold to zero will cause all elements to
7847 be individually printed. The default threshold is 10.
7849 @item show print repeats
7850 Display the current threshold for printing repeated identical
7853 @item set print null-stop
7854 @cindex @sc{null} elements in arrays
7855 Cause @value{GDBN} to stop printing the characters of an array when the first
7856 @sc{null} is encountered. This is useful when large arrays actually
7857 contain only short strings.
7860 @item show print null-stop
7861 Show whether @value{GDBN} stops printing an array on the first
7862 @sc{null} character.
7864 @item set print pretty on
7865 @cindex print structures in indented form
7866 @cindex indentation in structure display
7867 Cause @value{GDBN} to print structures in an indented format with one member
7868 per line, like this:
7883 @item set print pretty off
7884 Cause @value{GDBN} to print structures in a compact format, like this:
7888 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
7889 meat = 0x54 "Pork"@}
7894 This is the default format.
7896 @item show print pretty
7897 Show which format @value{GDBN} is using to print structures.
7899 @item set print sevenbit-strings on
7900 @cindex eight-bit characters in strings
7901 @cindex octal escapes in strings
7902 Print using only seven-bit characters; if this option is set,
7903 @value{GDBN} displays any eight-bit characters (in strings or
7904 character values) using the notation @code{\}@var{nnn}. This setting is
7905 best if you are working in English (@sc{ascii}) and you use the
7906 high-order bit of characters as a marker or ``meta'' bit.
7908 @item set print sevenbit-strings off
7909 Print full eight-bit characters. This allows the use of more
7910 international character sets, and is the default.
7912 @item show print sevenbit-strings
7913 Show whether or not @value{GDBN} is printing only seven-bit characters.
7915 @item set print union on
7916 @cindex unions in structures, printing
7917 Tell @value{GDBN} to print unions which are contained in structures
7918 and other unions. This is the default setting.
7920 @item set print union off
7921 Tell @value{GDBN} not to print unions which are contained in
7922 structures and other unions. @value{GDBN} will print @code{"@{...@}"}
7925 @item show print union
7926 Ask @value{GDBN} whether or not it will print unions which are contained in
7927 structures and other unions.
7929 For example, given the declarations
7932 typedef enum @{Tree, Bug@} Species;
7933 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
7934 typedef enum @{Caterpillar, Cocoon, Butterfly@}
7945 struct thing foo = @{Tree, @{Acorn@}@};
7949 with @code{set print union on} in effect @samp{p foo} would print
7952 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
7956 and with @code{set print union off} in effect it would print
7959 $1 = @{it = Tree, form = @{...@}@}
7963 @code{set print union} affects programs written in C-like languages
7969 These settings are of interest when debugging C@t{++} programs:
7972 @cindex demangling C@t{++} names
7973 @item set print demangle
7974 @itemx set print demangle on
7975 Print C@t{++} names in their source form rather than in the encoded
7976 (``mangled'') form passed to the assembler and linker for type-safe
7977 linkage. The default is on.
7979 @item show print demangle
7980 Show whether C@t{++} names are printed in mangled or demangled form.
7982 @item set print asm-demangle
7983 @itemx set print asm-demangle on
7984 Print C@t{++} names in their source form rather than their mangled form, even
7985 in assembler code printouts such as instruction disassemblies.
7988 @item show print asm-demangle
7989 Show whether C@t{++} names in assembly listings are printed in mangled
7992 @cindex C@t{++} symbol decoding style
7993 @cindex symbol decoding style, C@t{++}
7994 @kindex set demangle-style
7995 @item set demangle-style @var{style}
7996 Choose among several encoding schemes used by different compilers to
7997 represent C@t{++} names. The choices for @var{style} are currently:
8001 Allow @value{GDBN} to choose a decoding style by inspecting your program.
8004 Decode based on the @sc{gnu} C@t{++} compiler (@code{g++}) encoding algorithm.
8005 This is the default.
8008 Decode based on the HP ANSI C@t{++} (@code{aCC}) encoding algorithm.
8011 Decode based on the Lucid C@t{++} compiler (@code{lcc}) encoding algorithm.
8014 Decode using the algorithm in the @cite{C@t{++} Annotated Reference Manual}.
8015 @strong{Warning:} this setting alone is not sufficient to allow
8016 debugging @code{cfront}-generated executables. @value{GDBN} would
8017 require further enhancement to permit that.
8020 If you omit @var{style}, you will see a list of possible formats.
8022 @item show demangle-style
8023 Display the encoding style currently in use for decoding C@t{++} symbols.
8025 @item set print object
8026 @itemx set print object on
8027 @cindex derived type of an object, printing
8028 @cindex display derived types
8029 When displaying a pointer to an object, identify the @emph{actual}
8030 (derived) type of the object rather than the @emph{declared} type, using
8031 the virtual function table.
8033 @item set print object off
8034 Display only the declared type of objects, without reference to the
8035 virtual function table. This is the default setting.
8037 @item show print object
8038 Show whether actual, or declared, object types are displayed.
8040 @item set print static-members
8041 @itemx set print static-members on
8042 @cindex static members of C@t{++} objects
8043 Print static members when displaying a C@t{++} object. The default is on.
8045 @item set print static-members off
8046 Do not print static members when displaying a C@t{++} object.
8048 @item show print static-members
8049 Show whether C@t{++} static members are printed or not.
8051 @item set print pascal_static-members
8052 @itemx set print pascal_static-members on
8053 @cindex static members of Pascal objects
8054 @cindex Pascal objects, static members display
8055 Print static members when displaying a Pascal object. The default is on.
8057 @item set print pascal_static-members off
8058 Do not print static members when displaying a Pascal object.
8060 @item show print pascal_static-members
8061 Show whether Pascal static members are printed or not.
8063 @c These don't work with HP ANSI C++ yet.
8064 @item set print vtbl
8065 @itemx set print vtbl on
8066 @cindex pretty print C@t{++} virtual function tables
8067 @cindex virtual functions (C@t{++}) display
8068 @cindex VTBL display
8069 Pretty print C@t{++} virtual function tables. The default is off.
8070 (The @code{vtbl} commands do not work on programs compiled with the HP
8071 ANSI C@t{++} compiler (@code{aCC}).)
8073 @item set print vtbl off
8074 Do not pretty print C@t{++} virtual function tables.
8076 @item show print vtbl
8077 Show whether C@t{++} virtual function tables are pretty printed, or not.
8080 @node Pretty Printing
8081 @section Pretty Printing
8083 @value{GDBN} provides a mechanism to allow pretty-printing of values using
8084 Python code. It greatly simplifies the display of complex objects. This
8085 mechanism works for both MI and the CLI.
8087 For example, here is how a C@t{++} @code{std::string} looks without a
8091 (@value{GDBP}) print s
8093 static npos = 4294967295,
8095 <std::allocator<char>> = @{
8096 <__gnu_cxx::new_allocator<char>> = @{
8097 <No data fields>@}, <No data fields>
8099 members of std::basic_string<char, std::char_traits<char>,
8100 std::allocator<char> >::_Alloc_hider:
8101 _M_p = 0x804a014 "abcd"
8106 With a pretty-printer for @code{std::string} only the contents are printed:
8109 (@value{GDBP}) print s
8113 For implementing pretty printers for new types you should read the Python API
8114 details (@pxref{Pretty Printing API}).
8117 @section Value History
8119 @cindex value history
8120 @cindex history of values printed by @value{GDBN}
8121 Values printed by the @code{print} command are saved in the @value{GDBN}
8122 @dfn{value history}. This allows you to refer to them in other expressions.
8123 Values are kept until the symbol table is re-read or discarded
8124 (for example with the @code{file} or @code{symbol-file} commands).
8125 When the symbol table changes, the value history is discarded,
8126 since the values may contain pointers back to the types defined in the
8131 @cindex history number
8132 The values printed are given @dfn{history numbers} by which you can
8133 refer to them. These are successive integers starting with one.
8134 @code{print} shows you the history number assigned to a value by
8135 printing @samp{$@var{num} = } before the value; here @var{num} is the
8138 To refer to any previous value, use @samp{$} followed by the value's
8139 history number. The way @code{print} labels its output is designed to
8140 remind you of this. Just @code{$} refers to the most recent value in
8141 the history, and @code{$$} refers to the value before that.
8142 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
8143 is the value just prior to @code{$$}, @code{$$1} is equivalent to
8144 @code{$$}, and @code{$$0} is equivalent to @code{$}.
8146 For example, suppose you have just printed a pointer to a structure and
8147 want to see the contents of the structure. It suffices to type
8153 If you have a chain of structures where the component @code{next} points
8154 to the next one, you can print the contents of the next one with this:
8161 You can print successive links in the chain by repeating this
8162 command---which you can do by just typing @key{RET}.
8164 Note that the history records values, not expressions. If the value of
8165 @code{x} is 4 and you type these commands:
8173 then the value recorded in the value history by the @code{print} command
8174 remains 4 even though the value of @code{x} has changed.
8179 Print the last ten values in the value history, with their item numbers.
8180 This is like @samp{p@ $$9} repeated ten times, except that @code{show
8181 values} does not change the history.
8183 @item show values @var{n}
8184 Print ten history values centered on history item number @var{n}.
8187 Print ten history values just after the values last printed. If no more
8188 values are available, @code{show values +} produces no display.
8191 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
8192 same effect as @samp{show values +}.
8194 @node Convenience Vars
8195 @section Convenience Variables
8197 @cindex convenience variables
8198 @cindex user-defined variables
8199 @value{GDBN} provides @dfn{convenience variables} that you can use within
8200 @value{GDBN} to hold on to a value and refer to it later. These variables
8201 exist entirely within @value{GDBN}; they are not part of your program, and
8202 setting a convenience variable has no direct effect on further execution
8203 of your program. That is why you can use them freely.
8205 Convenience variables are prefixed with @samp{$}. Any name preceded by
8206 @samp{$} can be used for a convenience variable, unless it is one of
8207 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
8208 (Value history references, in contrast, are @emph{numbers} preceded
8209 by @samp{$}. @xref{Value History, ,Value History}.)
8211 You can save a value in a convenience variable with an assignment
8212 expression, just as you would set a variable in your program.
8216 set $foo = *object_ptr
8220 would save in @code{$foo} the value contained in the object pointed to by
8223 Using a convenience variable for the first time creates it, but its
8224 value is @code{void} until you assign a new value. You can alter the
8225 value with another assignment at any time.
8227 Convenience variables have no fixed types. You can assign a convenience
8228 variable any type of value, including structures and arrays, even if
8229 that variable already has a value of a different type. The convenience
8230 variable, when used as an expression, has the type of its current value.
8233 @kindex show convenience
8234 @cindex show all user variables
8235 @item show convenience
8236 Print a list of convenience variables used so far, and their values.
8237 Abbreviated @code{show conv}.
8239 @kindex init-if-undefined
8240 @cindex convenience variables, initializing
8241 @item init-if-undefined $@var{variable} = @var{expression}
8242 Set a convenience variable if it has not already been set. This is useful
8243 for user-defined commands that keep some state. It is similar, in concept,
8244 to using local static variables with initializers in C (except that
8245 convenience variables are global). It can also be used to allow users to
8246 override default values used in a command script.
8248 If the variable is already defined then the expression is not evaluated so
8249 any side-effects do not occur.
8252 One of the ways to use a convenience variable is as a counter to be
8253 incremented or a pointer to be advanced. For example, to print
8254 a field from successive elements of an array of structures:
8258 print bar[$i++]->contents
8262 Repeat that command by typing @key{RET}.
8264 Some convenience variables are created automatically by @value{GDBN} and given
8265 values likely to be useful.
8268 @vindex $_@r{, convenience variable}
8270 The variable @code{$_} is automatically set by the @code{x} command to
8271 the last address examined (@pxref{Memory, ,Examining Memory}). Other
8272 commands which provide a default address for @code{x} to examine also
8273 set @code{$_} to that address; these commands include @code{info line}
8274 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
8275 except when set by the @code{x} command, in which case it is a pointer
8276 to the type of @code{$__}.
8278 @vindex $__@r{, convenience variable}
8280 The variable @code{$__} is automatically set by the @code{x} command
8281 to the value found in the last address examined. Its type is chosen
8282 to match the format in which the data was printed.
8285 @vindex $_exitcode@r{, convenience variable}
8286 The variable @code{$_exitcode} is automatically set to the exit code when
8287 the program being debugged terminates.
8290 @vindex $_sdata@r{, inspect, convenience variable}
8291 The variable @code{$_sdata} contains extra collected static tracepoint
8292 data. @xref{Tracepoint Actions,,Tracepoint Action Lists}. Note that
8293 @code{$_sdata} could be empty, if not inspecting a trace buffer, or
8294 if extra static tracepoint data has not been collected.
8297 @vindex $_siginfo@r{, convenience variable}
8298 The variable @code{$_siginfo} contains extra signal information
8299 (@pxref{extra signal information}). Note that @code{$_siginfo}
8300 could be empty, if the application has not yet received any signals.
8301 For example, it will be empty before you execute the @code{run} command.
8304 @vindex $_tlb@r{, convenience variable}
8305 The variable @code{$_tlb} is automatically set when debugging
8306 applications running on MS-Windows in native mode or connected to
8307 gdbserver that supports the @code{qGetTIBAddr} request.
8308 @xref{General Query Packets}.
8309 This variable contains the address of the thread information block.
8313 On HP-UX systems, if you refer to a function or variable name that
8314 begins with a dollar sign, @value{GDBN} searches for a user or system
8315 name first, before it searches for a convenience variable.
8317 @cindex convenience functions
8318 @value{GDBN} also supplies some @dfn{convenience functions}. These
8319 have a syntax similar to convenience variables. A convenience
8320 function can be used in an expression just like an ordinary function;
8321 however, a convenience function is implemented internally to
8326 @kindex help function
8327 @cindex show all convenience functions
8328 Print a list of all convenience functions.
8335 You can refer to machine register contents, in expressions, as variables
8336 with names starting with @samp{$}. The names of registers are different
8337 for each machine; use @code{info registers} to see the names used on
8341 @kindex info registers
8342 @item info registers
8343 Print the names and values of all registers except floating-point
8344 and vector registers (in the selected stack frame).
8346 @kindex info all-registers
8347 @cindex floating point registers
8348 @item info all-registers
8349 Print the names and values of all registers, including floating-point
8350 and vector registers (in the selected stack frame).
8352 @item info registers @var{regname} @dots{}
8353 Print the @dfn{relativized} value of each specified register @var{regname}.
8354 As discussed in detail below, register values are normally relative to
8355 the selected stack frame. @var{regname} may be any register name valid on
8356 the machine you are using, with or without the initial @samp{$}.
8359 @cindex stack pointer register
8360 @cindex program counter register
8361 @cindex process status register
8362 @cindex frame pointer register
8363 @cindex standard registers
8364 @value{GDBN} has four ``standard'' register names that are available (in
8365 expressions) on most machines---whenever they do not conflict with an
8366 architecture's canonical mnemonics for registers. The register names
8367 @code{$pc} and @code{$sp} are used for the program counter register and
8368 the stack pointer. @code{$fp} is used for a register that contains a
8369 pointer to the current stack frame, and @code{$ps} is used for a
8370 register that contains the processor status. For example,
8371 you could print the program counter in hex with
8378 or print the instruction to be executed next with
8385 or add four to the stack pointer@footnote{This is a way of removing
8386 one word from the stack, on machines where stacks grow downward in
8387 memory (most machines, nowadays). This assumes that the innermost
8388 stack frame is selected; setting @code{$sp} is not allowed when other
8389 stack frames are selected. To pop entire frames off the stack,
8390 regardless of machine architecture, use @code{return};
8391 see @ref{Returning, ,Returning from a Function}.} with
8397 Whenever possible, these four standard register names are available on
8398 your machine even though the machine has different canonical mnemonics,
8399 so long as there is no conflict. The @code{info registers} command
8400 shows the canonical names. For example, on the SPARC, @code{info
8401 registers} displays the processor status register as @code{$psr} but you
8402 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
8403 is an alias for the @sc{eflags} register.
8405 @value{GDBN} always considers the contents of an ordinary register as an
8406 integer when the register is examined in this way. Some machines have
8407 special registers which can hold nothing but floating point; these
8408 registers are considered to have floating point values. There is no way
8409 to refer to the contents of an ordinary register as floating point value
8410 (although you can @emph{print} it as a floating point value with
8411 @samp{print/f $@var{regname}}).
8413 Some registers have distinct ``raw'' and ``virtual'' data formats. This
8414 means that the data format in which the register contents are saved by
8415 the operating system is not the same one that your program normally
8416 sees. For example, the registers of the 68881 floating point
8417 coprocessor are always saved in ``extended'' (raw) format, but all C
8418 programs expect to work with ``double'' (virtual) format. In such
8419 cases, @value{GDBN} normally works with the virtual format only (the format
8420 that makes sense for your program), but the @code{info registers} command
8421 prints the data in both formats.
8423 @cindex SSE registers (x86)
8424 @cindex MMX registers (x86)
8425 Some machines have special registers whose contents can be interpreted
8426 in several different ways. For example, modern x86-based machines
8427 have SSE and MMX registers that can hold several values packed
8428 together in several different formats. @value{GDBN} refers to such
8429 registers in @code{struct} notation:
8432 (@value{GDBP}) print $xmm1
8434 v4_float = @{0, 3.43859137e-038, 1.54142831e-044, 1.821688e-044@},
8435 v2_double = @{9.92129282474342e-303, 2.7585945287983262e-313@},
8436 v16_int8 = "\000\000\000\000\3706;\001\v\000\000\000\r\000\000",
8437 v8_int16 = @{0, 0, 14072, 315, 11, 0, 13, 0@},
8438 v4_int32 = @{0, 20657912, 11, 13@},
8439 v2_int64 = @{88725056443645952, 55834574859@},
8440 uint128 = 0x0000000d0000000b013b36f800000000
8445 To set values of such registers, you need to tell @value{GDBN} which
8446 view of the register you wish to change, as if you were assigning
8447 value to a @code{struct} member:
8450 (@value{GDBP}) set $xmm1.uint128 = 0x000000000000000000000000FFFFFFFF
8453 Normally, register values are relative to the selected stack frame
8454 (@pxref{Selection, ,Selecting a Frame}). This means that you get the
8455 value that the register would contain if all stack frames farther in
8456 were exited and their saved registers restored. In order to see the
8457 true contents of hardware registers, you must select the innermost
8458 frame (with @samp{frame 0}).
8460 However, @value{GDBN} must deduce where registers are saved, from the machine
8461 code generated by your compiler. If some registers are not saved, or if
8462 @value{GDBN} is unable to locate the saved registers, the selected stack
8463 frame makes no difference.
8465 @node Floating Point Hardware
8466 @section Floating Point Hardware
8467 @cindex floating point
8469 Depending on the configuration, @value{GDBN} may be able to give
8470 you more information about the status of the floating point hardware.
8475 Display hardware-dependent information about the floating
8476 point unit. The exact contents and layout vary depending on the
8477 floating point chip. Currently, @samp{info float} is supported on
8478 the ARM and x86 machines.
8482 @section Vector Unit
8485 Depending on the configuration, @value{GDBN} may be able to give you
8486 more information about the status of the vector unit.
8491 Display information about the vector unit. The exact contents and
8492 layout vary depending on the hardware.
8495 @node OS Information
8496 @section Operating System Auxiliary Information
8497 @cindex OS information
8499 @value{GDBN} provides interfaces to useful OS facilities that can help
8500 you debug your program.
8502 @cindex @code{ptrace} system call
8503 @cindex @code{struct user} contents
8504 When @value{GDBN} runs on a @dfn{Posix system} (such as GNU or Unix
8505 machines), it interfaces with the inferior via the @code{ptrace}
8506 system call. The operating system creates a special sata structure,
8507 called @code{struct user}, for this interface. You can use the
8508 command @code{info udot} to display the contents of this data
8514 Display the contents of the @code{struct user} maintained by the OS
8515 kernel for the program being debugged. @value{GDBN} displays the
8516 contents of @code{struct user} as a list of hex numbers, similar to
8517 the @code{examine} command.
8520 @cindex auxiliary vector
8521 @cindex vector, auxiliary
8522 Some operating systems supply an @dfn{auxiliary vector} to programs at
8523 startup. This is akin to the arguments and environment that you
8524 specify for a program, but contains a system-dependent variety of
8525 binary values that tell system libraries important details about the
8526 hardware, operating system, and process. Each value's purpose is
8527 identified by an integer tag; the meanings are well-known but system-specific.
8528 Depending on the configuration and operating system facilities,
8529 @value{GDBN} may be able to show you this information. For remote
8530 targets, this functionality may further depend on the remote stub's
8531 support of the @samp{qXfer:auxv:read} packet, see
8532 @ref{qXfer auxiliary vector read}.
8537 Display the auxiliary vector of the inferior, which can be either a
8538 live process or a core dump file. @value{GDBN} prints each tag value
8539 numerically, and also shows names and text descriptions for recognized
8540 tags. Some values in the vector are numbers, some bit masks, and some
8541 pointers to strings or other data. @value{GDBN} displays each value in the
8542 most appropriate form for a recognized tag, and in hexadecimal for
8543 an unrecognized tag.
8546 On some targets, @value{GDBN} can access operating-system-specific information
8547 and display it to user, without interpretation. For remote targets,
8548 this functionality depends on the remote stub's support of the
8549 @samp{qXfer:osdata:read} packet, see @ref{qXfer osdata read}.
8554 List the types of OS information available for the target. If the
8555 target does not return a list of possible types, this command will
8558 @kindex info os processes
8559 @item info os processes
8560 Display the list of processes on the target. For each process,
8561 @value{GDBN} prints the process identifier, the name of the user, and
8562 the command corresponding to the process.
8565 @node Memory Region Attributes
8566 @section Memory Region Attributes
8567 @cindex memory region attributes
8569 @dfn{Memory region attributes} allow you to describe special handling
8570 required by regions of your target's memory. @value{GDBN} uses
8571 attributes to determine whether to allow certain types of memory
8572 accesses; whether to use specific width accesses; and whether to cache
8573 target memory. By default the description of memory regions is
8574 fetched from the target (if the current target supports this), but the
8575 user can override the fetched regions.
8577 Defined memory regions can be individually enabled and disabled. When a
8578 memory region is disabled, @value{GDBN} uses the default attributes when
8579 accessing memory in that region. Similarly, if no memory regions have
8580 been defined, @value{GDBN} uses the default attributes when accessing
8583 When a memory region is defined, it is given a number to identify it;
8584 to enable, disable, or remove a memory region, you specify that number.
8588 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
8589 Define a memory region bounded by @var{lower} and @var{upper} with
8590 attributes @var{attributes}@dots{}, and add it to the list of regions
8591 monitored by @value{GDBN}. Note that @var{upper} == 0 is a special
8592 case: it is treated as the target's maximum memory address.
8593 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
8596 Discard any user changes to the memory regions and use target-supplied
8597 regions, if available, or no regions if the target does not support.
8600 @item delete mem @var{nums}@dots{}
8601 Remove memory regions @var{nums}@dots{} from the list of regions
8602 monitored by @value{GDBN}.
8605 @item disable mem @var{nums}@dots{}
8606 Disable monitoring of memory regions @var{nums}@dots{}.
8607 A disabled memory region is not forgotten.
8608 It may be enabled again later.
8611 @item enable mem @var{nums}@dots{}
8612 Enable monitoring of memory regions @var{nums}@dots{}.
8616 Print a table of all defined memory regions, with the following columns
8620 @item Memory Region Number
8621 @item Enabled or Disabled.
8622 Enabled memory regions are marked with @samp{y}.
8623 Disabled memory regions are marked with @samp{n}.
8626 The address defining the inclusive lower bound of the memory region.
8629 The address defining the exclusive upper bound of the memory region.
8632 The list of attributes set for this memory region.
8637 @subsection Attributes
8639 @subsubsection Memory Access Mode
8640 The access mode attributes set whether @value{GDBN} may make read or
8641 write accesses to a memory region.
8643 While these attributes prevent @value{GDBN} from performing invalid
8644 memory accesses, they do nothing to prevent the target system, I/O DMA,
8645 etc.@: from accessing memory.
8649 Memory is read only.
8651 Memory is write only.
8653 Memory is read/write. This is the default.
8656 @subsubsection Memory Access Size
8657 The access size attribute tells @value{GDBN} to use specific sized
8658 accesses in the memory region. Often memory mapped device registers
8659 require specific sized accesses. If no access size attribute is
8660 specified, @value{GDBN} may use accesses of any size.
8664 Use 8 bit memory accesses.
8666 Use 16 bit memory accesses.
8668 Use 32 bit memory accesses.
8670 Use 64 bit memory accesses.
8673 @c @subsubsection Hardware/Software Breakpoints
8674 @c The hardware/software breakpoint attributes set whether @value{GDBN}
8675 @c will use hardware or software breakpoints for the internal breakpoints
8676 @c used by the step, next, finish, until, etc. commands.
8680 @c Always use hardware breakpoints
8681 @c @item swbreak (default)
8684 @subsubsection Data Cache
8685 The data cache attributes set whether @value{GDBN} will cache target
8686 memory. While this generally improves performance by reducing debug
8687 protocol overhead, it can lead to incorrect results because @value{GDBN}
8688 does not know about volatile variables or memory mapped device
8693 Enable @value{GDBN} to cache target memory.
8695 Disable @value{GDBN} from caching target memory. This is the default.
8698 @subsection Memory Access Checking
8699 @value{GDBN} can be instructed to refuse accesses to memory that is
8700 not explicitly described. This can be useful if accessing such
8701 regions has undesired effects for a specific target, or to provide
8702 better error checking. The following commands control this behaviour.
8705 @kindex set mem inaccessible-by-default
8706 @item set mem inaccessible-by-default [on|off]
8707 If @code{on} is specified, make @value{GDBN} treat memory not
8708 explicitly described by the memory ranges as non-existent and refuse accesses
8709 to such memory. The checks are only performed if there's at least one
8710 memory range defined. If @code{off} is specified, make @value{GDBN}
8711 treat the memory not explicitly described by the memory ranges as RAM.
8712 The default value is @code{on}.
8713 @kindex show mem inaccessible-by-default
8714 @item show mem inaccessible-by-default
8715 Show the current handling of accesses to unknown memory.
8719 @c @subsubsection Memory Write Verification
8720 @c The memory write verification attributes set whether @value{GDBN}
8721 @c will re-reads data after each write to verify the write was successful.
8725 @c @item noverify (default)
8728 @node Dump/Restore Files
8729 @section Copy Between Memory and a File
8730 @cindex dump/restore files
8731 @cindex append data to a file
8732 @cindex dump data to a file
8733 @cindex restore data from a file
8735 You can use the commands @code{dump}, @code{append}, and
8736 @code{restore} to copy data between target memory and a file. The
8737 @code{dump} and @code{append} commands write data to a file, and the
8738 @code{restore} command reads data from a file back into the inferior's
8739 memory. Files may be in binary, Motorola S-record, Intel hex, or
8740 Tektronix Hex format; however, @value{GDBN} can only append to binary
8746 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
8747 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
8748 Dump the contents of memory from @var{start_addr} to @var{end_addr},
8749 or the value of @var{expr}, to @var{filename} in the given format.
8751 The @var{format} parameter may be any one of:
8758 Motorola S-record format.
8760 Tektronix Hex format.
8763 @value{GDBN} uses the same definitions of these formats as the
8764 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
8765 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
8769 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
8770 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
8771 Append the contents of memory from @var{start_addr} to @var{end_addr},
8772 or the value of @var{expr}, to the file @var{filename}, in raw binary form.
8773 (@value{GDBN} can only append data to files in raw binary form.)
8776 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
8777 Restore the contents of file @var{filename} into memory. The
8778 @code{restore} command can automatically recognize any known @sc{bfd}
8779 file format, except for raw binary. To restore a raw binary file you
8780 must specify the optional keyword @code{binary} after the filename.
8782 If @var{bias} is non-zero, its value will be added to the addresses
8783 contained in the file. Binary files always start at address zero, so
8784 they will be restored at address @var{bias}. Other bfd files have
8785 a built-in location; they will be restored at offset @var{bias}
8788 If @var{start} and/or @var{end} are non-zero, then only data between
8789 file offset @var{start} and file offset @var{end} will be restored.
8790 These offsets are relative to the addresses in the file, before
8791 the @var{bias} argument is applied.
8795 @node Core File Generation
8796 @section How to Produce a Core File from Your Program
8797 @cindex dump core from inferior
8799 A @dfn{core file} or @dfn{core dump} is a file that records the memory
8800 image of a running process and its process status (register values
8801 etc.). Its primary use is post-mortem debugging of a program that
8802 crashed while it ran outside a debugger. A program that crashes
8803 automatically produces a core file, unless this feature is disabled by
8804 the user. @xref{Files}, for information on invoking @value{GDBN} in
8805 the post-mortem debugging mode.
8807 Occasionally, you may wish to produce a core file of the program you
8808 are debugging in order to preserve a snapshot of its state.
8809 @value{GDBN} has a special command for that.
8813 @kindex generate-core-file
8814 @item generate-core-file [@var{file}]
8815 @itemx gcore [@var{file}]
8816 Produce a core dump of the inferior process. The optional argument
8817 @var{file} specifies the file name where to put the core dump. If not
8818 specified, the file name defaults to @file{core.@var{pid}}, where
8819 @var{pid} is the inferior process ID.
8821 Note that this command is implemented only for some systems (as of
8822 this writing, @sc{gnu}/Linux, FreeBSD, Solaris, Unixware, and S390).
8825 @node Character Sets
8826 @section Character Sets
8827 @cindex character sets
8829 @cindex translating between character sets
8830 @cindex host character set
8831 @cindex target character set
8833 If the program you are debugging uses a different character set to
8834 represent characters and strings than the one @value{GDBN} uses itself,
8835 @value{GDBN} can automatically translate between the character sets for
8836 you. The character set @value{GDBN} uses we call the @dfn{host
8837 character set}; the one the inferior program uses we call the
8838 @dfn{target character set}.
8840 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
8841 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
8842 remote protocol (@pxref{Remote Debugging}) to debug a program
8843 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
8844 then the host character set is Latin-1, and the target character set is
8845 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
8846 target-charset EBCDIC-US}, then @value{GDBN} translates between
8847 @sc{ebcdic} and Latin 1 as you print character or string values, or use
8848 character and string literals in expressions.
8850 @value{GDBN} has no way to automatically recognize which character set
8851 the inferior program uses; you must tell it, using the @code{set
8852 target-charset} command, described below.
8854 Here are the commands for controlling @value{GDBN}'s character set
8858 @item set target-charset @var{charset}
8859 @kindex set target-charset
8860 Set the current target character set to @var{charset}. To display the
8861 list of supported target character sets, type
8862 @kbd{@w{set target-charset @key{TAB}@key{TAB}}}.
8864 @item set host-charset @var{charset}
8865 @kindex set host-charset
8866 Set the current host character set to @var{charset}.
8868 By default, @value{GDBN} uses a host character set appropriate to the
8869 system it is running on; you can override that default using the
8870 @code{set host-charset} command. On some systems, @value{GDBN} cannot
8871 automatically determine the appropriate host character set. In this
8872 case, @value{GDBN} uses @samp{UTF-8}.
8874 @value{GDBN} can only use certain character sets as its host character
8875 set. If you type @kbd{@w{set target-charset @key{TAB}@key{TAB}}},
8876 @value{GDBN} will list the host character sets it supports.
8878 @item set charset @var{charset}
8880 Set the current host and target character sets to @var{charset}. As
8881 above, if you type @kbd{@w{set charset @key{TAB}@key{TAB}}},
8882 @value{GDBN} will list the names of the character sets that can be used
8883 for both host and target.
8886 @kindex show charset
8887 Show the names of the current host and target character sets.
8889 @item show host-charset
8890 @kindex show host-charset
8891 Show the name of the current host character set.
8893 @item show target-charset
8894 @kindex show target-charset
8895 Show the name of the current target character set.
8897 @item set target-wide-charset @var{charset}
8898 @kindex set target-wide-charset
8899 Set the current target's wide character set to @var{charset}. This is
8900 the character set used by the target's @code{wchar_t} type. To
8901 display the list of supported wide character sets, type
8902 @kbd{@w{set target-wide-charset @key{TAB}@key{TAB}}}.
8904 @item show target-wide-charset
8905 @kindex show target-wide-charset
8906 Show the name of the current target's wide character set.
8909 Here is an example of @value{GDBN}'s character set support in action.
8910 Assume that the following source code has been placed in the file
8911 @file{charset-test.c}:
8917 = @{72, 101, 108, 108, 111, 44, 32, 119,
8918 111, 114, 108, 100, 33, 10, 0@};
8919 char ibm1047_hello[]
8920 = @{200, 133, 147, 147, 150, 107, 64, 166,
8921 150, 153, 147, 132, 90, 37, 0@};
8925 printf ("Hello, world!\n");
8929 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
8930 containing the string @samp{Hello, world!} followed by a newline,
8931 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
8933 We compile the program, and invoke the debugger on it:
8936 $ gcc -g charset-test.c -o charset-test
8937 $ gdb -nw charset-test
8938 GNU gdb 2001-12-19-cvs
8939 Copyright 2001 Free Software Foundation, Inc.
8944 We can use the @code{show charset} command to see what character sets
8945 @value{GDBN} is currently using to interpret and display characters and
8949 (@value{GDBP}) show charset
8950 The current host and target character set is `ISO-8859-1'.
8954 For the sake of printing this manual, let's use @sc{ascii} as our
8955 initial character set:
8957 (@value{GDBP}) set charset ASCII
8958 (@value{GDBP}) show charset
8959 The current host and target character set is `ASCII'.
8963 Let's assume that @sc{ascii} is indeed the correct character set for our
8964 host system --- in other words, let's assume that if @value{GDBN} prints
8965 characters using the @sc{ascii} character set, our terminal will display
8966 them properly. Since our current target character set is also
8967 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
8970 (@value{GDBP}) print ascii_hello
8971 $1 = 0x401698 "Hello, world!\n"
8972 (@value{GDBP}) print ascii_hello[0]
8977 @value{GDBN} uses the target character set for character and string
8978 literals you use in expressions:
8981 (@value{GDBP}) print '+'
8986 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
8989 @value{GDBN} relies on the user to tell it which character set the
8990 target program uses. If we print @code{ibm1047_hello} while our target
8991 character set is still @sc{ascii}, we get jibberish:
8994 (@value{GDBP}) print ibm1047_hello
8995 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
8996 (@value{GDBP}) print ibm1047_hello[0]
9001 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
9002 @value{GDBN} tells us the character sets it supports:
9005 (@value{GDBP}) set target-charset
9006 ASCII EBCDIC-US IBM1047 ISO-8859-1
9007 (@value{GDBP}) set target-charset
9010 We can select @sc{ibm1047} as our target character set, and examine the
9011 program's strings again. Now the @sc{ascii} string is wrong, but
9012 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
9013 target character set, @sc{ibm1047}, to the host character set,
9014 @sc{ascii}, and they display correctly:
9017 (@value{GDBP}) set target-charset IBM1047
9018 (@value{GDBP}) show charset
9019 The current host character set is `ASCII'.
9020 The current target character set is `IBM1047'.
9021 (@value{GDBP}) print ascii_hello
9022 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
9023 (@value{GDBP}) print ascii_hello[0]
9025 (@value{GDBP}) print ibm1047_hello
9026 $8 = 0x4016a8 "Hello, world!\n"
9027 (@value{GDBP}) print ibm1047_hello[0]
9032 As above, @value{GDBN} uses the target character set for character and
9033 string literals you use in expressions:
9036 (@value{GDBP}) print '+'
9041 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
9044 @node Caching Remote Data
9045 @section Caching Data of Remote Targets
9046 @cindex caching data of remote targets
9048 @value{GDBN} caches data exchanged between the debugger and a
9049 remote target (@pxref{Remote Debugging}). Such caching generally improves
9050 performance, because it reduces the overhead of the remote protocol by
9051 bundling memory reads and writes into large chunks. Unfortunately, simply
9052 caching everything would lead to incorrect results, since @value{GDBN}
9053 does not necessarily know anything about volatile values, memory-mapped I/O
9054 addresses, etc. Furthermore, in non-stop mode (@pxref{Non-Stop Mode})
9055 memory can be changed @emph{while} a gdb command is executing.
9056 Therefore, by default, @value{GDBN} only caches data
9057 known to be on the stack@footnote{In non-stop mode, it is moderately
9058 rare for a running thread to modify the stack of a stopped thread
9059 in a way that would interfere with a backtrace, and caching of
9060 stack reads provides a significant speed up of remote backtraces.}.
9061 Other regions of memory can be explicitly marked as
9062 cacheable; see @pxref{Memory Region Attributes}.
9065 @kindex set remotecache
9066 @item set remotecache on
9067 @itemx set remotecache off
9068 This option no longer does anything; it exists for compatibility
9071 @kindex show remotecache
9072 @item show remotecache
9073 Show the current state of the obsolete remotecache flag.
9075 @kindex set stack-cache
9076 @item set stack-cache on
9077 @itemx set stack-cache off
9078 Enable or disable caching of stack accesses. When @code{ON}, use
9079 caching. By default, this option is @code{ON}.
9081 @kindex show stack-cache
9082 @item show stack-cache
9083 Show the current state of data caching for memory accesses.
9086 @item info dcache @r{[}line@r{]}
9087 Print the information about the data cache performance. The
9088 information displayed includes the dcache width and depth, and for
9089 each cache line, its number, address, and how many times it was
9090 referenced. This command is useful for debugging the data cache
9093 If a line number is specified, the contents of that line will be
9097 @node Searching Memory
9098 @section Search Memory
9099 @cindex searching memory
9101 Memory can be searched for a particular sequence of bytes with the
9102 @code{find} command.
9106 @item find @r{[}/@var{sn}@r{]} @var{start_addr}, +@var{len}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
9107 @itemx find @r{[}/@var{sn}@r{]} @var{start_addr}, @var{end_addr}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
9108 Search memory for the sequence of bytes specified by @var{val1}, @var{val2},
9109 etc. The search begins at address @var{start_addr} and continues for either
9110 @var{len} bytes or through to @var{end_addr} inclusive.
9113 @var{s} and @var{n} are optional parameters.
9114 They may be specified in either order, apart or together.
9117 @item @var{s}, search query size
9118 The size of each search query value.
9124 halfwords (two bytes)
9128 giant words (eight bytes)
9131 All values are interpreted in the current language.
9132 This means, for example, that if the current source language is C/C@t{++}
9133 then searching for the string ``hello'' includes the trailing '\0'.
9135 If the value size is not specified, it is taken from the
9136 value's type in the current language.
9137 This is useful when one wants to specify the search
9138 pattern as a mixture of types.
9139 Note that this means, for example, that in the case of C-like languages
9140 a search for an untyped 0x42 will search for @samp{(int) 0x42}
9141 which is typically four bytes.
9143 @item @var{n}, maximum number of finds
9144 The maximum number of matches to print. The default is to print all finds.
9147 You can use strings as search values. Quote them with double-quotes
9149 The string value is copied into the search pattern byte by byte,
9150 regardless of the endianness of the target and the size specification.
9152 The address of each match found is printed as well as a count of the
9153 number of matches found.
9155 The address of the last value found is stored in convenience variable
9157 A count of the number of matches is stored in @samp{$numfound}.
9159 For example, if stopped at the @code{printf} in this function:
9165 static char hello[] = "hello-hello";
9166 static struct @{ char c; short s; int i; @}
9167 __attribute__ ((packed)) mixed
9168 = @{ 'c', 0x1234, 0x87654321 @};
9169 printf ("%s\n", hello);
9174 you get during debugging:
9177 (gdb) find &hello[0], +sizeof(hello), "hello"
9178 0x804956d <hello.1620+6>
9180 (gdb) find &hello[0], +sizeof(hello), 'h', 'e', 'l', 'l', 'o'
9181 0x8049567 <hello.1620>
9182 0x804956d <hello.1620+6>
9184 (gdb) find /b1 &hello[0], +sizeof(hello), 'h', 0x65, 'l'
9185 0x8049567 <hello.1620>
9187 (gdb) find &mixed, +sizeof(mixed), (char) 'c', (short) 0x1234, (int) 0x87654321
9188 0x8049560 <mixed.1625>
9190 (gdb) print $numfound
9193 $2 = (void *) 0x8049560
9196 @node Optimized Code
9197 @chapter Debugging Optimized Code
9198 @cindex optimized code, debugging
9199 @cindex debugging optimized code
9201 Almost all compilers support optimization. With optimization
9202 disabled, the compiler generates assembly code that corresponds
9203 directly to your source code, in a simplistic way. As the compiler
9204 applies more powerful optimizations, the generated assembly code
9205 diverges from your original source code. With help from debugging
9206 information generated by the compiler, @value{GDBN} can map from
9207 the running program back to constructs from your original source.
9209 @value{GDBN} is more accurate with optimization disabled. If you
9210 can recompile without optimization, it is easier to follow the
9211 progress of your program during debugging. But, there are many cases
9212 where you may need to debug an optimized version.
9214 When you debug a program compiled with @samp{-g -O}, remember that the
9215 optimizer has rearranged your code; the debugger shows you what is
9216 really there. Do not be too surprised when the execution path does not
9217 exactly match your source file! An extreme example: if you define a
9218 variable, but never use it, @value{GDBN} never sees that
9219 variable---because the compiler optimizes it out of existence.
9221 Some things do not work as well with @samp{-g -O} as with just
9222 @samp{-g}, particularly on machines with instruction scheduling. If in
9223 doubt, recompile with @samp{-g} alone, and if this fixes the problem,
9224 please report it to us as a bug (including a test case!).
9225 @xref{Variables}, for more information about debugging optimized code.
9228 * Inline Functions:: How @value{GDBN} presents inlining
9231 @node Inline Functions
9232 @section Inline Functions
9233 @cindex inline functions, debugging
9235 @dfn{Inlining} is an optimization that inserts a copy of the function
9236 body directly at each call site, instead of jumping to a shared
9237 routine. @value{GDBN} displays inlined functions just like
9238 non-inlined functions. They appear in backtraces. You can view their
9239 arguments and local variables, step into them with @code{step}, skip
9240 them with @code{next}, and escape from them with @code{finish}.
9241 You can check whether a function was inlined by using the
9242 @code{info frame} command.
9244 For @value{GDBN} to support inlined functions, the compiler must
9245 record information about inlining in the debug information ---
9246 @value{NGCC} using the @sc{dwarf 2} format does this, and several
9247 other compilers do also. @value{GDBN} only supports inlined functions
9248 when using @sc{dwarf 2}. Versions of @value{NGCC} before 4.1
9249 do not emit two required attributes (@samp{DW_AT_call_file} and
9250 @samp{DW_AT_call_line}); @value{GDBN} does not display inlined
9251 function calls with earlier versions of @value{NGCC}. It instead
9252 displays the arguments and local variables of inlined functions as
9253 local variables in the caller.
9255 The body of an inlined function is directly included at its call site;
9256 unlike a non-inlined function, there are no instructions devoted to
9257 the call. @value{GDBN} still pretends that the call site and the
9258 start of the inlined function are different instructions. Stepping to
9259 the call site shows the call site, and then stepping again shows
9260 the first line of the inlined function, even though no additional
9261 instructions are executed.
9263 This makes source-level debugging much clearer; you can see both the
9264 context of the call and then the effect of the call. Only stepping by
9265 a single instruction using @code{stepi} or @code{nexti} does not do
9266 this; single instruction steps always show the inlined body.
9268 There are some ways that @value{GDBN} does not pretend that inlined
9269 function calls are the same as normal calls:
9273 You cannot set breakpoints on inlined functions. @value{GDBN}
9274 either reports that there is no symbol with that name, or else sets the
9275 breakpoint only on non-inlined copies of the function. This limitation
9276 will be removed in a future version of @value{GDBN}; until then,
9277 set a breakpoint by line number on the first line of the inlined
9281 Setting breakpoints at the call site of an inlined function may not
9282 work, because the call site does not contain any code. @value{GDBN}
9283 may incorrectly move the breakpoint to the next line of the enclosing
9284 function, after the call. This limitation will be removed in a future
9285 version of @value{GDBN}; until then, set a breakpoint on an earlier line
9286 or inside the inlined function instead.
9289 @value{GDBN} cannot locate the return value of inlined calls after
9290 using the @code{finish} command. This is a limitation of compiler-generated
9291 debugging information; after @code{finish}, you can step to the next line
9292 and print a variable where your program stored the return value.
9298 @chapter C Preprocessor Macros
9300 Some languages, such as C and C@t{++}, provide a way to define and invoke
9301 ``preprocessor macros'' which expand into strings of tokens.
9302 @value{GDBN} can evaluate expressions containing macro invocations, show
9303 the result of macro expansion, and show a macro's definition, including
9304 where it was defined.
9306 You may need to compile your program specially to provide @value{GDBN}
9307 with information about preprocessor macros. Most compilers do not
9308 include macros in their debugging information, even when you compile
9309 with the @option{-g} flag. @xref{Compilation}.
9311 A program may define a macro at one point, remove that definition later,
9312 and then provide a different definition after that. Thus, at different
9313 points in the program, a macro may have different definitions, or have
9314 no definition at all. If there is a current stack frame, @value{GDBN}
9315 uses the macros in scope at that frame's source code line. Otherwise,
9316 @value{GDBN} uses the macros in scope at the current listing location;
9319 Whenever @value{GDBN} evaluates an expression, it always expands any
9320 macro invocations present in the expression. @value{GDBN} also provides
9321 the following commands for working with macros explicitly.
9325 @kindex macro expand
9326 @cindex macro expansion, showing the results of preprocessor
9327 @cindex preprocessor macro expansion, showing the results of
9328 @cindex expanding preprocessor macros
9329 @item macro expand @var{expression}
9330 @itemx macro exp @var{expression}
9331 Show the results of expanding all preprocessor macro invocations in
9332 @var{expression}. Since @value{GDBN} simply expands macros, but does
9333 not parse the result, @var{expression} need not be a valid expression;
9334 it can be any string of tokens.
9337 @item macro expand-once @var{expression}
9338 @itemx macro exp1 @var{expression}
9339 @cindex expand macro once
9340 @i{(This command is not yet implemented.)} Show the results of
9341 expanding those preprocessor macro invocations that appear explicitly in
9342 @var{expression}. Macro invocations appearing in that expansion are
9343 left unchanged. This command allows you to see the effect of a
9344 particular macro more clearly, without being confused by further
9345 expansions. Since @value{GDBN} simply expands macros, but does not
9346 parse the result, @var{expression} need not be a valid expression; it
9347 can be any string of tokens.
9350 @cindex macro definition, showing
9351 @cindex definition, showing a macro's
9352 @item info macro @var{macro}
9353 Show the definition of the macro named @var{macro}, and describe the
9354 source location or compiler command-line where that definition was established.
9356 @kindex macro define
9357 @cindex user-defined macros
9358 @cindex defining macros interactively
9359 @cindex macros, user-defined
9360 @item macro define @var{macro} @var{replacement-list}
9361 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
9362 Introduce a definition for a preprocessor macro named @var{macro},
9363 invocations of which are replaced by the tokens given in
9364 @var{replacement-list}. The first form of this command defines an
9365 ``object-like'' macro, which takes no arguments; the second form
9366 defines a ``function-like'' macro, which takes the arguments given in
9369 A definition introduced by this command is in scope in every
9370 expression evaluated in @value{GDBN}, until it is removed with the
9371 @code{macro undef} command, described below. The definition overrides
9372 all definitions for @var{macro} present in the program being debugged,
9373 as well as any previous user-supplied definition.
9376 @item macro undef @var{macro}
9377 Remove any user-supplied definition for the macro named @var{macro}.
9378 This command only affects definitions provided with the @code{macro
9379 define} command, described above; it cannot remove definitions present
9380 in the program being debugged.
9384 List all the macros defined using the @code{macro define} command.
9387 @cindex macros, example of debugging with
9388 Here is a transcript showing the above commands in action. First, we
9389 show our source files:
9397 #define ADD(x) (M + x)
9402 printf ("Hello, world!\n");
9404 printf ("We're so creative.\n");
9406 printf ("Goodbye, world!\n");
9413 Now, we compile the program using the @sc{gnu} C compiler, @value{NGCC}.
9414 We pass the @option{-gdwarf-2} and @option{-g3} flags to ensure the
9415 compiler includes information about preprocessor macros in the debugging
9419 $ gcc -gdwarf-2 -g3 sample.c -o sample
9423 Now, we start @value{GDBN} on our sample program:
9427 GNU gdb 2002-05-06-cvs
9428 Copyright 2002 Free Software Foundation, Inc.
9429 GDB is free software, @dots{}
9433 We can expand macros and examine their definitions, even when the
9434 program is not running. @value{GDBN} uses the current listing position
9435 to decide which macro definitions are in scope:
9438 (@value{GDBP}) list main
9441 5 #define ADD(x) (M + x)
9446 10 printf ("Hello, world!\n");
9448 12 printf ("We're so creative.\n");
9449 (@value{GDBP}) info macro ADD
9450 Defined at /home/jimb/gdb/macros/play/sample.c:5
9451 #define ADD(x) (M + x)
9452 (@value{GDBP}) info macro Q
9453 Defined at /home/jimb/gdb/macros/play/sample.h:1
9454 included at /home/jimb/gdb/macros/play/sample.c:2
9456 (@value{GDBP}) macro expand ADD(1)
9457 expands to: (42 + 1)
9458 (@value{GDBP}) macro expand-once ADD(1)
9459 expands to: once (M + 1)
9463 In the example above, note that @code{macro expand-once} expands only
9464 the macro invocation explicit in the original text --- the invocation of
9465 @code{ADD} --- but does not expand the invocation of the macro @code{M},
9466 which was introduced by @code{ADD}.
9468 Once the program is running, @value{GDBN} uses the macro definitions in
9469 force at the source line of the current stack frame:
9472 (@value{GDBP}) break main
9473 Breakpoint 1 at 0x8048370: file sample.c, line 10.
9475 Starting program: /home/jimb/gdb/macros/play/sample
9477 Breakpoint 1, main () at sample.c:10
9478 10 printf ("Hello, world!\n");
9482 At line 10, the definition of the macro @code{N} at line 9 is in force:
9485 (@value{GDBP}) info macro N
9486 Defined at /home/jimb/gdb/macros/play/sample.c:9
9488 (@value{GDBP}) macro expand N Q M
9490 (@value{GDBP}) print N Q M
9495 As we step over directives that remove @code{N}'s definition, and then
9496 give it a new definition, @value{GDBN} finds the definition (or lack
9497 thereof) in force at each point:
9502 12 printf ("We're so creative.\n");
9503 (@value{GDBP}) info macro N
9504 The symbol `N' has no definition as a C/C++ preprocessor macro
9505 at /home/jimb/gdb/macros/play/sample.c:12
9508 14 printf ("Goodbye, world!\n");
9509 (@value{GDBP}) info macro N
9510 Defined at /home/jimb/gdb/macros/play/sample.c:13
9512 (@value{GDBP}) macro expand N Q M
9513 expands to: 1729 < 42
9514 (@value{GDBP}) print N Q M
9519 In addition to source files, macros can be defined on the compilation command
9520 line using the @option{-D@var{name}=@var{value}} syntax. For macros defined in
9521 such a way, @value{GDBN} displays the location of their definition as line zero
9522 of the source file submitted to the compiler.
9525 (@value{GDBP}) info macro __STDC__
9526 Defined at /home/jimb/gdb/macros/play/sample.c:0
9533 @chapter Tracepoints
9534 @c This chapter is based on the documentation written by Michael
9535 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
9538 In some applications, it is not feasible for the debugger to interrupt
9539 the program's execution long enough for the developer to learn
9540 anything helpful about its behavior. If the program's correctness
9541 depends on its real-time behavior, delays introduced by a debugger
9542 might cause the program to change its behavior drastically, or perhaps
9543 fail, even when the code itself is correct. It is useful to be able
9544 to observe the program's behavior without interrupting it.
9546 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
9547 specify locations in the program, called @dfn{tracepoints}, and
9548 arbitrary expressions to evaluate when those tracepoints are reached.
9549 Later, using the @code{tfind} command, you can examine the values
9550 those expressions had when the program hit the tracepoints. The
9551 expressions may also denote objects in memory---structures or arrays,
9552 for example---whose values @value{GDBN} should record; while visiting
9553 a particular tracepoint, you may inspect those objects as if they were
9554 in memory at that moment. However, because @value{GDBN} records these
9555 values without interacting with you, it can do so quickly and
9556 unobtrusively, hopefully not disturbing the program's behavior.
9558 The tracepoint facility is currently available only for remote
9559 targets. @xref{Targets}. In addition, your remote target must know
9560 how to collect trace data. This functionality is implemented in the
9561 remote stub; however, none of the stubs distributed with @value{GDBN}
9562 support tracepoints as of this writing. The format of the remote
9563 packets used to implement tracepoints are described in @ref{Tracepoint
9566 It is also possible to get trace data from a file, in a manner reminiscent
9567 of corefiles; you specify the filename, and use @code{tfind} to search
9568 through the file. @xref{Trace Files}, for more details.
9570 This chapter describes the tracepoint commands and features.
9574 * Analyze Collected Data::
9575 * Tracepoint Variables::
9579 @node Set Tracepoints
9580 @section Commands to Set Tracepoints
9582 Before running such a @dfn{trace experiment}, an arbitrary number of
9583 tracepoints can be set. A tracepoint is actually a special type of
9584 breakpoint (@pxref{Set Breaks}), so you can manipulate it using
9585 standard breakpoint commands. For instance, as with breakpoints,
9586 tracepoint numbers are successive integers starting from one, and many
9587 of the commands associated with tracepoints take the tracepoint number
9588 as their argument, to identify which tracepoint to work on.
9590 For each tracepoint, you can specify, in advance, some arbitrary set
9591 of data that you want the target to collect in the trace buffer when
9592 it hits that tracepoint. The collected data can include registers,
9593 local variables, or global data. Later, you can use @value{GDBN}
9594 commands to examine the values these data had at the time the
9597 Tracepoints do not support every breakpoint feature. Ignore counts on
9598 tracepoints have no effect, and tracepoints cannot run @value{GDBN}
9599 commands when they are hit. Tracepoints may not be thread-specific
9602 @cindex fast tracepoints
9603 Some targets may support @dfn{fast tracepoints}, which are inserted in
9604 a different way (such as with a jump instead of a trap), that is
9605 faster but possibly restricted in where they may be installed.
9607 @cindex static tracepoints
9608 @cindex markers, static tracepoints
9609 @cindex probing markers, static tracepoints
9610 Regular and fast tracepoints are dynamic tracing facilities, meaning
9611 that they can be used to insert tracepoints at (almost) any location
9612 in the target. Some targets may also support controlling @dfn{static
9613 tracepoints} from @value{GDBN}. With static tracing, a set of
9614 instrumentation points, also known as @dfn{markers}, are embedded in
9615 the target program, and can be activated or deactivated by name or
9616 address. These are usually placed at locations which facilitate
9617 investigating what the target is actually doing. @value{GDBN}'s
9618 support for static tracing includes being able to list instrumentation
9619 points, and attach them with @value{GDBN} defined high level
9620 tracepoints that expose the whole range of convenience of
9621 @value{GDBN}'s tracepoints support. Namelly, support for collecting
9622 registers values and values of global or local (to the instrumentation
9623 point) variables; tracepoint conditions and trace state variables.
9624 The act of installing a @value{GDBN} static tracepoint on an
9625 instrumentation point, or marker, is referred to as @dfn{probing} a
9626 static tracepoint marker.
9628 @code{gdbserver} supports tracepoints on some target systems.
9629 @xref{Server,,Tracepoints support in @code{gdbserver}}.
9631 This section describes commands to set tracepoints and associated
9632 conditions and actions.
9635 * Create and Delete Tracepoints::
9636 * Enable and Disable Tracepoints::
9637 * Tracepoint Passcounts::
9638 * Tracepoint Conditions::
9639 * Trace State Variables::
9640 * Tracepoint Actions::
9641 * Listing Tracepoints::
9642 * Listing Static Tracepoint Markers::
9643 * Starting and Stopping Trace Experiments::
9644 * Tracepoint Restrictions::
9647 @node Create and Delete Tracepoints
9648 @subsection Create and Delete Tracepoints
9651 @cindex set tracepoint
9653 @item trace @var{location}
9654 The @code{trace} command is very similar to the @code{break} command.
9655 Its argument @var{location} can be a source line, a function name, or
9656 an address in the target program. @xref{Specify Location}. The
9657 @code{trace} command defines a tracepoint, which is a point in the
9658 target program where the debugger will briefly stop, collect some
9659 data, and then allow the program to continue. Setting a tracepoint or
9660 changing its actions doesn't take effect until the next @code{tstart}
9661 command, and once a trace experiment is running, further changes will
9662 not have any effect until the next trace experiment starts.
9664 Here are some examples of using the @code{trace} command:
9667 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
9669 (@value{GDBP}) @b{trace +2} // 2 lines forward
9671 (@value{GDBP}) @b{trace my_function} // first source line of function
9673 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
9675 (@value{GDBP}) @b{trace *0x2117c4} // an address
9679 You can abbreviate @code{trace} as @code{tr}.
9681 @item trace @var{location} if @var{cond}
9682 Set a tracepoint with condition @var{cond}; evaluate the expression
9683 @var{cond} each time the tracepoint is reached, and collect data only
9684 if the value is nonzero---that is, if @var{cond} evaluates as true.
9685 @xref{Tracepoint Conditions, ,Tracepoint Conditions}, for more
9686 information on tracepoint conditions.
9688 @item ftrace @var{location} [ if @var{cond} ]
9689 @cindex set fast tracepoint
9690 @cindex fast tracepoints, setting
9692 The @code{ftrace} command sets a fast tracepoint. For targets that
9693 support them, fast tracepoints will use a more efficient but possibly
9694 less general technique to trigger data collection, such as a jump
9695 instruction instead of a trap, or some sort of hardware support. It
9696 may not be possible to create a fast tracepoint at the desired
9697 location, in which case the command will exit with an explanatory
9700 @value{GDBN} handles arguments to @code{ftrace} exactly as for
9703 @item strace @var{location} [ if @var{cond} ]
9704 @cindex set static tracepoint
9705 @cindex static tracepoints, setting
9706 @cindex probe static tracepoint marker
9708 The @code{strace} command sets a static tracepoint. For targets that
9709 support it, setting a static tracepoint probes a static
9710 instrumentation point, or marker, found at @var{location}. It may not
9711 be possible to set a static tracepoint at the desired location, in
9712 which case the command will exit with an explanatory message.
9714 @value{GDBN} handles arguments to @code{strace} exactly as for
9715 @code{trace}, with the addition that the user can also specify
9716 @code{-m @var{marker}} as @var{location}. This probes the marker
9717 identified by the @var{marker} string identifier. This identifier
9718 depends on the static tracepoint backend library your program is
9719 using. You can find all the marker identifiers in the @samp{ID} field
9720 of the @code{info static-tracepoint-markers} command output.
9721 @xref{Listing Static Tracepoint Markers,,Listing Static Tracepoint
9722 Markers}. For example, in the following small program using the UST
9728 trace_mark(ust, bar33, "str %s", "FOOBAZ");
9733 the marker id is composed of joining the first two arguments to the
9734 @code{trace_mark} call with a slash, which translates to:
9737 (@value{GDBP}) info static-tracepoint-markers
9738 Cnt Enb ID Address What
9739 1 n ust/bar33 0x0000000000400ddc in main at stexample.c:22
9745 so you may probe the marker above with:
9748 (@value{GDBP}) strace -m ust/bar33
9751 Static tracepoints accept an extra collect action --- @code{collect
9752 $_sdata}. This collects arbitrary user data passed in the probe point
9753 call to the tracing library. In the UST example above, you'll see
9754 that the third argument to @code{trace_mark} is a printf-like format
9755 string. The user data is then the result of running that formating
9756 string against the following arguments. Note that @code{info
9757 static-tracepoint-markers} command output lists that format string in
9758 the @samp{Data:} field.
9760 You can inspect this data when analyzing the trace buffer, by printing
9761 the $_sdata variable like any other variable available to
9762 @value{GDBN}. @xref{Tracepoint Actions,,Tracepoint Action Lists}.
9765 @cindex last tracepoint number
9766 @cindex recent tracepoint number
9767 @cindex tracepoint number
9768 The convenience variable @code{$tpnum} records the tracepoint number
9769 of the most recently set tracepoint.
9771 @kindex delete tracepoint
9772 @cindex tracepoint deletion
9773 @item delete tracepoint @r{[}@var{num}@r{]}
9774 Permanently delete one or more tracepoints. With no argument, the
9775 default is to delete all tracepoints. Note that the regular
9776 @code{delete} command can remove tracepoints also.
9781 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
9783 (@value{GDBP}) @b{delete trace} // remove all tracepoints
9787 You can abbreviate this command as @code{del tr}.
9790 @node Enable and Disable Tracepoints
9791 @subsection Enable and Disable Tracepoints
9793 These commands are deprecated; they are equivalent to plain @code{disable} and @code{enable}.
9796 @kindex disable tracepoint
9797 @item disable tracepoint @r{[}@var{num}@r{]}
9798 Disable tracepoint @var{num}, or all tracepoints if no argument
9799 @var{num} is given. A disabled tracepoint will have no effect during
9800 the next trace experiment, but it is not forgotten. You can re-enable
9801 a disabled tracepoint using the @code{enable tracepoint} command.
9803 @kindex enable tracepoint
9804 @item enable tracepoint @r{[}@var{num}@r{]}
9805 Enable tracepoint @var{num}, or all tracepoints. The enabled
9806 tracepoints will become effective the next time a trace experiment is
9810 @node Tracepoint Passcounts
9811 @subsection Tracepoint Passcounts
9815 @cindex tracepoint pass count
9816 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
9817 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
9818 automatically stop a trace experiment. If a tracepoint's passcount is
9819 @var{n}, then the trace experiment will be automatically stopped on
9820 the @var{n}'th time that tracepoint is hit. If the tracepoint number
9821 @var{num} is not specified, the @code{passcount} command sets the
9822 passcount of the most recently defined tracepoint. If no passcount is
9823 given, the trace experiment will run until stopped explicitly by the
9829 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
9830 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
9832 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
9833 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
9834 (@value{GDBP}) @b{trace foo}
9835 (@value{GDBP}) @b{pass 3}
9836 (@value{GDBP}) @b{trace bar}
9837 (@value{GDBP}) @b{pass 2}
9838 (@value{GDBP}) @b{trace baz}
9839 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
9840 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
9841 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
9842 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
9846 @node Tracepoint Conditions
9847 @subsection Tracepoint Conditions
9848 @cindex conditional tracepoints
9849 @cindex tracepoint conditions
9851 The simplest sort of tracepoint collects data every time your program
9852 reaches a specified place. You can also specify a @dfn{condition} for
9853 a tracepoint. A condition is just a Boolean expression in your
9854 programming language (@pxref{Expressions, ,Expressions}). A
9855 tracepoint with a condition evaluates the expression each time your
9856 program reaches it, and data collection happens only if the condition
9859 Tracepoint conditions can be specified when a tracepoint is set, by
9860 using @samp{if} in the arguments to the @code{trace} command.
9861 @xref{Create and Delete Tracepoints, ,Setting Tracepoints}. They can
9862 also be set or changed at any time with the @code{condition} command,
9863 just as with breakpoints.
9865 Unlike breakpoint conditions, @value{GDBN} does not actually evaluate
9866 the conditional expression itself. Instead, @value{GDBN} encodes the
9867 expression into an agent expression (@pxref{Agent Expressions}
9868 suitable for execution on the target, independently of @value{GDBN}.
9869 Global variables become raw memory locations, locals become stack
9870 accesses, and so forth.
9872 For instance, suppose you have a function that is usually called
9873 frequently, but should not be called after an error has occurred. You
9874 could use the following tracepoint command to collect data about calls
9875 of that function that happen while the error code is propagating
9876 through the program; an unconditional tracepoint could end up
9877 collecting thousands of useless trace frames that you would have to
9881 (@value{GDBP}) @kbd{trace normal_operation if errcode > 0}
9884 @node Trace State Variables
9885 @subsection Trace State Variables
9886 @cindex trace state variables
9888 A @dfn{trace state variable} is a special type of variable that is
9889 created and managed by target-side code. The syntax is the same as
9890 that for GDB's convenience variables (a string prefixed with ``$''),
9891 but they are stored on the target. They must be created explicitly,
9892 using a @code{tvariable} command. They are always 64-bit signed
9895 Trace state variables are remembered by @value{GDBN}, and downloaded
9896 to the target along with tracepoint information when the trace
9897 experiment starts. There are no intrinsic limits on the number of
9898 trace state variables, beyond memory limitations of the target.
9900 @cindex convenience variables, and trace state variables
9901 Although trace state variables are managed by the target, you can use
9902 them in print commands and expressions as if they were convenience
9903 variables; @value{GDBN} will get the current value from the target
9904 while the trace experiment is running. Trace state variables share
9905 the same namespace as other ``$'' variables, which means that you
9906 cannot have trace state variables with names like @code{$23} or
9907 @code{$pc}, nor can you have a trace state variable and a convenience
9908 variable with the same name.
9912 @item tvariable $@var{name} [ = @var{expression} ]
9914 The @code{tvariable} command creates a new trace state variable named
9915 @code{$@var{name}}, and optionally gives it an initial value of
9916 @var{expression}. @var{expression} is evaluated when this command is
9917 entered; the result will be converted to an integer if possible,
9918 otherwise @value{GDBN} will report an error. A subsequent
9919 @code{tvariable} command specifying the same name does not create a
9920 variable, but instead assigns the supplied initial value to the
9921 existing variable of that name, overwriting any previous initial
9922 value. The default initial value is 0.
9924 @item info tvariables
9925 @kindex info tvariables
9926 List all the trace state variables along with their initial values.
9927 Their current values may also be displayed, if the trace experiment is
9930 @item delete tvariable @r{[} $@var{name} @dots{} @r{]}
9931 @kindex delete tvariable
9932 Delete the given trace state variables, or all of them if no arguments
9937 @node Tracepoint Actions
9938 @subsection Tracepoint Action Lists
9942 @cindex tracepoint actions
9943 @item actions @r{[}@var{num}@r{]}
9944 This command will prompt for a list of actions to be taken when the
9945 tracepoint is hit. If the tracepoint number @var{num} is not
9946 specified, this command sets the actions for the one that was most
9947 recently defined (so that you can define a tracepoint and then say
9948 @code{actions} without bothering about its number). You specify the
9949 actions themselves on the following lines, one action at a time, and
9950 terminate the actions list with a line containing just @code{end}. So
9951 far, the only defined actions are @code{collect}, @code{teval}, and
9952 @code{while-stepping}.
9954 @code{actions} is actually equivalent to @code{commands} (@pxref{Break
9955 Commands, ,Breakpoint Command Lists}), except that only the defined
9956 actions are allowed; any other @value{GDBN} command is rejected.
9958 @cindex remove actions from a tracepoint
9959 To remove all actions from a tracepoint, type @samp{actions @var{num}}
9960 and follow it immediately with @samp{end}.
9963 (@value{GDBP}) @b{collect @var{data}} // collect some data
9965 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
9967 (@value{GDBP}) @b{end} // signals the end of actions.
9970 In the following example, the action list begins with @code{collect}
9971 commands indicating the things to be collected when the tracepoint is
9972 hit. Then, in order to single-step and collect additional data
9973 following the tracepoint, a @code{while-stepping} command is used,
9974 followed by the list of things to be collected after each step in a
9975 sequence of single steps. The @code{while-stepping} command is
9976 terminated by its own separate @code{end} command. Lastly, the action
9977 list is terminated by an @code{end} command.
9980 (@value{GDBP}) @b{trace foo}
9981 (@value{GDBP}) @b{actions}
9982 Enter actions for tracepoint 1, one per line:
9986 > collect $pc, arr[i]
9991 @kindex collect @r{(tracepoints)}
9992 @item collect @var{expr1}, @var{expr2}, @dots{}
9993 Collect values of the given expressions when the tracepoint is hit.
9994 This command accepts a comma-separated list of any valid expressions.
9995 In addition to global, static, or local variables, the following
9996 special arguments are supported:
10000 Collect all registers.
10003 Collect all function arguments.
10006 Collect all local variables.
10009 @vindex $_sdata@r{, collect}
10010 Collect static tracepoint marker specific data. Only available for
10011 static tracepoints. @xref{Tracepoint Actions,,Tracepoint Action
10012 Lists}. On the UST static tracepoints library backend, an
10013 instrumentation point resembles a @code{printf} function call. The
10014 tracing library is able to collect user specified data formatted to a
10015 character string using the format provided by the programmer that
10016 instrumented the program. Other backends have similar mechanisms.
10017 Here's an example of a UST marker call:
10020 const char master_name[] = "$your_name";
10021 trace_mark(channel1, marker1, "hello %s", master_name)
10024 In this case, collecting @code{$_sdata} collects the string
10025 @samp{hello $yourname}. When analyzing the trace buffer, you can
10026 inspect @samp{$_sdata} like any other variable available to
10030 You can give several consecutive @code{collect} commands, each one
10031 with a single argument, or one @code{collect} command with several
10032 arguments separated by commas; the effect is the same.
10034 The command @code{info scope} (@pxref{Symbols, info scope}) is
10035 particularly useful for figuring out what data to collect.
10037 @kindex teval @r{(tracepoints)}
10038 @item teval @var{expr1}, @var{expr2}, @dots{}
10039 Evaluate the given expressions when the tracepoint is hit. This
10040 command accepts a comma-separated list of expressions. The results
10041 are discarded, so this is mainly useful for assigning values to trace
10042 state variables (@pxref{Trace State Variables}) without adding those
10043 values to the trace buffer, as would be the case if the @code{collect}
10046 @kindex while-stepping @r{(tracepoints)}
10047 @item while-stepping @var{n}
10048 Perform @var{n} single-step instruction traces after the tracepoint,
10049 collecting new data after each step. The @code{while-stepping}
10050 command is followed by the list of what to collect while stepping
10051 (followed by its own @code{end} command):
10054 > while-stepping 12
10055 > collect $regs, myglobal
10061 Note that @code{$pc} is not automatically collected by
10062 @code{while-stepping}; you need to explicitly collect that register if
10063 you need it. You may abbreviate @code{while-stepping} as @code{ws} or
10066 @item set default-collect @var{expr1}, @var{expr2}, @dots{}
10067 @kindex set default-collect
10068 @cindex default collection action
10069 This variable is a list of expressions to collect at each tracepoint
10070 hit. It is effectively an additional @code{collect} action prepended
10071 to every tracepoint action list. The expressions are parsed
10072 individually for each tracepoint, so for instance a variable named
10073 @code{xyz} may be interpreted as a global for one tracepoint, and a
10074 local for another, as appropriate to the tracepoint's location.
10076 @item show default-collect
10077 @kindex show default-collect
10078 Show the list of expressions that are collected by default at each
10083 @node Listing Tracepoints
10084 @subsection Listing Tracepoints
10087 @kindex info tracepoints
10089 @cindex information about tracepoints
10090 @item info tracepoints @r{[}@var{num}@r{]}
10091 Display information about the tracepoint @var{num}. If you don't
10092 specify a tracepoint number, displays information about all the
10093 tracepoints defined so far. The format is similar to that used for
10094 @code{info breakpoints}; in fact, @code{info tracepoints} is the same
10095 command, simply restricting itself to tracepoints.
10097 A tracepoint's listing may include additional information specific to
10102 its passcount as given by the @code{passcount @var{n}} command
10106 (@value{GDBP}) @b{info trace}
10107 Num Type Disp Enb Address What
10108 1 tracepoint keep y 0x0804ab57 in foo() at main.cxx:7
10110 collect globfoo, $regs
10119 This command can be abbreviated @code{info tp}.
10122 @node Listing Static Tracepoint Markers
10123 @subsection Listing Static Tracepoint Markers
10126 @kindex info static-tracepoint-markers
10127 @cindex information about static tracepoint markers
10128 @item info static-tracepoint-markers
10129 Display information about all static tracepoint markers defined in the
10132 For each marker, the following columns are printed:
10136 An incrementing counter, output to help readability. This is not a
10139 The marker ID, as reported by the target.
10140 @item Enabled or Disabled
10141 Probed markers are tagged with @samp{y}. @samp{n} identifies marks
10142 that are not enabled.
10144 Where the marker is in your program, as a memory address.
10146 Where the marker is in the source for your program, as a file and line
10147 number. If the debug information included in the program does not
10148 allow @value{GDBN} to locate the source of the marker, this column
10149 will be left blank.
10153 In addition, the following information may be printed for each marker:
10157 User data passed to the tracing library by the marker call. In the
10158 UST backend, this is the format string passed as argument to the
10160 @item Static tracepoints probing the marker
10161 The list of static tracepoints attached to the marker.
10165 (@value{GDBP}) info static-tracepoint-markers
10166 Cnt ID Enb Address What
10167 1 ust/bar2 y 0x0000000000400e1a in main at stexample.c:25
10168 Data: number1 %d number2 %d
10169 Probed by static tracepoints: #2
10170 2 ust/bar33 n 0x0000000000400c87 in main at stexample.c:24
10176 @node Starting and Stopping Trace Experiments
10177 @subsection Starting and Stopping Trace Experiments
10181 @cindex start a new trace experiment
10182 @cindex collected data discarded
10184 This command takes no arguments. It starts the trace experiment, and
10185 begins collecting data. This has the side effect of discarding all
10186 the data collected in the trace buffer during the previous trace
10190 @cindex stop a running trace experiment
10192 This command takes no arguments. It ends the trace experiment, and
10193 stops collecting data.
10195 @strong{Note}: a trace experiment and data collection may stop
10196 automatically if any tracepoint's passcount is reached
10197 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
10200 @cindex status of trace data collection
10201 @cindex trace experiment, status of
10203 This command displays the status of the current trace data
10207 Here is an example of the commands we described so far:
10210 (@value{GDBP}) @b{trace gdb_c_test}
10211 (@value{GDBP}) @b{actions}
10212 Enter actions for tracepoint #1, one per line.
10213 > collect $regs,$locals,$args
10214 > while-stepping 11
10218 (@value{GDBP}) @b{tstart}
10219 [time passes @dots{}]
10220 (@value{GDBP}) @b{tstop}
10223 @cindex disconnected tracing
10224 You can choose to continue running the trace experiment even if
10225 @value{GDBN} disconnects from the target, voluntarily or
10226 involuntarily. For commands such as @code{detach}, the debugger will
10227 ask what you want to do with the trace. But for unexpected
10228 terminations (@value{GDBN} crash, network outage), it would be
10229 unfortunate to lose hard-won trace data, so the variable
10230 @code{disconnected-tracing} lets you decide whether the trace should
10231 continue running without @value{GDBN}.
10234 @item set disconnected-tracing on
10235 @itemx set disconnected-tracing off
10236 @kindex set disconnected-tracing
10237 Choose whether a tracing run should continue to run if @value{GDBN}
10238 has disconnected from the target. Note that @code{detach} or
10239 @code{quit} will ask you directly what to do about a running trace no
10240 matter what this variable's setting, so the variable is mainly useful
10241 for handling unexpected situations, such as loss of the network.
10243 @item show disconnected-tracing
10244 @kindex show disconnected-tracing
10245 Show the current choice for disconnected tracing.
10249 When you reconnect to the target, the trace experiment may or may not
10250 still be running; it might have filled the trace buffer in the
10251 meantime, or stopped for one of the other reasons. If it is running,
10252 it will continue after reconnection.
10254 Upon reconnection, the target will upload information about the
10255 tracepoints in effect. @value{GDBN} will then compare that
10256 information to the set of tracepoints currently defined, and attempt
10257 to match them up, allowing for the possibility that the numbers may
10258 have changed due to creation and deletion in the meantime. If one of
10259 the target's tracepoints does not match any in @value{GDBN}, the
10260 debugger will create a new tracepoint, so that you have a number with
10261 which to specify that tracepoint. This matching-up process is
10262 necessarily heuristic, and it may result in useless tracepoints being
10263 created; you may simply delete them if they are of no use.
10265 @cindex circular trace buffer
10266 If your target agent supports a @dfn{circular trace buffer}, then you
10267 can run a trace experiment indefinitely without filling the trace
10268 buffer; when space runs out, the agent deletes already-collected trace
10269 frames, oldest first, until there is enough room to continue
10270 collecting. This is especially useful if your tracepoints are being
10271 hit too often, and your trace gets terminated prematurely because the
10272 buffer is full. To ask for a circular trace buffer, simply set
10273 @samp{circular_trace_buffer} to on. You can set this at any time,
10274 including during tracing; if the agent can do it, it will change
10275 buffer handling on the fly, otherwise it will not take effect until
10279 @item set circular-trace-buffer on
10280 @itemx set circular-trace-buffer off
10281 @kindex set circular-trace-buffer
10282 Choose whether a tracing run should use a linear or circular buffer
10283 for trace data. A linear buffer will not lose any trace data, but may
10284 fill up prematurely, while a circular buffer will discard old trace
10285 data, but it will have always room for the latest tracepoint hits.
10287 @item show circular-trace-buffer
10288 @kindex show circular-trace-buffer
10289 Show the current choice for the trace buffer. Note that this may not
10290 match the agent's current buffer handling, nor is it guaranteed to
10291 match the setting that might have been in effect during a past run,
10292 for instance if you are looking at frames from a trace file.
10296 @node Tracepoint Restrictions
10297 @subsection Tracepoint Restrictions
10299 @cindex tracepoint restrictions
10300 There are a number of restrictions on the use of tracepoints. As
10301 described above, tracepoint data gathering occurs on the target
10302 without interaction from @value{GDBN}. Thus the full capabilities of
10303 the debugger are not available during data gathering, and then at data
10304 examination time, you will be limited by only having what was
10305 collected. The following items describe some common problems, but it
10306 is not exhaustive, and you may run into additional difficulties not
10312 Tracepoint expressions are intended to gather objects (lvalues). Thus
10313 the full flexibility of GDB's expression evaluator is not available.
10314 You cannot call functions, cast objects to aggregate types, access
10315 convenience variables or modify values (except by assignment to trace
10316 state variables). Some language features may implicitly call
10317 functions (for instance Objective-C fields with accessors), and therefore
10318 cannot be collected either.
10321 Collection of local variables, either individually or in bulk with
10322 @code{$locals} or @code{$args}, during @code{while-stepping} may
10323 behave erratically. The stepping action may enter a new scope (for
10324 instance by stepping into a function), or the location of the variable
10325 may change (for instance it is loaded into a register). The
10326 tracepoint data recorded uses the location information for the
10327 variables that is correct for the tracepoint location. When the
10328 tracepoint is created, it is not possible, in general, to determine
10329 where the steps of a @code{while-stepping} sequence will advance the
10330 program---particularly if a conditional branch is stepped.
10333 Collection of an incompletely-initialized or partially-destroyed object
10334 may result in something that @value{GDBN} cannot display, or displays
10335 in a misleading way.
10338 When @value{GDBN} displays a pointer to character it automatically
10339 dereferences the pointer to also display characters of the string
10340 being pointed to. However, collecting the pointer during tracing does
10341 not automatically collect the string. You need to explicitly
10342 dereference the pointer and provide size information if you want to
10343 collect not only the pointer, but the memory pointed to. For example,
10344 @code{*ptr@@50} can be used to collect the 50 element array pointed to
10348 It is not possible to collect a complete stack backtrace at a
10349 tracepoint. Instead, you may collect the registers and a few hundred
10350 bytes from the stack pointer with something like @code{*$esp@@300}
10351 (adjust to use the name of the actual stack pointer register on your
10352 target architecture, and the amount of stack you wish to capture).
10353 Then the @code{backtrace} command will show a partial backtrace when
10354 using a trace frame. The number of stack frames that can be examined
10355 depends on the sizes of the frames in the collected stack. Note that
10356 if you ask for a block so large that it goes past the bottom of the
10357 stack, the target agent may report an error trying to read from an
10361 If you do not collect registers at a tracepoint, @value{GDBN} can
10362 infer that the value of @code{$pc} must be the same as the address of
10363 the tracepoint and use that when you are looking at a trace frame
10364 for that tracepoint. However, this cannot work if the tracepoint has
10365 multiple locations (for instance if it was set in a function that was
10366 inlined), or if it has a @code{while-stepping} loop. In those cases
10367 @value{GDBN} will warn you that it can't infer @code{$pc}, and default
10372 @node Analyze Collected Data
10373 @section Using the Collected Data
10375 After the tracepoint experiment ends, you use @value{GDBN} commands
10376 for examining the trace data. The basic idea is that each tracepoint
10377 collects a trace @dfn{snapshot} every time it is hit and another
10378 snapshot every time it single-steps. All these snapshots are
10379 consecutively numbered from zero and go into a buffer, and you can
10380 examine them later. The way you examine them is to @dfn{focus} on a
10381 specific trace snapshot. When the remote stub is focused on a trace
10382 snapshot, it will respond to all @value{GDBN} requests for memory and
10383 registers by reading from the buffer which belongs to that snapshot,
10384 rather than from @emph{real} memory or registers of the program being
10385 debugged. This means that @strong{all} @value{GDBN} commands
10386 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
10387 behave as if we were currently debugging the program state as it was
10388 when the tracepoint occurred. Any requests for data that are not in
10389 the buffer will fail.
10392 * tfind:: How to select a trace snapshot
10393 * tdump:: How to display all data for a snapshot
10394 * save tracepoints:: How to save tracepoints for a future run
10398 @subsection @code{tfind @var{n}}
10401 @cindex select trace snapshot
10402 @cindex find trace snapshot
10403 The basic command for selecting a trace snapshot from the buffer is
10404 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
10405 counting from zero. If no argument @var{n} is given, the next
10406 snapshot is selected.
10408 Here are the various forms of using the @code{tfind} command.
10412 Find the first snapshot in the buffer. This is a synonym for
10413 @code{tfind 0} (since 0 is the number of the first snapshot).
10416 Stop debugging trace snapshots, resume @emph{live} debugging.
10419 Same as @samp{tfind none}.
10422 No argument means find the next trace snapshot.
10425 Find the previous trace snapshot before the current one. This permits
10426 retracing earlier steps.
10428 @item tfind tracepoint @var{num}
10429 Find the next snapshot associated with tracepoint @var{num}. Search
10430 proceeds forward from the last examined trace snapshot. If no
10431 argument @var{num} is given, it means find the next snapshot collected
10432 for the same tracepoint as the current snapshot.
10434 @item tfind pc @var{addr}
10435 Find the next snapshot associated with the value @var{addr} of the
10436 program counter. Search proceeds forward from the last examined trace
10437 snapshot. If no argument @var{addr} is given, it means find the next
10438 snapshot with the same value of PC as the current snapshot.
10440 @item tfind outside @var{addr1}, @var{addr2}
10441 Find the next snapshot whose PC is outside the given range of
10442 addresses (exclusive).
10444 @item tfind range @var{addr1}, @var{addr2}
10445 Find the next snapshot whose PC is between @var{addr1} and
10446 @var{addr2} (inclusive).
10448 @item tfind line @r{[}@var{file}:@r{]}@var{n}
10449 Find the next snapshot associated with the source line @var{n}. If
10450 the optional argument @var{file} is given, refer to line @var{n} in
10451 that source file. Search proceeds forward from the last examined
10452 trace snapshot. If no argument @var{n} is given, it means find the
10453 next line other than the one currently being examined; thus saying
10454 @code{tfind line} repeatedly can appear to have the same effect as
10455 stepping from line to line in a @emph{live} debugging session.
10458 The default arguments for the @code{tfind} commands are specifically
10459 designed to make it easy to scan through the trace buffer. For
10460 instance, @code{tfind} with no argument selects the next trace
10461 snapshot, and @code{tfind -} with no argument selects the previous
10462 trace snapshot. So, by giving one @code{tfind} command, and then
10463 simply hitting @key{RET} repeatedly you can examine all the trace
10464 snapshots in order. Or, by saying @code{tfind -} and then hitting
10465 @key{RET} repeatedly you can examine the snapshots in reverse order.
10466 The @code{tfind line} command with no argument selects the snapshot
10467 for the next source line executed. The @code{tfind pc} command with
10468 no argument selects the next snapshot with the same program counter
10469 (PC) as the current frame. The @code{tfind tracepoint} command with
10470 no argument selects the next trace snapshot collected by the same
10471 tracepoint as the current one.
10473 In addition to letting you scan through the trace buffer manually,
10474 these commands make it easy to construct @value{GDBN} scripts that
10475 scan through the trace buffer and print out whatever collected data
10476 you are interested in. Thus, if we want to examine the PC, FP, and SP
10477 registers from each trace frame in the buffer, we can say this:
10480 (@value{GDBP}) @b{tfind start}
10481 (@value{GDBP}) @b{while ($trace_frame != -1)}
10482 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
10483 $trace_frame, $pc, $sp, $fp
10487 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
10488 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
10489 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
10490 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
10491 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
10492 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
10493 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
10494 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
10495 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
10496 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
10497 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
10500 Or, if we want to examine the variable @code{X} at each source line in
10504 (@value{GDBP}) @b{tfind start}
10505 (@value{GDBP}) @b{while ($trace_frame != -1)}
10506 > printf "Frame %d, X == %d\n", $trace_frame, X
10516 @subsection @code{tdump}
10518 @cindex dump all data collected at tracepoint
10519 @cindex tracepoint data, display
10521 This command takes no arguments. It prints all the data collected at
10522 the current trace snapshot.
10525 (@value{GDBP}) @b{trace 444}
10526 (@value{GDBP}) @b{actions}
10527 Enter actions for tracepoint #2, one per line:
10528 > collect $regs, $locals, $args, gdb_long_test
10531 (@value{GDBP}) @b{tstart}
10533 (@value{GDBP}) @b{tfind line 444}
10534 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
10536 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
10538 (@value{GDBP}) @b{tdump}
10539 Data collected at tracepoint 2, trace frame 1:
10540 d0 0xc4aa0085 -995491707
10544 d4 0x71aea3d 119204413
10547 d7 0x380035 3670069
10548 a0 0x19e24a 1696330
10549 a1 0x3000668 50333288
10551 a3 0x322000 3284992
10552 a4 0x3000698 50333336
10553 a5 0x1ad3cc 1758156
10554 fp 0x30bf3c 0x30bf3c
10555 sp 0x30bf34 0x30bf34
10557 pc 0x20b2c8 0x20b2c8
10561 p = 0x20e5b4 "gdb-test"
10568 gdb_long_test = 17 '\021'
10573 @code{tdump} works by scanning the tracepoint's current collection
10574 actions and printing the value of each expression listed. So
10575 @code{tdump} can fail, if after a run, you change the tracepoint's
10576 actions to mention variables that were not collected during the run.
10578 Also, for tracepoints with @code{while-stepping} loops, @code{tdump}
10579 uses the collected value of @code{$pc} to distinguish between trace
10580 frames that were collected at the tracepoint hit, and frames that were
10581 collected while stepping. This allows it to correctly choose whether
10582 to display the basic list of collections, or the collections from the
10583 body of the while-stepping loop. However, if @code{$pc} was not collected,
10584 then @code{tdump} will always attempt to dump using the basic collection
10585 list, and may fail if a while-stepping frame does not include all the
10586 same data that is collected at the tracepoint hit.
10587 @c This is getting pretty arcane, example would be good.
10589 @node save tracepoints
10590 @subsection @code{save tracepoints @var{filename}}
10591 @kindex save tracepoints
10592 @kindex save-tracepoints
10593 @cindex save tracepoints for future sessions
10595 This command saves all current tracepoint definitions together with
10596 their actions and passcounts, into a file @file{@var{filename}}
10597 suitable for use in a later debugging session. To read the saved
10598 tracepoint definitions, use the @code{source} command (@pxref{Command
10599 Files}). The @w{@code{save-tracepoints}} command is a deprecated
10600 alias for @w{@code{save tracepoints}}
10602 @node Tracepoint Variables
10603 @section Convenience Variables for Tracepoints
10604 @cindex tracepoint variables
10605 @cindex convenience variables for tracepoints
10608 @vindex $trace_frame
10609 @item (int) $trace_frame
10610 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
10611 snapshot is selected.
10613 @vindex $tracepoint
10614 @item (int) $tracepoint
10615 The tracepoint for the current trace snapshot.
10617 @vindex $trace_line
10618 @item (int) $trace_line
10619 The line number for the current trace snapshot.
10621 @vindex $trace_file
10622 @item (char []) $trace_file
10623 The source file for the current trace snapshot.
10625 @vindex $trace_func
10626 @item (char []) $trace_func
10627 The name of the function containing @code{$tracepoint}.
10630 Note: @code{$trace_file} is not suitable for use in @code{printf},
10631 use @code{output} instead.
10633 Here's a simple example of using these convenience variables for
10634 stepping through all the trace snapshots and printing some of their
10635 data. Note that these are not the same as trace state variables,
10636 which are managed by the target.
10639 (@value{GDBP}) @b{tfind start}
10641 (@value{GDBP}) @b{while $trace_frame != -1}
10642 > output $trace_file
10643 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
10649 @section Using Trace Files
10650 @cindex trace files
10652 In some situations, the target running a trace experiment may no
10653 longer be available; perhaps it crashed, or the hardware was needed
10654 for a different activity. To handle these cases, you can arrange to
10655 dump the trace data into a file, and later use that file as a source
10656 of trace data, via the @code{target tfile} command.
10661 @item tsave [ -r ] @var{filename}
10662 Save the trace data to @var{filename}. By default, this command
10663 assumes that @var{filename} refers to the host filesystem, so if
10664 necessary @value{GDBN} will copy raw trace data up from the target and
10665 then save it. If the target supports it, you can also supply the
10666 optional argument @code{-r} (``remote'') to direct the target to save
10667 the data directly into @var{filename} in its own filesystem, which may be
10668 more efficient if the trace buffer is very large. (Note, however, that
10669 @code{target tfile} can only read from files accessible to the host.)
10671 @kindex target tfile
10673 @item target tfile @var{filename}
10674 Use the file named @var{filename} as a source of trace data. Commands
10675 that examine data work as they do with a live target, but it is not
10676 possible to run any new trace experiments. @code{tstatus} will report
10677 the state of the trace run at the moment the data was saved, as well
10678 as the current trace frame you are examining. @var{filename} must be
10679 on a filesystem accessible to the host.
10684 @chapter Debugging Programs That Use Overlays
10687 If your program is too large to fit completely in your target system's
10688 memory, you can sometimes use @dfn{overlays} to work around this
10689 problem. @value{GDBN} provides some support for debugging programs that
10693 * How Overlays Work:: A general explanation of overlays.
10694 * Overlay Commands:: Managing overlays in @value{GDBN}.
10695 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
10696 mapped by asking the inferior.
10697 * Overlay Sample Program:: A sample program using overlays.
10700 @node How Overlays Work
10701 @section How Overlays Work
10702 @cindex mapped overlays
10703 @cindex unmapped overlays
10704 @cindex load address, overlay's
10705 @cindex mapped address
10706 @cindex overlay area
10708 Suppose you have a computer whose instruction address space is only 64
10709 kilobytes long, but which has much more memory which can be accessed by
10710 other means: special instructions, segment registers, or memory
10711 management hardware, for example. Suppose further that you want to
10712 adapt a program which is larger than 64 kilobytes to run on this system.
10714 One solution is to identify modules of your program which are relatively
10715 independent, and need not call each other directly; call these modules
10716 @dfn{overlays}. Separate the overlays from the main program, and place
10717 their machine code in the larger memory. Place your main program in
10718 instruction memory, but leave at least enough space there to hold the
10719 largest overlay as well.
10721 Now, to call a function located in an overlay, you must first copy that
10722 overlay's machine code from the large memory into the space set aside
10723 for it in the instruction memory, and then jump to its entry point
10726 @c NB: In the below the mapped area's size is greater or equal to the
10727 @c size of all overlays. This is intentional to remind the developer
10728 @c that overlays don't necessarily need to be the same size.
10732 Data Instruction Larger
10733 Address Space Address Space Address Space
10734 +-----------+ +-----------+ +-----------+
10736 +-----------+ +-----------+ +-----------+<-- overlay 1
10737 | program | | main | .----| overlay 1 | load address
10738 | variables | | program | | +-----------+
10739 | and heap | | | | | |
10740 +-----------+ | | | +-----------+<-- overlay 2
10741 | | +-----------+ | | | load address
10742 +-----------+ | | | .-| overlay 2 |
10744 mapped --->+-----------+ | | +-----------+
10745 address | | | | | |
10746 | overlay | <-' | | |
10747 | area | <---' +-----------+<-- overlay 3
10748 | | <---. | | load address
10749 +-----------+ `--| overlay 3 |
10756 @anchor{A code overlay}A code overlay
10760 The diagram (@pxref{A code overlay}) shows a system with separate data
10761 and instruction address spaces. To map an overlay, the program copies
10762 its code from the larger address space to the instruction address space.
10763 Since the overlays shown here all use the same mapped address, only one
10764 may be mapped at a time. For a system with a single address space for
10765 data and instructions, the diagram would be similar, except that the
10766 program variables and heap would share an address space with the main
10767 program and the overlay area.
10769 An overlay loaded into instruction memory and ready for use is called a
10770 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
10771 instruction memory. An overlay not present (or only partially present)
10772 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
10773 is its address in the larger memory. The mapped address is also called
10774 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
10775 called the @dfn{load memory address}, or @dfn{LMA}.
10777 Unfortunately, overlays are not a completely transparent way to adapt a
10778 program to limited instruction memory. They introduce a new set of
10779 global constraints you must keep in mind as you design your program:
10784 Before calling or returning to a function in an overlay, your program
10785 must make sure that overlay is actually mapped. Otherwise, the call or
10786 return will transfer control to the right address, but in the wrong
10787 overlay, and your program will probably crash.
10790 If the process of mapping an overlay is expensive on your system, you
10791 will need to choose your overlays carefully to minimize their effect on
10792 your program's performance.
10795 The executable file you load onto your system must contain each
10796 overlay's instructions, appearing at the overlay's load address, not its
10797 mapped address. However, each overlay's instructions must be relocated
10798 and its symbols defined as if the overlay were at its mapped address.
10799 You can use GNU linker scripts to specify different load and relocation
10800 addresses for pieces of your program; see @ref{Overlay Description,,,
10801 ld.info, Using ld: the GNU linker}.
10804 The procedure for loading executable files onto your system must be able
10805 to load their contents into the larger address space as well as the
10806 instruction and data spaces.
10810 The overlay system described above is rather simple, and could be
10811 improved in many ways:
10816 If your system has suitable bank switch registers or memory management
10817 hardware, you could use those facilities to make an overlay's load area
10818 contents simply appear at their mapped address in instruction space.
10819 This would probably be faster than copying the overlay to its mapped
10820 area in the usual way.
10823 If your overlays are small enough, you could set aside more than one
10824 overlay area, and have more than one overlay mapped at a time.
10827 You can use overlays to manage data, as well as instructions. In
10828 general, data overlays are even less transparent to your design than
10829 code overlays: whereas code overlays only require care when you call or
10830 return to functions, data overlays require care every time you access
10831 the data. Also, if you change the contents of a data overlay, you
10832 must copy its contents back out to its load address before you can copy a
10833 different data overlay into the same mapped area.
10838 @node Overlay Commands
10839 @section Overlay Commands
10841 To use @value{GDBN}'s overlay support, each overlay in your program must
10842 correspond to a separate section of the executable file. The section's
10843 virtual memory address and load memory address must be the overlay's
10844 mapped and load addresses. Identifying overlays with sections allows
10845 @value{GDBN} to determine the appropriate address of a function or
10846 variable, depending on whether the overlay is mapped or not.
10848 @value{GDBN}'s overlay commands all start with the word @code{overlay};
10849 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
10854 Disable @value{GDBN}'s overlay support. When overlay support is
10855 disabled, @value{GDBN} assumes that all functions and variables are
10856 always present at their mapped addresses. By default, @value{GDBN}'s
10857 overlay support is disabled.
10859 @item overlay manual
10860 @cindex manual overlay debugging
10861 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
10862 relies on you to tell it which overlays are mapped, and which are not,
10863 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
10864 commands described below.
10866 @item overlay map-overlay @var{overlay}
10867 @itemx overlay map @var{overlay}
10868 @cindex map an overlay
10869 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
10870 be the name of the object file section containing the overlay. When an
10871 overlay is mapped, @value{GDBN} assumes it can find the overlay's
10872 functions and variables at their mapped addresses. @value{GDBN} assumes
10873 that any other overlays whose mapped ranges overlap that of
10874 @var{overlay} are now unmapped.
10876 @item overlay unmap-overlay @var{overlay}
10877 @itemx overlay unmap @var{overlay}
10878 @cindex unmap an overlay
10879 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
10880 must be the name of the object file section containing the overlay.
10881 When an overlay is unmapped, @value{GDBN} assumes it can find the
10882 overlay's functions and variables at their load addresses.
10885 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
10886 consults a data structure the overlay manager maintains in the inferior
10887 to see which overlays are mapped. For details, see @ref{Automatic
10888 Overlay Debugging}.
10890 @item overlay load-target
10891 @itemx overlay load
10892 @cindex reloading the overlay table
10893 Re-read the overlay table from the inferior. Normally, @value{GDBN}
10894 re-reads the table @value{GDBN} automatically each time the inferior
10895 stops, so this command should only be necessary if you have changed the
10896 overlay mapping yourself using @value{GDBN}. This command is only
10897 useful when using automatic overlay debugging.
10899 @item overlay list-overlays
10900 @itemx overlay list
10901 @cindex listing mapped overlays
10902 Display a list of the overlays currently mapped, along with their mapped
10903 addresses, load addresses, and sizes.
10907 Normally, when @value{GDBN} prints a code address, it includes the name
10908 of the function the address falls in:
10911 (@value{GDBP}) print main
10912 $3 = @{int ()@} 0x11a0 <main>
10915 When overlay debugging is enabled, @value{GDBN} recognizes code in
10916 unmapped overlays, and prints the names of unmapped functions with
10917 asterisks around them. For example, if @code{foo} is a function in an
10918 unmapped overlay, @value{GDBN} prints it this way:
10921 (@value{GDBP}) overlay list
10922 No sections are mapped.
10923 (@value{GDBP}) print foo
10924 $5 = @{int (int)@} 0x100000 <*foo*>
10927 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
10931 (@value{GDBP}) overlay list
10932 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
10933 mapped at 0x1016 - 0x104a
10934 (@value{GDBP}) print foo
10935 $6 = @{int (int)@} 0x1016 <foo>
10938 When overlay debugging is enabled, @value{GDBN} can find the correct
10939 address for functions and variables in an overlay, whether or not the
10940 overlay is mapped. This allows most @value{GDBN} commands, like
10941 @code{break} and @code{disassemble}, to work normally, even on unmapped
10942 code. However, @value{GDBN}'s breakpoint support has some limitations:
10946 @cindex breakpoints in overlays
10947 @cindex overlays, setting breakpoints in
10948 You can set breakpoints in functions in unmapped overlays, as long as
10949 @value{GDBN} can write to the overlay at its load address.
10951 @value{GDBN} can not set hardware or simulator-based breakpoints in
10952 unmapped overlays. However, if you set a breakpoint at the end of your
10953 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
10954 you are using manual overlay management), @value{GDBN} will re-set its
10955 breakpoints properly.
10959 @node Automatic Overlay Debugging
10960 @section Automatic Overlay Debugging
10961 @cindex automatic overlay debugging
10963 @value{GDBN} can automatically track which overlays are mapped and which
10964 are not, given some simple co-operation from the overlay manager in the
10965 inferior. If you enable automatic overlay debugging with the
10966 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
10967 looks in the inferior's memory for certain variables describing the
10968 current state of the overlays.
10970 Here are the variables your overlay manager must define to support
10971 @value{GDBN}'s automatic overlay debugging:
10975 @item @code{_ovly_table}:
10976 This variable must be an array of the following structures:
10981 /* The overlay's mapped address. */
10984 /* The size of the overlay, in bytes. */
10985 unsigned long size;
10987 /* The overlay's load address. */
10990 /* Non-zero if the overlay is currently mapped;
10992 unsigned long mapped;
10996 @item @code{_novlys}:
10997 This variable must be a four-byte signed integer, holding the total
10998 number of elements in @code{_ovly_table}.
11002 To decide whether a particular overlay is mapped or not, @value{GDBN}
11003 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
11004 @code{lma} members equal the VMA and LMA of the overlay's section in the
11005 executable file. When @value{GDBN} finds a matching entry, it consults
11006 the entry's @code{mapped} member to determine whether the overlay is
11009 In addition, your overlay manager may define a function called
11010 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
11011 will silently set a breakpoint there. If the overlay manager then
11012 calls this function whenever it has changed the overlay table, this
11013 will enable @value{GDBN} to accurately keep track of which overlays
11014 are in program memory, and update any breakpoints that may be set
11015 in overlays. This will allow breakpoints to work even if the
11016 overlays are kept in ROM or other non-writable memory while they
11017 are not being executed.
11019 @node Overlay Sample Program
11020 @section Overlay Sample Program
11021 @cindex overlay example program
11023 When linking a program which uses overlays, you must place the overlays
11024 at their load addresses, while relocating them to run at their mapped
11025 addresses. To do this, you must write a linker script (@pxref{Overlay
11026 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
11027 since linker scripts are specific to a particular host system, target
11028 architecture, and target memory layout, this manual cannot provide
11029 portable sample code demonstrating @value{GDBN}'s overlay support.
11031 However, the @value{GDBN} source distribution does contain an overlaid
11032 program, with linker scripts for a few systems, as part of its test
11033 suite. The program consists of the following files from
11034 @file{gdb/testsuite/gdb.base}:
11038 The main program file.
11040 A simple overlay manager, used by @file{overlays.c}.
11045 Overlay modules, loaded and used by @file{overlays.c}.
11048 Linker scripts for linking the test program on the @code{d10v-elf}
11049 and @code{m32r-elf} targets.
11052 You can build the test program using the @code{d10v-elf} GCC
11053 cross-compiler like this:
11056 $ d10v-elf-gcc -g -c overlays.c
11057 $ d10v-elf-gcc -g -c ovlymgr.c
11058 $ d10v-elf-gcc -g -c foo.c
11059 $ d10v-elf-gcc -g -c bar.c
11060 $ d10v-elf-gcc -g -c baz.c
11061 $ d10v-elf-gcc -g -c grbx.c
11062 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
11063 baz.o grbx.o -Wl,-Td10v.ld -o overlays
11066 The build process is identical for any other architecture, except that
11067 you must substitute the appropriate compiler and linker script for the
11068 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
11072 @chapter Using @value{GDBN} with Different Languages
11075 Although programming languages generally have common aspects, they are
11076 rarely expressed in the same manner. For instance, in ANSI C,
11077 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
11078 Modula-2, it is accomplished by @code{p^}. Values can also be
11079 represented (and displayed) differently. Hex numbers in C appear as
11080 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
11082 @cindex working language
11083 Language-specific information is built into @value{GDBN} for some languages,
11084 allowing you to express operations like the above in your program's
11085 native language, and allowing @value{GDBN} to output values in a manner
11086 consistent with the syntax of your program's native language. The
11087 language you use to build expressions is called the @dfn{working
11091 * Setting:: Switching between source languages
11092 * Show:: Displaying the language
11093 * Checks:: Type and range checks
11094 * Supported Languages:: Supported languages
11095 * Unsupported Languages:: Unsupported languages
11099 @section Switching Between Source Languages
11101 There are two ways to control the working language---either have @value{GDBN}
11102 set it automatically, or select it manually yourself. You can use the
11103 @code{set language} command for either purpose. On startup, @value{GDBN}
11104 defaults to setting the language automatically. The working language is
11105 used to determine how expressions you type are interpreted, how values
11108 In addition to the working language, every source file that
11109 @value{GDBN} knows about has its own working language. For some object
11110 file formats, the compiler might indicate which language a particular
11111 source file is in. However, most of the time @value{GDBN} infers the
11112 language from the name of the file. The language of a source file
11113 controls whether C@t{++} names are demangled---this way @code{backtrace} can
11114 show each frame appropriately for its own language. There is no way to
11115 set the language of a source file from within @value{GDBN}, but you can
11116 set the language associated with a filename extension. @xref{Show, ,
11117 Displaying the Language}.
11119 This is most commonly a problem when you use a program, such
11120 as @code{cfront} or @code{f2c}, that generates C but is written in
11121 another language. In that case, make the
11122 program use @code{#line} directives in its C output; that way
11123 @value{GDBN} will know the correct language of the source code of the original
11124 program, and will display that source code, not the generated C code.
11127 * Filenames:: Filename extensions and languages.
11128 * Manually:: Setting the working language manually
11129 * Automatically:: Having @value{GDBN} infer the source language
11133 @subsection List of Filename Extensions and Languages
11135 If a source file name ends in one of the following extensions, then
11136 @value{GDBN} infers that its language is the one indicated.
11154 C@t{++} source file
11160 Objective-C source file
11164 Fortran source file
11167 Modula-2 source file
11171 Assembler source file. This actually behaves almost like C, but
11172 @value{GDBN} does not skip over function prologues when stepping.
11175 In addition, you may set the language associated with a filename
11176 extension. @xref{Show, , Displaying the Language}.
11179 @subsection Setting the Working Language
11181 If you allow @value{GDBN} to set the language automatically,
11182 expressions are interpreted the same way in your debugging session and
11185 @kindex set language
11186 If you wish, you may set the language manually. To do this, issue the
11187 command @samp{set language @var{lang}}, where @var{lang} is the name of
11188 a language, such as
11189 @code{c} or @code{modula-2}.
11190 For a list of the supported languages, type @samp{set language}.
11192 Setting the language manually prevents @value{GDBN} from updating the working
11193 language automatically. This can lead to confusion if you try
11194 to debug a program when the working language is not the same as the
11195 source language, when an expression is acceptable to both
11196 languages---but means different things. For instance, if the current
11197 source file were written in C, and @value{GDBN} was parsing Modula-2, a
11205 might not have the effect you intended. In C, this means to add
11206 @code{b} and @code{c} and place the result in @code{a}. The result
11207 printed would be the value of @code{a}. In Modula-2, this means to compare
11208 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
11210 @node Automatically
11211 @subsection Having @value{GDBN} Infer the Source Language
11213 To have @value{GDBN} set the working language automatically, use
11214 @samp{set language local} or @samp{set language auto}. @value{GDBN}
11215 then infers the working language. That is, when your program stops in a
11216 frame (usually by encountering a breakpoint), @value{GDBN} sets the
11217 working language to the language recorded for the function in that
11218 frame. If the language for a frame is unknown (that is, if the function
11219 or block corresponding to the frame was defined in a source file that
11220 does not have a recognized extension), the current working language is
11221 not changed, and @value{GDBN} issues a warning.
11223 This may not seem necessary for most programs, which are written
11224 entirely in one source language. However, program modules and libraries
11225 written in one source language can be used by a main program written in
11226 a different source language. Using @samp{set language auto} in this
11227 case frees you from having to set the working language manually.
11230 @section Displaying the Language
11232 The following commands help you find out which language is the
11233 working language, and also what language source files were written in.
11236 @item show language
11237 @kindex show language
11238 Display the current working language. This is the
11239 language you can use with commands such as @code{print} to
11240 build and compute expressions that may involve variables in your program.
11243 @kindex info frame@r{, show the source language}
11244 Display the source language for this frame. This language becomes the
11245 working language if you use an identifier from this frame.
11246 @xref{Frame Info, ,Information about a Frame}, to identify the other
11247 information listed here.
11250 @kindex info source@r{, show the source language}
11251 Display the source language of this source file.
11252 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
11253 information listed here.
11256 In unusual circumstances, you may have source files with extensions
11257 not in the standard list. You can then set the extension associated
11258 with a language explicitly:
11261 @item set extension-language @var{ext} @var{language}
11262 @kindex set extension-language
11263 Tell @value{GDBN} that source files with extension @var{ext} are to be
11264 assumed as written in the source language @var{language}.
11266 @item info extensions
11267 @kindex info extensions
11268 List all the filename extensions and the associated languages.
11272 @section Type and Range Checking
11275 @emph{Warning:} In this release, the @value{GDBN} commands for type and range
11276 checking are included, but they do not yet have any effect. This
11277 section documents the intended facilities.
11279 @c FIXME remove warning when type/range code added
11281 Some languages are designed to guard you against making seemingly common
11282 errors through a series of compile- and run-time checks. These include
11283 checking the type of arguments to functions and operators, and making
11284 sure mathematical overflows are caught at run time. Checks such as
11285 these help to ensure a program's correctness once it has been compiled
11286 by eliminating type mismatches, and providing active checks for range
11287 errors when your program is running.
11289 @value{GDBN} can check for conditions like the above if you wish.
11290 Although @value{GDBN} does not check the statements in your program,
11291 it can check expressions entered directly into @value{GDBN} for
11292 evaluation via the @code{print} command, for example. As with the
11293 working language, @value{GDBN} can also decide whether or not to check
11294 automatically based on your program's source language.
11295 @xref{Supported Languages, ,Supported Languages}, for the default
11296 settings of supported languages.
11299 * Type Checking:: An overview of type checking
11300 * Range Checking:: An overview of range checking
11303 @cindex type checking
11304 @cindex checks, type
11305 @node Type Checking
11306 @subsection An Overview of Type Checking
11308 Some languages, such as Modula-2, are strongly typed, meaning that the
11309 arguments to operators and functions have to be of the correct type,
11310 otherwise an error occurs. These checks prevent type mismatch
11311 errors from ever causing any run-time problems. For example,
11319 The second example fails because the @code{CARDINAL} 1 is not
11320 type-compatible with the @code{REAL} 2.3.
11322 For the expressions you use in @value{GDBN} commands, you can tell the
11323 @value{GDBN} type checker to skip checking;
11324 to treat any mismatches as errors and abandon the expression;
11325 or to only issue warnings when type mismatches occur,
11326 but evaluate the expression anyway. When you choose the last of
11327 these, @value{GDBN} evaluates expressions like the second example above, but
11328 also issues a warning.
11330 Even if you turn type checking off, there may be other reasons
11331 related to type that prevent @value{GDBN} from evaluating an expression.
11332 For instance, @value{GDBN} does not know how to add an @code{int} and
11333 a @code{struct foo}. These particular type errors have nothing to do
11334 with the language in use, and usually arise from expressions, such as
11335 the one described above, which make little sense to evaluate anyway.
11337 Each language defines to what degree it is strict about type. For
11338 instance, both Modula-2 and C require the arguments to arithmetical
11339 operators to be numbers. In C, enumerated types and pointers can be
11340 represented as numbers, so that they are valid arguments to mathematical
11341 operators. @xref{Supported Languages, ,Supported Languages}, for further
11342 details on specific languages.
11344 @value{GDBN} provides some additional commands for controlling the type checker:
11346 @kindex set check type
11347 @kindex show check type
11349 @item set check type auto
11350 Set type checking on or off based on the current working language.
11351 @xref{Supported Languages, ,Supported Languages}, for the default settings for
11354 @item set check type on
11355 @itemx set check type off
11356 Set type checking on or off, overriding the default setting for the
11357 current working language. Issue a warning if the setting does not
11358 match the language default. If any type mismatches occur in
11359 evaluating an expression while type checking is on, @value{GDBN} prints a
11360 message and aborts evaluation of the expression.
11362 @item set check type warn
11363 Cause the type checker to issue warnings, but to always attempt to
11364 evaluate the expression. Evaluating the expression may still
11365 be impossible for other reasons. For example, @value{GDBN} cannot add
11366 numbers and structures.
11369 Show the current setting of the type checker, and whether or not @value{GDBN}
11370 is setting it automatically.
11373 @cindex range checking
11374 @cindex checks, range
11375 @node Range Checking
11376 @subsection An Overview of Range Checking
11378 In some languages (such as Modula-2), it is an error to exceed the
11379 bounds of a type; this is enforced with run-time checks. Such range
11380 checking is meant to ensure program correctness by making sure
11381 computations do not overflow, or indices on an array element access do
11382 not exceed the bounds of the array.
11384 For expressions you use in @value{GDBN} commands, you can tell
11385 @value{GDBN} to treat range errors in one of three ways: ignore them,
11386 always treat them as errors and abandon the expression, or issue
11387 warnings but evaluate the expression anyway.
11389 A range error can result from numerical overflow, from exceeding an
11390 array index bound, or when you type a constant that is not a member
11391 of any type. Some languages, however, do not treat overflows as an
11392 error. In many implementations of C, mathematical overflow causes the
11393 result to ``wrap around'' to lower values---for example, if @var{m} is
11394 the largest integer value, and @var{s} is the smallest, then
11397 @var{m} + 1 @result{} @var{s}
11400 This, too, is specific to individual languages, and in some cases
11401 specific to individual compilers or machines. @xref{Supported Languages, ,
11402 Supported Languages}, for further details on specific languages.
11404 @value{GDBN} provides some additional commands for controlling the range checker:
11406 @kindex set check range
11407 @kindex show check range
11409 @item set check range auto
11410 Set range checking on or off based on the current working language.
11411 @xref{Supported Languages, ,Supported Languages}, for the default settings for
11414 @item set check range on
11415 @itemx set check range off
11416 Set range checking on or off, overriding the default setting for the
11417 current working language. A warning is issued if the setting does not
11418 match the language default. If a range error occurs and range checking is on,
11419 then a message is printed and evaluation of the expression is aborted.
11421 @item set check range warn
11422 Output messages when the @value{GDBN} range checker detects a range error,
11423 but attempt to evaluate the expression anyway. Evaluating the
11424 expression may still be impossible for other reasons, such as accessing
11425 memory that the process does not own (a typical example from many Unix
11429 Show the current setting of the range checker, and whether or not it is
11430 being set automatically by @value{GDBN}.
11433 @node Supported Languages
11434 @section Supported Languages
11436 @value{GDBN} supports C, C@t{++}, D, Objective-C, Fortran, Java, Pascal,
11437 assembly, Modula-2, and Ada.
11438 @c This is false ...
11439 Some @value{GDBN} features may be used in expressions regardless of the
11440 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
11441 and the @samp{@{type@}addr} construct (@pxref{Expressions,
11442 ,Expressions}) can be used with the constructs of any supported
11445 The following sections detail to what degree each source language is
11446 supported by @value{GDBN}. These sections are not meant to be language
11447 tutorials or references, but serve only as a reference guide to what the
11448 @value{GDBN} expression parser accepts, and what input and output
11449 formats should look like for different languages. There are many good
11450 books written on each of these languages; please look to these for a
11451 language reference or tutorial.
11454 * C:: C and C@t{++}
11456 * Objective-C:: Objective-C
11457 * Fortran:: Fortran
11459 * Modula-2:: Modula-2
11464 @subsection C and C@t{++}
11466 @cindex C and C@t{++}
11467 @cindex expressions in C or C@t{++}
11469 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
11470 to both languages. Whenever this is the case, we discuss those languages
11474 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
11475 @cindex @sc{gnu} C@t{++}
11476 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
11477 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
11478 effectively, you must compile your C@t{++} programs with a supported
11479 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
11480 compiler (@code{aCC}).
11482 For best results when using @sc{gnu} C@t{++}, use the DWARF 2 debugging
11483 format; if it doesn't work on your system, try the stabs+ debugging
11484 format. You can select those formats explicitly with the @code{g++}
11485 command-line options @option{-gdwarf-2} and @option{-gstabs+}.
11486 @xref{Debugging Options,,Options for Debugging Your Program or GCC,
11487 gcc.info, Using the @sc{gnu} Compiler Collection (GCC)}.
11490 * C Operators:: C and C@t{++} operators
11491 * C Constants:: C and C@t{++} constants
11492 * C Plus Plus Expressions:: C@t{++} expressions
11493 * C Defaults:: Default settings for C and C@t{++}
11494 * C Checks:: C and C@t{++} type and range checks
11495 * Debugging C:: @value{GDBN} and C
11496 * Debugging C Plus Plus:: @value{GDBN} features for C@t{++}
11497 * Decimal Floating Point:: Numbers in Decimal Floating Point format
11501 @subsubsection C and C@t{++} Operators
11503 @cindex C and C@t{++} operators
11505 Operators must be defined on values of specific types. For instance,
11506 @code{+} is defined on numbers, but not on structures. Operators are
11507 often defined on groups of types.
11509 For the purposes of C and C@t{++}, the following definitions hold:
11514 @emph{Integral types} include @code{int} with any of its storage-class
11515 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
11518 @emph{Floating-point types} include @code{float}, @code{double}, and
11519 @code{long double} (if supported by the target platform).
11522 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
11525 @emph{Scalar types} include all of the above.
11530 The following operators are supported. They are listed here
11531 in order of increasing precedence:
11535 The comma or sequencing operator. Expressions in a comma-separated list
11536 are evaluated from left to right, with the result of the entire
11537 expression being the last expression evaluated.
11540 Assignment. The value of an assignment expression is the value
11541 assigned. Defined on scalar types.
11544 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
11545 and translated to @w{@code{@var{a} = @var{a op b}}}.
11546 @w{@code{@var{op}=}} and @code{=} have the same precedence.
11547 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
11548 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
11551 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
11552 of as: if @var{a} then @var{b} else @var{c}. @var{a} should be of an
11556 Logical @sc{or}. Defined on integral types.
11559 Logical @sc{and}. Defined on integral types.
11562 Bitwise @sc{or}. Defined on integral types.
11565 Bitwise exclusive-@sc{or}. Defined on integral types.
11568 Bitwise @sc{and}. Defined on integral types.
11571 Equality and inequality. Defined on scalar types. The value of these
11572 expressions is 0 for false and non-zero for true.
11574 @item <@r{, }>@r{, }<=@r{, }>=
11575 Less than, greater than, less than or equal, greater than or equal.
11576 Defined on scalar types. The value of these expressions is 0 for false
11577 and non-zero for true.
11580 left shift, and right shift. Defined on integral types.
11583 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
11586 Addition and subtraction. Defined on integral types, floating-point types and
11589 @item *@r{, }/@r{, }%
11590 Multiplication, division, and modulus. Multiplication and division are
11591 defined on integral and floating-point types. Modulus is defined on
11595 Increment and decrement. When appearing before a variable, the
11596 operation is performed before the variable is used in an expression;
11597 when appearing after it, the variable's value is used before the
11598 operation takes place.
11601 Pointer dereferencing. Defined on pointer types. Same precedence as
11605 Address operator. Defined on variables. Same precedence as @code{++}.
11607 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
11608 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
11609 to examine the address
11610 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
11614 Negative. Defined on integral and floating-point types. Same
11615 precedence as @code{++}.
11618 Logical negation. Defined on integral types. Same precedence as
11622 Bitwise complement operator. Defined on integral types. Same precedence as
11627 Structure member, and pointer-to-structure member. For convenience,
11628 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
11629 pointer based on the stored type information.
11630 Defined on @code{struct} and @code{union} data.
11633 Dereferences of pointers to members.
11636 Array indexing. @code{@var{a}[@var{i}]} is defined as
11637 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
11640 Function parameter list. Same precedence as @code{->}.
11643 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
11644 and @code{class} types.
11647 Doubled colons also represent the @value{GDBN} scope operator
11648 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
11652 If an operator is redefined in the user code, @value{GDBN} usually
11653 attempts to invoke the redefined version instead of using the operator's
11654 predefined meaning.
11657 @subsubsection C and C@t{++} Constants
11659 @cindex C and C@t{++} constants
11661 @value{GDBN} allows you to express the constants of C and C@t{++} in the
11666 Integer constants are a sequence of digits. Octal constants are
11667 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
11668 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
11669 @samp{l}, specifying that the constant should be treated as a
11673 Floating point constants are a sequence of digits, followed by a decimal
11674 point, followed by a sequence of digits, and optionally followed by an
11675 exponent. An exponent is of the form:
11676 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
11677 sequence of digits. The @samp{+} is optional for positive exponents.
11678 A floating-point constant may also end with a letter @samp{f} or
11679 @samp{F}, specifying that the constant should be treated as being of
11680 the @code{float} (as opposed to the default @code{double}) type; or with
11681 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
11685 Enumerated constants consist of enumerated identifiers, or their
11686 integral equivalents.
11689 Character constants are a single character surrounded by single quotes
11690 (@code{'}), or a number---the ordinal value of the corresponding character
11691 (usually its @sc{ascii} value). Within quotes, the single character may
11692 be represented by a letter or by @dfn{escape sequences}, which are of
11693 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
11694 of the character's ordinal value; or of the form @samp{\@var{x}}, where
11695 @samp{@var{x}} is a predefined special character---for example,
11696 @samp{\n} for newline.
11699 String constants are a sequence of character constants surrounded by
11700 double quotes (@code{"}). Any valid character constant (as described
11701 above) may appear. Double quotes within the string must be preceded by
11702 a backslash, so for instance @samp{"a\"b'c"} is a string of five
11706 Pointer constants are an integral value. You can also write pointers
11707 to constants using the C operator @samp{&}.
11710 Array constants are comma-separated lists surrounded by braces @samp{@{}
11711 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
11712 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
11713 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
11716 @node C Plus Plus Expressions
11717 @subsubsection C@t{++} Expressions
11719 @cindex expressions in C@t{++}
11720 @value{GDBN} expression handling can interpret most C@t{++} expressions.
11722 @cindex debugging C@t{++} programs
11723 @cindex C@t{++} compilers
11724 @cindex debug formats and C@t{++}
11725 @cindex @value{NGCC} and C@t{++}
11727 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use the
11728 proper compiler and the proper debug format. Currently, @value{GDBN}
11729 works best when debugging C@t{++} code that is compiled with
11730 @value{NGCC} 2.95.3 or with @value{NGCC} 3.1 or newer, using the options
11731 @option{-gdwarf-2} or @option{-gstabs+}. DWARF 2 is preferred over
11732 stabs+. Most configurations of @value{NGCC} emit either DWARF 2 or
11733 stabs+ as their default debug format, so you usually don't need to
11734 specify a debug format explicitly. Other compilers and/or debug formats
11735 are likely to work badly or not at all when using @value{GDBN} to debug
11741 @cindex member functions
11743 Member function calls are allowed; you can use expressions like
11746 count = aml->GetOriginal(x, y)
11749 @vindex this@r{, inside C@t{++} member functions}
11750 @cindex namespace in C@t{++}
11752 While a member function is active (in the selected stack frame), your
11753 expressions have the same namespace available as the member function;
11754 that is, @value{GDBN} allows implicit references to the class instance
11755 pointer @code{this} following the same rules as C@t{++}.
11757 @cindex call overloaded functions
11758 @cindex overloaded functions, calling
11759 @cindex type conversions in C@t{++}
11761 You can call overloaded functions; @value{GDBN} resolves the function
11762 call to the right definition, with some restrictions. @value{GDBN} does not
11763 perform overload resolution involving user-defined type conversions,
11764 calls to constructors, or instantiations of templates that do not exist
11765 in the program. It also cannot handle ellipsis argument lists or
11768 It does perform integral conversions and promotions, floating-point
11769 promotions, arithmetic conversions, pointer conversions, conversions of
11770 class objects to base classes, and standard conversions such as those of
11771 functions or arrays to pointers; it requires an exact match on the
11772 number of function arguments.
11774 Overload resolution is always performed, unless you have specified
11775 @code{set overload-resolution off}. @xref{Debugging C Plus Plus,
11776 ,@value{GDBN} Features for C@t{++}}.
11778 You must specify @code{set overload-resolution off} in order to use an
11779 explicit function signature to call an overloaded function, as in
11781 p 'foo(char,int)'('x', 13)
11784 The @value{GDBN} command-completion facility can simplify this;
11785 see @ref{Completion, ,Command Completion}.
11787 @cindex reference declarations
11789 @value{GDBN} understands variables declared as C@t{++} references; you can use
11790 them in expressions just as you do in C@t{++} source---they are automatically
11793 In the parameter list shown when @value{GDBN} displays a frame, the values of
11794 reference variables are not displayed (unlike other variables); this
11795 avoids clutter, since references are often used for large structures.
11796 The @emph{address} of a reference variable is always shown, unless
11797 you have specified @samp{set print address off}.
11800 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
11801 expressions can use it just as expressions in your program do. Since
11802 one scope may be defined in another, you can use @code{::} repeatedly if
11803 necessary, for example in an expression like
11804 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
11805 resolving name scope by reference to source files, in both C and C@t{++}
11806 debugging (@pxref{Variables, ,Program Variables}).
11809 In addition, when used with HP's C@t{++} compiler, @value{GDBN} supports
11810 calling virtual functions correctly, printing out virtual bases of
11811 objects, calling functions in a base subobject, casting objects, and
11812 invoking user-defined operators.
11815 @subsubsection C and C@t{++} Defaults
11817 @cindex C and C@t{++} defaults
11819 If you allow @value{GDBN} to set type and range checking automatically, they
11820 both default to @code{off} whenever the working language changes to
11821 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
11822 selects the working language.
11824 If you allow @value{GDBN} to set the language automatically, it
11825 recognizes source files whose names end with @file{.c}, @file{.C}, or
11826 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
11827 these files, it sets the working language to C or C@t{++}.
11828 @xref{Automatically, ,Having @value{GDBN} Infer the Source Language},
11829 for further details.
11831 @c Type checking is (a) primarily motivated by Modula-2, and (b)
11832 @c unimplemented. If (b) changes, it might make sense to let this node
11833 @c appear even if Mod-2 does not, but meanwhile ignore it. roland 16jul93.
11836 @subsubsection C and C@t{++} Type and Range Checks
11838 @cindex C and C@t{++} checks
11840 By default, when @value{GDBN} parses C or C@t{++} expressions, type checking
11841 is not used. However, if you turn type checking on, @value{GDBN}
11842 considers two variables type equivalent if:
11846 The two variables are structured and have the same structure, union, or
11850 The two variables have the same type name, or types that have been
11851 declared equivalent through @code{typedef}.
11854 @c leaving this out because neither J Gilmore nor R Pesch understand it.
11857 The two @code{struct}, @code{union}, or @code{enum} variables are
11858 declared in the same declaration. (Note: this may not be true for all C
11863 Range checking, if turned on, is done on mathematical operations. Array
11864 indices are not checked, since they are often used to index a pointer
11865 that is not itself an array.
11868 @subsubsection @value{GDBN} and C
11870 The @code{set print union} and @code{show print union} commands apply to
11871 the @code{union} type. When set to @samp{on}, any @code{union} that is
11872 inside a @code{struct} or @code{class} is also printed. Otherwise, it
11873 appears as @samp{@{...@}}.
11875 The @code{@@} operator aids in the debugging of dynamic arrays, formed
11876 with pointers and a memory allocation function. @xref{Expressions,
11879 @node Debugging C Plus Plus
11880 @subsubsection @value{GDBN} Features for C@t{++}
11882 @cindex commands for C@t{++}
11884 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
11885 designed specifically for use with C@t{++}. Here is a summary:
11888 @cindex break in overloaded functions
11889 @item @r{breakpoint menus}
11890 When you want a breakpoint in a function whose name is overloaded,
11891 @value{GDBN} has the capability to display a menu of possible breakpoint
11892 locations to help you specify which function definition you want.
11893 @xref{Ambiguous Expressions,,Ambiguous Expressions}.
11895 @cindex overloading in C@t{++}
11896 @item rbreak @var{regex}
11897 Setting breakpoints using regular expressions is helpful for setting
11898 breakpoints on overloaded functions that are not members of any special
11900 @xref{Set Breaks, ,Setting Breakpoints}.
11902 @cindex C@t{++} exception handling
11905 Debug C@t{++} exception handling using these commands. @xref{Set
11906 Catchpoints, , Setting Catchpoints}.
11908 @cindex inheritance
11909 @item ptype @var{typename}
11910 Print inheritance relationships as well as other information for type
11912 @xref{Symbols, ,Examining the Symbol Table}.
11914 @cindex C@t{++} symbol display
11915 @item set print demangle
11916 @itemx show print demangle
11917 @itemx set print asm-demangle
11918 @itemx show print asm-demangle
11919 Control whether C@t{++} symbols display in their source form, both when
11920 displaying code as C@t{++} source and when displaying disassemblies.
11921 @xref{Print Settings, ,Print Settings}.
11923 @item set print object
11924 @itemx show print object
11925 Choose whether to print derived (actual) or declared types of objects.
11926 @xref{Print Settings, ,Print Settings}.
11928 @item set print vtbl
11929 @itemx show print vtbl
11930 Control the format for printing virtual function tables.
11931 @xref{Print Settings, ,Print Settings}.
11932 (The @code{vtbl} commands do not work on programs compiled with the HP
11933 ANSI C@t{++} compiler (@code{aCC}).)
11935 @kindex set overload-resolution
11936 @cindex overloaded functions, overload resolution
11937 @item set overload-resolution on
11938 Enable overload resolution for C@t{++} expression evaluation. The default
11939 is on. For overloaded functions, @value{GDBN} evaluates the arguments
11940 and searches for a function whose signature matches the argument types,
11941 using the standard C@t{++} conversion rules (see @ref{C Plus Plus
11942 Expressions, ,C@t{++} Expressions}, for details).
11943 If it cannot find a match, it emits a message.
11945 @item set overload-resolution off
11946 Disable overload resolution for C@t{++} expression evaluation. For
11947 overloaded functions that are not class member functions, @value{GDBN}
11948 chooses the first function of the specified name that it finds in the
11949 symbol table, whether or not its arguments are of the correct type. For
11950 overloaded functions that are class member functions, @value{GDBN}
11951 searches for a function whose signature @emph{exactly} matches the
11954 @kindex show overload-resolution
11955 @item show overload-resolution
11956 Show the current setting of overload resolution.
11958 @item @r{Overloaded symbol names}
11959 You can specify a particular definition of an overloaded symbol, using
11960 the same notation that is used to declare such symbols in C@t{++}: type
11961 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
11962 also use the @value{GDBN} command-line word completion facilities to list the
11963 available choices, or to finish the type list for you.
11964 @xref{Completion,, Command Completion}, for details on how to do this.
11967 @node Decimal Floating Point
11968 @subsubsection Decimal Floating Point format
11969 @cindex decimal floating point format
11971 @value{GDBN} can examine, set and perform computations with numbers in
11972 decimal floating point format, which in the C language correspond to the
11973 @code{_Decimal32}, @code{_Decimal64} and @code{_Decimal128} types as
11974 specified by the extension to support decimal floating-point arithmetic.
11976 There are two encodings in use, depending on the architecture: BID (Binary
11977 Integer Decimal) for x86 and x86-64, and DPD (Densely Packed Decimal) for
11978 PowerPC. @value{GDBN} will use the appropriate encoding for the configured
11981 Because of a limitation in @file{libdecnumber}, the library used by @value{GDBN}
11982 to manipulate decimal floating point numbers, it is not possible to convert
11983 (using a cast, for example) integers wider than 32-bit to decimal float.
11985 In addition, in order to imitate @value{GDBN}'s behaviour with binary floating
11986 point computations, error checking in decimal float operations ignores
11987 underflow, overflow and divide by zero exceptions.
11989 In the PowerPC architecture, @value{GDBN} provides a set of pseudo-registers
11990 to inspect @code{_Decimal128} values stored in floating point registers.
11991 See @ref{PowerPC,,PowerPC} for more details.
11997 @value{GDBN} can be used to debug programs written in D and compiled with
11998 GDC, LDC or DMD compilers. Currently @value{GDBN} supports only one D
11999 specific feature --- dynamic arrays.
12002 @subsection Objective-C
12004 @cindex Objective-C
12005 This section provides information about some commands and command
12006 options that are useful for debugging Objective-C code. See also
12007 @ref{Symbols, info classes}, and @ref{Symbols, info selectors}, for a
12008 few more commands specific to Objective-C support.
12011 * Method Names in Commands::
12012 * The Print Command with Objective-C::
12015 @node Method Names in Commands
12016 @subsubsection Method Names in Commands
12018 The following commands have been extended to accept Objective-C method
12019 names as line specifications:
12021 @kindex clear@r{, and Objective-C}
12022 @kindex break@r{, and Objective-C}
12023 @kindex info line@r{, and Objective-C}
12024 @kindex jump@r{, and Objective-C}
12025 @kindex list@r{, and Objective-C}
12029 @item @code{info line}
12034 A fully qualified Objective-C method name is specified as
12037 -[@var{Class} @var{methodName}]
12040 where the minus sign is used to indicate an instance method and a
12041 plus sign (not shown) is used to indicate a class method. The class
12042 name @var{Class} and method name @var{methodName} are enclosed in
12043 brackets, similar to the way messages are specified in Objective-C
12044 source code. For example, to set a breakpoint at the @code{create}
12045 instance method of class @code{Fruit} in the program currently being
12049 break -[Fruit create]
12052 To list ten program lines around the @code{initialize} class method,
12056 list +[NSText initialize]
12059 In the current version of @value{GDBN}, the plus or minus sign is
12060 required. In future versions of @value{GDBN}, the plus or minus
12061 sign will be optional, but you can use it to narrow the search. It
12062 is also possible to specify just a method name:
12068 You must specify the complete method name, including any colons. If
12069 your program's source files contain more than one @code{create} method,
12070 you'll be presented with a numbered list of classes that implement that
12071 method. Indicate your choice by number, or type @samp{0} to exit if
12074 As another example, to clear a breakpoint established at the
12075 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
12078 clear -[NSWindow makeKeyAndOrderFront:]
12081 @node The Print Command with Objective-C
12082 @subsubsection The Print Command With Objective-C
12083 @cindex Objective-C, print objects
12084 @kindex print-object
12085 @kindex po @r{(@code{print-object})}
12087 The print command has also been extended to accept methods. For example:
12090 print -[@var{object} hash]
12093 @cindex print an Objective-C object description
12094 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
12096 will tell @value{GDBN} to send the @code{hash} message to @var{object}
12097 and print the result. Also, an additional command has been added,
12098 @code{print-object} or @code{po} for short, which is meant to print
12099 the description of an object. However, this command may only work
12100 with certain Objective-C libraries that have a particular hook
12101 function, @code{_NSPrintForDebugger}, defined.
12104 @subsection Fortran
12105 @cindex Fortran-specific support in @value{GDBN}
12107 @value{GDBN} can be used to debug programs written in Fortran, but it
12108 currently supports only the features of Fortran 77 language.
12110 @cindex trailing underscore, in Fortran symbols
12111 Some Fortran compilers (@sc{gnu} Fortran 77 and Fortran 95 compilers
12112 among them) append an underscore to the names of variables and
12113 functions. When you debug programs compiled by those compilers, you
12114 will need to refer to variables and functions with a trailing
12118 * Fortran Operators:: Fortran operators and expressions
12119 * Fortran Defaults:: Default settings for Fortran
12120 * Special Fortran Commands:: Special @value{GDBN} commands for Fortran
12123 @node Fortran Operators
12124 @subsubsection Fortran Operators and Expressions
12126 @cindex Fortran operators and expressions
12128 Operators must be defined on values of specific types. For instance,
12129 @code{+} is defined on numbers, but not on characters or other non-
12130 arithmetic types. Operators are often defined on groups of types.
12134 The exponentiation operator. It raises the first operand to the power
12138 The range operator. Normally used in the form of array(low:high) to
12139 represent a section of array.
12142 The access component operator. Normally used to access elements in derived
12143 types. Also suitable for unions. As unions aren't part of regular Fortran,
12144 this can only happen when accessing a register that uses a gdbarch-defined
12148 @node Fortran Defaults
12149 @subsubsection Fortran Defaults
12151 @cindex Fortran Defaults
12153 Fortran symbols are usually case-insensitive, so @value{GDBN} by
12154 default uses case-insensitive matches for Fortran symbols. You can
12155 change that with the @samp{set case-insensitive} command, see
12156 @ref{Symbols}, for the details.
12158 @node Special Fortran Commands
12159 @subsubsection Special Fortran Commands
12161 @cindex Special Fortran commands
12163 @value{GDBN} has some commands to support Fortran-specific features,
12164 such as displaying common blocks.
12167 @cindex @code{COMMON} blocks, Fortran
12168 @kindex info common
12169 @item info common @r{[}@var{common-name}@r{]}
12170 This command prints the values contained in the Fortran @code{COMMON}
12171 block whose name is @var{common-name}. With no argument, the names of
12172 all @code{COMMON} blocks visible at the current program location are
12179 @cindex Pascal support in @value{GDBN}, limitations
12180 Debugging Pascal programs which use sets, subranges, file variables, or
12181 nested functions does not currently work. @value{GDBN} does not support
12182 entering expressions, printing values, or similar features using Pascal
12185 The Pascal-specific command @code{set print pascal_static-members}
12186 controls whether static members of Pascal objects are displayed.
12187 @xref{Print Settings, pascal_static-members}.
12190 @subsection Modula-2
12192 @cindex Modula-2, @value{GDBN} support
12194 The extensions made to @value{GDBN} to support Modula-2 only support
12195 output from the @sc{gnu} Modula-2 compiler (which is currently being
12196 developed). Other Modula-2 compilers are not currently supported, and
12197 attempting to debug executables produced by them is most likely
12198 to give an error as @value{GDBN} reads in the executable's symbol
12201 @cindex expressions in Modula-2
12203 * M2 Operators:: Built-in operators
12204 * Built-In Func/Proc:: Built-in functions and procedures
12205 * M2 Constants:: Modula-2 constants
12206 * M2 Types:: Modula-2 types
12207 * M2 Defaults:: Default settings for Modula-2
12208 * Deviations:: Deviations from standard Modula-2
12209 * M2 Checks:: Modula-2 type and range checks
12210 * M2 Scope:: The scope operators @code{::} and @code{.}
12211 * GDB/M2:: @value{GDBN} and Modula-2
12215 @subsubsection Operators
12216 @cindex Modula-2 operators
12218 Operators must be defined on values of specific types. For instance,
12219 @code{+} is defined on numbers, but not on structures. Operators are
12220 often defined on groups of types. For the purposes of Modula-2, the
12221 following definitions hold:
12226 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
12230 @emph{Character types} consist of @code{CHAR} and its subranges.
12233 @emph{Floating-point types} consist of @code{REAL}.
12236 @emph{Pointer types} consist of anything declared as @code{POINTER TO
12240 @emph{Scalar types} consist of all of the above.
12243 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
12246 @emph{Boolean types} consist of @code{BOOLEAN}.
12250 The following operators are supported, and appear in order of
12251 increasing precedence:
12255 Function argument or array index separator.
12258 Assignment. The value of @var{var} @code{:=} @var{value} is
12262 Less than, greater than on integral, floating-point, or enumerated
12266 Less than or equal to, greater than or equal to
12267 on integral, floating-point and enumerated types, or set inclusion on
12268 set types. Same precedence as @code{<}.
12270 @item =@r{, }<>@r{, }#
12271 Equality and two ways of expressing inequality, valid on scalar types.
12272 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
12273 available for inequality, since @code{#} conflicts with the script
12277 Set membership. Defined on set types and the types of their members.
12278 Same precedence as @code{<}.
12281 Boolean disjunction. Defined on boolean types.
12284 Boolean conjunction. Defined on boolean types.
12287 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
12290 Addition and subtraction on integral and floating-point types, or union
12291 and difference on set types.
12294 Multiplication on integral and floating-point types, or set intersection
12298 Division on floating-point types, or symmetric set difference on set
12299 types. Same precedence as @code{*}.
12302 Integer division and remainder. Defined on integral types. Same
12303 precedence as @code{*}.
12306 Negative. Defined on @code{INTEGER} and @code{REAL} data.
12309 Pointer dereferencing. Defined on pointer types.
12312 Boolean negation. Defined on boolean types. Same precedence as
12316 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
12317 precedence as @code{^}.
12320 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
12323 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
12327 @value{GDBN} and Modula-2 scope operators.
12331 @emph{Warning:} Set expressions and their operations are not yet supported, so @value{GDBN}
12332 treats the use of the operator @code{IN}, or the use of operators
12333 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
12334 @code{<=}, and @code{>=} on sets as an error.
12338 @node Built-In Func/Proc
12339 @subsubsection Built-in Functions and Procedures
12340 @cindex Modula-2 built-ins
12342 Modula-2 also makes available several built-in procedures and functions.
12343 In describing these, the following metavariables are used:
12348 represents an @code{ARRAY} variable.
12351 represents a @code{CHAR} constant or variable.
12354 represents a variable or constant of integral type.
12357 represents an identifier that belongs to a set. Generally used in the
12358 same function with the metavariable @var{s}. The type of @var{s} should
12359 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
12362 represents a variable or constant of integral or floating-point type.
12365 represents a variable or constant of floating-point type.
12371 represents a variable.
12374 represents a variable or constant of one of many types. See the
12375 explanation of the function for details.
12378 All Modula-2 built-in procedures also return a result, described below.
12382 Returns the absolute value of @var{n}.
12385 If @var{c} is a lower case letter, it returns its upper case
12386 equivalent, otherwise it returns its argument.
12389 Returns the character whose ordinal value is @var{i}.
12392 Decrements the value in the variable @var{v} by one. Returns the new value.
12394 @item DEC(@var{v},@var{i})
12395 Decrements the value in the variable @var{v} by @var{i}. Returns the
12398 @item EXCL(@var{m},@var{s})
12399 Removes the element @var{m} from the set @var{s}. Returns the new
12402 @item FLOAT(@var{i})
12403 Returns the floating point equivalent of the integer @var{i}.
12405 @item HIGH(@var{a})
12406 Returns the index of the last member of @var{a}.
12409 Increments the value in the variable @var{v} by one. Returns the new value.
12411 @item INC(@var{v},@var{i})
12412 Increments the value in the variable @var{v} by @var{i}. Returns the
12415 @item INCL(@var{m},@var{s})
12416 Adds the element @var{m} to the set @var{s} if it is not already
12417 there. Returns the new set.
12420 Returns the maximum value of the type @var{t}.
12423 Returns the minimum value of the type @var{t}.
12426 Returns boolean TRUE if @var{i} is an odd number.
12429 Returns the ordinal value of its argument. For example, the ordinal
12430 value of a character is its @sc{ascii} value (on machines supporting the
12431 @sc{ascii} character set). @var{x} must be of an ordered type, which include
12432 integral, character and enumerated types.
12434 @item SIZE(@var{x})
12435 Returns the size of its argument. @var{x} can be a variable or a type.
12437 @item TRUNC(@var{r})
12438 Returns the integral part of @var{r}.
12440 @item TSIZE(@var{x})
12441 Returns the size of its argument. @var{x} can be a variable or a type.
12443 @item VAL(@var{t},@var{i})
12444 Returns the member of the type @var{t} whose ordinal value is @var{i}.
12448 @emph{Warning:} Sets and their operations are not yet supported, so
12449 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
12453 @cindex Modula-2 constants
12455 @subsubsection Constants
12457 @value{GDBN} allows you to express the constants of Modula-2 in the following
12463 Integer constants are simply a sequence of digits. When used in an
12464 expression, a constant is interpreted to be type-compatible with the
12465 rest of the expression. Hexadecimal integers are specified by a
12466 trailing @samp{H}, and octal integers by a trailing @samp{B}.
12469 Floating point constants appear as a sequence of digits, followed by a
12470 decimal point and another sequence of digits. An optional exponent can
12471 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
12472 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
12473 digits of the floating point constant must be valid decimal (base 10)
12477 Character constants consist of a single character enclosed by a pair of
12478 like quotes, either single (@code{'}) or double (@code{"}). They may
12479 also be expressed by their ordinal value (their @sc{ascii} value, usually)
12480 followed by a @samp{C}.
12483 String constants consist of a sequence of characters enclosed by a
12484 pair of like quotes, either single (@code{'}) or double (@code{"}).
12485 Escape sequences in the style of C are also allowed. @xref{C
12486 Constants, ,C and C@t{++} Constants}, for a brief explanation of escape
12490 Enumerated constants consist of an enumerated identifier.
12493 Boolean constants consist of the identifiers @code{TRUE} and
12497 Pointer constants consist of integral values only.
12500 Set constants are not yet supported.
12504 @subsubsection Modula-2 Types
12505 @cindex Modula-2 types
12507 Currently @value{GDBN} can print the following data types in Modula-2
12508 syntax: array types, record types, set types, pointer types, procedure
12509 types, enumerated types, subrange types and base types. You can also
12510 print the contents of variables declared using these type.
12511 This section gives a number of simple source code examples together with
12512 sample @value{GDBN} sessions.
12514 The first example contains the following section of code:
12523 and you can request @value{GDBN} to interrogate the type and value of
12524 @code{r} and @code{s}.
12527 (@value{GDBP}) print s
12529 (@value{GDBP}) ptype s
12531 (@value{GDBP}) print r
12533 (@value{GDBP}) ptype r
12538 Likewise if your source code declares @code{s} as:
12542 s: SET ['A'..'Z'] ;
12546 then you may query the type of @code{s} by:
12549 (@value{GDBP}) ptype s
12550 type = SET ['A'..'Z']
12554 Note that at present you cannot interactively manipulate set
12555 expressions using the debugger.
12557 The following example shows how you might declare an array in Modula-2
12558 and how you can interact with @value{GDBN} to print its type and contents:
12562 s: ARRAY [-10..10] OF CHAR ;
12566 (@value{GDBP}) ptype s
12567 ARRAY [-10..10] OF CHAR
12570 Note that the array handling is not yet complete and although the type
12571 is printed correctly, expression handling still assumes that all
12572 arrays have a lower bound of zero and not @code{-10} as in the example
12575 Here are some more type related Modula-2 examples:
12579 colour = (blue, red, yellow, green) ;
12580 t = [blue..yellow] ;
12588 The @value{GDBN} interaction shows how you can query the data type
12589 and value of a variable.
12592 (@value{GDBP}) print s
12594 (@value{GDBP}) ptype t
12595 type = [blue..yellow]
12599 In this example a Modula-2 array is declared and its contents
12600 displayed. Observe that the contents are written in the same way as
12601 their @code{C} counterparts.
12605 s: ARRAY [1..5] OF CARDINAL ;
12611 (@value{GDBP}) print s
12612 $1 = @{1, 0, 0, 0, 0@}
12613 (@value{GDBP}) ptype s
12614 type = ARRAY [1..5] OF CARDINAL
12617 The Modula-2 language interface to @value{GDBN} also understands
12618 pointer types as shown in this example:
12622 s: POINTER TO ARRAY [1..5] OF CARDINAL ;
12629 and you can request that @value{GDBN} describes the type of @code{s}.
12632 (@value{GDBP}) ptype s
12633 type = POINTER TO ARRAY [1..5] OF CARDINAL
12636 @value{GDBN} handles compound types as we can see in this example.
12637 Here we combine array types, record types, pointer types and subrange
12648 myarray = ARRAY myrange OF CARDINAL ;
12649 myrange = [-2..2] ;
12651 s: POINTER TO ARRAY myrange OF foo ;
12655 and you can ask @value{GDBN} to describe the type of @code{s} as shown
12659 (@value{GDBP}) ptype s
12660 type = POINTER TO ARRAY [-2..2] OF foo = RECORD
12663 f3 : ARRAY [-2..2] OF CARDINAL;
12668 @subsubsection Modula-2 Defaults
12669 @cindex Modula-2 defaults
12671 If type and range checking are set automatically by @value{GDBN}, they
12672 both default to @code{on} whenever the working language changes to
12673 Modula-2. This happens regardless of whether you or @value{GDBN}
12674 selected the working language.
12676 If you allow @value{GDBN} to set the language automatically, then entering
12677 code compiled from a file whose name ends with @file{.mod} sets the
12678 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN}
12679 Infer the Source Language}, for further details.
12682 @subsubsection Deviations from Standard Modula-2
12683 @cindex Modula-2, deviations from
12685 A few changes have been made to make Modula-2 programs easier to debug.
12686 This is done primarily via loosening its type strictness:
12690 Unlike in standard Modula-2, pointer constants can be formed by
12691 integers. This allows you to modify pointer variables during
12692 debugging. (In standard Modula-2, the actual address contained in a
12693 pointer variable is hidden from you; it can only be modified
12694 through direct assignment to another pointer variable or expression that
12695 returned a pointer.)
12698 C escape sequences can be used in strings and characters to represent
12699 non-printable characters. @value{GDBN} prints out strings with these
12700 escape sequences embedded. Single non-printable characters are
12701 printed using the @samp{CHR(@var{nnn})} format.
12704 The assignment operator (@code{:=}) returns the value of its right-hand
12708 All built-in procedures both modify @emph{and} return their argument.
12712 @subsubsection Modula-2 Type and Range Checks
12713 @cindex Modula-2 checks
12716 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
12719 @c FIXME remove warning when type/range checks added
12721 @value{GDBN} considers two Modula-2 variables type equivalent if:
12725 They are of types that have been declared equivalent via a @code{TYPE
12726 @var{t1} = @var{t2}} statement
12729 They have been declared on the same line. (Note: This is true of the
12730 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
12733 As long as type checking is enabled, any attempt to combine variables
12734 whose types are not equivalent is an error.
12736 Range checking is done on all mathematical operations, assignment, array
12737 index bounds, and all built-in functions and procedures.
12740 @subsubsection The Scope Operators @code{::} and @code{.}
12742 @cindex @code{.}, Modula-2 scope operator
12743 @cindex colon, doubled as scope operator
12745 @vindex colon-colon@r{, in Modula-2}
12746 @c Info cannot handle :: but TeX can.
12749 @vindex ::@r{, in Modula-2}
12752 There are a few subtle differences between the Modula-2 scope operator
12753 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
12758 @var{module} . @var{id}
12759 @var{scope} :: @var{id}
12763 where @var{scope} is the name of a module or a procedure,
12764 @var{module} the name of a module, and @var{id} is any declared
12765 identifier within your program, except another module.
12767 Using the @code{::} operator makes @value{GDBN} search the scope
12768 specified by @var{scope} for the identifier @var{id}. If it is not
12769 found in the specified scope, then @value{GDBN} searches all scopes
12770 enclosing the one specified by @var{scope}.
12772 Using the @code{.} operator makes @value{GDBN} search the current scope for
12773 the identifier specified by @var{id} that was imported from the
12774 definition module specified by @var{module}. With this operator, it is
12775 an error if the identifier @var{id} was not imported from definition
12776 module @var{module}, or if @var{id} is not an identifier in
12780 @subsubsection @value{GDBN} and Modula-2
12782 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
12783 Five subcommands of @code{set print} and @code{show print} apply
12784 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
12785 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
12786 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
12787 analogue in Modula-2.
12789 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
12790 with any language, is not useful with Modula-2. Its
12791 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
12792 created in Modula-2 as they can in C or C@t{++}. However, because an
12793 address can be specified by an integral constant, the construct
12794 @samp{@{@var{type}@}@var{adrexp}} is still useful.
12796 @cindex @code{#} in Modula-2
12797 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
12798 interpreted as the beginning of a comment. Use @code{<>} instead.
12804 The extensions made to @value{GDBN} for Ada only support
12805 output from the @sc{gnu} Ada (GNAT) compiler.
12806 Other Ada compilers are not currently supported, and
12807 attempting to debug executables produced by them is most likely
12811 @cindex expressions in Ada
12813 * Ada Mode Intro:: General remarks on the Ada syntax
12814 and semantics supported by Ada mode
12816 * Omissions from Ada:: Restrictions on the Ada expression syntax.
12817 * Additions to Ada:: Extensions of the Ada expression syntax.
12818 * Stopping Before Main Program:: Debugging the program during elaboration.
12819 * Ada Tasks:: Listing and setting breakpoints in tasks.
12820 * Ada Tasks and Core Files:: Tasking Support when Debugging Core Files
12821 * Ada Glitches:: Known peculiarities of Ada mode.
12824 @node Ada Mode Intro
12825 @subsubsection Introduction
12826 @cindex Ada mode, general
12828 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
12829 syntax, with some extensions.
12830 The philosophy behind the design of this subset is
12834 That @value{GDBN} should provide basic literals and access to operations for
12835 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
12836 leaving more sophisticated computations to subprograms written into the
12837 program (which therefore may be called from @value{GDBN}).
12840 That type safety and strict adherence to Ada language restrictions
12841 are not particularly important to the @value{GDBN} user.
12844 That brevity is important to the @value{GDBN} user.
12847 Thus, for brevity, the debugger acts as if all names declared in
12848 user-written packages are directly visible, even if they are not visible
12849 according to Ada rules, thus making it unnecessary to fully qualify most
12850 names with their packages, regardless of context. Where this causes
12851 ambiguity, @value{GDBN} asks the user's intent.
12853 The debugger will start in Ada mode if it detects an Ada main program.
12854 As for other languages, it will enter Ada mode when stopped in a program that
12855 was translated from an Ada source file.
12857 While in Ada mode, you may use `@t{--}' for comments. This is useful
12858 mostly for documenting command files. The standard @value{GDBN} comment
12859 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
12860 middle (to allow based literals).
12862 The debugger supports limited overloading. Given a subprogram call in which
12863 the function symbol has multiple definitions, it will use the number of
12864 actual parameters and some information about their types to attempt to narrow
12865 the set of definitions. It also makes very limited use of context, preferring
12866 procedures to functions in the context of the @code{call} command, and
12867 functions to procedures elsewhere.
12869 @node Omissions from Ada
12870 @subsubsection Omissions from Ada
12871 @cindex Ada, omissions from
12873 Here are the notable omissions from the subset:
12877 Only a subset of the attributes are supported:
12881 @t{'First}, @t{'Last}, and @t{'Length}
12882 on array objects (not on types and subtypes).
12885 @t{'Min} and @t{'Max}.
12888 @t{'Pos} and @t{'Val}.
12894 @t{'Range} on array objects (not subtypes), but only as the right
12895 operand of the membership (@code{in}) operator.
12898 @t{'Access}, @t{'Unchecked_Access}, and
12899 @t{'Unrestricted_Access} (a GNAT extension).
12907 @code{Characters.Latin_1} are not available and
12908 concatenation is not implemented. Thus, escape characters in strings are
12909 not currently available.
12912 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
12913 equality of representations. They will generally work correctly
12914 for strings and arrays whose elements have integer or enumeration types.
12915 They may not work correctly for arrays whose element
12916 types have user-defined equality, for arrays of real values
12917 (in particular, IEEE-conformant floating point, because of negative
12918 zeroes and NaNs), and for arrays whose elements contain unused bits with
12919 indeterminate values.
12922 The other component-by-component array operations (@code{and}, @code{or},
12923 @code{xor}, @code{not}, and relational tests other than equality)
12924 are not implemented.
12927 @cindex array aggregates (Ada)
12928 @cindex record aggregates (Ada)
12929 @cindex aggregates (Ada)
12930 There is limited support for array and record aggregates. They are
12931 permitted only on the right sides of assignments, as in these examples:
12934 (@value{GDBP}) set An_Array := (1, 2, 3, 4, 5, 6)
12935 (@value{GDBP}) set An_Array := (1, others => 0)
12936 (@value{GDBP}) set An_Array := (0|4 => 1, 1..3 => 2, 5 => 6)
12937 (@value{GDBP}) set A_2D_Array := ((1, 2, 3), (4, 5, 6), (7, 8, 9))
12938 (@value{GDBP}) set A_Record := (1, "Peter", True);
12939 (@value{GDBP}) set A_Record := (Name => "Peter", Id => 1, Alive => True)
12943 discriminant's value by assigning an aggregate has an
12944 undefined effect if that discriminant is used within the record.
12945 However, you can first modify discriminants by directly assigning to
12946 them (which normally would not be allowed in Ada), and then performing an
12947 aggregate assignment. For example, given a variable @code{A_Rec}
12948 declared to have a type such as:
12951 type Rec (Len : Small_Integer := 0) is record
12953 Vals : IntArray (1 .. Len);
12957 you can assign a value with a different size of @code{Vals} with two
12961 (@value{GDBP}) set A_Rec.Len := 4
12962 (@value{GDBP}) set A_Rec := (Id => 42, Vals => (1, 2, 3, 4))
12965 As this example also illustrates, @value{GDBN} is very loose about the usual
12966 rules concerning aggregates. You may leave out some of the
12967 components of an array or record aggregate (such as the @code{Len}
12968 component in the assignment to @code{A_Rec} above); they will retain their
12969 original values upon assignment. You may freely use dynamic values as
12970 indices in component associations. You may even use overlapping or
12971 redundant component associations, although which component values are
12972 assigned in such cases is not defined.
12975 Calls to dispatching subprograms are not implemented.
12978 The overloading algorithm is much more limited (i.e., less selective)
12979 than that of real Ada. It makes only limited use of the context in
12980 which a subexpression appears to resolve its meaning, and it is much
12981 looser in its rules for allowing type matches. As a result, some
12982 function calls will be ambiguous, and the user will be asked to choose
12983 the proper resolution.
12986 The @code{new} operator is not implemented.
12989 Entry calls are not implemented.
12992 Aside from printing, arithmetic operations on the native VAX floating-point
12993 formats are not supported.
12996 It is not possible to slice a packed array.
12999 The names @code{True} and @code{False}, when not part of a qualified name,
13000 are interpreted as if implicitly prefixed by @code{Standard}, regardless of
13002 Should your program
13003 redefine these names in a package or procedure (at best a dubious practice),
13004 you will have to use fully qualified names to access their new definitions.
13007 @node Additions to Ada
13008 @subsubsection Additions to Ada
13009 @cindex Ada, deviations from
13011 As it does for other languages, @value{GDBN} makes certain generic
13012 extensions to Ada (@pxref{Expressions}):
13016 If the expression @var{E} is a variable residing in memory (typically
13017 a local variable or array element) and @var{N} is a positive integer,
13018 then @code{@var{E}@@@var{N}} displays the values of @var{E} and the
13019 @var{N}-1 adjacent variables following it in memory as an array. In
13020 Ada, this operator is generally not necessary, since its prime use is
13021 in displaying parts of an array, and slicing will usually do this in
13022 Ada. However, there are occasional uses when debugging programs in
13023 which certain debugging information has been optimized away.
13026 @code{@var{B}::@var{var}} means ``the variable named @var{var} that
13027 appears in function or file @var{B}.'' When @var{B} is a file name,
13028 you must typically surround it in single quotes.
13031 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
13032 @var{type} that appears at address @var{addr}.''
13035 A name starting with @samp{$} is a convenience variable
13036 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
13039 In addition, @value{GDBN} provides a few other shortcuts and outright
13040 additions specific to Ada:
13044 The assignment statement is allowed as an expression, returning
13045 its right-hand operand as its value. Thus, you may enter
13048 (@value{GDBP}) set x := y + 3
13049 (@value{GDBP}) print A(tmp := y + 1)
13053 The semicolon is allowed as an ``operator,'' returning as its value
13054 the value of its right-hand operand.
13055 This allows, for example,
13056 complex conditional breaks:
13059 (@value{GDBP}) break f
13060 (@value{GDBP}) condition 1 (report(i); k += 1; A(k) > 100)
13064 Rather than use catenation and symbolic character names to introduce special
13065 characters into strings, one may instead use a special bracket notation,
13066 which is also used to print strings. A sequence of characters of the form
13067 @samp{["@var{XX}"]} within a string or character literal denotes the
13068 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
13069 sequence of characters @samp{["""]} also denotes a single quotation mark
13070 in strings. For example,
13072 "One line.["0a"]Next line.["0a"]"
13075 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF})
13079 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
13080 @t{'Max} is optional (and is ignored in any case). For example, it is valid
13084 (@value{GDBP}) print 'max(x, y)
13088 When printing arrays, @value{GDBN} uses positional notation when the
13089 array has a lower bound of 1, and uses a modified named notation otherwise.
13090 For example, a one-dimensional array of three integers with a lower bound
13091 of 3 might print as
13098 That is, in contrast to valid Ada, only the first component has a @code{=>}
13102 You may abbreviate attributes in expressions with any unique,
13103 multi-character subsequence of
13104 their names (an exact match gets preference).
13105 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
13106 in place of @t{a'length}.
13109 @cindex quoting Ada internal identifiers
13110 Since Ada is case-insensitive, the debugger normally maps identifiers you type
13111 to lower case. The GNAT compiler uses upper-case characters for
13112 some of its internal identifiers, which are normally of no interest to users.
13113 For the rare occasions when you actually have to look at them,
13114 enclose them in angle brackets to avoid the lower-case mapping.
13117 (@value{GDBP}) print <JMPBUF_SAVE>[0]
13121 Printing an object of class-wide type or dereferencing an
13122 access-to-class-wide value will display all the components of the object's
13123 specific type (as indicated by its run-time tag). Likewise, component
13124 selection on such a value will operate on the specific type of the
13129 @node Stopping Before Main Program
13130 @subsubsection Stopping at the Very Beginning
13132 @cindex breakpointing Ada elaboration code
13133 It is sometimes necessary to debug the program during elaboration, and
13134 before reaching the main procedure.
13135 As defined in the Ada Reference
13136 Manual, the elaboration code is invoked from a procedure called
13137 @code{adainit}. To run your program up to the beginning of
13138 elaboration, simply use the following two commands:
13139 @code{tbreak adainit} and @code{run}.
13142 @subsubsection Extensions for Ada Tasks
13143 @cindex Ada, tasking
13145 Support for Ada tasks is analogous to that for threads (@pxref{Threads}).
13146 @value{GDBN} provides the following task-related commands:
13151 This command shows a list of current Ada tasks, as in the following example:
13158 (@value{GDBP}) info tasks
13159 ID TID P-ID Pri State Name
13160 1 8088000 0 15 Child Activation Wait main_task
13161 2 80a4000 1 15 Accept Statement b
13162 3 809a800 1 15 Child Activation Wait a
13163 * 4 80ae800 3 15 Runnable c
13168 In this listing, the asterisk before the last task indicates it to be the
13169 task currently being inspected.
13173 Represents @value{GDBN}'s internal task number.
13179 The parent's task ID (@value{GDBN}'s internal task number).
13182 The base priority of the task.
13185 Current state of the task.
13189 The task has been created but has not been activated. It cannot be
13193 The task is not blocked for any reason known to Ada. (It may be waiting
13194 for a mutex, though.) It is conceptually "executing" in normal mode.
13197 The task is terminated, in the sense of ARM 9.3 (5). Any dependents
13198 that were waiting on terminate alternatives have been awakened and have
13199 terminated themselves.
13201 @item Child Activation Wait
13202 The task is waiting for created tasks to complete activation.
13204 @item Accept Statement
13205 The task is waiting on an accept or selective wait statement.
13207 @item Waiting on entry call
13208 The task is waiting on an entry call.
13210 @item Async Select Wait
13211 The task is waiting to start the abortable part of an asynchronous
13215 The task is waiting on a select statement with only a delay
13218 @item Child Termination Wait
13219 The task is sleeping having completed a master within itself, and is
13220 waiting for the tasks dependent on that master to become terminated or
13221 waiting on a terminate Phase.
13223 @item Wait Child in Term Alt
13224 The task is sleeping waiting for tasks on terminate alternatives to
13225 finish terminating.
13227 @item Accepting RV with @var{taskno}
13228 The task is accepting a rendez-vous with the task @var{taskno}.
13232 Name of the task in the program.
13236 @kindex info task @var{taskno}
13237 @item info task @var{taskno}
13238 This command shows detailled informations on the specified task, as in
13239 the following example:
13244 (@value{GDBP}) info tasks
13245 ID TID P-ID Pri State Name
13246 1 8077880 0 15 Child Activation Wait main_task
13247 * 2 807c468 1 15 Runnable task_1
13248 (@value{GDBP}) info task 2
13249 Ada Task: 0x807c468
13252 Parent: 1 (main_task)
13258 @kindex task@r{ (Ada)}
13259 @cindex current Ada task ID
13260 This command prints the ID of the current task.
13266 (@value{GDBP}) info tasks
13267 ID TID P-ID Pri State Name
13268 1 8077870 0 15 Child Activation Wait main_task
13269 * 2 807c458 1 15 Runnable t
13270 (@value{GDBP}) task
13271 [Current task is 2]
13274 @item task @var{taskno}
13275 @cindex Ada task switching
13276 This command is like the @code{thread @var{threadno}}
13277 command (@pxref{Threads}). It switches the context of debugging
13278 from the current task to the given task.
13284 (@value{GDBP}) info tasks
13285 ID TID P-ID Pri State Name
13286 1 8077870 0 15 Child Activation Wait main_task
13287 * 2 807c458 1 15 Runnable t
13288 (@value{GDBP}) task 1
13289 [Switching to task 1]
13290 #0 0x8067726 in pthread_cond_wait ()
13292 #0 0x8067726 in pthread_cond_wait ()
13293 #1 0x8056714 in system.os_interface.pthread_cond_wait ()
13294 #2 0x805cb63 in system.task_primitives.operations.sleep ()
13295 #3 0x806153e in system.tasking.stages.activate_tasks ()
13296 #4 0x804aacc in un () at un.adb:5
13299 @item break @var{linespec} task @var{taskno}
13300 @itemx break @var{linespec} task @var{taskno} if @dots{}
13301 @cindex breakpoints and tasks, in Ada
13302 @cindex task breakpoints, in Ada
13303 @kindex break @dots{} task @var{taskno}@r{ (Ada)}
13304 These commands are like the @code{break @dots{} thread @dots{}}
13305 command (@pxref{Thread Stops}).
13306 @var{linespec} specifies source lines, as described
13307 in @ref{Specify Location}.
13309 Use the qualifier @samp{task @var{taskno}} with a breakpoint command
13310 to specify that you only want @value{GDBN} to stop the program when a
13311 particular Ada task reaches this breakpoint. @var{taskno} is one of the
13312 numeric task identifiers assigned by @value{GDBN}, shown in the first
13313 column of the @samp{info tasks} display.
13315 If you do not specify @samp{task @var{taskno}} when you set a
13316 breakpoint, the breakpoint applies to @emph{all} tasks of your
13319 You can use the @code{task} qualifier on conditional breakpoints as
13320 well; in this case, place @samp{task @var{taskno}} before the
13321 breakpoint condition (before the @code{if}).
13329 (@value{GDBP}) info tasks
13330 ID TID P-ID Pri State Name
13331 1 140022020 0 15 Child Activation Wait main_task
13332 2 140045060 1 15 Accept/Select Wait t2
13333 3 140044840 1 15 Runnable t1
13334 * 4 140056040 1 15 Runnable t3
13335 (@value{GDBP}) b 15 task 2
13336 Breakpoint 5 at 0x120044cb0: file test_task_debug.adb, line 15.
13337 (@value{GDBP}) cont
13342 Breakpoint 5, test_task_debug () at test_task_debug.adb:15
13344 (@value{GDBP}) info tasks
13345 ID TID P-ID Pri State Name
13346 1 140022020 0 15 Child Activation Wait main_task
13347 * 2 140045060 1 15 Runnable t2
13348 3 140044840 1 15 Runnable t1
13349 4 140056040 1 15 Delay Sleep t3
13353 @node Ada Tasks and Core Files
13354 @subsubsection Tasking Support when Debugging Core Files
13355 @cindex Ada tasking and core file debugging
13357 When inspecting a core file, as opposed to debugging a live program,
13358 tasking support may be limited or even unavailable, depending on
13359 the platform being used.
13360 For instance, on x86-linux, the list of tasks is available, but task
13361 switching is not supported. On Tru64, however, task switching will work
13364 On certain platforms, including Tru64, the debugger needs to perform some
13365 memory writes in order to provide Ada tasking support. When inspecting
13366 a core file, this means that the core file must be opened with read-write
13367 privileges, using the command @samp{"set write on"} (@pxref{Patching}).
13368 Under these circumstances, you should make a backup copy of the core
13369 file before inspecting it with @value{GDBN}.
13372 @subsubsection Known Peculiarities of Ada Mode
13373 @cindex Ada, problems
13375 Besides the omissions listed previously (@pxref{Omissions from Ada}),
13376 we know of several problems with and limitations of Ada mode in
13378 some of which will be fixed with planned future releases of the debugger
13379 and the GNU Ada compiler.
13383 Currently, the debugger
13384 has insufficient information to determine whether certain pointers represent
13385 pointers to objects or the objects themselves.
13386 Thus, the user may have to tack an extra @code{.all} after an expression
13387 to get it printed properly.
13390 Static constants that the compiler chooses not to materialize as objects in
13391 storage are invisible to the debugger.
13394 Named parameter associations in function argument lists are ignored (the
13395 argument lists are treated as positional).
13398 Many useful library packages are currently invisible to the debugger.
13401 Fixed-point arithmetic, conversions, input, and output is carried out using
13402 floating-point arithmetic, and may give results that only approximate those on
13406 The GNAT compiler never generates the prefix @code{Standard} for any of
13407 the standard symbols defined by the Ada language. @value{GDBN} knows about
13408 this: it will strip the prefix from names when you use it, and will never
13409 look for a name you have so qualified among local symbols, nor match against
13410 symbols in other packages or subprograms. If you have
13411 defined entities anywhere in your program other than parameters and
13412 local variables whose simple names match names in @code{Standard},
13413 GNAT's lack of qualification here can cause confusion. When this happens,
13414 you can usually resolve the confusion
13415 by qualifying the problematic names with package
13416 @code{Standard} explicitly.
13419 Older versions of the compiler sometimes generate erroneous debugging
13420 information, resulting in the debugger incorrectly printing the value
13421 of affected entities. In some cases, the debugger is able to work
13422 around an issue automatically. In other cases, the debugger is able
13423 to work around the issue, but the work-around has to be specifically
13426 @kindex set ada trust-PAD-over-XVS
13427 @kindex show ada trust-PAD-over-XVS
13430 @item set ada trust-PAD-over-XVS on
13431 Configure GDB to strictly follow the GNAT encoding when computing the
13432 value of Ada entities, particularly when @code{PAD} and @code{PAD___XVS}
13433 types are involved (see @code{ada/exp_dbug.ads} in the GCC sources for
13434 a complete description of the encoding used by the GNAT compiler).
13435 This is the default.
13437 @item set ada trust-PAD-over-XVS off
13438 This is related to the encoding using by the GNAT compiler. If @value{GDBN}
13439 sometimes prints the wrong value for certain entities, changing @code{ada
13440 trust-PAD-over-XVS} to @code{off} activates a work-around which may fix
13441 the issue. It is always safe to set @code{ada trust-PAD-over-XVS} to
13442 @code{off}, but this incurs a slight performance penalty, so it is
13443 recommended to leave this setting to @code{on} unless necessary.
13447 @node Unsupported Languages
13448 @section Unsupported Languages
13450 @cindex unsupported languages
13451 @cindex minimal language
13452 In addition to the other fully-supported programming languages,
13453 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
13454 It does not represent a real programming language, but provides a set
13455 of capabilities close to what the C or assembly languages provide.
13456 This should allow most simple operations to be performed while debugging
13457 an application that uses a language currently not supported by @value{GDBN}.
13459 If the language is set to @code{auto}, @value{GDBN} will automatically
13460 select this language if the current frame corresponds to an unsupported
13464 @chapter Examining the Symbol Table
13466 The commands described in this chapter allow you to inquire about the
13467 symbols (names of variables, functions and types) defined in your
13468 program. This information is inherent in the text of your program and
13469 does not change as your program executes. @value{GDBN} finds it in your
13470 program's symbol table, in the file indicated when you started @value{GDBN}
13471 (@pxref{File Options, ,Choosing Files}), or by one of the
13472 file-management commands (@pxref{Files, ,Commands to Specify Files}).
13474 @cindex symbol names
13475 @cindex names of symbols
13476 @cindex quoting names
13477 Occasionally, you may need to refer to symbols that contain unusual
13478 characters, which @value{GDBN} ordinarily treats as word delimiters. The
13479 most frequent case is in referring to static variables in other
13480 source files (@pxref{Variables,,Program Variables}). File names
13481 are recorded in object files as debugging symbols, but @value{GDBN} would
13482 ordinarily parse a typical file name, like @file{foo.c}, as the three words
13483 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
13484 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
13491 looks up the value of @code{x} in the scope of the file @file{foo.c}.
13494 @cindex case-insensitive symbol names
13495 @cindex case sensitivity in symbol names
13496 @kindex set case-sensitive
13497 @item set case-sensitive on
13498 @itemx set case-sensitive off
13499 @itemx set case-sensitive auto
13500 Normally, when @value{GDBN} looks up symbols, it matches their names
13501 with case sensitivity determined by the current source language.
13502 Occasionally, you may wish to control that. The command @code{set
13503 case-sensitive} lets you do that by specifying @code{on} for
13504 case-sensitive matches or @code{off} for case-insensitive ones. If
13505 you specify @code{auto}, case sensitivity is reset to the default
13506 suitable for the source language. The default is case-sensitive
13507 matches for all languages except for Fortran, for which the default is
13508 case-insensitive matches.
13510 @kindex show case-sensitive
13511 @item show case-sensitive
13512 This command shows the current setting of case sensitivity for symbols
13515 @kindex info address
13516 @cindex address of a symbol
13517 @item info address @var{symbol}
13518 Describe where the data for @var{symbol} is stored. For a register
13519 variable, this says which register it is kept in. For a non-register
13520 local variable, this prints the stack-frame offset at which the variable
13523 Note the contrast with @samp{print &@var{symbol}}, which does not work
13524 at all for a register variable, and for a stack local variable prints
13525 the exact address of the current instantiation of the variable.
13527 @kindex info symbol
13528 @cindex symbol from address
13529 @cindex closest symbol and offset for an address
13530 @item info symbol @var{addr}
13531 Print the name of a symbol which is stored at the address @var{addr}.
13532 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
13533 nearest symbol and an offset from it:
13536 (@value{GDBP}) info symbol 0x54320
13537 _initialize_vx + 396 in section .text
13541 This is the opposite of the @code{info address} command. You can use
13542 it to find out the name of a variable or a function given its address.
13544 For dynamically linked executables, the name of executable or shared
13545 library containing the symbol is also printed:
13548 (@value{GDBP}) info symbol 0x400225
13549 _start + 5 in section .text of /tmp/a.out
13550 (@value{GDBP}) info symbol 0x2aaaac2811cf
13551 __read_nocancel + 6 in section .text of /usr/lib64/libc.so.6
13555 @item whatis [@var{arg}]
13556 Print the data type of @var{arg}, which can be either an expression or
13557 a data type. With no argument, print the data type of @code{$}, the
13558 last value in the value history. If @var{arg} is an expression, it is
13559 not actually evaluated, and any side-effecting operations (such as
13560 assignments or function calls) inside it do not take place. If
13561 @var{arg} is a type name, it may be the name of a type or typedef, or
13562 for C code it may have the form @samp{class @var{class-name}},
13563 @samp{struct @var{struct-tag}}, @samp{union @var{union-tag}} or
13564 @samp{enum @var{enum-tag}}.
13565 @xref{Expressions, ,Expressions}.
13568 @item ptype [@var{arg}]
13569 @code{ptype} accepts the same arguments as @code{whatis}, but prints a
13570 detailed description of the type, instead of just the name of the type.
13571 @xref{Expressions, ,Expressions}.
13573 For example, for this variable declaration:
13576 struct complex @{double real; double imag;@} v;
13580 the two commands give this output:
13584 (@value{GDBP}) whatis v
13585 type = struct complex
13586 (@value{GDBP}) ptype v
13587 type = struct complex @{
13595 As with @code{whatis}, using @code{ptype} without an argument refers to
13596 the type of @code{$}, the last value in the value history.
13598 @cindex incomplete type
13599 Sometimes, programs use opaque data types or incomplete specifications
13600 of complex data structure. If the debug information included in the
13601 program does not allow @value{GDBN} to display a full declaration of
13602 the data type, it will say @samp{<incomplete type>}. For example,
13603 given these declarations:
13607 struct foo *fooptr;
13611 but no definition for @code{struct foo} itself, @value{GDBN} will say:
13614 (@value{GDBP}) ptype foo
13615 $1 = <incomplete type>
13619 ``Incomplete type'' is C terminology for data types that are not
13620 completely specified.
13623 @item info types @var{regexp}
13625 Print a brief description of all types whose names match the regular
13626 expression @var{regexp} (or all types in your program, if you supply
13627 no argument). Each complete typename is matched as though it were a
13628 complete line; thus, @samp{i type value} gives information on all
13629 types in your program whose names include the string @code{value}, but
13630 @samp{i type ^value$} gives information only on types whose complete
13631 name is @code{value}.
13633 This command differs from @code{ptype} in two ways: first, like
13634 @code{whatis}, it does not print a detailed description; second, it
13635 lists all source files where a type is defined.
13638 @cindex local variables
13639 @item info scope @var{location}
13640 List all the variables local to a particular scope. This command
13641 accepts a @var{location} argument---a function name, a source line, or
13642 an address preceded by a @samp{*}, and prints all the variables local
13643 to the scope defined by that location. (@xref{Specify Location}, for
13644 details about supported forms of @var{location}.) For example:
13647 (@value{GDBP}) @b{info scope command_line_handler}
13648 Scope for command_line_handler:
13649 Symbol rl is an argument at stack/frame offset 8, length 4.
13650 Symbol linebuffer is in static storage at address 0x150a18, length 4.
13651 Symbol linelength is in static storage at address 0x150a1c, length 4.
13652 Symbol p is a local variable in register $esi, length 4.
13653 Symbol p1 is a local variable in register $ebx, length 4.
13654 Symbol nline is a local variable in register $edx, length 4.
13655 Symbol repeat is a local variable at frame offset -8, length 4.
13659 This command is especially useful for determining what data to collect
13660 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
13663 @kindex info source
13665 Show information about the current source file---that is, the source file for
13666 the function containing the current point of execution:
13669 the name of the source file, and the directory containing it,
13671 the directory it was compiled in,
13673 its length, in lines,
13675 which programming language it is written in,
13677 whether the executable includes debugging information for that file, and
13678 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
13680 whether the debugging information includes information about
13681 preprocessor macros.
13685 @kindex info sources
13687 Print the names of all source files in your program for which there is
13688 debugging information, organized into two lists: files whose symbols
13689 have already been read, and files whose symbols will be read when needed.
13691 @kindex info functions
13692 @item info functions
13693 Print the names and data types of all defined functions.
13695 @item info functions @var{regexp}
13696 Print the names and data types of all defined functions
13697 whose names contain a match for regular expression @var{regexp}.
13698 Thus, @samp{info fun step} finds all functions whose names
13699 include @code{step}; @samp{info fun ^step} finds those whose names
13700 start with @code{step}. If a function name contains characters
13701 that conflict with the regular expression language (e.g.@:
13702 @samp{operator*()}), they may be quoted with a backslash.
13704 @kindex info variables
13705 @item info variables
13706 Print the names and data types of all variables that are defined
13707 outside of functions (i.e.@: excluding local variables).
13709 @item info variables @var{regexp}
13710 Print the names and data types of all variables (except for local
13711 variables) whose names contain a match for regular expression
13714 @kindex info classes
13715 @cindex Objective-C, classes and selectors
13717 @itemx info classes @var{regexp}
13718 Display all Objective-C classes in your program, or
13719 (with the @var{regexp} argument) all those matching a particular regular
13722 @kindex info selectors
13723 @item info selectors
13724 @itemx info selectors @var{regexp}
13725 Display all Objective-C selectors in your program, or
13726 (with the @var{regexp} argument) all those matching a particular regular
13730 This was never implemented.
13731 @kindex info methods
13733 @itemx info methods @var{regexp}
13734 The @code{info methods} command permits the user to examine all defined
13735 methods within C@t{++} program, or (with the @var{regexp} argument) a
13736 specific set of methods found in the various C@t{++} classes. Many
13737 C@t{++} classes provide a large number of methods. Thus, the output
13738 from the @code{ptype} command can be overwhelming and hard to use. The
13739 @code{info-methods} command filters the methods, printing only those
13740 which match the regular-expression @var{regexp}.
13743 @cindex reloading symbols
13744 Some systems allow individual object files that make up your program to
13745 be replaced without stopping and restarting your program. For example,
13746 in VxWorks you can simply recompile a defective object file and keep on
13747 running. If you are running on one of these systems, you can allow
13748 @value{GDBN} to reload the symbols for automatically relinked modules:
13751 @kindex set symbol-reloading
13752 @item set symbol-reloading on
13753 Replace symbol definitions for the corresponding source file when an
13754 object file with a particular name is seen again.
13756 @item set symbol-reloading off
13757 Do not replace symbol definitions when encountering object files of the
13758 same name more than once. This is the default state; if you are not
13759 running on a system that permits automatic relinking of modules, you
13760 should leave @code{symbol-reloading} off, since otherwise @value{GDBN}
13761 may discard symbols when linking large programs, that may contain
13762 several modules (from different directories or libraries) with the same
13765 @kindex show symbol-reloading
13766 @item show symbol-reloading
13767 Show the current @code{on} or @code{off} setting.
13770 @cindex opaque data types
13771 @kindex set opaque-type-resolution
13772 @item set opaque-type-resolution on
13773 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
13774 declared as a pointer to a @code{struct}, @code{class}, or
13775 @code{union}---for example, @code{struct MyType *}---that is used in one
13776 source file although the full declaration of @code{struct MyType} is in
13777 another source file. The default is on.
13779 A change in the setting of this subcommand will not take effect until
13780 the next time symbols for a file are loaded.
13782 @item set opaque-type-resolution off
13783 Tell @value{GDBN} not to resolve opaque types. In this case, the type
13784 is printed as follows:
13786 @{<no data fields>@}
13789 @kindex show opaque-type-resolution
13790 @item show opaque-type-resolution
13791 Show whether opaque types are resolved or not.
13793 @kindex maint print symbols
13794 @cindex symbol dump
13795 @kindex maint print psymbols
13796 @cindex partial symbol dump
13797 @item maint print symbols @var{filename}
13798 @itemx maint print psymbols @var{filename}
13799 @itemx maint print msymbols @var{filename}
13800 Write a dump of debugging symbol data into the file @var{filename}.
13801 These commands are used to debug the @value{GDBN} symbol-reading code. Only
13802 symbols with debugging data are included. If you use @samp{maint print
13803 symbols}, @value{GDBN} includes all the symbols for which it has already
13804 collected full details: that is, @var{filename} reflects symbols for
13805 only those files whose symbols @value{GDBN} has read. You can use the
13806 command @code{info sources} to find out which files these are. If you
13807 use @samp{maint print psymbols} instead, the dump shows information about
13808 symbols that @value{GDBN} only knows partially---that is, symbols defined in
13809 files that @value{GDBN} has skimmed, but not yet read completely. Finally,
13810 @samp{maint print msymbols} dumps just the minimal symbol information
13811 required for each object file from which @value{GDBN} has read some symbols.
13812 @xref{Files, ,Commands to Specify Files}, for a discussion of how
13813 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
13815 @kindex maint info symtabs
13816 @kindex maint info psymtabs
13817 @cindex listing @value{GDBN}'s internal symbol tables
13818 @cindex symbol tables, listing @value{GDBN}'s internal
13819 @cindex full symbol tables, listing @value{GDBN}'s internal
13820 @cindex partial symbol tables, listing @value{GDBN}'s internal
13821 @item maint info symtabs @r{[} @var{regexp} @r{]}
13822 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
13824 List the @code{struct symtab} or @code{struct partial_symtab}
13825 structures whose names match @var{regexp}. If @var{regexp} is not
13826 given, list them all. The output includes expressions which you can
13827 copy into a @value{GDBN} debugging this one to examine a particular
13828 structure in more detail. For example:
13831 (@value{GDBP}) maint info psymtabs dwarf2read
13832 @{ objfile /home/gnu/build/gdb/gdb
13833 ((struct objfile *) 0x82e69d0)
13834 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
13835 ((struct partial_symtab *) 0x8474b10)
13838 text addresses 0x814d3c8 -- 0x8158074
13839 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
13840 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
13841 dependencies (none)
13844 (@value{GDBP}) maint info symtabs
13848 We see that there is one partial symbol table whose filename contains
13849 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
13850 and we see that @value{GDBN} has not read in any symtabs yet at all.
13851 If we set a breakpoint on a function, that will cause @value{GDBN} to
13852 read the symtab for the compilation unit containing that function:
13855 (@value{GDBP}) break dwarf2_psymtab_to_symtab
13856 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
13858 (@value{GDBP}) maint info symtabs
13859 @{ objfile /home/gnu/build/gdb/gdb
13860 ((struct objfile *) 0x82e69d0)
13861 @{ symtab /home/gnu/src/gdb/dwarf2read.c
13862 ((struct symtab *) 0x86c1f38)
13865 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
13866 linetable ((struct linetable *) 0x8370fa0)
13867 debugformat DWARF 2
13876 @chapter Altering Execution
13878 Once you think you have found an error in your program, you might want to
13879 find out for certain whether correcting the apparent error would lead to
13880 correct results in the rest of the run. You can find the answer by
13881 experiment, using the @value{GDBN} features for altering execution of the
13884 For example, you can store new values into variables or memory
13885 locations, give your program a signal, restart it at a different
13886 address, or even return prematurely from a function.
13889 * Assignment:: Assignment to variables
13890 * Jumping:: Continuing at a different address
13891 * Signaling:: Giving your program a signal
13892 * Returning:: Returning from a function
13893 * Calling:: Calling your program's functions
13894 * Patching:: Patching your program
13898 @section Assignment to Variables
13901 @cindex setting variables
13902 To alter the value of a variable, evaluate an assignment expression.
13903 @xref{Expressions, ,Expressions}. For example,
13910 stores the value 4 into the variable @code{x}, and then prints the
13911 value of the assignment expression (which is 4).
13912 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
13913 information on operators in supported languages.
13915 @kindex set variable
13916 @cindex variables, setting
13917 If you are not interested in seeing the value of the assignment, use the
13918 @code{set} command instead of the @code{print} command. @code{set} is
13919 really the same as @code{print} except that the expression's value is
13920 not printed and is not put in the value history (@pxref{Value History,
13921 ,Value History}). The expression is evaluated only for its effects.
13923 If the beginning of the argument string of the @code{set} command
13924 appears identical to a @code{set} subcommand, use the @code{set
13925 variable} command instead of just @code{set}. This command is identical
13926 to @code{set} except for its lack of subcommands. For example, if your
13927 program has a variable @code{width}, you get an error if you try to set
13928 a new value with just @samp{set width=13}, because @value{GDBN} has the
13929 command @code{set width}:
13932 (@value{GDBP}) whatis width
13934 (@value{GDBP}) p width
13936 (@value{GDBP}) set width=47
13937 Invalid syntax in expression.
13941 The invalid expression, of course, is @samp{=47}. In
13942 order to actually set the program's variable @code{width}, use
13945 (@value{GDBP}) set var width=47
13948 Because the @code{set} command has many subcommands that can conflict
13949 with the names of program variables, it is a good idea to use the
13950 @code{set variable} command instead of just @code{set}. For example, if
13951 your program has a variable @code{g}, you run into problems if you try
13952 to set a new value with just @samp{set g=4}, because @value{GDBN} has
13953 the command @code{set gnutarget}, abbreviated @code{set g}:
13957 (@value{GDBP}) whatis g
13961 (@value{GDBP}) set g=4
13965 The program being debugged has been started already.
13966 Start it from the beginning? (y or n) y
13967 Starting program: /home/smith/cc_progs/a.out
13968 "/home/smith/cc_progs/a.out": can't open to read symbols:
13969 Invalid bfd target.
13970 (@value{GDBP}) show g
13971 The current BFD target is "=4".
13976 The program variable @code{g} did not change, and you silently set the
13977 @code{gnutarget} to an invalid value. In order to set the variable
13981 (@value{GDBP}) set var g=4
13984 @value{GDBN} allows more implicit conversions in assignments than C; you can
13985 freely store an integer value into a pointer variable or vice versa,
13986 and you can convert any structure to any other structure that is the
13987 same length or shorter.
13988 @comment FIXME: how do structs align/pad in these conversions?
13989 @comment /doc@cygnus.com 18dec1990
13991 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
13992 construct to generate a value of specified type at a specified address
13993 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
13994 to memory location @code{0x83040} as an integer (which implies a certain size
13995 and representation in memory), and
13998 set @{int@}0x83040 = 4
14002 stores the value 4 into that memory location.
14005 @section Continuing at a Different Address
14007 Ordinarily, when you continue your program, you do so at the place where
14008 it stopped, with the @code{continue} command. You can instead continue at
14009 an address of your own choosing, with the following commands:
14013 @item jump @var{linespec}
14014 @itemx jump @var{location}
14015 Resume execution at line @var{linespec} or at address given by
14016 @var{location}. Execution stops again immediately if there is a
14017 breakpoint there. @xref{Specify Location}, for a description of the
14018 different forms of @var{linespec} and @var{location}. It is common
14019 practice to use the @code{tbreak} command in conjunction with
14020 @code{jump}. @xref{Set Breaks, ,Setting Breakpoints}.
14022 The @code{jump} command does not change the current stack frame, or
14023 the stack pointer, or the contents of any memory location or any
14024 register other than the program counter. If line @var{linespec} is in
14025 a different function from the one currently executing, the results may
14026 be bizarre if the two functions expect different patterns of arguments or
14027 of local variables. For this reason, the @code{jump} command requests
14028 confirmation if the specified line is not in the function currently
14029 executing. However, even bizarre results are predictable if you are
14030 well acquainted with the machine-language code of your program.
14033 @c Doesn't work on HP-UX; have to set $pcoqh and $pcoqt.
14034 On many systems, you can get much the same effect as the @code{jump}
14035 command by storing a new value into the register @code{$pc}. The
14036 difference is that this does not start your program running; it only
14037 changes the address of where it @emph{will} run when you continue. For
14045 makes the next @code{continue} command or stepping command execute at
14046 address @code{0x485}, rather than at the address where your program stopped.
14047 @xref{Continuing and Stepping, ,Continuing and Stepping}.
14049 The most common occasion to use the @code{jump} command is to back
14050 up---perhaps with more breakpoints set---over a portion of a program
14051 that has already executed, in order to examine its execution in more
14056 @section Giving your Program a Signal
14057 @cindex deliver a signal to a program
14061 @item signal @var{signal}
14062 Resume execution where your program stopped, but immediately give it the
14063 signal @var{signal}. @var{signal} can be the name or the number of a
14064 signal. For example, on many systems @code{signal 2} and @code{signal
14065 SIGINT} are both ways of sending an interrupt signal.
14067 Alternatively, if @var{signal} is zero, continue execution without
14068 giving a signal. This is useful when your program stopped on account of
14069 a signal and would ordinary see the signal when resumed with the
14070 @code{continue} command; @samp{signal 0} causes it to resume without a
14073 @code{signal} does not repeat when you press @key{RET} a second time
14074 after executing the command.
14078 Invoking the @code{signal} command is not the same as invoking the
14079 @code{kill} utility from the shell. Sending a signal with @code{kill}
14080 causes @value{GDBN} to decide what to do with the signal depending on
14081 the signal handling tables (@pxref{Signals}). The @code{signal} command
14082 passes the signal directly to your program.
14086 @section Returning from a Function
14089 @cindex returning from a function
14092 @itemx return @var{expression}
14093 You can cancel execution of a function call with the @code{return}
14094 command. If you give an
14095 @var{expression} argument, its value is used as the function's return
14099 When you use @code{return}, @value{GDBN} discards the selected stack frame
14100 (and all frames within it). You can think of this as making the
14101 discarded frame return prematurely. If you wish to specify a value to
14102 be returned, give that value as the argument to @code{return}.
14104 This pops the selected stack frame (@pxref{Selection, ,Selecting a
14105 Frame}), and any other frames inside of it, leaving its caller as the
14106 innermost remaining frame. That frame becomes selected. The
14107 specified value is stored in the registers used for returning values
14110 The @code{return} command does not resume execution; it leaves the
14111 program stopped in the state that would exist if the function had just
14112 returned. In contrast, the @code{finish} command (@pxref{Continuing
14113 and Stepping, ,Continuing and Stepping}) resumes execution until the
14114 selected stack frame returns naturally.
14116 @value{GDBN} needs to know how the @var{expression} argument should be set for
14117 the inferior. The concrete registers assignment depends on the OS ABI and the
14118 type being returned by the selected stack frame. For example it is common for
14119 OS ABI to return floating point values in FPU registers while integer values in
14120 CPU registers. Still some ABIs return even floating point values in CPU
14121 registers. Larger integer widths (such as @code{long long int}) also have
14122 specific placement rules. @value{GDBN} already knows the OS ABI from its
14123 current target so it needs to find out also the type being returned to make the
14124 assignment into the right register(s).
14126 Normally, the selected stack frame has debug info. @value{GDBN} will always
14127 use the debug info instead of the implicit type of @var{expression} when the
14128 debug info is available. For example, if you type @kbd{return -1}, and the
14129 function in the current stack frame is declared to return a @code{long long
14130 int}, @value{GDBN} transparently converts the implicit @code{int} value of -1
14131 into a @code{long long int}:
14134 Breakpoint 1, func () at gdb.base/return-nodebug.c:29
14136 (@value{GDBP}) return -1
14137 Make func return now? (y or n) y
14138 #0 0x004004f6 in main () at gdb.base/return-nodebug.c:43
14139 43 printf ("result=%lld\n", func ());
14143 However, if the selected stack frame does not have a debug info, e.g., if the
14144 function was compiled without debug info, @value{GDBN} has to find out the type
14145 to return from user. Specifying a different type by mistake may set the value
14146 in different inferior registers than the caller code expects. For example,
14147 typing @kbd{return -1} with its implicit type @code{int} would set only a part
14148 of a @code{long long int} result for a debug info less function (on 32-bit
14149 architectures). Therefore the user is required to specify the return type by
14150 an appropriate cast explicitly:
14153 Breakpoint 2, 0x0040050b in func ()
14154 (@value{GDBP}) return -1
14155 Return value type not available for selected stack frame.
14156 Please use an explicit cast of the value to return.
14157 (@value{GDBP}) return (long long int) -1
14158 Make selected stack frame return now? (y or n) y
14159 #0 0x00400526 in main ()
14164 @section Calling Program Functions
14167 @cindex calling functions
14168 @cindex inferior functions, calling
14169 @item print @var{expr}
14170 Evaluate the expression @var{expr} and display the resulting value.
14171 @var{expr} may include calls to functions in the program being
14175 @item call @var{expr}
14176 Evaluate the expression @var{expr} without displaying @code{void}
14179 You can use this variant of the @code{print} command if you want to
14180 execute a function from your program that does not return anything
14181 (a.k.a.@: @dfn{a void function}), but without cluttering the output
14182 with @code{void} returned values that @value{GDBN} will otherwise
14183 print. If the result is not void, it is printed and saved in the
14187 It is possible for the function you call via the @code{print} or
14188 @code{call} command to generate a signal (e.g., if there's a bug in
14189 the function, or if you passed it incorrect arguments). What happens
14190 in that case is controlled by the @code{set unwindonsignal} command.
14192 Similarly, with a C@t{++} program it is possible for the function you
14193 call via the @code{print} or @code{call} command to generate an
14194 exception that is not handled due to the constraints of the dummy
14195 frame. In this case, any exception that is raised in the frame, but has
14196 an out-of-frame exception handler will not be found. GDB builds a
14197 dummy-frame for the inferior function call, and the unwinder cannot
14198 seek for exception handlers outside of this dummy-frame. What happens
14199 in that case is controlled by the
14200 @code{set unwind-on-terminating-exception} command.
14203 @item set unwindonsignal
14204 @kindex set unwindonsignal
14205 @cindex unwind stack in called functions
14206 @cindex call dummy stack unwinding
14207 Set unwinding of the stack if a signal is received while in a function
14208 that @value{GDBN} called in the program being debugged. If set to on,
14209 @value{GDBN} unwinds the stack it created for the call and restores
14210 the context to what it was before the call. If set to off (the
14211 default), @value{GDBN} stops in the frame where the signal was
14214 @item show unwindonsignal
14215 @kindex show unwindonsignal
14216 Show the current setting of stack unwinding in the functions called by
14219 @item set unwind-on-terminating-exception
14220 @kindex set unwind-on-terminating-exception
14221 @cindex unwind stack in called functions with unhandled exceptions
14222 @cindex call dummy stack unwinding on unhandled exception.
14223 Set unwinding of the stack if a C@t{++} exception is raised, but left
14224 unhandled while in a function that @value{GDBN} called in the program being
14225 debugged. If set to on (the default), @value{GDBN} unwinds the stack
14226 it created for the call and restores the context to what it was before
14227 the call. If set to off, @value{GDBN} the exception is delivered to
14228 the default C@t{++} exception handler and the inferior terminated.
14230 @item show unwind-on-terminating-exception
14231 @kindex show unwind-on-terminating-exception
14232 Show the current setting of stack unwinding in the functions called by
14237 @cindex weak alias functions
14238 Sometimes, a function you wish to call is actually a @dfn{weak alias}
14239 for another function. In such case, @value{GDBN} might not pick up
14240 the type information, including the types of the function arguments,
14241 which causes @value{GDBN} to call the inferior function incorrectly.
14242 As a result, the called function will function erroneously and may
14243 even crash. A solution to that is to use the name of the aliased
14247 @section Patching Programs
14249 @cindex patching binaries
14250 @cindex writing into executables
14251 @cindex writing into corefiles
14253 By default, @value{GDBN} opens the file containing your program's
14254 executable code (or the corefile) read-only. This prevents accidental
14255 alterations to machine code; but it also prevents you from intentionally
14256 patching your program's binary.
14258 If you'd like to be able to patch the binary, you can specify that
14259 explicitly with the @code{set write} command. For example, you might
14260 want to turn on internal debugging flags, or even to make emergency
14266 @itemx set write off
14267 If you specify @samp{set write on}, @value{GDBN} opens executable and
14268 core files for both reading and writing; if you specify @kbd{set write
14269 off} (the default), @value{GDBN} opens them read-only.
14271 If you have already loaded a file, you must load it again (using the
14272 @code{exec-file} or @code{core-file} command) after changing @code{set
14273 write}, for your new setting to take effect.
14277 Display whether executable files and core files are opened for writing
14278 as well as reading.
14282 @chapter @value{GDBN} Files
14284 @value{GDBN} needs to know the file name of the program to be debugged,
14285 both in order to read its symbol table and in order to start your
14286 program. To debug a core dump of a previous run, you must also tell
14287 @value{GDBN} the name of the core dump file.
14290 * Files:: Commands to specify files
14291 * Separate Debug Files:: Debugging information in separate files
14292 * Index Files:: Index files speed up GDB
14293 * Symbol Errors:: Errors reading symbol files
14294 * Data Files:: GDB data files
14298 @section Commands to Specify Files
14300 @cindex symbol table
14301 @cindex core dump file
14303 You may want to specify executable and core dump file names. The usual
14304 way to do this is at start-up time, using the arguments to
14305 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
14306 Out of @value{GDBN}}).
14308 Occasionally it is necessary to change to a different file during a
14309 @value{GDBN} session. Or you may run @value{GDBN} and forget to
14310 specify a file you want to use. Or you are debugging a remote target
14311 via @code{gdbserver} (@pxref{Server, file, Using the @code{gdbserver}
14312 Program}). In these situations the @value{GDBN} commands to specify
14313 new files are useful.
14316 @cindex executable file
14318 @item file @var{filename}
14319 Use @var{filename} as the program to be debugged. It is read for its
14320 symbols and for the contents of pure memory. It is also the program
14321 executed when you use the @code{run} command. If you do not specify a
14322 directory and the file is not found in the @value{GDBN} working directory,
14323 @value{GDBN} uses the environment variable @code{PATH} as a list of
14324 directories to search, just as the shell does when looking for a program
14325 to run. You can change the value of this variable, for both @value{GDBN}
14326 and your program, using the @code{path} command.
14328 @cindex unlinked object files
14329 @cindex patching object files
14330 You can load unlinked object @file{.o} files into @value{GDBN} using
14331 the @code{file} command. You will not be able to ``run'' an object
14332 file, but you can disassemble functions and inspect variables. Also,
14333 if the underlying BFD functionality supports it, you could use
14334 @kbd{gdb -write} to patch object files using this technique. Note
14335 that @value{GDBN} can neither interpret nor modify relocations in this
14336 case, so branches and some initialized variables will appear to go to
14337 the wrong place. But this feature is still handy from time to time.
14340 @code{file} with no argument makes @value{GDBN} discard any information it
14341 has on both executable file and the symbol table.
14344 @item exec-file @r{[} @var{filename} @r{]}
14345 Specify that the program to be run (but not the symbol table) is found
14346 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
14347 if necessary to locate your program. Omitting @var{filename} means to
14348 discard information on the executable file.
14350 @kindex symbol-file
14351 @item symbol-file @r{[} @var{filename} @r{]}
14352 Read symbol table information from file @var{filename}. @code{PATH} is
14353 searched when necessary. Use the @code{file} command to get both symbol
14354 table and program to run from the same file.
14356 @code{symbol-file} with no argument clears out @value{GDBN} information on your
14357 program's symbol table.
14359 The @code{symbol-file} command causes @value{GDBN} to forget the contents of
14360 some breakpoints and auto-display expressions. This is because they may
14361 contain pointers to the internal data recording symbols and data types,
14362 which are part of the old symbol table data being discarded inside
14365 @code{symbol-file} does not repeat if you press @key{RET} again after
14368 When @value{GDBN} is configured for a particular environment, it
14369 understands debugging information in whatever format is the standard
14370 generated for that environment; you may use either a @sc{gnu} compiler, or
14371 other compilers that adhere to the local conventions.
14372 Best results are usually obtained from @sc{gnu} compilers; for example,
14373 using @code{@value{NGCC}} you can generate debugging information for
14376 For most kinds of object files, with the exception of old SVR3 systems
14377 using COFF, the @code{symbol-file} command does not normally read the
14378 symbol table in full right away. Instead, it scans the symbol table
14379 quickly to find which source files and which symbols are present. The
14380 details are read later, one source file at a time, as they are needed.
14382 The purpose of this two-stage reading strategy is to make @value{GDBN}
14383 start up faster. For the most part, it is invisible except for
14384 occasional pauses while the symbol table details for a particular source
14385 file are being read. (The @code{set verbose} command can turn these
14386 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
14387 Warnings and Messages}.)
14389 We have not implemented the two-stage strategy for COFF yet. When the
14390 symbol table is stored in COFF format, @code{symbol-file} reads the
14391 symbol table data in full right away. Note that ``stabs-in-COFF''
14392 still does the two-stage strategy, since the debug info is actually
14396 @cindex reading symbols immediately
14397 @cindex symbols, reading immediately
14398 @item symbol-file @r{[} -readnow @r{]} @var{filename}
14399 @itemx file @r{[} -readnow @r{]} @var{filename}
14400 You can override the @value{GDBN} two-stage strategy for reading symbol
14401 tables by using the @samp{-readnow} option with any of the commands that
14402 load symbol table information, if you want to be sure @value{GDBN} has the
14403 entire symbol table available.
14405 @c FIXME: for now no mention of directories, since this seems to be in
14406 @c flux. 13mar1992 status is that in theory GDB would look either in
14407 @c current dir or in same dir as myprog; but issues like competing
14408 @c GDB's, or clutter in system dirs, mean that in practice right now
14409 @c only current dir is used. FFish says maybe a special GDB hierarchy
14410 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
14414 @item core-file @r{[}@var{filename}@r{]}
14416 Specify the whereabouts of a core dump file to be used as the ``contents
14417 of memory''. Traditionally, core files contain only some parts of the
14418 address space of the process that generated them; @value{GDBN} can access the
14419 executable file itself for other parts.
14421 @code{core-file} with no argument specifies that no core file is
14424 Note that the core file is ignored when your program is actually running
14425 under @value{GDBN}. So, if you have been running your program and you
14426 wish to debug a core file instead, you must kill the subprocess in which
14427 the program is running. To do this, use the @code{kill} command
14428 (@pxref{Kill Process, ,Killing the Child Process}).
14430 @kindex add-symbol-file
14431 @cindex dynamic linking
14432 @item add-symbol-file @var{filename} @var{address}
14433 @itemx add-symbol-file @var{filename} @var{address} @r{[} -readnow @r{]}
14434 @itemx add-symbol-file @var{filename} @r{-s}@var{section} @var{address} @dots{}
14435 The @code{add-symbol-file} command reads additional symbol table
14436 information from the file @var{filename}. You would use this command
14437 when @var{filename} has been dynamically loaded (by some other means)
14438 into the program that is running. @var{address} should be the memory
14439 address at which the file has been loaded; @value{GDBN} cannot figure
14440 this out for itself. You can additionally specify an arbitrary number
14441 of @samp{@r{-s}@var{section} @var{address}} pairs, to give an explicit
14442 section name and base address for that section. You can specify any
14443 @var{address} as an expression.
14445 The symbol table of the file @var{filename} is added to the symbol table
14446 originally read with the @code{symbol-file} command. You can use the
14447 @code{add-symbol-file} command any number of times; the new symbol data
14448 thus read keeps adding to the old. To discard all old symbol data
14449 instead, use the @code{symbol-file} command without any arguments.
14451 @cindex relocatable object files, reading symbols from
14452 @cindex object files, relocatable, reading symbols from
14453 @cindex reading symbols from relocatable object files
14454 @cindex symbols, reading from relocatable object files
14455 @cindex @file{.o} files, reading symbols from
14456 Although @var{filename} is typically a shared library file, an
14457 executable file, or some other object file which has been fully
14458 relocated for loading into a process, you can also load symbolic
14459 information from relocatable @file{.o} files, as long as:
14463 the file's symbolic information refers only to linker symbols defined in
14464 that file, not to symbols defined by other object files,
14466 every section the file's symbolic information refers to has actually
14467 been loaded into the inferior, as it appears in the file, and
14469 you can determine the address at which every section was loaded, and
14470 provide these to the @code{add-symbol-file} command.
14474 Some embedded operating systems, like Sun Chorus and VxWorks, can load
14475 relocatable files into an already running program; such systems
14476 typically make the requirements above easy to meet. However, it's
14477 important to recognize that many native systems use complex link
14478 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
14479 assembly, for example) that make the requirements difficult to meet. In
14480 general, one cannot assume that using @code{add-symbol-file} to read a
14481 relocatable object file's symbolic information will have the same effect
14482 as linking the relocatable object file into the program in the normal
14485 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
14487 @kindex add-symbol-file-from-memory
14488 @cindex @code{syscall DSO}
14489 @cindex load symbols from memory
14490 @item add-symbol-file-from-memory @var{address}
14491 Load symbols from the given @var{address} in a dynamically loaded
14492 object file whose image is mapped directly into the inferior's memory.
14493 For example, the Linux kernel maps a @code{syscall DSO} into each
14494 process's address space; this DSO provides kernel-specific code for
14495 some system calls. The argument can be any expression whose
14496 evaluation yields the address of the file's shared object file header.
14497 For this command to work, you must have used @code{symbol-file} or
14498 @code{exec-file} commands in advance.
14500 @kindex add-shared-symbol-files
14502 @item add-shared-symbol-files @var{library-file}
14503 @itemx assf @var{library-file}
14504 The @code{add-shared-symbol-files} command can currently be used only
14505 in the Cygwin build of @value{GDBN} on MS-Windows OS, where it is an
14506 alias for the @code{dll-symbols} command (@pxref{Cygwin Native}).
14507 @value{GDBN} automatically looks for shared libraries, however if
14508 @value{GDBN} does not find yours, you can invoke
14509 @code{add-shared-symbol-files}. It takes one argument: the shared
14510 library's file name. @code{assf} is a shorthand alias for
14511 @code{add-shared-symbol-files}.
14514 @item section @var{section} @var{addr}
14515 The @code{section} command changes the base address of the named
14516 @var{section} of the exec file to @var{addr}. This can be used if the
14517 exec file does not contain section addresses, (such as in the
14518 @code{a.out} format), or when the addresses specified in the file
14519 itself are wrong. Each section must be changed separately. The
14520 @code{info files} command, described below, lists all the sections and
14524 @kindex info target
14527 @code{info files} and @code{info target} are synonymous; both print the
14528 current target (@pxref{Targets, ,Specifying a Debugging Target}),
14529 including the names of the executable and core dump files currently in
14530 use by @value{GDBN}, and the files from which symbols were loaded. The
14531 command @code{help target} lists all possible targets rather than
14534 @kindex maint info sections
14535 @item maint info sections
14536 Another command that can give you extra information about program sections
14537 is @code{maint info sections}. In addition to the section information
14538 displayed by @code{info files}, this command displays the flags and file
14539 offset of each section in the executable and core dump files. In addition,
14540 @code{maint info sections} provides the following command options (which
14541 may be arbitrarily combined):
14545 Display sections for all loaded object files, including shared libraries.
14546 @item @var{sections}
14547 Display info only for named @var{sections}.
14548 @item @var{section-flags}
14549 Display info only for sections for which @var{section-flags} are true.
14550 The section flags that @value{GDBN} currently knows about are:
14553 Section will have space allocated in the process when loaded.
14554 Set for all sections except those containing debug information.
14556 Section will be loaded from the file into the child process memory.
14557 Set for pre-initialized code and data, clear for @code{.bss} sections.
14559 Section needs to be relocated before loading.
14561 Section cannot be modified by the child process.
14563 Section contains executable code only.
14565 Section contains data only (no executable code).
14567 Section will reside in ROM.
14569 Section contains data for constructor/destructor lists.
14571 Section is not empty.
14573 An instruction to the linker to not output the section.
14574 @item COFF_SHARED_LIBRARY
14575 A notification to the linker that the section contains
14576 COFF shared library information.
14578 Section contains common symbols.
14581 @kindex set trust-readonly-sections
14582 @cindex read-only sections
14583 @item set trust-readonly-sections on
14584 Tell @value{GDBN} that readonly sections in your object file
14585 really are read-only (i.e.@: that their contents will not change).
14586 In that case, @value{GDBN} can fetch values from these sections
14587 out of the object file, rather than from the target program.
14588 For some targets (notably embedded ones), this can be a significant
14589 enhancement to debugging performance.
14591 The default is off.
14593 @item set trust-readonly-sections off
14594 Tell @value{GDBN} not to trust readonly sections. This means that
14595 the contents of the section might change while the program is running,
14596 and must therefore be fetched from the target when needed.
14598 @item show trust-readonly-sections
14599 Show the current setting of trusting readonly sections.
14602 All file-specifying commands allow both absolute and relative file names
14603 as arguments. @value{GDBN} always converts the file name to an absolute file
14604 name and remembers it that way.
14606 @cindex shared libraries
14607 @anchor{Shared Libraries}
14608 @value{GDBN} supports @sc{gnu}/Linux, MS-Windows, HP-UX, SunOS, SVr4, Irix,
14609 and IBM RS/6000 AIX shared libraries.
14611 On MS-Windows @value{GDBN} must be linked with the Expat library to support
14612 shared libraries. @xref{Expat}.
14614 @value{GDBN} automatically loads symbol definitions from shared libraries
14615 when you use the @code{run} command, or when you examine a core file.
14616 (Before you issue the @code{run} command, @value{GDBN} does not understand
14617 references to a function in a shared library, however---unless you are
14618 debugging a core file).
14620 On HP-UX, if the program loads a library explicitly, @value{GDBN}
14621 automatically loads the symbols at the time of the @code{shl_load} call.
14623 @c FIXME: some @value{GDBN} release may permit some refs to undef
14624 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
14625 @c FIXME...lib; check this from time to time when updating manual
14627 There are times, however, when you may wish to not automatically load
14628 symbol definitions from shared libraries, such as when they are
14629 particularly large or there are many of them.
14631 To control the automatic loading of shared library symbols, use the
14635 @kindex set auto-solib-add
14636 @item set auto-solib-add @var{mode}
14637 If @var{mode} is @code{on}, symbols from all shared object libraries
14638 will be loaded automatically when the inferior begins execution, you
14639 attach to an independently started inferior, or when the dynamic linker
14640 informs @value{GDBN} that a new library has been loaded. If @var{mode}
14641 is @code{off}, symbols must be loaded manually, using the
14642 @code{sharedlibrary} command. The default value is @code{on}.
14644 @cindex memory used for symbol tables
14645 If your program uses lots of shared libraries with debug info that
14646 takes large amounts of memory, you can decrease the @value{GDBN}
14647 memory footprint by preventing it from automatically loading the
14648 symbols from shared libraries. To that end, type @kbd{set
14649 auto-solib-add off} before running the inferior, then load each
14650 library whose debug symbols you do need with @kbd{sharedlibrary
14651 @var{regexp}}, where @var{regexp} is a regular expression that matches
14652 the libraries whose symbols you want to be loaded.
14654 @kindex show auto-solib-add
14655 @item show auto-solib-add
14656 Display the current autoloading mode.
14659 @cindex load shared library
14660 To explicitly load shared library symbols, use the @code{sharedlibrary}
14664 @kindex info sharedlibrary
14666 @item info share @var{regex}
14667 @itemx info sharedlibrary @var{regex}
14668 Print the names of the shared libraries which are currently loaded
14669 that match @var{regex}. If @var{regex} is omitted then print
14670 all shared libraries that are loaded.
14672 @kindex sharedlibrary
14674 @item sharedlibrary @var{regex}
14675 @itemx share @var{regex}
14676 Load shared object library symbols for files matching a
14677 Unix regular expression.
14678 As with files loaded automatically, it only loads shared libraries
14679 required by your program for a core file or after typing @code{run}. If
14680 @var{regex} is omitted all shared libraries required by your program are
14683 @item nosharedlibrary
14684 @kindex nosharedlibrary
14685 @cindex unload symbols from shared libraries
14686 Unload all shared object library symbols. This discards all symbols
14687 that have been loaded from all shared libraries. Symbols from shared
14688 libraries that were loaded by explicit user requests are not
14692 Sometimes you may wish that @value{GDBN} stops and gives you control
14693 when any of shared library events happen. Use the @code{set
14694 stop-on-solib-events} command for this:
14697 @item set stop-on-solib-events
14698 @kindex set stop-on-solib-events
14699 This command controls whether @value{GDBN} should give you control
14700 when the dynamic linker notifies it about some shared library event.
14701 The most common event of interest is loading or unloading of a new
14704 @item show stop-on-solib-events
14705 @kindex show stop-on-solib-events
14706 Show whether @value{GDBN} stops and gives you control when shared
14707 library events happen.
14710 Shared libraries are also supported in many cross or remote debugging
14711 configurations. @value{GDBN} needs to have access to the target's libraries;
14712 this can be accomplished either by providing copies of the libraries
14713 on the host system, or by asking @value{GDBN} to automatically retrieve the
14714 libraries from the target. If copies of the target libraries are
14715 provided, they need to be the same as the target libraries, although the
14716 copies on the target can be stripped as long as the copies on the host are
14719 @cindex where to look for shared libraries
14720 For remote debugging, you need to tell @value{GDBN} where the target
14721 libraries are, so that it can load the correct copies---otherwise, it
14722 may try to load the host's libraries. @value{GDBN} has two variables
14723 to specify the search directories for target libraries.
14726 @cindex prefix for shared library file names
14727 @cindex system root, alternate
14728 @kindex set solib-absolute-prefix
14729 @kindex set sysroot
14730 @item set sysroot @var{path}
14731 Use @var{path} as the system root for the program being debugged. Any
14732 absolute shared library paths will be prefixed with @var{path}; many
14733 runtime loaders store the absolute paths to the shared library in the
14734 target program's memory. If you use @code{set sysroot} to find shared
14735 libraries, they need to be laid out in the same way that they are on
14736 the target, with e.g.@: a @file{/lib} and @file{/usr/lib} hierarchy
14739 If @var{path} starts with the sequence @file{remote:}, @value{GDBN} will
14740 retrieve the target libraries from the remote system. This is only
14741 supported when using a remote target that supports the @code{remote get}
14742 command (@pxref{File Transfer,,Sending files to a remote system}).
14743 The part of @var{path} following the initial @file{remote:}
14744 (if present) is used as system root prefix on the remote file system.
14745 @footnote{If you want to specify a local system root using a directory
14746 that happens to be named @file{remote:}, you need to use some equivalent
14747 variant of the name like @file{./remote:}.}
14749 For targets with an MS-DOS based filesystem, such as MS-Windows and
14750 SymbianOS, @value{GDBN} tries prefixing a few variants of the target
14751 absolute file name with @var{path}. But first, on Unix hosts,
14752 @value{GDBN} converts all backslash directory separators into forward
14753 slashes, because the backslash is not a directory separator on Unix:
14756 c:\foo\bar.dll @result{} c:/foo/bar.dll
14759 Then, @value{GDBN} attempts prefixing the target file name with
14760 @var{path}, and looks for the resulting file name in the host file
14764 c:/foo/bar.dll @result{} /path/to/sysroot/c:/foo/bar.dll
14767 If that does not find the shared library, @value{GDBN} tries removing
14768 the @samp{:} character from the drive spec, both for convenience, and,
14769 for the case of the host file system not supporting file names with
14773 c:/foo/bar.dll @result{} /path/to/sysroot/c/foo/bar.dll
14776 This makes it possible to have a system root that mirrors a target
14777 with more than one drive. E.g., you may want to setup your local
14778 copies of the target system shared libraries like so (note @samp{c} vs
14782 @file{/path/to/sysroot/c/sys/bin/foo.dll}
14783 @file{/path/to/sysroot/c/sys/bin/bar.dll}
14784 @file{/path/to/sysroot/z/sys/bin/bar.dll}
14788 and point the system root at @file{/path/to/sysroot}, so that
14789 @value{GDBN} can find the correct copies of both
14790 @file{c:\sys\bin\foo.dll}, and @file{z:\sys\bin\bar.dll}.
14792 If that still does not find the shared library, @value{GDBN} tries
14793 removing the whole drive spec from the target file name:
14796 c:/foo/bar.dll @result{} /path/to/sysroot/foo/bar.dll
14799 This last lookup makes it possible to not care about the drive name,
14800 if you don't want or need to.
14802 The @code{set solib-absolute-prefix} command is an alias for @code{set
14805 @cindex default system root
14806 @cindex @samp{--with-sysroot}
14807 You can set the default system root by using the configure-time
14808 @samp{--with-sysroot} option. If the system root is inside
14809 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
14810 @samp{--exec-prefix}), then the default system root will be updated
14811 automatically if the installed @value{GDBN} is moved to a new
14814 @kindex show sysroot
14816 Display the current shared library prefix.
14818 @kindex set solib-search-path
14819 @item set solib-search-path @var{path}
14820 If this variable is set, @var{path} is a colon-separated list of
14821 directories to search for shared libraries. @samp{solib-search-path}
14822 is used after @samp{sysroot} fails to locate the library, or if the
14823 path to the library is relative instead of absolute. If you want to
14824 use @samp{solib-search-path} instead of @samp{sysroot}, be sure to set
14825 @samp{sysroot} to a nonexistent directory to prevent @value{GDBN} from
14826 finding your host's libraries. @samp{sysroot} is preferred; setting
14827 it to a nonexistent directory may interfere with automatic loading
14828 of shared library symbols.
14830 @kindex show solib-search-path
14831 @item show solib-search-path
14832 Display the current shared library search path.
14834 @cindex DOS file-name semantics of file names.
14835 @kindex set target-file-system-kind (unix|dos-based|auto)
14836 @kindex show target-file-system-kind
14837 @item set target-file-system-kind @var{kind}
14838 Set assumed file system kind for target reported file names.
14840 Shared library file names as reported by the target system may not
14841 make sense as is on the system @value{GDBN} is running on. For
14842 example, when remote debugging a target that has MS-DOS based file
14843 system semantics, from a Unix host, the target may be reporting to
14844 @value{GDBN} a list of loaded shared libraries with file names such as
14845 @file{c:\Windows\kernel32.dll}. On Unix hosts, there's no concept of
14846 drive letters, so the @samp{c:\} prefix is not normally understood as
14847 indicating an absolute file name, and neither is the backslash
14848 normally considered a directory separator character. In that case,
14849 the native file system would interpret this whole absolute file name
14850 as a relative file name with no directory components. This would make
14851 it impossible to point @value{GDBN} at a copy of the remote target's
14852 shared libraries on the host using @code{set sysroot}, and impractical
14853 with @code{set solib-search-path}. Setting
14854 @code{target-file-system-kind} to @code{dos-based} tells @value{GDBN}
14855 to interpret such file names similarly to how the target would, and to
14856 map them to file names valid on @value{GDBN}'s native file system
14857 semantics. The value of @var{kind} can be @code{"auto"}, in addition
14858 to one of the supported file system kinds. In that case, @value{GDBN}
14859 tries to determine the appropriate file system variant based on the
14860 current target's operating system (@pxref{ABI, ,Configuring the
14861 Current ABI}). The supported file system settings are:
14865 Instruct @value{GDBN} to assume the target file system is of Unix
14866 kind. Only file names starting the forward slash (@samp{/}) character
14867 are considered absolute, and the directory separator character is also
14871 Instruct @value{GDBN} to assume the target file system is DOS based.
14872 File names starting with either a forward slash, or a drive letter
14873 followed by a colon (e.g., @samp{c:}), are considered absolute, and
14874 both the slash (@samp{/}) and the backslash (@samp{\\}) characters are
14875 considered directory separators.
14878 Instruct @value{GDBN} to use the file system kind associated with the
14879 target operating system (@pxref{ABI, ,Configuring the Current ABI}).
14880 This is the default.
14885 @node Separate Debug Files
14886 @section Debugging Information in Separate Files
14887 @cindex separate debugging information files
14888 @cindex debugging information in separate files
14889 @cindex @file{.debug} subdirectories
14890 @cindex debugging information directory, global
14891 @cindex global debugging information directory
14892 @cindex build ID, and separate debugging files
14893 @cindex @file{.build-id} directory
14895 @value{GDBN} allows you to put a program's debugging information in a
14896 file separate from the executable itself, in a way that allows
14897 @value{GDBN} to find and load the debugging information automatically.
14898 Since debugging information can be very large---sometimes larger
14899 than the executable code itself---some systems distribute debugging
14900 information for their executables in separate files, which users can
14901 install only when they need to debug a problem.
14903 @value{GDBN} supports two ways of specifying the separate debug info
14908 The executable contains a @dfn{debug link} that specifies the name of
14909 the separate debug info file. The separate debug file's name is
14910 usually @file{@var{executable}.debug}, where @var{executable} is the
14911 name of the corresponding executable file without leading directories
14912 (e.g., @file{ls.debug} for @file{/usr/bin/ls}). In addition, the
14913 debug link specifies a 32-bit @dfn{Cyclic Redundancy Check} (CRC)
14914 checksum for the debug file, which @value{GDBN} uses to validate that
14915 the executable and the debug file came from the same build.
14918 The executable contains a @dfn{build ID}, a unique bit string that is
14919 also present in the corresponding debug info file. (This is supported
14920 only on some operating systems, notably those which use the ELF format
14921 for binary files and the @sc{gnu} Binutils.) For more details about
14922 this feature, see the description of the @option{--build-id}
14923 command-line option in @ref{Options, , Command Line Options, ld.info,
14924 The GNU Linker}. The debug info file's name is not specified
14925 explicitly by the build ID, but can be computed from the build ID, see
14929 Depending on the way the debug info file is specified, @value{GDBN}
14930 uses two different methods of looking for the debug file:
14934 For the ``debug link'' method, @value{GDBN} looks up the named file in
14935 the directory of the executable file, then in a subdirectory of that
14936 directory named @file{.debug}, and finally under the global debug
14937 directory, in a subdirectory whose name is identical to the leading
14938 directories of the executable's absolute file name.
14941 For the ``build ID'' method, @value{GDBN} looks in the
14942 @file{.build-id} subdirectory of the global debug directory for a file
14943 named @file{@var{nn}/@var{nnnnnnnn}.debug}, where @var{nn} are the
14944 first 2 hex characters of the build ID bit string, and @var{nnnnnnnn}
14945 are the rest of the bit string. (Real build ID strings are 32 or more
14946 hex characters, not 10.)
14949 So, for example, suppose you ask @value{GDBN} to debug
14950 @file{/usr/bin/ls}, which has a debug link that specifies the
14951 file @file{ls.debug}, and a build ID whose value in hex is
14952 @code{abcdef1234}. If the global debug directory is
14953 @file{/usr/lib/debug}, then @value{GDBN} will look for the following
14954 debug information files, in the indicated order:
14958 @file{/usr/lib/debug/.build-id/ab/cdef1234.debug}
14960 @file{/usr/bin/ls.debug}
14962 @file{/usr/bin/.debug/ls.debug}
14964 @file{/usr/lib/debug/usr/bin/ls.debug}.
14967 You can set the global debugging info directory's name, and view the
14968 name @value{GDBN} is currently using.
14972 @kindex set debug-file-directory
14973 @item set debug-file-directory @var{directories}
14974 Set the directories which @value{GDBN} searches for separate debugging
14975 information files to @var{directory}. Multiple directory components can be set
14976 concatenating them by a directory separator.
14978 @kindex show debug-file-directory
14979 @item show debug-file-directory
14980 Show the directories @value{GDBN} searches for separate debugging
14985 @cindex @code{.gnu_debuglink} sections
14986 @cindex debug link sections
14987 A debug link is a special section of the executable file named
14988 @code{.gnu_debuglink}. The section must contain:
14992 A filename, with any leading directory components removed, followed by
14995 zero to three bytes of padding, as needed to reach the next four-byte
14996 boundary within the section, and
14998 a four-byte CRC checksum, stored in the same endianness used for the
14999 executable file itself. The checksum is computed on the debugging
15000 information file's full contents by the function given below, passing
15001 zero as the @var{crc} argument.
15004 Any executable file format can carry a debug link, as long as it can
15005 contain a section named @code{.gnu_debuglink} with the contents
15008 @cindex @code{.note.gnu.build-id} sections
15009 @cindex build ID sections
15010 The build ID is a special section in the executable file (and in other
15011 ELF binary files that @value{GDBN} may consider). This section is
15012 often named @code{.note.gnu.build-id}, but that name is not mandatory.
15013 It contains unique identification for the built files---the ID remains
15014 the same across multiple builds of the same build tree. The default
15015 algorithm SHA1 produces 160 bits (40 hexadecimal characters) of the
15016 content for the build ID string. The same section with an identical
15017 value is present in the original built binary with symbols, in its
15018 stripped variant, and in the separate debugging information file.
15020 The debugging information file itself should be an ordinary
15021 executable, containing a full set of linker symbols, sections, and
15022 debugging information. The sections of the debugging information file
15023 should have the same names, addresses, and sizes as the original file,
15024 but they need not contain any data---much like a @code{.bss} section
15025 in an ordinary executable.
15027 The @sc{gnu} binary utilities (Binutils) package includes the
15028 @samp{objcopy} utility that can produce
15029 the separated executable / debugging information file pairs using the
15030 following commands:
15033 @kbd{objcopy --only-keep-debug foo foo.debug}
15038 These commands remove the debugging
15039 information from the executable file @file{foo} and place it in the file
15040 @file{foo.debug}. You can use the first, second or both methods to link the
15045 The debug link method needs the following additional command to also leave
15046 behind a debug link in @file{foo}:
15049 @kbd{objcopy --add-gnu-debuglink=foo.debug foo}
15052 Ulrich Drepper's @file{elfutils} package, starting with version 0.53, contains
15053 a version of the @code{strip} command such that the command @kbd{strip foo -f
15054 foo.debug} has the same functionality as the two @code{objcopy} commands and
15055 the @code{ln -s} command above, together.
15058 Build ID gets embedded into the main executable using @code{ld --build-id} or
15059 the @value{NGCC} counterpart @code{gcc -Wl,--build-id}. Build ID support plus
15060 compatibility fixes for debug files separation are present in @sc{gnu} binary
15061 utilities (Binutils) package since version 2.18.
15066 @cindex CRC algorithm definition
15067 The CRC used in @code{.gnu_debuglink} is the CRC-32 defined in
15068 IEEE 802.3 using the polynomial:
15070 @c TexInfo requires naked braces for multi-digit exponents for Tex
15071 @c output, but this causes HTML output to barf. HTML has to be set using
15072 @c raw commands. So we end up having to specify this equation in 2
15077 <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>
15078 + <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
15084 @math{x^{32} + x^{26} + x^{23} + x^{22} + x^{16} + x^{12} + x^{11}}
15085 @math{+ x^{10} + x^8 + x^7 + x^5 + x^4 + x^2 + x + 1}
15089 The function is computed byte at a time, taking the least
15090 significant bit of each byte first. The initial pattern
15091 @code{0xffffffff} is used, to ensure leading zeros affect the CRC and
15092 the final result is inverted to ensure trailing zeros also affect the
15095 @emph{Note:} This is the same CRC polynomial as used in handling the
15096 @dfn{Remote Serial Protocol} @code{qCRC} packet (@pxref{Remote Protocol,
15097 , @value{GDBN} Remote Serial Protocol}). However in the
15098 case of the Remote Serial Protocol, the CRC is computed @emph{most}
15099 significant bit first, and the result is not inverted, so trailing
15100 zeros have no effect on the CRC value.
15102 To complete the description, we show below the code of the function
15103 which produces the CRC used in @code{.gnu_debuglink}. Inverting the
15104 initially supplied @code{crc} argument means that an initial call to
15105 this function passing in zero will start computing the CRC using
15108 @kindex gnu_debuglink_crc32
15111 gnu_debuglink_crc32 (unsigned long crc,
15112 unsigned char *buf, size_t len)
15114 static const unsigned long crc32_table[256] =
15116 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
15117 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
15118 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
15119 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
15120 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
15121 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
15122 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
15123 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
15124 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
15125 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
15126 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
15127 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
15128 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
15129 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
15130 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
15131 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
15132 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
15133 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
15134 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
15135 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
15136 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
15137 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
15138 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
15139 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
15140 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
15141 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
15142 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
15143 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
15144 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
15145 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
15146 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
15147 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
15148 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
15149 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
15150 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
15151 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
15152 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
15153 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
15154 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
15155 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
15156 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
15157 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
15158 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
15159 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
15160 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
15161 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
15162 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
15163 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
15164 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
15165 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
15166 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
15169 unsigned char *end;
15171 crc = ~crc & 0xffffffff;
15172 for (end = buf + len; buf < end; ++buf)
15173 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
15174 return ~crc & 0xffffffff;
15179 This computation does not apply to the ``build ID'' method.
15183 @section Index Files Speed Up @value{GDBN}
15184 @cindex index files
15185 @cindex @samp{.gdb_index} section
15187 When @value{GDBN} finds a symbol file, it scans the symbols in the
15188 file in order to construct an internal symbol table. This lets most
15189 @value{GDBN} operations work quickly---at the cost of a delay early
15190 on. For large programs, this delay can be quite lengthy, so
15191 @value{GDBN} provides a way to build an index, which speeds up
15194 The index is stored as a section in the symbol file. @value{GDBN} can
15195 write the index to a file, then you can put it into the symbol file
15196 using @command{objcopy}.
15198 To create an index file, use the @code{save gdb-index} command:
15201 @item save gdb-index @var{directory}
15202 @kindex save gdb-index
15203 Create an index file for each symbol file currently known by
15204 @value{GDBN}. Each file is named after its corresponding symbol file,
15205 with @samp{.gdb-index} appended, and is written into the given
15209 Once you have created an index file you can merge it into your symbol
15210 file, here named @file{symfile}, using @command{objcopy}:
15213 $ objcopy --add-section .gdb_index=symfile.gdb-index \
15214 --set-section-flags .gdb_index=readonly symfile symfile
15217 There are currently some limitation on indices. They only work when
15218 for DWARF debugging information, not stabs. And, they do not
15219 currently work for programs using Ada.
15222 @node Symbol Errors
15223 @section Errors Reading Symbol Files
15225 While reading a symbol file, @value{GDBN} occasionally encounters problems,
15226 such as symbol types it does not recognize, or known bugs in compiler
15227 output. By default, @value{GDBN} does not notify you of such problems, since
15228 they are relatively common and primarily of interest to people
15229 debugging compilers. If you are interested in seeing information
15230 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
15231 only one message about each such type of problem, no matter how many
15232 times the problem occurs; or you can ask @value{GDBN} to print more messages,
15233 to see how many times the problems occur, with the @code{set
15234 complaints} command (@pxref{Messages/Warnings, ,Optional Warnings and
15237 The messages currently printed, and their meanings, include:
15240 @item inner block not inside outer block in @var{symbol}
15242 The symbol information shows where symbol scopes begin and end
15243 (such as at the start of a function or a block of statements). This
15244 error indicates that an inner scope block is not fully contained
15245 in its outer scope blocks.
15247 @value{GDBN} circumvents the problem by treating the inner block as if it had
15248 the same scope as the outer block. In the error message, @var{symbol}
15249 may be shown as ``@code{(don't know)}'' if the outer block is not a
15252 @item block at @var{address} out of order
15254 The symbol information for symbol scope blocks should occur in
15255 order of increasing addresses. This error indicates that it does not
15258 @value{GDBN} does not circumvent this problem, and has trouble
15259 locating symbols in the source file whose symbols it is reading. (You
15260 can often determine what source file is affected by specifying
15261 @code{set verbose on}. @xref{Messages/Warnings, ,Optional Warnings and
15264 @item bad block start address patched
15266 The symbol information for a symbol scope block has a start address
15267 smaller than the address of the preceding source line. This is known
15268 to occur in the SunOS 4.1.1 (and earlier) C compiler.
15270 @value{GDBN} circumvents the problem by treating the symbol scope block as
15271 starting on the previous source line.
15273 @item bad string table offset in symbol @var{n}
15276 Symbol number @var{n} contains a pointer into the string table which is
15277 larger than the size of the string table.
15279 @value{GDBN} circumvents the problem by considering the symbol to have the
15280 name @code{foo}, which may cause other problems if many symbols end up
15283 @item unknown symbol type @code{0x@var{nn}}
15285 The symbol information contains new data types that @value{GDBN} does
15286 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
15287 uncomprehended information, in hexadecimal.
15289 @value{GDBN} circumvents the error by ignoring this symbol information.
15290 This usually allows you to debug your program, though certain symbols
15291 are not accessible. If you encounter such a problem and feel like
15292 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
15293 on @code{complain}, then go up to the function @code{read_dbx_symtab}
15294 and examine @code{*bufp} to see the symbol.
15296 @item stub type has NULL name
15298 @value{GDBN} could not find the full definition for a struct or class.
15300 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
15301 The symbol information for a C@t{++} member function is missing some
15302 information that recent versions of the compiler should have output for
15305 @item info mismatch between compiler and debugger
15307 @value{GDBN} could not parse a type specification output by the compiler.
15312 @section GDB Data Files
15314 @cindex prefix for data files
15315 @value{GDBN} will sometimes read an auxiliary data file. These files
15316 are kept in a directory known as the @dfn{data directory}.
15318 You can set the data directory's name, and view the name @value{GDBN}
15319 is currently using.
15322 @kindex set data-directory
15323 @item set data-directory @var{directory}
15324 Set the directory which @value{GDBN} searches for auxiliary data files
15325 to @var{directory}.
15327 @kindex show data-directory
15328 @item show data-directory
15329 Show the directory @value{GDBN} searches for auxiliary data files.
15332 @cindex default data directory
15333 @cindex @samp{--with-gdb-datadir}
15334 You can set the default data directory by using the configure-time
15335 @samp{--with-gdb-datadir} option. If the data directory is inside
15336 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
15337 @samp{--exec-prefix}), then the default data directory will be updated
15338 automatically if the installed @value{GDBN} is moved to a new
15342 @chapter Specifying a Debugging Target
15344 @cindex debugging target
15345 A @dfn{target} is the execution environment occupied by your program.
15347 Often, @value{GDBN} runs in the same host environment as your program;
15348 in that case, the debugging target is specified as a side effect when
15349 you use the @code{file} or @code{core} commands. When you need more
15350 flexibility---for example, running @value{GDBN} on a physically separate
15351 host, or controlling a standalone system over a serial port or a
15352 realtime system over a TCP/IP connection---you can use the @code{target}
15353 command to specify one of the target types configured for @value{GDBN}
15354 (@pxref{Target Commands, ,Commands for Managing Targets}).
15356 @cindex target architecture
15357 It is possible to build @value{GDBN} for several different @dfn{target
15358 architectures}. When @value{GDBN} is built like that, you can choose
15359 one of the available architectures with the @kbd{set architecture}
15363 @kindex set architecture
15364 @kindex show architecture
15365 @item set architecture @var{arch}
15366 This command sets the current target architecture to @var{arch}. The
15367 value of @var{arch} can be @code{"auto"}, in addition to one of the
15368 supported architectures.
15370 @item show architecture
15371 Show the current target architecture.
15373 @item set processor
15375 @kindex set processor
15376 @kindex show processor
15377 These are alias commands for, respectively, @code{set architecture}
15378 and @code{show architecture}.
15382 * Active Targets:: Active targets
15383 * Target Commands:: Commands for managing targets
15384 * Byte Order:: Choosing target byte order
15387 @node Active Targets
15388 @section Active Targets
15390 @cindex stacking targets
15391 @cindex active targets
15392 @cindex multiple targets
15394 There are multiple classes of targets such as: processes, executable files or
15395 recording sessions. Core files belong to the process class, making core file
15396 and process mutually exclusive. Otherwise, @value{GDBN} can work concurrently
15397 on multiple active targets, one in each class. This allows you to (for
15398 example) start a process and inspect its activity, while still having access to
15399 the executable file after the process finishes. Or if you start process
15400 recording (@pxref{Reverse Execution}) and @code{reverse-step} there, you are
15401 presented a virtual layer of the recording target, while the process target
15402 remains stopped at the chronologically last point of the process execution.
15404 Use the @code{core-file} and @code{exec-file} commands to select a new core
15405 file or executable target (@pxref{Files, ,Commands to Specify Files}). To
15406 specify as a target a process that is already running, use the @code{attach}
15407 command (@pxref{Attach, ,Debugging an Already-running Process}).
15409 @node Target Commands
15410 @section Commands for Managing Targets
15413 @item target @var{type} @var{parameters}
15414 Connects the @value{GDBN} host environment to a target machine or
15415 process. A target is typically a protocol for talking to debugging
15416 facilities. You use the argument @var{type} to specify the type or
15417 protocol of the target machine.
15419 Further @var{parameters} are interpreted by the target protocol, but
15420 typically include things like device names or host names to connect
15421 with, process numbers, and baud rates.
15423 The @code{target} command does not repeat if you press @key{RET} again
15424 after executing the command.
15426 @kindex help target
15428 Displays the names of all targets available. To display targets
15429 currently selected, use either @code{info target} or @code{info files}
15430 (@pxref{Files, ,Commands to Specify Files}).
15432 @item help target @var{name}
15433 Describe a particular target, including any parameters necessary to
15436 @kindex set gnutarget
15437 @item set gnutarget @var{args}
15438 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
15439 knows whether it is reading an @dfn{executable},
15440 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
15441 with the @code{set gnutarget} command. Unlike most @code{target} commands,
15442 with @code{gnutarget} the @code{target} refers to a program, not a machine.
15445 @emph{Warning:} To specify a file format with @code{set gnutarget},
15446 you must know the actual BFD name.
15450 @xref{Files, , Commands to Specify Files}.
15452 @kindex show gnutarget
15453 @item show gnutarget
15454 Use the @code{show gnutarget} command to display what file format
15455 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
15456 @value{GDBN} will determine the file format for each file automatically,
15457 and @code{show gnutarget} displays @samp{The current BDF target is "auto"}.
15460 @cindex common targets
15461 Here are some common targets (available, or not, depending on the GDB
15466 @item target exec @var{program}
15467 @cindex executable file target
15468 An executable file. @samp{target exec @var{program}} is the same as
15469 @samp{exec-file @var{program}}.
15471 @item target core @var{filename}
15472 @cindex core dump file target
15473 A core dump file. @samp{target core @var{filename}} is the same as
15474 @samp{core-file @var{filename}}.
15476 @item target remote @var{medium}
15477 @cindex remote target
15478 A remote system connected to @value{GDBN} via a serial line or network
15479 connection. This command tells @value{GDBN} to use its own remote
15480 protocol over @var{medium} for debugging. @xref{Remote Debugging}.
15482 For example, if you have a board connected to @file{/dev/ttya} on the
15483 machine running @value{GDBN}, you could say:
15486 target remote /dev/ttya
15489 @code{target remote} supports the @code{load} command. This is only
15490 useful if you have some other way of getting the stub to the target
15491 system, and you can put it somewhere in memory where it won't get
15492 clobbered by the download.
15494 @item target sim @r{[}@var{simargs}@r{]} @dots{}
15495 @cindex built-in simulator target
15496 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
15504 works; however, you cannot assume that a specific memory map, device
15505 drivers, or even basic I/O is available, although some simulators do
15506 provide these. For info about any processor-specific simulator details,
15507 see the appropriate section in @ref{Embedded Processors, ,Embedded
15512 Some configurations may include these targets as well:
15516 @item target nrom @var{dev}
15517 @cindex NetROM ROM emulator target
15518 NetROM ROM emulator. This target only supports downloading.
15522 Different targets are available on different configurations of @value{GDBN};
15523 your configuration may have more or fewer targets.
15525 Many remote targets require you to download the executable's code once
15526 you've successfully established a connection. You may wish to control
15527 various aspects of this process.
15532 @kindex set hash@r{, for remote monitors}
15533 @cindex hash mark while downloading
15534 This command controls whether a hash mark @samp{#} is displayed while
15535 downloading a file to the remote monitor. If on, a hash mark is
15536 displayed after each S-record is successfully downloaded to the
15540 @kindex show hash@r{, for remote monitors}
15541 Show the current status of displaying the hash mark.
15543 @item set debug monitor
15544 @kindex set debug monitor
15545 @cindex display remote monitor communications
15546 Enable or disable display of communications messages between
15547 @value{GDBN} and the remote monitor.
15549 @item show debug monitor
15550 @kindex show debug monitor
15551 Show the current status of displaying communications between
15552 @value{GDBN} and the remote monitor.
15557 @kindex load @var{filename}
15558 @item load @var{filename}
15560 Depending on what remote debugging facilities are configured into
15561 @value{GDBN}, the @code{load} command may be available. Where it exists, it
15562 is meant to make @var{filename} (an executable) available for debugging
15563 on the remote system---by downloading, or dynamic linking, for example.
15564 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
15565 the @code{add-symbol-file} command.
15567 If your @value{GDBN} does not have a @code{load} command, attempting to
15568 execute it gets the error message ``@code{You can't do that when your
15569 target is @dots{}}''
15571 The file is loaded at whatever address is specified in the executable.
15572 For some object file formats, you can specify the load address when you
15573 link the program; for other formats, like a.out, the object file format
15574 specifies a fixed address.
15575 @c FIXME! This would be a good place for an xref to the GNU linker doc.
15577 Depending on the remote side capabilities, @value{GDBN} may be able to
15578 load programs into flash memory.
15580 @code{load} does not repeat if you press @key{RET} again after using it.
15584 @section Choosing Target Byte Order
15586 @cindex choosing target byte order
15587 @cindex target byte order
15589 Some types of processors, such as the MIPS, PowerPC, and Renesas SH,
15590 offer the ability to run either big-endian or little-endian byte
15591 orders. Usually the executable or symbol will include a bit to
15592 designate the endian-ness, and you will not need to worry about
15593 which to use. However, you may still find it useful to adjust
15594 @value{GDBN}'s idea of processor endian-ness manually.
15598 @item set endian big
15599 Instruct @value{GDBN} to assume the target is big-endian.
15601 @item set endian little
15602 Instruct @value{GDBN} to assume the target is little-endian.
15604 @item set endian auto
15605 Instruct @value{GDBN} to use the byte order associated with the
15609 Display @value{GDBN}'s current idea of the target byte order.
15613 Note that these commands merely adjust interpretation of symbolic
15614 data on the host, and that they have absolutely no effect on the
15618 @node Remote Debugging
15619 @chapter Debugging Remote Programs
15620 @cindex remote debugging
15622 If you are trying to debug a program running on a machine that cannot run
15623 @value{GDBN} in the usual way, it is often useful to use remote debugging.
15624 For example, you might use remote debugging on an operating system kernel,
15625 or on a small system which does not have a general purpose operating system
15626 powerful enough to run a full-featured debugger.
15628 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
15629 to make this work with particular debugging targets. In addition,
15630 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
15631 but not specific to any particular target system) which you can use if you
15632 write the remote stubs---the code that runs on the remote system to
15633 communicate with @value{GDBN}.
15635 Other remote targets may be available in your
15636 configuration of @value{GDBN}; use @code{help target} to list them.
15639 * Connecting:: Connecting to a remote target
15640 * File Transfer:: Sending files to a remote system
15641 * Server:: Using the gdbserver program
15642 * Remote Configuration:: Remote configuration
15643 * Remote Stub:: Implementing a remote stub
15647 @section Connecting to a Remote Target
15649 On the @value{GDBN} host machine, you will need an unstripped copy of
15650 your program, since @value{GDBN} needs symbol and debugging information.
15651 Start up @value{GDBN} as usual, using the name of the local copy of your
15652 program as the first argument.
15654 @cindex @code{target remote}
15655 @value{GDBN} can communicate with the target over a serial line, or
15656 over an @acronym{IP} network using @acronym{TCP} or @acronym{UDP}. In
15657 each case, @value{GDBN} uses the same protocol for debugging your
15658 program; only the medium carrying the debugging packets varies. The
15659 @code{target remote} command establishes a connection to the target.
15660 Its arguments indicate which medium to use:
15664 @item target remote @var{serial-device}
15665 @cindex serial line, @code{target remote}
15666 Use @var{serial-device} to communicate with the target. For example,
15667 to use a serial line connected to the device named @file{/dev/ttyb}:
15670 target remote /dev/ttyb
15673 If you're using a serial line, you may want to give @value{GDBN} the
15674 @w{@samp{--baud}} option, or use the @code{set remotebaud} command
15675 (@pxref{Remote Configuration, set remotebaud}) before the
15676 @code{target} command.
15678 @item target remote @code{@var{host}:@var{port}}
15679 @itemx target remote @code{tcp:@var{host}:@var{port}}
15680 @cindex @acronym{TCP} port, @code{target remote}
15681 Debug using a @acronym{TCP} connection to @var{port} on @var{host}.
15682 The @var{host} may be either a host name or a numeric @acronym{IP}
15683 address; @var{port} must be a decimal number. The @var{host} could be
15684 the target machine itself, if it is directly connected to the net, or
15685 it might be a terminal server which in turn has a serial line to the
15688 For example, to connect to port 2828 on a terminal server named
15692 target remote manyfarms:2828
15695 If your remote target is actually running on the same machine as your
15696 debugger session (e.g.@: a simulator for your target running on the
15697 same host), you can omit the hostname. For example, to connect to
15698 port 1234 on your local machine:
15701 target remote :1234
15705 Note that the colon is still required here.
15707 @item target remote @code{udp:@var{host}:@var{port}}
15708 @cindex @acronym{UDP} port, @code{target remote}
15709 Debug using @acronym{UDP} packets to @var{port} on @var{host}. For example, to
15710 connect to @acronym{UDP} port 2828 on a terminal server named @code{manyfarms}:
15713 target remote udp:manyfarms:2828
15716 When using a @acronym{UDP} connection for remote debugging, you should
15717 keep in mind that the `U' stands for ``Unreliable''. @acronym{UDP}
15718 can silently drop packets on busy or unreliable networks, which will
15719 cause havoc with your debugging session.
15721 @item target remote | @var{command}
15722 @cindex pipe, @code{target remote} to
15723 Run @var{command} in the background and communicate with it using a
15724 pipe. The @var{command} is a shell command, to be parsed and expanded
15725 by the system's command shell, @code{/bin/sh}; it should expect remote
15726 protocol packets on its standard input, and send replies on its
15727 standard output. You could use this to run a stand-alone simulator
15728 that speaks the remote debugging protocol, to make net connections
15729 using programs like @code{ssh}, or for other similar tricks.
15731 If @var{command} closes its standard output (perhaps by exiting),
15732 @value{GDBN} will try to send it a @code{SIGTERM} signal. (If the
15733 program has already exited, this will have no effect.)
15737 Once the connection has been established, you can use all the usual
15738 commands to examine and change data. The remote program is already
15739 running; you can use @kbd{step} and @kbd{continue}, and you do not
15740 need to use @kbd{run}.
15742 @cindex interrupting remote programs
15743 @cindex remote programs, interrupting
15744 Whenever @value{GDBN} is waiting for the remote program, if you type the
15745 interrupt character (often @kbd{Ctrl-c}), @value{GDBN} attempts to stop the
15746 program. This may or may not succeed, depending in part on the hardware
15747 and the serial drivers the remote system uses. If you type the
15748 interrupt character once again, @value{GDBN} displays this prompt:
15751 Interrupted while waiting for the program.
15752 Give up (and stop debugging it)? (y or n)
15755 If you type @kbd{y}, @value{GDBN} abandons the remote debugging session.
15756 (If you decide you want to try again later, you can use @samp{target
15757 remote} again to connect once more.) If you type @kbd{n}, @value{GDBN}
15758 goes back to waiting.
15761 @kindex detach (remote)
15763 When you have finished debugging the remote program, you can use the
15764 @code{detach} command to release it from @value{GDBN} control.
15765 Detaching from the target normally resumes its execution, but the results
15766 will depend on your particular remote stub. After the @code{detach}
15767 command, @value{GDBN} is free to connect to another target.
15771 The @code{disconnect} command behaves like @code{detach}, except that
15772 the target is generally not resumed. It will wait for @value{GDBN}
15773 (this instance or another one) to connect and continue debugging. After
15774 the @code{disconnect} command, @value{GDBN} is again free to connect to
15777 @cindex send command to remote monitor
15778 @cindex extend @value{GDBN} for remote targets
15779 @cindex add new commands for external monitor
15781 @item monitor @var{cmd}
15782 This command allows you to send arbitrary commands directly to the
15783 remote monitor. Since @value{GDBN} doesn't care about the commands it
15784 sends like this, this command is the way to extend @value{GDBN}---you
15785 can add new commands that only the external monitor will understand
15789 @node File Transfer
15790 @section Sending files to a remote system
15791 @cindex remote target, file transfer
15792 @cindex file transfer
15793 @cindex sending files to remote systems
15795 Some remote targets offer the ability to transfer files over the same
15796 connection used to communicate with @value{GDBN}. This is convenient
15797 for targets accessible through other means, e.g.@: @sc{gnu}/Linux systems
15798 running @code{gdbserver} over a network interface. For other targets,
15799 e.g.@: embedded devices with only a single serial port, this may be
15800 the only way to upload or download files.
15802 Not all remote targets support these commands.
15806 @item remote put @var{hostfile} @var{targetfile}
15807 Copy file @var{hostfile} from the host system (the machine running
15808 @value{GDBN}) to @var{targetfile} on the target system.
15811 @item remote get @var{targetfile} @var{hostfile}
15812 Copy file @var{targetfile} from the target system to @var{hostfile}
15813 on the host system.
15815 @kindex remote delete
15816 @item remote delete @var{targetfile}
15817 Delete @var{targetfile} from the target system.
15822 @section Using the @code{gdbserver} Program
15825 @cindex remote connection without stubs
15826 @code{gdbserver} is a control program for Unix-like systems, which
15827 allows you to connect your program with a remote @value{GDBN} via
15828 @code{target remote}---but without linking in the usual debugging stub.
15830 @code{gdbserver} is not a complete replacement for the debugging stubs,
15831 because it requires essentially the same operating-system facilities
15832 that @value{GDBN} itself does. In fact, a system that can run
15833 @code{gdbserver} to connect to a remote @value{GDBN} could also run
15834 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
15835 because it is a much smaller program than @value{GDBN} itself. It is
15836 also easier to port than all of @value{GDBN}, so you may be able to get
15837 started more quickly on a new system by using @code{gdbserver}.
15838 Finally, if you develop code for real-time systems, you may find that
15839 the tradeoffs involved in real-time operation make it more convenient to
15840 do as much development work as possible on another system, for example
15841 by cross-compiling. You can use @code{gdbserver} to make a similar
15842 choice for debugging.
15844 @value{GDBN} and @code{gdbserver} communicate via either a serial line
15845 or a TCP connection, using the standard @value{GDBN} remote serial
15849 @emph{Warning:} @code{gdbserver} does not have any built-in security.
15850 Do not run @code{gdbserver} connected to any public network; a
15851 @value{GDBN} connection to @code{gdbserver} provides access to the
15852 target system with the same privileges as the user running
15856 @subsection Running @code{gdbserver}
15857 @cindex arguments, to @code{gdbserver}
15859 Run @code{gdbserver} on the target system. You need a copy of the
15860 program you want to debug, including any libraries it requires.
15861 @code{gdbserver} does not need your program's symbol table, so you can
15862 strip the program if necessary to save space. @value{GDBN} on the host
15863 system does all the symbol handling.
15865 To use the server, you must tell it how to communicate with @value{GDBN};
15866 the name of your program; and the arguments for your program. The usual
15870 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
15873 @var{comm} is either a device name (to use a serial line) or a TCP
15874 hostname and portnumber. For example, to debug Emacs with the argument
15875 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
15879 target> gdbserver /dev/com1 emacs foo.txt
15882 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
15885 To use a TCP connection instead of a serial line:
15888 target> gdbserver host:2345 emacs foo.txt
15891 The only difference from the previous example is the first argument,
15892 specifying that you are communicating with the host @value{GDBN} via
15893 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
15894 expect a TCP connection from machine @samp{host} to local TCP port 2345.
15895 (Currently, the @samp{host} part is ignored.) You can choose any number
15896 you want for the port number as long as it does not conflict with any
15897 TCP ports already in use on the target system (for example, @code{23} is
15898 reserved for @code{telnet}).@footnote{If you choose a port number that
15899 conflicts with another service, @code{gdbserver} prints an error message
15900 and exits.} You must use the same port number with the host @value{GDBN}
15901 @code{target remote} command.
15903 @subsubsection Attaching to a Running Program
15905 On some targets, @code{gdbserver} can also attach to running programs.
15906 This is accomplished via the @code{--attach} argument. The syntax is:
15909 target> gdbserver --attach @var{comm} @var{pid}
15912 @var{pid} is the process ID of a currently running process. It isn't necessary
15913 to point @code{gdbserver} at a binary for the running process.
15916 @cindex attach to a program by name
15917 You can debug processes by name instead of process ID if your target has the
15918 @code{pidof} utility:
15921 target> gdbserver --attach @var{comm} `pidof @var{program}`
15924 In case more than one copy of @var{program} is running, or @var{program}
15925 has multiple threads, most versions of @code{pidof} support the
15926 @code{-s} option to only return the first process ID.
15928 @subsubsection Multi-Process Mode for @code{gdbserver}
15929 @cindex gdbserver, multiple processes
15930 @cindex multiple processes with gdbserver
15932 When you connect to @code{gdbserver} using @code{target remote},
15933 @code{gdbserver} debugs the specified program only once. When the
15934 program exits, or you detach from it, @value{GDBN} closes the connection
15935 and @code{gdbserver} exits.
15937 If you connect using @kbd{target extended-remote}, @code{gdbserver}
15938 enters multi-process mode. When the debugged program exits, or you
15939 detach from it, @value{GDBN} stays connected to @code{gdbserver} even
15940 though no program is running. The @code{run} and @code{attach}
15941 commands instruct @code{gdbserver} to run or attach to a new program.
15942 The @code{run} command uses @code{set remote exec-file} (@pxref{set
15943 remote exec-file}) to select the program to run. Command line
15944 arguments are supported, except for wildcard expansion and I/O
15945 redirection (@pxref{Arguments}).
15947 To start @code{gdbserver} without supplying an initial command to run
15948 or process ID to attach, use the @option{--multi} command line option.
15949 Then you can connect using @kbd{target extended-remote} and start
15950 the program you want to debug.
15952 @code{gdbserver} does not automatically exit in multi-process mode.
15953 You can terminate it by using @code{monitor exit}
15954 (@pxref{Monitor Commands for gdbserver}).
15956 @subsubsection Other Command-Line Arguments for @code{gdbserver}
15958 The @option{--debug} option tells @code{gdbserver} to display extra
15959 status information about the debugging process. The
15960 @option{--remote-debug} option tells @code{gdbserver} to display
15961 remote protocol debug output. These options are intended for
15962 @code{gdbserver} development and for bug reports to the developers.
15964 The @option{--wrapper} option specifies a wrapper to launch programs
15965 for debugging. The option should be followed by the name of the
15966 wrapper, then any command-line arguments to pass to the wrapper, then
15967 @kbd{--} indicating the end of the wrapper arguments.
15969 @code{gdbserver} runs the specified wrapper program with a combined
15970 command line including the wrapper arguments, then the name of the
15971 program to debug, then any arguments to the program. The wrapper
15972 runs until it executes your program, and then @value{GDBN} gains control.
15974 You can use any program that eventually calls @code{execve} with
15975 its arguments as a wrapper. Several standard Unix utilities do
15976 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
15977 with @code{exec "$@@"} will also work.
15979 For example, you can use @code{env} to pass an environment variable to
15980 the debugged program, without setting the variable in @code{gdbserver}'s
15984 $ gdbserver --wrapper env LD_PRELOAD=libtest.so -- :2222 ./testprog
15987 @subsection Connecting to @code{gdbserver}
15989 Run @value{GDBN} on the host system.
15991 First make sure you have the necessary symbol files. Load symbols for
15992 your application using the @code{file} command before you connect. Use
15993 @code{set sysroot} to locate target libraries (unless your @value{GDBN}
15994 was compiled with the correct sysroot using @code{--with-sysroot}).
15996 The symbol file and target libraries must exactly match the executable
15997 and libraries on the target, with one exception: the files on the host
15998 system should not be stripped, even if the files on the target system
15999 are. Mismatched or missing files will lead to confusing results
16000 during debugging. On @sc{gnu}/Linux targets, mismatched or missing
16001 files may also prevent @code{gdbserver} from debugging multi-threaded
16004 Connect to your target (@pxref{Connecting,,Connecting to a Remote Target}).
16005 For TCP connections, you must start up @code{gdbserver} prior to using
16006 the @code{target remote} command. Otherwise you may get an error whose
16007 text depends on the host system, but which usually looks something like
16008 @samp{Connection refused}. Don't use the @code{load}
16009 command in @value{GDBN} when using @code{gdbserver}, since the program is
16010 already on the target.
16012 @subsection Monitor Commands for @code{gdbserver}
16013 @cindex monitor commands, for @code{gdbserver}
16014 @anchor{Monitor Commands for gdbserver}
16016 During a @value{GDBN} session using @code{gdbserver}, you can use the
16017 @code{monitor} command to send special requests to @code{gdbserver}.
16018 Here are the available commands.
16022 List the available monitor commands.
16024 @item monitor set debug 0
16025 @itemx monitor set debug 1
16026 Disable or enable general debugging messages.
16028 @item monitor set remote-debug 0
16029 @itemx monitor set remote-debug 1
16030 Disable or enable specific debugging messages associated with the remote
16031 protocol (@pxref{Remote Protocol}).
16033 @item monitor set libthread-db-search-path [PATH]
16034 @cindex gdbserver, search path for @code{libthread_db}
16035 When this command is issued, @var{path} is a colon-separated list of
16036 directories to search for @code{libthread_db} (@pxref{Threads,,set
16037 libthread-db-search-path}). If you omit @var{path},
16038 @samp{libthread-db-search-path} will be reset to an empty list.
16041 Tell gdbserver to exit immediately. This command should be followed by
16042 @code{disconnect} to close the debugging session. @code{gdbserver} will
16043 detach from any attached processes and kill any processes it created.
16044 Use @code{monitor exit} to terminate @code{gdbserver} at the end
16045 of a multi-process mode debug session.
16049 @subsection Tracepoints support in @code{gdbserver}
16050 @cindex tracepoints support in @code{gdbserver}
16052 On some targets, @code{gdbserver} supports tracepoints, fast
16053 tracepoints and static tracepoints.
16055 For fast or static tracepoints to work, a special library called the
16056 @dfn{in-process agent} (IPA), must be loaded in the inferior process.
16057 This library is built and distributed as an integral part of
16058 @code{gdbserver}. In addition, support for static tracepoints
16059 requires building the in-process agent library with static tracepoints
16060 support. At present, the UST (LTTng Userspace Tracer,
16061 @url{http://lttng.org/ust}) tracing engine is supported. This support
16062 is automatically available if UST development headers are found in the
16063 standard include path when @code{gdbserver} is built, or if
16064 @code{gdbserver} was explicitly configured using @option{--with-ust}
16065 to point at such headers. You can explicitly disable the support
16066 using @option{--with-ust=no}.
16068 There are several ways to load the in-process agent in your program:
16071 @item Specifying it as dependency at link time
16073 You can link your program dynamically with the in-process agent
16074 library. On most systems, this is accomplished by adding
16075 @code{-linproctrace} to the link command.
16077 @item Using the system's preloading mechanisms
16079 You can force loading the in-process agent at startup time by using
16080 your system's support for preloading shared libraries. Many Unixes
16081 support the concept of preloading user defined libraries. In most
16082 cases, you do that by specifying @code{LD_PRELOAD=libinproctrace.so}
16083 in the environment. See also the description of @code{gdbserver}'s
16084 @option{--wrapper} command line option.
16086 @item Using @value{GDBN} to force loading the agent at run time
16088 On some systems, you can force the inferior to load a shared library,
16089 by calling a dynamic loader function in the inferior that takes care
16090 of dynamically looking up and loading a shared library. On most Unix
16091 systems, the function is @code{dlopen}. You'll use the @code{call}
16092 command for that. For example:
16095 (@value{GDBP}) call dlopen ("libinproctrace.so", ...)
16098 Note that on most Unix systems, for the @code{dlopen} function to be
16099 available, the program needs to be linked with @code{-ldl}.
16102 On systems that have a userspace dynamic loader, like most Unix
16103 systems, when you connect to @code{gdbserver} using @code{target
16104 remote}, you'll find that the program is stopped at the dynamic
16105 loader's entry point, and no shared library has been loaded in the
16106 program's address space yet, including the in-process agent. In that
16107 case, before being able to use any of the fast or static tracepoints
16108 features, you need to let the loader run and load the shared
16109 libraries. The simplest way to do that is to run the program to the
16110 main procedure. E.g., if debugging a C or C@t{++} program, start
16111 @code{gdbserver} like so:
16114 $ gdbserver :9999 myprogram
16117 Start GDB and connect to @code{gdbserver} like so, and run to main:
16121 (@value{GDBP}) target remote myhost:9999
16122 0x00007f215893ba60 in ?? () from /lib64/ld-linux-x86-64.so.2
16123 (@value{GDBP}) b main
16124 (@value{GDBP}) continue
16127 The in-process tracing agent library should now be loaded into the
16128 process; you can confirm it with the @code{info sharedlibrary}
16129 command, which will list @file{libinproctrace.so} as loaded in the
16130 process. You are now ready to install fast tracepoints, list static
16131 tracepoint markers, probe static tracepoints markers, and start
16134 @node Remote Configuration
16135 @section Remote Configuration
16138 @kindex show remote
16139 This section documents the configuration options available when
16140 debugging remote programs. For the options related to the File I/O
16141 extensions of the remote protocol, see @ref{system,
16142 system-call-allowed}.
16145 @item set remoteaddresssize @var{bits}
16146 @cindex address size for remote targets
16147 @cindex bits in remote address
16148 Set the maximum size of address in a memory packet to the specified
16149 number of bits. @value{GDBN} will mask off the address bits above
16150 that number, when it passes addresses to the remote target. The
16151 default value is the number of bits in the target's address.
16153 @item show remoteaddresssize
16154 Show the current value of remote address size in bits.
16156 @item set remotebaud @var{n}
16157 @cindex baud rate for remote targets
16158 Set the baud rate for the remote serial I/O to @var{n} baud. The
16159 value is used to set the speed of the serial port used for debugging
16162 @item show remotebaud
16163 Show the current speed of the remote connection.
16165 @item set remotebreak
16166 @cindex interrupt remote programs
16167 @cindex BREAK signal instead of Ctrl-C
16168 @anchor{set remotebreak}
16169 If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote
16170 when you type @kbd{Ctrl-c} to interrupt the program running
16171 on the remote. If set to off, @value{GDBN} sends the @samp{Ctrl-C}
16172 character instead. The default is off, since most remote systems
16173 expect to see @samp{Ctrl-C} as the interrupt signal.
16175 @item show remotebreak
16176 Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to
16177 interrupt the remote program.
16179 @item set remoteflow on
16180 @itemx set remoteflow off
16181 @kindex set remoteflow
16182 Enable or disable hardware flow control (@code{RTS}/@code{CTS})
16183 on the serial port used to communicate to the remote target.
16185 @item show remoteflow
16186 @kindex show remoteflow
16187 Show the current setting of hardware flow control.
16189 @item set remotelogbase @var{base}
16190 Set the base (a.k.a.@: radix) of logging serial protocol
16191 communications to @var{base}. Supported values of @var{base} are:
16192 @code{ascii}, @code{octal}, and @code{hex}. The default is
16195 @item show remotelogbase
16196 Show the current setting of the radix for logging remote serial
16199 @item set remotelogfile @var{file}
16200 @cindex record serial communications on file
16201 Record remote serial communications on the named @var{file}. The
16202 default is not to record at all.
16204 @item show remotelogfile.
16205 Show the current setting of the file name on which to record the
16206 serial communications.
16208 @item set remotetimeout @var{num}
16209 @cindex timeout for serial communications
16210 @cindex remote timeout
16211 Set the timeout limit to wait for the remote target to respond to
16212 @var{num} seconds. The default is 2 seconds.
16214 @item show remotetimeout
16215 Show the current number of seconds to wait for the remote target
16218 @cindex limit hardware breakpoints and watchpoints
16219 @cindex remote target, limit break- and watchpoints
16220 @anchor{set remote hardware-watchpoint-limit}
16221 @anchor{set remote hardware-breakpoint-limit}
16222 @item set remote hardware-watchpoint-limit @var{limit}
16223 @itemx set remote hardware-breakpoint-limit @var{limit}
16224 Restrict @value{GDBN} to using @var{limit} remote hardware breakpoint or
16225 watchpoints. A limit of -1, the default, is treated as unlimited.
16227 @item set remote exec-file @var{filename}
16228 @itemx show remote exec-file
16229 @anchor{set remote exec-file}
16230 @cindex executable file, for remote target
16231 Select the file used for @code{run} with @code{target
16232 extended-remote}. This should be set to a filename valid on the
16233 target system. If it is not set, the target will use a default
16234 filename (e.g.@: the last program run).
16236 @item set remote interrupt-sequence
16237 @cindex interrupt remote programs
16238 @cindex select Ctrl-C, BREAK or BREAK-g
16239 Allow the user to select one of @samp{Ctrl-C}, a @code{BREAK} or
16240 @samp{BREAK-g} as the
16241 sequence to the remote target in order to interrupt the execution.
16242 @samp{Ctrl-C} is a default. Some system prefers @code{BREAK} which
16243 is high level of serial line for some certain time.
16244 Linux kernel prefers @samp{BREAK-g}, a.k.a Magic SysRq g.
16245 It is @code{BREAK} signal followed by character @code{g}.
16247 @item show interrupt-sequence
16248 Show which of @samp{Ctrl-C}, @code{BREAK} or @code{BREAK-g}
16249 is sent by @value{GDBN} to interrupt the remote program.
16250 @code{BREAK-g} is BREAK signal followed by @code{g} and
16251 also known as Magic SysRq g.
16253 @item set remote interrupt-on-connect
16254 @cindex send interrupt-sequence on start
16255 Specify whether interrupt-sequence is sent to remote target when
16256 @value{GDBN} connects to it. This is mostly needed when you debug
16257 Linux kernel. Linux kernel expects @code{BREAK} followed by @code{g}
16258 which is known as Magic SysRq g in order to connect @value{GDBN}.
16260 @item show interrupt-on-connect
16261 Show whether interrupt-sequence is sent
16262 to remote target when @value{GDBN} connects to it.
16266 @item set tcp auto-retry on
16267 @cindex auto-retry, for remote TCP target
16268 Enable auto-retry for remote TCP connections. This is useful if the remote
16269 debugging agent is launched in parallel with @value{GDBN}; there is a race
16270 condition because the agent may not become ready to accept the connection
16271 before @value{GDBN} attempts to connect. When auto-retry is
16272 enabled, if the initial attempt to connect fails, @value{GDBN} reattempts
16273 to establish the connection using the timeout specified by
16274 @code{set tcp connect-timeout}.
16276 @item set tcp auto-retry off
16277 Do not auto-retry failed TCP connections.
16279 @item show tcp auto-retry
16280 Show the current auto-retry setting.
16282 @item set tcp connect-timeout @var{seconds}
16283 @cindex connection timeout, for remote TCP target
16284 @cindex timeout, for remote target connection
16285 Set the timeout for establishing a TCP connection to the remote target to
16286 @var{seconds}. The timeout affects both polling to retry failed connections
16287 (enabled by @code{set tcp auto-retry on}) and waiting for connections
16288 that are merely slow to complete, and represents an approximate cumulative
16291 @item show tcp connect-timeout
16292 Show the current connection timeout setting.
16295 @cindex remote packets, enabling and disabling
16296 The @value{GDBN} remote protocol autodetects the packets supported by
16297 your debugging stub. If you need to override the autodetection, you
16298 can use these commands to enable or disable individual packets. Each
16299 packet can be set to @samp{on} (the remote target supports this
16300 packet), @samp{off} (the remote target does not support this packet),
16301 or @samp{auto} (detect remote target support for this packet). They
16302 all default to @samp{auto}. For more information about each packet,
16303 see @ref{Remote Protocol}.
16305 During normal use, you should not have to use any of these commands.
16306 If you do, that may be a bug in your remote debugging stub, or a bug
16307 in @value{GDBN}. You may want to report the problem to the
16308 @value{GDBN} developers.
16310 For each packet @var{name}, the command to enable or disable the
16311 packet is @code{set remote @var{name}-packet}. The available settings
16314 @multitable @columnfractions 0.28 0.32 0.25
16317 @tab Related Features
16319 @item @code{fetch-register}
16321 @tab @code{info registers}
16323 @item @code{set-register}
16327 @item @code{binary-download}
16329 @tab @code{load}, @code{set}
16331 @item @code{read-aux-vector}
16332 @tab @code{qXfer:auxv:read}
16333 @tab @code{info auxv}
16335 @item @code{symbol-lookup}
16336 @tab @code{qSymbol}
16337 @tab Detecting multiple threads
16339 @item @code{attach}
16340 @tab @code{vAttach}
16343 @item @code{verbose-resume}
16345 @tab Stepping or resuming multiple threads
16351 @item @code{software-breakpoint}
16355 @item @code{hardware-breakpoint}
16359 @item @code{write-watchpoint}
16363 @item @code{read-watchpoint}
16367 @item @code{access-watchpoint}
16371 @item @code{target-features}
16372 @tab @code{qXfer:features:read}
16373 @tab @code{set architecture}
16375 @item @code{library-info}
16376 @tab @code{qXfer:libraries:read}
16377 @tab @code{info sharedlibrary}
16379 @item @code{memory-map}
16380 @tab @code{qXfer:memory-map:read}
16381 @tab @code{info mem}
16383 @item @code{read-sdata-object}
16384 @tab @code{qXfer:sdata:read}
16385 @tab @code{print $_sdata}
16387 @item @code{read-spu-object}
16388 @tab @code{qXfer:spu:read}
16389 @tab @code{info spu}
16391 @item @code{write-spu-object}
16392 @tab @code{qXfer:spu:write}
16393 @tab @code{info spu}
16395 @item @code{read-siginfo-object}
16396 @tab @code{qXfer:siginfo:read}
16397 @tab @code{print $_siginfo}
16399 @item @code{write-siginfo-object}
16400 @tab @code{qXfer:siginfo:write}
16401 @tab @code{set $_siginfo}
16403 @item @code{threads}
16404 @tab @code{qXfer:threads:read}
16405 @tab @code{info threads}
16407 @item @code{get-thread-local-@*storage-address}
16408 @tab @code{qGetTLSAddr}
16409 @tab Displaying @code{__thread} variables
16411 @item @code{get-thread-information-block-address}
16412 @tab @code{qGetTIBAddr}
16413 @tab Display MS-Windows Thread Information Block.
16415 @item @code{search-memory}
16416 @tab @code{qSearch:memory}
16419 @item @code{supported-packets}
16420 @tab @code{qSupported}
16421 @tab Remote communications parameters
16423 @item @code{pass-signals}
16424 @tab @code{QPassSignals}
16425 @tab @code{handle @var{signal}}
16427 @item @code{hostio-close-packet}
16428 @tab @code{vFile:close}
16429 @tab @code{remote get}, @code{remote put}
16431 @item @code{hostio-open-packet}
16432 @tab @code{vFile:open}
16433 @tab @code{remote get}, @code{remote put}
16435 @item @code{hostio-pread-packet}
16436 @tab @code{vFile:pread}
16437 @tab @code{remote get}, @code{remote put}
16439 @item @code{hostio-pwrite-packet}
16440 @tab @code{vFile:pwrite}
16441 @tab @code{remote get}, @code{remote put}
16443 @item @code{hostio-unlink-packet}
16444 @tab @code{vFile:unlink}
16445 @tab @code{remote delete}
16447 @item @code{noack-packet}
16448 @tab @code{QStartNoAckMode}
16449 @tab Packet acknowledgment
16451 @item @code{osdata}
16452 @tab @code{qXfer:osdata:read}
16453 @tab @code{info os}
16455 @item @code{query-attached}
16456 @tab @code{qAttached}
16457 @tab Querying remote process attach state.
16461 @section Implementing a Remote Stub
16463 @cindex debugging stub, example
16464 @cindex remote stub, example
16465 @cindex stub example, remote debugging
16466 The stub files provided with @value{GDBN} implement the target side of the
16467 communication protocol, and the @value{GDBN} side is implemented in the
16468 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
16469 these subroutines to communicate, and ignore the details. (If you're
16470 implementing your own stub file, you can still ignore the details: start
16471 with one of the existing stub files. @file{sparc-stub.c} is the best
16472 organized, and therefore the easiest to read.)
16474 @cindex remote serial debugging, overview
16475 To debug a program running on another machine (the debugging
16476 @dfn{target} machine), you must first arrange for all the usual
16477 prerequisites for the program to run by itself. For example, for a C
16482 A startup routine to set up the C runtime environment; these usually
16483 have a name like @file{crt0}. The startup routine may be supplied by
16484 your hardware supplier, or you may have to write your own.
16487 A C subroutine library to support your program's
16488 subroutine calls, notably managing input and output.
16491 A way of getting your program to the other machine---for example, a
16492 download program. These are often supplied by the hardware
16493 manufacturer, but you may have to write your own from hardware
16497 The next step is to arrange for your program to use a serial port to
16498 communicate with the machine where @value{GDBN} is running (the @dfn{host}
16499 machine). In general terms, the scheme looks like this:
16503 @value{GDBN} already understands how to use this protocol; when everything
16504 else is set up, you can simply use the @samp{target remote} command
16505 (@pxref{Targets,,Specifying a Debugging Target}).
16507 @item On the target,
16508 you must link with your program a few special-purpose subroutines that
16509 implement the @value{GDBN} remote serial protocol. The file containing these
16510 subroutines is called a @dfn{debugging stub}.
16512 On certain remote targets, you can use an auxiliary program
16513 @code{gdbserver} instead of linking a stub into your program.
16514 @xref{Server,,Using the @code{gdbserver} Program}, for details.
16517 The debugging stub is specific to the architecture of the remote
16518 machine; for example, use @file{sparc-stub.c} to debug programs on
16521 @cindex remote serial stub list
16522 These working remote stubs are distributed with @value{GDBN}:
16527 @cindex @file{i386-stub.c}
16530 For Intel 386 and compatible architectures.
16533 @cindex @file{m68k-stub.c}
16534 @cindex Motorola 680x0
16536 For Motorola 680x0 architectures.
16539 @cindex @file{sh-stub.c}
16542 For Renesas SH architectures.
16545 @cindex @file{sparc-stub.c}
16547 For @sc{sparc} architectures.
16549 @item sparcl-stub.c
16550 @cindex @file{sparcl-stub.c}
16553 For Fujitsu @sc{sparclite} architectures.
16557 The @file{README} file in the @value{GDBN} distribution may list other
16558 recently added stubs.
16561 * Stub Contents:: What the stub can do for you
16562 * Bootstrapping:: What you must do for the stub
16563 * Debug Session:: Putting it all together
16566 @node Stub Contents
16567 @subsection What the Stub Can Do for You
16569 @cindex remote serial stub
16570 The debugging stub for your architecture supplies these three
16574 @item set_debug_traps
16575 @findex set_debug_traps
16576 @cindex remote serial stub, initialization
16577 This routine arranges for @code{handle_exception} to run when your
16578 program stops. You must call this subroutine explicitly near the
16579 beginning of your program.
16581 @item handle_exception
16582 @findex handle_exception
16583 @cindex remote serial stub, main routine
16584 This is the central workhorse, but your program never calls it
16585 explicitly---the setup code arranges for @code{handle_exception} to
16586 run when a trap is triggered.
16588 @code{handle_exception} takes control when your program stops during
16589 execution (for example, on a breakpoint), and mediates communications
16590 with @value{GDBN} on the host machine. This is where the communications
16591 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
16592 representative on the target machine. It begins by sending summary
16593 information on the state of your program, then continues to execute,
16594 retrieving and transmitting any information @value{GDBN} needs, until you
16595 execute a @value{GDBN} command that makes your program resume; at that point,
16596 @code{handle_exception} returns control to your own code on the target
16600 @cindex @code{breakpoint} subroutine, remote
16601 Use this auxiliary subroutine to make your program contain a
16602 breakpoint. Depending on the particular situation, this may be the only
16603 way for @value{GDBN} to get control. For instance, if your target
16604 machine has some sort of interrupt button, you won't need to call this;
16605 pressing the interrupt button transfers control to
16606 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
16607 simply receiving characters on the serial port may also trigger a trap;
16608 again, in that situation, you don't need to call @code{breakpoint} from
16609 your own program---simply running @samp{target remote} from the host
16610 @value{GDBN} session gets control.
16612 Call @code{breakpoint} if none of these is true, or if you simply want
16613 to make certain your program stops at a predetermined point for the
16614 start of your debugging session.
16617 @node Bootstrapping
16618 @subsection What You Must Do for the Stub
16620 @cindex remote stub, support routines
16621 The debugging stubs that come with @value{GDBN} are set up for a particular
16622 chip architecture, but they have no information about the rest of your
16623 debugging target machine.
16625 First of all you need to tell the stub how to communicate with the
16629 @item int getDebugChar()
16630 @findex getDebugChar
16631 Write this subroutine to read a single character from the serial port.
16632 It may be identical to @code{getchar} for your target system; a
16633 different name is used to allow you to distinguish the two if you wish.
16635 @item void putDebugChar(int)
16636 @findex putDebugChar
16637 Write this subroutine to write a single character to the serial port.
16638 It may be identical to @code{putchar} for your target system; a
16639 different name is used to allow you to distinguish the two if you wish.
16642 @cindex control C, and remote debugging
16643 @cindex interrupting remote targets
16644 If you want @value{GDBN} to be able to stop your program while it is
16645 running, you need to use an interrupt-driven serial driver, and arrange
16646 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
16647 character). That is the character which @value{GDBN} uses to tell the
16648 remote system to stop.
16650 Getting the debugging target to return the proper status to @value{GDBN}
16651 probably requires changes to the standard stub; one quick and dirty way
16652 is to just execute a breakpoint instruction (the ``dirty'' part is that
16653 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
16655 Other routines you need to supply are:
16658 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
16659 @findex exceptionHandler
16660 Write this function to install @var{exception_address} in the exception
16661 handling tables. You need to do this because the stub does not have any
16662 way of knowing what the exception handling tables on your target system
16663 are like (for example, the processor's table might be in @sc{rom},
16664 containing entries which point to a table in @sc{ram}).
16665 @var{exception_number} is the exception number which should be changed;
16666 its meaning is architecture-dependent (for example, different numbers
16667 might represent divide by zero, misaligned access, etc). When this
16668 exception occurs, control should be transferred directly to
16669 @var{exception_address}, and the processor state (stack, registers,
16670 and so on) should be just as it is when a processor exception occurs. So if
16671 you want to use a jump instruction to reach @var{exception_address}, it
16672 should be a simple jump, not a jump to subroutine.
16674 For the 386, @var{exception_address} should be installed as an interrupt
16675 gate so that interrupts are masked while the handler runs. The gate
16676 should be at privilege level 0 (the most privileged level). The
16677 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
16678 help from @code{exceptionHandler}.
16680 @item void flush_i_cache()
16681 @findex flush_i_cache
16682 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
16683 instruction cache, if any, on your target machine. If there is no
16684 instruction cache, this subroutine may be a no-op.
16686 On target machines that have instruction caches, @value{GDBN} requires this
16687 function to make certain that the state of your program is stable.
16691 You must also make sure this library routine is available:
16694 @item void *memset(void *, int, int)
16696 This is the standard library function @code{memset} that sets an area of
16697 memory to a known value. If you have one of the free versions of
16698 @code{libc.a}, @code{memset} can be found there; otherwise, you must
16699 either obtain it from your hardware manufacturer, or write your own.
16702 If you do not use the GNU C compiler, you may need other standard
16703 library subroutines as well; this varies from one stub to another,
16704 but in general the stubs are likely to use any of the common library
16705 subroutines which @code{@value{NGCC}} generates as inline code.
16708 @node Debug Session
16709 @subsection Putting it All Together
16711 @cindex remote serial debugging summary
16712 In summary, when your program is ready to debug, you must follow these
16717 Make sure you have defined the supporting low-level routines
16718 (@pxref{Bootstrapping,,What You Must Do for the Stub}):
16720 @code{getDebugChar}, @code{putDebugChar},
16721 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
16725 Insert these lines near the top of your program:
16733 For the 680x0 stub only, you need to provide a variable called
16734 @code{exceptionHook}. Normally you just use:
16737 void (*exceptionHook)() = 0;
16741 but if before calling @code{set_debug_traps}, you set it to point to a
16742 function in your program, that function is called when
16743 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
16744 error). The function indicated by @code{exceptionHook} is called with
16745 one parameter: an @code{int} which is the exception number.
16748 Compile and link together: your program, the @value{GDBN} debugging stub for
16749 your target architecture, and the supporting subroutines.
16752 Make sure you have a serial connection between your target machine and
16753 the @value{GDBN} host, and identify the serial port on the host.
16756 @c The "remote" target now provides a `load' command, so we should
16757 @c document that. FIXME.
16758 Download your program to your target machine (or get it there by
16759 whatever means the manufacturer provides), and start it.
16762 Start @value{GDBN} on the host, and connect to the target
16763 (@pxref{Connecting,,Connecting to a Remote Target}).
16767 @node Configurations
16768 @chapter Configuration-Specific Information
16770 While nearly all @value{GDBN} commands are available for all native and
16771 cross versions of the debugger, there are some exceptions. This chapter
16772 describes things that are only available in certain configurations.
16774 There are three major categories of configurations: native
16775 configurations, where the host and target are the same, embedded
16776 operating system configurations, which are usually the same for several
16777 different processor architectures, and bare embedded processors, which
16778 are quite different from each other.
16783 * Embedded Processors::
16790 This section describes details specific to particular native
16795 * BSD libkvm Interface:: Debugging BSD kernel memory images
16796 * SVR4 Process Information:: SVR4 process information
16797 * DJGPP Native:: Features specific to the DJGPP port
16798 * Cygwin Native:: Features specific to the Cygwin port
16799 * Hurd Native:: Features specific to @sc{gnu} Hurd
16800 * Neutrino:: Features specific to QNX Neutrino
16801 * Darwin:: Features specific to Darwin
16807 On HP-UX systems, if you refer to a function or variable name that
16808 begins with a dollar sign, @value{GDBN} searches for a user or system
16809 name first, before it searches for a convenience variable.
16812 @node BSD libkvm Interface
16813 @subsection BSD libkvm Interface
16816 @cindex kernel memory image
16817 @cindex kernel crash dump
16819 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
16820 interface that provides a uniform interface for accessing kernel virtual
16821 memory images, including live systems and crash dumps. @value{GDBN}
16822 uses this interface to allow you to debug live kernels and kernel crash
16823 dumps on many native BSD configurations. This is implemented as a
16824 special @code{kvm} debugging target. For debugging a live system, load
16825 the currently running kernel into @value{GDBN} and connect to the
16829 (@value{GDBP}) @b{target kvm}
16832 For debugging crash dumps, provide the file name of the crash dump as an
16836 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
16839 Once connected to the @code{kvm} target, the following commands are
16845 Set current context from the @dfn{Process Control Block} (PCB) address.
16848 Set current context from proc address. This command isn't available on
16849 modern FreeBSD systems.
16852 @node SVR4 Process Information
16853 @subsection SVR4 Process Information
16855 @cindex examine process image
16856 @cindex process info via @file{/proc}
16858 Many versions of SVR4 and compatible systems provide a facility called
16859 @samp{/proc} that can be used to examine the image of a running
16860 process using file-system subroutines. If @value{GDBN} is configured
16861 for an operating system with this facility, the command @code{info
16862 proc} is available to report information about the process running
16863 your program, or about any process running on your system. @code{info
16864 proc} works only on SVR4 systems that include the @code{procfs} code.
16865 This includes, as of this writing, @sc{gnu}/Linux, OSF/1 (Digital
16866 Unix), Solaris, Irix, and Unixware, but not HP-UX, for example.
16872 @itemx info proc @var{process-id}
16873 Summarize available information about any running process. If a
16874 process ID is specified by @var{process-id}, display information about
16875 that process; otherwise display information about the program being
16876 debugged. The summary includes the debugged process ID, the command
16877 line used to invoke it, its current working directory, and its
16878 executable file's absolute file name.
16880 On some systems, @var{process-id} can be of the form
16881 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
16882 within a process. If the optional @var{pid} part is missing, it means
16883 a thread from the process being debugged (the leading @samp{/} still
16884 needs to be present, or else @value{GDBN} will interpret the number as
16885 a process ID rather than a thread ID).
16887 @item info proc mappings
16888 @cindex memory address space mappings
16889 Report the memory address space ranges accessible in the program, with
16890 information on whether the process has read, write, or execute access
16891 rights to each range. On @sc{gnu}/Linux systems, each memory range
16892 includes the object file which is mapped to that range, instead of the
16893 memory access rights to that range.
16895 @item info proc stat
16896 @itemx info proc status
16897 @cindex process detailed status information
16898 These subcommands are specific to @sc{gnu}/Linux systems. They show
16899 the process-related information, including the user ID and group ID;
16900 how many threads are there in the process; its virtual memory usage;
16901 the signals that are pending, blocked, and ignored; its TTY; its
16902 consumption of system and user time; its stack size; its @samp{nice}
16903 value; etc. For more information, see the @samp{proc} man page
16904 (type @kbd{man 5 proc} from your shell prompt).
16906 @item info proc all
16907 Show all the information about the process described under all of the
16908 above @code{info proc} subcommands.
16911 @comment These sub-options of 'info proc' were not included when
16912 @comment procfs.c was re-written. Keep their descriptions around
16913 @comment against the day when someone finds the time to put them back in.
16914 @kindex info proc times
16915 @item info proc times
16916 Starting time, user CPU time, and system CPU time for your program and
16919 @kindex info proc id
16921 Report on the process IDs related to your program: its own process ID,
16922 the ID of its parent, the process group ID, and the session ID.
16925 @item set procfs-trace
16926 @kindex set procfs-trace
16927 @cindex @code{procfs} API calls
16928 This command enables and disables tracing of @code{procfs} API calls.
16930 @item show procfs-trace
16931 @kindex show procfs-trace
16932 Show the current state of @code{procfs} API call tracing.
16934 @item set procfs-file @var{file}
16935 @kindex set procfs-file
16936 Tell @value{GDBN} to write @code{procfs} API trace to the named
16937 @var{file}. @value{GDBN} appends the trace info to the previous
16938 contents of the file. The default is to display the trace on the
16941 @item show procfs-file
16942 @kindex show procfs-file
16943 Show the file to which @code{procfs} API trace is written.
16945 @item proc-trace-entry
16946 @itemx proc-trace-exit
16947 @itemx proc-untrace-entry
16948 @itemx proc-untrace-exit
16949 @kindex proc-trace-entry
16950 @kindex proc-trace-exit
16951 @kindex proc-untrace-entry
16952 @kindex proc-untrace-exit
16953 These commands enable and disable tracing of entries into and exits
16954 from the @code{syscall} interface.
16957 @kindex info pidlist
16958 @cindex process list, QNX Neutrino
16959 For QNX Neutrino only, this command displays the list of all the
16960 processes and all the threads within each process.
16963 @kindex info meminfo
16964 @cindex mapinfo list, QNX Neutrino
16965 For QNX Neutrino only, this command displays the list of all mapinfos.
16969 @subsection Features for Debugging @sc{djgpp} Programs
16970 @cindex @sc{djgpp} debugging
16971 @cindex native @sc{djgpp} debugging
16972 @cindex MS-DOS-specific commands
16975 @sc{djgpp} is a port of the @sc{gnu} development tools to MS-DOS and
16976 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
16977 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
16978 top of real-mode DOS systems and their emulations.
16980 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
16981 defines a few commands specific to the @sc{djgpp} port. This
16982 subsection describes those commands.
16987 This is a prefix of @sc{djgpp}-specific commands which print
16988 information about the target system and important OS structures.
16991 @cindex MS-DOS system info
16992 @cindex free memory information (MS-DOS)
16993 @item info dos sysinfo
16994 This command displays assorted information about the underlying
16995 platform: the CPU type and features, the OS version and flavor, the
16996 DPMI version, and the available conventional and DPMI memory.
17001 @cindex segment descriptor tables
17002 @cindex descriptor tables display
17004 @itemx info dos ldt
17005 @itemx info dos idt
17006 These 3 commands display entries from, respectively, Global, Local,
17007 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
17008 tables are data structures which store a descriptor for each segment
17009 that is currently in use. The segment's selector is an index into a
17010 descriptor table; the table entry for that index holds the
17011 descriptor's base address and limit, and its attributes and access
17014 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
17015 segment (used for both data and the stack), and a DOS segment (which
17016 allows access to DOS/BIOS data structures and absolute addresses in
17017 conventional memory). However, the DPMI host will usually define
17018 additional segments in order to support the DPMI environment.
17020 @cindex garbled pointers
17021 These commands allow to display entries from the descriptor tables.
17022 Without an argument, all entries from the specified table are
17023 displayed. An argument, which should be an integer expression, means
17024 display a single entry whose index is given by the argument. For
17025 example, here's a convenient way to display information about the
17026 debugged program's data segment:
17029 @exdent @code{(@value{GDBP}) info dos ldt $ds}
17030 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
17034 This comes in handy when you want to see whether a pointer is outside
17035 the data segment's limit (i.e.@: @dfn{garbled}).
17037 @cindex page tables display (MS-DOS)
17039 @itemx info dos pte
17040 These two commands display entries from, respectively, the Page
17041 Directory and the Page Tables. Page Directories and Page Tables are
17042 data structures which control how virtual memory addresses are mapped
17043 into physical addresses. A Page Table includes an entry for every
17044 page of memory that is mapped into the program's address space; there
17045 may be several Page Tables, each one holding up to 4096 entries. A
17046 Page Directory has up to 4096 entries, one each for every Page Table
17047 that is currently in use.
17049 Without an argument, @kbd{info dos pde} displays the entire Page
17050 Directory, and @kbd{info dos pte} displays all the entries in all of
17051 the Page Tables. An argument, an integer expression, given to the
17052 @kbd{info dos pde} command means display only that entry from the Page
17053 Directory table. An argument given to the @kbd{info dos pte} command
17054 means display entries from a single Page Table, the one pointed to by
17055 the specified entry in the Page Directory.
17057 @cindex direct memory access (DMA) on MS-DOS
17058 These commands are useful when your program uses @dfn{DMA} (Direct
17059 Memory Access), which needs physical addresses to program the DMA
17062 These commands are supported only with some DPMI servers.
17064 @cindex physical address from linear address
17065 @item info dos address-pte @var{addr}
17066 This command displays the Page Table entry for a specified linear
17067 address. The argument @var{addr} is a linear address which should
17068 already have the appropriate segment's base address added to it,
17069 because this command accepts addresses which may belong to @emph{any}
17070 segment. For example, here's how to display the Page Table entry for
17071 the page where a variable @code{i} is stored:
17074 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
17075 @exdent @code{Page Table entry for address 0x11a00d30:}
17076 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
17080 This says that @code{i} is stored at offset @code{0xd30} from the page
17081 whose physical base address is @code{0x02698000}, and shows all the
17082 attributes of that page.
17084 Note that you must cast the addresses of variables to a @code{char *},
17085 since otherwise the value of @code{__djgpp_base_address}, the base
17086 address of all variables and functions in a @sc{djgpp} program, will
17087 be added using the rules of C pointer arithmetics: if @code{i} is
17088 declared an @code{int}, @value{GDBN} will add 4 times the value of
17089 @code{__djgpp_base_address} to the address of @code{i}.
17091 Here's another example, it displays the Page Table entry for the
17095 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
17096 @exdent @code{Page Table entry for address 0x29110:}
17097 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
17101 (The @code{+ 3} offset is because the transfer buffer's address is the
17102 3rd member of the @code{_go32_info_block} structure.) The output
17103 clearly shows that this DPMI server maps the addresses in conventional
17104 memory 1:1, i.e.@: the physical (@code{0x00029000} + @code{0x110}) and
17105 linear (@code{0x29110}) addresses are identical.
17107 This command is supported only with some DPMI servers.
17110 @cindex DOS serial data link, remote debugging
17111 In addition to native debugging, the DJGPP port supports remote
17112 debugging via a serial data link. The following commands are specific
17113 to remote serial debugging in the DJGPP port of @value{GDBN}.
17116 @kindex set com1base
17117 @kindex set com1irq
17118 @kindex set com2base
17119 @kindex set com2irq
17120 @kindex set com3base
17121 @kindex set com3irq
17122 @kindex set com4base
17123 @kindex set com4irq
17124 @item set com1base @var{addr}
17125 This command sets the base I/O port address of the @file{COM1} serial
17128 @item set com1irq @var{irq}
17129 This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use
17130 for the @file{COM1} serial port.
17132 There are similar commands @samp{set com2base}, @samp{set com3irq},
17133 etc.@: for setting the port address and the @code{IRQ} lines for the
17136 @kindex show com1base
17137 @kindex show com1irq
17138 @kindex show com2base
17139 @kindex show com2irq
17140 @kindex show com3base
17141 @kindex show com3irq
17142 @kindex show com4base
17143 @kindex show com4irq
17144 The related commands @samp{show com1base}, @samp{show com1irq} etc.@:
17145 display the current settings of the base address and the @code{IRQ}
17146 lines used by the COM ports.
17149 @kindex info serial
17150 @cindex DOS serial port status
17151 This command prints the status of the 4 DOS serial ports. For each
17152 port, it prints whether it's active or not, its I/O base address and
17153 IRQ number, whether it uses a 16550-style FIFO, its baudrate, and the
17154 counts of various errors encountered so far.
17158 @node Cygwin Native
17159 @subsection Features for Debugging MS Windows PE Executables
17160 @cindex MS Windows debugging
17161 @cindex native Cygwin debugging
17162 @cindex Cygwin-specific commands
17164 @value{GDBN} supports native debugging of MS Windows programs, including
17165 DLLs with and without symbolic debugging information.
17167 @cindex Ctrl-BREAK, MS-Windows
17168 @cindex interrupt debuggee on MS-Windows
17169 MS-Windows programs that call @code{SetConsoleMode} to switch off the
17170 special meaning of the @samp{Ctrl-C} keystroke cannot be interrupted
17171 by typing @kbd{C-c}. For this reason, @value{GDBN} on MS-Windows
17172 supports @kbd{C-@key{BREAK}} as an alternative interrupt key
17173 sequence, which can be used to interrupt the debuggee even if it
17176 There are various additional Cygwin-specific commands, described in
17177 this section. Working with DLLs that have no debugging symbols is
17178 described in @ref{Non-debug DLL Symbols}.
17183 This is a prefix of MS Windows-specific commands which print
17184 information about the target system and important OS structures.
17186 @item info w32 selector
17187 This command displays information returned by
17188 the Win32 API @code{GetThreadSelectorEntry} function.
17189 It takes an optional argument that is evaluated to
17190 a long value to give the information about this given selector.
17191 Without argument, this command displays information
17192 about the six segment registers.
17194 @item info w32 thread-information-block
17195 This command displays thread specific information stored in the
17196 Thread Information Block (readable on the X86 CPU family using @code{$fs}
17197 selector for 32-bit programs and @code{$gs} for 64-bit programs).
17201 This is a Cygwin-specific alias of @code{info shared}.
17203 @kindex dll-symbols
17205 This command loads symbols from a dll similarly to
17206 add-sym command but without the need to specify a base address.
17208 @kindex set cygwin-exceptions
17209 @cindex debugging the Cygwin DLL
17210 @cindex Cygwin DLL, debugging
17211 @item set cygwin-exceptions @var{mode}
17212 If @var{mode} is @code{on}, @value{GDBN} will break on exceptions that
17213 happen inside the Cygwin DLL. If @var{mode} is @code{off},
17214 @value{GDBN} will delay recognition of exceptions, and may ignore some
17215 exceptions which seem to be caused by internal Cygwin DLL
17216 ``bookkeeping''. This option is meant primarily for debugging the
17217 Cygwin DLL itself; the default value is @code{off} to avoid annoying
17218 @value{GDBN} users with false @code{SIGSEGV} signals.
17220 @kindex show cygwin-exceptions
17221 @item show cygwin-exceptions
17222 Displays whether @value{GDBN} will break on exceptions that happen
17223 inside the Cygwin DLL itself.
17225 @kindex set new-console
17226 @item set new-console @var{mode}
17227 If @var{mode} is @code{on} the debuggee will
17228 be started in a new console on next start.
17229 If @var{mode} is @code{off}, the debuggee will
17230 be started in the same console as the debugger.
17232 @kindex show new-console
17233 @item show new-console
17234 Displays whether a new console is used
17235 when the debuggee is started.
17237 @kindex set new-group
17238 @item set new-group @var{mode}
17239 This boolean value controls whether the debuggee should
17240 start a new group or stay in the same group as the debugger.
17241 This affects the way the Windows OS handles
17244 @kindex show new-group
17245 @item show new-group
17246 Displays current value of new-group boolean.
17248 @kindex set debugevents
17249 @item set debugevents
17250 This boolean value adds debug output concerning kernel events related
17251 to the debuggee seen by the debugger. This includes events that
17252 signal thread and process creation and exit, DLL loading and
17253 unloading, console interrupts, and debugging messages produced by the
17254 Windows @code{OutputDebugString} API call.
17256 @kindex set debugexec
17257 @item set debugexec
17258 This boolean value adds debug output concerning execute events
17259 (such as resume thread) seen by the debugger.
17261 @kindex set debugexceptions
17262 @item set debugexceptions
17263 This boolean value adds debug output concerning exceptions in the
17264 debuggee seen by the debugger.
17266 @kindex set debugmemory
17267 @item set debugmemory
17268 This boolean value adds debug output concerning debuggee memory reads
17269 and writes by the debugger.
17273 This boolean values specifies whether the debuggee is called
17274 via a shell or directly (default value is on).
17278 Displays if the debuggee will be started with a shell.
17283 * Non-debug DLL Symbols:: Support for DLLs without debugging symbols
17286 @node Non-debug DLL Symbols
17287 @subsubsection Support for DLLs without Debugging Symbols
17288 @cindex DLLs with no debugging symbols
17289 @cindex Minimal symbols and DLLs
17291 Very often on windows, some of the DLLs that your program relies on do
17292 not include symbolic debugging information (for example,
17293 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
17294 symbols in a DLL, it relies on the minimal amount of symbolic
17295 information contained in the DLL's export table. This section
17296 describes working with such symbols, known internally to @value{GDBN} as
17297 ``minimal symbols''.
17299 Note that before the debugged program has started execution, no DLLs
17300 will have been loaded. The easiest way around this problem is simply to
17301 start the program --- either by setting a breakpoint or letting the
17302 program run once to completion. It is also possible to force
17303 @value{GDBN} to load a particular DLL before starting the executable ---
17304 see the shared library information in @ref{Files}, or the
17305 @code{dll-symbols} command in @ref{Cygwin Native}. Currently,
17306 explicitly loading symbols from a DLL with no debugging information will
17307 cause the symbol names to be duplicated in @value{GDBN}'s lookup table,
17308 which may adversely affect symbol lookup performance.
17310 @subsubsection DLL Name Prefixes
17312 In keeping with the naming conventions used by the Microsoft debugging
17313 tools, DLL export symbols are made available with a prefix based on the
17314 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
17315 also entered into the symbol table, so @code{CreateFileA} is often
17316 sufficient. In some cases there will be name clashes within a program
17317 (particularly if the executable itself includes full debugging symbols)
17318 necessitating the use of the fully qualified name when referring to the
17319 contents of the DLL. Use single-quotes around the name to avoid the
17320 exclamation mark (``!'') being interpreted as a language operator.
17322 Note that the internal name of the DLL may be all upper-case, even
17323 though the file name of the DLL is lower-case, or vice-versa. Since
17324 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
17325 some confusion. If in doubt, try the @code{info functions} and
17326 @code{info variables} commands or even @code{maint print msymbols}
17327 (@pxref{Symbols}). Here's an example:
17330 (@value{GDBP}) info function CreateFileA
17331 All functions matching regular expression "CreateFileA":
17333 Non-debugging symbols:
17334 0x77e885f4 CreateFileA
17335 0x77e885f4 KERNEL32!CreateFileA
17339 (@value{GDBP}) info function !
17340 All functions matching regular expression "!":
17342 Non-debugging symbols:
17343 0x6100114c cygwin1!__assert
17344 0x61004034 cygwin1!_dll_crt0@@0
17345 0x61004240 cygwin1!dll_crt0(per_process *)
17349 @subsubsection Working with Minimal Symbols
17351 Symbols extracted from a DLL's export table do not contain very much
17352 type information. All that @value{GDBN} can do is guess whether a symbol
17353 refers to a function or variable depending on the linker section that
17354 contains the symbol. Also note that the actual contents of the memory
17355 contained in a DLL are not available unless the program is running. This
17356 means that you cannot examine the contents of a variable or disassemble
17357 a function within a DLL without a running program.
17359 Variables are generally treated as pointers and dereferenced
17360 automatically. For this reason, it is often necessary to prefix a
17361 variable name with the address-of operator (``&'') and provide explicit
17362 type information in the command. Here's an example of the type of
17366 (@value{GDBP}) print 'cygwin1!__argv'
17371 (@value{GDBP}) x 'cygwin1!__argv'
17372 0x10021610: "\230y\""
17375 And two possible solutions:
17378 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
17379 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
17383 (@value{GDBP}) x/2x &'cygwin1!__argv'
17384 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
17385 (@value{GDBP}) x/x 0x10021608
17386 0x10021608: 0x0022fd98
17387 (@value{GDBP}) x/s 0x0022fd98
17388 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
17391 Setting a break point within a DLL is possible even before the program
17392 starts execution. However, under these circumstances, @value{GDBN} can't
17393 examine the initial instructions of the function in order to skip the
17394 function's frame set-up code. You can work around this by using ``*&''
17395 to set the breakpoint at a raw memory address:
17398 (@value{GDBP}) break *&'python22!PyOS_Readline'
17399 Breakpoint 1 at 0x1e04eff0
17402 The author of these extensions is not entirely convinced that setting a
17403 break point within a shared DLL like @file{kernel32.dll} is completely
17407 @subsection Commands Specific to @sc{gnu} Hurd Systems
17408 @cindex @sc{gnu} Hurd debugging
17410 This subsection describes @value{GDBN} commands specific to the
17411 @sc{gnu} Hurd native debugging.
17416 @kindex set signals@r{, Hurd command}
17417 @kindex set sigs@r{, Hurd command}
17418 This command toggles the state of inferior signal interception by
17419 @value{GDBN}. Mach exceptions, such as breakpoint traps, are not
17420 affected by this command. @code{sigs} is a shorthand alias for
17425 @kindex show signals@r{, Hurd command}
17426 @kindex show sigs@r{, Hurd command}
17427 Show the current state of intercepting inferior's signals.
17429 @item set signal-thread
17430 @itemx set sigthread
17431 @kindex set signal-thread
17432 @kindex set sigthread
17433 This command tells @value{GDBN} which thread is the @code{libc} signal
17434 thread. That thread is run when a signal is delivered to a running
17435 process. @code{set sigthread} is the shorthand alias of @code{set
17438 @item show signal-thread
17439 @itemx show sigthread
17440 @kindex show signal-thread
17441 @kindex show sigthread
17442 These two commands show which thread will run when the inferior is
17443 delivered a signal.
17446 @kindex set stopped@r{, Hurd command}
17447 This commands tells @value{GDBN} that the inferior process is stopped,
17448 as with the @code{SIGSTOP} signal. The stopped process can be
17449 continued by delivering a signal to it.
17452 @kindex show stopped@r{, Hurd command}
17453 This command shows whether @value{GDBN} thinks the debuggee is
17456 @item set exceptions
17457 @kindex set exceptions@r{, Hurd command}
17458 Use this command to turn off trapping of exceptions in the inferior.
17459 When exception trapping is off, neither breakpoints nor
17460 single-stepping will work. To restore the default, set exception
17463 @item show exceptions
17464 @kindex show exceptions@r{, Hurd command}
17465 Show the current state of trapping exceptions in the inferior.
17467 @item set task pause
17468 @kindex set task@r{, Hurd commands}
17469 @cindex task attributes (@sc{gnu} Hurd)
17470 @cindex pause current task (@sc{gnu} Hurd)
17471 This command toggles task suspension when @value{GDBN} has control.
17472 Setting it to on takes effect immediately, and the task is suspended
17473 whenever @value{GDBN} gets control. Setting it to off will take
17474 effect the next time the inferior is continued. If this option is set
17475 to off, you can use @code{set thread default pause on} or @code{set
17476 thread pause on} (see below) to pause individual threads.
17478 @item show task pause
17479 @kindex show task@r{, Hurd commands}
17480 Show the current state of task suspension.
17482 @item set task detach-suspend-count
17483 @cindex task suspend count
17484 @cindex detach from task, @sc{gnu} Hurd
17485 This command sets the suspend count the task will be left with when
17486 @value{GDBN} detaches from it.
17488 @item show task detach-suspend-count
17489 Show the suspend count the task will be left with when detaching.
17491 @item set task exception-port
17492 @itemx set task excp
17493 @cindex task exception port, @sc{gnu} Hurd
17494 This command sets the task exception port to which @value{GDBN} will
17495 forward exceptions. The argument should be the value of the @dfn{send
17496 rights} of the task. @code{set task excp} is a shorthand alias.
17498 @item set noninvasive
17499 @cindex noninvasive task options
17500 This command switches @value{GDBN} to a mode that is the least
17501 invasive as far as interfering with the inferior is concerned. This
17502 is the same as using @code{set task pause}, @code{set exceptions}, and
17503 @code{set signals} to values opposite to the defaults.
17505 @item info send-rights
17506 @itemx info receive-rights
17507 @itemx info port-rights
17508 @itemx info port-sets
17509 @itemx info dead-names
17512 @cindex send rights, @sc{gnu} Hurd
17513 @cindex receive rights, @sc{gnu} Hurd
17514 @cindex port rights, @sc{gnu} Hurd
17515 @cindex port sets, @sc{gnu} Hurd
17516 @cindex dead names, @sc{gnu} Hurd
17517 These commands display information about, respectively, send rights,
17518 receive rights, port rights, port sets, and dead names of a task.
17519 There are also shorthand aliases: @code{info ports} for @code{info
17520 port-rights} and @code{info psets} for @code{info port-sets}.
17522 @item set thread pause
17523 @kindex set thread@r{, Hurd command}
17524 @cindex thread properties, @sc{gnu} Hurd
17525 @cindex pause current thread (@sc{gnu} Hurd)
17526 This command toggles current thread suspension when @value{GDBN} has
17527 control. Setting it to on takes effect immediately, and the current
17528 thread is suspended whenever @value{GDBN} gets control. Setting it to
17529 off will take effect the next time the inferior is continued.
17530 Normally, this command has no effect, since when @value{GDBN} has
17531 control, the whole task is suspended. However, if you used @code{set
17532 task pause off} (see above), this command comes in handy to suspend
17533 only the current thread.
17535 @item show thread pause
17536 @kindex show thread@r{, Hurd command}
17537 This command shows the state of current thread suspension.
17539 @item set thread run
17540 This command sets whether the current thread is allowed to run.
17542 @item show thread run
17543 Show whether the current thread is allowed to run.
17545 @item set thread detach-suspend-count
17546 @cindex thread suspend count, @sc{gnu} Hurd
17547 @cindex detach from thread, @sc{gnu} Hurd
17548 This command sets the suspend count @value{GDBN} will leave on a
17549 thread when detaching. This number is relative to the suspend count
17550 found by @value{GDBN} when it notices the thread; use @code{set thread
17551 takeover-suspend-count} to force it to an absolute value.
17553 @item show thread detach-suspend-count
17554 Show the suspend count @value{GDBN} will leave on the thread when
17557 @item set thread exception-port
17558 @itemx set thread excp
17559 Set the thread exception port to which to forward exceptions. This
17560 overrides the port set by @code{set task exception-port} (see above).
17561 @code{set thread excp} is the shorthand alias.
17563 @item set thread takeover-suspend-count
17564 Normally, @value{GDBN}'s thread suspend counts are relative to the
17565 value @value{GDBN} finds when it notices each thread. This command
17566 changes the suspend counts to be absolute instead.
17568 @item set thread default
17569 @itemx show thread default
17570 @cindex thread default settings, @sc{gnu} Hurd
17571 Each of the above @code{set thread} commands has a @code{set thread
17572 default} counterpart (e.g., @code{set thread default pause}, @code{set
17573 thread default exception-port}, etc.). The @code{thread default}
17574 variety of commands sets the default thread properties for all
17575 threads; you can then change the properties of individual threads with
17576 the non-default commands.
17581 @subsection QNX Neutrino
17582 @cindex QNX Neutrino
17584 @value{GDBN} provides the following commands specific to the QNX
17588 @item set debug nto-debug
17589 @kindex set debug nto-debug
17590 When set to on, enables debugging messages specific to the QNX
17593 @item show debug nto-debug
17594 @kindex show debug nto-debug
17595 Show the current state of QNX Neutrino messages.
17602 @value{GDBN} provides the following commands specific to the Darwin target:
17605 @item set debug darwin @var{num}
17606 @kindex set debug darwin
17607 When set to a non zero value, enables debugging messages specific to
17608 the Darwin support. Higher values produce more verbose output.
17610 @item show debug darwin
17611 @kindex show debug darwin
17612 Show the current state of Darwin messages.
17614 @item set debug mach-o @var{num}
17615 @kindex set debug mach-o
17616 When set to a non zero value, enables debugging messages while
17617 @value{GDBN} is reading Darwin object files. (@dfn{Mach-O} is the
17618 file format used on Darwin for object and executable files.) Higher
17619 values produce more verbose output. This is a command to diagnose
17620 problems internal to @value{GDBN} and should not be needed in normal
17623 @item show debug mach-o
17624 @kindex show debug mach-o
17625 Show the current state of Mach-O file messages.
17627 @item set mach-exceptions on
17628 @itemx set mach-exceptions off
17629 @kindex set mach-exceptions
17630 On Darwin, faults are first reported as a Mach exception and are then
17631 mapped to a Posix signal. Use this command to turn on trapping of
17632 Mach exceptions in the inferior. This might be sometimes useful to
17633 better understand the cause of a fault. The default is off.
17635 @item show mach-exceptions
17636 @kindex show mach-exceptions
17637 Show the current state of exceptions trapping.
17642 @section Embedded Operating Systems
17644 This section describes configurations involving the debugging of
17645 embedded operating systems that are available for several different
17649 * VxWorks:: Using @value{GDBN} with VxWorks
17652 @value{GDBN} includes the ability to debug programs running on
17653 various real-time operating systems.
17656 @subsection Using @value{GDBN} with VxWorks
17662 @kindex target vxworks
17663 @item target vxworks @var{machinename}
17664 A VxWorks system, attached via TCP/IP. The argument @var{machinename}
17665 is the target system's machine name or IP address.
17669 On VxWorks, @code{load} links @var{filename} dynamically on the
17670 current target system as well as adding its symbols in @value{GDBN}.
17672 @value{GDBN} enables developers to spawn and debug tasks running on networked
17673 VxWorks targets from a Unix host. Already-running tasks spawned from
17674 the VxWorks shell can also be debugged. @value{GDBN} uses code that runs on
17675 both the Unix host and on the VxWorks target. The program
17676 @code{@value{GDBP}} is installed and executed on the Unix host. (It may be
17677 installed with the name @code{vxgdb}, to distinguish it from a
17678 @value{GDBN} for debugging programs on the host itself.)
17681 @item VxWorks-timeout @var{args}
17682 @kindex vxworks-timeout
17683 All VxWorks-based targets now support the option @code{vxworks-timeout}.
17684 This option is set by the user, and @var{args} represents the number of
17685 seconds @value{GDBN} waits for responses to rpc's. You might use this if
17686 your VxWorks target is a slow software simulator or is on the far side
17687 of a thin network line.
17690 The following information on connecting to VxWorks was current when
17691 this manual was produced; newer releases of VxWorks may use revised
17694 @findex INCLUDE_RDB
17695 To use @value{GDBN} with VxWorks, you must rebuild your VxWorks kernel
17696 to include the remote debugging interface routines in the VxWorks
17697 library @file{rdb.a}. To do this, define @code{INCLUDE_RDB} in the
17698 VxWorks configuration file @file{configAll.h} and rebuild your VxWorks
17699 kernel. The resulting kernel contains @file{rdb.a}, and spawns the
17700 source debugging task @code{tRdbTask} when VxWorks is booted. For more
17701 information on configuring and remaking VxWorks, see the manufacturer's
17703 @c VxWorks, see the @cite{VxWorks Programmer's Guide}.
17705 Once you have included @file{rdb.a} in your VxWorks system image and set
17706 your Unix execution search path to find @value{GDBN}, you are ready to
17707 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}} (or
17708 @code{vxgdb}, depending on your installation).
17710 @value{GDBN} comes up showing the prompt:
17717 * VxWorks Connection:: Connecting to VxWorks
17718 * VxWorks Download:: VxWorks download
17719 * VxWorks Attach:: Running tasks
17722 @node VxWorks Connection
17723 @subsubsection Connecting to VxWorks
17725 The @value{GDBN} command @code{target} lets you connect to a VxWorks target on the
17726 network. To connect to a target whose host name is ``@code{tt}'', type:
17729 (vxgdb) target vxworks tt
17733 @value{GDBN} displays messages like these:
17736 Attaching remote machine across net...
17741 @value{GDBN} then attempts to read the symbol tables of any object modules
17742 loaded into the VxWorks target since it was last booted. @value{GDBN} locates
17743 these files by searching the directories listed in the command search
17744 path (@pxref{Environment, ,Your Program's Environment}); if it fails
17745 to find an object file, it displays a message such as:
17748 prog.o: No such file or directory.
17751 When this happens, add the appropriate directory to the search path with
17752 the @value{GDBN} command @code{path}, and execute the @code{target}
17755 @node VxWorks Download
17756 @subsubsection VxWorks Download
17758 @cindex download to VxWorks
17759 If you have connected to the VxWorks target and you want to debug an
17760 object that has not yet been loaded, you can use the @value{GDBN}
17761 @code{load} command to download a file from Unix to VxWorks
17762 incrementally. The object file given as an argument to the @code{load}
17763 command is actually opened twice: first by the VxWorks target in order
17764 to download the code, then by @value{GDBN} in order to read the symbol
17765 table. This can lead to problems if the current working directories on
17766 the two systems differ. If both systems have NFS mounted the same
17767 filesystems, you can avoid these problems by using absolute paths.
17768 Otherwise, it is simplest to set the working directory on both systems
17769 to the directory in which the object file resides, and then to reference
17770 the file by its name, without any path. For instance, a program
17771 @file{prog.o} may reside in @file{@var{vxpath}/vw/demo/rdb} in VxWorks
17772 and in @file{@var{hostpath}/vw/demo/rdb} on the host. To load this
17773 program, type this on VxWorks:
17776 -> cd "@var{vxpath}/vw/demo/rdb"
17780 Then, in @value{GDBN}, type:
17783 (vxgdb) cd @var{hostpath}/vw/demo/rdb
17784 (vxgdb) load prog.o
17787 @value{GDBN} displays a response similar to this:
17790 Reading symbol data from wherever/vw/demo/rdb/prog.o... done.
17793 You can also use the @code{load} command to reload an object module
17794 after editing and recompiling the corresponding source file. Note that
17795 this makes @value{GDBN} delete all currently-defined breakpoints,
17796 auto-displays, and convenience variables, and to clear the value
17797 history. (This is necessary in order to preserve the integrity of
17798 debugger's data structures that reference the target system's symbol
17801 @node VxWorks Attach
17802 @subsubsection Running Tasks
17804 @cindex running VxWorks tasks
17805 You can also attach to an existing task using the @code{attach} command as
17809 (vxgdb) attach @var{task}
17813 where @var{task} is the VxWorks hexadecimal task ID. The task can be running
17814 or suspended when you attach to it. Running tasks are suspended at
17815 the time of attachment.
17817 @node Embedded Processors
17818 @section Embedded Processors
17820 This section goes into details specific to particular embedded
17823 @cindex send command to simulator
17824 Whenever a specific embedded processor has a simulator, @value{GDBN}
17825 allows to send an arbitrary command to the simulator.
17828 @item sim @var{command}
17829 @kindex sim@r{, a command}
17830 Send an arbitrary @var{command} string to the simulator. Consult the
17831 documentation for the specific simulator in use for information about
17832 acceptable commands.
17838 * M32R/D:: Renesas M32R/D
17839 * M68K:: Motorola M68K
17840 * MicroBlaze:: Xilinx MicroBlaze
17841 * MIPS Embedded:: MIPS Embedded
17842 * OpenRISC 1000:: OpenRisc 1000
17843 * PA:: HP PA Embedded
17844 * PowerPC Embedded:: PowerPC Embedded
17845 * Sparclet:: Tsqware Sparclet
17846 * Sparclite:: Fujitsu Sparclite
17847 * Z8000:: Zilog Z8000
17850 * Super-H:: Renesas Super-H
17859 @item target rdi @var{dev}
17860 ARM Angel monitor, via RDI library interface to ADP protocol. You may
17861 use this target to communicate with both boards running the Angel
17862 monitor, or with the EmbeddedICE JTAG debug device.
17865 @item target rdp @var{dev}
17870 @value{GDBN} provides the following ARM-specific commands:
17873 @item set arm disassembler
17875 This commands selects from a list of disassembly styles. The
17876 @code{"std"} style is the standard style.
17878 @item show arm disassembler
17880 Show the current disassembly style.
17882 @item set arm apcs32
17883 @cindex ARM 32-bit mode
17884 This command toggles ARM operation mode between 32-bit and 26-bit.
17886 @item show arm apcs32
17887 Display the current usage of the ARM 32-bit mode.
17889 @item set arm fpu @var{fputype}
17890 This command sets the ARM floating-point unit (FPU) type. The
17891 argument @var{fputype} can be one of these:
17895 Determine the FPU type by querying the OS ABI.
17897 Software FPU, with mixed-endian doubles on little-endian ARM
17900 GCC-compiled FPA co-processor.
17902 Software FPU with pure-endian doubles.
17908 Show the current type of the FPU.
17911 This command forces @value{GDBN} to use the specified ABI.
17914 Show the currently used ABI.
17916 @item set arm fallback-mode (arm|thumb|auto)
17917 @value{GDBN} uses the symbol table, when available, to determine
17918 whether instructions are ARM or Thumb. This command controls
17919 @value{GDBN}'s default behavior when the symbol table is not
17920 available. The default is @samp{auto}, which causes @value{GDBN} to
17921 use the current execution mode (from the @code{T} bit in the @code{CPSR}
17924 @item show arm fallback-mode
17925 Show the current fallback instruction mode.
17927 @item set arm force-mode (arm|thumb|auto)
17928 This command overrides use of the symbol table to determine whether
17929 instructions are ARM or Thumb. The default is @samp{auto}, which
17930 causes @value{GDBN} to use the symbol table and then the setting
17931 of @samp{set arm fallback-mode}.
17933 @item show arm force-mode
17934 Show the current forced instruction mode.
17936 @item set debug arm
17937 Toggle whether to display ARM-specific debugging messages from the ARM
17938 target support subsystem.
17940 @item show debug arm
17941 Show whether ARM-specific debugging messages are enabled.
17944 The following commands are available when an ARM target is debugged
17945 using the RDI interface:
17948 @item rdilogfile @r{[}@var{file}@r{]}
17950 @cindex ADP (Angel Debugger Protocol) logging
17951 Set the filename for the ADP (Angel Debugger Protocol) packet log.
17952 With an argument, sets the log file to the specified @var{file}. With
17953 no argument, show the current log file name. The default log file is
17956 @item rdilogenable @r{[}@var{arg}@r{]}
17957 @kindex rdilogenable
17958 Control logging of ADP packets. With an argument of 1 or @code{"yes"}
17959 enables logging, with an argument 0 or @code{"no"} disables it. With
17960 no arguments displays the current setting. When logging is enabled,
17961 ADP packets exchanged between @value{GDBN} and the RDI target device
17962 are logged to a file.
17964 @item set rdiromatzero
17965 @kindex set rdiromatzero
17966 @cindex ROM at zero address, RDI
17967 Tell @value{GDBN} whether the target has ROM at address 0. If on,
17968 vector catching is disabled, so that zero address can be used. If off
17969 (the default), vector catching is enabled. For this command to take
17970 effect, it needs to be invoked prior to the @code{target rdi} command.
17972 @item show rdiromatzero
17973 @kindex show rdiromatzero
17974 Show the current setting of ROM at zero address.
17976 @item set rdiheartbeat
17977 @kindex set rdiheartbeat
17978 @cindex RDI heartbeat
17979 Enable or disable RDI heartbeat packets. It is not recommended to
17980 turn on this option, since it confuses ARM and EPI JTAG interface, as
17981 well as the Angel monitor.
17983 @item show rdiheartbeat
17984 @kindex show rdiheartbeat
17985 Show the setting of RDI heartbeat packets.
17989 @item target sim @r{[}@var{simargs}@r{]} @dots{}
17990 The @value{GDBN} ARM simulator accepts the following optional arguments.
17993 @item --swi-support=@var{type}
17994 Tell the simulator which SWI interfaces to support.
17995 @var{type} may be a comma separated list of the following values.
17996 The default value is @code{all}.
18009 @subsection Renesas M32R/D and M32R/SDI
18012 @kindex target m32r
18013 @item target m32r @var{dev}
18014 Renesas M32R/D ROM monitor.
18016 @kindex target m32rsdi
18017 @item target m32rsdi @var{dev}
18018 Renesas M32R SDI server, connected via parallel port to the board.
18021 The following @value{GDBN} commands are specific to the M32R monitor:
18024 @item set download-path @var{path}
18025 @kindex set download-path
18026 @cindex find downloadable @sc{srec} files (M32R)
18027 Set the default path for finding downloadable @sc{srec} files.
18029 @item show download-path
18030 @kindex show download-path
18031 Show the default path for downloadable @sc{srec} files.
18033 @item set board-address @var{addr}
18034 @kindex set board-address
18035 @cindex M32-EVA target board address
18036 Set the IP address for the M32R-EVA target board.
18038 @item show board-address
18039 @kindex show board-address
18040 Show the current IP address of the target board.
18042 @item set server-address @var{addr}
18043 @kindex set server-address
18044 @cindex download server address (M32R)
18045 Set the IP address for the download server, which is the @value{GDBN}'s
18048 @item show server-address
18049 @kindex show server-address
18050 Display the IP address of the download server.
18052 @item upload @r{[}@var{file}@r{]}
18053 @kindex upload@r{, M32R}
18054 Upload the specified @sc{srec} @var{file} via the monitor's Ethernet
18055 upload capability. If no @var{file} argument is given, the current
18056 executable file is uploaded.
18058 @item tload @r{[}@var{file}@r{]}
18059 @kindex tload@r{, M32R}
18060 Test the @code{upload} command.
18063 The following commands are available for M32R/SDI:
18068 @cindex reset SDI connection, M32R
18069 This command resets the SDI connection.
18073 This command shows the SDI connection status.
18076 @kindex debug_chaos
18077 @cindex M32R/Chaos debugging
18078 Instructs the remote that M32R/Chaos debugging is to be used.
18080 @item use_debug_dma
18081 @kindex use_debug_dma
18082 Instructs the remote to use the DEBUG_DMA method of accessing memory.
18085 @kindex use_mon_code
18086 Instructs the remote to use the MON_CODE method of accessing memory.
18089 @kindex use_ib_break
18090 Instructs the remote to set breakpoints by IB break.
18092 @item use_dbt_break
18093 @kindex use_dbt_break
18094 Instructs the remote to set breakpoints by DBT.
18100 The Motorola m68k configuration includes ColdFire support, and a
18101 target command for the following ROM monitor.
18105 @kindex target dbug
18106 @item target dbug @var{dev}
18107 dBUG ROM monitor for Motorola ColdFire.
18112 @subsection MicroBlaze
18113 @cindex Xilinx MicroBlaze
18114 @cindex XMD, Xilinx Microprocessor Debugger
18116 The MicroBlaze is a soft-core processor supported on various Xilinx
18117 FPGAs, such as Spartan or Virtex series. Boards with these processors
18118 usually have JTAG ports which connect to a host system running the Xilinx
18119 Embedded Development Kit (EDK) or Software Development Kit (SDK).
18120 This host system is used to download the configuration bitstream to
18121 the target FPGA. The Xilinx Microprocessor Debugger (XMD) program
18122 communicates with the target board using the JTAG interface and
18123 presents a @code{gdbserver} interface to the board. By default
18124 @code{xmd} uses port @code{1234}. (While it is possible to change
18125 this default port, it requires the use of undocumented @code{xmd}
18126 commands. Contact Xilinx support if you need to do this.)
18128 Use these GDB commands to connect to the MicroBlaze target processor.
18131 @item target remote :1234
18132 Use this command to connect to the target if you are running @value{GDBN}
18133 on the same system as @code{xmd}.
18135 @item target remote @var{xmd-host}:1234
18136 Use this command to connect to the target if it is connected to @code{xmd}
18137 running on a different system named @var{xmd-host}.
18140 Use this command to download a program to the MicroBlaze target.
18142 @item set debug microblaze @var{n}
18143 Enable MicroBlaze-specific debugging messages if non-zero.
18145 @item show debug microblaze @var{n}
18146 Show MicroBlaze-specific debugging level.
18149 @node MIPS Embedded
18150 @subsection MIPS Embedded
18152 @cindex MIPS boards
18153 @value{GDBN} can use the MIPS remote debugging protocol to talk to a
18154 MIPS board attached to a serial line. This is available when
18155 you configure @value{GDBN} with @samp{--target=mips-idt-ecoff}.
18158 Use these @value{GDBN} commands to specify the connection to your target board:
18161 @item target mips @var{port}
18162 @kindex target mips @var{port}
18163 To run a program on the board, start up @code{@value{GDBP}} with the
18164 name of your program as the argument. To connect to the board, use the
18165 command @samp{target mips @var{port}}, where @var{port} is the name of
18166 the serial port connected to the board. If the program has not already
18167 been downloaded to the board, you may use the @code{load} command to
18168 download it. You can then use all the usual @value{GDBN} commands.
18170 For example, this sequence connects to the target board through a serial
18171 port, and loads and runs a program called @var{prog} through the
18175 host$ @value{GDBP} @var{prog}
18176 @value{GDBN} is free software and @dots{}
18177 (@value{GDBP}) target mips /dev/ttyb
18178 (@value{GDBP}) load @var{prog}
18182 @item target mips @var{hostname}:@var{portnumber}
18183 On some @value{GDBN} host configurations, you can specify a TCP
18184 connection (for instance, to a serial line managed by a terminal
18185 concentrator) instead of a serial port, using the syntax
18186 @samp{@var{hostname}:@var{portnumber}}.
18188 @item target pmon @var{port}
18189 @kindex target pmon @var{port}
18192 @item target ddb @var{port}
18193 @kindex target ddb @var{port}
18194 NEC's DDB variant of PMON for Vr4300.
18196 @item target lsi @var{port}
18197 @kindex target lsi @var{port}
18198 LSI variant of PMON.
18200 @kindex target r3900
18201 @item target r3900 @var{dev}
18202 Densan DVE-R3900 ROM monitor for Toshiba R3900 Mips.
18204 @kindex target array
18205 @item target array @var{dev}
18206 Array Tech LSI33K RAID controller board.
18212 @value{GDBN} also supports these special commands for MIPS targets:
18215 @item set mipsfpu double
18216 @itemx set mipsfpu single
18217 @itemx set mipsfpu none
18218 @itemx set mipsfpu auto
18219 @itemx show mipsfpu
18220 @kindex set mipsfpu
18221 @kindex show mipsfpu
18222 @cindex MIPS remote floating point
18223 @cindex floating point, MIPS remote
18224 If your target board does not support the MIPS floating point
18225 coprocessor, you should use the command @samp{set mipsfpu none} (if you
18226 need this, you may wish to put the command in your @value{GDBN} init
18227 file). This tells @value{GDBN} how to find the return value of
18228 functions which return floating point values. It also allows
18229 @value{GDBN} to avoid saving the floating point registers when calling
18230 functions on the board. If you are using a floating point coprocessor
18231 with only single precision floating point support, as on the @sc{r4650}
18232 processor, use the command @samp{set mipsfpu single}. The default
18233 double precision floating point coprocessor may be selected using
18234 @samp{set mipsfpu double}.
18236 In previous versions the only choices were double precision or no
18237 floating point, so @samp{set mipsfpu on} will select double precision
18238 and @samp{set mipsfpu off} will select no floating point.
18240 As usual, you can inquire about the @code{mipsfpu} variable with
18241 @samp{show mipsfpu}.
18243 @item set timeout @var{seconds}
18244 @itemx set retransmit-timeout @var{seconds}
18245 @itemx show timeout
18246 @itemx show retransmit-timeout
18247 @cindex @code{timeout}, MIPS protocol
18248 @cindex @code{retransmit-timeout}, MIPS protocol
18249 @kindex set timeout
18250 @kindex show timeout
18251 @kindex set retransmit-timeout
18252 @kindex show retransmit-timeout
18253 You can control the timeout used while waiting for a packet, in the MIPS
18254 remote protocol, with the @code{set timeout @var{seconds}} command. The
18255 default is 5 seconds. Similarly, you can control the timeout used while
18256 waiting for an acknowledgment of a packet with the @code{set
18257 retransmit-timeout @var{seconds}} command. The default is 3 seconds.
18258 You can inspect both values with @code{show timeout} and @code{show
18259 retransmit-timeout}. (These commands are @emph{only} available when
18260 @value{GDBN} is configured for @samp{--target=mips-idt-ecoff}.)
18262 The timeout set by @code{set timeout} does not apply when @value{GDBN}
18263 is waiting for your program to stop. In that case, @value{GDBN} waits
18264 forever because it has no way of knowing how long the program is going
18265 to run before stopping.
18267 @item set syn-garbage-limit @var{num}
18268 @kindex set syn-garbage-limit@r{, MIPS remote}
18269 @cindex synchronize with remote MIPS target
18270 Limit the maximum number of characters @value{GDBN} should ignore when
18271 it tries to synchronize with the remote target. The default is 10
18272 characters. Setting the limit to -1 means there's no limit.
18274 @item show syn-garbage-limit
18275 @kindex show syn-garbage-limit@r{, MIPS remote}
18276 Show the current limit on the number of characters to ignore when
18277 trying to synchronize with the remote system.
18279 @item set monitor-prompt @var{prompt}
18280 @kindex set monitor-prompt@r{, MIPS remote}
18281 @cindex remote monitor prompt
18282 Tell @value{GDBN} to expect the specified @var{prompt} string from the
18283 remote monitor. The default depends on the target:
18293 @item show monitor-prompt
18294 @kindex show monitor-prompt@r{, MIPS remote}
18295 Show the current strings @value{GDBN} expects as the prompt from the
18298 @item set monitor-warnings
18299 @kindex set monitor-warnings@r{, MIPS remote}
18300 Enable or disable monitor warnings about hardware breakpoints. This
18301 has effect only for the @code{lsi} target. When on, @value{GDBN} will
18302 display warning messages whose codes are returned by the @code{lsi}
18303 PMON monitor for breakpoint commands.
18305 @item show monitor-warnings
18306 @kindex show monitor-warnings@r{, MIPS remote}
18307 Show the current setting of printing monitor warnings.
18309 @item pmon @var{command}
18310 @kindex pmon@r{, MIPS remote}
18311 @cindex send PMON command
18312 This command allows sending an arbitrary @var{command} string to the
18313 monitor. The monitor must be in debug mode for this to work.
18316 @node OpenRISC 1000
18317 @subsection OpenRISC 1000
18318 @cindex OpenRISC 1000
18320 @cindex or1k boards
18321 See OR1k Architecture document (@uref{www.opencores.org}) for more information
18322 about platform and commands.
18326 @kindex target jtag
18327 @item target jtag jtag://@var{host}:@var{port}
18329 Connects to remote JTAG server.
18330 JTAG remote server can be either an or1ksim or JTAG server,
18331 connected via parallel port to the board.
18333 Example: @code{target jtag jtag://localhost:9999}
18336 @item or1ksim @var{command}
18337 If connected to @code{or1ksim} OpenRISC 1000 Architectural
18338 Simulator, proprietary commands can be executed.
18340 @kindex info or1k spr
18341 @item info or1k spr
18342 Displays spr groups.
18344 @item info or1k spr @var{group}
18345 @itemx info or1k spr @var{groupno}
18346 Displays register names in selected group.
18348 @item info or1k spr @var{group} @var{register}
18349 @itemx info or1k spr @var{register}
18350 @itemx info or1k spr @var{groupno} @var{registerno}
18351 @itemx info or1k spr @var{registerno}
18352 Shows information about specified spr register.
18355 @item spr @var{group} @var{register} @var{value}
18356 @itemx spr @var{register @var{value}}
18357 @itemx spr @var{groupno} @var{registerno @var{value}}
18358 @itemx spr @var{registerno @var{value}}
18359 Writes @var{value} to specified spr register.
18362 Some implementations of OpenRISC 1000 Architecture also have hardware trace.
18363 It is very similar to @value{GDBN} trace, except it does not interfere with normal
18364 program execution and is thus much faster. Hardware breakpoints/watchpoint
18365 triggers can be set using:
18368 Load effective address/data
18370 Store effective address/data
18372 Access effective address ($SEA or $LEA) or data ($SDATA/$LDATA)
18377 When triggered, it can capture low level data, like: @code{PC}, @code{LSEA},
18378 @code{LDATA}, @code{SDATA}, @code{READSPR}, @code{WRITESPR}, @code{INSTR}.
18380 @code{htrace} commands:
18381 @cindex OpenRISC 1000 htrace
18384 @item hwatch @var{conditional}
18385 Set hardware watchpoint on combination of Load/Store Effective Address(es)
18386 or Data. For example:
18388 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
18390 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
18394 Display information about current HW trace configuration.
18396 @item htrace trigger @var{conditional}
18397 Set starting criteria for HW trace.
18399 @item htrace qualifier @var{conditional}
18400 Set acquisition qualifier for HW trace.
18402 @item htrace stop @var{conditional}
18403 Set HW trace stopping criteria.
18405 @item htrace record [@var{data}]*
18406 Selects the data to be recorded, when qualifier is met and HW trace was
18409 @item htrace enable
18410 @itemx htrace disable
18411 Enables/disables the HW trace.
18413 @item htrace rewind [@var{filename}]
18414 Clears currently recorded trace data.
18416 If filename is specified, new trace file is made and any newly collected data
18417 will be written there.
18419 @item htrace print [@var{start} [@var{len}]]
18420 Prints trace buffer, using current record configuration.
18422 @item htrace mode continuous
18423 Set continuous trace mode.
18425 @item htrace mode suspend
18426 Set suspend trace mode.
18430 @node PowerPC Embedded
18431 @subsection PowerPC Embedded
18433 @value{GDBN} provides the following PowerPC-specific commands:
18436 @kindex set powerpc
18437 @item set powerpc soft-float
18438 @itemx show powerpc soft-float
18439 Force @value{GDBN} to use (or not use) a software floating point calling
18440 convention. By default, @value{GDBN} selects the calling convention based
18441 on the selected architecture and the provided executable file.
18443 @item set powerpc vector-abi
18444 @itemx show powerpc vector-abi
18445 Force @value{GDBN} to use the specified calling convention for vector
18446 arguments and return values. The valid options are @samp{auto};
18447 @samp{generic}, to avoid vector registers even if they are present;
18448 @samp{altivec}, to use AltiVec registers; and @samp{spe} to use SPE
18449 registers. By default, @value{GDBN} selects the calling convention
18450 based on the selected architecture and the provided executable file.
18452 @kindex target dink32
18453 @item target dink32 @var{dev}
18454 DINK32 ROM monitor.
18456 @kindex target ppcbug
18457 @item target ppcbug @var{dev}
18458 @kindex target ppcbug1
18459 @item target ppcbug1 @var{dev}
18460 PPCBUG ROM monitor for PowerPC.
18463 @item target sds @var{dev}
18464 SDS monitor, running on a PowerPC board (such as Motorola's ADS).
18467 @cindex SDS protocol
18468 The following commands specific to the SDS protocol are supported
18472 @item set sdstimeout @var{nsec}
18473 @kindex set sdstimeout
18474 Set the timeout for SDS protocol reads to be @var{nsec} seconds. The
18475 default is 2 seconds.
18477 @item show sdstimeout
18478 @kindex show sdstimeout
18479 Show the current value of the SDS timeout.
18481 @item sds @var{command}
18482 @kindex sds@r{, a command}
18483 Send the specified @var{command} string to the SDS monitor.
18488 @subsection HP PA Embedded
18492 @kindex target op50n
18493 @item target op50n @var{dev}
18494 OP50N monitor, running on an OKI HPPA board.
18496 @kindex target w89k
18497 @item target w89k @var{dev}
18498 W89K monitor, running on a Winbond HPPA board.
18503 @subsection Tsqware Sparclet
18507 @value{GDBN} enables developers to debug tasks running on
18508 Sparclet targets from a Unix host.
18509 @value{GDBN} uses code that runs on
18510 both the Unix host and on the Sparclet target. The program
18511 @code{@value{GDBP}} is installed and executed on the Unix host.
18514 @item remotetimeout @var{args}
18515 @kindex remotetimeout
18516 @value{GDBN} supports the option @code{remotetimeout}.
18517 This option is set by the user, and @var{args} represents the number of
18518 seconds @value{GDBN} waits for responses.
18521 @cindex compiling, on Sparclet
18522 When compiling for debugging, include the options @samp{-g} to get debug
18523 information and @samp{-Ttext} to relocate the program to where you wish to
18524 load it on the target. You may also want to add the options @samp{-n} or
18525 @samp{-N} in order to reduce the size of the sections. Example:
18528 sparclet-aout-gcc prog.c -Ttext 0x12010000 -g -o prog -N
18531 You can use @code{objdump} to verify that the addresses are what you intended:
18534 sparclet-aout-objdump --headers --syms prog
18537 @cindex running, on Sparclet
18539 your Unix execution search path to find @value{GDBN}, you are ready to
18540 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}}
18541 (or @code{sparclet-aout-gdb}, depending on your installation).
18543 @value{GDBN} comes up showing the prompt:
18550 * Sparclet File:: Setting the file to debug
18551 * Sparclet Connection:: Connecting to Sparclet
18552 * Sparclet Download:: Sparclet download
18553 * Sparclet Execution:: Running and debugging
18556 @node Sparclet File
18557 @subsubsection Setting File to Debug
18559 The @value{GDBN} command @code{file} lets you choose with program to debug.
18562 (gdbslet) file prog
18566 @value{GDBN} then attempts to read the symbol table of @file{prog}.
18567 @value{GDBN} locates
18568 the file by searching the directories listed in the command search
18570 If the file was compiled with debug information (option @samp{-g}), source
18571 files will be searched as well.
18572 @value{GDBN} locates
18573 the source files by searching the directories listed in the directory search
18574 path (@pxref{Environment, ,Your Program's Environment}).
18576 to find a file, it displays a message such as:
18579 prog: No such file or directory.
18582 When this happens, add the appropriate directories to the search paths with
18583 the @value{GDBN} commands @code{path} and @code{dir}, and execute the
18584 @code{target} command again.
18586 @node Sparclet Connection
18587 @subsubsection Connecting to Sparclet
18589 The @value{GDBN} command @code{target} lets you connect to a Sparclet target.
18590 To connect to a target on serial port ``@code{ttya}'', type:
18593 (gdbslet) target sparclet /dev/ttya
18594 Remote target sparclet connected to /dev/ttya
18595 main () at ../prog.c:3
18599 @value{GDBN} displays messages like these:
18605 @node Sparclet Download
18606 @subsubsection Sparclet Download
18608 @cindex download to Sparclet
18609 Once connected to the Sparclet target,
18610 you can use the @value{GDBN}
18611 @code{load} command to download the file from the host to the target.
18612 The file name and load offset should be given as arguments to the @code{load}
18614 Since the file format is aout, the program must be loaded to the starting
18615 address. You can use @code{objdump} to find out what this value is. The load
18616 offset is an offset which is added to the VMA (virtual memory address)
18617 of each of the file's sections.
18618 For instance, if the program
18619 @file{prog} was linked to text address 0x1201000, with data at 0x12010160
18620 and bss at 0x12010170, in @value{GDBN}, type:
18623 (gdbslet) load prog 0x12010000
18624 Loading section .text, size 0xdb0 vma 0x12010000
18627 If the code is loaded at a different address then what the program was linked
18628 to, you may need to use the @code{section} and @code{add-symbol-file} commands
18629 to tell @value{GDBN} where to map the symbol table.
18631 @node Sparclet Execution
18632 @subsubsection Running and Debugging
18634 @cindex running and debugging Sparclet programs
18635 You can now begin debugging the task using @value{GDBN}'s execution control
18636 commands, @code{b}, @code{step}, @code{run}, etc. See the @value{GDBN}
18637 manual for the list of commands.
18641 Breakpoint 1 at 0x12010000: file prog.c, line 3.
18643 Starting program: prog
18644 Breakpoint 1, main (argc=1, argv=0xeffff21c) at prog.c:3
18645 3 char *symarg = 0;
18647 4 char *execarg = "hello!";
18652 @subsection Fujitsu Sparclite
18656 @kindex target sparclite
18657 @item target sparclite @var{dev}
18658 Fujitsu sparclite boards, used only for the purpose of loading.
18659 You must use an additional command to debug the program.
18660 For example: target remote @var{dev} using @value{GDBN} standard
18666 @subsection Zilog Z8000
18669 @cindex simulator, Z8000
18670 @cindex Zilog Z8000 simulator
18672 When configured for debugging Zilog Z8000 targets, @value{GDBN} includes
18675 For the Z8000 family, @samp{target sim} simulates either the Z8002 (the
18676 unsegmented variant of the Z8000 architecture) or the Z8001 (the
18677 segmented variant). The simulator recognizes which architecture is
18678 appropriate by inspecting the object code.
18681 @item target sim @var{args}
18683 @kindex target sim@r{, with Z8000}
18684 Debug programs on a simulated CPU. If the simulator supports setup
18685 options, specify them via @var{args}.
18689 After specifying this target, you can debug programs for the simulated
18690 CPU in the same style as programs for your host computer; use the
18691 @code{file} command to load a new program image, the @code{run} command
18692 to run your program, and so on.
18694 As well as making available all the usual machine registers
18695 (@pxref{Registers, ,Registers}), the Z8000 simulator provides three
18696 additional items of information as specially named registers:
18701 Counts clock-ticks in the simulator.
18704 Counts instructions run in the simulator.
18707 Execution time in 60ths of a second.
18711 You can refer to these values in @value{GDBN} expressions with the usual
18712 conventions; for example, @w{@samp{b fputc if $cycles>5000}} sets a
18713 conditional breakpoint that suspends only after at least 5000
18714 simulated clock ticks.
18717 @subsection Atmel AVR
18720 When configured for debugging the Atmel AVR, @value{GDBN} supports the
18721 following AVR-specific commands:
18724 @item info io_registers
18725 @kindex info io_registers@r{, AVR}
18726 @cindex I/O registers (Atmel AVR)
18727 This command displays information about the AVR I/O registers. For
18728 each register, @value{GDBN} prints its number and value.
18735 When configured for debugging CRIS, @value{GDBN} provides the
18736 following CRIS-specific commands:
18739 @item set cris-version @var{ver}
18740 @cindex CRIS version
18741 Set the current CRIS version to @var{ver}, either @samp{10} or @samp{32}.
18742 The CRIS version affects register names and sizes. This command is useful in
18743 case autodetection of the CRIS version fails.
18745 @item show cris-version
18746 Show the current CRIS version.
18748 @item set cris-dwarf2-cfi
18749 @cindex DWARF-2 CFI and CRIS
18750 Set the usage of DWARF-2 CFI for CRIS debugging. The default is @samp{on}.
18751 Change to @samp{off} when using @code{gcc-cris} whose version is below
18754 @item show cris-dwarf2-cfi
18755 Show the current state of using DWARF-2 CFI.
18757 @item set cris-mode @var{mode}
18759 Set the current CRIS mode to @var{mode}. It should only be changed when
18760 debugging in guru mode, in which case it should be set to
18761 @samp{guru} (the default is @samp{normal}).
18763 @item show cris-mode
18764 Show the current CRIS mode.
18768 @subsection Renesas Super-H
18771 For the Renesas Super-H processor, @value{GDBN} provides these
18776 @kindex regs@r{, Super-H}
18777 Show the values of all Super-H registers.
18779 @item set sh calling-convention @var{convention}
18780 @kindex set sh calling-convention
18781 Set the calling-convention used when calling functions from @value{GDBN}.
18782 Allowed values are @samp{gcc}, which is the default setting, and @samp{renesas}.
18783 With the @samp{gcc} setting, functions are called using the @value{NGCC} calling
18784 convention. If the DWARF-2 information of the called function specifies
18785 that the function follows the Renesas calling convention, the function
18786 is called using the Renesas calling convention. If the calling convention
18787 is set to @samp{renesas}, the Renesas calling convention is always used,
18788 regardless of the DWARF-2 information. This can be used to override the
18789 default of @samp{gcc} if debug information is missing, or the compiler
18790 does not emit the DWARF-2 calling convention entry for a function.
18792 @item show sh calling-convention
18793 @kindex show sh calling-convention
18794 Show the current calling convention setting.
18799 @node Architectures
18800 @section Architectures
18802 This section describes characteristics of architectures that affect
18803 all uses of @value{GDBN} with the architecture, both native and cross.
18810 * HPPA:: HP PA architecture
18811 * SPU:: Cell Broadband Engine SPU architecture
18816 @subsection x86 Architecture-specific Issues
18819 @item set struct-convention @var{mode}
18820 @kindex set struct-convention
18821 @cindex struct return convention
18822 @cindex struct/union returned in registers
18823 Set the convention used by the inferior to return @code{struct}s and
18824 @code{union}s from functions to @var{mode}. Possible values of
18825 @var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the
18826 default). @code{"default"} or @code{"pcc"} means that @code{struct}s
18827 are returned on the stack, while @code{"reg"} means that a
18828 @code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will
18829 be returned in a register.
18831 @item show struct-convention
18832 @kindex show struct-convention
18833 Show the current setting of the convention to return @code{struct}s
18842 @kindex set rstack_high_address
18843 @cindex AMD 29K register stack
18844 @cindex register stack, AMD29K
18845 @item set rstack_high_address @var{address}
18846 On AMD 29000 family processors, registers are saved in a separate
18847 @dfn{register stack}. There is no way for @value{GDBN} to determine the
18848 extent of this stack. Normally, @value{GDBN} just assumes that the
18849 stack is ``large enough''. This may result in @value{GDBN} referencing
18850 memory locations that do not exist. If necessary, you can get around
18851 this problem by specifying the ending address of the register stack with
18852 the @code{set rstack_high_address} command. The argument should be an
18853 address, which you probably want to precede with @samp{0x} to specify in
18856 @kindex show rstack_high_address
18857 @item show rstack_high_address
18858 Display the current limit of the register stack, on AMD 29000 family
18866 See the following section.
18871 @cindex stack on Alpha
18872 @cindex stack on MIPS
18873 @cindex Alpha stack
18875 Alpha- and MIPS-based computers use an unusual stack frame, which
18876 sometimes requires @value{GDBN} to search backward in the object code to
18877 find the beginning of a function.
18879 @cindex response time, MIPS debugging
18880 To improve response time (especially for embedded applications, where
18881 @value{GDBN} may be restricted to a slow serial line for this search)
18882 you may want to limit the size of this search, using one of these
18886 @cindex @code{heuristic-fence-post} (Alpha, MIPS)
18887 @item set heuristic-fence-post @var{limit}
18888 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
18889 search for the beginning of a function. A value of @var{0} (the
18890 default) means there is no limit. However, except for @var{0}, the
18891 larger the limit the more bytes @code{heuristic-fence-post} must search
18892 and therefore the longer it takes to run. You should only need to use
18893 this command when debugging a stripped executable.
18895 @item show heuristic-fence-post
18896 Display the current limit.
18900 These commands are available @emph{only} when @value{GDBN} is configured
18901 for debugging programs on Alpha or MIPS processors.
18903 Several MIPS-specific commands are available when debugging MIPS
18907 @item set mips abi @var{arg}
18908 @kindex set mips abi
18909 @cindex set ABI for MIPS
18910 Tell @value{GDBN} which MIPS ABI is used by the inferior. Possible
18911 values of @var{arg} are:
18915 The default ABI associated with the current binary (this is the
18926 @item show mips abi
18927 @kindex show mips abi
18928 Show the MIPS ABI used by @value{GDBN} to debug the inferior.
18931 @itemx show mipsfpu
18932 @xref{MIPS Embedded, set mipsfpu}.
18934 @item set mips mask-address @var{arg}
18935 @kindex set mips mask-address
18936 @cindex MIPS addresses, masking
18937 This command determines whether the most-significant 32 bits of 64-bit
18938 MIPS addresses are masked off. The argument @var{arg} can be
18939 @samp{on}, @samp{off}, or @samp{auto}. The latter is the default
18940 setting, which lets @value{GDBN} determine the correct value.
18942 @item show mips mask-address
18943 @kindex show mips mask-address
18944 Show whether the upper 32 bits of MIPS addresses are masked off or
18947 @item set remote-mips64-transfers-32bit-regs
18948 @kindex set remote-mips64-transfers-32bit-regs
18949 This command controls compatibility with 64-bit MIPS targets that
18950 transfer data in 32-bit quantities. If you have an old MIPS 64 target
18951 that transfers 32 bits for some registers, like @sc{sr} and @sc{fsr},
18952 and 64 bits for other registers, set this option to @samp{on}.
18954 @item show remote-mips64-transfers-32bit-regs
18955 @kindex show remote-mips64-transfers-32bit-regs
18956 Show the current setting of compatibility with older MIPS 64 targets.
18958 @item set debug mips
18959 @kindex set debug mips
18960 This command turns on and off debugging messages for the MIPS-specific
18961 target code in @value{GDBN}.
18963 @item show debug mips
18964 @kindex show debug mips
18965 Show the current setting of MIPS debugging messages.
18971 @cindex HPPA support
18973 When @value{GDBN} is debugging the HP PA architecture, it provides the
18974 following special commands:
18977 @item set debug hppa
18978 @kindex set debug hppa
18979 This command determines whether HPPA architecture-specific debugging
18980 messages are to be displayed.
18982 @item show debug hppa
18983 Show whether HPPA debugging messages are displayed.
18985 @item maint print unwind @var{address}
18986 @kindex maint print unwind@r{, HPPA}
18987 This command displays the contents of the unwind table entry at the
18988 given @var{address}.
18994 @subsection Cell Broadband Engine SPU architecture
18995 @cindex Cell Broadband Engine
18998 When @value{GDBN} is debugging the Cell Broadband Engine SPU architecture,
18999 it provides the following special commands:
19002 @item info spu event
19004 Display SPU event facility status. Shows current event mask
19005 and pending event status.
19007 @item info spu signal
19008 Display SPU signal notification facility status. Shows pending
19009 signal-control word and signal notification mode of both signal
19010 notification channels.
19012 @item info spu mailbox
19013 Display SPU mailbox facility status. Shows all pending entries,
19014 in order of processing, in each of the SPU Write Outbound,
19015 SPU Write Outbound Interrupt, and SPU Read Inbound mailboxes.
19018 Display MFC DMA status. Shows all pending commands in the MFC
19019 DMA queue. For each entry, opcode, tag, class IDs, effective
19020 and local store addresses and transfer size are shown.
19022 @item info spu proxydma
19023 Display MFC Proxy-DMA status. Shows all pending commands in the MFC
19024 Proxy-DMA queue. For each entry, opcode, tag, class IDs, effective
19025 and local store addresses and transfer size are shown.
19029 When @value{GDBN} is debugging a combined PowerPC/SPU application
19030 on the Cell Broadband Engine, it provides in addition the following
19034 @item set spu stop-on-load @var{arg}
19036 Set whether to stop for new SPE threads. When set to @code{on}, @value{GDBN}
19037 will give control to the user when a new SPE thread enters its @code{main}
19038 function. The default is @code{off}.
19040 @item show spu stop-on-load
19042 Show whether to stop for new SPE threads.
19044 @item set spu auto-flush-cache @var{arg}
19045 Set whether to automatically flush the software-managed cache. When set to
19046 @code{on}, @value{GDBN} will automatically cause the SPE software-managed
19047 cache to be flushed whenever SPE execution stops. This provides a consistent
19048 view of PowerPC memory that is accessed via the cache. If an application
19049 does not use the software-managed cache, this option has no effect.
19051 @item show spu auto-flush-cache
19052 Show whether to automatically flush the software-managed cache.
19057 @subsection PowerPC
19058 @cindex PowerPC architecture
19060 When @value{GDBN} is debugging the PowerPC architecture, it provides a set of
19061 pseudo-registers to enable inspection of 128-bit wide Decimal Floating Point
19062 numbers stored in the floating point registers. These values must be stored
19063 in two consecutive registers, always starting at an even register like
19064 @code{f0} or @code{f2}.
19066 The pseudo-registers go from @code{$dl0} through @code{$dl15}, and are formed
19067 by joining the even/odd register pairs @code{f0} and @code{f1} for @code{$dl0},
19068 @code{f2} and @code{f3} for @code{$dl1} and so on.
19070 For POWER7 processors, @value{GDBN} provides a set of pseudo-registers, the 64-bit
19071 wide Extended Floating Point Registers (@samp{f32} through @samp{f63}).
19074 @node Controlling GDB
19075 @chapter Controlling @value{GDBN}
19077 You can alter the way @value{GDBN} interacts with you by using the
19078 @code{set} command. For commands controlling how @value{GDBN} displays
19079 data, see @ref{Print Settings, ,Print Settings}. Other settings are
19084 * Editing:: Command editing
19085 * Command History:: Command history
19086 * Screen Size:: Screen size
19087 * Numbers:: Numbers
19088 * ABI:: Configuring the current ABI
19089 * Messages/Warnings:: Optional warnings and messages
19090 * Debugging Output:: Optional messages about internal happenings
19091 * Other Misc Settings:: Other Miscellaneous Settings
19099 @value{GDBN} indicates its readiness to read a command by printing a string
19100 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
19101 can change the prompt string with the @code{set prompt} command. For
19102 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
19103 the prompt in one of the @value{GDBN} sessions so that you can always tell
19104 which one you are talking to.
19106 @emph{Note:} @code{set prompt} does not add a space for you after the
19107 prompt you set. This allows you to set a prompt which ends in a space
19108 or a prompt that does not.
19112 @item set prompt @var{newprompt}
19113 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
19115 @kindex show prompt
19117 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
19121 @section Command Editing
19123 @cindex command line editing
19125 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
19126 @sc{gnu} library provides consistent behavior for programs which provide a
19127 command line interface to the user. Advantages are @sc{gnu} Emacs-style
19128 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
19129 substitution, and a storage and recall of command history across
19130 debugging sessions.
19132 You may control the behavior of command line editing in @value{GDBN} with the
19133 command @code{set}.
19136 @kindex set editing
19139 @itemx set editing on
19140 Enable command line editing (enabled by default).
19142 @item set editing off
19143 Disable command line editing.
19145 @kindex show editing
19147 Show whether command line editing is enabled.
19150 @xref{Command Line Editing}, for more details about the Readline
19151 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
19152 encouraged to read that chapter.
19154 @node Command History
19155 @section Command History
19156 @cindex command history
19158 @value{GDBN} can keep track of the commands you type during your
19159 debugging sessions, so that you can be certain of precisely what
19160 happened. Use these commands to manage the @value{GDBN} command
19163 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
19164 package, to provide the history facility. @xref{Using History
19165 Interactively}, for the detailed description of the History library.
19167 To issue a command to @value{GDBN} without affecting certain aspects of
19168 the state which is seen by users, prefix it with @samp{server }
19169 (@pxref{Server Prefix}). This
19170 means that this command will not affect the command history, nor will it
19171 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
19172 pressed on a line by itself.
19174 @cindex @code{server}, command prefix
19175 The server prefix does not affect the recording of values into the value
19176 history; to print a value without recording it into the value history,
19177 use the @code{output} command instead of the @code{print} command.
19179 Here is the description of @value{GDBN} commands related to command
19183 @cindex history substitution
19184 @cindex history file
19185 @kindex set history filename
19186 @cindex @env{GDBHISTFILE}, environment variable
19187 @item set history filename @var{fname}
19188 Set the name of the @value{GDBN} command history file to @var{fname}.
19189 This is the file where @value{GDBN} reads an initial command history
19190 list, and where it writes the command history from this session when it
19191 exits. You can access this list through history expansion or through
19192 the history command editing characters listed below. This file defaults
19193 to the value of the environment variable @code{GDBHISTFILE}, or to
19194 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
19197 @cindex save command history
19198 @kindex set history save
19199 @item set history save
19200 @itemx set history save on
19201 Record command history in a file, whose name may be specified with the
19202 @code{set history filename} command. By default, this option is disabled.
19204 @item set history save off
19205 Stop recording command history in a file.
19207 @cindex history size
19208 @kindex set history size
19209 @cindex @env{HISTSIZE}, environment variable
19210 @item set history size @var{size}
19211 Set the number of commands which @value{GDBN} keeps in its history list.
19212 This defaults to the value of the environment variable
19213 @code{HISTSIZE}, or to 256 if this variable is not set.
19216 History expansion assigns special meaning to the character @kbd{!}.
19217 @xref{Event Designators}, for more details.
19219 @cindex history expansion, turn on/off
19220 Since @kbd{!} is also the logical not operator in C, history expansion
19221 is off by default. If you decide to enable history expansion with the
19222 @code{set history expansion on} command, you may sometimes need to
19223 follow @kbd{!} (when it is used as logical not, in an expression) with
19224 a space or a tab to prevent it from being expanded. The readline
19225 history facilities do not attempt substitution on the strings
19226 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
19228 The commands to control history expansion are:
19231 @item set history expansion on
19232 @itemx set history expansion
19233 @kindex set history expansion
19234 Enable history expansion. History expansion is off by default.
19236 @item set history expansion off
19237 Disable history expansion.
19240 @kindex show history
19242 @itemx show history filename
19243 @itemx show history save
19244 @itemx show history size
19245 @itemx show history expansion
19246 These commands display the state of the @value{GDBN} history parameters.
19247 @code{show history} by itself displays all four states.
19252 @kindex show commands
19253 @cindex show last commands
19254 @cindex display command history
19255 @item show commands
19256 Display the last ten commands in the command history.
19258 @item show commands @var{n}
19259 Print ten commands centered on command number @var{n}.
19261 @item show commands +
19262 Print ten commands just after the commands last printed.
19266 @section Screen Size
19267 @cindex size of screen
19268 @cindex pauses in output
19270 Certain commands to @value{GDBN} may produce large amounts of
19271 information output to the screen. To help you read all of it,
19272 @value{GDBN} pauses and asks you for input at the end of each page of
19273 output. Type @key{RET} when you want to continue the output, or @kbd{q}
19274 to discard the remaining output. Also, the screen width setting
19275 determines when to wrap lines of output. Depending on what is being
19276 printed, @value{GDBN} tries to break the line at a readable place,
19277 rather than simply letting it overflow onto the following line.
19279 Normally @value{GDBN} knows the size of the screen from the terminal
19280 driver software. For example, on Unix @value{GDBN} uses the termcap data base
19281 together with the value of the @code{TERM} environment variable and the
19282 @code{stty rows} and @code{stty cols} settings. If this is not correct,
19283 you can override it with the @code{set height} and @code{set
19290 @kindex show height
19291 @item set height @var{lpp}
19293 @itemx set width @var{cpl}
19295 These @code{set} commands specify a screen height of @var{lpp} lines and
19296 a screen width of @var{cpl} characters. The associated @code{show}
19297 commands display the current settings.
19299 If you specify a height of zero lines, @value{GDBN} does not pause during
19300 output no matter how long the output is. This is useful if output is to a
19301 file or to an editor buffer.
19303 Likewise, you can specify @samp{set width 0} to prevent @value{GDBN}
19304 from wrapping its output.
19306 @item set pagination on
19307 @itemx set pagination off
19308 @kindex set pagination
19309 Turn the output pagination on or off; the default is on. Turning
19310 pagination off is the alternative to @code{set height 0}. Note that
19311 running @value{GDBN} with the @option{--batch} option (@pxref{Mode
19312 Options, -batch}) also automatically disables pagination.
19314 @item show pagination
19315 @kindex show pagination
19316 Show the current pagination mode.
19321 @cindex number representation
19322 @cindex entering numbers
19324 You can always enter numbers in octal, decimal, or hexadecimal in
19325 @value{GDBN} by the usual conventions: octal numbers begin with
19326 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
19327 begin with @samp{0x}. Numbers that neither begin with @samp{0} or
19328 @samp{0x}, nor end with a @samp{.} are, by default, entered in base
19329 10; likewise, the default display for numbers---when no particular
19330 format is specified---is base 10. You can change the default base for
19331 both input and output with the commands described below.
19334 @kindex set input-radix
19335 @item set input-radix @var{base}
19336 Set the default base for numeric input. Supported choices
19337 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
19338 specified either unambiguously or using the current input radix; for
19342 set input-radix 012
19343 set input-radix 10.
19344 set input-radix 0xa
19348 sets the input base to decimal. On the other hand, @samp{set input-radix 10}
19349 leaves the input radix unchanged, no matter what it was, since
19350 @samp{10}, being without any leading or trailing signs of its base, is
19351 interpreted in the current radix. Thus, if the current radix is 16,
19352 @samp{10} is interpreted in hex, i.e.@: as 16 decimal, which doesn't
19355 @kindex set output-radix
19356 @item set output-radix @var{base}
19357 Set the default base for numeric display. Supported choices
19358 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
19359 specified either unambiguously or using the current input radix.
19361 @kindex show input-radix
19362 @item show input-radix
19363 Display the current default base for numeric input.
19365 @kindex show output-radix
19366 @item show output-radix
19367 Display the current default base for numeric display.
19369 @item set radix @r{[}@var{base}@r{]}
19373 These commands set and show the default base for both input and output
19374 of numbers. @code{set radix} sets the radix of input and output to
19375 the same base; without an argument, it resets the radix back to its
19376 default value of 10.
19381 @section Configuring the Current ABI
19383 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
19384 application automatically. However, sometimes you need to override its
19385 conclusions. Use these commands to manage @value{GDBN}'s view of the
19392 One @value{GDBN} configuration can debug binaries for multiple operating
19393 system targets, either via remote debugging or native emulation.
19394 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
19395 but you can override its conclusion using the @code{set osabi} command.
19396 One example where this is useful is in debugging of binaries which use
19397 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
19398 not have the same identifying marks that the standard C library for your
19403 Show the OS ABI currently in use.
19406 With no argument, show the list of registered available OS ABI's.
19408 @item set osabi @var{abi}
19409 Set the current OS ABI to @var{abi}.
19412 @cindex float promotion
19414 Generally, the way that an argument of type @code{float} is passed to a
19415 function depends on whether the function is prototyped. For a prototyped
19416 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
19417 according to the architecture's convention for @code{float}. For unprototyped
19418 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
19419 @code{double} and then passed.
19421 Unfortunately, some forms of debug information do not reliably indicate whether
19422 a function is prototyped. If @value{GDBN} calls a function that is not marked
19423 as prototyped, it consults @kbd{set coerce-float-to-double}.
19426 @kindex set coerce-float-to-double
19427 @item set coerce-float-to-double
19428 @itemx set coerce-float-to-double on
19429 Arguments of type @code{float} will be promoted to @code{double} when passed
19430 to an unprototyped function. This is the default setting.
19432 @item set coerce-float-to-double off
19433 Arguments of type @code{float} will be passed directly to unprototyped
19436 @kindex show coerce-float-to-double
19437 @item show coerce-float-to-double
19438 Show the current setting of promoting @code{float} to @code{double}.
19442 @kindex show cp-abi
19443 @value{GDBN} needs to know the ABI used for your program's C@t{++}
19444 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
19445 used to build your application. @value{GDBN} only fully supports
19446 programs with a single C@t{++} ABI; if your program contains code using
19447 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
19448 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
19449 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
19450 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
19451 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
19452 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
19457 Show the C@t{++} ABI currently in use.
19460 With no argument, show the list of supported C@t{++} ABI's.
19462 @item set cp-abi @var{abi}
19463 @itemx set cp-abi auto
19464 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
19467 @node Messages/Warnings
19468 @section Optional Warnings and Messages
19470 @cindex verbose operation
19471 @cindex optional warnings
19472 By default, @value{GDBN} is silent about its inner workings. If you are
19473 running on a slow machine, you may want to use the @code{set verbose}
19474 command. This makes @value{GDBN} tell you when it does a lengthy
19475 internal operation, so you will not think it has crashed.
19477 Currently, the messages controlled by @code{set verbose} are those
19478 which announce that the symbol table for a source file is being read;
19479 see @code{symbol-file} in @ref{Files, ,Commands to Specify Files}.
19482 @kindex set verbose
19483 @item set verbose on
19484 Enables @value{GDBN} output of certain informational messages.
19486 @item set verbose off
19487 Disables @value{GDBN} output of certain informational messages.
19489 @kindex show verbose
19491 Displays whether @code{set verbose} is on or off.
19494 By default, if @value{GDBN} encounters bugs in the symbol table of an
19495 object file, it is silent; but if you are debugging a compiler, you may
19496 find this information useful (@pxref{Symbol Errors, ,Errors Reading
19501 @kindex set complaints
19502 @item set complaints @var{limit}
19503 Permits @value{GDBN} to output @var{limit} complaints about each type of
19504 unusual symbols before becoming silent about the problem. Set
19505 @var{limit} to zero to suppress all complaints; set it to a large number
19506 to prevent complaints from being suppressed.
19508 @kindex show complaints
19509 @item show complaints
19510 Displays how many symbol complaints @value{GDBN} is permitted to produce.
19514 @anchor{confirmation requests}
19515 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
19516 lot of stupid questions to confirm certain commands. For example, if
19517 you try to run a program which is already running:
19521 The program being debugged has been started already.
19522 Start it from the beginning? (y or n)
19525 If you are willing to unflinchingly face the consequences of your own
19526 commands, you can disable this ``feature'':
19530 @kindex set confirm
19532 @cindex confirmation
19533 @cindex stupid questions
19534 @item set confirm off
19535 Disables confirmation requests. Note that running @value{GDBN} with
19536 the @option{--batch} option (@pxref{Mode Options, -batch}) also
19537 automatically disables confirmation requests.
19539 @item set confirm on
19540 Enables confirmation requests (the default).
19542 @kindex show confirm
19544 Displays state of confirmation requests.
19548 @cindex command tracing
19549 If you need to debug user-defined commands or sourced files you may find it
19550 useful to enable @dfn{command tracing}. In this mode each command will be
19551 printed as it is executed, prefixed with one or more @samp{+} symbols, the
19552 quantity denoting the call depth of each command.
19555 @kindex set trace-commands
19556 @cindex command scripts, debugging
19557 @item set trace-commands on
19558 Enable command tracing.
19559 @item set trace-commands off
19560 Disable command tracing.
19561 @item show trace-commands
19562 Display the current state of command tracing.
19565 @node Debugging Output
19566 @section Optional Messages about Internal Happenings
19567 @cindex optional debugging messages
19569 @value{GDBN} has commands that enable optional debugging messages from
19570 various @value{GDBN} subsystems; normally these commands are of
19571 interest to @value{GDBN} maintainers, or when reporting a bug. This
19572 section documents those commands.
19575 @kindex set exec-done-display
19576 @item set exec-done-display
19577 Turns on or off the notification of asynchronous commands'
19578 completion. When on, @value{GDBN} will print a message when an
19579 asynchronous command finishes its execution. The default is off.
19580 @kindex show exec-done-display
19581 @item show exec-done-display
19582 Displays the current setting of asynchronous command completion
19585 @cindex gdbarch debugging info
19586 @cindex architecture debugging info
19587 @item set debug arch
19588 Turns on or off display of gdbarch debugging info. The default is off
19590 @item show debug arch
19591 Displays the current state of displaying gdbarch debugging info.
19592 @item set debug aix-thread
19593 @cindex AIX threads
19594 Display debugging messages about inner workings of the AIX thread
19596 @item show debug aix-thread
19597 Show the current state of AIX thread debugging info display.
19598 @item set debug dwarf2-die
19599 @cindex DWARF2 DIEs
19600 Dump DWARF2 DIEs after they are read in.
19601 The value is the number of nesting levels to print.
19602 A value of zero turns off the display.
19603 @item show debug dwarf2-die
19604 Show the current state of DWARF2 DIE debugging.
19605 @item set debug displaced
19606 @cindex displaced stepping debugging info
19607 Turns on or off display of @value{GDBN} debugging info for the
19608 displaced stepping support. The default is off.
19609 @item show debug displaced
19610 Displays the current state of displaying @value{GDBN} debugging info
19611 related to displaced stepping.
19612 @item set debug event
19613 @cindex event debugging info
19614 Turns on or off display of @value{GDBN} event debugging info. The
19616 @item show debug event
19617 Displays the current state of displaying @value{GDBN} event debugging
19619 @item set debug expression
19620 @cindex expression debugging info
19621 Turns on or off display of debugging info about @value{GDBN}
19622 expression parsing. The default is off.
19623 @item show debug expression
19624 Displays the current state of displaying debugging info about
19625 @value{GDBN} expression parsing.
19626 @item set debug frame
19627 @cindex frame debugging info
19628 Turns on or off display of @value{GDBN} frame debugging info. The
19630 @item show debug frame
19631 Displays the current state of displaying @value{GDBN} frame debugging
19633 @item set debug gnu-nat
19634 @cindex @sc{gnu}/Hurd debug messages
19635 Turns on or off debugging messages from the @sc{gnu}/Hurd debug support.
19636 @item show debug gnu-nat
19637 Show the current state of @sc{gnu}/Hurd debugging messages.
19638 @item set debug infrun
19639 @cindex inferior debugging info
19640 Turns on or off display of @value{GDBN} debugging info for running the inferior.
19641 The default is off. @file{infrun.c} contains GDB's runtime state machine used
19642 for implementing operations such as single-stepping the inferior.
19643 @item show debug infrun
19644 Displays the current state of @value{GDBN} inferior debugging.
19645 @item set debug lin-lwp
19646 @cindex @sc{gnu}/Linux LWP debug messages
19647 @cindex Linux lightweight processes
19648 Turns on or off debugging messages from the Linux LWP debug support.
19649 @item show debug lin-lwp
19650 Show the current state of Linux LWP debugging messages.
19651 @item set debug lin-lwp-async
19652 @cindex @sc{gnu}/Linux LWP async debug messages
19653 @cindex Linux lightweight processes
19654 Turns on or off debugging messages from the Linux LWP async debug support.
19655 @item show debug lin-lwp-async
19656 Show the current state of Linux LWP async debugging messages.
19657 @item set debug observer
19658 @cindex observer debugging info
19659 Turns on or off display of @value{GDBN} observer debugging. This
19660 includes info such as the notification of observable events.
19661 @item show debug observer
19662 Displays the current state of observer debugging.
19663 @item set debug overload
19664 @cindex C@t{++} overload debugging info
19665 Turns on or off display of @value{GDBN} C@t{++} overload debugging
19666 info. This includes info such as ranking of functions, etc. The default
19668 @item show debug overload
19669 Displays the current state of displaying @value{GDBN} C@t{++} overload
19671 @cindex expression parser, debugging info
19672 @cindex debug expression parser
19673 @item set debug parser
19674 Turns on or off the display of expression parser debugging output.
19675 Internally, this sets the @code{yydebug} variable in the expression
19676 parser. @xref{Tracing, , Tracing Your Parser, bison, Bison}, for
19677 details. The default is off.
19678 @item show debug parser
19679 Show the current state of expression parser debugging.
19680 @cindex packets, reporting on stdout
19681 @cindex serial connections, debugging
19682 @cindex debug remote protocol
19683 @cindex remote protocol debugging
19684 @cindex display remote packets
19685 @item set debug remote
19686 Turns on or off display of reports on all packets sent back and forth across
19687 the serial line to the remote machine. The info is printed on the
19688 @value{GDBN} standard output stream. The default is off.
19689 @item show debug remote
19690 Displays the state of display of remote packets.
19691 @item set debug serial
19692 Turns on or off display of @value{GDBN} serial debugging info. The
19694 @item show debug serial
19695 Displays the current state of displaying @value{GDBN} serial debugging
19697 @item set debug solib-frv
19698 @cindex FR-V shared-library debugging
19699 Turns on or off debugging messages for FR-V shared-library code.
19700 @item show debug solib-frv
19701 Display the current state of FR-V shared-library code debugging
19703 @item set debug target
19704 @cindex target debugging info
19705 Turns on or off display of @value{GDBN} target debugging info. This info
19706 includes what is going on at the target level of GDB, as it happens. The
19707 default is 0. Set it to 1 to track events, and to 2 to also track the
19708 value of large memory transfers. Changes to this flag do not take effect
19709 until the next time you connect to a target or use the @code{run} command.
19710 @item show debug target
19711 Displays the current state of displaying @value{GDBN} target debugging
19713 @item set debug timestamp
19714 @cindex timestampping debugging info
19715 Turns on or off display of timestamps with @value{GDBN} debugging info.
19716 When enabled, seconds and microseconds are displayed before each debugging
19718 @item show debug timestamp
19719 Displays the current state of displaying timestamps with @value{GDBN}
19721 @item set debugvarobj
19722 @cindex variable object debugging info
19723 Turns on or off display of @value{GDBN} variable object debugging
19724 info. The default is off.
19725 @item show debugvarobj
19726 Displays the current state of displaying @value{GDBN} variable object
19728 @item set debug xml
19729 @cindex XML parser debugging
19730 Turns on or off debugging messages for built-in XML parsers.
19731 @item show debug xml
19732 Displays the current state of XML debugging messages.
19735 @node Other Misc Settings
19736 @section Other Miscellaneous Settings
19737 @cindex miscellaneous settings
19740 @kindex set interactive-mode
19741 @item set interactive-mode
19742 If @code{on}, forces @value{GDBN} to operate interactively.
19743 If @code{off}, forces @value{GDBN} to operate non-interactively,
19744 If @code{auto} (the default), @value{GDBN} guesses which mode to use,
19745 based on whether the debugger was started in a terminal or not.
19747 In the vast majority of cases, the debugger should be able to guess
19748 correctly which mode should be used. But this setting can be useful
19749 in certain specific cases, such as running a MinGW @value{GDBN}
19750 inside a cygwin window.
19752 @kindex show interactive-mode
19753 @item show interactive-mode
19754 Displays whether the debugger is operating in interactive mode or not.
19757 @node Extending GDB
19758 @chapter Extending @value{GDBN}
19759 @cindex extending GDB
19761 @value{GDBN} provides two mechanisms for extension. The first is based
19762 on composition of @value{GDBN} commands, and the second is based on the
19763 Python scripting language.
19765 To facilitate the use of these extensions, @value{GDBN} is capable
19766 of evaluating the contents of a file. When doing so, @value{GDBN}
19767 can recognize which scripting language is being used by looking at
19768 the filename extension. Files with an unrecognized filename extension
19769 are always treated as a @value{GDBN} Command Files.
19770 @xref{Command Files,, Command files}.
19772 You can control how @value{GDBN} evaluates these files with the following
19776 @kindex set script-extension
19777 @kindex show script-extension
19778 @item set script-extension off
19779 All scripts are always evaluated as @value{GDBN} Command Files.
19781 @item set script-extension soft
19782 The debugger determines the scripting language based on filename
19783 extension. If this scripting language is supported, @value{GDBN}
19784 evaluates the script using that language. Otherwise, it evaluates
19785 the file as a @value{GDBN} Command File.
19787 @item set script-extension strict
19788 The debugger determines the scripting language based on filename
19789 extension, and evaluates the script using that language. If the
19790 language is not supported, then the evaluation fails.
19792 @item show script-extension
19793 Display the current value of the @code{script-extension} option.
19798 * Sequences:: Canned Sequences of Commands
19799 * Python:: Scripting @value{GDBN} using Python
19803 @section Canned Sequences of Commands
19805 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
19806 Command Lists}), @value{GDBN} provides two ways to store sequences of
19807 commands for execution as a unit: user-defined commands and command
19811 * Define:: How to define your own commands
19812 * Hooks:: Hooks for user-defined commands
19813 * Command Files:: How to write scripts of commands to be stored in a file
19814 * Output:: Commands for controlled output
19818 @subsection User-defined Commands
19820 @cindex user-defined command
19821 @cindex arguments, to user-defined commands
19822 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
19823 which you assign a new name as a command. This is done with the
19824 @code{define} command. User commands may accept up to 10 arguments
19825 separated by whitespace. Arguments are accessed within the user command
19826 via @code{$arg0@dots{}$arg9}. A trivial example:
19830 print $arg0 + $arg1 + $arg2
19835 To execute the command use:
19842 This defines the command @code{adder}, which prints the sum of
19843 its three arguments. Note the arguments are text substitutions, so they may
19844 reference variables, use complex expressions, or even perform inferior
19847 @cindex argument count in user-defined commands
19848 @cindex how many arguments (user-defined commands)
19849 In addition, @code{$argc} may be used to find out how many arguments have
19850 been passed. This expands to a number in the range 0@dots{}10.
19855 print $arg0 + $arg1
19858 print $arg0 + $arg1 + $arg2
19866 @item define @var{commandname}
19867 Define a command named @var{commandname}. If there is already a command
19868 by that name, you are asked to confirm that you want to redefine it.
19869 @var{commandname} may be a bare command name consisting of letters,
19870 numbers, dashes, and underscores. It may also start with any predefined
19871 prefix command. For example, @samp{define target my-target} creates
19872 a user-defined @samp{target my-target} command.
19874 The definition of the command is made up of other @value{GDBN} command lines,
19875 which are given following the @code{define} command. The end of these
19876 commands is marked by a line containing @code{end}.
19879 @kindex end@r{ (user-defined commands)}
19880 @item document @var{commandname}
19881 Document the user-defined command @var{commandname}, so that it can be
19882 accessed by @code{help}. The command @var{commandname} must already be
19883 defined. This command reads lines of documentation just as @code{define}
19884 reads the lines of the command definition, ending with @code{end}.
19885 After the @code{document} command is finished, @code{help} on command
19886 @var{commandname} displays the documentation you have written.
19888 You may use the @code{document} command again to change the
19889 documentation of a command. Redefining the command with @code{define}
19890 does not change the documentation.
19892 @kindex dont-repeat
19893 @cindex don't repeat command
19895 Used inside a user-defined command, this tells @value{GDBN} that this
19896 command should not be repeated when the user hits @key{RET}
19897 (@pxref{Command Syntax, repeat last command}).
19899 @kindex help user-defined
19900 @item help user-defined
19901 List all user-defined commands, with the first line of the documentation
19906 @itemx show user @var{commandname}
19907 Display the @value{GDBN} commands used to define @var{commandname} (but
19908 not its documentation). If no @var{commandname} is given, display the
19909 definitions for all user-defined commands.
19911 @cindex infinite recursion in user-defined commands
19912 @kindex show max-user-call-depth
19913 @kindex set max-user-call-depth
19914 @item show max-user-call-depth
19915 @itemx set max-user-call-depth
19916 The value of @code{max-user-call-depth} controls how many recursion
19917 levels are allowed in user-defined commands before @value{GDBN} suspects an
19918 infinite recursion and aborts the command.
19921 In addition to the above commands, user-defined commands frequently
19922 use control flow commands, described in @ref{Command Files}.
19924 When user-defined commands are executed, the
19925 commands of the definition are not printed. An error in any command
19926 stops execution of the user-defined command.
19928 If used interactively, commands that would ask for confirmation proceed
19929 without asking when used inside a user-defined command. Many @value{GDBN}
19930 commands that normally print messages to say what they are doing omit the
19931 messages when used in a user-defined command.
19934 @subsection User-defined Command Hooks
19935 @cindex command hooks
19936 @cindex hooks, for commands
19937 @cindex hooks, pre-command
19940 You may define @dfn{hooks}, which are a special kind of user-defined
19941 command. Whenever you run the command @samp{foo}, if the user-defined
19942 command @samp{hook-foo} exists, it is executed (with no arguments)
19943 before that command.
19945 @cindex hooks, post-command
19947 A hook may also be defined which is run after the command you executed.
19948 Whenever you run the command @samp{foo}, if the user-defined command
19949 @samp{hookpost-foo} exists, it is executed (with no arguments) after
19950 that command. Post-execution hooks may exist simultaneously with
19951 pre-execution hooks, for the same command.
19953 It is valid for a hook to call the command which it hooks. If this
19954 occurs, the hook is not re-executed, thereby avoiding infinite recursion.
19956 @c It would be nice if hookpost could be passed a parameter indicating
19957 @c if the command it hooks executed properly or not. FIXME!
19959 @kindex stop@r{, a pseudo-command}
19960 In addition, a pseudo-command, @samp{stop} exists. Defining
19961 (@samp{hook-stop}) makes the associated commands execute every time
19962 execution stops in your program: before breakpoint commands are run,
19963 displays are printed, or the stack frame is printed.
19965 For example, to ignore @code{SIGALRM} signals while
19966 single-stepping, but treat them normally during normal execution,
19971 handle SIGALRM nopass
19975 handle SIGALRM pass
19978 define hook-continue
19979 handle SIGALRM pass
19983 As a further example, to hook at the beginning and end of the @code{echo}
19984 command, and to add extra text to the beginning and end of the message,
19992 define hookpost-echo
19996 (@value{GDBP}) echo Hello World
19997 <<<---Hello World--->>>
20002 You can define a hook for any single-word command in @value{GDBN}, but
20003 not for command aliases; you should define a hook for the basic command
20004 name, e.g.@: @code{backtrace} rather than @code{bt}.
20005 @c FIXME! So how does Joe User discover whether a command is an alias
20007 You can hook a multi-word command by adding @code{hook-} or
20008 @code{hookpost-} to the last word of the command, e.g.@:
20009 @samp{define target hook-remote} to add a hook to @samp{target remote}.
20011 If an error occurs during the execution of your hook, execution of
20012 @value{GDBN} commands stops and @value{GDBN} issues a prompt
20013 (before the command that you actually typed had a chance to run).
20015 If you try to define a hook which does not match any known command, you
20016 get a warning from the @code{define} command.
20018 @node Command Files
20019 @subsection Command Files
20021 @cindex command files
20022 @cindex scripting commands
20023 A command file for @value{GDBN} is a text file made of lines that are
20024 @value{GDBN} commands. Comments (lines starting with @kbd{#}) may
20025 also be included. An empty line in a command file does nothing; it
20026 does not mean to repeat the last command, as it would from the
20029 You can request the execution of a command file with the @code{source}
20030 command. Note that the @code{source} command is also used to evaluate
20031 scripts that are not Command Files. The exact behavior can be configured
20032 using the @code{script-extension} setting.
20033 @xref{Extending GDB,, Extending GDB}.
20037 @cindex execute commands from a file
20038 @item source [-s] [-v] @var{filename}
20039 Execute the command file @var{filename}.
20042 The lines in a command file are generally executed sequentially,
20043 unless the order of execution is changed by one of the
20044 @emph{flow-control commands} described below. The commands are not
20045 printed as they are executed. An error in any command terminates
20046 execution of the command file and control is returned to the console.
20048 @value{GDBN} first searches for @var{filename} in the current directory.
20049 If the file is not found there, and @var{filename} does not specify a
20050 directory, then @value{GDBN} also looks for the file on the source search path
20051 (specified with the @samp{directory} command);
20052 except that @file{$cdir} is not searched because the compilation directory
20053 is not relevant to scripts.
20055 If @code{-s} is specified, then @value{GDBN} searches for @var{filename}
20056 on the search path even if @var{filename} specifies a directory.
20057 The search is done by appending @var{filename} to each element of the
20058 search path. So, for example, if @var{filename} is @file{mylib/myscript}
20059 and the search path contains @file{/home/user} then @value{GDBN} will
20060 look for the script @file{/home/user/mylib/myscript}.
20061 The search is also done if @var{filename} is an absolute path.
20062 For example, if @var{filename} is @file{/tmp/myscript} and
20063 the search path contains @file{/home/user} then @value{GDBN} will
20064 look for the script @file{/home/user/tmp/myscript}.
20065 For DOS-like systems, if @var{filename} contains a drive specification,
20066 it is stripped before concatenation. For example, if @var{filename} is
20067 @file{d:myscript} and the search path contains @file{c:/tmp} then @value{GDBN}
20068 will look for the script @file{c:/tmp/myscript}.
20070 If @code{-v}, for verbose mode, is given then @value{GDBN} displays
20071 each command as it is executed. The option must be given before
20072 @var{filename}, and is interpreted as part of the filename anywhere else.
20074 Commands that would ask for confirmation if used interactively proceed
20075 without asking when used in a command file. Many @value{GDBN} commands that
20076 normally print messages to say what they are doing omit the messages
20077 when called from command files.
20079 @value{GDBN} also accepts command input from standard input. In this
20080 mode, normal output goes to standard output and error output goes to
20081 standard error. Errors in a command file supplied on standard input do
20082 not terminate execution of the command file---execution continues with
20086 gdb < cmds > log 2>&1
20089 (The syntax above will vary depending on the shell used.) This example
20090 will execute commands from the file @file{cmds}. All output and errors
20091 would be directed to @file{log}.
20093 Since commands stored on command files tend to be more general than
20094 commands typed interactively, they frequently need to deal with
20095 complicated situations, such as different or unexpected values of
20096 variables and symbols, changes in how the program being debugged is
20097 built, etc. @value{GDBN} provides a set of flow-control commands to
20098 deal with these complexities. Using these commands, you can write
20099 complex scripts that loop over data structures, execute commands
20100 conditionally, etc.
20107 This command allows to include in your script conditionally executed
20108 commands. The @code{if} command takes a single argument, which is an
20109 expression to evaluate. It is followed by a series of commands that
20110 are executed only if the expression is true (its value is nonzero).
20111 There can then optionally be an @code{else} line, followed by a series
20112 of commands that are only executed if the expression was false. The
20113 end of the list is marked by a line containing @code{end}.
20117 This command allows to write loops. Its syntax is similar to
20118 @code{if}: the command takes a single argument, which is an expression
20119 to evaluate, and must be followed by the commands to execute, one per
20120 line, terminated by an @code{end}. These commands are called the
20121 @dfn{body} of the loop. The commands in the body of @code{while} are
20122 executed repeatedly as long as the expression evaluates to true.
20126 This command exits the @code{while} loop in whose body it is included.
20127 Execution of the script continues after that @code{while}s @code{end}
20130 @kindex loop_continue
20131 @item loop_continue
20132 This command skips the execution of the rest of the body of commands
20133 in the @code{while} loop in whose body it is included. Execution
20134 branches to the beginning of the @code{while} loop, where it evaluates
20135 the controlling expression.
20137 @kindex end@r{ (if/else/while commands)}
20139 Terminate the block of commands that are the body of @code{if},
20140 @code{else}, or @code{while} flow-control commands.
20145 @subsection Commands for Controlled Output
20147 During the execution of a command file or a user-defined command, normal
20148 @value{GDBN} output is suppressed; the only output that appears is what is
20149 explicitly printed by the commands in the definition. This section
20150 describes three commands useful for generating exactly the output you
20155 @item echo @var{text}
20156 @c I do not consider backslash-space a standard C escape sequence
20157 @c because it is not in ANSI.
20158 Print @var{text}. Nonprinting characters can be included in
20159 @var{text} using C escape sequences, such as @samp{\n} to print a
20160 newline. @strong{No newline is printed unless you specify one.}
20161 In addition to the standard C escape sequences, a backslash followed
20162 by a space stands for a space. This is useful for displaying a
20163 string with spaces at the beginning or the end, since leading and
20164 trailing spaces are otherwise trimmed from all arguments.
20165 To print @samp{@w{ }and foo =@w{ }}, use the command
20166 @samp{echo \@w{ }and foo = \@w{ }}.
20168 A backslash at the end of @var{text} can be used, as in C, to continue
20169 the command onto subsequent lines. For example,
20172 echo This is some text\n\
20173 which is continued\n\
20174 onto several lines.\n
20177 produces the same output as
20180 echo This is some text\n
20181 echo which is continued\n
20182 echo onto several lines.\n
20186 @item output @var{expression}
20187 Print the value of @var{expression} and nothing but that value: no
20188 newlines, no @samp{$@var{nn} = }. The value is not entered in the
20189 value history either. @xref{Expressions, ,Expressions}, for more information
20192 @item output/@var{fmt} @var{expression}
20193 Print the value of @var{expression} in format @var{fmt}. You can use
20194 the same formats as for @code{print}. @xref{Output Formats,,Output
20195 Formats}, for more information.
20198 @item printf @var{template}, @var{expressions}@dots{}
20199 Print the values of one or more @var{expressions} under the control of
20200 the string @var{template}. To print several values, make
20201 @var{expressions} be a comma-separated list of individual expressions,
20202 which may be either numbers or pointers. Their values are printed as
20203 specified by @var{template}, exactly as a C program would do by
20204 executing the code below:
20207 printf (@var{template}, @var{expressions}@dots{});
20210 As in @code{C} @code{printf}, ordinary characters in @var{template}
20211 are printed verbatim, while @dfn{conversion specification} introduced
20212 by the @samp{%} character cause subsequent @var{expressions} to be
20213 evaluated, their values converted and formatted according to type and
20214 style information encoded in the conversion specifications, and then
20217 For example, you can print two values in hex like this:
20220 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
20223 @code{printf} supports all the standard @code{C} conversion
20224 specifications, including the flags and modifiers between the @samp{%}
20225 character and the conversion letter, with the following exceptions:
20229 The argument-ordering modifiers, such as @samp{2$}, are not supported.
20232 The modifier @samp{*} is not supported for specifying precision or
20236 The @samp{'} flag (for separation of digits into groups according to
20237 @code{LC_NUMERIC'}) is not supported.
20240 The type modifiers @samp{hh}, @samp{j}, @samp{t}, and @samp{z} are not
20244 The conversion letter @samp{n} (as in @samp{%n}) is not supported.
20247 The conversion letters @samp{a} and @samp{A} are not supported.
20251 Note that the @samp{ll} type modifier is supported only if the
20252 underlying @code{C} implementation used to build @value{GDBN} supports
20253 the @code{long long int} type, and the @samp{L} type modifier is
20254 supported only if @code{long double} type is available.
20256 As in @code{C}, @code{printf} supports simple backslash-escape
20257 sequences, such as @code{\n}, @samp{\t}, @samp{\\}, @samp{\"},
20258 @samp{\a}, and @samp{\f}, that consist of backslash followed by a
20259 single character. Octal and hexadecimal escape sequences are not
20262 Additionally, @code{printf} supports conversion specifications for DFP
20263 (@dfn{Decimal Floating Point}) types using the following length modifiers
20264 together with a floating point specifier.
20269 @samp{H} for printing @code{Decimal32} types.
20272 @samp{D} for printing @code{Decimal64} types.
20275 @samp{DD} for printing @code{Decimal128} types.
20278 If the underlying @code{C} implementation used to build @value{GDBN} has
20279 support for the three length modifiers for DFP types, other modifiers
20280 such as width and precision will also be available for @value{GDBN} to use.
20282 In case there is no such @code{C} support, no additional modifiers will be
20283 available and the value will be printed in the standard way.
20285 Here's an example of printing DFP types using the above conversion letters:
20287 printf "D32: %Hf - D64: %Df - D128: %DDf\n",1.2345df,1.2E10dd,1.2E1dl
20291 @item eval @var{template}, @var{expressions}@dots{}
20292 Convert the values of one or more @var{expressions} under the control of
20293 the string @var{template} to a command line, and call it.
20298 @section Scripting @value{GDBN} using Python
20299 @cindex python scripting
20300 @cindex scripting with python
20302 You can script @value{GDBN} using the @uref{http://www.python.org/,
20303 Python programming language}. This feature is available only if
20304 @value{GDBN} was configured using @option{--with-python}.
20306 @cindex python directory
20307 Python scripts used by @value{GDBN} should be installed in
20308 @file{@var{data-directory}/python}, where @var{data-directory} is
20309 the data directory as determined at @value{GDBN} startup (@pxref{Data Files}). This directory, known as the @dfn{python directory},
20310 is automatically added to the Python Search Path in order to allow
20311 the Python interpreter to locate all scripts installed at this location.
20314 * Python Commands:: Accessing Python from @value{GDBN}.
20315 * Python API:: Accessing @value{GDBN} from Python.
20316 * Auto-loading:: Automatically loading Python code.
20319 @node Python Commands
20320 @subsection Python Commands
20321 @cindex python commands
20322 @cindex commands to access python
20324 @value{GDBN} provides one command for accessing the Python interpreter,
20325 and one related setting:
20329 @item python @r{[}@var{code}@r{]}
20330 The @code{python} command can be used to evaluate Python code.
20332 If given an argument, the @code{python} command will evaluate the
20333 argument as a Python command. For example:
20336 (@value{GDBP}) python print 23
20340 If you do not provide an argument to @code{python}, it will act as a
20341 multi-line command, like @code{define}. In this case, the Python
20342 script is made up of subsequent command lines, given after the
20343 @code{python} command. This command list is terminated using a line
20344 containing @code{end}. For example:
20347 (@value{GDBP}) python
20349 End with a line saying just "end".
20355 @kindex maint set python print-stack
20356 @item maint set python print-stack
20357 By default, @value{GDBN} will print a stack trace when an error occurs
20358 in a Python script. This can be controlled using @code{maint set
20359 python print-stack}: if @code{on}, the default, then Python stack
20360 printing is enabled; if @code{off}, then Python stack printing is
20364 It is also possible to execute a Python script from the @value{GDBN}
20368 @item source @file{script-name}
20369 The script name must end with @samp{.py} and @value{GDBN} must be configured
20370 to recognize the script language based on filename extension using
20371 the @code{script-extension} setting. @xref{Extending GDB, ,Extending GDB}.
20373 @item python execfile ("script-name")
20374 This method is based on the @code{execfile} Python built-in function,
20375 and thus is always available.
20379 @subsection Python API
20381 @cindex programming in python
20383 @cindex python stdout
20384 @cindex python pagination
20385 At startup, @value{GDBN} overrides Python's @code{sys.stdout} and
20386 @code{sys.stderr} to print using @value{GDBN}'s output-paging streams.
20387 A Python program which outputs to one of these streams may have its
20388 output interrupted by the user (@pxref{Screen Size}). In this
20389 situation, a Python @code{KeyboardInterrupt} exception is thrown.
20392 * Basic Python:: Basic Python Functions.
20393 * Exception Handling::
20394 * Values From Inferior::
20395 * Types In Python:: Python representation of types.
20396 * Pretty Printing API:: Pretty-printing values.
20397 * Selecting Pretty-Printers:: How GDB chooses a pretty-printer.
20398 * Disabling Pretty-Printers:: Disabling broken printers.
20399 * Inferiors In Python:: Python representation of inferiors (processes)
20400 * Threads In Python:: Accessing inferior threads from Python.
20401 * Commands In Python:: Implementing new commands in Python.
20402 * Parameters In Python:: Adding new @value{GDBN} parameters.
20403 * Functions In Python:: Writing new convenience functions.
20404 * Progspaces In Python:: Program spaces.
20405 * Objfiles In Python:: Object files.
20406 * Frames In Python:: Accessing inferior stack frames from Python.
20407 * Blocks In Python:: Accessing frame blocks from Python.
20408 * Symbols In Python:: Python representation of symbols.
20409 * Symbol Tables In Python:: Python representation of symbol tables.
20410 * Lazy Strings In Python:: Python representation of lazy strings.
20411 * Breakpoints In Python:: Manipulating breakpoints using Python.
20415 @subsubsection Basic Python
20417 @cindex python functions
20418 @cindex python module
20420 @value{GDBN} introduces a new Python module, named @code{gdb}. All
20421 methods and classes added by @value{GDBN} are placed in this module.
20422 @value{GDBN} automatically @code{import}s the @code{gdb} module for
20423 use in all scripts evaluated by the @code{python} command.
20425 @findex gdb.PYTHONDIR
20427 A string containing the python directory (@pxref{Python}).
20430 @findex gdb.execute
20431 @defun execute command [from_tty] [to_string]
20432 Evaluate @var{command}, a string, as a @value{GDBN} CLI command.
20433 If a GDB exception happens while @var{command} runs, it is
20434 translated as described in @ref{Exception Handling,,Exception Handling}.
20436 @var{from_tty} specifies whether @value{GDBN} ought to consider this
20437 command as having originated from the user invoking it interactively.
20438 It must be a boolean value. If omitted, it defaults to @code{False}.
20440 By default, any output produced by @var{command} is sent to
20441 @value{GDBN}'s standard output. If the @var{to_string} parameter is
20442 @code{True}, then output will be collected by @code{gdb.execute} and
20443 returned as a string. The default is @code{False}, in which case the
20444 return value is @code{None}.
20447 @findex gdb.breakpoints
20449 Return a sequence holding all of @value{GDBN}'s breakpoints.
20450 @xref{Breakpoints In Python}, for more information.
20453 @findex gdb.parameter
20454 @defun parameter parameter
20455 Return the value of a @value{GDBN} parameter. @var{parameter} is a
20456 string naming the parameter to look up; @var{parameter} may contain
20457 spaces if the parameter has a multi-part name. For example,
20458 @samp{print object} is a valid parameter name.
20460 If the named parameter does not exist, this function throws a
20461 @code{RuntimeError}. Otherwise, the parameter's value is converted to
20462 a Python value of the appropriate type, and returned.
20465 @findex gdb.history
20466 @defun history number
20467 Return a value from @value{GDBN}'s value history (@pxref{Value
20468 History}). @var{number} indicates which history element to return.
20469 If @var{number} is negative, then @value{GDBN} will take its absolute value
20470 and count backward from the last element (i.e., the most recent element) to
20471 find the value to return. If @var{number} is zero, then @value{GDBN} will
20472 return the most recent element. If the element specified by @var{number}
20473 doesn't exist in the value history, a @code{RuntimeError} exception will be
20476 If no exception is raised, the return value is always an instance of
20477 @code{gdb.Value} (@pxref{Values From Inferior}).
20480 @findex gdb.parse_and_eval
20481 @defun parse_and_eval expression
20482 Parse @var{expression} as an expression in the current language,
20483 evaluate it, and return the result as a @code{gdb.Value}.
20484 @var{expression} must be a string.
20486 This function can be useful when implementing a new command
20487 (@pxref{Commands In Python}), as it provides a way to parse the
20488 command's argument as an expression. It is also useful simply to
20489 compute values, for example, it is the only way to get the value of a
20490 convenience variable (@pxref{Convenience Vars}) as a @code{gdb.Value}.
20494 @defun write string
20495 Print a string to @value{GDBN}'s paginated standard output stream.
20496 Writing to @code{sys.stdout} or @code{sys.stderr} will automatically
20497 call this function.
20502 Flush @value{GDBN}'s paginated standard output stream. Flushing
20503 @code{sys.stdout} or @code{sys.stderr} will automatically call this
20507 @findex gdb.target_charset
20508 @defun target_charset
20509 Return the name of the current target character set (@pxref{Character
20510 Sets}). This differs from @code{gdb.parameter('target-charset')} in
20511 that @samp{auto} is never returned.
20514 @findex gdb.target_wide_charset
20515 @defun target_wide_charset
20516 Return the name of the current target wide character set
20517 (@pxref{Character Sets}). This differs from
20518 @code{gdb.parameter('target-wide-charset')} in that @samp{auto} is
20522 @node Exception Handling
20523 @subsubsection Exception Handling
20524 @cindex python exceptions
20525 @cindex exceptions, python
20527 When executing the @code{python} command, Python exceptions
20528 uncaught within the Python code are translated to calls to
20529 @value{GDBN} error-reporting mechanism. If the command that called
20530 @code{python} does not handle the error, @value{GDBN} will
20531 terminate it and print an error message containing the Python
20532 exception name, the associated value, and the Python call stack
20533 backtrace at the point where the exception was raised. Example:
20536 (@value{GDBP}) python print foo
20537 Traceback (most recent call last):
20538 File "<string>", line 1, in <module>
20539 NameError: name 'foo' is not defined
20542 @value{GDBN} errors that happen in @value{GDBN} commands invoked by Python
20543 code are converted to Python @code{RuntimeError} exceptions. User
20544 interrupt (via @kbd{C-c} or by typing @kbd{q} at a pagination
20545 prompt) is translated to a Python @code{KeyboardInterrupt}
20546 exception. If you catch these exceptions in your Python code, your
20547 exception handler will see @code{RuntimeError} or
20548 @code{KeyboardInterrupt} as the exception type, the @value{GDBN} error
20549 message as its value, and the Python call stack backtrace at the
20550 Python statement closest to where the @value{GDBN} error occured as the
20553 @findex gdb.GdbError
20554 When implementing @value{GDBN} commands in Python via @code{gdb.Command},
20555 it is useful to be able to throw an exception that doesn't cause a
20556 traceback to be printed. For example, the user may have invoked the
20557 command incorrectly. Use the @code{gdb.GdbError} exception
20558 to handle this case. Example:
20562 >class HelloWorld (gdb.Command):
20563 > """Greet the whole world."""
20564 > def __init__ (self):
20565 > super (HelloWorld, self).__init__ ("hello-world", gdb.COMMAND_OBSCURE)
20566 > def invoke (self, args, from_tty):
20567 > argv = gdb.string_to_argv (args)
20568 > if len (argv) != 0:
20569 > raise gdb.GdbError ("hello-world takes no arguments")
20570 > print "Hello, World!"
20573 (gdb) hello-world 42
20574 hello-world takes no arguments
20577 @node Values From Inferior
20578 @subsubsection Values From Inferior
20579 @cindex values from inferior, with Python
20580 @cindex python, working with values from inferior
20582 @cindex @code{gdb.Value}
20583 @value{GDBN} provides values it obtains from the inferior program in
20584 an object of type @code{gdb.Value}. @value{GDBN} uses this object
20585 for its internal bookkeeping of the inferior's values, and for
20586 fetching values when necessary.
20588 Inferior values that are simple scalars can be used directly in
20589 Python expressions that are valid for the value's data type. Here's
20590 an example for an integer or floating-point value @code{some_val}:
20597 As result of this, @code{bar} will also be a @code{gdb.Value} object
20598 whose values are of the same type as those of @code{some_val}.
20600 Inferior values that are structures or instances of some class can
20601 be accessed using the Python @dfn{dictionary syntax}. For example, if
20602 @code{some_val} is a @code{gdb.Value} instance holding a structure, you
20603 can access its @code{foo} element with:
20606 bar = some_val['foo']
20609 Again, @code{bar} will also be a @code{gdb.Value} object.
20611 A @code{gdb.Value} that represents a function can be executed via
20612 inferior function call. Any arguments provided to the call must match
20613 the function's prototype, and must be provided in the order specified
20616 For example, @code{some_val} is a @code{gdb.Value} instance
20617 representing a function that takes two integers as arguments. To
20618 execute this function, call it like so:
20621 result = some_val (10,20)
20624 Any values returned from a function call will be stored as a
20627 The following attributes are provided:
20630 @defivar Value address
20631 If this object is addressable, this read-only attribute holds a
20632 @code{gdb.Value} object representing the address. Otherwise,
20633 this attribute holds @code{None}.
20636 @cindex optimized out value in Python
20637 @defivar Value is_optimized_out
20638 This read-only boolean attribute is true if the compiler optimized out
20639 this value, thus it is not available for fetching from the inferior.
20642 @defivar Value type
20643 The type of this @code{gdb.Value}. The value of this attribute is a
20644 @code{gdb.Type} object.
20648 The following methods are provided:
20651 @defmethod Value cast type
20652 Return a new instance of @code{gdb.Value} that is the result of
20653 casting this instance to the type described by @var{type}, which must
20654 be a @code{gdb.Type} object. If the cast cannot be performed for some
20655 reason, this method throws an exception.
20658 @defmethod Value dereference
20659 For pointer data types, this method returns a new @code{gdb.Value} object
20660 whose contents is the object pointed to by the pointer. For example, if
20661 @code{foo} is a C pointer to an @code{int}, declared in your C program as
20668 then you can use the corresponding @code{gdb.Value} to access what
20669 @code{foo} points to like this:
20672 bar = foo.dereference ()
20675 The result @code{bar} will be a @code{gdb.Value} object holding the
20676 value pointed to by @code{foo}.
20679 @defmethod Value string @r{[}encoding@r{]} @r{[}errors@r{]} @r{[}length@r{]}
20680 If this @code{gdb.Value} represents a string, then this method
20681 converts the contents to a Python string. Otherwise, this method will
20682 throw an exception.
20684 Strings are recognized in a language-specific way; whether a given
20685 @code{gdb.Value} represents a string is determined by the current
20688 For C-like languages, a value is a string if it is a pointer to or an
20689 array of characters or ints. The string is assumed to be terminated
20690 by a zero of the appropriate width. However if the optional length
20691 argument is given, the string will be converted to that given length,
20692 ignoring any embedded zeros that the string may contain.
20694 If the optional @var{encoding} argument is given, it must be a string
20695 naming the encoding of the string in the @code{gdb.Value}, such as
20696 @code{"ascii"}, @code{"iso-8859-6"} or @code{"utf-8"}. It accepts
20697 the same encodings as the corresponding argument to Python's
20698 @code{string.decode} method, and the Python codec machinery will be used
20699 to convert the string. If @var{encoding} is not given, or if
20700 @var{encoding} is the empty string, then either the @code{target-charset}
20701 (@pxref{Character Sets}) will be used, or a language-specific encoding
20702 will be used, if the current language is able to supply one.
20704 The optional @var{errors} argument is the same as the corresponding
20705 argument to Python's @code{string.decode} method.
20707 If the optional @var{length} argument is given, the string will be
20708 fetched and converted to the given length.
20711 @defmethod Value lazy_string @r{[}encoding@r{]} @r{[}length@r{]}
20712 If this @code{gdb.Value} represents a string, then this method
20713 converts the contents to a @code{gdb.LazyString} (@pxref{Lazy Strings
20714 In Python}). Otherwise, this method will throw an exception.
20716 If the optional @var{encoding} argument is given, it must be a string
20717 naming the encoding of the @code{gdb.LazyString}. Some examples are:
20718 @samp{ascii}, @samp{iso-8859-6} or @samp{utf-8}. If the
20719 @var{encoding} argument is an encoding that @value{GDBN} does
20720 recognize, @value{GDBN} will raise an error.
20722 When a lazy string is printed, the @value{GDBN} encoding machinery is
20723 used to convert the string during printing. If the optional
20724 @var{encoding} argument is not provided, or is an empty string,
20725 @value{GDBN} will automatically select the encoding most suitable for
20726 the string type. For further information on encoding in @value{GDBN}
20727 please see @ref{Character Sets}.
20729 If the optional @var{length} argument is given, the string will be
20730 fetched and encoded to the length of characters specified. If
20731 the @var{length} argument is not provided, the string will be fetched
20732 and encoded until a null of appropriate width is found.
20736 @node Types In Python
20737 @subsubsection Types In Python
20738 @cindex types in Python
20739 @cindex Python, working with types
20742 @value{GDBN} represents types from the inferior using the class
20745 The following type-related functions are available in the @code{gdb}
20748 @findex gdb.lookup_type
20749 @defun lookup_type name [block]
20750 This function looks up a type by name. @var{name} is the name of the
20751 type to look up. It must be a string.
20753 If @var{block} is given, then @var{name} is looked up in that scope.
20754 Otherwise, it is searched for globally.
20756 Ordinarily, this function will return an instance of @code{gdb.Type}.
20757 If the named type cannot be found, it will throw an exception.
20760 An instance of @code{Type} has the following attributes:
20764 The type code for this type. The type code will be one of the
20765 @code{TYPE_CODE_} constants defined below.
20768 @defivar Type sizeof
20769 The size of this type, in target @code{char} units. Usually, a
20770 target's @code{char} type will be an 8-bit byte. However, on some
20771 unusual platforms, this type may have a different size.
20775 The tag name for this type. The tag name is the name after
20776 @code{struct}, @code{union}, or @code{enum} in C and C@t{++}; not all
20777 languages have this concept. If this type has no tag name, then
20778 @code{None} is returned.
20782 The following methods are provided:
20785 @defmethod Type fields
20786 For structure and union types, this method returns the fields. Range
20787 types have two fields, the minimum and maximum values. Enum types
20788 have one field per enum constant. Function and method types have one
20789 field per parameter. The base types of C@t{++} classes are also
20790 represented as fields. If the type has no fields, or does not fit
20791 into one of these categories, an empty sequence will be returned.
20793 Each field is an object, with some pre-defined attributes:
20796 This attribute is not available for @code{static} fields (as in
20797 C@t{++} or Java). For non-@code{static} fields, the value is the bit
20798 position of the field.
20801 The name of the field, or @code{None} for anonymous fields.
20804 This is @code{True} if the field is artificial, usually meaning that
20805 it was provided by the compiler and not the user. This attribute is
20806 always provided, and is @code{False} if the field is not artificial.
20808 @item is_base_class
20809 This is @code{True} if the field represents a base class of a C@t{++}
20810 structure. This attribute is always provided, and is @code{False}
20811 if the field is not a base class of the type that is the argument of
20812 @code{fields}, or if that type was not a C@t{++} class.
20815 If the field is packed, or is a bitfield, then this will have a
20816 non-zero value, which is the size of the field in bits. Otherwise,
20817 this will be zero; in this case the field's size is given by its type.
20820 The type of the field. This is usually an instance of @code{Type},
20821 but it can be @code{None} in some situations.
20825 @defmethod Type const
20826 Return a new @code{gdb.Type} object which represents a
20827 @code{const}-qualified variant of this type.
20830 @defmethod Type volatile
20831 Return a new @code{gdb.Type} object which represents a
20832 @code{volatile}-qualified variant of this type.
20835 @defmethod Type unqualified
20836 Return a new @code{gdb.Type} object which represents an unqualified
20837 variant of this type. That is, the result is neither @code{const} nor
20841 @defmethod Type range
20842 Return a Python @code{Tuple} object that contains two elements: the
20843 low bound of the argument type and the high bound of that type. If
20844 the type does not have a range, @value{GDBN} will raise a
20845 @code{RuntimeError} exception.
20848 @defmethod Type reference
20849 Return a new @code{gdb.Type} object which represents a reference to this
20853 @defmethod Type pointer
20854 Return a new @code{gdb.Type} object which represents a pointer to this
20858 @defmethod Type strip_typedefs
20859 Return a new @code{gdb.Type} that represents the real type,
20860 after removing all layers of typedefs.
20863 @defmethod Type target
20864 Return a new @code{gdb.Type} object which represents the target type
20867 For a pointer type, the target type is the type of the pointed-to
20868 object. For an array type (meaning C-like arrays), the target type is
20869 the type of the elements of the array. For a function or method type,
20870 the target type is the type of the return value. For a complex type,
20871 the target type is the type of the elements. For a typedef, the
20872 target type is the aliased type.
20874 If the type does not have a target, this method will throw an
20878 @defmethod Type template_argument n [block]
20879 If this @code{gdb.Type} is an instantiation of a template, this will
20880 return a new @code{gdb.Type} which represents the type of the
20881 @var{n}th template argument.
20883 If this @code{gdb.Type} is not a template type, this will throw an
20884 exception. Ordinarily, only C@t{++} code will have template types.
20886 If @var{block} is given, then @var{name} is looked up in that scope.
20887 Otherwise, it is searched for globally.
20892 Each type has a code, which indicates what category this type falls
20893 into. The available type categories are represented by constants
20894 defined in the @code{gdb} module:
20897 @findex TYPE_CODE_PTR
20898 @findex gdb.TYPE_CODE_PTR
20899 @item TYPE_CODE_PTR
20900 The type is a pointer.
20902 @findex TYPE_CODE_ARRAY
20903 @findex gdb.TYPE_CODE_ARRAY
20904 @item TYPE_CODE_ARRAY
20905 The type is an array.
20907 @findex TYPE_CODE_STRUCT
20908 @findex gdb.TYPE_CODE_STRUCT
20909 @item TYPE_CODE_STRUCT
20910 The type is a structure.
20912 @findex TYPE_CODE_UNION
20913 @findex gdb.TYPE_CODE_UNION
20914 @item TYPE_CODE_UNION
20915 The type is a union.
20917 @findex TYPE_CODE_ENUM
20918 @findex gdb.TYPE_CODE_ENUM
20919 @item TYPE_CODE_ENUM
20920 The type is an enum.
20922 @findex TYPE_CODE_FLAGS
20923 @findex gdb.TYPE_CODE_FLAGS
20924 @item TYPE_CODE_FLAGS
20925 A bit flags type, used for things such as status registers.
20927 @findex TYPE_CODE_FUNC
20928 @findex gdb.TYPE_CODE_FUNC
20929 @item TYPE_CODE_FUNC
20930 The type is a function.
20932 @findex TYPE_CODE_INT
20933 @findex gdb.TYPE_CODE_INT
20934 @item TYPE_CODE_INT
20935 The type is an integer type.
20937 @findex TYPE_CODE_FLT
20938 @findex gdb.TYPE_CODE_FLT
20939 @item TYPE_CODE_FLT
20940 A floating point type.
20942 @findex TYPE_CODE_VOID
20943 @findex gdb.TYPE_CODE_VOID
20944 @item TYPE_CODE_VOID
20945 The special type @code{void}.
20947 @findex TYPE_CODE_SET
20948 @findex gdb.TYPE_CODE_SET
20949 @item TYPE_CODE_SET
20952 @findex TYPE_CODE_RANGE
20953 @findex gdb.TYPE_CODE_RANGE
20954 @item TYPE_CODE_RANGE
20955 A range type, that is, an integer type with bounds.
20957 @findex TYPE_CODE_STRING
20958 @findex gdb.TYPE_CODE_STRING
20959 @item TYPE_CODE_STRING
20960 A string type. Note that this is only used for certain languages with
20961 language-defined string types; C strings are not represented this way.
20963 @findex TYPE_CODE_BITSTRING
20964 @findex gdb.TYPE_CODE_BITSTRING
20965 @item TYPE_CODE_BITSTRING
20968 @findex TYPE_CODE_ERROR
20969 @findex gdb.TYPE_CODE_ERROR
20970 @item TYPE_CODE_ERROR
20971 An unknown or erroneous type.
20973 @findex TYPE_CODE_METHOD
20974 @findex gdb.TYPE_CODE_METHOD
20975 @item TYPE_CODE_METHOD
20976 A method type, as found in C@t{++} or Java.
20978 @findex TYPE_CODE_METHODPTR
20979 @findex gdb.TYPE_CODE_METHODPTR
20980 @item TYPE_CODE_METHODPTR
20981 A pointer-to-member-function.
20983 @findex TYPE_CODE_MEMBERPTR
20984 @findex gdb.TYPE_CODE_MEMBERPTR
20985 @item TYPE_CODE_MEMBERPTR
20986 A pointer-to-member.
20988 @findex TYPE_CODE_REF
20989 @findex gdb.TYPE_CODE_REF
20990 @item TYPE_CODE_REF
20993 @findex TYPE_CODE_CHAR
20994 @findex gdb.TYPE_CODE_CHAR
20995 @item TYPE_CODE_CHAR
20998 @findex TYPE_CODE_BOOL
20999 @findex gdb.TYPE_CODE_BOOL
21000 @item TYPE_CODE_BOOL
21003 @findex TYPE_CODE_COMPLEX
21004 @findex gdb.TYPE_CODE_COMPLEX
21005 @item TYPE_CODE_COMPLEX
21006 A complex float type.
21008 @findex TYPE_CODE_TYPEDEF
21009 @findex gdb.TYPE_CODE_TYPEDEF
21010 @item TYPE_CODE_TYPEDEF
21011 A typedef to some other type.
21013 @findex TYPE_CODE_NAMESPACE
21014 @findex gdb.TYPE_CODE_NAMESPACE
21015 @item TYPE_CODE_NAMESPACE
21016 A C@t{++} namespace.
21018 @findex TYPE_CODE_DECFLOAT
21019 @findex gdb.TYPE_CODE_DECFLOAT
21020 @item TYPE_CODE_DECFLOAT
21021 A decimal floating point type.
21023 @findex TYPE_CODE_INTERNAL_FUNCTION
21024 @findex gdb.TYPE_CODE_INTERNAL_FUNCTION
21025 @item TYPE_CODE_INTERNAL_FUNCTION
21026 A function internal to @value{GDBN}. This is the type used to represent
21027 convenience functions.
21030 @node Pretty Printing API
21031 @subsubsection Pretty Printing API
21033 An example output is provided (@pxref{Pretty Printing}).
21035 A pretty-printer is just an object that holds a value and implements a
21036 specific interface, defined here.
21038 @defop Operation {pretty printer} children (self)
21039 @value{GDBN} will call this method on a pretty-printer to compute the
21040 children of the pretty-printer's value.
21042 This method must return an object conforming to the Python iterator
21043 protocol. Each item returned by the iterator must be a tuple holding
21044 two elements. The first element is the ``name'' of the child; the
21045 second element is the child's value. The value can be any Python
21046 object which is convertible to a @value{GDBN} value.
21048 This method is optional. If it does not exist, @value{GDBN} will act
21049 as though the value has no children.
21052 @defop Operation {pretty printer} display_hint (self)
21053 The CLI may call this method and use its result to change the
21054 formatting of a value. The result will also be supplied to an MI
21055 consumer as a @samp{displayhint} attribute of the variable being
21058 This method is optional. If it does exist, this method must return a
21061 Some display hints are predefined by @value{GDBN}:
21065 Indicate that the object being printed is ``array-like''. The CLI
21066 uses this to respect parameters such as @code{set print elements} and
21067 @code{set print array}.
21070 Indicate that the object being printed is ``map-like'', and that the
21071 children of this value can be assumed to alternate between keys and
21075 Indicate that the object being printed is ``string-like''. If the
21076 printer's @code{to_string} method returns a Python string of some
21077 kind, then @value{GDBN} will call its internal language-specific
21078 string-printing function to format the string. For the CLI this means
21079 adding quotation marks, possibly escaping some characters, respecting
21080 @code{set print elements}, and the like.
21084 @defop Operation {pretty printer} to_string (self)
21085 @value{GDBN} will call this method to display the string
21086 representation of the value passed to the object's constructor.
21088 When printing from the CLI, if the @code{to_string} method exists,
21089 then @value{GDBN} will prepend its result to the values returned by
21090 @code{children}. Exactly how this formatting is done is dependent on
21091 the display hint, and may change as more hints are added. Also,
21092 depending on the print settings (@pxref{Print Settings}), the CLI may
21093 print just the result of @code{to_string} in a stack trace, omitting
21094 the result of @code{children}.
21096 If this method returns a string, it is printed verbatim.
21098 Otherwise, if this method returns an instance of @code{gdb.Value},
21099 then @value{GDBN} prints this value. This may result in a call to
21100 another pretty-printer.
21102 If instead the method returns a Python value which is convertible to a
21103 @code{gdb.Value}, then @value{GDBN} performs the conversion and prints
21104 the resulting value. Again, this may result in a call to another
21105 pretty-printer. Python scalars (integers, floats, and booleans) and
21106 strings are convertible to @code{gdb.Value}; other types are not.
21108 Finally, if this method returns @code{None} then no further operations
21109 are peformed in this method and nothing is printed.
21111 If the result is not one of these types, an exception is raised.
21114 @node Selecting Pretty-Printers
21115 @subsubsection Selecting Pretty-Printers
21117 The Python list @code{gdb.pretty_printers} contains an array of
21118 functions or callable objects that have been registered via addition
21119 as a pretty-printer.
21120 Each @code{gdb.Progspace} contains a @code{pretty_printers} attribute.
21121 Each @code{gdb.Objfile} also contains a @code{pretty_printers}
21124 A function on one of these lists is passed a single @code{gdb.Value}
21125 argument and should return a pretty-printer object conforming to the
21126 interface definition above (@pxref{Pretty Printing API}). If a function
21127 cannot create a pretty-printer for the value, it should return
21130 @value{GDBN} first checks the @code{pretty_printers} attribute of each
21131 @code{gdb.Objfile} in the current program space and iteratively calls
21132 each enabled function (@pxref{Disabling Pretty-Printers})
21133 in the list for that @code{gdb.Objfile} until it receives
21134 a pretty-printer object.
21135 If no pretty-printer is found in the objfile lists, @value{GDBN} then
21136 searches the pretty-printer list of the current program space,
21137 calling each enabled function until an object is returned.
21138 After these lists have been exhausted, it tries the global
21139 @code{gdb.pretty_printers} list, again calling each enabled function until an
21140 object is returned.
21142 The order in which the objfiles are searched is not specified. For a
21143 given list, functions are always invoked from the head of the list,
21144 and iterated over sequentially until the end of the list, or a printer
21145 object is returned.
21147 Here is an example showing how a @code{std::string} printer might be
21151 class StdStringPrinter:
21152 "Print a std::string"
21154 def __init__ (self, val):
21157 def to_string (self):
21158 return self.val['_M_dataplus']['_M_p']
21160 def display_hint (self):
21164 And here is an example showing how a lookup function for the printer
21165 example above might be written.
21168 def str_lookup_function (val):
21170 lookup_tag = val.type.tag
21171 regex = re.compile ("^std::basic_string<char,.*>$")
21172 if lookup_tag == None:
21174 if regex.match (lookup_tag):
21175 return StdStringPrinter (val)
21180 The example lookup function extracts the value's type, and attempts to
21181 match it to a type that it can pretty-print. If it is a type the
21182 printer can pretty-print, it will return a printer object. If not, it
21183 returns @code{None}.
21185 We recommend that you put your core pretty-printers into a Python
21186 package. If your pretty-printers are for use with a library, we
21187 further recommend embedding a version number into the package name.
21188 This practice will enable @value{GDBN} to load multiple versions of
21189 your pretty-printers at the same time, because they will have
21192 You should write auto-loaded code (@pxref{Auto-loading}) such that it
21193 can be evaluated multiple times without changing its meaning. An
21194 ideal auto-load file will consist solely of @code{import}s of your
21195 printer modules, followed by a call to a register pretty-printers with
21196 the current objfile.
21198 Taken as a whole, this approach will scale nicely to multiple
21199 inferiors, each potentially using a different library version.
21200 Embedding a version number in the Python package name will ensure that
21201 @value{GDBN} is able to load both sets of printers simultaneously.
21202 Then, because the search for pretty-printers is done by objfile, and
21203 because your auto-loaded code took care to register your library's
21204 printers with a specific objfile, @value{GDBN} will find the correct
21205 printers for the specific version of the library used by each
21208 To continue the @code{std::string} example (@pxref{Pretty Printing API}),
21209 this code might appear in @code{gdb.libstdcxx.v6}:
21212 def register_printers (objfile):
21213 objfile.pretty_printers.add (str_lookup_function)
21217 And then the corresponding contents of the auto-load file would be:
21220 import gdb.libstdcxx.v6
21221 gdb.libstdcxx.v6.register_printers (gdb.current_objfile ())
21224 @node Disabling Pretty-Printers
21225 @subsubsection Disabling Pretty-Printers
21226 @cindex disabling pretty-printers
21228 For various reasons a pretty-printer may not work.
21229 For example, the underlying data structure may have changed and
21230 the pretty-printer is out of date.
21232 The consequences of a broken pretty-printer are severe enough that
21233 @value{GDBN} provides support for enabling and disabling individual
21234 printers. For example, if @code{print frame-arguments} is on,
21235 a backtrace can become highly illegible if any argument is printed
21236 with a broken printer.
21238 Pretty-printers are enabled and disabled by attaching an @code{enabled}
21239 attribute to the registered function or callable object. If this attribute
21240 is present and its value is @code{False}, the printer is disabled, otherwise
21241 the printer is enabled.
21243 @node Inferiors In Python
21244 @subsubsection Inferiors In Python
21245 @cindex inferiors in python
21247 @findex gdb.Inferior
21248 Programs which are being run under @value{GDBN} are called inferiors
21249 (@pxref{Inferiors and Programs}). Python scripts can access
21250 information about and manipulate inferiors controlled by @value{GDBN}
21251 via objects of the @code{gdb.Inferior} class.
21253 The following inferior-related functions are available in the @code{gdb}
21257 Return a tuple containing all inferior objects.
21260 A @code{gdb.Inferior} object has the following attributes:
21263 @defivar Inferior num
21264 ID of inferior, as assigned by GDB.
21267 @defivar Inferior pid
21268 Process ID of the inferior, as assigned by the underlying operating
21272 @defivar Inferior was_attached
21273 Boolean signaling whether the inferior was created using `attach', or
21274 started by @value{GDBN} itself.
21278 A @code{gdb.Inferior} object has the following methods:
21281 @defmethod Inferior threads
21282 This method returns a tuple holding all the threads which are valid
21283 when it is called. If there are no valid threads, the method will
21284 return an empty tuple.
21287 @findex gdb.read_memory
21288 @defmethod Inferior read_memory address length
21289 Read @var{length} bytes of memory from the inferior, starting at
21290 @var{address}. Returns a buffer object, which behaves much like an array
21291 or a string. It can be modified and given to the @code{gdb.write_memory}
21295 @findex gdb.write_memory
21296 @defmethod Inferior write_memory address buffer @r{[}length@r{]}
21297 Write the contents of @var{buffer} to the inferior, starting at
21298 @var{address}. The @var{buffer} parameter must be a Python object
21299 which supports the buffer protocol, i.e., a string, an array or the
21300 object returned from @code{gdb.read_memory}. If given, @var{length}
21301 determines the number of bytes from @var{buffer} to be written.
21304 @findex gdb.search_memory
21305 @defmethod Inferior search_memory address length pattern
21306 Search a region of the inferior memory starting at @var{address} with
21307 the given @var{length} using the search pattern supplied in
21308 @var{pattern}. The @var{pattern} parameter must be a Python object
21309 which supports the buffer protocol, i.e., a string, an array or the
21310 object returned from @code{gdb.read_memory}. Returns a Python @code{Long}
21311 containing the address where the pattern was found, or @code{None} if
21312 the pattern could not be found.
21316 @node Threads In Python
21317 @subsubsection Threads In Python
21318 @cindex threads in python
21320 @findex gdb.InferiorThread
21321 Python scripts can access information about, and manipulate inferior threads
21322 controlled by @value{GDBN}, via objects of the @code{gdb.InferiorThread} class.
21324 The following thread-related functions are available in the @code{gdb}
21327 @findex gdb.selected_thread
21328 @defun selected_thread
21329 This function returns the thread object for the selected thread. If there
21330 is no selected thread, this will return @code{None}.
21333 A @code{gdb.InferiorThread} object has the following attributes:
21336 @defivar InferiorThread num
21337 ID of the thread, as assigned by GDB.
21340 @defivar InferiorThread ptid
21341 ID of the thread, as assigned by the operating system. This attribute is a
21342 tuple containing three integers. The first is the Process ID (PID); the second
21343 is the Lightweight Process ID (LWPID), and the third is the Thread ID (TID).
21344 Either the LWPID or TID may be 0, which indicates that the operating system
21345 does not use that identifier.
21349 A @code{gdb.InferiorThread} object has the following methods:
21352 @defmethod InferiorThread switch
21353 This changes @value{GDBN}'s currently selected thread to the one represented
21357 @defmethod InferiorThread is_stopped
21358 Return a Boolean indicating whether the thread is stopped.
21361 @defmethod InferiorThread is_running
21362 Return a Boolean indicating whether the thread is running.
21365 @defmethod InferiorThread is_exited
21366 Return a Boolean indicating whether the thread is exited.
21370 @node Commands In Python
21371 @subsubsection Commands In Python
21373 @cindex commands in python
21374 @cindex python commands
21375 You can implement new @value{GDBN} CLI commands in Python. A CLI
21376 command is implemented using an instance of the @code{gdb.Command}
21377 class, most commonly using a subclass.
21379 @defmethod Command __init__ name @var{command_class} @r{[}@var{completer_class}@r{]} @r{[}@var{prefix}@r{]}
21380 The object initializer for @code{Command} registers the new command
21381 with @value{GDBN}. This initializer is normally invoked from the
21382 subclass' own @code{__init__} method.
21384 @var{name} is the name of the command. If @var{name} consists of
21385 multiple words, then the initial words are looked for as prefix
21386 commands. In this case, if one of the prefix commands does not exist,
21387 an exception is raised.
21389 There is no support for multi-line commands.
21391 @var{command_class} should be one of the @samp{COMMAND_} constants
21392 defined below. This argument tells @value{GDBN} how to categorize the
21393 new command in the help system.
21395 @var{completer_class} is an optional argument. If given, it should be
21396 one of the @samp{COMPLETE_} constants defined below. This argument
21397 tells @value{GDBN} how to perform completion for this command. If not
21398 given, @value{GDBN} will attempt to complete using the object's
21399 @code{complete} method (see below); if no such method is found, an
21400 error will occur when completion is attempted.
21402 @var{prefix} is an optional argument. If @code{True}, then the new
21403 command is a prefix command; sub-commands of this command may be
21406 The help text for the new command is taken from the Python
21407 documentation string for the command's class, if there is one. If no
21408 documentation string is provided, the default value ``This command is
21409 not documented.'' is used.
21412 @cindex don't repeat Python command
21413 @defmethod Command dont_repeat
21414 By default, a @value{GDBN} command is repeated when the user enters a
21415 blank line at the command prompt. A command can suppress this
21416 behavior by invoking the @code{dont_repeat} method. This is similar
21417 to the user command @code{dont-repeat}, see @ref{Define, dont-repeat}.
21420 @defmethod Command invoke argument from_tty
21421 This method is called by @value{GDBN} when this command is invoked.
21423 @var{argument} is a string. It is the argument to the command, after
21424 leading and trailing whitespace has been stripped.
21426 @var{from_tty} is a boolean argument. When true, this means that the
21427 command was entered by the user at the terminal; when false it means
21428 that the command came from elsewhere.
21430 If this method throws an exception, it is turned into a @value{GDBN}
21431 @code{error} call. Otherwise, the return value is ignored.
21433 @findex gdb.string_to_argv
21434 To break @var{argument} up into an argv-like string use
21435 @code{gdb.string_to_argv}. This function behaves identically to
21436 @value{GDBN}'s internal argument lexer @code{buildargv}.
21437 It is recommended to use this for consistency.
21438 Arguments are separated by spaces and may be quoted.
21442 print gdb.string_to_argv ("1 2\ \\\"3 '4 \"5' \"6 '7\"")
21443 ['1', '2 "3', '4 "5', "6 '7"]
21448 @cindex completion of Python commands
21449 @defmethod Command complete text word
21450 This method is called by @value{GDBN} when the user attempts
21451 completion on this command. All forms of completion are handled by
21452 this method, that is, the @key{TAB} and @key{M-?} key bindings
21453 (@pxref{Completion}), and the @code{complete} command (@pxref{Help,
21456 The arguments @var{text} and @var{word} are both strings. @var{text}
21457 holds the complete command line up to the cursor's location.
21458 @var{word} holds the last word of the command line; this is computed
21459 using a word-breaking heuristic.
21461 The @code{complete} method can return several values:
21464 If the return value is a sequence, the contents of the sequence are
21465 used as the completions. It is up to @code{complete} to ensure that the
21466 contents actually do complete the word. A zero-length sequence is
21467 allowed, it means that there were no completions available. Only
21468 string elements of the sequence are used; other elements in the
21469 sequence are ignored.
21472 If the return value is one of the @samp{COMPLETE_} constants defined
21473 below, then the corresponding @value{GDBN}-internal completion
21474 function is invoked, and its result is used.
21477 All other results are treated as though there were no available
21482 When a new command is registered, it must be declared as a member of
21483 some general class of commands. This is used to classify top-level
21484 commands in the on-line help system; note that prefix commands are not
21485 listed under their own category but rather that of their top-level
21486 command. The available classifications are represented by constants
21487 defined in the @code{gdb} module:
21490 @findex COMMAND_NONE
21491 @findex gdb.COMMAND_NONE
21493 The command does not belong to any particular class. A command in
21494 this category will not be displayed in any of the help categories.
21496 @findex COMMAND_RUNNING
21497 @findex gdb.COMMAND_RUNNING
21498 @item COMMAND_RUNNING
21499 The command is related to running the inferior. For example,
21500 @code{start}, @code{step}, and @code{continue} are in this category.
21501 Type @kbd{help running} at the @value{GDBN} prompt to see a list of
21502 commands in this category.
21504 @findex COMMAND_DATA
21505 @findex gdb.COMMAND_DATA
21507 The command is related to data or variables. For example,
21508 @code{call}, @code{find}, and @code{print} are in this category. Type
21509 @kbd{help data} at the @value{GDBN} prompt to see a list of commands
21512 @findex COMMAND_STACK
21513 @findex gdb.COMMAND_STACK
21514 @item COMMAND_STACK
21515 The command has to do with manipulation of the stack. For example,
21516 @code{backtrace}, @code{frame}, and @code{return} are in this
21517 category. Type @kbd{help stack} at the @value{GDBN} prompt to see a
21518 list of commands in this category.
21520 @findex COMMAND_FILES
21521 @findex gdb.COMMAND_FILES
21522 @item COMMAND_FILES
21523 This class is used for file-related commands. For example,
21524 @code{file}, @code{list} and @code{section} are in this category.
21525 Type @kbd{help files} at the @value{GDBN} prompt to see a list of
21526 commands in this category.
21528 @findex COMMAND_SUPPORT
21529 @findex gdb.COMMAND_SUPPORT
21530 @item COMMAND_SUPPORT
21531 This should be used for ``support facilities'', generally meaning
21532 things that are useful to the user when interacting with @value{GDBN},
21533 but not related to the state of the inferior. For example,
21534 @code{help}, @code{make}, and @code{shell} are in this category. Type
21535 @kbd{help support} at the @value{GDBN} prompt to see a list of
21536 commands in this category.
21538 @findex COMMAND_STATUS
21539 @findex gdb.COMMAND_STATUS
21540 @item COMMAND_STATUS
21541 The command is an @samp{info}-related command, that is, related to the
21542 state of @value{GDBN} itself. For example, @code{info}, @code{macro},
21543 and @code{show} are in this category. Type @kbd{help status} at the
21544 @value{GDBN} prompt to see a list of commands in this category.
21546 @findex COMMAND_BREAKPOINTS
21547 @findex gdb.COMMAND_BREAKPOINTS
21548 @item COMMAND_BREAKPOINTS
21549 The command has to do with breakpoints. For example, @code{break},
21550 @code{clear}, and @code{delete} are in this category. Type @kbd{help
21551 breakpoints} at the @value{GDBN} prompt to see a list of commands in
21554 @findex COMMAND_TRACEPOINTS
21555 @findex gdb.COMMAND_TRACEPOINTS
21556 @item COMMAND_TRACEPOINTS
21557 The command has to do with tracepoints. For example, @code{trace},
21558 @code{actions}, and @code{tfind} are in this category. Type
21559 @kbd{help tracepoints} at the @value{GDBN} prompt to see a list of
21560 commands in this category.
21562 @findex COMMAND_OBSCURE
21563 @findex gdb.COMMAND_OBSCURE
21564 @item COMMAND_OBSCURE
21565 The command is only used in unusual circumstances, or is not of
21566 general interest to users. For example, @code{checkpoint},
21567 @code{fork}, and @code{stop} are in this category. Type @kbd{help
21568 obscure} at the @value{GDBN} prompt to see a list of commands in this
21571 @findex COMMAND_MAINTENANCE
21572 @findex gdb.COMMAND_MAINTENANCE
21573 @item COMMAND_MAINTENANCE
21574 The command is only useful to @value{GDBN} maintainers. The
21575 @code{maintenance} and @code{flushregs} commands are in this category.
21576 Type @kbd{help internals} at the @value{GDBN} prompt to see a list of
21577 commands in this category.
21580 A new command can use a predefined completion function, either by
21581 specifying it via an argument at initialization, or by returning it
21582 from the @code{complete} method. These predefined completion
21583 constants are all defined in the @code{gdb} module:
21586 @findex COMPLETE_NONE
21587 @findex gdb.COMPLETE_NONE
21588 @item COMPLETE_NONE
21589 This constant means that no completion should be done.
21591 @findex COMPLETE_FILENAME
21592 @findex gdb.COMPLETE_FILENAME
21593 @item COMPLETE_FILENAME
21594 This constant means that filename completion should be performed.
21596 @findex COMPLETE_LOCATION
21597 @findex gdb.COMPLETE_LOCATION
21598 @item COMPLETE_LOCATION
21599 This constant means that location completion should be done.
21600 @xref{Specify Location}.
21602 @findex COMPLETE_COMMAND
21603 @findex gdb.COMPLETE_COMMAND
21604 @item COMPLETE_COMMAND
21605 This constant means that completion should examine @value{GDBN}
21608 @findex COMPLETE_SYMBOL
21609 @findex gdb.COMPLETE_SYMBOL
21610 @item COMPLETE_SYMBOL
21611 This constant means that completion should be done using symbol names
21615 The following code snippet shows how a trivial CLI command can be
21616 implemented in Python:
21619 class HelloWorld (gdb.Command):
21620 """Greet the whole world."""
21622 def __init__ (self):
21623 super (HelloWorld, self).__init__ ("hello-world", gdb.COMMAND_OBSCURE)
21625 def invoke (self, arg, from_tty):
21626 print "Hello, World!"
21631 The last line instantiates the class, and is necessary to trigger the
21632 registration of the command with @value{GDBN}. Depending on how the
21633 Python code is read into @value{GDBN}, you may need to import the
21634 @code{gdb} module explicitly.
21636 @node Parameters In Python
21637 @subsubsection Parameters In Python
21639 @cindex parameters in python
21640 @cindex python parameters
21641 @tindex gdb.Parameter
21643 You can implement new @value{GDBN} parameters using Python. A new
21644 parameter is implemented as an instance of the @code{gdb.Parameter}
21647 Parameters are exposed to the user via the @code{set} and
21648 @code{show} commands. @xref{Help}.
21650 There are many parameters that already exist and can be set in
21651 @value{GDBN}. Two examples are: @code{set follow fork} and
21652 @code{set charset}. Setting these parameters influences certain
21653 behavior in @value{GDBN}. Similarly, you can define parameters that
21654 can be used to influence behavior in custom Python scripts and commands.
21656 @defmethod Parameter __init__ name @var{command-class} @var{parameter-class} @r{[}@var{enum-sequence}@r{]}
21657 The object initializer for @code{Parameter} registers the new
21658 parameter with @value{GDBN}. This initializer is normally invoked
21659 from the subclass' own @code{__init__} method.
21661 @var{name} is the name of the new parameter. If @var{name} consists
21662 of multiple words, then the initial words are looked for as prefix
21663 parameters. An example of this can be illustrated with the
21664 @code{set print} set of parameters. If @var{name} is
21665 @code{print foo}, then @code{print} will be searched as the prefix
21666 parameter. In this case the parameter can subsequently be accessed in
21667 @value{GDBN} as @code{set print foo}.
21669 If @var{name} consists of multiple words, and no prefix parameter group
21670 can be found, an exception is raised.
21672 @var{command-class} should be one of the @samp{COMMAND_} constants
21673 (@pxref{Commands In Python}). This argument tells @value{GDBN} how to
21674 categorize the new parameter in the help system.
21676 @var{parameter-class} should be one of the @samp{PARAM_} constants
21677 defined below. This argument tells @value{GDBN} the type of the new
21678 parameter; this information is used for input validation and
21681 If @var{parameter-class} is @code{PARAM_ENUM}, then
21682 @var{enum-sequence} must be a sequence of strings. These strings
21683 represent the possible values for the parameter.
21685 If @var{parameter-class} is not @code{PARAM_ENUM}, then the presence
21686 of a fourth argument will cause an exception to be thrown.
21688 The help text for the new parameter is taken from the Python
21689 documentation string for the parameter's class, if there is one. If
21690 there is no documentation string, a default value is used.
21693 @defivar Parameter set_doc
21694 If this attribute exists, and is a string, then its value is used as
21695 the help text for this parameter's @code{set} command. The value is
21696 examined when @code{Parameter.__init__} is invoked; subsequent changes
21700 @defivar Parameter show_doc
21701 If this attribute exists, and is a string, then its value is used as
21702 the help text for this parameter's @code{show} command. The value is
21703 examined when @code{Parameter.__init__} is invoked; subsequent changes
21707 @defivar Parameter value
21708 The @code{value} attribute holds the underlying value of the
21709 parameter. It can be read and assigned to just as any other
21710 attribute. @value{GDBN} does validation when assignments are made.
21714 When a new parameter is defined, its type must be specified. The
21715 available types are represented by constants defined in the @code{gdb}
21719 @findex PARAM_BOOLEAN
21720 @findex gdb.PARAM_BOOLEAN
21721 @item PARAM_BOOLEAN
21722 The value is a plain boolean. The Python boolean values, @code{True}
21723 and @code{False} are the only valid values.
21725 @findex PARAM_AUTO_BOOLEAN
21726 @findex gdb.PARAM_AUTO_BOOLEAN
21727 @item PARAM_AUTO_BOOLEAN
21728 The value has three possible states: true, false, and @samp{auto}. In
21729 Python, true and false are represented using boolean constants, and
21730 @samp{auto} is represented using @code{None}.
21732 @findex PARAM_UINTEGER
21733 @findex gdb.PARAM_UINTEGER
21734 @item PARAM_UINTEGER
21735 The value is an unsigned integer. The value of 0 should be
21736 interpreted to mean ``unlimited''.
21738 @findex PARAM_INTEGER
21739 @findex gdb.PARAM_INTEGER
21740 @item PARAM_INTEGER
21741 The value is a signed integer. The value of 0 should be interpreted
21742 to mean ``unlimited''.
21744 @findex PARAM_STRING
21745 @findex gdb.PARAM_STRING
21747 The value is a string. When the user modifies the string, any escape
21748 sequences, such as @samp{\t}, @samp{\f}, and octal escapes, are
21749 translated into corresponding characters and encoded into the current
21752 @findex PARAM_STRING_NOESCAPE
21753 @findex gdb.PARAM_STRING_NOESCAPE
21754 @item PARAM_STRING_NOESCAPE
21755 The value is a string. When the user modifies the string, escapes are
21756 passed through untranslated.
21758 @findex PARAM_OPTIONAL_FILENAME
21759 @findex gdb.PARAM_OPTIONAL_FILENAME
21760 @item PARAM_OPTIONAL_FILENAME
21761 The value is a either a filename (a string), or @code{None}.
21763 @findex PARAM_FILENAME
21764 @findex gdb.PARAM_FILENAME
21765 @item PARAM_FILENAME
21766 The value is a filename. This is just like
21767 @code{PARAM_STRING_NOESCAPE}, but uses file names for completion.
21769 @findex PARAM_ZINTEGER
21770 @findex gdb.PARAM_ZINTEGER
21771 @item PARAM_ZINTEGER
21772 The value is an integer. This is like @code{PARAM_INTEGER}, except 0
21773 is interpreted as itself.
21776 @findex gdb.PARAM_ENUM
21778 The value is a string, which must be one of a collection string
21779 constants provided when the parameter is created.
21782 @node Functions In Python
21783 @subsubsection Writing new convenience functions
21785 @cindex writing convenience functions
21786 @cindex convenience functions in python
21787 @cindex python convenience functions
21788 @tindex gdb.Function
21790 You can implement new convenience functions (@pxref{Convenience Vars})
21791 in Python. A convenience function is an instance of a subclass of the
21792 class @code{gdb.Function}.
21794 @defmethod Function __init__ name
21795 The initializer for @code{Function} registers the new function with
21796 @value{GDBN}. The argument @var{name} is the name of the function,
21797 a string. The function will be visible to the user as a convenience
21798 variable of type @code{internal function}, whose name is the same as
21799 the given @var{name}.
21801 The documentation for the new function is taken from the documentation
21802 string for the new class.
21805 @defmethod Function invoke @var{*args}
21806 When a convenience function is evaluated, its arguments are converted
21807 to instances of @code{gdb.Value}, and then the function's
21808 @code{invoke} method is called. Note that @value{GDBN} does not
21809 predetermine the arity of convenience functions. Instead, all
21810 available arguments are passed to @code{invoke}, following the
21811 standard Python calling convention. In particular, a convenience
21812 function can have default values for parameters without ill effect.
21814 The return value of this method is used as its value in the enclosing
21815 expression. If an ordinary Python value is returned, it is converted
21816 to a @code{gdb.Value} following the usual rules.
21819 The following code snippet shows how a trivial convenience function can
21820 be implemented in Python:
21823 class Greet (gdb.Function):
21824 """Return string to greet someone.
21825 Takes a name as argument."""
21827 def __init__ (self):
21828 super (Greet, self).__init__ ("greet")
21830 def invoke (self, name):
21831 return "Hello, %s!" % name.string ()
21836 The last line instantiates the class, and is necessary to trigger the
21837 registration of the function with @value{GDBN}. Depending on how the
21838 Python code is read into @value{GDBN}, you may need to import the
21839 @code{gdb} module explicitly.
21841 @node Progspaces In Python
21842 @subsubsection Program Spaces In Python
21844 @cindex progspaces in python
21845 @tindex gdb.Progspace
21847 A program space, or @dfn{progspace}, represents a symbolic view
21848 of an address space.
21849 It consists of all of the objfiles of the program.
21850 @xref{Objfiles In Python}.
21851 @xref{Inferiors and Programs, program spaces}, for more details
21852 about program spaces.
21854 The following progspace-related functions are available in the
21857 @findex gdb.current_progspace
21858 @defun current_progspace
21859 This function returns the program space of the currently selected inferior.
21860 @xref{Inferiors and Programs}.
21863 @findex gdb.progspaces
21865 Return a sequence of all the progspaces currently known to @value{GDBN}.
21868 Each progspace is represented by an instance of the @code{gdb.Progspace}
21871 @defivar Progspace filename
21872 The file name of the progspace as a string.
21875 @defivar Progspace pretty_printers
21876 The @code{pretty_printers} attribute is a list of functions. It is
21877 used to look up pretty-printers. A @code{Value} is passed to each
21878 function in order; if the function returns @code{None}, then the
21879 search continues. Otherwise, the return value should be an object
21880 which is used to format the value. @xref{Pretty Printing API}, for more
21884 @node Objfiles In Python
21885 @subsubsection Objfiles In Python
21887 @cindex objfiles in python
21888 @tindex gdb.Objfile
21890 @value{GDBN} loads symbols for an inferior from various
21891 symbol-containing files (@pxref{Files}). These include the primary
21892 executable file, any shared libraries used by the inferior, and any
21893 separate debug info files (@pxref{Separate Debug Files}).
21894 @value{GDBN} calls these symbol-containing files @dfn{objfiles}.
21896 The following objfile-related functions are available in the
21899 @findex gdb.current_objfile
21900 @defun current_objfile
21901 When auto-loading a Python script (@pxref{Auto-loading}), @value{GDBN}
21902 sets the ``current objfile'' to the corresponding objfile. This
21903 function returns the current objfile. If there is no current objfile,
21904 this function returns @code{None}.
21907 @findex gdb.objfiles
21909 Return a sequence of all the objfiles current known to @value{GDBN}.
21910 @xref{Objfiles In Python}.
21913 Each objfile is represented by an instance of the @code{gdb.Objfile}
21916 @defivar Objfile filename
21917 The file name of the objfile as a string.
21920 @defivar Objfile pretty_printers
21921 The @code{pretty_printers} attribute is a list of functions. It is
21922 used to look up pretty-printers. A @code{Value} is passed to each
21923 function in order; if the function returns @code{None}, then the
21924 search continues. Otherwise, the return value should be an object
21925 which is used to format the value. @xref{Pretty Printing API}, for more
21929 @node Frames In Python
21930 @subsubsection Accessing inferior stack frames from Python.
21932 @cindex frames in python
21933 When the debugged program stops, @value{GDBN} is able to analyze its call
21934 stack (@pxref{Frames,,Stack frames}). The @code{gdb.Frame} class
21935 represents a frame in the stack. A @code{gdb.Frame} object is only valid
21936 while its corresponding frame exists in the inferior's stack. If you try
21937 to use an invalid frame object, @value{GDBN} will throw a @code{RuntimeError}
21940 Two @code{gdb.Frame} objects can be compared for equality with the @code{==}
21944 (@value{GDBP}) python print gdb.newest_frame() == gdb.selected_frame ()
21948 The following frame-related functions are available in the @code{gdb} module:
21950 @findex gdb.selected_frame
21951 @defun selected_frame
21952 Return the selected frame object. (@pxref{Selection,,Selecting a Frame}).
21955 @defun frame_stop_reason_string reason
21956 Return a string explaining the reason why @value{GDBN} stopped unwinding
21957 frames, as expressed by the given @var{reason} code (an integer, see the
21958 @code{unwind_stop_reason} method further down in this section).
21961 A @code{gdb.Frame} object has the following methods:
21964 @defmethod Frame is_valid
21965 Returns true if the @code{gdb.Frame} object is valid, false if not.
21966 A frame object can become invalid if the frame it refers to doesn't
21967 exist anymore in the inferior. All @code{gdb.Frame} methods will throw
21968 an exception if it is invalid at the time the method is called.
21971 @defmethod Frame name
21972 Returns the function name of the frame, or @code{None} if it can't be
21976 @defmethod Frame type
21977 Returns the type of the frame. The value can be one of
21978 @code{gdb.NORMAL_FRAME}, @code{gdb.DUMMY_FRAME}, @code{gdb.SIGTRAMP_FRAME}
21979 or @code{gdb.SENTINEL_FRAME}.
21982 @defmethod Frame unwind_stop_reason
21983 Return an integer representing the reason why it's not possible to find
21984 more frames toward the outermost frame. Use
21985 @code{gdb.frame_stop_reason_string} to convert the value returned by this
21986 function to a string.
21989 @defmethod Frame pc
21990 Returns the frame's resume address.
21993 @defmethod Frame block
21994 Return the frame's code block. @xref{Blocks In Python}.
21997 @defmethod Frame function
21998 Return the symbol for the function corresponding to this frame.
21999 @xref{Symbols In Python}.
22002 @defmethod Frame older
22003 Return the frame that called this frame.
22006 @defmethod Frame newer
22007 Return the frame called by this frame.
22010 @defmethod Frame find_sal
22011 Return the frame's symtab and line object.
22012 @xref{Symbol Tables In Python}.
22015 @defmethod Frame read_var variable @r{[}block@r{]}
22016 Return the value of @var{variable} in this frame. If the optional
22017 argument @var{block} is provided, search for the variable from that
22018 block; otherwise start at the frame's current block (which is
22019 determined by the frame's current program counter). @var{variable}
22020 must be a string or a @code{gdb.Symbol} object. @var{block} must be a
22021 @code{gdb.Block} object.
22024 @defmethod Frame select
22025 Set this frame to be the selected frame. @xref{Stack, ,Examining the
22030 @node Blocks In Python
22031 @subsubsection Accessing frame blocks from Python.
22033 @cindex blocks in python
22036 Within each frame, @value{GDBN} maintains information on each block
22037 stored in that frame. These blocks are organized hierarchically, and
22038 are represented individually in Python as a @code{gdb.Block}.
22039 Please see @ref{Frames In Python}, for a more in-depth discussion on
22040 frames. Furthermore, see @ref{Stack, ,Examining the Stack}, for more
22041 detailed technical information on @value{GDBN}'s book-keeping of the
22044 The following block-related functions are available in the @code{gdb}
22047 @findex gdb.block_for_pc
22048 @defun block_for_pc pc
22049 Return the @code{gdb.Block} containing the given @var{pc} value. If the
22050 block cannot be found for the @var{pc} value specified, the function
22051 will return @code{None}.
22054 A @code{gdb.Block} object has the following attributes:
22057 @defivar Block start
22058 The start address of the block. This attribute is not writable.
22062 The end address of the block. This attribute is not writable.
22065 @defivar Block function
22066 The name of the block represented as a @code{gdb.Symbol}. If the
22067 block is not named, then this attribute holds @code{None}. This
22068 attribute is not writable.
22071 @defivar Block superblock
22072 The block containing this block. If this parent block does not exist,
22073 this attribute holds @code{None}. This attribute is not writable.
22077 @node Symbols In Python
22078 @subsubsection Python representation of Symbols.
22080 @cindex symbols in python
22083 @value{GDBN} represents every variable, function and type as an
22084 entry in a symbol table. @xref{Symbols, ,Examining the Symbol Table}.
22085 Similarly, Python represents these symbols in @value{GDBN} with the
22086 @code{gdb.Symbol} object.
22088 The following symbol-related functions are available in the @code{gdb}
22091 @findex gdb.lookup_symbol
22092 @defun lookup_symbol name [block] [domain]
22093 This function searches for a symbol by name. The search scope can be
22094 restricted to the parameters defined in the optional domain and block
22097 @var{name} is the name of the symbol. It must be a string. The
22098 optional @var{block} argument restricts the search to symbols visible
22099 in that @var{block}. The @var{block} argument must be a
22100 @code{gdb.Block} object. The optional @var{domain} argument restricts
22101 the search to the domain type. The @var{domain} argument must be a
22102 domain constant defined in the @code{gdb} module and described later
22106 A @code{gdb.Symbol} object has the following attributes:
22109 @defivar Symbol symtab
22110 The symbol table in which the symbol appears. This attribute is
22111 represented as a @code{gdb.Symtab} object. @xref{Symbol Tables In
22112 Python}. This attribute is not writable.
22115 @defivar Symbol name
22116 The name of the symbol as a string. This attribute is not writable.
22119 @defivar Symbol linkage_name
22120 The name of the symbol, as used by the linker (i.e., may be mangled).
22121 This attribute is not writable.
22124 @defivar Symbol print_name
22125 The name of the symbol in a form suitable for output. This is either
22126 @code{name} or @code{linkage_name}, depending on whether the user
22127 asked @value{GDBN} to display demangled or mangled names.
22130 @defivar Symbol addr_class
22131 The address class of the symbol. This classifies how to find the value
22132 of a symbol. Each address class is a constant defined in the
22133 @code{gdb} module and described later in this chapter.
22136 @defivar Symbol is_argument
22137 @code{True} if the symbol is an argument of a function.
22140 @defivar Symbol is_constant
22141 @code{True} if the symbol is a constant.
22144 @defivar Symbol is_function
22145 @code{True} if the symbol is a function or a method.
22148 @defivar Symbol is_variable
22149 @code{True} if the symbol is a variable.
22153 The available domain categories in @code{gdb.Symbol} are represented
22154 as constants in the @code{gdb} module:
22157 @findex SYMBOL_UNDEF_DOMAIN
22158 @findex gdb.SYMBOL_UNDEF_DOMAIN
22159 @item SYMBOL_UNDEF_DOMAIN
22160 This is used when a domain has not been discovered or none of the
22161 following domains apply. This usually indicates an error either
22162 in the symbol information or in @value{GDBN}'s handling of symbols.
22163 @findex SYMBOL_VAR_DOMAIN
22164 @findex gdb.SYMBOL_VAR_DOMAIN
22165 @item SYMBOL_VAR_DOMAIN
22166 This domain contains variables, function names, typedef names and enum
22168 @findex SYMBOL_STRUCT_DOMAIN
22169 @findex gdb.SYMBOL_STRUCT_DOMAIN
22170 @item SYMBOL_STRUCT_DOMAIN
22171 This domain holds struct, union and enum type names.
22172 @findex SYMBOL_LABEL_DOMAIN
22173 @findex gdb.SYMBOL_LABEL_DOMAIN
22174 @item SYMBOL_LABEL_DOMAIN
22175 This domain contains names of labels (for gotos).
22176 @findex SYMBOL_VARIABLES_DOMAIN
22177 @findex gdb.SYMBOL_VARIABLES_DOMAIN
22178 @item SYMBOL_VARIABLES_DOMAIN
22179 This domain holds a subset of the @code{SYMBOLS_VAR_DOMAIN}; it
22180 contains everything minus functions and types.
22181 @findex SYMBOL_FUNCTIONS_DOMAIN
22182 @findex gdb.SYMBOL_FUNCTIONS_DOMAIN
22183 @item SYMBOL_FUNCTION_DOMAIN
22184 This domain contains all functions.
22185 @findex SYMBOL_TYPES_DOMAIN
22186 @findex gdb.SYMBOL_TYPES_DOMAIN
22187 @item SYMBOL_TYPES_DOMAIN
22188 This domain contains all types.
22191 The available address class categories in @code{gdb.Symbol} are represented
22192 as constants in the @code{gdb} module:
22195 @findex SYMBOL_LOC_UNDEF
22196 @findex gdb.SYMBOL_LOC_UNDEF
22197 @item SYMBOL_LOC_UNDEF
22198 If this is returned by address class, it indicates an error either in
22199 the symbol information or in @value{GDBN}'s handling of symbols.
22200 @findex SYMBOL_LOC_CONST
22201 @findex gdb.SYMBOL_LOC_CONST
22202 @item SYMBOL_LOC_CONST
22203 Value is constant int.
22204 @findex SYMBOL_LOC_STATIC
22205 @findex gdb.SYMBOL_LOC_STATIC
22206 @item SYMBOL_LOC_STATIC
22207 Value is at a fixed address.
22208 @findex SYMBOL_LOC_REGISTER
22209 @findex gdb.SYMBOL_LOC_REGISTER
22210 @item SYMBOL_LOC_REGISTER
22211 Value is in a register.
22212 @findex SYMBOL_LOC_ARG
22213 @findex gdb.SYMBOL_LOC_ARG
22214 @item SYMBOL_LOC_ARG
22215 Value is an argument. This value is at the offset stored within the
22216 symbol inside the frame's argument list.
22217 @findex SYMBOL_LOC_REF_ARG
22218 @findex gdb.SYMBOL_LOC_REF_ARG
22219 @item SYMBOL_LOC_REF_ARG
22220 Value address is stored in the frame's argument list. Just like
22221 @code{LOC_ARG} except that the value's address is stored at the
22222 offset, not the value itself.
22223 @findex SYMBOL_LOC_REGPARM_ADDR
22224 @findex gdb.SYMBOL_LOC_REGPARM_ADDR
22225 @item SYMBOL_LOC_REGPARM_ADDR
22226 Value is a specified register. Just like @code{LOC_REGISTER} except
22227 the register holds the address of the argument instead of the argument
22229 @findex SYMBOL_LOC_LOCAL
22230 @findex gdb.SYMBOL_LOC_LOCAL
22231 @item SYMBOL_LOC_LOCAL
22232 Value is a local variable.
22233 @findex SYMBOL_LOC_TYPEDEF
22234 @findex gdb.SYMBOL_LOC_TYPEDEF
22235 @item SYMBOL_LOC_TYPEDEF
22236 Value not used. Symbols in the domain @code{SYMBOL_STRUCT_DOMAIN} all
22238 @findex SYMBOL_LOC_BLOCK
22239 @findex gdb.SYMBOL_LOC_BLOCK
22240 @item SYMBOL_LOC_BLOCK
22242 @findex SYMBOL_LOC_CONST_BYTES
22243 @findex gdb.SYMBOL_LOC_CONST_BYTES
22244 @item SYMBOL_LOC_CONST_BYTES
22245 Value is a byte-sequence.
22246 @findex SYMBOL_LOC_UNRESOLVED
22247 @findex gdb.SYMBOL_LOC_UNRESOLVED
22248 @item SYMBOL_LOC_UNRESOLVED
22249 Value is at a fixed address, but the address of the variable has to be
22250 determined from the minimal symbol table whenever the variable is
22252 @findex SYMBOL_LOC_OPTIMIZED_OUT
22253 @findex gdb.SYMBOL_LOC_OPTIMIZED_OUT
22254 @item SYMBOL_LOC_OPTIMIZED_OUT
22255 The value does not actually exist in the program.
22256 @findex SYMBOL_LOC_COMPUTED
22257 @findex gdb.SYMBOL_LOC_COMPUTED
22258 @item SYMBOL_LOC_COMPUTED
22259 The value's address is a computed location.
22262 @node Symbol Tables In Python
22263 @subsubsection Symbol table representation in Python.
22265 @cindex symbol tables in python
22267 @tindex gdb.Symtab_and_line
22269 Access to symbol table data maintained by @value{GDBN} on the inferior
22270 is exposed to Python via two objects: @code{gdb.Symtab_and_line} and
22271 @code{gdb.Symtab}. Symbol table and line data for a frame is returned
22272 from the @code{find_sal} method in @code{gdb.Frame} object.
22273 @xref{Frames In Python}.
22275 For more information on @value{GDBN}'s symbol table management, see
22276 @ref{Symbols, ,Examining the Symbol Table}, for more information.
22278 A @code{gdb.Symtab_and_line} object has the following attributes:
22281 @defivar Symtab_and_line symtab
22282 The symbol table object (@code{gdb.Symtab}) for this frame.
22283 This attribute is not writable.
22286 @defivar Symtab_and_line pc
22287 Indicates the current program counter address. This attribute is not
22291 @defivar Symtab_and_line line
22292 Indicates the current line number for this object. This
22293 attribute is not writable.
22297 A @code{gdb.Symtab} object has the following attributes:
22300 @defivar Symtab filename
22301 The symbol table's source filename. This attribute is not writable.
22304 @defivar Symtab objfile
22305 The symbol table's backing object file. @xref{Objfiles In Python}.
22306 This attribute is not writable.
22310 The following methods are provided:
22313 @defmethod Symtab fullname
22314 Return the symbol table's source absolute file name.
22318 @node Breakpoints In Python
22319 @subsubsection Manipulating breakpoints using Python
22321 @cindex breakpoints in python
22322 @tindex gdb.Breakpoint
22324 Python code can manipulate breakpoints via the @code{gdb.Breakpoint}
22327 @defmethod Breakpoint __init__ spec @r{[}type@r{]} @r{[}wp_class@r{]}
22328 Create a new breakpoint. @var{spec} is a string naming the
22329 location of the breakpoint, or an expression that defines a
22330 watchpoint. The contents can be any location recognized by the
22331 @code{break} command, or in the case of a watchpoint, by the @code{watch}
22332 command. The optional @var{type} denotes the breakpoint to create
22333 from the types defined later in this chapter. This argument can be
22334 either: @code{BP_BREAKPOINT} or @code{BP_WATCHPOINT}. @var{type}
22335 defaults to @code{BP_BREAKPOINT}. The optional @var{wp_class}
22336 argument defines the class of watchpoint to create, if @var{type} is
22337 defined as @code{BP_WATCHPOINT}. If a watchpoint class is not
22338 provided, it is assumed to be a @var{WP_WRITE} class.
22341 The available watchpoint types represented by constants are defined in the
22346 @findex gdb.WP_READ
22348 Read only watchpoint.
22351 @findex gdb.WP_WRITE
22353 Write only watchpoint.
22356 @findex gdb.WP_ACCESS
22358 Read/Write watchpoint.
22361 @defmethod Breakpoint is_valid
22362 Return @code{True} if this @code{Breakpoint} object is valid,
22363 @code{False} otherwise. A @code{Breakpoint} object can become invalid
22364 if the user deletes the breakpoint. In this case, the object still
22365 exists, but the underlying breakpoint does not. In the cases of
22366 watchpoint scope, the watchpoint remains valid even if execution of the
22367 inferior leaves the scope of that watchpoint.
22370 @defivar Breakpoint enabled
22371 This attribute is @code{True} if the breakpoint is enabled, and
22372 @code{False} otherwise. This attribute is writable.
22375 @defivar Breakpoint silent
22376 This attribute is @code{True} if the breakpoint is silent, and
22377 @code{False} otherwise. This attribute is writable.
22379 Note that a breakpoint can also be silent if it has commands and the
22380 first command is @code{silent}. This is not reported by the
22381 @code{silent} attribute.
22384 @defivar Breakpoint thread
22385 If the breakpoint is thread-specific, this attribute holds the thread
22386 id. If the breakpoint is not thread-specific, this attribute is
22387 @code{None}. This attribute is writable.
22390 @defivar Breakpoint task
22391 If the breakpoint is Ada task-specific, this attribute holds the Ada task
22392 id. If the breakpoint is not task-specific (or the underlying
22393 language is not Ada), this attribute is @code{None}. This attribute
22397 @defivar Breakpoint ignore_count
22398 This attribute holds the ignore count for the breakpoint, an integer.
22399 This attribute is writable.
22402 @defivar Breakpoint number
22403 This attribute holds the breakpoint's number --- the identifier used by
22404 the user to manipulate the breakpoint. This attribute is not writable.
22407 @defivar Breakpoint type
22408 This attribute holds the breakpoint's type --- the identifier used to
22409 determine the actual breakpoint type or use-case. This attribute is not
22413 The available types are represented by constants defined in the @code{gdb}
22417 @findex BP_BREAKPOINT
22418 @findex gdb.BP_BREAKPOINT
22419 @item BP_BREAKPOINT
22420 Normal code breakpoint.
22422 @findex BP_WATCHPOINT
22423 @findex gdb.BP_WATCHPOINT
22424 @item BP_WATCHPOINT
22425 Watchpoint breakpoint.
22427 @findex BP_HARDWARE_WATCHPOINT
22428 @findex gdb.BP_HARDWARE_WATCHPOINT
22429 @item BP_HARDWARE_WATCHPOINT
22430 Hardware assisted watchpoint.
22432 @findex BP_READ_WATCHPOINT
22433 @findex gdb.BP_READ_WATCHPOINT
22434 @item BP_READ_WATCHPOINT
22435 Hardware assisted read watchpoint.
22437 @findex BP_ACCESS_WATCHPOINT
22438 @findex gdb.BP_ACCESS_WATCHPOINT
22439 @item BP_ACCESS_WATCHPOINT
22440 Hardware assisted access watchpoint.
22443 @defivar Breakpoint hit_count
22444 This attribute holds the hit count for the breakpoint, an integer.
22445 This attribute is writable, but currently it can only be set to zero.
22448 @defivar Breakpoint location
22449 This attribute holds the location of the breakpoint, as specified by
22450 the user. It is a string. If the breakpoint does not have a location
22451 (that is, it is a watchpoint) the attribute's value is @code{None}. This
22452 attribute is not writable.
22455 @defivar Breakpoint expression
22456 This attribute holds a breakpoint expression, as specified by
22457 the user. It is a string. If the breakpoint does not have an
22458 expression (the breakpoint is not a watchpoint) the attribute's value
22459 is @code{None}. This attribute is not writable.
22462 @defivar Breakpoint condition
22463 This attribute holds the condition of the breakpoint, as specified by
22464 the user. It is a string. If there is no condition, this attribute's
22465 value is @code{None}. This attribute is writable.
22468 @defivar Breakpoint commands
22469 This attribute holds the commands attached to the breakpoint. If
22470 there are commands, this attribute's value is a string holding all the
22471 commands, separated by newlines. If there are no commands, this
22472 attribute is @code{None}. This attribute is not writable.
22475 @node Lazy Strings In Python
22476 @subsubsection Python representation of lazy strings.
22478 @cindex lazy strings in python
22479 @tindex gdb.LazyString
22481 A @dfn{lazy string} is a string whose contents is not retrieved or
22482 encoded until it is needed.
22484 A @code{gdb.LazyString} is represented in @value{GDBN} as an
22485 @code{address} that points to a region of memory, an @code{encoding}
22486 that will be used to encode that region of memory, and a @code{length}
22487 to delimit the region of memory that represents the string. The
22488 difference between a @code{gdb.LazyString} and a string wrapped within
22489 a @code{gdb.Value} is that a @code{gdb.LazyString} will be treated
22490 differently by @value{GDBN} when printing. A @code{gdb.LazyString} is
22491 retrieved and encoded during printing, while a @code{gdb.Value}
22492 wrapping a string is immediately retrieved and encoded on creation.
22494 A @code{gdb.LazyString} object has the following functions:
22496 @defmethod LazyString value
22497 Convert the @code{gdb.LazyString} to a @code{gdb.Value}. This value
22498 will point to the string in memory, but will lose all the delayed
22499 retrieval, encoding and handling that @value{GDBN} applies to a
22500 @code{gdb.LazyString}.
22503 @defivar LazyString address
22504 This attribute holds the address of the string. This attribute is not
22508 @defivar LazyString length
22509 This attribute holds the length of the string in characters. If the
22510 length is -1, then the string will be fetched and encoded up to the
22511 first null of appropriate width. This attribute is not writable.
22514 @defivar LazyString encoding
22515 This attribute holds the encoding that will be applied to the string
22516 when the string is printed by @value{GDBN}. If the encoding is not
22517 set, or contains an empty string, then @value{GDBN} will select the
22518 most appropriate encoding when the string is printed. This attribute
22522 @defivar LazyString type
22523 This attribute holds the type that is represented by the lazy string's
22524 type. For a lazy string this will always be a pointer type. To
22525 resolve this to the lazy string's character type, use the type's
22526 @code{target} method. @xref{Types In Python}. This attribute is not
22531 @subsection Auto-loading
22532 @cindex auto-loading, Python
22534 When a new object file is read (for example, due to the @code{file}
22535 command, or because the inferior has loaded a shared library),
22536 @value{GDBN} will look for Python support scripts in several ways:
22537 @file{@var{objfile}-gdb.py} and @code{.debug_gdb_scripts} section.
22540 * objfile-gdb.py file:: The @file{@var{objfile}-gdb.py} file
22541 * .debug_gdb_scripts section:: The @code{.debug_gdb_scripts} section
22542 * Which flavor to choose?::
22545 The auto-loading feature is useful for supplying application-specific
22546 debugging commands and scripts.
22548 Auto-loading can be enabled or disabled.
22551 @kindex maint set python auto-load
22552 @item maint set python auto-load [yes|no]
22553 Enable or disable the Python auto-loading feature.
22555 @kindex maint show python auto-load
22556 @item maint show python auto-load
22557 Show whether Python auto-loading is enabled or disabled.
22560 When reading an auto-loaded file, @value{GDBN} sets the
22561 @dfn{current objfile}. This is available via the @code{gdb.current_objfile}
22562 function (@pxref{Objfiles In Python}). This can be useful for
22563 registering objfile-specific pretty-printers.
22565 @node objfile-gdb.py file
22566 @subsubsection The @file{@var{objfile}-gdb.py} file
22567 @cindex @file{@var{objfile}-gdb.py}
22569 When a new object file is read, @value{GDBN} looks for
22570 a file named @file{@var{objfile}-gdb.py},
22571 where @var{objfile} is the object file's real name, formed by ensuring
22572 that the file name is absolute, following all symlinks, and resolving
22573 @code{.} and @code{..} components. If this file exists and is
22574 readable, @value{GDBN} will evaluate it as a Python script.
22576 If this file does not exist, and if the parameter
22577 @code{debug-file-directory} is set (@pxref{Separate Debug Files}),
22578 then @value{GDBN} will look for @var{real-name} in all of the
22579 directories mentioned in the value of @code{debug-file-directory}.
22581 Finally, if this file does not exist, then @value{GDBN} will look for
22582 a file named @file{@var{data-directory}/python/auto-load/@var{real-name}}, where
22583 @var{data-directory} is @value{GDBN}'s data directory (available via
22584 @code{show data-directory}, @pxref{Data Files}), and @var{real-name}
22585 is the object file's real name, as described above.
22587 @value{GDBN} does not track which files it has already auto-loaded this way.
22588 @value{GDBN} will load the associated script every time the corresponding
22589 @var{objfile} is opened.
22590 So your @file{-gdb.py} file should be careful to avoid errors if it
22591 is evaluated more than once.
22593 @node .debug_gdb_scripts section
22594 @subsubsection The @code{.debug_gdb_scripts} section
22595 @cindex @code{.debug_gdb_scripts} section
22597 For systems using file formats like ELF and COFF,
22598 when @value{GDBN} loads a new object file
22599 it will look for a special section named @samp{.debug_gdb_scripts}.
22600 If this section exists, its contents is a list of names of scripts to load.
22602 @value{GDBN} will look for each specified script file first in the
22603 current directory and then along the source search path
22604 (@pxref{Source Path, ,Specifying Source Directories}),
22605 except that @file{$cdir} is not searched, since the compilation
22606 directory is not relevant to scripts.
22608 Entries can be placed in section @code{.debug_gdb_scripts} with,
22609 for example, this GCC macro:
22612 /* Note: The "MS" section flags are to remote duplicates. */
22613 #define DEFINE_GDB_SCRIPT(script_name) \
22615 .pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n\
22617 .asciz \"" script_name "\"\n\
22623 Then one can reference the macro in a header or source file like this:
22626 DEFINE_GDB_SCRIPT ("my-app-scripts.py")
22629 The script name may include directories if desired.
22631 If the macro is put in a header, any application or library
22632 using this header will get a reference to the specified script.
22634 @node Which flavor to choose?
22635 @subsubsection Which flavor to choose?
22637 Given the multiple ways of auto-loading Python scripts, it might not always
22638 be clear which one to choose. This section provides some guidance.
22640 Benefits of the @file{-gdb.py} way:
22644 Can be used with file formats that don't support multiple sections.
22647 Ease of finding scripts for public libraries.
22649 Scripts specified in the @code{.debug_gdb_scripts} section are searched for
22650 in the source search path.
22651 For publicly installed libraries, e.g., @file{libstdc++}, there typically
22652 isn't a source directory in which to find the script.
22655 Doesn't require source code additions.
22658 Benefits of the @code{.debug_gdb_scripts} way:
22662 Works with static linking.
22664 Scripts for libraries done the @file{-gdb.py} way require an objfile to
22665 trigger their loading. When an application is statically linked the only
22666 objfile available is the executable, and it is cumbersome to attach all the
22667 scripts from all the input libraries to the executable's @file{-gdb.py} script.
22670 Works with classes that are entirely inlined.
22672 Some classes can be entirely inlined, and thus there may not be an associated
22673 shared library to attach a @file{-gdb.py} script to.
22676 Scripts needn't be copied out of the source tree.
22678 In some circumstances, apps can be built out of large collections of internal
22679 libraries, and the build infrastructure necessary to install the
22680 @file{-gdb.py} scripts in a place where @value{GDBN} can find them is
22681 cumbersome. It may be easier to specify the scripts in the
22682 @code{.debug_gdb_scripts} section as relative paths, and add a path to the
22683 top of the source tree to the source search path.
22687 @chapter Command Interpreters
22688 @cindex command interpreters
22690 @value{GDBN} supports multiple command interpreters, and some command
22691 infrastructure to allow users or user interface writers to switch
22692 between interpreters or run commands in other interpreters.
22694 @value{GDBN} currently supports two command interpreters, the console
22695 interpreter (sometimes called the command-line interpreter or @sc{cli})
22696 and the machine interface interpreter (or @sc{gdb/mi}). This manual
22697 describes both of these interfaces in great detail.
22699 By default, @value{GDBN} will start with the console interpreter.
22700 However, the user may choose to start @value{GDBN} with another
22701 interpreter by specifying the @option{-i} or @option{--interpreter}
22702 startup options. Defined interpreters include:
22706 @cindex console interpreter
22707 The traditional console or command-line interpreter. This is the most often
22708 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
22709 @value{GDBN} will use this interpreter.
22712 @cindex mi interpreter
22713 The newest @sc{gdb/mi} interface (currently @code{mi2}). Used primarily
22714 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
22715 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
22719 @cindex mi2 interpreter
22720 The current @sc{gdb/mi} interface.
22723 @cindex mi1 interpreter
22724 The @sc{gdb/mi} interface included in @value{GDBN} 5.1, 5.2, and 5.3.
22728 @cindex invoke another interpreter
22729 The interpreter being used by @value{GDBN} may not be dynamically
22730 switched at runtime. Although possible, this could lead to a very
22731 precarious situation. Consider an IDE using @sc{gdb/mi}. If a user
22732 enters the command "interpreter-set console" in a console view,
22733 @value{GDBN} would switch to using the console interpreter, rendering
22734 the IDE inoperable!
22736 @kindex interpreter-exec
22737 Although you may only choose a single interpreter at startup, you may execute
22738 commands in any interpreter from the current interpreter using the appropriate
22739 command. If you are running the console interpreter, simply use the
22740 @code{interpreter-exec} command:
22743 interpreter-exec mi "-data-list-register-names"
22746 @sc{gdb/mi} has a similar command, although it is only available in versions of
22747 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
22750 @chapter @value{GDBN} Text User Interface
22752 @cindex Text User Interface
22755 * TUI Overview:: TUI overview
22756 * TUI Keys:: TUI key bindings
22757 * TUI Single Key Mode:: TUI single key mode
22758 * TUI Commands:: TUI-specific commands
22759 * TUI Configuration:: TUI configuration variables
22762 The @value{GDBN} Text User Interface (TUI) is a terminal
22763 interface which uses the @code{curses} library to show the source
22764 file, the assembly output, the program registers and @value{GDBN}
22765 commands in separate text windows. The TUI mode is supported only
22766 on platforms where a suitable version of the @code{curses} library
22769 @pindex @value{GDBTUI}
22770 The TUI mode is enabled by default when you invoke @value{GDBN} as
22771 either @samp{@value{GDBTUI}} or @samp{@value{GDBP} -tui}.
22772 You can also switch in and out of TUI mode while @value{GDBN} runs by
22773 using various TUI commands and key bindings, such as @kbd{C-x C-a}.
22774 @xref{TUI Keys, ,TUI Key Bindings}.
22777 @section TUI Overview
22779 In TUI mode, @value{GDBN} can display several text windows:
22783 This window is the @value{GDBN} command window with the @value{GDBN}
22784 prompt and the @value{GDBN} output. The @value{GDBN} input is still
22785 managed using readline.
22788 The source window shows the source file of the program. The current
22789 line and active breakpoints are displayed in this window.
22792 The assembly window shows the disassembly output of the program.
22795 This window shows the processor registers. Registers are highlighted
22796 when their values change.
22799 The source and assembly windows show the current program position
22800 by highlighting the current line and marking it with a @samp{>} marker.
22801 Breakpoints are indicated with two markers. The first marker
22802 indicates the breakpoint type:
22806 Breakpoint which was hit at least once.
22809 Breakpoint which was never hit.
22812 Hardware breakpoint which was hit at least once.
22815 Hardware breakpoint which was never hit.
22818 The second marker indicates whether the breakpoint is enabled or not:
22822 Breakpoint is enabled.
22825 Breakpoint is disabled.
22828 The source, assembly and register windows are updated when the current
22829 thread changes, when the frame changes, or when the program counter
22832 These windows are not all visible at the same time. The command
22833 window is always visible. The others can be arranged in several
22844 source and assembly,
22847 source and registers, or
22850 assembly and registers.
22853 A status line above the command window shows the following information:
22857 Indicates the current @value{GDBN} target.
22858 (@pxref{Targets, ,Specifying a Debugging Target}).
22861 Gives the current process or thread number.
22862 When no process is being debugged, this field is set to @code{No process}.
22865 Gives the current function name for the selected frame.
22866 The name is demangled if demangling is turned on (@pxref{Print Settings}).
22867 When there is no symbol corresponding to the current program counter,
22868 the string @code{??} is displayed.
22871 Indicates the current line number for the selected frame.
22872 When the current line number is not known, the string @code{??} is displayed.
22875 Indicates the current program counter address.
22879 @section TUI Key Bindings
22880 @cindex TUI key bindings
22882 The TUI installs several key bindings in the readline keymaps
22883 (@pxref{Command Line Editing}). The following key bindings
22884 are installed for both TUI mode and the @value{GDBN} standard mode.
22893 Enter or leave the TUI mode. When leaving the TUI mode,
22894 the curses window management stops and @value{GDBN} operates using
22895 its standard mode, writing on the terminal directly. When reentering
22896 the TUI mode, control is given back to the curses windows.
22897 The screen is then refreshed.
22901 Use a TUI layout with only one window. The layout will
22902 either be @samp{source} or @samp{assembly}. When the TUI mode
22903 is not active, it will switch to the TUI mode.
22905 Think of this key binding as the Emacs @kbd{C-x 1} binding.
22909 Use a TUI layout with at least two windows. When the current
22910 layout already has two windows, the next layout with two windows is used.
22911 When a new layout is chosen, one window will always be common to the
22912 previous layout and the new one.
22914 Think of it as the Emacs @kbd{C-x 2} binding.
22918 Change the active window. The TUI associates several key bindings
22919 (like scrolling and arrow keys) with the active window. This command
22920 gives the focus to the next TUI window.
22922 Think of it as the Emacs @kbd{C-x o} binding.
22926 Switch in and out of the TUI SingleKey mode that binds single
22927 keys to @value{GDBN} commands (@pxref{TUI Single Key Mode}).
22930 The following key bindings only work in the TUI mode:
22935 Scroll the active window one page up.
22939 Scroll the active window one page down.
22943 Scroll the active window one line up.
22947 Scroll the active window one line down.
22951 Scroll the active window one column left.
22955 Scroll the active window one column right.
22959 Refresh the screen.
22962 Because the arrow keys scroll the active window in the TUI mode, they
22963 are not available for their normal use by readline unless the command
22964 window has the focus. When another window is active, you must use
22965 other readline key bindings such as @kbd{C-p}, @kbd{C-n}, @kbd{C-b}
22966 and @kbd{C-f} to control the command window.
22968 @node TUI Single Key Mode
22969 @section TUI Single Key Mode
22970 @cindex TUI single key mode
22972 The TUI also provides a @dfn{SingleKey} mode, which binds several
22973 frequently used @value{GDBN} commands to single keys. Type @kbd{C-x s} to
22974 switch into this mode, where the following key bindings are used:
22977 @kindex c @r{(SingleKey TUI key)}
22981 @kindex d @r{(SingleKey TUI key)}
22985 @kindex f @r{(SingleKey TUI key)}
22989 @kindex n @r{(SingleKey TUI key)}
22993 @kindex q @r{(SingleKey TUI key)}
22995 exit the SingleKey mode.
22997 @kindex r @r{(SingleKey TUI key)}
23001 @kindex s @r{(SingleKey TUI key)}
23005 @kindex u @r{(SingleKey TUI key)}
23009 @kindex v @r{(SingleKey TUI key)}
23013 @kindex w @r{(SingleKey TUI key)}
23018 Other keys temporarily switch to the @value{GDBN} command prompt.
23019 The key that was pressed is inserted in the editing buffer so that
23020 it is possible to type most @value{GDBN} commands without interaction
23021 with the TUI SingleKey mode. Once the command is entered the TUI
23022 SingleKey mode is restored. The only way to permanently leave
23023 this mode is by typing @kbd{q} or @kbd{C-x s}.
23027 @section TUI-specific Commands
23028 @cindex TUI commands
23030 The TUI has specific commands to control the text windows.
23031 These commands are always available, even when @value{GDBN} is not in
23032 the TUI mode. When @value{GDBN} is in the standard mode, most
23033 of these commands will automatically switch to the TUI mode.
23035 Note that if @value{GDBN}'s @code{stdout} is not connected to a
23036 terminal, or @value{GDBN} has been started with the machine interface
23037 interpreter (@pxref{GDB/MI, ,The @sc{gdb/mi} Interface}), most of
23038 these commands will fail with an error, because it would not be
23039 possible or desirable to enable curses window management.
23044 List and give the size of all displayed windows.
23048 Display the next layout.
23051 Display the previous layout.
23054 Display the source window only.
23057 Display the assembly window only.
23060 Display the source and assembly window.
23063 Display the register window together with the source or assembly window.
23067 Make the next window active for scrolling.
23070 Make the previous window active for scrolling.
23073 Make the source window active for scrolling.
23076 Make the assembly window active for scrolling.
23079 Make the register window active for scrolling.
23082 Make the command window active for scrolling.
23086 Refresh the screen. This is similar to typing @kbd{C-L}.
23088 @item tui reg float
23090 Show the floating point registers in the register window.
23092 @item tui reg general
23093 Show the general registers in the register window.
23096 Show the next register group. The list of register groups as well as
23097 their order is target specific. The predefined register groups are the
23098 following: @code{general}, @code{float}, @code{system}, @code{vector},
23099 @code{all}, @code{save}, @code{restore}.
23101 @item tui reg system
23102 Show the system registers in the register window.
23106 Update the source window and the current execution point.
23108 @item winheight @var{name} +@var{count}
23109 @itemx winheight @var{name} -@var{count}
23111 Change the height of the window @var{name} by @var{count}
23112 lines. Positive counts increase the height, while negative counts
23115 @item tabset @var{nchars}
23117 Set the width of tab stops to be @var{nchars} characters.
23120 @node TUI Configuration
23121 @section TUI Configuration Variables
23122 @cindex TUI configuration variables
23124 Several configuration variables control the appearance of TUI windows.
23127 @item set tui border-kind @var{kind}
23128 @kindex set tui border-kind
23129 Select the border appearance for the source, assembly and register windows.
23130 The possible values are the following:
23133 Use a space character to draw the border.
23136 Use @sc{ascii} characters @samp{+}, @samp{-} and @samp{|} to draw the border.
23139 Use the Alternate Character Set to draw the border. The border is
23140 drawn using character line graphics if the terminal supports them.
23143 @item set tui border-mode @var{mode}
23144 @kindex set tui border-mode
23145 @itemx set tui active-border-mode @var{mode}
23146 @kindex set tui active-border-mode
23147 Select the display attributes for the borders of the inactive windows
23148 or the active window. The @var{mode} can be one of the following:
23151 Use normal attributes to display the border.
23157 Use reverse video mode.
23160 Use half bright mode.
23162 @item half-standout
23163 Use half bright and standout mode.
23166 Use extra bright or bold mode.
23168 @item bold-standout
23169 Use extra bright or bold and standout mode.
23174 @chapter Using @value{GDBN} under @sc{gnu} Emacs
23177 @cindex @sc{gnu} Emacs
23178 A special interface allows you to use @sc{gnu} Emacs to view (and
23179 edit) the source files for the program you are debugging with
23182 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
23183 executable file you want to debug as an argument. This command starts
23184 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
23185 created Emacs buffer.
23186 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
23188 Running @value{GDBN} under Emacs can be just like running @value{GDBN} normally except for two
23193 All ``terminal'' input and output goes through an Emacs buffer, called
23196 This applies both to @value{GDBN} commands and their output, and to the input
23197 and output done by the program you are debugging.
23199 This is useful because it means that you can copy the text of previous
23200 commands and input them again; you can even use parts of the output
23203 All the facilities of Emacs' Shell mode are available for interacting
23204 with your program. In particular, you can send signals the usual
23205 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
23209 @value{GDBN} displays source code through Emacs.
23211 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
23212 source file for that frame and puts an arrow (@samp{=>}) at the
23213 left margin of the current line. Emacs uses a separate buffer for
23214 source display, and splits the screen to show both your @value{GDBN} session
23217 Explicit @value{GDBN} @code{list} or search commands still produce output as
23218 usual, but you probably have no reason to use them from Emacs.
23221 We call this @dfn{text command mode}. Emacs 22.1, and later, also uses
23222 a graphical mode, enabled by default, which provides further buffers
23223 that can control the execution and describe the state of your program.
23224 @xref{GDB Graphical Interface,,, Emacs, The @sc{gnu} Emacs Manual}.
23226 If you specify an absolute file name when prompted for the @kbd{M-x
23227 gdb} argument, then Emacs sets your current working directory to where
23228 your program resides. If you only specify the file name, then Emacs
23229 sets your current working directory to to the directory associated
23230 with the previous buffer. In this case, @value{GDBN} may find your
23231 program by searching your environment's @code{PATH} variable, but on
23232 some operating systems it might not find the source. So, although the
23233 @value{GDBN} input and output session proceeds normally, the auxiliary
23234 buffer does not display the current source and line of execution.
23236 The initial working directory of @value{GDBN} is printed on the top
23237 line of the GUD buffer and this serves as a default for the commands
23238 that specify files for @value{GDBN} to operate on. @xref{Files,
23239 ,Commands to Specify Files}.
23241 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
23242 need to call @value{GDBN} by a different name (for example, if you
23243 keep several configurations around, with different names) you can
23244 customize the Emacs variable @code{gud-gdb-command-name} to run the
23247 In the GUD buffer, you can use these special Emacs commands in
23248 addition to the standard Shell mode commands:
23252 Describe the features of Emacs' GUD Mode.
23255 Execute to another source line, like the @value{GDBN} @code{step} command; also
23256 update the display window to show the current file and location.
23259 Execute to next source line in this function, skipping all function
23260 calls, like the @value{GDBN} @code{next} command. Then update the display window
23261 to show the current file and location.
23264 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
23265 display window accordingly.
23268 Execute until exit from the selected stack frame, like the @value{GDBN}
23269 @code{finish} command.
23272 Continue execution of your program, like the @value{GDBN} @code{continue}
23276 Go up the number of frames indicated by the numeric argument
23277 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
23278 like the @value{GDBN} @code{up} command.
23281 Go down the number of frames indicated by the numeric argument, like the
23282 @value{GDBN} @code{down} command.
23285 In any source file, the Emacs command @kbd{C-x @key{SPC}} (@code{gud-break})
23286 tells @value{GDBN} to set a breakpoint on the source line point is on.
23288 In text command mode, if you type @kbd{M-x speedbar}, Emacs displays a
23289 separate frame which shows a backtrace when the GUD buffer is current.
23290 Move point to any frame in the stack and type @key{RET} to make it
23291 become the current frame and display the associated source in the
23292 source buffer. Alternatively, click @kbd{Mouse-2} to make the
23293 selected frame become the current one. In graphical mode, the
23294 speedbar displays watch expressions.
23296 If you accidentally delete the source-display buffer, an easy way to get
23297 it back is to type the command @code{f} in the @value{GDBN} buffer, to
23298 request a frame display; when you run under Emacs, this recreates
23299 the source buffer if necessary to show you the context of the current
23302 The source files displayed in Emacs are in ordinary Emacs buffers
23303 which are visiting the source files in the usual way. You can edit
23304 the files with these buffers if you wish; but keep in mind that @value{GDBN}
23305 communicates with Emacs in terms of line numbers. If you add or
23306 delete lines from the text, the line numbers that @value{GDBN} knows cease
23307 to correspond properly with the code.
23309 A more detailed description of Emacs' interaction with @value{GDBN} is
23310 given in the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu}
23313 @c The following dropped because Epoch is nonstandard. Reactivate
23314 @c if/when v19 does something similar. ---doc@cygnus.com 19dec1990
23316 @kindex Emacs Epoch environment
23320 Version 18 of @sc{gnu} Emacs has a built-in window system
23321 called the @code{epoch}
23322 environment. Users of this environment can use a new command,
23323 @code{inspect} which performs identically to @code{print} except that
23324 each value is printed in its own window.
23329 @chapter The @sc{gdb/mi} Interface
23331 @unnumberedsec Function and Purpose
23333 @cindex @sc{gdb/mi}, its purpose
23334 @sc{gdb/mi} is a line based machine oriented text interface to
23335 @value{GDBN} and is activated by specifying using the
23336 @option{--interpreter} command line option (@pxref{Mode Options}). It
23337 is specifically intended to support the development of systems which
23338 use the debugger as just one small component of a larger system.
23340 This chapter is a specification of the @sc{gdb/mi} interface. It is written
23341 in the form of a reference manual.
23343 Note that @sc{gdb/mi} is still under construction, so some of the
23344 features described below are incomplete and subject to change
23345 (@pxref{GDB/MI Development and Front Ends, , @sc{gdb/mi} Development and Front Ends}).
23347 @unnumberedsec Notation and Terminology
23349 @cindex notational conventions, for @sc{gdb/mi}
23350 This chapter uses the following notation:
23354 @code{|} separates two alternatives.
23357 @code{[ @var{something} ]} indicates that @var{something} is optional:
23358 it may or may not be given.
23361 @code{( @var{group} )*} means that @var{group} inside the parentheses
23362 may repeat zero or more times.
23365 @code{( @var{group} )+} means that @var{group} inside the parentheses
23366 may repeat one or more times.
23369 @code{"@var{string}"} means a literal @var{string}.
23373 @heading Dependencies
23377 * GDB/MI General Design::
23378 * GDB/MI Command Syntax::
23379 * GDB/MI Compatibility with CLI::
23380 * GDB/MI Development and Front Ends::
23381 * GDB/MI Output Records::
23382 * GDB/MI Simple Examples::
23383 * GDB/MI Command Description Format::
23384 * GDB/MI Breakpoint Commands::
23385 * GDB/MI Program Context::
23386 * GDB/MI Thread Commands::
23387 * GDB/MI Program Execution::
23388 * GDB/MI Stack Manipulation::
23389 * GDB/MI Variable Objects::
23390 * GDB/MI Data Manipulation::
23391 * GDB/MI Tracepoint Commands::
23392 * GDB/MI Symbol Query::
23393 * GDB/MI File Commands::
23395 * GDB/MI Kod Commands::
23396 * GDB/MI Memory Overlay Commands::
23397 * GDB/MI Signal Handling Commands::
23399 * GDB/MI Target Manipulation::
23400 * GDB/MI File Transfer Commands::
23401 * GDB/MI Miscellaneous Commands::
23404 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
23405 @node GDB/MI General Design
23406 @section @sc{gdb/mi} General Design
23407 @cindex GDB/MI General Design
23409 Interaction of a @sc{GDB/MI} frontend with @value{GDBN} involves three
23410 parts---commands sent to @value{GDBN}, responses to those commands
23411 and notifications. Each command results in exactly one response,
23412 indicating either successful completion of the command, or an error.
23413 For the commands that do not resume the target, the response contains the
23414 requested information. For the commands that resume the target, the
23415 response only indicates whether the target was successfully resumed.
23416 Notifications is the mechanism for reporting changes in the state of the
23417 target, or in @value{GDBN} state, that cannot conveniently be associated with
23418 a command and reported as part of that command response.
23420 The important examples of notifications are:
23424 Exec notifications. These are used to report changes in
23425 target state---when a target is resumed, or stopped. It would not
23426 be feasible to include this information in response of resuming
23427 commands, because one resume commands can result in multiple events in
23428 different threads. Also, quite some time may pass before any event
23429 happens in the target, while a frontend needs to know whether the resuming
23430 command itself was successfully executed.
23433 Console output, and status notifications. Console output
23434 notifications are used to report output of CLI commands, as well as
23435 diagnostics for other commands. Status notifications are used to
23436 report the progress of a long-running operation. Naturally, including
23437 this information in command response would mean no output is produced
23438 until the command is finished, which is undesirable.
23441 General notifications. Commands may have various side effects on
23442 the @value{GDBN} or target state beyond their official purpose. For example,
23443 a command may change the selected thread. Although such changes can
23444 be included in command response, using notification allows for more
23445 orthogonal frontend design.
23449 There's no guarantee that whenever an MI command reports an error,
23450 @value{GDBN} or the target are in any specific state, and especially,
23451 the state is not reverted to the state before the MI command was
23452 processed. Therefore, whenever an MI command results in an error,
23453 we recommend that the frontend refreshes all the information shown in
23454 the user interface.
23458 * Context management::
23459 * Asynchronous and non-stop modes::
23463 @node Context management
23464 @subsection Context management
23466 In most cases when @value{GDBN} accesses the target, this access is
23467 done in context of a specific thread and frame (@pxref{Frames}).
23468 Often, even when accessing global data, the target requires that a thread
23469 be specified. The CLI interface maintains the selected thread and frame,
23470 and supplies them to target on each command. This is convenient,
23471 because a command line user would not want to specify that information
23472 explicitly on each command, and because user interacts with
23473 @value{GDBN} via a single terminal, so no confusion is possible as
23474 to what thread and frame are the current ones.
23476 In the case of MI, the concept of selected thread and frame is less
23477 useful. First, a frontend can easily remember this information
23478 itself. Second, a graphical frontend can have more than one window,
23479 each one used for debugging a different thread, and the frontend might
23480 want to access additional threads for internal purposes. This
23481 increases the risk that by relying on implicitly selected thread, the
23482 frontend may be operating on a wrong one. Therefore, each MI command
23483 should explicitly specify which thread and frame to operate on. To
23484 make it possible, each MI command accepts the @samp{--thread} and
23485 @samp{--frame} options, the value to each is @value{GDBN} identifier
23486 for thread and frame to operate on.
23488 Usually, each top-level window in a frontend allows the user to select
23489 a thread and a frame, and remembers the user selection for further
23490 operations. However, in some cases @value{GDBN} may suggest that the
23491 current thread be changed. For example, when stopping on a breakpoint
23492 it is reasonable to switch to the thread where breakpoint is hit. For
23493 another example, if the user issues the CLI @samp{thread} command via
23494 the frontend, it is desirable to change the frontend's selected thread to the
23495 one specified by user. @value{GDBN} communicates the suggestion to
23496 change current thread using the @samp{=thread-selected} notification.
23497 No such notification is available for the selected frame at the moment.
23499 Note that historically, MI shares the selected thread with CLI, so
23500 frontends used the @code{-thread-select} to execute commands in the
23501 right context. However, getting this to work right is cumbersome. The
23502 simplest way is for frontend to emit @code{-thread-select} command
23503 before every command. This doubles the number of commands that need
23504 to be sent. The alternative approach is to suppress @code{-thread-select}
23505 if the selected thread in @value{GDBN} is supposed to be identical to the
23506 thread the frontend wants to operate on. However, getting this
23507 optimization right can be tricky. In particular, if the frontend
23508 sends several commands to @value{GDBN}, and one of the commands changes the
23509 selected thread, then the behaviour of subsequent commands will
23510 change. So, a frontend should either wait for response from such
23511 problematic commands, or explicitly add @code{-thread-select} for
23512 all subsequent commands. No frontend is known to do this exactly
23513 right, so it is suggested to just always pass the @samp{--thread} and
23514 @samp{--frame} options.
23516 @node Asynchronous and non-stop modes
23517 @subsection Asynchronous command execution and non-stop mode
23519 On some targets, @value{GDBN} is capable of processing MI commands
23520 even while the target is running. This is called @dfn{asynchronous
23521 command execution} (@pxref{Background Execution}). The frontend may
23522 specify a preferrence for asynchronous execution using the
23523 @code{-gdb-set target-async 1} command, which should be emitted before
23524 either running the executable or attaching to the target. After the
23525 frontend has started the executable or attached to the target, it can
23526 find if asynchronous execution is enabled using the
23527 @code{-list-target-features} command.
23529 Even if @value{GDBN} can accept a command while target is running,
23530 many commands that access the target do not work when the target is
23531 running. Therefore, asynchronous command execution is most useful
23532 when combined with non-stop mode (@pxref{Non-Stop Mode}). Then,
23533 it is possible to examine the state of one thread, while other threads
23536 When a given thread is running, MI commands that try to access the
23537 target in the context of that thread may not work, or may work only on
23538 some targets. In particular, commands that try to operate on thread's
23539 stack will not work, on any target. Commands that read memory, or
23540 modify breakpoints, may work or not work, depending on the target. Note
23541 that even commands that operate on global state, such as @code{print},
23542 @code{set}, and breakpoint commands, still access the target in the
23543 context of a specific thread, so frontend should try to find a
23544 stopped thread and perform the operation on that thread (using the
23545 @samp{--thread} option).
23547 Which commands will work in the context of a running thread is
23548 highly target dependent. However, the two commands
23549 @code{-exec-interrupt}, to stop a thread, and @code{-thread-info},
23550 to find the state of a thread, will always work.
23552 @node Thread groups
23553 @subsection Thread groups
23554 @value{GDBN} may be used to debug several processes at the same time.
23555 On some platfroms, @value{GDBN} may support debugging of several
23556 hardware systems, each one having several cores with several different
23557 processes running on each core. This section describes the MI
23558 mechanism to support such debugging scenarios.
23560 The key observation is that regardless of the structure of the
23561 target, MI can have a global list of threads, because most commands that
23562 accept the @samp{--thread} option do not need to know what process that
23563 thread belongs to. Therefore, it is not necessary to introduce
23564 neither additional @samp{--process} option, nor an notion of the
23565 current process in the MI interface. The only strictly new feature
23566 that is required is the ability to find how the threads are grouped
23569 To allow the user to discover such grouping, and to support arbitrary
23570 hierarchy of machines/cores/processes, MI introduces the concept of a
23571 @dfn{thread group}. Thread group is a collection of threads and other
23572 thread groups. A thread group always has a string identifier, a type,
23573 and may have additional attributes specific to the type. A new
23574 command, @code{-list-thread-groups}, returns the list of top-level
23575 thread groups, which correspond to processes that @value{GDBN} is
23576 debugging at the moment. By passing an identifier of a thread group
23577 to the @code{-list-thread-groups} command, it is possible to obtain
23578 the members of specific thread group.
23580 To allow the user to easily discover processes, and other objects, he
23581 wishes to debug, a concept of @dfn{available thread group} is
23582 introduced. Available thread group is an thread group that
23583 @value{GDBN} is not debugging, but that can be attached to, using the
23584 @code{-target-attach} command. The list of available top-level thread
23585 groups can be obtained using @samp{-list-thread-groups --available}.
23586 In general, the content of a thread group may be only retrieved only
23587 after attaching to that thread group.
23589 Thread groups are related to inferiors (@pxref{Inferiors and
23590 Programs}). Each inferior corresponds to a thread group of a special
23591 type @samp{process}, and some additional operations are permitted on
23592 such thread groups.
23594 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
23595 @node GDB/MI Command Syntax
23596 @section @sc{gdb/mi} Command Syntax
23599 * GDB/MI Input Syntax::
23600 * GDB/MI Output Syntax::
23603 @node GDB/MI Input Syntax
23604 @subsection @sc{gdb/mi} Input Syntax
23606 @cindex input syntax for @sc{gdb/mi}
23607 @cindex @sc{gdb/mi}, input syntax
23609 @item @var{command} @expansion{}
23610 @code{@var{cli-command} | @var{mi-command}}
23612 @item @var{cli-command} @expansion{}
23613 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
23614 @var{cli-command} is any existing @value{GDBN} CLI command.
23616 @item @var{mi-command} @expansion{}
23617 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
23618 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
23620 @item @var{token} @expansion{}
23621 "any sequence of digits"
23623 @item @var{option} @expansion{}
23624 @code{"-" @var{parameter} [ " " @var{parameter} ]}
23626 @item @var{parameter} @expansion{}
23627 @code{@var{non-blank-sequence} | @var{c-string}}
23629 @item @var{operation} @expansion{}
23630 @emph{any of the operations described in this chapter}
23632 @item @var{non-blank-sequence} @expansion{}
23633 @emph{anything, provided it doesn't contain special characters such as
23634 "-", @var{nl}, """ and of course " "}
23636 @item @var{c-string} @expansion{}
23637 @code{""" @var{seven-bit-iso-c-string-content} """}
23639 @item @var{nl} @expansion{}
23648 The CLI commands are still handled by the @sc{mi} interpreter; their
23649 output is described below.
23652 The @code{@var{token}}, when present, is passed back when the command
23656 Some @sc{mi} commands accept optional arguments as part of the parameter
23657 list. Each option is identified by a leading @samp{-} (dash) and may be
23658 followed by an optional argument parameter. Options occur first in the
23659 parameter list and can be delimited from normal parameters using
23660 @samp{--} (this is useful when some parameters begin with a dash).
23667 We want easy access to the existing CLI syntax (for debugging).
23670 We want it to be easy to spot a @sc{mi} operation.
23673 @node GDB/MI Output Syntax
23674 @subsection @sc{gdb/mi} Output Syntax
23676 @cindex output syntax of @sc{gdb/mi}
23677 @cindex @sc{gdb/mi}, output syntax
23678 The output from @sc{gdb/mi} consists of zero or more out-of-band records
23679 followed, optionally, by a single result record. This result record
23680 is for the most recent command. The sequence of output records is
23681 terminated by @samp{(gdb)}.
23683 If an input command was prefixed with a @code{@var{token}} then the
23684 corresponding output for that command will also be prefixed by that same
23688 @item @var{output} @expansion{}
23689 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(gdb)" @var{nl}}
23691 @item @var{result-record} @expansion{}
23692 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
23694 @item @var{out-of-band-record} @expansion{}
23695 @code{@var{async-record} | @var{stream-record}}
23697 @item @var{async-record} @expansion{}
23698 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
23700 @item @var{exec-async-output} @expansion{}
23701 @code{[ @var{token} ] "*" @var{async-output}}
23703 @item @var{status-async-output} @expansion{}
23704 @code{[ @var{token} ] "+" @var{async-output}}
23706 @item @var{notify-async-output} @expansion{}
23707 @code{[ @var{token} ] "=" @var{async-output}}
23709 @item @var{async-output} @expansion{}
23710 @code{@var{async-class} ( "," @var{result} )* @var{nl}}
23712 @item @var{result-class} @expansion{}
23713 @code{"done" | "running" | "connected" | "error" | "exit"}
23715 @item @var{async-class} @expansion{}
23716 @code{"stopped" | @var{others}} (where @var{others} will be added
23717 depending on the needs---this is still in development).
23719 @item @var{result} @expansion{}
23720 @code{ @var{variable} "=" @var{value}}
23722 @item @var{variable} @expansion{}
23723 @code{ @var{string} }
23725 @item @var{value} @expansion{}
23726 @code{ @var{const} | @var{tuple} | @var{list} }
23728 @item @var{const} @expansion{}
23729 @code{@var{c-string}}
23731 @item @var{tuple} @expansion{}
23732 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
23734 @item @var{list} @expansion{}
23735 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
23736 @var{result} ( "," @var{result} )* "]" }
23738 @item @var{stream-record} @expansion{}
23739 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
23741 @item @var{console-stream-output} @expansion{}
23742 @code{"~" @var{c-string}}
23744 @item @var{target-stream-output} @expansion{}
23745 @code{"@@" @var{c-string}}
23747 @item @var{log-stream-output} @expansion{}
23748 @code{"&" @var{c-string}}
23750 @item @var{nl} @expansion{}
23753 @item @var{token} @expansion{}
23754 @emph{any sequence of digits}.
23762 All output sequences end in a single line containing a period.
23765 The @code{@var{token}} is from the corresponding request. Note that
23766 for all async output, while the token is allowed by the grammar and
23767 may be output by future versions of @value{GDBN} for select async
23768 output messages, it is generally omitted. Frontends should treat
23769 all async output as reporting general changes in the state of the
23770 target and there should be no need to associate async output to any
23774 @cindex status output in @sc{gdb/mi}
23775 @var{status-async-output} contains on-going status information about the
23776 progress of a slow operation. It can be discarded. All status output is
23777 prefixed by @samp{+}.
23780 @cindex async output in @sc{gdb/mi}
23781 @var{exec-async-output} contains asynchronous state change on the target
23782 (stopped, started, disappeared). All async output is prefixed by
23786 @cindex notify output in @sc{gdb/mi}
23787 @var{notify-async-output} contains supplementary information that the
23788 client should handle (e.g., a new breakpoint information). All notify
23789 output is prefixed by @samp{=}.
23792 @cindex console output in @sc{gdb/mi}
23793 @var{console-stream-output} is output that should be displayed as is in the
23794 console. It is the textual response to a CLI command. All the console
23795 output is prefixed by @samp{~}.
23798 @cindex target output in @sc{gdb/mi}
23799 @var{target-stream-output} is the output produced by the target program.
23800 All the target output is prefixed by @samp{@@}.
23803 @cindex log output in @sc{gdb/mi}
23804 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
23805 instance messages that should be displayed as part of an error log. All
23806 the log output is prefixed by @samp{&}.
23809 @cindex list output in @sc{gdb/mi}
23810 New @sc{gdb/mi} commands should only output @var{lists} containing
23816 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
23817 details about the various output records.
23819 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
23820 @node GDB/MI Compatibility with CLI
23821 @section @sc{gdb/mi} Compatibility with CLI
23823 @cindex compatibility, @sc{gdb/mi} and CLI
23824 @cindex @sc{gdb/mi}, compatibility with CLI
23826 For the developers convenience CLI commands can be entered directly,
23827 but there may be some unexpected behaviour. For example, commands
23828 that query the user will behave as if the user replied yes, breakpoint
23829 command lists are not executed and some CLI commands, such as
23830 @code{if}, @code{when} and @code{define}, prompt for further input with
23831 @samp{>}, which is not valid MI output.
23833 This feature may be removed at some stage in the future and it is
23834 recommended that front ends use the @code{-interpreter-exec} command
23835 (@pxref{-interpreter-exec}).
23837 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
23838 @node GDB/MI Development and Front Ends
23839 @section @sc{gdb/mi} Development and Front Ends
23840 @cindex @sc{gdb/mi} development
23842 The application which takes the MI output and presents the state of the
23843 program being debugged to the user is called a @dfn{front end}.
23845 Although @sc{gdb/mi} is still incomplete, it is currently being used
23846 by a variety of front ends to @value{GDBN}. This makes it difficult
23847 to introduce new functionality without breaking existing usage. This
23848 section tries to minimize the problems by describing how the protocol
23851 Some changes in MI need not break a carefully designed front end, and
23852 for these the MI version will remain unchanged. The following is a
23853 list of changes that may occur within one level, so front ends should
23854 parse MI output in a way that can handle them:
23858 New MI commands may be added.
23861 New fields may be added to the output of any MI command.
23864 The range of values for fields with specified values, e.g.,
23865 @code{in_scope} (@pxref{-var-update}) may be extended.
23867 @c The format of field's content e.g type prefix, may change so parse it
23868 @c at your own risk. Yes, in general?
23870 @c The order of fields may change? Shouldn't really matter but it might
23871 @c resolve inconsistencies.
23874 If the changes are likely to break front ends, the MI version level
23875 will be increased by one. This will allow the front end to parse the
23876 output according to the MI version. Apart from mi0, new versions of
23877 @value{GDBN} will not support old versions of MI and it will be the
23878 responsibility of the front end to work with the new one.
23880 @c Starting with mi3, add a new command -mi-version that prints the MI
23883 The best way to avoid unexpected changes in MI that might break your front
23884 end is to make your project known to @value{GDBN} developers and
23885 follow development on @email{gdb@@sourceware.org} and
23886 @email{gdb-patches@@sourceware.org}.
23887 @cindex mailing lists
23889 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
23890 @node GDB/MI Output Records
23891 @section @sc{gdb/mi} Output Records
23894 * GDB/MI Result Records::
23895 * GDB/MI Stream Records::
23896 * GDB/MI Async Records::
23897 * GDB/MI Frame Information::
23898 * GDB/MI Thread Information::
23901 @node GDB/MI Result Records
23902 @subsection @sc{gdb/mi} Result Records
23904 @cindex result records in @sc{gdb/mi}
23905 @cindex @sc{gdb/mi}, result records
23906 In addition to a number of out-of-band notifications, the response to a
23907 @sc{gdb/mi} command includes one of the following result indications:
23911 @item "^done" [ "," @var{results} ]
23912 The synchronous operation was successful, @code{@var{results}} are the return
23917 This result record is equivalent to @samp{^done}. Historically, it
23918 was output instead of @samp{^done} if the command has resumed the
23919 target. This behaviour is maintained for backward compatibility, but
23920 all frontends should treat @samp{^done} and @samp{^running}
23921 identically and rely on the @samp{*running} output record to determine
23922 which threads are resumed.
23926 @value{GDBN} has connected to a remote target.
23928 @item "^error" "," @var{c-string}
23930 The operation failed. The @code{@var{c-string}} contains the corresponding
23935 @value{GDBN} has terminated.
23939 @node GDB/MI Stream Records
23940 @subsection @sc{gdb/mi} Stream Records
23942 @cindex @sc{gdb/mi}, stream records
23943 @cindex stream records in @sc{gdb/mi}
23944 @value{GDBN} internally maintains a number of output streams: the console, the
23945 target, and the log. The output intended for each of these streams is
23946 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
23948 Each stream record begins with a unique @dfn{prefix character} which
23949 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
23950 Syntax}). In addition to the prefix, each stream record contains a
23951 @code{@var{string-output}}. This is either raw text (with an implicit new
23952 line) or a quoted C string (which does not contain an implicit newline).
23955 @item "~" @var{string-output}
23956 The console output stream contains text that should be displayed in the
23957 CLI console window. It contains the textual responses to CLI commands.
23959 @item "@@" @var{string-output}
23960 The target output stream contains any textual output from the running
23961 target. This is only present when GDB's event loop is truly
23962 asynchronous, which is currently only the case for remote targets.
23964 @item "&" @var{string-output}
23965 The log stream contains debugging messages being produced by @value{GDBN}'s
23969 @node GDB/MI Async Records
23970 @subsection @sc{gdb/mi} Async Records
23972 @cindex async records in @sc{gdb/mi}
23973 @cindex @sc{gdb/mi}, async records
23974 @dfn{Async} records are used to notify the @sc{gdb/mi} client of
23975 additional changes that have occurred. Those changes can either be a
23976 consequence of @sc{gdb/mi} commands (e.g., a breakpoint modified) or a result of
23977 target activity (e.g., target stopped).
23979 The following is the list of possible async records:
23983 @item *running,thread-id="@var{thread}"
23984 The target is now running. The @var{thread} field tells which
23985 specific thread is now running, and can be @samp{all} if all threads
23986 are running. The frontend should assume that no interaction with a
23987 running thread is possible after this notification is produced.
23988 The frontend should not assume that this notification is output
23989 only once for any command. @value{GDBN} may emit this notification
23990 several times, either for different threads, because it cannot resume
23991 all threads together, or even for a single thread, if the thread must
23992 be stepped though some code before letting it run freely.
23994 @item *stopped,reason="@var{reason}",thread-id="@var{id}",stopped-threads="@var{stopped}",core="@var{core}"
23995 The target has stopped. The @var{reason} field can have one of the
23999 @item breakpoint-hit
24000 A breakpoint was reached.
24001 @item watchpoint-trigger
24002 A watchpoint was triggered.
24003 @item read-watchpoint-trigger
24004 A read watchpoint was triggered.
24005 @item access-watchpoint-trigger
24006 An access watchpoint was triggered.
24007 @item function-finished
24008 An -exec-finish or similar CLI command was accomplished.
24009 @item location-reached
24010 An -exec-until or similar CLI command was accomplished.
24011 @item watchpoint-scope
24012 A watchpoint has gone out of scope.
24013 @item end-stepping-range
24014 An -exec-next, -exec-next-instruction, -exec-step, -exec-step-instruction or
24015 similar CLI command was accomplished.
24016 @item exited-signalled
24017 The inferior exited because of a signal.
24019 The inferior exited.
24020 @item exited-normally
24021 The inferior exited normally.
24022 @item signal-received
24023 A signal was received by the inferior.
24026 The @var{id} field identifies the thread that directly caused the stop
24027 -- for example by hitting a breakpoint. Depending on whether all-stop
24028 mode is in effect (@pxref{All-Stop Mode}), @value{GDBN} may either
24029 stop all threads, or only the thread that directly triggered the stop.
24030 If all threads are stopped, the @var{stopped} field will have the
24031 value of @code{"all"}. Otherwise, the value of the @var{stopped}
24032 field will be a list of thread identifiers. Presently, this list will
24033 always include a single thread, but frontend should be prepared to see
24034 several threads in the list. The @var{core} field reports the
24035 processor core on which the stop event has happened. This field may be absent
24036 if such information is not available.
24038 @item =thread-group-added,id="@var{id}"
24039 @itemx =thread-group-removed,id="@var{id}"
24040 A thread group was either added or removed. The @var{id} field
24041 contains the @value{GDBN} identifier of the thread group. When a thread
24042 group is added, it generally might not be associated with a running
24043 process. When a thread group is removed, its id becomes invalid and
24044 cannot be used in any way.
24046 @item =thread-group-started,id="@var{id}",pid="@var{pid}"
24047 A thread group became associated with a running program,
24048 either because the program was just started or the thread group
24049 was attached to a program. The @var{id} field contains the
24050 @value{GDBN} identifier of the thread group. The @var{pid} field
24051 contains process identifier, specific to the operating system.
24053 @itemx =thread-group-exited,id="@var{id}"
24054 A thread group is no longer associated with a running program,
24055 either because the program has exited, or because it was detached
24056 from. The @var{id} field contains the @value{GDBN} identifier of the
24059 @item =thread-created,id="@var{id}",group-id="@var{gid}"
24060 @itemx =thread-exited,id="@var{id}",group-id="@var{gid}"
24061 A thread either was created, or has exited. The @var{id} field
24062 contains the @value{GDBN} identifier of the thread. The @var{gid}
24063 field identifies the thread group this thread belongs to.
24065 @item =thread-selected,id="@var{id}"
24066 Informs that the selected thread was changed as result of the last
24067 command. This notification is not emitted as result of @code{-thread-select}
24068 command but is emitted whenever an MI command that is not documented
24069 to change the selected thread actually changes it. In particular,
24070 invoking, directly or indirectly (via user-defined command), the CLI
24071 @code{thread} command, will generate this notification.
24073 We suggest that in response to this notification, front ends
24074 highlight the selected thread and cause subsequent commands to apply to
24077 @item =library-loaded,...
24078 Reports that a new library file was loaded by the program. This
24079 notification has 4 fields---@var{id}, @var{target-name},
24080 @var{host-name}, and @var{symbols-loaded}. The @var{id} field is an
24081 opaque identifier of the library. For remote debugging case,
24082 @var{target-name} and @var{host-name} fields give the name of the
24083 library file on the target, and on the host respectively. For native
24084 debugging, both those fields have the same value. The
24085 @var{symbols-loaded} field reports if the debug symbols for this
24086 library are loaded. The @var{thread-group} field, if present,
24087 specifies the id of the thread group in whose context the library was loaded.
24088 If the field is absent, it means the library was loaded in the context
24089 of all present thread groups.
24091 @item =library-unloaded,...
24092 Reports that a library was unloaded by the program. This notification
24093 has 3 fields---@var{id}, @var{target-name} and @var{host-name} with
24094 the same meaning as for the @code{=library-loaded} notification.
24095 The @var{thread-group} field, if present, specifies the id of the
24096 thread group in whose context the library was unloaded. If the field is
24097 absent, it means the library was unloaded in the context of all present
24102 @node GDB/MI Frame Information
24103 @subsection @sc{gdb/mi} Frame Information
24105 Response from many MI commands includes an information about stack
24106 frame. This information is a tuple that may have the following
24111 The level of the stack frame. The innermost frame has the level of
24112 zero. This field is always present.
24115 The name of the function corresponding to the frame. This field may
24116 be absent if @value{GDBN} is unable to determine the function name.
24119 The code address for the frame. This field is always present.
24122 The name of the source files that correspond to the frame's code
24123 address. This field may be absent.
24126 The source line corresponding to the frames' code address. This field
24130 The name of the binary file (either executable or shared library) the
24131 corresponds to the frame's code address. This field may be absent.
24135 @node GDB/MI Thread Information
24136 @subsection @sc{gdb/mi} Thread Information
24138 Whenever @value{GDBN} has to report an information about a thread, it
24139 uses a tuple with the following fields:
24143 The numeric id assigned to the thread by @value{GDBN}. This field is
24147 Target-specific string identifying the thread. This field is always present.
24150 Additional information about the thread provided by the target.
24151 It is supposed to be human-readable and not interpreted by the
24152 frontend. This field is optional.
24155 Either @samp{stopped} or @samp{running}, depending on whether the
24156 thread is presently running. This field is always present.
24159 The value of this field is an integer number of the processor core the
24160 thread was last seen on. This field is optional.
24164 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
24165 @node GDB/MI Simple Examples
24166 @section Simple Examples of @sc{gdb/mi} Interaction
24167 @cindex @sc{gdb/mi}, simple examples
24169 This subsection presents several simple examples of interaction using
24170 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
24171 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
24172 the output received from @sc{gdb/mi}.
24174 Note the line breaks shown in the examples are here only for
24175 readability, they don't appear in the real output.
24177 @subheading Setting a Breakpoint
24179 Setting a breakpoint generates synchronous output which contains detailed
24180 information of the breakpoint.
24183 -> -break-insert main
24184 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
24185 enabled="y",addr="0x08048564",func="main",file="myprog.c",
24186 fullname="/home/nickrob/myprog.c",line="68",times="0"@}
24190 @subheading Program Execution
24192 Program execution generates asynchronous records and MI gives the
24193 reason that execution stopped.
24199 <- *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
24200 frame=@{addr="0x08048564",func="main",
24201 args=[@{name="argc",value="1"@},@{name="argv",value="0xbfc4d4d4"@}],
24202 file="myprog.c",fullname="/home/nickrob/myprog.c",line="68"@}
24207 <- *stopped,reason="exited-normally"
24211 @subheading Quitting @value{GDBN}
24213 Quitting @value{GDBN} just prints the result class @samp{^exit}.
24221 Please note that @samp{^exit} is printed immediately, but it might
24222 take some time for @value{GDBN} to actually exit. During that time, @value{GDBN}
24223 performs necessary cleanups, including killing programs being debugged
24224 or disconnecting from debug hardware, so the frontend should wait till
24225 @value{GDBN} exits and should only forcibly kill @value{GDBN} if it
24226 fails to exit in reasonable time.
24228 @subheading A Bad Command
24230 Here's what happens if you pass a non-existent command:
24234 <- ^error,msg="Undefined MI command: rubbish"
24239 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
24240 @node GDB/MI Command Description Format
24241 @section @sc{gdb/mi} Command Description Format
24243 The remaining sections describe blocks of commands. Each block of
24244 commands is laid out in a fashion similar to this section.
24246 @subheading Motivation
24248 The motivation for this collection of commands.
24250 @subheading Introduction
24252 A brief introduction to this collection of commands as a whole.
24254 @subheading Commands
24256 For each command in the block, the following is described:
24258 @subsubheading Synopsis
24261 -command @var{args}@dots{}
24264 @subsubheading Result
24266 @subsubheading @value{GDBN} Command
24268 The corresponding @value{GDBN} CLI command(s), if any.
24270 @subsubheading Example
24272 Example(s) formatted for readability. Some of the described commands have
24273 not been implemented yet and these are labeled N.A.@: (not available).
24276 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
24277 @node GDB/MI Breakpoint Commands
24278 @section @sc{gdb/mi} Breakpoint Commands
24280 @cindex breakpoint commands for @sc{gdb/mi}
24281 @cindex @sc{gdb/mi}, breakpoint commands
24282 This section documents @sc{gdb/mi} commands for manipulating
24285 @subheading The @code{-break-after} Command
24286 @findex -break-after
24288 @subsubheading Synopsis
24291 -break-after @var{number} @var{count}
24294 The breakpoint number @var{number} is not in effect until it has been
24295 hit @var{count} times. To see how this is reflected in the output of
24296 the @samp{-break-list} command, see the description of the
24297 @samp{-break-list} command below.
24299 @subsubheading @value{GDBN} Command
24301 The corresponding @value{GDBN} command is @samp{ignore}.
24303 @subsubheading Example
24308 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
24309 enabled="y",addr="0x000100d0",func="main",file="hello.c",
24310 fullname="/home/foo/hello.c",line="5",times="0"@}
24317 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
24318 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
24319 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
24320 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
24321 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
24322 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
24323 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
24324 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
24325 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
24326 line="5",times="0",ignore="3"@}]@}
24331 @subheading The @code{-break-catch} Command
24332 @findex -break-catch
24335 @subheading The @code{-break-commands} Command
24336 @findex -break-commands
24338 @subsubheading Synopsis
24341 -break-commands @var{number} [ @var{command1} ... @var{commandN} ]
24344 Specifies the CLI commands that should be executed when breakpoint
24345 @var{number} is hit. The parameters @var{command1} to @var{commandN}
24346 are the commands. If no command is specified, any previously-set
24347 commands are cleared. @xref{Break Commands}. Typical use of this
24348 functionality is tracing a program, that is, printing of values of
24349 some variables whenever breakpoint is hit and then continuing.
24351 @subsubheading @value{GDBN} Command
24353 The corresponding @value{GDBN} command is @samp{commands}.
24355 @subsubheading Example
24360 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
24361 enabled="y",addr="0x000100d0",func="main",file="hello.c",
24362 fullname="/home/foo/hello.c",line="5",times="0"@}
24364 -break-commands 1 "print v" "continue"
24369 @subheading The @code{-break-condition} Command
24370 @findex -break-condition
24372 @subsubheading Synopsis
24375 -break-condition @var{number} @var{expr}
24378 Breakpoint @var{number} will stop the program only if the condition in
24379 @var{expr} is true. The condition becomes part of the
24380 @samp{-break-list} output (see the description of the @samp{-break-list}
24383 @subsubheading @value{GDBN} Command
24385 The corresponding @value{GDBN} command is @samp{condition}.
24387 @subsubheading Example
24391 -break-condition 1 1
24395 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
24396 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
24397 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
24398 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
24399 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
24400 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
24401 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
24402 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
24403 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
24404 line="5",cond="1",times="0",ignore="3"@}]@}
24408 @subheading The @code{-break-delete} Command
24409 @findex -break-delete
24411 @subsubheading Synopsis
24414 -break-delete ( @var{breakpoint} )+
24417 Delete the breakpoint(s) whose number(s) are specified in the argument
24418 list. This is obviously reflected in the breakpoint list.
24420 @subsubheading @value{GDBN} Command
24422 The corresponding @value{GDBN} command is @samp{delete}.
24424 @subsubheading Example
24432 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
24433 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
24434 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
24435 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
24436 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
24437 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
24438 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
24443 @subheading The @code{-break-disable} Command
24444 @findex -break-disable
24446 @subsubheading Synopsis
24449 -break-disable ( @var{breakpoint} )+
24452 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
24453 break list is now set to @samp{n} for the named @var{breakpoint}(s).
24455 @subsubheading @value{GDBN} Command
24457 The corresponding @value{GDBN} command is @samp{disable}.
24459 @subsubheading Example
24467 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
24468 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
24469 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
24470 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
24471 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
24472 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
24473 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
24474 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
24475 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
24476 line="5",times="0"@}]@}
24480 @subheading The @code{-break-enable} Command
24481 @findex -break-enable
24483 @subsubheading Synopsis
24486 -break-enable ( @var{breakpoint} )+
24489 Enable (previously disabled) @var{breakpoint}(s).
24491 @subsubheading @value{GDBN} Command
24493 The corresponding @value{GDBN} command is @samp{enable}.
24495 @subsubheading Example
24503 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
24504 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
24505 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
24506 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
24507 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
24508 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
24509 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
24510 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
24511 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
24512 line="5",times="0"@}]@}
24516 @subheading The @code{-break-info} Command
24517 @findex -break-info
24519 @subsubheading Synopsis
24522 -break-info @var{breakpoint}
24526 Get information about a single breakpoint.
24528 @subsubheading @value{GDBN} Command
24530 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
24532 @subsubheading Example
24535 @subheading The @code{-break-insert} Command
24536 @findex -break-insert
24538 @subsubheading Synopsis
24541 -break-insert [ -t ] [ -h ] [ -f ] [ -d ] [ -a ]
24542 [ -c @var{condition} ] [ -i @var{ignore-count} ]
24543 [ -p @var{thread} ] [ @var{location} ]
24547 If specified, @var{location}, can be one of:
24554 @item filename:linenum
24555 @item filename:function
24559 The possible optional parameters of this command are:
24563 Insert a temporary breakpoint.
24565 Insert a hardware breakpoint.
24566 @item -c @var{condition}
24567 Make the breakpoint conditional on @var{condition}.
24568 @item -i @var{ignore-count}
24569 Initialize the @var{ignore-count}.
24571 If @var{location} cannot be parsed (for example if it
24572 refers to unknown files or functions), create a pending
24573 breakpoint. Without this flag, @value{GDBN} will report
24574 an error, and won't create a breakpoint, if @var{location}
24577 Create a disabled breakpoint.
24579 Create a tracepoint. @xref{Tracepoints}. When this parameter
24580 is used together with @samp{-h}, a fast tracepoint is created.
24583 @subsubheading Result
24585 The result is in the form:
24588 ^done,bkpt=@{number="@var{number}",type="@var{type}",disp="del"|"keep",
24589 enabled="y"|"n",addr="@var{hex}",func="@var{funcname}",file="@var{filename}",
24590 fullname="@var{full_filename}",line="@var{lineno}",[thread="@var{threadno},]
24591 times="@var{times}"@}
24595 where @var{number} is the @value{GDBN} number for this breakpoint,
24596 @var{funcname} is the name of the function where the breakpoint was
24597 inserted, @var{filename} is the name of the source file which contains
24598 this function, @var{lineno} is the source line number within that file
24599 and @var{times} the number of times that the breakpoint has been hit
24600 (always 0 for -break-insert but may be greater for -break-info or -break-list
24601 which use the same output).
24603 Note: this format is open to change.
24604 @c An out-of-band breakpoint instead of part of the result?
24606 @subsubheading @value{GDBN} Command
24608 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
24609 @samp{hbreak}, @samp{thbreak}, and @samp{rbreak}.
24611 @subsubheading Example
24616 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",
24617 fullname="/home/foo/recursive2.c,line="4",times="0"@}
24619 -break-insert -t foo
24620 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",
24621 fullname="/home/foo/recursive2.c,line="11",times="0"@}
24624 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
24625 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
24626 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
24627 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
24628 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
24629 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
24630 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
24631 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
24632 addr="0x0001072c", func="main",file="recursive2.c",
24633 fullname="/home/foo/recursive2.c,"line="4",times="0"@},
24634 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
24635 addr="0x00010774",func="foo",file="recursive2.c",
24636 fullname="/home/foo/recursive2.c",line="11",times="0"@}]@}
24638 -break-insert -r foo.*
24639 ~int foo(int, int);
24640 ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c,
24641 "fullname="/home/foo/recursive2.c",line="11",times="0"@}
24645 @subheading The @code{-break-list} Command
24646 @findex -break-list
24648 @subsubheading Synopsis
24654 Displays the list of inserted breakpoints, showing the following fields:
24658 number of the breakpoint
24660 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
24662 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
24665 is the breakpoint enabled or no: @samp{y} or @samp{n}
24667 memory location at which the breakpoint is set
24669 logical location of the breakpoint, expressed by function name, file
24672 number of times the breakpoint has been hit
24675 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
24676 @code{body} field is an empty list.
24678 @subsubheading @value{GDBN} Command
24680 The corresponding @value{GDBN} command is @samp{info break}.
24682 @subsubheading Example
24687 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
24688 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
24689 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
24690 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
24691 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
24692 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
24693 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
24694 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
24695 addr="0x000100d0",func="main",file="hello.c",line="5",times="0"@},
24696 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
24697 addr="0x00010114",func="foo",file="hello.c",fullname="/home/foo/hello.c",
24698 line="13",times="0"@}]@}
24702 Here's an example of the result when there are no breakpoints:
24707 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
24708 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
24709 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
24710 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
24711 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
24712 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
24713 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
24718 @subheading The @code{-break-passcount} Command
24719 @findex -break-passcount
24721 @subsubheading Synopsis
24724 -break-passcount @var{tracepoint-number} @var{passcount}
24727 Set the passcount for tracepoint @var{tracepoint-number} to
24728 @var{passcount}. If the breakpoint referred to by @var{tracepoint-number}
24729 is not a tracepoint, error is emitted. This corresponds to CLI
24730 command @samp{passcount}.
24732 @subheading The @code{-break-watch} Command
24733 @findex -break-watch
24735 @subsubheading Synopsis
24738 -break-watch [ -a | -r ]
24741 Create a watchpoint. With the @samp{-a} option it will create an
24742 @dfn{access} watchpoint, i.e., a watchpoint that triggers either on a
24743 read from or on a write to the memory location. With the @samp{-r}
24744 option, the watchpoint created is a @dfn{read} watchpoint, i.e., it will
24745 trigger only when the memory location is accessed for reading. Without
24746 either of the options, the watchpoint created is a regular watchpoint,
24747 i.e., it will trigger when the memory location is accessed for writing.
24748 @xref{Set Watchpoints, , Setting Watchpoints}.
24750 Note that @samp{-break-list} will report a single list of watchpoints and
24751 breakpoints inserted.
24753 @subsubheading @value{GDBN} Command
24755 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
24758 @subsubheading Example
24760 Setting a watchpoint on a variable in the @code{main} function:
24765 ^done,wpt=@{number="2",exp="x"@}
24770 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
24771 value=@{old="-268439212",new="55"@},
24772 frame=@{func="main",args=[],file="recursive2.c",
24773 fullname="/home/foo/bar/recursive2.c",line="5"@}
24777 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
24778 the program execution twice: first for the variable changing value, then
24779 for the watchpoint going out of scope.
24784 ^done,wpt=@{number="5",exp="C"@}
24789 *stopped,reason="watchpoint-trigger",
24790 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
24791 frame=@{func="callee4",args=[],
24792 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
24793 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
24798 *stopped,reason="watchpoint-scope",wpnum="5",
24799 frame=@{func="callee3",args=[@{name="strarg",
24800 value="0x11940 \"A string argument.\""@}],
24801 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
24802 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
24806 Listing breakpoints and watchpoints, at different points in the program
24807 execution. Note that once the watchpoint goes out of scope, it is
24813 ^done,wpt=@{number="2",exp="C"@}
24816 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
24817 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
24818 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
24819 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
24820 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
24821 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
24822 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
24823 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
24824 addr="0x00010734",func="callee4",
24825 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
24826 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c"line="8",times="1"@},
24827 bkpt=@{number="2",type="watchpoint",disp="keep",
24828 enabled="y",addr="",what="C",times="0"@}]@}
24833 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
24834 value=@{old="-276895068",new="3"@},
24835 frame=@{func="callee4",args=[],
24836 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
24837 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
24840 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
24841 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
24842 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
24843 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
24844 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
24845 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
24846 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
24847 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
24848 addr="0x00010734",func="callee4",
24849 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
24850 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",times="1"@},
24851 bkpt=@{number="2",type="watchpoint",disp="keep",
24852 enabled="y",addr="",what="C",times="-5"@}]@}
24856 ^done,reason="watchpoint-scope",wpnum="2",
24857 frame=@{func="callee3",args=[@{name="strarg",
24858 value="0x11940 \"A string argument.\""@}],
24859 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
24860 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
24863 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
24864 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
24865 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
24866 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
24867 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
24868 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
24869 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
24870 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
24871 addr="0x00010734",func="callee4",
24872 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
24873 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
24878 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
24879 @node GDB/MI Program Context
24880 @section @sc{gdb/mi} Program Context
24882 @subheading The @code{-exec-arguments} Command
24883 @findex -exec-arguments
24886 @subsubheading Synopsis
24889 -exec-arguments @var{args}
24892 Set the inferior program arguments, to be used in the next
24895 @subsubheading @value{GDBN} Command
24897 The corresponding @value{GDBN} command is @samp{set args}.
24899 @subsubheading Example
24903 -exec-arguments -v word
24910 @subheading The @code{-exec-show-arguments} Command
24911 @findex -exec-show-arguments
24913 @subsubheading Synopsis
24916 -exec-show-arguments
24919 Print the arguments of the program.
24921 @subsubheading @value{GDBN} Command
24923 The corresponding @value{GDBN} command is @samp{show args}.
24925 @subsubheading Example
24930 @subheading The @code{-environment-cd} Command
24931 @findex -environment-cd
24933 @subsubheading Synopsis
24936 -environment-cd @var{pathdir}
24939 Set @value{GDBN}'s working directory.
24941 @subsubheading @value{GDBN} Command
24943 The corresponding @value{GDBN} command is @samp{cd}.
24945 @subsubheading Example
24949 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
24955 @subheading The @code{-environment-directory} Command
24956 @findex -environment-directory
24958 @subsubheading Synopsis
24961 -environment-directory [ -r ] [ @var{pathdir} ]+
24964 Add directories @var{pathdir} to beginning of search path for source files.
24965 If the @samp{-r} option is used, the search path is reset to the default
24966 search path. If directories @var{pathdir} are supplied in addition to the
24967 @samp{-r} option, the search path is first reset and then addition
24969 Multiple directories may be specified, separated by blanks. Specifying
24970 multiple directories in a single command
24971 results in the directories added to the beginning of the
24972 search path in the same order they were presented in the command.
24973 If blanks are needed as
24974 part of a directory name, double-quotes should be used around
24975 the name. In the command output, the path will show up separated
24976 by the system directory-separator character. The directory-separator
24977 character must not be used
24978 in any directory name.
24979 If no directories are specified, the current search path is displayed.
24981 @subsubheading @value{GDBN} Command
24983 The corresponding @value{GDBN} command is @samp{dir}.
24985 @subsubheading Example
24989 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
24990 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
24992 -environment-directory ""
24993 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
24995 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
24996 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
24998 -environment-directory -r
24999 ^done,source-path="$cdir:$cwd"
25004 @subheading The @code{-environment-path} Command
25005 @findex -environment-path
25007 @subsubheading Synopsis
25010 -environment-path [ -r ] [ @var{pathdir} ]+
25013 Add directories @var{pathdir} to beginning of search path for object files.
25014 If the @samp{-r} option is used, the search path is reset to the original
25015 search path that existed at gdb start-up. If directories @var{pathdir} are
25016 supplied in addition to the
25017 @samp{-r} option, the search path is first reset and then addition
25019 Multiple directories may be specified, separated by blanks. Specifying
25020 multiple directories in a single command
25021 results in the directories added to the beginning of the
25022 search path in the same order they were presented in the command.
25023 If blanks are needed as
25024 part of a directory name, double-quotes should be used around
25025 the name. In the command output, the path will show up separated
25026 by the system directory-separator character. The directory-separator
25027 character must not be used
25028 in any directory name.
25029 If no directories are specified, the current path is displayed.
25032 @subsubheading @value{GDBN} Command
25034 The corresponding @value{GDBN} command is @samp{path}.
25036 @subsubheading Example
25041 ^done,path="/usr/bin"
25043 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
25044 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
25046 -environment-path -r /usr/local/bin
25047 ^done,path="/usr/local/bin:/usr/bin"
25052 @subheading The @code{-environment-pwd} Command
25053 @findex -environment-pwd
25055 @subsubheading Synopsis
25061 Show the current working directory.
25063 @subsubheading @value{GDBN} Command
25065 The corresponding @value{GDBN} command is @samp{pwd}.
25067 @subsubheading Example
25072 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
25076 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25077 @node GDB/MI Thread Commands
25078 @section @sc{gdb/mi} Thread Commands
25081 @subheading The @code{-thread-info} Command
25082 @findex -thread-info
25084 @subsubheading Synopsis
25087 -thread-info [ @var{thread-id} ]
25090 Reports information about either a specific thread, if
25091 the @var{thread-id} parameter is present, or about all
25092 threads. When printing information about all threads,
25093 also reports the current thread.
25095 @subsubheading @value{GDBN} Command
25097 The @samp{info thread} command prints the same information
25100 @subsubheading Example
25105 @{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
25106 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},state="running"@},
25107 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
25108 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
25109 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},state="running"@}],
25110 current-thread-id="1"
25114 The @samp{state} field may have the following values:
25118 The thread is stopped. Frame information is available for stopped
25122 The thread is running. There's no frame information for running
25127 @subheading The @code{-thread-list-ids} Command
25128 @findex -thread-list-ids
25130 @subsubheading Synopsis
25136 Produces a list of the currently known @value{GDBN} thread ids. At the
25137 end of the list it also prints the total number of such threads.
25139 This command is retained for historical reasons, the
25140 @code{-thread-info} command should be used instead.
25142 @subsubheading @value{GDBN} Command
25144 Part of @samp{info threads} supplies the same information.
25146 @subsubheading Example
25151 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
25152 current-thread-id="1",number-of-threads="3"
25157 @subheading The @code{-thread-select} Command
25158 @findex -thread-select
25160 @subsubheading Synopsis
25163 -thread-select @var{threadnum}
25166 Make @var{threadnum} the current thread. It prints the number of the new
25167 current thread, and the topmost frame for that thread.
25169 This command is deprecated in favor of explicitly using the
25170 @samp{--thread} option to each command.
25172 @subsubheading @value{GDBN} Command
25174 The corresponding @value{GDBN} command is @samp{thread}.
25176 @subsubheading Example
25183 *stopped,reason="end-stepping-range",thread-id="2",line="187",
25184 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
25188 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
25189 number-of-threads="3"
25192 ^done,new-thread-id="3",
25193 frame=@{level="0",func="vprintf",
25194 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
25195 @{name="arg",value="0x2"@}],file="vprintf.c",line="31"@}
25199 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25200 @node GDB/MI Program Execution
25201 @section @sc{gdb/mi} Program Execution
25203 These are the asynchronous commands which generate the out-of-band
25204 record @samp{*stopped}. Currently @value{GDBN} only really executes
25205 asynchronously with remote targets and this interaction is mimicked in
25208 @subheading The @code{-exec-continue} Command
25209 @findex -exec-continue
25211 @subsubheading Synopsis
25214 -exec-continue [--reverse] [--all|--thread-group N]
25217 Resumes the execution of the inferior program, which will continue
25218 to execute until it reaches a debugger stop event. If the
25219 @samp{--reverse} option is specified, execution resumes in reverse until
25220 it reaches a stop event. Stop events may include
25223 breakpoints or watchpoints
25225 signals or exceptions
25227 the end of the process (or its beginning under @samp{--reverse})
25229 the end or beginning of a replay log if one is being used.
25231 In all-stop mode (@pxref{All-Stop
25232 Mode}), may resume only one thread, or all threads, depending on the
25233 value of the @samp{scheduler-locking} variable. If @samp{--all} is
25234 specified, all threads (in all inferiors) will be resumed. The @samp{--all} option is
25235 ignored in all-stop mode. If the @samp{--thread-group} options is
25236 specified, then all threads in that thread group are resumed.
25238 @subsubheading @value{GDBN} Command
25240 The corresponding @value{GDBN} corresponding is @samp{continue}.
25242 @subsubheading Example
25249 *stopped,reason="breakpoint-hit",disp="keep",bkptno="2",frame=@{
25250 func="foo",args=[],file="hello.c",fullname="/home/foo/bar/hello.c",
25256 @subheading The @code{-exec-finish} Command
25257 @findex -exec-finish
25259 @subsubheading Synopsis
25262 -exec-finish [--reverse]
25265 Resumes the execution of the inferior program until the current
25266 function is exited. Displays the results returned by the function.
25267 If the @samp{--reverse} option is specified, resumes the reverse
25268 execution of the inferior program until the point where current
25269 function was called.
25271 @subsubheading @value{GDBN} Command
25273 The corresponding @value{GDBN} command is @samp{finish}.
25275 @subsubheading Example
25277 Function returning @code{void}.
25284 *stopped,reason="function-finished",frame=@{func="main",args=[],
25285 file="hello.c",fullname="/home/foo/bar/hello.c",line="7"@}
25289 Function returning other than @code{void}. The name of the internal
25290 @value{GDBN} variable storing the result is printed, together with the
25297 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
25298 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
25299 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
25300 gdb-result-var="$1",return-value="0"
25305 @subheading The @code{-exec-interrupt} Command
25306 @findex -exec-interrupt
25308 @subsubheading Synopsis
25311 -exec-interrupt [--all|--thread-group N]
25314 Interrupts the background execution of the target. Note how the token
25315 associated with the stop message is the one for the execution command
25316 that has been interrupted. The token for the interrupt itself only
25317 appears in the @samp{^done} output. If the user is trying to
25318 interrupt a non-running program, an error message will be printed.
25320 Note that when asynchronous execution is enabled, this command is
25321 asynchronous just like other execution commands. That is, first the
25322 @samp{^done} response will be printed, and the target stop will be
25323 reported after that using the @samp{*stopped} notification.
25325 In non-stop mode, only the context thread is interrupted by default.
25326 All threads (in all inferiors) will be interrupted if the
25327 @samp{--all} option is specified. If the @samp{--thread-group}
25328 option is specified, all threads in that group will be interrupted.
25330 @subsubheading @value{GDBN} Command
25332 The corresponding @value{GDBN} command is @samp{interrupt}.
25334 @subsubheading Example
25345 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
25346 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",
25347 fullname="/home/foo/bar/try.c",line="13"@}
25352 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
25356 @subheading The @code{-exec-jump} Command
25359 @subsubheading Synopsis
25362 -exec-jump @var{location}
25365 Resumes execution of the inferior program at the location specified by
25366 parameter. @xref{Specify Location}, for a description of the
25367 different forms of @var{location}.
25369 @subsubheading @value{GDBN} Command
25371 The corresponding @value{GDBN} command is @samp{jump}.
25373 @subsubheading Example
25376 -exec-jump foo.c:10
25377 *running,thread-id="all"
25382 @subheading The @code{-exec-next} Command
25385 @subsubheading Synopsis
25388 -exec-next [--reverse]
25391 Resumes execution of the inferior program, stopping when the beginning
25392 of the next source line is reached.
25394 If the @samp{--reverse} option is specified, resumes reverse execution
25395 of the inferior program, stopping at the beginning of the previous
25396 source line. If you issue this command on the first line of a
25397 function, it will take you back to the caller of that function, to the
25398 source line where the function was called.
25401 @subsubheading @value{GDBN} Command
25403 The corresponding @value{GDBN} command is @samp{next}.
25405 @subsubheading Example
25411 *stopped,reason="end-stepping-range",line="8",file="hello.c"
25416 @subheading The @code{-exec-next-instruction} Command
25417 @findex -exec-next-instruction
25419 @subsubheading Synopsis
25422 -exec-next-instruction [--reverse]
25425 Executes one machine instruction. If the instruction is a function
25426 call, continues until the function returns. If the program stops at an
25427 instruction in the middle of a source line, the address will be
25430 If the @samp{--reverse} option is specified, resumes reverse execution
25431 of the inferior program, stopping at the previous instruction. If the
25432 previously executed instruction was a return from another function,
25433 it will continue to execute in reverse until the call to that function
25434 (from the current stack frame) is reached.
25436 @subsubheading @value{GDBN} Command
25438 The corresponding @value{GDBN} command is @samp{nexti}.
25440 @subsubheading Example
25444 -exec-next-instruction
25448 *stopped,reason="end-stepping-range",
25449 addr="0x000100d4",line="5",file="hello.c"
25454 @subheading The @code{-exec-return} Command
25455 @findex -exec-return
25457 @subsubheading Synopsis
25463 Makes current function return immediately. Doesn't execute the inferior.
25464 Displays the new current frame.
25466 @subsubheading @value{GDBN} Command
25468 The corresponding @value{GDBN} command is @samp{return}.
25470 @subsubheading Example
25474 200-break-insert callee4
25475 200^done,bkpt=@{number="1",addr="0x00010734",
25476 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
25481 000*stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
25482 frame=@{func="callee4",args=[],
25483 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
25484 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
25490 111^done,frame=@{level="0",func="callee3",
25491 args=[@{name="strarg",
25492 value="0x11940 \"A string argument.\""@}],
25493 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
25494 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
25499 @subheading The @code{-exec-run} Command
25502 @subsubheading Synopsis
25505 -exec-run [--all | --thread-group N]
25508 Starts execution of the inferior from the beginning. The inferior
25509 executes until either a breakpoint is encountered or the program
25510 exits. In the latter case the output will include an exit code, if
25511 the program has exited exceptionally.
25513 When no option is specified, the current inferior is started. If the
25514 @samp{--thread-group} option is specified, it should refer to a thread
25515 group of type @samp{process}, and that thread group will be started.
25516 If the @samp{--all} option is specified, then all inferiors will be started.
25518 @subsubheading @value{GDBN} Command
25520 The corresponding @value{GDBN} command is @samp{run}.
25522 @subsubheading Examples
25527 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
25532 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
25533 frame=@{func="main",args=[],file="recursive2.c",
25534 fullname="/home/foo/bar/recursive2.c",line="4"@}
25539 Program exited normally:
25547 *stopped,reason="exited-normally"
25552 Program exited exceptionally:
25560 *stopped,reason="exited",exit-code="01"
25564 Another way the program can terminate is if it receives a signal such as
25565 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
25569 *stopped,reason="exited-signalled",signal-name="SIGINT",
25570 signal-meaning="Interrupt"
25574 @c @subheading -exec-signal
25577 @subheading The @code{-exec-step} Command
25580 @subsubheading Synopsis
25583 -exec-step [--reverse]
25586 Resumes execution of the inferior program, stopping when the beginning
25587 of the next source line is reached, if the next source line is not a
25588 function call. If it is, stop at the first instruction of the called
25589 function. If the @samp{--reverse} option is specified, resumes reverse
25590 execution of the inferior program, stopping at the beginning of the
25591 previously executed source line.
25593 @subsubheading @value{GDBN} Command
25595 The corresponding @value{GDBN} command is @samp{step}.
25597 @subsubheading Example
25599 Stepping into a function:
25605 *stopped,reason="end-stepping-range",
25606 frame=@{func="foo",args=[@{name="a",value="10"@},
25607 @{name="b",value="0"@}],file="recursive2.c",
25608 fullname="/home/foo/bar/recursive2.c",line="11"@}
25618 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
25623 @subheading The @code{-exec-step-instruction} Command
25624 @findex -exec-step-instruction
25626 @subsubheading Synopsis
25629 -exec-step-instruction [--reverse]
25632 Resumes the inferior which executes one machine instruction. If the
25633 @samp{--reverse} option is specified, resumes reverse execution of the
25634 inferior program, stopping at the previously executed instruction.
25635 The output, once @value{GDBN} has stopped, will vary depending on
25636 whether we have stopped in the middle of a source line or not. In the
25637 former case, the address at which the program stopped will be printed
25640 @subsubheading @value{GDBN} Command
25642 The corresponding @value{GDBN} command is @samp{stepi}.
25644 @subsubheading Example
25648 -exec-step-instruction
25652 *stopped,reason="end-stepping-range",
25653 frame=@{func="foo",args=[],file="try.c",
25654 fullname="/home/foo/bar/try.c",line="10"@}
25656 -exec-step-instruction
25660 *stopped,reason="end-stepping-range",
25661 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",
25662 fullname="/home/foo/bar/try.c",line="10"@}
25667 @subheading The @code{-exec-until} Command
25668 @findex -exec-until
25670 @subsubheading Synopsis
25673 -exec-until [ @var{location} ]
25676 Executes the inferior until the @var{location} specified in the
25677 argument is reached. If there is no argument, the inferior executes
25678 until a source line greater than the current one is reached. The
25679 reason for stopping in this case will be @samp{location-reached}.
25681 @subsubheading @value{GDBN} Command
25683 The corresponding @value{GDBN} command is @samp{until}.
25685 @subsubheading Example
25689 -exec-until recursive2.c:6
25693 *stopped,reason="location-reached",frame=@{func="main",args=[],
25694 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="6"@}
25699 @subheading -file-clear
25700 Is this going away????
25703 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25704 @node GDB/MI Stack Manipulation
25705 @section @sc{gdb/mi} Stack Manipulation Commands
25708 @subheading The @code{-stack-info-frame} Command
25709 @findex -stack-info-frame
25711 @subsubheading Synopsis
25717 Get info on the selected frame.
25719 @subsubheading @value{GDBN} Command
25721 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
25722 (without arguments).
25724 @subsubheading Example
25729 ^done,frame=@{level="1",addr="0x0001076c",func="callee3",
25730 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
25731 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@}
25735 @subheading The @code{-stack-info-depth} Command
25736 @findex -stack-info-depth
25738 @subsubheading Synopsis
25741 -stack-info-depth [ @var{max-depth} ]
25744 Return the depth of the stack. If the integer argument @var{max-depth}
25745 is specified, do not count beyond @var{max-depth} frames.
25747 @subsubheading @value{GDBN} Command
25749 There's no equivalent @value{GDBN} command.
25751 @subsubheading Example
25753 For a stack with frame levels 0 through 11:
25760 -stack-info-depth 4
25763 -stack-info-depth 12
25766 -stack-info-depth 11
25769 -stack-info-depth 13
25774 @subheading The @code{-stack-list-arguments} Command
25775 @findex -stack-list-arguments
25777 @subsubheading Synopsis
25780 -stack-list-arguments @var{print-values}
25781 [ @var{low-frame} @var{high-frame} ]
25784 Display a list of the arguments for the frames between @var{low-frame}
25785 and @var{high-frame} (inclusive). If @var{low-frame} and
25786 @var{high-frame} are not provided, list the arguments for the whole
25787 call stack. If the two arguments are equal, show the single frame
25788 at the corresponding level. It is an error if @var{low-frame} is
25789 larger than the actual number of frames. On the other hand,
25790 @var{high-frame} may be larger than the actual number of frames, in
25791 which case only existing frames will be returned.
25793 If @var{print-values} is 0 or @code{--no-values}, print only the names of
25794 the variables; if it is 1 or @code{--all-values}, print also their
25795 values; and if it is 2 or @code{--simple-values}, print the name,
25796 type and value for simple data types, and the name and type for arrays,
25797 structures and unions.
25799 Use of this command to obtain arguments in a single frame is
25800 deprecated in favor of the @samp{-stack-list-variables} command.
25802 @subsubheading @value{GDBN} Command
25804 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
25805 @samp{gdb_get_args} command which partially overlaps with the
25806 functionality of @samp{-stack-list-arguments}.
25808 @subsubheading Example
25815 frame=@{level="0",addr="0x00010734",func="callee4",
25816 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
25817 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@},
25818 frame=@{level="1",addr="0x0001076c",func="callee3",
25819 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
25820 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@},
25821 frame=@{level="2",addr="0x0001078c",func="callee2",
25822 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
25823 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="22"@},
25824 frame=@{level="3",addr="0x000107b4",func="callee1",
25825 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
25826 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="27"@},
25827 frame=@{level="4",addr="0x000107e0",func="main",
25828 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
25829 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="32"@}]
25831 -stack-list-arguments 0
25834 frame=@{level="0",args=[]@},
25835 frame=@{level="1",args=[name="strarg"]@},
25836 frame=@{level="2",args=[name="intarg",name="strarg"]@},
25837 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
25838 frame=@{level="4",args=[]@}]
25840 -stack-list-arguments 1
25843 frame=@{level="0",args=[]@},
25845 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
25846 frame=@{level="2",args=[
25847 @{name="intarg",value="2"@},
25848 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
25849 @{frame=@{level="3",args=[
25850 @{name="intarg",value="2"@},
25851 @{name="strarg",value="0x11940 \"A string argument.\""@},
25852 @{name="fltarg",value="3.5"@}]@},
25853 frame=@{level="4",args=[]@}]
25855 -stack-list-arguments 0 2 2
25856 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
25858 -stack-list-arguments 1 2 2
25859 ^done,stack-args=[frame=@{level="2",
25860 args=[@{name="intarg",value="2"@},
25861 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
25865 @c @subheading -stack-list-exception-handlers
25868 @subheading The @code{-stack-list-frames} Command
25869 @findex -stack-list-frames
25871 @subsubheading Synopsis
25874 -stack-list-frames [ @var{low-frame} @var{high-frame} ]
25877 List the frames currently on the stack. For each frame it displays the
25882 The frame number, 0 being the topmost frame, i.e., the innermost function.
25884 The @code{$pc} value for that frame.
25888 File name of the source file where the function lives.
25890 Line number corresponding to the @code{$pc}.
25893 If invoked without arguments, this command prints a backtrace for the
25894 whole stack. If given two integer arguments, it shows the frames whose
25895 levels are between the two arguments (inclusive). If the two arguments
25896 are equal, it shows the single frame at the corresponding level. It is
25897 an error if @var{low-frame} is larger than the actual number of
25898 frames. On the other hand, @var{high-frame} may be larger than the
25899 actual number of frames, in which case only existing frames will be returned.
25901 @subsubheading @value{GDBN} Command
25903 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
25905 @subsubheading Example
25907 Full stack backtrace:
25913 [frame=@{level="0",addr="0x0001076c",func="foo",
25914 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="11"@},
25915 frame=@{level="1",addr="0x000107a4",func="foo",
25916 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
25917 frame=@{level="2",addr="0x000107a4",func="foo",
25918 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
25919 frame=@{level="3",addr="0x000107a4",func="foo",
25920 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
25921 frame=@{level="4",addr="0x000107a4",func="foo",
25922 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
25923 frame=@{level="5",addr="0x000107a4",func="foo",
25924 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
25925 frame=@{level="6",addr="0x000107a4",func="foo",
25926 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
25927 frame=@{level="7",addr="0x000107a4",func="foo",
25928 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
25929 frame=@{level="8",addr="0x000107a4",func="foo",
25930 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
25931 frame=@{level="9",addr="0x000107a4",func="foo",
25932 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
25933 frame=@{level="10",addr="0x000107a4",func="foo",
25934 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
25935 frame=@{level="11",addr="0x00010738",func="main",
25936 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="4"@}]
25940 Show frames between @var{low_frame} and @var{high_frame}:
25944 -stack-list-frames 3 5
25946 [frame=@{level="3",addr="0x000107a4",func="foo",
25947 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
25948 frame=@{level="4",addr="0x000107a4",func="foo",
25949 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
25950 frame=@{level="5",addr="0x000107a4",func="foo",
25951 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
25955 Show a single frame:
25959 -stack-list-frames 3 3
25961 [frame=@{level="3",addr="0x000107a4",func="foo",
25962 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
25967 @subheading The @code{-stack-list-locals} Command
25968 @findex -stack-list-locals
25970 @subsubheading Synopsis
25973 -stack-list-locals @var{print-values}
25976 Display the local variable names for the selected frame. If
25977 @var{print-values} is 0 or @code{--no-values}, print only the names of
25978 the variables; if it is 1 or @code{--all-values}, print also their
25979 values; and if it is 2 or @code{--simple-values}, print the name,
25980 type and value for simple data types, and the name and type for arrays,
25981 structures and unions. In this last case, a frontend can immediately
25982 display the value of simple data types and create variable objects for
25983 other data types when the user wishes to explore their values in
25986 This command is deprecated in favor of the
25987 @samp{-stack-list-variables} command.
25989 @subsubheading @value{GDBN} Command
25991 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
25993 @subsubheading Example
25997 -stack-list-locals 0
25998 ^done,locals=[name="A",name="B",name="C"]
26000 -stack-list-locals --all-values
26001 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
26002 @{name="C",value="@{1, 2, 3@}"@}]
26003 -stack-list-locals --simple-values
26004 ^done,locals=[@{name="A",type="int",value="1"@},
26005 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
26009 @subheading The @code{-stack-list-variables} Command
26010 @findex -stack-list-variables
26012 @subsubheading Synopsis
26015 -stack-list-variables @var{print-values}
26018 Display the names of local variables and function arguments for the selected frame. If
26019 @var{print-values} is 0 or @code{--no-values}, print only the names of
26020 the variables; if it is 1 or @code{--all-values}, print also their
26021 values; and if it is 2 or @code{--simple-values}, print the name,
26022 type and value for simple data types, and the name and type for arrays,
26023 structures and unions.
26025 @subsubheading Example
26029 -stack-list-variables --thread 1 --frame 0 --all-values
26030 ^done,variables=[@{name="x",value="11"@},@{name="s",value="@{a = 1, b = 2@}"@}]
26035 @subheading The @code{-stack-select-frame} Command
26036 @findex -stack-select-frame
26038 @subsubheading Synopsis
26041 -stack-select-frame @var{framenum}
26044 Change the selected frame. Select a different frame @var{framenum} on
26047 This command in deprecated in favor of passing the @samp{--frame}
26048 option to every command.
26050 @subsubheading @value{GDBN} Command
26052 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
26053 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
26055 @subsubheading Example
26059 -stack-select-frame 2
26064 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26065 @node GDB/MI Variable Objects
26066 @section @sc{gdb/mi} Variable Objects
26070 @subheading Motivation for Variable Objects in @sc{gdb/mi}
26072 For the implementation of a variable debugger window (locals, watched
26073 expressions, etc.), we are proposing the adaptation of the existing code
26074 used by @code{Insight}.
26076 The two main reasons for that are:
26080 It has been proven in practice (it is already on its second generation).
26083 It will shorten development time (needless to say how important it is
26087 The original interface was designed to be used by Tcl code, so it was
26088 slightly changed so it could be used through @sc{gdb/mi}. This section
26089 describes the @sc{gdb/mi} operations that will be available and gives some
26090 hints about their use.
26092 @emph{Note}: In addition to the set of operations described here, we
26093 expect the @sc{gui} implementation of a variable window to require, at
26094 least, the following operations:
26097 @item @code{-gdb-show} @code{output-radix}
26098 @item @code{-stack-list-arguments}
26099 @item @code{-stack-list-locals}
26100 @item @code{-stack-select-frame}
26105 @subheading Introduction to Variable Objects
26107 @cindex variable objects in @sc{gdb/mi}
26109 Variable objects are "object-oriented" MI interface for examining and
26110 changing values of expressions. Unlike some other MI interfaces that
26111 work with expressions, variable objects are specifically designed for
26112 simple and efficient presentation in the frontend. A variable object
26113 is identified by string name. When a variable object is created, the
26114 frontend specifies the expression for that variable object. The
26115 expression can be a simple variable, or it can be an arbitrary complex
26116 expression, and can even involve CPU registers. After creating a
26117 variable object, the frontend can invoke other variable object
26118 operations---for example to obtain or change the value of a variable
26119 object, or to change display format.
26121 Variable objects have hierarchical tree structure. Any variable object
26122 that corresponds to a composite type, such as structure in C, has
26123 a number of child variable objects, for example corresponding to each
26124 element of a structure. A child variable object can itself have
26125 children, recursively. Recursion ends when we reach
26126 leaf variable objects, which always have built-in types. Child variable
26127 objects are created only by explicit request, so if a frontend
26128 is not interested in the children of a particular variable object, no
26129 child will be created.
26131 For a leaf variable object it is possible to obtain its value as a
26132 string, or set the value from a string. String value can be also
26133 obtained for a non-leaf variable object, but it's generally a string
26134 that only indicates the type of the object, and does not list its
26135 contents. Assignment to a non-leaf variable object is not allowed.
26137 A frontend does not need to read the values of all variable objects each time
26138 the program stops. Instead, MI provides an update command that lists all
26139 variable objects whose values has changed since the last update
26140 operation. This considerably reduces the amount of data that must
26141 be transferred to the frontend. As noted above, children variable
26142 objects are created on demand, and only leaf variable objects have a
26143 real value. As result, gdb will read target memory only for leaf
26144 variables that frontend has created.
26146 The automatic update is not always desirable. For example, a frontend
26147 might want to keep a value of some expression for future reference,
26148 and never update it. For another example, fetching memory is
26149 relatively slow for embedded targets, so a frontend might want
26150 to disable automatic update for the variables that are either not
26151 visible on the screen, or ``closed''. This is possible using so
26152 called ``frozen variable objects''. Such variable objects are never
26153 implicitly updated.
26155 Variable objects can be either @dfn{fixed} or @dfn{floating}. For the
26156 fixed variable object, the expression is parsed when the variable
26157 object is created, including associating identifiers to specific
26158 variables. The meaning of expression never changes. For a floating
26159 variable object the values of variables whose names appear in the
26160 expressions are re-evaluated every time in the context of the current
26161 frame. Consider this example:
26166 struct work_state state;
26173 If a fixed variable object for the @code{state} variable is created in
26174 this function, and we enter the recursive call, the the variable
26175 object will report the value of @code{state} in the top-level
26176 @code{do_work} invocation. On the other hand, a floating variable
26177 object will report the value of @code{state} in the current frame.
26179 If an expression specified when creating a fixed variable object
26180 refers to a local variable, the variable object becomes bound to the
26181 thread and frame in which the variable object is created. When such
26182 variable object is updated, @value{GDBN} makes sure that the
26183 thread/frame combination the variable object is bound to still exists,
26184 and re-evaluates the variable object in context of that thread/frame.
26186 The following is the complete set of @sc{gdb/mi} operations defined to
26187 access this functionality:
26189 @multitable @columnfractions .4 .6
26190 @item @strong{Operation}
26191 @tab @strong{Description}
26193 @item @code{-enable-pretty-printing}
26194 @tab enable Python-based pretty-printing
26195 @item @code{-var-create}
26196 @tab create a variable object
26197 @item @code{-var-delete}
26198 @tab delete the variable object and/or its children
26199 @item @code{-var-set-format}
26200 @tab set the display format of this variable
26201 @item @code{-var-show-format}
26202 @tab show the display format of this variable
26203 @item @code{-var-info-num-children}
26204 @tab tells how many children this object has
26205 @item @code{-var-list-children}
26206 @tab return a list of the object's children
26207 @item @code{-var-info-type}
26208 @tab show the type of this variable object
26209 @item @code{-var-info-expression}
26210 @tab print parent-relative expression that this variable object represents
26211 @item @code{-var-info-path-expression}
26212 @tab print full expression that this variable object represents
26213 @item @code{-var-show-attributes}
26214 @tab is this variable editable? does it exist here?
26215 @item @code{-var-evaluate-expression}
26216 @tab get the value of this variable
26217 @item @code{-var-assign}
26218 @tab set the value of this variable
26219 @item @code{-var-update}
26220 @tab update the variable and its children
26221 @item @code{-var-set-frozen}
26222 @tab set frozeness attribute
26223 @item @code{-var-set-update-range}
26224 @tab set range of children to display on update
26227 In the next subsection we describe each operation in detail and suggest
26228 how it can be used.
26230 @subheading Description And Use of Operations on Variable Objects
26232 @subheading The @code{-enable-pretty-printing} Command
26233 @findex -enable-pretty-printing
26236 -enable-pretty-printing
26239 @value{GDBN} allows Python-based visualizers to affect the output of the
26240 MI variable object commands. However, because there was no way to
26241 implement this in a fully backward-compatible way, a front end must
26242 request that this functionality be enabled.
26244 Once enabled, this feature cannot be disabled.
26246 Note that if Python support has not been compiled into @value{GDBN},
26247 this command will still succeed (and do nothing).
26249 This feature is currently (as of @value{GDBN} 7.0) experimental, and
26250 may work differently in future versions of @value{GDBN}.
26252 @subheading The @code{-var-create} Command
26253 @findex -var-create
26255 @subsubheading Synopsis
26258 -var-create @{@var{name} | "-"@}
26259 @{@var{frame-addr} | "*" | "@@"@} @var{expression}
26262 This operation creates a variable object, which allows the monitoring of
26263 a variable, the result of an expression, a memory cell or a CPU
26266 The @var{name} parameter is the string by which the object can be
26267 referenced. It must be unique. If @samp{-} is specified, the varobj
26268 system will generate a string ``varNNNNNN'' automatically. It will be
26269 unique provided that one does not specify @var{name} of that format.
26270 The command fails if a duplicate name is found.
26272 The frame under which the expression should be evaluated can be
26273 specified by @var{frame-addr}. A @samp{*} indicates that the current
26274 frame should be used. A @samp{@@} indicates that a floating variable
26275 object must be created.
26277 @var{expression} is any expression valid on the current language set (must not
26278 begin with a @samp{*}), or one of the following:
26282 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
26285 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
26288 @samp{$@var{regname}} --- a CPU register name
26291 @cindex dynamic varobj
26292 A varobj's contents may be provided by a Python-based pretty-printer. In this
26293 case the varobj is known as a @dfn{dynamic varobj}. Dynamic varobjs
26294 have slightly different semantics in some cases. If the
26295 @code{-enable-pretty-printing} command is not sent, then @value{GDBN}
26296 will never create a dynamic varobj. This ensures backward
26297 compatibility for existing clients.
26299 @subsubheading Result
26301 This operation returns attributes of the newly-created varobj. These
26306 The name of the varobj.
26309 The number of children of the varobj. This number is not necessarily
26310 reliable for a dynamic varobj. Instead, you must examine the
26311 @samp{has_more} attribute.
26314 The varobj's scalar value. For a varobj whose type is some sort of
26315 aggregate (e.g., a @code{struct}), or for a dynamic varobj, this value
26316 will not be interesting.
26319 The varobj's type. This is a string representation of the type, as
26320 would be printed by the @value{GDBN} CLI.
26323 If a variable object is bound to a specific thread, then this is the
26324 thread's identifier.
26327 For a dynamic varobj, this indicates whether there appear to be any
26328 children available. For a non-dynamic varobj, this will be 0.
26331 This attribute will be present and have the value @samp{1} if the
26332 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
26333 then this attribute will not be present.
26336 A dynamic varobj can supply a display hint to the front end. The
26337 value comes directly from the Python pretty-printer object's
26338 @code{display_hint} method. @xref{Pretty Printing API}.
26341 Typical output will look like this:
26344 name="@var{name}",numchild="@var{N}",type="@var{type}",thread-id="@var{M}",
26345 has_more="@var{has_more}"
26349 @subheading The @code{-var-delete} Command
26350 @findex -var-delete
26352 @subsubheading Synopsis
26355 -var-delete [ -c ] @var{name}
26358 Deletes a previously created variable object and all of its children.
26359 With the @samp{-c} option, just deletes the children.
26361 Returns an error if the object @var{name} is not found.
26364 @subheading The @code{-var-set-format} Command
26365 @findex -var-set-format
26367 @subsubheading Synopsis
26370 -var-set-format @var{name} @var{format-spec}
26373 Sets the output format for the value of the object @var{name} to be
26376 @anchor{-var-set-format}
26377 The syntax for the @var{format-spec} is as follows:
26380 @var{format-spec} @expansion{}
26381 @{binary | decimal | hexadecimal | octal | natural@}
26384 The natural format is the default format choosen automatically
26385 based on the variable type (like decimal for an @code{int}, hex
26386 for pointers, etc.).
26388 For a variable with children, the format is set only on the
26389 variable itself, and the children are not affected.
26391 @subheading The @code{-var-show-format} Command
26392 @findex -var-show-format
26394 @subsubheading Synopsis
26397 -var-show-format @var{name}
26400 Returns the format used to display the value of the object @var{name}.
26403 @var{format} @expansion{}
26408 @subheading The @code{-var-info-num-children} Command
26409 @findex -var-info-num-children
26411 @subsubheading Synopsis
26414 -var-info-num-children @var{name}
26417 Returns the number of children of a variable object @var{name}:
26423 Note that this number is not completely reliable for a dynamic varobj.
26424 It will return the current number of children, but more children may
26428 @subheading The @code{-var-list-children} Command
26429 @findex -var-list-children
26431 @subsubheading Synopsis
26434 -var-list-children [@var{print-values}] @var{name} [@var{from} @var{to}]
26436 @anchor{-var-list-children}
26438 Return a list of the children of the specified variable object and
26439 create variable objects for them, if they do not already exist. With
26440 a single argument or if @var{print-values} has a value of 0 or
26441 @code{--no-values}, print only the names of the variables; if
26442 @var{print-values} is 1 or @code{--all-values}, also print their
26443 values; and if it is 2 or @code{--simple-values} print the name and
26444 value for simple data types and just the name for arrays, structures
26447 @var{from} and @var{to}, if specified, indicate the range of children
26448 to report. If @var{from} or @var{to} is less than zero, the range is
26449 reset and all children will be reported. Otherwise, children starting
26450 at @var{from} (zero-based) and up to and excluding @var{to} will be
26453 If a child range is requested, it will only affect the current call to
26454 @code{-var-list-children}, but not future calls to @code{-var-update}.
26455 For this, you must instead use @code{-var-set-update-range}. The
26456 intent of this approach is to enable a front end to implement any
26457 update approach it likes; for example, scrolling a view may cause the
26458 front end to request more children with @code{-var-list-children}, and
26459 then the front end could call @code{-var-set-update-range} with a
26460 different range to ensure that future updates are restricted to just
26463 For each child the following results are returned:
26468 Name of the variable object created for this child.
26471 The expression to be shown to the user by the front end to designate this child.
26472 For example this may be the name of a structure member.
26474 For a dynamic varobj, this value cannot be used to form an
26475 expression. There is no way to do this at all with a dynamic varobj.
26477 For C/C@t{++} structures there are several pseudo children returned to
26478 designate access qualifiers. For these pseudo children @var{exp} is
26479 @samp{public}, @samp{private}, or @samp{protected}. In this case the
26480 type and value are not present.
26482 A dynamic varobj will not report the access qualifying
26483 pseudo-children, regardless of the language. This information is not
26484 available at all with a dynamic varobj.
26487 Number of children this child has. For a dynamic varobj, this will be
26491 The type of the child.
26494 If values were requested, this is the value.
26497 If this variable object is associated with a thread, this is the thread id.
26498 Otherwise this result is not present.
26501 If the variable object is frozen, this variable will be present with a value of 1.
26504 The result may have its own attributes:
26508 A dynamic varobj can supply a display hint to the front end. The
26509 value comes directly from the Python pretty-printer object's
26510 @code{display_hint} method. @xref{Pretty Printing API}.
26513 This is an integer attribute which is nonzero if there are children
26514 remaining after the end of the selected range.
26517 @subsubheading Example
26521 -var-list-children n
26522 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
26523 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
26525 -var-list-children --all-values n
26526 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
26527 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
26531 @subheading The @code{-var-info-type} Command
26532 @findex -var-info-type
26534 @subsubheading Synopsis
26537 -var-info-type @var{name}
26540 Returns the type of the specified variable @var{name}. The type is
26541 returned as a string in the same format as it is output by the
26545 type=@var{typename}
26549 @subheading The @code{-var-info-expression} Command
26550 @findex -var-info-expression
26552 @subsubheading Synopsis
26555 -var-info-expression @var{name}
26558 Returns a string that is suitable for presenting this
26559 variable object in user interface. The string is generally
26560 not valid expression in the current language, and cannot be evaluated.
26562 For example, if @code{a} is an array, and variable object
26563 @code{A} was created for @code{a}, then we'll get this output:
26566 (gdb) -var-info-expression A.1
26567 ^done,lang="C",exp="1"
26571 Here, the values of @code{lang} can be @code{@{"C" | "C++" | "Java"@}}.
26573 Note that the output of the @code{-var-list-children} command also
26574 includes those expressions, so the @code{-var-info-expression} command
26577 @subheading The @code{-var-info-path-expression} Command
26578 @findex -var-info-path-expression
26580 @subsubheading Synopsis
26583 -var-info-path-expression @var{name}
26586 Returns an expression that can be evaluated in the current
26587 context and will yield the same value that a variable object has.
26588 Compare this with the @code{-var-info-expression} command, which
26589 result can be used only for UI presentation. Typical use of
26590 the @code{-var-info-path-expression} command is creating a
26591 watchpoint from a variable object.
26593 This command is currently not valid for children of a dynamic varobj,
26594 and will give an error when invoked on one.
26596 For example, suppose @code{C} is a C@t{++} class, derived from class
26597 @code{Base}, and that the @code{Base} class has a member called
26598 @code{m_size}. Assume a variable @code{c} is has the type of
26599 @code{C} and a variable object @code{C} was created for variable
26600 @code{c}. Then, we'll get this output:
26602 (gdb) -var-info-path-expression C.Base.public.m_size
26603 ^done,path_expr=((Base)c).m_size)
26606 @subheading The @code{-var-show-attributes} Command
26607 @findex -var-show-attributes
26609 @subsubheading Synopsis
26612 -var-show-attributes @var{name}
26615 List attributes of the specified variable object @var{name}:
26618 status=@var{attr} [ ( ,@var{attr} )* ]
26622 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
26624 @subheading The @code{-var-evaluate-expression} Command
26625 @findex -var-evaluate-expression
26627 @subsubheading Synopsis
26630 -var-evaluate-expression [-f @var{format-spec}] @var{name}
26633 Evaluates the expression that is represented by the specified variable
26634 object and returns its value as a string. The format of the string
26635 can be specified with the @samp{-f} option. The possible values of
26636 this option are the same as for @code{-var-set-format}
26637 (@pxref{-var-set-format}). If the @samp{-f} option is not specified,
26638 the current display format will be used. The current display format
26639 can be changed using the @code{-var-set-format} command.
26645 Note that one must invoke @code{-var-list-children} for a variable
26646 before the value of a child variable can be evaluated.
26648 @subheading The @code{-var-assign} Command
26649 @findex -var-assign
26651 @subsubheading Synopsis
26654 -var-assign @var{name} @var{expression}
26657 Assigns the value of @var{expression} to the variable object specified
26658 by @var{name}. The object must be @samp{editable}. If the variable's
26659 value is altered by the assign, the variable will show up in any
26660 subsequent @code{-var-update} list.
26662 @subsubheading Example
26670 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
26674 @subheading The @code{-var-update} Command
26675 @findex -var-update
26677 @subsubheading Synopsis
26680 -var-update [@var{print-values}] @{@var{name} | "*"@}
26683 Reevaluate the expressions corresponding to the variable object
26684 @var{name} and all its direct and indirect children, and return the
26685 list of variable objects whose values have changed; @var{name} must
26686 be a root variable object. Here, ``changed'' means that the result of
26687 @code{-var-evaluate-expression} before and after the
26688 @code{-var-update} is different. If @samp{*} is used as the variable
26689 object names, all existing variable objects are updated, except
26690 for frozen ones (@pxref{-var-set-frozen}). The option
26691 @var{print-values} determines whether both names and values, or just
26692 names are printed. The possible values of this option are the same
26693 as for @code{-var-list-children} (@pxref{-var-list-children}). It is
26694 recommended to use the @samp{--all-values} option, to reduce the
26695 number of MI commands needed on each program stop.
26697 With the @samp{*} parameter, if a variable object is bound to a
26698 currently running thread, it will not be updated, without any
26701 If @code{-var-set-update-range} was previously used on a varobj, then
26702 only the selected range of children will be reported.
26704 @code{-var-update} reports all the changed varobjs in a tuple named
26707 Each item in the change list is itself a tuple holding:
26711 The name of the varobj.
26714 If values were requested for this update, then this field will be
26715 present and will hold the value of the varobj.
26718 @anchor{-var-update}
26719 This field is a string which may take one of three values:
26723 The variable object's current value is valid.
26726 The variable object does not currently hold a valid value but it may
26727 hold one in the future if its associated expression comes back into
26731 The variable object no longer holds a valid value.
26732 This can occur when the executable file being debugged has changed,
26733 either through recompilation or by using the @value{GDBN} @code{file}
26734 command. The front end should normally choose to delete these variable
26738 In the future new values may be added to this list so the front should
26739 be prepared for this possibility. @xref{GDB/MI Development and Front Ends, ,@sc{GDB/MI} Development and Front Ends}.
26742 This is only present if the varobj is still valid. If the type
26743 changed, then this will be the string @samp{true}; otherwise it will
26747 If the varobj's type changed, then this field will be present and will
26750 @item new_num_children
26751 For a dynamic varobj, if the number of children changed, or if the
26752 type changed, this will be the new number of children.
26754 The @samp{numchild} field in other varobj responses is generally not
26755 valid for a dynamic varobj -- it will show the number of children that
26756 @value{GDBN} knows about, but because dynamic varobjs lazily
26757 instantiate their children, this will not reflect the number of
26758 children which may be available.
26760 The @samp{new_num_children} attribute only reports changes to the
26761 number of children known by @value{GDBN}. This is the only way to
26762 detect whether an update has removed children (which necessarily can
26763 only happen at the end of the update range).
26766 The display hint, if any.
26769 This is an integer value, which will be 1 if there are more children
26770 available outside the varobj's update range.
26773 This attribute will be present and have the value @samp{1} if the
26774 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
26775 then this attribute will not be present.
26778 If new children were added to a dynamic varobj within the selected
26779 update range (as set by @code{-var-set-update-range}), then they will
26780 be listed in this attribute.
26783 @subsubheading Example
26790 -var-update --all-values var1
26791 ^done,changelist=[@{name="var1",value="3",in_scope="true",
26792 type_changed="false"@}]
26796 @subheading The @code{-var-set-frozen} Command
26797 @findex -var-set-frozen
26798 @anchor{-var-set-frozen}
26800 @subsubheading Synopsis
26803 -var-set-frozen @var{name} @var{flag}
26806 Set the frozenness flag on the variable object @var{name}. The
26807 @var{flag} parameter should be either @samp{1} to make the variable
26808 frozen or @samp{0} to make it unfrozen. If a variable object is
26809 frozen, then neither itself, nor any of its children, are
26810 implicitly updated by @code{-var-update} of
26811 a parent variable or by @code{-var-update *}. Only
26812 @code{-var-update} of the variable itself will update its value and
26813 values of its children. After a variable object is unfrozen, it is
26814 implicitly updated by all subsequent @code{-var-update} operations.
26815 Unfreezing a variable does not update it, only subsequent
26816 @code{-var-update} does.
26818 @subsubheading Example
26822 -var-set-frozen V 1
26827 @subheading The @code{-var-set-update-range} command
26828 @findex -var-set-update-range
26829 @anchor{-var-set-update-range}
26831 @subsubheading Synopsis
26834 -var-set-update-range @var{name} @var{from} @var{to}
26837 Set the range of children to be returned by future invocations of
26838 @code{-var-update}.
26840 @var{from} and @var{to} indicate the range of children to report. If
26841 @var{from} or @var{to} is less than zero, the range is reset and all
26842 children will be reported. Otherwise, children starting at @var{from}
26843 (zero-based) and up to and excluding @var{to} will be reported.
26845 @subsubheading Example
26849 -var-set-update-range V 1 2
26853 @subheading The @code{-var-set-visualizer} command
26854 @findex -var-set-visualizer
26855 @anchor{-var-set-visualizer}
26857 @subsubheading Synopsis
26860 -var-set-visualizer @var{name} @var{visualizer}
26863 Set a visualizer for the variable object @var{name}.
26865 @var{visualizer} is the visualizer to use. The special value
26866 @samp{None} means to disable any visualizer in use.
26868 If not @samp{None}, @var{visualizer} must be a Python expression.
26869 This expression must evaluate to a callable object which accepts a
26870 single argument. @value{GDBN} will call this object with the value of
26871 the varobj @var{name} as an argument (this is done so that the same
26872 Python pretty-printing code can be used for both the CLI and MI).
26873 When called, this object must return an object which conforms to the
26874 pretty-printing interface (@pxref{Pretty Printing API}).
26876 The pre-defined function @code{gdb.default_visualizer} may be used to
26877 select a visualizer by following the built-in process
26878 (@pxref{Selecting Pretty-Printers}). This is done automatically when
26879 a varobj is created, and so ordinarily is not needed.
26881 This feature is only available if Python support is enabled. The MI
26882 command @code{-list-features} (@pxref{GDB/MI Miscellaneous Commands})
26883 can be used to check this.
26885 @subsubheading Example
26887 Resetting the visualizer:
26891 -var-set-visualizer V None
26895 Reselecting the default (type-based) visualizer:
26899 -var-set-visualizer V gdb.default_visualizer
26903 Suppose @code{SomeClass} is a visualizer class. A lambda expression
26904 can be used to instantiate this class for a varobj:
26908 -var-set-visualizer V "lambda val: SomeClass()"
26912 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26913 @node GDB/MI Data Manipulation
26914 @section @sc{gdb/mi} Data Manipulation
26916 @cindex data manipulation, in @sc{gdb/mi}
26917 @cindex @sc{gdb/mi}, data manipulation
26918 This section describes the @sc{gdb/mi} commands that manipulate data:
26919 examine memory and registers, evaluate expressions, etc.
26921 @c REMOVED FROM THE INTERFACE.
26922 @c @subheading -data-assign
26923 @c Change the value of a program variable. Plenty of side effects.
26924 @c @subsubheading GDB Command
26926 @c @subsubheading Example
26929 @subheading The @code{-data-disassemble} Command
26930 @findex -data-disassemble
26932 @subsubheading Synopsis
26936 [ -s @var{start-addr} -e @var{end-addr} ]
26937 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
26945 @item @var{start-addr}
26946 is the beginning address (or @code{$pc})
26947 @item @var{end-addr}
26949 @item @var{filename}
26950 is the name of the file to disassemble
26951 @item @var{linenum}
26952 is the line number to disassemble around
26954 is the number of disassembly lines to be produced. If it is -1,
26955 the whole function will be disassembled, in case no @var{end-addr} is
26956 specified. If @var{end-addr} is specified as a non-zero value, and
26957 @var{lines} is lower than the number of disassembly lines between
26958 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
26959 displayed; if @var{lines} is higher than the number of lines between
26960 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
26963 is either 0 (meaning only disassembly) or 1 (meaning mixed source and
26967 @subsubheading Result
26969 The output for each instruction is composed of four fields:
26978 Note that whatever included in the instruction field, is not manipulated
26979 directly by @sc{gdb/mi}, i.e., it is not possible to adjust its format.
26981 @subsubheading @value{GDBN} Command
26983 There's no direct mapping from this command to the CLI.
26985 @subsubheading Example
26987 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
26991 -data-disassemble -s $pc -e "$pc + 20" -- 0
26994 @{address="0x000107c0",func-name="main",offset="4",
26995 inst="mov 2, %o0"@},
26996 @{address="0x000107c4",func-name="main",offset="8",
26997 inst="sethi %hi(0x11800), %o2"@},
26998 @{address="0x000107c8",func-name="main",offset="12",
26999 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
27000 @{address="0x000107cc",func-name="main",offset="16",
27001 inst="sethi %hi(0x11800), %o2"@},
27002 @{address="0x000107d0",func-name="main",offset="20",
27003 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
27007 Disassemble the whole @code{main} function. Line 32 is part of
27011 -data-disassemble -f basics.c -l 32 -- 0
27013 @{address="0x000107bc",func-name="main",offset="0",
27014 inst="save %sp, -112, %sp"@},
27015 @{address="0x000107c0",func-name="main",offset="4",
27016 inst="mov 2, %o0"@},
27017 @{address="0x000107c4",func-name="main",offset="8",
27018 inst="sethi %hi(0x11800), %o2"@},
27020 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
27021 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
27025 Disassemble 3 instructions from the start of @code{main}:
27029 -data-disassemble -f basics.c -l 32 -n 3 -- 0
27031 @{address="0x000107bc",func-name="main",offset="0",
27032 inst="save %sp, -112, %sp"@},
27033 @{address="0x000107c0",func-name="main",offset="4",
27034 inst="mov 2, %o0"@},
27035 @{address="0x000107c4",func-name="main",offset="8",
27036 inst="sethi %hi(0x11800), %o2"@}]
27040 Disassemble 3 instructions from the start of @code{main} in mixed mode:
27044 -data-disassemble -f basics.c -l 32 -n 3 -- 1
27046 src_and_asm_line=@{line="31",
27047 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
27048 testsuite/gdb.mi/basics.c",line_asm_insn=[
27049 @{address="0x000107bc",func-name="main",offset="0",
27050 inst="save %sp, -112, %sp"@}]@},
27051 src_and_asm_line=@{line="32",
27052 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
27053 testsuite/gdb.mi/basics.c",line_asm_insn=[
27054 @{address="0x000107c0",func-name="main",offset="4",
27055 inst="mov 2, %o0"@},
27056 @{address="0x000107c4",func-name="main",offset="8",
27057 inst="sethi %hi(0x11800), %o2"@}]@}]
27062 @subheading The @code{-data-evaluate-expression} Command
27063 @findex -data-evaluate-expression
27065 @subsubheading Synopsis
27068 -data-evaluate-expression @var{expr}
27071 Evaluate @var{expr} as an expression. The expression could contain an
27072 inferior function call. The function call will execute synchronously.
27073 If the expression contains spaces, it must be enclosed in double quotes.
27075 @subsubheading @value{GDBN} Command
27077 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
27078 @samp{call}. In @code{gdbtk} only, there's a corresponding
27079 @samp{gdb_eval} command.
27081 @subsubheading Example
27083 In the following example, the numbers that precede the commands are the
27084 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
27085 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
27089 211-data-evaluate-expression A
27092 311-data-evaluate-expression &A
27093 311^done,value="0xefffeb7c"
27095 411-data-evaluate-expression A+3
27098 511-data-evaluate-expression "A + 3"
27104 @subheading The @code{-data-list-changed-registers} Command
27105 @findex -data-list-changed-registers
27107 @subsubheading Synopsis
27110 -data-list-changed-registers
27113 Display a list of the registers that have changed.
27115 @subsubheading @value{GDBN} Command
27117 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
27118 has the corresponding command @samp{gdb_changed_register_list}.
27120 @subsubheading Example
27122 On a PPC MBX board:
27130 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",frame=@{
27131 func="main",args=[],file="try.c",fullname="/home/foo/bar/try.c",
27134 -data-list-changed-registers
27135 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
27136 "10","11","13","14","15","16","17","18","19","20","21","22","23",
27137 "24","25","26","27","28","30","31","64","65","66","67","69"]
27142 @subheading The @code{-data-list-register-names} Command
27143 @findex -data-list-register-names
27145 @subsubheading Synopsis
27148 -data-list-register-names [ ( @var{regno} )+ ]
27151 Show a list of register names for the current target. If no arguments
27152 are given, it shows a list of the names of all the registers. If
27153 integer numbers are given as arguments, it will print a list of the
27154 names of the registers corresponding to the arguments. To ensure
27155 consistency between a register name and its number, the output list may
27156 include empty register names.
27158 @subsubheading @value{GDBN} Command
27160 @value{GDBN} does not have a command which corresponds to
27161 @samp{-data-list-register-names}. In @code{gdbtk} there is a
27162 corresponding command @samp{gdb_regnames}.
27164 @subsubheading Example
27166 For the PPC MBX board:
27169 -data-list-register-names
27170 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
27171 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
27172 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
27173 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
27174 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
27175 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
27176 "", "pc","ps","cr","lr","ctr","xer"]
27178 -data-list-register-names 1 2 3
27179 ^done,register-names=["r1","r2","r3"]
27183 @subheading The @code{-data-list-register-values} Command
27184 @findex -data-list-register-values
27186 @subsubheading Synopsis
27189 -data-list-register-values @var{fmt} [ ( @var{regno} )*]
27192 Display the registers' contents. @var{fmt} is the format according to
27193 which the registers' contents are to be returned, followed by an optional
27194 list of numbers specifying the registers to display. A missing list of
27195 numbers indicates that the contents of all the registers must be returned.
27197 Allowed formats for @var{fmt} are:
27214 @subsubheading @value{GDBN} Command
27216 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
27217 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
27219 @subsubheading Example
27221 For a PPC MBX board (note: line breaks are for readability only, they
27222 don't appear in the actual output):
27226 -data-list-register-values r 64 65
27227 ^done,register-values=[@{number="64",value="0xfe00a300"@},
27228 @{number="65",value="0x00029002"@}]
27230 -data-list-register-values x
27231 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
27232 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
27233 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
27234 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
27235 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
27236 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
27237 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
27238 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
27239 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
27240 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
27241 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
27242 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
27243 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
27244 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
27245 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
27246 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
27247 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
27248 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
27249 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
27250 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
27251 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
27252 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
27253 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
27254 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
27255 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
27256 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
27257 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
27258 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
27259 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
27260 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
27261 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
27262 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
27263 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
27264 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
27265 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
27266 @{number="69",value="0x20002b03"@}]
27271 @subheading The @code{-data-read-memory} Command
27272 @findex -data-read-memory
27274 @subsubheading Synopsis
27277 -data-read-memory [ -o @var{byte-offset} ]
27278 @var{address} @var{word-format} @var{word-size}
27279 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
27286 @item @var{address}
27287 An expression specifying the address of the first memory word to be
27288 read. Complex expressions containing embedded white space should be
27289 quoted using the C convention.
27291 @item @var{word-format}
27292 The format to be used to print the memory words. The notation is the
27293 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
27296 @item @var{word-size}
27297 The size of each memory word in bytes.
27299 @item @var{nr-rows}
27300 The number of rows in the output table.
27302 @item @var{nr-cols}
27303 The number of columns in the output table.
27306 If present, indicates that each row should include an @sc{ascii} dump. The
27307 value of @var{aschar} is used as a padding character when a byte is not a
27308 member of the printable @sc{ascii} character set (printable @sc{ascii}
27309 characters are those whose code is between 32 and 126, inclusively).
27311 @item @var{byte-offset}
27312 An offset to add to the @var{address} before fetching memory.
27315 This command displays memory contents as a table of @var{nr-rows} by
27316 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
27317 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
27318 (returned as @samp{total-bytes}). Should less than the requested number
27319 of bytes be returned by the target, the missing words are identified
27320 using @samp{N/A}. The number of bytes read from the target is returned
27321 in @samp{nr-bytes} and the starting address used to read memory in
27324 The address of the next/previous row or page is available in
27325 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
27328 @subsubheading @value{GDBN} Command
27330 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
27331 @samp{gdb_get_mem} memory read command.
27333 @subsubheading Example
27335 Read six bytes of memory starting at @code{bytes+6} but then offset by
27336 @code{-6} bytes. Format as three rows of two columns. One byte per
27337 word. Display each word in hex.
27341 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
27342 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
27343 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
27344 prev-page="0x0000138a",memory=[
27345 @{addr="0x00001390",data=["0x00","0x01"]@},
27346 @{addr="0x00001392",data=["0x02","0x03"]@},
27347 @{addr="0x00001394",data=["0x04","0x05"]@}]
27351 Read two bytes of memory starting at address @code{shorts + 64} and
27352 display as a single word formatted in decimal.
27356 5-data-read-memory shorts+64 d 2 1 1
27357 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
27358 next-row="0x00001512",prev-row="0x0000150e",
27359 next-page="0x00001512",prev-page="0x0000150e",memory=[
27360 @{addr="0x00001510",data=["128"]@}]
27364 Read thirty two bytes of memory starting at @code{bytes+16} and format
27365 as eight rows of four columns. Include a string encoding with @samp{x}
27366 used as the non-printable character.
27370 4-data-read-memory bytes+16 x 1 8 4 x
27371 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
27372 next-row="0x000013c0",prev-row="0x0000139c",
27373 next-page="0x000013c0",prev-page="0x00001380",memory=[
27374 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
27375 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
27376 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
27377 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
27378 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
27379 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
27380 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
27381 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
27385 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27386 @node GDB/MI Tracepoint Commands
27387 @section @sc{gdb/mi} Tracepoint Commands
27389 The commands defined in this section implement MI support for
27390 tracepoints. For detailed introduction, see @ref{Tracepoints}.
27392 @subheading The @code{-trace-find} Command
27393 @findex -trace-find
27395 @subsubheading Synopsis
27398 -trace-find @var{mode} [@var{parameters}@dots{}]
27401 Find a trace frame using criteria defined by @var{mode} and
27402 @var{parameters}. The following table lists permissible
27403 modes and their parameters. For details of operation, see @ref{tfind}.
27408 No parameters are required. Stops examining trace frames.
27411 An integer is required as parameter. Selects tracepoint frame with
27414 @item tracepoint-number
27415 An integer is required as parameter. Finds next
27416 trace frame that corresponds to tracepoint with the specified number.
27419 An address is required as parameter. Finds
27420 next trace frame that corresponds to any tracepoint at the specified
27423 @item pc-inside-range
27424 Two addresses are required as parameters. Finds next trace
27425 frame that corresponds to a tracepoint at an address inside the
27426 specified range. Both bounds are considered to be inside the range.
27428 @item pc-outside-range
27429 Two addresses are required as parameters. Finds
27430 next trace frame that corresponds to a tracepoint at an address outside
27431 the specified range. Both bounds are considered to be inside the range.
27434 Line specification is required as parameter. @xref{Specify Location}.
27435 Finds next trace frame that corresponds to a tracepoint at
27436 the specified location.
27440 If @samp{none} was passed as @var{mode}, the response does not
27441 have fields. Otherwise, the response may have the following fields:
27445 This field has either @samp{0} or @samp{1} as the value, depending
27446 on whether a matching tracepoint was found.
27449 The index of the found traceframe. This field is present iff
27450 the @samp{found} field has value of @samp{1}.
27453 The index of the found tracepoint. This field is present iff
27454 the @samp{found} field has value of @samp{1}.
27457 The information about the frame corresponding to the found trace
27458 frame. This field is present only if a trace frame was found.
27459 @xref{GDB/MI Frame Information}, for description of this field.
27463 @subsubheading @value{GDBN} Command
27465 The corresponding @value{GDBN} command is @samp{tfind}.
27467 @subheading -trace-define-variable
27468 @findex -trace-define-variable
27470 @subsubheading Synopsis
27473 -trace-define-variable @var{name} [ @var{value} ]
27476 Create trace variable @var{name} if it does not exist. If
27477 @var{value} is specified, sets the initial value of the specified
27478 trace variable to that value. Note that the @var{name} should start
27479 with the @samp{$} character.
27481 @subsubheading @value{GDBN} Command
27483 The corresponding @value{GDBN} command is @samp{tvariable}.
27485 @subheading -trace-list-variables
27486 @findex -trace-list-variables
27488 @subsubheading Synopsis
27491 -trace-list-variables
27494 Return a table of all defined trace variables. Each element of the
27495 table has the following fields:
27499 The name of the trace variable. This field is always present.
27502 The initial value. This is a 64-bit signed integer. This
27503 field is always present.
27506 The value the trace variable has at the moment. This is a 64-bit
27507 signed integer. This field is absent iff current value is
27508 not defined, for example if the trace was never run, or is
27513 @subsubheading @value{GDBN} Command
27515 The corresponding @value{GDBN} command is @samp{tvariables}.
27517 @subsubheading Example
27521 -trace-list-variables
27522 ^done,trace-variables=@{nr_rows="1",nr_cols="3",
27523 hdr=[@{width="15",alignment="-1",col_name="name",colhdr="Name"@},
27524 @{width="11",alignment="-1",col_name="initial",colhdr="Initial"@},
27525 @{width="11",alignment="-1",col_name="current",colhdr="Current"@}],
27526 body=[variable=@{name="$trace_timestamp",initial="0"@}
27527 variable=@{name="$foo",initial="10",current="15"@}]@}
27531 @subheading -trace-save
27532 @findex -trace-save
27534 @subsubheading Synopsis
27537 -trace-save [-r ] @var{filename}
27540 Saves the collected trace data to @var{filename}. Without the
27541 @samp{-r} option, the data is downloaded from the target and saved
27542 in a local file. With the @samp{-r} option the target is asked
27543 to perform the save.
27545 @subsubheading @value{GDBN} Command
27547 The corresponding @value{GDBN} command is @samp{tsave}.
27550 @subheading -trace-start
27551 @findex -trace-start
27553 @subsubheading Synopsis
27559 Starts a tracing experiments. The result of this command does not
27562 @subsubheading @value{GDBN} Command
27564 The corresponding @value{GDBN} command is @samp{tstart}.
27566 @subheading -trace-status
27567 @findex -trace-status
27569 @subsubheading Synopsis
27575 Obtains the status of a tracing experiment. The result may include
27576 the following fields:
27581 May have a value of either @samp{0}, when no tracing operations are
27582 supported, @samp{1}, when all tracing operations are supported, or
27583 @samp{file} when examining trace file. In the latter case, examining
27584 of trace frame is possible but new tracing experiement cannot be
27585 started. This field is always present.
27588 May have a value of either @samp{0} or @samp{1} depending on whether
27589 tracing experiement is in progress on target. This field is present
27590 if @samp{supported} field is not @samp{0}.
27593 Report the reason why the tracing was stopped last time. This field
27594 may be absent iff tracing was never stopped on target yet. The
27595 value of @samp{request} means the tracing was stopped as result of
27596 the @code{-trace-stop} command. The value of @samp{overflow} means
27597 the tracing buffer is full. The value of @samp{disconnection} means
27598 tracing was automatically stopped when @value{GDBN} has disconnected.
27599 The value of @samp{passcount} means tracing was stopped when a
27600 tracepoint was passed a maximal number of times for that tracepoint.
27601 This field is present if @samp{supported} field is not @samp{0}.
27603 @item stopping-tracepoint
27604 The number of tracepoint whose passcount as exceeded. This field is
27605 present iff the @samp{stop-reason} field has the value of
27609 @itemx frames-created
27610 The @samp{frames} field is a count of the total number of trace frames
27611 in the trace buffer, while @samp{frames-created} is the total created
27612 during the run, including ones that were discarded, such as when a
27613 circular trace buffer filled up. Both fields are optional.
27617 These fields tell the current size of the tracing buffer and the
27618 remaining space. These fields are optional.
27621 The value of the circular trace buffer flag. @code{1} means that the
27622 trace buffer is circular and old trace frames will be discarded if
27623 necessary to make room, @code{0} means that the trace buffer is linear
27627 The value of the disconnected tracing flag. @code{1} means that
27628 tracing will continue after @value{GDBN} disconnects, @code{0} means
27629 that the trace run will stop.
27633 @subsubheading @value{GDBN} Command
27635 The corresponding @value{GDBN} command is @samp{tstatus}.
27637 @subheading -trace-stop
27638 @findex -trace-stop
27640 @subsubheading Synopsis
27646 Stops a tracing experiment. The result of this command has the same
27647 fields as @code{-trace-status}, except that the @samp{supported} and
27648 @samp{running} fields are not output.
27650 @subsubheading @value{GDBN} Command
27652 The corresponding @value{GDBN} command is @samp{tstop}.
27655 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27656 @node GDB/MI Symbol Query
27657 @section @sc{gdb/mi} Symbol Query Commands
27661 @subheading The @code{-symbol-info-address} Command
27662 @findex -symbol-info-address
27664 @subsubheading Synopsis
27667 -symbol-info-address @var{symbol}
27670 Describe where @var{symbol} is stored.
27672 @subsubheading @value{GDBN} Command
27674 The corresponding @value{GDBN} command is @samp{info address}.
27676 @subsubheading Example
27680 @subheading The @code{-symbol-info-file} Command
27681 @findex -symbol-info-file
27683 @subsubheading Synopsis
27689 Show the file for the symbol.
27691 @subsubheading @value{GDBN} Command
27693 There's no equivalent @value{GDBN} command. @code{gdbtk} has
27694 @samp{gdb_find_file}.
27696 @subsubheading Example
27700 @subheading The @code{-symbol-info-function} Command
27701 @findex -symbol-info-function
27703 @subsubheading Synopsis
27706 -symbol-info-function
27709 Show which function the symbol lives in.
27711 @subsubheading @value{GDBN} Command
27713 @samp{gdb_get_function} in @code{gdbtk}.
27715 @subsubheading Example
27719 @subheading The @code{-symbol-info-line} Command
27720 @findex -symbol-info-line
27722 @subsubheading Synopsis
27728 Show the core addresses of the code for a source line.
27730 @subsubheading @value{GDBN} Command
27732 The corresponding @value{GDBN} command is @samp{info line}.
27733 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
27735 @subsubheading Example
27739 @subheading The @code{-symbol-info-symbol} Command
27740 @findex -symbol-info-symbol
27742 @subsubheading Synopsis
27745 -symbol-info-symbol @var{addr}
27748 Describe what symbol is at location @var{addr}.
27750 @subsubheading @value{GDBN} Command
27752 The corresponding @value{GDBN} command is @samp{info symbol}.
27754 @subsubheading Example
27758 @subheading The @code{-symbol-list-functions} Command
27759 @findex -symbol-list-functions
27761 @subsubheading Synopsis
27764 -symbol-list-functions
27767 List the functions in the executable.
27769 @subsubheading @value{GDBN} Command
27771 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
27772 @samp{gdb_search} in @code{gdbtk}.
27774 @subsubheading Example
27779 @subheading The @code{-symbol-list-lines} Command
27780 @findex -symbol-list-lines
27782 @subsubheading Synopsis
27785 -symbol-list-lines @var{filename}
27788 Print the list of lines that contain code and their associated program
27789 addresses for the given source filename. The entries are sorted in
27790 ascending PC order.
27792 @subsubheading @value{GDBN} Command
27794 There is no corresponding @value{GDBN} command.
27796 @subsubheading Example
27799 -symbol-list-lines basics.c
27800 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
27806 @subheading The @code{-symbol-list-types} Command
27807 @findex -symbol-list-types
27809 @subsubheading Synopsis
27815 List all the type names.
27817 @subsubheading @value{GDBN} Command
27819 The corresponding commands are @samp{info types} in @value{GDBN},
27820 @samp{gdb_search} in @code{gdbtk}.
27822 @subsubheading Example
27826 @subheading The @code{-symbol-list-variables} Command
27827 @findex -symbol-list-variables
27829 @subsubheading Synopsis
27832 -symbol-list-variables
27835 List all the global and static variable names.
27837 @subsubheading @value{GDBN} Command
27839 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
27841 @subsubheading Example
27845 @subheading The @code{-symbol-locate} Command
27846 @findex -symbol-locate
27848 @subsubheading Synopsis
27854 @subsubheading @value{GDBN} Command
27856 @samp{gdb_loc} in @code{gdbtk}.
27858 @subsubheading Example
27862 @subheading The @code{-symbol-type} Command
27863 @findex -symbol-type
27865 @subsubheading Synopsis
27868 -symbol-type @var{variable}
27871 Show type of @var{variable}.
27873 @subsubheading @value{GDBN} Command
27875 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
27876 @samp{gdb_obj_variable}.
27878 @subsubheading Example
27883 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27884 @node GDB/MI File Commands
27885 @section @sc{gdb/mi} File Commands
27887 This section describes the GDB/MI commands to specify executable file names
27888 and to read in and obtain symbol table information.
27890 @subheading The @code{-file-exec-and-symbols} Command
27891 @findex -file-exec-and-symbols
27893 @subsubheading Synopsis
27896 -file-exec-and-symbols @var{file}
27899 Specify the executable file to be debugged. This file is the one from
27900 which the symbol table is also read. If no file is specified, the
27901 command clears the executable and symbol information. If breakpoints
27902 are set when using this command with no arguments, @value{GDBN} will produce
27903 error messages. Otherwise, no output is produced, except a completion
27906 @subsubheading @value{GDBN} Command
27908 The corresponding @value{GDBN} command is @samp{file}.
27910 @subsubheading Example
27914 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
27920 @subheading The @code{-file-exec-file} Command
27921 @findex -file-exec-file
27923 @subsubheading Synopsis
27926 -file-exec-file @var{file}
27929 Specify the executable file to be debugged. Unlike
27930 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
27931 from this file. If used without argument, @value{GDBN} clears the information
27932 about the executable file. No output is produced, except a completion
27935 @subsubheading @value{GDBN} Command
27937 The corresponding @value{GDBN} command is @samp{exec-file}.
27939 @subsubheading Example
27943 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
27950 @subheading The @code{-file-list-exec-sections} Command
27951 @findex -file-list-exec-sections
27953 @subsubheading Synopsis
27956 -file-list-exec-sections
27959 List the sections of the current executable file.
27961 @subsubheading @value{GDBN} Command
27963 The @value{GDBN} command @samp{info file} shows, among the rest, the same
27964 information as this command. @code{gdbtk} has a corresponding command
27965 @samp{gdb_load_info}.
27967 @subsubheading Example
27972 @subheading The @code{-file-list-exec-source-file} Command
27973 @findex -file-list-exec-source-file
27975 @subsubheading Synopsis
27978 -file-list-exec-source-file
27981 List the line number, the current source file, and the absolute path
27982 to the current source file for the current executable. The macro
27983 information field has a value of @samp{1} or @samp{0} depending on
27984 whether or not the file includes preprocessor macro information.
27986 @subsubheading @value{GDBN} Command
27988 The @value{GDBN} equivalent is @samp{info source}
27990 @subsubheading Example
27994 123-file-list-exec-source-file
27995 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c,macro-info="1"
28000 @subheading The @code{-file-list-exec-source-files} Command
28001 @findex -file-list-exec-source-files
28003 @subsubheading Synopsis
28006 -file-list-exec-source-files
28009 List the source files for the current executable.
28011 It will always output the filename, but only when @value{GDBN} can find
28012 the absolute file name of a source file, will it output the fullname.
28014 @subsubheading @value{GDBN} Command
28016 The @value{GDBN} equivalent is @samp{info sources}.
28017 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
28019 @subsubheading Example
28022 -file-list-exec-source-files
28024 @{file=foo.c,fullname=/home/foo.c@},
28025 @{file=/home/bar.c,fullname=/home/bar.c@},
28026 @{file=gdb_could_not_find_fullpath.c@}]
28031 @subheading The @code{-file-list-shared-libraries} Command
28032 @findex -file-list-shared-libraries
28034 @subsubheading Synopsis
28037 -file-list-shared-libraries
28040 List the shared libraries in the program.
28042 @subsubheading @value{GDBN} Command
28044 The corresponding @value{GDBN} command is @samp{info shared}.
28046 @subsubheading Example
28050 @subheading The @code{-file-list-symbol-files} Command
28051 @findex -file-list-symbol-files
28053 @subsubheading Synopsis
28056 -file-list-symbol-files
28061 @subsubheading @value{GDBN} Command
28063 The corresponding @value{GDBN} command is @samp{info file} (part of it).
28065 @subsubheading Example
28070 @subheading The @code{-file-symbol-file} Command
28071 @findex -file-symbol-file
28073 @subsubheading Synopsis
28076 -file-symbol-file @var{file}
28079 Read symbol table info from the specified @var{file} argument. When
28080 used without arguments, clears @value{GDBN}'s symbol table info. No output is
28081 produced, except for a completion notification.
28083 @subsubheading @value{GDBN} Command
28085 The corresponding @value{GDBN} command is @samp{symbol-file}.
28087 @subsubheading Example
28091 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
28097 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28098 @node GDB/MI Memory Overlay Commands
28099 @section @sc{gdb/mi} Memory Overlay Commands
28101 The memory overlay commands are not implemented.
28103 @c @subheading -overlay-auto
28105 @c @subheading -overlay-list-mapping-state
28107 @c @subheading -overlay-list-overlays
28109 @c @subheading -overlay-map
28111 @c @subheading -overlay-off
28113 @c @subheading -overlay-on
28115 @c @subheading -overlay-unmap
28117 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28118 @node GDB/MI Signal Handling Commands
28119 @section @sc{gdb/mi} Signal Handling Commands
28121 Signal handling commands are not implemented.
28123 @c @subheading -signal-handle
28125 @c @subheading -signal-list-handle-actions
28127 @c @subheading -signal-list-signal-types
28131 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28132 @node GDB/MI Target Manipulation
28133 @section @sc{gdb/mi} Target Manipulation Commands
28136 @subheading The @code{-target-attach} Command
28137 @findex -target-attach
28139 @subsubheading Synopsis
28142 -target-attach @var{pid} | @var{gid} | @var{file}
28145 Attach to a process @var{pid} or a file @var{file} outside of
28146 @value{GDBN}, or a thread group @var{gid}. If attaching to a thread
28147 group, the id previously returned by
28148 @samp{-list-thread-groups --available} must be used.
28150 @subsubheading @value{GDBN} Command
28152 The corresponding @value{GDBN} command is @samp{attach}.
28154 @subsubheading Example
28158 =thread-created,id="1"
28159 *stopped,thread-id="1",frame=@{addr="0xb7f7e410",func="bar",args=[]@}
28165 @subheading The @code{-target-compare-sections} Command
28166 @findex -target-compare-sections
28168 @subsubheading Synopsis
28171 -target-compare-sections [ @var{section} ]
28174 Compare data of section @var{section} on target to the exec file.
28175 Without the argument, all sections are compared.
28177 @subsubheading @value{GDBN} Command
28179 The @value{GDBN} equivalent is @samp{compare-sections}.
28181 @subsubheading Example
28186 @subheading The @code{-target-detach} Command
28187 @findex -target-detach
28189 @subsubheading Synopsis
28192 -target-detach [ @var{pid} | @var{gid} ]
28195 Detach from the remote target which normally resumes its execution.
28196 If either @var{pid} or @var{gid} is specified, detaches from either
28197 the specified process, or specified thread group. There's no output.
28199 @subsubheading @value{GDBN} Command
28201 The corresponding @value{GDBN} command is @samp{detach}.
28203 @subsubheading Example
28213 @subheading The @code{-target-disconnect} Command
28214 @findex -target-disconnect
28216 @subsubheading Synopsis
28222 Disconnect from the remote target. There's no output and the target is
28223 generally not resumed.
28225 @subsubheading @value{GDBN} Command
28227 The corresponding @value{GDBN} command is @samp{disconnect}.
28229 @subsubheading Example
28239 @subheading The @code{-target-download} Command
28240 @findex -target-download
28242 @subsubheading Synopsis
28248 Loads the executable onto the remote target.
28249 It prints out an update message every half second, which includes the fields:
28253 The name of the section.
28255 The size of what has been sent so far for that section.
28257 The size of the section.
28259 The total size of what was sent so far (the current and the previous sections).
28261 The size of the overall executable to download.
28265 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
28266 @sc{gdb/mi} Output Syntax}).
28268 In addition, it prints the name and size of the sections, as they are
28269 downloaded. These messages include the following fields:
28273 The name of the section.
28275 The size of the section.
28277 The size of the overall executable to download.
28281 At the end, a summary is printed.
28283 @subsubheading @value{GDBN} Command
28285 The corresponding @value{GDBN} command is @samp{load}.
28287 @subsubheading Example
28289 Note: each status message appears on a single line. Here the messages
28290 have been broken down so that they can fit onto a page.
28295 +download,@{section=".text",section-size="6668",total-size="9880"@}
28296 +download,@{section=".text",section-sent="512",section-size="6668",
28297 total-sent="512",total-size="9880"@}
28298 +download,@{section=".text",section-sent="1024",section-size="6668",
28299 total-sent="1024",total-size="9880"@}
28300 +download,@{section=".text",section-sent="1536",section-size="6668",
28301 total-sent="1536",total-size="9880"@}
28302 +download,@{section=".text",section-sent="2048",section-size="6668",
28303 total-sent="2048",total-size="9880"@}
28304 +download,@{section=".text",section-sent="2560",section-size="6668",
28305 total-sent="2560",total-size="9880"@}
28306 +download,@{section=".text",section-sent="3072",section-size="6668",
28307 total-sent="3072",total-size="9880"@}
28308 +download,@{section=".text",section-sent="3584",section-size="6668",
28309 total-sent="3584",total-size="9880"@}
28310 +download,@{section=".text",section-sent="4096",section-size="6668",
28311 total-sent="4096",total-size="9880"@}
28312 +download,@{section=".text",section-sent="4608",section-size="6668",
28313 total-sent="4608",total-size="9880"@}
28314 +download,@{section=".text",section-sent="5120",section-size="6668",
28315 total-sent="5120",total-size="9880"@}
28316 +download,@{section=".text",section-sent="5632",section-size="6668",
28317 total-sent="5632",total-size="9880"@}
28318 +download,@{section=".text",section-sent="6144",section-size="6668",
28319 total-sent="6144",total-size="9880"@}
28320 +download,@{section=".text",section-sent="6656",section-size="6668",
28321 total-sent="6656",total-size="9880"@}
28322 +download,@{section=".init",section-size="28",total-size="9880"@}
28323 +download,@{section=".fini",section-size="28",total-size="9880"@}
28324 +download,@{section=".data",section-size="3156",total-size="9880"@}
28325 +download,@{section=".data",section-sent="512",section-size="3156",
28326 total-sent="7236",total-size="9880"@}
28327 +download,@{section=".data",section-sent="1024",section-size="3156",
28328 total-sent="7748",total-size="9880"@}
28329 +download,@{section=".data",section-sent="1536",section-size="3156",
28330 total-sent="8260",total-size="9880"@}
28331 +download,@{section=".data",section-sent="2048",section-size="3156",
28332 total-sent="8772",total-size="9880"@}
28333 +download,@{section=".data",section-sent="2560",section-size="3156",
28334 total-sent="9284",total-size="9880"@}
28335 +download,@{section=".data",section-sent="3072",section-size="3156",
28336 total-sent="9796",total-size="9880"@}
28337 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
28344 @subheading The @code{-target-exec-status} Command
28345 @findex -target-exec-status
28347 @subsubheading Synopsis
28350 -target-exec-status
28353 Provide information on the state of the target (whether it is running or
28354 not, for instance).
28356 @subsubheading @value{GDBN} Command
28358 There's no equivalent @value{GDBN} command.
28360 @subsubheading Example
28364 @subheading The @code{-target-list-available-targets} Command
28365 @findex -target-list-available-targets
28367 @subsubheading Synopsis
28370 -target-list-available-targets
28373 List the possible targets to connect to.
28375 @subsubheading @value{GDBN} Command
28377 The corresponding @value{GDBN} command is @samp{help target}.
28379 @subsubheading Example
28383 @subheading The @code{-target-list-current-targets} Command
28384 @findex -target-list-current-targets
28386 @subsubheading Synopsis
28389 -target-list-current-targets
28392 Describe the current target.
28394 @subsubheading @value{GDBN} Command
28396 The corresponding information is printed by @samp{info file} (among
28399 @subsubheading Example
28403 @subheading The @code{-target-list-parameters} Command
28404 @findex -target-list-parameters
28406 @subsubheading Synopsis
28409 -target-list-parameters
28415 @subsubheading @value{GDBN} Command
28419 @subsubheading Example
28423 @subheading The @code{-target-select} Command
28424 @findex -target-select
28426 @subsubheading Synopsis
28429 -target-select @var{type} @var{parameters @dots{}}
28432 Connect @value{GDBN} to the remote target. This command takes two args:
28436 The type of target, for instance @samp{remote}, etc.
28437 @item @var{parameters}
28438 Device names, host names and the like. @xref{Target Commands, ,
28439 Commands for Managing Targets}, for more details.
28442 The output is a connection notification, followed by the address at
28443 which the target program is, in the following form:
28446 ^connected,addr="@var{address}",func="@var{function name}",
28447 args=[@var{arg list}]
28450 @subsubheading @value{GDBN} Command
28452 The corresponding @value{GDBN} command is @samp{target}.
28454 @subsubheading Example
28458 -target-select remote /dev/ttya
28459 ^connected,addr="0xfe00a300",func="??",args=[]
28463 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28464 @node GDB/MI File Transfer Commands
28465 @section @sc{gdb/mi} File Transfer Commands
28468 @subheading The @code{-target-file-put} Command
28469 @findex -target-file-put
28471 @subsubheading Synopsis
28474 -target-file-put @var{hostfile} @var{targetfile}
28477 Copy file @var{hostfile} from the host system (the machine running
28478 @value{GDBN}) to @var{targetfile} on the target system.
28480 @subsubheading @value{GDBN} Command
28482 The corresponding @value{GDBN} command is @samp{remote put}.
28484 @subsubheading Example
28488 -target-file-put localfile remotefile
28494 @subheading The @code{-target-file-get} Command
28495 @findex -target-file-get
28497 @subsubheading Synopsis
28500 -target-file-get @var{targetfile} @var{hostfile}
28503 Copy file @var{targetfile} from the target system to @var{hostfile}
28504 on the host system.
28506 @subsubheading @value{GDBN} Command
28508 The corresponding @value{GDBN} command is @samp{remote get}.
28510 @subsubheading Example
28514 -target-file-get remotefile localfile
28520 @subheading The @code{-target-file-delete} Command
28521 @findex -target-file-delete
28523 @subsubheading Synopsis
28526 -target-file-delete @var{targetfile}
28529 Delete @var{targetfile} from the target system.
28531 @subsubheading @value{GDBN} Command
28533 The corresponding @value{GDBN} command is @samp{remote delete}.
28535 @subsubheading Example
28539 -target-file-delete remotefile
28545 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28546 @node GDB/MI Miscellaneous Commands
28547 @section Miscellaneous @sc{gdb/mi} Commands
28549 @c @subheading -gdb-complete
28551 @subheading The @code{-gdb-exit} Command
28554 @subsubheading Synopsis
28560 Exit @value{GDBN} immediately.
28562 @subsubheading @value{GDBN} Command
28564 Approximately corresponds to @samp{quit}.
28566 @subsubheading Example
28576 @subheading The @code{-exec-abort} Command
28577 @findex -exec-abort
28579 @subsubheading Synopsis
28585 Kill the inferior running program.
28587 @subsubheading @value{GDBN} Command
28589 The corresponding @value{GDBN} command is @samp{kill}.
28591 @subsubheading Example
28596 @subheading The @code{-gdb-set} Command
28599 @subsubheading Synopsis
28605 Set an internal @value{GDBN} variable.
28606 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
28608 @subsubheading @value{GDBN} Command
28610 The corresponding @value{GDBN} command is @samp{set}.
28612 @subsubheading Example
28622 @subheading The @code{-gdb-show} Command
28625 @subsubheading Synopsis
28631 Show the current value of a @value{GDBN} variable.
28633 @subsubheading @value{GDBN} Command
28635 The corresponding @value{GDBN} command is @samp{show}.
28637 @subsubheading Example
28646 @c @subheading -gdb-source
28649 @subheading The @code{-gdb-version} Command
28650 @findex -gdb-version
28652 @subsubheading Synopsis
28658 Show version information for @value{GDBN}. Used mostly in testing.
28660 @subsubheading @value{GDBN} Command
28662 The @value{GDBN} equivalent is @samp{show version}. @value{GDBN} by
28663 default shows this information when you start an interactive session.
28665 @subsubheading Example
28667 @c This example modifies the actual output from GDB to avoid overfull
28673 ~Copyright 2000 Free Software Foundation, Inc.
28674 ~GDB is free software, covered by the GNU General Public License, and
28675 ~you are welcome to change it and/or distribute copies of it under
28676 ~ certain conditions.
28677 ~Type "show copying" to see the conditions.
28678 ~There is absolutely no warranty for GDB. Type "show warranty" for
28680 ~This GDB was configured as
28681 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
28686 @subheading The @code{-list-features} Command
28687 @findex -list-features
28689 Returns a list of particular features of the MI protocol that
28690 this version of gdb implements. A feature can be a command,
28691 or a new field in an output of some command, or even an
28692 important bugfix. While a frontend can sometimes detect presence
28693 of a feature at runtime, it is easier to perform detection at debugger
28696 The command returns a list of strings, with each string naming an
28697 available feature. Each returned string is just a name, it does not
28698 have any internal structure. The list of possible feature names
28704 (gdb) -list-features
28705 ^done,result=["feature1","feature2"]
28708 The current list of features is:
28711 @item frozen-varobjs
28712 Indicates presence of the @code{-var-set-frozen} command, as well
28713 as possible presense of the @code{frozen} field in the output
28714 of @code{-varobj-create}.
28715 @item pending-breakpoints
28716 Indicates presence of the @option{-f} option to the @code{-break-insert} command.
28718 Indicates presence of Python scripting support, Python-based
28719 pretty-printing commands, and possible presence of the
28720 @samp{display_hint} field in the output of @code{-var-list-children}
28722 Indicates presence of the @code{-thread-info} command.
28726 @subheading The @code{-list-target-features} Command
28727 @findex -list-target-features
28729 Returns a list of particular features that are supported by the
28730 target. Those features affect the permitted MI commands, but
28731 unlike the features reported by the @code{-list-features} command, the
28732 features depend on which target GDB is using at the moment. Whenever
28733 a target can change, due to commands such as @code{-target-select},
28734 @code{-target-attach} or @code{-exec-run}, the list of target features
28735 may change, and the frontend should obtain it again.
28739 (gdb) -list-features
28740 ^done,result=["async"]
28743 The current list of features is:
28747 Indicates that the target is capable of asynchronous command
28748 execution, which means that @value{GDBN} will accept further commands
28749 while the target is running.
28753 @subheading The @code{-list-thread-groups} Command
28754 @findex -list-thread-groups
28756 @subheading Synopsis
28759 -list-thread-groups [ --available ] [ --recurse 1 ] [ @var{group} ... ]
28762 Lists thread groups (@pxref{Thread groups}). When a single thread
28763 group is passed as the argument, lists the children of that group.
28764 When several thread group are passed, lists information about those
28765 thread groups. Without any parameters, lists information about all
28766 top-level thread groups.
28768 Normally, thread groups that are being debugged are reported.
28769 With the @samp{--available} option, @value{GDBN} reports thread groups
28770 available on the target.
28772 The output of this command may have either a @samp{threads} result or
28773 a @samp{groups} result. The @samp{thread} result has a list of tuples
28774 as value, with each tuple describing a thread (@pxref{GDB/MI Thread
28775 Information}). The @samp{groups} result has a list of tuples as value,
28776 each tuple describing a thread group. If top-level groups are
28777 requested (that is, no parameter is passed), or when several groups
28778 are passed, the output always has a @samp{groups} result. The format
28779 of the @samp{group} result is described below.
28781 To reduce the number of roundtrips it's possible to list thread groups
28782 together with their children, by passing the @samp{--recurse} option
28783 and the recursion depth. Presently, only recursion depth of 1 is
28784 permitted. If this option is present, then every reported thread group
28785 will also include its children, either as @samp{group} or
28786 @samp{threads} field.
28788 In general, any combination of option and parameters is permitted, with
28789 the following caveats:
28793 When a single thread group is passed, the output will typically
28794 be the @samp{threads} result. Because threads may not contain
28795 anything, the @samp{recurse} option will be ignored.
28798 When the @samp{--available} option is passed, limited information may
28799 be available. In particular, the list of threads of a process might
28800 be inaccessible. Further, specifying specific thread groups might
28801 not give any performance advantage over listing all thread groups.
28802 The frontend should assume that @samp{-list-thread-groups --available}
28803 is always an expensive operation and cache the results.
28807 The @samp{groups} result is a list of tuples, where each tuple may
28808 have the following fields:
28812 Identifier of the thread group. This field is always present.
28813 The identifier is an opaque string; frontends should not try to
28814 convert it to an integer, even though it might look like one.
28817 The type of the thread group. At present, only @samp{process} is a
28821 The target-specific process identifier. This field is only present
28822 for thread groups of type @samp{process} and only if the process exists.
28825 The number of children this thread group has. This field may be
28826 absent for an available thread group.
28829 This field has a list of tuples as value, each tuple describing a
28830 thread. It may be present if the @samp{--recurse} option is
28831 specified, and it's actually possible to obtain the threads.
28834 This field is a list of integers, each identifying a core that one
28835 thread of the group is running on. This field may be absent if
28836 such information is not available.
28839 The name of the executable file that corresponds to this thread group.
28840 The field is only present for thread groups of type @samp{process},
28841 and only if there is a corresponding executable file.
28845 @subheading Example
28849 -list-thread-groups
28850 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2"@}]
28851 -list-thread-groups 17
28852 ^done,threads=[@{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
28853 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},state="running"@},
28854 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
28855 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
28856 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},state="running"@}]]
28857 -list-thread-groups --available
28858 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2",cores=[1,2]@}]
28859 -list-thread-groups --available --recurse 1
28860 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
28861 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
28862 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},..]
28863 -list-thread-groups --available --recurse 1 17 18
28864 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
28865 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
28866 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},...]
28870 @subheading The @code{-add-inferior} Command
28871 @findex -add-inferior
28873 @subheading Synopsis
28879 Creates a new inferior (@pxref{Inferiors and Programs}). The created
28880 inferior is not associated with any executable. Such association may
28881 be established with the @samp{-file-exec-and-symbols} command
28882 (@pxref{GDB/MI File Commands}). The command response has a single
28883 field, @samp{thread-group}, whose value is the identifier of the
28884 thread group corresponding to the new inferior.
28886 @subheading Example
28891 ^done,thread-group="i3"
28894 @subheading The @code{-interpreter-exec} Command
28895 @findex -interpreter-exec
28897 @subheading Synopsis
28900 -interpreter-exec @var{interpreter} @var{command}
28902 @anchor{-interpreter-exec}
28904 Execute the specified @var{command} in the given @var{interpreter}.
28906 @subheading @value{GDBN} Command
28908 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
28910 @subheading Example
28914 -interpreter-exec console "break main"
28915 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
28916 &"During symbol reading, bad structure-type format.\n"
28917 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
28922 @subheading The @code{-inferior-tty-set} Command
28923 @findex -inferior-tty-set
28925 @subheading Synopsis
28928 -inferior-tty-set /dev/pts/1
28931 Set terminal for future runs of the program being debugged.
28933 @subheading @value{GDBN} Command
28935 The corresponding @value{GDBN} command is @samp{set inferior-tty} /dev/pts/1.
28937 @subheading Example
28941 -inferior-tty-set /dev/pts/1
28946 @subheading The @code{-inferior-tty-show} Command
28947 @findex -inferior-tty-show
28949 @subheading Synopsis
28955 Show terminal for future runs of program being debugged.
28957 @subheading @value{GDBN} Command
28959 The corresponding @value{GDBN} command is @samp{show inferior-tty}.
28961 @subheading Example
28965 -inferior-tty-set /dev/pts/1
28969 ^done,inferior_tty_terminal="/dev/pts/1"
28973 @subheading The @code{-enable-timings} Command
28974 @findex -enable-timings
28976 @subheading Synopsis
28979 -enable-timings [yes | no]
28982 Toggle the printing of the wallclock, user and system times for an MI
28983 command as a field in its output. This command is to help frontend
28984 developers optimize the performance of their code. No argument is
28985 equivalent to @samp{yes}.
28987 @subheading @value{GDBN} Command
28991 @subheading Example
28999 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
29000 addr="0x080484ed",func="main",file="myprog.c",
29001 fullname="/home/nickrob/myprog.c",line="73",times="0"@},
29002 time=@{wallclock="0.05185",user="0.00800",system="0.00000"@}
29010 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
29011 frame=@{addr="0x080484ed",func="main",args=[@{name="argc",value="1"@},
29012 @{name="argv",value="0xbfb60364"@}],file="myprog.c",
29013 fullname="/home/nickrob/myprog.c",line="73"@}
29018 @chapter @value{GDBN} Annotations
29020 This chapter describes annotations in @value{GDBN}. Annotations were
29021 designed to interface @value{GDBN} to graphical user interfaces or other
29022 similar programs which want to interact with @value{GDBN} at a
29023 relatively high level.
29025 The annotation mechanism has largely been superseded by @sc{gdb/mi}
29029 This is Edition @value{EDITION}, @value{DATE}.
29033 * Annotations Overview:: What annotations are; the general syntax.
29034 * Server Prefix:: Issuing a command without affecting user state.
29035 * Prompting:: Annotations marking @value{GDBN}'s need for input.
29036 * Errors:: Annotations for error messages.
29037 * Invalidation:: Some annotations describe things now invalid.
29038 * Annotations for Running::
29039 Whether the program is running, how it stopped, etc.
29040 * Source Annotations:: Annotations describing source code.
29043 @node Annotations Overview
29044 @section What is an Annotation?
29045 @cindex annotations
29047 Annotations start with a newline character, two @samp{control-z}
29048 characters, and the name of the annotation. If there is no additional
29049 information associated with this annotation, the name of the annotation
29050 is followed immediately by a newline. If there is additional
29051 information, the name of the annotation is followed by a space, the
29052 additional information, and a newline. The additional information
29053 cannot contain newline characters.
29055 Any output not beginning with a newline and two @samp{control-z}
29056 characters denotes literal output from @value{GDBN}. Currently there is
29057 no need for @value{GDBN} to output a newline followed by two
29058 @samp{control-z} characters, but if there was such a need, the
29059 annotations could be extended with an @samp{escape} annotation which
29060 means those three characters as output.
29062 The annotation @var{level}, which is specified using the
29063 @option{--annotate} command line option (@pxref{Mode Options}), controls
29064 how much information @value{GDBN} prints together with its prompt,
29065 values of expressions, source lines, and other types of output. Level 0
29066 is for no annotations, level 1 is for use when @value{GDBN} is run as a
29067 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
29068 for programs that control @value{GDBN}, and level 2 annotations have
29069 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
29070 Interface, annotate, GDB's Obsolete Annotations}).
29073 @kindex set annotate
29074 @item set annotate @var{level}
29075 The @value{GDBN} command @code{set annotate} sets the level of
29076 annotations to the specified @var{level}.
29078 @item show annotate
29079 @kindex show annotate
29080 Show the current annotation level.
29083 This chapter describes level 3 annotations.
29085 A simple example of starting up @value{GDBN} with annotations is:
29088 $ @kbd{gdb --annotate=3}
29090 Copyright 2003 Free Software Foundation, Inc.
29091 GDB is free software, covered by the GNU General Public License,
29092 and you are welcome to change it and/or distribute copies of it
29093 under certain conditions.
29094 Type "show copying" to see the conditions.
29095 There is absolutely no warranty for GDB. Type "show warranty"
29097 This GDB was configured as "i386-pc-linux-gnu"
29108 Here @samp{quit} is input to @value{GDBN}; the rest is output from
29109 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
29110 denotes a @samp{control-z} character) are annotations; the rest is
29111 output from @value{GDBN}.
29113 @node Server Prefix
29114 @section The Server Prefix
29115 @cindex server prefix
29117 If you prefix a command with @samp{server } then it will not affect
29118 the command history, nor will it affect @value{GDBN}'s notion of which
29119 command to repeat if @key{RET} is pressed on a line by itself. This
29120 means that commands can be run behind a user's back by a front-end in
29121 a transparent manner.
29123 The @code{server } prefix does not affect the recording of values into
29124 the value history; to print a value without recording it into the
29125 value history, use the @code{output} command instead of the
29126 @code{print} command.
29128 Using this prefix also disables confirmation requests
29129 (@pxref{confirmation requests}).
29132 @section Annotation for @value{GDBN} Input
29134 @cindex annotations for prompts
29135 When @value{GDBN} prompts for input, it annotates this fact so it is possible
29136 to know when to send output, when the output from a given command is
29139 Different kinds of input each have a different @dfn{input type}. Each
29140 input type has three annotations: a @code{pre-} annotation, which
29141 denotes the beginning of any prompt which is being output, a plain
29142 annotation, which denotes the end of the prompt, and then a @code{post-}
29143 annotation which denotes the end of any echo which may (or may not) be
29144 associated with the input. For example, the @code{prompt} input type
29145 features the following annotations:
29153 The input types are
29156 @findex pre-prompt annotation
29157 @findex prompt annotation
29158 @findex post-prompt annotation
29160 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
29162 @findex pre-commands annotation
29163 @findex commands annotation
29164 @findex post-commands annotation
29166 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
29167 command. The annotations are repeated for each command which is input.
29169 @findex pre-overload-choice annotation
29170 @findex overload-choice annotation
29171 @findex post-overload-choice annotation
29172 @item overload-choice
29173 When @value{GDBN} wants the user to select between various overloaded functions.
29175 @findex pre-query annotation
29176 @findex query annotation
29177 @findex post-query annotation
29179 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
29181 @findex pre-prompt-for-continue annotation
29182 @findex prompt-for-continue annotation
29183 @findex post-prompt-for-continue annotation
29184 @item prompt-for-continue
29185 When @value{GDBN} is asking the user to press return to continue. Note: Don't
29186 expect this to work well; instead use @code{set height 0} to disable
29187 prompting. This is because the counting of lines is buggy in the
29188 presence of annotations.
29193 @cindex annotations for errors, warnings and interrupts
29195 @findex quit annotation
29200 This annotation occurs right before @value{GDBN} responds to an interrupt.
29202 @findex error annotation
29207 This annotation occurs right before @value{GDBN} responds to an error.
29209 Quit and error annotations indicate that any annotations which @value{GDBN} was
29210 in the middle of may end abruptly. For example, if a
29211 @code{value-history-begin} annotation is followed by a @code{error}, one
29212 cannot expect to receive the matching @code{value-history-end}. One
29213 cannot expect not to receive it either, however; an error annotation
29214 does not necessarily mean that @value{GDBN} is immediately returning all the way
29217 @findex error-begin annotation
29218 A quit or error annotation may be preceded by
29224 Any output between that and the quit or error annotation is the error
29227 Warning messages are not yet annotated.
29228 @c If we want to change that, need to fix warning(), type_error(),
29229 @c range_error(), and possibly other places.
29232 @section Invalidation Notices
29234 @cindex annotations for invalidation messages
29235 The following annotations say that certain pieces of state may have
29239 @findex frames-invalid annotation
29240 @item ^Z^Zframes-invalid
29242 The frames (for example, output from the @code{backtrace} command) may
29245 @findex breakpoints-invalid annotation
29246 @item ^Z^Zbreakpoints-invalid
29248 The breakpoints may have changed. For example, the user just added or
29249 deleted a breakpoint.
29252 @node Annotations for Running
29253 @section Running the Program
29254 @cindex annotations for running programs
29256 @findex starting annotation
29257 @findex stopping annotation
29258 When the program starts executing due to a @value{GDBN} command such as
29259 @code{step} or @code{continue},
29265 is output. When the program stops,
29271 is output. Before the @code{stopped} annotation, a variety of
29272 annotations describe how the program stopped.
29275 @findex exited annotation
29276 @item ^Z^Zexited @var{exit-status}
29277 The program exited, and @var{exit-status} is the exit status (zero for
29278 successful exit, otherwise nonzero).
29280 @findex signalled annotation
29281 @findex signal-name annotation
29282 @findex signal-name-end annotation
29283 @findex signal-string annotation
29284 @findex signal-string-end annotation
29285 @item ^Z^Zsignalled
29286 The program exited with a signal. After the @code{^Z^Zsignalled}, the
29287 annotation continues:
29293 ^Z^Zsignal-name-end
29297 ^Z^Zsignal-string-end
29302 where @var{name} is the name of the signal, such as @code{SIGILL} or
29303 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
29304 as @code{Illegal Instruction} or @code{Segmentation fault}.
29305 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
29306 user's benefit and have no particular format.
29308 @findex signal annotation
29310 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
29311 just saying that the program received the signal, not that it was
29312 terminated with it.
29314 @findex breakpoint annotation
29315 @item ^Z^Zbreakpoint @var{number}
29316 The program hit breakpoint number @var{number}.
29318 @findex watchpoint annotation
29319 @item ^Z^Zwatchpoint @var{number}
29320 The program hit watchpoint number @var{number}.
29323 @node Source Annotations
29324 @section Displaying Source
29325 @cindex annotations for source display
29327 @findex source annotation
29328 The following annotation is used instead of displaying source code:
29331 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
29334 where @var{filename} is an absolute file name indicating which source
29335 file, @var{line} is the line number within that file (where 1 is the
29336 first line in the file), @var{character} is the character position
29337 within the file (where 0 is the first character in the file) (for most
29338 debug formats this will necessarily point to the beginning of a line),
29339 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
29340 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
29341 @var{addr} is the address in the target program associated with the
29342 source which is being displayed. @var{addr} is in the form @samp{0x}
29343 followed by one or more lowercase hex digits (note that this does not
29344 depend on the language).
29346 @node JIT Interface
29347 @chapter JIT Compilation Interface
29348 @cindex just-in-time compilation
29349 @cindex JIT compilation interface
29351 This chapter documents @value{GDBN}'s @dfn{just-in-time} (JIT) compilation
29352 interface. A JIT compiler is a program or library that generates native
29353 executable code at runtime and executes it, usually in order to achieve good
29354 performance while maintaining platform independence.
29356 Programs that use JIT compilation are normally difficult to debug because
29357 portions of their code are generated at runtime, instead of being loaded from
29358 object files, which is where @value{GDBN} normally finds the program's symbols
29359 and debug information. In order to debug programs that use JIT compilation,
29360 @value{GDBN} has an interface that allows the program to register in-memory
29361 symbol files with @value{GDBN} at runtime.
29363 If you are using @value{GDBN} to debug a program that uses this interface, then
29364 it should work transparently so long as you have not stripped the binary. If
29365 you are developing a JIT compiler, then the interface is documented in the rest
29366 of this chapter. At this time, the only known client of this interface is the
29369 Broadly speaking, the JIT interface mirrors the dynamic loader interface. The
29370 JIT compiler communicates with @value{GDBN} by writing data into a global
29371 variable and calling a fuction at a well-known symbol. When @value{GDBN}
29372 attaches, it reads a linked list of symbol files from the global variable to
29373 find existing code, and puts a breakpoint in the function so that it can find
29374 out about additional code.
29377 * Declarations:: Relevant C struct declarations
29378 * Registering Code:: Steps to register code
29379 * Unregistering Code:: Steps to unregister code
29383 @section JIT Declarations
29385 These are the relevant struct declarations that a C program should include to
29386 implement the interface:
29396 struct jit_code_entry
29398 struct jit_code_entry *next_entry;
29399 struct jit_code_entry *prev_entry;
29400 const char *symfile_addr;
29401 uint64_t symfile_size;
29404 struct jit_descriptor
29407 /* This type should be jit_actions_t, but we use uint32_t
29408 to be explicit about the bitwidth. */
29409 uint32_t action_flag;
29410 struct jit_code_entry *relevant_entry;
29411 struct jit_code_entry *first_entry;
29414 /* GDB puts a breakpoint in this function. */
29415 void __attribute__((noinline)) __jit_debug_register_code() @{ @};
29417 /* Make sure to specify the version statically, because the
29418 debugger may check the version before we can set it. */
29419 struct jit_descriptor __jit_debug_descriptor = @{ 1, 0, 0, 0 @};
29422 If the JIT is multi-threaded, then it is important that the JIT synchronize any
29423 modifications to this global data properly, which can easily be done by putting
29424 a global mutex around modifications to these structures.
29426 @node Registering Code
29427 @section Registering Code
29429 To register code with @value{GDBN}, the JIT should follow this protocol:
29433 Generate an object file in memory with symbols and other desired debug
29434 information. The file must include the virtual addresses of the sections.
29437 Create a code entry for the file, which gives the start and size of the symbol
29441 Add it to the linked list in the JIT descriptor.
29444 Point the relevant_entry field of the descriptor at the entry.
29447 Set @code{action_flag} to @code{JIT_REGISTER} and call
29448 @code{__jit_debug_register_code}.
29451 When @value{GDBN} is attached and the breakpoint fires, @value{GDBN} uses the
29452 @code{relevant_entry} pointer so it doesn't have to walk the list looking for
29453 new code. However, the linked list must still be maintained in order to allow
29454 @value{GDBN} to attach to a running process and still find the symbol files.
29456 @node Unregistering Code
29457 @section Unregistering Code
29459 If code is freed, then the JIT should use the following protocol:
29463 Remove the code entry corresponding to the code from the linked list.
29466 Point the @code{relevant_entry} field of the descriptor at the code entry.
29469 Set @code{action_flag} to @code{JIT_UNREGISTER} and call
29470 @code{__jit_debug_register_code}.
29473 If the JIT frees or recompiles code without unregistering it, then @value{GDBN}
29474 and the JIT will leak the memory used for the associated symbol files.
29477 @chapter Reporting Bugs in @value{GDBN}
29478 @cindex bugs in @value{GDBN}
29479 @cindex reporting bugs in @value{GDBN}
29481 Your bug reports play an essential role in making @value{GDBN} reliable.
29483 Reporting a bug may help you by bringing a solution to your problem, or it
29484 may not. But in any case the principal function of a bug report is to help
29485 the entire community by making the next version of @value{GDBN} work better. Bug
29486 reports are your contribution to the maintenance of @value{GDBN}.
29488 In order for a bug report to serve its purpose, you must include the
29489 information that enables us to fix the bug.
29492 * Bug Criteria:: Have you found a bug?
29493 * Bug Reporting:: How to report bugs
29497 @section Have You Found a Bug?
29498 @cindex bug criteria
29500 If you are not sure whether you have found a bug, here are some guidelines:
29503 @cindex fatal signal
29504 @cindex debugger crash
29505 @cindex crash of debugger
29507 If the debugger gets a fatal signal, for any input whatever, that is a
29508 @value{GDBN} bug. Reliable debuggers never crash.
29510 @cindex error on valid input
29512 If @value{GDBN} produces an error message for valid input, that is a
29513 bug. (Note that if you're cross debugging, the problem may also be
29514 somewhere in the connection to the target.)
29516 @cindex invalid input
29518 If @value{GDBN} does not produce an error message for invalid input,
29519 that is a bug. However, you should note that your idea of
29520 ``invalid input'' might be our idea of ``an extension'' or ``support
29521 for traditional practice''.
29524 If you are an experienced user of debugging tools, your suggestions
29525 for improvement of @value{GDBN} are welcome in any case.
29528 @node Bug Reporting
29529 @section How to Report Bugs
29530 @cindex bug reports
29531 @cindex @value{GDBN} bugs, reporting
29533 A number of companies and individuals offer support for @sc{gnu} products.
29534 If you obtained @value{GDBN} from a support organization, we recommend you
29535 contact that organization first.
29537 You can find contact information for many support companies and
29538 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
29540 @c should add a web page ref...
29543 @ifset BUGURL_DEFAULT
29544 In any event, we also recommend that you submit bug reports for
29545 @value{GDBN}. The preferred method is to submit them directly using
29546 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
29547 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
29550 @strong{Do not send bug reports to @samp{info-gdb}, or to
29551 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
29552 not want to receive bug reports. Those that do have arranged to receive
29555 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
29556 serves as a repeater. The mailing list and the newsgroup carry exactly
29557 the same messages. Often people think of posting bug reports to the
29558 newsgroup instead of mailing them. This appears to work, but it has one
29559 problem which can be crucial: a newsgroup posting often lacks a mail
29560 path back to the sender. Thus, if we need to ask for more information,
29561 we may be unable to reach you. For this reason, it is better to send
29562 bug reports to the mailing list.
29564 @ifclear BUGURL_DEFAULT
29565 In any event, we also recommend that you submit bug reports for
29566 @value{GDBN} to @value{BUGURL}.
29570 The fundamental principle of reporting bugs usefully is this:
29571 @strong{report all the facts}. If you are not sure whether to state a
29572 fact or leave it out, state it!
29574 Often people omit facts because they think they know what causes the
29575 problem and assume that some details do not matter. Thus, you might
29576 assume that the name of the variable you use in an example does not matter.
29577 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
29578 stray memory reference which happens to fetch from the location where that
29579 name is stored in memory; perhaps, if the name were different, the contents
29580 of that location would fool the debugger into doing the right thing despite
29581 the bug. Play it safe and give a specific, complete example. That is the
29582 easiest thing for you to do, and the most helpful.
29584 Keep in mind that the purpose of a bug report is to enable us to fix the
29585 bug. It may be that the bug has been reported previously, but neither
29586 you nor we can know that unless your bug report is complete and
29589 Sometimes people give a few sketchy facts and ask, ``Does this ring a
29590 bell?'' Those bug reports are useless, and we urge everyone to
29591 @emph{refuse to respond to them} except to chide the sender to report
29594 To enable us to fix the bug, you should include all these things:
29598 The version of @value{GDBN}. @value{GDBN} announces it if you start
29599 with no arguments; you can also print it at any time using @code{show
29602 Without this, we will not know whether there is any point in looking for
29603 the bug in the current version of @value{GDBN}.
29606 The type of machine you are using, and the operating system name and
29610 What compiler (and its version) was used to compile @value{GDBN}---e.g.@:
29611 ``@value{GCC}--2.8.1''.
29614 What compiler (and its version) was used to compile the program you are
29615 debugging---e.g.@: ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
29616 C Compiler''. For @value{NGCC}, you can say @kbd{@value{GCC} --version}
29617 to get this information; for other compilers, see the documentation for
29621 The command arguments you gave the compiler to compile your example and
29622 observe the bug. For example, did you use @samp{-O}? To guarantee
29623 you will not omit something important, list them all. A copy of the
29624 Makefile (or the output from make) is sufficient.
29626 If we were to try to guess the arguments, we would probably guess wrong
29627 and then we might not encounter the bug.
29630 A complete input script, and all necessary source files, that will
29634 A description of what behavior you observe that you believe is
29635 incorrect. For example, ``It gets a fatal signal.''
29637 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
29638 will certainly notice it. But if the bug is incorrect output, we might
29639 not notice unless it is glaringly wrong. You might as well not give us
29640 a chance to make a mistake.
29642 Even if the problem you experience is a fatal signal, you should still
29643 say so explicitly. Suppose something strange is going on, such as, your
29644 copy of @value{GDBN} is out of synch, or you have encountered a bug in
29645 the C library on your system. (This has happened!) Your copy might
29646 crash and ours would not. If you told us to expect a crash, then when
29647 ours fails to crash, we would know that the bug was not happening for
29648 us. If you had not told us to expect a crash, then we would not be able
29649 to draw any conclusion from our observations.
29652 @cindex recording a session script
29653 To collect all this information, you can use a session recording program
29654 such as @command{script}, which is available on many Unix systems.
29655 Just run your @value{GDBN} session inside @command{script} and then
29656 include the @file{typescript} file with your bug report.
29658 Another way to record a @value{GDBN} session is to run @value{GDBN}
29659 inside Emacs and then save the entire buffer to a file.
29662 If you wish to suggest changes to the @value{GDBN} source, send us context
29663 diffs. If you even discuss something in the @value{GDBN} source, refer to
29664 it by context, not by line number.
29666 The line numbers in our development sources will not match those in your
29667 sources. Your line numbers would convey no useful information to us.
29671 Here are some things that are not necessary:
29675 A description of the envelope of the bug.
29677 Often people who encounter a bug spend a lot of time investigating
29678 which changes to the input file will make the bug go away and which
29679 changes will not affect it.
29681 This is often time consuming and not very useful, because the way we
29682 will find the bug is by running a single example under the debugger
29683 with breakpoints, not by pure deduction from a series of examples.
29684 We recommend that you save your time for something else.
29686 Of course, if you can find a simpler example to report @emph{instead}
29687 of the original one, that is a convenience for us. Errors in the
29688 output will be easier to spot, running under the debugger will take
29689 less time, and so on.
29691 However, simplification is not vital; if you do not want to do this,
29692 report the bug anyway and send us the entire test case you used.
29695 A patch for the bug.
29697 A patch for the bug does help us if it is a good one. But do not omit
29698 the necessary information, such as the test case, on the assumption that
29699 a patch is all we need. We might see problems with your patch and decide
29700 to fix the problem another way, or we might not understand it at all.
29702 Sometimes with a program as complicated as @value{GDBN} it is very hard to
29703 construct an example that will make the program follow a certain path
29704 through the code. If you do not send us the example, we will not be able
29705 to construct one, so we will not be able to verify that the bug is fixed.
29707 And if we cannot understand what bug you are trying to fix, or why your
29708 patch should be an improvement, we will not install it. A test case will
29709 help us to understand.
29712 A guess about what the bug is or what it depends on.
29714 Such guesses are usually wrong. Even we cannot guess right about such
29715 things without first using the debugger to find the facts.
29718 @c The readline documentation is distributed with the readline code
29719 @c and consists of the two following files:
29721 @c inc-hist.texinfo
29722 @c Use -I with makeinfo to point to the appropriate directory,
29723 @c environment var TEXINPUTS with TeX.
29724 @include rluser.texi
29725 @include inc-hist.texinfo
29728 @node Formatting Documentation
29729 @appendix Formatting Documentation
29731 @cindex @value{GDBN} reference card
29732 @cindex reference card
29733 The @value{GDBN} 4 release includes an already-formatted reference card, ready
29734 for printing with PostScript or Ghostscript, in the @file{gdb}
29735 subdirectory of the main source directory@footnote{In
29736 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
29737 release.}. If you can use PostScript or Ghostscript with your printer,
29738 you can print the reference card immediately with @file{refcard.ps}.
29740 The release also includes the source for the reference card. You
29741 can format it, using @TeX{}, by typing:
29747 The @value{GDBN} reference card is designed to print in @dfn{landscape}
29748 mode on US ``letter'' size paper;
29749 that is, on a sheet 11 inches wide by 8.5 inches
29750 high. You will need to specify this form of printing as an option to
29751 your @sc{dvi} output program.
29753 @cindex documentation
29755 All the documentation for @value{GDBN} comes as part of the machine-readable
29756 distribution. The documentation is written in Texinfo format, which is
29757 a documentation system that uses a single source file to produce both
29758 on-line information and a printed manual. You can use one of the Info
29759 formatting commands to create the on-line version of the documentation
29760 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
29762 @value{GDBN} includes an already formatted copy of the on-line Info
29763 version of this manual in the @file{gdb} subdirectory. The main Info
29764 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
29765 subordinate files matching @samp{gdb.info*} in the same directory. If
29766 necessary, you can print out these files, or read them with any editor;
29767 but they are easier to read using the @code{info} subsystem in @sc{gnu}
29768 Emacs or the standalone @code{info} program, available as part of the
29769 @sc{gnu} Texinfo distribution.
29771 If you want to format these Info files yourself, you need one of the
29772 Info formatting programs, such as @code{texinfo-format-buffer} or
29775 If you have @code{makeinfo} installed, and are in the top level
29776 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
29777 version @value{GDBVN}), you can make the Info file by typing:
29784 If you want to typeset and print copies of this manual, you need @TeX{},
29785 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
29786 Texinfo definitions file.
29788 @TeX{} is a typesetting program; it does not print files directly, but
29789 produces output files called @sc{dvi} files. To print a typeset
29790 document, you need a program to print @sc{dvi} files. If your system
29791 has @TeX{} installed, chances are it has such a program. The precise
29792 command to use depends on your system; @kbd{lpr -d} is common; another
29793 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
29794 require a file name without any extension or a @samp{.dvi} extension.
29796 @TeX{} also requires a macro definitions file called
29797 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
29798 written in Texinfo format. On its own, @TeX{} cannot either read or
29799 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
29800 and is located in the @file{gdb-@var{version-number}/texinfo}
29803 If you have @TeX{} and a @sc{dvi} printer program installed, you can
29804 typeset and print this manual. First switch to the @file{gdb}
29805 subdirectory of the main source directory (for example, to
29806 @file{gdb-@value{GDBVN}/gdb}) and type:
29812 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
29814 @node Installing GDB
29815 @appendix Installing @value{GDBN}
29816 @cindex installation
29819 * Requirements:: Requirements for building @value{GDBN}
29820 * Running Configure:: Invoking the @value{GDBN} @file{configure} script
29821 * Separate Objdir:: Compiling @value{GDBN} in another directory
29822 * Config Names:: Specifying names for hosts and targets
29823 * Configure Options:: Summary of options for configure
29824 * System-wide configuration:: Having a system-wide init file
29828 @section Requirements for Building @value{GDBN}
29829 @cindex building @value{GDBN}, requirements for
29831 Building @value{GDBN} requires various tools and packages to be available.
29832 Other packages will be used only if they are found.
29834 @heading Tools/Packages Necessary for Building @value{GDBN}
29836 @item ISO C90 compiler
29837 @value{GDBN} is written in ISO C90. It should be buildable with any
29838 working C90 compiler, e.g.@: GCC.
29842 @heading Tools/Packages Optional for Building @value{GDBN}
29846 @value{GDBN} can use the Expat XML parsing library. This library may be
29847 included with your operating system distribution; if it is not, you
29848 can get the latest version from @url{http://expat.sourceforge.net}.
29849 The @file{configure} script will search for this library in several
29850 standard locations; if it is installed in an unusual path, you can
29851 use the @option{--with-libexpat-prefix} option to specify its location.
29857 Remote protocol memory maps (@pxref{Memory Map Format})
29859 Target descriptions (@pxref{Target Descriptions})
29861 Remote shared library lists (@pxref{Library List Format})
29863 MS-Windows shared libraries (@pxref{Shared Libraries})
29867 @cindex compressed debug sections
29868 @value{GDBN} will use the @samp{zlib} library, if available, to read
29869 compressed debug sections. Some linkers, such as GNU gold, are capable
29870 of producing binaries with compressed debug sections. If @value{GDBN}
29871 is compiled with @samp{zlib}, it will be able to read the debug
29872 information in such binaries.
29874 The @samp{zlib} library is likely included with your operating system
29875 distribution; if it is not, you can get the latest version from
29876 @url{http://zlib.net}.
29879 @value{GDBN}'s features related to character sets (@pxref{Character
29880 Sets}) require a functioning @code{iconv} implementation. If you are
29881 on a GNU system, then this is provided by the GNU C Library. Some
29882 other systems also provide a working @code{iconv}.
29884 On systems with @code{iconv}, you can install GNU Libiconv. If you
29885 have previously installed Libiconv, you can use the
29886 @option{--with-libiconv-prefix} option to configure.
29888 @value{GDBN}'s top-level @file{configure} and @file{Makefile} will
29889 arrange to build Libiconv if a directory named @file{libiconv} appears
29890 in the top-most source directory. If Libiconv is built this way, and
29891 if the operating system does not provide a suitable @code{iconv}
29892 implementation, then the just-built library will automatically be used
29893 by @value{GDBN}. One easy way to set this up is to download GNU
29894 Libiconv, unpack it, and then rename the directory holding the
29895 Libiconv source code to @samp{libiconv}.
29898 @node Running Configure
29899 @section Invoking the @value{GDBN} @file{configure} Script
29900 @cindex configuring @value{GDBN}
29901 @value{GDBN} comes with a @file{configure} script that automates the process
29902 of preparing @value{GDBN} for installation; you can then use @code{make} to
29903 build the @code{gdb} program.
29905 @c irrelevant in info file; it's as current as the code it lives with.
29906 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
29907 look at the @file{README} file in the sources; we may have improved the
29908 installation procedures since publishing this manual.}
29911 The @value{GDBN} distribution includes all the source code you need for
29912 @value{GDBN} in a single directory, whose name is usually composed by
29913 appending the version number to @samp{gdb}.
29915 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
29916 @file{gdb-@value{GDBVN}} directory. That directory contains:
29919 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
29920 script for configuring @value{GDBN} and all its supporting libraries
29922 @item gdb-@value{GDBVN}/gdb
29923 the source specific to @value{GDBN} itself
29925 @item gdb-@value{GDBVN}/bfd
29926 source for the Binary File Descriptor library
29928 @item gdb-@value{GDBVN}/include
29929 @sc{gnu} include files
29931 @item gdb-@value{GDBVN}/libiberty
29932 source for the @samp{-liberty} free software library
29934 @item gdb-@value{GDBVN}/opcodes
29935 source for the library of opcode tables and disassemblers
29937 @item gdb-@value{GDBVN}/readline
29938 source for the @sc{gnu} command-line interface
29940 @item gdb-@value{GDBVN}/glob
29941 source for the @sc{gnu} filename pattern-matching subroutine
29943 @item gdb-@value{GDBVN}/mmalloc
29944 source for the @sc{gnu} memory-mapped malloc package
29947 The simplest way to configure and build @value{GDBN} is to run @file{configure}
29948 from the @file{gdb-@var{version-number}} source directory, which in
29949 this example is the @file{gdb-@value{GDBVN}} directory.
29951 First switch to the @file{gdb-@var{version-number}} source directory
29952 if you are not already in it; then run @file{configure}. Pass the
29953 identifier for the platform on which @value{GDBN} will run as an
29959 cd gdb-@value{GDBVN}
29960 ./configure @var{host}
29965 where @var{host} is an identifier such as @samp{sun4} or
29966 @samp{decstation}, that identifies the platform where @value{GDBN} will run.
29967 (You can often leave off @var{host}; @file{configure} tries to guess the
29968 correct value by examining your system.)
29970 Running @samp{configure @var{host}} and then running @code{make} builds the
29971 @file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty}
29972 libraries, then @code{gdb} itself. The configured source files, and the
29973 binaries, are left in the corresponding source directories.
29976 @file{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
29977 system does not recognize this automatically when you run a different
29978 shell, you may need to run @code{sh} on it explicitly:
29981 sh configure @var{host}
29984 If you run @file{configure} from a directory that contains source
29985 directories for multiple libraries or programs, such as the
29986 @file{gdb-@value{GDBVN}} source directory for version @value{GDBVN},
29988 creates configuration files for every directory level underneath (unless
29989 you tell it not to, with the @samp{--norecursion} option).
29991 You should run the @file{configure} script from the top directory in the
29992 source tree, the @file{gdb-@var{version-number}} directory. If you run
29993 @file{configure} from one of the subdirectories, you will configure only
29994 that subdirectory. That is usually not what you want. In particular,
29995 if you run the first @file{configure} from the @file{gdb} subdirectory
29996 of the @file{gdb-@var{version-number}} directory, you will omit the
29997 configuration of @file{bfd}, @file{readline}, and other sibling
29998 directories of the @file{gdb} subdirectory. This leads to build errors
29999 about missing include files such as @file{bfd/bfd.h}.
30001 You can install @code{@value{GDBP}} anywhere; it has no hardwired paths.
30002 However, you should make sure that the shell on your path (named by
30003 the @samp{SHELL} environment variable) is publicly readable. Remember
30004 that @value{GDBN} uses the shell to start your program---some systems refuse to
30005 let @value{GDBN} debug child processes whose programs are not readable.
30007 @node Separate Objdir
30008 @section Compiling @value{GDBN} in Another Directory
30010 If you want to run @value{GDBN} versions for several host or target machines,
30011 you need a different @code{gdb} compiled for each combination of
30012 host and target. @file{configure} is designed to make this easy by
30013 allowing you to generate each configuration in a separate subdirectory,
30014 rather than in the source directory. If your @code{make} program
30015 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
30016 @code{make} in each of these directories builds the @code{gdb}
30017 program specified there.
30019 To build @code{gdb} in a separate directory, run @file{configure}
30020 with the @samp{--srcdir} option to specify where to find the source.
30021 (You also need to specify a path to find @file{configure}
30022 itself from your working directory. If the path to @file{configure}
30023 would be the same as the argument to @samp{--srcdir}, you can leave out
30024 the @samp{--srcdir} option; it is assumed.)
30026 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
30027 separate directory for a Sun 4 like this:
30031 cd gdb-@value{GDBVN}
30034 ../gdb-@value{GDBVN}/configure sun4
30039 When @file{configure} builds a configuration using a remote source
30040 directory, it creates a tree for the binaries with the same structure
30041 (and using the same names) as the tree under the source directory. In
30042 the example, you'd find the Sun 4 library @file{libiberty.a} in the
30043 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
30044 @file{gdb-sun4/gdb}.
30046 Make sure that your path to the @file{configure} script has just one
30047 instance of @file{gdb} in it. If your path to @file{configure} looks
30048 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
30049 one subdirectory of @value{GDBN}, not the whole package. This leads to
30050 build errors about missing include files such as @file{bfd/bfd.h}.
30052 One popular reason to build several @value{GDBN} configurations in separate
30053 directories is to configure @value{GDBN} for cross-compiling (where
30054 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
30055 programs that run on another machine---the @dfn{target}).
30056 You specify a cross-debugging target by
30057 giving the @samp{--target=@var{target}} option to @file{configure}.
30059 When you run @code{make} to build a program or library, you must run
30060 it in a configured directory---whatever directory you were in when you
30061 called @file{configure} (or one of its subdirectories).
30063 The @code{Makefile} that @file{configure} generates in each source
30064 directory also runs recursively. If you type @code{make} in a source
30065 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
30066 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
30067 will build all the required libraries, and then build GDB.
30069 When you have multiple hosts or targets configured in separate
30070 directories, you can run @code{make} on them in parallel (for example,
30071 if they are NFS-mounted on each of the hosts); they will not interfere
30075 @section Specifying Names for Hosts and Targets
30077 The specifications used for hosts and targets in the @file{configure}
30078 script are based on a three-part naming scheme, but some short predefined
30079 aliases are also supported. The full naming scheme encodes three pieces
30080 of information in the following pattern:
30083 @var{architecture}-@var{vendor}-@var{os}
30086 For example, you can use the alias @code{sun4} as a @var{host} argument,
30087 or as the value for @var{target} in a @code{--target=@var{target}}
30088 option. The equivalent full name is @samp{sparc-sun-sunos4}.
30090 The @file{configure} script accompanying @value{GDBN} does not provide
30091 any query facility to list all supported host and target names or
30092 aliases. @file{configure} calls the Bourne shell script
30093 @code{config.sub} to map abbreviations to full names; you can read the
30094 script, if you wish, or you can use it to test your guesses on
30095 abbreviations---for example:
30098 % sh config.sub i386-linux
30100 % sh config.sub alpha-linux
30101 alpha-unknown-linux-gnu
30102 % sh config.sub hp9k700
30104 % sh config.sub sun4
30105 sparc-sun-sunos4.1.1
30106 % sh config.sub sun3
30107 m68k-sun-sunos4.1.1
30108 % sh config.sub i986v
30109 Invalid configuration `i986v': machine `i986v' not recognized
30113 @code{config.sub} is also distributed in the @value{GDBN} source
30114 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
30116 @node Configure Options
30117 @section @file{configure} Options
30119 Here is a summary of the @file{configure} options and arguments that
30120 are most often useful for building @value{GDBN}. @file{configure} also has
30121 several other options not listed here. @inforef{What Configure
30122 Does,,configure.info}, for a full explanation of @file{configure}.
30125 configure @r{[}--help@r{]}
30126 @r{[}--prefix=@var{dir}@r{]}
30127 @r{[}--exec-prefix=@var{dir}@r{]}
30128 @r{[}--srcdir=@var{dirname}@r{]}
30129 @r{[}--norecursion@r{]} @r{[}--rm@r{]}
30130 @r{[}--target=@var{target}@r{]}
30135 You may introduce options with a single @samp{-} rather than
30136 @samp{--} if you prefer; but you may abbreviate option names if you use
30141 Display a quick summary of how to invoke @file{configure}.
30143 @item --prefix=@var{dir}
30144 Configure the source to install programs and files under directory
30147 @item --exec-prefix=@var{dir}
30148 Configure the source to install programs under directory
30151 @c avoid splitting the warning from the explanation:
30153 @item --srcdir=@var{dirname}
30154 @strong{Warning: using this option requires @sc{gnu} @code{make}, or another
30155 @code{make} that implements the @code{VPATH} feature.}@*
30156 Use this option to make configurations in directories separate from the
30157 @value{GDBN} source directories. Among other things, you can use this to
30158 build (or maintain) several configurations simultaneously, in separate
30159 directories. @file{configure} writes configuration-specific files in
30160 the current directory, but arranges for them to use the source in the
30161 directory @var{dirname}. @file{configure} creates directories under
30162 the working directory in parallel to the source directories below
30165 @item --norecursion
30166 Configure only the directory level where @file{configure} is executed; do not
30167 propagate configuration to subdirectories.
30169 @item --target=@var{target}
30170 Configure @value{GDBN} for cross-debugging programs running on the specified
30171 @var{target}. Without this option, @value{GDBN} is configured to debug
30172 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
30174 There is no convenient way to generate a list of all available targets.
30176 @item @var{host} @dots{}
30177 Configure @value{GDBN} to run on the specified @var{host}.
30179 There is no convenient way to generate a list of all available hosts.
30182 There are many other options available as well, but they are generally
30183 needed for special purposes only.
30185 @node System-wide configuration
30186 @section System-wide configuration and settings
30187 @cindex system-wide init file
30189 @value{GDBN} can be configured to have a system-wide init file;
30190 this file will be read and executed at startup (@pxref{Startup, , What
30191 @value{GDBN} does during startup}).
30193 Here is the corresponding configure option:
30196 @item --with-system-gdbinit=@var{file}
30197 Specify that the default location of the system-wide init file is
30201 If @value{GDBN} has been configured with the option @option{--prefix=$prefix},
30202 it may be subject to relocation. Two possible cases:
30206 If the default location of this init file contains @file{$prefix},
30207 it will be subject to relocation. Suppose that the configure options
30208 are @option{--prefix=$prefix --with-system-gdbinit=$prefix/etc/gdbinit};
30209 if @value{GDBN} is moved from @file{$prefix} to @file{$install}, the system
30210 init file is looked for as @file{$install/etc/gdbinit} instead of
30211 @file{$prefix/etc/gdbinit}.
30214 By contrast, if the default location does not contain the prefix,
30215 it will not be relocated. E.g.@: if @value{GDBN} has been configured with
30216 @option{--prefix=/usr/local --with-system-gdbinit=/usr/share/gdb/gdbinit},
30217 then @value{GDBN} will always look for @file{/usr/share/gdb/gdbinit},
30218 wherever @value{GDBN} is installed.
30221 @node Maintenance Commands
30222 @appendix Maintenance Commands
30223 @cindex maintenance commands
30224 @cindex internal commands
30226 In addition to commands intended for @value{GDBN} users, @value{GDBN}
30227 includes a number of commands intended for @value{GDBN} developers,
30228 that are not documented elsewhere in this manual. These commands are
30229 provided here for reference. (For commands that turn on debugging
30230 messages, see @ref{Debugging Output}.)
30233 @kindex maint agent
30234 @kindex maint agent-eval
30235 @item maint agent @var{expression}
30236 @itemx maint agent-eval @var{expression}
30237 Translate the given @var{expression} into remote agent bytecodes.
30238 This command is useful for debugging the Agent Expression mechanism
30239 (@pxref{Agent Expressions}). The @samp{agent} version produces an
30240 expression useful for data collection, such as by tracepoints, while
30241 @samp{maint agent-eval} produces an expression that evaluates directly
30242 to a result. For instance, a collection expression for @code{globa +
30243 globb} will include bytecodes to record four bytes of memory at each
30244 of the addresses of @code{globa} and @code{globb}, while discarding
30245 the result of the addition, while an evaluation expression will do the
30246 addition and return the sum.
30248 @kindex maint info breakpoints
30249 @item @anchor{maint info breakpoints}maint info breakpoints
30250 Using the same format as @samp{info breakpoints}, display both the
30251 breakpoints you've set explicitly, and those @value{GDBN} is using for
30252 internal purposes. Internal breakpoints are shown with negative
30253 breakpoint numbers. The type column identifies what kind of breakpoint
30258 Normal, explicitly set breakpoint.
30261 Normal, explicitly set watchpoint.
30264 Internal breakpoint, used to handle correctly stepping through
30265 @code{longjmp} calls.
30267 @item longjmp resume
30268 Internal breakpoint at the target of a @code{longjmp}.
30271 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
30274 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
30277 Shared library events.
30281 @kindex set displaced-stepping
30282 @kindex show displaced-stepping
30283 @cindex displaced stepping support
30284 @cindex out-of-line single-stepping
30285 @item set displaced-stepping
30286 @itemx show displaced-stepping
30287 Control whether or not @value{GDBN} will do @dfn{displaced stepping}
30288 if the target supports it. Displaced stepping is a way to single-step
30289 over breakpoints without removing them from the inferior, by executing
30290 an out-of-line copy of the instruction that was originally at the
30291 breakpoint location. It is also known as out-of-line single-stepping.
30294 @item set displaced-stepping on
30295 If the target architecture supports it, @value{GDBN} will use
30296 displaced stepping to step over breakpoints.
30298 @item set displaced-stepping off
30299 @value{GDBN} will not use displaced stepping to step over breakpoints,
30300 even if such is supported by the target architecture.
30302 @cindex non-stop mode, and @samp{set displaced-stepping}
30303 @item set displaced-stepping auto
30304 This is the default mode. @value{GDBN} will use displaced stepping
30305 only if non-stop mode is active (@pxref{Non-Stop Mode}) and the target
30306 architecture supports displaced stepping.
30309 @kindex maint check-symtabs
30310 @item maint check-symtabs
30311 Check the consistency of psymtabs and symtabs.
30313 @kindex maint cplus first_component
30314 @item maint cplus first_component @var{name}
30315 Print the first C@t{++} class/namespace component of @var{name}.
30317 @kindex maint cplus namespace
30318 @item maint cplus namespace
30319 Print the list of possible C@t{++} namespaces.
30321 @kindex maint demangle
30322 @item maint demangle @var{name}
30323 Demangle a C@t{++} or Objective-C mangled @var{name}.
30325 @kindex maint deprecate
30326 @kindex maint undeprecate
30327 @cindex deprecated commands
30328 @item maint deprecate @var{command} @r{[}@var{replacement}@r{]}
30329 @itemx maint undeprecate @var{command}
30330 Deprecate or undeprecate the named @var{command}. Deprecated commands
30331 cause @value{GDBN} to issue a warning when you use them. The optional
30332 argument @var{replacement} says which newer command should be used in
30333 favor of the deprecated one; if it is given, @value{GDBN} will mention
30334 the replacement as part of the warning.
30336 @kindex maint dump-me
30337 @item maint dump-me
30338 @cindex @code{SIGQUIT} signal, dump core of @value{GDBN}
30339 Cause a fatal signal in the debugger and force it to dump its core.
30340 This is supported only on systems which support aborting a program
30341 with the @code{SIGQUIT} signal.
30343 @kindex maint internal-error
30344 @kindex maint internal-warning
30345 @item maint internal-error @r{[}@var{message-text}@r{]}
30346 @itemx maint internal-warning @r{[}@var{message-text}@r{]}
30347 Cause @value{GDBN} to call the internal function @code{internal_error}
30348 or @code{internal_warning} and hence behave as though an internal error
30349 or internal warning has been detected. In addition to reporting the
30350 internal problem, these functions give the user the opportunity to
30351 either quit @value{GDBN} or create a core file of the current
30352 @value{GDBN} session.
30354 These commands take an optional parameter @var{message-text} that is
30355 used as the text of the error or warning message.
30357 Here's an example of using @code{internal-error}:
30360 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
30361 @dots{}/maint.c:121: internal-error: testing, 1, 2
30362 A problem internal to GDB has been detected. Further
30363 debugging may prove unreliable.
30364 Quit this debugging session? (y or n) @kbd{n}
30365 Create a core file? (y or n) @kbd{n}
30369 @cindex @value{GDBN} internal error
30370 @cindex internal errors, control of @value{GDBN} behavior
30372 @kindex maint set internal-error
30373 @kindex maint show internal-error
30374 @kindex maint set internal-warning
30375 @kindex maint show internal-warning
30376 @item maint set internal-error @var{action} [ask|yes|no]
30377 @itemx maint show internal-error @var{action}
30378 @itemx maint set internal-warning @var{action} [ask|yes|no]
30379 @itemx maint show internal-warning @var{action}
30380 When @value{GDBN} reports an internal problem (error or warning) it
30381 gives the user the opportunity to both quit @value{GDBN} and create a
30382 core file of the current @value{GDBN} session. These commands let you
30383 override the default behaviour for each particular @var{action},
30384 described in the table below.
30388 You can specify that @value{GDBN} should always (yes) or never (no)
30389 quit. The default is to ask the user what to do.
30392 You can specify that @value{GDBN} should always (yes) or never (no)
30393 create a core file. The default is to ask the user what to do.
30396 @kindex maint packet
30397 @item maint packet @var{text}
30398 If @value{GDBN} is talking to an inferior via the serial protocol,
30399 then this command sends the string @var{text} to the inferior, and
30400 displays the response packet. @value{GDBN} supplies the initial
30401 @samp{$} character, the terminating @samp{#} character, and the
30404 @kindex maint print architecture
30405 @item maint print architecture @r{[}@var{file}@r{]}
30406 Print the entire architecture configuration. The optional argument
30407 @var{file} names the file where the output goes.
30409 @kindex maint print c-tdesc
30410 @item maint print c-tdesc
30411 Print the current target description (@pxref{Target Descriptions}) as
30412 a C source file. The created source file can be used in @value{GDBN}
30413 when an XML parser is not available to parse the description.
30415 @kindex maint print dummy-frames
30416 @item maint print dummy-frames
30417 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
30420 (@value{GDBP}) @kbd{b add}
30422 (@value{GDBP}) @kbd{print add(2,3)}
30423 Breakpoint 2, add (a=2, b=3) at @dots{}
30425 The program being debugged stopped while in a function called from GDB.
30427 (@value{GDBP}) @kbd{maint print dummy-frames}
30428 0x1a57c80: pc=0x01014068 fp=0x0200bddc sp=0x0200bdd6
30429 top=0x0200bdd4 id=@{stack=0x200bddc,code=0x101405c@}
30430 call_lo=0x01014000 call_hi=0x01014001
30434 Takes an optional file parameter.
30436 @kindex maint print registers
30437 @kindex maint print raw-registers
30438 @kindex maint print cooked-registers
30439 @kindex maint print register-groups
30440 @item maint print registers @r{[}@var{file}@r{]}
30441 @itemx maint print raw-registers @r{[}@var{file}@r{]}
30442 @itemx maint print cooked-registers @r{[}@var{file}@r{]}
30443 @itemx maint print register-groups @r{[}@var{file}@r{]}
30444 Print @value{GDBN}'s internal register data structures.
30446 The command @code{maint print raw-registers} includes the contents of
30447 the raw register cache; the command @code{maint print cooked-registers}
30448 includes the (cooked) value of all registers, including registers which
30449 aren't available on the target nor visible to user; and the
30450 command @code{maint print register-groups} includes the groups that each
30451 register is a member of. @xref{Registers,, Registers, gdbint,
30452 @value{GDBN} Internals}.
30454 These commands take an optional parameter, a file name to which to
30455 write the information.
30457 @kindex maint print reggroups
30458 @item maint print reggroups @r{[}@var{file}@r{]}
30459 Print @value{GDBN}'s internal register group data structures. The
30460 optional argument @var{file} tells to what file to write the
30463 The register groups info looks like this:
30466 (@value{GDBP}) @kbd{maint print reggroups}
30479 This command forces @value{GDBN} to flush its internal register cache.
30481 @kindex maint print objfiles
30482 @cindex info for known object files
30483 @item maint print objfiles
30484 Print a dump of all known object files. For each object file, this
30485 command prints its name, address in memory, and all of its psymtabs
30488 @kindex maint print section-scripts
30489 @cindex info for known .debug_gdb_scripts-loaded scripts
30490 @item maint print section-scripts [@var{regexp}]
30491 Print a dump of scripts specified in the @code{.debug_gdb_section} section.
30492 If @var{regexp} is specified, only print scripts loaded by object files
30493 matching @var{regexp}.
30494 For each script, this command prints its name as specified in the objfile,
30495 and the full path if known.
30496 @xref{.debug_gdb_scripts section}.
30498 @kindex maint print statistics
30499 @cindex bcache statistics
30500 @item maint print statistics
30501 This command prints, for each object file in the program, various data
30502 about that object file followed by the byte cache (@dfn{bcache})
30503 statistics for the object file. The objfile data includes the number
30504 of minimal, partial, full, and stabs symbols, the number of types
30505 defined by the objfile, the number of as yet unexpanded psym tables,
30506 the number of line tables and string tables, and the amount of memory
30507 used by the various tables. The bcache statistics include the counts,
30508 sizes, and counts of duplicates of all and unique objects, max,
30509 average, and median entry size, total memory used and its overhead and
30510 savings, and various measures of the hash table size and chain
30513 @kindex maint print target-stack
30514 @cindex target stack description
30515 @item maint print target-stack
30516 A @dfn{target} is an interface between the debugger and a particular
30517 kind of file or process. Targets can be stacked in @dfn{strata},
30518 so that more than one target can potentially respond to a request.
30519 In particular, memory accesses will walk down the stack of targets
30520 until they find a target that is interested in handling that particular
30523 This command prints a short description of each layer that was pushed on
30524 the @dfn{target stack}, starting from the top layer down to the bottom one.
30526 @kindex maint print type
30527 @cindex type chain of a data type
30528 @item maint print type @var{expr}
30529 Print the type chain for a type specified by @var{expr}. The argument
30530 can be either a type name or a symbol. If it is a symbol, the type of
30531 that symbol is described. The type chain produced by this command is
30532 a recursive definition of the data type as stored in @value{GDBN}'s
30533 data structures, including its flags and contained types.
30535 @kindex maint set dwarf2 always-disassemble
30536 @kindex maint show dwarf2 always-disassemble
30537 @item maint set dwarf2 always-disassemble
30538 @item maint show dwarf2 always-disassemble
30539 Control the behavior of @code{info address} when using DWARF debugging
30542 The default is @code{off}, which means that @value{GDBN} should try to
30543 describe a variable's location in an easily readable format. When
30544 @code{on}, @value{GDBN} will instead display the DWARF location
30545 expression in an assembly-like format. Note that some locations are
30546 too complex for @value{GDBN} to describe simply; in this case you will
30547 always see the disassembly form.
30549 Here is an example of the resulting disassembly:
30552 (gdb) info addr argc
30553 Symbol "argc" is a complex DWARF expression:
30557 For more information on these expressions, see
30558 @uref{http://www.dwarfstd.org/, the DWARF standard}.
30560 @kindex maint set dwarf2 max-cache-age
30561 @kindex maint show dwarf2 max-cache-age
30562 @item maint set dwarf2 max-cache-age
30563 @itemx maint show dwarf2 max-cache-age
30564 Control the DWARF 2 compilation unit cache.
30566 @cindex DWARF 2 compilation units cache
30567 In object files with inter-compilation-unit references, such as those
30568 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF 2
30569 reader needs to frequently refer to previously read compilation units.
30570 This setting controls how long a compilation unit will remain in the
30571 cache if it is not referenced. A higher limit means that cached
30572 compilation units will be stored in memory longer, and more total
30573 memory will be used. Setting it to zero disables caching, which will
30574 slow down @value{GDBN} startup, but reduce memory consumption.
30576 @kindex maint set profile
30577 @kindex maint show profile
30578 @cindex profiling GDB
30579 @item maint set profile
30580 @itemx maint show profile
30581 Control profiling of @value{GDBN}.
30583 Profiling will be disabled until you use the @samp{maint set profile}
30584 command to enable it. When you enable profiling, the system will begin
30585 collecting timing and execution count data; when you disable profiling or
30586 exit @value{GDBN}, the results will be written to a log file. Remember that
30587 if you use profiling, @value{GDBN} will overwrite the profiling log file
30588 (often called @file{gmon.out}). If you have a record of important profiling
30589 data in a @file{gmon.out} file, be sure to move it to a safe location.
30591 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
30592 compiled with the @samp{-pg} compiler option.
30594 @kindex maint set show-debug-regs
30595 @kindex maint show show-debug-regs
30596 @cindex hardware debug registers
30597 @item maint set show-debug-regs
30598 @itemx maint show show-debug-regs
30599 Control whether to show variables that mirror the hardware debug
30600 registers. Use @code{ON} to enable, @code{OFF} to disable. If
30601 enabled, the debug registers values are shown when @value{GDBN} inserts or
30602 removes a hardware breakpoint or watchpoint, and when the inferior
30603 triggers a hardware-assisted breakpoint or watchpoint.
30605 @kindex maint set show-all-tib
30606 @kindex maint show show-all-tib
30607 @item maint set show-all-tib
30608 @itemx maint show show-all-tib
30609 Control whether to show all non zero areas within a 1k block starting
30610 at thread local base, when using the @samp{info w32 thread-information-block}
30613 @kindex maint space
30614 @cindex memory used by commands
30616 Control whether to display memory usage for each command. If set to a
30617 nonzero value, @value{GDBN} will display how much memory each command
30618 took, following the command's own output. This can also be requested
30619 by invoking @value{GDBN} with the @option{--statistics} command-line
30620 switch (@pxref{Mode Options}).
30623 @cindex time of command execution
30625 Control whether to display the execution time for each command. If
30626 set to a nonzero value, @value{GDBN} will display how much time it
30627 took to execute each command, following the command's own output.
30628 The time is not printed for the commands that run the target, since
30629 there's no mechanism currently to compute how much time was spend
30630 by @value{GDBN} and how much time was spend by the program been debugged.
30631 it's not possibly currently
30632 This can also be requested by invoking @value{GDBN} with the
30633 @option{--statistics} command-line switch (@pxref{Mode Options}).
30635 @kindex maint translate-address
30636 @item maint translate-address @r{[}@var{section}@r{]} @var{addr}
30637 Find the symbol stored at the location specified by the address
30638 @var{addr} and an optional section name @var{section}. If found,
30639 @value{GDBN} prints the name of the closest symbol and an offset from
30640 the symbol's location to the specified address. This is similar to
30641 the @code{info address} command (@pxref{Symbols}), except that this
30642 command also allows to find symbols in other sections.
30644 If section was not specified, the section in which the symbol was found
30645 is also printed. For dynamically linked executables, the name of
30646 executable or shared library containing the symbol is printed as well.
30650 The following command is useful for non-interactive invocations of
30651 @value{GDBN}, such as in the test suite.
30654 @item set watchdog @var{nsec}
30655 @kindex set watchdog
30656 @cindex watchdog timer
30657 @cindex timeout for commands
30658 Set the maximum number of seconds @value{GDBN} will wait for the
30659 target operation to finish. If this time expires, @value{GDBN}
30660 reports and error and the command is aborted.
30662 @item show watchdog
30663 Show the current setting of the target wait timeout.
30666 @node Remote Protocol
30667 @appendix @value{GDBN} Remote Serial Protocol
30672 * Stop Reply Packets::
30673 * General Query Packets::
30674 * Architecture-Specific Protocol Details::
30675 * Tracepoint Packets::
30676 * Host I/O Packets::
30678 * Notification Packets::
30679 * Remote Non-Stop::
30680 * Packet Acknowledgment::
30682 * File-I/O Remote Protocol Extension::
30683 * Library List Format::
30684 * Memory Map Format::
30685 * Thread List Format::
30691 There may be occasions when you need to know something about the
30692 protocol---for example, if there is only one serial port to your target
30693 machine, you might want your program to do something special if it
30694 recognizes a packet meant for @value{GDBN}.
30696 In the examples below, @samp{->} and @samp{<-} are used to indicate
30697 transmitted and received data, respectively.
30699 @cindex protocol, @value{GDBN} remote serial
30700 @cindex serial protocol, @value{GDBN} remote
30701 @cindex remote serial protocol
30702 All @value{GDBN} commands and responses (other than acknowledgments
30703 and notifications, see @ref{Notification Packets}) are sent as a
30704 @var{packet}. A @var{packet} is introduced with the character
30705 @samp{$}, the actual @var{packet-data}, and the terminating character
30706 @samp{#} followed by a two-digit @var{checksum}:
30709 @code{$}@var{packet-data}@code{#}@var{checksum}
30713 @cindex checksum, for @value{GDBN} remote
30715 The two-digit @var{checksum} is computed as the modulo 256 sum of all
30716 characters between the leading @samp{$} and the trailing @samp{#} (an
30717 eight bit unsigned checksum).
30719 Implementors should note that prior to @value{GDBN} 5.0 the protocol
30720 specification also included an optional two-digit @var{sequence-id}:
30723 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
30726 @cindex sequence-id, for @value{GDBN} remote
30728 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
30729 has never output @var{sequence-id}s. Stubs that handle packets added
30730 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
30732 When either the host or the target machine receives a packet, the first
30733 response expected is an acknowledgment: either @samp{+} (to indicate
30734 the package was received correctly) or @samp{-} (to request
30738 -> @code{$}@var{packet-data}@code{#}@var{checksum}
30743 The @samp{+}/@samp{-} acknowledgments can be disabled
30744 once a connection is established.
30745 @xref{Packet Acknowledgment}, for details.
30747 The host (@value{GDBN}) sends @var{command}s, and the target (the
30748 debugging stub incorporated in your program) sends a @var{response}. In
30749 the case of step and continue @var{command}s, the response is only sent
30750 when the operation has completed, and the target has again stopped all
30751 threads in all attached processes. This is the default all-stop mode
30752 behavior, but the remote protocol also supports @value{GDBN}'s non-stop
30753 execution mode; see @ref{Remote Non-Stop}, for details.
30755 @var{packet-data} consists of a sequence of characters with the
30756 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
30759 @cindex remote protocol, field separator
30760 Fields within the packet should be separated using @samp{,} @samp{;} or
30761 @samp{:}. Except where otherwise noted all numbers are represented in
30762 @sc{hex} with leading zeros suppressed.
30764 Implementors should note that prior to @value{GDBN} 5.0, the character
30765 @samp{:} could not appear as the third character in a packet (as it
30766 would potentially conflict with the @var{sequence-id}).
30768 @cindex remote protocol, binary data
30769 @anchor{Binary Data}
30770 Binary data in most packets is encoded either as two hexadecimal
30771 digits per byte of binary data. This allowed the traditional remote
30772 protocol to work over connections which were only seven-bit clean.
30773 Some packets designed more recently assume an eight-bit clean
30774 connection, and use a more efficient encoding to send and receive
30777 The binary data representation uses @code{7d} (@sc{ascii} @samp{@}})
30778 as an escape character. Any escaped byte is transmitted as the escape
30779 character followed by the original character XORed with @code{0x20}.
30780 For example, the byte @code{0x7d} would be transmitted as the two
30781 bytes @code{0x7d 0x5d}. The bytes @code{0x23} (@sc{ascii} @samp{#}),
30782 @code{0x24} (@sc{ascii} @samp{$}), and @code{0x7d} (@sc{ascii}
30783 @samp{@}}) must always be escaped. Responses sent by the stub
30784 must also escape @code{0x2a} (@sc{ascii} @samp{*}), so that it
30785 is not interpreted as the start of a run-length encoded sequence
30788 Response @var{data} can be run-length encoded to save space.
30789 Run-length encoding replaces runs of identical characters with one
30790 instance of the repeated character, followed by a @samp{*} and a
30791 repeat count. The repeat count is itself sent encoded, to avoid
30792 binary characters in @var{data}: a value of @var{n} is sent as
30793 @code{@var{n}+29}. For a repeat count greater or equal to 3, this
30794 produces a printable @sc{ascii} character, e.g.@: a space (@sc{ascii}
30795 code 32) for a repeat count of 3. (This is because run-length
30796 encoding starts to win for counts 3 or more.) Thus, for example,
30797 @samp{0* } is a run-length encoding of ``0000'': the space character
30798 after @samp{*} means repeat the leading @code{0} @w{@code{32 - 29 =
30801 The printable characters @samp{#} and @samp{$} or with a numeric value
30802 greater than 126 must not be used. Runs of six repeats (@samp{#}) or
30803 seven repeats (@samp{$}) can be expanded using a repeat count of only
30804 five (@samp{"}). For example, @samp{00000000} can be encoded as
30807 The error response returned for some packets includes a two character
30808 error number. That number is not well defined.
30810 @cindex empty response, for unsupported packets
30811 For any @var{command} not supported by the stub, an empty response
30812 (@samp{$#00}) should be returned. That way it is possible to extend the
30813 protocol. A newer @value{GDBN} can tell if a packet is supported based
30816 A stub is required to support the @samp{g}, @samp{G}, @samp{m}, @samp{M},
30817 @samp{c}, and @samp{s} @var{command}s. All other @var{command}s are
30823 The following table provides a complete list of all currently defined
30824 @var{command}s and their corresponding response @var{data}.
30825 @xref{File-I/O Remote Protocol Extension}, for details about the File
30826 I/O extension of the remote protocol.
30828 Each packet's description has a template showing the packet's overall
30829 syntax, followed by an explanation of the packet's meaning. We
30830 include spaces in some of the templates for clarity; these are not
30831 part of the packet's syntax. No @value{GDBN} packet uses spaces to
30832 separate its components. For example, a template like @samp{foo
30833 @var{bar} @var{baz}} describes a packet beginning with the three ASCII
30834 bytes @samp{foo}, followed by a @var{bar}, followed directly by a
30835 @var{baz}. @value{GDBN} does not transmit a space character between the
30836 @samp{foo} and the @var{bar}, or between the @var{bar} and the
30839 @cindex @var{thread-id}, in remote protocol
30840 @anchor{thread-id syntax}
30841 Several packets and replies include a @var{thread-id} field to identify
30842 a thread. Normally these are positive numbers with a target-specific
30843 interpretation, formatted as big-endian hex strings. A @var{thread-id}
30844 can also be a literal @samp{-1} to indicate all threads, or @samp{0} to
30847 In addition, the remote protocol supports a multiprocess feature in
30848 which the @var{thread-id} syntax is extended to optionally include both
30849 process and thread ID fields, as @samp{p@var{pid}.@var{tid}}.
30850 The @var{pid} (process) and @var{tid} (thread) components each have the
30851 format described above: a positive number with target-specific
30852 interpretation formatted as a big-endian hex string, literal @samp{-1}
30853 to indicate all processes or threads (respectively), or @samp{0} to
30854 indicate an arbitrary process or thread. Specifying just a process, as
30855 @samp{p@var{pid}}, is equivalent to @samp{p@var{pid}.-1}. It is an
30856 error to specify all processes but a specific thread, such as
30857 @samp{p-1.@var{tid}}. Note that the @samp{p} prefix is @emph{not} used
30858 for those packets and replies explicitly documented to include a process
30859 ID, rather than a @var{thread-id}.
30861 The multiprocess @var{thread-id} syntax extensions are only used if both
30862 @value{GDBN} and the stub report support for the @samp{multiprocess}
30863 feature using @samp{qSupported}. @xref{multiprocess extensions}, for
30866 Note that all packet forms beginning with an upper- or lower-case
30867 letter, other than those described here, are reserved for future use.
30869 Here are the packet descriptions.
30874 @cindex @samp{!} packet
30875 @anchor{extended mode}
30876 Enable extended mode. In extended mode, the remote server is made
30877 persistent. The @samp{R} packet is used to restart the program being
30883 The remote target both supports and has enabled extended mode.
30887 @cindex @samp{?} packet
30888 Indicate the reason the target halted. The reply is the same as for
30889 step and continue. This packet has a special interpretation when the
30890 target is in non-stop mode; see @ref{Remote Non-Stop}.
30893 @xref{Stop Reply Packets}, for the reply specifications.
30895 @item A @var{arglen},@var{argnum},@var{arg},@dots{}
30896 @cindex @samp{A} packet
30897 Initialized @code{argv[]} array passed into program. @var{arglen}
30898 specifies the number of bytes in the hex encoded byte stream
30899 @var{arg}. See @code{gdbserver} for more details.
30904 The arguments were set.
30910 @cindex @samp{b} packet
30911 (Don't use this packet; its behavior is not well-defined.)
30912 Change the serial line speed to @var{baud}.
30914 JTC: @emph{When does the transport layer state change? When it's
30915 received, or after the ACK is transmitted. In either case, there are
30916 problems if the command or the acknowledgment packet is dropped.}
30918 Stan: @emph{If people really wanted to add something like this, and get
30919 it working for the first time, they ought to modify ser-unix.c to send
30920 some kind of out-of-band message to a specially-setup stub and have the
30921 switch happen "in between" packets, so that from remote protocol's point
30922 of view, nothing actually happened.}
30924 @item B @var{addr},@var{mode}
30925 @cindex @samp{B} packet
30926 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
30927 breakpoint at @var{addr}.
30929 Don't use this packet. Use the @samp{Z} and @samp{z} packets instead
30930 (@pxref{insert breakpoint or watchpoint packet}).
30932 @cindex @samp{bc} packet
30935 Backward continue. Execute the target system in reverse. No parameter.
30936 @xref{Reverse Execution}, for more information.
30939 @xref{Stop Reply Packets}, for the reply specifications.
30941 @cindex @samp{bs} packet
30944 Backward single step. Execute one instruction in reverse. No parameter.
30945 @xref{Reverse Execution}, for more information.
30948 @xref{Stop Reply Packets}, for the reply specifications.
30950 @item c @r{[}@var{addr}@r{]}
30951 @cindex @samp{c} packet
30952 Continue. @var{addr} is address to resume. If @var{addr} is omitted,
30953 resume at current address.
30956 @xref{Stop Reply Packets}, for the reply specifications.
30958 @item C @var{sig}@r{[};@var{addr}@r{]}
30959 @cindex @samp{C} packet
30960 Continue with signal @var{sig} (hex signal number). If
30961 @samp{;@var{addr}} is omitted, resume at same address.
30964 @xref{Stop Reply Packets}, for the reply specifications.
30967 @cindex @samp{d} packet
30970 Don't use this packet; instead, define a general set packet
30971 (@pxref{General Query Packets}).
30975 @cindex @samp{D} packet
30976 The first form of the packet is used to detach @value{GDBN} from the
30977 remote system. It is sent to the remote target
30978 before @value{GDBN} disconnects via the @code{detach} command.
30980 The second form, including a process ID, is used when multiprocess
30981 protocol extensions are enabled (@pxref{multiprocess extensions}), to
30982 detach only a specific process. The @var{pid} is specified as a
30983 big-endian hex string.
30993 @item F @var{RC},@var{EE},@var{CF};@var{XX}
30994 @cindex @samp{F} packet
30995 A reply from @value{GDBN} to an @samp{F} packet sent by the target.
30996 This is part of the File-I/O protocol extension. @xref{File-I/O
30997 Remote Protocol Extension}, for the specification.
31000 @anchor{read registers packet}
31001 @cindex @samp{g} packet
31002 Read general registers.
31006 @item @var{XX@dots{}}
31007 Each byte of register data is described by two hex digits. The bytes
31008 with the register are transmitted in target byte order. The size of
31009 each register and their position within the @samp{g} packet are
31010 determined by the @value{GDBN} internal gdbarch functions
31011 @code{DEPRECATED_REGISTER_RAW_SIZE} and @code{gdbarch_register_name}. The
31012 specification of several standard @samp{g} packets is specified below.
31017 @item G @var{XX@dots{}}
31018 @cindex @samp{G} packet
31019 Write general registers. @xref{read registers packet}, for a
31020 description of the @var{XX@dots{}} data.
31030 @item H @var{c} @var{thread-id}
31031 @cindex @samp{H} packet
31032 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
31033 @samp{G}, et.al.). @var{c} depends on the operation to be performed: it
31034 should be @samp{c} for step and continue operations, @samp{g} for other
31035 operations. The thread designator @var{thread-id} has the format and
31036 interpretation described in @ref{thread-id syntax}.
31047 @c 'H': How restrictive (or permissive) is the thread model. If a
31048 @c thread is selected and stopped, are other threads allowed
31049 @c to continue to execute? As I mentioned above, I think the
31050 @c semantics of each command when a thread is selected must be
31051 @c described. For example:
31053 @c 'g': If the stub supports threads and a specific thread is
31054 @c selected, returns the register block from that thread;
31055 @c otherwise returns current registers.
31057 @c 'G' If the stub supports threads and a specific thread is
31058 @c selected, sets the registers of the register block of
31059 @c that thread; otherwise sets current registers.
31061 @item i @r{[}@var{addr}@r{[},@var{nnn}@r{]]}
31062 @anchor{cycle step packet}
31063 @cindex @samp{i} packet
31064 Step the remote target by a single clock cycle. If @samp{,@var{nnn}} is
31065 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
31066 step starting at that address.
31069 @cindex @samp{I} packet
31070 Signal, then cycle step. @xref{step with signal packet}. @xref{cycle
31074 @cindex @samp{k} packet
31077 FIXME: @emph{There is no description of how to operate when a specific
31078 thread context has been selected (i.e.@: does 'k' kill only that
31081 @item m @var{addr},@var{length}
31082 @cindex @samp{m} packet
31083 Read @var{length} bytes of memory starting at address @var{addr}.
31084 Note that @var{addr} may not be aligned to any particular boundary.
31086 The stub need not use any particular size or alignment when gathering
31087 data from memory for the response; even if @var{addr} is word-aligned
31088 and @var{length} is a multiple of the word size, the stub is free to
31089 use byte accesses, or not. For this reason, this packet may not be
31090 suitable for accessing memory-mapped I/O devices.
31091 @cindex alignment of remote memory accesses
31092 @cindex size of remote memory accesses
31093 @cindex memory, alignment and size of remote accesses
31097 @item @var{XX@dots{}}
31098 Memory contents; each byte is transmitted as a two-digit hexadecimal
31099 number. The reply may contain fewer bytes than requested if the
31100 server was able to read only part of the region of memory.
31105 @item M @var{addr},@var{length}:@var{XX@dots{}}
31106 @cindex @samp{M} packet
31107 Write @var{length} bytes of memory starting at address @var{addr}.
31108 @var{XX@dots{}} is the data; each byte is transmitted as a two-digit
31109 hexadecimal number.
31116 for an error (this includes the case where only part of the data was
31121 @cindex @samp{p} packet
31122 Read the value of register @var{n}; @var{n} is in hex.
31123 @xref{read registers packet}, for a description of how the returned
31124 register value is encoded.
31128 @item @var{XX@dots{}}
31129 the register's value
31133 Indicating an unrecognized @var{query}.
31136 @item P @var{n@dots{}}=@var{r@dots{}}
31137 @anchor{write register packet}
31138 @cindex @samp{P} packet
31139 Write register @var{n@dots{}} with value @var{r@dots{}}. The register
31140 number @var{n} is in hexadecimal, and @var{r@dots{}} contains two hex
31141 digits for each byte in the register (target byte order).
31151 @item q @var{name} @var{params}@dots{}
31152 @itemx Q @var{name} @var{params}@dots{}
31153 @cindex @samp{q} packet
31154 @cindex @samp{Q} packet
31155 General query (@samp{q}) and set (@samp{Q}). These packets are
31156 described fully in @ref{General Query Packets}.
31159 @cindex @samp{r} packet
31160 Reset the entire system.
31162 Don't use this packet; use the @samp{R} packet instead.
31165 @cindex @samp{R} packet
31166 Restart the program being debugged. @var{XX}, while needed, is ignored.
31167 This packet is only available in extended mode (@pxref{extended mode}).
31169 The @samp{R} packet has no reply.
31171 @item s @r{[}@var{addr}@r{]}
31172 @cindex @samp{s} packet
31173 Single step. @var{addr} is the address at which to resume. If
31174 @var{addr} is omitted, resume at same address.
31177 @xref{Stop Reply Packets}, for the reply specifications.
31179 @item S @var{sig}@r{[};@var{addr}@r{]}
31180 @anchor{step with signal packet}
31181 @cindex @samp{S} packet
31182 Step with signal. This is analogous to the @samp{C} packet, but
31183 requests a single-step, rather than a normal resumption of execution.
31186 @xref{Stop Reply Packets}, for the reply specifications.
31188 @item t @var{addr}:@var{PP},@var{MM}
31189 @cindex @samp{t} packet
31190 Search backwards starting at address @var{addr} for a match with pattern
31191 @var{PP} and mask @var{MM}. @var{PP} and @var{MM} are 4 bytes.
31192 @var{addr} must be at least 3 digits.
31194 @item T @var{thread-id}
31195 @cindex @samp{T} packet
31196 Find out if the thread @var{thread-id} is alive. @xref{thread-id syntax}.
31201 thread is still alive
31207 Packets starting with @samp{v} are identified by a multi-letter name,
31208 up to the first @samp{;} or @samp{?} (or the end of the packet).
31210 @item vAttach;@var{pid}
31211 @cindex @samp{vAttach} packet
31212 Attach to a new process with the specified process ID @var{pid}.
31213 The process ID is a
31214 hexadecimal integer identifying the process. In all-stop mode, all
31215 threads in the attached process are stopped; in non-stop mode, it may be
31216 attached without being stopped if that is supported by the target.
31218 @c In non-stop mode, on a successful vAttach, the stub should set the
31219 @c current thread to a thread of the newly-attached process. After
31220 @c attaching, GDB queries for the attached process's thread ID with qC.
31221 @c Also note that, from a user perspective, whether or not the
31222 @c target is stopped on attach in non-stop mode depends on whether you
31223 @c use the foreground or background version of the attach command, not
31224 @c on what vAttach does; GDB does the right thing with respect to either
31225 @c stopping or restarting threads.
31227 This packet is only available in extended mode (@pxref{extended mode}).
31233 @item @r{Any stop packet}
31234 for success in all-stop mode (@pxref{Stop Reply Packets})
31236 for success in non-stop mode (@pxref{Remote Non-Stop})
31239 @item vCont@r{[};@var{action}@r{[}:@var{thread-id}@r{]]}@dots{}
31240 @cindex @samp{vCont} packet
31241 Resume the inferior, specifying different actions for each thread.
31242 If an action is specified with no @var{thread-id}, then it is applied to any
31243 threads that don't have a specific action specified; if no default action is
31244 specified then other threads should remain stopped in all-stop mode and
31245 in their current state in non-stop mode.
31246 Specifying multiple
31247 default actions is an error; specifying no actions is also an error.
31248 Thread IDs are specified using the syntax described in @ref{thread-id syntax}.
31250 Currently supported actions are:
31256 Continue with signal @var{sig}. The signal @var{sig} should be two hex digits.
31260 Step with signal @var{sig}. The signal @var{sig} should be two hex digits.
31265 The optional argument @var{addr} normally associated with the
31266 @samp{c}, @samp{C}, @samp{s}, and @samp{S} packets is
31267 not supported in @samp{vCont}.
31269 The @samp{t} action is only relevant in non-stop mode
31270 (@pxref{Remote Non-Stop}) and may be ignored by the stub otherwise.
31271 A stop reply should be generated for any affected thread not already stopped.
31272 When a thread is stopped by means of a @samp{t} action,
31273 the corresponding stop reply should indicate that the thread has stopped with
31274 signal @samp{0}, regardless of whether the target uses some other signal
31275 as an implementation detail.
31278 @xref{Stop Reply Packets}, for the reply specifications.
31281 @cindex @samp{vCont?} packet
31282 Request a list of actions supported by the @samp{vCont} packet.
31286 @item vCont@r{[};@var{action}@dots{}@r{]}
31287 The @samp{vCont} packet is supported. Each @var{action} is a supported
31288 command in the @samp{vCont} packet.
31290 The @samp{vCont} packet is not supported.
31293 @item vFile:@var{operation}:@var{parameter}@dots{}
31294 @cindex @samp{vFile} packet
31295 Perform a file operation on the target system. For details,
31296 see @ref{Host I/O Packets}.
31298 @item vFlashErase:@var{addr},@var{length}
31299 @cindex @samp{vFlashErase} packet
31300 Direct the stub to erase @var{length} bytes of flash starting at
31301 @var{addr}. The region may enclose any number of flash blocks, but
31302 its start and end must fall on block boundaries, as indicated by the
31303 flash block size appearing in the memory map (@pxref{Memory Map
31304 Format}). @value{GDBN} groups flash memory programming operations
31305 together, and sends a @samp{vFlashDone} request after each group; the
31306 stub is allowed to delay erase operation until the @samp{vFlashDone}
31307 packet is received.
31309 The stub must support @samp{vCont} if it reports support for
31310 multiprocess extensions (@pxref{multiprocess extensions}). Note that in
31311 this case @samp{vCont} actions can be specified to apply to all threads
31312 in a process by using the @samp{p@var{pid}.-1} form of the
31323 @item vFlashWrite:@var{addr}:@var{XX@dots{}}
31324 @cindex @samp{vFlashWrite} packet
31325 Direct the stub to write data to flash address @var{addr}. The data
31326 is passed in binary form using the same encoding as for the @samp{X}
31327 packet (@pxref{Binary Data}). The memory ranges specified by
31328 @samp{vFlashWrite} packets preceding a @samp{vFlashDone} packet must
31329 not overlap, and must appear in order of increasing addresses
31330 (although @samp{vFlashErase} packets for higher addresses may already
31331 have been received; the ordering is guaranteed only between
31332 @samp{vFlashWrite} packets). If a packet writes to an address that was
31333 neither erased by a preceding @samp{vFlashErase} packet nor by some other
31334 target-specific method, the results are unpredictable.
31342 for vFlashWrite addressing non-flash memory
31348 @cindex @samp{vFlashDone} packet
31349 Indicate to the stub that flash programming operation is finished.
31350 The stub is permitted to delay or batch the effects of a group of
31351 @samp{vFlashErase} and @samp{vFlashWrite} packets until a
31352 @samp{vFlashDone} packet is received. The contents of the affected
31353 regions of flash memory are unpredictable until the @samp{vFlashDone}
31354 request is completed.
31356 @item vKill;@var{pid}
31357 @cindex @samp{vKill} packet
31358 Kill the process with the specified process ID. @var{pid} is a
31359 hexadecimal integer identifying the process. This packet is used in
31360 preference to @samp{k} when multiprocess protocol extensions are
31361 supported; see @ref{multiprocess extensions}.
31371 @item vRun;@var{filename}@r{[};@var{argument}@r{]}@dots{}
31372 @cindex @samp{vRun} packet
31373 Run the program @var{filename}, passing it each @var{argument} on its
31374 command line. The file and arguments are hex-encoded strings. If
31375 @var{filename} is an empty string, the stub may use a default program
31376 (e.g.@: the last program run). The program is created in the stopped
31379 @c FIXME: What about non-stop mode?
31381 This packet is only available in extended mode (@pxref{extended mode}).
31387 @item @r{Any stop packet}
31388 for success (@pxref{Stop Reply Packets})
31392 @anchor{vStopped packet}
31393 @cindex @samp{vStopped} packet
31395 In non-stop mode (@pxref{Remote Non-Stop}), acknowledge a previous stop
31396 reply and prompt for the stub to report another one.
31400 @item @r{Any stop packet}
31401 if there is another unreported stop event (@pxref{Stop Reply Packets})
31403 if there are no unreported stop events
31406 @item X @var{addr},@var{length}:@var{XX@dots{}}
31408 @cindex @samp{X} packet
31409 Write data to memory, where the data is transmitted in binary.
31410 @var{addr} is address, @var{length} is number of bytes,
31411 @samp{@var{XX}@dots{}} is binary data (@pxref{Binary Data}).
31421 @item z @var{type},@var{addr},@var{kind}
31422 @itemx Z @var{type},@var{addr},@var{kind}
31423 @anchor{insert breakpoint or watchpoint packet}
31424 @cindex @samp{z} packet
31425 @cindex @samp{Z} packets
31426 Insert (@samp{Z}) or remove (@samp{z}) a @var{type} breakpoint or
31427 watchpoint starting at address @var{address} of kind @var{kind}.
31429 Each breakpoint and watchpoint packet @var{type} is documented
31432 @emph{Implementation notes: A remote target shall return an empty string
31433 for an unrecognized breakpoint or watchpoint packet @var{type}. A
31434 remote target shall support either both or neither of a given
31435 @samp{Z@var{type}@dots{}} and @samp{z@var{type}@dots{}} packet pair. To
31436 avoid potential problems with duplicate packets, the operations should
31437 be implemented in an idempotent way.}
31439 @item z0,@var{addr},@var{kind}
31440 @itemx Z0,@var{addr},@var{kind}
31441 @cindex @samp{z0} packet
31442 @cindex @samp{Z0} packet
31443 Insert (@samp{Z0}) or remove (@samp{z0}) a memory breakpoint at address
31444 @var{addr} of type @var{kind}.
31446 A memory breakpoint is implemented by replacing the instruction at
31447 @var{addr} with a software breakpoint or trap instruction. The
31448 @var{kind} is target-specific and typically indicates the size of
31449 the breakpoint in bytes that should be inserted. E.g., the @sc{arm}
31450 and @sc{mips} can insert either a 2 or 4 byte breakpoint. Some
31451 architectures have additional meanings for @var{kind};
31452 see @ref{Architecture-Specific Protocol Details}.
31454 @emph{Implementation note: It is possible for a target to copy or move
31455 code that contains memory breakpoints (e.g., when implementing
31456 overlays). The behavior of this packet, in the presence of such a
31457 target, is not defined.}
31469 @item z1,@var{addr},@var{kind}
31470 @itemx Z1,@var{addr},@var{kind}
31471 @cindex @samp{z1} packet
31472 @cindex @samp{Z1} packet
31473 Insert (@samp{Z1}) or remove (@samp{z1}) a hardware breakpoint at
31474 address @var{addr}.
31476 A hardware breakpoint is implemented using a mechanism that is not
31477 dependant on being able to modify the target's memory. @var{kind}
31478 has the same meaning as in @samp{Z0} packets.
31480 @emph{Implementation note: A hardware breakpoint is not affected by code
31493 @item z2,@var{addr},@var{kind}
31494 @itemx Z2,@var{addr},@var{kind}
31495 @cindex @samp{z2} packet
31496 @cindex @samp{Z2} packet
31497 Insert (@samp{Z2}) or remove (@samp{z2}) a write watchpoint at @var{addr}.
31498 @var{kind} is interpreted as the number of bytes to watch.
31510 @item z3,@var{addr},@var{kind}
31511 @itemx Z3,@var{addr},@var{kind}
31512 @cindex @samp{z3} packet
31513 @cindex @samp{Z3} packet
31514 Insert (@samp{Z3}) or remove (@samp{z3}) a read watchpoint at @var{addr}.
31515 @var{kind} is interpreted as the number of bytes to watch.
31527 @item z4,@var{addr},@var{kind}
31528 @itemx Z4,@var{addr},@var{kind}
31529 @cindex @samp{z4} packet
31530 @cindex @samp{Z4} packet
31531 Insert (@samp{Z4}) or remove (@samp{z4}) an access watchpoint at @var{addr}.
31532 @var{kind} is interpreted as the number of bytes to watch.
31546 @node Stop Reply Packets
31547 @section Stop Reply Packets
31548 @cindex stop reply packets
31550 The @samp{C}, @samp{c}, @samp{S}, @samp{s}, @samp{vCont},
31551 @samp{vAttach}, @samp{vRun}, @samp{vStopped}, and @samp{?} packets can
31552 receive any of the below as a reply. Except for @samp{?}
31553 and @samp{vStopped}, that reply is only returned
31554 when the target halts. In the below the exact meaning of @dfn{signal
31555 number} is defined by the header @file{include/gdb/signals.h} in the
31556 @value{GDBN} source code.
31558 As in the description of request packets, we include spaces in the
31559 reply templates for clarity; these are not part of the reply packet's
31560 syntax. No @value{GDBN} stop reply packet uses spaces to separate its
31566 The program received signal number @var{AA} (a two-digit hexadecimal
31567 number). This is equivalent to a @samp{T} response with no
31568 @var{n}:@var{r} pairs.
31570 @item T @var{AA} @var{n1}:@var{r1};@var{n2}:@var{r2};@dots{}
31571 @cindex @samp{T} packet reply
31572 The program received signal number @var{AA} (a two-digit hexadecimal
31573 number). This is equivalent to an @samp{S} response, except that the
31574 @samp{@var{n}:@var{r}} pairs can carry values of important registers
31575 and other information directly in the stop reply packet, reducing
31576 round-trip latency. Single-step and breakpoint traps are reported
31577 this way. Each @samp{@var{n}:@var{r}} pair is interpreted as follows:
31581 If @var{n} is a hexadecimal number, it is a register number, and the
31582 corresponding @var{r} gives that register's value. @var{r} is a
31583 series of bytes in target byte order, with each byte given by a
31584 two-digit hex number.
31587 If @var{n} is @samp{thread}, then @var{r} is the @var{thread-id} of
31588 the stopped thread, as specified in @ref{thread-id syntax}.
31591 If @var{n} is @samp{core}, then @var{r} is the hexadecimal number of
31592 the core on which the stop event was detected.
31595 If @var{n} is a recognized @dfn{stop reason}, it describes a more
31596 specific event that stopped the target. The currently defined stop
31597 reasons are listed below. @var{aa} should be @samp{05}, the trap
31598 signal. At most one stop reason should be present.
31601 Otherwise, @value{GDBN} should ignore this @samp{@var{n}:@var{r}} pair
31602 and go on to the next; this allows us to extend the protocol in the
31606 The currently defined stop reasons are:
31612 The packet indicates a watchpoint hit, and @var{r} is the data address, in
31615 @cindex shared library events, remote reply
31617 The packet indicates that the loaded libraries have changed.
31618 @value{GDBN} should use @samp{qXfer:libraries:read} to fetch a new
31619 list of loaded libraries. @var{r} is ignored.
31621 @cindex replay log events, remote reply
31623 The packet indicates that the target cannot continue replaying
31624 logged execution events, because it has reached the end (or the
31625 beginning when executing backward) of the log. The value of @var{r}
31626 will be either @samp{begin} or @samp{end}. @xref{Reverse Execution},
31627 for more information.
31631 @itemx W @var{AA} ; process:@var{pid}
31632 The process exited, and @var{AA} is the exit status. This is only
31633 applicable to certain targets.
31635 The second form of the response, including the process ID of the exited
31636 process, can be used only when @value{GDBN} has reported support for
31637 multiprocess protocol extensions; see @ref{multiprocess extensions}.
31638 The @var{pid} is formatted as a big-endian hex string.
31641 @itemx X @var{AA} ; process:@var{pid}
31642 The process terminated with signal @var{AA}.
31644 The second form of the response, including the process ID of the
31645 terminated process, can be used only when @value{GDBN} has reported
31646 support for multiprocess protocol extensions; see @ref{multiprocess
31647 extensions}. The @var{pid} is formatted as a big-endian hex string.
31649 @item O @var{XX}@dots{}
31650 @samp{@var{XX}@dots{}} is hex encoding of @sc{ascii} data, to be
31651 written as the program's console output. This can happen at any time
31652 while the program is running and the debugger should continue to wait
31653 for @samp{W}, @samp{T}, etc. This reply is not permitted in non-stop mode.
31655 @item F @var{call-id},@var{parameter}@dots{}
31656 @var{call-id} is the identifier which says which host system call should
31657 be called. This is just the name of the function. Translation into the
31658 correct system call is only applicable as it's defined in @value{GDBN}.
31659 @xref{File-I/O Remote Protocol Extension}, for a list of implemented
31662 @samp{@var{parameter}@dots{}} is a list of parameters as defined for
31663 this very system call.
31665 The target replies with this packet when it expects @value{GDBN} to
31666 call a host system call on behalf of the target. @value{GDBN} replies
31667 with an appropriate @samp{F} packet and keeps up waiting for the next
31668 reply packet from the target. The latest @samp{C}, @samp{c}, @samp{S}
31669 or @samp{s} action is expected to be continued. @xref{File-I/O Remote
31670 Protocol Extension}, for more details.
31674 @node General Query Packets
31675 @section General Query Packets
31676 @cindex remote query requests
31678 Packets starting with @samp{q} are @dfn{general query packets};
31679 packets starting with @samp{Q} are @dfn{general set packets}. General
31680 query and set packets are a semi-unified form for retrieving and
31681 sending information to and from the stub.
31683 The initial letter of a query or set packet is followed by a name
31684 indicating what sort of thing the packet applies to. For example,
31685 @value{GDBN} may use a @samp{qSymbol} packet to exchange symbol
31686 definitions with the stub. These packet names follow some
31691 The name must not contain commas, colons or semicolons.
31693 Most @value{GDBN} query and set packets have a leading upper case
31696 The names of custom vendor packets should use a company prefix, in
31697 lower case, followed by a period. For example, packets designed at
31698 the Acme Corporation might begin with @samp{qacme.foo} (for querying
31699 foos) or @samp{Qacme.bar} (for setting bars).
31702 The name of a query or set packet should be separated from any
31703 parameters by a @samp{:}; the parameters themselves should be
31704 separated by @samp{,} or @samp{;}. Stubs must be careful to match the
31705 full packet name, and check for a separator or the end of the packet,
31706 in case two packet names share a common prefix. New packets should not begin
31707 with @samp{qC}, @samp{qP}, or @samp{qL}@footnote{The @samp{qP} and @samp{qL}
31708 packets predate these conventions, and have arguments without any terminator
31709 for the packet name; we suspect they are in widespread use in places that
31710 are difficult to upgrade. The @samp{qC} packet has no arguments, but some
31711 existing stubs (e.g.@: RedBoot) are known to not check for the end of the
31714 Like the descriptions of the other packets, each description here
31715 has a template showing the packet's overall syntax, followed by an
31716 explanation of the packet's meaning. We include spaces in some of the
31717 templates for clarity; these are not part of the packet's syntax. No
31718 @value{GDBN} packet uses spaces to separate its components.
31720 Here are the currently defined query and set packets:
31724 @item QAllow:@var{op}:@var{val}@dots{}
31725 @cindex @samp{QAllow} packet
31726 Specify which operations @value{GDBN} expects to request of the
31727 target, as a semicolon-separated list of operation name and value
31728 pairs. Possible values for @var{op} include @samp{WriteReg},
31729 @samp{WriteMem}, @samp{InsertBreak}, @samp{InsertTrace},
31730 @samp{InsertFastTrace}, and @samp{Stop}. @var{val} is either 0,
31731 indicating that @value{GDBN} will not request the operation, or 1,
31732 indicating that it may. (The target can then use this to set up its
31733 own internals optimally, for instance if the debugger never expects to
31734 insert breakpoints, it may not need to install its own trap handler.)
31737 @cindex current thread, remote request
31738 @cindex @samp{qC} packet
31739 Return the current thread ID.
31743 @item QC @var{thread-id}
31744 Where @var{thread-id} is a thread ID as documented in
31745 @ref{thread-id syntax}.
31746 @item @r{(anything else)}
31747 Any other reply implies the old thread ID.
31750 @item qCRC:@var{addr},@var{length}
31751 @cindex CRC of memory block, remote request
31752 @cindex @samp{qCRC} packet
31753 Compute the CRC checksum of a block of memory using CRC-32 defined in
31754 IEEE 802.3. The CRC is computed byte at a time, taking the most
31755 significant bit of each byte first. The initial pattern code
31756 @code{0xffffffff} is used to ensure leading zeros affect the CRC.
31758 @emph{Note:} This is the same CRC used in validating separate debug
31759 files (@pxref{Separate Debug Files, , Debugging Information in Separate
31760 Files}). However the algorithm is slightly different. When validating
31761 separate debug files, the CRC is computed taking the @emph{least}
31762 significant bit of each byte first, and the final result is inverted to
31763 detect trailing zeros.
31768 An error (such as memory fault)
31769 @item C @var{crc32}
31770 The specified memory region's checksum is @var{crc32}.
31774 @itemx qsThreadInfo
31775 @cindex list active threads, remote request
31776 @cindex @samp{qfThreadInfo} packet
31777 @cindex @samp{qsThreadInfo} packet
31778 Obtain a list of all active thread IDs from the target (OS). Since there
31779 may be too many active threads to fit into one reply packet, this query
31780 works iteratively: it may require more than one query/reply sequence to
31781 obtain the entire list of threads. The first query of the sequence will
31782 be the @samp{qfThreadInfo} query; subsequent queries in the
31783 sequence will be the @samp{qsThreadInfo} query.
31785 NOTE: This packet replaces the @samp{qL} query (see below).
31789 @item m @var{thread-id}
31791 @item m @var{thread-id},@var{thread-id}@dots{}
31792 a comma-separated list of thread IDs
31794 (lower case letter @samp{L}) denotes end of list.
31797 In response to each query, the target will reply with a list of one or
31798 more thread IDs, separated by commas.
31799 @value{GDBN} will respond to each reply with a request for more thread
31800 ids (using the @samp{qs} form of the query), until the target responds
31801 with @samp{l} (lower-case ell, for @dfn{last}).
31802 Refer to @ref{thread-id syntax}, for the format of the @var{thread-id}
31805 @item qGetTLSAddr:@var{thread-id},@var{offset},@var{lm}
31806 @cindex get thread-local storage address, remote request
31807 @cindex @samp{qGetTLSAddr} packet
31808 Fetch the address associated with thread local storage specified
31809 by @var{thread-id}, @var{offset}, and @var{lm}.
31811 @var{thread-id} is the thread ID associated with the
31812 thread for which to fetch the TLS address. @xref{thread-id syntax}.
31814 @var{offset} is the (big endian, hex encoded) offset associated with the
31815 thread local variable. (This offset is obtained from the debug
31816 information associated with the variable.)
31818 @var{lm} is the (big endian, hex encoded) OS/ABI-specific encoding of the
31819 the load module associated with the thread local storage. For example,
31820 a @sc{gnu}/Linux system will pass the link map address of the shared
31821 object associated with the thread local storage under consideration.
31822 Other operating environments may choose to represent the load module
31823 differently, so the precise meaning of this parameter will vary.
31827 @item @var{XX}@dots{}
31828 Hex encoded (big endian) bytes representing the address of the thread
31829 local storage requested.
31832 An error occurred. @var{nn} are hex digits.
31835 An empty reply indicates that @samp{qGetTLSAddr} is not supported by the stub.
31838 @item qGetTIBAddr:@var{thread-id}
31839 @cindex get thread information block address
31840 @cindex @samp{qGetTIBAddr} packet
31841 Fetch address of the Windows OS specific Thread Information Block.
31843 @var{thread-id} is the thread ID associated with the thread.
31847 @item @var{XX}@dots{}
31848 Hex encoded (big endian) bytes representing the linear address of the
31849 thread information block.
31852 An error occured. This means that either the thread was not found, or the
31853 address could not be retrieved.
31856 An empty reply indicates that @samp{qGetTIBAddr} is not supported by the stub.
31859 @item qL @var{startflag} @var{threadcount} @var{nextthread}
31860 Obtain thread information from RTOS. Where: @var{startflag} (one hex
31861 digit) is one to indicate the first query and zero to indicate a
31862 subsequent query; @var{threadcount} (two hex digits) is the maximum
31863 number of threads the response packet can contain; and @var{nextthread}
31864 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
31865 returned in the response as @var{argthread}.
31867 Don't use this packet; use the @samp{qfThreadInfo} query instead (see above).
31871 @item qM @var{count} @var{done} @var{argthread} @var{thread}@dots{}
31872 Where: @var{count} (two hex digits) is the number of threads being
31873 returned; @var{done} (one hex digit) is zero to indicate more threads
31874 and one indicates no further threads; @var{argthreadid} (eight hex
31875 digits) is @var{nextthread} from the request packet; @var{thread}@dots{}
31876 is a sequence of thread IDs from the target. @var{threadid} (eight hex
31877 digits). See @code{remote.c:parse_threadlist_response()}.
31881 @cindex section offsets, remote request
31882 @cindex @samp{qOffsets} packet
31883 Get section offsets that the target used when relocating the downloaded
31888 @item Text=@var{xxx};Data=@var{yyy}@r{[};Bss=@var{zzz}@r{]}
31889 Relocate the @code{Text} section by @var{xxx} from its original address.
31890 Relocate the @code{Data} section by @var{yyy} from its original address.
31891 If the object file format provides segment information (e.g.@: @sc{elf}
31892 @samp{PT_LOAD} program headers), @value{GDBN} will relocate entire
31893 segments by the supplied offsets.
31895 @emph{Note: while a @code{Bss} offset may be included in the response,
31896 @value{GDBN} ignores this and instead applies the @code{Data} offset
31897 to the @code{Bss} section.}
31899 @item TextSeg=@var{xxx}@r{[};DataSeg=@var{yyy}@r{]}
31900 Relocate the first segment of the object file, which conventionally
31901 contains program code, to a starting address of @var{xxx}. If
31902 @samp{DataSeg} is specified, relocate the second segment, which
31903 conventionally contains modifiable data, to a starting address of
31904 @var{yyy}. @value{GDBN} will report an error if the object file
31905 does not contain segment information, or does not contain at least
31906 as many segments as mentioned in the reply. Extra segments are
31907 kept at fixed offsets relative to the last relocated segment.
31910 @item qP @var{mode} @var{thread-id}
31911 @cindex thread information, remote request
31912 @cindex @samp{qP} packet
31913 Returns information on @var{thread-id}. Where: @var{mode} is a hex
31914 encoded 32 bit mode; @var{thread-id} is a thread ID
31915 (@pxref{thread-id syntax}).
31917 Don't use this packet; use the @samp{qThreadExtraInfo} query instead
31920 Reply: see @code{remote.c:remote_unpack_thread_info_response()}.
31924 @cindex non-stop mode, remote request
31925 @cindex @samp{QNonStop} packet
31927 Enter non-stop (@samp{QNonStop:1}) or all-stop (@samp{QNonStop:0}) mode.
31928 @xref{Remote Non-Stop}, for more information.
31933 The request succeeded.
31936 An error occurred. @var{nn} are hex digits.
31939 An empty reply indicates that @samp{QNonStop} is not supported by
31943 This packet is not probed by default; the remote stub must request it,
31944 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
31945 Use of this packet is controlled by the @code{set non-stop} command;
31946 @pxref{Non-Stop Mode}.
31948 @item QPassSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
31949 @cindex pass signals to inferior, remote request
31950 @cindex @samp{QPassSignals} packet
31951 @anchor{QPassSignals}
31952 Each listed @var{signal} should be passed directly to the inferior process.
31953 Signals are numbered identically to continue packets and stop replies
31954 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
31955 strictly greater than the previous item. These signals do not need to stop
31956 the inferior, or be reported to @value{GDBN}. All other signals should be
31957 reported to @value{GDBN}. Multiple @samp{QPassSignals} packets do not
31958 combine; any earlier @samp{QPassSignals} list is completely replaced by the
31959 new list. This packet improves performance when using @samp{handle
31960 @var{signal} nostop noprint pass}.
31965 The request succeeded.
31968 An error occurred. @var{nn} are hex digits.
31971 An empty reply indicates that @samp{QPassSignals} is not supported by
31975 Use of this packet is controlled by the @code{set remote pass-signals}
31976 command (@pxref{Remote Configuration, set remote pass-signals}).
31977 This packet is not probed by default; the remote stub must request it,
31978 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
31980 @item qRcmd,@var{command}
31981 @cindex execute remote command, remote request
31982 @cindex @samp{qRcmd} packet
31983 @var{command} (hex encoded) is passed to the local interpreter for
31984 execution. Invalid commands should be reported using the output
31985 string. Before the final result packet, the target may also respond
31986 with a number of intermediate @samp{O@var{output}} console output
31987 packets. @emph{Implementors should note that providing access to a
31988 stubs's interpreter may have security implications}.
31993 A command response with no output.
31995 A command response with the hex encoded output string @var{OUTPUT}.
31997 Indicate a badly formed request.
31999 An empty reply indicates that @samp{qRcmd} is not recognized.
32002 (Note that the @code{qRcmd} packet's name is separated from the
32003 command by a @samp{,}, not a @samp{:}, contrary to the naming
32004 conventions above. Please don't use this packet as a model for new
32007 @item qSearch:memory:@var{address};@var{length};@var{search-pattern}
32008 @cindex searching memory, in remote debugging
32009 @cindex @samp{qSearch:memory} packet
32010 @anchor{qSearch memory}
32011 Search @var{length} bytes at @var{address} for @var{search-pattern}.
32012 @var{address} and @var{length} are encoded in hex.
32013 @var{search-pattern} is a sequence of bytes, hex encoded.
32018 The pattern was not found.
32020 The pattern was found at @var{address}.
32022 A badly formed request or an error was encountered while searching memory.
32024 An empty reply indicates that @samp{qSearch:memory} is not recognized.
32027 @item QStartNoAckMode
32028 @cindex @samp{QStartNoAckMode} packet
32029 @anchor{QStartNoAckMode}
32030 Request that the remote stub disable the normal @samp{+}/@samp{-}
32031 protocol acknowledgments (@pxref{Packet Acknowledgment}).
32036 The stub has switched to no-acknowledgment mode.
32037 @value{GDBN} acknowledges this reponse,
32038 but neither the stub nor @value{GDBN} shall send or expect further
32039 @samp{+}/@samp{-} acknowledgments in the current connection.
32041 An empty reply indicates that the stub does not support no-acknowledgment mode.
32044 @item qSupported @r{[}:@var{gdbfeature} @r{[};@var{gdbfeature}@r{]}@dots{} @r{]}
32045 @cindex supported packets, remote query
32046 @cindex features of the remote protocol
32047 @cindex @samp{qSupported} packet
32048 @anchor{qSupported}
32049 Tell the remote stub about features supported by @value{GDBN}, and
32050 query the stub for features it supports. This packet allows
32051 @value{GDBN} and the remote stub to take advantage of each others'
32052 features. @samp{qSupported} also consolidates multiple feature probes
32053 at startup, to improve @value{GDBN} performance---a single larger
32054 packet performs better than multiple smaller probe packets on
32055 high-latency links. Some features may enable behavior which must not
32056 be on by default, e.g.@: because it would confuse older clients or
32057 stubs. Other features may describe packets which could be
32058 automatically probed for, but are not. These features must be
32059 reported before @value{GDBN} will use them. This ``default
32060 unsupported'' behavior is not appropriate for all packets, but it
32061 helps to keep the initial connection time under control with new
32062 versions of @value{GDBN} which support increasing numbers of packets.
32066 @item @var{stubfeature} @r{[};@var{stubfeature}@r{]}@dots{}
32067 The stub supports or does not support each returned @var{stubfeature},
32068 depending on the form of each @var{stubfeature} (see below for the
32071 An empty reply indicates that @samp{qSupported} is not recognized,
32072 or that no features needed to be reported to @value{GDBN}.
32075 The allowed forms for each feature (either a @var{gdbfeature} in the
32076 @samp{qSupported} packet, or a @var{stubfeature} in the response)
32080 @item @var{name}=@var{value}
32081 The remote protocol feature @var{name} is supported, and associated
32082 with the specified @var{value}. The format of @var{value} depends
32083 on the feature, but it must not include a semicolon.
32085 The remote protocol feature @var{name} is supported, and does not
32086 need an associated value.
32088 The remote protocol feature @var{name} is not supported.
32090 The remote protocol feature @var{name} may be supported, and
32091 @value{GDBN} should auto-detect support in some other way when it is
32092 needed. This form will not be used for @var{gdbfeature} notifications,
32093 but may be used for @var{stubfeature} responses.
32096 Whenever the stub receives a @samp{qSupported} request, the
32097 supplied set of @value{GDBN} features should override any previous
32098 request. This allows @value{GDBN} to put the stub in a known
32099 state, even if the stub had previously been communicating with
32100 a different version of @value{GDBN}.
32102 The following values of @var{gdbfeature} (for the packet sent by @value{GDBN})
32107 This feature indicates whether @value{GDBN} supports multiprocess
32108 extensions to the remote protocol. @value{GDBN} does not use such
32109 extensions unless the stub also reports that it supports them by
32110 including @samp{multiprocess+} in its @samp{qSupported} reply.
32111 @xref{multiprocess extensions}, for details.
32114 This feature indicates that @value{GDBN} supports the XML target
32115 description. If the stub sees @samp{xmlRegisters=} with target
32116 specific strings separated by a comma, it will report register
32120 This feature indicates whether @value{GDBN} supports the
32121 @samp{qRelocInsn} packet (@pxref{Tracepoint Packets,,Relocate
32122 instruction reply packet}).
32125 Stubs should ignore any unknown values for
32126 @var{gdbfeature}. Any @value{GDBN} which sends a @samp{qSupported}
32127 packet supports receiving packets of unlimited length (earlier
32128 versions of @value{GDBN} may reject overly long responses). Additional values
32129 for @var{gdbfeature} may be defined in the future to let the stub take
32130 advantage of new features in @value{GDBN}, e.g.@: incompatible
32131 improvements in the remote protocol---the @samp{multiprocess} feature is
32132 an example of such a feature. The stub's reply should be independent
32133 of the @var{gdbfeature} entries sent by @value{GDBN}; first @value{GDBN}
32134 describes all the features it supports, and then the stub replies with
32135 all the features it supports.
32137 Similarly, @value{GDBN} will silently ignore unrecognized stub feature
32138 responses, as long as each response uses one of the standard forms.
32140 Some features are flags. A stub which supports a flag feature
32141 should respond with a @samp{+} form response. Other features
32142 require values, and the stub should respond with an @samp{=}
32145 Each feature has a default value, which @value{GDBN} will use if
32146 @samp{qSupported} is not available or if the feature is not mentioned
32147 in the @samp{qSupported} response. The default values are fixed; a
32148 stub is free to omit any feature responses that match the defaults.
32150 Not all features can be probed, but for those which can, the probing
32151 mechanism is useful: in some cases, a stub's internal
32152 architecture may not allow the protocol layer to know some information
32153 about the underlying target in advance. This is especially common in
32154 stubs which may be configured for multiple targets.
32156 These are the currently defined stub features and their properties:
32158 @multitable @columnfractions 0.35 0.2 0.12 0.2
32159 @c NOTE: The first row should be @headitem, but we do not yet require
32160 @c a new enough version of Texinfo (4.7) to use @headitem.
32162 @tab Value Required
32166 @item @samp{PacketSize}
32171 @item @samp{qXfer:auxv:read}
32176 @item @samp{qXfer:features:read}
32181 @item @samp{qXfer:libraries:read}
32186 @item @samp{qXfer:memory-map:read}
32191 @item @samp{qXfer:sdata:read}
32196 @item @samp{qXfer:spu:read}
32201 @item @samp{qXfer:spu:write}
32206 @item @samp{qXfer:siginfo:read}
32211 @item @samp{qXfer:siginfo:write}
32216 @item @samp{qXfer:threads:read}
32222 @item @samp{QNonStop}
32227 @item @samp{QPassSignals}
32232 @item @samp{QStartNoAckMode}
32237 @item @samp{multiprocess}
32242 @item @samp{ConditionalTracepoints}
32247 @item @samp{ReverseContinue}
32252 @item @samp{ReverseStep}
32257 @item @samp{TracepointSource}
32262 @item @samp{QAllow}
32269 These are the currently defined stub features, in more detail:
32272 @cindex packet size, remote protocol
32273 @item PacketSize=@var{bytes}
32274 The remote stub can accept packets up to at least @var{bytes} in
32275 length. @value{GDBN} will send packets up to this size for bulk
32276 transfers, and will never send larger packets. This is a limit on the
32277 data characters in the packet, including the frame and checksum.
32278 There is no trailing NUL byte in a remote protocol packet; if the stub
32279 stores packets in a NUL-terminated format, it should allow an extra
32280 byte in its buffer for the NUL. If this stub feature is not supported,
32281 @value{GDBN} guesses based on the size of the @samp{g} packet response.
32283 @item qXfer:auxv:read
32284 The remote stub understands the @samp{qXfer:auxv:read} packet
32285 (@pxref{qXfer auxiliary vector read}).
32287 @item qXfer:features:read
32288 The remote stub understands the @samp{qXfer:features:read} packet
32289 (@pxref{qXfer target description read}).
32291 @item qXfer:libraries:read
32292 The remote stub understands the @samp{qXfer:libraries:read} packet
32293 (@pxref{qXfer library list read}).
32295 @item qXfer:memory-map:read
32296 The remote stub understands the @samp{qXfer:memory-map:read} packet
32297 (@pxref{qXfer memory map read}).
32299 @item qXfer:sdata:read
32300 The remote stub understands the @samp{qXfer:sdata:read} packet
32301 (@pxref{qXfer sdata read}).
32303 @item qXfer:spu:read
32304 The remote stub understands the @samp{qXfer:spu:read} packet
32305 (@pxref{qXfer spu read}).
32307 @item qXfer:spu:write
32308 The remote stub understands the @samp{qXfer:spu:write} packet
32309 (@pxref{qXfer spu write}).
32311 @item qXfer:siginfo:read
32312 The remote stub understands the @samp{qXfer:siginfo:read} packet
32313 (@pxref{qXfer siginfo read}).
32315 @item qXfer:siginfo:write
32316 The remote stub understands the @samp{qXfer:siginfo:write} packet
32317 (@pxref{qXfer siginfo write}).
32319 @item qXfer:threads:read
32320 The remote stub understands the @samp{qXfer:threads:read} packet
32321 (@pxref{qXfer threads read}).
32324 The remote stub understands the @samp{QNonStop} packet
32325 (@pxref{QNonStop}).
32328 The remote stub understands the @samp{QPassSignals} packet
32329 (@pxref{QPassSignals}).
32331 @item QStartNoAckMode
32332 The remote stub understands the @samp{QStartNoAckMode} packet and
32333 prefers to operate in no-acknowledgment mode. @xref{Packet Acknowledgment}.
32336 @anchor{multiprocess extensions}
32337 @cindex multiprocess extensions, in remote protocol
32338 The remote stub understands the multiprocess extensions to the remote
32339 protocol syntax. The multiprocess extensions affect the syntax of
32340 thread IDs in both packets and replies (@pxref{thread-id syntax}), and
32341 add process IDs to the @samp{D} packet and @samp{W} and @samp{X}
32342 replies. Note that reporting this feature indicates support for the
32343 syntactic extensions only, not that the stub necessarily supports
32344 debugging of more than one process at a time. The stub must not use
32345 multiprocess extensions in packet replies unless @value{GDBN} has also
32346 indicated it supports them in its @samp{qSupported} request.
32348 @item qXfer:osdata:read
32349 The remote stub understands the @samp{qXfer:osdata:read} packet
32350 ((@pxref{qXfer osdata read}).
32352 @item ConditionalTracepoints
32353 The remote stub accepts and implements conditional expressions defined
32354 for tracepoints (@pxref{Tracepoint Conditions}).
32356 @item ReverseContinue
32357 The remote stub accepts and implements the reverse continue packet
32361 The remote stub accepts and implements the reverse step packet
32364 @item TracepointSource
32365 The remote stub understands the @samp{QTDPsrc} packet that supplies
32366 the source form of tracepoint definitions.
32369 The remote stub understands the @samp{QAllow} packet.
32371 @item StaticTracepoint
32372 @cindex static tracepoints, in remote protocol
32373 The remote stub supports static tracepoints.
32378 @cindex symbol lookup, remote request
32379 @cindex @samp{qSymbol} packet
32380 Notify the target that @value{GDBN} is prepared to serve symbol lookup
32381 requests. Accept requests from the target for the values of symbols.
32386 The target does not need to look up any (more) symbols.
32387 @item qSymbol:@var{sym_name}
32388 The target requests the value of symbol @var{sym_name} (hex encoded).
32389 @value{GDBN} may provide the value by using the
32390 @samp{qSymbol:@var{sym_value}:@var{sym_name}} message, described
32394 @item qSymbol:@var{sym_value}:@var{sym_name}
32395 Set the value of @var{sym_name} to @var{sym_value}.
32397 @var{sym_name} (hex encoded) is the name of a symbol whose value the
32398 target has previously requested.
32400 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
32401 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
32407 The target does not need to look up any (more) symbols.
32408 @item qSymbol:@var{sym_name}
32409 The target requests the value of a new symbol @var{sym_name} (hex
32410 encoded). @value{GDBN} will continue to supply the values of symbols
32411 (if available), until the target ceases to request them.
32416 @item QTDisconnected
32423 @xref{Tracepoint Packets}.
32425 @item qThreadExtraInfo,@var{thread-id}
32426 @cindex thread attributes info, remote request
32427 @cindex @samp{qThreadExtraInfo} packet
32428 Obtain a printable string description of a thread's attributes from
32429 the target OS. @var{thread-id} is a thread ID;
32430 see @ref{thread-id syntax}. This
32431 string may contain anything that the target OS thinks is interesting
32432 for @value{GDBN} to tell the user about the thread. The string is
32433 displayed in @value{GDBN}'s @code{info threads} display. Some
32434 examples of possible thread extra info strings are @samp{Runnable}, or
32435 @samp{Blocked on Mutex}.
32439 @item @var{XX}@dots{}
32440 Where @samp{@var{XX}@dots{}} is a hex encoding of @sc{ascii} data,
32441 comprising the printable string containing the extra information about
32442 the thread's attributes.
32445 (Note that the @code{qThreadExtraInfo} packet's name is separated from
32446 the command by a @samp{,}, not a @samp{:}, contrary to the naming
32447 conventions above. Please don't use this packet as a model for new
32462 @xref{Tracepoint Packets}.
32464 @item qXfer:@var{object}:read:@var{annex}:@var{offset},@var{length}
32465 @cindex read special object, remote request
32466 @cindex @samp{qXfer} packet
32467 @anchor{qXfer read}
32468 Read uninterpreted bytes from the target's special data area
32469 identified by the keyword @var{object}. Request @var{length} bytes
32470 starting at @var{offset} bytes into the data. The content and
32471 encoding of @var{annex} is specific to @var{object}; it can supply
32472 additional details about what data to access.
32474 Here are the specific requests of this form defined so far. All
32475 @samp{qXfer:@var{object}:read:@dots{}} requests use the same reply
32476 formats, listed below.
32479 @item qXfer:auxv:read::@var{offset},@var{length}
32480 @anchor{qXfer auxiliary vector read}
32481 Access the target's @dfn{auxiliary vector}. @xref{OS Information,
32482 auxiliary vector}. Note @var{annex} must be empty.
32484 This packet is not probed by default; the remote stub must request it,
32485 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
32487 @item qXfer:features:read:@var{annex}:@var{offset},@var{length}
32488 @anchor{qXfer target description read}
32489 Access the @dfn{target description}. @xref{Target Descriptions}. The
32490 annex specifies which XML document to access. The main description is
32491 always loaded from the @samp{target.xml} annex.
32493 This packet is not probed by default; the remote stub must request it,
32494 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
32496 @item qXfer:libraries:read:@var{annex}:@var{offset},@var{length}
32497 @anchor{qXfer library list read}
32498 Access the target's list of loaded libraries. @xref{Library List Format}.
32499 The annex part of the generic @samp{qXfer} packet must be empty
32500 (@pxref{qXfer read}).
32502 Targets which maintain a list of libraries in the program's memory do
32503 not need to implement this packet; it is designed for platforms where
32504 the operating system manages the list of loaded libraries.
32506 This packet is not probed by default; the remote stub must request it,
32507 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
32509 @item qXfer:memory-map:read::@var{offset},@var{length}
32510 @anchor{qXfer memory map read}
32511 Access the target's @dfn{memory-map}. @xref{Memory Map Format}. The
32512 annex part of the generic @samp{qXfer} packet must be empty
32513 (@pxref{qXfer read}).
32515 This packet is not probed by default; the remote stub must request it,
32516 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
32518 @item qXfer:sdata:read::@var{offset},@var{length}
32519 @anchor{qXfer sdata read}
32521 Read contents of the extra collected static tracepoint marker
32522 information. The annex part of the generic @samp{qXfer} packet must
32523 be empty (@pxref{qXfer read}). @xref{Tracepoint Actions,,Tracepoint
32526 This packet is not probed by default; the remote stub must request it,
32527 by supplying an appropriate @samp{qSupported} response
32528 (@pxref{qSupported}).
32530 @item qXfer:siginfo:read::@var{offset},@var{length}
32531 @anchor{qXfer siginfo read}
32532 Read contents of the extra signal information on the target
32533 system. The annex part of the generic @samp{qXfer} packet must be
32534 empty (@pxref{qXfer read}).
32536 This packet is not probed by default; the remote stub must request it,
32537 by supplying an appropriate @samp{qSupported} response
32538 (@pxref{qSupported}).
32540 @item qXfer:spu:read:@var{annex}:@var{offset},@var{length}
32541 @anchor{qXfer spu read}
32542 Read contents of an @code{spufs} file on the target system. The
32543 annex specifies which file to read; it must be of the form
32544 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
32545 in the target process, and @var{name} identifes the @code{spufs} file
32546 in that context to be accessed.
32548 This packet is not probed by default; the remote stub must request it,
32549 by supplying an appropriate @samp{qSupported} response
32550 (@pxref{qSupported}).
32552 @item qXfer:threads:read::@var{offset},@var{length}
32553 @anchor{qXfer threads read}
32554 Access the list of threads on target. @xref{Thread List Format}. The
32555 annex part of the generic @samp{qXfer} packet must be empty
32556 (@pxref{qXfer read}).
32558 This packet is not probed by default; the remote stub must request it,
32559 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
32561 @item qXfer:osdata:read::@var{offset},@var{length}
32562 @anchor{qXfer osdata read}
32563 Access the target's @dfn{operating system information}.
32564 @xref{Operating System Information}.
32571 Data @var{data} (@pxref{Binary Data}) has been read from the
32572 target. There may be more data at a higher address (although
32573 it is permitted to return @samp{m} even for the last valid
32574 block of data, as long as at least one byte of data was read).
32575 @var{data} may have fewer bytes than the @var{length} in the
32579 Data @var{data} (@pxref{Binary Data}) has been read from the target.
32580 There is no more data to be read. @var{data} may have fewer bytes
32581 than the @var{length} in the request.
32584 The @var{offset} in the request is at the end of the data.
32585 There is no more data to be read.
32588 The request was malformed, or @var{annex} was invalid.
32591 The offset was invalid, or there was an error encountered reading the data.
32592 @var{nn} is a hex-encoded @code{errno} value.
32595 An empty reply indicates the @var{object} string was not recognized by
32596 the stub, or that the object does not support reading.
32599 @item qXfer:@var{object}:write:@var{annex}:@var{offset}:@var{data}@dots{}
32600 @cindex write data into object, remote request
32601 @anchor{qXfer write}
32602 Write uninterpreted bytes into the target's special data area
32603 identified by the keyword @var{object}, starting at @var{offset} bytes
32604 into the data. @var{data}@dots{} is the binary-encoded data
32605 (@pxref{Binary Data}) to be written. The content and encoding of @var{annex}
32606 is specific to @var{object}; it can supply additional details about what data
32609 Here are the specific requests of this form defined so far. All
32610 @samp{qXfer:@var{object}:write:@dots{}} requests use the same reply
32611 formats, listed below.
32614 @item qXfer:siginfo:write::@var{offset}:@var{data}@dots{}
32615 @anchor{qXfer siginfo write}
32616 Write @var{data} to the extra signal information on the target system.
32617 The annex part of the generic @samp{qXfer} packet must be
32618 empty (@pxref{qXfer write}).
32620 This packet is not probed by default; the remote stub must request it,
32621 by supplying an appropriate @samp{qSupported} response
32622 (@pxref{qSupported}).
32624 @item qXfer:spu:write:@var{annex}:@var{offset}:@var{data}@dots{}
32625 @anchor{qXfer spu write}
32626 Write @var{data} to an @code{spufs} file on the target system. The
32627 annex specifies which file to write; it must be of the form
32628 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
32629 in the target process, and @var{name} identifes the @code{spufs} file
32630 in that context to be accessed.
32632 This packet is not probed by default; the remote stub must request it,
32633 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
32639 @var{nn} (hex encoded) is the number of bytes written.
32640 This may be fewer bytes than supplied in the request.
32643 The request was malformed, or @var{annex} was invalid.
32646 The offset was invalid, or there was an error encountered writing the data.
32647 @var{nn} is a hex-encoded @code{errno} value.
32650 An empty reply indicates the @var{object} string was not
32651 recognized by the stub, or that the object does not support writing.
32654 @item qXfer:@var{object}:@var{operation}:@dots{}
32655 Requests of this form may be added in the future. When a stub does
32656 not recognize the @var{object} keyword, or its support for
32657 @var{object} does not recognize the @var{operation} keyword, the stub
32658 must respond with an empty packet.
32660 @item qAttached:@var{pid}
32661 @cindex query attached, remote request
32662 @cindex @samp{qAttached} packet
32663 Return an indication of whether the remote server attached to an
32664 existing process or created a new process. When the multiprocess
32665 protocol extensions are supported (@pxref{multiprocess extensions}),
32666 @var{pid} is an integer in hexadecimal format identifying the target
32667 process. Otherwise, @value{GDBN} will omit the @var{pid} field and
32668 the query packet will be simplified as @samp{qAttached}.
32670 This query is used, for example, to know whether the remote process
32671 should be detached or killed when a @value{GDBN} session is ended with
32672 the @code{quit} command.
32677 The remote server attached to an existing process.
32679 The remote server created a new process.
32681 A badly formed request or an error was encountered.
32686 @node Architecture-Specific Protocol Details
32687 @section Architecture-Specific Protocol Details
32689 This section describes how the remote protocol is applied to specific
32690 target architectures. Also see @ref{Standard Target Features}, for
32691 details of XML target descriptions for each architecture.
32695 @subsubsection Breakpoint Kinds
32697 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
32702 16-bit Thumb mode breakpoint.
32705 32-bit Thumb mode (Thumb-2) breakpoint.
32708 32-bit ARM mode breakpoint.
32714 @subsubsection Register Packet Format
32716 The following @code{g}/@code{G} packets have previously been defined.
32717 In the below, some thirty-two bit registers are transferred as
32718 sixty-four bits. Those registers should be zero/sign extended (which?)
32719 to fill the space allocated. Register bytes are transferred in target
32720 byte order. The two nibbles within a register byte are transferred
32721 most-significant - least-significant.
32727 All registers are transferred as thirty-two bit quantities in the order:
32728 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
32729 registers; fsr; fir; fp.
32733 All registers are transferred as sixty-four bit quantities (including
32734 thirty-two bit registers such as @code{sr}). The ordering is the same
32739 @node Tracepoint Packets
32740 @section Tracepoint Packets
32741 @cindex tracepoint packets
32742 @cindex packets, tracepoint
32744 Here we describe the packets @value{GDBN} uses to implement
32745 tracepoints (@pxref{Tracepoints}).
32749 @item QTDP:@var{n}:@var{addr}:@var{ena}:@var{step}:@var{pass}[:F@var{flen}][:X@var{len},@var{bytes}]@r{[}-@r{]}
32750 Create a new tracepoint, number @var{n}, at @var{addr}. If @var{ena}
32751 is @samp{E}, then the tracepoint is enabled; if it is @samp{D}, then
32752 the tracepoint is disabled. @var{step} is the tracepoint's step
32753 count, and @var{pass} is its pass count. If an @samp{F} is present,
32754 then the tracepoint is to be a fast tracepoint, and the @var{flen} is
32755 the number of bytes that the target should copy elsewhere to make room
32756 for the tracepoint. If an @samp{X} is present, it introduces a
32757 tracepoint condition, which consists of a hexadecimal length, followed
32758 by a comma and hex-encoded bytes, in a manner similar to action
32759 encodings as described below. If the trailing @samp{-} is present,
32760 further @samp{QTDP} packets will follow to specify this tracepoint's
32766 The packet was understood and carried out.
32768 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
32770 The packet was not recognized.
32773 @item QTDP:-@var{n}:@var{addr}:@r{[}S@r{]}@var{action}@dots{}@r{[}-@r{]}
32774 Define actions to be taken when a tracepoint is hit. @var{n} and
32775 @var{addr} must be the same as in the initial @samp{QTDP} packet for
32776 this tracepoint. This packet may only be sent immediately after
32777 another @samp{QTDP} packet that ended with a @samp{-}. If the
32778 trailing @samp{-} is present, further @samp{QTDP} packets will follow,
32779 specifying more actions for this tracepoint.
32781 In the series of action packets for a given tracepoint, at most one
32782 can have an @samp{S} before its first @var{action}. If such a packet
32783 is sent, it and the following packets define ``while-stepping''
32784 actions. Any prior packets define ordinary actions --- that is, those
32785 taken when the tracepoint is first hit. If no action packet has an
32786 @samp{S}, then all the packets in the series specify ordinary
32787 tracepoint actions.
32789 The @samp{@var{action}@dots{}} portion of the packet is a series of
32790 actions, concatenated without separators. Each action has one of the
32796 Collect the registers whose bits are set in @var{mask}. @var{mask} is
32797 a hexadecimal number whose @var{i}'th bit is set if register number
32798 @var{i} should be collected. (The least significant bit is numbered
32799 zero.) Note that @var{mask} may be any number of digits long; it may
32800 not fit in a 32-bit word.
32802 @item M @var{basereg},@var{offset},@var{len}
32803 Collect @var{len} bytes of memory starting at the address in register
32804 number @var{basereg}, plus @var{offset}. If @var{basereg} is
32805 @samp{-1}, then the range has a fixed address: @var{offset} is the
32806 address of the lowest byte to collect. The @var{basereg},
32807 @var{offset}, and @var{len} parameters are all unsigned hexadecimal
32808 values (the @samp{-1} value for @var{basereg} is a special case).
32810 @item X @var{len},@var{expr}
32811 Evaluate @var{expr}, whose length is @var{len}, and collect memory as
32812 it directs. @var{expr} is an agent expression, as described in
32813 @ref{Agent Expressions}. Each byte of the expression is encoded as a
32814 two-digit hex number in the packet; @var{len} is the number of bytes
32815 in the expression (and thus one-half the number of hex digits in the
32820 Any number of actions may be packed together in a single @samp{QTDP}
32821 packet, as long as the packet does not exceed the maximum packet
32822 length (400 bytes, for many stubs). There may be only one @samp{R}
32823 action per tracepoint, and it must precede any @samp{M} or @samp{X}
32824 actions. Any registers referred to by @samp{M} and @samp{X} actions
32825 must be collected by a preceding @samp{R} action. (The
32826 ``while-stepping'' actions are treated as if they were attached to a
32827 separate tracepoint, as far as these restrictions are concerned.)
32832 The packet was understood and carried out.
32834 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
32836 The packet was not recognized.
32839 @item QTDPsrc:@var{n}:@var{addr}:@var{type}:@var{start}:@var{slen}:@var{bytes}
32840 @cindex @samp{QTDPsrc} packet
32841 Specify a source string of tracepoint @var{n} at address @var{addr}.
32842 This is useful to get accurate reproduction of the tracepoints
32843 originally downloaded at the beginning of the trace run. @var{type}
32844 is the name of the tracepoint part, such as @samp{cond} for the
32845 tracepoint's conditional expression (see below for a list of types), while
32846 @var{bytes} is the string, encoded in hexadecimal.
32848 @var{start} is the offset of the @var{bytes} within the overall source
32849 string, while @var{slen} is the total length of the source string.
32850 This is intended for handling source strings that are longer than will
32851 fit in a single packet.
32852 @c Add detailed example when this info is moved into a dedicated
32853 @c tracepoint descriptions section.
32855 The available string types are @samp{at} for the location,
32856 @samp{cond} for the conditional, and @samp{cmd} for an action command.
32857 @value{GDBN} sends a separate packet for each command in the action
32858 list, in the same order in which the commands are stored in the list.
32860 The target does not need to do anything with source strings except
32861 report them back as part of the replies to the @samp{qTfP}/@samp{qTsP}
32864 Although this packet is optional, and @value{GDBN} will only send it
32865 if the target replies with @samp{TracepointSource} @xref{General
32866 Query Packets}, it makes both disconnected tracing and trace files
32867 much easier to use. Otherwise the user must be careful that the
32868 tracepoints in effect while looking at trace frames are identical to
32869 the ones in effect during the trace run; even a small discrepancy
32870 could cause @samp{tdump} not to work, or a particular trace frame not
32873 @item QTDV:@var{n}:@var{value}
32874 @cindex define trace state variable, remote request
32875 @cindex @samp{QTDV} packet
32876 Create a new trace state variable, number @var{n}, with an initial
32877 value of @var{value}, which is a 64-bit signed integer. Both @var{n}
32878 and @var{value} are encoded as hexadecimal values. @value{GDBN} has
32879 the option of not using this packet for initial values of zero; the
32880 target should simply create the trace state variables as they are
32881 mentioned in expressions.
32883 @item QTFrame:@var{n}
32884 Select the @var{n}'th tracepoint frame from the buffer, and use the
32885 register and memory contents recorded there to answer subsequent
32886 request packets from @value{GDBN}.
32888 A successful reply from the stub indicates that the stub has found the
32889 requested frame. The response is a series of parts, concatenated
32890 without separators, describing the frame we selected. Each part has
32891 one of the following forms:
32895 The selected frame is number @var{n} in the trace frame buffer;
32896 @var{f} is a hexadecimal number. If @var{f} is @samp{-1}, then there
32897 was no frame matching the criteria in the request packet.
32900 The selected trace frame records a hit of tracepoint number @var{t};
32901 @var{t} is a hexadecimal number.
32905 @item QTFrame:pc:@var{addr}
32906 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
32907 currently selected frame whose PC is @var{addr};
32908 @var{addr} is a hexadecimal number.
32910 @item QTFrame:tdp:@var{t}
32911 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
32912 currently selected frame that is a hit of tracepoint @var{t}; @var{t}
32913 is a hexadecimal number.
32915 @item QTFrame:range:@var{start}:@var{end}
32916 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
32917 currently selected frame whose PC is between @var{start} (inclusive)
32918 and @var{end} (inclusive); @var{start} and @var{end} are hexadecimal
32921 @item QTFrame:outside:@var{start}:@var{end}
32922 Like @samp{QTFrame:range:@var{start}:@var{end}}, but select the first
32923 frame @emph{outside} the given range of addresses (exclusive).
32926 Begin the tracepoint experiment. Begin collecting data from
32927 tracepoint hits in the trace frame buffer. This packet supports the
32928 @samp{qRelocInsn} reply (@pxref{Tracepoint Packets,,Relocate
32929 instruction reply packet}).
32932 End the tracepoint experiment. Stop collecting trace frames.
32935 Clear the table of tracepoints, and empty the trace frame buffer.
32937 @item QTro:@var{start1},@var{end1}:@var{start2},@var{end2}:@dots{}
32938 Establish the given ranges of memory as ``transparent''. The stub
32939 will answer requests for these ranges from memory's current contents,
32940 if they were not collected as part of the tracepoint hit.
32942 @value{GDBN} uses this to mark read-only regions of memory, like those
32943 containing program code. Since these areas never change, they should
32944 still have the same contents they did when the tracepoint was hit, so
32945 there's no reason for the stub to refuse to provide their contents.
32947 @item QTDisconnected:@var{value}
32948 Set the choice to what to do with the tracing run when @value{GDBN}
32949 disconnects from the target. A @var{value} of 1 directs the target to
32950 continue the tracing run, while 0 tells the target to stop tracing if
32951 @value{GDBN} is no longer in the picture.
32954 Ask the stub if there is a trace experiment running right now.
32956 The reply has the form:
32960 @item T@var{running}@r{[};@var{field}@r{]}@dots{}
32961 @var{running} is a single digit @code{1} if the trace is presently
32962 running, or @code{0} if not. It is followed by semicolon-separated
32963 optional fields that an agent may use to report additional status.
32967 If the trace is not running, the agent may report any of several
32968 explanations as one of the optional fields:
32973 No trace has been run yet.
32976 The trace was stopped by a user-originated stop command.
32979 The trace stopped because the trace buffer filled up.
32981 @item tdisconnected:0
32982 The trace stopped because @value{GDBN} disconnected from the target.
32984 @item tpasscount:@var{tpnum}
32985 The trace stopped because tracepoint @var{tpnum} exceeded its pass count.
32987 @item terror:@var{text}:@var{tpnum}
32988 The trace stopped because tracepoint @var{tpnum} had an error. The
32989 string @var{text} is available to describe the nature of the error
32990 (for instance, a divide by zero in the condition expression).
32991 @var{text} is hex encoded.
32994 The trace stopped for some other reason.
32998 Additional optional fields supply statistical and other information.
32999 Although not required, they are extremely useful for users monitoring
33000 the progress of a trace run. If a trace has stopped, and these
33001 numbers are reported, they must reflect the state of the just-stopped
33006 @item tframes:@var{n}
33007 The number of trace frames in the buffer.
33009 @item tcreated:@var{n}
33010 The total number of trace frames created during the run. This may
33011 be larger than the trace frame count, if the buffer is circular.
33013 @item tsize:@var{n}
33014 The total size of the trace buffer, in bytes.
33016 @item tfree:@var{n}
33017 The number of bytes still unused in the buffer.
33019 @item circular:@var{n}
33020 The value of the circular trace buffer flag. @code{1} means that the
33021 trace buffer is circular and old trace frames will be discarded if
33022 necessary to make room, @code{0} means that the trace buffer is linear
33025 @item disconn:@var{n}
33026 The value of the disconnected tracing flag. @code{1} means that
33027 tracing will continue after @value{GDBN} disconnects, @code{0} means
33028 that the trace run will stop.
33032 @item qTV:@var{var}
33033 @cindex trace state variable value, remote request
33034 @cindex @samp{qTV} packet
33035 Ask the stub for the value of the trace state variable number @var{var}.
33040 The value of the variable is @var{value}. This will be the current
33041 value of the variable if the user is examining a running target, or a
33042 saved value if the variable was collected in the trace frame that the
33043 user is looking at. Note that multiple requests may result in
33044 different reply values, such as when requesting values while the
33045 program is running.
33048 The value of the variable is unknown. This would occur, for example,
33049 if the user is examining a trace frame in which the requested variable
33055 These packets request data about tracepoints that are being used by
33056 the target. @value{GDBN} sends @code{qTfP} to get the first piece
33057 of data, and multiple @code{qTsP} to get additional pieces. Replies
33058 to these packets generally take the form of the @code{QTDP} packets
33059 that define tracepoints. (FIXME add detailed syntax)
33063 These packets request data about trace state variables that are on the
33064 target. @value{GDBN} sends @code{qTfV} to get the first vari of data,
33065 and multiple @code{qTsV} to get additional variables. Replies to
33066 these packets follow the syntax of the @code{QTDV} packets that define
33067 trace state variables.
33071 These packets request data about static tracepoint markers that exist
33072 in the target program. @value{GDBN} sends @code{qTfSTM} to get the
33073 first piece of data, and multiple @code{qTsSTM} to get additional
33074 pieces. Replies to these packets take the following form:
33078 @item m @var{address}:@var{id}:@var{extra}
33080 @item m @var{address}:@var{id}:@var{extra},@var{address}:@var{id}:@var{extra}@dots{}
33081 a comma-separated list of markers
33083 (lower case letter @samp{L}) denotes end of list.
33085 An error occurred. @var{nn} are hex digits.
33087 An empty reply indicates that the request is not supported by the
33091 @var{address} is encoded in hex.
33092 @var{id} and @var{extra} are strings encoded in hex.
33094 In response to each query, the target will reply with a list of one or
33095 more markers, separated by commas. @value{GDBN} will respond to each
33096 reply with a request for more markers (using the @samp{qs} form of the
33097 query), until the target responds with @samp{l} (lower-case ell, for
33100 @item qTSTMat:@var{address}
33101 This packets requests data about static tracepoint markers in the
33102 target program at @var{address}. Replies to this packet follow the
33103 syntax of the @samp{qTfSTM} and @code{qTsSTM} packets that list static
33104 tracepoint markers.
33106 @item QTSave:@var{filename}
33107 This packet directs the target to save trace data to the file name
33108 @var{filename} in the target's filesystem. @var{filename} is encoded
33109 as a hex string; the interpretation of the file name (relative vs
33110 absolute, wild cards, etc) is up to the target.
33112 @item qTBuffer:@var{offset},@var{len}
33113 Return up to @var{len} bytes of the current contents of trace buffer,
33114 starting at @var{offset}. The trace buffer is treated as if it were
33115 a contiguous collection of traceframes, as per the trace file format.
33116 The reply consists as many hex-encoded bytes as the target can deliver
33117 in a packet; it is not an error to return fewer than were asked for.
33118 A reply consisting of just @code{l} indicates that no bytes are
33121 @item QTBuffer:circular:@var{value}
33122 This packet directs the target to use a circular trace buffer if
33123 @var{value} is 1, or a linear buffer if the value is 0.
33127 @subsection Relocate instruction reply packet
33128 When installing fast tracepoints in memory, the target may need to
33129 relocate the instruction currently at the tracepoint address to a
33130 different address in memory. For most instructions, a simple copy is
33131 enough, but, for example, call instructions that implicitly push the
33132 return address on the stack, and relative branches or other
33133 PC-relative instructions require offset adjustment, so that the effect
33134 of executing the instruction at a different address is the same as if
33135 it had executed in the original location.
33137 In response to several of the tracepoint packets, the target may also
33138 respond with a number of intermediate @samp{qRelocInsn} request
33139 packets before the final result packet, to have @value{GDBN} handle
33140 this relocation operation. If a packet supports this mechanism, its
33141 documentation will explicitly say so. See for example the above
33142 descriptions for the @samp{QTStart} and @samp{QTDP} packets. The
33143 format of the request is:
33146 @item qRelocInsn:@var{from};@var{to}
33148 This requests @value{GDBN} to copy instruction at address @var{from}
33149 to address @var{to}, possibly adjusted so that executing the
33150 instruction at @var{to} has the same effect as executing it at
33151 @var{from}. @value{GDBN} writes the adjusted instruction to target
33152 memory starting at @var{to}.
33157 @item qRelocInsn:@var{adjusted_size}
33158 Informs the stub the relocation is complete. @var{adjusted_size} is
33159 the length in bytes of resulting relocated instruction sequence.
33161 A badly formed request was detected, or an error was encountered while
33162 relocating the instruction.
33165 @node Host I/O Packets
33166 @section Host I/O Packets
33167 @cindex Host I/O, remote protocol
33168 @cindex file transfer, remote protocol
33170 The @dfn{Host I/O} packets allow @value{GDBN} to perform I/O
33171 operations on the far side of a remote link. For example, Host I/O is
33172 used to upload and download files to a remote target with its own
33173 filesystem. Host I/O uses the same constant values and data structure
33174 layout as the target-initiated File-I/O protocol. However, the
33175 Host I/O packets are structured differently. The target-initiated
33176 protocol relies on target memory to store parameters and buffers.
33177 Host I/O requests are initiated by @value{GDBN}, and the
33178 target's memory is not involved. @xref{File-I/O Remote Protocol
33179 Extension}, for more details on the target-initiated protocol.
33181 The Host I/O request packets all encode a single operation along with
33182 its arguments. They have this format:
33186 @item vFile:@var{operation}: @var{parameter}@dots{}
33187 @var{operation} is the name of the particular request; the target
33188 should compare the entire packet name up to the second colon when checking
33189 for a supported operation. The format of @var{parameter} depends on
33190 the operation. Numbers are always passed in hexadecimal. Negative
33191 numbers have an explicit minus sign (i.e.@: two's complement is not
33192 used). Strings (e.g.@: filenames) are encoded as a series of
33193 hexadecimal bytes. The last argument to a system call may be a
33194 buffer of escaped binary data (@pxref{Binary Data}).
33198 The valid responses to Host I/O packets are:
33202 @item F @var{result} [, @var{errno}] [; @var{attachment}]
33203 @var{result} is the integer value returned by this operation, usually
33204 non-negative for success and -1 for errors. If an error has occured,
33205 @var{errno} will be included in the result. @var{errno} will have a
33206 value defined by the File-I/O protocol (@pxref{Errno Values}). For
33207 operations which return data, @var{attachment} supplies the data as a
33208 binary buffer. Binary buffers in response packets are escaped in the
33209 normal way (@pxref{Binary Data}). See the individual packet
33210 documentation for the interpretation of @var{result} and
33214 An empty response indicates that this operation is not recognized.
33218 These are the supported Host I/O operations:
33221 @item vFile:open: @var{pathname}, @var{flags}, @var{mode}
33222 Open a file at @var{pathname} and return a file descriptor for it, or
33223 return -1 if an error occurs. @var{pathname} is a string,
33224 @var{flags} is an integer indicating a mask of open flags
33225 (@pxref{Open Flags}), and @var{mode} is an integer indicating a mask
33226 of mode bits to use if the file is created (@pxref{mode_t Values}).
33227 @xref{open}, for details of the open flags and mode values.
33229 @item vFile:close: @var{fd}
33230 Close the open file corresponding to @var{fd} and return 0, or
33231 -1 if an error occurs.
33233 @item vFile:pread: @var{fd}, @var{count}, @var{offset}
33234 Read data from the open file corresponding to @var{fd}. Up to
33235 @var{count} bytes will be read from the file, starting at @var{offset}
33236 relative to the start of the file. The target may read fewer bytes;
33237 common reasons include packet size limits and an end-of-file
33238 condition. The number of bytes read is returned. Zero should only be
33239 returned for a successful read at the end of the file, or if
33240 @var{count} was zero.
33242 The data read should be returned as a binary attachment on success.
33243 If zero bytes were read, the response should include an empty binary
33244 attachment (i.e.@: a trailing semicolon). The return value is the
33245 number of target bytes read; the binary attachment may be longer if
33246 some characters were escaped.
33248 @item vFile:pwrite: @var{fd}, @var{offset}, @var{data}
33249 Write @var{data} (a binary buffer) to the open file corresponding
33250 to @var{fd}. Start the write at @var{offset} from the start of the
33251 file. Unlike many @code{write} system calls, there is no
33252 separate @var{count} argument; the length of @var{data} in the
33253 packet is used. @samp{vFile:write} returns the number of bytes written,
33254 which may be shorter than the length of @var{data}, or -1 if an
33257 @item vFile:unlink: @var{pathname}
33258 Delete the file at @var{pathname} on the target. Return 0,
33259 or -1 if an error occurs. @var{pathname} is a string.
33264 @section Interrupts
33265 @cindex interrupts (remote protocol)
33267 When a program on the remote target is running, @value{GDBN} may
33268 attempt to interrupt it by sending a @samp{Ctrl-C}, @code{BREAK} or
33269 a @code{BREAK} followed by @code{g},
33270 control of which is specified via @value{GDBN}'s @samp{interrupt-sequence}.
33272 The precise meaning of @code{BREAK} is defined by the transport
33273 mechanism and may, in fact, be undefined. @value{GDBN} does not
33274 currently define a @code{BREAK} mechanism for any of the network
33275 interfaces except for TCP, in which case @value{GDBN} sends the
33276 @code{telnet} BREAK sequence.
33278 @samp{Ctrl-C}, on the other hand, is defined and implemented for all
33279 transport mechanisms. It is represented by sending the single byte
33280 @code{0x03} without any of the usual packet overhead described in
33281 the Overview section (@pxref{Overview}). When a @code{0x03} byte is
33282 transmitted as part of a packet, it is considered to be packet data
33283 and does @emph{not} represent an interrupt. E.g., an @samp{X} packet
33284 (@pxref{X packet}), used for binary downloads, may include an unescaped
33285 @code{0x03} as part of its packet.
33287 @code{BREAK} followed by @code{g} is also known as Magic SysRq g.
33288 When Linux kernel receives this sequence from serial port,
33289 it stops execution and connects to gdb.
33291 Stubs are not required to recognize these interrupt mechanisms and the
33292 precise meaning associated with receipt of the interrupt is
33293 implementation defined. If the target supports debugging of multiple
33294 threads and/or processes, it should attempt to interrupt all
33295 currently-executing threads and processes.
33296 If the stub is successful at interrupting the
33297 running program, it should send one of the stop
33298 reply packets (@pxref{Stop Reply Packets}) to @value{GDBN} as a result
33299 of successfully stopping the program in all-stop mode, and a stop reply
33300 for each stopped thread in non-stop mode.
33301 Interrupts received while the
33302 program is stopped are discarded.
33304 @node Notification Packets
33305 @section Notification Packets
33306 @cindex notification packets
33307 @cindex packets, notification
33309 The @value{GDBN} remote serial protocol includes @dfn{notifications},
33310 packets that require no acknowledgment. Both the GDB and the stub
33311 may send notifications (although the only notifications defined at
33312 present are sent by the stub). Notifications carry information
33313 without incurring the round-trip latency of an acknowledgment, and so
33314 are useful for low-impact communications where occasional packet loss
33317 A notification packet has the form @samp{% @var{data} #
33318 @var{checksum}}, where @var{data} is the content of the notification,
33319 and @var{checksum} is a checksum of @var{data}, computed and formatted
33320 as for ordinary @value{GDBN} packets. A notification's @var{data}
33321 never contains @samp{$}, @samp{%} or @samp{#} characters. Upon
33322 receiving a notification, the recipient sends no @samp{+} or @samp{-}
33323 to acknowledge the notification's receipt or to report its corruption.
33325 Every notification's @var{data} begins with a name, which contains no
33326 colon characters, followed by a colon character.
33328 Recipients should silently ignore corrupted notifications and
33329 notifications they do not understand. Recipients should restart
33330 timeout periods on receipt of a well-formed notification, whether or
33331 not they understand it.
33333 Senders should only send the notifications described here when this
33334 protocol description specifies that they are permitted. In the
33335 future, we may extend the protocol to permit existing notifications in
33336 new contexts; this rule helps older senders avoid confusing newer
33339 (Older versions of @value{GDBN} ignore bytes received until they see
33340 the @samp{$} byte that begins an ordinary packet, so new stubs may
33341 transmit notifications without fear of confusing older clients. There
33342 are no notifications defined for @value{GDBN} to send at the moment, but we
33343 assume that most older stubs would ignore them, as well.)
33345 The following notification packets from the stub to @value{GDBN} are
33349 @item Stop: @var{reply}
33350 Report an asynchronous stop event in non-stop mode.
33351 The @var{reply} has the form of a stop reply, as
33352 described in @ref{Stop Reply Packets}. Refer to @ref{Remote Non-Stop},
33353 for information on how these notifications are acknowledged by
33357 @node Remote Non-Stop
33358 @section Remote Protocol Support for Non-Stop Mode
33360 @value{GDBN}'s remote protocol supports non-stop debugging of
33361 multi-threaded programs, as described in @ref{Non-Stop Mode}. If the stub
33362 supports non-stop mode, it should report that to @value{GDBN} by including
33363 @samp{QNonStop+} in its @samp{qSupported} response (@pxref{qSupported}).
33365 @value{GDBN} typically sends a @samp{QNonStop} packet only when
33366 establishing a new connection with the stub. Entering non-stop mode
33367 does not alter the state of any currently-running threads, but targets
33368 must stop all threads in any already-attached processes when entering
33369 all-stop mode. @value{GDBN} uses the @samp{?} packet as necessary to
33370 probe the target state after a mode change.
33372 In non-stop mode, when an attached process encounters an event that
33373 would otherwise be reported with a stop reply, it uses the
33374 asynchronous notification mechanism (@pxref{Notification Packets}) to
33375 inform @value{GDBN}. In contrast to all-stop mode, where all threads
33376 in all processes are stopped when a stop reply is sent, in non-stop
33377 mode only the thread reporting the stop event is stopped. That is,
33378 when reporting a @samp{S} or @samp{T} response to indicate completion
33379 of a step operation, hitting a breakpoint, or a fault, only the
33380 affected thread is stopped; any other still-running threads continue
33381 to run. When reporting a @samp{W} or @samp{X} response, all running
33382 threads belonging to other attached processes continue to run.
33384 Only one stop reply notification at a time may be pending; if
33385 additional stop events occur before @value{GDBN} has acknowledged the
33386 previous notification, they must be queued by the stub for later
33387 synchronous transmission in response to @samp{vStopped} packets from
33388 @value{GDBN}. Because the notification mechanism is unreliable,
33389 the stub is permitted to resend a stop reply notification
33390 if it believes @value{GDBN} may not have received it. @value{GDBN}
33391 ignores additional stop reply notifications received before it has
33392 finished processing a previous notification and the stub has completed
33393 sending any queued stop events.
33395 Otherwise, @value{GDBN} must be prepared to receive a stop reply
33396 notification at any time. Specifically, they may appear when
33397 @value{GDBN} is not otherwise reading input from the stub, or when
33398 @value{GDBN} is expecting to read a normal synchronous response or a
33399 @samp{+}/@samp{-} acknowledgment to a packet it has sent.
33400 Notification packets are distinct from any other communication from
33401 the stub so there is no ambiguity.
33403 After receiving a stop reply notification, @value{GDBN} shall
33404 acknowledge it by sending a @samp{vStopped} packet (@pxref{vStopped packet})
33405 as a regular, synchronous request to the stub. Such acknowledgment
33406 is not required to happen immediately, as @value{GDBN} is permitted to
33407 send other, unrelated packets to the stub first, which the stub should
33410 Upon receiving a @samp{vStopped} packet, if the stub has other queued
33411 stop events to report to @value{GDBN}, it shall respond by sending a
33412 normal stop reply response. @value{GDBN} shall then send another
33413 @samp{vStopped} packet to solicit further responses; again, it is
33414 permitted to send other, unrelated packets as well which the stub
33415 should process normally.
33417 If the stub receives a @samp{vStopped} packet and there are no
33418 additional stop events to report, the stub shall return an @samp{OK}
33419 response. At this point, if further stop events occur, the stub shall
33420 send a new stop reply notification, @value{GDBN} shall accept the
33421 notification, and the process shall be repeated.
33423 In non-stop mode, the target shall respond to the @samp{?} packet as
33424 follows. First, any incomplete stop reply notification/@samp{vStopped}
33425 sequence in progress is abandoned. The target must begin a new
33426 sequence reporting stop events for all stopped threads, whether or not
33427 it has previously reported those events to @value{GDBN}. The first
33428 stop reply is sent as a synchronous reply to the @samp{?} packet, and
33429 subsequent stop replies are sent as responses to @samp{vStopped} packets
33430 using the mechanism described above. The target must not send
33431 asynchronous stop reply notifications until the sequence is complete.
33432 If all threads are running when the target receives the @samp{?} packet,
33433 or if the target is not attached to any process, it shall respond
33436 @node Packet Acknowledgment
33437 @section Packet Acknowledgment
33439 @cindex acknowledgment, for @value{GDBN} remote
33440 @cindex packet acknowledgment, for @value{GDBN} remote
33441 By default, when either the host or the target machine receives a packet,
33442 the first response expected is an acknowledgment: either @samp{+} (to indicate
33443 the package was received correctly) or @samp{-} (to request retransmission).
33444 This mechanism allows the @value{GDBN} remote protocol to operate over
33445 unreliable transport mechanisms, such as a serial line.
33447 In cases where the transport mechanism is itself reliable (such as a pipe or
33448 TCP connection), the @samp{+}/@samp{-} acknowledgments are redundant.
33449 It may be desirable to disable them in that case to reduce communication
33450 overhead, or for other reasons. This can be accomplished by means of the
33451 @samp{QStartNoAckMode} packet; @pxref{QStartNoAckMode}.
33453 When in no-acknowledgment mode, neither the stub nor @value{GDBN} shall send or
33454 expect @samp{+}/@samp{-} protocol acknowledgments. The packet
33455 and response format still includes the normal checksum, as described in
33456 @ref{Overview}, but the checksum may be ignored by the receiver.
33458 If the stub supports @samp{QStartNoAckMode} and prefers to operate in
33459 no-acknowledgment mode, it should report that to @value{GDBN}
33460 by including @samp{QStartNoAckMode+} in its response to @samp{qSupported};
33461 @pxref{qSupported}.
33462 If @value{GDBN} also supports @samp{QStartNoAckMode} and it has not been
33463 disabled via the @code{set remote noack-packet off} command
33464 (@pxref{Remote Configuration}),
33465 @value{GDBN} may then send a @samp{QStartNoAckMode} packet to the stub.
33466 Only then may the stub actually turn off packet acknowledgments.
33467 @value{GDBN} sends a final @samp{+} acknowledgment of the stub's @samp{OK}
33468 response, which can be safely ignored by the stub.
33470 Note that @code{set remote noack-packet} command only affects negotiation
33471 between @value{GDBN} and the stub when subsequent connections are made;
33472 it does not affect the protocol acknowledgment state for any current
33474 Since @samp{+}/@samp{-} acknowledgments are enabled by default when a
33475 new connection is established,
33476 there is also no protocol request to re-enable the acknowledgments
33477 for the current connection, once disabled.
33482 Example sequence of a target being re-started. Notice how the restart
33483 does not get any direct output:
33488 @emph{target restarts}
33491 <- @code{T001:1234123412341234}
33495 Example sequence of a target being stepped by a single instruction:
33498 -> @code{G1445@dots{}}
33503 <- @code{T001:1234123412341234}
33507 <- @code{1455@dots{}}
33511 @node File-I/O Remote Protocol Extension
33512 @section File-I/O Remote Protocol Extension
33513 @cindex File-I/O remote protocol extension
33516 * File-I/O Overview::
33517 * Protocol Basics::
33518 * The F Request Packet::
33519 * The F Reply Packet::
33520 * The Ctrl-C Message::
33522 * List of Supported Calls::
33523 * Protocol-specific Representation of Datatypes::
33525 * File-I/O Examples::
33528 @node File-I/O Overview
33529 @subsection File-I/O Overview
33530 @cindex file-i/o overview
33532 The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the
33533 target to use the host's file system and console I/O to perform various
33534 system calls. System calls on the target system are translated into a
33535 remote protocol packet to the host system, which then performs the needed
33536 actions and returns a response packet to the target system.
33537 This simulates file system operations even on targets that lack file systems.
33539 The protocol is defined to be independent of both the host and target systems.
33540 It uses its own internal representation of datatypes and values. Both
33541 @value{GDBN} and the target's @value{GDBN} stub are responsible for
33542 translating the system-dependent value representations into the internal
33543 protocol representations when data is transmitted.
33545 The communication is synchronous. A system call is possible only when
33546 @value{GDBN} is waiting for a response from the @samp{C}, @samp{c}, @samp{S}
33547 or @samp{s} packets. While @value{GDBN} handles the request for a system call,
33548 the target is stopped to allow deterministic access to the target's
33549 memory. Therefore File-I/O is not interruptible by target signals. On
33550 the other hand, it is possible to interrupt File-I/O by a user interrupt
33551 (@samp{Ctrl-C}) within @value{GDBN}.
33553 The target's request to perform a host system call does not finish
33554 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
33555 after finishing the system call, the target returns to continuing the
33556 previous activity (continue, step). No additional continue or step
33557 request from @value{GDBN} is required.
33560 (@value{GDBP}) continue
33561 <- target requests 'system call X'
33562 target is stopped, @value{GDBN} executes system call
33563 -> @value{GDBN} returns result
33564 ... target continues, @value{GDBN} returns to wait for the target
33565 <- target hits breakpoint and sends a Txx packet
33568 The protocol only supports I/O on the console and to regular files on
33569 the host file system. Character or block special devices, pipes,
33570 named pipes, sockets or any other communication method on the host
33571 system are not supported by this protocol.
33573 File I/O is not supported in non-stop mode.
33575 @node Protocol Basics
33576 @subsection Protocol Basics
33577 @cindex protocol basics, file-i/o
33579 The File-I/O protocol uses the @code{F} packet as the request as well
33580 as reply packet. Since a File-I/O system call can only occur when
33581 @value{GDBN} is waiting for a response from the continuing or stepping target,
33582 the File-I/O request is a reply that @value{GDBN} has to expect as a result
33583 of a previous @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
33584 This @code{F} packet contains all information needed to allow @value{GDBN}
33585 to call the appropriate host system call:
33589 A unique identifier for the requested system call.
33592 All parameters to the system call. Pointers are given as addresses
33593 in the target memory address space. Pointers to strings are given as
33594 pointer/length pair. Numerical values are given as they are.
33595 Numerical control flags are given in a protocol-specific representation.
33599 At this point, @value{GDBN} has to perform the following actions.
33603 If the parameters include pointer values to data needed as input to a
33604 system call, @value{GDBN} requests this data from the target with a
33605 standard @code{m} packet request. This additional communication has to be
33606 expected by the target implementation and is handled as any other @code{m}
33610 @value{GDBN} translates all value from protocol representation to host
33611 representation as needed. Datatypes are coerced into the host types.
33614 @value{GDBN} calls the system call.
33617 It then coerces datatypes back to protocol representation.
33620 If the system call is expected to return data in buffer space specified
33621 by pointer parameters to the call, the data is transmitted to the
33622 target using a @code{M} or @code{X} packet. This packet has to be expected
33623 by the target implementation and is handled as any other @code{M} or @code{X}
33628 Eventually @value{GDBN} replies with another @code{F} packet which contains all
33629 necessary information for the target to continue. This at least contains
33636 @code{errno}, if has been changed by the system call.
33643 After having done the needed type and value coercion, the target continues
33644 the latest continue or step action.
33646 @node The F Request Packet
33647 @subsection The @code{F} Request Packet
33648 @cindex file-i/o request packet
33649 @cindex @code{F} request packet
33651 The @code{F} request packet has the following format:
33654 @item F@var{call-id},@var{parameter@dots{}}
33656 @var{call-id} is the identifier to indicate the host system call to be called.
33657 This is just the name of the function.
33659 @var{parameter@dots{}} are the parameters to the system call.
33660 Parameters are hexadecimal integer values, either the actual values in case
33661 of scalar datatypes, pointers to target buffer space in case of compound
33662 datatypes and unspecified memory areas, or pointer/length pairs in case
33663 of string parameters. These are appended to the @var{call-id} as a
33664 comma-delimited list. All values are transmitted in ASCII
33665 string representation, pointer/length pairs separated by a slash.
33671 @node The F Reply Packet
33672 @subsection The @code{F} Reply Packet
33673 @cindex file-i/o reply packet
33674 @cindex @code{F} reply packet
33676 The @code{F} reply packet has the following format:
33680 @item F@var{retcode},@var{errno},@var{Ctrl-C flag};@var{call-specific attachment}
33682 @var{retcode} is the return code of the system call as hexadecimal value.
33684 @var{errno} is the @code{errno} set by the call, in protocol-specific
33686 This parameter can be omitted if the call was successful.
33688 @var{Ctrl-C flag} is only sent if the user requested a break. In this
33689 case, @var{errno} must be sent as well, even if the call was successful.
33690 The @var{Ctrl-C flag} itself consists of the character @samp{C}:
33697 or, if the call was interrupted before the host call has been performed:
33704 assuming 4 is the protocol-specific representation of @code{EINTR}.
33709 @node The Ctrl-C Message
33710 @subsection The @samp{Ctrl-C} Message
33711 @cindex ctrl-c message, in file-i/o protocol
33713 If the @samp{Ctrl-C} flag is set in the @value{GDBN}
33714 reply packet (@pxref{The F Reply Packet}),
33715 the target should behave as if it had
33716 gotten a break message. The meaning for the target is ``system call
33717 interrupted by @code{SIGINT}''. Consequentially, the target should actually stop
33718 (as with a break message) and return to @value{GDBN} with a @code{T02}
33721 It's important for the target to know in which
33722 state the system call was interrupted. There are two possible cases:
33726 The system call hasn't been performed on the host yet.
33729 The system call on the host has been finished.
33733 These two states can be distinguished by the target by the value of the
33734 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
33735 call hasn't been performed. This is equivalent to the @code{EINTR} handling
33736 on POSIX systems. In any other case, the target may presume that the
33737 system call has been finished --- successfully or not --- and should behave
33738 as if the break message arrived right after the system call.
33740 @value{GDBN} must behave reliably. If the system call has not been called
33741 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
33742 @code{errno} in the packet. If the system call on the host has been finished
33743 before the user requests a break, the full action must be finished by
33744 @value{GDBN}. This requires sending @code{M} or @code{X} packets as necessary.
33745 The @code{F} packet may only be sent when either nothing has happened
33746 or the full action has been completed.
33749 @subsection Console I/O
33750 @cindex console i/o as part of file-i/o
33752 By default and if not explicitly closed by the target system, the file
33753 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
33754 on the @value{GDBN} console is handled as any other file output operation
33755 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
33756 by @value{GDBN} so that after the target read request from file descriptor
33757 0 all following typing is buffered until either one of the following
33762 The user types @kbd{Ctrl-c}. The behaviour is as explained above, and the
33764 system call is treated as finished.
33767 The user presses @key{RET}. This is treated as end of input with a trailing
33771 The user types @kbd{Ctrl-d}. This is treated as end of input. No trailing
33772 character (neither newline nor @samp{Ctrl-D}) is appended to the input.
33776 If the user has typed more characters than fit in the buffer given to
33777 the @code{read} call, the trailing characters are buffered in @value{GDBN} until
33778 either another @code{read(0, @dots{})} is requested by the target, or debugging
33779 is stopped at the user's request.
33782 @node List of Supported Calls
33783 @subsection List of Supported Calls
33784 @cindex list of supported file-i/o calls
33801 @unnumberedsubsubsec open
33802 @cindex open, file-i/o system call
33807 int open(const char *pathname, int flags);
33808 int open(const char *pathname, int flags, mode_t mode);
33812 @samp{Fopen,@var{pathptr}/@var{len},@var{flags},@var{mode}}
33815 @var{flags} is the bitwise @code{OR} of the following values:
33819 If the file does not exist it will be created. The host
33820 rules apply as far as file ownership and time stamps
33824 When used with @code{O_CREAT}, if the file already exists it is
33825 an error and open() fails.
33828 If the file already exists and the open mode allows
33829 writing (@code{O_RDWR} or @code{O_WRONLY} is given) it will be
33830 truncated to zero length.
33833 The file is opened in append mode.
33836 The file is opened for reading only.
33839 The file is opened for writing only.
33842 The file is opened for reading and writing.
33846 Other bits are silently ignored.
33850 @var{mode} is the bitwise @code{OR} of the following values:
33854 User has read permission.
33857 User has write permission.
33860 Group has read permission.
33863 Group has write permission.
33866 Others have read permission.
33869 Others have write permission.
33873 Other bits are silently ignored.
33876 @item Return value:
33877 @code{open} returns the new file descriptor or -1 if an error
33884 @var{pathname} already exists and @code{O_CREAT} and @code{O_EXCL} were used.
33887 @var{pathname} refers to a directory.
33890 The requested access is not allowed.
33893 @var{pathname} was too long.
33896 A directory component in @var{pathname} does not exist.
33899 @var{pathname} refers to a device, pipe, named pipe or socket.
33902 @var{pathname} refers to a file on a read-only filesystem and
33903 write access was requested.
33906 @var{pathname} is an invalid pointer value.
33909 No space on device to create the file.
33912 The process already has the maximum number of files open.
33915 The limit on the total number of files open on the system
33919 The call was interrupted by the user.
33925 @unnumberedsubsubsec close
33926 @cindex close, file-i/o system call
33935 @samp{Fclose,@var{fd}}
33937 @item Return value:
33938 @code{close} returns zero on success, or -1 if an error occurred.
33944 @var{fd} isn't a valid open file descriptor.
33947 The call was interrupted by the user.
33953 @unnumberedsubsubsec read
33954 @cindex read, file-i/o system call
33959 int read(int fd, void *buf, unsigned int count);
33963 @samp{Fread,@var{fd},@var{bufptr},@var{count}}
33965 @item Return value:
33966 On success, the number of bytes read is returned.
33967 Zero indicates end of file. If count is zero, read
33968 returns zero as well. On error, -1 is returned.
33974 @var{fd} is not a valid file descriptor or is not open for
33978 @var{bufptr} is an invalid pointer value.
33981 The call was interrupted by the user.
33987 @unnumberedsubsubsec write
33988 @cindex write, file-i/o system call
33993 int write(int fd, const void *buf, unsigned int count);
33997 @samp{Fwrite,@var{fd},@var{bufptr},@var{count}}
33999 @item Return value:
34000 On success, the number of bytes written are returned.
34001 Zero indicates nothing was written. On error, -1
34008 @var{fd} is not a valid file descriptor or is not open for
34012 @var{bufptr} is an invalid pointer value.
34015 An attempt was made to write a file that exceeds the
34016 host-specific maximum file size allowed.
34019 No space on device to write the data.
34022 The call was interrupted by the user.
34028 @unnumberedsubsubsec lseek
34029 @cindex lseek, file-i/o system call
34034 long lseek (int fd, long offset, int flag);
34038 @samp{Flseek,@var{fd},@var{offset},@var{flag}}
34040 @var{flag} is one of:
34044 The offset is set to @var{offset} bytes.
34047 The offset is set to its current location plus @var{offset}
34051 The offset is set to the size of the file plus @var{offset}
34055 @item Return value:
34056 On success, the resulting unsigned offset in bytes from
34057 the beginning of the file is returned. Otherwise, a
34058 value of -1 is returned.
34064 @var{fd} is not a valid open file descriptor.
34067 @var{fd} is associated with the @value{GDBN} console.
34070 @var{flag} is not a proper value.
34073 The call was interrupted by the user.
34079 @unnumberedsubsubsec rename
34080 @cindex rename, file-i/o system call
34085 int rename(const char *oldpath, const char *newpath);
34089 @samp{Frename,@var{oldpathptr}/@var{len},@var{newpathptr}/@var{len}}
34091 @item Return value:
34092 On success, zero is returned. On error, -1 is returned.
34098 @var{newpath} is an existing directory, but @var{oldpath} is not a
34102 @var{newpath} is a non-empty directory.
34105 @var{oldpath} or @var{newpath} is a directory that is in use by some
34109 An attempt was made to make a directory a subdirectory
34113 A component used as a directory in @var{oldpath} or new
34114 path is not a directory. Or @var{oldpath} is a directory
34115 and @var{newpath} exists but is not a directory.
34118 @var{oldpathptr} or @var{newpathptr} are invalid pointer values.
34121 No access to the file or the path of the file.
34125 @var{oldpath} or @var{newpath} was too long.
34128 A directory component in @var{oldpath} or @var{newpath} does not exist.
34131 The file is on a read-only filesystem.
34134 The device containing the file has no room for the new
34138 The call was interrupted by the user.
34144 @unnumberedsubsubsec unlink
34145 @cindex unlink, file-i/o system call
34150 int unlink(const char *pathname);
34154 @samp{Funlink,@var{pathnameptr}/@var{len}}
34156 @item Return value:
34157 On success, zero is returned. On error, -1 is returned.
34163 No access to the file or the path of the file.
34166 The system does not allow unlinking of directories.
34169 The file @var{pathname} cannot be unlinked because it's
34170 being used by another process.
34173 @var{pathnameptr} is an invalid pointer value.
34176 @var{pathname} was too long.
34179 A directory component in @var{pathname} does not exist.
34182 A component of the path is not a directory.
34185 The file is on a read-only filesystem.
34188 The call was interrupted by the user.
34194 @unnumberedsubsubsec stat/fstat
34195 @cindex fstat, file-i/o system call
34196 @cindex stat, file-i/o system call
34201 int stat(const char *pathname, struct stat *buf);
34202 int fstat(int fd, struct stat *buf);
34206 @samp{Fstat,@var{pathnameptr}/@var{len},@var{bufptr}}@*
34207 @samp{Ffstat,@var{fd},@var{bufptr}}
34209 @item Return value:
34210 On success, zero is returned. On error, -1 is returned.
34216 @var{fd} is not a valid open file.
34219 A directory component in @var{pathname} does not exist or the
34220 path is an empty string.
34223 A component of the path is not a directory.
34226 @var{pathnameptr} is an invalid pointer value.
34229 No access to the file or the path of the file.
34232 @var{pathname} was too long.
34235 The call was interrupted by the user.
34241 @unnumberedsubsubsec gettimeofday
34242 @cindex gettimeofday, file-i/o system call
34247 int gettimeofday(struct timeval *tv, void *tz);
34251 @samp{Fgettimeofday,@var{tvptr},@var{tzptr}}
34253 @item Return value:
34254 On success, 0 is returned, -1 otherwise.
34260 @var{tz} is a non-NULL pointer.
34263 @var{tvptr} and/or @var{tzptr} is an invalid pointer value.
34269 @unnumberedsubsubsec isatty
34270 @cindex isatty, file-i/o system call
34275 int isatty(int fd);
34279 @samp{Fisatty,@var{fd}}
34281 @item Return value:
34282 Returns 1 if @var{fd} refers to the @value{GDBN} console, 0 otherwise.
34288 The call was interrupted by the user.
34293 Note that the @code{isatty} call is treated as a special case: it returns
34294 1 to the target if the file descriptor is attached
34295 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
34296 would require implementing @code{ioctl} and would be more complex than
34301 @unnumberedsubsubsec system
34302 @cindex system, file-i/o system call
34307 int system(const char *command);
34311 @samp{Fsystem,@var{commandptr}/@var{len}}
34313 @item Return value:
34314 If @var{len} is zero, the return value indicates whether a shell is
34315 available. A zero return value indicates a shell is not available.
34316 For non-zero @var{len}, the value returned is -1 on error and the
34317 return status of the command otherwise. Only the exit status of the
34318 command is returned, which is extracted from the host's @code{system}
34319 return value by calling @code{WEXITSTATUS(retval)}. In case
34320 @file{/bin/sh} could not be executed, 127 is returned.
34326 The call was interrupted by the user.
34331 @value{GDBN} takes over the full task of calling the necessary host calls
34332 to perform the @code{system} call. The return value of @code{system} on
34333 the host is simplified before it's returned
34334 to the target. Any termination signal information from the child process
34335 is discarded, and the return value consists
34336 entirely of the exit status of the called command.
34338 Due to security concerns, the @code{system} call is by default refused
34339 by @value{GDBN}. The user has to allow this call explicitly with the
34340 @code{set remote system-call-allowed 1} command.
34343 @item set remote system-call-allowed
34344 @kindex set remote system-call-allowed
34345 Control whether to allow the @code{system} calls in the File I/O
34346 protocol for the remote target. The default is zero (disabled).
34348 @item show remote system-call-allowed
34349 @kindex show remote system-call-allowed
34350 Show whether the @code{system} calls are allowed in the File I/O
34354 @node Protocol-specific Representation of Datatypes
34355 @subsection Protocol-specific Representation of Datatypes
34356 @cindex protocol-specific representation of datatypes, in file-i/o protocol
34359 * Integral Datatypes::
34361 * Memory Transfer::
34366 @node Integral Datatypes
34367 @unnumberedsubsubsec Integral Datatypes
34368 @cindex integral datatypes, in file-i/o protocol
34370 The integral datatypes used in the system calls are @code{int},
34371 @code{unsigned int}, @code{long}, @code{unsigned long},
34372 @code{mode_t}, and @code{time_t}.
34374 @code{int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
34375 implemented as 32 bit values in this protocol.
34377 @code{long} and @code{unsigned long} are implemented as 64 bit types.
34379 @xref{Limits}, for corresponding MIN and MAX values (similar to those
34380 in @file{limits.h}) to allow range checking on host and target.
34382 @code{time_t} datatypes are defined as seconds since the Epoch.
34384 All integral datatypes transferred as part of a memory read or write of a
34385 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
34388 @node Pointer Values
34389 @unnumberedsubsubsec Pointer Values
34390 @cindex pointer values, in file-i/o protocol
34392 Pointers to target data are transmitted as they are. An exception
34393 is made for pointers to buffers for which the length isn't
34394 transmitted as part of the function call, namely strings. Strings
34395 are transmitted as a pointer/length pair, both as hex values, e.g.@:
34402 which is a pointer to data of length 18 bytes at position 0x1aaf.
34403 The length is defined as the full string length in bytes, including
34404 the trailing null byte. For example, the string @code{"hello world"}
34405 at address 0x123456 is transmitted as
34411 @node Memory Transfer
34412 @unnumberedsubsubsec Memory Transfer
34413 @cindex memory transfer, in file-i/o protocol
34415 Structured data which is transferred using a memory read or write (for
34416 example, a @code{struct stat}) is expected to be in a protocol-specific format
34417 with all scalar multibyte datatypes being big endian. Translation to
34418 this representation needs to be done both by the target before the @code{F}
34419 packet is sent, and by @value{GDBN} before
34420 it transfers memory to the target. Transferred pointers to structured
34421 data should point to the already-coerced data at any time.
34425 @unnumberedsubsubsec struct stat
34426 @cindex struct stat, in file-i/o protocol
34428 The buffer of type @code{struct stat} used by the target and @value{GDBN}
34429 is defined as follows:
34433 unsigned int st_dev; /* device */
34434 unsigned int st_ino; /* inode */
34435 mode_t st_mode; /* protection */
34436 unsigned int st_nlink; /* number of hard links */
34437 unsigned int st_uid; /* user ID of owner */
34438 unsigned int st_gid; /* group ID of owner */
34439 unsigned int st_rdev; /* device type (if inode device) */
34440 unsigned long st_size; /* total size, in bytes */
34441 unsigned long st_blksize; /* blocksize for filesystem I/O */
34442 unsigned long st_blocks; /* number of blocks allocated */
34443 time_t st_atime; /* time of last access */
34444 time_t st_mtime; /* time of last modification */
34445 time_t st_ctime; /* time of last change */
34449 The integral datatypes conform to the definitions given in the
34450 appropriate section (see @ref{Integral Datatypes}, for details) so this
34451 structure is of size 64 bytes.
34453 The values of several fields have a restricted meaning and/or
34459 A value of 0 represents a file, 1 the console.
34462 No valid meaning for the target. Transmitted unchanged.
34465 Valid mode bits are described in @ref{Constants}. Any other
34466 bits have currently no meaning for the target.
34471 No valid meaning for the target. Transmitted unchanged.
34476 These values have a host and file system dependent
34477 accuracy. Especially on Windows hosts, the file system may not
34478 support exact timing values.
34481 The target gets a @code{struct stat} of the above representation and is
34482 responsible for coercing it to the target representation before
34485 Note that due to size differences between the host, target, and protocol
34486 representations of @code{struct stat} members, these members could eventually
34487 get truncated on the target.
34489 @node struct timeval
34490 @unnumberedsubsubsec struct timeval
34491 @cindex struct timeval, in file-i/o protocol
34493 The buffer of type @code{struct timeval} used by the File-I/O protocol
34494 is defined as follows:
34498 time_t tv_sec; /* second */
34499 long tv_usec; /* microsecond */
34503 The integral datatypes conform to the definitions given in the
34504 appropriate section (see @ref{Integral Datatypes}, for details) so this
34505 structure is of size 8 bytes.
34508 @subsection Constants
34509 @cindex constants, in file-i/o protocol
34511 The following values are used for the constants inside of the
34512 protocol. @value{GDBN} and target are responsible for translating these
34513 values before and after the call as needed.
34524 @unnumberedsubsubsec Open Flags
34525 @cindex open flags, in file-i/o protocol
34527 All values are given in hexadecimal representation.
34539 @node mode_t Values
34540 @unnumberedsubsubsec mode_t Values
34541 @cindex mode_t values, in file-i/o protocol
34543 All values are given in octal representation.
34560 @unnumberedsubsubsec Errno Values
34561 @cindex errno values, in file-i/o protocol
34563 All values are given in decimal representation.
34588 @code{EUNKNOWN} is used as a fallback error value if a host system returns
34589 any error value not in the list of supported error numbers.
34592 @unnumberedsubsubsec Lseek Flags
34593 @cindex lseek flags, in file-i/o protocol
34602 @unnumberedsubsubsec Limits
34603 @cindex limits, in file-i/o protocol
34605 All values are given in decimal representation.
34608 INT_MIN -2147483648
34610 UINT_MAX 4294967295
34611 LONG_MIN -9223372036854775808
34612 LONG_MAX 9223372036854775807
34613 ULONG_MAX 18446744073709551615
34616 @node File-I/O Examples
34617 @subsection File-I/O Examples
34618 @cindex file-i/o examples
34620 Example sequence of a write call, file descriptor 3, buffer is at target
34621 address 0x1234, 6 bytes should be written:
34624 <- @code{Fwrite,3,1234,6}
34625 @emph{request memory read from target}
34628 @emph{return "6 bytes written"}
34632 Example sequence of a read call, file descriptor 3, buffer is at target
34633 address 0x1234, 6 bytes should be read:
34636 <- @code{Fread,3,1234,6}
34637 @emph{request memory write to target}
34638 -> @code{X1234,6:XXXXXX}
34639 @emph{return "6 bytes read"}
34643 Example sequence of a read call, call fails on the host due to invalid
34644 file descriptor (@code{EBADF}):
34647 <- @code{Fread,3,1234,6}
34651 Example sequence of a read call, user presses @kbd{Ctrl-c} before syscall on
34655 <- @code{Fread,3,1234,6}
34660 Example sequence of a read call, user presses @kbd{Ctrl-c} after syscall on
34664 <- @code{Fread,3,1234,6}
34665 -> @code{X1234,6:XXXXXX}
34669 @node Library List Format
34670 @section Library List Format
34671 @cindex library list format, remote protocol
34673 On some platforms, a dynamic loader (e.g.@: @file{ld.so}) runs in the
34674 same process as your application to manage libraries. In this case,
34675 @value{GDBN} can use the loader's symbol table and normal memory
34676 operations to maintain a list of shared libraries. On other
34677 platforms, the operating system manages loaded libraries.
34678 @value{GDBN} can not retrieve the list of currently loaded libraries
34679 through memory operations, so it uses the @samp{qXfer:libraries:read}
34680 packet (@pxref{qXfer library list read}) instead. The remote stub
34681 queries the target's operating system and reports which libraries
34684 The @samp{qXfer:libraries:read} packet returns an XML document which
34685 lists loaded libraries and their offsets. Each library has an
34686 associated name and one or more segment or section base addresses,
34687 which report where the library was loaded in memory.
34689 For the common case of libraries that are fully linked binaries, the
34690 library should have a list of segments. If the target supports
34691 dynamic linking of a relocatable object file, its library XML element
34692 should instead include a list of allocated sections. The segment or
34693 section bases are start addresses, not relocation offsets; they do not
34694 depend on the library's link-time base addresses.
34696 @value{GDBN} must be linked with the Expat library to support XML
34697 library lists. @xref{Expat}.
34699 A simple memory map, with one loaded library relocated by a single
34700 offset, looks like this:
34704 <library name="/lib/libc.so.6">
34705 <segment address="0x10000000"/>
34710 Another simple memory map, with one loaded library with three
34711 allocated sections (.text, .data, .bss), looks like this:
34715 <library name="sharedlib.o">
34716 <section address="0x10000000"/>
34717 <section address="0x20000000"/>
34718 <section address="0x30000000"/>
34723 The format of a library list is described by this DTD:
34726 <!-- library-list: Root element with versioning -->
34727 <!ELEMENT library-list (library)*>
34728 <!ATTLIST library-list version CDATA #FIXED "1.0">
34729 <!ELEMENT library (segment*, section*)>
34730 <!ATTLIST library name CDATA #REQUIRED>
34731 <!ELEMENT segment EMPTY>
34732 <!ATTLIST segment address CDATA #REQUIRED>
34733 <!ELEMENT section EMPTY>
34734 <!ATTLIST section address CDATA #REQUIRED>
34737 In addition, segments and section descriptors cannot be mixed within a
34738 single library element, and you must supply at least one segment or
34739 section for each library.
34741 @node Memory Map Format
34742 @section Memory Map Format
34743 @cindex memory map format
34745 To be able to write into flash memory, @value{GDBN} needs to obtain a
34746 memory map from the target. This section describes the format of the
34749 The memory map is obtained using the @samp{qXfer:memory-map:read}
34750 (@pxref{qXfer memory map read}) packet and is an XML document that
34751 lists memory regions.
34753 @value{GDBN} must be linked with the Expat library to support XML
34754 memory maps. @xref{Expat}.
34756 The top-level structure of the document is shown below:
34759 <?xml version="1.0"?>
34760 <!DOCTYPE memory-map
34761 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
34762 "http://sourceware.org/gdb/gdb-memory-map.dtd">
34768 Each region can be either:
34773 A region of RAM starting at @var{addr} and extending for @var{length}
34777 <memory type="ram" start="@var{addr}" length="@var{length}"/>
34782 A region of read-only memory:
34785 <memory type="rom" start="@var{addr}" length="@var{length}"/>
34790 A region of flash memory, with erasure blocks @var{blocksize}
34794 <memory type="flash" start="@var{addr}" length="@var{length}">
34795 <property name="blocksize">@var{blocksize}</property>
34801 Regions must not overlap. @value{GDBN} assumes that areas of memory not covered
34802 by the memory map are RAM, and uses the ordinary @samp{M} and @samp{X}
34803 packets to write to addresses in such ranges.
34805 The formal DTD for memory map format is given below:
34808 <!-- ................................................... -->
34809 <!-- Memory Map XML DTD ................................ -->
34810 <!-- File: memory-map.dtd .............................. -->
34811 <!-- .................................... .............. -->
34812 <!-- memory-map.dtd -->
34813 <!-- memory-map: Root element with versioning -->
34814 <!ELEMENT memory-map (memory | property)>
34815 <!ATTLIST memory-map version CDATA #FIXED "1.0.0">
34816 <!ELEMENT memory (property)>
34817 <!-- memory: Specifies a memory region,
34818 and its type, or device. -->
34819 <!ATTLIST memory type CDATA #REQUIRED
34820 start CDATA #REQUIRED
34821 length CDATA #REQUIRED
34822 device CDATA #IMPLIED>
34823 <!-- property: Generic attribute tag -->
34824 <!ELEMENT property (#PCDATA | property)*>
34825 <!ATTLIST property name CDATA #REQUIRED>
34828 @node Thread List Format
34829 @section Thread List Format
34830 @cindex thread list format
34832 To efficiently update the list of threads and their attributes,
34833 @value{GDBN} issues the @samp{qXfer:threads:read} packet
34834 (@pxref{qXfer threads read}) and obtains the XML document with
34835 the following structure:
34838 <?xml version="1.0"?>
34840 <thread id="id" core="0">
34841 ... description ...
34846 Each @samp{thread} element must have the @samp{id} attribute that
34847 identifies the thread (@pxref{thread-id syntax}). The
34848 @samp{core} attribute, if present, specifies which processor core
34849 the thread was last executing on. The content of the of @samp{thread}
34850 element is interpreted as human-readable auxilliary information.
34852 @include agentexpr.texi
34854 @node Trace File Format
34855 @appendix Trace File Format
34856 @cindex trace file format
34858 The trace file comes in three parts: a header, a textual description
34859 section, and a trace frame section with binary data.
34861 The header has the form @code{\x7fTRACE0\n}. The first byte is
34862 @code{0x7f} so as to indicate that the file contains binary data,
34863 while the @code{0} is a version number that may have different values
34866 The description section consists of multiple lines of @sc{ascii} text
34867 separated by newline characters (@code{0xa}). The lines may include a
34868 variety of optional descriptive or context-setting information, such
34869 as tracepoint definitions or register set size. @value{GDBN} will
34870 ignore any line that it does not recognize. An empty line marks the end
34873 @c FIXME add some specific types of data
34875 The trace frame section consists of a number of consecutive frames.
34876 Each frame begins with a two-byte tracepoint number, followed by a
34877 four-byte size giving the amount of data in the frame. The data in
34878 the frame consists of a number of blocks, each introduced by a
34879 character indicating its type (at least register, memory, and trace
34880 state variable). The data in this section is raw binary, not a
34881 hexadecimal or other encoding; its endianness matches the target's
34884 @c FIXME bi-arch may require endianness/arch info in description section
34887 @item R @var{bytes}
34888 Register block. The number and ordering of bytes matches that of a
34889 @code{g} packet in the remote protocol. Note that these are the
34890 actual bytes, in target order and @value{GDBN} register order, not a
34891 hexadecimal encoding.
34893 @item M @var{address} @var{length} @var{bytes}...
34894 Memory block. This is a contiguous block of memory, at the 8-byte
34895 address @var{address}, with a 2-byte length @var{length}, followed by
34896 @var{length} bytes.
34898 @item V @var{number} @var{value}
34899 Trace state variable block. This records the 8-byte signed value
34900 @var{value} of trace state variable numbered @var{number}.
34904 Future enhancements of the trace file format may include additional types
34907 @node Target Descriptions
34908 @appendix Target Descriptions
34909 @cindex target descriptions
34911 @strong{Warning:} target descriptions are still under active development,
34912 and the contents and format may change between @value{GDBN} releases.
34913 The format is expected to stabilize in the future.
34915 One of the challenges of using @value{GDBN} to debug embedded systems
34916 is that there are so many minor variants of each processor
34917 architecture in use. It is common practice for vendors to start with
34918 a standard processor core --- ARM, PowerPC, or MIPS, for example ---
34919 and then make changes to adapt it to a particular market niche. Some
34920 architectures have hundreds of variants, available from dozens of
34921 vendors. This leads to a number of problems:
34925 With so many different customized processors, it is difficult for
34926 the @value{GDBN} maintainers to keep up with the changes.
34928 Since individual variants may have short lifetimes or limited
34929 audiences, it may not be worthwhile to carry information about every
34930 variant in the @value{GDBN} source tree.
34932 When @value{GDBN} does support the architecture of the embedded system
34933 at hand, the task of finding the correct architecture name to give the
34934 @command{set architecture} command can be error-prone.
34937 To address these problems, the @value{GDBN} remote protocol allows a
34938 target system to not only identify itself to @value{GDBN}, but to
34939 actually describe its own features. This lets @value{GDBN} support
34940 processor variants it has never seen before --- to the extent that the
34941 descriptions are accurate, and that @value{GDBN} understands them.
34943 @value{GDBN} must be linked with the Expat library to support XML
34944 target descriptions. @xref{Expat}.
34947 * Retrieving Descriptions:: How descriptions are fetched from a target.
34948 * Target Description Format:: The contents of a target description.
34949 * Predefined Target Types:: Standard types available for target
34951 * Standard Target Features:: Features @value{GDBN} knows about.
34954 @node Retrieving Descriptions
34955 @section Retrieving Descriptions
34957 Target descriptions can be read from the target automatically, or
34958 specified by the user manually. The default behavior is to read the
34959 description from the target. @value{GDBN} retrieves it via the remote
34960 protocol using @samp{qXfer} requests (@pxref{General Query Packets,
34961 qXfer}). The @var{annex} in the @samp{qXfer} packet will be
34962 @samp{target.xml}. The contents of the @samp{target.xml} annex are an
34963 XML document, of the form described in @ref{Target Description
34966 Alternatively, you can specify a file to read for the target description.
34967 If a file is set, the target will not be queried. The commands to
34968 specify a file are:
34971 @cindex set tdesc filename
34972 @item set tdesc filename @var{path}
34973 Read the target description from @var{path}.
34975 @cindex unset tdesc filename
34976 @item unset tdesc filename
34977 Do not read the XML target description from a file. @value{GDBN}
34978 will use the description supplied by the current target.
34980 @cindex show tdesc filename
34981 @item show tdesc filename
34982 Show the filename to read for a target description, if any.
34986 @node Target Description Format
34987 @section Target Description Format
34988 @cindex target descriptions, XML format
34990 A target description annex is an @uref{http://www.w3.org/XML/, XML}
34991 document which complies with the Document Type Definition provided in
34992 the @value{GDBN} sources in @file{gdb/features/gdb-target.dtd}. This
34993 means you can use generally available tools like @command{xmllint} to
34994 check that your feature descriptions are well-formed and valid.
34995 However, to help people unfamiliar with XML write descriptions for
34996 their targets, we also describe the grammar here.
34998 Target descriptions can identify the architecture of the remote target
34999 and (for some architectures) provide information about custom register
35000 sets. They can also identify the OS ABI of the remote target.
35001 @value{GDBN} can use this information to autoconfigure for your
35002 target, or to warn you if you connect to an unsupported target.
35004 Here is a simple target description:
35007 <target version="1.0">
35008 <architecture>i386:x86-64</architecture>
35013 This minimal description only says that the target uses
35014 the x86-64 architecture.
35016 A target description has the following overall form, with [ ] marking
35017 optional elements and @dots{} marking repeatable elements. The elements
35018 are explained further below.
35021 <?xml version="1.0"?>
35022 <!DOCTYPE target SYSTEM "gdb-target.dtd">
35023 <target version="1.0">
35024 @r{[}@var{architecture}@r{]}
35025 @r{[}@var{osabi}@r{]}
35026 @r{[}@var{compatible}@r{]}
35027 @r{[}@var{feature}@dots{}@r{]}
35032 The description is generally insensitive to whitespace and line
35033 breaks, under the usual common-sense rules. The XML version
35034 declaration and document type declaration can generally be omitted
35035 (@value{GDBN} does not require them), but specifying them may be
35036 useful for XML validation tools. The @samp{version} attribute for
35037 @samp{<target>} may also be omitted, but we recommend
35038 including it; if future versions of @value{GDBN} use an incompatible
35039 revision of @file{gdb-target.dtd}, they will detect and report
35040 the version mismatch.
35042 @subsection Inclusion
35043 @cindex target descriptions, inclusion
35046 @cindex <xi:include>
35049 It can sometimes be valuable to split a target description up into
35050 several different annexes, either for organizational purposes, or to
35051 share files between different possible target descriptions. You can
35052 divide a description into multiple files by replacing any element of
35053 the target description with an inclusion directive of the form:
35056 <xi:include href="@var{document}"/>
35060 When @value{GDBN} encounters an element of this form, it will retrieve
35061 the named XML @var{document}, and replace the inclusion directive with
35062 the contents of that document. If the current description was read
35063 using @samp{qXfer}, then so will be the included document;
35064 @var{document} will be interpreted as the name of an annex. If the
35065 current description was read from a file, @value{GDBN} will look for
35066 @var{document} as a file in the same directory where it found the
35067 original description.
35069 @subsection Architecture
35070 @cindex <architecture>
35072 An @samp{<architecture>} element has this form:
35075 <architecture>@var{arch}</architecture>
35078 @var{arch} is one of the architectures from the set accepted by
35079 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
35082 @cindex @code{<osabi>}
35084 This optional field was introduced in @value{GDBN} version 7.0.
35085 Previous versions of @value{GDBN} ignore it.
35087 An @samp{<osabi>} element has this form:
35090 <osabi>@var{abi-name}</osabi>
35093 @var{abi-name} is an OS ABI name from the same selection accepted by
35094 @w{@code{set osabi}} (@pxref{ABI, ,Configuring the Current ABI}).
35096 @subsection Compatible Architecture
35097 @cindex @code{<compatible>}
35099 This optional field was introduced in @value{GDBN} version 7.0.
35100 Previous versions of @value{GDBN} ignore it.
35102 A @samp{<compatible>} element has this form:
35105 <compatible>@var{arch}</compatible>
35108 @var{arch} is one of the architectures from the set accepted by
35109 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
35111 A @samp{<compatible>} element is used to specify that the target
35112 is able to run binaries in some other than the main target architecture
35113 given by the @samp{<architecture>} element. For example, on the
35114 Cell Broadband Engine, the main architecture is @code{powerpc:common}
35115 or @code{powerpc:common64}, but the system is able to run binaries
35116 in the @code{spu} architecture as well. The way to describe this
35117 capability with @samp{<compatible>} is as follows:
35120 <architecture>powerpc:common</architecture>
35121 <compatible>spu</compatible>
35124 @subsection Features
35127 Each @samp{<feature>} describes some logical portion of the target
35128 system. Features are currently used to describe available CPU
35129 registers and the types of their contents. A @samp{<feature>} element
35133 <feature name="@var{name}">
35134 @r{[}@var{type}@dots{}@r{]}
35140 Each feature's name should be unique within the description. The name
35141 of a feature does not matter unless @value{GDBN} has some special
35142 knowledge of the contents of that feature; if it does, the feature
35143 should have its standard name. @xref{Standard Target Features}.
35147 Any register's value is a collection of bits which @value{GDBN} must
35148 interpret. The default interpretation is a two's complement integer,
35149 but other types can be requested by name in the register description.
35150 Some predefined types are provided by @value{GDBN} (@pxref{Predefined
35151 Target Types}), and the description can define additional composite types.
35153 Each type element must have an @samp{id} attribute, which gives
35154 a unique (within the containing @samp{<feature>}) name to the type.
35155 Types must be defined before they are used.
35158 Some targets offer vector registers, which can be treated as arrays
35159 of scalar elements. These types are written as @samp{<vector>} elements,
35160 specifying the array element type, @var{type}, and the number of elements,
35164 <vector id="@var{id}" type="@var{type}" count="@var{count}"/>
35168 If a register's value is usefully viewed in multiple ways, define it
35169 with a union type containing the useful representations. The
35170 @samp{<union>} element contains one or more @samp{<field>} elements,
35171 each of which has a @var{name} and a @var{type}:
35174 <union id="@var{id}">
35175 <field name="@var{name}" type="@var{type}"/>
35181 If a register's value is composed from several separate values, define
35182 it with a structure type. There are two forms of the @samp{<struct>}
35183 element; a @samp{<struct>} element must either contain only bitfields
35184 or contain no bitfields. If the structure contains only bitfields,
35185 its total size in bytes must be specified, each bitfield must have an
35186 explicit start and end, and bitfields are automatically assigned an
35187 integer type. The field's @var{start} should be less than or
35188 equal to its @var{end}, and zero represents the least significant bit.
35191 <struct id="@var{id}" size="@var{size}">
35192 <field name="@var{name}" start="@var{start}" end="@var{end}"/>
35197 If the structure contains no bitfields, then each field has an
35198 explicit type, and no implicit padding is added.
35201 <struct id="@var{id}">
35202 <field name="@var{name}" type="@var{type}"/>
35208 If a register's value is a series of single-bit flags, define it with
35209 a flags type. The @samp{<flags>} element has an explicit @var{size}
35210 and contains one or more @samp{<field>} elements. Each field has a
35211 @var{name}, a @var{start}, and an @var{end}. Only single-bit flags
35215 <flags id="@var{id}" size="@var{size}">
35216 <field name="@var{name}" start="@var{start}" end="@var{end}"/>
35221 @subsection Registers
35224 Each register is represented as an element with this form:
35227 <reg name="@var{name}"
35228 bitsize="@var{size}"
35229 @r{[}regnum="@var{num}"@r{]}
35230 @r{[}save-restore="@var{save-restore}"@r{]}
35231 @r{[}type="@var{type}"@r{]}
35232 @r{[}group="@var{group}"@r{]}/>
35236 The components are as follows:
35241 The register's name; it must be unique within the target description.
35244 The register's size, in bits.
35247 The register's number. If omitted, a register's number is one greater
35248 than that of the previous register (either in the current feature or in
35249 a preceeding feature); the first register in the target description
35250 defaults to zero. This register number is used to read or write
35251 the register; e.g.@: it is used in the remote @code{p} and @code{P}
35252 packets, and registers appear in the @code{g} and @code{G} packets
35253 in order of increasing register number.
35256 Whether the register should be preserved across inferior function
35257 calls; this must be either @code{yes} or @code{no}. The default is
35258 @code{yes}, which is appropriate for most registers except for
35259 some system control registers; this is not related to the target's
35263 The type of the register. @var{type} may be a predefined type, a type
35264 defined in the current feature, or one of the special types @code{int}
35265 and @code{float}. @code{int} is an integer type of the correct size
35266 for @var{bitsize}, and @code{float} is a floating point type (in the
35267 architecture's normal floating point format) of the correct size for
35268 @var{bitsize}. The default is @code{int}.
35271 The register group to which this register belongs. @var{group} must
35272 be either @code{general}, @code{float}, or @code{vector}. If no
35273 @var{group} is specified, @value{GDBN} will not display the register
35274 in @code{info registers}.
35278 @node Predefined Target Types
35279 @section Predefined Target Types
35280 @cindex target descriptions, predefined types
35282 Type definitions in the self-description can build up composite types
35283 from basic building blocks, but can not define fundamental types. Instead,
35284 standard identifiers are provided by @value{GDBN} for the fundamental
35285 types. The currently supported types are:
35294 Signed integer types holding the specified number of bits.
35301 Unsigned integer types holding the specified number of bits.
35305 Pointers to unspecified code and data. The program counter and
35306 any dedicated return address register may be marked as code
35307 pointers; printing a code pointer converts it into a symbolic
35308 address. The stack pointer and any dedicated address registers
35309 may be marked as data pointers.
35312 Single precision IEEE floating point.
35315 Double precision IEEE floating point.
35318 The 12-byte extended precision format used by ARM FPA registers.
35321 The 10-byte extended precision format used by x87 registers.
35324 32bit @sc{eflags} register used by x86.
35327 32bit @sc{mxcsr} register used by x86.
35331 @node Standard Target Features
35332 @section Standard Target Features
35333 @cindex target descriptions, standard features
35335 A target description must contain either no registers or all the
35336 target's registers. If the description contains no registers, then
35337 @value{GDBN} will assume a default register layout, selected based on
35338 the architecture. If the description contains any registers, the
35339 default layout will not be used; the standard registers must be
35340 described in the target description, in such a way that @value{GDBN}
35341 can recognize them.
35343 This is accomplished by giving specific names to feature elements
35344 which contain standard registers. @value{GDBN} will look for features
35345 with those names and verify that they contain the expected registers;
35346 if any known feature is missing required registers, or if any required
35347 feature is missing, @value{GDBN} will reject the target
35348 description. You can add additional registers to any of the
35349 standard features --- @value{GDBN} will display them just as if
35350 they were added to an unrecognized feature.
35352 This section lists the known features and their expected contents.
35353 Sample XML documents for these features are included in the
35354 @value{GDBN} source tree, in the directory @file{gdb/features}.
35356 Names recognized by @value{GDBN} should include the name of the
35357 company or organization which selected the name, and the overall
35358 architecture to which the feature applies; so e.g.@: the feature
35359 containing ARM core registers is named @samp{org.gnu.gdb.arm.core}.
35361 The names of registers are not case sensitive for the purpose
35362 of recognizing standard features, but @value{GDBN} will only display
35363 registers using the capitalization used in the description.
35370 * PowerPC Features::
35375 @subsection ARM Features
35376 @cindex target descriptions, ARM features
35378 The @samp{org.gnu.gdb.arm.core} feature is required for ARM targets.
35379 It should contain registers @samp{r0} through @samp{r13}, @samp{sp},
35380 @samp{lr}, @samp{pc}, and @samp{cpsr}.
35382 The @samp{org.gnu.gdb.arm.fpa} feature is optional. If present, it
35383 should contain registers @samp{f0} through @samp{f7} and @samp{fps}.
35385 The @samp{org.gnu.gdb.xscale.iwmmxt} feature is optional. If present,
35386 it should contain at least registers @samp{wR0} through @samp{wR15} and
35387 @samp{wCGR0} through @samp{wCGR3}. The @samp{wCID}, @samp{wCon},
35388 @samp{wCSSF}, and @samp{wCASF} registers are optional.
35390 The @samp{org.gnu.gdb.arm.vfp} feature is optional. If present, it
35391 should contain at least registers @samp{d0} through @samp{d15}. If
35392 they are present, @samp{d16} through @samp{d31} should also be included.
35393 @value{GDBN} will synthesize the single-precision registers from
35394 halves of the double-precision registers.
35396 The @samp{org.gnu.gdb.arm.neon} feature is optional. It does not
35397 need to contain registers; it instructs @value{GDBN} to display the
35398 VFP double-precision registers as vectors and to synthesize the
35399 quad-precision registers from pairs of double-precision registers.
35400 If this feature is present, @samp{org.gnu.gdb.arm.vfp} must also
35401 be present and include 32 double-precision registers.
35403 @node i386 Features
35404 @subsection i386 Features
35405 @cindex target descriptions, i386 features
35407 The @samp{org.gnu.gdb.i386.core} feature is required for i386/amd64
35408 targets. It should describe the following registers:
35412 @samp{eax} through @samp{edi} plus @samp{eip} for i386
35414 @samp{rax} through @samp{r15} plus @samp{rip} for amd64
35416 @samp{eflags}, @samp{cs}, @samp{ss}, @samp{ds}, @samp{es},
35417 @samp{fs}, @samp{gs}
35419 @samp{st0} through @samp{st7}
35421 @samp{fctrl}, @samp{fstat}, @samp{ftag}, @samp{fiseg}, @samp{fioff},
35422 @samp{foseg}, @samp{fooff} and @samp{fop}
35425 The register sets may be different, depending on the target.
35427 The @samp{org.gnu.gdb.i386.sse} feature is optional. It should
35428 describe registers:
35432 @samp{xmm0} through @samp{xmm7} for i386
35434 @samp{xmm0} through @samp{xmm15} for amd64
35439 The @samp{org.gnu.gdb.i386.avx} feature is optional and requires the
35440 @samp{org.gnu.gdb.i386.sse} feature. It should
35441 describe the upper 128 bits of @sc{ymm} registers:
35445 @samp{ymm0h} through @samp{ymm7h} for i386
35447 @samp{ymm0h} through @samp{ymm15h} for amd64
35451 The @samp{org.gnu.gdb.i386.linux} feature is optional. It should
35452 describe a single register, @samp{orig_eax}.
35454 @node MIPS Features
35455 @subsection MIPS Features
35456 @cindex target descriptions, MIPS features
35458 The @samp{org.gnu.gdb.mips.cpu} feature is required for MIPS targets.
35459 It should contain registers @samp{r0} through @samp{r31}, @samp{lo},
35460 @samp{hi}, and @samp{pc}. They may be 32-bit or 64-bit depending
35463 The @samp{org.gnu.gdb.mips.cp0} feature is also required. It should
35464 contain at least the @samp{status}, @samp{badvaddr}, and @samp{cause}
35465 registers. They may be 32-bit or 64-bit depending on the target.
35467 The @samp{org.gnu.gdb.mips.fpu} feature is currently required, though
35468 it may be optional in a future version of @value{GDBN}. It should
35469 contain registers @samp{f0} through @samp{f31}, @samp{fcsr}, and
35470 @samp{fir}. They may be 32-bit or 64-bit depending on the target.
35472 The @samp{org.gnu.gdb.mips.linux} feature is optional. It should
35473 contain a single register, @samp{restart}, which is used by the
35474 Linux kernel to control restartable syscalls.
35476 @node M68K Features
35477 @subsection M68K Features
35478 @cindex target descriptions, M68K features
35481 @item @samp{org.gnu.gdb.m68k.core}
35482 @itemx @samp{org.gnu.gdb.coldfire.core}
35483 @itemx @samp{org.gnu.gdb.fido.core}
35484 One of those features must be always present.
35485 The feature that is present determines which flavor of m68k is
35486 used. The feature that is present should contain registers
35487 @samp{d0} through @samp{d7}, @samp{a0} through @samp{a5}, @samp{fp},
35488 @samp{sp}, @samp{ps} and @samp{pc}.
35490 @item @samp{org.gnu.gdb.coldfire.fp}
35491 This feature is optional. If present, it should contain registers
35492 @samp{fp0} through @samp{fp7}, @samp{fpcontrol}, @samp{fpstatus} and
35496 @node PowerPC Features
35497 @subsection PowerPC Features
35498 @cindex target descriptions, PowerPC features
35500 The @samp{org.gnu.gdb.power.core} feature is required for PowerPC
35501 targets. It should contain registers @samp{r0} through @samp{r31},
35502 @samp{pc}, @samp{msr}, @samp{cr}, @samp{lr}, @samp{ctr}, and
35503 @samp{xer}. They may be 32-bit or 64-bit depending on the target.
35505 The @samp{org.gnu.gdb.power.fpu} feature is optional. It should
35506 contain registers @samp{f0} through @samp{f31} and @samp{fpscr}.
35508 The @samp{org.gnu.gdb.power.altivec} feature is optional. It should
35509 contain registers @samp{vr0} through @samp{vr31}, @samp{vscr},
35512 The @samp{org.gnu.gdb.power.vsx} feature is optional. It should
35513 contain registers @samp{vs0h} through @samp{vs31h}. @value{GDBN}
35514 will combine these registers with the floating point registers
35515 (@samp{f0} through @samp{f31}) and the altivec registers (@samp{vr0}
35516 through @samp{vr31}) to present the 128-bit wide registers @samp{vs0}
35517 through @samp{vs63}, the set of vector registers for POWER7.
35519 The @samp{org.gnu.gdb.power.spe} feature is optional. It should
35520 contain registers @samp{ev0h} through @samp{ev31h}, @samp{acc}, and
35521 @samp{spefscr}. SPE targets should provide 32-bit registers in
35522 @samp{org.gnu.gdb.power.core} and provide the upper halves in
35523 @samp{ev0h} through @samp{ev31h}. @value{GDBN} will combine
35524 these to present registers @samp{ev0} through @samp{ev31} to the
35527 @node Operating System Information
35528 @appendix Operating System Information
35529 @cindex operating system information
35535 Users of @value{GDBN} often wish to obtain information about the state of
35536 the operating system running on the target---for example the list of
35537 processes, or the list of open files. This section describes the
35538 mechanism that makes it possible. This mechanism is similar to the
35539 target features mechanism (@pxref{Target Descriptions}), but focuses
35540 on a different aspect of target.
35542 Operating system information is retrived from the target via the
35543 remote protocol, using @samp{qXfer} requests (@pxref{qXfer osdata
35544 read}). The object name in the request should be @samp{osdata}, and
35545 the @var{annex} identifies the data to be fetched.
35548 @appendixsection Process list
35549 @cindex operating system information, process list
35551 When requesting the process list, the @var{annex} field in the
35552 @samp{qXfer} request should be @samp{processes}. The returned data is
35553 an XML document. The formal syntax of this document is defined in
35554 @file{gdb/features/osdata.dtd}.
35556 An example document is:
35559 <?xml version="1.0"?>
35560 <!DOCTYPE target SYSTEM "osdata.dtd">
35561 <osdata type="processes">
35563 <column name="pid">1</column>
35564 <column name="user">root</column>
35565 <column name="command">/sbin/init</column>
35566 <column name="cores">1,2,3</column>
35571 Each item should include a column whose name is @samp{pid}. The value
35572 of that column should identify the process on the target. The
35573 @samp{user} and @samp{command} columns are optional, and will be
35574 displayed by @value{GDBN}. The @samp{cores} column, if present,
35575 should contain a comma-separated list of cores that this process
35576 is running on. Target may provide additional columns,
35577 which @value{GDBN} currently ignores.
35581 @node GNU Free Documentation License
35582 @appendix GNU Free Documentation License
35591 % I think something like @colophon should be in texinfo. In the
35593 \long\def\colophon{\hbox to0pt{}\vfill
35594 \centerline{The body of this manual is set in}
35595 \centerline{\fontname\tenrm,}
35596 \centerline{with headings in {\bf\fontname\tenbf}}
35597 \centerline{and examples in {\tt\fontname\tentt}.}
35598 \centerline{{\it\fontname\tenit\/},}
35599 \centerline{{\bf\fontname\tenbf}, and}
35600 \centerline{{\sl\fontname\tensl\/}}
35601 \centerline{are used for emphasis.}\vfill}
35603 % Blame: doc@cygnus.com, 1991.