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, sets unlimited
1035 terminal width and height @pxref{Screen Size}, and acts as if @kbd{set confirm
1036 off} were in 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}. Note that the inferior's entry still stays on the list
2485 of inferiors shown by @code{info inferiors}, but its Description will
2488 @kindex kill inferior @var{infno}
2489 @item kill inferior @var{infno}
2490 Kill the inferior identified by @value{GDBN} inferior number
2491 @var{infno}. Note that the inferior's entry still stays on the list
2492 of inferiors shown by @code{info inferiors}, but its Description will
2496 After the successful completion of a command such as @code{detach},
2497 @code{detach inferior}, @code{kill} or @code{kill inferior}, or after
2498 a normal process exit, the inferior is still valid and listed with
2499 @code{info inferiors}, ready to be restarted.
2502 To be notified when inferiors are started or exit under @value{GDBN}'s
2503 control use @w{@code{set print inferior-events}}:
2506 @kindex set print inferior-events
2507 @cindex print messages on inferior start and exit
2508 @item set print inferior-events
2509 @itemx set print inferior-events on
2510 @itemx set print inferior-events off
2511 The @code{set print inferior-events} command allows you to enable or
2512 disable printing of messages when @value{GDBN} notices that new
2513 inferiors have started or that inferiors have exited or have been
2514 detached. By default, these messages will not be printed.
2516 @kindex show print inferior-events
2517 @item show print inferior-events
2518 Show whether messages will be printed when @value{GDBN} detects that
2519 inferiors have started, exited or have been detached.
2522 Many commands will work the same with multiple programs as with a
2523 single program: e.g., @code{print myglobal} will simply display the
2524 value of @code{myglobal} in the current inferior.
2527 Occasionaly, when debugging @value{GDBN} itself, it may be useful to
2528 get more info about the relationship of inferiors, programs, address
2529 spaces in a debug session. You can do that with the @w{@code{maint
2530 info program-spaces}} command.
2533 @kindex maint info program-spaces
2534 @item maint info program-spaces
2535 Print a list of all program spaces currently being managed by
2538 @value{GDBN} displays for each program space (in this order):
2542 the program space number assigned by @value{GDBN}
2545 the name of the executable loaded into the program space, with e.g.,
2546 the @code{file} command.
2551 An asterisk @samp{*} preceding the @value{GDBN} program space number
2552 indicates the current program space.
2554 In addition, below each program space line, @value{GDBN} prints extra
2555 information that isn't suitable to display in tabular form. For
2556 example, the list of inferiors bound to the program space.
2559 (@value{GDBP}) maint info program-spaces
2562 Bound inferiors: ID 1 (process 21561)
2566 Here we can see that no inferior is running the program @code{hello},
2567 while @code{process 21561} is running the program @code{goodbye}. On
2568 some targets, it is possible that multiple inferiors are bound to the
2569 same program space. The most common example is that of debugging both
2570 the parent and child processes of a @code{vfork} call. For example,
2573 (@value{GDBP}) maint info program-spaces
2576 Bound inferiors: ID 2 (process 18050), ID 1 (process 18045)
2579 Here, both inferior 2 and inferior 1 are running in the same program
2580 space as a result of inferior 1 having executed a @code{vfork} call.
2584 @section Debugging Programs with Multiple Threads
2586 @cindex threads of execution
2587 @cindex multiple threads
2588 @cindex switching threads
2589 In some operating systems, such as HP-UX and Solaris, a single program
2590 may have more than one @dfn{thread} of execution. The precise semantics
2591 of threads differ from one operating system to another, but in general
2592 the threads of a single program are akin to multiple processes---except
2593 that they share one address space (that is, they can all examine and
2594 modify the same variables). On the other hand, each thread has its own
2595 registers and execution stack, and perhaps private memory.
2597 @value{GDBN} provides these facilities for debugging multi-thread
2601 @item automatic notification of new threads
2602 @item @samp{thread @var{threadno}}, a command to switch among threads
2603 @item @samp{info threads}, a command to inquire about existing threads
2604 @item @samp{thread apply [@var{threadno}] [@var{all}] @var{args}},
2605 a command to apply a command to a list of threads
2606 @item thread-specific breakpoints
2607 @item @samp{set print thread-events}, which controls printing of
2608 messages on thread start and exit.
2609 @item @samp{set libthread-db-search-path @var{path}}, which lets
2610 the user specify which @code{libthread_db} to use if the default choice
2611 isn't compatible with the program.
2615 @emph{Warning:} These facilities are not yet available on every
2616 @value{GDBN} configuration where the operating system supports threads.
2617 If your @value{GDBN} does not support threads, these commands have no
2618 effect. For example, a system without thread support shows no output
2619 from @samp{info threads}, and always rejects the @code{thread} command,
2623 (@value{GDBP}) info threads
2624 (@value{GDBP}) thread 1
2625 Thread ID 1 not known. Use the "info threads" command to
2626 see the IDs of currently known threads.
2628 @c FIXME to implementors: how hard would it be to say "sorry, this GDB
2629 @c doesn't support threads"?
2632 @cindex focus of debugging
2633 @cindex current thread
2634 The @value{GDBN} thread debugging facility allows you to observe all
2635 threads while your program runs---but whenever @value{GDBN} takes
2636 control, one thread in particular is always the focus of debugging.
2637 This thread is called the @dfn{current thread}. Debugging commands show
2638 program information from the perspective of the current thread.
2640 @cindex @code{New} @var{systag} message
2641 @cindex thread identifier (system)
2642 @c FIXME-implementors!! It would be more helpful if the [New...] message
2643 @c included GDB's numeric thread handle, so you could just go to that
2644 @c thread without first checking `info threads'.
2645 Whenever @value{GDBN} detects a new thread in your program, it displays
2646 the target system's identification for the thread with a message in the
2647 form @samp{[New @var{systag}]}. @var{systag} is a thread identifier
2648 whose form varies depending on the particular system. For example, on
2649 @sc{gnu}/Linux, you might see
2652 [New Thread 46912507313328 (LWP 25582)]
2656 when @value{GDBN} notices a new thread. In contrast, on an SGI system,
2657 the @var{systag} is simply something like @samp{process 368}, with no
2660 @c FIXME!! (1) Does the [New...] message appear even for the very first
2661 @c thread of a program, or does it only appear for the
2662 @c second---i.e.@: when it becomes obvious we have a multithread
2664 @c (2) *Is* there necessarily a first thread always? Or do some
2665 @c multithread systems permit starting a program with multiple
2666 @c threads ab initio?
2668 @cindex thread number
2669 @cindex thread identifier (GDB)
2670 For debugging purposes, @value{GDBN} associates its own thread
2671 number---always a single integer---with each thread in your program.
2674 @kindex info threads
2676 Display a summary of all threads currently in your
2677 program. @value{GDBN} displays for each thread (in this order):
2681 the thread number assigned by @value{GDBN}
2684 the target system's thread identifier (@var{systag})
2687 the current stack frame summary for that thread
2691 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2692 indicates the current thread.
2696 @c end table here to get a little more width for example
2699 (@value{GDBP}) info threads
2700 3 process 35 thread 27 0x34e5 in sigpause ()
2701 2 process 35 thread 23 0x34e5 in sigpause ()
2702 * 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
2708 @cindex debugging multithreaded programs (on HP-UX)
2709 @cindex thread identifier (GDB), on HP-UX
2710 For debugging purposes, @value{GDBN} associates its own thread
2711 number---a small integer assigned in thread-creation order---with each
2712 thread in your program.
2714 @cindex @code{New} @var{systag} message, on HP-UX
2715 @cindex thread identifier (system), on HP-UX
2716 @c FIXME-implementors!! It would be more helpful if the [New...] message
2717 @c included GDB's numeric thread handle, so you could just go to that
2718 @c thread without first checking `info threads'.
2719 Whenever @value{GDBN} detects a new thread in your program, it displays
2720 both @value{GDBN}'s thread number and the target system's identification for the thread with a message in the
2721 form @samp{[New @var{systag}]}. @var{systag} is a thread identifier
2722 whose form varies depending on the particular system. For example, on
2726 [New thread 2 (system thread 26594)]
2730 when @value{GDBN} notices a new thread.
2733 @kindex info threads (HP-UX)
2735 Display a summary of all threads currently in your
2736 program. @value{GDBN} displays for each thread (in this order):
2739 @item the thread number assigned by @value{GDBN}
2741 @item the target system's thread identifier (@var{systag})
2743 @item the current stack frame summary for that thread
2747 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2748 indicates the current thread.
2752 @c end table here to get a little more width for example
2755 (@value{GDBP}) info threads
2756 * 3 system thread 26607 worker (wptr=0x7b09c318 "@@") \@*
2758 2 system thread 26606 0x7b0030d8 in __ksleep () \@*
2759 from /usr/lib/libc.2
2760 1 system thread 27905 0x7b003498 in _brk () \@*
2761 from /usr/lib/libc.2
2764 On Solaris, you can display more information about user threads with a
2765 Solaris-specific command:
2768 @item maint info sol-threads
2769 @kindex maint info sol-threads
2770 @cindex thread info (Solaris)
2771 Display info on Solaris user threads.
2775 @kindex thread @var{threadno}
2776 @item thread @var{threadno}
2777 Make thread number @var{threadno} the current thread. The command
2778 argument @var{threadno} is the internal @value{GDBN} thread number, as
2779 shown in the first field of the @samp{info threads} display.
2780 @value{GDBN} responds by displaying the system identifier of the thread
2781 you selected, and its current stack frame summary:
2784 @c FIXME!! This example made up; find a @value{GDBN} w/threads and get real one
2785 (@value{GDBP}) thread 2
2786 [Switching to process 35 thread 23]
2787 0x34e5 in sigpause ()
2791 As with the @samp{[New @dots{}]} message, the form of the text after
2792 @samp{Switching to} depends on your system's conventions for identifying
2795 @vindex $_thread@r{, convenience variable}
2796 The debugger convenience variable @samp{$_thread} contains the number
2797 of the current thread. You may find this useful in writing breakpoint
2798 conditional expressions, command scripts, and so forth. See
2799 @xref{Convenience Vars,, Convenience Variables}, for general
2800 information on convenience variables.
2802 @kindex thread apply
2803 @cindex apply command to several threads
2804 @item thread apply [@var{threadno}] [@var{all}] @var{command}
2805 The @code{thread apply} command allows you to apply the named
2806 @var{command} to one or more threads. Specify the numbers of the
2807 threads that you want affected with the command argument
2808 @var{threadno}. It can be a single thread number, one of the numbers
2809 shown in the first field of the @samp{info threads} display; or it
2810 could be a range of thread numbers, as in @code{2-4}. To apply a
2811 command to all threads, type @kbd{thread apply all @var{command}}.
2813 @kindex set print thread-events
2814 @cindex print messages on thread start and exit
2815 @item set print thread-events
2816 @itemx set print thread-events on
2817 @itemx set print thread-events off
2818 The @code{set print thread-events} command allows you to enable or
2819 disable printing of messages when @value{GDBN} notices that new threads have
2820 started or that threads have exited. By default, these messages will
2821 be printed if detection of these events is supported by the target.
2822 Note that these messages cannot be disabled on all targets.
2824 @kindex show print thread-events
2825 @item show print thread-events
2826 Show whether messages will be printed when @value{GDBN} detects that threads
2827 have started and exited.
2830 @xref{Thread Stops,,Stopping and Starting Multi-thread Programs}, for
2831 more information about how @value{GDBN} behaves when you stop and start
2832 programs with multiple threads.
2834 @xref{Set Watchpoints,,Setting Watchpoints}, for information about
2835 watchpoints in programs with multiple threads.
2838 @kindex set libthread-db-search-path
2839 @cindex search path for @code{libthread_db}
2840 @item set libthread-db-search-path @r{[}@var{path}@r{]}
2841 If this variable is set, @var{path} is a colon-separated list of
2842 directories @value{GDBN} will use to search for @code{libthread_db}.
2843 If you omit @var{path}, @samp{libthread-db-search-path} will be reset to
2846 On @sc{gnu}/Linux and Solaris systems, @value{GDBN} uses a ``helper''
2847 @code{libthread_db} library to obtain information about threads in the
2848 inferior process. @value{GDBN} will use @samp{libthread-db-search-path}
2849 to find @code{libthread_db}. If that fails, @value{GDBN} will continue
2850 with default system shared library directories, and finally the directory
2851 from which @code{libpthread} was loaded in the inferior process.
2853 For any @code{libthread_db} library @value{GDBN} finds in above directories,
2854 @value{GDBN} attempts to initialize it with the current inferior process.
2855 If this initialization fails (which could happen because of a version
2856 mismatch between @code{libthread_db} and @code{libpthread}), @value{GDBN}
2857 will unload @code{libthread_db}, and continue with the next directory.
2858 If none of @code{libthread_db} libraries initialize successfully,
2859 @value{GDBN} will issue a warning and thread debugging will be disabled.
2861 Setting @code{libthread-db-search-path} is currently implemented
2862 only on some platforms.
2864 @kindex show libthread-db-search-path
2865 @item show libthread-db-search-path
2866 Display current libthread_db search path.
2868 @kindex set debug libthread-db
2869 @kindex show debug libthread-db
2870 @cindex debugging @code{libthread_db}
2871 @item set debug libthread-db
2872 @itemx show debug libthread-db
2873 Turns on or off display of @code{libthread_db}-related events.
2874 Use @code{1} to enable, @code{0} to disable.
2878 @section Debugging Forks
2880 @cindex fork, debugging programs which call
2881 @cindex multiple processes
2882 @cindex processes, multiple
2883 On most systems, @value{GDBN} has no special support for debugging
2884 programs which create additional processes using the @code{fork}
2885 function. When a program forks, @value{GDBN} will continue to debug the
2886 parent process and the child process will run unimpeded. If you have
2887 set a breakpoint in any code which the child then executes, the child
2888 will get a @code{SIGTRAP} signal which (unless it catches the signal)
2889 will cause it to terminate.
2891 However, if you want to debug the child process there is a workaround
2892 which isn't too painful. Put a call to @code{sleep} in the code which
2893 the child process executes after the fork. It may be useful to sleep
2894 only if a certain environment variable is set, or a certain file exists,
2895 so that the delay need not occur when you don't want to run @value{GDBN}
2896 on the child. While the child is sleeping, use the @code{ps} program to
2897 get its process ID. Then tell @value{GDBN} (a new invocation of
2898 @value{GDBN} if you are also debugging the parent process) to attach to
2899 the child process (@pxref{Attach}). From that point on you can debug
2900 the child process just like any other process which you attached to.
2902 On some systems, @value{GDBN} provides support for debugging programs that
2903 create additional processes using the @code{fork} or @code{vfork} functions.
2904 Currently, the only platforms with this feature are HP-UX (11.x and later
2905 only?) and @sc{gnu}/Linux (kernel version 2.5.60 and later).
2907 By default, when a program forks, @value{GDBN} will continue to debug
2908 the parent process and the child process will run unimpeded.
2910 If you want to follow the child process instead of the parent process,
2911 use the command @w{@code{set follow-fork-mode}}.
2914 @kindex set follow-fork-mode
2915 @item set follow-fork-mode @var{mode}
2916 Set the debugger response to a program call of @code{fork} or
2917 @code{vfork}. A call to @code{fork} or @code{vfork} creates a new
2918 process. The @var{mode} argument can be:
2922 The original process is debugged after a fork. The child process runs
2923 unimpeded. This is the default.
2926 The new process is debugged after a fork. The parent process runs
2931 @kindex show follow-fork-mode
2932 @item show follow-fork-mode
2933 Display the current debugger response to a @code{fork} or @code{vfork} call.
2936 @cindex debugging multiple processes
2937 On Linux, if you want to debug both the parent and child processes, use the
2938 command @w{@code{set detach-on-fork}}.
2941 @kindex set detach-on-fork
2942 @item set detach-on-fork @var{mode}
2943 Tells gdb whether to detach one of the processes after a fork, or
2944 retain debugger control over them both.
2948 The child process (or parent process, depending on the value of
2949 @code{follow-fork-mode}) will be detached and allowed to run
2950 independently. This is the default.
2953 Both processes will be held under the control of @value{GDBN}.
2954 One process (child or parent, depending on the value of
2955 @code{follow-fork-mode}) is debugged as usual, while the other
2960 @kindex show detach-on-fork
2961 @item show detach-on-fork
2962 Show whether detach-on-fork mode is on/off.
2965 If you choose to set @samp{detach-on-fork} mode off, then @value{GDBN}
2966 will retain control of all forked processes (including nested forks).
2967 You can list the forked processes under the control of @value{GDBN} by
2968 using the @w{@code{info inferiors}} command, and switch from one fork
2969 to another by using the @code{inferior} command (@pxref{Inferiors and
2970 Programs, ,Debugging Multiple Inferiors and Programs}).
2972 To quit debugging one of the forked processes, you can either detach
2973 from it by using the @w{@code{detach inferior}} command (allowing it
2974 to run independently), or kill it using the @w{@code{kill inferior}}
2975 command. @xref{Inferiors and Programs, ,Debugging Multiple Inferiors
2978 If you ask to debug a child process and a @code{vfork} is followed by an
2979 @code{exec}, @value{GDBN} executes the new target up to the first
2980 breakpoint in the new target. If you have a breakpoint set on
2981 @code{main} in your original program, the breakpoint will also be set on
2982 the child process's @code{main}.
2984 On some systems, when a child process is spawned by @code{vfork}, you
2985 cannot debug the child or parent until an @code{exec} call completes.
2987 If you issue a @code{run} command to @value{GDBN} after an @code{exec}
2988 call executes, the new target restarts. To restart the parent
2989 process, use the @code{file} command with the parent executable name
2990 as its argument. By default, after an @code{exec} call executes,
2991 @value{GDBN} discards the symbols of the previous executable image.
2992 You can change this behaviour with the @w{@code{set follow-exec-mode}}
2996 @kindex set follow-exec-mode
2997 @item set follow-exec-mode @var{mode}
2999 Set debugger response to a program call of @code{exec}. An
3000 @code{exec} call replaces the program image of a process.
3002 @code{follow-exec-mode} can be:
3006 @value{GDBN} creates a new inferior and rebinds the process to this
3007 new inferior. The program the process was running before the
3008 @code{exec} call can be restarted afterwards by restarting the
3014 (@value{GDBP}) info inferiors
3016 Id Description Executable
3019 process 12020 is executing new program: prog2
3020 Program exited normally.
3021 (@value{GDBP}) info inferiors
3022 Id Description Executable
3028 @value{GDBN} keeps the process bound to the same inferior. The new
3029 executable image replaces the previous executable loaded in the
3030 inferior. Restarting the inferior after the @code{exec} call, with
3031 e.g., the @code{run} command, restarts the executable the process was
3032 running after the @code{exec} call. This is the default mode.
3037 (@value{GDBP}) info inferiors
3038 Id Description Executable
3041 process 12020 is executing new program: prog2
3042 Program exited normally.
3043 (@value{GDBP}) info inferiors
3044 Id Description Executable
3051 You can use the @code{catch} command to make @value{GDBN} stop whenever
3052 a @code{fork}, @code{vfork}, or @code{exec} call is made. @xref{Set
3053 Catchpoints, ,Setting Catchpoints}.
3055 @node Checkpoint/Restart
3056 @section Setting a @emph{Bookmark} to Return to Later
3061 @cindex snapshot of a process
3062 @cindex rewind program state
3064 On certain operating systems@footnote{Currently, only
3065 @sc{gnu}/Linux.}, @value{GDBN} is able to save a @dfn{snapshot} of a
3066 program's state, called a @dfn{checkpoint}, and come back to it
3069 Returning to a checkpoint effectively undoes everything that has
3070 happened in the program since the @code{checkpoint} was saved. This
3071 includes changes in memory, registers, and even (within some limits)
3072 system state. Effectively, it is like going back in time to the
3073 moment when the checkpoint was saved.
3075 Thus, if you're stepping thru a program and you think you're
3076 getting close to the point where things go wrong, you can save
3077 a checkpoint. Then, if you accidentally go too far and miss
3078 the critical statement, instead of having to restart your program
3079 from the beginning, you can just go back to the checkpoint and
3080 start again from there.
3082 This can be especially useful if it takes a lot of time or
3083 steps to reach the point where you think the bug occurs.
3085 To use the @code{checkpoint}/@code{restart} method of debugging:
3090 Save a snapshot of the debugged program's current execution state.
3091 The @code{checkpoint} command takes no arguments, but each checkpoint
3092 is assigned a small integer id, similar to a breakpoint id.
3094 @kindex info checkpoints
3095 @item info checkpoints
3096 List the checkpoints that have been saved in the current debugging
3097 session. For each checkpoint, the following information will be
3104 @item Source line, or label
3107 @kindex restart @var{checkpoint-id}
3108 @item restart @var{checkpoint-id}
3109 Restore the program state that was saved as checkpoint number
3110 @var{checkpoint-id}. All program variables, registers, stack frames
3111 etc.@: will be returned to the values that they had when the checkpoint
3112 was saved. In essence, gdb will ``wind back the clock'' to the point
3113 in time when the checkpoint was saved.
3115 Note that breakpoints, @value{GDBN} variables, command history etc.
3116 are not affected by restoring a checkpoint. In general, a checkpoint
3117 only restores things that reside in the program being debugged, not in
3120 @kindex delete checkpoint @var{checkpoint-id}
3121 @item delete checkpoint @var{checkpoint-id}
3122 Delete the previously-saved checkpoint identified by @var{checkpoint-id}.
3126 Returning to a previously saved checkpoint will restore the user state
3127 of the program being debugged, plus a significant subset of the system
3128 (OS) state, including file pointers. It won't ``un-write'' data from
3129 a file, but it will rewind the file pointer to the previous location,
3130 so that the previously written data can be overwritten. For files
3131 opened in read mode, the pointer will also be restored so that the
3132 previously read data can be read again.
3134 Of course, characters that have been sent to a printer (or other
3135 external device) cannot be ``snatched back'', and characters received
3136 from eg.@: a serial device can be removed from internal program buffers,
3137 but they cannot be ``pushed back'' into the serial pipeline, ready to
3138 be received again. Similarly, the actual contents of files that have
3139 been changed cannot be restored (at this time).
3141 However, within those constraints, you actually can ``rewind'' your
3142 program to a previously saved point in time, and begin debugging it
3143 again --- and you can change the course of events so as to debug a
3144 different execution path this time.
3146 @cindex checkpoints and process id
3147 Finally, there is one bit of internal program state that will be
3148 different when you return to a checkpoint --- the program's process
3149 id. Each checkpoint will have a unique process id (or @var{pid}),
3150 and each will be different from the program's original @var{pid}.
3151 If your program has saved a local copy of its process id, this could
3152 potentially pose a problem.
3154 @subsection A Non-obvious Benefit of Using Checkpoints
3156 On some systems such as @sc{gnu}/Linux, address space randomization
3157 is performed on new processes for security reasons. This makes it
3158 difficult or impossible to set a breakpoint, or watchpoint, on an
3159 absolute address if you have to restart the program, since the
3160 absolute location of a symbol will change from one execution to the
3163 A checkpoint, however, is an @emph{identical} copy of a process.
3164 Therefore if you create a checkpoint at (eg.@:) the start of main,
3165 and simply return to that checkpoint instead of restarting the
3166 process, you can avoid the effects of address randomization and
3167 your symbols will all stay in the same place.
3170 @chapter Stopping and Continuing
3172 The principal purposes of using a debugger are so that you can stop your
3173 program before it terminates; or so that, if your program runs into
3174 trouble, you can investigate and find out why.
3176 Inside @value{GDBN}, your program may stop for any of several reasons,
3177 such as a signal, a breakpoint, or reaching a new line after a
3178 @value{GDBN} command such as @code{step}. You may then examine and
3179 change variables, set new breakpoints or remove old ones, and then
3180 continue execution. Usually, the messages shown by @value{GDBN} provide
3181 ample explanation of the status of your program---but you can also
3182 explicitly request this information at any time.
3185 @kindex info program
3187 Display information about the status of your program: whether it is
3188 running or not, what process it is, and why it stopped.
3192 * Breakpoints:: Breakpoints, watchpoints, and catchpoints
3193 * Continuing and Stepping:: Resuming execution
3195 * Thread Stops:: Stopping and starting multi-thread programs
3199 @section Breakpoints, Watchpoints, and Catchpoints
3202 A @dfn{breakpoint} makes your program stop whenever a certain point in
3203 the program is reached. For each breakpoint, you can add conditions to
3204 control in finer detail whether your program stops. You can set
3205 breakpoints with the @code{break} command and its variants (@pxref{Set
3206 Breaks, ,Setting Breakpoints}), to specify the place where your program
3207 should stop by line number, function name or exact address in the
3210 On some systems, you can set breakpoints in shared libraries before
3211 the executable is run. There is a minor limitation on HP-UX systems:
3212 you must wait until the executable is run in order to set breakpoints
3213 in shared library routines that are not called directly by the program
3214 (for example, routines that are arguments in a @code{pthread_create}
3218 @cindex data breakpoints
3219 @cindex memory tracing
3220 @cindex breakpoint on memory address
3221 @cindex breakpoint on variable modification
3222 A @dfn{watchpoint} is a special breakpoint that stops your program
3223 when the value of an expression changes. The expression may be a value
3224 of a variable, or it could involve values of one or more variables
3225 combined by operators, such as @samp{a + b}. This is sometimes called
3226 @dfn{data breakpoints}. You must use a different command to set
3227 watchpoints (@pxref{Set Watchpoints, ,Setting Watchpoints}), but aside
3228 from that, you can manage a watchpoint like any other breakpoint: you
3229 enable, disable, and delete both breakpoints and watchpoints using the
3232 You can arrange to have values from your program displayed automatically
3233 whenever @value{GDBN} stops at a breakpoint. @xref{Auto Display,,
3237 @cindex breakpoint on events
3238 A @dfn{catchpoint} is another special breakpoint that stops your program
3239 when a certain kind of event occurs, such as the throwing of a C@t{++}
3240 exception or the loading of a library. As with watchpoints, you use a
3241 different command to set a catchpoint (@pxref{Set Catchpoints, ,Setting
3242 Catchpoints}), but aside from that, you can manage a catchpoint like any
3243 other breakpoint. (To stop when your program receives a signal, use the
3244 @code{handle} command; see @ref{Signals, ,Signals}.)
3246 @cindex breakpoint numbers
3247 @cindex numbers for breakpoints
3248 @value{GDBN} assigns a number to each breakpoint, watchpoint, or
3249 catchpoint when you create it; these numbers are successive integers
3250 starting with one. In many of the commands for controlling various
3251 features of breakpoints you use the breakpoint number to say which
3252 breakpoint you want to change. Each breakpoint may be @dfn{enabled} or
3253 @dfn{disabled}; if disabled, it has no effect on your program until you
3256 @cindex breakpoint ranges
3257 @cindex ranges of breakpoints
3258 Some @value{GDBN} commands accept a range of breakpoints on which to
3259 operate. A breakpoint range is either a single breakpoint number, like
3260 @samp{5}, or two such numbers, in increasing order, separated by a
3261 hyphen, like @samp{5-7}. When a breakpoint range is given to a command,
3262 all breakpoints in that range are operated on.
3265 * Set Breaks:: Setting breakpoints
3266 * Set Watchpoints:: Setting watchpoints
3267 * Set Catchpoints:: Setting catchpoints
3268 * Delete Breaks:: Deleting breakpoints
3269 * Disabling:: Disabling breakpoints
3270 * Conditions:: Break conditions
3271 * Break Commands:: Breakpoint command lists
3272 * Save Breakpoints:: How to save breakpoints in a file
3273 * Error in Breakpoints:: ``Cannot insert breakpoints''
3274 * Breakpoint-related Warnings:: ``Breakpoint address adjusted...''
3278 @subsection Setting Breakpoints
3280 @c FIXME LMB what does GDB do if no code on line of breakpt?
3281 @c consider in particular declaration with/without initialization.
3283 @c FIXME 2 is there stuff on this already? break at fun start, already init?
3286 @kindex b @r{(@code{break})}
3287 @vindex $bpnum@r{, convenience variable}
3288 @cindex latest breakpoint
3289 Breakpoints are set with the @code{break} command (abbreviated
3290 @code{b}). The debugger convenience variable @samp{$bpnum} records the
3291 number of the breakpoint you've set most recently; see @ref{Convenience
3292 Vars,, Convenience Variables}, for a discussion of what you can do with
3293 convenience variables.
3296 @item break @var{location}
3297 Set a breakpoint at the given @var{location}, which can specify a
3298 function name, a line number, or an address of an instruction.
3299 (@xref{Specify Location}, for a list of all the possible ways to
3300 specify a @var{location}.) The breakpoint will stop your program just
3301 before it executes any of the code in the specified @var{location}.
3303 When using source languages that permit overloading of symbols, such as
3304 C@t{++}, a function name may refer to more than one possible place to break.
3305 @xref{Ambiguous Expressions,,Ambiguous Expressions}, for a discussion of
3308 It is also possible to insert a breakpoint that will stop the program
3309 only if a specific thread (@pxref{Thread-Specific Breakpoints})
3310 or a specific task (@pxref{Ada Tasks}) hits that breakpoint.
3313 When called without any arguments, @code{break} sets a breakpoint at
3314 the next instruction to be executed in the selected stack frame
3315 (@pxref{Stack, ,Examining the Stack}). In any selected frame but the
3316 innermost, this makes your program stop as soon as control
3317 returns to that frame. This is similar to the effect of a
3318 @code{finish} command in the frame inside the selected frame---except
3319 that @code{finish} does not leave an active breakpoint. If you use
3320 @code{break} without an argument in the innermost frame, @value{GDBN} stops
3321 the next time it reaches the current location; this may be useful
3324 @value{GDBN} normally ignores breakpoints when it resumes execution, until at
3325 least one instruction has been executed. If it did not do this, you
3326 would be unable to proceed past a breakpoint without first disabling the
3327 breakpoint. This rule applies whether or not the breakpoint already
3328 existed when your program stopped.
3330 @item break @dots{} if @var{cond}
3331 Set a breakpoint with condition @var{cond}; evaluate the expression
3332 @var{cond} each time the breakpoint is reached, and stop only if the
3333 value is nonzero---that is, if @var{cond} evaluates as true.
3334 @samp{@dots{}} stands for one of the possible arguments described
3335 above (or no argument) specifying where to break. @xref{Conditions,
3336 ,Break Conditions}, for more information on breakpoint conditions.
3339 @item tbreak @var{args}
3340 Set a breakpoint enabled only for one stop. @var{args} are the
3341 same as for the @code{break} command, and the breakpoint is set in the same
3342 way, but the breakpoint is automatically deleted after the first time your
3343 program stops there. @xref{Disabling, ,Disabling Breakpoints}.
3346 @cindex hardware breakpoints
3347 @item hbreak @var{args}
3348 Set a hardware-assisted breakpoint. @var{args} are the same as for the
3349 @code{break} command and the breakpoint is set in the same way, but the
3350 breakpoint requires hardware support and some target hardware may not
3351 have this support. The main purpose of this is EPROM/ROM code
3352 debugging, so you can set a breakpoint at an instruction without
3353 changing the instruction. This can be used with the new trap-generation
3354 provided by SPARClite DSU and most x86-based targets. These targets
3355 will generate traps when a program accesses some data or instruction
3356 address that is assigned to the debug registers. However the hardware
3357 breakpoint registers can take a limited number of breakpoints. For
3358 example, on the DSU, only two data breakpoints can be set at a time, and
3359 @value{GDBN} will reject this command if more than two are used. Delete
3360 or disable unused hardware breakpoints before setting new ones
3361 (@pxref{Disabling, ,Disabling Breakpoints}).
3362 @xref{Conditions, ,Break Conditions}.
3363 For remote targets, you can restrict the number of hardware
3364 breakpoints @value{GDBN} will use, see @ref{set remote
3365 hardware-breakpoint-limit}.
3368 @item thbreak @var{args}
3369 Set a hardware-assisted breakpoint enabled only for one stop. @var{args}
3370 are the same as for the @code{hbreak} command and the breakpoint is set in
3371 the same way. However, like the @code{tbreak} command,
3372 the breakpoint is automatically deleted after the
3373 first time your program stops there. Also, like the @code{hbreak}
3374 command, the breakpoint requires hardware support and some target hardware
3375 may not have this support. @xref{Disabling, ,Disabling Breakpoints}.
3376 See also @ref{Conditions, ,Break Conditions}.
3379 @cindex regular expression
3380 @cindex breakpoints at functions matching a regexp
3381 @cindex set breakpoints in many functions
3382 @item rbreak @var{regex}
3383 Set breakpoints on all functions matching the regular expression
3384 @var{regex}. This command sets an unconditional breakpoint on all
3385 matches, printing a list of all breakpoints it set. Once these
3386 breakpoints are set, they are treated just like the breakpoints set with
3387 the @code{break} command. You can delete them, disable them, or make
3388 them conditional the same way as any other breakpoint.
3390 The syntax of the regular expression is the standard one used with tools
3391 like @file{grep}. Note that this is different from the syntax used by
3392 shells, so for instance @code{foo*} matches all functions that include
3393 an @code{fo} followed by zero or more @code{o}s. There is an implicit
3394 @code{.*} leading and trailing the regular expression you supply, so to
3395 match only functions that begin with @code{foo}, use @code{^foo}.
3397 @cindex non-member C@t{++} functions, set breakpoint in
3398 When debugging C@t{++} programs, @code{rbreak} is useful for setting
3399 breakpoints on overloaded functions that are not members of any special
3402 @cindex set breakpoints on all functions
3403 The @code{rbreak} command can be used to set breakpoints in
3404 @strong{all} the functions in a program, like this:
3407 (@value{GDBP}) rbreak .
3410 @item rbreak @var{file}:@var{regex}
3411 If @code{rbreak} is called with a filename qualification, it limits
3412 the search for functions matching the given regular expression to the
3413 specified @var{file}. This can be used, for example, to set breakpoints on
3414 every function in a given file:
3417 (@value{GDBP}) rbreak file.c:.
3420 The colon separating the filename qualifier from the regex may
3421 optionally be surrounded by spaces.
3423 @kindex info breakpoints
3424 @cindex @code{$_} and @code{info breakpoints}
3425 @item info breakpoints @r{[}@var{n}@r{]}
3426 @itemx info break @r{[}@var{n}@r{]}
3427 Print a table of all breakpoints, watchpoints, and catchpoints set and
3428 not deleted. Optional argument @var{n} means print information only
3429 about the specified breakpoint (or watchpoint or catchpoint). For
3430 each breakpoint, following columns are printed:
3433 @item Breakpoint Numbers
3435 Breakpoint, watchpoint, or catchpoint.
3437 Whether the breakpoint is marked to be disabled or deleted when hit.
3438 @item Enabled or Disabled
3439 Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints
3440 that are not enabled.
3442 Where the breakpoint is in your program, as a memory address. For a
3443 pending breakpoint whose address is not yet known, this field will
3444 contain @samp{<PENDING>}. Such breakpoint won't fire until a shared
3445 library that has the symbol or line referred by breakpoint is loaded.
3446 See below for details. A breakpoint with several locations will
3447 have @samp{<MULTIPLE>} in this field---see below for details.
3449 Where the breakpoint is in the source for your program, as a file and
3450 line number. For a pending breakpoint, the original string passed to
3451 the breakpoint command will be listed as it cannot be resolved until
3452 the appropriate shared library is loaded in the future.
3456 If a breakpoint is conditional, @code{info break} shows the condition on
3457 the line following the affected breakpoint; breakpoint commands, if any,
3458 are listed after that. A pending breakpoint is allowed to have a condition
3459 specified for it. The condition is not parsed for validity until a shared
3460 library is loaded that allows the pending breakpoint to resolve to a
3464 @code{info break} with a breakpoint
3465 number @var{n} as argument lists only that breakpoint. The
3466 convenience variable @code{$_} and the default examining-address for
3467 the @code{x} command are set to the address of the last breakpoint
3468 listed (@pxref{Memory, ,Examining Memory}).
3471 @code{info break} displays a count of the number of times the breakpoint
3472 has been hit. This is especially useful in conjunction with the
3473 @code{ignore} command. You can ignore a large number of breakpoint
3474 hits, look at the breakpoint info to see how many times the breakpoint
3475 was hit, and then run again, ignoring one less than that number. This
3476 will get you quickly to the last hit of that breakpoint.
3479 @value{GDBN} allows you to set any number of breakpoints at the same place in
3480 your program. There is nothing silly or meaningless about this. When
3481 the breakpoints are conditional, this is even useful
3482 (@pxref{Conditions, ,Break Conditions}).
3484 @cindex multiple locations, breakpoints
3485 @cindex breakpoints, multiple locations
3486 It is possible that a breakpoint corresponds to several locations
3487 in your program. Examples of this situation are:
3491 For a C@t{++} constructor, the @value{NGCC} compiler generates several
3492 instances of the function body, used in different cases.
3495 For a C@t{++} template function, a given line in the function can
3496 correspond to any number of instantiations.
3499 For an inlined function, a given source line can correspond to
3500 several places where that function is inlined.
3503 In all those cases, @value{GDBN} will insert a breakpoint at all
3504 the relevant locations@footnote{
3505 As of this writing, multiple-location breakpoints work only if there's
3506 line number information for all the locations. This means that they
3507 will generally not work in system libraries, unless you have debug
3508 info with line numbers for them.}.
3510 A breakpoint with multiple locations is displayed in the breakpoint
3511 table using several rows---one header row, followed by one row for
3512 each breakpoint location. The header row has @samp{<MULTIPLE>} in the
3513 address column. The rows for individual locations contain the actual
3514 addresses for locations, and show the functions to which those
3515 locations belong. The number column for a location is of the form
3516 @var{breakpoint-number}.@var{location-number}.
3521 Num Type Disp Enb Address What
3522 1 breakpoint keep y <MULTIPLE>
3524 breakpoint already hit 1 time
3525 1.1 y 0x080486a2 in void foo<int>() at t.cc:8
3526 1.2 y 0x080486ca in void foo<double>() at t.cc:8
3529 Each location can be individually enabled or disabled by passing
3530 @var{breakpoint-number}.@var{location-number} as argument to the
3531 @code{enable} and @code{disable} commands. Note that you cannot
3532 delete the individual locations from the list, you can only delete the
3533 entire list of locations that belong to their parent breakpoint (with
3534 the @kbd{delete @var{num}} command, where @var{num} is the number of
3535 the parent breakpoint, 1 in the above example). Disabling or enabling
3536 the parent breakpoint (@pxref{Disabling}) affects all of the locations
3537 that belong to that breakpoint.
3539 @cindex pending breakpoints
3540 It's quite common to have a breakpoint inside a shared library.
3541 Shared libraries can be loaded and unloaded explicitly,
3542 and possibly repeatedly, as the program is executed. To support
3543 this use case, @value{GDBN} updates breakpoint locations whenever
3544 any shared library is loaded or unloaded. Typically, you would
3545 set a breakpoint in a shared library at the beginning of your
3546 debugging session, when the library is not loaded, and when the
3547 symbols from the library are not available. When you try to set
3548 breakpoint, @value{GDBN} will ask you if you want to set
3549 a so called @dfn{pending breakpoint}---breakpoint whose address
3550 is not yet resolved.
3552 After the program is run, whenever a new shared library is loaded,
3553 @value{GDBN} reevaluates all the breakpoints. When a newly loaded
3554 shared library contains the symbol or line referred to by some
3555 pending breakpoint, that breakpoint is resolved and becomes an
3556 ordinary breakpoint. When a library is unloaded, all breakpoints
3557 that refer to its symbols or source lines become pending again.
3559 This logic works for breakpoints with multiple locations, too. For
3560 example, if you have a breakpoint in a C@t{++} template function, and
3561 a newly loaded shared library has an instantiation of that template,
3562 a new location is added to the list of locations for the breakpoint.
3564 Except for having unresolved address, pending breakpoints do not
3565 differ from regular breakpoints. You can set conditions or commands,
3566 enable and disable them and perform other breakpoint operations.
3568 @value{GDBN} provides some additional commands for controlling what
3569 happens when the @samp{break} command cannot resolve breakpoint
3570 address specification to an address:
3572 @kindex set breakpoint pending
3573 @kindex show breakpoint pending
3575 @item set breakpoint pending auto
3576 This is the default behavior. When @value{GDBN} cannot find the breakpoint
3577 location, it queries you whether a pending breakpoint should be created.
3579 @item set breakpoint pending on
3580 This indicates that an unrecognized breakpoint location should automatically
3581 result in a pending breakpoint being created.
3583 @item set breakpoint pending off
3584 This indicates that pending breakpoints are not to be created. Any
3585 unrecognized breakpoint location results in an error. This setting does
3586 not affect any pending breakpoints previously created.
3588 @item show breakpoint pending
3589 Show the current behavior setting for creating pending breakpoints.
3592 The settings above only affect the @code{break} command and its
3593 variants. Once breakpoint is set, it will be automatically updated
3594 as shared libraries are loaded and unloaded.
3596 @cindex automatic hardware breakpoints
3597 For some targets, @value{GDBN} can automatically decide if hardware or
3598 software breakpoints should be used, depending on whether the
3599 breakpoint address is read-only or read-write. This applies to
3600 breakpoints set with the @code{break} command as well as to internal
3601 breakpoints set by commands like @code{next} and @code{finish}. For
3602 breakpoints set with @code{hbreak}, @value{GDBN} will always use hardware
3605 You can control this automatic behaviour with the following commands::
3607 @kindex set breakpoint auto-hw
3608 @kindex show breakpoint auto-hw
3610 @item set breakpoint auto-hw on
3611 This is the default behavior. When @value{GDBN} sets a breakpoint, it
3612 will try to use the target memory map to decide if software or hardware
3613 breakpoint must be used.
3615 @item set breakpoint auto-hw off
3616 This indicates @value{GDBN} should not automatically select breakpoint
3617 type. If the target provides a memory map, @value{GDBN} will warn when
3618 trying to set software breakpoint at a read-only address.
3621 @value{GDBN} normally implements breakpoints by replacing the program code
3622 at the breakpoint address with a special instruction, which, when
3623 executed, given control to the debugger. By default, the program
3624 code is so modified only when the program is resumed. As soon as
3625 the program stops, @value{GDBN} restores the original instructions. This
3626 behaviour guards against leaving breakpoints inserted in the
3627 target should gdb abrubptly disconnect. However, with slow remote
3628 targets, inserting and removing breakpoint can reduce the performance.
3629 This behavior can be controlled with the following commands::
3631 @kindex set breakpoint always-inserted
3632 @kindex show breakpoint always-inserted
3634 @item set breakpoint always-inserted off
3635 All breakpoints, including newly added by the user, are inserted in
3636 the target only when the target is resumed. All breakpoints are
3637 removed from the target when it stops.
3639 @item set breakpoint always-inserted on
3640 Causes all breakpoints to be inserted in the target at all times. If
3641 the user adds a new breakpoint, or changes an existing breakpoint, the
3642 breakpoints in the target are updated immediately. A breakpoint is
3643 removed from the target only when breakpoint itself is removed.
3645 @cindex non-stop mode, and @code{breakpoint always-inserted}
3646 @item set breakpoint always-inserted auto
3647 This is the default mode. If @value{GDBN} is controlling the inferior
3648 in non-stop mode (@pxref{Non-Stop Mode}), gdb behaves as if
3649 @code{breakpoint always-inserted} mode is on. If @value{GDBN} is
3650 controlling the inferior in all-stop mode, @value{GDBN} behaves as if
3651 @code{breakpoint always-inserted} mode is off.
3654 @cindex negative breakpoint numbers
3655 @cindex internal @value{GDBN} breakpoints
3656 @value{GDBN} itself sometimes sets breakpoints in your program for
3657 special purposes, such as proper handling of @code{longjmp} (in C
3658 programs). These internal breakpoints are assigned negative numbers,
3659 starting with @code{-1}; @samp{info breakpoints} does not display them.
3660 You can see these breakpoints with the @value{GDBN} maintenance command
3661 @samp{maint info breakpoints} (@pxref{maint info breakpoints}).
3664 @node Set Watchpoints
3665 @subsection Setting Watchpoints
3667 @cindex setting watchpoints
3668 You can use a watchpoint to stop execution whenever the value of an
3669 expression changes, without having to predict a particular place where
3670 this may happen. (This is sometimes called a @dfn{data breakpoint}.)
3671 The expression may be as simple as the value of a single variable, or
3672 as complex as many variables combined by operators. Examples include:
3676 A reference to the value of a single variable.
3679 An address cast to an appropriate data type. For example,
3680 @samp{*(int *)0x12345678} will watch a 4-byte region at the specified
3681 address (assuming an @code{int} occupies 4 bytes).
3684 An arbitrarily complex expression, such as @samp{a*b + c/d}. The
3685 expression can use any operators valid in the program's native
3686 language (@pxref{Languages}).
3689 You can set a watchpoint on an expression even if the expression can
3690 not be evaluated yet. For instance, you can set a watchpoint on
3691 @samp{*global_ptr} before @samp{global_ptr} is initialized.
3692 @value{GDBN} will stop when your program sets @samp{global_ptr} and
3693 the expression produces a valid value. If the expression becomes
3694 valid in some other way than changing a variable (e.g.@: if the memory
3695 pointed to by @samp{*global_ptr} becomes readable as the result of a
3696 @code{malloc} call), @value{GDBN} may not stop until the next time
3697 the expression changes.
3699 @cindex software watchpoints
3700 @cindex hardware watchpoints
3701 Depending on your system, watchpoints may be implemented in software or
3702 hardware. @value{GDBN} does software watchpointing by single-stepping your
3703 program and testing the variable's value each time, which is hundreds of
3704 times slower than normal execution. (But this may still be worth it, to
3705 catch errors where you have no clue what part of your program is the
3708 On some systems, such as HP-UX, PowerPC, @sc{gnu}/Linux and most other
3709 x86-based targets, @value{GDBN} includes support for hardware
3710 watchpoints, which do not slow down the running of your program.
3714 @item watch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]}
3715 Set a watchpoint for an expression. @value{GDBN} will break when the
3716 expression @var{expr} is written into by the program and its value
3717 changes. The simplest (and the most popular) use of this command is
3718 to watch the value of a single variable:
3721 (@value{GDBP}) watch foo
3724 If the command includes a @code{@r{[}thread @var{threadnum}@r{]}}
3725 clause, @value{GDBN} breaks only when the thread identified by
3726 @var{threadnum} changes the value of @var{expr}. If any other threads
3727 change the value of @var{expr}, @value{GDBN} will not break. Note
3728 that watchpoints restricted to a single thread in this way only work
3729 with Hardware Watchpoints.
3731 Ordinarily a watchpoint respects the scope of variables in @var{expr}
3732 (see below). The @code{-location} argument tells @value{GDBN} to
3733 instead watch the memory referred to by @var{expr}. In this case,
3734 @value{GDBN} will evaluate @var{expr}, take the address of the result,
3735 and watch the memory at that address. The type of the result is used
3736 to determine the size of the watched memory. If the expression's
3737 result does not have an address, then @value{GDBN} will print an
3741 @item rwatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]}
3742 Set a watchpoint that will break when the value of @var{expr} is read
3746 @item awatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]}
3747 Set a watchpoint that will break when @var{expr} is either read from
3748 or written into by the program.
3750 @kindex info watchpoints @r{[}@var{n}@r{]}
3751 @item info watchpoints
3752 This command prints a list of watchpoints, using the same format as
3753 @code{info break} (@pxref{Set Breaks}).
3756 If you watch for a change in a numerically entered address you need to
3757 dereference it, as the address itself is just a constant number which will
3758 never change. @value{GDBN} refuses to create a watchpoint that watches
3759 a never-changing value:
3762 (@value{GDBP}) watch 0x600850
3763 Cannot watch constant value 0x600850.
3764 (@value{GDBP}) watch *(int *) 0x600850
3765 Watchpoint 1: *(int *) 6293584
3768 @value{GDBN} sets a @dfn{hardware watchpoint} if possible. Hardware
3769 watchpoints execute very quickly, and the debugger reports a change in
3770 value at the exact instruction where the change occurs. If @value{GDBN}
3771 cannot set a hardware watchpoint, it sets a software watchpoint, which
3772 executes more slowly and reports the change in value at the next
3773 @emph{statement}, not the instruction, after the change occurs.
3775 @cindex use only software watchpoints
3776 You can force @value{GDBN} to use only software watchpoints with the
3777 @kbd{set can-use-hw-watchpoints 0} command. With this variable set to
3778 zero, @value{GDBN} will never try to use hardware watchpoints, even if
3779 the underlying system supports them. (Note that hardware-assisted
3780 watchpoints that were set @emph{before} setting
3781 @code{can-use-hw-watchpoints} to zero will still use the hardware
3782 mechanism of watching expression values.)
3785 @item set can-use-hw-watchpoints
3786 @kindex set can-use-hw-watchpoints
3787 Set whether or not to use hardware watchpoints.
3789 @item show can-use-hw-watchpoints
3790 @kindex show can-use-hw-watchpoints
3791 Show the current mode of using hardware watchpoints.
3794 For remote targets, you can restrict the number of hardware
3795 watchpoints @value{GDBN} will use, see @ref{set remote
3796 hardware-breakpoint-limit}.
3798 When you issue the @code{watch} command, @value{GDBN} reports
3801 Hardware watchpoint @var{num}: @var{expr}
3805 if it was able to set a hardware watchpoint.
3807 Currently, the @code{awatch} and @code{rwatch} commands can only set
3808 hardware watchpoints, because accesses to data that don't change the
3809 value of the watched expression cannot be detected without examining
3810 every instruction as it is being executed, and @value{GDBN} does not do
3811 that currently. If @value{GDBN} finds that it is unable to set a
3812 hardware breakpoint with the @code{awatch} or @code{rwatch} command, it
3813 will print a message like this:
3816 Expression cannot be implemented with read/access watchpoint.
3819 Sometimes, @value{GDBN} cannot set a hardware watchpoint because the
3820 data type of the watched expression is wider than what a hardware
3821 watchpoint on the target machine can handle. For example, some systems
3822 can only watch regions that are up to 4 bytes wide; on such systems you
3823 cannot set hardware watchpoints for an expression that yields a
3824 double-precision floating-point number (which is typically 8 bytes
3825 wide). As a work-around, it might be possible to break the large region
3826 into a series of smaller ones and watch them with separate watchpoints.
3828 If you set too many hardware watchpoints, @value{GDBN} might be unable
3829 to insert all of them when you resume the execution of your program.
3830 Since the precise number of active watchpoints is unknown until such
3831 time as the program is about to be resumed, @value{GDBN} might not be
3832 able to warn you about this when you set the watchpoints, and the
3833 warning will be printed only when the program is resumed:
3836 Hardware watchpoint @var{num}: Could not insert watchpoint
3840 If this happens, delete or disable some of the watchpoints.
3842 Watching complex expressions that reference many variables can also
3843 exhaust the resources available for hardware-assisted watchpoints.
3844 That's because @value{GDBN} needs to watch every variable in the
3845 expression with separately allocated resources.
3847 If you call a function interactively using @code{print} or @code{call},
3848 any watchpoints you have set will be inactive until @value{GDBN} reaches another
3849 kind of breakpoint or the call completes.
3851 @value{GDBN} automatically deletes watchpoints that watch local
3852 (automatic) variables, or expressions that involve such variables, when
3853 they go out of scope, that is, when the execution leaves the block in
3854 which these variables were defined. In particular, when the program
3855 being debugged terminates, @emph{all} local variables go out of scope,
3856 and so only watchpoints that watch global variables remain set. If you
3857 rerun the program, you will need to set all such watchpoints again. One
3858 way of doing that would be to set a code breakpoint at the entry to the
3859 @code{main} function and when it breaks, set all the watchpoints.
3861 @cindex watchpoints and threads
3862 @cindex threads and watchpoints
3863 In multi-threaded programs, watchpoints will detect changes to the
3864 watched expression from every thread.
3867 @emph{Warning:} In multi-threaded programs, software watchpoints
3868 have only limited usefulness. If @value{GDBN} creates a software
3869 watchpoint, it can only watch the value of an expression @emph{in a
3870 single thread}. If you are confident that the expression can only
3871 change due to the current thread's activity (and if you are also
3872 confident that no other thread can become current), then you can use
3873 software watchpoints as usual. However, @value{GDBN} may not notice
3874 when a non-current thread's activity changes the expression. (Hardware
3875 watchpoints, in contrast, watch an expression in all threads.)
3878 @xref{set remote hardware-watchpoint-limit}.
3880 @node Set Catchpoints
3881 @subsection Setting Catchpoints
3882 @cindex catchpoints, setting
3883 @cindex exception handlers
3884 @cindex event handling
3886 You can use @dfn{catchpoints} to cause the debugger to stop for certain
3887 kinds of program events, such as C@t{++} exceptions or the loading of a
3888 shared library. Use the @code{catch} command to set a catchpoint.
3892 @item catch @var{event}
3893 Stop when @var{event} occurs. @var{event} can be any of the following:
3896 @cindex stop on C@t{++} exceptions
3897 The throwing of a C@t{++} exception.
3900 The catching of a C@t{++} exception.
3903 @cindex Ada exception catching
3904 @cindex catch Ada exceptions
3905 An Ada exception being raised. If an exception name is specified
3906 at the end of the command (eg @code{catch exception Program_Error}),
3907 the debugger will stop only when this specific exception is raised.
3908 Otherwise, the debugger stops execution when any Ada exception is raised.
3910 When inserting an exception catchpoint on a user-defined exception whose
3911 name is identical to one of the exceptions defined by the language, the
3912 fully qualified name must be used as the exception name. Otherwise,
3913 @value{GDBN} will assume that it should stop on the pre-defined exception
3914 rather than the user-defined one. For instance, assuming an exception
3915 called @code{Constraint_Error} is defined in package @code{Pck}, then
3916 the command to use to catch such exceptions is @kbd{catch exception
3917 Pck.Constraint_Error}.
3919 @item exception unhandled
3920 An exception that was raised but is not handled by the program.
3923 A failed Ada assertion.
3926 @cindex break on fork/exec
3927 A call to @code{exec}. This is currently only available for HP-UX
3931 @itemx syscall @r{[}@var{name} @r{|} @var{number}@r{]} @dots{}
3932 @cindex break on a system call.
3933 A call to or return from a system call, a.k.a.@: @dfn{syscall}. A
3934 syscall is a mechanism for application programs to request a service
3935 from the operating system (OS) or one of the OS system services.
3936 @value{GDBN} can catch some or all of the syscalls issued by the
3937 debuggee, and show the related information for each syscall. If no
3938 argument is specified, calls to and returns from all system calls
3941 @var{name} can be any system call name that is valid for the
3942 underlying OS. Just what syscalls are valid depends on the OS. On
3943 GNU and Unix systems, you can find the full list of valid syscall
3944 names on @file{/usr/include/asm/unistd.h}.
3946 @c For MS-Windows, the syscall names and the corresponding numbers
3947 @c can be found, e.g., on this URL:
3948 @c http://www.metasploit.com/users/opcode/syscalls.html
3949 @c but we don't support Windows syscalls yet.
3951 Normally, @value{GDBN} knows in advance which syscalls are valid for
3952 each OS, so you can use the @value{GDBN} command-line completion
3953 facilities (@pxref{Completion,, command completion}) to list the
3956 You may also specify the system call numerically. A syscall's
3957 number is the value passed to the OS's syscall dispatcher to
3958 identify the requested service. When you specify the syscall by its
3959 name, @value{GDBN} uses its database of syscalls to convert the name
3960 into the corresponding numeric code, but using the number directly
3961 may be useful if @value{GDBN}'s database does not have the complete
3962 list of syscalls on your system (e.g., because @value{GDBN} lags
3963 behind the OS upgrades).
3965 The example below illustrates how this command works if you don't provide
3969 (@value{GDBP}) catch syscall
3970 Catchpoint 1 (syscall)
3972 Starting program: /tmp/catch-syscall
3974 Catchpoint 1 (call to syscall 'close'), \
3975 0xffffe424 in __kernel_vsyscall ()
3979 Catchpoint 1 (returned from syscall 'close'), \
3980 0xffffe424 in __kernel_vsyscall ()
3984 Here is an example of catching a system call by name:
3987 (@value{GDBP}) catch syscall chroot
3988 Catchpoint 1 (syscall 'chroot' [61])
3990 Starting program: /tmp/catch-syscall
3992 Catchpoint 1 (call to syscall 'chroot'), \
3993 0xffffe424 in __kernel_vsyscall ()
3997 Catchpoint 1 (returned from syscall 'chroot'), \
3998 0xffffe424 in __kernel_vsyscall ()
4002 An example of specifying a system call numerically. In the case
4003 below, the syscall number has a corresponding entry in the XML
4004 file, so @value{GDBN} finds its name and prints it:
4007 (@value{GDBP}) catch syscall 252
4008 Catchpoint 1 (syscall(s) 'exit_group')
4010 Starting program: /tmp/catch-syscall
4012 Catchpoint 1 (call to syscall 'exit_group'), \
4013 0xffffe424 in __kernel_vsyscall ()
4017 Program exited normally.
4021 However, there can be situations when there is no corresponding name
4022 in XML file for that syscall number. In this case, @value{GDBN} prints
4023 a warning message saying that it was not able to find the syscall name,
4024 but the catchpoint will be set anyway. See the example below:
4027 (@value{GDBP}) catch syscall 764
4028 warning: The number '764' does not represent a known syscall.
4029 Catchpoint 2 (syscall 764)
4033 If you configure @value{GDBN} using the @samp{--without-expat} option,
4034 it will not be able to display syscall names. Also, if your
4035 architecture does not have an XML file describing its system calls,
4036 you will not be able to see the syscall names. It is important to
4037 notice that these two features are used for accessing the syscall
4038 name database. In either case, you will see a warning like this:
4041 (@value{GDBP}) catch syscall
4042 warning: Could not open "syscalls/i386-linux.xml"
4043 warning: Could not load the syscall XML file 'syscalls/i386-linux.xml'.
4044 GDB will not be able to display syscall names.
4045 Catchpoint 1 (syscall)
4049 Of course, the file name will change depending on your architecture and system.
4051 Still using the example above, you can also try to catch a syscall by its
4052 number. In this case, you would see something like:
4055 (@value{GDBP}) catch syscall 252
4056 Catchpoint 1 (syscall(s) 252)
4059 Again, in this case @value{GDBN} would not be able to display syscall's names.
4062 A call to @code{fork}. This is currently only available for HP-UX
4066 A call to @code{vfork}. This is currently only available for HP-UX
4071 @item tcatch @var{event}
4072 Set a catchpoint that is enabled only for one stop. The catchpoint is
4073 automatically deleted after the first time the event is caught.
4077 Use the @code{info break} command to list the current catchpoints.
4079 There are currently some limitations to C@t{++} exception handling
4080 (@code{catch throw} and @code{catch catch}) in @value{GDBN}:
4084 If you call a function interactively, @value{GDBN} normally returns
4085 control to you when the function has finished executing. If the call
4086 raises an exception, however, the call may bypass the mechanism that
4087 returns control to you and cause your program either to abort or to
4088 simply continue running until it hits a breakpoint, catches a signal
4089 that @value{GDBN} is listening for, or exits. This is the case even if
4090 you set a catchpoint for the exception; catchpoints on exceptions are
4091 disabled within interactive calls.
4094 You cannot raise an exception interactively.
4097 You cannot install an exception handler interactively.
4100 @cindex raise exceptions
4101 Sometimes @code{catch} is not the best way to debug exception handling:
4102 if you need to know exactly where an exception is raised, it is better to
4103 stop @emph{before} the exception handler is called, since that way you
4104 can see the stack before any unwinding takes place. If you set a
4105 breakpoint in an exception handler instead, it may not be easy to find
4106 out where the exception was raised.
4108 To stop just before an exception handler is called, you need some
4109 knowledge of the implementation. In the case of @sc{gnu} C@t{++}, exceptions are
4110 raised by calling a library function named @code{__raise_exception}
4111 which has the following ANSI C interface:
4114 /* @var{addr} is where the exception identifier is stored.
4115 @var{id} is the exception identifier. */
4116 void __raise_exception (void **addr, void *id);
4120 To make the debugger catch all exceptions before any stack
4121 unwinding takes place, set a breakpoint on @code{__raise_exception}
4122 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Exceptions}).
4124 With a conditional breakpoint (@pxref{Conditions, ,Break Conditions})
4125 that depends on the value of @var{id}, you can stop your program when
4126 a specific exception is raised. You can use multiple conditional
4127 breakpoints to stop your program when any of a number of exceptions are
4132 @subsection Deleting Breakpoints
4134 @cindex clearing breakpoints, watchpoints, catchpoints
4135 @cindex deleting breakpoints, watchpoints, catchpoints
4136 It is often necessary to eliminate a breakpoint, watchpoint, or
4137 catchpoint once it has done its job and you no longer want your program
4138 to stop there. This is called @dfn{deleting} the breakpoint. A
4139 breakpoint that has been deleted no longer exists; it is forgotten.
4141 With the @code{clear} command you can delete breakpoints according to
4142 where they are in your program. With the @code{delete} command you can
4143 delete individual breakpoints, watchpoints, or catchpoints by specifying
4144 their breakpoint numbers.
4146 It is not necessary to delete a breakpoint to proceed past it. @value{GDBN}
4147 automatically ignores breakpoints on the first instruction to be executed
4148 when you continue execution without changing the execution address.
4153 Delete any breakpoints at the next instruction to be executed in the
4154 selected stack frame (@pxref{Selection, ,Selecting a Frame}). When
4155 the innermost frame is selected, this is a good way to delete a
4156 breakpoint where your program just stopped.
4158 @item clear @var{location}
4159 Delete any breakpoints set at the specified @var{location}.
4160 @xref{Specify Location}, for the various forms of @var{location}; the
4161 most useful ones are listed below:
4164 @item clear @var{function}
4165 @itemx clear @var{filename}:@var{function}
4166 Delete any breakpoints set at entry to the named @var{function}.
4168 @item clear @var{linenum}
4169 @itemx clear @var{filename}:@var{linenum}
4170 Delete any breakpoints set at or within the code of the specified
4171 @var{linenum} of the specified @var{filename}.
4174 @cindex delete breakpoints
4176 @kindex d @r{(@code{delete})}
4177 @item delete @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4178 Delete the breakpoints, watchpoints, or catchpoints of the breakpoint
4179 ranges specified as arguments. If no argument is specified, delete all
4180 breakpoints (@value{GDBN} asks confirmation, unless you have @code{set
4181 confirm off}). You can abbreviate this command as @code{d}.
4185 @subsection Disabling Breakpoints
4187 @cindex enable/disable a breakpoint
4188 Rather than deleting a breakpoint, watchpoint, or catchpoint, you might
4189 prefer to @dfn{disable} it. This makes the breakpoint inoperative as if
4190 it had been deleted, but remembers the information on the breakpoint so
4191 that you can @dfn{enable} it again later.
4193 You disable and enable breakpoints, watchpoints, and catchpoints with
4194 the @code{enable} and @code{disable} commands, optionally specifying
4195 one or more breakpoint numbers as arguments. Use @code{info break} to
4196 print a list of all breakpoints, watchpoints, and catchpoints if you
4197 do not know which numbers to use.
4199 Disabling and enabling a breakpoint that has multiple locations
4200 affects all of its locations.
4202 A breakpoint, watchpoint, or catchpoint can have any of four different
4203 states of enablement:
4207 Enabled. The breakpoint stops your program. A breakpoint set
4208 with the @code{break} command starts out in this state.
4210 Disabled. The breakpoint has no effect on your program.
4212 Enabled once. The breakpoint stops your program, but then becomes
4215 Enabled for deletion. The breakpoint stops your program, but
4216 immediately after it does so it is deleted permanently. A breakpoint
4217 set with the @code{tbreak} command starts out in this state.
4220 You can use the following commands to enable or disable breakpoints,
4221 watchpoints, and catchpoints:
4225 @kindex dis @r{(@code{disable})}
4226 @item disable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4227 Disable the specified breakpoints---or all breakpoints, if none are
4228 listed. A disabled breakpoint has no effect but is not forgotten. All
4229 options such as ignore-counts, conditions and commands are remembered in
4230 case the breakpoint is enabled again later. You may abbreviate
4231 @code{disable} as @code{dis}.
4234 @item enable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4235 Enable the specified breakpoints (or all defined breakpoints). They
4236 become effective once again in stopping your program.
4238 @item enable @r{[}breakpoints@r{]} once @var{range}@dots{}
4239 Enable the specified breakpoints temporarily. @value{GDBN} disables any
4240 of these breakpoints immediately after stopping your program.
4242 @item enable @r{[}breakpoints@r{]} delete @var{range}@dots{}
4243 Enable the specified breakpoints to work once, then die. @value{GDBN}
4244 deletes any of these breakpoints as soon as your program stops there.
4245 Breakpoints set by the @code{tbreak} command start out in this state.
4248 @c FIXME: I think the following ``Except for [...] @code{tbreak}'' is
4249 @c confusing: tbreak is also initially enabled.
4250 Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks,
4251 ,Setting Breakpoints}), breakpoints that you set are initially enabled;
4252 subsequently, they become disabled or enabled only when you use one of
4253 the commands above. (The command @code{until} can set and delete a
4254 breakpoint of its own, but it does not change the state of your other
4255 breakpoints; see @ref{Continuing and Stepping, ,Continuing and
4259 @subsection Break Conditions
4260 @cindex conditional breakpoints
4261 @cindex breakpoint conditions
4263 @c FIXME what is scope of break condition expr? Context where wanted?
4264 @c in particular for a watchpoint?
4265 The simplest sort of breakpoint breaks every time your program reaches a
4266 specified place. You can also specify a @dfn{condition} for a
4267 breakpoint. A condition is just a Boolean expression in your
4268 programming language (@pxref{Expressions, ,Expressions}). A breakpoint with
4269 a condition evaluates the expression each time your program reaches it,
4270 and your program stops only if the condition is @emph{true}.
4272 This is the converse of using assertions for program validation; in that
4273 situation, you want to stop when the assertion is violated---that is,
4274 when the condition is false. In C, if you want to test an assertion expressed
4275 by the condition @var{assert}, you should set the condition
4276 @samp{! @var{assert}} on the appropriate breakpoint.
4278 Conditions are also accepted for watchpoints; you may not need them,
4279 since a watchpoint is inspecting the value of an expression anyhow---but
4280 it might be simpler, say, to just set a watchpoint on a variable name,
4281 and specify a condition that tests whether the new value is an interesting
4284 Break conditions can have side effects, and may even call functions in
4285 your program. This can be useful, for example, to activate functions
4286 that log program progress, or to use your own print functions to
4287 format special data structures. The effects are completely predictable
4288 unless there is another enabled breakpoint at the same address. (In
4289 that case, @value{GDBN} might see the other breakpoint first and stop your
4290 program without checking the condition of this one.) Note that
4291 breakpoint commands are usually more convenient and flexible than break
4293 purpose of performing side effects when a breakpoint is reached
4294 (@pxref{Break Commands, ,Breakpoint Command Lists}).
4296 Break conditions can be specified when a breakpoint is set, by using
4297 @samp{if} in the arguments to the @code{break} command. @xref{Set
4298 Breaks, ,Setting Breakpoints}. They can also be changed at any time
4299 with the @code{condition} command.
4301 You can also use the @code{if} keyword with the @code{watch} command.
4302 The @code{catch} command does not recognize the @code{if} keyword;
4303 @code{condition} is the only way to impose a further condition on a
4308 @item condition @var{bnum} @var{expression}
4309 Specify @var{expression} as the break condition for breakpoint,
4310 watchpoint, or catchpoint number @var{bnum}. After you set a condition,
4311 breakpoint @var{bnum} stops your program only if the value of
4312 @var{expression} is true (nonzero, in C). When you use
4313 @code{condition}, @value{GDBN} checks @var{expression} immediately for
4314 syntactic correctness, and to determine whether symbols in it have
4315 referents in the context of your breakpoint. If @var{expression} uses
4316 symbols not referenced in the context of the breakpoint, @value{GDBN}
4317 prints an error message:
4320 No symbol "foo" in current context.
4325 not actually evaluate @var{expression} at the time the @code{condition}
4326 command (or a command that sets a breakpoint with a condition, like
4327 @code{break if @dots{}}) is given, however. @xref{Expressions, ,Expressions}.
4329 @item condition @var{bnum}
4330 Remove the condition from breakpoint number @var{bnum}. It becomes
4331 an ordinary unconditional breakpoint.
4334 @cindex ignore count (of breakpoint)
4335 A special case of a breakpoint condition is to stop only when the
4336 breakpoint has been reached a certain number of times. This is so
4337 useful that there is a special way to do it, using the @dfn{ignore
4338 count} of the breakpoint. Every breakpoint has an ignore count, which
4339 is an integer. Most of the time, the ignore count is zero, and
4340 therefore has no effect. But if your program reaches a breakpoint whose
4341 ignore count is positive, then instead of stopping, it just decrements
4342 the ignore count by one and continues. As a result, if the ignore count
4343 value is @var{n}, the breakpoint does not stop the next @var{n} times
4344 your program reaches it.
4348 @item ignore @var{bnum} @var{count}
4349 Set the ignore count of breakpoint number @var{bnum} to @var{count}.
4350 The next @var{count} times the breakpoint is reached, your program's
4351 execution does not stop; other than to decrement the ignore count, @value{GDBN}
4354 To make the breakpoint stop the next time it is reached, specify
4357 When you use @code{continue} to resume execution of your program from a
4358 breakpoint, you can specify an ignore count directly as an argument to
4359 @code{continue}, rather than using @code{ignore}. @xref{Continuing and
4360 Stepping,,Continuing and Stepping}.
4362 If a breakpoint has a positive ignore count and a condition, the
4363 condition is not checked. Once the ignore count reaches zero,
4364 @value{GDBN} resumes checking the condition.
4366 You could achieve the effect of the ignore count with a condition such
4367 as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that
4368 is decremented each time. @xref{Convenience Vars, ,Convenience
4372 Ignore counts apply to breakpoints, watchpoints, and catchpoints.
4375 @node Break Commands
4376 @subsection Breakpoint Command Lists
4378 @cindex breakpoint commands
4379 You can give any breakpoint (or watchpoint or catchpoint) a series of
4380 commands to execute when your program stops due to that breakpoint. For
4381 example, you might want to print the values of certain expressions, or
4382 enable other breakpoints.
4386 @kindex end@r{ (breakpoint commands)}
4387 @item commands @r{[}@var{range}@dots{}@r{]}
4388 @itemx @dots{} @var{command-list} @dots{}
4390 Specify a list of commands for the given breakpoints. The commands
4391 themselves appear on the following lines. Type a line containing just
4392 @code{end} to terminate the commands.
4394 To remove all commands from a breakpoint, type @code{commands} and
4395 follow it immediately with @code{end}; that is, give no commands.
4397 With no argument, @code{commands} refers to the last breakpoint,
4398 watchpoint, or catchpoint set (not to the breakpoint most recently
4399 encountered). If the most recent breakpoints were set with a single
4400 command, then the @code{commands} will apply to all the breakpoints
4401 set by that command. This applies to breakpoints set by
4402 @code{rbreak}, and also applies when a single @code{break} command
4403 creates multiple breakpoints (@pxref{Ambiguous Expressions,,Ambiguous
4407 Pressing @key{RET} as a means of repeating the last @value{GDBN} command is
4408 disabled within a @var{command-list}.
4410 You can use breakpoint commands to start your program up again. Simply
4411 use the @code{continue} command, or @code{step}, or any other command
4412 that resumes execution.
4414 Any other commands in the command list, after a command that resumes
4415 execution, are ignored. This is because any time you resume execution
4416 (even with a simple @code{next} or @code{step}), you may encounter
4417 another breakpoint---which could have its own command list, leading to
4418 ambiguities about which list to execute.
4421 If the first command you specify in a command list is @code{silent}, the
4422 usual message about stopping at a breakpoint is not printed. This may
4423 be desirable for breakpoints that are to print a specific message and
4424 then continue. If none of the remaining commands print anything, you
4425 see no sign that the breakpoint was reached. @code{silent} is
4426 meaningful only at the beginning of a breakpoint command list.
4428 The commands @code{echo}, @code{output}, and @code{printf} allow you to
4429 print precisely controlled output, and are often useful in silent
4430 breakpoints. @xref{Output, ,Commands for Controlled Output}.
4432 For example, here is how you could use breakpoint commands to print the
4433 value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
4439 printf "x is %d\n",x
4444 One application for breakpoint commands is to compensate for one bug so
4445 you can test for another. Put a breakpoint just after the erroneous line
4446 of code, give it a condition to detect the case in which something
4447 erroneous has been done, and give it commands to assign correct values
4448 to any variables that need them. End with the @code{continue} command
4449 so that your program does not stop, and start with the @code{silent}
4450 command so that no output is produced. Here is an example:
4461 @node Save Breakpoints
4462 @subsection How to save breakpoints to a file
4464 To save breakpoint definitions to a file use the @w{@code{save
4465 breakpoints}} command.
4468 @kindex save breakpoints
4469 @cindex save breakpoints to a file for future sessions
4470 @item save breakpoints [@var{filename}]
4471 This command saves all current breakpoint definitions together with
4472 their commands and ignore counts, into a file @file{@var{filename}}
4473 suitable for use in a later debugging session. This includes all
4474 types of breakpoints (breakpoints, watchpoints, catchpoints,
4475 tracepoints). To read the saved breakpoint definitions, use the
4476 @code{source} command (@pxref{Command Files}). Note that watchpoints
4477 with expressions involving local variables may fail to be recreated
4478 because it may not be possible to access the context where the
4479 watchpoint is valid anymore. Because the saved breakpoint definitions
4480 are simply a sequence of @value{GDBN} commands that recreate the
4481 breakpoints, you can edit the file in your favorite editing program,
4482 and remove the breakpoint definitions you're not interested in, or
4483 that can no longer be recreated.
4486 @c @ifclear BARETARGET
4487 @node Error in Breakpoints
4488 @subsection ``Cannot insert breakpoints''
4490 If you request too many active hardware-assisted breakpoints and
4491 watchpoints, you will see this error message:
4493 @c FIXME: the precise wording of this message may change; the relevant
4494 @c source change is not committed yet (Sep 3, 1999).
4496 Stopped; cannot insert breakpoints.
4497 You may have requested too many hardware breakpoints and watchpoints.
4501 This message is printed when you attempt to resume the program, since
4502 only then @value{GDBN} knows exactly how many hardware breakpoints and
4503 watchpoints it needs to insert.
4505 When this message is printed, you need to disable or remove some of the
4506 hardware-assisted breakpoints and watchpoints, and then continue.
4508 @node Breakpoint-related Warnings
4509 @subsection ``Breakpoint address adjusted...''
4510 @cindex breakpoint address adjusted
4512 Some processor architectures place constraints on the addresses at
4513 which breakpoints may be placed. For architectures thus constrained,
4514 @value{GDBN} will attempt to adjust the breakpoint's address to comply
4515 with the constraints dictated by the architecture.
4517 One example of such an architecture is the Fujitsu FR-V. The FR-V is
4518 a VLIW architecture in which a number of RISC-like instructions may be
4519 bundled together for parallel execution. The FR-V architecture
4520 constrains the location of a breakpoint instruction within such a
4521 bundle to the instruction with the lowest address. @value{GDBN}
4522 honors this constraint by adjusting a breakpoint's address to the
4523 first in the bundle.
4525 It is not uncommon for optimized code to have bundles which contain
4526 instructions from different source statements, thus it may happen that
4527 a breakpoint's address will be adjusted from one source statement to
4528 another. Since this adjustment may significantly alter @value{GDBN}'s
4529 breakpoint related behavior from what the user expects, a warning is
4530 printed when the breakpoint is first set and also when the breakpoint
4533 A warning like the one below is printed when setting a breakpoint
4534 that's been subject to address adjustment:
4537 warning: Breakpoint address adjusted from 0x00010414 to 0x00010410.
4540 Such warnings are printed both for user settable and @value{GDBN}'s
4541 internal breakpoints. If you see one of these warnings, you should
4542 verify that a breakpoint set at the adjusted address will have the
4543 desired affect. If not, the breakpoint in question may be removed and
4544 other breakpoints may be set which will have the desired behavior.
4545 E.g., it may be sufficient to place the breakpoint at a later
4546 instruction. A conditional breakpoint may also be useful in some
4547 cases to prevent the breakpoint from triggering too often.
4549 @value{GDBN} will also issue a warning when stopping at one of these
4550 adjusted breakpoints:
4553 warning: Breakpoint 1 address previously adjusted from 0x00010414
4557 When this warning is encountered, it may be too late to take remedial
4558 action except in cases where the breakpoint is hit earlier or more
4559 frequently than expected.
4561 @node Continuing and Stepping
4562 @section Continuing and Stepping
4566 @cindex resuming execution
4567 @dfn{Continuing} means resuming program execution until your program
4568 completes normally. In contrast, @dfn{stepping} means executing just
4569 one more ``step'' of your program, where ``step'' may mean either one
4570 line of source code, or one machine instruction (depending on what
4571 particular command you use). Either when continuing or when stepping,
4572 your program may stop even sooner, due to a breakpoint or a signal. (If
4573 it stops due to a signal, you may want to use @code{handle}, or use
4574 @samp{signal 0} to resume execution. @xref{Signals, ,Signals}.)
4578 @kindex c @r{(@code{continue})}
4579 @kindex fg @r{(resume foreground execution)}
4580 @item continue @r{[}@var{ignore-count}@r{]}
4581 @itemx c @r{[}@var{ignore-count}@r{]}
4582 @itemx fg @r{[}@var{ignore-count}@r{]}
4583 Resume program execution, at the address where your program last stopped;
4584 any breakpoints set at that address are bypassed. The optional argument
4585 @var{ignore-count} allows you to specify a further number of times to
4586 ignore a breakpoint at this location; its effect is like that of
4587 @code{ignore} (@pxref{Conditions, ,Break Conditions}).
4589 The argument @var{ignore-count} is meaningful only when your program
4590 stopped due to a breakpoint. At other times, the argument to
4591 @code{continue} is ignored.
4593 The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the
4594 debugged program is deemed to be the foreground program) are provided
4595 purely for convenience, and have exactly the same behavior as
4599 To resume execution at a different place, you can use @code{return}
4600 (@pxref{Returning, ,Returning from a Function}) to go back to the
4601 calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
4602 Different Address}) to go to an arbitrary location in your program.
4604 A typical technique for using stepping is to set a breakpoint
4605 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Catchpoints}) at the
4606 beginning of the function or the section of your program where a problem
4607 is believed to lie, run your program until it stops at that breakpoint,
4608 and then step through the suspect area, examining the variables that are
4609 interesting, until you see the problem happen.
4613 @kindex s @r{(@code{step})}
4615 Continue running your program until control reaches a different source
4616 line, then stop it and return control to @value{GDBN}. This command is
4617 abbreviated @code{s}.
4620 @c "without debugging information" is imprecise; actually "without line
4621 @c numbers in the debugging information". (gcc -g1 has debugging info but
4622 @c not line numbers). But it seems complex to try to make that
4623 @c distinction here.
4624 @emph{Warning:} If you use the @code{step} command while control is
4625 within a function that was compiled without debugging information,
4626 execution proceeds until control reaches a function that does have
4627 debugging information. Likewise, it will not step into a function which
4628 is compiled without debugging information. To step through functions
4629 without debugging information, use the @code{stepi} command, described
4633 The @code{step} command only stops at the first instruction of a source
4634 line. This prevents the multiple stops that could otherwise occur in
4635 @code{switch} statements, @code{for} loops, etc. @code{step} continues
4636 to stop if a function that has debugging information is called within
4637 the line. In other words, @code{step} @emph{steps inside} any functions
4638 called within the line.
4640 Also, the @code{step} command only enters a function if there is line
4641 number information for the function. Otherwise it acts like the
4642 @code{next} command. This avoids problems when using @code{cc -gl}
4643 on MIPS machines. Previously, @code{step} entered subroutines if there
4644 was any debugging information about the routine.
4646 @item step @var{count}
4647 Continue running as in @code{step}, but do so @var{count} times. If a
4648 breakpoint is reached, or a signal not related to stepping occurs before
4649 @var{count} steps, stepping stops right away.
4652 @kindex n @r{(@code{next})}
4653 @item next @r{[}@var{count}@r{]}
4654 Continue to the next source line in the current (innermost) stack frame.
4655 This is similar to @code{step}, but function calls that appear within
4656 the line of code are executed without stopping. Execution stops when
4657 control reaches a different line of code at the original stack level
4658 that was executing when you gave the @code{next} command. This command
4659 is abbreviated @code{n}.
4661 An argument @var{count} is a repeat count, as for @code{step}.
4664 @c FIX ME!! Do we delete this, or is there a way it fits in with
4665 @c the following paragraph? --- Vctoria
4667 @c @code{next} within a function that lacks debugging information acts like
4668 @c @code{step}, but any function calls appearing within the code of the
4669 @c function are executed without stopping.
4671 The @code{next} command only stops at the first instruction of a
4672 source line. This prevents multiple stops that could otherwise occur in
4673 @code{switch} statements, @code{for} loops, etc.
4675 @kindex set step-mode
4677 @cindex functions without line info, and stepping
4678 @cindex stepping into functions with no line info
4679 @itemx set step-mode on
4680 The @code{set step-mode on} command causes the @code{step} command to
4681 stop at the first instruction of a function which contains no debug line
4682 information rather than stepping over it.
4684 This is useful in cases where you may be interested in inspecting the
4685 machine instructions of a function which has no symbolic info and do not
4686 want @value{GDBN} to automatically skip over this function.
4688 @item set step-mode off
4689 Causes the @code{step} command to step over any functions which contains no
4690 debug information. This is the default.
4692 @item show step-mode
4693 Show whether @value{GDBN} will stop in or step over functions without
4694 source line debug information.
4697 @kindex fin @r{(@code{finish})}
4699 Continue running until just after function in the selected stack frame
4700 returns. Print the returned value (if any). This command can be
4701 abbreviated as @code{fin}.
4703 Contrast this with the @code{return} command (@pxref{Returning,
4704 ,Returning from a Function}).
4707 @kindex u @r{(@code{until})}
4708 @cindex run until specified location
4711 Continue running until a source line past the current line, in the
4712 current stack frame, is reached. This command is used to avoid single
4713 stepping through a loop more than once. It is like the @code{next}
4714 command, except that when @code{until} encounters a jump, it
4715 automatically continues execution until the program counter is greater
4716 than the address of the jump.
4718 This means that when you reach the end of a loop after single stepping
4719 though it, @code{until} makes your program continue execution until it
4720 exits the loop. In contrast, a @code{next} command at the end of a loop
4721 simply steps back to the beginning of the loop, which forces you to step
4722 through the next iteration.
4724 @code{until} always stops your program if it attempts to exit the current
4727 @code{until} may produce somewhat counterintuitive results if the order
4728 of machine code does not match the order of the source lines. For
4729 example, in the following excerpt from a debugging session, the @code{f}
4730 (@code{frame}) command shows that execution is stopped at line
4731 @code{206}; yet when we use @code{until}, we get to line @code{195}:
4735 #0 main (argc=4, argv=0xf7fffae8) at m4.c:206
4737 (@value{GDBP}) until
4738 195 for ( ; argc > 0; NEXTARG) @{
4741 This happened because, for execution efficiency, the compiler had
4742 generated code for the loop closure test at the end, rather than the
4743 start, of the loop---even though the test in a C @code{for}-loop is
4744 written before the body of the loop. The @code{until} command appeared
4745 to step back to the beginning of the loop when it advanced to this
4746 expression; however, it has not really gone to an earlier
4747 statement---not in terms of the actual machine code.
4749 @code{until} with no argument works by means of single
4750 instruction stepping, and hence is slower than @code{until} with an
4753 @item until @var{location}
4754 @itemx u @var{location}
4755 Continue running your program until either the specified location is
4756 reached, or the current stack frame returns. @var{location} is any of
4757 the forms described in @ref{Specify Location}.
4758 This form of the command uses temporary breakpoints, and
4759 hence is quicker than @code{until} without an argument. The specified
4760 location is actually reached only if it is in the current frame. This
4761 implies that @code{until} can be used to skip over recursive function
4762 invocations. For instance in the code below, if the current location is
4763 line @code{96}, issuing @code{until 99} will execute the program up to
4764 line @code{99} in the same invocation of factorial, i.e., after the inner
4765 invocations have returned.
4768 94 int factorial (int value)
4770 96 if (value > 1) @{
4771 97 value *= factorial (value - 1);
4778 @kindex advance @var{location}
4779 @itemx advance @var{location}
4780 Continue running the program up to the given @var{location}. An argument is
4781 required, which should be of one of the forms described in
4782 @ref{Specify Location}.
4783 Execution will also stop upon exit from the current stack
4784 frame. This command is similar to @code{until}, but @code{advance} will
4785 not skip over recursive function calls, and the target location doesn't
4786 have to be in the same frame as the current one.
4790 @kindex si @r{(@code{stepi})}
4792 @itemx stepi @var{arg}
4794 Execute one machine instruction, then stop and return to the debugger.
4796 It is often useful to do @samp{display/i $pc} when stepping by machine
4797 instructions. This makes @value{GDBN} automatically display the next
4798 instruction to be executed, each time your program stops. @xref{Auto
4799 Display,, Automatic Display}.
4801 An argument is a repeat count, as in @code{step}.
4805 @kindex ni @r{(@code{nexti})}
4807 @itemx nexti @var{arg}
4809 Execute one machine instruction, but if it is a function call,
4810 proceed until the function returns.
4812 An argument is a repeat count, as in @code{next}.
4819 A signal is an asynchronous event that can happen in a program. The
4820 operating system defines the possible kinds of signals, and gives each
4821 kind a name and a number. For example, in Unix @code{SIGINT} is the
4822 signal a program gets when you type an interrupt character (often @kbd{Ctrl-c});
4823 @code{SIGSEGV} is the signal a program gets from referencing a place in
4824 memory far away from all the areas in use; @code{SIGALRM} occurs when
4825 the alarm clock timer goes off (which happens only if your program has
4826 requested an alarm).
4828 @cindex fatal signals
4829 Some signals, including @code{SIGALRM}, are a normal part of the
4830 functioning of your program. Others, such as @code{SIGSEGV}, indicate
4831 errors; these signals are @dfn{fatal} (they kill your program immediately) if the
4832 program has not specified in advance some other way to handle the signal.
4833 @code{SIGINT} does not indicate an error in your program, but it is normally
4834 fatal so it can carry out the purpose of the interrupt: to kill the program.
4836 @value{GDBN} has the ability to detect any occurrence of a signal in your
4837 program. You can tell @value{GDBN} in advance what to do for each kind of
4840 @cindex handling signals
4841 Normally, @value{GDBN} is set up to let the non-erroneous signals like
4842 @code{SIGALRM} be silently passed to your program
4843 (so as not to interfere with their role in the program's functioning)
4844 but to stop your program immediately whenever an error signal happens.
4845 You can change these settings with the @code{handle} command.
4848 @kindex info signals
4852 Print a table of all the kinds of signals and how @value{GDBN} has been told to
4853 handle each one. You can use this to see the signal numbers of all
4854 the defined types of signals.
4856 @item info signals @var{sig}
4857 Similar, but print information only about the specified signal number.
4859 @code{info handle} is an alias for @code{info signals}.
4862 @item handle @var{signal} @r{[}@var{keywords}@dots{}@r{]}
4863 Change the way @value{GDBN} handles signal @var{signal}. @var{signal}
4864 can be the number of a signal or its name (with or without the
4865 @samp{SIG} at the beginning); a list of signal numbers of the form
4866 @samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the
4867 known signals. Optional arguments @var{keywords}, described below,
4868 say what change to make.
4872 The keywords allowed by the @code{handle} command can be abbreviated.
4873 Their full names are:
4877 @value{GDBN} should not stop your program when this signal happens. It may
4878 still print a message telling you that the signal has come in.
4881 @value{GDBN} should stop your program when this signal happens. This implies
4882 the @code{print} keyword as well.
4885 @value{GDBN} should print a message when this signal happens.
4888 @value{GDBN} should not mention the occurrence of the signal at all. This
4889 implies the @code{nostop} keyword as well.
4893 @value{GDBN} should allow your program to see this signal; your program
4894 can handle the signal, or else it may terminate if the signal is fatal
4895 and not handled. @code{pass} and @code{noignore} are synonyms.
4899 @value{GDBN} should not allow your program to see this signal.
4900 @code{nopass} and @code{ignore} are synonyms.
4904 When a signal stops your program, the signal is not visible to the
4906 continue. Your program sees the signal then, if @code{pass} is in
4907 effect for the signal in question @emph{at that time}. In other words,
4908 after @value{GDBN} reports a signal, you can use the @code{handle}
4909 command with @code{pass} or @code{nopass} to control whether your
4910 program sees that signal when you continue.
4912 The default is set to @code{nostop}, @code{noprint}, @code{pass} for
4913 non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and
4914 @code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the
4917 You can also use the @code{signal} command to prevent your program from
4918 seeing a signal, or cause it to see a signal it normally would not see,
4919 or to give it any signal at any time. For example, if your program stopped
4920 due to some sort of memory reference error, you might store correct
4921 values into the erroneous variables and continue, hoping to see more
4922 execution; but your program would probably terminate immediately as
4923 a result of the fatal signal once it saw the signal. To prevent this,
4924 you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
4927 @cindex extra signal information
4928 @anchor{extra signal information}
4930 On some targets, @value{GDBN} can inspect extra signal information
4931 associated with the intercepted signal, before it is actually
4932 delivered to the program being debugged. This information is exported
4933 by the convenience variable @code{$_siginfo}, and consists of data
4934 that is passed by the kernel to the signal handler at the time of the
4935 receipt of a signal. The data type of the information itself is
4936 target dependent. You can see the data type using the @code{ptype
4937 $_siginfo} command. On Unix systems, it typically corresponds to the
4938 standard @code{siginfo_t} type, as defined in the @file{signal.h}
4941 Here's an example, on a @sc{gnu}/Linux system, printing the stray
4942 referenced address that raised a segmentation fault.
4946 (@value{GDBP}) continue
4947 Program received signal SIGSEGV, Segmentation fault.
4948 0x0000000000400766 in main ()
4950 (@value{GDBP}) ptype $_siginfo
4957 struct @{...@} _kill;
4958 struct @{...@} _timer;
4960 struct @{...@} _sigchld;
4961 struct @{...@} _sigfault;
4962 struct @{...@} _sigpoll;
4965 (@value{GDBP}) ptype $_siginfo._sifields._sigfault
4969 (@value{GDBP}) p $_siginfo._sifields._sigfault.si_addr
4970 $1 = (void *) 0x7ffff7ff7000
4974 Depending on target support, @code{$_siginfo} may also be writable.
4977 @section Stopping and Starting Multi-thread Programs
4979 @cindex stopped threads
4980 @cindex threads, stopped
4982 @cindex continuing threads
4983 @cindex threads, continuing
4985 @value{GDBN} supports debugging programs with multiple threads
4986 (@pxref{Threads,, Debugging Programs with Multiple Threads}). There
4987 are two modes of controlling execution of your program within the
4988 debugger. In the default mode, referred to as @dfn{all-stop mode},
4989 when any thread in your program stops (for example, at a breakpoint
4990 or while being stepped), all other threads in the program are also stopped by
4991 @value{GDBN}. On some targets, @value{GDBN} also supports
4992 @dfn{non-stop mode}, in which other threads can continue to run freely while
4993 you examine the stopped thread in the debugger.
4996 * All-Stop Mode:: All threads stop when GDB takes control
4997 * Non-Stop Mode:: Other threads continue to execute
4998 * Background Execution:: Running your program asynchronously
4999 * Thread-Specific Breakpoints:: Controlling breakpoints
5000 * Interrupted System Calls:: GDB may interfere with system calls
5001 * Observer Mode:: GDB does not alter program behavior
5005 @subsection All-Stop Mode
5007 @cindex all-stop mode
5009 In all-stop mode, whenever your program stops under @value{GDBN} for any reason,
5010 @emph{all} threads of execution stop, not just the current thread. This
5011 allows you to examine the overall state of the program, including
5012 switching between threads, without worrying that things may change
5015 Conversely, whenever you restart the program, @emph{all} threads start
5016 executing. @emph{This is true even when single-stepping} with commands
5017 like @code{step} or @code{next}.
5019 In particular, @value{GDBN} cannot single-step all threads in lockstep.
5020 Since thread scheduling is up to your debugging target's operating
5021 system (not controlled by @value{GDBN}), other threads may
5022 execute more than one statement while the current thread completes a
5023 single step. Moreover, in general other threads stop in the middle of a
5024 statement, rather than at a clean statement boundary, when the program
5027 You might even find your program stopped in another thread after
5028 continuing or even single-stepping. This happens whenever some other
5029 thread runs into a breakpoint, a signal, or an exception before the
5030 first thread completes whatever you requested.
5032 @cindex automatic thread selection
5033 @cindex switching threads automatically
5034 @cindex threads, automatic switching
5035 Whenever @value{GDBN} stops your program, due to a breakpoint or a
5036 signal, it automatically selects the thread where that breakpoint or
5037 signal happened. @value{GDBN} alerts you to the context switch with a
5038 message such as @samp{[Switching to Thread @var{n}]} to identify the
5041 On some OSes, you can modify @value{GDBN}'s default behavior by
5042 locking the OS scheduler to allow only a single thread to run.
5045 @item set scheduler-locking @var{mode}
5046 @cindex scheduler locking mode
5047 @cindex lock scheduler
5048 Set the scheduler locking mode. If it is @code{off}, then there is no
5049 locking and any thread may run at any time. If @code{on}, then only the
5050 current thread may run when the inferior is resumed. The @code{step}
5051 mode optimizes for single-stepping; it prevents other threads
5052 from preempting the current thread while you are stepping, so that
5053 the focus of debugging does not change unexpectedly.
5054 Other threads only rarely (or never) get a chance to run
5055 when you step. They are more likely to run when you @samp{next} over a
5056 function call, and they are completely free to run when you use commands
5057 like @samp{continue}, @samp{until}, or @samp{finish}. However, unless another
5058 thread hits a breakpoint during its timeslice, @value{GDBN} does not change
5059 the current thread away from the thread that you are debugging.
5061 @item show scheduler-locking
5062 Display the current scheduler locking mode.
5065 @cindex resume threads of multiple processes simultaneously
5066 By default, when you issue one of the execution commands such as
5067 @code{continue}, @code{next} or @code{step}, @value{GDBN} allows only
5068 threads of the current inferior to run. For example, if @value{GDBN}
5069 is attached to two inferiors, each with two threads, the
5070 @code{continue} command resumes only the two threads of the current
5071 inferior. This is useful, for example, when you debug a program that
5072 forks and you want to hold the parent stopped (so that, for instance,
5073 it doesn't run to exit), while you debug the child. In other
5074 situations, you may not be interested in inspecting the current state
5075 of any of the processes @value{GDBN} is attached to, and you may want
5076 to resume them all until some breakpoint is hit. In the latter case,
5077 you can instruct @value{GDBN} to allow all threads of all the
5078 inferiors to run with the @w{@code{set schedule-multiple}} command.
5081 @kindex set schedule-multiple
5082 @item set schedule-multiple
5083 Set the mode for allowing threads of multiple processes to be resumed
5084 when an execution command is issued. When @code{on}, all threads of
5085 all processes are allowed to run. When @code{off}, only the threads
5086 of the current process are resumed. The default is @code{off}. The
5087 @code{scheduler-locking} mode takes precedence when set to @code{on},
5088 or while you are stepping and set to @code{step}.
5090 @item show schedule-multiple
5091 Display the current mode for resuming the execution of threads of
5096 @subsection Non-Stop Mode
5098 @cindex non-stop mode
5100 @c This section is really only a place-holder, and needs to be expanded
5101 @c with more details.
5103 For some multi-threaded targets, @value{GDBN} supports an optional
5104 mode of operation in which you can examine stopped program threads in
5105 the debugger while other threads continue to execute freely. This
5106 minimizes intrusion when debugging live systems, such as programs
5107 where some threads have real-time constraints or must continue to
5108 respond to external events. This is referred to as @dfn{non-stop} mode.
5110 In non-stop mode, when a thread stops to report a debugging event,
5111 @emph{only} that thread is stopped; @value{GDBN} does not stop other
5112 threads as well, in contrast to the all-stop mode behavior. Additionally,
5113 execution commands such as @code{continue} and @code{step} apply by default
5114 only to the current thread in non-stop mode, rather than all threads as
5115 in all-stop mode. This allows you to control threads explicitly in
5116 ways that are not possible in all-stop mode --- for example, stepping
5117 one thread while allowing others to run freely, stepping
5118 one thread while holding all others stopped, or stepping several threads
5119 independently and simultaneously.
5121 To enter non-stop mode, use this sequence of commands before you run
5122 or attach to your program:
5125 # Enable the async interface.
5128 # If using the CLI, pagination breaks non-stop.
5131 # Finally, turn it on!
5135 You can use these commands to manipulate the non-stop mode setting:
5138 @kindex set non-stop
5139 @item set non-stop on
5140 Enable selection of non-stop mode.
5141 @item set non-stop off
5142 Disable selection of non-stop mode.
5143 @kindex show non-stop
5145 Show the current non-stop enablement setting.
5148 Note these commands only reflect whether non-stop mode is enabled,
5149 not whether the currently-executing program is being run in non-stop mode.
5150 In particular, the @code{set non-stop} preference is only consulted when
5151 @value{GDBN} starts or connects to the target program, and it is generally
5152 not possible to switch modes once debugging has started. Furthermore,
5153 since not all targets support non-stop mode, even when you have enabled
5154 non-stop mode, @value{GDBN} may still fall back to all-stop operation by
5157 In non-stop mode, all execution commands apply only to the current thread
5158 by default. That is, @code{continue} only continues one thread.
5159 To continue all threads, issue @code{continue -a} or @code{c -a}.
5161 You can use @value{GDBN}'s background execution commands
5162 (@pxref{Background Execution}) to run some threads in the background
5163 while you continue to examine or step others from @value{GDBN}.
5164 The MI execution commands (@pxref{GDB/MI Program Execution}) are
5165 always executed asynchronously in non-stop mode.
5167 Suspending execution is done with the @code{interrupt} command when
5168 running in the background, or @kbd{Ctrl-c} during foreground execution.
5169 In all-stop mode, this stops the whole process;
5170 but in non-stop mode the interrupt applies only to the current thread.
5171 To stop the whole program, use @code{interrupt -a}.
5173 Other execution commands do not currently support the @code{-a} option.
5175 In non-stop mode, when a thread stops, @value{GDBN} doesn't automatically make
5176 that thread current, as it does in all-stop mode. This is because the
5177 thread stop notifications are asynchronous with respect to @value{GDBN}'s
5178 command interpreter, and it would be confusing if @value{GDBN} unexpectedly
5179 changed to a different thread just as you entered a command to operate on the
5180 previously current thread.
5182 @node Background Execution
5183 @subsection Background Execution
5185 @cindex foreground execution
5186 @cindex background execution
5187 @cindex asynchronous execution
5188 @cindex execution, foreground, background and asynchronous
5190 @value{GDBN}'s execution commands have two variants: the normal
5191 foreground (synchronous) behavior, and a background
5192 (asynchronous) behavior. In foreground execution, @value{GDBN} waits for
5193 the program to report that some thread has stopped before prompting for
5194 another command. In background execution, @value{GDBN} immediately gives
5195 a command prompt so that you can issue other commands while your program runs.
5197 You need to explicitly enable asynchronous mode before you can use
5198 background execution commands. You can use these commands to
5199 manipulate the asynchronous mode setting:
5202 @kindex set target-async
5203 @item set target-async on
5204 Enable asynchronous mode.
5205 @item set target-async off
5206 Disable asynchronous mode.
5207 @kindex show target-async
5208 @item show target-async
5209 Show the current target-async setting.
5212 If the target doesn't support async mode, @value{GDBN} issues an error
5213 message if you attempt to use the background execution commands.
5215 To specify background execution, add a @code{&} to the command. For example,
5216 the background form of the @code{continue} command is @code{continue&}, or
5217 just @code{c&}. The execution commands that accept background execution
5223 @xref{Starting, , Starting your Program}.
5227 @xref{Attach, , Debugging an Already-running Process}.
5231 @xref{Continuing and Stepping, step}.
5235 @xref{Continuing and Stepping, stepi}.
5239 @xref{Continuing and Stepping, next}.
5243 @xref{Continuing and Stepping, nexti}.
5247 @xref{Continuing and Stepping, continue}.
5251 @xref{Continuing and Stepping, finish}.
5255 @xref{Continuing and Stepping, until}.
5259 Background execution is especially useful in conjunction with non-stop
5260 mode for debugging programs with multiple threads; see @ref{Non-Stop Mode}.
5261 However, you can also use these commands in the normal all-stop mode with
5262 the restriction that you cannot issue another execution command until the
5263 previous one finishes. Examples of commands that are valid in all-stop
5264 mode while the program is running include @code{help} and @code{info break}.
5266 You can interrupt your program while it is running in the background by
5267 using the @code{interrupt} command.
5274 Suspend execution of the running program. In all-stop mode,
5275 @code{interrupt} stops the whole process, but in non-stop mode, it stops
5276 only the current thread. To stop the whole program in non-stop mode,
5277 use @code{interrupt -a}.
5280 @node Thread-Specific Breakpoints
5281 @subsection Thread-Specific Breakpoints
5283 When your program has multiple threads (@pxref{Threads,, Debugging
5284 Programs with Multiple Threads}), you can choose whether to set
5285 breakpoints on all threads, or on a particular thread.
5288 @cindex breakpoints and threads
5289 @cindex thread breakpoints
5290 @kindex break @dots{} thread @var{threadno}
5291 @item break @var{linespec} thread @var{threadno}
5292 @itemx break @var{linespec} thread @var{threadno} if @dots{}
5293 @var{linespec} specifies source lines; there are several ways of
5294 writing them (@pxref{Specify Location}), but the effect is always to
5295 specify some source line.
5297 Use the qualifier @samp{thread @var{threadno}} with a breakpoint command
5298 to specify that you only want @value{GDBN} to stop the program when a
5299 particular thread reaches this breakpoint. @var{threadno} is one of the
5300 numeric thread identifiers assigned by @value{GDBN}, shown in the first
5301 column of the @samp{info threads} display.
5303 If you do not specify @samp{thread @var{threadno}} when you set a
5304 breakpoint, the breakpoint applies to @emph{all} threads of your
5307 You can use the @code{thread} qualifier on conditional breakpoints as
5308 well; in this case, place @samp{thread @var{threadno}} before or
5309 after the breakpoint condition, like this:
5312 (@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
5317 @node Interrupted System Calls
5318 @subsection Interrupted System Calls
5320 @cindex thread breakpoints and system calls
5321 @cindex system calls and thread breakpoints
5322 @cindex premature return from system calls
5323 There is an unfortunate side effect when using @value{GDBN} to debug
5324 multi-threaded programs. If one thread stops for a
5325 breakpoint, or for some other reason, and another thread is blocked in a
5326 system call, then the system call may return prematurely. This is a
5327 consequence of the interaction between multiple threads and the signals
5328 that @value{GDBN} uses to implement breakpoints and other events that
5331 To handle this problem, your program should check the return value of
5332 each system call and react appropriately. This is good programming
5335 For example, do not write code like this:
5341 The call to @code{sleep} will return early if a different thread stops
5342 at a breakpoint or for some other reason.
5344 Instead, write this:
5349 unslept = sleep (unslept);
5352 A system call is allowed to return early, so the system is still
5353 conforming to its specification. But @value{GDBN} does cause your
5354 multi-threaded program to behave differently than it would without
5357 Also, @value{GDBN} uses internal breakpoints in the thread library to
5358 monitor certain events such as thread creation and thread destruction.
5359 When such an event happens, a system call in another thread may return
5360 prematurely, even though your program does not appear to stop.
5363 @subsection Observer Mode
5365 If you want to build on non-stop mode and observe program behavior
5366 without any chance of disruption by @value{GDBN}, you can set
5367 variables to disable all of the debugger's attempts to modify state,
5368 whether by writing memory, inserting breakpoints, etc. These operate
5369 at a low level, intercepting operations from all commands.
5371 When all of these are set to @code{off}, then @value{GDBN} is said to
5372 be @dfn{observer mode}. As a convenience, the variable
5373 @code{observer} can be set to disable these, plus enable non-stop
5376 Note that @value{GDBN} will not prevent you from making nonsensical
5377 combinations of these settings. For instance, if you have enabled
5378 @code{may-insert-breakpoints} but disabled @code{may-write-memory},
5379 then breakpoints that work by writing trap instructions into the code
5380 stream will still not be able to be placed.
5385 @item set observer on
5386 @itemx set observer off
5387 When set to @code{on}, this disables all the permission variables
5388 below (except for @code{insert-fast-tracepoints}), plus enables
5389 non-stop debugging. Setting this to @code{off} switches back to
5390 normal debugging, though remaining in non-stop mode.
5393 Show whether observer mode is on or off.
5395 @kindex may-write-registers
5396 @item set may-write-registers on
5397 @itemx set may-write-registers off
5398 This controls whether @value{GDBN} will attempt to alter the values of
5399 registers, such as with assignment expressions in @code{print}, or the
5400 @code{jump} command. It defaults to @code{on}.
5402 @item show may-write-registers
5403 Show the current permission to write registers.
5405 @kindex may-write-memory
5406 @item set may-write-memory on
5407 @itemx set may-write-memory off
5408 This controls whether @value{GDBN} will attempt to alter the contents
5409 of memory, such as with assignment expressions in @code{print}. It
5410 defaults to @code{on}.
5412 @item show may-write-memory
5413 Show the current permission to write memory.
5415 @kindex may-insert-breakpoints
5416 @item set may-insert-breakpoints on
5417 @itemx set may-insert-breakpoints off
5418 This controls whether @value{GDBN} will attempt to insert breakpoints.
5419 This affects all breakpoints, including internal breakpoints defined
5420 by @value{GDBN}. It defaults to @code{on}.
5422 @item show may-insert-breakpoints
5423 Show the current permission to insert breakpoints.
5425 @kindex may-insert-tracepoints
5426 @item set may-insert-tracepoints on
5427 @itemx set may-insert-tracepoints off
5428 This controls whether @value{GDBN} will attempt to insert (regular)
5429 tracepoints at the beginning of a tracing experiment. It affects only
5430 non-fast tracepoints, fast tracepoints being under the control of
5431 @code{may-insert-fast-tracepoints}. It defaults to @code{on}.
5433 @item show may-insert-tracepoints
5434 Show the current permission to insert tracepoints.
5436 @kindex may-insert-fast-tracepoints
5437 @item set may-insert-fast-tracepoints on
5438 @itemx set may-insert-fast-tracepoints off
5439 This controls whether @value{GDBN} will attempt to insert fast
5440 tracepoints at the beginning of a tracing experiment. It affects only
5441 fast tracepoints, regular (non-fast) tracepoints being under the
5442 control of @code{may-insert-tracepoints}. It defaults to @code{on}.
5444 @item show may-insert-fast-tracepoints
5445 Show the current permission to insert fast tracepoints.
5447 @kindex may-interrupt
5448 @item set may-interrupt on
5449 @itemx set may-interrupt off
5450 This controls whether @value{GDBN} will attempt to interrupt or stop
5451 program execution. When this variable is @code{off}, the
5452 @code{interrupt} command will have no effect, nor will
5453 @kbd{Ctrl-c}. It defaults to @code{on}.
5455 @item show may-interrupt
5456 Show the current permission to interrupt or stop the program.
5460 @node Reverse Execution
5461 @chapter Running programs backward
5462 @cindex reverse execution
5463 @cindex running programs backward
5465 When you are debugging a program, it is not unusual to realize that
5466 you have gone too far, and some event of interest has already happened.
5467 If the target environment supports it, @value{GDBN} can allow you to
5468 ``rewind'' the program by running it backward.
5470 A target environment that supports reverse execution should be able
5471 to ``undo'' the changes in machine state that have taken place as the
5472 program was executing normally. Variables, registers etc.@: should
5473 revert to their previous values. Obviously this requires a great
5474 deal of sophistication on the part of the target environment; not
5475 all target environments can support reverse execution.
5477 When a program is executed in reverse, the instructions that
5478 have most recently been executed are ``un-executed'', in reverse
5479 order. The program counter runs backward, following the previous
5480 thread of execution in reverse. As each instruction is ``un-executed'',
5481 the values of memory and/or registers that were changed by that
5482 instruction are reverted to their previous states. After executing
5483 a piece of source code in reverse, all side effects of that code
5484 should be ``undone'', and all variables should be returned to their
5485 prior values@footnote{
5486 Note that some side effects are easier to undo than others. For instance,
5487 memory and registers are relatively easy, but device I/O is hard. Some
5488 targets may be able undo things like device I/O, and some may not.
5490 The contract between @value{GDBN} and the reverse executing target
5491 requires only that the target do something reasonable when
5492 @value{GDBN} tells it to execute backwards, and then report the
5493 results back to @value{GDBN}. Whatever the target reports back to
5494 @value{GDBN}, @value{GDBN} will report back to the user. @value{GDBN}
5495 assumes that the memory and registers that the target reports are in a
5496 consistant state, but @value{GDBN} accepts whatever it is given.
5499 If you are debugging in a target environment that supports
5500 reverse execution, @value{GDBN} provides the following commands.
5503 @kindex reverse-continue
5504 @kindex rc @r{(@code{reverse-continue})}
5505 @item reverse-continue @r{[}@var{ignore-count}@r{]}
5506 @itemx rc @r{[}@var{ignore-count}@r{]}
5507 Beginning at the point where your program last stopped, start executing
5508 in reverse. Reverse execution will stop for breakpoints and synchronous
5509 exceptions (signals), just like normal execution. Behavior of
5510 asynchronous signals depends on the target environment.
5512 @kindex reverse-step
5513 @kindex rs @r{(@code{step})}
5514 @item reverse-step @r{[}@var{count}@r{]}
5515 Run the program backward until control reaches the start of a
5516 different source line; then stop it, and return control to @value{GDBN}.
5518 Like the @code{step} command, @code{reverse-step} will only stop
5519 at the beginning of a source line. It ``un-executes'' the previously
5520 executed source line. If the previous source line included calls to
5521 debuggable functions, @code{reverse-step} will step (backward) into
5522 the called function, stopping at the beginning of the @emph{last}
5523 statement in the called function (typically a return statement).
5525 Also, as with the @code{step} command, if non-debuggable functions are
5526 called, @code{reverse-step} will run thru them backward without stopping.
5528 @kindex reverse-stepi
5529 @kindex rsi @r{(@code{reverse-stepi})}
5530 @item reverse-stepi @r{[}@var{count}@r{]}
5531 Reverse-execute one machine instruction. Note that the instruction
5532 to be reverse-executed is @emph{not} the one pointed to by the program
5533 counter, but the instruction executed prior to that one. For instance,
5534 if the last instruction was a jump, @code{reverse-stepi} will take you
5535 back from the destination of the jump to the jump instruction itself.
5537 @kindex reverse-next
5538 @kindex rn @r{(@code{reverse-next})}
5539 @item reverse-next @r{[}@var{count}@r{]}
5540 Run backward to the beginning of the previous line executed in
5541 the current (innermost) stack frame. If the line contains function
5542 calls, they will be ``un-executed'' without stopping. Starting from
5543 the first line of a function, @code{reverse-next} will take you back
5544 to the caller of that function, @emph{before} the function was called,
5545 just as the normal @code{next} command would take you from the last
5546 line of a function back to its return to its caller
5547 @footnote{Unless the code is too heavily optimized.}.
5549 @kindex reverse-nexti
5550 @kindex rni @r{(@code{reverse-nexti})}
5551 @item reverse-nexti @r{[}@var{count}@r{]}
5552 Like @code{nexti}, @code{reverse-nexti} executes a single instruction
5553 in reverse, except that called functions are ``un-executed'' atomically.
5554 That is, if the previously executed instruction was a return from
5555 another function, @code{reverse-nexti} will continue to execute
5556 in reverse until the call to that function (from the current stack
5559 @kindex reverse-finish
5560 @item reverse-finish
5561 Just as the @code{finish} command takes you to the point where the
5562 current function returns, @code{reverse-finish} takes you to the point
5563 where it was called. Instead of ending up at the end of the current
5564 function invocation, you end up at the beginning.
5566 @kindex set exec-direction
5567 @item set exec-direction
5568 Set the direction of target execution.
5569 @itemx set exec-direction reverse
5570 @cindex execute forward or backward in time
5571 @value{GDBN} will perform all execution commands in reverse, until the
5572 exec-direction mode is changed to ``forward''. Affected commands include
5573 @code{step, stepi, next, nexti, continue, and finish}. The @code{return}
5574 command cannot be used in reverse mode.
5575 @item set exec-direction forward
5576 @value{GDBN} will perform all execution commands in the normal fashion.
5577 This is the default.
5581 @node Process Record and Replay
5582 @chapter Recording Inferior's Execution and Replaying It
5583 @cindex process record and replay
5584 @cindex recording inferior's execution and replaying it
5586 On some platforms, @value{GDBN} provides a special @dfn{process record
5587 and replay} target that can record a log of the process execution, and
5588 replay it later with both forward and reverse execution commands.
5591 When this target is in use, if the execution log includes the record
5592 for the next instruction, @value{GDBN} will debug in @dfn{replay
5593 mode}. In the replay mode, the inferior does not really execute code
5594 instructions. Instead, all the events that normally happen during
5595 code execution are taken from the execution log. While code is not
5596 really executed in replay mode, the values of registers (including the
5597 program counter register) and the memory of the inferior are still
5598 changed as they normally would. Their contents are taken from the
5602 If the record for the next instruction is not in the execution log,
5603 @value{GDBN} will debug in @dfn{record mode}. In this mode, the
5604 inferior executes normally, and @value{GDBN} records the execution log
5607 The process record and replay target supports reverse execution
5608 (@pxref{Reverse Execution}), even if the platform on which the
5609 inferior runs does not. However, the reverse execution is limited in
5610 this case by the range of the instructions recorded in the execution
5611 log. In other words, reverse execution on platforms that don't
5612 support it directly can only be done in the replay mode.
5614 When debugging in the reverse direction, @value{GDBN} will work in
5615 replay mode as long as the execution log includes the record for the
5616 previous instruction; otherwise, it will work in record mode, if the
5617 platform supports reverse execution, or stop if not.
5619 For architecture environments that support process record and replay,
5620 @value{GDBN} provides the following commands:
5623 @kindex target record
5627 This command starts the process record and replay target. The process
5628 record and replay target can only debug a process that is already
5629 running. Therefore, you need first to start the process with the
5630 @kbd{run} or @kbd{start} commands, and then start the recording with
5631 the @kbd{target record} command.
5633 Both @code{record} and @code{rec} are aliases of @code{target record}.
5635 @cindex displaced stepping, and process record and replay
5636 Displaced stepping (@pxref{Maintenance Commands,, displaced stepping})
5637 will be automatically disabled when process record and replay target
5638 is started. That's because the process record and replay target
5639 doesn't support displaced stepping.
5641 @cindex non-stop mode, and process record and replay
5642 @cindex asynchronous execution, and process record and replay
5643 If the inferior is in the non-stop mode (@pxref{Non-Stop Mode}) or in
5644 the asynchronous execution mode (@pxref{Background Execution}), the
5645 process record and replay target cannot be started because it doesn't
5646 support these two modes.
5651 Stop the process record and replay target. When process record and
5652 replay target stops, the entire execution log will be deleted and the
5653 inferior will either be terminated, or will remain in its final state.
5655 When you stop the process record and replay target in record mode (at
5656 the end of the execution log), the inferior will be stopped at the
5657 next instruction that would have been recorded. In other words, if
5658 you record for a while and then stop recording, the inferior process
5659 will be left in the same state as if the recording never happened.
5661 On the other hand, if the process record and replay target is stopped
5662 while in replay mode (that is, not at the end of the execution log,
5663 but at some earlier point), the inferior process will become ``live''
5664 at that earlier state, and it will then be possible to continue the
5665 usual ``live'' debugging of the process from that state.
5667 When the inferior process exits, or @value{GDBN} detaches from it,
5668 process record and replay target will automatically stop itself.
5671 @item record save @var{filename}
5672 Save the execution log to a file @file{@var{filename}}.
5673 Default filename is @file{gdb_record.@var{process_id}}, where
5674 @var{process_id} is the process ID of the inferior.
5676 @kindex record restore
5677 @item record restore @var{filename}
5678 Restore the execution log from a file @file{@var{filename}}.
5679 File must have been created with @code{record save}.
5681 @kindex set record insn-number-max
5682 @item set record insn-number-max @var{limit}
5683 Set the limit of instructions to be recorded. Default value is 200000.
5685 If @var{limit} is a positive number, then @value{GDBN} will start
5686 deleting instructions from the log once the number of the record
5687 instructions becomes greater than @var{limit}. For every new recorded
5688 instruction, @value{GDBN} will delete the earliest recorded
5689 instruction to keep the number of recorded instructions at the limit.
5690 (Since deleting recorded instructions loses information, @value{GDBN}
5691 lets you control what happens when the limit is reached, by means of
5692 the @code{stop-at-limit} option, described below.)
5694 If @var{limit} is zero, @value{GDBN} will never delete recorded
5695 instructions from the execution log. The number of recorded
5696 instructions is unlimited in this case.
5698 @kindex show record insn-number-max
5699 @item show record insn-number-max
5700 Show the limit of instructions to be recorded.
5702 @kindex set record stop-at-limit
5703 @item set record stop-at-limit
5704 Control the behavior when the number of recorded instructions reaches
5705 the limit. If ON (the default), @value{GDBN} will stop when the limit
5706 is reached for the first time and ask you whether you want to stop the
5707 inferior or continue running it and recording the execution log. If
5708 you decide to continue recording, each new recorded instruction will
5709 cause the oldest one to be deleted.
5711 If this option is OFF, @value{GDBN} will automatically delete the
5712 oldest record to make room for each new one, without asking.
5714 @kindex show record stop-at-limit
5715 @item show record stop-at-limit
5716 Show the current setting of @code{stop-at-limit}.
5718 @kindex set record memory-query
5719 @item set record memory-query
5720 Control the behavior when @value{GDBN} is unable to record memory
5721 changes caused by an instruction. If ON, @value{GDBN} will query
5722 whether to stop the inferior in that case.
5724 If this option is OFF (the default), @value{GDBN} will automatically
5725 ignore the effect of such instructions on memory. Later, when
5726 @value{GDBN} replays this execution log, it will mark the log of this
5727 instruction as not accessible, and it will not affect the replay
5730 @kindex show record memory-query
5731 @item show record memory-query
5732 Show the current setting of @code{memory-query}.
5736 Show various statistics about the state of process record and its
5737 in-memory execution log buffer, including:
5741 Whether in record mode or replay mode.
5743 Lowest recorded instruction number (counting from when the current execution log started recording instructions).
5745 Highest recorded instruction number.
5747 Current instruction about to be replayed (if in replay mode).
5749 Number of instructions contained in the execution log.
5751 Maximum number of instructions that may be contained in the execution log.
5754 @kindex record delete
5757 When record target runs in replay mode (``in the past''), delete the
5758 subsequent execution log and begin to record a new execution log starting
5759 from the current address. This means you will abandon the previously
5760 recorded ``future'' and begin recording a new ``future''.
5765 @chapter Examining the Stack
5767 When your program has stopped, the first thing you need to know is where it
5768 stopped and how it got there.
5771 Each time your program performs a function call, information about the call
5773 That information includes the location of the call in your program,
5774 the arguments of the call,
5775 and the local variables of the function being called.
5776 The information is saved in a block of data called a @dfn{stack frame}.
5777 The stack frames are allocated in a region of memory called the @dfn{call
5780 When your program stops, the @value{GDBN} commands for examining the
5781 stack allow you to see all of this information.
5783 @cindex selected frame
5784 One of the stack frames is @dfn{selected} by @value{GDBN} and many
5785 @value{GDBN} commands refer implicitly to the selected frame. In
5786 particular, whenever you ask @value{GDBN} for the value of a variable in
5787 your program, the value is found in the selected frame. There are
5788 special @value{GDBN} commands to select whichever frame you are
5789 interested in. @xref{Selection, ,Selecting a Frame}.
5791 When your program stops, @value{GDBN} automatically selects the
5792 currently executing frame and describes it briefly, similar to the
5793 @code{frame} command (@pxref{Frame Info, ,Information about a Frame}).
5796 * Frames:: Stack frames
5797 * Backtrace:: Backtraces
5798 * Selection:: Selecting a frame
5799 * Frame Info:: Information on a frame
5804 @section Stack Frames
5806 @cindex frame, definition
5808 The call stack is divided up into contiguous pieces called @dfn{stack
5809 frames}, or @dfn{frames} for short; each frame is the data associated
5810 with one call to one function. The frame contains the arguments given
5811 to the function, the function's local variables, and the address at
5812 which the function is executing.
5814 @cindex initial frame
5815 @cindex outermost frame
5816 @cindex innermost frame
5817 When your program is started, the stack has only one frame, that of the
5818 function @code{main}. This is called the @dfn{initial} frame or the
5819 @dfn{outermost} frame. Each time a function is called, a new frame is
5820 made. Each time a function returns, the frame for that function invocation
5821 is eliminated. If a function is recursive, there can be many frames for
5822 the same function. The frame for the function in which execution is
5823 actually occurring is called the @dfn{innermost} frame. This is the most
5824 recently created of all the stack frames that still exist.
5826 @cindex frame pointer
5827 Inside your program, stack frames are identified by their addresses. A
5828 stack frame consists of many bytes, each of which has its own address; each
5829 kind of computer has a convention for choosing one byte whose
5830 address serves as the address of the frame. Usually this address is kept
5831 in a register called the @dfn{frame pointer register}
5832 (@pxref{Registers, $fp}) while execution is going on in that frame.
5834 @cindex frame number
5835 @value{GDBN} assigns numbers to all existing stack frames, starting with
5836 zero for the innermost frame, one for the frame that called it,
5837 and so on upward. These numbers do not really exist in your program;
5838 they are assigned by @value{GDBN} to give you a way of designating stack
5839 frames in @value{GDBN} commands.
5841 @c The -fomit-frame-pointer below perennially causes hbox overflow
5842 @c underflow problems.
5843 @cindex frameless execution
5844 Some compilers provide a way to compile functions so that they operate
5845 without stack frames. (For example, the @value{NGCC} option
5847 @samp{-fomit-frame-pointer}
5849 generates functions without a frame.)
5850 This is occasionally done with heavily used library functions to save
5851 the frame setup time. @value{GDBN} has limited facilities for dealing
5852 with these function invocations. If the innermost function invocation
5853 has no stack frame, @value{GDBN} nevertheless regards it as though
5854 it had a separate frame, which is numbered zero as usual, allowing
5855 correct tracing of the function call chain. However, @value{GDBN} has
5856 no provision for frameless functions elsewhere in the stack.
5859 @kindex frame@r{, command}
5860 @cindex current stack frame
5861 @item frame @var{args}
5862 The @code{frame} command allows you to move from one stack frame to another,
5863 and to print the stack frame you select. @var{args} may be either the
5864 address of the frame or the stack frame number. Without an argument,
5865 @code{frame} prints the current stack frame.
5867 @kindex select-frame
5868 @cindex selecting frame silently
5870 The @code{select-frame} command allows you to move from one stack frame
5871 to another without printing the frame. This is the silent version of
5879 @cindex call stack traces
5880 A backtrace is a summary of how your program got where it is. It shows one
5881 line per frame, for many frames, starting with the currently executing
5882 frame (frame zero), followed by its caller (frame one), and on up the
5887 @kindex bt @r{(@code{backtrace})}
5890 Print a backtrace of the entire stack: one line per frame for all
5891 frames in the stack.
5893 You can stop the backtrace at any time by typing the system interrupt
5894 character, normally @kbd{Ctrl-c}.
5896 @item backtrace @var{n}
5898 Similar, but print only the innermost @var{n} frames.
5900 @item backtrace -@var{n}
5902 Similar, but print only the outermost @var{n} frames.
5904 @item backtrace full
5906 @itemx bt full @var{n}
5907 @itemx bt full -@var{n}
5908 Print the values of the local variables also. @var{n} specifies the
5909 number of frames to print, as described above.
5914 The names @code{where} and @code{info stack} (abbreviated @code{info s})
5915 are additional aliases for @code{backtrace}.
5917 @cindex multiple threads, backtrace
5918 In a multi-threaded program, @value{GDBN} by default shows the
5919 backtrace only for the current thread. To display the backtrace for
5920 several or all of the threads, use the command @code{thread apply}
5921 (@pxref{Threads, thread apply}). For example, if you type @kbd{thread
5922 apply all backtrace}, @value{GDBN} will display the backtrace for all
5923 the threads; this is handy when you debug a core dump of a
5924 multi-threaded program.
5926 Each line in the backtrace shows the frame number and the function name.
5927 The program counter value is also shown---unless you use @code{set
5928 print address off}. The backtrace also shows the source file name and
5929 line number, as well as the arguments to the function. The program
5930 counter value is omitted if it is at the beginning of the code for that
5933 Here is an example of a backtrace. It was made with the command
5934 @samp{bt 3}, so it shows the innermost three frames.
5938 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
5940 #1 0x6e38 in expand_macro (sym=0x2b600, data=...) at macro.c:242
5941 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
5943 (More stack frames follow...)
5948 The display for frame zero does not begin with a program counter
5949 value, indicating that your program has stopped at the beginning of the
5950 code for line @code{993} of @code{builtin.c}.
5953 The value of parameter @code{data} in frame 1 has been replaced by
5954 @code{@dots{}}. By default, @value{GDBN} prints the value of a parameter
5955 only if it is a scalar (integer, pointer, enumeration, etc). See command
5956 @kbd{set print frame-arguments} in @ref{Print Settings} for more details
5957 on how to configure the way function parameter values are printed.
5959 @cindex value optimized out, in backtrace
5960 @cindex function call arguments, optimized out
5961 If your program was compiled with optimizations, some compilers will
5962 optimize away arguments passed to functions if those arguments are
5963 never used after the call. Such optimizations generate code that
5964 passes arguments through registers, but doesn't store those arguments
5965 in the stack frame. @value{GDBN} has no way of displaying such
5966 arguments in stack frames other than the innermost one. Here's what
5967 such a backtrace might look like:
5971 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
5973 #1 0x6e38 in expand_macro (sym=<value optimized out>) at macro.c:242
5974 #2 0x6840 in expand_token (obs=0x0, t=<value optimized out>, td=0xf7fffb08)
5976 (More stack frames follow...)
5981 The values of arguments that were not saved in their stack frames are
5982 shown as @samp{<value optimized out>}.
5984 If you need to display the values of such optimized-out arguments,
5985 either deduce that from other variables whose values depend on the one
5986 you are interested in, or recompile without optimizations.
5988 @cindex backtrace beyond @code{main} function
5989 @cindex program entry point
5990 @cindex startup code, and backtrace
5991 Most programs have a standard user entry point---a place where system
5992 libraries and startup code transition into user code. For C this is
5993 @code{main}@footnote{
5994 Note that embedded programs (the so-called ``free-standing''
5995 environment) are not required to have a @code{main} function as the
5996 entry point. They could even have multiple entry points.}.
5997 When @value{GDBN} finds the entry function in a backtrace
5998 it will terminate the backtrace, to avoid tracing into highly
5999 system-specific (and generally uninteresting) code.
6001 If you need to examine the startup code, or limit the number of levels
6002 in a backtrace, you can change this behavior:
6005 @item set backtrace past-main
6006 @itemx set backtrace past-main on
6007 @kindex set backtrace
6008 Backtraces will continue past the user entry point.
6010 @item set backtrace past-main off
6011 Backtraces will stop when they encounter the user entry point. This is the
6014 @item show backtrace past-main
6015 @kindex show backtrace
6016 Display the current user entry point backtrace policy.
6018 @item set backtrace past-entry
6019 @itemx set backtrace past-entry on
6020 Backtraces will continue past the internal entry point of an application.
6021 This entry point is encoded by the linker when the application is built,
6022 and is likely before the user entry point @code{main} (or equivalent) is called.
6024 @item set backtrace past-entry off
6025 Backtraces will stop when they encounter the internal entry point of an
6026 application. This is the default.
6028 @item show backtrace past-entry
6029 Display the current internal entry point backtrace policy.
6031 @item set backtrace limit @var{n}
6032 @itemx set backtrace limit 0
6033 @cindex backtrace limit
6034 Limit the backtrace to @var{n} levels. A value of zero means
6037 @item show backtrace limit
6038 Display the current limit on backtrace levels.
6042 @section Selecting a Frame
6044 Most commands for examining the stack and other data in your program work on
6045 whichever stack frame is selected at the moment. Here are the commands for
6046 selecting a stack frame; all of them finish by printing a brief description
6047 of the stack frame just selected.
6050 @kindex frame@r{, selecting}
6051 @kindex f @r{(@code{frame})}
6054 Select frame number @var{n}. Recall that frame zero is the innermost
6055 (currently executing) frame, frame one is the frame that called the
6056 innermost one, and so on. The highest-numbered frame is the one for
6059 @item frame @var{addr}
6061 Select the frame at address @var{addr}. This is useful mainly if the
6062 chaining of stack frames has been damaged by a bug, making it
6063 impossible for @value{GDBN} to assign numbers properly to all frames. In
6064 addition, this can be useful when your program has multiple stacks and
6065 switches between them.
6067 On the SPARC architecture, @code{frame} needs two addresses to
6068 select an arbitrary frame: a frame pointer and a stack pointer.
6070 On the MIPS and Alpha architecture, it needs two addresses: a stack
6071 pointer and a program counter.
6073 On the 29k architecture, it needs three addresses: a register stack
6074 pointer, a program counter, and a memory stack pointer.
6078 Move @var{n} frames up the stack. For positive numbers @var{n}, this
6079 advances toward the outermost frame, to higher frame numbers, to frames
6080 that have existed longer. @var{n} defaults to one.
6083 @kindex do @r{(@code{down})}
6085 Move @var{n} frames down the stack. For positive numbers @var{n}, this
6086 advances toward the innermost frame, to lower frame numbers, to frames
6087 that were created more recently. @var{n} defaults to one. You may
6088 abbreviate @code{down} as @code{do}.
6091 All of these commands end by printing two lines of output describing the
6092 frame. The first line shows the frame number, the function name, the
6093 arguments, and the source file and line number of execution in that
6094 frame. The second line shows the text of that source line.
6102 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
6104 10 read_input_file (argv[i]);
6108 After such a printout, the @code{list} command with no arguments
6109 prints ten lines centered on the point of execution in the frame.
6110 You can also edit the program at the point of execution with your favorite
6111 editing program by typing @code{edit}.
6112 @xref{List, ,Printing Source Lines},
6116 @kindex down-silently
6118 @item up-silently @var{n}
6119 @itemx down-silently @var{n}
6120 These two commands are variants of @code{up} and @code{down},
6121 respectively; they differ in that they do their work silently, without
6122 causing display of the new frame. They are intended primarily for use
6123 in @value{GDBN} command scripts, where the output might be unnecessary and
6128 @section Information About a Frame
6130 There are several other commands to print information about the selected
6136 When used without any argument, this command does not change which
6137 frame is selected, but prints a brief description of the currently
6138 selected stack frame. It can be abbreviated @code{f}. With an
6139 argument, this command is used to select a stack frame.
6140 @xref{Selection, ,Selecting a Frame}.
6143 @kindex info f @r{(@code{info frame})}
6146 This command prints a verbose description of the selected stack frame,
6151 the address of the frame
6153 the address of the next frame down (called by this frame)
6155 the address of the next frame up (caller of this frame)
6157 the language in which the source code corresponding to this frame is written
6159 the address of the frame's arguments
6161 the address of the frame's local variables
6163 the program counter saved in it (the address of execution in the caller frame)
6165 which registers were saved in the frame
6168 @noindent The verbose description is useful when
6169 something has gone wrong that has made the stack format fail to fit
6170 the usual conventions.
6172 @item info frame @var{addr}
6173 @itemx info f @var{addr}
6174 Print a verbose description of the frame at address @var{addr}, without
6175 selecting that frame. The selected frame remains unchanged by this
6176 command. This requires the same kind of address (more than one for some
6177 architectures) that you specify in the @code{frame} command.
6178 @xref{Selection, ,Selecting a Frame}.
6182 Print the arguments of the selected frame, each on a separate line.
6186 Print the local variables of the selected frame, each on a separate
6187 line. These are all variables (declared either static or automatic)
6188 accessible at the point of execution of the selected frame.
6191 @cindex catch exceptions, list active handlers
6192 @cindex exception handlers, how to list
6194 Print a list of all the exception handlers that are active in the
6195 current stack frame at the current point of execution. To see other
6196 exception handlers, visit the associated frame (using the @code{up},
6197 @code{down}, or @code{frame} commands); then type @code{info catch}.
6198 @xref{Set Catchpoints, , Setting Catchpoints}.
6204 @chapter Examining Source Files
6206 @value{GDBN} can print parts of your program's source, since the debugging
6207 information recorded in the program tells @value{GDBN} what source files were
6208 used to build it. When your program stops, @value{GDBN} spontaneously prints
6209 the line where it stopped. Likewise, when you select a stack frame
6210 (@pxref{Selection, ,Selecting a Frame}), @value{GDBN} prints the line where
6211 execution in that frame has stopped. You can print other portions of
6212 source files by explicit command.
6214 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
6215 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
6216 @value{GDBN} under @sc{gnu} Emacs}.
6219 * List:: Printing source lines
6220 * Specify Location:: How to specify code locations
6221 * Edit:: Editing source files
6222 * Search:: Searching source files
6223 * Source Path:: Specifying source directories
6224 * Machine Code:: Source and machine code
6228 @section Printing Source Lines
6231 @kindex l @r{(@code{list})}
6232 To print lines from a source file, use the @code{list} command
6233 (abbreviated @code{l}). By default, ten lines are printed.
6234 There are several ways to specify what part of the file you want to
6235 print; see @ref{Specify Location}, for the full list.
6237 Here are the forms of the @code{list} command most commonly used:
6240 @item list @var{linenum}
6241 Print lines centered around line number @var{linenum} in the
6242 current source file.
6244 @item list @var{function}
6245 Print lines centered around the beginning of function
6249 Print more lines. If the last lines printed were printed with a
6250 @code{list} command, this prints lines following the last lines
6251 printed; however, if the last line printed was a solitary line printed
6252 as part of displaying a stack frame (@pxref{Stack, ,Examining the
6253 Stack}), this prints lines centered around that line.
6256 Print lines just before the lines last printed.
6259 @cindex @code{list}, how many lines to display
6260 By default, @value{GDBN} prints ten source lines with any of these forms of
6261 the @code{list} command. You can change this using @code{set listsize}:
6264 @kindex set listsize
6265 @item set listsize @var{count}
6266 Make the @code{list} command display @var{count} source lines (unless
6267 the @code{list} argument explicitly specifies some other number).
6269 @kindex show listsize
6271 Display the number of lines that @code{list} prints.
6274 Repeating a @code{list} command with @key{RET} discards the argument,
6275 so it is equivalent to typing just @code{list}. This is more useful
6276 than listing the same lines again. An exception is made for an
6277 argument of @samp{-}; that argument is preserved in repetition so that
6278 each repetition moves up in the source file.
6280 In general, the @code{list} command expects you to supply zero, one or two
6281 @dfn{linespecs}. Linespecs specify source lines; there are several ways
6282 of writing them (@pxref{Specify Location}), but the effect is always
6283 to specify some source line.
6285 Here is a complete description of the possible arguments for @code{list}:
6288 @item list @var{linespec}
6289 Print lines centered around the line specified by @var{linespec}.
6291 @item list @var{first},@var{last}
6292 Print lines from @var{first} to @var{last}. Both arguments are
6293 linespecs. When a @code{list} command has two linespecs, and the
6294 source file of the second linespec is omitted, this refers to
6295 the same source file as the first linespec.
6297 @item list ,@var{last}
6298 Print lines ending with @var{last}.
6300 @item list @var{first},
6301 Print lines starting with @var{first}.
6304 Print lines just after the lines last printed.
6307 Print lines just before the lines last printed.
6310 As described in the preceding table.
6313 @node Specify Location
6314 @section Specifying a Location
6315 @cindex specifying location
6318 Several @value{GDBN} commands accept arguments that specify a location
6319 of your program's code. Since @value{GDBN} is a source-level
6320 debugger, a location usually specifies some line in the source code;
6321 for that reason, locations are also known as @dfn{linespecs}.
6323 Here are all the different ways of specifying a code location that
6324 @value{GDBN} understands:
6328 Specifies the line number @var{linenum} of the current source file.
6331 @itemx +@var{offset}
6332 Specifies the line @var{offset} lines before or after the @dfn{current
6333 line}. For the @code{list} command, the current line is the last one
6334 printed; for the breakpoint commands, this is the line at which
6335 execution stopped in the currently selected @dfn{stack frame}
6336 (@pxref{Frames, ,Frames}, for a description of stack frames.) When
6337 used as the second of the two linespecs in a @code{list} command,
6338 this specifies the line @var{offset} lines up or down from the first
6341 @item @var{filename}:@var{linenum}
6342 Specifies the line @var{linenum} in the source file @var{filename}.
6344 @item @var{function}
6345 Specifies the line that begins the body of the function @var{function}.
6346 For example, in C, this is the line with the open brace.
6348 @item @var{filename}:@var{function}
6349 Specifies the line that begins the body of the function @var{function}
6350 in the file @var{filename}. You only need the file name with a
6351 function name to avoid ambiguity when there are identically named
6352 functions in different source files.
6355 Specifies the line at which the label named @var{label} appears.
6356 @value{GDBN} searches for the label in the function corresponding to
6357 the currently selected stack frame. If there is no current selected
6358 stack frame (for instance, if the inferior is not running), then
6359 @value{GDBN} will not search for a label.
6361 @item *@var{address}
6362 Specifies the program address @var{address}. For line-oriented
6363 commands, such as @code{list} and @code{edit}, this specifies a source
6364 line that contains @var{address}. For @code{break} and other
6365 breakpoint oriented commands, this can be used to set breakpoints in
6366 parts of your program which do not have debugging information or
6369 Here @var{address} may be any expression valid in the current working
6370 language (@pxref{Languages, working language}) that specifies a code
6371 address. In addition, as a convenience, @value{GDBN} extends the
6372 semantics of expressions used in locations to cover the situations
6373 that frequently happen during debugging. Here are the various forms
6377 @item @var{expression}
6378 Any expression valid in the current working language.
6380 @item @var{funcaddr}
6381 An address of a function or procedure derived from its name. In C,
6382 C@t{++}, Java, Objective-C, Fortran, minimal, and assembly, this is
6383 simply the function's name @var{function} (and actually a special case
6384 of a valid expression). In Pascal and Modula-2, this is
6385 @code{&@var{function}}. In Ada, this is @code{@var{function}'Address}
6386 (although the Pascal form also works).
6388 This form specifies the address of the function's first instruction,
6389 before the stack frame and arguments have been set up.
6391 @item '@var{filename}'::@var{funcaddr}
6392 Like @var{funcaddr} above, but also specifies the name of the source
6393 file explicitly. This is useful if the name of the function does not
6394 specify the function unambiguously, e.g., if there are several
6395 functions with identical names in different source files.
6402 @section Editing Source Files
6403 @cindex editing source files
6406 @kindex e @r{(@code{edit})}
6407 To edit the lines in a source file, use the @code{edit} command.
6408 The editing program of your choice
6409 is invoked with the current line set to
6410 the active line in the program.
6411 Alternatively, there are several ways to specify what part of the file you
6412 want to print if you want to see other parts of the program:
6415 @item edit @var{location}
6416 Edit the source file specified by @code{location}. Editing starts at
6417 that @var{location}, e.g., at the specified source line of the
6418 specified file. @xref{Specify Location}, for all the possible forms
6419 of the @var{location} argument; here are the forms of the @code{edit}
6420 command most commonly used:
6423 @item edit @var{number}
6424 Edit the current source file with @var{number} as the active line number.
6426 @item edit @var{function}
6427 Edit the file containing @var{function} at the beginning of its definition.
6432 @subsection Choosing your Editor
6433 You can customize @value{GDBN} to use any editor you want
6435 The only restriction is that your editor (say @code{ex}), recognizes the
6436 following command-line syntax:
6438 ex +@var{number} file
6440 The optional numeric value +@var{number} specifies the number of the line in
6441 the file where to start editing.}.
6442 By default, it is @file{@value{EDITOR}}, but you can change this
6443 by setting the environment variable @code{EDITOR} before using
6444 @value{GDBN}. For example, to configure @value{GDBN} to use the
6445 @code{vi} editor, you could use these commands with the @code{sh} shell:
6451 or in the @code{csh} shell,
6453 setenv EDITOR /usr/bin/vi
6458 @section Searching Source Files
6459 @cindex searching source files
6461 There are two commands for searching through the current source file for a
6466 @kindex forward-search
6467 @item forward-search @var{regexp}
6468 @itemx search @var{regexp}
6469 The command @samp{forward-search @var{regexp}} checks each line,
6470 starting with the one following the last line listed, for a match for
6471 @var{regexp}. It lists the line that is found. You can use the
6472 synonym @samp{search @var{regexp}} or abbreviate the command name as
6475 @kindex reverse-search
6476 @item reverse-search @var{regexp}
6477 The command @samp{reverse-search @var{regexp}} checks each line, starting
6478 with the one before the last line listed and going backward, for a match
6479 for @var{regexp}. It lists the line that is found. You can abbreviate
6480 this command as @code{rev}.
6484 @section Specifying Source Directories
6487 @cindex directories for source files
6488 Executable programs sometimes do not record the directories of the source
6489 files from which they were compiled, just the names. Even when they do,
6490 the directories could be moved between the compilation and your debugging
6491 session. @value{GDBN} has a list of directories to search for source files;
6492 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
6493 it tries all the directories in the list, in the order they are present
6494 in the list, until it finds a file with the desired name.
6496 For example, suppose an executable references the file
6497 @file{/usr/src/foo-1.0/lib/foo.c}, and our source path is
6498 @file{/mnt/cross}. The file is first looked up literally; if this
6499 fails, @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c} is tried; if this
6500 fails, @file{/mnt/cross/foo.c} is opened; if this fails, an error
6501 message is printed. @value{GDBN} does not look up the parts of the
6502 source file name, such as @file{/mnt/cross/src/foo-1.0/lib/foo.c}.
6503 Likewise, the subdirectories of the source path are not searched: if
6504 the source path is @file{/mnt/cross}, and the binary refers to
6505 @file{foo.c}, @value{GDBN} would not find it under
6506 @file{/mnt/cross/usr/src/foo-1.0/lib}.
6508 Plain file names, relative file names with leading directories, file
6509 names containing dots, etc.@: are all treated as described above; for
6510 instance, if the source path is @file{/mnt/cross}, and the source file
6511 is recorded as @file{../lib/foo.c}, @value{GDBN} would first try
6512 @file{../lib/foo.c}, then @file{/mnt/cross/../lib/foo.c}, and after
6513 that---@file{/mnt/cross/foo.c}.
6515 Note that the executable search path is @emph{not} used to locate the
6518 Whenever you reset or rearrange the source path, @value{GDBN} clears out
6519 any information it has cached about where source files are found and where
6520 each line is in the file.
6524 When you start @value{GDBN}, its source path includes only @samp{cdir}
6525 and @samp{cwd}, in that order.
6526 To add other directories, use the @code{directory} command.
6528 The search path is used to find both program source files and @value{GDBN}
6529 script files (read using the @samp{-command} option and @samp{source} command).
6531 In addition to the source path, @value{GDBN} provides a set of commands
6532 that manage a list of source path substitution rules. A @dfn{substitution
6533 rule} specifies how to rewrite source directories stored in the program's
6534 debug information in case the sources were moved to a different
6535 directory between compilation and debugging. A rule is made of
6536 two strings, the first specifying what needs to be rewritten in
6537 the path, and the second specifying how it should be rewritten.
6538 In @ref{set substitute-path}, we name these two parts @var{from} and
6539 @var{to} respectively. @value{GDBN} does a simple string replacement
6540 of @var{from} with @var{to} at the start of the directory part of the
6541 source file name, and uses that result instead of the original file
6542 name to look up the sources.
6544 Using the previous example, suppose the @file{foo-1.0} tree has been
6545 moved from @file{/usr/src} to @file{/mnt/cross}, then you can tell
6546 @value{GDBN} to replace @file{/usr/src} in all source path names with
6547 @file{/mnt/cross}. The first lookup will then be
6548 @file{/mnt/cross/foo-1.0/lib/foo.c} in place of the original location
6549 of @file{/usr/src/foo-1.0/lib/foo.c}. To define a source path
6550 substitution rule, use the @code{set substitute-path} command
6551 (@pxref{set substitute-path}).
6553 To avoid unexpected substitution results, a rule is applied only if the
6554 @var{from} part of the directory name ends at a directory separator.
6555 For instance, a rule substituting @file{/usr/source} into
6556 @file{/mnt/cross} will be applied to @file{/usr/source/foo-1.0} but
6557 not to @file{/usr/sourceware/foo-2.0}. And because the substitution
6558 is applied only at the beginning of the directory name, this rule will
6559 not be applied to @file{/root/usr/source/baz.c} either.
6561 In many cases, you can achieve the same result using the @code{directory}
6562 command. However, @code{set substitute-path} can be more efficient in
6563 the case where the sources are organized in a complex tree with multiple
6564 subdirectories. With the @code{directory} command, you need to add each
6565 subdirectory of your project. If you moved the entire tree while
6566 preserving its internal organization, then @code{set substitute-path}
6567 allows you to direct the debugger to all the sources with one single
6570 @code{set substitute-path} is also more than just a shortcut command.
6571 The source path is only used if the file at the original location no
6572 longer exists. On the other hand, @code{set substitute-path} modifies
6573 the debugger behavior to look at the rewritten location instead. So, if
6574 for any reason a source file that is not relevant to your executable is
6575 located at the original location, a substitution rule is the only
6576 method available to point @value{GDBN} at the new location.
6578 @cindex @samp{--with-relocated-sources}
6579 @cindex default source path substitution
6580 You can configure a default source path substitution rule by
6581 configuring @value{GDBN} with the
6582 @samp{--with-relocated-sources=@var{dir}} option. The @var{dir}
6583 should be the name of a directory under @value{GDBN}'s configured
6584 prefix (set with @samp{--prefix} or @samp{--exec-prefix}), and
6585 directory names in debug information under @var{dir} will be adjusted
6586 automatically if the installed @value{GDBN} is moved to a new
6587 location. This is useful if @value{GDBN}, libraries or executables
6588 with debug information and corresponding source code are being moved
6592 @item directory @var{dirname} @dots{}
6593 @item dir @var{dirname} @dots{}
6594 Add directory @var{dirname} to the front of the source path. Several
6595 directory names may be given to this command, separated by @samp{:}
6596 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
6597 part of absolute file names) or
6598 whitespace. You may specify a directory that is already in the source
6599 path; this moves it forward, so @value{GDBN} searches it sooner.
6603 @vindex $cdir@r{, convenience variable}
6604 @vindex $cwd@r{, convenience variable}
6605 @cindex compilation directory
6606 @cindex current directory
6607 @cindex working directory
6608 @cindex directory, current
6609 @cindex directory, compilation
6610 You can use the string @samp{$cdir} to refer to the compilation
6611 directory (if one is recorded), and @samp{$cwd} to refer to the current
6612 working directory. @samp{$cwd} is not the same as @samp{.}---the former
6613 tracks the current working directory as it changes during your @value{GDBN}
6614 session, while the latter is immediately expanded to the current
6615 directory at the time you add an entry to the source path.
6618 Reset the source path to its default value (@samp{$cdir:$cwd} on Unix systems). This requires confirmation.
6620 @c RET-repeat for @code{directory} is explicitly disabled, but since
6621 @c repeating it would be a no-op we do not say that. (thanks to RMS)
6623 @item show directories
6624 @kindex show directories
6625 Print the source path: show which directories it contains.
6627 @anchor{set substitute-path}
6628 @item set substitute-path @var{from} @var{to}
6629 @kindex set substitute-path
6630 Define a source path substitution rule, and add it at the end of the
6631 current list of existing substitution rules. If a rule with the same
6632 @var{from} was already defined, then the old rule is also deleted.
6634 For example, if the file @file{/foo/bar/baz.c} was moved to
6635 @file{/mnt/cross/baz.c}, then the command
6638 (@value{GDBP}) set substitute-path /usr/src /mnt/cross
6642 will tell @value{GDBN} to replace @samp{/usr/src} with
6643 @samp{/mnt/cross}, which will allow @value{GDBN} to find the file
6644 @file{baz.c} even though it was moved.
6646 In the case when more than one substitution rule have been defined,
6647 the rules are evaluated one by one in the order where they have been
6648 defined. The first one matching, if any, is selected to perform
6651 For instance, if we had entered the following commands:
6654 (@value{GDBP}) set substitute-path /usr/src/include /mnt/include
6655 (@value{GDBP}) set substitute-path /usr/src /mnt/src
6659 @value{GDBN} would then rewrite @file{/usr/src/include/defs.h} into
6660 @file{/mnt/include/defs.h} by using the first rule. However, it would
6661 use the second rule to rewrite @file{/usr/src/lib/foo.c} into
6662 @file{/mnt/src/lib/foo.c}.
6665 @item unset substitute-path [path]
6666 @kindex unset substitute-path
6667 If a path is specified, search the current list of substitution rules
6668 for a rule that would rewrite that path. Delete that rule if found.
6669 A warning is emitted by the debugger if no rule could be found.
6671 If no path is specified, then all substitution rules are deleted.
6673 @item show substitute-path [path]
6674 @kindex show substitute-path
6675 If a path is specified, then print the source path substitution rule
6676 which would rewrite that path, if any.
6678 If no path is specified, then print all existing source path substitution
6683 If your source path is cluttered with directories that are no longer of
6684 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
6685 versions of source. You can correct the situation as follows:
6689 Use @code{directory} with no argument to reset the source path to its default value.
6692 Use @code{directory} with suitable arguments to reinstall the
6693 directories you want in the source path. You can add all the
6694 directories in one command.
6698 @section Source and Machine Code
6699 @cindex source line and its code address
6701 You can use the command @code{info line} to map source lines to program
6702 addresses (and vice versa), and the command @code{disassemble} to display
6703 a range of addresses as machine instructions. You can use the command
6704 @code{set disassemble-next-line} to set whether to disassemble next
6705 source line when execution stops. When run under @sc{gnu} Emacs
6706 mode, the @code{info line} command causes the arrow to point to the
6707 line specified. Also, @code{info line} prints addresses in symbolic form as
6712 @item info line @var{linespec}
6713 Print the starting and ending addresses of the compiled code for
6714 source line @var{linespec}. You can specify source lines in any of
6715 the ways documented in @ref{Specify Location}.
6718 For example, we can use @code{info line} to discover the location of
6719 the object code for the first line of function
6720 @code{m4_changequote}:
6722 @c FIXME: I think this example should also show the addresses in
6723 @c symbolic form, as they usually would be displayed.
6725 (@value{GDBP}) info line m4_changequote
6726 Line 895 of "builtin.c" starts at pc 0x634c and ends at 0x6350.
6730 @cindex code address and its source line
6731 We can also inquire (using @code{*@var{addr}} as the form for
6732 @var{linespec}) what source line covers a particular address:
6734 (@value{GDBP}) info line *0x63ff
6735 Line 926 of "builtin.c" starts at pc 0x63e4 and ends at 0x6404.
6738 @cindex @code{$_} and @code{info line}
6739 @cindex @code{x} command, default address
6740 @kindex x@r{(examine), and} info line
6741 After @code{info line}, the default address for the @code{x} command
6742 is changed to the starting address of the line, so that @samp{x/i} is
6743 sufficient to begin examining the machine code (@pxref{Memory,
6744 ,Examining Memory}). Also, this address is saved as the value of the
6745 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
6750 @cindex assembly instructions
6751 @cindex instructions, assembly
6752 @cindex machine instructions
6753 @cindex listing machine instructions
6755 @itemx disassemble /m
6756 @itemx disassemble /r
6757 This specialized command dumps a range of memory as machine
6758 instructions. It can also print mixed source+disassembly by specifying
6759 the @code{/m} modifier and print the raw instructions in hex as well as
6760 in symbolic form by specifying the @code{/r}.
6761 The default memory range is the function surrounding the
6762 program counter of the selected frame. A single argument to this
6763 command is a program counter value; @value{GDBN} dumps the function
6764 surrounding this value. When two arguments are given, they should
6765 be separated by a comma, possibly surrounded by whitespace. The
6766 arguments specify a range of addresses to dump, in one of two forms:
6769 @item @var{start},@var{end}
6770 the addresses from @var{start} (inclusive) to @var{end} (exclusive)
6771 @item @var{start},+@var{length}
6772 the addresses from @var{start} (inclusive) to
6773 @code{@var{start}+@var{length}} (exclusive).
6777 When 2 arguments are specified, the name of the function is also
6778 printed (since there could be several functions in the given range).
6780 The argument(s) can be any expression yielding a numeric value, such as
6781 @samp{0x32c4}, @samp{&main+10} or @samp{$pc - 8}.
6783 If the range of memory being disassembled contains current program counter,
6784 the instruction at that location is shown with a @code{=>} marker.
6787 The following example shows the disassembly of a range of addresses of
6788 HP PA-RISC 2.0 code:
6791 (@value{GDBP}) disas 0x32c4, 0x32e4
6792 Dump of assembler code from 0x32c4 to 0x32e4:
6793 0x32c4 <main+204>: addil 0,dp
6794 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
6795 0x32cc <main+212>: ldil 0x3000,r31
6796 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
6797 0x32d4 <main+220>: ldo 0(r31),rp
6798 0x32d8 <main+224>: addil -0x800,dp
6799 0x32dc <main+228>: ldo 0x588(r1),r26
6800 0x32e0 <main+232>: ldil 0x3000,r31
6801 End of assembler dump.
6804 Here is an example showing mixed source+assembly for Intel x86, when the
6805 program is stopped just after function prologue:
6808 (@value{GDBP}) disas /m main
6809 Dump of assembler code for function main:
6811 0x08048330 <+0>: push %ebp
6812 0x08048331 <+1>: mov %esp,%ebp
6813 0x08048333 <+3>: sub $0x8,%esp
6814 0x08048336 <+6>: and $0xfffffff0,%esp
6815 0x08048339 <+9>: sub $0x10,%esp
6817 6 printf ("Hello.\n");
6818 => 0x0804833c <+12>: movl $0x8048440,(%esp)
6819 0x08048343 <+19>: call 0x8048284 <puts@@plt>
6823 0x08048348 <+24>: mov $0x0,%eax
6824 0x0804834d <+29>: leave
6825 0x0804834e <+30>: ret
6827 End of assembler dump.
6830 Here is another example showing raw instructions in hex for AMD x86-64,
6833 (gdb) disas /r 0x400281,+10
6834 Dump of assembler code from 0x400281 to 0x40028b:
6835 0x0000000000400281: 38 36 cmp %dh,(%rsi)
6836 0x0000000000400283: 2d 36 34 2e 73 sub $0x732e3436,%eax
6837 0x0000000000400288: 6f outsl %ds:(%rsi),(%dx)
6838 0x0000000000400289: 2e 32 00 xor %cs:(%rax),%al
6839 End of assembler dump.
6842 Some architectures have more than one commonly-used set of instruction
6843 mnemonics or other syntax.
6845 For programs that were dynamically linked and use shared libraries,
6846 instructions that call functions or branch to locations in the shared
6847 libraries might show a seemingly bogus location---it's actually a
6848 location of the relocation table. On some architectures, @value{GDBN}
6849 might be able to resolve these to actual function names.
6852 @kindex set disassembly-flavor
6853 @cindex Intel disassembly flavor
6854 @cindex AT&T disassembly flavor
6855 @item set disassembly-flavor @var{instruction-set}
6856 Select the instruction set to use when disassembling the
6857 program via the @code{disassemble} or @code{x/i} commands.
6859 Currently this command is only defined for the Intel x86 family. You
6860 can set @var{instruction-set} to either @code{intel} or @code{att}.
6861 The default is @code{att}, the AT&T flavor used by default by Unix
6862 assemblers for x86-based targets.
6864 @kindex show disassembly-flavor
6865 @item show disassembly-flavor
6866 Show the current setting of the disassembly flavor.
6870 @kindex set disassemble-next-line
6871 @kindex show disassemble-next-line
6872 @item set disassemble-next-line
6873 @itemx show disassemble-next-line
6874 Control whether or not @value{GDBN} will disassemble the next source
6875 line or instruction when execution stops. If ON, @value{GDBN} will
6876 display disassembly of the next source line when execution of the
6877 program being debugged stops. This is @emph{in addition} to
6878 displaying the source line itself, which @value{GDBN} always does if
6879 possible. If the next source line cannot be displayed for some reason
6880 (e.g., if @value{GDBN} cannot find the source file, or there's no line
6881 info in the debug info), @value{GDBN} will display disassembly of the
6882 next @emph{instruction} instead of showing the next source line. If
6883 AUTO, @value{GDBN} will display disassembly of next instruction only
6884 if the source line cannot be displayed. This setting causes
6885 @value{GDBN} to display some feedback when you step through a function
6886 with no line info or whose source file is unavailable. The default is
6887 OFF, which means never display the disassembly of the next line or
6893 @chapter Examining Data
6895 @cindex printing data
6896 @cindex examining data
6899 @c "inspect" is not quite a synonym if you are using Epoch, which we do not
6900 @c document because it is nonstandard... Under Epoch it displays in a
6901 @c different window or something like that.
6902 The usual way to examine data in your program is with the @code{print}
6903 command (abbreviated @code{p}), or its synonym @code{inspect}. It
6904 evaluates and prints the value of an expression of the language your
6905 program is written in (@pxref{Languages, ,Using @value{GDBN} with
6906 Different Languages}). It may also print the expression using a
6907 Python-based pretty-printer (@pxref{Pretty Printing}).
6910 @item print @var{expr}
6911 @itemx print /@var{f} @var{expr}
6912 @var{expr} is an expression (in the source language). By default the
6913 value of @var{expr} is printed in a format appropriate to its data type;
6914 you can choose a different format by specifying @samp{/@var{f}}, where
6915 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
6919 @itemx print /@var{f}
6920 @cindex reprint the last value
6921 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
6922 @dfn{value history}; @pxref{Value History, ,Value History}). This allows you to
6923 conveniently inspect the same value in an alternative format.
6926 A more low-level way of examining data is with the @code{x} command.
6927 It examines data in memory at a specified address and prints it in a
6928 specified format. @xref{Memory, ,Examining Memory}.
6930 If you are interested in information about types, or about how the
6931 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
6932 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
6936 * Expressions:: Expressions
6937 * Ambiguous Expressions:: Ambiguous Expressions
6938 * Variables:: Program variables
6939 * Arrays:: Artificial arrays
6940 * Output Formats:: Output formats
6941 * Memory:: Examining memory
6942 * Auto Display:: Automatic display
6943 * Print Settings:: Print settings
6944 * Pretty Printing:: Python pretty printing
6945 * Value History:: Value history
6946 * Convenience Vars:: Convenience variables
6947 * Registers:: Registers
6948 * Floating Point Hardware:: Floating point hardware
6949 * Vector Unit:: Vector Unit
6950 * OS Information:: Auxiliary data provided by operating system
6951 * Memory Region Attributes:: Memory region attributes
6952 * Dump/Restore Files:: Copy between memory and a file
6953 * Core File Generation:: Cause a program dump its core
6954 * Character Sets:: Debugging programs that use a different
6955 character set than GDB does
6956 * Caching Remote Data:: Data caching for remote targets
6957 * Searching Memory:: Searching memory for a sequence of bytes
6961 @section Expressions
6964 @code{print} and many other @value{GDBN} commands accept an expression and
6965 compute its value. Any kind of constant, variable or operator defined
6966 by the programming language you are using is valid in an expression in
6967 @value{GDBN}. This includes conditional expressions, function calls,
6968 casts, and string constants. It also includes preprocessor macros, if
6969 you compiled your program to include this information; see
6972 @cindex arrays in expressions
6973 @value{GDBN} supports array constants in expressions input by
6974 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
6975 you can use the command @code{print @{1, 2, 3@}} to create an array
6976 of three integers. If you pass an array to a function or assign it
6977 to a program variable, @value{GDBN} copies the array to memory that
6978 is @code{malloc}ed in the target program.
6980 Because C is so widespread, most of the expressions shown in examples in
6981 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
6982 Languages}, for information on how to use expressions in other
6985 In this section, we discuss operators that you can use in @value{GDBN}
6986 expressions regardless of your programming language.
6988 @cindex casts, in expressions
6989 Casts are supported in all languages, not just in C, because it is so
6990 useful to cast a number into a pointer in order to examine a structure
6991 at that address in memory.
6992 @c FIXME: casts supported---Mod2 true?
6994 @value{GDBN} supports these operators, in addition to those common
6995 to programming languages:
6999 @samp{@@} is a binary operator for treating parts of memory as arrays.
7000 @xref{Arrays, ,Artificial Arrays}, for more information.
7003 @samp{::} allows you to specify a variable in terms of the file or
7004 function where it is defined. @xref{Variables, ,Program Variables}.
7006 @cindex @{@var{type}@}
7007 @cindex type casting memory
7008 @cindex memory, viewing as typed object
7009 @cindex casts, to view memory
7010 @item @{@var{type}@} @var{addr}
7011 Refers to an object of type @var{type} stored at address @var{addr} in
7012 memory. @var{addr} may be any expression whose value is an integer or
7013 pointer (but parentheses are required around binary operators, just as in
7014 a cast). This construct is allowed regardless of what kind of data is
7015 normally supposed to reside at @var{addr}.
7018 @node Ambiguous Expressions
7019 @section Ambiguous Expressions
7020 @cindex ambiguous expressions
7022 Expressions can sometimes contain some ambiguous elements. For instance,
7023 some programming languages (notably Ada, C@t{++} and Objective-C) permit
7024 a single function name to be defined several times, for application in
7025 different contexts. This is called @dfn{overloading}. Another example
7026 involving Ada is generics. A @dfn{generic package} is similar to C@t{++}
7027 templates and is typically instantiated several times, resulting in
7028 the same function name being defined in different contexts.
7030 In some cases and depending on the language, it is possible to adjust
7031 the expression to remove the ambiguity. For instance in C@t{++}, you
7032 can specify the signature of the function you want to break on, as in
7033 @kbd{break @var{function}(@var{types})}. In Ada, using the fully
7034 qualified name of your function often makes the expression unambiguous
7037 When an ambiguity that needs to be resolved is detected, the debugger
7038 has the capability to display a menu of numbered choices for each
7039 possibility, and then waits for the selection with the prompt @samp{>}.
7040 The first option is always @samp{[0] cancel}, and typing @kbd{0 @key{RET}}
7041 aborts the current command. If the command in which the expression was
7042 used allows more than one choice to be selected, the next option in the
7043 menu is @samp{[1] all}, and typing @kbd{1 @key{RET}} selects all possible
7046 For example, the following session excerpt shows an attempt to set a
7047 breakpoint at the overloaded symbol @code{String::after}.
7048 We choose three particular definitions of that function name:
7050 @c FIXME! This is likely to change to show arg type lists, at least
7053 (@value{GDBP}) b String::after
7056 [2] file:String.cc; line number:867
7057 [3] file:String.cc; line number:860
7058 [4] file:String.cc; line number:875
7059 [5] file:String.cc; line number:853
7060 [6] file:String.cc; line number:846
7061 [7] file:String.cc; line number:735
7063 Breakpoint 1 at 0xb26c: file String.cc, line 867.
7064 Breakpoint 2 at 0xb344: file String.cc, line 875.
7065 Breakpoint 3 at 0xafcc: file String.cc, line 846.
7066 Multiple breakpoints were set.
7067 Use the "delete" command to delete unwanted
7074 @kindex set multiple-symbols
7075 @item set multiple-symbols @var{mode}
7076 @cindex multiple-symbols menu
7078 This option allows you to adjust the debugger behavior when an expression
7081 By default, @var{mode} is set to @code{all}. If the command with which
7082 the expression is used allows more than one choice, then @value{GDBN}
7083 automatically selects all possible choices. For instance, inserting
7084 a breakpoint on a function using an ambiguous name results in a breakpoint
7085 inserted on each possible match. However, if a unique choice must be made,
7086 then @value{GDBN} uses the menu to help you disambiguate the expression.
7087 For instance, printing the address of an overloaded function will result
7088 in the use of the menu.
7090 When @var{mode} is set to @code{ask}, the debugger always uses the menu
7091 when an ambiguity is detected.
7093 Finally, when @var{mode} is set to @code{cancel}, the debugger reports
7094 an error due to the ambiguity and the command is aborted.
7096 @kindex show multiple-symbols
7097 @item show multiple-symbols
7098 Show the current value of the @code{multiple-symbols} setting.
7102 @section Program Variables
7104 The most common kind of expression to use is the name of a variable
7107 Variables in expressions are understood in the selected stack frame
7108 (@pxref{Selection, ,Selecting a Frame}); they must be either:
7112 global (or file-static)
7119 visible according to the scope rules of the
7120 programming language from the point of execution in that frame
7123 @noindent This means that in the function
7138 you can examine and use the variable @code{a} whenever your program is
7139 executing within the function @code{foo}, but you can only use or
7140 examine the variable @code{b} while your program is executing inside
7141 the block where @code{b} is declared.
7143 @cindex variable name conflict
7144 There is an exception: you can refer to a variable or function whose
7145 scope is a single source file even if the current execution point is not
7146 in this file. But it is possible to have more than one such variable or
7147 function with the same name (in different source files). If that
7148 happens, referring to that name has unpredictable effects. If you wish,
7149 you can specify a static variable in a particular function or file,
7150 using the colon-colon (@code{::}) notation:
7152 @cindex colon-colon, context for variables/functions
7154 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
7155 @cindex @code{::}, context for variables/functions
7158 @var{file}::@var{variable}
7159 @var{function}::@var{variable}
7163 Here @var{file} or @var{function} is the name of the context for the
7164 static @var{variable}. In the case of file names, you can use quotes to
7165 make sure @value{GDBN} parses the file name as a single word---for example,
7166 to print a global value of @code{x} defined in @file{f2.c}:
7169 (@value{GDBP}) p 'f2.c'::x
7172 @cindex C@t{++} scope resolution
7173 This use of @samp{::} is very rarely in conflict with the very similar
7174 use of the same notation in C@t{++}. @value{GDBN} also supports use of the C@t{++}
7175 scope resolution operator in @value{GDBN} expressions.
7176 @c FIXME: Um, so what happens in one of those rare cases where it's in
7179 @cindex wrong values
7180 @cindex variable values, wrong
7181 @cindex function entry/exit, wrong values of variables
7182 @cindex optimized code, wrong values of variables
7184 @emph{Warning:} Occasionally, a local variable may appear to have the
7185 wrong value at certain points in a function---just after entry to a new
7186 scope, and just before exit.
7188 You may see this problem when you are stepping by machine instructions.
7189 This is because, on most machines, it takes more than one instruction to
7190 set up a stack frame (including local variable definitions); if you are
7191 stepping by machine instructions, variables may appear to have the wrong
7192 values until the stack frame is completely built. On exit, it usually
7193 also takes more than one machine instruction to destroy a stack frame;
7194 after you begin stepping through that group of instructions, local
7195 variable definitions may be gone.
7197 This may also happen when the compiler does significant optimizations.
7198 To be sure of always seeing accurate values, turn off all optimization
7201 @cindex ``No symbol "foo" in current context''
7202 Another possible effect of compiler optimizations is to optimize
7203 unused variables out of existence, or assign variables to registers (as
7204 opposed to memory addresses). Depending on the support for such cases
7205 offered by the debug info format used by the compiler, @value{GDBN}
7206 might not be able to display values for such local variables. If that
7207 happens, @value{GDBN} will print a message like this:
7210 No symbol "foo" in current context.
7213 To solve such problems, either recompile without optimizations, or use a
7214 different debug info format, if the compiler supports several such
7215 formats. For example, @value{NGCC}, the @sc{gnu} C/C@t{++} compiler,
7216 usually supports the @option{-gstabs+} option. @option{-gstabs+}
7217 produces debug info in a format that is superior to formats such as
7218 COFF. You may be able to use DWARF 2 (@option{-gdwarf-2}), which is also
7219 an effective form for debug info. @xref{Debugging Options,,Options
7220 for Debugging Your Program or GCC, gcc.info, Using the @sc{gnu}
7221 Compiler Collection (GCC)}.
7222 @xref{C, ,C and C@t{++}}, for more information about debug info formats
7223 that are best suited to C@t{++} programs.
7225 If you ask to print an object whose contents are unknown to
7226 @value{GDBN}, e.g., because its data type is not completely specified
7227 by the debug information, @value{GDBN} will say @samp{<incomplete
7228 type>}. @xref{Symbols, incomplete type}, for more about this.
7230 Strings are identified as arrays of @code{char} values without specified
7231 signedness. Arrays of either @code{signed char} or @code{unsigned char} get
7232 printed as arrays of 1 byte sized integers. @code{-fsigned-char} or
7233 @code{-funsigned-char} @value{NGCC} options have no effect as @value{GDBN}
7234 defines literal string type @code{"char"} as @code{char} without a sign.
7239 signed char var1[] = "A";
7242 You get during debugging
7247 $2 = @{65 'A', 0 '\0'@}
7251 @section Artificial Arrays
7253 @cindex artificial array
7255 @kindex @@@r{, referencing memory as an array}
7256 It is often useful to print out several successive objects of the
7257 same type in memory; a section of an array, or an array of
7258 dynamically determined size for which only a pointer exists in the
7261 You can do this by referring to a contiguous span of memory as an
7262 @dfn{artificial array}, using the binary operator @samp{@@}. The left
7263 operand of @samp{@@} should be the first element of the desired array
7264 and be an individual object. The right operand should be the desired length
7265 of the array. The result is an array value whose elements are all of
7266 the type of the left argument. The first element is actually the left
7267 argument; the second element comes from bytes of memory immediately
7268 following those that hold the first element, and so on. Here is an
7269 example. If a program says
7272 int *array = (int *) malloc (len * sizeof (int));
7276 you can print the contents of @code{array} with
7282 The left operand of @samp{@@} must reside in memory. Array values made
7283 with @samp{@@} in this way behave just like other arrays in terms of
7284 subscripting, and are coerced to pointers when used in expressions.
7285 Artificial arrays most often appear in expressions via the value history
7286 (@pxref{Value History, ,Value History}), after printing one out.
7288 Another way to create an artificial array is to use a cast.
7289 This re-interprets a value as if it were an array.
7290 The value need not be in memory:
7292 (@value{GDBP}) p/x (short[2])0x12345678
7293 $1 = @{0x1234, 0x5678@}
7296 As a convenience, if you leave the array length out (as in
7297 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
7298 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
7300 (@value{GDBP}) p/x (short[])0x12345678
7301 $2 = @{0x1234, 0x5678@}
7304 Sometimes the artificial array mechanism is not quite enough; in
7305 moderately complex data structures, the elements of interest may not
7306 actually be adjacent---for example, if you are interested in the values
7307 of pointers in an array. One useful work-around in this situation is
7308 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
7309 Variables}) as a counter in an expression that prints the first
7310 interesting value, and then repeat that expression via @key{RET}. For
7311 instance, suppose you have an array @code{dtab} of pointers to
7312 structures, and you are interested in the values of a field @code{fv}
7313 in each structure. Here is an example of what you might type:
7323 @node Output Formats
7324 @section Output Formats
7326 @cindex formatted output
7327 @cindex output formats
7328 By default, @value{GDBN} prints a value according to its data type. Sometimes
7329 this is not what you want. For example, you might want to print a number
7330 in hex, or a pointer in decimal. Or you might want to view data in memory
7331 at a certain address as a character string or as an instruction. To do
7332 these things, specify an @dfn{output format} when you print a value.
7334 The simplest use of output formats is to say how to print a value
7335 already computed. This is done by starting the arguments of the
7336 @code{print} command with a slash and a format letter. The format
7337 letters supported are:
7341 Regard the bits of the value as an integer, and print the integer in
7345 Print as integer in signed decimal.
7348 Print as integer in unsigned decimal.
7351 Print as integer in octal.
7354 Print as integer in binary. The letter @samp{t} stands for ``two''.
7355 @footnote{@samp{b} cannot be used because these format letters are also
7356 used with the @code{x} command, where @samp{b} stands for ``byte'';
7357 see @ref{Memory,,Examining Memory}.}
7360 @cindex unknown address, locating
7361 @cindex locate address
7362 Print as an address, both absolute in hexadecimal and as an offset from
7363 the nearest preceding symbol. You can use this format used to discover
7364 where (in what function) an unknown address is located:
7367 (@value{GDBP}) p/a 0x54320
7368 $3 = 0x54320 <_initialize_vx+396>
7372 The command @code{info symbol 0x54320} yields similar results.
7373 @xref{Symbols, info symbol}.
7376 Regard as an integer and print it as a character constant. This
7377 prints both the numerical value and its character representation. The
7378 character representation is replaced with the octal escape @samp{\nnn}
7379 for characters outside the 7-bit @sc{ascii} range.
7381 Without this format, @value{GDBN} displays @code{char},
7382 @w{@code{unsigned char}}, and @w{@code{signed char}} data as character
7383 constants. Single-byte members of vectors are displayed as integer
7387 Regard the bits of the value as a floating point number and print
7388 using typical floating point syntax.
7391 @cindex printing strings
7392 @cindex printing byte arrays
7393 Regard as a string, if possible. With this format, pointers to single-byte
7394 data are displayed as null-terminated strings and arrays of single-byte data
7395 are displayed as fixed-length strings. Other values are displayed in their
7398 Without this format, @value{GDBN} displays pointers to and arrays of
7399 @code{char}, @w{@code{unsigned char}}, and @w{@code{signed char}} as
7400 strings. Single-byte members of a vector are displayed as an integer
7404 @cindex raw printing
7405 Print using the @samp{raw} formatting. By default, @value{GDBN} will
7406 use a Python-based pretty-printer, if one is available (@pxref{Pretty
7407 Printing}). This typically results in a higher-level display of the
7408 value's contents. The @samp{r} format bypasses any Python
7409 pretty-printer which might exist.
7412 For example, to print the program counter in hex (@pxref{Registers}), type
7419 Note that no space is required before the slash; this is because command
7420 names in @value{GDBN} cannot contain a slash.
7422 To reprint the last value in the value history with a different format,
7423 you can use the @code{print} command with just a format and no
7424 expression. For example, @samp{p/x} reprints the last value in hex.
7427 @section Examining Memory
7429 You can use the command @code{x} (for ``examine'') to examine memory in
7430 any of several formats, independently of your program's data types.
7432 @cindex examining memory
7434 @kindex x @r{(examine memory)}
7435 @item x/@var{nfu} @var{addr}
7438 Use the @code{x} command to examine memory.
7441 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
7442 much memory to display and how to format it; @var{addr} is an
7443 expression giving the address where you want to start displaying memory.
7444 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
7445 Several commands set convenient defaults for @var{addr}.
7448 @item @var{n}, the repeat count
7449 The repeat count is a decimal integer; the default is 1. It specifies
7450 how much memory (counting by units @var{u}) to display.
7451 @c This really is **decimal**; unaffected by 'set radix' as of GDB
7454 @item @var{f}, the display format
7455 The display format is one of the formats used by @code{print}
7456 (@samp{x}, @samp{d}, @samp{u}, @samp{o}, @samp{t}, @samp{a}, @samp{c},
7457 @samp{f}, @samp{s}), and in addition @samp{i} (for machine instructions).
7458 The default is @samp{x} (hexadecimal) initially. The default changes
7459 each time you use either @code{x} or @code{print}.
7461 @item @var{u}, the unit size
7462 The unit size is any of
7468 Halfwords (two bytes).
7470 Words (four bytes). This is the initial default.
7472 Giant words (eight bytes).
7475 Each time you specify a unit size with @code{x}, that size becomes the
7476 default unit the next time you use @code{x}. For the @samp{i} format,
7477 the unit size is ignored and is normally not written. For the @samp{s} format,
7478 the unit size defaults to @samp{b}, unless it is explicitly given.
7479 Use @kbd{x /hs} to display 16-bit char strings and @kbd{x /ws} to display
7480 32-bit strings. The next use of @kbd{x /s} will again display 8-bit strings.
7481 Note that the results depend on the programming language of the
7482 current compilation unit. If the language is C, the @samp{s}
7483 modifier will use the UTF-16 encoding while @samp{w} will use
7484 UTF-32. The encoding is set by the programming language and cannot
7487 @item @var{addr}, starting display address
7488 @var{addr} is the address where you want @value{GDBN} to begin displaying
7489 memory. The expression need not have a pointer value (though it may);
7490 it is always interpreted as an integer address of a byte of memory.
7491 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
7492 @var{addr} is usually just after the last address examined---but several
7493 other commands also set the default address: @code{info breakpoints} (to
7494 the address of the last breakpoint listed), @code{info line} (to the
7495 starting address of a line), and @code{print} (if you use it to display
7496 a value from memory).
7499 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
7500 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
7501 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
7502 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
7503 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
7505 Since the letters indicating unit sizes are all distinct from the
7506 letters specifying output formats, you do not have to remember whether
7507 unit size or format comes first; either order works. The output
7508 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
7509 (However, the count @var{n} must come first; @samp{wx4} does not work.)
7511 Even though the unit size @var{u} is ignored for the formats @samp{s}
7512 and @samp{i}, you might still want to use a count @var{n}; for example,
7513 @samp{3i} specifies that you want to see three machine instructions,
7514 including any operands. For convenience, especially when used with
7515 the @code{display} command, the @samp{i} format also prints branch delay
7516 slot instructions, if any, beyond the count specified, which immediately
7517 follow the last instruction that is within the count. The command
7518 @code{disassemble} gives an alternative way of inspecting machine
7519 instructions; see @ref{Machine Code,,Source and Machine Code}.
7521 All the defaults for the arguments to @code{x} are designed to make it
7522 easy to continue scanning memory with minimal specifications each time
7523 you use @code{x}. For example, after you have inspected three machine
7524 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
7525 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
7526 the repeat count @var{n} is used again; the other arguments default as
7527 for successive uses of @code{x}.
7529 When examining machine instructions, the instruction at current program
7530 counter is shown with a @code{=>} marker. For example:
7533 (@value{GDBP}) x/5i $pc-6
7534 0x804837f <main+11>: mov %esp,%ebp
7535 0x8048381 <main+13>: push %ecx
7536 0x8048382 <main+14>: sub $0x4,%esp
7537 => 0x8048385 <main+17>: movl $0x8048460,(%esp)
7538 0x804838c <main+24>: call 0x80482d4 <puts@@plt>
7541 @cindex @code{$_}, @code{$__}, and value history
7542 The addresses and contents printed by the @code{x} command are not saved
7543 in the value history because there is often too much of them and they
7544 would get in the way. Instead, @value{GDBN} makes these values available for
7545 subsequent use in expressions as values of the convenience variables
7546 @code{$_} and @code{$__}. After an @code{x} command, the last address
7547 examined is available for use in expressions in the convenience variable
7548 @code{$_}. The contents of that address, as examined, are available in
7549 the convenience variable @code{$__}.
7551 If the @code{x} command has a repeat count, the address and contents saved
7552 are from the last memory unit printed; this is not the same as the last
7553 address printed if several units were printed on the last line of output.
7555 @cindex remote memory comparison
7556 @cindex verify remote memory image
7557 When you are debugging a program running on a remote target machine
7558 (@pxref{Remote Debugging}), you may wish to verify the program's image in the
7559 remote machine's memory against the executable file you downloaded to
7560 the target. The @code{compare-sections} command is provided for such
7564 @kindex compare-sections
7565 @item compare-sections @r{[}@var{section-name}@r{]}
7566 Compare the data of a loadable section @var{section-name} in the
7567 executable file of the program being debugged with the same section in
7568 the remote machine's memory, and report any mismatches. With no
7569 arguments, compares all loadable sections. This command's
7570 availability depends on the target's support for the @code{"qCRC"}
7575 @section Automatic Display
7576 @cindex automatic display
7577 @cindex display of expressions
7579 If you find that you want to print the value of an expression frequently
7580 (to see how it changes), you might want to add it to the @dfn{automatic
7581 display list} so that @value{GDBN} prints its value each time your program stops.
7582 Each expression added to the list is given a number to identify it;
7583 to remove an expression from the list, you specify that number.
7584 The automatic display looks like this:
7588 3: bar[5] = (struct hack *) 0x3804
7592 This display shows item numbers, expressions and their current values. As with
7593 displays you request manually using @code{x} or @code{print}, you can
7594 specify the output format you prefer; in fact, @code{display} decides
7595 whether to use @code{print} or @code{x} depending your format
7596 specification---it uses @code{x} if you specify either the @samp{i}
7597 or @samp{s} format, or a unit size; otherwise it uses @code{print}.
7601 @item display @var{expr}
7602 Add the expression @var{expr} to the list of expressions to display
7603 each time your program stops. @xref{Expressions, ,Expressions}.
7605 @code{display} does not repeat if you press @key{RET} again after using it.
7607 @item display/@var{fmt} @var{expr}
7608 For @var{fmt} specifying only a display format and not a size or
7609 count, add the expression @var{expr} to the auto-display list but
7610 arrange to display it each time in the specified format @var{fmt}.
7611 @xref{Output Formats,,Output Formats}.
7613 @item display/@var{fmt} @var{addr}
7614 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
7615 number of units, add the expression @var{addr} as a memory address to
7616 be examined each time your program stops. Examining means in effect
7617 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining Memory}.
7620 For example, @samp{display/i $pc} can be helpful, to see the machine
7621 instruction about to be executed each time execution stops (@samp{$pc}
7622 is a common name for the program counter; @pxref{Registers, ,Registers}).
7625 @kindex delete display
7627 @item undisplay @var{dnums}@dots{}
7628 @itemx delete display @var{dnums}@dots{}
7629 Remove item numbers @var{dnums} from the list of expressions to display.
7631 @code{undisplay} does not repeat if you press @key{RET} after using it.
7632 (Otherwise you would just get the error @samp{No display number @dots{}}.)
7634 @kindex disable display
7635 @item disable display @var{dnums}@dots{}
7636 Disable the display of item numbers @var{dnums}. A disabled display
7637 item is not printed automatically, but is not forgotten. It may be
7638 enabled again later.
7640 @kindex enable display
7641 @item enable display @var{dnums}@dots{}
7642 Enable display of item numbers @var{dnums}. It becomes effective once
7643 again in auto display of its expression, until you specify otherwise.
7646 Display the current values of the expressions on the list, just as is
7647 done when your program stops.
7649 @kindex info display
7651 Print the list of expressions previously set up to display
7652 automatically, each one with its item number, but without showing the
7653 values. This includes disabled expressions, which are marked as such.
7654 It also includes expressions which would not be displayed right now
7655 because they refer to automatic variables not currently available.
7658 @cindex display disabled out of scope
7659 If a display expression refers to local variables, then it does not make
7660 sense outside the lexical context for which it was set up. Such an
7661 expression is disabled when execution enters a context where one of its
7662 variables is not defined. For example, if you give the command
7663 @code{display last_char} while inside a function with an argument
7664 @code{last_char}, @value{GDBN} displays this argument while your program
7665 continues to stop inside that function. When it stops elsewhere---where
7666 there is no variable @code{last_char}---the display is disabled
7667 automatically. The next time your program stops where @code{last_char}
7668 is meaningful, you can enable the display expression once again.
7670 @node Print Settings
7671 @section Print Settings
7673 @cindex format options
7674 @cindex print settings
7675 @value{GDBN} provides the following ways to control how arrays, structures,
7676 and symbols are printed.
7679 These settings are useful for debugging programs in any language:
7683 @item set print address
7684 @itemx set print address on
7685 @cindex print/don't print memory addresses
7686 @value{GDBN} prints memory addresses showing the location of stack
7687 traces, structure values, pointer values, breakpoints, and so forth,
7688 even when it also displays the contents of those addresses. The default
7689 is @code{on}. For example, this is what a stack frame display looks like with
7690 @code{set print address on}:
7695 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
7697 530 if (lquote != def_lquote)
7701 @item set print address off
7702 Do not print addresses when displaying their contents. For example,
7703 this is the same stack frame displayed with @code{set print address off}:
7707 (@value{GDBP}) set print addr off
7709 #0 set_quotes (lq="<<", rq=">>") at input.c:530
7710 530 if (lquote != def_lquote)
7714 You can use @samp{set print address off} to eliminate all machine
7715 dependent displays from the @value{GDBN} interface. For example, with
7716 @code{print address off}, you should get the same text for backtraces on
7717 all machines---whether or not they involve pointer arguments.
7720 @item show print address
7721 Show whether or not addresses are to be printed.
7724 When @value{GDBN} prints a symbolic address, it normally prints the
7725 closest earlier symbol plus an offset. If that symbol does not uniquely
7726 identify the address (for example, it is a name whose scope is a single
7727 source file), you may need to clarify. One way to do this is with
7728 @code{info line}, for example @samp{info line *0x4537}. Alternately,
7729 you can set @value{GDBN} to print the source file and line number when
7730 it prints a symbolic address:
7733 @item set print symbol-filename on
7734 @cindex source file and line of a symbol
7735 @cindex symbol, source file and line
7736 Tell @value{GDBN} to print the source file name and line number of a
7737 symbol in the symbolic form of an address.
7739 @item set print symbol-filename off
7740 Do not print source file name and line number of a symbol. This is the
7743 @item show print symbol-filename
7744 Show whether or not @value{GDBN} will print the source file name and
7745 line number of a symbol in the symbolic form of an address.
7748 Another situation where it is helpful to show symbol filenames and line
7749 numbers is when disassembling code; @value{GDBN} shows you the line
7750 number and source file that corresponds to each instruction.
7752 Also, you may wish to see the symbolic form only if the address being
7753 printed is reasonably close to the closest earlier symbol:
7756 @item set print max-symbolic-offset @var{max-offset}
7757 @cindex maximum value for offset of closest symbol
7758 Tell @value{GDBN} to only display the symbolic form of an address if the
7759 offset between the closest earlier symbol and the address is less than
7760 @var{max-offset}. The default is 0, which tells @value{GDBN}
7761 to always print the symbolic form of an address if any symbol precedes it.
7763 @item show print max-symbolic-offset
7764 Ask how large the maximum offset is that @value{GDBN} prints in a
7768 @cindex wild pointer, interpreting
7769 @cindex pointer, finding referent
7770 If you have a pointer and you are not sure where it points, try
7771 @samp{set print symbol-filename on}. Then you can determine the name
7772 and source file location of the variable where it points, using
7773 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
7774 For example, here @value{GDBN} shows that a variable @code{ptt} points
7775 at another variable @code{t}, defined in @file{hi2.c}:
7778 (@value{GDBP}) set print symbol-filename on
7779 (@value{GDBP}) p/a ptt
7780 $4 = 0xe008 <t in hi2.c>
7784 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
7785 does not show the symbol name and filename of the referent, even with
7786 the appropriate @code{set print} options turned on.
7789 Other settings control how different kinds of objects are printed:
7792 @item set print array
7793 @itemx set print array on
7794 @cindex pretty print arrays
7795 Pretty print arrays. This format is more convenient to read,
7796 but uses more space. The default is off.
7798 @item set print array off
7799 Return to compressed format for arrays.
7801 @item show print array
7802 Show whether compressed or pretty format is selected for displaying
7805 @cindex print array indexes
7806 @item set print array-indexes
7807 @itemx set print array-indexes on
7808 Print the index of each element when displaying arrays. May be more
7809 convenient to locate a given element in the array or quickly find the
7810 index of a given element in that printed array. The default is off.
7812 @item set print array-indexes off
7813 Stop printing element indexes when displaying arrays.
7815 @item show print array-indexes
7816 Show whether the index of each element is printed when displaying
7819 @item set print elements @var{number-of-elements}
7820 @cindex number of array elements to print
7821 @cindex limit on number of printed array elements
7822 Set a limit on how many elements of an array @value{GDBN} will print.
7823 If @value{GDBN} is printing a large array, it stops printing after it has
7824 printed the number of elements set by the @code{set print elements} command.
7825 This limit also applies to the display of strings.
7826 When @value{GDBN} starts, this limit is set to 200.
7827 Setting @var{number-of-elements} to zero means that the printing is unlimited.
7829 @item show print elements
7830 Display the number of elements of a large array that @value{GDBN} will print.
7831 If the number is 0, then the printing is unlimited.
7833 @item set print frame-arguments @var{value}
7834 @kindex set print frame-arguments
7835 @cindex printing frame argument values
7836 @cindex print all frame argument values
7837 @cindex print frame argument values for scalars only
7838 @cindex do not print frame argument values
7839 This command allows to control how the values of arguments are printed
7840 when the debugger prints a frame (@pxref{Frames}). The possible
7845 The values of all arguments are printed.
7848 Print the value of an argument only if it is a scalar. The value of more
7849 complex arguments such as arrays, structures, unions, etc, is replaced
7850 by @code{@dots{}}. This is the default. Here is an example where
7851 only scalar arguments are shown:
7854 #1 0x08048361 in call_me (i=3, s=@dots{}, ss=0xbf8d508c, u=@dots{}, e=green)
7859 None of the argument values are printed. Instead, the value of each argument
7860 is replaced by @code{@dots{}}. In this case, the example above now becomes:
7863 #1 0x08048361 in call_me (i=@dots{}, s=@dots{}, ss=@dots{}, u=@dots{}, e=@dots{})
7868 By default, only scalar arguments are printed. This command can be used
7869 to configure the debugger to print the value of all arguments, regardless
7870 of their type. However, it is often advantageous to not print the value
7871 of more complex parameters. For instance, it reduces the amount of
7872 information printed in each frame, making the backtrace more readable.
7873 Also, it improves performance when displaying Ada frames, because
7874 the computation of large arguments can sometimes be CPU-intensive,
7875 especially in large applications. Setting @code{print frame-arguments}
7876 to @code{scalars} (the default) or @code{none} avoids this computation,
7877 thus speeding up the display of each Ada frame.
7879 @item show print frame-arguments
7880 Show how the value of arguments should be displayed when printing a frame.
7882 @item set print repeats
7883 @cindex repeated array elements
7884 Set the threshold for suppressing display of repeated array
7885 elements. When the number of consecutive identical elements of an
7886 array exceeds the threshold, @value{GDBN} prints the string
7887 @code{"<repeats @var{n} times>"}, where @var{n} is the number of
7888 identical repetitions, instead of displaying the identical elements
7889 themselves. Setting the threshold to zero will cause all elements to
7890 be individually printed. The default threshold is 10.
7892 @item show print repeats
7893 Display the current threshold for printing repeated identical
7896 @item set print null-stop
7897 @cindex @sc{null} elements in arrays
7898 Cause @value{GDBN} to stop printing the characters of an array when the first
7899 @sc{null} is encountered. This is useful when large arrays actually
7900 contain only short strings.
7903 @item show print null-stop
7904 Show whether @value{GDBN} stops printing an array on the first
7905 @sc{null} character.
7907 @item set print pretty on
7908 @cindex print structures in indented form
7909 @cindex indentation in structure display
7910 Cause @value{GDBN} to print structures in an indented format with one member
7911 per line, like this:
7926 @item set print pretty off
7927 Cause @value{GDBN} to print structures in a compact format, like this:
7931 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
7932 meat = 0x54 "Pork"@}
7937 This is the default format.
7939 @item show print pretty
7940 Show which format @value{GDBN} is using to print structures.
7942 @item set print sevenbit-strings on
7943 @cindex eight-bit characters in strings
7944 @cindex octal escapes in strings
7945 Print using only seven-bit characters; if this option is set,
7946 @value{GDBN} displays any eight-bit characters (in strings or
7947 character values) using the notation @code{\}@var{nnn}. This setting is
7948 best if you are working in English (@sc{ascii}) and you use the
7949 high-order bit of characters as a marker or ``meta'' bit.
7951 @item set print sevenbit-strings off
7952 Print full eight-bit characters. This allows the use of more
7953 international character sets, and is the default.
7955 @item show print sevenbit-strings
7956 Show whether or not @value{GDBN} is printing only seven-bit characters.
7958 @item set print union on
7959 @cindex unions in structures, printing
7960 Tell @value{GDBN} to print unions which are contained in structures
7961 and other unions. This is the default setting.
7963 @item set print union off
7964 Tell @value{GDBN} not to print unions which are contained in
7965 structures and other unions. @value{GDBN} will print @code{"@{...@}"}
7968 @item show print union
7969 Ask @value{GDBN} whether or not it will print unions which are contained in
7970 structures and other unions.
7972 For example, given the declarations
7975 typedef enum @{Tree, Bug@} Species;
7976 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
7977 typedef enum @{Caterpillar, Cocoon, Butterfly@}
7988 struct thing foo = @{Tree, @{Acorn@}@};
7992 with @code{set print union on} in effect @samp{p foo} would print
7995 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
7999 and with @code{set print union off} in effect it would print
8002 $1 = @{it = Tree, form = @{...@}@}
8006 @code{set print union} affects programs written in C-like languages
8012 These settings are of interest when debugging C@t{++} programs:
8015 @cindex demangling C@t{++} names
8016 @item set print demangle
8017 @itemx set print demangle on
8018 Print C@t{++} names in their source form rather than in the encoded
8019 (``mangled'') form passed to the assembler and linker for type-safe
8020 linkage. The default is on.
8022 @item show print demangle
8023 Show whether C@t{++} names are printed in mangled or demangled form.
8025 @item set print asm-demangle
8026 @itemx set print asm-demangle on
8027 Print C@t{++} names in their source form rather than their mangled form, even
8028 in assembler code printouts such as instruction disassemblies.
8031 @item show print asm-demangle
8032 Show whether C@t{++} names in assembly listings are printed in mangled
8035 @cindex C@t{++} symbol decoding style
8036 @cindex symbol decoding style, C@t{++}
8037 @kindex set demangle-style
8038 @item set demangle-style @var{style}
8039 Choose among several encoding schemes used by different compilers to
8040 represent C@t{++} names. The choices for @var{style} are currently:
8044 Allow @value{GDBN} to choose a decoding style by inspecting your program.
8047 Decode based on the @sc{gnu} C@t{++} compiler (@code{g++}) encoding algorithm.
8048 This is the default.
8051 Decode based on the HP ANSI C@t{++} (@code{aCC}) encoding algorithm.
8054 Decode based on the Lucid C@t{++} compiler (@code{lcc}) encoding algorithm.
8057 Decode using the algorithm in the @cite{C@t{++} Annotated Reference Manual}.
8058 @strong{Warning:} this setting alone is not sufficient to allow
8059 debugging @code{cfront}-generated executables. @value{GDBN} would
8060 require further enhancement to permit that.
8063 If you omit @var{style}, you will see a list of possible formats.
8065 @item show demangle-style
8066 Display the encoding style currently in use for decoding C@t{++} symbols.
8068 @item set print object
8069 @itemx set print object on
8070 @cindex derived type of an object, printing
8071 @cindex display derived types
8072 When displaying a pointer to an object, identify the @emph{actual}
8073 (derived) type of the object rather than the @emph{declared} type, using
8074 the virtual function table.
8076 @item set print object off
8077 Display only the declared type of objects, without reference to the
8078 virtual function table. This is the default setting.
8080 @item show print object
8081 Show whether actual, or declared, object types are displayed.
8083 @item set print static-members
8084 @itemx set print static-members on
8085 @cindex static members of C@t{++} objects
8086 Print static members when displaying a C@t{++} object. The default is on.
8088 @item set print static-members off
8089 Do not print static members when displaying a C@t{++} object.
8091 @item show print static-members
8092 Show whether C@t{++} static members are printed or not.
8094 @item set print pascal_static-members
8095 @itemx set print pascal_static-members on
8096 @cindex static members of Pascal objects
8097 @cindex Pascal objects, static members display
8098 Print static members when displaying a Pascal object. The default is on.
8100 @item set print pascal_static-members off
8101 Do not print static members when displaying a Pascal object.
8103 @item show print pascal_static-members
8104 Show whether Pascal static members are printed or not.
8106 @c These don't work with HP ANSI C++ yet.
8107 @item set print vtbl
8108 @itemx set print vtbl on
8109 @cindex pretty print C@t{++} virtual function tables
8110 @cindex virtual functions (C@t{++}) display
8111 @cindex VTBL display
8112 Pretty print C@t{++} virtual function tables. The default is off.
8113 (The @code{vtbl} commands do not work on programs compiled with the HP
8114 ANSI C@t{++} compiler (@code{aCC}).)
8116 @item set print vtbl off
8117 Do not pretty print C@t{++} virtual function tables.
8119 @item show print vtbl
8120 Show whether C@t{++} virtual function tables are pretty printed, or not.
8123 @node Pretty Printing
8124 @section Pretty Printing
8126 @value{GDBN} provides a mechanism to allow pretty-printing of values using
8127 Python code. It greatly simplifies the display of complex objects. This
8128 mechanism works for both MI and the CLI.
8130 For example, here is how a C@t{++} @code{std::string} looks without a
8134 (@value{GDBP}) print s
8136 static npos = 4294967295,
8138 <std::allocator<char>> = @{
8139 <__gnu_cxx::new_allocator<char>> = @{
8140 <No data fields>@}, <No data fields>
8142 members of std::basic_string<char, std::char_traits<char>,
8143 std::allocator<char> >::_Alloc_hider:
8144 _M_p = 0x804a014 "abcd"
8149 With a pretty-printer for @code{std::string} only the contents are printed:
8152 (@value{GDBP}) print s
8156 For implementing pretty printers for new types you should read the Python API
8157 details (@pxref{Pretty Printing API}).
8160 @section Value History
8162 @cindex value history
8163 @cindex history of values printed by @value{GDBN}
8164 Values printed by the @code{print} command are saved in the @value{GDBN}
8165 @dfn{value history}. This allows you to refer to them in other expressions.
8166 Values are kept until the symbol table is re-read or discarded
8167 (for example with the @code{file} or @code{symbol-file} commands).
8168 When the symbol table changes, the value history is discarded,
8169 since the values may contain pointers back to the types defined in the
8174 @cindex history number
8175 The values printed are given @dfn{history numbers} by which you can
8176 refer to them. These are successive integers starting with one.
8177 @code{print} shows you the history number assigned to a value by
8178 printing @samp{$@var{num} = } before the value; here @var{num} is the
8181 To refer to any previous value, use @samp{$} followed by the value's
8182 history number. The way @code{print} labels its output is designed to
8183 remind you of this. Just @code{$} refers to the most recent value in
8184 the history, and @code{$$} refers to the value before that.
8185 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
8186 is the value just prior to @code{$$}, @code{$$1} is equivalent to
8187 @code{$$}, and @code{$$0} is equivalent to @code{$}.
8189 For example, suppose you have just printed a pointer to a structure and
8190 want to see the contents of the structure. It suffices to type
8196 If you have a chain of structures where the component @code{next} points
8197 to the next one, you can print the contents of the next one with this:
8204 You can print successive links in the chain by repeating this
8205 command---which you can do by just typing @key{RET}.
8207 Note that the history records values, not expressions. If the value of
8208 @code{x} is 4 and you type these commands:
8216 then the value recorded in the value history by the @code{print} command
8217 remains 4 even though the value of @code{x} has changed.
8222 Print the last ten values in the value history, with their item numbers.
8223 This is like @samp{p@ $$9} repeated ten times, except that @code{show
8224 values} does not change the history.
8226 @item show values @var{n}
8227 Print ten history values centered on history item number @var{n}.
8230 Print ten history values just after the values last printed. If no more
8231 values are available, @code{show values +} produces no display.
8234 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
8235 same effect as @samp{show values +}.
8237 @node Convenience Vars
8238 @section Convenience Variables
8240 @cindex convenience variables
8241 @cindex user-defined variables
8242 @value{GDBN} provides @dfn{convenience variables} that you can use within
8243 @value{GDBN} to hold on to a value and refer to it later. These variables
8244 exist entirely within @value{GDBN}; they are not part of your program, and
8245 setting a convenience variable has no direct effect on further execution
8246 of your program. That is why you can use them freely.
8248 Convenience variables are prefixed with @samp{$}. Any name preceded by
8249 @samp{$} can be used for a convenience variable, unless it is one of
8250 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
8251 (Value history references, in contrast, are @emph{numbers} preceded
8252 by @samp{$}. @xref{Value History, ,Value History}.)
8254 You can save a value in a convenience variable with an assignment
8255 expression, just as you would set a variable in your program.
8259 set $foo = *object_ptr
8263 would save in @code{$foo} the value contained in the object pointed to by
8266 Using a convenience variable for the first time creates it, but its
8267 value is @code{void} until you assign a new value. You can alter the
8268 value with another assignment at any time.
8270 Convenience variables have no fixed types. You can assign a convenience
8271 variable any type of value, including structures and arrays, even if
8272 that variable already has a value of a different type. The convenience
8273 variable, when used as an expression, has the type of its current value.
8276 @kindex show convenience
8277 @cindex show all user variables
8278 @item show convenience
8279 Print a list of convenience variables used so far, and their values.
8280 Abbreviated @code{show conv}.
8282 @kindex init-if-undefined
8283 @cindex convenience variables, initializing
8284 @item init-if-undefined $@var{variable} = @var{expression}
8285 Set a convenience variable if it has not already been set. This is useful
8286 for user-defined commands that keep some state. It is similar, in concept,
8287 to using local static variables with initializers in C (except that
8288 convenience variables are global). It can also be used to allow users to
8289 override default values used in a command script.
8291 If the variable is already defined then the expression is not evaluated so
8292 any side-effects do not occur.
8295 One of the ways to use a convenience variable is as a counter to be
8296 incremented or a pointer to be advanced. For example, to print
8297 a field from successive elements of an array of structures:
8301 print bar[$i++]->contents
8305 Repeat that command by typing @key{RET}.
8307 Some convenience variables are created automatically by @value{GDBN} and given
8308 values likely to be useful.
8311 @vindex $_@r{, convenience variable}
8313 The variable @code{$_} is automatically set by the @code{x} command to
8314 the last address examined (@pxref{Memory, ,Examining Memory}). Other
8315 commands which provide a default address for @code{x} to examine also
8316 set @code{$_} to that address; these commands include @code{info line}
8317 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
8318 except when set by the @code{x} command, in which case it is a pointer
8319 to the type of @code{$__}.
8321 @vindex $__@r{, convenience variable}
8323 The variable @code{$__} is automatically set by the @code{x} command
8324 to the value found in the last address examined. Its type is chosen
8325 to match the format in which the data was printed.
8328 @vindex $_exitcode@r{, convenience variable}
8329 The variable @code{$_exitcode} is automatically set to the exit code when
8330 the program being debugged terminates.
8333 @vindex $_sdata@r{, inspect, convenience variable}
8334 The variable @code{$_sdata} contains extra collected static tracepoint
8335 data. @xref{Tracepoint Actions,,Tracepoint Action Lists}. Note that
8336 @code{$_sdata} could be empty, if not inspecting a trace buffer, or
8337 if extra static tracepoint data has not been collected.
8340 @vindex $_siginfo@r{, convenience variable}
8341 The variable @code{$_siginfo} contains extra signal information
8342 (@pxref{extra signal information}). Note that @code{$_siginfo}
8343 could be empty, if the application has not yet received any signals.
8344 For example, it will be empty before you execute the @code{run} command.
8347 @vindex $_tlb@r{, convenience variable}
8348 The variable @code{$_tlb} is automatically set when debugging
8349 applications running on MS-Windows in native mode or connected to
8350 gdbserver that supports the @code{qGetTIBAddr} request.
8351 @xref{General Query Packets}.
8352 This variable contains the address of the thread information block.
8356 On HP-UX systems, if you refer to a function or variable name that
8357 begins with a dollar sign, @value{GDBN} searches for a user or system
8358 name first, before it searches for a convenience variable.
8360 @cindex convenience functions
8361 @value{GDBN} also supplies some @dfn{convenience functions}. These
8362 have a syntax similar to convenience variables. A convenience
8363 function can be used in an expression just like an ordinary function;
8364 however, a convenience function is implemented internally to
8369 @kindex help function
8370 @cindex show all convenience functions
8371 Print a list of all convenience functions.
8378 You can refer to machine register contents, in expressions, as variables
8379 with names starting with @samp{$}. The names of registers are different
8380 for each machine; use @code{info registers} to see the names used on
8384 @kindex info registers
8385 @item info registers
8386 Print the names and values of all registers except floating-point
8387 and vector registers (in the selected stack frame).
8389 @kindex info all-registers
8390 @cindex floating point registers
8391 @item info all-registers
8392 Print the names and values of all registers, including floating-point
8393 and vector registers (in the selected stack frame).
8395 @item info registers @var{regname} @dots{}
8396 Print the @dfn{relativized} value of each specified register @var{regname}.
8397 As discussed in detail below, register values are normally relative to
8398 the selected stack frame. @var{regname} may be any register name valid on
8399 the machine you are using, with or without the initial @samp{$}.
8402 @cindex stack pointer register
8403 @cindex program counter register
8404 @cindex process status register
8405 @cindex frame pointer register
8406 @cindex standard registers
8407 @value{GDBN} has four ``standard'' register names that are available (in
8408 expressions) on most machines---whenever they do not conflict with an
8409 architecture's canonical mnemonics for registers. The register names
8410 @code{$pc} and @code{$sp} are used for the program counter register and
8411 the stack pointer. @code{$fp} is used for a register that contains a
8412 pointer to the current stack frame, and @code{$ps} is used for a
8413 register that contains the processor status. For example,
8414 you could print the program counter in hex with
8421 or print the instruction to be executed next with
8428 or add four to the stack pointer@footnote{This is a way of removing
8429 one word from the stack, on machines where stacks grow downward in
8430 memory (most machines, nowadays). This assumes that the innermost
8431 stack frame is selected; setting @code{$sp} is not allowed when other
8432 stack frames are selected. To pop entire frames off the stack,
8433 regardless of machine architecture, use @code{return};
8434 see @ref{Returning, ,Returning from a Function}.} with
8440 Whenever possible, these four standard register names are available on
8441 your machine even though the machine has different canonical mnemonics,
8442 so long as there is no conflict. The @code{info registers} command
8443 shows the canonical names. For example, on the SPARC, @code{info
8444 registers} displays the processor status register as @code{$psr} but you
8445 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
8446 is an alias for the @sc{eflags} register.
8448 @value{GDBN} always considers the contents of an ordinary register as an
8449 integer when the register is examined in this way. Some machines have
8450 special registers which can hold nothing but floating point; these
8451 registers are considered to have floating point values. There is no way
8452 to refer to the contents of an ordinary register as floating point value
8453 (although you can @emph{print} it as a floating point value with
8454 @samp{print/f $@var{regname}}).
8456 Some registers have distinct ``raw'' and ``virtual'' data formats. This
8457 means that the data format in which the register contents are saved by
8458 the operating system is not the same one that your program normally
8459 sees. For example, the registers of the 68881 floating point
8460 coprocessor are always saved in ``extended'' (raw) format, but all C
8461 programs expect to work with ``double'' (virtual) format. In such
8462 cases, @value{GDBN} normally works with the virtual format only (the format
8463 that makes sense for your program), but the @code{info registers} command
8464 prints the data in both formats.
8466 @cindex SSE registers (x86)
8467 @cindex MMX registers (x86)
8468 Some machines have special registers whose contents can be interpreted
8469 in several different ways. For example, modern x86-based machines
8470 have SSE and MMX registers that can hold several values packed
8471 together in several different formats. @value{GDBN} refers to such
8472 registers in @code{struct} notation:
8475 (@value{GDBP}) print $xmm1
8477 v4_float = @{0, 3.43859137e-038, 1.54142831e-044, 1.821688e-044@},
8478 v2_double = @{9.92129282474342e-303, 2.7585945287983262e-313@},
8479 v16_int8 = "\000\000\000\000\3706;\001\v\000\000\000\r\000\000",
8480 v8_int16 = @{0, 0, 14072, 315, 11, 0, 13, 0@},
8481 v4_int32 = @{0, 20657912, 11, 13@},
8482 v2_int64 = @{88725056443645952, 55834574859@},
8483 uint128 = 0x0000000d0000000b013b36f800000000
8488 To set values of such registers, you need to tell @value{GDBN} which
8489 view of the register you wish to change, as if you were assigning
8490 value to a @code{struct} member:
8493 (@value{GDBP}) set $xmm1.uint128 = 0x000000000000000000000000FFFFFFFF
8496 Normally, register values are relative to the selected stack frame
8497 (@pxref{Selection, ,Selecting a Frame}). This means that you get the
8498 value that the register would contain if all stack frames farther in
8499 were exited and their saved registers restored. In order to see the
8500 true contents of hardware registers, you must select the innermost
8501 frame (with @samp{frame 0}).
8503 However, @value{GDBN} must deduce where registers are saved, from the machine
8504 code generated by your compiler. If some registers are not saved, or if
8505 @value{GDBN} is unable to locate the saved registers, the selected stack
8506 frame makes no difference.
8508 @node Floating Point Hardware
8509 @section Floating Point Hardware
8510 @cindex floating point
8512 Depending on the configuration, @value{GDBN} may be able to give
8513 you more information about the status of the floating point hardware.
8518 Display hardware-dependent information about the floating
8519 point unit. The exact contents and layout vary depending on the
8520 floating point chip. Currently, @samp{info float} is supported on
8521 the ARM and x86 machines.
8525 @section Vector Unit
8528 Depending on the configuration, @value{GDBN} may be able to give you
8529 more information about the status of the vector unit.
8534 Display information about the vector unit. The exact contents and
8535 layout vary depending on the hardware.
8538 @node OS Information
8539 @section Operating System Auxiliary Information
8540 @cindex OS information
8542 @value{GDBN} provides interfaces to useful OS facilities that can help
8543 you debug your program.
8545 @cindex @code{ptrace} system call
8546 @cindex @code{struct user} contents
8547 When @value{GDBN} runs on a @dfn{Posix system} (such as GNU or Unix
8548 machines), it interfaces with the inferior via the @code{ptrace}
8549 system call. The operating system creates a special sata structure,
8550 called @code{struct user}, for this interface. You can use the
8551 command @code{info udot} to display the contents of this data
8557 Display the contents of the @code{struct user} maintained by the OS
8558 kernel for the program being debugged. @value{GDBN} displays the
8559 contents of @code{struct user} as a list of hex numbers, similar to
8560 the @code{examine} command.
8563 @cindex auxiliary vector
8564 @cindex vector, auxiliary
8565 Some operating systems supply an @dfn{auxiliary vector} to programs at
8566 startup. This is akin to the arguments and environment that you
8567 specify for a program, but contains a system-dependent variety of
8568 binary values that tell system libraries important details about the
8569 hardware, operating system, and process. Each value's purpose is
8570 identified by an integer tag; the meanings are well-known but system-specific.
8571 Depending on the configuration and operating system facilities,
8572 @value{GDBN} may be able to show you this information. For remote
8573 targets, this functionality may further depend on the remote stub's
8574 support of the @samp{qXfer:auxv:read} packet, see
8575 @ref{qXfer auxiliary vector read}.
8580 Display the auxiliary vector of the inferior, which can be either a
8581 live process or a core dump file. @value{GDBN} prints each tag value
8582 numerically, and also shows names and text descriptions for recognized
8583 tags. Some values in the vector are numbers, some bit masks, and some
8584 pointers to strings or other data. @value{GDBN} displays each value in the
8585 most appropriate form for a recognized tag, and in hexadecimal for
8586 an unrecognized tag.
8589 On some targets, @value{GDBN} can access operating-system-specific information
8590 and display it to user, without interpretation. For remote targets,
8591 this functionality depends on the remote stub's support of the
8592 @samp{qXfer:osdata:read} packet, see @ref{qXfer osdata read}.
8597 List the types of OS information available for the target. If the
8598 target does not return a list of possible types, this command will
8601 @kindex info os processes
8602 @item info os processes
8603 Display the list of processes on the target. For each process,
8604 @value{GDBN} prints the process identifier, the name of the user, and
8605 the command corresponding to the process.
8608 @node Memory Region Attributes
8609 @section Memory Region Attributes
8610 @cindex memory region attributes
8612 @dfn{Memory region attributes} allow you to describe special handling
8613 required by regions of your target's memory. @value{GDBN} uses
8614 attributes to determine whether to allow certain types of memory
8615 accesses; whether to use specific width accesses; and whether to cache
8616 target memory. By default the description of memory regions is
8617 fetched from the target (if the current target supports this), but the
8618 user can override the fetched regions.
8620 Defined memory regions can be individually enabled and disabled. When a
8621 memory region is disabled, @value{GDBN} uses the default attributes when
8622 accessing memory in that region. Similarly, if no memory regions have
8623 been defined, @value{GDBN} uses the default attributes when accessing
8626 When a memory region is defined, it is given a number to identify it;
8627 to enable, disable, or remove a memory region, you specify that number.
8631 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
8632 Define a memory region bounded by @var{lower} and @var{upper} with
8633 attributes @var{attributes}@dots{}, and add it to the list of regions
8634 monitored by @value{GDBN}. Note that @var{upper} == 0 is a special
8635 case: it is treated as the target's maximum memory address.
8636 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
8639 Discard any user changes to the memory regions and use target-supplied
8640 regions, if available, or no regions if the target does not support.
8643 @item delete mem @var{nums}@dots{}
8644 Remove memory regions @var{nums}@dots{} from the list of regions
8645 monitored by @value{GDBN}.
8648 @item disable mem @var{nums}@dots{}
8649 Disable monitoring of memory regions @var{nums}@dots{}.
8650 A disabled memory region is not forgotten.
8651 It may be enabled again later.
8654 @item enable mem @var{nums}@dots{}
8655 Enable monitoring of memory regions @var{nums}@dots{}.
8659 Print a table of all defined memory regions, with the following columns
8663 @item Memory Region Number
8664 @item Enabled or Disabled.
8665 Enabled memory regions are marked with @samp{y}.
8666 Disabled memory regions are marked with @samp{n}.
8669 The address defining the inclusive lower bound of the memory region.
8672 The address defining the exclusive upper bound of the memory region.
8675 The list of attributes set for this memory region.
8680 @subsection Attributes
8682 @subsubsection Memory Access Mode
8683 The access mode attributes set whether @value{GDBN} may make read or
8684 write accesses to a memory region.
8686 While these attributes prevent @value{GDBN} from performing invalid
8687 memory accesses, they do nothing to prevent the target system, I/O DMA,
8688 etc.@: from accessing memory.
8692 Memory is read only.
8694 Memory is write only.
8696 Memory is read/write. This is the default.
8699 @subsubsection Memory Access Size
8700 The access size attribute tells @value{GDBN} to use specific sized
8701 accesses in the memory region. Often memory mapped device registers
8702 require specific sized accesses. If no access size attribute is
8703 specified, @value{GDBN} may use accesses of any size.
8707 Use 8 bit memory accesses.
8709 Use 16 bit memory accesses.
8711 Use 32 bit memory accesses.
8713 Use 64 bit memory accesses.
8716 @c @subsubsection Hardware/Software Breakpoints
8717 @c The hardware/software breakpoint attributes set whether @value{GDBN}
8718 @c will use hardware or software breakpoints for the internal breakpoints
8719 @c used by the step, next, finish, until, etc. commands.
8723 @c Always use hardware breakpoints
8724 @c @item swbreak (default)
8727 @subsubsection Data Cache
8728 The data cache attributes set whether @value{GDBN} will cache target
8729 memory. While this generally improves performance by reducing debug
8730 protocol overhead, it can lead to incorrect results because @value{GDBN}
8731 does not know about volatile variables or memory mapped device
8736 Enable @value{GDBN} to cache target memory.
8738 Disable @value{GDBN} from caching target memory. This is the default.
8741 @subsection Memory Access Checking
8742 @value{GDBN} can be instructed to refuse accesses to memory that is
8743 not explicitly described. This can be useful if accessing such
8744 regions has undesired effects for a specific target, or to provide
8745 better error checking. The following commands control this behaviour.
8748 @kindex set mem inaccessible-by-default
8749 @item set mem inaccessible-by-default [on|off]
8750 If @code{on} is specified, make @value{GDBN} treat memory not
8751 explicitly described by the memory ranges as non-existent and refuse accesses
8752 to such memory. The checks are only performed if there's at least one
8753 memory range defined. If @code{off} is specified, make @value{GDBN}
8754 treat the memory not explicitly described by the memory ranges as RAM.
8755 The default value is @code{on}.
8756 @kindex show mem inaccessible-by-default
8757 @item show mem inaccessible-by-default
8758 Show the current handling of accesses to unknown memory.
8762 @c @subsubsection Memory Write Verification
8763 @c The memory write verification attributes set whether @value{GDBN}
8764 @c will re-reads data after each write to verify the write was successful.
8768 @c @item noverify (default)
8771 @node Dump/Restore Files
8772 @section Copy Between Memory and a File
8773 @cindex dump/restore files
8774 @cindex append data to a file
8775 @cindex dump data to a file
8776 @cindex restore data from a file
8778 You can use the commands @code{dump}, @code{append}, and
8779 @code{restore} to copy data between target memory and a file. The
8780 @code{dump} and @code{append} commands write data to a file, and the
8781 @code{restore} command reads data from a file back into the inferior's
8782 memory. Files may be in binary, Motorola S-record, Intel hex, or
8783 Tektronix Hex format; however, @value{GDBN} can only append to binary
8789 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
8790 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
8791 Dump the contents of memory from @var{start_addr} to @var{end_addr},
8792 or the value of @var{expr}, to @var{filename} in the given format.
8794 The @var{format} parameter may be any one of:
8801 Motorola S-record format.
8803 Tektronix Hex format.
8806 @value{GDBN} uses the same definitions of these formats as the
8807 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
8808 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
8812 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
8813 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
8814 Append the contents of memory from @var{start_addr} to @var{end_addr},
8815 or the value of @var{expr}, to the file @var{filename}, in raw binary form.
8816 (@value{GDBN} can only append data to files in raw binary form.)
8819 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
8820 Restore the contents of file @var{filename} into memory. The
8821 @code{restore} command can automatically recognize any known @sc{bfd}
8822 file format, except for raw binary. To restore a raw binary file you
8823 must specify the optional keyword @code{binary} after the filename.
8825 If @var{bias} is non-zero, its value will be added to the addresses
8826 contained in the file. Binary files always start at address zero, so
8827 they will be restored at address @var{bias}. Other bfd files have
8828 a built-in location; they will be restored at offset @var{bias}
8831 If @var{start} and/or @var{end} are non-zero, then only data between
8832 file offset @var{start} and file offset @var{end} will be restored.
8833 These offsets are relative to the addresses in the file, before
8834 the @var{bias} argument is applied.
8838 @node Core File Generation
8839 @section How to Produce a Core File from Your Program
8840 @cindex dump core from inferior
8842 A @dfn{core file} or @dfn{core dump} is a file that records the memory
8843 image of a running process and its process status (register values
8844 etc.). Its primary use is post-mortem debugging of a program that
8845 crashed while it ran outside a debugger. A program that crashes
8846 automatically produces a core file, unless this feature is disabled by
8847 the user. @xref{Files}, for information on invoking @value{GDBN} in
8848 the post-mortem debugging mode.
8850 Occasionally, you may wish to produce a core file of the program you
8851 are debugging in order to preserve a snapshot of its state.
8852 @value{GDBN} has a special command for that.
8856 @kindex generate-core-file
8857 @item generate-core-file [@var{file}]
8858 @itemx gcore [@var{file}]
8859 Produce a core dump of the inferior process. The optional argument
8860 @var{file} specifies the file name where to put the core dump. If not
8861 specified, the file name defaults to @file{core.@var{pid}}, where
8862 @var{pid} is the inferior process ID.
8864 Note that this command is implemented only for some systems (as of
8865 this writing, @sc{gnu}/Linux, FreeBSD, Solaris, Unixware, and S390).
8868 @node Character Sets
8869 @section Character Sets
8870 @cindex character sets
8872 @cindex translating between character sets
8873 @cindex host character set
8874 @cindex target character set
8876 If the program you are debugging uses a different character set to
8877 represent characters and strings than the one @value{GDBN} uses itself,
8878 @value{GDBN} can automatically translate between the character sets for
8879 you. The character set @value{GDBN} uses we call the @dfn{host
8880 character set}; the one the inferior program uses we call the
8881 @dfn{target character set}.
8883 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
8884 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
8885 remote protocol (@pxref{Remote Debugging}) to debug a program
8886 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
8887 then the host character set is Latin-1, and the target character set is
8888 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
8889 target-charset EBCDIC-US}, then @value{GDBN} translates between
8890 @sc{ebcdic} and Latin 1 as you print character or string values, or use
8891 character and string literals in expressions.
8893 @value{GDBN} has no way to automatically recognize which character set
8894 the inferior program uses; you must tell it, using the @code{set
8895 target-charset} command, described below.
8897 Here are the commands for controlling @value{GDBN}'s character set
8901 @item set target-charset @var{charset}
8902 @kindex set target-charset
8903 Set the current target character set to @var{charset}. To display the
8904 list of supported target character sets, type
8905 @kbd{@w{set target-charset @key{TAB}@key{TAB}}}.
8907 @item set host-charset @var{charset}
8908 @kindex set host-charset
8909 Set the current host character set to @var{charset}.
8911 By default, @value{GDBN} uses a host character set appropriate to the
8912 system it is running on; you can override that default using the
8913 @code{set host-charset} command. On some systems, @value{GDBN} cannot
8914 automatically determine the appropriate host character set. In this
8915 case, @value{GDBN} uses @samp{UTF-8}.
8917 @value{GDBN} can only use certain character sets as its host character
8918 set. If you type @kbd{@w{set target-charset @key{TAB}@key{TAB}}},
8919 @value{GDBN} will list the host character sets it supports.
8921 @item set charset @var{charset}
8923 Set the current host and target character sets to @var{charset}. As
8924 above, if you type @kbd{@w{set charset @key{TAB}@key{TAB}}},
8925 @value{GDBN} will list the names of the character sets that can be used
8926 for both host and target.
8929 @kindex show charset
8930 Show the names of the current host and target character sets.
8932 @item show host-charset
8933 @kindex show host-charset
8934 Show the name of the current host character set.
8936 @item show target-charset
8937 @kindex show target-charset
8938 Show the name of the current target character set.
8940 @item set target-wide-charset @var{charset}
8941 @kindex set target-wide-charset
8942 Set the current target's wide character set to @var{charset}. This is
8943 the character set used by the target's @code{wchar_t} type. To
8944 display the list of supported wide character sets, type
8945 @kbd{@w{set target-wide-charset @key{TAB}@key{TAB}}}.
8947 @item show target-wide-charset
8948 @kindex show target-wide-charset
8949 Show the name of the current target's wide character set.
8952 Here is an example of @value{GDBN}'s character set support in action.
8953 Assume that the following source code has been placed in the file
8954 @file{charset-test.c}:
8960 = @{72, 101, 108, 108, 111, 44, 32, 119,
8961 111, 114, 108, 100, 33, 10, 0@};
8962 char ibm1047_hello[]
8963 = @{200, 133, 147, 147, 150, 107, 64, 166,
8964 150, 153, 147, 132, 90, 37, 0@};
8968 printf ("Hello, world!\n");
8972 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
8973 containing the string @samp{Hello, world!} followed by a newline,
8974 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
8976 We compile the program, and invoke the debugger on it:
8979 $ gcc -g charset-test.c -o charset-test
8980 $ gdb -nw charset-test
8981 GNU gdb 2001-12-19-cvs
8982 Copyright 2001 Free Software Foundation, Inc.
8987 We can use the @code{show charset} command to see what character sets
8988 @value{GDBN} is currently using to interpret and display characters and
8992 (@value{GDBP}) show charset
8993 The current host and target character set is `ISO-8859-1'.
8997 For the sake of printing this manual, let's use @sc{ascii} as our
8998 initial character set:
9000 (@value{GDBP}) set charset ASCII
9001 (@value{GDBP}) show charset
9002 The current host and target character set is `ASCII'.
9006 Let's assume that @sc{ascii} is indeed the correct character set for our
9007 host system --- in other words, let's assume that if @value{GDBN} prints
9008 characters using the @sc{ascii} character set, our terminal will display
9009 them properly. Since our current target character set is also
9010 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
9013 (@value{GDBP}) print ascii_hello
9014 $1 = 0x401698 "Hello, world!\n"
9015 (@value{GDBP}) print ascii_hello[0]
9020 @value{GDBN} uses the target character set for character and string
9021 literals you use in expressions:
9024 (@value{GDBP}) print '+'
9029 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
9032 @value{GDBN} relies on the user to tell it which character set the
9033 target program uses. If we print @code{ibm1047_hello} while our target
9034 character set is still @sc{ascii}, we get jibberish:
9037 (@value{GDBP}) print ibm1047_hello
9038 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
9039 (@value{GDBP}) print ibm1047_hello[0]
9044 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
9045 @value{GDBN} tells us the character sets it supports:
9048 (@value{GDBP}) set target-charset
9049 ASCII EBCDIC-US IBM1047 ISO-8859-1
9050 (@value{GDBP}) set target-charset
9053 We can select @sc{ibm1047} as our target character set, and examine the
9054 program's strings again. Now the @sc{ascii} string is wrong, but
9055 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
9056 target character set, @sc{ibm1047}, to the host character set,
9057 @sc{ascii}, and they display correctly:
9060 (@value{GDBP}) set target-charset IBM1047
9061 (@value{GDBP}) show charset
9062 The current host character set is `ASCII'.
9063 The current target character set is `IBM1047'.
9064 (@value{GDBP}) print ascii_hello
9065 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
9066 (@value{GDBP}) print ascii_hello[0]
9068 (@value{GDBP}) print ibm1047_hello
9069 $8 = 0x4016a8 "Hello, world!\n"
9070 (@value{GDBP}) print ibm1047_hello[0]
9075 As above, @value{GDBN} uses the target character set for character and
9076 string literals you use in expressions:
9079 (@value{GDBP}) print '+'
9084 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
9087 @node Caching Remote Data
9088 @section Caching Data of Remote Targets
9089 @cindex caching data of remote targets
9091 @value{GDBN} caches data exchanged between the debugger and a
9092 remote target (@pxref{Remote Debugging}). Such caching generally improves
9093 performance, because it reduces the overhead of the remote protocol by
9094 bundling memory reads and writes into large chunks. Unfortunately, simply
9095 caching everything would lead to incorrect results, since @value{GDBN}
9096 does not necessarily know anything about volatile values, memory-mapped I/O
9097 addresses, etc. Furthermore, in non-stop mode (@pxref{Non-Stop Mode})
9098 memory can be changed @emph{while} a gdb command is executing.
9099 Therefore, by default, @value{GDBN} only caches data
9100 known to be on the stack@footnote{In non-stop mode, it is moderately
9101 rare for a running thread to modify the stack of a stopped thread
9102 in a way that would interfere with a backtrace, and caching of
9103 stack reads provides a significant speed up of remote backtraces.}.
9104 Other regions of memory can be explicitly marked as
9105 cacheable; see @pxref{Memory Region Attributes}.
9108 @kindex set remotecache
9109 @item set remotecache on
9110 @itemx set remotecache off
9111 This option no longer does anything; it exists for compatibility
9114 @kindex show remotecache
9115 @item show remotecache
9116 Show the current state of the obsolete remotecache flag.
9118 @kindex set stack-cache
9119 @item set stack-cache on
9120 @itemx set stack-cache off
9121 Enable or disable caching of stack accesses. When @code{ON}, use
9122 caching. By default, this option is @code{ON}.
9124 @kindex show stack-cache
9125 @item show stack-cache
9126 Show the current state of data caching for memory accesses.
9129 @item info dcache @r{[}line@r{]}
9130 Print the information about the data cache performance. The
9131 information displayed includes the dcache width and depth, and for
9132 each cache line, its number, address, and how many times it was
9133 referenced. This command is useful for debugging the data cache
9136 If a line number is specified, the contents of that line will be
9140 @node Searching Memory
9141 @section Search Memory
9142 @cindex searching memory
9144 Memory can be searched for a particular sequence of bytes with the
9145 @code{find} command.
9149 @item find @r{[}/@var{sn}@r{]} @var{start_addr}, +@var{len}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
9150 @itemx find @r{[}/@var{sn}@r{]} @var{start_addr}, @var{end_addr}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
9151 Search memory for the sequence of bytes specified by @var{val1}, @var{val2},
9152 etc. The search begins at address @var{start_addr} and continues for either
9153 @var{len} bytes or through to @var{end_addr} inclusive.
9156 @var{s} and @var{n} are optional parameters.
9157 They may be specified in either order, apart or together.
9160 @item @var{s}, search query size
9161 The size of each search query value.
9167 halfwords (two bytes)
9171 giant words (eight bytes)
9174 All values are interpreted in the current language.
9175 This means, for example, that if the current source language is C/C@t{++}
9176 then searching for the string ``hello'' includes the trailing '\0'.
9178 If the value size is not specified, it is taken from the
9179 value's type in the current language.
9180 This is useful when one wants to specify the search
9181 pattern as a mixture of types.
9182 Note that this means, for example, that in the case of C-like languages
9183 a search for an untyped 0x42 will search for @samp{(int) 0x42}
9184 which is typically four bytes.
9186 @item @var{n}, maximum number of finds
9187 The maximum number of matches to print. The default is to print all finds.
9190 You can use strings as search values. Quote them with double-quotes
9192 The string value is copied into the search pattern byte by byte,
9193 regardless of the endianness of the target and the size specification.
9195 The address of each match found is printed as well as a count of the
9196 number of matches found.
9198 The address of the last value found is stored in convenience variable
9200 A count of the number of matches is stored in @samp{$numfound}.
9202 For example, if stopped at the @code{printf} in this function:
9208 static char hello[] = "hello-hello";
9209 static struct @{ char c; short s; int i; @}
9210 __attribute__ ((packed)) mixed
9211 = @{ 'c', 0x1234, 0x87654321 @};
9212 printf ("%s\n", hello);
9217 you get during debugging:
9220 (gdb) find &hello[0], +sizeof(hello), "hello"
9221 0x804956d <hello.1620+6>
9223 (gdb) find &hello[0], +sizeof(hello), 'h', 'e', 'l', 'l', 'o'
9224 0x8049567 <hello.1620>
9225 0x804956d <hello.1620+6>
9227 (gdb) find /b1 &hello[0], +sizeof(hello), 'h', 0x65, 'l'
9228 0x8049567 <hello.1620>
9230 (gdb) find &mixed, +sizeof(mixed), (char) 'c', (short) 0x1234, (int) 0x87654321
9231 0x8049560 <mixed.1625>
9233 (gdb) print $numfound
9236 $2 = (void *) 0x8049560
9239 @node Optimized Code
9240 @chapter Debugging Optimized Code
9241 @cindex optimized code, debugging
9242 @cindex debugging optimized code
9244 Almost all compilers support optimization. With optimization
9245 disabled, the compiler generates assembly code that corresponds
9246 directly to your source code, in a simplistic way. As the compiler
9247 applies more powerful optimizations, the generated assembly code
9248 diverges from your original source code. With help from debugging
9249 information generated by the compiler, @value{GDBN} can map from
9250 the running program back to constructs from your original source.
9252 @value{GDBN} is more accurate with optimization disabled. If you
9253 can recompile without optimization, it is easier to follow the
9254 progress of your program during debugging. But, there are many cases
9255 where you may need to debug an optimized version.
9257 When you debug a program compiled with @samp{-g -O}, remember that the
9258 optimizer has rearranged your code; the debugger shows you what is
9259 really there. Do not be too surprised when the execution path does not
9260 exactly match your source file! An extreme example: if you define a
9261 variable, but never use it, @value{GDBN} never sees that
9262 variable---because the compiler optimizes it out of existence.
9264 Some things do not work as well with @samp{-g -O} as with just
9265 @samp{-g}, particularly on machines with instruction scheduling. If in
9266 doubt, recompile with @samp{-g} alone, and if this fixes the problem,
9267 please report it to us as a bug (including a test case!).
9268 @xref{Variables}, for more information about debugging optimized code.
9271 * Inline Functions:: How @value{GDBN} presents inlining
9274 @node Inline Functions
9275 @section Inline Functions
9276 @cindex inline functions, debugging
9278 @dfn{Inlining} is an optimization that inserts a copy of the function
9279 body directly at each call site, instead of jumping to a shared
9280 routine. @value{GDBN} displays inlined functions just like
9281 non-inlined functions. They appear in backtraces. You can view their
9282 arguments and local variables, step into them with @code{step}, skip
9283 them with @code{next}, and escape from them with @code{finish}.
9284 You can check whether a function was inlined by using the
9285 @code{info frame} command.
9287 For @value{GDBN} to support inlined functions, the compiler must
9288 record information about inlining in the debug information ---
9289 @value{NGCC} using the @sc{dwarf 2} format does this, and several
9290 other compilers do also. @value{GDBN} only supports inlined functions
9291 when using @sc{dwarf 2}. Versions of @value{NGCC} before 4.1
9292 do not emit two required attributes (@samp{DW_AT_call_file} and
9293 @samp{DW_AT_call_line}); @value{GDBN} does not display inlined
9294 function calls with earlier versions of @value{NGCC}. It instead
9295 displays the arguments and local variables of inlined functions as
9296 local variables in the caller.
9298 The body of an inlined function is directly included at its call site;
9299 unlike a non-inlined function, there are no instructions devoted to
9300 the call. @value{GDBN} still pretends that the call site and the
9301 start of the inlined function are different instructions. Stepping to
9302 the call site shows the call site, and then stepping again shows
9303 the first line of the inlined function, even though no additional
9304 instructions are executed.
9306 This makes source-level debugging much clearer; you can see both the
9307 context of the call and then the effect of the call. Only stepping by
9308 a single instruction using @code{stepi} or @code{nexti} does not do
9309 this; single instruction steps always show the inlined body.
9311 There are some ways that @value{GDBN} does not pretend that inlined
9312 function calls are the same as normal calls:
9316 You cannot set breakpoints on inlined functions. @value{GDBN}
9317 either reports that there is no symbol with that name, or else sets the
9318 breakpoint only on non-inlined copies of the function. This limitation
9319 will be removed in a future version of @value{GDBN}; until then,
9320 set a breakpoint by line number on the first line of the inlined
9324 Setting breakpoints at the call site of an inlined function may not
9325 work, because the call site does not contain any code. @value{GDBN}
9326 may incorrectly move the breakpoint to the next line of the enclosing
9327 function, after the call. This limitation will be removed in a future
9328 version of @value{GDBN}; until then, set a breakpoint on an earlier line
9329 or inside the inlined function instead.
9332 @value{GDBN} cannot locate the return value of inlined calls after
9333 using the @code{finish} command. This is a limitation of compiler-generated
9334 debugging information; after @code{finish}, you can step to the next line
9335 and print a variable where your program stored the return value.
9341 @chapter C Preprocessor Macros
9343 Some languages, such as C and C@t{++}, provide a way to define and invoke
9344 ``preprocessor macros'' which expand into strings of tokens.
9345 @value{GDBN} can evaluate expressions containing macro invocations, show
9346 the result of macro expansion, and show a macro's definition, including
9347 where it was defined.
9349 You may need to compile your program specially to provide @value{GDBN}
9350 with information about preprocessor macros. Most compilers do not
9351 include macros in their debugging information, even when you compile
9352 with the @option{-g} flag. @xref{Compilation}.
9354 A program may define a macro at one point, remove that definition later,
9355 and then provide a different definition after that. Thus, at different
9356 points in the program, a macro may have different definitions, or have
9357 no definition at all. If there is a current stack frame, @value{GDBN}
9358 uses the macros in scope at that frame's source code line. Otherwise,
9359 @value{GDBN} uses the macros in scope at the current listing location;
9362 Whenever @value{GDBN} evaluates an expression, it always expands any
9363 macro invocations present in the expression. @value{GDBN} also provides
9364 the following commands for working with macros explicitly.
9368 @kindex macro expand
9369 @cindex macro expansion, showing the results of preprocessor
9370 @cindex preprocessor macro expansion, showing the results of
9371 @cindex expanding preprocessor macros
9372 @item macro expand @var{expression}
9373 @itemx macro exp @var{expression}
9374 Show the results of expanding all preprocessor macro invocations in
9375 @var{expression}. Since @value{GDBN} simply expands macros, but does
9376 not parse the result, @var{expression} need not be a valid expression;
9377 it can be any string of tokens.
9380 @item macro expand-once @var{expression}
9381 @itemx macro exp1 @var{expression}
9382 @cindex expand macro once
9383 @i{(This command is not yet implemented.)} Show the results of
9384 expanding those preprocessor macro invocations that appear explicitly in
9385 @var{expression}. Macro invocations appearing in that expansion are
9386 left unchanged. This command allows you to see the effect of a
9387 particular macro more clearly, without being confused by further
9388 expansions. Since @value{GDBN} simply expands macros, but does not
9389 parse the result, @var{expression} need not be a valid expression; it
9390 can be any string of tokens.
9393 @cindex macro definition, showing
9394 @cindex definition, showing a macro's
9395 @item info macro @var{macro}
9396 Show the definition of the macro named @var{macro}, and describe the
9397 source location or compiler command-line where that definition was established.
9399 @kindex macro define
9400 @cindex user-defined macros
9401 @cindex defining macros interactively
9402 @cindex macros, user-defined
9403 @item macro define @var{macro} @var{replacement-list}
9404 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
9405 Introduce a definition for a preprocessor macro named @var{macro},
9406 invocations of which are replaced by the tokens given in
9407 @var{replacement-list}. The first form of this command defines an
9408 ``object-like'' macro, which takes no arguments; the second form
9409 defines a ``function-like'' macro, which takes the arguments given in
9412 A definition introduced by this command is in scope in every
9413 expression evaluated in @value{GDBN}, until it is removed with the
9414 @code{macro undef} command, described below. The definition overrides
9415 all definitions for @var{macro} present in the program being debugged,
9416 as well as any previous user-supplied definition.
9419 @item macro undef @var{macro}
9420 Remove any user-supplied definition for the macro named @var{macro}.
9421 This command only affects definitions provided with the @code{macro
9422 define} command, described above; it cannot remove definitions present
9423 in the program being debugged.
9427 List all the macros defined using the @code{macro define} command.
9430 @cindex macros, example of debugging with
9431 Here is a transcript showing the above commands in action. First, we
9432 show our source files:
9440 #define ADD(x) (M + x)
9445 printf ("Hello, world!\n");
9447 printf ("We're so creative.\n");
9449 printf ("Goodbye, world!\n");
9456 Now, we compile the program using the @sc{gnu} C compiler, @value{NGCC}.
9457 We pass the @option{-gdwarf-2} and @option{-g3} flags to ensure the
9458 compiler includes information about preprocessor macros in the debugging
9462 $ gcc -gdwarf-2 -g3 sample.c -o sample
9466 Now, we start @value{GDBN} on our sample program:
9470 GNU gdb 2002-05-06-cvs
9471 Copyright 2002 Free Software Foundation, Inc.
9472 GDB is free software, @dots{}
9476 We can expand macros and examine their definitions, even when the
9477 program is not running. @value{GDBN} uses the current listing position
9478 to decide which macro definitions are in scope:
9481 (@value{GDBP}) list main
9484 5 #define ADD(x) (M + x)
9489 10 printf ("Hello, world!\n");
9491 12 printf ("We're so creative.\n");
9492 (@value{GDBP}) info macro ADD
9493 Defined at /home/jimb/gdb/macros/play/sample.c:5
9494 #define ADD(x) (M + x)
9495 (@value{GDBP}) info macro Q
9496 Defined at /home/jimb/gdb/macros/play/sample.h:1
9497 included at /home/jimb/gdb/macros/play/sample.c:2
9499 (@value{GDBP}) macro expand ADD(1)
9500 expands to: (42 + 1)
9501 (@value{GDBP}) macro expand-once ADD(1)
9502 expands to: once (M + 1)
9506 In the example above, note that @code{macro expand-once} expands only
9507 the macro invocation explicit in the original text --- the invocation of
9508 @code{ADD} --- but does not expand the invocation of the macro @code{M},
9509 which was introduced by @code{ADD}.
9511 Once the program is running, @value{GDBN} uses the macro definitions in
9512 force at the source line of the current stack frame:
9515 (@value{GDBP}) break main
9516 Breakpoint 1 at 0x8048370: file sample.c, line 10.
9518 Starting program: /home/jimb/gdb/macros/play/sample
9520 Breakpoint 1, main () at sample.c:10
9521 10 printf ("Hello, world!\n");
9525 At line 10, the definition of the macro @code{N} at line 9 is in force:
9528 (@value{GDBP}) info macro N
9529 Defined at /home/jimb/gdb/macros/play/sample.c:9
9531 (@value{GDBP}) macro expand N Q M
9533 (@value{GDBP}) print N Q M
9538 As we step over directives that remove @code{N}'s definition, and then
9539 give it a new definition, @value{GDBN} finds the definition (or lack
9540 thereof) in force at each point:
9545 12 printf ("We're so creative.\n");
9546 (@value{GDBP}) info macro N
9547 The symbol `N' has no definition as a C/C++ preprocessor macro
9548 at /home/jimb/gdb/macros/play/sample.c:12
9551 14 printf ("Goodbye, world!\n");
9552 (@value{GDBP}) info macro N
9553 Defined at /home/jimb/gdb/macros/play/sample.c:13
9555 (@value{GDBP}) macro expand N Q M
9556 expands to: 1729 < 42
9557 (@value{GDBP}) print N Q M
9562 In addition to source files, macros can be defined on the compilation command
9563 line using the @option{-D@var{name}=@var{value}} syntax. For macros defined in
9564 such a way, @value{GDBN} displays the location of their definition as line zero
9565 of the source file submitted to the compiler.
9568 (@value{GDBP}) info macro __STDC__
9569 Defined at /home/jimb/gdb/macros/play/sample.c:0
9576 @chapter Tracepoints
9577 @c This chapter is based on the documentation written by Michael
9578 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
9581 In some applications, it is not feasible for the debugger to interrupt
9582 the program's execution long enough for the developer to learn
9583 anything helpful about its behavior. If the program's correctness
9584 depends on its real-time behavior, delays introduced by a debugger
9585 might cause the program to change its behavior drastically, or perhaps
9586 fail, even when the code itself is correct. It is useful to be able
9587 to observe the program's behavior without interrupting it.
9589 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
9590 specify locations in the program, called @dfn{tracepoints}, and
9591 arbitrary expressions to evaluate when those tracepoints are reached.
9592 Later, using the @code{tfind} command, you can examine the values
9593 those expressions had when the program hit the tracepoints. The
9594 expressions may also denote objects in memory---structures or arrays,
9595 for example---whose values @value{GDBN} should record; while visiting
9596 a particular tracepoint, you may inspect those objects as if they were
9597 in memory at that moment. However, because @value{GDBN} records these
9598 values without interacting with you, it can do so quickly and
9599 unobtrusively, hopefully not disturbing the program's behavior.
9601 The tracepoint facility is currently available only for remote
9602 targets. @xref{Targets}. In addition, your remote target must know
9603 how to collect trace data. This functionality is implemented in the
9604 remote stub; however, none of the stubs distributed with @value{GDBN}
9605 support tracepoints as of this writing. The format of the remote
9606 packets used to implement tracepoints are described in @ref{Tracepoint
9609 It is also possible to get trace data from a file, in a manner reminiscent
9610 of corefiles; you specify the filename, and use @code{tfind} to search
9611 through the file. @xref{Trace Files}, for more details.
9613 This chapter describes the tracepoint commands and features.
9617 * Analyze Collected Data::
9618 * Tracepoint Variables::
9622 @node Set Tracepoints
9623 @section Commands to Set Tracepoints
9625 Before running such a @dfn{trace experiment}, an arbitrary number of
9626 tracepoints can be set. A tracepoint is actually a special type of
9627 breakpoint (@pxref{Set Breaks}), so you can manipulate it using
9628 standard breakpoint commands. For instance, as with breakpoints,
9629 tracepoint numbers are successive integers starting from one, and many
9630 of the commands associated with tracepoints take the tracepoint number
9631 as their argument, to identify which tracepoint to work on.
9633 For each tracepoint, you can specify, in advance, some arbitrary set
9634 of data that you want the target to collect in the trace buffer when
9635 it hits that tracepoint. The collected data can include registers,
9636 local variables, or global data. Later, you can use @value{GDBN}
9637 commands to examine the values these data had at the time the
9640 Tracepoints do not support every breakpoint feature. Ignore counts on
9641 tracepoints have no effect, and tracepoints cannot run @value{GDBN}
9642 commands when they are hit. Tracepoints may not be thread-specific
9645 @cindex fast tracepoints
9646 Some targets may support @dfn{fast tracepoints}, which are inserted in
9647 a different way (such as with a jump instead of a trap), that is
9648 faster but possibly restricted in where they may be installed.
9650 @cindex static tracepoints
9651 @cindex markers, static tracepoints
9652 @cindex probing markers, static tracepoints
9653 Regular and fast tracepoints are dynamic tracing facilities, meaning
9654 that they can be used to insert tracepoints at (almost) any location
9655 in the target. Some targets may also support controlling @dfn{static
9656 tracepoints} from @value{GDBN}. With static tracing, a set of
9657 instrumentation points, also known as @dfn{markers}, are embedded in
9658 the target program, and can be activated or deactivated by name or
9659 address. These are usually placed at locations which facilitate
9660 investigating what the target is actually doing. @value{GDBN}'s
9661 support for static tracing includes being able to list instrumentation
9662 points, and attach them with @value{GDBN} defined high level
9663 tracepoints that expose the whole range of convenience of
9664 @value{GDBN}'s tracepoints support. Namelly, support for collecting
9665 registers values and values of global or local (to the instrumentation
9666 point) variables; tracepoint conditions and trace state variables.
9667 The act of installing a @value{GDBN} static tracepoint on an
9668 instrumentation point, or marker, is referred to as @dfn{probing} a
9669 static tracepoint marker.
9671 @code{gdbserver} supports tracepoints on some target systems.
9672 @xref{Server,,Tracepoints support in @code{gdbserver}}.
9674 This section describes commands to set tracepoints and associated
9675 conditions and actions.
9678 * Create and Delete Tracepoints::
9679 * Enable and Disable Tracepoints::
9680 * Tracepoint Passcounts::
9681 * Tracepoint Conditions::
9682 * Trace State Variables::
9683 * Tracepoint Actions::
9684 * Listing Tracepoints::
9685 * Listing Static Tracepoint Markers::
9686 * Starting and Stopping Trace Experiments::
9687 * Tracepoint Restrictions::
9690 @node Create and Delete Tracepoints
9691 @subsection Create and Delete Tracepoints
9694 @cindex set tracepoint
9696 @item trace @var{location}
9697 The @code{trace} command is very similar to the @code{break} command.
9698 Its argument @var{location} can be a source line, a function name, or
9699 an address in the target program. @xref{Specify Location}. The
9700 @code{trace} command defines a tracepoint, which is a point in the
9701 target program where the debugger will briefly stop, collect some
9702 data, and then allow the program to continue. Setting a tracepoint or
9703 changing its actions doesn't take effect until the next @code{tstart}
9704 command, and once a trace experiment is running, further changes will
9705 not have any effect until the next trace experiment starts.
9707 Here are some examples of using the @code{trace} command:
9710 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
9712 (@value{GDBP}) @b{trace +2} // 2 lines forward
9714 (@value{GDBP}) @b{trace my_function} // first source line of function
9716 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
9718 (@value{GDBP}) @b{trace *0x2117c4} // an address
9722 You can abbreviate @code{trace} as @code{tr}.
9724 @item trace @var{location} if @var{cond}
9725 Set a tracepoint with condition @var{cond}; evaluate the expression
9726 @var{cond} each time the tracepoint is reached, and collect data only
9727 if the value is nonzero---that is, if @var{cond} evaluates as true.
9728 @xref{Tracepoint Conditions, ,Tracepoint Conditions}, for more
9729 information on tracepoint conditions.
9731 @item ftrace @var{location} [ if @var{cond} ]
9732 @cindex set fast tracepoint
9733 @cindex fast tracepoints, setting
9735 The @code{ftrace} command sets a fast tracepoint. For targets that
9736 support them, fast tracepoints will use a more efficient but possibly
9737 less general technique to trigger data collection, such as a jump
9738 instruction instead of a trap, or some sort of hardware support. It
9739 may not be possible to create a fast tracepoint at the desired
9740 location, in which case the command will exit with an explanatory
9743 @value{GDBN} handles arguments to @code{ftrace} exactly as for
9746 @item strace @var{location} [ if @var{cond} ]
9747 @cindex set static tracepoint
9748 @cindex static tracepoints, setting
9749 @cindex probe static tracepoint marker
9751 The @code{strace} command sets a static tracepoint. For targets that
9752 support it, setting a static tracepoint probes a static
9753 instrumentation point, or marker, found at @var{location}. It may not
9754 be possible to set a static tracepoint at the desired location, in
9755 which case the command will exit with an explanatory message.
9757 @value{GDBN} handles arguments to @code{strace} exactly as for
9758 @code{trace}, with the addition that the user can also specify
9759 @code{-m @var{marker}} as @var{location}. This probes the marker
9760 identified by the @var{marker} string identifier. This identifier
9761 depends on the static tracepoint backend library your program is
9762 using. You can find all the marker identifiers in the @samp{ID} field
9763 of the @code{info static-tracepoint-markers} command output.
9764 @xref{Listing Static Tracepoint Markers,,Listing Static Tracepoint
9765 Markers}. For example, in the following small program using the UST
9771 trace_mark(ust, bar33, "str %s", "FOOBAZ");
9776 the marker id is composed of joining the first two arguments to the
9777 @code{trace_mark} call with a slash, which translates to:
9780 (@value{GDBP}) info static-tracepoint-markers
9781 Cnt Enb ID Address What
9782 1 n ust/bar33 0x0000000000400ddc in main at stexample.c:22
9788 so you may probe the marker above with:
9791 (@value{GDBP}) strace -m ust/bar33
9794 Static tracepoints accept an extra collect action --- @code{collect
9795 $_sdata}. This collects arbitrary user data passed in the probe point
9796 call to the tracing library. In the UST example above, you'll see
9797 that the third argument to @code{trace_mark} is a printf-like format
9798 string. The user data is then the result of running that formating
9799 string against the following arguments. Note that @code{info
9800 static-tracepoint-markers} command output lists that format string in
9801 the @samp{Data:} field.
9803 You can inspect this data when analyzing the trace buffer, by printing
9804 the $_sdata variable like any other variable available to
9805 @value{GDBN}. @xref{Tracepoint Actions,,Tracepoint Action Lists}.
9808 @cindex last tracepoint number
9809 @cindex recent tracepoint number
9810 @cindex tracepoint number
9811 The convenience variable @code{$tpnum} records the tracepoint number
9812 of the most recently set tracepoint.
9814 @kindex delete tracepoint
9815 @cindex tracepoint deletion
9816 @item delete tracepoint @r{[}@var{num}@r{]}
9817 Permanently delete one or more tracepoints. With no argument, the
9818 default is to delete all tracepoints. Note that the regular
9819 @code{delete} command can remove tracepoints also.
9824 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
9826 (@value{GDBP}) @b{delete trace} // remove all tracepoints
9830 You can abbreviate this command as @code{del tr}.
9833 @node Enable and Disable Tracepoints
9834 @subsection Enable and Disable Tracepoints
9836 These commands are deprecated; they are equivalent to plain @code{disable} and @code{enable}.
9839 @kindex disable tracepoint
9840 @item disable tracepoint @r{[}@var{num}@r{]}
9841 Disable tracepoint @var{num}, or all tracepoints if no argument
9842 @var{num} is given. A disabled tracepoint will have no effect during
9843 the next trace experiment, but it is not forgotten. You can re-enable
9844 a disabled tracepoint using the @code{enable tracepoint} command.
9846 @kindex enable tracepoint
9847 @item enable tracepoint @r{[}@var{num}@r{]}
9848 Enable tracepoint @var{num}, or all tracepoints. The enabled
9849 tracepoints will become effective the next time a trace experiment is
9853 @node Tracepoint Passcounts
9854 @subsection Tracepoint Passcounts
9858 @cindex tracepoint pass count
9859 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
9860 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
9861 automatically stop a trace experiment. If a tracepoint's passcount is
9862 @var{n}, then the trace experiment will be automatically stopped on
9863 the @var{n}'th time that tracepoint is hit. If the tracepoint number
9864 @var{num} is not specified, the @code{passcount} command sets the
9865 passcount of the most recently defined tracepoint. If no passcount is
9866 given, the trace experiment will run until stopped explicitly by the
9872 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
9873 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
9875 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
9876 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
9877 (@value{GDBP}) @b{trace foo}
9878 (@value{GDBP}) @b{pass 3}
9879 (@value{GDBP}) @b{trace bar}
9880 (@value{GDBP}) @b{pass 2}
9881 (@value{GDBP}) @b{trace baz}
9882 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
9883 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
9884 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
9885 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
9889 @node Tracepoint Conditions
9890 @subsection Tracepoint Conditions
9891 @cindex conditional tracepoints
9892 @cindex tracepoint conditions
9894 The simplest sort of tracepoint collects data every time your program
9895 reaches a specified place. You can also specify a @dfn{condition} for
9896 a tracepoint. A condition is just a Boolean expression in your
9897 programming language (@pxref{Expressions, ,Expressions}). A
9898 tracepoint with a condition evaluates the expression each time your
9899 program reaches it, and data collection happens only if the condition
9902 Tracepoint conditions can be specified when a tracepoint is set, by
9903 using @samp{if} in the arguments to the @code{trace} command.
9904 @xref{Create and Delete Tracepoints, ,Setting Tracepoints}. They can
9905 also be set or changed at any time with the @code{condition} command,
9906 just as with breakpoints.
9908 Unlike breakpoint conditions, @value{GDBN} does not actually evaluate
9909 the conditional expression itself. Instead, @value{GDBN} encodes the
9910 expression into an agent expression (@pxref{Agent Expressions}
9911 suitable for execution on the target, independently of @value{GDBN}.
9912 Global variables become raw memory locations, locals become stack
9913 accesses, and so forth.
9915 For instance, suppose you have a function that is usually called
9916 frequently, but should not be called after an error has occurred. You
9917 could use the following tracepoint command to collect data about calls
9918 of that function that happen while the error code is propagating
9919 through the program; an unconditional tracepoint could end up
9920 collecting thousands of useless trace frames that you would have to
9924 (@value{GDBP}) @kbd{trace normal_operation if errcode > 0}
9927 @node Trace State Variables
9928 @subsection Trace State Variables
9929 @cindex trace state variables
9931 A @dfn{trace state variable} is a special type of variable that is
9932 created and managed by target-side code. The syntax is the same as
9933 that for GDB's convenience variables (a string prefixed with ``$''),
9934 but they are stored on the target. They must be created explicitly,
9935 using a @code{tvariable} command. They are always 64-bit signed
9938 Trace state variables are remembered by @value{GDBN}, and downloaded
9939 to the target along with tracepoint information when the trace
9940 experiment starts. There are no intrinsic limits on the number of
9941 trace state variables, beyond memory limitations of the target.
9943 @cindex convenience variables, and trace state variables
9944 Although trace state variables are managed by the target, you can use
9945 them in print commands and expressions as if they were convenience
9946 variables; @value{GDBN} will get the current value from the target
9947 while the trace experiment is running. Trace state variables share
9948 the same namespace as other ``$'' variables, which means that you
9949 cannot have trace state variables with names like @code{$23} or
9950 @code{$pc}, nor can you have a trace state variable and a convenience
9951 variable with the same name.
9955 @item tvariable $@var{name} [ = @var{expression} ]
9957 The @code{tvariable} command creates a new trace state variable named
9958 @code{$@var{name}}, and optionally gives it an initial value of
9959 @var{expression}. @var{expression} is evaluated when this command is
9960 entered; the result will be converted to an integer if possible,
9961 otherwise @value{GDBN} will report an error. A subsequent
9962 @code{tvariable} command specifying the same name does not create a
9963 variable, but instead assigns the supplied initial value to the
9964 existing variable of that name, overwriting any previous initial
9965 value. The default initial value is 0.
9967 @item info tvariables
9968 @kindex info tvariables
9969 List all the trace state variables along with their initial values.
9970 Their current values may also be displayed, if the trace experiment is
9973 @item delete tvariable @r{[} $@var{name} @dots{} @r{]}
9974 @kindex delete tvariable
9975 Delete the given trace state variables, or all of them if no arguments
9980 @node Tracepoint Actions
9981 @subsection Tracepoint Action Lists
9985 @cindex tracepoint actions
9986 @item actions @r{[}@var{num}@r{]}
9987 This command will prompt for a list of actions to be taken when the
9988 tracepoint is hit. If the tracepoint number @var{num} is not
9989 specified, this command sets the actions for the one that was most
9990 recently defined (so that you can define a tracepoint and then say
9991 @code{actions} without bothering about its number). You specify the
9992 actions themselves on the following lines, one action at a time, and
9993 terminate the actions list with a line containing just @code{end}. So
9994 far, the only defined actions are @code{collect}, @code{teval}, and
9995 @code{while-stepping}.
9997 @code{actions} is actually equivalent to @code{commands} (@pxref{Break
9998 Commands, ,Breakpoint Command Lists}), except that only the defined
9999 actions are allowed; any other @value{GDBN} command is rejected.
10001 @cindex remove actions from a tracepoint
10002 To remove all actions from a tracepoint, type @samp{actions @var{num}}
10003 and follow it immediately with @samp{end}.
10006 (@value{GDBP}) @b{collect @var{data}} // collect some data
10008 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
10010 (@value{GDBP}) @b{end} // signals the end of actions.
10013 In the following example, the action list begins with @code{collect}
10014 commands indicating the things to be collected when the tracepoint is
10015 hit. Then, in order to single-step and collect additional data
10016 following the tracepoint, a @code{while-stepping} command is used,
10017 followed by the list of things to be collected after each step in a
10018 sequence of single steps. The @code{while-stepping} command is
10019 terminated by its own separate @code{end} command. Lastly, the action
10020 list is terminated by an @code{end} command.
10023 (@value{GDBP}) @b{trace foo}
10024 (@value{GDBP}) @b{actions}
10025 Enter actions for tracepoint 1, one per line:
10028 > while-stepping 12
10029 > collect $pc, arr[i]
10034 @kindex collect @r{(tracepoints)}
10035 @item collect @var{expr1}, @var{expr2}, @dots{}
10036 Collect values of the given expressions when the tracepoint is hit.
10037 This command accepts a comma-separated list of any valid expressions.
10038 In addition to global, static, or local variables, the following
10039 special arguments are supported:
10043 Collect all registers.
10046 Collect all function arguments.
10049 Collect all local variables.
10052 @vindex $_sdata@r{, collect}
10053 Collect static tracepoint marker specific data. Only available for
10054 static tracepoints. @xref{Tracepoint Actions,,Tracepoint Action
10055 Lists}. On the UST static tracepoints library backend, an
10056 instrumentation point resembles a @code{printf} function call. The
10057 tracing library is able to collect user specified data formatted to a
10058 character string using the format provided by the programmer that
10059 instrumented the program. Other backends have similar mechanisms.
10060 Here's an example of a UST marker call:
10063 const char master_name[] = "$your_name";
10064 trace_mark(channel1, marker1, "hello %s", master_name)
10067 In this case, collecting @code{$_sdata} collects the string
10068 @samp{hello $yourname}. When analyzing the trace buffer, you can
10069 inspect @samp{$_sdata} like any other variable available to
10073 You can give several consecutive @code{collect} commands, each one
10074 with a single argument, or one @code{collect} command with several
10075 arguments separated by commas; the effect is the same.
10077 The command @code{info scope} (@pxref{Symbols, info scope}) is
10078 particularly useful for figuring out what data to collect.
10080 @kindex teval @r{(tracepoints)}
10081 @item teval @var{expr1}, @var{expr2}, @dots{}
10082 Evaluate the given expressions when the tracepoint is hit. This
10083 command accepts a comma-separated list of expressions. The results
10084 are discarded, so this is mainly useful for assigning values to trace
10085 state variables (@pxref{Trace State Variables}) without adding those
10086 values to the trace buffer, as would be the case if the @code{collect}
10089 @kindex while-stepping @r{(tracepoints)}
10090 @item while-stepping @var{n}
10091 Perform @var{n} single-step instruction traces after the tracepoint,
10092 collecting new data after each step. The @code{while-stepping}
10093 command is followed by the list of what to collect while stepping
10094 (followed by its own @code{end} command):
10097 > while-stepping 12
10098 > collect $regs, myglobal
10104 Note that @code{$pc} is not automatically collected by
10105 @code{while-stepping}; you need to explicitly collect that register if
10106 you need it. You may abbreviate @code{while-stepping} as @code{ws} or
10109 @item set default-collect @var{expr1}, @var{expr2}, @dots{}
10110 @kindex set default-collect
10111 @cindex default collection action
10112 This variable is a list of expressions to collect at each tracepoint
10113 hit. It is effectively an additional @code{collect} action prepended
10114 to every tracepoint action list. The expressions are parsed
10115 individually for each tracepoint, so for instance a variable named
10116 @code{xyz} may be interpreted as a global for one tracepoint, and a
10117 local for another, as appropriate to the tracepoint's location.
10119 @item show default-collect
10120 @kindex show default-collect
10121 Show the list of expressions that are collected by default at each
10126 @node Listing Tracepoints
10127 @subsection Listing Tracepoints
10130 @kindex info tracepoints
10132 @cindex information about tracepoints
10133 @item info tracepoints @r{[}@var{num}@r{]}
10134 Display information about the tracepoint @var{num}. If you don't
10135 specify a tracepoint number, displays information about all the
10136 tracepoints defined so far. The format is similar to that used for
10137 @code{info breakpoints}; in fact, @code{info tracepoints} is the same
10138 command, simply restricting itself to tracepoints.
10140 A tracepoint's listing may include additional information specific to
10145 its passcount as given by the @code{passcount @var{n}} command
10149 (@value{GDBP}) @b{info trace}
10150 Num Type Disp Enb Address What
10151 1 tracepoint keep y 0x0804ab57 in foo() at main.cxx:7
10153 collect globfoo, $regs
10162 This command can be abbreviated @code{info tp}.
10165 @node Listing Static Tracepoint Markers
10166 @subsection Listing Static Tracepoint Markers
10169 @kindex info static-tracepoint-markers
10170 @cindex information about static tracepoint markers
10171 @item info static-tracepoint-markers
10172 Display information about all static tracepoint markers defined in the
10175 For each marker, the following columns are printed:
10179 An incrementing counter, output to help readability. This is not a
10182 The marker ID, as reported by the target.
10183 @item Enabled or Disabled
10184 Probed markers are tagged with @samp{y}. @samp{n} identifies marks
10185 that are not enabled.
10187 Where the marker is in your program, as a memory address.
10189 Where the marker is in the source for your program, as a file and line
10190 number. If the debug information included in the program does not
10191 allow @value{GDBN} to locate the source of the marker, this column
10192 will be left blank.
10196 In addition, the following information may be printed for each marker:
10200 User data passed to the tracing library by the marker call. In the
10201 UST backend, this is the format string passed as argument to the
10203 @item Static tracepoints probing the marker
10204 The list of static tracepoints attached to the marker.
10208 (@value{GDBP}) info static-tracepoint-markers
10209 Cnt ID Enb Address What
10210 1 ust/bar2 y 0x0000000000400e1a in main at stexample.c:25
10211 Data: number1 %d number2 %d
10212 Probed by static tracepoints: #2
10213 2 ust/bar33 n 0x0000000000400c87 in main at stexample.c:24
10219 @node Starting and Stopping Trace Experiments
10220 @subsection Starting and Stopping Trace Experiments
10224 @cindex start a new trace experiment
10225 @cindex collected data discarded
10227 This command takes no arguments. It starts the trace experiment, and
10228 begins collecting data. This has the side effect of discarding all
10229 the data collected in the trace buffer during the previous trace
10233 @cindex stop a running trace experiment
10235 This command takes no arguments. It ends the trace experiment, and
10236 stops collecting data.
10238 @strong{Note}: a trace experiment and data collection may stop
10239 automatically if any tracepoint's passcount is reached
10240 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
10243 @cindex status of trace data collection
10244 @cindex trace experiment, status of
10246 This command displays the status of the current trace data
10250 Here is an example of the commands we described so far:
10253 (@value{GDBP}) @b{trace gdb_c_test}
10254 (@value{GDBP}) @b{actions}
10255 Enter actions for tracepoint #1, one per line.
10256 > collect $regs,$locals,$args
10257 > while-stepping 11
10261 (@value{GDBP}) @b{tstart}
10262 [time passes @dots{}]
10263 (@value{GDBP}) @b{tstop}
10266 @cindex disconnected tracing
10267 You can choose to continue running the trace experiment even if
10268 @value{GDBN} disconnects from the target, voluntarily or
10269 involuntarily. For commands such as @code{detach}, the debugger will
10270 ask what you want to do with the trace. But for unexpected
10271 terminations (@value{GDBN} crash, network outage), it would be
10272 unfortunate to lose hard-won trace data, so the variable
10273 @code{disconnected-tracing} lets you decide whether the trace should
10274 continue running without @value{GDBN}.
10277 @item set disconnected-tracing on
10278 @itemx set disconnected-tracing off
10279 @kindex set disconnected-tracing
10280 Choose whether a tracing run should continue to run if @value{GDBN}
10281 has disconnected from the target. Note that @code{detach} or
10282 @code{quit} will ask you directly what to do about a running trace no
10283 matter what this variable's setting, so the variable is mainly useful
10284 for handling unexpected situations, such as loss of the network.
10286 @item show disconnected-tracing
10287 @kindex show disconnected-tracing
10288 Show the current choice for disconnected tracing.
10292 When you reconnect to the target, the trace experiment may or may not
10293 still be running; it might have filled the trace buffer in the
10294 meantime, or stopped for one of the other reasons. If it is running,
10295 it will continue after reconnection.
10297 Upon reconnection, the target will upload information about the
10298 tracepoints in effect. @value{GDBN} will then compare that
10299 information to the set of tracepoints currently defined, and attempt
10300 to match them up, allowing for the possibility that the numbers may
10301 have changed due to creation and deletion in the meantime. If one of
10302 the target's tracepoints does not match any in @value{GDBN}, the
10303 debugger will create a new tracepoint, so that you have a number with
10304 which to specify that tracepoint. This matching-up process is
10305 necessarily heuristic, and it may result in useless tracepoints being
10306 created; you may simply delete them if they are of no use.
10308 @cindex circular trace buffer
10309 If your target agent supports a @dfn{circular trace buffer}, then you
10310 can run a trace experiment indefinitely without filling the trace
10311 buffer; when space runs out, the agent deletes already-collected trace
10312 frames, oldest first, until there is enough room to continue
10313 collecting. This is especially useful if your tracepoints are being
10314 hit too often, and your trace gets terminated prematurely because the
10315 buffer is full. To ask for a circular trace buffer, simply set
10316 @samp{circular_trace_buffer} to on. You can set this at any time,
10317 including during tracing; if the agent can do it, it will change
10318 buffer handling on the fly, otherwise it will not take effect until
10322 @item set circular-trace-buffer on
10323 @itemx set circular-trace-buffer off
10324 @kindex set circular-trace-buffer
10325 Choose whether a tracing run should use a linear or circular buffer
10326 for trace data. A linear buffer will not lose any trace data, but may
10327 fill up prematurely, while a circular buffer will discard old trace
10328 data, but it will have always room for the latest tracepoint hits.
10330 @item show circular-trace-buffer
10331 @kindex show circular-trace-buffer
10332 Show the current choice for the trace buffer. Note that this may not
10333 match the agent's current buffer handling, nor is it guaranteed to
10334 match the setting that might have been in effect during a past run,
10335 for instance if you are looking at frames from a trace file.
10339 @node Tracepoint Restrictions
10340 @subsection Tracepoint Restrictions
10342 @cindex tracepoint restrictions
10343 There are a number of restrictions on the use of tracepoints. As
10344 described above, tracepoint data gathering occurs on the target
10345 without interaction from @value{GDBN}. Thus the full capabilities of
10346 the debugger are not available during data gathering, and then at data
10347 examination time, you will be limited by only having what was
10348 collected. The following items describe some common problems, but it
10349 is not exhaustive, and you may run into additional difficulties not
10355 Tracepoint expressions are intended to gather objects (lvalues). Thus
10356 the full flexibility of GDB's expression evaluator is not available.
10357 You cannot call functions, cast objects to aggregate types, access
10358 convenience variables or modify values (except by assignment to trace
10359 state variables). Some language features may implicitly call
10360 functions (for instance Objective-C fields with accessors), and therefore
10361 cannot be collected either.
10364 Collection of local variables, either individually or in bulk with
10365 @code{$locals} or @code{$args}, during @code{while-stepping} may
10366 behave erratically. The stepping action may enter a new scope (for
10367 instance by stepping into a function), or the location of the variable
10368 may change (for instance it is loaded into a register). The
10369 tracepoint data recorded uses the location information for the
10370 variables that is correct for the tracepoint location. When the
10371 tracepoint is created, it is not possible, in general, to determine
10372 where the steps of a @code{while-stepping} sequence will advance the
10373 program---particularly if a conditional branch is stepped.
10376 Collection of an incompletely-initialized or partially-destroyed object
10377 may result in something that @value{GDBN} cannot display, or displays
10378 in a misleading way.
10381 When @value{GDBN} displays a pointer to character it automatically
10382 dereferences the pointer to also display characters of the string
10383 being pointed to. However, collecting the pointer during tracing does
10384 not automatically collect the string. You need to explicitly
10385 dereference the pointer and provide size information if you want to
10386 collect not only the pointer, but the memory pointed to. For example,
10387 @code{*ptr@@50} can be used to collect the 50 element array pointed to
10391 It is not possible to collect a complete stack backtrace at a
10392 tracepoint. Instead, you may collect the registers and a few hundred
10393 bytes from the stack pointer with something like @code{*$esp@@300}
10394 (adjust to use the name of the actual stack pointer register on your
10395 target architecture, and the amount of stack you wish to capture).
10396 Then the @code{backtrace} command will show a partial backtrace when
10397 using a trace frame. The number of stack frames that can be examined
10398 depends on the sizes of the frames in the collected stack. Note that
10399 if you ask for a block so large that it goes past the bottom of the
10400 stack, the target agent may report an error trying to read from an
10404 If you do not collect registers at a tracepoint, @value{GDBN} can
10405 infer that the value of @code{$pc} must be the same as the address of
10406 the tracepoint and use that when you are looking at a trace frame
10407 for that tracepoint. However, this cannot work if the tracepoint has
10408 multiple locations (for instance if it was set in a function that was
10409 inlined), or if it has a @code{while-stepping} loop. In those cases
10410 @value{GDBN} will warn you that it can't infer @code{$pc}, and default
10415 @node Analyze Collected Data
10416 @section Using the Collected Data
10418 After the tracepoint experiment ends, you use @value{GDBN} commands
10419 for examining the trace data. The basic idea is that each tracepoint
10420 collects a trace @dfn{snapshot} every time it is hit and another
10421 snapshot every time it single-steps. All these snapshots are
10422 consecutively numbered from zero and go into a buffer, and you can
10423 examine them later. The way you examine them is to @dfn{focus} on a
10424 specific trace snapshot. When the remote stub is focused on a trace
10425 snapshot, it will respond to all @value{GDBN} requests for memory and
10426 registers by reading from the buffer which belongs to that snapshot,
10427 rather than from @emph{real} memory or registers of the program being
10428 debugged. This means that @strong{all} @value{GDBN} commands
10429 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
10430 behave as if we were currently debugging the program state as it was
10431 when the tracepoint occurred. Any requests for data that are not in
10432 the buffer will fail.
10435 * tfind:: How to select a trace snapshot
10436 * tdump:: How to display all data for a snapshot
10437 * save tracepoints:: How to save tracepoints for a future run
10441 @subsection @code{tfind @var{n}}
10444 @cindex select trace snapshot
10445 @cindex find trace snapshot
10446 The basic command for selecting a trace snapshot from the buffer is
10447 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
10448 counting from zero. If no argument @var{n} is given, the next
10449 snapshot is selected.
10451 Here are the various forms of using the @code{tfind} command.
10455 Find the first snapshot in the buffer. This is a synonym for
10456 @code{tfind 0} (since 0 is the number of the first snapshot).
10459 Stop debugging trace snapshots, resume @emph{live} debugging.
10462 Same as @samp{tfind none}.
10465 No argument means find the next trace snapshot.
10468 Find the previous trace snapshot before the current one. This permits
10469 retracing earlier steps.
10471 @item tfind tracepoint @var{num}
10472 Find the next snapshot associated with tracepoint @var{num}. Search
10473 proceeds forward from the last examined trace snapshot. If no
10474 argument @var{num} is given, it means find the next snapshot collected
10475 for the same tracepoint as the current snapshot.
10477 @item tfind pc @var{addr}
10478 Find the next snapshot associated with the value @var{addr} of the
10479 program counter. Search proceeds forward from the last examined trace
10480 snapshot. If no argument @var{addr} is given, it means find the next
10481 snapshot with the same value of PC as the current snapshot.
10483 @item tfind outside @var{addr1}, @var{addr2}
10484 Find the next snapshot whose PC is outside the given range of
10485 addresses (exclusive).
10487 @item tfind range @var{addr1}, @var{addr2}
10488 Find the next snapshot whose PC is between @var{addr1} and
10489 @var{addr2} (inclusive).
10491 @item tfind line @r{[}@var{file}:@r{]}@var{n}
10492 Find the next snapshot associated with the source line @var{n}. If
10493 the optional argument @var{file} is given, refer to line @var{n} in
10494 that source file. Search proceeds forward from the last examined
10495 trace snapshot. If no argument @var{n} is given, it means find the
10496 next line other than the one currently being examined; thus saying
10497 @code{tfind line} repeatedly can appear to have the same effect as
10498 stepping from line to line in a @emph{live} debugging session.
10501 The default arguments for the @code{tfind} commands are specifically
10502 designed to make it easy to scan through the trace buffer. For
10503 instance, @code{tfind} with no argument selects the next trace
10504 snapshot, and @code{tfind -} with no argument selects the previous
10505 trace snapshot. So, by giving one @code{tfind} command, and then
10506 simply hitting @key{RET} repeatedly you can examine all the trace
10507 snapshots in order. Or, by saying @code{tfind -} and then hitting
10508 @key{RET} repeatedly you can examine the snapshots in reverse order.
10509 The @code{tfind line} command with no argument selects the snapshot
10510 for the next source line executed. The @code{tfind pc} command with
10511 no argument selects the next snapshot with the same program counter
10512 (PC) as the current frame. The @code{tfind tracepoint} command with
10513 no argument selects the next trace snapshot collected by the same
10514 tracepoint as the current one.
10516 In addition to letting you scan through the trace buffer manually,
10517 these commands make it easy to construct @value{GDBN} scripts that
10518 scan through the trace buffer and print out whatever collected data
10519 you are interested in. Thus, if we want to examine the PC, FP, and SP
10520 registers from each trace frame in the buffer, we can say this:
10523 (@value{GDBP}) @b{tfind start}
10524 (@value{GDBP}) @b{while ($trace_frame != -1)}
10525 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
10526 $trace_frame, $pc, $sp, $fp
10530 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
10531 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
10532 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
10533 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
10534 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
10535 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
10536 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
10537 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
10538 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
10539 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
10540 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
10543 Or, if we want to examine the variable @code{X} at each source line in
10547 (@value{GDBP}) @b{tfind start}
10548 (@value{GDBP}) @b{while ($trace_frame != -1)}
10549 > printf "Frame %d, X == %d\n", $trace_frame, X
10559 @subsection @code{tdump}
10561 @cindex dump all data collected at tracepoint
10562 @cindex tracepoint data, display
10564 This command takes no arguments. It prints all the data collected at
10565 the current trace snapshot.
10568 (@value{GDBP}) @b{trace 444}
10569 (@value{GDBP}) @b{actions}
10570 Enter actions for tracepoint #2, one per line:
10571 > collect $regs, $locals, $args, gdb_long_test
10574 (@value{GDBP}) @b{tstart}
10576 (@value{GDBP}) @b{tfind line 444}
10577 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
10579 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
10581 (@value{GDBP}) @b{tdump}
10582 Data collected at tracepoint 2, trace frame 1:
10583 d0 0xc4aa0085 -995491707
10587 d4 0x71aea3d 119204413
10590 d7 0x380035 3670069
10591 a0 0x19e24a 1696330
10592 a1 0x3000668 50333288
10594 a3 0x322000 3284992
10595 a4 0x3000698 50333336
10596 a5 0x1ad3cc 1758156
10597 fp 0x30bf3c 0x30bf3c
10598 sp 0x30bf34 0x30bf34
10600 pc 0x20b2c8 0x20b2c8
10604 p = 0x20e5b4 "gdb-test"
10611 gdb_long_test = 17 '\021'
10616 @code{tdump} works by scanning the tracepoint's current collection
10617 actions and printing the value of each expression listed. So
10618 @code{tdump} can fail, if after a run, you change the tracepoint's
10619 actions to mention variables that were not collected during the run.
10621 Also, for tracepoints with @code{while-stepping} loops, @code{tdump}
10622 uses the collected value of @code{$pc} to distinguish between trace
10623 frames that were collected at the tracepoint hit, and frames that were
10624 collected while stepping. This allows it to correctly choose whether
10625 to display the basic list of collections, or the collections from the
10626 body of the while-stepping loop. However, if @code{$pc} was not collected,
10627 then @code{tdump} will always attempt to dump using the basic collection
10628 list, and may fail if a while-stepping frame does not include all the
10629 same data that is collected at the tracepoint hit.
10630 @c This is getting pretty arcane, example would be good.
10632 @node save tracepoints
10633 @subsection @code{save tracepoints @var{filename}}
10634 @kindex save tracepoints
10635 @kindex save-tracepoints
10636 @cindex save tracepoints for future sessions
10638 This command saves all current tracepoint definitions together with
10639 their actions and passcounts, into a file @file{@var{filename}}
10640 suitable for use in a later debugging session. To read the saved
10641 tracepoint definitions, use the @code{source} command (@pxref{Command
10642 Files}). The @w{@code{save-tracepoints}} command is a deprecated
10643 alias for @w{@code{save tracepoints}}
10645 @node Tracepoint Variables
10646 @section Convenience Variables for Tracepoints
10647 @cindex tracepoint variables
10648 @cindex convenience variables for tracepoints
10651 @vindex $trace_frame
10652 @item (int) $trace_frame
10653 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
10654 snapshot is selected.
10656 @vindex $tracepoint
10657 @item (int) $tracepoint
10658 The tracepoint for the current trace snapshot.
10660 @vindex $trace_line
10661 @item (int) $trace_line
10662 The line number for the current trace snapshot.
10664 @vindex $trace_file
10665 @item (char []) $trace_file
10666 The source file for the current trace snapshot.
10668 @vindex $trace_func
10669 @item (char []) $trace_func
10670 The name of the function containing @code{$tracepoint}.
10673 Note: @code{$trace_file} is not suitable for use in @code{printf},
10674 use @code{output} instead.
10676 Here's a simple example of using these convenience variables for
10677 stepping through all the trace snapshots and printing some of their
10678 data. Note that these are not the same as trace state variables,
10679 which are managed by the target.
10682 (@value{GDBP}) @b{tfind start}
10684 (@value{GDBP}) @b{while $trace_frame != -1}
10685 > output $trace_file
10686 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
10692 @section Using Trace Files
10693 @cindex trace files
10695 In some situations, the target running a trace experiment may no
10696 longer be available; perhaps it crashed, or the hardware was needed
10697 for a different activity. To handle these cases, you can arrange to
10698 dump the trace data into a file, and later use that file as a source
10699 of trace data, via the @code{target tfile} command.
10704 @item tsave [ -r ] @var{filename}
10705 Save the trace data to @var{filename}. By default, this command
10706 assumes that @var{filename} refers to the host filesystem, so if
10707 necessary @value{GDBN} will copy raw trace data up from the target and
10708 then save it. If the target supports it, you can also supply the
10709 optional argument @code{-r} (``remote'') to direct the target to save
10710 the data directly into @var{filename} in its own filesystem, which may be
10711 more efficient if the trace buffer is very large. (Note, however, that
10712 @code{target tfile} can only read from files accessible to the host.)
10714 @kindex target tfile
10716 @item target tfile @var{filename}
10717 Use the file named @var{filename} as a source of trace data. Commands
10718 that examine data work as they do with a live target, but it is not
10719 possible to run any new trace experiments. @code{tstatus} will report
10720 the state of the trace run at the moment the data was saved, as well
10721 as the current trace frame you are examining. @var{filename} must be
10722 on a filesystem accessible to the host.
10727 @chapter Debugging Programs That Use Overlays
10730 If your program is too large to fit completely in your target system's
10731 memory, you can sometimes use @dfn{overlays} to work around this
10732 problem. @value{GDBN} provides some support for debugging programs that
10736 * How Overlays Work:: A general explanation of overlays.
10737 * Overlay Commands:: Managing overlays in @value{GDBN}.
10738 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
10739 mapped by asking the inferior.
10740 * Overlay Sample Program:: A sample program using overlays.
10743 @node How Overlays Work
10744 @section How Overlays Work
10745 @cindex mapped overlays
10746 @cindex unmapped overlays
10747 @cindex load address, overlay's
10748 @cindex mapped address
10749 @cindex overlay area
10751 Suppose you have a computer whose instruction address space is only 64
10752 kilobytes long, but which has much more memory which can be accessed by
10753 other means: special instructions, segment registers, or memory
10754 management hardware, for example. Suppose further that you want to
10755 adapt a program which is larger than 64 kilobytes to run on this system.
10757 One solution is to identify modules of your program which are relatively
10758 independent, and need not call each other directly; call these modules
10759 @dfn{overlays}. Separate the overlays from the main program, and place
10760 their machine code in the larger memory. Place your main program in
10761 instruction memory, but leave at least enough space there to hold the
10762 largest overlay as well.
10764 Now, to call a function located in an overlay, you must first copy that
10765 overlay's machine code from the large memory into the space set aside
10766 for it in the instruction memory, and then jump to its entry point
10769 @c NB: In the below the mapped area's size is greater or equal to the
10770 @c size of all overlays. This is intentional to remind the developer
10771 @c that overlays don't necessarily need to be the same size.
10775 Data Instruction Larger
10776 Address Space Address Space Address Space
10777 +-----------+ +-----------+ +-----------+
10779 +-----------+ +-----------+ +-----------+<-- overlay 1
10780 | program | | main | .----| overlay 1 | load address
10781 | variables | | program | | +-----------+
10782 | and heap | | | | | |
10783 +-----------+ | | | +-----------+<-- overlay 2
10784 | | +-----------+ | | | load address
10785 +-----------+ | | | .-| overlay 2 |
10787 mapped --->+-----------+ | | +-----------+
10788 address | | | | | |
10789 | overlay | <-' | | |
10790 | area | <---' +-----------+<-- overlay 3
10791 | | <---. | | load address
10792 +-----------+ `--| overlay 3 |
10799 @anchor{A code overlay}A code overlay
10803 The diagram (@pxref{A code overlay}) shows a system with separate data
10804 and instruction address spaces. To map an overlay, the program copies
10805 its code from the larger address space to the instruction address space.
10806 Since the overlays shown here all use the same mapped address, only one
10807 may be mapped at a time. For a system with a single address space for
10808 data and instructions, the diagram would be similar, except that the
10809 program variables and heap would share an address space with the main
10810 program and the overlay area.
10812 An overlay loaded into instruction memory and ready for use is called a
10813 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
10814 instruction memory. An overlay not present (or only partially present)
10815 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
10816 is its address in the larger memory. The mapped address is also called
10817 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
10818 called the @dfn{load memory address}, or @dfn{LMA}.
10820 Unfortunately, overlays are not a completely transparent way to adapt a
10821 program to limited instruction memory. They introduce a new set of
10822 global constraints you must keep in mind as you design your program:
10827 Before calling or returning to a function in an overlay, your program
10828 must make sure that overlay is actually mapped. Otherwise, the call or
10829 return will transfer control to the right address, but in the wrong
10830 overlay, and your program will probably crash.
10833 If the process of mapping an overlay is expensive on your system, you
10834 will need to choose your overlays carefully to minimize their effect on
10835 your program's performance.
10838 The executable file you load onto your system must contain each
10839 overlay's instructions, appearing at the overlay's load address, not its
10840 mapped address. However, each overlay's instructions must be relocated
10841 and its symbols defined as if the overlay were at its mapped address.
10842 You can use GNU linker scripts to specify different load and relocation
10843 addresses for pieces of your program; see @ref{Overlay Description,,,
10844 ld.info, Using ld: the GNU linker}.
10847 The procedure for loading executable files onto your system must be able
10848 to load their contents into the larger address space as well as the
10849 instruction and data spaces.
10853 The overlay system described above is rather simple, and could be
10854 improved in many ways:
10859 If your system has suitable bank switch registers or memory management
10860 hardware, you could use those facilities to make an overlay's load area
10861 contents simply appear at their mapped address in instruction space.
10862 This would probably be faster than copying the overlay to its mapped
10863 area in the usual way.
10866 If your overlays are small enough, you could set aside more than one
10867 overlay area, and have more than one overlay mapped at a time.
10870 You can use overlays to manage data, as well as instructions. In
10871 general, data overlays are even less transparent to your design than
10872 code overlays: whereas code overlays only require care when you call or
10873 return to functions, data overlays require care every time you access
10874 the data. Also, if you change the contents of a data overlay, you
10875 must copy its contents back out to its load address before you can copy a
10876 different data overlay into the same mapped area.
10881 @node Overlay Commands
10882 @section Overlay Commands
10884 To use @value{GDBN}'s overlay support, each overlay in your program must
10885 correspond to a separate section of the executable file. The section's
10886 virtual memory address and load memory address must be the overlay's
10887 mapped and load addresses. Identifying overlays with sections allows
10888 @value{GDBN} to determine the appropriate address of a function or
10889 variable, depending on whether the overlay is mapped or not.
10891 @value{GDBN}'s overlay commands all start with the word @code{overlay};
10892 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
10897 Disable @value{GDBN}'s overlay support. When overlay support is
10898 disabled, @value{GDBN} assumes that all functions and variables are
10899 always present at their mapped addresses. By default, @value{GDBN}'s
10900 overlay support is disabled.
10902 @item overlay manual
10903 @cindex manual overlay debugging
10904 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
10905 relies on you to tell it which overlays are mapped, and which are not,
10906 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
10907 commands described below.
10909 @item overlay map-overlay @var{overlay}
10910 @itemx overlay map @var{overlay}
10911 @cindex map an overlay
10912 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
10913 be the name of the object file section containing the overlay. When an
10914 overlay is mapped, @value{GDBN} assumes it can find the overlay's
10915 functions and variables at their mapped addresses. @value{GDBN} assumes
10916 that any other overlays whose mapped ranges overlap that of
10917 @var{overlay} are now unmapped.
10919 @item overlay unmap-overlay @var{overlay}
10920 @itemx overlay unmap @var{overlay}
10921 @cindex unmap an overlay
10922 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
10923 must be the name of the object file section containing the overlay.
10924 When an overlay is unmapped, @value{GDBN} assumes it can find the
10925 overlay's functions and variables at their load addresses.
10928 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
10929 consults a data structure the overlay manager maintains in the inferior
10930 to see which overlays are mapped. For details, see @ref{Automatic
10931 Overlay Debugging}.
10933 @item overlay load-target
10934 @itemx overlay load
10935 @cindex reloading the overlay table
10936 Re-read the overlay table from the inferior. Normally, @value{GDBN}
10937 re-reads the table @value{GDBN} automatically each time the inferior
10938 stops, so this command should only be necessary if you have changed the
10939 overlay mapping yourself using @value{GDBN}. This command is only
10940 useful when using automatic overlay debugging.
10942 @item overlay list-overlays
10943 @itemx overlay list
10944 @cindex listing mapped overlays
10945 Display a list of the overlays currently mapped, along with their mapped
10946 addresses, load addresses, and sizes.
10950 Normally, when @value{GDBN} prints a code address, it includes the name
10951 of the function the address falls in:
10954 (@value{GDBP}) print main
10955 $3 = @{int ()@} 0x11a0 <main>
10958 When overlay debugging is enabled, @value{GDBN} recognizes code in
10959 unmapped overlays, and prints the names of unmapped functions with
10960 asterisks around them. For example, if @code{foo} is a function in an
10961 unmapped overlay, @value{GDBN} prints it this way:
10964 (@value{GDBP}) overlay list
10965 No sections are mapped.
10966 (@value{GDBP}) print foo
10967 $5 = @{int (int)@} 0x100000 <*foo*>
10970 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
10974 (@value{GDBP}) overlay list
10975 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
10976 mapped at 0x1016 - 0x104a
10977 (@value{GDBP}) print foo
10978 $6 = @{int (int)@} 0x1016 <foo>
10981 When overlay debugging is enabled, @value{GDBN} can find the correct
10982 address for functions and variables in an overlay, whether or not the
10983 overlay is mapped. This allows most @value{GDBN} commands, like
10984 @code{break} and @code{disassemble}, to work normally, even on unmapped
10985 code. However, @value{GDBN}'s breakpoint support has some limitations:
10989 @cindex breakpoints in overlays
10990 @cindex overlays, setting breakpoints in
10991 You can set breakpoints in functions in unmapped overlays, as long as
10992 @value{GDBN} can write to the overlay at its load address.
10994 @value{GDBN} can not set hardware or simulator-based breakpoints in
10995 unmapped overlays. However, if you set a breakpoint at the end of your
10996 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
10997 you are using manual overlay management), @value{GDBN} will re-set its
10998 breakpoints properly.
11002 @node Automatic Overlay Debugging
11003 @section Automatic Overlay Debugging
11004 @cindex automatic overlay debugging
11006 @value{GDBN} can automatically track which overlays are mapped and which
11007 are not, given some simple co-operation from the overlay manager in the
11008 inferior. If you enable automatic overlay debugging with the
11009 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
11010 looks in the inferior's memory for certain variables describing the
11011 current state of the overlays.
11013 Here are the variables your overlay manager must define to support
11014 @value{GDBN}'s automatic overlay debugging:
11018 @item @code{_ovly_table}:
11019 This variable must be an array of the following structures:
11024 /* The overlay's mapped address. */
11027 /* The size of the overlay, in bytes. */
11028 unsigned long size;
11030 /* The overlay's load address. */
11033 /* Non-zero if the overlay is currently mapped;
11035 unsigned long mapped;
11039 @item @code{_novlys}:
11040 This variable must be a four-byte signed integer, holding the total
11041 number of elements in @code{_ovly_table}.
11045 To decide whether a particular overlay is mapped or not, @value{GDBN}
11046 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
11047 @code{lma} members equal the VMA and LMA of the overlay's section in the
11048 executable file. When @value{GDBN} finds a matching entry, it consults
11049 the entry's @code{mapped} member to determine whether the overlay is
11052 In addition, your overlay manager may define a function called
11053 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
11054 will silently set a breakpoint there. If the overlay manager then
11055 calls this function whenever it has changed the overlay table, this
11056 will enable @value{GDBN} to accurately keep track of which overlays
11057 are in program memory, and update any breakpoints that may be set
11058 in overlays. This will allow breakpoints to work even if the
11059 overlays are kept in ROM or other non-writable memory while they
11060 are not being executed.
11062 @node Overlay Sample Program
11063 @section Overlay Sample Program
11064 @cindex overlay example program
11066 When linking a program which uses overlays, you must place the overlays
11067 at their load addresses, while relocating them to run at their mapped
11068 addresses. To do this, you must write a linker script (@pxref{Overlay
11069 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
11070 since linker scripts are specific to a particular host system, target
11071 architecture, and target memory layout, this manual cannot provide
11072 portable sample code demonstrating @value{GDBN}'s overlay support.
11074 However, the @value{GDBN} source distribution does contain an overlaid
11075 program, with linker scripts for a few systems, as part of its test
11076 suite. The program consists of the following files from
11077 @file{gdb/testsuite/gdb.base}:
11081 The main program file.
11083 A simple overlay manager, used by @file{overlays.c}.
11088 Overlay modules, loaded and used by @file{overlays.c}.
11091 Linker scripts for linking the test program on the @code{d10v-elf}
11092 and @code{m32r-elf} targets.
11095 You can build the test program using the @code{d10v-elf} GCC
11096 cross-compiler like this:
11099 $ d10v-elf-gcc -g -c overlays.c
11100 $ d10v-elf-gcc -g -c ovlymgr.c
11101 $ d10v-elf-gcc -g -c foo.c
11102 $ d10v-elf-gcc -g -c bar.c
11103 $ d10v-elf-gcc -g -c baz.c
11104 $ d10v-elf-gcc -g -c grbx.c
11105 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
11106 baz.o grbx.o -Wl,-Td10v.ld -o overlays
11109 The build process is identical for any other architecture, except that
11110 you must substitute the appropriate compiler and linker script for the
11111 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
11115 @chapter Using @value{GDBN} with Different Languages
11118 Although programming languages generally have common aspects, they are
11119 rarely expressed in the same manner. For instance, in ANSI C,
11120 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
11121 Modula-2, it is accomplished by @code{p^}. Values can also be
11122 represented (and displayed) differently. Hex numbers in C appear as
11123 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
11125 @cindex working language
11126 Language-specific information is built into @value{GDBN} for some languages,
11127 allowing you to express operations like the above in your program's
11128 native language, and allowing @value{GDBN} to output values in a manner
11129 consistent with the syntax of your program's native language. The
11130 language you use to build expressions is called the @dfn{working
11134 * Setting:: Switching between source languages
11135 * Show:: Displaying the language
11136 * Checks:: Type and range checks
11137 * Supported Languages:: Supported languages
11138 * Unsupported Languages:: Unsupported languages
11142 @section Switching Between Source Languages
11144 There are two ways to control the working language---either have @value{GDBN}
11145 set it automatically, or select it manually yourself. You can use the
11146 @code{set language} command for either purpose. On startup, @value{GDBN}
11147 defaults to setting the language automatically. The working language is
11148 used to determine how expressions you type are interpreted, how values
11151 In addition to the working language, every source file that
11152 @value{GDBN} knows about has its own working language. For some object
11153 file formats, the compiler might indicate which language a particular
11154 source file is in. However, most of the time @value{GDBN} infers the
11155 language from the name of the file. The language of a source file
11156 controls whether C@t{++} names are demangled---this way @code{backtrace} can
11157 show each frame appropriately for its own language. There is no way to
11158 set the language of a source file from within @value{GDBN}, but you can
11159 set the language associated with a filename extension. @xref{Show, ,
11160 Displaying the Language}.
11162 This is most commonly a problem when you use a program, such
11163 as @code{cfront} or @code{f2c}, that generates C but is written in
11164 another language. In that case, make the
11165 program use @code{#line} directives in its C output; that way
11166 @value{GDBN} will know the correct language of the source code of the original
11167 program, and will display that source code, not the generated C code.
11170 * Filenames:: Filename extensions and languages.
11171 * Manually:: Setting the working language manually
11172 * Automatically:: Having @value{GDBN} infer the source language
11176 @subsection List of Filename Extensions and Languages
11178 If a source file name ends in one of the following extensions, then
11179 @value{GDBN} infers that its language is the one indicated.
11197 C@t{++} source file
11203 Objective-C source file
11207 Fortran source file
11210 Modula-2 source file
11214 Assembler source file. This actually behaves almost like C, but
11215 @value{GDBN} does not skip over function prologues when stepping.
11218 In addition, you may set the language associated with a filename
11219 extension. @xref{Show, , Displaying the Language}.
11222 @subsection Setting the Working Language
11224 If you allow @value{GDBN} to set the language automatically,
11225 expressions are interpreted the same way in your debugging session and
11228 @kindex set language
11229 If you wish, you may set the language manually. To do this, issue the
11230 command @samp{set language @var{lang}}, where @var{lang} is the name of
11231 a language, such as
11232 @code{c} or @code{modula-2}.
11233 For a list of the supported languages, type @samp{set language}.
11235 Setting the language manually prevents @value{GDBN} from updating the working
11236 language automatically. This can lead to confusion if you try
11237 to debug a program when the working language is not the same as the
11238 source language, when an expression is acceptable to both
11239 languages---but means different things. For instance, if the current
11240 source file were written in C, and @value{GDBN} was parsing Modula-2, a
11248 might not have the effect you intended. In C, this means to add
11249 @code{b} and @code{c} and place the result in @code{a}. The result
11250 printed would be the value of @code{a}. In Modula-2, this means to compare
11251 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
11253 @node Automatically
11254 @subsection Having @value{GDBN} Infer the Source Language
11256 To have @value{GDBN} set the working language automatically, use
11257 @samp{set language local} or @samp{set language auto}. @value{GDBN}
11258 then infers the working language. That is, when your program stops in a
11259 frame (usually by encountering a breakpoint), @value{GDBN} sets the
11260 working language to the language recorded for the function in that
11261 frame. If the language for a frame is unknown (that is, if the function
11262 or block corresponding to the frame was defined in a source file that
11263 does not have a recognized extension), the current working language is
11264 not changed, and @value{GDBN} issues a warning.
11266 This may not seem necessary for most programs, which are written
11267 entirely in one source language. However, program modules and libraries
11268 written in one source language can be used by a main program written in
11269 a different source language. Using @samp{set language auto} in this
11270 case frees you from having to set the working language manually.
11273 @section Displaying the Language
11275 The following commands help you find out which language is the
11276 working language, and also what language source files were written in.
11279 @item show language
11280 @kindex show language
11281 Display the current working language. This is the
11282 language you can use with commands such as @code{print} to
11283 build and compute expressions that may involve variables in your program.
11286 @kindex info frame@r{, show the source language}
11287 Display the source language for this frame. This language becomes the
11288 working language if you use an identifier from this frame.
11289 @xref{Frame Info, ,Information about a Frame}, to identify the other
11290 information listed here.
11293 @kindex info source@r{, show the source language}
11294 Display the source language of this source file.
11295 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
11296 information listed here.
11299 In unusual circumstances, you may have source files with extensions
11300 not in the standard list. You can then set the extension associated
11301 with a language explicitly:
11304 @item set extension-language @var{ext} @var{language}
11305 @kindex set extension-language
11306 Tell @value{GDBN} that source files with extension @var{ext} are to be
11307 assumed as written in the source language @var{language}.
11309 @item info extensions
11310 @kindex info extensions
11311 List all the filename extensions and the associated languages.
11315 @section Type and Range Checking
11318 @emph{Warning:} In this release, the @value{GDBN} commands for type and range
11319 checking are included, but they do not yet have any effect. This
11320 section documents the intended facilities.
11322 @c FIXME remove warning when type/range code added
11324 Some languages are designed to guard you against making seemingly common
11325 errors through a series of compile- and run-time checks. These include
11326 checking the type of arguments to functions and operators, and making
11327 sure mathematical overflows are caught at run time. Checks such as
11328 these help to ensure a program's correctness once it has been compiled
11329 by eliminating type mismatches, and providing active checks for range
11330 errors when your program is running.
11332 @value{GDBN} can check for conditions like the above if you wish.
11333 Although @value{GDBN} does not check the statements in your program,
11334 it can check expressions entered directly into @value{GDBN} for
11335 evaluation via the @code{print} command, for example. As with the
11336 working language, @value{GDBN} can also decide whether or not to check
11337 automatically based on your program's source language.
11338 @xref{Supported Languages, ,Supported Languages}, for the default
11339 settings of supported languages.
11342 * Type Checking:: An overview of type checking
11343 * Range Checking:: An overview of range checking
11346 @cindex type checking
11347 @cindex checks, type
11348 @node Type Checking
11349 @subsection An Overview of Type Checking
11351 Some languages, such as Modula-2, are strongly typed, meaning that the
11352 arguments to operators and functions have to be of the correct type,
11353 otherwise an error occurs. These checks prevent type mismatch
11354 errors from ever causing any run-time problems. For example,
11362 The second example fails because the @code{CARDINAL} 1 is not
11363 type-compatible with the @code{REAL} 2.3.
11365 For the expressions you use in @value{GDBN} commands, you can tell the
11366 @value{GDBN} type checker to skip checking;
11367 to treat any mismatches as errors and abandon the expression;
11368 or to only issue warnings when type mismatches occur,
11369 but evaluate the expression anyway. When you choose the last of
11370 these, @value{GDBN} evaluates expressions like the second example above, but
11371 also issues a warning.
11373 Even if you turn type checking off, there may be other reasons
11374 related to type that prevent @value{GDBN} from evaluating an expression.
11375 For instance, @value{GDBN} does not know how to add an @code{int} and
11376 a @code{struct foo}. These particular type errors have nothing to do
11377 with the language in use, and usually arise from expressions, such as
11378 the one described above, which make little sense to evaluate anyway.
11380 Each language defines to what degree it is strict about type. For
11381 instance, both Modula-2 and C require the arguments to arithmetical
11382 operators to be numbers. In C, enumerated types and pointers can be
11383 represented as numbers, so that they are valid arguments to mathematical
11384 operators. @xref{Supported Languages, ,Supported Languages}, for further
11385 details on specific languages.
11387 @value{GDBN} provides some additional commands for controlling the type checker:
11389 @kindex set check type
11390 @kindex show check type
11392 @item set check type auto
11393 Set type checking on or off based on the current working language.
11394 @xref{Supported Languages, ,Supported Languages}, for the default settings for
11397 @item set check type on
11398 @itemx set check type off
11399 Set type checking on or off, overriding the default setting for the
11400 current working language. Issue a warning if the setting does not
11401 match the language default. If any type mismatches occur in
11402 evaluating an expression while type checking is on, @value{GDBN} prints a
11403 message and aborts evaluation of the expression.
11405 @item set check type warn
11406 Cause the type checker to issue warnings, but to always attempt to
11407 evaluate the expression. Evaluating the expression may still
11408 be impossible for other reasons. For example, @value{GDBN} cannot add
11409 numbers and structures.
11412 Show the current setting of the type checker, and whether or not @value{GDBN}
11413 is setting it automatically.
11416 @cindex range checking
11417 @cindex checks, range
11418 @node Range Checking
11419 @subsection An Overview of Range Checking
11421 In some languages (such as Modula-2), it is an error to exceed the
11422 bounds of a type; this is enforced with run-time checks. Such range
11423 checking is meant to ensure program correctness by making sure
11424 computations do not overflow, or indices on an array element access do
11425 not exceed the bounds of the array.
11427 For expressions you use in @value{GDBN} commands, you can tell
11428 @value{GDBN} to treat range errors in one of three ways: ignore them,
11429 always treat them as errors and abandon the expression, or issue
11430 warnings but evaluate the expression anyway.
11432 A range error can result from numerical overflow, from exceeding an
11433 array index bound, or when you type a constant that is not a member
11434 of any type. Some languages, however, do not treat overflows as an
11435 error. In many implementations of C, mathematical overflow causes the
11436 result to ``wrap around'' to lower values---for example, if @var{m} is
11437 the largest integer value, and @var{s} is the smallest, then
11440 @var{m} + 1 @result{} @var{s}
11443 This, too, is specific to individual languages, and in some cases
11444 specific to individual compilers or machines. @xref{Supported Languages, ,
11445 Supported Languages}, for further details on specific languages.
11447 @value{GDBN} provides some additional commands for controlling the range checker:
11449 @kindex set check range
11450 @kindex show check range
11452 @item set check range auto
11453 Set range checking on or off based on the current working language.
11454 @xref{Supported Languages, ,Supported Languages}, for the default settings for
11457 @item set check range on
11458 @itemx set check range off
11459 Set range checking on or off, overriding the default setting for the
11460 current working language. A warning is issued if the setting does not
11461 match the language default. If a range error occurs and range checking is on,
11462 then a message is printed and evaluation of the expression is aborted.
11464 @item set check range warn
11465 Output messages when the @value{GDBN} range checker detects a range error,
11466 but attempt to evaluate the expression anyway. Evaluating the
11467 expression may still be impossible for other reasons, such as accessing
11468 memory that the process does not own (a typical example from many Unix
11472 Show the current setting of the range checker, and whether or not it is
11473 being set automatically by @value{GDBN}.
11476 @node Supported Languages
11477 @section Supported Languages
11479 @value{GDBN} supports C, C@t{++}, D, Objective-C, Fortran, Java, Pascal,
11480 assembly, Modula-2, and Ada.
11481 @c This is false ...
11482 Some @value{GDBN} features may be used in expressions regardless of the
11483 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
11484 and the @samp{@{type@}addr} construct (@pxref{Expressions,
11485 ,Expressions}) can be used with the constructs of any supported
11488 The following sections detail to what degree each source language is
11489 supported by @value{GDBN}. These sections are not meant to be language
11490 tutorials or references, but serve only as a reference guide to what the
11491 @value{GDBN} expression parser accepts, and what input and output
11492 formats should look like for different languages. There are many good
11493 books written on each of these languages; please look to these for a
11494 language reference or tutorial.
11497 * C:: C and C@t{++}
11499 * Objective-C:: Objective-C
11500 * Fortran:: Fortran
11502 * Modula-2:: Modula-2
11507 @subsection C and C@t{++}
11509 @cindex C and C@t{++}
11510 @cindex expressions in C or C@t{++}
11512 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
11513 to both languages. Whenever this is the case, we discuss those languages
11517 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
11518 @cindex @sc{gnu} C@t{++}
11519 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
11520 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
11521 effectively, you must compile your C@t{++} programs with a supported
11522 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
11523 compiler (@code{aCC}).
11525 For best results when using @sc{gnu} C@t{++}, use the DWARF 2 debugging
11526 format; if it doesn't work on your system, try the stabs+ debugging
11527 format. You can select those formats explicitly with the @code{g++}
11528 command-line options @option{-gdwarf-2} and @option{-gstabs+}.
11529 @xref{Debugging Options,,Options for Debugging Your Program or GCC,
11530 gcc.info, Using the @sc{gnu} Compiler Collection (GCC)}.
11533 * C Operators:: C and C@t{++} operators
11534 * C Constants:: C and C@t{++} constants
11535 * C Plus Plus Expressions:: C@t{++} expressions
11536 * C Defaults:: Default settings for C and C@t{++}
11537 * C Checks:: C and C@t{++} type and range checks
11538 * Debugging C:: @value{GDBN} and C
11539 * Debugging C Plus Plus:: @value{GDBN} features for C@t{++}
11540 * Decimal Floating Point:: Numbers in Decimal Floating Point format
11544 @subsubsection C and C@t{++} Operators
11546 @cindex C and C@t{++} operators
11548 Operators must be defined on values of specific types. For instance,
11549 @code{+} is defined on numbers, but not on structures. Operators are
11550 often defined on groups of types.
11552 For the purposes of C and C@t{++}, the following definitions hold:
11557 @emph{Integral types} include @code{int} with any of its storage-class
11558 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
11561 @emph{Floating-point types} include @code{float}, @code{double}, and
11562 @code{long double} (if supported by the target platform).
11565 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
11568 @emph{Scalar types} include all of the above.
11573 The following operators are supported. They are listed here
11574 in order of increasing precedence:
11578 The comma or sequencing operator. Expressions in a comma-separated list
11579 are evaluated from left to right, with the result of the entire
11580 expression being the last expression evaluated.
11583 Assignment. The value of an assignment expression is the value
11584 assigned. Defined on scalar types.
11587 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
11588 and translated to @w{@code{@var{a} = @var{a op b}}}.
11589 @w{@code{@var{op}=}} and @code{=} have the same precedence.
11590 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
11591 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
11594 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
11595 of as: if @var{a} then @var{b} else @var{c}. @var{a} should be of an
11599 Logical @sc{or}. Defined on integral types.
11602 Logical @sc{and}. Defined on integral types.
11605 Bitwise @sc{or}. Defined on integral types.
11608 Bitwise exclusive-@sc{or}. Defined on integral types.
11611 Bitwise @sc{and}. Defined on integral types.
11614 Equality and inequality. Defined on scalar types. The value of these
11615 expressions is 0 for false and non-zero for true.
11617 @item <@r{, }>@r{, }<=@r{, }>=
11618 Less than, greater than, less than or equal, greater than or equal.
11619 Defined on scalar types. The value of these expressions is 0 for false
11620 and non-zero for true.
11623 left shift, and right shift. Defined on integral types.
11626 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
11629 Addition and subtraction. Defined on integral types, floating-point types and
11632 @item *@r{, }/@r{, }%
11633 Multiplication, division, and modulus. Multiplication and division are
11634 defined on integral and floating-point types. Modulus is defined on
11638 Increment and decrement. When appearing before a variable, the
11639 operation is performed before the variable is used in an expression;
11640 when appearing after it, the variable's value is used before the
11641 operation takes place.
11644 Pointer dereferencing. Defined on pointer types. Same precedence as
11648 Address operator. Defined on variables. Same precedence as @code{++}.
11650 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
11651 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
11652 to examine the address
11653 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
11657 Negative. Defined on integral and floating-point types. Same
11658 precedence as @code{++}.
11661 Logical negation. Defined on integral types. Same precedence as
11665 Bitwise complement operator. Defined on integral types. Same precedence as
11670 Structure member, and pointer-to-structure member. For convenience,
11671 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
11672 pointer based on the stored type information.
11673 Defined on @code{struct} and @code{union} data.
11676 Dereferences of pointers to members.
11679 Array indexing. @code{@var{a}[@var{i}]} is defined as
11680 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
11683 Function parameter list. Same precedence as @code{->}.
11686 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
11687 and @code{class} types.
11690 Doubled colons also represent the @value{GDBN} scope operator
11691 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
11695 If an operator is redefined in the user code, @value{GDBN} usually
11696 attempts to invoke the redefined version instead of using the operator's
11697 predefined meaning.
11700 @subsubsection C and C@t{++} Constants
11702 @cindex C and C@t{++} constants
11704 @value{GDBN} allows you to express the constants of C and C@t{++} in the
11709 Integer constants are a sequence of digits. Octal constants are
11710 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
11711 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
11712 @samp{l}, specifying that the constant should be treated as a
11716 Floating point constants are a sequence of digits, followed by a decimal
11717 point, followed by a sequence of digits, and optionally followed by an
11718 exponent. An exponent is of the form:
11719 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
11720 sequence of digits. The @samp{+} is optional for positive exponents.
11721 A floating-point constant may also end with a letter @samp{f} or
11722 @samp{F}, specifying that the constant should be treated as being of
11723 the @code{float} (as opposed to the default @code{double}) type; or with
11724 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
11728 Enumerated constants consist of enumerated identifiers, or their
11729 integral equivalents.
11732 Character constants are a single character surrounded by single quotes
11733 (@code{'}), or a number---the ordinal value of the corresponding character
11734 (usually its @sc{ascii} value). Within quotes, the single character may
11735 be represented by a letter or by @dfn{escape sequences}, which are of
11736 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
11737 of the character's ordinal value; or of the form @samp{\@var{x}}, where
11738 @samp{@var{x}} is a predefined special character---for example,
11739 @samp{\n} for newline.
11742 String constants are a sequence of character constants surrounded by
11743 double quotes (@code{"}). Any valid character constant (as described
11744 above) may appear. Double quotes within the string must be preceded by
11745 a backslash, so for instance @samp{"a\"b'c"} is a string of five
11749 Pointer constants are an integral value. You can also write pointers
11750 to constants using the C operator @samp{&}.
11753 Array constants are comma-separated lists surrounded by braces @samp{@{}
11754 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
11755 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
11756 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
11759 @node C Plus Plus Expressions
11760 @subsubsection C@t{++} Expressions
11762 @cindex expressions in C@t{++}
11763 @value{GDBN} expression handling can interpret most C@t{++} expressions.
11765 @cindex debugging C@t{++} programs
11766 @cindex C@t{++} compilers
11767 @cindex debug formats and C@t{++}
11768 @cindex @value{NGCC} and C@t{++}
11770 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use the
11771 proper compiler and the proper debug format. Currently, @value{GDBN}
11772 works best when debugging C@t{++} code that is compiled with
11773 @value{NGCC} 2.95.3 or with @value{NGCC} 3.1 or newer, using the options
11774 @option{-gdwarf-2} or @option{-gstabs+}. DWARF 2 is preferred over
11775 stabs+. Most configurations of @value{NGCC} emit either DWARF 2 or
11776 stabs+ as their default debug format, so you usually don't need to
11777 specify a debug format explicitly. Other compilers and/or debug formats
11778 are likely to work badly or not at all when using @value{GDBN} to debug
11784 @cindex member functions
11786 Member function calls are allowed; you can use expressions like
11789 count = aml->GetOriginal(x, y)
11792 @vindex this@r{, inside C@t{++} member functions}
11793 @cindex namespace in C@t{++}
11795 While a member function is active (in the selected stack frame), your
11796 expressions have the same namespace available as the member function;
11797 that is, @value{GDBN} allows implicit references to the class instance
11798 pointer @code{this} following the same rules as C@t{++}.
11800 @cindex call overloaded functions
11801 @cindex overloaded functions, calling
11802 @cindex type conversions in C@t{++}
11804 You can call overloaded functions; @value{GDBN} resolves the function
11805 call to the right definition, with some restrictions. @value{GDBN} does not
11806 perform overload resolution involving user-defined type conversions,
11807 calls to constructors, or instantiations of templates that do not exist
11808 in the program. It also cannot handle ellipsis argument lists or
11811 It does perform integral conversions and promotions, floating-point
11812 promotions, arithmetic conversions, pointer conversions, conversions of
11813 class objects to base classes, and standard conversions such as those of
11814 functions or arrays to pointers; it requires an exact match on the
11815 number of function arguments.
11817 Overload resolution is always performed, unless you have specified
11818 @code{set overload-resolution off}. @xref{Debugging C Plus Plus,
11819 ,@value{GDBN} Features for C@t{++}}.
11821 You must specify @code{set overload-resolution off} in order to use an
11822 explicit function signature to call an overloaded function, as in
11824 p 'foo(char,int)'('x', 13)
11827 The @value{GDBN} command-completion facility can simplify this;
11828 see @ref{Completion, ,Command Completion}.
11830 @cindex reference declarations
11832 @value{GDBN} understands variables declared as C@t{++} references; you can use
11833 them in expressions just as you do in C@t{++} source---they are automatically
11836 In the parameter list shown when @value{GDBN} displays a frame, the values of
11837 reference variables are not displayed (unlike other variables); this
11838 avoids clutter, since references are often used for large structures.
11839 The @emph{address} of a reference variable is always shown, unless
11840 you have specified @samp{set print address off}.
11843 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
11844 expressions can use it just as expressions in your program do. Since
11845 one scope may be defined in another, you can use @code{::} repeatedly if
11846 necessary, for example in an expression like
11847 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
11848 resolving name scope by reference to source files, in both C and C@t{++}
11849 debugging (@pxref{Variables, ,Program Variables}).
11852 In addition, when used with HP's C@t{++} compiler, @value{GDBN} supports
11853 calling virtual functions correctly, printing out virtual bases of
11854 objects, calling functions in a base subobject, casting objects, and
11855 invoking user-defined operators.
11858 @subsubsection C and C@t{++} Defaults
11860 @cindex C and C@t{++} defaults
11862 If you allow @value{GDBN} to set type and range checking automatically, they
11863 both default to @code{off} whenever the working language changes to
11864 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
11865 selects the working language.
11867 If you allow @value{GDBN} to set the language automatically, it
11868 recognizes source files whose names end with @file{.c}, @file{.C}, or
11869 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
11870 these files, it sets the working language to C or C@t{++}.
11871 @xref{Automatically, ,Having @value{GDBN} Infer the Source Language},
11872 for further details.
11874 @c Type checking is (a) primarily motivated by Modula-2, and (b)
11875 @c unimplemented. If (b) changes, it might make sense to let this node
11876 @c appear even if Mod-2 does not, but meanwhile ignore it. roland 16jul93.
11879 @subsubsection C and C@t{++} Type and Range Checks
11881 @cindex C and C@t{++} checks
11883 By default, when @value{GDBN} parses C or C@t{++} expressions, type checking
11884 is not used. However, if you turn type checking on, @value{GDBN}
11885 considers two variables type equivalent if:
11889 The two variables are structured and have the same structure, union, or
11893 The two variables have the same type name, or types that have been
11894 declared equivalent through @code{typedef}.
11897 @c leaving this out because neither J Gilmore nor R Pesch understand it.
11900 The two @code{struct}, @code{union}, or @code{enum} variables are
11901 declared in the same declaration. (Note: this may not be true for all C
11906 Range checking, if turned on, is done on mathematical operations. Array
11907 indices are not checked, since they are often used to index a pointer
11908 that is not itself an array.
11911 @subsubsection @value{GDBN} and C
11913 The @code{set print union} and @code{show print union} commands apply to
11914 the @code{union} type. When set to @samp{on}, any @code{union} that is
11915 inside a @code{struct} or @code{class} is also printed. Otherwise, it
11916 appears as @samp{@{...@}}.
11918 The @code{@@} operator aids in the debugging of dynamic arrays, formed
11919 with pointers and a memory allocation function. @xref{Expressions,
11922 @node Debugging C Plus Plus
11923 @subsubsection @value{GDBN} Features for C@t{++}
11925 @cindex commands for C@t{++}
11927 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
11928 designed specifically for use with C@t{++}. Here is a summary:
11931 @cindex break in overloaded functions
11932 @item @r{breakpoint menus}
11933 When you want a breakpoint in a function whose name is overloaded,
11934 @value{GDBN} has the capability to display a menu of possible breakpoint
11935 locations to help you specify which function definition you want.
11936 @xref{Ambiguous Expressions,,Ambiguous Expressions}.
11938 @cindex overloading in C@t{++}
11939 @item rbreak @var{regex}
11940 Setting breakpoints using regular expressions is helpful for setting
11941 breakpoints on overloaded functions that are not members of any special
11943 @xref{Set Breaks, ,Setting Breakpoints}.
11945 @cindex C@t{++} exception handling
11948 Debug C@t{++} exception handling using these commands. @xref{Set
11949 Catchpoints, , Setting Catchpoints}.
11951 @cindex inheritance
11952 @item ptype @var{typename}
11953 Print inheritance relationships as well as other information for type
11955 @xref{Symbols, ,Examining the Symbol Table}.
11957 @cindex C@t{++} symbol display
11958 @item set print demangle
11959 @itemx show print demangle
11960 @itemx set print asm-demangle
11961 @itemx show print asm-demangle
11962 Control whether C@t{++} symbols display in their source form, both when
11963 displaying code as C@t{++} source and when displaying disassemblies.
11964 @xref{Print Settings, ,Print Settings}.
11966 @item set print object
11967 @itemx show print object
11968 Choose whether to print derived (actual) or declared types of objects.
11969 @xref{Print Settings, ,Print Settings}.
11971 @item set print vtbl
11972 @itemx show print vtbl
11973 Control the format for printing virtual function tables.
11974 @xref{Print Settings, ,Print Settings}.
11975 (The @code{vtbl} commands do not work on programs compiled with the HP
11976 ANSI C@t{++} compiler (@code{aCC}).)
11978 @kindex set overload-resolution
11979 @cindex overloaded functions, overload resolution
11980 @item set overload-resolution on
11981 Enable overload resolution for C@t{++} expression evaluation. The default
11982 is on. For overloaded functions, @value{GDBN} evaluates the arguments
11983 and searches for a function whose signature matches the argument types,
11984 using the standard C@t{++} conversion rules (see @ref{C Plus Plus
11985 Expressions, ,C@t{++} Expressions}, for details).
11986 If it cannot find a match, it emits a message.
11988 @item set overload-resolution off
11989 Disable overload resolution for C@t{++} expression evaluation. For
11990 overloaded functions that are not class member functions, @value{GDBN}
11991 chooses the first function of the specified name that it finds in the
11992 symbol table, whether or not its arguments are of the correct type. For
11993 overloaded functions that are class member functions, @value{GDBN}
11994 searches for a function whose signature @emph{exactly} matches the
11997 @kindex show overload-resolution
11998 @item show overload-resolution
11999 Show the current setting of overload resolution.
12001 @item @r{Overloaded symbol names}
12002 You can specify a particular definition of an overloaded symbol, using
12003 the same notation that is used to declare such symbols in C@t{++}: type
12004 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
12005 also use the @value{GDBN} command-line word completion facilities to list the
12006 available choices, or to finish the type list for you.
12007 @xref{Completion,, Command Completion}, for details on how to do this.
12010 @node Decimal Floating Point
12011 @subsubsection Decimal Floating Point format
12012 @cindex decimal floating point format
12014 @value{GDBN} can examine, set and perform computations with numbers in
12015 decimal floating point format, which in the C language correspond to the
12016 @code{_Decimal32}, @code{_Decimal64} and @code{_Decimal128} types as
12017 specified by the extension to support decimal floating-point arithmetic.
12019 There are two encodings in use, depending on the architecture: BID (Binary
12020 Integer Decimal) for x86 and x86-64, and DPD (Densely Packed Decimal) for
12021 PowerPC. @value{GDBN} will use the appropriate encoding for the configured
12024 Because of a limitation in @file{libdecnumber}, the library used by @value{GDBN}
12025 to manipulate decimal floating point numbers, it is not possible to convert
12026 (using a cast, for example) integers wider than 32-bit to decimal float.
12028 In addition, in order to imitate @value{GDBN}'s behaviour with binary floating
12029 point computations, error checking in decimal float operations ignores
12030 underflow, overflow and divide by zero exceptions.
12032 In the PowerPC architecture, @value{GDBN} provides a set of pseudo-registers
12033 to inspect @code{_Decimal128} values stored in floating point registers.
12034 See @ref{PowerPC,,PowerPC} for more details.
12040 @value{GDBN} can be used to debug programs written in D and compiled with
12041 GDC, LDC or DMD compilers. Currently @value{GDBN} supports only one D
12042 specific feature --- dynamic arrays.
12045 @subsection Objective-C
12047 @cindex Objective-C
12048 This section provides information about some commands and command
12049 options that are useful for debugging Objective-C code. See also
12050 @ref{Symbols, info classes}, and @ref{Symbols, info selectors}, for a
12051 few more commands specific to Objective-C support.
12054 * Method Names in Commands::
12055 * The Print Command with Objective-C::
12058 @node Method Names in Commands
12059 @subsubsection Method Names in Commands
12061 The following commands have been extended to accept Objective-C method
12062 names as line specifications:
12064 @kindex clear@r{, and Objective-C}
12065 @kindex break@r{, and Objective-C}
12066 @kindex info line@r{, and Objective-C}
12067 @kindex jump@r{, and Objective-C}
12068 @kindex list@r{, and Objective-C}
12072 @item @code{info line}
12077 A fully qualified Objective-C method name is specified as
12080 -[@var{Class} @var{methodName}]
12083 where the minus sign is used to indicate an instance method and a
12084 plus sign (not shown) is used to indicate a class method. The class
12085 name @var{Class} and method name @var{methodName} are enclosed in
12086 brackets, similar to the way messages are specified in Objective-C
12087 source code. For example, to set a breakpoint at the @code{create}
12088 instance method of class @code{Fruit} in the program currently being
12092 break -[Fruit create]
12095 To list ten program lines around the @code{initialize} class method,
12099 list +[NSText initialize]
12102 In the current version of @value{GDBN}, the plus or minus sign is
12103 required. In future versions of @value{GDBN}, the plus or minus
12104 sign will be optional, but you can use it to narrow the search. It
12105 is also possible to specify just a method name:
12111 You must specify the complete method name, including any colons. If
12112 your program's source files contain more than one @code{create} method,
12113 you'll be presented with a numbered list of classes that implement that
12114 method. Indicate your choice by number, or type @samp{0} to exit if
12117 As another example, to clear a breakpoint established at the
12118 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
12121 clear -[NSWindow makeKeyAndOrderFront:]
12124 @node The Print Command with Objective-C
12125 @subsubsection The Print Command With Objective-C
12126 @cindex Objective-C, print objects
12127 @kindex print-object
12128 @kindex po @r{(@code{print-object})}
12130 The print command has also been extended to accept methods. For example:
12133 print -[@var{object} hash]
12136 @cindex print an Objective-C object description
12137 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
12139 will tell @value{GDBN} to send the @code{hash} message to @var{object}
12140 and print the result. Also, an additional command has been added,
12141 @code{print-object} or @code{po} for short, which is meant to print
12142 the description of an object. However, this command may only work
12143 with certain Objective-C libraries that have a particular hook
12144 function, @code{_NSPrintForDebugger}, defined.
12147 @subsection Fortran
12148 @cindex Fortran-specific support in @value{GDBN}
12150 @value{GDBN} can be used to debug programs written in Fortran, but it
12151 currently supports only the features of Fortran 77 language.
12153 @cindex trailing underscore, in Fortran symbols
12154 Some Fortran compilers (@sc{gnu} Fortran 77 and Fortran 95 compilers
12155 among them) append an underscore to the names of variables and
12156 functions. When you debug programs compiled by those compilers, you
12157 will need to refer to variables and functions with a trailing
12161 * Fortran Operators:: Fortran operators and expressions
12162 * Fortran Defaults:: Default settings for Fortran
12163 * Special Fortran Commands:: Special @value{GDBN} commands for Fortran
12166 @node Fortran Operators
12167 @subsubsection Fortran Operators and Expressions
12169 @cindex Fortran operators and expressions
12171 Operators must be defined on values of specific types. For instance,
12172 @code{+} is defined on numbers, but not on characters or other non-
12173 arithmetic types. Operators are often defined on groups of types.
12177 The exponentiation operator. It raises the first operand to the power
12181 The range operator. Normally used in the form of array(low:high) to
12182 represent a section of array.
12185 The access component operator. Normally used to access elements in derived
12186 types. Also suitable for unions. As unions aren't part of regular Fortran,
12187 this can only happen when accessing a register that uses a gdbarch-defined
12191 @node Fortran Defaults
12192 @subsubsection Fortran Defaults
12194 @cindex Fortran Defaults
12196 Fortran symbols are usually case-insensitive, so @value{GDBN} by
12197 default uses case-insensitive matches for Fortran symbols. You can
12198 change that with the @samp{set case-insensitive} command, see
12199 @ref{Symbols}, for the details.
12201 @node Special Fortran Commands
12202 @subsubsection Special Fortran Commands
12204 @cindex Special Fortran commands
12206 @value{GDBN} has some commands to support Fortran-specific features,
12207 such as displaying common blocks.
12210 @cindex @code{COMMON} blocks, Fortran
12211 @kindex info common
12212 @item info common @r{[}@var{common-name}@r{]}
12213 This command prints the values contained in the Fortran @code{COMMON}
12214 block whose name is @var{common-name}. With no argument, the names of
12215 all @code{COMMON} blocks visible at the current program location are
12222 @cindex Pascal support in @value{GDBN}, limitations
12223 Debugging Pascal programs which use sets, subranges, file variables, or
12224 nested functions does not currently work. @value{GDBN} does not support
12225 entering expressions, printing values, or similar features using Pascal
12228 The Pascal-specific command @code{set print pascal_static-members}
12229 controls whether static members of Pascal objects are displayed.
12230 @xref{Print Settings, pascal_static-members}.
12233 @subsection Modula-2
12235 @cindex Modula-2, @value{GDBN} support
12237 The extensions made to @value{GDBN} to support Modula-2 only support
12238 output from the @sc{gnu} Modula-2 compiler (which is currently being
12239 developed). Other Modula-2 compilers are not currently supported, and
12240 attempting to debug executables produced by them is most likely
12241 to give an error as @value{GDBN} reads in the executable's symbol
12244 @cindex expressions in Modula-2
12246 * M2 Operators:: Built-in operators
12247 * Built-In Func/Proc:: Built-in functions and procedures
12248 * M2 Constants:: Modula-2 constants
12249 * M2 Types:: Modula-2 types
12250 * M2 Defaults:: Default settings for Modula-2
12251 * Deviations:: Deviations from standard Modula-2
12252 * M2 Checks:: Modula-2 type and range checks
12253 * M2 Scope:: The scope operators @code{::} and @code{.}
12254 * GDB/M2:: @value{GDBN} and Modula-2
12258 @subsubsection Operators
12259 @cindex Modula-2 operators
12261 Operators must be defined on values of specific types. For instance,
12262 @code{+} is defined on numbers, but not on structures. Operators are
12263 often defined on groups of types. For the purposes of Modula-2, the
12264 following definitions hold:
12269 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
12273 @emph{Character types} consist of @code{CHAR} and its subranges.
12276 @emph{Floating-point types} consist of @code{REAL}.
12279 @emph{Pointer types} consist of anything declared as @code{POINTER TO
12283 @emph{Scalar types} consist of all of the above.
12286 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
12289 @emph{Boolean types} consist of @code{BOOLEAN}.
12293 The following operators are supported, and appear in order of
12294 increasing precedence:
12298 Function argument or array index separator.
12301 Assignment. The value of @var{var} @code{:=} @var{value} is
12305 Less than, greater than on integral, floating-point, or enumerated
12309 Less than or equal to, greater than or equal to
12310 on integral, floating-point and enumerated types, or set inclusion on
12311 set types. Same precedence as @code{<}.
12313 @item =@r{, }<>@r{, }#
12314 Equality and two ways of expressing inequality, valid on scalar types.
12315 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
12316 available for inequality, since @code{#} conflicts with the script
12320 Set membership. Defined on set types and the types of their members.
12321 Same precedence as @code{<}.
12324 Boolean disjunction. Defined on boolean types.
12327 Boolean conjunction. Defined on boolean types.
12330 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
12333 Addition and subtraction on integral and floating-point types, or union
12334 and difference on set types.
12337 Multiplication on integral and floating-point types, or set intersection
12341 Division on floating-point types, or symmetric set difference on set
12342 types. Same precedence as @code{*}.
12345 Integer division and remainder. Defined on integral types. Same
12346 precedence as @code{*}.
12349 Negative. Defined on @code{INTEGER} and @code{REAL} data.
12352 Pointer dereferencing. Defined on pointer types.
12355 Boolean negation. Defined on boolean types. Same precedence as
12359 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
12360 precedence as @code{^}.
12363 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
12366 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
12370 @value{GDBN} and Modula-2 scope operators.
12374 @emph{Warning:} Set expressions and their operations are not yet supported, so @value{GDBN}
12375 treats the use of the operator @code{IN}, or the use of operators
12376 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
12377 @code{<=}, and @code{>=} on sets as an error.
12381 @node Built-In Func/Proc
12382 @subsubsection Built-in Functions and Procedures
12383 @cindex Modula-2 built-ins
12385 Modula-2 also makes available several built-in procedures and functions.
12386 In describing these, the following metavariables are used:
12391 represents an @code{ARRAY} variable.
12394 represents a @code{CHAR} constant or variable.
12397 represents a variable or constant of integral type.
12400 represents an identifier that belongs to a set. Generally used in the
12401 same function with the metavariable @var{s}. The type of @var{s} should
12402 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
12405 represents a variable or constant of integral or floating-point type.
12408 represents a variable or constant of floating-point type.
12414 represents a variable.
12417 represents a variable or constant of one of many types. See the
12418 explanation of the function for details.
12421 All Modula-2 built-in procedures also return a result, described below.
12425 Returns the absolute value of @var{n}.
12428 If @var{c} is a lower case letter, it returns its upper case
12429 equivalent, otherwise it returns its argument.
12432 Returns the character whose ordinal value is @var{i}.
12435 Decrements the value in the variable @var{v} by one. Returns the new value.
12437 @item DEC(@var{v},@var{i})
12438 Decrements the value in the variable @var{v} by @var{i}. Returns the
12441 @item EXCL(@var{m},@var{s})
12442 Removes the element @var{m} from the set @var{s}. Returns the new
12445 @item FLOAT(@var{i})
12446 Returns the floating point equivalent of the integer @var{i}.
12448 @item HIGH(@var{a})
12449 Returns the index of the last member of @var{a}.
12452 Increments the value in the variable @var{v} by one. Returns the new value.
12454 @item INC(@var{v},@var{i})
12455 Increments the value in the variable @var{v} by @var{i}. Returns the
12458 @item INCL(@var{m},@var{s})
12459 Adds the element @var{m} to the set @var{s} if it is not already
12460 there. Returns the new set.
12463 Returns the maximum value of the type @var{t}.
12466 Returns the minimum value of the type @var{t}.
12469 Returns boolean TRUE if @var{i} is an odd number.
12472 Returns the ordinal value of its argument. For example, the ordinal
12473 value of a character is its @sc{ascii} value (on machines supporting the
12474 @sc{ascii} character set). @var{x} must be of an ordered type, which include
12475 integral, character and enumerated types.
12477 @item SIZE(@var{x})
12478 Returns the size of its argument. @var{x} can be a variable or a type.
12480 @item TRUNC(@var{r})
12481 Returns the integral part of @var{r}.
12483 @item TSIZE(@var{x})
12484 Returns the size of its argument. @var{x} can be a variable or a type.
12486 @item VAL(@var{t},@var{i})
12487 Returns the member of the type @var{t} whose ordinal value is @var{i}.
12491 @emph{Warning:} Sets and their operations are not yet supported, so
12492 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
12496 @cindex Modula-2 constants
12498 @subsubsection Constants
12500 @value{GDBN} allows you to express the constants of Modula-2 in the following
12506 Integer constants are simply a sequence of digits. When used in an
12507 expression, a constant is interpreted to be type-compatible with the
12508 rest of the expression. Hexadecimal integers are specified by a
12509 trailing @samp{H}, and octal integers by a trailing @samp{B}.
12512 Floating point constants appear as a sequence of digits, followed by a
12513 decimal point and another sequence of digits. An optional exponent can
12514 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
12515 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
12516 digits of the floating point constant must be valid decimal (base 10)
12520 Character constants consist of a single character enclosed by a pair of
12521 like quotes, either single (@code{'}) or double (@code{"}). They may
12522 also be expressed by their ordinal value (their @sc{ascii} value, usually)
12523 followed by a @samp{C}.
12526 String constants consist of a sequence of characters enclosed by a
12527 pair of like quotes, either single (@code{'}) or double (@code{"}).
12528 Escape sequences in the style of C are also allowed. @xref{C
12529 Constants, ,C and C@t{++} Constants}, for a brief explanation of escape
12533 Enumerated constants consist of an enumerated identifier.
12536 Boolean constants consist of the identifiers @code{TRUE} and
12540 Pointer constants consist of integral values only.
12543 Set constants are not yet supported.
12547 @subsubsection Modula-2 Types
12548 @cindex Modula-2 types
12550 Currently @value{GDBN} can print the following data types in Modula-2
12551 syntax: array types, record types, set types, pointer types, procedure
12552 types, enumerated types, subrange types and base types. You can also
12553 print the contents of variables declared using these type.
12554 This section gives a number of simple source code examples together with
12555 sample @value{GDBN} sessions.
12557 The first example contains the following section of code:
12566 and you can request @value{GDBN} to interrogate the type and value of
12567 @code{r} and @code{s}.
12570 (@value{GDBP}) print s
12572 (@value{GDBP}) ptype s
12574 (@value{GDBP}) print r
12576 (@value{GDBP}) ptype r
12581 Likewise if your source code declares @code{s} as:
12585 s: SET ['A'..'Z'] ;
12589 then you may query the type of @code{s} by:
12592 (@value{GDBP}) ptype s
12593 type = SET ['A'..'Z']
12597 Note that at present you cannot interactively manipulate set
12598 expressions using the debugger.
12600 The following example shows how you might declare an array in Modula-2
12601 and how you can interact with @value{GDBN} to print its type and contents:
12605 s: ARRAY [-10..10] OF CHAR ;
12609 (@value{GDBP}) ptype s
12610 ARRAY [-10..10] OF CHAR
12613 Note that the array handling is not yet complete and although the type
12614 is printed correctly, expression handling still assumes that all
12615 arrays have a lower bound of zero and not @code{-10} as in the example
12618 Here are some more type related Modula-2 examples:
12622 colour = (blue, red, yellow, green) ;
12623 t = [blue..yellow] ;
12631 The @value{GDBN} interaction shows how you can query the data type
12632 and value of a variable.
12635 (@value{GDBP}) print s
12637 (@value{GDBP}) ptype t
12638 type = [blue..yellow]
12642 In this example a Modula-2 array is declared and its contents
12643 displayed. Observe that the contents are written in the same way as
12644 their @code{C} counterparts.
12648 s: ARRAY [1..5] OF CARDINAL ;
12654 (@value{GDBP}) print s
12655 $1 = @{1, 0, 0, 0, 0@}
12656 (@value{GDBP}) ptype s
12657 type = ARRAY [1..5] OF CARDINAL
12660 The Modula-2 language interface to @value{GDBN} also understands
12661 pointer types as shown in this example:
12665 s: POINTER TO ARRAY [1..5] OF CARDINAL ;
12672 and you can request that @value{GDBN} describes the type of @code{s}.
12675 (@value{GDBP}) ptype s
12676 type = POINTER TO ARRAY [1..5] OF CARDINAL
12679 @value{GDBN} handles compound types as we can see in this example.
12680 Here we combine array types, record types, pointer types and subrange
12691 myarray = ARRAY myrange OF CARDINAL ;
12692 myrange = [-2..2] ;
12694 s: POINTER TO ARRAY myrange OF foo ;
12698 and you can ask @value{GDBN} to describe the type of @code{s} as shown
12702 (@value{GDBP}) ptype s
12703 type = POINTER TO ARRAY [-2..2] OF foo = RECORD
12706 f3 : ARRAY [-2..2] OF CARDINAL;
12711 @subsubsection Modula-2 Defaults
12712 @cindex Modula-2 defaults
12714 If type and range checking are set automatically by @value{GDBN}, they
12715 both default to @code{on} whenever the working language changes to
12716 Modula-2. This happens regardless of whether you or @value{GDBN}
12717 selected the working language.
12719 If you allow @value{GDBN} to set the language automatically, then entering
12720 code compiled from a file whose name ends with @file{.mod} sets the
12721 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN}
12722 Infer the Source Language}, for further details.
12725 @subsubsection Deviations from Standard Modula-2
12726 @cindex Modula-2, deviations from
12728 A few changes have been made to make Modula-2 programs easier to debug.
12729 This is done primarily via loosening its type strictness:
12733 Unlike in standard Modula-2, pointer constants can be formed by
12734 integers. This allows you to modify pointer variables during
12735 debugging. (In standard Modula-2, the actual address contained in a
12736 pointer variable is hidden from you; it can only be modified
12737 through direct assignment to another pointer variable or expression that
12738 returned a pointer.)
12741 C escape sequences can be used in strings and characters to represent
12742 non-printable characters. @value{GDBN} prints out strings with these
12743 escape sequences embedded. Single non-printable characters are
12744 printed using the @samp{CHR(@var{nnn})} format.
12747 The assignment operator (@code{:=}) returns the value of its right-hand
12751 All built-in procedures both modify @emph{and} return their argument.
12755 @subsubsection Modula-2 Type and Range Checks
12756 @cindex Modula-2 checks
12759 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
12762 @c FIXME remove warning when type/range checks added
12764 @value{GDBN} considers two Modula-2 variables type equivalent if:
12768 They are of types that have been declared equivalent via a @code{TYPE
12769 @var{t1} = @var{t2}} statement
12772 They have been declared on the same line. (Note: This is true of the
12773 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
12776 As long as type checking is enabled, any attempt to combine variables
12777 whose types are not equivalent is an error.
12779 Range checking is done on all mathematical operations, assignment, array
12780 index bounds, and all built-in functions and procedures.
12783 @subsubsection The Scope Operators @code{::} and @code{.}
12785 @cindex @code{.}, Modula-2 scope operator
12786 @cindex colon, doubled as scope operator
12788 @vindex colon-colon@r{, in Modula-2}
12789 @c Info cannot handle :: but TeX can.
12792 @vindex ::@r{, in Modula-2}
12795 There are a few subtle differences between the Modula-2 scope operator
12796 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
12801 @var{module} . @var{id}
12802 @var{scope} :: @var{id}
12806 where @var{scope} is the name of a module or a procedure,
12807 @var{module} the name of a module, and @var{id} is any declared
12808 identifier within your program, except another module.
12810 Using the @code{::} operator makes @value{GDBN} search the scope
12811 specified by @var{scope} for the identifier @var{id}. If it is not
12812 found in the specified scope, then @value{GDBN} searches all scopes
12813 enclosing the one specified by @var{scope}.
12815 Using the @code{.} operator makes @value{GDBN} search the current scope for
12816 the identifier specified by @var{id} that was imported from the
12817 definition module specified by @var{module}. With this operator, it is
12818 an error if the identifier @var{id} was not imported from definition
12819 module @var{module}, or if @var{id} is not an identifier in
12823 @subsubsection @value{GDBN} and Modula-2
12825 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
12826 Five subcommands of @code{set print} and @code{show print} apply
12827 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
12828 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
12829 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
12830 analogue in Modula-2.
12832 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
12833 with any language, is not useful with Modula-2. Its
12834 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
12835 created in Modula-2 as they can in C or C@t{++}. However, because an
12836 address can be specified by an integral constant, the construct
12837 @samp{@{@var{type}@}@var{adrexp}} is still useful.
12839 @cindex @code{#} in Modula-2
12840 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
12841 interpreted as the beginning of a comment. Use @code{<>} instead.
12847 The extensions made to @value{GDBN} for Ada only support
12848 output from the @sc{gnu} Ada (GNAT) compiler.
12849 Other Ada compilers are not currently supported, and
12850 attempting to debug executables produced by them is most likely
12854 @cindex expressions in Ada
12856 * Ada Mode Intro:: General remarks on the Ada syntax
12857 and semantics supported by Ada mode
12859 * Omissions from Ada:: Restrictions on the Ada expression syntax.
12860 * Additions to Ada:: Extensions of the Ada expression syntax.
12861 * Stopping Before Main Program:: Debugging the program during elaboration.
12862 * Ada Tasks:: Listing and setting breakpoints in tasks.
12863 * Ada Tasks and Core Files:: Tasking Support when Debugging Core Files
12864 * Ada Glitches:: Known peculiarities of Ada mode.
12867 @node Ada Mode Intro
12868 @subsubsection Introduction
12869 @cindex Ada mode, general
12871 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
12872 syntax, with some extensions.
12873 The philosophy behind the design of this subset is
12877 That @value{GDBN} should provide basic literals and access to operations for
12878 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
12879 leaving more sophisticated computations to subprograms written into the
12880 program (which therefore may be called from @value{GDBN}).
12883 That type safety and strict adherence to Ada language restrictions
12884 are not particularly important to the @value{GDBN} user.
12887 That brevity is important to the @value{GDBN} user.
12890 Thus, for brevity, the debugger acts as if all names declared in
12891 user-written packages are directly visible, even if they are not visible
12892 according to Ada rules, thus making it unnecessary to fully qualify most
12893 names with their packages, regardless of context. Where this causes
12894 ambiguity, @value{GDBN} asks the user's intent.
12896 The debugger will start in Ada mode if it detects an Ada main program.
12897 As for other languages, it will enter Ada mode when stopped in a program that
12898 was translated from an Ada source file.
12900 While in Ada mode, you may use `@t{--}' for comments. This is useful
12901 mostly for documenting command files. The standard @value{GDBN} comment
12902 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
12903 middle (to allow based literals).
12905 The debugger supports limited overloading. Given a subprogram call in which
12906 the function symbol has multiple definitions, it will use the number of
12907 actual parameters and some information about their types to attempt to narrow
12908 the set of definitions. It also makes very limited use of context, preferring
12909 procedures to functions in the context of the @code{call} command, and
12910 functions to procedures elsewhere.
12912 @node Omissions from Ada
12913 @subsubsection Omissions from Ada
12914 @cindex Ada, omissions from
12916 Here are the notable omissions from the subset:
12920 Only a subset of the attributes are supported:
12924 @t{'First}, @t{'Last}, and @t{'Length}
12925 on array objects (not on types and subtypes).
12928 @t{'Min} and @t{'Max}.
12931 @t{'Pos} and @t{'Val}.
12937 @t{'Range} on array objects (not subtypes), but only as the right
12938 operand of the membership (@code{in}) operator.
12941 @t{'Access}, @t{'Unchecked_Access}, and
12942 @t{'Unrestricted_Access} (a GNAT extension).
12950 @code{Characters.Latin_1} are not available and
12951 concatenation is not implemented. Thus, escape characters in strings are
12952 not currently available.
12955 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
12956 equality of representations. They will generally work correctly
12957 for strings and arrays whose elements have integer or enumeration types.
12958 They may not work correctly for arrays whose element
12959 types have user-defined equality, for arrays of real values
12960 (in particular, IEEE-conformant floating point, because of negative
12961 zeroes and NaNs), and for arrays whose elements contain unused bits with
12962 indeterminate values.
12965 The other component-by-component array operations (@code{and}, @code{or},
12966 @code{xor}, @code{not}, and relational tests other than equality)
12967 are not implemented.
12970 @cindex array aggregates (Ada)
12971 @cindex record aggregates (Ada)
12972 @cindex aggregates (Ada)
12973 There is limited support for array and record aggregates. They are
12974 permitted only on the right sides of assignments, as in these examples:
12977 (@value{GDBP}) set An_Array := (1, 2, 3, 4, 5, 6)
12978 (@value{GDBP}) set An_Array := (1, others => 0)
12979 (@value{GDBP}) set An_Array := (0|4 => 1, 1..3 => 2, 5 => 6)
12980 (@value{GDBP}) set A_2D_Array := ((1, 2, 3), (4, 5, 6), (7, 8, 9))
12981 (@value{GDBP}) set A_Record := (1, "Peter", True);
12982 (@value{GDBP}) set A_Record := (Name => "Peter", Id => 1, Alive => True)
12986 discriminant's value by assigning an aggregate has an
12987 undefined effect if that discriminant is used within the record.
12988 However, you can first modify discriminants by directly assigning to
12989 them (which normally would not be allowed in Ada), and then performing an
12990 aggregate assignment. For example, given a variable @code{A_Rec}
12991 declared to have a type such as:
12994 type Rec (Len : Small_Integer := 0) is record
12996 Vals : IntArray (1 .. Len);
13000 you can assign a value with a different size of @code{Vals} with two
13004 (@value{GDBP}) set A_Rec.Len := 4
13005 (@value{GDBP}) set A_Rec := (Id => 42, Vals => (1, 2, 3, 4))
13008 As this example also illustrates, @value{GDBN} is very loose about the usual
13009 rules concerning aggregates. You may leave out some of the
13010 components of an array or record aggregate (such as the @code{Len}
13011 component in the assignment to @code{A_Rec} above); they will retain their
13012 original values upon assignment. You may freely use dynamic values as
13013 indices in component associations. You may even use overlapping or
13014 redundant component associations, although which component values are
13015 assigned in such cases is not defined.
13018 Calls to dispatching subprograms are not implemented.
13021 The overloading algorithm is much more limited (i.e., less selective)
13022 than that of real Ada. It makes only limited use of the context in
13023 which a subexpression appears to resolve its meaning, and it is much
13024 looser in its rules for allowing type matches. As a result, some
13025 function calls will be ambiguous, and the user will be asked to choose
13026 the proper resolution.
13029 The @code{new} operator is not implemented.
13032 Entry calls are not implemented.
13035 Aside from printing, arithmetic operations on the native VAX floating-point
13036 formats are not supported.
13039 It is not possible to slice a packed array.
13042 The names @code{True} and @code{False}, when not part of a qualified name,
13043 are interpreted as if implicitly prefixed by @code{Standard}, regardless of
13045 Should your program
13046 redefine these names in a package or procedure (at best a dubious practice),
13047 you will have to use fully qualified names to access their new definitions.
13050 @node Additions to Ada
13051 @subsubsection Additions to Ada
13052 @cindex Ada, deviations from
13054 As it does for other languages, @value{GDBN} makes certain generic
13055 extensions to Ada (@pxref{Expressions}):
13059 If the expression @var{E} is a variable residing in memory (typically
13060 a local variable or array element) and @var{N} is a positive integer,
13061 then @code{@var{E}@@@var{N}} displays the values of @var{E} and the
13062 @var{N}-1 adjacent variables following it in memory as an array. In
13063 Ada, this operator is generally not necessary, since its prime use is
13064 in displaying parts of an array, and slicing will usually do this in
13065 Ada. However, there are occasional uses when debugging programs in
13066 which certain debugging information has been optimized away.
13069 @code{@var{B}::@var{var}} means ``the variable named @var{var} that
13070 appears in function or file @var{B}.'' When @var{B} is a file name,
13071 you must typically surround it in single quotes.
13074 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
13075 @var{type} that appears at address @var{addr}.''
13078 A name starting with @samp{$} is a convenience variable
13079 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
13082 In addition, @value{GDBN} provides a few other shortcuts and outright
13083 additions specific to Ada:
13087 The assignment statement is allowed as an expression, returning
13088 its right-hand operand as its value. Thus, you may enter
13091 (@value{GDBP}) set x := y + 3
13092 (@value{GDBP}) print A(tmp := y + 1)
13096 The semicolon is allowed as an ``operator,'' returning as its value
13097 the value of its right-hand operand.
13098 This allows, for example,
13099 complex conditional breaks:
13102 (@value{GDBP}) break f
13103 (@value{GDBP}) condition 1 (report(i); k += 1; A(k) > 100)
13107 Rather than use catenation and symbolic character names to introduce special
13108 characters into strings, one may instead use a special bracket notation,
13109 which is also used to print strings. A sequence of characters of the form
13110 @samp{["@var{XX}"]} within a string or character literal denotes the
13111 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
13112 sequence of characters @samp{["""]} also denotes a single quotation mark
13113 in strings. For example,
13115 "One line.["0a"]Next line.["0a"]"
13118 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF})
13122 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
13123 @t{'Max} is optional (and is ignored in any case). For example, it is valid
13127 (@value{GDBP}) print 'max(x, y)
13131 When printing arrays, @value{GDBN} uses positional notation when the
13132 array has a lower bound of 1, and uses a modified named notation otherwise.
13133 For example, a one-dimensional array of three integers with a lower bound
13134 of 3 might print as
13141 That is, in contrast to valid Ada, only the first component has a @code{=>}
13145 You may abbreviate attributes in expressions with any unique,
13146 multi-character subsequence of
13147 their names (an exact match gets preference).
13148 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
13149 in place of @t{a'length}.
13152 @cindex quoting Ada internal identifiers
13153 Since Ada is case-insensitive, the debugger normally maps identifiers you type
13154 to lower case. The GNAT compiler uses upper-case characters for
13155 some of its internal identifiers, which are normally of no interest to users.
13156 For the rare occasions when you actually have to look at them,
13157 enclose them in angle brackets to avoid the lower-case mapping.
13160 (@value{GDBP}) print <JMPBUF_SAVE>[0]
13164 Printing an object of class-wide type or dereferencing an
13165 access-to-class-wide value will display all the components of the object's
13166 specific type (as indicated by its run-time tag). Likewise, component
13167 selection on such a value will operate on the specific type of the
13172 @node Stopping Before Main Program
13173 @subsubsection Stopping at the Very Beginning
13175 @cindex breakpointing Ada elaboration code
13176 It is sometimes necessary to debug the program during elaboration, and
13177 before reaching the main procedure.
13178 As defined in the Ada Reference
13179 Manual, the elaboration code is invoked from a procedure called
13180 @code{adainit}. To run your program up to the beginning of
13181 elaboration, simply use the following two commands:
13182 @code{tbreak adainit} and @code{run}.
13185 @subsubsection Extensions for Ada Tasks
13186 @cindex Ada, tasking
13188 Support for Ada tasks is analogous to that for threads (@pxref{Threads}).
13189 @value{GDBN} provides the following task-related commands:
13194 This command shows a list of current Ada tasks, as in the following example:
13201 (@value{GDBP}) info tasks
13202 ID TID P-ID Pri State Name
13203 1 8088000 0 15 Child Activation Wait main_task
13204 2 80a4000 1 15 Accept Statement b
13205 3 809a800 1 15 Child Activation Wait a
13206 * 4 80ae800 3 15 Runnable c
13211 In this listing, the asterisk before the last task indicates it to be the
13212 task currently being inspected.
13216 Represents @value{GDBN}'s internal task number.
13222 The parent's task ID (@value{GDBN}'s internal task number).
13225 The base priority of the task.
13228 Current state of the task.
13232 The task has been created but has not been activated. It cannot be
13236 The task is not blocked for any reason known to Ada. (It may be waiting
13237 for a mutex, though.) It is conceptually "executing" in normal mode.
13240 The task is terminated, in the sense of ARM 9.3 (5). Any dependents
13241 that were waiting on terminate alternatives have been awakened and have
13242 terminated themselves.
13244 @item Child Activation Wait
13245 The task is waiting for created tasks to complete activation.
13247 @item Accept Statement
13248 The task is waiting on an accept or selective wait statement.
13250 @item Waiting on entry call
13251 The task is waiting on an entry call.
13253 @item Async Select Wait
13254 The task is waiting to start the abortable part of an asynchronous
13258 The task is waiting on a select statement with only a delay
13261 @item Child Termination Wait
13262 The task is sleeping having completed a master within itself, and is
13263 waiting for the tasks dependent on that master to become terminated or
13264 waiting on a terminate Phase.
13266 @item Wait Child in Term Alt
13267 The task is sleeping waiting for tasks on terminate alternatives to
13268 finish terminating.
13270 @item Accepting RV with @var{taskno}
13271 The task is accepting a rendez-vous with the task @var{taskno}.
13275 Name of the task in the program.
13279 @kindex info task @var{taskno}
13280 @item info task @var{taskno}
13281 This command shows detailled informations on the specified task, as in
13282 the following example:
13287 (@value{GDBP}) info tasks
13288 ID TID P-ID Pri State Name
13289 1 8077880 0 15 Child Activation Wait main_task
13290 * 2 807c468 1 15 Runnable task_1
13291 (@value{GDBP}) info task 2
13292 Ada Task: 0x807c468
13295 Parent: 1 (main_task)
13301 @kindex task@r{ (Ada)}
13302 @cindex current Ada task ID
13303 This command prints the ID of the current task.
13309 (@value{GDBP}) info tasks
13310 ID TID P-ID Pri State Name
13311 1 8077870 0 15 Child Activation Wait main_task
13312 * 2 807c458 1 15 Runnable t
13313 (@value{GDBP}) task
13314 [Current task is 2]
13317 @item task @var{taskno}
13318 @cindex Ada task switching
13319 This command is like the @code{thread @var{threadno}}
13320 command (@pxref{Threads}). It switches the context of debugging
13321 from the current task to the given task.
13327 (@value{GDBP}) info tasks
13328 ID TID P-ID Pri State Name
13329 1 8077870 0 15 Child Activation Wait main_task
13330 * 2 807c458 1 15 Runnable t
13331 (@value{GDBP}) task 1
13332 [Switching to task 1]
13333 #0 0x8067726 in pthread_cond_wait ()
13335 #0 0x8067726 in pthread_cond_wait ()
13336 #1 0x8056714 in system.os_interface.pthread_cond_wait ()
13337 #2 0x805cb63 in system.task_primitives.operations.sleep ()
13338 #3 0x806153e in system.tasking.stages.activate_tasks ()
13339 #4 0x804aacc in un () at un.adb:5
13342 @item break @var{linespec} task @var{taskno}
13343 @itemx break @var{linespec} task @var{taskno} if @dots{}
13344 @cindex breakpoints and tasks, in Ada
13345 @cindex task breakpoints, in Ada
13346 @kindex break @dots{} task @var{taskno}@r{ (Ada)}
13347 These commands are like the @code{break @dots{} thread @dots{}}
13348 command (@pxref{Thread Stops}).
13349 @var{linespec} specifies source lines, as described
13350 in @ref{Specify Location}.
13352 Use the qualifier @samp{task @var{taskno}} with a breakpoint command
13353 to specify that you only want @value{GDBN} to stop the program when a
13354 particular Ada task reaches this breakpoint. @var{taskno} is one of the
13355 numeric task identifiers assigned by @value{GDBN}, shown in the first
13356 column of the @samp{info tasks} display.
13358 If you do not specify @samp{task @var{taskno}} when you set a
13359 breakpoint, the breakpoint applies to @emph{all} tasks of your
13362 You can use the @code{task} qualifier on conditional breakpoints as
13363 well; in this case, place @samp{task @var{taskno}} before the
13364 breakpoint condition (before the @code{if}).
13372 (@value{GDBP}) info tasks
13373 ID TID P-ID Pri State Name
13374 1 140022020 0 15 Child Activation Wait main_task
13375 2 140045060 1 15 Accept/Select Wait t2
13376 3 140044840 1 15 Runnable t1
13377 * 4 140056040 1 15 Runnable t3
13378 (@value{GDBP}) b 15 task 2
13379 Breakpoint 5 at 0x120044cb0: file test_task_debug.adb, line 15.
13380 (@value{GDBP}) cont
13385 Breakpoint 5, test_task_debug () at test_task_debug.adb:15
13387 (@value{GDBP}) info tasks
13388 ID TID P-ID Pri State Name
13389 1 140022020 0 15 Child Activation Wait main_task
13390 * 2 140045060 1 15 Runnable t2
13391 3 140044840 1 15 Runnable t1
13392 4 140056040 1 15 Delay Sleep t3
13396 @node Ada Tasks and Core Files
13397 @subsubsection Tasking Support when Debugging Core Files
13398 @cindex Ada tasking and core file debugging
13400 When inspecting a core file, as opposed to debugging a live program,
13401 tasking support may be limited or even unavailable, depending on
13402 the platform being used.
13403 For instance, on x86-linux, the list of tasks is available, but task
13404 switching is not supported. On Tru64, however, task switching will work
13407 On certain platforms, including Tru64, the debugger needs to perform some
13408 memory writes in order to provide Ada tasking support. When inspecting
13409 a core file, this means that the core file must be opened with read-write
13410 privileges, using the command @samp{"set write on"} (@pxref{Patching}).
13411 Under these circumstances, you should make a backup copy of the core
13412 file before inspecting it with @value{GDBN}.
13415 @subsubsection Known Peculiarities of Ada Mode
13416 @cindex Ada, problems
13418 Besides the omissions listed previously (@pxref{Omissions from Ada}),
13419 we know of several problems with and limitations of Ada mode in
13421 some of which will be fixed with planned future releases of the debugger
13422 and the GNU Ada compiler.
13426 Currently, the debugger
13427 has insufficient information to determine whether certain pointers represent
13428 pointers to objects or the objects themselves.
13429 Thus, the user may have to tack an extra @code{.all} after an expression
13430 to get it printed properly.
13433 Static constants that the compiler chooses not to materialize as objects in
13434 storage are invisible to the debugger.
13437 Named parameter associations in function argument lists are ignored (the
13438 argument lists are treated as positional).
13441 Many useful library packages are currently invisible to the debugger.
13444 Fixed-point arithmetic, conversions, input, and output is carried out using
13445 floating-point arithmetic, and may give results that only approximate those on
13449 The GNAT compiler never generates the prefix @code{Standard} for any of
13450 the standard symbols defined by the Ada language. @value{GDBN} knows about
13451 this: it will strip the prefix from names when you use it, and will never
13452 look for a name you have so qualified among local symbols, nor match against
13453 symbols in other packages or subprograms. If you have
13454 defined entities anywhere in your program other than parameters and
13455 local variables whose simple names match names in @code{Standard},
13456 GNAT's lack of qualification here can cause confusion. When this happens,
13457 you can usually resolve the confusion
13458 by qualifying the problematic names with package
13459 @code{Standard} explicitly.
13462 Older versions of the compiler sometimes generate erroneous debugging
13463 information, resulting in the debugger incorrectly printing the value
13464 of affected entities. In some cases, the debugger is able to work
13465 around an issue automatically. In other cases, the debugger is able
13466 to work around the issue, but the work-around has to be specifically
13469 @kindex set ada trust-PAD-over-XVS
13470 @kindex show ada trust-PAD-over-XVS
13473 @item set ada trust-PAD-over-XVS on
13474 Configure GDB to strictly follow the GNAT encoding when computing the
13475 value of Ada entities, particularly when @code{PAD} and @code{PAD___XVS}
13476 types are involved (see @code{ada/exp_dbug.ads} in the GCC sources for
13477 a complete description of the encoding used by the GNAT compiler).
13478 This is the default.
13480 @item set ada trust-PAD-over-XVS off
13481 This is related to the encoding using by the GNAT compiler. If @value{GDBN}
13482 sometimes prints the wrong value for certain entities, changing @code{ada
13483 trust-PAD-over-XVS} to @code{off} activates a work-around which may fix
13484 the issue. It is always safe to set @code{ada trust-PAD-over-XVS} to
13485 @code{off}, but this incurs a slight performance penalty, so it is
13486 recommended to leave this setting to @code{on} unless necessary.
13490 @node Unsupported Languages
13491 @section Unsupported Languages
13493 @cindex unsupported languages
13494 @cindex minimal language
13495 In addition to the other fully-supported programming languages,
13496 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
13497 It does not represent a real programming language, but provides a set
13498 of capabilities close to what the C or assembly languages provide.
13499 This should allow most simple operations to be performed while debugging
13500 an application that uses a language currently not supported by @value{GDBN}.
13502 If the language is set to @code{auto}, @value{GDBN} will automatically
13503 select this language if the current frame corresponds to an unsupported
13507 @chapter Examining the Symbol Table
13509 The commands described in this chapter allow you to inquire about the
13510 symbols (names of variables, functions and types) defined in your
13511 program. This information is inherent in the text of your program and
13512 does not change as your program executes. @value{GDBN} finds it in your
13513 program's symbol table, in the file indicated when you started @value{GDBN}
13514 (@pxref{File Options, ,Choosing Files}), or by one of the
13515 file-management commands (@pxref{Files, ,Commands to Specify Files}).
13517 @cindex symbol names
13518 @cindex names of symbols
13519 @cindex quoting names
13520 Occasionally, you may need to refer to symbols that contain unusual
13521 characters, which @value{GDBN} ordinarily treats as word delimiters. The
13522 most frequent case is in referring to static variables in other
13523 source files (@pxref{Variables,,Program Variables}). File names
13524 are recorded in object files as debugging symbols, but @value{GDBN} would
13525 ordinarily parse a typical file name, like @file{foo.c}, as the three words
13526 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
13527 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
13534 looks up the value of @code{x} in the scope of the file @file{foo.c}.
13537 @cindex case-insensitive symbol names
13538 @cindex case sensitivity in symbol names
13539 @kindex set case-sensitive
13540 @item set case-sensitive on
13541 @itemx set case-sensitive off
13542 @itemx set case-sensitive auto
13543 Normally, when @value{GDBN} looks up symbols, it matches their names
13544 with case sensitivity determined by the current source language.
13545 Occasionally, you may wish to control that. The command @code{set
13546 case-sensitive} lets you do that by specifying @code{on} for
13547 case-sensitive matches or @code{off} for case-insensitive ones. If
13548 you specify @code{auto}, case sensitivity is reset to the default
13549 suitable for the source language. The default is case-sensitive
13550 matches for all languages except for Fortran, for which the default is
13551 case-insensitive matches.
13553 @kindex show case-sensitive
13554 @item show case-sensitive
13555 This command shows the current setting of case sensitivity for symbols
13558 @kindex info address
13559 @cindex address of a symbol
13560 @item info address @var{symbol}
13561 Describe where the data for @var{symbol} is stored. For a register
13562 variable, this says which register it is kept in. For a non-register
13563 local variable, this prints the stack-frame offset at which the variable
13566 Note the contrast with @samp{print &@var{symbol}}, which does not work
13567 at all for a register variable, and for a stack local variable prints
13568 the exact address of the current instantiation of the variable.
13570 @kindex info symbol
13571 @cindex symbol from address
13572 @cindex closest symbol and offset for an address
13573 @item info symbol @var{addr}
13574 Print the name of a symbol which is stored at the address @var{addr}.
13575 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
13576 nearest symbol and an offset from it:
13579 (@value{GDBP}) info symbol 0x54320
13580 _initialize_vx + 396 in section .text
13584 This is the opposite of the @code{info address} command. You can use
13585 it to find out the name of a variable or a function given its address.
13587 For dynamically linked executables, the name of executable or shared
13588 library containing the symbol is also printed:
13591 (@value{GDBP}) info symbol 0x400225
13592 _start + 5 in section .text of /tmp/a.out
13593 (@value{GDBP}) info symbol 0x2aaaac2811cf
13594 __read_nocancel + 6 in section .text of /usr/lib64/libc.so.6
13598 @item whatis [@var{arg}]
13599 Print the data type of @var{arg}, which can be either an expression or
13600 a data type. With no argument, print the data type of @code{$}, the
13601 last value in the value history. If @var{arg} is an expression, it is
13602 not actually evaluated, and any side-effecting operations (such as
13603 assignments or function calls) inside it do not take place. If
13604 @var{arg} is a type name, it may be the name of a type or typedef, or
13605 for C code it may have the form @samp{class @var{class-name}},
13606 @samp{struct @var{struct-tag}}, @samp{union @var{union-tag}} or
13607 @samp{enum @var{enum-tag}}.
13608 @xref{Expressions, ,Expressions}.
13611 @item ptype [@var{arg}]
13612 @code{ptype} accepts the same arguments as @code{whatis}, but prints a
13613 detailed description of the type, instead of just the name of the type.
13614 @xref{Expressions, ,Expressions}.
13616 For example, for this variable declaration:
13619 struct complex @{double real; double imag;@} v;
13623 the two commands give this output:
13627 (@value{GDBP}) whatis v
13628 type = struct complex
13629 (@value{GDBP}) ptype v
13630 type = struct complex @{
13638 As with @code{whatis}, using @code{ptype} without an argument refers to
13639 the type of @code{$}, the last value in the value history.
13641 @cindex incomplete type
13642 Sometimes, programs use opaque data types or incomplete specifications
13643 of complex data structure. If the debug information included in the
13644 program does not allow @value{GDBN} to display a full declaration of
13645 the data type, it will say @samp{<incomplete type>}. For example,
13646 given these declarations:
13650 struct foo *fooptr;
13654 but no definition for @code{struct foo} itself, @value{GDBN} will say:
13657 (@value{GDBP}) ptype foo
13658 $1 = <incomplete type>
13662 ``Incomplete type'' is C terminology for data types that are not
13663 completely specified.
13666 @item info types @var{regexp}
13668 Print a brief description of all types whose names match the regular
13669 expression @var{regexp} (or all types in your program, if you supply
13670 no argument). Each complete typename is matched as though it were a
13671 complete line; thus, @samp{i type value} gives information on all
13672 types in your program whose names include the string @code{value}, but
13673 @samp{i type ^value$} gives information only on types whose complete
13674 name is @code{value}.
13676 This command differs from @code{ptype} in two ways: first, like
13677 @code{whatis}, it does not print a detailed description; second, it
13678 lists all source files where a type is defined.
13681 @cindex local variables
13682 @item info scope @var{location}
13683 List all the variables local to a particular scope. This command
13684 accepts a @var{location} argument---a function name, a source line, or
13685 an address preceded by a @samp{*}, and prints all the variables local
13686 to the scope defined by that location. (@xref{Specify Location}, for
13687 details about supported forms of @var{location}.) For example:
13690 (@value{GDBP}) @b{info scope command_line_handler}
13691 Scope for command_line_handler:
13692 Symbol rl is an argument at stack/frame offset 8, length 4.
13693 Symbol linebuffer is in static storage at address 0x150a18, length 4.
13694 Symbol linelength is in static storage at address 0x150a1c, length 4.
13695 Symbol p is a local variable in register $esi, length 4.
13696 Symbol p1 is a local variable in register $ebx, length 4.
13697 Symbol nline is a local variable in register $edx, length 4.
13698 Symbol repeat is a local variable at frame offset -8, length 4.
13702 This command is especially useful for determining what data to collect
13703 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
13706 @kindex info source
13708 Show information about the current source file---that is, the source file for
13709 the function containing the current point of execution:
13712 the name of the source file, and the directory containing it,
13714 the directory it was compiled in,
13716 its length, in lines,
13718 which programming language it is written in,
13720 whether the executable includes debugging information for that file, and
13721 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
13723 whether the debugging information includes information about
13724 preprocessor macros.
13728 @kindex info sources
13730 Print the names of all source files in your program for which there is
13731 debugging information, organized into two lists: files whose symbols
13732 have already been read, and files whose symbols will be read when needed.
13734 @kindex info functions
13735 @item info functions
13736 Print the names and data types of all defined functions.
13738 @item info functions @var{regexp}
13739 Print the names and data types of all defined functions
13740 whose names contain a match for regular expression @var{regexp}.
13741 Thus, @samp{info fun step} finds all functions whose names
13742 include @code{step}; @samp{info fun ^step} finds those whose names
13743 start with @code{step}. If a function name contains characters
13744 that conflict with the regular expression language (e.g.@:
13745 @samp{operator*()}), they may be quoted with a backslash.
13747 @kindex info variables
13748 @item info variables
13749 Print the names and data types of all variables that are defined
13750 outside of functions (i.e.@: excluding local variables).
13752 @item info variables @var{regexp}
13753 Print the names and data types of all variables (except for local
13754 variables) whose names contain a match for regular expression
13757 @kindex info classes
13758 @cindex Objective-C, classes and selectors
13760 @itemx info classes @var{regexp}
13761 Display all Objective-C classes in your program, or
13762 (with the @var{regexp} argument) all those matching a particular regular
13765 @kindex info selectors
13766 @item info selectors
13767 @itemx info selectors @var{regexp}
13768 Display all Objective-C selectors in your program, or
13769 (with the @var{regexp} argument) all those matching a particular regular
13773 This was never implemented.
13774 @kindex info methods
13776 @itemx info methods @var{regexp}
13777 The @code{info methods} command permits the user to examine all defined
13778 methods within C@t{++} program, or (with the @var{regexp} argument) a
13779 specific set of methods found in the various C@t{++} classes. Many
13780 C@t{++} classes provide a large number of methods. Thus, the output
13781 from the @code{ptype} command can be overwhelming and hard to use. The
13782 @code{info-methods} command filters the methods, printing only those
13783 which match the regular-expression @var{regexp}.
13786 @cindex reloading symbols
13787 Some systems allow individual object files that make up your program to
13788 be replaced without stopping and restarting your program. For example,
13789 in VxWorks you can simply recompile a defective object file and keep on
13790 running. If you are running on one of these systems, you can allow
13791 @value{GDBN} to reload the symbols for automatically relinked modules:
13794 @kindex set symbol-reloading
13795 @item set symbol-reloading on
13796 Replace symbol definitions for the corresponding source file when an
13797 object file with a particular name is seen again.
13799 @item set symbol-reloading off
13800 Do not replace symbol definitions when encountering object files of the
13801 same name more than once. This is the default state; if you are not
13802 running on a system that permits automatic relinking of modules, you
13803 should leave @code{symbol-reloading} off, since otherwise @value{GDBN}
13804 may discard symbols when linking large programs, that may contain
13805 several modules (from different directories or libraries) with the same
13808 @kindex show symbol-reloading
13809 @item show symbol-reloading
13810 Show the current @code{on} or @code{off} setting.
13813 @cindex opaque data types
13814 @kindex set opaque-type-resolution
13815 @item set opaque-type-resolution on
13816 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
13817 declared as a pointer to a @code{struct}, @code{class}, or
13818 @code{union}---for example, @code{struct MyType *}---that is used in one
13819 source file although the full declaration of @code{struct MyType} is in
13820 another source file. The default is on.
13822 A change in the setting of this subcommand will not take effect until
13823 the next time symbols for a file are loaded.
13825 @item set opaque-type-resolution off
13826 Tell @value{GDBN} not to resolve opaque types. In this case, the type
13827 is printed as follows:
13829 @{<no data fields>@}
13832 @kindex show opaque-type-resolution
13833 @item show opaque-type-resolution
13834 Show whether opaque types are resolved or not.
13836 @kindex maint print symbols
13837 @cindex symbol dump
13838 @kindex maint print psymbols
13839 @cindex partial symbol dump
13840 @item maint print symbols @var{filename}
13841 @itemx maint print psymbols @var{filename}
13842 @itemx maint print msymbols @var{filename}
13843 Write a dump of debugging symbol data into the file @var{filename}.
13844 These commands are used to debug the @value{GDBN} symbol-reading code. Only
13845 symbols with debugging data are included. If you use @samp{maint print
13846 symbols}, @value{GDBN} includes all the symbols for which it has already
13847 collected full details: that is, @var{filename} reflects symbols for
13848 only those files whose symbols @value{GDBN} has read. You can use the
13849 command @code{info sources} to find out which files these are. If you
13850 use @samp{maint print psymbols} instead, the dump shows information about
13851 symbols that @value{GDBN} only knows partially---that is, symbols defined in
13852 files that @value{GDBN} has skimmed, but not yet read completely. Finally,
13853 @samp{maint print msymbols} dumps just the minimal symbol information
13854 required for each object file from which @value{GDBN} has read some symbols.
13855 @xref{Files, ,Commands to Specify Files}, for a discussion of how
13856 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
13858 @kindex maint info symtabs
13859 @kindex maint info psymtabs
13860 @cindex listing @value{GDBN}'s internal symbol tables
13861 @cindex symbol tables, listing @value{GDBN}'s internal
13862 @cindex full symbol tables, listing @value{GDBN}'s internal
13863 @cindex partial symbol tables, listing @value{GDBN}'s internal
13864 @item maint info symtabs @r{[} @var{regexp} @r{]}
13865 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
13867 List the @code{struct symtab} or @code{struct partial_symtab}
13868 structures whose names match @var{regexp}. If @var{regexp} is not
13869 given, list them all. The output includes expressions which you can
13870 copy into a @value{GDBN} debugging this one to examine a particular
13871 structure in more detail. For example:
13874 (@value{GDBP}) maint info psymtabs dwarf2read
13875 @{ objfile /home/gnu/build/gdb/gdb
13876 ((struct objfile *) 0x82e69d0)
13877 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
13878 ((struct partial_symtab *) 0x8474b10)
13881 text addresses 0x814d3c8 -- 0x8158074
13882 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
13883 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
13884 dependencies (none)
13887 (@value{GDBP}) maint info symtabs
13891 We see that there is one partial symbol table whose filename contains
13892 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
13893 and we see that @value{GDBN} has not read in any symtabs yet at all.
13894 If we set a breakpoint on a function, that will cause @value{GDBN} to
13895 read the symtab for the compilation unit containing that function:
13898 (@value{GDBP}) break dwarf2_psymtab_to_symtab
13899 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
13901 (@value{GDBP}) maint info symtabs
13902 @{ objfile /home/gnu/build/gdb/gdb
13903 ((struct objfile *) 0x82e69d0)
13904 @{ symtab /home/gnu/src/gdb/dwarf2read.c
13905 ((struct symtab *) 0x86c1f38)
13908 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
13909 linetable ((struct linetable *) 0x8370fa0)
13910 debugformat DWARF 2
13919 @chapter Altering Execution
13921 Once you think you have found an error in your program, you might want to
13922 find out for certain whether correcting the apparent error would lead to
13923 correct results in the rest of the run. You can find the answer by
13924 experiment, using the @value{GDBN} features for altering execution of the
13927 For example, you can store new values into variables or memory
13928 locations, give your program a signal, restart it at a different
13929 address, or even return prematurely from a function.
13932 * Assignment:: Assignment to variables
13933 * Jumping:: Continuing at a different address
13934 * Signaling:: Giving your program a signal
13935 * Returning:: Returning from a function
13936 * Calling:: Calling your program's functions
13937 * Patching:: Patching your program
13941 @section Assignment to Variables
13944 @cindex setting variables
13945 To alter the value of a variable, evaluate an assignment expression.
13946 @xref{Expressions, ,Expressions}. For example,
13953 stores the value 4 into the variable @code{x}, and then prints the
13954 value of the assignment expression (which is 4).
13955 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
13956 information on operators in supported languages.
13958 @kindex set variable
13959 @cindex variables, setting
13960 If you are not interested in seeing the value of the assignment, use the
13961 @code{set} command instead of the @code{print} command. @code{set} is
13962 really the same as @code{print} except that the expression's value is
13963 not printed and is not put in the value history (@pxref{Value History,
13964 ,Value History}). The expression is evaluated only for its effects.
13966 If the beginning of the argument string of the @code{set} command
13967 appears identical to a @code{set} subcommand, use the @code{set
13968 variable} command instead of just @code{set}. This command is identical
13969 to @code{set} except for its lack of subcommands. For example, if your
13970 program has a variable @code{width}, you get an error if you try to set
13971 a new value with just @samp{set width=13}, because @value{GDBN} has the
13972 command @code{set width}:
13975 (@value{GDBP}) whatis width
13977 (@value{GDBP}) p width
13979 (@value{GDBP}) set width=47
13980 Invalid syntax in expression.
13984 The invalid expression, of course, is @samp{=47}. In
13985 order to actually set the program's variable @code{width}, use
13988 (@value{GDBP}) set var width=47
13991 Because the @code{set} command has many subcommands that can conflict
13992 with the names of program variables, it is a good idea to use the
13993 @code{set variable} command instead of just @code{set}. For example, if
13994 your program has a variable @code{g}, you run into problems if you try
13995 to set a new value with just @samp{set g=4}, because @value{GDBN} has
13996 the command @code{set gnutarget}, abbreviated @code{set g}:
14000 (@value{GDBP}) whatis g
14004 (@value{GDBP}) set g=4
14008 The program being debugged has been started already.
14009 Start it from the beginning? (y or n) y
14010 Starting program: /home/smith/cc_progs/a.out
14011 "/home/smith/cc_progs/a.out": can't open to read symbols:
14012 Invalid bfd target.
14013 (@value{GDBP}) show g
14014 The current BFD target is "=4".
14019 The program variable @code{g} did not change, and you silently set the
14020 @code{gnutarget} to an invalid value. In order to set the variable
14024 (@value{GDBP}) set var g=4
14027 @value{GDBN} allows more implicit conversions in assignments than C; you can
14028 freely store an integer value into a pointer variable or vice versa,
14029 and you can convert any structure to any other structure that is the
14030 same length or shorter.
14031 @comment FIXME: how do structs align/pad in these conversions?
14032 @comment /doc@cygnus.com 18dec1990
14034 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
14035 construct to generate a value of specified type at a specified address
14036 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
14037 to memory location @code{0x83040} as an integer (which implies a certain size
14038 and representation in memory), and
14041 set @{int@}0x83040 = 4
14045 stores the value 4 into that memory location.
14048 @section Continuing at a Different Address
14050 Ordinarily, when you continue your program, you do so at the place where
14051 it stopped, with the @code{continue} command. You can instead continue at
14052 an address of your own choosing, with the following commands:
14056 @item jump @var{linespec}
14057 @itemx jump @var{location}
14058 Resume execution at line @var{linespec} or at address given by
14059 @var{location}. Execution stops again immediately if there is a
14060 breakpoint there. @xref{Specify Location}, for a description of the
14061 different forms of @var{linespec} and @var{location}. It is common
14062 practice to use the @code{tbreak} command in conjunction with
14063 @code{jump}. @xref{Set Breaks, ,Setting Breakpoints}.
14065 The @code{jump} command does not change the current stack frame, or
14066 the stack pointer, or the contents of any memory location or any
14067 register other than the program counter. If line @var{linespec} is in
14068 a different function from the one currently executing, the results may
14069 be bizarre if the two functions expect different patterns of arguments or
14070 of local variables. For this reason, the @code{jump} command requests
14071 confirmation if the specified line is not in the function currently
14072 executing. However, even bizarre results are predictable if you are
14073 well acquainted with the machine-language code of your program.
14076 @c Doesn't work on HP-UX; have to set $pcoqh and $pcoqt.
14077 On many systems, you can get much the same effect as the @code{jump}
14078 command by storing a new value into the register @code{$pc}. The
14079 difference is that this does not start your program running; it only
14080 changes the address of where it @emph{will} run when you continue. For
14088 makes the next @code{continue} command or stepping command execute at
14089 address @code{0x485}, rather than at the address where your program stopped.
14090 @xref{Continuing and Stepping, ,Continuing and Stepping}.
14092 The most common occasion to use the @code{jump} command is to back
14093 up---perhaps with more breakpoints set---over a portion of a program
14094 that has already executed, in order to examine its execution in more
14099 @section Giving your Program a Signal
14100 @cindex deliver a signal to a program
14104 @item signal @var{signal}
14105 Resume execution where your program stopped, but immediately give it the
14106 signal @var{signal}. @var{signal} can be the name or the number of a
14107 signal. For example, on many systems @code{signal 2} and @code{signal
14108 SIGINT} are both ways of sending an interrupt signal.
14110 Alternatively, if @var{signal} is zero, continue execution without
14111 giving a signal. This is useful when your program stopped on account of
14112 a signal and would ordinary see the signal when resumed with the
14113 @code{continue} command; @samp{signal 0} causes it to resume without a
14116 @code{signal} does not repeat when you press @key{RET} a second time
14117 after executing the command.
14121 Invoking the @code{signal} command is not the same as invoking the
14122 @code{kill} utility from the shell. Sending a signal with @code{kill}
14123 causes @value{GDBN} to decide what to do with the signal depending on
14124 the signal handling tables (@pxref{Signals}). The @code{signal} command
14125 passes the signal directly to your program.
14129 @section Returning from a Function
14132 @cindex returning from a function
14135 @itemx return @var{expression}
14136 You can cancel execution of a function call with the @code{return}
14137 command. If you give an
14138 @var{expression} argument, its value is used as the function's return
14142 When you use @code{return}, @value{GDBN} discards the selected stack frame
14143 (and all frames within it). You can think of this as making the
14144 discarded frame return prematurely. If you wish to specify a value to
14145 be returned, give that value as the argument to @code{return}.
14147 This pops the selected stack frame (@pxref{Selection, ,Selecting a
14148 Frame}), and any other frames inside of it, leaving its caller as the
14149 innermost remaining frame. That frame becomes selected. The
14150 specified value is stored in the registers used for returning values
14153 The @code{return} command does not resume execution; it leaves the
14154 program stopped in the state that would exist if the function had just
14155 returned. In contrast, the @code{finish} command (@pxref{Continuing
14156 and Stepping, ,Continuing and Stepping}) resumes execution until the
14157 selected stack frame returns naturally.
14159 @value{GDBN} needs to know how the @var{expression} argument should be set for
14160 the inferior. The concrete registers assignment depends on the OS ABI and the
14161 type being returned by the selected stack frame. For example it is common for
14162 OS ABI to return floating point values in FPU registers while integer values in
14163 CPU registers. Still some ABIs return even floating point values in CPU
14164 registers. Larger integer widths (such as @code{long long int}) also have
14165 specific placement rules. @value{GDBN} already knows the OS ABI from its
14166 current target so it needs to find out also the type being returned to make the
14167 assignment into the right register(s).
14169 Normally, the selected stack frame has debug info. @value{GDBN} will always
14170 use the debug info instead of the implicit type of @var{expression} when the
14171 debug info is available. For example, if you type @kbd{return -1}, and the
14172 function in the current stack frame is declared to return a @code{long long
14173 int}, @value{GDBN} transparently converts the implicit @code{int} value of -1
14174 into a @code{long long int}:
14177 Breakpoint 1, func () at gdb.base/return-nodebug.c:29
14179 (@value{GDBP}) return -1
14180 Make func return now? (y or n) y
14181 #0 0x004004f6 in main () at gdb.base/return-nodebug.c:43
14182 43 printf ("result=%lld\n", func ());
14186 However, if the selected stack frame does not have a debug info, e.g., if the
14187 function was compiled without debug info, @value{GDBN} has to find out the type
14188 to return from user. Specifying a different type by mistake may set the value
14189 in different inferior registers than the caller code expects. For example,
14190 typing @kbd{return -1} with its implicit type @code{int} would set only a part
14191 of a @code{long long int} result for a debug info less function (on 32-bit
14192 architectures). Therefore the user is required to specify the return type by
14193 an appropriate cast explicitly:
14196 Breakpoint 2, 0x0040050b in func ()
14197 (@value{GDBP}) return -1
14198 Return value type not available for selected stack frame.
14199 Please use an explicit cast of the value to return.
14200 (@value{GDBP}) return (long long int) -1
14201 Make selected stack frame return now? (y or n) y
14202 #0 0x00400526 in main ()
14207 @section Calling Program Functions
14210 @cindex calling functions
14211 @cindex inferior functions, calling
14212 @item print @var{expr}
14213 Evaluate the expression @var{expr} and display the resulting value.
14214 @var{expr} may include calls to functions in the program being
14218 @item call @var{expr}
14219 Evaluate the expression @var{expr} without displaying @code{void}
14222 You can use this variant of the @code{print} command if you want to
14223 execute a function from your program that does not return anything
14224 (a.k.a.@: @dfn{a void function}), but without cluttering the output
14225 with @code{void} returned values that @value{GDBN} will otherwise
14226 print. If the result is not void, it is printed and saved in the
14230 It is possible for the function you call via the @code{print} or
14231 @code{call} command to generate a signal (e.g., if there's a bug in
14232 the function, or if you passed it incorrect arguments). What happens
14233 in that case is controlled by the @code{set unwindonsignal} command.
14235 Similarly, with a C@t{++} program it is possible for the function you
14236 call via the @code{print} or @code{call} command to generate an
14237 exception that is not handled due to the constraints of the dummy
14238 frame. In this case, any exception that is raised in the frame, but has
14239 an out-of-frame exception handler will not be found. GDB builds a
14240 dummy-frame for the inferior function call, and the unwinder cannot
14241 seek for exception handlers outside of this dummy-frame. What happens
14242 in that case is controlled by the
14243 @code{set unwind-on-terminating-exception} command.
14246 @item set unwindonsignal
14247 @kindex set unwindonsignal
14248 @cindex unwind stack in called functions
14249 @cindex call dummy stack unwinding
14250 Set unwinding of the stack if a signal is received while in a function
14251 that @value{GDBN} called in the program being debugged. If set to on,
14252 @value{GDBN} unwinds the stack it created for the call and restores
14253 the context to what it was before the call. If set to off (the
14254 default), @value{GDBN} stops in the frame where the signal was
14257 @item show unwindonsignal
14258 @kindex show unwindonsignal
14259 Show the current setting of stack unwinding in the functions called by
14262 @item set unwind-on-terminating-exception
14263 @kindex set unwind-on-terminating-exception
14264 @cindex unwind stack in called functions with unhandled exceptions
14265 @cindex call dummy stack unwinding on unhandled exception.
14266 Set unwinding of the stack if a C@t{++} exception is raised, but left
14267 unhandled while in a function that @value{GDBN} called in the program being
14268 debugged. If set to on (the default), @value{GDBN} unwinds the stack
14269 it created for the call and restores the context to what it was before
14270 the call. If set to off, @value{GDBN} the exception is delivered to
14271 the default C@t{++} exception handler and the inferior terminated.
14273 @item show unwind-on-terminating-exception
14274 @kindex show unwind-on-terminating-exception
14275 Show the current setting of stack unwinding in the functions called by
14280 @cindex weak alias functions
14281 Sometimes, a function you wish to call is actually a @dfn{weak alias}
14282 for another function. In such case, @value{GDBN} might not pick up
14283 the type information, including the types of the function arguments,
14284 which causes @value{GDBN} to call the inferior function incorrectly.
14285 As a result, the called function will function erroneously and may
14286 even crash. A solution to that is to use the name of the aliased
14290 @section Patching Programs
14292 @cindex patching binaries
14293 @cindex writing into executables
14294 @cindex writing into corefiles
14296 By default, @value{GDBN} opens the file containing your program's
14297 executable code (or the corefile) read-only. This prevents accidental
14298 alterations to machine code; but it also prevents you from intentionally
14299 patching your program's binary.
14301 If you'd like to be able to patch the binary, you can specify that
14302 explicitly with the @code{set write} command. For example, you might
14303 want to turn on internal debugging flags, or even to make emergency
14309 @itemx set write off
14310 If you specify @samp{set write on}, @value{GDBN} opens executable and
14311 core files for both reading and writing; if you specify @kbd{set write
14312 off} (the default), @value{GDBN} opens them read-only.
14314 If you have already loaded a file, you must load it again (using the
14315 @code{exec-file} or @code{core-file} command) after changing @code{set
14316 write}, for your new setting to take effect.
14320 Display whether executable files and core files are opened for writing
14321 as well as reading.
14325 @chapter @value{GDBN} Files
14327 @value{GDBN} needs to know the file name of the program to be debugged,
14328 both in order to read its symbol table and in order to start your
14329 program. To debug a core dump of a previous run, you must also tell
14330 @value{GDBN} the name of the core dump file.
14333 * Files:: Commands to specify files
14334 * Separate Debug Files:: Debugging information in separate files
14335 * Index Files:: Index files speed up GDB
14336 * Symbol Errors:: Errors reading symbol files
14337 * Data Files:: GDB data files
14341 @section Commands to Specify Files
14343 @cindex symbol table
14344 @cindex core dump file
14346 You may want to specify executable and core dump file names. The usual
14347 way to do this is at start-up time, using the arguments to
14348 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
14349 Out of @value{GDBN}}).
14351 Occasionally it is necessary to change to a different file during a
14352 @value{GDBN} session. Or you may run @value{GDBN} and forget to
14353 specify a file you want to use. Or you are debugging a remote target
14354 via @code{gdbserver} (@pxref{Server, file, Using the @code{gdbserver}
14355 Program}). In these situations the @value{GDBN} commands to specify
14356 new files are useful.
14359 @cindex executable file
14361 @item file @var{filename}
14362 Use @var{filename} as the program to be debugged. It is read for its
14363 symbols and for the contents of pure memory. It is also the program
14364 executed when you use the @code{run} command. If you do not specify a
14365 directory and the file is not found in the @value{GDBN} working directory,
14366 @value{GDBN} uses the environment variable @code{PATH} as a list of
14367 directories to search, just as the shell does when looking for a program
14368 to run. You can change the value of this variable, for both @value{GDBN}
14369 and your program, using the @code{path} command.
14371 @cindex unlinked object files
14372 @cindex patching object files
14373 You can load unlinked object @file{.o} files into @value{GDBN} using
14374 the @code{file} command. You will not be able to ``run'' an object
14375 file, but you can disassemble functions and inspect variables. Also,
14376 if the underlying BFD functionality supports it, you could use
14377 @kbd{gdb -write} to patch object files using this technique. Note
14378 that @value{GDBN} can neither interpret nor modify relocations in this
14379 case, so branches and some initialized variables will appear to go to
14380 the wrong place. But this feature is still handy from time to time.
14383 @code{file} with no argument makes @value{GDBN} discard any information it
14384 has on both executable file and the symbol table.
14387 @item exec-file @r{[} @var{filename} @r{]}
14388 Specify that the program to be run (but not the symbol table) is found
14389 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
14390 if necessary to locate your program. Omitting @var{filename} means to
14391 discard information on the executable file.
14393 @kindex symbol-file
14394 @item symbol-file @r{[} @var{filename} @r{]}
14395 Read symbol table information from file @var{filename}. @code{PATH} is
14396 searched when necessary. Use the @code{file} command to get both symbol
14397 table and program to run from the same file.
14399 @code{symbol-file} with no argument clears out @value{GDBN} information on your
14400 program's symbol table.
14402 The @code{symbol-file} command causes @value{GDBN} to forget the contents of
14403 some breakpoints and auto-display expressions. This is because they may
14404 contain pointers to the internal data recording symbols and data types,
14405 which are part of the old symbol table data being discarded inside
14408 @code{symbol-file} does not repeat if you press @key{RET} again after
14411 When @value{GDBN} is configured for a particular environment, it
14412 understands debugging information in whatever format is the standard
14413 generated for that environment; you may use either a @sc{gnu} compiler, or
14414 other compilers that adhere to the local conventions.
14415 Best results are usually obtained from @sc{gnu} compilers; for example,
14416 using @code{@value{NGCC}} you can generate debugging information for
14419 For most kinds of object files, with the exception of old SVR3 systems
14420 using COFF, the @code{symbol-file} command does not normally read the
14421 symbol table in full right away. Instead, it scans the symbol table
14422 quickly to find which source files and which symbols are present. The
14423 details are read later, one source file at a time, as they are needed.
14425 The purpose of this two-stage reading strategy is to make @value{GDBN}
14426 start up faster. For the most part, it is invisible except for
14427 occasional pauses while the symbol table details for a particular source
14428 file are being read. (The @code{set verbose} command can turn these
14429 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
14430 Warnings and Messages}.)
14432 We have not implemented the two-stage strategy for COFF yet. When the
14433 symbol table is stored in COFF format, @code{symbol-file} reads the
14434 symbol table data in full right away. Note that ``stabs-in-COFF''
14435 still does the two-stage strategy, since the debug info is actually
14439 @cindex reading symbols immediately
14440 @cindex symbols, reading immediately
14441 @item symbol-file @r{[} -readnow @r{]} @var{filename}
14442 @itemx file @r{[} -readnow @r{]} @var{filename}
14443 You can override the @value{GDBN} two-stage strategy for reading symbol
14444 tables by using the @samp{-readnow} option with any of the commands that
14445 load symbol table information, if you want to be sure @value{GDBN} has the
14446 entire symbol table available.
14448 @c FIXME: for now no mention of directories, since this seems to be in
14449 @c flux. 13mar1992 status is that in theory GDB would look either in
14450 @c current dir or in same dir as myprog; but issues like competing
14451 @c GDB's, or clutter in system dirs, mean that in practice right now
14452 @c only current dir is used. FFish says maybe a special GDB hierarchy
14453 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
14457 @item core-file @r{[}@var{filename}@r{]}
14459 Specify the whereabouts of a core dump file to be used as the ``contents
14460 of memory''. Traditionally, core files contain only some parts of the
14461 address space of the process that generated them; @value{GDBN} can access the
14462 executable file itself for other parts.
14464 @code{core-file} with no argument specifies that no core file is
14467 Note that the core file is ignored when your program is actually running
14468 under @value{GDBN}. So, if you have been running your program and you
14469 wish to debug a core file instead, you must kill the subprocess in which
14470 the program is running. To do this, use the @code{kill} command
14471 (@pxref{Kill Process, ,Killing the Child Process}).
14473 @kindex add-symbol-file
14474 @cindex dynamic linking
14475 @item add-symbol-file @var{filename} @var{address}
14476 @itemx add-symbol-file @var{filename} @var{address} @r{[} -readnow @r{]}
14477 @itemx add-symbol-file @var{filename} @r{-s}@var{section} @var{address} @dots{}
14478 The @code{add-symbol-file} command reads additional symbol table
14479 information from the file @var{filename}. You would use this command
14480 when @var{filename} has been dynamically loaded (by some other means)
14481 into the program that is running. @var{address} should be the memory
14482 address at which the file has been loaded; @value{GDBN} cannot figure
14483 this out for itself. You can additionally specify an arbitrary number
14484 of @samp{@r{-s}@var{section} @var{address}} pairs, to give an explicit
14485 section name and base address for that section. You can specify any
14486 @var{address} as an expression.
14488 The symbol table of the file @var{filename} is added to the symbol table
14489 originally read with the @code{symbol-file} command. You can use the
14490 @code{add-symbol-file} command any number of times; the new symbol data
14491 thus read keeps adding to the old. To discard all old symbol data
14492 instead, use the @code{symbol-file} command without any arguments.
14494 @cindex relocatable object files, reading symbols from
14495 @cindex object files, relocatable, reading symbols from
14496 @cindex reading symbols from relocatable object files
14497 @cindex symbols, reading from relocatable object files
14498 @cindex @file{.o} files, reading symbols from
14499 Although @var{filename} is typically a shared library file, an
14500 executable file, or some other object file which has been fully
14501 relocated for loading into a process, you can also load symbolic
14502 information from relocatable @file{.o} files, as long as:
14506 the file's symbolic information refers only to linker symbols defined in
14507 that file, not to symbols defined by other object files,
14509 every section the file's symbolic information refers to has actually
14510 been loaded into the inferior, as it appears in the file, and
14512 you can determine the address at which every section was loaded, and
14513 provide these to the @code{add-symbol-file} command.
14517 Some embedded operating systems, like Sun Chorus and VxWorks, can load
14518 relocatable files into an already running program; such systems
14519 typically make the requirements above easy to meet. However, it's
14520 important to recognize that many native systems use complex link
14521 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
14522 assembly, for example) that make the requirements difficult to meet. In
14523 general, one cannot assume that using @code{add-symbol-file} to read a
14524 relocatable object file's symbolic information will have the same effect
14525 as linking the relocatable object file into the program in the normal
14528 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
14530 @kindex add-symbol-file-from-memory
14531 @cindex @code{syscall DSO}
14532 @cindex load symbols from memory
14533 @item add-symbol-file-from-memory @var{address}
14534 Load symbols from the given @var{address} in a dynamically loaded
14535 object file whose image is mapped directly into the inferior's memory.
14536 For example, the Linux kernel maps a @code{syscall DSO} into each
14537 process's address space; this DSO provides kernel-specific code for
14538 some system calls. The argument can be any expression whose
14539 evaluation yields the address of the file's shared object file header.
14540 For this command to work, you must have used @code{symbol-file} or
14541 @code{exec-file} commands in advance.
14543 @kindex add-shared-symbol-files
14545 @item add-shared-symbol-files @var{library-file}
14546 @itemx assf @var{library-file}
14547 The @code{add-shared-symbol-files} command can currently be used only
14548 in the Cygwin build of @value{GDBN} on MS-Windows OS, where it is an
14549 alias for the @code{dll-symbols} command (@pxref{Cygwin Native}).
14550 @value{GDBN} automatically looks for shared libraries, however if
14551 @value{GDBN} does not find yours, you can invoke
14552 @code{add-shared-symbol-files}. It takes one argument: the shared
14553 library's file name. @code{assf} is a shorthand alias for
14554 @code{add-shared-symbol-files}.
14557 @item section @var{section} @var{addr}
14558 The @code{section} command changes the base address of the named
14559 @var{section} of the exec file to @var{addr}. This can be used if the
14560 exec file does not contain section addresses, (such as in the
14561 @code{a.out} format), or when the addresses specified in the file
14562 itself are wrong. Each section must be changed separately. The
14563 @code{info files} command, described below, lists all the sections and
14567 @kindex info target
14570 @code{info files} and @code{info target} are synonymous; both print the
14571 current target (@pxref{Targets, ,Specifying a Debugging Target}),
14572 including the names of the executable and core dump files currently in
14573 use by @value{GDBN}, and the files from which symbols were loaded. The
14574 command @code{help target} lists all possible targets rather than
14577 @kindex maint info sections
14578 @item maint info sections
14579 Another command that can give you extra information about program sections
14580 is @code{maint info sections}. In addition to the section information
14581 displayed by @code{info files}, this command displays the flags and file
14582 offset of each section in the executable and core dump files. In addition,
14583 @code{maint info sections} provides the following command options (which
14584 may be arbitrarily combined):
14588 Display sections for all loaded object files, including shared libraries.
14589 @item @var{sections}
14590 Display info only for named @var{sections}.
14591 @item @var{section-flags}
14592 Display info only for sections for which @var{section-flags} are true.
14593 The section flags that @value{GDBN} currently knows about are:
14596 Section will have space allocated in the process when loaded.
14597 Set for all sections except those containing debug information.
14599 Section will be loaded from the file into the child process memory.
14600 Set for pre-initialized code and data, clear for @code{.bss} sections.
14602 Section needs to be relocated before loading.
14604 Section cannot be modified by the child process.
14606 Section contains executable code only.
14608 Section contains data only (no executable code).
14610 Section will reside in ROM.
14612 Section contains data for constructor/destructor lists.
14614 Section is not empty.
14616 An instruction to the linker to not output the section.
14617 @item COFF_SHARED_LIBRARY
14618 A notification to the linker that the section contains
14619 COFF shared library information.
14621 Section contains common symbols.
14624 @kindex set trust-readonly-sections
14625 @cindex read-only sections
14626 @item set trust-readonly-sections on
14627 Tell @value{GDBN} that readonly sections in your object file
14628 really are read-only (i.e.@: that their contents will not change).
14629 In that case, @value{GDBN} can fetch values from these sections
14630 out of the object file, rather than from the target program.
14631 For some targets (notably embedded ones), this can be a significant
14632 enhancement to debugging performance.
14634 The default is off.
14636 @item set trust-readonly-sections off
14637 Tell @value{GDBN} not to trust readonly sections. This means that
14638 the contents of the section might change while the program is running,
14639 and must therefore be fetched from the target when needed.
14641 @item show trust-readonly-sections
14642 Show the current setting of trusting readonly sections.
14645 All file-specifying commands allow both absolute and relative file names
14646 as arguments. @value{GDBN} always converts the file name to an absolute file
14647 name and remembers it that way.
14649 @cindex shared libraries
14650 @anchor{Shared Libraries}
14651 @value{GDBN} supports @sc{gnu}/Linux, MS-Windows, HP-UX, SunOS, SVr4, Irix,
14652 and IBM RS/6000 AIX shared libraries.
14654 On MS-Windows @value{GDBN} must be linked with the Expat library to support
14655 shared libraries. @xref{Expat}.
14657 @value{GDBN} automatically loads symbol definitions from shared libraries
14658 when you use the @code{run} command, or when you examine a core file.
14659 (Before you issue the @code{run} command, @value{GDBN} does not understand
14660 references to a function in a shared library, however---unless you are
14661 debugging a core file).
14663 On HP-UX, if the program loads a library explicitly, @value{GDBN}
14664 automatically loads the symbols at the time of the @code{shl_load} call.
14666 @c FIXME: some @value{GDBN} release may permit some refs to undef
14667 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
14668 @c FIXME...lib; check this from time to time when updating manual
14670 There are times, however, when you may wish to not automatically load
14671 symbol definitions from shared libraries, such as when they are
14672 particularly large or there are many of them.
14674 To control the automatic loading of shared library symbols, use the
14678 @kindex set auto-solib-add
14679 @item set auto-solib-add @var{mode}
14680 If @var{mode} is @code{on}, symbols from all shared object libraries
14681 will be loaded automatically when the inferior begins execution, you
14682 attach to an independently started inferior, or when the dynamic linker
14683 informs @value{GDBN} that a new library has been loaded. If @var{mode}
14684 is @code{off}, symbols must be loaded manually, using the
14685 @code{sharedlibrary} command. The default value is @code{on}.
14687 @cindex memory used for symbol tables
14688 If your program uses lots of shared libraries with debug info that
14689 takes large amounts of memory, you can decrease the @value{GDBN}
14690 memory footprint by preventing it from automatically loading the
14691 symbols from shared libraries. To that end, type @kbd{set
14692 auto-solib-add off} before running the inferior, then load each
14693 library whose debug symbols you do need with @kbd{sharedlibrary
14694 @var{regexp}}, where @var{regexp} is a regular expression that matches
14695 the libraries whose symbols you want to be loaded.
14697 @kindex show auto-solib-add
14698 @item show auto-solib-add
14699 Display the current autoloading mode.
14702 @cindex load shared library
14703 To explicitly load shared library symbols, use the @code{sharedlibrary}
14707 @kindex info sharedlibrary
14709 @item info share @var{regex}
14710 @itemx info sharedlibrary @var{regex}
14711 Print the names of the shared libraries which are currently loaded
14712 that match @var{regex}. If @var{regex} is omitted then print
14713 all shared libraries that are loaded.
14715 @kindex sharedlibrary
14717 @item sharedlibrary @var{regex}
14718 @itemx share @var{regex}
14719 Load shared object library symbols for files matching a
14720 Unix regular expression.
14721 As with files loaded automatically, it only loads shared libraries
14722 required by your program for a core file or after typing @code{run}. If
14723 @var{regex} is omitted all shared libraries required by your program are
14726 @item nosharedlibrary
14727 @kindex nosharedlibrary
14728 @cindex unload symbols from shared libraries
14729 Unload all shared object library symbols. This discards all symbols
14730 that have been loaded from all shared libraries. Symbols from shared
14731 libraries that were loaded by explicit user requests are not
14735 Sometimes you may wish that @value{GDBN} stops and gives you control
14736 when any of shared library events happen. Use the @code{set
14737 stop-on-solib-events} command for this:
14740 @item set stop-on-solib-events
14741 @kindex set stop-on-solib-events
14742 This command controls whether @value{GDBN} should give you control
14743 when the dynamic linker notifies it about some shared library event.
14744 The most common event of interest is loading or unloading of a new
14747 @item show stop-on-solib-events
14748 @kindex show stop-on-solib-events
14749 Show whether @value{GDBN} stops and gives you control when shared
14750 library events happen.
14753 Shared libraries are also supported in many cross or remote debugging
14754 configurations. @value{GDBN} needs to have access to the target's libraries;
14755 this can be accomplished either by providing copies of the libraries
14756 on the host system, or by asking @value{GDBN} to automatically retrieve the
14757 libraries from the target. If copies of the target libraries are
14758 provided, they need to be the same as the target libraries, although the
14759 copies on the target can be stripped as long as the copies on the host are
14762 @cindex where to look for shared libraries
14763 For remote debugging, you need to tell @value{GDBN} where the target
14764 libraries are, so that it can load the correct copies---otherwise, it
14765 may try to load the host's libraries. @value{GDBN} has two variables
14766 to specify the search directories for target libraries.
14769 @cindex prefix for shared library file names
14770 @cindex system root, alternate
14771 @kindex set solib-absolute-prefix
14772 @kindex set sysroot
14773 @item set sysroot @var{path}
14774 Use @var{path} as the system root for the program being debugged. Any
14775 absolute shared library paths will be prefixed with @var{path}; many
14776 runtime loaders store the absolute paths to the shared library in the
14777 target program's memory. If you use @code{set sysroot} to find shared
14778 libraries, they need to be laid out in the same way that they are on
14779 the target, with e.g.@: a @file{/lib} and @file{/usr/lib} hierarchy
14782 If @var{path} starts with the sequence @file{remote:}, @value{GDBN} will
14783 retrieve the target libraries from the remote system. This is only
14784 supported when using a remote target that supports the @code{remote get}
14785 command (@pxref{File Transfer,,Sending files to a remote system}).
14786 The part of @var{path} following the initial @file{remote:}
14787 (if present) is used as system root prefix on the remote file system.
14788 @footnote{If you want to specify a local system root using a directory
14789 that happens to be named @file{remote:}, you need to use some equivalent
14790 variant of the name like @file{./remote:}.}
14792 For targets with an MS-DOS based filesystem, such as MS-Windows and
14793 SymbianOS, @value{GDBN} tries prefixing a few variants of the target
14794 absolute file name with @var{path}. But first, on Unix hosts,
14795 @value{GDBN} converts all backslash directory separators into forward
14796 slashes, because the backslash is not a directory separator on Unix:
14799 c:\foo\bar.dll @result{} c:/foo/bar.dll
14802 Then, @value{GDBN} attempts prefixing the target file name with
14803 @var{path}, and looks for the resulting file name in the host file
14807 c:/foo/bar.dll @result{} /path/to/sysroot/c:/foo/bar.dll
14810 If that does not find the shared library, @value{GDBN} tries removing
14811 the @samp{:} character from the drive spec, both for convenience, and,
14812 for the case of the host file system not supporting file names with
14816 c:/foo/bar.dll @result{} /path/to/sysroot/c/foo/bar.dll
14819 This makes it possible to have a system root that mirrors a target
14820 with more than one drive. E.g., you may want to setup your local
14821 copies of the target system shared libraries like so (note @samp{c} vs
14825 @file{/path/to/sysroot/c/sys/bin/foo.dll}
14826 @file{/path/to/sysroot/c/sys/bin/bar.dll}
14827 @file{/path/to/sysroot/z/sys/bin/bar.dll}
14831 and point the system root at @file{/path/to/sysroot}, so that
14832 @value{GDBN} can find the correct copies of both
14833 @file{c:\sys\bin\foo.dll}, and @file{z:\sys\bin\bar.dll}.
14835 If that still does not find the shared library, @value{GDBN} tries
14836 removing the whole drive spec from the target file name:
14839 c:/foo/bar.dll @result{} /path/to/sysroot/foo/bar.dll
14842 This last lookup makes it possible to not care about the drive name,
14843 if you don't want or need to.
14845 The @code{set solib-absolute-prefix} command is an alias for @code{set
14848 @cindex default system root
14849 @cindex @samp{--with-sysroot}
14850 You can set the default system root by using the configure-time
14851 @samp{--with-sysroot} option. If the system root is inside
14852 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
14853 @samp{--exec-prefix}), then the default system root will be updated
14854 automatically if the installed @value{GDBN} is moved to a new
14857 @kindex show sysroot
14859 Display the current shared library prefix.
14861 @kindex set solib-search-path
14862 @item set solib-search-path @var{path}
14863 If this variable is set, @var{path} is a colon-separated list of
14864 directories to search for shared libraries. @samp{solib-search-path}
14865 is used after @samp{sysroot} fails to locate the library, or if the
14866 path to the library is relative instead of absolute. If you want to
14867 use @samp{solib-search-path} instead of @samp{sysroot}, be sure to set
14868 @samp{sysroot} to a nonexistent directory to prevent @value{GDBN} from
14869 finding your host's libraries. @samp{sysroot} is preferred; setting
14870 it to a nonexistent directory may interfere with automatic loading
14871 of shared library symbols.
14873 @kindex show solib-search-path
14874 @item show solib-search-path
14875 Display the current shared library search path.
14877 @cindex DOS file-name semantics of file names.
14878 @kindex set target-file-system-kind (unix|dos-based|auto)
14879 @kindex show target-file-system-kind
14880 @item set target-file-system-kind @var{kind}
14881 Set assumed file system kind for target reported file names.
14883 Shared library file names as reported by the target system may not
14884 make sense as is on the system @value{GDBN} is running on. For
14885 example, when remote debugging a target that has MS-DOS based file
14886 system semantics, from a Unix host, the target may be reporting to
14887 @value{GDBN} a list of loaded shared libraries with file names such as
14888 @file{c:\Windows\kernel32.dll}. On Unix hosts, there's no concept of
14889 drive letters, so the @samp{c:\} prefix is not normally understood as
14890 indicating an absolute file name, and neither is the backslash
14891 normally considered a directory separator character. In that case,
14892 the native file system would interpret this whole absolute file name
14893 as a relative file name with no directory components. This would make
14894 it impossible to point @value{GDBN} at a copy of the remote target's
14895 shared libraries on the host using @code{set sysroot}, and impractical
14896 with @code{set solib-search-path}. Setting
14897 @code{target-file-system-kind} to @code{dos-based} tells @value{GDBN}
14898 to interpret such file names similarly to how the target would, and to
14899 map them to file names valid on @value{GDBN}'s native file system
14900 semantics. The value of @var{kind} can be @code{"auto"}, in addition
14901 to one of the supported file system kinds. In that case, @value{GDBN}
14902 tries to determine the appropriate file system variant based on the
14903 current target's operating system (@pxref{ABI, ,Configuring the
14904 Current ABI}). The supported file system settings are:
14908 Instruct @value{GDBN} to assume the target file system is of Unix
14909 kind. Only file names starting the forward slash (@samp{/}) character
14910 are considered absolute, and the directory separator character is also
14914 Instruct @value{GDBN} to assume the target file system is DOS based.
14915 File names starting with either a forward slash, or a drive letter
14916 followed by a colon (e.g., @samp{c:}), are considered absolute, and
14917 both the slash (@samp{/}) and the backslash (@samp{\\}) characters are
14918 considered directory separators.
14921 Instruct @value{GDBN} to use the file system kind associated with the
14922 target operating system (@pxref{ABI, ,Configuring the Current ABI}).
14923 This is the default.
14928 @node Separate Debug Files
14929 @section Debugging Information in Separate Files
14930 @cindex separate debugging information files
14931 @cindex debugging information in separate files
14932 @cindex @file{.debug} subdirectories
14933 @cindex debugging information directory, global
14934 @cindex global debugging information directory
14935 @cindex build ID, and separate debugging files
14936 @cindex @file{.build-id} directory
14938 @value{GDBN} allows you to put a program's debugging information in a
14939 file separate from the executable itself, in a way that allows
14940 @value{GDBN} to find and load the debugging information automatically.
14941 Since debugging information can be very large---sometimes larger
14942 than the executable code itself---some systems distribute debugging
14943 information for their executables in separate files, which users can
14944 install only when they need to debug a problem.
14946 @value{GDBN} supports two ways of specifying the separate debug info
14951 The executable contains a @dfn{debug link} that specifies the name of
14952 the separate debug info file. The separate debug file's name is
14953 usually @file{@var{executable}.debug}, where @var{executable} is the
14954 name of the corresponding executable file without leading directories
14955 (e.g., @file{ls.debug} for @file{/usr/bin/ls}). In addition, the
14956 debug link specifies a 32-bit @dfn{Cyclic Redundancy Check} (CRC)
14957 checksum for the debug file, which @value{GDBN} uses to validate that
14958 the executable and the debug file came from the same build.
14961 The executable contains a @dfn{build ID}, a unique bit string that is
14962 also present in the corresponding debug info file. (This is supported
14963 only on some operating systems, notably those which use the ELF format
14964 for binary files and the @sc{gnu} Binutils.) For more details about
14965 this feature, see the description of the @option{--build-id}
14966 command-line option in @ref{Options, , Command Line Options, ld.info,
14967 The GNU Linker}. The debug info file's name is not specified
14968 explicitly by the build ID, but can be computed from the build ID, see
14972 Depending on the way the debug info file is specified, @value{GDBN}
14973 uses two different methods of looking for the debug file:
14977 For the ``debug link'' method, @value{GDBN} looks up the named file in
14978 the directory of the executable file, then in a subdirectory of that
14979 directory named @file{.debug}, and finally under the global debug
14980 directory, in a subdirectory whose name is identical to the leading
14981 directories of the executable's absolute file name.
14984 For the ``build ID'' method, @value{GDBN} looks in the
14985 @file{.build-id} subdirectory of the global debug directory for a file
14986 named @file{@var{nn}/@var{nnnnnnnn}.debug}, where @var{nn} are the
14987 first 2 hex characters of the build ID bit string, and @var{nnnnnnnn}
14988 are the rest of the bit string. (Real build ID strings are 32 or more
14989 hex characters, not 10.)
14992 So, for example, suppose you ask @value{GDBN} to debug
14993 @file{/usr/bin/ls}, which has a debug link that specifies the
14994 file @file{ls.debug}, and a build ID whose value in hex is
14995 @code{abcdef1234}. If the global debug directory is
14996 @file{/usr/lib/debug}, then @value{GDBN} will look for the following
14997 debug information files, in the indicated order:
15001 @file{/usr/lib/debug/.build-id/ab/cdef1234.debug}
15003 @file{/usr/bin/ls.debug}
15005 @file{/usr/bin/.debug/ls.debug}
15007 @file{/usr/lib/debug/usr/bin/ls.debug}.
15010 You can set the global debugging info directory's name, and view the
15011 name @value{GDBN} is currently using.
15015 @kindex set debug-file-directory
15016 @item set debug-file-directory @var{directories}
15017 Set the directories which @value{GDBN} searches for separate debugging
15018 information files to @var{directory}. Multiple directory components can be set
15019 concatenating them by a directory separator.
15021 @kindex show debug-file-directory
15022 @item show debug-file-directory
15023 Show the directories @value{GDBN} searches for separate debugging
15028 @cindex @code{.gnu_debuglink} sections
15029 @cindex debug link sections
15030 A debug link is a special section of the executable file named
15031 @code{.gnu_debuglink}. The section must contain:
15035 A filename, with any leading directory components removed, followed by
15038 zero to three bytes of padding, as needed to reach the next four-byte
15039 boundary within the section, and
15041 a four-byte CRC checksum, stored in the same endianness used for the
15042 executable file itself. The checksum is computed on the debugging
15043 information file's full contents by the function given below, passing
15044 zero as the @var{crc} argument.
15047 Any executable file format can carry a debug link, as long as it can
15048 contain a section named @code{.gnu_debuglink} with the contents
15051 @cindex @code{.note.gnu.build-id} sections
15052 @cindex build ID sections
15053 The build ID is a special section in the executable file (and in other
15054 ELF binary files that @value{GDBN} may consider). This section is
15055 often named @code{.note.gnu.build-id}, but that name is not mandatory.
15056 It contains unique identification for the built files---the ID remains
15057 the same across multiple builds of the same build tree. The default
15058 algorithm SHA1 produces 160 bits (40 hexadecimal characters) of the
15059 content for the build ID string. The same section with an identical
15060 value is present in the original built binary with symbols, in its
15061 stripped variant, and in the separate debugging information file.
15063 The debugging information file itself should be an ordinary
15064 executable, containing a full set of linker symbols, sections, and
15065 debugging information. The sections of the debugging information file
15066 should have the same names, addresses, and sizes as the original file,
15067 but they need not contain any data---much like a @code{.bss} section
15068 in an ordinary executable.
15070 The @sc{gnu} binary utilities (Binutils) package includes the
15071 @samp{objcopy} utility that can produce
15072 the separated executable / debugging information file pairs using the
15073 following commands:
15076 @kbd{objcopy --only-keep-debug foo foo.debug}
15081 These commands remove the debugging
15082 information from the executable file @file{foo} and place it in the file
15083 @file{foo.debug}. You can use the first, second or both methods to link the
15088 The debug link method needs the following additional command to also leave
15089 behind a debug link in @file{foo}:
15092 @kbd{objcopy --add-gnu-debuglink=foo.debug foo}
15095 Ulrich Drepper's @file{elfutils} package, starting with version 0.53, contains
15096 a version of the @code{strip} command such that the command @kbd{strip foo -f
15097 foo.debug} has the same functionality as the two @code{objcopy} commands and
15098 the @code{ln -s} command above, together.
15101 Build ID gets embedded into the main executable using @code{ld --build-id} or
15102 the @value{NGCC} counterpart @code{gcc -Wl,--build-id}. Build ID support plus
15103 compatibility fixes for debug files separation are present in @sc{gnu} binary
15104 utilities (Binutils) package since version 2.18.
15109 @cindex CRC algorithm definition
15110 The CRC used in @code{.gnu_debuglink} is the CRC-32 defined in
15111 IEEE 802.3 using the polynomial:
15113 @c TexInfo requires naked braces for multi-digit exponents for Tex
15114 @c output, but this causes HTML output to barf. HTML has to be set using
15115 @c raw commands. So we end up having to specify this equation in 2
15120 <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>
15121 + <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
15127 @math{x^{32} + x^{26} + x^{23} + x^{22} + x^{16} + x^{12} + x^{11}}
15128 @math{+ x^{10} + x^8 + x^7 + x^5 + x^4 + x^2 + x + 1}
15132 The function is computed byte at a time, taking the least
15133 significant bit of each byte first. The initial pattern
15134 @code{0xffffffff} is used, to ensure leading zeros affect the CRC and
15135 the final result is inverted to ensure trailing zeros also affect the
15138 @emph{Note:} This is the same CRC polynomial as used in handling the
15139 @dfn{Remote Serial Protocol} @code{qCRC} packet (@pxref{Remote Protocol,
15140 , @value{GDBN} Remote Serial Protocol}). However in the
15141 case of the Remote Serial Protocol, the CRC is computed @emph{most}
15142 significant bit first, and the result is not inverted, so trailing
15143 zeros have no effect on the CRC value.
15145 To complete the description, we show below the code of the function
15146 which produces the CRC used in @code{.gnu_debuglink}. Inverting the
15147 initially supplied @code{crc} argument means that an initial call to
15148 this function passing in zero will start computing the CRC using
15151 @kindex gnu_debuglink_crc32
15154 gnu_debuglink_crc32 (unsigned long crc,
15155 unsigned char *buf, size_t len)
15157 static const unsigned long crc32_table[256] =
15159 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
15160 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
15161 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
15162 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
15163 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
15164 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
15165 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
15166 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
15167 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
15168 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
15169 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
15170 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
15171 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
15172 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
15173 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
15174 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
15175 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
15176 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
15177 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
15178 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
15179 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
15180 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
15181 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
15182 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
15183 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
15184 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
15185 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
15186 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
15187 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
15188 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
15189 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
15190 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
15191 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
15192 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
15193 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
15194 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
15195 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
15196 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
15197 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
15198 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
15199 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
15200 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
15201 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
15202 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
15203 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
15204 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
15205 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
15206 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
15207 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
15208 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
15209 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
15212 unsigned char *end;
15214 crc = ~crc & 0xffffffff;
15215 for (end = buf + len; buf < end; ++buf)
15216 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
15217 return ~crc & 0xffffffff;
15222 This computation does not apply to the ``build ID'' method.
15226 @section Index Files Speed Up @value{GDBN}
15227 @cindex index files
15228 @cindex @samp{.gdb_index} section
15230 When @value{GDBN} finds a symbol file, it scans the symbols in the
15231 file in order to construct an internal symbol table. This lets most
15232 @value{GDBN} operations work quickly---at the cost of a delay early
15233 on. For large programs, this delay can be quite lengthy, so
15234 @value{GDBN} provides a way to build an index, which speeds up
15237 The index is stored as a section in the symbol file. @value{GDBN} can
15238 write the index to a file, then you can put it into the symbol file
15239 using @command{objcopy}.
15241 To create an index file, use the @code{save gdb-index} command:
15244 @item save gdb-index @var{directory}
15245 @kindex save gdb-index
15246 Create an index file for each symbol file currently known by
15247 @value{GDBN}. Each file is named after its corresponding symbol file,
15248 with @samp{.gdb-index} appended, and is written into the given
15252 Once you have created an index file you can merge it into your symbol
15253 file, here named @file{symfile}, using @command{objcopy}:
15256 $ objcopy --add-section .gdb_index=symfile.gdb-index \
15257 --set-section-flags .gdb_index=readonly symfile symfile
15260 There are currently some limitation on indices. They only work when
15261 for DWARF debugging information, not stabs. And, they do not
15262 currently work for programs using Ada.
15264 @node Symbol Errors
15265 @section Errors Reading Symbol Files
15267 While reading a symbol file, @value{GDBN} occasionally encounters problems,
15268 such as symbol types it does not recognize, or known bugs in compiler
15269 output. By default, @value{GDBN} does not notify you of such problems, since
15270 they are relatively common and primarily of interest to people
15271 debugging compilers. If you are interested in seeing information
15272 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
15273 only one message about each such type of problem, no matter how many
15274 times the problem occurs; or you can ask @value{GDBN} to print more messages,
15275 to see how many times the problems occur, with the @code{set
15276 complaints} command (@pxref{Messages/Warnings, ,Optional Warnings and
15279 The messages currently printed, and their meanings, include:
15282 @item inner block not inside outer block in @var{symbol}
15284 The symbol information shows where symbol scopes begin and end
15285 (such as at the start of a function or a block of statements). This
15286 error indicates that an inner scope block is not fully contained
15287 in its outer scope blocks.
15289 @value{GDBN} circumvents the problem by treating the inner block as if it had
15290 the same scope as the outer block. In the error message, @var{symbol}
15291 may be shown as ``@code{(don't know)}'' if the outer block is not a
15294 @item block at @var{address} out of order
15296 The symbol information for symbol scope blocks should occur in
15297 order of increasing addresses. This error indicates that it does not
15300 @value{GDBN} does not circumvent this problem, and has trouble
15301 locating symbols in the source file whose symbols it is reading. (You
15302 can often determine what source file is affected by specifying
15303 @code{set verbose on}. @xref{Messages/Warnings, ,Optional Warnings and
15306 @item bad block start address patched
15308 The symbol information for a symbol scope block has a start address
15309 smaller than the address of the preceding source line. This is known
15310 to occur in the SunOS 4.1.1 (and earlier) C compiler.
15312 @value{GDBN} circumvents the problem by treating the symbol scope block as
15313 starting on the previous source line.
15315 @item bad string table offset in symbol @var{n}
15318 Symbol number @var{n} contains a pointer into the string table which is
15319 larger than the size of the string table.
15321 @value{GDBN} circumvents the problem by considering the symbol to have the
15322 name @code{foo}, which may cause other problems if many symbols end up
15325 @item unknown symbol type @code{0x@var{nn}}
15327 The symbol information contains new data types that @value{GDBN} does
15328 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
15329 uncomprehended information, in hexadecimal.
15331 @value{GDBN} circumvents the error by ignoring this symbol information.
15332 This usually allows you to debug your program, though certain symbols
15333 are not accessible. If you encounter such a problem and feel like
15334 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
15335 on @code{complain}, then go up to the function @code{read_dbx_symtab}
15336 and examine @code{*bufp} to see the symbol.
15338 @item stub type has NULL name
15340 @value{GDBN} could not find the full definition for a struct or class.
15342 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
15343 The symbol information for a C@t{++} member function is missing some
15344 information that recent versions of the compiler should have output for
15347 @item info mismatch between compiler and debugger
15349 @value{GDBN} could not parse a type specification output by the compiler.
15354 @section GDB Data Files
15356 @cindex prefix for data files
15357 @value{GDBN} will sometimes read an auxiliary data file. These files
15358 are kept in a directory known as the @dfn{data directory}.
15360 You can set the data directory's name, and view the name @value{GDBN}
15361 is currently using.
15364 @kindex set data-directory
15365 @item set data-directory @var{directory}
15366 Set the directory which @value{GDBN} searches for auxiliary data files
15367 to @var{directory}.
15369 @kindex show data-directory
15370 @item show data-directory
15371 Show the directory @value{GDBN} searches for auxiliary data files.
15374 @cindex default data directory
15375 @cindex @samp{--with-gdb-datadir}
15376 You can set the default data directory by using the configure-time
15377 @samp{--with-gdb-datadir} option. If the data directory is inside
15378 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
15379 @samp{--exec-prefix}), then the default data directory will be updated
15380 automatically if the installed @value{GDBN} is moved to a new
15384 @chapter Specifying a Debugging Target
15386 @cindex debugging target
15387 A @dfn{target} is the execution environment occupied by your program.
15389 Often, @value{GDBN} runs in the same host environment as your program;
15390 in that case, the debugging target is specified as a side effect when
15391 you use the @code{file} or @code{core} commands. When you need more
15392 flexibility---for example, running @value{GDBN} on a physically separate
15393 host, or controlling a standalone system over a serial port or a
15394 realtime system over a TCP/IP connection---you can use the @code{target}
15395 command to specify one of the target types configured for @value{GDBN}
15396 (@pxref{Target Commands, ,Commands for Managing Targets}).
15398 @cindex target architecture
15399 It is possible to build @value{GDBN} for several different @dfn{target
15400 architectures}. When @value{GDBN} is built like that, you can choose
15401 one of the available architectures with the @kbd{set architecture}
15405 @kindex set architecture
15406 @kindex show architecture
15407 @item set architecture @var{arch}
15408 This command sets the current target architecture to @var{arch}. The
15409 value of @var{arch} can be @code{"auto"}, in addition to one of the
15410 supported architectures.
15412 @item show architecture
15413 Show the current target architecture.
15415 @item set processor
15417 @kindex set processor
15418 @kindex show processor
15419 These are alias commands for, respectively, @code{set architecture}
15420 and @code{show architecture}.
15424 * Active Targets:: Active targets
15425 * Target Commands:: Commands for managing targets
15426 * Byte Order:: Choosing target byte order
15429 @node Active Targets
15430 @section Active Targets
15432 @cindex stacking targets
15433 @cindex active targets
15434 @cindex multiple targets
15436 There are multiple classes of targets such as: processes, executable files or
15437 recording sessions. Core files belong to the process class, making core file
15438 and process mutually exclusive. Otherwise, @value{GDBN} can work concurrently
15439 on multiple active targets, one in each class. This allows you to (for
15440 example) start a process and inspect its activity, while still having access to
15441 the executable file after the process finishes. Or if you start process
15442 recording (@pxref{Reverse Execution}) and @code{reverse-step} there, you are
15443 presented a virtual layer of the recording target, while the process target
15444 remains stopped at the chronologically last point of the process execution.
15446 Use the @code{core-file} and @code{exec-file} commands to select a new core
15447 file or executable target (@pxref{Files, ,Commands to Specify Files}). To
15448 specify as a target a process that is already running, use the @code{attach}
15449 command (@pxref{Attach, ,Debugging an Already-running Process}).
15451 @node Target Commands
15452 @section Commands for Managing Targets
15455 @item target @var{type} @var{parameters}
15456 Connects the @value{GDBN} host environment to a target machine or
15457 process. A target is typically a protocol for talking to debugging
15458 facilities. You use the argument @var{type} to specify the type or
15459 protocol of the target machine.
15461 Further @var{parameters} are interpreted by the target protocol, but
15462 typically include things like device names or host names to connect
15463 with, process numbers, and baud rates.
15465 The @code{target} command does not repeat if you press @key{RET} again
15466 after executing the command.
15468 @kindex help target
15470 Displays the names of all targets available. To display targets
15471 currently selected, use either @code{info target} or @code{info files}
15472 (@pxref{Files, ,Commands to Specify Files}).
15474 @item help target @var{name}
15475 Describe a particular target, including any parameters necessary to
15478 @kindex set gnutarget
15479 @item set gnutarget @var{args}
15480 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
15481 knows whether it is reading an @dfn{executable},
15482 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
15483 with the @code{set gnutarget} command. Unlike most @code{target} commands,
15484 with @code{gnutarget} the @code{target} refers to a program, not a machine.
15487 @emph{Warning:} To specify a file format with @code{set gnutarget},
15488 you must know the actual BFD name.
15492 @xref{Files, , Commands to Specify Files}.
15494 @kindex show gnutarget
15495 @item show gnutarget
15496 Use the @code{show gnutarget} command to display what file format
15497 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
15498 @value{GDBN} will determine the file format for each file automatically,
15499 and @code{show gnutarget} displays @samp{The current BDF target is "auto"}.
15502 @cindex common targets
15503 Here are some common targets (available, or not, depending on the GDB
15508 @item target exec @var{program}
15509 @cindex executable file target
15510 An executable file. @samp{target exec @var{program}} is the same as
15511 @samp{exec-file @var{program}}.
15513 @item target core @var{filename}
15514 @cindex core dump file target
15515 A core dump file. @samp{target core @var{filename}} is the same as
15516 @samp{core-file @var{filename}}.
15518 @item target remote @var{medium}
15519 @cindex remote target
15520 A remote system connected to @value{GDBN} via a serial line or network
15521 connection. This command tells @value{GDBN} to use its own remote
15522 protocol over @var{medium} for debugging. @xref{Remote Debugging}.
15524 For example, if you have a board connected to @file{/dev/ttya} on the
15525 machine running @value{GDBN}, you could say:
15528 target remote /dev/ttya
15531 @code{target remote} supports the @code{load} command. This is only
15532 useful if you have some other way of getting the stub to the target
15533 system, and you can put it somewhere in memory where it won't get
15534 clobbered by the download.
15536 @item target sim @r{[}@var{simargs}@r{]} @dots{}
15537 @cindex built-in simulator target
15538 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
15546 works; however, you cannot assume that a specific memory map, device
15547 drivers, or even basic I/O is available, although some simulators do
15548 provide these. For info about any processor-specific simulator details,
15549 see the appropriate section in @ref{Embedded Processors, ,Embedded
15554 Some configurations may include these targets as well:
15558 @item target nrom @var{dev}
15559 @cindex NetROM ROM emulator target
15560 NetROM ROM emulator. This target only supports downloading.
15564 Different targets are available on different configurations of @value{GDBN};
15565 your configuration may have more or fewer targets.
15567 Many remote targets require you to download the executable's code once
15568 you've successfully established a connection. You may wish to control
15569 various aspects of this process.
15574 @kindex set hash@r{, for remote monitors}
15575 @cindex hash mark while downloading
15576 This command controls whether a hash mark @samp{#} is displayed while
15577 downloading a file to the remote monitor. If on, a hash mark is
15578 displayed after each S-record is successfully downloaded to the
15582 @kindex show hash@r{, for remote monitors}
15583 Show the current status of displaying the hash mark.
15585 @item set debug monitor
15586 @kindex set debug monitor
15587 @cindex display remote monitor communications
15588 Enable or disable display of communications messages between
15589 @value{GDBN} and the remote monitor.
15591 @item show debug monitor
15592 @kindex show debug monitor
15593 Show the current status of displaying communications between
15594 @value{GDBN} and the remote monitor.
15599 @kindex load @var{filename}
15600 @item load @var{filename}
15602 Depending on what remote debugging facilities are configured into
15603 @value{GDBN}, the @code{load} command may be available. Where it exists, it
15604 is meant to make @var{filename} (an executable) available for debugging
15605 on the remote system---by downloading, or dynamic linking, for example.
15606 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
15607 the @code{add-symbol-file} command.
15609 If your @value{GDBN} does not have a @code{load} command, attempting to
15610 execute it gets the error message ``@code{You can't do that when your
15611 target is @dots{}}''
15613 The file is loaded at whatever address is specified in the executable.
15614 For some object file formats, you can specify the load address when you
15615 link the program; for other formats, like a.out, the object file format
15616 specifies a fixed address.
15617 @c FIXME! This would be a good place for an xref to the GNU linker doc.
15619 Depending on the remote side capabilities, @value{GDBN} may be able to
15620 load programs into flash memory.
15622 @code{load} does not repeat if you press @key{RET} again after using it.
15626 @section Choosing Target Byte Order
15628 @cindex choosing target byte order
15629 @cindex target byte order
15631 Some types of processors, such as the MIPS, PowerPC, and Renesas SH,
15632 offer the ability to run either big-endian or little-endian byte
15633 orders. Usually the executable or symbol will include a bit to
15634 designate the endian-ness, and you will not need to worry about
15635 which to use. However, you may still find it useful to adjust
15636 @value{GDBN}'s idea of processor endian-ness manually.
15640 @item set endian big
15641 Instruct @value{GDBN} to assume the target is big-endian.
15643 @item set endian little
15644 Instruct @value{GDBN} to assume the target is little-endian.
15646 @item set endian auto
15647 Instruct @value{GDBN} to use the byte order associated with the
15651 Display @value{GDBN}'s current idea of the target byte order.
15655 Note that these commands merely adjust interpretation of symbolic
15656 data on the host, and that they have absolutely no effect on the
15660 @node Remote Debugging
15661 @chapter Debugging Remote Programs
15662 @cindex remote debugging
15664 If you are trying to debug a program running on a machine that cannot run
15665 @value{GDBN} in the usual way, it is often useful to use remote debugging.
15666 For example, you might use remote debugging on an operating system kernel,
15667 or on a small system which does not have a general purpose operating system
15668 powerful enough to run a full-featured debugger.
15670 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
15671 to make this work with particular debugging targets. In addition,
15672 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
15673 but not specific to any particular target system) which you can use if you
15674 write the remote stubs---the code that runs on the remote system to
15675 communicate with @value{GDBN}.
15677 Other remote targets may be available in your
15678 configuration of @value{GDBN}; use @code{help target} to list them.
15681 * Connecting:: Connecting to a remote target
15682 * File Transfer:: Sending files to a remote system
15683 * Server:: Using the gdbserver program
15684 * Remote Configuration:: Remote configuration
15685 * Remote Stub:: Implementing a remote stub
15689 @section Connecting to a Remote Target
15691 On the @value{GDBN} host machine, you will need an unstripped copy of
15692 your program, since @value{GDBN} needs symbol and debugging information.
15693 Start up @value{GDBN} as usual, using the name of the local copy of your
15694 program as the first argument.
15696 @cindex @code{target remote}
15697 @value{GDBN} can communicate with the target over a serial line, or
15698 over an @acronym{IP} network using @acronym{TCP} or @acronym{UDP}. In
15699 each case, @value{GDBN} uses the same protocol for debugging your
15700 program; only the medium carrying the debugging packets varies. The
15701 @code{target remote} command establishes a connection to the target.
15702 Its arguments indicate which medium to use:
15706 @item target remote @var{serial-device}
15707 @cindex serial line, @code{target remote}
15708 Use @var{serial-device} to communicate with the target. For example,
15709 to use a serial line connected to the device named @file{/dev/ttyb}:
15712 target remote /dev/ttyb
15715 If you're using a serial line, you may want to give @value{GDBN} the
15716 @w{@samp{--baud}} option, or use the @code{set remotebaud} command
15717 (@pxref{Remote Configuration, set remotebaud}) before the
15718 @code{target} command.
15720 @item target remote @code{@var{host}:@var{port}}
15721 @itemx target remote @code{tcp:@var{host}:@var{port}}
15722 @cindex @acronym{TCP} port, @code{target remote}
15723 Debug using a @acronym{TCP} connection to @var{port} on @var{host}.
15724 The @var{host} may be either a host name or a numeric @acronym{IP}
15725 address; @var{port} must be a decimal number. The @var{host} could be
15726 the target machine itself, if it is directly connected to the net, or
15727 it might be a terminal server which in turn has a serial line to the
15730 For example, to connect to port 2828 on a terminal server named
15734 target remote manyfarms:2828
15737 If your remote target is actually running on the same machine as your
15738 debugger session (e.g.@: a simulator for your target running on the
15739 same host), you can omit the hostname. For example, to connect to
15740 port 1234 on your local machine:
15743 target remote :1234
15747 Note that the colon is still required here.
15749 @item target remote @code{udp:@var{host}:@var{port}}
15750 @cindex @acronym{UDP} port, @code{target remote}
15751 Debug using @acronym{UDP} packets to @var{port} on @var{host}. For example, to
15752 connect to @acronym{UDP} port 2828 on a terminal server named @code{manyfarms}:
15755 target remote udp:manyfarms:2828
15758 When using a @acronym{UDP} connection for remote debugging, you should
15759 keep in mind that the `U' stands for ``Unreliable''. @acronym{UDP}
15760 can silently drop packets on busy or unreliable networks, which will
15761 cause havoc with your debugging session.
15763 @item target remote | @var{command}
15764 @cindex pipe, @code{target remote} to
15765 Run @var{command} in the background and communicate with it using a
15766 pipe. The @var{command} is a shell command, to be parsed and expanded
15767 by the system's command shell, @code{/bin/sh}; it should expect remote
15768 protocol packets on its standard input, and send replies on its
15769 standard output. You could use this to run a stand-alone simulator
15770 that speaks the remote debugging protocol, to make net connections
15771 using programs like @code{ssh}, or for other similar tricks.
15773 If @var{command} closes its standard output (perhaps by exiting),
15774 @value{GDBN} will try to send it a @code{SIGTERM} signal. (If the
15775 program has already exited, this will have no effect.)
15779 Once the connection has been established, you can use all the usual
15780 commands to examine and change data. The remote program is already
15781 running; you can use @kbd{step} and @kbd{continue}, and you do not
15782 need to use @kbd{run}.
15784 @cindex interrupting remote programs
15785 @cindex remote programs, interrupting
15786 Whenever @value{GDBN} is waiting for the remote program, if you type the
15787 interrupt character (often @kbd{Ctrl-c}), @value{GDBN} attempts to stop the
15788 program. This may or may not succeed, depending in part on the hardware
15789 and the serial drivers the remote system uses. If you type the
15790 interrupt character once again, @value{GDBN} displays this prompt:
15793 Interrupted while waiting for the program.
15794 Give up (and stop debugging it)? (y or n)
15797 If you type @kbd{y}, @value{GDBN} abandons the remote debugging session.
15798 (If you decide you want to try again later, you can use @samp{target
15799 remote} again to connect once more.) If you type @kbd{n}, @value{GDBN}
15800 goes back to waiting.
15803 @kindex detach (remote)
15805 When you have finished debugging the remote program, you can use the
15806 @code{detach} command to release it from @value{GDBN} control.
15807 Detaching from the target normally resumes its execution, but the results
15808 will depend on your particular remote stub. After the @code{detach}
15809 command, @value{GDBN} is free to connect to another target.
15813 The @code{disconnect} command behaves like @code{detach}, except that
15814 the target is generally not resumed. It will wait for @value{GDBN}
15815 (this instance or another one) to connect and continue debugging. After
15816 the @code{disconnect} command, @value{GDBN} is again free to connect to
15819 @cindex send command to remote monitor
15820 @cindex extend @value{GDBN} for remote targets
15821 @cindex add new commands for external monitor
15823 @item monitor @var{cmd}
15824 This command allows you to send arbitrary commands directly to the
15825 remote monitor. Since @value{GDBN} doesn't care about the commands it
15826 sends like this, this command is the way to extend @value{GDBN}---you
15827 can add new commands that only the external monitor will understand
15831 @node File Transfer
15832 @section Sending files to a remote system
15833 @cindex remote target, file transfer
15834 @cindex file transfer
15835 @cindex sending files to remote systems
15837 Some remote targets offer the ability to transfer files over the same
15838 connection used to communicate with @value{GDBN}. This is convenient
15839 for targets accessible through other means, e.g.@: @sc{gnu}/Linux systems
15840 running @code{gdbserver} over a network interface. For other targets,
15841 e.g.@: embedded devices with only a single serial port, this may be
15842 the only way to upload or download files.
15844 Not all remote targets support these commands.
15848 @item remote put @var{hostfile} @var{targetfile}
15849 Copy file @var{hostfile} from the host system (the machine running
15850 @value{GDBN}) to @var{targetfile} on the target system.
15853 @item remote get @var{targetfile} @var{hostfile}
15854 Copy file @var{targetfile} from the target system to @var{hostfile}
15855 on the host system.
15857 @kindex remote delete
15858 @item remote delete @var{targetfile}
15859 Delete @var{targetfile} from the target system.
15864 @section Using the @code{gdbserver} Program
15867 @cindex remote connection without stubs
15868 @code{gdbserver} is a control program for Unix-like systems, which
15869 allows you to connect your program with a remote @value{GDBN} via
15870 @code{target remote}---but without linking in the usual debugging stub.
15872 @code{gdbserver} is not a complete replacement for the debugging stubs,
15873 because it requires essentially the same operating-system facilities
15874 that @value{GDBN} itself does. In fact, a system that can run
15875 @code{gdbserver} to connect to a remote @value{GDBN} could also run
15876 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
15877 because it is a much smaller program than @value{GDBN} itself. It is
15878 also easier to port than all of @value{GDBN}, so you may be able to get
15879 started more quickly on a new system by using @code{gdbserver}.
15880 Finally, if you develop code for real-time systems, you may find that
15881 the tradeoffs involved in real-time operation make it more convenient to
15882 do as much development work as possible on another system, for example
15883 by cross-compiling. You can use @code{gdbserver} to make a similar
15884 choice for debugging.
15886 @value{GDBN} and @code{gdbserver} communicate via either a serial line
15887 or a TCP connection, using the standard @value{GDBN} remote serial
15891 @emph{Warning:} @code{gdbserver} does not have any built-in security.
15892 Do not run @code{gdbserver} connected to any public network; a
15893 @value{GDBN} connection to @code{gdbserver} provides access to the
15894 target system with the same privileges as the user running
15898 @subsection Running @code{gdbserver}
15899 @cindex arguments, to @code{gdbserver}
15901 Run @code{gdbserver} on the target system. You need a copy of the
15902 program you want to debug, including any libraries it requires.
15903 @code{gdbserver} does not need your program's symbol table, so you can
15904 strip the program if necessary to save space. @value{GDBN} on the host
15905 system does all the symbol handling.
15907 To use the server, you must tell it how to communicate with @value{GDBN};
15908 the name of your program; and the arguments for your program. The usual
15912 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
15915 @var{comm} is either a device name (to use a serial line) or a TCP
15916 hostname and portnumber. For example, to debug Emacs with the argument
15917 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
15921 target> gdbserver /dev/com1 emacs foo.txt
15924 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
15927 To use a TCP connection instead of a serial line:
15930 target> gdbserver host:2345 emacs foo.txt
15933 The only difference from the previous example is the first argument,
15934 specifying that you are communicating with the host @value{GDBN} via
15935 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
15936 expect a TCP connection from machine @samp{host} to local TCP port 2345.
15937 (Currently, the @samp{host} part is ignored.) You can choose any number
15938 you want for the port number as long as it does not conflict with any
15939 TCP ports already in use on the target system (for example, @code{23} is
15940 reserved for @code{telnet}).@footnote{If you choose a port number that
15941 conflicts with another service, @code{gdbserver} prints an error message
15942 and exits.} You must use the same port number with the host @value{GDBN}
15943 @code{target remote} command.
15945 @subsubsection Attaching to a Running Program
15947 On some targets, @code{gdbserver} can also attach to running programs.
15948 This is accomplished via the @code{--attach} argument. The syntax is:
15951 target> gdbserver --attach @var{comm} @var{pid}
15954 @var{pid} is the process ID of a currently running process. It isn't necessary
15955 to point @code{gdbserver} at a binary for the running process.
15958 @cindex attach to a program by name
15959 You can debug processes by name instead of process ID if your target has the
15960 @code{pidof} utility:
15963 target> gdbserver --attach @var{comm} `pidof @var{program}`
15966 In case more than one copy of @var{program} is running, or @var{program}
15967 has multiple threads, most versions of @code{pidof} support the
15968 @code{-s} option to only return the first process ID.
15970 @subsubsection Multi-Process Mode for @code{gdbserver}
15971 @cindex gdbserver, multiple processes
15972 @cindex multiple processes with gdbserver
15974 When you connect to @code{gdbserver} using @code{target remote},
15975 @code{gdbserver} debugs the specified program only once. When the
15976 program exits, or you detach from it, @value{GDBN} closes the connection
15977 and @code{gdbserver} exits.
15979 If you connect using @kbd{target extended-remote}, @code{gdbserver}
15980 enters multi-process mode. When the debugged program exits, or you
15981 detach from it, @value{GDBN} stays connected to @code{gdbserver} even
15982 though no program is running. The @code{run} and @code{attach}
15983 commands instruct @code{gdbserver} to run or attach to a new program.
15984 The @code{run} command uses @code{set remote exec-file} (@pxref{set
15985 remote exec-file}) to select the program to run. Command line
15986 arguments are supported, except for wildcard expansion and I/O
15987 redirection (@pxref{Arguments}).
15989 To start @code{gdbserver} without supplying an initial command to run
15990 or process ID to attach, use the @option{--multi} command line option.
15991 Then you can connect using @kbd{target extended-remote} and start
15992 the program you want to debug.
15994 @code{gdbserver} does not automatically exit in multi-process mode.
15995 You can terminate it by using @code{monitor exit}
15996 (@pxref{Monitor Commands for gdbserver}).
15998 @subsubsection Other Command-Line Arguments for @code{gdbserver}
16000 The @option{--debug} option tells @code{gdbserver} to display extra
16001 status information about the debugging process. The
16002 @option{--remote-debug} option tells @code{gdbserver} to display
16003 remote protocol debug output. These options are intended for
16004 @code{gdbserver} development and for bug reports to the developers.
16006 The @option{--wrapper} option specifies a wrapper to launch programs
16007 for debugging. The option should be followed by the name of the
16008 wrapper, then any command-line arguments to pass to the wrapper, then
16009 @kbd{--} indicating the end of the wrapper arguments.
16011 @code{gdbserver} runs the specified wrapper program with a combined
16012 command line including the wrapper arguments, then the name of the
16013 program to debug, then any arguments to the program. The wrapper
16014 runs until it executes your program, and then @value{GDBN} gains control.
16016 You can use any program that eventually calls @code{execve} with
16017 its arguments as a wrapper. Several standard Unix utilities do
16018 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
16019 with @code{exec "$@@"} will also work.
16021 For example, you can use @code{env} to pass an environment variable to
16022 the debugged program, without setting the variable in @code{gdbserver}'s
16026 $ gdbserver --wrapper env LD_PRELOAD=libtest.so -- :2222 ./testprog
16029 @subsection Connecting to @code{gdbserver}
16031 Run @value{GDBN} on the host system.
16033 First make sure you have the necessary symbol files. Load symbols for
16034 your application using the @code{file} command before you connect. Use
16035 @code{set sysroot} to locate target libraries (unless your @value{GDBN}
16036 was compiled with the correct sysroot using @code{--with-sysroot}).
16038 The symbol file and target libraries must exactly match the executable
16039 and libraries on the target, with one exception: the files on the host
16040 system should not be stripped, even if the files on the target system
16041 are. Mismatched or missing files will lead to confusing results
16042 during debugging. On @sc{gnu}/Linux targets, mismatched or missing
16043 files may also prevent @code{gdbserver} from debugging multi-threaded
16046 Connect to your target (@pxref{Connecting,,Connecting to a Remote Target}).
16047 For TCP connections, you must start up @code{gdbserver} prior to using
16048 the @code{target remote} command. Otherwise you may get an error whose
16049 text depends on the host system, but which usually looks something like
16050 @samp{Connection refused}. Don't use the @code{load}
16051 command in @value{GDBN} when using @code{gdbserver}, since the program is
16052 already on the target.
16054 @subsection Monitor Commands for @code{gdbserver}
16055 @cindex monitor commands, for @code{gdbserver}
16056 @anchor{Monitor Commands for gdbserver}
16058 During a @value{GDBN} session using @code{gdbserver}, you can use the
16059 @code{monitor} command to send special requests to @code{gdbserver}.
16060 Here are the available commands.
16064 List the available monitor commands.
16066 @item monitor set debug 0
16067 @itemx monitor set debug 1
16068 Disable or enable general debugging messages.
16070 @item monitor set remote-debug 0
16071 @itemx monitor set remote-debug 1
16072 Disable or enable specific debugging messages associated with the remote
16073 protocol (@pxref{Remote Protocol}).
16075 @item monitor set libthread-db-search-path [PATH]
16076 @cindex gdbserver, search path for @code{libthread_db}
16077 When this command is issued, @var{path} is a colon-separated list of
16078 directories to search for @code{libthread_db} (@pxref{Threads,,set
16079 libthread-db-search-path}). If you omit @var{path},
16080 @samp{libthread-db-search-path} will be reset to an empty list.
16083 Tell gdbserver to exit immediately. This command should be followed by
16084 @code{disconnect} to close the debugging session. @code{gdbserver} will
16085 detach from any attached processes and kill any processes it created.
16086 Use @code{monitor exit} to terminate @code{gdbserver} at the end
16087 of a multi-process mode debug session.
16091 @subsection Tracepoints support in @code{gdbserver}
16092 @cindex tracepoints support in @code{gdbserver}
16094 On some targets, @code{gdbserver} supports tracepoints, fast
16095 tracepoints and static tracepoints.
16097 For fast or static tracepoints to work, a special library called the
16098 @dfn{in-process agent} (IPA), must be loaded in the inferior process.
16099 This library is built and distributed as an integral part of
16100 @code{gdbserver}. In addition, support for static tracepoints
16101 requires building the in-process agent library with static tracepoints
16102 support. At present, the UST (LTTng Userspace Tracer,
16103 @url{http://lttng.org/ust}) tracing engine is supported. This support
16104 is automatically available if UST development headers are found in the
16105 standard include path when @code{gdbserver} is built, or if
16106 @code{gdbserver} was explicitly configured using @option{--with-ust}
16107 to point at such headers. You can explicitly disable the support
16108 using @option{--with-ust=no}.
16110 There are several ways to load the in-process agent in your program:
16113 @item Specifying it as dependency at link time
16115 You can link your program dynamically with the in-process agent
16116 library. On most systems, this is accomplished by adding
16117 @code{-linproctrace} to the link command.
16119 @item Using the system's preloading mechanisms
16121 You can force loading the in-process agent at startup time by using
16122 your system's support for preloading shared libraries. Many Unixes
16123 support the concept of preloading user defined libraries. In most
16124 cases, you do that by specifying @code{LD_PRELOAD=libinproctrace.so}
16125 in the environment. See also the description of @code{gdbserver}'s
16126 @option{--wrapper} command line option.
16128 @item Using @value{GDBN} to force loading the agent at run time
16130 On some systems, you can force the inferior to load a shared library,
16131 by calling a dynamic loader function in the inferior that takes care
16132 of dynamically looking up and loading a shared library. On most Unix
16133 systems, the function is @code{dlopen}. You'll use the @code{call}
16134 command for that. For example:
16137 (@value{GDBP}) call dlopen ("libinproctrace.so", ...)
16140 Note that on most Unix systems, for the @code{dlopen} function to be
16141 available, the program needs to be linked with @code{-ldl}.
16144 On systems that have a userspace dynamic loader, like most Unix
16145 systems, when you connect to @code{gdbserver} using @code{target
16146 remote}, you'll find that the program is stopped at the dynamic
16147 loader's entry point, and no shared library has been loaded in the
16148 program's address space yet, including the in-process agent. In that
16149 case, before being able to use any of the fast or static tracepoints
16150 features, you need to let the loader run and load the shared
16151 libraries. The simplest way to do that is to run the program to the
16152 main procedure. E.g., if debugging a C or C@t{++} program, start
16153 @code{gdbserver} like so:
16156 $ gdbserver :9999 myprogram
16159 Start GDB and connect to @code{gdbserver} like so, and run to main:
16163 (@value{GDBP}) target remote myhost:9999
16164 0x00007f215893ba60 in ?? () from /lib64/ld-linux-x86-64.so.2
16165 (@value{GDBP}) b main
16166 (@value{GDBP}) continue
16169 The in-process tracing agent library should now be loaded into the
16170 process; you can confirm it with the @code{info sharedlibrary}
16171 command, which will list @file{libinproctrace.so} as loaded in the
16172 process. You are now ready to install fast tracepoints, list static
16173 tracepoint markers, probe static tracepoints markers, and start
16176 @node Remote Configuration
16177 @section Remote Configuration
16180 @kindex show remote
16181 This section documents the configuration options available when
16182 debugging remote programs. For the options related to the File I/O
16183 extensions of the remote protocol, see @ref{system,
16184 system-call-allowed}.
16187 @item set remoteaddresssize @var{bits}
16188 @cindex address size for remote targets
16189 @cindex bits in remote address
16190 Set the maximum size of address in a memory packet to the specified
16191 number of bits. @value{GDBN} will mask off the address bits above
16192 that number, when it passes addresses to the remote target. The
16193 default value is the number of bits in the target's address.
16195 @item show remoteaddresssize
16196 Show the current value of remote address size in bits.
16198 @item set remotebaud @var{n}
16199 @cindex baud rate for remote targets
16200 Set the baud rate for the remote serial I/O to @var{n} baud. The
16201 value is used to set the speed of the serial port used for debugging
16204 @item show remotebaud
16205 Show the current speed of the remote connection.
16207 @item set remotebreak
16208 @cindex interrupt remote programs
16209 @cindex BREAK signal instead of Ctrl-C
16210 @anchor{set remotebreak}
16211 If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote
16212 when you type @kbd{Ctrl-c} to interrupt the program running
16213 on the remote. If set to off, @value{GDBN} sends the @samp{Ctrl-C}
16214 character instead. The default is off, since most remote systems
16215 expect to see @samp{Ctrl-C} as the interrupt signal.
16217 @item show remotebreak
16218 Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to
16219 interrupt the remote program.
16221 @item set remoteflow on
16222 @itemx set remoteflow off
16223 @kindex set remoteflow
16224 Enable or disable hardware flow control (@code{RTS}/@code{CTS})
16225 on the serial port used to communicate to the remote target.
16227 @item show remoteflow
16228 @kindex show remoteflow
16229 Show the current setting of hardware flow control.
16231 @item set remotelogbase @var{base}
16232 Set the base (a.k.a.@: radix) of logging serial protocol
16233 communications to @var{base}. Supported values of @var{base} are:
16234 @code{ascii}, @code{octal}, and @code{hex}. The default is
16237 @item show remotelogbase
16238 Show the current setting of the radix for logging remote serial
16241 @item set remotelogfile @var{file}
16242 @cindex record serial communications on file
16243 Record remote serial communications on the named @var{file}. The
16244 default is not to record at all.
16246 @item show remotelogfile.
16247 Show the current setting of the file name on which to record the
16248 serial communications.
16250 @item set remotetimeout @var{num}
16251 @cindex timeout for serial communications
16252 @cindex remote timeout
16253 Set the timeout limit to wait for the remote target to respond to
16254 @var{num} seconds. The default is 2 seconds.
16256 @item show remotetimeout
16257 Show the current number of seconds to wait for the remote target
16260 @cindex limit hardware breakpoints and watchpoints
16261 @cindex remote target, limit break- and watchpoints
16262 @anchor{set remote hardware-watchpoint-limit}
16263 @anchor{set remote hardware-breakpoint-limit}
16264 @item set remote hardware-watchpoint-limit @var{limit}
16265 @itemx set remote hardware-breakpoint-limit @var{limit}
16266 Restrict @value{GDBN} to using @var{limit} remote hardware breakpoint or
16267 watchpoints. A limit of -1, the default, is treated as unlimited.
16269 @item set remote exec-file @var{filename}
16270 @itemx show remote exec-file
16271 @anchor{set remote exec-file}
16272 @cindex executable file, for remote target
16273 Select the file used for @code{run} with @code{target
16274 extended-remote}. This should be set to a filename valid on the
16275 target system. If it is not set, the target will use a default
16276 filename (e.g.@: the last program run).
16278 @item set remote interrupt-sequence
16279 @cindex interrupt remote programs
16280 @cindex select Ctrl-C, BREAK or BREAK-g
16281 Allow the user to select one of @samp{Ctrl-C}, a @code{BREAK} or
16282 @samp{BREAK-g} as the
16283 sequence to the remote target in order to interrupt the execution.
16284 @samp{Ctrl-C} is a default. Some system prefers @code{BREAK} which
16285 is high level of serial line for some certain time.
16286 Linux kernel prefers @samp{BREAK-g}, a.k.a Magic SysRq g.
16287 It is @code{BREAK} signal followed by character @code{g}.
16289 @item show interrupt-sequence
16290 Show which of @samp{Ctrl-C}, @code{BREAK} or @code{BREAK-g}
16291 is sent by @value{GDBN} to interrupt the remote program.
16292 @code{BREAK-g} is BREAK signal followed by @code{g} and
16293 also known as Magic SysRq g.
16295 @item set remote interrupt-on-connect
16296 @cindex send interrupt-sequence on start
16297 Specify whether interrupt-sequence is sent to remote target when
16298 @value{GDBN} connects to it. This is mostly needed when you debug
16299 Linux kernel. Linux kernel expects @code{BREAK} followed by @code{g}
16300 which is known as Magic SysRq g in order to connect @value{GDBN}.
16302 @item show interrupt-on-connect
16303 Show whether interrupt-sequence is sent
16304 to remote target when @value{GDBN} connects to it.
16308 @item set tcp auto-retry on
16309 @cindex auto-retry, for remote TCP target
16310 Enable auto-retry for remote TCP connections. This is useful if the remote
16311 debugging agent is launched in parallel with @value{GDBN}; there is a race
16312 condition because the agent may not become ready to accept the connection
16313 before @value{GDBN} attempts to connect. When auto-retry is
16314 enabled, if the initial attempt to connect fails, @value{GDBN} reattempts
16315 to establish the connection using the timeout specified by
16316 @code{set tcp connect-timeout}.
16318 @item set tcp auto-retry off
16319 Do not auto-retry failed TCP connections.
16321 @item show tcp auto-retry
16322 Show the current auto-retry setting.
16324 @item set tcp connect-timeout @var{seconds}
16325 @cindex connection timeout, for remote TCP target
16326 @cindex timeout, for remote target connection
16327 Set the timeout for establishing a TCP connection to the remote target to
16328 @var{seconds}. The timeout affects both polling to retry failed connections
16329 (enabled by @code{set tcp auto-retry on}) and waiting for connections
16330 that are merely slow to complete, and represents an approximate cumulative
16333 @item show tcp connect-timeout
16334 Show the current connection timeout setting.
16337 @cindex remote packets, enabling and disabling
16338 The @value{GDBN} remote protocol autodetects the packets supported by
16339 your debugging stub. If you need to override the autodetection, you
16340 can use these commands to enable or disable individual packets. Each
16341 packet can be set to @samp{on} (the remote target supports this
16342 packet), @samp{off} (the remote target does not support this packet),
16343 or @samp{auto} (detect remote target support for this packet). They
16344 all default to @samp{auto}. For more information about each packet,
16345 see @ref{Remote Protocol}.
16347 During normal use, you should not have to use any of these commands.
16348 If you do, that may be a bug in your remote debugging stub, or a bug
16349 in @value{GDBN}. You may want to report the problem to the
16350 @value{GDBN} developers.
16352 For each packet @var{name}, the command to enable or disable the
16353 packet is @code{set remote @var{name}-packet}. The available settings
16356 @multitable @columnfractions 0.28 0.32 0.25
16359 @tab Related Features
16361 @item @code{fetch-register}
16363 @tab @code{info registers}
16365 @item @code{set-register}
16369 @item @code{binary-download}
16371 @tab @code{load}, @code{set}
16373 @item @code{read-aux-vector}
16374 @tab @code{qXfer:auxv:read}
16375 @tab @code{info auxv}
16377 @item @code{symbol-lookup}
16378 @tab @code{qSymbol}
16379 @tab Detecting multiple threads
16381 @item @code{attach}
16382 @tab @code{vAttach}
16385 @item @code{verbose-resume}
16387 @tab Stepping or resuming multiple threads
16393 @item @code{software-breakpoint}
16397 @item @code{hardware-breakpoint}
16401 @item @code{write-watchpoint}
16405 @item @code{read-watchpoint}
16409 @item @code{access-watchpoint}
16413 @item @code{target-features}
16414 @tab @code{qXfer:features:read}
16415 @tab @code{set architecture}
16417 @item @code{library-info}
16418 @tab @code{qXfer:libraries:read}
16419 @tab @code{info sharedlibrary}
16421 @item @code{memory-map}
16422 @tab @code{qXfer:memory-map:read}
16423 @tab @code{info mem}
16425 @item @code{read-sdata-object}
16426 @tab @code{qXfer:sdata:read}
16427 @tab @code{print $_sdata}
16429 @item @code{read-spu-object}
16430 @tab @code{qXfer:spu:read}
16431 @tab @code{info spu}
16433 @item @code{write-spu-object}
16434 @tab @code{qXfer:spu:write}
16435 @tab @code{info spu}
16437 @item @code{read-siginfo-object}
16438 @tab @code{qXfer:siginfo:read}
16439 @tab @code{print $_siginfo}
16441 @item @code{write-siginfo-object}
16442 @tab @code{qXfer:siginfo:write}
16443 @tab @code{set $_siginfo}
16445 @item @code{threads}
16446 @tab @code{qXfer:threads:read}
16447 @tab @code{info threads}
16449 @item @code{get-thread-local-@*storage-address}
16450 @tab @code{qGetTLSAddr}
16451 @tab Displaying @code{__thread} variables
16453 @item @code{get-thread-information-block-address}
16454 @tab @code{qGetTIBAddr}
16455 @tab Display MS-Windows Thread Information Block.
16457 @item @code{search-memory}
16458 @tab @code{qSearch:memory}
16461 @item @code{supported-packets}
16462 @tab @code{qSupported}
16463 @tab Remote communications parameters
16465 @item @code{pass-signals}
16466 @tab @code{QPassSignals}
16467 @tab @code{handle @var{signal}}
16469 @item @code{hostio-close-packet}
16470 @tab @code{vFile:close}
16471 @tab @code{remote get}, @code{remote put}
16473 @item @code{hostio-open-packet}
16474 @tab @code{vFile:open}
16475 @tab @code{remote get}, @code{remote put}
16477 @item @code{hostio-pread-packet}
16478 @tab @code{vFile:pread}
16479 @tab @code{remote get}, @code{remote put}
16481 @item @code{hostio-pwrite-packet}
16482 @tab @code{vFile:pwrite}
16483 @tab @code{remote get}, @code{remote put}
16485 @item @code{hostio-unlink-packet}
16486 @tab @code{vFile:unlink}
16487 @tab @code{remote delete}
16489 @item @code{noack-packet}
16490 @tab @code{QStartNoAckMode}
16491 @tab Packet acknowledgment
16493 @item @code{osdata}
16494 @tab @code{qXfer:osdata:read}
16495 @tab @code{info os}
16497 @item @code{query-attached}
16498 @tab @code{qAttached}
16499 @tab Querying remote process attach state.
16503 @section Implementing a Remote Stub
16505 @cindex debugging stub, example
16506 @cindex remote stub, example
16507 @cindex stub example, remote debugging
16508 The stub files provided with @value{GDBN} implement the target side of the
16509 communication protocol, and the @value{GDBN} side is implemented in the
16510 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
16511 these subroutines to communicate, and ignore the details. (If you're
16512 implementing your own stub file, you can still ignore the details: start
16513 with one of the existing stub files. @file{sparc-stub.c} is the best
16514 organized, and therefore the easiest to read.)
16516 @cindex remote serial debugging, overview
16517 To debug a program running on another machine (the debugging
16518 @dfn{target} machine), you must first arrange for all the usual
16519 prerequisites for the program to run by itself. For example, for a C
16524 A startup routine to set up the C runtime environment; these usually
16525 have a name like @file{crt0}. The startup routine may be supplied by
16526 your hardware supplier, or you may have to write your own.
16529 A C subroutine library to support your program's
16530 subroutine calls, notably managing input and output.
16533 A way of getting your program to the other machine---for example, a
16534 download program. These are often supplied by the hardware
16535 manufacturer, but you may have to write your own from hardware
16539 The next step is to arrange for your program to use a serial port to
16540 communicate with the machine where @value{GDBN} is running (the @dfn{host}
16541 machine). In general terms, the scheme looks like this:
16545 @value{GDBN} already understands how to use this protocol; when everything
16546 else is set up, you can simply use the @samp{target remote} command
16547 (@pxref{Targets,,Specifying a Debugging Target}).
16549 @item On the target,
16550 you must link with your program a few special-purpose subroutines that
16551 implement the @value{GDBN} remote serial protocol. The file containing these
16552 subroutines is called a @dfn{debugging stub}.
16554 On certain remote targets, you can use an auxiliary program
16555 @code{gdbserver} instead of linking a stub into your program.
16556 @xref{Server,,Using the @code{gdbserver} Program}, for details.
16559 The debugging stub is specific to the architecture of the remote
16560 machine; for example, use @file{sparc-stub.c} to debug programs on
16563 @cindex remote serial stub list
16564 These working remote stubs are distributed with @value{GDBN}:
16569 @cindex @file{i386-stub.c}
16572 For Intel 386 and compatible architectures.
16575 @cindex @file{m68k-stub.c}
16576 @cindex Motorola 680x0
16578 For Motorola 680x0 architectures.
16581 @cindex @file{sh-stub.c}
16584 For Renesas SH architectures.
16587 @cindex @file{sparc-stub.c}
16589 For @sc{sparc} architectures.
16591 @item sparcl-stub.c
16592 @cindex @file{sparcl-stub.c}
16595 For Fujitsu @sc{sparclite} architectures.
16599 The @file{README} file in the @value{GDBN} distribution may list other
16600 recently added stubs.
16603 * Stub Contents:: What the stub can do for you
16604 * Bootstrapping:: What you must do for the stub
16605 * Debug Session:: Putting it all together
16608 @node Stub Contents
16609 @subsection What the Stub Can Do for You
16611 @cindex remote serial stub
16612 The debugging stub for your architecture supplies these three
16616 @item set_debug_traps
16617 @findex set_debug_traps
16618 @cindex remote serial stub, initialization
16619 This routine arranges for @code{handle_exception} to run when your
16620 program stops. You must call this subroutine explicitly near the
16621 beginning of your program.
16623 @item handle_exception
16624 @findex handle_exception
16625 @cindex remote serial stub, main routine
16626 This is the central workhorse, but your program never calls it
16627 explicitly---the setup code arranges for @code{handle_exception} to
16628 run when a trap is triggered.
16630 @code{handle_exception} takes control when your program stops during
16631 execution (for example, on a breakpoint), and mediates communications
16632 with @value{GDBN} on the host machine. This is where the communications
16633 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
16634 representative on the target machine. It begins by sending summary
16635 information on the state of your program, then continues to execute,
16636 retrieving and transmitting any information @value{GDBN} needs, until you
16637 execute a @value{GDBN} command that makes your program resume; at that point,
16638 @code{handle_exception} returns control to your own code on the target
16642 @cindex @code{breakpoint} subroutine, remote
16643 Use this auxiliary subroutine to make your program contain a
16644 breakpoint. Depending on the particular situation, this may be the only
16645 way for @value{GDBN} to get control. For instance, if your target
16646 machine has some sort of interrupt button, you won't need to call this;
16647 pressing the interrupt button transfers control to
16648 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
16649 simply receiving characters on the serial port may also trigger a trap;
16650 again, in that situation, you don't need to call @code{breakpoint} from
16651 your own program---simply running @samp{target remote} from the host
16652 @value{GDBN} session gets control.
16654 Call @code{breakpoint} if none of these is true, or if you simply want
16655 to make certain your program stops at a predetermined point for the
16656 start of your debugging session.
16659 @node Bootstrapping
16660 @subsection What You Must Do for the Stub
16662 @cindex remote stub, support routines
16663 The debugging stubs that come with @value{GDBN} are set up for a particular
16664 chip architecture, but they have no information about the rest of your
16665 debugging target machine.
16667 First of all you need to tell the stub how to communicate with the
16671 @item int getDebugChar()
16672 @findex getDebugChar
16673 Write this subroutine to read a single character from the serial port.
16674 It may be identical to @code{getchar} for your target system; a
16675 different name is used to allow you to distinguish the two if you wish.
16677 @item void putDebugChar(int)
16678 @findex putDebugChar
16679 Write this subroutine to write a single character to the serial port.
16680 It may be identical to @code{putchar} for your target system; a
16681 different name is used to allow you to distinguish the two if you wish.
16684 @cindex control C, and remote debugging
16685 @cindex interrupting remote targets
16686 If you want @value{GDBN} to be able to stop your program while it is
16687 running, you need to use an interrupt-driven serial driver, and arrange
16688 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
16689 character). That is the character which @value{GDBN} uses to tell the
16690 remote system to stop.
16692 Getting the debugging target to return the proper status to @value{GDBN}
16693 probably requires changes to the standard stub; one quick and dirty way
16694 is to just execute a breakpoint instruction (the ``dirty'' part is that
16695 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
16697 Other routines you need to supply are:
16700 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
16701 @findex exceptionHandler
16702 Write this function to install @var{exception_address} in the exception
16703 handling tables. You need to do this because the stub does not have any
16704 way of knowing what the exception handling tables on your target system
16705 are like (for example, the processor's table might be in @sc{rom},
16706 containing entries which point to a table in @sc{ram}).
16707 @var{exception_number} is the exception number which should be changed;
16708 its meaning is architecture-dependent (for example, different numbers
16709 might represent divide by zero, misaligned access, etc). When this
16710 exception occurs, control should be transferred directly to
16711 @var{exception_address}, and the processor state (stack, registers,
16712 and so on) should be just as it is when a processor exception occurs. So if
16713 you want to use a jump instruction to reach @var{exception_address}, it
16714 should be a simple jump, not a jump to subroutine.
16716 For the 386, @var{exception_address} should be installed as an interrupt
16717 gate so that interrupts are masked while the handler runs. The gate
16718 should be at privilege level 0 (the most privileged level). The
16719 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
16720 help from @code{exceptionHandler}.
16722 @item void flush_i_cache()
16723 @findex flush_i_cache
16724 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
16725 instruction cache, if any, on your target machine. If there is no
16726 instruction cache, this subroutine may be a no-op.
16728 On target machines that have instruction caches, @value{GDBN} requires this
16729 function to make certain that the state of your program is stable.
16733 You must also make sure this library routine is available:
16736 @item void *memset(void *, int, int)
16738 This is the standard library function @code{memset} that sets an area of
16739 memory to a known value. If you have one of the free versions of
16740 @code{libc.a}, @code{memset} can be found there; otherwise, you must
16741 either obtain it from your hardware manufacturer, or write your own.
16744 If you do not use the GNU C compiler, you may need other standard
16745 library subroutines as well; this varies from one stub to another,
16746 but in general the stubs are likely to use any of the common library
16747 subroutines which @code{@value{NGCC}} generates as inline code.
16750 @node Debug Session
16751 @subsection Putting it All Together
16753 @cindex remote serial debugging summary
16754 In summary, when your program is ready to debug, you must follow these
16759 Make sure you have defined the supporting low-level routines
16760 (@pxref{Bootstrapping,,What You Must Do for the Stub}):
16762 @code{getDebugChar}, @code{putDebugChar},
16763 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
16767 Insert these lines near the top of your program:
16775 For the 680x0 stub only, you need to provide a variable called
16776 @code{exceptionHook}. Normally you just use:
16779 void (*exceptionHook)() = 0;
16783 but if before calling @code{set_debug_traps}, you set it to point to a
16784 function in your program, that function is called when
16785 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
16786 error). The function indicated by @code{exceptionHook} is called with
16787 one parameter: an @code{int} which is the exception number.
16790 Compile and link together: your program, the @value{GDBN} debugging stub for
16791 your target architecture, and the supporting subroutines.
16794 Make sure you have a serial connection between your target machine and
16795 the @value{GDBN} host, and identify the serial port on the host.
16798 @c The "remote" target now provides a `load' command, so we should
16799 @c document that. FIXME.
16800 Download your program to your target machine (or get it there by
16801 whatever means the manufacturer provides), and start it.
16804 Start @value{GDBN} on the host, and connect to the target
16805 (@pxref{Connecting,,Connecting to a Remote Target}).
16809 @node Configurations
16810 @chapter Configuration-Specific Information
16812 While nearly all @value{GDBN} commands are available for all native and
16813 cross versions of the debugger, there are some exceptions. This chapter
16814 describes things that are only available in certain configurations.
16816 There are three major categories of configurations: native
16817 configurations, where the host and target are the same, embedded
16818 operating system configurations, which are usually the same for several
16819 different processor architectures, and bare embedded processors, which
16820 are quite different from each other.
16825 * Embedded Processors::
16832 This section describes details specific to particular native
16837 * BSD libkvm Interface:: Debugging BSD kernel memory images
16838 * SVR4 Process Information:: SVR4 process information
16839 * DJGPP Native:: Features specific to the DJGPP port
16840 * Cygwin Native:: Features specific to the Cygwin port
16841 * Hurd Native:: Features specific to @sc{gnu} Hurd
16842 * Neutrino:: Features specific to QNX Neutrino
16843 * Darwin:: Features specific to Darwin
16849 On HP-UX systems, if you refer to a function or variable name that
16850 begins with a dollar sign, @value{GDBN} searches for a user or system
16851 name first, before it searches for a convenience variable.
16854 @node BSD libkvm Interface
16855 @subsection BSD libkvm Interface
16858 @cindex kernel memory image
16859 @cindex kernel crash dump
16861 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
16862 interface that provides a uniform interface for accessing kernel virtual
16863 memory images, including live systems and crash dumps. @value{GDBN}
16864 uses this interface to allow you to debug live kernels and kernel crash
16865 dumps on many native BSD configurations. This is implemented as a
16866 special @code{kvm} debugging target. For debugging a live system, load
16867 the currently running kernel into @value{GDBN} and connect to the
16871 (@value{GDBP}) @b{target kvm}
16874 For debugging crash dumps, provide the file name of the crash dump as an
16878 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
16881 Once connected to the @code{kvm} target, the following commands are
16887 Set current context from the @dfn{Process Control Block} (PCB) address.
16890 Set current context from proc address. This command isn't available on
16891 modern FreeBSD systems.
16894 @node SVR4 Process Information
16895 @subsection SVR4 Process Information
16897 @cindex examine process image
16898 @cindex process info via @file{/proc}
16900 Many versions of SVR4 and compatible systems provide a facility called
16901 @samp{/proc} that can be used to examine the image of a running
16902 process using file-system subroutines. If @value{GDBN} is configured
16903 for an operating system with this facility, the command @code{info
16904 proc} is available to report information about the process running
16905 your program, or about any process running on your system. @code{info
16906 proc} works only on SVR4 systems that include the @code{procfs} code.
16907 This includes, as of this writing, @sc{gnu}/Linux, OSF/1 (Digital
16908 Unix), Solaris, Irix, and Unixware, but not HP-UX, for example.
16914 @itemx info proc @var{process-id}
16915 Summarize available information about any running process. If a
16916 process ID is specified by @var{process-id}, display information about
16917 that process; otherwise display information about the program being
16918 debugged. The summary includes the debugged process ID, the command
16919 line used to invoke it, its current working directory, and its
16920 executable file's absolute file name.
16922 On some systems, @var{process-id} can be of the form
16923 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
16924 within a process. If the optional @var{pid} part is missing, it means
16925 a thread from the process being debugged (the leading @samp{/} still
16926 needs to be present, or else @value{GDBN} will interpret the number as
16927 a process ID rather than a thread ID).
16929 @item info proc mappings
16930 @cindex memory address space mappings
16931 Report the memory address space ranges accessible in the program, with
16932 information on whether the process has read, write, or execute access
16933 rights to each range. On @sc{gnu}/Linux systems, each memory range
16934 includes the object file which is mapped to that range, instead of the
16935 memory access rights to that range.
16937 @item info proc stat
16938 @itemx info proc status
16939 @cindex process detailed status information
16940 These subcommands are specific to @sc{gnu}/Linux systems. They show
16941 the process-related information, including the user ID and group ID;
16942 how many threads are there in the process; its virtual memory usage;
16943 the signals that are pending, blocked, and ignored; its TTY; its
16944 consumption of system and user time; its stack size; its @samp{nice}
16945 value; etc. For more information, see the @samp{proc} man page
16946 (type @kbd{man 5 proc} from your shell prompt).
16948 @item info proc all
16949 Show all the information about the process described under all of the
16950 above @code{info proc} subcommands.
16953 @comment These sub-options of 'info proc' were not included when
16954 @comment procfs.c was re-written. Keep their descriptions around
16955 @comment against the day when someone finds the time to put them back in.
16956 @kindex info proc times
16957 @item info proc times
16958 Starting time, user CPU time, and system CPU time for your program and
16961 @kindex info proc id
16963 Report on the process IDs related to your program: its own process ID,
16964 the ID of its parent, the process group ID, and the session ID.
16967 @item set procfs-trace
16968 @kindex set procfs-trace
16969 @cindex @code{procfs} API calls
16970 This command enables and disables tracing of @code{procfs} API calls.
16972 @item show procfs-trace
16973 @kindex show procfs-trace
16974 Show the current state of @code{procfs} API call tracing.
16976 @item set procfs-file @var{file}
16977 @kindex set procfs-file
16978 Tell @value{GDBN} to write @code{procfs} API trace to the named
16979 @var{file}. @value{GDBN} appends the trace info to the previous
16980 contents of the file. The default is to display the trace on the
16983 @item show procfs-file
16984 @kindex show procfs-file
16985 Show the file to which @code{procfs} API trace is written.
16987 @item proc-trace-entry
16988 @itemx proc-trace-exit
16989 @itemx proc-untrace-entry
16990 @itemx proc-untrace-exit
16991 @kindex proc-trace-entry
16992 @kindex proc-trace-exit
16993 @kindex proc-untrace-entry
16994 @kindex proc-untrace-exit
16995 These commands enable and disable tracing of entries into and exits
16996 from the @code{syscall} interface.
16999 @kindex info pidlist
17000 @cindex process list, QNX Neutrino
17001 For QNX Neutrino only, this command displays the list of all the
17002 processes and all the threads within each process.
17005 @kindex info meminfo
17006 @cindex mapinfo list, QNX Neutrino
17007 For QNX Neutrino only, this command displays the list of all mapinfos.
17011 @subsection Features for Debugging @sc{djgpp} Programs
17012 @cindex @sc{djgpp} debugging
17013 @cindex native @sc{djgpp} debugging
17014 @cindex MS-DOS-specific commands
17017 @sc{djgpp} is a port of the @sc{gnu} development tools to MS-DOS and
17018 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
17019 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
17020 top of real-mode DOS systems and their emulations.
17022 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
17023 defines a few commands specific to the @sc{djgpp} port. This
17024 subsection describes those commands.
17029 This is a prefix of @sc{djgpp}-specific commands which print
17030 information about the target system and important OS structures.
17033 @cindex MS-DOS system info
17034 @cindex free memory information (MS-DOS)
17035 @item info dos sysinfo
17036 This command displays assorted information about the underlying
17037 platform: the CPU type and features, the OS version and flavor, the
17038 DPMI version, and the available conventional and DPMI memory.
17043 @cindex segment descriptor tables
17044 @cindex descriptor tables display
17046 @itemx info dos ldt
17047 @itemx info dos idt
17048 These 3 commands display entries from, respectively, Global, Local,
17049 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
17050 tables are data structures which store a descriptor for each segment
17051 that is currently in use. The segment's selector is an index into a
17052 descriptor table; the table entry for that index holds the
17053 descriptor's base address and limit, and its attributes and access
17056 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
17057 segment (used for both data and the stack), and a DOS segment (which
17058 allows access to DOS/BIOS data structures and absolute addresses in
17059 conventional memory). However, the DPMI host will usually define
17060 additional segments in order to support the DPMI environment.
17062 @cindex garbled pointers
17063 These commands allow to display entries from the descriptor tables.
17064 Without an argument, all entries from the specified table are
17065 displayed. An argument, which should be an integer expression, means
17066 display a single entry whose index is given by the argument. For
17067 example, here's a convenient way to display information about the
17068 debugged program's data segment:
17071 @exdent @code{(@value{GDBP}) info dos ldt $ds}
17072 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
17076 This comes in handy when you want to see whether a pointer is outside
17077 the data segment's limit (i.e.@: @dfn{garbled}).
17079 @cindex page tables display (MS-DOS)
17081 @itemx info dos pte
17082 These two commands display entries from, respectively, the Page
17083 Directory and the Page Tables. Page Directories and Page Tables are
17084 data structures which control how virtual memory addresses are mapped
17085 into physical addresses. A Page Table includes an entry for every
17086 page of memory that is mapped into the program's address space; there
17087 may be several Page Tables, each one holding up to 4096 entries. A
17088 Page Directory has up to 4096 entries, one each for every Page Table
17089 that is currently in use.
17091 Without an argument, @kbd{info dos pde} displays the entire Page
17092 Directory, and @kbd{info dos pte} displays all the entries in all of
17093 the Page Tables. An argument, an integer expression, given to the
17094 @kbd{info dos pde} command means display only that entry from the Page
17095 Directory table. An argument given to the @kbd{info dos pte} command
17096 means display entries from a single Page Table, the one pointed to by
17097 the specified entry in the Page Directory.
17099 @cindex direct memory access (DMA) on MS-DOS
17100 These commands are useful when your program uses @dfn{DMA} (Direct
17101 Memory Access), which needs physical addresses to program the DMA
17104 These commands are supported only with some DPMI servers.
17106 @cindex physical address from linear address
17107 @item info dos address-pte @var{addr}
17108 This command displays the Page Table entry for a specified linear
17109 address. The argument @var{addr} is a linear address which should
17110 already have the appropriate segment's base address added to it,
17111 because this command accepts addresses which may belong to @emph{any}
17112 segment. For example, here's how to display the Page Table entry for
17113 the page where a variable @code{i} is stored:
17116 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
17117 @exdent @code{Page Table entry for address 0x11a00d30:}
17118 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
17122 This says that @code{i} is stored at offset @code{0xd30} from the page
17123 whose physical base address is @code{0x02698000}, and shows all the
17124 attributes of that page.
17126 Note that you must cast the addresses of variables to a @code{char *},
17127 since otherwise the value of @code{__djgpp_base_address}, the base
17128 address of all variables and functions in a @sc{djgpp} program, will
17129 be added using the rules of C pointer arithmetics: if @code{i} is
17130 declared an @code{int}, @value{GDBN} will add 4 times the value of
17131 @code{__djgpp_base_address} to the address of @code{i}.
17133 Here's another example, it displays the Page Table entry for the
17137 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
17138 @exdent @code{Page Table entry for address 0x29110:}
17139 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
17143 (The @code{+ 3} offset is because the transfer buffer's address is the
17144 3rd member of the @code{_go32_info_block} structure.) The output
17145 clearly shows that this DPMI server maps the addresses in conventional
17146 memory 1:1, i.e.@: the physical (@code{0x00029000} + @code{0x110}) and
17147 linear (@code{0x29110}) addresses are identical.
17149 This command is supported only with some DPMI servers.
17152 @cindex DOS serial data link, remote debugging
17153 In addition to native debugging, the DJGPP port supports remote
17154 debugging via a serial data link. The following commands are specific
17155 to remote serial debugging in the DJGPP port of @value{GDBN}.
17158 @kindex set com1base
17159 @kindex set com1irq
17160 @kindex set com2base
17161 @kindex set com2irq
17162 @kindex set com3base
17163 @kindex set com3irq
17164 @kindex set com4base
17165 @kindex set com4irq
17166 @item set com1base @var{addr}
17167 This command sets the base I/O port address of the @file{COM1} serial
17170 @item set com1irq @var{irq}
17171 This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use
17172 for the @file{COM1} serial port.
17174 There are similar commands @samp{set com2base}, @samp{set com3irq},
17175 etc.@: for setting the port address and the @code{IRQ} lines for the
17178 @kindex show com1base
17179 @kindex show com1irq
17180 @kindex show com2base
17181 @kindex show com2irq
17182 @kindex show com3base
17183 @kindex show com3irq
17184 @kindex show com4base
17185 @kindex show com4irq
17186 The related commands @samp{show com1base}, @samp{show com1irq} etc.@:
17187 display the current settings of the base address and the @code{IRQ}
17188 lines used by the COM ports.
17191 @kindex info serial
17192 @cindex DOS serial port status
17193 This command prints the status of the 4 DOS serial ports. For each
17194 port, it prints whether it's active or not, its I/O base address and
17195 IRQ number, whether it uses a 16550-style FIFO, its baudrate, and the
17196 counts of various errors encountered so far.
17200 @node Cygwin Native
17201 @subsection Features for Debugging MS Windows PE Executables
17202 @cindex MS Windows debugging
17203 @cindex native Cygwin debugging
17204 @cindex Cygwin-specific commands
17206 @value{GDBN} supports native debugging of MS Windows programs, including
17207 DLLs with and without symbolic debugging information.
17209 @cindex Ctrl-BREAK, MS-Windows
17210 @cindex interrupt debuggee on MS-Windows
17211 MS-Windows programs that call @code{SetConsoleMode} to switch off the
17212 special meaning of the @samp{Ctrl-C} keystroke cannot be interrupted
17213 by typing @kbd{C-c}. For this reason, @value{GDBN} on MS-Windows
17214 supports @kbd{C-@key{BREAK}} as an alternative interrupt key
17215 sequence, which can be used to interrupt the debuggee even if it
17218 There are various additional Cygwin-specific commands, described in
17219 this section. Working with DLLs that have no debugging symbols is
17220 described in @ref{Non-debug DLL Symbols}.
17225 This is a prefix of MS Windows-specific commands which print
17226 information about the target system and important OS structures.
17228 @item info w32 selector
17229 This command displays information returned by
17230 the Win32 API @code{GetThreadSelectorEntry} function.
17231 It takes an optional argument that is evaluated to
17232 a long value to give the information about this given selector.
17233 Without argument, this command displays information
17234 about the six segment registers.
17236 @item info w32 thread-information-block
17237 This command displays thread specific information stored in the
17238 Thread Information Block (readable on the X86 CPU family using @code{$fs}
17239 selector for 32-bit programs and @code{$gs} for 64-bit programs).
17243 This is a Cygwin-specific alias of @code{info shared}.
17245 @kindex dll-symbols
17247 This command loads symbols from a dll similarly to
17248 add-sym command but without the need to specify a base address.
17250 @kindex set cygwin-exceptions
17251 @cindex debugging the Cygwin DLL
17252 @cindex Cygwin DLL, debugging
17253 @item set cygwin-exceptions @var{mode}
17254 If @var{mode} is @code{on}, @value{GDBN} will break on exceptions that
17255 happen inside the Cygwin DLL. If @var{mode} is @code{off},
17256 @value{GDBN} will delay recognition of exceptions, and may ignore some
17257 exceptions which seem to be caused by internal Cygwin DLL
17258 ``bookkeeping''. This option is meant primarily for debugging the
17259 Cygwin DLL itself; the default value is @code{off} to avoid annoying
17260 @value{GDBN} users with false @code{SIGSEGV} signals.
17262 @kindex show cygwin-exceptions
17263 @item show cygwin-exceptions
17264 Displays whether @value{GDBN} will break on exceptions that happen
17265 inside the Cygwin DLL itself.
17267 @kindex set new-console
17268 @item set new-console @var{mode}
17269 If @var{mode} is @code{on} the debuggee will
17270 be started in a new console on next start.
17271 If @var{mode} is @code{off}, the debuggee will
17272 be started in the same console as the debugger.
17274 @kindex show new-console
17275 @item show new-console
17276 Displays whether a new console is used
17277 when the debuggee is started.
17279 @kindex set new-group
17280 @item set new-group @var{mode}
17281 This boolean value controls whether the debuggee should
17282 start a new group or stay in the same group as the debugger.
17283 This affects the way the Windows OS handles
17286 @kindex show new-group
17287 @item show new-group
17288 Displays current value of new-group boolean.
17290 @kindex set debugevents
17291 @item set debugevents
17292 This boolean value adds debug output concerning kernel events related
17293 to the debuggee seen by the debugger. This includes events that
17294 signal thread and process creation and exit, DLL loading and
17295 unloading, console interrupts, and debugging messages produced by the
17296 Windows @code{OutputDebugString} API call.
17298 @kindex set debugexec
17299 @item set debugexec
17300 This boolean value adds debug output concerning execute events
17301 (such as resume thread) seen by the debugger.
17303 @kindex set debugexceptions
17304 @item set debugexceptions
17305 This boolean value adds debug output concerning exceptions in the
17306 debuggee seen by the debugger.
17308 @kindex set debugmemory
17309 @item set debugmemory
17310 This boolean value adds debug output concerning debuggee memory reads
17311 and writes by the debugger.
17315 This boolean values specifies whether the debuggee is called
17316 via a shell or directly (default value is on).
17320 Displays if the debuggee will be started with a shell.
17325 * Non-debug DLL Symbols:: Support for DLLs without debugging symbols
17328 @node Non-debug DLL Symbols
17329 @subsubsection Support for DLLs without Debugging Symbols
17330 @cindex DLLs with no debugging symbols
17331 @cindex Minimal symbols and DLLs
17333 Very often on windows, some of the DLLs that your program relies on do
17334 not include symbolic debugging information (for example,
17335 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
17336 symbols in a DLL, it relies on the minimal amount of symbolic
17337 information contained in the DLL's export table. This section
17338 describes working with such symbols, known internally to @value{GDBN} as
17339 ``minimal symbols''.
17341 Note that before the debugged program has started execution, no DLLs
17342 will have been loaded. The easiest way around this problem is simply to
17343 start the program --- either by setting a breakpoint or letting the
17344 program run once to completion. It is also possible to force
17345 @value{GDBN} to load a particular DLL before starting the executable ---
17346 see the shared library information in @ref{Files}, or the
17347 @code{dll-symbols} command in @ref{Cygwin Native}. Currently,
17348 explicitly loading symbols from a DLL with no debugging information will
17349 cause the symbol names to be duplicated in @value{GDBN}'s lookup table,
17350 which may adversely affect symbol lookup performance.
17352 @subsubsection DLL Name Prefixes
17354 In keeping with the naming conventions used by the Microsoft debugging
17355 tools, DLL export symbols are made available with a prefix based on the
17356 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
17357 also entered into the symbol table, so @code{CreateFileA} is often
17358 sufficient. In some cases there will be name clashes within a program
17359 (particularly if the executable itself includes full debugging symbols)
17360 necessitating the use of the fully qualified name when referring to the
17361 contents of the DLL. Use single-quotes around the name to avoid the
17362 exclamation mark (``!'') being interpreted as a language operator.
17364 Note that the internal name of the DLL may be all upper-case, even
17365 though the file name of the DLL is lower-case, or vice-versa. Since
17366 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
17367 some confusion. If in doubt, try the @code{info functions} and
17368 @code{info variables} commands or even @code{maint print msymbols}
17369 (@pxref{Symbols}). Here's an example:
17372 (@value{GDBP}) info function CreateFileA
17373 All functions matching regular expression "CreateFileA":
17375 Non-debugging symbols:
17376 0x77e885f4 CreateFileA
17377 0x77e885f4 KERNEL32!CreateFileA
17381 (@value{GDBP}) info function !
17382 All functions matching regular expression "!":
17384 Non-debugging symbols:
17385 0x6100114c cygwin1!__assert
17386 0x61004034 cygwin1!_dll_crt0@@0
17387 0x61004240 cygwin1!dll_crt0(per_process *)
17391 @subsubsection Working with Minimal Symbols
17393 Symbols extracted from a DLL's export table do not contain very much
17394 type information. All that @value{GDBN} can do is guess whether a symbol
17395 refers to a function or variable depending on the linker section that
17396 contains the symbol. Also note that the actual contents of the memory
17397 contained in a DLL are not available unless the program is running. This
17398 means that you cannot examine the contents of a variable or disassemble
17399 a function within a DLL without a running program.
17401 Variables are generally treated as pointers and dereferenced
17402 automatically. For this reason, it is often necessary to prefix a
17403 variable name with the address-of operator (``&'') and provide explicit
17404 type information in the command. Here's an example of the type of
17408 (@value{GDBP}) print 'cygwin1!__argv'
17413 (@value{GDBP}) x 'cygwin1!__argv'
17414 0x10021610: "\230y\""
17417 And two possible solutions:
17420 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
17421 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
17425 (@value{GDBP}) x/2x &'cygwin1!__argv'
17426 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
17427 (@value{GDBP}) x/x 0x10021608
17428 0x10021608: 0x0022fd98
17429 (@value{GDBP}) x/s 0x0022fd98
17430 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
17433 Setting a break point within a DLL is possible even before the program
17434 starts execution. However, under these circumstances, @value{GDBN} can't
17435 examine the initial instructions of the function in order to skip the
17436 function's frame set-up code. You can work around this by using ``*&''
17437 to set the breakpoint at a raw memory address:
17440 (@value{GDBP}) break *&'python22!PyOS_Readline'
17441 Breakpoint 1 at 0x1e04eff0
17444 The author of these extensions is not entirely convinced that setting a
17445 break point within a shared DLL like @file{kernel32.dll} is completely
17449 @subsection Commands Specific to @sc{gnu} Hurd Systems
17450 @cindex @sc{gnu} Hurd debugging
17452 This subsection describes @value{GDBN} commands specific to the
17453 @sc{gnu} Hurd native debugging.
17458 @kindex set signals@r{, Hurd command}
17459 @kindex set sigs@r{, Hurd command}
17460 This command toggles the state of inferior signal interception by
17461 @value{GDBN}. Mach exceptions, such as breakpoint traps, are not
17462 affected by this command. @code{sigs} is a shorthand alias for
17467 @kindex show signals@r{, Hurd command}
17468 @kindex show sigs@r{, Hurd command}
17469 Show the current state of intercepting inferior's signals.
17471 @item set signal-thread
17472 @itemx set sigthread
17473 @kindex set signal-thread
17474 @kindex set sigthread
17475 This command tells @value{GDBN} which thread is the @code{libc} signal
17476 thread. That thread is run when a signal is delivered to a running
17477 process. @code{set sigthread} is the shorthand alias of @code{set
17480 @item show signal-thread
17481 @itemx show sigthread
17482 @kindex show signal-thread
17483 @kindex show sigthread
17484 These two commands show which thread will run when the inferior is
17485 delivered a signal.
17488 @kindex set stopped@r{, Hurd command}
17489 This commands tells @value{GDBN} that the inferior process is stopped,
17490 as with the @code{SIGSTOP} signal. The stopped process can be
17491 continued by delivering a signal to it.
17494 @kindex show stopped@r{, Hurd command}
17495 This command shows whether @value{GDBN} thinks the debuggee is
17498 @item set exceptions
17499 @kindex set exceptions@r{, Hurd command}
17500 Use this command to turn off trapping of exceptions in the inferior.
17501 When exception trapping is off, neither breakpoints nor
17502 single-stepping will work. To restore the default, set exception
17505 @item show exceptions
17506 @kindex show exceptions@r{, Hurd command}
17507 Show the current state of trapping exceptions in the inferior.
17509 @item set task pause
17510 @kindex set task@r{, Hurd commands}
17511 @cindex task attributes (@sc{gnu} Hurd)
17512 @cindex pause current task (@sc{gnu} Hurd)
17513 This command toggles task suspension when @value{GDBN} has control.
17514 Setting it to on takes effect immediately, and the task is suspended
17515 whenever @value{GDBN} gets control. Setting it to off will take
17516 effect the next time the inferior is continued. If this option is set
17517 to off, you can use @code{set thread default pause on} or @code{set
17518 thread pause on} (see below) to pause individual threads.
17520 @item show task pause
17521 @kindex show task@r{, Hurd commands}
17522 Show the current state of task suspension.
17524 @item set task detach-suspend-count
17525 @cindex task suspend count
17526 @cindex detach from task, @sc{gnu} Hurd
17527 This command sets the suspend count the task will be left with when
17528 @value{GDBN} detaches from it.
17530 @item show task detach-suspend-count
17531 Show the suspend count the task will be left with when detaching.
17533 @item set task exception-port
17534 @itemx set task excp
17535 @cindex task exception port, @sc{gnu} Hurd
17536 This command sets the task exception port to which @value{GDBN} will
17537 forward exceptions. The argument should be the value of the @dfn{send
17538 rights} of the task. @code{set task excp} is a shorthand alias.
17540 @item set noninvasive
17541 @cindex noninvasive task options
17542 This command switches @value{GDBN} to a mode that is the least
17543 invasive as far as interfering with the inferior is concerned. This
17544 is the same as using @code{set task pause}, @code{set exceptions}, and
17545 @code{set signals} to values opposite to the defaults.
17547 @item info send-rights
17548 @itemx info receive-rights
17549 @itemx info port-rights
17550 @itemx info port-sets
17551 @itemx info dead-names
17554 @cindex send rights, @sc{gnu} Hurd
17555 @cindex receive rights, @sc{gnu} Hurd
17556 @cindex port rights, @sc{gnu} Hurd
17557 @cindex port sets, @sc{gnu} Hurd
17558 @cindex dead names, @sc{gnu} Hurd
17559 These commands display information about, respectively, send rights,
17560 receive rights, port rights, port sets, and dead names of a task.
17561 There are also shorthand aliases: @code{info ports} for @code{info
17562 port-rights} and @code{info psets} for @code{info port-sets}.
17564 @item set thread pause
17565 @kindex set thread@r{, Hurd command}
17566 @cindex thread properties, @sc{gnu} Hurd
17567 @cindex pause current thread (@sc{gnu} Hurd)
17568 This command toggles current thread suspension when @value{GDBN} has
17569 control. Setting it to on takes effect immediately, and the current
17570 thread is suspended whenever @value{GDBN} gets control. Setting it to
17571 off will take effect the next time the inferior is continued.
17572 Normally, this command has no effect, since when @value{GDBN} has
17573 control, the whole task is suspended. However, if you used @code{set
17574 task pause off} (see above), this command comes in handy to suspend
17575 only the current thread.
17577 @item show thread pause
17578 @kindex show thread@r{, Hurd command}
17579 This command shows the state of current thread suspension.
17581 @item set thread run
17582 This command sets whether the current thread is allowed to run.
17584 @item show thread run
17585 Show whether the current thread is allowed to run.
17587 @item set thread detach-suspend-count
17588 @cindex thread suspend count, @sc{gnu} Hurd
17589 @cindex detach from thread, @sc{gnu} Hurd
17590 This command sets the suspend count @value{GDBN} will leave on a
17591 thread when detaching. This number is relative to the suspend count
17592 found by @value{GDBN} when it notices the thread; use @code{set thread
17593 takeover-suspend-count} to force it to an absolute value.
17595 @item show thread detach-suspend-count
17596 Show the suspend count @value{GDBN} will leave on the thread when
17599 @item set thread exception-port
17600 @itemx set thread excp
17601 Set the thread exception port to which to forward exceptions. This
17602 overrides the port set by @code{set task exception-port} (see above).
17603 @code{set thread excp} is the shorthand alias.
17605 @item set thread takeover-suspend-count
17606 Normally, @value{GDBN}'s thread suspend counts are relative to the
17607 value @value{GDBN} finds when it notices each thread. This command
17608 changes the suspend counts to be absolute instead.
17610 @item set thread default
17611 @itemx show thread default
17612 @cindex thread default settings, @sc{gnu} Hurd
17613 Each of the above @code{set thread} commands has a @code{set thread
17614 default} counterpart (e.g., @code{set thread default pause}, @code{set
17615 thread default exception-port}, etc.). The @code{thread default}
17616 variety of commands sets the default thread properties for all
17617 threads; you can then change the properties of individual threads with
17618 the non-default commands.
17623 @subsection QNX Neutrino
17624 @cindex QNX Neutrino
17626 @value{GDBN} provides the following commands specific to the QNX
17630 @item set debug nto-debug
17631 @kindex set debug nto-debug
17632 When set to on, enables debugging messages specific to the QNX
17635 @item show debug nto-debug
17636 @kindex show debug nto-debug
17637 Show the current state of QNX Neutrino messages.
17644 @value{GDBN} provides the following commands specific to the Darwin target:
17647 @item set debug darwin @var{num}
17648 @kindex set debug darwin
17649 When set to a non zero value, enables debugging messages specific to
17650 the Darwin support. Higher values produce more verbose output.
17652 @item show debug darwin
17653 @kindex show debug darwin
17654 Show the current state of Darwin messages.
17656 @item set debug mach-o @var{num}
17657 @kindex set debug mach-o
17658 When set to a non zero value, enables debugging messages while
17659 @value{GDBN} is reading Darwin object files. (@dfn{Mach-O} is the
17660 file format used on Darwin for object and executable files.) Higher
17661 values produce more verbose output. This is a command to diagnose
17662 problems internal to @value{GDBN} and should not be needed in normal
17665 @item show debug mach-o
17666 @kindex show debug mach-o
17667 Show the current state of Mach-O file messages.
17669 @item set mach-exceptions on
17670 @itemx set mach-exceptions off
17671 @kindex set mach-exceptions
17672 On Darwin, faults are first reported as a Mach exception and are then
17673 mapped to a Posix signal. Use this command to turn on trapping of
17674 Mach exceptions in the inferior. This might be sometimes useful to
17675 better understand the cause of a fault. The default is off.
17677 @item show mach-exceptions
17678 @kindex show mach-exceptions
17679 Show the current state of exceptions trapping.
17684 @section Embedded Operating Systems
17686 This section describes configurations involving the debugging of
17687 embedded operating systems that are available for several different
17691 * VxWorks:: Using @value{GDBN} with VxWorks
17694 @value{GDBN} includes the ability to debug programs running on
17695 various real-time operating systems.
17698 @subsection Using @value{GDBN} with VxWorks
17704 @kindex target vxworks
17705 @item target vxworks @var{machinename}
17706 A VxWorks system, attached via TCP/IP. The argument @var{machinename}
17707 is the target system's machine name or IP address.
17711 On VxWorks, @code{load} links @var{filename} dynamically on the
17712 current target system as well as adding its symbols in @value{GDBN}.
17714 @value{GDBN} enables developers to spawn and debug tasks running on networked
17715 VxWorks targets from a Unix host. Already-running tasks spawned from
17716 the VxWorks shell can also be debugged. @value{GDBN} uses code that runs on
17717 both the Unix host and on the VxWorks target. The program
17718 @code{@value{GDBP}} is installed and executed on the Unix host. (It may be
17719 installed with the name @code{vxgdb}, to distinguish it from a
17720 @value{GDBN} for debugging programs on the host itself.)
17723 @item VxWorks-timeout @var{args}
17724 @kindex vxworks-timeout
17725 All VxWorks-based targets now support the option @code{vxworks-timeout}.
17726 This option is set by the user, and @var{args} represents the number of
17727 seconds @value{GDBN} waits for responses to rpc's. You might use this if
17728 your VxWorks target is a slow software simulator or is on the far side
17729 of a thin network line.
17732 The following information on connecting to VxWorks was current when
17733 this manual was produced; newer releases of VxWorks may use revised
17736 @findex INCLUDE_RDB
17737 To use @value{GDBN} with VxWorks, you must rebuild your VxWorks kernel
17738 to include the remote debugging interface routines in the VxWorks
17739 library @file{rdb.a}. To do this, define @code{INCLUDE_RDB} in the
17740 VxWorks configuration file @file{configAll.h} and rebuild your VxWorks
17741 kernel. The resulting kernel contains @file{rdb.a}, and spawns the
17742 source debugging task @code{tRdbTask} when VxWorks is booted. For more
17743 information on configuring and remaking VxWorks, see the manufacturer's
17745 @c VxWorks, see the @cite{VxWorks Programmer's Guide}.
17747 Once you have included @file{rdb.a} in your VxWorks system image and set
17748 your Unix execution search path to find @value{GDBN}, you are ready to
17749 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}} (or
17750 @code{vxgdb}, depending on your installation).
17752 @value{GDBN} comes up showing the prompt:
17759 * VxWorks Connection:: Connecting to VxWorks
17760 * VxWorks Download:: VxWorks download
17761 * VxWorks Attach:: Running tasks
17764 @node VxWorks Connection
17765 @subsubsection Connecting to VxWorks
17767 The @value{GDBN} command @code{target} lets you connect to a VxWorks target on the
17768 network. To connect to a target whose host name is ``@code{tt}'', type:
17771 (vxgdb) target vxworks tt
17775 @value{GDBN} displays messages like these:
17778 Attaching remote machine across net...
17783 @value{GDBN} then attempts to read the symbol tables of any object modules
17784 loaded into the VxWorks target since it was last booted. @value{GDBN} locates
17785 these files by searching the directories listed in the command search
17786 path (@pxref{Environment, ,Your Program's Environment}); if it fails
17787 to find an object file, it displays a message such as:
17790 prog.o: No such file or directory.
17793 When this happens, add the appropriate directory to the search path with
17794 the @value{GDBN} command @code{path}, and execute the @code{target}
17797 @node VxWorks Download
17798 @subsubsection VxWorks Download
17800 @cindex download to VxWorks
17801 If you have connected to the VxWorks target and you want to debug an
17802 object that has not yet been loaded, you can use the @value{GDBN}
17803 @code{load} command to download a file from Unix to VxWorks
17804 incrementally. The object file given as an argument to the @code{load}
17805 command is actually opened twice: first by the VxWorks target in order
17806 to download the code, then by @value{GDBN} in order to read the symbol
17807 table. This can lead to problems if the current working directories on
17808 the two systems differ. If both systems have NFS mounted the same
17809 filesystems, you can avoid these problems by using absolute paths.
17810 Otherwise, it is simplest to set the working directory on both systems
17811 to the directory in which the object file resides, and then to reference
17812 the file by its name, without any path. For instance, a program
17813 @file{prog.o} may reside in @file{@var{vxpath}/vw/demo/rdb} in VxWorks
17814 and in @file{@var{hostpath}/vw/demo/rdb} on the host. To load this
17815 program, type this on VxWorks:
17818 -> cd "@var{vxpath}/vw/demo/rdb"
17822 Then, in @value{GDBN}, type:
17825 (vxgdb) cd @var{hostpath}/vw/demo/rdb
17826 (vxgdb) load prog.o
17829 @value{GDBN} displays a response similar to this:
17832 Reading symbol data from wherever/vw/demo/rdb/prog.o... done.
17835 You can also use the @code{load} command to reload an object module
17836 after editing and recompiling the corresponding source file. Note that
17837 this makes @value{GDBN} delete all currently-defined breakpoints,
17838 auto-displays, and convenience variables, and to clear the value
17839 history. (This is necessary in order to preserve the integrity of
17840 debugger's data structures that reference the target system's symbol
17843 @node VxWorks Attach
17844 @subsubsection Running Tasks
17846 @cindex running VxWorks tasks
17847 You can also attach to an existing task using the @code{attach} command as
17851 (vxgdb) attach @var{task}
17855 where @var{task} is the VxWorks hexadecimal task ID. The task can be running
17856 or suspended when you attach to it. Running tasks are suspended at
17857 the time of attachment.
17859 @node Embedded Processors
17860 @section Embedded Processors
17862 This section goes into details specific to particular embedded
17865 @cindex send command to simulator
17866 Whenever a specific embedded processor has a simulator, @value{GDBN}
17867 allows to send an arbitrary command to the simulator.
17870 @item sim @var{command}
17871 @kindex sim@r{, a command}
17872 Send an arbitrary @var{command} string to the simulator. Consult the
17873 documentation for the specific simulator in use for information about
17874 acceptable commands.
17880 * M32R/D:: Renesas M32R/D
17881 * M68K:: Motorola M68K
17882 * MicroBlaze:: Xilinx MicroBlaze
17883 * MIPS Embedded:: MIPS Embedded
17884 * OpenRISC 1000:: OpenRisc 1000
17885 * PA:: HP PA Embedded
17886 * PowerPC Embedded:: PowerPC Embedded
17887 * Sparclet:: Tsqware Sparclet
17888 * Sparclite:: Fujitsu Sparclite
17889 * Z8000:: Zilog Z8000
17892 * Super-H:: Renesas Super-H
17901 @item target rdi @var{dev}
17902 ARM Angel monitor, via RDI library interface to ADP protocol. You may
17903 use this target to communicate with both boards running the Angel
17904 monitor, or with the EmbeddedICE JTAG debug device.
17907 @item target rdp @var{dev}
17912 @value{GDBN} provides the following ARM-specific commands:
17915 @item set arm disassembler
17917 This commands selects from a list of disassembly styles. The
17918 @code{"std"} style is the standard style.
17920 @item show arm disassembler
17922 Show the current disassembly style.
17924 @item set arm apcs32
17925 @cindex ARM 32-bit mode
17926 This command toggles ARM operation mode between 32-bit and 26-bit.
17928 @item show arm apcs32
17929 Display the current usage of the ARM 32-bit mode.
17931 @item set arm fpu @var{fputype}
17932 This command sets the ARM floating-point unit (FPU) type. The
17933 argument @var{fputype} can be one of these:
17937 Determine the FPU type by querying the OS ABI.
17939 Software FPU, with mixed-endian doubles on little-endian ARM
17942 GCC-compiled FPA co-processor.
17944 Software FPU with pure-endian doubles.
17950 Show the current type of the FPU.
17953 This command forces @value{GDBN} to use the specified ABI.
17956 Show the currently used ABI.
17958 @item set arm fallback-mode (arm|thumb|auto)
17959 @value{GDBN} uses the symbol table, when available, to determine
17960 whether instructions are ARM or Thumb. This command controls
17961 @value{GDBN}'s default behavior when the symbol table is not
17962 available. The default is @samp{auto}, which causes @value{GDBN} to
17963 use the current execution mode (from the @code{T} bit in the @code{CPSR}
17966 @item show arm fallback-mode
17967 Show the current fallback instruction mode.
17969 @item set arm force-mode (arm|thumb|auto)
17970 This command overrides use of the symbol table to determine whether
17971 instructions are ARM or Thumb. The default is @samp{auto}, which
17972 causes @value{GDBN} to use the symbol table and then the setting
17973 of @samp{set arm fallback-mode}.
17975 @item show arm force-mode
17976 Show the current forced instruction mode.
17978 @item set debug arm
17979 Toggle whether to display ARM-specific debugging messages from the ARM
17980 target support subsystem.
17982 @item show debug arm
17983 Show whether ARM-specific debugging messages are enabled.
17986 The following commands are available when an ARM target is debugged
17987 using the RDI interface:
17990 @item rdilogfile @r{[}@var{file}@r{]}
17992 @cindex ADP (Angel Debugger Protocol) logging
17993 Set the filename for the ADP (Angel Debugger Protocol) packet log.
17994 With an argument, sets the log file to the specified @var{file}. With
17995 no argument, show the current log file name. The default log file is
17998 @item rdilogenable @r{[}@var{arg}@r{]}
17999 @kindex rdilogenable
18000 Control logging of ADP packets. With an argument of 1 or @code{"yes"}
18001 enables logging, with an argument 0 or @code{"no"} disables it. With
18002 no arguments displays the current setting. When logging is enabled,
18003 ADP packets exchanged between @value{GDBN} and the RDI target device
18004 are logged to a file.
18006 @item set rdiromatzero
18007 @kindex set rdiromatzero
18008 @cindex ROM at zero address, RDI
18009 Tell @value{GDBN} whether the target has ROM at address 0. If on,
18010 vector catching is disabled, so that zero address can be used. If off
18011 (the default), vector catching is enabled. For this command to take
18012 effect, it needs to be invoked prior to the @code{target rdi} command.
18014 @item show rdiromatzero
18015 @kindex show rdiromatzero
18016 Show the current setting of ROM at zero address.
18018 @item set rdiheartbeat
18019 @kindex set rdiheartbeat
18020 @cindex RDI heartbeat
18021 Enable or disable RDI heartbeat packets. It is not recommended to
18022 turn on this option, since it confuses ARM and EPI JTAG interface, as
18023 well as the Angel monitor.
18025 @item show rdiheartbeat
18026 @kindex show rdiheartbeat
18027 Show the setting of RDI heartbeat packets.
18031 @item target sim @r{[}@var{simargs}@r{]} @dots{}
18032 The @value{GDBN} ARM simulator accepts the following optional arguments.
18035 @item --swi-support=@var{type}
18036 Tell the simulator which SWI interfaces to support.
18037 @var{type} may be a comma separated list of the following values.
18038 The default value is @code{all}.
18051 @subsection Renesas M32R/D and M32R/SDI
18054 @kindex target m32r
18055 @item target m32r @var{dev}
18056 Renesas M32R/D ROM monitor.
18058 @kindex target m32rsdi
18059 @item target m32rsdi @var{dev}
18060 Renesas M32R SDI server, connected via parallel port to the board.
18063 The following @value{GDBN} commands are specific to the M32R monitor:
18066 @item set download-path @var{path}
18067 @kindex set download-path
18068 @cindex find downloadable @sc{srec} files (M32R)
18069 Set the default path for finding downloadable @sc{srec} files.
18071 @item show download-path
18072 @kindex show download-path
18073 Show the default path for downloadable @sc{srec} files.
18075 @item set board-address @var{addr}
18076 @kindex set board-address
18077 @cindex M32-EVA target board address
18078 Set the IP address for the M32R-EVA target board.
18080 @item show board-address
18081 @kindex show board-address
18082 Show the current IP address of the target board.
18084 @item set server-address @var{addr}
18085 @kindex set server-address
18086 @cindex download server address (M32R)
18087 Set the IP address for the download server, which is the @value{GDBN}'s
18090 @item show server-address
18091 @kindex show server-address
18092 Display the IP address of the download server.
18094 @item upload @r{[}@var{file}@r{]}
18095 @kindex upload@r{, M32R}
18096 Upload the specified @sc{srec} @var{file} via the monitor's Ethernet
18097 upload capability. If no @var{file} argument is given, the current
18098 executable file is uploaded.
18100 @item tload @r{[}@var{file}@r{]}
18101 @kindex tload@r{, M32R}
18102 Test the @code{upload} command.
18105 The following commands are available for M32R/SDI:
18110 @cindex reset SDI connection, M32R
18111 This command resets the SDI connection.
18115 This command shows the SDI connection status.
18118 @kindex debug_chaos
18119 @cindex M32R/Chaos debugging
18120 Instructs the remote that M32R/Chaos debugging is to be used.
18122 @item use_debug_dma
18123 @kindex use_debug_dma
18124 Instructs the remote to use the DEBUG_DMA method of accessing memory.
18127 @kindex use_mon_code
18128 Instructs the remote to use the MON_CODE method of accessing memory.
18131 @kindex use_ib_break
18132 Instructs the remote to set breakpoints by IB break.
18134 @item use_dbt_break
18135 @kindex use_dbt_break
18136 Instructs the remote to set breakpoints by DBT.
18142 The Motorola m68k configuration includes ColdFire support, and a
18143 target command for the following ROM monitor.
18147 @kindex target dbug
18148 @item target dbug @var{dev}
18149 dBUG ROM monitor for Motorola ColdFire.
18154 @subsection MicroBlaze
18155 @cindex Xilinx MicroBlaze
18156 @cindex XMD, Xilinx Microprocessor Debugger
18158 The MicroBlaze is a soft-core processor supported on various Xilinx
18159 FPGAs, such as Spartan or Virtex series. Boards with these processors
18160 usually have JTAG ports which connect to a host system running the Xilinx
18161 Embedded Development Kit (EDK) or Software Development Kit (SDK).
18162 This host system is used to download the configuration bitstream to
18163 the target FPGA. The Xilinx Microprocessor Debugger (XMD) program
18164 communicates with the target board using the JTAG interface and
18165 presents a @code{gdbserver} interface to the board. By default
18166 @code{xmd} uses port @code{1234}. (While it is possible to change
18167 this default port, it requires the use of undocumented @code{xmd}
18168 commands. Contact Xilinx support if you need to do this.)
18170 Use these GDB commands to connect to the MicroBlaze target processor.
18173 @item target remote :1234
18174 Use this command to connect to the target if you are running @value{GDBN}
18175 on the same system as @code{xmd}.
18177 @item target remote @var{xmd-host}:1234
18178 Use this command to connect to the target if it is connected to @code{xmd}
18179 running on a different system named @var{xmd-host}.
18182 Use this command to download a program to the MicroBlaze target.
18184 @item set debug microblaze @var{n}
18185 Enable MicroBlaze-specific debugging messages if non-zero.
18187 @item show debug microblaze @var{n}
18188 Show MicroBlaze-specific debugging level.
18191 @node MIPS Embedded
18192 @subsection MIPS Embedded
18194 @cindex MIPS boards
18195 @value{GDBN} can use the MIPS remote debugging protocol to talk to a
18196 MIPS board attached to a serial line. This is available when
18197 you configure @value{GDBN} with @samp{--target=mips-idt-ecoff}.
18200 Use these @value{GDBN} commands to specify the connection to your target board:
18203 @item target mips @var{port}
18204 @kindex target mips @var{port}
18205 To run a program on the board, start up @code{@value{GDBP}} with the
18206 name of your program as the argument. To connect to the board, use the
18207 command @samp{target mips @var{port}}, where @var{port} is the name of
18208 the serial port connected to the board. If the program has not already
18209 been downloaded to the board, you may use the @code{load} command to
18210 download it. You can then use all the usual @value{GDBN} commands.
18212 For example, this sequence connects to the target board through a serial
18213 port, and loads and runs a program called @var{prog} through the
18217 host$ @value{GDBP} @var{prog}
18218 @value{GDBN} is free software and @dots{}
18219 (@value{GDBP}) target mips /dev/ttyb
18220 (@value{GDBP}) load @var{prog}
18224 @item target mips @var{hostname}:@var{portnumber}
18225 On some @value{GDBN} host configurations, you can specify a TCP
18226 connection (for instance, to a serial line managed by a terminal
18227 concentrator) instead of a serial port, using the syntax
18228 @samp{@var{hostname}:@var{portnumber}}.
18230 @item target pmon @var{port}
18231 @kindex target pmon @var{port}
18234 @item target ddb @var{port}
18235 @kindex target ddb @var{port}
18236 NEC's DDB variant of PMON for Vr4300.
18238 @item target lsi @var{port}
18239 @kindex target lsi @var{port}
18240 LSI variant of PMON.
18242 @kindex target r3900
18243 @item target r3900 @var{dev}
18244 Densan DVE-R3900 ROM monitor for Toshiba R3900 Mips.
18246 @kindex target array
18247 @item target array @var{dev}
18248 Array Tech LSI33K RAID controller board.
18254 @value{GDBN} also supports these special commands for MIPS targets:
18257 @item set mipsfpu double
18258 @itemx set mipsfpu single
18259 @itemx set mipsfpu none
18260 @itemx set mipsfpu auto
18261 @itemx show mipsfpu
18262 @kindex set mipsfpu
18263 @kindex show mipsfpu
18264 @cindex MIPS remote floating point
18265 @cindex floating point, MIPS remote
18266 If your target board does not support the MIPS floating point
18267 coprocessor, you should use the command @samp{set mipsfpu none} (if you
18268 need this, you may wish to put the command in your @value{GDBN} init
18269 file). This tells @value{GDBN} how to find the return value of
18270 functions which return floating point values. It also allows
18271 @value{GDBN} to avoid saving the floating point registers when calling
18272 functions on the board. If you are using a floating point coprocessor
18273 with only single precision floating point support, as on the @sc{r4650}
18274 processor, use the command @samp{set mipsfpu single}. The default
18275 double precision floating point coprocessor may be selected using
18276 @samp{set mipsfpu double}.
18278 In previous versions the only choices were double precision or no
18279 floating point, so @samp{set mipsfpu on} will select double precision
18280 and @samp{set mipsfpu off} will select no floating point.
18282 As usual, you can inquire about the @code{mipsfpu} variable with
18283 @samp{show mipsfpu}.
18285 @item set timeout @var{seconds}
18286 @itemx set retransmit-timeout @var{seconds}
18287 @itemx show timeout
18288 @itemx show retransmit-timeout
18289 @cindex @code{timeout}, MIPS protocol
18290 @cindex @code{retransmit-timeout}, MIPS protocol
18291 @kindex set timeout
18292 @kindex show timeout
18293 @kindex set retransmit-timeout
18294 @kindex show retransmit-timeout
18295 You can control the timeout used while waiting for a packet, in the MIPS
18296 remote protocol, with the @code{set timeout @var{seconds}} command. The
18297 default is 5 seconds. Similarly, you can control the timeout used while
18298 waiting for an acknowledgment of a packet with the @code{set
18299 retransmit-timeout @var{seconds}} command. The default is 3 seconds.
18300 You can inspect both values with @code{show timeout} and @code{show
18301 retransmit-timeout}. (These commands are @emph{only} available when
18302 @value{GDBN} is configured for @samp{--target=mips-idt-ecoff}.)
18304 The timeout set by @code{set timeout} does not apply when @value{GDBN}
18305 is waiting for your program to stop. In that case, @value{GDBN} waits
18306 forever because it has no way of knowing how long the program is going
18307 to run before stopping.
18309 @item set syn-garbage-limit @var{num}
18310 @kindex set syn-garbage-limit@r{, MIPS remote}
18311 @cindex synchronize with remote MIPS target
18312 Limit the maximum number of characters @value{GDBN} should ignore when
18313 it tries to synchronize with the remote target. The default is 10
18314 characters. Setting the limit to -1 means there's no limit.
18316 @item show syn-garbage-limit
18317 @kindex show syn-garbage-limit@r{, MIPS remote}
18318 Show the current limit on the number of characters to ignore when
18319 trying to synchronize with the remote system.
18321 @item set monitor-prompt @var{prompt}
18322 @kindex set monitor-prompt@r{, MIPS remote}
18323 @cindex remote monitor prompt
18324 Tell @value{GDBN} to expect the specified @var{prompt} string from the
18325 remote monitor. The default depends on the target:
18335 @item show monitor-prompt
18336 @kindex show monitor-prompt@r{, MIPS remote}
18337 Show the current strings @value{GDBN} expects as the prompt from the
18340 @item set monitor-warnings
18341 @kindex set monitor-warnings@r{, MIPS remote}
18342 Enable or disable monitor warnings about hardware breakpoints. This
18343 has effect only for the @code{lsi} target. When on, @value{GDBN} will
18344 display warning messages whose codes are returned by the @code{lsi}
18345 PMON monitor for breakpoint commands.
18347 @item show monitor-warnings
18348 @kindex show monitor-warnings@r{, MIPS remote}
18349 Show the current setting of printing monitor warnings.
18351 @item pmon @var{command}
18352 @kindex pmon@r{, MIPS remote}
18353 @cindex send PMON command
18354 This command allows sending an arbitrary @var{command} string to the
18355 monitor. The monitor must be in debug mode for this to work.
18358 @node OpenRISC 1000
18359 @subsection OpenRISC 1000
18360 @cindex OpenRISC 1000
18362 @cindex or1k boards
18363 See OR1k Architecture document (@uref{www.opencores.org}) for more information
18364 about platform and commands.
18368 @kindex target jtag
18369 @item target jtag jtag://@var{host}:@var{port}
18371 Connects to remote JTAG server.
18372 JTAG remote server can be either an or1ksim or JTAG server,
18373 connected via parallel port to the board.
18375 Example: @code{target jtag jtag://localhost:9999}
18378 @item or1ksim @var{command}
18379 If connected to @code{or1ksim} OpenRISC 1000 Architectural
18380 Simulator, proprietary commands can be executed.
18382 @kindex info or1k spr
18383 @item info or1k spr
18384 Displays spr groups.
18386 @item info or1k spr @var{group}
18387 @itemx info or1k spr @var{groupno}
18388 Displays register names in selected group.
18390 @item info or1k spr @var{group} @var{register}
18391 @itemx info or1k spr @var{register}
18392 @itemx info or1k spr @var{groupno} @var{registerno}
18393 @itemx info or1k spr @var{registerno}
18394 Shows information about specified spr register.
18397 @item spr @var{group} @var{register} @var{value}
18398 @itemx spr @var{register @var{value}}
18399 @itemx spr @var{groupno} @var{registerno @var{value}}
18400 @itemx spr @var{registerno @var{value}}
18401 Writes @var{value} to specified spr register.
18404 Some implementations of OpenRISC 1000 Architecture also have hardware trace.
18405 It is very similar to @value{GDBN} trace, except it does not interfere with normal
18406 program execution and is thus much faster. Hardware breakpoints/watchpoint
18407 triggers can be set using:
18410 Load effective address/data
18412 Store effective address/data
18414 Access effective address ($SEA or $LEA) or data ($SDATA/$LDATA)
18419 When triggered, it can capture low level data, like: @code{PC}, @code{LSEA},
18420 @code{LDATA}, @code{SDATA}, @code{READSPR}, @code{WRITESPR}, @code{INSTR}.
18422 @code{htrace} commands:
18423 @cindex OpenRISC 1000 htrace
18426 @item hwatch @var{conditional}
18427 Set hardware watchpoint on combination of Load/Store Effective Address(es)
18428 or Data. For example:
18430 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
18432 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
18436 Display information about current HW trace configuration.
18438 @item htrace trigger @var{conditional}
18439 Set starting criteria for HW trace.
18441 @item htrace qualifier @var{conditional}
18442 Set acquisition qualifier for HW trace.
18444 @item htrace stop @var{conditional}
18445 Set HW trace stopping criteria.
18447 @item htrace record [@var{data}]*
18448 Selects the data to be recorded, when qualifier is met and HW trace was
18451 @item htrace enable
18452 @itemx htrace disable
18453 Enables/disables the HW trace.
18455 @item htrace rewind [@var{filename}]
18456 Clears currently recorded trace data.
18458 If filename is specified, new trace file is made and any newly collected data
18459 will be written there.
18461 @item htrace print [@var{start} [@var{len}]]
18462 Prints trace buffer, using current record configuration.
18464 @item htrace mode continuous
18465 Set continuous trace mode.
18467 @item htrace mode suspend
18468 Set suspend trace mode.
18472 @node PowerPC Embedded
18473 @subsection PowerPC Embedded
18475 @cindex DVC register
18476 @value{GDBN} supports using the DVC (Data Value Compare) register to
18477 implement in hardware simple hardware watchpoint conditions of the form:
18480 (@value{GDBP}) watch @var{ADDRESS|VARIABLE} \
18481 if @var{ADDRESS|VARIABLE} == @var{CONSTANT EXPRESSION}
18484 The DVC register will be automatically used whenever @value{GDBN} detects
18485 such pattern in a condition expression. This feature is available in native
18486 @value{GDBN} running on a Linux kernel version 2.6.34 or newer.
18488 @value{GDBN} provides the following PowerPC-specific commands:
18491 @kindex set powerpc
18492 @item set powerpc soft-float
18493 @itemx show powerpc soft-float
18494 Force @value{GDBN} to use (or not use) a software floating point calling
18495 convention. By default, @value{GDBN} selects the calling convention based
18496 on the selected architecture and the provided executable file.
18498 @item set powerpc vector-abi
18499 @itemx show powerpc vector-abi
18500 Force @value{GDBN} to use the specified calling convention for vector
18501 arguments and return values. The valid options are @samp{auto};
18502 @samp{generic}, to avoid vector registers even if they are present;
18503 @samp{altivec}, to use AltiVec registers; and @samp{spe} to use SPE
18504 registers. By default, @value{GDBN} selects the calling convention
18505 based on the selected architecture and the provided executable file.
18507 @kindex target dink32
18508 @item target dink32 @var{dev}
18509 DINK32 ROM monitor.
18511 @kindex target ppcbug
18512 @item target ppcbug @var{dev}
18513 @kindex target ppcbug1
18514 @item target ppcbug1 @var{dev}
18515 PPCBUG ROM monitor for PowerPC.
18518 @item target sds @var{dev}
18519 SDS monitor, running on a PowerPC board (such as Motorola's ADS).
18522 @cindex SDS protocol
18523 The following commands specific to the SDS protocol are supported
18527 @item set sdstimeout @var{nsec}
18528 @kindex set sdstimeout
18529 Set the timeout for SDS protocol reads to be @var{nsec} seconds. The
18530 default is 2 seconds.
18532 @item show sdstimeout
18533 @kindex show sdstimeout
18534 Show the current value of the SDS timeout.
18536 @item sds @var{command}
18537 @kindex sds@r{, a command}
18538 Send the specified @var{command} string to the SDS monitor.
18543 @subsection HP PA Embedded
18547 @kindex target op50n
18548 @item target op50n @var{dev}
18549 OP50N monitor, running on an OKI HPPA board.
18551 @kindex target w89k
18552 @item target w89k @var{dev}
18553 W89K monitor, running on a Winbond HPPA board.
18558 @subsection Tsqware Sparclet
18562 @value{GDBN} enables developers to debug tasks running on
18563 Sparclet targets from a Unix host.
18564 @value{GDBN} uses code that runs on
18565 both the Unix host and on the Sparclet target. The program
18566 @code{@value{GDBP}} is installed and executed on the Unix host.
18569 @item remotetimeout @var{args}
18570 @kindex remotetimeout
18571 @value{GDBN} supports the option @code{remotetimeout}.
18572 This option is set by the user, and @var{args} represents the number of
18573 seconds @value{GDBN} waits for responses.
18576 @cindex compiling, on Sparclet
18577 When compiling for debugging, include the options @samp{-g} to get debug
18578 information and @samp{-Ttext} to relocate the program to where you wish to
18579 load it on the target. You may also want to add the options @samp{-n} or
18580 @samp{-N} in order to reduce the size of the sections. Example:
18583 sparclet-aout-gcc prog.c -Ttext 0x12010000 -g -o prog -N
18586 You can use @code{objdump} to verify that the addresses are what you intended:
18589 sparclet-aout-objdump --headers --syms prog
18592 @cindex running, on Sparclet
18594 your Unix execution search path to find @value{GDBN}, you are ready to
18595 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}}
18596 (or @code{sparclet-aout-gdb}, depending on your installation).
18598 @value{GDBN} comes up showing the prompt:
18605 * Sparclet File:: Setting the file to debug
18606 * Sparclet Connection:: Connecting to Sparclet
18607 * Sparclet Download:: Sparclet download
18608 * Sparclet Execution:: Running and debugging
18611 @node Sparclet File
18612 @subsubsection Setting File to Debug
18614 The @value{GDBN} command @code{file} lets you choose with program to debug.
18617 (gdbslet) file prog
18621 @value{GDBN} then attempts to read the symbol table of @file{prog}.
18622 @value{GDBN} locates
18623 the file by searching the directories listed in the command search
18625 If the file was compiled with debug information (option @samp{-g}), source
18626 files will be searched as well.
18627 @value{GDBN} locates
18628 the source files by searching the directories listed in the directory search
18629 path (@pxref{Environment, ,Your Program's Environment}).
18631 to find a file, it displays a message such as:
18634 prog: No such file or directory.
18637 When this happens, add the appropriate directories to the search paths with
18638 the @value{GDBN} commands @code{path} and @code{dir}, and execute the
18639 @code{target} command again.
18641 @node Sparclet Connection
18642 @subsubsection Connecting to Sparclet
18644 The @value{GDBN} command @code{target} lets you connect to a Sparclet target.
18645 To connect to a target on serial port ``@code{ttya}'', type:
18648 (gdbslet) target sparclet /dev/ttya
18649 Remote target sparclet connected to /dev/ttya
18650 main () at ../prog.c:3
18654 @value{GDBN} displays messages like these:
18660 @node Sparclet Download
18661 @subsubsection Sparclet Download
18663 @cindex download to Sparclet
18664 Once connected to the Sparclet target,
18665 you can use the @value{GDBN}
18666 @code{load} command to download the file from the host to the target.
18667 The file name and load offset should be given as arguments to the @code{load}
18669 Since the file format is aout, the program must be loaded to the starting
18670 address. You can use @code{objdump} to find out what this value is. The load
18671 offset is an offset which is added to the VMA (virtual memory address)
18672 of each of the file's sections.
18673 For instance, if the program
18674 @file{prog} was linked to text address 0x1201000, with data at 0x12010160
18675 and bss at 0x12010170, in @value{GDBN}, type:
18678 (gdbslet) load prog 0x12010000
18679 Loading section .text, size 0xdb0 vma 0x12010000
18682 If the code is loaded at a different address then what the program was linked
18683 to, you may need to use the @code{section} and @code{add-symbol-file} commands
18684 to tell @value{GDBN} where to map the symbol table.
18686 @node Sparclet Execution
18687 @subsubsection Running and Debugging
18689 @cindex running and debugging Sparclet programs
18690 You can now begin debugging the task using @value{GDBN}'s execution control
18691 commands, @code{b}, @code{step}, @code{run}, etc. See the @value{GDBN}
18692 manual for the list of commands.
18696 Breakpoint 1 at 0x12010000: file prog.c, line 3.
18698 Starting program: prog
18699 Breakpoint 1, main (argc=1, argv=0xeffff21c) at prog.c:3
18700 3 char *symarg = 0;
18702 4 char *execarg = "hello!";
18707 @subsection Fujitsu Sparclite
18711 @kindex target sparclite
18712 @item target sparclite @var{dev}
18713 Fujitsu sparclite boards, used only for the purpose of loading.
18714 You must use an additional command to debug the program.
18715 For example: target remote @var{dev} using @value{GDBN} standard
18721 @subsection Zilog Z8000
18724 @cindex simulator, Z8000
18725 @cindex Zilog Z8000 simulator
18727 When configured for debugging Zilog Z8000 targets, @value{GDBN} includes
18730 For the Z8000 family, @samp{target sim} simulates either the Z8002 (the
18731 unsegmented variant of the Z8000 architecture) or the Z8001 (the
18732 segmented variant). The simulator recognizes which architecture is
18733 appropriate by inspecting the object code.
18736 @item target sim @var{args}
18738 @kindex target sim@r{, with Z8000}
18739 Debug programs on a simulated CPU. If the simulator supports setup
18740 options, specify them via @var{args}.
18744 After specifying this target, you can debug programs for the simulated
18745 CPU in the same style as programs for your host computer; use the
18746 @code{file} command to load a new program image, the @code{run} command
18747 to run your program, and so on.
18749 As well as making available all the usual machine registers
18750 (@pxref{Registers, ,Registers}), the Z8000 simulator provides three
18751 additional items of information as specially named registers:
18756 Counts clock-ticks in the simulator.
18759 Counts instructions run in the simulator.
18762 Execution time in 60ths of a second.
18766 You can refer to these values in @value{GDBN} expressions with the usual
18767 conventions; for example, @w{@samp{b fputc if $cycles>5000}} sets a
18768 conditional breakpoint that suspends only after at least 5000
18769 simulated clock ticks.
18772 @subsection Atmel AVR
18775 When configured for debugging the Atmel AVR, @value{GDBN} supports the
18776 following AVR-specific commands:
18779 @item info io_registers
18780 @kindex info io_registers@r{, AVR}
18781 @cindex I/O registers (Atmel AVR)
18782 This command displays information about the AVR I/O registers. For
18783 each register, @value{GDBN} prints its number and value.
18790 When configured for debugging CRIS, @value{GDBN} provides the
18791 following CRIS-specific commands:
18794 @item set cris-version @var{ver}
18795 @cindex CRIS version
18796 Set the current CRIS version to @var{ver}, either @samp{10} or @samp{32}.
18797 The CRIS version affects register names and sizes. This command is useful in
18798 case autodetection of the CRIS version fails.
18800 @item show cris-version
18801 Show the current CRIS version.
18803 @item set cris-dwarf2-cfi
18804 @cindex DWARF-2 CFI and CRIS
18805 Set the usage of DWARF-2 CFI for CRIS debugging. The default is @samp{on}.
18806 Change to @samp{off} when using @code{gcc-cris} whose version is below
18809 @item show cris-dwarf2-cfi
18810 Show the current state of using DWARF-2 CFI.
18812 @item set cris-mode @var{mode}
18814 Set the current CRIS mode to @var{mode}. It should only be changed when
18815 debugging in guru mode, in which case it should be set to
18816 @samp{guru} (the default is @samp{normal}).
18818 @item show cris-mode
18819 Show the current CRIS mode.
18823 @subsection Renesas Super-H
18826 For the Renesas Super-H processor, @value{GDBN} provides these
18831 @kindex regs@r{, Super-H}
18832 Show the values of all Super-H registers.
18834 @item set sh calling-convention @var{convention}
18835 @kindex set sh calling-convention
18836 Set the calling-convention used when calling functions from @value{GDBN}.
18837 Allowed values are @samp{gcc}, which is the default setting, and @samp{renesas}.
18838 With the @samp{gcc} setting, functions are called using the @value{NGCC} calling
18839 convention. If the DWARF-2 information of the called function specifies
18840 that the function follows the Renesas calling convention, the function
18841 is called using the Renesas calling convention. If the calling convention
18842 is set to @samp{renesas}, the Renesas calling convention is always used,
18843 regardless of the DWARF-2 information. This can be used to override the
18844 default of @samp{gcc} if debug information is missing, or the compiler
18845 does not emit the DWARF-2 calling convention entry for a function.
18847 @item show sh calling-convention
18848 @kindex show sh calling-convention
18849 Show the current calling convention setting.
18854 @node Architectures
18855 @section Architectures
18857 This section describes characteristics of architectures that affect
18858 all uses of @value{GDBN} with the architecture, both native and cross.
18865 * HPPA:: HP PA architecture
18866 * SPU:: Cell Broadband Engine SPU architecture
18871 @subsection x86 Architecture-specific Issues
18874 @item set struct-convention @var{mode}
18875 @kindex set struct-convention
18876 @cindex struct return convention
18877 @cindex struct/union returned in registers
18878 Set the convention used by the inferior to return @code{struct}s and
18879 @code{union}s from functions to @var{mode}. Possible values of
18880 @var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the
18881 default). @code{"default"} or @code{"pcc"} means that @code{struct}s
18882 are returned on the stack, while @code{"reg"} means that a
18883 @code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will
18884 be returned in a register.
18886 @item show struct-convention
18887 @kindex show struct-convention
18888 Show the current setting of the convention to return @code{struct}s
18897 @kindex set rstack_high_address
18898 @cindex AMD 29K register stack
18899 @cindex register stack, AMD29K
18900 @item set rstack_high_address @var{address}
18901 On AMD 29000 family processors, registers are saved in a separate
18902 @dfn{register stack}. There is no way for @value{GDBN} to determine the
18903 extent of this stack. Normally, @value{GDBN} just assumes that the
18904 stack is ``large enough''. This may result in @value{GDBN} referencing
18905 memory locations that do not exist. If necessary, you can get around
18906 this problem by specifying the ending address of the register stack with
18907 the @code{set rstack_high_address} command. The argument should be an
18908 address, which you probably want to precede with @samp{0x} to specify in
18911 @kindex show rstack_high_address
18912 @item show rstack_high_address
18913 Display the current limit of the register stack, on AMD 29000 family
18921 See the following section.
18926 @cindex stack on Alpha
18927 @cindex stack on MIPS
18928 @cindex Alpha stack
18930 Alpha- and MIPS-based computers use an unusual stack frame, which
18931 sometimes requires @value{GDBN} to search backward in the object code to
18932 find the beginning of a function.
18934 @cindex response time, MIPS debugging
18935 To improve response time (especially for embedded applications, where
18936 @value{GDBN} may be restricted to a slow serial line for this search)
18937 you may want to limit the size of this search, using one of these
18941 @cindex @code{heuristic-fence-post} (Alpha, MIPS)
18942 @item set heuristic-fence-post @var{limit}
18943 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
18944 search for the beginning of a function. A value of @var{0} (the
18945 default) means there is no limit. However, except for @var{0}, the
18946 larger the limit the more bytes @code{heuristic-fence-post} must search
18947 and therefore the longer it takes to run. You should only need to use
18948 this command when debugging a stripped executable.
18950 @item show heuristic-fence-post
18951 Display the current limit.
18955 These commands are available @emph{only} when @value{GDBN} is configured
18956 for debugging programs on Alpha or MIPS processors.
18958 Several MIPS-specific commands are available when debugging MIPS
18962 @item set mips abi @var{arg}
18963 @kindex set mips abi
18964 @cindex set ABI for MIPS
18965 Tell @value{GDBN} which MIPS ABI is used by the inferior. Possible
18966 values of @var{arg} are:
18970 The default ABI associated with the current binary (this is the
18981 @item show mips abi
18982 @kindex show mips abi
18983 Show the MIPS ABI used by @value{GDBN} to debug the inferior.
18986 @itemx show mipsfpu
18987 @xref{MIPS Embedded, set mipsfpu}.
18989 @item set mips mask-address @var{arg}
18990 @kindex set mips mask-address
18991 @cindex MIPS addresses, masking
18992 This command determines whether the most-significant 32 bits of 64-bit
18993 MIPS addresses are masked off. The argument @var{arg} can be
18994 @samp{on}, @samp{off}, or @samp{auto}. The latter is the default
18995 setting, which lets @value{GDBN} determine the correct value.
18997 @item show mips mask-address
18998 @kindex show mips mask-address
18999 Show whether the upper 32 bits of MIPS addresses are masked off or
19002 @item set remote-mips64-transfers-32bit-regs
19003 @kindex set remote-mips64-transfers-32bit-regs
19004 This command controls compatibility with 64-bit MIPS targets that
19005 transfer data in 32-bit quantities. If you have an old MIPS 64 target
19006 that transfers 32 bits for some registers, like @sc{sr} and @sc{fsr},
19007 and 64 bits for other registers, set this option to @samp{on}.
19009 @item show remote-mips64-transfers-32bit-regs
19010 @kindex show remote-mips64-transfers-32bit-regs
19011 Show the current setting of compatibility with older MIPS 64 targets.
19013 @item set debug mips
19014 @kindex set debug mips
19015 This command turns on and off debugging messages for the MIPS-specific
19016 target code in @value{GDBN}.
19018 @item show debug mips
19019 @kindex show debug mips
19020 Show the current setting of MIPS debugging messages.
19026 @cindex HPPA support
19028 When @value{GDBN} is debugging the HP PA architecture, it provides the
19029 following special commands:
19032 @item set debug hppa
19033 @kindex set debug hppa
19034 This command determines whether HPPA architecture-specific debugging
19035 messages are to be displayed.
19037 @item show debug hppa
19038 Show whether HPPA debugging messages are displayed.
19040 @item maint print unwind @var{address}
19041 @kindex maint print unwind@r{, HPPA}
19042 This command displays the contents of the unwind table entry at the
19043 given @var{address}.
19049 @subsection Cell Broadband Engine SPU architecture
19050 @cindex Cell Broadband Engine
19053 When @value{GDBN} is debugging the Cell Broadband Engine SPU architecture,
19054 it provides the following special commands:
19057 @item info spu event
19059 Display SPU event facility status. Shows current event mask
19060 and pending event status.
19062 @item info spu signal
19063 Display SPU signal notification facility status. Shows pending
19064 signal-control word and signal notification mode of both signal
19065 notification channels.
19067 @item info spu mailbox
19068 Display SPU mailbox facility status. Shows all pending entries,
19069 in order of processing, in each of the SPU Write Outbound,
19070 SPU Write Outbound Interrupt, and SPU Read Inbound mailboxes.
19073 Display MFC DMA status. Shows all pending commands in the MFC
19074 DMA queue. For each entry, opcode, tag, class IDs, effective
19075 and local store addresses and transfer size are shown.
19077 @item info spu proxydma
19078 Display MFC Proxy-DMA status. Shows all pending commands in the MFC
19079 Proxy-DMA queue. For each entry, opcode, tag, class IDs, effective
19080 and local store addresses and transfer size are shown.
19084 When @value{GDBN} is debugging a combined PowerPC/SPU application
19085 on the Cell Broadband Engine, it provides in addition the following
19089 @item set spu stop-on-load @var{arg}
19091 Set whether to stop for new SPE threads. When set to @code{on}, @value{GDBN}
19092 will give control to the user when a new SPE thread enters its @code{main}
19093 function. The default is @code{off}.
19095 @item show spu stop-on-load
19097 Show whether to stop for new SPE threads.
19099 @item set spu auto-flush-cache @var{arg}
19100 Set whether to automatically flush the software-managed cache. When set to
19101 @code{on}, @value{GDBN} will automatically cause the SPE software-managed
19102 cache to be flushed whenever SPE execution stops. This provides a consistent
19103 view of PowerPC memory that is accessed via the cache. If an application
19104 does not use the software-managed cache, this option has no effect.
19106 @item show spu auto-flush-cache
19107 Show whether to automatically flush the software-managed cache.
19112 @subsection PowerPC
19113 @cindex PowerPC architecture
19115 When @value{GDBN} is debugging the PowerPC architecture, it provides a set of
19116 pseudo-registers to enable inspection of 128-bit wide Decimal Floating Point
19117 numbers stored in the floating point registers. These values must be stored
19118 in two consecutive registers, always starting at an even register like
19119 @code{f0} or @code{f2}.
19121 The pseudo-registers go from @code{$dl0} through @code{$dl15}, and are formed
19122 by joining the even/odd register pairs @code{f0} and @code{f1} for @code{$dl0},
19123 @code{f2} and @code{f3} for @code{$dl1} and so on.
19125 For POWER7 processors, @value{GDBN} provides a set of pseudo-registers, the 64-bit
19126 wide Extended Floating Point Registers (@samp{f32} through @samp{f63}).
19129 @node Controlling GDB
19130 @chapter Controlling @value{GDBN}
19132 You can alter the way @value{GDBN} interacts with you by using the
19133 @code{set} command. For commands controlling how @value{GDBN} displays
19134 data, see @ref{Print Settings, ,Print Settings}. Other settings are
19139 * Editing:: Command editing
19140 * Command History:: Command history
19141 * Screen Size:: Screen size
19142 * Numbers:: Numbers
19143 * ABI:: Configuring the current ABI
19144 * Messages/Warnings:: Optional warnings and messages
19145 * Debugging Output:: Optional messages about internal happenings
19146 * Other Misc Settings:: Other Miscellaneous Settings
19154 @value{GDBN} indicates its readiness to read a command by printing a string
19155 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
19156 can change the prompt string with the @code{set prompt} command. For
19157 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
19158 the prompt in one of the @value{GDBN} sessions so that you can always tell
19159 which one you are talking to.
19161 @emph{Note:} @code{set prompt} does not add a space for you after the
19162 prompt you set. This allows you to set a prompt which ends in a space
19163 or a prompt that does not.
19167 @item set prompt @var{newprompt}
19168 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
19170 @kindex show prompt
19172 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
19176 @section Command Editing
19178 @cindex command line editing
19180 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
19181 @sc{gnu} library provides consistent behavior for programs which provide a
19182 command line interface to the user. Advantages are @sc{gnu} Emacs-style
19183 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
19184 substitution, and a storage and recall of command history across
19185 debugging sessions.
19187 You may control the behavior of command line editing in @value{GDBN} with the
19188 command @code{set}.
19191 @kindex set editing
19194 @itemx set editing on
19195 Enable command line editing (enabled by default).
19197 @item set editing off
19198 Disable command line editing.
19200 @kindex show editing
19202 Show whether command line editing is enabled.
19205 @xref{Command Line Editing}, for more details about the Readline
19206 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
19207 encouraged to read that chapter.
19209 @node Command History
19210 @section Command History
19211 @cindex command history
19213 @value{GDBN} can keep track of the commands you type during your
19214 debugging sessions, so that you can be certain of precisely what
19215 happened. Use these commands to manage the @value{GDBN} command
19218 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
19219 package, to provide the history facility. @xref{Using History
19220 Interactively}, for the detailed description of the History library.
19222 To issue a command to @value{GDBN} without affecting certain aspects of
19223 the state which is seen by users, prefix it with @samp{server }
19224 (@pxref{Server Prefix}). This
19225 means that this command will not affect the command history, nor will it
19226 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
19227 pressed on a line by itself.
19229 @cindex @code{server}, command prefix
19230 The server prefix does not affect the recording of values into the value
19231 history; to print a value without recording it into the value history,
19232 use the @code{output} command instead of the @code{print} command.
19234 Here is the description of @value{GDBN} commands related to command
19238 @cindex history substitution
19239 @cindex history file
19240 @kindex set history filename
19241 @cindex @env{GDBHISTFILE}, environment variable
19242 @item set history filename @var{fname}
19243 Set the name of the @value{GDBN} command history file to @var{fname}.
19244 This is the file where @value{GDBN} reads an initial command history
19245 list, and where it writes the command history from this session when it
19246 exits. You can access this list through history expansion or through
19247 the history command editing characters listed below. This file defaults
19248 to the value of the environment variable @code{GDBHISTFILE}, or to
19249 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
19252 @cindex save command history
19253 @kindex set history save
19254 @item set history save
19255 @itemx set history save on
19256 Record command history in a file, whose name may be specified with the
19257 @code{set history filename} command. By default, this option is disabled.
19259 @item set history save off
19260 Stop recording command history in a file.
19262 @cindex history size
19263 @kindex set history size
19264 @cindex @env{HISTSIZE}, environment variable
19265 @item set history size @var{size}
19266 Set the number of commands which @value{GDBN} keeps in its history list.
19267 This defaults to the value of the environment variable
19268 @code{HISTSIZE}, or to 256 if this variable is not set.
19271 History expansion assigns special meaning to the character @kbd{!}.
19272 @xref{Event Designators}, for more details.
19274 @cindex history expansion, turn on/off
19275 Since @kbd{!} is also the logical not operator in C, history expansion
19276 is off by default. If you decide to enable history expansion with the
19277 @code{set history expansion on} command, you may sometimes need to
19278 follow @kbd{!} (when it is used as logical not, in an expression) with
19279 a space or a tab to prevent it from being expanded. The readline
19280 history facilities do not attempt substitution on the strings
19281 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
19283 The commands to control history expansion are:
19286 @item set history expansion on
19287 @itemx set history expansion
19288 @kindex set history expansion
19289 Enable history expansion. History expansion is off by default.
19291 @item set history expansion off
19292 Disable history expansion.
19295 @kindex show history
19297 @itemx show history filename
19298 @itemx show history save
19299 @itemx show history size
19300 @itemx show history expansion
19301 These commands display the state of the @value{GDBN} history parameters.
19302 @code{show history} by itself displays all four states.
19307 @kindex show commands
19308 @cindex show last commands
19309 @cindex display command history
19310 @item show commands
19311 Display the last ten commands in the command history.
19313 @item show commands @var{n}
19314 Print ten commands centered on command number @var{n}.
19316 @item show commands +
19317 Print ten commands just after the commands last printed.
19321 @section Screen Size
19322 @cindex size of screen
19323 @cindex pauses in output
19325 Certain commands to @value{GDBN} may produce large amounts of
19326 information output to the screen. To help you read all of it,
19327 @value{GDBN} pauses and asks you for input at the end of each page of
19328 output. Type @key{RET} when you want to continue the output, or @kbd{q}
19329 to discard the remaining output. Also, the screen width setting
19330 determines when to wrap lines of output. Depending on what is being
19331 printed, @value{GDBN} tries to break the line at a readable place,
19332 rather than simply letting it overflow onto the following line.
19334 Normally @value{GDBN} knows the size of the screen from the terminal
19335 driver software. For example, on Unix @value{GDBN} uses the termcap data base
19336 together with the value of the @code{TERM} environment variable and the
19337 @code{stty rows} and @code{stty cols} settings. If this is not correct,
19338 you can override it with the @code{set height} and @code{set
19345 @kindex show height
19346 @item set height @var{lpp}
19348 @itemx set width @var{cpl}
19350 These @code{set} commands specify a screen height of @var{lpp} lines and
19351 a screen width of @var{cpl} characters. The associated @code{show}
19352 commands display the current settings.
19354 If you specify a height of zero lines, @value{GDBN} does not pause during
19355 output no matter how long the output is. This is useful if output is to a
19356 file or to an editor buffer.
19358 Likewise, you can specify @samp{set width 0} to prevent @value{GDBN}
19359 from wrapping its output.
19361 @item set pagination on
19362 @itemx set pagination off
19363 @kindex set pagination
19364 Turn the output pagination on or off; the default is on. Turning
19365 pagination off is the alternative to @code{set height 0}. Note that
19366 running @value{GDBN} with the @option{--batch} option (@pxref{Mode
19367 Options, -batch}) also automatically disables pagination.
19369 @item show pagination
19370 @kindex show pagination
19371 Show the current pagination mode.
19376 @cindex number representation
19377 @cindex entering numbers
19379 You can always enter numbers in octal, decimal, or hexadecimal in
19380 @value{GDBN} by the usual conventions: octal numbers begin with
19381 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
19382 begin with @samp{0x}. Numbers that neither begin with @samp{0} or
19383 @samp{0x}, nor end with a @samp{.} are, by default, entered in base
19384 10; likewise, the default display for numbers---when no particular
19385 format is specified---is base 10. You can change the default base for
19386 both input and output with the commands described below.
19389 @kindex set input-radix
19390 @item set input-radix @var{base}
19391 Set the default base for numeric input. Supported choices
19392 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
19393 specified either unambiguously or using the current input radix; for
19397 set input-radix 012
19398 set input-radix 10.
19399 set input-radix 0xa
19403 sets the input base to decimal. On the other hand, @samp{set input-radix 10}
19404 leaves the input radix unchanged, no matter what it was, since
19405 @samp{10}, being without any leading or trailing signs of its base, is
19406 interpreted in the current radix. Thus, if the current radix is 16,
19407 @samp{10} is interpreted in hex, i.e.@: as 16 decimal, which doesn't
19410 @kindex set output-radix
19411 @item set output-radix @var{base}
19412 Set the default base for numeric display. Supported choices
19413 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
19414 specified either unambiguously or using the current input radix.
19416 @kindex show input-radix
19417 @item show input-radix
19418 Display the current default base for numeric input.
19420 @kindex show output-radix
19421 @item show output-radix
19422 Display the current default base for numeric display.
19424 @item set radix @r{[}@var{base}@r{]}
19428 These commands set and show the default base for both input and output
19429 of numbers. @code{set radix} sets the radix of input and output to
19430 the same base; without an argument, it resets the radix back to its
19431 default value of 10.
19436 @section Configuring the Current ABI
19438 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
19439 application automatically. However, sometimes you need to override its
19440 conclusions. Use these commands to manage @value{GDBN}'s view of the
19447 One @value{GDBN} configuration can debug binaries for multiple operating
19448 system targets, either via remote debugging or native emulation.
19449 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
19450 but you can override its conclusion using the @code{set osabi} command.
19451 One example where this is useful is in debugging of binaries which use
19452 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
19453 not have the same identifying marks that the standard C library for your
19458 Show the OS ABI currently in use.
19461 With no argument, show the list of registered available OS ABI's.
19463 @item set osabi @var{abi}
19464 Set the current OS ABI to @var{abi}.
19467 @cindex float promotion
19469 Generally, the way that an argument of type @code{float} is passed to a
19470 function depends on whether the function is prototyped. For a prototyped
19471 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
19472 according to the architecture's convention for @code{float}. For unprototyped
19473 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
19474 @code{double} and then passed.
19476 Unfortunately, some forms of debug information do not reliably indicate whether
19477 a function is prototyped. If @value{GDBN} calls a function that is not marked
19478 as prototyped, it consults @kbd{set coerce-float-to-double}.
19481 @kindex set coerce-float-to-double
19482 @item set coerce-float-to-double
19483 @itemx set coerce-float-to-double on
19484 Arguments of type @code{float} will be promoted to @code{double} when passed
19485 to an unprototyped function. This is the default setting.
19487 @item set coerce-float-to-double off
19488 Arguments of type @code{float} will be passed directly to unprototyped
19491 @kindex show coerce-float-to-double
19492 @item show coerce-float-to-double
19493 Show the current setting of promoting @code{float} to @code{double}.
19497 @kindex show cp-abi
19498 @value{GDBN} needs to know the ABI used for your program's C@t{++}
19499 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
19500 used to build your application. @value{GDBN} only fully supports
19501 programs with a single C@t{++} ABI; if your program contains code using
19502 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
19503 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
19504 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
19505 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
19506 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
19507 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
19512 Show the C@t{++} ABI currently in use.
19515 With no argument, show the list of supported C@t{++} ABI's.
19517 @item set cp-abi @var{abi}
19518 @itemx set cp-abi auto
19519 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
19522 @node Messages/Warnings
19523 @section Optional Warnings and Messages
19525 @cindex verbose operation
19526 @cindex optional warnings
19527 By default, @value{GDBN} is silent about its inner workings. If you are
19528 running on a slow machine, you may want to use the @code{set verbose}
19529 command. This makes @value{GDBN} tell you when it does a lengthy
19530 internal operation, so you will not think it has crashed.
19532 Currently, the messages controlled by @code{set verbose} are those
19533 which announce that the symbol table for a source file is being read;
19534 see @code{symbol-file} in @ref{Files, ,Commands to Specify Files}.
19537 @kindex set verbose
19538 @item set verbose on
19539 Enables @value{GDBN} output of certain informational messages.
19541 @item set verbose off
19542 Disables @value{GDBN} output of certain informational messages.
19544 @kindex show verbose
19546 Displays whether @code{set verbose} is on or off.
19549 By default, if @value{GDBN} encounters bugs in the symbol table of an
19550 object file, it is silent; but if you are debugging a compiler, you may
19551 find this information useful (@pxref{Symbol Errors, ,Errors Reading
19556 @kindex set complaints
19557 @item set complaints @var{limit}
19558 Permits @value{GDBN} to output @var{limit} complaints about each type of
19559 unusual symbols before becoming silent about the problem. Set
19560 @var{limit} to zero to suppress all complaints; set it to a large number
19561 to prevent complaints from being suppressed.
19563 @kindex show complaints
19564 @item show complaints
19565 Displays how many symbol complaints @value{GDBN} is permitted to produce.
19569 @anchor{confirmation requests}
19570 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
19571 lot of stupid questions to confirm certain commands. For example, if
19572 you try to run a program which is already running:
19576 The program being debugged has been started already.
19577 Start it from the beginning? (y or n)
19580 If you are willing to unflinchingly face the consequences of your own
19581 commands, you can disable this ``feature'':
19585 @kindex set confirm
19587 @cindex confirmation
19588 @cindex stupid questions
19589 @item set confirm off
19590 Disables confirmation requests. Note that running @value{GDBN} with
19591 the @option{--batch} option (@pxref{Mode Options, -batch}) also
19592 automatically disables confirmation requests.
19594 @item set confirm on
19595 Enables confirmation requests (the default).
19597 @kindex show confirm
19599 Displays state of confirmation requests.
19603 @cindex command tracing
19604 If you need to debug user-defined commands or sourced files you may find it
19605 useful to enable @dfn{command tracing}. In this mode each command will be
19606 printed as it is executed, prefixed with one or more @samp{+} symbols, the
19607 quantity denoting the call depth of each command.
19610 @kindex set trace-commands
19611 @cindex command scripts, debugging
19612 @item set trace-commands on
19613 Enable command tracing.
19614 @item set trace-commands off
19615 Disable command tracing.
19616 @item show trace-commands
19617 Display the current state of command tracing.
19620 @node Debugging Output
19621 @section Optional Messages about Internal Happenings
19622 @cindex optional debugging messages
19624 @value{GDBN} has commands that enable optional debugging messages from
19625 various @value{GDBN} subsystems; normally these commands are of
19626 interest to @value{GDBN} maintainers, or when reporting a bug. This
19627 section documents those commands.
19630 @kindex set exec-done-display
19631 @item set exec-done-display
19632 Turns on or off the notification of asynchronous commands'
19633 completion. When on, @value{GDBN} will print a message when an
19634 asynchronous command finishes its execution. The default is off.
19635 @kindex show exec-done-display
19636 @item show exec-done-display
19637 Displays the current setting of asynchronous command completion
19640 @cindex gdbarch debugging info
19641 @cindex architecture debugging info
19642 @item set debug arch
19643 Turns on or off display of gdbarch debugging info. The default is off
19645 @item show debug arch
19646 Displays the current state of displaying gdbarch debugging info.
19647 @item set debug aix-thread
19648 @cindex AIX threads
19649 Display debugging messages about inner workings of the AIX thread
19651 @item show debug aix-thread
19652 Show the current state of AIX thread debugging info display.
19653 @item set debug dwarf2-die
19654 @cindex DWARF2 DIEs
19655 Dump DWARF2 DIEs after they are read in.
19656 The value is the number of nesting levels to print.
19657 A value of zero turns off the display.
19658 @item show debug dwarf2-die
19659 Show the current state of DWARF2 DIE debugging.
19660 @item set debug displaced
19661 @cindex displaced stepping debugging info
19662 Turns on or off display of @value{GDBN} debugging info for the
19663 displaced stepping support. The default is off.
19664 @item show debug displaced
19665 Displays the current state of displaying @value{GDBN} debugging info
19666 related to displaced stepping.
19667 @item set debug event
19668 @cindex event debugging info
19669 Turns on or off display of @value{GDBN} event debugging info. The
19671 @item show debug event
19672 Displays the current state of displaying @value{GDBN} event debugging
19674 @item set debug expression
19675 @cindex expression debugging info
19676 Turns on or off display of debugging info about @value{GDBN}
19677 expression parsing. The default is off.
19678 @item show debug expression
19679 Displays the current state of displaying debugging info about
19680 @value{GDBN} expression parsing.
19681 @item set debug frame
19682 @cindex frame debugging info
19683 Turns on or off display of @value{GDBN} frame debugging info. The
19685 @item show debug frame
19686 Displays the current state of displaying @value{GDBN} frame debugging
19688 @item set debug gnu-nat
19689 @cindex @sc{gnu}/Hurd debug messages
19690 Turns on or off debugging messages from the @sc{gnu}/Hurd debug support.
19691 @item show debug gnu-nat
19692 Show the current state of @sc{gnu}/Hurd debugging messages.
19693 @item set debug infrun
19694 @cindex inferior debugging info
19695 Turns on or off display of @value{GDBN} debugging info for running the inferior.
19696 The default is off. @file{infrun.c} contains GDB's runtime state machine used
19697 for implementing operations such as single-stepping the inferior.
19698 @item show debug infrun
19699 Displays the current state of @value{GDBN} inferior debugging.
19700 @item set debug lin-lwp
19701 @cindex @sc{gnu}/Linux LWP debug messages
19702 @cindex Linux lightweight processes
19703 Turns on or off debugging messages from the Linux LWP debug support.
19704 @item show debug lin-lwp
19705 Show the current state of Linux LWP debugging messages.
19706 @item set debug lin-lwp-async
19707 @cindex @sc{gnu}/Linux LWP async debug messages
19708 @cindex Linux lightweight processes
19709 Turns on or off debugging messages from the Linux LWP async debug support.
19710 @item show debug lin-lwp-async
19711 Show the current state of Linux LWP async debugging messages.
19712 @item set debug observer
19713 @cindex observer debugging info
19714 Turns on or off display of @value{GDBN} observer debugging. This
19715 includes info such as the notification of observable events.
19716 @item show debug observer
19717 Displays the current state of observer debugging.
19718 @item set debug overload
19719 @cindex C@t{++} overload debugging info
19720 Turns on or off display of @value{GDBN} C@t{++} overload debugging
19721 info. This includes info such as ranking of functions, etc. The default
19723 @item show debug overload
19724 Displays the current state of displaying @value{GDBN} C@t{++} overload
19726 @cindex expression parser, debugging info
19727 @cindex debug expression parser
19728 @item set debug parser
19729 Turns on or off the display of expression parser debugging output.
19730 Internally, this sets the @code{yydebug} variable in the expression
19731 parser. @xref{Tracing, , Tracing Your Parser, bison, Bison}, for
19732 details. The default is off.
19733 @item show debug parser
19734 Show the current state of expression parser debugging.
19735 @cindex packets, reporting on stdout
19736 @cindex serial connections, debugging
19737 @cindex debug remote protocol
19738 @cindex remote protocol debugging
19739 @cindex display remote packets
19740 @item set debug remote
19741 Turns on or off display of reports on all packets sent back and forth across
19742 the serial line to the remote machine. The info is printed on the
19743 @value{GDBN} standard output stream. The default is off.
19744 @item show debug remote
19745 Displays the state of display of remote packets.
19746 @item set debug serial
19747 Turns on or off display of @value{GDBN} serial debugging info. The
19749 @item show debug serial
19750 Displays the current state of displaying @value{GDBN} serial debugging
19752 @item set debug solib-frv
19753 @cindex FR-V shared-library debugging
19754 Turns on or off debugging messages for FR-V shared-library code.
19755 @item show debug solib-frv
19756 Display the current state of FR-V shared-library code debugging
19758 @item set debug target
19759 @cindex target debugging info
19760 Turns on or off display of @value{GDBN} target debugging info. This info
19761 includes what is going on at the target level of GDB, as it happens. The
19762 default is 0. Set it to 1 to track events, and to 2 to also track the
19763 value of large memory transfers. Changes to this flag do not take effect
19764 until the next time you connect to a target or use the @code{run} command.
19765 @item show debug target
19766 Displays the current state of displaying @value{GDBN} target debugging
19768 @item set debug timestamp
19769 @cindex timestampping debugging info
19770 Turns on or off display of timestamps with @value{GDBN} debugging info.
19771 When enabled, seconds and microseconds are displayed before each debugging
19773 @item show debug timestamp
19774 Displays the current state of displaying timestamps with @value{GDBN}
19776 @item set debugvarobj
19777 @cindex variable object debugging info
19778 Turns on or off display of @value{GDBN} variable object debugging
19779 info. The default is off.
19780 @item show debugvarobj
19781 Displays the current state of displaying @value{GDBN} variable object
19783 @item set debug xml
19784 @cindex XML parser debugging
19785 Turns on or off debugging messages for built-in XML parsers.
19786 @item show debug xml
19787 Displays the current state of XML debugging messages.
19790 @node Other Misc Settings
19791 @section Other Miscellaneous Settings
19792 @cindex miscellaneous settings
19795 @kindex set interactive-mode
19796 @item set interactive-mode
19797 If @code{on}, forces @value{GDBN} to operate interactively.
19798 If @code{off}, forces @value{GDBN} to operate non-interactively,
19799 If @code{auto} (the default), @value{GDBN} guesses which mode to use,
19800 based on whether the debugger was started in a terminal or not.
19802 In the vast majority of cases, the debugger should be able to guess
19803 correctly which mode should be used. But this setting can be useful
19804 in certain specific cases, such as running a MinGW @value{GDBN}
19805 inside a cygwin window.
19807 @kindex show interactive-mode
19808 @item show interactive-mode
19809 Displays whether the debugger is operating in interactive mode or not.
19812 @node Extending GDB
19813 @chapter Extending @value{GDBN}
19814 @cindex extending GDB
19816 @value{GDBN} provides two mechanisms for extension. The first is based
19817 on composition of @value{GDBN} commands, and the second is based on the
19818 Python scripting language.
19820 To facilitate the use of these extensions, @value{GDBN} is capable
19821 of evaluating the contents of a file. When doing so, @value{GDBN}
19822 can recognize which scripting language is being used by looking at
19823 the filename extension. Files with an unrecognized filename extension
19824 are always treated as a @value{GDBN} Command Files.
19825 @xref{Command Files,, Command files}.
19827 You can control how @value{GDBN} evaluates these files with the following
19831 @kindex set script-extension
19832 @kindex show script-extension
19833 @item set script-extension off
19834 All scripts are always evaluated as @value{GDBN} Command Files.
19836 @item set script-extension soft
19837 The debugger determines the scripting language based on filename
19838 extension. If this scripting language is supported, @value{GDBN}
19839 evaluates the script using that language. Otherwise, it evaluates
19840 the file as a @value{GDBN} Command File.
19842 @item set script-extension strict
19843 The debugger determines the scripting language based on filename
19844 extension, and evaluates the script using that language. If the
19845 language is not supported, then the evaluation fails.
19847 @item show script-extension
19848 Display the current value of the @code{script-extension} option.
19853 * Sequences:: Canned Sequences of Commands
19854 * Python:: Scripting @value{GDBN} using Python
19858 @section Canned Sequences of Commands
19860 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
19861 Command Lists}), @value{GDBN} provides two ways to store sequences of
19862 commands for execution as a unit: user-defined commands and command
19866 * Define:: How to define your own commands
19867 * Hooks:: Hooks for user-defined commands
19868 * Command Files:: How to write scripts of commands to be stored in a file
19869 * Output:: Commands for controlled output
19873 @subsection User-defined Commands
19875 @cindex user-defined command
19876 @cindex arguments, to user-defined commands
19877 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
19878 which you assign a new name as a command. This is done with the
19879 @code{define} command. User commands may accept up to 10 arguments
19880 separated by whitespace. Arguments are accessed within the user command
19881 via @code{$arg0@dots{}$arg9}. A trivial example:
19885 print $arg0 + $arg1 + $arg2
19890 To execute the command use:
19897 This defines the command @code{adder}, which prints the sum of
19898 its three arguments. Note the arguments are text substitutions, so they may
19899 reference variables, use complex expressions, or even perform inferior
19902 @cindex argument count in user-defined commands
19903 @cindex how many arguments (user-defined commands)
19904 In addition, @code{$argc} may be used to find out how many arguments have
19905 been passed. This expands to a number in the range 0@dots{}10.
19910 print $arg0 + $arg1
19913 print $arg0 + $arg1 + $arg2
19921 @item define @var{commandname}
19922 Define a command named @var{commandname}. If there is already a command
19923 by that name, you are asked to confirm that you want to redefine it.
19924 @var{commandname} may be a bare command name consisting of letters,
19925 numbers, dashes, and underscores. It may also start with any predefined
19926 prefix command. For example, @samp{define target my-target} creates
19927 a user-defined @samp{target my-target} command.
19929 The definition of the command is made up of other @value{GDBN} command lines,
19930 which are given following the @code{define} command. The end of these
19931 commands is marked by a line containing @code{end}.
19934 @kindex end@r{ (user-defined commands)}
19935 @item document @var{commandname}
19936 Document the user-defined command @var{commandname}, so that it can be
19937 accessed by @code{help}. The command @var{commandname} must already be
19938 defined. This command reads lines of documentation just as @code{define}
19939 reads the lines of the command definition, ending with @code{end}.
19940 After the @code{document} command is finished, @code{help} on command
19941 @var{commandname} displays the documentation you have written.
19943 You may use the @code{document} command again to change the
19944 documentation of a command. Redefining the command with @code{define}
19945 does not change the documentation.
19947 @kindex dont-repeat
19948 @cindex don't repeat command
19950 Used inside a user-defined command, this tells @value{GDBN} that this
19951 command should not be repeated when the user hits @key{RET}
19952 (@pxref{Command Syntax, repeat last command}).
19954 @kindex help user-defined
19955 @item help user-defined
19956 List all user-defined commands, with the first line of the documentation
19961 @itemx show user @var{commandname}
19962 Display the @value{GDBN} commands used to define @var{commandname} (but
19963 not its documentation). If no @var{commandname} is given, display the
19964 definitions for all user-defined commands.
19966 @cindex infinite recursion in user-defined commands
19967 @kindex show max-user-call-depth
19968 @kindex set max-user-call-depth
19969 @item show max-user-call-depth
19970 @itemx set max-user-call-depth
19971 The value of @code{max-user-call-depth} controls how many recursion
19972 levels are allowed in user-defined commands before @value{GDBN} suspects an
19973 infinite recursion and aborts the command.
19976 In addition to the above commands, user-defined commands frequently
19977 use control flow commands, described in @ref{Command Files}.
19979 When user-defined commands are executed, the
19980 commands of the definition are not printed. An error in any command
19981 stops execution of the user-defined command.
19983 If used interactively, commands that would ask for confirmation proceed
19984 without asking when used inside a user-defined command. Many @value{GDBN}
19985 commands that normally print messages to say what they are doing omit the
19986 messages when used in a user-defined command.
19989 @subsection User-defined Command Hooks
19990 @cindex command hooks
19991 @cindex hooks, for commands
19992 @cindex hooks, pre-command
19995 You may define @dfn{hooks}, which are a special kind of user-defined
19996 command. Whenever you run the command @samp{foo}, if the user-defined
19997 command @samp{hook-foo} exists, it is executed (with no arguments)
19998 before that command.
20000 @cindex hooks, post-command
20002 A hook may also be defined which is run after the command you executed.
20003 Whenever you run the command @samp{foo}, if the user-defined command
20004 @samp{hookpost-foo} exists, it is executed (with no arguments) after
20005 that command. Post-execution hooks may exist simultaneously with
20006 pre-execution hooks, for the same command.
20008 It is valid for a hook to call the command which it hooks. If this
20009 occurs, the hook is not re-executed, thereby avoiding infinite recursion.
20011 @c It would be nice if hookpost could be passed a parameter indicating
20012 @c if the command it hooks executed properly or not. FIXME!
20014 @kindex stop@r{, a pseudo-command}
20015 In addition, a pseudo-command, @samp{stop} exists. Defining
20016 (@samp{hook-stop}) makes the associated commands execute every time
20017 execution stops in your program: before breakpoint commands are run,
20018 displays are printed, or the stack frame is printed.
20020 For example, to ignore @code{SIGALRM} signals while
20021 single-stepping, but treat them normally during normal execution,
20026 handle SIGALRM nopass
20030 handle SIGALRM pass
20033 define hook-continue
20034 handle SIGALRM pass
20038 As a further example, to hook at the beginning and end of the @code{echo}
20039 command, and to add extra text to the beginning and end of the message,
20047 define hookpost-echo
20051 (@value{GDBP}) echo Hello World
20052 <<<---Hello World--->>>
20057 You can define a hook for any single-word command in @value{GDBN}, but
20058 not for command aliases; you should define a hook for the basic command
20059 name, e.g.@: @code{backtrace} rather than @code{bt}.
20060 @c FIXME! So how does Joe User discover whether a command is an alias
20062 You can hook a multi-word command by adding @code{hook-} or
20063 @code{hookpost-} to the last word of the command, e.g.@:
20064 @samp{define target hook-remote} to add a hook to @samp{target remote}.
20066 If an error occurs during the execution of your hook, execution of
20067 @value{GDBN} commands stops and @value{GDBN} issues a prompt
20068 (before the command that you actually typed had a chance to run).
20070 If you try to define a hook which does not match any known command, you
20071 get a warning from the @code{define} command.
20073 @node Command Files
20074 @subsection Command Files
20076 @cindex command files
20077 @cindex scripting commands
20078 A command file for @value{GDBN} is a text file made of lines that are
20079 @value{GDBN} commands. Comments (lines starting with @kbd{#}) may
20080 also be included. An empty line in a command file does nothing; it
20081 does not mean to repeat the last command, as it would from the
20084 You can request the execution of a command file with the @code{source}
20085 command. Note that the @code{source} command is also used to evaluate
20086 scripts that are not Command Files. The exact behavior can be configured
20087 using the @code{script-extension} setting.
20088 @xref{Extending GDB,, Extending GDB}.
20092 @cindex execute commands from a file
20093 @item source [-s] [-v] @var{filename}
20094 Execute the command file @var{filename}.
20097 The lines in a command file are generally executed sequentially,
20098 unless the order of execution is changed by one of the
20099 @emph{flow-control commands} described below. The commands are not
20100 printed as they are executed. An error in any command terminates
20101 execution of the command file and control is returned to the console.
20103 @value{GDBN} first searches for @var{filename} in the current directory.
20104 If the file is not found there, and @var{filename} does not specify a
20105 directory, then @value{GDBN} also looks for the file on the source search path
20106 (specified with the @samp{directory} command);
20107 except that @file{$cdir} is not searched because the compilation directory
20108 is not relevant to scripts.
20110 If @code{-s} is specified, then @value{GDBN} searches for @var{filename}
20111 on the search path even if @var{filename} specifies a directory.
20112 The search is done by appending @var{filename} to each element of the
20113 search path. So, for example, if @var{filename} is @file{mylib/myscript}
20114 and the search path contains @file{/home/user} then @value{GDBN} will
20115 look for the script @file{/home/user/mylib/myscript}.
20116 The search is also done if @var{filename} is an absolute path.
20117 For example, if @var{filename} is @file{/tmp/myscript} and
20118 the search path contains @file{/home/user} then @value{GDBN} will
20119 look for the script @file{/home/user/tmp/myscript}.
20120 For DOS-like systems, if @var{filename} contains a drive specification,
20121 it is stripped before concatenation. For example, if @var{filename} is
20122 @file{d:myscript} and the search path contains @file{c:/tmp} then @value{GDBN}
20123 will look for the script @file{c:/tmp/myscript}.
20125 If @code{-v}, for verbose mode, is given then @value{GDBN} displays
20126 each command as it is executed. The option must be given before
20127 @var{filename}, and is interpreted as part of the filename anywhere else.
20129 Commands that would ask for confirmation if used interactively proceed
20130 without asking when used in a command file. Many @value{GDBN} commands that
20131 normally print messages to say what they are doing omit the messages
20132 when called from command files.
20134 @value{GDBN} also accepts command input from standard input. In this
20135 mode, normal output goes to standard output and error output goes to
20136 standard error. Errors in a command file supplied on standard input do
20137 not terminate execution of the command file---execution continues with
20141 gdb < cmds > log 2>&1
20144 (The syntax above will vary depending on the shell used.) This example
20145 will execute commands from the file @file{cmds}. All output and errors
20146 would be directed to @file{log}.
20148 Since commands stored on command files tend to be more general than
20149 commands typed interactively, they frequently need to deal with
20150 complicated situations, such as different or unexpected values of
20151 variables and symbols, changes in how the program being debugged is
20152 built, etc. @value{GDBN} provides a set of flow-control commands to
20153 deal with these complexities. Using these commands, you can write
20154 complex scripts that loop over data structures, execute commands
20155 conditionally, etc.
20162 This command allows to include in your script conditionally executed
20163 commands. The @code{if} command takes a single argument, which is an
20164 expression to evaluate. It is followed by a series of commands that
20165 are executed only if the expression is true (its value is nonzero).
20166 There can then optionally be an @code{else} line, followed by a series
20167 of commands that are only executed if the expression was false. The
20168 end of the list is marked by a line containing @code{end}.
20172 This command allows to write loops. Its syntax is similar to
20173 @code{if}: the command takes a single argument, which is an expression
20174 to evaluate, and must be followed by the commands to execute, one per
20175 line, terminated by an @code{end}. These commands are called the
20176 @dfn{body} of the loop. The commands in the body of @code{while} are
20177 executed repeatedly as long as the expression evaluates to true.
20181 This command exits the @code{while} loop in whose body it is included.
20182 Execution of the script continues after that @code{while}s @code{end}
20185 @kindex loop_continue
20186 @item loop_continue
20187 This command skips the execution of the rest of the body of commands
20188 in the @code{while} loop in whose body it is included. Execution
20189 branches to the beginning of the @code{while} loop, where it evaluates
20190 the controlling expression.
20192 @kindex end@r{ (if/else/while commands)}
20194 Terminate the block of commands that are the body of @code{if},
20195 @code{else}, or @code{while} flow-control commands.
20200 @subsection Commands for Controlled Output
20202 During the execution of a command file or a user-defined command, normal
20203 @value{GDBN} output is suppressed; the only output that appears is what is
20204 explicitly printed by the commands in the definition. This section
20205 describes three commands useful for generating exactly the output you
20210 @item echo @var{text}
20211 @c I do not consider backslash-space a standard C escape sequence
20212 @c because it is not in ANSI.
20213 Print @var{text}. Nonprinting characters can be included in
20214 @var{text} using C escape sequences, such as @samp{\n} to print a
20215 newline. @strong{No newline is printed unless you specify one.}
20216 In addition to the standard C escape sequences, a backslash followed
20217 by a space stands for a space. This is useful for displaying a
20218 string with spaces at the beginning or the end, since leading and
20219 trailing spaces are otherwise trimmed from all arguments.
20220 To print @samp{@w{ }and foo =@w{ }}, use the command
20221 @samp{echo \@w{ }and foo = \@w{ }}.
20223 A backslash at the end of @var{text} can be used, as in C, to continue
20224 the command onto subsequent lines. For example,
20227 echo This is some text\n\
20228 which is continued\n\
20229 onto several lines.\n
20232 produces the same output as
20235 echo This is some text\n
20236 echo which is continued\n
20237 echo onto several lines.\n
20241 @item output @var{expression}
20242 Print the value of @var{expression} and nothing but that value: no
20243 newlines, no @samp{$@var{nn} = }. The value is not entered in the
20244 value history either. @xref{Expressions, ,Expressions}, for more information
20247 @item output/@var{fmt} @var{expression}
20248 Print the value of @var{expression} in format @var{fmt}. You can use
20249 the same formats as for @code{print}. @xref{Output Formats,,Output
20250 Formats}, for more information.
20253 @item printf @var{template}, @var{expressions}@dots{}
20254 Print the values of one or more @var{expressions} under the control of
20255 the string @var{template}. To print several values, make
20256 @var{expressions} be a comma-separated list of individual expressions,
20257 which may be either numbers or pointers. Their values are printed as
20258 specified by @var{template}, exactly as a C program would do by
20259 executing the code below:
20262 printf (@var{template}, @var{expressions}@dots{});
20265 As in @code{C} @code{printf}, ordinary characters in @var{template}
20266 are printed verbatim, while @dfn{conversion specification} introduced
20267 by the @samp{%} character cause subsequent @var{expressions} to be
20268 evaluated, their values converted and formatted according to type and
20269 style information encoded in the conversion specifications, and then
20272 For example, you can print two values in hex like this:
20275 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
20278 @code{printf} supports all the standard @code{C} conversion
20279 specifications, including the flags and modifiers between the @samp{%}
20280 character and the conversion letter, with the following exceptions:
20284 The argument-ordering modifiers, such as @samp{2$}, are not supported.
20287 The modifier @samp{*} is not supported for specifying precision or
20291 The @samp{'} flag (for separation of digits into groups according to
20292 @code{LC_NUMERIC'}) is not supported.
20295 The type modifiers @samp{hh}, @samp{j}, @samp{t}, and @samp{z} are not
20299 The conversion letter @samp{n} (as in @samp{%n}) is not supported.
20302 The conversion letters @samp{a} and @samp{A} are not supported.
20306 Note that the @samp{ll} type modifier is supported only if the
20307 underlying @code{C} implementation used to build @value{GDBN} supports
20308 the @code{long long int} type, and the @samp{L} type modifier is
20309 supported only if @code{long double} type is available.
20311 As in @code{C}, @code{printf} supports simple backslash-escape
20312 sequences, such as @code{\n}, @samp{\t}, @samp{\\}, @samp{\"},
20313 @samp{\a}, and @samp{\f}, that consist of backslash followed by a
20314 single character. Octal and hexadecimal escape sequences are not
20317 Additionally, @code{printf} supports conversion specifications for DFP
20318 (@dfn{Decimal Floating Point}) types using the following length modifiers
20319 together with a floating point specifier.
20324 @samp{H} for printing @code{Decimal32} types.
20327 @samp{D} for printing @code{Decimal64} types.
20330 @samp{DD} for printing @code{Decimal128} types.
20333 If the underlying @code{C} implementation used to build @value{GDBN} has
20334 support for the three length modifiers for DFP types, other modifiers
20335 such as width and precision will also be available for @value{GDBN} to use.
20337 In case there is no such @code{C} support, no additional modifiers will be
20338 available and the value will be printed in the standard way.
20340 Here's an example of printing DFP types using the above conversion letters:
20342 printf "D32: %Hf - D64: %Df - D128: %DDf\n",1.2345df,1.2E10dd,1.2E1dl
20346 @item eval @var{template}, @var{expressions}@dots{}
20347 Convert the values of one or more @var{expressions} under the control of
20348 the string @var{template} to a command line, and call it.
20353 @section Scripting @value{GDBN} using Python
20354 @cindex python scripting
20355 @cindex scripting with python
20357 You can script @value{GDBN} using the @uref{http://www.python.org/,
20358 Python programming language}. This feature is available only if
20359 @value{GDBN} was configured using @option{--with-python}.
20361 @cindex python directory
20362 Python scripts used by @value{GDBN} should be installed in
20363 @file{@var{data-directory}/python}, where @var{data-directory} is
20364 the data directory as determined at @value{GDBN} startup (@pxref{Data Files}). This directory, known as the @dfn{python directory},
20365 is automatically added to the Python Search Path in order to allow
20366 the Python interpreter to locate all scripts installed at this location.
20369 * Python Commands:: Accessing Python from @value{GDBN}.
20370 * Python API:: Accessing @value{GDBN} from Python.
20371 * Auto-loading:: Automatically loading Python code.
20374 @node Python Commands
20375 @subsection Python Commands
20376 @cindex python commands
20377 @cindex commands to access python
20379 @value{GDBN} provides one command for accessing the Python interpreter,
20380 and one related setting:
20384 @item python @r{[}@var{code}@r{]}
20385 The @code{python} command can be used to evaluate Python code.
20387 If given an argument, the @code{python} command will evaluate the
20388 argument as a Python command. For example:
20391 (@value{GDBP}) python print 23
20395 If you do not provide an argument to @code{python}, it will act as a
20396 multi-line command, like @code{define}. In this case, the Python
20397 script is made up of subsequent command lines, given after the
20398 @code{python} command. This command list is terminated using a line
20399 containing @code{end}. For example:
20402 (@value{GDBP}) python
20404 End with a line saying just "end".
20410 @kindex maint set python print-stack
20411 @item maint set python print-stack
20412 By default, @value{GDBN} will print a stack trace when an error occurs
20413 in a Python script. This can be controlled using @code{maint set
20414 python print-stack}: if @code{on}, the default, then Python stack
20415 printing is enabled; if @code{off}, then Python stack printing is
20419 It is also possible to execute a Python script from the @value{GDBN}
20423 @item source @file{script-name}
20424 The script name must end with @samp{.py} and @value{GDBN} must be configured
20425 to recognize the script language based on filename extension using
20426 the @code{script-extension} setting. @xref{Extending GDB, ,Extending GDB}.
20428 @item python execfile ("script-name")
20429 This method is based on the @code{execfile} Python built-in function,
20430 and thus is always available.
20434 @subsection Python API
20436 @cindex programming in python
20438 @cindex python stdout
20439 @cindex python pagination
20440 At startup, @value{GDBN} overrides Python's @code{sys.stdout} and
20441 @code{sys.stderr} to print using @value{GDBN}'s output-paging streams.
20442 A Python program which outputs to one of these streams may have its
20443 output interrupted by the user (@pxref{Screen Size}). In this
20444 situation, a Python @code{KeyboardInterrupt} exception is thrown.
20447 * Basic Python:: Basic Python Functions.
20448 * Exception Handling::
20449 * Values From Inferior::
20450 * Types In Python:: Python representation of types.
20451 * Pretty Printing API:: Pretty-printing values.
20452 * Selecting Pretty-Printers:: How GDB chooses a pretty-printer.
20453 * Disabling Pretty-Printers:: Disabling broken printers.
20454 * Inferiors In Python:: Python representation of inferiors (processes)
20455 * Threads In Python:: Accessing inferior threads from Python.
20456 * Commands In Python:: Implementing new commands in Python.
20457 * Parameters In Python:: Adding new @value{GDBN} parameters.
20458 * Functions In Python:: Writing new convenience functions.
20459 * Progspaces In Python:: Program spaces.
20460 * Objfiles In Python:: Object files.
20461 * Frames In Python:: Accessing inferior stack frames from Python.
20462 * Blocks In Python:: Accessing frame blocks from Python.
20463 * Symbols In Python:: Python representation of symbols.
20464 * Symbol Tables In Python:: Python representation of symbol tables.
20465 * Lazy Strings In Python:: Python representation of lazy strings.
20466 * Breakpoints In Python:: Manipulating breakpoints using Python.
20470 @subsubsection Basic Python
20472 @cindex python functions
20473 @cindex python module
20475 @value{GDBN} introduces a new Python module, named @code{gdb}. All
20476 methods and classes added by @value{GDBN} are placed in this module.
20477 @value{GDBN} automatically @code{import}s the @code{gdb} module for
20478 use in all scripts evaluated by the @code{python} command.
20480 @findex gdb.PYTHONDIR
20482 A string containing the python directory (@pxref{Python}).
20485 @findex gdb.execute
20486 @defun execute command [from_tty] [to_string]
20487 Evaluate @var{command}, a string, as a @value{GDBN} CLI command.
20488 If a GDB exception happens while @var{command} runs, it is
20489 translated as described in @ref{Exception Handling,,Exception Handling}.
20491 @var{from_tty} specifies whether @value{GDBN} ought to consider this
20492 command as having originated from the user invoking it interactively.
20493 It must be a boolean value. If omitted, it defaults to @code{False}.
20495 By default, any output produced by @var{command} is sent to
20496 @value{GDBN}'s standard output. If the @var{to_string} parameter is
20497 @code{True}, then output will be collected by @code{gdb.execute} and
20498 returned as a string. The default is @code{False}, in which case the
20499 return value is @code{None}. If @var{to_string} is @code{True}, the
20500 @value{GDBN} virtual terminal will be temporarily set to unlimited width
20501 and height, and its pagination will be disabled; @pxref{Screen Size}.
20504 @findex gdb.breakpoints
20506 Return a sequence holding all of @value{GDBN}'s breakpoints.
20507 @xref{Breakpoints In Python}, for more information.
20510 @findex gdb.parameter
20511 @defun parameter parameter
20512 Return the value of a @value{GDBN} parameter. @var{parameter} is a
20513 string naming the parameter to look up; @var{parameter} may contain
20514 spaces if the parameter has a multi-part name. For example,
20515 @samp{print object} is a valid parameter name.
20517 If the named parameter does not exist, this function throws a
20518 @code{RuntimeError}. Otherwise, the parameter's value is converted to
20519 a Python value of the appropriate type, and returned.
20522 @findex gdb.history
20523 @defun history number
20524 Return a value from @value{GDBN}'s value history (@pxref{Value
20525 History}). @var{number} indicates which history element to return.
20526 If @var{number} is negative, then @value{GDBN} will take its absolute value
20527 and count backward from the last element (i.e., the most recent element) to
20528 find the value to return. If @var{number} is zero, then @value{GDBN} will
20529 return the most recent element. If the element specified by @var{number}
20530 doesn't exist in the value history, a @code{RuntimeError} exception will be
20533 If no exception is raised, the return value is always an instance of
20534 @code{gdb.Value} (@pxref{Values From Inferior}).
20537 @findex gdb.parse_and_eval
20538 @defun parse_and_eval expression
20539 Parse @var{expression} as an expression in the current language,
20540 evaluate it, and return the result as a @code{gdb.Value}.
20541 @var{expression} must be a string.
20543 This function can be useful when implementing a new command
20544 (@pxref{Commands In Python}), as it provides a way to parse the
20545 command's argument as an expression. It is also useful simply to
20546 compute values, for example, it is the only way to get the value of a
20547 convenience variable (@pxref{Convenience Vars}) as a @code{gdb.Value}.
20550 @findex gdb.post_event
20551 @defun post_event event
20552 Put @var{event}, a callable object taking no arguments, into
20553 @value{GDBN}'s internal event queue. This callable will be invoked at
20554 some later point, during @value{GDBN}'s event processing. Events
20555 posted using @code{post_event} will be run in the order in which they
20556 were posted; however, there is no way to know when they will be
20557 processed relative to other events inside @value{GDBN}.
20559 @value{GDBN} is not thread-safe. If your Python program uses multiple
20560 threads, you must be careful to only call @value{GDBN}-specific
20561 functions in the main @value{GDBN} thread. @code{post_event} ensures
20565 (@value{GDBP}) python
20569 > def __init__(self, message):
20570 > self.message = message;
20571 > def __call__(self):
20572 > gdb.write(self.message)
20574 >class MyThread1 (threading.Thread):
20576 > gdb.post_event(Writer("Hello "))
20578 >class MyThread2 (threading.Thread):
20580 > gdb.post_event(Writer("World\n"))
20582 >MyThread1().start()
20583 >MyThread2().start()
20585 (@value{GDBP}) Hello World
20590 @defun write string
20591 Print a string to @value{GDBN}'s paginated standard output stream.
20592 Writing to @code{sys.stdout} or @code{sys.stderr} will automatically
20593 call this function.
20598 Flush @value{GDBN}'s paginated standard output stream. Flushing
20599 @code{sys.stdout} or @code{sys.stderr} will automatically call this
20603 @findex gdb.target_charset
20604 @defun target_charset
20605 Return the name of the current target character set (@pxref{Character
20606 Sets}). This differs from @code{gdb.parameter('target-charset')} in
20607 that @samp{auto} is never returned.
20610 @findex gdb.target_wide_charset
20611 @defun target_wide_charset
20612 Return the name of the current target wide character set
20613 (@pxref{Character Sets}). This differs from
20614 @code{gdb.parameter('target-wide-charset')} in that @samp{auto} is
20618 @findex gdb.solib_name
20619 @defun solib_name address
20620 Return the name of the shared library holding the given @var{address}
20621 as a string, or @code{None}.
20624 @findex gdb.decode_line
20625 @defun decode_line @r{[}expression@r{]}
20626 Return locations of the line specified by @var{expression}, or of the
20627 current line if no argument was given. This function returns a Python
20628 tuple containing two elements. The first element contains a string
20629 holding any unparsed section of @var{expression} (or @code{None} if
20630 the expression has been fully parsed). The second element contains
20631 either @code{None} or another tuple that contains all the locations
20632 that match the expression represented as @code{gdb.Symtab_and_line}
20633 objects (@pxref{Symbol Tables In Python}). If @var{expression} is
20634 provided, it is decoded the way that @value{GDBN}'s inbuilt
20635 @code{break} or @code{edit} commands do (@pxref{Specify Location}).
20638 @node Exception Handling
20639 @subsubsection Exception Handling
20640 @cindex python exceptions
20641 @cindex exceptions, python
20643 When executing the @code{python} command, Python exceptions
20644 uncaught within the Python code are translated to calls to
20645 @value{GDBN} error-reporting mechanism. If the command that called
20646 @code{python} does not handle the error, @value{GDBN} will
20647 terminate it and print an error message containing the Python
20648 exception name, the associated value, and the Python call stack
20649 backtrace at the point where the exception was raised. Example:
20652 (@value{GDBP}) python print foo
20653 Traceback (most recent call last):
20654 File "<string>", line 1, in <module>
20655 NameError: name 'foo' is not defined
20658 @value{GDBN} errors that happen in @value{GDBN} commands invoked by Python
20659 code are converted to Python @code{RuntimeError} exceptions. User
20660 interrupt (via @kbd{C-c} or by typing @kbd{q} at a pagination
20661 prompt) is translated to a Python @code{KeyboardInterrupt}
20662 exception. If you catch these exceptions in your Python code, your
20663 exception handler will see @code{RuntimeError} or
20664 @code{KeyboardInterrupt} as the exception type, the @value{GDBN} error
20665 message as its value, and the Python call stack backtrace at the
20666 Python statement closest to where the @value{GDBN} error occured as the
20669 @findex gdb.GdbError
20670 When implementing @value{GDBN} commands in Python via @code{gdb.Command},
20671 it is useful to be able to throw an exception that doesn't cause a
20672 traceback to be printed. For example, the user may have invoked the
20673 command incorrectly. Use the @code{gdb.GdbError} exception
20674 to handle this case. Example:
20678 >class HelloWorld (gdb.Command):
20679 > """Greet the whole world."""
20680 > def __init__ (self):
20681 > super (HelloWorld, self).__init__ ("hello-world", gdb.COMMAND_OBSCURE)
20682 > def invoke (self, args, from_tty):
20683 > argv = gdb.string_to_argv (args)
20684 > if len (argv) != 0:
20685 > raise gdb.GdbError ("hello-world takes no arguments")
20686 > print "Hello, World!"
20689 (gdb) hello-world 42
20690 hello-world takes no arguments
20693 @node Values From Inferior
20694 @subsubsection Values From Inferior
20695 @cindex values from inferior, with Python
20696 @cindex python, working with values from inferior
20698 @cindex @code{gdb.Value}
20699 @value{GDBN} provides values it obtains from the inferior program in
20700 an object of type @code{gdb.Value}. @value{GDBN} uses this object
20701 for its internal bookkeeping of the inferior's values, and for
20702 fetching values when necessary.
20704 Inferior values that are simple scalars can be used directly in
20705 Python expressions that are valid for the value's data type. Here's
20706 an example for an integer or floating-point value @code{some_val}:
20713 As result of this, @code{bar} will also be a @code{gdb.Value} object
20714 whose values are of the same type as those of @code{some_val}.
20716 Inferior values that are structures or instances of some class can
20717 be accessed using the Python @dfn{dictionary syntax}. For example, if
20718 @code{some_val} is a @code{gdb.Value} instance holding a structure, you
20719 can access its @code{foo} element with:
20722 bar = some_val['foo']
20725 Again, @code{bar} will also be a @code{gdb.Value} object.
20727 A @code{gdb.Value} that represents a function can be executed via
20728 inferior function call. Any arguments provided to the call must match
20729 the function's prototype, and must be provided in the order specified
20732 For example, @code{some_val} is a @code{gdb.Value} instance
20733 representing a function that takes two integers as arguments. To
20734 execute this function, call it like so:
20737 result = some_val (10,20)
20740 Any values returned from a function call will be stored as a
20743 The following attributes are provided:
20746 @defivar Value address
20747 If this object is addressable, this read-only attribute holds a
20748 @code{gdb.Value} object representing the address. Otherwise,
20749 this attribute holds @code{None}.
20752 @cindex optimized out value in Python
20753 @defivar Value is_optimized_out
20754 This read-only boolean attribute is true if the compiler optimized out
20755 this value, thus it is not available for fetching from the inferior.
20758 @defivar Value type
20759 The type of this @code{gdb.Value}. The value of this attribute is a
20760 @code{gdb.Type} object.
20764 The following methods are provided:
20767 @defmethod Value cast type
20768 Return a new instance of @code{gdb.Value} that is the result of
20769 casting this instance to the type described by @var{type}, which must
20770 be a @code{gdb.Type} object. If the cast cannot be performed for some
20771 reason, this method throws an exception.
20774 @defmethod Value dereference
20775 For pointer data types, this method returns a new @code{gdb.Value} object
20776 whose contents is the object pointed to by the pointer. For example, if
20777 @code{foo} is a C pointer to an @code{int}, declared in your C program as
20784 then you can use the corresponding @code{gdb.Value} to access what
20785 @code{foo} points to like this:
20788 bar = foo.dereference ()
20791 The result @code{bar} will be a @code{gdb.Value} object holding the
20792 value pointed to by @code{foo}.
20795 @defmethod Value dynamic_cast type
20796 Like @code{Value.cast}, but works as if the C@t{++} @code{dynamic_cast}
20797 operator were used. Consult a C@t{++} reference for details.
20800 @defmethod Value reinterpret_cast type
20801 Like @code{Value.cast}, but works as if the C@t{++} @code{reinterpret_cast}
20802 operator were used. Consult a C@t{++} reference for details.
20805 @defmethod Value string @r{[}encoding@r{]} @r{[}errors@r{]} @r{[}length@r{]}
20806 If this @code{gdb.Value} represents a string, then this method
20807 converts the contents to a Python string. Otherwise, this method will
20808 throw an exception.
20810 Strings are recognized in a language-specific way; whether a given
20811 @code{gdb.Value} represents a string is determined by the current
20814 For C-like languages, a value is a string if it is a pointer to or an
20815 array of characters or ints. The string is assumed to be terminated
20816 by a zero of the appropriate width. However if the optional length
20817 argument is given, the string will be converted to that given length,
20818 ignoring any embedded zeros that the string may contain.
20820 If the optional @var{encoding} argument is given, it must be a string
20821 naming the encoding of the string in the @code{gdb.Value}, such as
20822 @code{"ascii"}, @code{"iso-8859-6"} or @code{"utf-8"}. It accepts
20823 the same encodings as the corresponding argument to Python's
20824 @code{string.decode} method, and the Python codec machinery will be used
20825 to convert the string. If @var{encoding} is not given, or if
20826 @var{encoding} is the empty string, then either the @code{target-charset}
20827 (@pxref{Character Sets}) will be used, or a language-specific encoding
20828 will be used, if the current language is able to supply one.
20830 The optional @var{errors} argument is the same as the corresponding
20831 argument to Python's @code{string.decode} method.
20833 If the optional @var{length} argument is given, the string will be
20834 fetched and converted to the given length.
20837 @defmethod Value lazy_string @r{[}encoding@r{]} @r{[}length@r{]}
20838 If this @code{gdb.Value} represents a string, then this method
20839 converts the contents to a @code{gdb.LazyString} (@pxref{Lazy Strings
20840 In Python}). Otherwise, this method will throw an exception.
20842 If the optional @var{encoding} argument is given, it must be a string
20843 naming the encoding of the @code{gdb.LazyString}. Some examples are:
20844 @samp{ascii}, @samp{iso-8859-6} or @samp{utf-8}. If the
20845 @var{encoding} argument is an encoding that @value{GDBN} does
20846 recognize, @value{GDBN} will raise an error.
20848 When a lazy string is printed, the @value{GDBN} encoding machinery is
20849 used to convert the string during printing. If the optional
20850 @var{encoding} argument is not provided, or is an empty string,
20851 @value{GDBN} will automatically select the encoding most suitable for
20852 the string type. For further information on encoding in @value{GDBN}
20853 please see @ref{Character Sets}.
20855 If the optional @var{length} argument is given, the string will be
20856 fetched and encoded to the length of characters specified. If
20857 the @var{length} argument is not provided, the string will be fetched
20858 and encoded until a null of appropriate width is found.
20862 @node Types In Python
20863 @subsubsection Types In Python
20864 @cindex types in Python
20865 @cindex Python, working with types
20868 @value{GDBN} represents types from the inferior using the class
20871 The following type-related functions are available in the @code{gdb}
20874 @findex gdb.lookup_type
20875 @defun lookup_type name [block]
20876 This function looks up a type by name. @var{name} is the name of the
20877 type to look up. It must be a string.
20879 If @var{block} is given, then @var{name} is looked up in that scope.
20880 Otherwise, it is searched for globally.
20882 Ordinarily, this function will return an instance of @code{gdb.Type}.
20883 If the named type cannot be found, it will throw an exception.
20886 An instance of @code{Type} has the following attributes:
20890 The type code for this type. The type code will be one of the
20891 @code{TYPE_CODE_} constants defined below.
20894 @defivar Type sizeof
20895 The size of this type, in target @code{char} units. Usually, a
20896 target's @code{char} type will be an 8-bit byte. However, on some
20897 unusual platforms, this type may have a different size.
20901 The tag name for this type. The tag name is the name after
20902 @code{struct}, @code{union}, or @code{enum} in C and C@t{++}; not all
20903 languages have this concept. If this type has no tag name, then
20904 @code{None} is returned.
20908 The following methods are provided:
20911 @defmethod Type fields
20912 For structure and union types, this method returns the fields. Range
20913 types have two fields, the minimum and maximum values. Enum types
20914 have one field per enum constant. Function and method types have one
20915 field per parameter. The base types of C@t{++} classes are also
20916 represented as fields. If the type has no fields, or does not fit
20917 into one of these categories, an empty sequence will be returned.
20919 Each field is an object, with some pre-defined attributes:
20922 This attribute is not available for @code{static} fields (as in
20923 C@t{++} or Java). For non-@code{static} fields, the value is the bit
20924 position of the field.
20927 The name of the field, or @code{None} for anonymous fields.
20930 This is @code{True} if the field is artificial, usually meaning that
20931 it was provided by the compiler and not the user. This attribute is
20932 always provided, and is @code{False} if the field is not artificial.
20934 @item is_base_class
20935 This is @code{True} if the field represents a base class of a C@t{++}
20936 structure. This attribute is always provided, and is @code{False}
20937 if the field is not a base class of the type that is the argument of
20938 @code{fields}, or if that type was not a C@t{++} class.
20941 If the field is packed, or is a bitfield, then this will have a
20942 non-zero value, which is the size of the field in bits. Otherwise,
20943 this will be zero; in this case the field's size is given by its type.
20946 The type of the field. This is usually an instance of @code{Type},
20947 but it can be @code{None} in some situations.
20951 @defmethod Type array @var{n1} @r{[}@var{n2}@r{]}
20952 Return a new @code{gdb.Type} object which represents an array of this
20953 type. If one argument is given, it is the inclusive upper bound of
20954 the array; in this case the lower bound is zero. If two arguments are
20955 given, the first argument is the lower bound of the array, and the
20956 second argument is the upper bound of the array. An array's length
20957 must not be negative, but the bounds can be.
20960 @defmethod Type const
20961 Return a new @code{gdb.Type} object which represents a
20962 @code{const}-qualified variant of this type.
20965 @defmethod Type volatile
20966 Return a new @code{gdb.Type} object which represents a
20967 @code{volatile}-qualified variant of this type.
20970 @defmethod Type unqualified
20971 Return a new @code{gdb.Type} object which represents an unqualified
20972 variant of this type. That is, the result is neither @code{const} nor
20976 @defmethod Type range
20977 Return a Python @code{Tuple} object that contains two elements: the
20978 low bound of the argument type and the high bound of that type. If
20979 the type does not have a range, @value{GDBN} will raise a
20980 @code{RuntimeError} exception.
20983 @defmethod Type reference
20984 Return a new @code{gdb.Type} object which represents a reference to this
20988 @defmethod Type pointer
20989 Return a new @code{gdb.Type} object which represents a pointer to this
20993 @defmethod Type strip_typedefs
20994 Return a new @code{gdb.Type} that represents the real type,
20995 after removing all layers of typedefs.
20998 @defmethod Type target
20999 Return a new @code{gdb.Type} object which represents the target type
21002 For a pointer type, the target type is the type of the pointed-to
21003 object. For an array type (meaning C-like arrays), the target type is
21004 the type of the elements of the array. For a function or method type,
21005 the target type is the type of the return value. For a complex type,
21006 the target type is the type of the elements. For a typedef, the
21007 target type is the aliased type.
21009 If the type does not have a target, this method will throw an
21013 @defmethod Type template_argument n [block]
21014 If this @code{gdb.Type} is an instantiation of a template, this will
21015 return a new @code{gdb.Type} which represents the type of the
21016 @var{n}th template argument.
21018 If this @code{gdb.Type} is not a template type, this will throw an
21019 exception. Ordinarily, only C@t{++} code will have template types.
21021 If @var{block} is given, then @var{name} is looked up in that scope.
21022 Otherwise, it is searched for globally.
21027 Each type has a code, which indicates what category this type falls
21028 into. The available type categories are represented by constants
21029 defined in the @code{gdb} module:
21032 @findex TYPE_CODE_PTR
21033 @findex gdb.TYPE_CODE_PTR
21034 @item TYPE_CODE_PTR
21035 The type is a pointer.
21037 @findex TYPE_CODE_ARRAY
21038 @findex gdb.TYPE_CODE_ARRAY
21039 @item TYPE_CODE_ARRAY
21040 The type is an array.
21042 @findex TYPE_CODE_STRUCT
21043 @findex gdb.TYPE_CODE_STRUCT
21044 @item TYPE_CODE_STRUCT
21045 The type is a structure.
21047 @findex TYPE_CODE_UNION
21048 @findex gdb.TYPE_CODE_UNION
21049 @item TYPE_CODE_UNION
21050 The type is a union.
21052 @findex TYPE_CODE_ENUM
21053 @findex gdb.TYPE_CODE_ENUM
21054 @item TYPE_CODE_ENUM
21055 The type is an enum.
21057 @findex TYPE_CODE_FLAGS
21058 @findex gdb.TYPE_CODE_FLAGS
21059 @item TYPE_CODE_FLAGS
21060 A bit flags type, used for things such as status registers.
21062 @findex TYPE_CODE_FUNC
21063 @findex gdb.TYPE_CODE_FUNC
21064 @item TYPE_CODE_FUNC
21065 The type is a function.
21067 @findex TYPE_CODE_INT
21068 @findex gdb.TYPE_CODE_INT
21069 @item TYPE_CODE_INT
21070 The type is an integer type.
21072 @findex TYPE_CODE_FLT
21073 @findex gdb.TYPE_CODE_FLT
21074 @item TYPE_CODE_FLT
21075 A floating point type.
21077 @findex TYPE_CODE_VOID
21078 @findex gdb.TYPE_CODE_VOID
21079 @item TYPE_CODE_VOID
21080 The special type @code{void}.
21082 @findex TYPE_CODE_SET
21083 @findex gdb.TYPE_CODE_SET
21084 @item TYPE_CODE_SET
21087 @findex TYPE_CODE_RANGE
21088 @findex gdb.TYPE_CODE_RANGE
21089 @item TYPE_CODE_RANGE
21090 A range type, that is, an integer type with bounds.
21092 @findex TYPE_CODE_STRING
21093 @findex gdb.TYPE_CODE_STRING
21094 @item TYPE_CODE_STRING
21095 A string type. Note that this is only used for certain languages with
21096 language-defined string types; C strings are not represented this way.
21098 @findex TYPE_CODE_BITSTRING
21099 @findex gdb.TYPE_CODE_BITSTRING
21100 @item TYPE_CODE_BITSTRING
21103 @findex TYPE_CODE_ERROR
21104 @findex gdb.TYPE_CODE_ERROR
21105 @item TYPE_CODE_ERROR
21106 An unknown or erroneous type.
21108 @findex TYPE_CODE_METHOD
21109 @findex gdb.TYPE_CODE_METHOD
21110 @item TYPE_CODE_METHOD
21111 A method type, as found in C@t{++} or Java.
21113 @findex TYPE_CODE_METHODPTR
21114 @findex gdb.TYPE_CODE_METHODPTR
21115 @item TYPE_CODE_METHODPTR
21116 A pointer-to-member-function.
21118 @findex TYPE_CODE_MEMBERPTR
21119 @findex gdb.TYPE_CODE_MEMBERPTR
21120 @item TYPE_CODE_MEMBERPTR
21121 A pointer-to-member.
21123 @findex TYPE_CODE_REF
21124 @findex gdb.TYPE_CODE_REF
21125 @item TYPE_CODE_REF
21128 @findex TYPE_CODE_CHAR
21129 @findex gdb.TYPE_CODE_CHAR
21130 @item TYPE_CODE_CHAR
21133 @findex TYPE_CODE_BOOL
21134 @findex gdb.TYPE_CODE_BOOL
21135 @item TYPE_CODE_BOOL
21138 @findex TYPE_CODE_COMPLEX
21139 @findex gdb.TYPE_CODE_COMPLEX
21140 @item TYPE_CODE_COMPLEX
21141 A complex float type.
21143 @findex TYPE_CODE_TYPEDEF
21144 @findex gdb.TYPE_CODE_TYPEDEF
21145 @item TYPE_CODE_TYPEDEF
21146 A typedef to some other type.
21148 @findex TYPE_CODE_NAMESPACE
21149 @findex gdb.TYPE_CODE_NAMESPACE
21150 @item TYPE_CODE_NAMESPACE
21151 A C@t{++} namespace.
21153 @findex TYPE_CODE_DECFLOAT
21154 @findex gdb.TYPE_CODE_DECFLOAT
21155 @item TYPE_CODE_DECFLOAT
21156 A decimal floating point type.
21158 @findex TYPE_CODE_INTERNAL_FUNCTION
21159 @findex gdb.TYPE_CODE_INTERNAL_FUNCTION
21160 @item TYPE_CODE_INTERNAL_FUNCTION
21161 A function internal to @value{GDBN}. This is the type used to represent
21162 convenience functions.
21165 @node Pretty Printing API
21166 @subsubsection Pretty Printing API
21168 An example output is provided (@pxref{Pretty Printing}).
21170 A pretty-printer is just an object that holds a value and implements a
21171 specific interface, defined here.
21173 @defop Operation {pretty printer} children (self)
21174 @value{GDBN} will call this method on a pretty-printer to compute the
21175 children of the pretty-printer's value.
21177 This method must return an object conforming to the Python iterator
21178 protocol. Each item returned by the iterator must be a tuple holding
21179 two elements. The first element is the ``name'' of the child; the
21180 second element is the child's value. The value can be any Python
21181 object which is convertible to a @value{GDBN} value.
21183 This method is optional. If it does not exist, @value{GDBN} will act
21184 as though the value has no children.
21187 @defop Operation {pretty printer} display_hint (self)
21188 The CLI may call this method and use its result to change the
21189 formatting of a value. The result will also be supplied to an MI
21190 consumer as a @samp{displayhint} attribute of the variable being
21193 This method is optional. If it does exist, this method must return a
21196 Some display hints are predefined by @value{GDBN}:
21200 Indicate that the object being printed is ``array-like''. The CLI
21201 uses this to respect parameters such as @code{set print elements} and
21202 @code{set print array}.
21205 Indicate that the object being printed is ``map-like'', and that the
21206 children of this value can be assumed to alternate between keys and
21210 Indicate that the object being printed is ``string-like''. If the
21211 printer's @code{to_string} method returns a Python string of some
21212 kind, then @value{GDBN} will call its internal language-specific
21213 string-printing function to format the string. For the CLI this means
21214 adding quotation marks, possibly escaping some characters, respecting
21215 @code{set print elements}, and the like.
21219 @defop Operation {pretty printer} to_string (self)
21220 @value{GDBN} will call this method to display the string
21221 representation of the value passed to the object's constructor.
21223 When printing from the CLI, if the @code{to_string} method exists,
21224 then @value{GDBN} will prepend its result to the values returned by
21225 @code{children}. Exactly how this formatting is done is dependent on
21226 the display hint, and may change as more hints are added. Also,
21227 depending on the print settings (@pxref{Print Settings}), the CLI may
21228 print just the result of @code{to_string} in a stack trace, omitting
21229 the result of @code{children}.
21231 If this method returns a string, it is printed verbatim.
21233 Otherwise, if this method returns an instance of @code{gdb.Value},
21234 then @value{GDBN} prints this value. This may result in a call to
21235 another pretty-printer.
21237 If instead the method returns a Python value which is convertible to a
21238 @code{gdb.Value}, then @value{GDBN} performs the conversion and prints
21239 the resulting value. Again, this may result in a call to another
21240 pretty-printer. Python scalars (integers, floats, and booleans) and
21241 strings are convertible to @code{gdb.Value}; other types are not.
21243 Finally, if this method returns @code{None} then no further operations
21244 are peformed in this method and nothing is printed.
21246 If the result is not one of these types, an exception is raised.
21249 @value{GDBN} provides a function which can be used to look up the
21250 default pretty-printer for a @code{gdb.Value}:
21252 @findex gdb.default_visualizer
21253 @defun default_visualizer value
21254 This function takes a @code{gdb.Value} object as an argument. If a
21255 pretty-printer for this value exists, then it is returned. If no such
21256 printer exists, then this returns @code{None}.
21259 @node Selecting Pretty-Printers
21260 @subsubsection Selecting Pretty-Printers
21262 The Python list @code{gdb.pretty_printers} contains an array of
21263 functions or callable objects that have been registered via addition
21264 as a pretty-printer.
21265 Each @code{gdb.Progspace} contains a @code{pretty_printers} attribute.
21266 Each @code{gdb.Objfile} also contains a @code{pretty_printers}
21269 A function on one of these lists is passed a single @code{gdb.Value}
21270 argument and should return a pretty-printer object conforming to the
21271 interface definition above (@pxref{Pretty Printing API}). If a function
21272 cannot create a pretty-printer for the value, it should return
21275 @value{GDBN} first checks the @code{pretty_printers} attribute of each
21276 @code{gdb.Objfile} in the current program space and iteratively calls
21277 each enabled function (@pxref{Disabling Pretty-Printers})
21278 in the list for that @code{gdb.Objfile} until it receives
21279 a pretty-printer object.
21280 If no pretty-printer is found in the objfile lists, @value{GDBN} then
21281 searches the pretty-printer list of the current program space,
21282 calling each enabled function until an object is returned.
21283 After these lists have been exhausted, it tries the global
21284 @code{gdb.pretty_printers} list, again calling each enabled function until an
21285 object is returned.
21287 The order in which the objfiles are searched is not specified. For a
21288 given list, functions are always invoked from the head of the list,
21289 and iterated over sequentially until the end of the list, or a printer
21290 object is returned.
21292 Here is an example showing how a @code{std::string} printer might be
21296 class StdStringPrinter:
21297 "Print a std::string"
21299 def __init__ (self, val):
21302 def to_string (self):
21303 return self.val['_M_dataplus']['_M_p']
21305 def display_hint (self):
21309 And here is an example showing how a lookup function for the printer
21310 example above might be written.
21313 def str_lookup_function (val):
21315 lookup_tag = val.type.tag
21316 regex = re.compile ("^std::basic_string<char,.*>$")
21317 if lookup_tag == None:
21319 if regex.match (lookup_tag):
21320 return StdStringPrinter (val)
21325 The example lookup function extracts the value's type, and attempts to
21326 match it to a type that it can pretty-print. If it is a type the
21327 printer can pretty-print, it will return a printer object. If not, it
21328 returns @code{None}.
21330 We recommend that you put your core pretty-printers into a Python
21331 package. If your pretty-printers are for use with a library, we
21332 further recommend embedding a version number into the package name.
21333 This practice will enable @value{GDBN} to load multiple versions of
21334 your pretty-printers at the same time, because they will have
21337 You should write auto-loaded code (@pxref{Auto-loading}) such that it
21338 can be evaluated multiple times without changing its meaning. An
21339 ideal auto-load file will consist solely of @code{import}s of your
21340 printer modules, followed by a call to a register pretty-printers with
21341 the current objfile.
21343 Taken as a whole, this approach will scale nicely to multiple
21344 inferiors, each potentially using a different library version.
21345 Embedding a version number in the Python package name will ensure that
21346 @value{GDBN} is able to load both sets of printers simultaneously.
21347 Then, because the search for pretty-printers is done by objfile, and
21348 because your auto-loaded code took care to register your library's
21349 printers with a specific objfile, @value{GDBN} will find the correct
21350 printers for the specific version of the library used by each
21353 To continue the @code{std::string} example (@pxref{Pretty Printing API}),
21354 this code might appear in @code{gdb.libstdcxx.v6}:
21357 def register_printers (objfile):
21358 objfile.pretty_printers.add (str_lookup_function)
21362 And then the corresponding contents of the auto-load file would be:
21365 import gdb.libstdcxx.v6
21366 gdb.libstdcxx.v6.register_printers (gdb.current_objfile ())
21369 @node Disabling Pretty-Printers
21370 @subsubsection Disabling Pretty-Printers
21371 @cindex disabling pretty-printers
21373 For various reasons a pretty-printer may not work.
21374 For example, the underlying data structure may have changed and
21375 the pretty-printer is out of date.
21377 The consequences of a broken pretty-printer are severe enough that
21378 @value{GDBN} provides support for enabling and disabling individual
21379 printers. For example, if @code{print frame-arguments} is on,
21380 a backtrace can become highly illegible if any argument is printed
21381 with a broken printer.
21383 Pretty-printers are enabled and disabled by attaching an @code{enabled}
21384 attribute to the registered function or callable object. If this attribute
21385 is present and its value is @code{False}, the printer is disabled, otherwise
21386 the printer is enabled.
21388 @node Inferiors In Python
21389 @subsubsection Inferiors In Python
21390 @cindex inferiors in python
21392 @findex gdb.Inferior
21393 Programs which are being run under @value{GDBN} are called inferiors
21394 (@pxref{Inferiors and Programs}). Python scripts can access
21395 information about and manipulate inferiors controlled by @value{GDBN}
21396 via objects of the @code{gdb.Inferior} class.
21398 The following inferior-related functions are available in the @code{gdb}
21402 Return a tuple containing all inferior objects.
21405 A @code{gdb.Inferior} object has the following attributes:
21408 @defivar Inferior num
21409 ID of inferior, as assigned by GDB.
21412 @defivar Inferior pid
21413 Process ID of the inferior, as assigned by the underlying operating
21417 @defivar Inferior was_attached
21418 Boolean signaling whether the inferior was created using `attach', or
21419 started by @value{GDBN} itself.
21423 A @code{gdb.Inferior} object has the following methods:
21426 @defmethod Inferior threads
21427 This method returns a tuple holding all the threads which are valid
21428 when it is called. If there are no valid threads, the method will
21429 return an empty tuple.
21432 @findex gdb.read_memory
21433 @defmethod Inferior read_memory address length
21434 Read @var{length} bytes of memory from the inferior, starting at
21435 @var{address}. Returns a buffer object, which behaves much like an array
21436 or a string. It can be modified and given to the @code{gdb.write_memory}
21440 @findex gdb.write_memory
21441 @defmethod Inferior write_memory address buffer @r{[}length@r{]}
21442 Write the contents of @var{buffer} to the inferior, starting at
21443 @var{address}. The @var{buffer} parameter must be a Python object
21444 which supports the buffer protocol, i.e., a string, an array or the
21445 object returned from @code{gdb.read_memory}. If given, @var{length}
21446 determines the number of bytes from @var{buffer} to be written.
21449 @findex gdb.search_memory
21450 @defmethod Inferior search_memory address length pattern
21451 Search a region of the inferior memory starting at @var{address} with
21452 the given @var{length} using the search pattern supplied in
21453 @var{pattern}. The @var{pattern} parameter must be a Python object
21454 which supports the buffer protocol, i.e., a string, an array or the
21455 object returned from @code{gdb.read_memory}. Returns a Python @code{Long}
21456 containing the address where the pattern was found, or @code{None} if
21457 the pattern could not be found.
21461 @node Threads In Python
21462 @subsubsection Threads In Python
21463 @cindex threads in python
21465 @findex gdb.InferiorThread
21466 Python scripts can access information about, and manipulate inferior threads
21467 controlled by @value{GDBN}, via objects of the @code{gdb.InferiorThread} class.
21469 The following thread-related functions are available in the @code{gdb}
21472 @findex gdb.selected_thread
21473 @defun selected_thread
21474 This function returns the thread object for the selected thread. If there
21475 is no selected thread, this will return @code{None}.
21478 A @code{gdb.InferiorThread} object has the following attributes:
21481 @defivar InferiorThread num
21482 ID of the thread, as assigned by GDB.
21485 @defivar InferiorThread ptid
21486 ID of the thread, as assigned by the operating system. This attribute is a
21487 tuple containing three integers. The first is the Process ID (PID); the second
21488 is the Lightweight Process ID (LWPID), and the third is the Thread ID (TID).
21489 Either the LWPID or TID may be 0, which indicates that the operating system
21490 does not use that identifier.
21494 A @code{gdb.InferiorThread} object has the following methods:
21497 @defmethod InferiorThread switch
21498 This changes @value{GDBN}'s currently selected thread to the one represented
21502 @defmethod InferiorThread is_stopped
21503 Return a Boolean indicating whether the thread is stopped.
21506 @defmethod InferiorThread is_running
21507 Return a Boolean indicating whether the thread is running.
21510 @defmethod InferiorThread is_exited
21511 Return a Boolean indicating whether the thread is exited.
21515 @node Commands In Python
21516 @subsubsection Commands In Python
21518 @cindex commands in python
21519 @cindex python commands
21520 You can implement new @value{GDBN} CLI commands in Python. A CLI
21521 command is implemented using an instance of the @code{gdb.Command}
21522 class, most commonly using a subclass.
21524 @defmethod Command __init__ name @var{command_class} @r{[}@var{completer_class}@r{]} @r{[}@var{prefix}@r{]}
21525 The object initializer for @code{Command} registers the new command
21526 with @value{GDBN}. This initializer is normally invoked from the
21527 subclass' own @code{__init__} method.
21529 @var{name} is the name of the command. If @var{name} consists of
21530 multiple words, then the initial words are looked for as prefix
21531 commands. In this case, if one of the prefix commands does not exist,
21532 an exception is raised.
21534 There is no support for multi-line commands.
21536 @var{command_class} should be one of the @samp{COMMAND_} constants
21537 defined below. This argument tells @value{GDBN} how to categorize the
21538 new command in the help system.
21540 @var{completer_class} is an optional argument. If given, it should be
21541 one of the @samp{COMPLETE_} constants defined below. This argument
21542 tells @value{GDBN} how to perform completion for this command. If not
21543 given, @value{GDBN} will attempt to complete using the object's
21544 @code{complete} method (see below); if no such method is found, an
21545 error will occur when completion is attempted.
21547 @var{prefix} is an optional argument. If @code{True}, then the new
21548 command is a prefix command; sub-commands of this command may be
21551 The help text for the new command is taken from the Python
21552 documentation string for the command's class, if there is one. If no
21553 documentation string is provided, the default value ``This command is
21554 not documented.'' is used.
21557 @cindex don't repeat Python command
21558 @defmethod Command dont_repeat
21559 By default, a @value{GDBN} command is repeated when the user enters a
21560 blank line at the command prompt. A command can suppress this
21561 behavior by invoking the @code{dont_repeat} method. This is similar
21562 to the user command @code{dont-repeat}, see @ref{Define, dont-repeat}.
21565 @defmethod Command invoke argument from_tty
21566 This method is called by @value{GDBN} when this command is invoked.
21568 @var{argument} is a string. It is the argument to the command, after
21569 leading and trailing whitespace has been stripped.
21571 @var{from_tty} is a boolean argument. When true, this means that the
21572 command was entered by the user at the terminal; when false it means
21573 that the command came from elsewhere.
21575 If this method throws an exception, it is turned into a @value{GDBN}
21576 @code{error} call. Otherwise, the return value is ignored.
21578 @findex gdb.string_to_argv
21579 To break @var{argument} up into an argv-like string use
21580 @code{gdb.string_to_argv}. This function behaves identically to
21581 @value{GDBN}'s internal argument lexer @code{buildargv}.
21582 It is recommended to use this for consistency.
21583 Arguments are separated by spaces and may be quoted.
21587 print gdb.string_to_argv ("1 2\ \\\"3 '4 \"5' \"6 '7\"")
21588 ['1', '2 "3', '4 "5', "6 '7"]
21593 @cindex completion of Python commands
21594 @defmethod Command complete text word
21595 This method is called by @value{GDBN} when the user attempts
21596 completion on this command. All forms of completion are handled by
21597 this method, that is, the @key{TAB} and @key{M-?} key bindings
21598 (@pxref{Completion}), and the @code{complete} command (@pxref{Help,
21601 The arguments @var{text} and @var{word} are both strings. @var{text}
21602 holds the complete command line up to the cursor's location.
21603 @var{word} holds the last word of the command line; this is computed
21604 using a word-breaking heuristic.
21606 The @code{complete} method can return several values:
21609 If the return value is a sequence, the contents of the sequence are
21610 used as the completions. It is up to @code{complete} to ensure that the
21611 contents actually do complete the word. A zero-length sequence is
21612 allowed, it means that there were no completions available. Only
21613 string elements of the sequence are used; other elements in the
21614 sequence are ignored.
21617 If the return value is one of the @samp{COMPLETE_} constants defined
21618 below, then the corresponding @value{GDBN}-internal completion
21619 function is invoked, and its result is used.
21622 All other results are treated as though there were no available
21627 When a new command is registered, it must be declared as a member of
21628 some general class of commands. This is used to classify top-level
21629 commands in the on-line help system; note that prefix commands are not
21630 listed under their own category but rather that of their top-level
21631 command. The available classifications are represented by constants
21632 defined in the @code{gdb} module:
21635 @findex COMMAND_NONE
21636 @findex gdb.COMMAND_NONE
21638 The command does not belong to any particular class. A command in
21639 this category will not be displayed in any of the help categories.
21641 @findex COMMAND_RUNNING
21642 @findex gdb.COMMAND_RUNNING
21643 @item COMMAND_RUNNING
21644 The command is related to running the inferior. For example,
21645 @code{start}, @code{step}, and @code{continue} are in this category.
21646 Type @kbd{help running} at the @value{GDBN} prompt to see a list of
21647 commands in this category.
21649 @findex COMMAND_DATA
21650 @findex gdb.COMMAND_DATA
21652 The command is related to data or variables. For example,
21653 @code{call}, @code{find}, and @code{print} are in this category. Type
21654 @kbd{help data} at the @value{GDBN} prompt to see a list of commands
21657 @findex COMMAND_STACK
21658 @findex gdb.COMMAND_STACK
21659 @item COMMAND_STACK
21660 The command has to do with manipulation of the stack. For example,
21661 @code{backtrace}, @code{frame}, and @code{return} are in this
21662 category. Type @kbd{help stack} at the @value{GDBN} prompt to see a
21663 list of commands in this category.
21665 @findex COMMAND_FILES
21666 @findex gdb.COMMAND_FILES
21667 @item COMMAND_FILES
21668 This class is used for file-related commands. For example,
21669 @code{file}, @code{list} and @code{section} are in this category.
21670 Type @kbd{help files} at the @value{GDBN} prompt to see a list of
21671 commands in this category.
21673 @findex COMMAND_SUPPORT
21674 @findex gdb.COMMAND_SUPPORT
21675 @item COMMAND_SUPPORT
21676 This should be used for ``support facilities'', generally meaning
21677 things that are useful to the user when interacting with @value{GDBN},
21678 but not related to the state of the inferior. For example,
21679 @code{help}, @code{make}, and @code{shell} are in this category. Type
21680 @kbd{help support} at the @value{GDBN} prompt to see a list of
21681 commands in this category.
21683 @findex COMMAND_STATUS
21684 @findex gdb.COMMAND_STATUS
21685 @item COMMAND_STATUS
21686 The command is an @samp{info}-related command, that is, related to the
21687 state of @value{GDBN} itself. For example, @code{info}, @code{macro},
21688 and @code{show} are in this category. Type @kbd{help status} at the
21689 @value{GDBN} prompt to see a list of commands in this category.
21691 @findex COMMAND_BREAKPOINTS
21692 @findex gdb.COMMAND_BREAKPOINTS
21693 @item COMMAND_BREAKPOINTS
21694 The command has to do with breakpoints. For example, @code{break},
21695 @code{clear}, and @code{delete} are in this category. Type @kbd{help
21696 breakpoints} at the @value{GDBN} prompt to see a list of commands in
21699 @findex COMMAND_TRACEPOINTS
21700 @findex gdb.COMMAND_TRACEPOINTS
21701 @item COMMAND_TRACEPOINTS
21702 The command has to do with tracepoints. For example, @code{trace},
21703 @code{actions}, and @code{tfind} are in this category. Type
21704 @kbd{help tracepoints} at the @value{GDBN} prompt to see a list of
21705 commands in this category.
21707 @findex COMMAND_OBSCURE
21708 @findex gdb.COMMAND_OBSCURE
21709 @item COMMAND_OBSCURE
21710 The command is only used in unusual circumstances, or is not of
21711 general interest to users. For example, @code{checkpoint},
21712 @code{fork}, and @code{stop} are in this category. Type @kbd{help
21713 obscure} at the @value{GDBN} prompt to see a list of commands in this
21716 @findex COMMAND_MAINTENANCE
21717 @findex gdb.COMMAND_MAINTENANCE
21718 @item COMMAND_MAINTENANCE
21719 The command is only useful to @value{GDBN} maintainers. The
21720 @code{maintenance} and @code{flushregs} commands are in this category.
21721 Type @kbd{help internals} at the @value{GDBN} prompt to see a list of
21722 commands in this category.
21725 A new command can use a predefined completion function, either by
21726 specifying it via an argument at initialization, or by returning it
21727 from the @code{complete} method. These predefined completion
21728 constants are all defined in the @code{gdb} module:
21731 @findex COMPLETE_NONE
21732 @findex gdb.COMPLETE_NONE
21733 @item COMPLETE_NONE
21734 This constant means that no completion should be done.
21736 @findex COMPLETE_FILENAME
21737 @findex gdb.COMPLETE_FILENAME
21738 @item COMPLETE_FILENAME
21739 This constant means that filename completion should be performed.
21741 @findex COMPLETE_LOCATION
21742 @findex gdb.COMPLETE_LOCATION
21743 @item COMPLETE_LOCATION
21744 This constant means that location completion should be done.
21745 @xref{Specify Location}.
21747 @findex COMPLETE_COMMAND
21748 @findex gdb.COMPLETE_COMMAND
21749 @item COMPLETE_COMMAND
21750 This constant means that completion should examine @value{GDBN}
21753 @findex COMPLETE_SYMBOL
21754 @findex gdb.COMPLETE_SYMBOL
21755 @item COMPLETE_SYMBOL
21756 This constant means that completion should be done using symbol names
21760 The following code snippet shows how a trivial CLI command can be
21761 implemented in Python:
21764 class HelloWorld (gdb.Command):
21765 """Greet the whole world."""
21767 def __init__ (self):
21768 super (HelloWorld, self).__init__ ("hello-world", gdb.COMMAND_OBSCURE)
21770 def invoke (self, arg, from_tty):
21771 print "Hello, World!"
21776 The last line instantiates the class, and is necessary to trigger the
21777 registration of the command with @value{GDBN}. Depending on how the
21778 Python code is read into @value{GDBN}, you may need to import the
21779 @code{gdb} module explicitly.
21781 @node Parameters In Python
21782 @subsubsection Parameters In Python
21784 @cindex parameters in python
21785 @cindex python parameters
21786 @tindex gdb.Parameter
21788 You can implement new @value{GDBN} parameters using Python. A new
21789 parameter is implemented as an instance of the @code{gdb.Parameter}
21792 Parameters are exposed to the user via the @code{set} and
21793 @code{show} commands. @xref{Help}.
21795 There are many parameters that already exist and can be set in
21796 @value{GDBN}. Two examples are: @code{set follow fork} and
21797 @code{set charset}. Setting these parameters influences certain
21798 behavior in @value{GDBN}. Similarly, you can define parameters that
21799 can be used to influence behavior in custom Python scripts and commands.
21801 @defmethod Parameter __init__ name @var{command-class} @var{parameter-class} @r{[}@var{enum-sequence}@r{]}
21802 The object initializer for @code{Parameter} registers the new
21803 parameter with @value{GDBN}. This initializer is normally invoked
21804 from the subclass' own @code{__init__} method.
21806 @var{name} is the name of the new parameter. If @var{name} consists
21807 of multiple words, then the initial words are looked for as prefix
21808 parameters. An example of this can be illustrated with the
21809 @code{set print} set of parameters. If @var{name} is
21810 @code{print foo}, then @code{print} will be searched as the prefix
21811 parameter. In this case the parameter can subsequently be accessed in
21812 @value{GDBN} as @code{set print foo}.
21814 If @var{name} consists of multiple words, and no prefix parameter group
21815 can be found, an exception is raised.
21817 @var{command-class} should be one of the @samp{COMMAND_} constants
21818 (@pxref{Commands In Python}). This argument tells @value{GDBN} how to
21819 categorize the new parameter in the help system.
21821 @var{parameter-class} should be one of the @samp{PARAM_} constants
21822 defined below. This argument tells @value{GDBN} the type of the new
21823 parameter; this information is used for input validation and
21826 If @var{parameter-class} is @code{PARAM_ENUM}, then
21827 @var{enum-sequence} must be a sequence of strings. These strings
21828 represent the possible values for the parameter.
21830 If @var{parameter-class} is not @code{PARAM_ENUM}, then the presence
21831 of a fourth argument will cause an exception to be thrown.
21833 The help text for the new parameter is taken from the Python
21834 documentation string for the parameter's class, if there is one. If
21835 there is no documentation string, a default value is used.
21838 @defivar Parameter set_doc
21839 If this attribute exists, and is a string, then its value is used as
21840 the help text for this parameter's @code{set} command. The value is
21841 examined when @code{Parameter.__init__} is invoked; subsequent changes
21845 @defivar Parameter show_doc
21846 If this attribute exists, and is a string, then its value is used as
21847 the help text for this parameter's @code{show} command. The value is
21848 examined when @code{Parameter.__init__} is invoked; subsequent changes
21852 @defivar Parameter value
21853 The @code{value} attribute holds the underlying value of the
21854 parameter. It can be read and assigned to just as any other
21855 attribute. @value{GDBN} does validation when assignments are made.
21859 When a new parameter is defined, its type must be specified. The
21860 available types are represented by constants defined in the @code{gdb}
21864 @findex PARAM_BOOLEAN
21865 @findex gdb.PARAM_BOOLEAN
21866 @item PARAM_BOOLEAN
21867 The value is a plain boolean. The Python boolean values, @code{True}
21868 and @code{False} are the only valid values.
21870 @findex PARAM_AUTO_BOOLEAN
21871 @findex gdb.PARAM_AUTO_BOOLEAN
21872 @item PARAM_AUTO_BOOLEAN
21873 The value has three possible states: true, false, and @samp{auto}. In
21874 Python, true and false are represented using boolean constants, and
21875 @samp{auto} is represented using @code{None}.
21877 @findex PARAM_UINTEGER
21878 @findex gdb.PARAM_UINTEGER
21879 @item PARAM_UINTEGER
21880 The value is an unsigned integer. The value of 0 should be
21881 interpreted to mean ``unlimited''.
21883 @findex PARAM_INTEGER
21884 @findex gdb.PARAM_INTEGER
21885 @item PARAM_INTEGER
21886 The value is a signed integer. The value of 0 should be interpreted
21887 to mean ``unlimited''.
21889 @findex PARAM_STRING
21890 @findex gdb.PARAM_STRING
21892 The value is a string. When the user modifies the string, any escape
21893 sequences, such as @samp{\t}, @samp{\f}, and octal escapes, are
21894 translated into corresponding characters and encoded into the current
21897 @findex PARAM_STRING_NOESCAPE
21898 @findex gdb.PARAM_STRING_NOESCAPE
21899 @item PARAM_STRING_NOESCAPE
21900 The value is a string. When the user modifies the string, escapes are
21901 passed through untranslated.
21903 @findex PARAM_OPTIONAL_FILENAME
21904 @findex gdb.PARAM_OPTIONAL_FILENAME
21905 @item PARAM_OPTIONAL_FILENAME
21906 The value is a either a filename (a string), or @code{None}.
21908 @findex PARAM_FILENAME
21909 @findex gdb.PARAM_FILENAME
21910 @item PARAM_FILENAME
21911 The value is a filename. This is just like
21912 @code{PARAM_STRING_NOESCAPE}, but uses file names for completion.
21914 @findex PARAM_ZINTEGER
21915 @findex gdb.PARAM_ZINTEGER
21916 @item PARAM_ZINTEGER
21917 The value is an integer. This is like @code{PARAM_INTEGER}, except 0
21918 is interpreted as itself.
21921 @findex gdb.PARAM_ENUM
21923 The value is a string, which must be one of a collection string
21924 constants provided when the parameter is created.
21927 @node Functions In Python
21928 @subsubsection Writing new convenience functions
21930 @cindex writing convenience functions
21931 @cindex convenience functions in python
21932 @cindex python convenience functions
21933 @tindex gdb.Function
21935 You can implement new convenience functions (@pxref{Convenience Vars})
21936 in Python. A convenience function is an instance of a subclass of the
21937 class @code{gdb.Function}.
21939 @defmethod Function __init__ name
21940 The initializer for @code{Function} registers the new function with
21941 @value{GDBN}. The argument @var{name} is the name of the function,
21942 a string. The function will be visible to the user as a convenience
21943 variable of type @code{internal function}, whose name is the same as
21944 the given @var{name}.
21946 The documentation for the new function is taken from the documentation
21947 string for the new class.
21950 @defmethod Function invoke @var{*args}
21951 When a convenience function is evaluated, its arguments are converted
21952 to instances of @code{gdb.Value}, and then the function's
21953 @code{invoke} method is called. Note that @value{GDBN} does not
21954 predetermine the arity of convenience functions. Instead, all
21955 available arguments are passed to @code{invoke}, following the
21956 standard Python calling convention. In particular, a convenience
21957 function can have default values for parameters without ill effect.
21959 The return value of this method is used as its value in the enclosing
21960 expression. If an ordinary Python value is returned, it is converted
21961 to a @code{gdb.Value} following the usual rules.
21964 The following code snippet shows how a trivial convenience function can
21965 be implemented in Python:
21968 class Greet (gdb.Function):
21969 """Return string to greet someone.
21970 Takes a name as argument."""
21972 def __init__ (self):
21973 super (Greet, self).__init__ ("greet")
21975 def invoke (self, name):
21976 return "Hello, %s!" % name.string ()
21981 The last line instantiates the class, and is necessary to trigger the
21982 registration of the function with @value{GDBN}. Depending on how the
21983 Python code is read into @value{GDBN}, you may need to import the
21984 @code{gdb} module explicitly.
21986 @node Progspaces In Python
21987 @subsubsection Program Spaces In Python
21989 @cindex progspaces in python
21990 @tindex gdb.Progspace
21992 A program space, or @dfn{progspace}, represents a symbolic view
21993 of an address space.
21994 It consists of all of the objfiles of the program.
21995 @xref{Objfiles In Python}.
21996 @xref{Inferiors and Programs, program spaces}, for more details
21997 about program spaces.
21999 The following progspace-related functions are available in the
22002 @findex gdb.current_progspace
22003 @defun current_progspace
22004 This function returns the program space of the currently selected inferior.
22005 @xref{Inferiors and Programs}.
22008 @findex gdb.progspaces
22010 Return a sequence of all the progspaces currently known to @value{GDBN}.
22013 Each progspace is represented by an instance of the @code{gdb.Progspace}
22016 @defivar Progspace filename
22017 The file name of the progspace as a string.
22020 @defivar Progspace pretty_printers
22021 The @code{pretty_printers} attribute is a list of functions. It is
22022 used to look up pretty-printers. A @code{Value} is passed to each
22023 function in order; if the function returns @code{None}, then the
22024 search continues. Otherwise, the return value should be an object
22025 which is used to format the value. @xref{Pretty Printing API}, for more
22029 @node Objfiles In Python
22030 @subsubsection Objfiles In Python
22032 @cindex objfiles in python
22033 @tindex gdb.Objfile
22035 @value{GDBN} loads symbols for an inferior from various
22036 symbol-containing files (@pxref{Files}). These include the primary
22037 executable file, any shared libraries used by the inferior, and any
22038 separate debug info files (@pxref{Separate Debug Files}).
22039 @value{GDBN} calls these symbol-containing files @dfn{objfiles}.
22041 The following objfile-related functions are available in the
22044 @findex gdb.current_objfile
22045 @defun current_objfile
22046 When auto-loading a Python script (@pxref{Auto-loading}), @value{GDBN}
22047 sets the ``current objfile'' to the corresponding objfile. This
22048 function returns the current objfile. If there is no current objfile,
22049 this function returns @code{None}.
22052 @findex gdb.objfiles
22054 Return a sequence of all the objfiles current known to @value{GDBN}.
22055 @xref{Objfiles In Python}.
22058 Each objfile is represented by an instance of the @code{gdb.Objfile}
22061 @defivar Objfile filename
22062 The file name of the objfile as a string.
22065 @defivar Objfile pretty_printers
22066 The @code{pretty_printers} attribute is a list of functions. It is
22067 used to look up pretty-printers. A @code{Value} is passed to each
22068 function in order; if the function returns @code{None}, then the
22069 search continues. Otherwise, the return value should be an object
22070 which is used to format the value. @xref{Pretty Printing API}, for more
22074 @node Frames In Python
22075 @subsubsection Accessing inferior stack frames from Python.
22077 @cindex frames in python
22078 When the debugged program stops, @value{GDBN} is able to analyze its call
22079 stack (@pxref{Frames,,Stack frames}). The @code{gdb.Frame} class
22080 represents a frame in the stack. A @code{gdb.Frame} object is only valid
22081 while its corresponding frame exists in the inferior's stack. If you try
22082 to use an invalid frame object, @value{GDBN} will throw a @code{RuntimeError}
22085 Two @code{gdb.Frame} objects can be compared for equality with the @code{==}
22089 (@value{GDBP}) python print gdb.newest_frame() == gdb.selected_frame ()
22093 The following frame-related functions are available in the @code{gdb} module:
22095 @findex gdb.selected_frame
22096 @defun selected_frame
22097 Return the selected frame object. (@pxref{Selection,,Selecting a Frame}).
22100 @defun frame_stop_reason_string reason
22101 Return a string explaining the reason why @value{GDBN} stopped unwinding
22102 frames, as expressed by the given @var{reason} code (an integer, see the
22103 @code{unwind_stop_reason} method further down in this section).
22106 A @code{gdb.Frame} object has the following methods:
22109 @defmethod Frame is_valid
22110 Returns true if the @code{gdb.Frame} object is valid, false if not.
22111 A frame object can become invalid if the frame it refers to doesn't
22112 exist anymore in the inferior. All @code{gdb.Frame} methods will throw
22113 an exception if it is invalid at the time the method is called.
22116 @defmethod Frame name
22117 Returns the function name of the frame, or @code{None} if it can't be
22121 @defmethod Frame type
22122 Returns the type of the frame. The value can be one of
22123 @code{gdb.NORMAL_FRAME}, @code{gdb.DUMMY_FRAME}, @code{gdb.SIGTRAMP_FRAME}
22124 or @code{gdb.SENTINEL_FRAME}.
22127 @defmethod Frame unwind_stop_reason
22128 Return an integer representing the reason why it's not possible to find
22129 more frames toward the outermost frame. Use
22130 @code{gdb.frame_stop_reason_string} to convert the value returned by this
22131 function to a string.
22134 @defmethod Frame pc
22135 Returns the frame's resume address.
22138 @defmethod Frame block
22139 Return the frame's code block. @xref{Blocks In Python}.
22142 @defmethod Frame function
22143 Return the symbol for the function corresponding to this frame.
22144 @xref{Symbols In Python}.
22147 @defmethod Frame older
22148 Return the frame that called this frame.
22151 @defmethod Frame newer
22152 Return the frame called by this frame.
22155 @defmethod Frame find_sal
22156 Return the frame's symtab and line object.
22157 @xref{Symbol Tables In Python}.
22160 @defmethod Frame read_var variable @r{[}block@r{]}
22161 Return the value of @var{variable} in this frame. If the optional
22162 argument @var{block} is provided, search for the variable from that
22163 block; otherwise start at the frame's current block (which is
22164 determined by the frame's current program counter). @var{variable}
22165 must be a string or a @code{gdb.Symbol} object. @var{block} must be a
22166 @code{gdb.Block} object.
22169 @defmethod Frame select
22170 Set this frame to be the selected frame. @xref{Stack, ,Examining the
22175 @node Blocks In Python
22176 @subsubsection Accessing frame blocks from Python.
22178 @cindex blocks in python
22181 Within each frame, @value{GDBN} maintains information on each block
22182 stored in that frame. These blocks are organized hierarchically, and
22183 are represented individually in Python as a @code{gdb.Block}.
22184 Please see @ref{Frames In Python}, for a more in-depth discussion on
22185 frames. Furthermore, see @ref{Stack, ,Examining the Stack}, for more
22186 detailed technical information on @value{GDBN}'s book-keeping of the
22189 The following block-related functions are available in the @code{gdb}
22192 @findex gdb.block_for_pc
22193 @defun block_for_pc pc
22194 Return the @code{gdb.Block} containing the given @var{pc} value. If the
22195 block cannot be found for the @var{pc} value specified, the function
22196 will return @code{None}.
22199 A @code{gdb.Block} object has the following attributes:
22202 @defivar Block start
22203 The start address of the block. This attribute is not writable.
22207 The end address of the block. This attribute is not writable.
22210 @defivar Block function
22211 The name of the block represented as a @code{gdb.Symbol}. If the
22212 block is not named, then this attribute holds @code{None}. This
22213 attribute is not writable.
22216 @defivar Block superblock
22217 The block containing this block. If this parent block does not exist,
22218 this attribute holds @code{None}. This attribute is not writable.
22222 @node Symbols In Python
22223 @subsubsection Python representation of Symbols.
22225 @cindex symbols in python
22228 @value{GDBN} represents every variable, function and type as an
22229 entry in a symbol table. @xref{Symbols, ,Examining the Symbol Table}.
22230 Similarly, Python represents these symbols in @value{GDBN} with the
22231 @code{gdb.Symbol} object.
22233 The following symbol-related functions are available in the @code{gdb}
22236 @findex gdb.lookup_symbol
22237 @defun lookup_symbol name [block] [domain]
22238 This function searches for a symbol by name. The search scope can be
22239 restricted to the parameters defined in the optional domain and block
22242 @var{name} is the name of the symbol. It must be a string. The
22243 optional @var{block} argument restricts the search to symbols visible
22244 in that @var{block}. The @var{block} argument must be a
22245 @code{gdb.Block} object. The optional @var{domain} argument restricts
22246 the search to the domain type. The @var{domain} argument must be a
22247 domain constant defined in the @code{gdb} module and described later
22251 A @code{gdb.Symbol} object has the following attributes:
22254 @defivar Symbol symtab
22255 The symbol table in which the symbol appears. This attribute is
22256 represented as a @code{gdb.Symtab} object. @xref{Symbol Tables In
22257 Python}. This attribute is not writable.
22260 @defivar Symbol name
22261 The name of the symbol as a string. This attribute is not writable.
22264 @defivar Symbol linkage_name
22265 The name of the symbol, as used by the linker (i.e., may be mangled).
22266 This attribute is not writable.
22269 @defivar Symbol print_name
22270 The name of the symbol in a form suitable for output. This is either
22271 @code{name} or @code{linkage_name}, depending on whether the user
22272 asked @value{GDBN} to display demangled or mangled names.
22275 @defivar Symbol addr_class
22276 The address class of the symbol. This classifies how to find the value
22277 of a symbol. Each address class is a constant defined in the
22278 @code{gdb} module and described later in this chapter.
22281 @defivar Symbol is_argument
22282 @code{True} if the symbol is an argument of a function.
22285 @defivar Symbol is_constant
22286 @code{True} if the symbol is a constant.
22289 @defivar Symbol is_function
22290 @code{True} if the symbol is a function or a method.
22293 @defivar Symbol is_variable
22294 @code{True} if the symbol is a variable.
22298 The available domain categories in @code{gdb.Symbol} are represented
22299 as constants in the @code{gdb} module:
22302 @findex SYMBOL_UNDEF_DOMAIN
22303 @findex gdb.SYMBOL_UNDEF_DOMAIN
22304 @item SYMBOL_UNDEF_DOMAIN
22305 This is used when a domain has not been discovered or none of the
22306 following domains apply. This usually indicates an error either
22307 in the symbol information or in @value{GDBN}'s handling of symbols.
22308 @findex SYMBOL_VAR_DOMAIN
22309 @findex gdb.SYMBOL_VAR_DOMAIN
22310 @item SYMBOL_VAR_DOMAIN
22311 This domain contains variables, function names, typedef names and enum
22313 @findex SYMBOL_STRUCT_DOMAIN
22314 @findex gdb.SYMBOL_STRUCT_DOMAIN
22315 @item SYMBOL_STRUCT_DOMAIN
22316 This domain holds struct, union and enum type names.
22317 @findex SYMBOL_LABEL_DOMAIN
22318 @findex gdb.SYMBOL_LABEL_DOMAIN
22319 @item SYMBOL_LABEL_DOMAIN
22320 This domain contains names of labels (for gotos).
22321 @findex SYMBOL_VARIABLES_DOMAIN
22322 @findex gdb.SYMBOL_VARIABLES_DOMAIN
22323 @item SYMBOL_VARIABLES_DOMAIN
22324 This domain holds a subset of the @code{SYMBOLS_VAR_DOMAIN}; it
22325 contains everything minus functions and types.
22326 @findex SYMBOL_FUNCTIONS_DOMAIN
22327 @findex gdb.SYMBOL_FUNCTIONS_DOMAIN
22328 @item SYMBOL_FUNCTION_DOMAIN
22329 This domain contains all functions.
22330 @findex SYMBOL_TYPES_DOMAIN
22331 @findex gdb.SYMBOL_TYPES_DOMAIN
22332 @item SYMBOL_TYPES_DOMAIN
22333 This domain contains all types.
22336 The available address class categories in @code{gdb.Symbol} are represented
22337 as constants in the @code{gdb} module:
22340 @findex SYMBOL_LOC_UNDEF
22341 @findex gdb.SYMBOL_LOC_UNDEF
22342 @item SYMBOL_LOC_UNDEF
22343 If this is returned by address class, it indicates an error either in
22344 the symbol information or in @value{GDBN}'s handling of symbols.
22345 @findex SYMBOL_LOC_CONST
22346 @findex gdb.SYMBOL_LOC_CONST
22347 @item SYMBOL_LOC_CONST
22348 Value is constant int.
22349 @findex SYMBOL_LOC_STATIC
22350 @findex gdb.SYMBOL_LOC_STATIC
22351 @item SYMBOL_LOC_STATIC
22352 Value is at a fixed address.
22353 @findex SYMBOL_LOC_REGISTER
22354 @findex gdb.SYMBOL_LOC_REGISTER
22355 @item SYMBOL_LOC_REGISTER
22356 Value is in a register.
22357 @findex SYMBOL_LOC_ARG
22358 @findex gdb.SYMBOL_LOC_ARG
22359 @item SYMBOL_LOC_ARG
22360 Value is an argument. This value is at the offset stored within the
22361 symbol inside the frame's argument list.
22362 @findex SYMBOL_LOC_REF_ARG
22363 @findex gdb.SYMBOL_LOC_REF_ARG
22364 @item SYMBOL_LOC_REF_ARG
22365 Value address is stored in the frame's argument list. Just like
22366 @code{LOC_ARG} except that the value's address is stored at the
22367 offset, not the value itself.
22368 @findex SYMBOL_LOC_REGPARM_ADDR
22369 @findex gdb.SYMBOL_LOC_REGPARM_ADDR
22370 @item SYMBOL_LOC_REGPARM_ADDR
22371 Value is a specified register. Just like @code{LOC_REGISTER} except
22372 the register holds the address of the argument instead of the argument
22374 @findex SYMBOL_LOC_LOCAL
22375 @findex gdb.SYMBOL_LOC_LOCAL
22376 @item SYMBOL_LOC_LOCAL
22377 Value is a local variable.
22378 @findex SYMBOL_LOC_TYPEDEF
22379 @findex gdb.SYMBOL_LOC_TYPEDEF
22380 @item SYMBOL_LOC_TYPEDEF
22381 Value not used. Symbols in the domain @code{SYMBOL_STRUCT_DOMAIN} all
22383 @findex SYMBOL_LOC_BLOCK
22384 @findex gdb.SYMBOL_LOC_BLOCK
22385 @item SYMBOL_LOC_BLOCK
22387 @findex SYMBOL_LOC_CONST_BYTES
22388 @findex gdb.SYMBOL_LOC_CONST_BYTES
22389 @item SYMBOL_LOC_CONST_BYTES
22390 Value is a byte-sequence.
22391 @findex SYMBOL_LOC_UNRESOLVED
22392 @findex gdb.SYMBOL_LOC_UNRESOLVED
22393 @item SYMBOL_LOC_UNRESOLVED
22394 Value is at a fixed address, but the address of the variable has to be
22395 determined from the minimal symbol table whenever the variable is
22397 @findex SYMBOL_LOC_OPTIMIZED_OUT
22398 @findex gdb.SYMBOL_LOC_OPTIMIZED_OUT
22399 @item SYMBOL_LOC_OPTIMIZED_OUT
22400 The value does not actually exist in the program.
22401 @findex SYMBOL_LOC_COMPUTED
22402 @findex gdb.SYMBOL_LOC_COMPUTED
22403 @item SYMBOL_LOC_COMPUTED
22404 The value's address is a computed location.
22407 @node Symbol Tables In Python
22408 @subsubsection Symbol table representation in Python.
22410 @cindex symbol tables in python
22412 @tindex gdb.Symtab_and_line
22414 Access to symbol table data maintained by @value{GDBN} on the inferior
22415 is exposed to Python via two objects: @code{gdb.Symtab_and_line} and
22416 @code{gdb.Symtab}. Symbol table and line data for a frame is returned
22417 from the @code{find_sal} method in @code{gdb.Frame} object.
22418 @xref{Frames In Python}.
22420 For more information on @value{GDBN}'s symbol table management, see
22421 @ref{Symbols, ,Examining the Symbol Table}, for more information.
22423 A @code{gdb.Symtab_and_line} object has the following attributes:
22426 @defivar Symtab_and_line symtab
22427 The symbol table object (@code{gdb.Symtab}) for this frame.
22428 This attribute is not writable.
22431 @defivar Symtab_and_line pc
22432 Indicates the current program counter address. This attribute is not
22436 @defivar Symtab_and_line line
22437 Indicates the current line number for this object. This
22438 attribute is not writable.
22442 A @code{gdb.Symtab} object has the following attributes:
22445 @defivar Symtab filename
22446 The symbol table's source filename. This attribute is not writable.
22449 @defivar Symtab objfile
22450 The symbol table's backing object file. @xref{Objfiles In Python}.
22451 This attribute is not writable.
22455 The following methods are provided:
22458 @defmethod Symtab fullname
22459 Return the symbol table's source absolute file name.
22463 @node Breakpoints In Python
22464 @subsubsection Manipulating breakpoints using Python
22466 @cindex breakpoints in python
22467 @tindex gdb.Breakpoint
22469 Python code can manipulate breakpoints via the @code{gdb.Breakpoint}
22472 @defmethod Breakpoint __init__ spec @r{[}type@r{]} @r{[}wp_class@r{]}
22473 Create a new breakpoint. @var{spec} is a string naming the
22474 location of the breakpoint, or an expression that defines a
22475 watchpoint. The contents can be any location recognized by the
22476 @code{break} command, or in the case of a watchpoint, by the @code{watch}
22477 command. The optional @var{type} denotes the breakpoint to create
22478 from the types defined later in this chapter. This argument can be
22479 either: @code{BP_BREAKPOINT} or @code{BP_WATCHPOINT}. @var{type}
22480 defaults to @code{BP_BREAKPOINT}. The optional @var{wp_class}
22481 argument defines the class of watchpoint to create, if @var{type} is
22482 defined as @code{BP_WATCHPOINT}. If a watchpoint class is not
22483 provided, it is assumed to be a @var{WP_WRITE} class.
22486 The available watchpoint types represented by constants are defined in the
22491 @findex gdb.WP_READ
22493 Read only watchpoint.
22496 @findex gdb.WP_WRITE
22498 Write only watchpoint.
22501 @findex gdb.WP_ACCESS
22503 Read/Write watchpoint.
22506 @defmethod Breakpoint is_valid
22507 Return @code{True} if this @code{Breakpoint} object is valid,
22508 @code{False} otherwise. A @code{Breakpoint} object can become invalid
22509 if the user deletes the breakpoint. In this case, the object still
22510 exists, but the underlying breakpoint does not. In the cases of
22511 watchpoint scope, the watchpoint remains valid even if execution of the
22512 inferior leaves the scope of that watchpoint.
22515 @defivar Breakpoint enabled
22516 This attribute is @code{True} if the breakpoint is enabled, and
22517 @code{False} otherwise. This attribute is writable.
22520 @defivar Breakpoint silent
22521 This attribute is @code{True} if the breakpoint is silent, and
22522 @code{False} otherwise. This attribute is writable.
22524 Note that a breakpoint can also be silent if it has commands and the
22525 first command is @code{silent}. This is not reported by the
22526 @code{silent} attribute.
22529 @defivar Breakpoint thread
22530 If the breakpoint is thread-specific, this attribute holds the thread
22531 id. If the breakpoint is not thread-specific, this attribute is
22532 @code{None}. This attribute is writable.
22535 @defivar Breakpoint task
22536 If the breakpoint is Ada task-specific, this attribute holds the Ada task
22537 id. If the breakpoint is not task-specific (or the underlying
22538 language is not Ada), this attribute is @code{None}. This attribute
22542 @defivar Breakpoint ignore_count
22543 This attribute holds the ignore count for the breakpoint, an integer.
22544 This attribute is writable.
22547 @defivar Breakpoint number
22548 This attribute holds the breakpoint's number --- the identifier used by
22549 the user to manipulate the breakpoint. This attribute is not writable.
22552 @defivar Breakpoint type
22553 This attribute holds the breakpoint's type --- the identifier used to
22554 determine the actual breakpoint type or use-case. This attribute is not
22558 The available types are represented by constants defined in the @code{gdb}
22562 @findex BP_BREAKPOINT
22563 @findex gdb.BP_BREAKPOINT
22564 @item BP_BREAKPOINT
22565 Normal code breakpoint.
22567 @findex BP_WATCHPOINT
22568 @findex gdb.BP_WATCHPOINT
22569 @item BP_WATCHPOINT
22570 Watchpoint breakpoint.
22572 @findex BP_HARDWARE_WATCHPOINT
22573 @findex gdb.BP_HARDWARE_WATCHPOINT
22574 @item BP_HARDWARE_WATCHPOINT
22575 Hardware assisted watchpoint.
22577 @findex BP_READ_WATCHPOINT
22578 @findex gdb.BP_READ_WATCHPOINT
22579 @item BP_READ_WATCHPOINT
22580 Hardware assisted read watchpoint.
22582 @findex BP_ACCESS_WATCHPOINT
22583 @findex gdb.BP_ACCESS_WATCHPOINT
22584 @item BP_ACCESS_WATCHPOINT
22585 Hardware assisted access watchpoint.
22588 @defivar Breakpoint hit_count
22589 This attribute holds the hit count for the breakpoint, an integer.
22590 This attribute is writable, but currently it can only be set to zero.
22593 @defivar Breakpoint location
22594 This attribute holds the location of the breakpoint, as specified by
22595 the user. It is a string. If the breakpoint does not have a location
22596 (that is, it is a watchpoint) the attribute's value is @code{None}. This
22597 attribute is not writable.
22600 @defivar Breakpoint expression
22601 This attribute holds a breakpoint expression, as specified by
22602 the user. It is a string. If the breakpoint does not have an
22603 expression (the breakpoint is not a watchpoint) the attribute's value
22604 is @code{None}. This attribute is not writable.
22607 @defivar Breakpoint condition
22608 This attribute holds the condition of the breakpoint, as specified by
22609 the user. It is a string. If there is no condition, this attribute's
22610 value is @code{None}. This attribute is writable.
22613 @defivar Breakpoint commands
22614 This attribute holds the commands attached to the breakpoint. If
22615 there are commands, this attribute's value is a string holding all the
22616 commands, separated by newlines. If there are no commands, this
22617 attribute is @code{None}. This attribute is not writable.
22620 @node Lazy Strings In Python
22621 @subsubsection Python representation of lazy strings.
22623 @cindex lazy strings in python
22624 @tindex gdb.LazyString
22626 A @dfn{lazy string} is a string whose contents is not retrieved or
22627 encoded until it is needed.
22629 A @code{gdb.LazyString} is represented in @value{GDBN} as an
22630 @code{address} that points to a region of memory, an @code{encoding}
22631 that will be used to encode that region of memory, and a @code{length}
22632 to delimit the region of memory that represents the string. The
22633 difference between a @code{gdb.LazyString} and a string wrapped within
22634 a @code{gdb.Value} is that a @code{gdb.LazyString} will be treated
22635 differently by @value{GDBN} when printing. A @code{gdb.LazyString} is
22636 retrieved and encoded during printing, while a @code{gdb.Value}
22637 wrapping a string is immediately retrieved and encoded on creation.
22639 A @code{gdb.LazyString} object has the following functions:
22641 @defmethod LazyString value
22642 Convert the @code{gdb.LazyString} to a @code{gdb.Value}. This value
22643 will point to the string in memory, but will lose all the delayed
22644 retrieval, encoding and handling that @value{GDBN} applies to a
22645 @code{gdb.LazyString}.
22648 @defivar LazyString address
22649 This attribute holds the address of the string. This attribute is not
22653 @defivar LazyString length
22654 This attribute holds the length of the string in characters. If the
22655 length is -1, then the string will be fetched and encoded up to the
22656 first null of appropriate width. This attribute is not writable.
22659 @defivar LazyString encoding
22660 This attribute holds the encoding that will be applied to the string
22661 when the string is printed by @value{GDBN}. If the encoding is not
22662 set, or contains an empty string, then @value{GDBN} will select the
22663 most appropriate encoding when the string is printed. This attribute
22667 @defivar LazyString type
22668 This attribute holds the type that is represented by the lazy string's
22669 type. For a lazy string this will always be a pointer type. To
22670 resolve this to the lazy string's character type, use the type's
22671 @code{target} method. @xref{Types In Python}. This attribute is not
22676 @subsection Auto-loading
22677 @cindex auto-loading, Python
22679 When a new object file is read (for example, due to the @code{file}
22680 command, or because the inferior has loaded a shared library),
22681 @value{GDBN} will look for Python support scripts in several ways:
22682 @file{@var{objfile}-gdb.py} and @code{.debug_gdb_scripts} section.
22685 * objfile-gdb.py file:: The @file{@var{objfile}-gdb.py} file
22686 * .debug_gdb_scripts section:: The @code{.debug_gdb_scripts} section
22687 * Which flavor to choose?::
22690 The auto-loading feature is useful for supplying application-specific
22691 debugging commands and scripts.
22693 Auto-loading can be enabled or disabled.
22696 @kindex maint set python auto-load
22697 @item maint set python auto-load [yes|no]
22698 Enable or disable the Python auto-loading feature.
22700 @kindex maint show python auto-load
22701 @item maint show python auto-load
22702 Show whether Python auto-loading is enabled or disabled.
22705 When reading an auto-loaded file, @value{GDBN} sets the
22706 @dfn{current objfile}. This is available via the @code{gdb.current_objfile}
22707 function (@pxref{Objfiles In Python}). This can be useful for
22708 registering objfile-specific pretty-printers.
22710 @node objfile-gdb.py file
22711 @subsubsection The @file{@var{objfile}-gdb.py} file
22712 @cindex @file{@var{objfile}-gdb.py}
22714 When a new object file is read, @value{GDBN} looks for
22715 a file named @file{@var{objfile}-gdb.py},
22716 where @var{objfile} is the object file's real name, formed by ensuring
22717 that the file name is absolute, following all symlinks, and resolving
22718 @code{.} and @code{..} components. If this file exists and is
22719 readable, @value{GDBN} will evaluate it as a Python script.
22721 If this file does not exist, and if the parameter
22722 @code{debug-file-directory} is set (@pxref{Separate Debug Files}),
22723 then @value{GDBN} will look for @var{real-name} in all of the
22724 directories mentioned in the value of @code{debug-file-directory}.
22726 Finally, if this file does not exist, then @value{GDBN} will look for
22727 a file named @file{@var{data-directory}/python/auto-load/@var{real-name}}, where
22728 @var{data-directory} is @value{GDBN}'s data directory (available via
22729 @code{show data-directory}, @pxref{Data Files}), and @var{real-name}
22730 is the object file's real name, as described above.
22732 @value{GDBN} does not track which files it has already auto-loaded this way.
22733 @value{GDBN} will load the associated script every time the corresponding
22734 @var{objfile} is opened.
22735 So your @file{-gdb.py} file should be careful to avoid errors if it
22736 is evaluated more than once.
22738 @node .debug_gdb_scripts section
22739 @subsubsection The @code{.debug_gdb_scripts} section
22740 @cindex @code{.debug_gdb_scripts} section
22742 For systems using file formats like ELF and COFF,
22743 when @value{GDBN} loads a new object file
22744 it will look for a special section named @samp{.debug_gdb_scripts}.
22745 If this section exists, its contents is a list of names of scripts to load.
22747 @value{GDBN} will look for each specified script file first in the
22748 current directory and then along the source search path
22749 (@pxref{Source Path, ,Specifying Source Directories}),
22750 except that @file{$cdir} is not searched, since the compilation
22751 directory is not relevant to scripts.
22753 Entries can be placed in section @code{.debug_gdb_scripts} with,
22754 for example, this GCC macro:
22757 /* Note: The "MS" section flags are to remove duplicates. */
22758 #define DEFINE_GDB_SCRIPT(script_name) \
22760 .pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n\
22762 .asciz \"" script_name "\"\n\
22768 Then one can reference the macro in a header or source file like this:
22771 DEFINE_GDB_SCRIPT ("my-app-scripts.py")
22774 The script name may include directories if desired.
22776 If the macro is put in a header, any application or library
22777 using this header will get a reference to the specified script.
22779 @node Which flavor to choose?
22780 @subsubsection Which flavor to choose?
22782 Given the multiple ways of auto-loading Python scripts, it might not always
22783 be clear which one to choose. This section provides some guidance.
22785 Benefits of the @file{-gdb.py} way:
22789 Can be used with file formats that don't support multiple sections.
22792 Ease of finding scripts for public libraries.
22794 Scripts specified in the @code{.debug_gdb_scripts} section are searched for
22795 in the source search path.
22796 For publicly installed libraries, e.g., @file{libstdc++}, there typically
22797 isn't a source directory in which to find the script.
22800 Doesn't require source code additions.
22803 Benefits of the @code{.debug_gdb_scripts} way:
22807 Works with static linking.
22809 Scripts for libraries done the @file{-gdb.py} way require an objfile to
22810 trigger their loading. When an application is statically linked the only
22811 objfile available is the executable, and it is cumbersome to attach all the
22812 scripts from all the input libraries to the executable's @file{-gdb.py} script.
22815 Works with classes that are entirely inlined.
22817 Some classes can be entirely inlined, and thus there may not be an associated
22818 shared library to attach a @file{-gdb.py} script to.
22821 Scripts needn't be copied out of the source tree.
22823 In some circumstances, apps can be built out of large collections of internal
22824 libraries, and the build infrastructure necessary to install the
22825 @file{-gdb.py} scripts in a place where @value{GDBN} can find them is
22826 cumbersome. It may be easier to specify the scripts in the
22827 @code{.debug_gdb_scripts} section as relative paths, and add a path to the
22828 top of the source tree to the source search path.
22832 @chapter Command Interpreters
22833 @cindex command interpreters
22835 @value{GDBN} supports multiple command interpreters, and some command
22836 infrastructure to allow users or user interface writers to switch
22837 between interpreters or run commands in other interpreters.
22839 @value{GDBN} currently supports two command interpreters, the console
22840 interpreter (sometimes called the command-line interpreter or @sc{cli})
22841 and the machine interface interpreter (or @sc{gdb/mi}). This manual
22842 describes both of these interfaces in great detail.
22844 By default, @value{GDBN} will start with the console interpreter.
22845 However, the user may choose to start @value{GDBN} with another
22846 interpreter by specifying the @option{-i} or @option{--interpreter}
22847 startup options. Defined interpreters include:
22851 @cindex console interpreter
22852 The traditional console or command-line interpreter. This is the most often
22853 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
22854 @value{GDBN} will use this interpreter.
22857 @cindex mi interpreter
22858 The newest @sc{gdb/mi} interface (currently @code{mi2}). Used primarily
22859 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
22860 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
22864 @cindex mi2 interpreter
22865 The current @sc{gdb/mi} interface.
22868 @cindex mi1 interpreter
22869 The @sc{gdb/mi} interface included in @value{GDBN} 5.1, 5.2, and 5.3.
22873 @cindex invoke another interpreter
22874 The interpreter being used by @value{GDBN} may not be dynamically
22875 switched at runtime. Although possible, this could lead to a very
22876 precarious situation. Consider an IDE using @sc{gdb/mi}. If a user
22877 enters the command "interpreter-set console" in a console view,
22878 @value{GDBN} would switch to using the console interpreter, rendering
22879 the IDE inoperable!
22881 @kindex interpreter-exec
22882 Although you may only choose a single interpreter at startup, you may execute
22883 commands in any interpreter from the current interpreter using the appropriate
22884 command. If you are running the console interpreter, simply use the
22885 @code{interpreter-exec} command:
22888 interpreter-exec mi "-data-list-register-names"
22891 @sc{gdb/mi} has a similar command, although it is only available in versions of
22892 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
22895 @chapter @value{GDBN} Text User Interface
22897 @cindex Text User Interface
22900 * TUI Overview:: TUI overview
22901 * TUI Keys:: TUI key bindings
22902 * TUI Single Key Mode:: TUI single key mode
22903 * TUI Commands:: TUI-specific commands
22904 * TUI Configuration:: TUI configuration variables
22907 The @value{GDBN} Text User Interface (TUI) is a terminal
22908 interface which uses the @code{curses} library to show the source
22909 file, the assembly output, the program registers and @value{GDBN}
22910 commands in separate text windows. The TUI mode is supported only
22911 on platforms where a suitable version of the @code{curses} library
22914 @pindex @value{GDBTUI}
22915 The TUI mode is enabled by default when you invoke @value{GDBN} as
22916 either @samp{@value{GDBTUI}} or @samp{@value{GDBP} -tui}.
22917 You can also switch in and out of TUI mode while @value{GDBN} runs by
22918 using various TUI commands and key bindings, such as @kbd{C-x C-a}.
22919 @xref{TUI Keys, ,TUI Key Bindings}.
22922 @section TUI Overview
22924 In TUI mode, @value{GDBN} can display several text windows:
22928 This window is the @value{GDBN} command window with the @value{GDBN}
22929 prompt and the @value{GDBN} output. The @value{GDBN} input is still
22930 managed using readline.
22933 The source window shows the source file of the program. The current
22934 line and active breakpoints are displayed in this window.
22937 The assembly window shows the disassembly output of the program.
22940 This window shows the processor registers. Registers are highlighted
22941 when their values change.
22944 The source and assembly windows show the current program position
22945 by highlighting the current line and marking it with a @samp{>} marker.
22946 Breakpoints are indicated with two markers. The first marker
22947 indicates the breakpoint type:
22951 Breakpoint which was hit at least once.
22954 Breakpoint which was never hit.
22957 Hardware breakpoint which was hit at least once.
22960 Hardware breakpoint which was never hit.
22963 The second marker indicates whether the breakpoint is enabled or not:
22967 Breakpoint is enabled.
22970 Breakpoint is disabled.
22973 The source, assembly and register windows are updated when the current
22974 thread changes, when the frame changes, or when the program counter
22977 These windows are not all visible at the same time. The command
22978 window is always visible. The others can be arranged in several
22989 source and assembly,
22992 source and registers, or
22995 assembly and registers.
22998 A status line above the command window shows the following information:
23002 Indicates the current @value{GDBN} target.
23003 (@pxref{Targets, ,Specifying a Debugging Target}).
23006 Gives the current process or thread number.
23007 When no process is being debugged, this field is set to @code{No process}.
23010 Gives the current function name for the selected frame.
23011 The name is demangled if demangling is turned on (@pxref{Print Settings}).
23012 When there is no symbol corresponding to the current program counter,
23013 the string @code{??} is displayed.
23016 Indicates the current line number for the selected frame.
23017 When the current line number is not known, the string @code{??} is displayed.
23020 Indicates the current program counter address.
23024 @section TUI Key Bindings
23025 @cindex TUI key bindings
23027 The TUI installs several key bindings in the readline keymaps
23028 (@pxref{Command Line Editing}). The following key bindings
23029 are installed for both TUI mode and the @value{GDBN} standard mode.
23038 Enter or leave the TUI mode. When leaving the TUI mode,
23039 the curses window management stops and @value{GDBN} operates using
23040 its standard mode, writing on the terminal directly. When reentering
23041 the TUI mode, control is given back to the curses windows.
23042 The screen is then refreshed.
23046 Use a TUI layout with only one window. The layout will
23047 either be @samp{source} or @samp{assembly}. When the TUI mode
23048 is not active, it will switch to the TUI mode.
23050 Think of this key binding as the Emacs @kbd{C-x 1} binding.
23054 Use a TUI layout with at least two windows. When the current
23055 layout already has two windows, the next layout with two windows is used.
23056 When a new layout is chosen, one window will always be common to the
23057 previous layout and the new one.
23059 Think of it as the Emacs @kbd{C-x 2} binding.
23063 Change the active window. The TUI associates several key bindings
23064 (like scrolling and arrow keys) with the active window. This command
23065 gives the focus to the next TUI window.
23067 Think of it as the Emacs @kbd{C-x o} binding.
23071 Switch in and out of the TUI SingleKey mode that binds single
23072 keys to @value{GDBN} commands (@pxref{TUI Single Key Mode}).
23075 The following key bindings only work in the TUI mode:
23080 Scroll the active window one page up.
23084 Scroll the active window one page down.
23088 Scroll the active window one line up.
23092 Scroll the active window one line down.
23096 Scroll the active window one column left.
23100 Scroll the active window one column right.
23104 Refresh the screen.
23107 Because the arrow keys scroll the active window in the TUI mode, they
23108 are not available for their normal use by readline unless the command
23109 window has the focus. When another window is active, you must use
23110 other readline key bindings such as @kbd{C-p}, @kbd{C-n}, @kbd{C-b}
23111 and @kbd{C-f} to control the command window.
23113 @node TUI Single Key Mode
23114 @section TUI Single Key Mode
23115 @cindex TUI single key mode
23117 The TUI also provides a @dfn{SingleKey} mode, which binds several
23118 frequently used @value{GDBN} commands to single keys. Type @kbd{C-x s} to
23119 switch into this mode, where the following key bindings are used:
23122 @kindex c @r{(SingleKey TUI key)}
23126 @kindex d @r{(SingleKey TUI key)}
23130 @kindex f @r{(SingleKey TUI key)}
23134 @kindex n @r{(SingleKey TUI key)}
23138 @kindex q @r{(SingleKey TUI key)}
23140 exit the SingleKey mode.
23142 @kindex r @r{(SingleKey TUI key)}
23146 @kindex s @r{(SingleKey TUI key)}
23150 @kindex u @r{(SingleKey TUI key)}
23154 @kindex v @r{(SingleKey TUI key)}
23158 @kindex w @r{(SingleKey TUI key)}
23163 Other keys temporarily switch to the @value{GDBN} command prompt.
23164 The key that was pressed is inserted in the editing buffer so that
23165 it is possible to type most @value{GDBN} commands without interaction
23166 with the TUI SingleKey mode. Once the command is entered the TUI
23167 SingleKey mode is restored. The only way to permanently leave
23168 this mode is by typing @kbd{q} or @kbd{C-x s}.
23172 @section TUI-specific Commands
23173 @cindex TUI commands
23175 The TUI has specific commands to control the text windows.
23176 These commands are always available, even when @value{GDBN} is not in
23177 the TUI mode. When @value{GDBN} is in the standard mode, most
23178 of these commands will automatically switch to the TUI mode.
23180 Note that if @value{GDBN}'s @code{stdout} is not connected to a
23181 terminal, or @value{GDBN} has been started with the machine interface
23182 interpreter (@pxref{GDB/MI, ,The @sc{gdb/mi} Interface}), most of
23183 these commands will fail with an error, because it would not be
23184 possible or desirable to enable curses window management.
23189 List and give the size of all displayed windows.
23193 Display the next layout.
23196 Display the previous layout.
23199 Display the source window only.
23202 Display the assembly window only.
23205 Display the source and assembly window.
23208 Display the register window together with the source or assembly window.
23212 Make the next window active for scrolling.
23215 Make the previous window active for scrolling.
23218 Make the source window active for scrolling.
23221 Make the assembly window active for scrolling.
23224 Make the register window active for scrolling.
23227 Make the command window active for scrolling.
23231 Refresh the screen. This is similar to typing @kbd{C-L}.
23233 @item tui reg float
23235 Show the floating point registers in the register window.
23237 @item tui reg general
23238 Show the general registers in the register window.
23241 Show the next register group. The list of register groups as well as
23242 their order is target specific. The predefined register groups are the
23243 following: @code{general}, @code{float}, @code{system}, @code{vector},
23244 @code{all}, @code{save}, @code{restore}.
23246 @item tui reg system
23247 Show the system registers in the register window.
23251 Update the source window and the current execution point.
23253 @item winheight @var{name} +@var{count}
23254 @itemx winheight @var{name} -@var{count}
23256 Change the height of the window @var{name} by @var{count}
23257 lines. Positive counts increase the height, while negative counts
23260 @item tabset @var{nchars}
23262 Set the width of tab stops to be @var{nchars} characters.
23265 @node TUI Configuration
23266 @section TUI Configuration Variables
23267 @cindex TUI configuration variables
23269 Several configuration variables control the appearance of TUI windows.
23272 @item set tui border-kind @var{kind}
23273 @kindex set tui border-kind
23274 Select the border appearance for the source, assembly and register windows.
23275 The possible values are the following:
23278 Use a space character to draw the border.
23281 Use @sc{ascii} characters @samp{+}, @samp{-} and @samp{|} to draw the border.
23284 Use the Alternate Character Set to draw the border. The border is
23285 drawn using character line graphics if the terminal supports them.
23288 @item set tui border-mode @var{mode}
23289 @kindex set tui border-mode
23290 @itemx set tui active-border-mode @var{mode}
23291 @kindex set tui active-border-mode
23292 Select the display attributes for the borders of the inactive windows
23293 or the active window. The @var{mode} can be one of the following:
23296 Use normal attributes to display the border.
23302 Use reverse video mode.
23305 Use half bright mode.
23307 @item half-standout
23308 Use half bright and standout mode.
23311 Use extra bright or bold mode.
23313 @item bold-standout
23314 Use extra bright or bold and standout mode.
23319 @chapter Using @value{GDBN} under @sc{gnu} Emacs
23322 @cindex @sc{gnu} Emacs
23323 A special interface allows you to use @sc{gnu} Emacs to view (and
23324 edit) the source files for the program you are debugging with
23327 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
23328 executable file you want to debug as an argument. This command starts
23329 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
23330 created Emacs buffer.
23331 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
23333 Running @value{GDBN} under Emacs can be just like running @value{GDBN} normally except for two
23338 All ``terminal'' input and output goes through an Emacs buffer, called
23341 This applies both to @value{GDBN} commands and their output, and to the input
23342 and output done by the program you are debugging.
23344 This is useful because it means that you can copy the text of previous
23345 commands and input them again; you can even use parts of the output
23348 All the facilities of Emacs' Shell mode are available for interacting
23349 with your program. In particular, you can send signals the usual
23350 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
23354 @value{GDBN} displays source code through Emacs.
23356 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
23357 source file for that frame and puts an arrow (@samp{=>}) at the
23358 left margin of the current line. Emacs uses a separate buffer for
23359 source display, and splits the screen to show both your @value{GDBN} session
23362 Explicit @value{GDBN} @code{list} or search commands still produce output as
23363 usual, but you probably have no reason to use them from Emacs.
23366 We call this @dfn{text command mode}. Emacs 22.1, and later, also uses
23367 a graphical mode, enabled by default, which provides further buffers
23368 that can control the execution and describe the state of your program.
23369 @xref{GDB Graphical Interface,,, Emacs, The @sc{gnu} Emacs Manual}.
23371 If you specify an absolute file name when prompted for the @kbd{M-x
23372 gdb} argument, then Emacs sets your current working directory to where
23373 your program resides. If you only specify the file name, then Emacs
23374 sets your current working directory to to the directory associated
23375 with the previous buffer. In this case, @value{GDBN} may find your
23376 program by searching your environment's @code{PATH} variable, but on
23377 some operating systems it might not find the source. So, although the
23378 @value{GDBN} input and output session proceeds normally, the auxiliary
23379 buffer does not display the current source and line of execution.
23381 The initial working directory of @value{GDBN} is printed on the top
23382 line of the GUD buffer and this serves as a default for the commands
23383 that specify files for @value{GDBN} to operate on. @xref{Files,
23384 ,Commands to Specify Files}.
23386 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
23387 need to call @value{GDBN} by a different name (for example, if you
23388 keep several configurations around, with different names) you can
23389 customize the Emacs variable @code{gud-gdb-command-name} to run the
23392 In the GUD buffer, you can use these special Emacs commands in
23393 addition to the standard Shell mode commands:
23397 Describe the features of Emacs' GUD Mode.
23400 Execute to another source line, like the @value{GDBN} @code{step} command; also
23401 update the display window to show the current file and location.
23404 Execute to next source line in this function, skipping all function
23405 calls, like the @value{GDBN} @code{next} command. Then update the display window
23406 to show the current file and location.
23409 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
23410 display window accordingly.
23413 Execute until exit from the selected stack frame, like the @value{GDBN}
23414 @code{finish} command.
23417 Continue execution of your program, like the @value{GDBN} @code{continue}
23421 Go up the number of frames indicated by the numeric argument
23422 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
23423 like the @value{GDBN} @code{up} command.
23426 Go down the number of frames indicated by the numeric argument, like the
23427 @value{GDBN} @code{down} command.
23430 In any source file, the Emacs command @kbd{C-x @key{SPC}} (@code{gud-break})
23431 tells @value{GDBN} to set a breakpoint on the source line point is on.
23433 In text command mode, if you type @kbd{M-x speedbar}, Emacs displays a
23434 separate frame which shows a backtrace when the GUD buffer is current.
23435 Move point to any frame in the stack and type @key{RET} to make it
23436 become the current frame and display the associated source in the
23437 source buffer. Alternatively, click @kbd{Mouse-2} to make the
23438 selected frame become the current one. In graphical mode, the
23439 speedbar displays watch expressions.
23441 If you accidentally delete the source-display buffer, an easy way to get
23442 it back is to type the command @code{f} in the @value{GDBN} buffer, to
23443 request a frame display; when you run under Emacs, this recreates
23444 the source buffer if necessary to show you the context of the current
23447 The source files displayed in Emacs are in ordinary Emacs buffers
23448 which are visiting the source files in the usual way. You can edit
23449 the files with these buffers if you wish; but keep in mind that @value{GDBN}
23450 communicates with Emacs in terms of line numbers. If you add or
23451 delete lines from the text, the line numbers that @value{GDBN} knows cease
23452 to correspond properly with the code.
23454 A more detailed description of Emacs' interaction with @value{GDBN} is
23455 given in the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu}
23458 @c The following dropped because Epoch is nonstandard. Reactivate
23459 @c if/when v19 does something similar. ---doc@cygnus.com 19dec1990
23461 @kindex Emacs Epoch environment
23465 Version 18 of @sc{gnu} Emacs has a built-in window system
23466 called the @code{epoch}
23467 environment. Users of this environment can use a new command,
23468 @code{inspect} which performs identically to @code{print} except that
23469 each value is printed in its own window.
23474 @chapter The @sc{gdb/mi} Interface
23476 @unnumberedsec Function and Purpose
23478 @cindex @sc{gdb/mi}, its purpose
23479 @sc{gdb/mi} is a line based machine oriented text interface to
23480 @value{GDBN} and is activated by specifying using the
23481 @option{--interpreter} command line option (@pxref{Mode Options}). It
23482 is specifically intended to support the development of systems which
23483 use the debugger as just one small component of a larger system.
23485 This chapter is a specification of the @sc{gdb/mi} interface. It is written
23486 in the form of a reference manual.
23488 Note that @sc{gdb/mi} is still under construction, so some of the
23489 features described below are incomplete and subject to change
23490 (@pxref{GDB/MI Development and Front Ends, , @sc{gdb/mi} Development and Front Ends}).
23492 @unnumberedsec Notation and Terminology
23494 @cindex notational conventions, for @sc{gdb/mi}
23495 This chapter uses the following notation:
23499 @code{|} separates two alternatives.
23502 @code{[ @var{something} ]} indicates that @var{something} is optional:
23503 it may or may not be given.
23506 @code{( @var{group} )*} means that @var{group} inside the parentheses
23507 may repeat zero or more times.
23510 @code{( @var{group} )+} means that @var{group} inside the parentheses
23511 may repeat one or more times.
23514 @code{"@var{string}"} means a literal @var{string}.
23518 @heading Dependencies
23522 * GDB/MI General Design::
23523 * GDB/MI Command Syntax::
23524 * GDB/MI Compatibility with CLI::
23525 * GDB/MI Development and Front Ends::
23526 * GDB/MI Output Records::
23527 * GDB/MI Simple Examples::
23528 * GDB/MI Command Description Format::
23529 * GDB/MI Breakpoint Commands::
23530 * GDB/MI Program Context::
23531 * GDB/MI Thread Commands::
23532 * GDB/MI Program Execution::
23533 * GDB/MI Stack Manipulation::
23534 * GDB/MI Variable Objects::
23535 * GDB/MI Data Manipulation::
23536 * GDB/MI Tracepoint Commands::
23537 * GDB/MI Symbol Query::
23538 * GDB/MI File Commands::
23540 * GDB/MI Kod Commands::
23541 * GDB/MI Memory Overlay Commands::
23542 * GDB/MI Signal Handling Commands::
23544 * GDB/MI Target Manipulation::
23545 * GDB/MI File Transfer Commands::
23546 * GDB/MI Miscellaneous Commands::
23549 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
23550 @node GDB/MI General Design
23551 @section @sc{gdb/mi} General Design
23552 @cindex GDB/MI General Design
23554 Interaction of a @sc{GDB/MI} frontend with @value{GDBN} involves three
23555 parts---commands sent to @value{GDBN}, responses to those commands
23556 and notifications. Each command results in exactly one response,
23557 indicating either successful completion of the command, or an error.
23558 For the commands that do not resume the target, the response contains the
23559 requested information. For the commands that resume the target, the
23560 response only indicates whether the target was successfully resumed.
23561 Notifications is the mechanism for reporting changes in the state of the
23562 target, or in @value{GDBN} state, that cannot conveniently be associated with
23563 a command and reported as part of that command response.
23565 The important examples of notifications are:
23569 Exec notifications. These are used to report changes in
23570 target state---when a target is resumed, or stopped. It would not
23571 be feasible to include this information in response of resuming
23572 commands, because one resume commands can result in multiple events in
23573 different threads. Also, quite some time may pass before any event
23574 happens in the target, while a frontend needs to know whether the resuming
23575 command itself was successfully executed.
23578 Console output, and status notifications. Console output
23579 notifications are used to report output of CLI commands, as well as
23580 diagnostics for other commands. Status notifications are used to
23581 report the progress of a long-running operation. Naturally, including
23582 this information in command response would mean no output is produced
23583 until the command is finished, which is undesirable.
23586 General notifications. Commands may have various side effects on
23587 the @value{GDBN} or target state beyond their official purpose. For example,
23588 a command may change the selected thread. Although such changes can
23589 be included in command response, using notification allows for more
23590 orthogonal frontend design.
23594 There's no guarantee that whenever an MI command reports an error,
23595 @value{GDBN} or the target are in any specific state, and especially,
23596 the state is not reverted to the state before the MI command was
23597 processed. Therefore, whenever an MI command results in an error,
23598 we recommend that the frontend refreshes all the information shown in
23599 the user interface.
23603 * Context management::
23604 * Asynchronous and non-stop modes::
23608 @node Context management
23609 @subsection Context management
23611 In most cases when @value{GDBN} accesses the target, this access is
23612 done in context of a specific thread and frame (@pxref{Frames}).
23613 Often, even when accessing global data, the target requires that a thread
23614 be specified. The CLI interface maintains the selected thread and frame,
23615 and supplies them to target on each command. This is convenient,
23616 because a command line user would not want to specify that information
23617 explicitly on each command, and because user interacts with
23618 @value{GDBN} via a single terminal, so no confusion is possible as
23619 to what thread and frame are the current ones.
23621 In the case of MI, the concept of selected thread and frame is less
23622 useful. First, a frontend can easily remember this information
23623 itself. Second, a graphical frontend can have more than one window,
23624 each one used for debugging a different thread, and the frontend might
23625 want to access additional threads for internal purposes. This
23626 increases the risk that by relying on implicitly selected thread, the
23627 frontend may be operating on a wrong one. Therefore, each MI command
23628 should explicitly specify which thread and frame to operate on. To
23629 make it possible, each MI command accepts the @samp{--thread} and
23630 @samp{--frame} options, the value to each is @value{GDBN} identifier
23631 for thread and frame to operate on.
23633 Usually, each top-level window in a frontend allows the user to select
23634 a thread and a frame, and remembers the user selection for further
23635 operations. However, in some cases @value{GDBN} may suggest that the
23636 current thread be changed. For example, when stopping on a breakpoint
23637 it is reasonable to switch to the thread where breakpoint is hit. For
23638 another example, if the user issues the CLI @samp{thread} command via
23639 the frontend, it is desirable to change the frontend's selected thread to the
23640 one specified by user. @value{GDBN} communicates the suggestion to
23641 change current thread using the @samp{=thread-selected} notification.
23642 No such notification is available for the selected frame at the moment.
23644 Note that historically, MI shares the selected thread with CLI, so
23645 frontends used the @code{-thread-select} to execute commands in the
23646 right context. However, getting this to work right is cumbersome. The
23647 simplest way is for frontend to emit @code{-thread-select} command
23648 before every command. This doubles the number of commands that need
23649 to be sent. The alternative approach is to suppress @code{-thread-select}
23650 if the selected thread in @value{GDBN} is supposed to be identical to the
23651 thread the frontend wants to operate on. However, getting this
23652 optimization right can be tricky. In particular, if the frontend
23653 sends several commands to @value{GDBN}, and one of the commands changes the
23654 selected thread, then the behaviour of subsequent commands will
23655 change. So, a frontend should either wait for response from such
23656 problematic commands, or explicitly add @code{-thread-select} for
23657 all subsequent commands. No frontend is known to do this exactly
23658 right, so it is suggested to just always pass the @samp{--thread} and
23659 @samp{--frame} options.
23661 @node Asynchronous and non-stop modes
23662 @subsection Asynchronous command execution and non-stop mode
23664 On some targets, @value{GDBN} is capable of processing MI commands
23665 even while the target is running. This is called @dfn{asynchronous
23666 command execution} (@pxref{Background Execution}). The frontend may
23667 specify a preferrence for asynchronous execution using the
23668 @code{-gdb-set target-async 1} command, which should be emitted before
23669 either running the executable or attaching to the target. After the
23670 frontend has started the executable or attached to the target, it can
23671 find if asynchronous execution is enabled using the
23672 @code{-list-target-features} command.
23674 Even if @value{GDBN} can accept a command while target is running,
23675 many commands that access the target do not work when the target is
23676 running. Therefore, asynchronous command execution is most useful
23677 when combined with non-stop mode (@pxref{Non-Stop Mode}). Then,
23678 it is possible to examine the state of one thread, while other threads
23681 When a given thread is running, MI commands that try to access the
23682 target in the context of that thread may not work, or may work only on
23683 some targets. In particular, commands that try to operate on thread's
23684 stack will not work, on any target. Commands that read memory, or
23685 modify breakpoints, may work or not work, depending on the target. Note
23686 that even commands that operate on global state, such as @code{print},
23687 @code{set}, and breakpoint commands, still access the target in the
23688 context of a specific thread, so frontend should try to find a
23689 stopped thread and perform the operation on that thread (using the
23690 @samp{--thread} option).
23692 Which commands will work in the context of a running thread is
23693 highly target dependent. However, the two commands
23694 @code{-exec-interrupt}, to stop a thread, and @code{-thread-info},
23695 to find the state of a thread, will always work.
23697 @node Thread groups
23698 @subsection Thread groups
23699 @value{GDBN} may be used to debug several processes at the same time.
23700 On some platfroms, @value{GDBN} may support debugging of several
23701 hardware systems, each one having several cores with several different
23702 processes running on each core. This section describes the MI
23703 mechanism to support such debugging scenarios.
23705 The key observation is that regardless of the structure of the
23706 target, MI can have a global list of threads, because most commands that
23707 accept the @samp{--thread} option do not need to know what process that
23708 thread belongs to. Therefore, it is not necessary to introduce
23709 neither additional @samp{--process} option, nor an notion of the
23710 current process in the MI interface. The only strictly new feature
23711 that is required is the ability to find how the threads are grouped
23714 To allow the user to discover such grouping, and to support arbitrary
23715 hierarchy of machines/cores/processes, MI introduces the concept of a
23716 @dfn{thread group}. Thread group is a collection of threads and other
23717 thread groups. A thread group always has a string identifier, a type,
23718 and may have additional attributes specific to the type. A new
23719 command, @code{-list-thread-groups}, returns the list of top-level
23720 thread groups, which correspond to processes that @value{GDBN} is
23721 debugging at the moment. By passing an identifier of a thread group
23722 to the @code{-list-thread-groups} command, it is possible to obtain
23723 the members of specific thread group.
23725 To allow the user to easily discover processes, and other objects, he
23726 wishes to debug, a concept of @dfn{available thread group} is
23727 introduced. Available thread group is an thread group that
23728 @value{GDBN} is not debugging, but that can be attached to, using the
23729 @code{-target-attach} command. The list of available top-level thread
23730 groups can be obtained using @samp{-list-thread-groups --available}.
23731 In general, the content of a thread group may be only retrieved only
23732 after attaching to that thread group.
23734 Thread groups are related to inferiors (@pxref{Inferiors and
23735 Programs}). Each inferior corresponds to a thread group of a special
23736 type @samp{process}, and some additional operations are permitted on
23737 such thread groups.
23739 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
23740 @node GDB/MI Command Syntax
23741 @section @sc{gdb/mi} Command Syntax
23744 * GDB/MI Input Syntax::
23745 * GDB/MI Output Syntax::
23748 @node GDB/MI Input Syntax
23749 @subsection @sc{gdb/mi} Input Syntax
23751 @cindex input syntax for @sc{gdb/mi}
23752 @cindex @sc{gdb/mi}, input syntax
23754 @item @var{command} @expansion{}
23755 @code{@var{cli-command} | @var{mi-command}}
23757 @item @var{cli-command} @expansion{}
23758 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
23759 @var{cli-command} is any existing @value{GDBN} CLI command.
23761 @item @var{mi-command} @expansion{}
23762 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
23763 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
23765 @item @var{token} @expansion{}
23766 "any sequence of digits"
23768 @item @var{option} @expansion{}
23769 @code{"-" @var{parameter} [ " " @var{parameter} ]}
23771 @item @var{parameter} @expansion{}
23772 @code{@var{non-blank-sequence} | @var{c-string}}
23774 @item @var{operation} @expansion{}
23775 @emph{any of the operations described in this chapter}
23777 @item @var{non-blank-sequence} @expansion{}
23778 @emph{anything, provided it doesn't contain special characters such as
23779 "-", @var{nl}, """ and of course " "}
23781 @item @var{c-string} @expansion{}
23782 @code{""" @var{seven-bit-iso-c-string-content} """}
23784 @item @var{nl} @expansion{}
23793 The CLI commands are still handled by the @sc{mi} interpreter; their
23794 output is described below.
23797 The @code{@var{token}}, when present, is passed back when the command
23801 Some @sc{mi} commands accept optional arguments as part of the parameter
23802 list. Each option is identified by a leading @samp{-} (dash) and may be
23803 followed by an optional argument parameter. Options occur first in the
23804 parameter list and can be delimited from normal parameters using
23805 @samp{--} (this is useful when some parameters begin with a dash).
23812 We want easy access to the existing CLI syntax (for debugging).
23815 We want it to be easy to spot a @sc{mi} operation.
23818 @node GDB/MI Output Syntax
23819 @subsection @sc{gdb/mi} Output Syntax
23821 @cindex output syntax of @sc{gdb/mi}
23822 @cindex @sc{gdb/mi}, output syntax
23823 The output from @sc{gdb/mi} consists of zero or more out-of-band records
23824 followed, optionally, by a single result record. This result record
23825 is for the most recent command. The sequence of output records is
23826 terminated by @samp{(gdb)}.
23828 If an input command was prefixed with a @code{@var{token}} then the
23829 corresponding output for that command will also be prefixed by that same
23833 @item @var{output} @expansion{}
23834 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(gdb)" @var{nl}}
23836 @item @var{result-record} @expansion{}
23837 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
23839 @item @var{out-of-band-record} @expansion{}
23840 @code{@var{async-record} | @var{stream-record}}
23842 @item @var{async-record} @expansion{}
23843 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
23845 @item @var{exec-async-output} @expansion{}
23846 @code{[ @var{token} ] "*" @var{async-output}}
23848 @item @var{status-async-output} @expansion{}
23849 @code{[ @var{token} ] "+" @var{async-output}}
23851 @item @var{notify-async-output} @expansion{}
23852 @code{[ @var{token} ] "=" @var{async-output}}
23854 @item @var{async-output} @expansion{}
23855 @code{@var{async-class} ( "," @var{result} )* @var{nl}}
23857 @item @var{result-class} @expansion{}
23858 @code{"done" | "running" | "connected" | "error" | "exit"}
23860 @item @var{async-class} @expansion{}
23861 @code{"stopped" | @var{others}} (where @var{others} will be added
23862 depending on the needs---this is still in development).
23864 @item @var{result} @expansion{}
23865 @code{ @var{variable} "=" @var{value}}
23867 @item @var{variable} @expansion{}
23868 @code{ @var{string} }
23870 @item @var{value} @expansion{}
23871 @code{ @var{const} | @var{tuple} | @var{list} }
23873 @item @var{const} @expansion{}
23874 @code{@var{c-string}}
23876 @item @var{tuple} @expansion{}
23877 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
23879 @item @var{list} @expansion{}
23880 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
23881 @var{result} ( "," @var{result} )* "]" }
23883 @item @var{stream-record} @expansion{}
23884 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
23886 @item @var{console-stream-output} @expansion{}
23887 @code{"~" @var{c-string}}
23889 @item @var{target-stream-output} @expansion{}
23890 @code{"@@" @var{c-string}}
23892 @item @var{log-stream-output} @expansion{}
23893 @code{"&" @var{c-string}}
23895 @item @var{nl} @expansion{}
23898 @item @var{token} @expansion{}
23899 @emph{any sequence of digits}.
23907 All output sequences end in a single line containing a period.
23910 The @code{@var{token}} is from the corresponding request. Note that
23911 for all async output, while the token is allowed by the grammar and
23912 may be output by future versions of @value{GDBN} for select async
23913 output messages, it is generally omitted. Frontends should treat
23914 all async output as reporting general changes in the state of the
23915 target and there should be no need to associate async output to any
23919 @cindex status output in @sc{gdb/mi}
23920 @var{status-async-output} contains on-going status information about the
23921 progress of a slow operation. It can be discarded. All status output is
23922 prefixed by @samp{+}.
23925 @cindex async output in @sc{gdb/mi}
23926 @var{exec-async-output} contains asynchronous state change on the target
23927 (stopped, started, disappeared). All async output is prefixed by
23931 @cindex notify output in @sc{gdb/mi}
23932 @var{notify-async-output} contains supplementary information that the
23933 client should handle (e.g., a new breakpoint information). All notify
23934 output is prefixed by @samp{=}.
23937 @cindex console output in @sc{gdb/mi}
23938 @var{console-stream-output} is output that should be displayed as is in the
23939 console. It is the textual response to a CLI command. All the console
23940 output is prefixed by @samp{~}.
23943 @cindex target output in @sc{gdb/mi}
23944 @var{target-stream-output} is the output produced by the target program.
23945 All the target output is prefixed by @samp{@@}.
23948 @cindex log output in @sc{gdb/mi}
23949 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
23950 instance messages that should be displayed as part of an error log. All
23951 the log output is prefixed by @samp{&}.
23954 @cindex list output in @sc{gdb/mi}
23955 New @sc{gdb/mi} commands should only output @var{lists} containing
23961 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
23962 details about the various output records.
23964 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
23965 @node GDB/MI Compatibility with CLI
23966 @section @sc{gdb/mi} Compatibility with CLI
23968 @cindex compatibility, @sc{gdb/mi} and CLI
23969 @cindex @sc{gdb/mi}, compatibility with CLI
23971 For the developers convenience CLI commands can be entered directly,
23972 but there may be some unexpected behaviour. For example, commands
23973 that query the user will behave as if the user replied yes, breakpoint
23974 command lists are not executed and some CLI commands, such as
23975 @code{if}, @code{when} and @code{define}, prompt for further input with
23976 @samp{>}, which is not valid MI output.
23978 This feature may be removed at some stage in the future and it is
23979 recommended that front ends use the @code{-interpreter-exec} command
23980 (@pxref{-interpreter-exec}).
23982 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
23983 @node GDB/MI Development and Front Ends
23984 @section @sc{gdb/mi} Development and Front Ends
23985 @cindex @sc{gdb/mi} development
23987 The application which takes the MI output and presents the state of the
23988 program being debugged to the user is called a @dfn{front end}.
23990 Although @sc{gdb/mi} is still incomplete, it is currently being used
23991 by a variety of front ends to @value{GDBN}. This makes it difficult
23992 to introduce new functionality without breaking existing usage. This
23993 section tries to minimize the problems by describing how the protocol
23996 Some changes in MI need not break a carefully designed front end, and
23997 for these the MI version will remain unchanged. The following is a
23998 list of changes that may occur within one level, so front ends should
23999 parse MI output in a way that can handle them:
24003 New MI commands may be added.
24006 New fields may be added to the output of any MI command.
24009 The range of values for fields with specified values, e.g.,
24010 @code{in_scope} (@pxref{-var-update}) may be extended.
24012 @c The format of field's content e.g type prefix, may change so parse it
24013 @c at your own risk. Yes, in general?
24015 @c The order of fields may change? Shouldn't really matter but it might
24016 @c resolve inconsistencies.
24019 If the changes are likely to break front ends, the MI version level
24020 will be increased by one. This will allow the front end to parse the
24021 output according to the MI version. Apart from mi0, new versions of
24022 @value{GDBN} will not support old versions of MI and it will be the
24023 responsibility of the front end to work with the new one.
24025 @c Starting with mi3, add a new command -mi-version that prints the MI
24028 The best way to avoid unexpected changes in MI that might break your front
24029 end is to make your project known to @value{GDBN} developers and
24030 follow development on @email{gdb@@sourceware.org} and
24031 @email{gdb-patches@@sourceware.org}.
24032 @cindex mailing lists
24034 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
24035 @node GDB/MI Output Records
24036 @section @sc{gdb/mi} Output Records
24039 * GDB/MI Result Records::
24040 * GDB/MI Stream Records::
24041 * GDB/MI Async Records::
24042 * GDB/MI Frame Information::
24043 * GDB/MI Thread Information::
24046 @node GDB/MI Result Records
24047 @subsection @sc{gdb/mi} Result Records
24049 @cindex result records in @sc{gdb/mi}
24050 @cindex @sc{gdb/mi}, result records
24051 In addition to a number of out-of-band notifications, the response to a
24052 @sc{gdb/mi} command includes one of the following result indications:
24056 @item "^done" [ "," @var{results} ]
24057 The synchronous operation was successful, @code{@var{results}} are the return
24062 This result record is equivalent to @samp{^done}. Historically, it
24063 was output instead of @samp{^done} if the command has resumed the
24064 target. This behaviour is maintained for backward compatibility, but
24065 all frontends should treat @samp{^done} and @samp{^running}
24066 identically and rely on the @samp{*running} output record to determine
24067 which threads are resumed.
24071 @value{GDBN} has connected to a remote target.
24073 @item "^error" "," @var{c-string}
24075 The operation failed. The @code{@var{c-string}} contains the corresponding
24080 @value{GDBN} has terminated.
24084 @node GDB/MI Stream Records
24085 @subsection @sc{gdb/mi} Stream Records
24087 @cindex @sc{gdb/mi}, stream records
24088 @cindex stream records in @sc{gdb/mi}
24089 @value{GDBN} internally maintains a number of output streams: the console, the
24090 target, and the log. The output intended for each of these streams is
24091 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
24093 Each stream record begins with a unique @dfn{prefix character} which
24094 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
24095 Syntax}). In addition to the prefix, each stream record contains a
24096 @code{@var{string-output}}. This is either raw text (with an implicit new
24097 line) or a quoted C string (which does not contain an implicit newline).
24100 @item "~" @var{string-output}
24101 The console output stream contains text that should be displayed in the
24102 CLI console window. It contains the textual responses to CLI commands.
24104 @item "@@" @var{string-output}
24105 The target output stream contains any textual output from the running
24106 target. This is only present when GDB's event loop is truly
24107 asynchronous, which is currently only the case for remote targets.
24109 @item "&" @var{string-output}
24110 The log stream contains debugging messages being produced by @value{GDBN}'s
24114 @node GDB/MI Async Records
24115 @subsection @sc{gdb/mi} Async Records
24117 @cindex async records in @sc{gdb/mi}
24118 @cindex @sc{gdb/mi}, async records
24119 @dfn{Async} records are used to notify the @sc{gdb/mi} client of
24120 additional changes that have occurred. Those changes can either be a
24121 consequence of @sc{gdb/mi} commands (e.g., a breakpoint modified) or a result of
24122 target activity (e.g., target stopped).
24124 The following is the list of possible async records:
24128 @item *running,thread-id="@var{thread}"
24129 The target is now running. The @var{thread} field tells which
24130 specific thread is now running, and can be @samp{all} if all threads
24131 are running. The frontend should assume that no interaction with a
24132 running thread is possible after this notification is produced.
24133 The frontend should not assume that this notification is output
24134 only once for any command. @value{GDBN} may emit this notification
24135 several times, either for different threads, because it cannot resume
24136 all threads together, or even for a single thread, if the thread must
24137 be stepped though some code before letting it run freely.
24139 @item *stopped,reason="@var{reason}",thread-id="@var{id}",stopped-threads="@var{stopped}",core="@var{core}"
24140 The target has stopped. The @var{reason} field can have one of the
24144 @item breakpoint-hit
24145 A breakpoint was reached.
24146 @item watchpoint-trigger
24147 A watchpoint was triggered.
24148 @item read-watchpoint-trigger
24149 A read watchpoint was triggered.
24150 @item access-watchpoint-trigger
24151 An access watchpoint was triggered.
24152 @item function-finished
24153 An -exec-finish or similar CLI command was accomplished.
24154 @item location-reached
24155 An -exec-until or similar CLI command was accomplished.
24156 @item watchpoint-scope
24157 A watchpoint has gone out of scope.
24158 @item end-stepping-range
24159 An -exec-next, -exec-next-instruction, -exec-step, -exec-step-instruction or
24160 similar CLI command was accomplished.
24161 @item exited-signalled
24162 The inferior exited because of a signal.
24164 The inferior exited.
24165 @item exited-normally
24166 The inferior exited normally.
24167 @item signal-received
24168 A signal was received by the inferior.
24171 The @var{id} field identifies the thread that directly caused the stop
24172 -- for example by hitting a breakpoint. Depending on whether all-stop
24173 mode is in effect (@pxref{All-Stop Mode}), @value{GDBN} may either
24174 stop all threads, or only the thread that directly triggered the stop.
24175 If all threads are stopped, the @var{stopped} field will have the
24176 value of @code{"all"}. Otherwise, the value of the @var{stopped}
24177 field will be a list of thread identifiers. Presently, this list will
24178 always include a single thread, but frontend should be prepared to see
24179 several threads in the list. The @var{core} field reports the
24180 processor core on which the stop event has happened. This field may be absent
24181 if such information is not available.
24183 @item =thread-group-added,id="@var{id}"
24184 @itemx =thread-group-removed,id="@var{id}"
24185 A thread group was either added or removed. The @var{id} field
24186 contains the @value{GDBN} identifier of the thread group. When a thread
24187 group is added, it generally might not be associated with a running
24188 process. When a thread group is removed, its id becomes invalid and
24189 cannot be used in any way.
24191 @item =thread-group-started,id="@var{id}",pid="@var{pid}"
24192 A thread group became associated with a running program,
24193 either because the program was just started or the thread group
24194 was attached to a program. The @var{id} field contains the
24195 @value{GDBN} identifier of the thread group. The @var{pid} field
24196 contains process identifier, specific to the operating system.
24198 @itemx =thread-group-exited,id="@var{id}"
24199 A thread group is no longer associated with a running program,
24200 either because the program has exited, or because it was detached
24201 from. The @var{id} field contains the @value{GDBN} identifier of the
24204 @item =thread-created,id="@var{id}",group-id="@var{gid}"
24205 @itemx =thread-exited,id="@var{id}",group-id="@var{gid}"
24206 A thread either was created, or has exited. The @var{id} field
24207 contains the @value{GDBN} identifier of the thread. The @var{gid}
24208 field identifies the thread group this thread belongs to.
24210 @item =thread-selected,id="@var{id}"
24211 Informs that the selected thread was changed as result of the last
24212 command. This notification is not emitted as result of @code{-thread-select}
24213 command but is emitted whenever an MI command that is not documented
24214 to change the selected thread actually changes it. In particular,
24215 invoking, directly or indirectly (via user-defined command), the CLI
24216 @code{thread} command, will generate this notification.
24218 We suggest that in response to this notification, front ends
24219 highlight the selected thread and cause subsequent commands to apply to
24222 @item =library-loaded,...
24223 Reports that a new library file was loaded by the program. This
24224 notification has 4 fields---@var{id}, @var{target-name},
24225 @var{host-name}, and @var{symbols-loaded}. The @var{id} field is an
24226 opaque identifier of the library. For remote debugging case,
24227 @var{target-name} and @var{host-name} fields give the name of the
24228 library file on the target, and on the host respectively. For native
24229 debugging, both those fields have the same value. The
24230 @var{symbols-loaded} field reports if the debug symbols for this
24231 library are loaded. The @var{thread-group} field, if present,
24232 specifies the id of the thread group in whose context the library was loaded.
24233 If the field is absent, it means the library was loaded in the context
24234 of all present thread groups.
24236 @item =library-unloaded,...
24237 Reports that a library was unloaded by the program. This notification
24238 has 3 fields---@var{id}, @var{target-name} and @var{host-name} with
24239 the same meaning as for the @code{=library-loaded} notification.
24240 The @var{thread-group} field, if present, specifies the id of the
24241 thread group in whose context the library was unloaded. If the field is
24242 absent, it means the library was unloaded in the context of all present
24247 @node GDB/MI Frame Information
24248 @subsection @sc{gdb/mi} Frame Information
24250 Response from many MI commands includes an information about stack
24251 frame. This information is a tuple that may have the following
24256 The level of the stack frame. The innermost frame has the level of
24257 zero. This field is always present.
24260 The name of the function corresponding to the frame. This field may
24261 be absent if @value{GDBN} is unable to determine the function name.
24264 The code address for the frame. This field is always present.
24267 The name of the source files that correspond to the frame's code
24268 address. This field may be absent.
24271 The source line corresponding to the frames' code address. This field
24275 The name of the binary file (either executable or shared library) the
24276 corresponds to the frame's code address. This field may be absent.
24280 @node GDB/MI Thread Information
24281 @subsection @sc{gdb/mi} Thread Information
24283 Whenever @value{GDBN} has to report an information about a thread, it
24284 uses a tuple with the following fields:
24288 The numeric id assigned to the thread by @value{GDBN}. This field is
24292 Target-specific string identifying the thread. This field is always present.
24295 Additional information about the thread provided by the target.
24296 It is supposed to be human-readable and not interpreted by the
24297 frontend. This field is optional.
24300 Either @samp{stopped} or @samp{running}, depending on whether the
24301 thread is presently running. This field is always present.
24304 The value of this field is an integer number of the processor core the
24305 thread was last seen on. This field is optional.
24309 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
24310 @node GDB/MI Simple Examples
24311 @section Simple Examples of @sc{gdb/mi} Interaction
24312 @cindex @sc{gdb/mi}, simple examples
24314 This subsection presents several simple examples of interaction using
24315 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
24316 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
24317 the output received from @sc{gdb/mi}.
24319 Note the line breaks shown in the examples are here only for
24320 readability, they don't appear in the real output.
24322 @subheading Setting a Breakpoint
24324 Setting a breakpoint generates synchronous output which contains detailed
24325 information of the breakpoint.
24328 -> -break-insert main
24329 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
24330 enabled="y",addr="0x08048564",func="main",file="myprog.c",
24331 fullname="/home/nickrob/myprog.c",line="68",times="0"@}
24335 @subheading Program Execution
24337 Program execution generates asynchronous records and MI gives the
24338 reason that execution stopped.
24344 <- *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
24345 frame=@{addr="0x08048564",func="main",
24346 args=[@{name="argc",value="1"@},@{name="argv",value="0xbfc4d4d4"@}],
24347 file="myprog.c",fullname="/home/nickrob/myprog.c",line="68"@}
24352 <- *stopped,reason="exited-normally"
24356 @subheading Quitting @value{GDBN}
24358 Quitting @value{GDBN} just prints the result class @samp{^exit}.
24366 Please note that @samp{^exit} is printed immediately, but it might
24367 take some time for @value{GDBN} to actually exit. During that time, @value{GDBN}
24368 performs necessary cleanups, including killing programs being debugged
24369 or disconnecting from debug hardware, so the frontend should wait till
24370 @value{GDBN} exits and should only forcibly kill @value{GDBN} if it
24371 fails to exit in reasonable time.
24373 @subheading A Bad Command
24375 Here's what happens if you pass a non-existent command:
24379 <- ^error,msg="Undefined MI command: rubbish"
24384 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
24385 @node GDB/MI Command Description Format
24386 @section @sc{gdb/mi} Command Description Format
24388 The remaining sections describe blocks of commands. Each block of
24389 commands is laid out in a fashion similar to this section.
24391 @subheading Motivation
24393 The motivation for this collection of commands.
24395 @subheading Introduction
24397 A brief introduction to this collection of commands as a whole.
24399 @subheading Commands
24401 For each command in the block, the following is described:
24403 @subsubheading Synopsis
24406 -command @var{args}@dots{}
24409 @subsubheading Result
24411 @subsubheading @value{GDBN} Command
24413 The corresponding @value{GDBN} CLI command(s), if any.
24415 @subsubheading Example
24417 Example(s) formatted for readability. Some of the described commands have
24418 not been implemented yet and these are labeled N.A.@: (not available).
24421 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
24422 @node GDB/MI Breakpoint Commands
24423 @section @sc{gdb/mi} Breakpoint Commands
24425 @cindex breakpoint commands for @sc{gdb/mi}
24426 @cindex @sc{gdb/mi}, breakpoint commands
24427 This section documents @sc{gdb/mi} commands for manipulating
24430 @subheading The @code{-break-after} Command
24431 @findex -break-after
24433 @subsubheading Synopsis
24436 -break-after @var{number} @var{count}
24439 The breakpoint number @var{number} is not in effect until it has been
24440 hit @var{count} times. To see how this is reflected in the output of
24441 the @samp{-break-list} command, see the description of the
24442 @samp{-break-list} command below.
24444 @subsubheading @value{GDBN} Command
24446 The corresponding @value{GDBN} command is @samp{ignore}.
24448 @subsubheading Example
24453 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
24454 enabled="y",addr="0x000100d0",func="main",file="hello.c",
24455 fullname="/home/foo/hello.c",line="5",times="0"@}
24462 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
24463 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
24464 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
24465 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
24466 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
24467 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
24468 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
24469 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
24470 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
24471 line="5",times="0",ignore="3"@}]@}
24476 @subheading The @code{-break-catch} Command
24477 @findex -break-catch
24480 @subheading The @code{-break-commands} Command
24481 @findex -break-commands
24483 @subsubheading Synopsis
24486 -break-commands @var{number} [ @var{command1} ... @var{commandN} ]
24489 Specifies the CLI commands that should be executed when breakpoint
24490 @var{number} is hit. The parameters @var{command1} to @var{commandN}
24491 are the commands. If no command is specified, any previously-set
24492 commands are cleared. @xref{Break Commands}. Typical use of this
24493 functionality is tracing a program, that is, printing of values of
24494 some variables whenever breakpoint is hit and then continuing.
24496 @subsubheading @value{GDBN} Command
24498 The corresponding @value{GDBN} command is @samp{commands}.
24500 @subsubheading Example
24505 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
24506 enabled="y",addr="0x000100d0",func="main",file="hello.c",
24507 fullname="/home/foo/hello.c",line="5",times="0"@}
24509 -break-commands 1 "print v" "continue"
24514 @subheading The @code{-break-condition} Command
24515 @findex -break-condition
24517 @subsubheading Synopsis
24520 -break-condition @var{number} @var{expr}
24523 Breakpoint @var{number} will stop the program only if the condition in
24524 @var{expr} is true. The condition becomes part of the
24525 @samp{-break-list} output (see the description of the @samp{-break-list}
24528 @subsubheading @value{GDBN} Command
24530 The corresponding @value{GDBN} command is @samp{condition}.
24532 @subsubheading Example
24536 -break-condition 1 1
24540 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
24541 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
24542 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
24543 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
24544 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
24545 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
24546 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
24547 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
24548 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
24549 line="5",cond="1",times="0",ignore="3"@}]@}
24553 @subheading The @code{-break-delete} Command
24554 @findex -break-delete
24556 @subsubheading Synopsis
24559 -break-delete ( @var{breakpoint} )+
24562 Delete the breakpoint(s) whose number(s) are specified in the argument
24563 list. This is obviously reflected in the breakpoint list.
24565 @subsubheading @value{GDBN} Command
24567 The corresponding @value{GDBN} command is @samp{delete}.
24569 @subsubheading Example
24577 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
24578 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
24579 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
24580 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
24581 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
24582 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
24583 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
24588 @subheading The @code{-break-disable} Command
24589 @findex -break-disable
24591 @subsubheading Synopsis
24594 -break-disable ( @var{breakpoint} )+
24597 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
24598 break list is now set to @samp{n} for the named @var{breakpoint}(s).
24600 @subsubheading @value{GDBN} Command
24602 The corresponding @value{GDBN} command is @samp{disable}.
24604 @subsubheading Example
24612 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
24613 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
24614 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
24615 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
24616 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
24617 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
24618 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
24619 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
24620 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
24621 line="5",times="0"@}]@}
24625 @subheading The @code{-break-enable} Command
24626 @findex -break-enable
24628 @subsubheading Synopsis
24631 -break-enable ( @var{breakpoint} )+
24634 Enable (previously disabled) @var{breakpoint}(s).
24636 @subsubheading @value{GDBN} Command
24638 The corresponding @value{GDBN} command is @samp{enable}.
24640 @subsubheading Example
24648 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
24649 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
24650 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
24651 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
24652 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
24653 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
24654 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
24655 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
24656 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
24657 line="5",times="0"@}]@}
24661 @subheading The @code{-break-info} Command
24662 @findex -break-info
24664 @subsubheading Synopsis
24667 -break-info @var{breakpoint}
24671 Get information about a single breakpoint.
24673 @subsubheading @value{GDBN} Command
24675 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
24677 @subsubheading Example
24680 @subheading The @code{-break-insert} Command
24681 @findex -break-insert
24683 @subsubheading Synopsis
24686 -break-insert [ -t ] [ -h ] [ -f ] [ -d ] [ -a ]
24687 [ -c @var{condition} ] [ -i @var{ignore-count} ]
24688 [ -p @var{thread} ] [ @var{location} ]
24692 If specified, @var{location}, can be one of:
24699 @item filename:linenum
24700 @item filename:function
24704 The possible optional parameters of this command are:
24708 Insert a temporary breakpoint.
24710 Insert a hardware breakpoint.
24711 @item -c @var{condition}
24712 Make the breakpoint conditional on @var{condition}.
24713 @item -i @var{ignore-count}
24714 Initialize the @var{ignore-count}.
24716 If @var{location} cannot be parsed (for example if it
24717 refers to unknown files or functions), create a pending
24718 breakpoint. Without this flag, @value{GDBN} will report
24719 an error, and won't create a breakpoint, if @var{location}
24722 Create a disabled breakpoint.
24724 Create a tracepoint. @xref{Tracepoints}. When this parameter
24725 is used together with @samp{-h}, a fast tracepoint is created.
24728 @subsubheading Result
24730 The result is in the form:
24733 ^done,bkpt=@{number="@var{number}",type="@var{type}",disp="del"|"keep",
24734 enabled="y"|"n",addr="@var{hex}",func="@var{funcname}",file="@var{filename}",
24735 fullname="@var{full_filename}",line="@var{lineno}",[thread="@var{threadno},]
24736 times="@var{times}"@}
24740 where @var{number} is the @value{GDBN} number for this breakpoint,
24741 @var{funcname} is the name of the function where the breakpoint was
24742 inserted, @var{filename} is the name of the source file which contains
24743 this function, @var{lineno} is the source line number within that file
24744 and @var{times} the number of times that the breakpoint has been hit
24745 (always 0 for -break-insert but may be greater for -break-info or -break-list
24746 which use the same output).
24748 Note: this format is open to change.
24749 @c An out-of-band breakpoint instead of part of the result?
24751 @subsubheading @value{GDBN} Command
24753 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
24754 @samp{hbreak}, @samp{thbreak}, and @samp{rbreak}.
24756 @subsubheading Example
24761 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",
24762 fullname="/home/foo/recursive2.c,line="4",times="0"@}
24764 -break-insert -t foo
24765 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",
24766 fullname="/home/foo/recursive2.c,line="11",times="0"@}
24769 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
24770 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
24771 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
24772 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
24773 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
24774 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
24775 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
24776 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
24777 addr="0x0001072c", func="main",file="recursive2.c",
24778 fullname="/home/foo/recursive2.c,"line="4",times="0"@},
24779 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
24780 addr="0x00010774",func="foo",file="recursive2.c",
24781 fullname="/home/foo/recursive2.c",line="11",times="0"@}]@}
24783 -break-insert -r foo.*
24784 ~int foo(int, int);
24785 ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c,
24786 "fullname="/home/foo/recursive2.c",line="11",times="0"@}
24790 @subheading The @code{-break-list} Command
24791 @findex -break-list
24793 @subsubheading Synopsis
24799 Displays the list of inserted breakpoints, showing the following fields:
24803 number of the breakpoint
24805 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
24807 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
24810 is the breakpoint enabled or no: @samp{y} or @samp{n}
24812 memory location at which the breakpoint is set
24814 logical location of the breakpoint, expressed by function name, file
24817 number of times the breakpoint has been hit
24820 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
24821 @code{body} field is an empty list.
24823 @subsubheading @value{GDBN} Command
24825 The corresponding @value{GDBN} command is @samp{info break}.
24827 @subsubheading Example
24832 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
24833 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
24834 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
24835 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
24836 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
24837 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
24838 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
24839 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
24840 addr="0x000100d0",func="main",file="hello.c",line="5",times="0"@},
24841 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
24842 addr="0x00010114",func="foo",file="hello.c",fullname="/home/foo/hello.c",
24843 line="13",times="0"@}]@}
24847 Here's an example of the result when there are no breakpoints:
24852 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
24853 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
24854 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
24855 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
24856 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
24857 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
24858 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
24863 @subheading The @code{-break-passcount} Command
24864 @findex -break-passcount
24866 @subsubheading Synopsis
24869 -break-passcount @var{tracepoint-number} @var{passcount}
24872 Set the passcount for tracepoint @var{tracepoint-number} to
24873 @var{passcount}. If the breakpoint referred to by @var{tracepoint-number}
24874 is not a tracepoint, error is emitted. This corresponds to CLI
24875 command @samp{passcount}.
24877 @subheading The @code{-break-watch} Command
24878 @findex -break-watch
24880 @subsubheading Synopsis
24883 -break-watch [ -a | -r ]
24886 Create a watchpoint. With the @samp{-a} option it will create an
24887 @dfn{access} watchpoint, i.e., a watchpoint that triggers either on a
24888 read from or on a write to the memory location. With the @samp{-r}
24889 option, the watchpoint created is a @dfn{read} watchpoint, i.e., it will
24890 trigger only when the memory location is accessed for reading. Without
24891 either of the options, the watchpoint created is a regular watchpoint,
24892 i.e., it will trigger when the memory location is accessed for writing.
24893 @xref{Set Watchpoints, , Setting Watchpoints}.
24895 Note that @samp{-break-list} will report a single list of watchpoints and
24896 breakpoints inserted.
24898 @subsubheading @value{GDBN} Command
24900 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
24903 @subsubheading Example
24905 Setting a watchpoint on a variable in the @code{main} function:
24910 ^done,wpt=@{number="2",exp="x"@}
24915 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
24916 value=@{old="-268439212",new="55"@},
24917 frame=@{func="main",args=[],file="recursive2.c",
24918 fullname="/home/foo/bar/recursive2.c",line="5"@}
24922 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
24923 the program execution twice: first for the variable changing value, then
24924 for the watchpoint going out of scope.
24929 ^done,wpt=@{number="5",exp="C"@}
24934 *stopped,reason="watchpoint-trigger",
24935 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
24936 frame=@{func="callee4",args=[],
24937 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
24938 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
24943 *stopped,reason="watchpoint-scope",wpnum="5",
24944 frame=@{func="callee3",args=[@{name="strarg",
24945 value="0x11940 \"A string argument.\""@}],
24946 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
24947 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
24951 Listing breakpoints and watchpoints, at different points in the program
24952 execution. Note that once the watchpoint goes out of scope, it is
24958 ^done,wpt=@{number="2",exp="C"@}
24961 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
24962 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
24963 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
24964 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
24965 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
24966 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
24967 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
24968 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
24969 addr="0x00010734",func="callee4",
24970 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
24971 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c"line="8",times="1"@},
24972 bkpt=@{number="2",type="watchpoint",disp="keep",
24973 enabled="y",addr="",what="C",times="0"@}]@}
24978 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
24979 value=@{old="-276895068",new="3"@},
24980 frame=@{func="callee4",args=[],
24981 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
24982 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
24985 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
24986 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
24987 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
24988 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
24989 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
24990 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
24991 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
24992 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
24993 addr="0x00010734",func="callee4",
24994 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
24995 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",times="1"@},
24996 bkpt=@{number="2",type="watchpoint",disp="keep",
24997 enabled="y",addr="",what="C",times="-5"@}]@}
25001 ^done,reason="watchpoint-scope",wpnum="2",
25002 frame=@{func="callee3",args=[@{name="strarg",
25003 value="0x11940 \"A string argument.\""@}],
25004 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
25005 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
25008 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
25009 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
25010 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
25011 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
25012 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
25013 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
25014 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
25015 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
25016 addr="0x00010734",func="callee4",
25017 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
25018 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
25023 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25024 @node GDB/MI Program Context
25025 @section @sc{gdb/mi} Program Context
25027 @subheading The @code{-exec-arguments} Command
25028 @findex -exec-arguments
25031 @subsubheading Synopsis
25034 -exec-arguments @var{args}
25037 Set the inferior program arguments, to be used in the next
25040 @subsubheading @value{GDBN} Command
25042 The corresponding @value{GDBN} command is @samp{set args}.
25044 @subsubheading Example
25048 -exec-arguments -v word
25055 @subheading The @code{-exec-show-arguments} Command
25056 @findex -exec-show-arguments
25058 @subsubheading Synopsis
25061 -exec-show-arguments
25064 Print the arguments of the program.
25066 @subsubheading @value{GDBN} Command
25068 The corresponding @value{GDBN} command is @samp{show args}.
25070 @subsubheading Example
25075 @subheading The @code{-environment-cd} Command
25076 @findex -environment-cd
25078 @subsubheading Synopsis
25081 -environment-cd @var{pathdir}
25084 Set @value{GDBN}'s working directory.
25086 @subsubheading @value{GDBN} Command
25088 The corresponding @value{GDBN} command is @samp{cd}.
25090 @subsubheading Example
25094 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
25100 @subheading The @code{-environment-directory} Command
25101 @findex -environment-directory
25103 @subsubheading Synopsis
25106 -environment-directory [ -r ] [ @var{pathdir} ]+
25109 Add directories @var{pathdir} to beginning of search path for source files.
25110 If the @samp{-r} option is used, the search path is reset to the default
25111 search path. If directories @var{pathdir} are supplied in addition to the
25112 @samp{-r} option, the search path is first reset and then addition
25114 Multiple directories may be specified, separated by blanks. Specifying
25115 multiple directories in a single command
25116 results in the directories added to the beginning of the
25117 search path in the same order they were presented in the command.
25118 If blanks are needed as
25119 part of a directory name, double-quotes should be used around
25120 the name. In the command output, the path will show up separated
25121 by the system directory-separator character. The directory-separator
25122 character must not be used
25123 in any directory name.
25124 If no directories are specified, the current search path is displayed.
25126 @subsubheading @value{GDBN} Command
25128 The corresponding @value{GDBN} command is @samp{dir}.
25130 @subsubheading Example
25134 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
25135 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
25137 -environment-directory ""
25138 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
25140 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
25141 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
25143 -environment-directory -r
25144 ^done,source-path="$cdir:$cwd"
25149 @subheading The @code{-environment-path} Command
25150 @findex -environment-path
25152 @subsubheading Synopsis
25155 -environment-path [ -r ] [ @var{pathdir} ]+
25158 Add directories @var{pathdir} to beginning of search path for object files.
25159 If the @samp{-r} option is used, the search path is reset to the original
25160 search path that existed at gdb start-up. If directories @var{pathdir} are
25161 supplied in addition to the
25162 @samp{-r} option, the search path is first reset and then addition
25164 Multiple directories may be specified, separated by blanks. Specifying
25165 multiple directories in a single command
25166 results in the directories added to the beginning of the
25167 search path in the same order they were presented in the command.
25168 If blanks are needed as
25169 part of a directory name, double-quotes should be used around
25170 the name. In the command output, the path will show up separated
25171 by the system directory-separator character. The directory-separator
25172 character must not be used
25173 in any directory name.
25174 If no directories are specified, the current path is displayed.
25177 @subsubheading @value{GDBN} Command
25179 The corresponding @value{GDBN} command is @samp{path}.
25181 @subsubheading Example
25186 ^done,path="/usr/bin"
25188 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
25189 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
25191 -environment-path -r /usr/local/bin
25192 ^done,path="/usr/local/bin:/usr/bin"
25197 @subheading The @code{-environment-pwd} Command
25198 @findex -environment-pwd
25200 @subsubheading Synopsis
25206 Show the current working directory.
25208 @subsubheading @value{GDBN} Command
25210 The corresponding @value{GDBN} command is @samp{pwd}.
25212 @subsubheading Example
25217 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
25221 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25222 @node GDB/MI Thread Commands
25223 @section @sc{gdb/mi} Thread Commands
25226 @subheading The @code{-thread-info} Command
25227 @findex -thread-info
25229 @subsubheading Synopsis
25232 -thread-info [ @var{thread-id} ]
25235 Reports information about either a specific thread, if
25236 the @var{thread-id} parameter is present, or about all
25237 threads. When printing information about all threads,
25238 also reports the current thread.
25240 @subsubheading @value{GDBN} Command
25242 The @samp{info thread} command prints the same information
25245 @subsubheading Example
25250 @{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
25251 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},state="running"@},
25252 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
25253 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
25254 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},state="running"@}],
25255 current-thread-id="1"
25259 The @samp{state} field may have the following values:
25263 The thread is stopped. Frame information is available for stopped
25267 The thread is running. There's no frame information for running
25272 @subheading The @code{-thread-list-ids} Command
25273 @findex -thread-list-ids
25275 @subsubheading Synopsis
25281 Produces a list of the currently known @value{GDBN} thread ids. At the
25282 end of the list it also prints the total number of such threads.
25284 This command is retained for historical reasons, the
25285 @code{-thread-info} command should be used instead.
25287 @subsubheading @value{GDBN} Command
25289 Part of @samp{info threads} supplies the same information.
25291 @subsubheading Example
25296 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
25297 current-thread-id="1",number-of-threads="3"
25302 @subheading The @code{-thread-select} Command
25303 @findex -thread-select
25305 @subsubheading Synopsis
25308 -thread-select @var{threadnum}
25311 Make @var{threadnum} the current thread. It prints the number of the new
25312 current thread, and the topmost frame for that thread.
25314 This command is deprecated in favor of explicitly using the
25315 @samp{--thread} option to each command.
25317 @subsubheading @value{GDBN} Command
25319 The corresponding @value{GDBN} command is @samp{thread}.
25321 @subsubheading Example
25328 *stopped,reason="end-stepping-range",thread-id="2",line="187",
25329 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
25333 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
25334 number-of-threads="3"
25337 ^done,new-thread-id="3",
25338 frame=@{level="0",func="vprintf",
25339 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
25340 @{name="arg",value="0x2"@}],file="vprintf.c",line="31"@}
25344 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25345 @node GDB/MI Program Execution
25346 @section @sc{gdb/mi} Program Execution
25348 These are the asynchronous commands which generate the out-of-band
25349 record @samp{*stopped}. Currently @value{GDBN} only really executes
25350 asynchronously with remote targets and this interaction is mimicked in
25353 @subheading The @code{-exec-continue} Command
25354 @findex -exec-continue
25356 @subsubheading Synopsis
25359 -exec-continue [--reverse] [--all|--thread-group N]
25362 Resumes the execution of the inferior program, which will continue
25363 to execute until it reaches a debugger stop event. If the
25364 @samp{--reverse} option is specified, execution resumes in reverse until
25365 it reaches a stop event. Stop events may include
25368 breakpoints or watchpoints
25370 signals or exceptions
25372 the end of the process (or its beginning under @samp{--reverse})
25374 the end or beginning of a replay log if one is being used.
25376 In all-stop mode (@pxref{All-Stop
25377 Mode}), may resume only one thread, or all threads, depending on the
25378 value of the @samp{scheduler-locking} variable. If @samp{--all} is
25379 specified, all threads (in all inferiors) will be resumed. The @samp{--all} option is
25380 ignored in all-stop mode. If the @samp{--thread-group} options is
25381 specified, then all threads in that thread group are resumed.
25383 @subsubheading @value{GDBN} Command
25385 The corresponding @value{GDBN} corresponding is @samp{continue}.
25387 @subsubheading Example
25394 *stopped,reason="breakpoint-hit",disp="keep",bkptno="2",frame=@{
25395 func="foo",args=[],file="hello.c",fullname="/home/foo/bar/hello.c",
25401 @subheading The @code{-exec-finish} Command
25402 @findex -exec-finish
25404 @subsubheading Synopsis
25407 -exec-finish [--reverse]
25410 Resumes the execution of the inferior program until the current
25411 function is exited. Displays the results returned by the function.
25412 If the @samp{--reverse} option is specified, resumes the reverse
25413 execution of the inferior program until the point where current
25414 function was called.
25416 @subsubheading @value{GDBN} Command
25418 The corresponding @value{GDBN} command is @samp{finish}.
25420 @subsubheading Example
25422 Function returning @code{void}.
25429 *stopped,reason="function-finished",frame=@{func="main",args=[],
25430 file="hello.c",fullname="/home/foo/bar/hello.c",line="7"@}
25434 Function returning other than @code{void}. The name of the internal
25435 @value{GDBN} variable storing the result is printed, together with the
25442 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
25443 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
25444 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
25445 gdb-result-var="$1",return-value="0"
25450 @subheading The @code{-exec-interrupt} Command
25451 @findex -exec-interrupt
25453 @subsubheading Synopsis
25456 -exec-interrupt [--all|--thread-group N]
25459 Interrupts the background execution of the target. Note how the token
25460 associated with the stop message is the one for the execution command
25461 that has been interrupted. The token for the interrupt itself only
25462 appears in the @samp{^done} output. If the user is trying to
25463 interrupt a non-running program, an error message will be printed.
25465 Note that when asynchronous execution is enabled, this command is
25466 asynchronous just like other execution commands. That is, first the
25467 @samp{^done} response will be printed, and the target stop will be
25468 reported after that using the @samp{*stopped} notification.
25470 In non-stop mode, only the context thread is interrupted by default.
25471 All threads (in all inferiors) will be interrupted if the
25472 @samp{--all} option is specified. If the @samp{--thread-group}
25473 option is specified, all threads in that group will be interrupted.
25475 @subsubheading @value{GDBN} Command
25477 The corresponding @value{GDBN} command is @samp{interrupt}.
25479 @subsubheading Example
25490 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
25491 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",
25492 fullname="/home/foo/bar/try.c",line="13"@}
25497 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
25501 @subheading The @code{-exec-jump} Command
25504 @subsubheading Synopsis
25507 -exec-jump @var{location}
25510 Resumes execution of the inferior program at the location specified by
25511 parameter. @xref{Specify Location}, for a description of the
25512 different forms of @var{location}.
25514 @subsubheading @value{GDBN} Command
25516 The corresponding @value{GDBN} command is @samp{jump}.
25518 @subsubheading Example
25521 -exec-jump foo.c:10
25522 *running,thread-id="all"
25527 @subheading The @code{-exec-next} Command
25530 @subsubheading Synopsis
25533 -exec-next [--reverse]
25536 Resumes execution of the inferior program, stopping when the beginning
25537 of the next source line is reached.
25539 If the @samp{--reverse} option is specified, resumes reverse execution
25540 of the inferior program, stopping at the beginning of the previous
25541 source line. If you issue this command on the first line of a
25542 function, it will take you back to the caller of that function, to the
25543 source line where the function was called.
25546 @subsubheading @value{GDBN} Command
25548 The corresponding @value{GDBN} command is @samp{next}.
25550 @subsubheading Example
25556 *stopped,reason="end-stepping-range",line="8",file="hello.c"
25561 @subheading The @code{-exec-next-instruction} Command
25562 @findex -exec-next-instruction
25564 @subsubheading Synopsis
25567 -exec-next-instruction [--reverse]
25570 Executes one machine instruction. If the instruction is a function
25571 call, continues until the function returns. If the program stops at an
25572 instruction in the middle of a source line, the address will be
25575 If the @samp{--reverse} option is specified, resumes reverse execution
25576 of the inferior program, stopping at the previous instruction. If the
25577 previously executed instruction was a return from another function,
25578 it will continue to execute in reverse until the call to that function
25579 (from the current stack frame) is reached.
25581 @subsubheading @value{GDBN} Command
25583 The corresponding @value{GDBN} command is @samp{nexti}.
25585 @subsubheading Example
25589 -exec-next-instruction
25593 *stopped,reason="end-stepping-range",
25594 addr="0x000100d4",line="5",file="hello.c"
25599 @subheading The @code{-exec-return} Command
25600 @findex -exec-return
25602 @subsubheading Synopsis
25608 Makes current function return immediately. Doesn't execute the inferior.
25609 Displays the new current frame.
25611 @subsubheading @value{GDBN} Command
25613 The corresponding @value{GDBN} command is @samp{return}.
25615 @subsubheading Example
25619 200-break-insert callee4
25620 200^done,bkpt=@{number="1",addr="0x00010734",
25621 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
25626 000*stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
25627 frame=@{func="callee4",args=[],
25628 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
25629 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
25635 111^done,frame=@{level="0",func="callee3",
25636 args=[@{name="strarg",
25637 value="0x11940 \"A string argument.\""@}],
25638 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
25639 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
25644 @subheading The @code{-exec-run} Command
25647 @subsubheading Synopsis
25650 -exec-run [--all | --thread-group N]
25653 Starts execution of the inferior from the beginning. The inferior
25654 executes until either a breakpoint is encountered or the program
25655 exits. In the latter case the output will include an exit code, if
25656 the program has exited exceptionally.
25658 When no option is specified, the current inferior is started. If the
25659 @samp{--thread-group} option is specified, it should refer to a thread
25660 group of type @samp{process}, and that thread group will be started.
25661 If the @samp{--all} option is specified, then all inferiors will be started.
25663 @subsubheading @value{GDBN} Command
25665 The corresponding @value{GDBN} command is @samp{run}.
25667 @subsubheading Examples
25672 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
25677 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
25678 frame=@{func="main",args=[],file="recursive2.c",
25679 fullname="/home/foo/bar/recursive2.c",line="4"@}
25684 Program exited normally:
25692 *stopped,reason="exited-normally"
25697 Program exited exceptionally:
25705 *stopped,reason="exited",exit-code="01"
25709 Another way the program can terminate is if it receives a signal such as
25710 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
25714 *stopped,reason="exited-signalled",signal-name="SIGINT",
25715 signal-meaning="Interrupt"
25719 @c @subheading -exec-signal
25722 @subheading The @code{-exec-step} Command
25725 @subsubheading Synopsis
25728 -exec-step [--reverse]
25731 Resumes execution of the inferior program, stopping when the beginning
25732 of the next source line is reached, if the next source line is not a
25733 function call. If it is, stop at the first instruction of the called
25734 function. If the @samp{--reverse} option is specified, resumes reverse
25735 execution of the inferior program, stopping at the beginning of the
25736 previously executed source line.
25738 @subsubheading @value{GDBN} Command
25740 The corresponding @value{GDBN} command is @samp{step}.
25742 @subsubheading Example
25744 Stepping into a function:
25750 *stopped,reason="end-stepping-range",
25751 frame=@{func="foo",args=[@{name="a",value="10"@},
25752 @{name="b",value="0"@}],file="recursive2.c",
25753 fullname="/home/foo/bar/recursive2.c",line="11"@}
25763 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
25768 @subheading The @code{-exec-step-instruction} Command
25769 @findex -exec-step-instruction
25771 @subsubheading Synopsis
25774 -exec-step-instruction [--reverse]
25777 Resumes the inferior which executes one machine instruction. If the
25778 @samp{--reverse} option is specified, resumes reverse execution of the
25779 inferior program, stopping at the previously executed instruction.
25780 The output, once @value{GDBN} has stopped, will vary depending on
25781 whether we have stopped in the middle of a source line or not. In the
25782 former case, the address at which the program stopped will be printed
25785 @subsubheading @value{GDBN} Command
25787 The corresponding @value{GDBN} command is @samp{stepi}.
25789 @subsubheading Example
25793 -exec-step-instruction
25797 *stopped,reason="end-stepping-range",
25798 frame=@{func="foo",args=[],file="try.c",
25799 fullname="/home/foo/bar/try.c",line="10"@}
25801 -exec-step-instruction
25805 *stopped,reason="end-stepping-range",
25806 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",
25807 fullname="/home/foo/bar/try.c",line="10"@}
25812 @subheading The @code{-exec-until} Command
25813 @findex -exec-until
25815 @subsubheading Synopsis
25818 -exec-until [ @var{location} ]
25821 Executes the inferior until the @var{location} specified in the
25822 argument is reached. If there is no argument, the inferior executes
25823 until a source line greater than the current one is reached. The
25824 reason for stopping in this case will be @samp{location-reached}.
25826 @subsubheading @value{GDBN} Command
25828 The corresponding @value{GDBN} command is @samp{until}.
25830 @subsubheading Example
25834 -exec-until recursive2.c:6
25838 *stopped,reason="location-reached",frame=@{func="main",args=[],
25839 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="6"@}
25844 @subheading -file-clear
25845 Is this going away????
25848 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25849 @node GDB/MI Stack Manipulation
25850 @section @sc{gdb/mi} Stack Manipulation Commands
25853 @subheading The @code{-stack-info-frame} Command
25854 @findex -stack-info-frame
25856 @subsubheading Synopsis
25862 Get info on the selected frame.
25864 @subsubheading @value{GDBN} Command
25866 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
25867 (without arguments).
25869 @subsubheading Example
25874 ^done,frame=@{level="1",addr="0x0001076c",func="callee3",
25875 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
25876 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@}
25880 @subheading The @code{-stack-info-depth} Command
25881 @findex -stack-info-depth
25883 @subsubheading Synopsis
25886 -stack-info-depth [ @var{max-depth} ]
25889 Return the depth of the stack. If the integer argument @var{max-depth}
25890 is specified, do not count beyond @var{max-depth} frames.
25892 @subsubheading @value{GDBN} Command
25894 There's no equivalent @value{GDBN} command.
25896 @subsubheading Example
25898 For a stack with frame levels 0 through 11:
25905 -stack-info-depth 4
25908 -stack-info-depth 12
25911 -stack-info-depth 11
25914 -stack-info-depth 13
25919 @subheading The @code{-stack-list-arguments} Command
25920 @findex -stack-list-arguments
25922 @subsubheading Synopsis
25925 -stack-list-arguments @var{print-values}
25926 [ @var{low-frame} @var{high-frame} ]
25929 Display a list of the arguments for the frames between @var{low-frame}
25930 and @var{high-frame} (inclusive). If @var{low-frame} and
25931 @var{high-frame} are not provided, list the arguments for the whole
25932 call stack. If the two arguments are equal, show the single frame
25933 at the corresponding level. It is an error if @var{low-frame} is
25934 larger than the actual number of frames. On the other hand,
25935 @var{high-frame} may be larger than the actual number of frames, in
25936 which case only existing frames will be returned.
25938 If @var{print-values} is 0 or @code{--no-values}, print only the names of
25939 the variables; if it is 1 or @code{--all-values}, print also their
25940 values; and if it is 2 or @code{--simple-values}, print the name,
25941 type and value for simple data types, and the name and type for arrays,
25942 structures and unions.
25944 Use of this command to obtain arguments in a single frame is
25945 deprecated in favor of the @samp{-stack-list-variables} command.
25947 @subsubheading @value{GDBN} Command
25949 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
25950 @samp{gdb_get_args} command which partially overlaps with the
25951 functionality of @samp{-stack-list-arguments}.
25953 @subsubheading Example
25960 frame=@{level="0",addr="0x00010734",func="callee4",
25961 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
25962 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@},
25963 frame=@{level="1",addr="0x0001076c",func="callee3",
25964 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
25965 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@},
25966 frame=@{level="2",addr="0x0001078c",func="callee2",
25967 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
25968 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="22"@},
25969 frame=@{level="3",addr="0x000107b4",func="callee1",
25970 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
25971 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="27"@},
25972 frame=@{level="4",addr="0x000107e0",func="main",
25973 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
25974 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="32"@}]
25976 -stack-list-arguments 0
25979 frame=@{level="0",args=[]@},
25980 frame=@{level="1",args=[name="strarg"]@},
25981 frame=@{level="2",args=[name="intarg",name="strarg"]@},
25982 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
25983 frame=@{level="4",args=[]@}]
25985 -stack-list-arguments 1
25988 frame=@{level="0",args=[]@},
25990 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
25991 frame=@{level="2",args=[
25992 @{name="intarg",value="2"@},
25993 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
25994 @{frame=@{level="3",args=[
25995 @{name="intarg",value="2"@},
25996 @{name="strarg",value="0x11940 \"A string argument.\""@},
25997 @{name="fltarg",value="3.5"@}]@},
25998 frame=@{level="4",args=[]@}]
26000 -stack-list-arguments 0 2 2
26001 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
26003 -stack-list-arguments 1 2 2
26004 ^done,stack-args=[frame=@{level="2",
26005 args=[@{name="intarg",value="2"@},
26006 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
26010 @c @subheading -stack-list-exception-handlers
26013 @subheading The @code{-stack-list-frames} Command
26014 @findex -stack-list-frames
26016 @subsubheading Synopsis
26019 -stack-list-frames [ @var{low-frame} @var{high-frame} ]
26022 List the frames currently on the stack. For each frame it displays the
26027 The frame number, 0 being the topmost frame, i.e., the innermost function.
26029 The @code{$pc} value for that frame.
26033 File name of the source file where the function lives.
26035 Line number corresponding to the @code{$pc}.
26038 If invoked without arguments, this command prints a backtrace for the
26039 whole stack. If given two integer arguments, it shows the frames whose
26040 levels are between the two arguments (inclusive). If the two arguments
26041 are equal, it shows the single frame at the corresponding level. It is
26042 an error if @var{low-frame} is larger than the actual number of
26043 frames. On the other hand, @var{high-frame} may be larger than the
26044 actual number of frames, in which case only existing frames will be returned.
26046 @subsubheading @value{GDBN} Command
26048 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
26050 @subsubheading Example
26052 Full stack backtrace:
26058 [frame=@{level="0",addr="0x0001076c",func="foo",
26059 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="11"@},
26060 frame=@{level="1",addr="0x000107a4",func="foo",
26061 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
26062 frame=@{level="2",addr="0x000107a4",func="foo",
26063 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
26064 frame=@{level="3",addr="0x000107a4",func="foo",
26065 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
26066 frame=@{level="4",addr="0x000107a4",func="foo",
26067 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
26068 frame=@{level="5",addr="0x000107a4",func="foo",
26069 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
26070 frame=@{level="6",addr="0x000107a4",func="foo",
26071 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
26072 frame=@{level="7",addr="0x000107a4",func="foo",
26073 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
26074 frame=@{level="8",addr="0x000107a4",func="foo",
26075 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
26076 frame=@{level="9",addr="0x000107a4",func="foo",
26077 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
26078 frame=@{level="10",addr="0x000107a4",func="foo",
26079 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
26080 frame=@{level="11",addr="0x00010738",func="main",
26081 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="4"@}]
26085 Show frames between @var{low_frame} and @var{high_frame}:
26089 -stack-list-frames 3 5
26091 [frame=@{level="3",addr="0x000107a4",func="foo",
26092 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
26093 frame=@{level="4",addr="0x000107a4",func="foo",
26094 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
26095 frame=@{level="5",addr="0x000107a4",func="foo",
26096 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
26100 Show a single frame:
26104 -stack-list-frames 3 3
26106 [frame=@{level="3",addr="0x000107a4",func="foo",
26107 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
26112 @subheading The @code{-stack-list-locals} Command
26113 @findex -stack-list-locals
26115 @subsubheading Synopsis
26118 -stack-list-locals @var{print-values}
26121 Display the local variable names for the selected frame. If
26122 @var{print-values} is 0 or @code{--no-values}, print only the names of
26123 the variables; if it is 1 or @code{--all-values}, print also their
26124 values; and if it is 2 or @code{--simple-values}, print the name,
26125 type and value for simple data types, and the name and type for arrays,
26126 structures and unions. In this last case, a frontend can immediately
26127 display the value of simple data types and create variable objects for
26128 other data types when the user wishes to explore their values in
26131 This command is deprecated in favor of the
26132 @samp{-stack-list-variables} command.
26134 @subsubheading @value{GDBN} Command
26136 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
26138 @subsubheading Example
26142 -stack-list-locals 0
26143 ^done,locals=[name="A",name="B",name="C"]
26145 -stack-list-locals --all-values
26146 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
26147 @{name="C",value="@{1, 2, 3@}"@}]
26148 -stack-list-locals --simple-values
26149 ^done,locals=[@{name="A",type="int",value="1"@},
26150 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
26154 @subheading The @code{-stack-list-variables} Command
26155 @findex -stack-list-variables
26157 @subsubheading Synopsis
26160 -stack-list-variables @var{print-values}
26163 Display the names of local variables and function arguments for the selected frame. If
26164 @var{print-values} is 0 or @code{--no-values}, print only the names of
26165 the variables; if it is 1 or @code{--all-values}, print also their
26166 values; and if it is 2 or @code{--simple-values}, print the name,
26167 type and value for simple data types, and the name and type for arrays,
26168 structures and unions.
26170 @subsubheading Example
26174 -stack-list-variables --thread 1 --frame 0 --all-values
26175 ^done,variables=[@{name="x",value="11"@},@{name="s",value="@{a = 1, b = 2@}"@}]
26180 @subheading The @code{-stack-select-frame} Command
26181 @findex -stack-select-frame
26183 @subsubheading Synopsis
26186 -stack-select-frame @var{framenum}
26189 Change the selected frame. Select a different frame @var{framenum} on
26192 This command in deprecated in favor of passing the @samp{--frame}
26193 option to every command.
26195 @subsubheading @value{GDBN} Command
26197 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
26198 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
26200 @subsubheading Example
26204 -stack-select-frame 2
26209 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26210 @node GDB/MI Variable Objects
26211 @section @sc{gdb/mi} Variable Objects
26215 @subheading Motivation for Variable Objects in @sc{gdb/mi}
26217 For the implementation of a variable debugger window (locals, watched
26218 expressions, etc.), we are proposing the adaptation of the existing code
26219 used by @code{Insight}.
26221 The two main reasons for that are:
26225 It has been proven in practice (it is already on its second generation).
26228 It will shorten development time (needless to say how important it is
26232 The original interface was designed to be used by Tcl code, so it was
26233 slightly changed so it could be used through @sc{gdb/mi}. This section
26234 describes the @sc{gdb/mi} operations that will be available and gives some
26235 hints about their use.
26237 @emph{Note}: In addition to the set of operations described here, we
26238 expect the @sc{gui} implementation of a variable window to require, at
26239 least, the following operations:
26242 @item @code{-gdb-show} @code{output-radix}
26243 @item @code{-stack-list-arguments}
26244 @item @code{-stack-list-locals}
26245 @item @code{-stack-select-frame}
26250 @subheading Introduction to Variable Objects
26252 @cindex variable objects in @sc{gdb/mi}
26254 Variable objects are "object-oriented" MI interface for examining and
26255 changing values of expressions. Unlike some other MI interfaces that
26256 work with expressions, variable objects are specifically designed for
26257 simple and efficient presentation in the frontend. A variable object
26258 is identified by string name. When a variable object is created, the
26259 frontend specifies the expression for that variable object. The
26260 expression can be a simple variable, or it can be an arbitrary complex
26261 expression, and can even involve CPU registers. After creating a
26262 variable object, the frontend can invoke other variable object
26263 operations---for example to obtain or change the value of a variable
26264 object, or to change display format.
26266 Variable objects have hierarchical tree structure. Any variable object
26267 that corresponds to a composite type, such as structure in C, has
26268 a number of child variable objects, for example corresponding to each
26269 element of a structure. A child variable object can itself have
26270 children, recursively. Recursion ends when we reach
26271 leaf variable objects, which always have built-in types. Child variable
26272 objects are created only by explicit request, so if a frontend
26273 is not interested in the children of a particular variable object, no
26274 child will be created.
26276 For a leaf variable object it is possible to obtain its value as a
26277 string, or set the value from a string. String value can be also
26278 obtained for a non-leaf variable object, but it's generally a string
26279 that only indicates the type of the object, and does not list its
26280 contents. Assignment to a non-leaf variable object is not allowed.
26282 A frontend does not need to read the values of all variable objects each time
26283 the program stops. Instead, MI provides an update command that lists all
26284 variable objects whose values has changed since the last update
26285 operation. This considerably reduces the amount of data that must
26286 be transferred to the frontend. As noted above, children variable
26287 objects are created on demand, and only leaf variable objects have a
26288 real value. As result, gdb will read target memory only for leaf
26289 variables that frontend has created.
26291 The automatic update is not always desirable. For example, a frontend
26292 might want to keep a value of some expression for future reference,
26293 and never update it. For another example, fetching memory is
26294 relatively slow for embedded targets, so a frontend might want
26295 to disable automatic update for the variables that are either not
26296 visible on the screen, or ``closed''. This is possible using so
26297 called ``frozen variable objects''. Such variable objects are never
26298 implicitly updated.
26300 Variable objects can be either @dfn{fixed} or @dfn{floating}. For the
26301 fixed variable object, the expression is parsed when the variable
26302 object is created, including associating identifiers to specific
26303 variables. The meaning of expression never changes. For a floating
26304 variable object the values of variables whose names appear in the
26305 expressions are re-evaluated every time in the context of the current
26306 frame. Consider this example:
26311 struct work_state state;
26318 If a fixed variable object for the @code{state} variable is created in
26319 this function, and we enter the recursive call, the the variable
26320 object will report the value of @code{state} in the top-level
26321 @code{do_work} invocation. On the other hand, a floating variable
26322 object will report the value of @code{state} in the current frame.
26324 If an expression specified when creating a fixed variable object
26325 refers to a local variable, the variable object becomes bound to the
26326 thread and frame in which the variable object is created. When such
26327 variable object is updated, @value{GDBN} makes sure that the
26328 thread/frame combination the variable object is bound to still exists,
26329 and re-evaluates the variable object in context of that thread/frame.
26331 The following is the complete set of @sc{gdb/mi} operations defined to
26332 access this functionality:
26334 @multitable @columnfractions .4 .6
26335 @item @strong{Operation}
26336 @tab @strong{Description}
26338 @item @code{-enable-pretty-printing}
26339 @tab enable Python-based pretty-printing
26340 @item @code{-var-create}
26341 @tab create a variable object
26342 @item @code{-var-delete}
26343 @tab delete the variable object and/or its children
26344 @item @code{-var-set-format}
26345 @tab set the display format of this variable
26346 @item @code{-var-show-format}
26347 @tab show the display format of this variable
26348 @item @code{-var-info-num-children}
26349 @tab tells how many children this object has
26350 @item @code{-var-list-children}
26351 @tab return a list of the object's children
26352 @item @code{-var-info-type}
26353 @tab show the type of this variable object
26354 @item @code{-var-info-expression}
26355 @tab print parent-relative expression that this variable object represents
26356 @item @code{-var-info-path-expression}
26357 @tab print full expression that this variable object represents
26358 @item @code{-var-show-attributes}
26359 @tab is this variable editable? does it exist here?
26360 @item @code{-var-evaluate-expression}
26361 @tab get the value of this variable
26362 @item @code{-var-assign}
26363 @tab set the value of this variable
26364 @item @code{-var-update}
26365 @tab update the variable and its children
26366 @item @code{-var-set-frozen}
26367 @tab set frozeness attribute
26368 @item @code{-var-set-update-range}
26369 @tab set range of children to display on update
26372 In the next subsection we describe each operation in detail and suggest
26373 how it can be used.
26375 @subheading Description And Use of Operations on Variable Objects
26377 @subheading The @code{-enable-pretty-printing} Command
26378 @findex -enable-pretty-printing
26381 -enable-pretty-printing
26384 @value{GDBN} allows Python-based visualizers to affect the output of the
26385 MI variable object commands. However, because there was no way to
26386 implement this in a fully backward-compatible way, a front end must
26387 request that this functionality be enabled.
26389 Once enabled, this feature cannot be disabled.
26391 Note that if Python support has not been compiled into @value{GDBN},
26392 this command will still succeed (and do nothing).
26394 This feature is currently (as of @value{GDBN} 7.0) experimental, and
26395 may work differently in future versions of @value{GDBN}.
26397 @subheading The @code{-var-create} Command
26398 @findex -var-create
26400 @subsubheading Synopsis
26403 -var-create @{@var{name} | "-"@}
26404 @{@var{frame-addr} | "*" | "@@"@} @var{expression}
26407 This operation creates a variable object, which allows the monitoring of
26408 a variable, the result of an expression, a memory cell or a CPU
26411 The @var{name} parameter is the string by which the object can be
26412 referenced. It must be unique. If @samp{-} is specified, the varobj
26413 system will generate a string ``varNNNNNN'' automatically. It will be
26414 unique provided that one does not specify @var{name} of that format.
26415 The command fails if a duplicate name is found.
26417 The frame under which the expression should be evaluated can be
26418 specified by @var{frame-addr}. A @samp{*} indicates that the current
26419 frame should be used. A @samp{@@} indicates that a floating variable
26420 object must be created.
26422 @var{expression} is any expression valid on the current language set (must not
26423 begin with a @samp{*}), or one of the following:
26427 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
26430 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
26433 @samp{$@var{regname}} --- a CPU register name
26436 @cindex dynamic varobj
26437 A varobj's contents may be provided by a Python-based pretty-printer. In this
26438 case the varobj is known as a @dfn{dynamic varobj}. Dynamic varobjs
26439 have slightly different semantics in some cases. If the
26440 @code{-enable-pretty-printing} command is not sent, then @value{GDBN}
26441 will never create a dynamic varobj. This ensures backward
26442 compatibility for existing clients.
26444 @subsubheading Result
26446 This operation returns attributes of the newly-created varobj. These
26451 The name of the varobj.
26454 The number of children of the varobj. This number is not necessarily
26455 reliable for a dynamic varobj. Instead, you must examine the
26456 @samp{has_more} attribute.
26459 The varobj's scalar value. For a varobj whose type is some sort of
26460 aggregate (e.g., a @code{struct}), or for a dynamic varobj, this value
26461 will not be interesting.
26464 The varobj's type. This is a string representation of the type, as
26465 would be printed by the @value{GDBN} CLI.
26468 If a variable object is bound to a specific thread, then this is the
26469 thread's identifier.
26472 For a dynamic varobj, this indicates whether there appear to be any
26473 children available. For a non-dynamic varobj, this will be 0.
26476 This attribute will be present and have the value @samp{1} if the
26477 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
26478 then this attribute will not be present.
26481 A dynamic varobj can supply a display hint to the front end. The
26482 value comes directly from the Python pretty-printer object's
26483 @code{display_hint} method. @xref{Pretty Printing API}.
26486 Typical output will look like this:
26489 name="@var{name}",numchild="@var{N}",type="@var{type}",thread-id="@var{M}",
26490 has_more="@var{has_more}"
26494 @subheading The @code{-var-delete} Command
26495 @findex -var-delete
26497 @subsubheading Synopsis
26500 -var-delete [ -c ] @var{name}
26503 Deletes a previously created variable object and all of its children.
26504 With the @samp{-c} option, just deletes the children.
26506 Returns an error if the object @var{name} is not found.
26509 @subheading The @code{-var-set-format} Command
26510 @findex -var-set-format
26512 @subsubheading Synopsis
26515 -var-set-format @var{name} @var{format-spec}
26518 Sets the output format for the value of the object @var{name} to be
26521 @anchor{-var-set-format}
26522 The syntax for the @var{format-spec} is as follows:
26525 @var{format-spec} @expansion{}
26526 @{binary | decimal | hexadecimal | octal | natural@}
26529 The natural format is the default format choosen automatically
26530 based on the variable type (like decimal for an @code{int}, hex
26531 for pointers, etc.).
26533 For a variable with children, the format is set only on the
26534 variable itself, and the children are not affected.
26536 @subheading The @code{-var-show-format} Command
26537 @findex -var-show-format
26539 @subsubheading Synopsis
26542 -var-show-format @var{name}
26545 Returns the format used to display the value of the object @var{name}.
26548 @var{format} @expansion{}
26553 @subheading The @code{-var-info-num-children} Command
26554 @findex -var-info-num-children
26556 @subsubheading Synopsis
26559 -var-info-num-children @var{name}
26562 Returns the number of children of a variable object @var{name}:
26568 Note that this number is not completely reliable for a dynamic varobj.
26569 It will return the current number of children, but more children may
26573 @subheading The @code{-var-list-children} Command
26574 @findex -var-list-children
26576 @subsubheading Synopsis
26579 -var-list-children [@var{print-values}] @var{name} [@var{from} @var{to}]
26581 @anchor{-var-list-children}
26583 Return a list of the children of the specified variable object and
26584 create variable objects for them, if they do not already exist. With
26585 a single argument or if @var{print-values} has a value of 0 or
26586 @code{--no-values}, print only the names of the variables; if
26587 @var{print-values} is 1 or @code{--all-values}, also print their
26588 values; and if it is 2 or @code{--simple-values} print the name and
26589 value for simple data types and just the name for arrays, structures
26592 @var{from} and @var{to}, if specified, indicate the range of children
26593 to report. If @var{from} or @var{to} is less than zero, the range is
26594 reset and all children will be reported. Otherwise, children starting
26595 at @var{from} (zero-based) and up to and excluding @var{to} will be
26598 If a child range is requested, it will only affect the current call to
26599 @code{-var-list-children}, but not future calls to @code{-var-update}.
26600 For this, you must instead use @code{-var-set-update-range}. The
26601 intent of this approach is to enable a front end to implement any
26602 update approach it likes; for example, scrolling a view may cause the
26603 front end to request more children with @code{-var-list-children}, and
26604 then the front end could call @code{-var-set-update-range} with a
26605 different range to ensure that future updates are restricted to just
26608 For each child the following results are returned:
26613 Name of the variable object created for this child.
26616 The expression to be shown to the user by the front end to designate this child.
26617 For example this may be the name of a structure member.
26619 For a dynamic varobj, this value cannot be used to form an
26620 expression. There is no way to do this at all with a dynamic varobj.
26622 For C/C@t{++} structures there are several pseudo children returned to
26623 designate access qualifiers. For these pseudo children @var{exp} is
26624 @samp{public}, @samp{private}, or @samp{protected}. In this case the
26625 type and value are not present.
26627 A dynamic varobj will not report the access qualifying
26628 pseudo-children, regardless of the language. This information is not
26629 available at all with a dynamic varobj.
26632 Number of children this child has. For a dynamic varobj, this will be
26636 The type of the child.
26639 If values were requested, this is the value.
26642 If this variable object is associated with a thread, this is the thread id.
26643 Otherwise this result is not present.
26646 If the variable object is frozen, this variable will be present with a value of 1.
26649 The result may have its own attributes:
26653 A dynamic varobj can supply a display hint to the front end. The
26654 value comes directly from the Python pretty-printer object's
26655 @code{display_hint} method. @xref{Pretty Printing API}.
26658 This is an integer attribute which is nonzero if there are children
26659 remaining after the end of the selected range.
26662 @subsubheading Example
26666 -var-list-children n
26667 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
26668 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
26670 -var-list-children --all-values n
26671 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
26672 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
26676 @subheading The @code{-var-info-type} Command
26677 @findex -var-info-type
26679 @subsubheading Synopsis
26682 -var-info-type @var{name}
26685 Returns the type of the specified variable @var{name}. The type is
26686 returned as a string in the same format as it is output by the
26690 type=@var{typename}
26694 @subheading The @code{-var-info-expression} Command
26695 @findex -var-info-expression
26697 @subsubheading Synopsis
26700 -var-info-expression @var{name}
26703 Returns a string that is suitable for presenting this
26704 variable object in user interface. The string is generally
26705 not valid expression in the current language, and cannot be evaluated.
26707 For example, if @code{a} is an array, and variable object
26708 @code{A} was created for @code{a}, then we'll get this output:
26711 (gdb) -var-info-expression A.1
26712 ^done,lang="C",exp="1"
26716 Here, the values of @code{lang} can be @code{@{"C" | "C++" | "Java"@}}.
26718 Note that the output of the @code{-var-list-children} command also
26719 includes those expressions, so the @code{-var-info-expression} command
26722 @subheading The @code{-var-info-path-expression} Command
26723 @findex -var-info-path-expression
26725 @subsubheading Synopsis
26728 -var-info-path-expression @var{name}
26731 Returns an expression that can be evaluated in the current
26732 context and will yield the same value that a variable object has.
26733 Compare this with the @code{-var-info-expression} command, which
26734 result can be used only for UI presentation. Typical use of
26735 the @code{-var-info-path-expression} command is creating a
26736 watchpoint from a variable object.
26738 This command is currently not valid for children of a dynamic varobj,
26739 and will give an error when invoked on one.
26741 For example, suppose @code{C} is a C@t{++} class, derived from class
26742 @code{Base}, and that the @code{Base} class has a member called
26743 @code{m_size}. Assume a variable @code{c} is has the type of
26744 @code{C} and a variable object @code{C} was created for variable
26745 @code{c}. Then, we'll get this output:
26747 (gdb) -var-info-path-expression C.Base.public.m_size
26748 ^done,path_expr=((Base)c).m_size)
26751 @subheading The @code{-var-show-attributes} Command
26752 @findex -var-show-attributes
26754 @subsubheading Synopsis
26757 -var-show-attributes @var{name}
26760 List attributes of the specified variable object @var{name}:
26763 status=@var{attr} [ ( ,@var{attr} )* ]
26767 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
26769 @subheading The @code{-var-evaluate-expression} Command
26770 @findex -var-evaluate-expression
26772 @subsubheading Synopsis
26775 -var-evaluate-expression [-f @var{format-spec}] @var{name}
26778 Evaluates the expression that is represented by the specified variable
26779 object and returns its value as a string. The format of the string
26780 can be specified with the @samp{-f} option. The possible values of
26781 this option are the same as for @code{-var-set-format}
26782 (@pxref{-var-set-format}). If the @samp{-f} option is not specified,
26783 the current display format will be used. The current display format
26784 can be changed using the @code{-var-set-format} command.
26790 Note that one must invoke @code{-var-list-children} for a variable
26791 before the value of a child variable can be evaluated.
26793 @subheading The @code{-var-assign} Command
26794 @findex -var-assign
26796 @subsubheading Synopsis
26799 -var-assign @var{name} @var{expression}
26802 Assigns the value of @var{expression} to the variable object specified
26803 by @var{name}. The object must be @samp{editable}. If the variable's
26804 value is altered by the assign, the variable will show up in any
26805 subsequent @code{-var-update} list.
26807 @subsubheading Example
26815 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
26819 @subheading The @code{-var-update} Command
26820 @findex -var-update
26822 @subsubheading Synopsis
26825 -var-update [@var{print-values}] @{@var{name} | "*"@}
26828 Reevaluate the expressions corresponding to the variable object
26829 @var{name} and all its direct and indirect children, and return the
26830 list of variable objects whose values have changed; @var{name} must
26831 be a root variable object. Here, ``changed'' means that the result of
26832 @code{-var-evaluate-expression} before and after the
26833 @code{-var-update} is different. If @samp{*} is used as the variable
26834 object names, all existing variable objects are updated, except
26835 for frozen ones (@pxref{-var-set-frozen}). The option
26836 @var{print-values} determines whether both names and values, or just
26837 names are printed. The possible values of this option are the same
26838 as for @code{-var-list-children} (@pxref{-var-list-children}). It is
26839 recommended to use the @samp{--all-values} option, to reduce the
26840 number of MI commands needed on each program stop.
26842 With the @samp{*} parameter, if a variable object is bound to a
26843 currently running thread, it will not be updated, without any
26846 If @code{-var-set-update-range} was previously used on a varobj, then
26847 only the selected range of children will be reported.
26849 @code{-var-update} reports all the changed varobjs in a tuple named
26852 Each item in the change list is itself a tuple holding:
26856 The name of the varobj.
26859 If values were requested for this update, then this field will be
26860 present and will hold the value of the varobj.
26863 @anchor{-var-update}
26864 This field is a string which may take one of three values:
26868 The variable object's current value is valid.
26871 The variable object does not currently hold a valid value but it may
26872 hold one in the future if its associated expression comes back into
26876 The variable object no longer holds a valid value.
26877 This can occur when the executable file being debugged has changed,
26878 either through recompilation or by using the @value{GDBN} @code{file}
26879 command. The front end should normally choose to delete these variable
26883 In the future new values may be added to this list so the front should
26884 be prepared for this possibility. @xref{GDB/MI Development and Front Ends, ,@sc{GDB/MI} Development and Front Ends}.
26887 This is only present if the varobj is still valid. If the type
26888 changed, then this will be the string @samp{true}; otherwise it will
26892 If the varobj's type changed, then this field will be present and will
26895 @item new_num_children
26896 For a dynamic varobj, if the number of children changed, or if the
26897 type changed, this will be the new number of children.
26899 The @samp{numchild} field in other varobj responses is generally not
26900 valid for a dynamic varobj -- it will show the number of children that
26901 @value{GDBN} knows about, but because dynamic varobjs lazily
26902 instantiate their children, this will not reflect the number of
26903 children which may be available.
26905 The @samp{new_num_children} attribute only reports changes to the
26906 number of children known by @value{GDBN}. This is the only way to
26907 detect whether an update has removed children (which necessarily can
26908 only happen at the end of the update range).
26911 The display hint, if any.
26914 This is an integer value, which will be 1 if there are more children
26915 available outside the varobj's update range.
26918 This attribute will be present and have the value @samp{1} if the
26919 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
26920 then this attribute will not be present.
26923 If new children were added to a dynamic varobj within the selected
26924 update range (as set by @code{-var-set-update-range}), then they will
26925 be listed in this attribute.
26928 @subsubheading Example
26935 -var-update --all-values var1
26936 ^done,changelist=[@{name="var1",value="3",in_scope="true",
26937 type_changed="false"@}]
26941 @subheading The @code{-var-set-frozen} Command
26942 @findex -var-set-frozen
26943 @anchor{-var-set-frozen}
26945 @subsubheading Synopsis
26948 -var-set-frozen @var{name} @var{flag}
26951 Set the frozenness flag on the variable object @var{name}. The
26952 @var{flag} parameter should be either @samp{1} to make the variable
26953 frozen or @samp{0} to make it unfrozen. If a variable object is
26954 frozen, then neither itself, nor any of its children, are
26955 implicitly updated by @code{-var-update} of
26956 a parent variable or by @code{-var-update *}. Only
26957 @code{-var-update} of the variable itself will update its value and
26958 values of its children. After a variable object is unfrozen, it is
26959 implicitly updated by all subsequent @code{-var-update} operations.
26960 Unfreezing a variable does not update it, only subsequent
26961 @code{-var-update} does.
26963 @subsubheading Example
26967 -var-set-frozen V 1
26972 @subheading The @code{-var-set-update-range} command
26973 @findex -var-set-update-range
26974 @anchor{-var-set-update-range}
26976 @subsubheading Synopsis
26979 -var-set-update-range @var{name} @var{from} @var{to}
26982 Set the range of children to be returned by future invocations of
26983 @code{-var-update}.
26985 @var{from} and @var{to} indicate the range of children to report. If
26986 @var{from} or @var{to} is less than zero, the range is reset and all
26987 children will be reported. Otherwise, children starting at @var{from}
26988 (zero-based) and up to and excluding @var{to} will be reported.
26990 @subsubheading Example
26994 -var-set-update-range V 1 2
26998 @subheading The @code{-var-set-visualizer} command
26999 @findex -var-set-visualizer
27000 @anchor{-var-set-visualizer}
27002 @subsubheading Synopsis
27005 -var-set-visualizer @var{name} @var{visualizer}
27008 Set a visualizer for the variable object @var{name}.
27010 @var{visualizer} is the visualizer to use. The special value
27011 @samp{None} means to disable any visualizer in use.
27013 If not @samp{None}, @var{visualizer} must be a Python expression.
27014 This expression must evaluate to a callable object which accepts a
27015 single argument. @value{GDBN} will call this object with the value of
27016 the varobj @var{name} as an argument (this is done so that the same
27017 Python pretty-printing code can be used for both the CLI and MI).
27018 When called, this object must return an object which conforms to the
27019 pretty-printing interface (@pxref{Pretty Printing API}).
27021 The pre-defined function @code{gdb.default_visualizer} may be used to
27022 select a visualizer by following the built-in process
27023 (@pxref{Selecting Pretty-Printers}). This is done automatically when
27024 a varobj is created, and so ordinarily is not needed.
27026 This feature is only available if Python support is enabled. The MI
27027 command @code{-list-features} (@pxref{GDB/MI Miscellaneous Commands})
27028 can be used to check this.
27030 @subsubheading Example
27032 Resetting the visualizer:
27036 -var-set-visualizer V None
27040 Reselecting the default (type-based) visualizer:
27044 -var-set-visualizer V gdb.default_visualizer
27048 Suppose @code{SomeClass} is a visualizer class. A lambda expression
27049 can be used to instantiate this class for a varobj:
27053 -var-set-visualizer V "lambda val: SomeClass()"
27057 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27058 @node GDB/MI Data Manipulation
27059 @section @sc{gdb/mi} Data Manipulation
27061 @cindex data manipulation, in @sc{gdb/mi}
27062 @cindex @sc{gdb/mi}, data manipulation
27063 This section describes the @sc{gdb/mi} commands that manipulate data:
27064 examine memory and registers, evaluate expressions, etc.
27066 @c REMOVED FROM THE INTERFACE.
27067 @c @subheading -data-assign
27068 @c Change the value of a program variable. Plenty of side effects.
27069 @c @subsubheading GDB Command
27071 @c @subsubheading Example
27074 @subheading The @code{-data-disassemble} Command
27075 @findex -data-disassemble
27077 @subsubheading Synopsis
27081 [ -s @var{start-addr} -e @var{end-addr} ]
27082 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
27090 @item @var{start-addr}
27091 is the beginning address (or @code{$pc})
27092 @item @var{end-addr}
27094 @item @var{filename}
27095 is the name of the file to disassemble
27096 @item @var{linenum}
27097 is the line number to disassemble around
27099 is the number of disassembly lines to be produced. If it is -1,
27100 the whole function will be disassembled, in case no @var{end-addr} is
27101 specified. If @var{end-addr} is specified as a non-zero value, and
27102 @var{lines} is lower than the number of disassembly lines between
27103 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
27104 displayed; if @var{lines} is higher than the number of lines between
27105 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
27108 is either 0 (meaning only disassembly) or 1 (meaning mixed source and
27112 @subsubheading Result
27114 The output for each instruction is composed of four fields:
27123 Note that whatever included in the instruction field, is not manipulated
27124 directly by @sc{gdb/mi}, i.e., it is not possible to adjust its format.
27126 @subsubheading @value{GDBN} Command
27128 There's no direct mapping from this command to the CLI.
27130 @subsubheading Example
27132 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
27136 -data-disassemble -s $pc -e "$pc + 20" -- 0
27139 @{address="0x000107c0",func-name="main",offset="4",
27140 inst="mov 2, %o0"@},
27141 @{address="0x000107c4",func-name="main",offset="8",
27142 inst="sethi %hi(0x11800), %o2"@},
27143 @{address="0x000107c8",func-name="main",offset="12",
27144 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
27145 @{address="0x000107cc",func-name="main",offset="16",
27146 inst="sethi %hi(0x11800), %o2"@},
27147 @{address="0x000107d0",func-name="main",offset="20",
27148 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
27152 Disassemble the whole @code{main} function. Line 32 is part of
27156 -data-disassemble -f basics.c -l 32 -- 0
27158 @{address="0x000107bc",func-name="main",offset="0",
27159 inst="save %sp, -112, %sp"@},
27160 @{address="0x000107c0",func-name="main",offset="4",
27161 inst="mov 2, %o0"@},
27162 @{address="0x000107c4",func-name="main",offset="8",
27163 inst="sethi %hi(0x11800), %o2"@},
27165 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
27166 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
27170 Disassemble 3 instructions from the start of @code{main}:
27174 -data-disassemble -f basics.c -l 32 -n 3 -- 0
27176 @{address="0x000107bc",func-name="main",offset="0",
27177 inst="save %sp, -112, %sp"@},
27178 @{address="0x000107c0",func-name="main",offset="4",
27179 inst="mov 2, %o0"@},
27180 @{address="0x000107c4",func-name="main",offset="8",
27181 inst="sethi %hi(0x11800), %o2"@}]
27185 Disassemble 3 instructions from the start of @code{main} in mixed mode:
27189 -data-disassemble -f basics.c -l 32 -n 3 -- 1
27191 src_and_asm_line=@{line="31",
27192 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
27193 testsuite/gdb.mi/basics.c",line_asm_insn=[
27194 @{address="0x000107bc",func-name="main",offset="0",
27195 inst="save %sp, -112, %sp"@}]@},
27196 src_and_asm_line=@{line="32",
27197 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
27198 testsuite/gdb.mi/basics.c",line_asm_insn=[
27199 @{address="0x000107c0",func-name="main",offset="4",
27200 inst="mov 2, %o0"@},
27201 @{address="0x000107c4",func-name="main",offset="8",
27202 inst="sethi %hi(0x11800), %o2"@}]@}]
27207 @subheading The @code{-data-evaluate-expression} Command
27208 @findex -data-evaluate-expression
27210 @subsubheading Synopsis
27213 -data-evaluate-expression @var{expr}
27216 Evaluate @var{expr} as an expression. The expression could contain an
27217 inferior function call. The function call will execute synchronously.
27218 If the expression contains spaces, it must be enclosed in double quotes.
27220 @subsubheading @value{GDBN} Command
27222 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
27223 @samp{call}. In @code{gdbtk} only, there's a corresponding
27224 @samp{gdb_eval} command.
27226 @subsubheading Example
27228 In the following example, the numbers that precede the commands are the
27229 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
27230 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
27234 211-data-evaluate-expression A
27237 311-data-evaluate-expression &A
27238 311^done,value="0xefffeb7c"
27240 411-data-evaluate-expression A+3
27243 511-data-evaluate-expression "A + 3"
27249 @subheading The @code{-data-list-changed-registers} Command
27250 @findex -data-list-changed-registers
27252 @subsubheading Synopsis
27255 -data-list-changed-registers
27258 Display a list of the registers that have changed.
27260 @subsubheading @value{GDBN} Command
27262 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
27263 has the corresponding command @samp{gdb_changed_register_list}.
27265 @subsubheading Example
27267 On a PPC MBX board:
27275 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",frame=@{
27276 func="main",args=[],file="try.c",fullname="/home/foo/bar/try.c",
27279 -data-list-changed-registers
27280 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
27281 "10","11","13","14","15","16","17","18","19","20","21","22","23",
27282 "24","25","26","27","28","30","31","64","65","66","67","69"]
27287 @subheading The @code{-data-list-register-names} Command
27288 @findex -data-list-register-names
27290 @subsubheading Synopsis
27293 -data-list-register-names [ ( @var{regno} )+ ]
27296 Show a list of register names for the current target. If no arguments
27297 are given, it shows a list of the names of all the registers. If
27298 integer numbers are given as arguments, it will print a list of the
27299 names of the registers corresponding to the arguments. To ensure
27300 consistency between a register name and its number, the output list may
27301 include empty register names.
27303 @subsubheading @value{GDBN} Command
27305 @value{GDBN} does not have a command which corresponds to
27306 @samp{-data-list-register-names}. In @code{gdbtk} there is a
27307 corresponding command @samp{gdb_regnames}.
27309 @subsubheading Example
27311 For the PPC MBX board:
27314 -data-list-register-names
27315 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
27316 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
27317 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
27318 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
27319 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
27320 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
27321 "", "pc","ps","cr","lr","ctr","xer"]
27323 -data-list-register-names 1 2 3
27324 ^done,register-names=["r1","r2","r3"]
27328 @subheading The @code{-data-list-register-values} Command
27329 @findex -data-list-register-values
27331 @subsubheading Synopsis
27334 -data-list-register-values @var{fmt} [ ( @var{regno} )*]
27337 Display the registers' contents. @var{fmt} is the format according to
27338 which the registers' contents are to be returned, followed by an optional
27339 list of numbers specifying the registers to display. A missing list of
27340 numbers indicates that the contents of all the registers must be returned.
27342 Allowed formats for @var{fmt} are:
27359 @subsubheading @value{GDBN} Command
27361 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
27362 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
27364 @subsubheading Example
27366 For a PPC MBX board (note: line breaks are for readability only, they
27367 don't appear in the actual output):
27371 -data-list-register-values r 64 65
27372 ^done,register-values=[@{number="64",value="0xfe00a300"@},
27373 @{number="65",value="0x00029002"@}]
27375 -data-list-register-values x
27376 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
27377 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
27378 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
27379 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
27380 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
27381 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
27382 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
27383 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
27384 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
27385 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
27386 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
27387 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
27388 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
27389 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
27390 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
27391 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
27392 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
27393 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
27394 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
27395 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
27396 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
27397 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
27398 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
27399 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
27400 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
27401 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
27402 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
27403 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
27404 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
27405 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
27406 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
27407 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
27408 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
27409 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
27410 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
27411 @{number="69",value="0x20002b03"@}]
27416 @subheading The @code{-data-read-memory} Command
27417 @findex -data-read-memory
27419 This command is deprecated, use @code{-data-read-memory-bytes} instead.
27421 @subsubheading Synopsis
27424 -data-read-memory [ -o @var{byte-offset} ]
27425 @var{address} @var{word-format} @var{word-size}
27426 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
27433 @item @var{address}
27434 An expression specifying the address of the first memory word to be
27435 read. Complex expressions containing embedded white space should be
27436 quoted using the C convention.
27438 @item @var{word-format}
27439 The format to be used to print the memory words. The notation is the
27440 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
27443 @item @var{word-size}
27444 The size of each memory word in bytes.
27446 @item @var{nr-rows}
27447 The number of rows in the output table.
27449 @item @var{nr-cols}
27450 The number of columns in the output table.
27453 If present, indicates that each row should include an @sc{ascii} dump. The
27454 value of @var{aschar} is used as a padding character when a byte is not a
27455 member of the printable @sc{ascii} character set (printable @sc{ascii}
27456 characters are those whose code is between 32 and 126, inclusively).
27458 @item @var{byte-offset}
27459 An offset to add to the @var{address} before fetching memory.
27462 This command displays memory contents as a table of @var{nr-rows} by
27463 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
27464 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
27465 (returned as @samp{total-bytes}). Should less than the requested number
27466 of bytes be returned by the target, the missing words are identified
27467 using @samp{N/A}. The number of bytes read from the target is returned
27468 in @samp{nr-bytes} and the starting address used to read memory in
27471 The address of the next/previous row or page is available in
27472 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
27475 @subsubheading @value{GDBN} Command
27477 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
27478 @samp{gdb_get_mem} memory read command.
27480 @subsubheading Example
27482 Read six bytes of memory starting at @code{bytes+6} but then offset by
27483 @code{-6} bytes. Format as three rows of two columns. One byte per
27484 word. Display each word in hex.
27488 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
27489 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
27490 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
27491 prev-page="0x0000138a",memory=[
27492 @{addr="0x00001390",data=["0x00","0x01"]@},
27493 @{addr="0x00001392",data=["0x02","0x03"]@},
27494 @{addr="0x00001394",data=["0x04","0x05"]@}]
27498 Read two bytes of memory starting at address @code{shorts + 64} and
27499 display as a single word formatted in decimal.
27503 5-data-read-memory shorts+64 d 2 1 1
27504 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
27505 next-row="0x00001512",prev-row="0x0000150e",
27506 next-page="0x00001512",prev-page="0x0000150e",memory=[
27507 @{addr="0x00001510",data=["128"]@}]
27511 Read thirty two bytes of memory starting at @code{bytes+16} and format
27512 as eight rows of four columns. Include a string encoding with @samp{x}
27513 used as the non-printable character.
27517 4-data-read-memory bytes+16 x 1 8 4 x
27518 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
27519 next-row="0x000013c0",prev-row="0x0000139c",
27520 next-page="0x000013c0",prev-page="0x00001380",memory=[
27521 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
27522 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
27523 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
27524 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
27525 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
27526 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
27527 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
27528 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
27532 @subheading The @code{-data-read-memory-bytes} Command
27533 @findex -data-read-memory-bytes
27535 @subsubheading Synopsis
27538 -data-read-memory-bytes [ -o @var{byte-offset} ]
27539 @var{address} @var{count}
27546 @item @var{address}
27547 An expression specifying the address of the first memory word to be
27548 read. Complex expressions containing embedded white space should be
27549 quoted using the C convention.
27552 The number of bytes to read. This should be an integer literal.
27554 @item @var{byte-offset}
27555 The offsets in bytes relative to @var{address} at which to start
27556 reading. This should be an integer literal. This option is provided
27557 so that a frontend is not required to first evaluate address and then
27558 perform address arithmetics itself.
27562 This command attempts to read all accessible memory regions in the
27563 specified range. First, all regions marked as unreadable in the memory
27564 map (if one is defined) will be skipped. @xref{Memory Region
27565 Attributes}. Second, @value{GDBN} will attempt to read the remaining
27566 regions. For each one, if reading full region results in an errors,
27567 @value{GDBN} will try to read a subset of the region.
27569 In general, every single byte in the region may be readable or not,
27570 and the only way to read every readable byte is to try a read at
27571 every address, which is not practical. Therefore, @value{GDBN} will
27572 attempt to read all accessible bytes at either beginning or the end
27573 of the region, using a binary division scheme. This heuristic works
27574 well for reading accross a memory map boundary. Note that if a region
27575 has a readable range that is neither at the beginning or the end,
27576 @value{GDBN} will not read it.
27578 The result record (@pxref{GDB/MI Result Records}) that is output of
27579 the command includes a field named @samp{memory} whose content is a
27580 list of tuples. Each tuple represent a successfully read memory block
27581 and has the following fields:
27585 The start address of the memory block, as hexadecimal literal.
27588 The end address of the memory block, as hexadecimal literal.
27591 The offset of the memory block, as hexadecimal literal, relative to
27592 the start address passed to @code{-data-read-memory-bytes}.
27595 The contents of the memory block, in hex.
27601 @subsubheading @value{GDBN} Command
27603 The corresponding @value{GDBN} command is @samp{x}.
27605 @subsubheading Example
27609 -data-read-memory-bytes &a 10
27610 ^done,memory=[@{begin="0xbffff154",offset="0x00000000",
27612 contents="01000000020000000300"@}]
27617 @subheading The @code{-data-write-memory-bytes} Command
27618 @findex -data-write-memory-bytes
27620 @subsubheading Synopsis
27623 -data-write-memory-bytes @var{address} @var{contents}
27630 @item @var{address}
27631 An expression specifying the address of the first memory word to be
27632 read. Complex expressions containing embedded white space should be
27633 quoted using the C convention.
27635 @item @var{contents}
27636 The hex-encoded bytes to write.
27640 @subsubheading @value{GDBN} Command
27642 There's no corresponding @value{GDBN} command.
27644 @subsubheading Example
27648 -data-write-memory-bytes &a "aabbccdd"
27654 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27655 @node GDB/MI Tracepoint Commands
27656 @section @sc{gdb/mi} Tracepoint Commands
27658 The commands defined in this section implement MI support for
27659 tracepoints. For detailed introduction, see @ref{Tracepoints}.
27661 @subheading The @code{-trace-find} Command
27662 @findex -trace-find
27664 @subsubheading Synopsis
27667 -trace-find @var{mode} [@var{parameters}@dots{}]
27670 Find a trace frame using criteria defined by @var{mode} and
27671 @var{parameters}. The following table lists permissible
27672 modes and their parameters. For details of operation, see @ref{tfind}.
27677 No parameters are required. Stops examining trace frames.
27680 An integer is required as parameter. Selects tracepoint frame with
27683 @item tracepoint-number
27684 An integer is required as parameter. Finds next
27685 trace frame that corresponds to tracepoint with the specified number.
27688 An address is required as parameter. Finds
27689 next trace frame that corresponds to any tracepoint at the specified
27692 @item pc-inside-range
27693 Two addresses are required as parameters. Finds next trace
27694 frame that corresponds to a tracepoint at an address inside the
27695 specified range. Both bounds are considered to be inside the range.
27697 @item pc-outside-range
27698 Two addresses are required as parameters. Finds
27699 next trace frame that corresponds to a tracepoint at an address outside
27700 the specified range. Both bounds are considered to be inside the range.
27703 Line specification is required as parameter. @xref{Specify Location}.
27704 Finds next trace frame that corresponds to a tracepoint at
27705 the specified location.
27709 If @samp{none} was passed as @var{mode}, the response does not
27710 have fields. Otherwise, the response may have the following fields:
27714 This field has either @samp{0} or @samp{1} as the value, depending
27715 on whether a matching tracepoint was found.
27718 The index of the found traceframe. This field is present iff
27719 the @samp{found} field has value of @samp{1}.
27722 The index of the found tracepoint. This field is present iff
27723 the @samp{found} field has value of @samp{1}.
27726 The information about the frame corresponding to the found trace
27727 frame. This field is present only if a trace frame was found.
27728 @xref{GDB/MI Frame Information}, for description of this field.
27732 @subsubheading @value{GDBN} Command
27734 The corresponding @value{GDBN} command is @samp{tfind}.
27736 @subheading -trace-define-variable
27737 @findex -trace-define-variable
27739 @subsubheading Synopsis
27742 -trace-define-variable @var{name} [ @var{value} ]
27745 Create trace variable @var{name} if it does not exist. If
27746 @var{value} is specified, sets the initial value of the specified
27747 trace variable to that value. Note that the @var{name} should start
27748 with the @samp{$} character.
27750 @subsubheading @value{GDBN} Command
27752 The corresponding @value{GDBN} command is @samp{tvariable}.
27754 @subheading -trace-list-variables
27755 @findex -trace-list-variables
27757 @subsubheading Synopsis
27760 -trace-list-variables
27763 Return a table of all defined trace variables. Each element of the
27764 table has the following fields:
27768 The name of the trace variable. This field is always present.
27771 The initial value. This is a 64-bit signed integer. This
27772 field is always present.
27775 The value the trace variable has at the moment. This is a 64-bit
27776 signed integer. This field is absent iff current value is
27777 not defined, for example if the trace was never run, or is
27782 @subsubheading @value{GDBN} Command
27784 The corresponding @value{GDBN} command is @samp{tvariables}.
27786 @subsubheading Example
27790 -trace-list-variables
27791 ^done,trace-variables=@{nr_rows="1",nr_cols="3",
27792 hdr=[@{width="15",alignment="-1",col_name="name",colhdr="Name"@},
27793 @{width="11",alignment="-1",col_name="initial",colhdr="Initial"@},
27794 @{width="11",alignment="-1",col_name="current",colhdr="Current"@}],
27795 body=[variable=@{name="$trace_timestamp",initial="0"@}
27796 variable=@{name="$foo",initial="10",current="15"@}]@}
27800 @subheading -trace-save
27801 @findex -trace-save
27803 @subsubheading Synopsis
27806 -trace-save [-r ] @var{filename}
27809 Saves the collected trace data to @var{filename}. Without the
27810 @samp{-r} option, the data is downloaded from the target and saved
27811 in a local file. With the @samp{-r} option the target is asked
27812 to perform the save.
27814 @subsubheading @value{GDBN} Command
27816 The corresponding @value{GDBN} command is @samp{tsave}.
27819 @subheading -trace-start
27820 @findex -trace-start
27822 @subsubheading Synopsis
27828 Starts a tracing experiments. The result of this command does not
27831 @subsubheading @value{GDBN} Command
27833 The corresponding @value{GDBN} command is @samp{tstart}.
27835 @subheading -trace-status
27836 @findex -trace-status
27838 @subsubheading Synopsis
27844 Obtains the status of a tracing experiment. The result may include
27845 the following fields:
27850 May have a value of either @samp{0}, when no tracing operations are
27851 supported, @samp{1}, when all tracing operations are supported, or
27852 @samp{file} when examining trace file. In the latter case, examining
27853 of trace frame is possible but new tracing experiement cannot be
27854 started. This field is always present.
27857 May have a value of either @samp{0} or @samp{1} depending on whether
27858 tracing experiement is in progress on target. This field is present
27859 if @samp{supported} field is not @samp{0}.
27862 Report the reason why the tracing was stopped last time. This field
27863 may be absent iff tracing was never stopped on target yet. The
27864 value of @samp{request} means the tracing was stopped as result of
27865 the @code{-trace-stop} command. The value of @samp{overflow} means
27866 the tracing buffer is full. The value of @samp{disconnection} means
27867 tracing was automatically stopped when @value{GDBN} has disconnected.
27868 The value of @samp{passcount} means tracing was stopped when a
27869 tracepoint was passed a maximal number of times for that tracepoint.
27870 This field is present if @samp{supported} field is not @samp{0}.
27872 @item stopping-tracepoint
27873 The number of tracepoint whose passcount as exceeded. This field is
27874 present iff the @samp{stop-reason} field has the value of
27878 @itemx frames-created
27879 The @samp{frames} field is a count of the total number of trace frames
27880 in the trace buffer, while @samp{frames-created} is the total created
27881 during the run, including ones that were discarded, such as when a
27882 circular trace buffer filled up. Both fields are optional.
27886 These fields tell the current size of the tracing buffer and the
27887 remaining space. These fields are optional.
27890 The value of the circular trace buffer flag. @code{1} means that the
27891 trace buffer is circular and old trace frames will be discarded if
27892 necessary to make room, @code{0} means that the trace buffer is linear
27896 The value of the disconnected tracing flag. @code{1} means that
27897 tracing will continue after @value{GDBN} disconnects, @code{0} means
27898 that the trace run will stop.
27902 @subsubheading @value{GDBN} Command
27904 The corresponding @value{GDBN} command is @samp{tstatus}.
27906 @subheading -trace-stop
27907 @findex -trace-stop
27909 @subsubheading Synopsis
27915 Stops a tracing experiment. The result of this command has the same
27916 fields as @code{-trace-status}, except that the @samp{supported} and
27917 @samp{running} fields are not output.
27919 @subsubheading @value{GDBN} Command
27921 The corresponding @value{GDBN} command is @samp{tstop}.
27924 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27925 @node GDB/MI Symbol Query
27926 @section @sc{gdb/mi} Symbol Query Commands
27930 @subheading The @code{-symbol-info-address} Command
27931 @findex -symbol-info-address
27933 @subsubheading Synopsis
27936 -symbol-info-address @var{symbol}
27939 Describe where @var{symbol} is stored.
27941 @subsubheading @value{GDBN} Command
27943 The corresponding @value{GDBN} command is @samp{info address}.
27945 @subsubheading Example
27949 @subheading The @code{-symbol-info-file} Command
27950 @findex -symbol-info-file
27952 @subsubheading Synopsis
27958 Show the file for the symbol.
27960 @subsubheading @value{GDBN} Command
27962 There's no equivalent @value{GDBN} command. @code{gdbtk} has
27963 @samp{gdb_find_file}.
27965 @subsubheading Example
27969 @subheading The @code{-symbol-info-function} Command
27970 @findex -symbol-info-function
27972 @subsubheading Synopsis
27975 -symbol-info-function
27978 Show which function the symbol lives in.
27980 @subsubheading @value{GDBN} Command
27982 @samp{gdb_get_function} in @code{gdbtk}.
27984 @subsubheading Example
27988 @subheading The @code{-symbol-info-line} Command
27989 @findex -symbol-info-line
27991 @subsubheading Synopsis
27997 Show the core addresses of the code for a source line.
27999 @subsubheading @value{GDBN} Command
28001 The corresponding @value{GDBN} command is @samp{info line}.
28002 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
28004 @subsubheading Example
28008 @subheading The @code{-symbol-info-symbol} Command
28009 @findex -symbol-info-symbol
28011 @subsubheading Synopsis
28014 -symbol-info-symbol @var{addr}
28017 Describe what symbol is at location @var{addr}.
28019 @subsubheading @value{GDBN} Command
28021 The corresponding @value{GDBN} command is @samp{info symbol}.
28023 @subsubheading Example
28027 @subheading The @code{-symbol-list-functions} Command
28028 @findex -symbol-list-functions
28030 @subsubheading Synopsis
28033 -symbol-list-functions
28036 List the functions in the executable.
28038 @subsubheading @value{GDBN} Command
28040 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
28041 @samp{gdb_search} in @code{gdbtk}.
28043 @subsubheading Example
28048 @subheading The @code{-symbol-list-lines} Command
28049 @findex -symbol-list-lines
28051 @subsubheading Synopsis
28054 -symbol-list-lines @var{filename}
28057 Print the list of lines that contain code and their associated program
28058 addresses for the given source filename. The entries are sorted in
28059 ascending PC order.
28061 @subsubheading @value{GDBN} Command
28063 There is no corresponding @value{GDBN} command.
28065 @subsubheading Example
28068 -symbol-list-lines basics.c
28069 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
28075 @subheading The @code{-symbol-list-types} Command
28076 @findex -symbol-list-types
28078 @subsubheading Synopsis
28084 List all the type names.
28086 @subsubheading @value{GDBN} Command
28088 The corresponding commands are @samp{info types} in @value{GDBN},
28089 @samp{gdb_search} in @code{gdbtk}.
28091 @subsubheading Example
28095 @subheading The @code{-symbol-list-variables} Command
28096 @findex -symbol-list-variables
28098 @subsubheading Synopsis
28101 -symbol-list-variables
28104 List all the global and static variable names.
28106 @subsubheading @value{GDBN} Command
28108 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
28110 @subsubheading Example
28114 @subheading The @code{-symbol-locate} Command
28115 @findex -symbol-locate
28117 @subsubheading Synopsis
28123 @subsubheading @value{GDBN} Command
28125 @samp{gdb_loc} in @code{gdbtk}.
28127 @subsubheading Example
28131 @subheading The @code{-symbol-type} Command
28132 @findex -symbol-type
28134 @subsubheading Synopsis
28137 -symbol-type @var{variable}
28140 Show type of @var{variable}.
28142 @subsubheading @value{GDBN} Command
28144 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
28145 @samp{gdb_obj_variable}.
28147 @subsubheading Example
28152 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28153 @node GDB/MI File Commands
28154 @section @sc{gdb/mi} File Commands
28156 This section describes the GDB/MI commands to specify executable file names
28157 and to read in and obtain symbol table information.
28159 @subheading The @code{-file-exec-and-symbols} Command
28160 @findex -file-exec-and-symbols
28162 @subsubheading Synopsis
28165 -file-exec-and-symbols @var{file}
28168 Specify the executable file to be debugged. This file is the one from
28169 which the symbol table is also read. If no file is specified, the
28170 command clears the executable and symbol information. If breakpoints
28171 are set when using this command with no arguments, @value{GDBN} will produce
28172 error messages. Otherwise, no output is produced, except a completion
28175 @subsubheading @value{GDBN} Command
28177 The corresponding @value{GDBN} command is @samp{file}.
28179 @subsubheading Example
28183 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
28189 @subheading The @code{-file-exec-file} Command
28190 @findex -file-exec-file
28192 @subsubheading Synopsis
28195 -file-exec-file @var{file}
28198 Specify the executable file to be debugged. Unlike
28199 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
28200 from this file. If used without argument, @value{GDBN} clears the information
28201 about the executable file. No output is produced, except a completion
28204 @subsubheading @value{GDBN} Command
28206 The corresponding @value{GDBN} command is @samp{exec-file}.
28208 @subsubheading Example
28212 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
28219 @subheading The @code{-file-list-exec-sections} Command
28220 @findex -file-list-exec-sections
28222 @subsubheading Synopsis
28225 -file-list-exec-sections
28228 List the sections of the current executable file.
28230 @subsubheading @value{GDBN} Command
28232 The @value{GDBN} command @samp{info file} shows, among the rest, the same
28233 information as this command. @code{gdbtk} has a corresponding command
28234 @samp{gdb_load_info}.
28236 @subsubheading Example
28241 @subheading The @code{-file-list-exec-source-file} Command
28242 @findex -file-list-exec-source-file
28244 @subsubheading Synopsis
28247 -file-list-exec-source-file
28250 List the line number, the current source file, and the absolute path
28251 to the current source file for the current executable. The macro
28252 information field has a value of @samp{1} or @samp{0} depending on
28253 whether or not the file includes preprocessor macro information.
28255 @subsubheading @value{GDBN} Command
28257 The @value{GDBN} equivalent is @samp{info source}
28259 @subsubheading Example
28263 123-file-list-exec-source-file
28264 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c,macro-info="1"
28269 @subheading The @code{-file-list-exec-source-files} Command
28270 @findex -file-list-exec-source-files
28272 @subsubheading Synopsis
28275 -file-list-exec-source-files
28278 List the source files for the current executable.
28280 It will always output the filename, but only when @value{GDBN} can find
28281 the absolute file name of a source file, will it output the fullname.
28283 @subsubheading @value{GDBN} Command
28285 The @value{GDBN} equivalent is @samp{info sources}.
28286 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
28288 @subsubheading Example
28291 -file-list-exec-source-files
28293 @{file=foo.c,fullname=/home/foo.c@},
28294 @{file=/home/bar.c,fullname=/home/bar.c@},
28295 @{file=gdb_could_not_find_fullpath.c@}]
28300 @subheading The @code{-file-list-shared-libraries} Command
28301 @findex -file-list-shared-libraries
28303 @subsubheading Synopsis
28306 -file-list-shared-libraries
28309 List the shared libraries in the program.
28311 @subsubheading @value{GDBN} Command
28313 The corresponding @value{GDBN} command is @samp{info shared}.
28315 @subsubheading Example
28319 @subheading The @code{-file-list-symbol-files} Command
28320 @findex -file-list-symbol-files
28322 @subsubheading Synopsis
28325 -file-list-symbol-files
28330 @subsubheading @value{GDBN} Command
28332 The corresponding @value{GDBN} command is @samp{info file} (part of it).
28334 @subsubheading Example
28339 @subheading The @code{-file-symbol-file} Command
28340 @findex -file-symbol-file
28342 @subsubheading Synopsis
28345 -file-symbol-file @var{file}
28348 Read symbol table info from the specified @var{file} argument. When
28349 used without arguments, clears @value{GDBN}'s symbol table info. No output is
28350 produced, except for a completion notification.
28352 @subsubheading @value{GDBN} Command
28354 The corresponding @value{GDBN} command is @samp{symbol-file}.
28356 @subsubheading Example
28360 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
28366 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28367 @node GDB/MI Memory Overlay Commands
28368 @section @sc{gdb/mi} Memory Overlay Commands
28370 The memory overlay commands are not implemented.
28372 @c @subheading -overlay-auto
28374 @c @subheading -overlay-list-mapping-state
28376 @c @subheading -overlay-list-overlays
28378 @c @subheading -overlay-map
28380 @c @subheading -overlay-off
28382 @c @subheading -overlay-on
28384 @c @subheading -overlay-unmap
28386 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28387 @node GDB/MI Signal Handling Commands
28388 @section @sc{gdb/mi} Signal Handling Commands
28390 Signal handling commands are not implemented.
28392 @c @subheading -signal-handle
28394 @c @subheading -signal-list-handle-actions
28396 @c @subheading -signal-list-signal-types
28400 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28401 @node GDB/MI Target Manipulation
28402 @section @sc{gdb/mi} Target Manipulation Commands
28405 @subheading The @code{-target-attach} Command
28406 @findex -target-attach
28408 @subsubheading Synopsis
28411 -target-attach @var{pid} | @var{gid} | @var{file}
28414 Attach to a process @var{pid} or a file @var{file} outside of
28415 @value{GDBN}, or a thread group @var{gid}. If attaching to a thread
28416 group, the id previously returned by
28417 @samp{-list-thread-groups --available} must be used.
28419 @subsubheading @value{GDBN} Command
28421 The corresponding @value{GDBN} command is @samp{attach}.
28423 @subsubheading Example
28427 =thread-created,id="1"
28428 *stopped,thread-id="1",frame=@{addr="0xb7f7e410",func="bar",args=[]@}
28434 @subheading The @code{-target-compare-sections} Command
28435 @findex -target-compare-sections
28437 @subsubheading Synopsis
28440 -target-compare-sections [ @var{section} ]
28443 Compare data of section @var{section} on target to the exec file.
28444 Without the argument, all sections are compared.
28446 @subsubheading @value{GDBN} Command
28448 The @value{GDBN} equivalent is @samp{compare-sections}.
28450 @subsubheading Example
28455 @subheading The @code{-target-detach} Command
28456 @findex -target-detach
28458 @subsubheading Synopsis
28461 -target-detach [ @var{pid} | @var{gid} ]
28464 Detach from the remote target which normally resumes its execution.
28465 If either @var{pid} or @var{gid} is specified, detaches from either
28466 the specified process, or specified thread group. There's no output.
28468 @subsubheading @value{GDBN} Command
28470 The corresponding @value{GDBN} command is @samp{detach}.
28472 @subsubheading Example
28482 @subheading The @code{-target-disconnect} Command
28483 @findex -target-disconnect
28485 @subsubheading Synopsis
28491 Disconnect from the remote target. There's no output and the target is
28492 generally not resumed.
28494 @subsubheading @value{GDBN} Command
28496 The corresponding @value{GDBN} command is @samp{disconnect}.
28498 @subsubheading Example
28508 @subheading The @code{-target-download} Command
28509 @findex -target-download
28511 @subsubheading Synopsis
28517 Loads the executable onto the remote target.
28518 It prints out an update message every half second, which includes the fields:
28522 The name of the section.
28524 The size of what has been sent so far for that section.
28526 The size of the section.
28528 The total size of what was sent so far (the current and the previous sections).
28530 The size of the overall executable to download.
28534 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
28535 @sc{gdb/mi} Output Syntax}).
28537 In addition, it prints the name and size of the sections, as they are
28538 downloaded. These messages include the following fields:
28542 The name of the section.
28544 The size of the section.
28546 The size of the overall executable to download.
28550 At the end, a summary is printed.
28552 @subsubheading @value{GDBN} Command
28554 The corresponding @value{GDBN} command is @samp{load}.
28556 @subsubheading Example
28558 Note: each status message appears on a single line. Here the messages
28559 have been broken down so that they can fit onto a page.
28564 +download,@{section=".text",section-size="6668",total-size="9880"@}
28565 +download,@{section=".text",section-sent="512",section-size="6668",
28566 total-sent="512",total-size="9880"@}
28567 +download,@{section=".text",section-sent="1024",section-size="6668",
28568 total-sent="1024",total-size="9880"@}
28569 +download,@{section=".text",section-sent="1536",section-size="6668",
28570 total-sent="1536",total-size="9880"@}
28571 +download,@{section=".text",section-sent="2048",section-size="6668",
28572 total-sent="2048",total-size="9880"@}
28573 +download,@{section=".text",section-sent="2560",section-size="6668",
28574 total-sent="2560",total-size="9880"@}
28575 +download,@{section=".text",section-sent="3072",section-size="6668",
28576 total-sent="3072",total-size="9880"@}
28577 +download,@{section=".text",section-sent="3584",section-size="6668",
28578 total-sent="3584",total-size="9880"@}
28579 +download,@{section=".text",section-sent="4096",section-size="6668",
28580 total-sent="4096",total-size="9880"@}
28581 +download,@{section=".text",section-sent="4608",section-size="6668",
28582 total-sent="4608",total-size="9880"@}
28583 +download,@{section=".text",section-sent="5120",section-size="6668",
28584 total-sent="5120",total-size="9880"@}
28585 +download,@{section=".text",section-sent="5632",section-size="6668",
28586 total-sent="5632",total-size="9880"@}
28587 +download,@{section=".text",section-sent="6144",section-size="6668",
28588 total-sent="6144",total-size="9880"@}
28589 +download,@{section=".text",section-sent="6656",section-size="6668",
28590 total-sent="6656",total-size="9880"@}
28591 +download,@{section=".init",section-size="28",total-size="9880"@}
28592 +download,@{section=".fini",section-size="28",total-size="9880"@}
28593 +download,@{section=".data",section-size="3156",total-size="9880"@}
28594 +download,@{section=".data",section-sent="512",section-size="3156",
28595 total-sent="7236",total-size="9880"@}
28596 +download,@{section=".data",section-sent="1024",section-size="3156",
28597 total-sent="7748",total-size="9880"@}
28598 +download,@{section=".data",section-sent="1536",section-size="3156",
28599 total-sent="8260",total-size="9880"@}
28600 +download,@{section=".data",section-sent="2048",section-size="3156",
28601 total-sent="8772",total-size="9880"@}
28602 +download,@{section=".data",section-sent="2560",section-size="3156",
28603 total-sent="9284",total-size="9880"@}
28604 +download,@{section=".data",section-sent="3072",section-size="3156",
28605 total-sent="9796",total-size="9880"@}
28606 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
28613 @subheading The @code{-target-exec-status} Command
28614 @findex -target-exec-status
28616 @subsubheading Synopsis
28619 -target-exec-status
28622 Provide information on the state of the target (whether it is running or
28623 not, for instance).
28625 @subsubheading @value{GDBN} Command
28627 There's no equivalent @value{GDBN} command.
28629 @subsubheading Example
28633 @subheading The @code{-target-list-available-targets} Command
28634 @findex -target-list-available-targets
28636 @subsubheading Synopsis
28639 -target-list-available-targets
28642 List the possible targets to connect to.
28644 @subsubheading @value{GDBN} Command
28646 The corresponding @value{GDBN} command is @samp{help target}.
28648 @subsubheading Example
28652 @subheading The @code{-target-list-current-targets} Command
28653 @findex -target-list-current-targets
28655 @subsubheading Synopsis
28658 -target-list-current-targets
28661 Describe the current target.
28663 @subsubheading @value{GDBN} Command
28665 The corresponding information is printed by @samp{info file} (among
28668 @subsubheading Example
28672 @subheading The @code{-target-list-parameters} Command
28673 @findex -target-list-parameters
28675 @subsubheading Synopsis
28678 -target-list-parameters
28684 @subsubheading @value{GDBN} Command
28688 @subsubheading Example
28692 @subheading The @code{-target-select} Command
28693 @findex -target-select
28695 @subsubheading Synopsis
28698 -target-select @var{type} @var{parameters @dots{}}
28701 Connect @value{GDBN} to the remote target. This command takes two args:
28705 The type of target, for instance @samp{remote}, etc.
28706 @item @var{parameters}
28707 Device names, host names and the like. @xref{Target Commands, ,
28708 Commands for Managing Targets}, for more details.
28711 The output is a connection notification, followed by the address at
28712 which the target program is, in the following form:
28715 ^connected,addr="@var{address}",func="@var{function name}",
28716 args=[@var{arg list}]
28719 @subsubheading @value{GDBN} Command
28721 The corresponding @value{GDBN} command is @samp{target}.
28723 @subsubheading Example
28727 -target-select remote /dev/ttya
28728 ^connected,addr="0xfe00a300",func="??",args=[]
28732 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28733 @node GDB/MI File Transfer Commands
28734 @section @sc{gdb/mi} File Transfer Commands
28737 @subheading The @code{-target-file-put} Command
28738 @findex -target-file-put
28740 @subsubheading Synopsis
28743 -target-file-put @var{hostfile} @var{targetfile}
28746 Copy file @var{hostfile} from the host system (the machine running
28747 @value{GDBN}) to @var{targetfile} on the target system.
28749 @subsubheading @value{GDBN} Command
28751 The corresponding @value{GDBN} command is @samp{remote put}.
28753 @subsubheading Example
28757 -target-file-put localfile remotefile
28763 @subheading The @code{-target-file-get} Command
28764 @findex -target-file-get
28766 @subsubheading Synopsis
28769 -target-file-get @var{targetfile} @var{hostfile}
28772 Copy file @var{targetfile} from the target system to @var{hostfile}
28773 on the host system.
28775 @subsubheading @value{GDBN} Command
28777 The corresponding @value{GDBN} command is @samp{remote get}.
28779 @subsubheading Example
28783 -target-file-get remotefile localfile
28789 @subheading The @code{-target-file-delete} Command
28790 @findex -target-file-delete
28792 @subsubheading Synopsis
28795 -target-file-delete @var{targetfile}
28798 Delete @var{targetfile} from the target system.
28800 @subsubheading @value{GDBN} Command
28802 The corresponding @value{GDBN} command is @samp{remote delete}.
28804 @subsubheading Example
28808 -target-file-delete remotefile
28814 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28815 @node GDB/MI Miscellaneous Commands
28816 @section Miscellaneous @sc{gdb/mi} Commands
28818 @c @subheading -gdb-complete
28820 @subheading The @code{-gdb-exit} Command
28823 @subsubheading Synopsis
28829 Exit @value{GDBN} immediately.
28831 @subsubheading @value{GDBN} Command
28833 Approximately corresponds to @samp{quit}.
28835 @subsubheading Example
28845 @subheading The @code{-exec-abort} Command
28846 @findex -exec-abort
28848 @subsubheading Synopsis
28854 Kill the inferior running program.
28856 @subsubheading @value{GDBN} Command
28858 The corresponding @value{GDBN} command is @samp{kill}.
28860 @subsubheading Example
28865 @subheading The @code{-gdb-set} Command
28868 @subsubheading Synopsis
28874 Set an internal @value{GDBN} variable.
28875 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
28877 @subsubheading @value{GDBN} Command
28879 The corresponding @value{GDBN} command is @samp{set}.
28881 @subsubheading Example
28891 @subheading The @code{-gdb-show} Command
28894 @subsubheading Synopsis
28900 Show the current value of a @value{GDBN} variable.
28902 @subsubheading @value{GDBN} Command
28904 The corresponding @value{GDBN} command is @samp{show}.
28906 @subsubheading Example
28915 @c @subheading -gdb-source
28918 @subheading The @code{-gdb-version} Command
28919 @findex -gdb-version
28921 @subsubheading Synopsis
28927 Show version information for @value{GDBN}. Used mostly in testing.
28929 @subsubheading @value{GDBN} Command
28931 The @value{GDBN} equivalent is @samp{show version}. @value{GDBN} by
28932 default shows this information when you start an interactive session.
28934 @subsubheading Example
28936 @c This example modifies the actual output from GDB to avoid overfull
28942 ~Copyright 2000 Free Software Foundation, Inc.
28943 ~GDB is free software, covered by the GNU General Public License, and
28944 ~you are welcome to change it and/or distribute copies of it under
28945 ~ certain conditions.
28946 ~Type "show copying" to see the conditions.
28947 ~There is absolutely no warranty for GDB. Type "show warranty" for
28949 ~This GDB was configured as
28950 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
28955 @subheading The @code{-list-features} Command
28956 @findex -list-features
28958 Returns a list of particular features of the MI protocol that
28959 this version of gdb implements. A feature can be a command,
28960 or a new field in an output of some command, or even an
28961 important bugfix. While a frontend can sometimes detect presence
28962 of a feature at runtime, it is easier to perform detection at debugger
28965 The command returns a list of strings, with each string naming an
28966 available feature. Each returned string is just a name, it does not
28967 have any internal structure. The list of possible feature names
28973 (gdb) -list-features
28974 ^done,result=["feature1","feature2"]
28977 The current list of features is:
28980 @item frozen-varobjs
28981 Indicates presence of the @code{-var-set-frozen} command, as well
28982 as possible presense of the @code{frozen} field in the output
28983 of @code{-varobj-create}.
28984 @item pending-breakpoints
28985 Indicates presence of the @option{-f} option to the @code{-break-insert} command.
28987 Indicates presence of Python scripting support, Python-based
28988 pretty-printing commands, and possible presence of the
28989 @samp{display_hint} field in the output of @code{-var-list-children}
28991 Indicates presence of the @code{-thread-info} command.
28992 @item data-read-memory-bytes
28993 Indicates presense of the @code{-data-read-memory-bytes} and the
28994 @code{-data-write-memory-bytes} commands.
28998 @subheading The @code{-list-target-features} Command
28999 @findex -list-target-features
29001 Returns a list of particular features that are supported by the
29002 target. Those features affect the permitted MI commands, but
29003 unlike the features reported by the @code{-list-features} command, the
29004 features depend on which target GDB is using at the moment. Whenever
29005 a target can change, due to commands such as @code{-target-select},
29006 @code{-target-attach} or @code{-exec-run}, the list of target features
29007 may change, and the frontend should obtain it again.
29011 (gdb) -list-features
29012 ^done,result=["async"]
29015 The current list of features is:
29019 Indicates that the target is capable of asynchronous command
29020 execution, which means that @value{GDBN} will accept further commands
29021 while the target is running.
29025 @subheading The @code{-list-thread-groups} Command
29026 @findex -list-thread-groups
29028 @subheading Synopsis
29031 -list-thread-groups [ --available ] [ --recurse 1 ] [ @var{group} ... ]
29034 Lists thread groups (@pxref{Thread groups}). When a single thread
29035 group is passed as the argument, lists the children of that group.
29036 When several thread group are passed, lists information about those
29037 thread groups. Without any parameters, lists information about all
29038 top-level thread groups.
29040 Normally, thread groups that are being debugged are reported.
29041 With the @samp{--available} option, @value{GDBN} reports thread groups
29042 available on the target.
29044 The output of this command may have either a @samp{threads} result or
29045 a @samp{groups} result. The @samp{thread} result has a list of tuples
29046 as value, with each tuple describing a thread (@pxref{GDB/MI Thread
29047 Information}). The @samp{groups} result has a list of tuples as value,
29048 each tuple describing a thread group. If top-level groups are
29049 requested (that is, no parameter is passed), or when several groups
29050 are passed, the output always has a @samp{groups} result. The format
29051 of the @samp{group} result is described below.
29053 To reduce the number of roundtrips it's possible to list thread groups
29054 together with their children, by passing the @samp{--recurse} option
29055 and the recursion depth. Presently, only recursion depth of 1 is
29056 permitted. If this option is present, then every reported thread group
29057 will also include its children, either as @samp{group} or
29058 @samp{threads} field.
29060 In general, any combination of option and parameters is permitted, with
29061 the following caveats:
29065 When a single thread group is passed, the output will typically
29066 be the @samp{threads} result. Because threads may not contain
29067 anything, the @samp{recurse} option will be ignored.
29070 When the @samp{--available} option is passed, limited information may
29071 be available. In particular, the list of threads of a process might
29072 be inaccessible. Further, specifying specific thread groups might
29073 not give any performance advantage over listing all thread groups.
29074 The frontend should assume that @samp{-list-thread-groups --available}
29075 is always an expensive operation and cache the results.
29079 The @samp{groups} result is a list of tuples, where each tuple may
29080 have the following fields:
29084 Identifier of the thread group. This field is always present.
29085 The identifier is an opaque string; frontends should not try to
29086 convert it to an integer, even though it might look like one.
29089 The type of the thread group. At present, only @samp{process} is a
29093 The target-specific process identifier. This field is only present
29094 for thread groups of type @samp{process} and only if the process exists.
29097 The number of children this thread group has. This field may be
29098 absent for an available thread group.
29101 This field has a list of tuples as value, each tuple describing a
29102 thread. It may be present if the @samp{--recurse} option is
29103 specified, and it's actually possible to obtain the threads.
29106 This field is a list of integers, each identifying a core that one
29107 thread of the group is running on. This field may be absent if
29108 such information is not available.
29111 The name of the executable file that corresponds to this thread group.
29112 The field is only present for thread groups of type @samp{process},
29113 and only if there is a corresponding executable file.
29117 @subheading Example
29121 -list-thread-groups
29122 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2"@}]
29123 -list-thread-groups 17
29124 ^done,threads=[@{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
29125 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},state="running"@},
29126 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
29127 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
29128 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},state="running"@}]]
29129 -list-thread-groups --available
29130 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2",cores=[1,2]@}]
29131 -list-thread-groups --available --recurse 1
29132 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
29133 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
29134 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},..]
29135 -list-thread-groups --available --recurse 1 17 18
29136 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
29137 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
29138 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},...]
29142 @subheading The @code{-add-inferior} Command
29143 @findex -add-inferior
29145 @subheading Synopsis
29151 Creates a new inferior (@pxref{Inferiors and Programs}). The created
29152 inferior is not associated with any executable. Such association may
29153 be established with the @samp{-file-exec-and-symbols} command
29154 (@pxref{GDB/MI File Commands}). The command response has a single
29155 field, @samp{thread-group}, whose value is the identifier of the
29156 thread group corresponding to the new inferior.
29158 @subheading Example
29163 ^done,thread-group="i3"
29166 @subheading The @code{-interpreter-exec} Command
29167 @findex -interpreter-exec
29169 @subheading Synopsis
29172 -interpreter-exec @var{interpreter} @var{command}
29174 @anchor{-interpreter-exec}
29176 Execute the specified @var{command} in the given @var{interpreter}.
29178 @subheading @value{GDBN} Command
29180 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
29182 @subheading Example
29186 -interpreter-exec console "break main"
29187 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
29188 &"During symbol reading, bad structure-type format.\n"
29189 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
29194 @subheading The @code{-inferior-tty-set} Command
29195 @findex -inferior-tty-set
29197 @subheading Synopsis
29200 -inferior-tty-set /dev/pts/1
29203 Set terminal for future runs of the program being debugged.
29205 @subheading @value{GDBN} Command
29207 The corresponding @value{GDBN} command is @samp{set inferior-tty} /dev/pts/1.
29209 @subheading Example
29213 -inferior-tty-set /dev/pts/1
29218 @subheading The @code{-inferior-tty-show} Command
29219 @findex -inferior-tty-show
29221 @subheading Synopsis
29227 Show terminal for future runs of program being debugged.
29229 @subheading @value{GDBN} Command
29231 The corresponding @value{GDBN} command is @samp{show inferior-tty}.
29233 @subheading Example
29237 -inferior-tty-set /dev/pts/1
29241 ^done,inferior_tty_terminal="/dev/pts/1"
29245 @subheading The @code{-enable-timings} Command
29246 @findex -enable-timings
29248 @subheading Synopsis
29251 -enable-timings [yes | no]
29254 Toggle the printing of the wallclock, user and system times for an MI
29255 command as a field in its output. This command is to help frontend
29256 developers optimize the performance of their code. No argument is
29257 equivalent to @samp{yes}.
29259 @subheading @value{GDBN} Command
29263 @subheading Example
29271 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
29272 addr="0x080484ed",func="main",file="myprog.c",
29273 fullname="/home/nickrob/myprog.c",line="73",times="0"@},
29274 time=@{wallclock="0.05185",user="0.00800",system="0.00000"@}
29282 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
29283 frame=@{addr="0x080484ed",func="main",args=[@{name="argc",value="1"@},
29284 @{name="argv",value="0xbfb60364"@}],file="myprog.c",
29285 fullname="/home/nickrob/myprog.c",line="73"@}
29290 @chapter @value{GDBN} Annotations
29292 This chapter describes annotations in @value{GDBN}. Annotations were
29293 designed to interface @value{GDBN} to graphical user interfaces or other
29294 similar programs which want to interact with @value{GDBN} at a
29295 relatively high level.
29297 The annotation mechanism has largely been superseded by @sc{gdb/mi}
29301 This is Edition @value{EDITION}, @value{DATE}.
29305 * Annotations Overview:: What annotations are; the general syntax.
29306 * Server Prefix:: Issuing a command without affecting user state.
29307 * Prompting:: Annotations marking @value{GDBN}'s need for input.
29308 * Errors:: Annotations for error messages.
29309 * Invalidation:: Some annotations describe things now invalid.
29310 * Annotations for Running::
29311 Whether the program is running, how it stopped, etc.
29312 * Source Annotations:: Annotations describing source code.
29315 @node Annotations Overview
29316 @section What is an Annotation?
29317 @cindex annotations
29319 Annotations start with a newline character, two @samp{control-z}
29320 characters, and the name of the annotation. If there is no additional
29321 information associated with this annotation, the name of the annotation
29322 is followed immediately by a newline. If there is additional
29323 information, the name of the annotation is followed by a space, the
29324 additional information, and a newline. The additional information
29325 cannot contain newline characters.
29327 Any output not beginning with a newline and two @samp{control-z}
29328 characters denotes literal output from @value{GDBN}. Currently there is
29329 no need for @value{GDBN} to output a newline followed by two
29330 @samp{control-z} characters, but if there was such a need, the
29331 annotations could be extended with an @samp{escape} annotation which
29332 means those three characters as output.
29334 The annotation @var{level}, which is specified using the
29335 @option{--annotate} command line option (@pxref{Mode Options}), controls
29336 how much information @value{GDBN} prints together with its prompt,
29337 values of expressions, source lines, and other types of output. Level 0
29338 is for no annotations, level 1 is for use when @value{GDBN} is run as a
29339 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
29340 for programs that control @value{GDBN}, and level 2 annotations have
29341 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
29342 Interface, annotate, GDB's Obsolete Annotations}).
29345 @kindex set annotate
29346 @item set annotate @var{level}
29347 The @value{GDBN} command @code{set annotate} sets the level of
29348 annotations to the specified @var{level}.
29350 @item show annotate
29351 @kindex show annotate
29352 Show the current annotation level.
29355 This chapter describes level 3 annotations.
29357 A simple example of starting up @value{GDBN} with annotations is:
29360 $ @kbd{gdb --annotate=3}
29362 Copyright 2003 Free Software Foundation, Inc.
29363 GDB is free software, covered by the GNU General Public License,
29364 and you are welcome to change it and/or distribute copies of it
29365 under certain conditions.
29366 Type "show copying" to see the conditions.
29367 There is absolutely no warranty for GDB. Type "show warranty"
29369 This GDB was configured as "i386-pc-linux-gnu"
29380 Here @samp{quit} is input to @value{GDBN}; the rest is output from
29381 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
29382 denotes a @samp{control-z} character) are annotations; the rest is
29383 output from @value{GDBN}.
29385 @node Server Prefix
29386 @section The Server Prefix
29387 @cindex server prefix
29389 If you prefix a command with @samp{server } then it will not affect
29390 the command history, nor will it affect @value{GDBN}'s notion of which
29391 command to repeat if @key{RET} is pressed on a line by itself. This
29392 means that commands can be run behind a user's back by a front-end in
29393 a transparent manner.
29395 The @code{server } prefix does not affect the recording of values into
29396 the value history; to print a value without recording it into the
29397 value history, use the @code{output} command instead of the
29398 @code{print} command.
29400 Using this prefix also disables confirmation requests
29401 (@pxref{confirmation requests}).
29404 @section Annotation for @value{GDBN} Input
29406 @cindex annotations for prompts
29407 When @value{GDBN} prompts for input, it annotates this fact so it is possible
29408 to know when to send output, when the output from a given command is
29411 Different kinds of input each have a different @dfn{input type}. Each
29412 input type has three annotations: a @code{pre-} annotation, which
29413 denotes the beginning of any prompt which is being output, a plain
29414 annotation, which denotes the end of the prompt, and then a @code{post-}
29415 annotation which denotes the end of any echo which may (or may not) be
29416 associated with the input. For example, the @code{prompt} input type
29417 features the following annotations:
29425 The input types are
29428 @findex pre-prompt annotation
29429 @findex prompt annotation
29430 @findex post-prompt annotation
29432 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
29434 @findex pre-commands annotation
29435 @findex commands annotation
29436 @findex post-commands annotation
29438 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
29439 command. The annotations are repeated for each command which is input.
29441 @findex pre-overload-choice annotation
29442 @findex overload-choice annotation
29443 @findex post-overload-choice annotation
29444 @item overload-choice
29445 When @value{GDBN} wants the user to select between various overloaded functions.
29447 @findex pre-query annotation
29448 @findex query annotation
29449 @findex post-query annotation
29451 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
29453 @findex pre-prompt-for-continue annotation
29454 @findex prompt-for-continue annotation
29455 @findex post-prompt-for-continue annotation
29456 @item prompt-for-continue
29457 When @value{GDBN} is asking the user to press return to continue. Note: Don't
29458 expect this to work well; instead use @code{set height 0} to disable
29459 prompting. This is because the counting of lines is buggy in the
29460 presence of annotations.
29465 @cindex annotations for errors, warnings and interrupts
29467 @findex quit annotation
29472 This annotation occurs right before @value{GDBN} responds to an interrupt.
29474 @findex error annotation
29479 This annotation occurs right before @value{GDBN} responds to an error.
29481 Quit and error annotations indicate that any annotations which @value{GDBN} was
29482 in the middle of may end abruptly. For example, if a
29483 @code{value-history-begin} annotation is followed by a @code{error}, one
29484 cannot expect to receive the matching @code{value-history-end}. One
29485 cannot expect not to receive it either, however; an error annotation
29486 does not necessarily mean that @value{GDBN} is immediately returning all the way
29489 @findex error-begin annotation
29490 A quit or error annotation may be preceded by
29496 Any output between that and the quit or error annotation is the error
29499 Warning messages are not yet annotated.
29500 @c If we want to change that, need to fix warning(), type_error(),
29501 @c range_error(), and possibly other places.
29504 @section Invalidation Notices
29506 @cindex annotations for invalidation messages
29507 The following annotations say that certain pieces of state may have
29511 @findex frames-invalid annotation
29512 @item ^Z^Zframes-invalid
29514 The frames (for example, output from the @code{backtrace} command) may
29517 @findex breakpoints-invalid annotation
29518 @item ^Z^Zbreakpoints-invalid
29520 The breakpoints may have changed. For example, the user just added or
29521 deleted a breakpoint.
29524 @node Annotations for Running
29525 @section Running the Program
29526 @cindex annotations for running programs
29528 @findex starting annotation
29529 @findex stopping annotation
29530 When the program starts executing due to a @value{GDBN} command such as
29531 @code{step} or @code{continue},
29537 is output. When the program stops,
29543 is output. Before the @code{stopped} annotation, a variety of
29544 annotations describe how the program stopped.
29547 @findex exited annotation
29548 @item ^Z^Zexited @var{exit-status}
29549 The program exited, and @var{exit-status} is the exit status (zero for
29550 successful exit, otherwise nonzero).
29552 @findex signalled annotation
29553 @findex signal-name annotation
29554 @findex signal-name-end annotation
29555 @findex signal-string annotation
29556 @findex signal-string-end annotation
29557 @item ^Z^Zsignalled
29558 The program exited with a signal. After the @code{^Z^Zsignalled}, the
29559 annotation continues:
29565 ^Z^Zsignal-name-end
29569 ^Z^Zsignal-string-end
29574 where @var{name} is the name of the signal, such as @code{SIGILL} or
29575 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
29576 as @code{Illegal Instruction} or @code{Segmentation fault}.
29577 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
29578 user's benefit and have no particular format.
29580 @findex signal annotation
29582 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
29583 just saying that the program received the signal, not that it was
29584 terminated with it.
29586 @findex breakpoint annotation
29587 @item ^Z^Zbreakpoint @var{number}
29588 The program hit breakpoint number @var{number}.
29590 @findex watchpoint annotation
29591 @item ^Z^Zwatchpoint @var{number}
29592 The program hit watchpoint number @var{number}.
29595 @node Source Annotations
29596 @section Displaying Source
29597 @cindex annotations for source display
29599 @findex source annotation
29600 The following annotation is used instead of displaying source code:
29603 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
29606 where @var{filename} is an absolute file name indicating which source
29607 file, @var{line} is the line number within that file (where 1 is the
29608 first line in the file), @var{character} is the character position
29609 within the file (where 0 is the first character in the file) (for most
29610 debug formats this will necessarily point to the beginning of a line),
29611 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
29612 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
29613 @var{addr} is the address in the target program associated with the
29614 source which is being displayed. @var{addr} is in the form @samp{0x}
29615 followed by one or more lowercase hex digits (note that this does not
29616 depend on the language).
29618 @node JIT Interface
29619 @chapter JIT Compilation Interface
29620 @cindex just-in-time compilation
29621 @cindex JIT compilation interface
29623 This chapter documents @value{GDBN}'s @dfn{just-in-time} (JIT) compilation
29624 interface. A JIT compiler is a program or library that generates native
29625 executable code at runtime and executes it, usually in order to achieve good
29626 performance while maintaining platform independence.
29628 Programs that use JIT compilation are normally difficult to debug because
29629 portions of their code are generated at runtime, instead of being loaded from
29630 object files, which is where @value{GDBN} normally finds the program's symbols
29631 and debug information. In order to debug programs that use JIT compilation,
29632 @value{GDBN} has an interface that allows the program to register in-memory
29633 symbol files with @value{GDBN} at runtime.
29635 If you are using @value{GDBN} to debug a program that uses this interface, then
29636 it should work transparently so long as you have not stripped the binary. If
29637 you are developing a JIT compiler, then the interface is documented in the rest
29638 of this chapter. At this time, the only known client of this interface is the
29641 Broadly speaking, the JIT interface mirrors the dynamic loader interface. The
29642 JIT compiler communicates with @value{GDBN} by writing data into a global
29643 variable and calling a fuction at a well-known symbol. When @value{GDBN}
29644 attaches, it reads a linked list of symbol files from the global variable to
29645 find existing code, and puts a breakpoint in the function so that it can find
29646 out about additional code.
29649 * Declarations:: Relevant C struct declarations
29650 * Registering Code:: Steps to register code
29651 * Unregistering Code:: Steps to unregister code
29655 @section JIT Declarations
29657 These are the relevant struct declarations that a C program should include to
29658 implement the interface:
29668 struct jit_code_entry
29670 struct jit_code_entry *next_entry;
29671 struct jit_code_entry *prev_entry;
29672 const char *symfile_addr;
29673 uint64_t symfile_size;
29676 struct jit_descriptor
29679 /* This type should be jit_actions_t, but we use uint32_t
29680 to be explicit about the bitwidth. */
29681 uint32_t action_flag;
29682 struct jit_code_entry *relevant_entry;
29683 struct jit_code_entry *first_entry;
29686 /* GDB puts a breakpoint in this function. */
29687 void __attribute__((noinline)) __jit_debug_register_code() @{ @};
29689 /* Make sure to specify the version statically, because the
29690 debugger may check the version before we can set it. */
29691 struct jit_descriptor __jit_debug_descriptor = @{ 1, 0, 0, 0 @};
29694 If the JIT is multi-threaded, then it is important that the JIT synchronize any
29695 modifications to this global data properly, which can easily be done by putting
29696 a global mutex around modifications to these structures.
29698 @node Registering Code
29699 @section Registering Code
29701 To register code with @value{GDBN}, the JIT should follow this protocol:
29705 Generate an object file in memory with symbols and other desired debug
29706 information. The file must include the virtual addresses of the sections.
29709 Create a code entry for the file, which gives the start and size of the symbol
29713 Add it to the linked list in the JIT descriptor.
29716 Point the relevant_entry field of the descriptor at the entry.
29719 Set @code{action_flag} to @code{JIT_REGISTER} and call
29720 @code{__jit_debug_register_code}.
29723 When @value{GDBN} is attached and the breakpoint fires, @value{GDBN} uses the
29724 @code{relevant_entry} pointer so it doesn't have to walk the list looking for
29725 new code. However, the linked list must still be maintained in order to allow
29726 @value{GDBN} to attach to a running process and still find the symbol files.
29728 @node Unregistering Code
29729 @section Unregistering Code
29731 If code is freed, then the JIT should use the following protocol:
29735 Remove the code entry corresponding to the code from the linked list.
29738 Point the @code{relevant_entry} field of the descriptor at the code entry.
29741 Set @code{action_flag} to @code{JIT_UNREGISTER} and call
29742 @code{__jit_debug_register_code}.
29745 If the JIT frees or recompiles code without unregistering it, then @value{GDBN}
29746 and the JIT will leak the memory used for the associated symbol files.
29749 @chapter Reporting Bugs in @value{GDBN}
29750 @cindex bugs in @value{GDBN}
29751 @cindex reporting bugs in @value{GDBN}
29753 Your bug reports play an essential role in making @value{GDBN} reliable.
29755 Reporting a bug may help you by bringing a solution to your problem, or it
29756 may not. But in any case the principal function of a bug report is to help
29757 the entire community by making the next version of @value{GDBN} work better. Bug
29758 reports are your contribution to the maintenance of @value{GDBN}.
29760 In order for a bug report to serve its purpose, you must include the
29761 information that enables us to fix the bug.
29764 * Bug Criteria:: Have you found a bug?
29765 * Bug Reporting:: How to report bugs
29769 @section Have You Found a Bug?
29770 @cindex bug criteria
29772 If you are not sure whether you have found a bug, here are some guidelines:
29775 @cindex fatal signal
29776 @cindex debugger crash
29777 @cindex crash of debugger
29779 If the debugger gets a fatal signal, for any input whatever, that is a
29780 @value{GDBN} bug. Reliable debuggers never crash.
29782 @cindex error on valid input
29784 If @value{GDBN} produces an error message for valid input, that is a
29785 bug. (Note that if you're cross debugging, the problem may also be
29786 somewhere in the connection to the target.)
29788 @cindex invalid input
29790 If @value{GDBN} does not produce an error message for invalid input,
29791 that is a bug. However, you should note that your idea of
29792 ``invalid input'' might be our idea of ``an extension'' or ``support
29793 for traditional practice''.
29796 If you are an experienced user of debugging tools, your suggestions
29797 for improvement of @value{GDBN} are welcome in any case.
29800 @node Bug Reporting
29801 @section How to Report Bugs
29802 @cindex bug reports
29803 @cindex @value{GDBN} bugs, reporting
29805 A number of companies and individuals offer support for @sc{gnu} products.
29806 If you obtained @value{GDBN} from a support organization, we recommend you
29807 contact that organization first.
29809 You can find contact information for many support companies and
29810 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
29812 @c should add a web page ref...
29815 @ifset BUGURL_DEFAULT
29816 In any event, we also recommend that you submit bug reports for
29817 @value{GDBN}. The preferred method is to submit them directly using
29818 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
29819 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
29822 @strong{Do not send bug reports to @samp{info-gdb}, or to
29823 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
29824 not want to receive bug reports. Those that do have arranged to receive
29827 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
29828 serves as a repeater. The mailing list and the newsgroup carry exactly
29829 the same messages. Often people think of posting bug reports to the
29830 newsgroup instead of mailing them. This appears to work, but it has one
29831 problem which can be crucial: a newsgroup posting often lacks a mail
29832 path back to the sender. Thus, if we need to ask for more information,
29833 we may be unable to reach you. For this reason, it is better to send
29834 bug reports to the mailing list.
29836 @ifclear BUGURL_DEFAULT
29837 In any event, we also recommend that you submit bug reports for
29838 @value{GDBN} to @value{BUGURL}.
29842 The fundamental principle of reporting bugs usefully is this:
29843 @strong{report all the facts}. If you are not sure whether to state a
29844 fact or leave it out, state it!
29846 Often people omit facts because they think they know what causes the
29847 problem and assume that some details do not matter. Thus, you might
29848 assume that the name of the variable you use in an example does not matter.
29849 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
29850 stray memory reference which happens to fetch from the location where that
29851 name is stored in memory; perhaps, if the name were different, the contents
29852 of that location would fool the debugger into doing the right thing despite
29853 the bug. Play it safe and give a specific, complete example. That is the
29854 easiest thing for you to do, and the most helpful.
29856 Keep in mind that the purpose of a bug report is to enable us to fix the
29857 bug. It may be that the bug has been reported previously, but neither
29858 you nor we can know that unless your bug report is complete and
29861 Sometimes people give a few sketchy facts and ask, ``Does this ring a
29862 bell?'' Those bug reports are useless, and we urge everyone to
29863 @emph{refuse to respond to them} except to chide the sender to report
29866 To enable us to fix the bug, you should include all these things:
29870 The version of @value{GDBN}. @value{GDBN} announces it if you start
29871 with no arguments; you can also print it at any time using @code{show
29874 Without this, we will not know whether there is any point in looking for
29875 the bug in the current version of @value{GDBN}.
29878 The type of machine you are using, and the operating system name and
29882 What compiler (and its version) was used to compile @value{GDBN}---e.g.@:
29883 ``@value{GCC}--2.8.1''.
29886 What compiler (and its version) was used to compile the program you are
29887 debugging---e.g.@: ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
29888 C Compiler''. For @value{NGCC}, you can say @kbd{@value{GCC} --version}
29889 to get this information; for other compilers, see the documentation for
29893 The command arguments you gave the compiler to compile your example and
29894 observe the bug. For example, did you use @samp{-O}? To guarantee
29895 you will not omit something important, list them all. A copy of the
29896 Makefile (or the output from make) is sufficient.
29898 If we were to try to guess the arguments, we would probably guess wrong
29899 and then we might not encounter the bug.
29902 A complete input script, and all necessary source files, that will
29906 A description of what behavior you observe that you believe is
29907 incorrect. For example, ``It gets a fatal signal.''
29909 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
29910 will certainly notice it. But if the bug is incorrect output, we might
29911 not notice unless it is glaringly wrong. You might as well not give us
29912 a chance to make a mistake.
29914 Even if the problem you experience is a fatal signal, you should still
29915 say so explicitly. Suppose something strange is going on, such as, your
29916 copy of @value{GDBN} is out of synch, or you have encountered a bug in
29917 the C library on your system. (This has happened!) Your copy might
29918 crash and ours would not. If you told us to expect a crash, then when
29919 ours fails to crash, we would know that the bug was not happening for
29920 us. If you had not told us to expect a crash, then we would not be able
29921 to draw any conclusion from our observations.
29924 @cindex recording a session script
29925 To collect all this information, you can use a session recording program
29926 such as @command{script}, which is available on many Unix systems.
29927 Just run your @value{GDBN} session inside @command{script} and then
29928 include the @file{typescript} file with your bug report.
29930 Another way to record a @value{GDBN} session is to run @value{GDBN}
29931 inside Emacs and then save the entire buffer to a file.
29934 If you wish to suggest changes to the @value{GDBN} source, send us context
29935 diffs. If you even discuss something in the @value{GDBN} source, refer to
29936 it by context, not by line number.
29938 The line numbers in our development sources will not match those in your
29939 sources. Your line numbers would convey no useful information to us.
29943 Here are some things that are not necessary:
29947 A description of the envelope of the bug.
29949 Often people who encounter a bug spend a lot of time investigating
29950 which changes to the input file will make the bug go away and which
29951 changes will not affect it.
29953 This is often time consuming and not very useful, because the way we
29954 will find the bug is by running a single example under the debugger
29955 with breakpoints, not by pure deduction from a series of examples.
29956 We recommend that you save your time for something else.
29958 Of course, if you can find a simpler example to report @emph{instead}
29959 of the original one, that is a convenience for us. Errors in the
29960 output will be easier to spot, running under the debugger will take
29961 less time, and so on.
29963 However, simplification is not vital; if you do not want to do this,
29964 report the bug anyway and send us the entire test case you used.
29967 A patch for the bug.
29969 A patch for the bug does help us if it is a good one. But do not omit
29970 the necessary information, such as the test case, on the assumption that
29971 a patch is all we need. We might see problems with your patch and decide
29972 to fix the problem another way, or we might not understand it at all.
29974 Sometimes with a program as complicated as @value{GDBN} it is very hard to
29975 construct an example that will make the program follow a certain path
29976 through the code. If you do not send us the example, we will not be able
29977 to construct one, so we will not be able to verify that the bug is fixed.
29979 And if we cannot understand what bug you are trying to fix, or why your
29980 patch should be an improvement, we will not install it. A test case will
29981 help us to understand.
29984 A guess about what the bug is or what it depends on.
29986 Such guesses are usually wrong. Even we cannot guess right about such
29987 things without first using the debugger to find the facts.
29990 @c The readline documentation is distributed with the readline code
29991 @c and consists of the two following files:
29993 @c inc-hist.texinfo
29994 @c Use -I with makeinfo to point to the appropriate directory,
29995 @c environment var TEXINPUTS with TeX.
29996 @include rluser.texi
29997 @include inc-hist.texinfo
30000 @node Formatting Documentation
30001 @appendix Formatting Documentation
30003 @cindex @value{GDBN} reference card
30004 @cindex reference card
30005 The @value{GDBN} 4 release includes an already-formatted reference card, ready
30006 for printing with PostScript or Ghostscript, in the @file{gdb}
30007 subdirectory of the main source directory@footnote{In
30008 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
30009 release.}. If you can use PostScript or Ghostscript with your printer,
30010 you can print the reference card immediately with @file{refcard.ps}.
30012 The release also includes the source for the reference card. You
30013 can format it, using @TeX{}, by typing:
30019 The @value{GDBN} reference card is designed to print in @dfn{landscape}
30020 mode on US ``letter'' size paper;
30021 that is, on a sheet 11 inches wide by 8.5 inches
30022 high. You will need to specify this form of printing as an option to
30023 your @sc{dvi} output program.
30025 @cindex documentation
30027 All the documentation for @value{GDBN} comes as part of the machine-readable
30028 distribution. The documentation is written in Texinfo format, which is
30029 a documentation system that uses a single source file to produce both
30030 on-line information and a printed manual. You can use one of the Info
30031 formatting commands to create the on-line version of the documentation
30032 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
30034 @value{GDBN} includes an already formatted copy of the on-line Info
30035 version of this manual in the @file{gdb} subdirectory. The main Info
30036 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
30037 subordinate files matching @samp{gdb.info*} in the same directory. If
30038 necessary, you can print out these files, or read them with any editor;
30039 but they are easier to read using the @code{info} subsystem in @sc{gnu}
30040 Emacs or the standalone @code{info} program, available as part of the
30041 @sc{gnu} Texinfo distribution.
30043 If you want to format these Info files yourself, you need one of the
30044 Info formatting programs, such as @code{texinfo-format-buffer} or
30047 If you have @code{makeinfo} installed, and are in the top level
30048 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
30049 version @value{GDBVN}), you can make the Info file by typing:
30056 If you want to typeset and print copies of this manual, you need @TeX{},
30057 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
30058 Texinfo definitions file.
30060 @TeX{} is a typesetting program; it does not print files directly, but
30061 produces output files called @sc{dvi} files. To print a typeset
30062 document, you need a program to print @sc{dvi} files. If your system
30063 has @TeX{} installed, chances are it has such a program. The precise
30064 command to use depends on your system; @kbd{lpr -d} is common; another
30065 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
30066 require a file name without any extension or a @samp{.dvi} extension.
30068 @TeX{} also requires a macro definitions file called
30069 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
30070 written in Texinfo format. On its own, @TeX{} cannot either read or
30071 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
30072 and is located in the @file{gdb-@var{version-number}/texinfo}
30075 If you have @TeX{} and a @sc{dvi} printer program installed, you can
30076 typeset and print this manual. First switch to the @file{gdb}
30077 subdirectory of the main source directory (for example, to
30078 @file{gdb-@value{GDBVN}/gdb}) and type:
30084 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
30086 @node Installing GDB
30087 @appendix Installing @value{GDBN}
30088 @cindex installation
30091 * Requirements:: Requirements for building @value{GDBN}
30092 * Running Configure:: Invoking the @value{GDBN} @file{configure} script
30093 * Separate Objdir:: Compiling @value{GDBN} in another directory
30094 * Config Names:: Specifying names for hosts and targets
30095 * Configure Options:: Summary of options for configure
30096 * System-wide configuration:: Having a system-wide init file
30100 @section Requirements for Building @value{GDBN}
30101 @cindex building @value{GDBN}, requirements for
30103 Building @value{GDBN} requires various tools and packages to be available.
30104 Other packages will be used only if they are found.
30106 @heading Tools/Packages Necessary for Building @value{GDBN}
30108 @item ISO C90 compiler
30109 @value{GDBN} is written in ISO C90. It should be buildable with any
30110 working C90 compiler, e.g.@: GCC.
30114 @heading Tools/Packages Optional for Building @value{GDBN}
30118 @value{GDBN} can use the Expat XML parsing library. This library may be
30119 included with your operating system distribution; if it is not, you
30120 can get the latest version from @url{http://expat.sourceforge.net}.
30121 The @file{configure} script will search for this library in several
30122 standard locations; if it is installed in an unusual path, you can
30123 use the @option{--with-libexpat-prefix} option to specify its location.
30129 Remote protocol memory maps (@pxref{Memory Map Format})
30131 Target descriptions (@pxref{Target Descriptions})
30133 Remote shared library lists (@pxref{Library List Format})
30135 MS-Windows shared libraries (@pxref{Shared Libraries})
30139 @cindex compressed debug sections
30140 @value{GDBN} will use the @samp{zlib} library, if available, to read
30141 compressed debug sections. Some linkers, such as GNU gold, are capable
30142 of producing binaries with compressed debug sections. If @value{GDBN}
30143 is compiled with @samp{zlib}, it will be able to read the debug
30144 information in such binaries.
30146 The @samp{zlib} library is likely included with your operating system
30147 distribution; if it is not, you can get the latest version from
30148 @url{http://zlib.net}.
30151 @value{GDBN}'s features related to character sets (@pxref{Character
30152 Sets}) require a functioning @code{iconv} implementation. If you are
30153 on a GNU system, then this is provided by the GNU C Library. Some
30154 other systems also provide a working @code{iconv}.
30156 On systems with @code{iconv}, you can install GNU Libiconv. If you
30157 have previously installed Libiconv, you can use the
30158 @option{--with-libiconv-prefix} option to configure.
30160 @value{GDBN}'s top-level @file{configure} and @file{Makefile} will
30161 arrange to build Libiconv if a directory named @file{libiconv} appears
30162 in the top-most source directory. If Libiconv is built this way, and
30163 if the operating system does not provide a suitable @code{iconv}
30164 implementation, then the just-built library will automatically be used
30165 by @value{GDBN}. One easy way to set this up is to download GNU
30166 Libiconv, unpack it, and then rename the directory holding the
30167 Libiconv source code to @samp{libiconv}.
30170 @node Running Configure
30171 @section Invoking the @value{GDBN} @file{configure} Script
30172 @cindex configuring @value{GDBN}
30173 @value{GDBN} comes with a @file{configure} script that automates the process
30174 of preparing @value{GDBN} for installation; you can then use @code{make} to
30175 build the @code{gdb} program.
30177 @c irrelevant in info file; it's as current as the code it lives with.
30178 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
30179 look at the @file{README} file in the sources; we may have improved the
30180 installation procedures since publishing this manual.}
30183 The @value{GDBN} distribution includes all the source code you need for
30184 @value{GDBN} in a single directory, whose name is usually composed by
30185 appending the version number to @samp{gdb}.
30187 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
30188 @file{gdb-@value{GDBVN}} directory. That directory contains:
30191 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
30192 script for configuring @value{GDBN} and all its supporting libraries
30194 @item gdb-@value{GDBVN}/gdb
30195 the source specific to @value{GDBN} itself
30197 @item gdb-@value{GDBVN}/bfd
30198 source for the Binary File Descriptor library
30200 @item gdb-@value{GDBVN}/include
30201 @sc{gnu} include files
30203 @item gdb-@value{GDBVN}/libiberty
30204 source for the @samp{-liberty} free software library
30206 @item gdb-@value{GDBVN}/opcodes
30207 source for the library of opcode tables and disassemblers
30209 @item gdb-@value{GDBVN}/readline
30210 source for the @sc{gnu} command-line interface
30212 @item gdb-@value{GDBVN}/glob
30213 source for the @sc{gnu} filename pattern-matching subroutine
30215 @item gdb-@value{GDBVN}/mmalloc
30216 source for the @sc{gnu} memory-mapped malloc package
30219 The simplest way to configure and build @value{GDBN} is to run @file{configure}
30220 from the @file{gdb-@var{version-number}} source directory, which in
30221 this example is the @file{gdb-@value{GDBVN}} directory.
30223 First switch to the @file{gdb-@var{version-number}} source directory
30224 if you are not already in it; then run @file{configure}. Pass the
30225 identifier for the platform on which @value{GDBN} will run as an
30231 cd gdb-@value{GDBVN}
30232 ./configure @var{host}
30237 where @var{host} is an identifier such as @samp{sun4} or
30238 @samp{decstation}, that identifies the platform where @value{GDBN} will run.
30239 (You can often leave off @var{host}; @file{configure} tries to guess the
30240 correct value by examining your system.)
30242 Running @samp{configure @var{host}} and then running @code{make} builds the
30243 @file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty}
30244 libraries, then @code{gdb} itself. The configured source files, and the
30245 binaries, are left in the corresponding source directories.
30248 @file{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
30249 system does not recognize this automatically when you run a different
30250 shell, you may need to run @code{sh} on it explicitly:
30253 sh configure @var{host}
30256 If you run @file{configure} from a directory that contains source
30257 directories for multiple libraries or programs, such as the
30258 @file{gdb-@value{GDBVN}} source directory for version @value{GDBVN},
30260 creates configuration files for every directory level underneath (unless
30261 you tell it not to, with the @samp{--norecursion} option).
30263 You should run the @file{configure} script from the top directory in the
30264 source tree, the @file{gdb-@var{version-number}} directory. If you run
30265 @file{configure} from one of the subdirectories, you will configure only
30266 that subdirectory. That is usually not what you want. In particular,
30267 if you run the first @file{configure} from the @file{gdb} subdirectory
30268 of the @file{gdb-@var{version-number}} directory, you will omit the
30269 configuration of @file{bfd}, @file{readline}, and other sibling
30270 directories of the @file{gdb} subdirectory. This leads to build errors
30271 about missing include files such as @file{bfd/bfd.h}.
30273 You can install @code{@value{GDBP}} anywhere; it has no hardwired paths.
30274 However, you should make sure that the shell on your path (named by
30275 the @samp{SHELL} environment variable) is publicly readable. Remember
30276 that @value{GDBN} uses the shell to start your program---some systems refuse to
30277 let @value{GDBN} debug child processes whose programs are not readable.
30279 @node Separate Objdir
30280 @section Compiling @value{GDBN} in Another Directory
30282 If you want to run @value{GDBN} versions for several host or target machines,
30283 you need a different @code{gdb} compiled for each combination of
30284 host and target. @file{configure} is designed to make this easy by
30285 allowing you to generate each configuration in a separate subdirectory,
30286 rather than in the source directory. If your @code{make} program
30287 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
30288 @code{make} in each of these directories builds the @code{gdb}
30289 program specified there.
30291 To build @code{gdb} in a separate directory, run @file{configure}
30292 with the @samp{--srcdir} option to specify where to find the source.
30293 (You also need to specify a path to find @file{configure}
30294 itself from your working directory. If the path to @file{configure}
30295 would be the same as the argument to @samp{--srcdir}, you can leave out
30296 the @samp{--srcdir} option; it is assumed.)
30298 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
30299 separate directory for a Sun 4 like this:
30303 cd gdb-@value{GDBVN}
30306 ../gdb-@value{GDBVN}/configure sun4
30311 When @file{configure} builds a configuration using a remote source
30312 directory, it creates a tree for the binaries with the same structure
30313 (and using the same names) as the tree under the source directory. In
30314 the example, you'd find the Sun 4 library @file{libiberty.a} in the
30315 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
30316 @file{gdb-sun4/gdb}.
30318 Make sure that your path to the @file{configure} script has just one
30319 instance of @file{gdb} in it. If your path to @file{configure} looks
30320 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
30321 one subdirectory of @value{GDBN}, not the whole package. This leads to
30322 build errors about missing include files such as @file{bfd/bfd.h}.
30324 One popular reason to build several @value{GDBN} configurations in separate
30325 directories is to configure @value{GDBN} for cross-compiling (where
30326 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
30327 programs that run on another machine---the @dfn{target}).
30328 You specify a cross-debugging target by
30329 giving the @samp{--target=@var{target}} option to @file{configure}.
30331 When you run @code{make} to build a program or library, you must run
30332 it in a configured directory---whatever directory you were in when you
30333 called @file{configure} (or one of its subdirectories).
30335 The @code{Makefile} that @file{configure} generates in each source
30336 directory also runs recursively. If you type @code{make} in a source
30337 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
30338 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
30339 will build all the required libraries, and then build GDB.
30341 When you have multiple hosts or targets configured in separate
30342 directories, you can run @code{make} on them in parallel (for example,
30343 if they are NFS-mounted on each of the hosts); they will not interfere
30347 @section Specifying Names for Hosts and Targets
30349 The specifications used for hosts and targets in the @file{configure}
30350 script are based on a three-part naming scheme, but some short predefined
30351 aliases are also supported. The full naming scheme encodes three pieces
30352 of information in the following pattern:
30355 @var{architecture}-@var{vendor}-@var{os}
30358 For example, you can use the alias @code{sun4} as a @var{host} argument,
30359 or as the value for @var{target} in a @code{--target=@var{target}}
30360 option. The equivalent full name is @samp{sparc-sun-sunos4}.
30362 The @file{configure} script accompanying @value{GDBN} does not provide
30363 any query facility to list all supported host and target names or
30364 aliases. @file{configure} calls the Bourne shell script
30365 @code{config.sub} to map abbreviations to full names; you can read the
30366 script, if you wish, or you can use it to test your guesses on
30367 abbreviations---for example:
30370 % sh config.sub i386-linux
30372 % sh config.sub alpha-linux
30373 alpha-unknown-linux-gnu
30374 % sh config.sub hp9k700
30376 % sh config.sub sun4
30377 sparc-sun-sunos4.1.1
30378 % sh config.sub sun3
30379 m68k-sun-sunos4.1.1
30380 % sh config.sub i986v
30381 Invalid configuration `i986v': machine `i986v' not recognized
30385 @code{config.sub} is also distributed in the @value{GDBN} source
30386 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
30388 @node Configure Options
30389 @section @file{configure} Options
30391 Here is a summary of the @file{configure} options and arguments that
30392 are most often useful for building @value{GDBN}. @file{configure} also has
30393 several other options not listed here. @inforef{What Configure
30394 Does,,configure.info}, for a full explanation of @file{configure}.
30397 configure @r{[}--help@r{]}
30398 @r{[}--prefix=@var{dir}@r{]}
30399 @r{[}--exec-prefix=@var{dir}@r{]}
30400 @r{[}--srcdir=@var{dirname}@r{]}
30401 @r{[}--norecursion@r{]} @r{[}--rm@r{]}
30402 @r{[}--target=@var{target}@r{]}
30407 You may introduce options with a single @samp{-} rather than
30408 @samp{--} if you prefer; but you may abbreviate option names if you use
30413 Display a quick summary of how to invoke @file{configure}.
30415 @item --prefix=@var{dir}
30416 Configure the source to install programs and files under directory
30419 @item --exec-prefix=@var{dir}
30420 Configure the source to install programs under directory
30423 @c avoid splitting the warning from the explanation:
30425 @item --srcdir=@var{dirname}
30426 @strong{Warning: using this option requires @sc{gnu} @code{make}, or another
30427 @code{make} that implements the @code{VPATH} feature.}@*
30428 Use this option to make configurations in directories separate from the
30429 @value{GDBN} source directories. Among other things, you can use this to
30430 build (or maintain) several configurations simultaneously, in separate
30431 directories. @file{configure} writes configuration-specific files in
30432 the current directory, but arranges for them to use the source in the
30433 directory @var{dirname}. @file{configure} creates directories under
30434 the working directory in parallel to the source directories below
30437 @item --norecursion
30438 Configure only the directory level where @file{configure} is executed; do not
30439 propagate configuration to subdirectories.
30441 @item --target=@var{target}
30442 Configure @value{GDBN} for cross-debugging programs running on the specified
30443 @var{target}. Without this option, @value{GDBN} is configured to debug
30444 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
30446 There is no convenient way to generate a list of all available targets.
30448 @item @var{host} @dots{}
30449 Configure @value{GDBN} to run on the specified @var{host}.
30451 There is no convenient way to generate a list of all available hosts.
30454 There are many other options available as well, but they are generally
30455 needed for special purposes only.
30457 @node System-wide configuration
30458 @section System-wide configuration and settings
30459 @cindex system-wide init file
30461 @value{GDBN} can be configured to have a system-wide init file;
30462 this file will be read and executed at startup (@pxref{Startup, , What
30463 @value{GDBN} does during startup}).
30465 Here is the corresponding configure option:
30468 @item --with-system-gdbinit=@var{file}
30469 Specify that the default location of the system-wide init file is
30473 If @value{GDBN} has been configured with the option @option{--prefix=$prefix},
30474 it may be subject to relocation. Two possible cases:
30478 If the default location of this init file contains @file{$prefix},
30479 it will be subject to relocation. Suppose that the configure options
30480 are @option{--prefix=$prefix --with-system-gdbinit=$prefix/etc/gdbinit};
30481 if @value{GDBN} is moved from @file{$prefix} to @file{$install}, the system
30482 init file is looked for as @file{$install/etc/gdbinit} instead of
30483 @file{$prefix/etc/gdbinit}.
30486 By contrast, if the default location does not contain the prefix,
30487 it will not be relocated. E.g.@: if @value{GDBN} has been configured with
30488 @option{--prefix=/usr/local --with-system-gdbinit=/usr/share/gdb/gdbinit},
30489 then @value{GDBN} will always look for @file{/usr/share/gdb/gdbinit},
30490 wherever @value{GDBN} is installed.
30493 @node Maintenance Commands
30494 @appendix Maintenance Commands
30495 @cindex maintenance commands
30496 @cindex internal commands
30498 In addition to commands intended for @value{GDBN} users, @value{GDBN}
30499 includes a number of commands intended for @value{GDBN} developers,
30500 that are not documented elsewhere in this manual. These commands are
30501 provided here for reference. (For commands that turn on debugging
30502 messages, see @ref{Debugging Output}.)
30505 @kindex maint agent
30506 @kindex maint agent-eval
30507 @item maint agent @var{expression}
30508 @itemx maint agent-eval @var{expression}
30509 Translate the given @var{expression} into remote agent bytecodes.
30510 This command is useful for debugging the Agent Expression mechanism
30511 (@pxref{Agent Expressions}). The @samp{agent} version produces an
30512 expression useful for data collection, such as by tracepoints, while
30513 @samp{maint agent-eval} produces an expression that evaluates directly
30514 to a result. For instance, a collection expression for @code{globa +
30515 globb} will include bytecodes to record four bytes of memory at each
30516 of the addresses of @code{globa} and @code{globb}, while discarding
30517 the result of the addition, while an evaluation expression will do the
30518 addition and return the sum.
30520 @kindex maint info breakpoints
30521 @item @anchor{maint info breakpoints}maint info breakpoints
30522 Using the same format as @samp{info breakpoints}, display both the
30523 breakpoints you've set explicitly, and those @value{GDBN} is using for
30524 internal purposes. Internal breakpoints are shown with negative
30525 breakpoint numbers. The type column identifies what kind of breakpoint
30530 Normal, explicitly set breakpoint.
30533 Normal, explicitly set watchpoint.
30536 Internal breakpoint, used to handle correctly stepping through
30537 @code{longjmp} calls.
30539 @item longjmp resume
30540 Internal breakpoint at the target of a @code{longjmp}.
30543 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
30546 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
30549 Shared library events.
30553 @kindex set displaced-stepping
30554 @kindex show displaced-stepping
30555 @cindex displaced stepping support
30556 @cindex out-of-line single-stepping
30557 @item set displaced-stepping
30558 @itemx show displaced-stepping
30559 Control whether or not @value{GDBN} will do @dfn{displaced stepping}
30560 if the target supports it. Displaced stepping is a way to single-step
30561 over breakpoints without removing them from the inferior, by executing
30562 an out-of-line copy of the instruction that was originally at the
30563 breakpoint location. It is also known as out-of-line single-stepping.
30566 @item set displaced-stepping on
30567 If the target architecture supports it, @value{GDBN} will use
30568 displaced stepping to step over breakpoints.
30570 @item set displaced-stepping off
30571 @value{GDBN} will not use displaced stepping to step over breakpoints,
30572 even if such is supported by the target architecture.
30574 @cindex non-stop mode, and @samp{set displaced-stepping}
30575 @item set displaced-stepping auto
30576 This is the default mode. @value{GDBN} will use displaced stepping
30577 only if non-stop mode is active (@pxref{Non-Stop Mode}) and the target
30578 architecture supports displaced stepping.
30581 @kindex maint check-symtabs
30582 @item maint check-symtabs
30583 Check the consistency of psymtabs and symtabs.
30585 @kindex maint cplus first_component
30586 @item maint cplus first_component @var{name}
30587 Print the first C@t{++} class/namespace component of @var{name}.
30589 @kindex maint cplus namespace
30590 @item maint cplus namespace
30591 Print the list of possible C@t{++} namespaces.
30593 @kindex maint demangle
30594 @item maint demangle @var{name}
30595 Demangle a C@t{++} or Objective-C mangled @var{name}.
30597 @kindex maint deprecate
30598 @kindex maint undeprecate
30599 @cindex deprecated commands
30600 @item maint deprecate @var{command} @r{[}@var{replacement}@r{]}
30601 @itemx maint undeprecate @var{command}
30602 Deprecate or undeprecate the named @var{command}. Deprecated commands
30603 cause @value{GDBN} to issue a warning when you use them. The optional
30604 argument @var{replacement} says which newer command should be used in
30605 favor of the deprecated one; if it is given, @value{GDBN} will mention
30606 the replacement as part of the warning.
30608 @kindex maint dump-me
30609 @item maint dump-me
30610 @cindex @code{SIGQUIT} signal, dump core of @value{GDBN}
30611 Cause a fatal signal in the debugger and force it to dump its core.
30612 This is supported only on systems which support aborting a program
30613 with the @code{SIGQUIT} signal.
30615 @kindex maint internal-error
30616 @kindex maint internal-warning
30617 @item maint internal-error @r{[}@var{message-text}@r{]}
30618 @itemx maint internal-warning @r{[}@var{message-text}@r{]}
30619 Cause @value{GDBN} to call the internal function @code{internal_error}
30620 or @code{internal_warning} and hence behave as though an internal error
30621 or internal warning has been detected. In addition to reporting the
30622 internal problem, these functions give the user the opportunity to
30623 either quit @value{GDBN} or create a core file of the current
30624 @value{GDBN} session.
30626 These commands take an optional parameter @var{message-text} that is
30627 used as the text of the error or warning message.
30629 Here's an example of using @code{internal-error}:
30632 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
30633 @dots{}/maint.c:121: internal-error: testing, 1, 2
30634 A problem internal to GDB has been detected. Further
30635 debugging may prove unreliable.
30636 Quit this debugging session? (y or n) @kbd{n}
30637 Create a core file? (y or n) @kbd{n}
30641 @cindex @value{GDBN} internal error
30642 @cindex internal errors, control of @value{GDBN} behavior
30644 @kindex maint set internal-error
30645 @kindex maint show internal-error
30646 @kindex maint set internal-warning
30647 @kindex maint show internal-warning
30648 @item maint set internal-error @var{action} [ask|yes|no]
30649 @itemx maint show internal-error @var{action}
30650 @itemx maint set internal-warning @var{action} [ask|yes|no]
30651 @itemx maint show internal-warning @var{action}
30652 When @value{GDBN} reports an internal problem (error or warning) it
30653 gives the user the opportunity to both quit @value{GDBN} and create a
30654 core file of the current @value{GDBN} session. These commands let you
30655 override the default behaviour for each particular @var{action},
30656 described in the table below.
30660 You can specify that @value{GDBN} should always (yes) or never (no)
30661 quit. The default is to ask the user what to do.
30664 You can specify that @value{GDBN} should always (yes) or never (no)
30665 create a core file. The default is to ask the user what to do.
30668 @kindex maint packet
30669 @item maint packet @var{text}
30670 If @value{GDBN} is talking to an inferior via the serial protocol,
30671 then this command sends the string @var{text} to the inferior, and
30672 displays the response packet. @value{GDBN} supplies the initial
30673 @samp{$} character, the terminating @samp{#} character, and the
30676 @kindex maint print architecture
30677 @item maint print architecture @r{[}@var{file}@r{]}
30678 Print the entire architecture configuration. The optional argument
30679 @var{file} names the file where the output goes.
30681 @kindex maint print c-tdesc
30682 @item maint print c-tdesc
30683 Print the current target description (@pxref{Target Descriptions}) as
30684 a C source file. The created source file can be used in @value{GDBN}
30685 when an XML parser is not available to parse the description.
30687 @kindex maint print dummy-frames
30688 @item maint print dummy-frames
30689 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
30692 (@value{GDBP}) @kbd{b add}
30694 (@value{GDBP}) @kbd{print add(2,3)}
30695 Breakpoint 2, add (a=2, b=3) at @dots{}
30697 The program being debugged stopped while in a function called from GDB.
30699 (@value{GDBP}) @kbd{maint print dummy-frames}
30700 0x1a57c80: pc=0x01014068 fp=0x0200bddc sp=0x0200bdd6
30701 top=0x0200bdd4 id=@{stack=0x200bddc,code=0x101405c@}
30702 call_lo=0x01014000 call_hi=0x01014001
30706 Takes an optional file parameter.
30708 @kindex maint print registers
30709 @kindex maint print raw-registers
30710 @kindex maint print cooked-registers
30711 @kindex maint print register-groups
30712 @item maint print registers @r{[}@var{file}@r{]}
30713 @itemx maint print raw-registers @r{[}@var{file}@r{]}
30714 @itemx maint print cooked-registers @r{[}@var{file}@r{]}
30715 @itemx maint print register-groups @r{[}@var{file}@r{]}
30716 Print @value{GDBN}'s internal register data structures.
30718 The command @code{maint print raw-registers} includes the contents of
30719 the raw register cache; the command @code{maint print cooked-registers}
30720 includes the (cooked) value of all registers, including registers which
30721 aren't available on the target nor visible to user; and the
30722 command @code{maint print register-groups} includes the groups that each
30723 register is a member of. @xref{Registers,, Registers, gdbint,
30724 @value{GDBN} Internals}.
30726 These commands take an optional parameter, a file name to which to
30727 write the information.
30729 @kindex maint print reggroups
30730 @item maint print reggroups @r{[}@var{file}@r{]}
30731 Print @value{GDBN}'s internal register group data structures. The
30732 optional argument @var{file} tells to what file to write the
30735 The register groups info looks like this:
30738 (@value{GDBP}) @kbd{maint print reggroups}
30751 This command forces @value{GDBN} to flush its internal register cache.
30753 @kindex maint print objfiles
30754 @cindex info for known object files
30755 @item maint print objfiles
30756 Print a dump of all known object files. For each object file, this
30757 command prints its name, address in memory, and all of its psymtabs
30760 @kindex maint print section-scripts
30761 @cindex info for known .debug_gdb_scripts-loaded scripts
30762 @item maint print section-scripts [@var{regexp}]
30763 Print a dump of scripts specified in the @code{.debug_gdb_section} section.
30764 If @var{regexp} is specified, only print scripts loaded by object files
30765 matching @var{regexp}.
30766 For each script, this command prints its name as specified in the objfile,
30767 and the full path if known.
30768 @xref{.debug_gdb_scripts section}.
30770 @kindex maint print statistics
30771 @cindex bcache statistics
30772 @item maint print statistics
30773 This command prints, for each object file in the program, various data
30774 about that object file followed by the byte cache (@dfn{bcache})
30775 statistics for the object file. The objfile data includes the number
30776 of minimal, partial, full, and stabs symbols, the number of types
30777 defined by the objfile, the number of as yet unexpanded psym tables,
30778 the number of line tables and string tables, and the amount of memory
30779 used by the various tables. The bcache statistics include the counts,
30780 sizes, and counts of duplicates of all and unique objects, max,
30781 average, and median entry size, total memory used and its overhead and
30782 savings, and various measures of the hash table size and chain
30785 @kindex maint print target-stack
30786 @cindex target stack description
30787 @item maint print target-stack
30788 A @dfn{target} is an interface between the debugger and a particular
30789 kind of file or process. Targets can be stacked in @dfn{strata},
30790 so that more than one target can potentially respond to a request.
30791 In particular, memory accesses will walk down the stack of targets
30792 until they find a target that is interested in handling that particular
30795 This command prints a short description of each layer that was pushed on
30796 the @dfn{target stack}, starting from the top layer down to the bottom one.
30798 @kindex maint print type
30799 @cindex type chain of a data type
30800 @item maint print type @var{expr}
30801 Print the type chain for a type specified by @var{expr}. The argument
30802 can be either a type name or a symbol. If it is a symbol, the type of
30803 that symbol is described. The type chain produced by this command is
30804 a recursive definition of the data type as stored in @value{GDBN}'s
30805 data structures, including its flags and contained types.
30807 @kindex maint set dwarf2 always-disassemble
30808 @kindex maint show dwarf2 always-disassemble
30809 @item maint set dwarf2 always-disassemble
30810 @item maint show dwarf2 always-disassemble
30811 Control the behavior of @code{info address} when using DWARF debugging
30814 The default is @code{off}, which means that @value{GDBN} should try to
30815 describe a variable's location in an easily readable format. When
30816 @code{on}, @value{GDBN} will instead display the DWARF location
30817 expression in an assembly-like format. Note that some locations are
30818 too complex for @value{GDBN} to describe simply; in this case you will
30819 always see the disassembly form.
30821 Here is an example of the resulting disassembly:
30824 (gdb) info addr argc
30825 Symbol "argc" is a complex DWARF expression:
30829 For more information on these expressions, see
30830 @uref{http://www.dwarfstd.org/, the DWARF standard}.
30832 @kindex maint set dwarf2 max-cache-age
30833 @kindex maint show dwarf2 max-cache-age
30834 @item maint set dwarf2 max-cache-age
30835 @itemx maint show dwarf2 max-cache-age
30836 Control the DWARF 2 compilation unit cache.
30838 @cindex DWARF 2 compilation units cache
30839 In object files with inter-compilation-unit references, such as those
30840 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF 2
30841 reader needs to frequently refer to previously read compilation units.
30842 This setting controls how long a compilation unit will remain in the
30843 cache if it is not referenced. A higher limit means that cached
30844 compilation units will be stored in memory longer, and more total
30845 memory will be used. Setting it to zero disables caching, which will
30846 slow down @value{GDBN} startup, but reduce memory consumption.
30848 @kindex maint set profile
30849 @kindex maint show profile
30850 @cindex profiling GDB
30851 @item maint set profile
30852 @itemx maint show profile
30853 Control profiling of @value{GDBN}.
30855 Profiling will be disabled until you use the @samp{maint set profile}
30856 command to enable it. When you enable profiling, the system will begin
30857 collecting timing and execution count data; when you disable profiling or
30858 exit @value{GDBN}, the results will be written to a log file. Remember that
30859 if you use profiling, @value{GDBN} will overwrite the profiling log file
30860 (often called @file{gmon.out}). If you have a record of important profiling
30861 data in a @file{gmon.out} file, be sure to move it to a safe location.
30863 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
30864 compiled with the @samp{-pg} compiler option.
30866 @kindex maint set show-debug-regs
30867 @kindex maint show show-debug-regs
30868 @cindex hardware debug registers
30869 @item maint set show-debug-regs
30870 @itemx maint show show-debug-regs
30871 Control whether to show variables that mirror the hardware debug
30872 registers. Use @code{ON} to enable, @code{OFF} to disable. If
30873 enabled, the debug registers values are shown when @value{GDBN} inserts or
30874 removes a hardware breakpoint or watchpoint, and when the inferior
30875 triggers a hardware-assisted breakpoint or watchpoint.
30877 @kindex maint set show-all-tib
30878 @kindex maint show show-all-tib
30879 @item maint set show-all-tib
30880 @itemx maint show show-all-tib
30881 Control whether to show all non zero areas within a 1k block starting
30882 at thread local base, when using the @samp{info w32 thread-information-block}
30885 @kindex maint space
30886 @cindex memory used by commands
30888 Control whether to display memory usage for each command. If set to a
30889 nonzero value, @value{GDBN} will display how much memory each command
30890 took, following the command's own output. This can also be requested
30891 by invoking @value{GDBN} with the @option{--statistics} command-line
30892 switch (@pxref{Mode Options}).
30895 @cindex time of command execution
30897 Control whether to display the execution time for each command. If
30898 set to a nonzero value, @value{GDBN} will display how much time it
30899 took to execute each command, following the command's own output.
30900 The time is not printed for the commands that run the target, since
30901 there's no mechanism currently to compute how much time was spend
30902 by @value{GDBN} and how much time was spend by the program been debugged.
30903 it's not possibly currently
30904 This can also be requested by invoking @value{GDBN} with the
30905 @option{--statistics} command-line switch (@pxref{Mode Options}).
30907 @kindex maint translate-address
30908 @item maint translate-address @r{[}@var{section}@r{]} @var{addr}
30909 Find the symbol stored at the location specified by the address
30910 @var{addr} and an optional section name @var{section}. If found,
30911 @value{GDBN} prints the name of the closest symbol and an offset from
30912 the symbol's location to the specified address. This is similar to
30913 the @code{info address} command (@pxref{Symbols}), except that this
30914 command also allows to find symbols in other sections.
30916 If section was not specified, the section in which the symbol was found
30917 is also printed. For dynamically linked executables, the name of
30918 executable or shared library containing the symbol is printed as well.
30922 The following command is useful for non-interactive invocations of
30923 @value{GDBN}, such as in the test suite.
30926 @item set watchdog @var{nsec}
30927 @kindex set watchdog
30928 @cindex watchdog timer
30929 @cindex timeout for commands
30930 Set the maximum number of seconds @value{GDBN} will wait for the
30931 target operation to finish. If this time expires, @value{GDBN}
30932 reports and error and the command is aborted.
30934 @item show watchdog
30935 Show the current setting of the target wait timeout.
30938 @node Remote Protocol
30939 @appendix @value{GDBN} Remote Serial Protocol
30944 * Stop Reply Packets::
30945 * General Query Packets::
30946 * Architecture-Specific Protocol Details::
30947 * Tracepoint Packets::
30948 * Host I/O Packets::
30950 * Notification Packets::
30951 * Remote Non-Stop::
30952 * Packet Acknowledgment::
30954 * File-I/O Remote Protocol Extension::
30955 * Library List Format::
30956 * Memory Map Format::
30957 * Thread List Format::
30963 There may be occasions when you need to know something about the
30964 protocol---for example, if there is only one serial port to your target
30965 machine, you might want your program to do something special if it
30966 recognizes a packet meant for @value{GDBN}.
30968 In the examples below, @samp{->} and @samp{<-} are used to indicate
30969 transmitted and received data, respectively.
30971 @cindex protocol, @value{GDBN} remote serial
30972 @cindex serial protocol, @value{GDBN} remote
30973 @cindex remote serial protocol
30974 All @value{GDBN} commands and responses (other than acknowledgments
30975 and notifications, see @ref{Notification Packets}) are sent as a
30976 @var{packet}. A @var{packet} is introduced with the character
30977 @samp{$}, the actual @var{packet-data}, and the terminating character
30978 @samp{#} followed by a two-digit @var{checksum}:
30981 @code{$}@var{packet-data}@code{#}@var{checksum}
30985 @cindex checksum, for @value{GDBN} remote
30987 The two-digit @var{checksum} is computed as the modulo 256 sum of all
30988 characters between the leading @samp{$} and the trailing @samp{#} (an
30989 eight bit unsigned checksum).
30991 Implementors should note that prior to @value{GDBN} 5.0 the protocol
30992 specification also included an optional two-digit @var{sequence-id}:
30995 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
30998 @cindex sequence-id, for @value{GDBN} remote
31000 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
31001 has never output @var{sequence-id}s. Stubs that handle packets added
31002 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
31004 When either the host or the target machine receives a packet, the first
31005 response expected is an acknowledgment: either @samp{+} (to indicate
31006 the package was received correctly) or @samp{-} (to request
31010 -> @code{$}@var{packet-data}@code{#}@var{checksum}
31015 The @samp{+}/@samp{-} acknowledgments can be disabled
31016 once a connection is established.
31017 @xref{Packet Acknowledgment}, for details.
31019 The host (@value{GDBN}) sends @var{command}s, and the target (the
31020 debugging stub incorporated in your program) sends a @var{response}. In
31021 the case of step and continue @var{command}s, the response is only sent
31022 when the operation has completed, and the target has again stopped all
31023 threads in all attached processes. This is the default all-stop mode
31024 behavior, but the remote protocol also supports @value{GDBN}'s non-stop
31025 execution mode; see @ref{Remote Non-Stop}, for details.
31027 @var{packet-data} consists of a sequence of characters with the
31028 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
31031 @cindex remote protocol, field separator
31032 Fields within the packet should be separated using @samp{,} @samp{;} or
31033 @samp{:}. Except where otherwise noted all numbers are represented in
31034 @sc{hex} with leading zeros suppressed.
31036 Implementors should note that prior to @value{GDBN} 5.0, the character
31037 @samp{:} could not appear as the third character in a packet (as it
31038 would potentially conflict with the @var{sequence-id}).
31040 @cindex remote protocol, binary data
31041 @anchor{Binary Data}
31042 Binary data in most packets is encoded either as two hexadecimal
31043 digits per byte of binary data. This allowed the traditional remote
31044 protocol to work over connections which were only seven-bit clean.
31045 Some packets designed more recently assume an eight-bit clean
31046 connection, and use a more efficient encoding to send and receive
31049 The binary data representation uses @code{7d} (@sc{ascii} @samp{@}})
31050 as an escape character. Any escaped byte is transmitted as the escape
31051 character followed by the original character XORed with @code{0x20}.
31052 For example, the byte @code{0x7d} would be transmitted as the two
31053 bytes @code{0x7d 0x5d}. The bytes @code{0x23} (@sc{ascii} @samp{#}),
31054 @code{0x24} (@sc{ascii} @samp{$}), and @code{0x7d} (@sc{ascii}
31055 @samp{@}}) must always be escaped. Responses sent by the stub
31056 must also escape @code{0x2a} (@sc{ascii} @samp{*}), so that it
31057 is not interpreted as the start of a run-length encoded sequence
31060 Response @var{data} can be run-length encoded to save space.
31061 Run-length encoding replaces runs of identical characters with one
31062 instance of the repeated character, followed by a @samp{*} and a
31063 repeat count. The repeat count is itself sent encoded, to avoid
31064 binary characters in @var{data}: a value of @var{n} is sent as
31065 @code{@var{n}+29}. For a repeat count greater or equal to 3, this
31066 produces a printable @sc{ascii} character, e.g.@: a space (@sc{ascii}
31067 code 32) for a repeat count of 3. (This is because run-length
31068 encoding starts to win for counts 3 or more.) Thus, for example,
31069 @samp{0* } is a run-length encoding of ``0000'': the space character
31070 after @samp{*} means repeat the leading @code{0} @w{@code{32 - 29 =
31073 The printable characters @samp{#} and @samp{$} or with a numeric value
31074 greater than 126 must not be used. Runs of six repeats (@samp{#}) or
31075 seven repeats (@samp{$}) can be expanded using a repeat count of only
31076 five (@samp{"}). For example, @samp{00000000} can be encoded as
31079 The error response returned for some packets includes a two character
31080 error number. That number is not well defined.
31082 @cindex empty response, for unsupported packets
31083 For any @var{command} not supported by the stub, an empty response
31084 (@samp{$#00}) should be returned. That way it is possible to extend the
31085 protocol. A newer @value{GDBN} can tell if a packet is supported based
31088 A stub is required to support the @samp{g}, @samp{G}, @samp{m}, @samp{M},
31089 @samp{c}, and @samp{s} @var{command}s. All other @var{command}s are
31095 The following table provides a complete list of all currently defined
31096 @var{command}s and their corresponding response @var{data}.
31097 @xref{File-I/O Remote Protocol Extension}, for details about the File
31098 I/O extension of the remote protocol.
31100 Each packet's description has a template showing the packet's overall
31101 syntax, followed by an explanation of the packet's meaning. We
31102 include spaces in some of the templates for clarity; these are not
31103 part of the packet's syntax. No @value{GDBN} packet uses spaces to
31104 separate its components. For example, a template like @samp{foo
31105 @var{bar} @var{baz}} describes a packet beginning with the three ASCII
31106 bytes @samp{foo}, followed by a @var{bar}, followed directly by a
31107 @var{baz}. @value{GDBN} does not transmit a space character between the
31108 @samp{foo} and the @var{bar}, or between the @var{bar} and the
31111 @cindex @var{thread-id}, in remote protocol
31112 @anchor{thread-id syntax}
31113 Several packets and replies include a @var{thread-id} field to identify
31114 a thread. Normally these are positive numbers with a target-specific
31115 interpretation, formatted as big-endian hex strings. A @var{thread-id}
31116 can also be a literal @samp{-1} to indicate all threads, or @samp{0} to
31119 In addition, the remote protocol supports a multiprocess feature in
31120 which the @var{thread-id} syntax is extended to optionally include both
31121 process and thread ID fields, as @samp{p@var{pid}.@var{tid}}.
31122 The @var{pid} (process) and @var{tid} (thread) components each have the
31123 format described above: a positive number with target-specific
31124 interpretation formatted as a big-endian hex string, literal @samp{-1}
31125 to indicate all processes or threads (respectively), or @samp{0} to
31126 indicate an arbitrary process or thread. Specifying just a process, as
31127 @samp{p@var{pid}}, is equivalent to @samp{p@var{pid}.-1}. It is an
31128 error to specify all processes but a specific thread, such as
31129 @samp{p-1.@var{tid}}. Note that the @samp{p} prefix is @emph{not} used
31130 for those packets and replies explicitly documented to include a process
31131 ID, rather than a @var{thread-id}.
31133 The multiprocess @var{thread-id} syntax extensions are only used if both
31134 @value{GDBN} and the stub report support for the @samp{multiprocess}
31135 feature using @samp{qSupported}. @xref{multiprocess extensions}, for
31138 Note that all packet forms beginning with an upper- or lower-case
31139 letter, other than those described here, are reserved for future use.
31141 Here are the packet descriptions.
31146 @cindex @samp{!} packet
31147 @anchor{extended mode}
31148 Enable extended mode. In extended mode, the remote server is made
31149 persistent. The @samp{R} packet is used to restart the program being
31155 The remote target both supports and has enabled extended mode.
31159 @cindex @samp{?} packet
31160 Indicate the reason the target halted. The reply is the same as for
31161 step and continue. This packet has a special interpretation when the
31162 target is in non-stop mode; see @ref{Remote Non-Stop}.
31165 @xref{Stop Reply Packets}, for the reply specifications.
31167 @item A @var{arglen},@var{argnum},@var{arg},@dots{}
31168 @cindex @samp{A} packet
31169 Initialized @code{argv[]} array passed into program. @var{arglen}
31170 specifies the number of bytes in the hex encoded byte stream
31171 @var{arg}. See @code{gdbserver} for more details.
31176 The arguments were set.
31182 @cindex @samp{b} packet
31183 (Don't use this packet; its behavior is not well-defined.)
31184 Change the serial line speed to @var{baud}.
31186 JTC: @emph{When does the transport layer state change? When it's
31187 received, or after the ACK is transmitted. In either case, there are
31188 problems if the command or the acknowledgment packet is dropped.}
31190 Stan: @emph{If people really wanted to add something like this, and get
31191 it working for the first time, they ought to modify ser-unix.c to send
31192 some kind of out-of-band message to a specially-setup stub and have the
31193 switch happen "in between" packets, so that from remote protocol's point
31194 of view, nothing actually happened.}
31196 @item B @var{addr},@var{mode}
31197 @cindex @samp{B} packet
31198 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
31199 breakpoint at @var{addr}.
31201 Don't use this packet. Use the @samp{Z} and @samp{z} packets instead
31202 (@pxref{insert breakpoint or watchpoint packet}).
31204 @cindex @samp{bc} packet
31207 Backward continue. Execute the target system in reverse. No parameter.
31208 @xref{Reverse Execution}, for more information.
31211 @xref{Stop Reply Packets}, for the reply specifications.
31213 @cindex @samp{bs} packet
31216 Backward single step. Execute one instruction in reverse. No parameter.
31217 @xref{Reverse Execution}, for more information.
31220 @xref{Stop Reply Packets}, for the reply specifications.
31222 @item c @r{[}@var{addr}@r{]}
31223 @cindex @samp{c} packet
31224 Continue. @var{addr} is address to resume. If @var{addr} is omitted,
31225 resume at current address.
31228 @xref{Stop Reply Packets}, for the reply specifications.
31230 @item C @var{sig}@r{[};@var{addr}@r{]}
31231 @cindex @samp{C} packet
31232 Continue with signal @var{sig} (hex signal number). If
31233 @samp{;@var{addr}} is omitted, resume at same address.
31236 @xref{Stop Reply Packets}, for the reply specifications.
31239 @cindex @samp{d} packet
31242 Don't use this packet; instead, define a general set packet
31243 (@pxref{General Query Packets}).
31247 @cindex @samp{D} packet
31248 The first form of the packet is used to detach @value{GDBN} from the
31249 remote system. It is sent to the remote target
31250 before @value{GDBN} disconnects via the @code{detach} command.
31252 The second form, including a process ID, is used when multiprocess
31253 protocol extensions are enabled (@pxref{multiprocess extensions}), to
31254 detach only a specific process. The @var{pid} is specified as a
31255 big-endian hex string.
31265 @item F @var{RC},@var{EE},@var{CF};@var{XX}
31266 @cindex @samp{F} packet
31267 A reply from @value{GDBN} to an @samp{F} packet sent by the target.
31268 This is part of the File-I/O protocol extension. @xref{File-I/O
31269 Remote Protocol Extension}, for the specification.
31272 @anchor{read registers packet}
31273 @cindex @samp{g} packet
31274 Read general registers.
31278 @item @var{XX@dots{}}
31279 Each byte of register data is described by two hex digits. The bytes
31280 with the register are transmitted in target byte order. The size of
31281 each register and their position within the @samp{g} packet are
31282 determined by the @value{GDBN} internal gdbarch functions
31283 @code{DEPRECATED_REGISTER_RAW_SIZE} and @code{gdbarch_register_name}. The
31284 specification of several standard @samp{g} packets is specified below.
31289 @item G @var{XX@dots{}}
31290 @cindex @samp{G} packet
31291 Write general registers. @xref{read registers packet}, for a
31292 description of the @var{XX@dots{}} data.
31302 @item H @var{c} @var{thread-id}
31303 @cindex @samp{H} packet
31304 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
31305 @samp{G}, et.al.). @var{c} depends on the operation to be performed: it
31306 should be @samp{c} for step and continue operations, @samp{g} for other
31307 operations. The thread designator @var{thread-id} has the format and
31308 interpretation described in @ref{thread-id syntax}.
31319 @c 'H': How restrictive (or permissive) is the thread model. If a
31320 @c thread is selected and stopped, are other threads allowed
31321 @c to continue to execute? As I mentioned above, I think the
31322 @c semantics of each command when a thread is selected must be
31323 @c described. For example:
31325 @c 'g': If the stub supports threads and a specific thread is
31326 @c selected, returns the register block from that thread;
31327 @c otherwise returns current registers.
31329 @c 'G' If the stub supports threads and a specific thread is
31330 @c selected, sets the registers of the register block of
31331 @c that thread; otherwise sets current registers.
31333 @item i @r{[}@var{addr}@r{[},@var{nnn}@r{]]}
31334 @anchor{cycle step packet}
31335 @cindex @samp{i} packet
31336 Step the remote target by a single clock cycle. If @samp{,@var{nnn}} is
31337 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
31338 step starting at that address.
31341 @cindex @samp{I} packet
31342 Signal, then cycle step. @xref{step with signal packet}. @xref{cycle
31346 @cindex @samp{k} packet
31349 FIXME: @emph{There is no description of how to operate when a specific
31350 thread context has been selected (i.e.@: does 'k' kill only that
31353 @item m @var{addr},@var{length}
31354 @cindex @samp{m} packet
31355 Read @var{length} bytes of memory starting at address @var{addr}.
31356 Note that @var{addr} may not be aligned to any particular boundary.
31358 The stub need not use any particular size or alignment when gathering
31359 data from memory for the response; even if @var{addr} is word-aligned
31360 and @var{length} is a multiple of the word size, the stub is free to
31361 use byte accesses, or not. For this reason, this packet may not be
31362 suitable for accessing memory-mapped I/O devices.
31363 @cindex alignment of remote memory accesses
31364 @cindex size of remote memory accesses
31365 @cindex memory, alignment and size of remote accesses
31369 @item @var{XX@dots{}}
31370 Memory contents; each byte is transmitted as a two-digit hexadecimal
31371 number. The reply may contain fewer bytes than requested if the
31372 server was able to read only part of the region of memory.
31377 @item M @var{addr},@var{length}:@var{XX@dots{}}
31378 @cindex @samp{M} packet
31379 Write @var{length} bytes of memory starting at address @var{addr}.
31380 @var{XX@dots{}} is the data; each byte is transmitted as a two-digit
31381 hexadecimal number.
31388 for an error (this includes the case where only part of the data was
31393 @cindex @samp{p} packet
31394 Read the value of register @var{n}; @var{n} is in hex.
31395 @xref{read registers packet}, for a description of how the returned
31396 register value is encoded.
31400 @item @var{XX@dots{}}
31401 the register's value
31405 Indicating an unrecognized @var{query}.
31408 @item P @var{n@dots{}}=@var{r@dots{}}
31409 @anchor{write register packet}
31410 @cindex @samp{P} packet
31411 Write register @var{n@dots{}} with value @var{r@dots{}}. The register
31412 number @var{n} is in hexadecimal, and @var{r@dots{}} contains two hex
31413 digits for each byte in the register (target byte order).
31423 @item q @var{name} @var{params}@dots{}
31424 @itemx Q @var{name} @var{params}@dots{}
31425 @cindex @samp{q} packet
31426 @cindex @samp{Q} packet
31427 General query (@samp{q}) and set (@samp{Q}). These packets are
31428 described fully in @ref{General Query Packets}.
31431 @cindex @samp{r} packet
31432 Reset the entire system.
31434 Don't use this packet; use the @samp{R} packet instead.
31437 @cindex @samp{R} packet
31438 Restart the program being debugged. @var{XX}, while needed, is ignored.
31439 This packet is only available in extended mode (@pxref{extended mode}).
31441 The @samp{R} packet has no reply.
31443 @item s @r{[}@var{addr}@r{]}
31444 @cindex @samp{s} packet
31445 Single step. @var{addr} is the address at which to resume. If
31446 @var{addr} is omitted, resume at same address.
31449 @xref{Stop Reply Packets}, for the reply specifications.
31451 @item S @var{sig}@r{[};@var{addr}@r{]}
31452 @anchor{step with signal packet}
31453 @cindex @samp{S} packet
31454 Step with signal. This is analogous to the @samp{C} packet, but
31455 requests a single-step, rather than a normal resumption of execution.
31458 @xref{Stop Reply Packets}, for the reply specifications.
31460 @item t @var{addr}:@var{PP},@var{MM}
31461 @cindex @samp{t} packet
31462 Search backwards starting at address @var{addr} for a match with pattern
31463 @var{PP} and mask @var{MM}. @var{PP} and @var{MM} are 4 bytes.
31464 @var{addr} must be at least 3 digits.
31466 @item T @var{thread-id}
31467 @cindex @samp{T} packet
31468 Find out if the thread @var{thread-id} is alive. @xref{thread-id syntax}.
31473 thread is still alive
31479 Packets starting with @samp{v} are identified by a multi-letter name,
31480 up to the first @samp{;} or @samp{?} (or the end of the packet).
31482 @item vAttach;@var{pid}
31483 @cindex @samp{vAttach} packet
31484 Attach to a new process with the specified process ID @var{pid}.
31485 The process ID is a
31486 hexadecimal integer identifying the process. In all-stop mode, all
31487 threads in the attached process are stopped; in non-stop mode, it may be
31488 attached without being stopped if that is supported by the target.
31490 @c In non-stop mode, on a successful vAttach, the stub should set the
31491 @c current thread to a thread of the newly-attached process. After
31492 @c attaching, GDB queries for the attached process's thread ID with qC.
31493 @c Also note that, from a user perspective, whether or not the
31494 @c target is stopped on attach in non-stop mode depends on whether you
31495 @c use the foreground or background version of the attach command, not
31496 @c on what vAttach does; GDB does the right thing with respect to either
31497 @c stopping or restarting threads.
31499 This packet is only available in extended mode (@pxref{extended mode}).
31505 @item @r{Any stop packet}
31506 for success in all-stop mode (@pxref{Stop Reply Packets})
31508 for success in non-stop mode (@pxref{Remote Non-Stop})
31511 @item vCont@r{[};@var{action}@r{[}:@var{thread-id}@r{]]}@dots{}
31512 @cindex @samp{vCont} packet
31513 Resume the inferior, specifying different actions for each thread.
31514 If an action is specified with no @var{thread-id}, then it is applied to any
31515 threads that don't have a specific action specified; if no default action is
31516 specified then other threads should remain stopped in all-stop mode and
31517 in their current state in non-stop mode.
31518 Specifying multiple
31519 default actions is an error; specifying no actions is also an error.
31520 Thread IDs are specified using the syntax described in @ref{thread-id syntax}.
31522 Currently supported actions are:
31528 Continue with signal @var{sig}. The signal @var{sig} should be two hex digits.
31532 Step with signal @var{sig}. The signal @var{sig} should be two hex digits.
31537 The optional argument @var{addr} normally associated with the
31538 @samp{c}, @samp{C}, @samp{s}, and @samp{S} packets is
31539 not supported in @samp{vCont}.
31541 The @samp{t} action is only relevant in non-stop mode
31542 (@pxref{Remote Non-Stop}) and may be ignored by the stub otherwise.
31543 A stop reply should be generated for any affected thread not already stopped.
31544 When a thread is stopped by means of a @samp{t} action,
31545 the corresponding stop reply should indicate that the thread has stopped with
31546 signal @samp{0}, regardless of whether the target uses some other signal
31547 as an implementation detail.
31550 @xref{Stop Reply Packets}, for the reply specifications.
31553 @cindex @samp{vCont?} packet
31554 Request a list of actions supported by the @samp{vCont} packet.
31558 @item vCont@r{[};@var{action}@dots{}@r{]}
31559 The @samp{vCont} packet is supported. Each @var{action} is a supported
31560 command in the @samp{vCont} packet.
31562 The @samp{vCont} packet is not supported.
31565 @item vFile:@var{operation}:@var{parameter}@dots{}
31566 @cindex @samp{vFile} packet
31567 Perform a file operation on the target system. For details,
31568 see @ref{Host I/O Packets}.
31570 @item vFlashErase:@var{addr},@var{length}
31571 @cindex @samp{vFlashErase} packet
31572 Direct the stub to erase @var{length} bytes of flash starting at
31573 @var{addr}. The region may enclose any number of flash blocks, but
31574 its start and end must fall on block boundaries, as indicated by the
31575 flash block size appearing in the memory map (@pxref{Memory Map
31576 Format}). @value{GDBN} groups flash memory programming operations
31577 together, and sends a @samp{vFlashDone} request after each group; the
31578 stub is allowed to delay erase operation until the @samp{vFlashDone}
31579 packet is received.
31581 The stub must support @samp{vCont} if it reports support for
31582 multiprocess extensions (@pxref{multiprocess extensions}). Note that in
31583 this case @samp{vCont} actions can be specified to apply to all threads
31584 in a process by using the @samp{p@var{pid}.-1} form of the
31595 @item vFlashWrite:@var{addr}:@var{XX@dots{}}
31596 @cindex @samp{vFlashWrite} packet
31597 Direct the stub to write data to flash address @var{addr}. The data
31598 is passed in binary form using the same encoding as for the @samp{X}
31599 packet (@pxref{Binary Data}). The memory ranges specified by
31600 @samp{vFlashWrite} packets preceding a @samp{vFlashDone} packet must
31601 not overlap, and must appear in order of increasing addresses
31602 (although @samp{vFlashErase} packets for higher addresses may already
31603 have been received; the ordering is guaranteed only between
31604 @samp{vFlashWrite} packets). If a packet writes to an address that was
31605 neither erased by a preceding @samp{vFlashErase} packet nor by some other
31606 target-specific method, the results are unpredictable.
31614 for vFlashWrite addressing non-flash memory
31620 @cindex @samp{vFlashDone} packet
31621 Indicate to the stub that flash programming operation is finished.
31622 The stub is permitted to delay or batch the effects of a group of
31623 @samp{vFlashErase} and @samp{vFlashWrite} packets until a
31624 @samp{vFlashDone} packet is received. The contents of the affected
31625 regions of flash memory are unpredictable until the @samp{vFlashDone}
31626 request is completed.
31628 @item vKill;@var{pid}
31629 @cindex @samp{vKill} packet
31630 Kill the process with the specified process ID. @var{pid} is a
31631 hexadecimal integer identifying the process. This packet is used in
31632 preference to @samp{k} when multiprocess protocol extensions are
31633 supported; see @ref{multiprocess extensions}.
31643 @item vRun;@var{filename}@r{[};@var{argument}@r{]}@dots{}
31644 @cindex @samp{vRun} packet
31645 Run the program @var{filename}, passing it each @var{argument} on its
31646 command line. The file and arguments are hex-encoded strings. If
31647 @var{filename} is an empty string, the stub may use a default program
31648 (e.g.@: the last program run). The program is created in the stopped
31651 @c FIXME: What about non-stop mode?
31653 This packet is only available in extended mode (@pxref{extended mode}).
31659 @item @r{Any stop packet}
31660 for success (@pxref{Stop Reply Packets})
31664 @anchor{vStopped packet}
31665 @cindex @samp{vStopped} packet
31667 In non-stop mode (@pxref{Remote Non-Stop}), acknowledge a previous stop
31668 reply and prompt for the stub to report another one.
31672 @item @r{Any stop packet}
31673 if there is another unreported stop event (@pxref{Stop Reply Packets})
31675 if there are no unreported stop events
31678 @item X @var{addr},@var{length}:@var{XX@dots{}}
31680 @cindex @samp{X} packet
31681 Write data to memory, where the data is transmitted in binary.
31682 @var{addr} is address, @var{length} is number of bytes,
31683 @samp{@var{XX}@dots{}} is binary data (@pxref{Binary Data}).
31693 @item z @var{type},@var{addr},@var{kind}
31694 @itemx Z @var{type},@var{addr},@var{kind}
31695 @anchor{insert breakpoint or watchpoint packet}
31696 @cindex @samp{z} packet
31697 @cindex @samp{Z} packets
31698 Insert (@samp{Z}) or remove (@samp{z}) a @var{type} breakpoint or
31699 watchpoint starting at address @var{address} of kind @var{kind}.
31701 Each breakpoint and watchpoint packet @var{type} is documented
31704 @emph{Implementation notes: A remote target shall return an empty string
31705 for an unrecognized breakpoint or watchpoint packet @var{type}. A
31706 remote target shall support either both or neither of a given
31707 @samp{Z@var{type}@dots{}} and @samp{z@var{type}@dots{}} packet pair. To
31708 avoid potential problems with duplicate packets, the operations should
31709 be implemented in an idempotent way.}
31711 @item z0,@var{addr},@var{kind}
31712 @itemx Z0,@var{addr},@var{kind}
31713 @cindex @samp{z0} packet
31714 @cindex @samp{Z0} packet
31715 Insert (@samp{Z0}) or remove (@samp{z0}) a memory breakpoint at address
31716 @var{addr} of type @var{kind}.
31718 A memory breakpoint is implemented by replacing the instruction at
31719 @var{addr} with a software breakpoint or trap instruction. The
31720 @var{kind} is target-specific and typically indicates the size of
31721 the breakpoint in bytes that should be inserted. E.g., the @sc{arm}
31722 and @sc{mips} can insert either a 2 or 4 byte breakpoint. Some
31723 architectures have additional meanings for @var{kind};
31724 see @ref{Architecture-Specific Protocol Details}.
31726 @emph{Implementation note: It is possible for a target to copy or move
31727 code that contains memory breakpoints (e.g., when implementing
31728 overlays). The behavior of this packet, in the presence of such a
31729 target, is not defined.}
31741 @item z1,@var{addr},@var{kind}
31742 @itemx Z1,@var{addr},@var{kind}
31743 @cindex @samp{z1} packet
31744 @cindex @samp{Z1} packet
31745 Insert (@samp{Z1}) or remove (@samp{z1}) a hardware breakpoint at
31746 address @var{addr}.
31748 A hardware breakpoint is implemented using a mechanism that is not
31749 dependant on being able to modify the target's memory. @var{kind}
31750 has the same meaning as in @samp{Z0} packets.
31752 @emph{Implementation note: A hardware breakpoint is not affected by code
31765 @item z2,@var{addr},@var{kind}
31766 @itemx Z2,@var{addr},@var{kind}
31767 @cindex @samp{z2} packet
31768 @cindex @samp{Z2} packet
31769 Insert (@samp{Z2}) or remove (@samp{z2}) a write watchpoint at @var{addr}.
31770 @var{kind} is interpreted as the number of bytes to watch.
31782 @item z3,@var{addr},@var{kind}
31783 @itemx Z3,@var{addr},@var{kind}
31784 @cindex @samp{z3} packet
31785 @cindex @samp{Z3} packet
31786 Insert (@samp{Z3}) or remove (@samp{z3}) a read watchpoint at @var{addr}.
31787 @var{kind} is interpreted as the number of bytes to watch.
31799 @item z4,@var{addr},@var{kind}
31800 @itemx Z4,@var{addr},@var{kind}
31801 @cindex @samp{z4} packet
31802 @cindex @samp{Z4} packet
31803 Insert (@samp{Z4}) or remove (@samp{z4}) an access watchpoint at @var{addr}.
31804 @var{kind} is interpreted as the number of bytes to watch.
31818 @node Stop Reply Packets
31819 @section Stop Reply Packets
31820 @cindex stop reply packets
31822 The @samp{C}, @samp{c}, @samp{S}, @samp{s}, @samp{vCont},
31823 @samp{vAttach}, @samp{vRun}, @samp{vStopped}, and @samp{?} packets can
31824 receive any of the below as a reply. Except for @samp{?}
31825 and @samp{vStopped}, that reply is only returned
31826 when the target halts. In the below the exact meaning of @dfn{signal
31827 number} is defined by the header @file{include/gdb/signals.h} in the
31828 @value{GDBN} source code.
31830 As in the description of request packets, we include spaces in the
31831 reply templates for clarity; these are not part of the reply packet's
31832 syntax. No @value{GDBN} stop reply packet uses spaces to separate its
31838 The program received signal number @var{AA} (a two-digit hexadecimal
31839 number). This is equivalent to a @samp{T} response with no
31840 @var{n}:@var{r} pairs.
31842 @item T @var{AA} @var{n1}:@var{r1};@var{n2}:@var{r2};@dots{}
31843 @cindex @samp{T} packet reply
31844 The program received signal number @var{AA} (a two-digit hexadecimal
31845 number). This is equivalent to an @samp{S} response, except that the
31846 @samp{@var{n}:@var{r}} pairs can carry values of important registers
31847 and other information directly in the stop reply packet, reducing
31848 round-trip latency. Single-step and breakpoint traps are reported
31849 this way. Each @samp{@var{n}:@var{r}} pair is interpreted as follows:
31853 If @var{n} is a hexadecimal number, it is a register number, and the
31854 corresponding @var{r} gives that register's value. @var{r} is a
31855 series of bytes in target byte order, with each byte given by a
31856 two-digit hex number.
31859 If @var{n} is @samp{thread}, then @var{r} is the @var{thread-id} of
31860 the stopped thread, as specified in @ref{thread-id syntax}.
31863 If @var{n} is @samp{core}, then @var{r} is the hexadecimal number of
31864 the core on which the stop event was detected.
31867 If @var{n} is a recognized @dfn{stop reason}, it describes a more
31868 specific event that stopped the target. The currently defined stop
31869 reasons are listed below. @var{aa} should be @samp{05}, the trap
31870 signal. At most one stop reason should be present.
31873 Otherwise, @value{GDBN} should ignore this @samp{@var{n}:@var{r}} pair
31874 and go on to the next; this allows us to extend the protocol in the
31878 The currently defined stop reasons are:
31884 The packet indicates a watchpoint hit, and @var{r} is the data address, in
31887 @cindex shared library events, remote reply
31889 The packet indicates that the loaded libraries have changed.
31890 @value{GDBN} should use @samp{qXfer:libraries:read} to fetch a new
31891 list of loaded libraries. @var{r} is ignored.
31893 @cindex replay log events, remote reply
31895 The packet indicates that the target cannot continue replaying
31896 logged execution events, because it has reached the end (or the
31897 beginning when executing backward) of the log. The value of @var{r}
31898 will be either @samp{begin} or @samp{end}. @xref{Reverse Execution},
31899 for more information.
31903 @itemx W @var{AA} ; process:@var{pid}
31904 The process exited, and @var{AA} is the exit status. This is only
31905 applicable to certain targets.
31907 The second form of the response, including the process ID of the exited
31908 process, can be used only when @value{GDBN} has reported support for
31909 multiprocess protocol extensions; see @ref{multiprocess extensions}.
31910 The @var{pid} is formatted as a big-endian hex string.
31913 @itemx X @var{AA} ; process:@var{pid}
31914 The process terminated with signal @var{AA}.
31916 The second form of the response, including the process ID of the
31917 terminated process, can be used only when @value{GDBN} has reported
31918 support for multiprocess protocol extensions; see @ref{multiprocess
31919 extensions}. The @var{pid} is formatted as a big-endian hex string.
31921 @item O @var{XX}@dots{}
31922 @samp{@var{XX}@dots{}} is hex encoding of @sc{ascii} data, to be
31923 written as the program's console output. This can happen at any time
31924 while the program is running and the debugger should continue to wait
31925 for @samp{W}, @samp{T}, etc. This reply is not permitted in non-stop mode.
31927 @item F @var{call-id},@var{parameter}@dots{}
31928 @var{call-id} is the identifier which says which host system call should
31929 be called. This is just the name of the function. Translation into the
31930 correct system call is only applicable as it's defined in @value{GDBN}.
31931 @xref{File-I/O Remote Protocol Extension}, for a list of implemented
31934 @samp{@var{parameter}@dots{}} is a list of parameters as defined for
31935 this very system call.
31937 The target replies with this packet when it expects @value{GDBN} to
31938 call a host system call on behalf of the target. @value{GDBN} replies
31939 with an appropriate @samp{F} packet and keeps up waiting for the next
31940 reply packet from the target. The latest @samp{C}, @samp{c}, @samp{S}
31941 or @samp{s} action is expected to be continued. @xref{File-I/O Remote
31942 Protocol Extension}, for more details.
31946 @node General Query Packets
31947 @section General Query Packets
31948 @cindex remote query requests
31950 Packets starting with @samp{q} are @dfn{general query packets};
31951 packets starting with @samp{Q} are @dfn{general set packets}. General
31952 query and set packets are a semi-unified form for retrieving and
31953 sending information to and from the stub.
31955 The initial letter of a query or set packet is followed by a name
31956 indicating what sort of thing the packet applies to. For example,
31957 @value{GDBN} may use a @samp{qSymbol} packet to exchange symbol
31958 definitions with the stub. These packet names follow some
31963 The name must not contain commas, colons or semicolons.
31965 Most @value{GDBN} query and set packets have a leading upper case
31968 The names of custom vendor packets should use a company prefix, in
31969 lower case, followed by a period. For example, packets designed at
31970 the Acme Corporation might begin with @samp{qacme.foo} (for querying
31971 foos) or @samp{Qacme.bar} (for setting bars).
31974 The name of a query or set packet should be separated from any
31975 parameters by a @samp{:}; the parameters themselves should be
31976 separated by @samp{,} or @samp{;}. Stubs must be careful to match the
31977 full packet name, and check for a separator or the end of the packet,
31978 in case two packet names share a common prefix. New packets should not begin
31979 with @samp{qC}, @samp{qP}, or @samp{qL}@footnote{The @samp{qP} and @samp{qL}
31980 packets predate these conventions, and have arguments without any terminator
31981 for the packet name; we suspect they are in widespread use in places that
31982 are difficult to upgrade. The @samp{qC} packet has no arguments, but some
31983 existing stubs (e.g.@: RedBoot) are known to not check for the end of the
31986 Like the descriptions of the other packets, each description here
31987 has a template showing the packet's overall syntax, followed by an
31988 explanation of the packet's meaning. We include spaces in some of the
31989 templates for clarity; these are not part of the packet's syntax. No
31990 @value{GDBN} packet uses spaces to separate its components.
31992 Here are the currently defined query and set packets:
31996 @item QAllow:@var{op}:@var{val}@dots{}
31997 @cindex @samp{QAllow} packet
31998 Specify which operations @value{GDBN} expects to request of the
31999 target, as a semicolon-separated list of operation name and value
32000 pairs. Possible values for @var{op} include @samp{WriteReg},
32001 @samp{WriteMem}, @samp{InsertBreak}, @samp{InsertTrace},
32002 @samp{InsertFastTrace}, and @samp{Stop}. @var{val} is either 0,
32003 indicating that @value{GDBN} will not request the operation, or 1,
32004 indicating that it may. (The target can then use this to set up its
32005 own internals optimally, for instance if the debugger never expects to
32006 insert breakpoints, it may not need to install its own trap handler.)
32009 @cindex current thread, remote request
32010 @cindex @samp{qC} packet
32011 Return the current thread ID.
32015 @item QC @var{thread-id}
32016 Where @var{thread-id} is a thread ID as documented in
32017 @ref{thread-id syntax}.
32018 @item @r{(anything else)}
32019 Any other reply implies the old thread ID.
32022 @item qCRC:@var{addr},@var{length}
32023 @cindex CRC of memory block, remote request
32024 @cindex @samp{qCRC} packet
32025 Compute the CRC checksum of a block of memory using CRC-32 defined in
32026 IEEE 802.3. The CRC is computed byte at a time, taking the most
32027 significant bit of each byte first. The initial pattern code
32028 @code{0xffffffff} is used to ensure leading zeros affect the CRC.
32030 @emph{Note:} This is the same CRC used in validating separate debug
32031 files (@pxref{Separate Debug Files, , Debugging Information in Separate
32032 Files}). However the algorithm is slightly different. When validating
32033 separate debug files, the CRC is computed taking the @emph{least}
32034 significant bit of each byte first, and the final result is inverted to
32035 detect trailing zeros.
32040 An error (such as memory fault)
32041 @item C @var{crc32}
32042 The specified memory region's checksum is @var{crc32}.
32046 @itemx qsThreadInfo
32047 @cindex list active threads, remote request
32048 @cindex @samp{qfThreadInfo} packet
32049 @cindex @samp{qsThreadInfo} packet
32050 Obtain a list of all active thread IDs from the target (OS). Since there
32051 may be too many active threads to fit into one reply packet, this query
32052 works iteratively: it may require more than one query/reply sequence to
32053 obtain the entire list of threads. The first query of the sequence will
32054 be the @samp{qfThreadInfo} query; subsequent queries in the
32055 sequence will be the @samp{qsThreadInfo} query.
32057 NOTE: This packet replaces the @samp{qL} query (see below).
32061 @item m @var{thread-id}
32063 @item m @var{thread-id},@var{thread-id}@dots{}
32064 a comma-separated list of thread IDs
32066 (lower case letter @samp{L}) denotes end of list.
32069 In response to each query, the target will reply with a list of one or
32070 more thread IDs, separated by commas.
32071 @value{GDBN} will respond to each reply with a request for more thread
32072 ids (using the @samp{qs} form of the query), until the target responds
32073 with @samp{l} (lower-case ell, for @dfn{last}).
32074 Refer to @ref{thread-id syntax}, for the format of the @var{thread-id}
32077 @item qGetTLSAddr:@var{thread-id},@var{offset},@var{lm}
32078 @cindex get thread-local storage address, remote request
32079 @cindex @samp{qGetTLSAddr} packet
32080 Fetch the address associated with thread local storage specified
32081 by @var{thread-id}, @var{offset}, and @var{lm}.
32083 @var{thread-id} is the thread ID associated with the
32084 thread for which to fetch the TLS address. @xref{thread-id syntax}.
32086 @var{offset} is the (big endian, hex encoded) offset associated with the
32087 thread local variable. (This offset is obtained from the debug
32088 information associated with the variable.)
32090 @var{lm} is the (big endian, hex encoded) OS/ABI-specific encoding of the
32091 the load module associated with the thread local storage. For example,
32092 a @sc{gnu}/Linux system will pass the link map address of the shared
32093 object associated with the thread local storage under consideration.
32094 Other operating environments may choose to represent the load module
32095 differently, so the precise meaning of this parameter will vary.
32099 @item @var{XX}@dots{}
32100 Hex encoded (big endian) bytes representing the address of the thread
32101 local storage requested.
32104 An error occurred. @var{nn} are hex digits.
32107 An empty reply indicates that @samp{qGetTLSAddr} is not supported by the stub.
32110 @item qGetTIBAddr:@var{thread-id}
32111 @cindex get thread information block address
32112 @cindex @samp{qGetTIBAddr} packet
32113 Fetch address of the Windows OS specific Thread Information Block.
32115 @var{thread-id} is the thread ID associated with the thread.
32119 @item @var{XX}@dots{}
32120 Hex encoded (big endian) bytes representing the linear address of the
32121 thread information block.
32124 An error occured. This means that either the thread was not found, or the
32125 address could not be retrieved.
32128 An empty reply indicates that @samp{qGetTIBAddr} is not supported by the stub.
32131 @item qL @var{startflag} @var{threadcount} @var{nextthread}
32132 Obtain thread information from RTOS. Where: @var{startflag} (one hex
32133 digit) is one to indicate the first query and zero to indicate a
32134 subsequent query; @var{threadcount} (two hex digits) is the maximum
32135 number of threads the response packet can contain; and @var{nextthread}
32136 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
32137 returned in the response as @var{argthread}.
32139 Don't use this packet; use the @samp{qfThreadInfo} query instead (see above).
32143 @item qM @var{count} @var{done} @var{argthread} @var{thread}@dots{}
32144 Where: @var{count} (two hex digits) is the number of threads being
32145 returned; @var{done} (one hex digit) is zero to indicate more threads
32146 and one indicates no further threads; @var{argthreadid} (eight hex
32147 digits) is @var{nextthread} from the request packet; @var{thread}@dots{}
32148 is a sequence of thread IDs from the target. @var{threadid} (eight hex
32149 digits). See @code{remote.c:parse_threadlist_response()}.
32153 @cindex section offsets, remote request
32154 @cindex @samp{qOffsets} packet
32155 Get section offsets that the target used when relocating the downloaded
32160 @item Text=@var{xxx};Data=@var{yyy}@r{[};Bss=@var{zzz}@r{]}
32161 Relocate the @code{Text} section by @var{xxx} from its original address.
32162 Relocate the @code{Data} section by @var{yyy} from its original address.
32163 If the object file format provides segment information (e.g.@: @sc{elf}
32164 @samp{PT_LOAD} program headers), @value{GDBN} will relocate entire
32165 segments by the supplied offsets.
32167 @emph{Note: while a @code{Bss} offset may be included in the response,
32168 @value{GDBN} ignores this and instead applies the @code{Data} offset
32169 to the @code{Bss} section.}
32171 @item TextSeg=@var{xxx}@r{[};DataSeg=@var{yyy}@r{]}
32172 Relocate the first segment of the object file, which conventionally
32173 contains program code, to a starting address of @var{xxx}. If
32174 @samp{DataSeg} is specified, relocate the second segment, which
32175 conventionally contains modifiable data, to a starting address of
32176 @var{yyy}. @value{GDBN} will report an error if the object file
32177 does not contain segment information, or does not contain at least
32178 as many segments as mentioned in the reply. Extra segments are
32179 kept at fixed offsets relative to the last relocated segment.
32182 @item qP @var{mode} @var{thread-id}
32183 @cindex thread information, remote request
32184 @cindex @samp{qP} packet
32185 Returns information on @var{thread-id}. Where: @var{mode} is a hex
32186 encoded 32 bit mode; @var{thread-id} is a thread ID
32187 (@pxref{thread-id syntax}).
32189 Don't use this packet; use the @samp{qThreadExtraInfo} query instead
32192 Reply: see @code{remote.c:remote_unpack_thread_info_response()}.
32196 @cindex non-stop mode, remote request
32197 @cindex @samp{QNonStop} packet
32199 Enter non-stop (@samp{QNonStop:1}) or all-stop (@samp{QNonStop:0}) mode.
32200 @xref{Remote Non-Stop}, for more information.
32205 The request succeeded.
32208 An error occurred. @var{nn} are hex digits.
32211 An empty reply indicates that @samp{QNonStop} is not supported by
32215 This packet is not probed by default; the remote stub must request it,
32216 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
32217 Use of this packet is controlled by the @code{set non-stop} command;
32218 @pxref{Non-Stop Mode}.
32220 @item QPassSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
32221 @cindex pass signals to inferior, remote request
32222 @cindex @samp{QPassSignals} packet
32223 @anchor{QPassSignals}
32224 Each listed @var{signal} should be passed directly to the inferior process.
32225 Signals are numbered identically to continue packets and stop replies
32226 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
32227 strictly greater than the previous item. These signals do not need to stop
32228 the inferior, or be reported to @value{GDBN}. All other signals should be
32229 reported to @value{GDBN}. Multiple @samp{QPassSignals} packets do not
32230 combine; any earlier @samp{QPassSignals} list is completely replaced by the
32231 new list. This packet improves performance when using @samp{handle
32232 @var{signal} nostop noprint pass}.
32237 The request succeeded.
32240 An error occurred. @var{nn} are hex digits.
32243 An empty reply indicates that @samp{QPassSignals} is not supported by
32247 Use of this packet is controlled by the @code{set remote pass-signals}
32248 command (@pxref{Remote Configuration, set remote pass-signals}).
32249 This packet is not probed by default; the remote stub must request it,
32250 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
32252 @item qRcmd,@var{command}
32253 @cindex execute remote command, remote request
32254 @cindex @samp{qRcmd} packet
32255 @var{command} (hex encoded) is passed to the local interpreter for
32256 execution. Invalid commands should be reported using the output
32257 string. Before the final result packet, the target may also respond
32258 with a number of intermediate @samp{O@var{output}} console output
32259 packets. @emph{Implementors should note that providing access to a
32260 stubs's interpreter may have security implications}.
32265 A command response with no output.
32267 A command response with the hex encoded output string @var{OUTPUT}.
32269 Indicate a badly formed request.
32271 An empty reply indicates that @samp{qRcmd} is not recognized.
32274 (Note that the @code{qRcmd} packet's name is separated from the
32275 command by a @samp{,}, not a @samp{:}, contrary to the naming
32276 conventions above. Please don't use this packet as a model for new
32279 @item qSearch:memory:@var{address};@var{length};@var{search-pattern}
32280 @cindex searching memory, in remote debugging
32281 @cindex @samp{qSearch:memory} packet
32282 @anchor{qSearch memory}
32283 Search @var{length} bytes at @var{address} for @var{search-pattern}.
32284 @var{address} and @var{length} are encoded in hex.
32285 @var{search-pattern} is a sequence of bytes, hex encoded.
32290 The pattern was not found.
32292 The pattern was found at @var{address}.
32294 A badly formed request or an error was encountered while searching memory.
32296 An empty reply indicates that @samp{qSearch:memory} is not recognized.
32299 @item QStartNoAckMode
32300 @cindex @samp{QStartNoAckMode} packet
32301 @anchor{QStartNoAckMode}
32302 Request that the remote stub disable the normal @samp{+}/@samp{-}
32303 protocol acknowledgments (@pxref{Packet Acknowledgment}).
32308 The stub has switched to no-acknowledgment mode.
32309 @value{GDBN} acknowledges this reponse,
32310 but neither the stub nor @value{GDBN} shall send or expect further
32311 @samp{+}/@samp{-} acknowledgments in the current connection.
32313 An empty reply indicates that the stub does not support no-acknowledgment mode.
32316 @item qSupported @r{[}:@var{gdbfeature} @r{[};@var{gdbfeature}@r{]}@dots{} @r{]}
32317 @cindex supported packets, remote query
32318 @cindex features of the remote protocol
32319 @cindex @samp{qSupported} packet
32320 @anchor{qSupported}
32321 Tell the remote stub about features supported by @value{GDBN}, and
32322 query the stub for features it supports. This packet allows
32323 @value{GDBN} and the remote stub to take advantage of each others'
32324 features. @samp{qSupported} also consolidates multiple feature probes
32325 at startup, to improve @value{GDBN} performance---a single larger
32326 packet performs better than multiple smaller probe packets on
32327 high-latency links. Some features may enable behavior which must not
32328 be on by default, e.g.@: because it would confuse older clients or
32329 stubs. Other features may describe packets which could be
32330 automatically probed for, but are not. These features must be
32331 reported before @value{GDBN} will use them. This ``default
32332 unsupported'' behavior is not appropriate for all packets, but it
32333 helps to keep the initial connection time under control with new
32334 versions of @value{GDBN} which support increasing numbers of packets.
32338 @item @var{stubfeature} @r{[};@var{stubfeature}@r{]}@dots{}
32339 The stub supports or does not support each returned @var{stubfeature},
32340 depending on the form of each @var{stubfeature} (see below for the
32343 An empty reply indicates that @samp{qSupported} is not recognized,
32344 or that no features needed to be reported to @value{GDBN}.
32347 The allowed forms for each feature (either a @var{gdbfeature} in the
32348 @samp{qSupported} packet, or a @var{stubfeature} in the response)
32352 @item @var{name}=@var{value}
32353 The remote protocol feature @var{name} is supported, and associated
32354 with the specified @var{value}. The format of @var{value} depends
32355 on the feature, but it must not include a semicolon.
32357 The remote protocol feature @var{name} is supported, and does not
32358 need an associated value.
32360 The remote protocol feature @var{name} is not supported.
32362 The remote protocol feature @var{name} may be supported, and
32363 @value{GDBN} should auto-detect support in some other way when it is
32364 needed. This form will not be used for @var{gdbfeature} notifications,
32365 but may be used for @var{stubfeature} responses.
32368 Whenever the stub receives a @samp{qSupported} request, the
32369 supplied set of @value{GDBN} features should override any previous
32370 request. This allows @value{GDBN} to put the stub in a known
32371 state, even if the stub had previously been communicating with
32372 a different version of @value{GDBN}.
32374 The following values of @var{gdbfeature} (for the packet sent by @value{GDBN})
32379 This feature indicates whether @value{GDBN} supports multiprocess
32380 extensions to the remote protocol. @value{GDBN} does not use such
32381 extensions unless the stub also reports that it supports them by
32382 including @samp{multiprocess+} in its @samp{qSupported} reply.
32383 @xref{multiprocess extensions}, for details.
32386 This feature indicates that @value{GDBN} supports the XML target
32387 description. If the stub sees @samp{xmlRegisters=} with target
32388 specific strings separated by a comma, it will report register
32392 This feature indicates whether @value{GDBN} supports the
32393 @samp{qRelocInsn} packet (@pxref{Tracepoint Packets,,Relocate
32394 instruction reply packet}).
32397 Stubs should ignore any unknown values for
32398 @var{gdbfeature}. Any @value{GDBN} which sends a @samp{qSupported}
32399 packet supports receiving packets of unlimited length (earlier
32400 versions of @value{GDBN} may reject overly long responses). Additional values
32401 for @var{gdbfeature} may be defined in the future to let the stub take
32402 advantage of new features in @value{GDBN}, e.g.@: incompatible
32403 improvements in the remote protocol---the @samp{multiprocess} feature is
32404 an example of such a feature. The stub's reply should be independent
32405 of the @var{gdbfeature} entries sent by @value{GDBN}; first @value{GDBN}
32406 describes all the features it supports, and then the stub replies with
32407 all the features it supports.
32409 Similarly, @value{GDBN} will silently ignore unrecognized stub feature
32410 responses, as long as each response uses one of the standard forms.
32412 Some features are flags. A stub which supports a flag feature
32413 should respond with a @samp{+} form response. Other features
32414 require values, and the stub should respond with an @samp{=}
32417 Each feature has a default value, which @value{GDBN} will use if
32418 @samp{qSupported} is not available or if the feature is not mentioned
32419 in the @samp{qSupported} response. The default values are fixed; a
32420 stub is free to omit any feature responses that match the defaults.
32422 Not all features can be probed, but for those which can, the probing
32423 mechanism is useful: in some cases, a stub's internal
32424 architecture may not allow the protocol layer to know some information
32425 about the underlying target in advance. This is especially common in
32426 stubs which may be configured for multiple targets.
32428 These are the currently defined stub features and their properties:
32430 @multitable @columnfractions 0.35 0.2 0.12 0.2
32431 @c NOTE: The first row should be @headitem, but we do not yet require
32432 @c a new enough version of Texinfo (4.7) to use @headitem.
32434 @tab Value Required
32438 @item @samp{PacketSize}
32443 @item @samp{qXfer:auxv:read}
32448 @item @samp{qXfer:features:read}
32453 @item @samp{qXfer:libraries:read}
32458 @item @samp{qXfer:memory-map:read}
32463 @item @samp{qXfer:sdata:read}
32468 @item @samp{qXfer:spu:read}
32473 @item @samp{qXfer:spu:write}
32478 @item @samp{qXfer:siginfo:read}
32483 @item @samp{qXfer:siginfo:write}
32488 @item @samp{qXfer:threads:read}
32494 @item @samp{QNonStop}
32499 @item @samp{QPassSignals}
32504 @item @samp{QStartNoAckMode}
32509 @item @samp{multiprocess}
32514 @item @samp{ConditionalTracepoints}
32519 @item @samp{ReverseContinue}
32524 @item @samp{ReverseStep}
32529 @item @samp{TracepointSource}
32534 @item @samp{QAllow}
32541 These are the currently defined stub features, in more detail:
32544 @cindex packet size, remote protocol
32545 @item PacketSize=@var{bytes}
32546 The remote stub can accept packets up to at least @var{bytes} in
32547 length. @value{GDBN} will send packets up to this size for bulk
32548 transfers, and will never send larger packets. This is a limit on the
32549 data characters in the packet, including the frame and checksum.
32550 There is no trailing NUL byte in a remote protocol packet; if the stub
32551 stores packets in a NUL-terminated format, it should allow an extra
32552 byte in its buffer for the NUL. If this stub feature is not supported,
32553 @value{GDBN} guesses based on the size of the @samp{g} packet response.
32555 @item qXfer:auxv:read
32556 The remote stub understands the @samp{qXfer:auxv:read} packet
32557 (@pxref{qXfer auxiliary vector read}).
32559 @item qXfer:features:read
32560 The remote stub understands the @samp{qXfer:features:read} packet
32561 (@pxref{qXfer target description read}).
32563 @item qXfer:libraries:read
32564 The remote stub understands the @samp{qXfer:libraries:read} packet
32565 (@pxref{qXfer library list read}).
32567 @item qXfer:memory-map:read
32568 The remote stub understands the @samp{qXfer:memory-map:read} packet
32569 (@pxref{qXfer memory map read}).
32571 @item qXfer:sdata:read
32572 The remote stub understands the @samp{qXfer:sdata:read} packet
32573 (@pxref{qXfer sdata read}).
32575 @item qXfer:spu:read
32576 The remote stub understands the @samp{qXfer:spu:read} packet
32577 (@pxref{qXfer spu read}).
32579 @item qXfer:spu:write
32580 The remote stub understands the @samp{qXfer:spu:write} packet
32581 (@pxref{qXfer spu write}).
32583 @item qXfer:siginfo:read
32584 The remote stub understands the @samp{qXfer:siginfo:read} packet
32585 (@pxref{qXfer siginfo read}).
32587 @item qXfer:siginfo:write
32588 The remote stub understands the @samp{qXfer:siginfo:write} packet
32589 (@pxref{qXfer siginfo write}).
32591 @item qXfer:threads:read
32592 The remote stub understands the @samp{qXfer:threads:read} packet
32593 (@pxref{qXfer threads read}).
32596 The remote stub understands the @samp{QNonStop} packet
32597 (@pxref{QNonStop}).
32600 The remote stub understands the @samp{QPassSignals} packet
32601 (@pxref{QPassSignals}).
32603 @item QStartNoAckMode
32604 The remote stub understands the @samp{QStartNoAckMode} packet and
32605 prefers to operate in no-acknowledgment mode. @xref{Packet Acknowledgment}.
32608 @anchor{multiprocess extensions}
32609 @cindex multiprocess extensions, in remote protocol
32610 The remote stub understands the multiprocess extensions to the remote
32611 protocol syntax. The multiprocess extensions affect the syntax of
32612 thread IDs in both packets and replies (@pxref{thread-id syntax}), and
32613 add process IDs to the @samp{D} packet and @samp{W} and @samp{X}
32614 replies. Note that reporting this feature indicates support for the
32615 syntactic extensions only, not that the stub necessarily supports
32616 debugging of more than one process at a time. The stub must not use
32617 multiprocess extensions in packet replies unless @value{GDBN} has also
32618 indicated it supports them in its @samp{qSupported} request.
32620 @item qXfer:osdata:read
32621 The remote stub understands the @samp{qXfer:osdata:read} packet
32622 ((@pxref{qXfer osdata read}).
32624 @item ConditionalTracepoints
32625 The remote stub accepts and implements conditional expressions defined
32626 for tracepoints (@pxref{Tracepoint Conditions}).
32628 @item ReverseContinue
32629 The remote stub accepts and implements the reverse continue packet
32633 The remote stub accepts and implements the reverse step packet
32636 @item TracepointSource
32637 The remote stub understands the @samp{QTDPsrc} packet that supplies
32638 the source form of tracepoint definitions.
32641 The remote stub understands the @samp{QAllow} packet.
32643 @item StaticTracepoint
32644 @cindex static tracepoints, in remote protocol
32645 The remote stub supports static tracepoints.
32650 @cindex symbol lookup, remote request
32651 @cindex @samp{qSymbol} packet
32652 Notify the target that @value{GDBN} is prepared to serve symbol lookup
32653 requests. Accept requests from the target for the values of symbols.
32658 The target does not need to look up any (more) symbols.
32659 @item qSymbol:@var{sym_name}
32660 The target requests the value of symbol @var{sym_name} (hex encoded).
32661 @value{GDBN} may provide the value by using the
32662 @samp{qSymbol:@var{sym_value}:@var{sym_name}} message, described
32666 @item qSymbol:@var{sym_value}:@var{sym_name}
32667 Set the value of @var{sym_name} to @var{sym_value}.
32669 @var{sym_name} (hex encoded) is the name of a symbol whose value the
32670 target has previously requested.
32672 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
32673 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
32679 The target does not need to look up any (more) symbols.
32680 @item qSymbol:@var{sym_name}
32681 The target requests the value of a new symbol @var{sym_name} (hex
32682 encoded). @value{GDBN} will continue to supply the values of symbols
32683 (if available), until the target ceases to request them.
32688 @item QTDisconnected
32695 @xref{Tracepoint Packets}.
32697 @item qThreadExtraInfo,@var{thread-id}
32698 @cindex thread attributes info, remote request
32699 @cindex @samp{qThreadExtraInfo} packet
32700 Obtain a printable string description of a thread's attributes from
32701 the target OS. @var{thread-id} is a thread ID;
32702 see @ref{thread-id syntax}. This
32703 string may contain anything that the target OS thinks is interesting
32704 for @value{GDBN} to tell the user about the thread. The string is
32705 displayed in @value{GDBN}'s @code{info threads} display. Some
32706 examples of possible thread extra info strings are @samp{Runnable}, or
32707 @samp{Blocked on Mutex}.
32711 @item @var{XX}@dots{}
32712 Where @samp{@var{XX}@dots{}} is a hex encoding of @sc{ascii} data,
32713 comprising the printable string containing the extra information about
32714 the thread's attributes.
32717 (Note that the @code{qThreadExtraInfo} packet's name is separated from
32718 the command by a @samp{,}, not a @samp{:}, contrary to the naming
32719 conventions above. Please don't use this packet as a model for new
32734 @xref{Tracepoint Packets}.
32736 @item qXfer:@var{object}:read:@var{annex}:@var{offset},@var{length}
32737 @cindex read special object, remote request
32738 @cindex @samp{qXfer} packet
32739 @anchor{qXfer read}
32740 Read uninterpreted bytes from the target's special data area
32741 identified by the keyword @var{object}. Request @var{length} bytes
32742 starting at @var{offset} bytes into the data. The content and
32743 encoding of @var{annex} is specific to @var{object}; it can supply
32744 additional details about what data to access.
32746 Here are the specific requests of this form defined so far. All
32747 @samp{qXfer:@var{object}:read:@dots{}} requests use the same reply
32748 formats, listed below.
32751 @item qXfer:auxv:read::@var{offset},@var{length}
32752 @anchor{qXfer auxiliary vector read}
32753 Access the target's @dfn{auxiliary vector}. @xref{OS Information,
32754 auxiliary vector}. Note @var{annex} must be empty.
32756 This packet is not probed by default; the remote stub must request it,
32757 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
32759 @item qXfer:features:read:@var{annex}:@var{offset},@var{length}
32760 @anchor{qXfer target description read}
32761 Access the @dfn{target description}. @xref{Target Descriptions}. The
32762 annex specifies which XML document to access. The main description is
32763 always loaded from the @samp{target.xml} annex.
32765 This packet is not probed by default; the remote stub must request it,
32766 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
32768 @item qXfer:libraries:read:@var{annex}:@var{offset},@var{length}
32769 @anchor{qXfer library list read}
32770 Access the target's list of loaded libraries. @xref{Library List Format}.
32771 The annex part of the generic @samp{qXfer} packet must be empty
32772 (@pxref{qXfer read}).
32774 Targets which maintain a list of libraries in the program's memory do
32775 not need to implement this packet; it is designed for platforms where
32776 the operating system manages the list of loaded libraries.
32778 This packet is not probed by default; the remote stub must request it,
32779 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
32781 @item qXfer:memory-map:read::@var{offset},@var{length}
32782 @anchor{qXfer memory map read}
32783 Access the target's @dfn{memory-map}. @xref{Memory Map Format}. The
32784 annex part of the generic @samp{qXfer} packet must be empty
32785 (@pxref{qXfer read}).
32787 This packet is not probed by default; the remote stub must request it,
32788 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
32790 @item qXfer:sdata:read::@var{offset},@var{length}
32791 @anchor{qXfer sdata read}
32793 Read contents of the extra collected static tracepoint marker
32794 information. The annex part of the generic @samp{qXfer} packet must
32795 be empty (@pxref{qXfer read}). @xref{Tracepoint Actions,,Tracepoint
32798 This packet is not probed by default; the remote stub must request it,
32799 by supplying an appropriate @samp{qSupported} response
32800 (@pxref{qSupported}).
32802 @item qXfer:siginfo:read::@var{offset},@var{length}
32803 @anchor{qXfer siginfo read}
32804 Read contents of the extra signal information on the target
32805 system. The annex part of the generic @samp{qXfer} packet must be
32806 empty (@pxref{qXfer read}).
32808 This packet is not probed by default; the remote stub must request it,
32809 by supplying an appropriate @samp{qSupported} response
32810 (@pxref{qSupported}).
32812 @item qXfer:spu:read:@var{annex}:@var{offset},@var{length}
32813 @anchor{qXfer spu read}
32814 Read contents of an @code{spufs} file on the target system. The
32815 annex specifies which file to read; it must be of the form
32816 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
32817 in the target process, and @var{name} identifes the @code{spufs} file
32818 in that context to be accessed.
32820 This packet is not probed by default; the remote stub must request it,
32821 by supplying an appropriate @samp{qSupported} response
32822 (@pxref{qSupported}).
32824 @item qXfer:threads:read::@var{offset},@var{length}
32825 @anchor{qXfer threads read}
32826 Access the list of threads on target. @xref{Thread List Format}. The
32827 annex part of the generic @samp{qXfer} packet must be empty
32828 (@pxref{qXfer read}).
32830 This packet is not probed by default; the remote stub must request it,
32831 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
32833 @item qXfer:osdata:read::@var{offset},@var{length}
32834 @anchor{qXfer osdata read}
32835 Access the target's @dfn{operating system information}.
32836 @xref{Operating System Information}.
32843 Data @var{data} (@pxref{Binary Data}) has been read from the
32844 target. There may be more data at a higher address (although
32845 it is permitted to return @samp{m} even for the last valid
32846 block of data, as long as at least one byte of data was read).
32847 @var{data} may have fewer bytes than the @var{length} in the
32851 Data @var{data} (@pxref{Binary Data}) has been read from the target.
32852 There is no more data to be read. @var{data} may have fewer bytes
32853 than the @var{length} in the request.
32856 The @var{offset} in the request is at the end of the data.
32857 There is no more data to be read.
32860 The request was malformed, or @var{annex} was invalid.
32863 The offset was invalid, or there was an error encountered reading the data.
32864 @var{nn} is a hex-encoded @code{errno} value.
32867 An empty reply indicates the @var{object} string was not recognized by
32868 the stub, or that the object does not support reading.
32871 @item qXfer:@var{object}:write:@var{annex}:@var{offset}:@var{data}@dots{}
32872 @cindex write data into object, remote request
32873 @anchor{qXfer write}
32874 Write uninterpreted bytes into the target's special data area
32875 identified by the keyword @var{object}, starting at @var{offset} bytes
32876 into the data. @var{data}@dots{} is the binary-encoded data
32877 (@pxref{Binary Data}) to be written. The content and encoding of @var{annex}
32878 is specific to @var{object}; it can supply additional details about what data
32881 Here are the specific requests of this form defined so far. All
32882 @samp{qXfer:@var{object}:write:@dots{}} requests use the same reply
32883 formats, listed below.
32886 @item qXfer:siginfo:write::@var{offset}:@var{data}@dots{}
32887 @anchor{qXfer siginfo write}
32888 Write @var{data} to the extra signal information on the target system.
32889 The annex part of the generic @samp{qXfer} packet must be
32890 empty (@pxref{qXfer write}).
32892 This packet is not probed by default; the remote stub must request it,
32893 by supplying an appropriate @samp{qSupported} response
32894 (@pxref{qSupported}).
32896 @item qXfer:spu:write:@var{annex}:@var{offset}:@var{data}@dots{}
32897 @anchor{qXfer spu write}
32898 Write @var{data} to an @code{spufs} file on the target system. The
32899 annex specifies which file to write; it must be of the form
32900 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
32901 in the target process, and @var{name} identifes the @code{spufs} file
32902 in that context to be accessed.
32904 This packet is not probed by default; the remote stub must request it,
32905 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
32911 @var{nn} (hex encoded) is the number of bytes written.
32912 This may be fewer bytes than supplied in the request.
32915 The request was malformed, or @var{annex} was invalid.
32918 The offset was invalid, or there was an error encountered writing the data.
32919 @var{nn} is a hex-encoded @code{errno} value.
32922 An empty reply indicates the @var{object} string was not
32923 recognized by the stub, or that the object does not support writing.
32926 @item qXfer:@var{object}:@var{operation}:@dots{}
32927 Requests of this form may be added in the future. When a stub does
32928 not recognize the @var{object} keyword, or its support for
32929 @var{object} does not recognize the @var{operation} keyword, the stub
32930 must respond with an empty packet.
32932 @item qAttached:@var{pid}
32933 @cindex query attached, remote request
32934 @cindex @samp{qAttached} packet
32935 Return an indication of whether the remote server attached to an
32936 existing process or created a new process. When the multiprocess
32937 protocol extensions are supported (@pxref{multiprocess extensions}),
32938 @var{pid} is an integer in hexadecimal format identifying the target
32939 process. Otherwise, @value{GDBN} will omit the @var{pid} field and
32940 the query packet will be simplified as @samp{qAttached}.
32942 This query is used, for example, to know whether the remote process
32943 should be detached or killed when a @value{GDBN} session is ended with
32944 the @code{quit} command.
32949 The remote server attached to an existing process.
32951 The remote server created a new process.
32953 A badly formed request or an error was encountered.
32958 @node Architecture-Specific Protocol Details
32959 @section Architecture-Specific Protocol Details
32961 This section describes how the remote protocol is applied to specific
32962 target architectures. Also see @ref{Standard Target Features}, for
32963 details of XML target descriptions for each architecture.
32967 @subsubsection Breakpoint Kinds
32969 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
32974 16-bit Thumb mode breakpoint.
32977 32-bit Thumb mode (Thumb-2) breakpoint.
32980 32-bit ARM mode breakpoint.
32986 @subsubsection Register Packet Format
32988 The following @code{g}/@code{G} packets have previously been defined.
32989 In the below, some thirty-two bit registers are transferred as
32990 sixty-four bits. Those registers should be zero/sign extended (which?)
32991 to fill the space allocated. Register bytes are transferred in target
32992 byte order. The two nibbles within a register byte are transferred
32993 most-significant - least-significant.
32999 All registers are transferred as thirty-two bit quantities in the order:
33000 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
33001 registers; fsr; fir; fp.
33005 All registers are transferred as sixty-four bit quantities (including
33006 thirty-two bit registers such as @code{sr}). The ordering is the same
33011 @node Tracepoint Packets
33012 @section Tracepoint Packets
33013 @cindex tracepoint packets
33014 @cindex packets, tracepoint
33016 Here we describe the packets @value{GDBN} uses to implement
33017 tracepoints (@pxref{Tracepoints}).
33021 @item QTDP:@var{n}:@var{addr}:@var{ena}:@var{step}:@var{pass}[:F@var{flen}][:X@var{len},@var{bytes}]@r{[}-@r{]}
33022 Create a new tracepoint, number @var{n}, at @var{addr}. If @var{ena}
33023 is @samp{E}, then the tracepoint is enabled; if it is @samp{D}, then
33024 the tracepoint is disabled. @var{step} is the tracepoint's step
33025 count, and @var{pass} is its pass count. If an @samp{F} is present,
33026 then the tracepoint is to be a fast tracepoint, and the @var{flen} is
33027 the number of bytes that the target should copy elsewhere to make room
33028 for the tracepoint. If an @samp{X} is present, it introduces a
33029 tracepoint condition, which consists of a hexadecimal length, followed
33030 by a comma and hex-encoded bytes, in a manner similar to action
33031 encodings as described below. If the trailing @samp{-} is present,
33032 further @samp{QTDP} packets will follow to specify this tracepoint's
33038 The packet was understood and carried out.
33040 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
33042 The packet was not recognized.
33045 @item QTDP:-@var{n}:@var{addr}:@r{[}S@r{]}@var{action}@dots{}@r{[}-@r{]}
33046 Define actions to be taken when a tracepoint is hit. @var{n} and
33047 @var{addr} must be the same as in the initial @samp{QTDP} packet for
33048 this tracepoint. This packet may only be sent immediately after
33049 another @samp{QTDP} packet that ended with a @samp{-}. If the
33050 trailing @samp{-} is present, further @samp{QTDP} packets will follow,
33051 specifying more actions for this tracepoint.
33053 In the series of action packets for a given tracepoint, at most one
33054 can have an @samp{S} before its first @var{action}. If such a packet
33055 is sent, it and the following packets define ``while-stepping''
33056 actions. Any prior packets define ordinary actions --- that is, those
33057 taken when the tracepoint is first hit. If no action packet has an
33058 @samp{S}, then all the packets in the series specify ordinary
33059 tracepoint actions.
33061 The @samp{@var{action}@dots{}} portion of the packet is a series of
33062 actions, concatenated without separators. Each action has one of the
33068 Collect the registers whose bits are set in @var{mask}. @var{mask} is
33069 a hexadecimal number whose @var{i}'th bit is set if register number
33070 @var{i} should be collected. (The least significant bit is numbered
33071 zero.) Note that @var{mask} may be any number of digits long; it may
33072 not fit in a 32-bit word.
33074 @item M @var{basereg},@var{offset},@var{len}
33075 Collect @var{len} bytes of memory starting at the address in register
33076 number @var{basereg}, plus @var{offset}. If @var{basereg} is
33077 @samp{-1}, then the range has a fixed address: @var{offset} is the
33078 address of the lowest byte to collect. The @var{basereg},
33079 @var{offset}, and @var{len} parameters are all unsigned hexadecimal
33080 values (the @samp{-1} value for @var{basereg} is a special case).
33082 @item X @var{len},@var{expr}
33083 Evaluate @var{expr}, whose length is @var{len}, and collect memory as
33084 it directs. @var{expr} is an agent expression, as described in
33085 @ref{Agent Expressions}. Each byte of the expression is encoded as a
33086 two-digit hex number in the packet; @var{len} is the number of bytes
33087 in the expression (and thus one-half the number of hex digits in the
33092 Any number of actions may be packed together in a single @samp{QTDP}
33093 packet, as long as the packet does not exceed the maximum packet
33094 length (400 bytes, for many stubs). There may be only one @samp{R}
33095 action per tracepoint, and it must precede any @samp{M} or @samp{X}
33096 actions. Any registers referred to by @samp{M} and @samp{X} actions
33097 must be collected by a preceding @samp{R} action. (The
33098 ``while-stepping'' actions are treated as if they were attached to a
33099 separate tracepoint, as far as these restrictions are concerned.)
33104 The packet was understood and carried out.
33106 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
33108 The packet was not recognized.
33111 @item QTDPsrc:@var{n}:@var{addr}:@var{type}:@var{start}:@var{slen}:@var{bytes}
33112 @cindex @samp{QTDPsrc} packet
33113 Specify a source string of tracepoint @var{n} at address @var{addr}.
33114 This is useful to get accurate reproduction of the tracepoints
33115 originally downloaded at the beginning of the trace run. @var{type}
33116 is the name of the tracepoint part, such as @samp{cond} for the
33117 tracepoint's conditional expression (see below for a list of types), while
33118 @var{bytes} is the string, encoded in hexadecimal.
33120 @var{start} is the offset of the @var{bytes} within the overall source
33121 string, while @var{slen} is the total length of the source string.
33122 This is intended for handling source strings that are longer than will
33123 fit in a single packet.
33124 @c Add detailed example when this info is moved into a dedicated
33125 @c tracepoint descriptions section.
33127 The available string types are @samp{at} for the location,
33128 @samp{cond} for the conditional, and @samp{cmd} for an action command.
33129 @value{GDBN} sends a separate packet for each command in the action
33130 list, in the same order in which the commands are stored in the list.
33132 The target does not need to do anything with source strings except
33133 report them back as part of the replies to the @samp{qTfP}/@samp{qTsP}
33136 Although this packet is optional, and @value{GDBN} will only send it
33137 if the target replies with @samp{TracepointSource} @xref{General
33138 Query Packets}, it makes both disconnected tracing and trace files
33139 much easier to use. Otherwise the user must be careful that the
33140 tracepoints in effect while looking at trace frames are identical to
33141 the ones in effect during the trace run; even a small discrepancy
33142 could cause @samp{tdump} not to work, or a particular trace frame not
33145 @item QTDV:@var{n}:@var{value}
33146 @cindex define trace state variable, remote request
33147 @cindex @samp{QTDV} packet
33148 Create a new trace state variable, number @var{n}, with an initial
33149 value of @var{value}, which is a 64-bit signed integer. Both @var{n}
33150 and @var{value} are encoded as hexadecimal values. @value{GDBN} has
33151 the option of not using this packet for initial values of zero; the
33152 target should simply create the trace state variables as they are
33153 mentioned in expressions.
33155 @item QTFrame:@var{n}
33156 Select the @var{n}'th tracepoint frame from the buffer, and use the
33157 register and memory contents recorded there to answer subsequent
33158 request packets from @value{GDBN}.
33160 A successful reply from the stub indicates that the stub has found the
33161 requested frame. The response is a series of parts, concatenated
33162 without separators, describing the frame we selected. Each part has
33163 one of the following forms:
33167 The selected frame is number @var{n} in the trace frame buffer;
33168 @var{f} is a hexadecimal number. If @var{f} is @samp{-1}, then there
33169 was no frame matching the criteria in the request packet.
33172 The selected trace frame records a hit of tracepoint number @var{t};
33173 @var{t} is a hexadecimal number.
33177 @item QTFrame:pc:@var{addr}
33178 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
33179 currently selected frame whose PC is @var{addr};
33180 @var{addr} is a hexadecimal number.
33182 @item QTFrame:tdp:@var{t}
33183 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
33184 currently selected frame that is a hit of tracepoint @var{t}; @var{t}
33185 is a hexadecimal number.
33187 @item QTFrame:range:@var{start}:@var{end}
33188 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
33189 currently selected frame whose PC is between @var{start} (inclusive)
33190 and @var{end} (inclusive); @var{start} and @var{end} are hexadecimal
33193 @item QTFrame:outside:@var{start}:@var{end}
33194 Like @samp{QTFrame:range:@var{start}:@var{end}}, but select the first
33195 frame @emph{outside} the given range of addresses (exclusive).
33198 Begin the tracepoint experiment. Begin collecting data from
33199 tracepoint hits in the trace frame buffer. This packet supports the
33200 @samp{qRelocInsn} reply (@pxref{Tracepoint Packets,,Relocate
33201 instruction reply packet}).
33204 End the tracepoint experiment. Stop collecting trace frames.
33207 Clear the table of tracepoints, and empty the trace frame buffer.
33209 @item QTro:@var{start1},@var{end1}:@var{start2},@var{end2}:@dots{}
33210 Establish the given ranges of memory as ``transparent''. The stub
33211 will answer requests for these ranges from memory's current contents,
33212 if they were not collected as part of the tracepoint hit.
33214 @value{GDBN} uses this to mark read-only regions of memory, like those
33215 containing program code. Since these areas never change, they should
33216 still have the same contents they did when the tracepoint was hit, so
33217 there's no reason for the stub to refuse to provide their contents.
33219 @item QTDisconnected:@var{value}
33220 Set the choice to what to do with the tracing run when @value{GDBN}
33221 disconnects from the target. A @var{value} of 1 directs the target to
33222 continue the tracing run, while 0 tells the target to stop tracing if
33223 @value{GDBN} is no longer in the picture.
33226 Ask the stub if there is a trace experiment running right now.
33228 The reply has the form:
33232 @item T@var{running}@r{[};@var{field}@r{]}@dots{}
33233 @var{running} is a single digit @code{1} if the trace is presently
33234 running, or @code{0} if not. It is followed by semicolon-separated
33235 optional fields that an agent may use to report additional status.
33239 If the trace is not running, the agent may report any of several
33240 explanations as one of the optional fields:
33245 No trace has been run yet.
33248 The trace was stopped by a user-originated stop command.
33251 The trace stopped because the trace buffer filled up.
33253 @item tdisconnected:0
33254 The trace stopped because @value{GDBN} disconnected from the target.
33256 @item tpasscount:@var{tpnum}
33257 The trace stopped because tracepoint @var{tpnum} exceeded its pass count.
33259 @item terror:@var{text}:@var{tpnum}
33260 The trace stopped because tracepoint @var{tpnum} had an error. The
33261 string @var{text} is available to describe the nature of the error
33262 (for instance, a divide by zero in the condition expression).
33263 @var{text} is hex encoded.
33266 The trace stopped for some other reason.
33270 Additional optional fields supply statistical and other information.
33271 Although not required, they are extremely useful for users monitoring
33272 the progress of a trace run. If a trace has stopped, and these
33273 numbers are reported, they must reflect the state of the just-stopped
33278 @item tframes:@var{n}
33279 The number of trace frames in the buffer.
33281 @item tcreated:@var{n}
33282 The total number of trace frames created during the run. This may
33283 be larger than the trace frame count, if the buffer is circular.
33285 @item tsize:@var{n}
33286 The total size of the trace buffer, in bytes.
33288 @item tfree:@var{n}
33289 The number of bytes still unused in the buffer.
33291 @item circular:@var{n}
33292 The value of the circular trace buffer flag. @code{1} means that the
33293 trace buffer is circular and old trace frames will be discarded if
33294 necessary to make room, @code{0} means that the trace buffer is linear
33297 @item disconn:@var{n}
33298 The value of the disconnected tracing flag. @code{1} means that
33299 tracing will continue after @value{GDBN} disconnects, @code{0} means
33300 that the trace run will stop.
33304 @item qTV:@var{var}
33305 @cindex trace state variable value, remote request
33306 @cindex @samp{qTV} packet
33307 Ask the stub for the value of the trace state variable number @var{var}.
33312 The value of the variable is @var{value}. This will be the current
33313 value of the variable if the user is examining a running target, or a
33314 saved value if the variable was collected in the trace frame that the
33315 user is looking at. Note that multiple requests may result in
33316 different reply values, such as when requesting values while the
33317 program is running.
33320 The value of the variable is unknown. This would occur, for example,
33321 if the user is examining a trace frame in which the requested variable
33327 These packets request data about tracepoints that are being used by
33328 the target. @value{GDBN} sends @code{qTfP} to get the first piece
33329 of data, and multiple @code{qTsP} to get additional pieces. Replies
33330 to these packets generally take the form of the @code{QTDP} packets
33331 that define tracepoints. (FIXME add detailed syntax)
33335 These packets request data about trace state variables that are on the
33336 target. @value{GDBN} sends @code{qTfV} to get the first vari of data,
33337 and multiple @code{qTsV} to get additional variables. Replies to
33338 these packets follow the syntax of the @code{QTDV} packets that define
33339 trace state variables.
33343 These packets request data about static tracepoint markers that exist
33344 in the target program. @value{GDBN} sends @code{qTfSTM} to get the
33345 first piece of data, and multiple @code{qTsSTM} to get additional
33346 pieces. Replies to these packets take the following form:
33350 @item m @var{address}:@var{id}:@var{extra}
33352 @item m @var{address}:@var{id}:@var{extra},@var{address}:@var{id}:@var{extra}@dots{}
33353 a comma-separated list of markers
33355 (lower case letter @samp{L}) denotes end of list.
33357 An error occurred. @var{nn} are hex digits.
33359 An empty reply indicates that the request is not supported by the
33363 @var{address} is encoded in hex.
33364 @var{id} and @var{extra} are strings encoded in hex.
33366 In response to each query, the target will reply with a list of one or
33367 more markers, separated by commas. @value{GDBN} will respond to each
33368 reply with a request for more markers (using the @samp{qs} form of the
33369 query), until the target responds with @samp{l} (lower-case ell, for
33372 @item qTSTMat:@var{address}
33373 This packets requests data about static tracepoint markers in the
33374 target program at @var{address}. Replies to this packet follow the
33375 syntax of the @samp{qTfSTM} and @code{qTsSTM} packets that list static
33376 tracepoint markers.
33378 @item QTSave:@var{filename}
33379 This packet directs the target to save trace data to the file name
33380 @var{filename} in the target's filesystem. @var{filename} is encoded
33381 as a hex string; the interpretation of the file name (relative vs
33382 absolute, wild cards, etc) is up to the target.
33384 @item qTBuffer:@var{offset},@var{len}
33385 Return up to @var{len} bytes of the current contents of trace buffer,
33386 starting at @var{offset}. The trace buffer is treated as if it were
33387 a contiguous collection of traceframes, as per the trace file format.
33388 The reply consists as many hex-encoded bytes as the target can deliver
33389 in a packet; it is not an error to return fewer than were asked for.
33390 A reply consisting of just @code{l} indicates that no bytes are
33393 @item QTBuffer:circular:@var{value}
33394 This packet directs the target to use a circular trace buffer if
33395 @var{value} is 1, or a linear buffer if the value is 0.
33399 @subsection Relocate instruction reply packet
33400 When installing fast tracepoints in memory, the target may need to
33401 relocate the instruction currently at the tracepoint address to a
33402 different address in memory. For most instructions, a simple copy is
33403 enough, but, for example, call instructions that implicitly push the
33404 return address on the stack, and relative branches or other
33405 PC-relative instructions require offset adjustment, so that the effect
33406 of executing the instruction at a different address is the same as if
33407 it had executed in the original location.
33409 In response to several of the tracepoint packets, the target may also
33410 respond with a number of intermediate @samp{qRelocInsn} request
33411 packets before the final result packet, to have @value{GDBN} handle
33412 this relocation operation. If a packet supports this mechanism, its
33413 documentation will explicitly say so. See for example the above
33414 descriptions for the @samp{QTStart} and @samp{QTDP} packets. The
33415 format of the request is:
33418 @item qRelocInsn:@var{from};@var{to}
33420 This requests @value{GDBN} to copy instruction at address @var{from}
33421 to address @var{to}, possibly adjusted so that executing the
33422 instruction at @var{to} has the same effect as executing it at
33423 @var{from}. @value{GDBN} writes the adjusted instruction to target
33424 memory starting at @var{to}.
33429 @item qRelocInsn:@var{adjusted_size}
33430 Informs the stub the relocation is complete. @var{adjusted_size} is
33431 the length in bytes of resulting relocated instruction sequence.
33433 A badly formed request was detected, or an error was encountered while
33434 relocating the instruction.
33437 @node Host I/O Packets
33438 @section Host I/O Packets
33439 @cindex Host I/O, remote protocol
33440 @cindex file transfer, remote protocol
33442 The @dfn{Host I/O} packets allow @value{GDBN} to perform I/O
33443 operations on the far side of a remote link. For example, Host I/O is
33444 used to upload and download files to a remote target with its own
33445 filesystem. Host I/O uses the same constant values and data structure
33446 layout as the target-initiated File-I/O protocol. However, the
33447 Host I/O packets are structured differently. The target-initiated
33448 protocol relies on target memory to store parameters and buffers.
33449 Host I/O requests are initiated by @value{GDBN}, and the
33450 target's memory is not involved. @xref{File-I/O Remote Protocol
33451 Extension}, for more details on the target-initiated protocol.
33453 The Host I/O request packets all encode a single operation along with
33454 its arguments. They have this format:
33458 @item vFile:@var{operation}: @var{parameter}@dots{}
33459 @var{operation} is the name of the particular request; the target
33460 should compare the entire packet name up to the second colon when checking
33461 for a supported operation. The format of @var{parameter} depends on
33462 the operation. Numbers are always passed in hexadecimal. Negative
33463 numbers have an explicit minus sign (i.e.@: two's complement is not
33464 used). Strings (e.g.@: filenames) are encoded as a series of
33465 hexadecimal bytes. The last argument to a system call may be a
33466 buffer of escaped binary data (@pxref{Binary Data}).
33470 The valid responses to Host I/O packets are:
33474 @item F @var{result} [, @var{errno}] [; @var{attachment}]
33475 @var{result} is the integer value returned by this operation, usually
33476 non-negative for success and -1 for errors. If an error has occured,
33477 @var{errno} will be included in the result. @var{errno} will have a
33478 value defined by the File-I/O protocol (@pxref{Errno Values}). For
33479 operations which return data, @var{attachment} supplies the data as a
33480 binary buffer. Binary buffers in response packets are escaped in the
33481 normal way (@pxref{Binary Data}). See the individual packet
33482 documentation for the interpretation of @var{result} and
33486 An empty response indicates that this operation is not recognized.
33490 These are the supported Host I/O operations:
33493 @item vFile:open: @var{pathname}, @var{flags}, @var{mode}
33494 Open a file at @var{pathname} and return a file descriptor for it, or
33495 return -1 if an error occurs. @var{pathname} is a string,
33496 @var{flags} is an integer indicating a mask of open flags
33497 (@pxref{Open Flags}), and @var{mode} is an integer indicating a mask
33498 of mode bits to use if the file is created (@pxref{mode_t Values}).
33499 @xref{open}, for details of the open flags and mode values.
33501 @item vFile:close: @var{fd}
33502 Close the open file corresponding to @var{fd} and return 0, or
33503 -1 if an error occurs.
33505 @item vFile:pread: @var{fd}, @var{count}, @var{offset}
33506 Read data from the open file corresponding to @var{fd}. Up to
33507 @var{count} bytes will be read from the file, starting at @var{offset}
33508 relative to the start of the file. The target may read fewer bytes;
33509 common reasons include packet size limits and an end-of-file
33510 condition. The number of bytes read is returned. Zero should only be
33511 returned for a successful read at the end of the file, or if
33512 @var{count} was zero.
33514 The data read should be returned as a binary attachment on success.
33515 If zero bytes were read, the response should include an empty binary
33516 attachment (i.e.@: a trailing semicolon). The return value is the
33517 number of target bytes read; the binary attachment may be longer if
33518 some characters were escaped.
33520 @item vFile:pwrite: @var{fd}, @var{offset}, @var{data}
33521 Write @var{data} (a binary buffer) to the open file corresponding
33522 to @var{fd}. Start the write at @var{offset} from the start of the
33523 file. Unlike many @code{write} system calls, there is no
33524 separate @var{count} argument; the length of @var{data} in the
33525 packet is used. @samp{vFile:write} returns the number of bytes written,
33526 which may be shorter than the length of @var{data}, or -1 if an
33529 @item vFile:unlink: @var{pathname}
33530 Delete the file at @var{pathname} on the target. Return 0,
33531 or -1 if an error occurs. @var{pathname} is a string.
33536 @section Interrupts
33537 @cindex interrupts (remote protocol)
33539 When a program on the remote target is running, @value{GDBN} may
33540 attempt to interrupt it by sending a @samp{Ctrl-C}, @code{BREAK} or
33541 a @code{BREAK} followed by @code{g},
33542 control of which is specified via @value{GDBN}'s @samp{interrupt-sequence}.
33544 The precise meaning of @code{BREAK} is defined by the transport
33545 mechanism and may, in fact, be undefined. @value{GDBN} does not
33546 currently define a @code{BREAK} mechanism for any of the network
33547 interfaces except for TCP, in which case @value{GDBN} sends the
33548 @code{telnet} BREAK sequence.
33550 @samp{Ctrl-C}, on the other hand, is defined and implemented for all
33551 transport mechanisms. It is represented by sending the single byte
33552 @code{0x03} without any of the usual packet overhead described in
33553 the Overview section (@pxref{Overview}). When a @code{0x03} byte is
33554 transmitted as part of a packet, it is considered to be packet data
33555 and does @emph{not} represent an interrupt. E.g., an @samp{X} packet
33556 (@pxref{X packet}), used for binary downloads, may include an unescaped
33557 @code{0x03} as part of its packet.
33559 @code{BREAK} followed by @code{g} is also known as Magic SysRq g.
33560 When Linux kernel receives this sequence from serial port,
33561 it stops execution and connects to gdb.
33563 Stubs are not required to recognize these interrupt mechanisms and the
33564 precise meaning associated with receipt of the interrupt is
33565 implementation defined. If the target supports debugging of multiple
33566 threads and/or processes, it should attempt to interrupt all
33567 currently-executing threads and processes.
33568 If the stub is successful at interrupting the
33569 running program, it should send one of the stop
33570 reply packets (@pxref{Stop Reply Packets}) to @value{GDBN} as a result
33571 of successfully stopping the program in all-stop mode, and a stop reply
33572 for each stopped thread in non-stop mode.
33573 Interrupts received while the
33574 program is stopped are discarded.
33576 @node Notification Packets
33577 @section Notification Packets
33578 @cindex notification packets
33579 @cindex packets, notification
33581 The @value{GDBN} remote serial protocol includes @dfn{notifications},
33582 packets that require no acknowledgment. Both the GDB and the stub
33583 may send notifications (although the only notifications defined at
33584 present are sent by the stub). Notifications carry information
33585 without incurring the round-trip latency of an acknowledgment, and so
33586 are useful for low-impact communications where occasional packet loss
33589 A notification packet has the form @samp{% @var{data} #
33590 @var{checksum}}, where @var{data} is the content of the notification,
33591 and @var{checksum} is a checksum of @var{data}, computed and formatted
33592 as for ordinary @value{GDBN} packets. A notification's @var{data}
33593 never contains @samp{$}, @samp{%} or @samp{#} characters. Upon
33594 receiving a notification, the recipient sends no @samp{+} or @samp{-}
33595 to acknowledge the notification's receipt or to report its corruption.
33597 Every notification's @var{data} begins with a name, which contains no
33598 colon characters, followed by a colon character.
33600 Recipients should silently ignore corrupted notifications and
33601 notifications they do not understand. Recipients should restart
33602 timeout periods on receipt of a well-formed notification, whether or
33603 not they understand it.
33605 Senders should only send the notifications described here when this
33606 protocol description specifies that they are permitted. In the
33607 future, we may extend the protocol to permit existing notifications in
33608 new contexts; this rule helps older senders avoid confusing newer
33611 (Older versions of @value{GDBN} ignore bytes received until they see
33612 the @samp{$} byte that begins an ordinary packet, so new stubs may
33613 transmit notifications without fear of confusing older clients. There
33614 are no notifications defined for @value{GDBN} to send at the moment, but we
33615 assume that most older stubs would ignore them, as well.)
33617 The following notification packets from the stub to @value{GDBN} are
33621 @item Stop: @var{reply}
33622 Report an asynchronous stop event in non-stop mode.
33623 The @var{reply} has the form of a stop reply, as
33624 described in @ref{Stop Reply Packets}. Refer to @ref{Remote Non-Stop},
33625 for information on how these notifications are acknowledged by
33629 @node Remote Non-Stop
33630 @section Remote Protocol Support for Non-Stop Mode
33632 @value{GDBN}'s remote protocol supports non-stop debugging of
33633 multi-threaded programs, as described in @ref{Non-Stop Mode}. If the stub
33634 supports non-stop mode, it should report that to @value{GDBN} by including
33635 @samp{QNonStop+} in its @samp{qSupported} response (@pxref{qSupported}).
33637 @value{GDBN} typically sends a @samp{QNonStop} packet only when
33638 establishing a new connection with the stub. Entering non-stop mode
33639 does not alter the state of any currently-running threads, but targets
33640 must stop all threads in any already-attached processes when entering
33641 all-stop mode. @value{GDBN} uses the @samp{?} packet as necessary to
33642 probe the target state after a mode change.
33644 In non-stop mode, when an attached process encounters an event that
33645 would otherwise be reported with a stop reply, it uses the
33646 asynchronous notification mechanism (@pxref{Notification Packets}) to
33647 inform @value{GDBN}. In contrast to all-stop mode, where all threads
33648 in all processes are stopped when a stop reply is sent, in non-stop
33649 mode only the thread reporting the stop event is stopped. That is,
33650 when reporting a @samp{S} or @samp{T} response to indicate completion
33651 of a step operation, hitting a breakpoint, or a fault, only the
33652 affected thread is stopped; any other still-running threads continue
33653 to run. When reporting a @samp{W} or @samp{X} response, all running
33654 threads belonging to other attached processes continue to run.
33656 Only one stop reply notification at a time may be pending; if
33657 additional stop events occur before @value{GDBN} has acknowledged the
33658 previous notification, they must be queued by the stub for later
33659 synchronous transmission in response to @samp{vStopped} packets from
33660 @value{GDBN}. Because the notification mechanism is unreliable,
33661 the stub is permitted to resend a stop reply notification
33662 if it believes @value{GDBN} may not have received it. @value{GDBN}
33663 ignores additional stop reply notifications received before it has
33664 finished processing a previous notification and the stub has completed
33665 sending any queued stop events.
33667 Otherwise, @value{GDBN} must be prepared to receive a stop reply
33668 notification at any time. Specifically, they may appear when
33669 @value{GDBN} is not otherwise reading input from the stub, or when
33670 @value{GDBN} is expecting to read a normal synchronous response or a
33671 @samp{+}/@samp{-} acknowledgment to a packet it has sent.
33672 Notification packets are distinct from any other communication from
33673 the stub so there is no ambiguity.
33675 After receiving a stop reply notification, @value{GDBN} shall
33676 acknowledge it by sending a @samp{vStopped} packet (@pxref{vStopped packet})
33677 as a regular, synchronous request to the stub. Such acknowledgment
33678 is not required to happen immediately, as @value{GDBN} is permitted to
33679 send other, unrelated packets to the stub first, which the stub should
33682 Upon receiving a @samp{vStopped} packet, if the stub has other queued
33683 stop events to report to @value{GDBN}, it shall respond by sending a
33684 normal stop reply response. @value{GDBN} shall then send another
33685 @samp{vStopped} packet to solicit further responses; again, it is
33686 permitted to send other, unrelated packets as well which the stub
33687 should process normally.
33689 If the stub receives a @samp{vStopped} packet and there are no
33690 additional stop events to report, the stub shall return an @samp{OK}
33691 response. At this point, if further stop events occur, the stub shall
33692 send a new stop reply notification, @value{GDBN} shall accept the
33693 notification, and the process shall be repeated.
33695 In non-stop mode, the target shall respond to the @samp{?} packet as
33696 follows. First, any incomplete stop reply notification/@samp{vStopped}
33697 sequence in progress is abandoned. The target must begin a new
33698 sequence reporting stop events for all stopped threads, whether or not
33699 it has previously reported those events to @value{GDBN}. The first
33700 stop reply is sent as a synchronous reply to the @samp{?} packet, and
33701 subsequent stop replies are sent as responses to @samp{vStopped} packets
33702 using the mechanism described above. The target must not send
33703 asynchronous stop reply notifications until the sequence is complete.
33704 If all threads are running when the target receives the @samp{?} packet,
33705 or if the target is not attached to any process, it shall respond
33708 @node Packet Acknowledgment
33709 @section Packet Acknowledgment
33711 @cindex acknowledgment, for @value{GDBN} remote
33712 @cindex packet acknowledgment, for @value{GDBN} remote
33713 By default, when either the host or the target machine receives a packet,
33714 the first response expected is an acknowledgment: either @samp{+} (to indicate
33715 the package was received correctly) or @samp{-} (to request retransmission).
33716 This mechanism allows the @value{GDBN} remote protocol to operate over
33717 unreliable transport mechanisms, such as a serial line.
33719 In cases where the transport mechanism is itself reliable (such as a pipe or
33720 TCP connection), the @samp{+}/@samp{-} acknowledgments are redundant.
33721 It may be desirable to disable them in that case to reduce communication
33722 overhead, or for other reasons. This can be accomplished by means of the
33723 @samp{QStartNoAckMode} packet; @pxref{QStartNoAckMode}.
33725 When in no-acknowledgment mode, neither the stub nor @value{GDBN} shall send or
33726 expect @samp{+}/@samp{-} protocol acknowledgments. The packet
33727 and response format still includes the normal checksum, as described in
33728 @ref{Overview}, but the checksum may be ignored by the receiver.
33730 If the stub supports @samp{QStartNoAckMode} and prefers to operate in
33731 no-acknowledgment mode, it should report that to @value{GDBN}
33732 by including @samp{QStartNoAckMode+} in its response to @samp{qSupported};
33733 @pxref{qSupported}.
33734 If @value{GDBN} also supports @samp{QStartNoAckMode} and it has not been
33735 disabled via the @code{set remote noack-packet off} command
33736 (@pxref{Remote Configuration}),
33737 @value{GDBN} may then send a @samp{QStartNoAckMode} packet to the stub.
33738 Only then may the stub actually turn off packet acknowledgments.
33739 @value{GDBN} sends a final @samp{+} acknowledgment of the stub's @samp{OK}
33740 response, which can be safely ignored by the stub.
33742 Note that @code{set remote noack-packet} command only affects negotiation
33743 between @value{GDBN} and the stub when subsequent connections are made;
33744 it does not affect the protocol acknowledgment state for any current
33746 Since @samp{+}/@samp{-} acknowledgments are enabled by default when a
33747 new connection is established,
33748 there is also no protocol request to re-enable the acknowledgments
33749 for the current connection, once disabled.
33754 Example sequence of a target being re-started. Notice how the restart
33755 does not get any direct output:
33760 @emph{target restarts}
33763 <- @code{T001:1234123412341234}
33767 Example sequence of a target being stepped by a single instruction:
33770 -> @code{G1445@dots{}}
33775 <- @code{T001:1234123412341234}
33779 <- @code{1455@dots{}}
33783 @node File-I/O Remote Protocol Extension
33784 @section File-I/O Remote Protocol Extension
33785 @cindex File-I/O remote protocol extension
33788 * File-I/O Overview::
33789 * Protocol Basics::
33790 * The F Request Packet::
33791 * The F Reply Packet::
33792 * The Ctrl-C Message::
33794 * List of Supported Calls::
33795 * Protocol-specific Representation of Datatypes::
33797 * File-I/O Examples::
33800 @node File-I/O Overview
33801 @subsection File-I/O Overview
33802 @cindex file-i/o overview
33804 The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the
33805 target to use the host's file system and console I/O to perform various
33806 system calls. System calls on the target system are translated into a
33807 remote protocol packet to the host system, which then performs the needed
33808 actions and returns a response packet to the target system.
33809 This simulates file system operations even on targets that lack file systems.
33811 The protocol is defined to be independent of both the host and target systems.
33812 It uses its own internal representation of datatypes and values. Both
33813 @value{GDBN} and the target's @value{GDBN} stub are responsible for
33814 translating the system-dependent value representations into the internal
33815 protocol representations when data is transmitted.
33817 The communication is synchronous. A system call is possible only when
33818 @value{GDBN} is waiting for a response from the @samp{C}, @samp{c}, @samp{S}
33819 or @samp{s} packets. While @value{GDBN} handles the request for a system call,
33820 the target is stopped to allow deterministic access to the target's
33821 memory. Therefore File-I/O is not interruptible by target signals. On
33822 the other hand, it is possible to interrupt File-I/O by a user interrupt
33823 (@samp{Ctrl-C}) within @value{GDBN}.
33825 The target's request to perform a host system call does not finish
33826 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
33827 after finishing the system call, the target returns to continuing the
33828 previous activity (continue, step). No additional continue or step
33829 request from @value{GDBN} is required.
33832 (@value{GDBP}) continue
33833 <- target requests 'system call X'
33834 target is stopped, @value{GDBN} executes system call
33835 -> @value{GDBN} returns result
33836 ... target continues, @value{GDBN} returns to wait for the target
33837 <- target hits breakpoint and sends a Txx packet
33840 The protocol only supports I/O on the console and to regular files on
33841 the host file system. Character or block special devices, pipes,
33842 named pipes, sockets or any other communication method on the host
33843 system are not supported by this protocol.
33845 File I/O is not supported in non-stop mode.
33847 @node Protocol Basics
33848 @subsection Protocol Basics
33849 @cindex protocol basics, file-i/o
33851 The File-I/O protocol uses the @code{F} packet as the request as well
33852 as reply packet. Since a File-I/O system call can only occur when
33853 @value{GDBN} is waiting for a response from the continuing or stepping target,
33854 the File-I/O request is a reply that @value{GDBN} has to expect as a result
33855 of a previous @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
33856 This @code{F} packet contains all information needed to allow @value{GDBN}
33857 to call the appropriate host system call:
33861 A unique identifier for the requested system call.
33864 All parameters to the system call. Pointers are given as addresses
33865 in the target memory address space. Pointers to strings are given as
33866 pointer/length pair. Numerical values are given as they are.
33867 Numerical control flags are given in a protocol-specific representation.
33871 At this point, @value{GDBN} has to perform the following actions.
33875 If the parameters include pointer values to data needed as input to a
33876 system call, @value{GDBN} requests this data from the target with a
33877 standard @code{m} packet request. This additional communication has to be
33878 expected by the target implementation and is handled as any other @code{m}
33882 @value{GDBN} translates all value from protocol representation to host
33883 representation as needed. Datatypes are coerced into the host types.
33886 @value{GDBN} calls the system call.
33889 It then coerces datatypes back to protocol representation.
33892 If the system call is expected to return data in buffer space specified
33893 by pointer parameters to the call, the data is transmitted to the
33894 target using a @code{M} or @code{X} packet. This packet has to be expected
33895 by the target implementation and is handled as any other @code{M} or @code{X}
33900 Eventually @value{GDBN} replies with another @code{F} packet which contains all
33901 necessary information for the target to continue. This at least contains
33908 @code{errno}, if has been changed by the system call.
33915 After having done the needed type and value coercion, the target continues
33916 the latest continue or step action.
33918 @node The F Request Packet
33919 @subsection The @code{F} Request Packet
33920 @cindex file-i/o request packet
33921 @cindex @code{F} request packet
33923 The @code{F} request packet has the following format:
33926 @item F@var{call-id},@var{parameter@dots{}}
33928 @var{call-id} is the identifier to indicate the host system call to be called.
33929 This is just the name of the function.
33931 @var{parameter@dots{}} are the parameters to the system call.
33932 Parameters are hexadecimal integer values, either the actual values in case
33933 of scalar datatypes, pointers to target buffer space in case of compound
33934 datatypes and unspecified memory areas, or pointer/length pairs in case
33935 of string parameters. These are appended to the @var{call-id} as a
33936 comma-delimited list. All values are transmitted in ASCII
33937 string representation, pointer/length pairs separated by a slash.
33943 @node The F Reply Packet
33944 @subsection The @code{F} Reply Packet
33945 @cindex file-i/o reply packet
33946 @cindex @code{F} reply packet
33948 The @code{F} reply packet has the following format:
33952 @item F@var{retcode},@var{errno},@var{Ctrl-C flag};@var{call-specific attachment}
33954 @var{retcode} is the return code of the system call as hexadecimal value.
33956 @var{errno} is the @code{errno} set by the call, in protocol-specific
33958 This parameter can be omitted if the call was successful.
33960 @var{Ctrl-C flag} is only sent if the user requested a break. In this
33961 case, @var{errno} must be sent as well, even if the call was successful.
33962 The @var{Ctrl-C flag} itself consists of the character @samp{C}:
33969 or, if the call was interrupted before the host call has been performed:
33976 assuming 4 is the protocol-specific representation of @code{EINTR}.
33981 @node The Ctrl-C Message
33982 @subsection The @samp{Ctrl-C} Message
33983 @cindex ctrl-c message, in file-i/o protocol
33985 If the @samp{Ctrl-C} flag is set in the @value{GDBN}
33986 reply packet (@pxref{The F Reply Packet}),
33987 the target should behave as if it had
33988 gotten a break message. The meaning for the target is ``system call
33989 interrupted by @code{SIGINT}''. Consequentially, the target should actually stop
33990 (as with a break message) and return to @value{GDBN} with a @code{T02}
33993 It's important for the target to know in which
33994 state the system call was interrupted. There are two possible cases:
33998 The system call hasn't been performed on the host yet.
34001 The system call on the host has been finished.
34005 These two states can be distinguished by the target by the value of the
34006 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
34007 call hasn't been performed. This is equivalent to the @code{EINTR} handling
34008 on POSIX systems. In any other case, the target may presume that the
34009 system call has been finished --- successfully or not --- and should behave
34010 as if the break message arrived right after the system call.
34012 @value{GDBN} must behave reliably. If the system call has not been called
34013 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
34014 @code{errno} in the packet. If the system call on the host has been finished
34015 before the user requests a break, the full action must be finished by
34016 @value{GDBN}. This requires sending @code{M} or @code{X} packets as necessary.
34017 The @code{F} packet may only be sent when either nothing has happened
34018 or the full action has been completed.
34021 @subsection Console I/O
34022 @cindex console i/o as part of file-i/o
34024 By default and if not explicitly closed by the target system, the file
34025 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
34026 on the @value{GDBN} console is handled as any other file output operation
34027 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
34028 by @value{GDBN} so that after the target read request from file descriptor
34029 0 all following typing is buffered until either one of the following
34034 The user types @kbd{Ctrl-c}. The behaviour is as explained above, and the
34036 system call is treated as finished.
34039 The user presses @key{RET}. This is treated as end of input with a trailing
34043 The user types @kbd{Ctrl-d}. This is treated as end of input. No trailing
34044 character (neither newline nor @samp{Ctrl-D}) is appended to the input.
34048 If the user has typed more characters than fit in the buffer given to
34049 the @code{read} call, the trailing characters are buffered in @value{GDBN} until
34050 either another @code{read(0, @dots{})} is requested by the target, or debugging
34051 is stopped at the user's request.
34054 @node List of Supported Calls
34055 @subsection List of Supported Calls
34056 @cindex list of supported file-i/o calls
34073 @unnumberedsubsubsec open
34074 @cindex open, file-i/o system call
34079 int open(const char *pathname, int flags);
34080 int open(const char *pathname, int flags, mode_t mode);
34084 @samp{Fopen,@var{pathptr}/@var{len},@var{flags},@var{mode}}
34087 @var{flags} is the bitwise @code{OR} of the following values:
34091 If the file does not exist it will be created. The host
34092 rules apply as far as file ownership and time stamps
34096 When used with @code{O_CREAT}, if the file already exists it is
34097 an error and open() fails.
34100 If the file already exists and the open mode allows
34101 writing (@code{O_RDWR} or @code{O_WRONLY} is given) it will be
34102 truncated to zero length.
34105 The file is opened in append mode.
34108 The file is opened for reading only.
34111 The file is opened for writing only.
34114 The file is opened for reading and writing.
34118 Other bits are silently ignored.
34122 @var{mode} is the bitwise @code{OR} of the following values:
34126 User has read permission.
34129 User has write permission.
34132 Group has read permission.
34135 Group has write permission.
34138 Others have read permission.
34141 Others have write permission.
34145 Other bits are silently ignored.
34148 @item Return value:
34149 @code{open} returns the new file descriptor or -1 if an error
34156 @var{pathname} already exists and @code{O_CREAT} and @code{O_EXCL} were used.
34159 @var{pathname} refers to a directory.
34162 The requested access is not allowed.
34165 @var{pathname} was too long.
34168 A directory component in @var{pathname} does not exist.
34171 @var{pathname} refers to a device, pipe, named pipe or socket.
34174 @var{pathname} refers to a file on a read-only filesystem and
34175 write access was requested.
34178 @var{pathname} is an invalid pointer value.
34181 No space on device to create the file.
34184 The process already has the maximum number of files open.
34187 The limit on the total number of files open on the system
34191 The call was interrupted by the user.
34197 @unnumberedsubsubsec close
34198 @cindex close, file-i/o system call
34207 @samp{Fclose,@var{fd}}
34209 @item Return value:
34210 @code{close} returns zero on success, or -1 if an error occurred.
34216 @var{fd} isn't a valid open file descriptor.
34219 The call was interrupted by the user.
34225 @unnumberedsubsubsec read
34226 @cindex read, file-i/o system call
34231 int read(int fd, void *buf, unsigned int count);
34235 @samp{Fread,@var{fd},@var{bufptr},@var{count}}
34237 @item Return value:
34238 On success, the number of bytes read is returned.
34239 Zero indicates end of file. If count is zero, read
34240 returns zero as well. On error, -1 is returned.
34246 @var{fd} is not a valid file descriptor or is not open for
34250 @var{bufptr} is an invalid pointer value.
34253 The call was interrupted by the user.
34259 @unnumberedsubsubsec write
34260 @cindex write, file-i/o system call
34265 int write(int fd, const void *buf, unsigned int count);
34269 @samp{Fwrite,@var{fd},@var{bufptr},@var{count}}
34271 @item Return value:
34272 On success, the number of bytes written are returned.
34273 Zero indicates nothing was written. On error, -1
34280 @var{fd} is not a valid file descriptor or is not open for
34284 @var{bufptr} is an invalid pointer value.
34287 An attempt was made to write a file that exceeds the
34288 host-specific maximum file size allowed.
34291 No space on device to write the data.
34294 The call was interrupted by the user.
34300 @unnumberedsubsubsec lseek
34301 @cindex lseek, file-i/o system call
34306 long lseek (int fd, long offset, int flag);
34310 @samp{Flseek,@var{fd},@var{offset},@var{flag}}
34312 @var{flag} is one of:
34316 The offset is set to @var{offset} bytes.
34319 The offset is set to its current location plus @var{offset}
34323 The offset is set to the size of the file plus @var{offset}
34327 @item Return value:
34328 On success, the resulting unsigned offset in bytes from
34329 the beginning of the file is returned. Otherwise, a
34330 value of -1 is returned.
34336 @var{fd} is not a valid open file descriptor.
34339 @var{fd} is associated with the @value{GDBN} console.
34342 @var{flag} is not a proper value.
34345 The call was interrupted by the user.
34351 @unnumberedsubsubsec rename
34352 @cindex rename, file-i/o system call
34357 int rename(const char *oldpath, const char *newpath);
34361 @samp{Frename,@var{oldpathptr}/@var{len},@var{newpathptr}/@var{len}}
34363 @item Return value:
34364 On success, zero is returned. On error, -1 is returned.
34370 @var{newpath} is an existing directory, but @var{oldpath} is not a
34374 @var{newpath} is a non-empty directory.
34377 @var{oldpath} or @var{newpath} is a directory that is in use by some
34381 An attempt was made to make a directory a subdirectory
34385 A component used as a directory in @var{oldpath} or new
34386 path is not a directory. Or @var{oldpath} is a directory
34387 and @var{newpath} exists but is not a directory.
34390 @var{oldpathptr} or @var{newpathptr} are invalid pointer values.
34393 No access to the file or the path of the file.
34397 @var{oldpath} or @var{newpath} was too long.
34400 A directory component in @var{oldpath} or @var{newpath} does not exist.
34403 The file is on a read-only filesystem.
34406 The device containing the file has no room for the new
34410 The call was interrupted by the user.
34416 @unnumberedsubsubsec unlink
34417 @cindex unlink, file-i/o system call
34422 int unlink(const char *pathname);
34426 @samp{Funlink,@var{pathnameptr}/@var{len}}
34428 @item Return value:
34429 On success, zero is returned. On error, -1 is returned.
34435 No access to the file or the path of the file.
34438 The system does not allow unlinking of directories.
34441 The file @var{pathname} cannot be unlinked because it's
34442 being used by another process.
34445 @var{pathnameptr} is an invalid pointer value.
34448 @var{pathname} was too long.
34451 A directory component in @var{pathname} does not exist.
34454 A component of the path is not a directory.
34457 The file is on a read-only filesystem.
34460 The call was interrupted by the user.
34466 @unnumberedsubsubsec stat/fstat
34467 @cindex fstat, file-i/o system call
34468 @cindex stat, file-i/o system call
34473 int stat(const char *pathname, struct stat *buf);
34474 int fstat(int fd, struct stat *buf);
34478 @samp{Fstat,@var{pathnameptr}/@var{len},@var{bufptr}}@*
34479 @samp{Ffstat,@var{fd},@var{bufptr}}
34481 @item Return value:
34482 On success, zero is returned. On error, -1 is returned.
34488 @var{fd} is not a valid open file.
34491 A directory component in @var{pathname} does not exist or the
34492 path is an empty string.
34495 A component of the path is not a directory.
34498 @var{pathnameptr} is an invalid pointer value.
34501 No access to the file or the path of the file.
34504 @var{pathname} was too long.
34507 The call was interrupted by the user.
34513 @unnumberedsubsubsec gettimeofday
34514 @cindex gettimeofday, file-i/o system call
34519 int gettimeofday(struct timeval *tv, void *tz);
34523 @samp{Fgettimeofday,@var{tvptr},@var{tzptr}}
34525 @item Return value:
34526 On success, 0 is returned, -1 otherwise.
34532 @var{tz} is a non-NULL pointer.
34535 @var{tvptr} and/or @var{tzptr} is an invalid pointer value.
34541 @unnumberedsubsubsec isatty
34542 @cindex isatty, file-i/o system call
34547 int isatty(int fd);
34551 @samp{Fisatty,@var{fd}}
34553 @item Return value:
34554 Returns 1 if @var{fd} refers to the @value{GDBN} console, 0 otherwise.
34560 The call was interrupted by the user.
34565 Note that the @code{isatty} call is treated as a special case: it returns
34566 1 to the target if the file descriptor is attached
34567 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
34568 would require implementing @code{ioctl} and would be more complex than
34573 @unnumberedsubsubsec system
34574 @cindex system, file-i/o system call
34579 int system(const char *command);
34583 @samp{Fsystem,@var{commandptr}/@var{len}}
34585 @item Return value:
34586 If @var{len} is zero, the return value indicates whether a shell is
34587 available. A zero return value indicates a shell is not available.
34588 For non-zero @var{len}, the value returned is -1 on error and the
34589 return status of the command otherwise. Only the exit status of the
34590 command is returned, which is extracted from the host's @code{system}
34591 return value by calling @code{WEXITSTATUS(retval)}. In case
34592 @file{/bin/sh} could not be executed, 127 is returned.
34598 The call was interrupted by the user.
34603 @value{GDBN} takes over the full task of calling the necessary host calls
34604 to perform the @code{system} call. The return value of @code{system} on
34605 the host is simplified before it's returned
34606 to the target. Any termination signal information from the child process
34607 is discarded, and the return value consists
34608 entirely of the exit status of the called command.
34610 Due to security concerns, the @code{system} call is by default refused
34611 by @value{GDBN}. The user has to allow this call explicitly with the
34612 @code{set remote system-call-allowed 1} command.
34615 @item set remote system-call-allowed
34616 @kindex set remote system-call-allowed
34617 Control whether to allow the @code{system} calls in the File I/O
34618 protocol for the remote target. The default is zero (disabled).
34620 @item show remote system-call-allowed
34621 @kindex show remote system-call-allowed
34622 Show whether the @code{system} calls are allowed in the File I/O
34626 @node Protocol-specific Representation of Datatypes
34627 @subsection Protocol-specific Representation of Datatypes
34628 @cindex protocol-specific representation of datatypes, in file-i/o protocol
34631 * Integral Datatypes::
34633 * Memory Transfer::
34638 @node Integral Datatypes
34639 @unnumberedsubsubsec Integral Datatypes
34640 @cindex integral datatypes, in file-i/o protocol
34642 The integral datatypes used in the system calls are @code{int},
34643 @code{unsigned int}, @code{long}, @code{unsigned long},
34644 @code{mode_t}, and @code{time_t}.
34646 @code{int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
34647 implemented as 32 bit values in this protocol.
34649 @code{long} and @code{unsigned long} are implemented as 64 bit types.
34651 @xref{Limits}, for corresponding MIN and MAX values (similar to those
34652 in @file{limits.h}) to allow range checking on host and target.
34654 @code{time_t} datatypes are defined as seconds since the Epoch.
34656 All integral datatypes transferred as part of a memory read or write of a
34657 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
34660 @node Pointer Values
34661 @unnumberedsubsubsec Pointer Values
34662 @cindex pointer values, in file-i/o protocol
34664 Pointers to target data are transmitted as they are. An exception
34665 is made for pointers to buffers for which the length isn't
34666 transmitted as part of the function call, namely strings. Strings
34667 are transmitted as a pointer/length pair, both as hex values, e.g.@:
34674 which is a pointer to data of length 18 bytes at position 0x1aaf.
34675 The length is defined as the full string length in bytes, including
34676 the trailing null byte. For example, the string @code{"hello world"}
34677 at address 0x123456 is transmitted as
34683 @node Memory Transfer
34684 @unnumberedsubsubsec Memory Transfer
34685 @cindex memory transfer, in file-i/o protocol
34687 Structured data which is transferred using a memory read or write (for
34688 example, a @code{struct stat}) is expected to be in a protocol-specific format
34689 with all scalar multibyte datatypes being big endian. Translation to
34690 this representation needs to be done both by the target before the @code{F}
34691 packet is sent, and by @value{GDBN} before
34692 it transfers memory to the target. Transferred pointers to structured
34693 data should point to the already-coerced data at any time.
34697 @unnumberedsubsubsec struct stat
34698 @cindex struct stat, in file-i/o protocol
34700 The buffer of type @code{struct stat} used by the target and @value{GDBN}
34701 is defined as follows:
34705 unsigned int st_dev; /* device */
34706 unsigned int st_ino; /* inode */
34707 mode_t st_mode; /* protection */
34708 unsigned int st_nlink; /* number of hard links */
34709 unsigned int st_uid; /* user ID of owner */
34710 unsigned int st_gid; /* group ID of owner */
34711 unsigned int st_rdev; /* device type (if inode device) */
34712 unsigned long st_size; /* total size, in bytes */
34713 unsigned long st_blksize; /* blocksize for filesystem I/O */
34714 unsigned long st_blocks; /* number of blocks allocated */
34715 time_t st_atime; /* time of last access */
34716 time_t st_mtime; /* time of last modification */
34717 time_t st_ctime; /* time of last change */
34721 The integral datatypes conform to the definitions given in the
34722 appropriate section (see @ref{Integral Datatypes}, for details) so this
34723 structure is of size 64 bytes.
34725 The values of several fields have a restricted meaning and/or
34731 A value of 0 represents a file, 1 the console.
34734 No valid meaning for the target. Transmitted unchanged.
34737 Valid mode bits are described in @ref{Constants}. Any other
34738 bits have currently no meaning for the target.
34743 No valid meaning for the target. Transmitted unchanged.
34748 These values have a host and file system dependent
34749 accuracy. Especially on Windows hosts, the file system may not
34750 support exact timing values.
34753 The target gets a @code{struct stat} of the above representation and is
34754 responsible for coercing it to the target representation before
34757 Note that due to size differences between the host, target, and protocol
34758 representations of @code{struct stat} members, these members could eventually
34759 get truncated on the target.
34761 @node struct timeval
34762 @unnumberedsubsubsec struct timeval
34763 @cindex struct timeval, in file-i/o protocol
34765 The buffer of type @code{struct timeval} used by the File-I/O protocol
34766 is defined as follows:
34770 time_t tv_sec; /* second */
34771 long tv_usec; /* microsecond */
34775 The integral datatypes conform to the definitions given in the
34776 appropriate section (see @ref{Integral Datatypes}, for details) so this
34777 structure is of size 8 bytes.
34780 @subsection Constants
34781 @cindex constants, in file-i/o protocol
34783 The following values are used for the constants inside of the
34784 protocol. @value{GDBN} and target are responsible for translating these
34785 values before and after the call as needed.
34796 @unnumberedsubsubsec Open Flags
34797 @cindex open flags, in file-i/o protocol
34799 All values are given in hexadecimal representation.
34811 @node mode_t Values
34812 @unnumberedsubsubsec mode_t Values
34813 @cindex mode_t values, in file-i/o protocol
34815 All values are given in octal representation.
34832 @unnumberedsubsubsec Errno Values
34833 @cindex errno values, in file-i/o protocol
34835 All values are given in decimal representation.
34860 @code{EUNKNOWN} is used as a fallback error value if a host system returns
34861 any error value not in the list of supported error numbers.
34864 @unnumberedsubsubsec Lseek Flags
34865 @cindex lseek flags, in file-i/o protocol
34874 @unnumberedsubsubsec Limits
34875 @cindex limits, in file-i/o protocol
34877 All values are given in decimal representation.
34880 INT_MIN -2147483648
34882 UINT_MAX 4294967295
34883 LONG_MIN -9223372036854775808
34884 LONG_MAX 9223372036854775807
34885 ULONG_MAX 18446744073709551615
34888 @node File-I/O Examples
34889 @subsection File-I/O Examples
34890 @cindex file-i/o examples
34892 Example sequence of a write call, file descriptor 3, buffer is at target
34893 address 0x1234, 6 bytes should be written:
34896 <- @code{Fwrite,3,1234,6}
34897 @emph{request memory read from target}
34900 @emph{return "6 bytes written"}
34904 Example sequence of a read call, file descriptor 3, buffer is at target
34905 address 0x1234, 6 bytes should be read:
34908 <- @code{Fread,3,1234,6}
34909 @emph{request memory write to target}
34910 -> @code{X1234,6:XXXXXX}
34911 @emph{return "6 bytes read"}
34915 Example sequence of a read call, call fails on the host due to invalid
34916 file descriptor (@code{EBADF}):
34919 <- @code{Fread,3,1234,6}
34923 Example sequence of a read call, user presses @kbd{Ctrl-c} before syscall on
34927 <- @code{Fread,3,1234,6}
34932 Example sequence of a read call, user presses @kbd{Ctrl-c} after syscall on
34936 <- @code{Fread,3,1234,6}
34937 -> @code{X1234,6:XXXXXX}
34941 @node Library List Format
34942 @section Library List Format
34943 @cindex library list format, remote protocol
34945 On some platforms, a dynamic loader (e.g.@: @file{ld.so}) runs in the
34946 same process as your application to manage libraries. In this case,
34947 @value{GDBN} can use the loader's symbol table and normal memory
34948 operations to maintain a list of shared libraries. On other
34949 platforms, the operating system manages loaded libraries.
34950 @value{GDBN} can not retrieve the list of currently loaded libraries
34951 through memory operations, so it uses the @samp{qXfer:libraries:read}
34952 packet (@pxref{qXfer library list read}) instead. The remote stub
34953 queries the target's operating system and reports which libraries
34956 The @samp{qXfer:libraries:read} packet returns an XML document which
34957 lists loaded libraries and their offsets. Each library has an
34958 associated name and one or more segment or section base addresses,
34959 which report where the library was loaded in memory.
34961 For the common case of libraries that are fully linked binaries, the
34962 library should have a list of segments. If the target supports
34963 dynamic linking of a relocatable object file, its library XML element
34964 should instead include a list of allocated sections. The segment or
34965 section bases are start addresses, not relocation offsets; they do not
34966 depend on the library's link-time base addresses.
34968 @value{GDBN} must be linked with the Expat library to support XML
34969 library lists. @xref{Expat}.
34971 A simple memory map, with one loaded library relocated by a single
34972 offset, looks like this:
34976 <library name="/lib/libc.so.6">
34977 <segment address="0x10000000"/>
34982 Another simple memory map, with one loaded library with three
34983 allocated sections (.text, .data, .bss), looks like this:
34987 <library name="sharedlib.o">
34988 <section address="0x10000000"/>
34989 <section address="0x20000000"/>
34990 <section address="0x30000000"/>
34995 The format of a library list is described by this DTD:
34998 <!-- library-list: Root element with versioning -->
34999 <!ELEMENT library-list (library)*>
35000 <!ATTLIST library-list version CDATA #FIXED "1.0">
35001 <!ELEMENT library (segment*, section*)>
35002 <!ATTLIST library name CDATA #REQUIRED>
35003 <!ELEMENT segment EMPTY>
35004 <!ATTLIST segment address CDATA #REQUIRED>
35005 <!ELEMENT section EMPTY>
35006 <!ATTLIST section address CDATA #REQUIRED>
35009 In addition, segments and section descriptors cannot be mixed within a
35010 single library element, and you must supply at least one segment or
35011 section for each library.
35013 @node Memory Map Format
35014 @section Memory Map Format
35015 @cindex memory map format
35017 To be able to write into flash memory, @value{GDBN} needs to obtain a
35018 memory map from the target. This section describes the format of the
35021 The memory map is obtained using the @samp{qXfer:memory-map:read}
35022 (@pxref{qXfer memory map read}) packet and is an XML document that
35023 lists memory regions.
35025 @value{GDBN} must be linked with the Expat library to support XML
35026 memory maps. @xref{Expat}.
35028 The top-level structure of the document is shown below:
35031 <?xml version="1.0"?>
35032 <!DOCTYPE memory-map
35033 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
35034 "http://sourceware.org/gdb/gdb-memory-map.dtd">
35040 Each region can be either:
35045 A region of RAM starting at @var{addr} and extending for @var{length}
35049 <memory type="ram" start="@var{addr}" length="@var{length}"/>
35054 A region of read-only memory:
35057 <memory type="rom" start="@var{addr}" length="@var{length}"/>
35062 A region of flash memory, with erasure blocks @var{blocksize}
35066 <memory type="flash" start="@var{addr}" length="@var{length}">
35067 <property name="blocksize">@var{blocksize}</property>
35073 Regions must not overlap. @value{GDBN} assumes that areas of memory not covered
35074 by the memory map are RAM, and uses the ordinary @samp{M} and @samp{X}
35075 packets to write to addresses in such ranges.
35077 The formal DTD for memory map format is given below:
35080 <!-- ................................................... -->
35081 <!-- Memory Map XML DTD ................................ -->
35082 <!-- File: memory-map.dtd .............................. -->
35083 <!-- .................................... .............. -->
35084 <!-- memory-map.dtd -->
35085 <!-- memory-map: Root element with versioning -->
35086 <!ELEMENT memory-map (memory | property)>
35087 <!ATTLIST memory-map version CDATA #FIXED "1.0.0">
35088 <!ELEMENT memory (property)>
35089 <!-- memory: Specifies a memory region,
35090 and its type, or device. -->
35091 <!ATTLIST memory type CDATA #REQUIRED
35092 start CDATA #REQUIRED
35093 length CDATA #REQUIRED
35094 device CDATA #IMPLIED>
35095 <!-- property: Generic attribute tag -->
35096 <!ELEMENT property (#PCDATA | property)*>
35097 <!ATTLIST property name CDATA #REQUIRED>
35100 @node Thread List Format
35101 @section Thread List Format
35102 @cindex thread list format
35104 To efficiently update the list of threads and their attributes,
35105 @value{GDBN} issues the @samp{qXfer:threads:read} packet
35106 (@pxref{qXfer threads read}) and obtains the XML document with
35107 the following structure:
35110 <?xml version="1.0"?>
35112 <thread id="id" core="0">
35113 ... description ...
35118 Each @samp{thread} element must have the @samp{id} attribute that
35119 identifies the thread (@pxref{thread-id syntax}). The
35120 @samp{core} attribute, if present, specifies which processor core
35121 the thread was last executing on. The content of the of @samp{thread}
35122 element is interpreted as human-readable auxilliary information.
35124 @include agentexpr.texi
35126 @node Trace File Format
35127 @appendix Trace File Format
35128 @cindex trace file format
35130 The trace file comes in three parts: a header, a textual description
35131 section, and a trace frame section with binary data.
35133 The header has the form @code{\x7fTRACE0\n}. The first byte is
35134 @code{0x7f} so as to indicate that the file contains binary data,
35135 while the @code{0} is a version number that may have different values
35138 The description section consists of multiple lines of @sc{ascii} text
35139 separated by newline characters (@code{0xa}). The lines may include a
35140 variety of optional descriptive or context-setting information, such
35141 as tracepoint definitions or register set size. @value{GDBN} will
35142 ignore any line that it does not recognize. An empty line marks the end
35145 @c FIXME add some specific types of data
35147 The trace frame section consists of a number of consecutive frames.
35148 Each frame begins with a two-byte tracepoint number, followed by a
35149 four-byte size giving the amount of data in the frame. The data in
35150 the frame consists of a number of blocks, each introduced by a
35151 character indicating its type (at least register, memory, and trace
35152 state variable). The data in this section is raw binary, not a
35153 hexadecimal or other encoding; its endianness matches the target's
35156 @c FIXME bi-arch may require endianness/arch info in description section
35159 @item R @var{bytes}
35160 Register block. The number and ordering of bytes matches that of a
35161 @code{g} packet in the remote protocol. Note that these are the
35162 actual bytes, in target order and @value{GDBN} register order, not a
35163 hexadecimal encoding.
35165 @item M @var{address} @var{length} @var{bytes}...
35166 Memory block. This is a contiguous block of memory, at the 8-byte
35167 address @var{address}, with a 2-byte length @var{length}, followed by
35168 @var{length} bytes.
35170 @item V @var{number} @var{value}
35171 Trace state variable block. This records the 8-byte signed value
35172 @var{value} of trace state variable numbered @var{number}.
35176 Future enhancements of the trace file format may include additional types
35179 @node Target Descriptions
35180 @appendix Target Descriptions
35181 @cindex target descriptions
35183 @strong{Warning:} target descriptions are still under active development,
35184 and the contents and format may change between @value{GDBN} releases.
35185 The format is expected to stabilize in the future.
35187 One of the challenges of using @value{GDBN} to debug embedded systems
35188 is that there are so many minor variants of each processor
35189 architecture in use. It is common practice for vendors to start with
35190 a standard processor core --- ARM, PowerPC, or MIPS, for example ---
35191 and then make changes to adapt it to a particular market niche. Some
35192 architectures have hundreds of variants, available from dozens of
35193 vendors. This leads to a number of problems:
35197 With so many different customized processors, it is difficult for
35198 the @value{GDBN} maintainers to keep up with the changes.
35200 Since individual variants may have short lifetimes or limited
35201 audiences, it may not be worthwhile to carry information about every
35202 variant in the @value{GDBN} source tree.
35204 When @value{GDBN} does support the architecture of the embedded system
35205 at hand, the task of finding the correct architecture name to give the
35206 @command{set architecture} command can be error-prone.
35209 To address these problems, the @value{GDBN} remote protocol allows a
35210 target system to not only identify itself to @value{GDBN}, but to
35211 actually describe its own features. This lets @value{GDBN} support
35212 processor variants it has never seen before --- to the extent that the
35213 descriptions are accurate, and that @value{GDBN} understands them.
35215 @value{GDBN} must be linked with the Expat library to support XML
35216 target descriptions. @xref{Expat}.
35219 * Retrieving Descriptions:: How descriptions are fetched from a target.
35220 * Target Description Format:: The contents of a target description.
35221 * Predefined Target Types:: Standard types available for target
35223 * Standard Target Features:: Features @value{GDBN} knows about.
35226 @node Retrieving Descriptions
35227 @section Retrieving Descriptions
35229 Target descriptions can be read from the target automatically, or
35230 specified by the user manually. The default behavior is to read the
35231 description from the target. @value{GDBN} retrieves it via the remote
35232 protocol using @samp{qXfer} requests (@pxref{General Query Packets,
35233 qXfer}). The @var{annex} in the @samp{qXfer} packet will be
35234 @samp{target.xml}. The contents of the @samp{target.xml} annex are an
35235 XML document, of the form described in @ref{Target Description
35238 Alternatively, you can specify a file to read for the target description.
35239 If a file is set, the target will not be queried. The commands to
35240 specify a file are:
35243 @cindex set tdesc filename
35244 @item set tdesc filename @var{path}
35245 Read the target description from @var{path}.
35247 @cindex unset tdesc filename
35248 @item unset tdesc filename
35249 Do not read the XML target description from a file. @value{GDBN}
35250 will use the description supplied by the current target.
35252 @cindex show tdesc filename
35253 @item show tdesc filename
35254 Show the filename to read for a target description, if any.
35258 @node Target Description Format
35259 @section Target Description Format
35260 @cindex target descriptions, XML format
35262 A target description annex is an @uref{http://www.w3.org/XML/, XML}
35263 document which complies with the Document Type Definition provided in
35264 the @value{GDBN} sources in @file{gdb/features/gdb-target.dtd}. This
35265 means you can use generally available tools like @command{xmllint} to
35266 check that your feature descriptions are well-formed and valid.
35267 However, to help people unfamiliar with XML write descriptions for
35268 their targets, we also describe the grammar here.
35270 Target descriptions can identify the architecture of the remote target
35271 and (for some architectures) provide information about custom register
35272 sets. They can also identify the OS ABI of the remote target.
35273 @value{GDBN} can use this information to autoconfigure for your
35274 target, or to warn you if you connect to an unsupported target.
35276 Here is a simple target description:
35279 <target version="1.0">
35280 <architecture>i386:x86-64</architecture>
35285 This minimal description only says that the target uses
35286 the x86-64 architecture.
35288 A target description has the following overall form, with [ ] marking
35289 optional elements and @dots{} marking repeatable elements. The elements
35290 are explained further below.
35293 <?xml version="1.0"?>
35294 <!DOCTYPE target SYSTEM "gdb-target.dtd">
35295 <target version="1.0">
35296 @r{[}@var{architecture}@r{]}
35297 @r{[}@var{osabi}@r{]}
35298 @r{[}@var{compatible}@r{]}
35299 @r{[}@var{feature}@dots{}@r{]}
35304 The description is generally insensitive to whitespace and line
35305 breaks, under the usual common-sense rules. The XML version
35306 declaration and document type declaration can generally be omitted
35307 (@value{GDBN} does not require them), but specifying them may be
35308 useful for XML validation tools. The @samp{version} attribute for
35309 @samp{<target>} may also be omitted, but we recommend
35310 including it; if future versions of @value{GDBN} use an incompatible
35311 revision of @file{gdb-target.dtd}, they will detect and report
35312 the version mismatch.
35314 @subsection Inclusion
35315 @cindex target descriptions, inclusion
35318 @cindex <xi:include>
35321 It can sometimes be valuable to split a target description up into
35322 several different annexes, either for organizational purposes, or to
35323 share files between different possible target descriptions. You can
35324 divide a description into multiple files by replacing any element of
35325 the target description with an inclusion directive of the form:
35328 <xi:include href="@var{document}"/>
35332 When @value{GDBN} encounters an element of this form, it will retrieve
35333 the named XML @var{document}, and replace the inclusion directive with
35334 the contents of that document. If the current description was read
35335 using @samp{qXfer}, then so will be the included document;
35336 @var{document} will be interpreted as the name of an annex. If the
35337 current description was read from a file, @value{GDBN} will look for
35338 @var{document} as a file in the same directory where it found the
35339 original description.
35341 @subsection Architecture
35342 @cindex <architecture>
35344 An @samp{<architecture>} element has this form:
35347 <architecture>@var{arch}</architecture>
35350 @var{arch} is one of the architectures from the set accepted by
35351 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
35354 @cindex @code{<osabi>}
35356 This optional field was introduced in @value{GDBN} version 7.0.
35357 Previous versions of @value{GDBN} ignore it.
35359 An @samp{<osabi>} element has this form:
35362 <osabi>@var{abi-name}</osabi>
35365 @var{abi-name} is an OS ABI name from the same selection accepted by
35366 @w{@code{set osabi}} (@pxref{ABI, ,Configuring the Current ABI}).
35368 @subsection Compatible Architecture
35369 @cindex @code{<compatible>}
35371 This optional field was introduced in @value{GDBN} version 7.0.
35372 Previous versions of @value{GDBN} ignore it.
35374 A @samp{<compatible>} element has this form:
35377 <compatible>@var{arch}</compatible>
35380 @var{arch} is one of the architectures from the set accepted by
35381 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
35383 A @samp{<compatible>} element is used to specify that the target
35384 is able to run binaries in some other than the main target architecture
35385 given by the @samp{<architecture>} element. For example, on the
35386 Cell Broadband Engine, the main architecture is @code{powerpc:common}
35387 or @code{powerpc:common64}, but the system is able to run binaries
35388 in the @code{spu} architecture as well. The way to describe this
35389 capability with @samp{<compatible>} is as follows:
35392 <architecture>powerpc:common</architecture>
35393 <compatible>spu</compatible>
35396 @subsection Features
35399 Each @samp{<feature>} describes some logical portion of the target
35400 system. Features are currently used to describe available CPU
35401 registers and the types of their contents. A @samp{<feature>} element
35405 <feature name="@var{name}">
35406 @r{[}@var{type}@dots{}@r{]}
35412 Each feature's name should be unique within the description. The name
35413 of a feature does not matter unless @value{GDBN} has some special
35414 knowledge of the contents of that feature; if it does, the feature
35415 should have its standard name. @xref{Standard Target Features}.
35419 Any register's value is a collection of bits which @value{GDBN} must
35420 interpret. The default interpretation is a two's complement integer,
35421 but other types can be requested by name in the register description.
35422 Some predefined types are provided by @value{GDBN} (@pxref{Predefined
35423 Target Types}), and the description can define additional composite types.
35425 Each type element must have an @samp{id} attribute, which gives
35426 a unique (within the containing @samp{<feature>}) name to the type.
35427 Types must be defined before they are used.
35430 Some targets offer vector registers, which can be treated as arrays
35431 of scalar elements. These types are written as @samp{<vector>} elements,
35432 specifying the array element type, @var{type}, and the number of elements,
35436 <vector id="@var{id}" type="@var{type}" count="@var{count}"/>
35440 If a register's value is usefully viewed in multiple ways, define it
35441 with a union type containing the useful representations. The
35442 @samp{<union>} element contains one or more @samp{<field>} elements,
35443 each of which has a @var{name} and a @var{type}:
35446 <union id="@var{id}">
35447 <field name="@var{name}" type="@var{type}"/>
35453 If a register's value is composed from several separate values, define
35454 it with a structure type. There are two forms of the @samp{<struct>}
35455 element; a @samp{<struct>} element must either contain only bitfields
35456 or contain no bitfields. If the structure contains only bitfields,
35457 its total size in bytes must be specified, each bitfield must have an
35458 explicit start and end, and bitfields are automatically assigned an
35459 integer type. The field's @var{start} should be less than or
35460 equal to its @var{end}, and zero represents the least significant bit.
35463 <struct id="@var{id}" size="@var{size}">
35464 <field name="@var{name}" start="@var{start}" end="@var{end}"/>
35469 If the structure contains no bitfields, then each field has an
35470 explicit type, and no implicit padding is added.
35473 <struct id="@var{id}">
35474 <field name="@var{name}" type="@var{type}"/>
35480 If a register's value is a series of single-bit flags, define it with
35481 a flags type. The @samp{<flags>} element has an explicit @var{size}
35482 and contains one or more @samp{<field>} elements. Each field has a
35483 @var{name}, a @var{start}, and an @var{end}. Only single-bit flags
35487 <flags id="@var{id}" size="@var{size}">
35488 <field name="@var{name}" start="@var{start}" end="@var{end}"/>
35493 @subsection Registers
35496 Each register is represented as an element with this form:
35499 <reg name="@var{name}"
35500 bitsize="@var{size}"
35501 @r{[}regnum="@var{num}"@r{]}
35502 @r{[}save-restore="@var{save-restore}"@r{]}
35503 @r{[}type="@var{type}"@r{]}
35504 @r{[}group="@var{group}"@r{]}/>
35508 The components are as follows:
35513 The register's name; it must be unique within the target description.
35516 The register's size, in bits.
35519 The register's number. If omitted, a register's number is one greater
35520 than that of the previous register (either in the current feature or in
35521 a preceeding feature); the first register in the target description
35522 defaults to zero. This register number is used to read or write
35523 the register; e.g.@: it is used in the remote @code{p} and @code{P}
35524 packets, and registers appear in the @code{g} and @code{G} packets
35525 in order of increasing register number.
35528 Whether the register should be preserved across inferior function
35529 calls; this must be either @code{yes} or @code{no}. The default is
35530 @code{yes}, which is appropriate for most registers except for
35531 some system control registers; this is not related to the target's
35535 The type of the register. @var{type} may be a predefined type, a type
35536 defined in the current feature, or one of the special types @code{int}
35537 and @code{float}. @code{int} is an integer type of the correct size
35538 for @var{bitsize}, and @code{float} is a floating point type (in the
35539 architecture's normal floating point format) of the correct size for
35540 @var{bitsize}. The default is @code{int}.
35543 The register group to which this register belongs. @var{group} must
35544 be either @code{general}, @code{float}, or @code{vector}. If no
35545 @var{group} is specified, @value{GDBN} will not display the register
35546 in @code{info registers}.
35550 @node Predefined Target Types
35551 @section Predefined Target Types
35552 @cindex target descriptions, predefined types
35554 Type definitions in the self-description can build up composite types
35555 from basic building blocks, but can not define fundamental types. Instead,
35556 standard identifiers are provided by @value{GDBN} for the fundamental
35557 types. The currently supported types are:
35566 Signed integer types holding the specified number of bits.
35573 Unsigned integer types holding the specified number of bits.
35577 Pointers to unspecified code and data. The program counter and
35578 any dedicated return address register may be marked as code
35579 pointers; printing a code pointer converts it into a symbolic
35580 address. The stack pointer and any dedicated address registers
35581 may be marked as data pointers.
35584 Single precision IEEE floating point.
35587 Double precision IEEE floating point.
35590 The 12-byte extended precision format used by ARM FPA registers.
35593 The 10-byte extended precision format used by x87 registers.
35596 32bit @sc{eflags} register used by x86.
35599 32bit @sc{mxcsr} register used by x86.
35603 @node Standard Target Features
35604 @section Standard Target Features
35605 @cindex target descriptions, standard features
35607 A target description must contain either no registers or all the
35608 target's registers. If the description contains no registers, then
35609 @value{GDBN} will assume a default register layout, selected based on
35610 the architecture. If the description contains any registers, the
35611 default layout will not be used; the standard registers must be
35612 described in the target description, in such a way that @value{GDBN}
35613 can recognize them.
35615 This is accomplished by giving specific names to feature elements
35616 which contain standard registers. @value{GDBN} will look for features
35617 with those names and verify that they contain the expected registers;
35618 if any known feature is missing required registers, or if any required
35619 feature is missing, @value{GDBN} will reject the target
35620 description. You can add additional registers to any of the
35621 standard features --- @value{GDBN} will display them just as if
35622 they were added to an unrecognized feature.
35624 This section lists the known features and their expected contents.
35625 Sample XML documents for these features are included in the
35626 @value{GDBN} source tree, in the directory @file{gdb/features}.
35628 Names recognized by @value{GDBN} should include the name of the
35629 company or organization which selected the name, and the overall
35630 architecture to which the feature applies; so e.g.@: the feature
35631 containing ARM core registers is named @samp{org.gnu.gdb.arm.core}.
35633 The names of registers are not case sensitive for the purpose
35634 of recognizing standard features, but @value{GDBN} will only display
35635 registers using the capitalization used in the description.
35642 * PowerPC Features::
35647 @subsection ARM Features
35648 @cindex target descriptions, ARM features
35650 The @samp{org.gnu.gdb.arm.core} feature is required for ARM targets.
35651 It should contain registers @samp{r0} through @samp{r13}, @samp{sp},
35652 @samp{lr}, @samp{pc}, and @samp{cpsr}.
35654 The @samp{org.gnu.gdb.arm.fpa} feature is optional. If present, it
35655 should contain registers @samp{f0} through @samp{f7} and @samp{fps}.
35657 The @samp{org.gnu.gdb.xscale.iwmmxt} feature is optional. If present,
35658 it should contain at least registers @samp{wR0} through @samp{wR15} and
35659 @samp{wCGR0} through @samp{wCGR3}. The @samp{wCID}, @samp{wCon},
35660 @samp{wCSSF}, and @samp{wCASF} registers are optional.
35662 The @samp{org.gnu.gdb.arm.vfp} feature is optional. If present, it
35663 should contain at least registers @samp{d0} through @samp{d15}. If
35664 they are present, @samp{d16} through @samp{d31} should also be included.
35665 @value{GDBN} will synthesize the single-precision registers from
35666 halves of the double-precision registers.
35668 The @samp{org.gnu.gdb.arm.neon} feature is optional. It does not
35669 need to contain registers; it instructs @value{GDBN} to display the
35670 VFP double-precision registers as vectors and to synthesize the
35671 quad-precision registers from pairs of double-precision registers.
35672 If this feature is present, @samp{org.gnu.gdb.arm.vfp} must also
35673 be present and include 32 double-precision registers.
35675 @node i386 Features
35676 @subsection i386 Features
35677 @cindex target descriptions, i386 features
35679 The @samp{org.gnu.gdb.i386.core} feature is required for i386/amd64
35680 targets. It should describe the following registers:
35684 @samp{eax} through @samp{edi} plus @samp{eip} for i386
35686 @samp{rax} through @samp{r15} plus @samp{rip} for amd64
35688 @samp{eflags}, @samp{cs}, @samp{ss}, @samp{ds}, @samp{es},
35689 @samp{fs}, @samp{gs}
35691 @samp{st0} through @samp{st7}
35693 @samp{fctrl}, @samp{fstat}, @samp{ftag}, @samp{fiseg}, @samp{fioff},
35694 @samp{foseg}, @samp{fooff} and @samp{fop}
35697 The register sets may be different, depending on the target.
35699 The @samp{org.gnu.gdb.i386.sse} feature is optional. It should
35700 describe registers:
35704 @samp{xmm0} through @samp{xmm7} for i386
35706 @samp{xmm0} through @samp{xmm15} for amd64
35711 The @samp{org.gnu.gdb.i386.avx} feature is optional and requires the
35712 @samp{org.gnu.gdb.i386.sse} feature. It should
35713 describe the upper 128 bits of @sc{ymm} registers:
35717 @samp{ymm0h} through @samp{ymm7h} for i386
35719 @samp{ymm0h} through @samp{ymm15h} for amd64
35723 The @samp{org.gnu.gdb.i386.linux} feature is optional. It should
35724 describe a single register, @samp{orig_eax}.
35726 @node MIPS Features
35727 @subsection MIPS Features
35728 @cindex target descriptions, MIPS features
35730 The @samp{org.gnu.gdb.mips.cpu} feature is required for MIPS targets.
35731 It should contain registers @samp{r0} through @samp{r31}, @samp{lo},
35732 @samp{hi}, and @samp{pc}. They may be 32-bit or 64-bit depending
35735 The @samp{org.gnu.gdb.mips.cp0} feature is also required. It should
35736 contain at least the @samp{status}, @samp{badvaddr}, and @samp{cause}
35737 registers. They may be 32-bit or 64-bit depending on the target.
35739 The @samp{org.gnu.gdb.mips.fpu} feature is currently required, though
35740 it may be optional in a future version of @value{GDBN}. It should
35741 contain registers @samp{f0} through @samp{f31}, @samp{fcsr}, and
35742 @samp{fir}. They may be 32-bit or 64-bit depending on the target.
35744 The @samp{org.gnu.gdb.mips.linux} feature is optional. It should
35745 contain a single register, @samp{restart}, which is used by the
35746 Linux kernel to control restartable syscalls.
35748 @node M68K Features
35749 @subsection M68K Features
35750 @cindex target descriptions, M68K features
35753 @item @samp{org.gnu.gdb.m68k.core}
35754 @itemx @samp{org.gnu.gdb.coldfire.core}
35755 @itemx @samp{org.gnu.gdb.fido.core}
35756 One of those features must be always present.
35757 The feature that is present determines which flavor of m68k is
35758 used. The feature that is present should contain registers
35759 @samp{d0} through @samp{d7}, @samp{a0} through @samp{a5}, @samp{fp},
35760 @samp{sp}, @samp{ps} and @samp{pc}.
35762 @item @samp{org.gnu.gdb.coldfire.fp}
35763 This feature is optional. If present, it should contain registers
35764 @samp{fp0} through @samp{fp7}, @samp{fpcontrol}, @samp{fpstatus} and
35768 @node PowerPC Features
35769 @subsection PowerPC Features
35770 @cindex target descriptions, PowerPC features
35772 The @samp{org.gnu.gdb.power.core} feature is required for PowerPC
35773 targets. It should contain registers @samp{r0} through @samp{r31},
35774 @samp{pc}, @samp{msr}, @samp{cr}, @samp{lr}, @samp{ctr}, and
35775 @samp{xer}. They may be 32-bit or 64-bit depending on the target.
35777 The @samp{org.gnu.gdb.power.fpu} feature is optional. It should
35778 contain registers @samp{f0} through @samp{f31} and @samp{fpscr}.
35780 The @samp{org.gnu.gdb.power.altivec} feature is optional. It should
35781 contain registers @samp{vr0} through @samp{vr31}, @samp{vscr},
35784 The @samp{org.gnu.gdb.power.vsx} feature is optional. It should
35785 contain registers @samp{vs0h} through @samp{vs31h}. @value{GDBN}
35786 will combine these registers with the floating point registers
35787 (@samp{f0} through @samp{f31}) and the altivec registers (@samp{vr0}
35788 through @samp{vr31}) to present the 128-bit wide registers @samp{vs0}
35789 through @samp{vs63}, the set of vector registers for POWER7.
35791 The @samp{org.gnu.gdb.power.spe} feature is optional. It should
35792 contain registers @samp{ev0h} through @samp{ev31h}, @samp{acc}, and
35793 @samp{spefscr}. SPE targets should provide 32-bit registers in
35794 @samp{org.gnu.gdb.power.core} and provide the upper halves in
35795 @samp{ev0h} through @samp{ev31h}. @value{GDBN} will combine
35796 these to present registers @samp{ev0} through @samp{ev31} to the
35799 @node Operating System Information
35800 @appendix Operating System Information
35801 @cindex operating system information
35807 Users of @value{GDBN} often wish to obtain information about the state of
35808 the operating system running on the target---for example the list of
35809 processes, or the list of open files. This section describes the
35810 mechanism that makes it possible. This mechanism is similar to the
35811 target features mechanism (@pxref{Target Descriptions}), but focuses
35812 on a different aspect of target.
35814 Operating system information is retrived from the target via the
35815 remote protocol, using @samp{qXfer} requests (@pxref{qXfer osdata
35816 read}). The object name in the request should be @samp{osdata}, and
35817 the @var{annex} identifies the data to be fetched.
35820 @appendixsection Process list
35821 @cindex operating system information, process list
35823 When requesting the process list, the @var{annex} field in the
35824 @samp{qXfer} request should be @samp{processes}. The returned data is
35825 an XML document. The formal syntax of this document is defined in
35826 @file{gdb/features/osdata.dtd}.
35828 An example document is:
35831 <?xml version="1.0"?>
35832 <!DOCTYPE target SYSTEM "osdata.dtd">
35833 <osdata type="processes">
35835 <column name="pid">1</column>
35836 <column name="user">root</column>
35837 <column name="command">/sbin/init</column>
35838 <column name="cores">1,2,3</column>
35843 Each item should include a column whose name is @samp{pid}. The value
35844 of that column should identify the process on the target. The
35845 @samp{user} and @samp{command} columns are optional, and will be
35846 displayed by @value{GDBN}. The @samp{cores} column, if present,
35847 should contain a comma-separated list of cores that this process
35848 is running on. Target may provide additional columns,
35849 which @value{GDBN} currently ignores.
35853 @node GNU Free Documentation License
35854 @appendix GNU Free Documentation License
35863 % I think something like @colophon should be in texinfo. In the
35865 \long\def\colophon{\hbox to0pt{}\vfill
35866 \centerline{The body of this manual is set in}
35867 \centerline{\fontname\tenrm,}
35868 \centerline{with headings in {\bf\fontname\tenbf}}
35869 \centerline{and examples in {\tt\fontname\tentt}.}
35870 \centerline{{\it\fontname\tenit\/},}
35871 \centerline{{\bf\fontname\tenbf}, and}
35872 \centerline{{\sl\fontname\tensl\/}}
35873 \centerline{are used for emphasis.}\vfill}
35875 % Blame: doc@cygnus.com, 1991.